D2 Steel

Alloy D2 is a high carbon, high chromium tool steel alloyed with molybdenum and vanadium giving the steel grade high wear resistance, high compressive strength, good through-hardening properties, high stability with hardening and good tempering resistance as well as outstanding cutting edge retention. D2 can be nitrated without any reduction in hardness.

Applications

Applications for this tool steel include: cutting and stamping tools up to ¹⁵/₆₄ inch (6 mm), precision cutting tool up to ¹⁵/₃₂ inch (12 mm) thickness.

Heat treatment

Annealing

The steel should be protected and heated through to 1560°F (850°C). Then furnace cooled at 20°F (10°C) per hour to 1200°F (650°C), after that it can be freely cooled further in air.

Stress relieving

Heat the material through to 1200°F (650°C) after rough machining and hold for 2 hours. Cool slowly to 930°F (500°C), then it can be freely cooled further in air.

Hardening

Protect work pieces against decarburization and oxidation during hardening.

Preheat to 1110-1290°F (650-750°C).

Austenitizing temperature: 1810-1920°F (990-1050°C) hold that temperature for one hour per inch (25.4 mm) of maximum thickness. Remove the material (the container, if so protected) and cool to 150°F (66°C) in still air or mild dry air blast. Then temper immediately.

For large pieces use oil to quench, this may achieve higher hardness and wear resistance. Quench at a temperature of 1800°F (982°C) and hold the piece in the oil until the temperature reaches 1000-1200°F (538-649°C), then remove and cool further in air. The oil should have a temperature of 150°F (66°C).

Quenching media

• Oil for simple geometries
• Vacuum
• Forced air/gas
• Martempering bath or fluidized bed at 360-930°F (180-500°C), then cool in air

Make sure to temper as soon as the temperature of the tool reaches 120-160°F (50-70°C). D2 will harden through in all standard sizes.

Tempering

Choose the tempering temperature that needs to be achieved, temper twice and cool between tempering to room temperature. Do not let the tempering temperature drop below 360°F (182°C) and hold at the chosen temperature for a minimum of 2 hours.

For our tempering diagram, please click here

Dimensional changes

Dimensional changes during hardening and tempering should be added, with an addition of 0.15% per side if stress relieving is done between rough and semi-finishing. If this is not done the machining allowance should be increased accordingly.

Sub-zero treatment

As volume changes may occur over time, pieces needing maximum dimensional stability, as for example gauges or structural components should be sub-zero treated. The work piece should be sub-zero treated after quenching at a temperature between -95 to -110°F (-70 to -80°C) soaking for 3-4 hours followed by tempering. This treatment will increase the hardness by 154-160 BHN (1-3HRC). Due to cracking, it is not advised to use this treatment for intricate shapes. Follow the sub-zero treatment up with a series of tempering operations.

Electrical Discharge Machining (EDM)

Performing EDM in the hardened and tempered condition, remove the recast layer completely by stoning and polishing. Then giving the tool another temper at approx. 50°F (25°C) below the prior tempering temperature and soak at this temperature for 2 hours.

Machinability

Forging

Preheat the work piece through slowly to a temperature of 1300-1400°F (704-760°C), then increase the heat to 1850-1925°F (1010-1052°C). Do not let the temperature drop below 1700°F (927°C) and reheat the piece when needed. When finished forging equalize the part to approx. 1400-1500°F (760-816°C) and cool slowly in ashes or lime, etc. and anneal as soon as possible. 

Welding

Good results can be achieved, when welding tool steel, if the proper precautions are taken during welding (increased working temperature, joint preparation, choice of filler metals and the welding procedure). In the event that the part is to be polished or photo-etched, it is necessary to work with a suitable electrode type of matching composition.