Injection molds generally need to work in a high temperature environment of 150 to 200 degrees Celsius when producing plastic products in an injection molding machine. Therefore, in the process of manufacturing injection molds, the selection of raw materials needs to be very careful, which will It plays a crucial role in determining the overall service life of the injection mold and the quality of the plastic products produced in the later stage. So what performance requirements should be met when selecting the steel material for the injection mold?
1. Sufficient surface hardness and wear resistance
The hardness of the injection mold is usually below 50-60HRC, and the heat-treated mold should have sufficient surface hardness to ensure that the mold has sufficient rigidity. Due to the filling and flow of injection molding, the mold is required to bear large compressive stress and friction during operation, and the mold is required to maintain the stability of shape accuracy and dimensional accuracy to ensure that the mold has sufficient service life. The wear resistance of the mold depends on the chemical composition of the steel and the hardness of the heat treatment, so enhancing the hardness of the mold is beneficial to enhance its wear resistance.
2. Excellent machinability
Most injection molding molds require certain cutting processing and fitter repair in addition to EMD processing. In order to prolong the service life of the cutting tool, enhance the cutting performance, and reduce the surface roughness, the hardness of the steel for injection molds must be appropriate.
3. Carbon steel of 50 grades has certain strength and wear resistance, and is mostly used for mold base materials after quenching and tempering. High carbon tool steel and low alloy tool steel have high strength and wear resistance after heat treatment, and are mostly used for forming parts. However, high carbon tool steel is only suitable for the manufacture of formed parts with small size and simple shape due to its large deformation during heat treatment.
4. Good thermal stability
The shape of the parts of the injection mold is often complicated, and it is difficult to process after quenching. Therefore, it should be selected as far as possible with good thermal stability. When the two-color mold is formed after heat treatment, the linear expansion coefficient is small, the heat treatment deformation is small, and the size caused by the temperature difference is small. The change rate is small, the metallographic structure and the mold size are stable, and the processing can be reduced or no longer required to ensure the mold size accuracy and surface roughness requirements.
5. Good polishing performance
High-quality two-color injection molding products require a small roughness value on the surface of the cavity. For example, the surface roughness value of the injection mold cavity is required to be less than Ra0.1~0.25, and the optical surface requires Ra<0.01nm, and the cavity must be polished to reduce the surface roughness value. The steel selected for this purpose requires less material impurities, fine and uniform structure, no fiber orientation, and no pitting or orange peel defects during polishing.