A mold is composed of many parts. The quality of the parts directly affects the quality of the mold, and the final quality of the parts is guaranteed by the finishing. Therefore, it is important to control the finishing.

The processing of mold parts can be roughly divided into three categories according to the appearance and shape of the parts: plates, special-shaped parts and shafts. The common process is: rough machining-heat treatment (quenching, quenching and tempering)- Fine grinding-electrical machining-fitter (surface treatment)-assembly processing.

Heat treatment for the parts

In the heat treatment process of the parts, while obtaining the required hardness, it is also necessary to control the internal stress to ensure the dimensional stability of the parts during processing. Different materials have different treatment methods. With the development of the mold industry in recent years, the types of materials used have increased. In addition to Cr12, 40Cr, Cr12MoV, and cemented carbide, for some cores and cavities with high working strength and severe stress, new materials powder alloy steel can be used. , Such as V10, ASP23, etc., this kind of material has high thermal stability and good organization state.

For parts made of Cr12MoV, quenching is performed after rough machining. After quenching, the workpiece has a large residual stress, which is easy to cause cracks during finishing or work. After quenching, the parts should be tempered while hot to eliminate quenching stress. The quenching temperature is controlled at 900-1020℃, then cooled to 200-220℃, air-cooled from the furnace, and then quickly returned to the furnace for tempering at 220℃. This method is called a primary hardening process, which can obtain higher strength and wear resistance. In production, some workpieces with many corners and complex shapes are encountered, and tempering is not enough to eliminate the quenching stress. Stress relief annealing or multiple aging treatments are required before finishing to fully release the stress.

For powder alloy steel parts such as V10 and APS23, because they can withstand high temperature tempering, the secondary hardening process can be used during quenching, quenching at 1050-1080℃, and then tempering at 490-520℃ for many times. With high impact toughness and stability, it is very suitable for molds with chipping as the main failure mode. The cost of powder alloy steel is relatively high, but its performance is good, and it is forming a trend of widespread use.