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焊接变形和应力产生的原因和预防

来源:/  发布时间:2021-09-13 浏览次数:

焊接变形的基本形式有收缩变形、角变形、弯曲变形、波浪变形和扭曲变形等。焊接过程中,对焊件进行不均匀加热和冷却,是产生焊接应力和变形的根本原因。减少焊接应力与变形的工艺措施主要有:

The basic forms of welding deformation include shrinkage deformation, angular deformation, bending deformation, wave deformation and distortion deformation. Uneven heating and cooling of weldments during welding is the root cause of welding stress and deformation. The process measures to reduce welding stress and deformation mainly include:
一、预留收缩变形量根据理论计算和实践经验,在焊件备料及加工时预先考虑收缩余量,以便焊后工件达到所要求的形状、尺寸。
1、 Reserved shrinkage deformation according to theoretical calculation and practical experience, shrinkage allowance shall be considered in advance during material preparation and processing of weldments, so that the workpiece can reach the required shape and size after welding.
二、反变形法根据理论计算和实践经验,预先估计结构焊接变形的方向和大小,然后在焊接装配时给予一个方向相反、大小相等的预置变形,以抵消焊后产生的变形。
2、 According to theoretical calculation and practical experience, the inverse deformation method estimates the direction and size of structural welding deformation in advance, and then gives a preset deformation with opposite direction and equal size during welding assembly to offset the deformation after welding.
三、刚性固定法焊接时将焊件加以刚性固定,焊后待焊件冷却到室温后再去掉刚性固定,可有用防止角变形和波浪变形。此方法会加大焊接应力,只适用于塑性较好的低碳钢结构。
3、 When welding with rigid fixation method, the weldment shall be rigidly fixed. After welding, the rigid fixation shall be removed after the weldment is cooled to room temperature, which can effectively prevent angular deformation and wave deformation. This method will increase the welding stress and is only suitable for low carbon steel structures with good plasticity.
四、选择合理的焊接顺序尽量使焊缝自由收缩。焊接焊缝较多的结构件时,应先焊错开的短焊缝,再焊直通长焊缝,以防在焊缝交接处产生裂纹。如果焊缝较长,可采用逐步退焊法和跳焊法,使温度分布较均匀,从而减少了焊接应力和变形。
4、 Select a reasonable welding sequence to make the weld shrink freely as much as possible. When welding structural parts with many welds, the staggered short welds shall be welded first, and then the straight long welds shall be welded to prevent cracks at the joint of welds. If the weld is long, the step-by-step back welding method and skip welding method can be used to make the temperature distribution more uniform, so as to reduce the welding stress and deformation.
五、锤击焊缝法在焊缝的冷却过程中,用圆头小锤均匀迅速地锤击焊缝,使金属产生塑性延伸变形,抵消一部分焊接收缩变形,从而减小焊接应力和变形。
5、 Hammering weld method in the cooling process of the weld, use a small round head hammer to hammer the weld evenly and quickly, so as to make the metal produce plastic extension deformation and offset part of the welding shrinkage deformation, so as to reduce the welding stress and deformation.
六、加热“减应区”法焊接前,在焊接部位附近区域(称为减应区)进行加热使之伸长,焊后冷却时,加热区与焊缝一起收缩,可有用减小焊接应力和变形。
6、 Before welding by heating the "stress relief zone" method, heat the area near the welding part (called the stress relief zone) to make it elongate. When cooling after welding, the heating zone shrinks together with the weld, which can effectively reduce the welding stress and deformation.
七、焊前预热和焊后缓冷预热的目的是减少焊缝区与焊件其他部分的温差,降低焊缝区的冷却速度,使焊件能较均匀地冷却下来,从而减少焊接应力与变形。
7、 The purpose of preheating before welding and slow cooling and preheating after welding is to reduce the temperature difference between the weld area and other parts of the weldment, reduce the cooling rate of the weld area, so that the weldment can be cooled evenly, so as to reduce welding stress and deformation.

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