Tailored blank, hot press-formed product, method for manufacturing tailored blank, and method for manufacturing hot press-formed product

Abstract

To provide a tailored blank capable of suppressing breakage at a welded metal section.SOLUTION: A tailored blank 1 includes a first steel plate 10, a second steel plate 20 arranged so as to be butted against the first steel plate in a butting direction X, and a welded metal section 30 joins to the first steel plate and the second steel plate and extending in a crossing direction Y. At least one of the first steel plate and the second steel plate is an aluminum plated steel plate, and satisfies a first formula. A length L2 of the second steel plate in the cross direction varies depending on a position in the butting direction. When a distance between a position of the second steel plate resulting in a length L2 and the welded metal section in the butting direction is defined as a distance a, and when a pair of a length L2 and a distance a taking a minimum value of a second formula for a pair of a length L2 and a distance a which varies according to a position in the butting direction is defined as a length L2_min and a distance amin, a length Lw of the welded metal section in a cross direction satisfies a third formula for the length L2_min and the distance amin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tailored blank, a hot press-formed product, a method for manufacturing a tailored blank, and a method for manufacturing a hot press-formed product. [Background technology]

[0002] Conventionally, in hot press-formed products using aluminum-plated steel sheets, aluminum is mixed into the weld metal part, and the weld metal part may not be hardened during hot press forming (see, for example, Patent Documents 1 and 2). Two types of countermeasures have been proposed to address this problem.

[0003] The first measure is to prevent aluminum from being mixed into the weld metal by removing the aluminum plating layer from the aluminum-plated steel sheets before welding them together. The second solution is to supply austenitic welding materials during welding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5237263 [Patent Document 2] International Publication No. 2013 / 045497 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the first measure requires a process for removing the aluminum plating layer, and the second measure may cause aluminum to thicken at the weld edge (weld toe), where stirring of the molten weld metal is difficult.

[0006] The present invention has been made in consideration of these problems, and aims to provide a tailored blank, a hot press-formed product, a method for manufacturing a tailored blank, and a method for manufacturing a hot press-formed product that can suppress fracture at the weld metal portion. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention proposes the following means. (1) A first aspect of the present invention is a tailored blank comprising a first steel plate, a second steel plate arranged such that an end of the second steel plate butts against an end of the first steel plate in a butt direction, and a weld metal portion joining the end of the first steel plate and the end of the second steel plate and extending in a transverse direction intersecting the butt direction, wherein at least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, and formula (1) is satisfied, and the length L2 (mm) of the second steel plate in the transverse direction varies depending on the position in the butt direction, and the distance in the butt direction between the position of the second steel plate that corresponds to the length L2 and the weld metal portion when viewed from a direction perpendicular to both the butt direction and the transverse direction is defined as a (mm), and the pair of the length L2 and the distance a that takes the minimum value of formula (2) for the pair of the length L2 and the distance a that varies depending on the position in the butt direction is defined as the length L 2_min and the distance a min When the length L 2_min and the distance a min In contrast, the length L of the weld metal portion in the cross direction w (mm) satisfies equation (3). where T1 is the thickness (mm) of the first steel plate, H1 is the Vickers hardness of the first steel plate in the hot press-formed product obtained by hot press-forming the tailored blank, T2 is the thickness (mm) of the second steel plate, H2 is the Vickers hardness of the second steel plate in the hot press-formed product, and T w : thickness of the weld metal part (the thinner of the thickness T1 and the thickness T2) (mm), H w : Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more.

[0008]

number

[0009] (8) A second aspect of the present invention is a method for manufacturing a tailored blank, which comprises: an arrangement step of arranging an end of a first steel plate and an end of a second steel plate so that they butt against each other in a butt direction; and a welding step of joining the end of the first steel plate and the end of the second steel plate by welding to form a weld metal part extending in a transverse direction intersecting the butt direction, wherein at least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, and formula (4) is satisfied, and the length L2 (mm) of the second steel plate in the transverse direction varies depending on the position in the butt direction, and the distance in the butt direction between the position of the second steel plate that corresponds to the length L2 and the weld metal part when viewed from a direction perpendicular to both the butt direction and the transverse direction is defined as a (mm), and the pair of the length L2 and the distance a that takes the minimum value of formula (5) for the pair of the length L2 and the distance a that varies depending on the position in the butt direction is defined as the length L 2_min and the distance a min When the length L 2_min and the distance a min In contrast, the length L of the weld metal portion in the cross direction w (mm) satisfies equation (6). where T1 is the thickness (mm) of the first steel plate, H1 is the Vickers hardness of the first steel plate in the hot press-formed product obtained by hot press-forming the tailored blank, T2 is the thickness (mm) of the second steel plate, H2 is the Vickers hardness of the second steel plate in the hot press-formed product, and T w : thickness of the weld metal part (the thinner of the thickness T1 and the thickness T2) (mm), H w : Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more.

[0010]

number

[0011] Note that equation (4) is the same as equation (1), equation (5) is the same as equation (2), and equation (6) is the same as equation (3). In these inventions, by satisfying formula (1), the second steel plate in the hot press-formed product has a lower product of thickness and Vickers hardness, i.e., a lower rigidity, than the first steel plate. Therefore, for example, when a tensile force acts in the butt direction on a hot press-formed product obtained by hot press-forming a tailored blank, stress is concentrated on the second steel plate, making the second steel plate more susceptible to fracture than the first steel plate. As a result of extensive research, the inventors have found that the second steel plate is more likely to fracture in a direction that forms a 45° angle with respect to the weld metal portion when viewed from the perpendicular direction. 2_min and distance a min By satisfying equation (3) for the set, the length L of the second steel plate is formed before the weld metal part. 2_min and distance a min Therefore, in the hot press formed product, it is possible to prevent fracture at the welded metal portion.

[0012] (2) In the tailored blank described in (1) above, the constant A may be 1.0 or more and 1.5 or less. (9) In the method for producing a tailored blank according to (8) above, the constant A may be 1.0 or more and 1.5 or less. In these inventions, for example, the length L of the weld metal part is smaller than when the constant A is 0.9. w Therefore, in the hot press formed product, fracture at the welded metal portion can be more reliably suppressed.

[0013] (3) In the tailored blank described in (1) or (2), the aluminum-plated steel sheet may have an intermetallic compound layer and an aluminum plating layer provided on each surface of the base steel sheet in a thickness direction thereof, in that order from the base steel sheet side, and the sum of thicknesses of the intermetallic compound layer and the aluminum plating layer provided on at least one of the surfaces of the base steel sheet may be 10 μm or more. (10) In the method for manufacturing a tailored blank described in (8) or (9), the aluminum-plated steel sheet may have an intermetallic compound layer and an aluminum plating layer provided, in that order from the base steel sheet side, on each surface of the base steel sheet in a thickness direction, and the sum of thicknesses of the intermetallic compound layer and the aluminum plating layer provided on at least one of the surfaces of the base steel sheet may be 10 μm or more. In these inventions, the sum of the thicknesses of the intermetallic compound layer and the aluminum plating layer on at least one surface of the base steel sheet of the aluminum-plated steel sheet is 10 μm or more, and the incorporation of aluminum into the weld metal zone increases, thereby improving the corrosion resistance of the weld metal zone.

[0014] (4) In the tailored blank according to any one of (1) to (3), the weld metal portion may have a weld start point and a weld end point. (11) In the method for manufacturing a tailored blank according to any one of (8) to (10), the weld metal portion may have a weld start point and a weld end point. In these inventions, even when the weld metal portion has a weld start end and a weld end, fracture at the weld metal portion can be suppressed.

[0015] (5) In the tailored blank described in any one of (1) to (4), the aluminum concentration contained in the weld metal portion of the hot press-formed product may be 0.3 mass% or more and 2.5 mass% or less. (12) In the method for manufacturing a tailored blank described in any one of (8) to (11), the aluminum concentration contained in the weld metal portion of the hot press-formed product may be 0.3 mass% or more and 2.5 mass% or less. In these inventions, the aluminum concentration in the weld metal portion of the hot press-formed product is high, and therefore the corrosion resistance of the weld metal portion can be improved.

[0016] (6) In the tailored blank according to any one of (1) to (5), the hot press-formed product may be an automobile part. (13) In the method for producing a tailored blank according to any one of (8) to (12), the hot press-formed product may be an automobile part. In these inventions, the hot press-formed product in which fracture at the welded metal portion is suppressed can be preferably used as an automobile part.

[0017] (7) A third aspect of the present invention is a hot press-formed product comprising: a first steel plate; a second steel plate arranged such that an end of the second steel plate butts against an end of the first steel plate in a butt direction; and a weld metal portion joining the end of the first steel plate and the end of the second steel plate and extending in a transverse direction intersecting the butt direction, wherein at least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, and formula (7) is satisfied, and the length L2 (mm) of the second steel plate in the transverse direction changes depending on the position in the butt direction, and the distance in the butt direction between the position of the second steel plate that corresponds to the length L2 and the weld metal portion when viewed from a direction perpendicular to both the butt direction and the transverse direction is defined as a (mm), and the pair of the length L2 and the distance a that takes the minimum value of formula (8) for the pair of the length L2 and the distance a that changes depending on the position in the butt direction is defined as the length L2. 2_min and the distance a min When the length L 2_min and the distance a min In contrast, the length L of the weld metal portion in the cross direction w (mm) satisfies equation (9). where T1 is the thickness of the first steel plate (mm), H1 is the Vickers hardness of the first steel plate, T2 is the thickness of the second steel plate (mm), H2 is the Vickers hardness of the second steel plate, and T w: thickness of the weld metal part (the thinner of the thickness T1 and the thickness T2) (mm), H w : Vickers hardness of the weld metal part, A: a constant of 0.9 or more.

[0018]

number

[0019] (14) A fourth aspect of the present invention is a method for manufacturing a hot press-formed product, which comprises: an arrangement step of arranging an end of a first steel plate and an end of a second steel plate so that they butt against each other in a butting direction; a welding step of joining the end of the first steel plate and the end of the second steel plate by welding to form a weld metal part extending in a cross direction that intersects the butt-forming direction, thereby manufacturing a tailored blank; and a forming step of hot press-forming the tailored blank, wherein at least one of the first steel plate and the second steel plate is One of the steel plates is an aluminum-plated steel plate, and satisfies formula (10). The length L2 (mm) of the second steel plate in the cross direction varies depending on the position in the butt direction. When viewed from a direction perpendicular to both the butt direction and the cross direction, the distance in the butt direction between the position of the second steel plate at which the length L2 is obtained and the weld metal part is defined as a (mm). The set of the length L2 and the distance a that takes the minimum value of formula (11) for the set of the length L2 and the distance a that varies depending on the position in the butt direction is defined as the length L2. 2_min and the distance a min When the length L 2_min and the distance a min In contrast, the length L of the weld metal portion in the cross direction w (mm) is a manufacturing method for hot press-formed products that satisfies equation (12). where T1 is the thickness (mm) of the first steel plate, H1 is the Vickers hardness of the first steel plate in the hot press-formed product, T2 is the thickness (mm) of the second steel plate, H2 is the Vickers hardness of the second steel plate in the hot press-formed product, and T w : thickness of the weld metal part (the thinner of the thickness T1 and the thickness T2) (mm), H w: Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more.

[0020]

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[0021] Note that equation (10) is the same as equation (7), equation (11) is the same as equation (8), and equation (12) is the same as equation (9). In these inventions, by satisfying formula (7), the second steel plate in the hot press-formed product has a lower product of thickness and Vickers hardness, i.e., a lower rigidity, than the first steel plate. Therefore, for example, when a tensile force acts on the hot press-formed product in the butt direction, stress is concentrated in the second steel plate, making the second steel plate more susceptible to fracture than the first steel plate. As a result of extensive research, the inventors have found that the second steel plate is more likely to fracture in a direction that forms a 45° angle with respect to the weld metal portion when viewed from the perpendicular direction. 2_min and distance a min By satisfying equation (9) for the set of 2_min and distance a min Therefore, in the hot press formed product, it is possible to prevent fracture at the welded metal portion. [Effects of the Invention]

[0022] In the tailored blank, hot press-formed product, method for manufacturing a tailored blank, and method for manufacturing a hot press-formed product of the present invention, fracture at the weld metal portion can be suppressed. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a plan view of a tailored blank according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along the line A1-A1 in FIG. [Figure 3]1 is a flowchart showing a method for manufacturing a hot press-formed product according to one embodiment of the present invention. [Figure 4] FIG. 2 is a plan view of a hot-press-formed product in a first modified example of an embodiment of the present invention. [Figure 5] FIG. 10 is a plan view of a hot-press-formed product in a second modified example of an embodiment of the present invention. [Figure 6] FIG. 10 is a plan view of a hot-press-formed product in a third modified example of an embodiment of the present invention. [Figure 7] FIG. 10 is a plan view of a hot-press-formed product in a fourth modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, an embodiment of a tailored blank and a hot press-formed product according to the present invention will be described with reference to FIGS. As shown in Figures 1 and 2, a tailored blank (butt-welded steel plate) 1 of this embodiment includes a first steel plate 10, a second steel plate 20, and a weld metal portion 30. The first steel plate 10 and the second steel plate 20 are each formed in a flat plate shape. Below, the configurations of the first steel plate 10 and the second steel plate 20 will first be described.

[0025] <Aluminum-plated steel sheet> At least one of the first steel sheet 10 and the second steel sheet 20 is an aluminum-plated steel sheet. Fig. 2 shows an example in which both the first steel sheet 10 and the second steel sheet 20 are aluminum-plated steel sheets. As shown in Fig. 2, the first steel sheet 10 has an intermetallic compound layer 12 and an aluminum-plated layer 13 provided on each surface 11a, 11b of the base steel sheet 11 in the thickness direction Z, in that order from the base steel sheet 11 side. Note that Fig. 1 is a plan view of the tailored blank 1 as seen in the thickness direction Z. As shown in Fig. 2, the surface 11a is a surface facing a first side in the thickness direction Z of the base steel sheet 11. The surface 11b is a surface facing a second side opposite to the first side in the thickness direction Z of the base steel sheet 11. An intermetallic compound layer 12 and an aluminum plating layer 13 are provided on the surface 11a of the base steel sheet 11 in this order from the base steel sheet 11 side. An intermetallic compound layer 12 and an aluminum plating layer 13 are provided on the surface 11b of the base steel sheet 11 in this order from the base steel sheet 11 side.

[0026] The second steel plate 20 is configured in the same manner as the first steel plate 10. That is, in the second steel plate 20, an intermetallic compound layer 22 and an aluminum plating layer 23 are provided, in this order from the base steel plate 21 side, on each surface 21a, 21b in the thickness direction Z of the base steel plate 21. The thickness direction of the base steel plate 21 of the second steel plate 20 is aligned with the thickness direction Z of the base steel plate 11 of the first steel plate 10.

[0027] The hot press-formed product 1A is obtained by hot press-forming the tailored blank 1. Hereinafter, the hot press-formed first steel plate 10, second steel plate 20, and weld metal part 30 will be referred to as the first steel plate 10A, the second steel plate 20A, and the weld metal part 30A. The hot press-formed product 1A includes the first steel plate 10A, the second steel plate 20A, and the weld metal part 30A.

[0028] <Base material steel plate> The base steel sheet is a steel sheet before an aluminum plating layer is formed. The base steel sheet may be one obtained by a conventional method and is not particularly limited. The base steel sheet may be either a hot-rolled steel sheet or a cold-rolled steel sheet. The thickness of the base steel sheet is not particularly limited and may be a thickness according to the purpose. For example, the thickness of the base steel sheet may be such that the overall thickness of the steel sheet after the aluminum plating layer is formed is 0.8 mm to 4.0 mm, and further may be such that it is 1.0 mm to 3.0 mm.

[0029] As an example of the base steel plate, it is preferable to use a steel plate formed to have high mechanical strength (meaning various properties related to mechanical deformation and fracture, such as tensile strength, yield point, elongation, reduction in area, hardness, impact value, fatigue strength, etc.).

[0030] An example of a preferable chemical composition of the base steel sheet is, for example, the following chemical composition. In mass %, C: 0.02%~0.58%, Mn: 0.20%~3.00%, Al: 0.005%~0.06%, 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: The chemical composition is: 0% to 0.0100%, Mg: 0% to 0.05%, Ca: 0% to 0.05%, REM: 0% to 0.05%, Sn: 0% to 0.5%, Bi: 0% to 0.05%, Si: 0% to 2.00%, P: 0.03% or less, S: 0.010% or less, N: 0.010% or less, and the balance: Fe and impurities. In the following, "%" indicating the content of a component (element) means "% by mass." A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0031] <Aluminum plating layer> The aluminum plating layer is formed on both sides of the base steel sheet. The method for forming the aluminum plating layer is not particularly limited. For example, the aluminum plating layer may be formed on each surface of the base steel sheet by a hot-dip galvanizing method in which the base steel sheet is immersed in a molten metal bath containing aluminum as a main component to form an aluminum plating layer.

[0032] Here, the aluminum plating layer refers to a plating layer containing aluminum as a main component, and may contain 50% or more by mass of aluminum. Depending on the purpose, it may contain elements other than aluminum (e.g., Si, etc.), and it may also contain impurities that are mixed in during the manufacturing process, etc. Specifically, the aluminum plating layer may have a chemical composition that contains, for example, 5% to 12% by mass of Si (silicon), with the balance consisting of aluminum and impurities. Alternatively, it may have a chemical composition that contains, for example, 5% to 12% by mass of Si (silicon) and 2% to 4% by mass of Fe (iron), with the balance consisting of aluminum and impurities. When Si is contained within the above range, deterioration in workability and corrosion resistance can be suppressed, and the thickness of the intermetallic compound layer can be reduced.

[0033] The thickness of the aluminum plating layer is not particularly limited. For example, the average thickness is preferably in the range of 8 μm (micrometers) to 35 μm, and more preferably in the range of 15 μm to 30 μm. The thickness of the aluminum plating layer represents the average thickness.

[0034] The aluminum plating layer prevents corrosion of the steel sheet (improving corrosion resistance). Furthermore, the aluminum plating layer prevents the formation of scale (iron compounds) due to surface oxidation even when the steel sheet is heated to high temperatures during hot press forming. Furthermore, the aluminum plating layer has a higher boiling point and melting point than plating coatings made from organic materials and plating coatings made from other metallic materials (e.g., zinc-based materials). Therefore, when the steel sheet is formed by hot press forming, the coating does not evaporate, and the surface is highly protected.

[0035] The aluminum plating layer can be alloyed with iron (Fe) in the steel sheet due to heating during hot-dip plating and hot press forming. Therefore, the aluminum plating layer is not necessarily formed as a single layer with a uniform composition, but rather includes a partially alloyed layer (alloy layer).

[0036] <Intermetallic compound layer> The intermetallic compound layer is a layer formed at the boundary between the base steel sheet and the aluminum plating layer when an aluminum plating layer is formed on the base steel sheet. Specifically, the intermetallic compound layer is formed by a reaction between iron (Fe) of the base steel sheet and metals containing aluminum (Al) in a molten metal bath containing aluminum as the main component. The intermetallic compound layer is mainly composed of Fe x Al y (x and y are 1 or more). When the aluminum plating layer contains Si (silicon), Fe x Al y and Fe x Al y Si z (x, y, z each represent 1 or more)

[0037] The thickness of the intermetallic compound layer is not particularly limited, but may be, for example, in the range of 3 μm to 10 μm in average thickness, and preferably in the range of 4 μm to 8 μm. Note that the thickness of the intermetallic compound layer represents the average thickness. The thickness of the intermetallic compound layer can be controlled by the temperature and immersion time of the molten metal bath containing aluminum as the main component.

[0038] Here, the confirmation of the base steel sheet, the intermetallic compound layer, and the aluminum plating layer, and the measurement of the thicknesses of the intermetallic compound layer and the aluminum plating layer are carried out by the following methods.

[0039] The steel sheet is cut so that its cross section is exposed, and the cross section is polished. The polished cross section of the steel sheet is subjected to linear analysis from the surface of the steel sheet to the base steel sheet using an electron probe microanalyzer (FE-EPMA), and the aluminum and iron concentrations are measured. The measurement conditions are an acceleration voltage of 15 kV, a beam diameter of approximately 100 nm, an irradiation time per point of 1000 ms, a measurement pitch of 60 nm, and a measurement distance that allows the thickness of the coating layer to be measured, for example, approximately 30 μm to 80 μm in the thickness direction. The thickness of the base steel sheet and the thickness of the aluminum-plated steel sheet are preferably measured using an optical microscope or a micrometer.

[0040] As a result of measuring the aluminum concentration in the cross section of the steel sheet, a region where the aluminum (Al) concentration is less than 2.0 mass% is judged to be the base steel sheet, and a region where the aluminum concentration is 2.0 mass% or more is judged to be an intermetallic compound layer or an aluminum plating layer. Furthermore, among the intermetallic compound layer and the aluminum plating layer, a region where the iron (Fe) concentration is more than 4.0 mass% is judged to be an intermetallic compound layer, and a region where the iron concentration is 4 mass% or less is judged to be an aluminum plating layer. The thickness of the intermetallic compound layer is defined as the distance from the boundary of the base steel sheet to the boundary of the aluminum plating layer, and the thickness of the aluminum plating layer is defined as the distance from the boundary between the intermetallic compound layer and the aluminum plating layer to the steel sheet surface on which the aluminum plating layer is formed.

[0041] The thickness of the aluminum plating layer and the thickness of the intermetallic compound layer are measured by linear analysis from the surface of the steel sheet to the surface of the base steel sheet (the boundary between the base steel sheet and the intermetallic compound layer) as follows. The thickness of the aluminum plating layer is determined by measuring the thickness from the surface of the steel sheet having the aluminum plating layer to the intermetallic compound layer at any five positions according to the criteria described above, and averaging the measured values. The thickness of the intermetallic compound layer is determined in accordance with the above-mentioned criteria by measuring the thickness from the boundary between the intermetallic compound layer and the aluminum plating layer to the boundary between the intermetallic compound layer and the base steel sheet at any five positions, and the average of the determined values ​​is defined as the thickness of the intermetallic compound layer.

[0042] In the base steel sheet of the aluminum-plated steel sheet, it is preferable that the sum of the thicknesses of the intermetallic compound layer 22 and the aluminum-plated layer 23 provided on at least one surface (at least one of surfaces 11a, 11b, 21a, 21b) of the base steel sheet is 10 μm or more.

[0043] The thickness of the first steel plate 10 is determined by measuring the thickness of the first steel plate 10 at any five positions and averaging the measured values ​​to determine the thickness of the first steel plate 10. The same applies to the thickness of the second steel plate 20. Here, the thickness of the first steel plate 10 is defined as T1 (mm), and the thickness of the second steel plate 20 is defined as T2 (mm). In this embodiment, the thickness T2 is thinner than the thickness T1, although the thickness T2 may be equal to or greater than the thickness T1.

[0044] <Welded metal parts> 1 and 2, in the tailored blank 1, the end of the second steel plate 20 is arranged to abut against the end of the first steel plate 10 in a butting direction X in which the second steel plate 20 and the first steel plate 10 abut against each other. The butting direction X is a direction intersecting (orthogonal to) the thickness direction Z. The weld metal part 30 joins an end of the first steel plate 10 and an end of the second steel plate 20. The weld metal part 30 extends in a transverse direction Y that intersects with the butt direction X. The transverse direction Y is a direction that intersects (is perpendicular to) both the butt direction X and the thickness direction Z. The tailored blank 1 is manufactured using steel sheets 10, 20 from which the intermetallic compound layer 12 and the aluminum plating layer 13 at the end portions are not removed.

[0045] Here, the thickness of the weld metal portion 30 is T w (mm), and the thickness T w is equal to the thinner (less thicker) of thickness T1 and thickness T2. The concentration of aluminum contained in the weld metal portion 30A of the hot press-formed product 1A is preferably 0.3 mass % or more and 2.5 mass % or less. The aluminum concentration of the weld metal portion 30A is measured as follows. The hot press-formed product 1A is cut in a direction perpendicular to the weld metal part 30A, trimmed so that the cross section of the weld metal part 30A remains, and embedded in resin. The embedded hot press-formed product 1A is polished, and a mapping analysis is performed using an electron probe microanalyzer (FE-EPMA) from the surface of the hot press-formed product 1A to the base steel plates 11 and 21 to measure the aluminum concentration. The measurement conditions are an acceleration voltage of 15 kV, a beam diameter of approximately 100 nm, and an irradiation time of 1000 ms. The measurement pitch is a lattice of 5 μm pitches. The measured aluminum concentration values ​​of the weld metal part 30A are averaged to determine the average concentration.

[0046] As shown in Fig. 1, the weld metal part 30A has a weld start point 31 and a weld end point 32. Generally, the weld start point and the weld end point may be cut off (trimmed) after hot press forming. In this embodiment, the weld start point 31 and the weld end point 32 remain without being cut off from the hot press-formed product 1A. Note that the weld metal part 30A does not have to have a weld start point and a weld end point. Generally, the weld is stable in the areas of the weld metal part other than the weld start point and the weld end point. The weld start point and the weld end point are the areas where welding starts and ends, and for example, craters (depressions) are formed in these areas. Note that, in order to suppress thinning of the weld metal part 30A, welding may be performed while supplying a filler wire as necessary.

[0047] As shown in Fig. 1, in this embodiment, the length of the first steel plate 10 in the transverse direction Y is constant regardless of the position in the butt direction X. The length of the first steel plate 10 in the transverse direction Y is longer than the length of the second steel plate 20 in the transverse direction Y. Note that the length of the first steel plate 10 in the transverse direction Y is the same as the length L of the weld metal part 30. w As long as it is above, it may change depending on the position in the butting direction X, and the length of the first steel plate 10 in the cross direction Y is the length L of the weld metal part 30. w If it is equal to or greater than this, it may be shorter than the maximum length of the second steel plate 20 in the cross direction Y. In the following, in the butting direction X, the side of the first steel plate 10 relative to the second steel plate 20 will be referred to as the first side X1, and the side of the second steel plate 20 relative to the first steel plate 10 will be referred to as the second side X2. The length L2 (mm) of the second steel plate 20 in the transverse direction Y varies depending on the position in the butting direction X. In other words, the length of the second steel plate 20 in the transverse direction Y is not constant depending on the position in the butting direction X, and at a predetermined position in the butting direction X, the length L2 of the second steel plate 20 in the transverse direction Y is minimum.

[0048] When viewed from a direction (thickness direction Z) perpendicular to both the butt direction X and the cross direction Y shown in Fig. 1, the distance a (mm) between the position of the second steel plate 20 having the length L2 and the weld metal portion 30 in the butt direction X is defined. As shown in Fig. 2, the distance a is the distance between the position and the weld toe 30a of the weld metal portion 30 in the butt direction X. When the position of the weld toe 30a is different between one surface and the other surface of the second steel plate 20, for example, the distance a is set to the average value of the distance a on one surface of the second steel plate 20 and the distance a on the other surface.

[0049] The shapes of the hot press-formed first steel plate 10A, second steel plate 20A, and weld metal portion 30A are the same as those of the first steel plate 10, second steel plate 20, and weld metal portion 30, respectively, before hot press forming. That is, the thickness of the first steel plate 10A is equal to the thickness T1 of the first steel plate 10. The thickness of the second steel plate 20A is equal to the thickness T2 of the second steel plate 20. The thickness of the weld metal portion 30A is equal to the thickness T w is equal to.

[0050] Here, the pair of length L2 and distance a that takes the minimum value of Equation (16) for the pair of length L2 and distance a that changes depending on the position in the butting direction X is called length L 2_min and distance a min It is stipulated that:

[0051]

number

[0052] For example, a case will be described in which the second steel plate 20 has a plurality of positions where the length L2 is at its minimum value, which are shifted in the butting direction X. When the magnitudes of the plurality of minimum values ​​of the length L2 are equal, among the plurality of positions, the pair of the length L2 and the distance a corresponding to the position P3 (see FIGS. 1 and 2) where the distance a is smallest is the pair of the length L2 and the distance a. 2_min and distance a min It is stipulated that: In addition, if the minimum value of the length L2 at the position where the distance a is large is smaller than the minimum value of the length L2 at the position where the distance a is smaller than that position, the pair of the length L2 at the position where the distance a is large and the distance a is the length L 2_min and distance a min It may also be specified as follows.

[0053] The Vickers hardness (hereinafter simply referred to as Vickers hardness) of the hot press-formed first steel plate 10A, second steel plate 20A, and weld metal part 30A based on JIS Z 2244:2009 Vickers hardness test - Test method is greater (harder) than the Vickers hardness of the first steel plate 10, second steel plate 20, and weld metal part 30 before hot press-forming, respectively. The test force used to measure the Vickers hardness is 2.94 N (Newtons).

[0054] Here, the Vickers hardness of the hot press-formed first steel plate 10A is defined as H1 (HV). The Vickers hardness of the hot press-formed second steel plate 20A is defined as H2 (HV). The Vickers hardness of the weld metal part 30A is defined as H w The criterion for determining whether the first steel plate 10A and the second steel plate 20A have been hot press-formed is when the martensite area ratio is 80% or more. To make the martensite area ratio of the hot press-formed product 1A 80% or more, for example, the following hot stamping conditions can be applied to the tailored blank 1.

[0055] First, the tailored blank 1 is heated to a temperature range of 850 to 1000°C, held at that temperature range for 0.1 to 30.0 minutes, and then quickly transferred onto a die for press forming (hot stamping). The tailored blank 1 is then pressed, and the press-formed steel sheet is cooled in the die to a temperature range of 250°C or less by heat transfer between the steel sheet and the die. The average heating rate up to the temperature range of 850 to 1000°C may be 0.1 to 200°C / s. To obtain a hot press-formed product 1A with a martensite area fraction of 80% or more, the average cooling rate in the die must be equal to or higher than the critical cooling rate at which martensitic transformation occurs. Therefore, the average cooling rate in the die may be 20 to 200°C / s. Within the temperature range of 850 to 1000°C, the temperature may be varied or constant. Furthermore, to obtain a hot press-formed product 1A with a martensite area ratio of 80% or more, the material must be transported from the heating furnace to the die and press-formed onto the die faster than the start of the ferrite-pearlite transformation and bainite transformation. The time at which the ferrite-pearlite transformation and bainite transformation occur can be determined by attaching a thermocouple to the tailored blank 1 to measure the temperature and observing the heat generated by the transformation.

[0056] The area fraction of martensite can be measured by microscopic observation of the structure of the hot-press-formed product 1A at a position not affected by welding heat. Specifically, samples are taken from five locations on the thickness-direction cross section of the hot-press-formed product 1A: 1 / 8, 3 / 8, 5 / 8, and 7 / 8 of the plate thickness from the surface. These samples are etched using a Lepera etching solution, and a 100 μm square field of view is observed at 1000x magnification using an optical microscope. The area fraction of martensite is measured, assuming that the white to reddish-brown area within the observed field of view is martensite, and the average area fraction of martensite over the 20 observed fields of view can be used as the martensite area fraction of the hot-press-formed product 1A.

[0057] For example, Vickers hardness H1, H2, H wis measured on a reference cross section that passes through the center of the weld metal part 30A in the transverse direction Y and is perpendicular to the transverse direction Y. The Vickers hardness H1 of the first steel plate 10A is determined at the center of the thickness direction Z on the reference cross section, at three locations in the centers of three equal parts obtained by dividing the entire length of the first steel plate 10A in the butt direction X. The average of the determined values ​​is defined as the Vickers hardness H1. The Vickers hardness H2 of the second steel plate 20A is measured in the same manner as the Vickers hardness H1 of the first steel plate 10A.

[0058] As shown in Figure 2, the Vickers hardness H w is measured at six positions P1 on the reference cross section. The six positions P1 are a combination of two positions in the butt direction X and three positions in the thickness direction Z, for a total of six positions. The two positions in the butt direction X are the center of the weld metal part 30A in the butt direction X, and a position closer to the steel plate (second steel plate 20A) of the steel plates 10A, 20A having a smaller product of thickness and Vickers hardness than the center of the weld metal part 30A in the butt direction X. The three positions in the thickness direction Z are each surface layer of the weld metal part 30A in the thickness direction Z and the center between each surface layer. The Vickers hardness H is calculated by averaging the values ​​measured at the six positions. w Let's say.

[0059] At this time, the first steel plate 10A and the second steel plate 20A satisfy the formula (18).

[0060]

number

[0061] That is, the product of the thickness T2 and the Vickers hardness H2 of the second steel plate 20A is smaller than the product of the thickness T1 and the Vickers hardness H1 of the first steel plate 10A. The length L 2_min and distance a min In contrast, the length L of the weld metal portion 30 in the cross direction Y w (mm) satisfies equation (20).

[0062]

number

[0063] Here, A is a constant equal to or greater than 0.9. The constant A is preferably equal to or greater than 1.0 and equal to or less than 1.5, and more preferably equal to or greater than 1.0 and equal to or less than 1.2. The constant A may be 1.0 or 1.2. If the constant A exceeds 1.5, the weld line becomes excessively long, which increases the weight and cost. Equation (20) is derived from the geometric shape of the hot press-formed product 1A (tailored blank 1). Equation (20) uses the thickness T2 of the second steel plate 20A instead of the thickness of the base steel plate 21. It is considered that the intermetallic compound layer 22 and the aluminum plating layer 23 of the second steel plate 20A do not contribute to the strength of the second steel plate 20A as compared to the base steel plate 21. However, by using the thickness T2 of the second steel plate 20A, the length L of the weld metal part 30A can be reduced. w can be evaluated conservatively.

[0064] 1 and 2, in the hot press-formed product 1A, an end of the second steel plate 20A is arranged to abut against an end of the first steel plate 10A in the butting direction X. The weld metal portion 30A joins the end of the first steel plate 10A and the end of the second steel plate 20A. The weld metal portion 30A extends in the transverse direction Y.

[0065] The hot press-formed product 1A configured as described above is used for automobile parts such as B-pillars, for example.

[0066] Next, a method for manufacturing a hot press-formed product according to this embodiment for manufacturing the hot press-formed product 1A configured as above will be described. Fig. 3 is a flowchart showing a method S10 for manufacturing a hot press-formed product. First, a tailored blank manufacturing method of this embodiment (step S11 shown in FIG. 3) is performed to manufacture a tailored blank 1. In the tailored blank manufacturing method S11, an arrangement step (step S12) is performed. In the arrangement step S12, an end of the first steel plate 10 and an end of the second steel plate 20 are arranged so as to abut against each other in the butting direction X. In the steel plates 10, 20, the intermetallic compound layers 12, 22 and aluminum plating layers 13, 23 at the ends are not removed. When the placement step S12 is completed, the process proceeds to step S13.

[0067] Next, in the welding process (step S13), an end of the first steel plate 10 and an end of the second steel plate 20 are joined by welding to form a weld metal part 30 extending in the transverse direction Y, thereby producing the tailored blank 1. Laser welding, plasma welding, etc. can be used for welding. When the welding step S13 is completed, all steps in the tailored blank manufacturing method S11 are completed, and the process moves to step S16.

[0068] Next, in the forming step (step S16), the tailored blank 1 is hot press formed to produce a hot press-formed product 1A. For example, in the forming step S16, a heating and forming step is performed in which the tailored blank 1 is heated to a predetermined temperature and formed into a desired shape, followed by a quenching step in which the tailored blank 1 is quenched. For example, the heating conditions in the heating and forming step are such that the maximum temperature reached is 850°C to 1000°C. It is more preferable that the maximum temperature reached is 900°C to 950°C. The quenching step is performed by cooling the press-forming die or by spraying water directly onto the tailored blank 1 to cool it, for example. When the forming step S16 is completed, all steps of the method S10 for manufacturing a hot press-formed product are completed, and the hot press-formed product 1A is manufactured.

[0069] As described above, in the tailored blank 1 and tailored blank manufacturing method S11 of this embodiment, by satisfying formula (18), the product of thickness and Vickers hardness, i.e., rigidity, of the second steel plate 20A in the hot press-formed product 1A is lower than that of the first steel plate 10A. Therefore, for example, when a tensile force acts in the butt direction X on the hot press-formed product 1A obtained by hot press-forming the tailored blank 1, stress is concentrated in the second steel plate 20A, making the second steel plate 20A more susceptible to fracture than the first steel plate 10A. As a result of extensive research, the inventors have found that the second steel plate 20A is more likely to fracture in a direction that forms an angle of 45° with respect to the weld metal portion 30A when viewed from a direction perpendicular to both the butt direction and the cross direction. 2_min and distance a min By satisfying the formula (20) for the pair, the length L 2_min and distance a min Therefore, in the hot press-formed product 1A, it is possible to prevent the weld metal portion 30A from breaking.

[0070] By causing the hot press-formed product 1A to fracture at position P3 of the second steel plate 20A, the fracture conditions are more stable and measures to prevent fracture are easier to take than when the hot press-formed product 1A fractures at the weld metal portion 30A. By designing the hot press-formed product 1A to break at the second steel plate 20A, the hot press-formed product 1A can be caused to break in a state where it is more elongated than when the hot press-formed product 1A breaks at the weld metal part 30A. Therefore, it is possible to increase the amount of energy that the hot press-formed product 1A can absorb before breaking.

[0071] In the hot press-formed product 1A, the constant A may be 1.0 or more and 1.5 or less. For example, when the constant A is 1.0, the length L of the weld metal portion 30A is shorter than when the constant A is 0.9. w Therefore, in the hot press-formed product 1A, fracture at the weld metal portion 30A can be more reliably prevented. Furthermore, in the hot press-formed product 1A, in the base steel sheet of the aluminum-plated steel sheet, the sum of the thicknesses of the intermetallic compound layers 12, 22 and the aluminum plating layers 13, 23 provided on at least one surface (at least one of 11a, 11b, 21a, 21b) of the surfaces of the base steel sheet may each be 10 μm or more. When the sum of the thicknesses of the intermetallic compound layer and the aluminum plating layer on at least one surface of the surfaces of the base steel sheet of the aluminum-plated steel sheet is 10 μm or more, the incorporation of aluminum into the weld metal part 30A increases, thereby improving the corrosion resistance of the weld metal part 30A of the present application.

[0072] The weld metal part 30A may have a weld start point 31 and a weld end point 32. This makes it possible to prevent the hot press-formed product 1A from breaking at the weld metal part 30A, even when the weld metal part 30A has the weld start point 31 and the weld end point 32. The aluminum concentration in the weld metal portion 30A of the hot press-formed product 1A may be 0.3 mass % or more and 2.5 mass % or less. Because the aluminum concentration in the weld metal portion of the hot press-formed product is high, the corrosion resistance of the weld metal portion 30A can be improved.

[0073] The hot press-formed product 1A may be an automobile part, and therefore the hot press-formed product 1A in which fracture at the weld metal portion 30A is suppressed can be preferably used as an automobile part.

[0074] Furthermore, in the hot press-formed product 1A and the manufacturing method S10 for the hot press-formed product of this embodiment, by satisfying formula (18), the product of thickness and Vickers hardness, i.e., rigidity, of the second steel plate 20A in the hot press-formed product 1A is lower than that of the first steel plate 10A. Therefore, for example, when a tensile force acts on the hot press-formed product 1A in the butt direction X, stress is concentrated in the second steel plate 20A, making the second steel plate 20A more susceptible to fracture than the first steel plate 10A. As a result of extensive research, the inventors have found that the second steel plate 20A is more likely to fracture in a direction that forms an angle of 45° with respect to the weld metal portion 30A when viewed from a direction perpendicular to both the butt direction X and the cross direction Y. 2_min and distance a min By satisfying the formula (20) for the pair, the length L 2_min and distance a min Therefore, in the hot press-formed product 1A, it is possible to prevent the weld metal portion 30A from breaking.

[0075] The hot press-formed product 1A (tailored blank 1) of this embodiment can have a configuration that can be modified in various ways, as will be described below. As in the hot press-formed product 2A of the first modified example shown in FIG. 4, the length L of the weld metal portion 30A in the transverse direction Y w may be equal to the length in the cross direction Y of the first steel plate 10A. In this case, the length of the second steel plate 20A in the cross direction Y is a length L w The length of the second steel plate 20A in the cross direction Y is gradually shortened from the end of the first side X1 toward the second side X2, and is equal to the length L 2_min and distance a min The length of the second steel plate 20A in the transverse direction Y gradually increases from the position P3 toward the second side X2. The length of the second steel plate 20A in the transverse direction Y at the end of the second side X2 is shorter than the length of the second steel plate 20A in the transverse direction Y at the end of the first side X1.

[0076] For example, in the hot press-formed product 2A, the Vickers hardness H2 of the second steel plate 20A is 350 HV. w is 300HV. The shape of such a hot press-formed product 2A is such that the Vickers hardness of the second steel plate 20A is H2 and the Vickers hardness of the weld metal portion 30A is H w It is used when the difference between

[0077] In the hot press-formed product 3A of the second modified example shown in FIG. 5, the length in the cross direction Y of the second steel plate 20A at the end of the second side X2 and the length L at the position P3 are different from those of the hot press-formed product 2A. 2_min are each short. For example, in the hot press-formed product 3A, the Vickers hardness H2 of the second steel plate 20A is 400 HV. w is 200HV. The shape of such a hot press-formed product 3A is such that the Vickers hardness of the second steel plate 20A is H2 and the Vickers hardness of the weld metal portion 30A is H w It is used when the difference between In this case, the length L of the second steel plate 20A 2_min In order to increase the length, a hot press-formed product 4A of a third modified example shown in FIG. 6 is constructed.

[0078] In the hot press-formed product 4A, the portion of the second side X2 of the first steel plate 10A gradually becomes longer in the transverse direction Y as it approaches the second side X2. w are the Vickers hardnesses H2 and H3 of the second steel plate 20A and the weld metal portion 30A of the hot press-formed product 3A of the second modified example. w are identical to By configuring in this way, the length L of the weld metal portion 30A w can be made longer.

[0079] As in the hot press-formed product 5A of a fourth modified example shown in Fig. 7 , the length in the cross direction Y of the end portion on the second side X2 of the first steel plate 10A may be longer than the length in the cross direction Y of the other portion of the first steel plate 10A. In the fourth modified example, the length in the cross direction Y of the end portion on the first side X1 of the second steel plate 20A is longer than the length in the cross direction Y of the other portion of the second steel plate 20A. In the hot press-formed product 5A of the fourth modification, the length L of the weld metal portion 30A w can be made longer. The hot press-formed products 2A, 3A, 4A, and 5A of the modified examples configured as above can achieve the same effects as the hot press-formed product 1A of the present embodiment.

[0080] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and configuration changes, combinations, deletions, etc. are also included within the scope that does not deviate from the gist of the present invention.

[0081] (Example) EXAMPLES The present invention will be described in more detail below by specifically showing examples and comparative examples, but the present invention is not limited to the following examples. The hot press-formed products of Samples Nos. 1 to 6, whose specifications are shown in Table 1, were subjected to tensile tests.

[0082] [Table 1]

[0083] For example, the hot press-formed product of Sample No. 1 will be described. The first steel plate 10A has a thickness T1 of 1.6 mm and a Vickers hardness H1 of 500 HV. The second steel plate 20A has a thickness T2 of 1.2 mm and a Vickers hardness H2 of 400 HV. 2_min is 300mm. In the weld metal portion 30A, the thickness T w is 1.2 mm, and the Vickers hardness H w is 300HV and the length L w is 300mm. Distance a min is 0 mm. Constant A is set to 0.9. In this case, the value of the right side of equation (20) is 360 mm. In this case, (L w =300<360), which does not satisfy formula (20). Sample No. 1 is a comparative example. When a tensile test was carried out on the hot press-formed product of Sample No. 1, it broke at weld metal part 30 A. The breaking load in the tensile test was 305 kN (kilonewtons).

[0084] For example, hot press-formed products are used in automobile B-pillars. When a car is hit, a bending moment may act on the B-pillar, causing a tensile force to act on the outside of the B-pillar. If the breaking load in the tensile test is large, when the hot-pressed product is used in a B-pillar, it will be able to absorb energy more easily during a collision.

[0085] In the hot press-formed product of sample No. 2, the length L of the weld metal part 30A w is 400 mm. The value of the right side of equation (20) is 360 mm. In this case, (L w =400≧360), which satisfies the formula (20). Sample No. 2 is an example of the present invention. When a tensile test was performed on the hot press-formed product of Sample No. 2, it broke at position P3 of the second steel plate 20A. The breaking load in the tensile test was 365 kN. In Samples Nos. 1 to 6, both the first steel plate 10A and the second steel plate 20A were aluminum-plated steel plates. [Explanation of symbols]

[0086] 1. Tailored Blank 1A, 2A, 3A, 4A, 5A hot press formed products 10,10A 1st steel plate 11,21 Base steel plate 11a,11b,21a,21b surface 12,22 Intermetallic compound layer 13,23 Aluminum plating layer 20,20A 2nd steel plate 30,30A Welded metal parts 31 Weld start point 32 Welding End S10 Manufacturing method for hot press formed products S11 Tailored Blank Manufacturing Method S12 Placement process S13 Welding process S16 Molding process X butting direction Y cross direction Z thickness direction

Claims

1. A first steel plate; A second steel plate arranged so that an end portion thereof abuts against an end portion of the first steel plate in a butting direction; a weld metal portion that joins the end portion of the first steel plate and the end portion of the second steel plate and extends in a cross direction that crosses the butt direction; A tailored blank comprising: At least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, (1) formula is satisfied, The length L of the second steel plate in the cross direction ２ (mm) varies depending on the position in the butting direction, The length L when viewed from a direction perpendicular to both the butt direction and the cross direction. ２ The distance in the butting direction between the position of the second steel plate and the weld metal portion at which the above-mentioned condition is met is defined as a (mm), The length L which changes depending on the position in the butting direction ２ and the length L that takes the minimum value of equation (2) for the set of the distance a. ２ and the set of distances a are divided into the length L ２＿ｍｉｎ and the distance a ｍｉｎ When it is specified that The length L ２＿ｍｉｎ and the distance a ｍｉｎ In contrast, the length L of the weld metal portion in the cross direction ｗ (mm) satisfies formula (3), A tailored blank that does not include a case where the distance a min is zero. However, T １ : Thickness of the first steel plate (mm), H １ : Vickers hardness of the first steel plate in the hot press-formed product obtained by hot press-forming the tailored blank, T ２ : Thickness of the second steel plate (mm), H ２ : Vickers hardness of the second steel plate in the hot press-formed product, T ｗ : the thickness of the weld metal part (the thickness T １ and the thickness T ２ the thinner thickness of (mm), H ｗ : Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more. [Equation 1]

2. The tailored blank according to claim 1, wherein the constant A is equal to or greater than 1.0 and equal to or less than 1.

5.

3. The aluminum-plated steel sheet has an intermetallic compound layer and an aluminum plating layer provided on each surface of the base steel sheet in a thickness direction thereof, in this order from the base steel sheet side, 3. The tailored blank according to claim 1, wherein the sum of the thicknesses of the intermetallic compound layer and the aluminum plating layer provided on at least one of the surfaces of the base steel sheet is 10 μm or more.

4. The tailored blank according to claim 1 , wherein the weld metal portion has a weld start end and a weld end.

5. 5. The tailored blank according to claim 1, wherein the concentration of aluminum contained in the weld metal portion of the hot press-formed product is 0.3 mass% or more and 2.5 mass% or less.

6. The tailored blank according to claim 1 , wherein the hot press-formed product is an automobile part.

7. A first steel plate; A second steel plate arranged so that an end portion thereof abuts against an end portion of the first steel plate in a butting direction; a weld metal portion that joins the end portion of the first steel plate and the end portion of the second steel plate and extends in a cross direction that crosses the butt direction; A hot press-formed product comprising: At least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, (4) formula is satisfied, The length L of the second steel plate in the cross direction ２ (mm) varies depending on the position in the butting direction, The length L when viewed from a direction perpendicular to both the butt direction and the cross direction. ２ The distance in the butting direction between the position of the second steel plate and the weld metal portion at which the above-mentioned condition is met is defined as a (mm), The length L which changes depending on the position in the butting direction ２ and the length L that takes the minimum value of equation (5) for the set of the distance a. ２ and the set of distances a are divided into the length L ２＿ｍｉｎ and the distance a ｍｉｎ When it is specified that The length L ２＿ｍｉｎ and the distance a ｍｉｎ In contrast, the length L of the weld metal portion in the cross direction ｗ (mm) satisfies formula (6), A hot press-formed product, which does not include a case where the distance a min is zero. However, T １ : Thickness of the first steel plate (mm), H １ : Vickers hardness of the first steel plate, T ２ : Thickness of the second steel plate (mm), H ２ : Vickers hardness of the second steel plate, T ｗ : the thickness of the weld metal part (the thickness T １ and the thickness T ２ the thinner thickness of (mm), H ｗ : Vickers hardness of the weld metal part, A: a constant of 0.9 or more. [Equation 2]

8. an arrangement step of arranging an end of the first steel plate and an end of the second steel plate so that they butt against each other in a butting direction; a welding process of joining the end of the first steel plate and the end of the second steel plate by welding to form a weld metal part extending in a cross direction that crosses the butt direction; A method for manufacturing a tailored blank, comprising the steps of: At least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, (7) formula is satisfied, The length L of the second steel plate in the cross direction ２ (mm) varies depending on the position in the butting direction, The length L when viewed from a direction perpendicular to both the butt direction and the cross direction. ２ The distance in the butting direction between the position of the second steel plate and the weld metal portion at which the above-mentioned condition is met is defined as a (mm), The length L which changes depending on the position in the butting direction ２ and the length L that takes the minimum value of equation (8) for the set of the distance a. ２ and the set of distances a are divided into the length L ２＿ｍｉｎ and the distance a ｍｉｎ When it is specified that The length L ２＿ｍｉｎ and the distance a ｍｉｎ In contrast, the length L of the weld metal portion in the cross direction ｗ (mm) satisfies formula (9), A method for manufacturing a tailored blank that does not include a case where the distance a min is zero. However, T １ : Thickness of the first steel plate (mm), H １ : Vickers hardness of the first steel plate in the hot press-formed product obtained by hot press-forming the tailored blank, T ２ : Thickness of the second steel plate (mm), H ２ : Vickers hardness of the second steel plate in the hot press-formed product, T ｗ : the thickness of the weld metal part (the thickness T １ and the thickness T ２ the thinner thickness of (mm), H ｗ : Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more. [Equation 3]

9. The method for manufacturing a tailored blank according to claim 8, wherein the constant A is equal to or greater than 1.0 and equal to or less than 1.

5.

10. The aluminum-plated steel sheet has an intermetallic compound layer and an aluminum plating layer provided on each surface of the base steel sheet in a thickness direction thereof, in this order from the base steel sheet side, 10. The method for manufacturing a tailored blank according to claim 8 or 9, wherein the sum of the thicknesses of the intermetallic compound layer and the aluminum plating layer provided on at least one of the surfaces of the base steel sheet is 10 μm or more.

11. The method for manufacturing a tailored blank according to claim 8 , wherein the weld metal portion has a weld start end and a weld end end.

12. 12. The method for manufacturing a tailored blank according to claim 8, wherein the concentration of aluminum contained in the weld metal portion of the hot press-formed product is 0.3 mass% or more and 2.5 mass% or less.

13. The method for manufacturing a tailored blank according to any one of claims 8 to 12, wherein the hot press-formed product is an automobile part.

14. an arrangement step of arranging an end of the first steel plate and an end of the second steel plate so that they butt against each other in a butting direction; a welding process in which the end portion of the first steel plate and the end portion of the second steel plate are joined by welding to form a weld metal part extending in a transverse direction intersecting the butt direction, thereby manufacturing a tailored blank; a forming step of hot press forming the tailored blank; A method for manufacturing a hot press-formed product, comprising the steps of: At least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, (10) is satisfied, The length L of the second steel plate in the cross direction ２ (mm) varies depending on the position in the butting direction, The length L when viewed from a direction perpendicular to both the butt direction and the cross direction. ２ The distance in the butting direction between the position of the second steel plate and the weld metal portion at which the above-mentioned condition is met is defined as a (mm), The length L which changes depending on the position in the butting direction ２ and the length L that takes the minimum value of equation (11) for the set of the distance a. ２ and the set of distances a are divided into the length L ２＿ｍｉｎ and the distance a ｍｉｎ When it is specified that The length L ２＿ｍｉｎ and the distance a ｍｉｎ In contrast, the length L of the weld metal portion in the cross direction ｗ (mm) satisfies equation (12), The method for manufacturing a hot press-formed product does not include a case where the distance a min is zero. However, T １ : Thickness of the first steel plate (mm), H １ : Vickers hardness of the first steel plate in the hot press-formed product, T ２ : Thickness of the second steel plate (mm), H ２ : Vickers hardness of the second steel plate in the hot press-formed product, T ｗ : the thickness of the weld metal part (the thickness T １ and the thickness T ２ the thinner thickness of (mm), H ｗ : Vickers hardness of the weld metal portion in the hot press formed product, A: a constant of 0.9 or more. [Equation 4]

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