AISI Type T4 is made by adding 5% cobalt to the conventional 18% tungsten-4% chromium-1% vanadium (AISI Type T1) tool steel. The cobalt dissolves in the ferrite and strengthens the matrix of the steel whereas the other alloying elements form carbides. Thus the cobalt increases the hot or red hardness, thereby enabling the tool to maintain a higher hardness at elevated temperatures. Type T4 is well adapted for cutting hard, gritty materials such as cast iron or other abrasive materials and for cutting nonferrous alloys at high speeds. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on forming, heat treating, and machining. Filing Code: TS-395. Producer or source: Tool steel mills.