CN1291657A - Flux and process for forming slag of converter - Google Patents

Abstract

The invention provides a converter slagging flux and a slagging process using the flux. The flux is bauxite composed of the following components: Al ₂ O ₃ ≥ 45%, SiO ₂ ≤ 30%, Fe ₂ O ₃ 7-18%, the balance is impurities such as CaO, MgO, TiO ₂ , P, S, etc. The particle size of this ferrite is 5-30mm, and the amount used depends on the type of steel being made and the silicon content of the molten iron. The range is 1.6-9kg bauxite/ton of steel. The slag-making process is to add the first batch of slag-making material and half of the specified amount of bauxite at the beginning, and add the remaining part of bauxite when adding the second batch of materials. This flux and its slagging process are conducive to slagging , high desulfurization efficiency, good furnace protection effect, low cost and beneficial to improve the life of the ladle.

Description

Converter slagging flux and slagging process

The invention belongs to the field of converter steelmaking, in particular to a novel flux and a slagging process using the flux.

In the slagging process of converter steelmaking, in order to speed up the melting of lime and make the dephosphorization, desulfurization and blowing operations go smoothly, it is necessary to add a certain amount of flux. In the production practice of converter steelmaking so far, fluorite is the only or the most important flux.

The main component of fluorite is CaF ₂ , which has a low melting point and can significantly reduce the melting point of CaO, so it is widely used as a converter flux. However, fluorite has an erosive effect on the lining of the converter. After implementing the new process of slag splashing to protect the converter, due to the increase in the amount of MgO-containing materials, the MgO content in the slag is increased. The use of fluorite slag is not ideal, and the slag is prone to dryness and sticking guns. Moreover, fluorite has great corrosion on the slag-splashing layer, which is not conducive to slag-splashing to protect the furnace. In addition, when fluorite is used to make slag, some fluoride ions will volatilize and dissolve in the dust removal sewage, causing environmental pollution. The high price of fluorspar is not conducive to reducing costs.

The object of the present invention is to provide a new converter slagging flux and a slagging process using the flux, improve the slagging effect of the converter, improve the effect of slag splashing and reduce the slagging cost.

The object of the present invention is achieved through the following technical solutions: adopt the following composition of bauxite as slagging agent: Al ₂ O ₃ ≥ 45%, SiO ₂ ≤ 30%, Fe ₂ O ₃ 7～18% balance is CaO, MgO, TiO ₂ , P, S and other impurities, the particle size of this bauxite is 5-30mm. The amount of bauxite used is 1.6-9Kg/ton of steel.

Both Al ₂ O ₃ and Fe ₂ O ₃ in bauxite are fluxes, and Al ₂ O ₃ can form 3CaO·Al ₂ O ₃ and 12CaO·7Al ₂ O ₃ with CaO in lime, and the melting points of these two substances are respectively are 1535°C and 1455°C, therefore, Al ₂ O ₃ can lower the melting point of CaO and promote the melting of lime.

Therefore, bauxite is used as a flux, the higher the content of Al ₂ O ₃ the better; the less the content of SiO ₂ and other impurities, the better.

The converter slagging process using bauxite as a flux is as follows: when the oxygen lance is lowered and oxygen is blown, the first batch of slagging materials (active lime and lightly burned dolomite) and half of the specified bauxite amount are added, that is, 0 ．8～4.5kg/ton of steel. At the start of the second batch (activated lime and light burnt dolomite), about halfway through blowing, the remainder of the bauxite was added.

For the 180-ton converter steelmaking process with a blowing time of about 20 minutes, the first batch of materials, including active lime, light-burned dolomite and half of the specified amount of bauxite, is added at the beginning of blowing, that is, 0.8 to 4 ．5kg/ton of steel, when the blowing reaches 9-11 minutes, add the remaining part of the second batch of active lime and bauxite, which helps to avoid slag back-drying, in case of slag back-drying, it can be The gun position is increased by 200-800mm to promote slag removal.

The amount of bauxite added depends on the type of steel being made and the silicon content of the molten iron. When the molten iron contains Si ≥ 0.3%, the middle and lower limits are taken when blowing low-carbon steel, that is, 1.6-4kg bauxite/ton of steel, and the middle and upper limit is taken when blowing high-carbon steel, that is, 6 ~9kg bauxite/ton of steel.

When the molten iron contains Si<0.3%, the amount of bauxite added is 6-9kg/ton of steel. The molten iron contains low Si content, generates less SiO ₂ , generates less heat, and has poor slag fluidity, so the amount of flux should be added.

In a 180-ton converter in a steel plant, bauxite is used as a flux. When the molten iron Si is ≥ 0.3%, 0.4-0.8 tons of bauxite is added to each furnace of steel (equivalent to 2.3-4. 6kg/ton of steel), blowing for 3 to 4 minutes, the slag can be melted. Under the premise of controlling the lance position, there is basically no back-drying during the blowing process, and the final slag has good fluidity, and the entire slag melting process is better than that of fluorite. When the molten iron contains Si<0.2%, it is more difficult to melt the slag. During the blowing process, the phenomenon of slag re-drying is easy to occur. The amount of bauxite added should be increased to 1.1-1.5t (equivalent to 6-8.3Kg/ton of steel), and the slag situation is similar to that of fluorite.

Using bauxite as a flux, the slag can be observed to flow along the furnace lining when the furnace is turned down, indicating that the slag has good wettability with the furnace lining and is easy to bond with the furnace lining, which is beneficial to slag splashing to protect the furnace. The slag-splashing layer was almost invisible when the above-mentioned converter was turned over with fluorite before the test with bauxite. After the slag was made with bauxite, the lining bricks were almost invisible when the furnace was turned up, which indicated that there was a complete slag-splashing layer. To achieve the purpose of making steel on the slag-splashing layer, so as to protect the furnace by slag-splashing and prolong the service life of the furnace lining.

A large number of tests have proved that the use of the new flux ferrite of the present invention instead of fluorite slag has the following characteristics

1. It is beneficial to the slag in the blowing process.

2. It can improve the desulfurization rate of the converter, and the desulfurization rate is increased from 35% using fluorite to 49.4% using bauxite, an increase of 14%, but the dephosphorization rate is slightly worse.

3. To reduce the cost of slagging, the price of fluorite is 409 yuan/ton, and the price of bauxite is 120 yuan/ton, which can reduce the cost of slagging by 1.8 yuan/ton of steel.

4. It can significantly improve the effect of slag splashing to protect the furnace.

5. Reduce the fluorine content in converter dedusting water to meet the requirements of environmental protection standards.

6. Can significantly improve the life of the ladle.

Claims (6)

1. A converter slagging flux, characterized in that the flux consists of bauxite composed of the following components: Al ₂ O ₃ ≥ 45%, SiO ₂ ≤ 30%, Fe ₂ O ₃ 7-18%, and the balance It is CaO, MgO, TiO ₂ , P, S and other impurities. The particle size of this ferrite is 5-30mm, and the usage amount is 1.6-9kg ferrite/ton of steel. 2. The converter slagging flux according to claim 1, characterized in that: when the molten iron contains Si≥0.3% for blowing low-carbon steel, the usage amount is 1.6-4kg bauxite/ton of steel. 3. The converter slagging flux according to claim 1, characterized in that: when the molten iron contains Si < 0.3%, when blowing low-carbon steel, the usage amount is 6-9kg bauxite/ton of steel. 4. The converter slagging flux according to claim 1, characterized in that: when blowing high-carbon steel, the amount used is 6-9 kg of bauxite/ton of steel. 5. A slag-making process using the converter slagging flux described in claim 1, characterized in that: while adding the first batch of slagging materials active lime and lightly burned dolomite in the blowing of the lower oxygen lance, adding the prescribed bauxite Half of the amount, that is, 0.8 ~ 4.5kg/ton of steel; until the second batch of material is added, that is, half of the time of blowing, add the remaining part of bauxite. 6. The converter slagging process according to claim 5, characterized in that: when the total blowing time of the 180-ton converter is 20 minutes, the first batch of live lime and half of the specified amount, that is, 0.8 ～4.5Kg bauxite/ton steel, when the blowing reaches 9～10 minutes, add the second batch of active lime and the remaining part of bauxite, if the slag returns to dryness in the subsequent blowing process, then The gun position is increased by 200-800mm to promote slag removal.