高温服役对HP40Nb炉管焊接接头组织及性能的影响

Effect of High Temperature Service on Microstructure and Properties of HP40Nb Furnace Tube Joint

以一段服役7年左右的HP40Nb制氢转化炉管为对象,研究了高温服役过程对其焊接接头微观组织及力学性能的影响。观察分析了不同区域显微组织的特征和析出相的形态及分布情况,并测定了各区域的硬度、强度和冲击韧性等性能参数。结果表明:HP40Nb炉管焊接接头的熔敷金属中只有少量碳化物析出,而在母材中有大量的碳化物析出并聚集在奥氏体晶界上形成网链状;接头的抗拉强度只有少量下降,但其延伸率和冲击韧性均发生严重下降。

In this paper,the effects of high temperature service process on the microstructure and mechanical properties of welded joints were studied in a section of HP40 Nb hydrogen reformer tubes that have been in service for about 7 years. The characteristics of microstructure and the morphology and distribution of precipitated phases in different regions were observed and analyzed. The properties such as hardness,strength and impact toughness of each region were determined. The results showed that only a small amount of carbides were precipitated out from the deposited metal,lots of carbides were precipitated in the base metal and aggregated on the austenite grain boundary to form a network chain;the tensile strength of the joints only declined a little,but its elongation and impact toughness had been seriously reduced.