JP2002317221A - Gas blow tuyere structure for molten metal vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tuyere structure capable of reducing dent wear of a sleeve and a porous refractory and back-attack wear of a peripheral refractory. SOLUTION: In a gas blow tuyere of a molten metal vessel comprising a porous refractory (a) of a gas distribution part and a sleeve refractory (b) holding it, a working surface of the tuyere in contact with the molten metal is protruded from a working surface of a furnace bottom refractory (c) therearound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas blowing tuyere structure for a molten metal container having excellent durability.

[0002]

2. Description of the Related Art It is known that when refining a molten metal, oxygen or an inert gas or the like is blown in from a tuyere arranged at the furnace bottom of a molten metal container and stirred to improve the refining effect. However, the refining gas for stirring the molten metal is usually room temperature, which is extremely low with respect to the temperature of the molten metal, and the high temperature fluid abrasion due to the high flow velocity causes the porous refractory gas in the gas flow section. The wear of the object and the sleeve refractory that holds it increases. Since the tuyere life governs the life of the molten metal container, attempts have been made to suppress the wear of the tuyere and its surrounding refractories and extend the life.

Japanese Patent Application Laid-Open No. Hei 6-257948 discloses a tuyere and its surrounding structure having a two-stage structure of an upper stage (operating surface side) and a lower stage, and repairing only the worn upper stage to extend the service life. Aimed at. However, the service life of the molten metal container is simply increased by increasing the number of repairs, and it cannot be said that the life of the tuyere is substantially extended. Also, JP-A-8-24
Japanese Patent No. 6023 discloses that a tuyere sleeve is divided at least half in the longitudinal direction in the circumferential direction, and that the number of divisions is at least two or more. And the wear rate was reduced. However, this number of divisions is effective for damage to the sleeve in the early stage of operation, but when used for a long time, the molten metal tends to enter the joint joint, causing the sleeve to fall off or molten metal leakage The danger was high.

[0004]

SUMMARY OF THE INVENTION In order to clarify the problems that cannot be solved by the above-mentioned prior art, the wear from measuring the remaining thickness of the tuyeres (porous and sleeve refractories) in operation and the refractories around the tuyeres was investigated. The speed and the state of damage from each refractory after use were checked. Tuyere (porous and sleeve refractory)
Wear rate is 10 at the beginning from the start of operation to about 15 times.
It was found that the rate of erosion was as high as about 20 mm / time, but the rate of wear was as low as 2 to 5 mm / time after about 15 times. From the observation of the worn state, it was observed that the wear was dented from the sleeve refractory to the porous refractory. The former concave dent was presumed to be mainly caused by damage due to thermal shock, and it was confirmed from the measurement of the tuyere abrasion rate that it occurred particularly in the early stage of operation (between about 15 times from the start). After the middle stage of operation (after about 15 times), it was assumed that the surrounding refractory was worn (back attack) due to the gas ejected from the concave refractory porous refractory.

Accordingly, an object of the present invention is to provide a tuyere structure capable of reducing dent wear of a sleeve and a porous refractory and back attack wear of a surrounding refractory.

[0006]

SUMMARY OF THE INVENTION The tuyere structure of the present invention has been made in view of such a situation. The gist of the invention is that a tuyere in contact with the molten metal in a gas injection tuyere of a molten metal container composed of a porous (porous) refractory a in a gas flow portion and a sleeve refractory b holding the same. The present invention is characterized by having a structure in which the operating surface of the porous refractory protrudes from the surrounding furnace bottom refractory operating surface in a convex shape so that the tuyere life can be extended.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The porous refractory of the present invention and the sleeve refractory that holds the porous refractory have a structure that protrudes more than the refractory operating surface on the furnace bottom of the molten metal container. As a specific convex structure, as shown in FIG. 1, the porous refractory a and the sleeve refractory b have a cylindrical shape, and gas flows through a circular cross section of the porous refractory. As shown in FIG. 1, a tapered structure in which the diameter decreases toward the operating surface side, or a portion buried in the surrounding furnace bottom refractory c is tapered as shown in FIG. 2, and a portion protruding from the surrounding refractory is tapered. The same diameter may be used. This tapered structure has an effect of dispersing thermal stress due to thermal expansion and contraction of the surrounding furnace bottom refractory because the tuyere cannot be removed from the surrounding furnace bottom refractory c during operation. Further, as shown in FIG. 3, at the tuyere (sleeve and porous refractory) portion protruding from the surrounding furnace bottom refractory c, the shape of the sleeve refractory a may be changed to a small diameter in multiple steps. Alternatively, as shown in FIGS. 4 and 5, the height of the porous refractory a may be higher than that of the sleeve refractory b so that the working surface of the porous refractory a is further protruded. In any structure, the diameter of the gas flow section is determined so that a required gas flow rate can be secured.

The structure in which the tuyere protrudes in a convex shape has the following two effects. The first effect is to actively generate large wear in the early stage of operation, and to create a state in which the tuyere operating surface slightly protrudes from the furnace bottom or is at the same height after the middle period of operation when wear progresses slowly. This is the effect of extending the tuyere life. In the early stage of operation, wear caused by tensile stress generated inside the tuyere due to repeated thermal expansion and contraction due to thermal shock due to low temperature gas flow and hot operation is dominant. Since such wear occurs at a high temperature where the molten metal is in contact, it cannot be prevented only by improving the material and the like. However, for the wear confirmed up to about 15 times from the start of operation, the tuyere life is extended by protruding from the surrounding furnace bottom refractory by a height that does not affect the life even if the wear occurs I do. The second effect is porous and sleeve refractories,
Alternatively, the structure is such that the porous refractory is protruded, and there is an effect that abrasion wear of the refractory around the tuyere, that is, high-temperature fluid wear due to entrainment of gas bubbles can be avoided. The protrusion height of the porous or sleeve refractory may be obtained from the trend management of the wear rate in actual operation. For example, if it is confirmed in actual operation that the wear rate up to about 15 operations in the initial operation is about 10 mm / operation, the porous or sleeve refractory may be protruded by 10 mm / operation × 15 operations = 150 mm.

[0009]

[Example] Alumina-based porous material was used for the porous refractory, alumina-magnesia precast block was used for the sleeve refractory, and alumina-spinel irregular-shaped refractory was used for the furnace bottom refractory. A life test was carried out for this. As shown in FIGS. 6 and 7, the tuyere has a structure in which the tuyere having the features of the present invention is protruded from the surrounding furnace bottom refractory c in a convex shape. As a comparative example, the material is the same as the above, and as shown in FIG.
And a molten steel pot in which the operating surface of the sleeve refractory b was the same as the surrounding furnace bottom refractory c was prepared. FIG. 9 shows the result.
The wear rate of the tuyere of the present invention is about 10 times from the start of operation,
The same as that of the conventional tuyere structure,
After that, the wear rate became smaller than that of the conventional tuyere.
As described above, the tuyere structure of the present invention has an initial height higher than that of the conventional structure, and the number of times until the tuyere replacement is increased by about 30% from that of the conventional structure due to the realization of a low wear rate and the like.
The longevity of tuyere was demonstrated.

[0010]

The working surface of the tuyere (porous refractory and sleeve refractory) in contact with the molten metal has a structure that protrudes more convexly than the surrounding refractory working surface, so that it can be damaged by thermal shock during operation and It is possible to extend the tuyere life by avoiding the wear and the like caused by gas bubbles.

[Brief description of the drawings]

FIG. 1 shows a structure in which the outer peripheral surface of a porous and sleeve refractory has a tapered shape and protrudes from the surrounding refractory.

FIG. 2 shows a structure in which the outer peripheral surface of a porous and sleeve refractory has a tapered shape, and protrudes from the surrounding refractory so that the diameter of the protruding portion is the same.

FIG. 3 shows a structure in which the outer surfaces of a porous body and a sleeve refractory have a tapered shape, and the diameter of a protrusion of the sleeve refractory changes in multiple steps.

FIG. 4 shows a structure in which the outer peripheral surfaces of the porous and sleeve refractories have a tapered shape, and the porous refractories protrude more than the surrounding refractories.

FIG. 5 shows a structure in which the outer peripheral surfaces of a porous material and a sleeve refractory have a tapered shape, protrude more than surrounding refractories, and make the porous refractory more convex than a sleeve refractory.

FIG. 6 shows a tapered outer peripheral surface of a porous and sleeve refractory, and a protrusion of the sleeve refractory of 100 mm.
The structure where the diameter of the part changes at a height of 50 mm.

FIG. 7 shows a tapered outer peripheral surface of a porous and sleeve refractory, and the porous refractory is 10 times larger than the surrounding refractories.
Structure protruding 0mm convex.

FIG. 8 is a schematic view of a conventional tuyere refractory structure.

FIG. 9 shows the change in tuyere remaining thickness with respect to the number of tuyere uses.

[Explanation of symbols]

 a: Porous refractory b: Sleeve refractory c: Surrounding furnace bottom refractory

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K013 CA01 CA04 CA23 CC02 CF12 CF13 CF19 4K070 AB16 BA06 CG02

Claims (2)

[Claims] 1. A wing which comes into contact with a molten metal at a gas blowing tuyere of a molten metal container comprising a porous refractory (a) in a gas flow portion and a sleeve refractory (b) holding the porous refractory. A gas injection tuyere structure for a molten metal container, characterized in that the working surface of the mouth protrudes more convexly than the surrounding furnace bottom refractory working surface. 2. A gas injection tuyere of a molten metal container comprising a porous refractory (a) in a gas flow portion and a sleeve refractory (b) holding the porous refractory, wherein the porous refractory is provided. A gas injection tuyere structure for a molten metal container, characterized in that the operating surface of the gas turbine protrudes more convexly than the surrounding furnace bottom refractory operating surface.