JPH0692026B2 - Method for manufacturing lance for bubbling molten steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is arranged in a continuous casting tundish, and positively floats inclusions in molten steel flowing in the tundish to float on the surface of the molten steel. The present invention relates to a method for producing a lance for bubbling molten steel used when the lance is used to absorb the flux.

(Prior Art) For example, a tundish is required to have an important function of separating and removing slag and inclusions in molten steel to improve the quality of continuously cast steel.

As a method for removing inclusions in the tundish, a weir is provided in the tundish to control the molten steel flow in the tundish as disclosed in Japanese Utility Model Laid-Open No. 57-200353. For promoting floating separation of inclusions, and Japanese Patent Laid-Open Nos. 58-53357 and 58-116.
As disclosed in Japanese Patent No. 963 gazette, a conventional porous brick is provided on the bottom surface of the tundish, gas is blown into the molten steel through the porous brick, and the floating separation of inclusions in the molten steel is caused by the floating of the gas. There are ways to promote it, and all of these are being implemented.

However, the weir alone cannot float and completely remove fine inclusions that move along with the molten steel flow. Further, in the gas blowing from the conventional porous brick, since the pores of the porous brick have an irregular shape, even if the gas is blown at a low superficial velocity, the bubbles coalesce to generate nonuniform bubbles. Will end up. When non-uniform bubbles rise in the molten steel, a circulating flow occurs in the molten steel at the gas injection part and the effect of promoting the floating of inclusions is small, and the circulating flow spreads throughout the molten steel in the tundish, and conversely the flux on the molten steel surface or There is a great risk of involving slag.

Therefore, two of the present inventors have conducted research to find out a method for effectively removing inclusions in the molten steel in the tundish for continuous casting, and found that a uniform upward flow of bubbles in the molten steel in the tundish. It was found that the formation speed of inclusions in molten steel would be accelerated, and further research was conducted. As a result, we have found that a uniform upward flow of bubbles can be obtained by injecting gas into molten steel in a tundish through a perforated brick having upward through holes.

At that time, by setting the vent hole diameter and the vent hole interval for blowing the gas into the molten steel within an appropriate range, and further defining the superficial velocity of the blown gas within a certain range, a more uniform upward flow of bubbles in the molten steel. And the floating of inclusions in the molten steel is significantly promoted. The inclusions floating on the surface of the molten steel by such an upward flow are effectively absorbed by the flux floating here and separated from the molten steel, and since a uniform upward flow of bubbles causes a circulating flow in the molten steel. It does not occur, and therefore, there is no fear that the flux or slag on the surface of the molten steel will be entrained in the molten steel.

Furthermore, two of the inventors of the present invention continued to study the arrangement form of the gas dispersion in order to further improve the removal efficiency of inclusions, and found that all the molten steel flows had a uniform rising bubble zone. I found it important to go through.
From this, it can be said that it is advantageous to install a gas dispersion equal to the width of the tundish, but the perforated refractory that constitutes the gas dispersion is an integrated product from the viewpoint of the strength of the heat spall, cost, etc. It is often difficult to make and install large refractories.

On the other hand, as for the industrially important method of installing the gas dispersion, a method of embedding the gas dispersion as a tundish brick is generally considered, but as a result of research, the embedding method was used once ( 5 to 6 continuous casting) is the limit of brick life, and it is also found that there is a problem in terms of cost and work because the surrounding bricks are dismantled and replaced together with the replacement work.

Therefore, based on such knowledge, in a tundish for continuous casting of molten steel, the bottom surface of the tundish is installed at a position between the pouring port from the ladle and the pouring port into the mold. A gas dispersion composed of a perforated refractory in which the upward through holes are uniformly arranged, and provided on the upstream side of the gas dispersion so that the molten steel flow can form a uniform rising bubble zone from the gas dispersion. An apparatus for removing inclusions of molten steel is proposed in Japanese Patent Application No. 61-66649, which is characterized by comprising a weir that passes through, and is a third aspect of a lance type gas dispersion used in this apparatus. The one shown in the figure is shown.

That is, the gas dispersion 18 having an inverted T-shaped cross section,
Inert gas supply pipe 19 and subsequent branch pipe 20
And an air storage chamber 21 and a perforated refractory 22 provided at each tip of the branch pipe 20, and the entire perforated refractory 22 is protected by the refractory 23 except the tip. Is.
The lance type gas dispersion 18 is directly immersed in the tundish and placed on the bottom of the tundish.

(Problems to be Solved by the Invention) The above-mentioned invention is a useful method capable of solving the conventional problems, but a gas dispersion having a perforated refractory used in this method (hereinafter referred to as “lance for molten steel bubbling”) is used. It is extremely difficult to carry out this effective invention.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a molten steel bubbling lance that constitutes an apparatus proposed in Japanese Patent Application No. 61-66649.

(Means for Solving Problems) According to the present invention, after the outer frame is placed on the bottom plate, the air storage chamber forming cylinder is positioned and held in the outer frame at a required distance from the bottom plate. After placing an upper frame on the upper surface of the cylindrical body, a thin wire is stretched between the upper frame and the bottom plate at a required pitch, and then an irregular refractory material is filled between the outer frame and the bottom plate and dried. A first step of producing a block for molten steel bubbling, and a bottom plate is welded to each end face of the cylinders of the pair of molten steel bubbling blocks produced by the first step, and a T-shape is formed on these bottom plates. A second step of penetrating each branch end of the gas distribution pipe to be formed, and a wire mesh is wound around the main pipe part of the gas distribution pipe body assembled by the second step, and then the gas distribution pipe body is attached to the block. Positioned and held in the outer frame of the main body so that the end face and the tip of the main pipe are exposed Of the lance for molten steel bubbling, which is characterized in that it comprises a third step of filling the irregular frame-shaped refractory into the outer frame of the main body while applying a required vibration, and then drying. It is a manufacturing method.

(Operation) In the method for manufacturing a molten steel bubbling lance according to the present invention, after placing the outer frame on the bottom plate, the air storage chamber forming cylinder is positioned and held in the outer frame at a required distance from the bottom plate. Next, after placing an upper frame on the upper surface of the cylindrical body, a thin wire is stretched between the upper frame and the bottom plate at a required pitch, and then an irregular refractory material is filled between the outer frame and the bottom plate and dried. The first step of producing a molten steel bubbling block and the second step produced by the first step
A second step of welding a bottom plate to each end surface of the tubular body of the pair of molten steel bubbling blocks, and installing the respective branching tip end portions of the T-shaped gas flow pipes through these bottom plates; After the wire mesh is wound around the main pipe portion of the gas flow pipe body assembled in the second step, the gas flow pipe main body is positioned and held in the outer frame of the main body so that the end face of the block and the tip of the main pipe portion are exposed. Installed on the vibration table with
After that, it comprises a third step of filling the outer frame of the main body with an indefinite refractory while applying a required vibration and drying the block, so that it is provided with a molten steel bubbling block having pores of a constant pitch, and A lance for bubbling molten steel in which the branch portion functions as a weir can be easily manufactured.

(Example) Hereinafter, the method of the present invention will be described based on an example shown in the accompanying drawings.

FIG. 1 is an explanatory view of the method of the present invention, in which 1 is a bottom plate and 2
Is an outer frame placed on the bottom plate 1. In the present invention, however, the cylindrical body 3 for forming the air storage chamber is positioned and held in the outer frame 2 at a position spaced from the bottom plate 1 by a proper means (Fig. 1 (a)).

Next, the upper frame 4 is placed on the cylindrical body 3 and the upper surface set as described above, and the thin wires 5 are stretched at a constant pitch between the upper frame 4 and the bottom plate 1. The fine wire 5 may have a diameter of φ1 mm or less, and for example, a flammable material such as cellulose or a piano wire is used. This is because when the diameter exceeds φ1 mm, the bubble diameter becomes large and there is a high possibility of coalescence. The fine wire pitch is about 5 to 100 mm. If it is less than 5 mm, bubbles may coalesce, and if it exceeds 100 mm, the effect of floating inclusions is small.

Then, the irregular refractory material 6 is poured between the outer frame 2 and the bottom plate 1 (Fig. 1 (b)), and placed in a drying furnace in such a state, for example.
It is dried at 300 to 400 ° C. for 3 to 4 hours. At this time,
If a flammable wire is used as the thin wire 5, it will be burnt out.
The pores 7 having a diameter of 1 mm or less will be formed. Also, when using a piano wire, after drying, remove bottom plate 1, outer frame 2 and upper frame 4 and then pull them out to obtain φ1m in the same manner.
Since the pores 7 having a size of m or less are formed, the molten steel bubbling block 10 can be manufactured (FIG. 1 (c)).

This is the first step of the present invention.

In the molten steel bubbling block manufactured in this way,
The first view蓄気chamber bottom plate 9 provided on the upper surface of the cylindrical body 3 as shown in (d) the small diameter tube portion 9 ₁ a gas injection port is for welding.

Then, then a branch distal end of each of the gas flow pipe 11 through installed to the small diameter tube portion 9 ₁ of the block 10 gas flow pipe body 12 constituting the first view T-shaped as shown in (e) To manufacture.

This is the second step of the present invention.

Next, the gas flow pipe main body 12 assembled by the second process
Wire mesh 13 is wound around the main pipe portion and the branch portion. This wire mesh 13 is for providing a space in a gap with an irregular-shaped refractory material 14 described later in order to absorb thermal strain during preheating before casting and during casting. Then, the gas flow pipe main body 12 around which the wire net 13 is wound is positioned and held in the main body outer frame 15 having the same shape as this, that is, a T-shape. At this time, the end surface of the block 10 and the tip of the main pipe portion are exposed from the outer frame 15 of the main body.

After that, the main body outer frame holding the gas flow pipe main body 12 in position
15 is installed on the vibration table 16, and while the vibration of about 2 to 20 mm in amplitude is applied, the irregular shape refractory material 14 is placed inside the outer frame 15 of the main body.
Is poured (Fig. 1 (f)). The vibration is applied in order to prevent formation of a cavity in the amorphous refractory material 14 during pouring. Then, after the pouring is completed, it is left to stand, and when the irregular-shaped refractory 14 is solidified, the outer frame 15 of the main body is removed and put into a drying furnace, for example, at 300 to 400 ° C. for 3 to
The lance for molten steel bubbling according to the present invention is obtained by drying for 4 hours (Fig. 1 (g)).

This is the third step of the present invention.

Next, the result of manufacturing the molten steel bubbling lance by the method of the present invention will be described.

In the outer frame 2 on the bottom plate 1 shown in FIG. 1, a steel cylinder 3 having a thickness of 1.2 mm was held at a distance of 10 mm from the bottom plate 1, and then the upper frame 4 was placed.

A flammable thin wire 5 having an outer diameter of φ0.2 mm and made of cellulose is stretched between the bottom plate 1 and the upper frame 4 at a pitch of 15 mm, and the refractory material 6 having the components and properties shown in Table 1 below is formed. Poured.

Then, this was put into a drying oven and dried at 300 ° C. for 4 hours. As a result, the fine wire 5 was burnt out to become pores 7 having a diameter of 0.2 mm. The molten steel bubbling block 10 having the above can be manufactured.

Next, a 1.2 mm-thick steel accumulator bottom plate 9 is welded to the molten steel bubbling block 10, and then the outer diameter φ27.2 mm,
A gas flow pipe main body 12 is formed by penetrating and installing each branching end of a gas flow pipe 11 formed in a T-shape using a gas pipe (20ASTPG, schedule 80) having an inner diameter of φ19.4 mm so as to penetrate the small diameter pipe portion 9 _1. Was manufactured.

Finally, after the wire mesh 13 is double wound around the main pipe portion of the gas flow pipe main body 12, it is set on the vibration table 16 together with the main body outer frame 15, and the components shown in Table 2 below while giving an amplitude of 5 mm,
An unshaped refractory material 14 was poured.

Then, after the amorphous refractory 14 hardens, the outer frame 15 of the main body
The lance of the present invention was manufactured by removing the above and placing it in a drying oven and drying at 300 ° C. for 4 hours.

Next, the molten steel bubbling lance was attached to the tundish 8 as shown in FIG. 2, and bubbling was performed during casting.

At this time, as a result of bubbling at a superficial velocity of 3 to 4 cm / sec, hydrogen-induced cracking due to inclusions in the HIC-resistant steel was few, which had occurred in the past. In addition, inclusions were about 30% of the conventional content, and good results were obtained.

As an effect of the present invention, the forced floatation of inclusions and the refractories at both branch portions also serve as a weir, which is advantageous for floatation.

It was also found that it is possible to omit the tunnel weir that was previously used.

(Effect of the invention) As described above, in the method for manufacturing a molten steel bubbling lance according to the present invention, after the outer frame is placed on the bottom plate, the air storage chamber forming cylinder is provided in the outer frame at a predetermined distance from the bottom plate. Position and hold, then place the upper frame on the upper surface of the cylindrical body, and then stretch a thin wire at a required pitch between the upper frame and the bottom plate, and then form an irregular shape between the outer frame and the bottom plate. A first step of manufacturing a molten steel bubbling block by filling with a refractory and drying, and a bottom plate is welded to each end surface of the cylindrical body of the pair of molten steel bubbling blocks manufactured by the first step. At the same time, a second step of penetrating each branch tip of the T-shaped gas flow pipe on these bottom plates, and winding a wire mesh around the main pipe part of the gas flow pipe body assembled by the second process, The end face of the block and the leading end of the main pipe are exposed in this gas flow pipe main body. It is installed on the vibration table in a state where it is positioned and held in the outer frame of the main body, and after that, while the required vibration is applied, the outer frame of the main body is filled with the amorphous refractory material and the third step of drying is provided. Therefore, a molten steel bubbling block having pores with a constant pitch is provided, and a lance for molten steel bubbling in which the branch part functions as a weir can be easily manufactured. By inserting this lance from the upper surface of the tundish, leakage can be prevented. The danger of steel and the complexity of construction work can be eliminated. Furthermore, both branches form a weir, which makes it advantageous for floating inclusions, and the bubbling range has increased compared to the past.

[Brief description of drawings]

1 (a) to 1 (g) are drawings for sequentially explaining the method of the present invention, and FIG. 2 is an explanatory view of the installation position of a lance for molten steel bubbling produced by the method of the present invention on a tundish,
FIG. 3 is a schematic diagram of the lance previously proposed by two of the inventors. 1 is a bottom plate, 2 is an outer frame, 3 is a cylindrical body, 4 is an upper frame, 5 is a thin wire,
6 and 14 are amorphous refractories, 7 are pores, 9 is a bottom plate, 10 is a block, 11 is a gas flow pipe, 12 is a gas flow pipe main body, 13 is a wire mesh, and 15 is an outer frame of the main body.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Keiji Nakajima 1-3-3 Nishi-Nagasumotodori, Amagasaki City, Hyogo Prefecture Sumitomo Metal Industries, Ltd. Research Institute (72) Inventor Tagio Sugino Ogakie Kariya City, Aichi Prefecture Machi Nanto No. 1 Toshiba Ceramics Co., Ltd. Kariya Factory (72) Inventor Koji Higashiyama Kariga City, Aichi Prefecture Ogakie Town Nanto No. 1 Toshiba Ceramics Co., Ltd. Kariya Factory (72) Inventor Hideharu Yamamoto Kariya City, Aichi Prefecture No. 1 Minamifuji, Ogakie-cho Kariya Plant, Toshiba Ceramics Co., Ltd.

Claims (1)

[Claims] 1. After placing an outer frame on the bottom plate, a storage chamber forming cylinder is positioned and held in the outer frame at a required distance from the bottom plate, and then an upper frame is placed on the upper surface of the cylinder. First, a thin wire is stretched between the upper frame and the bottom plate at a required pitch, and then an amorphous refractory material is filled between the outer frame and the bottom plate and dried to produce a molten steel bubbling block. Step, and a bottom plate is welded to each end face of the cylindrical body of the pair of molten steel bubbling blocks manufactured by the first step, and each branching tip of each T-shaped gas distribution pipe is formed on the bottom plate. A second step of penetrating and installing the portion, and after winding a wire mesh around the main pipe portion of the gas flow pipe body assembled by the second step, the gas flow pipe body is exposed at the end face of the block and the tip of the main pipe portion. Place it on the vibrating table with it positioned and held in the outer frame of Required to impart vibrations filled with castable refractory in the main body outer frame while the third step method for producing a lance molten steel bubbling, characterized by comprising comprises a drying after that.