Views: 0 Author: Site Editor Publish Time: 2024-12-12 Origin: Site
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 track, so as to achieve automatic welding. Generally speaking, the all-position automatic welding device is composed of welding car, walking track, automatic control system and other parts. The purpose of developing the all-position automatic welding device is to improve the welding quality and labor productivity, and reduce the labor intensity of workers.
The welding trolley is a driving mechanism to realize the automatic welding process. It is installed on the welding track and moves in a circle along the pipe wall with the welding gun. It is one of the important links to realize the automatic welding of the pipe mouth. The welding trolley should have the characteristics of beautiful appearance, small size, light weight and easy operation. Its core part is the walking mechanism, wire feeding mechanism and welding gun swing adjustment mechanism. The traveling mechanism is composed of a motor and a gear transmission mechanism. In order to make the traveling motor execute the position and speed instructions issued by the computer control unit, the motor should be equipped with a speed measurement feedback mechanism to ensure that the motor is accurately aligned in each position of the pipe ring joint, and has a good speed tracking function. 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 enough driving torque. The welding torch swing adjustment mechanism should have the functions of the welding torch relative to the weld, the left and right end of the left and right, the up and down left and right attitude can be controlled, and the Angle of the welding torch can be adjusted. The above parts of the welding car are controlled automatically by the computer. After the program starts, the parts of the welding car coordinate their actions according to the logical sequence of the program. The welding process can also be manually intervened if needed, and the procedure can automatically adjust the welding parameters and execute according to the amount of intervention.
The track is a special mechanism stuck on the pipe for the walking and positioning of the welding car, and its structure directly affects the smoothness and position of the welding car, and also affects the welding quality. The track should meet the following conditions: easy to assemble and disassemble, easy to locate;
Reasonable structure, light weight; It has certain strength and hardness, wear resistance and corrosion resistance. There are two types of track: flexible track and rigid track. The so-called rigid track means that the body stiffness of the track is large and not easy to deform, while the flexible track is relatively rigid track. The two types of tracks each have their own characteristics. The rigid track positioning is accurate, the deformation after loading is small, which can ensure the smooth walking of the welding car, and the radial adjustment of the welding torch is small during welding, but the weight is large and the installation and disassembly are not convenient. The flexible track is easy to assemble and disassemble, lighter in weight, and less precise than the rigid track.
The stability of wire feeding directly affects the welding quality. Wire feeding methods can be simply divided into two ways: wire drawing and wire pushing. When drawing, the welding gun is close to the installation position of the wire feeder, and the resistance of the welding wire leaving the wire feeder is small during the welding process, so the wire feeding process can be ensured to be smooth, but the wire feeder and the wire tray must be installed on the welding car, which increases the weight of the welding car, which increases the difficulty of the tool disassembly, and the weight increase is easy to cause the welding car to walk unsmoothly. The use of small plates with a diameter of 0.8mm or 1.0m wire (with a weight of about 5kg) reduces the weight and load of the welding car, and makes the welding process easy to control, but has a certain impact on the welding efficiency. When the wire pushing method is used, the wire feeding mechanism is installed outside the welding car, reducing the volume and weight of the welding car, and you can use a high-power wire feeding machine and a large plate welding wire with a diameter of 1.2mm (the weight is about 20kg), so as to improve the welding efficiency. However, because the wire feeder is far away from the welding gun when pushing the wire, there must be a wire feeder hose connected between the two. When the welding wire is continuously pushed to the nozzle of the welding gun, the friction resistance of the welding wire is larger. Moreover, the bending degree of the wire feeder hose during the welding process has a certain impact on the stability of the wire feed, which causes poor wire feeding in serious cases. Therefore, the above factors must be fully considered when using the push-wire.
At present, in addition to manual welding, more pipeline welding is using submerged arc automatic welding process and gas shielded welding process.
Submerged arc automatic welding has the characteristics of good weld forming, high welding efficiency and low welding cost. For pipeline construction, submerged arc automatic welding can be used for double pipe joint welding, referred to as "two to one", that is, the welding gun is fixed in a certain position and the pipe rotates. Obviously, it is not possible to turn the pipe during long-distance pipe welding, so "two-to-one" can only be used for pipe prefabrication. If the submerged arc welding process is adopted for all-position automatic welding of pipelines, then the welding device must be equipped with a flux delivery, support and recovery mechanism, which makes the structure of the welding device more complicated, inconvenient for operation and assembly, and increases the load of the traveling car, affecting the smoothness of the car. Submerged arc welding generally adopts the welding method of thick wire and high current, which may cause welding defects such as droplet droop and flow due to high deposition rate for all-position automatic welding, affecting the forming and quality of the weld. Therefore, it is difficult to apply submerged arc welding to all-position automatic welding of pipelines.
The welding process with flux-cored wire and gas protection is adopted. If the welding process is formed multiple times, the cleaning time of each weld surface will be time-consuming. If it is forced to form, it is necessary to add a forming copper slider that moves with the welding gun and passes the circulating cooling water, which can greatly improve the welding efficiency, so that not only the structure of the welding device is complicated, but also the weight is increased. Because the price of the flux-cored wire is higher, and the gas source of the protective gas must be solved, the welding cost is higher. Although the single use of self-protecting welding wire saves the protective gas, it is difficult to clean the slag.
The welding process with solid core wire and gas protection, if the multi-pass molding, the welding process can be simply divided into three stages, filling and covering, without cleaning the weld surface and directly carrying out the next process, but the welding speed is slower than the forced molding. The protective gas is generally pure dioxide gas, carbon dioxide and argon or a mixture of carbon dioxide and oxygen. The mixture of carbon dioxide and argon can make the arc combustion stable and splash small during welding, but the argon gas source is difficult to find and the price is high during field construction. From the economic perspective, it is best to use pure carbon dioxide as a protective gas when welding oil pipelines. The use of carbon dioxide and argon as protective gases is ideal for construction in areas where conditions exist.
In the welding process, the walking speed of the welding car, the wire feed speed and the left and right vibration frequency of the welding gun are three main parameters, and the upper and lower adjustment of the welding gun can be not taken into account. The circumference of the pipe is divided into two semicircles with a vertical line, and then the two semicircles are divided equally in the clockwise and counterclockwise directions to determine the welding joints. The ideal welding parameters can be obtained at each joint of the weld through a large number of tests. However, the actual welding and test data will not be exactly the same, in the welding process can be adjusted according to the actual situation, such as wire feed speed, vibration frequency and other parameters. However, the adjustment of these parameters is interrelated, the wire feed speed is adjusted properly, the vibration frequency and the welding car speed are not necessarily suitable, and several parameters can be adjusted and matched only through a certain time of exploration. The situation is different with another control method. Taking the wire feed speed, the speed of the welding car and the vibration frequency of the welding gun as three dependent variables, the relationship between the wire feed speed, the traveling speed of the welding car and the vibration frequency of the welding gun was obtained in a spatial coordinate system with time as the independent variable and welding current and voltage as the boundary conditions, namely the space coordinate equation. In actual welding, each adjustment is to adjust the above three parameters at the same time, so as to ensure the accuracy of the adjustment process.
Facing the 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, the research of pipeline automatic welding device for all positions has very important practical significance to improve the pipeline construction level in our country.
