Ferritic heat-resistant cast steel having excellent hot water flow, gas defect resistance, toughness and machinability, and exhaust system parts comprising the same

摘要

A heat-resistant, ferritic cast steel having excellent melt flowability, gas defect resistance, toughness and machinability, which has a composition comprising by mass, C: 0.32-0.45%, Si: 0.85% or less, Mn: 0.15-2%, Ni: 1.5% or less, Cr: 16-23%, Nb: 3.2-4.5%, Nb/C: 9-11.5, N: 0.15% or less, S: (Nb/20 - 0.1) to 0.2%, W and/or Mo: 3.2% or less in total (W + Mo), the balance being Fe and inevitable impurities, and a structure in which the area ratio of a eutectic (´ + NbC) phase of ´ ferrite and Nb carbide (NbC) is 60-80%, and the area ratio of manganese chromium sulfide (MnCr)S is 0.2-1.2%, and an exhaust member made thereof.