不锈钢焊接接头高温服役脆性相析出的金相分析

Metallographic analysis for brittle phase separating of stainless steel welding joint at high temperature serving

以催化裂化装置中的输送烟气管道上的不锈钢焊接接头为研究对象,分析焊接接头的金相组织来研究其脆化的原因和规律,提出改善焊接质量的方法,为提高这一系列不锈钢焊接接头的质量以及在高温下的工作性能提供了可靠的依据。研究结果表明,奥氏体不锈钢焊接接头长期高温下脆化倾向主要有两方面原因,一方面由于带有粗大γ柱状晶的焊缝显微组织是不均匀的,奥氏体焊缝高温脆化倾向与焊缝中产生γ→σ相有关,γ→σ相主要沿晶界沉淀析出,导致接头严重脆化;另一方面,焊接时产生的焊接残余应力较大,高温环境使其强度提高而塑性下降。

Based on the fluid catalytic cracking gas pipeline transport of stainless steel welding joint for research object,the reasons and rules of embrittlementing were studied by analyzing the microstructure of the welded joint.The methods to improve the welding quality have been put forward ,and the reliable basis that can improve the quality of the welding joint of these series stainless steel at high temperatures and working performance were provided.The austenitic stainless steel welding joint long-term temperature tendency has two main reasons from the researching results,one of reasons is the γ columnar crystal weld microstructure is uneven,austenitic welding heat generated in weld improving tendency of γ→σ phase, γ→σ phase separated at the major grain to precipitate.On the other hand,welding joint has serious residual stress, high temperature make its strength and plasticity droped.