Technical field
[0001]
　The present invention relates to a galvanized steel sheet. The present invention is particularly ductility, bendability, excellent coating adhesion during hole expandability and bending deformation, and to high-strength galvanized steel sheet having excellent continuous bending fatigue properties.
　The present application, on November 5, 2014, claiming priority based on Japanese Patent Application No. 2014-225612, filed in Japan, the contents of which are incorporated here.
Background technique
[0002]
　Recently, there has been increasing mainly demand for high strength of the steel sheet used in the frame members of automobiles. In these high-strength steel sheet, the ductility in order to obtain a complicated member shape, moldability such bendability and stretch flange formability is required. Further, since the constantly subject to vibration when used as automotive parts, high fatigue resistance is also obtained. In addition, for automotive steel sheets, 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. Further, even does not lead to peeling of the plating layer, and a loss of adhesion between the plating layer and the base steel sheet, if the gap even slightly that portion Shojire, outside air or moisture from entering in a gap therebetween. Thus, anti-corrosion function is lost by the plating layer, the similarly early corrosion 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 form oxides in the interior of the steel sheet, reducing the oxide at the interface of the base steel and the plating layer which causes the plating peeling methods have been proposed. However, if for generating such oxides steel surface layer, the carbon of the steel sheet surface layer is gasified combines with oxygen, it results carbon is separated from the steel plate. Therefore, in the technique described in Patent Documents 1 to 3 have the strength of a region where the carbon is separated is significantly reduced in the steel plate. 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 limit strength is significantly decreased.
[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. In this case, in 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 limit strength is significantly decreased.
[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 according to 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, since the steel sheet described in Patent Document 8 is microstructure only soft ferrite, sufficient strength can not be obtained.
[0009]
　Here, after galvanizing treatment, galvannealed steel sheet which has been subjected to alloying treatment is widely used. 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, the coated steel sheet of Patent Document 9-11, 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.
　Patent Document 12, in the manufacture of hot-dip galvanized steel sheet Si-Mn-Al-containing matrix, and controls the entering material temperature, by regulating the galvanized and sectional area ratio in the interface alloy layer of the base steel sheet, technique for improving coating adhesion and spot weldability is disclosed.
The steel sheet described in Patent Document 12, Si-Mn oxide it has been stated that adversely affect the plating adhesion. However, a technique for reducing the Si-Mn oxide before the start plating is not disclosed in patent document 12. In Patent Document 12, (depending higher bath temperature plus 4 ° C., the bath temperature plus 28 ℃ at maximum a minimum the Al of the plating bath) for entering material temperature to be higher than the bath temperature for, the bath temperature stability , thus, leaving a problem in uniformity of the properties of the product.
CITATION
Patent Document
[0010]
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
[0011]
In view of the situation described above, the present invention is, ductility, excellent formability of the bendability and the steel sheet represented by stretch flangeability, fatigue properties, weldability, high strength molten with excellent corrosion resistance and plating adhesion there is provided a galvanized steel sheet.
Means for Solving the Problems
[0012]
　The present inventors have ductility, and formability of the bendability and the steel sheet represented by stretch flangeability, fatigue properties, weldability, in order to obtain a high strength galvanized steel sheet excellent in corrosion resistance and plating adhesion intensive extensive investigations. As a result, the present inventors have improved ductility and hole expandability (the stretch flangeability) by controlling the microstructure of the steel sheet to the proper tissue fraction. Further, the present inventors have improved the plating layer and the base material boundary from bending by controlling the volume fraction of the base material steel plate side of the hard phase of the steel sheet and fatigue resistance. Furthermore, the present inventors have found that the plating layer during ζ phase (FeZn 13 ) to produce a suppressed plating peeling by incorporating an origin and a coarse oxide breakdown therein. These result, the present inventors have found that without performing the alloying treatment of the plating layer, ductility, and formability of the bendability and steel typified by hole expandability (stretch-flangeability), fatigue resistance, weldability, found that hot-dip galvanized steel sheet excellent in corrosion resistance and plating adhesion is obtained.
[0013]
The present invention was completed on the basis of this finding, it is an aspect as follows.
(1) hot-dip galvanized steel sheet according to one embodiment of the present invention is composed of a galvanized layer formed on at least one surface of said base steel sheet and the base steel sheet, the base material steel plate is in mass% ,
　C:
　0.040
　~ 0.280%,
　Si: 0.05 ~ 2.00%, Mn: 0.50 ~ 3.50%, P: 0.0001
　~ 0.1000%, S: 0.0001
　0.0100%
　
　1.500%,~, N: 0.0001 ~ 0.0100%, O: 0.0001 ~ 0.0100%,
the chemical composition balance consisting of Fe and impurities Yes and,
　wherein the 1/8 thickness 1-3 / 8 thickness in the range of 1/4 thickness around from the surface of the base material steel plate, in a volume fraction, and ferrite phase following 97% 40%, bainite phases and bay bainitic ferrite phase and fresh martensite phase and tempering And and a more than 3% in total of hard tissue comprising one or more of martensite phase, 0-8% residual austenite phase volume fraction, total volume fraction of the pearlite phase and coarse cementite phase in 0 to 8% in the surface layer ranging from the interface of the galvanized layer and the base steel sheet to the steel sheet direction depth 20 [mu] m, the volume fraction of residual austenite is 0-3%, said in said surface layer ranges the volume fraction V1 of the hard tissue, which is the ratio V1 / V2 of the volume fraction V2 of the hard tissue in 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the steel sheet surface 0 have limited the microstructure in the range of .10 to 0.90, the galvanized layer, Fe content was 0% ultra-5%, Al content is 0% super% to 1.0% , and the include columnar crystals comprising a ζ phase, the molten zinc Me The ratio of surface (A *) of the ζ phase and the base steel sheet of the total interface between Tsu Ki layer and the base material steel plate (A) ((A * / A) × 100) is not less than 20%, wherein the base material steel plate is fine layer formed on the interface side, the average thickness 0.1 - 5.0 .mu.m finer layers, the ~ 0.1 average particle size of the ferrite phase in the microstructure layer 3 a .0Myuemu, wherein one or more oxides of Si and Mn contained in the finer layer, galvanized steel sheet maximum diameter of 0.01 ~ 0.4 .mu.m of the oxide.
[0014]
(2) the base material steel plate contains, by
　mass%,
　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 one or the containing two or more (1) was.
[0015]
(3) the base material steel plate contains, by
　mass%,
　Cr: 0.01 ~
　2.00%, Ni: 0.01 ~ 2.00%, Cu: 0.01 ~
　2.00%, Mo: 0.
　~ 2.00% 01, B: 0.0001
　~ 0.0100%, W: 0.01 ~ 2.00%,
containing one or more selected from among the above (1) or ( hot-dip galvanized steel sheet according to 2).
[0016]
(4) the base material steel plate containing, by
mass%, Ca, Ce, Mg, Zr, La, REM of one or the containing 0.0001 to 0.0100% of two or more in total (1) - ( galvanized steel sheet according to any one of 3).
[0017]
(5) In the above hot-dip galvanized layer, the interface between ζ crystal grains and the base material steel plate there is a coarse oxides of ζ crystal grains, 50% relative to the total interface between the ζ phase and the base steel sheet galvanized steel sheet according to any one of the following in the above (1) to (4).
[0018]
For (6) the hot-dip galvanizing layer, wherein the coating weight of one surface of the base material steel plate is 10 g / m 2 or more, 100 g / m 2 or less above (1) to according to any one of (5) hot-dip galvanized steel sheet.
Effect of the Invention
[0019]
According to the aspect of the present invention can provide formability, fatigue resistance, weldability, hot-dip galvanized steel sheet excellent in corrosion resistance and plating adhesion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
[Figure 1] of the cross section of the hot-dip galvanized steel sheet according to the present embodiment, an enlarged structural photograph including and neighboring galvanized layer / base steel sheet surface.
[Figure 2] of the cross section of the galvanized steel sheet according to the present embodiment, an enlarged photograph of a sectional structure of the vicinity including the galvanized layer / base steel sheet surface.
DESCRIPTION OF THE INVENTION
[0021]
Galvanized steel sheet according to the embodiment of the present invention, in mass%, C: 0.040 ~ 0.280% , Si: 0.01 ~ 2.00%, Mn: 0.50 ~ 3.50%, P: 0.0001 ~ 0.100%, S : 0.0001 ~ 0.0100%, Al: 0.001 ~ 1.500%, O: 0.0001 ~ 0.0100%, N: 0.0001 ~ containing 0.0100% the balance being the base steel sheet (hereinafter, simply referred to as steel.) having a chemical composition consisting of Fe and impurities surface galvanized layer (hereinafter, also simply referred to as a plating layer.) is formed it is those formed by.
Incidentally, the thickness of the base material steel plate is 0.6mm or more, it is suitable less than 5.0 mm. 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, not suitable. Further, when the thickness of the base material steel plate is 5.0mm or more, it becomes difficult to control the cooling in the manufacturing process, moldability without predetermined microstructure is obtained may be deteriorated.
[0022]
First described chemical components of the base material steel plate constituting the hot-dip galvanized steel sheet according to the embodiment of the present invention (composition). Note that [%] in the following description are [mass%].
[0023]
[C: 0.040 ~ 0.280%]
C is contained in order to increase the strength of the base material steel plate. However, if the content of C exceeds 0.280%, because the spot weldability is deteriorated, C content is at most 0.280%. In view of the spot weldability, the content of C is less than 0.250%, 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%.
[0024]
[Si: 0.05 ~ 2.00%]
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, the content is more than 2.00%, it tends to occur problems such as cast slab cracking. Therefore, the amount of Si should be 2.00% or less. 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 less 1.500%, more preferably at most 1.200%. On the other hand, the content of Si is less than 0.05%, in the plating step of the hot-dip galvanized steel sheet, coarse iron-based carbide is produced in large quantities, since the deterioration of the strength and moldability, the content of Si is 0. to 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.
[0025]
[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 deteriorates spot weldability of galvannealed steel sheets with 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 content of Mn should be 0.50% or more. For greater strength galvanized steel sheet, the content of Mn is 0.80% or more, more preferably 1.00% or more.
[0026]
[P: 0.0001 ~ 0.1000%]
P is an element which embrittle steel, further the content of P is more than 0.1000%, or cracking the cast slab, the slab during rolling since troubles such as cracks or is likely to occur, the content of P 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% and more preferably it is. Meanwhile, when the content of P less than 0.0001%, since with a significant increase in manufacturing cost, the P content is the lower limit value of 0.0001% to 0.0010% or more it is preferable.
[0027]
[S: 0.0001 ~ 0.0100%]
　S, since combined with Mn to form coarse MnS, which is an element to lower the ductility, formability such hole expandability (stretch-flange formability) and bending resistance, the content of S and 0.0100% or less. The S is also an element degrading the spot weldability. Therefore, the content of S 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, the 0.0001% as the lower limit value, preferably set to 0.0005% or more, and more preferably 0.0010% or more.
[0028]
[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 more preferably to less 1.200%, still more preferably 1.000% or less. On the other hand, the effect of the present embodiment even the lower limit of the content of Al is not particularly setting is exerted. However, Al is an impurity present in trace amounts in the raw material, accompanied by a substantial increase in production cost to the content thereof less than 0.001%. Therefore, Al content is 0.001% or more. Although Al is an element effective as a deoxidizer, the effect of deoxidation, in order to obtain more fully, the content of Al is more preferably set to 0.010% or more.
[0029]
[N: 0.0001 ~ 0.0100%]
　N forms coarse nitrides, ductile, because it is an element that degrades the formability such hole expandability (stretch-flange formability) and bending resistance, the added it is necessary to suppress the amount. 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 content of N is even without particularly setting effect of this embodiment is exhibited, 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.
[0030]
[O: 0.0001 ~ 0.0100%]
O forms an oxide, ductility hot-dip galvanized steel sheet, from degrading the formability such hole expandability (stretch-flange formability) and bending resistance, the content of it is necessary to suppress. 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 embodiment is exhibited without particularly, when the content of O and less than 0.0001% is accompanied with significant increase in manufacturing cost, 0 the lower limit .0001%. Preferably O content is 0.0003% or more, more preferably 0.0005% or more.
[0031]
Additional, the base steel sheet of the galvanized steel sheet according to the present embodiment, may be added the following elements as required.
[0032]
First, in the base steel sheet according to the present embodiment, further, Ti: 0.001 ~ 0.150%, Nb: 0.001 ~ 0.100%, V: 0.001 ~ 0.300%, of the one or may contain two or more species selected from.
[0033]
[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, contributes to increasing strength of the galvanized steel sheet 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%. In contrast, the lower limit of the content of Ti is the effect of the present embodiment is exhibited without particularly, in order to obtain a sufficient strength increasing effect by addition of Ti, the Ti content 0.001% or more there it is preferable. For even higher strength galvanized steel sheet, the content of Ti is more preferably 0.010% or more.
[0034]
[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 galvanized steel sheet it is an element. However, if the content of Nb exceeds 0.100% is possible for the deterioration of the formability of the galvanized steel sheet deposition number is in the carbonitride, Nb content is 0.100% or less more preferable. 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 is the effect of the present embodiment is exhibited without particularly, in order to obtain a sufficient strength increasing effect by the addition of Nb, the Nb content is 0.001% or more it is preferable. For even higher strength galvanized steel sheet, the content of Nb is more preferably 0.005% or more.
[0035]
[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 galvanized steel sheet it is an element. 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 content of V is the effect of the present embodiment is 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.
[0036]
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.
[0037]
[Cr: 0.01 ~ 2.00%]
Cr suppresses phase transformation at high temperature, an effective element for high strength galvanized steel sheet, instead of a part of the C and / or Mn it may be added. However, when the content of Cr exceeds 2.00%, since the workability is impaired productivity in hot drops, the content of Cr is preferably set to 2.00% or less, 1 and more preferably .20 percent. On the other hand, the lower limit of the content of Cr is the effect of the present embodiment is exhibited without particularly, in order to obtain a sufficient effect of strengthening due to addition of Cr, the content of Cr is 0.01% preferably or more, more preferably 0.10% or more.
[0038]
[Ni: 0.01 ~ 2.00%]
Ni suppresses phase transformation at high temperature, an effective element for high strength galvanized steel sheet, instead of a part of the C and / or Mn it may be added. However, when the content of Ni exceeds 2.00%, since the weldability is impaired, the content of Ni is preferably set to 2.00% or less, even more preferably less 1.20% . On the other hand, the lower limit of the Ni content is the effect of the present embodiment is exhibited without particularly, in order to obtain a sufficient effect of strengthening by Ni added, the Ni content is 0.01% or more it is preferably, more preferably 0.10% or more.
[0039]
[Cu: 0.01 ~ 2.00%]
Cu is an element to increase the strength of the galvanized steel sheet by the presence in the steel as fine particles, is added in place of part of C and / or Mn can do. However, when the Cu content exceeds 2.00%, since the weldability is impaired, the content of Cu is preferably set to 2.00% or less, even more preferably less 1.20% . On the other hand, the effect of the present embodiment also the lower limit of the Cu content is not specified particularly is exerted, in order to obtain a sufficient effect of hot-dip galvanized steel sheet and high strength due to addition of Cu, the Cu content 0 is preferably .01% or more, more preferably 0.10% or more.
[0040]
[Mo: 0.01 ~ 2.00%]
Mo suppresses phase transformation at high temperature, an effective element for high strength galvanized steel sheet, instead of a part of the C and / or Mn it may be added. However, if it exceeds 2.00% content of Mo, since the workability is impaired productivity in hot drops, the content of Mo is preferably set to 2.00% or less, 1 and more preferably .20 percent. On the other hand, the lower limit of the content of Mo is the effect of the present embodiment is exhibited without particularly, in order to obtain a sufficient effect of strengthening by Mo addition, the content of Mo is 0.01% preferably or more, more preferably 0.05% or more.
[0041]
[B: 0.0001 ~ 0.0100%]
B suppresses phase transformation at high temperature, an effective element for high strength galvanized steel sheet, instead of a part of the C and / or Mn it may be added. 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, even if the lower limit of the content of B is not particularly defined, but the effect of this embodiment is exhibited, in order to obtain a sufficient effect of strengthening due to the addition of B, the content of B 0.0001% it is preferable that the above. For increasing the strength of the additional hot-dip galvanized steel sheet, the content of B is more preferably 0.0005% or more.
[0042]
[W: 0.01 ~ 2.00%]
　W suppresses phase transformation at high temperature, an effective element for high strength galvanized steel sheet, instead of a part of the C and / or Mn it may be added. However, when the content of W exceeds 2.00%, since the productivity workability impaired by between heat is reduced, the content of W is preferably from 2.00%, 1.20% by more preferably less. On the other hand, the lower limit of the content of W is the effect of the present embodiment is exhibited without particularly determined, in order to obtain a high strength by W sufficiently, the content of W is 0.01% or more it is preferable, more preferably 0.10% or more.
[0043]
Further the base material steel plate in the molten zinc plated steel sheet of the present embodiment, as other elements, Ca, Ce, Mg, Zr , La, 0.0001 ~ 0.0100% in one or more the sum of REM it may be contained. 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 an impurity, the effect of the present embodiment is exhibited as containing elements of the lanthanide series other than those La and Ce. Moreover, the effect of the present embodiment is exhibited as the addition of metal La and Ce.
[0044]
Ca, Ce, Mg, Zr, La, REM is an element effective for improving the formability of galvannealed steel sheets 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%, the may impair the ductility, the total of the content of each element is preferably 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 embodiment is exhibited without particularly, formability of galvannealed steel sheets in order to obtain a sufficient effect of improving, 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.
[0045]
In the chemical components in the hot-dip galvanized steel sheet according to the present embodiment, the remainder of the elements described above is Fe and 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.
[0046]
Why organization defined the base steel sheet of the galvanized steel sheet according to the embodiment of the present invention is as follows.
[0047]
(Microstructure)
microstructure in the base material steel plate of such hot-dip galvanized steel sheet to an embodiment of the present invention, the 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base material steel plate , the ferrite phase (hereinafter, ferrite hereinafter) is at a volume fraction of 40% or more and 97% or less, bainite phase (hereinafter, bainite hereinafter) and bainitic ferrite phase (hereinafter, Bay of bainitic ferrite) and fresh martensite site-phase (hereinafter, fresh referred martensite) and tempered martensite phase (hereinafter, referred to as tempered martensite) total hard tissue comprising one or more of is not less than 3% by volume fraction, the residual austenite phase (hereinafter a 0-8% of residual austenite) by volume fraction (including 0%), pearlite (hereinafter, the pearlite U) and coarse cementite phase (hereinafter, those sum of the called cementite) is to 0 to 8% volume fraction (including 0%).
[0048]
"Ferrite"
ferrite is an organization that has excellent ductility. However, ferrite is due to low intensity since it is soft, not obtained galvanized steel sheet sufficient tensile maximum strength when the volume fraction of the ferrite is 97 percent. Therefore, the volume fraction of ferrite is 97% or less. To increase the maximum tensile strength of the galvanized steel sheet, the volume fraction of ferrite is preferably set to less 92%, and more preferably 85% or less.
Furthermore, the maximum tensile strength is obtained a galvanized steel sheet of more than 950 MPa, more preferably to the volume fraction of ferrite and 80% or less, more preferably 70% or less. Meanwhile, the volume fraction of the ferrite is sufficient ductility is not obtained at less than 40%, the volume fraction of ferrite is 40% or more. It is preferable that the volume fraction of ferrite and 45% or more, more preferably 50% or more.
[0049]
"Residual austenite"
residual austenite strength galvanized steel sheet - an organization to improve the ductility balance. On the other hand, the residual austenite is transformed into hard martensite with the deformation, to serve as starting points of fracture, since the stretch flangeability is degraded, and 8% the upper limit of the volume fraction of retained austenite. From the viewpoint of formability of hot-dip galvanized steel sheet, it is preferable volume fraction of residual austenite is small, preferably 5% or less, more preferably 0 to 3% (including 0%). The volume fraction of retained austenite of galvanized steel sheet is smaller preferably, may be 0%.
[0050]
"Hard tissue"
to increase the maximum tensile strength of the galvanized steel sheet, a bainite and bainitic ferrite and fresh martensite and the volume fraction of hard structures consisting of one or more of the tempered martensite in total more than 3% There is a need to. To increase the maximum tensile strength of the galvanized steel sheet, the volume fraction of hard structures is preferably set to 7% or more, more preferably 15% or more. On the other hand, limits since the ductility of the hot-dip galvanized steel sheet excessively increase the volume fraction of hard structures is deteriorated, the volume fraction of hard structures to 60% or less. In this respect, the volume fraction of hard structures is preferably set to 55% or less, more preferably 50% or less.
[0051]
"Bainitic ferrite and / or bainite"
bainitic ferrite and / or bainite is the excellent tissue balance formability and strength of the galvanized steel sheet, 60% or less of the bainitic ferrite at a volume fraction and it is preferable to / or bainite is contained in the steel sheet structure. Further, bainitic ferrite and / or bainite, soft ferrite and hard martensite, a microstructure having an intermediate intensity of tempered martensite and residual austenite, it contained more than 5% from the viewpoint of the stretch flangeability still more preferably, it is more preferably contained by 10% or more. On the other hand, if the bainitic ferrite and / or volume fraction of bainite is more than 60%, increases excessively the yield stress is not preferable because the shape fixability is concerned to degrade.
[0052]
"Tempered martensite"
tempered martensite is a structure to improve the tensile strength of the galvanized steel sheet increases, it may be contained less than 60% volume fraction in the steel sheet structure. From the viewpoint of tensile strength, the volume fraction of tempered martensite is preferably 5% or more. On the other hand, if the volume fraction of tempered martensite contained in the steel sheet structure is more than 60%, increases excessively the yield stress is not preferable because the shape fixability is concerned to degrade.
[0053]
"Fresh martensite"
fresh martensite is included but greatly improve the tensile strength of the galvanized steel sheet, on the one hand in order to degrade the stretch flangeability become starting points of fracture, 30% or less at a volume fraction in the steel sheet structure it is preferred that the. Particularly more preferable that the volume fraction of fresh martensite is 20% or less in order to increase the hole expandability, further preferably 10% or less.

The scope of the claims
[Claim 1]
Consists of a base steel sheet and galvanized layer formed on at least one surface of the base steel sheet,
　the base material steel plate is a
　mass%, C: 0.040 ~
　0.280%, Si: 0.
　～ 2.00
　Pasento 05,
　Mn: 0.50 ～ 3.50 Pasento, P: 0.0001 ～ 0.1000 Pasento,
　S: 0.0001 ～ 0.0100 Pasento, Al: 0.001 ～ 1.500 Pasento ,
　N: 0.0001
　~ 0.0100%, O: 0.0001 ~ 0.0100%,
the balance has a chemical composition consisting of Fe and impurities,
　and about a quarter thickness from the surface of the base steel sheet in 1/8 thickness ~ 3/8 thick ranges, volume fraction,
　and ferrite phase following 97% 40%,
　of the bainite phase and bainitic ferrite phase and fresh martensite phase and tempered martensite phase rigid assembly consisting of one or more The and a total of 3% or more,
　0-8% residual austenite phase by volume fraction,
　the sum of the pearlite phase and coarse cementite phase is 0-8% in the volume fraction,
　the galvanized layer and the surface layer ranging from the interface of the base material steel plate to the steel plate direction depth 20 [mu] m,
　the volume fraction of residual austenite is 0-3%, the volume fraction V1 of the hard tissue in the surface layer ranging from the surface of the steel sheet 1 / 4 thickness center and the 1/8 thickness 1-3 / 8 which is the ratio V1 / V2 of the volume fraction V2 of the hard tissue in the range of thickness in the range of 0.10 to 0.90 microstructure of has,
　the Fe content of the galvannealed layer is 0% ultra-5% Al content is 0% super% to 1.0%, columnar crystals made of ζ phase to the galvanized layer wherein the
　total surfactant (a between the galvanized layer and the base steel sheet Interface (A *) the ratio of ((A * / A) × 100) is not less than 20%, fine layer on the interface side in the base material steel plate formed between the ζ phase and the base steel sheet of the is the is 0.1 ~ 5.0 .mu.m average thickness of the fine layer, the average particle size of the ferrite phase in the finer layer becomes 0.1 ~ 3.0 [mu] m, Si and Mn in the fine layer one or more oxides are contained, galvanized steel sheet maximum diameter of 0.01 ~ 0.4 .mu.m of the oxide.
[Claim 2]
　Characterized in that said base material steel plate contains, by
　mass%,
　Ti: 0.001 ~ 0.150%,
　Nb: 0.001 ~ 0.100%, V: 0.001 ~ 0.300%,
selected from among 1 hot-dip galvanized steel sheet according to claim 1 containing more species or in combination.
[Claim 3]
　Characterized in that said base material steel plate contains, by
　mass%,
　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%,
the melting of claim 1 or 2 containing one or two or more species selected from among zinc-plated steel plate.
[Claim 4]
　Characterized in that said base material steel plate containing, by
mass%, Ca, Ce, Mg, Zr, La, any one of claims 1 to 3 containing from 0.0001 to 0.0100% of one or two or more kinds in total of REM galvanized steel sheet according to item.
[Claim 5]
　In the molten zinc plated layer, the proportion of the interface between the ζ phase and the base material steel plate (A *) of the interfacial formed between coarse ζ oxides are present crystal grains and the base material steel plate (A **) ( (a ** / a *) × 100) is hot-dip galvanized steel sheet according to any one of claims 1 to 4, 50% or less.
[Claim 6]
　Wherein 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 galvanized steel sheet according to any one of claims 1 to 5 or less.