Cover Alloy Improves Ductile Iron Production

Elkem’s recently introduced cover alloy, Topseed®, is changing the way that our customers think about their magnesium ferrosilicon treatment process.

Designed to,

  • Improve magnesium recovery
  • Conditions the reaction slag
  • Increase residual nucleation levels
  • Improve process stability,

Topseed® has already proved to be a great benefit in many foundries across North America, Europe and Asia.

Topseed, is a relatively dense product. Being closely graded, the product provides a complete and even covering of the MgFeSi alloy in a properly designed ladle pocket. When the iron is tapped into the ladle, the onset of the Mg reaction is delayed considerably.
Topseed is applied at 0.4-1.0% addition rate normally depending on the ladle design, the magnesium content of the MgFeSi, ladle pocket dimensions and the metal temperature.

  1. Improved Magnesium Recovery
    Magnesium recovery is increased through the use of Topseed® cover alloy. Through the delayed contact between the cast iron and the MgFeSi alloy, there is a greater ferrostatic head of iron in the ladle when the reaction does start. The result is increased magnesium vapour/cast iron contact and thus the recovery efficiency is improved.
    This allows for a decrease in reactive magnesium content of the MgFeSi alloy (for example from 6% to 4.5%) and thus have less negative effect on the nucleation levels. The use of low Mg content Elmag® nodulariser and Lamet ® nodulariser in conjunction with Topseed® has proved very efficient in many foundries.
  2. Slag Conditioning
    Most reaction slags from nodularising treatments are liquid when the operators remove these from the ladle. This can be an inefficient and environmentally unfriendly process with many airborne particles from unexpanded perlite based coagulants. The addition of barium as a part of the Topseed® composition changes the slag phases to a solid and more easily removed dross. This also encourages the slag to precipitate in the treatment ladle rather than further down the casting process and cleaner stopper rods, pouring vessels and less dross inclusions result.
  3. Increased nucleation potential.
    Nucleation levels in base iron are critical to the subsequent physical and mechanical properties of the iron. Topseed® has a positive influence on the nucleation levels as it contains balanced additions of Ba, Ca and Al, all of which are beneficial positive contributors to nucleation.
    Higher nucleation levels in the treated metal can mean less susceptibility to shrinkage and chill and thus the demand for subsequent inoculation may be reduced.
  4. Improved process stability.
    Very consistent Mg residual levels are found when using Topseed® cover alloy. One foundry which uses a high Mg containing alloy has variations in their Mg of ±0.002% Mg, a factor of 3-4 better than their previous process. This has enabled them to optimise their MgFeSi and inoculants additions.

For further information, please contact your local Elkem representative or

Asia (exc China):