一种低焊接裂纹敏感性钢的奥氏体粗化温度研究

通过高温淬火试验观察试验钢奥氏体晶粒尺寸的变化情况.结合金相和TEM观察、显微硬度和第二相粒子的溶解度积公式分析了加热温度和保温时间对试验钢奥氏体晶粒粗化温度、第二相粒子的溶解情况以及显微硬度值的影响.结果表明:试验钢的奥氏体粗化温度在1200℃附近.当加热温度低于1200℃时,大量细小的第二相粒子阻碍奥氏体晶粒粗化;当加热温度高于1200℃时,细小的第二相粒子溶解,奥氏体晶粒出现异常长大.确定试验钢的合理加热温度为1150～1200℃,在此范围内可获得淬火组织的显微硬度值低于HV330.

Study on Austenite Grain Coarsening Temperature of a Steel with Low Sensitivity to Weld Crack

The change in austenite grain size of a steel with low sensitivity to weld crack was investigated via high-temperature quenching test. The correlation between reheating temperature, holding time, starting temperature for austenite grain coarsening and micro-hardness was discussed via metalloscope/TEM observation, hardness test and the equations of second phase particles' solubility product. The results showed that the austenite grain coarsening temperature of specimens is about 1200°C. When the reheating temperature is lower than 1200°C, a great number of fine second phase particles will hinder the austenite grains from coarsening, and they will be dissolved and growing abnormally when higher than 1200°C. It was found that the reasonable reheating temperature range is from 1150°C to 1200°C, within which micro-hardness of quenched structure is lower than HV330.