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Die Casting Defect Analysis: Key Issues & Solutions (一)

The die casting process involves numerous variables, making consistent quality a key challenge. Understanding common defects is essential for process optimization.

1. Oxide Slag Inclusion

Causes: Dirty charge materials; excessive recycled material; poor gating system design; incomplete slag removal; improper pouring introducing slag; insufficient holding time after melt treatment.

Solutions: Use cleaned charge materials; reduce recycled material; improve gating design; use appropriate fluxes; ensure smooth, slag-preventive pouring; allow adequate holding time after refinement.

2. Gas Porosity / Blisters

Causes: Air entrapment in molten metal; excessive lubricant; incorrect flow direction causing vortices; ingates too small leading to high velocity and vent blockage; poor gating/venting design; deep cavities hindering exhaust.

Solutions: Use proper slow-shot speed; check runner smoothness and taper; ensure vents are large, unblocked, and correctly located; avoid excessive die lubricant and low die temperature; use vacuum; add/repair vents; modify sprue spreader; enlarge ingates; design effective vents and overflows.

3. Shrinkage Porosity / Cavities

Causes: High gas content in charge; overheating near ingates; improper part placement in die; excessive pouring temperature/speed; part design with severe thickness variations; high metal temperature.

Solutions: Control coating/sand core moisture; optimize part placement and lower pouring temperature/speed; increase pressure; adjust die temperature locally; add process holes in thick sections; lower metal temperature.

4. Cracks

Causes: Poor part design (sharp corners, uneven walls); localized die overheating; high pouring temperature; short cooling time; heat treatment overheating; excessive residual stress; cracking during ejection/trimming.

Solutions: Improve part design (larger fillets, uniform walls); check for hot spots; increase pressure holding time; adjust die closed/open time; increase draft angles; add ejector pins; check for die misalignment/deformation; verify alloy composition; control solidification via gating; lower pouring temperature; control cooling time.

This article is based on general die-casting process knowledge, and the solutions provided are directional recommendations. Specific applications must be evaluated based on actual equipment, mold, and material conditions.