SU1511283A1 - Method of melting rail steel from high-phosphorus iron in oxygen converter - Google Patents

Abstract

The invention relates to the field of metallurgy, and more specifically to steelmaking in an oxygen converter from high-phosphorus pig iron. The purpose of the invention is to reduce the phosphorus content in steel with a carbon content of at least 0.5% and to prevent emissions when cast iron is cast. The goal is achieved due to the fact that 1.4-4.0 kg / ton of fluorspar steel is added to the slag of the previous smelting left in the converter before draining high-phosphorus pig iron — to liquefy the slag and better assimilate lime, and then a mixture of carbon-containing material and lime at a ratio of 0.05: 0.2 in the amount of 20 ... 50 kg / t of steel. 1 tab.

Description

The invention relates to metallurgy, specifically to the smelting of rail steel B by an oxygen converter from highly phosphorous cast iron.

The purpose of the invention is to reduce the phosphorus content in steel with a carbon content of at least 0.5% and to prevent emissions when cast iron is cast.

According to the method, 1.4-4.0 kg / t of fluorspar steel are placed on the previous slag melting slab, then a mixture of carbonaceous material and lime at a ratio of 0.05-0.2 in the amount of 20-50 kg / t of steel.

Fluorspar is set down to increase the liquid mobility of the left slag of the previous smelting and more intensive dissolution of lime. This technique contributes to the accelerated production of basic slag with a high refining ability. However, the rapid dissolution of lime occurs while mixing it with slag. Otherwise, the lime, which is attached to the slag, does not dissolve well and floats on it in the form of a lump. To mix the lime with the slag, it must be mixed with the carbon-containing material. The latter, when interacting with iron oxide and the formation of carbon monoxide, counteracts the work of lime.

At. when planting fluorspar less than 1.4 kg / t of steel, the left slag quickly loses liquid mobility and the lime is not mixed with the introduction of the mixture

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is in the slag. If the amount of fluorspar to enter more than 4.0 kg / ton of steel, the liquid active slag is retained after the mixture is added for a long time, but it is not safe from TOMKI for the formation of an explosion when casting iron.

In the first minutes of purging the main slag with high phosphorus cnoco6Hocfbro, 20-50 kg / ton of steel containing a mixture of carbonaceous material and lime should be applied to the left slag in the converter.

When the additive mixture is less than 20 kg / t of steel, slag during its intermediate download (6-8 minutes of purging) has insufficient basicity. In addition, it retains a high fluidity, and this, as noted above, is dangerous.

If the additive mixture is more than 50 kg / ton of steel, then lime is used irrationally, since it remains in the slag, with many insoluble pieces of it.

To obtain a slag with a high refining capacity, it is necessary that the ratio of carbon-containing material and IchCot be 0.05-0.2.

If this ratio is less than 0.05, then the lime is poorly kneaded in the slag, since sparging is insufficient. In addition, the slag is not completely neutralized. Pouring iron on liquid slag with a high content of ferrous oxide is dangerous.

When using a mixture with a ratio of carbon-containing material and lime more than 0.2, lime s I dissolves poorly to slag due to i rapid slag coagulation due to a sharp decrease in its oxidability. : P r and m er. In the 350-tonne converter, 0.7 t of fluorspar, then a mixture of carbon-containing material (coal) and lime with a ratio of 0.1 in the amount of 15 tons are deposited on the left slag of the previous smelting, 35 tons of scrap are poured and 305 tons of highly phosphorus pig iron are cast (P 1.2A%). The purge starts with an oxygen consumption of 1150 m3 / min. The position of a tuyere 3.5 m to two minutes of production, then the tuyere is lowered to a level of 1–5 m. After steady ignition of the heat, 10 tons of i

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20

25

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50 55

35

40

45

STI and purge intensity is reduced to 800 m3 / min. In the eighth minute, the purge is stopped and the intermediate slag is downloaded. At the 9th minute of the purge, 10 tons of lime and 0.5 tons of fluorspar were injected into the converter. The purge rate is 800. The position of the tuyere 1.5 m. At the twelfth minute download the intermediate slag. On the thirteenth, 7 tons of lime and 0.25 tons of fluorspar were introduced into the converter.

The process stops when the carbon content in the metal is 0.72, phosphorus is 0.02, the temperature of the steel. The content of phosphorus pentoxide in the first intermediate slag is 14.6%, in the second - 9.21.

The metal in the ladle is acidified with silica-manganese in the amount of 3.6 tons, ferrosilicon (65%) - 0.66 tons and aluminum - 100 kg.

Get rail steel of the following composition: carbon 0.73; manganese 0.82; silicon 0,2b; phosphorus 0.025, sulfur 0.02 and aluminum 0.02. Melting takes place without significant emissions of metal and slag from the converter. Steel yield 0.9%. Technological indicators of pilot-industrial melts, carried out on the proposed (with going beyond the optimal values) and by known methods, are shown in the table.

Experiments show that the best results in reducing the phosphorus content in steel were achieved in options 4-6. At the same time on swimming trunks of the proposed method in comparison with the known phosphorus content is reduced by 0,020-0,023%.

Claims (1)

Invention Formula The method of smelting rail steel in an oxygen converter from high-phosphorus cast iron, which includes leaving the previous smelting slag, introducing carbon-containing material into the slag, lime, casting iron, oxidizing the melt with alternating position of the tuyere, slag loading and obtaining standard slag and metal, that, in order to reduce the phosphorus content in steel with a carbon content of at least 0.5% and Pre 51511283 to prevent emissions, when pouring in something else, a mixture of carbon-containing guna is put on the left slag, additional material and lime, and fluoride spackle, respectively, is introduced in a ratio of 0.05-0.2 in the amount of 20 limewood 1, -, 0 kg / t of steel, after. 50 kg / t steel.