JP2002180119A - Refining agent for molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive refining agent for molten iron which has excellent desulfurizing effect and is safely used. SOLUTION: This refining agent for molten iron contains carbon and magnesium oxide (and/or magnesium hydroxide) as the essential components, and further, one or more kinds among calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismuth-manganese-calcium, boron oxide, boric acid and calcium fluoride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot metal refining agent, and more particularly to a hot metal refining agent for removing impurities from hot metal at low cost and efficiently.

[0002]

2. Description of the Related Art Conventionally, sulfur in steel lowers the toughness and hot workability of steel materials, and tends to segregate during solidification.
This causes non-uniformity of the steel material, and also causes local deterioration of the material. Therefore, it was necessary to remove as much of the sulfur in the steel as possible.

[0003] Since metallic magnesium has a strong affinity for sulfur and has a very large desulfurizing ability, conventionally, metallic magnesium has been used as a desulfurizing agent in a pretreatment process of hot metal. As a method for adding metallic magnesium to hot metal, there is a method in which coke or steel plate waste is pressed and impregnated with metallic magnesium, which is immersed in hot metal with a refractory plunging bell, or a method in which the surface is exposed to a salt. A method of blowing metal magnesium or magnesium-aluminum alloy particles or a mixture of lime and magnesium into hot metal.

However, when metallic magnesium is used as a desulfurizing agent, there are the following problems (1) to (3). (1) Since metallic magnesium has a low boiling point of 1107 ° C and a high vapor pressure, when it comes into contact with hot metal, it vaporizes violently. Therefore, when metal magnesium is used as the desulfurizing agent, the desulfurization efficiency is low. (2) As described above, the metallic magnesium vaporizes violently, and the hot metal may suddenly boil. Therefore, great care must be taken when adding the hot metal to the hot metal. (3) Since magnesium metal requires a large amount of energy and is expensive to manufacture, desulfurization treatment using magnesium metal is expensive.

In view of the above problems (1) to (3), the inventors of the present invention have proposed, as disclosed in Japanese Patent Application Laid-Open No. 2000-109920, "a mixture of magnesium oxide and carbon And a method of desulfurizing hot metal characterized by injecting into hot water (hereinafter, this invention is referred to as "prior invention").

[0006]

SUMMARY OF THE INVENTION According to the above prior art, when a composite material comprising magnesium oxide and carbon is immersed in hot metal at a high temperature, magnesium oxide is reduced to carbon and Mg is removed.
The present invention has been made based on an experimental result that a gas is generated and the Mg gas reacts with sulfur in the hot metal to generate MgS.

[0007] However, in the "method of desulfurizing hot metal in which a mixture of magnesium oxide and carbon is blown into hot metal by a carrier gas" according to this prior invention, the desulfurization effect is insufficient because the ratio of magnesium oxide to be reduced is insufficient. It is hardly the most ideal. In addition, in this prior invention, there is a possibility that the generated MgS may be again involved in the hot metal.

[0008] The present invention has been made in view of the above problems, and it is an object of the present invention to provide a refining agent for molten iron that has a better desulfurization effect, is safer to use, and has a lower cost than the prior invention. Is to provide.

[0009]

Means for Solving the Problems The present inventors prepared a sample by further mixing other components with a mixture comprising magnesium oxide (and / or magnesium hydroxide) and carbon,
A reaction experiment with hot metal was performed. As a result, the following (a) to (d)
The fact turned out.

(A) In a mixture of magnesium oxide (and / or magnesium hydroxide) and carbon, calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, water One of lithium oxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride
Mixing more than one component increases the reduction ratio of magnesium oxide. (b) M generated by the reaction between Mg gas and sulfur in hot metal
gS floats on the hot metal bath surface and may be re-engaged in the hot metal due to the movement of the hot metal flow.
(And / or magnesium hydroxide) and a mixture of carbon and calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, oxide By combining one or more of the following components: boron, boric acid and calcium fluoride
The amount of MgS involved is significantly reduced.

(C) According to the above (a) and (b), that is, a mixture of magnesium oxide (and / or magnesium hydroxide) and carbon is mixed with calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, The desulfurization effect is enhanced by blending one or more of sodium, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride. When the total content of carbon and magnesium oxide (and / or magnesium hydroxide) is 50 to 80% by weight, calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide , Lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride The refining agent, in which the total content of one or more components in theium is 20 to 50% by weight, and the content of other components is 15% by weight or less, the desulfurization effect is even higher. (d) The weight ratio of carbon to magnesium oxide (and / or magnesium hydroxide) also affects the desulfurization effect. If the ratio is in the range of “0.1: 1 to 10: 1”, the desulfurization effect is reduced. Is the highest.

The present inventors have completed the hot metal refining agent of the present invention based on the above findings (a) to (d). That is, in the hot metal refining agent of the present invention, the following components are essential components: carbon, magnesium oxide and / or magnesium hydroxide as chemical components, and calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, oxide One of sodium, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride
At least 0.1% of the weight of carbon and the total weight of magnesium oxide and / or magnesium hydroxide in terms of magnesium oxide is 0.1: 1. The total content of the weight of carbon and the weight of magnesium oxide and / or magnesium hydroxide in terms of magnesium oxide is 50 to 80% by weight; Calcium, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide,
The total content of at least one of lithium hydroxide, bismagnesium calcium, boron oxide, boric acid, and calcium fluoride is 20 to 50% by weight, and the content of other components is 15% by weight or less. (Claim 3).

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refining agent for hot metal, and as described above, contains carbon as a chemical component,
Magnesium oxide and / or magnesium hydroxide as essential components, and calcium carbonate, calcium oxide,
Calcium hydroxide, sodium carbonate, sodium oxide,
It is characterized by containing one or more of iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride.

When the refining agent of the present invention is added to hot metal, carbon in the refining agent reduces magnesium oxide (and / or magnesium hydroxide) to generate Mg gas. The generated Mg gas further reacts with sulfur in the hot metal to generate MgS. When the generated MgS is separated from the hot metal, it is desulfurized.

And calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride. When containing one or more,
The rate of reduction of magnesium oxide (and / or magnesium hydroxide) increases. In addition, the generated MgS is dissolved in these components, becomes a slag together, floats on the bath surface, and is less likely to be involved in the hot metal again. Due to these causes,
The desulfurization effect is improved.

In the refining agent of the present invention, the weight of carbon and
The total content of magnesium oxide and / or magnesium hydroxide in terms of weight in terms of magnesium oxide is 50.
The content is desirably in the range of from about 80% by weight to about 80% by weight. When the content is less than 50% by weight, the desulfurization effect is low as compared with the above range (see Table 2 below).
Of Example 4), and when it exceeds 80% by weight,
Calcium carbonate, calcium oxide, calcium hydroxide,
The content of at least one of sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride is reduced, and the above-mentioned reduction rate by the component is reduced. And the desulfurization effect similarly decreases (see the column of Example 3 in Table 2 below).

Further, calcium carbonate, calcium oxide,
Calcium hydroxide, sodium carbonate, sodium oxide,
The total content of at least one of iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride is 20 to 5;
It is desirably 0% by weight. When the content is less than 20% by weight, the content is too small, and the desulfurization effect is improved, but the increase in the reduction rate is reduced, and as a result, the degree of the desulfurization effect is small. On the other hand, when the content exceeds 50% by weight, the content of “carbon, magnesium oxide and / or magnesium hydroxide” decreases, and the desulfurization effect decreases.

Further, calcium carbonate, calcium oxide,
Calcium hydroxide, sodium carbonate, sodium oxide,
Except for one or more components of iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride, the refining agent contains other components such as metals, alloys, carbides, nitrides. Or boride may be blended. However, its content is 15
It is desirable that the content be not more than weight%. If the content exceeds 15% by weight, the desulfurization effect deteriorates.

The weight ratio of carbon to magnesium oxide (and / or magnesium hydroxide) in the refining agent (weight ratio converted to magnesium oxide when magnesium hydroxide is used) is "0.1: 1 to 10: 1. Is desirable. If the weight ratio is less than 0.1: 1, magnesium oxide (and / or magnesium hydroxide) will not be sufficiently reduced to carbon, and the desulfurization effect will be reduced. If it exceeds 10: 1, a large amount of carbon remains after the reaction, hinders the reaction between the Mg gas and the sulfur in the hot metal, and reduces the desulfurization effect.

On the other hand, it is used for producing the refining agent of the present invention.
Natural and artificial raw materials can be used.
As a raw material of magnesium oxide, calcined magnesia,
Melted magnesia, calcined magnesia and magnesium hydroxide
Can be used. Black as carbon material
Examples include lead and carbon. Among them, the earth ring
Of environmental improvement, resource recycling and steelmaking cost reduction
From magnesia-carbon bricks and dolomite bricks
The use of waste is desirable. In addition, calcium carbonate and oxide
Raw lime (CaO) or limestone (CaCO_Three),
Various industrial saws for sodium carbonate and sodium oxide
Fluorite can be used for calcium fluoride. acid
FeO, Fe_TwoO_ThreeAnd Fe_ThreeO _FourThe raw material containing
Can be used.

The raw material constituting the refining agent has a particle size of 5
The particle size ratio of not more than 00 μm and not more than 100 μm among the individual raw materials is desirably 80% by weight. If the particle size is too large, the reaction rate will be slow and the desulfurization effect will be reduced. As a method for adding the refining agent of the present invention to hot metal, a method of blowing the refining agent with a carrier gas such as nitrogen or argon can be used.

[0022]

Next, examples of the present invention will be described together with comparative examples.
The present invention will be specifically described, but the present invention is not limited by the following Examples 1 to 4.

(Examples 1 to 4, Comparative Example) The raw materials shown in Table 1 were blended in the same proportions (% by weight) as shown in Table 1, and
~ 4 refining agents were produced. For comparison, as shown in Table 1, a refining agent (comparative example) composed of graphite (30% by weight) and magnesium oxide (70% by weight) was prepared.

[0024]

[Table 1]

With respect to the scouring agents of Examples 1 to 4 and the scouring agent of Comparative Example, the following Test Example 1 (test using a high-frequency furnace) and Test Example 2 (test using a real furnace) were performed. The results are shown in Table 2.

[0026]

[Table 2]

Test Example 1 Using a high-frequency furnace, 100 kg of hot metal having the components shown in Table 2 was melted in a graphite crucible, and the temperature of the hot metal was maintained at 1300 ° C. to 1380 ° C. Thereafter, 300 g of each of the scouring agents of Examples 1 to 4 and Comparative Example was blown into the hot metal with a carrier gas of argon. Processing time is 15
Minutes.

As a result, as shown in Table 2, in Test Example 1, the sulfur concentration in the hot metal before the treatment was “0.10% by weight”, but after the treatment, the refining agent of the comparative example was used. Is "0.05
% By weight ". Examples 1 and 2
If the refining agent is used, in each case up to “0.02% by weight”
Further, when the refining agents of Example 3 and Example 4 were used, both were reduced to "0.03% by weight". Further, when the refining agents of Examples 1 to 4 were used, a phenomenon such as vaporization of magnesium did not occur so much during the refining process as compared with the case of the comparative example, and a safe desulfurization operation was performed.

(Test Example 2) Using a real furnace, molten iron having the components shown in Table 2 was melted for 150 tons, and the temperature of the molten iron was maintained at 1350 ° C. Then, through a refractory lance, the hot metal in the actual furnace was injected with a carrier gas of nitrogen into Examples 1-4 and Comparative Example 1.
Was blown at a rate of 25 kg / m ³ (gas) for 15 minutes. The weight of each blown refining agent was 300 kg.

In Test Example 2, as shown in Table 2, almost the same results as in Test Example 1 were obtained. That is, even under the conditions of the actual furnace, a large desulfurization effect of the hot metal could be realized by using the refining agents of Examples 1 to 4. Further, even under these conditions, during the treatment, a phenomenon such as magnesium vaporization did not occur so much, and safe operation was possible. Further, it has been found that the cost is reduced by 30 to 60% when the refining agent of the present invention is used as compared with the case where the conventional metal magnesium is used.

[0031]

As described in detail above, the refining agent according to the present invention has an excellent effect that sulfur in hot metal can be effectively removed at low cost and in a safe operation. Further, by setting the ratio of the weight of carbon to the weight of magnesium oxide and / or magnesium hydroxide converted to magnesium oxide in the range of 0.1: 1 to 10: 1, a higher desulfurization effect can be obtained. The effect is obtained.

Further, in the refining agent according to the present invention, the total content of the weight of carbon and the total amount of magnesium oxide and / or magnesium hydroxide in terms of magnesium oxide is 50 to 80% by weight, and calcium carbonate, The total content of at least one of calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride is 20
By setting the content of the other components to 50% by weight or less and 15% by weight or less, a higher desulfurization effect can be obtained.

Continuing from the front page (72) Inventor ▲ Lin Way ▼ 4-7-1, Kudankita, Chiyoda-ku, Tokyo Shinagawa White Brick Co., Ltd. F-term (reference) 4K001 AA10 BA24 EA04 KA05 KA06 KA07 KA10 4K014 AA02 AB01 AB02 AB03 AB04 AB06 AB09 AB11 AB12 AB13 AB16 AB18 AB21 AB28 AC14 AC16 AD27

Claims (3)

[Claims] 1. A hot metal refining agent which is chemically
Carbon, magnesium oxide and / or magnesium hydroxide as essential components, and calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, lithium hydroxide, bismagnesium Calcium, boron oxide,
A hot metal refining agent comprising one or more of boric acid and calcium fluoride. 2. The weight of carbon, magnesium oxide and / or
2. The refining agent for hot metal according to claim 1, wherein the ratio of the total amount of magnesium hydroxide to the weight in terms of magnesium oxide is 0.1: 1 to 10: 1. 3. 3. The weight of carbon, magnesium oxide and / or
Or, the total content of magnesium hydroxide in terms of the weight in terms of magnesium oxide is 50 to 80% by weight, and calcium carbonate, calcium oxide, calcium hydroxide, sodium carbonate, sodium oxide, iron oxide, lithium carbonate, lithium oxide, 1 of lithium hydroxide, bismagnesium calcium, boron oxide, boric acid and calcium fluoride
The refining agent for hot metal according to claim 1 or 2, wherein the total content of at least one species is 20 to 50% by weight, and the content of other components is 15% by weight or less.