What are the general requirements for plastic mold manufacturing steel? As for the rigid requirements for plastic mold manufacturing, here is a brief introduction to nought.
When pressing plastics, it can be divided into two types: one is thermosetting plastic, the other is thermoplastics.
Thermosetting plastics, such as bakelite powder, are pressed and permanently formed under heating and pressure. The bakelite dies are periodically subjected to pressure and continue to be heated at 150~200 C.
Thermoplastic plastics, such as polyvinyl chloride, are usually molded by injection molding. Plastic is heated in an independent heating chamber and then injected into a cold mold with softening state, which makes it hard to shape.
The normal operating temperature of injection moulds is 120~180 C, and the temperature is as high as 260 C. But when working, the water cooling cavity is usually used, so the heat, stress and wear degree are lighter. Only some varieties, such as chlorinated and fluorinated plastics, release harmful gas when they are pressed, and have greater erosion on the cavity.
According to the working conditions and characteristics of precision plastic moulds, the following requirements are required for steel used for plastic moulds:
(1) the steel needs to be very clean to obtain highly glossy surface. Therefore, it requires less inclusions, less segregation, dense structure and high surface hardness.
2. The surface should be wear resistant and corrosion resistant, requiring a certain surface hardened layer. Generally, it should be above 45hrc, and the surface finish must remain unchanged for a long time.
It has enough strength and toughness to withstand load without deformation or breakage.
4. Heat treatment has small deformation to ensure interchangeability and accuracy.
It has good electrical processing ability.