铂重整装置临氢系统Cr5Mo钢管道长期服役后的组织和性能

Microstructure and Mechanical Properties of Cr5Mo Steel Taken from Pt-hydroformer Vessel Pipeline after Long-term Service

研究了炼油厂铂重整装置临氢系统Cr5Mo钢管道于510℃服役14年后的显微组织和力学性能,试验结果表明:母材组织比较稳定,片状珠光体未发生完全球化,碳化物没有发生明显的聚集长大;固溶体中仍保持较高的铬和钼的含量,碳化物基本类型未发生改变;室温和高温瞬时拉伸性能以及冲击韧性与新管基本相同,无热脆现象发生;焊接接头热影响区(HAZ)的过热区已由马氏体转变为回火屈氏体,征熔合线焊缝侧的类马氏体也已发生了回火,并在熔合线附近出现了增碳层;焊接接头的室温和高温瞬时强度高于母材,但其塑韧性均较低,因而是裂纹萌生和扩展的一个较为薄弱的环节。

The microstructure and mechanical properties of Cr5Mo steel taken from Pt-hydroformer vessel p(?)peline which had serviced in oil refinery for 14 years at 510℃ were studied.The experimental results showed that the microstructure of base metal is relatively stable and thelamellar pearlite was not spheroidized completely.The carbides did not collect or grow up.Thehigh contents of chromium and molybdenum were still remained in solid solution.The primarytype of carbides have not been changed.The room temperature and high temperature tensileproperties as well as impact toughness compared with that of commercial virgin CrsMo steel werenearly identical.And no thermal embrittlement occured too.The microstrtucture of overheated zonein heat affected zone(HAZ)of weld joint had been transformed from martensite to temperedtroostite.The martensite-like structure on weld metal side in the vicinity of fusion line had beentempered and carbon-enriched zone appeared nearby fusion line.The room temperature and hightemperature strength of weld joint were stronger than that of base metal.But its ductility andthoughness were lower than that of base metal.Therefore,the weld joint was a weak zone tocrack initiation and propagation.