JPH08325628A - Method and material for desulfurizing molten metal - Google Patents

Abstract

PURPOSE: To provide an effective desulfurizer and an efficient desulfurization method by making the desulfurizability of each desulfurizer exhibited.

CONSTITUTION: The desulfurizer for a fused metal comprises 10-95 wt.% a calcium aluminate on which 12CaO.7Al₂O₃ is main component and the balance component composing of normal desulfurizer components. In desulfurization of a fused metal with adding the desulfurizer, the desulfurization of the fuzed metal is characterized in using a desulfurizer comprising 10-95 wt.% calcium alminate contg. 12CaO.7Al₂O₃ as main component.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to the use of molten metal for the purpose of improving the operating efficiency as well as improving the operating efficiency of desulfurization materials used in the desulfurization treatment of molten metal such as hot metal, molten steel and molten ferroalloy. The present invention relates to a desulfurization material and a desulfurization method.

[0002]

2. Description of the Related Art In the production of various metals such as steel, sulfur is a harmful element except in specific cases, so a so-called desulfurization process is performed to remove sulfur in the melting stage of the production process. With regard to the method, some desulfurization treatment technologies have been established today through various changes along with the desulfurization material used.

Taking steel as an example, the flow of hot metal pretreatment → converter refining → molten steel secondary refining has been generalized in response to the recent demands for high quality and high purity, and desulfurization treatment has a flow. It is an important item at each stage.

In these desulfurization treatments, a desulfurization material is blown into a molten metal, or charged and agitated. However, the most commonly used desulfurization material in Japan at present is quick lime. , Soda ash, carbide, and in recent years, metallic magnesium has a tendency to be put into practical use. Each of these materials is used as a plain desulfurization material, and in many cases, they are used in combination with each other as a composite desulfurization material.

Further, one of the applicants of the present invention suppresses the formation of a mixture of slag and metal (referred to as an overlay), which is deposited in a reaction vessel such as a speeded car produced by the hot metal desulfurization treatment without impairing the desulfurization treatment efficiency. For that purpose, "a method for treating hot metal desulfurization with calcium aluminate and a desulfurization slag has been proposed (JP-A-5-222425).

[0006]

The above-mentioned conventional desulfurization method using desulfurization material has the following problems in use efficiency and operability of the desulfurization material.

That is, since the desulfurization efficiency of quick lime is low, the basic unit used becomes large, which causes a decrease in the temperature of the molten metal and an increase in the amount of desulfurization slag generated. Furthermore, because the desulfurization slag has poor fluidity, the workability of the slag is poor, and securing a place for dumping the slag is also an issue.

As for soda ash, a large amount of white smoke is generated during the desulfurization treatment, so that equipment for environmental protection is required, and during the treatment, the refractory material around the periphery of the molten metal is largely melted, and the desulfurization slag remains. Due to the inclusion of sodium ions in the product, it is necessary to take measures to protect it from environmental pollution.

[0009] Regarding carbide, there are problems in environmental protection measures against acetylene gas generated during desulfurization treatment and special storage management as a dangerous substance.

Although magnesium has better desulfurization efficiency than the above, it is basically expensive and the desulfurization cost is high. Therefore, it is desired that the desulfurization purpose be achieved with a smaller amount of use.

In addition to the above-mentioned problems of each desulfurization material, there are the following common problems.

That is, the above desulfurization material reacts with and combines with sulfur in the molten metal in the desulfurization treatment to generate a sulfide,
Although the desulfurization reaction proceeds, on the other hand, the re-sulfurization reaction in which the generated sulfide is dissociated also proceeds at the same time, which means that the desulfurization effect of each desulfurization material is low.

Further, although the technique disclosed in the above-mentioned publication is intended only to suppress the formation of so-called "covering", the present inventors have developed 12CaO.7Al ₂ O ₃
The present invention has been developed based on the finding that the use of the contained desulfurization material can enhance the working efficiency of the desulfurization material.

[0014]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems and to provide a desulfurizing material and a desulfurizing method which allow the desulfurizing ability of each desulfurizing material to be exhibited more effectively and more efficiently.

The technical constitution of the present invention is 12CaO / 7A.
l ₂ O ₃ as the main component of calcium aluminate 10
In the desulfurization of the molten metal by the addition of the desulfurization material for the molten metal and the desulfurization material, the desulfurization material used contains 10 to 95% by weight of the desulfurization material.
A method for desulfurizing a molten metal, comprising a calcium aluminate containing 2CaO.7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ) as a main component.

In the present invention, the desulfurization material refers to a single product such as quick lime, soda ash, carbide, magnesium, etc., which is usually used for desulfurization of molten metal, or a composite product of a combination thereof, and the indication of the amount used is also the same. Shall be handled.

Calcium aluminate containing C ₁₂ A ₇ as a main component does not exist in nature, and for example, the composition of slag at the time of refining steel is similar to that of C ₁₂ A ₇ .
Although there is an example in which quick lime, aluminum ash, fluorspar, etc. are appropriately added to make a synthetic slag, no practical example of a synthetic product that has been melted from the beginning to have C ₁₂ A ₇ as a main component is found.

The calcium aluminate containing C ₁₂ A ₇ as a main component used in the present invention is melted as follows.
That is, limestone and bauxite are made into a mixture based on the composition ratio of C ₁₂ A ₇ , melted in a continuous melting furnace, discharged into a cooling container, cooled, and ground.

Such molten calcium aluminate is C ₁₂
In addition to A ₇ as the main component, about 2% as unavoidable impurities
In addition to SiO ₂ , the oxides of metals such as Ti, Fe and Mg may be contained.

In addition to the above melting method, CaO
It is also possible to use a powdery mixture of 40 to 70% by weight and Al ₂ O _{3 of} 30 to 60% by weight, which is crushed after sintering.

FIG. 1 is a phase diagram of a CaO--Al ₂ O ₃ binary system containing C ₁₂ A ₇ which is a main component of the present invention. In the figure, the melting point of C ₁₂ A ₇ is shown at about 1385 ° C.

FIG. 2 shows the sulfide absorption capacity corresponding to each composition of the CaO--Al ₂ O ₃ --SiO ₂ ternary system. The number in the figure is an index showing the size of sulfide absorption capacity,
It has been shown that the composition corresponding to C ₁₂ A ₇ has a large sulfide absorption capacity.

Calcium aluminate containing C ₁₂ A ₇ as a main component has a lower melting point and a lower heat of dissolution (453 kcal / kg) than the metal to be desulfurized as described above, and has a sulfide absorption capacity. It has excellent characteristics such as having.

The inventors of the present invention have paid attention to the above points, and have developed the melting process and conducted field tests for practical use, and as a result, have achieved the intended purpose.

In the present invention, the amount of calcium aluminate containing C ₁₂ A ₇ as a main component is 10 to 10% of that of the desulfurizing material used.
95% by weight is because the use effect of calcium aluminate is less than 10% by weight, and the desulfurization function of the desulfurization material is reduced when more than 95% by weight. It is a thing.

Further, the particle size of the calcium aluminate used in the present invention is not particularly limited, but it may be in accordance with the particle size of the desulfurizing material, and it is commonly used that the particle size is 1 mm in the blowing method.
In the following, the particle size is 1 to 3 mm in the charging and stirring method.

[0027]

In the desulfurization treatment of molten metal, the sulfur in the molten metal reacts with the desulfurization material used, and depending on the type of desulfurization material, C
It produces sulfides such as aS, Na ₂ S, MnS, and MgS, respectively. The sulfide generated at this time floats up, is absorbed and separated in the slag on the surface of the molten metal, and desulfurization proceeds.

However, the sulfide once separated in the slag is dissociated at the slag-molten metal interface, and the reaction for re-sulfurization also proceeds at the same time. In this way, the final desulfurization target value is achieved by consuming a considerable amount of desulfurization material while both the actions of desulfurization and re-sulfurization are repeated.

According to the present invention, the sulfide produced by the reaction with the desulfurization material is trapped and absorbed by the calcium aluminate, so that the vulcanization is suppressed and, as a result, the desulfurization material is used in a smaller amount to achieve the intended purpose. Can be achieved.

The reaction scheme of desulfurization and re-sulfurization in the desulfurization treatment of molten metal is shown below. Chemical formula 1 is based on the conventional method,
Formula 2 is according to the present invention.

[0031]

Embodiments of the present invention will be described below.

[Examples 1 to 3 and Comparative Example 1] 250t
When performing desulfurization treatment on the hot metal in the ladle by blowing the desulfurization material, three types of desulfurization materials having different C ₁₂ A ₇ compounding ratios were used as Examples 1 to 3, respectively. This is referred to as Comparative Example 1. Used C ₁₂ A ₇
Is produced by melting, and its particle size is 1 mm, similar to desulfurization material.
The chemical components are as shown in Table 1 below.

Table 2 shows the implementation conditions and the results. As is clear from Table 2, it is clear that the use of C ₁₂ A ₇ reduces the amount of desulfurization material blown in, and that even if the amount of expensive Mg used is reduced, a sufficient desulfurization effect can be obtained.
Further, the effect of improving the operation is great, such as the reduction of the blowing amount, the shortening of the blowing time, and the reduction of the temperature drop of the molten metal.

[Example 4 and Comparative Example 2] Desulfurization treatment of ferrochrome molten metal which is ferroalloy was put in a 40t holding furnace,
In carrying out the stirring method, the same molten C ₁₂ A ₇ as in Examples 1 to 3 is used as Example 4, and the conventional method is shown as Comparative Example 2. The conventional desulfurization material is C
an aC ₂ plain, the particle size is 1mm or less, the particle size of the C ₁₂ A ₇ whereas a 1 to 3 mm. The conditions and results of the implementation are shown in Table 3, and also in this example, the conventional desulfurization target could be sufficiently achieved even if the amount of the conventional desulfurization material used was reduced.

[0035]

[0036]

Since the present invention is constructed as described above, it has the following effects.

In the present invention, paying attention to the characteristics of calcium aluminate containing C ₁₂ A ₇ as a main component, that is, sulfide absorption capacity and low melting point, it is possible to prevent re-sulfurization of molten metal during desulfurization treatment,
The desulfurization material is intended to fully exhibit the desulfurization effect originally possessed by the desulfurization material.

According to the present invention, the unit consumption of desulfurization material is reduced, and the total amount used for desulfurization treatment including C ₁₂ A ₇ can be reduced. Therefore, the treatment time can be shortened and the temperature loss of molten metal can be reduced. The improvement effect is large throughout the operation, such as the reduction of slag.

[0039] In particular, although Mg in the desulfurization material is expensive because of its high desulfurization ability, its application is currently limited, but since the present invention reduces the basic unit used,
Combined with the low pollution of the generated slag, it can be expected to expand its applications in the future.

[Brief description of drawings]

FIG. 1 is a CaO—Al ₂ O ₃ binary system phase diagram.

FIG. 2 is a diagram showing sulfide absorption capacity corresponding to each composition of CaO—Al ₂ O ₃ —SiO ₂ ternary system.

Front Page Continuation (72) Inventor Chierry Dumas 92210 Saint Cloud Boulevard Durray Republique 158 (72) Inventor Akihiko Namba 7-13 Inagedai-cho, Inage-ku, Chiba-shi, Chiba (72) Inventor Nakajima Yoshi Tokyo 3-9-4 Denenchofu, Ota-ku (72) Inventor Shigeru Matsuyama 998-340 Inuzuka, Oyama City, Tochigi Prefecture

Claims (4)

[Claims] 1. Containing 10 to 95% by weight of calcium aluminate containing 12CaO.7Al ₂ O ₃ as a main component,
Others are desulfurization materials for molten metals, which consist of ordinary desulfurization material components. 2. In the desulfurization of a molten metal by adding a desulfurizing material, 10 to 95% by weight of the desulfurizing material used is 12CaO.
A method for desulfurizing a molten metal, which comprises calcium aluminate containing 7Al ₂ O ₃ as a main component. 3. The composition according to claim 1, which contains 10 to 95% by weight of calcium aluminate containing 12CaO.7Al ₂ O ₃ as a main component and comprises at least one desulfurizing material component of Mg, CaO and CaC ₂ . Desulfurization material for molten metal. 4. A calcium aluminate containing 12CaO.7Al ₂ O ₃ as a main component in an amount of 10 to 95 wt% and Mg,
A method for desulfurizing a molten metal, which comprises using a desulfurization material having a composition containing at least one of CaO and CaC ₂ .