Relationship between continuous cooling transformation behavior and chromium content of multi-component white cast iron

摘要

Multi-component white cast iron contains basically 5 mass% of Cr, Mo, W, V, each and 2 mass% of C and Co. The effect of Cr content in the cast iron on continuous cooling transformation behavior was investigated by varying Cr content from 1 mass% to 9 mass%. The austenitizing temperatures used in this experiment were 1273K and 1373K. For up to 5 mass% Cr, the critical cooling rates of pearlite transformation (V{sub}(c-p)) were 0.15 K 5 at 1273K and 0.08 K 5 at 1373K austenitization. As Cr content was increased to more than 5 mass%, however, both the V{sub}(C-P) decreasd gradually, and at 9 mass% Cr, they were 0.055K 5 and 0.029K 5, respectively. The critical cooling rate of bainite transformation (V{sub}(C-B)) decreased continuously with an increase in Cr content. The relations can be expressed by the following equations; 1273K austenitization: V{sub}(C-B) = 5.1 e{sup}(-0.4·% Cr) 1373K austenitization: V{sub}(C-B) = 5.0 e{sup}(-0.5·% Cr) Regardless of the austenitizing temperature, the Ms temperature decreased as the Cr content rose to 5 mass%, increasing to over 5 mass% Cr. Mf temperature was seen in irons containing more than 5 mass% Cr and in the case of 1273K austenitization, and it rose with an increase in Cr content. The maximum macro-hardness of transformed specimen decreased uniformly as Cr content increased.