What is a launder in a foundry?

A launder (molten‑metal launder) is a sloped, refractory‑lined channel/trough in foundries and casthouses, used to convey molten metal (aluminum, iron, copper etc.) by gravity between production units. In aluminum casting, it is widely called molten aluminum launder,

Structure

- Outer: steel / metal shell for mechanical strength
- Inner: high‑performance refractory lining (precast refractory, ceramic‑fiber, fused‑silica material), resistant to high temperature, corrosion and molten‑metal wetting; boron‑nitride coating is often applied to resist sticking aluminum.
- Available as open‑type or covered / insulated‑type; modular segmented design is common for easy maintenance and replacement.

Core functions

1. Transport molten metal**: Gravity‑driven delivery from melting furnace → holding furnace → degassing unit, filter box → casting machine / DC casting station.
2. Control flow**: Gentle flow to reduce turbulence, splashing, oxide dross and inclusion generation, avoid casting defects.
3. Thermal retention**: Reduce heat loss to prevent premature solidification of melt. Heated launders are adopted for long‑distance transfer.
4. Integrated melt treatment**: The launder path can accommodate inline degassing, filtration, grain refinement, serving as an active metallurgical processing zone, not merely a simple channel.

Launder vs Trough

They are frequently interchangeable:

- Though: Simple short‑run open channel for temporary transfer.
- Launder: Engineered heavy‑duty channel with premium refractory lining, covers, modular joints, compatible with inline refining equipment for long‑term continuous production.