Welding condition determination method, welding method, and computer-readable program

Abstract

The thickness of the weld layer at each position on the weld line is limited to a predetermined range, while improving the uniformity of the groove depth after welding around the entire circumference of the weld line. [Solution] A welding condition determination method for determining the welding conditions of a branch pipe joint 9 using an automatic welding device comprises steps S12 and S21 to S26. Step S12 is a step of measuring the groove dimensions, which indicate the cross-sectional shape of the groove formed on the outer surface 911 of the base pipe 91 in the branch pipe joint 9, at each position on the circumferential welding line 93. Step S25 is a step of determining the target weld cross-sectional area at each position on the welding line 93, within a range of greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or less than or equal to a predetermined threshold. Step S26 is a step of determining the welding conditions at each position on the welding line 93 based on the target weld cross-sectional area at each position on the welding line 93.

Description

[Technical Field]

[0001] This invention relates to a technique for determining welding conditions for branch pipe joints using an automatic welding device. [Background technology]

[0002] Conventionally, automatic welding of branch pipe joints (also called saddle-shaped joints), which connect small-diameter branch pipes to the outer surface of a main pipe, has been performed using automatic welding equipment. In branch pipe joints, the cross-sectional shape and slope of the groove differ depending on the position on the weld line around the branch pipe (i.e., the position in the circumferential direction around the branch pipe). For example, in a branch pipe joint, the groove cross-sectional area increases as it approaches the valley position where the outer surface of the branch pipe and the circumferential direction of the main pipe are perpendicular. For this reason, in automatic welding of branch pipe joints using automatic welding equipment, the welding conditions are changed according to the position on the weld line.

[0003] For example, Patent Document 1 proposes a technique for automatic welding of branch pipe joints in which the welding speed is minimized at the valley position and increased as the welding speed moves away from the valley position. This increases the amount of welded material at the valley position where the groove cross-sectional area is large. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-328828 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, the technology proposed in Patent Document 1 relates to a set-on type in which groove processing is performed on the tip of the branch pipe, and not to a set-in type in which groove processing is performed on the outer surface of the main pipe. Furthermore, when performing multi-layer welding on a branch pipe joint, it is preferable that the layer thickness of the bead of each layer be kept within a predetermined range, and that the groove depth after welding each layer be substantially uniform along the entire length of the weld line, but no means for achieving such a suitable multi-layer welding is described in Patent Document 1.

[0006] The present invention has been made in view of the above problems, and its main objective is to improve the uniformity of the groove depth after welding around the entire circumference of the weld line while limiting the thickness of the weld layer at each position on the weld line to a predetermined range. [Means for solving the problem]

[0007] One aspect of the present invention is a welding condition determination method for determining welding conditions of a branch pipe joint using an automatic welding device, comprising: a) measuring the groove dimensions, which indicate the cross-sectional shape of the groove formed on the outer surface of the base pipe in a branch pipe joint where a branch pipe having a smaller diameter than the base pipe is connected to the outer surface of the base pipe, at each position on the circumferential welding line; b) determining the upper and lower limits of the welded cross-sectional area at each position on the welding line, based on the groove dimensions at each position on the welding line; and c) setting a provisional target welded cross-sectional area at each position on the welding line based on the upper and lower limits of the welded cross-sectional area at each position on the welding line. The process includes: d) determining the expected groove depth, which is the groove depth after welding assuming that welding is performed at each position on the weld line with the provisional target weld cross-sectional area; e) setting a target groove depth for the entire weld line based on the expected groove depth at each position on the weld line; f) determining the target weld cross-sectional area at each position on the weld line, within a range of greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or less than or equal to a predetermined threshold; and g) determining the welding conditions at each position on the weld line based on the target weld cross-sectional area at each position on the weld line.

[0008] Aspect 2 of the present invention is the welding condition determination method of Aspect 1, and for each welding layer of the multi-layer welding performed on the branch pipe joint, the steps a) to g) are carried out.

[0009] Aspect 3 of the present invention is the welding condition determination method of Aspect 1 (which may also be Aspect 1 or 2), and the temporary target weld cross-sectional area at each position on the weld line is the arithmetic mean of the upper limit cross-sectional area and the lower limit cross-sectional area at each position on the weld line.

[0010] Aspect 4 of the present invention is the welding condition determination method of Aspect 1 (which may be any one of Aspects 1 to 3), and the target groove depth is the arithmetic mean of the expected groove depths at each position on the weld line.

[0011] Aspect 5 of the present invention is the welding condition determination method of Aspect 1 (which may be any one of Aspects 1 to 4), and the welding conditions at each position on the weld line determined in the step g) include at least one of the welding speed and the welding current.

[0012] Aspect 6 of the present invention is the welding condition determination method of Aspect 1 (which may be any one of Aspects 1 to 5), and in the step a), the inclination angle of the weld line with respect to the horizontal plane considering the moving direction of the torch at each position on the weld line is measured. The weaving width of the torch at each position on the weld line is obtained based on the inclination angle at each position on the weld line.

[0013] Aspect 7 of the present invention is a welding condition determination method for determining welding conditions for a branch pipe joint using an automatic welding device, comprising: h) in a branch pipe joint in which a branch pipe having a smaller diameter than the main pipe is connected to the outer surface of the main pipe, the steps of measuring the inclination angle of the weld line with respect to the horizontal plane, taking into account the direction of movement of the torch, at each position on the circumferential welding line for a groove formed on the outer surface of the main pipe; and i) the step of determining the weaving width of the torch, which is one of the welding conditions at each position on the welding line, based on the inclination angle at each position on the welding line.

[0014] Aspect 8 of the present invention is a welding method for a branch pipe joint using an automatic welding device, comprising the steps of: placing an object on which the branch pipe joint is to be installed in a predetermined position; and performing welding on the branch pipe joint without changing the position of the object by driving a torch based on welding conditions determined by any one of the welding condition determination methods of aspects 1 to 7.

[0015] Aspect 9 of the present invention is a computer-readable program for determining welding conditions for a branch pipe joint by an automatic welding device, wherein the program is executed on a computer and includes the steps of: a) measuring the groove dimensions, which represent the cross-sectional shape of the groove formed on the outer surface of the base pipe in a branch pipe joint connecting a branch pipe having a smaller diameter than the base pipe to the outer surface of the base pipe, at each position on the circumferential welding line; b) determining the upper and lower limits of the welded cross-sectional area, which are the upper and lower limits of the welded cross-sectional area at each position on the welding line, based on the groove dimensions at each position on the welding line; and c) determining the provisional target welded cross-sectional area at each position on the welding line, based on the upper limit cross-sectional area at each position on the welding line. The process involves: d) setting based on the product and the lower limit cross-sectional area; e) determining the expected groove depth, which is the groove depth after welding assuming that welding is performed at the provisional target welding cross-sectional area at each position on the weld line; f) determining the target groove depth for the entire weld line based on the expected groove depth at each position on the weld line; g) determining the target welding cross-sectional area at each position on the weld line, within a range of greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or less than or equal to a predetermined threshold; and g) determining the welding conditions at each position on the weld line based on the target welding cross-sectional area at each position on the weld line.

[0016] Aspect 10 of the present invention is a computer-readable program for determining welding conditions for a branch pipe joint by an automatic welding device, wherein when the program is executed on a computer, the following steps are performed: h) In a branch pipe joint in which a branch pipe having a smaller diameter than the main pipe is connected to the outer surface of the main pipe, the inclination angle of the weld line with respect to the horizontal plane is measured at each position on the circumferential weld line, taking into account the direction of movement of the torch, for a groove formed on the outer surface of the main pipe; and i) The weaving width of the torch, which is one of the welding conditions at each position on the weld line, is determined based on the inclination angle at each position on the weld line. [Effects of the Invention]

[0017] In this invention, it is possible to improve the uniformity of the groove depth after welding around the entire circumference of the weld line while limiting the thickness of the weld layer at each position on the weld line to a predetermined range. [Brief explanation of the drawing]

[0018] [Figure 1] This is a perspective view showing a branch pipe joint welded by a welding method according to one embodiment. [Figure 2] This is a cross-sectional view of a branch pipe joint at the ridge of a weld line. [Figure 3] This is a cross-sectional view of a branch pipe joint at the valley of a weld line. [Figure 4] This is a diagram conceptually illustrating the configuration of an automatic welding machine. [Figure 5] This is a diagram showing the configuration of the control unit. [Figure 6] This diagram shows the flow of automatic welding for branch pipe joints. [Figure 7] This is a cross-sectional view of a branch pipe joint. [Figure 8] This is a cross-sectional view of a branch pipe joint. [Figure 9] This diagram shows the process for determining welding conditions. [Figure 10] This figure shows the relationship between the groove bottom width, the number of passes, and the upper and lower cross-sectional areas. [Figure 11] This is a cross-sectional view of a branch pipe joint. [Figure 12] This is a cross-sectional view of a branch pipe joint. [Figure 13] This is a cross-sectional view of a branch pipe joint. [Figure 14] This is a cross-sectional view of a branch pipe joint. [Figure 15] This diagram shows the process for determining welding conditions. [Modes for carrying out the invention]

[0019] Figure 1 is a perspective view showing an example of a branch pipe joint 9 welded by a welding method according to one embodiment of the present invention. The branch pipe joint 9 is a joint in which a branch pipe 92 is connected to the outer surface 911 of a main pipe 91, and is also called a saddle-type joint. The main pipe 91 is a substantially cylindrical member, or a part of a substantially cylindrical member in the circumferential direction. The branch pipe 92 is a substantially cylindrical member having a smaller diameter (i.e., outer diameter) than the main pipe 91. For example, the outer diameter of the branch pipe 92 is approximately 1.4 m, and the outer diameter of the main pipe 91 is approximately 3 m. The sizes of the branch pipe 92 and the main pipe 91 can be varied.

[0020] In the example shown in Figure 1, the branch pipe 92 is connected to the outer surface 911 of the main pipe 91 approximately perpendicularly. In other words, the branch pipe 92 is connected to the outer surface 911 of the main pipe 91 such that the central axis J2 of the branch pipe 92 intersects the central axis (not shown) of the main pipe 91 approximately perpendicularly.

[0021] In the branch pipe joint 9, a circumferential weld line 93 is provided around the entire circumference of the branch pipe 92 at the contact point between the branch pipe 92 and the main pipe 91. The weld line 93 has a saddle-like shape. Specifically, the weld line 93 comprises two ridges 931 and two valleys 932. The two ridges 931 are located 180° apart from each other in the circumferential direction (hereinafter also simply referred to as the "circumferential direction") with respect to the central axis J2. The two valleys 932 are also located 180° apart from each other in the circumferential direction. The two ridges 931 are located above the two valleys 932 in Figure 1. In the example shown in Figure 1, the vertical direction in Figure 1 roughly coincides with the direction of gravity.

[0022] Figure 2 is an enlarged view of the cross-section of the branch pipe joint 9 cut along a virtual plane passing through the ridge 931 of the weld line 93 and the central axis J2 of the branch pipe 92 in Figure 1. Figure 3 is an enlarged view of the cross-section of the branch pipe joint 9 cut along a virtual plane passing through the valley 932 of the weld line 93 and the central axis J2 of the branch pipe 92 in Figure 1. Figures 2 and 3 show the state before welding is performed on the groove 94 provided on the weld line 93. As shown in Figures 2 and 3, the groove 94 is provided on the outer surface 911 of the main pipe 91. That is, the branch pipe joint 9 is a set-in type joint in which a groove is formed on the outer surface 911 of the main pipe 91.

[0023] In the cross-section shown in Figure 2, the outer surface 921 of the branch pipe 92 and the outer surface 911 of the main pipe 91 are approximately perpendicular to each other. In the cross-section shown in Figure 3, the outer surface 911 of the main pipe 91 slopes downward in the radial direction (hereinafter also simply referred to as the "radial direction") around the central axis J2 (see Figure 1) as it moves away from the outer surface 921 of the branch pipe 92. In other words, the outer surface 911 of the main pipe 91 is inclined from a direction perpendicular to the outer surface 921 of the branch pipe 92, and the angle between the outer surface 921 of the branch pipe 92 and the outer surface 911 of the main pipe 91 is greater than 90°. In Figure 1, the parts of the outer surface 911 of the main pipe 91 and the outer surface 921 of the branch pipe 92 shown in Figures 2 and 3 are indicated by dashed lines.

[0024] The depth d of the groove 94 in the ridge portion 931 as illustrated in Figure 2. r0 This refers to the depth d of the groove 94 in the valley 932 as illustrated in Figure 3. v0 It is larger than. In the examples shown in Figures 2 and 3, the bevel angle of the bevel 94 at the ridge 931 is approximately the same as the bevel angle of the bevel 94 at the valley 932. Also, the width of the lower end of the bevel 94 (i.e., the bottom width of the bevel 94) at the ridge 931 and the valley 932 is approximately the same. Therefore, the width of the upper end of the bevel 94 at the ridge 931 is larger than the width of the upper end of the bevel 94 at the valley 932.

[0025] Figure 4 is a conceptual diagram showing the configuration of an automatic welding apparatus 1 used for welding a branch pipe joint 9. The automatic welding apparatus 1 comprises a torch 2, a rocking mechanism 3, and a control unit 8. The tip of the welding wire 21 extends from the tip of the torch 2 (the lower end in the example shown in Figure 4). The control unit 8 controls the configuration of the torch 2, the moving mechanism (described later), and the rocking mechanism 3, etc.

[0026] The torch 2 is held by a moving mechanism (not shown) and is capable of moving in three dimensions by this mechanism. When welding the branch pipe joint 9 is performed by the automatic welding apparatus 1, the torch 2 is moved along the welding line 93 by the moving mechanism, with the position of the torch 2 adjusted so that the tip of the torch 2 is close to the groove 94. This moving mechanism may, for example, be equipped with a robotic arm, or it may be equipped with a self-propelled trolley and rails equipped with an electric motor or the like. The structure of this moving mechanism can be modified in various ways.

[0027] The oscillating mechanism 3 is connected to the torch 2 and drives the torch 2. The oscillating mechanism 3 rotates the torch 2 around the pivot axis J3, causing the tip of the torch 2 to oscillate in a direction approximately perpendicular to the plane of the paper. The tip of the torch 2 reciprocates in a plane approximately perpendicular to the direction of movement of the torch 2 by the above-mentioned moving mechanism (i.e., the tangential direction of the welding line 93). This enables weaving welding to be performed on the groove 94. The oscillating mechanism 3 is equipped with, for example, an electric motor. The structure of the oscillating mechanism 3 can be modified in various ways.

[0028] Figure 5 shows the configuration of the control unit 8. The control unit 8 has the configuration of a typical computer system, including a CPU 81, a GPU 82, a ROM 83, a RAM 84, a fixed disk 85, a display 86, an input unit 87, a reader 88, a communication unit 89, and a bus 80.

[0029] The CPU 81 performs various arithmetic operations. The GPU 82 performs various arithmetic operations related to image processing. The ROM 83 stores the basic program. The RAM 84 stores various information. The fixed disk 85 stores information. The display 86 is a display unit that displays various information such as images. The input unit 87 includes a keyboard 87a and a mouse 87b that accept input from the operator. The reader 88 reads information from computer-readable recording media 881 such as optical disks, magnetic disks, magneto-optical disks, and memory cards. The display 86, keyboard 87a, mouse 87b, and reader 88 are connected to the bus 80 via an interface I / F. The communication unit 89 sends and receives signals to and from external devices of the control unit 8. The bus 80 is a signal circuit that connects the CPU 81, GPU 82, ROM 83, RAM 84, fixed disk 85, display 86, input unit 87, reader 88, and communication unit 89.

[0030] In the control unit 8, program 882 is read in advance from the recording medium 881 via the reader 88 and stored in the fixed disk 85. Program 882 may also be stored in the fixed disk 85 via a network. The CPU 81 and GPU 82 perform arithmetic processing using RAM 84 and the fixed disk 85 according to program 882. The CPU 81 and GPU 82 function as the arithmetic unit in the control unit 8. Other configurations besides the CPU 81 and GPU 82 that function as the arithmetic unit may also be employed.

[0031] In the automatic welding apparatus 1 shown in Figure 4, the control unit 8 performs calculations and other processing according to the program 882, thereby realizing the groove state acquisition unit 801, the welding condition acquisition unit 802, and the storage unit 803 as functional configurations. Specifically, the groove state acquisition unit 801 and the welding condition acquisition unit 802 are realized by a CPU 81, GPU 82, ROM 83, RAM 84, fixed disk 85, and their peripheral configurations. The storage unit 803 is mainly realized by RAM 84 and fixed disk 85. All or part of the functions of the groove state acquisition unit 801, the welding condition acquisition unit 802, and the storage unit 803 may be realized by dedicated electrical circuits. Alternatively, these functions may be realized by multiple computers.

[0032] Next, the process of automatic welding of the branch pipe joint 9 using the automatic welding device 1 will be explained. Figure 6 is a diagram showing the process of this automatic welding. In this automatic welding, first, the object on which the branch pipe joint 9 will be installed (i.e., the object to be welded) is placed in a predetermined position on a mounting surface such as the floor of the work site (step S11). This mounting surface is, for example, a horizontal plane that is approximately perpendicular to the direction of gravity. In step S11, for example, the object to be welded is placed so that the central axis J2 of the branch pipe 92 is approximately parallel to the direction of gravity.

[0033] Next, the automatic welding apparatus 1 measures the groove dimensions, which indicate the cross-sectional shape of the groove 94, at multiple positions on the welding line 93 (step S12). The cross-sectional shape of the groove 94 at one position on the welding line 93 refers to the shape of the groove 94 in a cross section perpendicular to the tangent line that extends horizontally in contact with the welding line 93 at that position. The groove dimensions include, for example, the groove depth d0 and the groove angle θ on the base pipe 91 side, as shown in Figure 7. m0 , the groove angle θ on the branch pipe 92 side b0 This includes the width B0 in the radial direction (i.e., radial direction around the central axis J2) at the lower end of the groove 94.

[0034] In step S12, for example, the groove dimensions are measured by wire touch sensing by the automatic welding apparatus 1. Specifically, the automatic welding apparatus 1 applies a weak current to the welding wire 21 (see Figure 4) of the torch 2, and the movement mechanism displaces the torch 2 to bring the welding wire 21 into contact with the groove 94, etc. When the welding wire 21 comes into contact with the main pipe 91 or branch pipe 92, current is supplied, and information related to this current supply is sent to the groove state acquisition unit 801 (see Figure 4) of the control unit 8. Based on this information, the groove state acquisition unit 801 acquires the cross-sectional shape (i.e., groove dimensions) of the groove 94 at a position on the welding line 93.

[0035] In the automatic welding apparatus 1, the torch 2 is moved in steps along the welding line 93 by the above-described movement mechanism by a predetermined distance, and the groove dimensions are measured in the same manner as described above. In the automatic welding apparatus 1, the groove dimensions are measured at each position in the circumferential direction of the welding line 93 (i.e., the circumferential direction centered on the central axis J2 of the branch pipe 92) by the repeated step-by-step movement of the torch 2 and the contact of the welding wire 21 with the groove 94, etc. In step S12, the groove state acquisition unit 801 acquires the groove dimensions in the circumferential direction at intervals of approximately 20 mm, for example. Based on the measurement results at each position of the welding line 93, the groove state acquisition unit 801 can also acquire information relating to the overall shape of the welding line 93. Note that the acquisition of groove dimensions by the groove state acquisition unit 801 does not necessarily have to be at intervals of approximately 20 mm, and this interval may be changed as appropriate. Furthermore, the acquisition of groove dimensions by the groove condition acquisition unit 801 does not necessarily have to be performed at equal intervals. For example, the interval for acquiring groove dimensions (i.e., the measurement interval) may be arbitrarily changed for each position based on the inclination angle (described later) or the rate of change of groove dimensions at each position on the weld line 93.

[0036] The measurement of the groove dimensions in step S12 does not necessarily have to be performed by the wire touch sensing described above, but may be performed by various other methods. For example, the groove dimensions may be measured by bringing a probe attached to the torch 2 into contact with the groove 94. Alternatively, the groove dimensions may be measured non-contact using a laser displacement meter attached to the torch 2. Or, the measurement of the groove dimensions may be performed by a device other than the automatic welding apparatus 1.

[0037] Next, based on the groove dimensions measured in step S12, the welding condition acquisition unit 802 (see Figure 4) of the control unit 8 determines the welding conditions at each position on the welding line 93 (step S13). These welding conditions include, for example, at least one of the following: welding speed (i.e., the speed at which the torch 2 moves along the welding line 93) and welding current. Other conditions besides welding speed and welding current may also be included in the welding conditions. For example, welding voltage may be included in the welding conditions. Furthermore, if weaving welding is performed in the automatic welding apparatus 1, weaving conditions such as the oscillation frequency of the torch 2 by the oscillation mechanism 3 and the weaving width may also be included in the welding conditions. Details of the determination of the welding conditions in step S13 will be described later.

[0038] When step S13 is completed, the control unit 8 drives the torch 2 based on the welding conditions obtained in step S13, and welding is performed on the branch pipe joint 9 (step S14). At each position on the welding line 93, the control unit 8 drives the torch 2 based on the welding conditions corresponding to each position obtained in step S13. For example, when welding is performed while the torch 2 is moved along the welding line 93 by the moving mechanism, the movement speed of the torch 2 by the moving mechanism at each position on the welding line 93 (i.e., the welding speed) is changed according to the welding conditions for each position obtained in step S13.

[0039] This enables suitable welding even in branch pipe joints 9 where the groove dimensions differ depending on the circumferential position. Therefore, in this embodiment, no device such as a positioner is used to change the orientation of the object to be welded on which the branch pipe joint 9 is attached during welding of the branch pipe joint 9 in step S14. In other words, welding of the branch pipe joint 9 in step S14 is performed without changing the orientation of the object to be welded from the start to the end of welding.

[0040] In this embodiment, as shown in Figure 8, lamination welding (also called multilayer welding) is performed on the groove 94 of the branch pipe joint 9 by laminating two or more weld layers 95 in the depth direction of the groove 94. The weld layer 95 may be formed by a single weld bead, or by two or more weld beads aligned in the width direction of the groove 94 (i.e., in the direction perpendicular to the weld line 93 in the groove 94). In this lamination welding, before the formation of each weld layer 95 (step S14) begins, the groove dimensions are measured in step S12 and the welding conditions are determined in step S13. In other words, in this lamination welding, steps S12 to S14 are repeated for each weld layer 95 that is formed.

[0041] Next, with reference to Figure 9, the specific procedure for determining the welding conditions in step S13 will be explained. In determining the welding conditions, first, based on the groove dimensions at each position on the weld line 93 obtained in step S12 (see Figure 7), the upper limit cross-sectional area, which is the upper limit of the welded cross-sectional area at each position, and the lower limit cross-sectional area, which is the lower limit of the welded cross-sectional area at that position, are determined (step S21). The welding cross-sectional area refers to the welding cross-sectional area per pass when a single welding layer 95 is formed by multiple passes (i.e., multiple weld beads). Furthermore, when a single welding layer 95 is formed by a single pass, the welding cross-sectional area refers to the welding cross-sectional area per welding layer 95. Similarly, when laminated welding is performed as described above, the welding cross-sectional area refers to the welding cross-sectional area per pass of a single welding layer 95.

[0042] In step S21, first, the upper limit value and the lower limit value pre-stored in the storage unit 803 are read out for the layer thickness of the first welding layer 95 to be formed in subsequent step S14. The upper limit value and the lower limit value are common values for each position on the welding line 93. The upper limit value and the lower limit value of the layer thickness are set based on, for example, the mechanical properties required for the welding layer 95 and the like.

[0043] Subsequently, for one position on the welding line 93, the welding cross-sectional area necessary to achieve the upper limit value of the layer thickness is calculated using the root opening angle θ on the main pipe 91 side measured in step S12 m0 (see FIG. 7), the root opening angle θ on the branch pipe 92 side b0 , and the radial width B0 at the lower end of the root opening 94 (hereinafter also referred to as the "root opening lower end width B0"), and is set as the above-mentioned upper limit cross-sectional area. Also, for the one position on the welding line 93, the welding cross-sectional area necessary to achieve the lower limit value of the layer thickness is calculated using the root opening angle θ m0 , θ b0 , and the root opening lower end width B0, and is set as the above-mentioned lower limit cross-sectional area. The upper limit cross-sectional area and the lower limit cross-sectional area are obtained in the same manner as above for other positions on the welding line 93. Thereby, the upper limit cross-sectional area and the lower limit cross-sectional area at each position on the welding line 93 are obtained. When the root opening angle θ m0 , θ b0 , and / or the root opening lower end width B0 differ depending on the position on the welding line 93, the upper limit cross-sectional area and the lower limit cross-sectional area also differ depending on the position on the welding line 93.

[0044] In step S21, the upper and lower cross-sectional areas do not necessarily have to be determined by the method described above, and may be determined by various other methods. For example, if the weld cross-sectional area is large, the heat input to the base pipe 91 and branch pipe 92 may be excessive, so an upper cross-sectional area may be set to prevent such excessive heat input. Also, if the weld cross-sectional area is small, the shape of the weld bead may become convex contrary to the intention, so a lower cross-sectional area may be set to suppress the convexity of the weld bead. Alternatively, the upper and lower cross-sectional areas may be set by combining these methods for setting the upper and lower cross-sectional areas with the method for setting the upper and lower cross-sectional areas based on the upper and lower limits of the layer thickness described above.

[0045] Figure 10 shows an example of the relationship between the groove lower end width B0 and the number of passes, and the upper and lower cross-sectional areas described above. The number of passes refers to the number of weld beads that form one weld layer 95 (i.e., the number of weld beads aligned in the width direction of the groove 94 in the weld layer 95). Figure 10 shows the groove angle θ on the base pipe 91 side described above. m0 , and the groove angle θ on the branch pipe 92 side. b0 However, this figure assumes that the groove 94 is constant in the depth direction. In Figure 10, the horizontal axis shows the groove lower end width B0, and the vertical axis shows the value obtained by dividing the welded cross-sectional area of ​​the weld layer 95 by the number of passes of the weld layer 95. In Figure 10, the upper limit cross-sectional area is denoted by reference numeral 78, and the lower limit cross-sectional area is denoted by reference numeral 79.

[0046] Figure 10 is divided into multiple regions 71-76 that are arranged consecutively along the horizontal axis. In Figure 10, each of the regions 71-76 is enclosed by a dashed line. Region 71 corresponds to the case where one weld layer 95 is formed in one pass, region 72 corresponds to the case where one weld layer 95 is formed in two passes, region 73 corresponds to the case where one weld layer 95 is formed in three passes, region 74 corresponds to the case where one weld layer 95 is formed in four passes, region 75 corresponds to the case where one weld layer 95 is formed in five passes, and region 76 corresponds to the case where one weld layer 95 is formed in six passes.

[0047] Once step S21 is completed, a provisional target welding cross-sectional area is set for one position on the weld line 93 based on the upper and lower cross-sectional areas determined in step S21. For example, the provisional target welding cross-sectional area is the arithmetic mean of the upper and lower cross-sectional areas. Similarly, provisional target welding cross-sectional areas are set for other positions on the weld line 93. As a result, the provisional target welding cross-sectional area at each position on the weld line 93 is set based on the upper and lower cross-sectional areas determined in step S21 (step S22).

[0048] When step S22 is completed, assuming that welding is performed at one position on the weld line 93 to achieve the provisional target weld cross-sectional area set in step S22, as shown in Figure 11, the depth d of the groove 94 after welding is a1 (Hereafter, "Expected bevel depth d a1 It is also called ). Specifically, the provisional target welding cross-sectional area and the groove angle θ measured in step S12 are required. m0 ,θ b0 , and the thickness t of the welded layer 95 when the provisional target welding cross-sectional area is achieved using the groove lower edge width B0 (see Figure 7) a1 (Hereafter, "Tentative target layer thickness t" a1 It is also called ).) is required. Then, the provisional target layer thickness t is obtained from the groove depth d0 measured in step S12. a1 By subtracting this, the expected groove depth d a1 The expected groove depth d is calculated. a1 The same method can be used to determine the expected groove depth d at other locations on the weld line 93. a1 This is required (step S23).

[0049] Once step S23 is complete, the target groove depth common to the entire weld line 93 is determined by the expected groove depth d at each position on the weld line 93, which was determined in step S23. a1 It is set based on (step S24). For example, the target groove depth is the expected groove depth d at each position on the weld line 93. a1 It is the arithmetic mean of [the given numbers].

[0050] When step S24 is completed, the final target weld cross-sectional area (hereinafter also referred to as the "target weld cross-sectional area") at one position on the weld line 93 is determined by the target groove depth set in step S24, the groove depth d0 measured in step S12, and the groove angle θ. m0 ,θ b0 The upper and lower cross-sectional areas are determined based on the groove lower end width B0, and the upper and lower cross-sectional areas determined in step S21.

[0051] Specifically, the target layer thickness is determined by subtracting the target groove depth, which is the ideal groove depth for the entire weld line 93 after forming one weld layer 95, from the current groove depth d0 at the given location. Subsequently, the weld cross-sectional area corresponding to the target layer thickness (hereinafter also referred to as the "corresponding weld cross-sectional area") is determined by the groove depth d0 and groove angle θ measured in step S12. m0 ,θ b0 The target welding cross-sectional area is calculated using the groove lower end width B0. Next, the corresponding welding cross-sectional area is compared with the upper and lower limit cross-sectional areas at that location. If the corresponding welding cross-sectional area is greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, the corresponding welding cross-sectional area is set as the target welding cross-sectional area at that location. On the other hand, if the corresponding welding cross-sectional area is greater than the upper limit cross-sectional area, the upper limit cross-sectional area is set as the target welding cross-sectional area at that location, and if the corresponding welding cross-sectional area is less than the lower limit cross-sectional area, the lower limit cross-sectional area is set as the target welding cross-sectional area at that location.

[0052] In the welding condition acquisition unit 802, the target weld cross-sectional area is determined for other positions on the welding line 93 in the same manner as described above. This allows for the determination of the target weld cross-sectional area at each position on the welding line 93 that minimizes the difference between the groove depth after welding and the target groove depth, within a range greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area (step S25). Alternatively, in step S25, the target weld cross-sectional area is determined that minimizes the difference between the groove depth after welding and the target groove depth to less than or equal to a predetermined threshold. This threshold is obtained by adding a predetermined value to the minimum difference between the groove depth after welding and the target groove depth. This predetermined value is, for example, 2 mm. This predetermined value may be 2 mm or less (for example, 1 mm).

[0053] Once step S25 is completed, the welding conditions at each position on the weld line 93 are determined by the welding condition acquisition unit 802 based on the target weld cross-sectional area at each position on the weld line 93 determined in step S25 (step S26). The determination of welding conditions based on the target weld cross-sectional area may be performed by various known methods. In this embodiment, the welding current and welding voltage are fixed to predetermined values, and the welding speed at each position on the weld line 93 is determined as one of the above welding conditions.

[0054] If the weld layer 95 to be formed by the welding conditions determined in step S26 is composed of multiple weld beads, the target weld cross-sectional area for each weld bead is set by dividing the target weld cross-sectional area by the number of weld beads, and the welding conditions, such as the welding speed when forming each weld bead are determined based on the target weld cross-sectional area for each weld bead.

[0055] Once the welding conditions at each position on the weld line 93 are determined by steps S21 to S26 (i.e., step S13), welding is performed on the branch pipe joint 9 based on these welding conditions (step S14), and the first weld layer 95 is formed as shown in Figure 12.

[0056] As described above, in determining the welding conditions in step S13, the target weld cross-sectional area at each position on the weld line 93 is determined within a range greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or equal to the predetermined threshold. Therefore, after the formation of the first weld layer 95, the thickness of the weld layer 95 at each position on the weld line 93 can be kept above the lower limit and less than or equal to the upper limit, while reducing the variation in groove depth d1 depending on the position on the weld line 93. In other words, the uniformity of groove depth d1 around the entire circumference of the weld line 93 can be improved while limiting the thickness of the weld layer 95 at each position on the weld line 93 within a predetermined range.

[0057] For example, before the formation of the first weld layer 95, the depth d of the groove 94 in the ridge portion 931 r0 (See Figure 2) As described above, the depth d of the groove 94 in the valley 932 v0 (See Figure 3) is larger than the above. In the automatic welding apparatus 1, welding is performed under the welding conditions determined in steps S12 to S13 above to form the first weld layer 95, thereby improving the uniformity of the groove depth d1 around the entire circumference of the weld line 93, as described above. Therefore, as shown in Figures 13 and 14, the groove depth d of the ridge portion 931 after the formation of the first weld layer 95 r1 and groove depth d of valley 932 v1 The difference is the groove depth d of the ridge portion 931 before the formation of the first weld layer 95. r0 and groove depth d of valley 932 v0 It is possible to make the difference smaller than that.

[0058] Once the formation of the first weld layer 95 is complete, the groove dimensions, which indicate the shape of the groove 94 after the formation of the first weld layer 95, are measured at each position on the weld line 93 in substantially the same manner as described above (step S12). As a result, as shown in Figure 12, the groove depth d1 and the groove angle θ on the base pipe 91 side at each position are determined. m1 , the groove angle θ on the branch pipe 92 side b1 And the groove lower end width B1 is obtained. In the example shown in Figure 12, the groove angle θ on the main pipe 91 side is obtained. m1, and the groove angle θ on the branch pipe 92 side. b1 These are the groove angles θ on the main tube 91 side shown in Figure 7. m0 , and the groove angle θ on the branch pipe 92 side. b0 It is essentially the same as this.

[0059] Once step S12 is completed, steps S13 to S14 are performed in substantially the same manner as described above, thereby forming the second weld layer 95. In the automatic welding apparatus 1, the groove dimensions at each position of the weld layer 95 are measured after the formation of the first weld layer 95 and before the formation of the second weld layer 95. Therefore, even if changes in the shape of the groove 94 occur during the formation of the first weld layer 95, the second weld layer 95 can be formed with high accuracy.

[0060] In the automatic welding apparatus 1, welding of the branch pipe joint 9 is completed by stacking multiple welding layers 95. In each of the multiple welding layers 95, the thickness of the welding layer 95 at each position on the welding line 93 is limited to a predetermined range, similar to the first welding layer 95, while improving the uniformity of the groove depth d1 around the entire circumference of the welding line 93 after the formation of each layer. Therefore, the uniformity of the groove depth d1 around the entire circumference of the welding line 93 after the formation of the multiple welding layers 95 is further improved.

[0061] As described above, the welding condition determination method for determining the welding conditions of a branch pipe joint 9 by the automatic welding apparatus 1 comprises steps S12 and S21 to S26. Step S12 is a step of measuring the groove dimensions, which indicate the cross-sectional shape of the groove 94 formed on the outer surface 911 of the main pipe 91, at each position on the circumferential welding line 93 in a branch pipe joint 9 in which a branch pipe 92 having a smaller diameter than the main pipe 91 is connected to the outer surface 911 of the main pipe 91. Step S21 is a step of determining the upper and lower limits of the welded cross-sectional area at each position on the welding line 93, based on the groove dimensions at each position on the welding line 93. Step S22 is a step of setting a provisional target welded cross-sectional area at each position on the welding line 93 based on the upper and lower limits of the welded cross-sectional area at each position on the welding line 93. Step S23 is the process of determining the expected groove depth, which is the groove depth after welding, assuming that welding is performed at a provisional target welding cross-sectional area at each position on the weld line 93. Step S24 is the process of setting the target groove depth for the entire weld line 93 based on the expected groove depth at each position on the weld line 93. Step S25 is the process of determining the target welding cross-sectional area at each position on the weld line 93, within a range of greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or reaches a predetermined threshold. Step S26 is the process of determining the welding conditions at each position on the weld line 93 based on the target welding cross-sectional area at each position on the weld line 93. As a result, as described above, it is possible to improve the uniformity of the groove depth after welding around the entire circumference of the weld line 93 while limiting the thickness of the weld layer 95 at each position on the weld line 93 to a predetermined range.

[0062] As described above, preferably, steps S12 and S21 to S26 are performed for each weld layer 95 of the laminated welding performed on the branch pipe joint 9. This further improves the uniformity of the groove depth around the entire circumference of the weld line 93 after the completion of the laminated welding.

[0063] As described above, the provisional target welding cross-sectional area at each position on the weld line 93 is preferably the arithmetic mean of the upper limit and lower limit cross-sectional areas at each position on the weld line 93. This allows the provisional target welding cross-sectional area to be set appropriately in step S22.

[0064] As described above, the target groove depth is preferably the arithmetic mean of the expected groove depths at each position on the weld line 93. This allows the target groove depth to be set appropriately in step S24.

[0065] As described above, the welding conditions at each position on the weld line 93 determined in step S26 preferably include at least one of the welding speed and welding current. This makes it possible to suitably achieve the target weld cross-sectional area at each position on the weld line 93.

[0066] As described above, the welding method for a branch pipe joint 9 using the automatic welding apparatus 1 comprises the steps of: placing the object on which the branch pipe joint 9 is to be installed (i.e., the object to be welded) in a predetermined position (step S11); and driving the torch 2 based on the welding conditions determined by the welding condition determination method described above, thereby performing welding on the branch pipe joint 9 without changing the position of the object to be welded (step S14). As a result, changing the position of the object to be welded by a positioner or the like is unnecessary, making it possible to easily and effectively weld large branch pipe joints 9 to be welded objects.

[0067] As described above, in the automatic welding apparatus 1, steps S12 and S21 to S26 are performed by executing program 882 on the computer. This makes it possible to improve the uniformity of the groove depth after welding around the entire circumference of the welding line 93 while limiting the thickness of the welding layer 95 at each position on the welding line 93 to a predetermined range, similar to the above.

[0068] In the branch pipe joint 9 described above, the inclination (i.e., slope) of the bottom of the groove 94 with respect to the horizontal plane differs depending on the position on the weld line 93. For example, in the ridge section 931 and valley section 932 shown in Figure 1, the bottom of the groove 94 is approximately horizontal, while in the position between the ridge section 931 and the valley section 932, the bottom of the groove 94 is inclined with respect to the horizontal plane. Furthermore, between the ridge section 931 and the valley section 932, the inclination of the bottom of the groove 94 gradually increases as it moves away from the ridge section 931 and the valley section 932.

[0069] When performing weaving welding on a weld line 93 whose inclination changes in this manner, if the oscillation range of the tip of the torch 2 by the oscillation mechanism 3 (hereinafter also referred to as the "weaving width") is kept constant, the width of the weld bead may vary depending on its position on the weld line 93. Specifically, if the bottom of the groove 94 slopes downward toward the front in the welding direction (i.e., the direction of movement of the torch 2), the spread of the molten pool in the width direction of the groove 94 may become excessive, and the width of the weld bead may become larger than intended. Conversely, if the bottom of the groove 94 slopes upward toward the front in the welding direction, the spread of the molten pool in the width direction of the groove 94 may become insufficient, and the width of the weld bead may become smaller than intended.

[0070] Therefore, in the automatic welding apparatus 1, when weaving welding is performed, the control unit 8 controls the oscillating mechanism 3 based on the inclination angle at each position on the welding line 93, thereby adjusting the weaving width of the torch 2 at each position.

[0071] In adjusting the weaving width, first, during the measurement of the groove dimensions in step S12 (see Figure 6) described above, the groove state acquisition unit 801 (see Figure 4) of the control unit 8 determines the inclination angle of the weld line 93 with respect to the horizontal plane, taking into account the direction of movement of the torch 2 at each position on the weld line 93. The inclination angle is the angle formed between the projection of the bottom of the groove 94 onto the horizontal plane and the bottom of the groove 94 on a virtual plane that includes the projection and the center line in the width direction of the bottom of the groove 94.

[0072] Specifically, for example, the absolute coordinates of the bottom of the groove 94 at each position on the weld line 93 are measured by wire touch sensing, and the inclination angle at each position is determined based on the measured values. The origin of these absolute coordinates is fixed, for example, on the aforementioned mounting surface (for example, the floor of the work site). The inclination angle is negative if the bottom of the groove 94 slopes downward toward the front in the welding direction (i.e., the direction of movement of the torch 2), and positive if the bottom of the groove 94 slopes upward toward the front in the welding direction. Note that the measurement of the inclination angle is not limited to the above example and may be performed by various known methods.

[0073] In the welding condition acquisition unit 802, the weaving width of the torch 2 at each position on the welding line 93 is determined based on the inclination angle at that position and is included in the welding conditions acquired in step S26. Specifically, for example, the weaving width at the ridge 931 and valley 932 where the inclination angle is 0° (hereinafter also referred to as the "reference weaving width") is determined by a known method. Then, at each position on the welding line 93, the weaving width at each position is determined by adding a value obtained by multiplying the inclination angle at each position by a predetermined coefficient to the reference weaving width. The acquisition of the weaving width as described above may be performed in parallel with steps S21 to S26 shown in Figure 9, or it may be performed before or after steps S21 to S26.

[0074] When welding of the branch pipe joint 9 is performed by the automatic welding device 1, the oscillating mechanism 3 is controlled at each position on the welding line 93 based on the weaving width included in the welding conditions, and the weaving width of the torch 2 is adjusted to the desired size. Specifically, the weaving width becomes larger than the standard weaving width on an uphill slope, and smaller than the standard weaving width on a downhill slope.

[0075] Thus, in step S12, the inclination angle of the weld line 93 with respect to the horizontal plane may be measured, taking into account the direction of movement of the torch 2 at each position on the weld line 93. The weaving width of the torch 2 at each position on the weld line 93 is then determined based on the inclination angle at each position on the weld line 93. This improves the uniformity of the weld bead width around the entire circumference of the weld line 93.

[0076] Preferably, for each weld layer 95 of the laminated welding performed on the branch pipe joint 9, the above-mentioned inclination angle measurement and weaving width acquisition are carried out. This improves the uniformity of groove depth by controlling the welding speed and other factors as described above, and even if the inclination of the weld line 93 differs for each weld layer 95, the uniformity of the weld bead width around the entire circumference of the weld line 93 can be improved in each weld layer 95.

[0077] In the automatic welding apparatus 1, the measurement of the inclination angle and acquisition of the weaving width described above may be performed independently of the acquisition of the groove dimensions and the determination of welding conditions based on the weld cross-sectional area described above (steps S12, S21-S26).

[0078] In this case, the welding condition determination method for determining the welding conditions of the branch pipe joint 9 by the automatic welding apparatus 1 comprises steps S31 and S32, as shown in Figure 15. Step S31 is a step of measuring the inclination angle of the weld line with respect to the horizontal plane, taking into account the direction of movement of the torch 2, at each position on the circumferential weld line 93 for the groove 94 formed on the outer surface 911 of the main pipe 91 in the branch pipe joint 9, which connects a branch pipe 92 having a smaller diameter than the main pipe 91 to the outer surface 911 of the main pipe 91. Step S32 is a step of determining the weaving width of the torch 2, which is one of the welding conditions at each position on the weld line 93, based on the inclination angle at each position on the weld line 93. This makes it possible to improve the uniformity of the width of the weld bead around the entire circumference of the weld line 93, in substantially the same manner as described above.

[0079] Furthermore, the welding method for the branch pipe joint 9 using the automatic welding apparatus 1 includes the steps of: placing the object on which the branch pipe joint 9 is to be installed (i.e., the object to be welded) in a predetermined position (step S11); and driving the torch 2 based on the welding conditions (i.e., the weaving width of the torch 2) determined by the welding condition determination method described above, thereby performing welding on the branch pipe joint 9 without changing the position of the object to be welded (step S14). As a result, changing the position of the object to be welded by a positioner or the like is unnecessary, making it possible to easily and effectively weld large branch pipe joints 9 to be welded objects.

[0080] In the automatic welding apparatus 1, steps S31 to S32 are performed by executing program 882 on the computer. This makes it possible to improve the uniformity of the width of the weld bead around the entire circumference of the weld line 93, as described above.

[0081] The welding condition determination method, welding method, and program described above can be modified in various ways.

[0082] For example, in steps S21, S23, and S25 described above, the groove angle on the main pipe 91 side and the groove angle on the branch pipe 92 side do not necessarily have to be the measured values ​​from step S12; for example, the design value of the groove angle may be used. In this case, the groove dimension measured in step S12 does not have to include the groove angle.

[0083] In step S22, the provisional target welding cross-sectional area does not necessarily have to be the arithmetic mean of the upper and lower cross-sectional areas, and may be set in various ways based on the upper and lower cross-sectional areas. For example, the provisional target welding cross-sectional area may be the arithmetic mean (i.e., weighted mean) of the upper and lower cross-sectional areas after multiplying each by a predetermined weighting coefficient.

[0084] In step S24, the target groove depth is not necessarily the expected groove depth d at each position on the weld line 93. a1 It does not need to be the arithmetic mean of the expected groove depth d at each position.a1 It may be set in various ways based on this. For example, the expected groove depth d at each location. a1 Alternatively, the target groove depth may be calculated by multiplying the target groove depth by a weighting coefficient corresponding to its position on the weld line 93, and then obtaining the arithmetic mean (i.e., weighted mean).

[0085] The welding conditions determined in step S26 do not necessarily have to include at least one of the welding speed and welding current, but may include only parameters other than welding speed and welding current (e.g., weaving width).

[0086] The determination of the welding conditions described above (steps S21 to S26 and step S32) does not necessarily have to be performed by the automatic welding apparatus 1. For example, it may be performed by executing program 882 on another device, such as a computer independent of the automatic welding apparatus 1.

[0087] The above-described method for determining welding conditions and welding method may also be applied to single-layer welding in which no welding layer 95 is laminated.

[0088] The bevel angle on the main pipe 91 side and the bevel angle on the branch pipe 92 side of the branch pipe joint 9 do not necessarily have to be constant in the depth direction of the bevel 94. In this case, the bevel angle on the main pipe 91 side measured in step S12 is, for example, the bevel angle on the main pipe 91 side at the lower end of the bevel 94. The same applies to the bevel angle on the branch pipe 92 side.

[0089] In the example described above, the branch pipe 92 of the branch pipe joint 9 is connected perpendicularly to the outer surface 911 of the main pipe 91. However, the method for determining the welding conditions and the welding method described above are also applicable to branch pipe joints 9 in which the branch pipe 92 is connected not perpendicularly (i.e., at an angle) to the outer surface 911 of the main pipe 91.

[0090] The above-described method for determining welding conditions may be used when determining welding conditions for a branch pipe joint 9, which is performed while changing the orientation of the object to be welded using a positioner or the like.

[0091] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other. [Explanation of symbols]

[0092] 1. Automatic welding equipment 2 Torches 9. Branch pipe fittings 91 Main tube 92 Branch pipe 93 Welding line 94 Bevel 95 Weld Layers 882 Program 911 Outer surface (of the main tube) Steps S11-S14, S21-S26, S31-S32

Claims

1. A method for determining welding conditions for branch pipe joints using an automatic welding device, a) In a branch pipe joint connecting a branch pipe having a smaller diameter than the main pipe to the outer surface of the main pipe, the steps of measuring the groove dimensions, which indicate the cross-sectional shape of the groove formed on the outer surface of the main pipe, at each position on the circumferential weld line, b) A step of determining the upper and lower limits of the welded cross-sectional area at each position on the weld line, based on the groove dimensions at each position on the weld line, c) A step of setting the provisional target welding cross-sectional area at each position on the weld line based on the upper limit cross-sectional area and the lower limit cross-sectional area at each position on the weld line, d) A step of determining the expected groove depth, which is the groove depth after welding, assuming that welding is performed at each position on the weld line with the provisional target welding cross-sectional area. e) A step of setting a target groove depth for the entire weld line based on the expected groove depth at each position on the weld line, f) A step of determining a target weld cross-sectional area at each position on the weld line, within a range greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or less than or equal to a predetermined threshold, g) A step of determining the welding conditions at each position on the weld line based on the target weld cross-sectional area at each position on the weld line, A welding condition determination method comprising:

2. A method for determining welding conditions according to claim 1, A welding condition determination method wherein steps a) to g) are performed for each welding layer of the laminated welding performed on the branch pipe joint.

3. A method for determining welding conditions according to claim 1, A welding condition determination method wherein the provisional target welding cross-sectional area at each position on the welding line is the arithmetic mean of the upper limit cross-sectional area and the lower limit cross-sectional area at each position on the welding line.

4. A method for determining welding conditions according to claim 1, A welding condition determination method wherein the target groove depth is the arithmetic mean of the expected groove depths at each position on the weld line.

5. A method for determining welding conditions according to claim 1, A welding condition determination method wherein the welding conditions at each position on the weld line determined in step g) include at least one of the welding speed and the welding current.

6. A method for determining welding conditions according to claim 1, In step a) above, the inclination angle of the weld line with respect to the horizontal plane is measured, taking into account the direction of movement of the torch at each position on the weld line. A welding condition determination method wherein the weaving width of the torch at each position on the welding line is determined based on the inclination angle at each position on the welding line.

7. A method for determining welding conditions for branch pipe joints using an automatic welding device, h) In a branch pipe joint connecting a branch pipe having a smaller diameter than the main pipe to the outer surface of the main pipe, the steps include measuring the angle of inclination of the weld line with respect to the horizontal plane at each position on the circumferential weld line, taking into account the direction of movement of the torch, with respect to the groove formed on the outer surface of the main pipe, i) A step of determining the weaving width of the torch, which is one of the welding conditions at each position on the weld line, based on the inclination angle at each position on the weld line, A welding condition determination method comprising:

8. A welding method for branch pipe joints using an automatic welding device, The process of placing the object on which the branch pipe joint is provided in a predetermined position, A step of welding the branch pipe joint without changing the orientation of the object by driving the torch based on the welding conditions determined by the welding condition determination method described in any one of claims 1 to 7, A welding method comprising the following features.

9. A computer-readable program for determining welding conditions for branch pipe joints using an automatic welding machine, When the aforementioned program is executed on a computer, a) In a branch pipe joint connecting a branch pipe having a smaller diameter than the main pipe to the outer surface of the main pipe, the steps of measuring the groove dimensions, which indicate the cross-sectional shape of the groove formed on the outer surface of the main pipe, at each position on the circumferential weld line, b) A step of determining the upper and lower limits of the welded cross-sectional area at each position on the weld line, based on the groove dimensions at each position on the weld line, c) A step of setting the provisional target welding cross-sectional area at each position on the weld line based on the upper limit cross-sectional area and the lower limit cross-sectional area at each position on the weld line, d) A step of determining the expected groove depth, which is the groove depth after welding, assuming that welding is performed at each position on the weld line with the provisional target welding cross-sectional area. e) A step of setting a target groove depth for the entire weld line based on the expected groove depth at each position on the weld line, f) A step of determining a target weld cross-sectional area at each position on the weld line, within a range greater than or equal to the lower limit cross-sectional area and less than or equal to the upper limit cross-sectional area, such that the difference between the groove depth after welding and the target groove depth is minimized or less than or equal to a predetermined threshold, g) A step of determining the welding conditions at each position on the weld line based on the target weld cross-sectional area at each position on the weld line, A computer-readable program that performs [some action].

10. A computer-readable program for determining welding conditions for branch pipe joints using an automatic welding machine, When the aforementioned program is executed on a computer, h) In a branch pipe joint connecting a branch pipe having a smaller diameter than the main pipe to the outer surface of the main pipe, the steps include measuring the angle of inclination of the weld line with respect to the horizontal plane at each position on the circumferential weld line, taking into account the direction of movement of the torch, with respect to the groove formed on the outer surface of the main pipe, i) A step of determining the weaving width of the torch, which is one of the welding conditions at each position on the weld line, based on the inclination angle at each position on the weld line, A computer-readable program that performs [some action].

Images