抄録
The purpose of this research is to examine the effects of melting conditions and mechanical properties of the specimens, which were cast into the green sand mould of 20-mm diameter, on the evaluation for the quality of flake graphite cast iron. Furthermore, the relation between chemical composition and deflection on the evaluation values for quality was examined on the as-cast specimens. The results obtained are summarized as follows:
(1) On the quality evaluation, the Reifegrad (RG), the relative bending load (RB), the relative hardness (RH) and the relative hardness related to the bending load (RHb) of the cast iron prepared by reducing-refining melting are superior to those of the cast irons prepared by non-reducing refining melting.
(2) From the standpoint of the quality evaluation, the ranges of most suitable chemical composition for the cast irons prepared by the reducing-refining melting are as follows:
Total Carbon 2.90∼3.50% Silicon 1.75∼2.23% Manganese 0.72∼0.84% Phosphorus 0.064∼0.120%
Sulfur 0.020∼0.150% Oxygen 9∼30 ppm
(3) The suitable chemical compositions of the cast irons prepared by nonreducing-refining melting are within the bounds of the following ranges:
Total Carbon 3.05∼3.10% Silicon 1.30∼1.36% Manganese 0.84∼0.88% Phosphorus 0.10%
Sulfur 0.023∼0.026%
(4) The relation between quality evaluation values and deflection was investigated, and the following equations which may explain the values of deflection (D) were obtained:
RB=40.33+14.46D, RHb=1.385−0.088D.
