Composite liner for silicon steel annular heating furnace platform and assembly method

Abstract

The invention discloses a composite liner for a silicon steel annular heating furnace platform and an assembly method, the composite liner comprises an upper gasket, a lower gasket and a liner core, the liner core is arranged between the upper gasket and the lower gasket, the upper gasket and the lower gasket are steel plates made of the same material as a steel coil, and the liner core is a microporous heat insulation pad made of an oxide ceramic fiber material. The method comprises the following steps: manufacturing an upper gasket, a lower gasket and a cushion core with the same size specification and sequentially arranging; fixing holes are formed in the outer ring every 36 degrees and the inner ring every 60 degrees in the circumferential direction, and bolts penetrate through the holes and then are fastened through nuts; the composite liner made of the upper gasket, the lower gasket and the liner core is laid on the furnace platform with the circle center of the heating furnace platform as the datum point. According to the composite liner and the assembling method, the defects of a traditional metal liner are overcome, the heat insulation and heat preservation effects of the furnace bottom are improved, and therefore the defects of edge cutting amount, end deformation, edge cracking and the like of a steel coil are reduced, the silicon steel product quality and the production efficiency are improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical equipment, and particularly relates to a composite gasket for a silicon steel ring heating furnace hearth and an assembly method thereof. Background Art

[0002] The upper structure of the silicon steel ring heating furnace hearth from bottom to top is successively a support brick, a sector brick, a metal chassis, a metal gasket, a steel coil, and a steel cover. Before each loading of the steel coil onto the hearth, a layer of metal gasket needs to be laid first, and after the steel coil is loaded, a protective temperature rise production is carried out using the steel cover.

[0003] The currently used metal gasket has no heat preservation function for the steel coil. As the trolley advances in the furnace, in the vertical direction of the steel coil, the steel coil directly contacts the bottom metal chassis through the metal gasket. Since the heat is transferred from the burners outside the steel cover to the inside of the steel cover, most of the heat transferred into the steel cover accumulates in the upper part of the steel coil, resulting in a phenomenon where the upper part of the steel coil has a high temperature and the lower part has a low temperature. And according to the second law of thermodynamics, the heat absorbed by the steel coil is quickly exchanged with the relatively low-temperature hearth, exacerbating the temperature difference between the top and bottom of the steel coil, and extremely likely to cause the "big head and small head" deformation of the steel coil. At the same time, the heated steel coil is indirectly in contact with the metal chassis through the metal gasket, and the steel coil is greatly affected by the deformation of the metal chassis in the hot state. During the process of thermal expansion and contraction, the plate shape at the bottom of the steel coil is poor, and the plate shape at the bottom of the steel coil is even cracked or defective when entering the subsequent uncoiling process, resulting in problems in uncoiling operation and affecting the yield and other quality problems of the grain-oriented silicon steel products. Secondly, in the circumferential direction, since the outer ring of the metal chassis is closer to the burners, with the attenuation of heat, there is a phenomenon where the temperature of the outer ring of the bottom metal chassis is high and the temperature of the inner ring is low, which is likely to cause uneven temperature at the bottom end face of the steel coil, different crystal phases of the inner and outer ring steel coils, and problems of steel coil end face adhesion. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a composite gasket for a silicon steel ring heating furnace hearth and an assembly method thereof. The composite gasket and the assembly method solve the defects of the traditional metal gasket, improve the heat insulation and heat preservation effects of the furnace bottom, thereby reducing defects such as the trimming amount, end deformation, and edge cracking of the steel coil, improving the quality and production efficiency of silicon steel products, and reducing production costs.

[0005] To solve the above technical problems, the composite gasket for a silicon steel ring heating furnace hearth of the present invention includes an upper gasket, a lower gasket, and a gasket core. The gasket core is arranged between the upper gasket and the lower gasket. The upper gasket and the lower gasket are steel plates made of the same material as the steel coil. The gasket core is a microporous heat insulation pad made of an oxide ceramic fiber material, and its components are 55 - 75wt% Al 2 O 3 、15 - 25wt% SiO 2 、5 - 17wt% ZrO 2 and 3 - 5wt% Y2 O 3 。

[0006] Furthermore, the thickness of the core pad is 10 - 35 mm.

[0007] A method for assembling the above composite liner, characterized by comprising the following steps: Step 1, fabricate upper gaskets, lower gaskets and core pads with the same dimensional specifications; Step 2, leave fixing holes circumferentially every 36° for the outer ring and every 60° for the inner ring on the upper gaskets, lower gaskets and core pads; Step 3, place the processed lower gasket on a horizontal plane for alignment; Step 4, insert fixing bolts through the fixing holes of the lower gasket, place the core pad on the surface of the lower gasket, and align the outer diameter of the core pad with the lower gasket, then insert the fixing bolts through the fixing holes of the core pad; Step 5, place the upper gasket on the surface of the core pad, align and lay it with the core pad and the lower gasket, and after inserting the fixing bolts through the fixing holes of the upper gasket, tighten with nuts; Step 6, take the center of the heating furnace hearth as the reference point, and lay the composite liner made of the upper gasket, lower gasket and core pad on the hearth.

[0008] Since the composite liner and the assembling method for the silicon steel ring - shaped heating furnace hearth of the present invention adopt the above - mentioned technical solutions, that is, the composite liner includes an upper gasket, a lower gasket and a core pad, the core pad is arranged between the upper gasket and the lower gasket, the upper and lower gaskets are steel plates with the same material as the steel coil, and the core pad is a microporous heat - insulating pad made of oxide ceramic fiber material. This method fabricates upper gaskets, lower gaskets and core pads with the same dimensional specifications and arranges them in sequence; leave fixing holes circumferentially every 36° for the outer ring and every 60° for the inner ring, and tighten with nuts after inserting bolts through the holes; take the center of the heating furnace hearth as the reference point, and lay the composite liner made of the upper gasket, lower gasket and core pad on the hearth. This composite liner and assembling method solve the defects of traditional metal liners, improve the heat - insulating and heat - preserving effects of the furnace bottom, thereby reducing defects such as the trimming amount, end deformation and edge cracking of the steel coil, improving the quality and production efficiency of silicon steel products, and reducing production costs. Description of the Drawings

[0009] The following further elaborates on the present invention in conjunction with the drawings and embodiments: Figure 1 It is a schematic structural diagram of the composite liner for the silicon steel ring - shaped heating furnace hearth of the present invention. Detailed Embodiments

[0010] Embodiments are as follows Figure 1As shown, the composite liner for the hearth of a silicon steel annular heating furnace of the present invention comprises an upper gasket 1, a lower gasket 2 and a gasket core 3, wherein the gasket core 3 is arranged between the upper gasket 1 and the lower gasket 2, wherein the upper gasket 1 and the lower gasket 2 are steel plates of the same material as the steel coil, and the gasket core 3 is a microporous heat insulating pad made of oxide ceramic fiber material, wherein the composition is 55-75wt% Al 2 O 3 、15~25wt% SiO 2 、5~17wt% ZrO 2 and 3~5wt% Y 2 O 3 .

[0011] The upper and lower gaskets are made of the same steel plate as the steel coil. Through special design, the gasket surface is more stable in chemical composition and crystal structure than the steel coil product. This significant advantage greatly improves the overall tensile strength of the composite gasket. During the heating and cooling process, the addition of the high tensile strength gasket surface effectively reduces the thermal stress effect of the furnace on the steel coil, and also releases the thermal stress generated during the thermal expansion and contraction of the steel coil, thereby ensuring the stability and safety of the steel coil during the heating process and increasing the forming rate and yield rate of the crystal inside the upper steel coil product.

[0012] The core of the pad is made of high-performance microporous thermal insulation material, which has a unique microporous structure that can capture and fix air, thereby forming an efficient thermal insulation barrier inside. This design allows the core and the steel cover to form a relatively closed heating environment, effectively preventing the rapid transfer of heat from the steel coil to the low-temperature furnace, thereby reducing the temperature difference between the top and bottom of the steel coil, and significantly reducing the risk of deformation of the steel coil caused by uneven heating at the top and bottom. At the same time, in the radial direction of the bottom, the microporous structure of the thermal insulation material also promotes the uniform distribution of heat, ensures uniform heating of the bottom end face, further reduces the temperature difference between the inner diameter and the outer diameter, effectively prevents the problems of steel coil end face adhesion and curling caused by uneven radial temperature at the bottom, and avoids the inner steel ring from falling off during the lifting process due to the difference in expansion coefficients between the inner and outer rings. This composite pad provides a stable load-bearing interface and annealing platform for the steel coil during the heating process, and plays an efficient and uniform insulation effect, thereby improving product quality.

[0013] The fiber material of the core pad has the advantages of low thermal conductivity, large heat capacity and low cost. 2 O 3 、SiO 2 、ZrO 2 , Y 2 O 3 Oxide ceramics are made into high-purity, porous oxide ceramic fibers as the thermal insulation core of the annular furnace.

[0014] The chemical composition of the core pad is closely related to its performance. Deviations in composition and content will affect its physical and chemical properties and service performance. Accurately controlling the composition and content of the fibers is the basis for the stable use of high-performance fibers.

[0015] Al 2 O 3 The fiber has good high-temperature resistance. Using it as the main body of the core pad can improve the expansion coefficient and chemical stability of the core pad. This core pad is prepared from nanofibers stacked along the crystal plane by the most stable α-Al 2 O 3 nanosheets. Since a MgAl 2 O 4 crystallization inhibitor is formed between the nanosheets, the prepared α-Al 2 O 3 nanofibers exhibit good high-temperature heat insulation performance at 1400 - 1600 °C. The test results show that the optimal content of Al 2 O 3 fibers is 55 - 75 wt%.

[0016] SiO 2 is the main framework for forming the core pad. The experimental results show that when its content is 15 - 25 wt%, increasing its content can improve the melting temperature, chemical stability, and mechanical strength of the fiber; SiO 2 has a low thermal conductivity (0.0058 W·m –1 ·K –1 ), effectively improving the strength of the core pad.

[0017] ZrO 2 has a low solid thermal conductivity and a relatively high infrared refractive index, making it an ideal high-temperature heat insulation material. However, when the temperature is higher than 1100 °C, the ZrO 2 phase in the ZrO 2 fibers transforms from the monoclinic phase to the tetragonal phase and undergoes an obvious volume shrinkage of 3 - 7%. Moreover, when the temperature further increases, the ZrO 2 grains grow significantly, and the cracks generated inside the fibers cause a significant reduction in their mechanical properties. The experimental results show that after heat treatment at 1200 °C for SiO 2 and ZrO 2 fibers, the grain growth in the fibers is obvious, resulting in a significant decrease in the strength and flexibility of the fiber membrane, limiting its application at higher temperatures. Therefore, suppressing the phase transformation and abnormal grain growth of ZrO 2 in the ZrO 2 fibers is extremely important.

[0018] Using Y 2 O 3It has a high average infrared reflectivity of up to 92% in the near-infrared band and has significant advantages in isolating radiative heat transfer under high-temperature conditions. In ZrO 2 fibers, an appropriate amount of Y 2 O 3 is added as a stabilizer, and the effects of Y 2 O 3 content on fiber diameter, grain size, and fiber mechanical properties are experimentally studied to inhibit the phase transformation of ZrO 2 at high temperatures and thus improve its stability. The research results show that when the content of Y 2 O 3 is 3-5%, the phase transformation of ZrO 2 at high temperatures is effectively inhibited, and the composite fiber maintains a stable cubic phase structure at 700-1450 °C. At the same time, it is distributed at the grain boundaries and plays a pinning role, thus inhibiting grain growth. The mechanical properties and stability of the core pad are effectively improved.

[0019] Preferably, the thickness of the core pad 3 is 10-35 mm.

[0020] To enable the core pad to achieve a better heat insulation effect, the influence of its thickness on heat insulation and heat preservation performance is studied.

[0021] In the loose structure of the core pad, the main ways of heat transfer are gas heat conduction, solid heat conduction, and thermal radiation. The heating in the annular furnace acts on the surface of the upper gasket, causing the surface temperature to rise rapidly and radiate heat outward. The heating heat flux is much greater than the radiation heat dissipation heat flux. Therefore, the temperature at each point inside the unit will continue to rise. For the middle core pad, heat can be conducted through the fiber material itself and the gas around the fiber, and can also be transferred between the fibers in the form of thermal radiation. Therefore, the total thermal resistance of the core pad insulation unit is composed of the conduction thermal resistance and the radiation thermal resistance in parallel. The conduction thermal resistance of the thin layer of heat insulation fiber material can be expressed as: R C =Δ / λ where R C is the conduction thermal resistance, Δ is the core pad thickness, and λ is the average thermal conductivity of the solid and gas in the fiber material.

[0022] Since the optimum temperature in the annular furnace is constant, the heat transfer resistance of the core pad is required to be constant. Calculations and tests show that the thickness of the core pad is best between 10-35mm. When the thickness of the core pad is <10mm, the heat insulation and thermal insulation effects are not obvious, and defects such as product plate shape and elephant feet cannot be improved well. When the thickness of the pad core is >35mm, when the thin layer is at room temperature, the radiation thermal resistance between the upper and lower surfaces is very large, and the total thermal resistance is often reflected as the conduction thermal resistance of the fiber material. Therefore, the thermal conductivity of the fiber material measured at room temperature can better meet the insulation needs. When the temperature rises, the radiation thermal resistance shows an obvious nonlinear change and decreases rapidly. When the temperature is greater than 850℃, radiation heat transfer dominates. When the temperature continues to rise, when the radiation thermal resistance is less than the thermal conduction thermal resistance, a "thermal short circuit" phenomenon will occur, and the thermal insulation effect of the core pad will deteriorate.

[0023] A composite liner assembly method as described above, characterized in that it comprises the following steps: Step 1: Make an upper gasket, a lower gasket and a gasket core with the same size and specifications; Step 2: The upper gasket, the lower gasket and the gasket core are provided with fixing holes along the circumferential direction at every 36° on the outer ring and every 60° on the inner ring; Step 3: Place the processed lower gasket on a horizontal surface for easy alignment; Step 4: Use fixing bolts to penetrate the fixing holes of the lower gasket, place the gasket core on the surface of the lower gasket, and align the outer diameter of the gasket core with the lower gasket, and penetrate the fixing bolts into the fixing holes of the gasket core; Step 5: Place the upper gasket on the surface of the gasket core and align it with the gasket core and the lower gasket. Insert the fixing bolts into the fixing holes of the upper gasket and tighten them with nuts. Step 6: Lay the composite gasket made of the upper gasket, the lower gasket and the gasket core on the furnace table with the center of the heating furnace table as the reference point.

[0024] After the composite liner is installed, the lower end surface of the steel coil is positioned above the composite liner as a whole and placed in a furnace for heating. After the steel coil is cooled, a tape measure is used to measure the upper and lower diameters of the steel coil, and during the uncoiling process, the integrity of the uncoiling plate shape is checked to see if there is any bonding, thereby verifying the quality of the composite liner and assembly.

[0025] The composite liner assembles the upper and lower gaskets and the core pad into a structural unit in a certain way and is installed at the bottom of the furnace to play the role of bearing heat insulation and heat preservation.

[0026] Three composite liners of different materials and thicknesses were used to carry out actual application tests on site. Thirty rolled steel coils were tested. The following conclusions were drawn, as shown in Table 1: Table 1 Improvement of mechanical properties of composite liner after it was put into production

[0027] Based on the annual output of finished products of 480,000 tons, of which 85% are specifications of 0.23mm and below, and the annual large coil volume of 120,000 tons (of which 50% are specifications of 0.23mm and below), the yield rate of all genuine products with specifications of 0.23mm and below can be increased by 0.6%, generating benefits of approximately 20 million per year.

[0028] Within the chemical composition range of the composite liner, the specific chemical composition and thickness design are shown in Table 2, and the improvement of the mechanical properties of the composite liner after it is put into production is shown in Table 3.

[0029] Table 2 Composition of Examples 1-5 (wt%)

[0030] Table 3 Improvement of mechanical properties of the composite liner after it was put into production

[0031] With the development of silicon steel and new energy vehicle industries, silicon steel products are moving towards ultra-thinness and ultra-high strength, which puts forward new requirements for product surface quality and mechanical properties. The performance of the original ring furnace cannot meet the needs of production line production.

[0032] In response to the above-mentioned problems that after heating in the current silicon steel ring furnace, the steel plate has deformation, edge cracks, elephant feet, different crystal phases of the inner and outer ring steel coils, and adhesion of the end faces of the steel coils, the present application innovatively designs an integrated composite liner for a ring furnace to improve the above defects, improve the heat insulation and thermal insulation effects of the furnace bottom, thereby reducing the amount of trimming, elephant feet and edge cracks and other defects of the product, greatly improving product quality and production efficiency, reducing production costs, and has a good prospect for promotion and application in the field of heating furnaces.

Claims

1. A composite liner for a silicon steel annular heating furnace, characterized in that: It includes an upper gasket, a lower gasket and a gasket core, the gasket core is arranged between the upper gasket and the lower gasket, the upper gasket and the lower gasket are steel plates of the same material as the steel coil, and the gasket core is a microporous thermal insulation pad made of oxide ceramic fiber material, and its components are 55-75wt% Al2O3, 15-25wt% SiO2, 5-17wt% ZrO2 and 3-5wt% Y2O3.

2. The composite liner for the hearth of a silicon steel annular heating furnace according to claim 1, characterized in that: The thickness of the core pad is 10 to 35 mm.

3. A method for assembling a composite liner for a silicon steel annular heating furnace according to claim 1 or 2, characterized in that The steps include: Step 1: Make an upper gasket, a lower gasket and a gasket core with the same size and specifications; Step 2: The upper gasket, the lower gasket and the gasket core are provided with fixing holes along the circumferential direction at every 36° on the outer ring and every 60° on the inner ring; Step 3: Place the processed lower gasket on a horizontal surface for easy alignment; Step 4: Use fixing bolts to penetrate the fixing holes of the lower gasket, place the gasket core on the surface of the lower gasket, and align the outer diameter of the gasket core with the lower gasket, and penetrate the fixing bolts into the fixing holes of the gasket core; Step 5: Place the upper gasket on the surface of the gasket core and align it with the gasket core and the lower gasket. Insert the fixing bolts into the fixing holes of the upper gasket and tighten them with nuts. Step 6: Lay the composite gasket made of the upper gasket, the lower gasket and the gasket core on the furnace table with the center of the heating furnace table as the reference point.

Images