Steel material, steel material welding method and unit

Abstract

An object of the present disclosure is to provide a steel material that can ensure corrosion resistance on the edge surface.An object of the present disclosure is also to provide a welding method and unit for steel material that can ensure corrosion resistance on the edge surface. [Solution] According to the present disclosure, there is provided a steel material 1 having an edge surface 11, characterized in that an overlay weld 13 is formed on at least a portion of an exposed surface 12 of the edge surface 11 that is exposed to a corrosive environment. Also, according to the present disclosure, there is provided a method for welding steel materials. Also, according to the present disclosure, there is provided a unit including a plurality of steel materials.

Description

[Technical Field]

[0001] The present disclosure relates to steel products, methods for welding steel products, and units. [Background technology]

[0002] Steel materials exposed to severely corrosive environments, such as underwater, are required to have a certain level of corrosion resistance. For example, the plate surfaces of plate-shaped steel materials may be coated or provided with a stainless steel lining to ensure corrosion resistance. Furthermore, in joint structures in which the end faces of plate-shaped or pipe-shaped steel materials are butt-joined, the edges (also referred to as end faces) of the steel materials are covered by welding, so there is little concern about corrosion. For example, in the techniques disclosed in Patent Document 1 or Patent Document 2, the edges of members made of different metals are joined to each other by overlay welding.

[0003] However, there is a problem in that the edge surfaces other than the above-mentioned joints are often exposed to a corrosive environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-234418 [Patent Document 2] Japanese Patent Application Publication No. 2017-121656 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that, particularly when the thickness of a steel material increases, the corrosion resistance of the edge surface cannot be ensured due to component segregation in the thickness direction of the steel material. Therefore, the present inventors have investigated a method for ensuring the corrosion resistance of the edge surface. The present disclosure aims to provide a steel material that can ensure corrosion resistance on the edge surface. [Means for solving the problem]

[0006] The steel material according to the present disclosure is A steel material having an edge surface, The present invention is characterized in that an overlay weld is formed on at least a part of the edge surface that is exposed to a corrosive environment. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a steel material capable of ensuring corrosion resistance on the edge surface. According to the present disclosure, it is possible to provide a steel material welding method and unit capable of ensuring corrosion resistance on the edge surface. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a steel material according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic cross-sectional view illustrating an exposed surface when steel materials of different thicknesses are joined together in a steel material according to an embodiment of the present disclosure. FIG. [Figure 3] FIG. 10 is a schematic plan view for explaining a modified example of a steel material according to an embodiment of the present disclosure, showing the vicinity of a corner of the steel material. [Figure 4] FIG. 10 is a schematic plan view for explaining another modified example of the steel material according to an embodiment of the present disclosure, showing the vicinity of a corner of the steel material. [Figure 5] FIG. 1 is a schematic plan view for explaining a welding method according to an embodiment of the present disclosure. [Figure 6] 1A to 1C are diagrams for explaining steps of a welding method according to an embodiment of the present disclosure. [Figure 7] 10A to 10C are diagrams for explaining steps of a welding method according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described using examples, but it is clear that the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be used as examples, but other numerical values ​​and materials may be used as long as the effects of the invention according to the present disclosure are obtained. Furthermore, the components of the following embodiments can be combined with each other. Furthermore, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0010] [First embodiment] Hereinafter, a steel material 1 according to an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 shows a schematic cross-sectional view for explaining the steel material 1 according to this embodiment. In the example of Fig. 1, the steel material 1 is a plate-shaped member. Fig. 1 is a view of the vicinity of an end of the steel material 1, and is a cross-sectional view of a cross section parallel to the plate thickness direction of the steel material 1. As shown in Fig. 1, the steel material 1 has an edge surface 11. In the example of Fig. 1, the edge surface 11 is an exposed surface 12 that is exposed to a corrosive environment. An overlay weld 13 is formed on the exposed surface 12.

[0011] 1 to 7, the X coordinate axis, the Y coordinate axis, and the Z coordinate axis are perpendicular to each other. In the example of Fig. 1, the thickness direction of the steel material 1 is parallel to the Z coordinate axis.

[0012] (Steel) The steel material 1 is not particularly limited, but may be a steel material (e.g., SS400) containing, as its chemical composition, P: 0.05 mass % or less and S: 0.05 mass % or less. The chemical composition of the steel material 1 may be determined by referring to a mill sheet that lists the steel type and chemical components. However, instead of using such a method, the steel plate to be used may be specified by a trade name or the like, and the determination may be made based on the specifications of this steel material.

[0013] The steel material 1 may be stainless steel. Examples of the steel material 1 include SUS312L and SUS430. When applied to marine structures, SUS312L is more preferable.

[0014] Furthermore, the steel material 1 may be a nickel-based alloy or the like. A nickel-based alloy is an alloy whose main component is nickel (nickel content is 50% by mass or more). The chemical composition of the steel material 1 may be determined by referring to a mill sheet that lists the steel type and chemical components. However, instead of using such a method, the material to be used may be specified by a trade name or the like, and the material of the steel material 1 may be specified based on the specifications of this material.

[0015] The steel material 1 may be a plate-shaped member made of the above-mentioned material, such as a steel plate or a stainless steel plate. The steel material 1 may be a pipe-shaped steel material made of the above-mentioned material.

[0016] The thickness of the steel material 1 is not particularly limited, but when the thickness of the steel material 1 is 6 mm or more, the corrosion resistance of the edge surface 11 tends to decrease. Therefore, for example, the thickness of the steel material 1 may be 6 mm or more, 10 mm or more, 20 mm or more, etc. The thickness of the steel material 1 can be measured using a vernier caliper.

[0017] The steel material may be a material having a predetermined pitting potential exceeding the predetermined pitting potential. The predetermined pitting potential is not particularly limited, but is, for example, 800 mV. The pitting potential is measured in accordance with the pitting potential test of JIS G 0577.

[0018] Furthermore, the steel material 1 may be made by overlapping a plurality of steel materials. For example, the steel material 1 may be made by overlapping a plurality of steel plates so that the plate surfaces of different steel plates face each other. The thicknesses of the overlapping steel plates may be different from each other. In this case, the overlapping steel materials may have substantially the same shape when viewed from a direction perpendicular to the plate surfaces of the steel materials, and the edge surfaces of the overlapping steel materials may be flush and substantially aligned. The overlapping steel materials may be joined to each other by welding, adhesive, caulking, bolting, etc., or a combination of these.

[0019] Furthermore, the steel material 1 may be one in which a plurality of steel materials are joined by welding. For example, a plurality of steel materials may be joined by welding to form the steel material 1. For example, the edge surfaces of a plurality of steel plates may be joined by butt welding to form a plate-shaped steel material 1 made of a plurality of steel plates.

[0020] (Edge) The edge surface 11 is included in the end of the steel material 1, and in the case of a plate-shaped steel material, it is a surface that is angled with respect to the plate surface of the steel material. The edge surface 11 may be perpendicular to the plate surfaces 1a and 1b of the steel material 1, but is not limited to this. In the case where the steel material is a pipe, the edge surface is a surface that is included in the end of the steel material and intersects with the inner or outer surface of the pipe.

[0021] For example, when the edge surface 11 is perpendicular to the plate surface 1a of the steel material 1, the height of the edge surface 11 in the plate thickness direction of the steel material 1 (the length of the edge surface 11 in the plate thickness direction of the steel material 1) is the same as the plate thickness of the steel material 1. Furthermore, if a tapered portion is provided at the end of the steel material 1, the tapered portion is also included in the edge surface 11.

[0022] Generally, while the chemical composition of the steel plate surface is uniform, elemental segregation occurs near the center of the steel plate in the thickness direction. Because the edge surface is a surface parallel to the thickness direction of the steel plate, elemental segregation is observed in the in-plane direction of the edge surface. Therefore, by examining the distribution of chemical elements in the thickness direction of any surface and checking whether elemental segregation exists, it is possible to determine whether the surface is an edge surface. Furthermore, since such elemental segregation becomes more pronounced as the thickness of the steel plate 1 increases, as described above, the corrosion resistance of the edge surface 11 tends to decrease when the thickness of the steel plate 1 exceeds a certain value. Generally, the sum of the areas of the plate surfaces 1a and 1b of the steel material 1 is larger than the sum of the areas of the edge surfaces 11.

[0023] (exposed surface) The portion of the edge surface 11 that is exposed to a corrosive environment is referred to as the exposed surface 12. Examples of corrosive environments include underwater and in the air. Specifically, underwater refers to the submerged portion that is in contact with flowing seawater, and in the air refers to the portion above the water that is exposed to sea salt particles and seawater splashes. For example, a portion of the edge surface 11 that is covered by a lining member or the like is not exposed to a corrosive environment, and is therefore not the exposed surface 12. For the same reason, a portion where the edge surfaces 11 of the steel material 1 are butted together and joined by welding or the like is also not the exposed surface 12. The exposed surface 12 may be the entire edge surface 11. Alternatively, the exposed surface 12 may be a part of the edge surface 11. For example, if a part of the edge surface 11 is covered with a lining member and the other part of the edge surface 11 is exposed to a corrosive environment, the exposed part of the edge surface 11 is the exposed surface 12.

[0024] Next, a case will be described in which steel materials of different thicknesses are joined at their edge surfaces. Fig. 2 shows a schematic cross-sectional view illustrating the exposed surface 12 when steel materials (1, 2) of different thicknesses are joined together. As shown in Fig. 2, when steel materials 1 and 2 of different thicknesses are joined with their edge surfaces 11 and 21 facing each other, the area where steel materials 1 and 2 are joined is not included in the exposed surface 12. The exposed surface 12 in such a joint is the area excluding the joint area by joint 10.

[0025] In the steel material 1 according to this embodiment, the thickness of the steel material 1 may exceed a predetermined thickness. Here, the predetermined thickness may be, for example, a thickness related to quality assurance that guarantees the corrosion resistance of the edge surface.

[0026] Here, Fig. 3 shows another example in which steel materials of different thicknesses are joined at their edge surfaces. In the example of Fig. 3, steel materials (1, 2) of different thicknesses are joined together, similar to Fig. 2. A tapered portion 15 is provided at the end of the thicker steel material 1.

[0027] As in the example of Figure 3, when a tapered portion 15 is provided at the end of the steel material 1, the tapered portion 15 also has the same level of corrosion resistance as the edge surface 11. Therefore, when the tapered portion 15 is not provided with a lining or the like and is exposed to a corrosive environment, the tapered portion 15 is also included in the exposed surface 12.

[0028] (Overlay welding) In the steel material 1 according to this embodiment, an overlay weld 13 is formed on at least a part of an exposed surface 12 of the edge surface 11 that is exposed to a corrosive environment. As described above, elemental segregation occurs in the thickness direction of the steel material 1, and elemental segregation is observed on the edge surface 11 of the steel material 1. The corrosion resistance of the area where such elemental segregation occurs is inferior to that of other areas. Therefore, even if the desired chemical composition is obtained on the surface 1a or 1b of the steel material 1 and a certain level of corrosion resistance is achieved, corrosion resistance may not be ensured, particularly at the center of the edge surface 11 in the thickness direction. However, in the steel material 1 according to this embodiment, by providing an overlay weld 13 on the exposed surface 12, the exposed surface 12 can be prevented from being exposed to a corrosive environment. Therefore, in the steel material 1 according to this embodiment, corrosion resistance of the edge surface 11 can be ensured.

[0029] In the steel material 1 according to this embodiment, the overlay weld 13 may be formed on the entire exposed surface 12. For example, providing the overlay weld 13 on the edge surface 11 has the effect of improving strength more than providing a SUS lining. Therefore, by forming the overlay weld 13 on the entire exposed surface 12, the strength of the steel material 1 can be improved.

[0030] In the steel material 1 according to this embodiment, the overlay weld 13 may be made up of one or more layers. When the overlay weld 13 is made up of one or more layers, there is an effect that the welding period is shortened when the overlay weld 13 is made up of a single layer. Furthermore, when the overlay weld 13 is made up of multiple layers, there is an effect that the corrosion resistance of the surface layer of the overlay weld 13 is improved.

[0031] In the steel material 1 according to this embodiment, the welding material constituting the overlay weld 13 may be corrosion-resistant. The welding material constituting the overlay weld 13 is, for example, a nickel-based alloy. Preferred welding materials constituting the overlay weld 13 are not particularly limited, but examples include Hastelloy (registered trademark) and Inconel (registered trademark). By forming the overlay weld 13 itself from a corrosion-resistant welding material, the corrosion resistance of the exposed surface 12 can be more reliably ensured.

[0032] (Variation) A modified example of the steel material 1 according to the first embodiment will be described below with reference to FIG. 4. FIG. 4 is a plan view of the steel material 1 viewed from a direction perpendicular to its plate surface 1a. The steel material 1 shown in FIG. 4 is a plate having a first edge surface 11A, a second edge surface 11B, and a corner 14 connecting the first edge surface 11A and the second edge surface 11B. FIG. 4 is a diagram showing the vicinity of the corner 14 of the plate-shaped steel material 1. In this steel material 1, the exposed surface 12 includes a first exposed surface 12A corresponding to the first edge surface 11A and a second exposed surface 12B corresponding to the second edge surface 11B. In the example of FIG. 4, the first exposed surface 12A is the entire first edge surface 11A, and the second exposed surface 12B is the entire second edge surface 11B. In this steel material 1, an overlay weld 13 is formed across the first exposed surface 12A and the second exposed surface 12B, sandwiching the corner 14. By forming the overlay weld 13 across the first exposed surface 12A and the second exposed surface 12B, which are connected at the corner 14, and sandwiching the corner 14, corrosion resistance at the corner 14 can be ensured.

[0033] 4, the overlay weld 13 is formed on a part of the first edge surface 11A and the second edge surface 11B, but the overlay weld 13 may be formed over the entire first edge surface 11A and the second edge surface 11B. Moreover, the overlay weld 13 may be formed on other corners or other edge surfaces not shown in FIG.

[0034] 4, when forming an overlay weld across a corner, for example, the overlay weld may be formed by continuously performing overlay welding from one edge surface to the other edge surface of the edges that sandwich the corner. Alternatively, after forming an overlay weld on each edge surface, a further overlay weld may be formed on the corner so as to connect these overlay welds.

[0035] The shape of the steel material 1 is not limited to a rectangular plate material as seen from a direction perpendicular to the plate surface as shown in Fig. 4, but may be a circle, an ellipse, a triangle, a polygon, or a combination of these shapes as seen from a direction perpendicular to the plate surface. In addition, the corners may be chamfered to a curved or flat surface.

[0036] Furthermore, the edge surface 11 of the steel material 1 does not necessarily extend in a fixed direction, but may be curved or bent. For example, in the case of a plate-shaped steel material whose plate surface has been bent, the edge surface is also deformed along the shape of the plate surface of the steel material. In the case of a steel material that is a pipe, the edge surface is included in the end of the steel material and intersects with the inner or outer surface of the pipe.

[0037] [Second embodiment] A welding method according to one embodiment of the present disclosure will be described below. The welding method according to the second embodiment is a welding method for the steel material 1 according to the first embodiment described above. Therefore, the various configurations described in the first embodiment can also be applied to the second embodiment. In this embodiment, a plate-shaped steel material (plate material) will be described as an example, but the steel material is not limited to a plate material.

[0038] The welding method according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a plan view of a plate-shaped steel material 3 viewed from a direction perpendicular to its plate surface 3a. The welding method according to this embodiment includes a plate material preparation process for preparing a plate material as the steel material 3, a first buildup welding process for forming an buildup weld in a first area of ​​the exposed surface, and a second buildup welding process for forming an buildup weld in a second area of ​​the exposed surface.

[0039] In the plate material preparation step, a plate material is prepared as the steel material 3. As shown in FIG. 5, the steel material 3 has plate surfaces 3a and 3b, and edge surfaces (31A, 31B, 31C, 31D). In the example of FIG. 5, the edge surfaces (31A, 31B, 31C, 31D) correspond to exposed surfaces (32A, 32B, 32C, 32D), respectively. Furthermore, the edge surfaces 31A and 31B are connected at corner 34A, the edge surfaces 31B and 31C are connected at corner 34B, the edge surfaces 31C and 31D are connected at corner 34C, and the edge surfaces 31D and 31A are connected at corner 34D.

[0040] In the first overlay welding step, an overlay weld is formed in a first area of ​​the exposed surface. In the example of Fig. 5, the first area is exposed surface 32B, and overlay weld 33A is formed from corner 34A in the direction indicated by arrow P1. Note that the starting point of the overlay welding step (the point where formation of overlay welds 33A, 33B begins) is not limited to the corner as illustrated in Fig. 5, and may be anywhere on the exposed surface.

[0041] In the second overlay welding step, an overlay weld is formed in a second area of ​​the exposed surface. In the example of Fig. 5, the second area is exposed surface 32D, and overlay weld 33B is formed from corner 34C in the direction indicated by arrow P2.

[0042] The first range is not limited to exposed surface 32B, and may include exposed surface 32A and exposed surface 32C. Similarly, the second range is not limited to exposed surface 32D, and may include exposed surface 32A and exposed surface 32C. Furthermore, the direction in which overlay welding is performed (the direction in which the overlay weld bead is formed) is not limited to P1 or P2.

[0043] In the welding method according to this embodiment, the first overlay welding step and the second overlay welding step are performed in parallel. That is, in the example of Fig. 5, the step of forming overlay weld 33A on exposed surface 32B from corner 34A in the direction indicated by arrow P1 and the step of forming overlay weld 33B on exposed surface 32D from corner 34C in the direction indicated by arrow P2 are performed in parallel. Here, performing overlay welding in parallel does not necessarily mean that the overlay welding is performed at the same time, but also includes the case where the first overlay welding step and the second overlay welding step are performed at partially overlapping times.

[0044] In this way, by carrying out the first buildup welding process and the second buildup welding process in parallel, the time for the entire welding process can be shortened.

[0045] Furthermore, the first and second ranges may be located within the same edge surface or within different edge surfaces. For example, if the steel material is a plate-shaped steel material 3 having a rectangular plate surface 3a as shown in FIG. 5, the first and second ranges may be set within any range of the exposed surfaces (32A, 32B, 32C, 32D) of each edge surface (31A, 31B, 31C, 31D) corresponding to each side of the rectangle. For example, if the steel material 3 is a plate material having a disk-shaped or elliptical plate surface, the edge surface is not separated by corners and has a single edge surface. In this case, the first and second ranges may be set within a single edge surface. Furthermore, the first range and the second range are basically different ranges, but they may partially overlap.

[0046] [Third embodiment] Hereinafter, a welding method according to an embodiment of the present disclosure will be described with reference to FIG. 6. FIG. 6 is a cross-sectional view of a plate-shaped steel material 1 in a cross section parallel to the plate thickness direction, showing the vicinity of an end of the steel material 1. Each of (a) to (c) in FIG. 6 is a diagram for explaining the flow of the welding method according to this embodiment. The welding method according to the third embodiment is a welding method for the steel material 1 according to the above-mentioned first embodiment. Therefore, the various configurations described in the first embodiment can also be applied to the third embodiment. In this embodiment, a plate-shaped steel material (plate material) will be described as an example, but it is not intended that the steel material be limited to a plate material.

[0047] The welding method according to this embodiment includes a first plate material preparation process for preparing a first plate material 4 as a steel material, a second plate material preparation process for preparing a second plate material 5 as a steel material, a first overlay welding process for forming an overlay weld 43 on an exposed surface 42 of the first plate material 4, and a second overlay welding process for forming an overlay weld 53 on an exposed surface 52 of the second plate material 5.

[0048] As shown in Fig. 6(a), in the first plate material preparation step, a first plate material 4 is prepared. Similarly, in the second plate material preparation step, a second plate material 5 is prepared. The first plate material 4 or the second plate material 5 can have the same configuration as the steel material 1 of the first embodiment.

[0049] 6(b), in the first overlay welding step, an overlay weld 43 is formed on an exposed surface 42 of a prepared first plate material 4. Similarly, in the second overlay welding step, an overlay weld 53 is formed on an exposed surface 52 of a prepared second plate material 5. The build-up weld 43 or the build-up weld 53 can have the same configuration as the build-up weld 13 of the first embodiment. In the example of Fig. 6, the edge surfaces (41, 51) correspond to the exposed surfaces (42, 52), respectively.

[0050] In the welding method of this embodiment, the first overlay welding step and the second overlay welding step are performed in parallel, which has the effect of shortening the time required for the entire welding process. Here, performing buildup welding in parallel does not necessarily mean that the buildup welding is performed simultaneously, as in the second embodiment, but also includes the case where the first buildup welding process and the second buildup welding process are performed at timings that partially overlap.

[0051] Furthermore, in the welding method according to this embodiment, after the first overlay welding step and the second overlay welding step are completed, the first plate 4 on which the overlay weld 43 has been formed and the second plate 5 on which the overlay weld 53 has been formed may be overlapped as shown in (c) of Fig. 6. For example, as shown in (c) of Fig. 6, the first plate 4 and the second plate 5 are overlapped so that the plate surface 4b of the first plate 4 and the plate surface 5a of the second plate 5 face each other. The overlapped first plate 4 and second plate 5 may be joined to each other by welding, adhesive, caulking, bolting, or the like, or a combination of these.

[0052] In the example of Fig. 6, for convenience, the first plate 4 and the second plate 5 are shown to have approximately the same thickness, but the thicknesses of the first plate 4 and the second plate 5 may be different. Also, in the example of Fig. 6, the edge surface 41 and the edge surface 51 are arranged to be flush, but this is not limited to this. In other words, the arrangement of the edge surface 41 and the edge surface 51 may be different in the direction parallel to the plate surface.

[0053] The welding method according to this embodiment makes it possible to manufacture a unit including a plurality of steel plate materials. This unit is, for example, a unit 100 as shown in FIG. 6(c).

[0054] In this unit 100, the multiple plate materials (4, 5) are arranged such that the plate surface 4b of one plate material (first plate material 4) is overlapped with the plate surface 5a of another plate material (second plate material 5), and the plate surface 4a opposite to the plate surface 4b of the one plate material (first plate material 4) and the plate surface 5b opposite to the plate surface 5a of the other plate material (second plate material 5) are exposed. In this unit 100, overlay welds (43, 53) are formed on at least a portion of exposed surfaces (42, 52) of edge surfaces (41, 51) of plate materials (4, 5) that are exposed to a corrosive environment. Also, in this unit, there is a gap S between the overlay weld 43 of one plate material (first plate material 4) and the overlay weld 53 of another plate material (second plate material 5). As described above, in this unit 100, the first plate material 4 on which the overlay weld 43 is formed and the second plate material 5 on which the overlay weld 53 is formed are overlapped, so the overlay weld 43 and the overlay weld 53 are not joined, and the gap S can be seen at the boundary between them.

[0055] [Fourth embodiment] Hereinafter, a welding method according to an embodiment of the present disclosure will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view of a plate-shaped steel material 1 in a cross section parallel to the plate thickness direction, showing the vicinity of an end of the steel material 1. Each of (a) to (c) in FIG. 7 is a diagram for explaining the flow of the welding method according to this embodiment. The welding method according to the fourth embodiment is a welding method for the steel material 1 according to the above-mentioned first embodiment. Therefore, the various configurations described in the first embodiment can also be applied to the fourth embodiment. In this embodiment, a plate-shaped steel material (plate material) will be described as an example, but it is not intended that the steel material be limited to a plate material.

[0056] The welding method according to this embodiment includes a first plate material preparation process for preparing a first plate material 6 as a steel material, a second plate material preparation process for preparing a second plate material 7 as a steel material, a superposition process for superposing the first plate material 6 and the second plate material 7, and an overlay welding process for forming an overlay weld on the exposed surfaces (62, 72) of the superposed first plate material 6 and second plate material 7.

[0057] As shown in (a) of Fig. 7, in the first plate material preparation step, a first plate material 6 is prepared. Similarly, in the second plate material preparation step, a second plate material 7 is prepared. The first plate material 6 or the second plate material 7 can have the same configuration as the steel material 1 of the first embodiment.

[0058] As shown in (b) of Figure 7, in the overlapping step, the first plate material 6 and the second plate material 7 are overlapped. In the example of (b) of Figure 7, the first plate material 6 and the second plate material 7 are overlapped so that the plate surface 6b of the first plate material 6 and the plate surface 7a of the second plate material 7 face each other. The overlapped first plate material 4 and second plate material 5 may be joined to each other by welding, adhesive, caulking, bolting, etc., or a combination of these.

[0059] Next, in the build-up welding step, as shown in FIG. 7(c), build-up welds 63 are formed on the exposed surfaces (62, 72) of the overlapped first plate material 6 and second plate material 7.

[0060] According to the above welding method, the welding of the edge surfaces of the first plate material and the second plate material can be combined into one process, thereby simplifying the work process.

[0061] In the welding method according to this embodiment, the buildup welding process includes a first buildup welding process for forming a buildup weld in a first area of ​​the exposed surfaces (62, 72) of the overlapping first plate material 6 and second plate material 7, and a second buildup welding process for forming a buildup weld in a second area of ​​the exposed surfaces (62, 72) of the overlapping first plate material 6 and second plate material 7, and the first buildup welding process and the second buildup welding process may be carried out in parallel. As in the welding method of the second embodiment, by performing buildup welding in parallel on the first and second ranges of the exposed surfaces (62, 72) of the overlapping first and second plate materials 6 and 7, the overall time required for the welding process can be shortened.

[0062] The welding method according to this embodiment makes it possible to manufacture a unit including a plurality of steel plate materials. This unit is, for example, unit 200 as shown in FIG. 7(c).

[0063] In this unit 200, the plate surface 6b of one plate (first plate 6) and the plate surface 7a of another plate (second plate 7) are overlapped, and the plate surface 6a opposite the plate surface 6b of the one plate (first plate 6) and the plate surface 7b opposite the plate surface 7a of the other plate (second plate 7) are exposed. In this unit 200, an overlay weld 63 is formed on at least a part of the exposed surfaces (62, 72) of the edge surfaces (61, 71) of the plate materials (6, 7) that are exposed to a corrosive environment. In this unit 200, the overlay weld 63 of one plate material (first plate material 6) and the overlay weld 73 of the other plate material (second plate material 7) are continuous; in other words, an overlay weld 83 consisting of the overlay weld 63 and the overlay weld 73 is formed across the edge surfaces (61, 71) of the plate materials (6, 7).

[0064] The first plate material 6 and the second plate material 7 may have the same shape when viewed from a plane perpendicular to the plate surfaces, or may have different shapes when viewed from a plane perpendicular to the plate surfaces.

[0065] In the above-described embodiment, the overlay weld may be formed by any one of TIG (Tungsten Inert Gas) welding, MIG (Metal Inert Gas) welding, and MAG (Metal Active Gas) welding.

[0066] (Addendum) The structure and welding method according to the above embodiment can be understood, for example, as follows. (1) A steel material according to one embodiment of the present disclosure is A steel material having an edge surface, The present invention is characterized in that an overlay weld is formed on at least a part of the edge surface that is exposed to a corrosive environment. According to the above steel material, the corrosion resistance of the edge surface can be ensured by the overlay weld formed on the exposed surface.

[0067] (2) For the steel material in (1) above, The length of the exposed surface in the thickness direction of the steel material may be the thickness of the steel material and may exceed a predetermined thickness.

[0068] (3) In the case of the steel material (1) or (2) above, A weld overlay may be formed on the entire exposed surface. The above steel material has the effect of improving the strength of the steel material.

[0069] (4) In the steel material according to any one of the above (1) to (3), The weld overlay may consist of one or more layers. The above-mentioned steel material has the effect of shortening the welding period when the overlay weld is a single layer, and has the effect of improving the corrosion resistance of the surface layer of the overlay weld when the overlay weld is a multi-layer.

[0070] (5) In the steel material according to any one of (1) to (4) above, The steel material is a plate material, The plate material has a first edge surface, a second edge surface, and a corner portion connecting the first edge surface and the second edge surface, the exposed surface includes a first exposed surface corresponding to the first edge surface and a second exposed surface corresponding to the second edge surface, The overlay weld may be formed across the corner portion from the first exposed surface to the second exposed surface. According to the above steel material, by forming an overlay weld across the corner portion and the first exposed surface and the second exposed surface that are connected at the corner portion, corrosion resistance at the corner portion can be ensured.

[0071] (6) In the steel material according to any one of the above (1) to (5), The steel material may be stainless steel. The above steel material has the effect of imparting high corrosion resistance to the steel material itself.

[0072] (7) In the steel material according to any one of the above (1) to (6), The welding material constituting the overlay weld may be corrosion resistant. According to the above-mentioned steel material, the overlay weld itself is formed from a corrosion-resistant welding material, so that the corrosion resistance of the exposed surface can be more reliably ensured.

[0073] (8) In the steel material described in (7) above, The welding material constituting the overlay weld may be made of a nickel-based alloy. The above steel material has the effect of imparting high corrosion resistance to the welded portion.

[0074] (9) In the steel material according to any one of the above (1) to (8), The steel may be a material that exceeds a predetermined pitting potential.

[0075] (10) In the steel material according to any one of (1) to (9) above, The overlay weld may be formed by any one of TIG welding, MIG welding, and MAG welding.

[0076] (11) A welding method for steel materials according to one embodiment of the present disclosure includes: The welding method for steel materials according to any one of (1) to (10) above, a plate material preparation process for preparing the steel material; a first overlay welding step of forming an overlay weld in a first area of ​​the exposed surface; A second overlay welding step of forming an overlay weld in a second range of the exposed surface, The first overlay welding step and the second overlay welding step are performed in parallel. According to the above welding method, the overall time required for the welding process can be reduced.

[0077] (12) A welding method for steel materials according to one embodiment of the present disclosure includes: The welding method for steel materials according to any one of (1) to (10) above, a first steel material preparation step of preparing a first steel material as the steel material; a second steel material preparation step of preparing a second steel material as the steel material; A first overlay welding process of forming an overlay weld on the exposed surface of the first steel material; A second overlay welding process of forming an overlay weld on the exposed surface of the second steel material, The first overlay welding step and the second overlay welding step are performed in parallel. According to the above welding method, the overall time required for the welding process can be reduced.

[0078] (13) A welding method for steel materials according to one embodiment of the present disclosure, The welding method for steel materials according to any one of (1) to (10) above, a first steel material preparation step of preparing a first steel material as the steel material; a second steel material preparation step of preparing a second steel material as the steel material; a superposing step of superposing the first steel material and the second steel material; The method is characterized by including an overlay welding process for forming an overlay weld on the exposed surfaces of the overlapped first steel material and the second steel material. According to the above welding method, welding of the edge surfaces of the first steel material and the second steel material can be combined into one process, thereby providing the effect of simplifying the work process.

[0079] (14) In the welding method for steel materials described in (13) above, The overlay welding process, A first overlay welding process of forming an overlay weld in a first range of the exposed surfaces of the first steel material and the second steel material that are overlapped; A second overlay welding process of forming an overlay weld in a second range of the exposed surfaces of the overlapped first steel material and the second steel material, The first overlay welding step and the second overlay welding step may be performed in parallel. According to the above welding method, the overall time required for the welding process can be reduced.

[0080] (15) A unit according to one embodiment of the present disclosure includes: A unit comprising a plurality of steel members, The plurality of steel materials are arranged such that a plate surface of one of the steel materials is overlapped with a plate surface of another of the steel materials, an overlay weld is formed on at least a part of an exposed surface of the edge of the steel material that is exposed to a corrosive environment; The method is characterized in that there is a gap between the overlay weld of one of the steel materials and the overlay weld of the other of the steel materials. According to the above-described unit, the presence of gaps between the overlay welded portions has the effect of facilitating separation of the steel materials when releasing the joint between the steel materials.

[0081] (16) A unit according to one embodiment of the present disclosure includes: A unit comprising a plurality of steel members, The plurality of steel materials are arranged such that a plate surface of one of the steel materials is overlapped with a plate surface of another of the steel materials, an overlay weld is formed on at least a part of an exposed surface of the edge of the steel material that is exposed to a corrosive environment; The method is characterized in that the overlay weld of one of the steel materials is continuous with the overlay weld of another of the steel materials. The above unit has the effect of sealing the gaps between the steel members and making the edge surfaces of the unit smooth. [Industrial Applicability]

[0082] According to the steel material of the present disclosure, corrosion resistance of the edge surface can be ensured. Furthermore, according to the welding method and unit of the steel material of the present disclosure, corrosion resistance of the edge surface can be ensured. Therefore, the invention of the present disclosure is extremely useful industrially. [Explanation of symbols]

[0083] 1, 2, 3, 4, 5, 6, 7, Steel 11, 11C, 11D edge 11A First edge 11B Second edge 12, 12C, 12D exposed surface 12A 1st exposed surface 12B 2nd exposed surface 13, 23, 33 Overlay weld 14, 14A, 14B, 14C, 14D Corner 10 Joint 100, 200 units

Claims

1. A steel material having an edge surface, A build-up weld is formed on at least a part of the edge surface that is exposed to a corrosive environment. A steel material characterized by:

2. The thickness of the steel material exceeds a predetermined thickness. The steel material according to claim 1 .

3. An overlay weld is formed on the entire exposed surface.

3. The steel material according to claim 1 or 2.

4. The overlay weld consists of one or more layers, 3. The steel material according to claim 1 or 2.

5. The steel material is a plate material, The plate material has a first edge surface, a second edge surface, and a corner portion connecting the first edge surface and the second edge surface, The exposed surface includes a first exposed surface corresponding to the first edge surface and a second exposed surface corresponding to the second edge surface, The overlay weld portion is formed across the corner portion from the first exposed surface to the second exposed surface.

3. The steel material according to claim 1 or 2.

6. The steel material is stainless steel.

3. The steel material according to claim 1 or 2.

7. The welding material constituting the overlay weld portion has corrosion resistance.

3. The steel material according to claim 1 or 2.

8. The welding material constituting the overlay weld portion is made of a nickel-based alloy. The steel material according to claim 7 .

9. The steel material is a material that exceeds a predetermined pitting potential.

3. The steel material according to claim 1 or 2.

10. The overlay weld portion is formed by any one of TIG welding, MIG welding, and MAG welding.

3. The steel material according to claim 1 or 2.

11. The welding method for steel materials according to claim 1 or 2, a steel material preparation step of preparing the steel material; a first overlay welding step of forming an overlay weld in a first range of the exposed surface; A second overlay welding step of forming an overlay weld in a second range of the exposed surface, The first overlay welding process and the second overlay welding process are performed in parallel. A method for welding steel materials.

12. The welding method for steel materials according to claim 1 or 2, a first steel material preparation step of preparing a first steel material as the steel material; a second steel material preparation step of preparing a second steel material as the steel material; A first overlay welding process of forming an overlay weld on the exposed surface of the first steel material; A second overlay welding process of forming an overlay weld on the exposed surface of the second steel material, The first overlay welding process and the second overlay welding process are performed in parallel. A method for welding steel materials.

13. The welding method for steel materials according to claim 1 or 2, a first steel material preparation step of preparing a first steel material as the steel material; a second steel material preparation step of preparing a second steel material as the steel material; a superposing step of superposing the first steel material and the second steel material; An overlay welding process for forming an overlay weld on the exposed surface of the first steel material and the second steel material that are overlapped, A method for welding steel materials.

14. The overlay welding process, A first overlay welding process of forming an overlay weld in a first range of the exposed surfaces of the first steel material and the second steel material that are overlapped; A second overlay welding process of forming an overlay weld in a second range of the exposed surfaces of the overlapped first steel material and the second steel material, The first overlay welding process and the second overlay welding process are performed in parallel. The method for welding steel materials according to claim 13.

15. A unit comprising a plurality of steel members, The plurality of steel materials are arranged such that a plate surface of one of the steel materials is overlapped with a plate surface of another of the steel materials, an overlay weld is formed on at least a part of an exposed surface of the edge of the steel material that is exposed to a corrosive environment; There is a gap between the overlay weld of one of the steel materials and the overlay weld of the other of the steel materials. A unit characterized by:

16. A unit comprising a plurality of steel members, The plurality of steel materials are arranged such that a plate surface of one of the steel materials is overlapped with a plate surface of another of the steel materials, an overlay weld is formed on at least a part of an exposed surface of the edge of the steel material that is exposed to a corrosive environment; The overlay weld of one of the steel materials is continuous with the overlay weld of the other of the steel materials. A unit characterized by:

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