Thermal Expansion Behavior of Alloyed Pearlitic Flake Graphite Cast Irons

Precise understanding of thermal expansion behavior of flake graphite cast irons is essential to know the thermal fatigue resistance of these irons when used for elevated temperature application like diesel engine components, ingot moulds, hot mill rolls, glass moulds, dies, etc. Twenty-three pearlitic flake graphite irons having identical base compositions (levels of sulfur, manganese, phosphorus, dissolved gases, and trace elements) having two levels of carbon (3.93 percent and 3.00 percent) and alloyed with elements such as molybdenum, vanadium, chromium, tin, nickel, copper, antimony, and aluminum were produced by carburizing steel scrap in an electric melting furnace. Thermal expansion behavior of all these irons were studied with the help of a dilatometer to determine the influence of graphite morphology and chemical composition. It is seen from the results that thermal contraction of flake graphite irons follows a different path during cooling than the thermal expansion path followed during heating. Further increase in graphitic carbon and coarseness of graphite tend to lower the coefficient of thermal expansion. Additions like molybdenum/copper at high level help in reducing thermal expansion; higher content of tin/antimony/aluminum/silicon tend to increase it while chromium/nickel/copper at low level have no effect. The present investigation has thus provided information regarding thermal expansion/contraction behavior of twenty-three flake graphite irons having almost all commonly used alloying elements.