EP0849366A1 - Process for desulfuration of pig iron - Google Patents

Abstract

Desulphurisation of pig iron, prior to steel production in oxygen blown converters, is carried out by intimate contact with a ground secondary metallurgical slag having a basicity of ≥ 4, a low iron content of 4-6 wt.% and a phosphorus content of ≤ 0.4 wt.%, optionally mixed with calcium carbide and magnesium. Preferably, all the components have a particle size of less than 1 mm, the average particle size being 0.3 mm for the calcium carbide, 0.5 mm for the magnesium and 0.7 mm for the slag.

Description

The invention relates to a method for desulfurization for further processing Steel in pig iron converters determines pig iron melts according to the Preamble of claim 1.

A generic method is known from DE 38 36 549 C1. With this The process is called desulfurization slag in the oxygen blowing process accruing converter slag added. The converter slag is optionally in liquid form directly from the converter to the pig iron certain treatment pan filled and then the pig iron on the Poured slag. Alternatively, it is suggested that after casting from the Converter cooled converter slag in small pieces with a maximum piece size of 50 mm and to be added to the pig iron in this form. Disadvantageous in the known method, the low sulfide capacity is that used Converter slag so that the proportion of additional expensive desulfurization reagents is still very high.

DE 88 16 829.8 U1 describes as a means for desulfurization of Pig iron melting indicated a mixture of calcium carbide and magnesium. Around to ensure good dosing during injection and to ensure segregation to prevent even during long standing and during transport, it is proposed that the bulk density and the grain size of both components in the same range lie. In a preferred embodiment, both components are with one coated oily liquid. As a result, there is still the possibility of segregation lower and the dosing is possible even more precisely.

The object of the invention is to provide a process for the desulfurization of pig iron to indicate, in which the proportion of the usual expensive desulfurization reagents such as Calcium carbide and magnesium significantly reduced and the amount of amount of slag to be disposed of and disposed of is reduced.

This object is achieved with the in the characterizing part of claim 1 specified features solved. Advantageous further training is part of Subclaims.

In contrast to the known prior art, no converter slag, but a slag obtained in secondary metallurgy, e.g. B. Ladle slag or calcium carbide together with magnesium or slag with calcium carbide and magnesium as a solid mixture in ground form used. Through the upstream grinding the Desulfurization reagents pneumatically conveyable and improve the Desulfurization conditions, because of the small grain size the specific Surface is enlarged. The grain size is for all used Reagents below 1 mm, the average for calcium carbide 0.03 mm, for Magnesium is 0.5 mm and 0.7 mm for the slag. The advantage of using This slag can be seen in that it has a basicity of at least 4 and low iron content in the range of 4 - 6 percent by weight and phosphorus content ≤ 0.4 percent by weight. Since the ladle slag usually has another has an average relative humidity of 8%, this z. B. one Grind drying to avoid caking in the diving lance. The secondary metallurgical slag prepared in this way is suitable, optionally via a Immersion lance directly in the pig iron treatment or blast furnace pan or in the Cast iron gutter to be introduced.

By using a ladle slag as a desulfurization reagent reduced the cost of the hot metal desulfurization process. At the same time reduces the amount of slag to be disposed of and disposed of, which in turn has a cost-effective effect.

The method according to the invention is explained in more detail using an example.

200 t of pig iron with an S content of 500 ppm are placed in a treatment pan filled. By blowing in 100% ground ladle slag (20 kg / t Pig iron) the sulfur content in the pig iron is reduced within 15 min. on salaries Lowered to <200 ppm. The further desulfurization takes place with the addition of Calcium carbide and magnesium.

Claims (6)

Process for the desulphurization of pig iron melts intended for further processing into steel in oxygen blow-up converters, in which the melt poured into a ladle is brought into close contact with a slag which is produced in the steel production process and contains calcium oxide and other desulphurization reagents, the slag being processed into small pieces before being used.
characterized,
that as slag the slag obtained in secondary metallurgy with a basicity of min. 4 and low iron contents in the range of 4 - 6 percent by weight and phosphorus contents in the range of ≤ 0.4 percent by weight in ground form alone or the slag obtained in secondary metallurgy is used together with calcium carbide and magnesium as a solid mixture in ground form. Method according to claim 1,
characterized,
that the grain size of the desulfurization reagents is less than 1 mm, the average being set for calcium carbide 0.3 mm, for magnesium 0.5 mm and for the slag 0.7 mm. Process according to claims 1 and 2,
characterized,
that the slag is subjected to a drying treatment. Method according to one of claims 1 -3,
characterized,
that the desulfurization reagents are blown into the melt under excess pressure. Method according to one of claims 1-4,
characterized,
that the desulfurization reagents are introduced directly into the pig iron, blast furnace or pig iron gutter. Method according to one of claims 1-5,
characterized,
that the slag is used for a pre-desulfurization of the pig iron and the further desulfurization is carried out with the addition of calcium carbide and magnesium.