咬边（undercut），是指由于焊接参数选择不当，或操作方法不正确，沿焊趾的母材部位产生的沟槽或凹陷。咬边将减少母材的有效截面积、在咬边处可能引起应力集中、特别是低合金高强钢的焊接，咬边的边缘组织被淬硬，易引起裂纹。
焊接熔池平静，飞溅小，不咬边，焊缝成形美观。
Quite molten pool, little spatter and no undercut ensure workpiece be in good welding appearance.
这个焊口以宏观检查发现明显的气孔和超长的咬边。
This welded seam is found an obvious air hole and an unqualified undercut with macroscopic check.
介绍了汽车消声器纵缝咬边胀合技术及其咬边芯模机构的设计计算。
Expanding and closing technique of core-die of longitudinal seam occlusion machine for automobile silencer and design calculation of such mechanics have been introduced.
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