Carbon buildup refers to the dark, adherent substance formed on mold surfaces when die casting release agents and plunger lubricants undergo sintering and carbonization upon contact with high-temperature aluminum melt and molds. It manifests as:
Black deposits on molds (easily wiped off in mild cases; requires scraping in severe cases).
Rough, uneven surfaces on aluminum castings, accompanied by sticking or film formation.
Based on kzy’s expertise and industry experience, carbon buildup often targets:
Thick-walled casting areas.
High-temperature mold surfaces.
Understanding the above patterns, we identify high temperature as a key trigger. Below are specific factors:
Elevated Aluminum Melt & Mold Temperatures
Normal mold temps: 200–280℃ (pre-spray); 180–250℃ (post-spray). If mold temp exceeds 350℃ with poor cooling, release agents (with lower heat resistance) carbonize/decompose under high heat and fast aluminum melt scouring. Some form a film, and repeated spraying worsens buildup. High aluminum melt temp has the same effect.
Thick-Walled Castings
Thick parts require more high-temperature liquid aluminum, generating excess heat. Localized high temps demand stronger temperature resistance from release agents—making buildup more likely.
Rough Mold Surfaces
More release agent flows into grooves on rough molds. Under heat, some agents carbonize; others form a release film. Fast aluminum melt flushes decomposed agents into grooves, causing buildup—a critical factor.
Excessive Plunger Stroke Time
Slow melt flow generates excess heat, compromising release agent performance.
Poor Mold Design
Improper melt flow/distribution causes localized solidification/flow (excess heat). Insufficient venting leads to heat accumulation, promoting buildup.
Overapplication of Release Agent
High concentration, low dilution ratio, or excessive spraying leaves a thick film. Only a thin layer is needed—residual agent carbonizes over time.
Excessive Plunger Lubricant
Often causes blackening near the casting’s inner gate.
Each cause has a targeted fix:
For High-Temp Buildup: Adjust aluminum melt and mold temps to optimal ranges. This reduces buildup and extends mold life.
For Thick-Walled Castings: Add vents or enhance cooling systems to lower local heat—ensuring smooth, shiny castings.
For Rough Molds: Nitride new molds to boost hardness. Regularly maintain molds (prevent rust) and use non-corrosive release agents.
For Excessive Plunger Stroke Time: Optimize plunger speed.
For Poor Mold Design: Simulate melt flow and verify venting in advance to avoid buildup, cold shuts, or porosity.
For Overapplied Release Agent: Test different dilution ratios under consistent conditions to find the minimal effective volume.
For Excessive Plunger Lubricant: Use the recommended dosage.
For more information about Causes and Solutions of Carbon Buildup in Die Casting Release Agents (Addressing Carbon Deposits on or die-casting auxiliary materials, and if you need customized die-casting release agent, please contact 15021483232 (same as Wechat)
