Technical field
[0001]
The present invention relates to a high strength galvanized steel sheet, a high strength galvanized steel sheet, more particularly having excellent impact resistance and plating adhesion, various applications, relates to a plated steel sheet that can be applied, for example, as an automobile strength member.
BACKGROUND
[0002]
　Galvanized steel sheet, including the automotive, are frequently used home appliances, building materials and the like. The automotive steel sheet pressed into complex shapes, applied with a very high formability is required, by in recent years has increased demand for automotive rustproof performance, galvanized steel sheet for automobile steel sheets case has increased to be.
[0003]
　In recent years, from the viewpoint of vehicle body weight reduction, expanding demand for high-strength steel sheet excellent in strength and ductility. For example, Patent Document 1, the steel sheet microstructure, the ferrite phase, bainite phase, and steel sheets and organizations three phases of austenite phase are mixed is disclosed. Further, the steel sheet, during molding, the residual austenite that has been disclosed is a steel sheet utilizing transformation induced plasticity exhibiting high ductility by the transformation to martensite.
[0004]
　Steel of this type, for example, C from 0.05 to 0.4 mass%, 0.2-3.0 mass% of Si, and Mn and 0.1 to 2.5 mass%, 2-phase region after annealing, the form the composite structure by controlling the temperature pattern of the cooling process. Therefore, without using an expensive alloy element, and a feature that the required properties can be secured. Recently, even in such a high-strength steel sheet, in order to ensure the corrosion resistance was galvanized steel sheet base metal surface, expanding demand for high-strength galvanized steel sheet.
[0005]
　Such high-strength steel sheet, not only the strength member of the inner plate applications, a shock possible from stones and obstacles come flying at the time of vehicle running, even increased chance of being applied as an outer surface member ing. Furthermore, when applied to complicated-shaped member, a high workability is required. For high-strength galvanized steel sheet, and when receiving an impact from stones and obstacles flying during running, assuming coating adhesion, such as during heavy working, not only the usual 60 ° V bending test, ball impact test and, coating adhesion is required to be secured in harsh evaluation methods such as drawbead test.
[0006]
　Furthermore, 180 in the very severe working receiving sites such as ° bent top part, since the cracks in the plating and base steel, even after subjected to chemical conversion treatment and electrodeposition coating, from the site corrosion is likely to occur. If corrosion little in the region occurs, it occurs hydrogen penetration than the corroded portions, especially if the base material is a high strength steel sheet, increased risk of hydrogen embrittlement cracking.
[0007]
　If the high-strength steel sheet subjected to galvanizing in a continuous galvanizing line, the Si content of the steel sheet exceeds 0.3 mass%, the plating wettability is greatly reduced. Therefore, in the Sendzimir method using a conventional Al-containing plating bath, and non-plating occurs, there is a problem that the appearance quality is deteriorated. Further, in order to significantly reduced at the same time coating adhesion, ensuring the coating adhesion at the time of impact or when heavy working has been difficult.
[0008]
　This is during reduction annealing, the steel sheet surface, an external oxide film containing an oxide wettability contains bad Si and Mn that are produced are said to be responsible for the melted Zn.
[0009]
　As means for solving this problem, Patent Document 2, in advance, by heating the steel sheet in an atmosphere of air ratio 0.9-1.2, to produce a Fe oxide, then, H 2 reduction zone comprising in, after the thickness of the oxide to 500Å or less, a method of performing plating in a bath with the addition of the Mn and Al have been proposed. However, the real line, since Tsuban various steel sheets containing various additive elements, it is difficult to control the precisely the thickness of the oxide, narrow manufacturing conditions range in the actual machine, a problem that It was. Although the effect of improving the plating adhesion of wettability and normal processing can be expected, the effect of improving the plating adhesion upon impact or during strong working was small.
[0010]
　Other non-coating suppression means, Patent Document 3, by applying a specific plating to lower, a method of improving the plating properties is disclosed. However, in this method, the hot dip plating line, in front of the annealing furnace, fresh, or providing the plating equipment, or, in the electroplating line, it is necessary to perform the pre-plating process. In any case, it expected to increase in significant manufacturing cost. Moreover, and plating adhesion upon impact or during large deformation, the effect of improving the working portion corrosion resistance was small.
[0011]
　On the other hand, Patent Document 4, during annealing, to adjust the oxygen potential of the annealing atmosphere, without oxidizing the Fe in the steel sheet, method of producing the hot-dip galvanized steel sheet is disclosed. In this approach, the oxidizable elements Si and Mn, etc. in the steel, is internally oxidized by controlling the oxygen potential of the atmosphere, by suppressing the formation of an external oxide film, to achieve an improvement in plating properties there. By applying this technique, although it guarantees sufficient adhesion at the time of normal processing, plating adhesion upon impact or during strong working, also the effect of improving the working portion corrosion resistance could not be expected.
CITATION
Patent Document
[0012]
Patent Document 1: JP-A-05-59429 JP
Patent Document 2: JP-A-04-276057
Patent Document 3: JP 2003-105514 Patent Publication
Patent Document 4: Japanese Patent No. 4718782
Summary of the Invention
Problems that the Invention is to Solve
[0013]
　The present invention was made in view of the situation as described above, and an object thereof is to provide a shock peeling resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
Means for Solving the Problems
[0014]
　The present inventors have conducted extensive studies in order to solve the above problems. As a result, even with a steel sheet containing Si and Mn in a large amount as be plated, by forming the convex alloy layer in the plating layer of high-strength hot-dip galvanized steel sheet, the impact time and intensity coating adhesion during processing and found that remarkably improved. Further, the structure of the concurrently plate matrix side, the fine layer, the decarburized layer, by controlling the three-layer structure of the inner layer, such as a 180 ° bend parietal, even in the processing of an extremely severe strain on, It was found to significantly suppress the generation and extension of cracks penetrating to the plating layer surface of the base material as a starting point. Further, a plating layer and the steel sheet base material by the above structure, while maintaining a high strength of 590 MPa, found an effect of remarkably improving the working portion corrosion resistance and without the invention.
[0015]
　The present invention has been made based on the above findings and has as its gist is as follows.
[0016]
(1)
C: 0.05 ~ 0.4
wt%, Si: 0.4 ~ 3.0
mass%, Mn: 1.0 ~ 4.0
mass%, P: 0.0001 ~ 0.1 weight% ,
S: 0.0001 ~ 0.01
mass%, Al: 0.005 ~ 0.1
wt%, N: 0.0005 ~ 0.01
mass%, O: 0.0001 ~ 0.01 mass%
containing and, the balance being Fe and unavoidable impurities,
　on the tension plate matrix strength is not less than 590 MPa, Fe: 0.01 ~ 6.9 wt%, Al: 0.01 ~ 1.0 wt%, the balance a high strength galvanized steel sheet having a galvanized layer composed of Zn and unavoidable impurities,
　the plating layer has a convex alloy layer in contact with the plate matrix, the number density of the convex alloy layer section 4 per unit length of the interface plate matrix and the plating layer as seen from the direction is at / mm or more, the interfacial Maximum diameter of the convex alloy layer is not more 100μm or less in,
　the steel sheet base material, and a fine layer in direct contact with the interface between the plate matrix and the plating layer,
　in contact with the fine layer, of the plate matrix a decarburized layer existing in a square side,
　said and a fine layer and internal layers other than the decarburized layer,
　wherein the 0.1 ~ 5 [mu] m average thickness of the finer layer, the average particle of the ferrite phase in the finer layer diameter of 0.1 ~ 3μm,
　The decarburized layer average thickness 10 ~ 200 [mu] m of the average particle size of the ferrite phase in decarburized layer within a is 5 ~ 30 [mu] m, the average volume fraction of the ferrite phase in the decarburized layer is 70% or more, the remaining structure is austenite , bainite consists martensite or pearlite,
　the ratio Hv (surf) / Hv (bulk ) of 0.3 to 0 mean decarburized layer Vickers hardness Hv mean (surf) and the inner layer Vickers hardness Hv (bulk). is 8,
　the fine layer, the decarburized layer, and the layer on the convex alloy layer, characterized in that it contains one or more oxides of Si and Mn, impact resistance and processing unit high-strength galvanized steel sheet excellent in corrosion resistance.
[0017]
(2)
　the fine layer, oxide containing in a layer of the decarburized layer, and the convex alloy layer, SiO 2 , Mn 2 SiO 4 , MnSiO 3 , Fe 2 SiO 4 , FeSiO 3 , 1 species of MnO or and characterized in that two or more, a high strength galvanized steel sheet excellent in impact resistance and processing unit corrosion resistance according to (1).
[0018]
(3)
　contained in the convex alloy layer, the maximum diameter of the oxide is 0.05 ~ 0.4 .mu.m, the number density of 20 to 100 / [mu] m 2 , characterized in that a, the (1) or (2) according to, impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
[0019]
(4)
　the contained finer layer, the maximum diameter of the oxide is 0.01 ~ 0.2 [mu] m, the number density of 20 to 100 / mm 2 , characterized in that a, (1) to (3) according to any, impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
[0020]
(5)
　wherein the outermost surface of the galvanized layer, characterized in that there is no convex alloy layer, wherein according to any one of (1) to (4), excellent impact resistance and machining portion corrosion resistance high-strength hot-dip galvanized steel sheet.
[0021]
(6)
　plate matrix
further, Ti: 0.001 ~ 0.15
wt%, Nb: 0.001 ~ 0.10 wt%,
characterized in that it contains one or two of the ( 1) to according to any one of (5), impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
[0022]
(7)
　plate matrix
further, Mo: 0.01 ~ 2.0
wt%, Cr: 0.01 ~ 2.0
wt%, Ni: 0.01 ~ 2.0
wt%, Cu: 0.01 to 2.0
mass%, B: 0.0001 ~ 0.01 mass%,
characterized in that it contains one or more, according to any one of (1) to (6), impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
Effect of the invention
[0023]
　High strength galvannealed steel sheet of the present invention is a high strength steel sheet containing Si and Mn in a large amount is set to the original plate, it is possible to secure the plating adhesion upon impact or during strong working, also 180 ° also in extremely severe working unit such as a bent top portion, showing excellent processing unit corrosion, which made it possible to provide a high strength galvannealed steel sheet, the inner and outer plates and high-strength member for an automobile it is very effective as applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024]
FIG. 1 is a diagram showing an example of a schematic view of a cross-sectional structure of the high strength galvanized steel sheet of the present invention.
A cross-sectional photograph of FIG. 2 inner layer of a cross-sectional photograph and present invention Examples of the internal layer of the comparative example.
DESCRIPTION OF THE INVENTION
[0025]
　Hereinafter, according to an embodiment of the present invention will be described in detail for the high strength galvanized steel sheet and a manufacturing method thereof having excellent impact delamination resistance and processing unit corrosion.
[0026]
　High-strength hot-dip galvanized steel sheet of the present
invention, C: 0.05 ~ 0.4
wt%, Si: 0.4 ~ 3.0
mass%, Mn: 1.0 ~ 4.0
mass%, P: 0 .0001 to 0.1
wt%, S: 0.0001 ~ 0.01
mass%, Al: 0.005 to 0.1
wt%, N: 0.0005 - 0.01
mass%, O: 0.0001 ~ 0.01 wt%
and containing the balance being Fe and unavoidable impurities,
　on the tension plate matrix strength is not less than 590 MPa, Fe: 0.01 - 6.9 wt%, Al: 0.01 to 1.0 mass%, a high strength galvanized steel sheet having a galvanized layer and the balance Zn and unavoidable impurities,
　the plating layer has a convex alloy layer in contact with the plate matrix, convex unit length equivalent of the interface number density of Jo alloy layer and the steel base material as viewed from a cross-sectional direction plating layer Ri is 4 particles / mm or more, there is a maximum diameter of the convex alloy layer 100μm or less in the interface,
　the steel sheet base material, and a surface in direct contact with the fine layer of the plate matrix plating layer,
　wherein contact with the fine layer, and the decarburized layer present on the inner side of the plate matrix,
　wherein and a fine layer and non-decarburized layer of the inner layer,
　wherein the 0.1 ~ 5 [mu] m average thickness of the fine layer , an average particle diameter of 0.1 ~ 3 [mu] m of the ferrite phase in the finer layer,
　The decarburized layer average thickness 10 ~ 200 [mu] m of the average particle size of the ferrite phase in decarburized layer within a is 5 ~ 30 [mu] m, the average volume fraction of the ferrite phase in the decarburized layer is 70% or more,
　the remaining structure is austenite , bainite consists martensite or pearlite,
　the ratio Hv (surf) / Hv (bulk ) of 0.3 to 0 mean decarburized layer Vickers hardness Hv mean (surf) and the inner layer Vickers hardness Hv (bulk). is 8,
　the fine layer, the decarburized layer, and the layer in the convex alloy layer, characterized in that it contains one or more oxides of Si and Mn.
　In the high-strength galvanized steel sheet of the present invention, the plating layer shows a fine layer, the decarburized layer, and a cross-sectional schematic view of an inner layer in FIG.
[0027]
"Convex-shaped alloy layer in the plating layer"
　In the high strength galvanized steel sheet of the present invention, by incorporating the convex alloy layer on the plating layer, it is possible to secure the plating adhesion upon impact or during large deformation. By the convex alloy layer 2 as shown in FIG. 1 contained in the plating layer, it is possible to form large irregularities at the interface of the steel sheet base material and the plated layer, shocked or large deformation, plate matrix and even when a strong shearing stress toward the interface worked plating layer, the effect of improving the remarkable coating adhesion by an anchor effect can be expected. The form of the convex alloy layer 2, than coarse convex alloy layer is formed sparsely in the form of small convex alloy layer is dispersed, higher anchoring effect can be expected. Therefore, the maximum diameter of the convex alloy layer 2 at the interface of the base material 4 and the plating layer 1 shown in 3 of FIG. 1, can not be expected valid anchor effect too large in the case of 100μm greater. Maximum length of the order convex alloy layer the upper limit of the (maximum diameter 3) was 100 [mu] m. Preference is given to the upper limit is 40 [mu] m. Further, there is no particular limitation on the convex alloy layer 2 of the maximum length of the lower limit is preferably set to 3μm or more. Regarding also the number density of the convex alloy layer, the steel sheet of the base material and the plated layer interface and when viewed from the cross-sectional direction, by four or more per interface length 1mm of plate matrix and the plating layer, adhesiveness effect of improving is expressed. On the other hand, the number density of the convex alloy layer 100 pieces / mm greater, not only the effect is saturated, thereby potentially exacerbating the chipping resistance. Therefore, it is desirable that the upper limit of the number density of the convex alloy layer and 100 / mm. Preference is given to a range of 10 to 60 / mm. As shown in FIG. 1, the convex alloy layer 2 is in contact at the interface of the base material 4 and the plating layer 1 has a intruded structure in a convex shape in the plating layer 1 from the interface. Convex alloy layer 2, as long as it enters the plating layer 1 in contact with the surface 3, the shape is arbitrary. Convex alloy layer 2 is in contact without the intervention of the Fe-Al phase in the interface between the base material 3, since it protrudes into the plating layer 1, it is believed to improve the coating adhesion by an anchor effect.
[0028]
　Convex alloy layer in the present invention, as described below, in which was formed by applying a mild alloying heat treatment after the plating bath immersion. In the plating bath, directly crystallized form at the interface between the molten zinc and the steel base material, columnar ζ phase fine (FeZn 13 ) and δ1 phase (FeZn 7 ) of the fine columnar crystals (hereinafter, the bath crystals Desho ) it may be co-located with the convex alloy layer but not in any way adversely affect the effects of the present invention, the effect of enhancing adhesion upon impact or during strong working can not be expected. Therefore, to distinguish the convex alloy layer and the bath crystals Desho, convex alloy layer has a thickness thereof 2μm or more and Fe-Al phase forming the interface between the convex alloy layer and the steel sheet base material those that are not, to be defined. There is no particular limitation on the upper limit of the thickness of the convex alloy layer, but is preferably not greater than 90% of the plated layer total thickness. Directly crystallized form at the interface between the convex alloy layer and the steel sheet base material, there is no Fe-Al phase between the interface. Convex alloy layer for contacting directly without going through the base material and Fe-Al phase, is considered to be effective in improving adhesion.
[0029]
　The types of phase constituting the convex alloy layer, is not particularly limited, is an intermetallic compound phase of FeZn system, zeta phase (FeZn 13 ), .delta.1 phase (FeZn 7 ), .GAMMA.1 phase (Fe 5 Zn 21 ), gamma phase (Fe 3 Zn 10 selected from), more preferably a single phase structure or multiphase structure.
[0030]
"Measurement method of the convex alloy layer"
　method of measuring the maximum length and number density of the convex alloy layer is etched with 0.5% nital after section embedded polishing, and photographed by optical microscope of 200 magnifications, the unit obtaining the number density per length. Further, in the same photograph, measuring the maximum length of the convex alloy layer. By shooting five photograph 200 times for one sample to measure the length of the convex alloy layer for each of the maximum value among them, in the sample, the maximum length of the convex alloy layer.
[0031]
　Further, the convex alloy layer is produced by alloying reaction from the interface of the plating layer and the steel sheet base material, the convex alloy layer reaches the resurfacing of the plated layer reduces the surface gloss, appearance uniformity decreases . Therefore, in the high strength galvanized steel sheet of the present invention, it is more preferred that there is no protruding alloy layer on the outermost surface of the galvanized layer.
[0032]
"Fe concentration in the plating layer"
　mentioned above, in the high strength galvanized layer of the present invention, the form control convex alloy layer is important. By the Fe concentration is 0.01% by mass or more, it can be contained convex alloy layer on the plating layer. Also the Fe concentration progress Some alloying reaction until plating layer surface to more than 6.9 mass%, the effect of improving coating adhesion is reduced. For this reason, the Fe concentration in the coating layer limited to the range of 0.01 to 6.9 wt%. Preferably be 2.0 to 6.9 mass%.
[0033]
"Al concentration in the plating layer"
　Al concentration in the plating layer can not control the excessive Fe-Zn reaction in the plating bath, the structural control of the plating layer becomes difficult is less than 0.01 wt% . Further, the Al concentration is 1.0 wt%, dense Al in the plating layer surface 2 O 3 for the film to form, there is a possibility of inhibiting the spot weldability. From the viewpoint of structural control of the plating layer, it is more preferable that the Al concentration in the plating layer of 0.03 wt% to 0.8 wt%. More preferably, in a range of from 0.1 wt% to 0.5 wt%.
[0034]
"Other unavoidable impurities"
　in the embodiments of the present invention, the galvanized layer, Pb, Sb, Si, Sn , Mg, Mn, Ni, Cr, Co, Ca, Cu, Li, Ti, Be, Bi, sr, in, Cs, or may be one or containing two or more REM, or mixed. Etc. galvanized layer, contain one or two or more of said elements, or even those mixed, the effect of the present invention is not impaired, the corrosion resistance and workability can be improved by that amount The preferred case also.
[0035]
"Plating composition measuring method"
　to measure the Fe concentration in the coating layer, and Al concentration, the plating layer was dissolved in 5% HCl aqueous solution was added inhibitor may be quantified by the solution to ICP analysis .
[0036]
"Structure of the steel sheet base metal"
　in the high-strength galvanized steel sheet of the present invention, the structure of the steel base metal will be described in detail.
[0037]
"Fine layer"
　as shown in FIG. 1, in the high strength galvanized steel sheet of the present invention, the steel base metal has a fine layer 5 in direct contact with the surface of the plate matrix and the plating layer. Are a layer consisting of very fine grains finer layer 5 in the main ferrite phase is formed, such as 180 ° bent top part, even a portion of the extremely severe strain on crack from the inside plate matrix it is possible to suppress generation and the subsequent crack extension.
[0038]
　By the average thickness of the fine layer and above 0.1 [mu] m, the effect of suppressing express cracking or stretching during processing. Also be 5μm than the average thickness of the finer layer is in the plating bath, excessive alloying proceeds, the plating layer structure can not be obtained in the present invention. It is therefore defined as the average thickness of the fine layer in the range of 0.1 ~ 5 [mu] m. Preferably in a range of from 0.1 ~ 3 [mu] m average thickness of the fine layer. Further, by setting the average particle size of the ferrite phase of the finer layer and above 0.1 [mu] m, the effect of suppressing cracking and stretch at the time of processing is expressed, its effect is limited when the 3μm greater. Therefore the average particle size of the ferrite phase of the finer layer is limited to a range of 0.1 ~ 3 [mu] m. It is preferably in a range of 0.1 ~ 2 [mu] m.
[0039]
　In the present invention, to produce a fine layer and a decarburized layer as described later, annealed at conditions controlled to a specific atmosphere at a specific temperature range in the annealing step. As a result, at a certain temperature range, the decarburization reaction proceeds in the plate matrix surface. Since the plate matrix in fine layer is decarburized, the constituent phases of the finer layer except for oxide or inclusion particles are substantially ferrite phase of the metallic tissue.
[0040]
　In the present invention, the effect of the presence of fine layer on the steel sheet base metal is to suppress the cracks and stretch when large deformation as described above. At the same time, the plate matrix surface to refine the ferrite grain size in the heat alloying treatment step after hot-dip galvanizing for forming the convex alloy layer, and the plate matrix galvanized layer Fe- It has the effect of promoting Zn alloying reaction. Therefore, in the state of having a fine layer, the heat input required for the formation of the convex alloy layer is kept low, it is possible to lower temperature the heating temperature in the alloying process. When the low temperature of the heating temperature in the alloying process, for Fe-Zn reaction rate decreases, the convex alloy layer becomes easy to reduce the reaction before covering the entire plating layer, which can be manufactured You can increase the range of conditions.
[0041]
"Method of measuring fine layer"
　To measure the finer layer, a cross section processed by CP (Cross section polisher) device, observing the reflected electron image with FE-SEM (Field Emission Scanning Electron Microscopy) in 5000-fold and it may be measured an average crystal grain size of the ferrite phase having an average thickness and miniaturization layer of fine layer. Definition of the fine layer has an average particle size of the ferrite phase in the steel sheet base material the uppermost portion is the case in the decarburized it is 1/2 or less of the average particle size of the ferrite phase is defined as the finer layer is present. The average particle size of the ferrite phase in the finer layer, the extra half to become a boundary of an average particle size of the ferrite phase in the decarburized layer is defined as finer layer and decarburized layer boundary.
[0042]
"Decarburized layer"
　in the high-strength galvanized steel sheet of the present invention, as shown in FIG. 1, decarburized layer 6 is present. Decarburized 6 Internal layer 7 hard phase compared to the (remaining structure 9) the volume fraction is low in, for strength is also low, the 180 ° bent head top portion, the starting point of cracks even in severe strain on the less likely, it is possible to suppress the generation of cracks 180 ° bent head top portion. The average thickness of the decarburized layer With more than 10 [mu] m, expressed the effect of suppressing crack generation in 180 ° bent top part, when 200μm greater characteristics of decarburized layer lowers the tensile strength of the entire plate matrix put away. For this reason it is limited to a range of 10 ~ 200μm. Preferably, in a range of from 30 ~ 150 [mu] m.
[0043]
"Steel sheet structure in the decarburized layer"
　in the decarburized layer 6 is mainly as a ferrite phase 8 is shown in FIG. 1, the austenite phase remaining structure 9, bainite phase, martensite phase, one of pearlite or 2 occupied by more species, a mixed organization. In decarburized 6 the volume fraction of the ferrite phase by 70% or more, the average hardness of the decarburized layer 6 is lowered sufficiently relative to the inner layer 7, the effect of suppressing crack generation in the 180 ° bent top portion express. The average particle size of the ferrite phase in the decarburized layer is poor in the effect of softening the decarburized layer is less than 5 [mu] m. Also there is a possibility that poor low-temperature toughness of the average particle size of the ferrite phase in the decarburized layer and 30μm greater. Therefore, the average particle size of the ferrite phase in the decarburized layer is limited to the range of 5 ~ 30 [mu] m. Further, the decarburized layer by the structure of this invention, the ratio of the average Vickers hardness Hv of de average coal seam Vickers hardness Hv (surf) and inner layer (bulk) Hv a (surf) / Hv (bulk) 0 It may range from .3 to 0.8. In 180 ° bent top part, in order to suppress the occurrence of cracks near the interface of the plating layer surface and the plate matrix, it is necessary to lower the hardness of the decarburized layer on the bulk hardness. For Hv (surf) / Hv (bulk ) hardness is less than 0.3 of decarburized layer is too low, it can adversely affect the strength of the entire plate matrix. Further, the Hv (surf) / Hv (bulk ) of 0.8 greater, in order to the internal layer decarburized layer is not sufficiently soft, cracks occur in the 180 ° bent head top portion. Therefore the present invention is limited Hv a (surf) / Hv (bulk) in the range of 0.3-0.8. Preferably is to Hv a (surf) / Hv (bulk) and the range of 0.3-0.6.
[0044]
"Decarburized layer measurement method"
　to measure the thickness decarburized layer, first a cross-section of a steel sheet embedded polished, from the interface of the steel sheet base material and the plated layer on the steel sheet base metal, measured hardness curve micro Vickers and, determining the thickness of the layer hardness relative hardness of the inner layer is decreased. The thickness of the obtained layer are those containing both decarburized layer thickness and miniaturization layer thickness, the thickness of the layer was determined with a micro Vickers minus the fine layer thickness was determined by the method of the are, de the coal seam thickness. Further, the average value of the measured hardness at decarburized layer and Hv (surf), the average value of the measured hardness in the inner layer may be set to Hv (bulk).
[0045]
　Also determine the volume fraction of the ferrite phase in the decarburized layer, a sample was taken as an observation plane parallel plate thickness cross section in the rolling direction of the plate matrix, polished viewing surface, and nital etching, the decarburized layer, was observed with FE-SEM to measure the area fraction of ferrite phase can be regarded as a volume fraction have it. Also it is possible to measure the particle diameter of the ferrite phase at the same time.
[0046]
"Tissue Internal layer"
　structure of the inner layer in the present invention, the tensile strength of the steel sheet is not less than 590MPa, Hv (surf) / Hv (bulk) is particularly Ownership as long ensured range of 0.3-0.8 is not limited, from the viewpoint of ensuring a balance of strength and ductility, the ferrite phase of 50% or more, the remaining structure 9 martensite, austenite, bainite, is preferably a structure consisting perlite.
[0047]
"Improvement of the working portion corrosion resistance"
　in the high strength galvanized steel sheet of the present invention has a convex alloy layer in the plating layer, having a fine layer and a decarburized layer on the steel sheet base metal. Although the effect of each alone is as described above, by the presence of these as all invention, the conventional not be expected, such as 180 ° bent top portion, a very severe strain on the processing unit in significant improvement in corrosion resistance is obtained. Even only convex alloy layer is present, cracks occur due to distortion is large in the plate matrix surface layer of 180 ° bent top portion if there is no finer layer and decarburized in a surface plate matrix, results to crack penetrates to the plating layer surface, the processing unit corrosion resistance decreases. Moreover even the steel base metal has a fine layer and decarburized layer, if the convex alloy layer is present, at 180 ° bent top portion, although the crack can be suppressed in the plate matrix surface, the mother to follow for distortion of the timber is large plating layer is deformed, the plating layer is exfoliated reduced significantly adhesion in the vicinity of the interface plate matrix and the plating layer, the processing unit corrosion resistance decreases.
[0048]
　Convex alloy layer in the present invention, the fine layer, in a state where all of the decarburized layer is present only without cracks generated from plate matrix surface layer portion in 180 ° bending top portion, also the presence of the convex alloy layer by the anchor effect, it is a region where the plating layer to follow the deformation of the plate matrix is ​​deformed without adhesion in plating layer near the interface with the plate matrix is ​​lowered, nor the plating peel off. Therefore, it is possible to remarkably improve the processing unit corrosion.
[0049]
"Oxide"
　in the high strength galvanized steel sheet of the present invention, the fine layer, in the decarburized layer, and the layer on the convex alloy layer, an oxide containing one or more of Si and Mn contains. Further, the fine layer, the type of decarburized layer, oxide containing convexly alloy layer, SiO 2 , Mn 2 SiO 4 , MnSiO 3 , Fe 2 SiO 4 , FeSiO 3 , 1 kind or selected from the group consisting of MnO and more preferably 2 or more.
[0050]
"Oxides of the convex alloy layer"
　effect of forming the convex alloy layer 2 in the plating layer 1, as described above, a coating adhesion improving upon impact and during large deformation. As described below, during the annealing of the steel sheet base material, at a specific temperature range, to form an internal oxide of the steel sheet base material surface is subjected to mild alloying during the heat treatment after hot-dip galvanizing, forming a convex alloy layer make. By the above reaction, since it is possible to form the convex alloy layer 2 as shown in FIG. 1, the convex alloy layer comprises an unavoidably oxide. Oxides contained in the convex alloy layer has a maximum diameter of 0.05 ~ 0.4 .mu.m, the number density of 20 to 100 / [mu] m 2 is more preferable.
[0051]
"Oxide fine layer"
　in the present invention, as described below, in a specific temperature range during annealing, to form an internal oxide inside plate matrix, the internal oxide particles, plate matrix surface layer by suppressing the growth of ferrite phase crystal, it is possible to form a fine layer 5 having a structure as shown in FIG. Therefore the finer layer include unavoidably oxide. Oxide contained in the fine layer has a maximum diameter, 0.01 [mu] m ~ 0.2 [mu] m, the number density of 20 to 100 / [mu] m 2 is more preferable.
[0052]
"Measurement of oxide"
　existence of the oxide layer, the type of identification, maximum diameter, in the measurement of number density, after a thin film sample section of the plated steel sheet FIB (Focused Ion Beam) processing to, in FE-TEM (Field Emission Transmission Electron Microscopy), carried out by observing at magnification of 30000 times. For one sample, and 5 field imaging, the average value of the number density of oxide throughout the entire field of view, the number density of the sample. Further, the maximum value of the diameter of the oxide, which is measured in the entire field of view, of the sample, the maximum diameter of the oxide.
[0053]
"Chemical composition of the steel sheet base material"
　structuring the high-strength galvanized steel sheet according to the embodiment of the present invention will be described chemical composition of the base material steel plate.
[0054]
　C: C is effective it is contained more than 0.05 wt% A element to increase the strength of the steel, the upper limit since excessive when the content strength decreases the workability too elevated 0.4 the mass%. From the viewpoint of weldability and workability, preferably in the range 0.07 to 0.3 mass%.
[0055]
　Si: Si is an effective element for improving the strength without reducing the ductility, it is effective to add more than 0.4 mass%. On the other hand the addition exceeds 3.0 mass%, decrease in ductility occurs with the effect of increasing the strength is saturated. The remarkable plating wettability deteriorates significantly worsen the appearance. Therefore the upper limit was made 3.0 mass%. Preferably, it is in the range of 0.5 to 2.5 mass%.
[0056]
　Mn: Mn is an important element for strengthening, adding more than 1.0 mass%. However, easily cracked the slab exceeds 4.0 mass%, for deteriorated spot weldability, the upper limit of 4.0 mass%. From the viewpoint of strength and formability, preferably in the range of 1.5 to 3.5 wt%.
[0057]
　P: P is also because it is an element that reduces the workability while increasing the strength of the steel, the upper limit is made 0.1 mass%. Since refining costs in order to reduce the P less than 0.0001 mass% is great, the lower limit is set to 0.0001 mass%. Strength, balance of processability and cost, it is preferable that 0.005 to 0.02 mass%.
[0058]
　S: S is an element which lowers hot workability of the steel, the corrosion resistance. Hot workability exceeds 0.01 mass%, in order to deteriorate the corrosion resistance, the upper limit is 0.01 mass%. Also, since to less than 0.0001% by mass it is economically disadvantageous, the lower limit is 0.0001 wt%. However, since the surface defects excessively reduced S easily occurs, preferably 0.001 mass% or more.
[0059]
　Al: Al is added as a deoxidizing element of steel, and grain refinement of the hot rolled material by AlN, and to improve the material suppresses the coarsening of crystal grains in a series of heat treatment processes 0.005 wt% or more There is a need. However, because it may deteriorate the weldability exceeds 0.1 wt%, 0.1 wt% or less. Further, from the viewpoint of reducing the surface defects by alumina clusters it is preferably set to 0.08 mass% or less.
[0060]
　N: N is an upper limit because decrease the workability while increasing the strength of steel to 0.01 mass%. If that specifically require high workability is more preferably set to 0.005 mass% or less. N is preferably as less but, since requires excessive costs to be reduced to less than 0.0005%, the lower limit is set to 0.0005 mass%.
[0061]
　O: O forms an oxide, from degrading the ductility and stretch flangeability, it is necessary to suppress the content. When the content of O exceeds 0.010%, since the stretch flangeability of the deterioration becomes remarkable, the upper limit of the O content is set to 0.010%. Preferably further the content of O is 0.007% or less, and more preferably 0.005% or less. O lower limit of the content of, the effect of the present invention are exhibited without particularly, when the content of O and less than 0.0001% is accompanied with significant increase of production costs, 0. 0001 percent as the lower limit. Preferably O content is 0.0003% or more, more preferably 0.0005% or more.
[0062]
　Additional, the plate matrix of such hot-dip galvanized steel sheet to an embodiment of the present invention may be added the following elements as required.
[0063]
　Ti: Ti is precipitation strengthening, by dislocation strengthening through suppression of fine grain strengthening and recrystallization of a ferrite grain growth inhibiting an element which contributes to the strength increase of the steel sheet. However, if the content of Ti exceeds 0.150%, the deterioration of the formability deposition number is in the carbonitride content of Ti is more preferably less 0.150%. From the viewpoint of moldability, the content of Ti is more preferably less 0.080%. The lower limit of the content of Ti is the effect of the present invention are exhibited without particularly, in order to obtain a sufficient strength increasing effect by addition of Ti and the content of Ti is 0.001% or more preferable. For even higher strength of a steel sheet, the content of Ti is more preferably 0.010% or more.
[0064]
　Nb: nb is precipitation strengthening, by dislocation strengthening through suppression of fine grain strengthening and recrystallization of a ferrite grain growth inhibiting an element which contributes to the strength increase of the steel sheet. However, if the content of Nb exceeds 0.100%, the deterioration of the formability deposition number is in the carbonitride, Nb content is more preferably 0.100% or less. From the viewpoint of formability, the Nb content is more preferably 0.050% or less. The lower limit of the Nb content effect is exhibited of the present invention without particularly setting, to obtain a sufficient strength increasing effect by Nb addition, it is preferable that the content of Nb is 0.001% or more . For even higher strength of steel sheet, the Nb content is more preferably 0.010% or more.
[0065]
　Mo: Mo suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn. If the content of Mo is exceeds 2.00% since the workability is impaired productivity in hot drops, the content of Mo is preferably set to 2.00% or less, 1.40 % by further preferably less. The lower limit of the content of Mo is the effect of the present invention are exhibited without particularly, in order to obtain a sufficient effect of strengthening by Mo addition, the content of Mo is 0.01% or more it is preferable, more preferably 0.10% or more.
[0066]
　Cr: cr suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn. 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, 1.40 % by further preferably less. Although the lower limit of the content of Cr the effect of the invention 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% or more it is preferable, more preferably 0.10% or more.
[0067]
　Ni: Ni suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn. 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, more preferably not more than 1.40%. It is the lower limit of the content of Ni is the effect of the invention is exhibited without particularly, to obtain a sufficient effect of strengthening by Ni addition, the content of Ni is 0.01% or more it is preferred, more preferably 0.10% or more.
[0068]
　Cu: Cu is an element to increase the strength by the presence in the steel as fine particles, can be added in place of part of C and / or Mn. When the content of Cu exceeds 2.00%, since the weldability is impaired, the content of Cu is preferably set to 2.00% or less, more preferably not more than 1.40%. It is the lower limit of the content of Cu effect of the invention is exhibited without particularly, to obtain a sufficient effect of strengthening due to the addition of Cu, the content of Cu is 0.01% or more it is preferred, more preferably 0.10% or more.
[0069]
　B: B suppresses phase transformation at high temperature, an effective element for high strength, may be added instead of a part of the C and / or Mn. When the content of B exceeds 0.010%, since the workability impaired by productivity in hot drops, the content of B is preferably set to 0.010% or less. From the viewpoint of productivity, the content of B is more preferably 0.006% or less. Although the effect of the lower limit of the content is also present invention without particularly setting of B is exerted, in order to obtain the effect of strengthening due to the addition of B sufficiently, the content of B is 0.0001% or more it is preferable. For further increasing the strength, the content of B is more preferably 0.0005% or more.
[0070]
"Manufacturing method"
　Next, a method for manufacturing a high strength galvanized steel sheet of the present invention. The high intensity method of manufacturing a galvanized steel sheet of the present invention, a slab having a composition as set forth in the the original plate, hot rolling, cooling, winding, pickling, after cold rolling, heating annealing at CGL after, it was immersed in molten zinc plating bath, a high-strength galvanized steel sheet.
[0071]
　Slab subjected to hot rolling is not particularly limited as long as it was produced in a continuous casting slab or thin slab caster or the like. The continuous casting is carried out immediately after hot rolling the cast - fits in processes such as direct rolling (CC-DR).
[0072]
　Finishing temperature of hot rolling is not particularly limited, and more preferably to 850 ~ 970 ° C. From the viewpoint of securing the press formability of the steel sheet. Although the cooling conditions and the coiling temperature is not particularly limited after hot rolling, coiling temperature avoids material variation in the coil end portions is increased, and in order to avoid the pickling of deterioration due to the increase in scale thickness is set to 750 ° C. or less, also prone to edge cracking when coiling temperature is too low during cold rolling, it is more preferable to also for 550 ° C. or higher to strip breakage in extreme cases. Then in order to remove the mill scale scale, was subjected to usual pickling, the rolling reduction of cold rolling may under normal conditions, the rolling reduction for the purpose of obtaining the most improved workability 50% it is more preferable to be. On the other hand, it is required a great deal of cold-rolled load to perform cold rolling at a rolling reduction of over 85%, and more preferably set to 85% or less.
[0073]
　It was subjected to cold rolling as described above, carrying out the hot-dip galvanizing. As an example of a method for producing a high strength galvanized steel sheet of the present invention, the atmosphere in applying the hot-dip galvanized steel sheet having a composition as set forth in the, H 2 and containing 0.1 to 20% by volume, the remainder N 2 , H 2 O, O 2 and atmosphere consisting and inevitable impurities, the atmosphere between 650 and the maximum heating temperature, -1.7 ≦ log (P H2 O / P H2 of) ≦ -0.6 as an atmosphere satisfying, after raising heated at an average heating rate of 0.5 ~ 5 ℃ / s, subjected to annealing by continuous cooling at an average cooling rate 0.1 ~ 200 ℃ / s then up to 650 ° C., between 650 ° C.-500 ° C. and cooled at an average cooling rate of 3 ~ 200 ℃ / s, galvanizing bath temperature: 450 - 470 ° C., the steel sheet temperature at the time of plating bath enters: 430 ~ galvanizing bath under the condition of 500 ° C. after immersion in, 1 ~ 50s heating alloying treatment at 400 ~ 440 ° C. It is preferable to, and then cooled to room temperature.
[0074]
　The galvanizing is preferably carried out in total reducing furnace of a continuous hot dipping equipment. The atmosphere during annealing, H 2 and containing 0.1 to 20 vol%, the remainder N 2 , H 2 O, O 2 and atmosphere consisting and unavoidable impurities. When hydrogen is less than 0.1% by volume, can not be sufficiently reduced the oxide film present on the surface of the steel sheet layer, it can not be ensured plating wettability. Therefore, the amount of hydrogen reduction annealing atmosphere is set to 0.1% by volume or more. When the hydrogen in the reducing annealing atmosphere is more than 20 vol%, dew point (water vapor partial pressure P H2 O excessively increased corresponding to) is, it is necessary to introduce a facility to prevent condensation. Introduction of new facilities, since causes an increase in production cost, the amount of hydrogen reduction annealing atmosphere is set to 20% by volume or less. More preferably is to 15% by volume or less than 0.5% by volume.
[0075]
　The atmosphere between a temperature 650 ~ maximum heating
temperature, -1.7 ≦ log (P H2 O / P H2 ) ≦ -0.6
as the atmosphere satisfying, heating at an average heating rate 0.5 ~ 5 ° C. / s fine layer 5 and, as shown in Figure 1 of the present invention by heating, decarburized layer 6 is formed. The 650 temperature range below ° C., a state in which the recrystallization of the steel sheet structure is hardly started. The temperature range of 650 ° C. or higher, recrystallization begins, recrystallization grains nucleated, gradually grain growth. In such a temperature range, log (P of the atmosphere during annealing H2 O / P H2 enhanced), by an atmosphere of oxidizable side, internal oxidation of Si and Mn in the steel base material in the surface layer of the steel sheet base material are allowed, in the internal oxide particles inhibit the grain growth of recrystallized grains of the steel sheet base material, plate matrix surface layer fine recrystallized grains are formed, it is possible to form a fine layer 5. Further, it is the volume fraction of the steel sheet base material surface of the ferrite phase decarburization in plate matrix surface layer at the same time as the internal oxidation progresses is increased, to form a decarburized layer 6. Atmosphere between a temperature of 650 ° C. ~ maximum heating temperature log (P H2 O / P H2 for) is less than -1.7, the Si and Mn is little internal oxidation in steel surface layer and also does not progress decarburization, it is impossible to form a fine layer or decarburized layer. The Log (P H2O / P H2) -0.6 than that and adversely affect decarburized layer thickness becomes too large in the overall strength of the steel base material. Therefore ≦ log -1.7 (P H2 O / P H2 is preferably in the range of) ≦ -0.6. More preferably, -1.3 ≦ log (P H2 O / P H2 is to a) ≦ -0.7. The average heating rate in this temperature range at the 5 ° C. / s greater can not be obtained plate matrix surface recrystallization progresses fine layer before the internal oxide particles form. Also it is impossible to sufficiently secure the time for decarburization reaction proceeds, it is impossible to form a decarburized layer. Meanwhile, the average heating rate is less than 0.5 ° C. / s in this temperature range, excessively proceeds and decarbonization reaction plate matrix overall strength may be lowered. Therefore, the average heating rate between 650 ° C. ~ maximum heating temperature is preferably in the range of 0.5 ~ 5 ℃ / s. More preferably to an average heating rate in the range of 0.5 ~ 3 ℃ / s.
[0076]
　Although the maximum heating temperature is not particularly limited, in the 900 ° C. greater because there is a risk that the plate-shaped at high temperatures through plate becomes poor, preferably in the range of 800 ~ 900 ° C..
[0077]
　After the heating the heating in the present invention, it performs annealing continuously. For annealing time is not particularly limited, it may be set conditions as needed, from the viewpoint of the surface properties of the economy and the plate is preferably in the range of 1s ~ 300 s. More preferably in the range of 30s ~ 150s.
[0078]
　After the annealing completion, then cooled to the plating bath immersion temperature. The average cooling rate from the maximum heating temperature to 650 ° C. is 0
. It is desirable that the 1 ~ 200 ℃ / s. Cooling rate, 0. Be less than 1 ° C. / s is undesirable since the productivity is significantly impaired. Also, increasing the excessive cooling rate, since the may lead to high production cost, so the upper limit is preferably made 200 ° C. / s. Cooling rate at 650 ~ 500 ° C. is preferably in the 3 ~ 200 ℃ / s. When the cooling rate is too small, the austenite in the cooling process is transformed into pearlite structure, it is difficult to secure a more than 3% austenite volume fraction. Therefore, it is preferable to 3 ° C. / s lower limit. On the other hand, the cooling rate as the increase, there is no any problem on the material, to raise excessively cooling rate, and thus lead to high production cost. Therefore, it is preferable that the upper limit is 200 ° C. / s. For cooling method may be a roll cooling, air cooling, water cooling and any method in combination of these.
[0079]
　Plating bath temperature at galvanizing step is preferably set to 450 ~ 470 ° C.. Plating bath temperature becomes unstable bath temperature control is less than 450 ° C., there is a concern that the bath will be partially solidified. Further, when the bath temperature is higher than 470 ° C., equipment life, such as sink roll and zinc pot is shortened. Therefore, bath temperature of galvanizing bath is preferably set to 450 ~ 470 ° C..
[0080]
　Entering sheet temperature of the steel sheet in the plating bath is preferably set to 430 ~ 500 ° C.. When entering sheet temperature lower than 430 ° C., reduction of the plating bath temperature is significantly, it is necessary to provide a large amount of heat to the plating bath in order to stabilize the bath temperature. It is preferable to this for the lower limit 430 ° C.. Also, when entering sheet temperature is 500 ° C. greater can not control the alloying reaction of Fe and Zn in the bath, it is difficult to control the deposition amount. Therefore it is preferable to set the upper limit 500 ° C..
[0081]
　The Al concentration in the plating bath, but are not particularly limited, in order to form the convex alloy phase in the plating layer, the effective Al concentration (total Al concentration in the bath - total Fe concentration in the bath) to 0 it is preferably in the range of .03 to 0.8 wt%. More preferably is to range from 0.08 to 0.3 mass%.
[0082]
　After immersion in the plating bath, it is preferred that 400 to process 1s ~ 50s heated alloyed ~ 440 ° C., then cooled to room temperature. In the heating alloying step, by alloying at low temperature, allowed to proceed for local alloying reaction, it can be formed convex alloy layer in a high-strength galvanized steel sheet of the present invention. Without forming the convex alloyed layer for most local alloying reaction does not occur in the alloying temperature is less than 400 ° C., it is preferable that the lower limit to 400 ° C.. The cause alloying reaction at 440 ° C. greater is expanded to the whole rather than local, since to obtain a form of convex alloy layer becomes difficult, it is preferable that an upper limit of 440 ° C.. Also not formed is convex alloy layer is less than the heating time 1s, since the 50s than excessively long line lengths alloying furnace, it is preferable to set the heating time in the range of 1s ~ 50s.
[0083]
　In the present invention, before the convex alloy layer that produces from the interface of the plating layer and the steel sheet base material reaches the surface of the plating layer, it is preferable to stop heat alloying treatment. Further, by Tsuban steel steel of the same components to be manufactured in advance, 400 in the temperature range of ~ 440 ° C., in previously determined heating time required to complete the alloying reaction to the surface proceeds put it is desirable. By heating maintained at 10 to 80% of the time of pre-heating time required for complete alloying obtained (alloying completion time), it is fabricated accurately without reaching the convex alloy layer to the plated layer surface it is possible.
Example 1
[0084]
　Next, a description will be given of an embodiment of the present invention. Conditions of Example is an example of conditions adopted for confirming the workability and effects of the present invention, the present invention is not limited to this single example of conditions. The present invention does not depart from the gist of the present invention, as long as they achieve the object of the present invention, it is capable of adopting various conditions.
[0085]
　The slab having the composition shown in Table 1 were heated to 1150 ~ 1250 ° C., by performing the hot rolling so that the finishing temperature is 850 ~ 970 ° C., and the hot rolled steel strip having a thickness of 2.4 mm. After pickling, subjected to cold rolling, the cold-rolled steel strip having a thickness of 1.0 mm, and Tsuban the galvanizing line under the conditions shown in Table 2, the galvanized steel sheet Experimental Examples 1-34 It was produced.
[0086]
[Table 1]

[0087]
[Table 2]

[0088]
　For steel sheet each experimental example was prepared by the above method, subjected to evaluation tests as described below, the results are shown in Table 3-1 and 3-2.
[0089]
[Table 3-1]

[0090]
[Table 3-2]

[0091]
　Coating weight of the plating layer, the plating layer of the evaluation surface was dissolved in inhibitor containing hydrochloric acid, it was determined by the weight method. At the same time, Fe in the lysate, the Al by quantifying with ICP, Fe concentration in the plating layer was measured Al concentration.
[0092]
　Maximum length, the number density of the convex alloy layer in the coating layer, as described above, after mirror-polished in cross-section embedded, etched by immersion for 1 to 3 seconds to 0.5 wt% nital corrosion solution, It was determined by observing at 200-power optical microscope.
[0093]
　The average thickness of the fine layer of the steel sheet base material, the average particle size of the ferrite phase in the finer layer, as described above, the cross-section and CP processing, observed at 5000 times the backscattered electron image of at FE-SEM It was measured by.
[0094]
　The average thickness of the decarburized layer of the steel sheet base material, as described above, is mirror-polished after cross implantation, from the surface of the plate matrix and the plating layer on the steel sheet base metal, measured hardness curve micro Vickers , from the thickness of the layer hardness relative hardness of the inner layer is reduced, it was determined by subtracting the fine layer thickness obtained previously.
[0095]
　The average particle size of the ferrite phase in decarburization in an average volume fraction of the ferrite phase in the decarburized layer, as described above, is etched with 3% nital after section embedded abrasive, in the decarburized layer, secondary electrons FE-SEM It was determined by observing at 2000 times the image.
[0096]
　Hv (surf) / Hv (bulk), as described above, after the cross section embedded abrasive, the average value Hv of decarburized layer of the micro-Vickers hardness (surf) and the mean value of the micro-Vickers hardness of the inner layer Hv the (bulk) measured, it was determined by calculating the ratio.
[0097]
　Convex alloy layer, finer layer, in the decarburized layer, the presence or absence of the oxide type, maximum diameter, to determine the number density, as described above, after manufacturing the thin film sample cross section of the plated steel sheet by FIB processing It was performed by observing at magnification of 30000 times with FE-TEM.
[0098]
　In the tensile test, the tensile strength, the steel sheet of each experimental example, by processing the No. 5 test piece described in JIS Z 2201, measured in accordance with the test method described in JIS Z 2241, tensile strength (MPa) did.
[0099]
　Coating adhesion assuming a standard processing was evaluated by V bending test. The V bending test, using a 60 ° V bending molds. Evaluation plane, to come to the inner side of the bend, by using a mold is the curvature radius of 1mm tip, bending and machining into 60 °, taped bend inward, was peeled off the tape. From the release condition of the peeled plating layer with tape, and rated the powdering property. Evaluation ○: no peeling, △: There is peeling, ×: There is significant peeling, and then, was passed ○.
[0100]
　Upon receipt of an impact, and strength assumed plating adhesion the time of processing was evaluated by ball impact test. Ball impact test from a height 60cm, the mold 25mm diameter tip hemispherical, is dropped into molten plated steel sheet as a weight 3.2 kg, the protrusions of the deformed fused plated steel sheets, loupe observation and then a tape peeling It was evaluated Te. The rating is ◎◎: no peeling and cracking, ◎: Nashi small cracks are present locally but problem, ○: Nashi exist locally minute cracks and peeling, but the problem, △: large peeling is present problem Yes, ×: peeling There are significantly a problem, and then, ◎◎, ◎, was passed ○.
[0101]
　Further, the processing portion corrosion resistance in the site that received the very severe working, 0T bend (180 ° contact bending) were investigated by the sample after the test. As the evaluation site bent outer top portion of the bending 0T, subjected to a chemical conversion treatment and electrodeposition coating under the following conditions for the sample after bending 0T.
Chemical conversion treatment: the zinc phosphate treatment
coating weight 2.5 g / m @ 2
electrodeposition coating: Pb-free epoxy electrodeposition paint
film thickness 20μm
　Thereafter, the accelerated corrosion test shown in JASO-M609-91, red rust from 0T bend the top portion There were evaluated the number of cycles that occur. For the results, and scored on the basis of the following criteria, ◎◎, ◎, was passed ○. ◎◎: After 150cyc elapsed also rust, white rust without the occurrence of, ◎: 150cyc elapsed after the rust No-minor white rust, ○: No 120cyc after the rust-minor white rust, △: 60cyc after the red rust, × : 30cyc after red rust.
[0102]
　From Table 3, the present invention example are all strong working time of coating adhesion, and strong working time of the working portion corrosion resistance and has a pass level. Comparative Examples not satisfying the scope of the present invention are all strong coating adhesion and at the time of processing, poor processability portion corrosion resistance during large deformation. Figure 2 shows a cross-sectional photograph of the inner layer of the comparative example is assumed to correspond to the experiment numbers 8, a cross-sectional photograph of the inner layer of the present invention example is assumed to correspond to the experiment numbers 13.
DESCRIPTION OF SYMBOLS
[0103]
1 plated layer
2 protruding alloy layer
3 the measuring direction of the diameter of the convex alloy layer
4 plate matrix
5 fine layer
6 decarburized
7 inner layer
8 ferrite phase
9 the remaining structure (austenite phase, bainite phase, martensite phase, pearlite one of the phases)

The scope of the claims
[Requested item 1]
C: 0.05 ~ 0.4
wt%, Si: 0.4 ~ 3.0
mass%, Mn: 1.0 ~ 4.0
mass%, P: 0.0001 ~ 0.1
weight%, S: 0.0001-0.01
mass%, Al: 0.005 ~ 0.1
wt%, N: 0.0005 ~ 0.01
mass%, O: 0.0001-0.01 wt%
and containing the balance There of Fe and unavoidable impurities,
　on the tension plate matrix strength is not less than 590 MPa, Fe: 0.01 ~ 6.9 wt%, Al: 0.01 ~ 1.0 wt%, the balance Zn and unavoidable a high strength galvanized steel sheet having a galvanized layer composed of impurities,
　the plating layer has a convex alloy layer in contact with the plate matrix, see number density of the convex alloy layer from the cross-sectional direction steel plates and the base material and 4 per unit length of the interface of the plating layer / mm or more, put on the interface That the maximum diameter of the convex alloy layer is not more 100μm or less,
　the steel sheet base material, and a surface in direct contact with the fine layer of the plate matrix plating layer,
　in contact with the fine layer, of the plate matrix a decarburized layer existing in a square side,
　said and a fine layer and internal layers other than the decarburized layer,
　wherein the 0.1 ~ 5 [mu] m average thickness of the finer layer, the average particle of the ferrite phase in the finer layer diameter of 0.1 ~ 3μm,
　The decarburized layer average thickness 10 ~ 200 [mu] m of the average particle size of the ferrite phase in decarburized layer within a is 5 ~ 30 [mu] m, the average volume fraction of the ferrite phase in the decarburized layer is 70% or more, the remaining structure is austenite , bainite consists martensite or pearlite,
　the ratio Hv (surf) / Hv (bulk ) of 0.3 to 0 mean decarburized layer Vickers hardness Hv mean (surf) and the inner layer Vickers hardness Hv (bulk). is 8,
　the fine layer, the decarburized layer, and the layer on the convex alloy layer, characterized in that it contains one or more oxides of Si and Mn, impact resistance and processing unit high-strength galvanized steel sheet excellent in corrosion resistance.
[Requested item 2]
　The fine layer, oxide containing in a layer of the decarburized layer, and the convex alloy layer, SiO 2 , Mn 2 SiO 4 , MnSiO 3 , Fe 2 SiO 4 , FeSiO 3 , 1 or more kinds of MnO and characterized in that, the impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance according to claim 1.
[Requested item 3]
　Contained in the convex alloy layer, the maximum diameter of 0.05 ~ 0.4 .mu.m of oxide, the number density of 20 to 100 / [mu] m 2 , characterized in that a, according to claim 1 or 2 , impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
[Requested item 4]
　Wherein contained in fine layer, the maximum diameter of the oxide is 0.01 ~ 0.2 [mu] m, the number density of 20 to 100 / mm 2 , characterized in that a, any one of claims 1 to 3, high-strength hot-dip galvanized steel sheet, having excellent impact resistance and machining portion corrosion resistance according to (1).
[Requested item 5]
　The convex alloy layer on the outermost surface of the galvanized layer is characterized by the absence, of any one of claims 1 to 4, high-strength hot excellent in impact resistance and processing unit corrosion resistance zinc-plated steel plate.
[Requested item 6]
　Plate matrix
further, Ti: 0.001 ~ 0.15
wt%, Nb: 0.001 ~ 0.10 wt%,
characterized in that it contains one or two, according steels 1-5 either according to item 1, impact resistance and high strength galvanized steel sheet excellent in processability portion corrosion resistance.
[Requested item 7]
　Plate matrix
further, Mo: 0.01 ~ 2.0
wt%, Cr: 0.01 ~ 2.0
wt%, Ni: 0.01 ~ 2.0
wt%, Cu: 0.01 ~ 2. 0
wt%, B: 0.0001 ~ 0.01 mass%,
characterized by containing one or two or more of, as claimed in any one of claims steels 1-6, impact resistance and high-strength galvanized steel sheet excellent in processability portion corrosion resistance.