热处理工艺对1500MPa级低碳Nb-Ti低合金钢组织及性能的影响  

Effects of process on microstructure and mechanical properties of 1500 MPa grade low carbon Nb-Ti low alloy steel

作　　者：杨庚蔚[1,2] 雍岐龙[2] 孙新军[2] 李昭东[2] 李晓闲[1,2] 

机构地区：[1]昆明理工大学材料科学与工程学院,云南昆明650093 [2]钢铁研究总院工程用钢研究所,北京100081

出　　处：《材料热处理学报》2013年第7期65-72,共8页Transactions of Materials and Heat Treatment

基　　金：国家重点基础研究发展计划(2010CB630805)

摘　　要：通过低成本成分设计,在控制轧制的基础上,分别采用直接淬火(DQ)、直接淬火+回火(DQ+T)以及再加热淬火+回火(RQ+T)工艺成功制得了抗拉强度1500 MPa级经济型低合金高强高韧钢。对比研究了DQ、DQ+T和RQ+T 3种工艺钢的微观组织和力学性能。结果表明:DQ工艺钢的微观组织为板条马氏体+少量铁素体及残留奥氏体的复相组织,其抗拉强度和屈服强度分别为1750 MPa和1300 MPa,-40℃下冲击吸收功为37 J。200℃回火1 h后,试验钢位错密度降低,大量细小ε碳化物在板条内析出。DQ+T工艺钢屈服强度达到1400 MPa,-40℃下冲击功为43 J。试验钢直接淬火后再加热至880℃,获得了平均晶粒尺寸为5.7μm的细小等轴奥氏体。相比于DQ及DQ+T工艺钢,RQ+T工艺钢获得了更高的韧性,冲击功达到56 J。研究发现,未溶的(Nb,Ti)(C,N)粒子能有效抑制奥氏体晶粒长大。组织细化及残留奥氏体是RQ+T工艺钢获得高韧性最主要的原因。Based on the chemical composition design of low cost and controlled rolling,an economical high strength and high toughness low alloy steel with tensile strength of 1500 MPa grade was obtained by using three processes of direct quenching（DQ）,direct quenching＋tempering（DQ＋T）,reheating and quenching＋tempering（RQ＋T）.Effects of the three processes on microstructure and mechanical properties of the steel were investigated and compared.The results indicate that the microstructure of directly quenched（DQ） steel is composed of lath martensite,ferrite and retained austenite.The tensile strength and yield strength of DQ steel is 1750 MPa and 1300 MPa,respectively,-40 ℃ Charpy impact energy is 37 J.After tempering at 200 ℃ for 1 h,the dislocation density of the steel decreases and fine ε carbide precipitates within the lath.The yield strength and the Charpy impact energy of DQ＋T steel are increased to 1400 MPa and 43 J,respectively.Fine equiaxial austenite with the average grain size of 5.7 μm in the steel is obtained after reheating at 880 ℃.The-40 ℃ Charpy impact energy of the RQ＋T steel is 56 J,which is higher than those of DQ steel and DQ＋T steel.It is found that undissolved（Nb,Ti）（C,N） particles can inhibit the austenite growth effectively.The improved toughness of RQ＋T steel is attributed to the grain refinement and retained austenite.

关 键 词：低合金高强高韧钢 直接淬火 扁平奥氏体 板条马氏体 强韧化机理 

分 类 号：TG142.33[一般工业技术—材料科学与工程]