Grain refining is the addition of particles to molten aluminium that act as nucleation sites during solidification, producing many small equiaxed grains instead of a few large columnar ones. The standard refiner is aluminium-titanium-boron master alloy, mainly AlTi5B1 or AlTi3B1, which carries titanium diboride and titanium aluminide particles. It is added as rod fed into the launder before casting, or as waffle or tablets in the furnace.
Why it matters when buying
- Fine grains reduce hot cracking, improve feeding and surface finish, and give more uniform mechanical properties in billets, slabs and castings.
- Billet and slab buyers often specify grain size; ask the cast house whether in-line refining is used.
- For refiner purchases, check Ti and B content, particle size and agglomerates; poor quality rod can introduce inclusions.
- Grain refiners can lose effectiveness if held too long in the melt, so dosing practice matters.
- In EC grade aluminium, titanium hurts conductivity, so refining practice differs for conductor rod.
Typical uses
DC casting of 6063 billets and rolling slab, foil stock, and foundry alloys such as A356. See master alloys.