AUSTENITIC HEAT-RESISTANT CAST STEEL HAVING EXCELLENT THERMAL FATIGUE CHARACTERISTICS, AND EXHAUST SYSTEM COMPONENT COMPRISING SAME.

摘要

This austenitic heat-resistant cast steel having excellent thermal fatigue characteristics contains, by mass, 0.3-0.6% C, 0.5-3% Si, 0.5-2% Mn, 15-30% Cr, 6-30% Ni, 0.6-5% Nb, 0.01-0.5% N, and 0.01-0.5% S, wherein C/N is 4-7, and the remainder comprises Fe and unavoidable impurities. The ratio A/B, of the Cr carbide formation index A to the Nb carbide formation index B, is 0.6-1.7, wherein A is represented by formula (1): A=8.5C-Nb+0.05Cr+0.65Ni-5, and B is represented by formula (2): B=7.8Nb.