Glossary A-CC-CD-EF-GG-II-MN-PP-SS-SS-TT-VW Injection the process of forcing molten metal into a die. Insert a piece of material, usually steel, which is placed in a die so that when molten metal is cast around it becomes an integral part of the die casting. lmpression (A) cavity in a die. (B) the mark or recess left by a ball or penetrator of a hardness tester. Metal saver core used primarily to reduce amount of metal in a casting and to avoid sections of excessive thickness. Multiple cavity die a die having more than one duplicate impression.