金型鋳鉄鋳物の冷却速度を表す因子の検討

抄録

  Iron castings with cylindrical plate and spherical shapes were cast into metal molds. Some parameters to express average cooling rate and solidification time of castings and a parameter which shows temperature variation of molds were discussed. Graphite structure of cast iron was classified by cooling rate.
  Mold ratio (volume ratio of mold to casting) and metal mold ratio (thickness ratio in cross-section of mold to casting) were not good parameters to express cooling rate V_av. Ratio of (volume V_c/surface A_c)² of casting was good such as shown in the following equation;
      V_av=267.2 (V_c/A_c)^2×(0.90)
This relation is not affected by the shape of casings.
  For the solidification time, (volume/surface area)² ratio was also suitable as a parameter and the solidification time t_f is;
      t_f=1.43(V_c/A_c)??
where, (V_c/A_c)??=(V_c/A_c)²×Y. Y is corrected coefficient : for cylindrical castings Y=1.00, for plate castings Y=1.27, and for spherical castings Y=0.75.
  For temperature variation of molds, mold ratio was good as a parameter. Fine D-type graphIte will probably be obtained at the cooling rate between 12 to 23.5°C/sec.