Silicon Magnesium FeSiMg 5% 6% for Ductile Iron Production and Graphite Nodularization

Ductile iron earns its strength from graphite that solidifies as nodules rather than flakes, and that shape change starts with magnesium. Pure magnesium is too reactive to drop into an open ladle, so foundries take the element inside a ferrosilicon carrier: FeSiMg 5% and 6% release magnesium as the alloy dissolves, at a rate the operator can follow. The 5% window suits thin-section work, low-sulphur base iron and small heats where an overshoot is expensive to correct. The 6% window keeps magnesium in reserve for heavy sections, higher-sulphur scrap and longer holding before pouring. ZhenAn holds both windows as lump and as screened granules, and each lot leaves with chemistry matched to the grade table below.

Both levels arrive as silver-grey lump with a bright crystalline fracture and no slag skin on the broken face. The alloy is brittle, so it breaks along clean planes and keeps its screened fraction through bagging, transport and the drop into a treatment vessel. Foundries running bell or plunger stations normally take 10–50 mm lump; smaller ladles and in-stream feeding work better with 5–20 mm or granules from 0.25–2 mm to 1–5 mm. Packaging follows the plant: 25 kg woven bags on pallets, or 1000 kg jumbo bags where a crane feeds the hopper. Keep the stock under cover, because damp bags promote surface oxidation and crumbling, and a weathered lot reads as an old lot on the floor.

Those windows come from the grade table published on this site, and they are written as ranges on purpose: a single magnesium figure cannot describe a treatment alloy. Ask for a lot certificate that repeats every window element by element, then compare it with the charge weight you actually calculated. If a supplier quotes only "Mg 6%" with no silicon, calcium or rare earth line, the certificate will not tell you whether a treatment change came from the alloy or from the practice.

The clearest case for the 5% level is a thin-wall job with a clean charge: brake hardware, small valve bodies, thin covers and parts that are poured within minutes of treatment. Magnesium fades as the heat waits, so an alloy with less headroom loses less when the pouring line slows down. The 6% level belongs on heavier work, where the section takes longer to solidify and the residual has to survive a deep mould.

• Heavy machine bases and frames, where the last metal out of the ladle still has to nodularize.
• Jobs charged with high-sulphur pig iron or oily returns, which consume magnesium before it reaches the mould.
• Shops that treat one large ladle and pour several moulds from it.
• Foundries switching between thin and heavy work on the same line, where one 6% alloy covers both ends.

Four numbers decide the quote: the magnesium window, the screened fraction, the tonnage per shipment and the packing. Add the base iron sulphur level and the treatment method, because both change how much alloy the heat needs, and a supplier who knows them can flag a mismatch before the container ships. Confirm whether the certificate should follow the lot or the shipment, and whether a retained sample is expected. Delivery on this site is stated as 7–14 days from receipt of advance payment, so a plant running a tight treatment schedule should place the order against that clock rather than against the day the vessel sails. Payment terms are usually agreed per order, with T/T and letter of credit both in use.