Causes of mould damage during die-casting process

 

　　1, the die temperature

　　Mould should be preheated to a certain temperature before production, or chilling when high temperature liquid metal filling, which resulted in increased mold temperature gradient layers, zinc die casting thermal stress forming, make the mould surface cracks, even cracking.

　　During the process of production, the die temperature increases continuously, and when the mold temperature is overheating, it is easy to produce adhesion mode, die casting machine and the motion parts fail to cause the surface damage of the mould.

　　The cooling temperature control system should be set up to keep the mold working temperature within a certain range.

　　2, the filling

　　With high pressure and high speed, the metal liquid will have a severe impact and erosion on the mold, resulting in mechanical stress and thermal stress. During the impact process, Multi slider die casting machine the metal fluid, impurities, gas and the surface of the mold can produce complex chemical action, and accelerate corrosion and crack production. When the liquid metal is gas, low pressure area in the cavity expansion first, when the gas pressure, blasting introversion, Die casting pull out the metal particles on the surface of the cavity and damage, the crack due to cavitation.

　　3, open mould

　　In the process of core and mold opening, mechanical stress can be generated when certain components have deformation.

　　4. Production process

　　In each of the die casting process, due to the mold with liquid metal, the heat exchange between the mould surface temperature changes periodically, cause periodic thermal expansion and contraction, produce periodic thermal stress. If the surface of the die is stressed by heating during casting, the mould surface will be tensile stress due to cooling. When this kind of alternating stress is repeated, the internal accumulation of the mould becomes more and more large. When the stress exceeds the fatigue limit of the material, the surface of the mould cracks.

In the process of processing and processing, the causes of die failure in die casting are made

 

　　In die-casting production, the most common form of mould damage is cracking and cracking. Stress is the main cause of mould damage. Thermal, mechanical, Die casting chemical and operational shocks are all sources of stress, including mechanical stress and thermal stress. Stress is generated by:

　　(1). In the process of tooling and manufacturing

　　1. Quality of blank forging

　　Some moulds produce only a few hundred pieces and crack, and cracks develop quickly. Is probably the only when forging to ensure the appearance size, Multi slider die casting machine and the dendritic crystals and inclusions in the steel carbide and loose defects such as shrinkage cavity, bubble along the processing method is lengthen, forming streamline, die casting machine the streamline of after the last of the quenching distortion and cracking in the process of using, embrittlement, failure has enormous influence on the tendency.

　　2. The shear stress generated during the final processing of cars, milling and planing can be eliminated by annealing in the middle.

　　3. During the grinding of hardened steel, zinc die casting the grinding stress is produced, resulting in frictional heat during grinding, resulting in a softening layer and decarburization layer, which reduces the thermal fatigue strength and can easily lead to thermal cracking and early cracks. Of h13 steel after fine grinding, can be heated to 510-510 ℃, to one hour per 25 mm insulation thickness for eliminating stress annealing.

　　4. Electric spark processing produces stress. The surface of the mould produces a layer of enriched electrode elements and dielectric elements, which are hard and brittle. The layer itself has cracks and stresses. When the electric spark is processed, the high frequency should be used to minimize the white light layer. The polishing method must be removed and tempered. The tempering is carried out at the three level tempering temperature.

　　(2) in the process of mould processing

　　Heat treatment undeserved, can cause mold cracking prematurely discarded, especially by conditioning only, not for quenching, surface nitriding process again, can appear in die casting for thousands of times after surface crack and craze.

　　Is generated when the steel quenching stress, thermal stress of cooling process with phase transformation of the organization result of stress superposition, quenching stress was the cause of shape, craze, solid temper must be carried out to eliminate stress.