Manufacturing method of lap fillet welded joint, method of setting overlap width of lap fillet welded joint, and lap fillet welded joint

Abstract

To provide a technique for suppressing a welding deformation amount of a lap fillet-welded joint without needing an additional machining step.SOLUTION: A method for welding a lap fillet-welded joint comprises a welding step of fillet-welding the edge of a first steel material and the surface of a second steel material so as to form a welded part along the edge of the first steel material. In the welding step, the first and second steel materials are welded so as to satisfy (W0-2.0≤W1≤W0+2.0)and (0.5≤T / t≤1.5) in a section orthogonal to the welding line direction of the welded part, in which W1 denotes the lap width (mm) of the first and second steel materials, T denotes the thickness (mm) of the first steel material, and t denotes the thickness (mm) of the second steel material. W0 is calculated by (W0=6(T / t)+6s) in the case of T≥t, and calculated by (W0=16-10(t / T)+6s) in the case of T<t, in which s denotes a gap (mm) between the first and second steel materials.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a manufacturing method of a lap fillet welded joint, a method for setting the overlap width of a lap fillet welded joint, and a lap fillet welded joint. [Background technology]

[0002] In the manufacture of automobile exhaust system parts and the like, lap fillet welding is used, in which two parts are overlapped and the end of one part is welded to the surface of the other part. In fillet weld joints obtained by lap fillet welding, the thermal contraction of the weld is restrained by the base material during welding, which generates residual stress in the weld and can result in welding distortion.

[0003] If the welding distortion of a fillet welded joint becomes large, it becomes necessary to add a correction process or review the processing conditions to ensure the reliability of the part, which increases manufacturing costs. For this reason, it is necessary to keep the welding distortion as small as possible.

[0004] In this regard, various techniques have been proposed to reduce the amount of welding distortion. For example, Patent Document 1 discloses a welded joint structural material in which a bent portion or a thick portion is formed at the end of one of a pair of members to be lap-welded. Patent Document 1 describes that the bent portion or the thick portion absorbs welding heat, thereby suppressing welding distortion.

[0005] Furthermore, for example, Patent Document 2 discloses a method of overlapping and fillet welding a first steel plate and a second steel plate. In the method disclosed in Patent Document 2, a reinforcing portion is provided on the surface of the first steel plate opposite to the surface that contacts the second steel plate, and then fillet welding is performed so that the weld metal covers the area between the end of the reinforcing portion, the end of the first steel plate, and the surface of the second steel plate. Patent Document 2 describes that performing fillet welding in the above manner suppresses welding distortion of the welded joint. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-263235 [Patent Document 2] International Publication No. 2017 / 047665 Summary of the Invention [Problem to be solved by the invention]

[0007] However, to achieve the welded joint structure disclosed in Patent Document 1, a step of forming a bent portion or a thick portion in one of the members is required. Furthermore, the method disclosed in Patent Document 2 requires a step of providing a reinforcing portion. Thus, the techniques disclosed in Patent Documents 1 and 2 require an additional processing step in addition to the welding step. As a result, the manufacturing cost of the welded joint increases.

[0008] Therefore, an object of the present invention is to provide a technique for suppressing the amount of welding distortion in a lap fillet welded joint without requiring an additional processing step. [Means for solving the problem]

[0009] The present invention relates to the following method for manufacturing a lap fillet welded joint, a method for setting the overlap width of a lap fillet welded joint, and a lap fillet welded joint.

[0010] (1) A welding process is provided in which a part of a first steel material having a predetermined thickness is overlapped on a second steel material having a predetermined thickness, and the edge portion of the first steel material and a surface of the second steel material are fillet welded together by fillet welding so as to form a weld along the edge portion of the first steel material; In the welding step, the first steel material and the second steel material are welded together so that the following formulas (i) and (ii) are satisfied in a cross section perpendicular to the weld line direction of the weld portion. W0-2.0≦W1≦W0+2.0 (i) 0.5≦T / t≦1.5 (ii) In the above formula, W1 represents the overlapping width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, and t represents the thickness (mm) of the second steel material. Also, W0 is obtained by the following formula (iii) when T ≥ t, and is obtained by formula (iv) when T < t. W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

[0011] (2) The method for manufacturing the lap fillet weld joint according to (1) above, wherein in the welding step, welding is performed using an austenitic stainless steel filler metal.

[0012] (3) The method for manufacturing the lap fillet weld joint according to (1) or (2) above, wherein the gap between the first steel material and the second steel material is 0.2 mm or more.

[0013] (4) A method for setting the overlapping width of the first steel material and the second steel material when manufacturing a lap fillet weld joint by performing fillet welding on the edge of the first steel material and the surface of the second steel material so that a weld portion is formed along the edge of the first steel material in a state where a part of the first steel material having a predetermined thickness is overlapped on the second steel material having a predetermined thickness, In a cross-section perpendicular to the welding line direction of the weld portion, the overlapping width is set so that the following formulas (i) and (ii) are satisfied. A method for setting the overlapping width of a lap fillet weld joint. W0 - 2.0 ≤ W1 ≤ W0 + 2.0 ···(i) 0.5 ≤ T / t ≤ 1.5 ···(ii) In the above formula, W1 represents the overlapping width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, and t represents the thickness (mm) of the second steel material. Also, W0 is obtained by the following formula (iii) when T ≥ t, and is obtained by formula (iv) when T < t. W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

[0014] (5) The method for setting the overlap width of the lap fillet weld joint according to the above (4), wherein the gap between the first steel material and the second steel material is 0.2 mm or more.

[0015] (6) A lap fillet weld joint in which a part of a first steel material having a predetermined thickness is overlapped on a second steel material having a predetermined thickness, and the edge and the surface of the second steel material are fillet welded by a weld formed along the edge of the first steel material, A lap fillet weld joint that satisfies the following formulas (v) and (ii) in a cross section perpendicular to the welding line direction of the weld portion. W0 - 3.2 ≤ W2 ≤ W0 + 1.2 ···(v) 0.5 ≤ T / t ≤ 1.5 ···(ii) In the above formula, W2 represents the overlap width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, and t represents the thickness (mm) of the second steel material. Also, W0 is obtained by the following formula (iii) when T ≥ t, and is obtained by formula (iv) when T < t. W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

[0016] (7) The lap fillet weld joint according to the above (6), wherein the gap between the first steel material and the second steel material is 0.2 mm or more.

Advantages of the Invention

[0017] According to the present invention, by appropriately setting the overlap width between the first steel material and the second steel material, it is possible to suppress the amount of welding deformation of the lap fillet weld joint without requiring an additional processing step.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a diagram showing an example of a lap fillet weld joint. [Figure 2] FIG. 2 is a diagram showing an example of deformation of the upper steel material. [Figure 3] FIG. 3 is a diagram showing an example of a deformation mode of the lower steel material. [Figure 4] FIG. 4 is a diagram showing a case where both the upper and lower steel materials are deformed so as to be convex on the rear side. [Figure 5] FIG. 5 is a diagram showing a case where both the upper steel material and the lower steel material are deformed so as to be convex on the front side. [Figure 6] FIG. 6 is a diagram showing a case where the upper steel material and the lower steel material are deformed in opposite directions. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing the vicinity of the welded portion of the lap fillet welded joint of FIG. [Figure 8] FIG. 8 is a diagram for explaining a method for manufacturing a lap fillet welded joint. [Figure 9] FIG. 9 is a diagram showing a modified example of a lap fillet welded joint. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Study by the inventor) The present inventors have conducted detailed studies on techniques for suppressing the amount of welding distortion in lap fillet welded joints. Specifically, they conducted detailed studies on welding distortion in a fillet lap welded joint 100 (hereinafter abbreviated as welded joint 100) having two steel materials 10, 12 as shown in Fig. 1. As a result, they have obtained the findings described below. In Fig. 1, (a) is a perspective view showing the welded joint 100, and (b) is a schematic cross-sectional view showing the bb portion of the welded joint 100 in (a).

[0020] The welded joint 100 shown in FIG. 1 is manufactured in the same manner as a conventional fillet lap welded joint by overlapping a portion of steel material 10 on steel material 12 and fillet welding edge portion 10a of steel material 10 to surface 12a of steel material 12 so that a weld (weld metal) 14 is formed along edge portion 10a of steel material 10.

[0021] 1(b) shows a stacking direction X of the steel materials 10 and 12. The stacking direction X is a direction parallel to the thickness direction of the steel materials 10 and 12. In the following description, the steel material 10 side in the stacking direction X is the front side of the welded joint 100, and the steel material 12 side is the back side of the welded joint 100.

[0022] As shown in FIG. 1, in a welded joint 100, a weld 14 is located on the surface of a steel material 12. Therefore, in the stacking direction X, the center of the weld 14 is located closer to the front side than to the center of the welded joint 100. As a result, in the vicinity of the weld 14, thermal contraction is greater on the front side of the welded joint 100 than on the back side. As a result, when viewed from a direction Z (hereinafter referred to as the width direction Z of the weld 14) perpendicular to the stacking direction X and the weld line direction Y of the weld 14, a force acts on the steel material 10 to deform it in a convex shape toward the back side (the steel material 12 side) as shown by arrow A in FIG. 2.

[0023] On the other hand, due to the thermal contraction of the welded portion 14 in the width direction Z, a force acts on the steel material 12 to deform it into a V-shape with the welded portion 14 as the bottom when viewed from the weld line direction Y of the welded portion 14. Furthermore, due to the thermal contraction of the welded portion 14 in the weld line direction Y, a force acts on the steel material 12 to buckle it so that it becomes convex toward the front side (the steel material 10 side) when viewed from the width direction Z, as shown by arrow B in Fig. 3 .

[0024] In this way, in the welded joint 100, thermal contraction of the welded portion 14 during welding causes forces to act on the steel material 10 and the steel material 12 in opposite directions, tending to deform them. It is believed that in the welded joint 100, the force tending to deform the steel material 10 and the force tending to deform the steel material 12 influence each other, causing welding deformation.

[0025] As a result of detailed investigation into this point, the inventors have found that the overlap width W1 between the steel material 10 and the steel material 12 (the length in the width direction Z of the part where the steel material 10 and the steel material 12 overlap each other) has a significant effect on the deformation mode of the welded joint 100.

[0026] Specifically, it was found that by increasing the overlap width W1, the deformation of steel material 10 tends to become dominant over the deformation of steel material 12. As a result, it was found that not only steel material 10 but also steel material 12 may deform so as to be convex toward the back side (steel material 12 side), as shown by arrows A and B1 in Fig. 4 .

[0027] It was also found that by reducing the overlap width W1, the deformation of steel material 12 tends to become dominant over the deformation of steel material 10. As a result, it was found that not only steel material 12 but also steel material 10 may deform so as to be convex toward the front side (steel material 10 side), as shown by arrows A1 and B in Fig. 5 .

[0028] It was also found that by appropriately setting the overlap width W1, the steel materials 10 and 12 deform in opposite directions, as shown by arrows A and B in Figure 6. In this case, it was found that the deformations of the steel materials 10 and 12 in the opposite directions cancel each other out, thereby suppressing the welding deformation of the welded joint 100 compared to the cases shown in Figures 4 and 5 (where the steel materials 10 and 12 deform in the same direction). Hereinafter, the overlap width that can minimize the welding deformation of the welded joint 100 is referred to as the optimal overlap width value.

[0029] As a result of further investigation, the inventors have found that the thickness of the steel materials 10, 12 also has a significant effect on the welding deformation of the welded joint 100. Therefore, the optimum value of the overlap width also varies depending on the thickness of the steel materials 10, 12.

[0030] Specifically, the amount of deformation of the steel materials 10, 12 during welding decreases as the thickness increases. For example, when the thickness of the steel material 12 is greater than the thickness of the steel material 10, the amount of deformation of the steel material 10 increases and the amount of deformation of the steel material 12 decreases. In this case, it is possible to increase the influence of the deformation of the steel material 12 by, for example, reducing the overlap width W1. This causes the deformations of the steel material 10 and the steel material 12 to cancel each other out, and it is possible to suppress welding deformation of the welded joint 100.

[0031] On the other hand, when the thickness of the steel material 10 is greater than the thickness of the steel material 12, the amount of deformation of the steel material 10 decreases and the amount of deformation of the steel material 12 increases. In this case, in order to reduce the welding deformation of the welded joint 100, it is conceivable to increase the influence of the deformation of the steel material 10, for example, by increasing the overlap width W1. This causes the deformations of the steel material 10 and the steel material 12 to cancel each other out, and the welding deformation of the welded joint 100 can be suppressed.

[0032] When manufacturing the welded joint 100, a gap s may be provided between the steel material 10 and the steel material 12 in the stacking direction X, as shown in Fig. 7, due to various factors. As a result of studies by the present inventors, it has been found that the gap s between the steel material 10 and the steel material 12 also greatly affects the welding deformation of the welded joint 100. Therefore, the optimum value of the overlap width also changes depending on the size of the gap s between the steel material 10 and the steel material 12.

[0033] Specifically, it has been found that the larger the gap s, the more easily the steel material 12 deforms. Therefore, when the gap s is large, it is conceivable to increase the influence of the deformation of the steel material 10 by increasing the overlap width W1. This causes the deformations of the steel material 10 and the steel material 12 to cancel each other out, and it is possible to suppress welding deformation of the welded joint 100.

[0034] Based on the above findings, as a result of further study by the present inventor on the appropriate overlap width, it has been found that by welding the steel material 10 and the steel material 12 such that the following equations (i) and (ii) are satisfied in a cross-section orthogonal to the welding line direction Y of the welded portion 14, the welding deformation of the welded joint 100 can be suppressed. W0 - 2.0 ≤ W1 ≤ W0 + 2.0 ···(i) 0.5 ≤ T / t ≤ 1.5 ···(ii) In the above equations, W1 represents the overlap width (mm) of the steel material 10 and the steel material 12, T represents the thickness (mm) of the steel material 10, and t represents the thickness (mm) of the steel material 12. Also, W0 is the optimum value of the overlap width of the steel material 10 and the steel material 12. When T ≥ t, it is obtained by the following equation (iii), and when T < t, it is obtained by equation (iv). W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above equations, s represents the gap (mm) between the steel material 10 and the steel material 12, and it is 0 or more.

[0035] (Embodiment of the Present Invention) Hereinafter, a method for manufacturing an overlap fillet welded joint according to an embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a diagram for explaining a method for manufacturing an overlap fillet welded joint according to an embodiment of the present invention. In the following, the case of manufacturing the welded joint 100 shown in FIG. 1 will be described. Note that the method for manufacturing an overlap fillet welded joint according to the present embodiment includes a method for setting the overlap width of the overlap fillet welded joint. In the present embodiment, the steel material 10 corresponds to the first steel material, and the steel material 12 corresponds to the second steel material.

[0036] As shown in FIG. 8( a), when manufacturing a welded joint 100, first, a portion of the steel material 10 is overlapped on the steel material 12. In this specification, overlapping a portion of the steel material 10 on the steel material 12 means arranging the steel material 10 and the steel material 12 so that a portion of the steel material 10 overlaps the steel material 12 when viewed in the thickness direction of the steel material 12. Therefore, overlapping a portion of the steel material 10 on the steel material 12 is not limited to placing a portion of the steel material 10 on the steel material 12 so that it contacts the steel material 12, but also includes placing a portion of the steel material 10 on the steel material 12 so that a gap is formed between the steel material 10 and the steel material 12. In the following description, the steel material arranged on the upper side will be referred to as the upper steel material, and the steel material arranged on the lower side will be referred to as the lower steel material.

[0037] As the material for the upper steel material 10 and the lower steel material 12, various steels such as carbon steel or stainless steel (ferritic stainless steel, austenitic stainless steel, duplex stainless steel, etc.) can be used. In this embodiment, the upper steel material 10 and the lower steel material 12 are each steel plates. In this embodiment, the thickness of the upper steel material 10 and the lower steel material 12 is set to, for example, 0.5 mm or more and 4.0 mm or less.

[0038] Next, as shown in Figures 1 and 8(b), a welding machine 20 (see Figure 8) and a filler metal (not shown) are used to fillet weld the edge 10a of the upper steel material 10 to the surface 12a of the lower steel material 12 so as to form a weld (weld metal) 14 along the edge 10a of the upper steel material 10 (welding process). This produces a welded joint 100. Note that Figure 8(b) shows the torch of the welding machine 20. As the filler metal, for example, austenitic stainless steel or duplex stainless steel can be used.

[0039] In the welding process, the upper steel material 10 and the lower steel material 12 are welded together while being held by a holding member (not shown). With reference to Figures 1, 7 and 8, in this embodiment, the upper steel material 10 and the lower steel material 12 are welded together so that the following formulas (i) and (ii) are satisfied in a cross section of the welded portion 14 that is perpendicular to the weld line direction Y. W0 - 2.0 ≤ W1 ≤ W0 + 2.0 ···(i) 0.5 ≤ T / t ≤ 1.5 ···(ii) In the above formula, W1 represents the overlapping width (mm) of the upper steel material 10 and the lower steel material 12, T represents the thickness (mm) of the upper steel material 10, and t represents the thickness (mm) of the lower steel material 12. Also, W0 is the optimal value of the overlapping width of the upper steel material 10 and the lower steel material 12. When T ≥ t, it is obtained by the following formula (iii), and when T < t, it is obtained by formula (iv). W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above formula, s represents the gap (mm) between the upper steel material 10 and the lower steel material 12.

[0040] In this embodiment, the gap s between the upper steel material 10 and the lower steel material 12 is set to be 0 mm or more. The gap s may not be provided. When there is a gap s, the upper limit value of the gap s is set to be not more than the smallest value among 1.0 mm, the thickness T (mm) of the upper steel material 10, and the thickness t (mm) of the lower steel material 12. For example, when the thickness T is 0.4 mm and the thickness t is 0.6 mm, the gap s is set to be not more than 0.4 mm. Also, for example, when the thickness T is 1.2 mm and the thickness t is 1.1 mm, the gap s is set to be not more than 1.0 mm.

[0041] As described above, when there is a gap s, the larger the gap s, the smaller the interaction between the upper steel material 10 and the lower steel material 12, and the less likely it is for the upper steel material 10 and the lower steel material 12 to come into contact, which makes the lower steel material 12 more likely to deform. In other words, the larger the gap s, the more likely it is for welding deformation to occur in the welded joint 100. Therefore, the present invention is preferably used when there is a gap s, that is, when the gap s is larger than 0 mm, more preferably when it is 0.1 mm or more, and even more preferably when it is 0.2 mm or more.

[0042] In addition, when the gap s continuously exists in the welding line direction Y, the interaction between the upper steel material 10 and the lower steel material 12 tends to be reduced. Therefore, the effect of the present invention is preferably used in the welded joint 100 in which a portion where the gap s is larger than 0 mm continuously exists for 50 mm or more along the welding line direction Y.

[0043] In this embodiment, the heat input amount in the welding process is set to, for example, 150 to 300 J / mm, and the welding speed is set to 10 to 20 mm / s. As the shielding gas, for example, a mixed gas of argon and oxygen is used.

[0044] Since the welded portion 14 melts into the edge portion 10a of the upper steel material 10, in the welded joint 100, the overlapping width W2 between the upper steel material 10 and the lower steel material 12 is about 0.8 to 1.2 mm smaller than the overlapping width W1 between the upper steel material 10 and the lower steel material 12 before welding. Therefore, it is preferable that the welded joint 100 according to the present embodiment satisfies the following equations (v) and (ii) in the cross section orthogonal to the welding line direction Y of the welded portion 14. W0 - 3.2 ≤ W2 ≤ W0 + 1.2 ···(v) 0.5 ≤ T / t ≤ 1.5 ···(ii) In the above equations, W2 represents the overlapping width (mm) between the upper steel material 10 and the lower steel material 12, T represents the thickness (mm) of the upper steel material 10, and t represents the thickness (mm) of the lower steel material 12. In addition, W0 is the optimum value of the overlapping width between the upper steel material 10 and the lower steel material 12. When T ≥ t, it is obtained by the following equation (iii), and when T < t, it is obtained by equation (iv). W0 = 6(T / t) + 6s ···(iii) W0 = 16 - 10(t / T) + 6s ···(iv) In the above equations, s represents the gap (mm) between the upper steel material 10 and the lower steel material 12.

[0045] As shown in Figure 7, in the lap fillet welded joint of this embodiment, the position 14a of the weld 14 that is most deeply penetrated into the upper steel material 10 is taken as the end of the upper steel material 10, and the overlap width W2 of the upper steel material 10 and the lower steel material 12 in the welded joint 100 is determined.

[0046] According to this embodiment, the amount of welding deformation is suppressed by appropriately setting the overlap width W1 (W2) between the upper steel material 10 and the lower steel material 12. Therefore, no additional processing steps (special processing for suppressing the amount of welding deformation, such as heat treatment, straightening, or installation of reinforcing parts) are required. This reduces the cost required for additional processing steps. In other words, it is possible to provide a technology for suppressing the amount of welding deformation of a lap fillet welded joint at low cost.

[0047] (Variation) In the above-described embodiment, the case where steel plates (plate-shaped members) are used as the first steel material and the second steel material has been described. However, the shapes of the first steel material and the second steel material are not limited to the above-described example, and steel materials of various shapes can be used as the first steel material and the second steel material. For example, a cylindrical steel material (steel pipe) may be used as the first steel material and / or the second steel material. Furthermore, formed products of various shapes may be used as the first steel material and / or the second steel material. Specifically, for example, the present invention may be applied to a welded joint 100 as shown in FIG. 9.

[0048] In the welded joint 100 shown in FIG. 9, both the upper steel material 10 (outer steel material) and the lower steel material 12 (inner steel material) have a cylindrical shape. In this embodiment, too, by manufacturing the welded joint 100 so as to satisfy the above-mentioned requirements, the amount of welding deformation can be suppressed without requiring any additional processing steps. Note that in the welded joint 100 shown in FIG. 9, the upper steel material 10 and the lower steel material 12 have a cylindrical shape, but the upper steel material 10 and the lower steel material 12 may also have a rectangular cylindrical shape. Furthermore, formed products of various other shapes may be used as the upper steel material 10 and the lower steel material 12.

[0049] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0050] Welded joints having a configuration similar to that of the welded joint 100 shown in Figures 1 and 7 were fabricated by varying the thickness T of the upper steel material 10, the thickness t of the lower steel material 12, the gap s between the upper steel material 10 and the lower steel material 12, and the overlap width W1 between the upper steel material 10 and the lower steel material 12, and the magnitude of welding distortion occurring in the welded joint was investigated. Specifically, two rectangular steel plates measuring 60 mm x 150 mm were prepared as test plates, and the back surface of one steel plate (upper steel material 10) was positioned so that the long side of the back surface of the other steel plate (lower steel material 12) overlapped. Arc welding was performed to join one end face extending in the thickness direction of the upper steel plate to the surface of the lower steel plate, which was approximately perpendicular to the back surface, to obtain a welded joint. The length of the weld 14 was 100 mm. The welding conditions and investigation results are shown in Table 1 below. Ferritic stainless steel (NSSC436S: 17Cr-1.2Mo-0.2Ti-0.09Si-0.02C,N manufactured by Nippon Steel Stainless Steel Corporation) and austenitic stainless steel (SUS316L) were used as the materials for the upper steel material 10 and the lower steel material 12. Austenitic stainless steel (WEL MIG 308 manufactured by Nippon Welding Rod Co., Ltd.) was used as the filler metal, and Ar + 2% O2 was used as the shielding gas.

[0051] In Table 1, as shown in Figures 7 and 8, overlap width W1 represents the overlap width of the upper steel material 10 and the lower steel material 12 during welding, the optimal overlap width W0 is the value calculated using the above-mentioned formula (iii) or (iv), and overlap width W2 represents the overlap width of the upper steel material 10 and the lower steel material 12 in the welded joint 100 as shown in Figure 7. Also, in Table 1, "convex on the front" in the weld joint column indicates that the upper steel material 10 or the lower steel material 12 has deformed so as to be convex toward the front side in the stacking direction X when viewed from the width direction Z of the welded portion 14, and "convex on the back" indicates that the upper steel material 10 or the lower steel material 12 has deformed so as to be convex toward the back side in the stacking direction X when viewed from the width direction Z. Also, the deformation amount of the welded joint in Table 1 refers to the deformation amount in the stacking direction X of the portion of the lower steel material 12 where the welded portion 14 is formed. The deformation amount was measured on the back surface 12b of the lower steel material 12 (see FIG. 1(b)). Specifically, the position in the stacking direction X of the part of the back surface 12b corresponding to the weld 14 was measured along the weld line direction Y of the weld 14, and the difference between the highest position and the lowest position in the stacking direction X was taken as the deformation amount. When the lower steel material 12 was deformed so as to be convex toward the back side, the average value of the heights of the measurement start point (one end of the measurement area in the weld line direction Y) and the measurement end point (the other end of the measurement area in the weld line direction Y) was taken as the height of the highest position. When the lower steel material 12 was deformed so as to be convex toward the front side, the average value of the heights of the measurement start point and the measurement end point was taken as the height of the lowest position.

[0052] [Table 1]

[0053] As shown in Table 1, in the welded joints of the examples of the present invention, Nos. 2, 4, 9, 11, 15, 17, 18, and 21, in which the difference between the overlap width W1 of the upper steel material 10 and the lower steel material 12 during welding and the optimal overlap width W0 was 2.0 mm or less, the upper steel material 10 and the lower steel material 12 deformed in opposite directions in the lamination direction X. As a result, the deformations of the upper steel material 10 and the lower steel material 12 canceled each other out, and welding deformation could be suppressed.

[0054] On the other hand, in the welded joints of the comparative examples Nos. 1, 3, 5 to 8, 10, 12 to 14, 16, 19, 20, and 22, in which the difference between the overlap width W1 of the upper steel material 10 and the lower steel material 12 during welding and the optimal overlap width W0 was 3.0 mm or more, the upper steel material 10 and the lower steel material 12 deformed in the same direction in the lamination direction X. Therefore, in each of the welded joints of the comparative examples, the amount of deformation was larger than that of the welded joints of the invention examples in which the thicknesses and gaps s of the upper steel material 10 and the lower steel material 12 were the same.

[0055] From the above results, it can be seen that the manufacturing method of a lap fillet welded joint that satisfies the requirements of the present invention can suppress the amount of welding distortion of the welded joint. In particular, it can be seen that the present invention can sufficiently suppress welding distortion of the welded joint 100 even when austenitic stainless steel, which is prone to welding distortion, is used as the filler metal.

[0056] Among the welded joints of the comparative examples, in welded joints Nos. 1, 7, 8, 10, 13, 14, 16, and 20, the overlap width W1 of the upper steel material 10 and the lower steel material 12 during welding was smaller than the optimal overlap width W0, and it is believed that deformation of the lower steel material 12 was dominant compared to deformation of the upper steel material 10. For this reason, it is believed that in welded joints Nos. 1, 7, 8, 10, 13, 14, 16, and 20, both the upper steel material 10 and the lower steel material 12 were deformed so as to be convex on the front side. Furthermore, in welded joints Nos. 3, 5, 6, 12, 19, and 22, the overlap width W1 of the upper steel material 10 and the lower steel material 12 during welding was larger than the optimal overlap width W0, and it is believed that deformation of the upper steel material 10 was dominant compared to deformation of the lower steel material 12. For this reason, it is believed that in welded joints Nos. 3, 5, 6, 12, 19, and 22, both the upper steel material 10 and the lower steel material 12 were deformed so as to be convex on the back side. [Industrial Applicability]

[0057] According to the present invention, by appropriately setting the overlap width between the first steel material and the second steel material, the amount of welding deformation of the lap fillet welded joint can be suppressed without requiring any additional processing steps. [Explanation of symbols]

[0058] 10,12 Steel material 10a Edge 12a surface 12b Back 14 Welded parts 100 Welded joints

Claims

1. a welding process in which, in a state in which a part of a first steel material having a predetermined thickness is overlapped on a second steel material having a predetermined thickness, the edge portion of the first steel material and a surface of the second steel material are fillet welded together so as to form a weld along the edge portion of the first steel material; In the welding step, the first steel material and the second steel material are welded using an austenitic stainless steel filler metal so that the following expressions (i) and (ii) are satisfied in a cross section orthogonal to a weld line direction of the weld portion. W ０ -2.0≦W １ ≦W ０ +2.0 ・・・(i) 0.5≦T / t≦1.5...(ii) In the above formula, W １ represents the overlap width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, and t represents the thickness (mm) of the second steel material. Also, W ０ When T≧t, it is calculated by the following formula (iii), and when T<t, it is calculated by the following formula (iv). W ０ =6(T / t)+6s ・・・(iii) W ０ =16-10(t / T)+6s ・・・(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

2. The method for manufacturing a lap fillet welded joint according to claim 1, wherein a gap between the first steel material and the second steel material is 0.2 mm or more.

3. A method for setting an overlap width between a first steel material and a second steel material when manufacturing a lap fillet welded joint by overlapping a portion of a first steel material having a predetermined thickness on a second steel material having a predetermined thickness and fillet welding the edge portion of the first steel material and a surface of the second steel material so as to form a weld along the edge portion of the first steel material, A method for setting an overlap width of a lap fillet welded joint, wherein the overlap width is set so that the following formulas (i) and (ii) are satisfied in a cross section of the weld perpendicular to the weld line direction: W ０ -2.0≦W １ ≦W ０ +2.0 ・・・(i) 0.5≦T / t≦1.5...(ii) In the above formula, W １ represents the overlap width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, and t represents the thickness (mm) of the second steel material. Also, W ０ When T≧t, it is calculated by the following formula (iii), and when T<t, it is calculated by the following formula (iv). W ０ =6(T / t)+6s ・・・(iii) W ０ =16-10(t / T)+6s ・・・(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

4. 4. The method for setting an overlap width of a lap fillet welded joint according to claim 3, wherein a gap between the first steel material and the second steel material is 0.2 mm or more.

5. A lap fillet welded joint in which a portion of a first steel material having a predetermined thickness is overlapped on a second steel material having a predetermined thickness, and the edge portion and a surface of the second steel material are fillet welded by a weld formed along the edge portion of the first steel material, A lap fillet welded joint, wherein the following formulas (v) and (ii) are satisfied in a cross section of the weld portion perpendicular to the weld line direction: W ０ -3.2≦W ２ ≦W ０ +1.2 ・・・(v) 0.5≦T / t≦1.5...(ii) In the above formula, W ２ represents the overlap width (mm) of the first steel material and the second steel material, T represents the thickness (mm) of the first steel material, t represents the thickness (mm) of the second steel material, and W2 is determined by taking the position of the weld that is most deeply penetrated into the first steel material as the end of the first steel material. Also, W ０ When T≧t, it is calculated by the following formula (iii), and when T<t, it is calculated by the following formula (iv). W ０ =6(T / t)+6s ・・・(iii) W ０ =16-10(t / T)+6s ・・・(iv) In the above formula, s represents the gap (mm) between the first steel material and the second steel material, and is 0 or more.

6. The lap fillet welded joint according to claim 5, wherein a gap between the first steel material and the second steel material is 0.2 mm or more.

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