Technical field
[0001]
　The present invention relates to an excellent hot-dip galvanized steel sheet in the plating adhesion.
　The present application, on November 05, 2014, claiming priority based on Japanese Patent Application No. 2014-225398, filed in Japan, the contents of which are incorporated here.
Background technique
[0002]
　Mainly for steel sheet used in the frame member of an automobile, there has been a growing demand for higher strength. In these high-strength steel sheets, for obtaining an excellent moldability high strength, it is common to add alloying elements typified by contributing Si and Mn for improving the strength. However, alloying elements typified by Si and Mn also has effects of lowering the coating adhesion.
　As for the automobile steel sheet, since the commonly used outdoors, that is superior corrosion resistance required is usually.
[0003]
　However, in applications such as the outer plate of the motor vehicle, subjected to a severe bending a peripheral portion of the plate by press working (bending heme) it is usual. Further not only the automobile outer plate, in other applications, harsh bending or by pressing, is often used by applying such hole expansion processing. When subjected to such harsh bending and hole expansion processing on conventional galvanized steel sheet, in its working portion, the plating layer was sometimes peeled off from the base material steel plate. If the plating layer is peeled off in this way, the corrosion resistance of the change is lost, there is early corrosion base steel sheet, rusting occurs problems. Also even does not lead to peeling of the plating layer, the plating layer and in adhesion between the base steel sheet is lost, if Shojire voids even slightly in that portion, and the outside air or moisture penetrates into the gap, plating anti-corrosion function is lost by layer. As a result, the same early corrosion to the base steel sheet, rusting occurs.
　These problems, as the high-strength steel sheet used is subjected to such severe bending, plated steel sheet having a galvanized layer has excellent adhesion of the plating layer to the base material steel plate is strongly desired there.
[0004]
　To enhance the adhesion of the plating layer, for example, as typified by Patent Documents 1 to 3, to generate an internal oxidation of the steel sheet, the base steel which causes plated peeling the plating layer and the oxide at the interface how to reduce have been proposed. However, if for generating such oxides steel surface layer, the carbon of the steel sheet surface layer is gasified combine with oxygen. As a result, the detached from carbon steel, the strength of the area where the carbon is separated is significantly reduced. If the strength of the steel sheet surface layer is decreased, fatigue resistance which depends strongly on the properties of the surface layer portion deteriorates, there is a concern that the fatigue strength is significantly reduced.
[0005]
　Alternatively, in order to improve the adhesion of the plating layer, Patent Document 4, by performing adding a new annealing process and pickling step prior to the general annealing process, modify the base steel sheet surface, plating how to improve adhesion have been proposed. However, in the method described in Patent Document 4, with respect to the production method of general high strength plated steel sheet, since the process is increased, there is a problem in terms of cost.
[0006]
　Further, in Patent Document 5, to remove the carbon from the surface layer portion of the base steel sheet, a method of increasing the adhesiveness of the plating has been proposed. However, in the method described in Patent Document 5, significantly reduced the strength of the region to remove the carbon. Therefore, the method described in Patent Document 5, fatigue resistance is deteriorated strongly dependent on the characteristics of the surface layer portion, there is a concern that the fatigue strength is significantly reduced.
[0007]
　In Patent Document 6, 7, Mn in the coating layer, controlling the Al and Si amount to a preferred range, the steel sheet having improved plating adhesion have been proposed. The steel sheet described in Patent Documents 6 and 7, it is necessary to control the element content in the coating layer during manufacture with high precision, large load on operation, there is a problem in cost.
[0008]
　As a method to improve the coating adhesion, Patent Document 8, a high-strength steel sheet has been proposed microstructure of the steel sheet is composed of only ferrite. However, the steel sheet described in Patent Document 8, since the microstructure is only soft ferrite, not sufficiently high strength can be obtained.
[0009]
　Here, galvannealed steel sheets subjected to alloying treatment is widely used after galvanizing treatment. Alloying treatment, the plated layer is heated to a temperature above the melting point of Zn, a large amount of Fe atoms are diffused in the plating layer during the base steel sheet during the certain plating layer in the process of a layer of Zn-Fe alloy mainly . For example, Patent Document 9,10,11 excellent galvannealed steel sheet coating adhesion have been proposed. However, to fully alloyed plating layer, it is necessary to heat the steel plate to a high temperature. Heating the steel to a high temperature, the steel sheet inside the microstructure altered easily generated particularly coarse iron-based carbides, due to that the characteristics of the steel sheet is impaired, which is undesirable.
[0010]
　Patent Document 12, galvanized steel sheet basis steel sheet comprises Si, Mn, one or more selected from the group consisting of Al is described. Patent Document 12, in the manufacturing process, it is described that control the plating bath penetration temperature of base steel sheet. Further, Patent Document 12, defining the area ratio of the cross section of the alloy layer formed at the interface between the base steel sheet and the plated layer, and excellent hot-dip galvanized steel sheet in a plating adhesion and spot weldability is disclosed there.
[0011]
　Patent Document 12, Si in the surface, the steel sheet Mn oxide is present, when the invaded by molten zinc plating bath, non-plating galvanizing is not performed is mentioned that a large amount occurs. However, Patent Document 12, Si, reduce the Mn oxide before the start plating technique is not disclosed. In Patent Document 12, the plating bath penetration temperature of the base steel sheet, higher than hot-dip galvanizing bath temperature. Depending on the Al content in the molten zinc plating bath, the plating bath penetration temperature of the base steel sheet at a minimum, to 4 ° C. ultra higher than hot-dip galvanizing bath temperature is increased up to 28 ° C.. Therefore, in Patent Document 12, there is a case where uniformity of characteristics bath temperature stability and hence product becomes insufficient.
CITATION
Patent Document
[0012]
Patent Document 1: Japanese Laid-Open Patent Publication No. 2008-019465
Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-060742
Patent Document 3: Japanese Laid-Open Patent Publication No. 9-176815
Patent Document 4: Japanese Patent Laid-Open 2001-026853 Publication No.
Patent Document 5: Japanese Laid-open Patent Publication No. 2002-088459
Patent Document 6: Japanese Laid-open Patent Publication No. 2003-055751
Patent Document 7: Japanese Laid-open Patent Publication No. 2003-096541
Patent Document 8: Japanese Patent Laid-open 2005 Publication No. -200750
Patent Document 9: Japanese Unexamined Patent Publication No. 11-140587
Patent Document 10: Japanese Laid-open Patent Publication No. 2001-303226
Patent Document 11: Japanese Laid-open Patent Publication No. 2005-060743
Patent Document 12: Japanese Laid table No. 2013-541645 Gazette
Summary of the Invention
Problems that the Invention is to Solve
[0013]
　In view of the situation described above, the present invention is, strength, ductility, hole expandability, it is an object to provide a superior hot-dip galvanized steel sheet in the plating adhesion.
Means for Solving the Problems
[0014]
　The present inventors have conducted extensive studies in order to obtain good galvanized steel sheet coating adhesion. As a result, the present inventors have, zeta phase in the plating layer (FeZn 13 were found to suppress the plating peeling by incorporating) Thus, without performing the alloying treatment of the plating layer, excellent hot-dip galvanized steel sheet in the plating adhesion can be obtained.
[0015]
　The present invention was completed on the basis of this finding, the embodiment is as follows.
[0016]
(1) consists of a galvanized layer formed on at least one surface of said base steel sheet and the base steel sheet,
　the galvanized layer on the surface of the steel sheet, Fe content of 0% super-5 % or less and is the Al content is 0% or less super to 1.0%, including columnar crystals composed of ζ phase, further, more than 20% of the total interface between the galvanized layer and the base steel sheet there is covered in ζ phase, all the interface in the galvanized layer, the interface formed between ζ crystal grains and the base material steel plate there is a coarse oxides of ζ crystal grains, and the ζ phase and the base steel sheet is 50% or less with respect to,
the base material steel plate containing, by
　　mass%, C:
　　0.040 ~ 0.400%,
　　Si: 0.05 ~ 2.50%, Mn: 0.50 ~ 3.50
　　Pasento, P:
　　0.0001 ～ 0.1000 Pasento, S: 0.0001 ～
　　0.0100 Pasento, Al: 0.00 The
　　~
　　1.500% 1, N: 0.0001 ~ 0.0100%, O: 0.0001 ~ 0.0100%,
the balance has a chemical composition consisting of Fe and unavoidable impurities,
　the melt and the base steel sheet has a surface in direct contact with the fine layer of the galvanized layer, the average thickness of 0.1 to 5.0 .mu.m finer layer, the average particle size of the ferrite phase in the fine layer is from 0.1 to a 3.0 [mu] m, 1 kind or comprise two or more oxides, galvanized steel sheet maximum diameter of 0.01 ~ 0.4 .mu.m of the oxides of Si and Mn in the fine layer.
(2) For the galvanized layer, the coating weight of one surface of the base material steel plate is 10 g / m 2 or more, 100 g / m 2 hot-dip galvanized steel sheet according to or less (1).
(3) the base material steel plate contains, by mass%,
　　further,
　　Ti: 0.001 ~ 0.150%,
　　Nb: 0.001 ~ 0.100%, V: 0.001 ~ 0.300%,
of the hot-dip galvanized steel sheet according to contain one or more selected from (1) or (2).
(4) the base material steel plate contains, by mass%,
　　further,
　　Cr: 0.01 ~
　　2.00%, Ni: 0.01 ~ 2.00%, Cu: 0.01 ~
　　2.00%, Mo:
　　~ 2.00% 0.01, B:
　　0.0001 ~ 0.0100%, W: 0.01 ~ 2.00%,
containing one or two or more species selected from among (1) - hot-dip galvanized steel sheet according to any one of (3).
(5) the base material steel plate contains, by mass%,
furthermore, Ca, Ce, Mg, Zr, La, contain from 0.0001 to 0.0100% in total of one or more of REM (1) ~ hot-dip galvanized steel sheet according to any one of (4).
Effect of the Invention
[0017]
　According to this aspect of the present invention can provide strength, ductility, hole expandability, excellent hot-dip galvanized steel sheet in the plating adhesion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
[Figure 1] of the cross section of the hot-dip galvanized steel sheet according to the present embodiment is a scanning electron microscope (SEM) photograph of a cross section including and neighboring galvanized layer / base steel sheet surface.
FIG. 2 is a field emission scanning electron microscope (FE-SEM) photograph of a section of the galvanized steel sheet according to the present embodiment.
DESCRIPTION OF THE INVENTION
[0019]
　Galvanized steel sheet according to the embodiment of the present invention, the base steel sheet (hereinafter, simply referred to as steel.) And galvanized layer formed on at least one surface of the steel sheet (hereinafter, simply referred to as a plating layer.) consisting of.
　Plating layer, Fe content is not more than 0% Ultra-5% Al content is not more than 0% super% to 1.0%, including columnar crystals composed of ζ phase. Plating layer, the plating layer and the base material more than 20% of the total interface between the steel sheet is coated on the zeta phase, zeta phase and the matrix there is coarse oxides of the interface between the steel sheet zeta grains and the matrix the proportion of the interface formed between the steel sheet is 50% or less.
[0020]
　First, a description will be given zinc plating layer constituting the hot-dip galvanized steel sheet according to the embodiment of the embodiment of the present invention. Note that [%] in the following description are [mass%].
[0021]
(Plating layer)
　in embodiments of the present invention, the galvanized layer, Fe content is not more than 0% super-5.0%, Al content is 0% or less super to 1.0%. Further, the galvanized layer Ag, B, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Ge, Hf, I, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni , Pb, Rb, Sb, Si , Sn, Sr, Ta, Ti, V, W, Zr, or may be one or containing two or more REM, or mixed. Thus, galvanized layer, contain one or two or more of said elements, or even those mixed, the effect of the present invention is not impaired, the corrosion resistance and workability by the content If such is improved preferably also.
　In the present embodiment, galvanized layer includes columnar crystals composed of ζ phase, characterized in that more than 20% of the total interface between the plated layer and the base steel sheet is covered with the ζ phase .
　Further, the adhesion amount of hot-dip galvanizing layer on one surface of the base material steel plate is 10 g / m 2 or more, 100 g / m 2 is preferably less.
[0022]
: [Fe content in galvanized layer 0% Ultra to 5.0% or less]
　Since the coating adhesion and the Fe content is increased to deteriorate the galvanized layer, and a Fe content of 5.0% or less There is a need to. To enhance the coating adhesion Further, Fe content in the coating layer is preferably set to 4.0% or less, more preferably 3% or less. The lower limit of the Fe content in the plating layer is 0 percent. The Fe content is less than 0.5%, the ζ phase may not be sufficiently obtained needed to improve the adhesion. Therefore, Fe content in the coating layer is preferably 0.5% or more, further preferably 1.0% or more.
[0023]
: [Al content in the galvanized layer 0% super% to 1.0% or less]
　Since the coating adhesion between the Al content is increased to deteriorate the galvanized layer, and an Al content of 1.0% or less There is a need to. To enhance the coating adhesion Further, Al content in the coating layer is preferably set to 0.8% or less, further preferably 0.5% or less. The lower limit of the Al content in the plating layer is 0 percent. The Al content to less than 0.01%, it is necessary to lower the Al concentration in the plating bath excessively. When extremely lowered Al concentration in the plating bath, the plating adhesion alloying increasingly Fe content in the coating layer by excessively progress of the plating layer is degraded. Therefore, Al content of the plating layer is preferably 0.01% or more. In this respect, Al content of the plating layer is more preferably 0.05% or more.
[0024]
　さらに、溶融亜鉛めっき層はＡｇ、Ｂ、Ｂｅ、Ｂｉ、Ｃａ、Ｃｄ、Ｃｏ、Ｃｒ、Ｃｓ、Ｃｕ、Ｇｅ、Ｈｆ、Ｉ、Ｋ、Ｌａ、Ｌｉ、Ｍｇ、Ｍｎ、Ｍｏ、Ｎａ、Ｎｂ、Ｎｉ、Ｐｂ、Ｒｂ、Ｓｂ、Ｓｉ、Ｓｎ、Ｓｒ、Ｔａ、Ｔｉ、Ｖ、Ｗ、Ｚｒ、ＲＥＭの１種または２種以上を含有、あるいは混入するものであってもよい。溶融亜鉛めっき層が、上記の元素の１種または２種以上を含有、あるいは混入するものであっても、本発明の効果は損なわれず、その含有量によっては耐食性や加工性が改善される等好ましい場合もある。
[0025]
"Ζ phase"
　in Figure 1 shows a scanning electron microscope (SEM) photograph of a cross section of the galvanized steel sheet according to the present embodiment. As shown in FIG. 1, galvanized layer of the present invention, zeta phase is an alloy of Fe and Zn (FeZn 13 including columnar crystals made of). Particularly among all the interface between the plated layer and the base steel sheet, the ratio of the interface ζ phase is in contact with the base steel sheet is characterized in that 20% or more. Thus, coarse oxides over longer diameter 0.2μm containing Si and / or Mn can serve as a starting point for peeling is taken into ζ phase from the base steel sheet surface. This coarse oxides by becomes difficult act as starting points of fracture to improve the adhesion of the plating layer. From this viewpoint, it is preferable that the interface ζ phase and the base steel sheet is plated layer and the ratio for all of the interface between the base steel sheet is 25% or more, more preferably 30% or more. Incidentally, the interface of the ζ phase and the base steel sheet is the upper limit of the percentage of all of the interface between the plating layer and the base steel sheet is not particularly defined, but may be 100%. Incidentally, when the major axis of the oxide containing Si and / or Mn is 0.2 [mu] m or more, cracks starting from the oxide becomes significant, when the major axis is less than 0.2 [mu] m, less likely serve as a starting point of cracks . This degree of stress concentration at the time of deformation of the galvanized steel sheet, in order to vary the size of the oxide. Specifically, as the oxide is large (major axis is long), the stress is easily concentrated during deformation, the plating layer is likely to peel.
[0026]
　On the other hand, not taken into coarse oxides ζ phase containing Si and / or Mn, the interface coarse oxides of ζ phase and the base steel sheet is present, the effect of improving the plating adhesion by ζ phase is not sufficiently obtained , which is not preferable. Therefore, coarse oxides zeta exists grains and the ratio of the interface between the base steel sheet (coarse oxides containing zeta grains), zeta phase and the base steel sheet of the crystal of zeta phase (zeta grain) to 50% or less for all of the interface between. If the ratio of the interface between the coarse oxide-containing ζ crystal grains and the base material steel plate is 50% or less, coarse oxide is sufficiently reduced containing Si and / or Mn are present without being incorporated into the ζ phase. The ratio of the interface between the coarse oxide-containing ζ crystal grains and the base material steel plate is preferably 35% or less for all of the interface between the ζ phase and the base steel sheet. The interface between the ζ phase and the base steel sheet, preferably as or more coarse oxides diameter 0.2μm less. Of all the interface between the ζ phase and the base steel sheet, it is most preferred ratio of surfactants coarse oxide-containing ζ grain makes with the base steel sheet is 0%.
[0027]
　Moreover, galvanized layer δ1 phase (FeZn 7 may also contain a). However, to increase the fraction of δ1-phase, was immersed base steel sheet in the plating bath, it is necessary to advance the alloying of the plating layer by heating the base steel sheet, tensile properties of the base material steel plate is deteriorated by heating to. It is preferable from this point of view, the fraction of δ1 phase is small. Particularly among all the interface between the plating layer and the base steel sheet, it is preferable that the ratio of the interface δ1 phase is in contact with the base material steel plate is 20% or less.
[0028]
　Proportion interface between the ζ phase and the base steel sheet in the present invention accounts for all of the interface between the plating layer and the base steel sheet and the interface δ1 phase and the base steel sheet is occupied by all of the interface between the plating layer and the base steel sheet ratios can be determined in the following manner.
　That is, a sample is taken from the hot-dip galvanized steel sheet, as an observation plane parallel to sheet thickness cross section in the rolling direction of the base material steel plate. The viewing surface was mirror-polished, field emission scanning electron microscope (FE-SEM: Field Emission Scanning Electron Microscope) using a total L of the length of the interface between the plating layer and the base steel sheet was observed 200μm or more and to observe until. The sum L of the lengths interface is observed until the above 200 [mu] m is to the inside of one thickness section L may be observed until more than 200 [mu] m, a plurality of plate thickness in a cross section L is 200 [mu] m or more and it may be observed until.
[0029]
　In the same field as the field of observation of the L, the crystal grains exhibit columnar is ζ phase or δ1 phase, measuring the total L1 of the ζ phase and δ1 phases and the length of the interface between the base steel sheet. Subsequently, in the same field as the field of observation of the L1, perform high-resolution crystal orientation analysis by EBSD (Electron Bach-Scattering Diffraction) method using a FE-SEM, it performs identification of .delta.1 phase, .delta.1 phase and the matrix the sum is L2 length of the interface of the steel sheet.
　(L1-L2) / L with ζ phase and the interface of the base material steel plate is regarded as a percentage of all of the interface between the plating layer and the base steel sheet.
　Similarly, the interface between the δ1 phase and the base steel sheet with a L2 / L is considered as a percentage of all of the interface between the plating layer and the base steel sheet.
　Incidentally, separation of the ζ phase and δ1 phase, may be performed by a method other than the above EBSD method. For example, field emission electron probe micro-analyzer: by (FE-EPMA Field Emission Electron Probe MicroAnalyser), performed Zn element mapping in the plating layer, it may be performed to determine the difference Zn amount of ζ-phase and δ1 phases Absent.
[0030]
　Also, among the crystals of zeta phase (zeta grains), the rate of the interface of coarse oxide zeta exists grains and (coarse oxides containing zeta grains) and the base steel sheet is obtained in the following manner. That is, in the same field as the field of observation of the L, zeta phase and the base material interface to the observation of the steel sheet, zeta phase and the base steel sheet and the interface over long diameter 0.2μm coarse oxide is zeta grain (coarse obtaining an oxide containing ζ grains). Oxide existing in an interface between the ζ phase and the base steel sheet of the plating layer appear dark compared to the surrounding in backscattered electron (BSE) image of the SEM. Therefore, whether oxides at the interface between the ζ phase and the base steel sheet of the plating layer is present, by observing the reflected electron (BSE) image of the SEM in the same field as the field of view observed L, and the periphery determining the difference in brightness between the. Further, each oxide is determined by measuring the major axis on the observation plane, the major axis is determined more than 0.2μm coarse oxides. Then, a length of the interface between the coarse oxide-containing ζ crystal grains and the base steel sheet to obtain a total L ** length of the interface. By determining the L ** / (L1-L2), of all the interface between the ζ phase and the base steel sheet, the ratio of surface coarse oxide-containing ζ grain makes with the base steel sheet is obtained.
[0031]
　In order to clearly revealing the ζ phase, the observation surface of the sample after mirror polishing, may be subjected to a corrosion of the observation plane by using the etchant such as nital.
[0032]
[Adhesion amount of hot-dip galvanizing: 10 ~ 100 g / m 2 ]
　is not sufficient corrosion resistance is obtained with a small amount of adhesion to the base material steel plate one surface of galvanized layer fear. Therefore, adhesion of the base material steel plate one surface of the plating layer is 10 g / m 2 preferably not less than. From the viewpoint of corrosion resistance, coating weight 20 g / m 2 and more preferably at least, 30 g / m 2 or more is more preferable. On the other hand, when the amount is large adhesion of the plating layer becomes severe electrode wear when performing spot welding, there is a possibility that the deterioration of the decrease and welded joint strength of the welding nugget diameter when subjected to welding continuously occurs. Therefore, the coating weight of the plating layer 100 g / m 2 is preferably not more than. In view of the continuous weldability, coating weight 93 g / m 2 , more preferably at most, 85 g / m 2 and more preferably not more than.
[0033]
　Galvanized steel sheet of the present invention includes the plated layer, has a fine layer of the base steel sheet is shown below.
　The fine layer, the average particle size of the ferrite phase present in the outermost layer is a region that is 1/2 or less of the average particle size of the ferrite phase in the lower layer. The average particle size of the ferrite phase in the finer layer, the extra half to become a boundary of an average particle size of the ferrite phase in the lower layer, define the boundary of the fine layer and the underlying.
[0034]
　Finer layer is in direct contact with the interface between the base steel sheet galvanized layer. The average thickness of the finer layer is 0.1 ~ 5.0 .mu.m. The average particle size of the ferrite phase in the finer layer is 0.1 ~ 3.0 [mu] m. Miniaturization layer contains one or more oxides of Si and Mn, the maximum diameter of the oxide is 0.01 ~ 0.4 .mu.m.
[0035]
　If the average thickness of the finer layer is 0.1μm or more, when processing galvanized steel sheet, occurrence and spreading of cracks can be suppressed. Therefore, the average thickness of the finer layer is not less than 0.1 [mu] m, it is preferable to 1.0μm or more. The average thickness of 5.0μm or less finer layer can be formed while suppressing excessive alloying in the plating bath. Therefore, Fe content in the coating layer can be prevented the deterioration of coating adhesion due to excessively large. Therefore, the average thickness of the finer layer is not more than 5.0 .mu.m, it is preferable to 3.0μm or less.
[0036]
　By the average particle size of the ferrite phase of the finer layer and above 0.1 [mu] m, when processing galvanized steel sheet, occurrence and spreading of cracks can be suppressed. Therefore, the average grain size of the ferrite phase of the finer layer is not less than 0.1 [mu] m, it is preferable to 1.0μm or more. Further, when the average particle size of the ferrite phase of the finer layer and 3.0μm greater than the effect of suppressing the generation and extension of cracks is limited. Therefore, the average grain size of the ferrite phase of the finer layer is set to 3.0μm or less, it is preferable to 2.0μm or less.
[0037]
　The one or more oxides of Si and Mn contained in the finer layer, e.g., SiO 2 , Mn 2 SiO 4 , MnSiO 3 , Fe 2 SiO 4 , FeSiO 3 selected from among, MnO one or two or more thereof.
　When the maximum diameter of the one or more oxides of Si and Mn contained in the finer layer is in 0.01μm or more, to form a fine layer, generation of ζ phase is sufficiently promoted a plating layer can be formed. Maximum diameter of the oxides is preferably 0.05μm or more. Further, the fine layer maximum diameter of 0.4μm or less of the above oxides can be formed while suppressing excessive alloying of the plating layer. Maximum diameter of the oxides is preferably 0.2μm or less.
[0038]
　The average particle size of the ferrite phase in an average thickness and miniaturization layer of finer layer is measured by the following methods. From galvanized steel sheet, a sample is taken as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate. The observation surface of the sample is processed by CP (Cross section polisher) device, a reflection electron image at FE-SEM (Field Emission Scanning Electron Microscopy) was observed at 5000-fold, measured.
[0039]
　Maximum diameter of the one or more oxides of Si and Mn contained in the fine layer is measured by the following methods. From galvanized steel sheet, a sample is taken as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate. The observation surface of the sample FIB (Focused Ion Beam) is processed to produce a thin film sample. Thereafter, the thin film sample is observed at a magnification of 30000 times with a FE-TEM (Field Emission Transmission Electr on Microscopy). 5-field observation of each film sample, the maximum diameter of oxides measured by the total field of view, the maximum diameter of the oxide in the thin film sample.
[0040]
　Chemical composition of the base material steel plate constituting the hot-dip galvanized steel sheet according to the present embodiment in the following (composition) will be described. Note that [%] in the following description are [mass%].
[0041]
[C: 0.040 ~ 0.400%]
　C is an element added to enhance the strength of the base material steel plate. However, if the content of C exceeds 0.400%, and the spot weldability is deteriorated, not preferable, C content is at most 0.400%. In view of the spot weldability, the content of C is less than 0.300%, more preferably at most 0.220%. On the other hand, when the content of C is less than 0.040%, strength is lowered, it becomes difficult to secure a sufficient tensile maximum strength, C content is 0.040% or more. In order to increase the strength further, it is preferable that the content of C is more than 0.055%, and more preferably not less than 0.070%.
[0042]
[Si: 0.05 ~ 2.50%]
　Si suppresses the formation of iron-based carbides in the base material steel plate, is an element to increase the strength and formability. However, Si is also an element embrittle the steel, when the content exceeds 2.50%, troubles such as cast slab cracking tends to occur. Therefore, the Si content should be not more than 2.50%. Moreover, Si is an oxide formed on the surface of the base steel sheet in the annealing step, significantly impair the adhesion of the plating. From this viewpoint, the content of Si is preferably not more than 2.00%, more preferably at most 1.60%. On the other hand, is less than 0.05% content of Si, in the plating step of the hot-dip galvanized steel sheet, coarse iron-based carbide is produced in large quantities, the strength and the formability deteriorates. Therefore, the Si content is 0.05% or more. Incidentally, from the viewpoint of suppressing the formation of iron-based carbides, the content of Si is 0.10% or more, more preferably 0.25% or more.
[0043]
[Mn: 0.50 ~ 3.50%]
　Mn is added to increase the strength by enhancing the hardenability of the base steel sheet. However, if the content of Mn exceeds 3.50%, the coarse Mn concentrated portion in the plate thickness central portion of the base steel sheet occurs, embrittlement is likely to occur, the troubles such as cast slab cracking It occurs more easily. Therefore, the content of Mn should be not more than 3.50%. Also it deteriorates spot weldability if the content of Mn is increased. Therefore, the content of Mn is less than 3.00%, more preferably at most 2.80%. On the other hand, when the content of Mn is less than 0.50%, since the soft tissue is formed in large quantities during the cooling after annealing, it is difficult to ensure a sufficiently high maximum tensile strength. Therefore, the Mn content is 0.50% or more. For greater strength, the content of Mn is 0.80% or more, more preferably 1.00% or more.
[0044]
[P: 0.0001 ~ 0.1000%]
　P is an element which embrittle the steel is even when the content of P is more than 0.1000%, tends to occur problems such as cast slab cracking . Therefore, the P content is not more than 0.1000%. Also, P is also an element embrittle the melted portion caused by spot welding, in order to obtain a sufficient welded joint strength, the content of P is preferably set to less 0.0400%, or less 0.0200% it is more preferable to be. Meanwhile, when the content of P less than 0.0001% is accompanied by a significant increase in manufacturing cost. Therefore, the P content is set to 0.0001% or more, preferably 0.0010% or more.
[0045]
[S: 0.0001 ~ 0.0100%]
　S is combined with Mn to form coarse MnS, which is an element to lower the ductility, formability such stretch flangeability and bendability. Therefore, the content of S and 0.0100% or less. The S is also an element degrading the spot weldability. Therefore, S content is preferably set to 0.0060% or less, and more preferably to less 0.0035%. Meanwhile, when the content of S to less than 0.0001% is accompanied by a significant increase in manufacturing cost. Therefore, the S content is set to 0.0001% or more, preferably not less than 0.0005%, and more preferably 0.0010% or more.
[0046]
[Al: 0.001 ~ 1.500%]
　Al is an element to embrittle steel. When the content of Al exceeds 1.500%, the more likely to occur troubles such as cast slab cracking, the content of Al is less 1.500%. Also, since the spot weldability if the content of Al is increased to deteriorate, the content of Al is preferably set to less 1.200%, and more preferably 1.000% or less. On the other hand, although even lower limit of the content of Al is not particularly defined effect of the present invention is exhibited, Al is inevitable impurities present in trace amounts in the raw material, the content thereof to less than 0.001% is accompanied by a significant increase in the production cost. Therefore, Al content is 0.001% or more. The Al is an effective element as a deoxidizing agent, the effect of deoxidation, in order to obtain more fully, the content of Al is preferably set to 0.010% or more.
[0047]
[N: 0.0001 ~ 0.0100%]
　N forms coarse nitrides, ductile, because it is an element that degrades the formability such stretch flangeability and bendability, it is possible to suppress the amount preferable. When the content of N exceeds 0.0100% since the formability deterioration becomes remarkable, the upper limit of the N content is 0.0100%. The excessive addition of N, since the cause of blowholes during welding, the content is small is better. From these viewpoints, it is preferable that the N content is not more than 0.0070%, and more preferably 0.0050% or less. On the other hand, the lower limit of the N content, the effect of the present invention are exhibited without particularly, when the content of N to less than 0.0001% leads to a significant increase in manufacturing cost. Therefore, the lower limit of the N content is 0.0001% or more. Preferably N content is 0.0003% or more, more preferably 0.0005% or more.
[0048]
[O: 0.0001 ~ 0.0100%]
　O forms an oxide, ductility, from degrading the formability such stretch flangeability and bendability, it is preferable to suppress the content. When the content of O exceeds 0.0100% since the formability deterioration becomes remarkable, the upper limit of the O content is 0.0100%. More preferably the content of O is 0.0050% or less, more preferably 0.0030% or less. O lower limit of the content of, the effect of the present invention without particularly setting is exhibited, when the content of O and less than 0.0001% is accompanied by a significant increase in manufacturing cost. Therefore, the lower limit 0.0001%. Preferably O content is 0.0003% or more, more preferably 0.0005% or more.
[0049]
[Si + 0.7Al ≧ 0.30]
　Si and Al are element for suppressing generation of carbides due to the bainite transformation. To obtain a residual austenite, it is preferable to add Si and / or Al more than a certain amount. It is preferable that the addition amount of the additive amount of Al of Si from the point of view satisfies the following equation 2. More preferably the value of formula 2 of the left side (Si + 0.7Al) is 0.45 or more, further preferably 0.70 or more.
　　Si + 0.7Al ≧ 0.30 ··· (Equation 2)
　However, Si and Al of the formula 2 and the addition amount of each element (mass%).
[0050]
　Furthermore, the base steel sheet of galvanized steel sheet according to the embodiment of the present invention may be added the following elements as required.
　Specifically, in addition to the above chemical components, Ti: 0.001 ~ 0.150%, Nb: 0.001 ~ 0.100%, V: 0.001 ~ 0.300%, selected from among it may contain one or two or more.
[0051]
[Ti: 0.001 ~ 0.150%]
　Ti is precipitation strengthening, fine grain strengthening by ferrite grain growth inhibition, and the dislocation strengthening through suppression of recrystallization, contribute to the strength increase of the base material steel plate it is an element. However, if the content of Ti exceeds 0.150%, the deterioration of the formability deposition number is in the carbonitride content of Ti is preferably not more than 0.150%. From the viewpoint of moldability, the content of Ti is more preferably less 0.080%. On the other hand, the lower limit of the content of Ti, the effect of the present invention are exhibited without particularly. In order to obtain a strength increasing effect by Ti addition sufficiently, the content of Ti is preferably 0.001% or more. For even higher strength of the base material steel plate, the content of Ti is more preferably 0.010% or more.
[0052]
[Nb: 0.001 ~ 0.100%]
　Nb is precipitation strengthening, by dislocation strengthening through suppression of fine grain strengthening and recrystallization of a ferrite grain growth suppression, contribute to the strength increase of the base material steel plate element it is. However, if the content of Nb exceeds 0.100%, the deterioration of the formability deposition number is in the carbonitride, Nb content is more preferably 0.100% or less. From the viewpoint of formability, the Nb content is more preferably 0.060% or less. On the other hand, the lower limit of the content of Nb, the effect of the present invention are exhibited without particularly. To obtain the strength increasing effect of Nb added sufficiently, the content of Nb is preferably 0.001% or more. For even higher strength of the base material steel plate, the content of Nb is more preferably 0.005% or more.
[0053]
[V: 0.001 ~ 0.300%]
　V is precipitation strengthening, by dislocation strengthening through suppression of fine grain strengthening and recrystallization of a ferrite grain growth suppression, contribute to the strength increase of the base material steel plate element it is. However, if the content of V exceeds 0.300% formability increasingly precipitation of carbonitrides degrades. Therefore, the content of V is less than 0.300%, more preferably not more than 0.200%. On the other hand, the lower limit of the V content, the effect of the present invention are exhibited without particularly. To obtain the strength increasing effect due to the addition of V sufficiently, it is preferable that the content of V is 0.001% or more, more preferably 0.010% or more.
[0054]
　In the base material steel plate of the present embodiment, furthermore, Cr: 0.01 ~ 2.00%, Ni: 0.01 ~ 2.00%, Cu: 0.01 ~ 2.00%, Mo: 0.01 ~ 2.00%, B: 0.0001 ~ 0.0100%, W: 0.01 ~ 2.00%, 1 kind or may contain two or more species selected from among.
[0055]
[Cr: 0.01 ~ 2.00%]
　Cr suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn . However, when the content of Cr exceeds 2.00%, workability is impaired productivity in hot drops. Therefore, the content of Cr is preferably set to 2.00% or less, more preferably not more than 1.20%. On the other hand, the lower limit of the content of Cr, the effect of the present invention are exhibited without particularly. To obtain the effect of increasing the strength by adding Cr sufficiently, it is preferable that the content of Cr is 0.01% or more, further preferably 0.10% or more.
[0056]
[Ni: 0.01 ~ 2.00%]
　Ni suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn . However, when the content of Ni exceeds 2.00%, weldability is impaired. Therefore, the content of Ni is preferably set to 2.00% or less, more preferably not more than 1.20%. On the other hand, the lower limit of the content of Ni, the effect of the present invention are exhibited without particularly. To obtain a sufficient effect of strengthening by Ni added, the Ni content is preferably 0.01% or more, further preferably 0.10% or more.
[0057]
[Cu: 0.01 ~ 2.00%]
　Cu is an element to increase the strength by the presence in the steel as fine particles, can be added in place of part of C and / or Mn. However, when the Cu content exceeds 2.00%, weldability is impaired. Therefore, the Cu content is preferably set to 2.00% or less, more preferably not more than 1.20%. On the other hand, the lower limit of the Cu content, the effect of the present invention are exhibited without particularly. To obtain a sufficient effect of strengthening by Cu addition, the content of Cu is preferably 0.01% or more, further preferably 0.10% or more.
[0058]
[Mo: 0.01 ~ 2.00%]
　Mo suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn . However, when the content of Mo exceeds 2.00%, workability is impaired productivity in hot drops. Therefore, the content of Mo is preferably set to 2.00% or less, more preferably not more than 1.20%. On the other hand, the lower limit of the content of Mo, the effect of the present invention are exhibited without particularly. To obtain the effect of increasing the strength by adding Mo sufficiently, it is preferable that the content of Mo is 0.01% or more, more preferably 0.05% or more.
[0059]
[B: 0.0001 ~ 0.0100%]
　B suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn . However, when the content of B exceeds 0.0100% since the workability is impaired productivity in hot drops, the content of B is preferably set to 0.0100% or less. From the viewpoint of productivity, the content of B is more preferably 0.0050% or less. On the other hand, the lower limit of the B content, the effect of the present invention are exhibited without particularly. To obtain a sufficient effect of strengthening the by the addition of B, and the content of B is preferably set to 0.0001% or more. For further increasing the strength, the content of B is more preferably 0.0005% or more.
[0060]
[W: 0.01 ~ 2.00%]
　W suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn . However, when the content of W exceeds 2.00%, workability is impaired productivity in hot drops. Therefore, the content of W is preferably not more than 2.00%, more preferably not more than 1.20%. On the other hand, the lower limit of the content of W, the effect of the present invention is exhibited without being specifically defined. To obtain a sufficient high strength by the W, preferably W content is 0.01% or more, further preferably 0.10% or more.
[0061]
　Further the base material steel plate in the molten zinc plated steel sheet of an embodiment of the present invention, as other elements, Ca, Ce, Mg, Zr , La, 0.0001 ~ 1 kind or two or more kinds in total REM 0. it may contain 0100%. Added reason for these elements are as follows.
　It is to be noted that the REM, is an abbreviation of Rare Earth Metal, it refers to the elements belonging to the lanthanide series. In an embodiment of the present invention, the REM and Ce which is often added in misch metal, it may contain a composite elements of the lanthanoid series in addition to La and Ce. As inevitable impurities, the effect of the present invention is exhibited as containing elements of the lanthanide series other than those La and Ce. Moreover, the effect of the present invention is exhibited as the addition of metal La and Ce.
[0062]
　Ca, Ce, Mg, Zr, La, REM is an element effective for improvement of moldability may be added alone or in combination. However, Ca, Ce, Mg, Zr, La, if the total of one or more of the content of REM exceeds 0.0100%, it may impair the ductility. Therefore, it is preferable that the total amount of each element is 0.0100% or less, more preferably not more than 0.0070%. On the other hand, Ca, Ce, Mg, Zr, La, the lower limit of one or more of the content of REM, the effect of the present invention are exhibited without particularly. To obtain the effect of improving the formability of the base material steel plate sufficiently, it is preferable that the total content of these elements is 0.0001% or more. From the viewpoint of moldability, Ca, Ce, Mg, Zr, La, a total of one or more of the content of REM is more preferably at 0.0010% or more.
[0063]
　In the chemical components in the base material steel plate of the plated steel sheet according to the present embodiment, the remainder of the elements described above are Fe and unavoidable impurities. Incidentally, the above-described Ti, Nb, V, Cr, Ni, Cu, Mo, B, for the W, both to contain trace amounts of less than each of the lower limit as an impurity is allowed. Further, Ca, Ce, Mg, Zr, La, for also REM, to contain trace amounts of less than the lower limit of the total amount as an impurity is permitted.
[0064]
(Microstructure)
　is not particularly limited microstructure of the base material steel plate of such hot-dip galvanized steel sheet to an embodiment of the present invention, it is preferable that the microstructure has the following configuration.
[0065]
　The base steel sheet of the galvanized steel sheet according to the embodiment of the present invention, the particulate ferrite, acicular ferrite, non-recrystallized ferrite, pearlite, bainite, bainitic ferrite, martensite, tempered martensite, residual austenite, coarse it may have a microstructure consisting of one or more of cementite. The base steel sheet, in order to obtain characteristics according to application of the galvanized steel sheet, each phase, breakdown of the volume fraction of each tissue, the tissue size can be appropriately selected placement.
[0066]
"Residual austenite"
　residual austenite, the strength - a ductility balance largely increase tissue. The volume fraction of retained austenite in the 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base steel sheet is less than 1%, the strength - is less effective to increase the ductility balance. Therefore, it is preferable that the volume fraction of retained austenite is 1% or more. Strength - To increase the ductility balance, volume fraction of retained austenite is preferably 3% or more, more preferably 5% or more. On the other hand, to obtain a large amount of residual austenite, it is necessary to increase the amount of C to be added significantly, as a result, there is significantly impair concerned weldability by a large amount of C. Therefore, the volume fraction of residual austenite preferably 25% or less. Further, the residual austenite is transformed into hard martensite with the deformation, the martensite by acting as starting points of fracture, stretch flangeability is degraded. Therefore, the volume fraction of the retained austenite is more preferably not more than 20%.
[0067]
　The volume fraction of each tissue contained in the base steel sheet of the galvanized steel sheet according to the embodiment of the present invention can be measured, for example, by the following method.
[0068]
　Base steel sheet structure ferrite included, bainitic ferrite, bainite, tempered martensite, fresh martensite volume fraction of pearlite and coarse cementite galvanized steel sheet of the present embodiment is calculated by the following method . As the observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate, a sample is taken. Polishing the observation surface of the sample, to nital etching. 1/4 of the plate thickness of the observation plane around 1/8 thickness 1-3 / 8 thickness range field emission scanning electron microscope (FE-SEM: Field Emission Scanning Electron Microscope) area fraction was observed with the measure, regarded as the volume fraction have it.
[0069]
　The volume fraction of retained austenite contained in the base material steel sheet structure of galvanized steel sheet of the present embodiment is evaluated by X-ray diffraction method. In 1/8 thickness 1-3 / 8 thickness ranging from a thickness of the surface finish a plane parallel mirror to the plate surface, to measure the area fraction of FCC iron by X-ray diffractometry, it with a volume of residual austenite a fraction.
[0070]
　Further, in the hot-dip galvanized steel sheet according to the present embodiment, the thickness of the base material steel plate is not particularly limited, the flatness of the hot-dip galvanized steel sheet, from the viewpoint of controllability of cooling, the thickness of the base material steel plate 0 .6mm above, it is preferable the range of less than 5.0 mm.
[0071]
(Method of manufacturing a galvanized steel sheet)
　will be described in detail how to manufacture a galvanized steel sheet according to the embodiment of the present invention.
[0072]
　Method for producing a coated steel sheet according to the present embodiment includes a annealing step, a plating step, and a post-plating cooling step. Annealing step, the base steel sheet, the average heating rate between 600 ~ 750 ° C. as 1.0 ° C. / sec or more, heating to 750 ° C. or higher. Plating process, 450 ~ 470 ° C. The plating bath temperature, the steel plate temperature 440 ~ 480 ° C. at the time of plating bath enters, base material steel plate under the condition that the effective Al amount in the plating bath and 0.050 to 0.180 wt% by immersion in a galvanizing bath to form a plating layer with galvanized surface of the steel sheet. After plating cooling step after the plating step, satisfying the following formula course of cooling until 350 ° C. is described below (1).
[0073]
　To produce the hot-dip galvanized steel sheet according to the embodiment of the present invention, first to produce the base material steel plate.
　The base steel sheet is to cast a slab that was added alloy elements in accordance with the characteristics, subjected to hot rolling, is produced by applying a cold rolling.
　Follows is a detailed description of each manufacturing step.
[0074]
"Casting process"
　First of all, casting a slab to be subjected to hot rolling. It is preferable chemical composition of the slab (composition) is a component of the above. Slab subjected to hot rolling, it is possible to use those produced by such a continuous casting slab or thin slab caster.
[0075]
"Hot rolling process"
　in the hot rolling step, for suppressing the anisotropy of the crystal orientation due to casting, it is preferable that the heating temperature of the slab 1080 ° C. or higher. The heating temperature of the slab, more preferably, to 1150 ° C. or higher. The upper limit of the heating temperature of the slab is not particularly defined. To heat the slab exceed 1300 ° C., it is necessary to introduce a large amount of energy, leading to a significant increase in manufacturing cost. Therefore, the heating temperature of the slab is preferably set to 1300 ° C. or less.
[0076]
　After heating the slabs, performing hot rolling. The completion temperature of hot rolling (rolling completion temperature) of less than 850 ° C., increased rolling reaction force, it is difficult to get a thickness of a specified stable. Therefore, completion temperature of hot rolling is preferably set to 850 ° C. or higher, more preferably 875 ° C. or higher. On the other hand, the completion temperature of the hot rolling in a 980 ° C. than the apparatus for heating the steel sheet in the process from the end of heating of the slab until the completion of hot rolling is required, it requires high costs. Therefore, it is preferable to a completion temperature of the hot rolling and 980 ° C. or less, and more preferably set to 960 ° C. or less.
[0077]
　Then, taking up the hot-rolled steel sheet after hot rolling as a coil. The average cooling rate in the course of cooling until winding from hot rolling is preferably set to 10 ° C. / sec or more. This is because the advancing more transformation at low temperature, to a fine particle size of the hot-rolled steel sheet, in order to refine the effective crystal grain size of the base material steel plate after cold rolling and annealing.
[0078]
　Coiling temperature of hot-rolled steel sheet is preferably set to 350 ° C. or higher 750 ° C. or less. This is the microstructure of the hot-rolled steel sheet, perlite and / or major axis is generated by dispersing a more coarse cementite 1 [mu] m, the distortion introduced by cold rolling to localize, various crystal orientations in the annealing step in order to reverse transformation to austenite. This is, refining the effective crystal grains of the base material steel plate after annealing. When the coiling temperature is below 350 ° C., it may pearlite and / or coarse cementite is not generated, which is not preferable. Furthermore, lowering the strength of the hot rolled steel sheet, for performing easily cold rolling, it is more preferable to increase the coiling temperature above 450 ° C.. On the other hand, when the coiling temperature exceeds 750 ° C., pearlite and ferrite are produced in a long strip shape in the rolling direction, respectively, the effective crystal grain of the base material steel plate to produce a ferrite portion after cold rolling and annealing is extended in the rolling direction There tends to be as coarse, undesirable. Further, in order to fine the effective crystal grain size of the base material steel plate after annealing, it is more preferable to reduce the coiling temperature to 680 ° C. or less.
[0079]
　Next, the pickling of hot rolled steel sheet manufactured in this way. Pickling, since it is intended to remove oxide on the surface of the hot-rolled steel sheet, it is important for plating improvement of the base material steel plate. Pickling, may be the one time, it may be performed a plurality of times.
[0080]
"Cold process"
　Next, obtain a cold-rolled steel sheet by performing cold rolling on the hot-rolled steel sheet after pickling.
　In cold rolling, the total rolling reduction exceeds 85%, ductility of the steel sheet is lost, increases risk of the steel sheet during cold rolling is broken. Therefore, the total reduction rate is preferably set to 85% or less. From this viewpoint, the total reduction ratio is more preferably be 75% or less, more preferably 70% or less. Lower limit of the total reduction ratio in the cold rolling step is not particularly defined. The total reduction ratio is less than 0.05%, the shape of the base material steel plate becomes inhomogeneous, plating does not uniformly adhered, appearance is impaired. Therefore, preferably 0.05% or more and more preferably be 0.10% or more. Incidentally, the cold rolling is preferably performed in multiple passes, the distribution of rolling reduction to the number of passes and each pass of the cold rolling is not limited.
[0081]
　Further, reduction rate sum of 10% of the cold rolling, in the range of less than 20%, then recrystallization does not proceed sufficiently in the annealing step, coarse crystals lost malleable contains a large amount of dislocations grain remains near the surface, there are cases where the bending resistance and the fatigue characteristics deteriorate. To avoid this, to reduce the total rolling reduction, it is effective to in the minor accumulation of dislocations in the crystal grains leave malleable grains. Alternatively, to increase the total rolling reduction, sufficiently advanced recrystallization in annealing step, it is effective to a worked structure in the storage is small recrystallized grains of dislocation therein. From the viewpoint of the minor accumulation of dislocations in the crystal grains, it is preferable that the total reduction ratio is 10% or less in the cold rolling step, more preferably it is 5.0% or less. On the other hand, sufficiently proceed recrystallization in annealing step, it is preferable that the total reduction ratio of 20% or more, further preferably 30% or more.
[0082]
"Annealing step"
　in the embodiments of the present invention, subjected to annealing cold-rolled steel sheet. In an embodiment of the present invention, it is preferable to use a continuous annealing plating line having a preheating zone and reduction zone and the plating zone. Then, a preheating zone while annealing step is passed through a reducing zone, exit the annealing step until arriving to the plating zone, it is preferable to perform the plating process in the plating zone.
[0083]
　As described above, when using a continuous annealing plating line annealing process and plating process, for example, it is preferable to use a method described below.
　Heating rate in the annealing step, through the processing time in the preheating zone, associated with the progression of decarburization in the steel surface layer portion. When the heating rate in the annealing process is slow, because prolonged exposure to an oxidizing atmosphere in the preheating zone, decarburized in the steel sheet surface layer portion progresses. Further, an excessively heating rate is slow, progressed oxidation of the steel sheet, there is a case where coarse oxides within the steel sheet is produced. In particular, the heating rate at 600 ~ 750 ° C. is important, to avoid excessive decarburization and oxidation of the steel sheet surface layer portion, the average heating rate during this period to 1.0 ° C. / sec or more. To avoid decarburization of the steel sheet surface layer portion, it preferably has an average heating rate between 600 ~ 750 ° C. to 1.5 ° C. / sec or more, and more preferably set to 2.0 ° C. / sec or more. Average heating rate at 600 ~ 750 ° C. is to ensure a processing time in the preheating zone, in order to promote the formation of ζ phase, preferably in a 50 ° C. / sec or less. When the average heating rate is less than 50 ° C. / sec, of the total interface between the plated layer and the base steel sheet, more large-plated layer of the ratio of the interface between the ζ phase and the base steel sheet is obtained. To fully promote the formation of ζ phase is more preferably an average heating rate is 10 ° C. / sec or less.
[0084]
　In the preheating zone, an oxidation treatment for forming the Fe oxide coating of suitable thickness on the steel surface layer portion. At this time, a mixed gas of air and fuel gas for preheating burner air ratio shown below in the preheating zone is 0.7 or more, thereby Tsuban while heating the steel sheet temperature of 400 ~ 800 ° C..
　The "air ratio", and the volume of air contained in the mixed gas per unit volume is the ratio of air volume to be theoretically required to fully combust the fuel gas contained in the mixed gas per unit volume, represented by the following formula.
　[Volume of air contained in the unit volume gas mixture (m air ratio = 3 )] / [volume of air to be theoretically required to fully combust the fuel gas contained in the mixed gas per unit volume (m 3 ) ]}
　in the present embodiment, by performing the preheating in the base steel sheet of the above conditions it passes through the preheating zone to form a Fe oxide film of 0.01 ~ 5.0 .mu.m in the surface layer of the base material steel plate. Fe oxide film (oxide) produced in the steel sheet surface layer portion is reduced in the reduction zone, an excellent surface coating adhesion.
[0085]
　When the air ratio of the is too large beyond 1.2 is generated excess Fe oxide film on the steel sheet surface layer portion, for decarburized layer bloated after reduction. Therefore, it is preferable that an air ratio above 1.2 or less, more preferably 1.1 or less. When the air ratio is too small and less than 0.7 are not obtained a predetermined oxide. Therefore, the air ratio is 0.7 or more, preferably 0.8 or more.
　Further, the steel sheet temperature to Tsuban preheating zone when less than 400 ° C., can not form a sufficient oxide layer. Therefore, the steel sheet temperature (completion of preheating temperature) to Tsuban the preheating zone is set to 400 ° C. or higher, preferably to 600 ° C. or higher. On the other hand, the steel sheet temperature for Tsuban preheating zone at a high temperature exceeding 800 ° C., can not be reduced with subsequent reduction zone, oxide containing coarse Si and / or Mn is generated on the surface of the steel sheet. To grow excessively oxidized film, it is difficult to keep the thickness of the decarburized layer within a predetermined range. Therefore, the steel sheet temperature for Tsuban the preheating zone is set to 800 ° C. or less, preferably set to 750 ° C. or less.
[0086]
　The maximum heating temperature in the annealing step, in order to control the fraction of the microstructure involved in formability of the steel sheet in a predetermined range is an important factor. When the maximum heating temperature is low, undissolved coarse iron-based carbide in the steel, the formability deteriorates. The iron-based carbide is sufficiently dissolved, to increase the moldability, the maximum heating temperature is set to 750 ° C. or higher. In particular, in order to obtain retained austenite, the maximum heating temperature is preferably set to (Ac1 + 50) ℃ or higher. Although best upper limit of the heating temperature is not particularly set, in view of coating adhesion, to reduce the oxide of the base metal steel sheet surface, preferably to 950 ° C. or less, and more preferably set to 900 ° C. or less.
[0087]
　Ac1 point of the steel sheet is the starting point of each austenite reverse transformation. Specifically, the Ac1 point, cut a small piece from steel sheet after hot rolling, heating to 1200 ° C. at 10 ° C. / sec, it is obtained by measuring therebetween volume expansion.
[0088]
　Maximum heating temperature (750 ° C. or higher) in the annealing step, reaches the reduction zone. This reducing zone, reducing the thin Fe oxide coating of the resulting steel sheet surface in the preheating zone, enhancing the coating adhesion. Therefore, in an atmosphere of reduction zone, the water vapor partial pressure P (H 2 O) and hydrogen partial pressure P (H 2 ratio), P (H 2 O) / P (H 2 ) is from 0.0001 to 2.00 to. P (H 2 O) / P (H 2 in) is less than 0.0001, Si and / or Mn oxide serving as a starting point for plating peeling from being formed on the outermost surface layer. On the other hand, P (H 2 O) / P (H 2 If) exceeds 2.00, miniaturization proceeds excessively in the steel sheet surface layer, since the alloying of the plating layer progresses excessively, the coating adhesion is degraded . Furthermore, P (H 2 O) / P (H 2 If) exceeds 3.00, decarburization progresses excessively, the base steel sheet surface layer of the hard phase is significantly reduced. From the above point of view, P (H 2 O) / P (H 2 is preferably in the) range from 0.002 to 1.50 and more preferably in the range of 0.005 to 1.20.
[0089]
　As described above, P (H in the reduction zone 2 O) / P (H 2 formed on the) is from 0.0001 to 2.00, the starting point of the plating peeling Si and / or Mn oxides outermost layer without the fine oxides of maximum diameter to the inside of the steel sheet surface layer is 0.01 ~ 0.4 .mu.m Si and / or Mn is formed. Fine oxides of Si and / or Mn suppresses the growth of Fe recrystallization during annealing. In addition, water vapor in a reducing atmosphere in order to decarburizing the surface layer of the base material, the base material the surface layer after annealing is a ferrite. As a result, the surface layer of the base material after annealing, and the average thickness of a 0.1 ~ 5.0 .mu.m, the mean particle size of the ferrite phase is 0.1 ~ 3.0 [mu] m, the maximum diameter of 0. 01 fine layer containing an oxide of ~ a 0.4 .mu.m Si and / or Mn is formed.
[0090]
　Of annealing step, manufacturing conditions in the pre-plating cooling (before plating cooling step) from after reaching the maximum heating temperature up to the plating bath, the effect of the present invention is exhibited without being specifically defined. On the other hand, in order to obtain a residual austenite, in order to suppress the formation of pearlite and cementite, in the plating before the cooling step, preferably in a an average cooling rate from 750 ° C. to 700 ° C. 1.0 ° C. / sec or more, further, preferably in the average cooling rate from 700 ° C. to 500 ° C. 5.0 ° C. / sec or more. The upper limit of the average cooling rate is not particularly provided, in order to obtain an excessively large average cooling rate, the refrigerant that does not interfere with the special cooling equipment or plating step is required, which is not preferable. In this respect, the average cooling rate in the above temperature range is preferably set to 100 ° C. / sec or less, more preferably to 70 ° C. / sec or less.
[0091]
　Following plating before cooling step, to obtain the tempered martensite, until the steel sheet temperature reaches the plating bath after reaching the 500 ° C., and the steel sheet was a the predetermined time staying in a predetermined temperature range as the martensitic transformation process it may be. Martensitic transformation treatment temperature, a martensitic transformation start temperature Ms point is the upper limit, it is more preferable that the upper limit is (Ms point -20 ° C.). Martensitic transformation treatment is preferably the lower limit 50 ° C., and more preferably the lower limit and 100 ° C.. Further, the martensitic transformation treatment time is preferably 1 second to 100 seconds, more preferably 10 seconds to 60 seconds. Note that martensite obtained by martensitic transformation process is changed to the tempered martensite by entering the high temperature of the plating bath at a plating step.
[0092]
　Incidentally, Ms point is calculated by the following equation.
　Ms point [℃] = 541-474C / (1 -VF) -15Si-35Mn-17Cr-17Ni + 19Al
[0093]
　In the above formula, VF represents the volume fraction of the ferrite, C, Si, Mn, Cr , Ni, Al is the amount of the respective elements (mass%).
　Incidentally, it is difficult to measure the volume fraction of the ferrite directly during manufacture. Therefore, in determining the Ms point in the present invention, it cuts out pieces of the previous cold-rolled steel sheet to Tsuban a continuous annealing line, annealing at the same temperature history as if was Tsuban the small pieces to a continuous annealing line Te, and measuring the change in volume of the piece of ferrite, it has a numerical value calculated using the result as the volume fraction VF of the ferrite.
[0094]
　After a further pre-plating cooling step, to obtain a residual austenite, it may be steel to a predetermined time staying in a temperature range of 250 ° C. ~ 500 ° C. as bainite transformation treatment. When bainite transformation treatment temperature exceeds 500 ° C., it advances the generation of pearlite and / or coarse cementite, residual austenite can not be obtained. Therefore, the bainite transformation treatment temperature is preferably set to 500 ° C. or less. To promote the concentration of carbon into austenite due to bainitic transformation, bainite transformation treatment temperature is more preferably set to 485 ° C. or less, still more preferably 470 ° C. or less. Below the 250 ° C. bainite transformation treatment temperature is not proceed bainite transformation is insufficient, the residual austenite can not be obtained. Therefore, the bainite transformation treatment temperature is preferably 250 ° C. or higher. Order to promote bainite transformation effectively, the bainite transformation treatment temperature is more preferably set to 300 ° C. or higher and more preferably be 340 ° C. or higher.
　Further, the bainite transformation treatment time, to obtain a residual austenite proceed sufficiently bainite transformation, more preferably 15 seconds or more, and more preferably not less than 25 seconds. Further, the bainite transformation treatment time, in order to suppress the formation of pearlite and / or coarse cementite, preferably to less 500 seconds, more preferably at most 300 seconds.
　Incidentally, after the pre-plating cooling step, when performing both the bainite transformation treatment and martensite transformation treatment, for construction order is to be performed martensitic transformation treatment before bainite transformation treatment.
[0095]
"Plating step"
　will be immersed base material steel plate obtained in this manner in the plating bath.
　Plating bath has a composition of zinc was mainly, effective Al amount is a value obtained by subtracting the total amount of Fe from the total amount of Al in the plating bath is 0.050 to 0.180 wt%. The effective amount of Al in the plating bath is below 0.050% progressed excessively penetration of Fe in the plating layer, since the plating adhesion is impaired, it is necessary to 0.050% or more. In this respect, the effective amount of Al in the plating bath is preferably at least 0.065%, more preferably at least 0.070%. On the other hand, if the effective Al amount in the plating bath is more than 0.180%, the Al oxide system generates the boundaries of the base steel sheet and the plating layer, the movement of the Fe and Zn atoms in the boundary is inhibited, zeta generation phase is suppressed, coating adhesion is significantly impaired. In this respect, the effective amount of Al in the plating bath is required to be less 0.180%, preferably to 0.150% or less, more preferably it is less 0.135%.
[0096]
　めっき浴は、Ａｇ、Ｂ、Ｂｅ、Ｂｉ、Ｃａ、Ｃｄ、Ｃｏ、Ｃｒ、Ｃｓ、Ｃｕ、Ｇｅ、Ｈｆ、Ｉ、Ｋ、Ｌａ、Ｌｉ、Ｍｇ、Ｍｎ、Ｍｏ、Ｎａ、Ｎｂ、Ｎｉ、Ｐｂ、Ｒｂ、Ｓｂ、Ｓｉ、Ｓｎ、Ｓｒ、Ｔａ、Ｔｉ、Ｖ、Ｗ、Ｚｒ、ＲＥＭの１種または２種以上の元素が混入されているものであってもよく、各元素の含有量によっては、溶融亜鉛めっき層の耐食性や加工性が改善される等好ましい場合もある。
[0097]
　In addition, the temperature of the plating bath is set to 450 ℃ ~ 470 ℃. Is less than the plating bath temperature of 450 ° C., increases excessively, the viscosity of the plating bath, it is difficult to control the thickness of the plating layer, disfiguring galvanized steel sheet. Accordingly, the temperature of the plating bath was set to 450 ° C. or higher, it is preferable to 455 ° C. or higher. On the other hand, a large amount of fumes is generated and the plating bath temperature exceeds 470 ° C., it is difficult to safely manufactured. Therefore, the plating bath temperature was 470 ° C. or less, it is preferable to 465 ° C. or less.
[0098]
　Further, when the steel sheet temperature in the base steel sheet enters the plating bath is below 440 ° C., in order to stabilize the plating bath temperature at 450 ° C. or higher, since it is necessary to provide a large amount of heat in the plating bath, practically it is not suitable. On the other hand, if it exceeds the temperature of the steel strip is 480 ° C. at the time of the base steel sheet enters the plating bath, in order to stabilize the plating bath temperature to 470 ° C. or less, necessary to introduce the facility for heat removal a large amount of heat from the plating bath There are, it is not suitable in terms of production cost. Therefore, in order to stabilize the bath temperature of the plating bath, the temperature of the plating bath entrance of the base material steel plate 440 ° C. or higher, and 480 ° C. or less. In addition, in order to properly control the generation behavior of the ζ phase, the temperature of the plating bath ingress of the base steel sheet is 450 ° C. or higher, further preferably limited to 470 ° C. or less.
[0099]
　Temperature of the plating bath is preferably stable at a temperature in the range of 450 ~ 470 ° C.. When the temperature of the plating bath is unstable, zeta phase in the coating layer becomes uneven, leading to non-uniformity of appearance and adhesion of the plated layer. In order to stabilize the temperature of the plating bath, it is preferable to substantially match the temperature of the plating bath and the steel sheet temperature at the time of the plating bath entrance. Specifically, the temperature control of the limits of the actual production facility, it is desirable to be within ± 4 ° C. in a plating bath temperature of the steel sheet temperature at the time of plating bath entry, be within ± 2 ℃ plating bath temperature more preferable.
[0100]
　Incidentally, after the plating bath immersion, for a proper coating weight, spraying high-pressure gas mainly composed of nitrogen on the surface of the steel sheet, it is preferred to remove the excess zinc surface.
[0101]
"After plating cooling step"
　after the plating bath process, in a plating after the cooling step up to the room temperature, the course of cooling until 350 ° C. to control the cooling process so as to satisfy the following formula (1). Thus, an appropriate amount of ζ phase is obtained in the plating layer.
　It is to be T (t) [℃] steel plate temperature in the formula (1), t [sec] is the elapsed time starting from the time when the steel sheet leaves the plating bath, t 1 [s] is steel sheet steel temperature when exiting from the plating bath as a starting point is the elapsed time until 350 ° C., W * Al [wt%] is effective Al amount in the plating bath. Furthermore, epsilon, is θ and μ are constant term, respectively, 2.62 × 10 7 , 9.13 × 10 3 , 1.0 × 10 -1 is.
[0102]
[Number 1]

[0103]
　The formula (1) is an expression relating the generation behavior of the ζ phase, indicating that as the value of the above formula (1) is large, generation of ζ phase in the coating layer progresses. High steel sheet temperature is, the more processing time is long, the value of the above formula (1) increases. Further, the effective amount of Al in the plating bath is increased, the value of the equation (1) becomes small, generation of ζ phase is inhibited. Incidentally, the steel sheet temperature in the temperature range of 350 ° C. or less, diffusion of Fe atoms from the base material steel plate into the plating layer is hardly proceed, formation of ζ phase is substantially stopped. Therefore, the equation (1) is a steel sheet temperature calculated in the range of more than 350 ° C..
[0104]
　In the plating after the cooling step after immersion in the plating bath, the value of the above formula (1) is not sufficient ζ phase is obtained plating layer and below 0.40, coating adhesion is impaired. When the value of the above formula (1) is 0.40 or more, the generation of ζ phase is sufficiently promoted, and the ζ phase and the base steel sheet of the total interface between galvanized layer and the base steel sheet the ratio of the interface is 20% or more. If the value of the above formula (1) is 0.40 or more, the proportion of the interface formed between the coarse ζ oxides are present crystal grains and the base material steel plate of the interface between the ζ phase and the base steel sheet It becomes 50% or less. Therefore, in order to obtain a sufficient coating adhesion, as the value of the above formula (1) is 0.40 or more, it is necessary to control the cooling process. To improve the coating adhesion, it is preferable that the value of the above formula (1) is subjected to a cooling process so that the 0.50 or more, more preferably be 0.60 or more. On the other hand, when the value of the above formula (1) in the cooling process becomes excessively large, the process proceeds alloying of the plating layer, Fe content in the coating layer is excessively large, the coating adhesion is impaired. From this viewpoint, it is necessary to control the cooling process so that the value of the above formula (1) becomes 2.20 or less. To enhance the coating adhesion, the cooling process is preferably controlled so that the value of the above formula (1) is 2.00 or less, more preferably be controlled to be 1.80 or less.
[0105]
　Here, after removal from the plating bath, increasing the temperature of the steel sheet, plating adhesion value is significantly increased by the above formula (1) is deteriorated. Moreover, altered microstructure of the steel sheet, the strength is reduced without a predetermined residual austenite is obtained. Furthermore, there is concern that formability is deteriorated to generate coarse carbides. Therefore, temperature of the steel sheet after removal from the bath, among the temperature of the steel sheet before plating bath immersion and plating bath temperature should not exceed the temperature of the higher.
　On the other hand, as seen in the production method of the general hot-dip galvanized steel sheets, when subjected to rapid cooling after immersion in the plating bath, the value of the above formula (1) is significantly reduced. As a result, sufficient ζ phase is obtained, coating adhesion is deteriorated. To keep the value of the above formula (1) in a predetermined range, for example, performs the isothermal holding treatment for a certain period of time after removal from the coating bath, it may also be followed by rapid cooling.
　Further, if the value of the equation (1) remains in a predetermined range, it may be subjected to any other temperature control. That is, the value of the above formula (1) is as long as the temperature control to be within the scope of the present invention may be employed any cooling control mode. For example, it may be a cooling mode in which rapid cooling after the isothermal holding treatment or may be a cooling mode of performing slow cooling for approximately constant speed.
[0106]
　Moreover, the cooling process satisfying the above formula (1), after a sufficient amount of ζ phase is obtained in the plating layer, to obtain a residual austenite, 15 seconds to 500 seconds at a temperature range of 250 ° C.-350 ° C. may be performed bainite transformation process applied to dwell. Is less than the bainite transformation treatment temperature is 250 ° C., retained austenite generated martensite is not sufficiently obtained. Therefore, the bainite transformation treatment temperature is preferably 250 ° C. or higher, and more preferably set to 300 ° C. or higher. On the other hand when the bainite transformation treatment temperature exceeds 350 ° C., the diffusion of Fe atoms from the base material steel plate into the plating layer proceeds excessively, the coating adhesion is deteriorated. Therefore, the bainite transformation treatment temperature is preferably 350 ° C. or less, and more preferably set to 340 ° C. or less.
　When bainite transformation treatment time is 15 seconds or more, the effect of performing the bainite transformation treatment is sufficiently obtained. It is more preferable bainite transformation treatment time is 25 seconds or more. When bainite transformation treatment time is less than 500 seconds, it is possible to perform the bainite transformation treatment efficiently. It is more preferable bainite transformation treatment time is 300 seconds or less.
[0107]
　Further, in order to further stabilize the residual austenite, after cooling to 250 ° C. or less, it may be subjected to a reheating treatment. Treatment temperature and the treatment time of the re-heat treatment may be appropriately set according to the target properties. However, re-heating temperature is sufficient effect can not be obtained is less than 250 ° C.. Therefore, re-heating temperature is preferably set to 250 ° C. or higher, more preferably to 280 ° C. or higher. When reheating temperature exceeds 350 ° C., the diffusion of Fe atoms from the base material steel plate into the plating layer proceeds excessively, the coating adhesion is deteriorated. Therefore, re-heating temperature is preferably set to 350 ° C. or less, and more preferably set to 340 ° C. or less.
　Further, since the re-heating time is saturated with treatment effect exceeds 1000 seconds, the processing time is preferably 1000 seconds or less.
[0108]
　Although it is possible to manufacture a galvanized steel sheet according to the present embodiment by the manufacturing method described above, the present invention is not limited to the above embodiment.
[0109]
　For example, in the manufacturing method of the embodiment described above, after the plating step, the cooling process until 350 ° C. has been described as an example a case in which the "post-plating cooling step" satisfying the above formula (1), after plating cooling process, the course of cooling until 350 ° C. may not satisfy the above formula (1). In this case, in order to cool the process until 350 ° C. to produce a similar hot-dip galvanized steel sheet and if it meets the above formula (1), it is necessary to appropriately control the plating bath immersion time.
[0110]
　This is by increasing the plating bath immersion time, along with the generation of ζ phase in the plating bath is accelerated, and Si and / or Mn oxides present on the surface of the base material steel plate formed of the plating layer This is because the reaction is accelerated with the Al in the plating bath. By reaction with Al in the plating bath and the oxides, a part of the oxides present on the surface of the base material steel plate is reduced, the Si and / or Mn oxide number and amount present on the surface of the base material steel plate It is reduced.
[0111]
　To obtain the above effects by increasing the plating bath immersion time, it is necessary to the plating bath immersion time of 3 seconds or more, preferably 5 seconds or more, and more preferably 7 seconds or more, more preferably 10 seconds or more to. Plating bath immersion time by 10 seconds or more, the course of cooling until 350 ° C. satisfies the above expression (1) similar hot-dip galvanized steel sheet in the case of performing the "post-plating cooling step" is obtained. As a result, coarse oxides of the interface between galvanized layer ratio of the interface between the ζ phase and the base steel sheet of the total interface between the base steel sheet at 20% or more, the ζ phase and the base steel sheet there ratio of the interface formed between the existing ζ crystal grains and the base steel sheet is obtained of 50% or less of the plating layer.
[0112]
　When manufacturing a galvanized steel sheet, when using the method of the plating bath immersion time 10 seconds or more, after plating the cooling process, the cooling process to 350 ° C. may not satisfy equations (1) . Accordingly, even in a production line of hard galvanized steel sheets perform "post-plating cooling process" described above, may be easily prepared galvanized steel sheet of the present embodiment.
[0113]
　Plating bath immersion time, depending on the Al content in the plating bath, it can be appropriately determined. Plating bath immersion time, in order to ensure good productivity, it is preferably 20 seconds or less, not more than 15 seconds, more preferably.
[0114]
　For example, in the embodiment of the present invention, it may on the surface of the galvanized layer of the galvanized steel sheet obtained by the method described above, be given a coating composed of a composite oxide containing phosphorus oxide and / or phosphorus Absent.
　Film comprising phosphorus oxide and / or composite oxide containing phosphorus, can function as a lubricant when processing galvanized steel sheet, to protect the galvanized layer formed on the surface of the base material steel plate can.
[0115]
　Further, in this embodiment, may be subjected to the molten zinc plated steel sheet was cooled to room temperature, cold rolling at a reduction rate of 3.00% or less for the straightening.
[0116]
　The manufacturing method of hot-dip galvanized steel sheet according to the embodiment of the present invention have been described above, the thickness of the base material steel plate is 0.6mm or more, to be applied to the manufacture of hot-dip galvanized steel sheet is less than 5.0mm It is preferred. When the thickness of the base material steel plate is less than 0.6 mm, it becomes difficult to maintain the shape of the base material steel plate flat, it may not be appropriate. Further, when the thickness of the base material steel plate is 5.0mm or more, there is a case where the control of the cooling in the annealing step and the plating step becomes difficult.
Example
[0117]
　Examples of the present invention will be described. The conditions of the present embodiment is an example of conditions adopted for confirming the workability and effects of the present invention. The present invention is not limited to this single example of conditions. The present invention does not depart from the gist of the present invention, as long as they achieve the object of the present invention may employ various conditions.
[0118]
"Example 1"
　casting a slab having Tables 1-4 show the chemical components of the A ~ BJ (composition), thermal hot-rolled process conditions shown in Table 5,6,17 (slab heating temperature, rolling completion temperature) and during rolling, it cooled in hot rolling process conditions shown in Table 5,6,17 (average cooling rate from the hot rolling finished to coiling, coiling temperature), to obtain a hot rolled steel sheet.
　Thereafter, by performing pickling hot-rolled steel sheet, subjected to cold rolling cold rolling step under the conditions shown in Table 5,6,17 (rolling reduction), to obtain a cold-rolled steel sheet.
[0119]
　Next, the obtained cold-rolled steel sheet air ratio in the heating process conditions (preheating zone in the annealing step shown in Tables 7 to 9, 18, completion of preheating temperature in the preheating zone, H in the reducing zone atmosphere 2 O and H 2 and partial pressure ratio (P (H 2 O) / P (H 2 ), the average heating rate in a temperature range of 600 ~ 750 ° C., the maximum heating temperature Tm) were annealed in. Incidentally, the preheating of examples 1-96 completion temperature was in the range of 645 - 718 ° C..
　subsequently, before plating cooling step conditions shown in tables 7 to 9, 18 (average cooling rate in the temperature range of the cooling rate 1 (750 - 700 ° C.), cooling rate 2 (average cooling rate in the temperature range of 700 ~ 500 ° C.), bainite transformation treatment 1 conditions (treatment temperature, treatment time) was subjected to cooling treatment at the martensitic transformation (processing temperature, processing time)). in addition, the bainite transformation process 1, the martensitic transformation process Condition field of the processing for not have steel sheet subjected to the blank.
[0120]
　Then, a plating process conditions shown in Tables 10 to 12 and 19 (effective Al amount, the plating bath temperature (bath temperature), enters the temperature of the steel sheet, immersion time) was immersed in a zinc plating bath, the plated.
　After the plating process, the cooling after the plating are shown in Tables 10 to 12, 19 cooling step conditions (Equation (1), the bainite transformation treatment two conditions (treatment temperature, treatment time), reheating treatment conditions (treatment temperature, treatment time)) treatment was subjected to. Note that the bainite transformation treatment 2, condition column of the process for did not steel sheet subjected to the reheating treatment was blank.
　Moreover, subjected to cold rolling under the conditions shown in Tables 10 to 12 and 19 (reduction ratio) to obtain a plated steel sheet of the experimental examples 1 to 103 (however, in some experimental examples, even those who discontinued the experiment is there).
[0121]
　In the obtained plated steel sheets (Experimental Examples 1 to 103), was observed in the microstructure and the plating layer of the base material steel plate. It shows the observation results of microstructure and the plating layer of the base steel sheet in Table 13,14,20.
[0122]
　First, a sample was taken as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate plated steel sheet. The observation surface of the sample, perform high-resolution crystal orientation analysis by tissue observation and EBSD method using a field emission scanning electron microscope (FE-SEM), 1/8 thickness around a quarter of the thickness 1-3 / 8 to observe the microstructure in the thickness range were identified constituencies. In Table 13,14,20, F granular ferrite, WF acicular ferrite, NRF is non-recrystallized ferrite, P is perlite, theta is coarse cementite, BF bainitic ferrite, B is bainite, M represents martensite , tM is tempered martensite, gamma represents the residual austenite were observed respectively.
[0123]
　In addition, a small piece of 25 mm × 25 mm from the coated steel sheet was taken as a test specimen. In the plate 1/8 thickness 1-3 / 8 thickness in the range from the surface of the thickness of the test piece, finish plane parallel to the mirror to the plate surface, measuring the volume fraction of residual austenite (gamma fraction) by X-ray diffractometry did.
[0124]
　Further, the plated steel sheet, samples were taken as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate. The observation surface of the sample, perform observation by field emission scanning electron microscope (FE-SEM), and observed the surface of the plating layer and the base steel sheet. By the method described above from the result, the ratio of the interface ζ phase and the base steel sheet to the entire interface between the plated layer and the base steel sheet (boundary surface occupation ratio), the interface of the δ1 phase and the base steel sheet is plated layer and the base material percentage of the total surface of the steel sheet (boundary surface occupation ratio) of all the interface between the ζ phase and the base steel sheet, the ratio (oxide interface formed between the coarse oxide is present ζ crystal grains and the base material steel plate was determined existing ratio of the boundary surface of) the.
[0125]
　Coating weight of plating is to melt the plated layer by using a hydrochloric acid inhibitor containing, was determined by comparing the weights before and after melting.
[0126]
　Further, the plated steel sheet, a sample was taken as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate, using the measuring method described above, in direct contact with the interface between the base steel sheet galvanized layer fine the average thickness of the layer (average thickness of the fine layer), and the average particle size of the ferrite phase in the fine layer (mean particle size of the ferrite phase), one of Si and Mn in fine layer or the maximum diameter of two or more oxide (maximum diameter of the oxide) was determined. The results are shown in Table 13,14,20 a.
[0127]
　Then, in order to examine the characteristics of the plated steel sheet was subjected tensile test, the hole expansion test, bending test, adhesion evaluation test, spot welding test, corrosion test, chipping resistance test, the powdering test. Table 15, 16, 21, shows the characteristic in each of the experimental examples.
[0128]
　Tensile test, creates a No. 5 test piece described from plated steel sheet in JIS Z 2201, performed by the method described in JIS Z2241, were calculated yield strength YS, tensile maximum strength TS, total elongation El. The tensile properties, tensile maximum strength TS and rated the case of more than 420MPa as good.
　Hole expansion test was conducted by the method described in JIS Z 2256. Among the formability, ductility (total elongation) El and hole expandability λ will vary with the maximum tensile strength TS, strength, ductility and hole expandability and good if they meet the following expression (3).
　TS 1.5 × El × lambda 0.5　≧ 2.0 × 10　　6 · · · formula (3)
[0129]
　Plating adhesion, compared plated steel sheet had a tensile strain uniaxial 5%, was subjected to DuPont impact test. Plated steel sheet after impact test to joining the adhesive tape, then peeling, a case where plating was not peeled as acceptable (○), and the case where plating is peeled off as unacceptable (×). DuPont impact test, using the shot type that the radius of curvature of the tip and 1/2 inch, was performed by dropping a 3kg of the weight from a height of 1 m.
[0130]
　Spot weldability was evaluated by a continuous RBI test. In welding conditions the diameter of the molten portion is 5.3 to 5.7 times the thickness square root, 1000 times perform spot welding in succession, the diameter of the molten portion first point d 1 and 1000 goal d 1000 were compared with, d 1000 / d 1 was passed when is not less than 0.90 (○), unacceptable in the case of less than 0.90 (×).
[0131]
　The evaluation of the corrosion resistance, using a test piece cut out a plated steel sheet to 0.99 × 70 mm. The test piece was subjected to dip-type chemical conversion treatment of zinc phosphate, followed subjected to cationic electrodeposition coating 20μm, the further intermediate coating 35 [mu] m, it was subjected to overcoating 35 [mu] m, the back surface and the end was sealed with electrical tape. The corrosion resistance test, using the CCT to one cycle SST6hr → dry 4hr → wet 4hr → freezing 4hr. Evaluation of corrosion resistance after painting is subjected to crosscut reaching the base steel sheet with a cutter to painted surfaces, was measured blister width after CCT60 cycles. Evaluated as acceptable if the width 3.0mm or less swelling (○), it was unacceptable in the case of 3.0mm greater (×).
[0132]
　Chipping resistance was evaluated using a test piece cut out plated steel sheet 70 mm × 150 mm. First, the test piece, degreasing automotive, formation of chemical conversion film, the three-coat painting steps were performed. Then, while cooling holding the test piece to -20 ° C., air pressure 2 kgf / cm 2 was irradiated with crushed stone (0.3 ~ 0.5g) 10 pieces of vertically. Irradiation of crushed stone was repeated five times for each specimen. Thereafter, each test piece, and observing the total of 50 chipping traces were evaluated according to the following criteria depending on the position of the peeling interface. Peeling boundary is above the plating layer what is (plated layer - - surface conversion coating or electrodeposition coating, intermediate coating paint interface) (○) and then, the plating layer - that interfacial peeling at the base iron is also one was used as a (×).
[0133]
　Powdering property, in order to evaluate the workability of the plating layer was evaluated using the V bending (JIS Z 2248). The plated steel sheet was cut into 50 × 90 mm, a molded body formed by 1R-90 ° V-shaped die press and the specimen. In valleys of each specimen were performed tape peeling. Specifically, detached by pressing a cellophane tape having a width of 24mm on the bent portion of the specimen was determined length 90mm portion of the cellophane tape was visually. The evaluation criteria were as follows. Peeling of the plating layer is a of less than 5% relative to the processing unit area and (○), peeling of the plating layer was from 5 percent relative to the processing unit area as (×).
[0134]
[Table 1]

[0135]
[Table 2]

[0136]
[table 3]

[0137]
[Table 4]

[0138]
[table 5]

[0139]
[Table 6]

[0140]
[Table 7]

[0141]
[Table 8]

[0142]
[Table 9]

[0143]
[Table 10]

[0144]
[Table 11]

[0145]
[Table 12]

[0146]
[Table 13]

[0147]
[Table 14]

[0148]
[Table 15]

[0149]
[Table 16]

[0150]
[Table 17]

[0151]
[Table 18]

[0152]
[Table 19]

[0153]
[Table 20]

[0154]
[Table 21]

[0155]
　Experimental Example 87 has a small content and C, the volume fraction of the hard phase is small, can not be obtained sufficient tensile strength, TS 1.5 × El × lambda 0.5 is an example in which reduced.
　Experimental Example 88 has a large content and C, the spot weldability and formability is deteriorated, TS 1.5 × El × lambda 0.5 is an example in which reduced.
[0156]
　Experimental Example 89 has a large content of Si, in casting process, because the slab is broken during cooling is an example of interrupted experiments.
[0157]
　Experimental Example 90 has a small content of Mn, the annealing step and the plating step generates a large amount of pearlite and coarse cementite, is not sufficiently obtained tensile strength and formability of the steel sheet, TS 1.5 × El × lambda 0.5 is an example in which reduced.
　Experimental Example 91 has a large content of Mn, in the hot rolling process, since the slab is broken during heating, an example in which interrupt the experiment.
[0158]
　Experimental Example 92 has a large amount of P, since the slab is broken during the heating in the hot rolling process, an example in which interrupt the experiment.
[0159]
　Experimental Example 93 has a large content of S, a large amount of coarse sulfide is generated, ductility and hole expandability fatigue resistance is degraded, TS 1.5 × El × lambda 0.5 are examples of reduced .
[0160]
　Experimental Example 94 has a large amount of Al, in casting process, because the slab is broken during cooling is an example of interrupted experiments.
[0161]
　Experimental Example 95 has a large amount of N, a large amount of coarse nitrides are generated, ductility and hole expandability are deteriorated, TS 1.5 × El × lambda 0.5 is an example in which reduced.
[0162]
　Experimental Example 96 has a large amount of O, since a large amount of coarse oxides are produced, the ductility and hole expandability are deteriorated, TS 1.5 × El × lambda 0.5 is an example in which reduced.
[0163]
　Experimental Example 6 is an example in which was not subjected to cold rolling to hot-rolled steel sheet, poor flatness of the plate, without performing the annealing process, an example in which the experiment was discontinued.
　Experimental Example 35, the rolling reduction in cold rolling is too large, the steel sheet is broken, an example in which the experiment was discontinued.
[0164]
　Experimental Example 33 has a small heating rate in the annealing process, the growth of oxide in the base steel sheet proceeds excessively, since coarse oxides as a starting point of fracture on the surface of the base material steel plate has occurred, plating adhesion and powdering is an example of ring resistance was deteriorated.
　Experimental Example C99, the high completion of preheating temperature, since coarse oxides containing Si and Mn on the steel sheet surface before plating generated number, the interface formed between ζ crystal grains exist coarse oxides and the base steel sheet , an example in which more than 50% of the total interface between ζ phase and the base steel sheet, plating adhesion is inferior.
[0165]
　Experimental Example 9 has a small air ratio in the residual heat zone of the annealing step, a low boundary surface occupation ratio of the ζ phase, non-plating occurs in a portion of the steel sheet, the appearance is an example of plating adhesion and corrosion resistance is deteriorated.
　Experimental Example 43 has a high air ratio in the residual heat zone of the annealing process, since the decarburization of the steel sheet surface has progressed excessively, thickened average thickness of the finer layer, TS 1.5 × El × lambda 0.5 is reduced, an example in which sufficient characteristics were not obtained.
[0166]
　Experimental Example 83, water vapor partial pressure P in the reduction zone of the annealing process (H 2 O) and hydrogen partial pressure P (H 2 ratio), P (H 2 O) / P (H 2 ) is small, the surface layer of the grain diameter not miniaturized, since the generation of the ζ phase in the plating layer did not proceed, an example in which the coating adhesion is deteriorated. Experimental Example 83, no fine layer is formed, the average grain size of the ferrite phase at the surface of the base steel sheet is 3.6 [mu] m, an oxide of the steel sheet inside the range to a depth of 0.5μm from the surface the maximum diameter of less than 0.01 [mu] m.
　Experimental Example 40, water vapor partial pressure P in the reduction zone of the annealing process (H 2 O) and hydrogen partial pressure P (H 2 ratio), P (H 2 O) / P (H 2 ) is large, the base material steel plate the surface layer of it is too thick fine layer, since the alloying of the plating layer has proceeded excessively, coating adhesion, powdering resistance and chipping resistance are examples degraded.
[0167]
　Experimental Example 66, the effective Al amount is excessive small in the plating bath in the plating process, the value of the expression 1 becomes excessive, increases excessively the Fe% in the coating layer, sufficient coating adhesion can not be obtained Example it is.
　Experimental Example 77, the effective Al amount in the plating bath in the plating process is too large, the value of the expression 1 is excessively small, [delta] phase at the interface of the plating layer and the base steel sheet is not sufficiently generated, sufficient coating adhesiveness sex is an example that can not be obtained.
[0168]
　Experimental Example 3, the value of formula 1 in the plating process is that too small, [delta] phase at the interface of the plating layer and the base steel sheet is not sufficiently generated, are examples of satisfactory plating adhesion can not be obtained.
　Experimental Example 26 is excessively large value of the formula 1 in the plating step, increases excessively the Fe% in the coating layer is an example that can not be obtained a sufficient coating adhesion.
[0169]
　Experimental Example 68 is an example that a reheating immediately after plating bath immersion, increases excessively the Fe% in the coating layer, an example in which sufficient coating adhesion was not obtained.
[0170]
　Experimental Examples other than the above, strength, ductility, hole expandability, high strength galvanized steel sheet excellent in coating adhesion is an example obtained.
[0171]
　In particular, experimental examples 1,2,4,5,7,10,12 ~ 15,17,18,25,27 ~ 31,34,36 ~ 39,41,42,55,62,65,76,78, 82,97,98,100 to 103, contain residual austenite, are examples of high-strength galvanized steel sheet was obtained having a coating adhesion and excellent moldability.
[0172]
"Example 2"
　were taken test specimens from plated steel sheets of Example 1 obtained in "Example 1". Then polished by ion milling as an observation plane parallel plate thickness cross section in the rolling direction of the base material steel plate of the test piece, a field emission scanning electron microscope (FE-SEM), the reflected electrons under conditions of an acceleration voltage 5kV was obtained (BSE) image. The results are shown in Figure 2.
　As shown in FIG. 2, the plated steel sheet of Experimental Example 1, a plating layer containing a columnar crystal composed of ζ phase was formed. In addition, the base material steel plate of the plated steel sheets of Example 1, the fine layer in direct contact with the interface between the plating layer was formed. As shown in FIG. 2, the fine layer of the plated steel sheet of Example 1, (look dark portion compared to the surrounding) oxide was contained.
[0173]
"Example 3"
　The cold-rolled steel sheet produced in the same manner as the plated steel sheet "Example 1" obtained in Experimental Example 1, subjected to annealing process in the same manner as the plated steel sheet of Experimental Example 1, was obtained annealed sheets . The annealed sheet, plating process conditions shown in Table 22 (effective Al amount, the plating bath temperature (bath temperature), enters the temperature of the steel sheet, immersion time) was plated by immersion in a zinc plating bath.
　After the plating process, was subjected to cooling treatment after plating are shown in Table 22 the cooling step conditions (Equation (1)). Moreover, subjected to cold rolling under the conditions shown in Table 22 (rolling reduction), to obtain a plated steel sheet of Examples 104-111.
[0174]
　The resulting plated steel sheet in the same manner as "Example 1" was observed in plating layer of the base material steel plate. The results are shown in Table 22.
　Further, the plated steel sheet obtained in the same manner as "Example 1", the volume fraction of residual austenite (gamma fraction) was measured.
　Further, the plated steel sheet obtained in the same manner as "Example 1" was determined adhesion amount of the plating. The results are shown in Table 22.
　Further, in the same manner as in "Example 1" for plated steel sheets was determined and the average thickness of the finer layer, and the average particle size of the ferrite phase, and a maximum diameter of oxides. The results are shown in Table 22.
　Further, the plated steel sheet obtained in the same manner as "Example 1" was carried out a tensile test, a hole expansion test, bending test, adhesion evaluation test, spot welding test, a corrosion test. The results are shown in Table 22.
　Further, for the results in Experimental Example 1, shown in Table 22.
[0175]
[Table 22]

[0176]
　As shown in Table 22, Experimental Examples 105-111 are examples of the present invention has good coating adhesion was also excellent spot weldability and corrosion resistance.
　In contrast, as shown in Table 22, Experiment 104, the plating layer and of the total interface between the base steel sheet, occupied by the interface between the zeta phase and the base steel sheet ratio (zeta boundary surface occupation ratio) is 20 since less than percent, it was insufficient plating adhesion and spot weldability.
[0177]
　Having described in detail the embodiments of the present invention, the above-described embodiment is merely both illustrate concrete examples of implementing the present invention. The present invention scope by these embodiments should not be construed as limiting. That is, the present invention, without departing from the spirit or essential characteristics thereof, can be implemented in various forms.
Industrial Applicability
[0178]
　The present invention is an effective technique for superior hot-dip galvanized steel sheet in the plating adhesion. Then, the present invention can provide an excellent hot-dip galvanized steel sheet in a plating adhesion after molding.

The scope of the claims
[Claim 1]
　Consists of a base steel sheet and the base material galvanized layer formed on at least one surface of steel sheet,
　the galvanized layer on the surface of the steel sheet, Fe content of 0% Ultra and 5% or less There, Al content is not more than 0% super% to 1.0%, including columnar crystals composed of ζ phase, further, the galvanized layer of 20% or more of ζ phase of the total interface between the base steel sheet the coated, in the galvanized layer, the interface formed between ζ crystal grains and the base material steel plate there is a coarse oxides of ζ crystal grains with respect to the total interface between the ζ phase and the base steel sheet 50% or less,
the base material steel plate containing, by
　　mass% C:
　　0.040 ~
　　0.400% Si: 0.05 ~ 2.50% Mn: 0.50 ~
　　3.50% P : 0.0001
　　～ 0.1000 Pasento, S: 0.0001
　　～ 0.0100 Pasento, Al: 0.001 ～ 1
　　% .500,
　　N: 0.0001 ~ 0.0100%, O: 0.0001 ~ 0.0100%,
the balance has a chemical composition consisting of Fe and unavoidable impurities,
　wherein the galvanized layer and the base steel sheet has a fine layer in direct contact with the interface with the is 0.1 ~ 5.0 .mu.m average thickness of the finer layer, average particle size 0.1 ~ 3.0 [mu] m of the ferrite phase in the finer layer , and the one or comprise two or more oxides, galvanized steel sheet maximum diameter of 0.01 ~ 0.4 .mu.m of the oxides of Si and Mn in the fine layer.
[Claim 2]
　For the galvanized layer, the coating weight of one surface of the base material steel plate is 10 g / m 2 or more, 100 g / m 2 hot-dip galvanized steel sheet according to claim 1 or less.
[Claim 3]
　Characterized in that said base material steel plate contains, by mass%,
　　further,
　　Ti: 0.001 ~ 0.150%,
　　Nb: 0.001 ~ 0.100%, V: 0.001 ~ 0.300%,
selected from among hot-dip galvanized steel sheet according to claim 1 or claim 2 containing one or more was.
[Claim 4]
　Characterized in that said base material steel plate contains, by mass%,
　　further,
　　Cr: 0.01
　　~ 2.00%, Ni: 0.01 ~ 2.00%, Cu: 0.01
　　~ 2.00%, Mo: 0.01
　　2.00% ~, B:
　　0.0001 ~ 0.0100%, W: 0.01 ~ 2.00%,
claims 1 to 3 containing one or two or more species selected from among galvanized steel sheet according to any one of.
[Claim 5]
　Characterized in that said base material steel plate contains, by mass%,
furthermore, Ca, Ce, Mg, Zr, La, claims 1 to 4 containing 0.0001 to 0.0100% in total of one or more of REM galvanized steel sheet according to any one of.