两相区淬火+回火对600 MPa级低合金高强钢组织与性能的影响

Effect of intercritical quenching and tempering on microstructure and mechancial properties of 600 MPa HSLA steel

对某600 MPa级低合金高强钢采用了淬火+回火的热处理方式,研究了不同回火温度以及不同淬火温度对其组织性能的影响。结果表明,随着回火温度的升高,屈服强度、抗拉强度以及屈强比都呈下降趋势,伸长率逐渐上升,在620 ℃以上回火时出现第二类回火脆性,导致冲击性能急剧降低;在淬火温度达到820℃后得到的两相区淬火组织为铁素体+粒状贝氏体,有利于阻止裂纹的扩展,确保有较高的冲击性能。

A 600 MPa high strength low alloy(HSLA)steel was heat treated by quenching and tempering,and influence of different tempering temperature and different quenching temperature on its microstructure and mechanical properties were investigated.The results show that the tensile strength,yield strength and yield ratio of the steel decrease with the increase of tempering temperature,but the elongation increases gradually.Type II temper brittleness appears when the tempering temperature is above 620℃,which result in sharp decrease of the impact performance.When the quenching temperature reaches 820℃,ferrite+granular bainite microstructure is obtained,which is conducive to preventing the crack propagation and ensure high impact performance.