Abstract: The effect of finishing temperature (800 ~850 °C ) and cooling rate (2 〜20 ℃/s) on structure and mechanical properties of microalloying steel Q55OD plate (/% ： 0. 06C, 0. 20Si, I. 60Mn, 0. 010P, 0. 001S, 0. 10Mo, 0. 06Nb, 0. 01V, 0. 02Ti) has been studied by using thermo-mechanical simulator Gleeble-3800. Results show that with decreasing finishing temperature and increasing cooling rate after rolling, the granular bainite in steel gradually decreases, and the lath bainite gradually increases, as a results the yield and tensile strength of steel increasing trend is obvious and the - 20 ℃ toughness is improved but the elongation of steel is decreasing trend ； with finishing temperature 850 °C and cooling rate 15 - 20 ℃/s the steel Q550D has better strength-toughness comprehensive properties, i. e. tensile strength is about 750 MPa, yield strength 650 MPa, elongation 39% and -20 ℃ impact energy 65 J.

Key words: Microalloying Steel Q55OD, Thermal Simulation, Finishing Temperature, Cooling Rate, Structure, Mechanical Properties

摘要： 通过Gleeble-3800热模拟试验机,研究了终轧温度(800～950℃)和冷却速度(2～20℃/s)对Q550D微合金钢板(/%:0.06C、0.20Si、1.60Mn、0.010P、0 001S、0.10Mo、0.06Nb、0.01V、0.02Ti)的组织和力学性能的影响。结果表明,随着终轧温度的降低和轧后冷却速度的增加,粒状贝氏体逐渐减少,板条贝氏体逐渐增多,钢的屈服和抗拉强度提高的趋势比较明显,-20℃韧性得到改善,但伸长率呈下降趋势;在终轧温度为850℃、冷却速度为15～20℃/s时,Q550D钢具有较好的综合强韧性,即抗拉强度约为750 MPa,屈服强度650 MPa,伸长率39%,-20℃冲击功65 J。

关键词: Q550D微合金钢, 热模拟, 终轧温度, 冷却速度, 组织, 力学性能