L6 Tool Steel - 1.2714 - 55NiCrMoV7 - SAE L6 - JIS ~SKT 4

Heat treatment

Annealing

Heat the material slowly and uniformly to a temperature of 1202-1292°F (650-700°C) and hold at temperature for 1 hour per inch (25.4 mm) of thickness, but a minimum of 2 hours. Cool slowly in the furnace by 50°F (10°C) per hour to 1000°F (538°C), then continue cooling in air.

For improved machinability cool slowly in the furnace to a temperature of 1250°F (677°C) and hold at that temperature for 8 hours, then cooling it to room temperature in air.

Stress relieving

Heat the work pieces uniformly to a temperature range of 1050-1250°F (566-677°C) and soak for 2 hours. Finish this process off by cooling the parts down in the furnace to 900°F (482°C) and then to ambient temperature in air.

Hardening

Preheat the parts uniformly to a temperature of 1250-1350°F (677-732°C), then continue to austenitizing temperature of 1500-1550 (816-843°C) and hold for 10-30 minutes at this temperature.

To protect the material from excessive scale or decarburization either heat the parts in neutral salt, pack it in cast-iron chips or spend coke or heat in a protective atmosphere or vacuum furnace.

Quenching media

• Oil, warmed – parts should be cooled down to 120-150°F (49-66°C) or until it can be held by hand and then tempered immediately.

• Air – this method of quenching is done for tools with less than 1 inch (25.4 mm) sections. Air quenching is the safer option for intricate sections as air quenching compared to oil quenching will distort parts less.

Tempering

To avoid cracking, temper L6 immediately after quenching. Hold at the chosen tempering temperature for 1 hour per inch (25.4 mm) of thickness, but for at least 4 hours and cool to room temperature. L6 can be tempered at a temperature range of 450-800°F (232-427°C) without getting brittle. To minimize internal stresses for parts with a greater cross section than 6 inches (152.4 mm) and/or to improve stability in tools being EDM’d after the heat treatment, it is recommended to soak the material for 8-10 hours.

For our tempering diagram, please click here.

Sub-zero treatment

Sub-zero treatment can be done as an extension of a quench from the austenitizing treatment or it can be done after tempering.

Machinability

Forging

Heat the work piece slowly and uniformly to a temperature of 1800-1900°F (982-1038°C). Do not let the temperature drop below 1600°F (871°C) and reheat the material as often as needed. After the forging process is done slowly cool the parts in lime, dry ash or in the furnace.

Welding

L6 is generally weldable, it should be pre- and post-heated. For more in detail information please contact your welding shop.