热处理对14MnVTiRE钢4 mm薄板组织和力学性能的影响

14MnVTiRE钢[/%:0.10～0.15C、0.30～0.60Si、1.20～1.60Mn、0.03～0.09V、0.07～0.16Ti、0.10～0.15RE(加入量)]4 mm薄板的生产流程为180 t顶底复吹转炉-180 mm×1 260 mm连铸板坯-连轧-卷取工艺。在连铸时由结晶器喂φ2.5 mm RE丝。试验研究了950℃正火,950℃正火+690℃1～5 h回火对薄板组织和力学性能的影响。结果表明,正火后钢的组织为铁素体+细珠光体,在正火+690℃回火1～3 h钢中的珠光体片层碳化物发生球化,分布在晶界和晶粒内部,随回火时间进一步增加,碳化物呈点状和三角形,全部分布在晶界,材料的强度降低很大。14MnVTiRE钢薄板的最佳热处理工艺为950℃正火+690℃1～2 h回火,其屈服强度为510～610MPa,抗拉强度630～680 MPa,伸长率22%～25%。

Effect of Heat Treatment on Structure and Mechanical Properties of 4 mm Sheet of Steel 14MnVTiRE

The production flow sheet for 4mm sheet of steel 14MnVTiRE[/%:0.10～0.15C,0.30～0.60Si, 1.20～1.60Mn,0.03～0.09V,0.07～0.16Ti,0.10～0.15RE(adding amount)]is 180 t top and bottom combined blowing converter-180 mm×1260 mm casting slab-continuous rolling-coiling process.During casting theΦ2.5 mm RE wire is feeding in mold.The effect of 950℃normalizing and 950℃normalizing+690℃1～5 h tempering on structure and mechanical properties of sheet is tested and studied.Results show that structure of normalized steel is ferrite+fine pearlite, in normalized+690℃1～3 h tempered steel the spheroidizing of lamella carbide in pearlite occurs and the spheroidized carbide is distributed at grain boundary and inner of grain,with further increasing tempering time the carbide presents particle and triangle shape and all carbide is distributed at grain boundary led to large decrease of material strength.The opti- mum heat treatment process for steel 14MnVTiRE sheet is 950℃normalizing+690℃1～2 h tempering,its yield strength is 510～610 MPa,tensile strength 630～680 MPa and elongation 22%～25%.