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中强低合金钢焊缝的人字裂纹

CHEVRON CRACKING IN MEDIUM STRENGTH LOW ALLOY STEEL WELDS

  • 摘要: 采用多层埋弧焊方法,研究了低合金钢焊缝人字裂纹。该裂纹的表面形态是:裂纹走向与焊缝纵向成45°角,并由焊缝柱晶界小段裂纹与穿柱晶小段裂纹连接成阶梯扩展途径,裂纹断口为韧窝或准解理。离子探针分析证实,锰、硫、磷、镍等元素与人字裂纹无直接联系;硅在断裂过程中析出:氢的增加有助于裂纹的产生。对人字裂纹的产生条件和形成机理作了探讨。提出人字裂纹断裂模型,屈服强度低于500N/mm2的焊缝金属,在较大的塑性应变消耗和残余应力作用下,可能产生人字裂纹。

     

    Abstract: With a series of wire and flux combinations the chevron cracking in multipass submerged are welds has been studied. The morphology of the cracks was observed by means of the optical microscope and scanning electron microscope. The test results show the cracking being oriented at an angle approximately 45°to the plate surface in longitudinal sections. Chevron cracking is composed of small cracks created individually in the columnar boundaries and within the columnars of the welds. The fracture showed dimple or quasi-cleavage. Ion microprobe analysis verified that Mn, S, P and Ni have no direct relations to chevron cracking. There existed the segregation of Si along the chevron crack path. Weld metal of yield strength lower than 500N/mm2 subjected to high plastic deformation consumption and residual stress may be liable to chevron. cracking.

     

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