Gas porosity in aluminum die-castings mainly stems from three sources:
① Inadequate degassing during melting: Especially with high-silicone release agents, unsuitable melting temperatures or times result in high hydrogen content in molten aluminum. Subsequent solidification with poor exhaust easily causes porosity.
② Turbulent flow during filling: Entrapped gas—akin to making sparkling water at home—introduces excess air into the part.
③ Gas from release agents and other factors: Primarily from the gas evolution of release agents and incomplete drying after spraying. Additional sources include gas emitted from punch oil and vacuum extraction issues. Gas removal is critical: if mold design is flawed or exhaust is poor, gas precipitation during solidification will lead to porosity.
There is a connection to die-casting release agents—particularly those with high gas evolution, such as oil-based release agents, volatile additives, or when spraying is not fully dried.
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