采用热膨胀法测定了高镍铬离心复合铸造球磨铸铁轧辊的相变点,根据其临界转变温度,进行正火和回火试验,研究了热处理工艺对轧辊工作层性能的影响。结果表明,860℃和890℃正火时,轧辊工作层硬度值较高;正火温度为920℃时,冷却后残留奥氏体(Ar)量增多,硬度明显下降;正火温度为830℃时,出现硬度较低的珠光体组织。860℃正火冷却后,在400℃回火时应力消除比较完全,碳化物尚未长大,细小且均匀弥散的分布在针状马氏体基体上,轧辊工作层硬度较高,有利于阻止裂纹的扩展。
Dilatometry was used to determine the phase transformation temperature of a high Ni -Cr centrifugal composite ductile cast iron rolls.Based on the critical transformation temperature , the ductile cast iron rolls were quenched and tempered , and effects of normalizing temperature and tempering temperature on microstructure and mechanical properties were investigated .The results show that hardness of the ductile cast iron roll is higher when normalized at 860-890 ℃.The amount of retained austenite increases when the normalizing temperature is above 890 ℃, which leads to obvious decrement of the hardness .When normalized at 830 ℃, pearlite with lower hardness forms .When normalized at 860 ℃and tempered at 400 ℃, residual stress in the ductile cast iron roll was fully removed , and the fine carbides uniformly and dispersedly distribute in martensite and the hardness is relatively higher which is of benefit to restrain crack propagation .
