The high-carborn high –chromiun cold work tool steels . identified bi the letter D . are characterized by carbon contents ranging from 1.5 to 2.35% carbon and nominal chromium content of 12%. The steels containing molybdenum can be air gardened. While the molybdenum-free grade(D3) is hardened by quenching in oil.
It is not recommended that D series steels be normalized. Generally these steel are supplied in the annealed condition . but they should be annealed after forging and prior to reardenig Tools that cannot be ground after gardening are sometimes stress relieved after rough machining. Espe-cially those that have delicate designs or that vary markedly in cross section. In many instances.
Preheating prior to austenitizing relieves ma-chining stresses adequately.