How Does The Die-Casting Mold Improve The Damage Caused By Stress?
Stresses include thermal stresses and mechanical stresses, mainly due to mechanical, chemical, and operational shocks. Heat is specifically produced in the following ways.
1. In the process of die casting production
(1) The 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 is continuously increased. When the mold temperature is overheated, the mold is easily generated, and the moving parts are broken, resulting in damage to the mold surface.
(3) The mold should be preheated to a certain temperature before production. Otherwise, when the high temperature molten metal is filled, chilling occurs, which causes the temperature gradient of the inner and outer layers of the mold to increase, forming thermal stress, causing the surface of the mold to crack or even crack.
2. 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. Solid must be tempered to eliminate stress.
(2) Improper heat treatment will cause the mold to crack and prematurely scrap, especially the quenching and tempering, no quenching, and then the surface nitriding process, surface cracking and cracking will occur after several thousand die casting.
3. In the mold manufacturing process
(1) EDM produces stress
The surface of the mold produces a white bright layer rich in electrode elements and dielectric elements, which is hard and brittle. This layer itself has cracks and stress. EDM should use a high frequency to minimize the white bright layer, must be polished and removed, and tempered, and tempered at the tempering temperature.
(2) The quality of rough forging
Some molds produce cracks only when they are produced in a few hundred pieces, and cracks develop rapidly. It is possible that only the outer dimensions are ensured during forging, and the loose defects such as dendrites, inclusions, shrinkage cavities, and bubbles in the steel are stretched and elongated along the processing to form a streamline, which is the last of the streamlines. The quenching deformation, cracking, brittle cracking during use, and failure tendency have a great influence.
(3) Grinding stress occurs during hardening of 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.
(4) Cutting stress generated during final machining such as turning, milling, planing, etc., which can be eliminated by intermediate annealing.
It is believed that in the above three processes, as far as possible, step by step and careful inspection will inevitably reduce the loss caused by stress, and the output of the die-casting mold will also be improved to some extent.