论文部分内容阅读
采用砂型、金属型、水冷浇注制备含Cr量为12%的过共晶铸铁。研究冷却速度变化对Cr12铸铁凝固组织中碳化物形成特征及碳化物类型转变的影响,探讨了碳化物类型发生转变的原因。结果表明:冷却速度对碳化物尺寸和碳化物类型有很大影响。在砂型和金属型冷却试样中,凝固组织的组成和初生碳化物的形貌没有明显变化,凝固组织均由块状的M7C3型初生碳化物和菊花状的共晶团(M7C3+奥氏体)所组成。金属型冷却试样的碳化物尺寸和共晶团尺寸比砂型试样的细小。水冷条件下,凝固组织中的碳化物有明显的方向性,碳化物尺寸明显减小,凝固组织中出现了M3C+M7C3混合型碳化物,冷却速度的差异改变了碳化物的类型。
The use of sand, metal, water-cooled cast with Cr content of 12% of hypereutectic cast iron. The influence of cooling rate on the carbide formation and carbide type transformation in the solidified microstructure of Cr12 cast iron was studied. The reason for the change of carbide type was also discussed. The results show that the cooling rate has a great influence on the carbide size and carbide type. In the sand and metal cooling samples, the composition of the solidified structure and the morphology of the primary carbide did not change significantly. The solidified structure consisted of massive M7C3 primary carbides and chrysanthemum eutectic (M7C3 + austenite) Composed of. The carbide size and eutectic size of the metal-cooled specimens are smaller than that of the sand specimens. In the condition of water cooling, the carbide in solidified structure has obvious directionality, the size of carbide decreases obviously, and the mixed carbide of M3C + M7C3 appears in the solidified structure. The difference of cooling rate changes the type of carbide.