D6 Steel: Key Precautions for Heat Treatment, Use & Maintenance

Notes for Heat Treatment Process

Annealing

The as-delivered D6 steel raw material that has already been annealed does not need repeated annealing. Re-annealing is only required for reprocessing after forging or quenching. Clean the oxide scale and impurities on the steel surface before annealing to prevent impurity penetration from affecting the hardness uniformity. Strictly control the temperature between 850℃ and 880℃, and adopt isothermal annealing process for D6 steel: cool to the specified range for isothermal holding after heat preservation, and finally cool with the furnace to the low-temperature range before discharging and air cooling. Too fast cooling rate will lead to high hardness, and only the hardness meets the standard after normal annealing can the subsequent cutting performance be guaranteed.

Quenching

The quenching temperature of D6 steel is controlled between 975℃ and 1025℃, adjust the specific temperature according to the size and shape of the die. Calculate the holding time according to the corresponding proportion of thickness to avoid uneven hardness caused by insufficient holding. Oil cooling is preferred as the quenching medium, which can obtain higher hardness and wear resistance, and the hardness can reach a high range after quenching. Ensure uniform and sufficient cooling for large-size workpieces to avoid insufficient hardening of the core of D6 steel.

Tempering

D6 steel must be tempered in time after quenching, it is better to leave an interval of no more than several hours to completely eliminate the quenching stress and avoid spontaneous cracking during placement. The tempering temperature is controlled between 150℃ and 250℃, adjust it according to the required hardness and toughness, and keep the tempering for a sufficient time. The hardness after tempering will decrease slightly with the increase of temperature, but the toughness will increase synchronously, so it is necessary to balance the hardness and toughness indexes of D6 steel to select parameters.

Notes for Scene Selection

Recommended Adapted Scenes

It is suitable for high-wear-resistance required cold-working conditions such as blanking dies, cold extrusion dies, cold heading dies and wire drawing dies. It can keep the cutting edge sharp for a long time, reduce the number of grinding times and greatly improve production efficiency. It can also be adapted to large-size workpieces, and realizes full-section hardening relying on the high hardenability of D6 steel. It can also be used to manufacture measuring tools such as measuring fixtures and gauges that require stable dimensions, or injection molding and die-casting cooling dies with low performance requirements.

Inappropriate Scenes to Avoid

It is not recommended for working conditions subject to large alternating impact loads. D6 steel has limited toughness and is prone to crack under large impact. Do not use it directly in strong corrosive environments. Although it contains chromium and has certain corrosion resistance, it can only adapt to humid and slightly corrosive environments. Strong corrosion requires surface treatments such as nitriding and titanium plating in advance. It is also not suitable for scenes with extremely high machinability requirements and low cost requirements, because D6 steel is difficult to process and has a high overall cost.

Notes for Daily Maintenance

Clean the working surface of D6 steel in time after use. After each operation, clean the iron chips, residues and oil stains at the cutting edge and cavity of D6 steel to avoid corrosive residues from adhering to D6 steel for a long time and damaging the surface accuracy and material of D6 steel.

For idle storage protection of D6 steel, store D6 steel in a dry and ventilated environment for long-term storage, apply anti-rust oil to key working surfaces such as cutting edge and cavity of D6 steel to avoid rust affecting the use accuracy of D6 steel.

For standard grinding operation of D6 steel, when grinding the worn cutting edge of D6 steel, control the single feed amount to avoid a large amount of cutting heat generated by too fast feed, which will lead to softening of the surface material of the D6 steel cutting edge and reduce the subsequent wear resistance of D6 steel. Cemented carbide grinding wheels are preferred for grinding D6 steel.

For regular inspection of D6 steel products, check the wear amount of the cutting edge and the size of the die cavity of D6 steel regularly in mass production scenarios, deal with tiny cracks on D6 steel in time to avoid crack expansion leading to the overall scrap of the D6 steel die.