JPH10332279A - Brick for lining for container for molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax the generation of a thermal stress due to repetition of heating and cooling by embedding a metallic wire vertically to a contact surface between an internal part and the molten metal, to cause breakage to hardly occur by increasing the strength of a brick, and further to cause a part, to which breakage occurs, to hardly fall even when the breakage occurs. SOLUTION: Metallic wires 1 are embedded at intervals of a specified distance through the overall length in a longitudinal direction of a brick, and an opening part 2 for inserting a tuyere is formed in a central part. In a case of a tuyere brick, since a thermal stress is generated vertical to a working surface, the embedded metallic wires reinforce a brick and prevents breakage of the brick. The material of the brick is not especially limited but may be magnesia carbon, and the other alumina carbon brick may be an alumina-SIC- carbon brick. The material of the embedding metallic wire is especially limited, and preferably a stainless steel being a material, such as SUS304 and SUS410, having high thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a furnace for refining molten metal,
The lining brick of a ladle or the like that holds molten metal (collectively referred to as “molten metal container”), more specifically, is resistant to thermal stress applied to the lining brick of the molten metal container. Regarding high brick.

[0002]

2. Description of the Related Art The lining brick of a refining furnace for molten metal such as a converter is subjected to a heat cycle of heating and cooling by repetition of a high temperature state and a low temperature state during refining and empty furnace.
When a tuyere that blows gas is provided, the brick around the tuyere is placed in a state where thermal stress is likely to be generated due to the gas cooling effect. Furthermore, the lining brick of the ladle containing the molten metal also undergoes a heat cycle of heating and cooling by repeated use, so that the brick is likely to generate thermal stress.

In particular, since the temperature gradient in the brick around the tuyere of a converter (hereinafter referred to as tuyere brick) is sharp, the thermal stress caused by the temperature gradient increases, and the thermal stress often exceeds the strength of the brick. Value. As a result, the tuyere brick is cracked and a part of the tuyere brick falls off, resulting in a problem that the wear rate increases.

Therefore, in order to reduce such a temperature gradient, attempts have been made to provide a heat insulating layer between the tuyere and the tuyere brick around the tuyere.

Japanese Patent Application Laid-Open No. Sho 59-20417 discloses that the thermal conductivity between a metal tuyere and a refractory tuyere brick is small,
In addition, it has been proposed to insert and insert a tube made of a ceramic material having high strength.

However, even with such a structure, the cracks due to the thermal stress generated in the ceramic tube cannot be suppressed, and the cracks propagate to the tuyere brick outside thereof. It is not a drastic measure that can be done. In addition, ceramic tubes are liable to be cracked by impact, so that they need to be handled with care, and there is also a problem that the construction is troublesome.

Further, Japanese Patent Laid-Open Publication No. Hei 3-21212 proposes a structure in which the tuyere outer periphery is insulated with a graphite sheet. However, since graphite is used for the heat insulating material, oxidation loss is generally caused by oxygen blown from the tuyere as a refining gas or carbon dioxide blown as a tuyere cooling gas, and FeO concentrated around the tuyere is present.
There is a problem that oxidation wear and the like due to the system melt cannot be avoided.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to alleviate the generation of thermal stress applied to a brick by repeated heating and cooling, and to increase the strength of the brick so that cracks are less likely to occur. An object of the present invention is to provide a brick in which the cracked portion is hardly dropped even if the crack occurs.

[0009]

The gist of the present invention is to provide a smelting furnace for treating molten metal and a brick lined on the inner surface of a molten metal container such as a ladle for accommodating the molten metal. The brick has a metal wire buried perpendicular to the contact surface (hereinafter referred to as the operating surface). The embedding angle of the metal wire is desirably perpendicular to the operating surface. However, even if the metal wire is slightly inclined from the perpendicular, the effect obtained is not changed.

[0010] The purpose of embedding the metal wire is to reduce the temperature gradient of the brick by increasing the thermal conductivity of the brick to reduce the thermal stress generated, and to reinforce the brick to improve the strength. . In addition, the buried metal wire
Even if a crack occurs in the brick, it also plays a role of retaining the brick in the cracked portion and preventing falling off.

The state of cracks was investigated for tuyere bricks of steelmaking converters, which have the largest temperature gradient among the bricks for lining of molten metal containers and are liable to crack. A tuyere pipe is inserted into the tuyere brick at the center.
The tuyere pipe has a double structure, in which oxygen gas for refining flows through the inner tube, and carbon dioxide gas or the like flows through the outer tube. Therefore, the tuyere brick portion in contact with the tuyere pipe is subjected to strong cooling, and its temperature is reduced to about 500 ° C. even in the vicinity of the operating surface. On the other hand, the tuyere brick at a portion away from the contact surface with the tuyere pipe is heated by the heat conduction from the molten metal in the furnace to a high temperature. The temperature of this part is higher as it is closer to the inside of the furnace.
The temperature reaches a high temperature of about ° C, and the temperature gradually decreases toward the outside of the furnace. As described above, the tuyere brick has a low-temperature portion near the tuyere pipe and a high-temperature portion other than the tuyere pipe, and as a result, a temperature gradient is formed in the brick. This temperature gradient increases as it approaches the tip of the tuyere, and the generation of thermal stress is proportional to this. The direction of the thermal stress is parallel to the contact surface with the tuyere pipe, that is, perpendicular to the operating surface. The generated thermal stress exceeds the strength of the brick.
A crack is generated in the inside of m and almost parallel to the working surface, and the crack progresses.

[0012] Brick cracking also occurs in lining bricks in areas other than the brick around the tuyere. In this case, the repetition of the heat cycle of the furnace causes the occurrence of cracks. That is, the operating surface of the brick rises to a high temperature equivalent to the molten metal when the molten metal is contained in the furnace, but is cooled by being exposed to the atmosphere after discharging the molten metal. In such a situation, since the operating surface of the brick is rapidly cooled, a temperature gradient is formed between the operating surface and the brick, and thermal stress parallel to the operating surface is generated. The generated thermal stress exceeds the strength of the brick, causing a brick crack perpendicular to the working surface.

Therefore, in order to prevent the lining brick from being worn out, it is necessary to prevent a sharp temperature gradient from being generated, to increase the strength of the brick, and to prevent the brick from falling off even if a crack occurs. Is required. As a result of various studies on bricks satisfying these conditions, the following brick structure was conceived.

That is, by arranging an arbitrary number of metal wires inside to reinforce the brick, the generation of cracks is suppressed, and even if cracks occur, the bricks are dropped by the holding effect of the metal wires. To prevent. Furthermore, utilizing the high thermal conductivity of the metal wire, the cooling in the longitudinal direction is promoted, and the thermal gradient of the brick is reduced. It has been found that this makes it possible to extend the life of tuyere bricks and lining bricks installed at other locations.

[0015]

FIG. 1 shows the structure of a tuyere brick of the brick of the present invention. FIG. 1A shows a plan view, and FIG. 1B shows a vertical cross section taken along the line AA ′. A metal wire 1 is buried at regular intervals over the entire length of the brick in the longitudinal direction, and an opening 2 for tuyere insertion is provided at the center. In the case of tuyere bricks, thermal stress is generated perpendicular to the working surface, so the buried metal wire serves to reinforce the brick and is effective in preventing cracking of the brick.

FIG. 2 shows the structure of the wear brick of the brick of the present invention. FIG. 2- (a) shows a plan view,
FIG. 2- (b) shows a vertical section taken along the line AA '. In this case, there is no opening for tuyere insertion, and the whole has a structure in which metal wires are embedded at regular intervals. For wear bricks,
Since the thermal stress is generated in parallel with the operating surface, the burying of the buried metal wire has an effect not to reinforce the brick but to promote the cooling, and to reduce the temperature gradient to suppress the generation of the thermal stress.

There is no particular limitation on the material of the brick. Magnesia carbon brick generally used as tuyere brick of a converter may be used. In addition, alumina carbon brick and alumina-SiC-carbon brick can be used.

The material of the metal wire to be buried is not particularly limited, but a material that is hardly oxidized and melted even at a high temperature, has high strength, and has high thermal conductivity is desirable. For example, SUS30
4. Stainless steel such as SUS410 (JIS G 4309) is suitable.

The metal wire is buried perpendicular to the operating surface from the viewpoint of promoting heat removal to the outer periphery of the furnace and holding the brick when a crack occurs. It is desirable that the length of the metal wire be 70% or more in terms of the length of the brick from the operating surface, since cracking of the brick reaches up to about 60% of the length of the brick from the operating surface.

The distance between the central axes of the metal wires is preferably in the range of 10 mm to 50 mm. If the length is less than 10 mm, it takes time to manufacture the brick, and if it exceeds 50 mm, the heat conduction inside the brick is locally increased, and a new thermal strain is generated instead.

The diameter of the metal wire is 0.5 mm to 5 m.
m is desirable. If it is less than 0.5 mm, it is easy to cut, and if it exceeds 5 mm, it is liable to be damaged by the molten metal in contact.

FIG. 3 is a schematic view of a vertical section of a brick structure around a gas injection tuyere using the brick of the present invention. Permanent bricks (non-consumable bricks) 4 are piled inside the iron shell 3, and wear bricks (consumable bricks) 5 are piled further inside. However, the tuyere brick (consumable brick) 7 around the tuyere pipe 6 has an integral structure for convenience of opening a through-hole into which the tuyere pipe 6 is inserted at the center, and is directly piled from the iron shell.

[0023]

【Example】

(Example 1) Two double-tube tuyeres having an outer diameter of 19 mm were installed at the bottom of a 10-ton test converter, and each tuyere was surrounded by a vertical
mm, 150 mm in width, 600 mm in length, the material is magnesia carbon containing 25% of carbon, and two metal wires made of SUS304 having a length of 600 mm and a diameter of 2 mm are internally provided.
Tuyere bricks that were regularly buried in parallel with the longitudinal direction at a pitch of 5 mm were installed. 0.5 cubic meters per minute of carbon dioxide per minute from the outer tubes of the two double tube tuyeres at the bottom of the furnace, and oxygen from the inner tube at a standard condition of 0.5 cubic meters per minute.
I blew 3 cubic meters.

As a comparative example, a magnesia carbon brick having the same material and the same dimensions without a metal wire inside was installed as a tuyere brick. The bottom blowing gas was the same as the above conditions.

Under the above facility conditions, 10 tons of hot metal was charged and decarburization refining was repeated five times for about 20 minutes each. Molten steel temperature after decarburization refining is 1625-1655
C, the carbon content was 0.06 to 0.08%, and the slag amount was 60 to 75 kg per molten steel t. Since the last decarburization refining, the carbon content of the tuyere and the surrounding
% Of magnesia carbon tuyere bricks were compared.

When a tuyere brick in which a metal wire made of SUS304 is buried inside the brick is used, the tuyere wear amount and the tuyere brick wear amount are each 0.1 hour per hour of decarburization refining.
They were 5 mm and 0.45 mm.

On the other hand, SUS304 is placed inside the brick.
Of tuyere and tuyere brick when normal tuyere bricks without embedded metal wire are used are as follows.
They were 0.7 mm and 0.65 mm per hour, respectively. It is clear that the application of the brick of the present invention can reduce the amount of tuyere and tuyere brick wear by about 30%.

(Example 2) A 1-ton vertical shaft was placed on the belly of a 10-ton test converter.
50mm, 150mm wide, 600mm long,
Wear brick made of magnesia carbon material containing 15% carbon and having a length of 500 mm and a diameter of 1.5 mm and made of SUS410 metal wire buried regularly in parallel with the longitudinal direction at a pitch of 30 mm in three rows and three rows. Were installed partially. Carbon dioxide was blown at 0.5 cubic meters per minute under standard conditions and oxygen was blown at 0.3 cubic meters per minute under standard conditions from the two double tube bottom tuyeres.

As a comparison, magnesia carbon bricks of the same material and the same dimensions as those of wear bricks, which are not buried with metal wires inside, were installed at the same position on the furnace belly under the same bottom blowing conditions.

Under the above facility conditions, 10 tons of hot metal was charged, and decarburization refining was repeated five times for about 20 minutes each. Molten steel temperature after decarburization refining is 1620-1650
C, the carbon content was 0.06 to 0.09%, and the slag amount was 55 to 65 kg per molten steel t. After the last decarburization refining was completed, the amount of wear of the nine bricks installed at the positions was compared.

When a brick in which a metal wire made of SUS410 was embedded was used, the amount of wear of the brick was 0.35 mm per hour for decarburization and refining.

On the other hand, SUS410 is placed inside the brick.
When ordinary bricks without embedded metal wires are used, the amount of brick wear is 0.60 per hour per hour of decarburization and refining.
mm. It is clear that the amount of wear of the furnace belly brick can be suppressed by about 40% by applying the brick of the present invention.

[0033]

According to the brick of the present invention, since the metal wire is buried inside, the brick is hardly cracked, and it is hard to crack and drop off. Further, since heat removal from the furnace is promoted, generation of thermal stress is suppressed. As a result, the tuyere brick can greatly extend the life of the wear brick.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a tuyere brick in which a metal wire is embedded, (a) is a plan view, and (b) is a vertical sectional view taken along the line AA ′ of (a).

FIGS. 2A and 2B are diagrams showing a structure of a wear brick in which a metal wire is embedded, wherein FIG. 2A is a plan view and FIG. 2B is a vertical sectional view taken along line AA ′ of FIG.

FIG. 3 is a schematic vertical sectional view showing a brick structure around a gas injection tuyere.

[Explanation of symbols]

 1: Metal wire 2: Through hole for tuyere pipe insertion 3: Iron shell 4: Permanent brick 5: Wear brick 6: Tuyere pipe 7: Tuyere brick

Claims (1)

[Claims] 1. A brick for lining a container for a molten metal, comprising a metal wire buried perpendicular to a contact surface with the molten metal inside the brick.