1 forming defects
Such deficiencies occur mainly on the surface of die-castings, most can be seen visually. Less cast and corner defects such as not filling speed-related; Flow marks appear around the gate, in addition to outside the laminar effect, and die temperature; Matt surface, cold shut defect caused mainly by the melt temperature is too low, prone to swirl away from the gate area and two alloy flow interchanges, when changing the gate or increased fluid temperature will be eliminated.
Control of such defects, in addition to the gating system design, is more important to select the appropriate die casting method. Conventional low temperature high speed casting die casting process of law, high speed die casting method and low temperature low speed die casting method. Low temperature casting can reduce the burning of liquid alloys and their erosion, high-speed shooting high quality surface can be obtained, by low-temperature high-speed die-cast copper alloys, in the production of thin-walled aluminum alloy advantage is obvious; Wall thickness of the die casting method is mainly used for high temperature low medium adverse impact, easy filling and core on die casting, high temperatures to meet the form requirements, lower filling speed can decrease the flow impact on the core trends; Contradiction is the stomata of thick-walled parts and pressure feeding, often used by low-temperature low-speed die cast.
2 mold release defects
Strain, deformation is a common mold release defects. Stripping slope when the alloy flow speed causes the cavity surfaces sticking due to overheating, and release non-sticking, deformation, cracks and other defects, was launched by the introduction of institution of uneven temperature, alloy hydraulic high pressure casting mold due to longer factors. After stripping the visible marks of injury on the surface of the casting and even deformed, you should increase the pressure casting mold release wax coat of tilt, or. In order to control this type of defect, except to ensure that the launch sector of launch force distribution uniform, at the time of the gate design also pay special attention to the alloy liquid flows into the cavity of the Guide, try to avoid molten alloy flow positive impact with the core, while suitable for die casting process parameters and a slightly longer casting time.
3 blowhole defects
Blowhole defects are the most common type of casting defects on the thin-walled parts mainly for the bubble on the surface and invisible micro-holes when you die castings polishing, coating, can cause foaming of coating; In thick-walled parts mainly for the deep hole, severe osteoporosis, shrinkage is going on. Porosity defects for many reasons, foremost among them is the filling of the exhaust is impeded and wrapped. Control and prevention of this type of flaws, mainly to ensure reasonable exhaust system of die-casting, smoothly, eliminating or reducing the unit when filling cavities alloy fluids crashing. The following points should be noted: (1) now in designs featured Ingate design formula of a lot of information, but the gate section are approximate values that are calculated. At the time of inner gate design, be sure to leave repair mode according to practical experience, so that, after trial modification. Experience has shown that the gate area is large, to ensure transmission of pressure, easy to process compensation through the injection speed adjustment. (2) ensure the row overflow system of die casting mould and smooth. (3) selection of die casting process parameters, in the premise of meeting the forming process, should try to lower casting temperature, injection speed, injection pressure. (4) die casting thickness of the coating should be moderate, uniform thickness.
4 Gold similar defects
Gold defects often show a similar internal organization of casting Crystal large, metal hard spots and nonmetallic properties hard points. For crystalline defects, Al-Si alloy modification process can be used, and other alloys are mainly control alloy melting temperature and holding time. Sources of hard metal point is no penetration of alloys, recycled materials, such as iron, non-metallic hard points are mainly of recycled materials sand, stove paint. Control this type of defect is mainly to ensure that the composition of raw materials purchased pass to strictly enforce the rules during the smelting process, controlling the chemical composition changes, and strengthen the management of recycled material, mixed with impurities is strictly prohibited.