[China Glass Network] With the advent of winter, tempered glass (especially outdoor) is two thousand points higher than the previous season, and tempered glass is a kind of prestressed glass. There is compressive stress on the surface and tensile stress inside. Generally, the glass is in a state of balance of force. However, there are a small amount of impurities in the glass raw material.
As time goes by, and the temperature in winter is large during the day and night, a phase change occurs and the volume increases. In particular, the temperature inside the house is high, and the temperature outside the house is low, which is different from the temperature inside and outside the glass on the window, which in turn destroys the compressive stress and tensile stress balance of the tempered glass, and breaks itself. It is called self-explosion in the industry.
To improve the yield of tempered glass, the following must be done:
First, the glass must be edging before tempering. The quality of glass edging plays a decisive role in the rate of tempering. When the glass is cut, small, very fine cracks are left on the edges, which are almost invisible to the naked eye. There are two functions of edging, one is aesthetic, and the other is to not break easily during tempering and improve the yield of tempered glass.
Second, adjust the process parameters of tempering. The tempering process parameters are mainly the heating temperature, the heating time, the wind pressure time of the tempering cooling and the tempering cooling time. The temperature of the tempering is inversely proportional to the heating time, and the higher the temperature, the shorter the heating time. However, when we temper the thick glass of 12mm or more, if the furnace temperature is too high, it is easy to fry the furnace inside the furnace. Of course, there are many reasons for the fryer, and the furnace temperature setting is too high. It is recommended that the glass of 12 mm or more be set to a temperature of about 665 ° during tempering, and the heating time should be appropriately extended. A reasonable heating time needs to be selected after the temperature is determined. In general, the heating time per millimeter is about 40 seconds. However, it is necessary to increase the heating time by 10% when tempering the glass of the large layout, and increase the heating time by 10% when tempering the perforated and angled glass. Dialectical mastery of heating time and heating temperature is very important, and is also the key to improving the yield of tempered glass.
Third, the importance of uniform heating of the glass. The glass is actually a cube with 4 sides and 6 sides. The heating of the upper and lower sides of the glass is relatively slow. When tempering large-format glass, the middle of the glass tends to be heated slowly. Sometimes the tempered glass will form a pot shape (especially a large-format glass close to a square). It is caused by the excessive heating of the edge and the slow heating in the middle, that is, after the heating is completed, the temperature of the edge of the glass is much higher than the temperature in the middle of the glass. If the glass of the large layout is heated uniformly, it is better to set the temperature of the furnace to a temperature in the middle of the heating curve (lateral) to be higher than the set temperature by 10 degrees, and the temperature of the side is lower than the set temperature by 10 degrees. The tempered glass thus has a uniform degree of uniformity and uniformity.
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