Abstract: The test 600 MPa grade high strength steel (/% : 0.23C, 0.67Si, 1.35Mn, 0.028P, 0.023S, 0.131V, 0.033Nb) is melted by a 25 kg vacuum induction furnace and hot-rolled to 16 mm x 180 mm slab product. With dilatometric test combined with structure metalloscopy and microhardness test the continuous cooling transformation expansion curves of steel HRB600 at cooling rate 0.1-100 ℃/s have been measured by hot simulation testing machine Thermecmastor-Z to got the continuous cooling transformation (CCT) curves of the steel and the transformed structure of steel is studied. Results show that with austenizing at 850 ℃，as cooling rate less than 3 °C/s the structure of tested V-Nb microalloying high strength steel HRB600 is proeutecloid ferrite + pearlite； with cooling rate 5 ℃/s the minor martensite occurs in structure to effect the welding behavior of steel ； and with cooling rate up to 100 ℃/s the martensite structure is obtained in steel.

Key words: V-Nb Microalloying, HRB600 Hot-Rolled High Strength Reinforcing Bar, Continuous Cooling Transformation ( CCT) Curves, Structure

摘要： 试验用600 MPa级高强度钢(/%:0.23C,0.67Si,1.35Mn,0.028P,0.023S,0.131V,0.033Nb),由25kg真空感应炉冶炼,并热轧成16 mm×180 mm扁材。利用膨胀法结合金相分析及硬度在Thermecmastor-Z热模拟试验机上测定了HRB600钢在冷却速率0.1~100℃/s下的连续冷却转变膨胀曲线,获得了该钢的连续冷却转变曲线(CCT曲线)并研究了该钢转变后的组织。结果表明,850℃奥氏体时,冷却速率小于3℃/s时试验V-Nb微合金化高强度钢HRB600的组织为先共析铁素体+珠光体,当冷却速率为5℃/s时,出现少量马氏体,影响钢筋的焊接性能,当冷却速率达100℃/s时可获得马氏体组织。

关键词: V-Nb微合金化, HRB600热轧带肋高强度钢筋, 连续冷却转变(CCT)曲线, 组织