Hot stamped products

Abstract

This hot stamp molded article comprises a base steel material and a plating layer that is formed on the surface of the base steel material; the plating layer has a chemical composition that contains, in mass%, 0.000010% to 3.0% of Sc, more than 15.0% but not more than 95.0% of Fe, 0% to 80.0% of Al, 0% to 20.0% of Si, and a total content of 0% to 5.0% of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi and In, with the balance being made up of 5.0% or more of Zn and impurities; and an η-Zn phase is present in the vicinity of the surface of the plating layer.

Description

[Technical Field]

[0001] The present invention relates to a hot stamped product. This application claims priority based on Japanese Patent Application No. 2022-003723, filed on January 13, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, there has been a demand for reducing the consumption of chemical fuels in order to protect the environment and prevent global warming. This demand is no exception, for example, for automobiles, which are essential means of transportation for daily life and activities. In response to this demand, efforts have been made to improve fuel efficiency in automobiles by reducing the weight of the vehicle body. Since many automobile structures are formed from iron, particularly steel plates, reducing the thickness of these steel plates to reduce their weight is highly effective in reducing the weight of the vehicle body. However, simply reducing the thickness of steel plates to reduce their weight is a concern as it reduces the strength of the structure and reduces safety. Therefore, in order to reduce the thickness of steel plates, it is necessary to increase the mechanical strength of the steel plates used so as not to reduce the strength of the structure. Therefore, research and development is being conducted on steel sheets that can maintain or increase their mechanical strength even when made thinner than previously used steel sheets by increasing their mechanical strength. Such steel sheets are being demanded not only in the automobile manufacturing industry but also in various other manufacturing industries.

[0003] Generally, materials with high mechanical strength tend to have poor shape fixability during bending and other forming processes, making the process itself difficult when they are processed into complex shapes. One method for solving this formability problem is the so-called "hot pressing method (hot stamping, high-temperature pressing, die quenching)." In this hot pressing method, the material to be formed is first heated to a high temperature, and the heated, softened material is pressed to form the material, and then cooled after, or simultaneously with, the forming.

[0004] According to this hot pressing method, the material is first heated to a high temperature to soften it, and then pressed in its softened state, making it easy to press the material. Therefore, this hot pressing process can produce press-formed products that have both good shape fixability and high mechanical strength. In particular, when the material is steel, the mechanical strength of the press-formed product can be increased by the quenching effect caused by cooling after forming.

[0005] However, when this hot pressing method is applied to steel sheets, heating to high temperatures, for example, above 800°C, causes the iron and other components on the surface to oxidize, forming scale (oxides). Therefore, a process for removing this scale (descaling process) is required after hot pressing, which reduces productivity. Furthermore, for components that require corrosion resistance, the surface of the component must be subjected to rust prevention treatment or metal coating after processing, which requires a surface cleaning process and a surface treatment process, which also reduces productivity.

[0006] One method that has been considered to suppress such a decrease in productivity is to apply a coating such as plating to the steel sheet before hot stamping, thereby improving corrosion resistance and eliminating the descaling process. Generally, various materials, such as organic and inorganic materials, are used for coating the steel sheet. Among these, zinc-based plating, which has a sacrificial corrosion protection effect, is often applied to steel sheets from the viewpoints of its corrosion protection performance and steel sheet production technology.

[0007] For example, Patent Document 1 discloses a hot-pressed steel sheet member having a chemical composition containing, by mass%, C: 0.30% or more and less than 0.50%, Si: 0.01% or more and 2.0% or less, Mn: 0.5% or more and 3.5% or less, Sb: 0.001% or more and 0.020% or less, P: 0.05% or less, S: 0.01% or less, Al: 0.01% or more and 1.00% or less, and N: 0.01% or less, with the balance being Fe and unavoidable impurities, and having a microstructure in which the average crystal grain size of prior austenite grains is 8 μm or less, the volume fraction of martensite is 90% or more, and the amount of solute C is 25% or less of the total C, and having a tensile strength of 1780 MPa or more, and further having an Al-based plating layer or a Zn-based plating layer on the surface. Patent Document 1 discloses that by applying a plating layer to the surface of a steel sheet, oxidation of the steel sheet surface due to hot pressing can be prevented, and furthermore, the corrosion resistance of hot-pressed steel sheet members can be improved. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2019 / 093384 Summary of the Invention [Problem to be solved by the invention]

[0009] As described above, forming a plating layer containing Zn (zinc-based plating layer) on the surface of a steel sheet has been practiced to prevent oxidation of the steel sheet surface due to hot pressing and to improve the corrosion resistance of the steel member after hot pressing. When such a plated steel sheet having a zinc-based plating layer is heated to a high temperature by hot stamping, welding, or the like, some of the Zn evaporates and the remaining Zn is alloyed with Fe that diffuses from the steel sheet substrate. As a result of studies by the present inventors, it has been found that when Zn evaporates, the corrosion resistance after painting of a steel member (molded product) obtained by hot stamping, welding, or the like decreases. However, no consideration is given to corrosion resistance after painting in Patent Document 1. Therefore, an object of the present invention is to provide a formed product (hot-stamped product) obtained by a hot stamping process using a plated steel sheet having a Zn-containing plating layer as a raw material, which formed product has excellent corrosion resistance after painting. [Means for solving the problem]

[0010] The present inventors have conducted research to improve the corrosion resistance after painting of hot stamped products obtained from plated steel sheets having a Zn-containing coating layer, and have found that the corrosion resistance after painting can be improved by adding a predetermined amount of Sc to the coating layer.

[0011] The present invention has been made in light of the above findings. [1] A hot stamped product according to one aspect of the present invention has a base steel material and a coating layer formed on a surface of the base steel material, and the coating layer has a chemical composition, in mass%, of Sc: 0.000010 to 3.0%, Fe: more than 15.0% but not more than 95.0%, Al: 0 to 80.0%, Si: 0 to 20.0%, Mg: 0 to 3.0%, Ca: 0 to 3.0%, La: 0 to 0.5%, Ce: 0 to 0.5%, Y: 0 to 0.5%, Cr: 0 to 1.0%, Ti: 0 to 1.0%, Ni: 0 to 1.0%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 1.0%, Cu: 0 to 1.0%, Mn: 0 to 1.0%, Sr: Zn: 0-0.5%, Sb: 0-0.5%, Pb: 0-0.5%, B: 0-0.5%, Li: 0-1.0%, Zr: 0-1.0%, Mo: 0-1.0%, W: 0-0.5%, Ag: 0-1.0%, P: 0-0.5%, Sn: 0-1.0%, Bi: 0-1.0%, In: 0-1.0%, and the balance: 5.0% or more of Zn and impurities, and the total content of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In is 0-5.0%, and an η-Zn phase is present on the surface of the plating layer. [2] In the hot-stamped product described in [1], the chemical composition of the coating layer may contain, in mass%, 15.0% or more of Zn and 0.00050 to 0.30% of Sc, and in a cross section of the coating layer, an area fraction of an intermetallic compound phase containing, in mass%, 3 to 40% of Sc, 3 to 50% of Zn, 3 to 50% of Fe, 0 to 50% of Al, and 0 to 30% of Si may be 0.1% or more. [3] In the hot-stamped product described in [2], the chemical composition of the plating layer may contain, in mass %, 15.0% or more of Zn and 0.010 to 0.30% of Sc. [4] In the hot stamped product according to any one of [1] to [3], the chemical composition of the coating layer contains, in mass%, 30.0 to 80.0% Al, and Fe4Al is present near the surface of the coating layer. 13 Phases may be present. [Effects of the Invention]

[0012] According to the above-described aspect of the present invention, a hot stamped product having excellent corrosion resistance after painting can be provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic diagram showing the shape of a molded product after hat molding. DETAILED DESCRIPTION OF THE INVENTION

[0014] A hot-stamped product according to one embodiment of the present invention (also referred to as the hot-stamped product according to this embodiment, or simply as the product according to this embodiment) will be described. The hot-stamped product according to this embodiment includes a base steel material and a coating layer formed on the surface of the base steel material. The chemical composition of the coating layer includes, in mass%, 0.000010 to 3.0% Sc and more than 15.0% but not more than 95.0% Fe. The chemical composition of the coating layer may optionally contain 0 to 80.0% Al and 0 to 20.0% Si. The coating layer may also optionally contain one or more elements selected from Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In in a total amount of 5.0% or less. The balance of the chemical composition is 5.0% or more Zn, in mass%, and impurities. Furthermore, in the hot stamped product according to this embodiment, the η-Zn phase is present near the surface of the plating layer. The hot stamped product according to this embodiment further contains Fe4Al in the plating layer (particularly the surface). 13 It is preferred that a phase is present (formed). Furthermore, in the hot stamped product according to this embodiment, the area ratio of an intermetallic compound phase containing, by mass%, 3 to 40% Sc, 3 to 50% Zn, 3 to 50% Fe, 0 to 50% Al, and 0 to 30% Si is preferably 0.1% or more in a cross section of the plating layer. The reasons for each limitation will be explained below.

[0015] [Base steel material] For the formed product according to this embodiment, the plating layer is important, and the type of base steel is not particularly limited. The type may be determined depending on the product to which it is applied, the required strength, plate thickness, etc. The base steel is, for example, a hot-stamped steel material using a hot-rolled mild steel plate as specified in JIS G3131:2018 or a cold-rolled steel plate as specified in JIS G3141:2021 as a base plate.

[0016] [Plating layer] The molded product according to this embodiment has a plating layer on at least a portion of the surface of the base steel material. The plating layer may be formed on one side or both sides of the base steel material.

[0017] <Chemical composition> The chemical composition of the plating layer of the molded article according to this embodiment will be described below. Hereinafter, % regarding the content of each element means % by mass.

[0018] Sc: 0.000010~3.0% Sc is an important element in the plating layer of the molded article according to this embodiment. When a plated steel sheet having a zinc-based plating layer is heated to high temperatures during processes such as hot stamping and welding, some of the zinc (Zn) evaporates. However, if the plating layer contains 0.000010% or more of Sc, the evaporation of Zn at high temperatures is suppressed. The suppression of Zn evaporation also suppresses the decrease in the Zn content in the Zn-Fe alloy formed on the surface by heating to high temperatures, improving the corrosion resistance after painting in hot-stamped products. Conventionally, even if a trace amount of Sc was contained as an impurity in a raw material, it was removed by refining. Therefore, Sc is hardly contained in the coating layer of conventional plated steel sheets or hot-stamped products obtained from the plated steel sheets. Even in rare cases where Sc is mixed in as an impurity, it has been confirmed that the Sc content is 0.000004% (0.04 ppm) or less. In contrast, the present inventors have newly discovered that a Sc content of 0.000010% (0.10 ppm) or more suppresses Zn evaporation. Although the mechanism by which the inclusion of Sc prevents Zn from evaporating even when heated to high temperatures is not yet clear, a thin oxide film containing Zn oxide (and Al oxide if Al is included) forms on the surface of the plating layer after plating in an oxygen-containing environment such as the atmosphere. It is assumed that Sc migrates into this oxide film when the temperature rises due to heating, etc., and modifies the oxide film, thereby preventing Zn evaporation. If the Sc content in the coating layer is less than 0.000010%, the evaporation of Zn is not suppressed, and the effect of improving the corrosion resistance after painting in the hot stamped product cannot be obtained. Therefore, the Sc content is set to 0.000010% or more. The Sc content is preferably 0.000050% or more, 0.00010% or more, 0.00025% or more, or 0.00050% or more, and more preferably 0.010% or more, 0.025% or more, 0.050% or more, or 0.10% or more. On the other hand, if the Sc content exceeds 3.0%, the effect saturates and the cost increases. Therefore, the Sc content is set to 3.0% or less. If necessary, the Sc content may be set to 1.5% or less, 0.80% or less, or 0.40% or less. Furthermore, if the Sc content exceeds 0.30%, it may be difficult to prepare the plating bath, so the Sc content may be set to 0.30% or less.

[0019] Fe: more than 15.0%, less than 95.0% Fe is contained in the coating layer by diffusing from the base sheet to the coating layer during manufacturing, or by diffusing from the base sheet and alloying with Zn in the coating layer when exposed to high temperatures such as hot stamping or welding. In hot stamping, the Fe content in the coating layer generally exceeds 15.0% due to alloying between the coating layer and the base steel. Therefore, the Fe content is set to exceed 15.0%. The Fe content may be 18.0% or more, 20.0% or more, 23.0% or more, 26.0% or more, 30.0% or more, 35.0% or more, or 40.0% or more, as necessary. On the other hand, if the Fe content exceeds 95.0%, the Zn content becomes too low, resulting in reduced corrosion resistance after painting. Therefore, the Fe content is set to 95.0% or less. The Fe content may be set to 90.0% or less, 85.0% or less, 80.0% or less, 75.0% or less, 70.0% or less, 65.0% or less, or 60.0% or less, as necessary.

[0020] Al: 0 to 80.0% Al is an element effective for improving corrosion resistance in a plating layer containing aluminum (Al) and zinc (Zn). Furthermore, Al contributes to the formation of an alloy layer (Al-Fe alloy layer) and is also an element effective for improving plating adhesion. To fully obtain the above effects, Al may be contained. To obtain the above effects, the Al content is preferably 5.0% or more, more preferably 10.0% or more, 15.0% or more, 20.0% or more, or 25.0% or more. Furthermore, under conditions where the Al content is 30.0% or more or 35.0% or more, Fe4Al in the plating layer can be obtained. 13 This phase is formed, and the corrosion resistance after painting, particularly the corrosion resistance against blistering of the paint film, is further improved. Therefore, the Al content is more preferably 30.0% or more, or 35.0% or more. On the other hand, if the Al content exceeds 80.0%, the Zn content becomes too low, resulting in a decrease in corrosion resistance after painting. Therefore, the Al content is set to 80.0% or less. The Al content is preferably 70.0% or less or 65.0% or less, more preferably 60.0% or less, 55.0% or less, or 50.0% or less.

[0021] Si: 0 to 20.0% Si is an element that has the effect of preventing the alloy layer formed between the steel sheet and the plating layer from becoming excessively thick, thereby improving the adhesion between the steel sheet and the plating layer. Furthermore, when Si is contained together with Mg, it forms a compound with Mg and contributes to improving corrosion resistance after painting. Therefore, Si may be contained. To obtain the above effects, the Si content is preferably 0.05% or more, more preferably 0.1% or more, 0.2% or more, or 0.5% or more, and even more preferably 1.0% or more, or 1.5% or more. On the other hand, if the Si content exceeds 20.0%, the Sc-containing intermetallic compound in the plated steel sheet as a base material contains a large amount of Si, which increases the melting point of the Sc-containing intermetallic compound phase. In this case, even when the plated steel sheet is exposed to high temperatures, the Sc-containing intermetallic compound does not melt, and Sc does not function sufficiently. As a result, the Zn evaporation suppression effect of Sc is not fully achieved. Therefore, the Si content is set to 20.0% or less. From the viewpoint of the workability of the plated layer, the Si content may be set to 15.0% or less, 10.0% or less, 7.0% or less, 5.0% or less, 3.5% or less, or 2.5% or less.

[0022] The plating layer of the molded article according to this embodiment may contain Zn and impurities in addition to the elements mentioned above. To ensure corrosion resistance after painting, the Zn content is set to 5.0% or more. The Zn content is preferably 15.0% or more. In particular, a Zn content of 15.0% or more further improves corrosion resistance after painting, particularly corrosion resistance to erosion of the base steel. The Zn content is preferably 7.0% or more, 10.0% or less, 15.0% or more, 18.0% or more, 21.0% or more, 25.0%, or 30.0% or more. On the other hand, the Zn content is less than 85.0%. If necessary, the Zn content may be 80.0% or less, 70.0% or less, 60.0% or less, 55.0% or less, 50.0% or less, or 45.0% or less.

[0023] Furthermore, the chemical composition of the plating layer of the molded product according to this embodiment may contain one or more elements selected from the group consisting of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In, each in the following ranges and in a total content of 5.0% or less, for the purpose of improving various properties or as impurities. These elements do not necessarily need to be contained, so the lower limit of the content of these elements is 0%.

[0024] Mg: 0-3.0% Mg is an element that has the effect of increasing the corrosion resistance of the plating layer, and therefore may be contained. On the other hand, if the Mg content exceeds 3.0%, the workability of the coating layer decreases. Furthermore, problems in manufacturing occur, such as an increase in the amount of dross generated in the coating bath. Therefore, the Mg content is set to 3.0% or less. The Mg content may also be set to 2.0% or less, 1.0% or less, 0.5% or less, or 0.2% or less.

[0025] Ca: 0 to 3.0% Ca is an element that, when contained in the coating layer, reduces the amount of dross that tends to form during coating operations as the Mg content increases, thereby improving coating manufacturability. Therefore, Ca may be contained. On the other hand, if the Ca content is high, CaZn 11 Ca-based intermetallic compounds, including Ca-phases, are formed, which reduces corrosion resistance. Therefore, the Ca content is set to 3.0% or less. The Ca content may also be set to 2.0% or less, 1.0% or less, 0.5% or less, or 0.2% or less.

[0026] La: 0 to 0.5% Ce: 0 to 0.5% Y: 0 to 0.5% If the La content, Ce content, or Y content is excessive, the viscosity of the plating bath increases, which may make preparation of the plating bath itself difficult. Therefore, the La content, Ce content, and Y content are each set to 0.5% or less. The La content, Ce content, and Y content may also be set to 0.2% or less or 0.1% or less.

[0027] Cr: 0 to 1.0% Ti: 0 to 1.0% Ni: 0 to 1.0% Co: 0 to 0.25% V: 0 to 0.25% Nb: 0 to 1.0% Cu: 0 to 1.0% Mn: 0 to 1.0% Sr: 0 to 0.5% Sb: 0 to 0.5% Pb: 0 to 0.5% B: 0 to 0.5% Li: 0 to 1.0% Zr: 0 to 1.0% Mo: 0 to 1.0% W: 0 to 0.5% Ag: 0-1.0% P: 0 to 0.5% These elements have the effect of improving corrosion resistance on the acid side by substituting Al, Zn, etc. in the plating layer and shifting the potential to the noble side, and therefore may be contained. On the other hand, excessive amounts of these elements may form intermetallic compounds, which may deteriorate corrosion resistance on the acid side and / or alkaline side. Therefore, the contents of Cr, Ti, Ni, Nb, Cu, Mn, Li, Zr, Mo, and Ag are each limited to 1.0% or less, the contents of Co and V are each limited to 0.25% or less, and the contents of Sr, Sb, Pb, B, W, and P are each limited to 0.5% or less. The contents of Cr, Ti, Ni, Nb, Cu, Mn, Li, Zr, Mo, and Ag may each be limited to 0.5%, 0.3%, or 0.2%, respectively. The contents of Co and V may each be limited to 0.10%, 0.05%, or 0.03%, respectively. The contents of Sr, Sb, Pb, B, W, and P may each be limited to 0.2% or 0.1% or less.

[0028] Sn: 0 to 1.0% Sn is an element that increases the rate of magnesium dissolution in a plating layer containing Zn, Al, and Mg. It also forms intermetallic compounds that significantly improve the acid and alkaline corrosion resistance of the plating. Therefore, Sn may be included. On the other hand, if the dissolution rate of Mg increases, the corrosion resistance of the flat surface deteriorates. Also, the corrosion resistance on the acid side deteriorates significantly. Therefore, the Sn content is set to 1.0% or less. The Sn content may also be set to 0.5% or less, 0.3% or less, or 0.2% or less.

[0029] Bi: 0 to 1.0% In: 0 to 1.0% Bi and In are elements that form intermetallic compounds that improve alkaline corrosion resistance, and therefore may be contained. On the other hand, if the Bi content or In content exceeds 1.0%, the corrosion resistance on the acid side is significantly deteriorated, so the Bi content and In content are each set to 1.0% or less.

[0030] Even if the content of each of the above-mentioned elements Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In is within the above-mentioned range, if the total content exceeds 5.0%, corrosion resistance on the acid side and / or the alkaline side may deteriorate, or the viscosity of the plating bath may increase, making preparation of the plating bath itself difficult. Therefore, the total content of these elements is set to 0 to 5.0%.

[0031] The chemical composition of the plating layer is measured by the following method. First, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel (for example, 10% hydrochloric acid plus 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to obtain an acid solution. Next, the obtained acid solution is measured by ICP analysis to determine the chemical composition of the plating layer.

[0032] <Organization> In the plating layer of the molded product according to this embodiment, the η-Zn phase exists near the surface. The η-Zn phase is a phase that exhibits good sacrificial corrosion protection against Fe in atmospheric environments. Therefore, the inclusion of the η-Zn phase in the plating layer (especially the surface) further improves corrosion resistance after painting. The η-Zn phase is a hcp structure phase with a small amount of Fe dissolved in it. In the formed product according to this embodiment, as described below, a plated steel sheet containing an intermetallic compound phase containing Sc and having an equivalent circle diameter (equivalent circle diameter) of 5.0 μm or less at a predetermined area ratio (a region having an equivalent circle diameter of 5.0 μm or less and containing 3.0 mass% or more of Sc) is used as the base steel sheet. When such a base steel sheet is heated to a high temperature by hot stamping, welding, or the like, it is assumed that the Sc present as the intermetallic compound phase migrates into the oxide film on the surface as the temperature rises due to heating, etc., and modifies the oxide film, thereby suppressing the evaporation of Zn. The evaporation of Zn due to high-temperature heating is suppressed, and the η-Zn phase is formed near the surface during subsequent cooling.

[0033] Furthermore, in the molded article according to this embodiment, the area ratio of an intermetallic compound phase containing, by mass %, 3 to 40% Sc, 3 to 50% Zn, 3 to 50% Fe, 0 to 50% Al, and 0 to 30% Si is preferably 0.1% or more in the cross section of the plating layer, which further improves corrosion resistance after painting. Such an intermetallic compound phase containing a relatively large amount of Zn together with Sc can be obtained by increasing the Zn content and the Sc content, using a plated steel sheet containing the above-mentioned intermetallic compound phase containing Sc and having an equivalent circle diameter of 5.0 μm or less at a predetermined area ratio as a base steel sheet, and suppressing the evaporation of Zn due to high-temperature heating.

[0034] In addition, the plating layer of the molded product according to this embodiment contains Fe4Al near the surface. 13 Preferably, a phase is present. Fe4Al 13 The FeAl phase contributes more to improving corrosion resistance than the FeAl phase, which is generally formed near the surface of a coating layer containing Fe and Al. 13 The presence (formation) of this phase further improves corrosion resistance after painting.

[0035] Near the surface of the coating layer, η-Zn phase and Fe4Al 13 The presence or absence of the phase is evaluated by XRD measurement. Specifically, XRD measurement is performed by irradiating the surface of the coating layer with X-rays using a Cu tube as the X-ray source, and if a peak is present at 42.9 to 43.6° in 2θ, it is determined that the η-Zn phase is present. Also, if a peak is present at 25.0 to 25.8° in 2θ, it is determined that the η-Zn phase is present. 13 It is determined that a phase exists. In this embodiment, if an intensity that is 1.5 times or more the intensity of the baseline is detected within a predetermined range of 2θ, it is determined that a peak exists.

[0036] The area ratio of the Sc-containing intermetallic compound phase in the plating layer can be determined by the following method. Five samples are taken so that the cross section of the plating layer in the thickness direction can be observed. For these samples, a rectangular area of ​​100 μm in the thickness direction and 500 μm in the direction perpendicular to the thickness direction is defined as one field of view, and a total of five fields of view are photographed using EDS at 1500x magnification to obtain mapping images. The spot diameter should be 1 to 10 nm, the voltage should be 15 kV, and the current should be 10 nA. From the Sc element distribution image of the obtained mapping image, the "Analyze" function of the image analysis software "ImageJ" was used to determine the area of ​​the region containing 3-40% Sc, 3-50% Zn, 3-50% Fe, 0-50% Al, and 0-30% Si by mass, and the area ratio relative to the observed field of view was calculated. The average of the five fields of view was calculated, and this was taken as the area ratio of the intermetallic compound phase.

[0037] When galvanized steel sheets are resistance spot welded together, or when cold-rolled steel sheets are resistance spot welded to galvanized steel sheets, cracks called liquid metal embrittlement (LME) cracks can occur at the spot welds. LME cracks occur when the heat generated during resistance spot welding melts the zinc in the galvanized layer, causing the molten zinc to penetrate the grain boundaries of the steel sheet structure at the weld, resulting in tensile stress acting on the steel sheet. The conditions for cracks to occur are that the molten zinc comes into contact with the solid steel sheet during welding, and that tensile stress (strain) acts at that point. The higher the strength of the steel sheet, the greater the susceptibility to LME cracking tends to be. When a zinc-containing coated steel sheet is subjected to hot stamping to form a bent portion, there is a concern that LME cracking may occur. However, in the formed product according to this embodiment, LME cracking is suppressed. Although the detailed mechanism is unknown, it is assumed that the inclusion of Sc changes the impurity elements in the liquid phase Zn present during forming, thereby suppressing LME cracking. Therefore, it is preferable that the formed product according to this embodiment is free of LME cracking.

[0038] The presence or absence of LME cracks is judged by visually inspecting the appearance of the bent part after hot stamping.

[0039] <Adhesion amount> The coating weight per side of the plating layer (hereinafter simply referred to as coating weight) is 20 to 160 g / m 2 is preferred. The coating weight of the plating layer is 20g / m 2 If the coating weight is less than 160g / m, sufficient corrosion resistance may not be obtained. 2 If the coating weight is more than 30 g / m, the adhesion of the plating layer will decrease and the plating may peel off. 2 More than 40g / m 2 More than 50g / m 2 or more than 60g / m 2 It may be more than 140 g / m 2 Below 120g / m 2 Below 100g / m 2 or less than 90g / m 2 The following may also be used.

[0040] The amount of adhesion can be measured by the following method. First, a 30mm x 30mm sample is taken from the molded product, and the plating layer is stripped and dissolved from this sample using an acid containing an inhibitor that suppresses corrosion of the base steel (for example, an acid made by adding 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to 10% hydrochloric acid). The weight change of the plated steel sheet after stripping and dissolution is measured, and the adhesion weight is calculated from the results.

[0041] The shape of the formed product according to this embodiment is not particularly limited. That is, it may be a flat plate obtained by hot stamping without deformation, or a formed body formed by hot stamping. However, a formed body having a flat shape (i.e., a flat plate) can be easily obtained without the need for hot working such as hot stamping, so there is no need to use a hot stamped product. For this reason, with regard to the shape of the formed product according to this embodiment, flat shapes are generally not applicable, except for exceptions such as for test purposes. Those skilled in the art can easily identify whether a product is hot stamped by a known method, for example, by analyzing the structure and strength of the base steel of the formed body. For example, by comparative analysis of the hardness of the bent portion and the hardness of the flat portion of the steel, it is possible to easily identify whether the product is produced by cold working or hot stamping.

[0042] The thickness of the molded article according to this embodiment is not limited, but is preferably 0.5 to 3.0 mm, taking into consideration the intended use and the like.

[0043] [Manufacturing method] The effects of the formed product according to the present embodiment can be obtained as long as it has the above-mentioned characteristics, regardless of the manufacturing method. However, the formed product according to the present embodiment can be manufactured by hot stamping or the like on a plated steel sheet having a plating layer that contains Sc and in which the area ratio of intermetallic compound phases containing Sc and having an equivalent circle diameter of 5.0 μm or less is 0.1 to 10.0% in a cross section in the thickness direction of the plating layer. The manufacturing conditions for the formed product according to this embodiment are characterized by the plated steel sheet that is the raw material, and the conditions for hot stamping, etc. are not limited. When hot stamping is performed, known conditions may be used. For example, the plated steel sheet according to this embodiment may be heated to 850 to 1000°C, held for 0 to 600 seconds, and then formed in a mold and rapidly cooled at the same time.

[0044] The plated steel sheet that serves as the raw material will be described below. The plated steel sheet (sometimes referred to as the plated steel sheet according to the present embodiment) used as the raw material for the molded product according to the present embodiment comprises a steel sheet, a plating layer formed on the surface of the steel sheet, and an oxide film having a thickness of 10 nm or more formed on the surface of the plating layer. The chemical composition of the plating layer is, in mass %, 0.000010 to 4.0% Sc, and may optionally contain Al, Fe, and Si. Also, optionally, the plating layer may further contain one or more of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, Ag, and Sn in a total amount of 5.0% or less, with the balance being Zn and impurities. Furthermore, in the plated steel sheet according to the present embodiment, the area fraction of an intermetallic compound phase containing Sc and having an equivalent circle diameter of 5.0 μm or less in a cross section of the plating layer in the thickness direction is 0.1 to 10.0%.

[0045] [Steel plate] The steel sheet (original sheet for plating) included in the plated steel sheet according to this embodiment is not particularly limited. It may be determined based on the product to which it is applied, the required strength, sheet thickness, etc. For example, a hot-rolled mild steel sheet as specified in JIS G3131:2018 or a cold-rolled steel sheet as specified in JIS G3141:2021 can be used.

[0046] [Plating layer] The plated steel sheet according to this embodiment has a plating layer on at least a portion of the surface of the steel sheet. The plating layer may be formed on one side or both sides of the steel sheet. This plating layer becomes the plating layer of the formed product according to this embodiment after undergoing hot stamping or the like.

[0047] <Chemical composition> The chemical composition of the plating layer of the plated steel sheet according to this embodiment will be described below. Hereinafter, % regarding the content of each element means % by mass.

[0048] Sc: 0.000010~4.0% If the Sc content in the coating layer is less than 0.000010%, the effect of suppressing Zn evaporation cannot be obtained. Therefore, the Sc content is set to 0.000010% or more. The Sc content is preferably 0.00050% or more, and more preferably 0.010% or more. On the other hand, if the Sc content exceeds 4.0%, the effect saturates and the cost increases. Therefore, the Sc content is set to 4.0% or less. Furthermore, if the Sc content exceeds 0.30%, it may be difficult to prepare the plating bath, so the Sc content may be set to 0.30% or less.

[0049] Al: 0 to 93.0% Al is an element effective for improving corrosion resistance in a plating layer containing aluminum (Al) and zinc (Zn). Furthermore, Al contributes to the formation of an alloy layer (Al-Fe alloy layer) and is also an element effective for improving plating adhesion. To fully achieve the above effect, Al may be contained. To achieve the above effect, the Al content is preferably 5.0% or more, and more preferably 10.0% or more. Furthermore, Al is an element that forms a strong oxide film on the surface of the plating layer and has the effect of suppressing Zn evaporation. To achieve this effect, the Al content is preferably 19.0% or more. On the other hand, if the Al content exceeds 93.0%, the Zn content becomes too small, resulting in a decrease in corrosion resistance after painting. Therefore, the Al content is set to 93.0% or less. The Al content is preferably 90.0% or less.

[0050] Fe: 0 to 15.0% Iron can be present in the coating layer due to diffusion from the original plate to the coating layer during manufacturing. In particular, in the case of hot-dip coating, iron can be present up to 15.0%. However, if the iron content is 15.0% or less, the effect on corrosion resistance after painting is small. Therefore, the iron content is set to 15.0% or less.

[0051] Si: 0 to 20.0% Si is an element that has the effect of preventing an excessively thick alloy layer from being formed between the steel sheet and the plating layer when a plating layer is formed on the steel sheet, thereby improving the adhesion between the steel sheet and the plating layer. Furthermore, when Si is contained together with Mg, it forms a compound with Mg and contributes to improving corrosion resistance after painting. Therefore, Si may be contained. To obtain the above effects, the Si content is preferably 0.05% or more, and more preferably 1.0% or more. On the other hand, if the Si content exceeds 20.0%, the large amount of Si contained in the Sc-containing intermetallic compound raises the melting point of the Sc-containing intermetallic compound phase. In this case, even when the plated steel sheet is exposed to high temperatures, the Sc-containing intermetallic compound does not melt, and Sc does not sufficiently interact with Zn. As a result, the Zn evaporation suppression effect of Sc cannot be fully achieved. Therefore, the Si content is set to 20.0% or less. From the viewpoint of the workability of the plated layer, the Si content may be set to 10.0% or less.

[0052] In addition to the elements described above, the plating layer of the plated steel sheet according to this embodiment may contain Zn and impurities. However, for the purpose of improving various properties, or as an impurity, one or more elements selected from the group consisting of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In may be contained. Since these elements do not necessarily need to be contained, the lower limit is 0%. The Zn content is 7.0% or more. The preferred contents of these elements and the reasons for limiting them are the same as those explained for the hot stamped product, and therefore will not be explained here.

[0053] The chemical composition of the plated steel sheet used as a raw material may be selected within the above range so as to achieve the chemical composition of the plating layer desired to be obtained in the hot-stamped product, after previously examining the relationship between the chemical composition of the plated steel sheet used as a raw material and the chemical composition of the plating layer of the hot-stamped product after hot stamping.

[0054] The chemical composition of the plating layer is measured by the following method. First, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel (for example, 10% hydrochloric acid plus 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to obtain an acid solution. Next, the obtained acid solution is measured by ICP analysis to determine the chemical composition of the plating layer.

[0055] <Organization> In the plating layer of the plated steel sheet (base steel sheet) according to this embodiment, the area ratio of the intermetallic compound phase containing Sc and having an equivalent circle diameter of 5.0 μm or less is 0.1 to 10.0% in a cross section in the thickness direction of the plating layer. The area ratio of the intermetallic compound phase containing Sc and having an equivalent circle diameter of 5.0 μm or less is preferably 1.0 to 10.0%. Intermetallic compound phases with an equivalent circle diameter of 5.0 μm or less can come into contact with the surrounding η-Zn phase and act more effectively to suppress Zn evaporation than when they are dissolved in the α-Al phase or when their equivalent circle diameter is large. The above effect can be sufficiently obtained if the area ratio of the Sc-containing intermetallic compound phase with an equivalent circle diameter of 5.0 μm or less is 0.1% or more. The area ratio of the Sc-containing intermetallic compound phase with an equivalent circle diameter of 5.0 μm or less is more preferably 1.0% or more. On the other hand, in order to make the area ratio of the Sc-containing intermetallic compound phase having an equivalent circle diameter of 5.0 μm or less exceed 10.0%, an Sc content of more than 4.0% is required, which increases costs. Therefore, it is preferable to make the area ratio of the Sc-containing intermetallic compound phase having an equivalent circle diameter of 5.0 μm or less 10.0% or less. There is no lower limit for the equivalent circle diameter of the target intermetallic compound phase, but from the viewpoint of measurement accuracy, it is preferable to target intermetallic compound phases having an equivalent circle diameter of 0.1 μm or more. The area ratio of the Sc-containing intermetallic compound phase having an equivalent circle diameter of 5.0 μm or less can be controlled by the Sc content and the cooling conditions after plating, which will be described later.

[0056] The area ratio of the Sc-containing intermetallic compound phase having an equivalent circle diameter of 5.0 μm or less in the cross section of the plating layer can be determined by the following method. Five samples were taken so that the cross section of the plating layer in the thickness direction could be observed. Each of these samples was taken at a rectangular area of ​​100 μm in the thickness direction and 500 μm in the direction perpendicular to the thickness direction, with one field of view being one rectangular area. Images of each field, for a total of five fields, were taken at 1500x magnification using EDS to obtain mapping images. From the Sc element distribution image in this mapping image, the "Analyze" function of the image analysis software "ImageJ" was used to determine the area ratio of the region with an equivalent circle diameter of 5.0 μm or less and containing 3.0 mass% or more of Sc relative to the observed field. The average of the five fields was calculated to determine the area ratio of the intermetallic compound phase containing Sc and with an equivalent circle diameter of 5.0 μm or less.

[0057] <Adhesion amount> The coating weight per side of the plating layer is 20 to 160 g / m 2 is preferred. The coating weight of the plating layer is 20g / m 2 If the coating weight is less than 160g / m, sufficient corrosion resistance may not be obtained. 2 If it exceeds this value, the adhesion of the plating layer may decrease, and the plating may peel off.

[0058] The amount of adhesion can be measured by the following method. A 30mm x 30mm sample is taken from the plated steel sheet, and the plating layer is stripped and dissolved from this sample using an acid containing an inhibitor that suppresses corrosion of the base steel (for example, an acid made by adding 1% Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.) to 10% hydrochloric acid). The weight change of the plated steel sheet after stripping and dissolution is measured, and the adhesion weight is calculated from the results.

[0059] [Oxide film] In the plated steel sheet according to this embodiment, an oxide film having a thickness of 10 nm or more is present on the surface of the plated layer. The oxide film can suppress the evaporation of Zn when the plated steel sheet is heated to a high temperature during hot stamping, for example. If the thickness of the oxide film is less than 10 nm, the evaporation of Zn cannot be suppressed, resulting in a decrease in red rust resistance. There is no upper limit to the thickness of the oxide film, but it may be 50 nm or less.

[0060] The thickness of the oxide film is determined by a method using a high-frequency glow discharge optical emission spectrometer (GDS). Specifically, the surface of the test piece is placed in an Ar atmosphere, and with glow plasma generated, the surface is sputtered and analyzed in the depth direction. Elements are identified from the element-specific emission spectrum wavelengths emitted by excited atoms in the glow plasma, and the emission intensity of the identified elements is estimated. Depth data is estimated from the sputtering time. The relationship between sputtering time and sputtering depth is determined in advance using a standard sample, and the sputtering time is converted to sputtering depth. The sputtering depth converted from the sputtering time is defined as the depth from the surface. The obtained emission intensity is converted to mass % by creating a calibration curve. The depth measured in this way from the outermost surface to the position where the O content is 5% by mass is measured. This is done at three locations, and the average of the depths measured at the three locations to the position where the O content is 5% by mass is taken as the thickness of the oxide film.

[0061] The plated steel sheet according to this embodiment can be produced, for example, by undergoing the following step of forming a plating layer containing Sc (plating layer forming step).

[0062] <Plating layer formation process> The method for forming the plating layer is not limited, but a hot dip plating method is an example. In the case of hot dip plating, methods including (I) to (III) can be employed. (I) Immerse a steel sheet (base sheet) in a hot dip coating bath containing Sc, (II) The steel sheet is removed from the plating bath, and the coating weight is controlled using wiping gas or the like. (III) Cool to room temperature.

[0063] (I) Immersion in plating bath A coating layer is formed on the surface of a steel sheet by immersing the steel sheet in a hot dip coating bath containing Sc. The chemical composition of the coating bath may, for example, contain 0.000010 to 4.0% Sc, and further contain Al, Si, Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In depending on the chemical composition of the coating layer to be finally obtained, with the balance being Zn and impurities. The steel sheet may be subjected to a heat reduction treatment before being immersed in the coating bath. For example, the surface of the steel sheet to be immersed in the coating bath is subjected to a heat reduction treatment at 800°C in an N2-5% H2 gas atmosphere in a furnace with an oxygen concentration of 20 ppm or less, and then air-cooled with N2 gas until the immersed sheet temperature reaches the bath temperature +20°C, after which the steel sheet is immersed in the coating bath. The immersion time in the coating bath is preferably about 1 to 10 seconds.

[0064] (II) Raising After immersion in the plating bath in (I), the steel sheet is removed from the plating bath and the coating weight is controlled with wiping gas such as N2 gas.

[0065] (III) Cooling The steel sheet with the controlled coating weight is cooled to room temperature. By setting the average cooling rate from the bath temperature to (bath temperature -50°C) to 5°C / sec or less and the average cooling rate from (bath temperature -50°C) to 100°C to 20°C / sec or more, the formation of intermetallic compounds containing Sc and having a circle equivalent diameter of 5.0 μm or less is promoted. If the average cooling rate from the bath temperature to (bath temperature - 50°C) exceeds 5°C / sec, Sc will be in solid solution in the α-Al phase. Sc dissolved in the α-Al phase will not crystallize as an intermetallic compound phase. Therefore, to prevent Sc from being solid-dissolved in the α-Al phase, the average cooling rate from the bath temperature to (bath temperature - 50°C) is set to 5°C / sec or less. Preferably, it is 3°C / sec or less. Thereafter, during cooling from the bath temperature to (bath temperature -50°C), the Sc that did not dissolve in the α-Al phase is concentrated in a Zn-based liquid phase, and by cooling at an average cooling rate of 20°C / sec or more from (bath temperature -50°C) to 100°C, it crystallizes as a fine intermetallic compound phase. If the average cooling rate from (bath temperature -50°C) to 100°C is less than 20°C / sec, coarse intermetallic compounds crystallize, and the number density of Sc-containing intermetallic compounds with an equivalent circle diameter of 5.0 μm or less decreases. The average cooling rate is preferably 30°C / sec or more.

[0066] A technique for applying an acidic solution to the surface of plated steel sheets to form patterns has been proposed. Although the mechanism is unclear, the plated steel sheets according to this embodiment are not subjected to an acidic solution because applying an acidic solution dissolves the oxide film on the surface, making it impossible to prevent Zn evaporation. Without applying an acidic solution, the oxide film on the surface of the plating layer would be 10 nm or thicker. As a result, Zn evaporation is suppressed during the hot stamping process, improving red rust resistance. [Example]

[0067] Examples of the present invention will be described below. The examples shown below are examples of the present invention, and the present invention is not limited to the examples described below.

[0068] A 1.6 mm thick steel sheet containing 0.2 mass% C and 1.3 mass% Mn was used as the base sheet for plating. A plating bath containing 0.00001 to 4.0 mass% Sc, and optionally Al, Si, Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In, with the balance being Zn and impurities, was prepared. The plated original sheet was cut into a size of 200 mm x 100 mm, and then plated in a batch-type hot dip plating test device. To form the plating layer, the surface of the plated base sheet before immersion in the plating bath was subjected to a heating reduction treatment at 800°C in an N2-5% H2 gas atmosphere in a furnace with an oxygen concentration of 20 ppm or less, and then air-cooled with N2 gas until the immersed plate temperature reached the bath temperature +20°C.Then, the plate was immersed in a plating bath at a bath temperature of 400 to 700°C for approximately 3 seconds. After immersion in the plating bath, the workpiece was pulled up at a pulling speed of 20 to 200 mm / sec. During the pulling-up, the plating deposition weight was controlled using N2 wiping gas. After the steel sheets were pulled out of the coating bath, they were cooled from the coating bath temperature to room temperature under the conditions shown in Table 1. In this way, coated steel sheets No. 1 to No. 35 were produced. In each step, the sheet temperature was measured using a thermocouple spot-welded to the center of the original sheet to be plated.

[0069] The area ratio of the Sc-containing intermetallic compound phase having an equivalent circle diameter of 5.0 μm or less was determined from the plated steel sheet in the same manner as above. The results are shown in Table 1.

[0070] Furthermore, a 180 mm × 50 mm blank was cut from the obtained plated steel sheet, and this blank was subjected to hot stamping by heating, holding for a certain period of time, and then hat-forming using a die, followed by simultaneous quenching to obtain a hot stamped product. The following three conditions were used: Condition A: The plated steel sheet is placed in a furnace at 900°C, and after the temperature of the plated steel sheet reaches the furnace temperature -10°C, it is held in the furnace for 100 seconds, then removed from the furnace and hat-formed using a hat-forming mold at room temperature, and the mold is rapidly cooled. Condition B: The plated steel sheet is placed in a furnace at 900°C, and after the temperature of the plated steel sheet reaches the furnace temperature -10°C, it is held in the furnace for 240 seconds, then removed from the furnace and hat-formed using a hat-forming mold at room temperature, and the mold is rapidly cooled. Condition C: The plated steel sheet is heated to 900°C at an average heating rate of 80°C / sec by high-frequency induction heating or electrical heating, then the heating is stopped and the hat forming is performed using a hat forming die that is at room temperature, and the die is rapidly cooled. The shape of the hot stamped product after hat forming was as shown in Figure 1. For the chemical composition analysis of the plating layer and cross-sectional structure observation described below, a sample taken from the bottom of the figure (the area surrounded by the dotted line) was used.

[0071] The chemical composition of the plating layer of the hot stamped product was measured by the following method. A 30mm x 30mm sample was taken from the bottom of the hat-shaped hot-stamped product, and this sample was immersed in a 10% HCl aqueous solution containing 1% Hibilon (A-6) to pickle and remove the plating layer.The elements dissolved in the solution were then analyzed by ICP analysis to measure the chemical composition of the plating layer.The chemical composition of the plating layer is shown in Table 2. In addition, another 30 × 30 mm sample was taken from the bottom of the hat-shaped hot stamped product, and the η-Zn phase and Fe4Al phase were found in the coating layer. 13 The presence or absence of the phase was evaluated by irradiating the surface of the plating layer with X-rays in the same manner as described above. The coating weight of the plating layer was determined in the same manner as above. In addition, the area ratio of the intermetallic compound phase containing, in mass%, 3 to 40% Sc, 3 to 50% Zn, 3 to 50% Fe, 0 to 50% Al, and 0 to 30% Si in the cross section of the coating layer of the hot stamped product was determined in the same manner as above. The results are shown in Tables 2 and 3. The A value in Table 2 is the total content of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In.

[0072] The hot stamped products were also evaluated for corrosion resistance after painting. In this example, the corrosion depth of the base steel and the blister width of the coating were evaluated as the corrosion resistance after painting. Specifically, an 80 x 50 mm sample was taken from the bottom of the hot-stamped product and zinc phosphate treated according to the SD5350 system (Nippon Paint Industrial Coatings standard). This sample was then electrocoated (PN110 Powernics Gray, Nippon Paint Industrial Coatings standard) to a thickness of 20 μm and baked at 150°C for 20 minutes. A cut was then made in the center of the sample, reaching the steel substrate. The sample was then subjected to a combined cyclic corrosion test according to JIS H 8502:1999, Section 8.1, Neutral Salt Spray Cycle Test Method. The depth of corrosion of the steel substrate from the cut and the width of the paint blister were measured.

[0073] The erosion depth of the steel substrate was measured using a laser displacement meter after removing the sample at the 240th cycle and peeling off the electrodeposition coating and plating layer.

[0074] The corrosion resistance after painting was evaluated as follows: if the erosion depth of the base steel was less than 0.3 mm, it was rated "AAA", if it was 0.3 to less than 0.6 mm, it was rated "AA", if it was 0.6 to 1.0 mm, it was rated "A", and if it was more than 1.0 mm, it was rated "B". In addition, the coating blister width was rated as "AAA" if it was less than 0.3 mm from the cut point at 120 cycles, "AA" if it was 0.3 to 0.6 mm, "A" if it was 0.6 to 1.0 mm, and "B" if it was more than 1.0 mm. The results are shown in Table 3.

[0075] [Table 1]

[0076] [Table 2]

[0077] [Table 3]

[0078] As shown in Tables 1 to 3, Nos. 2 to 5, 8, 10 to 13, 15 to 17, 19 to 22, 24 to 27, 29, 30, and 32 to 35, which are invention examples in which the content of each element, including Sc, in the coating layer is within a predetermined range, exhibit excellent corrosion resistance after painting. Furthermore, the higher the Sc content, the better the corrosion resistance after painting. Furthermore, when the coating layer has a high Zn content, the erosion depth of the base steel is particularly small. Furthermore, when the coating layer has a high Al content and Fe4Al is deposited on the coating layer, 13 When the phase is present, the width of the coating blister is particularly small. Furthermore, in these cases, LME cracking was suppressed in the bent parts of the hot stamped steel.

[0079] On the other hand, the comparative examples Nos. 1, 6, 7, 9, 14, 18, 23, 28, and 31 had poor corrosion resistance after painting. In No. 1, the Al content of the coating layer was excessive and the Zn content was low, so sufficient η-Zn phase was not formed, resulting in a decrease in corrosion resistance after painting. In Nos. 6, 7, and 31, the plating layer did not contain Sc, or the content was too low, so a sufficient η-Zn phase was not formed, resulting in reduced corrosion resistance after painting. In No. 18, the Fe content in the coating layer was excessive and the Zn content was low, which prevented the formation of a sufficient η-Zn phase, resulting in a decrease in corrosion resistance after painting. In No. 23, the Si content was high, and the effect of Sc was not fully achieved, which resulted in insufficient formation of the η-Zn phase, resulting in a decrease in corrosion resistance after painting. In Nos. 9, 14, and 28, the Sc-containing intermetallic compound phase with a circle equivalent diameter of 5.0 μm or less was not sufficiently formed in the coated steel sheet, and therefore sufficient η-Zn phase was not formed, resulting in a decrease in corrosion resistance after painting. [Industrial Applicability]

[0080] According to the present invention, a hot-stamped product having excellent corrosion resistance after painting can be provided. This hot-stamped product can be applied to automobile parts and the like, and has high industrial applicability.

Claims

1. A base steel material, a plating layer formed on the surface of the base steel material; and The chemical composition of the plating layer is, in mass%, Sc:0.000010~3.0%, Fe: more than 15.0%, less than 95.0%, Al: 0-80.0%, Si: 0-20.0%, Mg: 0-3.0%, Ca: 0-3.0%, La: 0 to 0.5%, Ce: 0-0.5%, Y: 0 to 0.5%, Cr: 0-1.0%, Ti: 0 to 1.0%, Ni: 0-1.0%, Co: 0-0.25%, V: 0 to 0.25%, Nb: 0 to 1.0%, Cu: 0 to 1.0%, Mn: 0 to 1.0%, Sr: 0 to 0.5%, Sb: 0 to 0.5%, Pb: 0 to 0.5%, B: 0 to 0.5%, Li: 0 to 1.0%, Zr: 0 to 1.0%, Mo: 0-1.0%, W: 0 to 0.5%, Ag: 0-1.0%, P: 0 to 0.5%, Sn: 0 to 1.0%, Bi: 0-1.0%, In: 0 to 1.0%, and Balance: 5.0% or more of Zn and impurities; and The total content of Mg, Ca, La, Ce, Y, Cr, Ti, Ni, Co, V, Nb, Cu, Mn, Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, P, Sn, Bi, and In is 0 to 5.0%; an η-Zn phase is present near the surface of the plating layer; A hot stamped product characterized by:

2. The chemical composition of the plating layer is, in mass %, Contains Zn: 15.0% or more and Sc: 0.00050 to 0.30%; In a cross section of the plating layer, the area ratio of an intermetallic compound phase containing, by mass%, 3 to 40% Sc, 3 to 50% Zn, 3 to 50% Fe, 0 to 50% Al, and 0 to 30% Si is 0.1% or more. The hot stamped product according to claim 1 .

3. The chemical composition of the plating layer is, in mass %, Contains Zn: 15.0% or more and Sc: 0.010 to 0.30%; The hot stamped product according to claim 2 .

4. The chemical composition of the plating layer contains, in mass%, Al: 30.0 to 80.0%; Fe is present near the surface of the plating layer. ４ Al １３ There is a phase The hot stamped product according to any one of claims 1 to 3.

Images