ASTM A600 specification covers tungsten-type and molybdenum-type high-speed steels available as annealed, hot-rolled bars, forgings, plate, sheet, or strip, and annealed,cold-finished bars or forgings used primarily in the fabrication of tools.
In ASTM A600 here are Seven types of tungsten high-speed tool steels designated T1, T2, etc., seventeen types of molybdenum high-speed tool steels designated M1, M2, M35, M42 etc., and two intermediate high speed steels designated as M50 and M52 are covered. Selection will depend upon design, service conditions, and mechanical properties.
AISI/ASTM T1 tool steel is one of the original tungsten high speed steel. T1 high speed steel is an air or oil hardening tool steel which has good comprehensive performance.
ASTM A600 tool steel M35 is a medium-alloyed high speed tool steel. It is also known as HSSE or HSS-E which is similar to M2, but with 5% cobalt added, which makes better hot hardness and wear resistance.
AISI high speed steel material M42 tool steel is a molybdenum-series high-speed steel alloy with an additional 8% cobalt. High-speed steel M42 steel is widely used in metal manufacturing industries and in cutting tools manufacturing.