KR20040042537A - Converter working method of phosphorous added low carbon steel using ladle slag - Google Patents

Abstract

PURPOSE: A converter operation method of phosphorus added low carbon steel using ladle slag is provided to recycle ladle slag and reduce manufacturing cost by injecting ladle slag instead of expensive ferro alloy of Fe-P and removing lower oxides in slag using slag deoxidizer, thereby reducing phosphorus in slag into molten steel. CONSTITUTION: In a converter operation of phosphorus added low carbon steel containing 0.03 to 0.05 wt.% of phosphorus, the converter operation method of phosphorus added low carbon steel using ladle slag is characterized in that P in molten steel is increased by injecting fluorite and large quantities of quicklime as a slag preparation agent into molten steel and injecting waste ladle slag and a small quantity of quicklime instead of Fe-P into molten steel in the tapping step, and injecting slag deoxidizer into molten steel after completion of tapping, thereby reducing P2O5 in slag, wherein the ladle slag contains 6 to 8 wt.% of P2O5, wherein the ladle slag comprises 0.5 to 1.5 wt.% of T.Fe, 40 to 45 wt.% of CaO, 8 to 12 wt.% of SiO2, 15 to 25 wt.% of Al2O3, 6 to 8 wt.% of MgO, 3 to 5 wt.% of MnO, 6 to 8 wt.% of P2O5 and other inevitable impurities, wherein the ladle slag is injected into molten steel after it is generated in the steelmaking process, air cooled in a slag yard and transferred to a converter hopper so that the ladle slag is stored in the converter hopper, and wherein the slag deoxidizer comprises 55 to 65 wt.% of CaCO3 and 35 to 45 wt.% of Al.

Description

Converter working method of phosphorous added low carbon steel using ladle slag}

The present invention relates to a molten steel operation method of a low carbon steel, more specifically, during the tapping operation of the low carbon steel, the ladle slag is added in place of high-priced alloy iron such as Fe-P, and after the completion of the tapping, By removing the lower oxide in the slag to reduce the phosphorus in the slag to molten steel, the present invention relates to a molten steel operation method of the additive low carbon steel using a ladle slag that can recycle the ladle slag and reduce the cost.

In general, a converter is a process of manufacturing molten steel by charging scrap iron and molten iron and blowing oxygen through an upper lance to burn impurities in molten iron or to exist in slag.

Therefore, in the converter process, hundreds of steel grades are produced, and various alloy iron and special alloy iron are put in order to manufacture the steel that meets the demand of the demand.

In particular, in addition, if a low-carbon Steel is as shown in Figure 1, when blowing the basis weight of the disclosed (S10) after the calcium oxide (CaO) and calcium fluoride (CaF ₂₎ and (S12), blowing is completed (S14) starts the tapping (S16), quicklime, fluorspar and Fe-P are added to the alloy steel during the tapping operation (S18 to S20). When the tapping is completed (S22), the ladle is transferred to the degassing process, which is a later step (S24).

In such a process, Fe-P, an expensive special alloy iron, is injected to increase the manufacturing cost.

On the other hand, in order to prepare ladle slag in the process of manufacturing additive-added steel, quicklime, fluorspar, and Fe-P are added, and the distribution ratio of P ₂ O ₅ in the ladle slag is adjusted by the distribution ratio of phosphorus in molten steel and phosphorus in slag. The amount will increase. In particular, in the case of added steel of 0.08 to 0.12 by weight, P ₂ O ₅ is increased to 6 to 8%.

The composition of the ladle slag is after the vacuum degassing step T.Fe: 0.5 ~ 1.5%, CaO: 40 ~ 45%, SiO ₂ : 8 ~ 12%, Al ₂ O ₃ : 15 ~ 25 %, MgO: 6-8%, MnO: 3-5%, P ₂ O ₅ : 6-8%, and other unavoidable impurities.

The ladle slag thus made is cast as shown in FIG. 2 after completion of casting (S30), and is disposed in the slag port (S32), transferred to the slag yard, and is discharged (S34), and cooled with water (S36), and then using a dump. It is transferred to the waste treatment plant (S38) is to be discarded as steel waste (S40).

Therefore, the expensive phosphorus and the recyclable CaO contained in the ladle slag is discarded.

The present invention was made in view of the above-mentioned matters, and recycled ladle slag to substitute for quicklime, fluorspar and Fe-P during the tapping operation, and after finishing the tapping, lower oxides in the slag were used by using the slag phthalate. It is an object of the present invention to provide a molten steel operation method of added low carbon steel using ladle slag that can recycle ladle slag and reduce cost by reducing phosphorus in slag into molten steel while removing the slag.

Other objects and advantages of the invention will be described below and will be appreciated by the practice of the invention. Furthermore, the objects and advantages of the present invention can be realized by means and combinations indicated in the appended claims.

1 is a flowchart of a converter operation process of a conventional low-carbon additive steel,

2 is a flowchart for processing a conventional ladle slag;

3 is a flow chart showing a molten steel operation method of the added low carbon steel using a ladle slag according to the present invention,

Figure 4 is a schematic diagram illustrating the reaction when the slag phthalate is added in accordance with the present invention,

5 is a graph showing the relationship between T.Fe and P when a ladle slag as a waste and a deoxidizer are added according to the present invention.

The molten steel operation method of the added low carbon steel using the ladle slag of the present invention for achieving the above object, in the converter operation for the added low carbon steel of 0.03 to 0.05% phosphorus content by weight, slag preparation in the tapping step Instead of zero fluorspar and a large amount of quicklime and Fe-P, waste ladle slag and a small amount of quicklime are added, and after completion of tapping, slag phthalate is added to reduce P ₂ O ₅ in slag to raise P in molten steel. It is characterized by.

Preferably, the ladle slag by weight, P ₂ O ₅ is in the range of 6-8%, in particular T.Fe: 0.5 ~ 1.5%, CaO: 40 ~ 45%, SiO ₂ : 8-12%, Al ₂ O ₃ : 15-25%, MgO: 6-8%, MnO: 3-5%, P ₂ O ₅ : 6-8%, and other inevitable impurities.

And, preferably, the ladle slag is generated in the steelmaking process, air-cooled in the slag yard, transported to the converter ground hopper, stored, and then introduced.

Further preferably, the slagtal acid agent is a composition of CaCO ₃ : 55-65%, Al: 35-45%.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a flow chart showing a molten steel operation method of the added low carbon steel using a ladle slag according to the present invention.

Referring to this, T.Fe: 0.5 to 1.5%, CaO: 40 to 45%, SiO ₂ : 8 to 12%, Al ₂ O ₃ : 15 to 25%, MgO: 6 to 8%, MnO: 3 to 5 When ladle slag having a composition of%, P ₂ O ₅ : 6 to 8%, and other unavoidable impurities is generated (S70), it is air-cooled in the slag yard (S72), and then transported and stored in the converter hopper (S74). ).

Such ladle slag is introduced in the tapping step (S54 ~ S60) (S58), when the slag composition is met with molten molten steel is changed as follows, which is affected by the end point oxygen.

That is, T.Fe: 10-18%, CaO: 40-45%, SiO ₂ : 8-12%, Al ₂ O ₃ : 5-8%, MgO: 6-8%, MnO: 0.5-1.5%, P ₂ O ₅ : 6-8%, and other unavoidable slag.

In order to reduce P ₂ O ₅ in this composition to 1-1.5%, oxides such as FeO, MnO, and P ₂ O ₅ must be reduced in the composition, which occurs while reacting with oxygen according to the following oxide stability order.

Oxide stability ranking: CaO> Al ₂ O ₃ > SiO ₂ >MnO>FeO> P ₂ O ₅

The tapping is completed (S60), the slag phthalate in the slag oxidizer input step (S62) is subjected to the following reaction.

CaCO ₃ = CaO + CO ₂

In this way, as shown in Figure 4 while increasing the interfacial area of the slag is reacted as follows according to the oxide instability rank.

3FeO + 2Al = 3Fe + Al ₂ O ₃

3MnO + 2Al = 3Mn + Al ₂ O ₃

3P ₂ O ₅ + 10Al = 6P + 5Al ₂ O ₃

As described above, Al forms stable Al ₂ O ₃ , and Fe and P separated from oxygen react with each other and settle into molten steel as follows.

Fe + P = FeP

According to the above-described reaction schemes 1, 2, 3, the composition of the slag is changed as follows.

That is, T.Fe: 1 to 1.5%, CaO: 40 to 45%, SiO ₂ : 6 to 8%, Al ₂ O ₃ : 15 to 25%, MgO: 6 to 8%, MnO: 0.5 to 1.5%, P ₂ O ₅ : 1 to 1.5%, and other unavoidable impurities.

As a result of the change in the slag composition, the phosphorus (P) in the slag is settled in the molten steel and the phosphorus in the molten steel rises, which is obtained by the following equation.

An increase amount of P = P ₂ O ₅ content of the ladle slag {× injected tapping of P ₂ O ₅ content-de San ladle P ₂ O ₅ content in the slag ladle slag amount ÷} × amount of the molten steel

According to the above formula, phosphorus of 0.009% per 1,000 kg of ladle slag is increased.

Hereinafter, embodiments of the present invention will be described in detail.

<Example>

The exit from the converter shall be 275 tons.

Table 1 shows the composition of the added low carbon steel of 0.03 to 0.05% by weight.

C Mn Si P S Al 0.002 ~ 0.005 0.65-0.75 0.2 or less 0.03-0.05 0.015 or less 0.02-0.06

Table 2 shows the molten steel composition after the converter refining is completed.

C Mn P S 0.2-0.6 0.07-0.12 0.015 ~ 0.22 0.007 ~ 0.015

Such converter endpoint composition will depend on the endpoint oxygen.

Table 3 shows the input amount of ferroalloy in the prior art for reference.

Ferroalloy Input (㎏) CaO CaF ₂ Fe-P 1,000 150 250

Here, P content in Fe-P is 0.22 to 0.27%, and a real rate is 85%.

Next, Table 4 shows the amounts of quicklime and ladle slag added according to the present invention.

CaO Ladle slag 200 kg 2,000 kg

In the present invention, the reason for adding about 200 kg of quicklime (CaO) is that the amount of CaO in the ladle slag is 40 to 45%, and the reason for not adding the fluorite (CaF ₂ ) is 15 to 25 Al in the ladle slag. This is because the melting point of slag is dropped to%, so that the input is not necessary.

Table 5 shows the amount of slag deoxidizer injected according to the end point oxygen.

End point oxygen (PPM) Carbonate input amount (㎏) Less than 600 650 600-700 750 700-800 850 800-900 950 900-1,000 1,050 More than 1,000 1,200

The reason for adding the amount of deoxidizer is as follows.

Since the phosphorus deoxidized during the low-grade oxide in slag P ₂ O ₅ to 1 ~ 1.5% FeO, MnO deoxygenation as would the regulation of a deoxidizer by the following calculation.

1.Calculation of oxygen in T.Fe

1-1) Oxygen content in FeO is O / FeO = 16/72 = 22%

1-2) T.Fe content in slag (FeO content in T.Fe is over 90%)

1-3) Oxygen content in FeO × T.Fe content in slag = Oxygen in T.Fe

2. Calculation of oxygen in MnO

2-1) Oxygen content in MnO is O / MnO = 16/71 = 22.5%

2-2) MnO content in slag

2-3) Oxygen content in MnO × MnO content in slag = Oxygen in MnO

3.Calculation of oxygen in P ₂ O ₅

3-1) the oxygen content of the P ₂ O ₅ is _{5O / P 2 O 5 = 56.3} %

3-2) P ₂ O ₅ content of slag

3-3) Oxygen content in P ₂ O ₅ × P ₂ O ₅ content in slag = Oxygen in P ₂ O ₅

The amount of MnO and P ₂ O ₅ in the ladle slag added during tapping is almost fixed, and T. Fe is changed according to the change of the end point oxygen, thus limiting the amount of slag deoxidizer as described above.

Table 6 shows the amount of phosphorus in molten steel when Fe-P is added in the prior art.

division End point P amount (%) Fe-P input amount (㎏) P amount after leaving (%) Conventional Example 1 0.018 250 0.037 Conventional Example 2 0.015 250 0.034 Conventional Example 3 0.022 250 0.041 Conventional Example 4 0.021 250 0.040 Conventional Example 5 0.019 250 0.038 Conventional Example 6 0.019 250 0.038 Conventional Example 7 0.017 250 0.036 Conventional Example 8 0.019 250 0.038 Conventional Example 9 0.018 250 0.037 Conventional Example 10 0.022 250 0.041

Table 7 shows the ladle slag during tapping in accordance with the present invention, and the amount of molten steel in the molten steel when the deoxidizer (CaCO ₃ : 55-65%, Al: 35-45%) was added after tapping.

division End point oxygen (PPM) End point P amount (%) Deoxidant input amount (㎏) P amount after deoxidation (%) P ₂ O ₅ (%) Example 1 545 0.020 650 0.038 1.2 Example 2 496 0.020 600 0.037 1.5 Example 3 563 0.018 650 0.035 1.4 Example 4 652 0.018 750 0.036 1.0 Example 5 482 0.022 600 0.039 1.2 Example 6 752 0.019 850 0.033 1.8 Example 7 812 0.016 950 0.033 1.2 Example 8 655 0.017 750 0.034 1.3 Example 9 623 0.018 750 0.035 1.1 Example 10 612 0.019 750 0.037 1.0 Example 11 645 0.021 750 0.039 1.0 Example 12 789 0.018 900 0.036 1.2 Example 13 912 0.015 1,050 0.032 1.4 Example 14 812 0.015 950 0.032 1.5 Example 15 562 0.020 600 0.038 1.3 Example 16 542 0.020 600 0.037 1.2 Example 17 635 0.019 750 0.037 1.2 Example 18 702 0.017 750 0.035 1.2 Example 19 502 0.018 650 0.036 1.1 Example 20 489 0.022 600 0.040 0.8

Compared with the conventional example of Table 6, when the ladle slag as waste and the deoxidizer are added as shown in the examples of Table 7, the effect of adding the conventional Fe-P can be obtained as shown in FIG. there was.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this, The person of ordinary skill in the art to which this invention belongs, Of course, various modifications and variations are possible within the scope of the claims to be described below.

According to the present invention, by manufacturing the low-added low carbon steel using the ladle slag generated in the steelmaking process, to recycle the ladle slag as waste, to reduce the quicklime and fluorspar injected for slag preparation, and to raise the phosphorus in the molten steel In order to reduce the expensive Fe-P input for the purpose, it is possible to achieve the effect of contributing to the development of environment-friendly steelmaking industry by applying the work using waste.

Claims (5)

In converter operation for the added low carbon steel having a phosphorus content of 0.03 to 0.05% by weight, Instead of fluorspar, a large amount of quicklime, and Fe-P, which are used as slag preparations in the tapping step, waste ladle slag and a small amount of quicklime are added.After finishing the tapping, slag phthalate is added to reduce the P ₂ O ₅ in the slag. A converter operation method of an added low carbon steel using a ladle slag characterized by raising P in molten steel. The method of claim 1, Wherein the ladle slag by weight, P ₂ O ₅ is a converter operation method of the low-carbon steel added by using a ladle slag, characterized in that in the range of 6-8%. The method according to claim 1 or 2, The ladle slag is T.Fe: 0.5 to 1.5%, CaO: 40 to 45%, SiO ₂ : 8 to 12%, Al ₂ O ₃ : 15 to 25%, MgO: 6 to 8%, MnO: 3 to 5 %, P ₂ O ₅ : 6 to 8%, and the method of operating a converter of a low-carbon steel added by using a ladle slag, characterized in that the composition of other unavoidable impurities. The method according to claim 1 or 2, The ladle slag is generated in the steelmaking process is air-cooled in the slag yard, transported and stored in the converter ground hopper, the converter operation method of the added low carbon steel using a ladle slag characterized in that the input. The method according to claim 1 or 2, The slag phthalic acid is CaCO ₃ : 55 ~ 65%, Al: 35 ~ 45% composition, characterized in that the composition of the converter operation of the low-carbon steel added with a ladle slag.