Annealing – Generally furnished annealed. Bring part up slowly (400°F/hour) to 1,550°F, and hold at temperature for at least one hour/inch of greatest cross section. Slow cool in the furnace (50°F/hour) to 1,000°F. Then allow cooling to continue in the furnace or still air.
Hardening – Bring up to pre-heat temperature at a rate not to exceed 400°F/hour. For large and intricate items, heat to a uniform 1,150°F/1,250°F, then elevate temp. to 1300°F/1400°F and hold for uniformity. Smaller and less intricate pieces may skip the first step and proceed right to 1300°F/1400°F. Take slowly to the hardening temp. of 1725°F. Hold at temperature (furnace or salt) for 30 minutes for the first inch of thickness, allow an additional 15 minutes for each additional inch of thickness.
Quenching – In air, pressurized gas, or warm oil to 150° F/125°F. Larger sections should be quenched in oil. If using an oil quench, then quench until black (900°F), cool in still air to 150°F/125°F.
Tempering Chart – Immediately after quench, hold at temp. for one hour/inch of greatest cross section (2hrs min.), then air cool to room temperature. Optimum tempering temp. for cold work tools is 400°F. Resulting hardness will be approximately 57 Rockwell “C”, which provides the maximum benefit of toughness to hardness. For sections larger than 6″ diameter, hold at tempering temperature for a min. of 6 hours. For hot work applications double tempering is required.
@ 400°F typical hardness Rockwell “C” 57 (air); Rockwell “C” 58.5 (oil);
@ 1,100°F typical hardness Rockwell “C” 48 (air); Rockwell “C” 48.5 (oil).
* Above values are typical and are not guaranteed.