淬火工艺对大口径石油套管组织与性能的影响

Influence of quenching process on microstructure and properties of large diameter oil casing

对热轧25MnV钢石油套管进行了不同工艺的淬火热处理试验,通过组织观察和力学性能测试等手段,对比研究了直接淬水冷却至室温和水-空-水交替淬火两种工艺对合金显微组织与力学性能的影响。结果表明:水-空-水交替淬火可有效减缓石油套管的淬火内应力,所得马氏体+下贝氏体的复相组织可降低淬火裂纹产生和扩展的趋势,提高了石油套管的使用安全性。经590℃×65 min回火后,套管的抗拉强度达到932 MPa,屈服强度为870 MPa,横向冲击功高达55 J,综合力学性能远远超过当前的调质态套管,分析认为这归功于复相组织中微细孪晶马氏体的减少以及部分下贝氏体和少量残留奥氏体等二次析出相的综合作用。

Hot rolled 25MnV steel was quenched by different quenching process. The influence of quenching cooling methods including direct quenching by water cooling to room temperature and water-air alternative quenching on mierostrueture and mechanical properties of the steel was studied by microstrueture observation and mechanical property tests. The results show that under the condition of water-air- water alternative quenching, the quenching internal stress of the experimental steel can be effectively reduced, and the duplex micro structure of martensite and lower bainite decreases the tendency of cracking for the oill casing. After tempering at 590 ~C for 65 min, tensile strength, yield strength and impact energy of the steel reach 932 MPa, 870 MPa and 55 J, respectively, much higher than that of the commercial oil easing steel. It is suggested that the improvement of mechanical properties is attributed to the duplex microstructure of lath martensite, lower bainite small amount of residual austenite in the steel by water-air-water alternative quenching.