A stable glazed ceramic hot-bending rock plate and a preparation method thereof

Abstract

This invention belongs to the field of ceramic materials and processing technology, and relates to a stable glazed ceramic hot-bent slab and its preparation method. The invention includes a green body and a glaze. The green body adopts a multi-component composite flux system, including 20-25 parts quartz, 18-22 parts calcined kaolin, 18-22 parts potassium feldspar, 22-25 parts sodium feldspar, 8-12 parts wollastonite, 2-3 parts magnesium oxide, 0.2-0.5 parts iron oxide, and 0.1-0.3 parts titanium dioxide. The glaze includes 50-70 parts frit glaze, 0.5-5 parts coloring oxide, 2-6 parts alumina, and 1-4 parts zinc oxide. Through innovative green body and glaze formulations and optimized secondary hot-bending heat treatment processes, this invention achieves a hot-bending temperature ≤1150℃ and a holding time ≤60min. The resulting ceramic hot-bent slab has advantages such as high forming accuracy, no surface cracks, good strength retention, small glaze color difference, and low energy consumption, and has good prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials and processing technology, and relates to a stable glazed ceramic hot-bending slab and its preparation method. In particular, it relates to a ceramic hot-bending slab that can achieve high-precision, non-destructive forming, including its body formula, matching glaze formula, and secondary hot-bending heat treatment process. Background Technology

[0002] Ceramic slabs, as a new type of high-performance building decoration material, are widely used in countertops, walls, and floors due to their excellent properties such as high strength, scratch resistance, high temperature resistance, and impermeability. In recent years, with the increasing demand for irregular decorations, hot-bent ceramic slabs have gradually attracted attention. They are formed by heating the slabs to soften them and then bending them into shapes, making them suitable for curved countertops, column cladding, curved background walls, and other applications.

[0003] Current production methods for hot-bent ceramic slabs primarily involve preparing finished slabs first, followed by a secondary heating and softening process. This means the slab blank is first sintered at high temperature to form the finished slab, then softened by secondary heating to a specific temperature, subsequently bent using a mold, and finally annealed and cooled. In similar solutions, some manufacturers introduce a certain proportion of plasticizing materials or fluxes into the slab formulation to improve its ductility and forming stability during hot bending.

[0004] However, the inventors found in long-term production practice that the existing production process still has the following defects: (1) Large springback at the bend and low forming accuracy: Due to improper control of the high temperature viscosity of the blank, the high temperature plastic deformation capacity of the slab material during the hot bending process is insufficient, and the internal stress is not completely released during the cooling stage, resulting in a large deviation in the forming angle of the hot-bent slab after cooling (usually ±2-3°). Especially at the bend, springback is likely to occur, resulting in a large deviation between the finished product angle and the mold design angle, making it difficult to meet the high precision splicing requirements and affecting the installation accuracy and aesthetics. (2) The surface is prone to cracking, producing micro-cracks or crazing: During the hot bending process, the expansion coefficients of the glaze and the blank are not matched, resulting in thermal stress concentration during heating and cooling, or gas escaping from the inside of the blank during secondary heating, which can easily cause bulging, micro-cracks or even cracking of the glaze, resulting in fine cracks on the surface of the hot-bent slab, especially on the curved outer arc surface, which can even lead to the breakage of the slab in severe cases. (3) Significant decrease in strength after hot bending: During the high-temperature hot bending process, the original stable crystalline phase structure formed by sintering is destroyed, and there is a lack of effective crystalline phase reconstruction mechanism. Therefore, after the existing slabs undergo a second hot bending, their bending strength generally decreases by 10%-20%, affecting the product's service life and safety. (4) Low production efficiency and high energy consumption: The existing hot bending process mostly adopts a single-piece batch heating method, which has a long heating and cooling cycle, high energy consumption, and difficulty in achieving continuous production, resulting in high manufacturing costs.

[0005] In summary, existing ceramic hot-bent slabs still suffer from problems such as poor forming accuracy, unstable surface quality, decreased mechanical properties, low production efficiency, and high production costs in terms of material composition design and production process. Systematic improvements are urgently needed in the slab formulation system and hot-bending process. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of large bending springback, easy surface cracking, decreased mechanical properties, and low production efficiency in existing hot-bent ceramic slabs. It proposes a stable glazed ceramic hot-bent slab and its preparation method. Through innovative body formulation, a matching glaze system, and optimized secondary hot-bending heat treatment process, a hot-bending temperature ≤1150℃, holding time ≤60min, energy consumption reduced by 30%-40%, stable glaze, strong decorative effect, color difference ΔE <3.0, and gloss retention rate ≥90% are achieved. The resulting ceramic hot-bent slab has comprehensive advantages such as low-temperature and high-efficiency hot bending, significant energy saving, high forming precision, no surface cracks, good strength retention, and small glaze color difference. It is suitable for irregular decorative scenarios such as curved countertops, cylindrical coverings, and curved background walls, and has good industrial application prospects.

[0007] The technical solution of this invention is: This invention provides a formula for a heat-bendable ceramic slab blank, a slab glaze formula, and a secondary heat treatment process for the slab. Details are as follows: This invention provides a stable glazed ceramic hot-bent slab, comprising a body and a glaze; The billet adopts a K2O-Na2O-CaO-MgO multi-component composite flux system to replace the traditional single flux. By introducing MgO, it works synergistically with CaO, K2O and Na2O to significantly reduce the glass transition temperature and softening temperature of the billet. The measured softening initiation temperature is about 1100℃, which allows hot bending to be completed below 1150℃, while avoiding excessive melting at high temperatures that could cause the billet to collapse.

[0008] The green body formula includes the following components in parts by weight: 20-25 parts of quartz (SiO2); 18-22 parts of calcined kaolin (Al2Si2O7) are used to provide Al2O3, which improves the whiteness and high-temperature strength of the body. Compared with traditional raw kaolin, calcined kaolin has a lower loss on ignition and higher structural stability, which helps to reduce the amount of gas released during the first firing and second hot bending process (reducing the loss on ignition, which is controlled below 0.1%), and preventing the glaze from producing pores or bubbles due to the exhaust gas during the second heating. This effectively avoids glaze bulging or micro-cracks caused by gas escape, and the strength retention rate of the finished product is over 95%.

[0009] Potassium feldspar (KAlSi3O8) 18-22 parts; 22-25 parts of albite (NaAlSi3O8); 8-12 parts of wollastonite (CaSiO3) are used to introduce CaO, adjust the coefficient of expansion of the green body, and promote the formation of crystal phases; 2-3 parts of magnesium oxide (MgO) are used to introduce MgO and form a multi-component composite flux system with CaO, K2O and Na2O, which effectively reduces the softening temperature of the billet and widens the hot bending forming window. Iron oxide (Fe2O3) 0.2-0.5 parts, used to adjust the color tone of the green body; 0.1-0.3 parts of titanium dioxide (TiO2) are used to improve the whiteness and hiding power of the glaze.

[0010] The glaze and the body have matching coefficients of thermal expansion, thus ensuring synchronous deformation, no cracking, and no peeling during the hot bending process.

[0011] The glaze formulation is a composite glaze system that matches the above-mentioned body, and its components, by weight, include: Base glaze: 50-70 parts frit glaze, purchased from Hualang Glaze Co., Ltd., TB-888; The coloring oxide is 0.5-5 parts, which is one or more combinations of iron oxide, cobalt oxide, and chromium oxide (Fe2O3 / CoO / Cr2O3); Stabilizer: 2-6 parts of alumina (Al2O3); Coloring aid: 1-4 parts zinc oxide (ZnO).

[0012] Furthermore, the Al2O3 content in the glaze is controlled at 28%-29%. Existing conventional hot-bending slab glazes often rely on excessive alkali metals (Na2O, K2O) as fluxes to ensure a smooth glaze surface during secondary heating, but this drastically increases the coefficient of thermal expansion of the glaze layer. To solve this problem, this invention creatively employs 1-4 parts zinc oxide in conjunction with 2-6 parts of the high-temperature stabilizer alumina.

[0013] The glaze formula matches the body formula in terms of coefficient of thermal expansion (the body's coefficient of thermal expansion is approximately 6.5-7.5 × 10⁻). 6 / ℃), ensuring a color difference ΔE of less than 3.0 before and after hot bending and preventing cracking. Free alumina acts as a "network forging" repair element, firmly locking in the silicon-oxygen network and preventing excessive melting and flow of the glaze when heated to 1150℃, which would disrupt the uniformity of the expansion coefficient. With this unique formulation, the glaze layer shrinks slightly less than the internal body during the cooling stage after hot bending, thus spontaneously forming a dense micro-compressive stress layer on the glaze surface, perfectly offsetting the strong tensile stress generated on the outer arc surface during hot bending deformation.

[0014] Furthermore, the chemical composition of the green body, by mass percentage, is: SiO2 66-70%, Al2O3 16-18%, Fe2O3 0.2-0.5%, CaO 4.5-5.5%, MgO 2.0-3.5%, K2O 3.0-4.0%, Na2O 2.5-3.5%, TiO2 0.1-0.3%, and loss on ignition ≤0.1%.

[0015] The above-mentioned billet formulation employs a high-aluminum content design, controlling the Al2O3 content at 16-18%. This ensures the billet possesses a certain degree of high-temperature plasticity while maintaining sufficient skeletal strength, preventing uncontrolled deformation and collapse during hot bending due to excessive softening. A detailed analysis follows: Al2O3 plays a decisive role in the high-temperature skeletal support of this formulation. When the Al2O3 content is <16%, the high-temperature skeletal strength of the billet is insufficient within the 1150℃ hot bending range, easily leading to excessive softening and a hot bending collapse rate >5%, resulting in loss of original thickness and shape stability. Conversely, when the Al2O3 content is >18%, the billet's refractoriness is too high, failing to generate sufficient glassy liquid phase at 1150℃, resulting in extremely poor plasticity. Forced bending under pressure will cause direct fracture of the outer arc surface. The golden range of 16-18% perfectly balances "plasticity" and "support strength."

[0016] Furthermore, the coefficient of thermal expansion of the billet is 6.5-7.5×10⁻⁶. -6 The coefficient of thermal expansion of the glaze is 6.5-7.5 × 10⁻⁶ °C, which matches the coefficient of thermal expansion of the body. -6 / ℃.

[0017] This invention also provides a method for preparing the stable glazed ceramic hot-bent slab as described in any of the above claims, employing a two-stage hot-bending heat treatment process, including the following steps: (1) The dried green slabs are placed in a roller kiln for a first firing at a temperature of 1180-1200℃ and held for 10-15 min. After the first firing, the slabs must be slowly cooled to room temperature along the kiln line. After passing stress testing and appearance quality inspection, they can be transferred to the hot bending workshop for use. This room temperature transfer process completely releases the residual internal stress from the first firing.

[0018] (2) Heat the flat rock slab after one firing to 1000℃ at a heating rate of 3-8℃ / min; then continue to heat to 1100-1150℃ at a heating rate of 3-8℃ / min, and hold for 30-60 min. For hot-bent rock slabs with large curvature or complex curved surfaces, apply a uniform pressure of 0.01-0.05 MPa to the rock slab while holding it to assist in forming. (3) After molding, the temperature is slowly cooled to 600℃ at a rate of 1-5℃ / min, and then naturally cooled to room temperature. The cooled rock slab is then post-processed to obtain the hot-bent rock slab product.

[0019] This invention employs a two-stage hot bending heat treatment process to form a synergistic structure of crystalline phase and glass phase: during the first firing process (1180-1200℃), a stable crystalline phase mainly composed of mullite and anorthite is formed inside the blank, which together with the glass phase formed by the multi-component composite flux constitutes a dense structure; during the second hot bending (1100-1150℃), the glass phase softens to provide plastic deformation capability, while the crystalline phase skeleton maintains the overall strength of the material, thereby achieving precise molding without cracking, taking into account both plasticity and strength.

[0020] Further, in step (1), the body components and glaze components are ball-milled and mixed until the fineness is ≤0.5% on a 250-mesh sieve. After spray granulation, the mixture is pressed into a flat ceramic slab green body (prepared using the above-mentioned body and glaze formulations). The green body is dried at 100-150°C until the moisture content is ≤0.5%, and then fired once in a roller kiln under an oxidizing atmosphere at a firing temperature of 1180-1200°C. The holding time at the highest temperature is 10-15 min, resulting in a flat ceramic slab that meets national standards. The resulting flat slab is then slowly cooled to room temperature along the kiln line. In this step, "highest temperature section" refers to the physical region in the kiln where the temperature is highest and remains constant. "Slowly cooled along the kiln line" means that the slab does not need to be transported to a cooling kiln, but is directly cooled slowly on the current production line as it is conveyed by the roller conveyor.

[0021] Furthermore, in step (2), the flat rock slab after one firing is placed on a cleaned hot bending mold, and the mold containing the rock slab is heated to 1000°C at a heating rate of 3-8°C / min, and then the temperature continues to rise at the same rate. When the temperature rises to 1100-1150°C, the heat preservation and deformation stage is entered, and the heat preservation time is 30-60 min. During the heat preservation and deformation stage, a uniform pressure of 0.01-0.05 MPa is applied to the rock slab (for the hot bending requirements of rock slabs with large curvature or complex curved surfaces) to assist in the forming and ensure that the rock slab and the mold fit tightly.

[0022] In step (2) above, to prevent high-temperature adhesion, a high-temperature resistant insulating layer with a thickness of 1-2mm is evenly applied to the contact surface between the rock slab and the mold to prevent adhesion. The mold is made of heat-resistant alloy or refractory ceramic material. The surface of the mold must be cleaned before use, and its curvature is designed according to the target product.

[0023] The high-temperature resistant insulating layer used in this invention is mainly composed of alumina powder, which can be purchased from the market.

[0024] During the heating phase, a heating rate of 3-8℃ / min can ensure uniform temperature inside and outside the slab, avoiding cracking due to excessive temperature difference.

[0025] During the heat preservation and deformation stage, within the temperature range of 1100-1150℃, the glass phase in the slab blank begins to soften, and the multi-component composite flux system is fully activated. Under its own weight and the action of the mold, the slab undergoes bending deformation. Experiments show that the slab begins to possess the ability to deform under its own weight at 1100℃ (i.e., begins the glass transition), and at 1150℃, it exhibits sufficient plastic flow, enabling precise molding of complex curves. Furthermore, within this temperature range, the glaze color remains stable without significant discoloration.

[0026] During the forming and pressurizing stages, the pressure applied by the mechanical pressurizing device can assist in forming, which is especially suitable for hot bending requirements of large arcs or complex curved surfaces.

[0027] Furthermore, in step (3), after the slab is formed, it is first slowly cooled to 600°C at a cooling rate of 1-5°C / min to safely pass the quartz crystal transformation point. After the temperature drops below 600°C, it is naturally cooled to room temperature. After the cooled slab passes the inspection, the edges are trimmed and the surface is cleaned to obtain the hot-bent slab product.

[0028] In step (3) above, after the molding is completed, the crucial annealing and cooling stage begins. This slow cooling process can effectively eliminate the thermal stress generated during hot bending and prevent the slab from springing back, cracking, or residual stress concentration during the cooling process.

[0029] The beneficial effects of this invention are: (1) The present invention has high hot bending forming precision and small bending angle springback. By introducing a K2O-Na2O-CaO-MgO multi-component composite flux system into the billet formulation, the synergistic effect of this system reduces the softening temperature of the billet and optimizes the high-temperature viscosity curve. By combining a high aluminum content design (16-18%) and calcined kaolin, the billet has suitable plastic flow capacity within the hot bending temperature range (1100-1150℃). The softening initiation temperature is controlled at about 1100℃, and hot bending can be completed below 1150℃. At the same time, a slow cooling process of 1-5℃ / min is adopted in the annealing stage. The slow cooling annealing process realizes the full release of stress, effectively eliminates the internal stress generated during hot bending, and avoids the bending angle springback phenomenon after cooling. Actual measurements show that the forming angle of the hot-bent slab of the present invention deviates from the mold design angle by less than ±0.5°, which is significantly better than the prior art (usually the deviation is ±2-3°).

[0030] (2) This invention employs a composite glaze system. By adding zinc oxide as a color-adjusting agent to the glaze formula and controlling the proportion of coloring oxides, the color of the glaze is ensured to be stable during the secondary hot bending process. The glaze obtained by this invention has a small color difference and a stable decorative effect. According to the color difference meter test, the color difference ΔE of the glaze before and after hot bending is <3.0, which meets the requirements of the national standard GB / T 23266-2009. Moreover, the gloss retention rate of the glaze after hot bending is ≥90%, which meets the needs of high-end decoration.

[0031] (3) By introducing zinc oxide and aluminum oxide to regulate the thermal expansion coefficient of the glaze, the expansion coefficient is adjusted to match the body, so that the glaze layer forms a micro-compression stress layer, which effectively solves the cracking problem in the hot bending process; no cracking occurs in the hot bending process, the surface quality is excellent, the crack rate is <1%, the glaze integrity rate is >99%, and there are no bulges or pinholes; the mechanical properties are stable after hot bending and the retention rate is high; according to the test, the bending strength retention rate of the rock slab after hot bending of the present invention is ≥95% (strength after hot bending / strength before hot bending), which hardly decreases and is much higher than the existing technology (usually decreases by 10%-20%).

[0032] (4) The present invention uses a multi-component composite flux system to reduce the softening temperature of the billet to about 1100℃, and hot bending can be completed at 1100-1150℃ with a holding time of only 30-60 min. Compared with the existing hot bending process that usually requires more than 1200℃ and 2-3 hours of holding time, the hot bending temperature of the present invention is low, which can reduce energy consumption by about 30%-40%, shorten the production cycle, and increase production efficiency, making it suitable for continuous production. Attached Figure Description

[0033] Figure 1 The process flow diagram for the secondary hot bending heat treatment provided by this invention.

[0034] Figure 2 This is a photograph of the initial bending deformation of the rock slab sample in Experiment Example 1 after being kept at 1100℃ for 15 min.

[0035] Figure 3 This is a photograph of the rock slab sample from Test Example 1 after it was kept at 1150℃ for 15 min and then fully bonded and deformed.

[0036] Figure 4 This is a photograph of the rock slab sample from Experiment Example 1 after it was heated to 1200℃ and held for 15 minutes to show its deformation state.

[0037] Figure 5 This is a micrograph of the rock slab sample from Experiment Example 1.

[0038] Figure 6 The results of firing the rock slab sample in Test Example 2 at 1200℃ are shown.

[0039] Figure 7 The results of firing the rock slab sample in Test Example 2 at 1150°C are shown. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0042] The hot bending forming of ceramic slabs is based on the thermoplastic transformation characteristics and stress control mechanism of ceramic materials, and controllable forming is achieved through multi-process collaboration.

[0043] This invention first prepares the green body and glaze according to the green body formula and glaze formula respectively. After pressing and glazing, the green body is fired once at 1180~1200℃, producing a flat and qualified flat ceramic slab in the single firing process. The slab already possesses basic mechanical properties and surface quality after the first firing. It then undergoes a secondary hot bending heat treatment process. The flat slab is placed on a customized mold with an isolation layer, and then placed in a controlled atmosphere electric furnace. The furnace temperature is raised to 1000℃ at a preset rate of 3~8℃ / min, and then further raised to the deformation temperature range of 1100~1150℃, held for 30~60 min. At this temperature, the multi-component composite flux (K2O-Na2O-CaO-MgO system) in the slab body promotes the full softening of the glass phase. Under its own weight or with the aid of an auxiliary pressurizing device (0.01~0.05 MPa pressure can be applied to large arcs or complex curved surfaces), the slab bends against the mold, achieving precise hot bending forming. After molding, the cooling rate is controlled through a slow cooling annealing process, decreasing to 600℃ at a rate of 1~5℃ / min, followed by natural cooling. This allows the internal stress of the slab to be released slowly, eliminating thermal stress and preventing springback and cracking. The result is a hot-bent ceramic slab with stable shape, excellent surface quality, and minimal color difference in the glaze. Finally, after inspection, trimming, and cleaning, a qualified hot-bent slab is obtained.

[0044] Because the green body formula of this invention adopts a multi-component composite flux system, the softening temperature is reduced (the measured softening initiation temperature is about 1100℃), which allows hot bending to be completed below 1150℃; the glaze formula matches the coefficient of thermal expansion of the green body, and a stabilizer is introduced to ensure that the glaze surface does not crack or change color after hot bending; combined with reasonable heating, heat preservation, and annealing processes, it effectively solves the technical problems of large bending corner springback, easy surface cracking, reduced strength, and low production efficiency in the prior art.

[0045] The entire hot bending forming process achieves controllable forming of flat slabs into curved surfaces by precisely controlling process parameters such as temperature, time, and pressure, utilizing the thermoplastic transformation law of ceramic materials, and combining stress control technology. The various processes are interconnected and work synergistically, which not only ensures forming accuracy and appearance quality, but also guarantees the mechanical stability of the finished product, in line with the academic norms of ceramic inorganic material processing and the actual needs of industrial production.

[0046] Example 1 The green body formula of this embodiment, by weight, is as follows: 22 parts quartz, 20 parts calcined kaolin, 20 parts potassium feldspar, 24 parts sodium feldspar, 10 parts wollastonite, 2.5 parts magnesium oxide, 0.3 parts iron oxide, and 0.2 parts titanium dioxide.

[0047] The glaze formula in this embodiment is in parts by weight: The frit glaze TB-888 contains 60 parts cobalt oxide, 2.8 parts cobalt oxide, 4 parts aluminum oxide, and 2.5 parts zinc oxide.

[0048] like Figure 1 As shown, this embodiment provides a secondary hot bending heat treatment process for ceramic hot-bent slabs. This process utilizes the above-mentioned green body and glaze formula to prepare ceramic hot-bent slabs, and includes the following steps: (1) First firing: Weigh each component according to the formula of body and glaze, mix each component with spheroidal graphite until the fineness is ≤0.5% on 250 mesh sieve, and after spray granulation, press it into shape using a 30,000-ton press at 45 MPa pressure; send the pressed green body into the drying kiln and dry it at 120℃ until the moisture content is ≤0.5%, and then fire it once in the roller kiln in an oxidizing atmosphere at a firing temperature of 1190℃, holding the highest temperature section for 13 min to obtain a flat ceramic slab, which is slowly cooled to room temperature along the kiln line. After passing stress testing and appearance quality inspection, it is transferred to the hot bending workshop for use. (2) Preparation before hot bending: Place the flat rock slab after one firing on the cleaned hot bending mold, and evenly brush a 1.5 mm thick high temperature resistant isolation layer on the contact surface between the rock slab and the mold. (3) Heating stage: The mold containing the rock slab is sent into the controlled atmosphere electric furnace and heated to 1000℃ at a heating rate of 5℃ / min; (4) Deformation and heat preservation: When the furnace temperature continues to rise to 1125℃ at a heating rate of 5℃ / min, it is kept at that temperature for 45 min; (5) Molding and pressurization: When the slab is a large arc or a complex curved surface, apply a uniform pressure of 0.3 MPa to the slab to assist in molding and ensure that the slab fits tightly with the mold; (6) Annealing and cooling: After molding, the furnace is first cooled slowly to 600°C at a cooling rate of 3°C / min, and then cooled naturally to room temperature. (7) Post-processing: After the cooled hot-bent rock slab passes inspection, the edges are trimmed and the surface is cleaned to obtain the finished product.

[0049] Tests showed that the finished product obtained in this embodiment had excellent color consistency, dense glaze without cracks at the corners, precise forming angles, and virtually no strength reduction.

[0050] Experimental Example 1 Hot bending rock slab heating deformation test 1. Experimental Objectives Test the softening point or glass transition temperature of hot-bent rock slabs.

[0051] The planned standard 20256916-T-609, "Determination of Softening Point, Linear Thermal Expansion Coefficient and Glass Transition Temperature of Microcrystalline Ceramics: Thermomechanical Analysis (TMA) and Differential Scanning Calorimetry (DSC)," is under development and is expected to be published around 2027. The adjacent industry standard JC / T 2755-2023, "Test Method for High-Temperature Specific Heat Capacity of Fine Ceramics: Differential Scanning Calorimetry (DSC)," can be used.

[0052] 2. Experimental Materials and Equipment The experimental material was the finished rock slab obtained in Example 1.

[0053] Heating is performed using a controllable atmosphere resistance heating tube furnace.

[0054] 3. Experimental Procedure The slab sample and supporting iron block were placed together into the furnace, with the slab horizontally positioned inside. The furnace was kept under normal air atmosphere and atmospheric pressure. A manually controlled, gradual heating method was used, with a target temperature of 1000-1200℃.

[0055] The slab was heated in a muffle furnace at a rate of 5°C / min to 1100°C and held for 15 min. Under its own weight, the slab began to soften and bend, as shown in the following figure. Figure 2 As shown. Then, the temperature was increased to 1150℃ at the same rate and held for 15 minutes. The slab became more curved, and both sides began to contact the wall of the quartz tube. The slab softened completely and began to adhere, exhibiting a completely collapsed state, as shown. Figure 3 As shown. Then, the temperature was further increased to 1200℃ and held for 15 minutes. The rock slab completely lost its plate-like structure, became molten, and began to flow, clearly entering a viscous flow state, as shown. Figure 4 As shown. Figure 5 This is a metallographic micrograph of the finished slab after it has been fired at 1200℃ and held for 15 minutes. At this point, air bubbles appeared inside the slab, and the experiment proved that the sample was already in an "overfired" state at this temperature.

[0056] Stop heating, turn off the power, and the slab cools down in the furnace.

[0057] 4. Experimental Conclusions The softening temperature range of this sintered stone slab is 1000-1200℃. It begins to deform under its own weight at 1100℃, indicating the onset of the glass transition. At 1200℃, it reaches a molten state with maximum fluidity, having entered a viscous flow state. Experiments have shown that the ideal hot bending temperature for this finished sintered stone slab is within the range where the material begins to soften but has not yet undergone drastic chemical decomposition or volume expansion; the optimal deformation temperature range is 1100-1150℃.

[0058] Experimental Example 2 Ceramic sample firing test 1. Experimental Objective This experiment aims to perform high-temperature sintering of hot-bent slate using a box-type resistance furnace (muffle furnace). By employing a set stepped heating curve, the process of debinding, dehydration, and high-temperature densification sintering of the hot-bent slate was completed, allowing the glaze on the ceramic body surface to completely melt and spread evenly, forming a dense, glossy vitreous glaze. The macroscopic morphology, surface gloss, glaze condition, and structural integrity of the sintered samples were then observed in detail.

[0059] 2. Experimental Equipment and Materials Experimental equipment: TC4L-14 box-type muffle furnace produced by Henan Enge Kiln Machinery Equipment Co., Ltd., rated voltage 220V, rated power 4kW, maximum working temperature 1400℃, working chamber size 15×15×20 cm, maximum working temperature 1400℃, intelligent program temperature control.

[0060] Load-bearing vessel: a rectangular corundum (alumina) ark.

[0061] Experimental sample: The finished rock slab obtained in Example 1.

[0062] 3. Experimental Procedure The working chamber of the TC4L-14 box-type muffle furnace has dimensions of 15×15×20 cm. To ensure the slate could be placed inside the furnace for firing and to prevent the sample from contacting the furnace wall, a CNC three-blade cutting machine from Baotao Machinery was used to cut the slate slab obtained in Example 1. The cutting speed was 3 m / min, and circulating water cooling was used throughout the process to prevent high-temperature erosion of the glaze. Regularly sized samples were obtained, with dimensions of 8×1.5×1 cm.

[0063] The furnace is filled with a pure argon atmosphere at normal pressure.

[0064] The cut rock slabs were divided into two groups: one as the experimental group and the other as the control group.

[0065] Check the grounding, temperature control system, ammeter, and voltmeter status of the muffle furnace to confirm that the equipment is fault-free; place the ceramic samples to be fired in the experimental group steadily into the corundum crucible, ensuring that the samples do not directly contact the crucible wall to avoid high-temperature adhesion; place the crucible in the center of the muffle furnace working chamber to ensure uniform heating; close the furnace door, confirm that the seal is good, set the temperature control program, and start the muffle furnace.

[0066] The experimental group of slabs was fired using a three-stage stepped heating and natural cooling process curve, with an initial temperature of room temperature (23℃).

[0067] The first stage involves heating from 23℃ to 300℃ at a rate of 5℃ / min for 56 minutes, followed by holding at 300℃ for 15 minutes. During this preheating stage, residual moisture and volatile organic compounds in the green body and glaze are slowly removed.

[0068] The second stage involves further heating from 300℃ to 1100℃ at a rate of 5℃ / min for 160 minutes. The temperature is then held at 1100℃ for 15 minutes. During this medium-to-high temperature heating stage, the glaze gradually melts, and the body undergoes crystal transformation and densification reactions.

[0069] The third stage involves further heating from 1100℃ to 1150℃ at a rate of 5℃ / min for 20 minutes. This temperature is then maintained at 1150℃ for 15 minutes. This process allows the glaze to completely melt and flow evenly, forming a vitreous glaze layer. Simultaneously, it promotes solid-phase reactions and liquid-phase sintering between the green body particles, improving the density and mechanical properties of the green body.

[0070] Cooling stage: After the heat preservation is completed, turn off the power of the muffle furnace and let the sample cool naturally to room temperature with the furnace; after the temperature inside the furnace drops to room temperature, open the furnace door, take out the corundum crucible, and observe the state of the sample.

[0071] The control group's slab firing also employed a three-stage stepped heating and natural cooling process. The difference between this control group and the experimental group lies in: The third stage involves further heating from 1100℃ to 1200℃ at a rate of 5℃ / min for 20 minutes. The temperature is then held at 1200℃ for 15 minutes.

[0072] 4. Experimental Conclusions After the control group's ceramic slab was heated to 1200℃, the sample adhered to the corundum pot, indicating that 1200℃ was too high for this ceramic slab. The glaze melted and flowed, and the bottom stuck to the crucible, indicating overfiring. The sample surface formed a uniform vitrified glaze layer with slight cloudiness and the precipitation of tiny crystals, but no large-area cracking or bubbling occurred, indicating that the firing temperature was sufficient and the sample adequately drained moisture during the preheating stage (see...). Figure 6 ).

[0073] The experimental group of slabs was heated to 1150℃ and then stopped. The glaze had successfully vitrified, forming a uniform, glassy glaze layer without large areas of matte or cloudy finish, indicating sufficient firing temperature and a complete transformation of the glaze from a powder state to a continuous glass phase. The glaze surface exhibited good overall uniformity, without blistering, pinholes, or large-area loss of gloss, indicating appropriate control of the furnace temperature field and firing process. The glaze layer and the body were tightly bonded, without cracking or peeling, indicating a good match between the thermal expansion coefficients of the glaze and the body, and no destructive stress was generated during cooling (see [reference]). Figure 7 ).

[0074] Experiments have shown that a temperature range of 1100-1150℃ is most suitable for this rock slab.

[0075] Example 2 The green body formula of this embodiment, by weight, is as follows: 20 parts quartz, 18 parts calcined kaolin, 18 parts potassium feldspar, 22 parts sodium feldspar, 8 parts wollastonite, 2 parts magnesium oxide, 0.2 parts iron oxide, and 0.1 parts titanium dioxide. The glaze formula in this embodiment, by weight, is as follows: 50 parts of frit glaze TB-888, 0.5 parts of iron oxide, 2 parts of aluminum oxide, and 1 part of zinc oxide.

[0076] This embodiment provides a secondary hot bending heat treatment process for ceramic hot-bent slabs. This process utilizes the above-mentioned green body and glaze formula to prepare ceramic hot-bent slabs, and includes the following steps: (1) First firing: Weigh each component according to the body and glaze formula, mix each component with spheroidal graphite until the fineness is ≤0.5% on a 250-mesh sieve, and after spray granulation, press it into shape using a 30,000-ton press at 45 MPa pressure; send the pressed green body into a drying kiln and dry it at 100℃ until the moisture content is ≤0.5%, and then fire it once in a roller kiln with an oxidizing atmosphere at a firing temperature of 1180℃, holding the highest temperature section for 10 min to obtain a flat ceramic slab, which is slowly cooled to room temperature along the kiln line. After passing stress testing and appearance quality inspection, it is transferred to the hot bending workshop for use. (2) Preparation before hot bending: Place the flat rock slab after one firing on the cleaned hot bending mold, and evenly apply a 1 mm thick high temperature resistant isolation layer to the contact surface between the rock slab and the mold. (3) Heating stage: The mold containing the rock slab is sent into the controlled atmosphere electric furnace and heated to 1000℃ at a heating rate of 3℃ / min; (4) Deformation and heat preservation: When the furnace temperature continues to rise to 1100℃ at a heating rate of 3℃ / min, it is kept at that temperature for 60 min; (5) Molding and pressurization: When the slab is a large arc or a complex curved surface, apply a uniform pressure of 0.05 MPa to the slab to assist in molding and ensure that the slab fits tightly with the mold; (6) Annealing and cooling: After molding, the furnace is first cooled slowly to 600°C at a cooling rate of 1°C / min, and then cooled naturally to room temperature. (7) Post-processing: After the cooled hot-bent rock slab passes inspection, the edges are trimmed and the surface is cleaned to obtain the finished product.

[0077] Example 3 The green body formula of this embodiment, by weight, is as follows: 25 parts quartz, 22 parts calcined kaolin, 22 parts potassium feldspar, 25 parts sodium feldspar, 12 parts wollastonite, 3 parts magnesium oxide, 0.5 parts iron oxide, and 0.3 parts titanium dioxide. The glaze formula in this embodiment, by weight, is: 70 parts frit glaze TB-888, 5 parts chromium oxide, 6 parts aluminum oxide, and 4 parts zinc oxide.

[0078] This embodiment provides a secondary hot bending heat treatment process for ceramic hot-bent slabs. This process utilizes the above-mentioned green body and glaze formula to prepare ceramic hot-bent slabs, and includes the following steps: (1) First firing: Weigh each component according to the body and glaze formula, mix each component with spheroidal graphite until the fineness is ≤0.5% on a 250-mesh sieve, and after spray granulation, press it into shape using a 30,000-ton press at 45 MPa pressure; send the pressed green body into a drying kiln and dry it at 150℃ until the moisture content is ≤0.5%, and then fire it once in a roller kiln with an oxidizing atmosphere at a firing temperature of 1200℃, holding the highest temperature section for 15 min to obtain a flat ceramic slab, which is slowly cooled to room temperature along the kiln line, and after passing stress testing and appearance quality inspection, it is transferred to the hot bending workshop for use; (2) Preparation before hot bending: Place the flat rock slab after one firing on the cleaned hot bending mold, and evenly apply a 2 mm thick high temperature resistant isolation layer to the contact surface between the rock slab and the mold. (3) Heating stage: The mold containing the rock slab is sent into the controlled atmosphere electric furnace and heated to 1000℃ at a heating rate of 8℃ / min; (4) Deformation and heat preservation: When the furnace temperature continues to rise to 1150℃ at a heating rate of 8℃ / min, it is kept at that temperature for 30 min; (5) Molding and pressurization: When the slab is a large arc or a complex curved surface, apply a uniform pressure of 0.05 MPa to the slab to assist in molding and ensure that the slab fits tightly with the mold; (6) Annealing and cooling: After molding, the furnace is first cooled slowly to 600°C at a cooling rate of 5°C / min, and then cooled naturally to room temperature. (7) Post-processing: After the cooled hot-bent rock slab passes inspection, the edges are trimmed and the surface is cleaned to obtain the finished product.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A stable glazed ceramic hot-bent slab, characterized in that, Including the body and glaze; The billet adopts a K2O-Na2O-CaO-MgO multi-component composite flux system, and its formula includes the following components in parts by weight: quartz 20-25 parts, calcined kaolin 18-22 parts, potassium feldspar 18-22 parts, sodium feldspar 22-25 parts, wollastonite 8-12 parts, magnesium oxide 2-3 parts, iron oxide 0.2-0.5 parts, and titanium dioxide 0.1-0.3 parts; The glaze formulation includes the following components in parts by weight: 50-70 parts frit glaze, 0.5-5 parts coloring oxide, 2-6 parts aluminum oxide, and 1-4 parts zinc oxide; wherein the coloring oxide is one or more of iron oxide, cobalt oxide, and chromium oxide.

2. The stable glazed ceramic hot-bent slab according to claim 1, characterized in that, The chemical composition of the billet, by mass percentage, is as follows: SiO2 66-70%, Al2O3 16-18%, Fe2O3 0.2-0.5%, CaO 4.5-5.5%, MgO 2.0-3.5%, K2O 3.0-4.0%, Na2O 2.5-3.5%, TiO2 0.1-0.3%, with a loss on ignition ≤0.1%.

3. The stable glazed ceramic hot-bent slab according to claim 1, characterized in that, The coefficient of thermal expansion of the billet is 6.5-7.5×10⁻⁶. -6 The coefficient of thermal expansion of the glaze is 6.5-7.5 × 10⁻⁶ °C, which matches the coefficient of thermal expansion of the body. -6 / ℃.

4. The method for preparing a stable glazed ceramic hot-bent slab according to any one of claims 1-3, characterized in that, The process employs a two-stage hot bending heat treatment, including the following steps: (1) The dried green body is placed in a roller kiln for a single firing at a temperature of 1180-1200℃ and held for 10-15 minutes. (2) Heat the flat rock slab after one firing to 1000℃ at a heating rate of 3-8℃ / min; then continue to heat to 1100-1150℃ at a heating rate of 3-8℃ / min and hold for 30-60 min; for hot bending requirements of large arc or complex curved surfaces, apply a uniform pressure of 0.01-0.05 MPa to the rock slab while holding for heat to assist in forming; (3) After molding, the temperature is slowly cooled to 600℃ at a rate of 1-5℃ / min, and then naturally cooled to room temperature. The cooled rock slab is then post-processed to obtain the hot-bent rock slab product.

5. The preparation method according to claim 4, characterized in that, In step (1), the body components and glaze components are ball-milled and mixed until the fineness is ≤0.5% on a 250-mesh sieve. After spray granulation, the mixture is pressed into a flat ceramic slab green body. The green body is dried at 100-150°C until the moisture content is ≤0.5%. Then, it is fired once in a roller kiln at a firing temperature of 1180-1200°C. The holding time at the highest temperature section is 10-15 min. The resulting flat slab is slowly cooled to room temperature along the kiln line.

6. The preparation method according to claim 4, characterized in that, In step (2), the flat rock slab after one firing is placed on a clean hot bending mold. The mold containing the rock slab is heated to 1000℃ at a heating rate of 3-8℃ / min, and then the same heating rate is continued. When the temperature reaches 1100-1150℃, the heat preservation and deformation stage is entered, and the heat preservation time is 30-60 min. For hot bending requirements with large arc or complex curved surfaces, a uniform pressure of 0.01-0.05MPa is applied to the rock slab during the heat preservation and deformation stage to assist in forming and ensure that the rock slab and the mold fit tightly.

7. The preparation method according to claim 4, characterized in that, In step (3), after the slab is formed, it is first slowly cooled to 600°C at a cooling rate of 1-5°C / min to safely pass the quartz crystal transformation point. After the temperature drops below 600°C, it is naturally cooled to room temperature. After the cooled slab passes inspection, the edges are trimmed and the surface is cleaned to obtain the hot-bent slab product.

Images