Austenitize at 2050°F in salt*
Oil quench to room temperature or salt quench at 1050°F, then air cool to room temperature.
Stress relieve at 300°F - one hour - air cool
Refrigerate at -100°F - equalize - air warm
Double temper at 975°F - 2 hours each - air cool
Resulting hardness Rockwell C61-64
*Time is 30 minutes at temperature. BG-42 requires a longer cycle than normally associated with high speed steel.
The refrigeration cycle is incorporated into the treatment in order to assist in the transformation of retained austenite. To minimize the danger of cracking, the stress relief has been installed at no sacrifice of subsequent hardness response. Multiple tempering , perhaps four times, is recommended when minimum retained austenite is essential.