Mold parts heat treatment
For the mold part to obtain the required hardness of heat treatment, it is necessary to control the internal stress of the heat treatment of the part, so that the dimensional tolerance and form position tolerance can be stable during and after the processing of the part.The process should take into account economy, material hardenability, hardenability, hyperthermal sensitivity and decarburization sensitivity.
With the development of the mold industry in recent years, there are many kinds of materials used. Apart from CrWMn, Cr12, 40Cr, GCr15, Cr12MoV, 9Mn2V cemented carbide, new material powder alloy steel, such as S2, S3, V10, APS23S1, G2, G3, G4, G8 and so on, can be used for some dies with high working strength and severe stress.The material has high thermal stability and good microstructure.Generally, the workpiece retains internal stress after quenching, which can easily lead to subsequent finishing or cracking in work. After quenching, the workpiece should be tempered when it is hot to eliminate the quenching stress.For workpieces with complex shapes and many internal and external angles, tempering is sometimes not enough to eliminate the quenching stress. It is necessary to conduct de-stress annealing or multiple aging treatment before finishing, so as to fully release the stress.Take different methods according to different requirements.Take the part made of Cr12 as the material for example, after rough processing and quenching, the cooling method only includes air cooling (the heated workpiece is cooled in air. This method is simple to operate, the workpiece deforms little, but the hardness is low, and the surface is easy to be oxidized.Suitable for small size, high precision, uneven thickness of the workpiece), oil cooling (puts the workpiece heated oil, cooled to 300 ℃ ~ 200 ℃, remove the cooling in the air.This method is easy to operate, the workpiece is hard, but deformation is large, easy to produce workpiece deformation, suitable for large size, simple shape workpiece), plate clamping in the air cooling (the heated workpiece is placed between two iron plate or copper plate to cool in the air.This method is more complicated, but the workpiece is less deformed, which is only suitable for the workpiece of a special shape.), fractional quenching (the workpiece is heated and placed in the nitrocellulose which is higher than the temperature of Ms point and stays for a certain period of time. After the internal and external temperatures of the workpiece are basically the same, the workpiece is taken out and cooled in the air.This method can not only guarantee the workpiece hardness, but also reduce the deformation of workpiece.Powder alloy steel parts, such as the V10, APS23 because its can bear high temperature tempering, quenching can be adopted when the secondary hardening process, 1040 ℃ ~ 1080 ℃ quenching, with 490 ℃ ~ 520 ℃ high temperature tempering and for many times, can obtain higher impact toughness and stability, to collapse as the main failure forms of blade mould.