D2 Tool Steel - High-Carbon, High-Chromium, hot-Work Steel.

A popular grade for toolmakers, D2 is used in a wide variety of tool making applications. Typical applications include blanking dies and punches for sheet in stainless steel, brass, copper, zinc and hard abrasive materials generally. Other application include deep drawing dies, cupping dies, forming dies, sheet metal forming rolls, shear blades for strip and sheet including flying shears, circular cutters for cold rolled strip, trimmer dies, thread rolling dies, cold extrusion dies, broaches, plug gauges, ring gauges, special taps, straybolt taps, brick and tile mould liners, master hobs for cold hobbing plastic moulds and cut moulds for plastics.

Heat the D2 tool steel slowly and uniformly to 700°C then more rapidly to 900-1040°C. After forging cool down slowly.

D2 is supplied in the annealed and machineable condition. Re-annealing will only be necessary if the steel has been forged or hardened by the toolmaker. To anneal, heat slowly and uniformly to 900°C. Soak for three to four hours and allow to cool in the furnace to room temperature. Re-heat to 800-1040°C and again soak for three to four hours. Allow to cool in the furnace to room temperature.

When tools made from D2 tool steel are heavily machined, ground or otherwise subjected to cold work, the relief of internal strains is advisable before hardening to minimise the possibility of distortion. Stress relieving should be done after rough machining. To stress relieve, heat the component to 600-650°C. Soak well and cool in the furnace or in air. The tools may then be finish machined before hardening.

It is preferable to heat the tools in a controlled atmosphere. If this is not possible, pack hardening is recommended. A reducing atmosphere is desirable. Pre heat the D2 tool steel component to 750-800°C. and allow to soak at this temperature. The tools may then be brought up to 1000-1040°C for air cooling, or 980°C for oil quenching. Soak thoroughly at the temperature for thirty minutes per 25mm of ruling section, then cool or quench accordingly. It is important not to exceed 1020°C when heating for hardening.   

Martempering is an alternative hardening procedure which may be used when suitable salt bath equipment is available. By this method internal strain, distortion and risk of quench cracking are reduced to the minimum. Pre-heat dry at 300-400°C. Pre-heat in salt at 800-850°C holding in the salt for ten minutes per inch of ruling section. Raise to the hardening temperature of 950-980°C holding in the salt for ten minutes per inch of ruling section. Marquench in salt at 230-250°C holding in the bath for five minutes 25mm of ruling section. Cool in still air. Tempering will be necessary.

Double tempering is recommended. Tempering of D2 tool steel should be done with the least possible delay after hardening, preferably when the tools are still hand warm. Select a suitable tempering temperature, bearing in mind the service requirements. Heat slowly and uniformly. When the D2 component has reached the desired temperature, soak for at least one hour per 25mm of section. The second tempering should be a repetition of the first. 

Heat treatment temperatures, including rate of heating, cooling and soaking times will vary due to factors such as the shape and size of each D2 steel component. Other considerations during the heat treatment process include the type of furnace, quenching medium and work piece transfer facilities. Please consult your heat treatment provider for full guidance on heat treatment of tool steels.