How to reduce welding residual stress?

Welding stress is an important factor causing various welding cracks in welded joints, and the residual stress in welded parts will affect the service life of structures. Therefore, in order to improve the welding quality of the whole component, measures must be taken to control and reduce the welding residual stress. In order to reduce welding residual stress, the following technological measures should be taken: 1. Use reasonable welding sequence and direction (1) Weld on the welding plane, to ensure that the longitudinal weld and the transverse weld (especially the transverse) can freely shrink. For butt welds, the welding direction should be toward the free end. (2) weld the weld with large shrinkage first. If there are butt welds and fillet welds on the structure, the butt welds with large shrinkage should be welded first. (3) weld transverse short welds first. (4) Weld seams with larger stress at work shall be welded first to make the internal stress distribution reasonable. (5) When welding cross butt welds, welding sequence must be adopted to ensure that the crossing points are not prone to defects. When welding t-shaped welds and cross welds, the weld that should be welded at the intersection should be cleaned and welded in accordance with the correct order, so as to make the transverse contraction of T-shaped welds and cross welds more free and help to avoid cracks at the intersection of welds. 2, reduce the local rigidity of welding structure As the rigidity of the structure increases, the welding stress increases accordingly. Therefore, reducing the local rigidity of the welded component is beneficial to reducing the stress. When welding the closed weld or its larger rigidity weld, the anti-deformation method can be adopted to reduce the local rigidity of the structure or the method of opening the easing groove near the weld to reduce the local rigidity of the welding site. 3, heating “stress reduction zone” When welding, heat the parts that hinder the free expansion of the welding area to make it expand and contract simultaneously with the welding area. The welding stress can be reduced, which is called the heating “stress reduction zone” method, or synchronous shrinkage method. The heating area is called the “stress reduction zone”. 4, using “cold welding” method to reduce welding residual stress The principle of “cold welding” is to make the temperature distribution on the welding structure as uniform as possible, requiring the local temperature of the weld to be controlled as low as possible, and at the same time, the volume of this part in the overall welding structure is as small as possible. The method of minimizing the temperature difference in the structure can effectively reduce the welding residual stress and the tendency of thermal stress crack. In cold welding operation, small diameter electrode, small welding current, welding a very short weld. For example, repair welding of cast iron is only 10~40mm per section. Welding rigid components, each welding only one or half of the electrode, after each welding, to cool to not hot, can weld the next weld. 5, hammer weld In the cooling process of each weld, a small hammer hammer is used to hammer the weld, so that the weld metal is affected by the hammer to produce plastic tensile deformation and extend around, offset the contraction of the weld and reduce the internal stress. Hammering should be kept uniform and moderate, avoid hammering excessive and produce too deep hammering mark. 6. Preheat before welding The purpose of preheating before welding is to reduce the temperature gradient of welding zone and structure, reduce the constraint degree, and achieve the purpose of reducing the internal stress of welding. Preheating of welding parts before welding can be whole preheating, or partial preheating of welding area. Preheating methods include integral heating in furnace, local far infrared heating, local power frequency heating, flame heating and so on.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods