Basic properties of Japanese plastic die steels

Abrasive:

It is necessary to carry out highly mirror processing for transparent plastic products such as fan blades, TV front case, stereo system case or cosmetic pattern cover mould. Plastic lens or plastic disc also requires cavity surface roughness Ra in 0.01μm below the mirror. In the process of mirror processing and grinding, it is necessary to prevent the generation of pores. The pores result from hard nonmetallic inclusions or thick carbides sandwiced inside the steel. These inclusions or carbides have poor adhesion with the matrix, and are easy to peel off. They fall off from the matrix to form pores during grinding. When the hardness of plastic die steel is low, the abrasive material or into the matrix, or bring grinding scars. Not only should the external defects such as high hardness be reduced, but also the hardness difference with inclusions be small, so that the matrix and inclusions are evenly ground to reduce the incidence of pores. (Note: Japanese plastic mold steel used for high mirror plastic mold steel types are: Japan Datong mold steel NAK80, S-STAR, G-STAR, D-STAR, PD613, NAK-PRM, NAK101, and Japan Hitachi mold steel HPM38, HPM50, CENA1, etc.) The relationship between surface pitting production and hardness is shown in Fig. 1.

Etch machinability:

In the dust cover, makeup case, OA output amplifier equipment and other emphasis on the design of the opaque plastic products, in order to eliminate the gloss or increase decorative additional patterns. This pattern attached to the surface of the mold is implemented through etching processing.

The etching process caused by chemical reaction is greatly affected by the quality of die material and its history. Because of the chemical composition, crystal structure, grain size, etching shape, roughness, luster is not the same. There is also the existence of composition segregation or tissue segregation of die materials, resulting in etching chaos, damage to the appearance of products. Therefore, it is necessary to be a plastic mold material without segregation, uniform structure, fine grain size, especially without segregation of composition or structure.

Weldability:

Plastic mold due to the design changes after the creative plan or processing half of the surface defects often have welding repair. Of course, as a mold material, it is hoped that the welding repair is easy, and the part of the repair does not produce etching chaos.

In addition according to the type of resin requirements of corrosion resistance, wear resistance.