轧后冷却工艺对Si-Mn-Cr-Ni-Mo低合金超高强钢组织和性能的影响  

Influence of cooling process on microstructure and properties of a Si-Mn-Cr-Ni-Mo ultra-high strength low alloy steel

作　　者：万德成 董长征[2] 蔡庆伍[2] 张恒磊 

机构地区：[1]华北理工大学河北省现代冶金技术重点实验室,河北唐山063009 [2]北京科技大学冶金工程研究院,北京100083 [3]北京有色金属研究总院,北京100088

出　　处：《材料热处理学报》2015年第5期107-111,共5页Transactions of Materials and Heat Treatment

摘　　要：设计了一种以无碳化物贝氏体为主要组织的1500 MPa级Si-Mn-Cr-Ni-Mo系超高强度钢,对比研究了实验钢轧后经空冷、先水冷至550℃后空冷和先水冷至450℃后空冷3种冷却工艺的显微组织和力学性能。结果表明:实验钢轧后直接空冷获得无碳化物贝氏体+少量M/A组织,先水冷后空冷得到无碳化物贝氏体+少量马氏体组织。组织中对性能尤其是韧性性能有显著影响的残留奥氏体薄膜的形貌和分布随冷却工艺的变化而变化,空冷冷却残留奥氏体薄膜分布在贝氏体铁素体板条间,先水冷再空冷冷却残留奥氏体薄膜不仅存在于贝氏体铁素体板条间,在板条内部也可以观察到少量细小的膜状残留奥氏体,分割贝氏体铁素体板条,起到了细化晶粒的作用,有益于实验钢力学性能的提升。先水冷至550℃后空冷,实验钢的抗拉强度可达1600 MPa,-20℃冲击吸收功为28 J,具有最优的综合力学性能。A novel sort of 1500 MPa grade Si-Mn-Cr-Ni-Mo ultra-high strength low alloy steel was designed. The microstructure and mechanical properties of the experimental steel under different cooling processes( air cooling,quenching to 550 ℃ + air cooling and quenching to 450 ℃ + air cooling) after hot-rolling were investigated. The result show that when the steel is cooled by air cooling after hot rolling,the microstructure consists of CFB( carbon free bainite) and M/A,and the CFB and martensite microstructure is observed in the steel cooled by water and then air cooling. The morphology and distribution of the retained austenite films are changed under different cooling processes,which is very important to mechanical properties of the steel. The retained austenite films are observed between bainite ferrite laths under air cooling,while the retained austenite films are found not only between the bainitic ferrite laths but also in the bainitic ferrite laths for the steel by water and air cooling. These retained austenite films in ferrite laths divide the bainitic ferrite laths into smaller one,which is equal to grain refinement. Under air cooling from 550 ℃ after an initial water cooling,the experimental steel has excellent comprehensive mechanical properties,its tensile strength is 1600 MPa,the impact absorbing energy at- 20 ℃ is 28 J.

关 键 词：超高强钢 冷却工艺 无碳化物贝氏体 残留奥氏体 

分 类 号：TG142.1[一般工业技术—材料科学与工程] TG335[金属学及工艺—金属材料]