First, in the process of die-casting

1. A cooling temperature control system should be set to keep the working temperature of the mold within a certain range.

2.During the production process, the mold temperature keeps rising. When the mold temperature is too hot, it is easy to produce sticky molds, and the moving parts fail to cause damage to the mold surface.

3. Precise plastic molds should be preheated to a certain temperature before production. Otherwise, when the high-temperature metal liquid is filled, it will cause chilling, which will cause the temperature gradient inside and outside the mold to increase, forming thermal stress, cracking and even cracking the mold surface.

Second, during the mold processing

1. The stress generated during quenching of steel is the result of the superposition of thermal stress during cooling and the structural stress during phase change. Quenching stress is the cause of deformation and cracking. It must be tempered to eliminate stress.

2. Improper heat treatment will cause the mold to crack and be scrapped prematurely, especially using only quenching and tempering, and then surface nitriding process, surface cracking and cracking will occur after thousands of die casting.

Third, in the mold processing and manufacturing process

1. EDM produces stress. A bright white layer rich in electrode elements and dielectric elements is produced on the surface of the mold, which is hard and brittle. This layer itself has cracks and stress. High frequency should be used in EDM to minimize the white bright layer. It must be polished and removed, and tempered. Tempering is performed at tempering temperature.

2. Quality problems of blank forging. Some molds cracked after only a few hundred pieces were produced, and cracks developed quickly. It may be that only the external dimensions are guaranteed during forging, and dendritic crystals, inclusion carbides, shrinkage holes, air bubbles and other loose defects in the steel are extended and elongated along the processing to form a streamline. This streamline is the last one in the future. Hardening deformation, cracking, brittle cracking during use, and failure tendency have a great impact.

3. Grinding stress is generated during grinding of quenched steel, frictional heat is generated during grinding, and a softened layer and a decarburized layer are generated, which reduces the thermal fatigue strength and easily causes hot cracking and early cracking. After finishing the h13 steel, it can be heated to 510-570 ° C and maintained at a thickness of 25mm for one hour for stress relief annealing.

4. Cutting stress generated during turning, milling, planing and other final processing, this stress can be eliminated by intermediate annealing.

I believe that in the above three processes, try to follow the steps as much as possible, and carefully check, it will inevitably reduce the loss caused by stress, and the output of plastic molds will be improved to a certain extent.