KR101008072B1 - Method for Refinig Molten Pig Iron in Converter - Google Patents

Abstract

The present invention relates to a converter refining method of an ironworks, and to provide a converter refining method capable of tapping molten steel without measuring molten steel temperature and dissolved oxygen concentration after completion of converter refining.

In the converter refining process, the molten steel temperature and carbon concentration are measured at a 70-80% supply point of total oxygen, and when either of the dynamic molten steel temperature and carbon concentration is equal to or lower than the target value, it is blown under normal conditions. Then, tapping is performed, and if the measured dynamic molten steel temperature and carbon concentration are both higher than the target value, the estimated endpoint molten steel temperature is obtained. If the estimated endpoint molten steel temperature is higher than the target endpoint molten steel temperature, the estimated endpoint molten steel temperature is After cooling by adding a coolant until the target end point temperature is lower than the target end point temperature, the molten steel temperature and dissolved oxygen concentration are measured, and tapping is performed. When the measured dynamic molten steel temperature and carbon concentration are lower than the target value, the estimated value is estimated. After determining the end point dissolved oxygen concentration, if the estimated end point dissolved oxygen concentration is 700ppm or less, after performing drilling, In the case where the estimated end point dissolved oxygen concentration exceeds 700ppm, the converter refining method is performed by adding heat source agent until the estimated end point dissolved oxygen concentration becomes 700ppm or less, and then tapping.

Converter, dynamic, tapping, refining, end steel temperature, end oxygen concentration

Description

Method for Refining Molten Pig Iron in Converter

1 is a graph that differentiates the dynamics of steel grades in which deoxidation occurs during tapping

2 is a graph of stratified dynamics of steel grades tapping with non-deoxidation during tapping

3 is a graph showing a working method according to a converter dynamic measurement result

The present invention relates to a converter refining method of an ironworks, and more particularly, to a converter refining method that can be pulled out without measuring the molten steel temperature and dissolved oxygen concentration after completion of the converter refining operation.

In general, in the converter refining method, after the operator performs the residual slag coating work to protect the refractory of the converter, during the scrap-loading operation and the charter loading operation, the drilling worker performs the charter ratio and the components in the charter (ie, Carbon, silicon, manganese, phosphorus, sulphur), molten iron temperature, scrap metal, and more than 35 kinds of information to obtain a thermal balance, compared to the charges that had been previously refined to obtain a similar charge and appropriate heat balance Thermal blending is performed to obtain.

As shown in FIGS. 1 and 2, the target temperature of the molten steel varies according to deoxidation and non-deoxidation during the tapping operation, and the ideal dynamic temperature desired by workers, carbon is “Group 1” of FIGS. 1 and 2.

After the chartering is completed, converter refining work is performed, and from the start of the drilling, it protects thermal balance and converter refractory in the converter, and absorbs impurities such as silicon, manganese, phosphorus, and sulfur in the charter. In order to make slag, additional materials such as iron ore, quicklime, fluorspar, small dolomite, and ferrosilicon will be added.

Refining reaction in the converter is an oxidation reaction to remove impurities in the molten iron by the reaction as shown in the following reaction formula (1).

Scheme 1

C + _1/2 O ₂ = CO ( _gas )

Si + O ₂ = SiO ₂ ( _Slag )

Mn + _1/2 O ₂ = MnO ( _Slag )

2P + _5/2 O2 = P ₂ O ₅ ( _Slag )

In order to measure the temperature in the converter furnace during the converter refining process, a probe which can know the temperature, sampling and carbon is equipped, and when the steel refining process is 70 ~ 80%, Temperature and carbon are measured using a probe mounted on a sub lance. This is called dynamic.

 The purpose of measuring the temperature and carbon of the current molten steel as described above is to determine how to adjust the temperature and carbon of the current molten steel in order to have the target temperature and dissolved oxygen concentration after the refining of the converter.

1 and 2, if the molten steel is a temperature and carbon belonging to Group 1 as shown in Figs. 1 and 2, the target molten steel will have the temperature and dissolved oxygen concentration of the target molten steel after completion of converter refining. You can continue without refining.

In addition, in the case of Group 2, the dynamic viewpoint is late, and in the case of Group 4, the dynamic viewpoint is early, so that refining may be performed without modifying the target as in the case of ① shown in FIG.

In the case of Group 3, it corresponds to the case of ② in FIG. 3, and the heat balance is wrong, and a lot of coolant, such as ore, has been added, and a heat source must be added during refining to correct it in the same direction as ④ in FIG.

In addition, in case of Group 5, the worker has determined that the heat balance is wrong in case of ③ in FIG. 3 and that the slag loosening condition in the furnace is poor, and the direction must be corrected as in ⑤ in FIG.

As for the dynamic as described above, the workers directly determine the conversion and perform the converter, and the required oxygen consumption is obtained in the same manner as in the following relation (1).

[Relationship 1]

Required oxygen = (end point temperature-dynamic measurement temperature) × temperature increase coefficient + oxygen flow rate during dynamic measurement

During the converter refining, workers attach probes to the sub-lances to measure molten steel temperature and oxygen.

When the refining work is completed, the operator deposits the sub lance and checks the temperature and oxygen of the molten steel. If the measured temperature and oxygen are the target temperatures, the worker performs the tapping operation, which transfers the molten steel to the ladle. It will be re-retrained again.

As described above, the conventional converter tapping method has the following problems.

Since the accuracy of the slag in the furnace is reduced by the operator's manual measurement during converter refining, the temperature rise factor is incorrectly applied when measuring the temperature in the state where the converter refining is completed using the required oxygen after the thermometer is calculated to the target temperature after dynamic measurement. If the temperature is lower than the temperature, the re-blowing is performed. If the temperature is higher, the cooling is performed.

In the case of re-refining, the increase of iron grains in slag causes the rapid decrease of furnace refractory material due to the decrease of error rate of molten steel and the increase of molten steel retention time.

When cooling is performed, oxygen is supplied to the molten steel more than necessary to increase the dissolved oxygen in the molten steel, thereby increasing the deoxidizer during the tapping operation, and consequently increasing the non-metallic inclusions in the ladle to deteriorate the quality.

When calculating the required oxygen amount after the dynamic measurement, the operator calculates manually using the calculator, and also depends on the five senses of the operator, there is a problem that the higher or lower than the target end point temperature caused by frequent mistakes of the operator.

Although it is possible to estimate the target temperature of the molten steel when the converter is pursuing the required oxygen amount, it is difficult to measure the dissolved oxygen, so even if the worker takes the target temperature, the dissolved oxygen is low.

In addition, to measure the end temperature and dissolved oxygen in the molten steel after completion of the converter, the probe is mounted on the sub lance to measure the temperature and dissolved oxygen of the molten steel, thereby increasing the manufacturing cost of the molten steel by using the probe. When measuring the temperature and dissolved oxygen, there is a problem of rapidly reducing energy loss and burnout of refractory refractory due to a drop in temperature of molten steel and an increase in residence time of molten steel.

MEANS TO SOLVE THE PROBLEM The present inventor made the research and experiment in order to solve the above-mentioned all the problems of the prior art, and proposes this invention based on the result, This invention uses the dynamic model of the converter, and after completion of converter refining, By predicting temperature and dissolved oxygen and controlling converter refining by using this, we want to provide converter refining method that can make tapping more quickly without measuring molten steel temperature and dissolved oxygen concentration after completion of converter refining in certain cases. There is this.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

In the converter refining method,

Setting a target endpoint steel temperature, a target endpoint dissolved oxygen concentration and a target endpoint carbon concentration;

Dynamic molten steel temperature and carbon concentration were measured at 70-80% of the total oxygen supplied to the refining process;

When one of the measured dynamic molten steel temperature and carbon concentration is equal to or lower than the target value, the remaining oxygen is blown under normal conditions when the measured dynamic molten steel temperature and carbon concentration is compared to the target end molten steel temperature and target end carbon concentration. While performing the training, and then going to class;                     

If the measured dynamic molten steel temperature and carbon concentration are both above or below the target value,

The required oxygen amount f required from the dynamic to the end point is obtained by the following equation (2);

[Relationship 2]

f = (c × o) + (k × t)

[Where f = amount of oxygen required

         c = (carbon concentration measured in dynamics-target end point carbon concentration) (%)

         o = amount of oxygen required to react with carbon (Nm3)

k = temperature increase coefficient according to slag amount (℃ / Nm ³ )

             t = (Target molten steel temperature-measured molten steel temperature at dynamic) (℃)]

When the measured dynamic molten steel temperature and carbon concentration are both higher than the target value, the estimated end point molten steel temperature is obtained by the following equation (3), and when the estimated end point molten temperature is lower than the target end point molten steel temperature, the equation (2) is obtained. Performing blowing while blowing in the required amount of oxygen determined by the method, and then tapping;

[Relationship 3]

End Steel Temperature (℃) = Required Oxygen (N㎥) ÷ Temperature Coefficient According to Slag

If the estimated end point molten steel temperature is higher than the target end point molten steel temperature, a coolant is added until the estimated end point molten steel temperature is lower than the target end point molten steel temperature, and the required oxygen content at that time is obtained by the above formula (2). After blowing while blowing the amount of oxygen, the end steel temperature and end dissolved oxygen concentration were measured, and then tapping was performed;

If the measured dynamic molten steel temperature and carbon concentration are both lower than the target value, the estimated end point dissolved oxygen concentration is obtained by the following equation (4);

[Relationship 4]

x = {(Oxygen amount required to burn carbon with carbon content × 0.1% as measured by dynamics) × Oxygen yield of 1 Nm ³ in terms of Kg × Oxygen chamber yield} / Molten steel amount + Oxygen required × 0.5

When the estimated end-point dissolved oxygen concentration is 700 ppm or less, the blow is performed while blowing as much as the required oxygen amount determined by Equation (2), and then tapping is performed;

When the estimated end point dissolved oxygen concentration exceeds 700 ppm, a heat source agent is added until the estimated end point dissolved oxygen concentration is 700 ppm or less, and the required oxygen amount at that time is obtained by the above formula (2). The present invention relates to a converter refining method comprising performing blowing while blowing, and then tapping.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention is applied to the converter refining method.

In order to perform converter refining according to the present invention, it is necessary to set the target end point steel temperature, the target end point dissolved oxygen concentration, and the target end point carbon concentration.

The dynamic molten steel temperature and carbon concentration are measured at 70-80% of the total oxygen supplied to the refining process.

The total oxygen injected into the converter refining process is about 12,000-14,000 Nm ³ .

Refining process after dynamic when any one of the dynamic molten steel temperature and carbon concentration measured in comparison with the dynamic molten steel temperature and carbon concentration measured as described above and the target end molten steel temperature and target end carbon concentration is equal to or lower than the target value Is carried out while blowing the remaining oxygen under normal conditions, and then tapping without measuring the end-point steel temperature and the end-point dissolved oxygen concentration.

Usually, the oxygen blowing (supply) amount is about 2,000 to 3,500 Nm ³ / min in the refining process after the dynamics.

When both the dynamic molten steel temperature and the carbon concentration measured as described above are higher or lower than the target value, the required oxygen amount f required from the dynamic to the end point is obtained by the following equation (2).

[Relationship 2]

f = (c × o) + (k × t)

[Where f = amount of oxygen required

         c = (carbon concentration measured in dynamics-target end point carbon concentration) (%)

         o = amount of oxygen required to react with carbon (Nm3)

k = temperature increase coefficient according to the amount of slag (℃ / Nm ³ )

             t = (Target molten steel temperature-measured molten steel temperature at dynamic) (℃)]

It is preferable to obtain the temperature rising coefficient k according to the amount of slag by the following formula (2a).

[Relationship 2a]                     

k = 10.4 + 0.765 x (the amount of slag)

Examples of the temperature rise coefficient (k) value according to the slag amount are shown in Table 1 below.

Slag amount (ton) Temperature rise coefficient (℃ / Nm ³ ) 15 to 20 23 ± 2 21-25 28 ± 2 26-30 32 ± 2 Over 31 35 ± 2

In the above formula 2a, the slag amount can be obtained by the following formula (2aa).

[Relationship 2aa]

Slag amount = residual slag + quicklime (input during refining operation) + light dolomite (input during refining operation) + pulmonary dolomite (input during refining operation) + (silicone in molten iron-estimated end point silicon) + (manganese in molten iron- Estimated end manganese) + (in middle of molten iron-estimated end in) + (titanium in molten iron-estimated end titanium) + total F of estimated slag (T.Fe)

When the measured dynamic molten steel temperature and carbon concentration are both higher than the target value, the estimated end point molten steel temperature is obtained by the following equation (3), and when the estimated end point molten temperature is lower than the target end point molten steel temperature, the above equation (2) Blowing is performed while blowing the required amount of oxygen determined by the step, and tapping is performed without measuring the end-point steel temperature and the end-point dissolved oxygen concentration.

[Relationship 3]

End Steel Temperature (℃) = Required Oxygen (N㎥) ÷ Temperature Coefficient According to Slag                     

In addition, when the estimated end point molten steel temperature is higher than the target end point molten steel temperature, a coolant is added until the estimated end point molten steel temperature is lower than the target end point molten steel temperature, and the required oxygen content at that time is obtained by the above formula (2). Blowing is performed while taking in the required amount of oxygen, and the tapping is performed after measuring the end point steel temperature and the end point dissolved oxygen concentration.

It is preferable to calculate | fill the input amount (kg) of the said coolant by following formula (3a).

[Relationship 3a]

Coolant input amount (Kg) = (Estimate end point molten steel temperature-target end point steel temperature) (℃) x Temperature compensation amount (℃)

An example of the temperature correction amount and the oxygen generation amount for each coolant is shown in Table 2 below.

Coolant (Kg) Temperature compensation amount (℃) Oxygen generation amount (N㎥) ironstone 0.0233 0.19 Sintered ore 0.0209 0.16 HBI 0.0067 0.02 Briquettes 0.0098 0.065

The coolant may be appropriately selected in consideration of the temperature correction amount and oxygen generation amount for each coolant in Table 2 above.

As described above, performing the tapping after measuring the end point steel temperature and the end point dissolved oxygen concentration often results in the manufacture of slag having a poor ability to absorb impurities in the furnace due to a significant thermal balance calculation miss during the converter refining operation. In order to generate more accurate end point steel temperature and end point dissolved oxygen concentration value.

On the other hand, when the measured dynamic molten steel temperature and carbon concentration are both lower than the target value, the estimated end point dissolved oxygen concentration (x) is obtained by the following equation (4).

[Relationship 4]

x = {(Oxygen amount required to burn carbon with carbon content × 0.1% as measured by dynamics) × Oxygen yield of 1 Nm ³ in terms of Kg × Oxygen chamber yield} / Molten steel amount + Oxygen required × 0.5

Next, when the estimated end-point dissolved oxygen concentration is 700 ppm or less, blowing is carried out by blowing as much as necessary oxygen amount determined by the above formula (2), and then tapping is performed without measuring the end-point steel temperature and the end-point dissolved oxygen concentration, and exceeds 700 ppm. In this case, the heat source agent is added until the estimated end point dissolved oxygen is 700 ppm or less, the required oxygen content is calculated by the above formula (2), blown by blowing the required oxygen amount, and then the end melting steel temperature and the end point dissolved The tapping may be performed without measuring the oxygen concentration.

It is preferable to calculate | fill the input amount (kg) of the said heat source agent by following formula (4a).

[Relationship 4a]

Heat source input amount (Kg) = Temperature correction amount due to dissolved oxygen (℃) × Temperature correction amount according to heat source agent (℃)

The temperature correction amount by the dissolved oxygen can be obtained by the following formula (4aa).

[Relationship 4aa]

Temperature correction amount by dissolved oxygen = 0.05 + 0.0343 x (estimated end point dissolved oxygen concentration-700)                     

An example of the temperature correction amount and the required oxygen amount for each heat source agent is shown in Table 3 below.

Heat source agent (Kg) Temperature compensation amount (℃) Required oxygen (N㎥) Fe-Si 0.08 0.64 Coke 0.0197 0.93

The heat source agent may be appropriately selected in consideration of the temperature correction amount and the required oxygen amount for each heat source agent of Table 3.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

As shown in Table 4, the converter refining operation was carried out according to the conventional method [(1-10) and the present invention method [Example (1-20)], and the BAP arrival temperature, refining time and end point steel temperature and dissolved oxygen concentration were measured. And the results are shown in Table 4 below.

Conventional Examples (1 to 5) are deoxidized steel species, and Conventional Examples (6 to 10) are refined non-deoxidized steel species, Examples (1 to 10) are deoxidized steel species, and Examples (11 to 20) are deoxidized steel species. The steel grade is refined.

In Examples 8, 15, 16, and 17, when the estimated end point molten steel temperature is higher than the target end point molten steel temperature, the tapping is performed by the conventional tapping method of measuring the end point molten steel temperature and the end point dissolved oxygen concentration. This is usually because the control of phosphorus in the molten steel is poor, and the temperature is measured by measuring the temperature of the molten steel in order to promote the reaction between slag and the agitation power of the low-odor gas blowing from the low odor by waiting in the converter for a predetermined time. This is to ensure the security.                     

 As described above, the present invention can predict the molten steel temperature and dissolved oxygen concentration after the converter refining is completed using the dynamic model of the converter, so that the steel can be moved immediately without measuring the temperature and dissolved oxygen in the converter refining state. In addition, it has the effect of bringing practical advantages such as protection of converter refractory due to shortened residence time of molten steel in converter, reduction of temperature of molten steel, use of probe to measure molten steel temperature and oxygen, and reduction of work load of workers. .

Claims (1)

In the converter refining method, Setting a target endpoint steel temperature, a target endpoint dissolved oxygen concentration and a target endpoint carbon concentration; Measuring the dynamic molten steel temperature and carbon concentration at 70-80% of the total amount of oxygen supplied to the refining process; When one of the measured dynamic molten steel temperature and carbon concentration is equal to or lower than the target value, the remaining oxygen is blown under normal conditions when the measured dynamic molten steel temperature and carbon concentration are compared to the target end molten steel temperature and target end carbon concentration. While performing the training, and then going to class; If the measured dynamic molten steel temperature and carbon concentration are both above or below the target value, The required oxygen amount f required from the dynamic to the end point is obtained by the following equation (2); [Relationship 2] f = (c × o) + (k × t) [Where f = amount of oxygen required          c = (carbon concentration measured in dynamics-target end point carbon concentration) (%)          o = amount of oxygen required to react with carbon (Nm3) k = temperature increase coefficient according to slag amount (℃ / Nm ³ )          t = (Target molten steel temperature-measured molten steel temperature at dynamic) (℃)] When the measured dynamic molten steel temperature and carbon concentration are both higher than the target value, the estimated end point molten steel temperature is obtained by the following equation (3), and when the estimated end point molten temperature is lower than the target end point molten steel temperature, the equation (2) is obtained. Performing blowing while blowing in the required amount of oxygen determined by the method, and then tapping; [Relationship 3] End Steel Temperature (℃) = Required Oxygen (N㎥) ÷ Temperature Coefficient According to Slag If the estimated end point molten steel temperature is higher than the target end point molten steel temperature, a coolant is added until the estimated end point molten steel temperature is lower than the target end point molten steel temperature, and the required oxygen content at that time is obtained by the above formula (2). After blowing while blowing the amount of oxygen, the end steel temperature and end dissolved oxygen concentration were measured, and then tapping was performed; If the measured dynamic molten steel temperature and carbon concentration are both lower than the target value, the estimated end point dissolved oxygen concentration is obtained by the following equation (4); [Relationship 4] x = {(carbon content measured in dynamics × amount of oxygen required to burn 0.1% of carbon) × value of oxygen of 1 Nm ³ in terms of Kg × actual oxygen yield} / melt amount + required oxygen × 0.5 When the estimated end-point dissolved oxygen concentration is 700 ppm or less, the blow is performed while blowing as much as the required oxygen amount determined by Equation (2), and then tapping is performed; When the estimated end point dissolved oxygen concentration exceeds 700 ppm, a heat source agent is added until the estimated end point dissolved oxygen concentration is 700 ppm or less, and the required oxygen amount at that time is obtained by the above formula (2). A converter refining method comprising performing a blow while blowing and then tapping

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