JPH08260024A - Production of deoxidation refining agent for iron and steel - Google Patents

Abstract

PURPOSE: To provide a method for producing a deoxidation refining agent for molten steel capable of effectively removing the product of deoxidation and easily producing a large amt. of clean steel. CONSTITUTION: Aluminium is formed as particles of a grain size of <=5mm. The surfaces of these particles are wetted with an aq. sodium silicate and fine powder of CaCO3 is added and mixed to and with such particles and is adhered to the wet surfaces of the Al particles. The particles are dried to fix the CaCO3 to the surfaces of the Al particles, by which the fine powder is formed to the particle form. The deoxidation refining agent for iron and steel produced in such a manner accelerates the formation of larger inclusions as the CaCO3 is dissociated to CaO and CO2 by the heat of the molten steel and the CO2 generates very small and drastic stirring flow when the refining agent is added into the molten steel. Simultaneously, the CaO efficiently absorbs the Al2 O3 which is the inclusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a deoxidizing and refining agent for steel used for deoxidizing molten steel.

[0002]

2. Description of the Related Art Conventionally, as a method of deoxidizing and refining molten steel, a method of adding a deoxidizing agent such as Al to undeoxidized molten steel has been a well-known technique. It is known that a large amount of inclusions such as alumina clusters are generated as acid products, which remain in the steel and become internal defects, thereby deteriorating the quality of the steel material.

Therefore, when adding a deoxidizing agent, the molten steel is forcibly stirred by using an inert gas blowing stirrer, an electromagnetic induction stirrer, or the like, to coagulate and fuse alumina and the like suspended in the molten steel. Treatment, and further, CaO, CaO-Al
Clean steel is manufactured by injecting reducing slag such as ₂ O ₃ into molten steel, adsorbing and removing alumina and the like suspended in the molten steel, and floating inclusions. .

[0004]

However, according to the prior art, when performing stirring by injecting an inert gas or electromagnetic induction, deoxidation using a reducing slag which reacts relatively slowly is performed. In such a case, for example, LF method or A
A dedicated smelting vessel as used in the SEA-SKF method was required. For this reason, a huge amount of capital investment is required, and a special out-of-pile smelting facility must be added to the normal steelmaking equipment line. Due to restrictions, it could not always be easily introduced.

Further, even when the inert gas is blown or the stirring is performed by electromagnetic induction, it is not easy to sufficiently remove the alumina and the like suspended in the molten steel. Unless agitated, the steel material may be defective. On the other hand, if the agitation is performed over a long period of time, the steelmaking process may be prevented from proceeding sequentially.

[0006] Therefore, the present invention provides a method for producing a deoxidizing and refining agent for molten steel, which can remove deoxidized products more effectively than in the past and can easily produce large quantities of clean steel. With the goal.

[0007]

Means for Solving the Problems, Action, and Effect In order to achieve the above-mentioned object, a method for producing a deoxidizing refining agent for steel according to the present invention is described as follows. Then, calcium carbonate particles or powder are added and mixed, and the calcium carbonate particles or powder are adhered to the surfaces of the aluminum or aluminum-containing particles to form particles.

[0008] This is the result of earnest research by the applicants,
In carrying out deoxidation of molten steel, a gas releasing substance that releases gas in the molten steel and a deoxidizing substance that binds to oxygen in the molten steel are simultaneously added to the undeoxidized molten steel, and a deoxidized product is added. During the reaction that takes place, the method of imparting the flow of molten steel in advance to the local parts subjected to the reaction promotes the deoxidation reaction in the molten steel, and the aggregation, enlargement, and floating of inclusions generated by the deoxidation reaction It has been found that the separation is remarkably accelerated, and furthermore, various studies have been made on a deoxidizing refining agent capable of easily performing such a deoxidizing method.

Here, the above-mentioned Al or Al-containing material is a deoxidizing substance that binds to oxygen in molten steel, and is pure metal Al.
Needless to say, an alloy or a composition containing Al to a certain extent or more may be used, but in order to effectively promote deoxidation, an alloy containing 20% or more of pure Al is desirable. In addition, the particles of Al or Al-containing materials are desirably those having a particle size of about 5 mm or less from the viewpoint that they can be easily dissolved in molten steel, and those having a particle size of about 100 mesh or more from the viewpoint of easy handling as powders. Things are good. More specifically, dissolving the new lump Al, a particulate metal Al having an average particle size of about 5 mm or less, obtained by an atomizing method, metal Al or A
When aluminum alloy is melted, aluminum dross generated on the surface of the molten metal is pulverized and processed, and a granular material containing 20% or more of Al pure content adjusted to 100 mesh or more and 5 mm or less, Al chips generated by machining Can be used alone or in combination.

Furthermore, CaCO ₃ is the outgassing material to release gas in the molten steel, the heat of the molten steel CO ₂ and CaO
At the same time, CO ₂ rapidly agitates the molten steel locally and locally, and at the same time, CaO fuses with the deoxidized product to act to promote the floating and separation of the deoxidized product.
The size of CaCO ₃ is a particle or a powder having a size of not more than that which can be attached to the particle surface of Al or an Al-containing substance, and more specifically, a size adjusted to a particle size of about 100 mesh or less is desirable. . In addition, CaCO
The amount of ₃ is desirably set to 10 to 70% by weight relative to Al or Al-containing material. This is Al
Or, when the weight ratio to the Al content is less than 10%, C
Both O ₂ and CaO decrease in the production amount, and the expected effects cannot be sufficiently obtained. If the production amount exceeds 70%, the amount of CaO with respect to Al becomes excessive, and the time required for slag removal only increases.

[0011] In addition, the surface of the particles of Al or Al-containing material has C
The method of adhering aCO ₃ may be any method, for example, a method of adhering with an appropriate binder, mixing Al particles and CaCO ₃ particles, and applying a physical force such as high-speed collision. Although a method of attaching is considered, a simpler method is Al or Al.
Wet the particle surface of the inclusions and add CaCO ₃
The powder is added, mixed, and adhered.
Al or Al by the method of drying at about
CaCO ₃ powder can be fixed on the surface of the inclusion. In addition, in order to wet the particle surface of Al or the Al-containing substance, a liquid such as water which can be evaporated in a later drying process may be used, and a material which can become a binder such as sodium silicate or polyethylene oxide may be used during combustion. It is desirable to moisten it with a dilute solution or the like, although the smoke generation is small.

[0012] The deoxidizing refining agent thus produced is formed in the form of particles, and more specifically, Al or A
It is a particle in which the surface of the l-containing material is coated with CaCO ₃ , or a composite deoxidizing refining agent in which such particles gather and adhere to each other to form secondary particles.

As is apparent from the above description, the aluminum or aluminum-containing material is made into particles having a particle size of 5 mm or less, and the surface of the aluminum or aluminum-containing material particles is wetted. , Adding and mixing the calcium carbonate fine powder to adhere to the surface of the wet aluminum or aluminum-containing material,
By drying the aluminum or aluminum-containing substance having calcium carbonate attached to the surface and fixing the calcium carbonate on the surface of the aluminum or aluminum-containing substance, the desired action and effect can be obtained in a relatively simple and simple process. It is desirable because a good deoxidizing refining agent can be produced.

By the way, other than the above-mentioned production method, a deoxidizing and refining agent having an intended action and effect can be produced. For example, as described in claim 3, a powder of aluminum or an aluminum-containing material and a powder of calcium carbonate are mixed, and a binder is further added to form a particulate deoxidizing refining agent for steel. The manufacturing method is that.

That is, powder of Al or Al-containing material, Ca
What is obtained by mixing with CO ₃ powder is a mere mixture in powder form, but can be formed into particles by adding a binder thereto. Has the same action and effect as the deoxidizing refining agent obtained by the production method described above, and can be used as the intended deoxidizing refining agent. As a binder, a dilute solution of sodium silicate, polyethylene oxide, or the like may be used as described above.

In the method for producing a deoxidizing and refining agent for steel described above, the aluminum or the aluminum-containing material has an aluminum purity of 20 to 100%, and the calcium carbonate contains the aluminum or the aluminum. It is desirable that the content be 10 to 70% by weight based on the content.

That is, as described above, in order to effectively promote deoxidation, it is desirable that the Al or the Al-containing material contains 20% or more of the Al pure content. In order to promote Ca, it is desirable that CaCO ₃ be 10 to 70% by weight with respect to Al or Al-containing material. Therefore, if a deoxidizing refining agent is produced by optimally adjusting these conditions, a deoxidizing refining agent having excellent functions and effects can be obtained.

[0018]

Next, embodiments of the present invention will be described. (1) Preparation of composite deoxidizing refining agent Al particles containing 99.7% of metal Al (particle size: 0.5 to 1.0 m)
m) To 700 g, 50 g of a 5% aqueous sodium silicate solution as a binder was added, and mixed with a rotary mixer until the whole was wetted. Next, 300 g of calcium carbonate fine powder having an average particle size of 5 to 6 μm, a CaO content of 53% or more, a SiO ₂ content of less than 2.0%, and a loss on ignition of 41 to 44% is added and mixed, and taken out of the mixer. Let dry. As a result, a target product in which the surface of the Al particles was coated with the fine calcium carbonate powder was obtained. (2) Production of Clean Steel [Part 1] In a graphite crucible having an inner diameter of 145 mm set in a high-frequency induction furnace, 10 kg of a commercially available S25C steel bar was melted. After 5 minutes from the meltdown, the fused silica tube (inner diameter 8
mm × 12 mm in outer diameter), and 20 g of the above-mentioned composite deoxidizing and refining agent was injected together with N ₂ gas. This is 1570
After holding at 10 ° C. for 10 minutes, a cast steel mold (inner diameter 50 mm
× height 100 mm) (sample 1).

Similarly, 10 kg of S25C steel bar was melted in a graphite crucible, and 3 minutes after melting and 5 minutes after melting.
After one minute, 20 g of the above-mentioned complex deoxidizing and refining agent was added by an overhead method, and the mixture was stirred with a silica tube. This was kept at 1570 ° C. for 10 minutes, and then cast into the same cast steel mold as above (Sample 2).

Further, for comparison, 10 kg of S25C steel bar was melted in a graphite crucible, kept at 1570 ° C. for 10 minutes without adding the composite deoxidizing refining agent, and then cast into the same cast steel as above. (Sample 3). (3) Measurement / comparison test of inclusions [Part 1] For each of the three types of samples obtained by the above-described method, three vertical and vertical positions on the axis were measured using ASTM-E4.
Inclusions were measured and compared by five methods. Table 1 shows the test results. Note that the test results are the average of the results of preparing two samples and measuring them.

[0021]

[Table 1]

As is apparent from the above results, by adding the above-mentioned complex deoxidizing refining agent, B-based inclusions, which are oxide-based inclusions represented by alumina, can be reduced. In particular, when the composite deoxidizing refining agent is blown into molten steel by an injection method, an excellent cleaning effect is exhibited. (4) Production of Clean Steel [Part 2] Next, the case where the above-mentioned composite deoxidizing refining agent is blown by the injection method in which a particularly excellent cleaning effect is recognized,
For comparison with the case where a deoxidizer made of ordinary metal Al was blown, clean steel was manufactured by the following two methods.

First, 10 kg of molten steel equivalent to S45C melted in a high-frequency melting furnace was discharged into a ladle lined with zircon bricks, and immediately 20 g of the above-mentioned complex deoxidizing and refining agent was injected together with N ₂ gas. This at 1650 ° C for 10
After holding for 1 minute, molten steel was drawn out and cast into a cast steel mold (inner diameter 35 mm × height 100 mm) (sample 4).

For comparison, 10 kg of the molten steel similarly melted in the high-frequency melting furnace was discharged into a ladle and immediately injected with 20 g of a deoxidizing agent composed of metal Al particles together with N ₂ gas. After holding this at 1650 ° C. for 10 minutes, molten steel was drawn out and cast into the same mold as above (Sample 5). (5) Inclusion measurement / comparison test [Part 2] For each of the two types of samples obtained by the above-described method, three vertical and axial lower and upper positions were determined by ASTM-E4.
Inclusions were measured and compared by five methods. Table 2 shows the test results. The test result is an average of the results of preparing five samples and measuring them.

[0025]

[Table 2]

As is evident from the above results, the injection of the above-mentioned complex deoxidizing refining agent allows the metal A
Inclusions can be reduced as compared with the case where 1 is injected. In particular, it has been found that, of course, B-based inclusions caused by the addition of Al can be reduced, but also A-, C-, and D-based inclusions can be reduced. This is because CO ₂ is released from calcium carbonate, expands rapidly and becomes a foamed state, and in the very vicinity of the substance serving as inclusions, a small, rapid and irregular stirring flow is generated in the molten steel, and It is considered that the chance of collision significantly increased, and the large inclusions floated up and were separated from the molten steel.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various embodiments can be adopted without departing from the gist of the present invention. For example, in the examples, the method of attaching calcium carbonate particles or powder to the surface of aluminum particles to form particles was shown.For example, a powder of aluminum or an aluminum-containing material was mixed with a powder of calcium carbonate. In addition, a deoxidizing and refining agent having the same function and effect can be manufactured by a method of forming particles with Al and CaCO ₃ as main components, for example, by adding a binder to form particles.

In the embodiment, the surface of the Al particles is moistened with an aqueous solution of sodium silicate. However, CaCO ₃ can be adhered by simply moistening with water, and particularly, the surface properties of the Al particles are rough. In this case, CaCO ₃ can be more easily attached. Also, if a binder is used, Ca
Although CO ₃ can be adhered in a more stable state, as the binder in this case, a substance which emits less smoke during combustion, such as sodium silicate or polyethylene oxide shown in the examples, is preferable.

Claims (4)

[Claims] Claims 1. A calcium carbonate particle or powder is added to and mixed with aluminum or aluminum-containing particles, and the calcium carbonate particle or powder is adhered to the surface of the aluminum or aluminum-containing particles.
A method for producing a deoxidizing and refining agent for steel, wherein the agent is formed into particles. 2. The method for producing a deoxidizing and refining agent for steel according to claim 1, wherein the aluminum or the aluminum-containing material has a particle size of 5 m.
m or less, particles of the aluminum or aluminum-containing material are wetted, and the fine powder of calcium carbonate is added and mixed to adhere to the surface of the wet aluminum or aluminum-containing material. A method for producing a deoxidizing and refining agent for steel, comprising drying aluminum or an aluminum-containing substance to which calcium carbonate has adhered, and fixing the calcium carbonate on the surface of the aluminum or aluminum-containing substance. 3. A method for producing a deoxidizing and refining agent for steel, which comprises mixing a powder of aluminum or an aluminum-containing substance and a powder of calcium carbonate, further adding a binder, and forming the mixture into particles. 4. The method for producing a deoxidizing and refining agent for steel according to any one of claims 1 to 3, wherein the aluminum or the aluminum-containing material has an aluminum purity of 20 to 100%, and the calcium carbonate is A method for producing a deoxidizing refining agent for steel, characterized in that the weight ratio with respect to the aluminum or aluminum-containing material is 10 to 70%.