High-generation large-size overflow brick and heating process design method thereof

Abstract

The invention discloses an advanced large-size overflow brick and a heating process design method thereof, and belongs to the technical field of glass substrate manufacturing. According to the method, on the basis of a constructed mathematical model of a temperature rising section and a heat preservation section of the overflow brick, a temperature stress design curve of the temperature rising process of the overflow brick is drawn, and multi-dimensional indexes including a maximum safety tensile stress curve, an inside and outside temperature difference curve, a center tensile stress curve, a surface pressure stress curve, a maximum up and down temperature difference curve and a clamping air cylinder pressure curve are covered; the center tensile stress of each heating section and each heat preservation section of the overflow brick is smaller than or equal to the maximum safety tensile stress of the thickness center of the overflow brick, and the heating process design of the high-generation large-size overflow brick is completed. Based on the design method provided by the invention, the charting monitoring of the heating process is realized, the potential safety risk can be identified and adjusted in real time, and powerful technical support is provided for the design, optimization and verification of an efficient and safe advanced forming process.

Description

Technical Field

[0001] The invention relates to the technical field of glass substrate manufacturing, and in particular to a high-generation large-size overflow brick and a heating process design method thereof. Background Art

[0002] The glass substrates used in the general TFT-LCD (thin film transistor display) flat panel display manufacturing field are manufactured by overflow pull-down. In the molding process, the molten glass melted by the glass melting furnace is supplied to the molten overflow pull-down molding device for manufacturing. The control of glass substrate thickness uniformity, residual stress and warpage is one of the particularly important process technologies, and they are all related to the design and process control of the overflow molding annealing device. The glass liquid flows over the surface of the overflow brick and converges and bonds to form a glass ribbon at the root of the overflow surface on both sides of the overflow brick. Under the action of gravity and traction, the glass ribbon overcomes the internal friction viscous resistance, and the thickness gradually decreases to the target product thickness. The pulling roller is located far enough downstream of the device so that the glass ribbon has been cooled and has sufficient rigidity during pulling. The thickness distribution below the tip (root) of the overflow brick is strongly correlated with the cooling rate of this section. Faced with the ever-changing challenges of display technology, such as higher definition, faster refresh rate, denser circuit integration, narrow frame design, improved panel aperture ratio, and large-size high-generation manufacturing, oxide (such as IGZO) technology came into being. With its excellent performance and moderate cost, it has opened up a new era for G10.5 generation and even larger production lines. It is widely used in the field of high-end LCD TVs and OLED TVs, and has become a powerful supplement to a-Si and LTPS technologies. In this context, the heating process of overflow bricks is the core link in the manufacture of glass substrates, and its importance is self-evident. The carefully designed heating and insulation stages of the process are designed to ensure that the overflow bricks reach the best working state, so as to stably and evenly supply the glass liquid, thereby producing glass substrates with uniform thickness and excellent quality.

[0003] However, potential defects such as microcracks and pores in the original materials of overflow bricks, as well as their sensitivity in high stress environments, place stringent requirements on their thermal shock stability. Among the two major models for evaluating thermal shock stability, the thermal shock fracture model builds the theoretical foundation for optimizing the heating process and accurately predicting thermal stress, while the thermal shock damage model goes a step further and deeply analyzes how stress concentration promotes the fracture mechanism of materials under low stress conditions, providing a solid theoretical basis for the analysis of actual fracture cases. In addition, the heating and insulation process of overflow bricks is a complex thermal shock response process, which is closely related to the linear thermal expansion coefficient, Young's modulus and Poisson's ratio, thermal conductivity, heat capacity and thickness of the material, as well as the heating / cooling rate, surface heat transfer convection coefficient, etc. Any sudden changes in the external environment or operating parameters, such as sealing failure, accidental intrusion of hot and cold airflows, sudden increase in temperature difference between the forming area and the annealing area, or fluctuations in power and cooling control, may cause abnormal accumulation of stress inside the overflow brick. Once the flexural strength limit of the overflow brick material is exceeded, the internal stress of the overflow brick may accumulate abnormally. , which leads to a surge in the risk of fracture.

[0004] With the rapid progress of production technology and the leap of product specifications to higher generations, the volume of overflow bricks has expanded dramatically. This change not only amplifies the potential threat of internal microcracks, pores and other defects, aggravates the natural attenuation of strength, but also makes the distribution of defects tend to be discrete, posing a severe challenge to the uniformity of material strength. In such a complex environment, even if the established process conditions are followed, it is inevitable that the surface stress level will rise significantly, thereby reducing the safety factor of the production process and putting forward more stringent requirements on the thermal shock stability of overflow bricks. Given that the safety and stability of the molding heating process are directly related to the smooth docking, effective wetting and stable lead plate manufacturing of glass substrates, how to minimize potential risks through the fine design of the heating process of overflow bricks has become an urgent and important technical issue facing current industry technicians. Therefore, based on the thermal shock fracture model and thermal shock damage model, combined with the unique properties of high-generation large-size overflow bricks, providing a scientific and efficient heating process design method has become a technical problem that the current technicians in this field need to overcome. Summary of the invention

[0005] The purpose of the present invention is to provide a high-generation large-size overflow brick and a heating process design method thereof, so as to overcome the risk of breakage and damage caused by the excessively large volume of overflow bricks in the traditional heating process when facing higher generations.

[0006] The present invention solves the above technical problems through the following technical solutions: A method for designing a heating process for high-generation large-size overflow bricks comprises the following steps: Step 1: Divide the overflow brick heating process into a combination of several heating sections and insulation sections; construct the maximum safe tensile stress at the thickness center of the overflow brick based on the material parameters of the overflow brick; construct the mathematical models of the overflow brick heating section and insulation section based on the theory of heat conduction and thermal stress; design the maximum upper and lower temperature difference and clamping cylinder pressure of the overflow brick; Step 2: Based on the mathematical model of the overflow brick heating section and the insulation section constructed in step 1, calculate the internal and external temperature difference, central tensile stress and surface compressive stress of the overflow brick; Step 3: Draw the temperature stress design curve of the overflow brick heating process, including the maximum safe tensile stress curve at the thickness center of the overflow brick, the internal and external temperature difference curve, the central tensile stress curve, the surface compressive stress curve, the maximum upper and lower temperature difference curve and the clamping cylinder pressure curve; Step 4. According to the curve drawn in step 3, the central tensile stress of each heating section and insulation section of the overflow brick is made ≤ the maximum safe tensile stress at the center of the thickness of the overflow brick, thus completing the heating process design of high-generation large-size overflow bricks.

[0007] Furthermore, in step one, in each combination of a heating section and a heat preservation section, there are one or more heating sections and one heat preservation section.

[0008] Furthermore, the heating rate of the heating section is greater than 0; and the heating rate of the heat preservation section is equal to 0.

[0009] Furthermore, in step 1, the maximum safe tensile stress at the thickness center of the overflow brick is:

[0010] in, The maximum safe tensile stress of overflow brick; It is the flexural strength of overflow brick.

[0011] Furthermore, in step 1, the mathematical model of the overflow brick heating section specifically includes: Surface temperature of overflow brick in thickness direction :

[0012] When the previous section of the heating section is the insulation section, the center temperature of the overflow brick in the thickness direction :

[0013] When the previous section of the heating section is the insulation section, the average temperature of the overflow brick in the thickness direction :

[0014] When the previous section of the heating section is the heating section, the center temperature of the overflow brick in the thickness direction :

[0015] When the previous section of the heating section is the heating section, the average temperature of the overflow brick in the thickness direction :

[0016] in, ; ; ; is the initial surface temperature of the overflow brick in the thickness direction during the heating stage; is the density of the overflow brick; is the specific heat capacity of the overflow brick; is the thermal conductivity of the overflow brick; is the heating rate; is the half thickness of the overflow brick; is the Fourier number, t is the total heating time from 0 to the heating section; a is the diffusion coefficient; is the surface temperature of the overflow brick in the thickness direction of the heating stage, equal to ; is an exponential function with the natural constant e as base; is the correction term, a is the center temperature of the overflow brick thickness direction corresponding to the total heating time of the previous heating section, and the corresponding heating rate is the heating rate of the previous heating section, b is the center temperature of the overflow brick thickness direction corresponding to the total heating time of the previous heating section, and the corresponding heating rate is the heating rate of this section, but does not include the correction term; is the correction term, c is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating stage, and the corresponding heating rate is the heating rate of the previous heating stage; It is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section. The corresponding heating rate is the heating rate of this section, but does not include the correction term.

[0017] Furthermore, in step 1, the mathematical model of the overflow brick insulation section specifically includes: Surface temperature of overflow brick in thickness direction :

[0018] The center temperature of the overflow brick in the thickness direction :

[0019] Average temperature of overflow brick in thickness direction :

[0020] in, ; ; ; is the initial surface temperature of the overflow brick in the thickness direction of the insulation section; is the surface temperature of the overflow brick in the thickness direction of the insulation section, equal to ; is the initial center temperature of the overflow brick in the thickness direction of the insulation section; is an exponential function with the natural constant e as base; is the half thickness of the overflow brick; is the Fourier number, t is the total insulation time from 0 to the insulation section; a is the diffusion coefficient.

[0021] Furthermore, in step 2, the temperature difference between the inside and outside of the overflow brick for:

[0022] Central tensile stress for:

[0023] Surface compressive stress for:

[0024] in, is the surface temperature of the overflow brick in the thickness direction; is the center temperature of the overflow brick in the thickness direction; E is the Young's modulus of the overflow brick; α is the linear thermal expansion coefficient of the overflow brick; μ is the Poisson's ratio of the overflow brick.

[0025] Furthermore, in step 1, the maximum upper and lower temperature difference of the overflow brick is designed to be:

[0026] in, The temperature collected by the temperature sensor on the top of the overflow brick; The temperature collected by the temperature sensor at the bottom of the overflow brick; For overflow brick at temperature The corresponding flexural strength when is the distance between the upper temperature sensor and the lower temperature sensor of the overflow brick; for The distance from the tip of the overflow brick; is the safety factor; E is the Young's modulus of the overflow brick; α is the linear thermal expansion coefficient of the overflow brick; μ is the Poisson's ratio of the overflow brick; is the thermal conductivity of the overflow brick; h is the convection radiation surface heat dissipation coefficient.

[0027] Furthermore, in step 1, the clamping cylinder pressure is designed to be: When the overflow brick is heated to When the clamping cylinder pressure is 0; when the overflow brick is heated to When the clamping cylinder pressure is less than the overflow brick weight times; when the overflow brick temperature rises When the clamping cylinder pressure is ≤ the overflow brick weight times; The weight of the overflow brick includes the weight of the overflow brick body, the weight of the overflow trough glass, and the weight of the glass from the overflow weir to the overflow surface of the overflow brick tip.

[0028] A high-generation large-size overflow brick is designed using the high-generation large-size overflow brick heating process design method.

[0029] Compared with the prior art, the positive and progressive effects of the present invention are: The present invention provides a method for designing a heating process for high-generation large-size overflow bricks. A mathematical model for the molding heating and insulation process is established based on the theory of heat conduction and thermal stress; a design benchmark for molding heating and insulation is established based on the thermal shock fracture and thermal shock damage model. The overflow brick heating process is divided into a number of heating sections and insulation sections. Based on the constructed mathematical models of the overflow brick heating section and insulation section, a temperature stress design curve for the overflow brick heating process is drawn, covering multi-dimensional indicators such as the maximum safe tensile stress curve, the internal and external temperature difference curve, the center tensile stress curve, the surface compressive stress curve, the maximum upper and lower temperature difference curve, and the clamping cylinder pressure curve; the center tensile stress of each heating section and insulation section of the overflow brick is made ≤ the maximum safe tensile stress at the center of the thickness of the overflow brick, and the heating process design for high-generation large-size overflow bricks is completed.

[0030] Furthermore, through the generation, structural size, volume size and heating rate distribution of overflow bricks in each section, the number of heating sections and insulation sections can be flexibly controlled. By increasing the number of heating sections and insulation section groups, the efficiency of the heating process can be improved, the overall heating time can be shortened, and a smooth transition of temperature changes can be ensured, reducing the problem of thermal stress concentration caused by rapid temperature changes.

[0031] The high-generation large-size overflow bricks designed using the design method of the present invention can realize graphical monitoring of the heating process, facilitate instant identification and adjustment of potential safety risks, and provide strong technical support for the design, optimization and verification of efficient and safe high-generation molding processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 It is a schematic diagram of the overflow system structure of the present invention; Figure 2 This is a schematic diagram of the overflow pull-down structure of the present invention; Figure 3 Schematic diagram of temperature and thermal stress distribution in the thickness direction of the overflow brick of the present invention; Figure 4 Schematic diagram of the temperature difference and stress distribution of the overflow brick of the present invention; Figure 5 A schematic diagram of temperature difference and stress distribution is provided for the overflow brick heating process design in the present invention; Figure 6 A schematic diagram of the temperature difference and stress distribution of the overflow brick heating process design in the present invention; In the figure: 1- overflow brick; 2- overflow trough; 3- glass liquid feeding device; 4- overflow brick root; 5- drainage plate; 6- molded glass substrate; 7- downward pulling direction of glass substrate; -Glass substrate specification width; -Glass substrate lead width. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings, which are intended to explain the present invention rather than to limit it.

[0035] See also Figure 1 , the overflow system is composed of an overflow brick 1 and a glass liquid feeding device 3. An overflow trough 2 is provided in the overflow brick 1, and the bottom of the overflow brick 1 is the overflow brick root 4; when the glass substrate is manufactured by molten overflow, the glass liquid melted by the glass melting furnace is supplied to the glass liquid feeding device 3 in the molten overflow molding device in the molding process, and overflows along the overflow trough 2 through both sides of the overflow brick 1, and forms a glass substrate below the overflow brick root 4. In the process of the glass melt moving from the proximal end to the distal end of the overflow trough, it is pushed by the mass force and pressure in the running direction, overcomes the laminar viscous resistance and flows downward from the overflow weir. The fluid dynamics equation based on this principle integrates the effects of the above forces and is the basis for the design of the overflow trough. On the vertical surface of the overflow, the mass force and pressure are large enough, and the viscosity is relatively low, the influence of the lateral surface tension is small, and there is almost no lateral contraction; on the inclined surface, the mass force and pressure components along the inclined surface are significantly reduced, and the viscosity gradually increases, the effect of the lateral surface tension is prominent, and a significant lateral contraction occurs. Therefore, a platinum drain plate 5 is provided at the far and near ends of the overflow brick slope to partially resist the lateral shrinkage of the glass.

[0036] See also Figure 2 The guide plate is used as the molding basis of the glass substrate. During the process of pulling down the glass substrate, the molded glass substrate 5 moves downward along the glass substrate pulling direction 6. is the width of the glass substrate, is the width of the glass substrate lead.

[0037] See also Figure 3 , which is a schematic diagram of the thickness equivalent structure of the overflow brick plate. During the heating process of the overflow brick, tensile stress is generated inside (center) and compressive stress is generated outside (surface). The black dotted line is the 0 stress dividing line in the thickness direction. The internal temperature, internal and external temperature difference and internal stress of the overflow brick are approximately parabolic distribution along the thickness direction. Due to sudden reasons (sudden changes in the environment or heating rate) during the heating process of the overflow brick, the surface temperature changes sharply and the internal and external temperature difference increases sharply (sudden cooling and heating), resulting in instantaneous thermal stress exceeding the flexural strength, making it difficult to resist thermal shock impact, and cracks nucleate near the surface and break. The internal and external temperature difference of the overflow brick corresponding to the thermal stress reaching the flexural strength limit is the maximum temperature difference at the beginning of damage. The rapidly cooled surface is tensile stress (positive value: more dangerous), and the rapidly heated surface is compressive stress (negative value). The thermal shock fracture model can be used for the design and optimization of the overflow brick heating process to ensure the safety margin of normal heating and prevent the occurrence of malicious process events.

[0038] See also Figure 4 The temperature difference between the upper and lower parts of the overflow brick generates compressive stress in the upper part of the overflow brick and tensile stress in the lower part of the overflow brick closer to the tip. In fact, the ideal instantaneous thermal stress is almost impossible to achieve. Due to factors such as heat conduction and heat dissipation, the maximum thermal stress occurs with a lag and the value is reduced. Thermal conductivity, heat dissipation coefficient and thickness can be calculated using the Biot criterion. To express, The smaller (the greater the thermal conductivity, the thinner the thickness and the smaller the surface heat dissipation), the better the thermal stability. The temperature difference between the upper and lower overflow bricks will produce thermal stress on the surface of the overflow bricks under the action of heat convection heat dissipation. Considering the safety of the overflow brick heating, the size of the temperature difference between the upper and lower overflow bricks should be controlled.

[0039] During the preparation of overflow bricks, due to the mismatch of thermal expansion and elastic deformation between inclusions and the matrix, significant residual internal stress will be generated near the interface between inclusions and the matrix, which may cause micro cracking in severe cases. During the sintering process of overflow bricks, abnormally grown grains will affect the overall uniformity of the material and lead to local stress concentration. Any other microstructural defects near the abnormally grown grains may lead to a reduction in local material strength. During the working process of overflow bricks, the residual internal stress near the interface between inclusions and the matrix will supplement the external stress, thereby inducing micro cracks. If the fracture toughness of the inclusions is higher than that of the matrix, micro cracks will be generated inside the matrix near the interface between inclusions and the matrix; if the fracture toughness of the inclusions is lower than that of the matrix, micro cracks induced by the residual internal stress appear inside the inclusions. Under the action of external force, when the size of the inclusions is larger than a certain critical value, micro cracking occurs. There are always internal structural defects such as pores, inclusions, grain boundaries and surface machining scratches in actual overflow brick materials. There will be a significant stress concentration effect in the areas near these defects. When the maximum tensile stress reaches or exceeds the theoretical fracture strength of the material, the overflow brick will break.

[0040] The larger the volume of the overflow brick, the greater the surface stress (heat conduction) generated by the same internal and external temperature difference; the larger the volume, the lower the safety factor of strength or the worse the thermal shock stability under the same process conditions. In addition, the larger the volume of the overflow brick, the greater the probability of defects, strength reduction and fracture; the larger the volume, the greater the discreteness of the defect distribution and the worse the uniformity of the strength distribution.

[0041] The present invention provides a method for designing a heating process for a high-generation large-size overflow brick, comprising the following steps: Establish mathematical models of overflow brick heating process and insulation process; divide the overflow brick heating process into several heating sections and insulation sections. The number of heating sections and insulation sections depends on the generation or structural size, volume size and heating rate distribution of each section of the overflow brick. It is necessary to ensure that the tensile stress at the thickness center of the overflow brick in each heating section and insulation section does not exceed the maximum safe tensile stress at the thickness center of the overflow brick; calculate the surface temperature in the thickness direction of the overflow brick, the center temperature in the thickness direction of the overflow brick, the average temperature in the thickness direction of the overflow brick, the temperature difference between the inside and outside of the overflow brick (the temperature difference between the surface and the center in the thickness direction of the overflow brick), the tensile stress in the thickness direction of the overflow brick, the surface compressive stress in the thickness direction of the overflow brick, the maximum safe tensile stress of the overflow brick (the flexural strength of the overflow brick) during the heating and insulation process of the overflow brick. ), the maximum upper and lower temperature difference of the overflow brick (that is, the maximum temperature difference between the upper and lower temperature sensors MSU and MSD of the overflow brick) and the clamping cylinder pressure, etc.

[0042] Based on the above calculations, the temperature stress design curve of the overflow brick heating process is drawn, including the overflow brick maximum safe tensile stress curve, the overflow brick internal and external temperature difference curve, the overflow brick thickness direction center tensile stress curve, the overflow brick thickness direction surface compressive stress curve, the overflow brick maximum upper and lower temperature difference curve and the clamping cylinder pressure curve. Each heating stage should be marked with the design heating speed of that stage, and the temperature and stress changes during the heating process should be displayed graphically to detect and correct safety risks at any time; based on the above steps, the high-generation large-size overflow brick heating process design is completed and submitted for production line process implementation.

[0043] Regarding the temperature rise section of the overflow brick: Assume that the half thickness of the overflow brick is The heating rate is , The transient temperature of the air around the overflow brick at any moment + , is the initial temperature of the environment around the overflow brick, and heat is exchanged with the overflow brick according to the convection law. The coordinate in the thickness direction is , the thickness center is the coordinate origin, any position time The temperature is The relative position coordinates are defined as , diffusion coefficient , Fourier number , the temperature distribution of the overflow brick at any time has nothing to do with the initial conditions, but only with the boundary conditions. Then:

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] in, for The relative position at time is The instantaneous temperature of the overflow brick; for Average temperature of overflow bricks at all times; for Time location The center temperature of the overflow brick; for Time location The surface temperature of the overflow brick; for The temperature difference between the inside and outside of the overflow brick at any time (the temperature difference between the surface and the center); for The relative position at time is Thermal stress of overflow bricks; is the density of the overflow brick; is the specific heat capacity of the overflow brick; is the thermal conductivity of the overflow brick; ; is the Young’s modulus of the overflow brick; is the linear thermal expansion coefficient of the overflow brick; is the Poisson’s ratio of the overflow brick; For the shape factor of the overflow brick, the present invention takes .

[0050] In particular, the temperature distribution of the overflow brick is proportional to the heating rate. When the temperature drops, the surface of the overflow brick is tensile stress and the center is compressive stress; when the temperature rises, the surface of the overflow brick is compressive stress and the center is tensile stress. The temperature of the overflow brick continues to converge rapidly with time, and is distributed parabolically along the thickness direction. The temperature gradient field is in a quasi-steady state (independent of time). If the overflow brick is heated for a long enough time, the temperature and thermal stress of the overflow brick tend to be stable, and the internal The temperature and thermal stress calculation formula at is:

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] Regarding the insulation section of the overflow brick: Assume that the half thickness of the overflow brick is , The transient temperature of the air around the overflow brick at any moment (can be obtained through the overflow brick temperature rise mathematical model), is the initial temperature of the environment around the overflow brick, and heat is exchanged with the overflow brick according to the convection law. The coordinate in the thickness direction is , the thickness center is the coordinate origin, any position time The temperature is The relative position coordinates are defined as , diffusion coefficient , Fourier number During insulation, the overflow bricks are in thermal equilibrium with the surrounding air and convective heat transfer can be ignored. is the initial condition of the overflow brick center during insulation (which can be obtained through the mathematical model of overflow brick heating). The temperature distribution of the overflow brick at any time has nothing to do with the initial condition and is only related to the boundary condition. Then:

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] In particular, as the holding time continues to converge rapidly, the internal and external temperatures tend to be consistent, the internal and external temperature difference tends to 0, and the internal and external stresses tend to 0. That is, if the holding time is long enough, then:

[0063]

[0064]

[0065] in, It can be obtained through the mathematical model of the temperature rise of overflow bricks before insulation (accumulation of each temperature rise stage), or It is the highest temperature before insulation.

[0066] Specifically, the specific formula for the maximum safe tensile stress of the overflow brick is:

[0067] in, The maximum safe tensile stress of overflow brick; is the flexural strength of overflow brick; Corresponding to all temperatures in the heating process, different temperatures correspond to The values ​​are different, the higher the temperature, the smaller the value.

[0068] Specifically, the specific formula for the internal and external temperature difference of the overflow brick heating process is:

[0069] in, is the surface temperature of the overflow brick in the thickness direction; is the center temperature of the overflow brick in the thickness direction; Relative position 1 (surface) in the thickness direction of the overflow brick Surface temperature at the moment; The relative position of overflow brick in thickness direction is 0 (center) Surface temperature at the moment; The size indicates the uniformity of temperature in the thickness direction of the overflow brick.

[0070] In particular, the specific formula for the surface temperature of the overflow brick in the thickness direction is: Heating stage:

[0071] Insulation section:

[0072] in, It is the initial surface temperature of the overflow brick in the thickness direction of the heating section, that is, the initial ambient temperature. If the heating section is preceded by an insulation section, then the surface temperature in the thickness direction of the overflow brick corresponding to the total heating time of the heating section before the insulation section; if the heating section is preceded by a heating section, then the surface temperature in the thickness direction of the overflow brick corresponding to the total heating time of the heating section before the heating section. is the initial surface temperature of the overflow brick in the thickness direction of a certain insulation section, that is, the initial ambient temperature, specifically, the surface temperature of the overflow brick in the thickness direction corresponding to the total heating time of the heating section before the insulation section; is the heating rate of a certain heating section; The corresponding time range is from 0 to the total heating time of a certain heating section.

[0073] In particular, the specific formula for the center temperature of the overflow brick in the thickness direction is: Heating section (the previous section is the insulation section):

[0074] Heating section (the previous section is the heating section):

[0075] Insulation section:

[0076] in, is the surface temperature of the overflow brick in the thickness direction of the heating section or insulation section, that is, ; is the initial center temperature of the overflow brick in the thickness direction of the insulation section, specifically, the center temperature of the overflow brick in the thickness direction corresponding to the total heating time of the heating section before the insulation section; is the correction item; The center temperature of the overflow brick in the thickness direction corresponding to the total heating time of the previous heating stage, corresponding to the heating speed of the previous heating stage; It is the center temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section, except that the heating rate is replaced by the heating rate of this section, but does not include the correction term.

[0077] Specifically, the specific formula for the tensile stress in the overflow brick heating process is:

[0078] in, The thickness direction of overflow brick The average temperature at the time.

[0079] In particular, the specific formula for the average temperature of the overflow brick in the thickness direction is: Heating section (the previous section is the insulation section):

[0080] Heating section (the previous section is the heating section):

[0081] Insulation section:

[0082] in, is the surface temperature of the overflow brick in the thickness direction of the heating section or insulation section, that is, ; is the correction item; is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating stage, corresponding to the heating speed of the previous heating stage; It is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section, except that the heating rate is replaced by the heating rate of this section, but does not include the correction term.

[0083] Specifically, the specific formula for the surface compressive stress of the overflow brick heating process is:

[0084] Specifically, the specific formula for the maximum upper and lower temperature difference of the overflow brick (i.e., the maximum temperature difference between the upper and lower temperature sensors MSU and MSD of the overflow brick) is:

[0085] in, Corresponding to temperature Flexural strength of overflow bricks; for and spacing; for Distance from the tip of the overflow brick; is the safety factor; h is the convection radiation surface heat dissipation coefficient.

[0086] Specifically, the overflow brick heating process includes: (1) heating temperature When the clamping cylinder pressure is 0; (2) Heating temperature When the clamping cylinder pressure does not exceed the overflow brick weight times; (3) Heating temperature When the clamping cylinder pressure does not exceed the overflow brick weight times.

[0087] In particular, the weight of the overflow brick includes the weight of the overflow brick body, the weight of the overflow trough glass, and the glass on the overflow surface from the overflow weir to the overflow brick tip. The specific data is provided by the overflow brick structure designer.

[0088] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0089] The high-generation large-size overflow brick heating process design method of the present invention comprises the following steps: Step 1: Divide the overflow brick heating process into a combination of several heating sections and insulation sections; construct the maximum safe tensile stress at the thickness center of the overflow brick based on the material parameters of the overflow brick; construct the mathematical models of the overflow brick heating section and insulation section based on the theory of heat conduction and thermal stress; design the maximum upper and lower temperature difference and clamping cylinder pressure of the overflow brick; 1.1 The overflow brick heating process is divided into several heating sections and insulation sections, including: The overflow brick heating process includes a plurality of heating sections and insulation sections, each combination includes a plurality of heating sections and one insulation section; each heating section has a certain temperature range, heating speed and heating time, and each insulation section has a certain insulation time.

[0090] Among them, the heating process of the overflow brick includes a combination of multiple heating sections and insulation sections, each combination includes one or more heating sections and one insulation section; each heating section has a certain temperature range, heating speed and heating time, and each insulation section has a certain insulation time; when the length and volume of the overflow brick increase, by increasing the number of heating sections and insulation section groups, the speed of each heating section can be increased, the overall heating process time can be reduced, and the heating efficiency can be improved.

[0091] The heating section and insulation section of the overflow brick heating process are divided as follows: (1) Heating process combination classification below G9.5 generation (such as G8.5 generation): heating section 1, insulation section 1; heating section 2 to heating section 7, insulation section 2; (2) Heating process combination classification of G9.5 generation: heating section 1, insulation section 1; heating section 2 to heating section 7 are divided into two stages of insulation, namely heating section 2 to heating section 4, insulation section 2; heating section 5 to heating section 7, insulation section 3; (3) Heating process combination classification above G9.5 generation (such as G10.5 generation or greater): heating section 1, insulation section 1; heating section 2 to heating section 7 are divided into three stages of insulation, namely heating section 2 to heating section 3, insulation section 2; heating section 4 to heating section 5, insulation section 3; heating section 6 to heating section 7, insulation section 4.

[0092] Among them, the temperature distribution of the heating section is: heating section 1, the temperature range is , heating time Since the absolute temperature of the overflow bricks in this stage is relatively low, there is no safety risk in the heating process according to the design; in the second heating stage, the temperature range is The heating time is determined by the heating speed; the temperature range of heating stage three is The heating time is determined by the heating speed; in heating stage 4, the temperature range is The heating time is determined by the heating speed; in heating stage five, the temperature range is The heating time is determined by the heating speed; the temperature range of heating stage 6 is The heating time is determined by the heating speed; the temperature range of heating stage seven is The heating time is determined by the heating speed.

[0093] Heating speed of the insulation section , constant temperature, insulation time After a sufficient period of heat preservation, the internal and external temperatures tend to be consistent, the internal and external temperature difference tends to 0, and the stress .

[0094] In fact, the division of the heating section and the insulation section of the overflow brick heating process is not limited to the above combination. When the length and volume of the overflow brick increase, by increasing the number of heating sections and insulation sections, the speed of each heating section can be increased, the overall heating process time can be reduced, and the heating efficiency can be improved. For example, it can be optimized and adjusted according to the relationship between the stress and the maximum safe tensile stress of the overflow brick, provided that the heating speed of each heating section is optimized to ensure that the tensile stress at the center of the thickness of the overflow brick in each heating section does not exceed the maximum safe tensile stress at the center of the thickness of the overflow brick; for another example, it can also be optimized and adjusted according to the relationship between the strain point temperature of the glass substrate (such as LTPs and IGZO or other glass substrates) and the stress and the maximum safe tensile stress of the overflow brick, provided that the heating speed of each heating section is optimized to ensure that the tensile stress at the center of the thickness of the overflow brick in each heating section does not exceed the maximum safe tensile stress at the center of the thickness of the overflow brick.

[0095] 1.2 Based on the material parameters of the overflow brick, the maximum safe tensile stress at the thickness center of the overflow brick is constructed, specifically:

[0096] in, The maximum safe tensile stress of overflow brick; is the flexural strength of overflow brick; Corresponding to all temperatures in the heating process, different temperatures correspond to The values ​​are different, the higher the temperature, the smaller the value.

[0097] 1.3 Based on the theory of heat conduction and thermal stress, mathematical models of the overflow brick heating section and insulation section are constructed respectively, specifically: L1: Calculate the surface temperature of the overflow brick in the thickness direction: Heating stage:

[0098] Insulation section:

[0099] in, ; ; ; Relative position 1 (surface) in the thickness direction of the overflow brick Surface temperature at the moment; It is the initial surface temperature of the overflow brick in the thickness direction of the heating section, that is, the initial ambient temperature. If the heating section is preceded by an insulation section, then the surface temperature in the thickness direction of the overflow brick corresponding to the total heating time of the heating section before the insulation section; if the heating section is preceded by a heating section, then the surface temperature in the thickness direction of the overflow brick corresponding to the total heating time of the heating section before the heating section. is the initial surface temperature of the overflow brick in the thickness direction of a certain insulation section, that is, the initial ambient temperature, specifically, the surface temperature of the overflow brick in the thickness direction corresponding to the total heating time of the heating section before the insulation section; is the heating rate of a certain heating section; is the density of the overflow brick; is the specific heat capacity of the overflow brick; is the thermal conductivity of the overflow brick; is the half thickness of the overflow brick; is the Fourier number, the corresponding time t is the total heating time from 0 to the heating section; a is the diffusion coefficient.

[0100] L2: Calculate the center temperature of the overflow brick in the thickness direction: Heating section (the previous section is the insulation section):

[0101] Heating section (the previous section is the heating section):

[0102] Insulation section:

[0103] in, The relative position of overflow brick in thickness direction is 0 (center) Surface temperature at the moment; is the surface temperature of the overflow brick in the thickness direction of the heating section or insulation section, that is, ; is the initial center temperature of the overflow brick in the thickness direction of the insulation section, specifically, the center temperature of the overflow brick in the thickness direction corresponding to the total heating time of the heating section before the insulation section; is the correction item; The center temperature of the overflow brick in the thickness direction corresponding to the total heating time of the previous heating stage, corresponding to the heating speed of the previous heating stage; It is the center temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section, except that the heating rate is replaced by the heating rate of this section, but does not include the correction term.

[0104] L3: Calculate the average temperature of the overflow brick in the thickness direction: Heating section (the previous section is the insulation section):

[0105] Temperature rising section (the previous section is the temperature rising section):

[0106] Insulation section:

[0107] in, is the surface temperature of the overflow brick in the thickness direction of the heating section or insulation section, that is, ; is the correction item; is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating stage, corresponding to the heating speed of the previous heating stage; It is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section, except that the heating rate is replaced by the heating rate of this section, but does not include the correction term.

[0108] 1.4 Design the maximum upper and lower temperature difference of the overflow brick (i.e., the maximum temperature difference between the upper and lower temperature sensors MSU and MSD of the overflow brick) and the clamping cylinder pressure, specifically:

[0109] in, Corresponding to temperature Flexural strength of overflow bricks; for and spacing; for Distance from the tip of the overflow brick; is the safety factor; h is the convection radiation surface heat dissipation coefficient; is the Young's modulus of the overflow brick; μ is the Poisson's ratio of the overflow brick.

[0110] The specific design of the overflow brick clamping cylinder pressure is: (1) Heating temperature When the clamping cylinder pressure is 0; (2) Heating temperature When the clamping cylinder pressure does not exceed the overflow brick weight times; (3) Heating temperature When the clamping cylinder pressure does not exceed the overflow brick weight times.

[0111] Among them, the weight of the overflow brick includes the weight of the overflow brick body, the weight of the overflow trough glass and the glass on the overflow surface from the overflow weir to the overflow brick tip. The specific data is provided by the overflow brick structure designer.

[0112] Step 2: Based on the mathematical model of the overflow brick heating section and the insulation section constructed in step 1, calculate the internal and external temperature difference, central tensile stress and surface compressive stress of the overflow brick, specifically: S1: Calculate the internal and external temperature difference of the overflow brick heating process:

[0113] in, is the surface temperature of the overflow brick in the thickness direction; is the center temperature of the overflow brick in the thickness direction; The size indicates the uniformity of temperature in the thickness direction of the overflow brick.

[0114] S2: Calculate the tensile stress of the overflow brick heating process center:

[0115] S3: Calculate the surface compressive stress of overflow brick during heating process:

[0116] Step 3: Draw the temperature stress design curve of the overflow brick heating process, including the maximum safe tensile stress curve at the thickness center of the overflow brick, the internal and external temperature difference curve, the central tensile stress curve, the surface compressive stress curve, the maximum upper and lower temperature difference curve and the clamping cylinder pressure curve; Step 4. Based on the above-mentioned combined division of the heating section and the insulation section and the optimization analysis of the heating rate, draw the temperature stress design curve of the overflow brick heating process, including the overflow brick maximum safe tensile stress curve, the overflow brick inside and outside temperature difference curve, the overflow brick thickness direction center tensile stress curve, the overflow brick thickness direction surface compressive stress curve, the overflow brick maximum upper and lower temperature difference curve and the clamping cylinder pressure curve.

[0117] according to Figure 5 As shown in the figure, it is the heating process design curve and related design data of a large overflow brick; according to Figure 6 As shown in the figure, it is another temperature rise process design curve and related design data of the large overflow brick. The difference between the two temperature rise process curves is: Figure 5 It adopts two heating sections and a heat preservation section combination. Figure 6 The three heating stages and the heat preservation stage are combined. Figure 6 A higher heating rate and a shorter total heating process time can be used to achieve the purpose of heating the overflow brick, which is more efficient and safer.

[0118] The present invention provides a high-generation large-size overflow brick heating process design method, and establishes a mathematical model of the molding heating and insulation process based on the theory of heat conduction and thermal stress; and establishes a design benchmark for molding heating and insulation based on the thermal shock fracture and thermal shock damage model. The overflow brick heating process is divided into several heating sections and insulation sections, and the surface temperature in the thickness direction of the overflow brick, the center temperature in the thickness direction of the overflow brick, the average temperature in the thickness direction of the overflow brick, the internal and external temperature difference of the overflow brick (the temperature difference between the surface and the center in the thickness direction of the overflow brick), the tensile stress in the thickness direction of the overflow brick, the compressive stress on the surface in the thickness direction of the overflow brick, the maximum safe tensile stress of the overflow brick (1⁄9 of the flexural strength of the overflow brick), the maximum upper and lower temperature difference of the overflow brick (that is, the maximum temperature difference between the upper and lower temperature sensors MSU and MSD of the overflow brick) and the clamping cylinder pressure are calculated during the heating and insulation process of the overflow brick. Based on the above calculations, the temperature stress design curve of the overflow brick heating process is drawn, including the overflow brick maximum safe tensile stress curve, the overflow brick inside and outside temperature difference curve, the overflow brick thickness direction center tensile stress curve, the overflow brick thickness direction surface compressive stress curve, the overflow brick maximum upper and lower temperature difference curve and the clamping cylinder pressure curve. The number of heating sections and insulation sections depends on the generation or structural size of the overflow brick, the volume size and the heating rate distribution of each section. It is necessary to ensure that the tensile stress at the center of the overflow brick thickness of each heating section and insulation section does not exceed the maximum safe tensile stress at the center of the overflow brick thickness. Based on the standardized design method and process of the heating process of the present invention, the temperature and stress changes during the heating process can be automatically displayed in a graphical manner, and safety risks can be discovered and corrected at any time, providing technical support for the design, optimization and verification of high-generation molding heating processes.

[0119] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A high-generation large-size overflow brick heating process design method, characterized in that: The following steps are involved: Step 1: Divide the overflow brick heating process into a combination of several heating sections and insulation sections; construct the maximum safe tensile stress at the thickness center of the overflow brick based on the material parameters of the overflow brick; construct the mathematical models of the overflow brick heating section and insulation section based on the theory of heat conduction and thermal stress; design the maximum upper and lower temperature difference and clamping cylinder pressure of the overflow brick; Step 2: Based on the mathematical model of the overflow brick heating section and the insulation section constructed in step 1, calculate the internal and external temperature difference, central tensile stress and surface compressive stress of the overflow brick; Step 3: Draw the temperature stress design curve of the overflow brick heating process, including the maximum safe tensile stress curve at the thickness center of the overflow brick, the internal and external temperature difference curve, the central tensile stress curve, the surface compressive stress curve, the maximum upper and lower temperature difference curve and the clamping cylinder pressure curve; Step 4. According to the curve drawn in step 3, the central tensile stress of each heating section and insulation section of the overflow brick is made ≤ the maximum safe tensile stress at the center of the thickness of the overflow brick, thus completing the heating process design of high-generation large-size overflow bricks.

2. According to claim 1, a high-generation large-size overflow brick heating process design method is characterized in that: In step 1, in each combination of a heating section and a heat preservation section, there are one or more heating sections and one heat preservation section.

3. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: The heating rate of the heating section is greater than 0; the heating rate of the insulation section is equal to 0.

4. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: In step 1, the maximum safe tensile stress at the thickness center of the overflow brick is: in, The maximum safe tensile stress of overflow brick; It is the flexural strength of overflow brick.

5. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: In step 1, the mathematical model of the overflow brick heating section specifically includes: Surface temperature of overflow brick in thickness direction : When the previous section of the heating section is the insulation section, the center temperature of the overflow brick in the thickness direction : When the previous section of the heating section is the insulation section, the average temperature of the overflow brick in the thickness direction : When the previous section of the heating section is the heating section, the center temperature of the overflow brick in the thickness direction : When the previous section of the heating section is the heating section, the average temperature of the overflow brick in the thickness direction : in, ; ; ; The initial surface temperature of the overflow brick in the thickness direction during the heating stage; is the density of the overflow brick; is the specific heat capacity of the overflow brick; is the thermal conductivity of the overflow brick; is the heating rate; is the half thickness of the overflow brick; is the Fourier number, t is the total heating time from 0 to the heating section; a is the diffusion coefficient; is the surface temperature of the overflow brick in the thickness direction of the heating stage, equal to ; is an exponential function with the natural constant e as base; is the correction term, a is the center temperature of the overflow brick thickness direction corresponding to the total heating time of the previous heating section, and the corresponding heating rate is the heating rate of the previous heating section, b is the center temperature of the overflow brick thickness direction corresponding to the total heating time of the previous heating section, and the corresponding heating rate is the heating rate of this section, but does not include the correction term; is the correction term, c is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating stage, and the corresponding heating rate is the heating rate of the previous heating stage; It is the average temperature in the thickness direction of the overflow brick corresponding to the total heating time of the previous heating section. The corresponding heating rate is the heating rate of this section, but does not include the correction term.

6. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: In step 1, the mathematical model of the overflow brick insulation section specifically includes: Surface temperature of overflow brick in thickness direction : The center temperature of the overflow brick in the thickness direction : Average temperature of overflow brick in thickness direction : in, ; ; ; is the initial surface temperature of the overflow brick in the thickness direction of the insulation section; is the surface temperature of the overflow brick in the thickness direction of the insulation section, equal to ; is the initial center temperature of the overflow brick in the thickness direction of the insulation section; is an exponential function with the natural constant e as base; is the half thickness of the overflow brick; is the Fourier number, t is the total insulation time from 0 to the insulation section; a is the diffusion coefficient.

7. A method for designing a heating process for high-generation large-size overflow bricks according to claim 5 or 6, characterized in that: In step 2, the temperature difference between the inside and outside of the overflow brick for: Central tensile stress for: Surface compressive stress for: in, is the surface temperature of the overflow brick in the thickness direction; is the center temperature of the overflow brick in the thickness direction; E is the Young's modulus of the overflow brick; α is the linear thermal expansion coefficient of the overflow brick; μ is the Poisson's ratio of the overflow brick.

8. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: In step 1, the maximum upper and lower temperature difference of the overflow brick is designed to be: in, The temperature collected by the temperature sensor on the top of the overflow brick; The temperature collected by the temperature sensor at the bottom of the overflow brick; For overflow brick at temperature The corresponding flexural strength when is the distance between the upper temperature sensor and the lower temperature sensor of the overflow brick; for The distance from the tip of the overflow brick; is the safety factor; E is the Young's modulus of the overflow brick; α is the linear thermal expansion coefficient of the overflow brick; μ is the Poisson's ratio of the overflow brick; is the thermal conductivity of the overflow brick; h is the convection radiation surface heat dissipation coefficient.

9. The method for designing a heating process for high-generation large-size overflow bricks according to claim 1 is characterized in that: In step 1, the clamping cylinder pressure is designed to be: When the overflow brick is heated to When the clamping cylinder pressure is 0; when the overflow brick is heated to When the clamping cylinder pressure is less than the overflow brick weight times; when the overflow brick temperature rises When the clamping cylinder pressure is less than the overflow brick weight times; The weight of the overflow brick includes the weight of the overflow brick body, the weight of the overflow trough glass, and the weight of the glass from the overflow weir to the overflow surface of the overflow brick tip.

10. A high-generation large-size overflow brick, characterized in that: The high-generation large-size overflow brick heating process design method is designed by using any one of claims 1 to 9.

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