KR101490187B1 - Method of refining molten steel - Google Patents

Abstract

The present invention relates to a refining method for molten steel, comprising the steps of: preparing a deoxidized molten steel; Extracting the molten steel to analyze a component; Injecting oxygen into the molten steel according to a result of analysis of the molten steel; Discharging the generated slag on the molten steel; And a step of adding the additive into the molten steel and stirring the molten steel to remove the phosphorus component, so that the phosphorus component contained in the molten steel can be easily removed.

Description

TECHNICAL FIELD The present invention relates to a method of refining molten steel,

The present invention relates to a refining method of molten steel, and more particularly, to a refining method of molten steel capable of easily removing phosphorus (P) components contained in molten steel deoxidized.

In general, the phosphorus (P) component contained in molten steel is segregated in the cast steel during continuous casting, causing quality defects, and particularly cracking of the material under extreme environments, adversely affecting the product. As a result, under extreme conditions, materials such as pressure vessels and pipes are mainly used for ultra-low-strength steels which are resistant to stress corrosion cracking caused by hydrogen organic cracking or sulfides.

On the other hand, the steelmaking process proceeds in the order of the iron pre-treatment process, the converter refining process, the secondary refining process, and the continuous casting process.

At this time, the converter refining process charges hot metal and scrap into the converter and blows oxygen (O ₂ ) gas of high purity through the lance, so that the carbon and impurities in the charcoal are converted into the oxide of CO gas or slag The molten steel from which impurities have been removed through this process is called molten steel.

The slag layer formed in the reaction of removing the oxide form of the slag actively reacts with the molten iron by stirring action by the impact energy of the off-gas (N ₂ , Ar) and pure oxygen to stably remove the impurities in the molten iron, Lt; / RTI > plays a very important role in removing and stabilizing the component (P).

Conventionally, for the process of removing the phosphorus (P) component, the phosphorus phosphorus is removed while performing double slag operation and talline operation.

On the other hand, in the talline operation other than the converter process, when the phosphorus component is higher than the target value in the molten steel which is molten and introduced, the burnt lime is injected into the upper part of the molten steel to be introduced, and the inert gas is blown The phosphorus component in the molten steel reacts with the FeO in the slag to form the phosphorus oxide (P ₂ O ₅ ) by the strong agitation of the inert gas, and the phosphorus oxide reacts with the quicklime again to form the stabilized complex phosphorous oxide, .

However, in the case of molten steel subjected to deoxidation, the state of the slag is stable, and the concentration of FeO required for the talline reaction is low, so that the desired talline effect can not be obtained.

KR 2000-0020060 A1

The present invention provides a refining method of molten steel capable of easily removing phosphorus components in molten steel.

The present invention provides a refining method of molten steel capable of improving the quality of a product to be produced.

The refining method of molten steel according to an embodiment of the present invention is a refining method of molten steel subjected to deoxidation treatment, comprising the steps of: preparing a deoxidized molten steel; Extracting the molten steel to analyze a component; Injecting oxygen into the molten steel according to a result of analysis of the molten steel; Discharging the generated slag on the molten steel; And injecting the additive into the molten steel and stirring the molten steel to remove the phosphorus component.

The step of analyzing the components may measure the amount of Al dissolved in the molten steel.

When the dissolved amount of Al contained in the molten steel is 0.001 wt%, oxygen of 0.03 to 0.09 Nm 3 / mol of the molten steel can be blown in the process of injecting the oxygen.

The process of blowing oxygen can be performed in a vacuum degassing refining facility (Rheinstahl Hüttenwerke & Heraus Oxygen Blowing, RH-OB) or Composition Adjustment by Argon Sealed Bubbling-Oxygen Blowing (CAS-OB).

And slag containing Al ₂ O ₃ may be formed on the molten steel in the course of injecting oxygen into the molten steel.

The additive may include calcium oxide (CaO).

When the target P [P] concentration is 0.001% in the process of adding the additive, additives of 0.45 to 0.61 kg / ton of molten steel can be input.

The process of adding the additive and stirring the molten steel may be performed at the same time.

The stirring of the molten steel may be performed for 1 to 15 minutes by blowing an inert gas into the lower part of the molten steel.

The process for removing the phosphorus component may be performed in a ladle furnace.

According to the embodiment of the present invention, it is possible to easily remove the phosphorus component contained in molten steel subjected to deoxidation. That is, since the slag is stabilized in the deoxidized molten steel and the concentration of FeO required for the talline is low, it is difficult to obtain the target talline effect. Therefore, it is possible to enhance the talline efficiency by performing the talline operation after forcibly injecting oxygen into the deoxidized molten steel and removing the inclusions generated by oxygen blowing to increase the activity of FeO. Accordingly, the quality of the molten steel can be improved, and the quality of the finally produced product can be improved.

1 is a flowchart showing a refining method of molten steel according to an embodiment of the present invention;

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Wherein like reference numerals refer to like elements throughout.

1 is a flowchart showing a refining method of molten steel according to an embodiment of the present invention.

The method for refining molten steel according to an embodiment of the present invention includes the steps of preparing deoxidized molten steel (S100), analyzing the components by sampling deoxidized molten steel (S110) A process S120 of discharging slag generated in accordance with the oxygen blowing, a step S140 of injecting the additive into the molten steel, and a process S200 of stirring the slag by performing the tilting process.

Deoxidized molten steel is used to prevent break-out, which is an accident that molten steel leaks out of the mold during casting, and to prevent product defects such as pin-holes, Oxygen used for decarburization and decarburization may be Al-killed steel deoxidized from ladle to aluminum (Al) during refining. Such aluminum killed steel should be subjected to a talline operation to remove the phosphorus content when the concentration of the phosphorus component is measured above the target value. However, in the case of deoxidized steels such as aluminum killed steels, the slag is stabilized and the concentration of FeO required for the talline reaction is remarkably low, making it difficult to obtain the desired talline effect.

Therefore, in the present invention, oxygen is forcedly blown into the deoxidized molten steel to increase the FeO concentration in the molten steel, and the slag containing a large amount of Al ₂ O ₃ generated at this time can be discharged to enhance the activity of FeO, thereby improving the talline effect.

Thus, molten steel deoxidized in the previous step is introduced into the ladle. When the deoxidized molten steel is prepared, molten steel is sampled to analyze the components. At this time, the component analysis of molten steel can measure the dissolved amount (Sol-Al) of Al in the molten steel. The amount of Al dissolved can be used as an index to measure the degree of deoxidation of molten steel. That is, since deoxidation of molten steel is performed by injecting Al into molten steel, it can be judged that the higher the amount of Al dissolved, the higher the degree of deoxidation of molten steel.

When the dissolved amount (% by weight) of Al in the molten steel is measured, the amount of injected oxygen is calculated according to the dissolved amount of Al and taken into molten steel. At this time, when the dissolved amount of Al contained in the molten steel is 0.001 wt%, oxygen of 0.03 to 0.09 Nm 3 / mol of the molten steel can be injected. The intake amount of oxygen can be increased at a constant rate as the dissolved amount of Al contained in molten steel is increased. If the amount of oxygen injected into the molten steel is smaller than the specified range, it is difficult to obtain the desired talline effect. If the amount of oxygen is larger than the range, the effect of improving the talline efficiency is not greatly affected and the quality of the molten steel is deteriorated.

Such a blowing process of oxygen may be performed in a vacuum degassing refiner (Rheinstahl Hüttenwerke & Heraus Oxygen Blowing, RH-OB) or Composition Adjustment by Argon Sealed bubbling-Oxygen Blowing (CAS-OB). At this time, the oxygen injection in the vacuum degassing refining equipment can be performed in an upstream manner.

When oxygen is blown into the molten steel, oxygen and Al in the molten steel react with each other to produce slag containing Al ₂ O ₃ on the molten steel. Since Al ₂ O ₃ inhibits the activity of FeO in the molten steel, slag on the molten steel is skimmed using a skimmer.

After discharging the slag, the ladle containing the molten steel is moved to a Ladle Furnace (LF) facility.

Then, an additive for talline is introduced into the molten steel, and molten steel is stirred to perform the talline process.

Caustic soda (CaO) may be used as an additive, and the amount of the CaO may be set according to the concentration of phosphorus to be removed (P [P] concentration). For example, if the P [P] concentration is 0.001%, the quicklime of 0.45 to 0.61 kg / mol of the molten steel can be input. In this case, the additive can be added to the upper part of the molten steel. If the amount of the quicklime is less than the prescribed range, the desired talline efficiency can not be obtained. If the amount is larger than the indicated range, There is a problem that the quality of the molten steel is deteriorated due to the impurities acting as impurities.

Since the additive is put into the upper part of the molten steel, the molten steel can be stirred for smooth mixing with the molten steel. At this time, the stirring of molten steel may be performed simultaneously with the addition of the additive, or may be carried out before the addition of the additive, or after the addition of the additive.

Stirring of the molten steel may be performed by dipping the lance into the molten steel bottom and then blowing the inert gas to bubble the molten steel to form a strong flow in the molten steel. As the inert gas, argon may be used. During molten steel agitation, the inert gas may be blown at a flow rate of 50 to 150 Nm 3 / hr. If the amount of the inert gas to be blown is less than the recommended range, the additive and the molten steel are not mixed smoothly to obtain the desired talline effect. If the amount of blown is larger than the recommended range The molten steel is scattered by the bubbles generated by the bubbling or the strong flow, and the talline efficiency is not greatly improved.

If the agitation time is shorter than the suggested range, the reaction time between phosphorus, FeO and CaO is short and the desired talline effect can not be obtained. If the blowing amount is longer than the indicated range There is a problem in that the temperature of the molten steel is lowered and the temperature rising process of the molten steel is required in the subsequent process.

The tallen process as described above can be carried out by the reaction according to the following formulas 1) to 3).

2 [P] + 5 (FeO) = P ₂ O ₅ + 5Fe

(CaO) + P ₂ O ₅ = 4 CaO · P ₂ O ₅

Equation 3) 2 [P] + 5 (FeO) + 4 (CaO) = 4CaO · P 2 O 5 + 5Fe

Hereinafter, an example of talling the deoxidized molten steel by the refining method of molten steel according to the embodiment of the present invention will be described.

The molten steel used here is Al-Killed steel, and the amount of molten steel used is 330 tons. Aluminum killed steel is a steel in which oxygen is used for decarburization process by performing decarburization process using oxygen and then adding aluminum (Al).

Table 1 below shows the amount of oxygen taken in accordance with the dissolved amount of Al measured by taking deoxidized molten steel.

Sol-Al (wt%) 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 The amount of oxygen (Nm 3) 150 200 250 300 350 400 450 500 550

Referring to Table 1, the amount of oxygen taken in the molten steel can be taken in a range of 50 to 150 Nm 3. Such a value is included in the range of the amount of oxygen injected according to the amount of dissolved Al described above.

Table 2 below shows the amount of quicklime introduced and the agitation time according to the target talline concentration.

[P] 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 Quicklime (kg) 200 350 500 650 800 950 1100 1250 1400 Stirring time (minute) 3 4 5 6 7 8 9 10 11

According to Table 2, the amount of fresh lime added is 150 to 200 kg and the agitation time is 3 to 11 minutes according to the target desorption [P] concentration. These values are included in the amount of the quicklime and the stirring time described above.

The present inventors obtained the process conditions shown in Tables 1 and 2 through repeated experiments, and it was possible to efficiently remove phosphorus contained in the deoxidized molten steel through such process conditions.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

Claims (11)

As a refining method of a deoxidized molten steel,
Preparing a deoxidized molten steel;
Extracting the molten steel to analyze a component;
Injecting oxygen into the molten steel according to a result of analysis of the molten steel;
Discharging the generated slag on the molten steel; And
Adding an additive into the molten steel and stirring the molten steel to remove the phosphorus component;
/ RTI >
In the process of analyzing the above components
And the amount of Al contained in the molten steel is measured. delete The method according to claim 1,
0.0 > to 0.09 Nm < / RTI > of molten steel when the dissolved amount of Al contained in the molten steel is 0.001 wt% in the course of blowing oxygen. The method of claim 3,
The process for blowing oxygen includes:
A refining method of molten steel performed in vacuum degassing refining equipment (Rheinstahl Hüttenwerke & Heraus Oxygen Blowing, RH-OB) or Composition Adjustment by Argon Sealed bubbling-Oxygen Blowing (CAS-OB). The method according to claim 1,
And a slag containing Al ₂ O ₃ is formed on the molten steel in the process of injecting oxygen into the molten steel. The method according to claim 1,
Wherein the additive comprises calcium oxide (CaO). The method of claim 6,
The additive of 0.45 to 0.61 kg / ton of molten steel is injected when the target desorption [P] concentration is 0.001% in the process of adding the additive. The method of claim 6,
Wherein the step of injecting the additive and the step of stirring the molten steel are carried out at the same time. The method of claim 8,
Wherein the stirring of the molten steel is performed for 1 to 15 minutes by blowing an inert gas into the lower part of the molten steel. The method according to claim 1,
The process for removing the phosphorus component is performed by a ladle furnace. The method according to any one of claims 1 to 10,
Wherein the deoxidized molten steel is Al-Killed steel.

Images