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

摘要

A heat-resistant, austenitic cast steel having excellent thermal fatigue properties, comprising by mass 0.3-0.6% of C, 0.5-3% of Si, 0.5-2% of Mn, 15-30% of Cr, 6-30% of Ni, 0.6-5% of Nb, 0.01-0.5% ofN, and 0.01-0.5% of S, C/N being 4-7, and the balance being Fe and inevitable impurities; and a ratio A/B of a Cr-carbide-forming index A to a Nb-carbide-forming index B being 0.6-1.7, wherein A and B are expressed by the formula (1) of A = 8.5C - Nb + 0.05Cr + 0.65Ni - 5, and the formula (2) of B = 7.8Nb.