[0001] The present invention concerns a desulphurizing mixture for the hot treatment of
cast iron in the steel production.
[0002] It is already well known that the presence of great quantities of sulphur in the
fluid cast iron determines the result of a brittle and crystalline steel.
[0003] It oftenly occurs, furthermore, that the percentage of the sulphur present at the
beginning of the treatment is of 0,040% in weight, and even more, and a good de- sulphurizer
should reduce said value to 0,01%, which means a quantity acceptable in view of the
end product.
[0004] At present, it is known to the art that, for the desulphurization of cast iron, a
mixture of 70% calcium carbide = CaCO
2, and of 30% calcium carbonate = CaC0
3 is used. As lime proves to have more affinity with sulphur = S than.with iron = Fe,
in the treated cast iron the following reaction takes place:
[0005] As it is evident, in said reaction the sulphur will be reduced to calcium sulphide
= CaS, that will remain in the bath in the form of slag and will be eliminated, thus
obtaining the standard value of 0,01% according to the needs.
[0006] It is the aim of the present invention to realize a desulphurizing mixture for the
treatment of cast iron using easily obtainable materials that will furnish, as the
known ones, good qualitative results.
[0007] The aim is reached by the mixture according to the present invention, characterized
in that the same improves the mechanical movements of the bath, said movements being
determinant for obtaining the desulphurization, said mixture consisting in:
[0008] In the percentage values of the calcium oxide and of the magnesium oxide, the variant
of calcium hydrate = Ca(OH
2), in a weight percentage from 1% to 30%, may be provided for the same purposes.
[0009] In a preferred variant being exemplifying and not limiting, the mixture according
to the present invention consists in:
[0010] The function of the components is the following: the calcium carbonate will be decomposed
into:
whereby the forming of carbon dioxide C0
2 molecules in the treated mass highly agitates the bath, improving the reaction of
exchange with the sulphur = S.
[0011] The eventual presence of magnesium = Mg compounds is due to the relevant affinity
of magnesium with sulphur = S.
[0012] Furthermore, as the treatment will be effected, according to the present invention,
in torpedo waggons, by a lime injection or blowing in, causing a temperature lowering,
the presence of the fluorite = CaF
2 keeps the mixture fluid, lowering the melting point.
[0013] In a further variant, the mixture comprises alumina percentages for improving the
efficiency of the treatment.
1. A desulphurizing mixture for the treatment of cast iron that will improve the mechanical
movements of the bath, characterized in:
2. A desulphurizing mixture for the treatment of cast iron according to claim 1, characterized
in the presence of calcium hydrate = Ca(OH2) in a percentage from 1% to 30%, in replacement of similar quantities of calcium
oxide = Ca0 and magnesium oxide = MgO.
3. A desulphurizing mixture for the treatment of cast iron according to claim 1, characterized
in the following components and weight percentages:
4. A desulphurizing mixture for the treatment of cast iron according to claim 1, characterized
in the presence of alumina for improving the efficiency of said treatment.
