According to thermodynamics and kinetics of phase transformation,a mathematical model of phase transformation was proposed,and the microstructure evolution of an 82B rod at different cooling rates was simulated by usi...According to thermodynamics and kinetics of phase transformation,a mathematical model of phase transformation was proposed,and the microstructure evolution of an 82B rod at different cooling rates was simulated by using the FEM software Marc/Mentat,based on the measurement of time-temperature transformation（TTT）curves of the 82B rod.The simulated results were in good agreement with the actual measurements.From the results of computer simulation it was found that the cooling rate of the 82B rod,after laying,should be controlled within 5-8 ℃/s.In the microstructure of rod there were over 95% of pearlite volume fraction and a small quantity of dispersive martensite（less than 5%）.展开更多
With the investigated subject of 82B rod, the interlamellar spacings of pearlite at different isothermal transformation temperatures and different cooling rates during continuous cooling transformation were measured, ...With the investigated subject of 82B rod, the interlamellar spacings of pearlite at different isothermal transformation temperatures and different cooling rates during continuous cooling transformation were measured, and the effect of the isothermal transformation temperature and cooling rate on the interlamellar spacing was analyzed quantitatively. Moreover, the relationship models between undercooling and interlamellar spacing were presented by data regression. The experimental results show that the relationship between undercooling and reciprocal interlamellar spacing remains linear when the undercooling is not very large, or else, the interlamellar spacing tends to be constant and the relationship will deviate from linearity.展开更多
为探明Φ12.5 mm 82B硬线盘条网状渗碳体形成机理,采用碳元素分析与金相组织检测相结合的方法,研究盘条径向上碳元素分布规律及不同级别网状渗碳体的显微金相组织。研究结果表明:在铸坯冷却过程中渗碳体沿奥氏体晶界析出,而w(C)高是形...为探明Φ12.5 mm 82B硬线盘条网状渗碳体形成机理,采用碳元素分析与金相组织检测相结合的方法,研究盘条径向上碳元素分布规律及不同级别网状渗碳体的显微金相组织。研究结果表明:在铸坯冷却过程中渗碳体沿奥氏体晶界析出,而w(C)高是形成网状渗碳体的主要原因,在盘条径向上w(C)呈抛物线规律分布,w(C)随距中心点距离的增大先升高后降低,在距中心点4~4.5 mm的点位上w(C)达到峰值,最高为0.827%,C偏析指数为1.02;网状渗碳体等级随着w(C)增大而升高,当网状渗碳体达到2级时,晶界处存在较强的应力集中,裂纹快速发展,盘条的质量大幅降低,引发拉拔脆断;通过优化控冷参数,1级以下级别网碳出现概率提高了4.73%,达到96.33%,钢材质量均匀性大幅提升。展开更多
基金Item Sponsored by the National Doctorate Fund by the Ministry of Education of China(20020008011)
文摘According to thermodynamics and kinetics of phase transformation,a mathematical model of phase transformation was proposed,and the microstructure evolution of an 82B rod at different cooling rates was simulated by using the FEM software Marc/Mentat,based on the measurement of time-temperature transformation（TTT）curves of the 82B rod.The simulated results were in good agreement with the actual measurements.From the results of computer simulation it was found that the cooling rate of the 82B rod,after laying,should be controlled within 5-8 ℃/s.In the microstructure of rod there were over 95% of pearlite volume fraction and a small quantity of dispersive martensite（less than 5%）.
文摘With the investigated subject of 82B rod, the interlamellar spacings of pearlite at different isothermal transformation temperatures and different cooling rates during continuous cooling transformation were measured, and the effect of the isothermal transformation temperature and cooling rate on the interlamellar spacing was analyzed quantitatively. Moreover, the relationship models between undercooling and interlamellar spacing were presented by data regression. The experimental results show that the relationship between undercooling and reciprocal interlamellar spacing remains linear when the undercooling is not very large, or else, the interlamellar spacing tends to be constant and the relationship will deviate from linearity.
文摘为探明Φ12.5 mm 82B硬线盘条网状渗碳体形成机理,采用碳元素分析与金相组织检测相结合的方法,研究盘条径向上碳元素分布规律及不同级别网状渗碳体的显微金相组织。研究结果表明:在铸坯冷却过程中渗碳体沿奥氏体晶界析出,而w(C)高是形成网状渗碳体的主要原因,在盘条径向上w(C)呈抛物线规律分布,w(C)随距中心点距离的增大先升高后降低,在距中心点4~4.5 mm的点位上w(C)达到峰值,最高为0.827%,C偏析指数为1.02;网状渗碳体等级随着w(C)增大而升高,当网状渗碳体达到2级时,晶界处存在较强的应力集中,裂纹快速发展,盘条的质量大幅降低,引发拉拔脆断;通过优化控冷参数,1级以下级别网碳出现概率提高了4.73%,达到96.33%,钢材质量均匀性大幅提升。
