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Refining agent and refining method

a technology of refining agent and molten iron, which is applied in the direction of furnace details, furnaces, crucible furnaces, etc., can solve the problems of not being able to exert economic effects, raw materials, metal mg, and high cost, and achieves increased reactivity, high efficiency, and the effect of increasing the rate of mgo changing into mg vapor

Inactive Publication Date: 2005-11-24
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] An object of the present invention is to provide a refining agent, which uses a Mg source and allows molten iron refining to be performed efficiently and inexpensively, and a refining method using the agent.
[0027] According to the present invention, since Al, MgO, and CaO are used as main components, the rate of MgO changing into Mg vapor is increased. Since a material, in which MgO and CaO are close to or in contact with each other in a minute state, is used as a MgO source and CaO source, the reactivity is increased. Accordingly, refining of molten iron, using a Mg source, can be performed with an extremely high efficiency. Where dolomite, which is inexpensive, is used as a MgO source and CaO source having a material, in which MgO and CaO are close to or in contact with each other in a minute state, refining of molten iron, using a Mg source, can be performed with an extremely high efficiency and inexpensively.
[0028] Where Al, MgO, and CaO are used as main components, while the Al used as a reducing agent is partly replaced with C, which is inexpensive, refining of molten iron can be also performed inexpensively. In this case, where a material having a material, in which MgO and CaO are close to or in contact with each other in a minute state, is used as a MgO source and CaO source, refining of molten iron, using a Mg source, can be performed with an extremely high efficiency. Where dolomite, which is inexpensive, is used as such a MgO source and CaO source, refining of molten iron, using a Mg source, can be performed with an extremely high efficiency and inexpensively.
[0029] A refining agent according to the present invention exerts an excellent refining effect, where it is applied to desulfurization of molten pig iron, or desulfurization or deoxidation of molten steel, and it allows inclusion control after deoxidation of molten steel to reduce the number of product defects.

Problems solved by technology

However, although Mg desulfurization has such an advantage, it is out of the mainstream.
This is so, because the raw material, i.e., metal Mg, is expensive, and there has been found no merit, which can surpass inexpensive CaO, where being used as the main component in desulfurization flux.
However, the technique of Jpn. Pat. Appln. KOKAI Publication No. 10-17913 cannot allow all the Mg of MgO to change into metal Mg, but causes the Mg of MgO to be partly left as magnesia spinel MgO.Al2O3, as shown in the formula (3).
Accordingly, since the refining efficiency of this technique is not necessarily sufficient, it is less than enough to exert the economical effect described above.
In addition, although MgO and Al are less expensive than Mg, they are not so inexpensive; which creates demands for flux still less expensive.

Method used

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  • Refining agent and refining method

Examples

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first embodiment

(1) First Embodiment

[0046] A refining agent according to the first embodiment of the present invention contains Al, MgO, and CaO as main components, and includes a material, in which MgO and CaO are close to or in contact with each other in a minute state, as a MgO source and CaO source. Typically, it includes dolomite as a MgO source and CaO source. When the refining agent is supplied into molten iron, it produces Mg vapor due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

[0047] In the present invention, since CaO is added, Mg vapor is produced in accordance with the following formulas (4) to (7), in place of the formula (3).

6MgO+4Al+CaO→6Mg(g)+CaO.2Al2O3  (4)

3MgO+2Al+CaO→3Mg(g)+CaO.Al2O3  (5)

21MgO+14Al+12CaO→21Mg(g)+12CaO.7Al2O3  (6)

3MgO+2Al+3CaO→3Mg(g)+3CaO.Al2O3  (7)

[0048] In the formula (3), MgO in the starting substance is partly consumed in producing MgO.Al2O3, and thus the ratio of MgO changing into Mg vapor is suppressed to 75% at mo...

second embodiment

(2) Second Embodiment

[0063] A refining agent according to the second embodiment of the present invention contains Al, C, MgO, and CaO as main components. When the refining agent is supplied into molten iron, it produces Mg vapor and a complex oxide of CaO and Al2O3 due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

[0064] In the embodiment described above, although Al is used as a reducing agent, Al is relatively expensive. Accordingly, in this embodiment, Al and C are used together as a reducing agent, so that the Al quality is reduced to make flux inexpensive.

[0065]FIG. 5 is a view showing the relationship between the Al / MgO value, which is on the horizontal axis, of a refining agent, and the Mg reduction rate, which is on the vertical axis, in the case of containing no C, and in the case of adding C(C / MgO=0.3 and 1.0). This result was obtained by adding a refining agent to molten iron at a temperature of 1,300 or more, with CaO / MgO=2.0.

[0066] ...

example 1

[0192] In this example, refining agents according to the present invention and refining agents according to comparative examples were used to desulfurize 200 tons of molten pig iron in a ladle, by a mechanically stirring setup. The molten pig iron used in the treatment was, in advance, subjected to desiliconization treatment at two stages of a runner in a cast house of a blast furnace, and a molten pig iron ladle used as a pig iron-receiving container, following tapping from a blast furnace. With the pre-desiliconization, the molten pig iron composition was set such that [Si]=0.05 to 0.10 mass %, [C]=4.3 to 4.6 mass %, [Mn]=0.22 to 0.41 mass %, [P]=0.10 to 0.13 mass %, and [S] before the treatment=0.040 to 0.042 mass %. The molten pig iron temperature was 1,330 to 1,430° C. Each refining agent according to the present invention was used in a form prepared by mixing and crushing the following materials to have an average particle size 0.6 mm, or a form prepared by pelletizing them. S...

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Abstract

A refining agent contains Al, MgO, and CaO as main components, and uses dolomite as a MgO source and CaO source. When the refining agent is supplied into molten iron, it produces Mg vapor due to a reaction in the molten iron, and causes a refining reaction by the Mg vapor.

Description

TECHNICAL FIELD [0001] The present invention relates to a molten iron refining agent and refining method. BACKGROUND ART [0002] Refining agents for molten iron or molten steel are required to be inexpensive, as well as causing an effective refining reaction. For example, desulfurization flux widely used in desulfurization of molten pig iron, such as 95 mass % CaO and 5 mass % CaF2, contains CaO, which is inexpensive, as the main component. Metal Mg is also known as desulfurization flux for molten pig iron. Metal Mg readily reacts with S contained in molten pig iron and produces MgS. Since Mg has a low boiling point of 1,107° C., it is vaporized in molten pig iron at a temperature of 1,250 to 1,500° C., and generates Mg vapor. A desulfurization reaction by Mg and a desulfurization reaction by CaO are expressed by the following formulas (1) and (2). Mg+S→(MgS)  (1) (CaO)+S→(CaS)+O  (2) [0003] Specifically, Mg vapor dissolves in molten pig iron, reacts with sulfur S contained in the mo...

Claims

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Application Information

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IPC IPC(8): C21B3/04C21C1/02C21C7/04C21C7/06C21C7/064C21C7/072C21C7/076
CPCC21B3/04C21C1/025C21C7/04C21C7/076C21C7/0645C21C7/072C21C7/06Y02P10/20Y02W30/50C21C1/02
Inventor NAKAI, YOSHIEMURAI, TAKESHIMATSUNO, HIDETOSHIKIKUCHI, YOSHITERUTAKAHASHI, KENJINIMURA, YOICHISHIMIZU, HIROSHIISAWA, TOMOOKAWASHIMA, TAKESHIOKAMURA, TATSUYA
Owner JFE STEEL CORP
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