Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Yes, you can braze cast metals successfully, but it requires some important considerations because castings (especially cast iron, cast aluminum, and cast magnesium) behave differently than wrought metals.

1. Cast Iron (Gray, Ductile, Malleable)

Yes, very commonly brazed.

Best method: Oxy-acetylene torch brazing with bronze filler (e.g., RBCuZn-A or “nickel bronze”).

Key issues:Cast iron has graphite flakes or nodules that oxidize and form porosity if overheated.

Surface oxides and absorbed oils/soot in the pores must be completely removed.

Pre-clean mechanically (grinding) + chemically (hot caustic or acid pickle), then flux heavily.

Use a good cast-iron brazing flux (often boric acid-based high-temperature flux).

2. Cast Aluminum

Yes, can be brazed, but it’s trickier than welding.

Preferred methods:Torch brazing with aluminum-silicon filler (4047/Al-Si12) and aggressive fluoride-based flux (e.g., Alcoa 63, Harris Al-Braze).

Furnace/vacuum brazing (common in industry for heat exchangers).

Challenges:Thick magnesium-containing oxide layer forms instantly.

Many cast alloys (especially 300-series like 356, 319, A356) contain magnesium, which makes the oxide even harder to remove → need very active flux or special techniques (nocolok flux in furnace brazing).

Overheating quickly causes collapse or liquation of low-melting eutectics.

Die-cast aluminum (high zinc or magnesium) can usually be brazed if the zinc doesn’t burn off too badly.

3. Cast Steel

Behaves almost like wrought steel; brazing is straightforward with standard bronze or silver fillers.

4. Cast Magnesium

Possible but rare outside aerospace.

Requires special fluxes and very careful temperature control because magnesium ignites easily.