SU1027235A1 - Method for smelting steel - Google Patents

Description

The invention relates to ferrous metallurgy, in particular to the smelting of silicon steel in arc furnaces.

There is a known method of smelting silicon steel, in which the intermediate product is first smelted in a converter, then melt is deoxidized and doped with ferrosilicon in a ladle, after which the metal evacuates and sets a certain amount of aluminum during vacuuming 1 for nitrogen.

The disadvantage of this method is the impossibility of removing sulfur from the melt, since in its implementation it is impossible to obtain slag with a high desulfurization ability. The addition of ferrosilicon to an undiluted metal (deoxidation and doping occur in the ladle at the same time) leads to high and uncontrollable silicon burns and contamination of the metal with fine inclusions of silica, resulting in a deterioration of the magnetic characteristics of the finished steel.

The closest in technical essence and the achieved effect is the method of steel smelting, including melting, decarburizing the melt with gaseous oxygen, downloading oxidizing slag, adding aluminum, silicon, lime and fluorspar to the furnace, doping in the ladle, melting the furnace with furnace slag as it leaves the furnace and vacuuming, with simultaneous purging of the melt with argon f2 2

However, according to the well-known technological scheme, the overflow from the shovel into the ladle and the associated increase in the nitrogen content in the melt during the helium and the additional oxidation of the metal with oxygen in the atmosphere are retained. In addition, the presence in the smelting scheme of processing of the overwork in two steps slows down the smelting, requires additional overheating of the metal in the furnace, which in turn causes an increased waste of alloying elements and oxidants. J The aim of the invention is to improve the quality and magnetic characteristics of steel.

The goal is achieved by the method of steel smelting, O involving melting, decarburization of the melt with gaseous oxygen, downloading of oxidizing slag, aluminum, silicon, lime and fluorite dopant furnace, doping in the ladle, melt processing with furnace slag and vacuuming with simultaneous melting. purging the melt with argon, aluminum and silicon are introduced into the Furnace in an amount of 0.1.0-0.14 and 0.10-0.15 kg / ton of steel per 1 kg / ton of slag-forming steel, respectively, introduced into the furnace after oxidizing slag is charged, and vacuums Starting after the argon flow rate has been adjusted to purge the melt in the skull, it ensures the release of the molten slag on the surface equal to 10-20% of the total surface area in the ladle.

The method was tested in the smelting of electrical steel alloyed with 3 silicon, in an LLP-ton arc furnace. On the basis of the melts carried out, it was found that desulphurization of steel with furnace slag is quite effective when it is discharged from the furnace and subsequently processed in vacuum in a vacuum only if by the time of production a sufficiently chemically active slag is formed in relation to sulfur while ensuring that aluminum steel at a level of 0.02-0.03.

Average data on the content of elements in the experimental swimming trunks are given in Table 5. 1 and 2. .Table 1

table 2

0.0235

0,017

Taking into account the actual sulfur distribution coefficient, to obtain the final sulfur content in the steel at the level of 0.005-0.007%, it is necessary to have at least kg / ton of slag melt of the indicated composition / The indicated slag compositions are reached if after the oxidative slag is loaded into the furnace, after each kilogram of the oxidation period of slag-forming 0,100, 1 kg / ton of aluminum and 0.10-0.15 kg / ton of silicon. The deposited aluminum is almost completely oxidized by the oxygen of the metal and residual slag, forming alumina passing into the slag. Two-thirds of the silicon additive is transferred to the metal, and a third is oxidized to form silica, which transfers to: slag. These ratios of additives allow the formation of a sufficiently active slag, with the help of which sulfur is removed during the process of melt production from the furnace and during the treatment with argon in vacuum.

The addition of aluminum in an amount of less than 0.10 kg / t per 1 kg / t of slag-forming materials leads to insufficient deoxidation of the shalk and metal, while the necessary alumina content in the slag is not reached, which leads to slag with a lower sulfur absorption capacity.

The addition of aluminum in the amount of more than O, W kg / t per 1. kg / t of slag-forming improves; properties of the slag, an increase in its sulfur-holding capacity, however, this improvement in slag properties is not possible

0.011

0,0053

0.021

0.029

used in the processing, metal slag due to insufficient I contact duration of slag and metal. The processing time is limited by the temperature conditions of the smelting. Thus, a higher consumption of such an expensive material, such as aluminum, is not justified in the subsequent use of slag with a high content of alumina. In addition, the addition of aluminum more than O, N kg / t per 1 kg / t of slag-forming leads to an increase in the residual aluminum content in the metal, which leads to a deterioration of the magnetic characteristics of the steel.

Silicon addition in the amount of less than 0.10 kg / t per 1 kg / t of slag-forming materials, introduced into the furnace after oxidative slag has accumulated, leads to insufficient deoxidation of the metal and slag, which in turn entails additional aluminum consumption. Additive more than 0.15 kg / t per 1 kg / t slag-forming leads to an increase of

5, the silica content of the slag due to the oxidation of silicon with metal and slag oxygen, which impairs the desulfurization ability of the slag.

0

The specified amount of slag (45-50 kg / t) reaches an additive of 20-25 kg / t of lime and 3-5 kg / t of fluorspar, taking into account the residual oxidizing slag, the amount of which in experimental melts is 5-10 kg / t because the completely oxidizing slag cannot be downloaded.

If the amount of residual slag (in composition is iron-iron at a level of kg / t, then 25 kg / t of lime and 3 kg / t of fluorspar are seated.

With a larger amount of residual slag (at the level of kg / t) in the neUb, less “lime 20 kg / t and 5 kg / t of fluorspar are seated. The presence of a certain amount of residual slag contributes to the rapid dissolution of the new slag-forming additive and the formation of a new slag. A differentiated aluminum and silicon additive for deoxidation, depending on the slag-forming consumption, ensures the production of aluminum oxides, silicon and calcium in the slag in optimal ratios from the point of view of desulphurisation capacity of the slag.

After the metal is released from the furnace and treated with furnace slag, the metal with the bucket is placed in a vacuum chamber and the chamber is not covered with a lid. This argon flow is used to blow the melt in the ladle, which provides the melt to be exposed on the surface equal to 10-20 of the total area noBepxHoqTH in a ladle. After that, continuous purging with argon, cover the chamber with a lid and begin evacuating. Setting the optimal flow rate of argon on the open chamber facilitates visual observation of the behavior of the metal in the ladle. It is difficult to perform this operation during vacuuming, and in some cases it is not possible at all, since the smoke produced during vacuuming is impeded by observation of the melt behavior in the ladle, the amount of which is significant, especially in the first minutes of the melt. The control of argon consumption on the instruments does not provide an objective control, since the total consumption on the instrument is recorded for purging and leaks, which are unavoidable during the purging process.

When argon is consumed with the surface of the melt exposed on the area of its 10% melt is not sufficiently intensively mixed, the exchange processes between the metal and slag, the metal and the gas phase do not develop in full measure.

With argon consumption, accompanied by metal abuse over an area of over 201 the entire surface area

in the ladle, the melt is agitated so intensely that slag can be ejected from the ladle during the vacuuming process.

As shown by pilot plsvki, mixing of the melt under vacuum with argon with a flow rate that, at atmospheric pressure, the exposure of the melt to / area 10-20% of the total surface area in the ladle is accompanied by

efficient removal of hydrogen, sulfur and non-metallic inclusions from the melt.

PRI me R 1. The steel is smelted in a 100 ton arc furnace. The mixture consists of scrap steel and cast iron. After the charge is melted and the bath is heated to 1 ° C, the furnace is turned off and the oxidation period is carried out by blowing the melt with gaseous oxygen through a roof tuyere with an intensity of nm / h. When the carbon content reaches 0.022% and the temperature reaches 1–60 ° C, the purge is stopped and the oxidizing slag is charged. The amount of residual slag is about 700 kg (7 kg / t). After downloading the slag 4 to the kiln, 2000 kg (20 kg / t) of lime and 500 kg (5 kg / g) of fluorspar are set down. The number of deoxidizers, sit down in the furnace, calculated as follows.

oryr 51 (65%): 300: -0.65 60 kg,

After the addition of slag-forming and deoxidizing agents, the furnace is turned on for 5 minutes, then the metal and slag are mixed by padding and the smelting is released into the ladle. By the time of release, the slag contains wt.%: 3102 Al20.a22, l; CaO 52; FeO 3.23; MgO 10, U5; MnO 1.27

s 0,051.

A 65% ferrosilicon is placed in the bottom of a steel-teeming ladle equipped with a device for unstoppable casting and a porous tank for argon flushing to set up the alloy (about 8 tons of L). The metal bucket is installed in the chamber, the temperature is measured and the required flow rate of argon is set, regulating its supply with a valve and completing the release of the melt surface in the ladle from slag over an area of 10–20% of the total surface area. Having installed the required flow rate of argon, cover the chamber with a lid and begin evacuating the melt. vacuum is carried out for 15 minutes, gradually increasing the vacuum in the chamber to mm Hg, the holding at the specified pressure is 5 minutes. At the end of the vacuuming, the bucket with metal is fed to the spike. The finished metal contains,%: O, 032 Si 2 , 9T; Mp OD7-, S 0.007; N 0.008; A1 0.018; OO, UN. P. p. And R 2. Melting is performed according to the technology of analogue to Example 1 Upon reaching the carbon content of 0.019 and the temperature of the bath 1670 ° C oxygen is switched off, oxidative slag is loaded, containing up to 60 FeO. The residual amount of slag is about 500 kg (5 kg / t. The 2500 mm 25 kg / ton of lime and 500 kg (5 kg / ton) of fluorspar are seated by the Dumping Machine. The amount of aluminum and silicon squeezed into the deoxidation furnace is: 0, 1 (25 + 5.), 2 kg / t XX 100 kg G5i 0.15 125 + 5; ", 5 kg / t X 5 ... X 100 kg F.esi (, 65,690 kg For the rapid formation of slag, furnace they turn on the bath for 7 minutes, stir the bath and melt it into the ladle. Metal vacuum treatment is carried out according to the technology similar to that described in Example 1. The finished metal contains,%: C 0.029, Si 3.02, Mp 0.20 V 0.005; N 0.009; O 0.0038 A1 0.022. When introducing the proposed smelting technology in the electric steel-melting shop of the Cherepovets Metallurgical Plant, it was possible to reduce the casting of cast slabs and hot rolled rolled products due to defects in the gas bubble, fpeu (HHa, reduce the metal contamination by nonmetallic inclusions, improve the structure cast metal, increase the yield of higher grades of electrical steels. In addition, it was possible to improve the range of technical and economic indicators of smelting in comparison with the previously applied technology under the scheme with alloying in a furnace and without vacuum treatment (Table 3).

T1102723512

The annual economic effect from the release of useful slabs in the depletion of deoxidizing agents into electric furnaces and in the smelting shop and in sheet dressers of additional materials is, with an annual decrease in the duration of smelting, producing 10 thousand tons of electric energy consumption, an increase in s thousand roubles.

Claims (1)

METHOD OF MELTING STEEL, including melting, decarburization- ·. the melt with gaseous oxygen, the loading of oxidizing slag ', the addition of aluminum, silicon, lime and fluorspar to the furnace, alloying in a ladle, processing the melt with furnace slag and evacuation with simultaneous purging of the melt with argon, characterized in that, in order to improve the quality and magnetic characteristics of steel, aluminum and silicon are introduced into the furnace in the amount of, respectively, 0.100.14 and 0.10-0.15 kg / t of steel per 1 kg / t of steel slag-forming introduced. into the furnace after downloading the oxidizing slag, and evacuation begins after the argon consumption for purging is established, providing g release of the melt from the slag on the surface equal to 1.0-20% of the total surface area in the ladle. SU „„ 1027235 1 1027235! 2