JP2016182620A - Pipe laser welding method and coil manufactured using welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe laser welding method and a coil manufactured using the welding method, capable of ensuring a process welding length for a crater process and sufficiently performing the crater process when laser welding is performed on a plurality of pipes disposed to be adjacent in parallel.SOLUTION: At least one adjacent pipe adjacent to a to-be-welded pipe in parallel is disposed, and each position where the to-be-welded pipe is closest to the adjacent pipe in a joint part is defined as a closest position. Welding is performed in a predetermined laser output state clockwise and counterclockwise from a starting end near the closest position. A plurality of paths each starts from a portion near the adjacent or single closest position, a distance between a connection point where each path is connected to the facing path in the predetermined laser output state and the closest position forward in a welding progress direction is equal to or larger than a process welding length at which a crater process is performed toward a terminal end while gradually reducing a laser output.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser welding method for a pipe that welds pipe-to-tube joints in a plurality of passes, and in particular, one of a plurality of pipes arranged adjacent to each other in parallel is a U-shaped pipe or a short pipe. The present invention relates to a laser welding method for pipes when joining the like, and a coil manufactured using the welding method.

  In the field of boiler production, etc., specifically, a U-shaped tube or a short tube is joined to a straight pipe, and adjacent straight pipes are joined together to produce a coil, or fixed to a tube sheet. When joining another pipe to a pipe, it is necessary to perform welding on one of a plurality of pipes arranged adjacent to each other in parallel. Conventionally, in such pipe welding, all-around welding using a laser as a heat source has been proposed, but a pipe adjacent to the welded pipe (hereinafter referred to as an adjacent pipe) is arranged close to the welded pipe. In this case, it is difficult to perform welding by arranging a laser head between the welded pipe and the adjacent pipe.

  In recent years, several welding methods that can be applied even when the distance between the outer surfaces of the welded pipe and the adjacent pipe (hereinafter referred to as an adjacent pipe interval) is narrow have been proposed. For example, as one means for manufacturing a coil having an interval between adjacent pipes smaller than about 40 to 50 mm, the coil can be disposed between the welded pipe and the adjacent pipe and can be rotated along the outer surface of the welded pipe. A laser welding apparatus (for example, Patent Document 1) using a small laser head has been proposed. Since a small laser head such as that used in the laser welding apparatus described in Patent Document 1 is limited in cooling capacity, the laser welding apparatus described in Patent Document 1 is a thick plate that requires irradiation with a high-power laser. It is difficult to apply to back wave welding and high-speed welding.

  As another means for manufacturing a coil having an interval between adjacent pipes smaller than about 40 to 50 mm, a straight line connecting a position where the welded pipe and the adjacent pipe are closest to each other (hereinafter referred to as the closest approach position) at the joint. There has been proposed a coil manufacturing apparatus and manufacturing method (for example, Patent Document 2) in which a welding range is divided into two, and welding is performed half a cycle using two laser heads. In the coil manufacturing method in which welding is performed half a turn using two laser heads, it is not necessary to reduce the size of the laser head so that the laser head can be arranged between the welded pipe and the adjacent pipe. It is possible to increase the wall thickness of the tube that can be deeply penetrated and to improve the welding speed.

JP-A-9-52186 Japanese Patent No. 5523045

  In laser welding, a crater dent is generated at the end of the path. Since the crater causes welding cracks and the like, it is necessary to perform crater processing that fills the crater by down-slope control or the like that gently lowers the laser output at the terminal portion.

  In the coil manufacturing method described in Patent Document 2, when half-circular welding is performed in two passes starting from the vicinity of the closest approach position, a predetermined laser output state is maintained up to another closest position ahead in the welding progress direction. Then, after passing the closest approach position, the laser output is gradually reduced to perform crater processing. However, as will be described later, since there is a limit to the range in which the laser beam can be irradiated from the laser light source of each laser head to the welded pipe without being blocked by the adjacent pipe, it passes past the closest approach position in the welding progress direction. Therefore, it has been difficult to sufficiently perform the crater process by gradually reducing the laser output within the irradiation possible range. That is, in the half-circular welding in two passes starting from the vicinity of the closest approach position, the processing weld length for crater processing is not sufficiently secured, and as a result, there is a possibility that the crater processing is not sufficiently performed.

  The present invention has been made in view of the above-mentioned problems, and ensures sufficient processing weld length for crater processing when laser welding is performed on a plurality of tubes arranged adjacent to each other in parallel with each other. It is an object of the present invention to provide a laser welding method for a tube that can be processed and a coil manufactured by using the welding method.

  A tube laser welding method according to a first aspect of the present invention for solving the above-described problem is a tube laser welding method in which a joint between a tube and a tube is welded in a plurality of passes, and is adjacent to a welded tube in parallel. At least one adjacent pipe is arranged, and each position where the welded pipe and the adjacent pipe are closest to each other at the joint is defined as the closest position, and clockwise and counterclockwise from the starting end near the closest position. Welding is performed in a predetermined laser output state, and each of the plurality of passes proceeds from the vicinity of an adjacent or single closest approach position, and a connection point connected to the opposite path in the laser output state, and a welding progress direction front The distance from the closest approach position is equal to or longer than the processing welding length in which the laser output is gradually reduced toward the end to perform crater processing.

  The tube laser welding method according to the second invention is the tube laser welding method according to the first invention, wherein two of the adjacent tubes are arranged on both sides on the same plane of the welded tube. Welding is performed by four passes that proceed from the vicinity of the approach position.

  A tube laser welding method according to a third aspect of the present invention is the tube laser welding method according to the first or second aspect of the present invention, wherein the welded tube contains 0.005 to 2.0% of Al by mass%. Features.

According to a fourth aspect of the present invention, there is provided a tube laser welding method according to any one of the first to third aspects, wherein a filler material containing a deoxidizer is used.
The coil which concerns on 5th invention joins at least a straight pipe and a U-shaped pipe | tube with the laser welding method of the pipe | tube which concerns on 2nd invention, and is manufactured in the same U-shape connected or independent on the same plane.

  In the pipe laser welding method according to the first invention described above, welding is performed in a predetermined laser output state clockwise and counterclockwise from the start end in the vicinity of each closest approach position, and the laser output is gradually reduced toward the end. Crater processing. Each path travels from the vicinity of an adjacent or single closest approach position and connects to the opposite path in a predetermined laser output state, that is, a laser output state that is not subjected to downslope control for crater processing. A weld bead having no crack (in particular, in the case of reverse wave welding, the reverse wave bead) is formed. In each pass, crater treatment is performed by gradually reducing the laser output from a point (hereinafter referred to as a connection point) that connects with the opposite path in a predetermined laser output state. The most important effect is that the distance between the connection point and the closest approach position in front of the welding direction is longer than the treatment weld length for crater treatment. There is in point to be able to do.

It is a figure which shows the laser welding method of the pipe | tube in Example 1 of this invention. It is a figure which shows step by step the laser welding method of the pipe | tube in Example 1 of this invention. It is a graph which shows increase / decrease in the laser output in Example 1 of this invention. It is a figure which shows the irradiation method of the laser beam in Example 1 of this invention. It is a figure which shows the laser welding method of the pipe | tube in Example 2 of this invention. It is a figure which shows the laser welding method of the pipe | tube in Example 3 of this invention. It is a figure which shows the laser welding method of the pipe | tube in Example 4 of this invention.

Embodiments of the present invention will be specifically described below with reference to the drawings.
In each figure, 1 is a pipe to be welded and 2 is an adjacent pipe. P1 to P4 indicate the closest positions of the welded pipe 1 and each adjacent pipe 2. Arrows indicate paths, and paths A to H progress from the base end of each arrow toward the tip. Of each arrow, the solid line portion indicates welding in a predetermined laser output state, that is, a laser output state in which downslope control for crater processing is not performed. The crater process performed by reducing is shown.

  1-4 proceeds from the vicinity of the two closest approach positions P1 and P2 when two adjacent pipes 2 are arranged on both sides on the same plane of the pipe 1 to be welded. This is a pipe laser welding method in which welding is performed by one pass. As shown in FIGS. 4A to 4B, the closest approach position between the welded pipe 1 and the upper adjacent pipe 2 in the figure is P1, and the closest approach position between the welded pipe 1 and the lower adjacent pipe 2 in the figure. Is P2, P1 is at the 12 o'clock position, and P2 is at the 6 o'clock position. 1 and 2, the hatched portion in the welded pipe 1 represents a weld bead formed at the joint, and a series of weld beads formed in the same pass are hatched in the same direction. Yes. In addition, although Example 1 demonstrates the case where a joining part carries out back-surface welding by one layer, the application object of this invention is not limited to first layer back-surface welding, It can apply also to multilayer overlay welding etc.

  Path A starts at 11:30 in the vicinity of P1, starts welding at a predetermined laser output state until the 3 o'clock position, which is the connection point with pass B, and gradually decreases the laser output from that 3 o'clock position. The crater process is performed, and the laser output is turned off at the 4 o'clock position. The increase / decrease of the laser output during welding by pass A is shown in FIG. 3 (a). The laser output is kept constant from the 11:30 position to the 3 o'clock position, and from the 3 o'clock position to 4 o'clock. It is adjusted so that it gradually decreases to the position of. As shown in FIGS. 1 and 2, a weld bead is formed at the joint of the welded pipe 1. However, when welding is performed at a constant welding speed from the start end of the pass, complete penetration is realized and the reverse wave is achieved. Is formed after a certain degree of welding. An unbroken back bead is formed at the start end by a usual method such as adjusting the position of the start end of the pass in anticipation of the weld length required to achieve complete penetration. Thereafter, a constant penetration depth is maintained by keeping the laser output constant. In the terminal portion, the penetration depth gradually decreases by gradually reducing the output for crater processing.

  Path B starts at 6:30 in the vicinity of P2, starts welding at a predetermined laser output state up to the 3 o'clock position, which is the connection point with pass A, and gradually reduces the laser output from that 3 o'clock position. The crater process is performed, and the laser output is turned off at the 2 o'clock position.

  Path C starts at 12:30 in the vicinity of P1, starts welding at a predetermined laser output state until 9 o'clock, which is the connection point with pass D, and gradually reduces laser output from that 9 o'clock position. The crater process is performed and the laser output is turned off at the 8 o'clock position.

  Path D starts at 5:30 in the vicinity of P2, starts welding at a predetermined laser output state up to the 9 o'clock position, which is the connection point with pass C, and gradually reduces the laser output from that 9 o'clock position. The crater process is performed, and the laser output is turned off at the 10 o'clock position.

  In the above description, each path is referred to as paths A to D for convenience, but the order of the paths is not particularly limited. For example, welding may be performed in the order of pass A, pass D, pass B, and pass C, or after welding is performed simultaneously with pass A and pass D located diagonally, and then welded simultaneously with pass B and pass C. You may go.

  The ratio of the lengths of the opposing paths is not particularly limited, and the length of each path may be changed by moving the position of the connection point to either the P1 side or the P2 side. For example, the connection point between the path A and the path B is set to the 4 o'clock position, and the path A is welded in a predetermined laser output state from the 11:30 position to the 4 o'clock position, and then from the 4 o'clock position to 5 o'clock. The crater process is performed up to the position of 4 and the path B is welded in a predetermined laser output state from the 6:30 position to the 4 o'clock position and then the crater process is performed from the 4 o'clock position to the 3 o'clock position. Good.

  Further, the processing weld length for crater processing is not limited to one hour (30 °), and a processing welding length necessary to perform sufficient crater processing may be set according to welding conditions. . Specifically, the processing weld length for the crater processing is appropriately set according to the wall thickness, the pipe diameter, the steel type of the welded pipe 1, the laser output, the welding speed, the number of adjacent pipes 2, and the like. Can do.

  With reference to FIG. 4, the irradiation method of the laser beam 3 in each pass will be described. 4A to 4D relate to a method of irradiating the laser beam 3 during welding by paths A to D, respectively. When a row is formed by a plurality of tubes arranged adjacent to each other in parallel, and a laser light source (not shown) is arranged on one side of the row, the laser light source of the welded tube 1 is It is impossible to irradiate the laser beam 3 on the non-arranged joint. Further, it is desirable that the laser beam 3 is irradiated perpendicularly to the welded tube 1 from the viewpoint of energy efficiency. However, as shown in FIG. 4, in the vicinity of the closest positions P1 and P2, a laser beam from a laser light source is used. Since the light 3 is blocked by the adjacent tube 2, it is difficult to irradiate the welded tube 1 with the laser beam 3 vertically. Therefore, in the vicinity of the closest positions P1 and P2, it is necessary to perform welding while keeping the irradiation angle of the laser beam 3 (the angle formed between the tangent to the welded tube 1 and the laser beam 3) low. Draw multiple trajectories parallel to each other. Thereafter, the laser beam 3 is irradiated perpendicularly to the welded pipe 1 to draw an arc-shaped locus.

  The range in which the laser beam 3 can be irradiated from the laser light source, and the range in which the laser beam 3 can be irradiated perpendicularly to the welded tube 1 include the interval between adjacent tubes, the tube diameters of the welded tube 1 and the adjacent tube 2. Depends on the accuracy and focal length of the welding device.

Embodiment 2 of the present invention will be described with reference to FIG. In addition, about the structure similar to Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.
In the second embodiment, as shown in FIG. 5 (a), three adjacent pipes 2 are arranged in three directions at equal angles and at equal angles with respect to the welded pipe 1, and the welded pipe 1 and the adjacent pipe 2 form a Y-shape. This is a welding method in the case where is formed. P1 is the closest approach position between the welded pipe 1 and the upper adjacent pipe 2 in the figure, P2 is the closest approach position between the welded pipe 1 and the lower right adjacent pipe 2 in the figure, and the welded pipe 1 is lower left in the figure. Let P3 be the closest position to the adjacent pipe 2, P1 is at the 12 o'clock position, P2 is at the 4 o'clock position, and P3 is at the 8 o'clock position.

  As shown in FIG. 5B, the path A traveling clockwise from the vicinity of P1 and the path B traveling counterclockwise from the vicinity of P2 are connected at the 2 o'clock position. Similarly, the path C and the path D are connected at the 10 o'clock position, and the path E and the path F are connected at the 6 o'clock position.

  Even in this embodiment in which three adjacent pipes 2 are arranged with respect to the welded pipe 1, by setting the connection points between the paths in consideration of the three closest approach positions, it is sufficient for a sufficient processing weld length. Crater processing becomes possible.

Embodiment 3 of the present invention will be described with reference to FIG. In addition, about the structure similar to Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.
In the third embodiment, as shown in FIG. 6A, four adjacent pipes 2 are arranged at equal angles and equal angles in four directions with respect to the welded pipe 1, and a cross is formed by the welded pipe 1 and the adjacent pipe 2. It is the welding method in the case of being formed. The closest approach position between the welded pipe 1 and the upper adjacent pipe 2 in the figure is P1, the closest approach position between the welded pipe 1 and the right adjacent pipe 2 in the figure is P2, and the welded pipe 1 is lower in the figure. The closest approach position with the adjacent pipe 2 is P3, the closest approach position between the welded pipe 1 and the adjacent pipe 2 on the left in the figure is P4, P1 is the 12 o'clock position, P2 is the 3 o'clock position, and P3 is 6 The hour position, P4, is at the 9 o'clock position.

  As shown in FIG. 6B, the path A that travels clockwise from the vicinity of P1 and the path B that travels counterclockwise from the vicinity of P2 are connected at the 1:30 position. Similarly, the path C and the path D are connected at the 10:30 position, the path E and the path F are connected at the 4:30 position, and the path G and the path H are connected at the 7:30 position.

  Even in this embodiment in which four adjacent pipes 2 are arranged with respect to the welded pipe 1, by setting the connection points between the paths in consideration of the four closest approach positions, it is sufficient for a sufficient processing weld length. Crater processing becomes possible.

Embodiment 4 of the present invention will be described with reference to FIG. In addition, about the structure similar to Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.
In Example 4, as shown in FIG. 7A, the adjacent pipes 2 are arranged at equal distances on both sides and both sides of the welded pipe 1, and a T-shape is formed by the welded pipe 1 and the adjacent pipe 2. It is the welding method in. The closest approach position between the welded pipe 1 and the upper adjacent pipe 2 in the figure is P1, the closest approach position between the welded pipe 1 and the adjacent pipe 2 on the right side in the figure is P2, and the welded pipe 1 and the left side in the figure. Let P3 be the closest position to the adjacent pipe 2, and P1 is at the 12 o'clock position, P2 is at the 3 o'clock position, and P3 is at the 9 o'clock position.

  As shown in FIG. 7B, the path A that travels clockwise from the vicinity of P1 and the path B that travels counterclockwise from the vicinity of P2 are connected at the 1:30 position. Similarly, the path C and the path D are connected at the 10:30 position, and the path E and the path F are connected at the 6 o'clock position.

  Even in this embodiment in which the adjacent pipe 2 is arranged asymmetrically with respect to the welded pipe 1, by setting the connection point between the paths in consideration of the closest approach positions, it is sufficient to cover a sufficient processing weld length. Crater processing is possible.

  Examples 1 to 4 described above exemplify typical cases where the laser welding method for pipes according to the present invention is applicable, and the present invention is not limited to the examples described above. The present invention can also be applied to the case where only one adjacent tube 2 is arranged with respect to the welded tube 1 or when the adjacent tube 2 is arranged with various distances and various angles with respect to the welded tube 1.

  In addition, when performing multi-layer welding using the pipe laser welding method according to the present invention, each layer may be formed by the plurality of passes described above, and multi-layer welding is performed by sufficiently performing crater treatment at the end of each pass. Occurrence of weld defects such as weld cracks in the initial layer, intermediate layer, and final layer of the part is suppressed.

  In general, double welding is applied to the start and / or end of a pass, and also in the tube laser welding method according to the present invention, the start and end of each pass becomes a double weld. Because the oxygen in the atmosphere (shield gas or air) dissolves in the weld bead at the joint, the weld bead may have a higher oxygen content than the base metal. It tends to be higher. Moreover, in double welding, since welding is performed again on the weld completion part in which slag (oxide) exists on the surface, oxygen is easily taken into the weld bead. For this reason, the oxygen content in the weld bead is increased, oxygen is supersaturated when the weld bead is solidified, and blow holes that are welding defects may occur. In particular, when welding is performed without using a shielding gas or when welding is performed using an active gas such as carbon dioxide gas, the risk of generating blow holes increases.

  In Examples 1 to 4, the composition of the welded pipe 1 was not described in detail, but in order to suppress the occurrence of blowholes in the double welded portion, the welded pipe 1 is a steel containing a large amount of deoxidizing elements. It is effective to make it. Since the welded pipe 1 contains a large amount of deoxidizing element, oxygen taken into the weld bead of the double welded portion is combined with the deoxidized element contained in the welded pipe 1 and discharged from the weld bead as slag. . Thereby, generation | occurrence | production of the blowhole resulting from a double welding part can be suppressed, and it becomes possible to prevent the deterioration of welding quality.

  Specifically, the welded pipe 1 needs to contain 0.005% or more by mass% of Al, which is a strong deoxidizing element, and if the Al content is less than 0.005%, The effect of suppressing the occurrence is not expected. If the Al content exceeds 2.0%, the toughness of the joint is adversely affected, so the Al content needs to be 2.0% or less. Preferably, the welded pipe 1 contains 0.02 to 1.5% of Al.

  It is also effective to use a filler material containing a deoxidizing agent in order to suppress the occurrence of blow holes in the double welded portion. As the deoxidizer, Ti, Si, Mn and the like are employed in addition to Al. As a method of using a filler material, a method of inserting an insert material into a butt joint portion or feeding a wire-like filler material to a joint portion is adopted, but it is not limited to these methods. Absent.

  The tube laser welding method according to the present invention is particularly preferably used for manufacturing a coil. Since the coil manufactured by using the laser welding method for a pipe according to the present invention is appropriately cratered, there are few welding defects such as weld cracks, and the coil can withstand use in a high-temperature boiler or the like.

  By the way, in this specification, although the Example which welds the welding area demarcated by the adjacent closest approach position by two mutually opposing passes was shown, the laser welding method of the pipe | tube which concerns on this invention is 1 The present invention can also be applied to a case where two welding sections are welded by three or more passes. For example, when welding one welding section with three passes of passes A to C, as long as crater processing can be sufficiently performed over a sufficient processing weld length at the end of each pass, one closest approach position In addition to the path A that progresses clockwise from the vicinity and the path B that progresses counterclockwise from the vicinity of the other closest approach position, it proceeds clockwise or counterclockwise starting from the vicinity of the connection point between the path A and the path B. Welding may be performed by pass C.

  The pipe laser welding method according to the present invention can be used in laser welding of a plurality of pipes arranged in parallel and adjacent to each other. In addition to the manufacture of coils, the pipe construction and construction of various pressure vessels and various plants. Is available.

1 Welded pipe 2 Adjacent pipe 3 Laser light

Claims (5)

A laser welding method for a pipe that welds pipe-to-tube joints in multiple passes,
At least one adjacent pipe adjacent in parallel to the welded pipe is arranged, and each position at which the welded pipe and the adjacent pipe are closest to each other at the joint is defined as a closest position, and a starting end near the closest position Weld in a predetermined laser output state clockwise and counterclockwise from
Each of the plurality of paths proceeds from the vicinity of the adjacent or single closest approach position, and the distance between the connection path connecting the opposing path and the laser output state and the closest position in front of the welding progress direction is terminated. A laser welding method for a tube, characterized in that the length is equal to or longer than a processing welding length in which crater processing is performed by gradually reducing the laser output toward   The said adjacent pipe is arrange | positioned on both sides on the same plane of the said to-be-welded pipe, and welding is performed by four passes which advance from the two said closest approach positions. Tube laser welding method.   3. The laser welding method for a pipe according to claim 1, wherein the welded pipe contains 0.005 to 2.0% of Al by mass%.   The laser welding method for a pipe according to any one of claims 1 to 3, wherein a filler material containing a deoxidizer is used.   A coil manufactured by joining at least a straight pipe and a U-shaped pipe by the laser welding method for a pipe according to claim 2, and connecting or independently manufacturing them on the same plane.

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