How to choose injection mold materials


The injection molding mold is subjected to the combined […]

The injection molding mold is subjected to the combined action of force and heat when it is working. Its working conditions are different from the cold-punching mold. The force received includes the pressure when the mold is closed, the pressure of the melt in the cavity, and the pulling force when the mold is opened. The pressure of the melt is the main factor, and the injection molding mold generally works at a certain temperature, and the temperature fluctuates.
In addition, injection molding molds are also subject to plastic friction and may be corroded by corrosive gases when working. The working conditions of injection molding molds are relatively harsh. To ensure that the mold has a certain life, the injection molding mold materials, especially the molded parts materials, must Meet certain requirements.
First: Excellent machining performance: Choose steel grades that are easy to cut and can be processed with high precision. Medium carbon steel and medium carbon alloy steel are the most commonly used. This is especially important for large molds. For parts that require EDM, It is also required that the burn hardened layer of this steel is thinner.

Second: Excellent polishing performance: Most of the working surface of the formed parts needs to be polished to reach the mirror surface, Ra<0.05um, and the hardness has exceeded 40hrc. However, a too hard surface will make it difficult to polish. The microstructure of the steel should be uniform and dense, with more impurities Few, no blemishes and pinpoints.
Third: Good wear resistance and fatigue resistance: The cavity is not only eroded by the high-pressure plastic melt, but also affected by the temperature stress of alternating cold and heat. The selected steel grade should make the injection molding mold reduce the number of polishing and repairing molds , It can maintain the dimensional accuracy of the cavity for a long time, and meet the requirements of the injection mold for the service life of mass production. It is especially important for the injection molding production of more than 300,000 injections and fiber reinforced plastics.
Fourth: Corrosion resistance: For some plastics, such as polyvinyl chloride and flame-retardant plastics, steel types with corrosion resistance must be considered.