30CrMnSi钢CO_(2)焊接冶金缺陷形成机制研究

Formation Mechanism of Metallurgical Defects in 30CrMnSi Steel during CO_(2) Welding

目的解决30CrMnSi钢焊接性差,用CO_(2)气体保护焊接时易产生裂纹、气孔等缺陷的问题。方法通过刚性拘束焊接裂纹试验模拟某型飞机后边条盒段在实际焊接过程中母材所受到的拘束,针对焊接裂纹类型及形态,确定焊接裂纹的形成机制。同时,对焊缝中的气孔进行了分析。结果接头中容易产生冷裂纹,在高应力条件下,应力集中发生在微裂纹尖端,最终在氢的影响下开裂。结论采用能量密度比较集中的TIG焊替代原来采用的CO_(2)气体保护焊有利于减少或消除气孔缺陷。可以通过优化结构设计和焊接次序,降低应力集中,来减轻焊接热作用对裂纹敏感性的影响。同时,避免在拐角处或焊接可达性差的位置施焊,可以降低气孔率。

The work aims to solve the problems of cracks,pores and other defects in 30CrMnSi during CO_(2) gas shielded welding due to poor weldability.A rigid restraint welding crack test was conducted to simulate the restraint of the base metal during the actual welding process of the rear box section of a certain aircraft,and the formation mechanism of the welding crack was determined according to the types and forms of welding cracks.At the same time,the porosity in the weld was analyzed.Cold cracks were easy to occur in the joint.Under high stress conditions,stress concentration occurred at the tip of the mi-cro-crack,and finally a cold crack penetrating the weld was formed under the effect of hydrogen.TIG welding with relatively concentrated energy density is considered to replace the original CO_(2) gas shielded welding,which is also conducive to reducing or eliminating porosity defects.The structural design and welding sequence can be optimized to reduce stress concentration,thereby reducing the effect of welding heat on crack sensitivity.At the same time,welding should be avoided at corners or posi-tions with poor welding accessibility,so as to effectively reduce porosity.