JP2001335821A - Dephosphorizing agent for molten iron and dephosphorizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the dephosphorizing efficiency equal to or more than that in the case of using fluorite without using the fluorite in a method for removing the phosphorus from molten iron containing Si. SOLUTION: This dephosphorizing agent contains 0.02-0.10 pts.wt. of Na2O and 0.05-1.10 pts.wt. of Al2O3 based on 1 pts.wt. of CaO. Alternatively, waste glass, glass cullet or meta-sodium silicate is used as Na2O raw material. In the dephosphorizing method for molten iron, the above dephosphorizing agent is used and the ratio of (CaO/SiO2) in slag composition at the completion of treatment, is <=2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dephosphorizing agent and a dephosphorizing method for effectively performing dephosphorization and refining of hot metal.

[0002]

2. Description of the Related Art Conventionally, in the steel industry, when dephosphorizing hot metal, as described in Japanese Patent No. 01202305,
In order to improve the reaction characteristics with CaO as the main component, CaF ₂
A refining agent to which a substance having a high effect of melting CaO, which is stable at a high temperature in the hot metal processing temperature range, such as CaCl ₂ and CaCl ₂ , is used. However, from the viewpoint of global environmental conservation, the use of fluorite as a source of CaF ₂ that has been generally used until now has been limited, and in order to cope with the tendency to increase the production of steel with a lower phosphorus concentration. Requires a new refining method without CaF ₂ .

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to realize a method for removing phosphorus from hot metal which does not use fluorite but achieves a dephosphorization efficiency equal to or higher than that of the case of using fluorite. Things.

[0004]

That is, the gist of the present invention is to provide a method for dephosphorizing hot metal using a refining agent, wherein quicklime is used as a main raw material, and an alumina source and a soda component are added thereto. Add glass dust or glass cullet or meta-sodium silicate, and add Na ₂ O to 1 part by weight of CaO.
And 0.02-0.10 parts by weight, using a refining agent was 0.05 to 0.10 parts by weight Al ₂ O ₃ minutes, in the processing end that implementing the dephosphorization process the value of (CaO / SiO ₂₎ 2.5 as follows Features.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS CaO-based refining agents have been known for a long time to contain Na ₂ O to greatly increase their dephosphorization and desulfurization abilities (ADVANCED PHYSICAL CHEMISTRY FOR PROCESS M
ETALLURGY, 1997, p.61 [Academic preess]). However,
Na ₂ O itself is extremely active and highly hygroscopic,
Generally, it is used in the form of Na ₂ CO ₃ . But Na ₂
When CO ₃ is at high temperature and comes into contact with hot metal with a high concentration of [C], it is vaporized and lost by the reaction of equation (1), refining efficiency is extremely poor, and use in the form of Na ₂ CO ₃ is not economical. Absent.

Na ₂ O + [C] = 2Na (g) + CO Na ₂ CO ₃ +3 [C] = 2Na + 3CO (1).

On the other hand, the addition of alumina (Al ₂ O ₃ )
It is also known that the effect of lowering the melting point of aO is relatively large. However, when melted together with CaO, it acts as an acidic component and reduces the ability of phosphorus to absorb phosphorus. Therefore, there is an urgent need to invent a new refining agent and a dephosphorization method without impairing the utilization efficiency of CaO.

[0008] The present inventors have found that the as the help melting of CaO with the use of Al ₂ O _3, and various studies how to compensate for the decrease of dephosphorizing capacity by Al ₂ O ₃ used in Na ₂ O.

[0009] Na ₂ O is a strongly basic oxide, and its activity is greatly reduced when coexisting with SiO _2, and is extremely stable even when in contact with hot metal. That is, when Na ₂ O is protected by SiO ₂ and melts in CaO when it comes into contact with molten iron and melts, its dephosphorizing ability is exhibited. As such Na ₂ O source, soda lime glass (soda glass), glass cullet used as a raw material of soda glass, and sodium metasilicate are easily available and stable even when in contact with hot metal at high temperature. It is.

[0010] The dephosphorizing ability developed when dissolved with CaO increases with an increase in the concentration of Na ₂ O. On the other hand, the amount of decomposition and vaporization reaction of the molten slag shown in the equation (1) is also large, and the amount of dephosphorization is also large. The amount of white smoke generated by the air also increases. In other words, the Na content that has been introduced is not involved in the dephosphorization reaction, is wasted, and is not economical. Therefore, the appropriate amount of soda glass, glass cullet, and sodium metasilicate is CaO 1
Relative to the weight part, it is 0.02-0.10 parts by weight as Na ₂ O content.

In order to reduce the melting point of CaO, which is a main component of the present invention, and to increase the liquid phase ratio, a sufficient liquid phase ratio cannot be secured with the above Na content. Al ₂ from the viewpoint of securing the liquid phase ratio
The more O ₃ is added, the better, but it inhibits the dephosphorization ability. Further, the addition amount of Al ₂ O ₃ is preferably as low as possible to prevent the refractory material from being damaged. Therefore, the appropriate value is limited to the range of 0.05 to 0.10.

In the present invention, the value of the basicity (CaO / SiO ₂ ) of the slag after the dephosphorization treatment is important. In other words, (CaO / SiO
_If the value of ₂ ) is large, the melting point of slag becomes high,
The ratio of the liquid phase involved in the dephosphorization reaction decreases, the activity of Na ₂ O increases, the vaporization loss of Na increases, the function cannot be sufficiently enjoyed, and the dephosphorization effect does not increase. Therefore, (CaO
The upper limit of / SiO ₂ ) is 2.5.

[0013]

EXAMPLE A dephosphorization treatment was carried out using 100 tons of hot metal having a Si content of 0.35 to 0.4 (mass%) and a temperature in the range of 1340 ° C. to 1370 ° C. using an upper-bottom blow converter. CaO-based refining agent of the present invention, with respect to CaO 1 part by weight, the Na ₂ O content and 0.02-0.10 parts by weight, was 0.05 to 0.10 parts by weight Al ₂ O ₃ minutes. As the Na source, the substances shown in Table 1 were mixed and used. 18 (kg / ton) to 24 (kg / ton) per unit weight of hot metal. In any case, (CaO / S
iO ₂ ) values ranged from 1.8 to 2.1.

[0014]

[Table 1]

FIG. 1 shows the results obtained when a conventional refining agent mixed with fluorite was used so that CaF ₂ became 5 mass%, when only lime without fluorite was added, and when the refining agent of the present invention was input. In hot metal
[P] shows changes in concentration. According to the method of the present invention, a dephosphorization rate equal to or higher than that when using fluorite can be secured, and the P concentration at the end of dephosphorization can be reduced.

However, the average composition of the soda glass, glass cullet, and sodium metasilicate used was as shown in Table 1, and Al ₂ O ₃ was used as an alumina for industrial use with a content of 90 (mass%) or more. Was used.

[0017]

According to the present method, dephosphorization and refining of hot metal in harmony with the environment can be performed without using fluorite.

[Brief description of the drawings]

FIG. 1 is a drawing showing a temporal change of phosphorus in hot metal during a dephosphorization treatment.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masao Yamauchi 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside Nippon Steel Corporation (72) Inventor Keiji Hata 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Corporation F term in the Kimitsu Works (reference) 4K014 AA03 AB02 AB03

Claims (3)

[Claims] Respect 1. A CaO 1 part by weight, the Na ₂ O content: 0.02 to 0.1
And 0 parts by weight, dephosphorization agent Molten characterized in that a 0.05 to 0.10 parts by weight Al ₂ O ₃ minutes. 2. A dephosphorizing agent for molten iron according to claim 1, wherein glass scrap, glass cullet or sodium meta-silicate is used as a raw material of Na ₂ O. 3. A method for performing a dephosphorization treatment using a refining agent, wherein the (CaO / SiO ₂ ) value of the slag composition at the end of the treatment is 2.5 or less using the dephosphorization agent according to claim 1 or 2. Hot metal dephosphorization method characterized by performing.