HEAT-RESISTANT FERRITIC CAST STEEL HAVING EXCELLENT MELT FLOWABILITY FREEDOM FROM GAS DEFECT TOUGHNESS AND MACHINABILITY AND EXHAUST SYSTEM COMPONENT COMPRISING SAME

摘要

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 / , N: not more than 0.15%, S: (Nb / 20-0.1) to 0.2%, W and / or Mo: not more than 3.2% in total (W + Mo), the balance being Fe and unavoidable impurities, And the area ratio of the niobium carbide (NbC) in the process (隆 + NbC) is 60 to 80% and the area ratio of the manganese chromium sulfide (MnCr) S is 0.2 to 1.2%, excellent melt flowability, A ferrite-base heat-resistant cast steel having gas resistance, toughness and machinability, and an exhaust system part made of the same.