JPS61157610A - Slag coating method of converter - Google Patents

Abstract

PURPOSE:To prolong the furnace life and also to decrease the suspension time of a furnace and the consumption of a slag modifying agent or the like by coating the residual slag in a converter on the inside wall surface of the converter and thereafter cooling forcedly the above-mentioned coating layer. CONSTITUTION:After the tapping of a converter 3 executed with a refractory 2, a modifying agent such as dolomite is added to the residual slag 4 in the inside of the converter 3 and a slag coating layer 6 is formed on an inside wall surface 7 by blowing gas such as Ar and N2 into the converter from the tuyeres 5 and dissipating the slga 4. Thereafter a forced-cooling lance 9 which is provided with plural pieces of liquid spray nozzles 10a-10f to a tip part 8 of a cylindrical body is vertically hung in the converter 3 freely movably up and down and for example, water as liquid is fed to the lance 9 via a pressure-feed installation and the dissipation is performed through the tip part 8 to cool forcedly the slag coating layer 6. By such a method, the strengthened coating layer 6 can be formed and the wear of the refractory 2 is inhibited and the prolongation of the life of furnace body can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of slag coating an inner wall surface of a converter.

[Conventional technology]

In general, the cost of refractories accounts for an extremely large portion of the refining cost of molten iron in top-blown, bottom-blown, or top-bottom blown converters.For this reason, the refractory lining of the converter is It is important to suppress wear and tear as much as possible to extend the life of the furnace body, and this is a technical issue that must be solved by the workers involved. As for the method of prolonging the service life, dolomite or the like is added to the residual slag after tapping the ff-wrought molten steel to modify the residual slag, and then the furnace body is simply rocked to coat the inner surface of the furnace wall. method [hereinafter simply referred to as the swing coating method], or as in Japanese Patent Publication No. 59-38282, gas is blown into the furnace through tuyere provided at the bottom of the converter to blow up the slag remaining in the furnace. , and a method of performing slag coating by rocking the converter (hereinafter simply referred to as tuyere blow-up coating), etc. have been proposed.

[Problem that the invention seeks to solve]

However, with conventional methods, such as the above-mentioned rocking coating method, it is possible to sufficiently coat the parts that become horizontal surfaces during rocking on the charging and tapping sides, but it is impossible to coat the parts corresponding to the trunnions (vertical parts). be. On the other hand, the tuyere blow-up coating method has the advantage of wide tolerance on the spray surface.

However, in common with the above-mentioned rocking coating method, the slag coating layer on the furnace inner wall surface is simply welded to the inner wall brick surface, so almost all of it melts off due to molten steel stirring during the next charge refining. Therefore, the slag coating must be repeated frequently to protect the furnace inner wall.

For this reason, the downtime of the converter itself required for coating increases, resulting in a significant drop in the productivity of the converter, and dolomite added to the residual slag due to repeated coating.
This results in a large loss of slab modifiers such as magnesia or gas blown into the tuyeres, and the lifespan of the converter is shortened because the coating layer melts off even during refining, making it difficult to achieve the desired long root life. It has drawbacks such as the inability to

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problem, and is intended to sufficiently bond a slag coating layer to the inner wall surface of the furnace, thereby preventing the slag coating layer d from being worn away by the refined molten steel or slab. The present invention extends the life of the refractory lining of the converter by making the slag coating layer sustainable for a long period of time, thereby suppressing the increase in converter downtime and the consumption of slab modifier and tuyere blowing gas. The purpose is to provide a possible slag coating method.

[Means for solving problems]

The gist of the present invention for achieving the above object is that after adding a modifier to the residual slag or residual slab in the converter, the residual slag is coated on the inner wall surface of the converter, and then the coating layer is This is a slag coating method for a converter, which is characterized by forced cooling.

The slag coating method for a converter according to the present invention will be explained below.

The present inventors conducted various studies and experiments regarding the wear and tear of the slag coating layer, which has been sufficiently coated with the converter slag coating material on the wall brick surface of the furnace interior. The present invention was achieved based on the findings obtained as a result.

In other words, the present inventors have discovered that even if the furnace wall is coated with residual slag after refining and tapping of the converter, or with a coating material in which dolomite, a modifier, or magnesia, etc. is added to the slag, no damage occurs during refining. We investigated the causes that can be easily removed. As a result, the present inventors found that the surface of the slag coating layer is in a semi-molten state and is abraded by the molten steel or slab during refining, and that the slag coating layer immediately after coating on the inner wall surface has a high strength. As mentioned above, it was found that in addition to physical wear, elution due to reaction with slag was progressing as much as possible because it was weak in terms of physical strength and the compositional density was also coarse and fine.

The present invention has obtained the following knowledge based on the above-mentioned knowledge; In order to improve the durability of the slag coating layer, it is possible to use the residual slag in the converter or a coating material with a modifier added to the residual slag. After coating the inner wall surface with a certain slag, the slab coating layer is forcedly cooled, so that the surface of the slag coating layer shrinks and solidifies to form a hard, dense refractory layer.

This hard and dense slag coating layer can sufficiently suppress physical wear caused by molten steel and slag during refining and reaction elution caused by slag, thereby greatly extending its life span.

In this way, the present invention breaks down the conventional wisdom of proactively retaining heat on the refractory surface of the furnace body to prevent spalling, cracking, etc. of the refractory when attempting to extend the life of the converter. hand,
It is possible to extend the life of the converter by using forced cooling as described above.

As a cooling medium for forced cooling of the slag coating layer, gas fluids such as air, nitrogen, and low-temperature steam, or liquids such as water and oil are used in liquid form or in mist form through spraying, etc. However, by spraying this onto the surface of the aforementioned coating layer, a reinforcing slag coating layer can be effectively formed.

In addition, if this forced cooling is too supercooling, not only the slag coating layer but also the internal refractories such as dolomite and magnesia bricks will be cooled, so the internal bricks may undergo a spalling phenomenon or the slag This causes a difference in shrinkage between the adhesive surface of the coating layer and the brick, causing the slag coating layer to peel off. In order to suppress this flaking phenomenon, a semi-solidified soft layer is formed between the slag coating layer and the brick layer by forced cooling depending on the layer thickness of the slag coating, for example by controlling the amount of gas in spraying or the amount of water in spraying. It is preferable to strongly cool it. This semi-solid soft layer exhibits extremely excellent effects in absorbing impact caused by molten steel, slag, etc. and adhesion between the hardened coating layer of the slag coating layer and bricks.

〔Example〕

Next, an embodiment of the slag coating method according to the present invention will be described.

FIG. 1 is a cross-sectional view showing the concept of the slag coating of the present invention, and FIG. 2 is a cross-sectional view of the tip of a forced cooling lance.

First, refining is performed in a converter 3 in which a refractory lining 2 is installed on an iron shell 1, and the molten iron is tapped.
3 tons of dolomite as a modifier is added to the residual slag 4 of ~B tons, and then Ar,
A gas containing nitrogen or some oxidizing gas is blown into the converter to scatter the residual slag 4 and coat the inner wall surface 7 of the converter with a slag coating layer 6. Then, for example, a single tube,
Alternatively, liquid can be sprayed onto the raw end 8 of a cylindrical body made of a double pipe or the like by suspending a forced cooling lance 9 provided with a plurality of nozzles 10a-1Of into the converter 3 so as to be able to rise and fall freely. For example, water is supplied as a liquid through pressure feeding equipment (not shown) such as a pump. The conditions for the lance 9 at this time are determined depending on the thickness of the coating layer. For example, lifting speed 1-6
m/see, the water injection pressure is 5 to 8 to 9/cd, the water injection amount is 60 to 300e/-, and it is dissipated as shown by the arrow, but when using a gas fluid such as air nitrogen, the above water amount It is necessary to supply a larger amount of cold gas than
Sufficient forced cooling cannot be achieved unless the lifting speed of the lance 9 is also slowed down.

Further, the tip portion 8 of the lance 9 is directed toward the inner wall 7 of the converter 3, and the lance 9 has nozzles 10a to 10f arranged alternately, or has a single hole or a plurality of nozzles.
It may move up and down and rotate itself.

Table 1 shows the results of slag coating of a 170 ton converter compared with the conventional method.
Although the military law clearly requires fewer slag coatings, the life of the furnace is greatly extended, and the furnace life is also reduced, and the consumption of slab modifiers, etc. is greatly reduced. It can be seen that it is extremely excellent.

Table 1 [Effects of the Invention] As described above, by using the slag coating method of the present invention, a strong slag coating layer is formed, which is less likely to melt down during the next charge refining, and can sufficiently protect the furnace inner wall. As a result, the wear and tear of the bricks is suppressed, and the lifespan of the furnace body is extended.

Furthermore, the present invention is an excellent slag coating method that can be carried out extremely economically by reducing the downtime of the furnace and eliminating the large consumption of slag modifiers and the like associated with the slab coating.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the concept of slag coating of the present invention, and FIG. 2 is a cross-sectional explanatory view of the tip of a forced cooling lance. 1... Iron shell, 2... Lining refractory, 43... Converter, 4... Residual slag or slag with addition of modifier, 5... Tuyere, 6... slag coating layer,
7... Converter inner wall surface, 8... Tip of forced cooling lance, 9... Forced cooling lance, 1Qa-f... Nozzle for liquid spraying. Agent: Patent attorney Masamitsu Akizawa and 2 other people

Claims (1)

[Claims] (1) A converter characterized in that after adding a modifier to the residual slag or residual slag in the converter, the residual slag is coated on the inner wall surface of the converter, and then the coating layer is forcedly cooled. Furnace slag coating method.