JP2000328122A - Foaming depressant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To depress foaming with a small quantity of depressant in a short time and to obtain excellent efficiency and economization by containing not less than a specified content of aluminum and that of sulfur in a foaming depressant restraining the foaming of slag. SOLUTION: The foaming depressant contains >=25 wt.% aluminum and >=2 wt.% sulfur. This foaming depressant is desirable to be used in a molten iron pretreatment for desiliconization, dephosphorization or desulfurization of the molten iron. The aluminum has the effect for reducing the oxidizing degree in the slag causing the foaming by adding at >=25 wt.% to the whole foaming depressant. The sulfur has the effect for reducing the interface tension of the slag/metal. Since the oxidizing degree in the slag is reduced and the slag/metal interface tension is reduced by this depressant, keeping of bubbles in the slag becomes difficult, and since the breakage of the bubbles is promoted, the foaming can be depressed with small quantity of depressant in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forming inhibitor which suppresses slag forming in pretreatment of hot metal supplied to, for example, converter steelmaking.

[0002]

2. Description of the Related Art In the pretreatment of hot metal such as cast-bed desiliconization, ladle and torpedo injection desiliconization, ladle dephosphorization and desulfurization, torpedo dephosphorization, desulfurization, and converter type hot metal dephosphorization, the carbon content in Reacts with oxygen sources such as iron oxide and oxygen gas,
Forming occurs. When the forming is severe, the forming slag overflows from a container such as a pot or a torpedo and hinders the operation. In order to secure the free board in the container so as not to overflow, it is necessary to reduce the charging amount, which causes a decrease in productivity. Therefore, it is important to suppress the forming that causes these.

Hitherto, in order to suppress such forming, various forming inhibitors have been devised and their use has been attempted.

For example, Japanese Patent Publication No. Sho 63-42684 discloses a method of sequentially adding a substance obtained by mixing a light metal powder having a specific gravity of 5 or less and a carbonaceous powder and a substance obtained by mixing a carbonaceous powder and a calcium chloride powder. Is disclosed. Japanese Patent Publication No. 63-68368 discloses a forming inhibitor comprising a light metal powder having a specific gravity of 5 or less, a carbonaceous powder and sodium nitrate.

On the other hand, as a method of suppressing the forming,
Reduction of the surface tension of the slag, reduction of the viscosity of the slag, mechanical destruction of the slag bubbles, and the like have been considered. For example, in Japanese Patent Application Laid-Open No. 63-137116, a diagram of a factor of forming is shown, and the cause of the forming is studied in detail. Japanese Patent Publication No. Sho 63-42684 describes slag forming factors such as viscosity, surface tension, existence of suspended particles, and oxidation of suspended carbon-saturated iron fine particles.

[0006]

However, the above-mentioned prior art has a problem that the time required for forming sedation is long and it is not always efficient. In addition, the conventional forming inhibitor requires a relatively large amount, and thus has a problem in economy.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a forming inhibitor which can calm forming in a small amount and in a short time, and is excellent in efficiency and economy. And

[0008]

As described above, as a method of suppressing slag forming, reduction of the surface tension of the slag, reduction of the viscosity of the slag, mechanical destruction of the slag bubbles, and the like can be considered. The inventors focused on the slag / metal interfacial tension and studied the suppression of slag forming. As a result, the aluminum-containing material is added to reduce the degree of oxidation in the slag which causes forming, and the addition of sulfur reduces the slag / metal interfacial tension, making it difficult to maintain bubbles in the slag. It was found that it was possible to promote foam breaking.

The present invention has been made on the basis of such findings, and is a forming inhibitor for suppressing slag forming, which contains at least 25 wt% of aluminum and at least 2 wt% of sulfur. It is intended to provide a forming inhibitor characterized by the following.

[0010] Such a forming agent is preferably used in hot metal pretreatment for desiliconizing, dephosphorizing, or desulfurizing hot metal.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The forming inhibitor of the present invention contains 25% or more of aluminum and 2% or more of sulfur.

[0012] Aluminum forms 2% of the entire forming agent.
Addition of 5 wt% or more has an effect of reducing the degree of oxidation in slag which causes forming. If the amount is less than 25%, the above effect is insufficient. As the aluminum source, aluminum ash, recycled aluminum, aluminum scrap, and the like can be suitably used.

Sulfur has an effect of reducing the slag / metal interfacial tension, but in order to obtain the effect, it is necessary to add 2 wt% or more to the entire forming inhibitor. The sulfur source is not particularly limited, but gypsum, desulfurized slag, iron sulfide and the like can be suitably used. In particular, desulfurized slag is effective from the aspect of resource recycling and is economically significant.

In the present invention, components other than aluminum and sulfur are not particularly limited. Components other than aluminum and sulfur will vary depending on the aluminum and sulfur sources used. Further, components usually used as a forming inhibitor may be added to the aluminum source and the sulfur source. Examples of such components include carbonaceous material (C), lime (CaO), and paper sludge.

According to the forming inhibitor having such a structure, the degree of oxidation in the slag is reduced and the interfacial tension of the slag / metal is reduced, so that it is difficult to maintain the bubbles in the slag and the foaming is promoted. Therefore, forming can be calmed down in a small amount and in a short time.

[0016]

EXAMPLES (Example 1) A forming agent within the scope of the present invention and a conventional forming agent were added to suppress hot metal forming during desiliconization of a blast furnace cast floor, and the forming calming effect was investigated. In addition, using aluminum ash (Al = 30 wt%) as a conventional forming inhibitor,
As the forming inhibitor of the present invention, gypsum (S = 18.7 wt%) is added to aluminum ash and mixed with 20 wt% of aluminum ash (Al = 25 wt%, S = 15.6 wt%).
%).

As a result, as shown in FIG. 1, when the conventional forming inhibitor was used, [Si] = 0.25
When desiliconizing from wt% to 0.15 wt%, the basic unit required for forming calming was 0.5 kg / t-hot metal, but when the forming inhibitor of the present invention was used, it was necessary for calming calming. The basic unit is 0.2 kg / t-hot metal, and it has been found that the required amount is 40% of the conventional amount.

(Example 2) At the end of dephosphorization blowing in a converter-type dephosphorization treatment path, when a forming inhibitor was not added, a forming agent within the scope of the present invention and a conventional forming inhibitor were added, respectively. The forming sedation time was investigated for the case. In addition, 1 kg / t of coke and paper sludge were respectively added as conventional forming inhibitors, and 1 kg / t of the one used in Example 1 was added as the forming inhibitor of the present invention.

As a result, as shown in FIG. 2, when the forming inhibitor was not added, it took 1 minute until the forming was calmed down.
It took 0 minutes, and it took 5 minutes to calm the forming when the conventional forming inhibitor was used, whereas in the case of the present invention, it was confirmed that the calming of the foaming took 2 minutes. Thus, it has been found that the forming inhibitor of the present invention has an extremely large forming suppressing effect.

[0020]

As described above, according to the present invention,
Forming can be calmed down in a small amount and in a short time, and a forming inhibitor excellent in efficiency and economy can be obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a comparison of a forming inhibitor basic unit between a forming inhibitor of the present invention and a conventional forming inhibitor.

FIG. 2 is a diagram showing a comparison of the forming sedation time when a forming inhibitor is not added, when a conventional forming inhibitor is used, and when a forming inhibitor of the present invention is used.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiteru Kikuchi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Kenji Takahashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Kenzo Yamada 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Japan In-tube (72) Inventor Atsushi Yamaguchi 2-2-2, Marunouchi, Chiyoda-ku, Tokyo Steel pipe mining F term in the company (reference) 4K014 AA01 AA02 AA03 AB21

Claims (2)

[Claims] 1. A forming inhibitor which suppresses slag forming, characterized by containing aluminum by 25% by weight or more and sulfur by 2% by weight or more. 2. The method according to claim 1, which is used in hot metal pretreatment for desiliconizing, dephosphorizing or desulfurizing hot metal.
3. The forming inhibitor according to item 1.