The all-position automatic welding of the pipeline means that when the pipeline is relatively fixed, the welding trolley drives the welding torch to move around the pipe wall along the rail, thereby realizing automatic welding. In general, the all-position automatic welding device consists of a welded trolley, a walking track, an automatic control system, and the like. The purpose of developing a full-position automatic welding device is to improve the welding quality and labor productivity and reduce the labor intensity of workers.
Welding trolley
The welding trolley is a driving mechanism for realizing the automatic welding process. It is installed on the welding track and carries a circular motion along the pipe wall with the welding torch, which is one of the important links for automatic welding of the nozzle. The welding trolley should have the characteristics of beautiful appearance, small size, light weight and convenient operation. Its core part is the running mechanism, the wire feeding mechanism and the welding gun swing adjustment mechanism. The traveling mechanism is composed of a motor and a gear transmission mechanism. In order for the traveling motor to execute the position and speed command issued by the computer control unit, the motor should be provided with a speed feedback mechanism to ensure that the motor is accurately aligned at each position of the pipe loop, and has a comparative Good speed tracking. The wire feeding mechanism must ensure that the wire feeding speed is accurate and stable, has a small moment of inertia, has good dynamic performance, and should have sufficient driving torque. The welding gun swing adjustment mechanism should have the function of the welding gun swinging to the left and right sides of the weld, the left and right ends staying, the upper and lower left and right postures can be controlled, and the angle of the welding gun can be adjusted. Each of the above parts of the welding trolley is programmed and automatically controlled by a computer. After the program is started, the various parts of the welding carriage are coordinated according to the logical sequence of the program. The welding process can also be manually intervened when needed, and the program can automatically adjust the welding parameters and execute according to the amount of intervention.
Welding track
The track is a special mechanism that is installed on the pipe for the walking and positioning of the welding trolley. Its structure directly affects the smoothness and position of the welding trolley, which affects the welding quality. The track should meet the following conditions: easy to assemble and disassemble, easy to position; reasonable structure, light weight; certain strength and hardness, wear resistance, corrosion resistance. The track is divided into two types: flexible track and rigid track. The so-called rigid orbit means that the body of the track has a large rigidity and is not easily deformed, and the flexible track is a relatively rigid track. Both types of tracks each have their own characteristics. The rigid track is positioned accurately and the deformation after loading is small, which ensures that the welding trolley runs smoothly. The radial adjustment of the welding torch is small when welding, but the weight is large and the assembly and disassembly is not convenient. The flexible track is easy to assemble and disassemble, and the weight is light, and the precision is not high.
Wire feeding method
The smoothness of the wire directly affects the quality of the weld. The wire feeding method can be simply divided into two methods: drawing and pushing. When the wire is drawn, the welding gun is close to the wire feeding machine. During the welding process, the wire receives less resistance after leaving the wire feeder, so the wire feeding process can be ensured smoothly, but the wire feeder and the wire spool must be installed in the welding car. In the above, the weight of the welding trolley is increased, which increases the difficulty of manual assembly and disassembly, and the weight increase is also likely to cause the welding trolley to walk unevenly. The use of a small wire welding wire (weight of about 5 kg) with a diameter of 0.8 mm or 1.0 mm reduces the weight and load of the welding trolley, and makes the welding process easy to control, but has a certain influence on the welding efficiency. When the push wire method is adopted, the wire feeding mechanism is installed outside the welding trolley, and the volume and weight of the welding trolley are reduced, and a high-power wire feeder and a large-disc wire having a diameter of 1.2 mm (weight of about 20 kg) can be used. Thereby improving the welding efficiency. However, since the wire feeder is far away from the welding torch when the wire is pushed, a wire feeding hose is required between the two, and when the welding wire is continuously pushed to the welding gun nozzle, the welding wire is subjected to a large frictional resistance, and during the welding process, The bending degree of the wire feeding hose has a certain influence on the smoothness of the wire feeding. In severe cases, the wire feeding is not smooth, so the above factors must be fully considered when using the wire.
Welding process selection
At present, in addition to manual welding, most of the pipeline welding is the submerged arc automatic welding process and the gas shielded welding process.
Submerged arc automatic welding has the characteristics of good weld formation, high welding efficiency and low welding cost. For pipeline construction, submerged arc automatic welding can be used for double pipe joint welding, which is referred to as “two in oneâ€, that is, the welding gun is fixed at a certain Position, the tube rotates. Obviously, it is impossible to rotate the pipe during long-distance pipe welding, so "two-in-one" can only be used for prefabrication of the pipe. If the full-position automatic welding of the pipeline adopts the submerged arc welding process, the welding device must be equipped with the placing, supporting and recycling mechanism of the flux, which makes the structure of the welding device more complicated, which brings inconvenience to the operation and assembly and disassembly, and increases The load of the walking trolley affects the stability of the trolley walking. Submerged arc welding generally adopts coarse welding wire and high current welding method. For all-position automatic welding, welding defects such as drooping and flow may occur due to high deposition rate, which affects the forming and quality of the weld, so the submerged arc will be Welding is difficult to achieve in all-position automatic welding of pipes.
The welding process using flux-cored wire and gas protection, if it is formed in multiple passes, it takes time and labor to clean the surface of the weld; if it is forced to form, it must be equipped with a formed copper slider that moves with the welding torch and is connected. By circulating cooling water, the welding efficiency can be greatly improved, so that not only the structure of the welding device is complicated, but also the weight is increased. Because of the high price of the flux-cored wire and the solution of the gas source for shielding gas, the welding cost is high. The use of a self-shielded welding wire alone, while saving the shielding gas, has the problem of difficulty in cleaning the slag. The welding process using solid wire and gas protection, if multi-pass molding, the welding process can be easily divided into three stages of bottoming, filling and covering, without directly cleaning the surface of the weld, but proceeding directly to the next process, but welding The speed is slower than forcing. The shielding gas is generally pure carbon dioxide gas, carbon dioxide and argon or a mixed gas of carbon dioxide and oxygen. The mixed gas of carbon dioxide and argon can make the arc combustion during welding stable and the splash is small. However, in the field construction, the argon gas source is difficult to find and the price is high. From the economic point of view, when welding the oil pipeline, it is best to try to Pure carbon dioxide is used as a shielding gas. It is ideal to use carbon dioxide and argon as protective gases in areas where conditions permit.
control method
During the welding process, the walking speed of the welding trolley, the wire feeding speed and the left and right vibration frequency of the welding torch are three main parameters, and the upper and lower adjustment of the welding torch can be ignored. Use a vertical line to divide the circumference of the tube into two semicircles, and then divide the two semicircles in a clockwise and counterclockwise direction to define the welded joint. The ideal welding parameters can be obtained at each node of the weld by a large number of tests. However, the actual welding and testing data will not be exactly the same. During the welding process, the welding parameters, such as wire feeding speed and vibration frequency, can be adjusted according to actual conditions. However, the adjustment of these parameters is related to each other. The wire feed speed is adjusted properly. The vibration frequency and the welding speed are not necessarily suitable. Only a certain time can be used to adjust and match several parameters. If another control method is used, the situation is not the same. The wire feeding speed, the welding speed of the welding carriage and the vibration frequency of the welding gun are taken as three dependent variables in a space coordinate system, with time as the independent variable, welding current and voltage as the boundary conditions, and finally the wire feeding speed and welding are obtained. The relationship between the walking speed of the trolley and the vibration frequency of the welding torch, that is, the space coordinate equation. In the actual welding, each adjustment is adjusted simultaneously with the above three parameters to ensure the accuracy of the adjustment process.
In the face of increasingly fierce international market competition, in order to occupy a place in the pipeline welding market, it is necessary to improve the construction equipment and technical level. Therefore, it is of great practical significance to study the full-position automatic welding device of pipelines to improve the pipeline construction level in China.
Welding trolley
The welding trolley is a driving mechanism for realizing the automatic welding process. It is installed on the welding track and carries a circular motion along the pipe wall with the welding torch, which is one of the important links for automatic welding of the nozzle. The welding trolley should have the characteristics of beautiful appearance, small size, light weight and convenient operation. Its core part is the running mechanism, the wire feeding mechanism and the welding gun swing adjustment mechanism. The traveling mechanism is composed of a motor and a gear transmission mechanism. In order for the traveling motor to execute the position and speed command issued by the computer control unit, the motor should be provided with a speed feedback mechanism to ensure that the motor is accurately aligned at each position of the pipe loop, and has a comparative Good speed tracking. The wire feeding mechanism must ensure that the wire feeding speed is accurate and stable, has a small moment of inertia, has good dynamic performance, and should have sufficient driving torque. The welding gun swing adjustment mechanism should have the function of the welding gun swinging to the left and right sides of the weld, the left and right ends staying, the upper and lower left and right postures can be controlled, and the angle of the welding gun can be adjusted. Each of the above parts of the welding trolley is programmed and automatically controlled by a computer. After the program is started, the various parts of the welding carriage are coordinated according to the logical sequence of the program. The welding process can also be manually intervened when needed, and the program can automatically adjust the welding parameters and execute according to the amount of intervention.
Welding track
The track is a special mechanism that is installed on the pipe for the walking and positioning of the welding trolley. Its structure directly affects the smoothness and position of the welding trolley, which affects the welding quality. The track should meet the following conditions: easy to assemble and disassemble, easy to position; reasonable structure, light weight; certain strength and hardness, wear resistance, corrosion resistance. The track is divided into two types: flexible track and rigid track. The so-called rigid orbit means that the body of the track has a large rigidity and is not easily deformed, and the flexible track is a relatively rigid track. Both types of tracks each have their own characteristics. The rigid track is positioned accurately and the deformation after loading is small, which ensures that the welding trolley runs smoothly. The radial adjustment of the welding torch is small when welding, but the weight is large and the assembly and disassembly is not convenient. The flexible track is easy to assemble and disassemble, and the weight is light, and the precision is not high.
Wire feeding method
The smoothness of the wire directly affects the quality of the weld. The wire feeding method can be simply divided into two methods: drawing and pushing. When the wire is drawn, the welding gun is close to the wire feeding machine. During the welding process, the wire receives less resistance after leaving the wire feeder, so the wire feeding process can be ensured smoothly, but the wire feeder and the wire spool must be installed in the welding car. In the above, the weight of the welding trolley is increased, which increases the difficulty of manual assembly and disassembly, and the weight increase is also likely to cause the welding trolley to walk unevenly. The use of a small wire welding wire (weight of about 5 kg) with a diameter of 0.8 mm or 1.0 mm reduces the weight and load of the welding trolley, and makes the welding process easy to control, but has a certain influence on the welding efficiency. When the push wire method is adopted, the wire feeding mechanism is installed outside the welding trolley, and the volume and weight of the welding trolley are reduced, and a high-power wire feeder and a large-disc wire having a diameter of 1.2 mm (weight of about 20 kg) can be used. Thereby improving the welding efficiency. However, since the wire feeder is far away from the welding torch when the wire is pushed, a wire feeding hose is required between the two, and when the welding wire is continuously pushed to the welding gun nozzle, the welding wire is subjected to a large frictional resistance, and during the welding process, The bending degree of the wire feeding hose has a certain influence on the smoothness of the wire feeding. In severe cases, the wire feeding is not smooth, so the above factors must be fully considered when using the wire.
Welding process selection
At present, in addition to manual welding, most of the pipeline welding is the submerged arc automatic welding process and the gas shielded welding process.
Submerged arc automatic welding has the characteristics of good weld formation, high welding efficiency and low welding cost. For pipeline construction, submerged arc automatic welding can be used for double pipe joint welding, which is referred to as “two in oneâ€, that is, the welding gun is fixed at a certain Position, the tube rotates. Obviously, it is impossible to rotate the pipe during long-distance pipe welding, so "two-in-one" can only be used for prefabrication of the pipe. If the full-position automatic welding of the pipeline adopts the submerged arc welding process, the welding device must be equipped with the placing, supporting and recycling mechanism of the flux, which makes the structure of the welding device more complicated, which brings inconvenience to the operation and assembly and disassembly, and increases The load of the walking trolley affects the stability of the trolley walking. Submerged arc welding generally adopts coarse welding wire and high current welding method. For all-position automatic welding, welding defects such as drooping and flow may occur due to high deposition rate, which affects the forming and quality of the weld, so the submerged arc will be Welding is difficult to achieve in all-position automatic welding of pipes.
The welding process using flux-cored wire and gas protection, if it is formed in multiple passes, it takes time and labor to clean the surface of the weld; if it is forced to form, it must be equipped with a formed copper slider that moves with the welding torch and is connected. By circulating cooling water, the welding efficiency can be greatly improved, so that not only the structure of the welding device is complicated, but also the weight is increased. Because of the high price of the flux-cored wire and the solution of the gas source for shielding gas, the welding cost is high. The use of a self-shielded welding wire alone, while saving the shielding gas, has the problem of difficulty in cleaning the slag. The welding process using solid wire and gas protection, if multi-pass molding, the welding process can be easily divided into three stages of bottoming, filling and covering, without directly cleaning the surface of the weld, but proceeding directly to the next process, but welding The speed is slower than forcing. The shielding gas is generally pure carbon dioxide gas, carbon dioxide and argon or a mixed gas of carbon dioxide and oxygen. The mixed gas of carbon dioxide and argon can make the arc combustion during welding stable and the splash is small. However, in the field construction, the argon gas source is difficult to find and the price is high. From the economic point of view, when welding the oil pipeline, it is best to try to Pure carbon dioxide is used as a shielding gas. It is ideal to use carbon dioxide and argon as protective gases in areas where conditions permit.
control method
During the welding process, the walking speed of the welding trolley, the wire feeding speed and the left and right vibration frequency of the welding torch are three main parameters, and the upper and lower adjustment of the welding torch can be ignored. Use a vertical line to divide the circumference of the tube into two semicircles, and then divide the two semicircles in a clockwise and counterclockwise direction to define the welded joint. The ideal welding parameters can be obtained at each node of the weld by a large number of tests. However, the actual welding and testing data will not be exactly the same. During the welding process, the welding parameters, such as wire feeding speed and vibration frequency, can be adjusted according to actual conditions. However, the adjustment of these parameters is related to each other. The wire feed speed is adjusted properly. The vibration frequency and the welding speed are not necessarily suitable. Only a certain time can be used to adjust and match several parameters. If another control method is used, the situation is not the same. The wire feeding speed, the welding speed of the welding carriage and the vibration frequency of the welding gun are taken as three dependent variables in a space coordinate system, with time as the independent variable, welding current and voltage as the boundary conditions, and finally the wire feeding speed and welding are obtained. The relationship between the walking speed of the trolley and the vibration frequency of the welding torch, that is, the space coordinate equation. In the actual welding, each adjustment is adjusted simultaneously with the above three parameters to ensure the accuracy of the adjustment process.
In the face of increasingly fierce international market competition, in order to occupy a place in the pipeline welding market, it is necessary to improve the construction equipment and technical level. Therefore, it is of great practical significance to study the full-position automatic welding device of pipelines to improve the pipeline construction level in China.
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