鋳鉄円筒鋳物の機械的強度と共晶セル組織に及ぼす冷却速度の影響

抄録

  It was found that the cooling rate of castings becomes smaller as the diameter of cores becomes smaller with the increase of the sectional area and mass of castings and moreover that the cooling rate varies with the number of eutectic cell and mechanical strength¹⁾. The solidification time of cylindrical castings is a function of n-th power of casting' modulus. The n-th value of an index number is obtained to be n=1.74 in numerical calculation and n=1.76 in experimental value, and thus in both cases approximates n≒1.8. As a result, an equation of the solidification time of castings expressed as t_f=K(V/S)^1.8 is obtained. (2) A straight linear relationship, by the logarithmic graph, can be established between n-th power of casting' modulus (M), average cooling rate (V_s) and number of eutectic cells (N_e), from which equations V_s=BM^−nf, N_e=FM^−nf are obtained. Here, the f value becomes close to f≒1, thus n=1.8 is obtained. (3) The mechanical strength is considered to be closely related to the reciprocal of the casting' modulus, and the appropriate equation obtained was σ_B=K₁[1/(V/S)]ⁿ, H_B=K₂[1/(V/S)]ⁿ, wherein the K value varies with mass and material quality. (4) The relationship between the cooling rate of the cylindrical castings, mechanical strength and number of eutectic cell is σ_B=C₁V_s^f, H_B=C₂V_s^f, N_e=EV_s^f. (5) While, the relationship between mechanical strength and the number of eutectic cell is σ_B=H₁N_e^f, H_B=H₂N_e^f. Thus, these relationships are considered to be expressed in general terms by the following equation : Y=aX^b.