JP2006000869A - Automatic circumferential welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic circumferential welding method of a base material to an attachment ring capable of preventing cracks, and manufacturing a container of long durability and lifetime. <P>SOLUTION: A welding starting part is welded under the initial welding condition with the predetermined heat input, a main weld part is welded under the main welding condition with the heat input higher than that of the initial welding condition, and a welding terminating part is welded under the terminating welding condition with the heat input lower than that of the main part welding condition. Before completing the welding step of the welding terminating part, a welding torch is retracted in the direction separating from a base material along an attachment ring y, and a welding terminating point as the position of retraction is welded under the crater treatment condition. Since a crater treated part 22b formed in the welding terminating point is shifted more to the attachment ring y side than a crater treated part 22a formed in the conventional circumferential welding method, a portion extending above a base material surface is reduced in size or lost compared with the shape of the main weld part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a welding bead by arc welding to an annular connection boundary line edge between a base material constituting a main body of a container and a mounting ring member fitted in a through hole formed in the base material. The present invention relates to an automatic circumferential welding method in which fillet welding is performed over substantially the entire circumference while forming.

  There is a pressure vessel W as a general vessel in which the components are joined by an automatic circumferential welding method using a welding robot or the like (see FIG. 1). In the pressure vessel W, the base material x constituting the main body of the container and the attachment ring material y fitted in the through hole formed in the base material x are joined by a circumferential welding method. That is, the attachment ring member y is fitted into the through hole of the base material x, and the welding bead is formed by arc welding on the annular connection boundary line edge z between the base material x and the attachment ring member y. Fillet welding is performed over the entire circumference, and the base material x and the mounting ring material y are integrally joined.

  By the way, in the circumferential welding method by arc welding, a crack is likely to occur due to poor welding at a portion (welding start end portion) from the welding start point of the welding bead to the position immediately after that and a welding end point. That is, at the welding start end, since the base material and the mounting ring are still at a low temperature during welding, the amount of heat input is rapidly dissipated, and the weld does not easily melt. Insufficient And, when there is this welding failure, the welding start end portion is not only insufficiently welded due to insufficient penetration of the welded portion, but also has a main welding formed over the entire circumference. Since the penetration is partially insufficient as compared with the penetration of the part, it also causes stress concentration when the container is subjected to a pressure load. When this stress concentration occurs in the welded portion where the penetration is insufficient, cracks are likely to occur at the welding start end. On the other hand, at the welding end point, the welding metal is solidified without reaching the welding end point completely by cutting the arc suddenly when finishing the welding, etc., resulting in insufficient weld bead thickness and poor welding. A weld bead indentation called a crater remains. When the crater is present at the welding end point, not only is the weld bead thickness insufficient, but sufficient strength cannot be obtained, and cracking is likely to occur because it is easily cooled.

  Therefore, in the conventional automatic circumferential welding method, the following circumferential welding method is performed in order to eliminate the above-mentioned welding failure. That is, first, the welding start end portion is welded under a welding initial condition that provides a predetermined heat input, and then the main welding portion that extends over the entire circumference is welded under a main welding condition that provides a higher heat input than the welding initial condition. Subsequently, in order to eliminate the lack of penetration at the weld start end, a weld bead is superimposed on the weld bead surface of the weld start end, and the weld bead is superimposed on the weld bead surface of the weld start end. This portion (welding end portion) is welded under the welding end condition that provides a lower heat input than the main welding conditions. Finally, at the welding end point, in order to prevent the weld metal from rapidly cooling and to secure the weld bead wall thickness, welding (crater treatment process) is performed under the crater treatment conditions that result in a low heat input at a fixed position. finish. Here, the amount of heat input refers to the amount of electrical energy applied per unit welding distance during welding.

  Moreover, according to the circumferential welding method described in Patent Document 1, the welding bead at the welding start end portion is a welding step of the welding end portion that overlaps the weld bead on the welding bead surface of the welding start end portion in the conventional circumferential welding method. After forming the weld bead on the surface, the welding torch is turned back, and the weld bead is further piled on the molten pool (the melted portion of the weld bead) generated in the formed weld bead, and then the crater. It has been proposed to perform processing steps. As a result, it is shown that the molten pool that easily causes craters is built up, and the crater treatment process becomes more efficient.

JP-A-10-99965

  The conventional automatic circumferential welding method and the circumferential welding method described in Patent Document 1 (hereinafter referred to as the conventional circumferential welding method) are insufficient penetration and welding at the welding start end when performing circumferential welding by arc welding. It solves the welding failure of the occurrence of a crater at the end point, and suppresses the occurrence of cracks due to the welding failure.

  By the way, in a pressure vessel, in order to inspect the quality and the presence / absence of welding defects, various accuracy tests are performed, and all tests need to pass. One of the items of the accuracy test is a pressure cycle test, which consists of repeatedly performing a pressurization test at a predetermined pressure on the pressure vessel. In this test, the pressure vessel is inspected for its durability life and fails if the number of repeated pressurization tests does not satisfy the acceptance standard value or more.

  Here, the inventors performed a pressure cycle test, a pressure load experiment, etc. on the container in which the base material and the mounting ring member were joined by the conventional circumferential welding method, and the durable life of the container Surveyed and researched. As a result, the container in which the base material and the mounting ring material are joined by the conventional circumferential welding method is used when circumferential welding is performed by arc welding in which the welding is insufficient at the start end and the crater is generated at the end of welding. In spite of the weld defect of the above, the pressure cycle test is still concerned that cracks may occur in the vicinity of the crater treatment part after the number of repetitions less than the acceptance standard value. there were.

  In addition, the present inventors have made the base material constituting the container body an aluminum alloy, and by fitting the mounting ring material through the through-hole formed in the base material, Circumferential welding was sequentially performed by the conventional circumferential welding method on the annular connection boundary line edges of the base material and the mounting ring material respectively generated on the inner surface side, and the base material and the mounting ring material were joined. And the pressure cycle test, the pressure load experiment, etc. were performed with respect to this joined container, and the durable life of this container was investigated and researched. As a result, even in the case of this container, despite the lack of welding at the start of welding and the occurrence of craters at the end of welding, the welding failure when performing circumferential welding by arc welding, still, In the pressure test of the pressure cycle test, there was a concern that cracks may occur in the welded portion other than the periphery of the crater processing portion in addition to the periphery of the crater processing portion due to the number of repetitions less than the acceptance standard value. .

  Therefore, the present invention solves the above-mentioned problems and makes it possible to manufacture a container having a long durability life without cracks as compared with a container manufactured by a conventional circumferential welding method. A circumferential welding method is proposed.

  The present invention provides a welding bead by arc welding to an annular connection boundary line edge between a base material constituting a main body of a container and a mounting ring member fitted in a through hole formed in the base material. Fillet welding is performed over substantially the entire circumference while forming, and the welding start end is welded under welding initial conditions that achieve a predetermined heat input, and the main welding part over substantially the entire circumference is higher than the welding initial conditions. Automatic circumferential welding where welding is performed under the main welding conditions for heat input, the weld end overlapping the welding start end is welded under the welding end for lower heat input than the main welding conditions, and the welding end is welded under crater processing conditions In the method, before the end of the welding process of the welding end portion, the welding torch is retracted in a direction away from the base material along the attachment ring member, and the crater processing process is performed at the retracted position. This is a circumferential welding method.

  Here, the crater treatment step is as follows. In arc welding, when the welding is finished, the arc is suddenly cut, etc., so that the weld metal does not reach the welding end point completely and solidifies, resulting in insufficient weld bead wall thickness. A weld bead indentation called a crater remains. When this crater is present at the welding end point, the welding end point is not only sufficient for obtaining a sufficient strength because the weld bead is insufficient in wall thickness, but is also susceptible to cracking because it is easily cooled. . Therefore, at the welding end point, welding is performed under a crater processing condition that results in a low heat input at a fixed position, and the arc is cut after ensuring a sufficient thickness of the weld bead so that no crater is generated at the welding end point. To. This welding process at the welding end point is called a crater treatment process.

  In the conventional circumferential welding method, in order to eliminate welding defects such as insufficient penetration at the welding start end and generation of craters at the welding end point, the welding end portion is overlapped on the weld bead surface of the welding start end portion. The crater processing step of ensuring the thickness of the weld bead at the welding end point immediately after the welding step and the welding step at the welding end portion is performed. However, since the welding process and the crater treatment process of the welding end part are performed on the weld bead surface of the welding start end part, the shape of the welding end part and the crater processing part formed on the weld bead surface of the welding start end part However, compared with the shape of the main weld formed over substantially the entire circumference, it tends to spread on the base material surface, and in particular, since the crater treatment process is performed at a fixed position, The shape of the formed crater processing part is a part of which extends greatly on the substrate surface.

  Since the part extending on the base material surface of this crater processing part is partially extended compared to the shape of the main welding part formed over substantially the entire circumference, When the container receives a pressure load, it causes stress concentration. Therefore, in a container in which the base material and the mounting ring material are joined by the conventional circumferential welding method, when the container is subjected to a pressure load, it extends on the base material surface compared to the shape of the main welded portion. Due to the concentration of stress in the existing part, cracks are likely to occur around the crater processing part. In addition, the portion extending on the base material surface compared to the shape of the main welded part often cannot be fused with the base material and is simply in a state of overlapping with the base material (overlap). Therefore, when the stress concentration occurs in the extending portion, the overlapping overlapped portion is peeled off and cracked, and a crack is likely to occur around the crater processing portion.

  Therefore, by using the automatic circumferential welding method of the present invention, the crater processing portion formed by the crater processing step at the welding end point is closer to the mounting ring material side than the crater processing portion formed by the conventional circumferential welding method. In other words, in the crater processing portion, the portion extending on the base material surface is reduced or reduced in comparison with the shape of the main welded portion. It will disappear. As a result, when the container is subjected to a pressure load, the stress concentration generated in the portion extending on the base material surface is reduced or eliminated compared to the shape of the main welded portion. Generation | occurrence | production can be suppressed and the durable life of a container can be improved. In addition, since the portion extending on the base material surface is reduced or disappeared compared to the shape of the main welded portion, the occurrence of the overlap portion that is likely to occur in the extending portion is suppressed, In addition, since the stress concentration generated in the extended portion is also relaxed or eliminated, it is possible to suppress the occurrence of cracks due to the overlap portion around the crater treatment portion, and to improve the durability life of the container. Can do.

  In the above-described automatic circumferential welding method of the present invention, during the welding process of the welding end portion, the welding torch is gradually brought closer to the retreat position where the crater treatment process is performed, and the welding torch before the end of the welding process of the welding end portion is performed. By welding so as to shorten the retracted distance, the welding end portion and the crater processing portion are integrally formed, which is more preferable.

  Here, the present inventors performed a pressure cycle test, a pressure load experiment, etc. with respect to the container by which the base material and the attachment ring material were joined by the conventional circumferential welding method. Then, they have intensively studied the relationship between the shape of the crater processing part formed by the crater processing step and the cracks that can occur around the crater processing part. As a result, particularly in the case where the portion of the crater treatment portion extending on the base material surface partially extends on the base material surface by about 3 mm or more compared to the shape of the main welding portion, the crater treatment is particularly effective. It came to the conclusion that cracks are likely to occur around the part. Therefore, in the automatic circumferential welding method, an automatic circumferential welding method is proposed in which the welding torch is retracted approximately 3 mm to approximately 5 mm in a direction away from the base material along the mounting ring.

  By using this method, the crater processing portion formed by the crater processing step at the welding end point shifts by about 3 mm to about 5 mm on the mounting ring side as compared with the crater processing portion formed by the conventional circumferential welding method. Will be formed. And in this crater process part, compared with the shape of this welding part, the part extended on the base-material surface will lose | disappear, and when a container receives a pressure load, it arises in this extended part. The stress concentration disappears, and the generation of cracks around the crater processing portion can be completely suppressed. In addition, as a result of the disappearance of the portion extending on the base material surface as compared with the shape of the main welded portion, the overlap portion generated in the extending portion also disappears. The occurrence of cracks due to the overlap portion can also be completely suppressed. Therefore, by this automatic circumferential welding method, it is possible to manufacture a container having a long durability life in which no crack is generated around the crater processing portion. Here, the upper limit is set to about 5 mm. In the crater processing portion formed by the conventional circumferential welding method, the portion extending on the base material surface is basically compared with the shape of the main welding portion. This is because it does not extend over the surface of the base material by about 5 mm or more compared to the shape of the main welded portion, and the weld termination portion and the crater treatment portion are integrally formed.

  On the other hand, the material of the base material constituting the main body of the container is an aluminum alloy, and is generated on the outer surface side and the inner surface side of the base material by fitting the mounting ring material through the through-hole formed in the base material. When performing fillet welding over substantially the entire circumference while sequentially forming a weld bead by arc welding with respect to the annular connection boundary edge of the base material and the mounting ring material, An automatic circumferential welding method is proposed in which the leg length of the weld bead on the substrate surface side of the main weld is approximately 0.8 to 1.5 times the plate thickness of the substrate. .

  By fitting the attachment ring material through the through hole formed in the substrate, the annular connection boundary line edge between the base material and the attachment ring material respectively generated on the outer surface side and the inner surface side of the substrate is sequentially applied. In the case where fillet welding is performed over substantially the entire circumference while forming a weld bead by arc welding, the welds formed on the outer surface side and the inner surface side of the base material have different shapes and penetrations. When the container receives a pressure load, the stress load on each welded portion is different, which causes a problem in strength. Therefore, it is desirable that the welds formed on the outer surface side and the inner surface side of the base material have the same shape and penetration, and sufficient penetration is required in terms of strength.

  Here, in order to ensure sufficient penetration of the welded portion, if the amount of heat input to the base material and the mounting ring material is increased during welding, the welded portions are formed facing each other with the base material sandwiched therebetween. In the circumferential welding performed sequentially, the amount of heat input to the base material in the circumferential welding performed later is applied to the welded portion formed by the circumferential welding performed earlier. Thereby, in the welded part formed by the circumferential welding performed previously, the low melting-point compound produced | generated in this welded part may melt | dissolve, and there exists a possibility of producing a micro crack in this welded part. In addition, as the amount of heat input to the base material during welding increases, the welds formed on the outer surface side and inner surface side of the base material each have a longer weld bead width (leg length) on the base material surface side. It becomes. As a result, the toe ends of the weld beads of the welded portions formed on the outer surface side and the inner surface side of the base material cannot be fused with the base material, and are easily overlapped with the base material (overlap). In addition, when the leg length of the weld bead on the substrate surface side becomes long, when the container is subjected to a pressure load, the stress concentration generated in the welded portion formed on the outer surface side and the inner surface side of the substrate is strong. Tend to be. That is, when the leg length of the weld bead on the base material surface side of the weld portion formed on each of the outer surface side and the inner surface side of the base material becomes long, sufficient penetration of the weld portion is ensured, but welding Since the amount of heat input to the base material at the time becomes high, micro cracks may occur in the welded portion formed by the circumferential welding performed earlier, and the toe end of the weld bead of the welded portion may become an overlap portion. is there. Furthermore, since the stress concentration generated in the welded portion formed on the outer surface side and the inner surface side of the base material also becomes strong, the welded portion peels off due to welding failure called microcracking or overlap, and this cracking starts. Due to this, fatigue failure occurs and a crack occurs in the container.

  Here, the present inventors insert an attachment ring material through a through-hole formed in the substrate, thereby forming an annular structure of the base material and the attachment ring material respectively generated on the outer surface side and the inner surface side of the substrate. A pressure cycle test, a pressure load experiment, and the like were sequentially performed on the connection boundary line edge with respect to the container in which the base material and the mounting ring member were joined by the conventional circumferential welding method. Then, the inventors studied diligently about the relationship between the shape of the welded portion and a crack that may occur in the welded portion other than the periphery of the crater processing portion. As a result, by restricting the length of the leg length of the weld bead on the substrate surface side of the main weld portion formed over substantially the entire circumference with respect to the plate thickness of the substrate, welding other than around the crater processing portion is performed. It was clarified that the occurrence of cracks in the part can be suppressed. And when the leg length of the weld bead on the base material surface side of the main weld portion formed over substantially the entire circumference is less than about 0.8 times the plate thickness of the base material, and In the case where the length is longer than about 1.5 times, it was concluded that cracks are likely to occur in the welded portion other than the periphery of the crater processing portion.

  Therefore, in the automatic circumferential welding method, the leg length of the weld bead on the substrate surface side of the main weld is limited to approximately 0.8 times to approximately 1.5 times the plate thickness of the substrate. As a result, sufficient penetration of the welds formed on the outer surface side and the inner surface side of the base material is ensured, and micro cracks generated by circumferential welding performed earlier, and the outer surface side and inner surface side of the base material In addition, the welding failure of overlapping portions at the toes of the weld bead of the welded portions formed respectively is eliminated, and stress concentration generated in the welded portion is alleviated. Thereby, not only the occurrence of cracks in the vicinity of the crater treatment part by the automatic circumferential welding method, but also cracks occurring in the weld parts other than the vicinity of the crater treatment part can be suppressed, and the durability life of the container can be further increased. Improvements can be made. Here, the lower limit is set to approximately 0.8 times when the leg length of the weld bead on the substrate surface side of the main weld is less than approximately 0.8 times the plate thickness of the substrate. This is because sufficient penetration cannot be obtained in the welded portion, which causes a problem in strength.

  In the automatic circumferential welding method of the present invention, the welding torch is retracted in the direction away from the base material along the mounting ring before the welding end portion welding process is completed, and the crater processing step is performed at the retracted position. Since the crater treatment part formed by the crater treatment process at the welding end point is formed by shifting to the attachment ring material side, compared to the crater treatment part formed by the conventional circumferential welding method, Of the crater processing portion, the portion extending on the base material surface is reduced or disappeared as compared with the shape of the main welding portion. Thereby, when the container is subjected to a pressure load, the stress concentration generated in the extending part is relaxed or eliminated, and the occurrence of an overlap part that is likely to occur in the extending part is suppressed. The occurrence of cracks around the crater processing section can be suppressed, and the durability life of the container can be improved.

  Further, in the automatic circumferential welding method, the automatic circumferential welding method in which the welding torch is retracted by about 3 mm to about 5 mm in a direction away from the base material along the attachment ring member, is formed by a crater processing step at a welding end point. Compared to the crater processing part formed by the conventional circumferential welding method, the crater processing part is formed with a shift of about 3 mm to about 5 mm on the mounting ring material side, so the shape of the main welding part of the crater processing part As compared with the above, the portion extending on the substrate surface disappears. As a result, when the container is subjected to a pressure load, the stress concentration generated in the extending portion disappears, and the overlap portion generated in the extending portion also disappears. A container having a long durability life without cracks can be produced.

  On the other hand, the material of the base material is an aluminum alloy, and the base material and the mounting ring material respectively generated on the outer surface side and the inner surface side of the base material by fitting the mounting ring material through the through hole formed in the base material. In the present invention, in the automatic circumferential welding method, the leg length of the weld bead on the substrate surface side of the main welded portion is set in the automatic circumferential welding method. The leg length of the weld bead on the substrate surface side of the main weld is limited because the length is approximately 0.8 to 1.5 times the plate thickness of the substrate. Formed in length. Thus, sufficient penetration of the welded portions formed on the outer surface side and the inner surface side of the base material is ensured, and micro cracks generated by circumferential welding performed first, and the outer surface side of the base material And the weld failure formed by the weld bead formed on the inner surface side at the toe of the weld bead are eliminated, and stress concentration generated in the weld is relieved. Therefore, it is possible to suppress not only cracking around the crater processing part by the automatic circumferential welding method, but also cracks occurring in the welded part other than the crater processing part, and further improve the durability life of the container Can be achieved.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a general pressure vessel W as a vessel in which joining between constituent members is performed by an automatic circumferential welding method using a welding robot or the like. This pressure vessel W is composed of a body portion 31 (x), mirror portions 32 (x), 32 (x), an instrument seat mounting ring 33 (y), a drain seat mounting ring 34 (y), and the like. It is comprised by joining between members. Then, the body 31 (x) or the mirror part 32 (x), 32 (x) is fitted into a base material x constituting the main body of the pressure vessel W and a through hole formed in the base material x. Joining with the attachment ring material y which comprises an instrument seat, a drain seat, etc. is performed by the following automatic arc welding apparatus.

  FIG. 2 is a schematic view of an automatic arc welding apparatus according to an embodiment of the present invention. By such an automatic arc welding apparatus, an annular connection boundary edge z between the base material x constituting the main body of the pressure vessel W and the mounting ring member y fitted into the through hole 35 formed in the base material x. Are joined by arc welding. This automatic arc welding apparatus includes a welding robot 1 that performs arc welding, a robot control apparatus 2 that performs operation control of the welding robot 1 in accordance with a control program, a jig 4 for fixing a workpiece 3, a computer 5, and a welding power source. A device 6 is provided. The computer 5 stores a welding process control program and is connected to each device such as the robot control device 2 and the welding power source device 6 to appropriately output a control signal according to the progress of the welding process to operate each device. . The computer 5 includes a display device such as a CRT and an input device such as a keyboard, and can set various welding conditions performed by the operator in the welding process. Further, the welding power source device 6 supplies current, a welding wire 9, gas, and the like to the welding torch 8 by a wire feeding device or the like (not shown).

  A welding torch 8 that supports the welding wire 9 is attached to the wrist 11 of the welding robot. A rotating device 7 is provided at a connection portion between the wrist portion 11 of the welding robot and the arm portion 12 of the welding robot, and the wrist portion 11 of the welding robot is rotated by the rotating device 7. The rotation speed of the rotation device 7 is controlled by a robot control device 2 including a control board connected to the welding robot 1. During welding, the rotating device 7 rotates the wrist portion 11 of the welding robot to cause the welding torch 8 to move around the connection boundary edge z between the base material x and the mounting ring y. Then, circumferential welding is performed over substantially the entire circumference by causing the welding wire 9 to sequentially face the connection boundary edge z.

  Next, the control mechanism of the heat input amount of the automatic arc welding apparatus will be described. The computer 5 can set four welding conditions, that is, an initial welding condition, a main welding condition, a welding termination condition, and a crater processing condition (see FIG. 3). In the welding initial condition, the main welding condition, and the welding termination condition, the current amount and voltage amount of the welding torch 8 and the rotation speed (welding speed) and rotation angle (welding distance) of the rotating device 7 can be set, respectively. On the other hand, in the crater processing condition, since welding is performed at one point, the current amount, voltage amount, and welding time of the welding torch 8 can be set. That is, the amount of heat input is adjusted by the current amount, voltage amount, welding speed, or welding time of the welding torch 8, and the welding distance in each welding process is determined by the rotation angle of the rotating device 7. When the operator sets each welding condition via the computer 5 before starting welding, a control signal is output from the computer 5 to the robot control device 2 and the welding power source device 6 after starting welding. The amount of current, the amount of voltage, and the rotation speed of the rotating device 7 are adjusted, and welding according to each welding condition is executed in order. Since the welding robot 1, the welding torch 8 and the like used in the embodiment of the present invention are general, detailed description thereof is omitted.

  Below, one Example which welded the mirror part 32 (x) of the said pressure vessel W and the drain ring mounting ring 34 (y) using this automatic arc welding apparatus is demonstrated. In this embodiment, the welding start end is welded at a welding initial condition that provides a predetermined amount of heat input, and the main welding part that extends over the entire circumference is welded at a main welding condition that provides a higher heat input than the welding initial condition. The welding end portion that overlaps the part is welded under the welding end condition where the heat input is lower than the main welding condition, and the welding end point is welded under the crater processing condition.

  In the initial welding conditions of this embodiment, a predetermined amount of heat input is realized by performing arc welding with the welding torch 8 as a predetermined current amount and voltage amount and the rotating device 7 as a predetermined rotation speed. Also, under the main welding conditions, by increasing the current amount and the voltage amount of the welding torch 8 as compared with the initial welding conditions, welding is performed by realizing a higher heat input than the initial welding conditions. On the other hand, in the welding termination condition, a lower heat input is achieved than in the main welding condition by increasing the rotation speed of the rotating device 7 than in the main welding condition. It should be noted that the values of the conventional welding conditions are preferably used for the parameters of the current amount, voltage amount, rotational speed of the rotating device 7 and welding time of the welding torch 8 under the initial welding conditions, main welding conditions, and crater processing conditions. it can.

  Next, the circumferential welding process of the present embodiment will be described in order with reference to the formation diagram of the weld bead 21 (FIG. 4). First, after welding is started, welding is started under welding initial conditions that provide a predetermined heat input, and a weld bead 21a at the welding start end is formed. When the welding process at the welding start end is completed, a signal is sent from the computer 5 to the robot control device 2 and the welding power source device 6 to increase the current amount and voltage amount of the welding torch 8, Under this main welding condition, welding is performed over substantially the entire circumference. In the welding process of the main welded portion, the mirror portion 32 (x) is also warmed, so that a stable weld bead 21b is formed in a state where a sufficient amount of penetration is ensured.

  When the welding process of the main welding part over substantially the entire circumference is completed under the main welding conditions, a control signal is sent from the computer 5 to the robot control device 2 to increase the rotation speed of the rotating device 7. And welding is performed on the welding termination conditions used as the amount of heat input lower than this welding condition, and the welding bead 21c of a welding termination part is piled up on the welding bead 21a formed in the welding start edge part. In the welding process of the welding end portion, a weld bead 21c having a smaller amount of deposited metal than the main weld portion is formed.

  Before the end of the welding process at the welding end, a control signal is sent from the computer 5 to the robot controller 2 and the welding torch 8 is moved to the retracted position. Next, welding is performed at the retracted position under the crater processing conditions. That is, a stop signal is output from the computer 5 to the robot control device 2 to stop the rotation of the rotating device 7 and a control signal to the welding power source device 6 is output to set the welding end point with the set current amount and voltage amount. Are welded for a predetermined time, and the crater processing part 22 is formed. Thereafter, the welding torch 8 is moved backward by a control signal from the computer 5 to complete the circumferential welding process.

  The crater processing part 22b formed in this way is shifted to the drain seat mounting ring 34 (y) side as shown in FIG. 5, compared to the crater processing part 22a formed by the conventional circumferential welding method. It becomes. Therefore, the part extended on the mirror part surface rather than the shape of the weld bead 21b of the main welding part formed in the conventional crater processing part 22a disappears. As a result, when the container is subjected to a pressure load, the stress concentration generated in the extending portion disappears, and the overlapping portion that easily occurs in the extending portion also disappears. Thus, the generation of cracks around the crater treatment part can be completely suppressed, and a container having a long durability life can be manufactured.

  In the next embodiment, a drain seat mounting ring member 34 (y) is fitted into a through hole 35 formed in the mirror portion 32 (x), whereby the outer surface side and the inner surface side of the mirror portion 32 (x). The fillet welding is performed over the entire circumference by arc welding sequentially on the annular connection boundary line edge z between the mirror portion 32 (x) and the drain ring mounting ring 34 (y) generated respectively. (See FIG. 6). The leg length h of the weld bead on the mirror surface side of the main weld formed by arc welding is approximately 0.8 to 1.5 times the plate thickness t of the mirror 32 (x). The present invention relates to an automatic circumferential welding method for achieving a length. Since the automatic arc welding apparatus, welding conditions, and the like are the same as those in the above embodiment, description thereof is omitted.

  The leg length h of the weld bead on the mirror surface side of the main welding portion formed by circumferential welding by arc welding is the amount of heat input to the mirror portion 32 (x) under the main welding conditions and the welding wire used in the week welding. It is substantially determined by the diameter and the nerai position of the welding wire 9 shown in FIG. Below, the comparison of the welding result of Example A and Comparative Example B is shown.

  In the example i, the leg length h of the weld bead on the mirror surface side of the main weld is approximately 0.8 to 1.5 times the plate thickness t of the mirror 32 (x). In addition, the current amount of the welding torch 8 is 240 A, the voltage amount is 24 V, the welding speed is 70 cm / min, the welding wire diameter is 1.6 mm, and the nebulization position of the welding wire 9 is the center nerai (see FIG. 7). Under this welding condition, the leg length h of the weld bead on the mirror surface side of the main weld was approximately 1.2 times the plate thickness t of the mirror 32 (x). On the other hand, Comparative Example B is a case where the current amount of the welding torch 8 is 240 A, the voltage amount is 24 V, the welding speed is 70 cm / min, the welding wire diameter is φ1.6 mm, and the nebulization position of the welding wire 9 is the outer nerai (FIG. 7). Under this welding condition, the leg length h of the weld bead on the mirror surface side of the main weld was approximately 1.9 times the plate thickness t of the mirror 32 (x).

  Next, a pressure cycle test was performed on each of the containers joined under these welding conditions. As a result, the container of Example A in which the leg length h of the weld bead on the mirror surface side of the main weld was approximately 1.2 times the plate thickness t of the mirror 32 (x) was The number of pressurization tests of 2.9 MPa, which is the acceptance standard value of the pressure cycle test, was 12,000 times or more and passed (see FIG. 8). On the other hand, the container of Comparative Example B in which the leg length h of the weld bead on the mirror surface side of the main weld is approximately 1.9 times the plate thickness t of the mirror 32 (x) is the pressure in the container. As early as less than 12,000 pressure tests of 2.9 MPa, which is the pass standard value for the cycle test (about 2600 times), a crack k occurred in the weld formed under the above welding conditions, and the pressure cycle test failed. (See FIG. 9).

  As can be seen from this result, the leg length h of the weld bead on the substrate surface side of the main weld portion formed over substantially the entire circumference with respect to the plate thickness t of the substrate x is about 0.8 times to about It turns out that generation | occurrence | production of the crack in welding parts other than the crater process part periphery can be suppressed by restrict | limiting to length 1.5 times. And the leg length h of the weld bead on the substrate surface side of the main weld portion formed over substantially the entire circumference with respect to the plate thickness t of the substrate x is less than about 0.8 times. When it becomes, and when it becomes longer than about 1.5 times, it turns out that it is easy to produce a crack in welding parts other than the crater processing part periphery.

  That is, in the automatic circumferential welding method, the leg length h of the weld bead on the base material surface side of the main welded portion is approximately 0.8 times to approximately 1.5 times the plate thickness t of the base material x. By using the automatic circumferential welding method as described above, the leg length h of the weld bead on the substrate surface side of the main weld portion is formed to a limited length. And, thereby, sufficient penetration of the welded portion formed on the outer surface side and the inner surface side of the base material x is ensured, and micro cracks generated in the welded portion formed by the circumferential welding performed first, And the welding failure of the overlap part at the toe of the weld bead of the weld part formed on the outer surface side and the inner surface side of the base material x is eliminated, and the stress concentration generated in the weld part is alleviated. Will be. Therefore, it is possible to suppress not only cracking around the crater processing part by the automatic circumferential welding method, but also cracks occurring in the welding part other than the vicinity of the crater processing part, and further improve the durability life of the container. Can be achieved.

  Unlike the above-described embodiment, when the body 31 (x) and the instrument seat mounting ring 33 (y) are circumferentially welded, etc., the body 31 (x) is cylindrical. The annular connection boundary line edge z between x) and the instrument seat mounting ring member 33 (y) is not on one plane. Therefore, in order to cause the computer 5 to control the position of the welding torch 8 in order to move the welding torch 8 provided in the welding robot 1 along the connection boundary edge z during circumferential welding with the automatic arc welding apparatus. The control program is input.

It is a block diagram showing the specific example of a pressure vessel. It is the schematic showing the automatic arc welding apparatus of a present Example. It is explanatory drawing showing the welding conditions of a present Example. It is explanatory drawing showing the weld bead of a present Example. It is explanatory drawing showing the crater process part of a present Example. It is an enlarged view showing the welding part of a present Example. It is explanatory drawing showing the nerai position of a welding wire. It is sectional drawing showing the welding part after the pressure cycle test of Example i. It is sectional drawing showing the welding part after the pressure cycle test of the comparative example b.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding robot 2 Robot control device 3 Work 4 Jig 5 Computer 6 Welding power supply device 7 Rotating device 8 Welding torch 9 Welding wire 11 Wrist part of welding robot 12 Arm part of welding robot 21 Welding bead 21a Welding bead (welding start part)
21b Weld bead (main weld)
21c Weld beads (welding end)
22 Crater processing part 22a Conventional crater processing part 22b Crater processing part 31 (x) Body 32 (x) Mirror part 33 (y) Instrument seat mounting ring 34 (y) For drain seat Mounting ring 35 Through hole x Base material y Mounting ring z Connection boundary edge h Weld bead leg length t Thickness k Crack

Claims (3)

While forming a weld bead by arc welding on the annular connection boundary line edge between the base material constituting the container body and the mounting ring member fitted in the through hole formed in the base material, the welding bead is substantially formed. Fillet welding is performed over the entire circumference, the welding start end is welded under the initial welding conditions that provide a predetermined amount of heat input, and the main welded part over the entire circumference has a higher heat input than the initial welding conditions. In the automatic circumferential welding method in which welding is performed under the main welding conditions, the welding end portion overlapping the welding start end portion is welded under the welding end condition with a lower heat input than the main welding conditions, and the welding end point is welded under the crater processing conditions.
The automatic circumferential welding method characterized in that, before the end of the welding process of the welding end portion, the welding torch is retracted in a direction away from the base material along the attachment ring member, and the crater treatment process is performed at the retracted position. .   The automatic circumferential welding method according to claim 1, wherein the welding torch is retracted approximately 3 mm to approximately 5 mm in a direction away from the base material along the attachment ring member. The material of the base material is an aluminum alloy, and the base material and the mounting ring material respectively formed on the outer surface side and the inner surface side of the base material by fitting the mounting ring material through the through hole formed in the base material. When performing fillet welding over substantially the entire circumference while sequentially forming a weld bead by arc welding with respect to the annular connection boundary edge,
3. The leg length of the weld bead on the substrate surface side of the main weld portion is approximately 0.8 times to approximately 1.5 times the plate thickness of the substrate. The automatic circumferential welding method described.