Tensile strengths, nodular irons

Ferrous valves are also available in nodular (ductile) iron, which has tensile strength and yield point approximately equal to cast carbon steel at temperatures of 343°C (6.50°F) and below and only slightly less elongation. 

Nodular cast iron has higher tensile strength than gray iron and will give good service up to 1600 F (871 C). It can be used in tension. Cast irons oxidize quite rapidly at high temperatures, although they are not as susceptible to oxidation as is steel. 

Using the data represented in Figure 6.19, specify equations relating tensile strength and Brinell hardness for brass and nodular cast iron, similar to Equations 6.20a and 6.20b for steels. 

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