This document provides guidelines for a uniform system to group metallic materials for welding and other purposes. It defines grouping systems for steels, aluminum and its alloys, nickel and its alloys, copper and its alloys, titanium and its alloys, zirconium and its alloys, and cast irons. The groupings are based on elemental composition ranges specified in material standards and designations. Tables 1 through 3 define the grouping systems for each material class.