The present invention strength, ductility, hole expandability, about good galvanized steel sheet uniformity of the plating adhesion and appearance.
BACKGROUND
[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 alloying elements typified by contributing Si and Mn for improving the strength is contained. 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 causing plating peeling an oxide of the interface between the plating layer 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]
　On the other hand, for example, in the galvanized steel sheet described in Patent Document 12, the occurrence of appearance unevenness been a problem derived from the non-uniformity of the Fe content of the plating layer in the width direction.
CITATION
Patent Document
[0011]
Patent Document 1: JP 2008-019465 Patent Publication
Patent Document 2: JP 2005-060742 Patent Publication
Patent Document 3: JP-A-9-176815
Patent Document 4: JP 2001-026853 Patent Publication
Patent Document 5: JP 2002-088459 JP
Patent Document 6: JP 2003-055751 Patent Publication
Patent Document 7: JP 2003-096541 JP
Patent Document 8: JP 2005-200750 JP
Patent Document 9: JP-A 11-140587 JP
Patent Document 10: JP 2001-303226 JP
Patent Document 11: JP 2005-060743 JP
Patent Document 12: WO 2016/072477
Summary of the Invention
Problems that the Invention is to Solve
[0012]
　In view of the situation described above, the present invention is to provide strength, ductility, hole expandability, spot weldability, excellent hot-dip galvanized steel sheet uniformity of the plating adhesion and appearance.
Means for Solving the Problems
[0013]
　The present inventors have conducted extensive studies in order to obtain good galvanized steel sheet uniformity of the plating adhesion and appearance. As a result, even with a steel sheet containing Si and Mn in a large amount as a plating original plate, formed at the interface between the plated layer and the base material steel plate formed by using the plating bath which a specific amount of Al is contained is immediately below the Fe-Al alloy layer could be suppressed cracking and propagation during processing by forming a specific refinement layer electrode composed of fine grains of the ferrite phase, it plating peeling as a starting point It has been found that can be suppressed. In the case of using a steel sheet containing Si and Mn in a large amount as be plated, the internal oxide layer in the width direction of the steel sheet is formed nonuniformly, it is Fe content of the plating layer of the molten zinc plated steel sheet due becomes uneven, uneven appearance revealed that occur. Accordingly, the present inventors have further conducted intensive studies on factors internal oxide layer is formed nonuniformly, it is clearly in the oxygen concentration difference in the width direction after winding the hot-rolled steel sheet became. The present inventors have conducted further intensive studies in order to suppress the appearance unevenness due to such plating layer. As a result, by controlling the thickness of the fine layer and Fe-Al alloy layer in the width direction of the steel sheet in a specific range, it is possible to obtain a galvanized steel sheet excellent in uniformity of appearance as well plating adhesion it has been found that can be.
[0014]
　The present invention was completed on the basis of this finding, the embodiment is as follows.
[0015]
　(1)
　A hot dip galvanized steel sheet having on at least one side of the galvanized layer of the base material steel plate,
　the base material steel plate containing, by
　mass%, C: 0.040% ~
　0.400%, Si:
　%
　~ 2.50 0.05%, Mn: 0.50% ~
　3.50%, P: 0.0001% ~ 0.1000%, S: 0.0001% ~
　0.0100%, Al: 0.
　%
　~ 1.500 001%, N:
　0.0001% ~ 0.0100%, O: 0.0001% ~ 0.0100%, Ti:
　0.000% ~ 0.150%, Nb: 0.000%
　0.100%
~,
　~ 0.300%, Cr: 0.00% ~ 2.00%, Ni:
　0.00% ~ 2.00%, Cu: 0.00% ~ 2
　Pasento .00,
　Mo: 0.00 The Pasento ～ 2.00 Pasento, B: 0.0000 Pasento ～
　0.0100 Pasento, W: 0.00 The Pasento
　% 2.00, Ca, Ce, Mg, Zr, La and REM: 0.0000% ~ 0.0100% in total, and
　balance: Fe and impurities,
Has a chemical composition expressed in,
　the Fe content in the molten galvanizing layer is not more than 0% and 3.0% Al content of not more than 0% and 1.0%,
　the hot-dip galvanized has a Fe-Al alloy layer at the interface between the the layer base material steel plate,
　the thickness of the Fe-Al alloy layer becomes 0.1 [mu] m ~ 2.0 .mu.m,
　the in the width direction of the base material steel plate Fe- the difference between the maximum value and the minimum value of the thickness of the Al alloy layer is within 0.5 [mu] m,
　the base material in the steel sheet has a fine layer in direct contact with the Fe-Al alloy layer, the fine layer average thickness of 0.1 [mu] m ~ 5.0 .mu.m of the an average particle diameter of 0.1 [mu] m ~ 3.0 [mu] m of the ferrite phase in the finer layer, one of Si and Mn in the fine layer or containing seeds or more oxides, the maximum diameter of the oxide is 0.01 [mu] m ~ 0.4 .mu.m,
　the mother Galvanized steel sheet, wherein a difference between the maximum value and the minimum value of the thickness of the finer layer in the width direction of the steel sheet is within 2.0 .mu.m.
[0016]
　(2)
　the base material steel sheet, Si content (wt%) [Si], satisfy the equation 1 below when the Al content (mass%) and [Al],
　the total thickness of the base material steel plate against, wherein the residual austenite at 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base steel sheet is 1% or more in volume fraction (1 hot-dip galvanized steel sheet according to).
　[Si] +0.7 [Al] ≧ 0.30 ( Equation 1)
[0017]
　(3)
　coating weight per one side in the hot-dip galvanized layer is 10 g / m 2 or more 100 g / m 2 galvanized steel sheet according to (1) or (2) is not more than.
[0018]
　(4)
　In the above chemical
　composition,
　Ti: 0.001% ~ 0.150%, Nb: 0.001% ~ 0.100%, or
　V: 0.001% ~ 0.300%,
　or any of these hot-dip galvanized steel sheet according to any one of the characterized in that the combination is satisfied (1) to (3).
[0019]
　(5)
　In the above chemical
　composition,
　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%, or
　W: 0.01% ~ 2.00%,
　or any combination thereof is possible, characterized in that satisfy (1) to ( hot-dip galvanized steel sheet according to any one of 4).
[0020]
　(6)
　In the above chemical
　composition, Ca, Ce, Mg, Zr, La and REM: 0.0001% ~ 0.0100% in total
　either which is possible, characterized in that satisfy (1) to (5) 1 hot-dip galvanized steel sheet according to One.
The invention's effect
[0021]
　The present invention can provide strength, ductility, hole expandability, spot weldability, excellent hot-dip galvanized steel sheet uniformity of the plating adhesion and appearance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022]
[1] Figure 1 is a sectional view showing a hot-dip galvanized steel sheet according to the embodiment of the present invention.
DESCRIPTION OF THE INVENTION
[0023]
　It will be described in detail embodiments of the present invention.
[0024]
　First, the hot-dip galvanized steel sheet according to the embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 is a sectional view showing a hot-dip galvanized steel sheet according to the embodiment of the present invention. Galvanized steel sheet 1 according to this embodiment includes a galvanized layer 3 on the surface of the base material steel plate 2, the Fe-Al alloy layer 4 at the interface between the galvanized layer 3 and the base steel sheet second surface provided, comprising a base steel sheet 2, and the fine layer 5 in contact with the Fe-Al alloy layer 4, and a decarburized layer 6.
[0025]
　(Base material steel plate 2)
　is described the chemical composition of the slab used in the base material steel plate 2 and their preparation constitute the galvanized steel sheet 1 according to the embodiment of the present invention. Although details will be described later, galvanized steel sheet 1 according to the embodiment of the present invention, the cast slab, hot rolling, cold rolling, is produced through the annealing and plating. Therefore, the chemical composition of the slab used in the base material steel plate 2 and its preparation, not only the properties of the base material steel plate 2, is taken into consideration these processes. In the following description, a unit of content of each element contained in the base material steel plate 2 or slab "%" is especially meant to "mass%" unless otherwise specified. The base steel sheet is, C: 0.040% ~ 0.400% , Si: 0.05% ~ 2.50%, Mn: 0.50% ~ 3.50%, P: 0.0001% ~ 0. 1000%, S: 0.0001% ~ 0.0100%, Al: 0.001% ~ 1.500%, N: 0.0001% ~ 0.0100%, O: 0.0001% ~ 0.0100% , Ti: 0.000% ~ 0.150% , Nb: 0.000% ~ 0.100%, V: 0.000% ~ 0.300%, Cr: 0.00% ~ 2.00%, Ni : 0.00% ~ 2.00%, Cu : 0.00% ~ 2.00%, Mo: 0.00% ~ 2.00%, B: 0.0000% ~ 0.0100%, W: 0 .00% ~ 2.00%, Ca, Ce, Mg, Zr, La and REM: 0.0000% ~ 0.0100% in total, and the balance: Fe and impurities In it has a chemical composition represented. As the impurity, those included in raw materials such as ores and scrap, intended to be included in the manufacturing process, it is exemplified.
[0026]
　(C: 0.040% ~ 0.400%)
　C increases the strength of the base material steel plate. C content is 0.400% greater than the spot weldability is deteriorated. Therefore, C content is at most 0.400%. In view of spot weldability, C content is preferably not more than 0.300%, more preferably at most 0.220%. In order to obtain higher strength, C content is preferably 0.055% or more, more preferably 0.070% or more.
[0027]
　(Si: 0.05% ~
　2.50%) Si is to suppress the formation of iron-based carbides in the base steel sheet, increasing the strength and formability. Meanwhile, Si causes the steel embrittlement. The Si content is 2.50% greater than is likely cracked cast slabs. Therefore, Si content is at most 2.50%. Si is an oxide formed on the surface of the base steel sheet during annealing, for significantly impair the adhesiveness of the plating, Si content is preferably not more than 2.00%, more preferably less 1.60% to. The Si content is less than 0.05%, when plating the base steel sheet, coarse iron-based carbide is produced in large quantities, the strength and formability is deteriorated. Therefore, Si content is less than 0.05%. From the viewpoint of suppressing the generation of iron-based carbide, Si content is preferably 0.10% or more, more preferably 0.25% or more.
[0028]
　(Mn: 0.50% ~
　3.50%) Mn enhances the strength by enhancing the hardenability of the base material steel plate. The Mn content is 3.50% greater, caused high portion of Mn concentration in the thickness center portion of the base steel sheet, embrittlement easily occurs, is likely cracked cast slabs. Therefore, Mn content is at most 3.50%. From the viewpoint of spot weldability is deteriorated, Mn content is preferably not more than 3.00%, more preferably at most 2.80%. The Mn content 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 tensile strength. Therefore, Mn content is 0.50% or more. In order to obtain higher strength, Mn content is preferably 0.80% or more, more preferably 1.00% or more.
[0029]
　(P: 0.0001% ~ 0.1000%)
　P causes embrittlement of steel. The P content is 0.1000% greater than is likely cracked cast slabs. Accordingly, P content is at most 0.1000%. Also, P is, embrittle the portion melted by spot welding. In order to obtain sufficient strength of the welded joint, P content is preferably not more than 0.0400%, more preferably at most 0.0200%. The P content is less than 0.0001%, significantly increases the manufacturing cost. Accordingly, P content is set to 0.0001% or more, preferably 0.0010% or more.
[0030]
　(S: 0.0001% ~ 0.0100%)
　S is combined with Mn to form coarse MnS, ductility lowers the formability such stretch flangeability and bendability. Thus, S content is 0.0100% or less. Further, S is deteriorates the spot weldability. Thus, S content is preferably set to 0.0060% or less, more preferably at most 0.0035%. S content is less than 0.0001%, the manufacturing cost is greatly increased. Thus, S content is set to 0.0001% or more, preferably 0.0005% or more, more preferably 0.0010% or more.
[0031]
　(Al: 0.001% ~
　1.500%) Al causes embrittlement of steel. The Al content is 1.500% greater than is likely cracked cast slabs. Therefore, Al content is at most 1.500%. From the viewpoint of spot weldability is deteriorated, Al content is preferably not more than 1.200%, more preferably at most 1.000%. The lower limit of the Al content is not particularly limited, Al is contained as an impurity in steel. The Al content to less than 0.001%, the production cost is greatly increased. Therefore, Al content is 0.001% or more. Al is a deoxidizing element of steel. To obtain the deoxidizing effect more fully, Al content is preferably 0.010% or more.
[0032]
　(N: 0.0001% ~ 0.0100%)
　N forms coarse nitrides, ductility, degrading the formability such stretch flangeability and bendability. The N content is 0.0100% greater, moldability is remarkably deteriorated. Therefore, N content is 0.0100% or less. When the N content is excessive, since the blowhole may occur during welding, the N content is preferably not more than 0.0070%, more preferably 0.0050% or less. The lower limit of N content is not particularly limited, N is contained in steel as an impurity. The N content to less than 0.0001%, the manufacturing cost is greatly increased. Therefore, N content is 0.0001% or more, preferably 0.0003% or more, more preferably 0.0005% or more.
[0033]
　(O: 0.0001% ~ 0.0100%)
　O forms oxides, ductility, degrading the formability such stretch flangeability and bendability. The O content is 0.0100% greater, moldability is remarkably deteriorated. Therefore, O content is set to 0.0100% or less, preferably 0.0050% or less, more preferably 0.0030% or less. The lower limit of O content is not particularly limited, O is an impurity contained in steel. O content of the to less than 0.0001%, the manufacturing cost is greatly increased. Therefore, N content is 0.0001% or more, preferably 0.0003% or more, more preferably 0.0005% or more.
[0034]
　([Si] +0.7 [Al] : 0.30 or
　more) Si and Al suppresses the formation of carbides due to the bainite transformation. To obtain a residual austenite, it is preferable that the Si and / or Al is contained more than a predetermined amount. By obtaining the residual austenite is because TRIP effect. In this respect, the base steel sheet is, Si content (wt%) [Si], it is preferable to satisfy the expression 1 below when Al content (mass%) and [Al]. That is, the value of the left side of the equation 1 below ([Si] +0.7 [Al] ) is preferably 0.30 or more, more preferably 0.45 or more, further preferably 0.70 or more.
　[Si] +0.7 [Al] ≧ 0.30 ( Equation 1)
[0035]
　Ti, Nb, V, Cr, Ni, Cu, Mo, B, W, Ca, Ce, Mg, Zr, La and REM is not an essential element, may optionally be contained in limits a predetermined amount on the steel sheet it is an optional element.
[0036]
　(Ti: 0.000% ~
　0.150%) Ti is precipitation strengthening, fine grain strengthening by ferrite grain growth inhibition, and the dislocation strengthening through suppression of recrystallization, increasing the strength of the steel sheet. Therefore, Ti may be contained. The Ti content of 0.150 percent, the more the precipitation of carbonitrides, may be degraded formability. Therefore, Ti content is at most 0.150%. From the viewpoint of moldability, Ti content is preferably not more than 0.080%. The lower limit of the Ti content is not particularly limited, in order to obtain the effect of enhancing the strength sufficiently, the Ti content is preferably 0.001% or more. To obtain more fully the effect, Ti content is more preferably 0.010% or more.
[0037]
　(Nb: 0.000% ~
　0.100%) Nb is precipitation strengthening, fine grain strengthening by ferrite grain growth inhibition, and the dislocation strengthening through suppression of recrystallization, increasing the strength of the steel sheet. Therefore, Nb may be contained. The Nb content 0.100 percent, the more the precipitation of carbonitrides, moldability may deteriorate. Therefore, Nb content is 0.100% or less. From the viewpoint of moldability, Nb content is preferably not more than 0.060%. The lower limit of Nb content is not particularly limited, in order to obtain the effect of enhancing the strength sufficiently, the Nb content is preferably 0.001% or more. To obtain more fully the effect, Nb content is more preferably 0.005% or more.
[0038]
　(V: 0.000% ~ 0.300%)
　V is precipitation strengthening, fine grain strengthening by ferrite grain growth inhibition, and the dislocation strengthening through suppression of recrystallization, increasing the strength of the steel sheet. Thus, V may be contained. The V content is 0.300% greater, increases the precipitation of carbonitrides, may be degraded formability. Therefore, V content is not more than 0.300%, preferably not more than 0.200%. The lower limit of V content is not particularly limited, in order to obtain the effect of enhancing the strength sufficiently, the V content is preferably 0.001% or more, more preferably 0.010% or more.
[0039]
　(Cr: 0.00% ~
　2.00%) Cr suppresses phase transformation at high temperature, further increasing the strength of the steel sheet. Thus, Cr may be contained instead of a part of the C and / or Mn. The Cr content of 2.00 percent, productivity is impaired processability in hot rolling may be reduced. Therefore, Cr content is not more than 2.00%, preferably not more than 1.20%. The lower limit of Cr content is not particularly limited, in order to obtain the effect of enhancing the strength more sufficiently, the Cr content is preferably 0.01% or more, more preferably 0.10% or more.
[0040]
　(Ni: 0.00% ~
　2.00%) Ni suppresses phase transformation at high temperature, further increasing the strength of the steel sheet. Accordingly, Ni may be contained instead of a part of the C and / or Mn. The Ni content of 2.00 percent, which may weldability is impaired. Therefore, Ni content is not more than 2.00%, preferably not more than 1.20%. The lower limit of Ni content is not particularly limited, in order to obtain the effect of enhancing the strength more satisfactory, the content of Ni is preferably 0.01% or more, more preferably 0.10% or more.
[0041]
　(Cu: 0.00% ~
　2.00%) Cu enhances the strength by the presence in the steel as fine particles. Therefore, Cu may be contained instead of a part of the C and / or Mn. The Cu content of 2.00 percent, which may weldability is impaired. Therefore, Cu content is not more than 2.00%, preferably not more than 1.20%. The lower limit of Cu content is not particularly limited, in order to obtain the effect of enhancing the strength more sufficiently, the Cu content is preferably 0.01% or more, more preferably 0.10% or more.
[0042]
　(Mo: 0.00% ~
　2.00%) Mo suppresses phase transformation at high temperature, further increasing the strength of the steel sheet. Therefore, Mo may be contained instead of a part of the C and / or Mn. The Mo content is 2.00% greater, productivity is impaired processability in hot rolling may be reduced. Therefore, Mo content is not more than 2.00%, preferably not more than 1.20%. The lower limit of Mo content is not particularly limited, in order to obtain the effect of enhancing the strength more sufficiently, the Mo content is preferably 0.01% or more, more preferably 0.05% or more.
[0043]
　(B: 0.0000% ~ 0.0100%)
　B suppresses phase transformation at high temperature, further increasing the strength of the steel sheet. Thus, B may be contained instead of a part of the C and / or Mn. The B content is 0.0100% greater, productivity is impaired processability in hot rolling may be reduced. Therefore, B content is 0.0100% or less. From the viewpoint of productivity, B content is preferably 0.0050% or less. The lower limit of B content is not particularly limited, in order to obtain a further increase effect of strength sufficient, B content is preferably 0.0001% or more, more preferably 0.0005% or more.
[0044]
　(W: 0.00% ~ 2.00%)
　W suppresses phase transformation at high temperature, further increasing the strength of the steel sheet. Therefore, W is may be contained instead of a part of the C and / or Mn. The W content of 2.00 percent, productivity is impaired processability in hot rolling may be reduced. Therefore, W content is not more than 2.00%, preferably not more than 1.20%. The lower limit of the W content is not particularly limited, in order to obtain the effect of enhancing the strength more sufficiently, the W content is preferably 0.01% or more, more preferably 0.10% or more.
[0045]
　(Ca, Ce, Mg, Zr , La and REM:
　0.0000% ~ 0.0100% in total) Ca, Ce, Mg, Zr, La or REM improves the moldability. Therefore, Ca, Ce, Mg, Zr , La or REM may be contained. Ca, Ce, Mg, Zr, in the 0.0100% than the content of La and REM are in total, it may impair the ductility. Therefore, Ca, and Ce, Mg, Zr, the content of La and REM and 0.0100% or less in total, preferably not more than 0.0070% in total. Ca, Ce, Mg, Zr, but the lower limit of the content of La and REM is limited, in order to obtain the effect of improving the formability of the steel sheet sufficiently, Ca, Ce, Mg, Zr, La and REM the content of preferably the total 0.0001% or more, and more preferably in total 0.0010% or more. Note that the REM, is an abbreviation of Rare Earth Metal, refers to an element belonging to the lanthanoid series. In embodiments of the present invention, REM and Ce is added as for example mischmetal, in addition to elemental lanthanoid series La and Ce may be contained in combination. Elements of the lanthanide series other than La and Ce may be contained as an impurity. The metal La and metal Ce may be contained.
[0046]
　Incidentally, Ti, Nb, V, Cr, Ni, Cu, Mo, B and W, may contain if it is less than the lower limit of the content of the respective elements as impurities. Ca, Ce, Mg, Zr, for also La and REM, may contain if it is less than the lower limit value of the total amount as an impurity.
[0047]
　(Galvanized layer 3)
　[Fe content in molten zinc plating layer 3: 0 percent to 3.0%]
　Fe content in galvanized layer 3 is less 0% and 3.0%. It is difficult Fe content is substantially produce galvanized layer 3 is 0%. Therefore, Fe content is over 0%. From the viewpoint of ensuring coating adhesion, Fe content is preferably 0.3% or more, more preferably 0.5% or more. Fe content is 3.0%, the coating adhesion is degraded. Therefore, Fe content is 3.0% or less. From the viewpoint of ensuring coating adhesion, Fe content is preferably 2.5% or less, more preferably 2.0% or less.
[0048]
　[Al content in the galvanized layer 3 amount: 0% and 1.0%]
　Al content in the galvanized layer 3 is less 0% and 1.0%. In the Al content is 0%, the alloying proceeds generated by the Zn-Fe alloy Fe atoms diffuse into the galvanized layer 3, coating adhesion is reduced. Therefore, Al content is set to 0 percent. Of inhibition of the progression of such alloying, Al content is preferably 0.1% or more, more preferably 0.2% or more. Al content is 1.0%, the coating adhesion is degraded. Therefore, Al content is 1.0% or less. From the viewpoint of ensuring coating adhesion, Al content is preferably not more than 0.8%, more preferably 0.5% or less.
[0049]
　[Coating weight per one side in the galvanized layer 3: 10 g / m 2 or more 100 g / m 2 or less]
　coating weight is 10 g / m 2 is less than, sufficient corrosion resistance can not be obtained. Accordingly, coating weight is preferably 10 g / m 2 and more. From the viewpoint of corrosion resistance, coating weight, more preferably 20 g / m 2 and more, more preferably 30 g / m 2 and more. Amount plating adhesion 100 g / m 2 in greater becomes severe electrode wear when performing spot welding, the welding nugget diameter is reduced when performing the welding in succession, the strength of the welded joint may deteriorate . Accordingly, coating weight is preferably 100 g / m 2 or less. In view of the continuous weldability, coating weight, more preferably 93 g / m 2 and less, more preferably 85 g / m 2 or less.
[0050]
　The galvanized layer 3, 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, 1 or more may be contained among Zr and REM. By these elements are contained, the corrosion resistance and workability can be improved.
[0051]
　The galvanized layer 3, zeta phase (FeZn 13 columnar crystals may be contained consisting). From the standpoint of plating adhesion, the coating ratio of the ζ phase at all the interface between the galvanized layer 3 and the base material steel plate 2, preferably less than 20%.
[0052]
　(Fe-Al alloy layer
　4) [Fe-Al thickness of the alloy layer 4: 0.1μm ~ 2.0μm]
　In an embodiment of the present invention, the interface between the galvanized layer 3 and the base steel sheet second surface the Fe-Al alloy layer 4 is formed. The formation of the Fe-Al alloy layer 4, and suppress the alloying of Zn-Fe alloy is produced, it is possible to suppress the reduction in coating adhesion. Furthermore, it is possible to suppress the occurrence of appearance irregularity by uneven alloying. Appearance unevenness due to uneven alloying is than galvannealed steel sheet which has been subjected to alloying treatment after hot-dip galvanizing process, is likely to occur towards the hot-dip galvanized steel sheet not subjected to alloying treatment. The thickness of the Fe-Al alloy layer 4 is less than 0.1 [mu] m, coating adhesion and appearance is deteriorated. Therefore, the thickness of the Fe-Al alloy layer 4 is not less than 0.1 [mu] m. The thickness of the Fe-Al alloy layer 4 is in the 2.0μm greater, plating adhesion is degraded. Therefore, the thickness of the Fe-Al alloy layer 4 was set to 2.0μm or less, preferably 1.0μm or less.
[0053]
　[The difference between the maximum thickness and the minimum value of the Fe-Al alloy layer 4 in the width direction of the base material steel plate 2: within 0.5 [mu] m]
　The thickness of the Fe-Al alloy layer 4 in the width direction of the base material steel plate 2 the difference between the maximum value and the minimum value of the thickness of the Fe-Al from both edges of the alloy layer 4 of a total of 8 points between the position and each position during a 7 equal portions of 50 mm Fe-Al alloy layer 4 measured, it means the difference between the maximum value and the minimum value among them. As the thickness of the Fe-Al alloy layer 4 is thin, alloying proceeds easily to Zn-Fe alloy is formed. Therefore, as the difference between the thickness of the Fe-Al alloy layer 4 in the width direction of the base material steel plate 2 is large, it becomes uneven alloying. The difference between the maximum value and the minimum value of the thickness of the Fe-Al alloy layer 4 is in the 0.5μm greater uniformity of coating adhesion and plating appearance is degraded. Thus, the difference between the maximum thickness and the minimum value of the Fe-Al alloy layer 4 was within a 0.5 [mu] m, preferably within the 0.4 .mu.m, more preferably within 0.3 [mu] m.
[0054]
　(Fine layer 5)
　in the base steel sheet in 2 includes a fine layer 5 in contact with the Fe-Al alloy layer 4, and a decarburized layer 6. Fine layer 5 and the decarburized layer 6 is a layer produced by decarburization reaction under controlled conditions in a specific temperature range and specific atmosphere to proceed when annealed as described below. Therefore, the tissue constituting the fine layer 5, except for the oxide or inclusion particles are substantially ferritic phase 7 is mainly for some organizations constituting the decarburized layer 6, an oxide or inclusion particles With the exception, substantially ferrite phase 8 is the subject. Specifically, it is the volume fraction of the ferrite phase 7,8 70%, the balance being austenite phase, bainite phase, one or more mixed structure of martensite phase and pearlite phase. Fine layer 5 has an average particle size of the ferrite phase 7 in the outermost portion of the base material steel plate 2 is present when the decarburized 6 is 1/2 or less of the average particle size of the ferrite phase 8. Boundary between the decarburized layer 6 fine layer 5 has an average particle size of the ferrite phase 7 in fine layer 5, a half than to become boundary having an average particle diameter of the ferrite phase 8 in decarburized layer 6.
[0055]
　Average thickness of the fine layer 5: 0.1μm ~ 5.0μm]
　In less than 0.1 [mu] m average thickness of the fine layer 5, because cracks occur, it is impossible to suppress the extension, coating adhesion There deteriorated. Therefore, the average thickness of the fine layer 5 is not less than 0.1 [mu] m, preferably not less than 0.2 [mu] m, more preferably at least 0.3 [mu] m. The average thickness of the fine layer 5 is in the 5.0μm greater than proceeds alloying the Zn-Fe alloy is produced, since the Fe content in the galvanizing layer 3 is increased, plating adhesion is degraded . Therefore, the average thickness of the fine layer 5 is not more than 5.0 .mu.m, preferably less 4.0 .mu.m, more preferably from 3.0 [mu] m.
[0056]
　Average particle size of the ferrite phase 7: 0.1 [mu] m ~ 3.0 [mu] m]
　When the average particle size of the ferrite phase 7 is less than 0.1 [mu] m, because cracks occur, it is impossible to suppress the extension, coating adhesion deteriorates to. Therefore, the average particle size of the ferrite phase 7 to more than 0.1 [mu] m. The average particle size of the ferrite phase 7 In 3.0μm greater, plating adhesion is degraded. Therefore, the average particle size of the ferrite phase 7 and 3.0μm or less, preferably 2.0μm or less.
[0057]
　The average particle size of the ferrite phase 7 in miniaturization layer an average thickness of 5 and finer layer 5 is measured by the following methods. From galvanized steel sheet 1, to collect the sample and observation surface of a cross section parallel to the rolling direction of the base material steel plate 2. 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.
[0058]
　Maximum diameter of the oxide: 0.01μm ~ 0.4μm]
　The fine layer 5, one or more oxides of Si and Mn is contained. As oxide, for example, SiO 2 , Mn 2 SiO 4 , MnSiO 3 , Fe 2 SiO 4 , FeSiO 3 , 1 or more selected from the group consisting of MnO and the like. The oxides, as described later, is formed on the base steel sheet in 2 at a specific temperature range during annealing. The growth of the ferrite phase crystals in the surface layer of the base material steel plate 2 is suppressed by the oxide particles, the fine layer 5 is formed. The maximum diameter is less than 0.01μm oxide, since the fine layer 5 is not sufficiently formed, the coating adhesion is deteriorated. Accordingly, the maximum diameter of the oxide is equal to or greater than 0.01 [mu] m, preferably not less than 0.05 .mu.m. The maximum diameter of the oxide is 0.4μm greater than the ferrite phase 7 are coarsened, with fine layer 5 is not sufficiently formed, since the oxide itself becomes a starting point of the plating peeling, coating adhesion is deteriorated. Accordingly, the maximum diameter of oxides and 0.4μm or less, preferably 0.2μm or less.
[0059]
　Maximum diameter of the oxide is measured by the following methods. From galvanized steel sheet 1, to collect the sample and observation surface of a cross section parallel to the rolling direction of the base material steel plate 2. 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 the oxide the maximum diameter of the measured measurement values ​​in the entire field of view.
[0060]
　[The difference between the maximum thickness and the minimum value of the base material steel plate 2 in miniaturization layer in the width direction 5: 2.0 .mu.m within]
　a maximum thickness of the base material steel plate 2 in miniaturization layer in the width direction 5 the difference between the minimum value, measuring both edges from a total of eight positions between the position and each position during a 7 equal portions of 50mm fine layer 5 thickness of the fine layer 5, the maximum value among them to mean the difference between the minimum value. The thicker the thickness of the finer layer 5, alloying proceeds easily to Zn-Fe alloy is formed. Therefore, as the difference between the thickness of the base material fine layer in the width direction of the steel plate 2 5 is large, it becomes uneven alloying. The difference between the maximum value and the minimum value of the thickness of the fine layer 5 is in the 2.0μm greater uniformity of coating adhesion and plating appearance is degraded. Thus, the difference between the maximum value and the minimum value of the thickness of the fine layer 5 is within the 2.0 .mu.m, preferably within a 1.5 [mu] m, more preferably within 1.0 .mu.m.
[0061]
　(Microstructure)
　is not particularly limited in microstructure base steel sheet 2 in galvanized steel sheet 1 according to the embodiment of the present invention, it is preferable that the following microstructure. Characteristics of the steel sheet varies depending microstructure. When quantifying the microstructure, for quantifying the whole area of the steel sheet is not practical, the 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base material steel plate 2 the microstructure was quantified as microstructure representative of the steel sheet, specified. Central portion of the plate thickness, because the microstructure is changed by strong solidification segregation, it can not be said microstructure representative of steel. The vicinity of the surface layer of the base steel sheet 2, in order to change the microstructure by reaction with local temperature changes and / or the outside air, it can not be said microstructure representative of steel.
[0062]
　Microstructure of the base material steel plate 2 in the galvanized steel sheet 1 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, it may be one or more of the coarse cementite. Base steel sheet 2, in order to obtain characteristics according to application of the galvanized steel sheet 1, each phase, breakdown of the volume fraction of each tissue, the tissue size can be appropriately selected placement.
[0063]
　[Retained austenite: at least 1%
　residual austenite is balanced greatly enhances tissue between strength and ductility. 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 material steel plate 2 is less than 1%, less effect of improving the balance between strength and ductility If there is a. Therefore, the volume fraction of residual austenite is preferably 1% or more. To further enhance the balance between strength and ductility, the volume fraction of residual austenite is more preferably set to 3% or more, more preferably 5% or more. To obtain a large amount of retained austenite, considerably increasing the C content. However, there is significantly impair concerned weldability by a large amount of C. Therefore, the volume fraction of residual austenite is preferably not more than 25%. Residual austenite is transformed into hard martensite with the deformation, by the martensite acts as starting points of fracture, which may stretch flangeability is degraded. Therefore, the volume fraction of the retained austenite is more preferably 20% or less.
[0064]
　The volume fraction of each tissue contained in the base steel sheet 2 of the galvanized steel sheet 1 according to the embodiment of the present invention is measured, for example, by the following method.
[0065]
　The volume fraction of retained austenite contained in the base material steel plate 2 in the galvanized steel sheet 1 according to the present embodiment is evaluated by X-ray diffraction method. In 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base material steel plate 2, finishing the surface parallel to the plate surface to mirror surface, FCC by X-ray diffractometry (Face Centered Cubic) measuring the area fraction of the iron, the measured value and the volume fraction of retained austenite.
[0066]
　Ferrite contained in the base material steel plate 2 in the galvanized steel sheet 1 according to this embodiment, bainitic ferrite, bainite, tempered martensite, fresh martensite volume fraction of pearlite and coarse cementite, the field emission scanning electron microscopy: measured by (FE-SEM Field Emission Scanning electron microscope). Collecting a sample with the observation plane section parallel to the rolling direction of the base material steel plate 2. Polishing the observation surface of the sample, to nital etching. Plate 1/4 thick thickness of the observation plane mainly the 1/8 thickness 1-3 / 8 of thickness range was observed with FE-SEM and the area fraction was measured, it views the measured value and the volume fraction.
[0067]
　In hot-dip galvanized steel sheet 1 according to this embodiment, the thickness of the base material steel plate 2 is not particularly limited. Flatness of the hot-dip galvanized steel sheet 1, from the viewpoint of controllability of cooling, the plate thickness of the base material steel plate 2 is preferably less than 5.0mm or 0.6 mm.
[0068]
　Next, a method for manufacturing a galvanized steel sheet according to the embodiment of the present invention. In this way, casting of slab having the above chemical composition, hot rolling, cold rolling, annealing, cooling after the plating and plating performed. In cooling during and / or after plating and annealing and plating is performed bainite transformation treatment as necessary to obtain a residual austenite.
[0069]
　(Casting)
　First, casting a slab subjected to hot rolling. Slab subjected to hot rolling, it is possible to use those produced by a continuous casting slab or thin slab caster or the like.
[0070]
　(Hot rolling)
　for suppressing the anisotropy of the crystal orientation due to casting, the heating temperature of the slab is preferably set to 1080 ° C. or more, more preferably 1150 ° C. or higher. On the other hand, the upper limit of the heating temperature of the slab is not particularly limited. The heating temperature of the slab is 1300 ° C. greater than might put a large amount of energy, there is the production cost is greatly increased. Therefore, the heating temperature of the slab is preferably a 1300 ° C. or less.
[0071]
　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 stably obtain a predetermined thickness. Therefore, completion temperature of the hot rolling preferably is a 850 ° C. or higher, more preferably 875 ° C. or higher. The completion temperature is 980 ° C. greater than the hot rolling, after heating the slab ends and before hot rolling is completed, there is a case of heating the steel sheet, it may cost increases. Therefore, completion temperature of hot rolling is preferably set to 980 ° C. or less, more preferably 960 ° C. or less.
[0072]
　Then, taking up the hot-rolled steel sheet after hot rolling as a coil. The average cooling rate during cooling to the winding before or after hot rolling, preferably 10 ° C. / sec or more. By advancing a 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.
[0073]
　Coiling temperature, preferably 350 ° C. or higher 750 ° C. or less. As the microstructure of the hot-rolled steel sheet, perlite and / or major axis is generated by dispersing a more coarse cementite 1 [mu] m, to localize distortion introduced into hot-rolled steel sheet by cold rolling. Thereafter, in order to reverse transformation to austenite various crystal orientations in the annealing. Thus, refining the effective crystal grains of the base material steel plate after annealing. The coiling temperature is lower than 350 ° C., there is a case where pearlite and / or coarse cementite does not generate. Therefore, the coiling temperature is preferably between 350 ° C. or higher. The strength of the hot rolled steel sheet was low, because easily performed cold rolling, coiling temperature is more preferably at 450 ° C. or higher. The coiling temperature 750 ° C. greater than the long strip of pearlite and ferrite is generated in the rolling direction, the effective crystal grain of the base material steel plate to produce a ferrite after cold rolling and annealing, and elongation in the rolling direction, coarse Sometimes. Therefore, the coiling temperature is preferably between 750 ° C. or less. To refine the effective crystal grain size of the base material steel plate after annealing, the coiling temperature is more preferably at 680 ° C. or less. After taking up the hot-rolled steel sheet, there is when the internal oxide layer is towards the center portion is formed thicker than the edge portion of the steel sheet, internal oxidation layer is unevenly formed under the scale layer. This coiling temperature becomes noticeable above 650 ° C.. Pickling the internal oxide layer is described below, if not removed by the cold-rolling, since the fine layer and Fe-Al alloy layer is formed nonuniformly, is deteriorated uniformity of coating adhesion and appearance there is a possibility. Therefore, the coiling temperature is further preferably 650 ° C. or less.
[0074]
　Next, pickled hot-rolled steel sheet manufactured in this way. Pickling in order to remove the oxide formed on the surface of the hot-rolled steel sheet, which contributes to the plating improvement of the base material steel plate. Pickling may be carried out at one time, it may be divided into multiple times. Internal oxide layer to be generated under the scale layer, uniform formation of the fine layer and Fe-Al alloy layer, in order to ensure the uniformity of the appearance due it is better to as much as possible removed to strengthen the pickling . Pickling conditions, if removal internal oxide layer is not particularly limited. For example, in terms of pickling efficiency and economy, the pickling is preferably used hydrochloric acid. The conditions for removing the internal oxide layer, for example, the concentration of hydrochloric acid is preferably 5 mass% or more of hydrogen chloride, pickling temperature are preferably set to 80 ° C. or higher, pickling time is preferably 30 seconds or more. For example, the coiling temperature is 650 ° C. greater, better to remove as much as possible internal oxidation layer to strengthen the pickling well, pickling time is more preferably 60 seconds or more.
[0075]
　(Cold rolling)
　Next, a cold rolling to hot-rolled steel sheet after pickling. The total reduction of 85 percent, the ductility of the steel sheet is lost, it may steel is broken during cold rolling. Therefore, the total rolling reduction is preferably set to 85% or less, more preferably 75% or less, more preferably 70% or less. The lower limit of the total reduction ratio is not particularly limited. The total reduction ratio is less than 0.05%, the shape of the base material steel plate becomes inhomogeneous, plating does not uniformly adhered, there is the appearance is impaired. Therefore, the total rolling reduction is preferably set to 0.05% or more, more preferably 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.
[0076]
　The total reduction ratio is less than 10 percent 20 percent, recrystallization does not proceed sufficiently in the subsequent annealing, for coarse grains lost malleable it contains a large amount of dislocations remains near the surface of the steel sheet, bending sometimes sex and fatigue characteristics are degraded. Therefore, to reduce the total rolling reduction, it is effective to in the minor accumulation of dislocations in the crystal grains leave malleable grains. Or, by increasing the total reduction ratio, sufficiently advanced recrystallization in annealing, it is effective to a worked structure within the accumulation of dislocation is small recrystallized grains. From the viewpoint of the minor accumulation of dislocations in the crystal grains, the total reduction ratio preferably is 10% or less, more preferably 5.0% or less. Meanwhile, in order to promote recrystallization sufficiently in annealing, the total rolling reduction is preferably 20% or more, more preferably 30% or more.
[0077]
　(Annealing)
　Next, subjected to annealing cold-rolled steel sheet. The annealing, it is preferable to use a continuous annealing plating line having a preheating zone and a soaking zone and the plating zone. While annealing cold-rolled steel sheet is passed through a preheating zone and a soaking zone, cold-rolled steel sheet annealing is completed before reaching the plating zone, it is preferable to carry out the plating in the plating zone.
[0078]
　As described above, when using a continuous annealing plating line, for example, it is preferable to use a method described below. In particular, to uniformly produce a predetermined fine layer and Fe-Al alloy layer, in order to ensure the uniformity of the coating adhesion and appearance, control of the atmosphere and the heating system in the preheating zone, the control of the atmosphere in the soaking zone it is important.
[0079]
　In the preheating zone, the water vapor partial pressure P (H 2 O) and hydrogen partial pressure P (H 2 is a Log value of a ratio of) Log (P (H 2 O) / P (H 2 a)) -1.7 in an atmosphere controlled to ~ -0.2, using a preheating burner air ratio is 0.7 to 1.0 to the sheet passing the cold rolled steel sheet while heating to 400 ° C. - 800 ° C.. In the preheating zone, the water vapor partial pressure P (H 2 O) and hydrogen partial pressure P (H 2 by adjusting the ratio between) In preheating zone by adjusting the air ratio, it is prevented that the oxide film of the strong deoxidizing element, such as Si, is formed on the surface of the steel sheet. Thereby adjusting the air ratio, water vapor partial pressure P (H 2 O) and hydrogen partial pressure P (H 2 by adjusting the ratio of), In this way a subsequent plating process, thereby suppressing the excessive Fe-Zn alloy reaction at the grain boundary of the steel sheet surface, Fe-Al alloy reaction to occur selectively. By Fe-Al alloy reaction occurs selectively, encourage the formation of a uniform Fe-Al alloy layer, it is possible to obtain excellent plating adhesiveness, appearance uniform. Log (P (H 2 O) / P (H 2In)) is -0.2 greater, it is likely to occur Fe-Zn alloyed with subsequent plating step, Fe concentration in the plating is increased. Thereby, plating adhesion property is lowered, also tends to occur appearance unevenness. On the other hand, Log (P (H 2 O) / P (H 2 is less than)) is -1.7 generates the portion with high carbon concentration on the surface of the steel sheet, since the fine layer on the surface does not form, plating adhesion sex is reduced.
[0080]
　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 air ratio is greater than 1.0, is produced excess Fe oxide film on the surface layer portion of the steel sheet, the decarburized layer after annealing bloated, also excessively generated fine layer. Therefore, alloying of excessive plating proceeds, coating adhesion, chipping resistance and powdering resistance decreases. Therefore, the air ratio is preferably 1.0 or less, more preferably 0.9 or less. In the air ratio is less than 0.7, not fine layer is formed, plating adhesion is degraded. Therefore, the air ratio is preferably 0.7 or more, more preferably 0.8 or more.
[0081]
　Temperature of the steel sheet to Tsuban the preheating zone is less than 400 ° C., it is impossible to form a sufficiently fine layer. Therefore, the temperature of the steel sheet to Tsuban the preheating zone is preferably set to 400 ° C. or higher, more preferably 600 ° C. or higher. The temperature of the steel sheet to Tsuban the preheating zone is 800 ° C. greater than oxides containing coarse Si and / or Mn is formed on the surface of the steel sheet, plating adhesion is degraded. Therefore, the temperature of the steel sheet to Tsuban the preheating zone is preferably set to 800 ° C. or less, more preferably 750 ° C. or less.
[0082]
　Internal oxidation proceeds heating rate in the preheating zone is slow, coarse oxides in the interior of the steel sheet is produced. In particular, the heating rate at 600 ° C. ~ 750 ° C. is important. To suppress the coarse oxides the surface layer portion of the steel sheet is excessively decarburized is generated, the average heating rate at 600 ° C. ~ 750 ° C. preferably to 1.0 ° C. / sec or more. Is less than the average heating rate 1.0 ° C. / sec, coarse oxides miniaturization layer is generated, plating adhesion and powdering resistance is lowered. Therefore, the average heating rate is preferably between 1.0 ° C. / sec or more. From the viewpoint of suppressing the coarse oxides surface portion is excessively decarburization of the steel sheet is produced, the average heating rate is more preferably set to 1.5 ° C. / sec or more, more preferably 2.0 ° C. / sec or more to be. From the viewpoint of ensuring the processing time in the preheating zone, the average heating rate is preferably between 50 ° C. / sec or less. Average heating rate 50 ° C. / sec or less, uniform easy miniaturization layer is obtained, coating adhesion and uniformity excellent galvanized layer appearance is obtained.
[0083]
　The maximum heating temperature in annealing, for controlling the volume 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 preferably between 750 ° C. or higher. In particular, in order to obtain retained austenite, the maximum heating temperature is more preferably from (Ac1 + 50) ℃ or higher. Although the maximum upper limit of the heating temperature is not particularly limited, from the viewpoint of plating adhesion, in order to reduce the oxides generated on the surface of the base steel sheet, the maximum heating temperature is preferably 950 ° C. follows and, more preferably 900 ° C. or less.
[0084]
　Ac1 point of the steel sheet is the starting point of each austenite reverse transformation. Specifically, the Ac1 point, cut out pieces from hot-rolled steel sheet after hot rolling, heating to 1200 ° C. at 10 ° C. / sec, is obtained by measuring therebetween volume expansion.
[0085]
　The maximum heating temperature in the annealing is reached in a soaking zone. Atmosphere in the soaking is Log (P (H 2 O) / P (H 2 for controlling)) to -1.7 ~ -0.2. Log (P (H 2 O) / P (H 2 )) is less than -1.7, not fine layer formation, coating adhesion is reduced. Thus, Log (P (H 2 O) / P (H 2 )) is preferably a -1.7 or more. Log (P (H 2 O) / P (H 2 in)) is -0.2 than the decarburization progresses excessively, with the hard phase in the surface layer of the base steel sheet is significantly reduced, miniaturization layer coarse oxides are formed, coating adhesion and powdering resistance is lowered. Thus, Log (P (H 2 O) / P (H 2 )) is preferably -0.2 or less.
[0086]
Log 　in soaking (P (H 2 O) / P (H 2 )) in the -1.7 ~ -0.2, the outermost surface of Si oxide serving as a starting point for plating peeling and / or Mn oxides steel not formed in the layer, Si and / or fine oxide of Mn a maximum diameter of 0.01 [mu] m ~ 0.4 .mu.m in the interior of the surface layer of the steel sheet is formed. Fine oxides of Si and / or Mn suppresses the growth of Fe recrystallization during annealing. Also, water vapor in the annealing atmosphere for decarburized surface layer of the base material steel plate, the microstructure in the surface layer of the base material steel plate after annealing becomes a ferrite phase. As a result, the surface layer of the base material steel plate after annealing, the average thickness is 0.1 [mu] m ~ 5.0 .mu.m, the mean particle size of the ferrite phase is 0.1 [mu] m ~ 3.0 [mu] m, the maximum diameter 0. is 01μm ~ 0.4μm Si and / or refinement layer containing an oxide of Mn is formed.
[0087]
　Cooling conditions before plating after reaching the maximum heating temperature to reach the plating bath is not particularly limited. In order to obtain retained austenite, suppresses the formation of pearlite and cementite. Therefore, as the cooling conditions before plating, the average cooling rate from 750 ° C. to 700 ° C. is preferably set to 1.0 ° C. / sec or more, and more preferably 5.0 ° C. / sec or more. The average upper limit of the cooling rate is not particularly limited, in order to obtain an overly large average cooling rate may also be used refrigerant that does not interfere with the special cooling equipment or plating. In this respect, the average cooling rate from 750 ° C. to 700 ° C. is preferably set to 100 ° C. / sec or less, more preferably from 70 ° C. / sec or less.
[0088]
　Following the pre-plating cooling, in order to obtain the tempered martensite, until the temperature of the steel sheet to reach the plating bath after reaching the 500 ° C., a certain time the steel plate to a predetermined temperature range as the martensitic transformation process it may be stationary. Martensitic transformation treatment temperature is preferably not more than martensitic transformation starting temperature (Ms point), more preferably from (Ms point -20) ° C. or less. Martensitic transformation treatment temperature is preferably set to 50 ° C. or higher, more preferably 100 ° C. or higher. Martensitic transformation treatment time is preferably 1 second to 100 seconds, more preferably from 10 seconds to 60 seconds. Note that martensite obtained by martensitic transformation process is changed to the tempered martensite by steel sheet entering the hot plating bath in performing plating.
[0089]
　The volume fraction of ferrite VF (%), C content (wt%) [C], Si content (wt%) [Si], Mn content (mass%) [Mn], Cr content (mass%) of [Cr], Ni content (wt%) [Ni], when Al content (mass%) and [Al], it is possible to Ms point is calculated by the following equation. Incidentally, it is difficult to measure the volume fraction of the ferrite directly during manufacture the galvanized steel sheet. Therefore, cut out pieces of the previous cold-rolled steel sheet to Tsuban a continuous annealing line, and annealed at the same temperature history as if was Tsuban the small pieces to a continuous annealing line, to measure the volume change of the ferrite in the strip , the value calculated using the measured values volume fraction of ferrite and (VF).
　Ms point [℃] = 541-474 [C] / (1-VF) -15 [Si] -35 [Mn] -17 [Cr] -17 [Ni] +19 [Al]
[0090]
　After pre-plating cooling, in order to obtain a residual austenite, it may be a predetermined time staying in a temperature range of a steel sheet as bainite transformation treatment 250 ℃ ~ 500 ℃. Bainite transformation treatment may be carried out between the annealing and plating may be carried out at the time of the post-plating cooling may be carried out both at cooling during and after plating the annealing and plating.
[0091]
　When performing bainite transformation treatment both at cooling during and after plating the annealing and plating, the sum of the residence time of the bainite transformation treatment is preferably 500 seconds or less than 15 seconds. In less than 15 seconds sum of dwell time, not advance bainite transformation enough, not sufficient residual austenite is obtained. Therefore, the sum of the residence time is preferably not less than 15 seconds, more preferably at least 25 seconds. In 500 seconds than the sum of the residence time, perlite and / or coarse cementite is produced. Therefore, the sum of the residence time is preferably not more than 500 seconds, more preferably at most 300 seconds.
[0092]
　When performing bainite transformation treatment between annealing and plating, the bainite transformation treatment temperature is 500 ° C. greater, produces pearlite and / or coarse cementite, residual austenite can not be obtained. Therefore, the bainite transformation treatment temperature is preferably between 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, more preferably 470 ° C. or less. Is less than the bainite transformation treatment temperature is 250 ° C., without proceeding to the bainite transformation is insufficient, the residual austenite can not be obtained. Therefore, the bainite transformation treatment temperature is preferably between 250 ° C. or higher. Order to promote bainite transformation effectively, bainite transformation treatment temperature is more preferably set to 300 ° C. or higher, more preferably to 340 ° C. or higher. Incidentally, after the pre-plating cooling, when performing both bainite transformation treatment and martensite transformation process, and to perform the martensitic transformation treatment prior to the bainite transformation treatment.
[0093]
　(Plating)
　Next, immersing the resulting base material steel plate in a 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 0.180% to 0.250% by weight. The effective amount of Al in the plating bath is less than 0.180 mass%, Fe-Al without alloy layer is sufficiently formed, Fe penetrates into the molten galvanizing layer, coating adhesion is impaired. Thus, the effective amount of Al in the plating bath is preferably set to 0.180 mass% or more, more preferably set to 0.185 mass% or more, further preferably 0.190 mass% or more. The effective amount of Al in the plating bath is more than 0.250 mass%, Fe-Al alloy layer at the interface between the surface and the galvanized layer of the base material steel plate is excessively generated, the coating adhesion is impaired. Thus, the effective amount of Al in the plating bath is preferably set to 0.250 mass% or less, more preferably not more than 0.240 wt%, more preferably less 0.230 mass%.
[0094]
　The plating bath, 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, 1 or more elements of Zr and REM may be contained. Depending content of each element is improved corrosion resistance and workability of the galvanized layer.
[0095]
　Is less than the plating bath temperature of 440 ° C., increases excessively, the viscosity of the plating bath, it is difficult to control the thickness of the galvanized layer, disfiguring galvanized steel sheet. Therefore, the temperature of the plating bath is preferably set to 440 ° C. or higher, more preferably 445 ° C. or higher. The plating bath temperature of 470 ° C. greater, a large amount of fumes generated, it is difficult to safely manufactured. Thus, the plating bath temperature is preferably set to 470 ° C. or less, more preferably 460 ° C. or less.
[0096]
　The temperature is lower than 430 ° C. of the steel sheet when the base steel sheet enters the plating bath, in order to stabilize the temperature of the plating bath at 440 ° C. or higher, to provide a large amount of heat in the plating bath is not practical. Therefore, the temperature of the steel sheet at the time of the base steel sheet enters the plating bath, preferably 430 ° C. or higher. To form a predetermined Fe-Al alloy layer, the temperature of the steel sheet at the time of the base steel sheet enters the plating bath, more preferably 440 ° C. or higher. Since the base material steel plate at the temperature of 480 ° C. greater than the steel sheet at the time of entering the plating bath, the temperature of the plating bath to stabilize at 470 ° C. or less, introducing equipment for heat removal a large amount of heat from the plating bath, the manufacturing cost is high. Therefore, the temperature of the steel sheet at the time of the base steel sheet enters the plating bath, preferably 480 ° C. or less. To form a predetermined Fe-Al alloy layer, the temperature of the steel sheet at the time of the base steel sheet enters the plating bath, more preferably 470 ° C. or less.
[0097]
　Temperature of the plating bath is more preferably stable at a temperature in the range of 440 ℃ ~ 470 ℃. When the temperature of the plating bath is unstable, Fe content of Fe-Al alloy layer and galvanized layer becomes uneven, the appearance of the plating layer becomes uneven, the coating adhesion is deteriorated. The temperature of the plating bath in order to stabilize, it is preferable to substantially match the temperature of the plating bath of the steel sheet at the time of entering the plating bath. Specifically, the temperature control of the limits of the actual production facility, it is desirable to be within ± 10 ℃ of temperature of the plating bath of the steel sheet at the time of entering the plating bath, ± 5 ° C. the temperature of the plating bath it is more preferably within.
[0098]
　Note that after immersion in the plating bath, for a given 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. Then cooled to room temperature. Upon cooling, the diffusion of Fe atoms from the base material steel plate to galvanized layer is hardly proceed to a temperature (350 ° C.) to produce the ζ phase is substantially stopped, in order to ensure the coating adhesion, cooling rate preferably at a 1 ° C. / sec or more.
[0099]
　After cooling to 350 ° C., in order to obtain a residual austenite may be subjected to bainitic transformation process to stop in a temperature range of 250 ℃ ~ 350 ℃. Is less than the bainite transformation treatment temperature is 250 ° C., without proceeding to the bainite transformation is insufficient, the residual austenite is not sufficiently obtained. Therefore, the bainite transformation treatment temperature is preferably between 250 ° C. or higher. Order to promote bainite transformation effectively, the bainite transformation treatment temperature is more preferably from 300 ° C. or higher. The 350 ° C. than the bainite transformation treatment temperature is, Fe atoms diffuse excessively from the base steel sheet to hot-dip galvanizing layer, coating adhesion is deteriorated. Therefore, the bainite transformation treatment temperature is preferably set to 350 ° C. or less, more preferably 340 ° C. or less.
[0100]
　To further stabilize the residual austenite, after cooling to 250 ° C. or less, may be subjected to a reheating treatment. The treatment temperature and treatment time of reheating, may be set as necessary. If it is less than reheating temperature is 250 ° C., sufficient effect can not be obtained. Therefore, the reheating treatment temperature is preferably set to 250 ° C. or higher, more preferably 280 ° C. or higher. The 350 ° C. greater reheating temperature, Fe atoms are diffused from the base material steel plate galvanized layer, coating adhesion is deteriorated. Therefore, the reheating treatment temperature is preferably set to 350 ° C. or less, more preferably 330 ° C. or less. The reheating time is 1000 seconds greater than the effect is saturated. Therefore, re-heating time is preferably not more than 1000 seconds.
[0101]
　In this way, it is possible to manufacture a galvanized steel sheet according to the embodiment of the present invention.
[0102]
　In embodiments of the present invention, for example, 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 good. Film comprising phosphorus oxide and / or composite oxide containing phosphorus, can function as a lubricant when processing galvanized steel sheet, protects the galvanized layer formed on the surface of the base material steel plate be able to.
[0103]
　In an embodiment of the present invention, for example, the galvanized steel sheet was cooled to room temperature, the reduction rate may be subjected to cold rolled or less 3.00% for straightening.
[0104]
　The method for producing a hot-dip galvanized steel sheet according to the embodiment of the present invention is preferably the thickness of the base material steel plate is applied to the manufacture of hot-dip galvanized steel sheet is less than 5.0mm or 0.6 mm. The thickness is less than 0.6mm of the base material steel plate, it may become difficult to maintain the shape of the base material steel plate flat. In the plate 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 and plating becomes difficult.
[0105]
　The above embodiments are all merely illustrate concrete examples of implementing the present invention, in which technical scope of the present invention should not be limitedly interpreted. That is, the present invention is its technical idea or without departing from the essential characteristics thereof, can be implemented in various forms.
Example
[0106]
　Next, a description will be given of an embodiment of the present invention. Conditions in examples are 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, it is capable of adopting various conditions.
[0107]
　Table 1 - Chemical composition shown in Table 4 were cast (steel types A ~ grades AT) slabs having, hot rolled under the conditions shown in Table 5 and Table 6 (slab heating temperature, rolling completion temperature), 5 and Table Table conditions shown in 6 (average cooling rate from the hot rolling finished to coiling, the coiling temperature) was cooled in to obtain hot-rolled steel sheet. Thereafter, using 10% hydrochloric acid 80 ° C., at pickling time shown in Tables 5 and 6, subjected to a pickling hot-rolled steel sheet is subjected to cold rolling at a reduction ratio shown in Tables 5 and 6, cold rolled to obtain a steel plate. Table 1 Underline in through Table 4 indicates that the numerical value is outside the scope of the present invention. The remainder of the steel types A ~ grades AT was the Fe and impurities. Underlined in Table 5 to Table 6 indicates that the numerical value is outside the range suitable for producing a galvanized steel sheet.
[0108]
　Next, the obtained cold-rolled steel sheet, the conditions shown in Table 7 and Table 8 (air ratio in the preheating zone, the preheating completion temperature in the preheating zone, Log in preheating zone atmosphere (P (H 2 O) / P ( H 2 )), Log in reduction zone atmosphere (P (H 2 O) / P (H 2 annealing in)), the average heating rate in a temperature range of 600 ° C. ~ 750 ° C., the maximum heating temperature (Tm)) gave. Note that completion of preheating temperature of Experimental Examples 1 to 50 were in the range of 623 ° C.-722 ° C.. Then, the conditions shown in Tables 7 and 8 (average cooling rate in the temperature range of the cooling rate 1 (750 ℃ ~ 700 ℃) , average cooling rate in the temperature range of the cooling rate 2 (700 ℃ ~ 500 ℃) , bainite transformation treatment 1 conditions (treatment temperature, treatment time) was subjected to cooling treatment at the martensitic transformation (processing temperature, processing time)). Note that the bainite transformation treatment 1, the steel sheet was not subjected to martensitic transformation process, the condition column of the process in Table 7 and Table 8 - was described as "". Table 7 underlined in through Table 8 indicates that the numerical value is outside the range suitable for producing a galvanized steel sheet.
[0109]
　Then, the plating conditions shown in Tables 9 and 10 (effective Al amount, the temperature of the plating bath (bath temperature), enters the temperature of the steel sheet, immersion time) was immersed in a zinc plating bath, the plated. After plating, the conditions shown in Table 9 and 10 (average cooling rate in the temperature range of the cooling rate (after plating steel sheet temperature of ~ 350 ° C.), bainite transformation treatment two conditions (treatment temperature, treatment time), reheating treatment conditions (treatment temperature, was subjected to cooling treatment in the processing time)). Note that the bainite transformation treatment 2, for the steel sheets not subjected to reheating, the condition column of the processing table 9 and in Table 10 - was described as "". Moreover, subjected to cold rolling at a reduction ratio shown in Table 9 and Table 10, to obtain a hot-dip galvanized steel sheets of Experimental Examples 1 to 97. However, in some experimental examples, some of which was interrupted experiments. Tables 9 and 10 in Table underline indicates that the numerical value is outside the range suitable for producing a galvanized steel sheet.
[0110]
　The obtained plated steel sheets (Experimental Examples 1 to 97), was observed in the microstructure and galvanized layer of the base material steel plate. Table 11 and Table 12 shows the observation results of microstructure and galvanized layer of the base material steel plate. Underlined in Table 11 and in Table 12 indicates that the number is out of range of the present invention.
[0111]
　First, samples were taken in which the viewing surface of a cross section parallel to the rolling direction of the base material steel plate from galvanized 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), the surface of the base material steel plate, the plate thickness of the base material steel plate 1/8 observing the microstructure in the thickness 1-3 / 8 range of thickness, it was identified constituencies. In Table 13 and Table 14, 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.
[0112]
　It was also collected pieces of 25 mm × 25 mm from the galvanized steel sheet as a test piece. 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.
[0113]
　Coating weight of plating is to melt the hot-dip galvanized layer with hydrochloric acid inhibitor containing, was determined by comparing the weights before and after melting. Further, by quantifying the Fe and Al in ICP, it was measured Fe concentration and the Al concentration in the molten galvanizing layer.
[0114]
　Moreover, the galvanized steel sheet, samples were taken in which the viewing surface of a cross section parallel to the rolling direction of the base material steel plate, using the measuring method described above, the interface between the surface and the galvanized layer of the base material steel plate the average thickness of the formed Fe-Al alloy layer, and the difference between the maximum value and the minimum value of the thickness of the Fe-Al alloy layer in the width direction of the base material steel plate, miniaturization layer in contact with the Fe-Al alloy layer and the average thickness, the difference between the maximum thickness and the minimum value of the refinement layer in the width direction of the base material steel plate, and an average particle size of the ferrite phase in the fine layer of Si and Mn in fine layer of the calculated maximum value of the diameters of one or more oxides. The results are shown in Tables 11 and 12.
[0115]
　Next, in order to examine the properties of galvanized steel sheet, tensile test, the hole expansion test, bending test, adhesion evaluation test, spot welding test, corrosion test, chipping resistance test, powdering resistance test uniformity evaluation of coating appearance It was carried out. Table 13 and Table 14 shows the characteristics in each of the experimental examples.
[0116]
　Tensile test, creates a No. 5 test piece described in JIS Z 2201 from the galvanized steel sheet, conducted by the method described in JIS Z 2241, the yield strength (YS), maximum tensile strength (TS), total elongation (El ) was determined. The tensile properties, tensile maximum strength (TS) was evaluated in the case of more than 420MPa as good.
[0117]
　Hole expansion test was conducted by the method described in JIS Z 2256. Among the formability, ductility (total elongation) (El) and hole expandability (lambda) varies with the maximum tensile strength (TS), but the strength in the case satisfies the formula (2) below, the ductility and hole the expandability was considered good.
　TS 1.5 × El × lambda 0.5　≧ 2.0 × 10　　6 · · · formula (2)
[0118]
　Plating adhesion, compared galvanized steel sheets gave a tensile strain uniaxial 5%, was subjected to DuPont impact test. Galvanized steel sheet after impact test to joining the adhesive tape, then peeling, a case where plating is not peeled particularly good (◎) and then, the case where the plating is peeled off by 5% or more and poor (×), plating peeling was the case of less than 5% better (○). 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.
[0119]
　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 where is 0.90 or more good (○), and the case of less than 0.90 and bad (×).
[0120]
　The evaluation of the corrosion resistance, using a test piece cut out of galvanized steel sheet 150 mm × 70 mm. The test piece was subjected to dip-type chemical conversion treatment of zinc phosphate, followed 20μm subjected to cationic electrodeposition coating, after subjecting 35 [mu] m of intercoat, a topcoat of 35 [mu] m, the back surface and the end was sealed with electrical tape. The corrosion resistance test was used SST6hr, dried 4hr, wet 4hr, the CCT to one cycle refrigeration 4hr. Evaluation of corrosion resistance after painting, subjected to crosscut reaching the base steel sheet with a cutter to painted surfaces, was measured swelling width after CCT60 cycles. Where blistering width of 3.0mm or less was considered good (○), and in the case of 3.0mm greater than the bad (×).
[0121]
　Chipping resistance was evaluated using a test piece cut out hot-dip galvanized steel sheet to 70 mm × 150 mm. First, were conducted on specimens, degreasing automotive, formation of chemical conversion film, a three-coat paint. Then, while cooling holding the test piece to -20 ° C., 2 kgf / cm 2 of crushed stone in air pressure (0.3 g ~ 0.5 g) was irradiated ten vertically. Irradiation of crushed stone was repeated five times for each specimen. Thereafter, each test piece, and observing the total of 50 chipping mark was evaluated according to the following criteria based on the position of the peeling interface. Peeling boundary is above the galvanizing layer (galvanized layer - interface conversion coating, or electrodeposition coating - intercoat interface paint) what is considered good (○), the plating layer - the interface delamination at base iron what is even one was as bad (×).
[0122]
　Powdering property, in order to evaluate the workability of hot-dip galvanizing layer was evaluated using the V bending (JIS Z 2248). The galvanized steel sheet was cut into 50 mm × 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 galvanizing layer is as good as 5% or less of the processing unit area (○), peeling of the galvanized layer has poor things than 5% relative to the processing unit area (×) .
[0123]
　Uniformity Evaluation appearance, the brightness of the eight points of the position where the position and therebetween 50mm from both edges 7 equal parts in the width direction of the steel sheet (L * value) was measured, by subtracting the minimum value from the maximum value difference good of less than 5 (○), somewhat poor (△) those 5 or more and less than 10, and those 10 or more defective (×).

WE claims

[Requested item 1]
　A galvanized steel sheet having at least one hot-dip galvanizing layer on the side of the base material steel plate,
　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%, S:
　0.0001% ~ 0.0100%, Al: 0.001% ~
　% 1.500,
　N: 0.0001%
　~ 0.0100%, O: 0.0001% ~ 0.0100%, Ti:
　0.000% ~ 0.150%, Nb: 0.000% ~ 0.
　Pasento 100,
　V:
　0.000 Pasento ～ 0.300 Pasento, Cr: 0.00 The Pasento ～ 2.00 Pasento,
　Ni: 0.00 The Pasento ～ 2.00 Pasento, Cu: 0.00 The Pasento ～ 2.00 Pasento ,
　Mo:
　0.00 The Pasento ～ 2.00 Pasento, B: 0.0000 Pasento
　～ 0.0100 Pasento, W: 0.00 The Pasento ～ 2.
　% 0, Ca, Ce, Mg, Zr, La and REM: 0.0000% ~ 0.0100% in total, and
　balance: Fe and impurities,
Has a chemical composition expressed in,
　the Fe content in the molten galvanizing layer is not more than 0% and 3.0% Al content of not more than 0% and 1.0%,
　the hot-dip galvanized has a Fe-Al alloy layer at the interface between the the layer base material steel plate,
　the thickness of the Fe-Al alloy layer becomes 0.1 [mu] m ~ 2.0 .mu.m,
　the in the width direction of the base material steel plate Fe- the difference between the maximum value and the minimum value of the thickness of the Al alloy layer is within 0.5 [mu] m,
　the base material in the steel sheet has a fine layer in direct contact with the Fe-Al alloy layer, the fine layer average thickness of 0.1 [mu] m ~ 5.0 .mu.m of the an average particle diameter of 0.1 [mu] m ~ 3.0 [mu] m of the ferrite phase in the finer layer, one of Si and Mn in the fine layer or containing seeds or more oxides, the maximum diameter of the oxide is 0.01 [mu] m ~ 0.4 .mu.m,
　the mother Galvanized steel sheet, wherein a difference between the maximum value and the minimum value of the thickness of the finer layer in the width direction of the steel sheet is within 2.0 .mu.m.
[Requested item 2]
　The base steel sheet is, Si content (wt%) [Si], satisfy the equation 1 below when the Al content (mass%) and [Al],
　relative to the total thickness of the base material steel plate , according to claim 1, wherein the residual austenite at 1/8 thickness 1-3 / 8 thickness range around the 1/4 thickness from the surface of the base steel sheet is 1% or more by volume fraction hot-dip galvanized steel sheet.
　[Si] +0.7 [Al] ≧ 0.30 ( Equation 1)
[Requested item 3]
　Coating weight per one side in the hot-dip galvanized layer is 10 g / m 2 or more 100 g / m 2 hot-dip galvanized steel sheet according to claim 1 or 2, wherein the or less.
[Requested item 4]
　In the chemical
　composition,
　Ti: 0.001% ~ 0.150%, Nb: 0.001% ~ 0.100%, or
　V: 0.001% ~ 0.300%,
　or any combination thereof satisfied galvanized steel sheet according to any one of claims 1 to 3, characterized in that.
[Requested item 5]
　In the chemical
　composition,
　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%, or
　W: 0.01% ~ 2.00%,
　or any one of claims 1 to 4, characterized in that any combination of these are met hot-dip galvanized steel sheet according to item 1.
[Requested item 6]
　In the chemical
　composition, Ca, Ce, Mg, Zr, La and REM: 0.0001% ~ 0.0100% in total
　melt according to any one of claims 1 to 5, characterized in that is satisfied zinc-plated steel plate.