KR20020080304A - Method for manufacturing composite deoxidizer of molten steel and the composite deoxidizer by using the mothod thereof - Google Patents

Abstract

PURPOSE: A composite deoxidizer is provided which has high density by adding a reinforcing element to aluminum matrix, and a method is provided which deoxidizes and alloys molten steel and slag using the composite deoxidizer is provided. CONSTITUTION: In a deoxidizer injected into molten metal during manufacturing of steel and iron, the composite deoxidizer is characterized in that the deoxidizer increases relative specific gravity for molten metal by solidifying aluminum in an iron pipe. The method for treating molten steel using a composite deoxidizer comprises the steps of injecting the composite deoxidizer into molten metal, specific gravity of the composite deoxidizer has an initial density of 0.4 or more compared with density of molten steel by adding a metal reinforcing element to aluminum matrix; and melting the composite deoxidizer into molten metal as continuously increasing relative density of the composite deoxidizer to 1.00 to 1.05. The method for deoxidizing slag using a slag deoxidizer is characterized in that the slag deoxidizer is manufactured by adding 20 to 50 wt.% of additive CaO and 10 to 30 wt.% of reinforcing element iron piece to molten metal of 15 wt.% of Mg and 85 wt.% of Al. The method for deoxidizing slag using a slag deoxidizer is characterized in that slag is deoxidized above the slag deoxidizer by injecting the manufactured slag deoxidizer into slag after manufacturing the slag deoxidizer by adding 20 to 50 wt.% of additive CaO and 10 to 30 wt.% of reinforcing element iron piece to molten metal of 15 wt.% of Mg and 85 wt.% of Al.

Description

Composite deoxidizer and method for treating molten steel and slag using the same {Method for manufacturing composite deoxidizer of molten steel and the composite deoxidizer by using the mothod

The present invention relates to a method for producing a composite deoxidizer and a method for treating molten steel and slag using the composite deoxidizer prepared by the above method and the composite deoxidizer, and more specifically, a reinforcing element is added to an aluminum base to increase its density. It relates to a method of deoxidizing and alloying molten steel and slag using a composite deoxidizer and the deoxidizer.

Generally, oxygen refining is performed by injecting oxygen into molten steel for the purpose of removing C, Si, P and other impurities in the steelmaking process. As refining progresses, the oxygen content gradually increases in the molten steel, and at the end of steelmaking, a considerable amount of oxygen remains in the molten steel.

Such oxygen reacts with C at the time of ingot to form bubbles, causing incomplete ingots, or forming inclusions such as oxides, thereby deteriorating the quality of steel. Deoxidation removes this oxygen from molten steel and reduces oxygen content to reduce inclusions, as well as to adjust the shape and distribution of inclusions to create clean steel.

Therefore, the existing deoxidizer is mainly made of Al, ingot, wire (wire), etc. to be added in the steelmaking process. However, as can be seen in Figure 2b, according to the known method, when the molten steel is treated with pure aluminum, the aluminum currently used in the steelmaking and steelmaking process has a low melting point and low density, consumption is high and recovery rate is low It has been pointed out.

Therefore, pure Al has a low density, so the density of molten steel (Density, 6.9g / c㎥) is about 0.35 times less because the density of pure Al is 2.4g / c㎥. For this reason, when Al is added to the molten metal, its specific gravity is low, so it is not mixed in the molten metal, but immediately melts into water droplets and flows into slag. According to the test results, about 54% or more of pure Al is lost in vain. In some steel mills, the proportion of deoxidation is low even during slag calcination, causing the entire plant to experience problems during steelmaking due to smoke and gas release during the steelmaking process. Test results show that deoxidation has a great effect.

However, until now, the method has been published in the patent by attempting to add Al to Fe molten metal in order to increase the specific gravity to Al, but Fe-Al makes an intermetallic compound and the melting temperature is 1400 ~ 1500 ℃, so This is a problem and especially expensive to manufacture. In this case, steelmaking must be performed for a long time, which results in a process against the current steelmaking and steelmaking processes in which rapid operation is a trend.

It is an object of the present invention to provide a method for producing a composite deoxidizer which is capable of maintaining the high density, low melting point and low cost of pure aluminum while eliminating the above defects.

Another object of the present invention is to provide a complex deoxidizer capable of treating molten steel while eliminating the defects while maintaining high density, low melting point and low cost of pure aluminum.

It is still another object of the present invention to provide a method for treating molten steel which is capable of treating molten steel while eliminating the above defects while maintaining high density and low melting point and low cost of pure aluminum.

This object of the present invention is a composite deoxidizer prepared by adding a reinforcing element to a molten melt of Al as a deoxidizer researched and developed by a new casting method named Macro Heterogeneous Composite Casting Alloy (MHCCA). MHCCA), unlike the previous pure aluminum deoxidizer, this complex deoxidizer increases the density in the molten metal when it is added in molten steel to the bottom of the molten metal, and the aluminum dissolves and the Fe falls and dissolves. Significant improvements have been made in cost reduction and steel quality improvement.

Complex deoxidizer according to the present invention and a method of treating molten steel and slag using the same will be clearly understood by the embodiments described in detail below with reference to the accompanying drawings.

Figure 1 is a longitudinal cross-sectional view after the composite deoxidizer production

Figure 2a is a melting process diagram showing a state in which the composite deoxidizer is melted while circulating in the molten metal according to the present invention

Figure 2b is a dissolution process diagram in the molten metal of the conventional aluminum deoxidizer

The composite deoxidizer according to the present invention is prepared through a number of processes, such as dissolving pure aluminum of high purity in a furnace and slowly adding and mixing a metal piece, which is a reinforcing element having a high melting point, into an aluminum molten metal. Since the metal-reinforced element has a higher specific gravity than aluminum, the metal-reinforced element is sunk in the lower part, and thus, if it is mixed well so as to be uniformly dispersed, it is prevented from sinking.

In general, the alloy is prepared by administering a metal having a low melting point in a molten metal having a high melting point, but the complex deoxidizer of the present invention is administered in a manner in which a metal (metal-reinforced element) having a high melting point is administered in a metal melt having a low melting point. It will be called a breakthrough. In the present invention, as the metal reinforcing elements to be administered in the molten metal, one or two or more of rare earth metals, Fe, Ca, Si, Mg, and Ti may be used, and in another configuration, Fe-Mn, which is a double alloy of aluminum, Fe-Si, Fe-Al, Fe-Ti, Fe-Ce may be used, and tri-alloy Fe-Si-Ca, Al-Si-Ca, etc. may be used for aluminum, and alloys of more complicated composition may be used. Of course it can. The schematic shape of the composite oxide is shown in FIG. The white part represents an aluminum base part, and the black part represents a metal reinforcing element composed of one or two or three or more of Fe, Ca, Si, Mg, Ti or rare earth metals. In addition, steel reinforcing elements are used as steel pipes, steel pieces, iron wire pieces, etc., the size of 0.1mm-50mm, the weight of 0.1g-50g small pieces, including added to increase the specific gravity in the aluminum base.

The composite deoxidizer according to an embodiment of the present invention was prepared by putting a high melting point steel ball in a molten aluminum having a low melting point, and was used as a deoxidizer during steelmaking by making a size suitable for the use of the deoxidizer.

In another embodiment of the present invention, as a method of increasing the specific gravity of aluminum, it is also possible to simply bind steel bars to aluminum to increase the specific gravity of aluminum, or to increase the specific gravity of steel blocks or round rods on aluminum. It is also possible to squeeze and solidify aluminum in the iron container, which will also be included in the scope of the invention.

In addition, according to the present invention, when the aluminum is put into the melt together with the iron base alloy, it has a density of 4.0 g / cm 3 compared to the molten steel density (6.9 g / cm 3), and thus has an initial specific gravity of 0.5 or more. In the form of a composite deoxidizer containing Al, C, Si, Mn, Fe in the component range (% by weight), aluminum and iron base alloys are added to the melt.

Al25-50

C0.05 to 0.90

Si0.05 to 1.50

Mn 0.15 to 1.25

Fe balance

The composite deoxidizer contains other components in the form of aluminum base and iron base alloy as reinforcement components. The dissolution of aluminum in molten steel continuously increases the relative specific gravity of the composite deoxidizer to molten steel from 1.00 to 1.05. A method for treating molten steel by a composite deoxidizer is provided.

According to the invention, the method ensures suitable conditions for the dissolution of aluminum in the molten steel. Treatment of molten steel with a composite deoxidizer, in which aluminum is included as a matrix component and the initial low melting point is maintained, causes rapid dissolution in the melt. The treatment of molten steel with a composite deoxidizer, in which the iron base alloy is a reinforcing component, is made heavy as necessary. In other words, when comparing the density of the composite deoxidizer compared to the density of molten steel, the relative specific gravity increases to 0.55 ~ 0.70. At this density, complex deoxidizers do not float into slag and easily enter the circulating melt to undergo deoxidation and chemical reactions in molten steel.

During the treatment of molten steel with Al-Fe alloy deoxidizer, only aluminum is melted first, then the iron balls are separated and dissolved and Al is dissolved again. The reinforcement component does not melt from the iron base alloy until the aluminum is completely dissolved. This is because the reinforcement component aluminum, which is heavier than the density of molten steel, persists, the density of the composite deoxidizer continuously increases during melting, and at the moment when the entire aluminum is dissolved, the relative specific gravity with molten steel has a value of 1.00 to 1.05 as compared with the density of molten steel. It is a reason.

After aluminum is dissolved, the reinforcing component is melted from the iron base alloy. Its composition is similar to that of molten steel. Therefore, the reinforcing part of the composite deoxidizer is easily mixed with the molten steel and completely melted.

During the treatment of molten steel with Al-Fe base alloys, the composite deoxidizer fragments decompose into debris due to the effect of convection. Gradually these fragments break down into smaller fragments.

The combination of reduced fragment size and increased fragment density of the composite deoxidizer dissolves aluminum more rapidly into molten steel and distributes it more uniformly in the melt. Therefore, aluminum loss is reduced and deoxidation by aluminum and stability of the alloy are ensured.

If it is in the range of 25 to 50% by weight of aluminum in the composite deoxidizer, the most preferable conditions for the treatment of molten steel are provided. If the aluminum content in the composite deoxidizer is low, the cooling effect of the composite deoxidizer in the melt becomes stronger because of the necessity of increasing the reinforcing component portion and increasing the amount of the composite deoxidizer. The larger the aluminum content in the composite deoxidizer, the lower the density, the poorer the mixing into the melt, and the greater the aluminum loss.

Controlling the content of C, Si, Mn, Fe in the composite deoxidizer within the ranges given above depends on the need for reinforcing components to obtain something similar to the element content for the content of the treated steel. However, the treatment of molten steel with Al-Fe base alloy composite deoxidizer does not change its chemical composition.

Example

Steels having a content of 0.25% C, 0.70% Mn, 0.25% Si, 0.02% S, 0.03% P were melted in an electric furnace and finally deoxidized to aluminum in the ladle upon yield of the melt outside of the electric furnace. A composite deoxidizer containing Al in the molten steel was taken from 1/6 to 1/3 of the volume of the ladle. Several samples were selected from the ladle to test oxygen and aluminum content prior to steel injection. The composite deoxidizer containing aluminum was preliminarily obtained by mixing carbon steel and liquid aluminum. For comparison, the steel was deoxidized by the above method, i.e. pure aluminum pieces were charged into the melt by means of a steel weight. The amount of pure aluminum and the weight of steel were appropriate for the consumption of aluminum and reinforcing components.

The efficiency of the steel treatment was evaluated using the ratio of aluminum consumption and the ratio of aluminum loss.

Non-K _using the aluminum consumption is calculated by the following expression.

K _using = (Al _rest + Al _o ) ^* 100 / Al _Σo (1)

Where Al _rest is the residual amount of aluminum in the steel,%,

Al _o is the aluminum consumption of dissolved oxygen in the reaction

2 [Al] + 3 [O] = Al ₂ O ₃

Al _o = ([O] _initial- [O] _eventual ) ^* (2 ^* 27/3 ^* 16) (2)

[O] _initial and [O] _eventual content of dissolved oxygen in steel before and after deoxidizing steel with aluminum

Al _Σ is the aluminum consumption in deoxidation of steel,%

The dissolved oxygen content is calculated as follows.

lg [% O]-e _o ^o [% O] = lg a _o + Σe _o ^R [% R] (3)

e _o ^o and e _o ^R are variables of the interaction of oxygen with oxygen and the components of steel (R).

a _o is the activity of oxygen in the liquid steel,%

a value of lg _o was determined experimentally by charging the electrochemical sensors in the liquid steel. A sensor of ZrO ₂ + 17% Y ₂ O _{3 with} control electrode M _O + M _O O ₂ was used for the measurement. in this case,

lg a _o = 2,685-(10,087 ^* E + 5660) / T (4)

Where E is the measured value of the electromotive force sensor, mV

T temperature, ° K

The aluminum loss ratio is calculated by the following equation.

K _loses = 100-k _using (5)

Steel treatment methods are shown in Tables 1 and 2.

As shown in <Table 1> and <Table 2>, the composite deoxidizer of No. 1 component of <Table 1> has the initial density of 4000g / cm 3 as shown in No. 1 of <Table 2>. The relative specific gravity of was 0.58, the specific gravity of the Al melting point was 0.53 Al, the specific gravity of the final melting point was 1.05, the residual Al content was 0.028, the used Al ratio was 66%, and the consumed Al ratio was 34%. On the other hand, the aluminum of No. 5 in Table 1 using pure aluminum, as shown in No. 5 in Table 2, had a density of initial state of 2700g / cm3 and a relative specificity with molten steel of 0.39. The point specific gravity was 0.35 and there was almost no change in specific gravity. The residual Al content was 0.012%, the used Al ratio was 46%, and the consumed Al ratio was 54%.

As can be seen in the embodiments of Table 2, the composite deoxidizer of the present invention has a relative specific gravity of 0.4 or more, which is 0.3 for the slag of the molten metal, so that the composite deoxidizer passes through the slag into the molten metal. It is the minimum specific gravity value, and the composite deoxidizer of the present invention did not exceed 1.05 in the specific gravity of the molten metal as a result of the measurement.

If the aluminum consumption required for steel treatment is the same (0.1%), the aluminum content in the composite deoxidizer is low, so the deoxidation requirement of the Al-Fe base alloy composite deoxidizer is 2 to 4 times higher than that of pure aluminum. 50, and pure aluminum is 100%)

The initial density of the Al-Fe base alloy composite deoxidizer is 1.47 to 1.92 times higher than that of pure aluminum. The difference in density increases during the dissolution process. That is, the initial value of melt | dissolution is 1.52-2.04, and can reach to 3 at the end.

However, the ratio of aluminum consumption increased from 0.46 to 0.64 to 0.77, which means that it increased by 39 to 67%. Therefore, aluminum loss is reduced from 54% to 23 to 36%.

According to the present invention, the efficiency of the steel is ensured by improving the quality of the steel by effectively deoxidizing the steelmaking process. This quality is improved by increasing the specific gravity in the molten metal to deoxidize deeper and fuse the aluminum more stably, and evenly distribute the aluminum to reduce losses than injecting pure aluminum.

In particular, as mentioned above, the use of this composite deoxidizer makes it possible to produce clean steel with a clean interior of the steel, which can greatly improve the quality of the steel. The reason is that the aluminum deoxidizer can be dissolved in the depth of molten metal during the deoxidation, so that the loss of aluminum can be reduced and the aluminum can be dissolved in a stable manner, thereby increasing the deoxidation effect during steelmaking.

In addition, the deoxidizer Ca and rare earth metal, which are not mentioned here, were also used by this method, which resulted in the use of less deoxidizer and a significant reduction in oxygen defects in the steel.

In addition, when used as a slag oxidizer, the specific gravity of the slag phthalate is increased by adding 20 to 50 wt% of urea CaO to 15% Mg + 85% Al molten metal and adding 10 to 30 wt% of iron flakes as a reinforcing element. Since it is high, slagtal acid is placed directly under the slag, so that the generation of smoke is minimized and the gas is prevented, but the slagtal acid has a great effect.

As described above, the deoxidizer introduced into the molten metal during the steelmaking and the steelmaking according to the present invention has a higher specific gravity than the aluminum in the aluminum base, and a metal piece, which is a reinforcing element having a higher melting point, is employed and is higher than the density in the molten metal, unlike conventional pure aluminum deoxidizer. As the aluminum is dissolved and Fe is later dissolved, it decomposes the deoxidation effect of aluminum as it is added to the lower part of the bottom of the molten metal, thereby reducing the cost and dramatically improving the quality of the steel. Particularly, when Al is added to the ladle, When gas is produced, this invention is introduced into the molten steel process, and it reacts directly to the molten metal, thereby reducing the generation of dust and gas, and thus has an excellent effect of being environmentally friendly.

Claims (5)

In the deoxidizer introduced into the molten metal during steelmaking and steelmaking, the deoxidizing agent solidifies aluminum in the steel pipe to increase the relative specific gravity of the molten metal. Dropping a complex deoxidizer in the molten metal having an initial density of 0.4 or more compared to molten steel by adding a metal reinforcing element as a reinforcing component to the aluminum base; And dissolving the composite deoxidizer while dissolving in the molten metal while continuously increasing the relative density of the composite deoxidizer to 1.00 to 1.05. Slag which deoxidizes slag by using slag deoxidizer, which is manufactured by adding 20 ~ 50wt% of additive element CaO to 15% Mg + 85% Al molten metal and adding 10 ~ 30wt% of reinforcing element iron slag Deoxidation method. When used as a slag slate, slag talsate is prepared by adding 20 ~ 50wt% of urea CaO to 15% Mg + 85% Al molten metal and 10 ~ 30wt% of the iron element as a reinforcing element. When used as slag oxidizer, 20% to 50wt% of urea CaO is added to 15% Mg + 85% Al molten metal, and 10 ~ 30wt% of iron flakes as reinforcing element is added to the slag to deoxidize directly under slag. Slagtal acid method using a slagtal acid agent characterized in that.