65Mn弹簧钢盘条相变组织分析

Analysis of phase transformation microstructure of 65Mn spring steel wire rod

为合理制定65Mn盘条控冷工艺和球化退火工艺,使用热模拟相变膨胀法,结合金相组织分析及硬度试验方法,研究65Mn弹簧钢的组织相变规律。试验测定了65Mn动态连续转变CCT曲线,同时测定了该钢种的Ac1、Ac3、Ar1、Ar3等临界相变点温度,结果表明,当冷却速度低于7℃/s时,仅发生铁素体和珠光体组织相变,此时钢中组织为索氏体+珠光体+铁素体,索氏体含量随冷却速度的增加而增加。冷却速度大于7℃/s时,开始发生马氏体相变。冷却速度大于30℃/s时仅发生马氏体相变。采用本试验研究成果,制定了合理的65Mn盘条控冷工艺,生产出了力学性能合格的65Mn盘条。同时制定了合适的盘条球化退火工艺,供下游用户参考,用户使用该工艺对盘条进行球化退火处理,可获得均匀的球化组织。

To reasonably design the cooling-controlled process and spheroidizing annealing process for 65 Mn wire rod,using the thermal simulated phase change expansion method combined with the microstructure analysis and hardness test method,the microstructure phase transformation law of 65 Mn spring steel was studied. The dynamic continuous transition CCT curve of 65 Mn steel was Measured. At the same time,the critical phase transition temperature of Ac1,Ac3,Ar1 and Ar3 of 65 Mn steel were measured. The results showed that only when the cooling rate was lower than 7 ℃/s,there was only the phase transformation of ferrite and pearlite. There were sorbite,pearlite and ferrite,and the content of sorbite increased with the increase of the cooling rate. When the cooling rate was greater than 7 ℃/s,the martensitic transformation occured. While,when the cooling rate was greater than 30 ℃/s,only the martensitic transformation occured. Using the experimental results,a reasonable cooling-controlled process of 65 Mn wire rod was put forward. The 65 Mn wire rod with qualified mechanical properties was produced. At the same time,a suitable spheroidizing annealing process was proposed for downstream user’s as reference. The uniform spheroidizing tissue was obtained by adopting that process.