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焊接缺陷的产生过程是十分复杂的,既有冶金的原因,也受到应力和变形的作用,缺陷对焊接结构承载能力有非常显著的影响。焊接缺陷容易出现在焊缝及其附近地区,而那些地区正是结构中拉伸残余应力最大的地方。焊接缺陷一般包括有未焊透、未熔合、裂纹、夹杂、气孔、咬边、焊穿和焊缝成型不良等。正是由于这些缺陷的存在,它不仅削弱了焊缝的有效工件断面,同时也会带来应力集中,显著降低焊缝金属的强度和韧性,对动载强度和疲劳强度更为不利。这些都可能成为发生失效事故的隐患。
The welding process is very complicated, both of the reasons of metallurgy and the effects of stress and deformation. The defects have a very significant influence on the bearing capacity of the welded structure. Weld defects tend to appear in the weld and its vicinity, and those areas are where tensile residual stresses are greatest in the structure. Weld defects generally include impermeable, unfused, cracked, inclusions, porosity, undercut, weld penetration, and poor weld formation. It is because of these defects that not only weakens the effective workpiece section of the weld, but also brings about stress concentration, significantly reducing the strength and toughness of the weld metal, which is more unfavorable to the dynamic load strength and fatigue strength. These can be hidden dangers of failure.