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在两相区+亚温区球化退火工艺的基础上,对SCM435冷镦钢进行球化退火试验。根据SCM435钢的化学成分,利用Thermo-Calc软件进行热力学计算得到对应的A_1、A_3温度分别为728℃、780℃。在综合分析影响球化效果因素的基础上,重点考虑亚温区保温温度、保温时间对球化效果的影响,依次进行试验方案的设定。由试验结果可知:当在两相区温度为758℃,保温30 min时,亚温区保温温度688~698℃,保温4~5 h时,会得到良好的球化效果和较低的硬度;缩短两相区保温时间为25 min时,亚温段在698℃下保温4 h,就可以得到很好的球化组织和较低的硬度。
Based on the spheroidizing annealing process in two-phase zone + sub-temperature zone, the spheroidizing annealing test of SCM435 cold heading steel was carried out. According to the chemical composition of SCM435 steel, thermodynamic calculation using Thermo-Calc software resulted in the corresponding A_1, A_3 temperatures were 728 ℃, 780 ℃. Based on the comprehensive analysis of the factors influencing the spheroidization, the influence of the holding temperature and the holding time of the sub-temperature zone on the spheroidizing effect is mainly considered, and the setting of the experimental scheme is carried out in turn. From the test results, it can be seen that when the two-phase zone temperature is 758 ℃ and holding time is 30 min, the holding temperature in the sub-temperature zone is 688 ~ 698 ℃ and the holding time is 4 ~ 5 h, the good spheroidizing effect and low hardness are obtained; Shortening the two-phase zone holding time of 25 min, the sub-temperature segment at 698 ℃ for 4 h, you can get a good ball organization and lower hardness.