JP3283715B2 - Hot metal desiliconization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desiliconizing hot metal with high efficiency.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for improvement of hot metal quality due to demands for production of high-grade steel and reduction of refining costs in a steelmaking process. For this reason, a desiliconization treatment is usually performed by introducing a desiliconization agent into the hot metal. As a method of performing desiliconization,
Cast-bed desiliconization method in which a desiliconizing agent is introduced into the hot metal flowing through the tapping gutter in front of the blast furnace, or injection method in which the desiliconizing agent is injected into the hot metal with a carrier gas after receiving the hot metal in a receiving vessel. Alternatively, there is a placing method in which a desiliconizing agent is previously charged in a receiving container before receiving iron, and both are generally widely used techniques.

If a part of the prior art is shown, for example,
No. 10528 discloses that Fe ₂ is contained in hot metal at a relatively low temperature.
A method in which a desiliconizing agent containing O ₃ as a main component is blown into a hot metal container, and Japanese Patent Publication No. Sho 61-45681 discloses a method in which hot metal poured from a blast furnace is desiliconized through hot metal flowing through a tapping gutter through a lance. A method for adding an agent is disclosed.

Japanese Unexamined Patent Publication (Kokai) No. 63-303006 also discloses that dust generated from a converter is used as iron oxide in a desiliconizing agent blown into a hot metal of a container such as a mixed iron car through a blowing lance. A method is presented. These are all examples for removing silicon from the hot metal, and many other known techniques as a desiliconization method are known.

[0005]

An important point in such a method for adding a desiliconizing agent is that the desiliconizing agent added to the hot metal is melted and sufficiently slagged, and the slagging desiliconizing agent is added. And hot metal sufficiently contact and react efficiently.

However, in the above-described conventional desiliconization methods, when trying to reduce silicon to a target silicon concentration by a single method, respectively, the cast-bed desiliconization method and the put-in desiliconization method are individually performed. Because of the large amount of desiliconization, a large amount of desiliconization agent is added in a short time or at a time, resulting in insufficient slagging of the desiliconizing agent or insufficient stirring after slagging. For this reason, the efficiency of the desiliconization reaction is low, and a significant improvement in the efficiency of the desiliconization cannot be expected.

In addition, the injection method has a problem that the blowing rate of the desiliconizing agent is limited due to facility capacity, and when a large amount of desiliconization is required, the distribution of the entire process is disturbed by extending the processing time.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed in order to solve the above-mentioned problem in hot metal desiliconization and to efficiently desiliconize hot metal. According to the present invention, the above object is to provide a method for de-siliconizing hot metal in a pig iron receiving vessel, in which a powder containing iron oxide is melted as a first step.
2 kg or more per ton and silicon concentration after the first stage treatment
The desiliconizing agent amount was calculated to be 0.3% to 0.5%.
The silicic acid is placed in the receiving vessel in advance, and then the hot metal from the blast furnace is dropped into the receiving vessel and stirred while stirring, and then, as a second step, a lance is inserted into the hot metal in the receiving vessel. This is achieved by a method for desiliconizing hot metal, which comprises immersing and blowing a desiliconizing agent to desiliconize to a target silicon concentration.

[0009] Further , the above object is to provide a first-stage desiliconizing agent.
And put a powder with a maximum particle diameter of at least 5 mm
Achieved by the method for desiliconizing hot metal.
You.

Further, the above object has been attained by the method for desiliconizing hot metal, wherein a powder containing dust collected in a steelmaking process is used as a first-stage desiliconizing agent. You.

[0011]

As described above, various methods have been proposed as a method for desiliconizing hot metal, but each method has advantages and disadvantages including the above-mentioned problems. For example, in the cast bed desiliconization method, the slagging of the desiliconizing agent is insufficient, the stirring with the hot metal is insufficient, the reaction efficiency is low, and the target hot metal silicon concentration is, for example, the dephosphorization / It has been difficult to carry out desiliconization to a low silicon concentration required in the desulfurization step.

If this process is forcibly performed, a large increase in the amount of the desiliconizing agent and the formation of the desiliconized slag at the time of receiving the hot metal into the pig iron receiving vessel are performed. There is a problem. There is exactly the same problem in the in-situ desiliconization method, and desiliconization up to a low silicon concentration has been considered impossible.

The present invention is directed to a desiliconization method which solves the above problem and enables desiliconization to a low silicon concentration with extremely high desiliconization efficiency as compared with the conventional method. The present inventors have compared the experimental results and problems during the desiliconization treatment according to the conventional method in detail, and as a result, as the silicon concentration in the hot metal decreases due to the desiliconization treatment, the desiliconization efficiency gradually decreases. It was found that the change was significantly different depending on each desiliconization method.

That is, as shown in FIG. 1, in the injection method and the storage desiliconization method, although the desiliconization efficiency varies due to the variation of the hot metal temperature, the hot metal stirring conditions during the processing, etc. According to the method, the desiliconization efficiency is high in a high silicon concentration region, but when the amount of desiliconization increases in a low silicon concentration region, the desiliconization efficiency sharply decreases and the efficiency rapidly deteriorates.

On the other hand, in the injection method, the desiliconization efficiency varies due to the variation of the hot metal temperature, the hot metal stirring conditions during the treatment, and the like. Generally, the desiliconization efficiency at a high silicon concentration is not high. It has been found that there is a characteristic that a relatively high desiliconization efficiency can be maintained at a low silicon concentration as compared with the method or the placing method.

The present invention pays attention to this point, and performs the first stage of the desiliconization method in the optimum desiliconization amount range in the high silicon region and the second stage in the low silicon region. By dividing into two stages, a method was developed that can maintain extremely high desiliconization efficiency up to a low silicon concentration compared to the conventional desiliconization method.

That is, in the method for desiliconizing hot metal in a pig iron receiving vessel, as a first step, when desiliconizing from a high silicon concentration, a desiliconizing agent is placed in the pig iron receiving vessel in advance, and the blast furnace is When the hot metal is received in the hot metal container from the hot metal container, the hot metal is agitated by the dropping force of the hot metal, so that a part of the silicon in the high silicon concentration region of the hot metal is put into the hot metal. Obtain the desiliconization efficiency, and as the second step, obtain a high desiliconization efficiency in the low silicon concentration region, which is a feature of the injection method, by immersing a lance in hot metal in a storage vessel and blowing a desiliconization agent. Things.

As a result, an extremely high desiliconization efficiency can be obtained as compared with the conventional method as the average desiliconization efficiency during the desiliconization treatment, and the desiliconization treatment can be easily performed to the final target silicon concentration. Becomes

Here, the amount of the desiliconizing agent in the first stage is 1 t of hot metal.
2kg or more and the silicon concentration after the first stage treatment is 0.3
% To 0.5%. 2 per ton of hot metal
When the weight is less than kg, the desiliconization power in the first stage is small and the function of dividing the desiliconization process into two stages cannot be sufficiently exhibited, and the processing load on the injection desiliconization in the second stage increases, and The meaning divided into two stages is halved, and the conventional problem is not solved.

On the other hand, the silicon concentration after the first stage treatment is 0.3
%, The efficiency of desiliconization is clearly reduced as compared with the injection method, and the effect of the present invention cannot be exhibited.

[0021] The silicon temperature after the first stage treatment is 0.3% or more.
As shown in FIG. 1, when the concentration is 0.5%, the desiliconization efficiencies of both the placing method and the injection method are almost the same due to variations in the respective reaction efficiencies, and are extremely superior to either method. It is not recognized as having sex. Therefore, when performing the desiliconization treatment according to the present invention, the operating conditions such as the influence on the logistics of the post-process restricted by the capacity of the injection desiliconization facility, the capacity of the hot metal pig iron receiving vessel, the shape, and the capacity of the inserted powder charging facility are taken into account. Thus, an appropriate concentration can be targeted as the silicon concentration after the first stage treatment.

The particle size of the desiliconizing agent in the first stage is as follows.
At least the maximum particle size needs to be 5 mm. By maintaining this particle size, slagging of the desiliconizing agent proceeds, and a marked improvement in reaction efficiency can be expected. Maximum particle diameter is 5m
m, the slagging of the desiliconizing agent during the reaction becomes insufficient,
As shown in FIG. 2, the reaction efficiency decreases.

Further, it is desirable to use a powder containing dust collected in an iron making process such as a converter as the first-stage desiliconizing agent. As a desiliconizing agent, iron oxide is generally used as an oxygen supply source, and in most cases, iron ore powder (generally referred to as pellet feed) is often used as a desiliconizing agent containing iron oxide. . Thus, the iron oxide contained in the pellet feed is Fe ₂ O ₃ or Fe ₃ O ₄
Contains oxygen in the form of

When this Fe ₂ O ₃ or Fe ₃ O ₄ is exposed to a high temperature atmosphere, it is easily thermally decomposed to release oxygen, and the FeO
Becomes However, when iron ore-based iron oxide such as pellet feed, which is used as a conventional desiliconizing agent, is used as the desiliconizing agent in the first stage, the temperature rise at the time of receiving the iron in the first stage of the desiliconizing suddenly increases. Thermal decomposition of iron oxide occurs and oxygen is generated rapidly, and oxygen is supplied faster than the desiliconization reaction rate.As a result, unreacted oxygen escapes out of the system or excess oxygen is It may cause a decarburization reaction with the carbon in the hot metal, and as a result, may not be involved in desiliconization.

In the present invention, in order to avoid such a problem, the use of iron-making dust such as a converter mainly composed of FeO as a form of iron oxide prevents rapid oxygen decomposition due to thermal decomposition, thereby improving stability. And made it possible to supply oxygen necessary for desiliconization. Therefore, as the desiliconizing agent, if it is a powder mainly composed of FeO as iron oxide, for example, the scale (iron oxide film) on the surface of the manufactured slab
And scales for coil rolling.

[0026]

The method of the present invention will be described in more detail with reference to the following examples. Table 1 summarizes the implementation conditions and implementation results. In any of the examples, the average desiliconization efficiency was about 10% compared to the conventional desiliconization method using only injection.
As a result, the time required for the desiliconization treatment was shortened and the amount of the desiliconizing agent used was reduced.

Here, the amount of the desiliconizing agent in the first stage is determined by equipment such as powder cutting ability at the time of implementation and dust collecting ability at the blast furnace iron receiving place.
It is necessary to input an appropriate amount depending on the operating conditions.
In addition, the powder containing iron oxide alone may be used as the storage silicide in the first stage, but depending on the silicon oxide generated by the silicification, powdered lime is used as a powder for preventing the formation of forming. And powder such as converter slag may be mixed and charged. In this case, the maximum particle diameter of the forming-preventing powder must be 5 mm. Further, after the end of the first stage processing, the desiliconized slag generated in the first stage before the second stage processing may be discharged.

[0028]

[Table 1]

[0029]

According to the present invention, the desiliconization treatment can be efficiently performed, and the effect of reducing the time required for the desiliconization treatment and the amount of use of the desiliconization agent can be obtained. In addition, even when the silicon concentration in the hot metal is high and a large reduction in the amount of desiliconization is required, it is possible to perform the desiliconization without extending the treatment time, and to stabilize the hot metal logistics, This is a useful technology.

[Brief description of the drawings]

FIG. 1 is a comparison diagram of the desiliconization efficiency by the desiliconization method

FIG. 2 is a graph showing the relationship between the maximum particle size of the deoxidizing agent and the efficiency of desiliconization.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masanobu Kumakura 1 Nishinosu, Oji, Oita, Oita Prefecture Inside Nippon Steel Corporation (72) Inventor Takamichi Akahoshi 1 Nishinosu, Oji, Oita, Oita New Japan (56) References JP-A-5-9534 (JP, A) JP-A-63-203715 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21C 1/04

Claims (3)

(57) [Claims] In a method for de-siliconizing hot metal in a pig iron receiving vessel, as a first step, a powder containing iron oxide is heated to 1 ton.
2 kg or more per unit and the silicon concentration after the first stage treatment is 0.1 kg.
Desilicicizing agent whose amount is calculated to be 3% to 0.5%
The leave placed previously placed in受銑vessel, and受銑while stirring to drop the hot metal from thereafter furnace to受銑container, then immersing the lance into molten pig iron in受銑container in the second stage And desiliconizing the molten metal to a target silicon concentration by blowing a desiliconizing agent. 2. The method for desiliconizing hot metal according to claim 1, wherein a powder having a maximum particle diameter of at least 5 mm is placed as a desiliconizing agent in the first stage. As 3. A first stage of the de-珪剤, de珪方method of hot metal according to claim 1, wherein the use of powder containing a dust collecting dust generated in the manufacturing process of steelworks.