JPH0813019A - Refractory for blowing gas, having through hole - Google Patents

Abstract

PURPOSE:To provide the structure of a new type refractory for blowing gas, in which the leakage of steel caused by the erosion of a brick in use is prevented and the safety and the high durability can be guaranteed and the end point of use can be judged. CONSTITUTION:The refractory for blowing gas having a through hole is composed of two-step structure of a high durability-dense quality refractory 2 having <=0.3mm thickness of the through hole 1 at the upper step and a dense quality refractory 4 having <=0.6mm thickness of the through hole 3 and a little deteriorated metal infiltration at the lower step. The upper step refractory is effective in the prevention of molten steel invasion and in the metal infiltration resistance (high durability) and the lower step refractory has the function to intentionally make the molten steel, to intrude in to cause metal infiltration and permeability hindrance. By this constitution, as a result, the end point can be judged. Further, the permeable refractory can be arranged at the middle step or the lowermost step to make the three-step structure for the absolute defenses to prevent the leakage of steel even for the molten steel having low viscosity and easy-to- intrude into the through hole in the some operational condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas blowing refractory called a porous plug which is attached to the bottom of a converter, a ladle or the like and used for molten steel treatment.

[0002]

2. Description of the Related Art Such a gas blowing refractory is intended to homogenize the temperature of molten steel accompanying stirring of molten steel by injecting gas into molten steel, homogenize molten steel components, and improve secondary refining effect. Widely used for floating non-metallic inclusions.

However, the gas-blowing refractory material suffers from a serious accident called steel leakage when it is used beyond its use limit because melting damage progresses during operation and the operating surface deteriorates. The following measures have been proposed as means for ensuring the safety against steel leakage in the gas-blowing refractory due to this melting damage.

(1) A method for determining the replacement time based on the change in the shape of the gas protruding surface (Japanese Patent Laid-Open No. 63-76813),
(2) A method in which a refractory dense block having low air permeability is embedded in the lower central part of the porous plug, and the replacement time is determined by the time when the central part looks red and the peripheral part appears black (Japanese Patent Laid-Open No. 63-76813). ), (3) A composite type in which a concave portion is provided on the bottom surface of the porous brick main body, and a porous brick having a larger air permeability than the porous brick main body is incorporated in the concave portion (Japanese Utility Model Publication No. 2-48243), (4)
One porous brick having a plurality of through-holes, with a half-through hole penetrating through halfway (Actual No. Sho 63-9
No. 0562), (5) When melted over the safety limit, molten metal under refining is inserted into the gas blowing hole to obstruct ventilation, thereby notifying the replacement time (Actual No. Sho 63-5).
(6963), (6) A porous material that becomes a highly viscous glass is placed under the porous brick by the heat of molten steel, and fills the gas blow-out hole when it melts beyond the safety limit (JP-A-63-76813). Gazette), (7) one having a two-stage structure in which a refractory having a through-hole structure is arranged in the upper stage, and a breathable porous refractory is arranged in the lower stage (Actual No. Sho 63-162854)
Gazette), (8) One refractory material or a plurality of refractory materials divided in a plane parallel to the gas blowing direction and juxtaposed and combined with each other, and having a slit-like through hole (Jpn.
No. 4434) is proposed.

However, all of these structures relate to whether or not the porous plug can be continuously used. And
In the above structures (1) to (3), since the shape and color tone of the bricks in a red-hot state located several meters apart are visually determined, the results vary depending on the determiner, and the accuracy is not good.

Similarly, in the case of the structure (4), the change in the gas injection amount during use is visually determined, so that the reliability is poor.
Further, in this case, even if it is determined that continuous use is possible, steel leakage may occur due to brick meltdown during use, and safety cannot necessarily be said to be high.

Next, in the structures (5) and (6) that obstruct the ventilation, the temperature range of the actual operation is wide, and therefore it is often difficult to accurately determine the end point of allowable use.

Further, in the structure (7), there is no clear regulation on the shape and size of the vent hole, which causes a problem of backflow of molten steel in some cases.

Furthermore, in the structure of (8), the question of the safety against steel leakage still remains.

[0010]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a safe and highly durable refractory structure for gas injection capable of preventing steel leakage due to melting damage of bricks in use and determining the end point of use. To do.

[0011]

DISCLOSURE OF THE INVENTION The present invention is a gas having an upper and lower structure in which a refractory having a through hole is arranged in an upper stage, and a breathable porous refractory or a refractory having a through hole is arranged in a lower stage. The blowing refractory is characterized in that a dense refractory having a through hole having a thickness of 0.3 mm or less is arranged in a portion in contact with the molten steel of the upper refractory.

In this structure, the breathable refractory can be arranged in the middle or the bottom to form a three-stage structure.

The refractory material in the lower stage above secures a ventilation amount,
A slightly porous refractory is used rather than a dense refractory in the upper stage so that molten steel may enter.

[0014]

The dense refractory material in contact with the molten steel can prevent the molten steel from entering and ensure the gas blowing property, that is, the reliability of bubbling.

In the dense refractory material in the lower stage, the amount of ventilation can be secured, the penetration of molten steel is caused, the ventilation is obstructed, and the use limit can be judged.

Further, by providing a breathable refractory material under the lower bricks or between the upper and lower bricks to form a three-tiered structure, leakage steel can be prevented even for molten steel that easily penetrates through holes having low viscosity. It becomes possible to do.

[0017]

EXAMPLES Example 1 FIG. 1 shows a structure 10 of a gas blown refractory having through holes of the present invention made for testing. In the figure,
It consists of an upper dense refractory 2 having a through hole 1 and a lower dense refractory 4 also having a through hole 3, and a dense castable 5 is provided on the side surface thereof, and the whole is made of a metal cylinder 6 Has a structure supported by.

The dense refractory 2 in the upper stage can prevent the infiltration of molten steel and is gas-blown, that is, bubbling is provided with through holes having a small metal infiltration, for example, Al.
₂ O ₃ -MgO, which is a highly durable compact refractory material, the dense refractory material 4 in the lower stage can secure an air flow rate, cause molten steel to invade, obstructing air flow, and enable use limit judgment. The metal infiltration by the through holes 3 is slightly larger than that of the upper dense refractory material.

Example 2 FIG. 2 shows a refractory structure 20 in which three layers of breathable refractories 7 are arranged under the dense refractory 4 in the lower stage below the dense refractory 2 in the upper stage. Show. These refractories have a structure in which a dense castable 5 is provided on the side surface and is housed in a metal tubular body 6.

Example 3 FIG. 3 shows another example 30 of the three-stage structure. As shown in FIG. 3, the breathable refractory 7 is replaced by the upper dense refractory 2,
It is also possible to have a three-stage structure arranged between the dense refractory materials 4 in the lower stage.

The upper refractory 2 in each of the above embodiments
And the through holes 1 and 3 formed in each of the lower refractories 4 can be arbitrarily provided, but FIGS. 4 to 6 are sectional views (a1 to a2) and (b-1) of this formation mode. ~ 3).

The conditions of the through holes were examined in the gas-blowing refractory material shown in each of the above examples.

In selecting the thickness of the through-hole, a test assuming an actual furnace was carried out to find a thickness capable of preventing metal intrusion.

As a test method, the thickness is 0.3,
Sample shape φ50-180 with 0.6 and 0.9 mm
A L-stiffness refractory was prepared and submitted for testing.

The conditions are steel type SS41, molten steel amount 280K.
g, Ar gas was used as the blowing gas, the blowing time was 2 minutes, and the molten steel was left at a temperature of 1600 ° C. for 60 minutes after the gas was blown to intentionally cause the molten steel to enter the through holes, and then the molten steel was discharged.

Table 1 shows that the sample after cooling was collected and the state of penetration of molten steel into the through hole was examined by X-ray.

[0027]

[Table 1] As a result of the above-described test on the depth of molten steel penetration depending on the thickness of the through hole, the thickness of the through hole capable of preventing the penetration of molten steel is 0.
It was found to be 3 mm or less. Further, from the viewpoint of gas injection reliability, it is desirable that the thickness is between 0.2 and 0.3 mm.

Further, in consideration of the through-hole structure in the lower part, it is considered appropriate that the through-hole thickness in the lower part is 0.6 mm or less in order to prevent the ventilation due to the invasion of molten steel and enable the end point determination. To be Among them, the range of 0.4 to 0.6 mm is desirable from the viewpoint of gas injection reliability.

The material of the highly durable castable for the purpose of preventing metal infiltration into the base material castable portion forming the through hole was examined.

Table 2 shows the test results.

[0031]

[Table 2] Castable to prevent metal infiltration is resistant to metal infiltration,
Both corrosion resistance was good.

A refractory material having a thickness of 0.2 to 0.3 mm was made into the upper structure by using the materials shown in the above-mentioned examples.

The lower part is made of a conventional material such as high-purity alumina aggregate and has a thickness of 0.4 to 0.6 m.
formed to m.

Based on the above test results, as shown in FIGS. 4 to 6, a through-hole type new structural product was selected according to operating conditions and supplied to an actual furnace.

In the high-alumina castable material in the lower part, molten steel is intentionally caused to invade and air flow is obstructed.

[0036]

According to the present invention, the following effects can be obtained.

(1) It is possible to obtain a gas-blown refractory which can prevent the occurrence of steel leakage due to melting damage.

(2) Since the end point can be determined, safety and high durability can be guaranteed.

(3) Bubbling High durability can be guaranteed without impairing reliability.

(4) The service life of the refractory structure for blowing gas is extended.

(5) Since the castable body with high durability, which is excellent in mechanical and thermal characteristics and metal infiltration property, is used in the main body, the service life as a structure is extended, and as a result, the molten steel treatment efficiency is improved as a whole. Can be improved.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 shows another embodiment of the present invention.

FIG. 3 shows another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a mode of forming the through holes of the upper, middle and lower refractories in the present invention.

FIG. 5 is a cross-sectional view showing a mode of forming the through holes of the upper, middle and lower refractories in the present invention.

FIG. 6 is a cross-sectional view showing a mode of forming the through holes of the upper, middle and lower refractories in the present invention.

[Explanation of symbols]

10, 20, 30 Structure of a gas-filled refractory material having through-holes according to the present invention 1,3 Through-holes 2 Upper-stage dense refractory material 4 Lower-stage dense refractory material 5 Dense castable 6 Metal cylinder 7 Ventilation Refractory

Claims (2)

[Claims] 1. A gas-injection refractory having an upper and lower structure in which a refractory having a through hole is arranged in an upper stage and a porous refractory having a through hole or a refractory having a through hole is arranged in a lower stage. A refractory for gas injection having a dense refractory having a through hole having a thickness of 0.3 mm or less provided in a portion in contact with the molten metal of the refractory. 2. The structure according to claim 1, wherein the gas-permeable refractory has a through hole having a breathable refractory arranged in a middle or lowermost stage to form a three-stage structure.