FeSiMg 5% 7% Lump and Granules for Nodular Cast Iron Manufacturing and Foundry Treatment

The form of the FeSiMg alloy determines how it meets the molten iron. FeSiMg 5% 7% lump is dropped, plunged, or packed into a pocket and dissolves over seconds; granules are metered, blown, or fed into a stream and dissolve almost instantly. A plant that treats in a ladle wants lump, because a coarse piece sinks through the slag and works at depth. A plant that treats in the mould or in the pouring stream wants granules, because a fine, dry particle reacts exactly where the metal is. Choosing between them is a question about the treatment station, not about price per tonne.

Lump arrives as broken cast cake, screened to a stated cut. A 10–50 mm cut is the usual charge for a plunger bell; 5–20 mm suits a smaller ladle or a hand-shovelled pocket. The pieces are dense, angular, and free of dust when fresh, and they can be weighed by the bag on a floor scale.
Granules are the same alloy crushed finer and screened to 1–5 mm or 0.25–2 mm. They flow, so they can be metered by volume, blown through a lance, or dispensed into a mould pocket. The trade-off is surface area: a granule carries far more surface per kilogram than a lump, so it picks up moisture and loses magnesium faster in storage. Granules should be used from a sealed bag, and a bag that has been open for a week should not be relied upon for a critical heat.
Dosing differs with the form as well. A cored-wire line typically runs 0.5–0.9% alloy by weight against a base sulphur below 0.02%, while a sandwich pocket uses 1.0–1.5% of the melt weight to reach the same residual magnesium.

The chemistry behind those fractions follows the GB/T 4138-2015 grade windows. The 5% family runs 4.0–6.0% magnesium as FeSiMg5Re2, with 1.0–3.0% rare earth, silicon at the 45.0% minimum, 2.0–3.0% calcium, and aluminium at or below 1.0%. The 7% family runs 6.0–8.0% magnesium as FeSiMg7Re1 or FeSiMg7Re3, with rare earth at 0.5–1.5% or 2.0–4.0% respectively, the same silicon floor, and calcium at 1.0–1.5% or 2.0–3.5%. Iron balances both, and typical delivery runs 45–48% silicon.
The point of listing fractions beside chemistry is that the two are bought together. A 7% granule and a 7% lump share a certificate but not a dissolution rate, and a plant that changes form without changing its charge calculation will see a different residual on the first heat.

• Ladle cover treatment, where lump is placed over the pocket and the iron is poured onto it.
• Plunger treatment, where a bell drives lump under the surface and holds it there.
• In-mould treatment, where a granule dose sits in a chamber and reacts as the mould fills.
• Stream inoculation and stream nodulization on automatic lines, where a metered feed is the only practical route.
• Small jobbing heats, where a weighed bag of 5–20 mm lump is charged by hand.

A foundry making both heavy and small work often keeps two forms in stock: lump for the ladle station and granules for the in-mould line. That is a stock decision as much as a metallurgical one, because granules age faster in an open bag.

Order sheets that name only "FeSiMg" leave the supplier to choose the form, and the first sign of a wrong choice is a treatment that behaves differently from the trial.