Method for manufacturing welded steel sheets, method for manufacturing tailored blanks, method for manufacturing hot press-formed products, welded steel sheets, tailored blanks, and hot press-formed products

Abstract

To provide a method for manufacturing welded steel sheets that suppresses the reduction in welding strength of tailored blanks caused by surface coatings, as well as a method for manufacturing tailored blanks and a method for manufacturing hot-pressed products. [Solution] A method for manufacturing a welded steel sheet, comprising: a first step of preparing a plated steel sheet having a base steel sheet, an Al plating layer, an intermetallic compound layer, and a surface film provided on at least one of the Al plating layers provided on one side of the base steel sheet or on both sides of the base steel sheet, the film containing a binder resin, carbon black, and a metal oxide, and having an average thickness of 0.5 to 5.0 μm; and a second step of forming an intermetallic compound layer or an exposed portion of the base steel sheet along the edge of the plated steel sheet in the area where welding is planned at the edge of the plated steel sheet by laser processing; and a method for manufacturing a tailored blank and a method for manufacturing a hot press-formed product using the same.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing welded steel sheets, a method for manufacturing tailored blanks, a method for manufacturing hot press-formed products, welded steel sheets, tailored blanks, and hot press-formed products. [Background technology]

[0002] In recent years, from the perspective of protecting the global environment, reducing CO2 gas emissions has become an urgent issue in the automotive sector, particularly in reducing the weight of automobile bodies. In response, there has been active research into applying high-strength steel sheets. The strength of steel sheets (including plated steel sheets) is also increasing.

[0003] On the other hand, when forming high-strength steel sheets, the formability decreases as the strength of the steel sheet increases. In particular, high-strength steel sheets with a tensile strength exceeding 1500 MPa have poor ductility, making it difficult to cold press form them into the complex shapes of automotive structural components.

[0004] Hot press forming (also known as "hot stamping") is attracting attention as one of the technologies for forming automotive components. In hot press forming, a steel sheet for hot pressing is heated to a high temperature and pressed in a temperature range above the Ar3 transformation temperature. Furthermore, in hot press forming, the pressed steel sheet is rapidly cooled by heat removal using a die, causing a transformation to occur simultaneously with the forming process while press pressure is applied. As a result, hot press forming is a technology that can manufacture press-formed products with high strength and excellent shape retention.

[0005] Regarding hot press forming technology, for example, Patent Document 1 describes a steel sheet having a surface treatment film on the entire surface of at least one of its surfaces, wherein the surface treatment film has an emissivity of 60% or more at a wavelength of 8.0 μm at 25°C, and the surface treatment film contains one or more oxides selected from the group consisting of carbon black, Zr oxide, and Ti oxide, and the carbon black and the oxides are dispersed throughout the surface treatment film, and the surface treatment film has a silica content of 0 to 0.3 g / m². 2The amount of carbon black and oxide deposited is X CB (g / m 2 ), X Oxide (g / m 2 When ) then, the following equation (1): 118.9 ≤ 24280 / {6700 / (100 + 76 × X CB ) + 18000 / (130 + 65 × X Oxide A steel sheet for hot stamping that satisfies )} ≤ 332.0 is disclosed.

[0006] On the other hand, in order to improve the yield and functionality of press-formed automotive components, tailored blanks, which are made by joining the ends of at least two steel plates together (or overlapping the ends) using laser welding, plasma welding, etc., are being used as press-formed materials (Patent Document 2, etc.). Tailored blanks allow for the joining of multiple welded steel plates according to the purpose, enabling the free variation of plate thickness and strength within a single component. As a result, using tailored blanks improves the functionality of automotive components and reduces the number of parts in an automotive component. Furthermore, by using tailored blanks for hot press forming, high-strength press-formed parts can be manufactured with freely adjustable plate thickness, strength, and other properties.

[0007] It is known that steel sheets for manufacturing tailored blanks can be obtained, for example, by laser cutting an Al-plated steel sheet (e.g., a coil of that steel sheet) into an arbitrary shape (Patent Document 2, etc.).

[0008] On the other hand, if components of the Al plating layer are mixed into the weld metal, the hardenability of the weld metal decreases, leading to a problem of reduced joint strength after hot stamping. Therefore, a solution is known in which the Al plating layer of the area to be welded is removed by laser processing (Patent Document 3, etc.). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 7620242 [Patent Document 2] Patent No. 7056738 [Patent Document 3] Patent No. 6397047 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, even if the Al plating layer in the area to be welded is removed by laser processing, the presence of a surface film can still reduce the weld strength. This is because a thick surface film can hinder removal by laser processing, resulting in more of the Al plating layer remaining than expected, and the components of the Al plating layer mixing into the weld metal.

[0011] Therefore, the object of this disclosure is to provide a method for manufacturing welded steel sheets that suppresses the decrease in weld strength of tailored blanks caused by surface coatings, and a method for manufacturing tailored blanks and a method for manufacturing hot press-formed products that utilize the same. Another object of this disclosure is to provide a welded steel sheet in which the reduction in weld strength of a tailored blank caused by a surface coating is suppressed, as well as a tailored blank and a hot-pressed product using the same. [Means for solving the problem]

[0012] The means for solving the problem include the following: <1> A first step of preparing a plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layer provided on one side of the base steel sheet or the Al plating layer provided on both sides of the base steel sheet, containing a binder resin, carbon black and metal oxide, and having an average thickness of 0.5 to 5.0 μm, a second step of removing the surface coating and the Al plating layer, or removing the surface coating, the Al plating layer and the intermetallic compound layer, along the edge of the plated steel sheet, at a planned welding portion at the edge of the plated steel sheet by laser processing, to form an exposed portion of the intermetallic compound layer or the base steel sheet; A method for manufacturing a welded steel sheet, comprising: <2> The method for manufacturing a welded steel sheet according to <1>, wherein in the second step, the surface coating and the Al plating layer are removed, or the surface coating, the Al plating layer and the intermetallic compound layer are removed, so that the exposed portion of the intermetallic compound layer or the base steel sheet is formed adjacent to the end edge of the plated steel sheet. <3> The method for manufacturing a welded steel sheet according to <1>, wherein in the second step, the surface coating and the Al plating layer are removed, or the surface coating, the Al plating layer and the intermetallic compound layer are removed, so that the exposed portion of the intermetallic compound layer or the base steel sheet is formed spaced apart from the end edge of the plated steel sheet. <4> The method for manufacturing a welded steel sheet according to <1> or <2>, wherein the metal oxide is one or more metal oxides selected from the group consisting of Zr oxide, Zn oxide, and Ti oxide. <5> The method for manufacturing a welded steel sheet according to <3>, wherein the metal oxide is one or more metal oxides selected from the group consisting of Zr oxide, Zn oxide, and Ti oxide. <6> a step of obtaining a welded steel sheet by the method for manufacturing a welded steel sheet according to any one of <1> to <5>; a step of welding two or more welded steel sheets each obtained by the method for manufacturing a welded steel sheet according to any one of <1> to <5> at their planned welding portions, and connecting them with a weld metal. A method for manufacturing a tailored blank, comprising: <7> a step of obtaining a tailored blank by the method for manufacturing a tailored blank according to <6>; a step of subjecting the tailored blank obtained by the method for manufacturing a tailored blank according to <6> to hot press forming. A method for manufacturing a hot-press formed article, comprising: <8> a plated steel sheet comprising: a base steel sheet, an Al plating layer provided on one side or both sides of the base steel sheet, an intermetallic compound layer provided between the base steel sheet and the Al plating layer and containing iron and aluminum, and a surface coating layer provided on at least one of the Al plating layer provided on one side of the base steel sheet or the Al plating layers provided on both sides of the base steel sheet, containing a binder resin, carbon black and a metal oxide, and having an average thickness of 0.5 to 5.0 μm; and the intermetallic compound layer or an exposed portion of the base steel sheet provided along the edge of the plated steel sheet at a planned welding portion of the edge of the plated steel sheet; A welded steel sheet comprising: <9> Two or more welded steel sheets according to <8>, comprising the welded steel sheet; and a weld metal connecting the planned welding portions of the two or more welded steel sheets; A tailored blank comprising: <10> A hot-press formed article of the tailored blank according to <9>. Effects of the Invention

[0013] According to the present disclosure, there are provided a method for manufacturing a welded steel sheet that suppresses a decrease in the welding strength of a tailored blank caused by a surface coating, as well as a method for manufacturing a tailored blank and a method for manufacturing a hot-press formed article using the same. Another object of the present disclosure is to provide a welded steel sheet in which a decrease in the welding strength of a tailored blank caused by a surface coating is suppressed, as well as a tailored blank and a hot-press formed article using the same. Brief Description of the Drawings

[0014] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the planned welding portion of the welded steel sheet of the present disclosure. [Figure 2] Figure 2 is a schematic cross-sectional view showing another example of the planned welding portion of the welded steel sheet of the present disclosure. [Figure 3] Figure 3 is a schematic diagram showing an example of a cross-section of a weld in a tailored blank according to this disclosure. [Modes for carrying out the invention]

[0015] The following describes in detail an example of a preferred embodiment of this disclosure. In this disclosure, a numerical range represented using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Regarding the content of components (elements), for example, the content of C (carbon) may be expressed as "C amount." The content of other elements may also be expressed similarly. The term "cross-section" in the context of welded steel plates refers to the cross-section obtained by cutting the plate in the direction of its thickness. The term "edge" of a welded steel plate refers to the area located around the welded steel plate, specifically the area within an average of 5 mm from the edge of the welded steel plate. The "edge" of a welded steel sheet refers to the point where the edge meets the opposite side of the sheet in the thickness direction (i.e., the surface of the welded steel sheet). The term "end face" of a welded steel plate refers to the face perpendicular to the thickness direction between opposing surfaces in a direction perpendicular to the thickness direction.

[0016] <Manufacturing method for welded steel sheets / Welded steel sheets> The method for manufacturing welded steel sheets disclosed herein is: A first step to prepare a plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layers provided on one side of the base steel sheet or on both sides of the base steel sheet, containing a binder resin, carbon black and metal oxide, and having an average thickness of 0.5 to 5.0 μm. A second step involves using laser processing to remove the surface film and Al plating layer along the edge of the plated steel sheet in the area where welding is planned on the edge of the plated steel sheet, or to remove the surface film, Al plating layer and intermetallic compound layer, thereby forming an exposed intermetallic compound layer or base steel sheet. It holds.

[0017] According to the manufacturing method of welded steel sheets in this disclosure, A plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layers provided on one side of the base steel sheet or the Al plating layers provided on both sides of the base steel sheet, containing a binder resin, carbon black and metal oxide, and having an average thickness of 0.5 to 5.0 μm. In the area where welding is planned at the edge of the plated steel sheet, an intermetallic compound layer or an exposed portion of the base steel sheet is provided along the edge of the plated steel sheet, A welded steel sheet having the above characteristics (the welded steel sheet of this disclosure) is obtained.

[0018] In the method for manufacturing welded steel sheets described herein, a surface film containing a binder resin, carbon black, and metal oxide is thinned to an average thickness of 0.5 to 5.0 μm. In this state, an intermetallic compound layer or an exposed portion of the base steel sheet is formed at the welded portion of the edge of the plated steel sheet by laser processing. This suppresses interference of laser processing by the surface film, and the Al plating layer is sufficiently removed by laser processing. As a result, the mixing of components of the Al plating layer into the weld metal can be suppressed. Therefore, the manufacturing method of welded steel sheets according to this disclosure provides welded steel sheets that suppress the reduction in welding strength of tailored blanks caused by surface coatings.

[0019] The details of the manufacturing method for welded steel sheets according to this disclosure are described below.

[0020] (First step) In the first step, the plated steel sheet is prepared. The plated steel sheet to be prepared is a plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layer provided on one side of the base steel sheet or the Al plating layer provided on both sides of the base steel sheet.

[0021] [Base material steel plate] The base steel sheet is the steel sheet to which the intermetallic compound layer and the Al plating layer are to be applied (i.e., the steel sheet to which Al plating is to be applied). The base steel sheet can be any sheet obtained by conventional methods and is not particularly limited. The base steel sheet may be either a hot-rolled steel sheet or a cold-rolled steel sheet.

[0022] The thickness of the base steel plate is preferably 0.7 to 3.2 mm, and more preferably 1.0 to 2.6 mm. From the viewpoint of ensuring the tensile strength of the base steel plate, it is preferable that the thickness of the base steel plate be 0.7 mm or more. On the other hand, productivity in the cutting process improves when the thickness of the base steel sheet is 3.2 mm or less. Therefore, it is preferable that the thickness of the base steel plate be within the above range. The thickness of the base steel plate is determined by measuring the thickness at five arbitrary points on the welded steel plate, excluding the edges, using a micrometer (Mitutoyo Corporation CPM-MX), and taking the arithmetic mean of these measurements.

[0023] The base steel sheet should preferably be a steel sheet formed to have high mechanical strength (meaning various properties related to mechanical deformation and fracture, such as tensile strength, yield point, elongation, reduction of area, hardness, impact value, fatigue strength, etc.). Specifically, a steel sheet with a tensile strength of 400 to 2700 MPa may be used. Furthermore, steel plates with low mechanical strength may be used as the base material. Specifically, these include 1300 MPa, 1200 MPa, 1000 MPa, 600 MPa, and 500 MPa classes. For example, in the case of a B-pillar of an automobile, it is desirable to use a steel plate with a tensile strength of 1500 to 2000 MPa class for the upper and central parts where deformation is to be prevented, and a steel plate with a tensile strength of 500 MPa to 1500 MPa class for the lower part, which is the energy absorption part. More preferably, the lower part should be a steel plate with a tensile strength of 600 MPa to 1300 MPa class.

[0024] Examples of preferred chemical compositions for the base steel sheet include the following: In other words, a preferred base steel sheet is, in terms of mass%, C: 0.02%~0.58%, Mn: 0.20%~3.00% Al: 0.005%~0.060%, Ti: 0%~0.20%, Nb: 0%~0.20%, V: 0%~1.0%, W: 0%~1.0%, Cr: 0%~1.0%, Mo: 0%~1.0%, Cu: 0%~1.0%, Ni: 0%~1.0%, B: 0%~0.0100%, Ca: 0%~0.05%, Mg: 0%~0.05% REM: 0%~0.05%, Bi: 0%~0.05%, Si: 0%~2.00% Sn: 0%~0.5% P: 0.03% or less, S: 0.010% or less, N: 0.010% or less, and, The remainder includes a base steel sheet having a chemical composition consisting of Fe and impurities. Note that the "%" indicated below to show the content of components (elements) means "mass percent".

[0025] (C: 0.02%~0.58%) Carbon (C) is an important element that enhances the hardenability of the base steel sheet and primarily determines the strength after quenching. Furthermore, it lowers the A3 point and promotes lower quenching temperatures. If the C content is less than 0.02%, its effect may not be sufficient. Therefore, it is preferable to have a C content of 0.02% or more. On the other hand, if the C content exceeds 0.58%, the toughness of the quenched area deteriorates significantly. Therefore, it is preferable to have a C content of 0.58% or less. Preferably, it is 0.45% or less.

[0026] (Mn: 0.20%~3.00%) Mn is a very effective element for improving the hardenability of the base steel sheet and ensuring stable strength after quenching. If the Mn content is less than 0.20%, its effect may not be sufficient. Therefore, it is preferable to have an Mn content of 0.20% or more, preferably 0.80% or more. On the other hand, if the Mn content exceeds 3.00%, not only does its effect saturate, but it may also become difficult to ensure stable strength after quenching. Therefore, it is preferable to have an Mn content of 3.00% or less, preferably 2.40% or less.

[0027] (Al: 0.005%~0.060%) Al functions as a deoxidizing element. Furthermore, Al reduces oxide inclusions that adversely affect the mechanical strength of the base steel sheet. When the Al content is less than 0.005%, it may be difficult to obtain the above effects. Therefore, it is preferable to have an Al content of 0.005% or more. On the other hand, when the Al content exceeds 0.060%, the above effects saturate, making it cost-inefficient. Therefore, it is preferable to have an Al content of 0.060% or less.

[0028] (Ti:0%~0.20%, Nb:0%~0.20%, V:0%~1.0%, W:0%~1.0%) Ti, Nb, V, and W are elements that promote the interdiffusion of Fe and Al in the Al plating layer and the base steel sheet. Therefore, at least one of Ti, Nb, V, and W may be included in the base steel sheet. However, if 1) the amount of Ti and Nb exceeds 0.20%, or 2) the amount of V and W exceeds 1.0%, the effect of the above action saturates, making it cost-inefficient. Therefore, it is preferable to keep the amount of Ti and Nb at 0.20% or less, and the amount of V and W at 1.0% or less. Preferably, the amount of Ti and Nb is 0.15% or less, and the amount of V and W is 0.5% or less. To more reliably obtain the effect of the above action, it is preferable to keep the amount of Ti and Nb at 0.01% or more, and the amount of V and W at 0.1% or more.

[0029] (Cr:0%~1.0%, Mo:0%~1.0%, Cu:0%~1.0%, Ni:0%~1.0%, B:0%~0.0100%) Cr, Mo, Cu, Ni, and B are effective elements for improving the hardenability of the base steel sheet and ensuring stable strength after quenching. Therefore, one or more of these elements may be included. However, if the content of Cr, Mo, Cu, and Ni exceeds 1.0% or the amount of B exceeds 0.0100%, the above effects saturate, making it cost-inefficient. Therefore, it is preferable to keep the content of Cr, Mo, Cu, and Ni at 1.0% or less. Also, the amount of B is preferably 0.0100% or less, and more preferably 0.0080% or less. To more reliably obtain the above effects, it is preferable to satisfy either the content of Cr, Mo, Cu, and Ni at 0.1% or more, or the content of B at 0.0010% or more.

[0030] (Ca:0%~0.05%, Mg:0%~0.05%, REM:0%~0.05%) Ca, Mg, and REM have the effect of refining the morphology of inclusions in steel and preventing the occurrence of cracks during hot press forming caused by inclusions. Therefore, one or more of these elements may be included. However, if added in excess, the effect of refining the morphology of inclusions in steel will saturate, and only increase costs. Therefore, it is preferable to keep the amount of Ca at 0.05% or less, the amount of Mg at 0.05% or less, and the amount of REM at 0.05% or less. To more reliably obtain the effects of the above actions, it is preferable to satisfy at least one of the following: the amount of Ca at 0.0005% or more, the amount of Mg at 0.0005% or more, and the amount of REM at 0.0005% or more.

[0031] Here, REM refers to the total of 17 elements including Sc, Y, and lanthanides, and the REM content mentioned above refers to the total content of these elements. In the case of lanthanides, they are added industrially in the form of mischmetal.

[0032] (Bi: 0%~0.05%) Bi acts as a solidification nucleus during the solidification process of molten steel and is an element that suppresses segregation of Mn and other elements. Therefore, Bi may be included. In particular, Bi has the effect of suppressing the deterioration of toughness caused by Mn segregation. Therefore, it is preferable to include Bi in such steel types. However, if the amount of Bi exceeds 0.05%, the effect of the above action will saturate, leading to an increase in cost. Therefore, the amount of Bi should be 0.05% or less. Preferably, it is 0.02% or less. Furthermore, in order to more reliably obtain the effect of the above action, it is preferable to have a Bi amount of 0.0002% or more. Even more preferably, it is 0.0005% or more.

[0033] (Si: 0%~2.00%) Si is a solid solution strengthening element and can be effectively utilized up to 2.00%. However, if the Si content exceeds 2.00%, there is a concern that problems may occur in the plating properties. Therefore, when Si is included, it is preferable to keep the Si content to 2.00% or less. The preferred upper limit is 1.40% or less, and more preferably 1.00% or less. The lower limit is not particularly limited, but to more reliably obtain the effects of the above action, 0.01% or more is preferred.

[0034] (Sn: 0%~0.5%) Sn is an element that improves the corrosion resistance of exposed steel. Therefore, Sn may be included in the base steel sheet. However, including more than 0.5% Sn in the base steel sheet will lead to embrittlement of the base steel sheet. Therefore, the amount of Sn should be 0.5% or less. Preferably, the amount of Sn is 0.3% or less. Furthermore, to more reliably obtain the effects resulting from the above action, it is preferable to have a Sn content of 0.02% or more. More preferably, the Sn content is 0.04% or more.

[0035] (P: 0%~0.03%) P is an element present as an impurity. Excessive P content can easily reduce the toughness of the base steel sheet. Therefore, the P content should be 0.03% or less, preferably 0.01% or less. There is no need to specify a lower limit for the P content; it may be 0% or greater. From a cost perspective, it is preferable to have a P content of 0.0002% or more.

[0036] (S: 0%~0.010%) S is an element present as an impurity, forming MnS and causing the base steel sheet to become brittle. Therefore, the amount of S should ideally be 0.010% or less. A more desirable amount of S is 0.004% or less. There is no need to specify a lower limit for the amount of S. The amount of S may be 0% or greater. From a cost standpoint, it is preferable to have an amount of 0.0002% or more.

[0037] (N: 0%~0.010%) N is an element present as an impurity that forms inclusions in steel and degrades toughness after hot press forming. Therefore, the amount of N should preferably be 0.010% or less. Preferably, it should be 0.008% or less, and more preferably 0.005% or less. There is no need to specify a lower limit for the amount of N. The amount of N may be 0% or greater than 0%. From a cost standpoint, it is preferable to have 0.0002% or more.

[0038] (Remainder) The remainder consists of Fe and impurities. Here, impurities refer to components contained in raw materials such as ore and scrap, or components that are mixed in during the manufacturing process, and do not refer to components that were intentionally included in the base steel sheet.

[0039] [Al plating layer] The Al plating layer is a layer formed after applying Al plating to a base steel sheet, excluding the intermetallic compound layer. The method for forming the Al plating layer is not particularly limited. For example, the Al plating layer can be formed on one or both sides of the base steel sheet by a hot-dip galvanizing method. The hot-dip galvanizing method involves immersing the base steel sheet in a molten metal bath mainly containing aluminum, thereby applying Al plating to both sides of the base steel sheet.

[0040] Here, the Al plating layer is a plating layer mainly containing aluminum, and it is sufficient if it contains 50% by mass or more of aluminum. Depending on the purpose, it may also contain elements other than aluminum (for example, silicon), and may contain impurities that are introduced during the manufacturing process. Specifically, examples of Al plating layers include an Al plating layer having a chemical composition in which, by mass%, 5% to 12% Si (silicon) is present and the remainder consists of aluminum and impurities, or an Al plating layer having a chemical composition in which, by mass%, 5% to 12% Si (silicon), 2% to 4% Fe (iron), and the remainder consists of aluminum and impurities. In particular, incorporating Si within the above range into the Al plating layer can suppress the deterioration of workability and corrosion resistance. Furthermore, the thickness of the intermetallic compound layer can be reduced. Incidentally, the impurities refer to components that are exemplified by components mixed in during the manufacturing process and are not components intentionally contained in the Al plating layer.

[0041] The thickness of the Al plating layer is not particularly limited, but for example, the average thickness is preferably 8 μm or more, more preferably 15 μm or more. Further, the average thickness of the Al plating layer is, for example, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and even more preferably 30 μm or less.

[0042] [Intermetallic Compound Layer] The intermetallic compound layer is an intermetallic compound layer formed between the base steel sheet and the Al plating layer (that is, at the boundary portion) when Al plating is applied to the base steel sheet to form the Al plating layer. Specifically, the intermetallic compound layer is formed by the reaction between iron (Fe) of the base steel sheet and a metal containing aluminum (Al) in a molten metal bath mainly containing aluminum. The intermetallic compound layer is mainly composed of Fe x Al y It is formed of a plurality of types of compounds represented by (x and y each represent 1 or more). When the Al plating layer contains Si (silicon), Fe x Al y and Fe x Al y Si z It is formed of a plurality of types of compounds represented by (x, y and z each represent 1 or more).

[0043] The thickness of the intermetallic compound layer is not particularly limited, but for example, the average thickness is preferably 1 μm or more, more preferably 3 μm or more, and still more preferably 4 μm or more. Further, the average thickness of the intermetallic compound layer is, for example, preferably 10 μm or less, and more preferably 8 μm or less. Incidentally, the thickness of the intermetallic compound layer can be controlled by the temperature of the molten metal bath mainly containing aluminum and the immersion time.

[0044] Here, the combined thickness of the intermetallic compound layer and the Al plating layer is preferably 9 to 60 μm on average, and more preferably 15 to 45 μm. When the combined thickness of the intermetallic compound layer and the Al plating layer is within the above range, the plating performance can be appropriately achieved.

[0045] "Surface coating" The surface coating contains a binder resin, carbon black, and metal oxide. The surface coating may also contain other components.

[0046] As the binder resin, either a water-soluble or water-dispersible water-based resin that dissolves or disperses in water, or a solvent-based resin that dissolves or disperses in an organic solvent, may be used. However, from the standpoint of manufacturing cost and environmental suitability, water-based resins are preferred.

[0047] Examples of water-based resins include water-soluble or water-dispersible resins such as polyester resins, urethane resins, polyolefin resins, acrylic resins, epoxy resins, phenolic resins, and mixed resins of two or more of these resins. Examples of solvent-based resins include polyester resins, urethane resins, epoxy resins, acrylic resins, and mixed resins of two or more of these resins.

[0048] Here, the binder resin may be a crosslinked resin having a crosslinked structure or a non-crosslinked resin without a crosslinked structure, but a non-crosslinked resin is preferable from the viewpoint of low-temperature film formation of the coating film. As the crosslinking agent (curing agent) that imparts a crosslinked structure to the binder resin, a water-soluble crosslinking agent is preferred. Specifically, melamine, isocyanates, silane compounds, zirconium compounds, titanium compounds, etc. are preferred as crosslinking agents.

[0049] The binder resin content is 20 to 98% by mass relative to the surface film, preferably 40 to 90% by mass, and more preferably 60 to 80% by mass.

[0050] (Carbon Black) Examples of carbon black include well-known types such as Ketjen black, oil furnace black, channel black (i.e., gas black), and acetylene black.

[0051] The carbon black content is 1 to 20% by mass, preferably 5 to 20% by mass, and more preferably 10 to 20% by mass. If the carbon black content is less than 1% by mass, high laser irradiation energy is required during laser cutting, which increases the height of the dross. If the carbon black content exceeds 20% by mass, the cost of surface coating formation increases. Therefore, the carbon black content shall be within the above range. The lower limit of the carbon black content is preferably 3% by mass, 5% by mass, 7% by mass, or 10% by mass.

[0052] (Metal oxides) Examples of metal oxides include Zr oxide, Zn oxide, and Ti oxide. Among these, one or more metal oxides selected from the group consisting of Zr oxide, Zn oxide, and Ti oxide are preferred. These metal oxides tend to improve lubricity during hot pressing and also enhance corrosion resistance after painting. The metal oxide content is 1 to 60% by mass, preferably 5 to 40% by mass, and more preferably 10 to 20% by mass, relative to the surface film.

[0053] (Other ingredients) Other components include well-known additives such as surfactants.

[0054] (Thickness of the surface coating) The surface film thickness is 0.5 to 5.0 μm on average. If the average thickness of the surface coating is less than 0.5 μm, the heating rate during hot stamping will not improve, and the original function of the surface coating will not be fully realized. If the average thickness of the surface coating exceeds 5.0 μm, a decrease in welding strength due to the surface coating will occur. Therefore, the average thickness of the surface film shall be within the above range. The average thickness of the surface film is preferably 0.5 to 3.0 μm, and more preferably 0.5 to 2.0 μm.

[0055] The method for measuring the average thickness of the Al plating layer, intermetallic compound layer, and surface film is as follows. In a welded steel plate, a steel slab is collected from the area excluding the edges by cutting along the thickness direction of the plate. A steel billet is embedded in epoxy resin, and the cut surface is polished to obtain a sample. The cross-section of the obtained sample is subjected to linear analysis using an electron beam microanalyzer (FE-EPMA) from the surface of the welded steel plate inward, along the thickness direction. The elements to be analyzed in the linear analysis will be Fe and Al. The measurement conditions will be an acceleration voltage of 15kV, a beam diameter of approximately 100nm, and an irradiation time of 1000ms. The measurement pitch will be a grid pattern with a 5μm pitch. Based on the resulting line analysis, by focusing on the concentration changes of specific elements from the base steel sheet towards the surface film, the interfaces between the Al plating layer and the intermetallic compound layer, the intermetallic compound layer and the base steel sheet, and the Al plating layer and the surface film are identified. Specifically, based on the line analysis results from the base steel sheet side, the region with an aluminum concentration of less than 0.06 mass% is considered the base steel sheet, the region with an aluminum concentration of 0.06 mass% or more is considered the intermetallic compound layer, the region with an aluminum concentration of 0.06 mass% or more and an iron concentration of less than 4 mass% is considered the Al plating layer, and the region with an aluminum concentration of less than 0.06 mass% is considered the surface film, and each interface is determined accordingly. Furthermore, the determination of the boundary between the surface film and the plating layer can be made more accurate by monitoring not only the aluminum concentration but also the concentrations of the binder resin components and elements specific to carbon black contained in the surface film. The length along the thickness direction of the interface between the intermetallic compound layer and the base steel sheet, and the interface between the Al plating layer and the intermetallic compound layer, is defined as the thickness of the intermetallic compound layer. The length along the thickness direction of the Al plating layer is defined as the interface between the Al plating layer and the intermetallic compound layer and the interface between the Al plating layer and the surface film. The length along the thickness direction between the identified interface between the Al plating layer and the surface film and the surface region considered to be the surface film is defined as the thickness of the surface film. Then, the above procedure is performed five times to determine the arithmetic mean of the thicknesses of the Al plating layer, the intermetallic compound layer, and the surface film.

[0056] (Second process) In the second step, laser processing is used to form an intermetallic compound layer or an exposed portion of the base steel sheet along the edge of the plated steel sheet where welding is planned.

[0057] Furthermore, when forming an exposed portion of the intermetallic compound layer, the surface coating and the Al plating layer are removed by laser processing. On the other hand, when forming exposed portions of the base steel sheet, the surface coating, Al plating layer, and intermetallic compound layer are removed by laser processing.

[0058] Here, the planned welding area on the edge of the plated steel sheet refers to the edge of the plated steel sheet (i.e., the welded steel sheet) where the weld metal will be formed when the resulting welded steel sheet is welded. When forming an exposed portion of the intermetallic compound layer, the Al plating layer may remain on a portion of the exposed portion of the intermetallic compound layer, or the base steel sheet may be exposed. However, when observing the exposed portion of the intermetallic compound layer from the thickness direction of the base steel sheet, the area ratio of the exposed intermetallic compound layer should be, for example, 80 area% or more (preferably 90 area% or more or 95 area% or more). Furthermore, when forming an exposed portion of the base steel sheet, an intermetallic compound layer may remain on a portion of the exposed portion of the base steel sheet. However, when observing the exposed portion of the base steel sheet from the thickness direction of the base steel sheet, the area ratio of the exposed base steel sheet should be, for example, 80 area% or more (preferably 90 area% or more or 95 area% or more).

[0059] In the second step, the configuration of the area to be welded (i.e., the configuration that forms the intermetallic compound layer or the exposed portion of the base steel plate) may be either the first configuration or the second configuration described below.

[0060] -First Mode- (1) A first embodiment in which the intermetallic compound layer or the exposed portion of the base steel sheet is formed adjacent to the edge of the plated steel sheet (see Figure 1). In the first embodiment, the surface coating and the Al plating layer are removed, or the surface coating, the Al plating layer and the intermetallic compound layer are removed, such that the intermetallic compound layer or the exposed portion of the base steel sheet is formed adjacent to the edge of the plated steel sheet. In other words, in the first embodiment, the intermetallic compound layer or the exposed portion of the base steel sheet is formed on the edge of the plated steel sheet without leaving the surface film, Al plating layer, and intermetallic compound layer. In the first embodiment, the characteristics of the resulting hot-pressed product are such that it is desirable to reduce the components of the surface coating and Al plating layer mixed into the weld metal.

[0061] In the first embodiment, the width of the exposed portion of the intermetallic compound layer or base steel sheet (see T1 in Figure 1) is preferably 0.5 to 5.0 mm, and more preferably 1.0 to 4.0 mm.

[0062] -Second aspect- (2) A second embodiment in which the intermetallic compound layer or the exposed portion of the base steel sheet is formed spaced apart from the edge of the plated steel sheet (see Figure 2). In the second embodiment, the surface coating and the Al plating layer are removed, or the surface coating, the Al plating layer and the intermetallic compound layer are removed, such that the intermetallic compound layer or the exposed portion of the base steel sheet is formed spaced apart from the edge of the plated steel sheet. In other words, in the second embodiment, the surface film, the Al plating layer, and the intermetallic compound layer are left on the edge side of the plated steel sheet to form an exposed portion of the intermetallic compound layer or the base steel sheet. In the second embodiment, the characteristics of the resulting hot-pressed product indicate that it is desirable to incorporate an appropriate amount of surface coating and Al plating layer components into the weld metal.

[0063] In a second embodiment, the width of the exposed portion of the intermetallic compound layer or base steel sheet (see T1 in Figure 2) is preferably 0.45 to 4.0 mm, and more preferably 0.9 to 3.4 mm. Furthermore, the width of the "surface film, Al plating layer, and intermetallic compound layer" remaining on the edge of the plated steel sheet (see T2 in Figure 2) is preferably 0.05 to 1.0 mm, and more preferably 0.1 to 0.6 mm. In particular, when laser welding is used during the fabrication of tailored blanks, the width of the first exposed portion 22 is preferably 0.5 mm or more, and preferably 1.5 mm or less. When plasma welding is used during the fabrication of the tailored blank, the width of the first exposed portion 22 is preferably 1.0 mm or more, and preferably 4.0 mm or less.

[0064] In Figures 1 and 2, 100 represents a welded steel sheet, 101 represents a plated steel sheet, 101A represents the area to be welded, 10 represents the base steel sheet, 12 represents the Al plating layer, 14 represents the intermetallic compound layer, 16 represents the surface film, 100A represents the exposed portion of the intermetallic compound layer or base steel sheet, and 100B represents the "surface film, Al plating layer, and intermetallic compound layer" remaining on the edge of the plated steel sheet. In Figures 1 and 2, T1 represents the width of the intermetallic compound layer or the exposed portion of the base steel sheet, and T2 represents the width of the "surface film, Al plating layer, and intermetallic compound layer" remaining on the edge of the plated steel sheet.

[0065] In the second step, well-known laser processing methods such as laser ablation (evaporation removal) and laser gouging (melting removal) can be used to remove the intermetallic compound layer or the exposed base steel sheet.

[0066] The conditions for laser ablation processing are as follows, for example: • Laser source: Short-pulse laser Pulse width: 450 fs ~ 100 ns • Nominal output: 50~1000W • Pulse energy: 0.2~200mJ • Laser scanning speed: 30-8000 mm / min

[0067] The conditions for laser gouging are, for example, as follows: • Laser source: Semiconductor laser • Assist gas: Nitrogen • Assist gas injection volume: 3-8 kgf / cm² 2 Laser output: 500-5000W • Laser scanning speed: 1000-8000 mm / min

[0068] <Manufacturing method for tailored blanks / Tailored blanks> The method for manufacturing a tailored blank as disclosed herein is: A step of obtaining a welded steel sheet by the manufacturing method of a welded steel sheet described above in this disclosure, A step of welding two or more welded steel plates, each having a welded steel plate obtained by the manufacturing method of the welded steel plate described above, at a welding area and joining them with weld metal, It holds.

[0069] According to the manufacturing method of tailored blanks of this disclosure, Two or more welded steel plates having the welded steel plate of this disclosure, Weld metal that connects the planned weld portions of two or more welded steel plates, A tailored blank (the tailored blank of this disclosure) having the above characteristics is obtained.

[0070] Specifically, in the method for manufacturing a tailored blank according to this disclosure, two or more welded steel plates are welded together and connected with weld metal to obtain the desired tailored blank (see Figure 3). In Figure 3, 200 represents a tailored blank, 100 represents a welded steel plate, and 120 represents the weld metal. In Figure 3, 101 represents the plated steel sheet, 10 represents the base steel sheet, 12 represents the Al plating layer, 14 represents the intermetallic compound layer, and 16 represents the surface film.

[0071] In the method for manufacturing a tailored blank according to this disclosure, two or more welded steel plates may be used in combination depending on the purpose. The two or more welded steel plates used to obtain the tailored blank may, for example, be steel plates of the same strength class, or steel plates of different strength classes. Furthermore, steel plates of the same thickness may be used, or steel plates of different thicknesses may be used. However, the method for manufacturing a tailored blank according to this disclosure applies the welded steel sheet obtained by the method for manufacturing a welded steel sheet according to this disclosure (i.e., the welded steel sheet of this disclosure) to at least one of two or more welded steel sheets. In other words, if the welded steel sheet obtained by the method for manufacturing a welded steel sheet according to this disclosure (i.e., the welded steel sheet of this disclosure) is applied to at least one of two or more welded steel sheets, a welded steel sheet other than the welded steel sheet obtained by the method for manufacturing a welded steel sheet according to this disclosure (i.e., the welded steel sheet of this disclosure) may be used.

[0072] The method for manufacturing a tailored blank according to the present disclosure may be a method for manufacturing a tailored blank in which two or more welded steel plates are overlapped and welded together, or a method for manufacturing a tailored blank in which two or more welded steel plates are butt-welded together.

[0073] In the manufacturing method of tailored blanks according to this disclosure, the welding method is not particularly limited and examples include laser welding (laser beam welding) and arc welding. Examples of arc welding include plasma welding, MIG (Metal Inert Gas) welding, and MAG (Metal Active Gas) welding, with plasma welding being a preferred arc welding method. The welding conditions can be selected according to the desired conditions, such as the thickness of the steel plate to be welded. Furthermore, welding may be performed while supplying filler wire as needed.

[0074] <Manufacturing method for hot-pressed products / Hot-pressed products> The method for manufacturing a hot-pressed product according to this disclosure is: A step of obtaining a tailored blank by the method for manufacturing a tailored blank described above, A step of hot press forming a tailored blank obtained by the method for manufacturing a tailored blank as described above, It holds.

[0075] In the method for manufacturing hot press-formed articles of this disclosure, the desired hot press-formed article is obtained by hot press-forming a tailored blank obtained by the method for manufacturing a tailored blank of this disclosure. In other words, according to the method for manufacturing a hot press-formed article of the present disclosure, a hot press-formed article of a tailored blank of the present disclosure can be obtained.

[0076] Specifically, the method for manufacturing a hot press-formed product according to this disclosure allows for the production of a hot press-formed product as follows: First, the tailored blank is heated to a high temperature to soften it. Then, using a mold, the softened tailored blank is formed by hot press forming (i.e., hot stamping), cooled, and quenched to obtain a hot-pressed product of the desired shape. By quenching the hot-pressed product through heating and cooling, a hot-pressed product with a high tensile strength, for example, of approximately 1500 MPa or more, can be obtained.

[0077] In addition to conventional electric furnaces and radiant tube furnaces, heating methods such as infrared heating, electrostatic heating, and induction heating can be used when performing hot press forming.

[0078] The maximum temperature achievable during hot press forming is not particularly limited, but is preferably, for example, 850°C to 1000°C. In hot press forming, since heating must occur in the austenite region, a temperature of around 900°C to 950°C is usually adopted.

[0079] In hot press forming, a tailored blank heated to a high temperature is press-formed in a mold cooled by water cooling or the like, and simultaneously hardened by the cooling in the mold. Alternatively, if necessary, water may be sprayed directly onto the blank material through gaps in the mold for water cooling. This process yields a hot press-formed product of the desired shape.

[0080] The applications of the hot-pressed products of this disclosure are not particularly limited and include, for example, various automotive components such as automobile bodies and various components for industrial machinery. Examples of automotive components include, specifically, various pillars; stabilizers, door beams, roof rails, bumpers and other reinforcements; frames; arms and other various parts.

[0081] <Other> The welded steel sheet obtained by the manufacturing method of the welded steel sheet of this disclosure is not limited to a welded steel sheet for the production of tailored blanks, but may also be, for example, a welded steel sheet for steel pipes. A steel pipe to which a welded steel sheet obtained by the manufacturing method of the welded steel sheet of the present disclosure is applied comprises, for example, a weld metal and a welded steel sheet of the present disclosure which is formed in an open tubular shape with two circumferential edges facing each other, and to which the two circumferential edges are connected to the weld metal.

[0082] On the other hand, a steel pipe to which a tailored blank obtained by the manufacturing method of the tailored blank of the present disclosure is applied comprises, for example, a weld metal and a tailored blank obtained by the manufacturing method of the tailored blank of the present disclosure, which is formed in an open tubular shape with two circumferential edges facing each other, and the two circumferential edges are connected to the weld metal.

[0083] The method for forming the welded steel plate and tailored blank into a tubular shape is not particularly limited and may be any method, such as the UOE method or the bending roll method. Furthermore, the welding after forming the tubular shape is not particularly limited and includes, for example, laser welding; plasma welding; electric resistance welding; or electric resistance welding using high-frequency induction heating. [Examples]

[0084] The following are examples of embodiments of this disclosure, but this disclosure is not limited to the following embodiments. It is clear to those skilled in the art that various variations or modifications can be conceived within the scope of the ideas described in the claims, and these will naturally fall within the technical scope of this disclosure.

[0085] <Example 1> As the base steel sheet, a base steel sheet was prepared having a chemical composition of C:0.24%, Mn:1.22%, Al:0.020%, Ti:0.02%, Cr:0.2%, B:0.0025%, Si:0.25%, P:0.02%, S:0.002%, N:0.001%, with the remainder being Fe and impurities, and having a strength class of 1500 MPa after hot pressing. Next, both sides of the base steel sheet were plated with Al using the Zenzimer method with an Al plating bath consisting of Si:9%:the remainder:Al and impurities. The resulting Al plating layer had a chemical composition of Si:9%:Fe:3%:the remainder:Al and impurities. In the Al plating process, the amount of Al plating layer after plating was adjusted using the gas wiping method to the values ​​shown in Table 1. Through the above operations, an Al-plated steel sheet was obtained.

[0086] Next, a surface film forming treatment solution was prepared containing a water-soluble urethane resin as a binder, carbon black (CB), and Zn oxide (ZnO) as a metal oxide. Then, the treatment solution was applied to one side of the Al-plated steel sheet using a roll coater, and the coating film was baked at 80°C to form a surface film with the average thickness shown in Table 1. The composition of the treatment solution (i.e., the composition of the surface film) was as shown in Table 1. Through the above operations, a coated Al-plated steel sheet was obtained.

[0087] Next, the coated aluminum-plated steel sheet was cut using a shearing machine to produce welded steel sheets measuring 50 x 100 mm.

[0088] Next, the surface coating and Al plating layer were removed from the cut-out welded steel plate so that an exposed portion of the intermetallic compound layer was formed adjacent to the edge of the plated steel plate at the planned welding area (one of the four edges) (see Figure 1). The width of the exposed portion of the intermetallic compound layer was as shown in Table 1. The surface coating and Al plating layer were removed by laser ablation using a Q-switched laser as the laser source. The conditions for the laser ablation process are shown in Table 1.

[0089] Through the above operations, two welded steel plates were obtained. Then, after butting the ends of the two welded steel plates at the points to be welded together, they were welded under the following conditions to obtain a tailored blank. The laser welding conditions were adjusted to achieve through-welding within the range of laser output 3.0 to 5.0 kW and welding speed 4.0 m / min to 7.0 m / min.

[0090] <Examples 2-6, Comparative Example 1> As shown in Table 1, welded steel plates were obtained in the same manner as in Example 1, except that various conditions were changed, and then tailored blanks were obtained. However, in some cases, the surface coating and the Al plating layer were removed from the cut-out coated Al-plated steel sheet in the area to be welded, so that the intermetallic compound layer was exposed at intervals from the edge of the plated steel sheet (see Figure 2). The width of the exposed portion of the intermetallic compound layer and the remaining "surface film, Al plating layer, and intermetallic compound layer" on the edges of the plated steel sheet (indicated as "remaining plating width" in the table) are as shown in Table 1.

[0091] <Rating> The weld strength (strength of the weld metal) of the tailored blanks in each example was evaluated as follows.

[0092] (Tensile test) Each example of a tailored blank was hot-pressed in a furnace heated to 920°C for 4 minutes to obtain a press-formed product. From the resulting press-formed product, a dumbbell-shaped test specimen with a welded section was taken as a test piece for tensile strength testing. The test specimen had a parallel section distance of 20 mm and a parallel section width of 15 mm, and was taken so that a weld line ran along the entire width direction perpendicular to the longitudinal direction in the center of the parallel section. Tensile tests were performed under the condition of a crosshead displacement rate of 10 mm / min until the test specimen fractured. Measurements were taken for a total of 10 tests (N=10), and any specimen that fractured in the weld metal was considered unsuccessful (NG).

[0093] [Table 1]

[0094] From the above results, it can be seen that in this embodiment, a welded steel sheet is obtained that suppresses the decrease in weld strength of the tailored blank caused by the surface coating, compared to the comparative example. [Explanation of Symbols]

[0095] 10 Base steel plate 12 Al plating layer 14 Intermetallic compound layer 16 Surface coating 100 Welded Steel Plates 100A Intermetallic compound layer or exposed portion of base steel plate 100B "Surface film, Al plating layer, and intermetallic compound layer" remaining on the edges of plated steel sheets. 101 Plated steel sheet 101A Welding Schedule 120 Weld metal 200 Tailored Blanks

Claims

1. A first step of preparing a plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layer provided on one side of the base steel sheet or the Al plating layer provided on both sides of the base steel sheet, containing a binder resin, carbon black and metal oxide, and having an average thickness of 0.5 to 5.0 μm, A second step involves using laser processing to remove the surface film and the Al plating layer along the edge of the plated steel sheet in the area where welding is planned on the edge of the plated steel sheet, or to remove the surface film, the Al plating layer and the intermetallic compound layer, thereby forming an exposed portion of the intermetallic compound layer or the base steel sheet. A method for manufacturing welded steel sheets having the following characteristics.

2. The method for manufacturing a welded steel sheet according to claim 1, wherein in the second step, the surface film and the Al plating layer are removed so that the intermetallic compound layer or the exposed portion of the base steel sheet is formed adjacent to the edge of the plated steel sheet, or the surface film, the Al plating layer and the intermetallic compound layer are removed.

3. The method for manufacturing a welded steel sheet according to claim 1, wherein in the second step, the surface film and the Al plating layer are removed so as to form the intermetallic compound layer or the exposed portion of the base steel sheet spaced apart from the edge of the plated steel sheet, or the surface film, the Al plating layer and the intermetallic compound layer are removed.

4. The method for manufacturing a welded steel sheet according to claim 2, wherein the metal oxide is one or more metal oxides selected from the group consisting of Zr oxide, Zn oxide, and Ti oxide.

5. The method for manufacturing a welded steel sheet according to claim 3, wherein the metal oxide is one or more metal oxides selected from the group consisting of Zr oxide, Zn oxide, and Ti oxide.

6. A step of obtaining a welded steel sheet by a method for manufacturing a welded steel sheet according to any one of claims 1 to 5, A step of welding two or more welded steel plates, each having a welded steel plate obtained by the method for manufacturing a welded steel plate according to any one of claims 1 to 5, at a welding area and joining them with weld metal, A method for manufacturing a tailored blank having [a specific characteristic].

7. A step of obtaining a tailored blank by the method for manufacturing a tailored blank described in claim 6, A step of hot press forming a tailored blank obtained by the method for manufacturing a tailored blank described in claim 6, A method for manufacturing a hot press-formed product having the following characteristics.

8. A plated steel sheet having a base steel sheet, an Al plating layer provided on one or both sides of the base steel sheet, an intermetallic compound layer containing iron and aluminum provided between the base steel sheet and the Al plating layer, and a surface film provided on at least one of the Al plating layer provided on one side of the base steel sheet or the Al plating layer provided on both sides of the base steel sheet, containing a binder resin, carbon black and metal oxide, and having an average thickness of 0.5 to 5.0 μm, The portion of the plated steel sheet that is to be welded at the edge of the plated steel sheet, the intermetallic compound layer provided along the edge of the plated steel sheet, or the exposed portion of the base steel sheet, A welded steel plate.

9. Two or more welded steel plates having the welded steel plate described in claim 8, Weld metal connecting the planned weld portions of the two or more welded steel plates, A tailored blank with [specific feature].

10. A hot-pressed product of a tailored blank as described in claim 9.

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