JP2014100724A - Welding method, welding unit, and method of installing welding robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the temperature of the back surface of a welding part within a specified heating restriction range.SOLUTION: In a welding unit 6, welding is carried out two or more times by a welding robot 1 along a plurality of welding passes set in such a way that beads are overlapped over a welding part. The welding is stopped temporarily between the welding along a first welding pass and the welding along a second welding pass, and the welding unit 6 waits until a second start condition determined on the basis of a specified heating restriction is met. The welding along the first welding pass is continued while meeting a first continuation condition determined on the basis of the heating restriction, and the welding along the second welding pass is continued while meeting a second continuation condition determined on the basis of the heating restriction. Since a waiting step between welding passes is thus managed on the basis of the heating restriction and continuation of welding along each welding pass is also managed on the basis of the heating restriction, in each welding along each welding pass, the temperature of the back surface of the welding part is controllable within a specified heating restriction.

Description

  The present invention relates to a technique for welding an object.

  Conventionally, in order to repair a steel exhaust pipe installed in an incineration facility, a power plant or the like, a steel plate is welded to the outer surface of the exhaust pipe. In general, the inner surface of the exhaust pipe is painted to protect the exhaust pipe or is provided with a lining material. Therefore, when welding to the outer surface of the exhaust tube, it is necessary to suppress the temperature rise on the inner surface so that the inner coating film and lining material are not deteriorated or damaged by heating.

  For example, in Patent Document 1 and Patent Document 2, in the weaving bead method in which weld beads (hereinafter simply referred to as “beads”) are alternately applied to two members to be welded, the subsequent beads are compared with the preceding beads. The technique which suppresses a temperature rise by constructing so that a clearance gap may be disclosed is disclosed. Patent Document 1 discloses that a CD (capacitor discharge) welding method is used to suppress a temperature rise on the back surface of a welded portion when welding a stud pin to a cylinder.

Japanese Patent No. 5039801 JP 2011-161460 A

  By the way, in the welding method of patent document 1 and patent document 2, the part in which a bead is not provided is intermittently provided along the junction part of two to-be-welded members. For this reason, there exists a possibility that joining strength may be insufficient or the uniformity of joining strength may fall. Moreover, when the said welding method is used, it is difficult to confirm whether the back surface temperature of an actual junction part is in the range of a predetermined heating restriction | limiting.

  This invention is made | formed in view of the said subject, and makes it the main objective to make the back surface temperature of a welding part into the range of the predetermined heating restriction | limiting.

  The invention according to claim 1 is a welding method in which welding is performed a plurality of times along a plurality of welding paths set so that a bead overlaps a welded portion of an object, and a) the object of the object Based on the heating restriction on the back surface of the welded portion, a first continuation condition that is a welding continuation condition of the first welding pass, a second start condition that is a welding start condition of the second welding pass, and the second welding A step of preparing a second continuation condition that is a welding continuation condition of the pass; b) a step of starting welding along the first welding pass; and c) the first welding pass while satisfying the first continuation condition. , Continuing welding at the end of the first welding pass, d) waiting until the second start condition is satisfied, and e) satisfying the second start condition. Starting welding along the second welding path , And a step of continuing the welding along the second weld pass while satisfying f) the second continuation condition, terminates the weld at the end point of the second welding pass.

  Invention of Claim 2 is the welding method of Claim 1, Comprising: It is said 2nd start condition that the back surface temperature of the said welding part is below a predetermined threshold temperature, Said d) process D2) a step of measuring the surface temperature of the weld, d2) a step of determining whether the second start condition is successful based on the measurement result of the surface temperature, and d3) the second start condition is satisfied. Until the step d1) and the step d2) are repeated.

  Invention of Claim 3 is a welding method of Claim 1 or 2, Comprising: The said c) process measures the surface temperature of the 1st bead formed on c1) said 1st welding pass. And c2) detecting a high temperature region in which a surface temperature of the first bead is equal to or higher than the first temperature and equal to or lower than a second temperature higher than the first temperature, and obtains a length of the high temperature region. And c3) repeating the b1) step and the b2) step until welding is completed at the end point of the first welding pass, and the length of the high temperature region is a predetermined first. It is the first continuation condition that the length is equal to or shorter than the length, and the step e) includes the step e1) measuring the surface temperature of the second bead formed on the second welding pass, and e2) the step The surface temperature of the second bead is higher than the first temperature and lower than the second temperature. Detecting a region and acquiring the length of the high temperature region; e3) repeating the steps e1) and e2) until welding is completed at the end point of the second welding pass; The second continuation condition is that the high-temperature region has a length equal to or less than a predetermined second length.

  According to a fourth aspect of the present invention, there is provided a welding unit for performing welding a plurality of times along a plurality of welding paths set so that a bead overlaps a welded portion of an object, the robot arm and the robot arm A first continuation condition, which is a welding continuation condition of the first welding pass, determined based on a welding robot having a welding torch attached to the tip of the welding object and a heating restriction on the back surface of the welding part of the object A storage unit for storing a second start condition that is a welding start condition of the second welding pass, and a second continuation condition that is a welding continuation condition of the second welding pass, the first continuation condition, the first And a control unit that controls the welding robot by determining whether the start condition and the second continuation condition are satisfied. Under the control of the control unit, the welding robot a) welds along the first welding path. Start B) a step of continuing welding along the first welding pass while satisfying the first continuation condition, and ending the welding at an end point of the first welding pass; and c) the second start. A step of waiting until a condition is satisfied, d) a step of starting welding along the second welding path in a state where the second start condition is satisfied, and e) the step of satisfying the second continuation condition A step of continuing welding along the second welding pass and ending the welding at the end point of the second welding pass.

  The invention according to claim 5 is the welding unit according to claim 4, wherein the welding unit is attached to the tip portion of the robot arm and measures the surface temperature of the welded portion, and the measurement region is in the welding torch. It is further provided with a temperature sensor relatively fixed with respect to the second start condition that the back surface temperature of the weld is equal to or lower than a predetermined threshold temperature, and the step c) includes c1) the temperature sensor. Measuring the surface temperature of the welded portion, c2) determining the success or failure of the second start condition based on the output from the temperature sensor, and c3) determining whether the second start condition is satisfied. A step of repeating the step c1) and the step c2) until it is satisfied.

  The invention according to claim 6 is the welding unit according to claim 4, wherein the welding unit is attached to the tip portion of the robot arm to measure the surface temperature of the welded portion, and the measurement region is in the welding torch. A temperature sensor relatively fixed with respect to the surface; b) the step of b1) measuring the surface temperature of the first bead formed on the first welding pass; and b2) the first. Detecting a high temperature region in which a surface temperature of the bead is not less than a first temperature and not more than a second temperature higher than the first temperature, and obtaining a length of the high temperature region; b3) the first A step of repeating the step b1) and the step b2) until the welding is finished at the end point of the welding pass, and the length of the high temperature region is equal to or less than a predetermined first length, A first continuation condition, wherein the step d) d1) a step of measuring the surface temperature of the second bead formed on the second welding pass; and d2) a high temperature at which the surface temperature of the second bead is not less than the first temperature and not more than the second temperature. Detecting a region and acquiring the length of the high temperature region; and d3) repeating the steps d1) and d2) until welding is completed at the end point of the second welding pass. The second continuation condition is that the high-temperature region has a length equal to or less than a predetermined second length.

  A seventh aspect of the present invention is the welding unit according to any one of the fourth to sixth aspects, further comprising a digital pulse power source that supplies power to the welding torch.

The invention according to claim 8 is the welding unit according to any one of claims 4 to 7, wherein a plurality of studs are stud-welded to the surface of an object, and the welds are attached to the plurality of studs. A robot support section for supporting the robot, and the relationship between the diameter d of each of the plurality of studs and the plate thickness t of the object satisfies d ≦ (2 ^0.5 · t).

The invention according to claim 9 is a method for installing a welding robot, the step of stud welding a plurality of studs to the surface of an object, the step of attaching a robot support portion to the plurality of studs, and the robot support portion And a step of attaching a welding robot to the plurality of studs, and the relationship between the diameter d of each of the plurality of studs and the plate thickness t of the object satisfies d ≦ (2 ^0.5 · t).

  In this invention, the back surface temperature of a welding part can be made into the range of predetermined heating restrictions.

It is a figure which shows the structure of the welding unit which concerns on one embodiment of this invention. It is a side view which shows the welding robot installed in the cylinder. It is a figure which shows an example of the temperature distribution of the welding part displayed on a display part. It is a figure which shows the flow of the installation method of a welding robot. It is a figure which shows the relationship between the diameter of a volt | bolt, the board thickness of an exhaust pipe, and a back surface temperature. It is a figure which shows the steel plate welded to the exhaust pipe. It is sectional drawing of a steel plate and an exhaust pipe. It is a figure which shows the flow of welding of the steel plate with respect to an exhaust pipe. It is a figure which shows the flow of welding of the steel plate with respect to an exhaust pipe. It is a figure which shows the flow of welding of the steel plate with respect to an exhaust pipe. It is a figure which shows a part of flow of welding. It is a figure which shows a part of flow of welding. It is a figure which shows a part of flow of welding. It is a figure which shows a part of flow of welding. It is a figure which shows a part of flow of welding. It is a figure which shows the change of back surface temperature. It is a cross-sectional macro photograph of a welding part. It is a cross-sectional macro photograph of the welding part which welded the comparative example.

  FIG. 1 is a diagram showing a configuration of a welding unit 6 according to an embodiment of the present invention. The welding unit 6 includes a welding robot 1, a drive power source 2, a temperature sensor 3, a storage unit 41, a control unit 42, and a display unit 43. Below, the case where a steel plate is welded to the outer surface of the steel exhaust pipe installed in the incineration facility, the power plant, etc. with the welding unit 6 is demonstrated.

  FIG. 2 is a side view of the welding robot 1 attached to the outer surface 92 of the exhaust pipe 91. In FIG. 2, the exhaust pipe 91 and the steel plate 94, which are objects to be welded, are shown in cross section. The outer surface 92 and the inner surface 93 of the exhaust tube 91 are the front surface and the back surface of the object to be welded, respectively. A protective film such as a coating film or a lining material is provided on the inner surface 93 of the exhaust tube 91. The welding robot 1 performs MAG welding (metal active gas welding), which is a kind of arc welding, on the exhaust pipe 91 and the steel plate 94. The welding robot 1 includes a robot arm 11 having multiple degrees of freedom (for example, 6 degrees of freedom) and a welding torch 12. The welding torch 12 is attached to the tip 111 of the robot arm 11 and is moved three-dimensionally by the robot arm 11.

  A wind resistant nozzle 13 is provided at the tip of the welding torch 12. The wind-resistant nozzle 13 can increase the flow rate of the shielding gas to about 200 liters per minute. Thereby, welding can be performed even in an environment where the wind speed is about 10 m / sec. The welding torch 12 is supplied with welding power from the drive power source 2 (see FIG. 1). A low voltage digital pulse power supply is used as the drive power supply 2.

  The temperature sensor 3 measures the surface temperature of the welded portion on the exhaust pipe 91. Specifically, the temperature sensor 3 captures an image of the weld on the outer surface 92 of the exhaust pipe 91 and acquires an image of the temperature distribution of the weld. The image output from the temperature sensor 3 is displayed on the display unit 43 (see FIG. 1). The temperature sensor 3 is attached to the tip 111 of the robot arm 11 and is moved three-dimensionally together with the welding torch 12 by the robot arm 11. The measurement area of the temperature sensor 3 is fixed relative to the welding torch 12.

  FIG. 3 is a diagram illustrating an example of the temperature distribution of the welded portion displayed on the display unit 43. The left portion in the figure is a steel plate 94, and in FIG. 3, the vicinity of the corner portion of the steel plate 94 subjected to the R treatment is shown. FIG. 3 shows a state in the process of forming a first bead 961 described later. A portion surrounded by a solid line denoted by reference numeral 81 corresponds to a portion where welding is performed by the welding torch 12 and has the highest temperature. A portion surrounded by a broken line denoted by reference numeral 82 corresponds to a portion where a bead has been formed by welding, and the temperature is lower than that of the above-described highest temperature portion 81. The temperature of the highest temperature part 81 is about 1500 ° C., for example. The temperature of the portion surrounded by the reference numeral 82 is less than about 1500 ° C., and becomes higher as the temperature approaches the highest temperature portion 81.

  The storage unit 41 and the control unit 42 shown in FIG. 1 have a general computer system configuration in which a CPU that performs various arithmetic processes, a ROM that stores basic programs, and a RAM that stores various types of information are connected to a bus line. ing. The storage unit 41 stores various information related to welding performed by the welding robot 1. The control unit 42 controls the operation of the welding robot 1 such as the movement of the welding torch 12 by the robot arm 11 and the start, stop, interruption and restart of welding.

  As shown in FIG. 2, the welding unit 6 further includes a robot support portion 51 and a plurality of bolts 52. The plurality of bolts 52 are joined to the outer surface 92 of the exhaust tube 91. In the present embodiment, six bolts 52 are joined to the exhaust cylinder 91. Specifically, two rows of bolts in which three bolts 52 are arranged in the vertical direction are provided in the horizontal direction.

  The robot support unit 51 is attached to the plurality of bolts 52 and supports the welding robot 1. The robot support portion 51 is connected to the substantially plate-like first part 511 extending in the horizontal direction, the substantially plate-like second part 512 spreading in the vertical direction, and the first part 511 and the second part 512. The 3rd site | part 513 of this is provided. The second portion 512 is joined to the end of the first portion 511 on the exhaust tube 91 side and faces the outer surface 92 of the exhaust tube 91. Six through holes are provided in the second portion 512. The third part 513 is joined to the lower surface of the first part 511 and the surface of the second part 512 opposite to the exhaust tube 91, and reinforces the joining of the first part 511 and the second part 512.

  FIG. 4 is a diagram illustrating a flow of an installation method of the welding robot 1. The plurality of bolts 52 are stud welded substantially perpendicularly to the outer surface 92 of the exhaust tube 91 by a welding machine for stud welding (step S01). Each bolt 52 is a stud joined by stud welding. Subsequently, a nut 53 is attached to each bolt 52, and the nut 53 is welded to the bolt 52 in the vicinity of the exhaust pipe 91 (step S02).

  Next, six bolts 52 are respectively inserted into the six through holes of the second portion 512. The second portion 512 is in contact with the nut 53 welded to each bolt 52. A nut 54 is attached to each bolt 52, and the second portion 512 is sandwiched between the nut 53 and the nut 54. Thereby, the robot support part 51 is attached to the plurality of bolts 52, and the relative position of the robot support part 51 with respect to the exhaust pipe 91 is determined (step S03). Further, the inclination of the first portion 511 with respect to the horizontal direction is adjusted by changing the degree of tightening of the plurality of nuts 54.

  Thereafter, the welding robot 1 is detachably attached to the first portion 511 of the robot support portion 51 with a bolt or the like (step S04). Usually, since the outer surface 92 of the exhaust pipe 91 is a curved surface, if the welding robot 1 is positioned with reference to the outer surface 92, there is a limit to the improvement of the position accuracy of the welding robot 1. As described above, the nut 53 is welded to each bolt 52, and the robot support portion 51 is positioned with reference to the nut 53, whereby the relative position of the welding robot 1 with respect to the exhaust tube 91 can be determined with high accuracy.

  When the bolt 52 is welded in step S01, the temperature of the inner surface 93 of the portion of the exhaust pipe 91 where the bolt 52 is welded (hereinafter referred to as “back surface temperature”) increases. In stud welding, as the diameter d of the bolt 52 increases, the amount of increase in the back surface temperature also increases. On the other hand, when the plate thickness t of the exhaust pipe 91 at the site where the bolt 52 is welded is large, the amount of increase in the back surface temperature is small.

FIG. 5 is a diagram showing the relationship between the diameter d of the bolt 52 and the plate thickness t of the exhaust pipe 91 and the back surface temperature. In FIG. 5, the straight line denoted by reference numeral 85 indicates d = 2 ^0.5 · t (= √ (2) · t), and the straight line denoted by reference numeral 86 indicates d = 0.4t. With respect to the bolt 52 that is normally used in stud welding, the diameter d of the bolt 52 is set to 85 or less, that is, the back surface temperature is set to (2 ^0.5 ) times or less of the plate thickness t of the exhaust pipe 91. The maximum temperature can be 80 ° C. or lower. Further, from the viewpoint of securing the bonding strength of the bolt 52 to the exhaust tube 91, the diameter d of the bolt 52 is preferably not less than the straight line 86, that is, not less than 0.4 times the plate thickness t of the exhaust tube 91. . In the installation method of the welding robot 1 described above, the diameter d of the bolt 52 is about 0.9 times the plate thickness t of the exhaust pipe 91.

  Thereby, the raise of the back surface temperature at the time of stud welding of the volt | bolt 52 can be suppressed. As a result, it is possible to suppress or prevent the coating film and the lining material provided on the inner surface 93 of the exhaust pipe 91 from being deteriorated or damaged by the heat at the time of stud welding. Moreover, when the welding unit 6 is removed from the exhaust pipe 91 by making the diameter of the bolt 52 relatively small, an operator can easily remove the bolt 52 with a hammer or the like from the outer surface 92 of the exhaust pipe 91. Can do.

  Next, welding of the steel plate 94 to the exhaust tube 91 by the welding unit 6 will be described. FIG. 6 is a view showing a steel plate 94 welded to the exhaust tube 91. The steel plate 94 is welded to the annular welded portion 95 provided over the entire circumference of the steel plate 94 by the above-described welding unit 6 to form a bead 96, whereby the outer surface 92 of the exhaust tube 91 is formed. Welded. The welded portion 95 is an edge over the entire circumference of the surface of the steel plate 94 that contacts the exhaust tube 91, and a portion in the vicinity of the edge of the steel plate 94 and the exhaust tube 91.

  FIG. 7 is an enlarged view showing a cross section cut at a position A-A in FIG. 6. As shown in FIG. 7, the beads 96 are formed by overlapping the first bead 961, the second bead 962, the third bead 963, the fourth bead 964, the fifth bead 965, and the sixth bead formed on the welded portion 95. 966 and a seventh bead 967. The bead 96 is formed by sequentially performing a plurality of times of welding along a plurality of welding paths set so that the first bead 961 to the seventh bead 967 overlap on the welded portion 95.

  Specifically, the first bead 961 is formed by performing MAG welding while the welding torch 12 of the welding robot 1 moves along the annular first welding path set over the entire circumference of the welded portion 95. Is formed. The first bead 961 is formed clockwise in FIG. When the first bead 961 is formed, welding by the welding robot 1 is performed along the annular second welding path set over the entire circumference of the welded portion 95 to form the second bead 962. . The starting point of the second welding pass is approximately located on a cross section that includes the starting point of the first welding pass and is perpendicular to the first welding pass. The formation of the second bead 962 is also performed clockwise in FIG.

  Similarly, the formation of the third bead 963, the fourth bead 964, the fifth bead 965, the sixth bead 966, and the seventh bead 967 along the third to seventh welding paths is clockwise in FIG. It is performed sequentially. Each of the third to seventh welding passes is annularly set over the entire circumference of the welded portion 95, similarly to the first and second welding passes. Further, the start points of the third to seventh welding passes are approximately located on the cross section including the start point of the first welding pass and perpendicular to the first welding pass, like the start point of the second welding pass. To do.

  In the following, FIG. A thru | or FIG. A method for welding the steel plate 94 to the exhaust tube 91 will be described in more detail with reference to FIG. First, based on the heating restriction on the inner surface 93 (that is, the back surface) of the welded portion 95 of the exhaust tube 91, the welding start conditions of the first to seventh welding passes and the first to seventh welding passes are determined. Each welding continuation condition is determined. In the following description, the welding start condition and the welding continuation condition of the first welding pass are referred to as “first start condition” and “first continuation condition”, respectively. Further, the welding start condition and the welding continuation condition of the second welding pass are referred to as “second start condition” and “second continuation condition”, respectively. The same applies to the welding start conditions and the welding continuation conditions of the third to seventh welding passes.

  The heating restriction is a heating state allowed on the inner surface 93 of the welded portion 95. The first start condition is a condition for determining whether or not welding can be started along the first welding pass at the start point of the first welding pass. When the first start condition is satisfied, the first welding condition is satisfied. Welding along the path, that is, formation of the first bead 961 is started. The second start condition is a condition for determining whether or not welding can be started along the second weld pass at the start point of the second weld pass. When the second start condition is satisfied, the second weld pass is determined. , That is, the formation of the second bead 962 is started. Similarly, the third to seventh start conditions are conditions for determining whether or not to start welding along the third to seventh welding passes at the start points of the third to seventh welding passes.

  In the present embodiment, the heating restriction on the inner surface 93 of the welded portion 95 is that the time during which the temperature of the inner surface 93 of the welded portion 95 (hereinafter referred to as “back surface temperature”) is continuously maintained at 80 ° C. or higher is 25 seconds. It is the following. The first start condition and the second start condition are that the back surface temperature of the welded portion 95 is equal to or lower than a predetermined threshold temperature. Similarly, the third to seventh start conditions are that the back surface temperature of the welded portion 95 is equal to or lower than the threshold temperature. The threshold temperature is 40 ° C., for example.

  The first continuation condition is a condition for determining whether or not welding can be continuously performed during the execution of welding along the first welding path. While the first continuation condition is satisfied, welding along the first welding path, that is, formation of the first bead 961 is continued. When the first continuation condition is not satisfied, the welding is temporarily interrupted, and when the first continuation condition is satisfied, welding along the first welding path is resumed. The second continuation condition is a condition for determining whether or not the welding can be continuously performed during the welding along the second welding path. While the second continuation condition is satisfied, the welding along the second welding path, that is, the formation of the second bead 962 is continued. When the second continuation condition is not satisfied, the welding is temporarily stopped, and when the second continuation condition is satisfied, welding along the second welding path is resumed. Similarly, the third to seventh continuation conditions are conditions for determining whether or not the welding along the third to seventh welding passes can be continuously performed.

  In the present embodiment, the first continuation condition is that, in the temperature distribution of the welded portion 95 displayed on the display unit 43, the length L1 of the high temperature region 961a of the first bead 961 shown in FIG. Is less than or equal to. The high temperature region 961a is a region where the surface temperature of the first bead 961 is equal to or higher than a predetermined first temperature and equal to or lower than a predetermined second temperature. The first temperature is 200 ° C. higher than the normal temperature and higher than the threshold temperature, and the second temperature is 800 ° C. higher than the first temperature. In FIG. 3, the high temperature region 961a is surrounded by a solid line denoted by reference numeral 83. The length of the hot zone 961a is measured along the first welding pass. The first length is 37 mm, for example.

  The second continuation condition is that, in the temperature distribution of the weld portion 95 displayed on the display unit 43, the length of the high temperature region of the second bead 962 is equal to or less than a predetermined second length. As described above, the high temperature region is a region where the surface temperature of the second bead 962 is not lower than the first temperature (200 ° C.) and not higher than the second temperature (800 ° C.). The second length is, for example, 42 mm. Similarly, in the third to seventh continuation conditions, the length of the high temperature region of the third bead 963 to the seventh bead 967 is equal to or less than the third to seventh length. For example, the third length is 51 mm, the fourth length is 50 mm, and the fifth length is 37 mm. The sixth length is 36 mm and the seventh length is 48 mm.

  The back surface temperature and the maintenance time related to the heating restriction are variously changed depending on the type of the protective film provided on the inner surface 93 of the exhaust pipe 91. The threshold temperature according to the first to seventh start conditions is variously changed according to the above heating limitation, the material of the exhaust pipe 91, the plate thickness, and the like. Similarly, the first to seventh lengths according to the first to seventh continuation conditions are also changed in various ways depending on the heating limitation and the material and plate thickness of the exhaust pipe 91. The heating limit, the first to seventh start conditions, and the first to seventh continuation conditions are determined by experiments and simulations. The determined first to seventh start conditions and first to seventh continuation conditions are stored and prepared in advance in the storage unit 41 (see FIG. 1) (step S11).

  In the welding unit 6, the robot arm 11 of the welding robot 1 is controlled by the control unit 42, and the welding torch 12 and the temperature sensor 3 are moved to a position corresponding to the start point of the first welding pass. The steel plate 94 is temporarily attached to the outer surface 92 of the exhaust tube 91 in advance. Subsequently, the controller 42 determines whether or not the first start condition is met (step S12). Specifically, the distribution of the surface temperature of the welded portion 95 including the start point of the first welding pass is measured by the temperature sensor 3, and the measurement result is sent to the control unit 42. Based on the measurement result, the control unit 42 determines whether or not the first start condition is satisfied, that is, whether or not the back surface temperature of the welded portion 95 is 40 ° C. or less. In step S12, for example, the back surface temperature may be obtained from the surface temperature of the welded portion 95 based on a prior simulation or the like. Moreover, when the surface temperature is 40 ° C. or lower, the back surface temperature may be determined to be 40 ° C. or lower.

  If the first start condition is not satisfied, the process waits until the first start condition is satisfied. When it is difficult to satisfy the first start condition due to the influence of the outside air temperature or the like, for example, the entire welded portion 95 may be cooled. When the first start condition is satisfied, welding along the first welding pass is started (step S13). Then, while satisfying the first continuation condition, the welding torch 12 and the temperature sensor 3 move, the welding along the first welding pass is continued, and the welding is terminated at the end point of the first welding pass (step S14). .

  FIG. A and FIG. B is a figure which shows the detail of operation | movement of the welding unit 6 in welding along a 1st welding path. When welding is started, the surface temperature of the first bead 961 formed on the first welding pass is measured by the temperature sensor 3 (step S41). The measurement result by the temperature sensor 3 is sent to the control unit 42, and the control unit 42 acquires the length L1 (see FIG. 3) of the high temperature region 961a having a surface temperature of 200 ° C. or higher and 800 ° C. or lower (step S42). Then, the control unit 42 determines whether or not the length L1 of the high temperature region 961a is equal to or shorter than the first length (37 mm), that is, whether or not the first continuation condition is satisfied (step S43). If the first continuation condition is satisfied, welding is continued.

  On the other hand, when the first continuation condition is not satisfied, that is, when the length L1 of the high temperature region 961a is longer than the first length, the welding by the welding torch 12 is interrupted and the welding torch 12 and the temperature sensor 3 move. Stops (step S44). Then, in the state where the welding is interrupted, the surface temperature of the first bead 961 is measured and the length L1 of the high temperature region 961a is acquired (steps S45 and S46) as in steps S41 and S42. In the welding unit 6, steps S45 and S46 are repeated until the first continuation condition is satisfied (step S47), that is, until the length L1 of the high temperature region 961a is equal to or less than the first length. When the first continuation condition is satisfied, welding is resumed (step S48).

  In the welding unit 6, the above-described steps S41 to S43 (steps S41 to S48 when the welding is interrupted) are repeated until the welding torch 12 reaches the end point of the first welding pass (step S49). When the first bead 961 is formed up to the end point of the first welding pass, the welding along the first welding pass is completed at the end point.

  When the formation of the first bead 961 is finished, the welding by the welding torch 12 is stopped, and the movement of the welding torch 12 and the temperature sensor 3 is also stopped. The welding torch 12 and the temperature sensor 3 stand by in a stopped state until the second start condition is satisfied (step S15).

  Specifically, as shown in FIG. 10, the distribution of the surface temperature of the welded portion 95 including the start point of the second welding pass is measured by the temperature sensor 3, and the measurement result is sent to the control unit 42 (step S51). ). Based on the measurement result, the control unit 42 determines whether or not the second start condition is satisfied, that is, whether or not the back surface temperature of the welded portion 95 is 40 ° C. or less (step S52). In step S52, for example, the back surface temperature may be obtained from the surface temperature of the welded portion 95 based on a prior simulation or the like. Moreover, when the surface temperature is 40 ° C. or lower, the back surface temperature may be determined to be 40 ° C. or lower. If the second start condition is not satisfied, steps S51 and S52 are repeated until the second start condition is satisfied. When it is difficult to satisfy the second start condition due to the influence of the outside temperature or the like, or when it is desired to shorten the waiting time, for example, the entire welded portion 95 may be cooled.

  When the second start condition is satisfied, the welding standby state is canceled, and welding along the second welding pass is started (step S16). Then, while satisfying the second continuation condition, the welding torch 12 and the temperature sensor 3 move, the welding along the second welding path is continued, and the welding ends at the end point of the second welding path (step S17). .

  FIG. A and FIG. B is a figure which shows the detail of operation | movement of the welding unit 6 in welding along a 2nd welding path. The welding flow along the second welding path is the same as the welding flow along the first welding path. When welding is started, the surface temperature of the second bead 962 formed on the second welding pass is measured by the temperature sensor 3 (step S61). The measurement result by the temperature sensor 3 is sent to the control unit 42, and the control unit 42 acquires the length of the high temperature region where the surface temperature is 200 ° C. or higher and 800 ° C. or lower (step S62). Then, the control unit 42 determines whether or not the length of the high temperature region is equal to or shorter than the second length (42 mm) described above, that is, whether or not the second continuation condition is satisfied (step S63). If the second continuation condition is satisfied, welding is continued.

  On the other hand, when the second continuation condition is not satisfied, that is, when the length of the high temperature region is longer than the second length, welding by the welding torch 12 is interrupted, and the movement of the welding torch 12 and the temperature sensor 3 is stopped. (Step S64). Then, in the state where the welding is interrupted, the surface temperature of the second bead 962 is measured and the length of the high temperature region is acquired (steps S65 and S66), similarly to steps S61 and S62. In the welding unit 6, steps S65 and S66 are repeated until the second continuation condition is satisfied (step S67), that is, until the length of the high temperature region becomes equal to or shorter than the second length. When the second continuation condition is satisfied, welding is resumed (step S68).

  In the welding unit 6, the steps S61 to S63 described above (steps S61 to S67 when the welding is interrupted) are repeated until the welding torch 12 reaches the end point of the second welding pass (step S69). When the second bead 962 is formed up to the end point of the second welding pass, the welding along the second welding pass is completed at the end point.

  When the formation of the second bead 962 is finished, the welding by the welding torch 12 is stopped, and the movement of the welding torch 12 and the temperature sensor 3 is also stopped. The welding torch 12 and the temperature sensor 3 stand by in a stopped state until the third start condition is satisfied (step S18). The specific operation during standby is the same as steps S51 to S52 shown in FIG. When the third start condition is satisfied, the welding standby state is canceled, and welding along the third welding pass is started (step S19). Then, while satisfying the third continuation condition, the welding torch 12 and the temperature sensor 3 move, the welding along the third welding pass is continued, and the welding ends at the end point of the third welding pass (step S20). . Specific operation during welding is shown in FIG. A and FIG. B. Steps S41 to S49 shown in FIG. A and FIG. This is the same as steps S61 to S69 shown in B.

  Similarly, the process waits until the fourth start condition is satisfied. When the fourth start condition is satisfied, welding along the fourth welding path is started (steps S21 and S22). Welding along the fourth welding pass is continued while satisfying the fourth continuation condition, and the welding ends at the end point of the fourth welding pass (step S23). Then, it waits until 5th start conditions are satisfy | filled, and welding along a 5th welding pass is started (step S24, S25). Welding is continued while satisfying the fifth continuation condition, and ends at the end point of the fifth welding pass (step S26).

  Next, the process waits until the sixth start condition is satisfied, and welding along the sixth welding pass is started (steps S27 and S28). Welding is continued while satisfying the sixth continuation condition, and ends at the end point of the sixth welding pass (step S29). And it waits until 7th start conditions are satisfy | filled, and welding along a 7th welding pass is started (step S30, S31). Welding is continued while satisfying the seventh continuation condition, and ends at the end point of the seventh welding pass (step S32). Thereby, as shown in FIGS. 6 and 7, the bead 96 is formed in the welded portion 95 around the steel plate 94, and the welding of the steel plate 94 to the outer surface 92 of the exhaust tube 91 is completed.

  As described above, in the welding unit 6, the welding robot 1 performs welding a plurality of times along a plurality of welding paths set so that the beads overlap on the welded portion 95, so that only once is performed. As compared with the case where the steel plate 94 is welded to the exhaust pipe 91 by welding, the rise of the back surface temperature of the welded portion 95 can be suppressed.

  In addition, until the welding is temporarily stopped between the welding along the first welding pass and the welding along the second welding pass, and the second start condition determined based on the above heating limit is satisfied, Wait without starting welding. The same applies to the standby process between other welding passes. Thus, by managing the standby process between the welding passes based on the heating restriction, the back surface temperature of the welded portion 95 can be set within a predetermined heating restriction range.

  Further, the welding along the first welding path is continued while satisfying the first continuation condition determined based on the heating restriction, and the welding along the second welding path is determined based on the heating restriction. It is continued while satisfying the continuation conditions. The same applies to welding along other welding paths. Thus, the continuation of the welding along each welding path is managed based on the heating limit, so that the back surface temperature of the welded portion 95 at the time of performing the welding along each welding path is within the range of the predetermined heating limit. can do.

  FIG. 12 is a diagram illustrating a change in the back surface temperature at a predetermined position on the welded portion 95. FIG. 12 shows the back surface temperature when the same welding as the welding of the steel plate 94 to the exhaust pipe 91 by the welding unit 6 is reproduced in a state where the back surface temperature of the welded portion 95 can be measured. The seven peaks of the back surface temperature in the figure are temperatures when the welding torch 12 passes over the predetermined position in welding along the first to seventh welding paths. Each peak temperature is about 110 ° C. or more and about 140 ° C. or less, and the time during which the back surface temperature is continuously maintained at 80 ° C. or more in the vicinity of each peak is 25 seconds or less.

  FIG. 13 is a cross-sectional macro photograph of the bead 96 formed by the welding unit 6. FIG. 14 is a cross-sectional macro photograph of a bead formed by a welding method of a comparative example different from welding by the welding unit 6. In the welding method of the comparative example, a bead having a leg length approximately equal to the bead 96 is formed by one hand stick welding along one welding path. The dilution rate in FIG. 13 is about 40% of the dilution rate in FIG.

  Thus, in the welding unit 6, the back surface temperature of the welding part 95 can be made into the range of a predetermined heating restriction | limiting. Moreover, compared with the welding method of a comparative example, the dilution rate in the welding part 95 can be made low (namely, the penetration to the welding part 95 can be made small). As a result, damage to the protective film provided on the inner surface 93 of the exhaust tube 91 can be suppressed or prevented.

  As described above, in the welding unit 6, based on the process of measuring the surface temperature of the welded portion 95 and the measurement result of the surface temperature in the standby process (step S <b> 15) before starting welding along the second welding pass. The process of determining whether or not the second start condition is satisfied (steps S51 and S52) is repeated until the second start condition is satisfied. Thereby, the success or failure of the second start condition can be accurately determined. The same applies to the standby process before the start of welding along the third to seventh welding passes.

  In the welding unit 6, in the welding along the first welding path, a step of measuring the surface temperature of the first bead 961 and a high temperature of the surface temperature of the first temperature to the second temperature (200 ° C. to 800 ° C.). The process of obtaining the length L1 of the region 961a (steps S41 and S42) is repeated until the end point of the first welding pass. And if the 1st continuation condition that length L1 of high temperature field 961a is below the 1st length (37mm) is fulfilled, welding will be continued, and if the 1st continuation condition is not fulfilled, 1st The welding is interrupted until the continuation condition is met. Thereby, in welding along a 1st welding pass, the success or failure of 1st continuation conditions can be judged easily and accurately.

  Further, in the welding along the second welding path, the step of measuring the surface temperature of the second bead 962, and the length of the high temperature region where the surface temperature is not lower than the first temperature and not higher than the second temperature (200 ° C. or higher and 800 ° C. or lower). The process (steps S61 and S62) for acquiring the length is repeated until the end point of the second welding pass. And if the 2nd continuation condition that the length of a high temperature field is below the 2nd length (42mm) is fulfilled, welding will be continued, and when the 2nd continuation condition is not fulfilled, the 2nd continuation condition Welding is interrupted until Thereby, in welding along a 2nd welding path, the success or failure of 2nd continuation conditions can be judged easily and accurately. The same applies to welding along the third to seventh welding paths.

  As described above, in the welding unit 6, the wind resistant nozzle 13 is provided at the tip of the welding torch 12, so that welding can be performed even in an environment where the wind speed is about 10 m / second. For this reason, the welding unit 6 is particularly suitable for outdoor welding such as welding to the outer surface 92 of the exhaust pipe 91 which is an outdoor structure. In the welding unit 6, a digital pulse power source is used as the driving power source 2. Thereby, the low heat input to the welding part 95 is easily realizable.

  Further, in the welding unit 6, the robot support portion 51 is attached to the outer surface 92 of the exhaust pipe 91, which is an object to be welded, and the welding robot 1 is supported by the robot support portion 51. Thereby, even if the exhaust pipe 91 is in a state of being shaken by the influence of wind or the like, the welding robot 1 is fixed relative to the welded portion 95, and welding can be performed with high accuracy.

  Various modifications can be made in the above-described welding unit 6 and welding method.

  The second start condition is not limited to the back surface temperature of the welded portion 95 being equal to or lower than a predetermined threshold temperature. For example, the elapsed time after the end of welding along the first welding pass is equal to or longer than a predetermined threshold time. It may be. The threshold time is determined in advance based on the relationship between the elapsed time after the end of welding and the temperature of the back surface obtained by experiments and simulations. Alternatively, the second start condition may be that the surface temperature of the welded portion 95 is equal to or lower than a predetermined threshold temperature. The same applies to other welding start conditions.

  The first temperature and the second temperature that define the high temperature region 961a according to the first continuation condition may be changed as appropriate. However, the first temperature is set higher than normal temperature and higher than the threshold temperature, and the second temperature is set higher than the first temperature. Further, the first continuation condition is not limited to the length of the high temperature region 961a being equal to or shorter than the first length. For example, the size of the maximum temperature portion 81 is equal to or smaller than a predetermined size. May be. The same applies to the second to seventh continuation conditions.

  The types of the drive power source 2 and the temperature sensor 3 may be variously changed. For example, what displays the temperature of each position in the welding part 95 numerically as the temperature sensor 3 may be utilized. Further, the temperature sensor 3 does not necessarily need to be attached to the distal end portion 111 of the robot arm 11. For example, a temperature sensor that simultaneously measures the entire temperature of the welded portion 95 is fixed relative to the exhaust pipe 91. May be.

  The welding by the welding robot 1 may be arc welding other than MAG welding, or may be welding other than arc welding such as laser welding. Moreover, if the relative position of the welding robot 1 with respect to the exhaust pipe 91 does not change greatly due to wind or the like, the welding robot 1 does not necessarily have to be attached to the robot support portion 51 attached to the exhaust pipe 91. For example, the welding robot 1 may be installed in a gondola located in the vicinity of the exhaust pipe 91.

  In the above-described welding method, the number of welding passes is not limited to seven as long as welding is performed a plurality of times along a plurality of welding passes set so that the beads overlap the welded portion 95. In addition, the installation method of the welding robot shown to step S01-S04 may be utilized in the case of installation of the welding robot which does not perform the said welding along several welding paths.

  In the above-described welding method, whether or not the second start condition is successful is determined by the control unit 42. The success or failure of the second start condition is determined by an operator viewing the surface temperature of the welded portion 95 displayed on the display unit 43. You may judge. When determining that the second start condition is satisfied, the worker instructs the welding robot 1 to start welding along the second welding path. Also in this case, the success or failure of the second start condition can be determined with high accuracy. The same applies to the determination of success or failure of other welding start conditions.

  The success or failure of the first to seventh continuation conditions may be determined by the operator by visually observing the distribution of the surface temperature of the welded portion 95 displayed on the display unit 43. Alternatively, the length of the above-described high-temperature region is acquired by the control unit 42 and displayed on the display unit 43, and the operator visually determines the success or failure of the first to seventh continuation conditions by viewing the displayed length. Also good. If the worker determines that the first to seventh continuation conditions are satisfied, the worker causes welding robot 1 to continue welding. If the worker determines that the first to seventh continuation conditions are not satisfied, welding by welding robot 1 is performed. Interrupt. Also in this case, the success or failure of the first to seventh continuation conditions can be easily and accurately determined.

  Furthermore, in the above welding method, welding to the welded portion 95 may be performed by semi-automatic welding or hand bar welding by an operator without using the welding robot 1. Even in this case, as described above, the standby temperature between the welding passes is managed according to the welding start condition determined based on the predetermined heating limit, so that the back surface temperature of the welded portion 95 is reduced. Can be within the range. In addition, by controlling the continuation of welding along each welding pass according to the welding continuation condition determined based on the heating restriction, the back surface temperature of the welded portion 95 at the time of performing welding along each welding pass is controlled by the heating restriction. Can be within range.

  The welding unit 6 and the welding method may be used for welding to various objects other than the welding of the steel plate 94 to the exhaust pipe 91.

  The configurations in the above-described embodiments and modifications may be combined as appropriate as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 1 Welding robot 2 Driving power supply 3 Temperature sensor 6 Welding unit 11 Robot arm 12 Welding torch 41 Storage part 42 Control part 51 Robot support part 52 Bolt 91 Exhaust pipe 92 (exhaust pipe) outer surface 93 (exhaust pipe) inner surface 94 Steel plate 95 Welded portion 96 Bead 111 (Robot arm) tip 961 First bead 961a High temperature region 962 Second bead 963 Third bead 964 Fourth bead 965 Fifth bead 966 Sixth bead 967 Seventh bead S01 to S04, S11 to S32 , S41 to S49, S51 to S52, S61 to S69 Steps

Claims (9)

A welding method for performing welding a plurality of times along a plurality of welding paths set so that a bead overlaps a welded portion of an object,
a) a first continuation condition that is a welding continuation condition of the first welding pass, a second start condition that is a welding start condition of the second welding pass, based on the heating restriction on the back surface of the welded portion of the object; And preparing a second continuation condition that is a welding continuation condition of the second welding pass;
b) starting welding along the first welding path;
c) continuing the welding along the first welding pass while satisfying the first continuation condition, and ending the welding at the end point of the first welding pass;
d) waiting until the second start condition is satisfied;
e) starting welding along the second welding path in a state where the second start condition is satisfied;
f) continuing the welding along the second welding pass while satisfying the second continuation condition, and ending the welding at the end point of the second welding pass;
A welding method comprising: The welding method according to claim 1,
That the back surface temperature of the weld is below a predetermined threshold temperature is the second start condition,
Step d)
d1) measuring the surface temperature of the weld,
d2) determining the success or failure of the second start condition based on the measurement result of the surface temperature;
d3) repeating the steps d1) and d2) until the second start condition is satisfied;
A welding method comprising: The welding method according to claim 1 or 2,
Step c)
c1) measuring the surface temperature of the first bead formed on the first welding pass;
c2) detecting a high temperature region in which the surface temperature of the first bead is equal to or higher than the first temperature and equal to or lower than a second temperature higher than the first temperature, and acquiring a length of the high temperature region;
c3) repeating the step b1) and the step b2) until welding is terminated at the end point of the first welding pass;
With
The first continuation condition is that the length of the high temperature region is equal to or less than a predetermined first length,
Step e)
e1) measuring a surface temperature of the second bead formed on the second welding pass;
e2) detecting a high temperature region in which the surface temperature of the second bead is not less than the first temperature and not more than the second temperature, and obtaining a length of the high temperature region;
e3) repeating the step e1) and the step e2) until welding is terminated at the end point of the second welding pass;
With
It is the second continuation condition that the length of the high temperature region is equal to or less than a predetermined second length. A welding unit that performs welding a plurality of times along a plurality of welding paths set so that a bead overlaps a welded portion of an object,
A welding robot having a robot arm and a welding torch attached to the tip of the robot arm;
The first continuation condition, which is the welding continuation condition of the first welding pass, and the second start condition, which is the welding start condition of the second welding pass, are determined based on the heating restriction on the back surface of the welded portion of the object. And a storage unit for storing a second continuation condition that is a welding continuation condition of the second welding pass;
A controller that controls the welding robot by determining success or failure of the first continuation condition, the second start condition, and the second continuation condition;
With
The welding robot is controlled by the control unit.
a) starting welding along the first welding path;
b) continuing the welding along the first welding pass while satisfying the first continuation condition, and ending the welding at the end point of the first welding pass;
c) waiting until the second start condition is satisfied;
d) starting welding along the second welding path in a state where the second start condition is satisfied;
e) continuing the welding along the second welding pass while satisfying the second continuation condition, and ending the welding at the end point of the second welding pass;
A welding unit characterized by performing. The welding unit according to claim 4,
A temperature sensor attached to the tip of the robot arm to measure the surface temperature of the weld, and further comprising a temperature sensor fixed relative to the welding torch;
That the back surface temperature of the weld is below a predetermined threshold temperature is the second start condition,
Step c)
c1) measuring the surface temperature of the weld with the temperature sensor;
c2) a step of determining whether or not the second start condition is satisfied based on an output from the temperature sensor;
c3) repeating the c1) step and the c2) step until the second start condition is satisfied;
A welding unit comprising: The welding unit according to claim 4,
A temperature sensor attached to the tip of the robot arm to measure the surface temperature of the weld, and further comprising a temperature sensor fixed relative to the welding torch;
Step b)
b1) measuring the surface temperature of the first bead formed on the first welding pass;
b2) detecting a high temperature region in which the surface temperature of the first bead is equal to or higher than the first temperature and equal to or lower than a second temperature higher than the first temperature, and obtaining a length of the high temperature region;
b3) repeating the b1) step and the b2) step until welding is terminated at the end point of the first welding pass;
With
The first continuation condition is that the length of the high temperature region is equal to or less than a predetermined first length,
Step d)
d1) measuring the surface temperature of the second bead formed on the second welding pass;
d2) detecting a high temperature region in which the surface temperature of the second bead is not less than the first temperature and not more than the second temperature, and obtaining a length of the high temperature region;
d3) repeating the step d1) and the step d2) until welding is finished at the end point of the second welding pass;
With
The welding unit according to claim 2, wherein the second continuation condition is that the length of the high temperature region is equal to or less than a predetermined second length. The welding unit according to any one of claims 4 to 6,
A welding unit further comprising a digital pulse power source for supplying electric power to the welding torch. The welding unit according to any one of claims 4 to 7,
A plurality of studs stud-welded to the surface of the object;
A robot support portion attached to the plurality of studs to support the welding robot;
Further comprising
The relationship between the diameter d of each of the plurality of studs and the thickness t of the object is:
d ≦ (2 ^0.5 · t)
A welding unit characterized by satisfying A method for installing a welding robot,
A step of stud welding a plurality of studs to the surface of the object;
Attaching a robot support to the plurality of studs;
Attaching a welding robot to the robot support;
With
The relationship between the diameter d of each of the plurality of studs and the thickness t of the object is:
d ≦ (2 ^0.5 · t)
A welding robot installation method characterized by satisfying