JPS58141319A - Manufacture of metal refining agent - Google Patents

Abstract

PURPOSE:To inhibit the evaporation loss of Ca and to increase the deoxidizing and desulfurizing effects on a molten metal by calcining briquettes of a blend of a CaO-base oxide with an Al-base metallic reducing agent at a prescribed temp. CONSTITUTION:A CaO-base oxide is blended with an Al-base metallic reducing agent, and the blend is calcined at 850-1,350 deg.C in an inert atmosphere to obtain a product consisting essentially of a Ca-Al alloy, CaO and Al2O3. The evaporation of Ca in the metal refining agent manufactured by this method is inhibited in molten steel, and the deoxidizing and desulfurizing effects on the molten metal are increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a refining agent used for deoxidizing, desulfurizing, dephosphorizing, etc. molten metal such as molten steel.

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 highly clean steels are generally refined by desulfurization and dephosphorization at the hot metal stage.
Furthermore, it is manufactured by refining molten steel outside the furnace. The purpose of outside-furnace refining is advanced desulfurization and mainly h
It is used for deoxidizing by removing itOs-based inclusions and controlling the morphology of inclusions, and may also be added for the purpose of dephosphorization.

Although the details of the refining agent used in such out-of-furnace refining differ depending on the purpose, it is common to use a combination of a so-called flux mainly composed of 'CaO and a Ca-based metal additive. In particular, it is said that the use of metallic Ca or its alloy is essential for controlling the form of inclusions.

Metallic Ca or its alloy additive is a CaSi alloy,
Ca or FiCa + AA' iron or aluminum clad wires are commonly used. The former is relatively inexpensive, but has poor Ca addition efficiency, especially Si-1esS.

Al-killed steel has drawbacks that make it unusable. On the other hand, clad wire has excellent dosing efficiency, but its use is limited because it is expensive.

For the flux mainly composed of CaO, kllt for 1CaO
Generally, one or a mixture of two of Ox and CaF2 is used. However, since flux alone cannot control the morphology of inclusions, it is used in combination with the metal additives mentioned above.

The present invention is a metal refining process aimed at increasing the effect of deoxidizing, desulfurizing, dephosphorizing, and controlling the form of inclusions by efficiently acting on molten steel by suppressing the evaporation loss of Ca, which has a high vapor pressure in molten steel. The present invention provides a method for producing the agent.

In various experiments on Ca addition to molten steel, Ca-based alloys and Ca
When a flux containing O is combined to form individual particles or briquettes of a refining agent and these particles or briquettes are added to molten steel, the evaporation loss of Ca can be kept extremely low; It was discovered that the more homogeneous mixing of the alloy phase and flux phase in particles or briquettes, the more effective it is in suppressing evaporation loss of Ca, and that the Ca-based metal-flux bonding refining agent with a high degree of homogeneous mixing It has been found that it can be easily produced by reducing CaO with Al, leading to the present invention.

That is, in the present invention, a metal reducing agent mainly composed of M is mixed with an oxide mainly composed of CaO, formed into a briquette or the like, and fired in an inert atmosphere to perform a reduction reaction of CaO.
By alloying the generated Ca with M, the evaporation and loss of Ca is suppressed, resulting in Ca-M alloy, CaO1k1203.
This is a method of obtaining a product containing as a main component, turning the product into powder, granules, or agglomerates of desired particle size, and using this as a metal refining agent.

Several methods have been proposed for producing Ca-AJI alloys, but for example, carbon reduction of CaO and AA'tOa using an electric furnace is difficult to operate efficiently on an industrial scale, and to 1500-1600℃
There is also a method of melting and separating Ca-41 alloy and slag by reacting at high temperatures, but since the temperature is high and in the atmosphere, Al
The loss of evaporation, oxidation, and nitridation of Ca and Ca is large, making it difficult to put it into practical use on an industrial scale.

On the other hand, in the reduction reaction of CaO with Al in the method of the present invention, there is no need to separate the alloy phase and the flux (slag) phase, and moreover, the amount of Ca-M produced can be set to an effective content as a refining agent. Therefore, the reduction reaction can be easily carried out at a relatively low temperature. and M2O present in the molten steel.

A flux with a mixed composition of Ca-Am! and CaO is used as Ca-Am! A great advantage of the manufacturing method of the present invention is that it can be obtained all at once together with the alloy.

It is a metal reducing agent. The former uses CaO alone or a mixture of oxides, chlorides, fluorides, etc., which will be described later, and the latter uses Al alone or a mixture of 8i, Mg, etc., which will be described later, with Al or alloyed with M. These are powdered, made into briquettes, and reacted.During the reaction, M melts and penetrates into the oxide, so the particle size is not very important for re-raw materials, but 1w
It is preferably about 1 or less. To make briquettes, compression molding may be performed using a briquette machine or the like, or granulation may be performed by adding a primary binder such as starch or CMC. Therefore, briquette molding in the present invention includes all of these granular, block-like, and other molded products. The size of the briquettes is not particularly limited, but a range of 5 to 50 m5+ is appropriate.

The composition of the oxide and reducing agent is determined based on the following reaction formula depending on the composition of the intended refining agent.

3CaO+2# →3Ca + ATOs =...
(1) Since the reaction does not proceed completely, the generated Ca becomes an alloy with the raw material kl, and M2O combines with CaO to become a flux. By alloying with Ca t-Al) C
Evaporation and loss of a is suppressed.

The refining agent of the present invention obtained in this way has Ca-M alloy, Cab, and I'-1120s as main components, which are bonded together. It is preferable that the content of these champions is 70% by weight or more (the same applies hereinafter). A typical component that can be contained as the remaining component is CaF2, which is preferably used in a range of 3 (1) or less.

CaF2 exists independently in the flux phase, but C
It is effective to increase the content as the aO/A 120g increases. CaF, when added to molten steel, effectively acts to promote slag formation of the flux phase. However, since the effect will be saturated if it is added in excess of 30 g, it is better to use less than 30 g.

If the desirable component range is shown above, Ca-IJ alloy 20-5
0%, CaO+A7!20, 80~50%, CaF
2@~30chi.

And the Ca content in the Ca-Al alloy is 20-50%,
The CaO/Al2O3 weight ratio in the flux phase is 0.9~
A value between 5.0 and 5.0 is most suitable.

In order to obtain a refining agent having the above-mentioned desired composition excluding CaF2, the mixing ratio of the raw materials CaO and M should be set to a Ca9M weight ratio of 0.5 to 4.0, taking into account the above formula (1) and some evaporation of Ca.
It may be used within the range of 0.

The reason why the composition of the refining agent according to the present invention is preferable is as follows. Ca-AA! If the alloy content is less than 20%, the refining effect of this alloy will be reduced9 and the amount of refining agent used will increase. Moreover, when it exceeds 50%, the effect of inhibiting Ca evaporation due to a relative decrease in the amount of flux decreases.

The reason why a Ca content of 20 to 50% in a Ca alloy is particularly suitable is that when the Ca content is lower than 20 yen, the amount of accompanying M increases, and when used as a refining agent, a large amount of M remains in the steel. It is undesirable because the refining effect decreases, and if it exceeds 50%, it not only becomes difficult to manufacture, but also reduces the refining effect.
This is because the vapor pressure of

The reason why a CaO/Al2O3 weight ratio of 0.9 to 5.0 is particularly suitable is that when it is less than 0.9, it is effective for desulfurization (CaO component is small9, and the desulfurization rate decreases, and when it exceeds 5.0, the melting point becomes high). If too much, slag formation is inhibited.

The refining agent obtained by the method of the present invention has Ca
-Al alloy, mainly composed of J20s (CaO%), more preferably containing CaF2 in a certain amount or less, but in addition to this, a small amount of CaC1, Na2
It can contain elements such as O%8i, Mg%Ba, Ni, and rare earths, or oxides of these elements. The content of these small amounts of components is preferably 10% or less. Ca
In order to make the refining agent contain F2 and small amounts of these components, they may be added to the raw materials.

In the case of oxides, even if some of them are reduced by Kl or Ca during the heating process, there is no problem as long as the metal produced is not harmful to the intended refining agent.

In the case of metals, these are mainly Ca-AA! and alloy,
The compound becomes a flux component.

Calcination for the reduction reaction is preferably carried out at 850 to 1350°C, preferably 1000 to 1200°C, under an inert atmosphere such as argon. Although it is possible to conduct the reaction in the air or in a nitrogen atmosphere, it is not very preferable because aluminum nitride and the like will be generated and the reaction will be suppressed.

If the temperature is lower than 850°C, no reaction will occur, and if the temperature exceeds 1350°C, not only will there be no advantage in terms of the reaction, but a large amount of Ca will evaporate.

The pressure of the atmosphere may be reduced to some extent to promote the reaction.
Drying and pressurizing can also be performed for the purpose of suppressing evaporation of Ca and the like.

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 vertical shaft furnace, a retort furnace, etc. may be used, and the raw material may be moved by means such as rolling for the purpose of promoting the reaction or continuous operation.

The briquettes after firing can be used as they are as a refining agent, but they can also be crushed into granules or further crushed into granular powder.

Even after pulverization, each particle has an alloy phase and a flux phase bonded together.

When this is investigated using an optical microscope or an X-ray microanalyzer, extremely fine Ca leakage, CakJl, etc.
-A1 alloy phase and 12 CaO-7Aft O, or CaO
A complex mixture of flux phases is observed.

The important role of the flux phase in the refining agent according to the present invention is to appropriately control the dissolution of the Ca-A41 alloy phase into the molten steel when the refining agent is added to the molten steel. In other words, when the Ca-Al alloy is added, the flux phase does not act on the molten steel instantaneously and cause rapid evaporation, but is gradually dissolved into the molten steel, thereby achieving sufficient efficiency (C
It has the role of acting on a. Further, the flux phase effectively captures and removes deoxidation products such as A&Oa present in desulfurization and molten steel.

Since the refining agent according to the present invention is manufactured by a solid-liquid reduction method, the alloy phase and flux phase are mixed and bonded together by sintering, diffusion, etc., and when added to molten steel, the alloy phase Since the phase is prevented from coming into sudden contact with the molten steel, the above-mentioned role can be fully fulfilled. Moreover, its effect is far greater than, for example, a refining agent consisting of a simple mixture of alloy powder and flux powder.

Example Raw materials: 670 parts of quicklime containing 97.5% Ca and 330 parts of M alloy powder containing 190% A were thoroughly mixed and molded into almond-shaped briquettes. This briquette was charged into a sealable internally heated horizontal bogie furnace, and after the atmosphere was replaced with Arl atmospheric pressure, the temperature was raised to 1100° C. and maintained for 3 hours for firing. After the furnace was cooled, we attempted to quantify the briquettes discharged from the furnace by chemical analysis, and found that Ca 16.7%, A122.5%, ('ao 37
．． 0%, A&Os 21.5%. According to X-ray diffraction, CaA7. , CaO112CaO57M^
A clear peak was observed. The Ca content of the metal phase is estimated to be about 40 inches. Furthermore, after pulverizing this briquette to a total of 60 meshes used for injection,
When the collected powder single particles were examined using a microscope and an X-ray microanalyzer, a structure in which a metal phase and a flux phase were mixed was observed in all of the particles.

Next, we will show the results of using this fine powder particle as a refining agent for molten steel.

In a high frequency induction furnace (electrofused magnesia lining), 30
A Kf l'J -Si killed steel was prepared, and the refining agent and the refining agent shown in Table 1 as a comparative example were added at 0.8% based on the weight of the molten steel under an argon atmosphere.After 15 minutes, the molten steel was converted into gold. Cast into a mold.

In addition, by observing the addition situation of the refining agent, it was found that the present invention.
In fact, no sudden generation of fume was observed after the addition, indicating that rapid evaporation of Ca was suppressed.

Table 1 In the table, the composition of the present invention and the comparative example are Ca-Al composition, Ca
The contents of -8i, CaO, and k12Ql were the same. In addition, the O mark in the table indicates fine calcium aluminization.Applicant: Sei Kikuchi, agent of Showa Denko Co., Ltd. Hand appearance correction form (self-Jl) Date of September 1980: Kazuo Kusugi, Commissioner of the Patent Office, 1, Indication of the case Showa 1957 Patent ■Cei 19696 No. 2, Name of the invention Method for manufacturing metal seitaku agent 3, Relationship with the case of the person making the amendment Patent applicant address No. 9, 1-13 Shiba Daimon, Sei-ku, Tokyo Name C20
0) Showa Denko Co., Ltd. Representative Yomoto Yasunobu Number 1 Agent 1FJf Showa Denko Co., Ltd. 1113-9 Shiba Daimon-cho, Igui-ku, Tokyo 105 03-432-5111 (Representative) 6
, Contents of Amendment - 1 The description in Book 1IJII is amended as shown below.

(1) Page 5, line 1, FAI, 0. J followed by a flux composition with a large trapping ability such as r, i.e. 12CaO 7 m,
I'm joining O3J.

(2) On page 5, line 2, ``Mixed composition of RCAO'' has been corrected to ``Mixed composition with RCAO''.

(3) 5th purchase, 12th line, corrected "re-MIRJ" to "r-bi-tier fee."

(4) Crl! on page 11, lines 15-16! lCaO,
7A1. O, J and Aino r12caoe7AIL O
, J.

(5) @13W Table 1 No. 17) 2 rows ILA rca-
Delete "31".

Claims (2)

[Claims] (1) A method for producing a CaO reduction reaction refining agent by blending an oxide mainly consisting of CaO with a metal reducing agent mainly consisting of M, making it into briquettes, and firing it in an inert atmosphere. (2) The method for producing a metal refining agent according to claim 1, wherein the firing temperature is 850 to 1350°C.