AISI SAE D-2 Tool Steel

1.2379 AISI D2 is a high carbon, high chromium, molybdenum, vanadium, air hardening tool steel which offershigh surface hardness, good wear resistance, through hardening properties, dimensional stability and high resistance to tempering effect. 1.2379 X155CrVMo12-1 tool steel is also suitable for vacuum hardening.

1.2379 AISI D2 is one of the cold work, high carbon, high chromium type tool steel. D2 is a deep hardening, highly wear resistant alloy. It hardens upon air cooling so as to have minimum distortion after heat treatment. 1.2379 AISI D2 tool steel used for long run tooling applications where wear resistance is important, such as blanking or forming dies and thread rolling dies, cutting tools, stamping, woodworking, moulding tools for plastics. Toughness better than in D3. Possibility of nitriding.

AISI D2 is a high-carbon, high-chromium tool steel alloyed with molybdenum and vanadium characterized by:

• High wear resistance
• High compressive strength
• Good through-hardening properties
• High stability in hardening
• Good resistance to tempering-back.

AISI D2 is recommended for tools requiring very high wear resistance, combined with moderate toughness (shock-resistance). AISI D2 can be supplied in various finishes, including the hot-rolled, pre-machined and fine machined condition.

Forging: Heat slowly and uniformly to 700°C then more rapidly to 900/1040°C.  After forging 1.2379 cool slowly.

Annealing: Anneal at 850°C and slow furnace cool. Hardness after annealing will be approx. 225 brinell.
Hardening: Pre heat the 1.2379 component slowly to 750/780°C and thoroughly soak. Continue heating to the final hardening temperature of 1000/1030°C and allow the component to be heated through. Quenching in oil or cool in air.

Pieces requiring maximum dimensional stability should be sub-zero treated, as volume changes may occur over the course of time. This applies, for example, to measuring tools such as gauges and certain structural components. Immediately after quenching the piece should be sub-zero treated to between –95 to –110°F (–70 and –80°C)—soaking time 3–4 hours— followed by tempering. Sub-zero treatment will give a hardness increase of 1–3 HRC. Avoid intricate shapes as there will be risk of cracking. Sub-zero treatment must always be followed by a series of tempering operations

Tempering: Heat uniformly and thoroughly at the selected tempering temperature and hold for at least one hour per inch of total thickness. Double tempering of 1.2379  is recommended to be carried out with intermediate cooling to room temperature.

Stress Relieving: machining operations have been heavy or if the 1.2379 tool has an unbalanced section, remove stresses before hardening by heating up to 700°C, equalise, then cool slowly.

Hard Chromium Plating: After hard chromium plating tempering of 1.2379 tool steel is recommended at 180°C for 4 hours to avoid hydrogen embrittlement. Tempering is to be performed immediately after chromium plating.

Welding: Good results when welding tool steel can be achieved if proper precautions are taken during welding (elevated working temperature, joint preparation, choice of consumables and welding procedure). If the tool is to be polished or photoetched, it is necessary to work with an electrode type of matching composition.Due to the high risk of crack formation welding of 1.2379 tool steel should be avoided, if possible. When, howe ver welding is essential, the following serves as a guide:

A.   Welding of soft annealed 1.2379 tool steel.
·       Preheat to 300 - 500°C
·       Weld at 300-500°C
·       Immediately stress relieve
Electrode: Cr-Mo alloy electrode for welding structural steel.

B.    Welding in connection with hardening of soft annealed 1.2379 tool steel.
·       Heat to austenitizing temperature.
·       Cool to approx. 500°C
·       Weld at approx. 500°C
·       Cool to approx. 100°C in the same way as at normal hardening, then temper to desired hardness. Double tempering will
reduce the risk of crack formation.
Electrode: Hard facing electrode.

C.    Repair welding of 1.2379 tool steel in hardened and tempered condition.
·       Preheat to the tempering temperature (min. 200°C) previously used.
·       Weld at tempering temperature
·     Heat immediately to tempering temperature, but max. 300°C. Soaking time 2 hours.

Electrode: Hard facing electrode.