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当球墨铸铁需要进行表面淬火时,通常事先正火,增加基体中的珠光体量,以便易于得到所需的淬硬层。但随着奥氏体含碳量的增高,淬硬层中的孪晶马氏体量增加,使脆性增加。为了获得位差马氏体组织,以改善淬硬层的性能,我们对珠光体基体和铁素体基体的球墨铸铁,经高频淬火后的淬硬层组织进行了研究。结果表明,铸态球墨铸铁含有较多的铁素体,不经正火可直接进行高频淬火,反而能够获得位错马氏体淬硬层,不但简化了工序,而且可以改善淬火层的性能。
When ductile iron needs to be surface-hardened, it is usually normalized in advance to increase the amount of pearlite in the matrix so that the desired hardened layer can be easily obtained. However, as the carbon content of austenite increases, the amount of twin martensite in the hardened layer increases, thereby increasing the brittleness. In order to obtain the difference martensite structure and improve the properties of the hardened layer, we studied the ductile iron of the pearlite matrix and the ferrite matrix through the hardened layer after high-frequency quenching. The results show that as-cast ductile iron contains more ferrite and can be directly quenched without normalizing. Instead, the dislocated martensite hardened layer can be obtained, which not only simplifies the process but also improves the properties of the hardened layer .