柴油机不锈钢散热管焊缝早期开裂原因分析

Early Cracking Failure Analysis of the Welded Seam for Stainless Steel Radiating Pipe in a Diesel Engine

某柴油机散热用奥氏体不锈钢焊接弯管焊缝发生早期开裂,采用宏观分析、金相分析、扫描电镜及能谱分析、化学成分分析等对弯管开裂的原因进行了分析。结果表明:焊缝的早期开裂属应力腐蚀开裂,其早期失效主要是由于焊接工艺及焊丝选择不当所致,冷却水中氯离子的存在造成接头强度下降、耐蚀性能降低,形成裂纹源,裂纹在应力作用下迅速扩展导致开裂。

Macro-analysis, metallographic analysis, scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDAX） and chemical composition analysis were adopted to study the reason for early cracking failure of the welded seam for stainless steel radiating pipe in a diesel engine. The results show that the early cracking caused by stress corrosiorL The early failure was mainly attributed to improper welding technique and inappropriate welding electrode, which formed the crack source because of decreased strength in the joint zone. The existance of Cl^- in cooling water might be the enviromnental reason for SCC to occur.