JPH08143942A - Plug for gas blowing and its manufacture - Google Patents

Abstract

PURPOSE: To provide a plug for gas blowing which can control the number of using times and prolong the service life even in the case of being made of a castable refractory and can contribute to the stability of molten steel quality. CONSTITUTION: In the plug for gas blowing provided with plural gas passages 2 passing through the plug main body 1 made of the castable refractory in the axial direction, the worn part of the castable refractory in the plug main body is exfoliated in order from upper weak joined layer 5 for every steel receiving treatment and new surface to be blown with gas is formed by forming plural weak joined layers 5 extending in the radius direction in the plug main body at a prescribed interval in the axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas injection plug for injecting gas into molten steel metal such as molten steel and a method for producing the same, and particularly to a gas injection plug made of castable refractory which is a dense refractory and its production. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, a gas injection plug of this type has been disclosed in, for example, Japanese Examined Patent Publication No. 61-49274 and Japanese Utility Model Publication No. 2-221.
As disclosed in Japanese Patent No. 38, No. 38, a plug body made of a dense refractory material such as castable refractory material is provided with a plurality of axially penetrating holes or slit-shaped gas passages, and the porous refractory material The gas flow has a larger flow rate than that of a gas injecting plug made of a substance, in which gas is flown between particles, and the abrasion resistance is excellent. Therefore, the ratio is gradually increasing. The gas injection plug made of this castable refractory is manufactured by casting the castable refractory in a plug molding die having a plurality of gas passage forming members built therein.

[0003]

However, in the conventional gas-blowing plug made of castable refractory, molten steel or slag penetrates into the plug body at the time of steel receiving treatment, and peels off the upper part of the plug body at the next steel receiving treatment. The thickness of the plug varies, and generally cracks and peels off at a position considerably deeper than the damage depth, resulting in a problem that the life of the plug is shortened. In addition, there are cases in which peeling does not occur well, and there is the inconvenience of causing poor gas blowing and degrading the quality of molten steel.
On the other hand, in the case of a gas injection plug made of a porous refractory material, a damaged portion is peeled and worn by a certain thickness so that a new use surface is always exposed (for example, Japanese Utility Model Publication No. 6-5409).
JP-A-62-70158, JP-A-57-70158
No. 56540) is known, but all of them are impossible or difficult to manufacture by cast molding using castable refractories. Therefore, the present invention provides a gas injection plug capable of controlling the number of times of use and extending the useful life and contributing to the quality stability of molten steel even if it is made of a castable refractory, and a manufacturing method thereof. The purpose is to

[0004]

In order to solve the above problems, a gas injection plug of the present invention is a gas injection plug having a plurality of gas passages penetrating in the axial direction in a plug body made of castable refractory. A plurality of weak bonding layers extending in the radial direction are formed in the plug body in the axial direction at required intervals. It is preferable that the distance between the weak bonding layers substantially corresponds to the penetration depth of molten steel or slag into the plug body in one steel receiving process. Further, the method for producing a gas injection plug of the present invention requires a castable refractory when producing a gas injection plug in which a castable refractory is cast in a plug molding die having a plurality of gas passage forming members built therein. This step is characterized in that this step of performing weakening treatment on the upper surface after casting to the position is repeated a plurality of times. As the bonding weakening treatment, it is preferable to dry and cure the upper surface of each layer of the castable refractory material. The joint weakening treatment may be formation of a thin oil layer on the upper surface of each layer of the castable refractory material. Further, as the weakening treatment for bonding, coarse refractory particles may be laid on the upper surface of each layer of the castable refractory material.

[0005]

In the gas blowing plug and the method for manufacturing the same according to the present invention, the castable refractory in the plug body is sequentially arranged from the upper weak joining layer formed by the weakening treatment at the time of manufacturing for each one steel receiving treatment. The worn portion is peeled off, and a new gas blowing surface is formed.

The distance between the weak joining layers is determined by adding an appropriate depth to the depth of penetration of molten steel or the like into the plug body in a single steel receiving treatment in consideration of safety, for example, the maximum penetration depth of molten steel or the like. Saga 1
In the case of 0 mm, it is desirable to add about 3 mm and about 13 mm. Further, the drying and hardening treatment in the bonding weakening treatment on the upper surface of each layer of the castable refractory material is performed by applying hot air only to the upper surface of each layer of the castable refractory material for several tens of seconds to several minutes or by microwave heating. Further, the formation of a thin oil layer on the upper surface of each layer of the castable refractory in the joint weakening treatment is performed by applying machine oil, grease or other mineral oil, animal or vegetable oil, etc. to a thickness of about several μm. Furthermore, the laying of the refractory coarse particles in the bonding weakening treatment on the upper surface of the castable refractory is performed by the refractory coarse particles of the same material as the castable refractory and having a size of about 5 to 0.5 mm.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an embodiment of a gas injection plug of the present invention. This gas injection plug is a frustoconical plug body 1 made of a castable refractory which is a dense refractory, and a flat body provided through the plug body 1 in the axial direction (vertical direction in FIG. 1). A plurality of gas passages 2 having a slit shape with an arcuate cross section, and a plug body 1
A plurality of extending in the radial direction (the left-right direction in FIG. 1) in the plug body 1. The iron shell 3 covers the outer peripheral surface and the bottom surface of the plug 3 and the gas introducing pipe 4 attached to the bottom surface of the iron shell 3. The weak bonding layers 5 are formed at required intervals in the axial direction, for example, at intervals substantially corresponding to the penetration depth of molten steel or slag into the plug body 1 in one steel receiving process. Each weak bonding layer 5 is a portion where the castable refractory material forming the plug body 1 has a weak bonding strength, and enables partial peeling of the plug body worn by one steel receiving process. In FIG. 1, 6 is a gas reservoir for accumulating the gas introduced from the gas introduction pipe 4.

In order to manufacture the above gas injection plug for a 250-ton ladle, first, as shown in FIG. 2, a bottomed inverted truncated cone having a bottom inner diameter of 150 mm, a top inner diameter of 220 mm, and a height of 325 mm. In order to form the gas passage 2 having the above-described slit shape having an arcuate plane cross-section in the plug mold 11, a plurality of gas passage forming members 12 made of a stainless steel thin plate are appropriately built. Next, castable refractory 13 is placed in the plug mold 11 up to the required position, that is, 3 mm when the maximum depth of penetration of molten steel or slag into the plug body 1 is 10 mm in a single steel receiving treatment. Added 13
Castable refractories 13 after casting to a height of mm
As a bonding weakening treatment for weakening the bonding strength of the upper surface of the above, a treatment of drying and hardening the upper surface for 30 seconds with hot air at a temperature of 80 ° C. was performed. The hardening and curing of the upper surface of the castable refractory 13 promotes the hardening of the upper surface of the castable refractory 13, so that the weak bonding layer 5 that weakens the bonding with the castable refractory 13 to be cast next is formed. It was Next, after casting the castable refractory 13 and drying and hardening the upper surface of the castable refractory 13 to increase the height to 195 mm by repeating this 14 times, the castable refractory 13 is further 130 mm in consideration of safety during actual use. After casting the castable refractory 13 having a total length of 325 mm, the whole was heated and cured in the same manner as a normal castable product. Then, after the entire castable refractory 13 was heated and cured, each gas passage forming member 12 was pulled out and demolded to obtain the plug body 1. After that, the iron shell 3 and the gas introduction pipe 4 were set in the plug body 1 to obtain a 250 ton ladle gas injection plug.

The gas injection plug was set in a 250-ton ladle, and when the molten steel was received, argon gas was blown from the gas passage 2 at a rate of 800 to 1000 liters per minute to stir the molten steel. After the molten steel was cast after the stirring, the operation of receiving the next molten steel and stirring the gas was sequentially repeated. In the repetition of this operation, the castable refractory is sequentially peeled off at the positions of the weak bonding layers 5 of the first layer, the second layer, ... Thus, the gas stirring process could be carried out 15 times in total, and no gas stirring failure occurred during this period.
For comparison, when a gas agitation process was performed using a conventional gas injection plug having the same outer diameter dimension as that of the present invention and castable refractory at one time, castable refractory during steel receiving treatment The thickness of peeling is different,
In general, cracks occur at a position considerably deeper than the damage depth and peel off, so the plug life must be shortened.
Further, in some cases, the flaking did not occur well, which resulted in poor gas blowing, resulting in deterioration of the quality of the molten steel.

In the above embodiment, the case where the gas passage has the shape of a slit having a flat arc shape in cross section has been described, but the present invention is not limited to this, and the gas passage forming member having a plurality of rods, for example. It may be a hole-shaped one formed by using. Also in this case, the bonding weakening treatment for forming the weak bonding layer is not limited to the drying / curing treatment, but may be performed by forming a thin oil layer on the upper surface of the castable refractory or by the upper surface of the castable refractory. It may also be carried out by laying coarse particles of refractory.

[0011]

As described above, according to the gas injection plug and the method of manufacturing the same of the present invention, the upper weak bonding layer formed by the bonding weakening treatment at the time of manufacturing every one steel receiving treatment. Since the wearable parts of the castable refractory in the plug body are peeled off and a new gas blowing surface is formed, control of the number of times of use and extension of the service life of the castable refractory are achieved. be able to.
Further, by controlling the number of times of use, the safety of the gas stirring process can be ensured. Furthermore, there is no gas blow failure,
It has the effect of contributing to the quality safety of molten steel.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a gas injection plug of the present invention.

FIG. 2 is a cross-sectional view showing one step of manufacturing the gas injection plug of FIG.

[Explanation of symbols]

 1 Plug Body 2 Gas Passage 5 Weak Bonding Layer 11 Plug Mold 12 Gas Passage Forming Member 13 Castable Refractory

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Indo No. 1 Minamito, Ogakie-cho, Kariya city, Aichi Toshiba Ceramics Co., Ltd. Kariya factory Lamix Co., Ltd. Kariya Plant (72) Inventor, Tamotsu Wakita, No. 1 Nanto, Ogakie-cho, Kariya City, Aichi Toshiba Ceramics Corp., Kariya Plant

Claims (6)

[Claims] 1. A gas injection plug, comprising a plug body made of castable refractory and provided with a plurality of gas passages penetrating in the axial direction, wherein a plurality of weak bonding layers extending in the radial direction are formed on the plug body. A gas injection plug characterized in that it is formed at a required interval in the direction. 2. The gas injection plug according to claim 1, wherein the distance between the weak joining layers is substantially equivalent to the depth of penetration of molten steel or slag into the plug body in one steel receiving process. . 3. A gas injection plug for casting a castable refractory in a plug molding die having a plurality of gas passage forming members, wherein the castable refractory is cast to a required position and then the upper surface thereof is cast. A method for manufacturing a gas injection plug, which comprises repeating this step of performing a weakening treatment a plurality of times. 4. The method for manufacturing a gas injection plug according to claim 3, wherein the weakening treatment is a drying / curing treatment on the upper surface of each layer of the castable refractory material. 5. The method for manufacturing a gas injection plug according to claim 3, wherein the weakening treatment is formation of a thin oil layer on the upper surface of each layer of the castable refractory material. 6. The method for manufacturing a gas injection plug according to claim 3, wherein the weakening treatment is laying coarse refractory particles on the upper surface of each layer of the castable refractory material.