新型MQ-P-T技术在高铬铸球中的应用

Application of novel MQ-P-T processes proposed to white cast iron balls

利用水和空气作为淬火介质,对直径为80 mm的Fe-2.4C-12Cr高铬铸球进行多循环淬火-分配-回火(MQ-P-T)处理,并与常规正火和油淬处理后的同尺寸试样的力学性能和微观组织进行对比分析。通过微观表征技术,对MQ-P-T处理后高铬铸铁的强韧化机制进行了探讨。结果表明,经MQ-P-T处理后的高铬铸球径向硬度平均值约为60 HRC,比空冷铸球径向平均硬度约高出17 HRC,比油淬处理试样约提高5 HRC。经MQ-P-T处理后铸球冲击韧度平均值达到12.6 J/cm2,约为空冷冲击韧度的4倍,约为油淬冲击韧度的2倍。经MQ-P-T处理后铸球具有高的硬度和硬度均匀性,其冲击性能亦大大提高。经MQ-P-T处理后铸铁优异的力学性能主要归因于马氏体基体、相当数量的二次碳化物和稳定的残留奥氏体组织。

Based on microstructure desired,Fe-2. 4C-12Cr（ mass fraction, %） white cast iron balls are treated by a multicycle quenching-partitioning-tempering（ MQ-P-T） process,and such a complex process is first simply performed by alternating water quenching and air cooling. For comparison,the white cast iron balls also were treated by conventional normalization（ NOR） process and oil quenching process,respectively. The resultant microstructure was characterized and the effect of the heat treatments on the mechanical properties was evaluated. By means of microscopic characterization technique,the toughening mechanism of white cast iron balls treated by MQ-P-T process was discussed. The results show that,the hardness of 60 HRC are obtained on MQ-P-T white cast iron balls,while the average values in NOR and oil quenching balls are 43 HRC and 55 HRC,respectively. The impact toughness of MQ-P-T ball is 12. 6 J / cm2,which is 4 times larger than NOR ball and 2 times oil quenching one. Microstructural characterization reveals that excellent mechanical properties of the MQ-P-T balls are attributed to the combination of martensite matrix and considerable secondary carbides as well as retained austenite.