What method is used to minimize welding deformation?

【Summary Description】 Reduce welding deformation What method is used to minimize the welding deformation of two welds of 15-meter-long channel steel? 1. two welds of 15 meters long channel steel, the host did not give the welding form, position, length, leg height and structure of the weldment. We are just exploring what method to use to minimize welding deformation. 2. the following, we mainly discuss several common methods to prevent or reduce welding deformation: 1. Anti-deformation method When assembling before welding, the amount of deformation in the opposite direction is preset to offset (compensate) welding deformation. This method is called Anti-deformation method. 2. Use assembly and welding sequence to control deformation; The use of reasonable assembly and welding procedures to reduce deformation is an effective and good method in production practice. Many structures have symmetrical cross-sectional shapes and symmetrical weld arrangements, but bending or twisting deformation occurs after welding. This is mainly caused by unreasonable assembly and welding sequences, that is, the deformation caused by various welds fails to offset each other, deformation then occurs. 3. Use the welding sequence to affect the degree of deformation of the welding structure, and pay attention to the following principles when arranging the welding sequence: 1) Try to use symmetrical welding. For work with symmetrical welds, it is best to weld symmetrically by pairs of welders. In this way, the deformation caused by each weld can be partially offset. 2) For some structures with asymmetric weld arrangement, the side with less weld seams shall be welded first. 3) According to the characteristics of different welding sequences, the welding deformation is controlled by welding procedures. There are five common welding sequences, namely: a. piecewise back welding method. this method is suitable for welding in various space positions. except vertical welding, arc baffle can be set when steel is thicker and weld seam is longer, and many people weld at the same time. The advantage is that the heat affected zone can be reduced and deformation can be avoided. Each section shall be 0.5-1m long. B. sub-segment back welding method is suitable for welding medium plate or thin steel plate. its advantage is that the intermediate heat dissipation is fast and the temperature difference between the two ends of the weld is reduced. The temperature of the weld heat affected zone will not increase sharply to reduce or avoid thermal expansion deformation. This method is particularly suitable for flat and overhead welding. C jump welding method in addition to vertical welding, flat welding, horizontal welding, overhead welding three methods are applicable, mostly used in 6-thick steel plate long weld and cast iron, stainless steel, copper welding, can disperse weld heat, avoid or reduce deformation. The weld length of each section of steel is between-; Cast iron welds shall be treated according to cast iron welding specifications; Due to the fast heat conduction of stainless steel and copper, the length of each section should not exceed (the thin plate should be shorter). d. Alternating welding method This welding method is basically the same as the jump welding method, except that the welding distance of each section is elongated, which is especially suitable for thin plates and long welds. This method is suitable for weldments with short welds. In order to reduce deformation, the welding is finished at both ends by the center. 3. Rigid fixed method Rigid fixed method to reduce deformation is very effective, and welding without excessive consideration of the welding sequence. The disadvantage is that some large parts are not easy to fix, and after the removal of the fixed after welding, the weldment still has a little deformation and a large residual stress. This method is suitable for welding thin-walled materials with thickness less than 6mm and good toughness. If it is used in conjunction with the anti-deformation method, the effect is better. For weldments with complex shape, small size and mass production, a special welding fixture that can rotate can be designed to prevent deformation and improve productivity. When the workpiece is large and the number is small, some supports or tie rods can be temporarily welded on the parts prone to deformation to increase the rigidity of the workpiece and effectively reduce the welding deformation. 3. Heat dissipation method Heat dissipation method is also called forced cooling method, that is, the heat at the welding place is quickly dissipated, so that the metal heating surface near the weld is greatly reduced, and the purpose of reducing welding deformation is achieved. 4. Hammering weld method Hammering weld method, that is, knocking the weld with a round head hammer, can reduce welding deformation and stress. Therefore, the proper forging of the weld, so that its elongation to compensate for this shortening, you can reduce the deformation and stress. Hammering force should be uniform, generally 0.5Kg-1.0Kg hand hammer, its end is rounded (R = 3-5mm). The bottom layer and surface weld bead are generally not hammered to avoid cold hardening of the metal surface. After welding the other passes, hammer immediately until the surface of the weld is hit with a uniform and dense point.

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