Shrinkage

Our advice helps you reduce shrinkage porosity

Optimising chemistry, temperature and sand conditions can help to reduce shrinkage porosity, but the use of prime quality MgFeSi alloys and inoculants is also crucial.

A foundry was having difficulty in producing calipers free from porosity in the area furthest from the live risers. They were using a MgFeSi nodulariser with 6% Mg and 1.5% Rare Earths. Inoculation was with a calcium/barium containing FeSi.

The alloy system was changed to a Lamet® nodulariser containing only lanthanum as the RE source, and the inoculant was changed to Ultraseed® Ce.

Lamet® nodulariser is proven to reduce shrinkage, and in combination with Ultraseed® Ce inoculant provides the maximum graphite expansion during solidification to counter shrinkage in ductile iron components.

The picture below shows micro-shrinkage porosity attributed to poor selection of treatment alloys. Correct selection of alloys reduces shrinkage and produces castings which are acceptable to the end-user.

Micro shrinkage porosity

Safety-critical ductile iron components, such as brake calipers, must have very low levels of porosity.

6% Mg, 1% RE with CaBa inoculant                      Lamet® with Ultraseed® Ce inoculant

6% Mg, 1% RE with CaBa inoculant     Lamet® with Ultraseed® Ce inoculant

Lamet® nodulariser is renowned for promoting a high nodule number and generating new nodules during the solidification process. This continual growth of graphite provides an expansion effect which counters the natural shrinkage of the iron and thus reduces the incidence of shrinkage porosity. Ultraseed® Ce inoculant has been designed to provide new nucleation sites during solidification. The combination of Lamet® and Ultraseed® Ce is particularly powerful in the fight against shrinkage.

Elkem’s experienced technical staff can help you understand shrinkage mechanisms and find cost-effective solutions.