SU1693081A1 - Method of making electrical steel - Google Patents

Abstract

The invention relates to metallurgy, in particular to methods of after-treatment of steel, and can be applied to the production of low carbon and low grain electrical, for example, dynamic steel. The purpose of the invention is to improve the quality by reducing the sulfur content and reducing the carburization, reducing the consumption of aluminum. In the production of electrical steel, a mixture of lime, fluorspar and alumina-containing material (preferably mullite) is used in the quality of the refining material in a ratio of (4-8): 1: (1-4). The mixture is fed in the amount of 8–16 kg / t of steel into the melt stream at the outlet, after which 0.3–1.0 min after the end of the mixture input is introduced aluminum wire, and the duration of the exposure before the wire introduction increases proportionally to the increase in the mixture consumption . The use of technology allows to increase the sulfur content to 0.005%, to exclude carburization of the melt. 1 tab. (Ls

Description

The invention relates to metallurgy, in particular to methods of after-treatment of steel, and can be applied to the production of low carbon and low sulfur electrical, for example, dynamo steel.

The purpose of the invention is to improve the quality by reducing the sulfur content and reducing the carburization.

The deacidification of the metal stream with aluminum wire reduces the consumption of aluminum by 1.5-2.5 times as compared with the deoxidation of metal by lumpy or powdered aluminum, which leads

to reduce the amount of the resulting. Under these conditions, the use of a slag-forming mixture with a ratio of lime, fluorspar and mullite (4–8): 1: (1–4) ensures the production of liquid homogeneous slag with high desulphating capacity and, as a result, low ( no more than 0.005%) of sulfur content in electrical steel.

It was established by experiments that slag to contain the required desulfurization of steel should contain,%: CaO 40-55; SaRa 5-10; ADOZ 25-35; SI02 5-15. This slag composition is provided by the proposed

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the ratio of the components of the mixture at its consumption of 8-16 kg / t of steel.

- When the mix ratio is (more than 8): 1: (less than 1), a heterogeneous slag is formed with chunks of undissolved lime, with the result that steel desulfurization deteriorates sharply and the final sulfur content in electrical steel becomes more than 0.01%, which is unacceptable

When the mix ratio is (less than 4): 1: (more than 4), a viscous, heterogeneous slag is formed with pieces of insoluble mullite and a low (less than 35%) content of CaO. Steel with such slag is practically not desulfurized.

The content of CaCO3 in lime within the range of 5–25% is necessary to accelerate slag formation in the ladle due to the grinding of the lime pieces released during the heating of CO2. In addition, CO2 released from lime contributes to the loosening of the mixture on the metal mirror, which prevents the formation of large slag conglomerates of the mixture, which can cause metal splashes from the ladle after the release of smelting.

When the CaCO3 content in lime is less than 5%, the lime pieces are not destroyed and do not have time to dissolve in the slag within 3-7 minutes of smelting from the converter, which negatively affects the desulfurization of steel. Increasing the content of CaCO3 more than 25% is unacceptable because of the additional cooling and carburization of the metal.

At high aluminum contents, as is the case in dynamo steel (0.3-0.6% At), carbon dioxide released during the decomposition of CaCO3 is partially reduced by aluminum with carbon to metal, which is unacceptable.

The established start interval for the introduction of aluminum wire into the stream after 0.3–1 min after the introduction of the slag-forming mixture into the ladle ensures effective desulfurization of the steel without its carburization. The value of 0.3 min relates to the case of an additive of a small amount of a mixture of 8 kg / t and a short duration of release of 3 min, and 1 minute to an additive in a bucket of 16 kg / ton of mixture and a duration of release of smelting 7 minutes

In the case of the introduction of aluminum wire in less than 0.3 minutes after the addition of the mixture, carburization of steel takes place, and more than 1 minute - deterioration of desulfurization.

PRI me R 1. Dinamna steel was smelted in a 165-ton converter on a metal stock of 747 kg / t of pig iron with a sulfur content of 0.028% and 357 kg / t of imported scrap.

The melt was purged for 18 minutes with oxygen of 99.5% purity with a flow rate of 50 Nm3 / t. As a slag-forming agent, 80 kg / ton of metallurgical lime were placed in the converter.

Intermediate before release from the converter contained,%: C 0.03; Mp 0.09; P 0.009; S 0,018, and had a temperature of 1640 ° C. Melting converter was produced in

0 bucket with sour stuffed lining. 10 seconds after the start of the release, the ladle was set for 40 s of 8 kg / t of slag-forming mixture of lime, fluorspar and mullite, taken in a ratio of 4: 1: 1. Lime of gas firing in pieces of 10-60 mm contained 92% CaO + MdO and 5% CaCO3 as a drop. Lime, fluorspar with a content of 60-70% CaF2 and crushed mullite fractions of 0-10 mm (waste lining

0 buckets) with a content of 62% were fed into the workshop along the path of bulk materials, they were poured through metering devices into a receiving bin, from which they were fed into the bucket by wheelbarrow.

5At the end of the additive mixture into the ladle from the tray

ferrosilicon (65% Si) and metallic manganese were seated.

The introduction of aluminum wire with a diameter of 12 mm was started 0.3 minutes after the completion of the slag-forming additive.

0 mixture and continued to enter for the entire duration of the release of melting, which amounted to 3 minutes. The consumption of aluminum wire was 5 kg / t steel. The resulting slag was homogeneous, fluid, contained,

5% by weight: CaO 40; CaF2 10, ABOz 35; SI02 15. In the finished steel after purging the metal in the ladle with argon contained, wt.%: C 0.03; S 0.005; AI 0.3, which meets the requirements for the chemical composition of dynamo steel III, and

0 doping groups of not more than 0.03% C, 0.05% S, and 0.3-0.6% AI.

EXAMPLE 2 Melting was carried out in the same way as in Example 1, the composition of the slag-forming mixture corresponded to the upper level of the specified limits, the final chemical composition of the steel corresponded to the requirements for dynamo steel.

PRI me R 3. The technological parameters of melting corresponded to intermediate

0 values of the proposed limits. In terms of C, S and A content, the mixture was prepared to match the required values.

EXAMPLE 4. Melting was carried out above the upper level of the proposed limits on the composition of the slag-forming mixture, its consumption, the content of CaCO3 in lime, with less than the specified time limit for the start of the addition of aluminum wire after the end of the additive was used (with the mixture). unsatisfactory desulfation of 0.02-0.010%, additional carburization of steel 0.02-0.05%, which was associated with the formation of heterogeneous slag (with pieces of insoluble lime) slag, and the reduction of aluminum carbon from C Cos. On melting after release from the vessel occurred splashing from the ladle slag due to the floating of adhering fute- Rovkov slagging slagging mixture. In view of the unsatisfactory chemical composition of C and S was discarded melting.

PRI me R 5. Melting was carried out outside the lower level of the proposed limits on the composition of the slag-forming mixture, its consumption, the content of CaCO3 in lime and exceeding the upper limit of the start time for the addition of aluminum wire. In this melting, there was practically no desulfurization of the metal due to the low CaO content in the resulting slag. After purging the steel in the ladle with argon, the slag was viscous with pieces of undissolved mullite. Due to the high sulfur content (0.018%), smelting was rejected.

 Example 6. As a comparison, the melting is shown, which was made according to the prototype version. Planck was carried out under the same conditions (in a 165-ton converter and released into a bucket with an acid lining). A mixture of lime, fluorspar, limestone, and pig aluminum was used as a desulfurizer, which was placed in a ladle before release of smelting in the amount of 12 kg / ton. Aluminum wire insertion is not applied. The result was

significant carburization of the metal due to carbon reduction from CaCO3 (from 0.93 to 0.05%), which led to the separation of steel from the third alloying group. The consumption of aluminum on this smelting was almost 2 times higher than in examples 1-3.

These examples are summarized in the table.

Thus, the production of dynamic steel according to the proposed method, within the recommended limits of technology, allows for the deep desulfurization of steel (l 0.005% S), avoiding metal carbonization, reducing the consumption of aluminum and, ultimately, ensuring the production of high dynamic steel. quality.

Claims (1)

Invention Formula A method for the production of electrical steel, which includes melting in a converter, producing melt in a ladle with slag cut-off, and introducing refining material, aluminum wire and deoxidizing agents into the ladle, in order to improve the quality by reducing the sulfur content. and reducing carbonization, reducing the consumption of aluminum, a mixture of fluorspar lime and alumina-containing material, preferably mullite, is used as a refining material in a ratio of (4–8): 1: (1–4), with es is administered in an amount of 8-16 kg / t steel, the wire is administered through 0,3-1.0 minutes after completion of the adding the mixture, and the duration of exposure to the start of inputting wire increases proportionally to the mixture flow. Technological parameters of steel production Huimer steel production -y-g- | --d -j ---- Content in the metal before release, wt.%: carbon0.030.02 - 0.025 sulfur0.0 (80.0300.025 The composition of the slag-forming mixture, dol: lime 8o fluorspar111 mullit1 3 Content of CaCOA in lime, May.525-8 Slag consumption mixtures, kg / t 81612 The time of addition of the slag-and-euuzeum mixture after the start of the smelting production, s102015 The duration of the additive IL-co-mixture, SAO605Q 0.02 0.015 9 1, 5 3 20 5 70 0.03 0.020 3 one 0.5 28 6 20 35 o.oz 0.030 five one 8 15 1 (0 60 Huimer 0.03 0.020 o.oz 0.030 3 one 0.5 28 6 20 35 five one 8 15 1 (0 60 1693081 & Table continuation