RU2278168C1 - High magnesium flux - Google Patents

Abstract

FIELD: ferrous metallurgy, in particular flux for steel=making industry.

SUBSTANCE: claimed magnesium-containing rock-based flux contains (mass %): magnesium oxides 90.0-92.0; calcium oxides 2.00-5.00; and balance: target additive. As starting raw materials hydrate form of magnesium-containing rock are used. Flux additionally carbon may contain, and in this case flux comprises magnesium oxides 80.0-82.0; calcium oxides 2.00-5.00; carbon 8.00-12.0; and balance: target additive.

EFFECT: intensified slag-forming process; improved protection of converter casing.

2 cl, 2 tbl, 1 ex

Description

The invention relates to ferrous metallurgy, in particular to fluxes for steelmaking.

Today, steel production uses fluxes based on magnesia-silicate (Mg ₂ SiO ₄ ) or magnesia-carbonate rocks (MgCO ₂ ) from natural materials: magnesite, forsterite, dolomite, etc.

Known magnesia flux (see Patent RU No. 2205232), including a mixture of slag-forming components in the form of oxides of magnesium, aluminum, iron, silicon and calcium, and as components of the slag-forming mixture use ferruginous dolomite containing oxides of magnesium, aluminum, iron, silicon and calcium in the following ratio of components, wt.%: MgO 32.0-33.5; Al ₂ O ₃ 0.5-0.95; Fe ₂ O ₃ 2.0-5.0; SiO ₂ 2.5-3.0; CaO - the rest.

The closest to the claimed invention a composition of the same purpose, adopted as a prototype for both variants of the invention, on the set of essential features is the composition of the well-known lime-magnesia flux (see Patent RU No. 2145357) with a low melting point and high reactivity for its dissolution in steelmaking slag melts containing, wt.%: 26.0-35.0 magnesium oxides, 0.3-7.0 aluminum oxides, 5.0-15.0 iron oxides, 0.5-7.0 silicon oxides and the rest - calcium oxides.

The general applied technological scheme for the production of these fluxes:

fine grinding of the mixture wet or dry;

mixing with other components with the addition of sintering additives such as scale, iron-containing slag and cyclone dust, etc. (in this case, the content of MDO ranges from 35 to 50%);

sintering of this mixture in rotary kilns at a sufficiently high temperature (t = 1570-1670 ° C), while in the furnace the mixture is granulated and sintered to form a strong and low-porous surface film, which is necessary to give the flux granules sufficient mechanical strength for transportation and low surface porosity in order to avoid saturation by physical moisture during storage and transportation.

The reasons that impede the achievement of the following technical results include:

1) the inability to achieve a high content of magnesium oxide in the production of flux due to its low content in the used natural raw materials;

2) high thermal heating in the production of flux;

3) low chemical activity of the flux when it enters the slag of the converter - due to the high temperature of heat treatment of the flux during its production, high density and low porosity (the heating temperature of the flux in the converter should be higher than the melting temperature of sintering additives (i.e., t = 1550-1650 ° FROM));

4) increased flux consumption to obtain the desired effect in the converter. (today at ZSMK OJSC in Novokuznetsk, the flux consumption is 15-30 kg / t of steel, at other enterprises - up to 80 kg / t.);

5) a long assimilation time of flux in the slag, i.e. long time steel production in the converter.

The problem to which the invention is directed, is to improve the slag regime of oxygen-converter smelting and increase the life of the converter by using a new high-magnesia flux.

The technical result that can be obtained by implementing the claimed invention is to intensify the process of slag formation and better protection of the converter lining.

The specified technical result is achieved due to the fact that the known flux for the production of steel based on magnesia-containing rocks contains ingredients in the following ratio, wt.%:

I - option

Magnesium oxides - 90.0-92.0

Calcium Oxides - 2.00-5.00

The rest is the target supplement,

II - option

Magnesium oxides - 80.0-82.0

Calcium Oxides - 2.00-5.00

Carbon - 8.00-12.0

The rest is the target supplement

and the hydrated form of magnesia-containing rocks is used as a feedstock for its production.

Thus, the inventive high-magnesia flux contains magnesium oxides in an effective amount of 80.0-92.0, wt.%.

The target additive is a mixture of components (a small percentage of the total mass of flux up to 10 wt.%), Which are neutral carriers from the circle traditionally used in compositions for this purpose, which can be represented by oxides of silicon, iron and aluminum, as well as other ingredients , which are, in particular, binders in the process of briquetting (briquetting) flux.

The intensification of the process of slag formation is achieved by reducing the rate of assimilation of flux in the converter to 1-2 minutes due to an increase in the rate of release of magnesium oxide as a result of molecular shock - intensive dehydration of the flux with the formation of magnesium oxide.

A significant amount of calcium and magnesium oxides contributes to the formation of fusible spinels with low melting points.

Bearing in mind that the lining of modern steelmaking units consists of magnesian refractories, in order to reduce their consumption, steelmaking slags should contain the necessary amount of magnesium oxides in equilibrium with the magnesium oxides in the refractories. The amount of magnesium oxides in the flux is determined by the obtained content of magnesium oxides in the slag after the flux is supplied to the steelmaking unit.

In the claimed invention, the natural material used as a raw material contains a large amount of magnesium oxide (80-92 wt.% Per calcined substance), a sufficient amount of which is formed when flux enters hot slag. Magnesium oxide, having a high chemical activity, intensively reacts with slags, significantly reducing their chemical activity with respect to the magnesia lining of the converter, with its further thickening and drawing on the lining in the form of a skull. With such protection of the lining, the converter service life is increased from 1500-2000 heats (in the prototype) to 6000 -10000 heats.

To thicken the slag when applying the skull on the lining and partially compensate for heat loss during the release of hydrated water, a flux is added (according to the second embodiment of the invention) additionally containing carbon in the following ratio of ingredients, wt.%:

Magnesium oxides - 80.0-82.0

Calcium Oxides - 2.00-5.00

Carbon-8.00-12.0

The rest is the target supplement

An additional technical result, which consists in reducing energy and labor costs in the production of flux, is achieved due to the fact that:

- flux for steelmaking in the converter is obtained on the basis of the hydrated form of magnesia-containing rocks, i.e. raw materials are used, the processing technology of which eliminates the labor-consuming and energy-intensive process of heat treatment of flux;

- the process of slag formation occurs at a sufficiently low temperature for heating flux.

Savings are also achieved due to a significant reduction in flux consumption (from 15-80 kg / t of steel in the prototype to 5-10 kg / t during the implementation of the claimed invention) due to the use of natural material with a high content of magnesium oxide.

The claimed high-magnesia flux for steelmaking in a converter is obtained on the basis of the hydrated form of magnesian-containing rocks. Natural material is brucite (Mg (OH) ₂ ).

The flux is made from brucite semi-dry pressing method on presses or briquetting machines. In this case, the porosity of the flux briquette from it is close to zero with sufficient mechanical strength, which allows the transportation and storage of flux data.

The characteristics of brucite are given in table 1.

Table 1 Mass fraction of oxides,% MgO Cao SiO ₂ Fe ₂ O ₃ Raw 62.0-68.0 0.9-2.0 0.5-1.0 0.12-0.2 Per calcined substance 90.0-97.5 1.4-5.0 0.8-3.5 0.2-0.3

Table 2 shows the physicochemical parameters of high-magnitude fluxes VFM-1 (according to the first embodiment of the invention) and Navy-2 (second embodiment of the invention):

table 2 Name Navy-1 Navy-2 Chemical composition: % MgO 90.0-92.0 80.0-82.0 Cao 2.00-5.00 2.00-5.00 FROM - 8.00-12.0 Target supplement 3.00-8.00 1-10 Tensile strength in compression - not less than: n / mm ² fifteen fifteen Mastering time in slag, min 1-2 1-2

An example of the use of flux in converter smelting and the application of a skull. When flux gets on the hot slag of the converter (t = 1500-1600 ° C), a molecular hydroblow occurs as the flux is heated. This effect begins at a sufficiently low temperature for heating flux (400-500 ° C). Intensive flux dehydration occurs with the formation of magnesium oxide (the release of chemically bound water). The porosity sharply increases and many cracks and microcracks are formed (since in the flux up to 30% hydrated water, the porosity is reached 50-55%).

The process is fast enough. Magnesium oxide, having a high chemical activity, intensively reacts with slag along newly formed cracks and microcracks, significantly reducing the chemical activity of slag in relation to the magnesia lining of the converter, with its further thickening and drawing on the lining in the form of a skull. The dissolution time of the flux in the slag is 1-2 minutes.

To improve slag formation and reduce the chemical activity of slag, a flux is introduced at the first stage with a maximum content of magnesium (Navy-1) MgO> 90%.

To thicken the slag when applying the skull in the converter and partially compensate for heat loss during the release of hydrated water, a flux of the VMF-2 brand is introduced with a carbon content of up to 10%. As a result, saturation of the slag with magnesium is quickly achieved, in the future - its thickening and, due to this, the application of a skull on the converter lining; converter steel production time is reduced; converter service life increases - up to 6000-10000 heats; labor-intensive and energy-consuming flux heat treatment process is excluded; significantly reduced overall labor costs in the production of fluxes. The shape of the flux is a briquette of 40 × 60 × 40 or any other form of a given volume (balls, granules, etc.).

These fluxes are supposed to be used at all metallurgical plants producing steel in converters equipped with magnesia-containing lining.

Claims (2)

1. The flux for the production of steel based on magnesia-containing rocks, containing oxides of magnesium, calcium and the target additive, characterized in that it contains ingredients in the following ratio, wt.%: Magnesium oxides 90.0-92.0 Calcium oxides 2.00-5.00 Target supplement Rest and as the feedstock for its production using the hydrated form of magnesia-containing rocks. 2. The flux for the production of steel based on magnesia-containing rocks, containing oxides of magnesium, calcium and the target additive, characterized in that it additionally contains carbon in the following ratio of ingredients, wt.%: Magnesium oxides 80.0-82.0 Calcium oxides 2.00-5.00 Carbon 8.00-12.0 Target supplement Rest and as the feedstock for its production using the hydrated form of magnesia-containing rocks.