JP2002161307A - Slag coating method used in furnace exclusive for dephosphorization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slag coating method that securely repairs an exclusive dephosphorization furnace used for removal of phosphorus from molten pig iron without increase in repair costs or failure in the durability of repaired sections. SOLUTION: In dephosphorization treatment using an exclusive dephosphorination converter 1, the converter 1 is fed at first with only a part of the total charge V of molten pig iron 2 to be processed, a charge volume ranging from one half or more to two thirds or less of the total charge V. After the dephosphorization of the initial charge in the converter is completed and processed molten metal is taken out, the second charge is made using the remaining molten pig iron in the range of one thirds or more to one half or less of the total charge volume V so as to feed the converter with molten pig iron up to the depth of 500 mm or more from the bottom of the bath but in any way not deeper than one half of the height (Ho) from the entrance level to the bed of the converter 1. Then, oxygen blowing is followed for decarburization, completing slag coating on the exclusive dephosphorization converter 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slag coating method for a dephosphorization furnace, for example, to extend the life of a furnace for a dephosphorization furnace dedicated to dephosphorization blowing in hot metal pretreatment. The present invention relates to a slag coating method.

[0002]

2. Description of the Related Art Dephosphorization blowing and decarburization blowing are performed together using the same converter, or decarburization blowing is performed on hot metal pre-treated hot metal stored in a converter. In a general operation using a furnace, it is known that the brick wear of this converter is suppressed as the slag basicity (CaO / SiO ₂ ) is higher, the MgO concentration is higher, or the TFe is lower. Have been. Therefore, in order to extend the furnace life of the converter, the slag basicity (CaO / S
So-called slag coating, in which slag is coated on the surface of the lining of a converter by increasing both the concentration of iO ₂ ) and MgO, has been performed.

For example, JP-A-61-157610 and JP-A-61-56223 disclose an invention in which slag is applied to a furnace wall by performing forced cooling after performing slag coating. In the publication, 1 part per 100 parts by mass of slag remaining in the converter is
5 to 2 pieces of bulk basic refractory having a size of 00 to 200 mm
Japanese Patent Application Laid-Open No. 3-68712 discloses a method of controlling the slag composition by calming and holding after charging 0 mass parts, and discloses an invention in which a solidified material or brick waste is charged into a furnace after tapping. Have been.

[0004]

Incidentally, in order to reduce the refining cost, there is a case where hot metal dephosphorization is carried out by a converter dedicated to dephosphorization. FIG. 6 is an explanatory diagram schematically showing a situation in which hot metal dephosphorization is performed using the converter 11 dedicated to dephosphorization.

As shown in FIG. 6, when hot metal dephosphorization is carried out using a converter for exclusive use of dephosphorization, the treatment temperature of hot metal 12 is low and the basicity of slag 13 is low in order to prioritize the dephosphorization operation. Due to the low basicity, the slag 13 cannot be attached to the surface of the lining of the converter 11 dedicated to dephosphorization. Therefore, in order to extend the life of the converter by repairing the damaged lining, it is necessary to periodically perform repair using a baking material or the like. For this reason, there has been a problem that the repair cost increases and the durability of the repaired baked material is insufficient.

Further, since a large amount of low basicity slag and ingot 14 adhere to the inner surface of the converter 11 dedicated to dephosphorization in order to process hot metal at a low temperature, a large amount of adherence occurs when decarburization blowing is performed subsequently. The low basicity slag and the ingot 14 melt to increase the amount of slag. For this reason, an abnormal reaction such as slopping occurs, and it becomes difficult to continue blowing and the tapping operation itself becomes impossible.

It is an object of the present invention to reliably repair a dephosphorization furnace such as a dephosphorization converter for performing hot metal dephosphorization without increasing the repair cost and losing the durability of the repair part. A slag coating method for a dephosphorization-dedicated furnace that can be provided, thereby prolonging the furnace life of the dephosphorization-dedicated furnace.

[0008]

The inventor of the present invention has studied in detail the cause of the inability of slag coating to be performed on a furnace dedicated to dephosphorization, and found that the cause is as described in the following items (1) to (3). found.

(1) Slag basicity during dephosphorization blowing (CaO
/ SiO ₂ ) is significantly reduced, for example, to about 2.0 or less even during normal operation.

(2) The treatment temperature of the hot metal during the dephosphorization blowing has been lowered because the dephosphorization operation has priority.

(3) When decarburization blowing is performed after dephosphorization blowing, a large amount of low basicity slag attached to the inner surface of the converter for exclusive use of dephosphorization is dissolved, and the slag basicity (CaO / SiO ₂₎ ) Is further reduced.

[0012] Therefore, in order to reliably perform slag coating on the lining of the furnace dedicated to dephosphorization, dephosphorization is blown with a high slag basicity and high temperature operation, and the influence of low basicity slag adhered to the furnace. It is necessary to carry out decarburization blowing so as not to receive it.

Therefore, the present inventor has conducted further studies, and as a result, has conducted a dephosphorization treatment after pouring a part of the total amount of the hot metal to be treated into the dephosphorization furnace. After tapping the hot metal that has been dephosphorized, the remaining amount of the total charge is poured into this dedicated dephosphorization furnace to perform decarburization blowing.
In other words, by performing two-stage pouring, the reaction area of the dephosphorization furnace at the time of blowing can be lowered from the normal position, and without operating troubles such as blow-through,
It is possible to effectively suppress the dissolution of the low basicity slag adhered to the dephosphorization furnace, thereby enabling slag coating by performing decarburization blowing using the dephosphorization furnace. Was found.

Further, the present inventors have found that slag basicity and M
Regarding the gO concentration, since the dephosphorization operation is performed at a low temperature when the dephosphorization-only furnace is used, it is not necessary to increase the basicity and the MgO concentration to the extent that ordinary decarburization blowing is performed. It has been found that durability can be ensured.

Further, the inventor of the present invention discharges the molten steel that has been decarburized and blown on the molten metal that has been subjected to the dephosphorization treatment and that has been tapped, so that the molten metal can be charged next time. It has been found that it can be used as hot metal for decarburization furnaces, and that decarburization blowing can be performed without component adjustment or operation hindrance.

The present invention has been made based on these new and important findings.

According to the present invention, when the dephosphorization treatment in the hot metal pretreatment is performed using a dephosphorization furnace, a part of the total charge V of the hot metal to be treated is supplied to the dephosphorization furnace. After pouring V ₁ and performing the dephosphorization treatment, the hot metal subjected to the dephosphorization treatment is discharged, and then the remaining amount V of the total charge V is supplied to the dephosphorization furnace from which the hot metal is discharged. _This is a slag coating method for a dephosphorization furnace, characterized in that slag coating is performed on the dephosphorization furnace by pouring iron ₂ and performing decarburization blowing.

In the slag coating method for a dephosphorization furnace according to the present invention, it is exemplified that the dephosphorization furnace is a converter.

In the slag coating method for a dephosphorization furnace according to the present invention, a part V ₁ of the total charged amount V is not less than (１ ／) V and (２). V and the remaining amount V ₂ is (1/3) V
When the distance from the furnace port of the furnace dedicated to dephosphorization to the hearth is H ₀ (mm), the molten steel bath depth (mm) is 500 (mm) or more (H) _0/2 ) (mm)
It is desirable to satisfy the following.

In the slag coating method for a dephosphorization furnace according to the present invention, the slag in the decarburization blowing has a basicity (CaO / SiO ₂ ) of not less than 2.5 and not more than 3.5. , MgO concentration of 3 to 5% by mass
Is desirable.

Further, in the slag coating method for a furnace for exclusive use of dephosphorization according to the present invention, it is preferable that the end point temperature of the decarburization blowing is 1640 ° C. or less.

Further, in the slag coating method for a dephosphorization furnace according to the present invention, the slag coating is performed by introducing a cooling material of 10 (kg / T) or more into molten slag remaining in the furnace after decarburization blowing. Preferably, this is done by quenching the slag, thereby solidifying the molten slag.

In the slag coating method of the furnace for exclusive use of dephosphorization according to the present invention, it is preferable that the cold material is at least one of scrap, brick waste and pig iron.

In the slag coating method for a dephosphorization furnace according to the present invention, it is preferable that curing is performed for about 10 minutes or more and 240 minutes or less after charging a cold material.

Further, in the slag coating method for a dephosphorization furnace according to the present invention, the decarburized hot metal is discharged on the hot metal which has been dephosphorized and discharged. ,desirable.

Further, in the slag coating method for a dephosphorization furnace according to the present invention, the decarbonized molten steel is supplied to a dephosphorization furnace for decharging the next charge. desirable.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a slag coating method for a dephosphorization furnace according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the embodiment, a case where the dephosphorization-only furnace is a dephosphorization-only converter is taken as an example.

FIG. 1 is an explanatory view schematically showing a slag coating method according to the present embodiment. As shown in the figure,
In the present embodiment, when performing dephosphorization of the molten iron pretreatment with dephosphorization dedicated converter 1, the molten iron 2a in the portion of the amount V ₁ of the total charge amount V of hot metal 2 to be processed A first step of pouring hot metal 2a subjected to the dephosphorization treatment after pouring and performing a dephosphorization treatment; and a remaining amount V ₂ of the total charged amount V after the first step. The second step of pouring molten iron 2b and performing decarburization blowing is performed, so to speak, so-called two-stage pouring. Therefore, the first step and the second step will be sequentially described.

(First Step) As a first step, the hot metal 2 to be treated contained in the ladle 3
After the dephosphorization process by Chuzuku part of the amount V ₁ of the of the total charge amount V, and the hot metal made the dephosphorization, the ladle 4 dephosphorization dedicated converter 1 Take a bath.

Here, a part V ₁ of the total charge amount V ₁
Means that (1/2) V or more and (2/3) V or less are preferably satisfied. That is, this partial amount V ₁ becomes (1 /
2) If it is less than V will not be able to perform dephosphorization blowing with dephosphorization dedicated converter 1, whereas, when this partial quantity V ₁ exceeds (2/3) V, in the next charge This is because it becomes impossible to perform slag coating of ordinary pig iron.

Other conditions, such as the pouring means to the dephosphorization-only converter 1 and the means for tapping from the dephosphorization-only converter 1, are the same as those commonly known in the operation of this type of dephosphorization-only converter 1. Since the means may be used, the description is omitted here.

The hot metal 2a discharged from the ladle 4 waits until the molten metal is discharged from the ladle 5 in this state. In the present embodiment, the first step is performed as described above.

(Second Step) As a second step, after the completion of the first step, that is, the hot metal 2a that has been subjected to the dephosphorization treatment in this manner is discharged from the hot metal 2a to become an empty dephosphorization-only converter. Furnace 1
To, by performing the decarburization blowing was Chuzuku the hot metal 2b of the remaining amount V ₂ of the total charge amount V, performs slag coating for dephosphorization dedicated converter 1.

Here, the remaining amount V ₂ of the total charging amount V
And, since it is a part of the quantity V ₁ is (1/2) V or more (2/3) V or less as described above is (1/3) V or more (1/2) V or less.

When the distance from the furnace port of the converter 1 for dephosphorization to the hearth is H ₀ (mm), the depth H _X (mm) of the molten steel bath is 500 (remaining amount V ₂ ). mm) or more (H
_0/2) (mm) that satisfies the following desirable. Resulting operations impediments blow such molten steel bath depth H _X is is less than 500 (mm), can not be operated. On the other hand, when the remaining amount V ₂ is not less than (１ ／) V and not more than (１ ／) V, the molten steel bath depth H _X is naturally (H _0/2 ).
(Mm) or less.

Here, the distance H ₀ from the furnace port of the converter 1 exclusively for dephosphorization to the hearth is usually 2500 (mm) or more and 1500 or more.
0 (mm) or less.

The slag coating on the dephosphorization converter 1 is performed by solidifying slag remaining in the furnace after decarburization blowing. The solidification of this slag
The slag is quenched by rapidly cooling the slag by adding at least 10 (kg / T) of a cold material composed of at least one of scrap, brick waste and pig iron to the slag,
It is desirable to reduce the curing time for slag coating. The curing time for the slag coating is, for example, about 10 minutes or more after charging the cold material.
Minutes or less are exemplified.

The slag coating is performed on any of the charging side, the tapping side, and the hearth of the converter 1 for dephosphorization, and is sufficiently performed in substantially the entire area of the converter 1 for dephosphorization.

As described above, the pouring amount V in the first step
_By controlling the pouring amount V ₂ in each of the _first and second steps to an optimum value, a converter 1 dedicated to dephosphorization during blowing is provided.
Can be lowered from the normal position, and excessive dissolution of slag attached to the dephosphorization-dedicated converter 1 can be suppressed without operating troubles such as blow-through.

For this reason, according to the present embodiment, decarburization blowing can be performed using the dephosphorization-dedicated converter 1 after dephosphorization blowing without causing operational troubles such as blow-through.
Slag coating can be reliably performed on the lining of the converter 1 dedicated to dephosphorization.

The slag basicity (CaO / SiO ₂ ) in the decarburization blowing using the converter 1 for dephosphorization is 2.5.
Not less than 3.5 and the MgO concentration is 3% by mass.
The content is desirably at least 5% by mass. That is, since the slag basicity (CaO / SiO ₂ ) and MgO concentration are low-temperature dephosphorization operations, it is not necessary to increase the basicity and the MgO concentration to the extent that ordinary decarburization blowing is performed. Slag basicity (CaO / SiO ₂ ): 2.5 or more and 3.5 or less and MgO concentration: 3 mass% or more and 5 mass%
Even below, the durability of the slag coating formed in the converter 1 for dephosphorization can be sufficiently ensured.

The decarburization blowing end point temperature is 1640.
If the temperature is lower than or equal to 0 ° C., a decrease in basicity due to dissolution of the low basicity slag adhered to the converter 1 exclusively for dephosphorization can be suppressed, so that it is desirable. From a similar viewpoint, the end point temperature of the decarburization blowing is 160
More preferably, the temperature is 0 ° C or higher and 1620 ° C or lower.

In this embodiment, decarburization blowing is performed by using the converter 1 exclusively for dephosphorization and operating at a high basicity and a high temperature in this way, and is not affected by slag adhering to the furnace. Decarburization blowing can be performed, and slag coating can be performed on the lining of the converter 1 exclusively for dephosphorization.

In the present embodiment, the second step is performed as described above. In the present embodiment, after the decarburization blowing using the dedicated converter for dephosphorization is finished, the hot metal 2a subjected to the dephosphorization treatment is discharged from the ladle 4 to the ladle 5, On the hot metal 2a received by the ladle 5, the hot metal 2b that has been decarburized is tapped.

The hot metal 2a, 2b stored in the ladle 5 is supplied to the decarburization furnace 6 in the next step.

In any case, according to the present embodiment, decarburization blowing can be performed without hindering the operation.

The lower the temperature of the dephosphorization reaction of the hot metal is, the more advantageous it is. However, in this embodiment, since the dephosphorization of the hot metal is performed using the converter 1 for dephosphorization, the low-temperature tapping operation is possible. The dephosphorization characteristics are improved, and the amount of the solvent used can be reduced.

Further, in this embodiment, since the amount of the solvent used can be reduced, it is possible to suppress a decrease in the cleanliness of the molten steel.

In this embodiment, dephosphorization blowing and decarburization blowing are not performed at the same time, so that operation inhibition such as slopping, refractory erosion, and the like caused by the simultaneous execution can be eliminated.

As described above, the slag coating method for the dephosphorization converter 1 according to the present embodiment can reduce the dephosphorization converter 1 for dephosphorizing hot metal by increasing the repair cost and deficient durability of the repair part. It can be reliably repaired without accompanying.

[0051]

EXAMPLES Further, the slag coating method of the converter for exclusive use of dephosphorization according to the present invention will be described more specifically with reference to examples.

The case where slag coating is performed on the charging side of the converter for exclusive use of dephosphorization 1 by the method according to the present invention shown in FIG. 1 (example of the present invention) and the case where repair using a baking material or the like is performed , Durability and brick thickness transition were investigated. FIG. 2 is a graph showing the results of the study on durability, and FIG. 3 is a graph showing the transition of brick thickness. In FIG. 2, (C / S) indicates slag basicity (CaO
/ SiO ₂ ). Table 1 shows the slag coating compositions of the two examples of the present invention in FIG.

[0053]

[Table 1]

From the graphs of FIGS. 2 and 3, the durability of the slag coating of the example of the present invention is about three times as high as that of the conventional repair using a baked material. It can be seen that the life of the furnace body was improved.

Further, from the graph shown in FIG. 2, no improvement in the serviceability index was observed for any of the slag basicity (CaO / SiO ₂ ) and MgO concentration even at a high concentration. Basicity (CaO / SiO ₂ ): 2.
5 to 3.5, MgO concentration: 3 to 5% by mass
It can be seen that durability can be sufficiently improved by the following.

FIG. 4 is a graph showing the effect of the tapping temperature. From the graph shown in FIG. 4, it can be seen that the slag basicity decreases as the tapping temperature increases, thereby increasing the amount of slag dissolved in the furnace. Therefore, it is understood that the tapping temperature, that is, the end point temperature of the decarburization blowing is desirably 1640 ° C. or less.

Further, FIG. 5 shows the refractory costs for both the present invention example and the conventional example as index values.

As shown in the graph of FIG. 5, according to the example of the present invention, since the coating with decarburized blown slag is performed in the converter 1 exclusively for dephosphorization, the refractory erosion is significantly suppressed as compared with the conventional example. 40% of repair cost due to extension of refractory life
We were able to reduce the weakness.

Further, the life of the converter 1 for dephosphorization is improved by the example of the present invention, and the furnace can be operated for a long period of time, so that the pretreatment ratio can be improved and the slag can be reduced. .

[0060]

As described in detail above, according to the present invention, a dephosphorization furnace such as a dephosphorization converter for hot metal dephosphorization requires an increase in repair cost and a lack of durability of the repair part. Not
A slag coating method for a dephosphorization furnace that can be surely repaired can be provided, thereby extending the furnace life of the dephosphorization furnace. The significance of the present invention having such an effect is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a slag coating method according to an embodiment.

FIG. 2 is a graph showing the results of a study on durability in an example in an indexed manner.

FIG. 3 is a graph showing a change in brick thickness in an example.

FIG. 4 is a graph showing the effect of tapping temperature in Examples.

FIG. 5 is a graph showing refractory costs for both the present invention example and the conventional example in an indexed manner.

FIG. 6 is an explanatory view schematically showing a situation in which hot metal dephosphorization is performed using a converter dedicated to dephosphorization.

[Explanation of symbols]

1 dephosphorization dedicated converter 2 hot metal 2b 3, 4, 5 ladle 6 decarburization furnace hot metal 2b amount V ₂ of the molten iron 2a amount V ₁ to be processed

Claims (10)

[Claims] When performing a dephosphorization treatment in a hot metal pretreatment by using a dephosphorization furnace, a part of the total amount (V) of the hot metal to be treated is charged into the dephosphorization furnace. After pouring (V ₁ ) and performing the dephosphorization treatment, the dephosphorization-treated hot metal is discharged, and then the total charge (V) is supplied to the dephosphorization furnace from which the hot metal is discharged. A slag coating method for the dephosphorization-only furnace by pouring the remaining amount (V ₂ ) of the above-mentioned iron and performing decarburization blowing. 2. The method according to claim 1, wherein the furnace for dephosphorization is a converter. 3. The partial amount (V ₁ ) is (１ ／) V
Not less than (２) V and the remaining amount (V ₂ ) is not less than (１ ／) V and (１ ／) V
V or less, and when the distance from the furnace port of the furnace dedicated to dephosphorization to the hearth is H ₀ (mm), the molten steel bath depth (m
The slag coating method according to claim 1 or 2, wherein m) satisfies not less than 500 (mm) and not more than (H _0/2 ) (mm). 4. The slag in the decarburization blowing has a slag basicity (CaO / SiO ₂ ) of 2.5 or more and 3.5 or less and an MgO concentration of 3 to 5% by mass. A slag coating method for a dephosphorization-only furnace according to any one of claims 3 to 3. 5. The decarburization blowing end point temperature is 1640 ° C.
The slag coating method of the furnace for exclusive use of dephosphorization according to claim 4, which is as follows. 6. The slag coating is performed by solidifying the molten slag by adding a cooling material to the molten slag remaining in the furnace for exclusive use of dephosphorization after the decarburization blowing by 10 kg / T or more. Claims 1 to 5 which are performed
The slag coating method for a furnace dedicated to dephosphorization according to any one of the above. 7. The slag coating method according to claim 6, wherein the cold material is at least one of scrap, brick waste, and pig iron. 8. The slag coating method for a dephosphorization furnace according to claim 6, wherein curing is performed for about 10 minutes to 240 minutes after the cooling material is charged. 9. The method according to claim 1, wherein the hot metal subjected to the decarburization treatment is tapped on the hot metal subjected to the dephosphorization treatment and discharged. A slag coating method for a furnace dedicated to dephosphorization. 10. The decarburized molten steel is supplied to a dephosphorization furnace for decarburizing the next charge.
The slag coating method for a furnace dedicated to dephosphorization according to any one of claims 1 to 8.