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0引言对于工业界而言,焊接无疑是一种非常重要的加工技术之一。而且在许多行业,焊接是一种首选的连接方法,因此,保证焊缝达到满意的力学性能和安全性能要求就显得尤为关键。金属材料的熔化焊接可能带来各种问题。首先,焊接过程中产生的热会带来对力学性能影响显著的热循环。其次,这些热循环会导致金属的局部膨胀,冷却时就会导致残余应力的产生。这些残余应力可能导致材料变形,而更为重要的是,会产生附加载荷,可能使整个应力增加,进而影响结构的完整性。总的说来,焊接过程易产生导致结构在服役过程中过早失效的冶金缺欠和加工缺欠,如裂纹、气孔和未熔合等。1焊接安全的基本措施由于上述不利影响,在焊接过程中必须采取措施避免对材料性能产生严重的损伤或缺陷。所以,至关重要的一点就是当进行焊接时,要考虑到所有可能影响焊缝性能的因素。当人们想到焊接被用于桥梁、发电站等重要工程时,焊缝的重要性就勿需多言了。多年来,这些观点已经被人们所认识并采取了各种措施来防止在建造和服役过程中的过早失效,这些措施包括对焊接工艺及焊机
0 Introduction For the industry, welding is undoubtedly one of the most important processing techniques. And in many industries, welding is a preferred method of joining, so it is critical to ensure that the welds meet the desired mechanical and safety performance requirements. Fusion welding of metal materials can cause various problems. First, the heat generated during the welding process brings about thermal cycles that have a significant effect on the mechanical properties. Second, these thermal cycles cause local expansion of the metal, which, when cooled, can lead to residual stresses. These residual stresses can cause the material to deform and, more importantly, generate additional loads that can increase the overall stress and thus the structural integrity. In general, the welding process tends to create metallurgical imperfections and processing imperfections that lead to premature failure of the structure during service, such as cracks, porosity and fusion. 1 The basic measures of welding safety Due to the above adverse effects, measures must be taken during the welding process to avoid serious damage to the material properties or defects. Therefore, it is crucial to consider all the factors that can affect the performance of the weld when welding. When people think of welding is used for bridges, power plants and other important projects, the importance of the weld on Needless to say. Over the years, these ideas have been recognized and taken a variety of measures to prevent premature failure in the construction and service process, including the welding process and welding machine