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Causes of die damage in die casting production

2020-08-30 22:38:19

Causes of die damage in die casting production are as follows:

In die casting production, the common forms of die damage are cracks. Stress is the main cause of mold damage. Thermal, mechanical, chemical, and operational shocks are all sources of stress, including mechanical stress and thermal stress. Stress occurs in:

(1) During the die machining and manufacturing process

1. The quality of rough forging. Some dies have cracks after only a few hundred pieces are produced, and the cracks develop very quickly. It is possible that only the outer dimensions are guaranteed during forging, and the loose defects such as dendrites, carbide inclusions, shrinkage cavities, and air bubbles in the steel are extended and elongated along the processing method to form streamlines. This streamline affects the fsubsequent hardening deformation, cracking, embrittlement, and failure tendency have great influence.

2. Cutting stress generated during final machining such as turning, milling, and planing can be eliminated by intermediate annealing.

3. Grinding stress is generated during grinding of hardened steel, friction heat is generated during grinding, softening layer and decarburization layer are generated, thermal fatigue strength is reduced, and thermal cracking and early cracking are easily caused. After the h13 steel is finely ground, it can be heated to 510-570℃, and keep for one hour at a thickness of every 25mm for stress relief annealing.

4. EDM produces stress. The surface of the mold produces a bright white layer rich in electrical and dielectric elements, which is hard and brittle. This layer itself will have cracks and stress. High frequency should be used in EDM to reduce the white layer, and then the polishing method should be used to remove, and tempering treatment, tempering at the third tempering temperature.

(2) During mold treatment

Improper heat treatment will lead to cracking of the mold and premature scrapping, especially if only quenching and tempering is used, and the surface nitriding process is performed without hardening, surface cracks and cracks will occur after several thousand stamping parts. The stress generated when steel is hardened is the result of the superposition of the thermal stress during the cooling process and the structural stress during the phase transformation. The hardening stress is the cause of deformation and cracking, and it is tempered to eliminate the stress.

(3) During casting

The mold should be preheated to the temperature before production, otherwise, chilling will occur when the high temperature molten metal is filled, which will cause the temperature gradient of the inner and outer layers of the mold to increase, leading to thermal stress, and causing the mold surface to crack. During casting, the mold temperature continues to rise. When the mold temperature is overheated, it is easy to stick to the mold,and the moving parts are out of order,which leads to the mold surface damage. A cooling temperature control system should be installed to keep the mold working temperature within the range.




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