一、铸件“料硬”的分类灰铸铁“料硬”发生的部位大都在毛坯件的局部。如:棱角、凹槽、凸面、表面等处。对这些部位进行断口检查,可以归纳为全白口、麻口、灰口断面夹有表面1.5min-2mm的白口层和全灰口四种。基本上可分为白口类、灰夹白类和灰口类三类断口组织。其中“料硬”问题多集中在后两类。全白口问题较明显,容易克服,但灰夹白类和灰口类的解决却比较难。对灰夹白类的白口层进行化学成份和金相组织检查,结果如表1所示。其硬度HB值均在275～310之间;对灰口类进行检查的结果见表2。(铸件材质要求HT20-40牌号)。从表2可见,凡属“料硬”铸件,其硅量 First, the casting “material hard” classification Gray cast iron “material hard” parts are mostly in the rough parts. Such as: angular, groove, convex, surface and other places. Fracture inspection of these parts can be summarized as all white, Ma Hau, gray cross-section of the surface of the folder 1.5min-2mm white mouth and full gray mouth four. Basically divided into white mouth class, gray folder white and gray mouth three types of fracture organization. One of the “expected hard” problems are more concentrated in the latter two categories. All-white issue more obvious, easy to overcome, but the gray folder white and gray mouth class is more difficult to solve. The gray stratum white stratum chemical composition and metallographic examination, the results shown in Table 1. The hardness HB value is between 275 ~ 310; the gray mouth class to check the results in Table 2. (Casting material requirements HT20-40 grade). Can be seen from Table 2, all “material hard” castings, the silicon volume