SU1518383A1 - Composition for refining steel in ladle - Google Patents

Abstract

This invention relates to ferrous metallurgy, namely to secondary treatment of steel. The purpose of the invention is to improve the refining properties of the mixture when processing steel in a ladle. The mixture contains,%: 9–12 coke, 55–65 limestone, 12–25 aluminum, and 8–14 grade A technical lignosulfonates. The alumina formed after deoxidation participates in the removal of sulfur and non-metallic sulfide inclusions from steel. Technical lignosulfonates not only fix the mixture on the refractory lining of the bottom of the casting ladle, but also decompose, give lignosulfone salts of potassium, calcium, sodium, which liquefy oxide inclusions, which accelerates their coalescence and removal from the metal. The use of the mixture allows reducing the content,%: of hydrogen by 34-37, a measure of 50-52, oxide inclusions by 55-59, sulphide inclusions by 45-48, reducing scrap by 7.4 kg / ton of steel. 1 tab.

Description

This invention relates to ferrous metallurgy, namely to secondary treatment of steel.

The purpose of the invention is to improve the refining properties of the mixture.

The mixture for bucket refining of steel contains coke, deoxidizer, oxides to alci, thinner in the following ratios, Mac.Z:

Aluminum 15-25

Known to 55-65

Technical lignosulfonates brand A 8-14

Cox9-12

Sieve materials are mixed and the binder is added until a homogeneous mass is obtained. The binder not only holds the particles together, but also ensures their attachment to the refractory bottom of the ladle. In the preparatory ladle, the smelting is released from the furnace.

The mixture on the bottom of the bucket is heated by the metal. Aluminum melts and flows from the mixture into the mixture, where it reacts with

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with

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with

dissolved oxygen to form oKCH / ia aluminum.

The limestone in the mixture decomposes to produce carbon dioxide stirring steel in the ladle. The resulting freshly calcined dispersed calcium oxide (CaO) is a desulfurizer, the refining abilities of which further increase with the formation of low-melting compounds with aluminum oxide and oxides from the decomposition of lignosulfonates.

Carbon dioxide (COj) bubbles are a chemical vacuum relative to hydrogen dissolved in steel. The subsequent regeneration of carbon dioxide by coke carbon is accompanied by a twofold increase in the volume of gas that does not contain hydrogen. Due to this, the refining properties of the mixture are significantly improved, since degassing conditions are improved and mass transfer processes between the metal and slag are intensified due to mixing with a large volume of gas.

When the content in the mixture is more than 25% of aluminum, its refining ability is low. This is due to the fact that the amount of alumina significantly exceeds the amount required for the formation of low-melting compounds with calcium oxide. Lignosulfonates are completely consumed to liquefy the refractory mixture of aluminum and calcium oxides. Liquid complex compounds are not formed, which, together with a lower purge intensity, due to the low yield of carbon monoxide due to the lack of other ingredients, worsens steel refining from non-metallic inclusions.

The use of a mixture containing more than 65% limestone is not accompanied by significant steel refining from non-metallic inclusions. The negative effect is due to the release of calcium oxide in quantities greater than required for the formation of low-melting compounds with alumina resulting from steel deoxidation. All lignosulfonate is spent on liquefying calcium oxides and aluminum and is not enough to lower the melting point of the oxides present in the metal. Fusible

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five

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complex compounds lU are formed, which makes it difficult to increase inclusiveness and reduce their speed of removal from steel, reducing the refining effect of isp. This mixture is used.

The treatment of steel with a mixture containing more than 14% of technical lngosulfonates is not effective from the point of view of degassing, since the binding materials of the active participation in hydrogen improvement are not accepted. The available coke is not enough to absorb excess binder, which leads to the spin-on liquidity of technical lignosulfonates. When the upper layer is placed in the KOBCI mixture, the binder is depleted, which reduces the mechanical strength of the dried material. Its top layer during the melt production is eroded, splashes out and decomposes in the pshak, which reduces the degree of refining of the steel mixture.

A mixture containing more than 12% of coke does not allow sufficiently complete refining of steel from harmful impurities. The negative effect of excess coke is explained by the following. A considerable amount of binder is spent on its impregnation, which reduces the strength of the mixture to be attached to the refractory foot 1) O1) ladle box. With the release of smelting, cMecii expands - M11 jet, detaches from the refractor, floats on the surface of the melt, where it decomposes, without having a refining effect on the steel. Excessive coke is not involved in carbon dioxide reduction and is a passive scum that is not involved in refining steel.

The use of the mixture containing less than 12% of aluminum does not allow 31 {) (|) to refined steel from 1metahshchnyh inclusions. This is due both to the lack of aluminum oxide to the formation of liquid compounds with an oxide to silicon and to the increased oxidation of alloying from ferroalloys. Solid alumina and calcium oxides are not efficiently removing sulfur and sulphide inclusions, and the lack of aluminum for deep metal deoxidation increases the pollution of steel and oxide inclusions.

With a content of less than 55% wear on sms si, its refining capacity is low. This is due to the fact that the calcium oxide HHca of the calcium oxide that is formed during shaking is not enough to form light-plastic compounds with aluminum oxide. The lignosulfonates contained in the mixture are completely consumed in the decomposition of refractory calcium and aluminum oxides. Liquid complex oxides from deoxidation products do not form, which, together with a lower purge rate due to the low yield of carbon monoxide, worsens steel refining from non-metallic inclusions.

The mixture, containing; and less than 8% of technical lignosulfonates, has insufficient refining ability. This is due to the poor fixing of the material on the bottom of the pouring ladle. Poor fixation is caused by the high consumption of a binder for impregnation of porous coke in the process of mixing the ingredients. The remaining amount of lignosulfonates is not enough to firmly adhere the mixture to the oi of the bucket. When the bucket is filled, the mixture is torn off from the futer and floats on the metal surface, where it decomposes without significant refining effect on the coal.

The treatment has become a mixture containing less than 9% of coke and is not accompanied by a significant removal of water. This is because coke carbon is not enough to reduce all carbon dioxide produced from limestone decomposition. The volume of gas released from the mixture is small, which reduces the efficiency of degassing

Poor protection of the metal in the bucket and the jet with a small volume of gas emitted from the mixture, from the oxidizing effect of the atmosphere, can lead to increased oxidation of the alloying materials and, consequently, to greater contamination with steel oxide inclusions.

Example. The 20GL steel is melted in the main electric arc furnace. The mass of smelting is 7.5 tons. The mixture consists of 60% limestone, 19% granulated aluminum of the AV-91 brand (GOST 295-79-E), 11% of technical lignosulfonates of the A grade (OST 13-183-83), 10% of ground coke production 2.5-5 mm (GOST 18686-84). Mix consumption 5.0 kg / ton steel Pre-mixed materials for 2 min before release are placed n: yudgs: tovitel- Hhiii for casting a ladle, which is given to the smelting during drying. The temperature of the steel in front of the hopper is 1 LOBO-1 L81 / i :, the sulfur content is O, 03) - (), O 8%. Before} Chl | - start-up of smelting from the furnace of the oxygen reduction of the determination of the content of hydrogen and non-metallic inclusions in the steel. Throughout the entire release of the needle from the furnace, intensive mixing of the tall melt melt by pop-up gas bubbles occurs with the donkey. After calming down the steel, the ladle is transferred to the plz a live span and begins to be cast. In parallel with the marking, samples are taken for the content of hydrogen and non-metallic inclusions in steel.

The mixture is also tested in an outdated manner when the melt is released from the furnace in the process of filling the ladle from the level corresponding to 1/5-3 / 4 of the volume of metal being produced.

Samples from known tests are taken in the same way as when testing a proposed item.

The table below contains information about changes (all contents are harmful for the refining of times. Exp .: with Ml:. im.

H: The data presented here shows that the maximum refining ability possesses the proposed mixture IripitMepb 1-3 /. 1: e application reduces the content of hydrogen in the stalp by 34–37%, sulfur by 50–52% of oxide inclusions — by sulphide inclusions — by 45–48%, and also reduces scrap by 7, H kg / t sts1li.

Formula and 3 L1 b ete n and

A mixture for steel refining of steel, containing coke,; silicon, limestone, and a diluent, characterized in that, in order to improve the refined properties, technical grade lignosulfonates with the ratio of ingredients, wt.%:

Aluminum 12-25

Known to 55-65

Technical leagues ossulfonates grade L 8-14

Cox9-12

Claims (1)

Claim A mixture for ladle steel refining containing coke, aluminum, limestone and a thinner, characterized in that, in order to improve the refined properties, technical grade A lignosulfonates are used as a thinner in the ratio of ingredients, May.%: Aluminum 12-25 Limestone 55-65 Technical lignosulfonates of the brand Λ 8 -14 Coke 9-12 Example The composition of the mixture, 7 Reduced steel content 7 Coke Aluminum Famous nanny Technical lignosulfonates hydrogen sulfur Oxy ’Dov sulfides 1 9 12 65 14 37 fifty 55 47 2 10 19 60 eleven 34 52 59 48 3 12 25 55 8 36 fifty 59 45 4 ' eleven 26 54 9 26 28 44 22 5 8 18 59 fifteen 22 34 34 29th 6 10 eleven 66 thirteen 34 26 28 23 7 thirteen 17 63 7 18 31 37 28 8 Known method 20 44 ' fifty 39