According to the AISI classification system, chromium hot-work tool steels are designated as group H steels. This series of steel start H1 from H1 to H19.
D2 is tool steel and its content of carbon is 1.5%, the chromium content is 11.5%. The hardness will up to 60HRC by heat treatment. It also can be called DIN 1.2379 steel. DIN 1.2379 steel has good wear resistance and toughness. But its corrosion resistance is not good.