Recarburizers

A recarburiser is a high-carbon addition material used to adjust and restore carbon content in molten iron or steel. It is added during melting or ladle treatment when the carbon level falls below the target specification, especially when the charge mix contains a high proportion of steel scrap or low-carbon metallics. Recarburisers help foundries and steelmakers reach target carbon levels without depending only on carbon-rich charge materials.

Sulfur is a critical selection criterion because it directly affects final metallurgy. Ductile iron (GJS / GGG) and compacted graphite iron (CGI) require very low residual sulfur to support effective magnesium treatment. Excess sulfur carried in by the recarburiser can reduce magnesium recovery, increase treatment demand, and negatively affect nodularity. Grey iron is more tolerant of sulfur, making cost-effective moderate-sulfur grades viable where the sulfur budget allows.

For ductile iron (GJS / GGG) and compacted graphite iron (CGI), recarburiser grades with %S at or below 0.06% are generally recommended. PREMCO EG (99.0% C, 0.04% S), PREMCO SG (98.5% C, 0.05% S), PROCARB SG (98.5% C, 0.05% S), and PROCARB SGP (97.5% C, 0.06% S) fall within this ultra-low-sulfur range. Their low nitrogen content, typically 0.05-0.06% N, also helps reduce the risk of nitrogen-related porosity in sensitive ductile iron applications.

Grey iron (GJL / GG) is generally more tolerant of sulfur than ductile iron, so a wider recarburiser grade selection is available. PREMCO 10 through PREMCO 40, PRIMCO 50, PROCARB 99, the CARBON 99 GPR series, CARBOSTEEL, CARBON PELLETS, CARBON CA, and CARBON 90 cover the %S 0.10-1.50% range used in grey iron practice. Final grade selection depends on the target iron chemistry, sulfur budget, nitrogen tolerance, melt shop practice, casting section thickness, and cost requirements. For thin-section grey iron or applications sensitive to nitrogen defects, lower-nitrogen grades should be preferred even when sulfur tolerance is higher.

Nitrogen dissolved from the recarburiser can contribute to sub-surface nitrogen porosity or pinholes in castings if total nitrogen pickup exceeds the solubility limit during solidification. This risk can be especially relevant in grey iron and thin-section castings. Ultra-low-nitrogen grades such as PREMCO EG, PREMCO SG, PREMCO 10, and PROCARB SG, all at 0.05% N, help reduce nitrogen pickup from the recarburiser and lower the risk of nitrogen-related porosity. For applications tolerant of moderate nitrogen levels, cost-effective grades with higher sulfur and nitrogen may be considered.

Yes. OPTES Group metallurgy specialists provide grade selection support based on alloy type, target carbon level, process conditions, sulfur and nitrogen budgets, charge mix, melt practice, and cost requirements. OPTES supplies James Durrans recarburisers from the UK to foundries and steelmakers across MENA and Africa. Contact OPTES for a technical consultation to select the suitable grade for your process.