均热温度对590MPa级热镀锌双相钢组织与性能的影响

Effect of soaking temperature on microstructure and properties of 590 MPa grade hot-dip galvanized dual phase steel

将C-Mn钢分别加热至760、800和850℃均热120 s后,快速冷却至460℃以模拟热镀锌工艺。退火后对试验钢进行预应变（2%）和烘烤处理（170℃×20 min）以测量其烘烤硬化（BH）值。通过金相显微镜、扫描电镜、拉伸等技术,研究了均热温度对590 MPa级热镀锌双相钢微观组织、力学性能和烘烤硬化性能的影响。结果表明,在760~850℃范围内退火时,试验钢中未观察到贝氏体组织,微观组织由铁素体和马氏体组成,抗拉强度均达到590 MPa以上。热镀锌双相钢在800℃退火时,具有优良的综合力学性能,其屈服强度为295 MPa,抗拉强度为606 MPa,伸长率为32.1%,强塑积为19 450 MPa·%。随着均热温度提高,BH值呈先增加后降低趋势;均热温度为800℃时,BH达最大值81 MPa。

C-Mn steel were respectively soaked at 760 ℃, 800 ℃ and 850 ℃ for 120 s, and then rapidly cooled to 460 ℃ to simulate the hot-dip galvanizing. The pre-straining （2%） and baking treatment （ 170 ℃ for 20 min） were carried out to measure the BH values after annealing cycle. The influences of the soaking temperature on microstructure, mechanical properties and bake-hardening behavior of the 590 MPa grade hot-clip galvanized dual phase steel were investigated by means of microscope, SEM, tensile test machine and so on. The results show that the microstrueture is composed of ferrite and martensite when annealed at 760-850 ℃, and no bainite is observed. Therefore, the tensile strength of the hot-dip galvanized dual phase steel reaches more than 590 MPa. The steel with excellent comprehensive properties （Rp0.2 =295 MPa, Rm =606 MPa, A =32.1% , Rm ×A = 19 450 MPa · % ） are obtained by annealing at 800 ℃. The BH value increases first and then decreases with increasing the soaking temperature from 760 ℃ to 850 ℃. And the BH value reaches maximum value （81 MPa） at the soaking temperature of 800 ℃.