Al BASED PLATED STEEL SHEET, METHOD FOR MANUFACTURING TAILORED BLANK, METHOD FOR MANUFACTURING Al BASED PLATED STEEL SHEET, AND TAILORED BLANK

Abstract

To provide: an Al based plated steel sheet capable of easily rationalizing the amount of Al mixed into the weld bead of a tailored blank; a method for manufacturing a tailored blank; an Al based plated steel sheet; and a tailored blank.SOLUTION: An Al based plated steel sheet, including a plating layer provided on one or both surfaces of a base steel sheet and using Al as a main component, has a first area having a plating layer on a surface having the plating layer of the Al based plated steel sheet and a second area having the thickness of the plating layer thinner than that in the first area. The second area is provided in the vicinity of the end surface of the Al based plated steel sheet; and the length of the second area along the end surface of the Al based plated steel sheet is less than 20 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an Al-based plated steel sheet, a method for producing a tailored blank, a method for producing an Al-based plated steel sheet, and a tailored blank. [Background technology]

[0002] Hot stamping is a manufacturing technique in which steel sheets are heated to high temperatures and press-formed at temperatures above the Ar3 transformation temperature. Welded steel sheets called tailored blanks are sometimes used as steel sheets for hot stamping. Tailored blanks are obtained by butting the ends of multiple steel sheets together and welding them. Tailored blanks are a type of butt welded joint.

[0003] A tailored blank includes multiple steel plates and butt welds that join them. The multiple steel plates usually have different properties such as thickness, strength, and surface treatment. This allows the tailored blank to improve the functionality of a formed part manufactured by hot stamping. For example, by arranging thick steel plates in areas where strength is required and thin steel plates in other areas, it is possible to achieve a lightweight and strong formed part. Moreover, the tailored blank makes it easy to manufacture such a formed part with high functionality.

[0004] The steel sheet used as the material for tailored blanks is often Al-based plated steel sheet. Al-based plated steel sheet is a plated steel sheet with a plating layer mainly composed of Al on one or both sides. Since Al-based plating has a high melting point, it acts to prevent surface oxidation of the base steel sheet during hot stamping of tailored blanks.

[0005] However, when aluminum-plated steel sheets are butt-welded, aluminum gets mixed into the weld bead (weld metal). Excessive aluminum can soften the weld bead and reduce the joint strength of the weld. Therefore, various techniques have been proposed to suppress the mixing of aluminum into the weld bead of tailored blanks.

[0006] Patent Document 1 aims to provide a manufacturing process that prevents the formation of intermetallic regions, which are the initiation source of fracture, in a welded assembly. Patent Document 1 discloses a plate comprising a steel substrate and a precoat in contact with the substrate and consisting of a layer of an intermetallic compound on which a layer of an alloy is placed, characterized in that on at least one precoated surface of the plate, regions located around the periphery of the plate have the layer of alloy removed, and the precoat is an aluminum alloy or aluminum.

[0007] Patent Document 2 aims to provide a steel welded part with an aluminum or aluminum alloy coating that ensures the elongation resistance, corrosion resistance, and tensile strength of the welded joint after hot pressing. Patent Document 2 discloses a steel welded blank with an aluminum or aluminum alloy coating, the steel welded blank being composed of a steel substrate and a coating; the coating has an intermetallic compound alloy layer in contact with the substrate and a metal alloy layer on the intermetallic compound alloy layer; on at least one coating surface of the welded blank, the coating within the welded region of the welded blank is entirely removed, and an end face of the coating on the side of the coating within the removed welded region forms an angle β with a plane perpendicular to the surface of the substrate parallel to the weld seam, β being 5 to 60°; and the welded region of the steel welded blank from which the coating has been removed has a width of 0.4 mm to 1.0 mm.

[0008] On the other hand, it has been recently revealed that a small amount of Al mixed into the weld bead improves the corrosion resistance of the weld bead. In other words, it is preferable to mix an appropriate amount of Al into the weld bead of a tailored blank.

[0009] Patent Document 3 aims to provide a steel plate for butt welding, which maintains the post-painting corrosion resistance of the weld metal part formed during butt welding while suppressing a decrease in fatigue strength. Patent Document 3 discloses a steel plate including a first plating part in which an intermetallic compound layer and an aluminum plating layer are provided on the surface of the base steel plate in this order from the base steel plate side, a first exposed part in which the base steel plate is exposed, and a second plating part in which an intermetallic compound layer and an aluminum plating layer are provided on the surface of the base steel plate in this order from the base steel plate side, in which the first plating part, the first exposed part, the second plating part, and the edge of the steel plate are arranged in this order on at least one surface of the base steel plate in a first direction perpendicular to the thickness direction of the steel plate and extending from the first plating part toward one edge of the steel plate, and in which at least the first plating part, the first exposed part, and the edge of the steel plate are arranged in this order on the other surface of the base steel plate in the first direction. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 5237263 [Patent Document 2] Patent No. 6829312 [Patent Document 3] International Publication No. 2019 / 093440 Summary of the Invention [Problem to be solved by the invention]

[0011] According to the technology of Patent Document 3, the amount of Al mixed into the weld bead of a tailored blank can be optimized, and both the joint strength and the corrosion resistance of the weld bead can be increased. However, in order to obtain this effect using the technology of Patent Document 3, the first exposed portion needs to be formed with high machining accuracy. In order to facilitate the manufacture of tailored blanks, there is a demand for a technology that can optimize the amount of Al mixed into the weld bead even with low machining accuracy.

[0012] The present invention provides an Al-based plated steel sheet, a manufacturing method for a tailored blank, an Al-based plated steel sheet, and a tailored blank, which facilitates the optimization of the amount of Al mixed into the weld bead of a tailored blank. [Means for solving the problem]

[0013] The gist of the present invention is as follows.

[0014] (1) An Al-based plated steel sheet according to a first aspect of the present invention is an Al-based plated steel sheet comprising a base steel sheet and a plating layer mainly composed of Al provided on one or both surfaces of the base steel sheet, wherein the surface of the Al-based plated steel sheet on which the plating layer is provided is provided with a first region in which the plating layer is present and a second region in which the plating layer is thinner than the first region, the second region is provided in the vicinity of an end face of the Al-based plated steel sheet, and the length of the second region along the end face of the Al-based plated steel sheet is less than 20 mm. (2) In the plated steel sheet according to the above (1), preferably, the distance between the second region and the end face of the Al-based plated steel sheet is not less than 0 mm and not more than 1.5 mm. (3) Preferably, in the Al-based plated steel sheet described in (1) or (2) above, two or more of the second regions are provided, and the distance between the second regions along the end face of the Al-based plated steel sheet is 1 mm or more and 50 mm or less. (4) Preferably, in the Al-based plated steel sheet according to any one of (1) to (3) above, three or more of the second regions are provided, the intervals between the second regions along the end face of the Al-based plated steel sheet are approximately uniform, and the lengths of the second regions along the end face of the Al-based plated steel sheet are approximately uniform. (5) In the aluminum-based plated steel sheet according to any one of the above (1) to (4), preferably, a length of the second region along the end face of the aluminum-based plated steel sheet is 1 mm or more. (6) In the Al-based plated steel sheet according to any one of (1) to (5) above, preferably, the length of the second region along a direction perpendicular to the end face of the Al-based plated steel sheet is 0.1 mm or more and 1.5 mm or less. (7) Preferably, in the aluminum-based plated steel sheet according to any one of the above (1) to (6), the second region has a rectangular shape. (8) Preferably, in the Al-based plated steel sheet according to any one of the above (1) to (7), a third region, in which the plating layer is thinner than the first region, is provided on the surface of the Al-based plated steel sheet on which the plating layer is provided, the third region extends continuously along the end face of the Al-based plated steel sheet, and the second region is disposed between the third region and the end face of the Al-based plated steel sheet. (9) In the aluminum-based plated steel sheet according to (8) above, the second region and the third region are preferably in contact with each other. (10) Preferably, in the Al-based plated steel sheet according to any one of (1) to (9) above, the plating layer in the second region has a thickness of 0 mm. (11) Preferably, in the aluminum-based plated steel sheet according to any one of (8) to (10) above, the thickness of the plating layer in the third region is 0 mm.

[0015] (12) A method for producing a tailored blank according to a second aspect of the present invention includes a step of butt-welding end faces of a plurality of steel sheets, at least one of which is an Al-based plated steel sheet according to any one of the above (1) to (11). (13) Preferably, in the method for producing a tailored blank described above in (12), a toe of a weld bead formed by the butt welding step is disposed inside the second region of the Al-based plated steel sheet. (14) Preferably, in the method for manufacturing a tailored blank described in (12) above, at least one of the steel sheets is the Al-based plated steel sheet described in (8) above, and a toe of a weld bead formed by the butt welding step is disposed inside the second region or third region of the Al-based plated steel sheet.

[0016] (15) A method for producing an Al-based plated steel sheet according to a third aspect of the present invention is a method for producing an Al-based plated steel sheet according to any one of the above (1) to (11), comprising the steps of: preparing an Al-based plated original sheet comprising a base steel sheet and a plating layer mainly composed of Al provided over the entirety of one or both surfaces of the base steel sheet; and removing a part of the plating layer of the Al-based plated original sheet.

[0017] (16) A tailored blank according to a fourth aspect of the present invention is a tailored blank comprising a plurality of steel sheets and weld beads joining ends of the steel sheets, wherein one or more of the steel sheets is an Al-based plated steel sheet comprising a base steel sheet and a plating layer mainly composed of Al provided on one or both surfaces of the base steel sheet, wherein the surface of the Al-based plated steel sheet on which the plating layer is provided is provided with a first region in which the plating layer is present and a second region in which the plating layer is thinner than the first region, wherein the second region is in contact with the weld bead and the length of the second region along the extension direction of the weld bead is less than 20 mm. (17) Preferably, in the tailored blank described in (16) above, two or more of the second regions are provided, and the distance between the second regions along the extension direction of the weld bead is 1 mm or more and 50 mm or less. (18) Preferably, in the tailored blank described in (16) or (17) above, three or more of the second regions are provided, the spacing between the second regions along the extension direction of the weld bead is approximately uniform, and the lengths of the second regions along the extension direction of the weld bead are approximately uniform. Effect of the Invention

[0018] Effects of the Invention According to the present invention, it is possible to provide an Al-based plated steel sheet, a manufacturing method for a tailored blank, a manufacturing method for an Al-based plated steel sheet, and a tailored blank, which facilitate the optimization of the amount of Al mixed into the weld bead of a tailored blank. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1 is a perspective view of an example of an Al-based plated steel sheet. [Diagram 2] FIG. 2 is a perspective view of an example of two Al-based plated steel sheets whose end faces are butted against each other. [Diagram 3] FIG. 2 is a perspective view of an example of an Al-based plated steel sheet in the middle of welding a butt joint portion. [Figure 4] FIG. 2 is a perspective view of an example of a tailored blank. [Diagram 5] FIG. 2 is a plan view of an example of an Al-based plated steel sheet in the process of welding a butt joint. [Figure 6A] FIG. 2 is a plan view of an example of an Al-based plated steel sheet. [Figure 6B] FIG. 2 is a plan view of an example of an Al-based plated steel sheet. [Figure 6C] FIG. 2 is a plan view of an example of an Al-based plated steel sheet. [Figure 6D] FIG. 2 is a plan view of an example of an Al-based plated steel sheet. [Figure 7A] FIG. 2 is a schematic view of an Al-based plated steel sheet of Comparative Example 1. [Figure 7B] FIG. 2 is a schematic view of an Al-based plated steel sheet of Comparative Example 2. [Figure 7C] FIG. 2 is a schematic view of an Al-based plated steel sheet of Comparative Example 3. [Figure 7D] FIG. 1 is a schematic diagram of an Al-based plated steel sheet of Example 1. [Figure 7E] FIG. 2 is a schematic view of an Al-based plated steel sheet of Example 2. [Figure 7F] FIG. 1 is a schematic view of an Al-based plated steel sheet of Example 3. [Figure 7G] FIG. 1 is a schematic view of an Al-based plated steel sheet of Example 4. [Figure 7H] FIG. 1 is a schematic view of an Al-based plated steel sheet of Example 5. [Figure 7I] FIG. 1 is a schematic diagram of an Al-based plated steel sheet of Example 6. [Figure 7J] FIG. 1 is a schematic diagram of an Al-based plated steel sheet of Example 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (1. Aluminum-plated steel sheet) As shown in FIG. 1 etc., an Al-based plated steel sheet 1 according to a first embodiment of the present invention is an Al-based plated steel sheet 1 comprising a base steel sheet 11 and a plating layer 12 containing Al as a main component, which is provided on one or both surfaces of the base steel sheet 11, wherein a first region 121 in which the plating layer 12 is provided and a second region 122 in which the plating layer 12 is thinner than the first region 121 are provided on the surface of the Al-based plated steel sheet 1 on which the plating layer 12 is provided, the second region 122 is provided in the vicinity of an end face 13 of the Al-based plated steel sheet 1, and the length L of the second region 122 along the end face 13 of the Al-based plated steel sheet 1 is less than 20 mm.

[0021] (Base Steel Sheet 11) The Al-based plated steel sheet 1 according to this embodiment has a base steel sheet 11. The base steel sheet 11 is a steel sheet that will be the material of the tailored blank 2.

[0022] (Plating layer 12) The Al-based plated steel sheet 1 according to this embodiment has a plating layer 12 provided on one or both surfaces of a base steel sheet 11. The plating layer 12 is a plating layer whose main component is Al, i.e., an Al-based plating layer. The plating layer 12 whose main component is Al is a plating layer 12 in which the proportion of Al in the chemical composition of the plating layer 12 is the highest, or a plating layer 12 in which the concentration of Al in the chemical composition of the plating layer 12 is 50 mass % or more. Therefore, the plating layer 12 whose main component is Al (hereinafter simply referred to as "plating layer 12") can contain alloy elements other than Al.

[0023] (First region 121 and second region 122) The surface of the Al-based plated steel sheet 1 according to this embodiment has a first region 121 and a second region 122. Note that "the surface of the Al-based plated steel sheet 1" refers to the surface on which the plating layer 12 is provided. The first region 121 is the region where the plating layer 12 is present. The second region 122 refers to the region where the plating layer 12 is thinner than the first region 121. Note that the second region 122 also includes a region where the plating layer 12 is 0 mm thick. The region where the plating layer 12 is 0 mm thick refers to a region where the plating layer 12 is not present and the base steel sheet 11 is exposed.

[0024] When the plating layer 12 is provided on both sides of the Al-based plated steel sheet 1, the second region 122 may be provided on at least one side of the Al-based plated steel sheet 1. As long as the second region 122 is provided on at least one side of the Al-based plated steel sheet 1, it can exhibit the effects described below.

[0025] The second region 122 is provided in the vicinity of the end face 13 of the Al-based plated steel sheet 1. As exemplified in FIG. 1 etc., the second region 122 may be in contact with the end face 13. That is, the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 may be 0 mm. On the other hand, as exemplified in FIG. 6A , the second region 122 may be separated from the end face 13. When the Al-based plated steel sheet 1 is used to manufacture a tailored blank 2, the end face 13 adjacent to which the second region 122 is provided is butt-welded. Then, a part or the whole of the second region 122 is taken into the weld bead 21.

[0026] The distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 is not particularly specified. As described later, the second region 122 is provided in order to control the amount of Al mixed into the molten pool 3. Therefore, at least a part of the second region 122 needs to be provided inside the portion to be welded. The portion to be welded is a region that will become the weld bead 21 after welding. The distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 may be determined depending on the portion to be welded. A suitable example of the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 will be described later.

[0027] (Length L of second region 122) The length L of the second region 122 along the end surface 13 of the Al-based plated steel sheet 1 (hereinafter simply referred to as "the length L of the second region 122") is less than 20 mm. The length L of the second region 122 may be 18 mm or less, 15 mm or less, or 12 mm or less. The lower limit of the length L of the second region 122 is not particularly limited and may be any value greater than 0 mm. When there are multiple second regions 122, the lengths L of the multiple second regions 122 may be approximately the same or different. Note that approximately the same in this specification means that all values ​​are within the range of the average value ±10%.

[0028] In addition, the "end surface 13" in the specification of the length L of the second region 122 refers to the end surface 13 of the Al-based plated steel sheet 1, which is disposed near the second region 122 and is butt-welded when manufacturing the tailored blank 2. In the Al-based plated steel sheet 1 illustrated in FIG. 1, the length L of the second region 122 along the end surface 13 on the lower left side of the paper surface, which is indicated by reference numeral 13, is set to 20 mm or less. As illustrated in FIG. 1 and the like, when a plurality of second regions 122 are arranged in the vicinity of one end surface 13, the end surface 13 can be regarded as the end surface 13 to be butt-welded. When the Al-based plated steel sheet 1 is provided with a third region 123 as illustrated in FIG. 6C and FIG. 6D, the end surface 13 provided with the third region 123 can be regarded as the end surface 13 to be butt-welded. Details of the third region 123 will be described later.

[0029] (Action and effect) The Al-based plated steel sheet 1 according to this embodiment is used for manufacturing a tailored blank 2. When manufacturing the tailored blank 2, end faces 13 of two Al-based plated steel sheets 1 are butted together as shown in FIG. 2. Then, as shown in FIG. 3, the butted portion is heated by welding heat to form a molten pool 3. The molten pool 3 is a pool of molten metal formed by heat during welding. Note that welding means (laser, welding torch, etc.) are omitted in FIG. 3. The arrow in FIG. 3 indicates the welding direction. The molten pool 3 solidifies to become a weld bead 21. When welding of the end faces 13 of the two Al-based plated steel sheets 1 is completed, a tailored blank 2 shown in FIG. 4 is obtained. The butted end faces 13 of the Al-based plated steel sheets 1 become a weld line during butt welding.

[0030] The Al-based plated steel sheet 1 according to this embodiment has, on its surface, a second region 122 in which the plating layer 12 is thin. The second region 122 controls the Al content of a weld bead 21 of a tailored blank 2 obtained by welding the Al-based plated steel sheet 1 within an appropriate range.

[0031] The second region 122 is provided in the vicinity of the end face 13 of the Al-based plated steel sheet 1. Therefore, as shown in Fig. 5, the second region 122 is taken into the molten pool 3 when the butt portion of the end face 13 is welded. Therefore, the second region 122, in which the plating layer 12 is thin, reduces the amount of the plating layer 12 that is taken into the molten pool 3. As a result, the second region 122 reduces the Al concentration in the weld bead 21 that is formed when the molten pool 3 solidifies.

[0032] However, Al contained in weld bead 21 serves to improve the corrosion resistance of weld bead 21. It is preferable that weld bead 21 incorporates a small amount of plating layer 12.

[0033] Therefore, in the hot-dip galvanized steel sheet according to this embodiment, the length L of the second region 122 is set to be less than 20 mm. In general, the length of the molten pool 3 along the weld line exceeds 20 mm, and therefore the length L of the second region 122 is shorter than the length of the molten pool 3 along the weld line. This prevents an extreme decrease in the Al concentration in the weld bead 21. If the length L of the second region 122 exceeds the length of the molten pool 3, little or no coating layer 12 will be mixed into the molten pool 3 in the second region 122. As a result, the Al concentration in the weld bead 21 becomes significantly insufficient, and the corrosion resistance of the weld bead 21 is impaired.

[0034] Moreover, the second region 122 of the Al-based plated steel sheet 1 according to the present embodiment has an advantage that high dimensional accuracy is not required. In the prior art, an attempt has been made to control the amount of inflow into the weld bead 21 by thinly removing the plating layer 12 and leaving a thin portion. However, this method requires highly accurate control of the depth to which the plating layer 12 is removed. In the prior art, an attempt has been made to control the amount of inflow into the weld bead 21 by removing the plating layer 12 in a strip shape and leaving the plating layer 12 between the strip-shaped plating removal portion and the end face 13. However, this method also requires highly accurate control of the width of the plating layer 12 left at the tip of the steel sheet. Therefore, in the prior art, it is difficult to remove the plating layer 12. On the other hand, the second region 122 of the Al-based plated steel sheet 1 according to the present embodiment can be easily manufactured because high dimensional accuracy is not required.

[0035] The most basic aspect of the Al-based plated steel sheet 1 according to this embodiment has been described above. A more preferred aspect will now be described.

[0036] (Distance D between second region 122 and end surface 13 of Al-based plated steel sheet 1) In the Al-based plated steel sheet 1 illustrated in Fig. 1, the second region 122 is in contact with the end surface 13 of the Al-based plated steel sheet 1. That is, the distance D between the second region 122 and the end surface 13 of the Al-based plated steel sheet 1 is 0 mm. On the other hand, as shown in Fig. 6A, the distance D between the second region 122 and the end surface 13 of the Al-based plated steel sheet 1 may be more than 0 mm. Even if the distance D between the second region 122 and the end surface 13 of the Al-based plated steel sheet 1 is more than 0 mm, the second region 122 is taken into the molten pool 3, thereby obtaining an effect of controlling the Al content of the weld bead 21. The distance D between the second region 122 and the end surface 13 of the Al-based plated steel sheet 1 may be 0.1 mm or more, 0.5 mm or more, 1.0 mm or more, or 2.0 mm or more.

[0037] The upper limit of the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 can be appropriately selected according to the thickness of the weld bead 21 provided on the Al-based plated steel sheet 1. The thickness of the weld bead 21 of a typical tailored blank 2 is about 2.0 mm at most. Therefore, the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 may be 1.5 mm or less, 1.0 mm or less, or 0.5 mm or less. However, there are cases where the weld bead 21 is made thicker than usual by weaving welding or the like. Therefore, the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 may be a value exceeding the above-mentioned preferable upper limit. When there are two or more second regions 122, the distance D between the second region 122 and the end face 13 of the Al-based plated steel sheet 1 may be substantially the same in all the second regions 122, or may vary.

[0038] (Number and Spacing of Second Regions 122) There is no particular limitation on the number of second regions 122 provided in the Al-based plated steel sheet 1. As shown in Fig. 6A, only one second region 122 may be provided in the Al-based plated steel sheet 1. By providing the second regions 122 only in portions of the tailored blank 2 where it is required to increase the strength of the weld bead 21 and not providing the second regions 122 in other portions, the functionality of the tailored blank 2 can be improved.

[0039] On the other hand, as shown in FIG. 1, two or more second regions 122 may be provided in the Al-based plated steel sheet 1. In this case, the distance S between the second regions 122 along the end face 13 of the Al-based plated steel sheet 1 (hereinafter simply referred to as the "distance S between the second regions 122") is not particularly limited. The distance S between the second regions 122 can be appropriately selected according to the amount of Al required for the weld bead 21. A suitable example of the distance S between the second regions 122 is 1 mm or more and 50 mm or less. The distance S between the second regions 122 may be 2 mm or more, 5 mm or more, or 10 mm or more. The distance S between the second regions 122 may be 40 mm or less, 30 mm or less, or 20 mm or less.

[0040] On the other hand, the interval S between the second regions 122 may be allowed to exceed 50 mm. When the interval S between the second regions 122 is long, the Al concentration of the weld bead 21 is high between the second regions 122, and an area with low strength is locally formed. However, the Al concentration of the weld bead 21 in the second regions 122 and in the area close thereto is low, and the area has sufficient strength. As a result, even if the interval S between the second regions 122 exceeds 50 mm, the tailored blank can exhibit the necessary strength. In addition, when the interval S between the second regions 122 is large, the weld bead 21 between the second regions 122 exhibits higher corrosion resistance than the weld bead 21 in the vicinity of the second regions 122. From the viewpoint of improving the corrosion resistance of the weld bead 21, it is preferable to increase the interval S between the second regions 122.

[0041] When three or more second regions 122 are provided in the Al-based plated steel sheet 1, the second regions 122 may be provided at regular intervals. That is, as illustrated in Fig. 1, the intervals S between all of the second regions may be substantially the same. In this case, it is preferable that not only the intervals S between the second regions but also the lengths L of all of the second regions 122 are substantially the same. This makes it possible to uniform the amount of plating layer 12 flowing into the weld bead 21 along the weld line direction of the weld bead 21.

[0042] On the other hand, the spacing S between the second regions 122 can be narrowed in portions where increased strength of the weld bead 21 is required, and the spacing S between the second regions 122 can be widened in portions where corrosion resistance is required. In this case, the spacings S1, S2, S3... between the second regions will not be constant, and therefore the amount of plating layer 12 that flows into the weld bead 21 will not be uniform. However, by changing the spacing S between the second regions in accordance with the structure of the tailored blank 2, the functionality of the tailored blank 2 can be improved.

[0043] (Lower limit value of length L of second region 122 along end surface 13 of Al-based plated steel sheet 1) The lower limit of the length L of the second region 122 may be any value greater than 0 mm. Even if the length L of the second region 122 is short, it is possible to suppress the amount of the coating layer 12 flowing into the molten pool 3 by increasing the number of the second regions 122 and narrowing the interval S between the second regions. On the other hand, from the viewpoint of reducing the manufacturing cost of the second regions 122, it is preferable to increase the length L of the second region 122 and reduce the number of the second regions 122. For example, the length L of the second region 122 may be 1 mm or more, 5 mm or more, or 10 mm or more. When there are two or more second regions 122, the length L of each of the second regions 122 may be substantially the same or may vary.

[0044] (Length of the second region 122 along a direction perpendicular to the end surface 13 of the Al-based plated steel sheet 1) The length of the second region 122 along the direction perpendicular to the end face 13 of the Al-based plated steel sheet 1 (hereinafter referred to as "width W1 of the second region 122") is not particularly limited. As illustrated in FIG. 5, the toe of the weld bead 21 is preferably located inside the second region 122 (or a third region 123 described later). Therefore, the width W1 of the second region 122 can be appropriately selected according to the thickness of the weld bead 21. The width W1 of the second region 122 is preferably 0.1 mm or more, 0.3 mm or more, or 0.5 mm or more. The width W1 of the second region 122 is preferably 1.5 mm or less, 1.2 mm or less, or 1.0 mm or less. When there are two or more second regions 122, the width W1 of the second region 122 may be substantially the same in all the second regions 122 or may vary.

[0045] (Shape of second region 122) As illustrated in FIG. 1, the second region 122 preferably has a rectangular shape. This makes it easy to form the second region 122. On the other hand, the second region 122 may have a non-rectangular shape such as an ellipse. For example, as illustrated in FIG. 6B, the second region 122 may be an ellipse. The second region 122 may have various shapes such as a parallelogram, a circle, and a trapezoid. In FIG. 1, the outer edge of the rectangular second region 122 facing the end face 13 is parallel to the end face 13. However, the angle between the outer edge of the second region 122 and the end face 13 of the Al-based plated steel sheet 1 can also be appropriately selected depending on the configuration of the tailored blank 2. When there are two or more second regions 122, the shapes of the second regions 122 may be the same or different in all the second regions 122.

[0046] When the second region 122 is not rectangular along the end face, the length L, width W1, and interval S of the second region 122 are defined as follows. The length L of the second region 122 is the maximum length of the second region 122 measured parallel to the end face. In other words, the maximum length of an imaginary line inside the second region 122 and parallel to the end face is the length L of the second region 122. For example, when the second region 122 has an elliptical shape with its minor axis parallel to the end face as shown in Fig. 6B, the length L of the second region 122 is the length of the minor axis of the ellipse. The width W1 of the second region 122 is the maximum value of the width of the second region 122 measured perpendicular to the end face. In other words, the maximum value of the length of an imaginary line inside the second region 122 and perpendicular to the end face is the width W1 of the second region 122. For example, when the second region 122 has an elliptical shape with its major axis perpendicular to the end face as shown in Fig. 6B, the width W1 of the second region 122 is the length of the major axis of the ellipse. The spacing S between the two second regions 122 is the minimum spacing, measured parallel to the end surface, between the second regions 122. In other words, the minimum length of an imaginary line that is between the second regions 122 and parallel to the end surface is the spacing S between the second regions 122.

[0047] (Third Area 123) The Al-based plated steel sheet 1 may further include a third region 123 as illustrated in Fig. 6C and Fig. 6D. The third region 123 is a region in which the coating layer 12 is thinner than the first region 121 (or the coating layer 12 is not present), similar to the second region 122. However, unlike the second region 122, the third region 123 extends continuously along the end surface 13 of the Al-based plated steel sheet 1. The length of the third region 123 along the end surface 13 of the Al-based plated steel sheet 1 is more than 20 mm. The third region 123 is disposed closer to the center of the Al-based plated steel sheet 1 than the second region 122. That is, the second region 122 is disposed between the third region 123 and the end surface 13 of the Al-based plated steel sheet 1. The third region 123 makes it easier to control the amount of the coating layer 12 flowing into the molten pool 3.

[0048] As illustrated in FIG. 6C, the second region 122 and the third region 123 may be in contact with each other. On the other hand, as illustrated in FIG. 6D, the second region 122 and the third region 123 may be spaced apart from each other. In either case, the effect of making it easier to control the amount of the coating layer 12 flowing into the molten pool 3 can be obtained. When there are a plurality of second regions 122, some of the second regions 122 may be in contact with the third region 123 and some of the second regions 122 may be spaced apart from each other. By changing the distance between the second region 122 and the third region 123, the amount of Al flowing into the molten pool can be controlled. When it is desired to reduce the amount of Al in the weld bead 21 to increase the joining strength, it is preferable that the second region 122 and the third region 123 are in contact with each other. On the other hand, when it is desired to increase the amount of Al in the weld bead 21 to increase the corrosion resistance, it is preferable that the second region 122 and the third region 123 are spaced apart from each other.

[0049] When the second region 122 and the third region 123 are in contact with each other, a virtual line along the edge of the third region 123 on the end face 13 side may be regarded as a boundary between the second region 122 and the third region 123 for convenience. When measuring the width W1, etc. of the second region 122, the virtual line may be regarded as the edge of the second region 122.

[0050] The thickness of the plating layer 12 in the second region 122 and the thickness of the plating layer 12 in the third region 123 are not particularly limited. The thickness of the plating layer 12 in the second region 122 and the thickness of the plating layer 12 in the third region 123 may be 0 mm. That is, the plating layer 12 may be completely removed in the second region 122 or the third region 123, and the base steel sheet 11 may be exposed. From the viewpoint of ease of production, it is preferable that the plating layer 12 is completely removed in the second region 122 and / or the third region 123.

[0051] On the other hand, the plating layer 12 may remain thinly in the second region 122 or the third region 123. Even in this case, the second region 122 or the third region 123 can exert the effect of controlling the Al content of the weld bead 21. For example, the value t2 / t1 calculated from the thickness t1 of the plating layer 12 in the first region 121 and the thickness t2 of the plating layer 12 in the second region 122 may be set to a range of 0.10 to 0.90. t2 / t1 may be set to 0.15 or more, 0.20 or more, or 0.40 or more. t2 / t1 may be set to 0.85 or less, 0.80 or less, or 0.60 or less. In addition, the value t3 / t1 calculated from the thickness t1 of the plating layer 12 in the first region 121 and the thickness t3 of the plating layer 12 in the third region 123 may be set to a range of 0.10 to 0.90. t3 / t1 may be set to 0.15 or more, 0.20 or more, or 0.40 or more. t3 / t1 may be set to 0.85 or less, 0.80 or less, or 0.60 or less.

[0052] (2. Manufacturing method of tailored blank 2) Next, a method for manufacturing a tailored blank 2 according to a second aspect of the present invention will be described. The method for manufacturing a tailored blank 2 according to this embodiment includes a step of butt-welding end faces 13 of a plurality of steel sheets, at least one of which is the Al-based plated steel sheet 1 according to this embodiment.

[0053] According to the tailored blank 2 of this embodiment, the Al content of the weld bead 21 can be easily controlled by using the second region 122. Therefore, according to the tailored blank 2 of this embodiment, it is possible to manufacture a tailored blank 2 having a weld bead 21 that has both corrosion resistance and bonding strength.

[0054] During butt welding, as shown in Fig. 3 to Fig. 5, it is preferable to dispose the toe of a weld bead 21 formed by the butt welding process inside the second region 122 or the third region 123 of the Al-based plated steel sheet 1. The toe refers to the point where the surface of the base material (Al-based plated steel sheet 1) and the surface of the weld bead 21 intersect. This makes it possible to prevent the plating layer 12 from concentrating at the toe of the weld bead 21, and further increase the bonding strength of the weld bead 21.

[0055] (3. Method for producing Al-based plated steel sheet 1) Next, a description will be given of a manufacturing method of the Al-based plated steel sheet 1 according to the third aspect of the present invention. The manufacturing method of the Al-based plated steel sheet 1 according to this embodiment is the same as the manufacturing method of the Al-based plated steel sheet 1 according to the first aspect described above, and includes a step of preparing an Al-based plated original sheet including a base steel sheet 11 and a plating layer 12 mainly composed of Al provided over the entirety of one or both surfaces of the base steel sheet 11, and a step of removing a part of the plating layer of the Al-based plated original sheet.

[0056] The Al-based plated base sheet includes a base steel sheet 11 and a plating layer 12 containing Al as a main component. Unlike the plating layer 12 of the Al-based plated steel sheet 1 according to the first embodiment, the plating layer 12 of the Al-based plated base sheet is provided over the entire surface of one or both surfaces of the base steel sheet 11. That is, the Al-based plated base sheet does not include the second region 122 and the third region 123 shown in Fig. 1 and the like.

[0057] Except for the absence of the second region 122 and the like, the plating layer 12 of the Al-based plated base sheet is the same as the plating layer 12 of the Al-based plated steel sheet 1 according to the first embodiment. A plated steel sheet manufactured by a known method such as hot-dip plating can be used as the Al-based plated base sheet. The manufacturing method of the Al-based plated steel sheet 1 may further include a plating step for forming the plating layer 12 on the surface of the base steel sheet 11. On the other hand, a commercially available plated steel sheet may be purchased and used as the Al-based plated base sheet.

[0058] The method for producing the Al-based plated steel sheet 1 according to the third embodiment includes a step of removing a part of the plating layer 12 of the Al-based plated original sheet. By removing the part of the plating layer 12, the second region 122 of the Al-based plated steel sheet 1 according to the first embodiment can be formed. Moreover, the step of removing the part of the plating layer 12 of the Al-based plated original sheet can also form the third region 123 of the Al-based plated steel sheet 1 according to the first embodiment.

[0059] There is no limitation on the means for removing a portion of the plating layer 12. The portion of the plating layer 12 may be removed by mechanical means such as cutting and grinding. The portion of the plating layer 12 may be removed by using a laser beam.

[0060] The plating layer 12 may be removed throughout its entire thickness to expose the base steel sheet 11. Alternatively, only the surface layer of the plating layer 12 may be removed to reduce the thickness of the plating layer 12 without exposing the base steel sheet 11. The removal depth of the plating layer 12 can be appropriately changed by known means.

[0061] (4. Tailored Blank 2) Next, a tailored blank 2 according to a fourth aspect of the present invention will be described. The tailored blank 2 according to this embodiment is a tailored blank comprising a plurality of steel sheets and weld beads joining the ends of the steel sheets, in which one or more of the steel sheets is an Al-based plated steel sheet comprising a base steel sheet and a plating layer containing Al as a main component provided on one or both surfaces of the base steel sheet, in which a first region in which the plating layer is provided and a second region in which the plating layer is thinner than the first region are provided on the surface of the Al-based plated steel sheet on which the plating layer is provided, the second region is in contact with the weld bead, and the length of the second region along the extending direction of the weld bead is less than 20 mm.

[0062] The tailored blank 2 is obtained by butting the end faces of multiple steel plates together and welding them. The tailored blank 2 is a type of butt welded joint. The multiple steel plates may differ in one or more of various properties such as plate thickness, strength, and surface treatment. This allows the tailored blank to improve the functionality of the formed part manufactured by hot stamping.

[0063] In the tailored blank 2, at least one of the multiple steel sheets is an Al-based plated steel sheet. The Al-based plated steel sheet includes a base steel sheet 11 and a plating layer containing Al as a main component, which is provided on one or both surfaces of the base steel sheet. The Al-based plated steel sheet of the tailored blank 2 is obtained by butt-welding an end surface 13 of the Al-based plated steel sheet 1 according to the first embodiment to an end surface of another steel sheet. The base steel sheet and plating layer of the Al-based plated steel sheet of the tailored blank 2 can be the same as the base steel sheet 11 and plating layer 12 of the Al-based plated steel sheet 1 according to the first embodiment.

[0064] In the Al-based plated steel sheet of the tailored blank 2, a first region where the plated layer is provided and a second region where the plated layer is thinner than the first region are provided on the surface where the plated layer is provided. The first region of the Al-based plated steel sheet of the tailored blank 2 can be the same as the first region 121 of the Al-based plated steel sheet 1 according to the first embodiment.

[0065] The second region of the Al-based plated steel sheet of the tailored blank 2 is in contact with the weld bead 21. By butt-welding the end face 13 of the Al-based plated steel sheet 1 according to the first embodiment to an end face of another steel sheet so that the weld bead 21 grows to the second region, the second region can be brought into contact with the weld bead 21.

[0066] Except for the position, the second region of the Al-based plated steel sheet of the tailored blank 2 can be substantially the same as the second region 122 of the Al-based plated steel sheet 1 according to the first embodiment. Moreover, various aspects of the Al-based plated steel sheet 1 according to the first embodiment can be applied to the Al-based plated steel sheet of the tailored blank 2. In this case, the term "end surface 13 of the Al-based plated steel sheet 1" defining the Al-based plated steel sheet 1 according to the first embodiment can be read as "weld bead 21" or "extending direction of the weld bead 21".

[0067] For example, in the Al-based plated steel sheet 1 according to the first embodiment, the length of the second region 122 along the end face 13 of the Al-based plated steel sheet 1 is set to be less than 20 mm. In the Al-based plated steel sheet of the tailored blank 2, the length of the second region along the extending direction of the weld bead 21 is set to be less than 20 mm.

[0068] Similar to the Al-based plated steel sheet 1 according to the first embodiment, two or more second regions may be provided on the surface of the Al-based plated steel sheet of the tailored blank 2. In the tailored blank 2, the distance between the second regions along the extending direction of the weld bead may be 1 mm or more and 50 mm or less.

[0069] Similar to the Al-based plated steel sheet 1 according to the first embodiment, three or more second regions may be provided on the surface of the Al-based plated steel sheet of the tailored blank 2. In the tailored blank 2, the intervals between the second regions along the extension direction of the weld bead may be approximately uniform. Furthermore, in the tailored blank 2, the lengths of the second regions along the extension direction of the weld bead may be approximately uniform.

[0070] Although the embodiment of the present invention has been described above, the present invention is not limited thereto and can be appropriately modified without departing from the technical idea of ​​the invention. More preferred examples of the Al-based plated steel sheet 1, the manufacturing method of the tailored blank 2, the manufacturing method of the Al-based plated steel sheet 1, and the tailored blank 2 according to the present embodiment will be described below. Unless otherwise specified, the preferred examples described below are applicable to all of the Al-based plated steel sheet 1, the manufacturing method of the tailored blank 2, the manufacturing method of the Al-based plated steel sheet 1, and the tailored blank 2.

[0071] (Base Steel Sheet 11) The configuration of the base steel sheet 11 is not particularly limited, but a suitable example of the configuration of the base steel sheet 11 will be described below.

[0072] The base steel sheet 11 is obtained by a normal manufacturing method including, for example, hot rolling, cold rolling, heat treatment, etc. The base steel sheet 11 may be a hot-rolled steel sheet or a cold-rolled steel sheet.

[0073] The thickness of the base steel sheet 11 can be appropriately selected depending on the application of the Al-based plated steel sheet 1. When the application of the Al-based plated steel sheet 1 is the manufacture of tailored blanks 2, the thickness of the base steel sheet 11 is preferably, for example, 0.8 mm or more, 1.0 mm or more, or 1.2 mm or more. In this case, the thickness of the base steel sheet 11 is preferably, for example, 4.0 mm or less, 3.0 mm or less, or 2.0 mm or less.

[0074] Suitable examples of the chemical components of the base steel sheet 11 are, in mass %, C: 0.02% to 0.58%, Mn: 0.20% to 3.00%, Al: 0.005% to 0.20%, Ti: 0% to 0.20%, Nb: 0% to 0.20%, V: 0% to 1.0%, W: 0% to 1.0%, Cr: 0% to 1.0%, Mo: 0% to 1.0%, Cu: 0% to The aluminum-based plated steel sheet 11 includes the following components: 1.0%, Ni: 0% to 1.0%, B: 0% to 0.0100%, Mg: 0% to 0.05%, Ca: 0% to 0.05%, REM: 0% to 0.05%, Bi: 0% to 0.05%, Si: 0% to 2.00%, P: 0.03% or less, S: 0.010% or less, N: 0.010% or less, and the balance: Fe and impurities. The impurities refer to components that are mixed in due to various factors in raw materials such as ores or scraps, or in the manufacturing process, during industrial production of steel materials, and are allowed within a range that does not adversely affect the Al-based plated steel sheet 1 according to the present embodiment. The chemical components of the base steel sheet 11 can be measured according to JIS G 0321:2017 "Methods for analyzing steel products and their permissible variations".

[0075] The tensile strength of the base steel sheet 11 can be appropriately selected depending on the application of the Al-based plated steel sheet 1. For example, when the application of the Al-based plated steel sheet 1 is to ensure the strength of a press-molded product, the tensile strength of the base steel sheet 11 is preferably 1300 MPa or more, 1500 MPa or more, or 1800 MPa or more. On the other hand, when the application of the Al-based plated steel sheet 1 is to manufacture an exterior material for ensuring the design of a press-molded product, the tensile strength of the base steel sheet 11 is preferably 300 MPa or more, 400 MPa or more, or 500 MPa or more. The tensile strength of the base steel sheet 11 can be measured according to JIS Z 2241:2011 "Metallic Material Tensile Test Method".

[0076] The Vickers hardness of the base steel sheet 11 can be appropriately selected depending on the application of the Al-based plated steel sheet 1. For example, when the application of the Al-based plated steel sheet 1 is to ensure the strength of a press-molded product, the Vickers hardness of the base steel sheet 11 is preferably 400Hv or more, 450Hv or more, or 500Hv or more. On the other hand, when the application of the Al-based plated steel sheet 1 is to manufacture an exterior material for ensuring the design of a press-molded product, the Vickers hardness of the base steel sheet 11 is preferably 90Hv or more, 120Hv or more, or 150Hv or more. The hardness of the base steel sheet 11 can be measured according to JIS Z 2244:2009 "Vickers hardness test - Test method". The test force for measuring the Vickers hardness of the base steel sheet 11 is 500g.

[0077] (Plating layer 12) Examples of alloy elements other than Al contained in the plating layer 12 include Si and Fe. Si and Fe have the function of improving the corrosion resistance and the like of the plating layer 12. One suitable example of the plating layer 12 has a chemical composition containing, by mass%, 5% to 12% Si, with the balance containing aluminum and impurities. Another suitable example of the plating layer 12 has a chemical composition containing, by mass%, 5% to 12% Si and 2% to 4% Fe, with the balance containing aluminum and impurities.

[0078] The thickness and coating weight of the plating layer 12 are not particularly limited. A suitable example of the thickness of the plating layer 12 is 8 μm to 50 μm. A suitable example of the coating weight of the plating layer 12 per side is 30 g / m 2 ~120g / m 2 It is.

[0079] (Intermetallic compound layer) The plating layer 12 may have an intermetallic compound layer. The intermetallic compound layer is formed along the interface between the plating layer 12 and the base steel sheet 11. The intermetallic compound layer is mainly composed of Fe x Al y (x and y are numbers equal to or greater than 1). When the plating layer 12 contains Si, the intermetallic compound layer is preferably formed of a plurality of types of compounds represented by Fe x Al y and Fe xAl y S z It is preferable that the insulating layer is formed of a plurality of types of compounds represented by the formula (x, y, and z each represent a number of 1 or more).

[0080] The thickness of the intermetallic compound layer is not particularly limited, but may be, for example, an average thickness of 3 μm or more, and preferably 4 μm or more. The thickness of the intermetallic compound layer may be, for example, an average thickness of 10 μm or less, and preferably 8 μm or less. The thickness of the intermetallic compound layer refers to the average thickness in the first region 121. The thickness of the intermetallic compound layer can be controlled by the temperature and immersion time of the molten metal bath mainly containing aluminum.

[0081] (Size and position of third region 123) The third region 123 may be formed across the entire width of the Al-based plated steel sheet 1, as illustrated in Figures 6C and 6D. Alternatively, the third region 123 may be formed intermittently. In this case, the length of the third region 123 along the end surface 13 of the Al-based plated steel sheet 1 may be any value greater than 20 mm.

[0082] The distance D between the third region 123 and the end face of the Al-based plated steel sheet 1 is not particularly limited. For example, the distance D between the third region 123 and the end face of the Al-based plated steel sheet 1 may be within a range of 0.1 mm or more and 1.5 mm or less. The length of the third region 123 along the direction perpendicular to the end face 13 of the Al-based plated steel sheet 1 (i.e., the width of the third region 123) is also not particularly limited. For example, the width of the third region 123 may be within a range of 0.2 mm or more and 2.5 mm or less. The position and width of the third region 123 can be appropriately selected so that the toe of the weld bead 21 is disposed inside the second region 122 or the third region 123.

[0083] (Positional relationship of second region 122 during welding) When manufacturing the tailored blank 2, at least one base steel sheet may be the Al-based plated steel sheet 1 according to this embodiment. Even when an Al-based plated steel sheet 1 having the second region 122 and an Al-based plated steel sheet 1 not having the second region 122 are butt-welded as illustrated in Fig. 5, the second region 122 can exert an effect of preferably controlling the Al content of the weld bead 21.

[0084] On the other hand, as illustrated in Fig. 2 to Fig. 4, the two base steel sheets may be the Al-based plated steel sheets 1 according to this embodiment. In this case, the positional relationship of the second region 122 is not particularly limited and can be appropriately set according to the configuration of the tailored blank 2. For example, when it is necessary to uniformize the Al amount of the weld bead 21 along the weld line direction, it is preferable to adopt the configuration illustrated in Fig. 2. In the configuration illustrated in Fig. 2, the second region 122 of one Al-based plated steel sheet 1 is butted against the first region 121 of the other Al-based plated steel sheet 1. This makes it possible to uniformize the amount of the plating layer 12 flowing into the molten pool 3.

[0085] (Welding method) The welding method for manufacturing the tailored blank 2 is not particularly limited. Suitable examples of the welding method include laser welding and arc welding. The chemical composition of the weld bead 21 may be adjusted by adding a filler material such as a filler wire to the molten pool 3. The welding conditions are also not particularly limited. The welding conditions can be appropriately selected depending on the thickness, chemical composition, etc. of the Al-based plated steel sheet 1.

[0086] (Method of forming second region 122 and third region 123) The method of forming the second region 122 and the third region 123 is not particularly limited. The plating layer 12 may be formed on the entire surface of the base steel sheet 11, and then the plating layer 12 may be removed. In this case, the means for removing the plating layer 12 includes cutting, grinding, and the like. The plating layer 12 may also be removed by laser processing such as laser gouging. On the other hand, the plating layer 12 may not be formed in the second region 122 and the third region 123 of the base steel sheet 11, and the plating layer 12 may be formed only in the first region 121. For example, the second region 122 and the third region 123 of the base steel sheet 11 are masked, and then the plating layer 12 is formed, thereby making it possible to manufacture an Al-based plated steel sheet 1 having a suitable second region 122 and third region 123. EXAMPLES

[0087] The effects of one embodiment of the present invention will be explained more specifically with reference to an example. However, the conditions in the example are merely an example of conditions adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to this example of conditions. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0088] Tailored blanks were manufactured by butt welding various Al-based plated steel sheets having the shapes shown in Tables 1 and 2. Schematic diagrams of these Al-based plated steel sheets are shown in Figs. 7A to 7J. Note that these drawings do not accurately depict the shapes of the samples. The values ​​shown in the tables are the actual values. For example, the number of second regions 122 arranged differs between the tables and the drawings, but the number shown in the tables is the actual number.

[0089] Comparative Example 1 shown in FIG. 7A is a conventional example that does not have the second region 122 and the third region 123.

[0090] 7B is a conventional example having only a plating-removed portion spaced apart from the end face of the Al-based plated steel sheet and extending continuously along the end face. That is, Comparative Example 2 is an Al-based plated steel sheet having only a third region 123 without a second region 122.

[0091] Comparative Example 3 shown in Fig. 7C has a plurality of rectangular second regions 122 in contact with the end face, but these are comparative examples in which the length L is excessive. All the second regions 122 in Comparative Example 3 have the same shape. Moreover, the second regions 122 in Comparative Example 3 are provided at equal intervals.

[0092] Example 1 shown in FIG. 7D is an example having one rectangular second region 122 in contact with the end face.

[0093] Example 2 shown in Fig. 7E is an example having a plurality of rectangular second regions 122 in contact with the end face. The shapes of all the second regions 122 in Example 2 were the same. Moreover, the second regions 122 in Example 2 were provided at non-equidistant intervals. Specifically, S1 and S2 shown in Table 1 were alternately adopted as the intervals between the second regions 122.

[0094] 7F is an example having a plurality of rectangular second regions 122 in contact with the end surface. The shapes of all the second regions 122 in Example 3 were the same. The second regions 122 in Example 3 were provided at equal intervals.

[0095] Example 4 shown in Fig. 7G is an example having a plurality of rectangular second regions 122 in contact with the end face, and further provided with third regions 123. The shapes of all the second regions 122 in Example 4 were the same. The second regions 122 in Example 4 were provided at equal intervals.

[0096] 7H shows an embodiment having a plurality of rectangular second regions 122 spaced apart from the end face. The shapes of all the second regions 122 in the embodiment 5 are the same. The second regions 122 in the embodiment 5 are provided at equal intervals.

[0097] Example 6 shown in Fig. 7I is an example having a plurality of elliptical second regions 122 spaced apart from the end face. The shapes of all the second regions 122 in Example 6 were the same. The second regions 122 in Example 6 were provided at equal intervals.

[0098] Example 7 shown in Fig. 7J is an example having a plurality of rectangular second regions 122 in contact with the end surface, similar to Example 3. The shapes of all second regions 122 in Example 7 were set to the same value. The second regions 122 in Example 7 were provided at equal intervals. However, while in Example 3 the plating was removed so as to expose the base steel sheet, in Example 7 the plating was removed thinly so as not to expose the base steel sheet.

[0099] In all of these examples, the Al-plated steel sheet had a thickness of 1.3 mm and had a strength of 1800 MPa after hot stamping. In the production of the tailored blank, the Al-plated steel sheet of the above example and an Al-plated steel sheet not having the second region and the third region and having a thickness of 1.8 mm and having a strength of 1800 MPa after hot stamping were butted together and laser-welded to produce the tailored blanks shown in Tables 1 and 2. The welding conditions were adjusted to form a weld bead with a width of 1.6 mm in the production of all the tailored blanks. At this time, the center line of the weld bead was aligned with the mating surface of the steel sheet. The dashed lines in Figs. 7A to 7J show the shape of the outer edge of the weld bead. The width w of the weld bead in the steel sheets in Figs. 7A to 7J was 0.8 mm (=1.6 mm / 2) in all of the examples.

[0100] The manufactured tailored blank was held in a furnace heated to 920°C for 4 minutes, and then hot pressed using a water-cooled die to produce a flat hot stamped product.

[0101] The strength and corrosion resistance of these hot stamped products were evaluated.

[0102] For the strength evaluation, test pieces for evaluating static tensile strength were taken from the hot stamped product. The shape of the test piece was a rectangular test piece with a parallel part distance of 60 mm and a parallel part width of 25 mm. The test piece was taken from the center of the parallel part so that it included a weld bead over the entire width of the parallel part in a direction perpendicular to the longitudinal direction of the parallel part. A static tensile test was performed using this test piece. A test piece was judged as passing if a fracture occurred in the base material part on the thinner side of the plate, and as failing if a fracture occurred in the weld bead.

[0103] The corrosion resistance evaluation was performed by a corrosion resistance test after painting. After the hot stamp molded product was subjected to chemical conversion treatment, electrodeposition coating was performed, and a corrosion resistance test after painting was performed. The chemical conversion treatment was performed using a chemical conversion treatment liquid PB-SX35T manufactured by Nippon Parkerizing Co., Ltd. For the electrodeposition coating, cationic electrodeposition paint Powernics 110 manufactured by Nippon Paint was used, and the hot stamp molded product was subjected to electrodeposition coating with a target film thickness of 15 μm. The hot stamp molded product subjected to the electrodeposition coating was washed with water, and then heated and baked at 170 ° C for 20 minutes to prepare a test plate. Except for Example 1, evaluation test pieces with a length of 65 mm and a width of 100 mm were taken from the test plate. In addition, the evaluation test pieces were taken from the test plate so that the weld bead was arranged in the center of the width. On the other hand, in Example 1, the size of the evaluation test piece was set to a length of 30 mm and a width of 100 mm. In addition, the evaluation test pieces were taken from the test plate so that the weld bead was arranged in the center of the width. Furthermore, an evaluation test piece was taken from the center of the weld bead in the longitudinal direction so that the second region was included. Using this test piece, the JASO M610-92 automotive part appearance corrosion test was performed, and the corrosion resistance after painting was evaluated based on the corrosion state after 360 cycles (120 days). The maximum corrosion depth was measured with a point micrometer, and a maximum corrosion depth of less than 0.2 mm was judged as passing, and a maximum corrosion depth of 0.2 mm or more was judged as failing.

[0104] For each example, 20 tailored blanks were manufactured and the number of rejected products was evaluated. If there were zero rejected products, it was recorded as "Good", if there was one rejected product, it was recorded as "Good", and if there were two or more rejected products, it was recorded as "Poor". Examples that were "Good" for both strength and corrosion resistance were judged to be Al-based plated steel sheets in which it is easy to optimize the amount of Al mixed into the weld bead.

[0105] [Table 1]

[0106] [Table 2]

[0107] [Table 3]

[0108] In Comparative Example 1 in which the second region was not provided, the Al content in the weld bead was excessive, and the tailored blank strength of some samples was unacceptable. In Comparative Example 2 in which only the third region was provided instead of the second region, the Al content of the weld bead was insufficient, resulting in a sample in which the corrosion resistance of the tailored blank was insufficient. In Comparative Example 3 in which the length of the second region was excessive, the Al content of the weld bead was insufficient, resulting in a sample in which the corrosion resistance of the tailored blank was insufficient. On the other hand, in the examples in which the second region was appropriately provided, the amount of Al mixed into the weld bead of all samples could be optimized, and as a result, both the strength and corrosion resistance of the tailored blank of all samples were good. [Explanation of symbols]

[0109] 1. Aluminum-plated steel sheet 11 Base steel sheet 12 Plating layer 121 First area 122 Second area 123 Third Area 13 End face L Length of the second region (length of the second region along the edge of the aluminum-based plated steel sheet) W1 Width of the second region (length of the second region along the direction perpendicular to the end surface of the aluminum-based plated steel sheet) W2 Width of the third region (length of the third region along the direction perpendicular to the end face of the aluminum-based plated steel sheet) S Interval between second regions D Distance between the second region and the end face of the Al-based plated steel sheet d Distance between the third region and the end face of the Al-based plated steel sheet 2 Tailored Blank 21 Weld Bead 3 Molten pool

Claims

1. A base steel sheet; A plating layer mainly composed of Al provided on one or both surfaces of the base steel sheet; An Al-based plated steel sheet comprising: a first region in which the plating layer is provided and a second region in which the plating layer is thinner than the first region are provided on the surface of the Al-based plated steel sheet; The second region is provided in the vicinity of an end surface of the Al-based plated steel sheet, The length of the second region along the end surface of the Al-based plated steel sheet is less than 20 mm. Aluminum-plated steel sheet.

2. The distance between the second region and the end face of the Al-based plated steel sheet is 0 mm or more and 1.5 mm or less. The aluminum-based plated steel sheet according to claim 1 .

3. Two or more of the second regions are provided, A distance between the second regions along the end surface of the Al-based plated steel sheet is 1 mm or more and 50 mm or less. The aluminum-based plated steel sheet according to claim 1 .

4. Three or more of the second regions are provided, The intervals between the second regions along the end surface of the Al-based plated steel sheet are substantially uniform, The length of the second region along the end surface of the Al-based plated steel sheet is approximately the same. The aluminum-based plated steel sheet according to claim 1 .

5. The length of the second region along the end surface of the Al-based plated steel sheet is 1 mm or more. The aluminum-based plated steel sheet according to claim 1 .

6. The length of the second region along a direction perpendicular to the end surface of the Al-based plated steel sheet is 0.1 mm or more and 1.5 mm or less. The aluminum-based plated steel sheet according to claim 1 .

7. The second region is rectangular in shape. The aluminum-based plated steel sheet according to claim 1 .

8. a third region in which the plating layer is thinner than the first region is provided on the surface of the Al-based plated steel sheet, the third region extends continuously along the end surface of the Al-based plated steel sheet, The second region is disposed between the third region and the end surface of the Al-based plated steel sheet. The aluminum-based plated steel sheet according to claim 1 .

9. The second region and the third region are in contact with each other. The aluminum-based plated steel sheet according to claim 8 .

10. The thickness of the plating layer in the second region is 0 mm. The aluminum-based plated steel sheet according to claim 1 .

11. The thickness of the plating layer in the third region is 0 mm. The aluminum-based plated steel sheet according to claim 8 .

12. The method includes a step of butt welding end surfaces of a plurality of steel plates, At least one of the steel sheets is an Al-based plated steel sheet according to any one of claims 1 to 11. A manufacturing method of tailored blanks.

13. A toe of a weld bead formed by the butt welding step is disposed inside the second region of the Al-based plated steel sheet. A method for manufacturing a tailored blank according to claim 12.

14. At least one of the steel sheets is the Al-based plated steel sheet according to claim 8, The toe of the weld bead formed by the butt welding step is disposed inside the second region or the third region of the Al-based plated steel sheet. A method for manufacturing a tailored blank according to claim 12.

15. A method for producing an Al-based plated steel sheet according to any one of claims 1 to 11, A step of preparing an Al-based plating base sheet comprising a base steel sheet and a plating layer containing Al as a main component, the plating layer being provided over the entire surface of one or both surfaces of the base steel sheet; removing a portion of the plating layer of the Al-based plating base sheet; A method for producing an Al-based plated steel sheet comprising the steps of:

16. A plurality of steel plates; A weld bead that joins the ends of the steel plates; A tailored blank comprising: one or more of the steel sheets is an Al-based plated steel sheet comprising a base steel sheet and a plating layer containing Al as a main component provided on one or both surfaces of the base steel sheet, a first region in which the plating layer is provided and a second region in which the plating layer is thinner than the first region are provided on the surface of the Al-based plated steel sheet; The second region is in contact with the weld bead, The length of the second region along the extension direction of the weld bead is less than 20 mm. Tailored blank.

17. Two or more of the second regions are provided, The distance between the second regions along the extending direction of the weld bead is 1 mm or more and 50 mm or less.

17. A tailored blank according to claim 16.

18. Three or more of the second regions are provided, The intervals between the second regions along the extension direction of the weld bead are substantially uniform, The length of the second region along the extension direction of the weld bead is approximately the same.

17. A tailored blank according to claim 16.

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