Plastic Mold Steel Performance Requirements
With the rapid development of the manufacturing industry, plastic molds are indispensable tools in plastic molding processing, and the proportion of total mold production has increased year by year. With the development and continuous production of high-performance plastics, the types of plastic products are increasing. The use continues to expand, and the products are becoming more sophisticated, larger, and more complex. The molding production is developing at a high speed, and the working conditions of the mold are becoming more complicated.
(1) Plastic deformation failure
The surface of the plastic model cavity is pressed and heated to cause plastic deformation failure, especially when the small mold is working on large tonnage equipment, it is more likely to cause overload plastic deformation.The material strength and toughness of the plastic mold are insufficient, and the deformation resistance is low. Another reason for the plastic deformation failure is that the hardened layer on the surface of the mold cavity is too thin, the deformation resistance is insufficient, or the working temperature is higher than the tempering temperature, and the phase change softening occurs. And the mold failed early.
The main cause of the fracture is structural stress, thermal stress or insufficient temper due to structural and temperature differences. At the temperature of use, the retained austenite is transformed into martensite, causing local volume expansion, resulting from tissue stress generated inside the mold.
(3) Wear and corrosion of the cavity surface
The plastic melt flows in the cavity with a certain pressure, and the solidified plastic parts are released from the mold, causing friction on the molding surface of the mold and causing wear. The root cause of the failure of the plastic mold wear is the friction between the mold and the material. However, the specific form of wear and the wear process are related to many factors, such as the pressure, temperature, material deformation speed and lubrication status of the mold during operation.
When the material used in the plastic mold and the heat treatment are unreasonable, the cavity surface of the plastic mold has low hardness and poor wear resistance, and the performance is as follows: the dimensional difference of the cavity surface due to wear and deformation; the roughness value becomes higher due to the pulling of the hair The surface quality deteriorates.
Especially when solid materials are used to enter the mold cavity, it can exacerbate the wear of the cavity face. In addition, the plastics contain chlorine, fluorine and other components to decompose the corrosive gases HC1 and HF, causing corrosion and wear on the cavity surface of the plastic mold, resulting in failure. If the wear and tear are accompanied by wear and damage, the coating or other protective layer on the surface of the cavity is destroyed, which will promote the corrosion process. The intersection of the two types of damage accelerates the corrosion-wear failure.