0001]The present invention relates to a hot stamping molded article.
BACKGROUND
[0002]Structural member (molded article) used in an automobile or the like, to enhance both the strength and dimensional accuracy, it may be produced by hot stamping (hot press). In producing a molded body by a hot stamp, a steel sheet Ac 3 heated above points, quenched with pressing in a mold. That is, in the manufacture, perform the press working and quenching at the same time. According to hot stamping, high dimensional accuracy, and it is possible to produce shaped bodies of high strength.
[0003]
　On the other hand, moldings produced by hot stamping, because it is processed at high temperatures, the scale is formed on the surface. Accordingly, by using the plated steel plate as a steel sheet for hot stamping, (see Patent Documents 1 to 3) to suppress the formation of scale, yet the technique for improving the corrosion resistance has been proposed.
[0004]
　For example, hot press steel sheet are disclosed Zn plating layer was formed on the Patent Document 1. The high strength automobile member for aluminum coated steel sheet is disclosed which Al plating layer was formed on the patent document 2. Further, Patent Document 3, various elements hot Zn-plated steel for press, which is the addition of Mn or the like in the plating layer of the Zn-plated steel sheet is disclosed.
CITATION
Patent Document
[0005]
Patent Document 1: JP 2003-73774 JP
Patent Document 2: JP 2003-49256 JP
Patent Document 3: JP 2005-113233 JP
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　In Patent Document 1 technique, for Zn after hot stamping remains in steel surface layer, it can be expected high sacrificial protection effect. However, since Zn is steel sheet is processed in a molten state, the molten Zn to penetrate the steel sheet, there is a possibility that cracking occurs inside the steel. This cracking is referred to as the liquid metal embrittlement cracking (Liquid Metal Embrittlement, hereinafter also referred to as "LME".). And, due to the LME, fatigue characteristics of the steel sheet is degraded.
[0007]
　In the present situation, in order to avoid the occurrence of LME, it is necessary to appropriately control the heating conditions during steel processing. Specifically, all of the molten Zn is diffused in the steel sheet, and a method of heating until Fe-Zn solid solution is employed. However, for these methods, it is necessary to prolonged heating, resulting in a problem that productivity is lowered.
[0008]
　Further, in the technique of Patent Document 2, since Al is used a higher melting point than the Zn in the plating layer, it may enter the molten metal is steel as in Patent Document 1 is low. Accordingly, to obtain excellent fatigue characteristics, it is expected to have excellent fatigue properties of the molded body after thus hot stamping. However, the steel material Al plating layer is formed, during the phosphating carried out before application of automotive parts, there is a problem that it becomes difficult to form a phosphate film. In other words, phosphating property by the steel is not sufficiently obtained, there is a concern that corrosion resistance after painting is lowered.
[0009]
　Further, in the technique of Patent Document 3, by reforming the surface layer (oxide film) after the hot stamping, while improving the spot weldability, by the addition to elemental, hot stamp still LME occurs there is a possibility that the fatigue properties of the steel material can not be obtained sufficiently. Further, by the addition to elemental, not only fatigue characteristics of the steel material, which may lower the phosphating properties.
[0010]
　The present invention is to solve the above problems, and an object thereof is to provide fatigue characteristics, spot weldability, and excellent corrosion resistance after painting and the hot stamping molding.
Means for Solving the Problems
[0011]
　The present invention has been made to solve the above problems, and the gist of the hot stamping material below.
[0012]
　(1) A hot stamping member and a base material and the base material plated layer formed on the surface of,
　the plating layer, in order from the base material side, the interface layer, the intermediate layer and the oxide layer wherein,
　the interface layer is tissue alpha iron, Fe 3 comprises one or more FeAl alloy selected from Al and FeAl, and the total area ratio of the FeAl alloy is 90% or more,
　the intermediate layer, Fe (Al, Zn) 2 , Fe 2 (Al, Zn) 5 and Fe (Al, Zn) 3 comprises one or more Fe-Al-Zn phase selected from, and wherein the Fe- the total area ratio of the Al-Zn phase is 50% or more,
　the average composition of said intermediate layer is, in terms of
　mass% Al: 30 ~ 50%,
　and, Zn: 15 ~ 30% wherein the
　said oxide layer an average thickness is at 3.0μm or less, and, Mg content .05 ~ 1.00 g / m 2 is,
　hot stamping molding.
[0013]
　(2) the interface layer has an average thickness is 1.0μm or more,
　hot stamping molded article according to the above (1).
[0014]
　(3) the total content of Al and Zn of the plating layer is 20 ~ 100 g / m 2 is,
　hot stamping molded article according to (1) or (2).
[0015]
　(4) wherein the Fe-Al-Zn phase total area ratio of the intermediate layer is 90% or more,
　hot stamping molding according to any one of (1) to (3).
[0016]
　(5) The plated layer, by mass%, further comprises from 0.1 to 15% of Si,
　the intermediate layer, Fe 3 (Al, Si) and Fe (Al, Si) 1 kind or is selected from further comprises two Fe-Al-Si phase and the Fe-Al-Zn phase and the total area ratio of the Fe-Al-Si phase is 90% or more,
　from the (1) to (3) hot stamping molded article according to any one of.
The invention's effect
[0017]
　According to the present invention, it is possible to obtain the fatigue characteristics, spot weldability, and excellent corrosion resistance after painting and the hot stamping molding.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
FIG. 1 is a diagram for explaining the structure of a hot stamping molded body according to an embodiment of the present invention.
FIG. 2 is an example of an image in which the cross section of the hot stamping member SEM observation according to an embodiment of the present invention.
DESCRIPTION OF THE INVENTION
[0019]
　The present inventors have found that the anti-LME resistance during hot stamping was investigated how to achieve both corrosion resistance after spot weldability and painted hot stamping molding.
[0020]
　First, the present inventors have examined a method of improving the corrosion resistance after painting of the molded body. As a result, by containing Mg in the plating layer during the molding body has been found to be able to improve corrosion resistance. However, when manufacturing a molded body containing Mg in the plating layer, LME is likely to occur during hot stamping, fatigue characteristics has been found to deteriorate. Further, Mg content in the coating layer is also reduced spot weldability is excessive.
[0021]
　Therefore, the present inventors have found that without deteriorating the fatigue characteristics and spot weldability was conducted extensive studies on how to improve the corrosion resistance. As a result, oxidation of the plated layer and the layer made mainly of Fe-Al alloy of the base metal, a layer of the surface layer side oxide, with a structure including a layer positioned in the middle, which is formed on the surface by concentrating the appropriate amount of Mg in the layer of the object, it revealed that it is possible to secure a good balance of all characteristics of the.
[0022]
　The present invention has been made based on the above findings. It will be described in detail below each requirement of the present invention.
[0023]
　(A) the overall configuration
　FIG. 1 is a diagram for explaining the structure of a hot stamping molded body according to an embodiment of the present invention. Also, FIG. 2 is an example of an image in which the cross section of the hot stamping member SEM observation according to an embodiment of the present invention. As shown in FIG. 1 and 2, hot stamping molded article 1 according to an embodiment of the present invention, and a plating layer 20 formed on the surface of the base 10 and the base material 10.
[0024]
　(B) the base material
　fatigue properties is an object of the hot stamping molded body according to the present embodiment, spot weldability, and improving the corrosion resistance after painting is realized by the configuration of the plating layer. Accordingly, the base material of the hot stamping molded body according to the present embodiment is not particularly limited. However, if the components of the base material is in the range described below, fatigue properties, spot weldability, and in addition to the corrosion resistance after painting, the molded body having suitable mechanical properties.
[0025]
　Reasons for limiting each element is as follows. Incidentally, "%" for the content in the following description means "mass%".
[0026]
　C: 0.05 ~ 0.4%
　carbon (C) is an element to increase the strength of the hot stamping molding. When C content is too small, not the effect. On the other hand, the C content is excessive, toughness of the steel is lowered. Therefore, C content is 0.05 to 0.4%. C content is more preferably in is 0.10% or more, more preferably 0.13% or more. Also, C content is preferably not more than 0.35%.
[0027]
　Si: 0.5% or less
　Silicon (Si) is inevitably contained, which is an element having an effect of deoxidizing steel. However, when the Si content is excessive, Si in the steel diffuses during heating of hot stamping, and oxide is formed on the surface of the steel sheet, reducing the phosphating properties. Si further, Ac of the steel plate 3 is an element to increase the points, Ac 3 the points is increased, there is a possibility that the heating temperature during hot stamping may exceed the evaporation temperature of the Zn plating. Therefore, Si content is 0.5% or less. Si content is preferably 0.3% or less, and more preferably 0.2% or less. From the viewpoint of the product performance is not constrained lower limit of Si content, to be used for the purpose of deoxidation to above, substantially the lower value exists. Depending on the deoxidation level required, usually 0.05%.
[0028]
　Mn: 0.5 ~ 2.5%
　manganese (Mn) increases the hardenability, is an element to increase the strength of the steel material after the hot stamping. When Mn content is too small, not the effect is obtained. On the other hand, when the Mn content is excessive, this effect is saturated. Therefore, Mn content is 0.5 to 2.5%. Mn content is preferably 0.6% or more, more preferably 0.7% or more. Further, it is preferable Mn content is less 2.4%, and more preferably not more than 2.3%.
[0029]
　P: 0.03% or less
　phosphorus (P) is an impurity contained in steel. P reduces the toughness of the steel segregates on grain boundaries, reducing the resistance to delayed fracture. Accordingly, P content is 0.03% or less. P content is preferably as small as possible.
[0030]
　S: 0.01% or less
　Sulfur (S) is an impurity contained in steel. S is to form a sulfide to lower the toughness of the steel, reduce the resistance to delayed fracture. Thus, S content is 0.01% or less. S content is preferably as small as possible.
[0031]
　sol. Al: 0.1% or less
　of aluminum (Al) are generally used in deoxidation purposes of steel, is an element inevitably contained. However, the Al content is excessive, deoxidation is being performed sufficiently, Ac of the steel plate 3 was elevated points, there is a possibility that the heating temperature during hot stamping exceeds the vaporization temperature of the Zn plating. Therefore, Al content is 0.1% or less. Al content is preferably 0.05% or less. To obtain the above effect, Al content is preferably 0.01% or more. In the present specification, Al content, sol. It means the content of Al (acid soluble Al).
[0032]
　N: 0.01% or less
　Nitrogen (N) is an impurity which is inevitably contained in steel. N reduces the toughness of the steel by forming nitrides. N Further, when B is contained in steel, B binding to reduce solid solute B amount and reduces the turn hardenability. Therefore, N content is 0.01% or less. N content is preferably as small as possible.
[0033]
　B: 0 ~ 0.005%
　boron (B) increases the hardenability of steel, because it has an effect of increasing the strength of the steel material after the hot stamping, it may be contained as needed. However, when the B content is excessive, this effect is saturated. Therefore, B content is 0.005% or less. To obtain the above-mentioned effects, B content is preferably 0.0001% or more.
[0034]
　Ti: 0 ~ 0.1%
　of titanium (Ti) combines with N to form a nitride. If this is the Ti and N to bind to, is suppressed binding of B and N, the decrease in hardenability by BN formation can be suppressed. Therefore, it may be contained as necessary Ti. However, the effect is saturated and the Ti content is excessive, further, Ti nitrides excessively precipitated lowers the toughness of the steel. Therefore, Ti content is 0.1% or less. Incidentally, Ti by its pinning effect, to refine the austenite grain size during hot stamping heating, thereby enhancing the toughness, etc. of the steel material. To obtain the above-mentioned effects, Ti content is preferably 0.01% or more.
[0035]
　Cr: 0 ~ 0.5%
　Chromium (Cr), since it has an effect to enhance the hardenability of steel, may be contained as needed. However, the Cr content is excessive, Cr carbide is formed. The Cr carbide, since the hardly soluble when heated hot stamp, it austenitizing hardly proceeds, hardenability is reduced. Therefore, Cr content is 0.5% or less. To obtain the above effect, Cr content is preferably 0.1% or more.
[0036]
　Mo: 0 ~ 0.5%
　of molybdenum (Mo), in order to have the effect of increasing the hardenability of steel, may be contained as needed. However, when the Mo content is excessive, the effect is saturated. Therefore, Mo content is 0.5% or less. To obtain the above-mentioned effects, Mo content is preferably 0.05% or more.
[0037]
　Nb: 0 ~ 0.1%
　niobium (Nb) is to form a carbide, the grain refining during hot stamping, because it has an effect of enhancing the toughness of the steel, may be contained as needed. However, when the Nb content is excessive, not only the effect is saturated, the hardenability decreases. Therefore, Nb content is 0.1% or less. To obtain the above effect, Nb content is preferably 0.02% or more.
[0038]
　Ni: 0 ~ 1.0%
　nickel (Ni) has the effect of increasing the toughness of the steel. Ni is further upon heating in a hot stamp, suppressing embrittlement due to the presence of the molten Zn. Therefore, it may be contained if necessary Ni. However, the Ni content is excessive, these effects are saturated. Therefore, Ni content is 1.0% or less. To obtain the above-mentioned effects, Ni content is preferably 0.1% or more.
[0039]
　In the chemical composition of the base material constituting the hot stamping molded article of the present embodiment, the balance being Fe and impurities. Here, the impurities, in producing the steel industrially, ore or scrap that can be incorporated into component as a raw material, or a component that may be mixed due to the manufacturing environment, intentionally added means are non component.
[0040]
　(C) plating layer
　as shown in Figure 1, the plating layer 20 in the present embodiment, in order from the base material 10 side, including the interface layer 21, middle layer 22 and the oxide layer 23. For each of the layers will be described in detail. In the present specification, the average film thickness is intended to mean the average of the maximum film thickness and the minimum thickness of the layer of interest (film).
[0041]
　Interfacial layer 21 is formed adjacent to the base member 10, composed of a structure mainly of Fe-Al alloy. In the present invention, the FeAl alloys, alpha iron, Fe 3 is a general term for Al and FeAl. That is, the interface layer 21, the tissue is alpha iron, Fe 3 contains at least one element selected from Al and FeAl. Further, Fe-Al alloy is to be mainly a total area ratio of the Fe-Al alloy means that 90% or more. Preferably the total area ratio of the Fe-Al alloy is 95% or more, more preferably 99% or more.
[0042]
　Al content in the interfacial layer 21, in mass%, not more than 30%, the Al content approaches the preform 10 is reduced. By interfacial layer 21 is formed adjacent the base material 10, it is possible to suppress the LME. In addition, the Fe-Al alloy, because, sometimes Zn or Si or the like is dissolved, during interfacial layer 21, Zn: 10% or less, Si: may contain 10% or less.
[0043]
　In order to improve the fatigue properties and the like due to the resistance LME resistance preferably has an average thickness of the interface layer 21 is 1.0μm or more, more preferably 2.0μm or more. The lower limit of the average thickness of the interfacial layer 21, 5.0 .mu.m, and more preferably a 6.0μm or 7.0 .mu.m,.
[0044]
　It is not necessary to define the upper limit of the average thickness of the interface layer, the interface layer 21 having an average thickness greater than 15.0μm, because it may degrade the performance of the corrosion resistance and the like, is not preferred. Therefore, the average thickness of the interface layer 21 is preferably not more than 15.0 .mu.m. The upper limit of the average thickness of the interface layer 21, 12.0 .mu.m, and more preferably 11.0μm or 10.0 [mu] m,.
[0045]
　The intermediate layer 22 is composed of structure mainly of Fe-Al-Zn phase. In the present invention, the Fe-Al-Zn phase, Fe (Al, Zn) 2 , Fe 2 (Al, Zn) 5 and Fe (Al, Zn) 3 is a general term for. That is, the intermediate layer 22, the tissue is Fe (Al, Zn) 2 , Fe 2 (Al, Zn) 5 and Fe (Al, Zn) 3 contains at least one element selected from the. Further, Fe-Al-Zn phase and is the subject, the total area ratio of the Fe-Al-Zn phase means that 50% or more. Incidentally, in the case containing no Si in the plating layer, the total area ratio of the Fe-Al-Zn phase is preferably 90% or more, more preferably 95% or more, 99% or more it is more preferable.
[0046]
　On the other hand, as described later, by including Si in the plating layer, it is possible to improve the adhesion between the base material and the plated layer. In this case, the intermediate layer 22 further includes a Fe-Al-Si phase. The Fe-Al-Si phase, Fe 3 is a general term for (Al, Si) and Fe (Al, Si). That is, the intermediate layer 22, Fe 3 further comprising one or two kinds selected from (Al, Si) and Fe (Al, Si). In this case, the total area ratio of the Fe-Al-Zn phase and Fe-Al-Si phase is preferably 90% or more, more preferably 95% or more, further preferably 99% or more .
[0047]
　The intermediate layer 22 is a mass%, Al: 30 ~ 50%, and, Zn: having an average composition comprising 15 to 30%, a.
[0048]
　The Al content in the intermediate layer 22 by 30% or more, it is possible to improve the fatigue properties by suppressing the LME. Also, the Al content by 50% or less, it is possible to ensure excellent phosphating property is improved corrosion resistance after painting. Al content is preferably at least 32%, and more preferably 35% or more. Further, Al content is preferably not more than 48%, and more preferably 45% or less.
[0049]
　The Zn content in the intermediate layer 22 by 15% or more, it is possible to ensure excellent phosphating property, it is possible to improve the corrosion resistance after painting. Further, by setting the Zn content is 30% or less, it is possible to improve the fatigue properties by suppressing the LME. Zn content is preferably at least 17%, and more preferably 20% or more. Further, Zn content is preferably at most 28%, more preferably not more than 25%.
[0050]
　Furthermore, by reducing the Mg content in the intermediate layer 22, it is possible to improve the resistance to LME resistance. Therefore, Mg content is preferably 1.0% or less. Further, when the intermediate layer 22 comprises Fe-Al-Si phase in the intermediate layer 22 Si: it may contain 25% or less.
[0051]
　Not provided any special restriction on the thickness of the intermediate layer. However, when the thickness of the intermediate layer is small, the performance of the corrosion resistance of the molded article is lowered, the thickness of the intermediate layer is preferably set to more than 5.0 .mu.m. Further, the film thickness of the intermediate layer is excessively large, the production cost is high, there is the heating time becomes longer concern during further hot stamping. Therefore, the thickness of the intermediate layer is less desirable 30.0.
[0052]
　Oxide layer 23 is an oxide layer of Zn mainly comprises Mg. Here, the oxide layer of Zn mainly specifically, more than 50 wt% of the metal components contained in the oxide is meant to be Zn. The presence of the oxide layer 23, is improved phosphating properties. However, if the oxide layer 23 is too thick, since an adverse effect on the corrosion resistance and weldability and the like of the molded article, the average thickness of the oxide layer 23 is set to 3.0μm or less. In order to improve the performance such as spot weldability and corrosion resistance after coating of the hot stamping molded article, the average thickness of the oxide layer 23 is preferably set to 2.0μm or less.
[0053]
　By containing the Mg in the oxide layer 23, it is possible to improve the corrosion resistance after painting. To obtain this effect, Mg content in the oxide layer 23 is 0.05 g / m 2 and more. However, Mg oxides since the electric resistance is high, the spot weldability is lowered if the content is increased. To ensure the spot weldability, Mg content is 1.00 g / m 2 is required to be less.
[0054]
　To containing Mg is in the oxide of the hot stamping material, may be contained Mg in the plating layer of the prior hot stamping, a film containing Mg in the form of painting or the like is formed on the plated steel sheet it may have been generated.
[0055]
　Cr, Ca, Sr, Ti, etc., and is easily oxidized as with Mg, thickening as oxides on the surface layer of the molded article. Therefore, it may contain these elements in the oxide layer 23. However, since the electrical resistance is high as with Mg oxides thereof, when excessively concentrated, there is a possibility that the weldability of the hot stamping molded article deteriorates. Therefore, the total content of Mg, Cr, Ca, Sr and Ti in the oxide layer 23, 2.0 g / m 2 preferably not more than.
[0056]
　The total content of Al and Zn in the plating layer 20 is 20 ~ 100 g / m 2 is preferably. The total content of Al and Zn, 20 g / m 2 by the above, it is possible to obtain the effect obtained by providing the plated layer 20 on the surface of the base 10. On the other hand, the total content of the 100 g / m 2 by mass or less, both can be achieved manufacturing cost reduction by suppressing raw material costs of the hot stamping material, to ensure the weldability of the hot stamping member can. The total content of above 30 g / m 2 is preferably at least, 90 g / m 2 preferably not more than.
[0057]
　Plating layer 20, by mass%, preferably further comprising 0.1 to 15% of Si. The Si content of the plating layer by 0.1% or more, it is possible to improve the adhesion between the base material and the plated layer. On the other hand, the Si content by 15% or less, it is possible to secure the performance of corrosion resistance and weldability and the like of the hot stamping molding. Is preferably the Si content is 0.3% or more, preferably 10% or less.
[0058]
　Although not provided any special restriction on the thickness of the whole plated layer 20, it is preferable that a 6.0μm greater from the viewpoint of securing corrosion resistance, whereas, be 48.0μm or less from the viewpoint of economy preferable.
[0059]
　In the present invention, the interface layer, the tissue of the intermediate layer and the oxide layer, the average composition and thickness, and chemical composition of the plating layer shall be determined by the following methods.
[0060]
　First, cut perpendicular the compact to the surface, polishing the cross-section. Then, the concentration of each element in each region of the interfacial layer and the intermediate layer in this cross section is analyzed by electron microprobe (EPMA). At this time, the film thickness direction vertical to 25% or more from the thickness center of each layer in 20μm or more regions in the width direction, performs mapping analysis, and the use of the average composition. Accordingly, the content of Al and Zn in the interface layer, and Al of the intermediate layer, which determine the content of Zn and Mg.
[0061]
　The average Si content in the entire plating layer is determined by the following method. First, the EPMA, performing line analysis in 0.2μm pitch toward the surface side of the plating layer from the base material side. Then, by obtaining the average value of the measurement results of the plating layer, the average composition of the entire plating layer. When performed continuously measured from the base material side to the surface side of the plating layer, a portion where the Fe concentration is lower than the average composition of the base material and one end of the plating layer, the metal component contained in the oxide layer Zn concentration the portion which becomes less than 50 mass% as the other end portion of the plating layer, during which the region is plated layer of. The line analysis was carried out at five or more, and adopting the average value.
[0062]
　The total content of Al and Zn contained in the plated layer, a hot stamp compact was dissolved in hydrochloric acid, it can be measured by inducing lysates coupled plasma atomic emission spectrometry (ICP analysis). By using this method, it is possible to determine the amount of Al and Zn separately.
[0063]
　When dissolving the plated steel material before hot stamping heated in order to dissolve only the plating layer, it is common to add suppressing inhibitor dissolution of Fe in the base material in hydrochloric acid. However, since the plating layer of the hot stamping molded article contains a Fe, in the above method, not sufficiently soluble plating layer of a hot stamping molded article.
[0064]
　Therefore, the plating in the Al and Zn content of the molded body at the time of obtaining by ICP analysis, with hydrochloric acid without addition of the inhibitor, a method of dissolving the plated layer at a liquid temperature of 40 ~ 50 ° C. are suitable. Further, in order to check whether there are no remaining melt of plating components such Al or Zn after dissolution, it is desirable to composition analysis of the surface of the hot stamping body after dissolution in EPMA. Above-described analysis must be carried out in a region which is not processed in the molded body.
[0065]
　The content of the Mg, Cr, Ca, Sr and Ti which the oxide layer can be prepared by dissolving the hot-stamping body ammonium dichromate solution, lysates measured by ICP analysis. By using the above solution, it is possible to dissolve only the oxide layer. By using this method, it is possible to obtain Mg, Cr, Ca, the content of Sr and Ti individually.
[0066]
　Furthermore, the tissue interface layer and the intermediate layer is obtained by crystal structure analysis by TEM. Furthermore, the interface layer, the thickness of the intermediate layer and the oxide layer, the photograph of the above cross-section taken with SEM, obtained by this micrograph image analysis.
[0067]
　Note that the structure of the plating layer of the molded body according to the present embodiment is not substantially uniform along a direction parallel to the surface of the molded body. In particular, the interface layer, the thickness of the intermediate layer and the oxide layer may often differ in an area which is not processed and the machining area. Thus, above-described analysis must be carried out in a region which is not processed in the molded body. State of the plating layer in the area which is not processed is within the above range moldings, are considered to be molded body according to the present embodiment.
[0068]
　(D) a manufacturing method
　manufacturing method of hot stamping molded article of the present embodiment includes a step of producing a hot stamping plated steel and the step of hot stamping against hot stamping plated steel. Further, in the step of producing the hot stamping plated steel, a step of producing a preform of the hot stamping plated steel, and a step of forming a Al-Zn plating layer on the base material of the hot stamping plated steel included. Furthermore, prior to the step of hot stamping, if necessary, may be subjected to anti-rust oil film forming step and the blanking process. Hereinafter, each step will be described in detail.
[0069]
[Base material manufacturing process]
　In the preform manufacturing process, to produce a preform of the hot stamping plated steel. For example, to produce a molten steel having the same chemical composition as the chemical composition of the base metal of a hot stamping molded article according to the present embodiment illustrated above. Then, by using this molten steel, or to produce a slab by casting, or, to produce an ingot by ingot-making method.
[0070]
　Then, by a slab or ingot is hot rolled, the base material of the hot stamping plated steel (hot-rolled sheet) is obtained. Note that performs pickling process on the hot-rolled plate, cold rolled steel sheet obtained by performing cold rolling may be the base material of the hot stamping plated steel against hot-rolled sheet after pickling.
[0071]
[Plating process]
　The plating process, to form a Al-Zn-Mg plating layer on the base material of plating steel for the hot stamping, to produce a hot stamping plated steel. The method of forming the Al-Zn-Mg plating layer may be a hot-dip plating process, spray coating process, such as vapor plating, may be any other process. To increase the adhesion between the base material and the plated layer, it is preferred to incorporate Si in the plating layer.
[0072]
　Formation example of Al-Zn-Mg plating layer by hot dipping process is as follows. That is, the base material, Al, Zn, and immersed in a molten plating bath consisting of Mg and impurities, depositing a plating layer on the surface of the base material. Then, raise the preform plating layer is deposited from a plating bath.
[0073]
　Incidentally, as described above, for the hot stamping material, the total content of Al and Zn in the plating layer is 20 ~ 100 g / m 2 is preferably. To ensure this total content is in this step, the total content of Al and Zn in the plating layer at the time of pulling up the base material from the plating bath, 20 ~ 100 g / m 2 it is important to the .
[0074]
　In this step, the pulling speed of the steel sheet from the plating bath, by appropriately adjusting the flow rate of wiping gas, it is possible to adjust the total content of Al and Zn in the plating layer.
[0075]
　Further, as described above, in the plating layer of the hot stamping material, the intermediate layer is, in mass%, comprising 30 to 50% Al, 15 to 30% and Zn. For even the content of the Al and Zn, mainly, it can be controlled in this process (plating step). Specifically, the Al content in the plating bath in this process together with 40 to 60%, by the Zn content is 40-60%, the content of Al and Zn in the hot stamping member it can be in the range.
[0076]
　In the case of forming the Al-Zn-Mg plating layer by hot dipping process, Mg content in the plating bath is preferably from 0.5 to 2.0% 1.0 to 1.5% it is more preferable to be. Depending on the amount of deposition of plated steel sheet, the high Mg concentration of the plating bath, since the Mg content of the zinc plating is increased, Mg content in the surface layer oxide of the molded article is increased, the weldability decrease is a concern. A decrease in the resistance to LME resistance by Mg in the intermediate layer remains beyond 1.0% is also a concern. On the other hand, when the low Mg concentration of the plating bath, Mg content in the surface layer oxide of the molded article is lowered, there is a concern that not after sufficient painting corrosion resistance is obtained.
[0077]
　When using a hot-dip plating bath containing no Mg, the treatment liquid containing an Mg oxide further layer of plating layer was applied by a bar coater, by baking and drying in an oven, it may be painted Mg. When performing Mg painting, the Mg content of applying 0.050 ~ 1.00 g / m 2 preferably between.
[0078]
Hot stamping step]
　In the hot stamping step, the hot stamping to the above hot stamping plated steel. Normal hot stamping is carried out by steel is heated to hot stamping temperature range (hot working temperature range), then the steel hot working, further cooling the steel. According to conventional hot stamping techniques, in order to shorten the manufacturing time, it is good that as large as possible a heating rate of the steel material. Further, since the alloying of the plating layer when heating the steel to a hot stamping temperature range progresses sufficiently, conventional hot stamping techniques, not important to control the heating condition of the steel.
[0079]
　However, the hot stamp process for manufacturing a hot stamp molded body according to the present embodiment, with respect to hot stamping plated steel, after performing alloying heat treatment is heated to hot stamping temperature (quenching heating temperature) and hot-working and cooling. Hot stamping plated steel when to warm to hot stamping temperature, by performing the alloying heat treatment for a predetermined time held in a predetermined temperature range, it is possible to form a plating layer having the above-described configuration.
[0080]
　The hot stamping process, first, charged hot stamping plated steel material heating furnace (gas furnace, an electric furnace, an infrared furnace or the like). In a heating furnace, a hot stamping plated steel was heated to a temperature range of 500 ~ 750 ° C., performing an alloying heat treatment for 10 ~ 450s retained within this temperature range. By performing the alloying heat treatment, Fe of the base material is diffused in the plating layer, the alloying proceeds. This alloying, plating layer, in this order from the base material side, the interface layer, changes to include an intermediate layer and an oxide layer. Incidentally, the alloying heating temperature need not be constant, may vary within a range of 500 ~ 750 ° C..
[0081]
　When alloying heating temperature is lower than 500 ° C., the rate is very small the plating layer is alloyed, since the heating time is extended extremely, in addition to undesirable from the viewpoint of productivity, formation of the intermediate layer is insufficient it may become. On the other hand, when the alloying heating temperature exceeds 750 ° C., the growth of the oxide layer in this process is excessively accelerated, weldability of the hot stamping body is lowered.
[0082]
　Further, when the alloying heating time is less than 10s, since alloying of the plating layer is not completed, the interface layer described above, but the plating layer having an intermediate layer and oxide layer is obtained. On the other hand, alloying heating time exceeds 450s, growth of the oxide becomes excessive, also leading to reduction in productivity.
[0083]
　Hot stamping plated steel, heating conditions for heating to alloying heating temperature described above is not particularly limited. However, from the viewpoint of productivity, the heating time is short, it is desirable.
[0084]
　After alloying heat treatment is completed, Ac 3 to heat the hot stamping plated steel to a temperature range of point ~ 950 ° C., followed by a hot working. At this time, plating steel temperature for hot stamp Ac 3 to limit the time within a temperature range of point ~ 950 ° C. (oxidation temperature range) below 60s. When plating steel temperature for hot stamping is in oxidation temperature range, the oxide layer of the surface layer of the plating layer is grown. When the time-plated steel temperature for hot stamping is in the oxidation temperature range is more than 60s, oxide film is excessively grown, a decrease in weldability of the shaped body is concerned. On the other hand, the rate of formation of the oxide coating is very fast, the lower limit of the time-plated steel temperature for hot stamping is in oxidation temperature range is 0s greater. However, when the heating of the hot stamping plated steel was made in a non-oxidizing atmosphere such as a 100% nitrogen atmosphere, since the oxide layer is not formed, the heating of the hot stamping plated steel is carried out in an oxidizing atmosphere such as air atmosphere.
[0085]
　As long as the time the hot stamping plated steel material temperature is within the oxidation temperature range is less than 60s, conditions such as heating rate and maximum heating temperature is not particularly defined, it is possible to select various conditions that may perform hot stamp .
[0086]
　Next, a hot stamping plated steel that has been removed from the furnace, press molding using a mold. In this step, simultaneously with this pressing, quenching the steel material by the mold. The the mold and the cooling medium (e.g. water) is circulated, mold encourage heat extraction of the hot stamping plated steel, quenching is performed. Through the above steps, it is possible to produce a hot stamping molded article.
[0087]
　Although how to heat the hot stamping plated steel material as an example using a heating furnace may be heated hot stamping plated steel by electric heating. Even in this case, the steel material was heated for a predetermined time by electrical heating, performing press molding the steel material using a mold.
[0088]
[Rustproof oil film forming step]
　rustproof oil film forming step, after the plating treatment step, and before the hot stamping process, forms a rustproof oil film by coating a rust preventive oil on the surface of the hot stamping plated steel There may be optionally included in the production process. If the time from when the hot stamping plated steel is produced until the hot stamping is carried out is long, there is a possibility that the surface of the hot stamping plated steel is oxidized. However, since the surface of the hot stamping plated steel rust oil film is formed is not easily oxidized by rustproof oil film forming step, rustproof oil film forming step, can suppress the formation of scale of the molded article. In addition, the method of forming the anti-corrosion oil film can also be used any known technique.
[0089]
[Blanking processing step]
　This step, after the rust preventive oil film forming step, and before the hot stamping process, carried out shearing and / or punching against hot stamping plated steel, specific shape the steel a step of forming a. Shear plane of the steel material after blanking working is easily oxidized. However, if it is pre-rust oil film is formed on the steel surface, rust-preventive oil spreads to some extent on the shear plane. This makes it possible to suppress oxidation of the steel material after blanking working.
[0090]
　Having described an embodiment of the present invention, the above-described embodiments are merely illustrative of the present invention. Accordingly, the present invention is not limited to the embodiment described above, in a range not departing from its spirit, it is possible to appropriately design changed.
[0091]
　The following examples illustrate the present invention more specifically, the present invention is not limited to these examples.
Example 1
[0092]
　First, prepare the base material. That is, using a molten steel having a chemical composition shown in Table 1, were produced slabs by continuous casting. Then the slab was hot-rolled to produce a hot-rolled steel sheet, after further pickled hot-rolled steel sheet to produce a cold-rolled steel sheet by performing cold rolling. Then, a base material using the cold-rolled steel sheet in the production of hot stamping molded article (thickness 1.4 mm).
[0093]
[Table 1]

[0094]
　Next, using the thus produced preform, according the manufacturing conditions shown in Table 2, to prepare a hot stamping plated steel (material No.1 ~ 28). Moreover, the immersion time in the plating bath during the plating process and 5s, cooling rate to 450 ° C. after pulled up from the plating bath was set to 10 ° C. / s.
[0095]
[Table 2]

[0096]
　Then, with respect to the hot stamping plated steel, after heating at the conditions shown in Table 3 (heating No.1 ~ 9), immediately using a hand press, subjected to V bending simulating hot stamp, It was produced hot stamping of each test example. The shape of the mold was a shape such that the outer portion of the bending radius by V bending is stretched about 15% at bending ends. Further, even at a cooling rate is low part at the time of processing, to the extent martensitic transformation start point (410 ° C.), was hardened so that the 50 ° C. / s or more cooling rate.
[0097]
[table 3]

[0098]
　A flat plate portion of the hot stamping molding of the test examples obtained, for structure observation of the plating layer, ICP for analysis, excised spot weldability evaluation test and for corrosion resistance after painting evaluation test pieces for testing, further bent portion It was cut out test pieces for resistance to LME resistance evaluation test from.
[0099]
　The structure test piece for observation of the plating layer, after polishing the cross section perpendicular to the surface of the molded product, using the EPMA, the content of Al and Zn in the interface layer, and the intermediate layer Al, containing Zn and Mg It was measured amount. In EPMA analysis, the thickness direction vertical to 25% or more from the thickness center of each layer in 20μm or more regions in the width direction, a mapping analysis to calculate the mean composition.
[0100]
　Further, when obtaining the average Si content in the entire plated layer, EPMA by, toward the surface side of the plating layer from the base material side performs line analysis at 0.2μm pitch, an average of the measurement results of the plating layer value was calculated. Line analysis was carried out in five, and the average was taken as the average composition of the entire plating layer.
[0101]
　Furthermore, the cross section was photographed by SEM, the micrographs by image analysis to measure the thickness of each layer. For each layer of tissue was determined by performing crystal structure analysis by TEM respect flakes taken from the same location of the test strip.
[0102]
　And, for the ICP analytical test strip, after dissolving the plated layer in the 50 ° C. HCl, lysates by ICP analysis to determine the total content of Al and Zn contained in the plated layer. Similarly, the ICP analytical test strip to dissolve only an oxide layer with ammonium bichromate solution, lysates by ICP analysis was determined Mg, Cr, Ca, the content of Sr and Ti .
[0103]
　Next, as shown below, anti-LME resistance evaluation test was carried out spot weldability evaluation test and corrosion resistance after coating evaluation test.
[0104]
[Resistance LME Evaluation Test]
[0105]
　For the cross section in the thickness direction of the anti LME resistance evaluation test test piece for each test example, by observing the reflected electron image by SEM and the reflection electron detector to observe the occurrence of LME. At this time, it was a case where cracks to the base material (Fe concentration of 98% or more places) is progressing the LME occur. Then, Yu (1) which cracking does not occur, cracks were evaluated what extends to the base material over the plating layer impossible (4).
[0106]
　Incidentally, if the determination of the end position of the cracks is difficult in the above observation, using an energy dispersive X-ray microanalyzer, the surrounding area of ​​the crack end position, to perform energy dispersive X-ray analysis of (EDS) in, and determines whether the crack until the base material extends. In this case, Al, the total content of Zn is the plating layer areas that exceed 0.5%, the inner region of the steel was identified as the base material than that.
[0107]
[Spot Weldability Evaluation Test]
　relative to the weldability evaluation test test piece for each test example, by using a DC power supply, was carried out spot welding by pressure 350 kgf. Perform tests at various welding current, a nugget diameter of a weld is a lower limit value exceeding 4.7 mm, will increase the value of appropriate welding current, and the upper limit dust generated value during welding . Then, it sets the value between the upper and lower limit values and the proper current range was the difference between the upper limit value and the lower limit value as an index of spot weldability. In the evaluation of the spot weldability, excellent what the value is more than 1.5A (1), the good ones less than 1.0A 1.5A (2), those less than 0.5A 1.0A Yes (3), it was evaluated as bad (4) of less than 0.5A.
[0108]
[Corrosion resistance after painting evaluation test]
　with respect to corrosion resistance after painting evaluation test test piece for each test example, Nippon Parkerizing Co., Ltd. of surface conditioning treatment agent (trade name: Prepalene X) with the surface conditioning at room temperature 20s went. Then, Japan Parkerizing zinc phosphate treatment solution Co., Ltd. (trade name: PALBOND 3020) was performed using a phosphoric acid salt treatment. Specifically, the temperature of the processing solution and 43 ° C., and 120s immersed molded body to the treatment liquid. Thus, Phosphate coated surface of the steel material is formed.
[0109]
　After performing the phosphating described above, for each shaped body, in the Nippon Paint Co., Ltd. of cationic electrodeposition paint, and electrodeposition coating in the slope energizing voltage 160 V, further baking temperature 170 ° C. 20 minutes to baking. Thickness control of the coating after electrodeposition coating, a hot stamping previous steel, electrodeposition coating was carried out under the conditions to be 15 [mu] m.
[0110]
　On the molding body after the electrodeposition coating, crosscut to reach the steel base material were carried out composite corrosion test (JASO M610 cycle). Evaluate the corrosion resistance at paint blistering width, 180 cycles Yu those composite corrosion test coating after performing a blister width of 2.0mm below (1), 2.0mm ultra 3.0mm a good following ones ( 2), 3.0mm ultra-4.0mm allowed the following things (3), was evaluated as bad (4) those of 4.0mm greater.
[0111]
[Evaluation Results]
　In the present invention, the fatigue characteristics (resistance to LME resistance), and its object is to provide a spot weldability, and excellent well-balanced in all the corrosion resistance after coating a hot stamping molded article. Therefore, taking into account the results of evaluation Overall, any also as acceptable overall evaluation B at least impossible was not in overall evaluation A one and test were also excellent or good in the test, either those of the overall evaluation C there is impossible in the test was a failure. The results are shown in Table 4.
[0112]
[Table 4]

[0113]
　As is apparent from Table 4, hot stamping molded body according to the present invention, the fatigue characteristics (resistance to LME resistance), spot weldability, and it was confirmed that excellent well-balanced in all corrosion resistance after painting.
Industrial Applicability
[0114]
　According to the present invention, it is possible to obtain the fatigue characteristics, spot weldability, and excellent corrosion resistance after painting and the hot stamping molding. Therefore, hot stamping molded body according to the present invention can be suitably used as a structural member or the like used in an automobile or the like.

WE CLAIM

A hot stamping member and a base material and the base material plated layer formed on the surface of,
　the plating layer includes sequentially from the base material side, the interface layer, the intermediate layer and the oxide layer,
　the the interfacial layer tissue alpha iron, Fe 3 comprises one or more FeAl alloy selected from Al and FeAl, and the total area ratio of the FeAl alloy is 90% or more,
　the intermediate layer , Fe (Al, Zn) 2 , Fe 2 (Al, Zn) 5 and Fe (Al, Zn) 3 comprises one or more Fe-Al-Zn phase selected from, and wherein the Fe-Al-Zn total area of the phase is not less than 50%,
　the average composition of said intermediate layer is, by
　mass% Al: 30 ~ 50%,
　and, Zn: 15 ~ 30% wherein the
　said oxide layer has an average thickness is at 3.0μm or less, and, Mg content 0.0 ~ 0.50 g / m 2 is,
　hot stamping molding.
[Requested item 2]
　It said interfacial layer has an average thickness is 1.0μm or more,
　hot stamping molded article according to claim 1.
[Requested item 3]
　The total content of Al and Zn of the plating layer is 20 ~ 100 g / m 2 is,
　according to claim 1 or hot stamping molded product according to claim 2.
[Requested item 4]
　Wherein the Fe-Al-Zn phase total area ratio of the intermediate layer is 90% or more,
　hot stamping molding according to any one of claims 1 to 3.
[Requested item 5]
　The plating layer is in mass%, further comprises from 0.1 to 15% of Si,
　the intermediate layer, Fe 3 (Al, Si) and Fe (Al, Si) from the one or two selected further comprising a Fe-Al-Si phase and the Fe-Al-Zn phase and the total area ratio of the Fe-Al-Si phase is 90% or more,
　to any of claims 1 to 3 hot stamping body according.