Application Guide · Ductile / Nodular Iron
In ductile iron, sulphur is the enemy of nodularity. The right recarburizer raises carbon to spec while keeping sulphur and nitrogen low — protecting your magnesium treatment and casting quality.
In short: For ductile (nodular) iron, use a fully-graphitized, low-sulphur recarburizer — graphitized petroleum coke (GPC) or graphite electrode scrap (GES) at S ≤ 0.05%. Gas calcined anthracite (GCA) is a lower-cost option where its higher sulphur and lower absorption are acceptable.
Ductile (nodular) iron depends on a magnesium treatment to grow graphite as spheres rather than flakes. Sulphur reacts preferentially with magnesium, consuming it and forming dross and slag — so every extra 0.01% of sulphur from your carbon additive means more MgFeSi treatment alloy, more dross defects and less reliable nodularity.
That is why ductile iron foundries specify low-sulphur recarburizers. A fully-graphitized carbon source with S ≤ 0.05% protects the magnesium recovery, improves nodule count and gives more consistent mechanical properties.
Carbon that has been heat-treated above ~2500 °C develops a crystalline graphite lattice. This 'graphitized' carbon dissolves into the iron faster and more completely — typically 90–95% absorption — and is inherently low in sulphur and nitrogen. Both graphitized petroleum coke (GPC) and graphite electrode scrap (GES) fall in this category.
Non-graphitized carbons such as gas calcined anthracite (GCA) are more economical but have lower absorption and higher residual sulphur, so they are better suited to grey iron and cost-sensitive grades than to premium ductile iron.
GPC is the premium choice: F.C. ≥ 98.5%, S ≤ 0.05%, very low nitrogen and consistent absorption. GES delivers essentially the same metallurgical performance (it is recycled, fully-graphitized electrode material) at a 10–20% lower price, with slightly higher ash. GCA is the budget option — acceptable for many grey-iron and some ductile applications, but its higher sulphur makes it a weaker fit for high-integrity nodular castings.
Typical addition rates for ductile iron run around 8–12 kg of recarburizer per tonne, depending on charge make-up and target carbon. Fine and medium sizes (0.5–3mm, 0.5–5mm) are common for induction-furnace charging and ladle additions.
Give your supplier the target carbon, your maximum sulphur and nitrogen, your furnace type (induction vs cupola) and preferred size fraction. Ask for a Certificate of Analysis on every lot and a pre-shipment sample for your own lab. Global Vista supplies all three recarburizer types from qualified Chinese plants with lot-traceable COAs and third-party inspection on request.
Premium low-sulphur recarburizer, F.C. ≥ 98.5%, S ≤ 0.05% — the benchmark for ductile iron.
View product →Same graphitized performance as GPC at 10–20% lower cost.
View product →Cost-effective option for grey iron and price-sensitive grades.
View product →A fully-graphitized, low-sulphur recarburizer — graphitized petroleum coke (GPC) or graphite electrode scrap (GES) at S ≤ 0.05%. These protect the magnesium treatment, give 90–95% absorption and consistent nodularity.
Sulphur consumes the magnesium used to spheroidise graphite, increasing treatment-alloy cost and causing dross and poor nodule formation. Low-sulphur carbon additives preserve magnesium recovery.
Typically 8–12 kg of recarburizer per tonne of iron, depending on charge composition and target carbon. Confirm with trials for your specific furnace and charge.
GCA can work for some ductile grades and is cheaper, but its higher sulphur and lower absorption make GPC or GES the safer choice for high-integrity nodular castings.
Tell us your target carbon, maximum sulphur, furnace type and size fraction — we'll recommend a grade and quote FOB/CIF to your port.
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