HS and HSS are describing the same steel HS (High Speed) Steel or HSS (High Speed Steel).HSS-E has added cobalt and is used for machining material with a high hardness and long cutting channels where high temperatures might be generated.AHSS belongs to the group of unalloyed steel and name the modern, high strength, unalloyed cold work steels. AHSS stands for “Advanced High Strength Steel” and does not belong to the high speed steel group by definition.