Heat resistant spheroidal graphite cast iron, method of manufacturing the same and engine exhaust system part including the same

1. A heat resistant spheroidal graphite cast iron for an engine component, comprising:

carbon (C) in a range from 3.2 weight percent to 3.4 weight percent, silicon (Si) in a range from 4.3 weight percent to 4.8 weight percent, manganese (Mn) in a range from 0.2 weight percent to 0.3 weight percent, molybdenum (Mo) in a range from 0.8 weight percent to 1.0 weight percent, vanadium (V) in a range from 0.4 weight percent to 0.6 weight percent, chrome (Cr) in range from 0.2 weight percent to 0.4 weight percent, niobium (Nb) in a range from 0.2 weight percent to 0.4 weight percent, barium (Ba) in a range from 0.0045 weight percent to 0.0075 weight percent, inevitable impurities, and a remainder of iron (Fe), based on a total weight of the heat resistant spheroidal graphite cast iron,

wherein a content ratio of chrome (Cr) and barium (Ba) (Cr/Ba) is in a range from 26 to 89.

2. The heat resistant spheroidal graphite cast iron of claim 1 , wherein the heat resistant spheroidal graphite cast iron has tensile strength of about 670 Mpa or more at a room temperature, and has high temperature tensile strength of 100 Mpa or more at 700° C. and of 59 Mpa or more at 800° C.

3. The heat resistant spheroidal graphite cast iron of claim 1 , wherein the heat resistant spheroidal graphite cast iron has a thermal expansion coefficient of about 13.5 μm/m·° C. or less, and has eutectoid transformation temperature of from about 920° C. to about 940° C.

4. The heat resistant spheroidal graphite cast iron of claim 1 , wherein the heat resistant spheroidal graphite cast iron has high temperature tensile strength of from 59 Mpa to 70 Mpa at 800° C.

5. The heat resistant spheroidal graphite cast iron of claim 1 , wherein the heat resistant spheroidal graphite cast iron comprises a ferrite structure occupying an area of about 50% or more and a pearlite structure occupying an area of 40% or less in a total area, and

wherein graphite having a spheroidal shape is precipitated in the ferrite structure and carbide is precipitated in the pearlite structure.

6. A component of engine exhaust system comprising the heat resistant spheroidal graphite cast iron according to claim 1 .

7. A method of manufacturing heat resistant spheroidal graphite cast iron, comprising:

forming a molten cast iron including carbon (C) in a range from about 3.2 weight percent to about 3.4 weight percent, silicon (Si) in a range from about 4.3 weight percent to about 4.8 weight percent, manganese (Mn) in a range from about 0.2 weight percent to about 0.3 weight percent, molybdenum (Mo) in a range from about 0.8 weight percent to about 1.0 weight percent, vanadium (V) in a range from about 0.4 weight percent to about 0.6 weight percent, chrome (Cr) in a range from about 0.2 weight percent to about 0.4 weight percent, niobium (Nb) in a range from about 0.2 weight percent to about 0.4 weight percent, inevitable impurities, and a remainder of iron (Fe), based on a total weight;

tapping the molten cast iron into a ladle; and

injecting the tapped molten cast iron into a mold

wherein, prior to injecting the tapped molten cast iron into the mold, barium (Ba) is added into the molten cast iron in a range from about 0.0045 weight percent to about 0.0075 weight percent, and a content ratio of chrome (Cr) and barium (Ba) (Cr/Ba) is in a range from about 26 to 89.

8. The method of claim 7 , wherein tapping the molten cast iron into the ladle comprises adding a first inoculants into the molten cast iron, and wherein injecting the tapped molten cast iron into the mold comprises adding a second inoculant into the molten cast iron.

9. The method of claim 7 , wherein forming the molten cast iron comprises

forming a preliminary molten cast iron;

analyzing the preliminary molten cast iron by a thermal analysis or a mass spectrometer; and

adding a deficient ingredient into the preliminary molten cast iron.