Manufacturing method for tubular members

Abstract

This improves the processability of tubular members formed by spiral tube manufacturing. [Solution] The method for manufacturing a tubular member comprises spirally winding a plate-shaped metal member having first and second edges located at both ends in the width direction, and butting the first and second edges of the metal member together to form the metal member into a tubular shape extending along its axis. The manufacturing method also comprises irradiating the butt joint between the first and second edges of the tubular-shaped metal member with laser light to perform laser welding, and irradiating the inner circumferential surface of the tubular-shaped metal member with the laser light that has passed through the butt joint to perform heat treatment.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a tubular member.

Background Art

[0002] As described in Patent Document 1, spiral tube making is known in which a long steel plate is spirally wound and both ends in the width direction of the steel plate are welded to form a tubular member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the steel material used for spiral tube making is made of high-tensile steel, softening may occur in the heat-affected zone adjacent to the welded part. On the other hand, when the steel material is made of general steel other than high-tensile steel, hardening may occur at the welded part. Due to these reasons, it may be difficult to process the tubular member formed by spiral tube making.

[0005] In one aspect of the present disclosure, it is desirable to improve the workability of the tubular member formed by spiral tube making.

Means for Solving the Problems

[0006] One aspect of the present disclosure is a method for manufacturing a tubular member, comprising: spirally winding a plate-shaped metal member having first and second edges located at both ends in the width direction, and butting the first and second edges of the metal member together to form the metal member into a tubular shape extending along its axis; irradiating the butt joint portion, which is the part where the first and second edges of the tubular-shaped metal member are butted together, with laser light to perform laser welding between the first and second edges; and irradiating the inner circumferential surface of the tubular-shaped metal member with the laser light that has passed through the butt joint portion to perform heat treatment on the inner circumferential surface of the metal member.

[0007] According to the above configuration, when spiral pipe formation is performed by laser welding, the laser beam passing through the butt joint heats the metal component. Therefore, the processability of the tubular component formed by spiral pipe formation can be improved.

[0008] In one aspect of this disclosure, the metal member may be made of general steel, which has a tensile strength of less than 780 MPa. The laser beam that has passed through the butt joint may be irradiated onto the normal portion of the metal member, which is the part that has not been affected by laser welding, and a heat treatment may be performed to improve the hardness of the normal portion.

[0009] According to the above configuration, in the tubular members, a hardened welded area is formed at the butt joint by laser welding. In addition, a hardened area is formed between the butt joints of the tubular members by the laser light that passes through the butt joint during laser welding. Therefore, when the tubular members are deformed, the areas where deformation is likely to occur are divided, thereby promoting more uniform deformation of the tubular members. Consequently, the processability of tubular members formed by spiral tubing can be improved.

[0010] In one aspect of this disclosure, the metal member may be made of high-tensile steel, which is a steel material with a tensile strength of 780 MPa or more. The laser beam that has passed through the butt joint may be irradiated onto the normal portion of the metal member, which is the portion that has not been affected by laser welding, and a heat treatment may be performed to reduce the hardness of the normal portion.

[0011] According to the above configuration, a welded area having a softened HAZ (Heat-Affected Zone) is formed at the butt joint of the tubular members by laser welding. Furthermore, a softened HAZ is formed between the butt joints of the tubular members by the laser light that passes through the joint during laser welding. This reduces stress concentration when the tubular members are deformed. Consequently, the processability of tubular members formed by spiral tubing can be improved.

[0012] One aspect of the present disclosure is a method for manufacturing a tubular member, wherein the laser beam is irradiated in a direction substantially perpendicular to the axis. According to the above configuration, the laser beam that passes through the butt joint during laser welding can be irradiated to approximately the center of the metal member. Therefore, in a tubular member, the distance between the welded portion formed at the butt joint and the portion heat-treated by the laser beam that passed through the butt joint can be made to be approximately constant. Consequently, the processability of the tubular member formed by spiral tubing can be improved.

[0013] In one aspect of this disclosure, the metal member may be made of general steel, which has a tensile strength of less than 780 MPa. The laser beam that has passed through the butt joint may be irradiated onto the butt joint that has been laser-welded beforehand, and a heat treatment may be performed to reduce the hardness of the butt joint.

[0014] According to the above configuration, the hardness of the welded joint formed at the butt joint by laser welding can be reduced, thereby mitigating stress concentration when deforming the tubular member. Therefore, the processability of the tubular member formed by spiral tubing can be improved.

[0015] In one aspect of this disclosure, the metal member may be made of high-tensile steel, which is a steel material with a tensile strength of 780 MPa or more. The laser beam that has passed through the butt joint may be irradiated onto the butt joint that has been laser-welded beforehand, and a heat treatment may be performed to improve the hardness of the butt joint.

[0016] According to the above configuration, a welded joint with a softened heat-affected zone (HAZ) is formed at the butt joint of the tubular members by laser welding. Therefore, the hardness of the HAZ can be improved by the laser light that passes through the butt joint during laser welding. This can alleviate stress concentration when the tubular members are deformed, and as a result, the processability of the tubular members formed by spiral tubing can be improved.

[0017] One aspect of the present disclosure is a method for manufacturing a tubular member, wherein the direction of the abutted first and second edges when the tubularly formed metal member is viewed from the side is defined as the inclination direction, and the laser beam is irradiated in a direction parallel to the inclination direction.

[0018] According to the above configuration, heat treatment can be performed by the laser beam that has passed through the butt joint in the vicinity of the welding area where laser welding of the butt joint is performed. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1A is an explanatory diagram of the forming step and welding step in the first and second embodiments. Figure 1B is a graph showing the distribution of hardness of a metal member made of general steel material before and after irradiation with laser light in the first embodiment. [Figure 2] Figure 2A is an explanatory diagram of the bending step in the first embodiment. Figure 2B is a graph showing the hardness distribution of a metal member made of high-tensile steel before and after irradiation with laser light in the second embodiment. [Figure 3] Figure 3 is an explanatory diagram of the bending step in the second embodiment. [Figure 4] Figure 4A is an explanatory diagram of the forming step and welding step in the third and fourth embodiments. Figure 4B is a graph showing the distribution of hardness of the welded joint in a metal member made of general steel material before and after irradiation with laser light in the third embodiment. [Figure 5]FIG. 5 is a graph showing the hardness distribution of the welded portion in the metal member made of high-tensile steel before and after the irradiation of the laser beam in the fourth embodiment.

Mode for Carrying Out the Invention

[0020] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. First Embodiment] [(1) Overview] The manufacturing method of the tubular member 2 according to the first embodiment includes a forming step, a welding step, and a bending step (see FIG. 1A). In the forming step and the welding step, a tubular member 2 that extends straight along the axis A is manufactured from the metal member 1 by spiral tube manufacturing. Note that the axis A passes through the center of the cross section orthogonal to the stretching direction in the tubular member 2. Further, as an example, the tubular member 2 has a cylindrical shape, and the cross section orthogonal to the axis A is circular.

[0021] The metal member 1 is a plate-like member that extends straight with a constant width and has first and second edge portions 10 and 11 located at both ends in the width direction. Further, in the first embodiment, as an example, the metal member 1 is made of a general steel material whose tensile strength is less than 780 MPa.

[0022] [(2) Forming Step] In the forming step, a forming machine (not shown) feeds out the metal member 1 along the axis A while relatively rotating the metal member 1, and forms the metal member 1 in a spiral shape (see FIG. 1A). As a result, the metal member 1 is formed into a tube that extends straight along the axis A, and the first edge portion 10 and the second edge portion 11 are brought into contact with each other. That is, by fixing the tip of the metal member 1 to a jig (not shown) and forming the metal member 1 in a spiral shape, the metal member 1 is formed into a tube without using a mandrel. Hereinafter, the portion where the first and second edge portions 10 and 11 in the spirally formed tubular member 2 are brought into contact with each other is referred to as a butted portion 12. <0oo00102> [(3) Welding Step] The welding step proceeds simultaneously with the forming step, and the butt joint 12 of the metal member 1, which was formed in a spiral shape during the forming step, is laser-welded (see Figure 1A). As a result, the first and second edges 10 and 11 of the butt joint 12 are joined together, forming the tubular member 2.

[0024] The laser welding apparatus 6 used in the welding step comprises a laser head 60, an assist gas nozzle 61, and a laser oscillator (not shown). The laser welding apparatus 6 may, for example, be configured as a fiber laser. Of course, it is not limited to this, and the laser welding apparatus 6 can have various configurations.

[0025] The laser head 60 irradiates the laser beam L generated by the laser oscillator. The laser head 60 irradiates the laser beam L from the outside of the spirally shaped metal member 1 toward the abutting portion 12.

[0026] The position of the laser head 60 and the irradiation direction of the laser beam L are fixed. As described above, the molding machine feeds the metal member 1 to the first side F. Therefore, in the spirally formed metal member 1, the welding area W, which is the area where the laser beam L is irradiated and welding is performed, is displaced relative to the opposite side of the first side F (hereinafter referred to as the second side S) on the butt joint 12. As a result, the first and second edges 10 and 11 of the butt joint 12 are joined, and a welded portion 3 that extends continuously from the butt joint 12 is formed. Note that the position of the laser head 60 and / or the irradiation direction of the laser beam L may be variable, and the position and / or irradiation direction may be changed as appropriate during the spiral pipe forming process.

[0027] Then, by irradiating the butt joint 12 with laser light L, a molten portion is formed on the first and second edges 10 and 11, and a HAZ is formed adjacent to this portion. The welded portion 3 includes the molten portion and the HAZ portions located on both sides of the molten portion.

[0028] Furthermore, an assist gas nozzle 61 is positioned on the outside of the spirally formed metal member 1, which injects assist gas toward the welding area W on the outer surface of the metal member 1. As an example, the assist gas nozzle 61 is positioned on the second side S of the welding area W, but the position of the assist gas nozzle 61 is not limited to this and can be determined as appropriate.

[0029] Furthermore, an assist gas nozzle 61 is also positioned inside the spirally shaped metal member 1. For example, the assist gas nozzle 61 injects assist gas to the first side F approximately parallel to axis A. Note that no laser head is positioned inside the metal member 1.

[0030] Furthermore, a shielding gas or the like may be injected instead of the assist gas, and these gases may be used in combination. In addition, the direction of gas injection may be perpendicular to axis A.

[0031] [(4) Backside break] In the welding step, the laser head 60 irradiates laser light L in a direction approximately perpendicular to axis A (see Figure 1A). "Approximately perpendicular" means that the direction of the laser light L is approximately perpendicular to axis A, and that the laser light L intersects axis A or passes near axis A. For example, the laser head 60 is positioned above the metal member 1, but the position of the laser head 60 is not limited to this and can be determined as appropriate.

[0032] As described above, the welding area W irradiated by the laser beam L is formed at the butt joint 12 on the outer circumferential surface of the metal member 1, which is formed in a spiral shape during the forming step. A portion of the laser beam L irradiated onto the welding area W passes through the butt joint 12 and irradiates the inner circumferential surface 13 of the metal member 1. Hereafter, the passage of a portion of the laser beam L through the butt joint 12 will be referred to as "penetration to the back."

[0033] Furthermore, the laser welding apparatus 6 may be set so that the laser beam L is more likely to penetrate the back of the weld. Specifically, in the laser welding apparatus 6, for example, the output intensity distribution of the laser beam L may be adjusted using a DOE so that the center of the irradiation area of ​​the laser beam L has a relatively higher output intensity than the outer periphery. This makes it easier for keyholes to form in the welding area W, and as a result, easier for penetrate to occur.

[0034] In addition, the laser welding apparatus 6 may be configured to form a point-shaped laser beam L irradiation area and a ring-shaped laser beam L irradiation area surrounding the point-shaped irradiation area. This allows the laser beam forming the point-shaped irradiation area to pass through to the back while the butt joint 12 is welded by the ring-shaped irradiation area.

[0035] Furthermore, the laser welding apparatus 6 may irradiate, for example, multiple types of laser light L with different wavelengths. It may also weld the butt joint 12 with laser light L of a specific wavelength while simultaneously generating back-side penetration with laser light L of other wavelengths. Alternatively, the focal points of the laser light L for welding and the laser light L for back-side penetration may be individually adjusted so that these laser beams L are suitably irradiated onto the butt joint 12 and the inner circumferential surface 13.

[0036] Then, in the heat treatment region 13A on the inner circumferential surface 13 of the spirally formed metal member 1, where the laser light L that has passed through to the back is irradiated, the metal member 1 is heat-treated, and a heat treatment section 5 is formed in the heat treatment region 13A after irradiation with the laser light L.

[0037] Furthermore, the laser beam L is irradiated in a direction substantially perpendicular to the axis A. Also, as the metal member 1 is fed to the first side F, the heat treatment region 13A is also displaced relative to the second side S along the abutment portion 12. Therefore, the heat treatment region 13A is formed substantially in the center of the width direction of the spirally formed metal member 1. The heat treatment portion 5 is formed substantially in the center of the width direction of the spirally formed metal member 1, and substantially in the center of the width direction of the metal member 1 on the inner circumferential surface 13 of the tubular member 2, extending along the abutment portion 12. That is, the abutment portion 12 and the heat treatment portion 5 extend substantially parallel to each other.

[0038] In other words, the heat treatment area 13A and the heat treatment area 5 are formed in the part of the metal member 1 other than the welded part 3, or in other words, in the part of the metal member 1 that is not affected by laser welding (hereinafter referred to as the normal part 4).

[0039] [(5) Regarding heat treatment] The metal member 1 of the first embodiment is made of general steel. As a result, the hardness of the welded portion 3 increases. That is, in general steel, the welded portion is harder than the unwelded portion. In addition, the laser light L irradiated onto the inner circumferential surface 13 by back-through heat treatment (in other words, quenching) is performed to increase the hardness of the normal portion 4.

[0040] In other words, as shown by the distribution D0 in Figure 1B, the hardness of the normal portion 4 of the metal member 1 is constant. However, as shown by the distribution D1 in Figure 1B, the hardness of the welded portion 3 and the heat-treated portion 5 formed by the heat treatment is higher than that of the normal portion 4. Specifically, the hardness distribution of the cross-section (hereinafter simply referred to as the cross-section) perpendicular to the stretching direction in the welded portion 3 and the heat-treated portion 5 is a Gaussian distribution, with the center in the width direction being the hardest, and the hardness decreasing towards both ends in the width direction.

[0041] [(6) Bending step] The tubular member 2 formed in the forming and welding steps has spirally extending welded sections 3 and heat-treated sections 5, which are arranged alternately along axis A at approximately constant intervals (see Figure 2A). In addition, the welded sections 3 and heat-treated sections 5 have increased hardness compared to the normal sections 4. In the bending step, the tubular member 2 is bent, resulting in all or part of the tubular member 2 becoming curved.

[0042] [2. Second Embodiment] [(1) Overview] The manufacturing method of the second embodiment also includes the same forming step, welding step, and bending step as the first embodiment. The forming step and welding step perform spiral pipe formation in the same way as the first embodiment, and a tubular member 2 is manufactured (see Figure 1A). However, the manufacturing method of the second embodiment differs from the first embodiment in that the metal member 1 is made of high-tensile steel, which is a steel material with a tensile strength of 780 MPa or more. The differences between the manufacturing method of the second embodiment and the first embodiment will be explained below.

[0043] [(2) Welding Step] In the welding step of the second embodiment, similar to the first embodiment, a welded portion 3 is formed on the butt joint portion 12 of the metal member 1, which was formed spirally in the forming step, by laser welding (see Figure 1A). Also, similar to the first embodiment, a portion of the laser light L irradiated onto the welding area W passes through to the inner circumferential surface 13 of the metal member 1. Then, heat treatment is performed in the heat treatment area 13A where the laser light L is irradiated, and a heat treatment section 5 is formed. Furthermore, the heat treatment area 13A and the heat treatment section 5 are formed in the normal portion 4 of the metal member 1, more specifically, approximately in the center in the width direction of the metal member 1.

[0044] [(3) Regarding heat treatment] The metal member 1 of the second embodiment is made of high-tensile steel. Therefore, areas with reduced hardness are likely to occur in the welded area 3. In other words, in high-tensile steel, areas that are welded tend to be softer than areas that are not welded. In addition, the laser light L irradiated onto the inner circumferential surface 13 by back-through heat treatment (in other words, annealing) is performed to reduce the hardness of the normal area 4.

[0045] In other words, as shown by the distribution D2 in Figure 2B, the hardness of the normal portion 4 of the metal member 1 is constant. However, as shown by the distribution D3 in Figure 2B, the hardness decreases in the welded portion 3 and the heat-treated portion 5 formed by the heat treatment. Specifically, the hardness decreases in the heat-induced zones (HAZs) located at both ends in the width direction of the cross-section of the welded portion 3 and the heat-treated portion 5. On the other hand, in the center of the cross-section of the welded portion 3 and the heat-treated portion 5 in the width direction, in other words, in the portion where melting occurred due to irradiation with laser light L, the hardness increases slightly near the boundary with the HAZ, but it has a hardness similar to that of the normal portion 4.

[0046] [(4) Bending step] The tubular member 2 formed in the forming and welding steps has spirally extending welded sections 3 and heat-treated sections 5, which are arranged alternately along axis A at approximately constant intervals (see Figure 3). In addition, each of the welded section 3 and heat-treated section 5 has HAZ 30 and 50 with reduced hardness formed at both ends in the width direction. HAZ 30 and 50 extend together with the welded section 3 or heat-treated section 5. In the bending step, the tubular member 2 is bent, resulting in all or part of the tubular member 2 becoming curved.

[0047] [3. Third Embodiment] [(1) Overview] The manufacturing method of the third embodiment also includes a molding step, a welding step, and a bending step, similar to the first embodiment. The molding step and the welding step perform spiral pipe formation, and a tubular member 2 is manufactured (see Figure 4A). However, the manufacturing method of the third embodiment differs from that of the first embodiment in the angle of the laser beam L irradiated from the laser head 60 during the welding step. The differences between the manufacturing method of the third embodiment and that of the first embodiment will be described below.

[0048] [(2) Welding Step] In the laser welding step of the third embodiment, the laser head 60 also irradiates the laser beam L from the outside of the spirally formed metal member 1 toward the butt joint 12 (see Figure 4A). As a result, a welded joint 3 similar to that of the first embodiment is formed.

[0049] However, in the third embodiment, the irradiation direction of the laser beam L from the laser head 60 is not in a direction substantially perpendicular to the axis A, but in a direction inclined with respect to the axis A. Then, a portion of the laser beam L irradiated onto the welding area W passes through to the back, as in the first embodiment, but in the third embodiment, the laser beam that passes through to the back is irradiated onto the welded portion 3 on the inner circumferential surface 13 of the metal member 1. In other words, a heat treatment area 13A is formed in the welded portion 3, and heat treatment is performed on the welded portion 3.

[0050] In the third embodiment, as an example, the irradiation direction of the laser beam L is parallel to the inclination direction. The inclination direction refers to the direction in which the first and second edges 10 and 11 extend when the spirally shaped metal member 1 and the tubular member 2 are viewed from the side from a direction perpendicular to the axis A.

[0051] In other words, when the spirally formed metal member 1 and the tubular member 2 are viewed from the side from a direction perpendicular to the axis A, the first and second edges 10 and 11 extending from the welding area W are located on the extension of the laser beam L from the laser head 60.

[0052] [(3) Regarding heat treatment] In the third embodiment, the metal member 1 is made of general steel, so the hardness of the welded joint 3 increases. Then, a heat treatment (in other words, annealing) is performed on the welded joint 3 by laser light L irradiated from the inner circumferential surface 13 side by back-through, which reduces the hardness of the welded joint 3.

[0053] In other words, as already explained, the hardness distribution D4 of the cross-section in the welded joint 3 is a Gaussian distribution (see Figure 4B). When the above heat treatment is performed on the welded joint 3, the hardness of the welded joint 3 decreases, as shown by distribution D5. More specifically, the hardness of the hardened portion of the welded joint 3 decreases due to irradiation with laser light L, and the hardness of the welded joint 3 approaches that of the normal portion 4.

[0054] [4. Fourth Embodiment] [(1) Overview] The manufacturing method of the fourth embodiment also includes a forming step, a welding step, and a bending step, similar to the third embodiment. The forming step and the welding step perform spiral pipe formation, and a tubular member 2 is manufactured (see Figure 4A). However, the manufacturing method of the fourth embodiment differs from the third embodiment in that the metal member 1 is made of high-tensile steel. The differences between the manufacturing method of the fourth embodiment and the third embodiment will be explained below.

[0055] [(2) Welding Step] In the welding step of the fourth embodiment, similar to the third embodiment, a welded portion 3 is formed on the butt joint 12 of the metal member 1 that was formed spirally in the forming step by laser welding (see Figure 4A). Also, similar to the third embodiment, a portion of the laser light L irradiated onto the welding area W passes through to the back and is irradiated onto the welded portion 3 from the inner circumferential surface 13 side. Then, a heat treatment area 13A is formed on the welded portion 3, and the welded portion 3 is heat treated.

[0056] [(3) Regarding heat treatment] Since the metal member 1 of the fourth embodiment is made of high-tensile steel, the hardness of the welded portion 3 decreases as described above. Then, a heat treatment (in other words, quenching) is performed to increase the hardness of the welded portion 3 by laser light L irradiated onto the welded portion 3 from the inner circumferential surface 13 side by back-through.

[0057] In other words, as already explained, in the welded joint 3, a HAZ 30 with reduced hardness is formed at each end in the width direction, and the hardness is distributed in the cross-section of the welded joint 3 as shown by distribution D6 in Figure 5. When the heat treatment described above is performed on the welded joint 3, the hardness of the HAZ 30 increases as shown by distribution D7, and the difference in hardness in the welded joint 3 is mitigated.

[0058] [5. Effects] (1) According to the first to fourth embodiments, when spiral pipe formation is performed by laser welding, the laser beam L that passes through the butt joint 12 is used to heat-treat the metal member 1. As a result, the processability of the tubular member 2 formed by spiral pipe formation can be improved.

[0059] (2) In other words, in the first embodiment, hardening occurs at the welded portion 3, but between the welded portions 3 of the tubular member 2, a heat-treated portion 5 is formed, which is hardened by the laser light L that penetrates to the back. Therefore, when bending the tubular member 2, the areas in the tubular member 2 that are prone to deformation are divided, thereby promoting more uniform deformation of the tubular member 2.

[0060] Furthermore, the heat treatment section 5 is located approximately in the center of the width direction of the metal member 1, and in the tubular member 2, the distance between the welded section 3 and the heat treatment section 5 in the direction of axis A is approximately constant. As a result, the easily bendable parts of the tubular member 2 can be distributed more appropriately, and the bending process can encourage the tubular member 2 to bend more in an arc shape.

[0061] (3) In the second embodiment, a softened HAZ 30 is formed in the welded portion 3, but a heat treatment portion 5 having a softened HAZ 50 is formed between the welded portions 3 of the tubular member 2 by the laser light L that penetrates to the back. This makes it possible to alleviate stress concentration when bending the tubular member 2.

[0062] Furthermore, the heat treatment section 5 is located approximately in the center of the width direction of the metal member 1, and in the tubular member 2, the distance between the welded section 3 and the heat treatment section 5 in the direction of axis A is approximately constant. Therefore, the stress generated in the tubular member 2 due to bending can be better distributed.

[0063] (4) In addition, in the third embodiment, the welded portion 3 is irradiated with laser light L that has passed through to the back, so the hardness of the welded portion 3 can be reduced, thereby mitigating stress concentration when bending the tubular member 2.

[0064] (5) In the fourth embodiment, the hardness of the HAZ 30 in the welded portion 3 is increased by irradiating the welded portion 3 with the laser light L that has passed through to the back. This makes it possible to alleviate stress concentration when bending the tubular member 2.

[0065] (6) In addition, in the third and fourth embodiments, the irradiation direction of the laser beam L from the laser head 60 is parallel to the inclination direction of the butt joint 12 in the spirally formed metal member 1 or tubular member 2. Therefore, a heat treatment area 13A can be formed near the welding area W where laser welding is performed.

[0066] [6. Other Embodiments] (1) In the first to fourth embodiments, the tubular member 2 is manufactured from a metal member 1 made of general steel or high-tensile steel. However, the invention is not limited to this, and in the first to fourth embodiments, the tubular member 2 may be manufactured from a metal member 1 made of a metal material other than general steel and high-tensile steel.

[0067] (2) In the first and second embodiments, the laser head 60 irradiates laser light L in a direction substantially perpendicular to the axis A. However, the direction of the laser light L irradiated from the laser head 60 can be appropriately determined within a range in which the laser light L that passes through the back irradiates the normal portion 4 on the inner circumferential surface 13 of the spirally formed metal member 1 or tubular member 2.

[0068] (3) In the third and fourth embodiments, the laser head 60 irradiates the laser beam L in an irradiation direction parallel to the inclination direction. However, the direction of the laser beam L irradiated from the laser head 60 can be appropriately determined within the range in which the laser beam L irradiates the inner circumferential surface 13 side of the welded part 3.

[0069] (4) The manufacturing method of the tubular member 2 in the first to fourth embodiments does not have to include a bending step. Furthermore, the tubular member 2 manufactured by this manufacturing method may be subjected to deformation processes other than bending.

[0070] (5) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, some of the configurations of the above embodiment may be omitted. Furthermore, at least some of the configurations of the above embodiment may be added to or replaced with the configurations of other above embodiments. [Explanation of Symbols]

[0071] A...axis, W...welding area, F...first side, S...second side, L...laser beam, 1...metal member, 10...first edge, 11...second edge, 12...butt joint, 13...inner surface, 13A...heat treatment area, 2...tubular member, 3...welded area, 30...HAZ, 4...normal area, 5...heat treatment area, 50...HAZ, 6...laser welding device, 60...laser head, 61...assist gas nozzle.

Claims

1. A method for manufacturing a tubular member, A plate-shaped metal member having first and second edges located at both ends in the width direction is wound in a spiral shape, and the first and second edges of the metal member are brought together to form the metal member into a tubular shape extending along its axis. The process involves irradiating a laser beam onto the butt joint, which is the portion where the first edge and the second edge of the tubularly shaped metal member meet, and performing laser welding between the first edge and the second edge. The laser beam that has passed through the butt joint is irradiated onto the inner circumferential surface of the tubularly formed metal member, thereby performing heat treatment on the inner circumferential surface of the metal member. A method for manufacturing a tubular member comprising the above.

2. A method for manufacturing a tubular member according to claim 1, The aforementioned metal member is made of general steel material having a tensile strength of less than 780 MPa. The laser beam that has passed through the butt joint is irradiated onto the normal portion of the metal member, which is the part unaffected by the laser welding, and the heat treatment is performed to improve the hardness of the normal portion. A method for manufacturing tubular members.

3. A method for manufacturing a tubular member according to claim 1, The aforementioned metal member is made of high-tensile steel, which is a steel material with a tensile strength of 780 MPa or more. The laser beam that has passed through the butt joint is irradiated onto the normal portion of the metal member, which is the part unaffected by the laser welding, and the heat treatment is performed to reduce the hardness of the normal portion. A method for manufacturing tubular members.

4. A method for manufacturing a tubular member according to claim 2 or claim 3, The laser light is irradiated in a direction substantially perpendicular to the axis. A method for manufacturing tubular members.

5. A method for manufacturing a tubular member according to claim 1, The aforementioned metal member is made of general steel material having a tensile strength of less than 780 MPa. The laser beam that has passed through the butt joint is irradiated onto the butt joint where the laser welding has been performed earlier, and the heat treatment is carried out to reduce the hardness of the butt joint. A method for manufacturing tubular members.

6. A method for manufacturing a tubular member according to claim 1, The aforementioned metal member is made of high-tensile steel, which is a steel material with a tensile strength of 780 MPa or more. The laser beam that has passed through the butt joint is irradiated onto the butt joint where the laser welding has been performed earlier, and the heat treatment is carried out to improve the hardness of the butt joint. A method for manufacturing tubular members.

7. A method for manufacturing a tubular member according to claim 5 or claim 6, When the tubular metal member is viewed from the side, the direction of the abutted first and second edges is defined as the inclination direction. The laser light is irradiated in a direction parallel to the tilt direction. A method for manufacturing tubular members.

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