SU1360200A1 - Method of melting steel from low-manganese pig iron - Google Patents

Abstract

The invention relates to ferrous metallurgy and can be used in the smelting of steel from low manganese iron. The purpose of the invention is to reduce the consumption of manganese-containing ferroalloys by increasing the manganese content in the metal at the time of the end of the purge and the increase in the steel input. When steel is smelted at the expense of 90–92 "/ o of oxygen, smelting briefly raises the tuyere by 1.5-3.0 caliber relative to the working position while simultaneously adding carbonaceous materials (iron shavings, ground coke, dust Composer, etc.). .e.) in the amount of 1–4 kg / t and lower the lance to the working position after using 95–97% oxygen. A brief rise of the tuyere raises the temperature of the bath, and in combination with an additive of carbon-containing substance, it facilitates the transition of manganese from slag to metal. 1 tab. C !! b (L

Description

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The invention relates to ferrous metallurgy, specifically to methods for smelting steel in oxygen converters from special cast irons, such as low manganese. The purpose of the invention is to reduce the consumption of manganese-containing ferroalloys by increasing the manganese content in the metal at the time of blowing and increasing the steel yield.

To increase the residual manganese content, a purge mode is necessary, which provides rational conditions for slag formation during the oxygen blowing process while simultaneously reducing manganese at the end of the purge. In the process of refining the technology of low-manganese iron, it was experimentally established that, in order to increase the residual manganese content at the end of the blowdown, the tuyere is lifted by using 90–92% of the total oxygen required for smelting by 1.5–3.0 caliber from the working position with the simultaneous introduction of carbon-containing materials in the amount of 1-4 kg / t, and after consuming 95-97 / o of oxygen, the tuyere is lowered to the working position.

Research has shown that the optimum amount of lifting the tuyere while simultaneously introducing carbon-containing materials is 1.5-3.0 of the above caliber. With an increase in the height of the tuyere above the metal level of more than 3.0 calibers, the process of oxidizing manganese by increasing the slag oxidation begins to dominate over the manganese reduction associated with an increase in the temperature of the metal and slag, which ultimately leads to a decrease in the residual manganese content in the metal and an increase in consumption manganese ferroalloys. In addition, due to the greater oxidation of iron, the yield of steel can be reduced. With an increase in the height of the tuyere above the metal level of less than 1.5 of these calibers, the bath temperature and slag fluid mobility decrease, i.e., the thermodynamic and kinetic conditions of manganese recovery from slag deteriorate due to a decrease in slag oxidation. In addition, part of the carbonaceous materials begins to interact with the metal, and not with the slag. These processes begin to prevail over the increase in manganese, associated with a decrease in slag oxidation. Thus, the residual manganese content will eventually decrease and the consumption of manganese ferroalloys will increase. Reducing the liquid mobility of the slag can heterogenize the slag, which increases the removal of metal, reduces the yield of steel, and also impairs the refining ability of the slag, in particular with respect to sulfur.

During the industrial tests of the proposed method, it was confirmed that

raising the tuyere to a height of more than 3.0 or less than 1.5 of the calibres from the working position while simultaneously introducing carbon-containing materials reduces the residual manganese content by 0.03%,

the consumption of silico-manganese increases by 0.1 tons for smelting with a mass of 250 tons, the consumption of steel decreases by 0.2%.

The raising of the tuyere should be carried out simultaneously with the introduction of carbon-containing materials in the amount of 1-4 kg / ton. Increasing the height of the tuyere above the metal level should reduce the residual manganese content in the metal at the end of the purge. However, the simultaneous introduction of carbon-containing material allows to increase its

content. This is due to the fact that the carbon-containing material interacts more in this case with the slag and restores the oxides of manganese. When a carbon-containing material is introduced less than I kg / t, the reduction efficiency of manganese oxides sharply decreases due to the increased activity of manganese oxides in the slag, and the introduction of carbon-containing material more than 4 kg / ton does not contribute to the reduction of activity and efficiency of carbon-containing

material drops sharply.

When 95–97% of oxygen is consumed, the lance is lowered to the working position. In this case, a better interaction of slag and metal occurs, which, under conditions of increasing metal temperature, contributes to obtaining high residual manganese contents in the metal. By reducing the position of the tuyere by consuming less than 95% of oxygen, the time of exposure of the carbon-containing material to the slag phase is reduced, which leads to a decrease in manganese in the metal, and by decreasing the position of the tuyere by consuming more than 97% of oxygen, the iron loss to the slag decreases and the yield of metal decreases without effectively increasing manganese content

at the end of the purge.

As a carbon-containing material, iron chips can be used. When this is achieved waste-free technology, increased metal yield. The presence of manganese in the iron shavings contributes to its increase in the metal at the end of the purge. As a carbon-containing material, you can also enter anthracite, carbon electrode fight, dust

Depending on the progress of the process, the moment at which the position of the tuyere changes, as well as the amount of carbon-containing material being changed.

Entering carbon-containing material in the form of a powder contributes to its more effective impact on the slag melt due to closer contact and a larger contact surface.

The proposed steel smelting modes were determined as a result of the experimental heats, carried out during the redistribution of low-manganese iron in oxygen converters. Testing the proposed method of steelmaking from low-manganese iron was carried out in 350 tons of converters using iron with a manganese content of 0.15-0.25%.

Example I. In a 350 t converter, during the redistribution of pig iron with the content of manganese O in it, approximately 25 tons of slag were obtained with a manganese oxide content of 1.5 / o. According to the proposed method, I t (3 kg / t) of iron shavings was introduced on one smelting, and 1 t (3 kg / t) of coke on another smelting. The chip composition is as follows: 5% carbon, 1% manganese, 1.5% silicon. Coke has a carbon content of 86%. At the end of the blowdown when the amount of carbon was 0.07%, using the chips, the manganese content was 0.16%, when using coke - 0.17%, according to the prototype - 0.10%. . The calculation of the reduction of manganese from slag is given. At 25 tons of slag with a manganese oxide content of 1.5 / o, 0.375 tons of MpO are contained in the slag.

I option. Used iron shavings.

In 1 ton of chips, the outcome of the given composition, contains 0.05 tons; OO t Mp; 0.015 t Si:

a) recovery of MpO from slag carbon pig iron (MpO + C - - Mn + {CO). On the basis of this equation, 0.05 tons of chips will restore 0.3 tons of MpO from slag, and 0.23 tons of mp will pass into the metal.

b) recovery of MpO from slag by silicon pig-iron chips 2 (MpO) -f Si. (SiOj) -f). From this equation, 0.015 t of Si chips will recover 0.076 t MpO from slag, and 0.059 t Mp will be transferred to the metal.

c) It shavings will contribute to the metal due to the manganese content in it 0.01 t Mn.

Thus, I t of iron shavings will restore the total of slag to 0.376 tons of MpO, i.e., all the MpO contained in the slag. In total, it will go from slag and chips to a metal of 0.3 tons of Mn, i.e. 350 tons - 0.08% for smelting, including 0.065% of manganese due to the carbon of the cast iron chips. If, without the use of cast iron shavings, the residual manganese is 0.10%, then with the full assimilation of manganese using chips, according to the proposed method, it can be 0.18%. .

Option 2. Coke is used.

1 ton of coke contains 0.86 tonnes of carbon. Recovery of MpO from slag by coke coke (MpO) -f Smokhs Mp.

Proceeding from this equation, the uterode contained in the coke is sufficient to recover the entire MpO (0.375 tons), while the metal will transfer 0.29 t Mp, i.e. for melting with a mass of 350 tons - 0.08%. The remaining carbon is spent on the recovery of other oxides from slag, which have a stronger affinity for oxygen than manganese. Partially excess coke can interact, for example, with the oxygen of the metal. .

Example 2. A 350 tons converter was filled with 100 tons of scrap, 12 tons of lime were added and 300 tons of phosphorus were poured, 0.020% of sulfur at 405 ° С With 1 ton of 6 minutes of crusher 8 tons of lime and 0.5 tons of fluorspar were added. The purge was started at the position of the tuyere 38 of the above calibers (I reduced the caliber is 132 mm), with its gradual decrease in the consumption of 4500 m of oxygen to 15 of the calibers shown (working position). By consuming 91% of the oxygen (18200 m Oj) required for smelting, the lance was raised to 17 calibers given (to 2 calibers given). Simultaneously with the increase of the tuyere, 950 kg of iron shavings were planted. After consuming 96% of oxygen (19200 m O), the lance was lowered to the working position (15 calibers given) and purged until the end

5 purge. At the end of the purge received metal containing 0.07% carbon; 0.009% phosphorus; 0.018% sulfur with a manganese content of 0.15% at 1640 ° C.

1.5 tons of bw were used for reducing.

Q likomangantsa and 0.3 tons of ferrosilicon. Got steel of the following composition: 0.10% carbon; 0.12% silicon; 0.43% manganese. The metal yield is 91.2%.

To test the effectiveness of the proposed method, we conducted experimental melting at

5 known method.

The data obtained are shown in the table.

Studies have shown that the proposed method (experiments I-4) makes it possible to increase the manganese content at the end of the blowdown by 0.05%, reduce the consumption of silicomanganese by 0.2 tons for smelting or 0.6 kg / ton of melted steel and increase the yield steel, by 0.3%.

Claims (1)

Invention Formula Those purged with an oxidizing gas, such as oxygen, with a variable tuyere position, supplying oxygen after the initial slag is brought in at the working position of the tuyere 13-18 of the calibres above the bath level, characterized in that in order to reduce the consumption of manganese-containing ferroalloys by increasing the manganese content in the metal at the time of termination of the purge and increase in the steel output, after the supply of 90-92 / o of oxygen from its consumption to the purge, lift the lance by 1.5-3.0 caliber from the working position while carbon is introduced dsoderzhaschih materials in an amount of I - 4 kg / m, and after a 95-97% oxygen to flow from its blowing lance is lowered to the working position.  Prototype method Nf is the height of the tuyere above the metal level.