In die casting production, the most common form of mold […]
In die casting production, the most common form of mold damage is cracking and cracking. 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 is generated by:
(1) The quality problem of blank forging in the process of mold manufacturing of syringe manufacturers.
1. Some molds produce cracks after only a few hundred pieces, and the cracks develop quickly. It may be that only the appearance size is guaranteed during forging, and loose defects such as dendrites, inclusion carbides, shrinkage holes, and bubbles in the steel are extended and elongated along the processing method to form a streamline. The final quenching deformation, cracking, embrittlement during use, and failure tendency have a great influence.
2. The cutting stress generated during the final processing of turning, milling and planing, etc. This stress can be eliminated by intermediate annealing.
3. Grinding stress is generated during the grinding of quenched steel, frictional heat is generated during grinding, and a softening layer and a decarburized layer are generated, which reduces the thermal fatigue strength and easily leads to thermal cracking and early cracking. After fine grinding of h13 steel, it can be heated to 510-570 ℃, and the stress relief annealing is carried out with a thickness of 25mm for one hour.
4. EDM produces stress. A white bright layer rich in electrode elements and dielectric elements is produced on the surface of the mold, which is hard and brittle. This layer itself will have cracks and stress. High frequency should be used in EDM to minimize the white bright layer. It must be removed by polishing and tempered. The tempering is carried out at the third tempering temperature.
(2) Improper heat treatment in the mold processing process of the syringe manufacturer will cause the mold to crack and be scrapped prematurely, especially only quenching and tempering, without quenching, and then surface nitriding process, surface turtle will appear after thousands of die-casting Cracked and cracked. The stress generated during steel quenching is the result of the superposition of the thermal stress during cooling and the tissue stress during phase transformation. The quenching stress is the cause of deformation and cracking, and it must be tempered to eliminate the stress.
(3) During the die-casting production process, 1. The mold temperature mold should be preheated to a certain temperature before production. Otherwise, when the high-temperature metal liquid is filled, chilling will occur, resulting in an increase in the temperature gradient of the inner and outer layers of the mold, forming thermal stress, which The surface of the mold is cracked or even cracked. During the production process, the mold temperature continues to rise. When the mold temperature is overheated, it is easy to produce sticky molds, and the moving parts fail to cause damage to the mold surface. A cooling temperature control system should be set to keep the mold working temperature within a certain range.