[ Chinese wardrobe network ] 1 chemical tempering method A tempering method that chemically changes the surface composition of a glass to increase the surface lamination stress to increase the mechanical strength and thermal stability of the glass is called a chemical tempering method. Since it enhances glass by ion exchange, it is also called ion exchange enhancement. According to the type of exchanged ions and the temperature of ion exchange, it can be further divided into an ion exchange method (referred to as a low temperature method) lower than the transition point and an ion exchange method (referred to as a high temperature method) higher than the transition point temperature. The principle of the chemical enhancement method is to change the surface composition of the glass according to the mechanism of ion diffusion, and immerse the glass in the high-temperature molten salt at a certain temperature, and the alkali metal ions in the glass and the alkali metal ions in the molten salt are diffused. Interchange occurs, causing "crowding", which causes compressive stress on the glass surface, thereby increasing the strength of the glass. According to the network structure theory of glass, the glassy substance consists of a disordered three-dimensional network consisting of oxygen-containing ionic polyhedrons whose centers are occupied by s Al or P ions. These ions together with the oxygen ions form a network filled with alkali metal ions (; nNa , K ) and alkaline earth metal ions. Among them, the alkali metal ions are more active and easily precipitated from the interior of the glass. The chemical tempering method is based on the natural diffusion and interdiffusion of ions to change the composition of the surface layer of the glass to form a surface compressive stress layer. However, the surface compressive stress layer produced by the ion exchange method is relatively thin, sensitive to surface micro-defects, and small surface scratches are sufficient to reduce the strength of the glass. Advantages and Disadvantages: The strength of chemically reinforced glass is close to that of physical reinforced glass, the thermal stability is good, the processing temperature is low, the product is not easily deformed, and the product is not limited by thickness and geometry. The equipment is simple and the product is easy to realize. However, compared with physical tempered glass, chemical tempered glass has a long production cycle (long-term exchange time of several tens of hours), low efficiency and high production cost (the molten salt cannot be recycled, and the purity requirement is high), and the debris is similar to ordinary glass. Poor performance, and its performance is unstable (poor chemical stability), physical properties such as mechanical strength and impact strength are easy to subside (also known as slack), and the strength is quickly attenuated at any time. Scope of application: Chemical tempered glass is widely used in flat glass of different thickness, thin-walled glass and bottle shaped glass products, and can also be used for fireproof glass. 2 physical tempering method The principle of physical tempering is to rapidly cool the glass after heating to a suitable temperature, so that the surface of the glass shrinks sharply, and compressive stress is generated. The middle layer of the glass is cooled slowly, and it is too late to shrink, so that tensile stress is formed and the glass is obtained with high strength. Generally speaking, the higher the cooling strength, the greater the strength of the glass. There are many physical tempering methods, which can be divided into: gas medium tempering method, liquid medium tempering method, particle tempering method, fog tempering method, etc. according to the cooling medium. 2.1 Gas medium tempering method Gas medium tempering method, namely air cooling tempering method. Including horizontal air cushion tempering, horizontal roller tempering, vertical tempering and other methods. The so-called air-cooling tempering method is a production method in which the glass is heated to a softening temperature (650 to 700 ° C) close to the glass, and then air is simultaneously blown on both sides to rapidly cool the glass to increase the mechanical strength and thermal stability of the glass. . Quenching of heated glass is an important part of the production of tempered glass by physical tempering. The basic requirement for quenching glass is to quickly and uniformly cool, so as to obtain uniform distributed stress. In order to obtain uniform cooling glass, cooling must be required. The device effectively dissipates the heat, facilitates the removal of accidental broken glass and minimizes its noise. Advantages and disadvantages: The advantages of air-cooled tempering are lower cost, higher output, higher mechanical strength, thermal shock resistance (maximum safe working temperature up to 287.78.c) and high heat resistance gradient (can withstand 204. 44. C), and in addition to enhancing mechanical strength, air-cooled tempered glass can form small fragments when broken, which can reduce the damage to the human body. However, there are certain requirements on the thickness and shape of the glass (the minimum thickness of the glass tempered by the domestic equipment is generally about 3 mm), and the cooling rate is slow and the energy consumption is high. For the thin glass, there is still a problem of glass deformation during the tempering process. Can not be applied in areas where optical quality requirements are high. Scope of application: At present, air tempering technology is widely used, and air tempered glass is mostly used in automobiles, ships, and buildings. 2.2 Liquid medium tempering method Liquid medium tempering method, ie liquid cooling method. The so-called liquid cooling method is to heat the glass to a point close to the softening point, and then to temper in a quench tank filled with liquid. At this time, as the cooling medium, a brine such as a mixed brine of potassium nitrate, potassium nitrite, sodium nitrate, sodium nitrite or the like can be used. In addition, mineral oil can also be used as the cooling medium, and it is of course also possible to add an additive such as toluene or carbon tetrachloride to the mineral oil. Some special quenching oils and silicone oils can also be used. In the case of liquid tempering, since the edge portion of the glass sheet first enters the quenching groove, cracking due to uneven stress occurs. In order to solve this problem, it may be pre-cooled by air cooling or spraying, and then placed in an organic liquid to be quenched. It is also possible to put water and an organic solution in the quenching tank, and the organic solution floats on the water. When the heated glass is placed in the tank, the organic solution acts as a pre-cooling, absorbs a part of the heat, and then rapidly cools into the water. It is also possible to use a liquid spray method by immersing in a cooling liquid, but it is generally used by an immersion method. The Triplex company in the United Kingdom first used a liquid medium method to temper glass with a thickness of 0.75 to 1.5 mm in the 1980s, ending the history of physical tempering that cannot temper thin glass. The difficulty of the liquid tempering method is to establish a reasonable liquid cooling process system. Two problems should be paid attention to during liquid cooling and tempering: one is to produce an excessively high compressive stress layer, and the other is to avoid glass cracking. Advantages and disadvantages: According to the liquid medium tempering method, since the specific heat of water is large and the heat of vaporization is high, the amount is greatly reduced, so that the energy consumption is reduced, the cost is reduced, and the cooling rate is fast, the safety performance is high, and the deformation is small. Since the glass is heated and inserted into the liquid medium upon cooling, the glass sheet having a large area is easily affected by heat unevenness and affects the quality and the yield. Scope of application: It is mainly suitable for tempering thin glass with various areas such as glasses. LCD glass, optical instrument glass, etc. 2.3 Particle tempering method This method is a process for heating glass to a temperature close to the softening temperature and quenching the alumina particles in the fluidized bed by solid particles, generally having a particle size of less than 200 m. Theoretically, the use of solids as a cooling medium can produce thinner, lighter, and stronger tempered glass. Therefore, in the mid-1970s and early 1980s, the United Kingdom, Japan, Belgium, and Germany continued to apply this technology. For production. Advantages and disadvantages: The particle tempering method can temper ultra-thin glass. High strength and good quality. It is an advanced technology for the manufacture of high performance tempered glass. The new process of particle tempering is compared with the traditional wind tempering process. The cooling medium has a large cooling energy and is suitable for tempering ultra-thin glass, and the energy saving effect is remarkable (energy saving is about 40%). However, the cooling medium of the particle tempering process is costly. Scope of application: high strength, high precision thin glass and ultra-thin glass. 2.4 Fog tempering method Using atomized water as the cooling medium, the spray venting equipment can make the glass more uniform in the tempering process, consume less energy, and have better performance after tempering. The spray venting apparatus is composed of a plurality of grid-shaped barrel structures which are juxtaposed to each other and arranged on the bottom plate, and each of the barrel structures is constituted by a bottom plate, a partition plate, a nozzle and a plurality of exhaust ports L. Similar to the gas method, but the cooling medium used is not air, but atomized water. It is characterized in that the glass is tempered by using atomized water as a cooling medium. The specific heat of water is large, and the heat of vaporization of water in all liquids is also the highest. During the tempering process of the glass, the water mist is continuously sprayed onto the surface of the heated glass, and the atomized water in the form of particles rapidly absorbs heat to become water of 100 ° C, and then gasifies, and the specific heat of the water is utilized and the heat of vaporization is utilized. This feature is high. A large amount of heat on the surface of the glass is instantaneously taken away (absorbed), and the glass is quenched and tempered to cause permanent compressive stress on the surface of the glass, thereby increasing the tensile strength of the glass and tempering the glass. The water mist (atomized water) can be sprayed onto the surface of the heated glass by a compressed air blowing method, a steam blowing method or a hydraulic spraying method, and the atomized water rapidly absorbs heat and vaporizes due to contact with the red hot glass. If it is allowed to spread freely. It will affect the uniform cooling of the glass and easily break the glass. to this end. A unique spray venting device is required to allow the vaporized and expanded moisture to be pumped away. It does not spread along the surface of the glass." Advantages and disadvantages of fog steel: The cooling medium is easy to obtain, the cost is low, the environment is not polluted, and the thin glass which cannot be tempered by general gas, liquid and particle tempering can be tempered. However, cooling uniformity is more difficult to control. Scope of application: Because its cooling system is difficult to control, it is currently used less. 3 Conclusion In summary, chemical tempering is suitable for tempering thin glass, glass requiring high precision or complex shape, and most of its products are used for special purposes such as glasses, aerospace glass, and substrate glass for electronics. However, the chemical tempering products have a short life span of generally less than 3 years, while the physical tempered product has a service life of more than 30 years; the particulate tempered glass process can produce high-quality thin tempered glass with high strength and no stress streaks, but it will affect the surface quality of the glass; The liquid tempered glass process is suitable for the tempering of small-sized thin glass and ultra-thin glass. In addition, acid corrosion also affects the strength of the glass. The principle of acid corrosion is to remove the surface crack layer of the glass by acid etching or passivate the crack tip to reduce the stress concentration to restore the inherent high strength characteristics of the glass. It is also possible to combine the above-mentioned several glass reinforcement technologies organically, to exert their respective strengths, and to fully increase the strength of the glass, thereby forming a so-called comprehensive reinforcement technology. Manual Medical Bed,3 Cranks Hospital Bed,Manual Patient Medical Bed,Adjustable Crank Patient Bed Jiangmen Jia Mei Medical Products Co.,Ltd. , https://www.jmmedicalequipment.com