M238 ASSAB high-quality Pre-hardened plastic mold steel, this steel is P20 plus 1.1% nickel, steel surface to the center of uniform hardness, good cutting, EDM and polishing excellent performance, suitable for gasification,
Hard chromium plating and titanium. Uniform hardness and metallurgical structure, has a special heat treatment and hard to 30-34HRC, good polishing performance, easy to reach a mirror-polished, low deformation after use, and the materials available rate, reduce costs, the size requirements for high plastic mold, especially for electrical erosion operation.
Factory state: pre-and hard to 980-1080N/mm2 (30-34HRC)
     This has been heat-treated steel, even hardness, up to 278-311HB ,29-33HRC, never made ​​mold variant, cutting and polishing performance for electrical erosion operation can be used as flame hardened, chrome plated and nitrided.

M238 chemical composition:

     Carbon C: 0.95

     Chromium Cr; 0.5

Tungsten w: 0.5

Manganese Mn: 1.1

Si Si: 0.3

Vanadium V: 0.1

M238 heat treatment process:

     Forging :1050-850 ℃ furnace cooling. Mass recovery :850-900 ℃ furnace cooling.

Stress Relief: Redu even after 1-2 hours in the furnace to stay cool.

Quenching: Oil 840-860 ℃ or air :860-880 ℃. Stay at least 10 minutes, more than 20mm in thickness more than 1mm see every 1 / 2 minutes, so the hardness of approximately 54HRC.

Tempering: tempering time to stay at least one hour, 20mm more than 20mm thick will have more and more every hour.

:720-740 ℃ annealing and heat through insulation sufficient time, then cooling with the furnace to 600 ℃, then cooling in air, from hardness of approximately 240HB (highest)