Influence of Cooling Rate on As Cast Microstrucutre of Multi-component White Cast Iron

Abstract

  Four kinds of multi-component white cast irons with different combinations of carbide type were poured into furan molds with different diameters, and cooling curves were taken using a R thermocouple inserted at the center of each mold cavity. The microstructural components in as cast iron, such as γ dendrite arm spacing (D_p), diameter (D_MC) of MC carbide, lamellar spacing (λ_M2C) of M₂C carbide, area fraction (S_eut) of (γ + M₂C) eutectic or that of both (γ + M₂C) plus ( γ + M₇C₃) eutectics, were well related to each characteristic cooling rate, while the area fraction of MC carbide was little affected by the cooling rate. The relations are expressed by, D_P = 25.1 ⋅ V_P^-0.36 (V_P : cooling rate during precipitation of primary γ ), D_MC = 4.4⋅ V_E-MC^-0.18 (V_E-MC : cooling rate during precipitation of ( γ + MC) eutectic), λ_M2C = (1.1∼2.0)⋅V_E-M2C^{-0.28∼-0.21} (V_E-M2C : cooling rate during precipitation of (γ + M₂C) eutectic, S_eut = (2.0∼15.3)⋅V_A^{-0.23∼-0.16} (V_A : average cooling rate from start to end of solidification)