1992 年 32 巻 11 号 p. 1163-1169
An experimental study has been made of the effects of alloying elements and austenite destabilization heat treatment on the graphitization in the as-cast and heat treated condition, of a high chromium cast irons containing 3.8%C-11%Cr-2.3%Si-5.5%Ni-1.3%Mn-1.2%Mo as hypereutectic alloy and 3.4%C-7.5%Cr-2.5%Si-1%Mn-1.3%Mo as hypoeutectic alloy. The granular graphites are crystallized in the matrix hypereutectic high chromium cast irons containing copper, phosphorous and vanadium in as-cast state, but the aluminum alloyed melt is solidified with the flake type graphite. The concentrations of graphitizers of silicon, nickel and copper appear higher in the graphite-matrix interface than in the matrix but the concentration of chromium appears very low comparing to that in the matrix. This means that it is possible to substitute copper for nickel which is commonly adopted as a graphitization element in high chromium rolls containing crystallized graphite. Inoculating the hypoeutectic alloys with metallic aluminum and ferrosilicon powder in inoculant dressing process, it is possible to crystallize granular type graphite instead of flake type graphite and increase also the volume of graphite. The number and volume of graphite increase remarkably as the high chromium cast iron containing crystallized graphite are heat treated at 950°C for 90 min. Such an increase of graphite is because a temper carbon and the secondary graphite are precipitated by the first stage graphitization. This result must be considered in dressing the graphite volume fraction in manufacturing high chromium rolls containing crystallized graphite.
