Types H10 to H19 exhibit controlled chromium content alongside various other alloying elements. The initial four types, which include molybdenum, demonstrate outstanding toughness and a high capacity for hardening. As a result, they are commonly employed in cold work applications that demand toughness even at relatively elevated levels of hardness.
Types H21 to H26 feature controlled tungsten content in combination with other alloying components. These steels offer superior resistance to the softening effects of elevated service temperatures but possess a lower level of toughness.
Types H41 to H43 represent low-carbon adaptations of molybdenum high-speed tool steels (refer to Note 1), exhibiting characteristics akin to the tungsten-based types.
See ASTM A681