Welding production assembly process

【Summary Description】 The assembly process of welded structure production is the process of fixing the parts and blanks that make up the structure in the correct mutual position to form components, parts or structures. The finished product (structure, component, assembly) can be produced by welding. The poor assembly quality makes it impossible to obtain high-quality products, which first affects the quality of welding. The more highly mechanized and automated the welding process, the higher the requirements for assembly quality. The assembly process is still a heavy process, accounting for about 25% to 35% of the total processing workload of the structure. The fixed parts of the assembly commonly used positioning welding, assembly welding fixture to achieve. For fixing parts by tack welding, the tack weld is required to have certain strength and rigidity. For example, when the fixed parts are taken out of the assembly fixture or assembly position and transported to the welding station, welding and excessive deformation shall not be caused. The tack weld shall also be able to reduce welding deformation. The location and size of the tack weld shall be convenient for welding and shall not affect the quality and working capacity of the welded joint and structure. The weld section size of tack welding should not be too large, and it should be arranged at the position of basic weld as far as possible, so that it can be completely remelted during welding. Where tack welds must be placed without welds, they shall be carefully removed after structural welding has been completed. Some in the assembly welding fixture to complete the assembly welding sequence, you do not need to tack welding. (1) Assembly process method 1) According to the positioning method, it is divided into marking assembly method and tire fixture assembly method. For a single piece of small batch, simple structure of the product can be used to assemble, called the line assembly method. According to the design drawing in the parts of the mutual position line, and then use simple spiral, wedge and cam clamp to fix the parts, meet the requirements of the drawing to be fixed, such as crane beam assembly. Crane metal structure assembly, analysis frame assembly, etc. Another assembly method is suitable for the assembly of tire fixtures in batch and mass production, such as using a template or positioning device to find the right position, or assembling positioning welding on a special assembly welding fixture, or directly completing the welding. This requires less assembly workers than scribing assembly requires less skill level of workers, and has higher efficiency, and the labor intensity of workers is reduced. Therefore, even if a single piece is produced in a small batch, it can be assembled by a universal assembly jig. 2) According to the assembly and welding sequence, it is divided into: overall assembly and welding; Welding while assembling; Assemble and weld according to components; Finally, there are three types of assembly and welding. ① After the individual parts are assembled into a structure one by one, all the welding is completed. This is only applicable to products with a small batch and simple structure. ② The individual parts are assembled one by one, and then welded, re-assembled, and re-welded until the entire structure is completed. This assembly method is similar to ①, because the structure is more complex, it is difficult to complete the assembly at one time, this method is also suitable for a single piece of small batch production structure, such as large vertical oil tank, spherical container construction site. ③ Divide the structure into several components and parts, assemble and weld each component and part separately, and then assemble the qualified components and parts into the structure and weld the total assembly weld. This method is called sub-component assembly method. Commonly used in large quantities and batch production conditions, and for some complex structure of the product, even a single piece of small batch production nature, the use of sub-component assembly method also has great advantages. This method has high assembly welding quality and improves the working conditions of workers, because this method divides large and complex structures into light, small and simple structures (components, parts, etc.), which is convenient for assembly and welding, and can change some space position welds into flat welding welds, which can greatly increase the workload in the workshop and workshop, thereby reducing the workload in the field conditions, but also can easily control the welding stress and deformation, easy to use the assembly welding fixture. This sub-component assembly method, can improve labor productivity, shorten the production cycle, this is because the sub-components to facilitate the implementation of specialized production, workers need to master the production process is relatively simple, and can be more use of tire clamps, eliminate or reduce the waiting time between the various processes. The assembly by this method also simplifies the tire fixture, reduces the cost, and obtains higher technical and economic indicators. 3) According to the location of assembly work, it is divided into fixed location assembly method and flow assembly method. In actual production, the location of product assembly may be fixed, and workers of all types of work serve the products to be made, which are mostly heavy-duty structures with small output, such as beams of large hydraulic presses, turbine wheels, etc. Product assembly locations are more likely to flow along the station, with workers assembling and welding at fixed stations, such as the assembly and welding of gondola cars and tankers. (2) The formulation of the assembly process The contents of the assembly process include the assembly sequence of parts, components and components, the assembly sequence, the assembly method used in each step, and the specifications and models of tire fixtures, tools and equipment used in the assembly. In the development of the assembly process to consider and before and after the process of convergence, especially for the future of each process, welding process should bring favorable effects, such as easy to weld, easy to control stress and deformation. When developing the assembly process, pay attention to the selection of the positioning base and part tolerance. There are two ways to assemble and weld the structure with machined parts: first, the whole structure is finished, and then machined after annealing to eliminate stress, such as the welding base of the internal combustion engine of the diesel locomotive, the seat ring of the water turbine, the three beams of the 60000kN hydraulic press, etc. The other is to process the parts first, and then use a special device with sufficient rigidity for assembly and welding, such as the arm of the car crane, the frame of the excavator, etc.

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