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高速钢重复淬火时会产生奥氏体晶粒(A晶粒)的异常长大,结果产生萘断口组织。萘断口是高速钢热处理过程中的缺陷之一,其宏观断口在掠射光照射下,由于各个晶面不同的反光能力而闪烁着晶萘一样的光泽,故被命名为萘断口(也称为鱼鳞状断口)。其微观组织表现为局部或全部晶粒异常粗大。在力学性能方面,其硬度和红硬性与具有正常断口的组织无明显差异,但其脆性很大,冲击、拉伸弯曲、扭转值都比正常断口组织低的多。高速工具钢萘断口主要产生于不进行中间处理情况下的重复淬火;热加工工艺不当;淬火时冷却工艺不当等。目前,除了在重复淬火前进行长时间的高温退火外还没有其它可行的预处理工艺。为此,我们试验了预防萘断口产生的前处理工艺。结果表明,不需进行费时、费能的高温退火而用极简单的一次短时间中间处理工艺就能完全防止在重复淬火时产生的萘状断口。
High-speed steel quenching will produce austenite grains (A grain) abnormal growth, resulting in naphthalene fracture organization. The fracture of naphthalene is one of the defects in the heat treatment process of HSS. The macroscopic fracture is shining with the same luster as crystalline naphthalene due to the different reflective ability of each crystal face under the grazing radiation. Therefore, it is named as naphthalene fracture (also called scale Fracture). The microstructure of the local or all showed abnormal coarse grains. In terms of mechanical properties, its hardness and red hardness and normal fracture with no significant difference between the organization, but its great brittleness, impact, tensile bending, torsion values are much lower than normal fracture tissue. High-speed tool steel naphthalene fracture is mainly generated in the case of no intermediate treatment of repeated quenching; improper thermal processing; quenching, improper cooling process. At present, there is no other feasible pretreatment process besides long-term high-temperature annealing before repeated quenching. To this end, we have tested the pretreatment process for the prevention of naphthalene breakage. The results show that naphthalene fractures produced during repeated quenching can be completely prevented with a very simple, short-time, intermediate treatment without the need for time consuming, expensive annealing.