大规格高强度钢筋轧后余热处理工艺探讨

Discussion about the Postrolling Residual Heat Treatment Process of Large Gauge and High Strength Reinforced Bar

采用20MnSi连铸坯、轧后余热处理工艺生产的大规格(/40mm)钢筋外层厚度2.0～3.4mm,过渡层厚度1.7～3.5mm,屈服强度不小于530MPa,抗拉强度不小于610MPa,符合BS4449标准460MPa级钢筋的要求。钢筋的金相组织:外层,回火索氏体;过渡层,索氏体+珠光体+铁素体+贝氏体;心部,贝氏体+珠光体+铁素体。试验选定的加热温度为1080～1100℃,终轧速度3.4～3.7m/s;冷却方式是管内流水冷却,冷却水量500～660m3/h,水压0.40～1.0MPa。

Large gauge and high strength reinforced bars（ Φ 40mm ）, which meet the needs of BS4449 standard 460MPa grade, were preduced with 20MnSi continuous casting slabs and postrolling residual heat treatment process. Detection resuhs shown that the thicknesses of the outer layer and the transition layer of the reinfurced bar are respectively 2.0- 3.4mm and 1.7 - 3.5mm; the yield intensity is not less than 530MPa and the tensile strength is not less than 610MPa; the microstructure of the outer layer is composed of tempered sarbite; the transition layer： sorbitc, pearlite, ferrite and bainite; the core： hainite, pearlite and ferrite. Selective technological parameters by testing are that heating temperature is 1080 - 1100℃, finishing speed is 3.4 - 3.7 m/s, the type of cooling is running water cooling in pipe, the flow rate of cooling water is 500 - 660m^2/h and the water pressurs is 0.40 - 1.0MPa.