Reasons and preventive measures for damage to die-casting production molds

1、 Reasons for damage to die-casting production molds:

The most common form of mold damage in die-casting production is cracking. Stress is the main cause of mold damage. Thermal, mechanical, chemical, and operational impacts are all sources of stress, including mechanical stress and thermal stress. Stress is generated from:

（1） In the process of mold processing and manufacturing, 1. Quality issues with blank forging. Some molds only produce a few hundred pieces before cracks appear, and the cracks develop quickly. It is possible that during forging, only the external dimensions were guaranteed, while loose defects such as dendritic crystals, inclusions of carbides, shrinkage cavities, and bubbles in the steel were extended and elongated along the processing method, forming streamline lines. These streamline lines have a significant impact on the final quenching deformation, cracking, brittle fracture, and failure tendency during use in the future. 2. The cutting stress generated during final processing such as turning, milling, and planing can be eliminated through intermediate annealing. 3. During the grinding of quenched steel, grinding stress is generated, frictional heat is generated, resulting in softening and decarburization layers, which reduce the thermal fatigue strength and easily lead to thermal cracking and early cracking. After precision grinding, H13 steel can be heated to 510-570 ℃ and subjected to stress relief annealing with a thickness of every 25mm held for one hour. 4. Electrical discharge machining generates stress. A white bright layer enriched with electrode and dielectric elements is formed on the surface of the mold, which is hard and brittle. This layer itself will have cracks and stress. During electrical discharge machining, a high frequency should be used to minimize the white bright layer, which must be removed by polishing and tempered at a third level tempering temperature.   

（2） Improper heat treatment during die treatment will lead to die cracking and premature scrapping. In particular, if only quenching and tempering are used, but not quenching, and then surface nitriding process is used, surface cracking and cracking will occur after thousands of die casting times. The stress generated during steel quenching is the result of the superposition of thermal stress during the cooling process and structural stress during phase transformation. Quenching stress is the cause of deformation and cracking, and tempering must be carried out to eliminate stress.   

（3） In the process of die-casting production, 1. Mold temperature: The mold should be preheated to a certain temperature before production. Otherwise, when the high-temperature metal liquid is filled, it will produce rapid cooling, causing an increase in temperature gradient between the inner and outer layers of the mold, forming thermal stress, and causing the surface of the mold to crack or even crack. During the production process, the mold temperature continues to rise. When the mold temperature overheats, it is easy to cause mold sticking and malfunction of moving parts, resulting in surface damage to the mold. A cooling and temperature control system should be installed to maintain the working temperature of the mold within a certain range.