This material specification applies to those grades of gray iron castings intended for a wide range of automotive applications. This standard describes the material properties, not specific casting properties, based on data obtained from separately cast test samples. Any specific property required from a particular casting or section of that casting shall be identified on the engineering drawing.

Material Description. Gray iron is a cast iron in which the free graphite, in the form of flakes, precipitates throughout the metallic matrix. It is the graphite flakes which account for the excellent machinability, wear resistance, damping capacity, low shrinkage characteristics and generally higher thermal conductivity.

Symbols. Not applicable.

Applicability. Gray cast iron is a low-cost material with good hardness, strength, and rigidity. It has excellent castability for complex designs and demonstrates exceptional dampening capacity and thermal shock resistance. The gray cast iron characteristics lend themselves to a wide variety of applications which include cylinder blocks and heads, cylinder liners, bearing caps, camshafts, manifolds, pump bodies and housings, and valve bodies.

Remarks. This specification has resulted in the consolidation of several similar GM North America specifications. Appendix A, Table A1 depicts the GMNA deleted standards and the applicable global replacement grades. Also listed in Appendix A, Table A1 are specialty grades required for special purpose castings. Appendix B, Table B1 shows the relationship between the new global grades, their tensile strengths, the superceded GM regional grades and the corresponding International Standard grade