汽车结构用热轧酸洗板QStE420的开发

Development of hot rolled and pickled automotive steel QStE420

为开发汽车结构用热轧酸洗板QSt E420,设计了3种不同Nb含量的试验钢,借助Gleeble 3800热模拟试验机测量得到试验钢的CCT曲线,并对试验钢的组织和性能进行了测试。结果表明：铁素体相变开始温度并不是随着Nb含量增加而线性下降,而是先降低后升高。Nb添加量为0.03%时,试验钢的性能能够满足QSt E420钢的要求。根据CCT测试及实验室轧制结果,设计汽车结构用热轧酸洗板QSt E420工业化生产的终轧温度为（850±20）℃,卷取温度为（580±20）℃,试制试验钢板组织由铁素体和珠光体组成,力学性能优异,完全满足标准的要求。

In order to develop the hot rolled and pickled steel QSt E420,three kinds of steel samples with different Nb contents were designed.A Gleeble 3800 thermomechanical simulator was employed to study the continuous cooling transformation（ CCT） kinetics of the samples.The metallographic structures and mechanical properties of the samples were also tested.The results shows that the onset transformation temperatures of ferrite are not decreased with the increase of Nb content linearly,but decreases firstly and increases subsequently.The sample with 0.03% Nb addition can meet the requirements of the QSt E420 steel.Based on the results of the CCT tests and Laboratory rolling experiments,the finish rolling temperature and coiling temperature for industrial production of the hot rolled and pickled automotive steel QStE420 are（ 850 ± 20） ℃ and（ 580 ± 20） ℃,respectively.The microstructure of the steel sample is composed of ferrite and pearlite.Excellent mechanical properties are obtained which fully meet the requirements of the standard.