Vacuum casting is a special casting technology that extracts air from the mold cavity during the casting process to reduce the internal pores of the casting and improve the density and mechanical properties of the casting.
Its working principle and specific steps are as follows:
Process principle: The core goal of vacuum casting is to reduce the air pressure in the mold cavity (usually to 10-100Pa) to reduce the air and gas impurities involved when the molten metal is filled, thereby avoiding common defects such as pores and looseness in traditional casting. In ordinary casting, the air in the mold cavity will be compressed when the molten metal is filled at a high speed, forming bubbles that remain inside the casting; while vacuum casting makes the mold cavity in a negative pressure state by evacuating air in advance or evacuating air while filling the mold, so that the molten metal flows more smoothly and the amount of gas precipitation is greatly reduced.
Process flow:
Mold preparation: The mold needs to be preheated to a specific temperature (such as 150-250℃), and the mold release agent is sprayed to ensure the sealing of the mold (key parts such as parting surface and slider need to be strictly sealed).
Vacuuming stage: After closing the mold, the air in the mold cavity is extracted through the vacuum channel in the mold, and the vacuum degree reaches the set value (such as ≤50Pa). For complex structure castings, continuous vacuuming can be performed during the metal liquid filling process.
Metal liquid filling and pressurization: Molten metal (such as aluminum alloy, magnesium alloy) is injected into the mold cavity at a certain speed through the injection punch, and the vacuum system maintains negative pressure to reduce filling resistance and turbulence. After filling, the injection punch applies high pressure (usually 50-100MPa) to promote metal liquid shrinkage.
Cooling and demolding: The casting is cooled and solidified in the mold. After reaching the demolding temperature, the mold is opened, the casting is taken out and subsequent processing (such as deburring, heat treatment) is carried out.
Process advantages:
Improved casting quality: improved density (density can reach more than 98% of the theoretical value), and mechanical properties (tensile strength, elongation) are improved by 10%-30%. Excellent surface quality, can be directly electroplated, painted and other post-processing, without the need for de-porosity process.
Strong adaptability: Suitable for thin-walled parts (wall thickness ≤ 1mm) and complex structural parts, such as automobile engine cylinders, gearbox housings, etc.
Production efficiency and cost: Although the equipment cost is 20%-30% higher than ordinary casting, the scrap rate is reduced (≤ 5%), and the post-processing cost is reduced, and the comprehensive cost advantage is significant. Of course, if you have large-scale vacuum casting needs, you can choose to cooperate with Mulan Metal. Mulan Metal has 12 years of metal casting experience and has helped customers in more than 30 countries to complete the production and processing of various vacuum castings. We look forward to your cooperation consultation.
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