Knowledge

Analysis and Solution of Common Quality Problems of Tempered Glass



There are many appearances of tempered glass quality problems, we appear in the production process in accordance with its different stages, it is divided into two categories: ① quality defects caused by the appearance of toughened glass appearance, such as: point defects (Bubbles, inclusions), scratches, optical deformation, etc .; ② appearance quality problems caused by the steel processing, such as: the problem of flatness of tempered glass (wave pattern, fit, deformation of the board), optical problems Central gray, stress spots are too heavy, iridescent phenomenon), white, scratched, pitting and so on.

 

First, the defects caused by the appearance of the original quality problems and the reasons for the more common are: punctate defects (bubbles, inclusions), scratches, optical deformation. Bubbles, inclusions and optical deformation are inherent defects of the original plate, scratches in the original glass production and handling process formed.

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If the original film does not meet the corresponding standard requirements, not only will the tempered glass in the appearance of quality does not meet the "tempered glass" national standards, but also greatly increase the tempered glass fryer, uneven stress distribution, blew , The mechanical strength is reduced, the thermal stability and various safety risks are worsened. As a result, the shutdown of the tempering furnace and the cleaning of the furnace lead to the decrease of the product yield and the production efficiency and the increase of the production cost, resulting in unnecessary waste.

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Tempered glass manufacturers even through the adjustment of the technological parameters of the furnace can not avoid such quality problems, and enterprises can only strictly control the production management system, to strengthen staff training, so that operators master the content of the inspection standards and the corresponding Inspection methods, the original glass strict screening, to avoid the problem of the original piece of glass into the re-processing stage.

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Second, the appearance of quality problems caused by the toughening process are more common: flatness problems of tempered glass (wave pattern, fit, deformation of the board), optical problems (gray in the center, cloudy spots, iridescence phenomenon) , White, scratched, pitting and so on.

 

1, the problem of poor flatness of tempered glass

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The problem of poor flatness of tempered glass can be divided into two categories:

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Category 1, curved tempered glass surface roughness problem. Often, these kinds of problems consider its coincidence index. When the finished products of curved toughened glass do not meet the design requirements, the following three kinds of phenomena will occur:

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1) finished glass and design requirements appear distorted. This shows that the need for bending the glass in the roller position is not placed correctly, the curved glass center line with the roller is not parallel, if this happens, the operator needs to re-adjust the position of the glass on the stage, so that the glass Curved centerline and roller in parallel.

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2) The finished glass and the design of bending depth appear different. This shows that the process of setting parameters of steel has a problem: In the heating stage, the glass heating temperature is not enough; in the cooling stage, the main wind grille and the lower outlet when the wind is not synchronized, when the hair to open a hair dryer, a hair dryer . If the lower air outlet to open the first hair, then the glass after bending depth will increase, on the contrary, the first air outlet to open the hair, the glass bending depth after molding will be reduced, not according to the design of the arc. At this point the operator can re-adjust the process parameters, adjust the glass bending depth.

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Finished glass surface quality does not meet the design requirements. Operators can adjust the heating time of bending and quenching time, or bending section of the transmission chain of tension, through the process parameters of steel or equipment to solve these problems.

 

Class 2, flat tempered glass flatness problem. Such problems are mainly the following five kinds of situations:

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1) glass in the heating of the upper and lower surface temperature difference caused by glass deformation

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① toughened glass surface upward. This phenomenon is due to the glass heated in a heating furnace, the upper surface of the glass appears higher temperature than the temperature of the lower surface of the glass to maintain the state of cooling into the cooling chamber, in the cooling process, when the glass on the lower surface Of the cooling temperature and wind pressure and other conditions are the same, due to the glass surface temperature is high, after cooling the contraction of the upper surface is greater than the lower surface, there will be bending upward deformation of the glass surface phenomenon.

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This situation occurs, you can increase the temperature at the bottom of the furnace, minimize the glass surface temperature difference.

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② toughened glass surface down. This phenomenon is due to the glass heated in a heating furnace, the lower surface of the glass appears higher temperature than the temperature of the surface, maintaining the temperature state of the glass into the cooling chamber cooling, during cooling, when the glass on the lower surface Of the cooling temperature and wind pressure and other conditions are the same, because the glass under the surface temperature is high, after cooling the lower surface of the shrinkage is greater than the upper surface, there will be downward bending glass plate phenomenon.

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When this happens, the temperature at the bottom of the furnace can be reduced to minimize the temperature difference between the upper and lower surfaces of the glass.

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2) glass in the middle of the heating and the temperature difference between the glass deformation

 

After the glass is heated in the heating furnace, if the temperature in the middle part is higher than the temperature in the middle part, the amount of shrinkage in the middle part of the glass with a higher temperature during the cooling process will be larger than that in the lower temperature part When the glass is cooled to room temperature, the size of the edge of the glass will be larger than the size of the middle part, and a large compressive stress will be formed on the edge of the glass, causing the glass plate to buckle downward.

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Similarly, after the glass is heated in a heating furnace, if the temperature of the edge is higher than the temperature of the middle part, the amount of shrinkage in the middle part of the glass at a higher temperature during cooling will be larger than that in the part with a lower temperature Shrinkage, when the glass was cooled to room temperature, the size of the middle part of the glass will be greater than the size of the edge of the glass edge to form a larger tensile stress, resulting in bending the glass plate upward deformation phenomenon.

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Occurrence of these two cases, you can adjust the tempered furnace heating temperature of the local parameters or change the arrangement of pieces to solve the installation.

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3) random temperature distribution caused by uneven glass deformation

Stochastic uneven temperature distribution is mainly due to poor equipment status. The heating wire of the tempering furnace has partial damage, the position of the temperature sensor changes or is distorted, and the unwinding of the glass on the roller table and the like causes the glass to be heated unevenly. This random temperature distribution will lead to non-uniform temperature distribution in the direction of the plate surface after the glass is heated. Irregular and irregular shrinkage occurs in different areas of the glass during cooling, which directly leads to the poor local flatness of the glass plate surface. This situation occurs, companies can develop reasonable equipment maintenance, loading system to solve.

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4) roller deformation caused by the glass deformation

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Rolling deformation can be divided into hot roller deformation and roller wear deformation.

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① roller deformation caused by deformation of the glass.

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Due to the very good thermal shock resistance and thermal stability of ceramic and quartz materials, roller tables in tempering furnaces are generally made of such materials. Although the heat resistance of these two materials, but due to uneven internal structure of roller, after long-term use or improper heating, can lead to thermal deformation at high temperatures. The glass that has been moved on such a deformed roller table also deforms as a result, eventually resulting in poor surface smoothness.

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② roller wear deformation caused by deformation of the glass

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In the tempered glass manufacturer, when the toughening furnace roller appears more firmly bonded impurities, it is usually used to remove the grinding method. In the long-term production process, the roller after repeated grinding and long-term use can easily lead to wear and tear, and these wear due to different degrees, the roller will appear uneven thickness problems, and ultimately lead to the movement of the glass in the roller Deformation occurred, that plate surface is not flat.

 

In addition, the roller in the same tempering furnace, due to the replacement of time, that is, each roller is worn to varying degrees, when the glass is heated in the overall uneven surface of the roller to the softening temperature and exercise, Very prone to deformation of the board. This situation occurs not only in the heating chamber, but also in the cooling chamber.

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Occurrence of these two conditions, companies can develop a regular, reasonable roller inspection management system to solve.

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5) tempered glass wave pattern

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Wave pattern refers to the surface of the glass has a continuous ups and downs, in severe cases can touch the surface of the glass can feel. The main reasons for this phenomenon are the following four conditions: ① tempering furnace temperature is too high, heating time is too long. When this happens, it can be solved by adjusting the parameters of the tempering process, lowering the heating temperature of the tempering furnace or reducing the heating time. ② The bending deformation of the rollers or the individual roller diameters and the roller height exceed the standard. This happens, you can replace or adjust the height of the roller to solve; ③ roller rotation or transmission speed is too slow.

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This happens, you can properly speed up the roller rotation or transmission speed to solve; ④ In the tempered cooling process stage, the glass is reciprocating swinging in the cooling device in the tempering furnace, this time period, if the glass as a whole High temperature or wind pressure is too low, it will make the glass surface wave-shaped bending. When this happens, we should promptly reduce the furnace temperature and heating time.