Material Properties Gray Cast Iron Astm Class 20 admin May 20, 2016 Material Properties for Gray Cast Iron Astm Class 20 Physical specifications of materials. Materials Gray Cast Iron Description Astm Class 20 Density g/cc 7.15 lb/in^3 0.258 Hardness Brinell unless specified 156 Tensile Strength ultimate Mpa 152 Ksi 22.04 Yield Strength MPa Ksi Modulus of Elasticity Gpa 83 10^6 Psi 12.028985488 Poisson’s Ratio 0.29 %Elongation at break %Reduction of area Izod Impact J Ft-lb Fracture Toughness Mpa(m)^0.5 Ksi(in)^0.5 Thermal conductivity W/m-K 50 Btu/ft-h-F 28.9017341 Specific Heat Cpacity J/g-K Btu/lb-F Coefficient of thermal expansion 1E-6/K 13.5 1E-6/F 7.5112781895 Electrical Resistivity Ohm-cm 0.00008