This inoculant is very powerful and gives high nodule count with powerful chill reduction,and reduces shrinkage tendency of the casting. It has a low oxide content and reacts with the iron in a clean manner with little dross formation.
It performs well in grey iron containing above 0.05% sulphur and promotes a good graphite structure. It also does better in this class of iron than other specialist inoculants.
Various inoculants can be used to enhance the microstructure of cast iron. The physical properties of the inoculants determine their effect on the castings, such as their shrinkage tendency and mechanical characteristics. The microstructure of ductile cast iron can vary significantly depending on the type and amount of inoculant used during the pretreatment process, the charge material, the spheroidization method, and the inoculation process itself.
Strontium inoculant has a powerful chill removal effect and promotes a fine, uniform type A graphite structure. It is particularly effective in grey irons containing 0.05% sulphur or higher, and can also be used for low sulphur cast irons if the addition rate is reduced.
Zirconium incorporated into strontium ferrosilicon has two further effects: it improves the fluidity of molten iron and can prevent the formation of nitrogen blowholes. It also refines the graphite flake size to a fine, evenly distributed type A graphite and reduces white mouth defects. It is more effective than calcium alone in reducing the tendency of castings to develop a cementite structure.
Inoculants are used to promote the nucleation of graphite in the molten iron. They can be introduced in the form of a nodulizing grade ferrosilicon that is added to a clean, deslagged melt in the furnace or an inoculating alloy that is added either to the stream of iron filling the ladle or as part of the cast iron itself.
The inoculant should have a low melting point and a high surface energy to attract carbon atoms from the molten metal. The inoculant should also have a chemical composition that is compatible with the base charge and melt temperature of the cast iron.
The inoculant should also have slag-resistant properties to prevent the formation of chill and white mouth. In addition, it should be easy to add and dissolve in the molten iron. Lastly, it should have a stable and long-lasting effect on the casting process. This is because the inoculant can lose its effectiveness due to changes in the metallurgical conditions of the melt.
The inoculant alloy according to the invention can be used in the treatment of thick parts of ferro-silicon-based cast iron. It contains between 0.005 and 3% by weight of rare earth elements and also contains between 0.2 and 2% by weight of antimony, which makes it a nodulating alloy. It can be used in the context of the inoculation of a melt bath and also in the pre-conditioning of the cast iron.
When the inoculation process is not well controlled, the formation of degenerate graphite and/or chunky graphite can reduce the mechanical properties of the cast iron. To prevent these defects, the smelter generally proceeds to the addition of pure antimony in the liquid iron. The sulfides formed by these elements have lattice parameters that are very similar to those of graphite and therefore act as a nucleation catalyst. This allows the sulfides to initiate the graphite nucleation and growth mechanism in the melt. The inoculant is thus very efficient.
Silicon carbide is an inorganic material with a low neutron cross section and good resistant to radiation damage. It can be used as a deoxidiser in the steel industry to remove impurities in the melt. Fine silicon carbide can also be used to inoculate gray and ductile cast irons. It enhances the microstructure parameters and plastic properties of these materials by promoting graphite nucleation and increasing the number of eutectic clusters in grey iron and eutectic balls in ductile iron.
Elkem produces a range of ferro-silicon inoculants for grey and ductile cast irons. These are available in a wide variety of sizes suited to the foundry industry. The most commonly used product is SMZ (an analogue to CP) which is a 65% Si based ferro-silicon inoculant and contains controlled amounts of calcium, zirconium, manganese and barium. The granules are available for both ladle and in-stream use. This inoculant gives very low dross content, high chill removal and excellent graphite morphology. It is a powerful inoculant for grey irons containing over 0.05% sulphur and requires a lower addition rate than other inoculants.
English
Write a Message