A new inoculant was developed for reliably solidifying ferritic ductile iron with thin wall dimensions. The inoculant contains calcium but very little aluminum, which results in low dross formation.
Metallographic observations show that the strontium nucleating agent refines the microstructure of the alloy, reducing the length and number of chromium carbide needles. Energy-dispersive spectroscopy analysis shows that the carbide phase share is reduced, too.
Ferro silicon strontium inoculant is one of the most effective promotion elemtnts. It can improve graphite morphology in molten iron and reduce chill depth,shrinkage defects of casting. In addition, it has the characteristic of reducing calcium level in molten iron to lower the melting point,which can significantly reduce the cooling rate of the molten metal and avoid casting density loss.
IM SR is an inoculating alloy made of 75% ferrosilicon containing controlled amounts of calcium, zirconium, manganese, barium and aluminum. It has been used for many years in the cast iron industry and is particularly suited for situations where there is an increased tendency to shrinkage.
Sphere-o-Dox (SOD) is a proprietary blend of oxy-sulfide-forming elements that replaces high-potency rare earth based inoculants in numerous foundries. SOD can significantly increase the inoculation effectiveness of standard 75% fsi foundry grade inoculants in both gray and ductile irons. In ductile irons, SOD can increase nodule count and ferrite levels, reduce carbides, and improve elongation.
Unlike most regular inoculants, this inoculant has very low levels of Aluminum and Calcium. Small amounts of these elements seriously reduce the nucleation efficiency of Sr-containing inoculants. This is one of the reasons that Superseed is the most successful inoculant ever developed. It is able to achieve a much greater reduction in chill than all other inoculants.
It is produced by reacting in a submerged arc furnace with quartz, scrap iron and a carbon source to produce a liquid ferrosilicon melt. The liquid ferrosilicon is then mixed with strontium silicon, zirconium silicon or a mixture of the two.
The inoculant is then added to molten iron in order to facilitate the formation of eutectic crystals. In gray irons, this results in reduced chill and carbide formation and improved machinability. In ductile irons, the inoculant can help improve nodule count and ferrite levels and may reduce gummy deposits. The inoculant is also able to reduce shrinkage and bleeding in thin wall parts, as well as non-uniform wall thickness.
The present invention provides a new type of inoculant which is effective for promoting the inoculation of cast iron, particularly corrosion-resistant and steam and water pressure gray iron with strict requirements on the surface of the casting. The inoculant is based on ferrosilicon and contains a combination of calcium, strontium and zirconium.
The inoculant is produced by adding a suitable form of strontium to a liquid bath of ferrosilicon, such as through the addition of a strontium carbonate or sulfate. The sulfate is especially preferred for this purpose because it is less likely to cause undesirable metallurgical reactions than the carbonate.
The inoculant is subsequently added to the molten bath of gray cast iron to be reacted with the metal elements of the cast iron. Compared to a sample treated with a commercial silicon-bearing inoculant and an untreated sample, the results demonstrate that the invented inoculant remarkably reduces the chill phenomenon and thereby produces a casting with superior characteristics.
A low Calcium content in the inoculant, combined with a low Aluminum level in the inoculant, helps to keep the dross (slag) to a minimum. This is especially important for those foundries that produce shell molded castings, which require annealing to remove carbides.
This inoculant is also effective in cooling the melt and reducing the amount of residual calcium that causes chill. It can be used as an in-ladle addition or as a spheroidizer/nodulizer in a tundish cover ladle.
This inoculant has been developed to help the foundry industry better meet government pollution regulations and improve operating efficiencies within their companies. It uses a computer information system that incorporates artificial intelligence to automate specialized expertise and then provides that expert advice to a wide variety of geographically-dispersed foundry operators. The system identifies potential pollutants and recommends methods to prevent them. It is a very useful tool for small foundries, which often have limited in-house expertise.
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