等温温度对82B高碳钢过冷奥氏体转变的影响

Effect of isothermal temperature on undercooled austenite transformation of82B high carbon steel

为研究等温温度和冷却速度对82B盘条钢组织演变规律的影响,采用DIL805A热膨胀仪测定了其静态CCT曲线和等温转变热膨胀曲线,利用扫描电镜分析了工艺参数对过冷奥氏体转变的影响,并讨论了相变孕育时间和持续时间的变化原因。结果表明:随着等温温度的降低,相变孕育时间和持续时间都呈现逐渐缩短的趋势,组织中非片层状形貌含量逐渐增多,在610℃等温及以10℃/s冷却的试验钢相变孕育时间和持续时间分别为6. 61s和16. 50s;而随着冷却速度的增加,相变持续时间呈现先增大后减小的趋势; 610℃等温得到的微观组织主要由片层状珠光体组成,且随着冷速的增加,珠光体片层间距逐渐减小; 550℃等温组织中出现了大量的非片层状组织形貌,珠光体的分布变得杂乱无章。

In order to study the influence of isothermal temperature and cooling rate on mierostructure evolution of 82B wire rod,the statics CCT curves and isothermal transformation thermal expansion curves were measured by DIL805A dilatometer,and the influence of technological parameters on the microstrueture evolution were analyzed by using SEM,and the reasons for the change of phase transition incubation time and duration were also discussed.The results show that with the decrease of isothermal temperature,the phase transition incubation time and duration tend to be gradually reduced,and the content of non-lamellar microconstituents in the microstructure is increased gradually.When the isothermal temperature is 610℃ and the cooling rate is 10℃/s,the phase transition incubation time is 6.61s and the duration is 16.50s.With the increase of cooling rate,the duration of phase transformation first increases and then decreases.The microstructure at isothermal temperature 610℃ mainly consist of lamellar pearlite.With the increase of cooling rate,the pearlite interlaminar spacing is gradually reduced;when the isothermal temperature is 550℃,a large amount of non-lamellar microconstituents is appeared,and at the same time,the distribution of pearlite also becomes disorganized.