X80管线钢及其接头的低温韧性和显微组织

Study on low temperature toughness and microstructure on base metal and welded joint of X80 pipeline steel

分别利用示波冲击韧性试验、硬度试验和光学显微镜、透射电镜研究了X80管线钢及其焊管接头的力学性能和显微组织。试验结果表明,X80钢及其焊管接头具有良好的韧性,其中焊缝的韧性最高,焊接热影响区粗晶区因受焊接热效应引起晶粒粗化和形成脆性组织,故韧性最低。试验钢由针状铁素体和少量块状铁素体组成,焊缝为典型的针状铁素体组织,焊接热影响区粗晶区以粒状贝氏体为主。焊接热影响区熔合线附近的硬度值最高,越远离熔合线硬度值越低,并逐渐接近母材的硬度值。

The mechanics properties and microstructure of base metal and welded joint of X80 pipeline steel were investigated by oscillo-impact toughness test, micro-hardness test, optical microscope and TEM test. The results show that the toughness of base metal and welded joints of X80 was good. The toughness of weld metal is the highest while the coarse grained region in the HAZ is the lowest because of welding thermal cycle and formation of brittle microstructure. The microstructures are acicular ferrite and a little massive ferrite in base metal, typical acicular ferrite in weld metal and granular bainite in coarse grain zone of the HAZ. The hardness in HAZ adjacent to the weld bond is the highest and then gradually descends to the level of base metal.