SU1696495A1 - Steelmaking process - Google Patents

Abstract

The invention relates to methods for the production of steel, especially high-quality, in modern high-performance melting units of mining metallurgy. The purpose of the invention is to reduce the content of line and globular oxide inclusions at the same level of sulfur and sulphide inclusions. The metal smelted in the steel-to-steel unit is produced without slag and is treated in the ladle with slag produced in the ladle from a solid mixture of lime and fluorspar during deoxidation of the metal and slag with aluminum and silicon. If necessary, purge with inert gas. Materials containing iron oxides in a total amount of 2–5 kg of iron oxides per ton of steel are placed in portions in the first half of the production in batches. Moreover, the first portion is at least 1 kg per ton of steel. The content of stitched and globular inclusions decreases to 25 25-0.5 points. 1 tab. yo

Description

The invention relates to methods for the production of steel, especially high-grade, in modern high-performance melting units of the steel industry.

The purpose of the invention is to reduce the content of line and globular oxide inclusions at the same level of sulfur and sulphide inclusions.

In the case of adding iron oxides from a solid oxidant at the beginning of production to the slag composition (based on calculation of 8-17%), the slag melting temperature decreases, which favorably affects the slag formation rate, its refining ability (reduced viscosity, increased elution to metal etc.), which provides the best metal refining from deoxidation products. In addition, the oxidized slag particles emulsified into the metal, which have not yet been deoxidized at the beginning of the discharge, have a low desulfurization ability, and a sulfide shell is not immediately formed on their surface. Therefore, such particles have time to be enlarged to critical

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measures (50-60 µm), which ensure their removal from steel, even when the slag particles are deacidified and the sulfide envelope is subsequently formed, which appears on the surface of the slag particle after its deoxidation as a result of metal desulfurization. As a result, the steel is not contaminated with globular oxide slag inclusions of complex composition. The deacidification of the slag in the ladle provides the necessary level of desulfurization of the metal without contamination with its globular inclusions.

The proposed amount of slag oxidizers, 2-5 kg of iron oxides per ton of steel is necessary to create the desired level of slag oxidation at different stages of smelting production, depending on the steel grade, technology, type of smelting unit.

The upper limit of the consumption of iron oxides 5 kg per 1 ton of steel is due to the following: the amount of slag based on lime and fluorspar formed in the ladle usually does not exceed 2-2.5%, 5 kg of iron oxides constitute another 0.5%. Thus, the amount with iron oxides is about 3%. There is not enough metal heat to melt more slag. The amount of iron oxides in this slag, without regard to slag deoxidation, is " 17%.

At the same time, an increase in the concentration of iron oxides requires an increase in the consumption of deoxidizing agents for slag deoxidation; therefore, it is impractical to exceed the limit of 5 kg of iron oxides per 1 ton.

With a lower input limit of 2 kg / t, the amount of iron oxides is 0.2% and their content in the slag is 58%.

Decreasing the content of iron oxides does not reliably remove stitched and globular inclusions.

The lower limit of the introduction of the first portion of 1 kg of iron oxides per ton of steel can be justified as follows: the minimum amount of slag formed in the ladle based on lime and fluorspar is about 1.0%. With fewer, the results of processing, for example desulfurization, are not significant. 1 kg / t is 0.1%, taking iron oxides into account, the amount of slag is 1.1% and the maximum amount of iron oxides in this slag is "9%."

This amount of iron oxides is maximally possible, in practice it is significantly lower due to the deoxidation of slag by metal, including for medium and high carbon steels. For example, carbon deoxidation is possible for bearing steels. Thus, the content of iron oxides even at the beginning of the release may be reduced to 5-6%, which is very close

to the point of view of contamination with globular inclusions, the content of ferrous oxide in the slag is 5%. Therefore, squatting less than 1 kg of iron oxides per 1 ton of steel in the first portion is impractical.

0 Example 1. Bearing steel grade SHKh15SG is melted in a 40-ton furnace on a fresh charge. In the furnace melts after the charge is melted, the oxidation period is carried out, then the oxide slag is swayed by 50-60% and the carbon, chromium, and manganese contents are refined under the furnace slag residues. Before the release of smelting the remains of slag are downloaded. Lump deoxidizers are placed on the bottom of the bucket.

0 (ferrosilicon and aluminum) for the deoxidation of slag and metal. At the beginning of the release, after the discharge of 5% of the metal, a slag mixture is placed in the ladle: 750 kg of lime, 200 kg of fluorspar and solid oxidizer - 240

5 kg of iron ore pellets (magnetite content of about 85%), which corresponds to the upper limit of the addition of iron oxides 5 kg / t. This amount of the concentrate is set down in the first half.

0 bucket. The temperature of the metal before the release of melting 1840 ° C. The results of smelting: the temperature of the steel in the ladle is 1525 ° С, the sulfur content in the finished steel is 0.010%, the average score of non-metallic inclusions:

5 sulfides 2.25; line oxides 2.65; globular oxides 0.4.

Example 2. In the smelting of 100 tons of the furnace, after melting the charge and carrying out the oxidation period, oxidative slag is pumped up by 60-70% and the metal is refined in the furnace according to the content of carbon, chromium and manganese. The temperature of the metal before the release of melting 1620 ° C. Melting is carried out in a steel breaking bucket equipped with a device for flushing the metal with argon through the gate opening. At the beginning of production, the smelting tends to cut off the furnace slag, quickly tilting the furnace. After draining 10% of the metal in

0 ladle injected slag mixtures 800 kg of lime, 200 kg of fluorspar, lump ferrosilicium and aluminum for deoxidation of metal and slag, as well as solid oxidizers - 250 kg of iron ore pellets

5 (2 kg / t - the lower limit). This amount of pellets is introduced when filling 1/3 of the ladle. Then, without interruption, the remaining metal in the furnace is drained. During the discharge, the metal in the ladle is flushed with argon through a pipe in a gate.

The results of smelting: the temperature of the steel in the ladle 1540 ° C. The sulfur content in the finished steel is 0.016%, the average score of non-metallic inclusions: sulfides 2.5; line oxides 2,7; globular oxides 0.25.

PRI me R 3. In the smelting of steel ShKh15 in an arc furnace with a capacity of 100 tons in a fresh charge after melting the charge and conducting an oxidation period, oxidative slag is pumped up to 70%. Launching of steel on chemical composition was carried out in Lechi. The temperature of the steel before the release of 1630 ° C. With the release of the first portions of metal in the ladle, slag mixture is injected: 1000 kg of lime, 250 kg of fluorspar and 130 kg of ore pellets, which is 1.0 kg / t —the lower limit of the amount of pellets that are deposited with the first batch. A second portion of pellets of 2 kg / ton 200 kg is set to 50% before filling the bucket. The slag is formed quickly, despite the minimum amount of pellets in the first batch, apparently due to the ingress of a certain amount of kiln slag.

Melting results: sulfur content in steel is 0.014%, nonmetallic inclusions: sulfides 2.30 points, line oxides 2.45 points, globular oxides 0.35 (rolled diameter of 90 mm).

In general, for all experimental melts, the degree of desulfurization is 40-80%. The points of the lowercase and lower oxides are reduced.

especially globular inclusions in comparison with the known method (slag mixture without the addition of oxidizing agents).

The research results are presented in the table.

Thus, only the addition of iron oxides in the specified amounts and at the specified time delays the process of desulfurization, at the same time providing it in the second half of the release. It is this combination that guarantees simultaneous refining from oxide nonmetallic inclusions and sulfur.

Claims (1)

Claim Method A method for producing steel, including melting the charge, an oxidation period, discharging metal without slag and treating in a ladle with slag from a solid mixture of lime and fluorspar, deoxidizing metal and slag with aluminum and silicon containing materials, if necessary, with an inert gas purge, characterized in that, in order to reduce the content of stitched and globular oxide inclusions with the same level of sulfur and sulphide inclusions, in the first half of the production, materials are placed in portions s iron oxides, a total amount of 2-5 kg iron oxide per 1 ton of steel, wherein the first portion is not less than 1 kg per 1 tonne of steel.