弛豫处理对低碳贝氏体钢组织性能的影响

Effect of relaxation process on microstructure and property in low carbon bainitic steels

用膨胀法测定了贝氏体钢的连续冷却转变曲线,对转变产物进行了显微组织观察,研究了冷却速率对贝氏体组织形成的影响,并讨论了合金元素对试验钢性能的影响。研究表明,试验钢在冷却速率为2℃/s时已有较多的贝氏体组织发生转变;合金元素V抑制了铁素体和珠光体的转变;Cr提高了贝氏体开始转变的温度。结果表明,在很宽温度围内都可以得到以贝氏体为主的转变组织;V的加入扩大了贝氏体转变区,细化了铁素体晶粒;适量Cr的加入提高了试验钢的抗拉强度,并降低了屈强比。

Continuous cooling transformation（CCT）diagram for bainitic steels was measured at different cooling rates with the dilatometer,the transformation phases were observed.The effect of different cooling rate on the transformation of bainite and the effect of the microalloy elements on mechanical properties of the experimental steels were studied.The results show that the greater bainite in the steels is observed at cooling rate of 2 ℃/s;the ferrite and the pearlite transformation can be suppressed due to the alloying V;the starting temperature for bainite transformation is enhance due to the Cr element.The results indicate that the microstructure which is based mainly on the bainite can be obtained in large range of cooling rate;the zone of bainite transformation is expanded and the grain is refined by adding the element V;the yield strength-ultimate tensile strength ratio of the experimental steels is reduced by adding the right amount of element Cr.