Manufacturing – Casting methods - European Aluminium Association

1.10.5 Possible defects and ways to avoid them
Defect Non-fills and cold shuts Gas porosity and blisters
Possible main
cause for defects
Way to avoid
defects
Examples
Solid fraction too high;
mould filling speed too
low; mould too cold.
Increase liquid fraction;
increase speed; heat
mould more.
Non-fills
Source: EFU
Defect Inclusions (mainly oxides)
Possible main cause for
defects
Way to avoid defects
Examples
Defect Shrinkage porosity
Possible main cause for
defects
Way to avoid defects
Turbulent mould filling; runner's geometry
not adequate; not enough venting; water
in mould; die parting agent produces
gases.
Use smooth runners with cylindrical cross
sections. If necessary, use vacuum.
Gas porosity and blisters
Source: Alcan
Retention system for oxide skin of metal not efficient
enough; two metal fronts hit together.
Use and optimise oxide retention systems; fronts with
oxides should be brought into overflows.
Inclusions
Source: Alcan
Feeding of large cross sections is not good enough.
Dimension runner and gating systems for good feeding;
use numerical simulation to control and optimise them.
Version 2002 © European Aluminium Association (auto@eaa.be) 65