Grain refinement

KBF4 K2TiF6 Release of F2 to atmosphere Formation of HF

Long transports from producer to user

What are the optimum grain sizes in various alloys in relation to casting processes, e.g. billet, slab, sheet etc. Much can be saved by enough grain refiner to obtain safe casts.

Larger grain size in slabs - lower rolling forces?
Will larger grain sizes in billets have benficial effects for extrusion?

Type of nucleus

TiC

TiB2

Particle size distribution

Correlation particle size - undercooling

Type of alloying element

Poisoning elements: Zr, Cr, (Mn)

Strength of growth restriction factor

Phase diagram data.
Element k m (k-1)m
Ti 9 30.7 245
Si 0.14 -7.1 6.1
Mg 0.51 -6.2 3.0
Fe 0.02 -3 2.9
Cu 0.17 -3.4 2.8
Zn 0.4 -1.6 1.0
Mn 0.94 -1.6 0.1

Annual consumption of 80 million tonnes of Al is grain refined with 100 000 tonnes of grain refiner = 1.25 kg/t

Average addition rate where Optifine is used is < 0.3 kg/t, i.e. 75 % less. If extended to whole consumption of grain refiners, 25 000 tonnes will propably suffice to grain refine all aluminium.

Lower cost

Quality improvement -
less amount of boride particles

Underämne

Narrow particle size distribution

Favourable growth conditions

Titanium

High alloying

Low levels of poisonous elements

Large variations in grain refiner efficiencies
Probably due to particle size distribution

Grain refinement tests

Particle measurements