JPH0669261U - Immersion pipe structure of vacuum degassing tank - Google Patents

Abstract

(57) [Summary] [Purpose] The inert gas supplied to the immersion pipe is efficiently made into small bubbles in the molten steel without concentrating on the refractory surface,
Also, by suppressing the refractory erosion damage above the inert gas injection position, the dip pipe replacement frequency is reduced,
Furthermore, the degassing refining process time is shortened by increasing the melt reflux rate. [Composition] An inclined surface with an increased inner diameter is formed upward from the position where the gas supply hole is formed on the wall surface of the refractory lining, or the jet outlet of the gas supply hole is provided with the lining refractory above the spout. A protruding portion is formed so as to protrude inward from the wall surface.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a submerged pipe structure of a vacuum degassing tank used in a reflux type vacuum degassing method.

[0002]

[Prior art]

 The reflux vacuum degassing method, which is also called the RH method, is applicable to the production of high-purity steel materials because it can reduce impure gas, nonmetallic inclusions, etc. in the steel.

The vacuum degassing tank to be used is provided with two dipping pipes composed of an ascending pipe and a descending pipe, and the ascending pipe and the descending pipe are immersed in molten steel such as a ladle for use. By depressurizing the inside of the vacuum degassing tank, the molten steel is sucked up from the riser pipe, an inert gas is blown from the gas inlet for recirculation, and the molten steel is guided into the vacuum degassing tank by utilizing the gas levitation force. Then, the molten steel is circulated by being lowered from the downcomer pipe, and degassing refining processing is performed.

In the reflux type vacuum degassing method, various measures have been taken so far to increase the molten steel processing capacity. As one of them, the inner diameter of the entire immersion pipe is increased with the aim of increasing the reflux flow rate. Is being done.

However, such a method suffers from various restrictions due to problems with other related equipment, requires remodeling of the equipment, and the lining layer of the immersion pipe is thin, resulting in a short life. The replacement work becomes complicated.

Further, in order to increase the reflux speed and shorten the degassing treatment time, an immersion pipe of a vacuum degassing tank having a plurality of gas blowing holes is disclosed in Japanese Utility Model Laid-Open No. 1-164752.

FIG. 5 is a vertical cross-sectional view showing the structure of the immersion pipe 20 disclosed in the publication, in which 21 is a split fired refractory material, 22 is an outer castable metal, 23 is a core metal, and 24 is It is a mounting flange. The supplied inert gas is blown into the molten steel in the molten steel flow passage 26 sucked up by a degassing tank (not shown) from the gas blowing hole 25 of the fired refractory 21.

In order to efficiently perform degassing and removal of non-metallic inclusions by promoting recirculation of molten steel during such gas blowing, it is necessary to reduce the bubble diameter of the inert gas to be blown in the molten steel. Is required.

However, since the inert gas blowing hole 25 is on the same plane as the wall surface of the refractory lining 21 in the dipping pipe 20, the dipping pipe 20 becomes large bubbles due to the collection of gas rising along the wall surface and blows into this. Due to the so-called back attack caused by the turbulent flow of molten steel rising together with the generated inert gas, there is a problem that the refractory erosion damage becomes large over about 200 mm above the gas injection position.

[0010]

[Problems to be solved by the device]

 The problem to be solved in the present invention is that the inert gas supplied to the immersion pipe is efficiently made into small bubbles in the molten steel without gathering in the vicinity of the refractory surface, and the refractory above the inert gas injection position is By suppressing erosion damage, it is possible to reduce the frequency of replacement of the immersion pipe, and to accelerate the molten steel circulation speed to shorten the degassing refining process time.

[0011]

[Means for Solving Problems]

 The present invention relates to a submerged pipe of a vacuum degassing tank in which a gas injection hole for injecting an inert gas is provided on a wall surface of a refractory lining which forms a molten steel flow passage, from a position where the gas injection port of the gas injection hole is arranged. The above problem was solved by forming an inclined surface in which the inner diameter of the molten steel flow passage was enlarged upward.

The angle of inclination of the inclined surface is preferably within about 18 degrees, particularly 3 to 12 degrees, with respect to the vertical line in the molten steel flow passage of the rising pipe or the extension line of the lower wall surface of the gas injection port. Good

Further, in a submersion pipe of a vacuum degassing tank in which a gas injection hole for injecting an inert gas is provided on a wall surface of a refractory lining which forms a molten steel flow passage, the injection port of the gas injection hole is located above the injection port. It is also possible to form a projecting portion projecting 30 to 50 mm inside the wall surface of the refractory lining.

As the lining refractory material, there are used fired bricks, unfired bricks, blocks of an amorphous material, and the like.

[0015]

[Action]

 It is known that the inert gas blown into the molten steel generally rises and diffuses within an angle range of about 24 degrees (12 degrees from the center line) upward as shown in FIG. The present invention utilizes this property.By letting gas flow toward the circumferential side of the lining along the diffusion angle of the inert gas, gas aggregation is eliminated, and the rising rate of molten steel is accelerated, and the inert gas blown in is also accelerated. It is possible to efficiently recirculate molten steel with gas.

FIG. 4 is a diagram showing the relationship between the inclination angle and the reduction amount of carbon in steel. As shown in FIG. 4, particularly when the inclination angle is in the range of 3 to 12 degrees, an excellent effect can be seen. Was given. The upper limit of the tilt angle is preferably about 18 degrees. Above this, as a structural problem, the lining layer above the gas inlet of the riser becomes thinner, resulting in a shorter life.

In addition, such an effect can be obtained by forming the gas inlet of the gas injection hole 30 to 50 mm inward from the wall surface of the lining refractory at the upper portion of the injection opening without forming the above-mentioned inclined surface. Can be played similarly.

In other words, by forming the inclined surface or the protruding portion, the inner diameter of the upper portion of the gas inlet of the rising pipe becomes a size that matches the gas diffusion angle, so that the molten steel that rises by reducing the collection of inert gas bubbles It reduces turbulent flow, reduces erosion, and accelerates perfusion velocity.

[0019]

【Example】

 FIG. 1 is a vertical sectional view of a dip tube structure of a vacuum degassing tank showing a first embodiment of the present invention.

In the figure, 1a, 1b and 1c are three-tiered refractory linings, 2 is an outer castable, and 3 is a core for holding a refractory and a gas seal formed in the outer castables 2. Gold and 4 are mounting flanges.

The refractory linings 1 a, 1 b, 1 c form a molten steel flow passage 5 having a horizontal horizontal section inside. A gas injection hole 6 communicating with an inert gas injection pipe (not shown) is formed in the middle lining refractory 1b. Further, the inner diameter is increased from D ₁ to D ₂ from the position where the gas inlet 7 of the refractory lining 1b is formed to the upper side, and this is the inclined surface 8. In this embodiment, the inclined surface 8 is formed so as to form an angle of 12 degrees with respect to the extension line of the lower wall surface from the position where the gas injection port 7 is provided.

In the above-mentioned configuration, the inert gas supplied from the inert gas supply pipe is supplied from the inert gas injection hole 6 of the lining refractory 1b to the inside of the molten steel flow passage 5 in a vacuum degassing tank (not shown). It is blown into the molten steel that is sucked up by. At that time, since a 12-degree inclined surface 8 is formed on the wall surface above the inert gas inlet 7, the injected inert gas rises while diffusing without being biased to the inclined surface 8. As a result, the collection of bubbles is eliminated and the recirculation velocity can be increased. In addition, the inert gas diffuses and rises to match the angle of the inclined surface 8 above the gas inlet 7, and the turbulent flow of molten steel due to the inert gas and the lining refractory wall surface above the gas inlet 7 is reduced, resulting in erosion. The effect is reduced and the dip tube replacement frequency is reduced.

When the dip pipe shown in FIG. 1 was used in an actual RH furnace tank, it took 20 minutes for the conventional structure to reduce the carbon content in steel to 10 ⁻³ × 15% (minute / charge). It was possible in 15 minutes. Further, the refractory life of the immersion pipe is improved to 110 times from the conventional treatment of 45 to 50 times, the frequency of immersion pipe replacement is reduced, and the vacuum degassing treatment capacity can be greatly improved with a simple structure. did it.

Further, FIG. 2 is a vertical sectional view showing a second embodiment of the present invention. In the embodiment shown in FIG. 2, the parts corresponding to the immersion pipe structure of the vacuum degassing tank of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The dip tube of this embodiment is composed of four stages of first, second, third and fourth refractory linings 10a, 10b, 10c and 10d, and is used as a third refractory lining 10c. An inert gas blow-in hole 6 is provided, and further, a protrusion 11 is formed by projecting 30 mm inward from the wall surfaces of the first, second, and fourth refractory linings 10a, 10b, 10d to form a gas blow-in port. 7 is provided.

It should be noted that the gas injection hole 6 is bored upward so that the rising molten steel flow can be easily injected, and the projection 11 is also angled to reduce the resistance of the molten steel flow.

Even with such a structure, due to the step between the protruding portion 11 of the third refractory 10c and the second refractory 10b, the refractory and the inert gas bubbles are blown to the upper part for about 200 mm. It is possible to reduce the generation of turbulent flow of the contained molten steel, and it is possible to obtain the same effect as that of the embodiment of FIG. 1 having a tilt angle of 12 degrees. In particular, the shape of the refractory lining is simpler than that of Fig. 1.

[0028]

[Effect of device]

 The present invention has the following effects.

(1) Due to the formation of the inclined surface or the protrusion, the inert gas is effectively diffused, the specific gravity of the molten steel in the rising pipe can be uniformly reduced, the reflux velocity is improved, and the molten steel degassing reaction is improved. Acceleration has been achieved and it has become possible to improve the efficiency of degassing and refining.

(2) Since the back attack of the blown gas is reduced, the erosion of the refractory is reduced, and the life of the immersion pipe is improved.

(3) The vacuum degassing treatment capacity was greatly improved by reducing the frequency of immersion tube replacement.

(4) Construction can be performed without changing the conventional metal structure of the immersion pipe.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a dip tube structure of a vacuum degassing tank according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view of a dip tube structure of a vacuum degassing tank according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a gas diffusion state in molten steel.

FIG. 4 is a diagram showing a relationship between an inclination angle and a reduction amount of carbon in steel.

FIG. 5 is a vertical sectional view showing a conventional immersion pipe structure.

[Explanation of symbols]

 1a-1c, 10a-10d Inner refractory 2 Outer castable 3 Core metal 4 Flange 5 Molten steel flow passage 6 Gas injection hole 7 Gas injection port 8 Inclined surface 11 Projection part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Takashi Miki Inventor Takashi Miki, Kashima-cho, Kashima-cho, 3 Oita, Kashima Steel Works, Sumitomo Metal Industries, Ltd. Address: Sumitomo Metal Industries Co., Ltd. Kashima Works

Claims (2)

[Scope of utility model registration request] 1. A submerged pipe of a vacuum degassing tank having a gas injection hole for injecting an inert gas in a wall surface of a refractory lining which forms a molten steel flow passage, in which a gas injection port of the gas injection hole is provided. From the above, an immersion pipe structure of a vacuum degassing tank, characterized in that an inclined surface in which the inner diameter of the molten steel flow passage is enlarged is formed. 2. In a dip tube of a vacuum degassing tank having a gas injection hole for injecting an inert gas on a wall surface of a refractory lining which forms a molten steel flow passage, the gas injection port of the gas injection hole is the same. A submerged pipe structure for a vacuum degassing tank, characterized in that a projecting portion is formed so as to project inward from a wall surface of the molten steel flow passage at an upper portion of the injection port.