海洋采油平台R4S级系泊链用钢热处理工艺研究

Study on Heat Treatment Process of Mooring Chain of Rank R4S Grade for Offshore Platform

海洋采油平台用R4S级系泊链条具有更高的力学性能要求,而链条最薄弱环节焊缝区的韧性和屈强比往往难以满足船检规范要求。本文模拟链条实际生产过程采用"等效连续调质热处理"的方法,研究热处理工艺对焊缝区的组织和力学性能的影响。结果表明:加入适量的细化晶粒元素,采用温度960℃+保温时间60 min+水冷的淬火工艺,获得板条马氏体+残余奥氏体(包括M-A岛)及少量混合贝氏体组织,提高焊缝区强韧性和降低屈强比;经600℃×1 h+水冷的工艺回火后,焊缝区的韧性、屈强比最优,可较好地满足ABS、BV船检规范的要求。

Offshore oil platform mooring chain of rank R4 S needs high level requirements of mechanical performance,while the weak link of the chain lays on the weld zone. The toughness and yield ratio are often difficult to meet the requirements of classification society standards. A ＂pseudo-continuous transfer of heat treatment equivalent＂ method is used to simulate the actual chain production process and study the effect of heat treatment process on microstructure and mechanical properties of the weld zone. The results show that：adding to the right amount of grain-refining elements,with the temperature 960 ℃ ＋ holding time of 60 min ＋ water quenching process, the microstructure of lath martensite and residual austenite（including M-A Island） and a small amount of mixed bainite can be obtained,increasing the strength and toughness of weld zone while decreasing the yield strength ratio. The microstructure is good for improving the toughness and reduce yield ratio of the weld zone, which can well meet the ABS and BV classification society standards.