Abstract
The thermal expansion coefficients of Invar are quite low, normally at (1~2)x10-6/oC(or(0.56~1.1)x10-6/oF). However, due to the low C and Si contents in the alloys (C<0.2%,Si<0.4%), and the austenitic phase in the microstructure, Invar experiences relatively poor machinability and castability. The high-Ni (34~37%) austenitic cast irons, due to their relatively high C and Si contents in the alloys (2%