MTD 3 is a Mn-Cr-Mo-V plate steel used in cavity molds. ArcelorMittal USA MTD steels comprise a family of prehardened alloy plate steels developed for a variety of mold, tool, and die applications. This datasheet provides information on composition. It also includes information on forming, heat treating, machining, and joining. Filing Code: SA-798. Producer or source: ArcelorMittal USA, Plate.