抄録
Invar (Fe-36 % Ni) and Super-Invar (Fe-32 % Ni-5 % Co) are the most famous low thermal expansive Fe-alloy, but they have not been used for castings. We have investigated low thermal expansive cast irons that might have superior castability, machinability and damping capacity. We began the basic research on the relation between the mean coefficient of linear expansion and Ni-Co contents in Fe-2 % C-1 % Si, and examined many specimens which were made with a rapid melting and casting laboratory equipment. These data were analyzed with NAIS (Numerical Analysis with Interpolating System). The results were as follows. (1) At 373K, the minimum mean coefficient of linear expansion was -0.17 × 10-6/K in 24.3 % Ni-11.9 % Co in experimental value and -0.19 × 10-6/K in 24.3 % Ni-12.0 % Co in predicted value with NAIS. (2) At 473K, the minimum mean coefficient of linear expansion was -0.61 × 10-6/K in 24.3 % Ni-11.9 % Co in experimental value and -0.94 × 10-6/K in 24.4 % Ni-12.3 % Co in predicted value with NAIS. (3) Only a few quantities of martensite were found in austenite when the microstructures of the specimens with the minimum mean coefficient of linear expansion were examined.
