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

Abstract

To provide a hot press molded product which suppresses breakage at a weld metal section and ensures dimensional accuracy at a part where ends of two members are butted together, at least one of the members being an aluminum plated member.SOLUTION: A hot press molded product 1A includes: a first member 10A; a second member 30A whose end is arranged so as to butt against an end of the first member; and a welded metal section 50A which joins the end of the first member and the end of the second member. At least one of the first member and the second member is an aluminum plated member. A longitudinal direction X of hot press molded product is defined in a neighborhood part of the weld metal section in the time when the hot press molded product is developed in a flat state, and when viewed in a thickness direction Z of the second member after the hot press molded product is developed in a flat shape, and, the weld metal section is curved toward either side along the longitudinal direction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to hot press-formed articles, tailored blanks, methods for manufacturing hot press-formed articles, and methods for manufacturing tailored blanks. [Background technology]

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

[0003] The first countermeasure is to remove the aluminum plating layer from the aluminum-plated steel sheets before welding them together, thereby suppressing the inclusion of aluminum in the weld metal. The second solution is to supply austenitic welding material during welding.

[0004] Furthermore, the edges of the aluminum-plated steel sheets are formed in a straight line when viewed from above, and tailored blanks are manufactured by welding the edges of the aluminum-plated steel sheets together in a butt joint. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5237263 [Patent Document 2] International Publication No. 2013 / 045497 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the first countermeasure requires a process to remove the aluminum plating layer. In the second countermeasure, there is a risk of aluminum concentration at the weld edge (weld toe), where stirring of the molten weld metal is less likely. Also, when joining steel plates together, if the dimensional accuracy of the butt joint is low, a gap may form at the joint, causing thinning of the weld metal and potentially reducing its strength.

[0007] The present invention has been made in view of these problems, and aims to provide a hot press-formed product, a tailored blank, a method for manufacturing a hot press-formed product, and a method for manufacturing a tailored blank, which can suppress fracture at the weld metal portion and ensure dimensional accuracy at the point where the ends of two steel plates are joined together, with at least one of the steel plates (members) being an aluminum-plated steel plate (aluminum-plated member). [Means for solving the problem]

[0008] To solve the aforementioned problems, this invention proposes the following means. (1) A first aspect of the present invention is a hot press-formed product comprising: a first member; a second member whose end abuts against the end of the first member; and a welded metal portion that joins the end of the first member and the end of the second member, wherein at least one of the first member and the second member is an aluminum-plated member, and the longitudinal direction of the hot press-formed product is defined for the portion near the welded metal portion when the hot press-formed product is unfolded into a planar shape, and when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is curved in a convex shape toward either side along the longitudinal direction.

[0009] (11) A second aspect of the present invention is a method for manufacturing a hot press-formed product, comprising: an arrangement step of arranging the end of a first steel plate and the end of a second steel plate so as to abut each other; 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 portion and manufacture a tailored blank; and a forming step of hot press-forming the tailored blank to obtain a first member from the first steel plate and a second member from the second steel plate, wherein at least one of the first member and the second member is an aluminum-plated member, and the longitudinal direction of the hot press-formed product in the vicinity of the weld metal portion when the hot press-formed product is unfolded into a planar shape is defined, and when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the weld metal portion is curved in a convex shape toward either side along the longitudinal direction.

[0010] In these inventions, when a hot-pressed product is unfolded into a planar shape and viewed in the thickness direction, the weld metal portion is curved in a convex shape toward one side along the longitudinal direction. Here, a convex curve means that the entire weld metal portion is convex and does not include any concave parts. However, it may include some straight lines as long as it does not include parts where straight lines intersect. For this reason, in the tailored blank before hot-press forming of the hot-pressed product, the ends of the first and second steel plates that are butted together are such that one end is curved in a convex shape toward one side along the longitudinal direction, and the other end is curved in a concave shape toward one side along the longitudinal direction. Consequently, for example, even if the end of the second steel plate moves so as to swing around the butted ends on the unfolded plane relative to the ends of the first steel plate that are butted together, the distance between the ends does not change as easily as when the ends are straight. Therefore, dimensional accuracy can be ensured at the joint where the ends of the steel plates (components) are butted together. Furthermore, because the weld metal is curved, when a tensile force is applied to the hot-pressed product in the longitudinal direction, the external force acting in the direction of opening the weld metal is suppressed. Therefore, fracture of the hot-pressed product at the weld metal can be prevented.

[0011] (2) In the hot press-formed product described in (1) above, the hot press-formed product has the weld metal portion, at least a part of the first member connected to the weld metal portion, and at least a part of the second member connected to the weld metal portion, and has a shaft portion extending in a predetermined direction, the longitudinal direction may correspond to the predetermined direction. (12) In the method for manufacturing a hot press-formed product described in (11) above, the hot press-formed product has the weld metal portion, at least a part of the first member connected to the weld metal portion, and at least a part of the second member connected to the weld metal portion, and has a shaft portion extending in a predetermined direction, the longitudinal direction may correspond to the predetermined direction. These inventions allow the hot-pressed product to have a shaft portion extending in a predetermined direction, and for example, when a tensile force is applied in the predetermined direction in which the shaft portion extends, it is possible to suppress fracture of the hot-pressed product at the weld metal portion.

[0012] (3) The hot press-formed product described in (1) or (2) above may satisfy formula (1). T w H w <T2H2<T1H1··(1) However, T1: thickness of the first member (mm), H1: Vickers hardness of the first member (HV), T2: thickness of the second member (mm), H2: Vickers hardness of the second member (HV), T w : The thickness of the welded metal portion (the thinner of the thickness T1 and the thickness T2) (mm), H w : This is the Vickers hardness (HV) of the welded metal portion. (13) The method for manufacturing a hot press-formed product described in (11) or (12) above may satisfy formula (2). T w H w <T2H2<T1H1··(2) However, T1: thickness of the first member (mm), H1: Vickers hardness of the first member of the hot-pressed product (HV), T2: thickness of the second member (mm), H2: Vickers hardness of the second member of the hot-pressed product (HV), Tw : Thickness of the welded metal part (the thinner one of the thickness T1 and the thickness T2) (mm), H w : It is the Vickers hardness (HV) of the welded metal part of the hot press-formed product. Note that Equation (2) is the same as Equation (1). In these inventions, in the hot press-formed product, the product of the thickness and the Vickers hardness, that is, the rigidity, increases in the order of the welded metal part, the second member, and the first member. Generally, in a hot press-formed product including an aluminum-plated member, the rigidity of the welded metal part is smaller than the rigidity of the member. If the left inequality of Equation (1) is satisfied and the rigidity of the welded metal part is smaller than the rigidity of the member, stress is more likely to concentrate on the welded metal part. However, when the hot press-formed product is developed in a planar shape and viewed in the thickness direction, since the welded metal part is curved, when a tensile force acts in the longitudinal direction on the hot press-formed product, the external force acting in the direction in which the welded metal part opens is suppressed. Therefore, since the effects of the present invention can be significantly exhibited, it is preferable that the rigidity of the welded metal part is smaller than the rigidity of the member. Also, by satisfying the right inequality of Equation (1) and making the rigidity of the second member smaller than that of the first member, stress can be concentrated on the second member among the first member and the second member, and it becomes easier to break at the second member. Thereby, the countermeasure against breakage in the hot press-formed product can be concentrated on the second member.

[0013] (4) In the hot press-formed product according to any one of (1) to (3) above, the first member has a first part first piece and a first part second piece connected via a first part first ridge line to the first part first piece. The second member has a second part first piece joined to the first part first piece via the welded metal part, a second part first ridge line joined to the first part first ridge line via the welded metal part, and a second part second piece connected via the second part first piece and the second part first ridge line and joined to the first part second piece via the welded metal part. When the hot press-formed product is flattened and viewed in the thickness direction of the second member, at the first intersection, which is the intersection of the outer edge of the hot press-formed product on the side opposite to the second part first ridge line of the second part first piece and the welded metal part, of the two angles formed by the portion of the welded metal part continuous with the first intersection and the longitudinal direction passing through the first intersection, the angle of the angle with the minimum value is 15° or more and 60° or less. At the second intersection, which is the intersection of the outer edge of the hot press-formed product on the side opposite to the second part first ridge line of the second part second piece and the welded metal part, when the second part second piece is used as a reference, of the two angles formed by the portion of the welded metal part continuous with the second intersection and the longitudinal direction passing through the second intersection, the angle of the angle with the minimum value is 15° or more and 60° or less. At the third intersection, which is the intersection of the second part first ridge line and the welded metal part, of the four angles formed by the portion of the welded metal part continuous with the third intersection and the longitudinal direction passing through the third intersection, the angle of the angle with the minimum value may be 30° or more and 75° or less.

[0014] (14) In the method for manufacturing a hot press-formed product described in any one of (11) to (13) above, the first member has a first piece of the first part and a second piece of the first part connected to the first piece of the first part via the first ridge of the first part, and the second member has a first piece of the second part joined to the first piece of the first part via the weld metal portion, a first ridge of the second part joined to the first ridge of the first part via the weld metal portion, and a second piece of the second part connected to the first piece of the second part via the first ridge of the second part and joined to the second piece of the first part via the weld metal portion, and when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second aluminum-plated member, the first intersection point is the intersection point between the outer edge of the hot press-formed product on the opposite side of the first ridge of the second part of the first piece of the second part and the weld metal portion, with the first piece of the second part as the reference, The hot-pressed product may be manufactured such that, of the two angles formed by the portion of the welded metal part connected to the first intersection and the longitudinal direction passing through the first intersection, the angle with the smallest angle is 15° or more and 60° or less; at the second intersection, which is the intersection of the welded metal part and the outer edge of the hot-pressed product on the opposite side of the second ridge of the second piece of the second part, with the second piece of the second part as the reference, the angle with the smallest angle formed by the portion of the welded metal part connected to the second intersection and the longitudinal direction passing through the second intersection is 15° or more and 60° or less; and at the third intersection, which is the intersection of the first ridge of the second part and the welded metal part, the angle with the smallest angle formed by the four angles formed by the portion of the welded metal part connected to the third intersection and the longitudinal direction passing through the third intersection is 30° or more and 75° or less.

[0015] In these inventions, the inventors, after diligent study, have found the following: For example, when a tensile force is applied to a hot-pressed product in the longitudinal direction, crack initiation points are likely to occur in the portion connected to the first intersection of the weld metal, the portion connected to the second intersection of the weld metal, and the portion connected to the third intersection of the weld metal. Therefore, by setting the angle as described above, even if a first ridge is formed on the hot-pressed product, it is possible to further suppress fracture of the hot-pressed product at the weld metal portion due to the tensile force applied to each of the aforementioned portions.

[0016] (5) In the hot press-formed product described in (4) above, the first member has a third piece of the first part which is connected to the first piece of the first part via the first ridge of the first part and to the second piece of the first part via the second ridge of the first part, and the second member has a second ridge of the second part which is joined to the second ridge of the first part via the weld metal portion, and a third piece of the second part which is connected to the first piece of the second part via the first ridge of the second part and to the second piece of the second part via the second ridge of the second part and to the third piece of the first part via the weld metal portion. (15) In the method for manufacturing a hot press-formed product described in (14) above, the first member of the hot press-formed product has a third piece of the first part which is connected to the first piece of the first part via the first ridge of the first part and to the second piece of the first part via the second ridge of the first part, and the second member of the hot press-formed product may have a second ridge of the second part which is joined to the second ridge of the first part via the weld metal portion, and a third piece of the second part which is connected to the first piece of the second part via the first ridge of the second part and to the second piece of the second part via the second ridge of the second part. In these inventions, both members can be constructed from three pieces connected via ridges.

[0017] (6) In the hot press-formed product described in any one of (1) to (5) above, when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the weld metal portion may be in the shape of a circular arc or an elliptical arc. (16) In the method for manufacturing a hot press-formed product described in any one of (11) to (15) above, the hot press-formed product may be manufactured such that when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the weld metal portion is in the shape of a circular arc or an elliptical arc. In these inventions, when a hot-pressed product is unfolded into a planar shape and viewed in the thickness direction, the weld metal portion becomes a gentle curve, which allows the stress on the weld metal portion to be distributed. Therefore, fracture of the hot-pressed product at the weld metal portion can be further suppressed.

[0018] (7) In the hot press-formed product described in (6) above, when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the weld metal portion is arc-shaped, and the ratio of the radius of the weld metal portion to the distance between both ends of the weld metal portion of the hot press-formed product may be 0.52 or more and 2.88 or less. (17) In the method for manufacturing a hot press-formed product described in (16) above, when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the weld metal portion is arc-shaped, and the hot press-formed product may be manufactured such that the ratio of the radius of the weld metal portion to the distance between both ends of the weld metal portion of the hot press-formed product is 0.52 or more and 2.88 or less. These inventions make it possible to form the weld metal portion into an arc shape while maintaining the angle at a predetermined value. Therefore, dimensional accuracy at the butt joint can be further improved, and fracture of the hot-pressed product at the weld metal portion can be further suppressed.

[0019] (8) In the hot press-formed product described in any one of (1) to (7) above, the concentration of aluminum contained in the weld metal portion may be 0.3% by mass or more and 2.5% by mass or less. (18) In the method for manufacturing a hot press-formed product described in any one of (11) to (17) above, the concentration of aluminum contained in the weld metal portion after hot press forming may be 0.3% by mass or more and 2.5% by mass or less. In these inventions, the high aluminum concentration in the weld metal portion of the hot-pressed product improves the corrosion resistance of the weld metal portion.

[0020] (9) The hot press-formed product described in any one of (1) to (8) above may be an automobile part. (19) In the method for manufacturing a hot press-formed product described in any one of (11) to (18) above, the hot press-formed product may be a part for an automobile. These inventions suppress fracture at the welded metal portion and ensure dimensional accuracy at the point where the ends of two steel plates, at least one of which is an aluminum-plated steel plate, are joined together. Hot-pressed products can be preferably used as automotive parts.

[0021] (10) A third aspect of the present invention is a tailored blank comprising a first steel plate, a second steel plate whose end abuts against the end of the first steel plate, and a weld metal portion that joins the end of the first steel plate and the end of the second steel plate, wherein at least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, and when the longitudinal direction of the portion of the tailored blank near the weld metal portion is defined, the weld metal portion is curved in a convex shape toward either side along the longitudinal direction when viewed in the thickness direction of the second member.

[0022] (20) A fourth aspect of the present invention is a method for manufacturing a tailored blank, comprising: an arrangement step of arranging the end of a first steel plate and the end of a second steel plate so as to abut; 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 portion, wherein at least one of the first steel plate and the second steel plate is an aluminum-plated steel plate, and when the longitudinal direction of the portion of the tailored blank near the weld metal portion is defined, the weld metal portion is curved in a convex shape toward either side along the longitudinal direction when viewed in the thickness direction of the second member.

[0023] In these inventions, when the tailored blank is viewed in the thickness direction, the weld metal portion is curved in a convex shape toward one side along the longitudinal direction. Therefore, in the tailored blank, the ends of the first and second steel plates that are butted together are such that one end is curved in a convex shape toward one side along the longitudinal direction, and the other end is curved in a concave shape toward one side along the longitudinal direction. Consequently, for example, even if the end of the second steel plate moves so as to swing around the butted ends relative to the ends of the first steel plate, the distance between the ends does not change as easily as when the ends are straight. Therefore, dimensional accuracy can be ensured at the joint where the ends of the steel plates are butted together. Furthermore, because the weld metal is curved, when a tensile force is applied to the hot-pressed product in the longitudinal direction, the external force acting in the direction of opening the weld metal is suppressed. Therefore, fracture of the hot-pressed product at the weld metal can be prevented. [Effects of the Invention]

[0024] The hot-pressed product, tailored blank, method for manufacturing the hot-pressed product, and method for manufacturing the tailored blank of the present invention suppress fracture at the weld metal portion and ensure dimensional accuracy at the point where the ends of the steel plates (members) are joined together. [Brief explanation of the drawing]

[0025] [Figure 1] This is a plan view of a tailored blank according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view along the cutting line A1-A1 in Figure 1. [Figure 3] This is a plan view of a hot-pressed part according to one embodiment of the present invention. [Figure 4] This is a view taken in the direction of arrow B1 in Figure 3. [Figure 5] This figure shows the shape of the hot-pressed product when it is unfolded into a flat surface. [Figure 6] This is a flowchart showing a method for manufacturing a hot press-formed product according to one embodiment of the present invention. [Figure 7] This diagram illustrates the arrangement process in the manufacturing method of the hot-pressed product. [Figure 8] This figure shows the shape of Sample No. 1 when it is unfolded into a flat surface. [Figure 9] This figure shows the shape of Sample No. 2 when it is unfolded into a flat surface. [Figure 10] This figure shows the shape of Sample No. 3 when it is unfolded into a flat surface. [Modes for carrying out the invention]

[0026] Hereinafter, an embodiment of the tailored blank and hot-pressed product according to the present invention will be described with reference to Figures 1 to 10. As shown in Figures 1 and 2, the tailored blank (butt-jointed steel plate) 1 of this embodiment comprises a first steel plate 10, a second steel plate 30, and a weld metal portion 50. The first steel plate 10 and the second steel plate 30 are each formed in a flat plate shape. At least one of the first steel plate and the second steel plate is an aluminum-plated steel plate. The end of the second steel plate 30 is positioned to abut against the end of the first steel plate 10. The welded metal portion 50 joins the end of the first steel plate 10 to the end of the second steel plate 30.

[0027] Figures 3 and 4 show a hot-pressed product 1A obtained by hot-pressing a tailored blank 1. The hot-pressed product 1A comprises a first member 10A, a second member 30A, and a welded metal portion 50A. At least one of the first member and the second member is an aluminum-plated member. The aluminum-plated member is obtained by hot-pressing an aluminum-plated steel sheet. The criterion for determining whether an aluminum-plated component has been hot-press-formed is when the martensite area ratio is 80% or more. To achieve a martensite area ratio of 80% or more in a hot-press-formed product, for example, the following hot stamping conditions can be applied to a tailored blank.

[0028] First, the tailored blank is heated to a temperature range of 850-1000°C and held at this temperature range for 0.1-30.0 minutes. After that, it is quickly transferred to a mold and press-formed (hot stamped). Subsequently, the tailored blank is pressurized, and the press-formed steel sheet is cooled to a temperature range of 250°C or lower within the mold by heat transfer between the steel sheet and the mold. The average heating rate to the 850-1000°C temperature range should be 0.1-200°C / s. The average cooling rate within the mold must be above the critical cooling rate at which martensitic transformation occurs in order to obtain a hot-press-formed product with a martensitic area ratio of 80% or more. Therefore, the average cooling rate within the mold should be 20-200°C / s. Within the 850-1000°C temperature range, the temperature may be varied or kept constant. Furthermore, in order to obtain a hot-pressed product with a martensite area ratio of 80% or more, the transport time from the heating furnace to the mold must be faster than the start of the ferrite-pearlite transformation and bainite transformation, and the product must be transported to the mold and press-formed. The time at which the ferrite-pearlite transformation and bainite transformation occur can be investigated by attaching a thermocouple to the tailored blank, measuring the temperature, and observing the heat generated during the transformation.

[0029] The area ratio of martensite can be determined by microscopic observation of the microstructure in a location unaffected by welding heat in a hot-pressed product. Specifically, samples are taken from five locations on the thickness-direction cross-section of the hot-pressed product, at positions 1 / 8, 3 / 8, 5 / 8, and 7 / 8 of the plate thickness from the surface. These samples are etched using a Repera etching solution, and a 100 μm square field of view is observed at 1000x magnification using an optical microscope. Within the observed field of view, areas appearing white to reddish-brown are identified as martensite, and the area ratio of martensite is measured. The average of the area ratios of martensite in the 20 observed fields of view can be used as the martensite area ratio of the hot-pressed product. The first member 10A is obtained from the first steel plate 10 by hot press forming. Similarly, the second member 30A and the welded metal part 50A are obtained from the second steel plate 30 and the welded metal part 50, respectively, by hot press forming. The end of the second member 30A is positioned to abut against the end of the first member 10A. The welded metal portion 50A joins the end of the first member 10A to the end of the second member 30A.

[0030] The hot-pressed product 1A has a welded metal portion 50A, a first member 10A connected to the welded metal portion 50A, and a second member 30A connected to the welded metal portion 50A, and is equipped with a shaft portion 1B extending in a predetermined direction U. Let us describe the case where the second member 30A has an extension shape 30B that extends in a direction intersecting a predetermined direction U from the end of the second member 30A opposite to the welded metal portion 50A. Note that the extension shape 30B may be an extension of a part of the second member, or it may be a separate member connected to the second member. When defining the shaft portion 1B, the shaft portion 1B extending in the predetermined direction U is determined by the welded metal portion 50A, the first member 10A, and the second member 30A, without considering the extension shape 30B of the second member 30A. In other words, the shaft portion is recognized as a member that has a welded metal portion, at least a part of a first member connected to the welded metal portion, and at least a part of a second member connected to the welded metal portion, and extends in a predetermined direction.

[0031] In the tailored blank 1 shown in Figure 1, the extension shape 30C corresponding to the extension shape 30B of the hot press-formed product 1A is not considered. In Figure 1, the longitudinal direction of the hot-pressed product 1A in the vicinity of the weld metal portion 50 is defined as the longitudinal direction X. The vicinity of the weld metal portion 50, as used here, refers to, for example, the area 20 times the width of the weld metal portion 50, centered on the widthwise center of the tailored blank 1 (hot-pressed product 1A) when viewed from above. The longitudinal direction X corresponds to the predetermined direction U (it is parallel).

[0032] Below, we will first describe the composition of the first steel plate 10 and the second steel plate 30 of the tailored blank 1.

[0033] <Aluminum-plated steel sheet> At least one of the first steel sheet 10 and the second steel sheet 30 is an aluminum-plated steel sheet. Figure 2 shows an example where both the first steel sheet 10 and the second steel sheet 30 are aluminum-plated steel sheets. As shown in Figure 2, in the first steel sheet 10, an intermetallic compound layer 12 and an aluminum plating layer 13 are provided on each surface 11a and 11b of the base steel sheet 11 in the thickness direction Z, starting from the base steel sheet 11 side. Figure 1 is a plan view of the tailored blank 1 as seen in the thickness direction Z. As shown in Figure 2, surface 11a is the surface facing the first side in the thickness direction Z of the base steel sheet 11. Surface 11b is the surface facing the second side opposite to the first side in the thickness direction Z of the base steel sheet 11. On surface 11a of the base steel sheet 11, an intermetallic compound layer 12 and an aluminum plating layer 13 are provided in order from the base steel sheet 11 side. On surface 11b of the base steel sheet 11, an intermetallic compound layer 12 and an aluminum plating layer 13 are provided in order from the base steel sheet 11 side.

[0034] The second steel sheet 30 is constructed in the same manner as the first steel sheet 10. Specifically, in the second steel sheet 30, an intermetallic compound layer 32 and an aluminum plating layer 33 are provided on each surface 31a and 31b of the base steel sheet 31 in the thickness direction Z, starting from the base steel sheet 31 side. The thickness direction of the base steel sheet 31 of the second steel sheet 30 is aligned with the thickness direction Z of the base steel sheet 11 of the first steel sheet 10.

[0035] Hot-pressed product 1A is obtained by hot-pressing a tailored blank 1. Hereinafter, the hot-press-formed first steel plate 10, second steel plate 30, and welded metal portion 50 will be referred to as the first member 10A, the second member 30A, and the welded metal portion 50A. The hot-press-formed product 1A comprises the first member 10A, the second member 30A, and the welded metal portion 50A.

[0036] <Base material steel plate> The base steel sheet is the steel sheet before the aluminum plating layer is applied. The base steel sheet can be any sheet 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 can be any thickness appropriate for the purpose and is not particularly limited. For example, the thickness of the base steel sheet, as the total thickness of the steel sheet after the aluminum plating layer is applied, can be 0.8 mm to 4.0 mm, or further, 1.0 mm to 3.0 mm.

[0037] As an example of a base steel sheet, it is preferable to use 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.).

[0038] Examples of preferred chemical compositions for the base steel sheet include the following: 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: It has a chemical composition consisting of 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 remainder being Fe and impurities. In the following, "%" indicating the content of components (elements) means "mass%". Numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0039] <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 plating method, in which the base steel sheet is immersed in a molten metal bath mainly containing aluminum to form the aluminum plating layer.

[0040] Here, the aluminum 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, Si, etc.), and may contain impurities that are introduced during the manufacturing process. Specifically, the aluminum plating layer may have a chemical composition consisting of 5% to 12% by mass of Si (silicon), with the remainder being aluminum and impurities. Alternatively, it may have a chemical composition consisting of 5% to 12% by mass of Si (silicon) and 2% to 4% by mass of Fe (iron), with the remainder being aluminum and impurities. By incorporating Si within the above range, the decrease in processability and corrosion resistance can be suppressed. Furthermore, the thickness of the intermetallic compound layer can be reduced.

[0041] The thickness of the aluminum plating layer is not particularly limited. For example, the average thickness is often in the range of 8 μm (micrometers) to 35 μm, and preferably in the range of 15 μm to 30 μm. Note that the thickness of the aluminum plating layer represents the average thickness.

[0042] The aluminum plating layer prevents corrosion of steel sheets (improves corrosion resistance). Furthermore, when steel sheets are processed by hot press forming, the aluminum plating layer prevents the formation of scale (iron compounds) due to surface oxidation, even when heated to high temperatures. Additionally, the aluminum plating layer has higher boiling and melting points than plating with organic materials or other metallic materials (e.g., zinc-based materials). Therefore, when forming steel sheets by hot press forming, the coating does not evaporate, resulting in a high level of surface protection.

[0043] During heating in hot dip plating and hot press forming, the aluminum plating layer can alloy with iron (Fe) in the steel sheet. Therefore, the aluminum plating layer is not necessarily formed as a single layer with a constant component composition, and may include a partially alloyed layer (alloy layer).

[0044] <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 the aluminum plating layer is provided on the base steel sheet. Specifically, the intermetallic compound layer is formed by the reaction of iron (Fe) in the base steel sheet with a metal containing aluminum (Al) in a molten metal bath mainly containing aluminum. The intermetallic compound layer mainly consists of Fe x Al y (where x and y represent 1 or more) and is formed by a plurality of types of compounds. When the aluminum plating layer contains Si (silicon), it consists of Fe x Al y and Fe x Al y Si z (where x, y, and z represent 1 or more) and is formed by a plurality of types of compounds.

[0045] The thickness of the intermetallic compound layer is not particularly limited, but for example, it is often in the range of 3 μm to 10 μm in terms of 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. Note that the thickness of the intermetallic compound layer can be controlled by the temperature and immersion time of the molten metal bath mainly containing aluminum.

[0046] Here, the confirmation of the base steel sheet, the intermetallic compound layer, and the aluminum plating layer, as well as the measurement of the thickness of the intermetallic compound layer and the aluminum plating layer, are carried out by the following methods.

[0047] The steel plate is cut so that its cross-section is exposed, and the cross-section is polished. The polished cross-section of the steel plate is then subjected to line analysis from the surface to the base steel plate using an electron probe microanalyser (FE-EPMA) to measure the aluminum and iron concentrations. The measurement conditions are an acceleration voltage of 15kV, a beam diameter of approximately 100nm, an irradiation time of 1000ms per point, a measurement pitch of 60nm, and a measurement distance that allows for measurement of the thickness of the plating layer, for example, approximately 30μm to 80μm in the thickness direction. The thickness of the base steel sheet and the aluminum-plated steel sheet are preferably measured using an optical microscope or micrometer.

[0048] As a measurement of the aluminum concentration in the cross-section of the steel plate, the region where the aluminum (Al) concentration is less than 2.0 mass% is determined to be the base steel plate, and the region where the aluminum concentration is 2.0 mass% or more is determined to be either the intermetallic compound layer or the aluminum plating layer. Furthermore, within the intermetallic compound layer and the aluminum plating layer, the region where the iron (Fe) concentration exceeds 4.0 mass% is determined to be the intermetallic compound layer, and the region where the iron concentration is 4.0 mass% or less is determined to be the 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. Furthermore, 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 surface of the steel sheet where the aluminum plating layer is formed.

[0049] The thickness of the aluminum plating layer and the intermetallic compound layer are measured by line 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 according to the aforementioned criteria by measuring the thickness from the surface of the steel sheet with the aluminum plating layer to the intermetallic compound layer at five arbitrary locations, and averaging these values. The thickness of the intermetallic compound layer is determined according to the aforementioned 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 five arbitrary locations, and averaging these values ​​to determine the thickness of the intermetallic compound layer.

[0050] Next, we will explain the details of the shape and other aspects of Tailored Blank 1. As shown in Figures 1 and 2, in the following, the side of the longitudinal direction X that is on the side of the first steel plate 10 relative to the second steel plate 30 will be referred to as the first side X1. The side of the longitudinal direction X that is on the side of the second steel plate 30 relative to the first steel plate 10 will be referred to as the second side X2. The second side X2 is the side that is moving from the first steel plate 10 toward the second steel plate 30 along the longitudinal direction X. The directions perpendicular to the longitudinal direction X and the thickness direction Z are called the orthogonal directions Y. One of the orthogonal directions Y is called the first side Y1, and the other orthogonal direction Y opposite to the first side Y1 is called the second side Y2. The thickness direction Z is the thickness direction of the first steel plate 10 and the thickness direction of the second steel plate 30.

[0051] As shown in Figure 1, the first steel plate 10 has a first piece 16 of the first part, a second piece 17 of the first part, and a third piece 18 of the first part. Part 1, first piece 16, Part 1, second piece 17, and Part 1, third piece 18 are each flat. The outer edge 16a of the second side X2 in the first piece 16 of the first part is a curved shape that gradually slopes toward the first side X1 as it approaches the first side Y1. The outer edge 18a of the second side X2 in the third piece 18 of the first part is a curved shape that is convex toward the second side X2. Here, a convex curved shape means that it is convex over the entire area of ​​the welded metal part and does not include any concave parts. However, it may include some straight lines as long as it does not include any parts where straight lines intersect. The third piece 18 of the first part is positioned on the second side Y2 than the first piece 16 of the first part. The third piece 18 of the first part is connected to the first piece 16 of the first part via the planned first ridge line portion 21 of the first part. Note that connection here means that it is connected directly without the use of other members. However, if it is connected via a part of the same member, for example, the first steel plate 10, it may be connected indirectly via other pieces or ridge lines. The planned first ridge section 21 of the first part is the part where the first steel plate 10 is planned to be folded to form the first ridge 21A of the first part, which will be described later. The planned first ridge section 21 of the first part extends along the longitudinal direction X. The first steel plate 10 is not folded in the planned first ridge section 21 of the first part. Furthermore, indicators such as marking lines may be provided in the planned section 21 of the first ridge of Part 1.

[0052] The outer edge 16b of the first piece 16 of the first part, opposite to the planned first ridge line portion 21 of the first part, is inclined so as it approaches the first side Y1, it gradually slopes toward the first side X1. The outer edge 16b is more aligned with the longitudinal direction X than the outer edge 16a. The center of the longitudinal direction X at the end of the second side Y2 of the first piece 16 of the first part, and the center of the longitudinal direction X at the end of the first side Y1 of the third piece 18 of the first part, coincide with each other.

[0053] The outer edge 17a of the second piece 17 of the first part, on the second side X2, is curved in a way that gradually slopes toward the first side X1 as it moves toward the second side Y2. The second piece 17 of the first part is positioned on the second side Y2 than the third piece 18 of the first part. The second piece 17 of the first part is connected to the third piece 18 of the first part via the planned second ridge section 22 of the first part. The planned second ridge section 22 of the first part is the part of the first steel plate 10 that is planned to be folded to form the second ridge 22A of the first part, which will be described later. The planned second ridge section 22 of the first part is positioned on the second side Y2 than the planned first ridge section 21 of the first part and extends along the longitudinal direction X. The first steel plate 10 is not folded at the planned second ridge section 22 of the first part.

[0054] In the second piece 17 of the first part, the outer edge 17b opposite to the planned second ridge line 22 of the first part gradually slopes toward the first side X1 as it approaches the second side Y2. The outer edge 17b is more aligned with the longitudinal direction X than the outer edge 17a. The center of the longitudinal direction X at the end of the first side Y1 of the second piece 17 of the first part, and the center of the longitudinal direction X at the end of the second side Y2 of the third piece 18 of the first part, coincide with each other. As described above, the second piece 17 of the first part is connected to the first piece 16 of the first part via the first ridge line planned section 21 of the first part, the third piece 18 of the first part, and the second ridge line planned section 22 of the first part.

[0055] The second steel plate 30 has a second part first piece 36, a second part second piece 37, and a second part third piece 38. Part 2, first piece 36, Part 2, second piece 37, and Part 2, third piece 38 are all flat. The outer edge 36a of the first piece 36 of the second part is a curved shape that gradually slopes toward the first side X1 as it approaches the first side Y1. The first piece 36 of the second part is positioned on the second side X2 of the first steel plate 10 compared to the first piece 16 of the first part. The first piece 36 of the second part is joined to the first piece 16 of the first part via the weld metal portion 50.

[0056] The outer edge 38a of the third piece 38 of the second part is curved in a concave shape toward the second side X2. The third piece 38 of the second part is positioned on the second side Y2 than the first piece 36 of the second part. The third piece 38 of the second part is connected to the first piece 36 of the second part via the planned first ridge section 41 of the second part. The planned first ridge section 41 of the second part is the part of the second steel plate 30 that is planned to be folded to form the first ridge 41A of the second part, which will be described later. The planned first ridge section 41 of the second part extends along the longitudinal direction X. The second steel plate 30 is not folded at the planned first ridge section 41 of the second part. The second part third piece 38 is positioned on the second side X2 of the first steel plate 10 compared to the first part third piece 18. The second part third piece 38 is joined to the first part third piece 18 via the weld metal portion 50.

[0057] The outer edge 36b of the first piece 36 of the second part, opposite to the planned first ridge line portion 41 of the second part, is inclined so as it approaches the first side Y1, it gradually slopes toward the first side X1. The outer edge 36b is more aligned with the longitudinal direction X than the outer edge 36a. The outer edge 36b and the outer edge 16b of the first piece 16 of the first part are arranged on the same straight line. The outer edges 36b and 16b are the outer edges of the tailored blank 1 (hot press-formed product 1A) opposite to the planned first ridge line portion 41 (first ridge line 41A) of the first piece 36 of the second part. The center of the longitudinal direction X at the end of the second side Y2 of the first piece 36 of the second part, and the center of the longitudinal direction X at the end of the first side Y1 of the third piece 38 of the second part, coincide with each other. The planned first ridge section 41 of the second part and the planned first ridge section 21 of the first steel plate 10 are arranged on the same straight line.

[0058] The outer edge 37a of the second piece 37 of the second part is curved, gradually sloping toward the first side X1 as it approaches the second side Y2. The second piece 37 of the second part is positioned second to the left Y2 than the third piece 38 of the second part. The second piece 37 of the second part is connected to the third piece 38 of the second part via the planned second ridge section 42 of the second part. The planned second ridge section 42 of the second part is the portion of the second steel plate 30 that is planned to be folded to form the second ridge 42A of the second part, which will be described later. The planned second ridge section 42 of the second part is positioned second to the left Y2 than the planned first ridge section 41 of the second part and extends along the longitudinal direction X. The second steel plate 30 is not folded at the planned second ridge section 42 of the second part. The outer edge 37b of the second piece 37 of the second part, opposite to the planned second ridge line section 42 (planned first ridge line section 41) of the second part, gradually slopes toward the first side X1 as it approaches the second side Y2. The outer edge 37b is more aligned with the longitudinal direction X than the outer edge 37a. As described above, the second piece 37 of the second part is connected to the first piece 36 of the second part via the first ridge line planned section 41 of the second part, the third piece 38 of the second part, and the second ridge line planned section 42 of the second part.

[0059] The second piece 37 of the second part is joined to the second piece 17 of the first part via a welded metal portion 50. The outer edge 37b of the second piece 37 of the second part and the outer edge 17b of the second piece 17 of the first part are aligned on the same straight line. The planned second ridge line portion 42 of the second part and the planned second ridge line portion 22 of the first steel plate 10 are aligned on the same straight line. The outer edges 37b and 17b are the outer edges of the tailored blank 1 (hot press-formed product 1A) on the opposite side of the planned first ridge line portion 41 (first ridge line 41A) of the second piece 37 of the second part.

[0060] The weld metal portion 50 is a curved shape that is symmetrical with respect to the center of the Y-direction perpendicular to the tailored blank 1. The shape of the weld metal portion 50 is not limited as long as it is a convex curve, but from the viewpoint of stress distribution, it is preferable to have a shape that is symmetrical with respect to the center of the Y-direction perpendicular to the tailored blank 1. The weld metal portion 50 is a curved shape that is convex toward the second side X2. More specifically, the weld metal portion 50 is an arc shape that is convex toward the second side X2. The first side Y1 end of the weld metal portion 50 is the portion of the weld metal portion 50 that is connected to the outer edge 36b of the second part first piece 36. The second side Y2 end of the weld metal portion 50 is the portion of the weld metal portion 50 that is connected to the outer edge 37b of the second part second piece 37.

[0061] The weld metal portion 50 has a weld start end 56 and a weld end end 57. For example, the weld start end 56 is provided at the end of the first side Y1 of the weld metal portion 50. The weld end end 57 is provided at the end of the second side Y2 of the weld metal portion 50. Generally, the weld start and end points may be cut off (trimmed) after hot press forming. In this embodiment, the weld start point 56 and weld end point 57 remain on the hot press formed product 1A without being cut off. Note that the weld metal portion 50A does not necessarily have a weld start point 56 and a weld end point 57. Generally, the weld is stable in areas of the weld metal other than the weld start and end points. The weld start and end points are where welding begins and ends, and for example, craters (depressions) are formed in these areas. It is preferable that the weld metal portion 50A has a weld start end 56 and a weld end end 57. Even if the hot press-formed product 1A has a weld start end 56 and a weld end end 57, fracture at the weld metal portion 50A can be suppressed, and the fracture suppression effect at the weld metal portion of this application can be more effectively realized. The concentration of aluminum contained in the weld metal part 50A is preferably 0.3% by mass or more and 2.5% by mass or less.

[0062] The aluminum concentration in the weld metal part 50A is measured as follows. The hot-pressed part 1A is cut perpendicular to the weld metal part 50A, trimmed so that the cross-section of the weld metal part 50A remains, and embedded in resin. The embedded hot-pressed part 1A is polished, and the aluminum concentration is measured by mapping and analyzing the surface of the hot-pressed part 1A to the base steel plates 11 and 31 using an electron beam microanalyzer (FE-EPMA). The measurement conditions are an acceleration voltage of 15kV, a beam diameter of approximately 100nm, and an irradiation time of 1000ms. The measurement pitch is a grid pattern with a 5μm pitch. The measured aluminum concentration of the weld metal part is averaged to determine the average concentration.

[0063] As shown in Figure 1, at the first intersection Q1, which is the intersection point between the outer edge (36b and 16b) of the first side Y1 of the tailored blank 1 and the weld metal portion 50, with the first piece 36 of the second part as the reference, the angle that is smallest between the portion of the weld metal portion 50 that is connected to the first intersection Q1 and the longitudinal direction X passing through the first intersection Q1 is called the first outer edge angle θ11. The first outer edge angle θ11 is greater than 0° and less than or equal to 90°. Here, the specific method for measuring the first outer edge angle θ11 is as follows: At a position 20 mm away from the first intersection Q1 toward the second side Y2, the first outer edge angle θ11 is defined as the angle with the smallest angle between the line connecting the point where the longitudinal direction X intersects with the weld metal portion 50 and the first intersection Q1, and the longitudinal direction passing through the first intersection Q1.

[0064] With the second piece 37 of the second part as the reference, at the second intersection Q2, which is the intersection point between the outer edge (37b and 17b) of the second side Y2 of the tailored blank 1 and the weld metal portion 50, the angle with the smallest angle between the portion of the weld metal portion 50 connected to the second intersection Q2 and the longitudinal direction X passing through the second intersection Q2 is called the second outer edge angle θ12. The second outer edge angle θ12 is greater than 0° and less than or equal to 90°. Here, the specific method for measuring the second outer edge angle θ12 is as follows: At a position 20 mm away from the second intersection Q2 toward the first side Y1, the second outer edge angle θ12 is defined as the angle with the smallest angle between the line connecting the point where the longitudinal direction X intersects with the weld metal part 50 and the second intersection Q2, and the longitudinal direction passing through the second intersection Q2. The outer edge angles θ11 and θ12 are preferably between 15° and 60°, respectively.

[0065] At the third intersection Q3, which is the intersection point between the extension of the planned first ridge line 21 of the first part or the planned first ridge line 41 of the second part (first ridge line 41A of the second part) and the welded metal part 50, the angle of the smallest of the four angles formed by the portion of the welded metal part 50 connected to the third intersection Q3 and the longitudinal direction X passing through the third intersection Q3 is called the first ridge angle θ21. Here, the specific method for measuring the first ridge angle θ21 is as follows: At positions 20 mm away from the third intersection Q3 towards the first side Y1 and the second side Y2, the angle with the smallest angle among the four angles formed by the line connecting the point where the longitudinal direction X intersects with the weld metal part 50 and the third intersection Q3, and the longitudinal direction passing through the third intersection Q3, is defined as the first ridge angle θ21.

[0066] At the fourth intersection Q4, which is the intersection point between the extension of the planned second ridge section 22 of the first part or the planned second ridge section 42 of the second part (second ridge 42A of the second part) and the welded metal section 50, the angle of the smallest of the four angles formed by the portion of the welded metal section 50 connected to the fourth intersection Q4 and the longitudinal direction X passing through the fourth intersection Q4 is called the second ridge angle θ22. Here, the specific method for measuring the second ridge angle θ22 is as follows: At positions 20 mm away from the fourth intersection Q4 towards the first side Y1 and the second side Y2, the angle with the smallest angle among the four angles formed by the line connecting the point where the longitudinal direction X intersects with the weld metal part 50 and the fourth intersection Q4, and the longitudinal direction passing through the fourth intersection Q4, is defined as the second ridge angle θ22. The angles of the ridge lines θ21 and θ22 are preferably between 30° and 75°, respectively.

[0067] Next, we will describe the details of the shape and other aspects of the hot-pressed product 1A. As shown in Figure 4, the hot-pressed product 1A is U-shaped when viewed in the longitudinal direction X. However, the shape of the hot-pressed product is not limited to a U-shape; for example, it may be a hat shape with flanges on both sides. As shown in Figures 3 and 4, the first member 10A has the first piece 16 of the first part, the second piece 17 of the first part, and the third piece 18 of the first part. The third piece 18 of the first part is connected to the first piece 16 of the first part via the first ridge line 21A of the first part. The third piece 18 of the first part is connected to the first piece 16 of the first part via the first ridge line 21A of the first part. The second piece 17 of the first part is connected to the third piece 18 of the first part via the second ridge line 22A of the first part. That is, the third piece 18 of the first part is positioned between the first ridge line 21A of the first part and the second piece 17 of the first part. The third piece 18 of the first part is connected to the second piece 17 of the first part via the second ridge line 22A of the first part. As described above, the second piece 17 of the first part is connected to the first piece 16 of the first part via the first ridge line 21A of the first part, the third piece 18 of the first part, and the second ridge line 22A of the first part. The first ridge line 21A of the first part and the second ridge line 22A of the first part are formed in the first steel plate 10 at the positions where the planned first ridge line portion 21 and the planned second ridge line portion 22 of the first part are formed, respectively.

[0068] The second member 30A has the first piece 36 of the second part, the second piece 37 of the second part, and the third piece 38 of the second part. The first piece 36 of the second part is joined to the first piece 16 of the first part via a welded metal portion 50A. The third piece 38 of the second part is connected to the first piece 36 of the second part via the first ridge line 41A of the second part. That is, the first ridge line 41A of the second part is joined to the first ridge line 21A of the first part via the weld metal portion 50A. The second piece 37 of the second part is connected to the third piece 38 of the second part via the second ridge line 42A of the second part. That is, the third piece 38 of the second part is positioned between the first ridge line 41A of the second part and the second piece 37 of the second part. The second ridge line 42A of the second part is joined to the second ridge line 22A of the first part via the weld metal portion 50A. The third piece 38 of the second part is connected to the second piece 37 of the second part via the second ridge line 42A of the second part. The third piece 38 of the second part is connected to the first piece 36 of the second part via the first ridge line 41A of the second part.

[0069] Here, the distance between the two ends of the weld metal portion 50A of the hot-pressed product 1A is defined as L1. The weld metal portion 50A has a weld start end 56 and a weld end end 57. The distance L1 is also the distance between the weld start end 56 and the weld end end 57 of the weld metal portion 50A of the hot-pressed product 1A that has not been unfolded.

[0070] As described above, the second piece 37 of the second part is connected to the first piece 36 of the second part via the first ridge line 41A of the second part, the third piece 38 of the second part, and the second ridge line 42A of the second part. The first ridge line 41A and the second ridge line 42A of the second part are formed in the second steel plate 30 at the positions where the planned first ridge line portion 41 and the planned second ridge line portion 42 of the second part are formed, respectively. The third piece 38 of the second part is joined to the third piece 18 of the first part via a welded metal portion 50A. The second piece 37 of the second part is joined to the second piece 17 of the first part via a welded metal portion 50A.

[0071] Figure 5 shows the shape of the hot-pressed product 1A when it is unfolded into a planar shape. For example, the unfolding of the hot-pressed product 1A can be performed by deforming the hot-pressed product 1A under the same conditions as the heating conditions in the molding process S16 of the hot-pressed product manufacturing method S10 described later. The unfolding of the hot-pressed product 1A can be performed without changing the shape of each of the pieces 16, 17, 18, 36, 37, and 38, for example by rotating pieces 16, 17, 36, and 37 around the edges 21A, 22A, 41A, and 42A with respect to the third pieces 18 and 38. Alternatively, the shapes of each piece 16, 17, 18, 36, 37, and 38 can be obtained by taking photographs of each piece or by scanning each piece. Then, based on the obtained shapes of each piece 16, 17, 18, 36, 37, and 38, the shape of the hot-pressed product 1A when unfolded can be estimated.

[0072] The second side X2 is the side that extends from the first member 10A to the second member 30A along the longitudinal direction X. When the hot-pressed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A is curved in a convex shape toward the second side X2. More specifically, the weld metal portion 50 is arc-shaped, convex toward the second side X2. The ratio of the radius of the weld metal portion 50A to the distance L1 is preferably 0.52 or more and 2.88 or less. When the radius ratio is 0.52 or more, the outer edge angles θ11 and θ12 become 15° or more, ensuring cutting accuracy by mold blanks or laser cutting. On the other hand, when the radius ratio is 2.88 or less, at least one of the outer edge angles θ11 and θ12 and the ridge angles θ21 and θ22 becomes 80° or less, further preventing the hot press-formed product from fracturing at the weld metal portion. Furthermore, the welded metal portion 50A may be in the shape of an elliptical arc that is convex toward the second side X2.

[0073] The Vickers hardness of the first member 10A, based on JIS Z 2244:2009 Vickers hardness test - test method (hereinafter simply referred to as Vickers hardness), is greater (harder) than the Vickers hardness of the first steel plate 10. Similarly, the Vickers hardness of the second member 30A and the weld metal part 50A are greater than the Vickers hardness of the second steel plate 30 and the weld metal part 50, respectively. The test force used to measure Vickers hardness is 2.94 N (Newtons).

[0074] Here, the hot-pressed product 1A is defined as follows. Note that Figure 2 is also a cross-sectional view of the cutting line A2-A2 in Figure 3. As shown in Figure 2, the thickness of the first member 10A is defined as T1 (mm). Here, the thickness T1 of the first member 10A is determined by measuring the thickness of the first member 10A at five arbitrary locations using a micrometer or the like, and averaging the values ​​obtained. The Vickers hardness of the first member 10A is defined as H1 (HV). Here, the Vickers hardness H1 of the first member 10A is determined at three points: the center of the region obtained by dividing the entire length of the first member 10A in the longitudinal direction X into three equal parts, at the center of the region in the thickness direction Z of the first member 10A. The average of these determined values ​​is taken as the Vickers hardness H1. The thickness of the second member 30A is specified as T2 (mm). The Vickers hardness of the second member 30A is specified as H2 (HV). The thickness of the weld metal part 50A is specified as T w (mm) is specified, and the thickness T w This value is equal to the thinner of the two thicknesses, T1 and T2. The thickness and Vickers hardness of the second member 30A are determined in the same way as for the first member 10A. The Vickers hardness of the weld metal part 50A is H w It is defined as (HV). The thickness T1 of the first member 10A is equal to the thickness of the first steel plate 10. Similarly, the thickness T2 of the second member 30A and the thickness T of the welded metal part 50A are equal. w This is equal to the thickness of the second steel plate 30 and the thickness of the welded metal part 50, respectively.

[0075] At this time, the hot-pressed product 1A satisfies equation (1). T w H w <T2H2<T1H1··(1) Here, the product of thickness and Vickers hardness corresponds to stiffness. The concentration of aluminum contained in the weld metal part 50A is preferably 0.3% by mass or more and 2.5% by mass or less. Hot-pressed product 1A is used, for example, in automotive parts such as B-pillars. Furthermore, the shape of the tailored blank 1 shown in Figure 1 is also the shape of the hot-pressed product 1A when it is unfolded into a planar shape and viewed in the thickness direction Z.

[0076] Here, the plane passing through the center of the orthogonal direction Y in the weld metal portion 50A and perpendicular to the orthogonal direction Y is called the reference plane. As shown in Figure 2, the Vickers hardness H of the weld metal portion 50A w The measurement is taken at six locations P1 on the reference plane. Three of the six locations P1 are measured at the center of the longitudinal direction X of the weld metal portion 50A. The other three locations P1 are measured at positions closer to the thinner member (second member 30A) of members 10A and 30A than the center of the longitudinal direction X of the weld metal portion 50A. The three locations P1 are the center of each surface layer in the thickness direction Z of the weld metal 50A, and the center between each surface layer. The average of the values ​​obtained at the six locations is used to determine the Vickers hardness H. w Let's assume that.

[0077] Next, the method for manufacturing a hot press-formed product 1A, which is configured as described above, according to this embodiment will be explained. Figure 6 is a flowchart showing the method for manufacturing a hot press-formed product S10. The outer edge of the second side X2 of the first steel plate 10 is formed in advance as a curved shape that is convex toward the second side X2. The outer edge of the first side X1 of the second steel plate 30 is formed as a curved shape that is concave toward the second side X2. In the steel plates 10 and 30, the intermetallic compound layers 12 and 32 and the aluminum plating layers 13 and 33 at the edges are not removed.

[0078] First, the tailored blank manufacturing method of this embodiment (step S11 shown in Figure 6) is performed to manufacture the tailored blank 1. In the tailored blank manufacturing method S11, a placement step (step S12) is performed. In the placement step S12, as shown in Figure 7, the ends of the first steel plate 10 and the second steel plate 30 are placed so that they abut in the longitudinal direction X. Once the placement process S12 is completed, the process moves to step S13.

[0079] Next, in the welding process (step S13), as shown in Figure 1, the end of the first steel plate 10 and the end of the second steel plate 30 are joined by welding to form a weld metal portion 50 and to manufacture the tailored blank 1. Laser welding, plasma welding, etc., can be used for welding. Once welding process S13 is completed, all steps of the tailored blank manufacturing method S11 are finished, and the process moves on to step S16.

[0080] Next, in the forming process (step S16), the tailored blank 1 is hot-press formed to create a first ridge line 21A and a second ridge line 22A on the first member 10A obtained from the first steel sheet 10. A second ridge line 41A and a second ridge line 42A are formed on the second member 30A obtained from the second steel sheet 30. For example, hot press forming is performed by heating a tailored blank 1 and shaping it into a predetermined form, and then quenching the tailored blank 1 that has been shaped into the predetermined form. For example, the heating conditions in the heating and forming process 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 process is performed by cooling the mold used for press forming, or by directly spraying water onto the tailored blank 1 to cool it. The first ridge line 21A and the second ridge line 22A of the first part are formed by folding the first steel plate 10 at the locations of the planned first ridge line 21 and the planned second ridge line 22 of the first part. The first ridge line 41A and the second ridge line 42A of the second part are formed by folding the second steel plate 30 at the locations of the planned first ridge line 41 and the planned second ridge line 42 of the second part.

[0081] In the hot press-formed product manufacturing method S10, taking the form shown in Figure 5 as an example, the hot press-formed product 1A is manufactured such that when the hot press-formed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A is curved in a convex shape toward the second side X2. More specifically, in the hot press-formed product manufacturing method S10, the hot press-formed product 1A is manufactured such that when the hot press-formed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A is arced in a convex shape toward the second side X2. In this case, it is preferable to manufacture the hot press-formed product 1A such that the ratio of the radius of the weld metal portion 50A to the distance L1 is 0.52 or more and 2.88 or less.

[0082] When the molding process S16 is completed, all steps of the manufacturing method S10 for the hot press-formed product are completed, and the hot press-formed product 1A is manufactured.

[0083] As described above, in the hot press-formed product 1A and the manufacturing method S10 of the hot press-formed product of this embodiment, when the hot press-formed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A is curved in a convex shape toward the second side X2. For this reason, in the tailored blank 1 before hot press forming of the hot press-formed product 1A, the ends of the first and second steel plates 10 and 30 that are butted against each other are such that the end of the first steel plate 10 is curved in a convex shape toward the second side X2, and the end of the second steel plate 30 is curved in a concave shape toward the second side X2. Therefore, for example, even if the end of the second steel plate 30 moves so as to swing around the butted ends on the unfolded plane relative to the ends of the first steel plate 10 that are butted against each other, the distance between the ends does not change as easily as when the ends are straight. Furthermore, because the weld metal portion 50A is curved, when a tensile force is applied to the hot-pressed product 1A in the longitudinal direction X, the external force acting in the direction of opening the weld metal portion 50A is suppressed. Therefore, it is possible to suppress the hot-pressed product 1A from fracturing at the weld metal portion 50A. Therefore, dimensional accuracy can be ensured at the joint where the ends of the steel plates 10 and 30 are butted together, and fracture of the hot-pressed product 1A at the welded metal portion 50A can be suppressed.

[0084] Preferably, the hot-pressed product 1A has a welded metal portion 50A, at least a part of the first member 10A connected to the welded metal portion 50A, and at least a part of the second member 30A connected to the welded metal portion, and includes a shaft portion 1B extending in a predetermined direction. The shaft portion 1B of the hot-pressed product 1A extends in a predetermined direction U, and the longitudinal direction X corresponds to the predetermined direction U. Therefore, for example, when a tensile force is applied in the predetermined direction U to which the shaft portion 1B extends, it is possible to suppress fracture of the hot-pressed product 1A at the welded metal portion 50A.

[0085] It is preferable that the hot-pressed product 1A satisfies equation (1). In the hot-pressed product 1A, the product of thickness and Vickers hardness, i.e., stiffness, increases in the order of weld metal portion 50A, second member 30A, and first member 10A. Generally, in hot-pressed products, the stiffness of the weld metal portion is less than the stiffness of the member, satisfying the inequality on the left side of equation (1). If the stiffness of the weld metal portion is less than the stiffness of the member, stress tends to concentrate more in the weld metal portion. However, when the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction, the curved shape of the weld metal portion suppresses the external force acting in the direction of opening the weld metal portion when a tensile force is applied to the hot-pressed product in the longitudinal direction. Therefore, it is preferable that the stiffness of the weld metal portion is less than the stiffness of the member, as this allows the effects of the present invention to be significantly realized. Furthermore, by satisfying the inequality on the right side of equation (1) and making the rigidity of the second member less than that of the first member, stress can be concentrated in the second member 30A of the two members 30A, making the second member 30A more prone to fracture. This allows the fracture prevention measures in the hot-pressed product 1A to be concentrated on the second member 30A.

[0086] The outer edge angles θ11 and θ12 are 15° to 60°, respectively, and the ridge angles θ21 and θ22 are 30° to 75°, respectively. As a result of diligent research, the inventors have found the following: For example, when a tensile force is applied to the hot-pressed product 1A in the longitudinal direction X, crack initiation points are likely to occur in the portion of the weld metal part 50A connected to the first intersection Q1, the portion connected to the second intersection Q2, the portion connected to the third intersection Q3, and the portion connected to the fourth intersection Q4. Therefore, by setting the outer edge angles θ11 and θ12 and the ridge angles θ21 and θ22 as described above, even if ridges 41A and 42A are formed on the hot-pressed product, it is possible to more reliably suppress fracture of the hot-pressed product 1A at the weld metal part 50A due to the tensile force applied to each of the aforementioned portions.

[0087] Preferably, the first member 10A has a first part third piece 18 which is connected to the first part first piece 16 via the first edge line 21A of the first part and to the second part second piece 17 via the second edge line 22A of the first part, and the second member 30A has a second part second edge line 42A which is joined to the second part second edge line 22A of the first part via a welded metal portion 50A, a second part first piece 36 which is connected to the second part first edge line 41A of the second part and to the second part second piece 37 which is connected to the second part second edge line 42A of the second part and to the third part second piece 18 which is joined to the welded metal portion 50A. As a result, the first member 10A can be made up of three pieces 16, 17, and 18 connected via ridges 21A and 22A, and the second member 30A can be made up of three pieces 36, 37, and 38 connected via ridges 41A and 42A.

[0088] When the hot-pressed product 1A is unfolded into a planar shape and viewed in the thickness direction Z of the second member 30A, it is preferable that the weld metal portion 50A is arc-shaped or elliptical arc-shaped (the hot-pressed product 1A is manufactured so that the weld metal portion 50A is arc-shaped or elliptical arc-shaped). Therefore, when the hot-pressed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A has a gentle curve, and the stress on the weld metal portion can be distributed. Consequently, fracture of the hot-pressed product 1A at the weld metal portion 50A can be further suppressed. Furthermore, when the weld metal portion 50A is arc-shaped, it is preferable that the ratio of the radius of the weld metal portion 50A to the distance L1 between both ends of the weld metal portion 50A is between 0.52 and 2.88 (the hot press-formed product 1A is manufactured so that the ratio is between 0.52 and 2.88). This allows the weld metal portion 50A to be arc-shaped while maintaining the angle at a predetermined value. Consequently, the dimensional accuracy at the butt joint can be further improved, and fracture of the hot press-formed product 1A at the weld metal portion 50A can be further suppressed.

[0089] It is preferable that the concentration of aluminum contained in the weld metal part 50A is 0.3% by mass or more and 2.5% by mass or less. Because the aluminum concentration in the weld metal part 50A is high, the corrosion resistance of the weld metal part 50A can be improved.

[0090] The hot-pressed product 1A is preferably used as an automotive part. Since reliability is required for automotive parts, the hot-pressed product 1A, which ensures dimensional accuracy at the butt joint of the ends of the steel plates 10 and 30, can be preferably used as an automotive part.

[0091] Furthermore, in the tailored blank 1 and the manufacturing method S11 of the tailored blank of this embodiment, when the tailored blank 1 is viewed in the thickness direction Z, the weld metal portion 50 is curved in a convex shape toward the second side X2. Therefore, in the tailored blank 1, the ends of the first and second steel plates 10 and 30 that are butted against each other are such that the end of the first steel plate 10 is curved in a convex shape toward the second side X2, and the end of the second steel plate 30 is curved in a concave shape toward the second side X2. Consequently, for example, even if the end of the second steel plate 30 moves so as to swing around the butted ends relative to the ends of the first steel plate 10, the distance between the ends does not change as easily as when the ends are straight. Furthermore, because the weld metal portion 50 of the tailored blank 1 is curved, when a tensile force is applied to the hot-pressed product 1A in the longitudinal direction X, the external force acting in the direction of opening the weld metal portion 50A is suppressed. Therefore, it is possible to suppress the fracture of the hot-pressed product 1A at the weld metal portion 50A. Therefore, dimensional accuracy can be ensured at the joint where the ends of the steel plates 10 and 30 are butted together, and fracture of the hot-pressed product 1A at the welded metal portion 50A can be suppressed.

[0092] (Examples) Next, we will explain the results of tensile tests conducted using hot-pressed products. Tensile tests were performed on hot-pressed products of samples No. 1 to 3, with the specifications shown in Table 1 and Figures 8 to 10. Both the first and second members were made of aluminum-plated material.

[0093] [Table 1]

[0094] Figures 8 to 10 show the shape of the hot-pressed product when it is unfolded into a flat surface. In the hot-pressed products of samples No. 1 to 3, the negative side (first side Y1) of the orthogonal direction Y of the hot-pressed product was set as the origin of the orthogonal direction Y. The width (length in the orthogonal direction Y) of members 10A and 30A was set to 400 mm. The position of the first ridge line 41A of the second part in the orthogonal direction Y was set to 100 mm. Figures 8 to 10 are extracted views of the vicinity of the weld metal part 50A, and the longitudinal direction of each sample is the X direction.

[0095] For samples No. 1 to 3, the thickness and Vickers hardness were set as follows. The thickness T1 of the first member 10A was set to 1.6 mm. The Vickers hardness H1 of the first member 10A was set to 500 HV. The thickness T2 of the second member 30A was set to 1.2 mm. The Vickers hardness H2 of the second member 30A was set to 400 HV. Thickness T of the weld metal part 50A w The thickness was set to 1.2 mm. The Vickers hardness of the weld metal part 50A was H. w This was set to 300HV.

[0096] For example, in the hot-pressed product of Sample No. 1, the radius of the weld metal portion 50A was set to 250 mm. The first outer edge angle θ11 was set to 37°. The first ridge angle θ21 was set to 66°. The second ridge angle θ22 was set to 66°. The second outer edge angle θ12 was set to 37°. The weld metal portion 50A was assumed to be a symmetrical arc shape. A tensile test was performed using the hot-pressed product of sample No. 1. As a result, fracture occurred at the second member 30A, with a fracture load of 568 kN.

[0097] Similarly, tensile tests were also performed on the hot-pressed products of samples No. 2 and 3. As shown in Figure 10, the weld metal portion 50A in the hot-pressed product of sample No. 3 is a straight line extending along the orthogonal direction Y. Therefore, the radius of the weld metal portion 50A is not specified for sample No. 3. Samples No. 1 and 2 are hot-pressed products that serve as examples, while sample No. 3 is a comparative example. In the hot-pressed products of Samples No. 1 and 2, the weld metal portion 50A is curved and convex, so the distance between the ends of the steel plates 10 and 30 during butt joint does not change easily, resulting in high dimensional accuracy of the butt joint and the formation of a weld metal portion 50A without thinning. On the other hand, in the hot-pressed product of Sample No. 3, the weld metal portion 50A is straight, so the distance between the ends of the steel plates 10 and 30 during butt joint changes easily, resulting in low dimensional accuracy of the butt joint and the presence of thinning in the weld metal portion 50A. In the hot-pressed products of Samples No. 1 and 2, fracture at the weld metal portion 50A was suppressed and the fracture load was increased compared to the hot-pressed product of Sample No. 3. This is because the dimensional accuracy of the butt joint portion of the hot-pressed products of Samples No. 1 and 2 was higher, which distributed the load on the weld metal portion 50A and improved the fracture load.

[0098] 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 modifications, combinations, deletions, etc., of the configuration are also included without departing from the spirit of the present invention. For example, in the above embodiment, when the hot-pressed product 1A is unfolded into a planar shape and viewed in the thickness direction Z, the weld metal portion 50A may be a curved shape that is convex toward the first side X1. In the tailored blank 1 as well, when viewed in the thickness direction Z, the weld metal portion 50 may be a curved shape that is convex toward the first side X1.

[0099] In the tailored blank 1, the first steel plate 10 does not have to have the third piece 18 of the first part and the planned second ridge line portion 22 of the first part. The first steel plate 10 may be composed of four or more pieces. The second steel plate 30 does not have to have the third piece 38 of the second part and the planned second ridge line portion 42 of the second part. The steel plate 30 may be composed of four or more pieces. The same applies to the first member 10A and the second member 30A in the hot-pressed product 1A.

[0100] The weld metal parts 50 and 50A do not need to be curved, but rather convex arcs or elliptical arcs toward the second side X2. The hot-pressed product 1A does not need to satisfy equation (1). [Explanation of Symbols]

[0101] 1 Tailored Blank 1A Hot press-formed product 1B Shaft 10 First steel plate 10A First Member 16 Part 1 Part 1 17 Part 1 Part 2 18 Part 1 Part 3 21 Part 1, First Ridge (Planned Section) 21A Part 1 1st ridgeline 22 Part 1, Second Ridge (Planned Section) 22A Part 1 2nd ridgeline 30 Second steel plate 30A Second component 36 Part 2 Part 1 36d, 38d outer edge 37 Part 2 Part 2 38 Part 2 Part 3 41 Part 2, First Ridge (Planned Section) 41A Part 2 1st ridgeline 42. Part 2, Second Ridge (Planned Section) 42A Part 2 2nd ridgeline 50, 50A Weld metal part 56 Weld start 57 Weld termination Q1 1st intersection Q2 2nd intersection Q3 3rd intersection Q4 4th intersection S10 Method for manufacturing hot-pressed products S11 Tailored Blank Manufacturing Method S12 Placement process S13 Welding Process S16 Molding process U in a predetermined direction X Longitudinal direction

Claims

1. First member and A second member is positioned such that its end abuts against the end of the first member, A welded metal portion that joins the end of the first member and the end of the second member, A hot press-formed product comprising, At least one of the first member and the second member is an aluminum plated member. The longitudinal direction of the hot-pressed product with respect to the portion near the welded metal when the hot-pressed product is unfolded into a planar shape is defined as follows: When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is curved in a convex shape toward either side along the longitudinal direction. The aluminum concentration in the welded metal portion is 0.3% by mass or more and 2.5% by mass or less. A hot-pressed product in which, when the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is arc-shaped or elliptical arc-shaped.

2. The hot press-formed product has the weld metal portion, at least a part of the first member connected to the weld metal portion, and at least a part of the second member connected to the weld metal portion, and includes a shaft portion extending in a predetermined direction. The hot press-formed product according to claim 1, wherein the longitudinal direction corresponds to the predetermined direction.

3. (1) A hot press-formed article according to claim 1 or 2, satisfying formula (1). T ｗ H ｗ <T ２ H ２ <T １ H １ ・・(1) However, T １ : The thickness (mm) of the first member, H １ : The Vickers hardness (HV) of the first member, T ２ : The thickness (mm) of the second member, H ２ : The Vickers hardness (HV) of the second member, T ｗ : The thickness of the welded metal part (the thinner one of the thickness T １ and the thickness T ２ )(mm), H ｗ : The Vickers hardness (HV) of the welded metal part.

4. The first member is, Part 1, Piece 1, The first piece of the first part and the second piece of the first part connected via the first ridge of the first part, It has, The second member is, The first piece of the first part and the first piece of the second part joined via the welded metal portion, The first ridge of the first part and the first ridge of the second part joined via the welded metal portion, The second piece of the second part is connected to the first piece of the second part via the first ridge of the second part, and the second piece of the second part is joined to the second piece of the first part via the welded metal portion, It has, When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, With respect to the first piece of the second part, at the first intersection point which is the intersection point between the outer edge of the hot-pressed product on the opposite side of the first ridge of the second part of the first piece and the welded metal portion, the angle of the smallest angle between the portion of the welded metal portion connected to the first intersection point and the longitudinal direction passing through the first intersection point is 15° or more and 60° or less. With the second piece of the second part as the reference, at the second intersection point, which is the intersection point between the outer edge of the hot-pressed product on the opposite side of the second piece of the second part from the first ridge of the second part and the welded metal portion, the angle of the smallest angle between the portion of the welded metal portion connected to the second intersection point and the longitudinal direction passing through the second intersection point is 15° or more and 60° or less. The hot press-formed product according to any one of claims 1 to 3, wherein at the third intersection, which is the intersection of the first ridge of the second part and the welded metal part, the angle of the smallest angle among the four angles made between the portion of the welded metal part connected to the third intersection and the longitudinal direction passing through the third intersection is 30° or more and 75° or less.

5. The first member has a third piece of the first part which is connected to the first piece of the first part via the first ridge of the first part, and connected to the second piece of the first part via the second ridge of the first part. The second member is, The second ridge of the first part and the second ridge of the second part joined via the welded metal portion, The first piece of the second part is connected to the first ridge of the second part, the second piece of the second part is connected to the second ridge of the second part, and the third piece of the second part is joined to the third piece of the first part via the welded metal portion, A hot press-formed article according to claim 4, having the following characteristics.

6. When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is arc-shaped. The hot press-formed product according to claim 1, wherein the ratio of the radius of the welded metal portion to the distance between both ends of the welded metal portion of the hot press-formed product is 0.52 or more and 2.88 or less.

7. A hot-pressed product according to any one of claims 1 to 6, which is a part for an automobile.

8. The hot press-formed product according to any one of claims 1 to 7, wherein the welded metal portion has a weld start end and a weld end.

9. First steel plate and, A second steel plate is positioned such that its end abuts against the end of the first steel plate, A welded metal portion that joins the end of the first steel plate and the end of the second steel plate, A tailored blank equipped with, At least one of the first steel sheet and the second steel sheet is an aluminum-plated steel sheet. The longitudinal direction in the vicinity of the weld metal portion of the tailored blank is defined, When viewed in the thickness direction of the second steel plate, the weld metal portion is curved in a convex shape toward either side along the longitudinal direction. The aluminum concentration in the welded metal portion is 0.3% by mass or more and 2.5% by mass or less. A tailored blank in which, when viewed in the thickness direction, the weld metal portion is arc-shaped or elliptical arc-shaped.

10. A positioning step in which the end of the first steel plate and the end of the second steel plate are positioned to abut against each other, A welding process to manufacture a tailored blank by joining the end of the first steel plate and the end of the second steel plate by welding to form a weld metal portion, A forming step comprising hot-press forming the tailored blank to obtain a first member from the first steel plate and a second member from the second steel plate, A method for manufacturing hot press-formed products, which involves performing the following steps to produce a hot press-formed product: At least one of the first member and the second member is an aluminum plated member. The longitudinal direction of the hot-pressed product in the vicinity of the welded metal portion when the hot-pressed product is unfolded into a planar shape is defined as follows: When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is curved in a convex shape toward either side along the longitudinal direction. The aluminum concentration in the welded metal portion is 0.3% by mass or more and 2.5% by mass or less. A method for manufacturing a hot-pressed product, wherein when the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction, the welded metal portion is arc-shaped or elliptical arc-shaped.

11. The hot press-formed product has the weld metal portion, at least a part of the first member connected to the weld metal portion, and at least a part of the second member connected to the weld metal portion, and includes a shaft portion extending in a predetermined direction. The method for manufacturing a hot press-formed product according to claim 10, wherein the longitudinal direction corresponds to the predetermined direction.

12. The method for manufacturing a hot press-formed article according to claim 10 or 11, wherein the hot press-formed article satisfies formula (2). T ｗ H ｗ <T ２ H ２ <T １ H １ ・・(2) However, T １ : Thickness of the first member (mm), H １ : Vickers hardness (HV), T of the first member of the hot press-formed product ２ : Thickness of the second member (mm), H ２ : Vickers hardness (HV), T of the second member of the hot press-formed product ｗ : The thickness of the welded metal portion (the thickness T) １ and the thickness T ２ (Of which, the thinner thickness) (mm), H ｗ : This is the Vickers hardness (HV) of the weld metal portion of the hot-pressed product.

13. The first member is, Part 1, Piece 1, The first piece of the first part and the second piece of the first part connected via the first ridge of the first part, It has, The second member is, The first piece of the first part and the first piece of the second part joined via the welded metal portion, The first ridge of the first part and the first ridge of the second part joined via the welded metal portion, The second piece of the second part is connected to the first piece of the second part via the first ridge of the second part, and the second piece of the second part is joined to the second piece of the first part via the welded metal portion, It has, When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, With the first piece of the second part as the reference, at the first intersection point which is the intersection point between the outer edge of the hot-pressed product on the opposite side of the first ridge of the second part of the first piece and the welded metal portion, the angle of the smallest angle between the portion of the welded metal portion connected to the first intersection and the longitudinal direction passing through the first intersection is 15° or more and 60° or less. With the second piece of the second part as the reference, at the second intersection, which is the point where the outer edge of the hot-pressed product on the opposite side of the second piece of the second part from the first ridge of the second part intersects with the welded metal portion, the angle of the smallest angle between the portion of the welded metal portion connected to the second intersection and the longitudinal direction passing through the second intersection is 15° or more and 60° or less. A method for manufacturing a hot press-formed product according to any one of claims 10 to 12, wherein at the third intersection, which is the intersection point of the first ridge line of the second part and the welded metal part, the hot press-formed product is manufactured such that the angle of the smallest angle among the four angles made between the portion of the welded metal part connected to the third intersection and the longitudinal direction passing through the third intersection is 30° or more and 75° or less.

14. The first member of the hot press-formed product has a third piece of the first part which is connected to the first piece of the first part via the first ridge of the first part, and connected to the second piece of the first part via the second ridge of the first part. The second member of the hot press-formed product is The second ridge of the first part and the second ridge of the second part joined via the welded metal portion, A method for manufacturing a hot press-formed product according to claim 13, comprising: a first piece of the second part connected to the first ridge of the second part; a second piece of the second part connected to the second ridge of the second part; and a third piece of the second part joined to the third piece of the first part via the welded metal portion.

15. A method for manufacturing a hot press-formed product according to any one of claims 10 to 14, wherein the hot press-formed product is manufactured such that when the hot press-formed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is in the shape of a circular arc or an elliptical arc.

16. When the hot-pressed product is unfolded into a planar shape and viewed in the thickness direction of the second member, the welded metal portion is arc-shaped. The method for manufacturing a hot press-formed product according to claim 15, wherein the hot press-formed product is manufactured such that the ratio of the radius of the welded metal portion to the distance between both ends of the welded metal portion of the hot press-formed product is 0.52 or more and 2.88 or less.

17. The method for manufacturing a hot press-formed product according to any one of claims 10 to 16, wherein the hot press-formed product is a part for an automobile.

18. The method for manufacturing a hot press-formed product according to any one of claims 10 to 17, wherein the weld metal portion has a weld start end and a weld end.

19. A positioning step in which the end of the first steel plate and the end of the second steel plate are positioned to abut against each other, A welding step 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 portion, A method for manufacturing tailored blanks, which involves performing the following to produce tailored blanks: At least one of the first steel sheet and the second steel sheet is an aluminum-plated steel sheet. When defining the longitudinal direction in the portion of the tailored blank near the weld metal, When viewed in the thickness direction of the second steel plate, the weld metal portion is curved in a convex shape toward either side along the longitudinal direction. The concentration of aluminum contained in the welded metal part after hot press forming is 0.3% by mass or more and 2.5% by mass or less. A method for manufacturing a tailored blank, wherein, when viewed in the thickness direction, the welded metal portion is arc-shaped or elliptical arc-shaped.

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