Ca-Ba-Al-Si vs Si-Ba-Ca: choosing an inoculant for ductile iron
Both contain barium. The difference is how much aluminium and calcium they bring, and how they behave in thin sections and long pours.
Inoculation is a small addition with an outsized effect on graphite shape, chill depth and machinability. Ca-Ba-Al-Si and Si-Ba-Ca are two common choices; the right one depends on section thickness, pouring time and the base iron.
KRIS supplies Ca-Ba-Al-Si and Si-Ba-Ca inoculants in 3–10 mm and 10–30 mm, with 25 kg trial bags and a COA per lot. Tell us the section thickness and pouring time and we will recommend a grade.
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Calcium barium aluminium silicon inoculants combine strong deoxidation with a barium addition that slows fading. The aluminium content helps in grey iron and in some ductile iron treatments, but it must be controlled where aluminium is restricted.
Silicon barium calcium alloys are used where a strong deoxidising effect and good inoculation are needed without adding much aluminium. They are often chosen for thin-wall castings and long pouring times.
| Property | Ca-Ba-Al-Si | Si-Ba-Ca |
|---|---|---|
| Main role | Inoculation + deoxidation | Inoculation + strong deoxidation |
| Aluminium | Present, moderate | Low |
| Fading resistance | Good | Good |
| Typical use | Grey and ductile iron, general foundry | Thin-wall, long-pour ductile iron |
Barium and fading
Barium slows the breakdown of the inoculating effect, which matters when the mould is filled slowly or the metal travels a long distance. For thin sections, the window between inoculation and solidification is short, so a slow-fading inoculant is often worth the premium.
Selection checklist
- Check the aluminium limit on the final casting specification.
- Match the particle size to the treatment method: 3–10 mm for ladle addition, finer for stream inoculation.
- Run a trial with a retained sample and compare chill depth and graphite size.
- Keep the addition rate stable — more is not always better, and can increase slag.
FAQ
Can the two inoculants be used together?
They can, but it is usually better to optimise one addition than to stack two. If you need both deoxidation and inoculation, discuss the sequence with your foundry engineer.
Does particle size matter more than chemistry?
It often does. A well-matched size dissolves at the right time; the wrong size either floats out or dissolves too late.
This note is general information for buyers. It is not trading, financial or investment advice. Specifications must be confirmed against the COA for each lot.