Construction method of refractory material on opening of heating furnace, and heating furnace with opening to which refractory material is applied by the same

Abstract

To provide a construction method of refractory material on an opening of a heating furnace allowing replacement work of radiant tubes to be easily carried out, and upon the replacement work of the refractory material on the opening, allowing the replacement work to be carried out without removing the radiant tube.SOLUTION: A construction method of refractory material on an opening of a heating furnace comprises a step of installing a heat insulation block provided with a crystalline alumina fiber mat around the opening such that an end surface of the crystalline alumina fiber mat faces the opening side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for applying a refractory material to an opening of a heating furnace, and to a heating furnace having an opening thereof applied with the refractory material by the method. [Background technology]

[0002] Generally, the refractory material in heating furnaces such as cold rolling annealing furnaces is constructed as a paper lining structure in which ceramic fiber mats are stuck onto studs installed in the furnace shell and laminated. The ceramic fiber mats contain foreign matter that did not break down into fibers during spinning, known as shot, which, when scattered into the furnace, can cause scratches on the steel sheet. For this reason, methods have been adopted in which the outermost surface of the furnace interior is covered with stainless steel sheet or with fibers with a low shot rate.

[0003] In addition, the heating furnace has an opening for inserting and removing radiant tubes, and the end face of this opening is generally covered with a stainless steel plate in order to protect the refractory material from friction and other factors associated with inserting and removing the radiant tubes. However, this stainless steel frame deforms due to heat, which creates a problem in that when replacing the radiant tube, the deformed stainless steel frame interferes with the radiant tube, making the replacement difficult.

[0004] Therefore, there is a method of covering the opening with a mat made of alumina fibers that are less susceptible to thermal deformation and have a low shot content (Patent Documents 1 and 2), but because the surface of the alumina fiber mat is exposed on the end face of the opening, there is a problem in that the surface of the alumina fiber mat is easily damaged, such as being rolled up by friction caused by inserting and removing the radiant tube.

[0005] Furthermore, in the above-mentioned method of protecting the end faces of the openings with stainless steel plates or alumina fiber mats, the radiant tubes must be removed during replacement work, and the use of a crane is essential to remove the radiant tubes, which creates the problem that it is difficult to find time to perform the replacement work during limited regular maintenance periods due to the speed limitations of crane work. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2006-10107 [Patent Document 2] Patent Publication No. 2013-22162 Summary of the Invention [Problem to be solved by the invention]

[0007] Based on the above, the present invention aims to provide a method for installing fire-resistant material at the opening of a heating furnace, which makes it easy to replace radiant tubes and allows the replacement of the fire-resistant material at the opening to be performed without removing the radiant tubes, and a heating furnace in which fire-resistant material has been installed at the opening using this method. [Means for solving the problem]

[0008] As a result of extensive research aimed at solving the above problems, the present inventors have discovered the following. By placing an insulating block with a crystalline alumina fiber mat around the opening of the heating furnace and positioning the mat so that its edge faces the opening, the opening can be formed by the edge of the mat, which prevents shot from scattering and improves the abrasion and scratch resistance of the opening. Unlike conventional methods, there is no need to place a stainless steel frame or alumina fiber mat between the fireproofing material and the component inserted into the opening (such as a radiant tube) to protect the fireproofing material. This means that when repairing the fireproofing material around the opening, the repair work can be carried out without removing the radiant tube, etc.

[0009] Based on the above, the present inventors have completed the following invention. [1] A method for installing a fireproof material at the opening of a heating furnace, a step of placing an insulating block comprising a crystalline alumina fiber mat around the opening so that an end face of the crystalline alumina fiber mat faces the opening, How to install fireproofing material on furnace openings. [2] The method for installing a refractory material to an opening of a heating furnace according to [1], wherein the crystalline alumina fiber mat is folded to form the insulating block.

[0010] [3] The method for installing refractory material in the opening of a heating furnace according to [1] or [2], wherein the insulating block is provided with a metal fitting for fixing the block on the side that contacts the furnace shell. [4] The method for installing a refractory material to an opening of a heating furnace according to any one of [1] to [3], wherein the insulating block has a mat of crystalline alumina fiber on the opening side and a mat of amorphous ceramic fiber adjacent to the mat of crystalline alumina fiber.

[0011] [5] The method for applying a fireproof material to an opening of a heating furnace according to any one of [1] to [4], further comprising a pre-process step of removing the existing stainless steel frame. [6] The method for applying a refractory material to an opening of a heating furnace according to any one of [1] to [5], wherein the opening is an opening for installing a radiant tube.

[0012] [7] A heating furnace in which a fireproof material is installed at the opening of the heating furnace by the installation method described in any one of [1] to [6]. [Effects of the Invention]

[0013] According to the method for applying refractory material to the opening of a heating furnace of the present invention, the opening is formed with a crystalline alumina fiber mat, which eliminates the need to cover the surface with a stainless steel frame, making it easier to insert and remove radiant tubes. Furthermore, replacing the refractory material around the opening does not require removing the radiant tube, which makes the work of replacing the refractory material around the opening more efficient. [Brief explanation of the drawings]

[0014] [Figure 1] Fig. 1(a) is a perspective view of a heat insulating block 10 used in the present invention, and Fig. 1(b) is a schematic diagram showing a method for manufacturing the heat insulating block 10. [Figure 2] FIG. 2 is a schematic diagram showing the state of the refractory material around the opening when the opening is viewed from inside the annealing furnace. [Figure 3] Fig. 3(a) is a perspective view of a composite block, and Fig. 3(b) is a schematic diagram showing a state in which the surface of the composite block is covered with a mat 11 of crystalline alumina fibers. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, as an example of an embodiment of the present invention, a method for applying a refractory material to an opening of a heating furnace and a heating furnace having an opening of the heating furnace applied with the refractory material by the method will be described, but the scope of the present invention is not limited to the embodiment described below. Unless otherwise specified, the description "a to b" indicating a numerical range means "a or more and b or less," and also includes the meanings "preferably greater than a" and "preferably smaller than b." Furthermore, even if the upper and lower limits of the numerical ranges in this specification are slightly outside the numerical range specified by the present invention, they are considered to be included in the equivalent range of the present invention as long as they have the same functional effects as those within the numerical range.

[0016] <How to install fireproofing material on the opening of a heating furnace> The method of applying refractory material to an opening of a heating furnace of the present invention includes a step of placing an insulating block comprising a crystalline alumina fiber mat around the opening so that the end face of the crystalline alumina fiber mat faces the opening side.

[0017] (Thermal insulation block 10 comprising a mat 11 of crystalline alumina fibers) As shown in Figure 1(a) as a perspective view of an insulating block 10 and in Figure 1(b) as a conceptual diagram of the manufacturing process of the insulating block 10, the insulating block 10 shown as one embodiment comprises a mat 11 of folded crystalline alumina fibers, and preferably has a block fixing bracket 12 on the side that contacts the furnace shell.

[0018] Folded crystalline alumina fiber mat11 Examples of the alumina fibers forming the folded crystalline alumina fiber mat 11 include alumina / silica, and single or composite fibers of zirconia, spinel, titania, and calcia containing alumina / silica. Among these, alumina / silica fibers, particularly polycrystalline alumina / silica fibers, are preferred in terms of heat resistance, fiber strength (toughness), and safety. Alumina / silica fibers with an alumina ratio of 70 to 80% by mass and a silica ratio of 30 to 20% by mass are particularly preferred.

[0019] The shot content of the crystalline alumina fibers constituting the crystalline alumina fiber mat, as specified by JIS R-3312, is preferably 2% or less for sizes of 212 μm or more, preferably 2% or less for sizes of 45 μm or more, and more preferably less than 1% for sizes of 5 μm or more.

[0020] As the crystalline alumina fiber mat 11, a mat (needle blanket) in which a needling process is applied to an aggregate of crystalline alumina fibers that does not substantially contain fibers with a diameter of 3 μm or less is preferred, for the reason that it improves heat resistance and durability while ensuring safety. The bulk density of the crystalline alumina fiber is not particularly limited, but from the viewpoint of the heat resistance and strength of the heat insulating block 10 to be formed, it is preferred that the bulk density be 85 kg / m 3~150kg / m 3 is preferred, and 90 kg / m 3 ~140kg / m 3 is more preferable. The thickness of the crystalline alumina fiber mat 11 is appropriately selected, but is preferably 10 to 30 mm, more preferably 12.5 to 27 mm, from the viewpoints of workability and strength. If the thickness is too thin, work becomes time-consuming, and if the thickness is too thick, there is a problem that it is difficult to maintain the structure when folded. The size of the crystalline alumina fiber mat 11 is not particularly limited, and can be cut to a suitable size depending on the size of the desired heat insulating block.

[0021] Crystalline alumina fiber mat 11 folding methods The folding method of the crystalline alumina fiber mat 11 is not particularly limited as long as it has folds on the surface of the insulating block 10 that will be installed in the furnace shell (surface P1 on which the block fixing bracket 12 is installed in Figure 1(a)). From the viewpoint of firmly fixing the insulating block 10 to the furnace shell, it is preferable that there be at least two folds on the surface P1 of the insulating block 10 that will be installed in the furnace shell, and more preferably four or more folds. The upper limit of the number of folds depends on the size of the insulating block 10, but is preferably 10 or less, and more preferably 8 or less. In the embodiment shown in Figure 1(a), five folds are formed on the surface P1 of the insulating block 10 that will be installed in the furnace shell.

[0022] The folding method of the crystalline alumina fiber mat 11 may be to fold one long mat zigzag as shown in Figure 1(b), or to combine multiple long mats zigzag folded together, or to prepare multiple mats folded in half and assemble them with the folds aligned on the side P1.

[0023] There is no particular limitation on the bulk density of the insulating block 10, but it is preferably 96 kg / m 3 ~160kg / m 3 is preferred, and 100 kg / m 3 ~140kg / m3 It is preferable that the folded crystalline alumina fiber mat 11 constituting the insulating block 10 is ultimately in a compressed state. In other words, it is preferable that the folded crystalline alumina fiber mat 11 is compressed with the beam 14, which will be described later, inserted and fixed in place. Furthermore, by achieving a predetermined bulk density, it is possible to prevent shot from passing through if there is a ceramic fiber block on the backside, and it also has the effect of improving resistance to friction and impact when inserting and removing radiant tubes, i.e., durability.

[0024] The compression ratio is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, from the viewpoint of improving the heat resistance and durability of the insulating block 10. Furthermore, from the viewpoint of preventing deformation of the beam 14, the upper limit is preferably 40% or less. Note that by increasing the compression ratio, the bulk density of the insulating block 10 increases, improving the heat resistance and durability of the insulating block 10.

[0025] The insulation block 10 can be compressed and its structure maintained by stitching it with an alumina rope or the like. The bulk density of the insulation block 10 can also be increased by folding and stacking the crystalline alumina fiber mat 11, compressing it by pressing down on both sides of the compressed surface with pressure plates 16 such as plywood or metal plates, and securing it with bands 18. While Fig. 1(a) shows a configuration in which the compression is maintained by bands 18 and pressure plates 16, the compressed state can also be maintained by bands 18 alone, without using pressure plates 16.

[0026] After installation, the bands 18 are cut to release the compression of the insulating blocks 10, allowing the insulating blocks 10 to be tightly attached to each other and fixed to the furnace shell.

[0027] 12 block fixing brackets A block fixing bracket 12 can be attached to the surface P1 of the insulating block 10 that contacts the furnace shell. The insulating block 10 is installed in the furnace shell by connecting the block fixing bracket 12 to a stud provided on the furnace shell (for example, by inserting the stud provided on the furnace shell into a hole 122 provided in the block fixing bracket 12 and fastening it with a nut from the crystalline alumina fiber mat 11 side on the back surface of the block fixing bracket 12). Alternatively, the insulating block 10 can be installed in the furnace shell by welding a stud to the block fixing bracket 12, passing the stud through a hole formed in the furnace shell, and fastening it from outside the furnace with a nut or the like.

[0028] The block fixing metal fittings 12 can be formed as a plate-like body extending in the stacking direction of the folded crystalline alumina fiber mat 11, as shown in Figure 1(a), and from the viewpoint of providing strength, it is preferable that the cross section be U-shaped.

[0029] As shown in FIG. 1(b), the block fixing metal fitting 12 preferably has a hole 122 in the center of the lamination direction of the crystalline alumina fiber mat 11, or preferably has a stud instead of a hole at the same location. A slit for inserting the blade 142 of the beam 14 is formed in a plate-like body extending in the lamination direction of the folded crystalline alumina fiber mat 11.

[0030] From the viewpoint of strength and heat resistance, the material of the block fixing metal fittings 12 is preferably heat-resistant stainless steel such as SUS310S or SUS304.

[0031] (Method of manufacturing the heat insulating block 10) An example of a method for manufacturing the heat insulating block 10 will be described below.

[0032] First, a crystalline alumina fiber mat 11 having a desired width and length is cut out. The cut crystalline alumina fiber mat 11 is alternately folded and stacked as shown in Fig. 1(b). Also, as shown in Fig. 1(b), a beam 14 is attached inside the fold of the crystalline alumina fiber mat 11 so that the edge faces the furnace shell side of the insulation block 10 to be formed. The beam 14 has the function of fixing the block fixing metal fitting 12 and the folded crystalline alumina fiber mat 11, and as shown in the figure, is inserted into the folded portion of the crystalline alumina fiber mat 11, and the blade 142 of the beam 14 penetrates the mat 11 and protrudes toward the furnace shell side of the insulation block 10, and as will be explained later, this blade is fixed to the block fixing metal fitting 12. Furthermore, since the beam 14 is inserted into the crystalline alumina fiber mat 11 and is located on the furnace wall side when installed on the furnace wall, damage due to heat can be suppressed.

[0033] The number of beams 14 is not particularly limited as long as it can attach the block fixing metal fittings 12, but from the viewpoint of bonding strength, it is preferably four or more. The material of the beams 14 is not particularly limited as long as it can exhibit heat resistance when used in a furnace, but examples thereof include SUS310S and SUS304. The shape of the beams 14 is not particularly limited as long as it can fix the folded crystalline alumina fiber mat 11 and the block fixing metal fittings 12, but examples thereof include a shape in which a triangular blade is welded to a round bar as shown in the figure.

[0034] Note that if the crystalline alumina fiber mat 11 is not folded zigzag but is instead stacked as a plate, the beam 14 cannot be used to secure the block fixing hardware 12 and the crystalline alumina fiber mat. In this case, a cross bar to which a support bracket is welded is inserted so as to penetrate the stacked mat. While the present invention does not exclude the use of such a cross bar, from the standpoint of durability, it is preferable to use the beam 14 to secure the block fixing hardware 12 and the crystalline alumina fiber mat 11.

[0035] 1(b), guide pipes 15 can also be attached inside the folds of the crystalline alumina fiber mat 11. The holes in the guide pipes 15 correspond to the holes 122 in the block fixing brackets 12, and serve as guides for tightening nuts from inside the furnace to join the studs provided on the furnace shell to the block fixing brackets 12 fixed to the insulation blocks 10. The number of guide pipes 15 in the insulation blocks 10 corresponds to the number of studs corresponding to each insulation block 10. Note that after the nuts have been tightened, the guide pipes 15 are preferably removed, as their function has been fulfilled. As mentioned above, the guide pipe 15 is used when a stud is formed in the furnace shell and connected to the block fixing bracket 12. However, in a configuration in which a stud is formed in the block fixing bracket 12 and this stud is passed through a hole formed in the furnace shell to fix the furnace shell and the block fixing bracket 12, the guide pipe 15 is not necessary.

[0036] The material of the guide pipe 15 is not particularly limited, and metal, cardboard, or plastic cylinders can be used. The inner diameter depends on the diameter of the stud and the size of the bolt, but is preferably 10 to 30 mm. Furthermore, it is preferable to use nuts made of heat-resistant stainless steel such as SUS310S or SUS304.

[0037] Generally, a crystalline alumina fiber mat 11 placed on a furnace wall is fixed to the furnace wall by its own repulsive force, but the block fixing metal fittings 12 are used to firmly fix the insulating block 10 to the furnace wall in addition to the repulsive force of the mat. Because the block fixing metal fittings 12 are attached to the furnace wall (steel shell), they are preferably made of a material that can suppress damage from heat, and are preferably made of heat-resistant stainless steel such as SUS310S or SUS304.

[0038] 1(a), the sides are then held down with similarly sized holding plates 16, and the crystalline alumina fiber mat 11 is compressed to a predetermined thickness in the lamination direction via the holding plates 16 using a compression packing machine or the like, and fixed with bands 18. The bands 18 are used to compress and fix the insulation block 10 to a predetermined size. There are no particular restrictions on the material of the bands 18 as long as they perform this function, but for example, polypropylene (PP) bands, polyethylene (PE) bands, iron bands, etc. can be used.

[0039] The pressure plates 16 are attached to the sides of the insulation blocks 10 and serve to protect the insulation blocks 10 when they are compressed by the bands 18. After the insulation block unit 100, which includes multiple insulation blocks 10, is installed on the furnace wall, the bands 18 are cut and the pressure plates 16 are removed. The material of the pressure plates 16 is not particularly limited and can be selected as appropriate from plywood, wood, steel, plastic, cardboard, and the like. The shape of the pressure plates 16 is not particularly limited, but is selected to match the shape of the side surfaces of the insulation blocks 10. The size of the pressure plates 16 is not particularly specified, but it is preferable that they be slightly larger than the size of the insulation blocks 10.

[0040] Thereafter, the block fixing metal fitting 12 is attached to the blade 142 of the beam 14 protruding from the crystalline alumina fiber mat 11. For example, the block fixing metal fitting 12 can be fixed to the beam 14 by passing the blade 142 of the beam 14 through a slit 124 provided in the block fixing metal fitting 12, bending the blade, and fastening it with welding or screws.

[0041] (Step of placing the heat insulating block 10 at the opening of the heating furnace) Heating furnaces and heat treatment furnaces have many openings for burners, entrances and exits for maintenance personnel, etc. For example, as shown in Fig. 2, the furnace shell 50 of an annealing furnace (an example of a heating furnace) is provided with an opening 70 through which a radiant tube (not shown) can be inserted and removed. Fig. 2 shows a schematic diagram of the opening 70 as seen from inside the furnace. Furthermore, openings may be formed on the upper and lower sides of the heating furnace as entrances and exits, and such openings are also within the scope of the present invention.

[0042] In the method for applying the refractory material 30 of the present invention, the heat insulating block 10 is installed around the opening 70 so that the end face of the crystalline alumina fiber mat 11 faces the opening. As a result, the opening of the annealing furnace is formed by the end face of the crystalline alumina fiber mat 11. In the embodiment shown in Fig. 2, the heat insulating block 10 is set around the entire periphery of the opening so that the end face faces the opening side, so that the entire periphery of the opening is formed by the end face of the crystalline alumina fiber mat 11.

[0043] The crystalline alumina fiber mat 11 has better abrasion resistance and scratch resistance at the end faces than at the flat faces, so the above configuration provides durability against friction and impact, even when a radiant tube is inserted or removed from the opening. Here, the plane of the crystalline alumina fiber mat 11 refers to the front and back surfaces of the mat 11 in Figure 1(b) that come into contact with the beam 14 and the block fixing hardware 12, and the end surfaces of the crystalline alumina fiber mat 11 refer to the surfaces that form the end portions of the mat 11 other than the plane (including the cut surfaces of the mat 11). Furthermore, the crystalline alumina fiber mat 11 has a low level of shot, eliminating the risk of these shot diffusing into the furnace. Therefore, there is no need to cover the surface with a stainless steel frame. Furthermore, because the crystalline alumina fiber mat 11 does not deform due to heat, it does not interfere with the radiant tubes when they are inserted or removed, allowing for smooth insertion and removal of the radiant tubes.

[0044] The effects of the present invention can be obtained if at least a portion of the opening is formed by the end face of the crystalline alumina fiber mat 11 of the insulating block 10, but it is preferable to form the entire circumference of the opening by the end face of the crystalline alumina fiber mat 11 of the insulating block 10 in order to maximize the effects of the present invention.

[0045] The refractory material 30 adjacent to the insulating block 10 comprising a crystalline alumina fiber mat 11 installed to cover the periphery of the opening may be a similar insulating block 10, or alternatively, an insulating block 20 comprising an amorphous ceramic fiber mat may be installed. The insulating block 20 comprising an amorphous ceramic fiber mat has the same construction as the insulating block 10 described above, except that the mat is made of amorphous ceramic fiber.

[0046] Amorphous ceramic fibers are produced by spinning alumina and silica raw materials molten at high temperatures into fibers using a centrifugal spinning method or a blowing method using high-speed compressed air. Amorphous ceramic fibers contain non-fibrous particles, or shot, that remain in a particulate form and cannot be fully fused into fibers, but this is preferable from a cost perspective. Therefore, in the present invention, they can be used as the refractory material 30 other than the insulation block 10 that forms the opening. Furthermore, when an insulating block 20 equipped with an amorphous ceramic fiber mat is used, it is preferable to place a crystalline alumina fiber mat 11 on the furnace inside of the insulating block 20 to prevent shot from scattering from the block 20, so that the ceramic fiber mat is not exposed to the furnace inside.

[0047] It is also possible to integrate the insulating block 10 comprising the crystalline alumina fiber mat 11 and the insulating block 20 comprising the amorphous ceramic fiber mat by sewing them together with a heat-resistant rope such as an alumina rope. For example, the insulating block 10 comprising the crystalline alumina fiber mat 11 forming the opening shown in Figure 2 and the insulating block 20 comprising the adjacent ceramic fiber mat can be integrated by sewing them together with an alumina rope to form a single insulating block (also called a composite block).

[0048] Figure 3(a) shows a perspective view of a composite block made by integrating insulating block 10 and insulating block 20. When insulating block 10 and insulating block 20 are integrated, production costs can be reduced by reducing the amount of crystalline alumina fiber mat 11 used, but it is preferable that the width W1 of the crystalline alumina fiber mat 11 installed around the opening be 50 mm or more. This allows production costs to be reduced while maintaining wear resistance and durability when inserting and removing radiant tubes. Furthermore, by using such a composite block, it is possible to improve the efficiency of installing the heat insulating block that forms the opening.

[0049] When a composite block is used, the surface of the insulating block 20 exposed to the furnace interior can be covered with a crystalline alumina fiber mat 11, as shown in Figure 3(b). In this case, for example, the crystalline alumina fiber mat 11 can be placed over the surface of the insulating block 20 and sewn to the insulating block 20 with an alumina rope or the like, or can be adhered with a heat-resistant adhesive. Alternatively, by sandwiching the tip portion 115 of the crystalline alumina fiber mat 11 between the composite blocks and covering the surface of the insulating block 20 with the crystalline alumina fiber mat 11, shot scattering can be further prevented.

[0050] <Heating furnace> As described above, by placing an insulating block 10 comprising a crystalline alumina fiber mat 11 around an opening formed in the furnace shell 50 of the heating furnace so that the end face of the crystalline alumina fiber mat 11 faces the opening, it is possible to provide resistance to frictional impacts, for example, when inserting or removing a radiant tube. Furthermore, since the opening is made of a mat 11 of crystalline alumina fiber with a low shot content, there is no need to cover it with a stainless steel frame, and therefore there is no interference when inserting or removing the radiant tube. The heating furnace of the present invention in which the refractory material 30 is installed by the installation method of the present invention as described above has the above-mentioned effects. [Industrial Applicability]

[0051] According to the method for applying refractory material to the opening of a heating furnace of the present invention, the opening is formed by the end face of a crystalline alumina fiber mat, eliminating the need to cover the surface with a stainless steel frame, making it easier to insert and remove radiant tubes. Furthermore, replacing the refractory material around the opening does not require removing the radiant tube, making the work of replacing the refractory material around the opening more efficient. [Explanation of symbols]

[0052] 10: Insulation block 11: Folded crystalline alumina fiber mat 12: Block fixing hardware 14: Beam 15: Guide pipe 20: Thermal insulation block made of ceramic fiber mat 30: Fireproof material 70: Opening of the heating furnace

Claims

1. A method for installing a refractory material at an opening of a heating furnace, comprising: a step of placing an insulating block comprising a crystalline alumina fiber mat around the opening so that an end face of the crystalline alumina fiber mat faces the opening, How to install fireproofing material on furnace openings.

2. 2. The method of applying a refractory material to an opening of a heating furnace according to claim 1, wherein the crystalline alumina fiber mat is folded to form the insulating block.

3. 3. The method for installing a refractory material at an opening of a heating furnace according to claim 1, wherein the heat insulating block is provided with a metal fitting for fastening the block on a side that contacts the furnace shell.

4. 3. The method for installing a refractory material to an opening of a heating furnace according to claim 1 or 2, wherein the insulating block is provided with the crystalline alumina fiber mat on the opening side and with an amorphous ceramic fiber mat adjacent to the crystalline alumina fiber mat.

5. 3. The method for applying a refractory material to an opening of a heating furnace according to claim 1, further comprising a pre-processing step of removing an existing stainless steel frame.

6. 3. The method for applying a refractory material to an opening of a heating furnace according to claim 1, wherein the opening is an opening for installing a radiant tube.

7. A heating furnace in which a fireproof material is applied to an opening of the heating furnace by the application method of claim 1 or 2.

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