Refractory insulation and refractory lining structure for molten vessels

Abstract

We provide highly durable, heat-insulating, and fire-resistant materials. [Solution] The heat-insulating refractory material 10 comprises a refractory material 1 having a recess 3 formed by a bottom portion 11 and a peripheral wall portion 12, and a heat-insulating material 2 disposed in the recess 3, wherein the refractory material 1 has a curved portion 13 that curves outward in a convex shape at least a part of the boundary between the bottom portion 11 and the peripheral wall portion 12 in the recess 3 and the boundary between the peripheral wall portions 12 themselves.

Description

Technical Field

[0001] The present invention relates to a heat-insulating refractory and a refractory lining structure of a melting vessel using the same.

Background Art

[0002] In various industrial furnaces such as melting furnaces and heating furnaces, heat-insulating refractories are used for the purpose of reducing heat loss (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses a furnace floor material for a heating furnace, which is composed of a container-shaped refractory shaped to have a recess and refractory fibers filled in the recess.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The furnace floor material described in Patent Document 1 enhances mechanical strength with a container-shaped refractory and enhances heat insulation performance with refractory fibers filled in the recess. When such a refractory having a recess is repeatedly heated and expands and contracts repeatedly, tensile stress or compressive stress may act at the boundary between the bottom and the side wall of the recess, resulting in cracks. When cracks, breaks, or chips occur, it is necessary to replace the furnace floor material, increasing the working cost and material cost of the industrial furnace.

[0006] Therefore, there is a need to realize a heat-insulating refractory with excellent durability.

Means for Solving the Problems

[0007] The heat-insulating refractory material according to the present invention comprises a refractory material having a recess formed by a bottom portion and a peripheral wall portion, and a heat-insulating material disposed in the recess, wherein the refractory material has a curved portion that curves outward in a convex shape at least a part of the boundary between the bottom portion and the peripheral wall portion and the boundary between the peripheral wall portions in the recess.

[0008] With this configuration, even if the heat-insulating refractory material is repeatedly heated and expands and contracts, the stress generated inside the refractory material is distributed by the curved section, making it less likely for stress to concentrate at the boundary between the bottom and the surrounding wall. Therefore, the occurrence of cracks at the boundary between the bottom and the surrounding wall is suppressed, and the durability of the heat-insulating refractory material can be improved. In addition, because the refractory material has a curved section, the thickness of the bottom and surrounding wall that constitute the recess can also be increased, making it possible to improve the strength of the refractory material itself.

[0009] In one embodiment, the heat-insulating fire-resistant material according to the present invention preferably has a ratio of the radius of curvature of the curved portion to the height dimension of the recess, which is 0.2 or more and 1 or less.

[0010] This configuration allows for the suppression of stress concentration at the boundary between the bottom and the surrounding wall, and also allows for the placement of sufficient insulation material in the recess to ensure the thermal insulation properties of the heat-insulating refractory material.

[0011] In one embodiment of the present invention, it is preferable that the refractory material has a void between the bottom and the thermal insulation material.

[0012] With this configuration, the voids function as an insulating layer, which reduces the heat flux passing through the insulating refractory material, thereby improving the insulating performance of the refractory material.

[0013] In one embodiment, the heat-insulating refractory material according to the present invention preferably includes a microporous heat-insulating material.

[0014] This configuration allows for the use of heat-insulating refractory materials as linings for various industrial furnaces.

[0015] In one embodiment of the heat-insulating refractory material according to the present invention, it is preferable that at least a portion of the heat-insulating material is covered by a covering portion.

[0016] This configuration enhances the water resistance of the microporous insulation material through the covering, thereby suppressing deterioration even when exposed to moisture or water vapor, and improving the durability of the refractory insulation material.

[0017] The refractory lining structure of a molten container according to the present invention is characterized in that, from the outside of the molten container, it has a steel shell, a permanent refractory layer, and a workpiece refractory layer in this order, and the permanent refractory layer includes a heat insulating refractory as described in any of the above embodiments.

[0018] This configuration, with its high thermal insulation performance, allows for a thinner refractory lining. As a result, the amount of molten metal in the melting vessel increases, improving operational efficiency. Furthermore, if the refractory lining thickness is kept the same as conventional methods, the steel shell temperature decreases, reducing energy loss.

[0019] Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments. [Brief explanation of the drawing]

[0020] [Figure 1] This is a cross-sectional view of the heat-insulating fire-resistant material according to the first embodiment. [Figure 2] This is a plan view of the heat-insulating fire-resistant material according to the first embodiment. [Figure 3] This is a cross-sectional view of a heat-insulating refractory material according to the second embodiment. [Figure 4] This is a cross-sectional view of a heat-insulating refractory material according to the third embodiment. [Figure 5] This is a schematic diagram showing an example of a molten vessel constructed with the lining structure according to the present invention. [Modes for carrying out the invention]

[0021] An embodiment of the heat-insulating refractory according to the present invention will be described with reference to the drawings. The heat-insulating refractory is not limited to the following embodiments, and various modifications are possible without departing from the gist thereof.

[0022] As shown in FIGS. 1 and 2, the heat-insulating refractory 10 according to the present embodiment includes a refractory 1 and a heat-insulating material 2. The refractory 1 has a recess 3 with its upper end open, and the recess 3 is formed by a bottom portion 11 and a peripheral wall portion 12. The heat-insulating material 2 is disposed in the recess 3. In the following description, a portion of the heat-insulating refractory 10 related to the recess 3 including the heat-insulating material 2 may be referred to as a heat-insulating portion 21.

[0023] The heat-insulating refractory 10 is used, for example, as a furnace floor material of a heating furnace or a heat-insulating material for various industrial furnaces such as a molten steel ladle. When the heat-insulating refractory 10 is used, the surface of the side of the refractory 1 opposite to the surface where the recess 3 is formed is used as the operating surface side.

[0024] The thermal conductivity of the heat-insulating refractory 10 is preferably less than 1.5 W / (m·K), more preferably less than 0.6 W / (m·K), still more preferably less than 0.4 W / (m·K), and even more preferably less than 0.35 W / (m·K). The value of the thermal conductivity is a value calculated by heating the flat surface (the surface on the side of the bottom portion 11) of the heat-insulating refractory 10 and obtaining the temperature gradient on the flat surface and the surface where the heat-insulating material 2 is disposed on the side opposite to the flat surface. The thermal conductivity in the present embodiment is, for example, the thermal conductivity in the two layers of the refractory 1 and the heat-insulating material 2 disposed in the recess 3.

[0025] As shown in Figure 1, a curved portion 13 is formed at the boundary between the bottom portion 11 and the peripheral wall portion 12 of the recess 3, which curves outward in a convex shape. Outward refers to the direction toward the outer surface of the refractory material 1, not the direction toward the recess 3 from the bottom portion 11 or the peripheral wall portion 12. The curved portion 13 may be a circular arc or an elliptical arc. Furthermore, it is not limited to a circular or elliptical arc, and the boundary between the bottom portion 11 and the peripheral wall portion 12 may be chamfered. By having the curved portion 13 in the refractory material 1, the thickness of the bottom portion 11 and the peripheral wall portion 12 near the corners of the recess 3 can be increased compared to the case where the curved portion 13 is not present. Preferably, the recess 3 is a circular arc in cross-section, and in this case, the ratio of the radius of curvature R of the curved portion 13 to the height dimension h of the recess 3 (R / h) should be 0.2 or more and 1 or less. If R / h is 0.2 or higher, the stress acting on the boundary between the bottom 11 and the peripheral wall 12 due to repeated heating of the heat-insulating refractory material 10 is distributed to the bottom 11 and the peripheral wall 12, making it easier to suppress the occurrence of cracks. If R / h is 1 or lower, it is easier to place a sufficient amount of heat-insulating material 2 in the recess 3, making it easier to improve the heat insulation performance. R / h is more preferably 0.25 or higher and 0.5 or lower.

[0026] The ratio (h / H) of the height dimension h of the recess 3 to the height dimension H of the refractory material 1 should be between 0.2 and 0.8. If h / H is 0.2 or greater, it is easier to place a sufficient amount of insulating material 2 in the recess 3, thereby improving the insulating performance. If h / H is 0.8 or less, it is easier to ensure the strength of the refractory material 1.

[0027] The recess 3 is formed approximately in the center of the refractory material 1. In plan view, the recess 3 according to this embodiment is approximately rectangular, as shown in Figure 2, and a curved portion 13 that curves outward in a convex shape is formed at the boundary between its peripheral wall portions 12. The curved portion 13 may be the same as or different from the curved portion 13 formed at the boundary between the bottom portion 11 and the peripheral wall portion 12, and may be a circular arc or an elliptical arc. The shape of the recess 3 in plan view is not limited to approximately rectangular and can be arbitrarily determined, for example, it may be circular, elliptical, or polygonal. Furthermore, a curved portion 13 does not have to be formed at the boundary between the peripheral wall portions 12; instead of a curved portion 13, a chamfer may be formed at the boundary between the peripheral wall portions 12.

[0028] The area of ​​the recess 3 in plan view should be 0.50 to 0.74 times the area of ​​the refractory material 1. If the area of ​​the recess 3 is 0.50 times or more, it is easier to place the insulating material 2 in the recess 3, and thus easier to improve the insulating performance. If the area of ​​the recess 3 is 0.74 times or less, it is easier to ensure the strength of the refractory material 1.

[0029] The thickness of the peripheral wall portion 12 in the horizontal direction is preferably approximately the same in the longitudinal and transverse directions of the refractory material 1, but it may be different. If the thickness of the peripheral wall portion 12 is constant, it is easier to suppress the concentration of stress acting on the peripheral wall portion 12 due to the expansion and contraction of the refractory material 1 in a part of the peripheral wall portion 12, and thus easier to prevent the occurrence of cracks.

[0030] In this embodiment, curved portions 13 are formed at all boundaries between the bottom portion 11 and the peripheral wall portion 12, and at all boundaries between the peripheral wall portions 12 themselves. However, the curved portions 13 may be formed at least in part of these boundaries.

[0031] The material of the refractory material 1 should be selected according to the application of the heat-insulating refractory material 10. The refractory material 1 can be composed of, for example, alumina, high-alumina, alumina-silica, silica, or magnesia. Among these, it is preferable that the refractory material 1 be composed of a high-alumina refractory material with alumina content of about 70% by mass. High-alumina refractory materials are preferable as container-shaped refractory materials having recesses 3 because they have a relatively small coefficient of thermal expansion and high strength.

[0032] The thermal insulation material 2 may fill the entire space of the recess 3, but it is preferable that it be slightly spaced apart from the bottom 11 and the peripheral wall 12. For example, the size of the gap between them should be between 0.3 mm and 1.0 mm. If the size of the gap is 0.3 mm or more, it is easier to place the thermal insulation material 2 in the recess 3, and interference between the bottom 11, the peripheral wall 12 and the thermal insulation material 2 becomes less likely. If the size of the gap is 1.0 mm or less, the thermal insulation material 2 placed in the recess 3 will be less likely to move, thus stabilizing the shape of the thermal insulation refractory material 10. Adhesive may be placed between the thermal insulation material 2 and the bottom 11 or the peripheral wall 12. The adhesive can fix the thermal insulation material 2 in the recess 3, thereby further stabilizing the shape of the thermal insulation refractory material 10. The adhesive can be, for example, a vinyl acetate-based adhesive, but is not limited to this.

[0033] The thermal insulation material 2 includes, for example, amorphous refractory insulation materials having refractory insulation fibers, refractory insulation bricks such as high-alumina refractories, ceramic fibers, and microporous insulation materials. The thermal insulation material 2 may be selected from one of these types, or it may be formed by a combination of multiple types. It is preferable to use a microporous insulation material as the thermal insulation material 2, as it has higher thermal insulation performance than still air. Because microporous insulation materials have a smaller thermal shrinkage rate than ceramic fibers, even if the thermal insulation refractory material 10 is repeatedly heated, the formation of gaps between the thermal insulation material 2 and the bottom 11 and peripheral wall 12 is suppressed, and the thermal insulation performance of the thermal insulation refractory material 10 can be maintained over a long period of time. In particular, it is more preferable if the thermal shrinkage rate of the microporous insulation material at 1400°C × 24h, as measured according to JIS R3311, is 2.5% or less, as this allows the thermal insulation performance to be maintained over a long period of time. Furthermore, for microporous insulation materials, a thermal conductivity of 0.1 (W / m·K) or less at 600°C, as measured according to JIS A1412-2, is preferable as it further improves insulation performance.

[0034] Next, a method for manufacturing the heat-insulating refractory material 10 according to this embodiment will be described. First, a process for manufacturing a refractory material 1 is carried out to obtain a refractory material 1 having a recess 3. The refractory material 1 may be manufactured by pressure molding the refractory material to be used as a raw material using a mold corresponding to the recess 3, or it may be manufactured by pour molding of an amorphous refractory material using a core corresponding to the recess 3. In either case, the refractory material 1 can be obtained in the same manner as the normal refractory material manufacturing process, except for the use of a mold or core corresponding to the recess 3. In the case of pressure molding, the refractory material and binder are weighed, mixed and kneaded, placed in a mold, molded using a friction press or hydraulic press, and then fired at a predetermined temperature to obtain the refractory material 1. In the case of pour molding, the refractory material, binder, water, etc. are weighed in the same manner as in pressure molding, mixed and kneaded, poured into a mold with a core, degassed and cured, and then fired at a predetermined temperature to obtain the refractory material 1.

[0035] Subsequently, by placing the heat insulating material 2 in the recess 3 of the refractory material 1, a heat insulating refractory material 10 is obtained. When placing the thermal insulation material 2 into the recess 3, an adhesive may be applied to the surface of the thermal insulation material 2 or the recess 3 before placing the thermal insulation material 2 into the recess 3.

[0036] [Second Embodiment] The heat-insulating refractory material 10 according to the second embodiment will be described with reference to Figure 3. The refractory material 1 according to the second embodiment has a gap 14 between the bottom portion 11 and the heat-insulating material 2. The other components are the same as those of the first embodiment, so the same components as the first embodiment will not be described.

[0037] The void portion 14 is a space within the recess 3 where the insulating material 2 is not placed, and a layer of air is formed in the void portion 14. Because the refractory material 1 has a void portion 14, the layer of air formed in the void portion 14 improves the insulating effect of the insulating refractory material 10. In this embodiment, the insulating portion 21 is formed by the insulating material 2 and the void portion 14, so the thermal conductivity of the insulating portion 21 can be reduced by the void portion 14. The vertical dimension of the void portion 14 (i.e., the dimension between the bottom portion 11 and the insulating material 2) is preferably 20 mm or less. This makes it less likely for convective heat transfer to occur in the void portion 14, so it is possible to make the heat flux passing through the insulating refractory material 10 smaller. Considering the general size of refractory materials used as hearth materials for various heating furnaces and insulating materials for various industrial furnaces, the vertical dimension of the void portion 14 is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1 mm or less. It is preferable that the vertical dimension of the gap 14 is 3 mm or less, as this reduces the likelihood of interference between the heat insulating material 2 and the refractory material 1 placed in the recess 3. As described in the first embodiment, it is preferable that the dimension between the heat insulating material 2 and the bottom 11 or peripheral wall 12 of the refractory material 1 be 0.3 mm or more, from the viewpoint of facilitating the placement of the heat insulating material 2 in the recess 3.

[0038] The void 14 is formed when the corners of the rectangular heat insulating material 2 placed in the recess 3 catch on the curved portion 13. If heat insulating material 2 without corners is used, the void 14 may be formed by applying adhesive to the outer surface of the heat insulating material 2 or to each surface of the peripheral wall portion 12 in the recess 3 to fix the heat insulating material 2 in the recess 3. Alternatively, the void 14 may be formed by placing a rod-shaped or square-shaped support material to support the heat insulating material 2 on the upper surface of the bottom portion 11, and then placing the heat insulating material 2 on top of the support material so that the upper surface of the bottom portion 11 and the heat insulating material 2 do not come into contact.

[0039] [Third Embodiment] The heat-insulating refractory material 10 according to the third embodiment will be described with reference to Figure 4. At least a portion of the heat-insulating material 2 according to the third embodiment is covered by the covering portion 4. Therefore, the heat-insulating portion 21 according to this embodiment is composed of the heat-insulating material 2 covered by the covering portion 4. The other configurations are the same as in the first embodiment, so the same configurations as in the first embodiment will not be described.

[0040] As shown in Figure 4, the covering portion 4 covers the entire surface of the thermal insulation material 2. The covering portion 4 is waterproof or water-repellent, and can be, for example, aluminum foil, aluminum glass cloth tape, or a silicone-based water-repellent material. The covering portion 4 suppresses contact between the thermal insulation material 2 and moisture, so that when the thermal insulation refractory material 10 is installed, moisture contained in castables, mortar, etc., does not come into contact with the thermal insulation material 2, and shrinkage and cracking of the thermal insulation material 2 due to reaction with moisture are suppressed.

[0041] The thickness of the covering portion 4 can be determined arbitrarily, but it is preferable to set it to 0.01 mm or more and 0.5 mm or less, and more preferably to 0.01 mm or more and 0.2 mm or less, in order to suppress the reaction between aluminum and the heat insulating material 2.

[0042] The covering portion 4 is formed by attaching aluminum foil or aluminum glass cloth tape to the surface of the heat insulating material 2. When the covering portion 4 is made of a silicone-based water-repellent material, the covering portion 4 is formed by impregnating the heat insulating material 2 with the silicone-based water-repellent material.

[0043] [Refractory lining structure of molten vessels] As shown in Figure 5, the refractory lining structure of the molten container 5 according to this embodiment has, from the outside of the molten container 5, a steel shell 50, permanent refractory layers 51 and 52, and a workpiece refractory layer 53 in that order.

[0044] The permanent refractory layer includes any of the heat-insulating refractory materials 10 according to the first to third embodiments described above. The permanent refractory layer may also be configured to include multiple layers containing heat-insulating refractory materials, in which case at least one of the multiple layers may include any of the heat-insulating refractory materials 10 according to the first to third embodiments described above.

[0045] The permanent refractory layer of the refractory lining structure according to this embodiment comprises a first heat-insulating refractory layer 51 arranged adjacent to the steel shell 50 and a second heat-insulating refractory layer 52 arranged adjacent to the workpiece refractory layer 53, wherein the second heat-insulating refractory layer 52 is configured to include any of the heat-insulating refractory materials 10 according to the first to third embodiments described above.

[0046] Examples of applicable first heat-insulating refractory materials include, but are not limited to, molded bricks of type B (JIS classification B1 to B6). The first heat-insulating refractory layer 51 has a bricklaying structure of such molded bricks, and its thickness during construction is, for example, 30 mm to 150 mm.

[0047] The second layer 52 of the heat-insulating refractory material has a brickwork structure of the heat-insulating refractory material 10 according to any of the first to third embodiments described above, and its thickness during construction is, for example, 30 mm or more and 150 mm or less.

[0048] Applicable workpiece refractories include, but are not limited to, alumina-magnesia castables. The thickness of the workpiece refractory layer 53 during construction is, for example, between 100 mm and 2000 mm.

[0049] Furthermore, the refractory lining structure according to this embodiment is not limited to the configuration described above, and mortar may be applied between the steel shell 50 and the permanent refractory layer, and between layers in the permanent refractory layer, as needed.

[0050] Examples of molten metal containers 5 to which the refractory lining structure according to this embodiment can be applied include, but are not limited to, a molten metal ladle used to transport molten metal extracted from a blast furnace to the next ironmaking process.

[0051] The refractory lining structure according to this embodiment can be applied to both the side walls and the bottom of the molten container 5, but it can be more preferably applied to the side walls of the molten container 5, where the effects of the thermal load are particularly large. In the case of the refractory lining structure according to this embodiment, a microporous thermal insulation material can also be applied to the bottom of the molten container 5.

[0052] In the refractory lining structure according to this embodiment, the high thermal insulation performance allows for a thinner refractory lining thickness. As a result, the amount of molten metal in the melting vessel increases, improving operational efficiency. Furthermore, in the refractory lining structure according to this embodiment, the high thermal insulation performance means that if the refractory lining thickness is the same as conventional methods, the steel shell temperature decreases, reducing energy loss. Therefore, the high thermal insulation performance of the refractory lining structure according to this embodiment can be utilized for either of the above effects.

[0053] [Examples] The present invention will be further described below with reference to examples. However, the following examples are not limiting to the present invention.

[0054] (Insulating and refractory material) A refractory material 1 was fabricated using a high-alumina refractory material containing approximately 70% by mass of alumina, in which the ratio of the radius of curvature R of the curved portion 13 to the height dimension h of the recess 3 (R / h) was 0.25. The height dimension h of the recess 3 was set to 12 mm. The refractory material 1 was manufactured by friction pressing using a mold corresponding to the recess 3. Ceramic fiberboard, microporous insulation material, refractory insulation brick, or amorphous refractory insulation material was placed in the recess 3 of the manufactured refractory material 1 as the insulation material 2, resulting in Examples 1 to 4 as shown in Table 1. IsoWool BSSR board (manufactured by Isolite Industry Co., Ltd.) was used as the ceramic fiberboard, LTC-HT (manufactured by Isolite Industry Co., Ltd.) as the microporous insulation material, A7 (manufactured by Isolite Industry Co., Ltd.) as the refractory insulation brick, and F-Tamp 16W (manufactured by Isolite Industry Co., Ltd.) as the amorphous refractory insulation material. In all of Examples 1 to 3, the insulation material 2 was placed in the recess 3 so as not to leave any gaps between the insulation material 2 and the bottom portion 11 and the peripheral wall portion 12. In Example 4, an amorphous refractory insulating material was poured into the recess 3 and fired at a predetermined temperature to obtain a refractory insulating material 10.

[0055] [Table 1]

[0056] Furthermore, in Example 5, a heat-insulating refractory material 10 was prepared in the same manner as in Example 2, except that it had a void portion 14. The height dimension of the void portion 14 in Example 5 was 2 mm.

[0057] A heat-insulating refractory material 10 without recesses 3 and heat-insulating material 2 was prepared using the material of the refractory material 1 according to Examples 1 to 5, and this was designated as Comparative Example 1. Comparative Example 1 corresponds to a rectangular high-alumina refractory material without recesses 3.

[0058] The thermal insulation performance was evaluated for each of Examples 1-5 and Comparative Example 1. The thermal insulation performance was evaluated by placing the flat side of the insulating refractory material 10 in a heating furnace and heating it. After the heated surface reached 600°C, the amount of heat transferred to the opposite side of the heated surface was photographed with a thermal camera, the temperature was measured, and the thermal conductivity was calculated. The thermal conductivity was determined for structures consisting of two layers, refractory material 1 and insulating material 2, in Examples 1-4 and Examples 6-9; for a structure consisting of three layers, refractory material 1, void 14, and insulating material 2, in Example 5; and for a structure consisting of one layer, refractory material 1, in Comparative Example 1. The thermal insulation performance was evaluated by classifying the results as follows: "A" if the calculated thermal conductivity was less than 0.35 W / (m·K), "B" if the thermal conductivity was 0.35 W / (m·K) or more but less than 0.40 W / (m·K), "C" if the thermal conductivity was 0.40 W / (m·K) or more but less than 0.60 W / (m·K), "D" if the thermal conductivity was 0.60 W / (m·K) or more but less than 1.50 W / (m·K), and "E" if the thermal conductivity was 1.50 W / (m·K) or more. The results obtained are shown in Table 1.

[0059] Compared to Comparative Example 1, which lacked the recess 3 and the thermal insulation material 2, Examples 1 to 5 all exhibited good thermal insulation performance. Examples 2 and 5, which used a microporous thermal insulation material as the thermal insulation material 2, showed excellent thermal insulation performance. In particular, Example 5, which had the void portion 14, had the lowest thermal conductivity, indicating that the thermal insulation performance of the thermal insulation refractory material 10 can be improved by having the void portion 14.

[0060] Next, the crack formation of the heat-insulating refractory material 10 due to repeated heating was evaluated. As shown in Table 2, the crack evaluation was performed on Examples 1, 6-9, and Comparative Example 2, each with different R / h values ​​for the curved portion 13. Examples 6-9 are heat-insulating refractory materials 10 prepared in the same manner as Example 1, except that the R / h value is different. Comparative Example 2 is a heat-insulating refractory material prepared in the same manner as Example 1, except that it does not have a curved portion 13.

[0061] [Table 2]

[0062] The evaluation of crack formation was performed by heating the surface of the bottom 11 of refractory material 1 (the side opposite to the side where the insulating material 2 is placed) to 1200°C, then subjecting it to a thermal cycle of 10 cycles of heating to room temperature, and observing the condition of the recess 3 of refractory material 1 after the test. The evaluation of cracks was as follows: "A" for no crack formation, "B" for microcracks less than 30 mm in length, "C" for small cracks between 30 mm and 60 mm in length, and "D" for large cracks of 60 mm or more that made the material unusable. The obtained results are shown in Table 2. The results of the thermal insulation performance evaluation are also shown in Table 2.

[0063] Comparative Example 2, which does not have a curved portion 13, showed large cracks at the boundary between the bottom portion 11 and the peripheral wall portion 12 or at the boundary of the peripheral wall portion 12. However, Examples 1, 6-9, which have a curved portion 13, showed only minor cracks or no cracks at all. From these results, it can be seen that the presence of a curved portion 13 in the refractory material 1 can suppress the occurrence of cracks in the refractory material 1. Since the results for Examples 1, 7-9 were B or higher, it is suggested that the occurrence of cracks can be further suppressed if the R / h is 0.25 or higher. Furthermore, as shown in Table 2, the thermal insulation performance evaluation results were all C, which indicates that even if the R / h is different, the thermal insulation performance does not change if other conditions are the same.

[0064] Next, an evaluation of water resistance was conducted. As shown in Table 3, this evaluation was performed on the heat-insulating refractory materials 10 of Examples 10 to 12, which were prepared using Example 2 and the heat-insulating material 2 whose surface was covered with the covering part 4. In Example 10, LTC-HT (manufactured by Isolite Industries Co., Ltd.) was used as the heat-insulating material 2 and aluminum foil was used as the covering part 4, so that the entire surface of the heat-insulating material 2 was covered with the covering part 4. Example 10 was prepared in the same manner as Example 2, except that the covering part 4 was used. Example 11 was prepared in the same manner as Example 10, except that aluminum glass cloth tape was used as the covering part 4, and Example 12 was prepared in the same manner as Example 10, except that the covering part 4 was formed by impregnating the heat-insulating material 2 with a silicone-based water-repellent material.

[0065] [Table 3]

[0066] Water resistance was evaluated based on the dimensional change of the insulating material 2 after applying refractory mortar to the side of the insulating refractory material 10 where the insulating material 2 was placed and heating it at 900°C for 24 hours. Specifically, the dimensions of the insulating material 2 covered by the covering part 4 and the dimensions of the insulating material 2 after removing the refractory mortar after heating were measured, and the linear shrinkage rate was calculated. The water resistance evaluation was performed by assigning "A" to a linear shrinkage rate of less than 0.8%, "B" to a linear shrinkage rate of 0.8% or more and less than 2.0%, "C" to a linear shrinkage rate of 2.0% or more and less than 7.5%, and "D" to a linear shrinkage rate of 7.5% or more. The obtained results are shown in Table 3. The evaluation results for Examples 6, 9-11 were all C or higher, indicating that the shrinkage was at a level that would not interfere with use. Compared to Example 2, which does not have the covering portion 4, Examples 10-12, which have the covering portion 4, had smaller linear shrinkage rates, indicating that the presence of the covering portion 4 in the thermal insulation material 2 can improve water resistance. In particular, Examples 10 and 11 showed the smallest linear shrinkage rates and excellent water resistance.

[0067] Next, an evaluation of the thickness of the voids was conducted. This evaluation was performed on the heat-insulating refractory materials 10 of Examples 5, 13-16, each having voids of various thicknesses, as shown in Table 4.

[0068] For the evaluation of thermal insulation, the degree of heat transfer in the void was evaluated in three stages. When there is a void, there is no conduction heat transfer, which is heat conduction between solids, and if the thickness of the void is below a certain level, convection heat transfer, which is heat transfer by fluid, is unlikely to occur, so it was evaluated as "A", which is the best thermal insulation performance. When the thickness of the void is greater than 5 mm, convection heat transfer occurs easily and heat is transferred easily, so it was evaluated as "B". When the void thickness is 0 mm, heat conduction between solids occurs due to contact, so it was evaluated as "C". Note that the evaluation of thermal insulation performance related to the thickness of the void was evaluated using different criteria than the thermal insulation performance evaluation in Tables 1 and 2 above.

[0069] The ease of placing the insulation material was evaluated in two stages, depending on whether or not processing of the insulation material was necessary. When the void thickness was 2 mm or more, the insulation material could be placed as is, so it was evaluated as "A". When the void thickness was 1 mm or less, the insulation material needed to be processed to match the shape of the radius of curvature R of the curved section 13, so it was evaluated as "B".

[0070] The evaluation of the quality stability of the insulation material was the same as that for its thermal insulation performance. Since the operating temperature varies depending on the type of insulation material, selecting an insulation material with the desired operating temperature will not affect the quality, but a higher thermal insulation performance was given a better evaluation.

[0071] The presence or absence of interference between the thermal insulation material and the refractory material was evaluated in three stages according to the thickness of the void. The smaller the void thickness, the easier it is for the thermal insulation material to remain in its designated position, so a void thickness of 3 mm or less was evaluated as "A". As the void thickness increases, the position where the thermal insulation material 2 shifts when the fixing force of the thermal insulation material 2 in the recess 3 is lost also increases, so a void thickness of more than 3 mm but less than 8 mm was evaluated as "B", and a void thickness of 8 mm or more was evaluated as "C".

[0072] The overall evaluation was as follows: "A" if all items were A, "B" if there was one B, and "C" if there were two or more B's.

[0073] [Table 4]

[0074] (Refractory lining structure) Next, the case in which the heat insulating refractory material 10 was lined to the molten container 5 and its thickness was varied was evaluated. In this embodiment, the refractory lining structure of the molten container 5 is provided in the following order from the outside of the molten container 5: a steel shell 50, a first heat insulating refractory layer 51 (permanent refractory layer), a second heat insulating refractory layer 52 (permanent refractory layer), and a work refractory layer 53 (alumina-magnesia castable). Alumina mortar was applied to a thickness of 3 mm between the first heat insulating refractory layer 51 and the second heat insulating refractory layer 52, and between the steel shell 50 and the first heat insulating refractory layer 51.

[0075] In Comparative Example 1 of the refractory lining structure, a Class B refractory insulating brick (JIS classification B4) was used as the first insulating refractory material, and a non-recessed alumina brick (fired brick with an Al2O3 value of 70% to 80%), as shown in Comparative Example 1 of Table 1, was used as the second insulating refractory material. In Examples 1 to 3 of the refractory lining structure, Class B refractory insulating bricks (JIS classification B4) of different thicknesses were used as the first insulating refractory material, and a recessed alumina brick (recessed fired brick with an Al2O3 value of 70% to 80%) was used as the second insulating refractory material, with a microporous insulating material (thickness 10 mm) covered with alumina glass cloth tape, with a 2 mm gap in the recess (recess edge thickness 15 mm).

[0076] [Table 5]

[0077] When the thickness of the first heat-insulating refractory on the steel shell 50 side is reduced, the amount of molten metal increases and the surface temperature of the steel shell 50 also rises. However, the steel shell temperature remains lower than that of the comparative example, demonstrating superior heat insulation. Reducing the thickness of the lining increases the amount of molten metal and improves operational efficiency. On the other hand, the effect of the heat load also increases with the increase in the amount of molten metal. However, it was found that by using the heat-insulating refractory of the present invention, a high heat insulation effect can be maintained even when the thickness of the lining is reduced. Furthermore, it was found that when the thickness of the refractory lining is the same as that of the comparative example, the steel shell temperature decreases, thus reducing energy loss. [Industrial applicability]

[0078] This invention can be used in heat-insulating refractory materials equipped with heat-insulating materials. [Explanation of symbols]

[0079] 1: Refractory 2: Insulation materials 3: Recess 10: Heat-insulating and fire-resistant materials 11: Bottom 12: Peripheral wall part 13: Curved section 14:Void part 4: Covering part 5: Melting vessel 50: Iron skin 51: The first layer of insulating refractory material (permanent refractory layer) 52: Second layer of insulating refractory material (permanent refractory layer) 53: Workpiece refractory layer H: Dimensions R: radius of curvature

Claims

1. A refractory material having a recess formed by the bottom and the surrounding wall, The recess comprises a heat insulating material, The aforementioned refractory material is a heat-insulating refractory material having a curved portion that curves outward in a convex shape at least a part of the boundary between the bottom portion and the peripheral wall portion in the recess and the boundary between the peripheral wall portions.

2. The heat-insulating fire-resistant material according to claim 1, wherein the ratio of the radius of curvature of the curved portion to the height dimension of the recess is 0.2 or more and 1 or less.

3. The refractory material is the heat insulating refractory material according to claim 2, having a void between the bottom and the heat insulating material.

4. The aforementioned heat insulating material is a heat insulating refractory material according to claim 1, which includes a microporous heat insulating material.

5. The heat insulating refractory material according to claim 4, wherein at least a portion of the heat insulating material is covered by a covering portion.

6. A refractory lining structure for a molten vessel, comprising, from the outside of the molten vessel, a steel shell, a permanent refractory layer, and a workpiece refractory layer, The refractory lining structure for a melting vessel comprises a permanent refractory layer containing a heat insulating refractory as described in any one of claims 1 to 5.

7. A molten vessel having the refractory lining structure described in claim 6.

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