临界区淬火工艺对Cr-Ti-B系微碳钢组织及织构的影响

Effect of intercritical quenching process on microstructure and texture of Cr-Ti-B micro-carbon steel

采用10℃/s和100℃/s两种加热速率对Cr-Ti-B系微碳钢进行不同温度的临界区淬火处理,到温后保温90 s,分析了加热速率和淬火温度对微碳钢组织的影响规律,并探讨了相变对基体织构的影响机制。结果表明,经10℃/s加热,在低临界区淬火温度(780℃)时,马氏体呈岛状分布,随淬火温度升高,出现马氏体和贝氏体的复合组织。经100℃/s加热,在低临界区淬火温度(780℃)时,马氏体呈链状分布,随淬火温度升高,出现呈网状分布的马氏体。加热速率会明显影响加热过程中的奥氏体形核,慢速加热时主要在铁素体晶界处形核,而快速加热时在珠光体内部形核。10℃/s加热下的试样在830℃具有较强的γ织构和较弱的Goss织构,而100℃/s加热下的试样在830℃具有较强的Goss织构和较弱的γ织构。淬火过程中{110}取向晶粒发生选择性相变有助于削弱Goss织构。

Cr-Ti-B micro-carbon steel was intercritically quenched at different temperatures under heating rates of 10℃/s and 100℃/s,respectively,after reaching the temperature,held for 90 s.The effects of heating rate and quenching temperature on microstructure were analyzed,and the effect mechanism of phase transformation on matrix texture was also discussed.The results show that martensite exhibits island distribution at low intercritical quenching temperature(780℃)when heated at 10℃/s.With the increase of quenching temperature,the composite structure of martensite and bainite is observed.When heated at 100℃/s,martensite shows chain distribution at low intercritical quenching temperature(780℃),and martensite with network distribution appears with the increase of quenching temperature.The nucleation of austenite is obviously affected by heating rate.Nucleation occurs on the grain boundary of ferrite during slow heating,while nucleation occurs inside pearlite during rapid heating.The specimen heated at 10℃/s has strongγtexture and weak Goss texture when quenched at 830℃,while the specimen heated at 100℃/s has strong Goss texture and weakγtexture when quenched at 830℃.The selective phase transformation of{110}oriented grains during quenching is beneficial to weaken Goss texture.