Die-casting moulds can only be put into mass production after heat treatment, and the quality of heat treatment is related to the quality of die-casting molds. Die casting molds with poor heat treatment will burst normally. The damage to the die-casting enterprise cannot be ignored, and the delivery time will be delayed.
To ensure the quality of the die-casting mold, each heat treatment process is carried out in strict accordance with the standards, and the next process is entered after the detection is correct. All die-casting mold procedures must be strictly implemented to ensure the quality of the die-casting mold after heat treatment.
Pre-heat treatment of die-cast tooling is to improve the organization and softening of die-cast tooling steel for ease of machining, stress relief, and the ideal original structure of heat treatment. Pre-heat treatment for some large mold components is the final heat treatment. Pre-heat treatment commonly uses normalizing and annealing.
The purpose of normalizing is to improve organization and refine grain. It can be the pre-heat treatment of die-cast tooling, and can also be the final heat treatment. The organization from both normalizing and annealing is pearlite.
During the quality inspection, the key point of die-cast tooling is the inspection of process parameters. Namely, during the process of normalizing and annealing, check the implementation of process parameter which is the most important, and after the process, the main check is for hardness, microstructure, decarburized depth, the purpose of normalizing and annealing, banding, and network carbide, etc.
Judgment of normalizing and annealing detection for die cast tooling.
1. Super-hard: The super-hardness of medium carbon steel is usually caused by the high temperature and fast cooling rate of the die-casting die during annealing. The super hardness of high carbon steel is caused by low and insufficient temperature.
2. Network structure: This structure usually appears in sub-steel and hypereutectoid steel of die-casting mold. Reticulated ferrite appears in hypereutectoid steel, and reticulated carbide appears in hypereutectoid steel. They are caused by overheating temperatures and slow cooling rates and can be eliminated by normalizing.
3. Decarburization: The die-casting mold is normalized or annealed in an air furnace. The workpiece is heated without gas protection, and the metal surface is oxidized to form decarburization.
4. Graphite carbon: It is produced by the decomposition of carbides, mainly due to the overheating temperature and pressure holding time of the die casting mold. After graphite carbon appears in the steel, it will be found that the quenching hardness is low, the soft spot, the strength is low, the brittleness is large, and the fracture is grey-black.