How to reduce mold heat treatment deformation?

Reducing deformation during mold heat treatment requires systematic control from four aspects: material selection, structural design, manufacturing process, and heat treatment technology. The core is to reduce the difference in internal and external stress and improve tissue uniformity.

Optimize materials and improve the original structure

Choosing micro deformed steel grades such as 1.2379 and D2 high alloy steel, due to their high content of carbide forming elements (Cr, Mo, V), there is more residual austenite during quenching, which can counteract martensitic transformation expansion and significantly reduce deformation.
Control the distribution of carbides: When carbides are in the form of bands or blocks, it is easy to cause uneven expansion/contraction. Electric slag remelted steel should be selected, and coarse carbides should be crushed by forging to make them finely dispersed.
Pre heat treatment adjustment of microstructure: The forged steel is subjected to quenching and tempering treatment to obtain a uniform martensite structure and reduce the tendency of final heat treatment deformation.

Optimize mold structure design

Avoid sudden changes in cross-section: rounded corners are used at the boundary between thickness and thickness to reduce stress concentration.
Strive for symmetrical design: Asymmetric structures are prone to distortion due to uneven cooling, and a combination structure can be used instead of overall processing.
Add process holes or reinforcing ribs: improve cooling uniformity, or add ribs to parts that are prone to swelling after quenching to limit deformation.

Standardize manufacturing processes and eliminate residual stresses

Stress relief annealing after rough machining: Hold at 630-680 ℃ for 3-4 hours and cool in the furnace to eliminate residual stress generated by mechanical processing and prevent superposition with quenching stress.
Reasonably arrange the process sequence: For molds with clear deformation patterns, trial quenching can be conducted to determine the deformation trend and reserve machining allowance; Or first perform overall heat treatment and then cut into shape (such as semi-circular molds).
Post grinding aging treatment: eliminates grinding stress, stabilizes dimensions, and prevents further deformation during use.

Precise control of heat treatment process parameters

Reasonable heating:
Adopting multi-stage preheating (such as preheating twice at 550 ℃ and 850 ℃) to reduce thermal stress.
Control the heating speed, especially for high alloy steels with poor thermal conductivity, to avoid excessive temperature difference between the inside and outside caused by rapid heating.
Scientific selection of quenching method:
Graded quenching: briefly stay in a salt bath at 250-400 ℃ to make the internal and external temperatures consistent before air cooling, significantly reducing deformation.
Isothermal quenching: It undergoes isothermal transformation in the bainite region, with extremely low structural stress, making it suitable for complex thin-walled molds.
Pre cooling quenching: After being taken out of the furnace, it is first pre cooled in air to 720-760 ℃ to reduce thermal stress.
Fully tempered:
High alloy steel requires 2-3 high-temperature tempering processes (such as 500~520 ℃) to completely eliminate residual austenite and internal stress.
Insufficient tempering can lead to continued structu