JPS58197231A - Metal refining agent and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a refining agent showing efficient action in molten steel while inhibiting the loss of Ca due to evaporation and having superior power of capturing inclusions by adding Si to a metal refining agent consisting of a Ca- Al alloy, CaO and Al2O3 united in a body. CONSTITUTION:This refining agent is a Ca-Si alloy or a Ca-Si-Al alloy united tightly with a flux contg. CaO and Al2O3 as principal components. Powder of CaO-base oxide, powder of pure Al or an Al alloy as an Al-base reducing agent, and powder of Si-base metal or an Al-Si alloy contg. almost equal amounts of Al and Si are briquetted. The briquettes are calcined in an inert atmosphere to cause a reaction, and the CaO is reduced to obtain the refining agent consisting of said components. When the refining agent is used in deoxidation, desulfurization, dephosphorization or other stage, a significant effect can be shown, giving extremely clean steel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a metal refining agent used for deoxidizing molten steel; desulfurization, dephosphorization, etc., and a method for producing the same.

In recent years, the demand for so-called high-cleanliness steel, which has a high degree of reliability under extremely harsh environmental conditions, has been increasing further. These high-clean steels highly deoxidize, desulfurize, and
Manufactured by dephosphorization treatment.

Particularly difficult aspects of these refining processes include deoxidation by removing AAO3 inclusions, control of the morphology of inclusions, and advanced desulfurization and dephosphorization.

The details of the refining agent used in molten steel refining for such purposes vary depending on the purpose, or a combination of a CaO-based flux and an O-based alloy additive is generally used. In particular, it is said that the use of metallic Ca or O alloys is essential for controlling the morphology of inclusions. As the metallic Ca or ferrule alloy additive, clad wire containing ferrule and calcium silicon are used.

However, the former method is expensive and its use is limited, and the latter method has disadvantages such as low zero addition efficiency and the generated fumes that worsen the working environment.

When using flux together with a spun metal or Ca alloy, add the flux and then add the metal Ca or C.
It is common to add the a-alloy separately to the molten metal; if it is simply mixed and added, the metal phase and the flux phase will essentially separate in the molten steel, resulting in high steam formation at the molten steel temperature. It is not foolish not to be able to suppress the evaporation loss of Ca under pressure, and the effect of trapping inclusions cannot be sufficiently exhibited.

The present invention eliminates these drawbacks, and provides a novel refining agent that suppresses the evaporation loss of Ca, which has a high vapor pressure in molten steel, works efficiently, and has an excellent ability to capture inclusions, as well as its rational and efficient method. This provides an economical manufacturing method.

The present inventors previously described Ca-M alloy, CaO and 403
proposed a powder-like or lump-like metal refining agent (Japanese Patent Application No. 57-19697), which has the following main components and which are combined together, and a method for producing the same (Japanese Patent Application No. 57-19696). Subsequently, as a result of further research, it was found that by incorporating Si into the reducing agent in the above manufacturing method, the reaction efficiency could be increased, and the generated Ca could be reliably captured by Sl, increasing the 1 content in the alloy. , 5-containing alloy phase and flux phase are closely combined and the accompanying 8i effect makes it possible to suppress the evaporation loss of 0 in molten steel to an extremely low level, resulting in excellent effects in deoxidation, desulfurization, dephosphorization, etc. It was discovered that it can be used as a refining agent, and the present invention was developed based on this discovery.

That is, the refining agent according to the present invention is an O-Si alloy or a Ca-
This is a metal refining agent in the form of powder or lumps, in which 8i-AJJ alloy and a flux mainly composed of CaO and A40s are tightly bonded. Another invention is to mix a #-Si alloy or/and a metal mainly composed of M and a metal mainly composed of 81 with an oxide mainly composed of CaO to form a briquette, and then sinter it in an inert atmosphere. The resulting Ca is captured by alloying with Sl or Si and M, and is then converted into a Ca-Si alloy or a Ca-Si alloy.
A refining agent in which the -81-M alloy and a flux containing CaO and AAQ as main components are tightly and integrally bonded together is obtained.

The present invention will be explained in detail below.

The refining agent of the present invention is mainly composed of -Si alloy or Ca-81-M alloy, CaO and A4!03. It is preferable that these components are contained in an amount of 70% or more (the same applies hereinafter by weight). A typical preferred component other than the three components mentioned above is CaF2, and it is preferable to use it in a range of 30 or less. Although CaF2 exists independently in the flux, it is effective to increase its content as the ratio CaO/A4 increases. When added to molten steel, CaF2 effectively acts to promote slag formation of the flux phase. However, if it is added in an amount exceeding 30%, the effect will be saturated, so it is better to use it in an amount below 30%. In addition to CaF2, CaCA2 and other chlorides, Na2O, and S are added to promote the bonding of each component of the refining agent or to improve the refining effect.
An oxide such as iO2, a rare earth element such as Mg, Ba, Fe%Ni, or an oxide thereof may be contained in a total amount of 10 parts or less.

Since 5 in 2 inhibits the refining effect, it is desirable to set it to 5 or less. These metals mainly form an alloy phase, and the oxides form a flux phase.

If the desirable component ranges are shown above, Ca-Si alloy or C
a-8i-Al1 alloy 30-65%, CaO+A403
70-35%, CaF 20-30%. and C
Ca content in the a-Si alloy or Ca-81-M alloy is 30 to 60, Ca0A40 in the flux phase
3 weight ratio is suitably between 0.9 and 3.0.

If the concentration of Ca--Si alloy or Ca-81-M alloy is less than 30, the refining effect of these alloys will be reduced and the amount of refining agent used will increase. Moreover, when the coefficient is 65 or more, the flux amount is relatively reduced, and the Ca evaporation suppressing effect is reduced. C
The reason why a 0 content of 30 to 60 parts in the a-Si alloy or Ca-8i-Al1 alloy is particularly suitable is that when the 0 content is less than 30 parts, the amount of Si''i! or Sl and M that is incidentally included is large. 9. Si or M remaining in the molten steel has a negative effect on the quality of the steel, and the refining effect of O is reduced.Also, if Ca exceeds 60%, the evaporation loss of iron in the molten steel increases. This is because it is not very economical.Furthermore, when producing an alloy containing iron by the M reduction method (9) described later, it is difficult to increase the Ca content to 60 or more.

Si in Ca-8+gold alloy or Ca-8i-Al1 alloy
The content is desirably 10% or more. When the Si content is less than 10°, no improvement in reaction efficiency is observed when producing by the CaO M reduction method described below, and it is difficult to obtain a tighter integral bond between the alloy phase and the flux phase.

Therefore, when added to molten steel, the effect of suppressing the dissipation of molten steel becomes insufficient.

The alloy phase may be a Ca-Si alloy or a Ca-Si2M alloy. When using the C1-81-M alloy, it is possible to suppress the Si content and obtain the same refining effect, so it is possible to suppress the amount of phosphorus picked up in the molten steel. Also,
According to the present invention, Ca-81-M
When an excessive amount of M is blended with the aim of forming an alloy, the reduction of CaO is promoted and it becomes easier to obtain an alloy phase with a high Ca content. Ca-Si alloy or Ca-8i-IJ gold alloy can be selected as appropriate depending on the type of steel to be applied.

Cab/A40s weight ratio in flux phase is 0.9-3
．． The reason why 0 is particularly suitable is that when it is less than 0.9, the CaO component effective in desulfurization decreases, resulting in a decrease in desulfurization ability. Also 3,
If it exceeds 0, the melting point becomes too high and slag formation is inhibited.

In the present invention, the important role of the flux phase is that when a refining agent is added to molten steel, the Ca-Si alloy phase or the Ca-8i
- Appropriately control the dissolution of the AJI alloy phase into molten steel. That is, the flux phase is Ca-Si alloy or Ca
When the -8i-Al1 alloy is added to molten steel, Ca is gradually dissolved into the molten steel without causing rapid evaporation of Ca due to instantaneous action on the molten steel.
It has the role of making it work efficiently. The flux phase also effectively captures and removes desulfurization reaction products and deoxidation products such as l'40s.

In order to fulfill this role, the refining agent of the present invention has a structure in which the alloy phase and the flux phase are tightly bonded together. At least until the refining agent is added to molten steel, it is necessary that the alloy phase and flux phase are combined together. More preferably, it is important that the alloy phase and flux phase remain in close contact even after being added to molten steel, so that refining by zero and capture of inclusions by the flux phase can easily occur.

This refining agent also includes particles in which alloy particles and flux particles are bonded together using a primary binder or the like.

However, when the refining agent is added to molten steel, the primary binder immediately decomposes and the particles separate into an alloy phase and a flux phase. In order to strengthen the bond between the alloy phase and the flux phase, it is effective to bond them in the form of sintering, solid solution, diffusion, etc. More preferably, as obtained by the method of the present invention, the M alloy phase penetrates into the fine pores of CaO to cause a reduction reaction of CaO, and the generated O alloy phase and slag (flux) phase mutually form a matrix. It is most preferable to form a tight integral bond such that For example, as shown in FIG. 1, a tight integral bond is one in which the alloy phase and the flux phase are finely interwoven and bonded firmly and uniformly.

In a refining agent having such a tight bond, the 0 alloy phase and the flux phase maintain an integral bond not only in the case of briquettes or rather large grains, but also in the case of fine powder. For example, if you have a refining agent that exceeds 1 hour, you can crush it to 0.
When 5 to 10 samples were selected and examined, more than 70 of them were composed of a combination of an alloy phase and a flux phase.

The size of the refining agent of the present invention includes powders of 1τ or less, granules, or lumps such as briquettes. Powder is usually used in the injection process, and there are no particular restrictions on the size of granular or lumpy products. The refining agent according to the present invention can be used not only for refining molten steel but also for treating molten metals such as hot metal and aluminum alloys.

Next, the method for producing the refining agent of the present invention is explained. Examples include a method of reducing CaOf with metal silicon, a method of reducing silica and quicklime with a carbonaceous reducing agent, and a method of reducing silica with calcium carbide and a carbonaceous reducing agent. However, when these methods are used, the evaporation loss of the produced agglomerates is large, and the O content in the obtained alloy is limited to about 38% at most, and when used as a refining agent, the amount used is large. It will be disadvantageous. Furthermore, in the case of the above method, there are drawbacks such as the unavoidable formation of components such as Sin, which are undesirable for the purpose of desulfurization and dephosphorization of molten steel, and the need to separate and remove the slag phase.

In contrast, in the method of the present invention, CaO is reduced with a reducing agent mainly composed of M, and the generated 0 is captured by a metal phase mainly composed of Si or an alloy phase composed of Sl and M, thereby reducing the 0-containing A high amount of alloy phase is obtained. In addition, the slag phase that is generated is mainly composed of 1'-403', which combines with excess CaO and 12Ca0.
7 Forms a slag and cous phase mainly composed of 03. This flux phase has an excellent ability to capture inclusions mainly composed of A40s present in molten steel.

According to the method of the present invention, a reducing agent mainly composed of M and a metal phase composed of a Si mirror penetrate into the pores of CaO, and at the same time the reduction reaction of CaO is carried out and the generated 0 is captured. A major feature is that a refining agent in which an alloy phase containing Ca and a flux phase mainly composed of CaO and M20 are tightly and integrally bonded can be obtained at once.

, Hereinafter, the present invention will be explained in detail.

The raw materials are an oxide mainly composed of CaO, a reducing agent mainly composed of Mk, and a metal mainly composed of Sl. Quicklime is the most affordable oxide based on CaO. Pure aluminum or aluminum alloy is used as the reducing agent mainly containing M. Metals containing Si as a main component can be used, and those with a high Si content are preferred. In addition, Al-8i with the same M and Si contents
An alloy may be used to adjust the missing components. These are powdered, made into briquettes, and reacted. The reaction occurs when kl or M and Si melt and permeate into the oxide. In this case, the addition of Si promotes the permeation of the metal into the silicon oxide, so that the efficiency of the CaO reduction reaction can be increased compared to when M is used alone. Although the particle size of the raw material is not very important, it is preferably about 1 particle or less.

To make briquettes, compression molding may be performed using a briquette machine, etc. Also, granulation may be performed by adding a binder such as starch or CMC.The size of briquettes is not particularly limited, but A range of ~50 gates is appropriate.

The combination of oxide and reducing agent depends on the composition of the refining agent mentioned above.
It is determined based on the following reaction formula.

3 CaO+ 2A7 →3 Ca 10, 8 & Os
・-=・(i) Either the generated Ca is captured by the coexisting Sl and becomes a Ca-Si alloy, or the excess M is also added to form a Ca-Si alloy.
It becomes a-8i-AJJ alloy. Furthermore, M2O5 combines with excess CaO to form mcao.ngoai. According to the above reaction, CaO is first reduced only by M.

As the Si/Al ratio in the blended raw materials increases, Ca
The reduction rate of O is improved, and the O content in the produced alloy is 60%.
It can be raised up to 1. However, from the table, 81 is just 9
When it becomes excessive, 8i becomes involved in the reduction reaction, and the slag (flux) phase becomes CaO-A403-8in,
This is not preferable because it becomes a ternary element. When Si is used as a reducing agent, a slag containing mainly Ca--Si alloy and 2 CaO--Sin is produced, but a slag containing a large amount of SiO2 is not preferable because it has a poor refining effect on molten steel. In order to suppress the SiO□ content in the refining agent to less than 5%, Ca in the raw material
O/(-AJ-4-Si) is 25 or less
/1'J ratio 1d is preferably about 4 or less.

In addition, CaF2, CaCl2, Na2O, M
g, Ba.

When Fe%Ni rare earth elements or their oxides are contained, these elements or oxides may be blended into the raw materials.

Firing at 850°C to 1350°C, preferably 1000°C to
It is preferable to carry out the reaction at 1200° C. in an inert atmosphere such as argon. Although it is not impossible to do so in the air or in a nitrogen atmosphere, the production reaction of 0 is inhibited by the production of aluminum nitride or the like. If the temperature is lower than 850°C, no reaction will occur, and if the temperature exceeds 1350°C, there will be no advantage in terms of the reaction, and instead it will result in evaporative loss of O.

The pressure may be reduced to some extent in order to promote the reaction, or may be slightly increased in order to suppress evaporation of 0.

The type of firing furnace is not particularly limited as long as the atmosphere can be substantially controlled. For example, a horizontal bogie furnace, a shaft furnace, a retort furnace, etc. may be used, and the raw material may be moved using means such as rolling for the purpose of continuous operation.

The briquettes after firing can be used as a refining agent even to that size, but they can also be crushed into granules or powder.

In the refining agent thus obtained, Ca-8i alloy or Ca-8i-Al1 alloy and a flux phase mainly composed of CaO and M2O3 form a tight integral bond. When observed with an optical microscope or X-ray microanalyzer, Ca-8i or Ca-8i-M is present in the flux phase mainly composed of CaO and 12Ca0.7M203.
It is observed that fine particles of the alloy are mixed together.

For example, FIG. 1 shows Ca-8i obtained in Example 2.
-# This is a microscopic structure photograph of a refining agent in which the alloy and the flux phase form a tight and integral bond. In the figure, the white part is the alloy phase.
The black part is the flux phase.

It can be seen that the two are closely connected.

When the alloy phase and the flux phase are tightly combined as in the present invention, when added to molten steel, it suppresses the alloy phase from coming into contact with the molten steel rapidly, preventing zero evaporation loss and maximizing the addition effect. able to demonstrate. In addition, since inclusions generated at the same time can be captured immediately, the refining effect is much more pronounced than when a simple mixture of alloy and flux is used.

Example 1゜540 parts of quicklime containing 0975% Ca, crushed to less than 1 as raw materials, M containing 1'J 90% K
110 parts of alloy powder and 350 parts of metal silicon powder containing 98% Si were thoroughly mixed and molded into almond-shaped briquettes. The briquettes were charged into a sealable internally heated horizontal bogie furnace and replaced with 1 atm of argon.
The temperature was raised to 1100°C and maintained for 3 hours for firing.

After the furnace was cooled, the briquettes discharged from the furnace were chemically analyzed and found to contain 23.6% Ca, 33.0% 5i, and 19% CaO.
, 1%, ATOs2o, 3aj. According to X-ray diffraction, CaSi2.12Ca0.7All! 203
A clear peak was observed.

The zero content of the alloy phase is about 42 modulus.

Furthermore, this briquette is finely ground to a total of 60 mm,
When single particles of the powder were collected and observed using a microscope and an X-ray microanalyzer, it was found that most of the particles had a combined structure of alloy phase and flux phase.

Next, we will show the results of refining molten steel using this fine powder.

In a high frequency induction furnace with magnesia lining, 30
9 Al1-8i killed steel was melted, and the refining agent and the refining agent shown in Table 1, which had the same chemical composition as a comparative example and were prepared by simple mixing, were added to the molten steel at a heavy seismic ratio. After adding 0.8% and refining for 15 minutes, the molten steel was cast into a mold.

Samples were taken from the ingots and analyzed for S content and inclusions. The results obtained are shown in Table 1.

In addition, when observing the addition status of the refining agent, the addition of the present invention was observed.

When the agent was used, no sudden generation of fume was observed upon addition, and rapid evaporation of Ca was suppressed. On the other hand, when a single mixed product was added, generation of fume was observed.

Table 1 In the table, ○ marks indicate that fine calcium aluminate-based inclusions or fine spherical CaO-A403-Ca5-based inclusions were observed, and X marks indicate that these inclusions were not observed and were considered ATO3 clusters. This shows the presence of flaky MnS inclusions.

Example 2 As raw materials, 550 parts of quicklime containing 97.5% CaO pulverized to 1- or less, 28 parts of M alloy powder containing 790% A
After thoroughly mixing 170 parts of metal silicon powder containing 0.0 parts and 98% of 5i, it was molded into almond-shaped briquettes.

The briquettes were charged into a sealable internally heated horizontal bogie furnace, and after purging with 1 atm of argon, the temperature was raised to 1150° C. and maintained for 3 hours. As a result of chemical analysis of the briquettes discharged after cooling the furnace, Ca023.6% and M15.9% were found.

5i16.5%, CaO18.9%, A&0320.1
It was made up of %. When observed using this briquette microscope and an X-ray microanalyzer, it was observed that the alloy phase and flux phase were finely integrated. 1st
The figure shows a photo of the microscopic structure of this refining agent. The O content of the alloy phase was about 42%.

Further, when this Briqueratra was completely pulverized to 60 meshes and single particles of the powder were collected and observed, it was confirmed that most of the particles were a combination of alloy and flux.

Next, Table 1 also shows the results of adding this fine powder to molten steel as a refining agent. For comparison, Ca-S with the same composition
A simple mixture of 1-A1 alloy powder and flux was used. The addition conditions were the same as in Example 1 except for the refining agent.

The addition of the refining agent according to the present invention was extremely quiet and no fume was observed. On the other hand, when a simple mixture was added, some fume generation was observed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a microscopic structural diagram showing the state of tight bonding between the alloy phase and the flux phase of the refining agent obtained in Example 2. Patent applicant Sei Kikuchi, patent attorney representing Showa Denko Co., Ltd. - 1st) Compensation 375 ii Procedural amendment (voluntary) September 1980 7% Commissioner of the Japan Patent Office Wakasugi Wakasugi 1, Indication of the case 1982 Patent Application No. 80089 2, Name of the invention Gold JiIt spermatozoa and its manufacturing method 3, Relationship with the case of the person making the amendment Patent applicant address 13-9 Shiba Daimon-chome, Minato-ku, Tokyo Name (20
0) Showa Denko Co., Ltd. Representative Yasunobu Kishimoto 4, Agent residence Higashi*s? M Ward Shiba Daimon-chome 13-9 Showa Denko Co., Ltd. 105 03-432-51N (Representative) (1
) 6. Contents of the amendment The description in the specification of the application will be amended as follows. (1) On page 12, line 7, after "Si-based metal" add "Metal silicon, ferrosilicon, ferroaluminum silicon". (2) From page 14, lines 1 to 2, r Ca F,
, C: aCl, , Na, 01Mg, Bas Fe. "Ni rare earth element" means rCaF, Ca C1
, Nas Mg, Bab Fes Nis rare earth elements. (3) At the end of page 14, line 4: [Metal elements form an alloy phase, and fluorides, chlorides, oxides, etc. form a flux phase. ” to join. (4) On page 17, line 6, add “alloy powder and flux powder” after “have”. (2)

Claims (1)

[Scope of Claims] (1) A metal refining agent comprising a Ca-8i alloy or a Ca-8i-AJJ alloy and a flux whose main components are caO and M2O3. (21Ca-8i alloy or Ca-8i-A1 alloy 30
-65 section, CaO+A40370~35%, CaF2
The metal refining agent according to claim 1, consisting of 0 to 30 parts. (3) A briquette is made by blending an oxide mainly composed of CaO with a kl-8i alloy and/or a metal mainly composed of M and a metal mainly composed of Si, and is fired in an inert atmosphere to form a briquette. Perform reduction and add Ca-8i alloy or Ca-8i-Ate alloy, CaO and 820g
A method for producing a metal refining agent, characterized by obtaining a product containing as a main component. (4) The method for producing a metal refining agent according to claim 3, wherein the firing temperature is 850°C to 1350°C.