Gas injection plug, refractory unit, and method for manufacturing a refractory unit

Abstract

A gas injection plug, which can be removed and replaced from the mass block, is easily secured to the mass block, at least until it is installed in the furnace. [Solution] The gas blowing plug 1 is a gas blowing plug that is fixed to the inner hole 71 of the mass block 7 and comprises a plug body 2 having a gas flow passage and a metal case 3 covering the outer circumference of the plug body 2. The metal case 3 has a protruding portion 31 that extends from the outer circumference of the plug body 2 to the outer surface 7A of the mass block 7, and a locking fitting 11 is attached to at least a part of the outer circumference 31A of the protruding portion 31 of the metal case 3.

Description

Technical Field

[0001] The present invention relates to a gas injection plug, a refractory unit, and a method for manufacturing the refractory unit.

Background Art

[0002] For the purpose of improving the refining efficiency of molten metal such as molten steel, a gas injection plug is installed at the bottom of a molten metal container such as a ladle. An inert gas such as argon gas or nitrogen is blown into the molten metal through the gas injection plug. Conventionally, such a gas injection plug has a structure in which a refractory having air permeability is covered with a metal case. The periphery of the gas injection plug is covered with a non-ventilated block-shaped castable refractory, and this block-shaped castable refractory is called a mass block (or tuyere brick).

[0003] Since molten steel also penetrates into the gas flow path of the gas injection plug, its service life is shorter than that of other parts of the molten metal container. Therefore, the gas injection plug needs to be replaced with a new one earlier than other parts of the molten metal container. As the replacement type of the gas injection plug, there are two main types: a type in which the gas injection plug and the mass block are completely integrated and the gas injection plug is replaced together with the mass block; and a configuration in which the gas injection plug is inserted and mounted in a hole provided in the center of the mass block, and only the gas injection plug can be pulled out and replaced with a new one.

[0004] The latter type of gas injection plug is manufactured with ease of use at the furnace construction site in mind, and is pre-installed in the inner bore of the mass block, and shipped from the factory as an integrated unit with the mass block. Japanese Patent Publication No. 2010-138479 (Patent Document 1) proposes a gas injection plug that is integrated with the mass block. Patent Document 1 discloses a porous gas injection plug, which is inserted into the inner bore of a mass block and fixed in place for use as an integrated unit, with its outer circumference covered by an iron case. The porous plug is characterized by extending the tip of the outer iron case of the porous plug upwards, and by making multiple cuts in the extended portion of the iron case to create a strip-like shape, making it easier to bend outwards. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-138479 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The porous plug for gas blowing described in Patent Document 1 is configured such that the strip-shaped portion of the extension of the iron case is bent outward and fixed to the mass block. Therefore, even if vibrations are applied when it is shipped from the manufacturing site and transported to the furnace construction site, and then installed in the furnace at the furnace construction site, it is less likely to come off the mass block and is easy to handle as a single unit. However, fixing the porous plug for gas blowing described in Patent Document 1 to the mass block requires making numerous cuts in the extension portion of the iron case, and then bending this cut portion by hammering it, making the fixing process time-consuming. In addition, the impact of hammering and bending the extension portion of the iron case may create a gap between the iron case and the plug body, in which case it is necessary to fill the gap with a repair material, which adds further time and effort. Thus, there is still room for improvement in the technology for fixing a gas blowing plug, which can be removed and replaced from the mass block, to the furnace until it is installed.

[0007] In view of the above circumstances, the present invention aims to provide a way to easily fix a gas injection plug, which can be removed and replaced from the mass block, to the mass block, at least until it is installed in the furnace. [Means for solving the problem]

[0008] The gas injection plug according to the present invention comprises a plug body having a gas flow passage and a metal case covering the outer circumference of the plug body, and is fixed to an inner hole of a mass block, wherein the metal case has a protruding portion that extends from the outer circumference of the plug body to the outer surface of the mass block, and a locking fitting is joined to at least a part of the outer circumference of the protruding portion of the metal case.

[0009] The refractory unit according to the present invention is characterized by comprising the gas injection plug and a mass block in which the gas injection plug is fixed to an internal bore.

[0010] A method for manufacturing a refractory unit according to the present invention comprises a gas injection plug and a mass block in which the gas injection plug is fixed to an inner hole, and is characterized by comprising: a plug preparation step of preparing a plug preparation body having a plug body having a gas flow passage and a metal case covering the outer circumference of the plug body, and having a protruding portion from which the metal case protrudes from the outer circumference of the plug body; a plug installation step of installing the plug preparation body in the inner hole of the mass block such that the protruding portion of the metal case protrudes to the outer surface of the mass block; and a fitting joining step of joining a locking fitting to at least a part of the outer circumference of the protruding portion of the metal case.

[0011] With these configurations, a locking fitting is attached to at least a portion of the outer circumference of the protruding part of the metal case of the gas injection plug, allowing the gas injection plug to be easily fixed to the mass block while still being removable and replaceable from the mass block. Therefore, when the refractory unit, which is an integrated mass block and gas injection plug, is manufactured and transported to the furnace construction site, and further when the refractory unit is installed in the molten metal container, it is possible to prevent the gas injection plug from falling out of the mass block.

[0012] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

[0013] In one embodiment of the gas injection plug according to the present invention, it is preferable that the locking fitting is joined to the outer circumference of the protruding portion of the metal case by welding.

[0014] This configuration makes it easy to attach the locking mechanism to at least a portion of the outer circumference of the protruding part of the metal case.

[0015] In one embodiment, the gas blowing plug according to the present invention is a cylindrical fitting in which the outer circumference of the protruding portion of the metal case has a male threaded portion, and the locking fitting has a female threaded portion on its inner circumference, wherein the locking fitting is preferably joined to the outer circumference of the protruding portion by screwing the female threaded portion into the male threaded portion.

[0016] This configuration makes it easier to join the locking fitting to at least a portion of the outer circumference of the protrusion on the metal case by means other than welding.

[0017] In one embodiment of the gas blowing plug according to the present invention, it is preferable that a plurality of the locking fittings are joined to the outer circumference of the protruding portion of the metal case at substantially equal intervals.

[0018] This configuration makes it easier to secure the gas injection plug to the edge of the inner bore of the mass block almost evenly.

[0019] In one embodiment, the gas blowing plug according to the present invention preferably has a widthwise length along the radial direction of the protruding portion of the locking fitting of 5 mm or more and 50 mm or less, and a thickness of 1 mm or more and 10 mm or less.

[0020] This configuration allows the locking mechanism attached to the gas injection plug to easily catch on the edge of the inner hole of the mass block, thus providing sufficient fixing strength for the gas injection plug to the mass block. Furthermore, since the locking mechanism does not protrude excessively from the outer surface of the mass block, it offers excellent workability when transporting the integrated mass block and installation into the furnace at the construction site.

[0021] Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments, with reference to the drawings. [Brief explanation of the drawing]

[0022] [Figure 1] This is a longitudinal cross-sectional view of a refractory unit according to the first embodiment. [Figure 2]It is a longitudinal sectional view of a gas injection plug according to the first embodiment. [Figure 3] It is a top view of the refractory unit of FIG. 1. [Figure 4] It is a diagram showing a procedure for manufacturing a plug preparation according to the first embodiment. [Figure 5] It is a diagram showing a procedure for manufacturing a refractory unit according to the first embodiment. [Figure 6] It is a diagram showing a procedure for manufacturing a refractory unit according to the first embodiment. [Figure 7] It is a diagram showing a procedure for manufacturing a refractory unit according to the first embodiment. [Figure 8] It is a diagram showing a method for manufacturing a refractory unit according to the first embodiment. [Figure 9] It is a diagram showing another procedure for manufacturing a refractory unit according to the first embodiment. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​[Modes for carrying out the invention]

[0023] 1. First Embodiment A first embodiment of the gas injection plug, refractory unit, and method for manufacturing the refractory unit according to the present invention will be described with reference to the drawings. Below, an example will be described in which the gas injection plug according to the present invention is applied to a gas injection plug 1 (hereinafter simply referred to as "plug 1") installed at the bottom of a molten metal refining vessel and a refractory unit 100 equipped therewith.

[0024] [Plug configuration] The plug 1 according to this embodiment is fixed to the inner bore 71 of the mass block 7 and comprises a plug body 2 having a gas flow passage and a metal case 3 covering the outer circumference of the plug body 2 (Figures 1 and 2). The plug body 2 comprises a core portion 21 and an outer circumference portion 22 surrounding the core portion 21. The core portion 21 has a recess that becomes a gas pool 5 at its base end surface 21B. The metal case 3 comprises a cylindrical base portion 32 and a bottom plate portion 33 extending from the enlarged diameter end of the cylindrical base portion 32. The bottom plate portion 33 has an air supply pipe 34 in its approximate center, and the air supply pipe 34 and the gas pool 5 are in fluid communication. The plug 1 is a porous plug that plays the role of discharging gas supplied from the base end 1B side from the tip surface 1A, and the core portion 21 made of porous refractory material functions as a gas flow passage. The arrow X in Figure 2 indicates the direction of gas flow.

[0025] The tip of plug 1 refers to the side exposed to the inside of the molten metal refining vessel when plug 1 is in use (the upper side in Figure 1), and the base of plug 1 refers to the side facing outwards from the molten metal refining vessel when plug 1 is in use (the lower side in Figure 1). Therefore, the tip surface 1A of plug 1 is exposed to molten metal when in use. The side surface of plug 1 is a tapered surface that widens in diameter from the tip side to the base side. When plug 1 has reached the end of its lifespan after use, it can be replaced by pulling it out from the outer surface 7B side of the inner bore 71 of the mass block 7, which is on the outside of the molten metal refining vessel.

[0026] In this embodiment, the core portion 21 is made of a porous refractory material. The porous refractory material can be any porous refractory material commonly used in this art, such as high-alumina or magnesia refractory materials. That is, the porous refractory material is a press-molded product that may contain metal oxides such as alumina, magnesia, or chromia. Furthermore, the porous refractory material may also contain carbon, mullite, zirconia compounds, boron compounds, clay, etc.

[0027] The shape of the core portion 21 is not particularly limited and can be any shape, such as a frustoconical or pyramidal shape. In this embodiment, as an example, an example in which the core portion 21 is frustoconical is shown (Figures 2 and 3). The tip surface 21A of the core portion 21 is circular.

[0028] The outer perimeter portion 22 is made of dense refractory material and is provided in such a manner that it surrounds the core portion 21 in the circumferential direction. The dense refractory material constituting the outer perimeter portion 22 can be any dense refractory material commonly used in this field, such as high-alumina refractory material, alumina-magnesia refractory material, or alumina-spinel refractory material. In other words, dense refractory material is a pourable material that may contain metal oxides such as alumina, magnesia, and spinel. Furthermore, dense refractory material may also contain alumina cement, silica flower, metal powder, dispersant, etc.

[0029] In this embodiment, an example is shown where the outer peripheral portion 22 is cylindrical. Correspondingly, the tip surface 1A and cross-section of the plug 1 are circular (Figure 3). Note that the cross-sectional shapes of the core portion 21 and the outer peripheral portion 22 may be different, or both may have the same cross-sectional shape (circular and circular, etc.).

[0030] The metal case 3 is a metal case that houses the core portion 21 and the outer peripheral portion 22. As described above, the metal case 3 consists of a cylindrical base portion 32 and a bottom plate portion 33 having an air supply pipe 34. The cylindrical base portion 32 and the bottom plate portion 33 of the metal case 3 are joined by welding or the like. The metal case 3 is open on the tip side of the plug 1, and therefore the core portion 21 and the outer peripheral portion 22 are exposed on the tip surface 1A of the plug 1. On the other hand, the side surface of the outer peripheral portion 22 surrounding the core portion 21 is surrounded by the cylindrical base portion 32 of the metal case 3, and the base end sides of the core portion 21 and the outer peripheral portion 22 are covered by the bottom plate portion 33 of the metal case 3.

[0031] The metals constituting the cylindrical base portion 32, bottom plate portion 33, and air supply pipe 34 of the metal case 3 are not particularly limited and may be, for example, SS400, SUS304, SPCC, etc. The air supply pipe 34 may be a steel pipe such as SGP, STPG (for example, STPG370), etc. The metals constituting the cylindrical base portion 32, bottom plate portion 33, and air supply pipe 34 of the metal case 3 may be the same metal or different metals. For example, the metals constituting the cylindrical base portion 32 and the bottom plate portion 33 may be the same metal or different metals to the extent that they can be welded to each other. Also, the metals constituting the bottom plate portion 33 and the air supply pipe 34 may be the same metal or different metals to the extent that they can be welded to each other.

[0032] The base end face 21B of the core portion 21 has a recess, which serves as a gas pool 5. The gas pool 5 is a space in which no physical member is provided, and functions as a space for the gas flowing in from the air supply pipe 34 to diffuse laterally in the core portion 21 (in a direction intersecting the longitudinal direction of the plug 1).

[0033] Gas supplied to the plug 1 from a gas source (not shown) travels through the air supply pipe 34 to the gas pool 5, where it diffuses radially through the core portion 21 of the plug 1 and enters the pores of the core portion 21 from the base end face 21B. The gas then travels further through the core portion 21 and flows into the molten metal refining container from the tip face 21A. Thus, in the plug 1 according to this embodiment, the path through which the gas flows into the molten metal refining container is the path indicated by arrow X, passing through the tip face 21A. This allows gas to be blown into the molten metal inside the molten metal refining container via the plug 1.

[0034] In the present invention, the metal case 3 has a protrusion 31 that projects from the outer circumference of the plug body 2 onto the outer surface 7A of the mass block 7 (Figures 1 and 2). A locking fitting 11 is welded to at least a portion of the outer circumference 31A of the protrusion 31 of the metal case 3. In the drawings of this application, the welded locations are indicated by welding symbols, but the approximately entire length in the thickness direction of the locking fitting 11 is welded to the outer circumference of the protrusion 31. The protrusion length of the protrusion 31 of the metal case 3 is not particularly limited as long as the locking fitting 11, which will be described later, can be attached, but for example, a length of 1 mm or more and 10 mm or less can be adopted. If the protrusion length is 1 mm or more, it is easy to attach the locking fitting 11. If the protrusion length is 10 mm or less, the locking fitting 11 does not protrude excessively from the outer surface 7A of the mass block 7, so it is easier to transport the refractory unit 100, which is an integral part with the mass block 7, to the furnace construction site and when installing it in the furnace. The protruding length of the protruding portion 31 of the metal case 3 is more preferably 2 mm or more, and even more preferably 3 mm or more. Furthermore, the protruding length of the protruding portion 31 of the metal case 3 is more preferably 9 mm or less, and even more preferably 8 mm or less.

[0035] In this embodiment, the locking fitting 11 is a rectangular plate-like piece of metal. The metal may be, for example, SS400, SUS304, SPCC, etc. The metal constituting the metal case 3 and the metal constituting the locking fitting 11 may be the same metal, or they may be different metals to the extent that they can be welded to each other. It is desirable that the locking fitting 11 melts when it comes into contact with the molten steel during furnace operation, and it is desirable that the melting point of the metal constituting the locking fitting 11 is lower than the melting temperature of the molten steel. In this way, the locking fitting 11 disappears when the plug 1 is replaced, and it does not hinder replacement when the plug 1 is removed from the mass block 7 and replaced with a new one.

[0036] In this embodiment, two locking fittings 11 are joined by welding to opposing positions on the outer circumference 31A of the protruding portion 31 of the metal case 3. That is, two locking fittings 11 are joined to the outer circumference 31A of the protruding portion 31 of the metal case 3 at approximately equal intervals. By joining multiple locking fittings 11 to the outer circumference 31A of the protruding portion 31 at approximately equal intervals in this way, it is easier to lock the plug 1 to the edge of the inner hole 71 of the mass block 7 at approximately equal intervals.

[0037] In this embodiment, one of the long sides of the plate-shaped piece of the locking fitting 11 melts and shrinks during welding to the metal case, so that the welded locking fitting 11 conforms to the outer curved surface of the protruding portion 31 of the metal case 3 (Figure 3). In this embodiment, the widthwise length W1 of the locking fitting 11 along the radial direction of the protruding portion 31 after welding is 5 mm or more and 50 mm or less, and the thickness of the locking fitting 11 after welding is 1 mm or more and 10 mm or less. As in this example, if the widthwise length W1 of the locking fitting 11 is 5 mm or more, it is easier to hook the plug 1 onto the edge of the inner hole 71 of the mass block 7 and secure it, and it is easier to obtain fixing strength. If the widthwise length W1 of the locking fitting 11 is 50 mm or less, the locking fitting 11 does not protrude excessively from the outer surface 7A of the mass block 7, so it is easier to transport the refractory unit 100, which is an integral part with the mass block 7, to the furnace construction site and when installing it in the furnace. The widthwise length W1 of the locking fitting 11 is more preferably 8 mm or more, and even more preferably 10 mm or more. Furthermore, the widthwise length W1 of the locking fitting 11 is more preferably 45 mm or less, and even more preferably 40 mm or less. Also, if the thickness of the locking fitting 11 is 1 mm or more, it is easier to hook the plug 1 onto the edge of the inner hole 71 of the mass block 7 and lock it in place, and easier to obtain fixing strength. If the thickness of the locking fitting 11 is 10 mm or less, the locking fitting 11 does not protrude excessively from the outer surface 7A of the mass block 7, making it easier to transport the refractory unit 100, which is an integral part of the mass block 7, to the furnace construction site and easier to install in the furnace. The thickness of the locking fitting 11 is more preferably 2 mm or more, and even more preferably 3 mm or more. Furthermore, the thickness of the locking fitting 11 is more preferably 9 mm or less, and even more preferably 8 mm or less.

[0038] Furthermore, in this embodiment, the length (L1) of the protruding portion 31 of the metal case 3 along the outer circumference 31A of the locking fitting 11 after welding is set to 5 mm or more and 50 mm or less. As in this example, if the length (L1) of the protruding portion 31 along the outer circumference 31A is 5 mm or more, it is easier to hook the plug 1 onto the edge of the inner hole 71 of the mass block 7 and lock it in place, and it is easier to obtain fixing strength. If the length (L1) of the protruding portion 31 along the outer circumference 31A is 50 mm or less, the locking fitting 11 does not protrude excessively from the outer surface 7A of the mass block 7, so it is easier to transport the refractory unit 100, which is an integral part with the mass block 7, to the furnace construction site and when installing it in the furnace. It is more preferable that the length (L1) of the protruding portion 31 along the outer circumference 31A is 8 mm or more, and even more preferable that it is 10 mm or more.

[0039] [Refractory Unit] As shown in Figures 1 and 3, the refractory unit 100 according to this embodiment is a plug-mass block integrated unit comprising a plug 1 and a mass block 7 to which the plug 1 is fixed in an inner hole 71. The refractory unit 100 is shipped from the manufacturing plant as an integrated unit and transported to the furnace construction site, where it is installed at the bottom of the molten metal refining vessel. When the plug 1 reaches the end of its lifespan after use, only the plug 1 is removed from the refractory unit 100 and replaced.

[0040] In the refractory unit 100, mortar 4 is interposed between the metal case 3 surrounding the outer circumference of the plug 1 and the inner bore 71 of the mass block 7. Instead of mortar 4, an adhesive such as refractory putty may be interposed. More specifically, a release agent is applied to the surface of the metal case 3 or a release sheet is interposed (not shown), and the mortar 4 is on top of that. The mortar 4 may contain carbon raw materials such as graphite to reduce scorching during furnace operation.

[0041] The mass block 7 according to this embodiment is made of a commonly used, non-permeable castable refractory material, and its material is not particularly limited. The shape of the inner bore 71 of the mass block 7 is not particularly limited as long as it corresponds to the shape of the plug 1. In this embodiment, it is a tapered surface that follows the side shape of the plug 1. The size of the mass block 7 is, for example, 200-800 mm in width x 200-800 mm in depth x 200-800 mm in height. In this embodiment, an example is shown in which lifting fittings 8 for lifting and moving by crane are attached to two opposing surfaces (outer surfaces 7C, 7D) of the mass block 7. The lifting fittings 8 only need to be attached to at least one of the outer surfaces of the mass block 7 (outer surfaces 7A, 7C, 7D, 7E, 7F), and the mounting surface of the lifting fittings 8 is not limited. In addition to the example of this embodiment, other examples include attaching them to two surfaces 7E and 7F, attaching them to four surfaces 7C, 7D, 7E, and 7F, and attaching them to one surface 7A. Furthermore, considering ease of work, it is preferable to use eye bolts or the like for the suspension fitting 8, as they are easy to attach and detach.

[0042] In this embodiment, the refractory unit 100 has a locking fitting 11 attached to at least a portion of the outer circumference 31A of the protruding portion 31 of the metal case 3 of the plug 1, thereby fixing the plug 1 to the inner hole 71 of the mass block 7. Therefore, when the refractory unit, which is an integrated mass block 7 and plug 1, is manufactured and transported to the furnace construction site, and further when the refractory unit is installed in the molten metal container, the plug 1 is prevented from falling out of the inner hole 71 of the mass block 7. With this configuration, the plug 1 can be removed and replaced from the mass block 7, while at least until it is installed in the furnace, it is possible to make it difficult for the plug 1 to come off the mass block 7.

[0043] Furthermore, even when the locking fitting 11 is not attached, as shown in Figure 6 later, adhesive mortar 4 is interposed between the plug and the inner hole 71 of the mass block 7, forming a single unit. However, if this single unit is shipped from the manufacturing plant in the delivery position shown in Figure 1 and subjected to vibration and shock by a crane or the like during transportation to the furnace construction site and installation at the furnace construction site, the mortar 4 interposed between the inner hole 71 and the plug will be subjected to stress due to the weight of the plug, causing cracks and other damage, and potentially leading to the plug 1 falling out. In contrast, in the refractory unit 100 according to this embodiment, the locking fitting 11 is attached so as to lock onto the edge of the inner hole 71 of the mass block 7. Therefore, even if the refractory unit 100 is subjected to vibration and shock, the mortar 4 interposed between the inner hole 71 and the plug 1 will not be subjected to strong stress. As a result, cracking and collapse of the mortar 4 during transportation to the furnace construction site and installation can be prevented. Furthermore, even if the mortar 4 cracks or collapses due to some factor, the plug 1 is secured to the edge of the inner hole 71 of the mass block 7, preventing it from falling out of the mass block. In addition, since the plug 1 according to this embodiment is fixed to the inner hole 71 of the mass block 7 without being subjected to impact such as being struck with a hammer, cracks and other damage are less likely to occur in the mortar 4.

[0044] [Manufacturing method for refractory units] Next, the manufacturing method of the refractory unit 100 will be described. The plug 1 is completed within the refractory unit 100 as the refractory unit 100 is completed.

[0045] The method for manufacturing the refractory unit 100 includes a plug preparation step of preparing a plug preparation body 1a (hereinafter also referred to as plug preparation body 1a), a plug installation step of installing the plug preparation body 1a in the inner hole 71 of the mass block, and a fitting joining step of joining a locking fitting 11 to the outer circumference 31A of the protruding portion 31 of the metal case 3 of the plug preparation body 1a.

[0046] (Plug preparation process) The plug preparation step is a step of preparing a plug preparation body 1a, which is a step prior to joining the locking fitting 11. The plug preparation step is a step of preparing a plug preparation body 1a having a plug body 2 having a gas flow passage and a metal case 3 covering the outer circumference of the plug body 2, and having a protruding portion 31 from which the metal case 3 protrudes from the outer circumference of the plug body 2. To that extent, the method of manufacturing the plug preparation body 1a is not limited. In the plug preparation body 1a according to this embodiment, the tip of the metal case 3 extends from the outer circumference of the plug body 2 and protrudes from the tip surface 2A of the plug body 2.

[0047] The following describes a manufacturing method for the outer-circumferential casting type plug preparation 1a as an example of a manufacturing method for the plug preparation 1a. As shown in Figure 4, the manufacturing method for the outer-circumferential casting type plug preparation 1a includes a first step (S1) of manufacturing the core portion 21, a second step (S2) of installing the core portion 21 in the metal case 3 using a plug manufacturing support 25, a third step (S3) of pouring and curing the outer-circumferential portion 22a of the core portion 21 into the space between the core portion 21 and the metal case 3, a fourth step (S4) of drying the core portion 21 and the outer-circumferential portion 22a, and a fifth step (S5) of attaching the air supply pipe 34.

[0048] (1) First step (S1) In the first step, a pre-molded body is prepared and fired to create a core portion 21 made of porous refractory material. The porous refractory material used here is as listed above, and the core portion 21 can be prepared using commonly used equipment and auxiliary materials.

[0049] (2) Second process (S2) In the second step, the core portion 21 is placed at the center of the space inside the metal case 3 using the support 25 (S2 in Figure 4). Specifically, the support 25 comprises a pressing member 25a having a downwardly projecting projection and being slidable in the vertical direction, and a support base 25b having a circumferential groove 25c formed on its upper surface. The cylindrical base portion 32 of the metal case 3 is installed on the support 25 by inserting and holding the tip of the cylindrical base portion 32 of the metal case 3 into the circumferential groove 25c. The core portion 21 is positioned on the support base 25b with the recess that will become the gas pool 5 facing upward, and then the tip surface of the projection of the pressing member 25a is lowered and the recess is pressed with the tip surface to install it on the support 25. The protruding length of the projection portion 31 of the metal case 3 can be determined by adjusting the depth of the circumferential groove 25c provided on the support base 25b.

[0050] (3) Third step (S3) In the third step, the outer periphery 22a of the core portion 21 is poured into the space between the core portion 21 and the cylindrical base portion 32 of the metal case 3, and cured (S3 in Figure 4). Specifically, after pouring the dense refractory material, it is cured for 12 to 18 hours until it hardens. The dense refractory material used here is as listed above. In addition, commonly used tools and auxiliary agents may be used for pouring and curing the material.

[0051] (4) Fourth step (S4) Subsequently, the cured, integrated product of the cylindrical base portion 32, core portion 21, and outer peripheral portion 22a of the metal case 3 is removed from the support 25 and dried. Known equipment and firing conditions can be used for drying. The drying temperature is, for example, 500°C or less.

[0052] (5) Fifth step (S5) In the fifth step, the air supply pipe 34 is attached to the bottom plate portion 33 having the air supply pipe 34 by welding or other means to the enlarged end of the cylindrical base portion 32 of the integrated metal case 3 obtained in the fourth step. In this embodiment, the cylindrical base portion 32 and the bottom plate portion 33 of the metal case 3 are integrated in the fifth step, but the configuration of the metal case 3 is not limited to this.

[0053] From the above steps, a plug preparation 1a is prepared. The plug preparation 1a is formed by a core portion 21 and an outer peripheral portion 22 and has a plug body 2 having a gas flow passage, and a metal case 3 covering the outer circumference of the plug body 2. As described above, the plug preparation 1a has a protrusion 31 from which the metal case 3 protrudes from the outer circumference of the plug body 2.

[0054] (Plug installation process) Next, the plug installation process will be described. The plug installation process involves inserting the plug preparation 1a into the inner hole 71 of the mass block 7 to install it.

[0055] First, the mass block 7 is placed on the mounting base 9 with its outer surface 7B facing upwards. The inner bore 71 of the mass block 7 is pre-coated with adhesive mortar 4. After a release agent (not shown) is applied to the outer surface of the metal case 3 of the plug preparation 1a, the mortar 4 for bonding the mass block is applied.

[0056] Next, the plug preparation 1a is inserted from the outer surface 7B side of the inner hole 71 of the mass block 7 so as to align the longitudinal central axis of the inner hole 71 with the longitudinal central axis of the plug preparation 1a (Figures 5 and 6). Using a hydraulic jack or the like, the plug preparation 1a is pushed in until the outer surface 7A of the mass block 7 and the tip surface 2A of the plug body 2 of the plug preparation 1a are approximately flush (Figure 6). At this time, the protruding portion 31 of the metal case 3 of the plug preparation 1a protrudes from the outer surface 7A of the mass block 7. The mounting base 9 has a space on the tip surface 2A side of the plug body 2, and this space serves as a clearance for the protruding portion 31 of the metal case 3. In this way, the plug preparation 1a is inserted into the inner hole 71 of the mass block 7 and installed.

[0057] (Curing process) Next, the mortar 4 interposed between the plug preparation 1a and the inner bore 71 of the mass block 7 is dried and hardened (cured). In this embodiment, before curing, the mass block 7 on which the plug preparation 1a is installed is changed to a position where the longitudinal central axis of the inner bore 71 of the mass block 7 is oriented sideways (horizontal direction) (Figure 7). Curing in such a sideways position makes it easier to suppress the flow and movement of the mortar 4 during curing. This change in position can be done, for example, by hooking a crane hook onto the lifting fitting 8 and then inverting it with a reversing machine. The curing process is carried out by leaving it on the mounting table 9 in the cured position at room temperature for about 12 to 18 hours (for example, overnight).

[0058] (Metal fitting process) After the curing process described above, a fitting joining process is performed in which a fitting is joined to the plug preparation 1a inside the inner hole 71 of the mass block 7. In this embodiment, the locking fitting 11 is joined to the outer circumference 31A of the protruding portion 31 of the metal case 3 by welding. According to this embodiment, the plug 1 can be easily fixed to the inner hole 71 of the mass block 7 simply by joining the locking fitting 11 to the outer circumference 31A of the protruding portion 31 of the metal case 3. Furthermore, since the locking fitting 11 is joined by welding, it is easier to join. In this embodiment, the fitting joining process can be performed in either a horizontal position (Figure 8) or a vertical position (Figure 9). The choice of which position, horizontal or vertical, to perform the fitting joining process can be determined based on the delivery position of the completed refractory unit 100, the workability of the fitting joining process, etc.

[0059] (Metal fitting process in a sideways position) The lateral orientation is a position in which the protruding portion 31 of the metal case 3 is positioned on the side of the mass block 7, and in this embodiment, it is the same orientation as in the curing process (Figure 7). When the locking fitting 11 is welded to the outer circumference 31A of the protruding portion 31 of the metal case 3 in this lateral orientation (Figure 8), there is no need to change the orientation from the curing process, thus saving the effort of changing the orientation. In the fitting joining process in the lateral orientation, it is necessary to support the locking fitting 11 against the vertical surface of the mass block 7 and perform the welding work, so the vertical orientation, which will be described later, may be easier for welding work. For this reason, considering all factors, this orientation is more likely to be adopted when the completed refractory unit 100 is delivered in an orientation in which the longitudinal central axis of the inner bore 71 of the mass block 7 is oriented in the lateral direction (approximately horizontal direction).

[0060] (Metal fitting process in a vertical orientation) The vertical orientation is the orientation in which the tip surface 1A of the plug preparation 1a and the protruding portion 31 of the metal case 3 are positioned facing upward, and the protruding portion 31 is positioned on the upper surface of the mass block 7. In other words, the vertical orientation is the same orientation as when the refractory unit 100 is installed on the molten metal container (Figure 10). In the fitting joining process in the vertical orientation, first, the mass block 7 on which the plug preparation 1a is installed is changed from the cured orientation (Figure 7) to the vertical orientation shown in Figure 9. Then, the locking fitting 11 is welded to the outer circumference 31A of the protruding portion 31 of the metal case 3 (Figure 10). In the fitting joining process in the vertical orientation, the locking fitting 11 can be welded to the outer circumference 31A of the protruding portion 31 while the locking fitting 11 is supported so as to rest on the horizontal surface of the mass block 7, making it easier to position the locking fitting 11 in the desired position and facilitating the welding work. The vertical orientation for joining metal fittings is even easier to adopt when the refractory unit 100 is delivered in a vertical orientation.

[0061] 2. Modified form of the first embodiment Next, modifications of the plug 1 and refractory unit 100 according to the first embodiment will be described. Note that the configurations disclosed in each of the following modifications can be applied in combination with the configurations disclosed in the above embodiment and other modifications, as long as no inconsistencies arise.

[0062] In the above embodiment, a configuration was described as in which two locking fittings 11 are joined by welding to opposing positions on the outer circumference 31A of the protruding portion 31 of the metal case 3. However, the position and number of locking fittings 11 joined to the plug 1 according to the present invention are not particularly limited. The number of locking fittings 11 may be one or three or more. For example, as shown in Figure 11, four locking fittings 11 may be joined at approximately equal intervals. Increasing the number of locking fittings 11 in this way can further increase the fixing strength of the plug 1 to the mass block 7.

[0063] In the above embodiment, a configuration was described as in which the length (L1) of the locking fitting 11 along the outer circumference 31A of the protruding portion 31 of the metal case 3 after welding is 5 mm or more and 50 mm or less. However, in the plug 1 according to the present invention, the length of the locking fitting along the outer circumference 31A of the protruding portion 31 is not particularly limited and can be appropriately selected according to the required fixing strength, etc. For example, as shown in Figures 12 to 14, the length of the locking fitting along the outer circumference 31A of the protruding portion 31 may be increased. In this case, the locking fitting may be a plate-shaped fitting curved to follow the outer circumference 31A of the protruding portion 31 of the metal case 3.

[0064] In detail, the locking fitting 12 shown in Figure 12 has a length (L2) of 25 mm to 80 mm along the outer circumference 31A of the protruding portion 31 after welding, and in Figure 12, three locking fittings 12 are joined to the outer circumference 31A of the protruding portion 31 at approximately equal intervals. In this configuration, approximately 50% of the total circumference of the outer circumference 31A of the protruding portion 31 is covered by the joints of the three locking fittings 12. Furthermore, the locking fitting 13 shown in Figure 13 has a length (L3) of 20 mm to 60 mm along the outer circumference 31A of the protruding portion 31 after welding, and in Figure 13, four locking fittings 13 are joined to the outer circumference 31A of the protruding portion 31 at approximately equal intervals. In this configuration, approximately 50% of the total circumference of the outer circumference 31A of the protruding portion 31 is covered by the joints of the four locking fittings 13. Furthermore, the locking fitting 14 shown in Figure 14 is ring-shaped, and in Figure 14, the inner edge of the ring-shaped locking fitting 14 is welded to the entire circumference of the outer circumference 31A of the protrusion 31. That is, in Figure 14, the inner edge of the locking fitting 14 is welded to the entire circumference of the outer circumference 31A of the protrusion 31 of the metal case 3, and the length of the joint is 150 mm to 500 mm. As shown in the examples in Figures 12 to 14, if the length of the joint of one or more locking fittings is increased to, for example, 50% or more of the total length of the outer circumference 31A of the protrusion 31 of the metal case 3, the fixing strength of the plug 1 to the mass block 7 tends to be particularly excellent. However, in the present invention, the length of the joint of one or more locking fittings is not particularly limited to the total length of the outer circumference 31A of the protrusion 31 of the metal case 3, and may be, for example, 5% or more, preferably 10% or more. The widthwise lengths (W2, W3) and thicknesses of the locking fittings 12 to 14 shown in Figures 12 to 14 are the same as the widthwise lengths (W1) and thicknesses of the locking fitting 11.

[0065] In the above embodiment, the locking fitting 11 was described as a metal plate-shaped piece. However, the shape of the locking fitting joined to the plug 1 according to the present invention is not limited to a plate-shaped piece, and may be fittings of various cross-sectional shapes. For example, wire-shaped locking fittings 15 and 16 as shown in Figures 15 to 17 may be used. The cross-sectional shape, diameter, length, etc. of the wire-shaped locking fittings 15 and 16 are not particularly limited as long as they can be joined to the outer circumference of the protrusion 31 of the metal case 3, but for example, if the cross-sectional shape is approximately circular, a fitting with a diameter of 5 mm to 10 mm may be used. If the diameter of the locking fitting 15 is 5 mm or more, it is easier to hook the plug 1 onto the edge of the inner hole 71 of the mass block 7 and lock it in place, and easier to obtain fixing strength. If the diameter of the locking fitting 15 is 10 mm or less, the locking fitting 15 does not protrude excessively from the outer surface 7A of the mass block 7, thus providing excellent workability when transporting the refractory unit 100, which is an integral part of the mass block 7, to the furnace construction site and when installing it in the furnace.

[0066] As a detailed example of a wire-shaped locking fitting, as shown in Figures 15 and 16, a long locking fitting 15 may be formed into a ring shape and joined to the entire circumference of the outer periphery 31A of the protruding portion 31 of the metal case 3. In Figure 16, the length of the joint is 150 mm to 500 mm. Alternatively, as shown in Figure 17, two wire-shaped locking fittings 16 may be used, and the length of the joint may be approximately 50% of the entire circumference of the outer periphery 31A of the protruding portion 31.

[0067] 3. Second Embodiment Next, the plug 10 and refractory unit 200 according to the second embodiment will be described with reference to Figures 18 and 19. Components common to the first embodiment will be denoted by the same reference numerals, and their descriptions will be simplified or explained accordingly.

[0068] In this embodiment, the plug 10 has a male thread on the outer circumference 35A of the protruding portion 35 of the metal case 3. The locking fitting 17 is a cylindrical fitting and has a female thread on its inner circumference. In this embodiment, the locking fitting 17 is joined to the outer circumference 35A of the protruding portion 35 by screwing the male thread and the female thread together.

[0069] In this embodiment, the locking fitting 17 can be joined to the outer circumference 35A of the protrusion 35 of the metal case 3 by a method other than welding, thereby forming a refractory unit 200 in which the plug 10 and the mass block 7 are integrated.

[0070] 4. Other Embodiments Other embodiments of the plug, refractory unit, and method for manufacturing the refractory unit according to the present invention will be described below. Note that the configurations disclosed in each of the following embodiments can be applied in combination with configurations disclosed in other embodiments, as long as this does not create a contradiction.

[0071] In the above embodiment, a configuration in which a locking fitting is joined to the outer circumference 31A of the protruding portion 31 of the metal case 3 by welding or screwing was described as an example. However, in the present invention, as long as a locking fitting of a separate component is joined to the outer circumference 31A of the protruding portion 31 of the metal case 3 of the plug 1, the joining method is not limited. For example, the outer circumference 31A of the protruding portion 31 of the metal case 3 and the locking fitting may be joined by methods such as shrink fitting.

[0072] In the above embodiment, an example was described in which the plug body 2 is made of a porous plug. However, in the present invention, the plug body 2 is not limited in its configuration as long as it plays the role of discharging gas supplied from the base end 1B side from the tip surface 1A. For example, the gas flow passage of the plug body 2 may be a plug made of multiple thin tubes, a plug made of multiple slits, etc.

[0073] In the above embodiment, a configuration in which the base end surface 21B of the core portion 21 has a recess that serves as a gas pool 5 was described as an example. However, the presence or absence of the gas pool 5 and its configuration are not particularly limited in the present invention. For example, a gas pool may be provided between the base end surface 21B of the core portion 21 and the base end surface 22B of the outer peripheral portion 22 and the bottom plate portion 33 of the metal case 3.

[0074] In the above embodiment, an example of a manufacturing method in which the metal fitting joining process is performed after the curing process was described. However, in the present invention, the presence or absence of the curing process and its order are not limited. For example, the metal fitting joining process may be performed on the plug preparation 1a before the curing process is completed.

[0075] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention. [Examples]

[0076] The present invention will be further described below with reference to examples. However, the following examples are not limiting to the present invention.

[0077] <Example 1> The refractory unit of Example 1 was manufactured by the following process. (Plug preparation process) The plug preparation 1a shown in Figure 5 was manufactured using the method of the first embodiment shown in Figure 4. In particular, the plug preparation 1a had an inner diameter of 65 mm at the tip surface 1A of the plug 1, the material of the cylindrical base portion 32 of the metal case 3 was SS400, the thickness of the metal case 3 was 1 mm, and the protrusion dimension of the metal case 3 from the outer circumference of the plug body 2 was 5 mm.

[0078] (Process of installing plugs into mass blocks) In the first embodiment shown in Figures 5 and 6, the plug preparation 1a was placed in the inner hole 71 of the mass block 7 so that the protruding portion 31 of the metal case 3 protruded from the outer surface 7A of the mass block 7. Then, the mass block 7 was changed to the position shown in Figure 7 (curing position) and left to stand at room temperature overnight (approximately 12 hours) to allow the mortar 4 to dry and harden (curing). After curing, the protrusion dimension of the protruding portion 31 of the metal case 3 from the outer surface 7A of the mass block 7 was 5 mm.

[0079] (Metal fitting process) Two locking fittings 11 were welded to the outer circumference 31A of the protruding portion 31 of the metal case 3 of the plug preparation 1a fixed in the inner hole 71 of the mass block 7, in a curing position, i.e., a lateral position as shown in Figure 8. A rectangular metal plate (SS400) with a width of 20 mm, a length of 30 mm, and a thickness of 5 mm was used as the locking fitting 11. After joining the locking fitting 11 to the protruding portion 31 of the metal case 3, the width W1 was 20 mm, the length L1 was 30 mm, and the thickness was 5 mm. In this way, the refractory unit of Example 1 was manufactured.

[0080] <Example 2> The refractory unit was manufactured in the same manner as in Example 1, except that the metal fitting joining process was performed in the vertical orientation shown in Figure 10. The dimensions of the locking fitting 11 after joining to the protrusion 31 of the metal case 3 were approximately the same as in Example 1.

[0081] <Comparative Example 1> Instead of the metal fitting joining process, in the vertical orientation shown in Figure 9, a notch was made in the metal case 3 of the plug preparation 1a fixed to the inner hole 71 of the mass block 7 so that the protruding portion 31 was strip-shaped. The strip-shaped portion of the metal case with the notch was then hammered and bent outwards to fix the plug to the mass block. Otherwise, the refractory unit was manufactured in the same manner as in Example 2.

[0082] The refractory units of the examples and comparative examples were evaluated by the following method.

[0083] (Workability of plug fixing work) The working time for the plug fixing process was measured for Examples 1 and 2 and Comparative Example 1. Specifically, the time for the metal fitting joining process was measured for Examples 1 and 2, and the time for the work performed in place of the metal fitting joining process was measured for Comparative Example 1.

[0084] (Durability against vibrations during transportation and installation) The refractory units of Examples 1 and 2 and Comparative Example 1 were transported from the manufacturing plant to the furnace construction site under similar conditions and then installed on the bottom of the molten metal container. Specifically, they were loaded onto trucks using forklifts and cranes from the manufacturing plant and transported by truck to the furnace construction site, a journey of four hours. Upon arrival at the furnace construction site, each refractory unit was moved and transported from the truck using forklifts and cranes, and then installed on the bottom of the molten metal container using a crane. In Example 1, the units were transported in a horizontal position and then changed to a vertical position at the construction site before installation. In Example 2 and Comparative Example 1, the units were transported in a vertical position and installed in that position.

[0085] The refractory unit of Comparative Example 1 required approximately 5 minutes for the work of making cuts in the protruding part of the metal case and bending the resulting strip-shaped portion with a hammer. In contrast, the refractory unit of Example 1 only required welding the locking fitting to the outer circumference of the protruding part of the metal case, and the plug could be fixed to the mass block in approximately 3 minutes. The refractory unit of Example 2, which was joined in a vertical position, allowed the locking fitting to be supported on the horizontal surface of the mass block, making it easier to position the locking fitting relative to the outer circumference of the protruding part of the metal case, and the locking fitting could be joined in approximately 2 minutes. The refractory unit of Example 2 was superior in terms of ease of joining compared to Example 1.

[0086] The refractory units of Examples 1 and 2 and Comparative Example 1 were subjected to vibrations during movement by crane and transportation by truck, but in all cases the plugs did not fall out of the internal holes of the mass blocks or shift out of the internal holes, and the refractory units could be installed at the bottom of the molten metal containers. [Industrial applicability]

[0087] The present invention can be used, for example, as a gas injection plug installed at the bottom of a molten metal container such as a ladle. [Explanation of Symbols]

[0088] 1, 10: Gas injection plug 2: Plug body 3: Metal case 31, 35:Protrusion 31A, 35A: Outer circumference of the protruding part 4: Mortar 7: Mass Block 71: Inner bore of mass block 7A~7F: Outer surface of the mass block 11: Locking hardware 100, 200: Refractory Unit

Claims

1. A gas injection plug having a plug body with a gas flow passage and a metal case covering the outer circumference of the plug body, which is fixed to the inner bore of a mass block, The metal case has a protrusion that extends from the outer circumference of the plug body to the outer surface of the mass block, A gas blowing plug, wherein a locking fitting is attached to at least a portion of the outer circumference of the protruding part of the metal case.

2. The gas blowing plug according to claim 1, wherein the locking fitting is joined to the outer circumference of the protruding portion of the metal case by welding.

3. The gas blowing plug according to claim 1, wherein the outer circumference of the protruding portion of the metal case has a male threaded portion, and the locking fitting is a cylindrical fitting having a female threaded portion on its inner circumference, and the locking fitting is joined to the outer circumference of the protruding portion by screwing the female threaded portion into the male threaded portion.

4. The gas blowing plug according to claim 1, wherein a plurality of the locking fittings are joined at substantially equal intervals to the outer circumference of the protruding portion of the metal case.

5. The gas blowing plug according to claim 4, wherein the length in the width direction along the radial direction of the protruding portion of the locking fitting is 5 mm or more and 50 mm or less, and the thickness of the locking fitting is 1 mm or more and 10 mm or less.

6. A refractory unit comprising a gas injection plug according to any one of claims 1 to 5, and a mass block in which the gas injection plug is fixed to an internal bore.

7. A method for manufacturing a refractory unit, comprising a gas injection plug and a mass block in which the gas injection plug is fixed to an internal bore, A plug preparation step involves preparing a plug preparation body having a plug body with a gas flow passage and a metal case covering the outer circumference of the plug body, wherein the metal case has a protruding portion that extends from the outer circumference of the plug body. A plug installation step involves installing the plug preparation in the inner bore of the mass block such that the protruding portion of the metal case protrudes from the outer surface of the mass block, A method for manufacturing a refractory unit, comprising: a fitting joining step of joining a locking fitting to at least a portion of the outer circumference of the protruding part of the metal case.

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