Typical Young's modulus values of cast irons at room temperature are given in the following chart.
Note* : Gray cast iron does not obey Hooke's law, and the Young's modulus in tension is usually determined arbitrarily as the slope of the line connecting the origin of the stress-strain curve with the point corresponding to 25% of the tensile strength (secant modulus). The Young's modulus of gray iron varies considerably. Thus, in using measured strain to calculate stress, it is essential to measure the modulus of the particular gray iron specimen being considered.
Note** :The modulus of elasticity of ductile iron in tension lies in the range of 162 to 170 GPa (23.5 × 10^{6} to 24.5 × 10^{6} psi) and does not vary greatly with grade.