WM SCK represents a chemical balance which provides an optimum combination of toughness, wear resistance, and minimum distortion during heat treatment. It is recognized that the addition of nickel, with this carbon content, greatly enhances the impact strength, while air hardening characteristics are readily achieved with this composition. While lacking some of the extreme abrasion resistance of the high carbon-high chromium die steels, WM SCK provides equivalent freedom from distortion, and vastly increased toughness.
Heating for forging must be done slowly and uniformly. Soak through at 1900-2000°F, and reheat as often as necessary, stopping work when the temperature drops below 1700°F. After forging cool slowly in lime, mica, dry ashes, or furnace. SCK should always be annealed after forging.
Heat slowly to 1600-1650°F, hold until the entire mass is heated through, and cool slowly in the furnace (25°F per hour) to about 1000°F, after which the cooling rate may be increased. Suitable precautions must be taken to prevent excessive carburization or decarburization.
SCK is an air hardening steel, and will develop full hardness on cooling in still air. If the scaled surface resulting from air cooling is objectionable, the part may be quenched in oil until it has lost its color (1000-1200°F), and then allowed to cool in still air. Parts should be allowed to cool to 150°F, or to where they can be held in the bare hand, and then tempered immediately.
For the optimum combination of hardness and mechanical properties, it is recommended that SCK be tempered at or beyond its maximum secondary hardness, or in the range of 900-1000°F. Double tempering is recommended. The following chart may be used as a guide to the hardness which may be expected after air cooling and tempering at the indicated temperatures.