轧后冷却条件对低碳贝氏体钢组织性能的影响

Effect of cooling conditions after rolling on microstructure and properties of a low-carbon bainitic steel

为了研究轧后不同冷却条件对高强低碳贝氏体钢组织和性能的影响,采用热模拟试验、扫描电镜、透射电镜和拉伸试验等手段,阐明不同冷却条件下高强低碳贝氏体钢的组织和性能变化规律。结果表明,在终冷温度为510℃时,组织以粒状贝氏体为主,终冷温度为450℃时以板条状贝氏体为主,前者组织中具有更多岛状马氏体;随着冷却速率提高,粒状贝氏体和板条状贝氏体尺寸细化,岛状马氏体减少。此外,不同冷却速率下,较低的终冷温度均具有更高的相变速率,冷却速率为50℃/s时,贝氏体相变速率最大。另外,终冷温度较高时,试验钢呈现出更好的塑性,强度随冷速变化较小;终冷温度较低时,试验钢呈现出更高的强度,但塑性较低,冷却速率对强度有较大的影响。

In order to investigate the effect of different cooling conditions after rolling on microstructure and mechanical properties of a high-strength low-carbon bainitic steel,the dilatometry,field emission SEM,TEM and tensile tests were utilized to clarify the microstructural evolution and property changes of a high-strength low-carbon bainitic steel under different cooling conditions.The results show that,with a final cooling temperature of 510℃and 450℃in the bainite transformation area,the microstructure mainly composed of GB and BF respectively,and more island like martensite was found in the former condition.Moreover,GB and BF microstructure were refined and the portion of island like martensite was reduced as the cooling rate increased.At different cooling conditions,a lower final cooling temperature always led to a higher phase transformation speed,and the highest phase transformation speed acquired at the condition of a cooling rate of 50℃/s.With a higher final cooling temperature,better plasticity and smaller strength variation acquired.On the contrary contrast,superior strength acquired,but lower plasticity and remarkably strength fluctuation.