Socket installation structure of refractory article

Abstract

A socket installation structure of a refractory article is designed to prevent gas leakage therein. A first flange is provided between an outward end and an inward end of a socket, and a face of the first flange on the side of an inward end thereof is bonded to an article body of the refractory article through a sealing material. Further, a face of the first flange on the side of an outward end thereof faces a metal plate disposed around the outward end or a second flange provided on the side of the outward end, through a low thermally-conductive material layer made of a low thermally-conductive material having a thermal conductivity at room temperature of 40 (W/(m.Math.K)) or less.

Claims

1. A socket installation structure of a refractory article having an article body, comprising: a socket internally provided with a gas introduction through-hole for introducing gas to an inside of the article body and configured to allow a gas supply pipe to be connected to the gas introduction through-hole; and a metal plate disposed to surround a part or an entirety of the article body and lie around one end of the socket or the gas introduction through-hole on an outward side of the article body (this end will hereinafter be referred to simply as “outward end”), wherein the socket has a first flange at a position between the outward end and the other end of the socket or the gas introduction through-hole on an inward side of the article body (this end will hereinafter be referred to simply as “inward end”), and wherein a face of the first flange on the side of the inward end is bonded to the article body through a sealing material, and a face of the first flange on the side of the outward end faces the metal plate or a second flange provided to the socket on the side of the outward end with respect to the first flange, through a layer made of a low thermally-conductive material having a thermal conductivity of 40 (W/(m.Math.K)) or less at room temperature, and wherein the metal plate and a part or an entirety of an outer periphery of the socket are joined together.

2. The socket installation structure as claimed in claim 1, wherein the structure satisfies the following formula 1:
λ≤0.1359L.sup.2−0.7849L+1.4793  Formula 1 where L denotes a thickness (mm) of the layer, and λ denotes a thermal conductivity (W/(m.Math.K)) at room temperature of the low thermally-conductive material.

3. The socket installation structure as claimed in claim 2, wherein the thickness L (mm) of the layer satisfying the formula 1 is a length including a socket axis directional length variation ΔL (mm) which is determined according to an angle θ (degree) of the face of the first flange located on the side of the inward end and in contact with the article body through the sealing material, with respect to an axis direction of the socket, and a length variation Δt (mm) of a thickness of the sealing material between the face of the first flange on the side of the inward end and the article body, in a direction perpendicular to the face of the first flange on the side of the inward end.

4. The socket installation structure as claimed in claim 3, wherein the ΔL satisfies the following formula 2:
ΔL≤5.76×Δt/sin θ  Formula 2.

5. The socket installation structure as claimed in claim 3, wherein the ΔL is 23 mm or less, and the L is 43 mm or less.

6. The socket installation structure as claimed in claim 1, wherein the low thermally-conductive material is a material having a thermal conductivity at room temperature of 2.5 (W/(m.Math.K)) or less.

7. The socket installation structure as claimed in claim 1, wherein the low thermally-conductive material is a material having a thermal conductivity at room temperature of 0.5 (W/(m.Math.K)) or less.

8. The socket installation structure as claimed in claim 1, wherein the low thermally-conductive material is air.

9. The socket installation structure as claimed in claim 1, wherein each of the face of the first flange on the side of the inward end, and a face of the article body in contact with the face of the first flange through the sealing material, has a conical shape which extends from its starting point on an inward side toward an outward side of the gas induction through-hole, at an angle of greater than 0 degree to less than 90 degrees with respect to a central axis of the gas introduction through-hole.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1A to 1C are schematic sectional views taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing some examples of a socket installation structure of a refractory article according to the present invention, in which a sealing section extends along a plane perpendicular to an axis direction of the socket, wherein: FIG. 1A shows an example where a first, inward, flange of the socket is disposed at a position relatively close to an outer periphery of an article body of the refractory article, and an inward end of the socket on an inward side of the article body is disposed inside the article body; FIG. 1B shows an example where the first, inward, flange of the socket is disposed at a position relatively close to the outer periphery of the article body, and the inward end of the socket is extended to reach a gas pool provided inside the article body; and FIG. 1C shows an example similar to that in FIG. 1B, wherein the first, inward, flange is provided more inwardly to allow the length of a low thermally-conductive material layer to be increased.

(2) FIGS. 2A and 2B are schematic sectional views taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing some examples of a socket installation structure of a refractory article according to the present invention, in which a sealing section extends along a plane inclined with respect to an axis direction of the socket, wherein: FIG. 2A shows an example where a first, inward, flange of the socket is disposed at a position relatively close to the outer periphery of the article body, and an inward end of the socket on the inward side of the article body is disposed inside the article body; and FIG. 2B shows an example where the first, inward, flange of the socket is provided more inwardly, as compared with the example in FIG. 2A, to allow the length of the low thermally-conductive material layer to be increased, and the inward end of the socket is extended to reach the gas pool provided inside the article body.

(3) FIGS. 3A and 3B are schematic sectional views taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing some examples of a socket installation structure of a refractory article according to the present invention, in which a sealing section extends along a plane inclined with respect to an axis direction of the socket, to reach an inward end of the socket, wherein: FIG. 3A shows an example where a first, inward, flange of the socket is disposed at a position relatively close to the outer periphery of the article body, and an inward end of the socket on the inward side of the article body is disposed inside the article body; and FIG. 3B shows an example where the first, inward, flange of the socket is provided more inwardly, as compared with the example in FIG. 3A, to allow the length of the low thermally-conductive material layer to be increased, and the inward end of the socket is extended to reach the gas pool provided inside the article body.

(4) FIG. 4 is a schematic sectional view taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing an example of a socket installation structure of a refractory article according to the present invention, which is devoid of a second flange to be provided on the side of an outward end of the socket.

(5) FIG. 5 is a schematic sectional view taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing an example of a socket installation structure of a refractory article according to the present invention, in which an externally-threaded portion is provided in an outer periphery of one end of the socket on an outward side of the article body.

(6) FIG. 6 is a graph showing a thermal conductivity λ (W/(m.Math.K)) at room temperature of a low thermally-conductive material in relation to a socket axis directional thickness L (mm) of the low thermally-conductive material layer, under the condition that the temperature of a sealing material is kept at 100° C. (based on formula 3).

(7) FIG. 7 is a graph showing a relationship between the angle θ (degree) of a sealing face and a socket axis directional length variation ΔL (mm) of the sealing material, with respect to each thickness variation Δt (mm) in a direction perpendicular to the sealing face.

(8) FIG. 8 is a graph showing a relationship between ΔL (mm) and Δt (mm), when the angle θ is 10 (degree) in FIG. 7, i.e., when ΔL (mm) has a maximum value.

(9) FIG. 9 is a schematic sectional view taken along a plane passing through a central axis of a gas introduction through-hole provided inside a socket, showing an example of a socket installation structure of a conventional refractory article.

DESCRIPTION OF EMBODIMENTS

(10) As mentioned above, one cause for gas leakage around a socket in a socket installation structure of a refractory article such as a refractory nozzle is deformation of a part of the socket or alteration of a sealing material. Particularly, in a case where an outer periphery of an outermost portion of the socket is welded to a metal plate provided around an outer periphery of a cylindrical article body of the refractory article, due to heat during the welding, a part of the socket deforms to form a gap with respect to the sealing member, or the temperature of the sealing member containing water is rapidly raised to a vaporization temperature or more of water, i.e., 100° C. or more to form, inside the sealing material, defects such as pores allowing gas to pass therethrough.

(11) Further, generally, after installing the sealing material, with a view to removal of water contained in the sealing material and improvement in strength of the sealing material, the article body (including the socket installation structure) is subjected to heat treatment such as drying.

(12) In addition to the above cause due to welding, rapid thermal conduction from an outer periphery of the article body during such heat treatment such as drying is also likely to cause the deformation or alteration.

(13) The present invention is intended to prevent a situation where, due to heat such as welding heat from the outer periphery of the refractory body, i.e., from the outside of the socket, volatile matters such as water contained in the sealing material are rapidly vaporized to cause breaking of the microstructure of the sealing material.

(14) A material of the socket, i.e., a ferrous metal, has a thermal conductivity at room temperature of about 70 to 80 (W/(m.Math.K)). As seen in many convectional socket installation structures, the diameter of a socket is maintained at approximately the same value between axial opposite ends thereof, and, in a case where a sealing member is provided at each of the ends, a sealing face is set within the range of the diameter.

(15) Compared with this, in the present invention, a low thermally-conductive material layer is formed between axial opposite ends of the socket to suppress thermal conduction in the axis direction of the socket, thereby preventing rapid temperature rise in a sealing section.

(16) In this temperature range, the transfer of heat is mainly based on conduction, and radiation and convection are ignorable.

(17) Although the low thermally-conductive material may have any thermal conductivity lower than that of a material of the socket, i.e., a ferrous metal, it preferably has the lowest possible thermal conductivity, because such a material is less likely to be influenced by fluctuation of thermal conditions, thereby more reliably obtaining the intended effect.

(18) Through unsteady thermal calculation, the inventors have found that, under the condition that the temperature of a sealing material in contact with a first flange provided on the side of an inward end of the article body is kept at 100° C., a thermal conductivity λ (W/(m.Math.K)) at room temperature of the low thermally-conductive material satisfies the following formula 3, in relation to a socket axis directional thickness L (mm) of the low thermally-conductive material layer:
λ=0.1359L.sup.2−0.7849L+1.4793  Formula 3

(19) That is, a temperature of the sealing material never exceeds 100° C. by using a low thermally-conductive material having λ equal to or less than the λ in the formula 3, i.e., having λ whose value≤(right-hand side of the formula 3). A formula expressing this relation is the aforementioned formula 1.

(20) The relationship between L and λ based on the formula 3 is shown in FIG. 6.

(21) The formula 3 is based on values measured during actual operation of welding the entire periphery of the socket to the metal casing on the side of the outer periphery of the article body. Although the time period of this welding operation varies depending on a welding method, it is about 10 seconds to about several ten seconds at a maximum.

(22) In this calculation, the temperature of a welding area was set to 600° C. (which is a value measured by a thermoviewer, and the bulk specific gravity of the low thermally-conductive material was set to 3.0. When the bulk specific gravity is less than this value, λ becomes smaller with respect to the same L.

(23) Paraphrasing this result, the thickness L is a matter of design choice, i.e., may be arbitrarily determined and set according to the structure, shape, etc., of the article body, and, by selecting a material having a thermal conductivity satisfying the formula 1 according to such a thickness, the temperature of the sealing material can be kept at about 100° C. or less, so that it is possible to install the socket so as to prevent formation of defects in the sealing material.

(24) In the present invention, a maximum thickness of the low thermally-conductive material layer required when a maximum thermal conductivity of a refractory material is set to 40 (W/(m.Math.K)) is calculated as about 20 mm based on the formula 2, and the thickness L (mm) can be set to the extent that it satisfies the formula 1 according to the thermal conductivity.

(25) In a case where the sealing material contains a liquid other than water, such as a solvent, the temperature of the sealing material is basically set based on a vaporization temperature of the solvent, as in the case of water. Generally, the vaporization temperature of a non-aqueous solvent for use in a refractory material, is greater than 100° C. Thus, as long as the sealing material containing a non-aqueous solvent satisfies the formula 1 formulated based on 100° C., defects are less likely to be formed in the sealing material.

(26) From a viewpoint of more reliably suppressing a temperature rise of the sealing material, the thermal conductivity of the material used for the low thermally-conductive material layer is preferable set to the lowest possible value. For example, it is preferable to use a material other than metal, carbon, a strongly-covalent compound and the like, such as a refractory material consisting mainly of an oxide, and particularly, considering easiness of installation, to use a material having a thermal conductivity at room temperature of about 2.5 (W/(m.Math.K)) or less, such as mortar including alumina mortar, alumina-silica mortar and silica mortar.

(27) In the socket installation stricture, the low thermally-conductive material layer does not have a function of supporting the socket, i.e., needs not withstand a mechanical stress, so that it may be made of a low-strength material such as a heat insulating material, inorganic fibers or a mixture thereof having a thermal conductivity at room temperature of about 0.5 (W/(m.Math.K)) or less.

(28) Further, most preferably, the low thermally-conductive material is air which has a significantly low thermal conductivity at room temperature of about 0.024 (W/(m.Math.K)), i.e., the low thermally-conductive material layer is a void space, from a viewpoint of providing a highest heat insulating effect, and producing the socket installation structure easily and at low cost.

(29) The above thermal conductivity was measured in accordance with JIS R2251.

(30) Each of a face of the first flange provided between an outward end and an inward end of the socket and on the side of the inward end, and a face of the article body in contact with the face of the first flange through the sealing material, may be formed in a conical shape whose diameter gradually increases toward an outward side of the gas induction through-hole, with respect to a central axis of the gas introduction through-hole (which is coaxial with the axis of the socket). That is, each of the faces may be formed in a shape which extends from its starting point on an inward side toward the outward side of the gas induction through-hole, at an angle (hereinafter also referred to as “inclination angle”) of greater than 0 degree to less than 90 degrees with respect to the central axis of the gas introduction through-hole.

(31) Thus, when an external force is applied to the socket in the axis direction of the socket, the socket is moved toward the ventral axis of the gas induction through-hole of the article body, so that a thickness between an outer peripheral surface of the socket and the article body is uniformized, thereby providing enhanced uniformity of the sealing material.

(32) Further, although the socket expands when heat is applied thereto during use, etc., the expansion of the socket is greater than that of the article body, so that the inclined face of the socket can provide enhanced contactability with respect to a layer of the sealing material while avoiding local stress concentration, thereby reducing the risk of breaking of the article body around the socket.

(33) The first flange is preferably formed such that the inclined portion thereof extends up to the inward end of the socket (see FIGS. 3A and 3B). In this case, a non-inclined region (parallel to the axis of the socket) of the outer peripheral surface of the socket is reduced, so that the socket can be easily installed at a high degree of accuracy. Further, a portion of the sealing material between the inward face of the first flange and the contact face of the article body, which is important for sealability, is broadened and uniformized, so that it is possible to more enhance the sealability.

(34) From a viewpoint of enhancing the heat insulating effect, the socket axis directional thickness L of the low thermally-conductive material layer is preferably increased as long as possible, and the first flange on the inward side of the article body is preferably provided inwardly as far as possible (see FIGS. 1C, 2B and 3B).

(35) Further, when the first flange on the inward side of the article body is provided inwardly as far as possible, it is possible to stabilize a socket fixation force against an external force from the outside of the socket. For the same region, the length of the socket itself, i.e., the length between the outward end and the inward end of the socket, is preferably increased as long as possible (see FIGS. 1B, 2B and 3B).

(36) The above inclination angle θ may be set appropriately and arbitrarily, according to the size of the first flange, the diameter and accuracy of a socket-installation recess of the article body, the accuracy of the sealing face of each of the socket and the article body, and others.

(37) The thickness of the sealing material can vary depending on the configuration/properties of the sealing material, allowable errors in shape specifications of the socket and the article body, variation in operation during socket installation, and others.

(38) Such a phenomenon is more likely to occur, in a case where a second flange to be provided on the side of the outward end of the socket is prepared separately from the remaining portion of the socket, and after installing the remaining portion, the second flange is installed to the socket or the metal plate by welding or other fixing means.

(39) In the case where the sealing face of each of the first flange and the article body is configured as an inclined face, as the inclination angle θ (degree) of the sealing face becomes smaller, a length variation ΔL (mm) of the sealing material in the axis direction of the socket with respect to a thickness variation Δt (mm) of the sealing material in a direction perpendicular to the sealing face, i.e., a variation in position of the socket in a radial direction of the article body, becomes larger.

(40) The ΔL and Δt geometrically have the relationship expressed as the following formula 4:
ΔL=Δt/sin θ  Formula 4

(41) A relationship between ΔL and θ in each case where Δt is set to 1, 2, 3 and 4 (mm) is shown in FIG. 7.

(42) For example, in a case where the inclination angle θ is set to 10 (degree) which is considered to be realistically a minimum value, and the thickness variation Δt (mm) of the sealing material in a direction perpendicular to the sealing face, is set to 4 (mm) which is considered to be realistically a maximum value, the socket axis directional length variation ΔL (mm) is about 23 (mm).

(43) For example, the relationship between ΔL and Δt in a case where the value of Δt at an inclination angle θ=10 (degree) varies is expressed as the following formula 5, as shown in FIG. 8.
ΔL=5.76×Δt  Formula 5

(44) As above, L (mm) in the formula 2 preferably includes the ΔL (mm) which is calculated according to the relationship between the inclination angle θ, and the thickness variation Δt (mm) of the sealing material in a direction perpendicular to the sealing face.

(45) Integrating the formulas 4 and 5 into a single formula, the aforementioned formula 2: ΔL≤5.76×Δt/sin θ is obtained.

(46) From viewpoints of: (1) increasing the area of the sealing section; (2) ensuring or enhancing the heat insulating effect of the low thermally-conductive material layer; and (3) enhancing mechanical stability against an external force applied to the socket, the size of the first flange is preferably increased as large as possible.

(47) In this case, the first flange may be formed in a size enough to avoid causing breaking of the article body of the refractory article such as a refractory nozzle or a refractory plug, in relation to a shape such as the degree of curve of a portion of the article body corresponding to the first flange, (i.e., a curvature in a case where the portion has a circular shape), a distance from an end of the first flange, etc. Further, in the case where the portion of the article body corresponding to the first flange has a circular shape, the first flange may be curved in conformity with the curvature thereof.

(48) A part or the entirety of the outer periphery of the socket needs to be joined and fixed to the metal plate on the side of the outer periphery of the article body.

(49) As this joining method, it is possible to employ an appropriate technique, such as: spot welding of a part of the outer periphery of the socket; welding all around the outer periphery of the socket; or thread engagement through a thread joint structure formed between the socket and the metal plate. The outer periphery of the socket and the metal plate on the side of the outer periphery of the article body need not necessarily be kept in a tightly sealed state therebetween, but are only necessary to be fixed to each other.

(50) This fixed position may be at the outer periphery of the socket (designated by the reference sign 7 in FIG. 4), or may be at an outermost periphery of a second flange additionally provided on the outer periphery of the socket (designated by the reference sign 7 in FIGS. 1A-C to 3A and B).

EXAMPLES

Example A

(51) With regard to: an inventive example 1 having the structure as shown in FIGS. 1A-C, wherein the socket axis directional thickness of the low thermally-conductive material layer was set to 10 mm, and the low thermally-conductive material was composed of an alumina mortar having a thermal conductivity at room temperature of about 2.5 (W/(m.Math.K)); an inventive example 2 having the structure as shown in FIGS. 1A-C, wherein the socket axis directional thickness of the low thermally-conductive material layer was set to 10 mm, and the low thermally-conductive material was composed of a heat insulating material having a thermal conductivity at room temperature of about 0.5 (W/(m.Math.K)); and a inventive example 3 having the structure as shown in FIGS. 1A-C, wherein the socket axis directional thickness of the low thermally-conductive material layer was set to 10 mm, and the low thermally-conductive material was composed of air, the presence or absence of air leakage was checked and compared with each other by a laboratory test at room temperature, together with a comparative example 1 having a conventional structure as shown in FIG. 9.

(52) The entire outer periphery of the socket was welded to the metal plate on the side of the outer periphery of the article body.

(53) The pressure of compressed air for checking air leakage was set up to 0.5 MPa. When there is a pressure drop after leaving for 3 hours, the example was evaluated as having air leakage, and, when there is no pressure drop after leaving for 3 hours, the example was evaluated as having no air leakage.

(54) As a result, the comparative example 1 had air leakage, whereas each of the inventive examples 1 to 3 had no air leakage.

Example B

(55) Example B shows a result obtained by subjecting the inventive example 3 and the comparative example 1 to actual casting operation, wherein the refractory article was formed as an upper nozzle for continuous casting.

(56) As a result, the comparative example had a leakage occurrence frequency of about 3%, whereas the inventive example 3 had no leakage, i.e., a leakage occurrence frequency of 0%.

LIST OF REFERENCE SIGNS

(57) 1: sealing section having the most enhanced contactability in a region in which a sealing material is filled 2: sealing material 3: first flange provided on an inward side of an article body of a refractory article 4: low thermally-conductive material layer 5: second flange provided on an outward side of the article body 6: metal plate provided on the side of an outer periphery of the article body 7: joint area between a socket and the metal plate provided around the outer periphery of the article body 8: threaded portion 9: gas introduction through-hole 10: axis of the gas introduction through-hole and the socket 11: gas pool 20: socket 30: article body L: thickness of the low thermally-conductive material layer from the second flange provided on the outward side of the article body or the metal plate provided on the side of the outer periphery of the article body θ: angle of an inclined portion of the first flange provided on the inward side of the article body