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China flood light suppliers|Do you know the knowledge of tempered glass?|

2022/09/02

Tempered glass/Reinforced glass is safety glass. Tempered glass is actually a kind of prestressed glass. In order to improve the strength of the glass, chemical or physical methods are usually used to form compressive stress on the surface of the glass. When the glass is subjected to external force, it first offsets the surface stress, thereby improving the bearing capacity and enhancing the resistance of the glass itself. Wind pressure, cold and heat, impact, etc. Pay attention to distinguish it from glass fiber reinforced plastic.

Feature Editing Broadcast

safety

When the glass is damaged by external force, the fragments will be broken into small particles with obtuse angles similar to honeycombs, which are not easy to cause serious harm to the human body.

high strength

The impact strength of tempered glass with the same thickness is 3 to 5 times that of ordinary glass, and the bending strength is 3 to 5 times that of ordinary glass.

Thermal stability

Tempered glass has good thermal stability, the temperature difference that can withstand is 3 times that of ordinary glass, and it can withstand a temperature difference of 300 °C.

advantage

The first is that the strength is several times higher than that of ordinary glass, and it is resistant to bending.

Second, it is safe to use. The increased bearing capacity improves the fragile nature. Even if the tempered glass is damaged, it will be small fragments without acute angles, which greatly reduces the damage to the human body. Compared with ordinary glass, the resistance to rapid cooling and rapid heating of tempered glass is improved by 3 to 5 times. It is a type of safety glass. To ensure the safety of qualified materials for high-rise buildings.

shortcoming

Disadvantages of tempered glass:

1. The tempered glass can no longer be cut and processed. The glass can only be processed to the required shape before tempering, and then tempered.

2. Although the strength of tempered glass is stronger than that of ordinary glass, tempered glass has the possibility of self-explosion (self-breaking), while ordinary glass does not have the possibility of self-explosion.

3. The surface of the tempered glass will be uneven (wind spots), with a slight thickness thinning. The reason for the thinning is that after the glass is softened by hot melt, it is rapidly cooled by strong wind, so that the crystal gap inside the glass becomes smaller and the pressure becomes larger, so the glass is thinner after tempering than before tempering. Under normal circumstances, 4~6mm glass will be thinned by 0.2~0.8mm after tempering, and 8~20mm glass will be thinned by 0.9~1.8mm after tempering. The specific degree depends on the equipment, which is why tempered glass cannot be used as a mirror.

4. The flat glass used for construction after passing through the tempering furnace (physical tempering) will generally be deformed, and the degree of deformation is determined by the equipment and technicians. To a certain extent, the decorative effect is affected (except for special needs).

Preparing Editing Broadcast

Tempered glass is obtained by first cutting ordinary annealed glass to the required size, then heating it to about 700 degrees close to the softening point, and then rapidly and uniformly cooling it (usually 5-6MM glass is heated at 700 degrees for about 240 seconds, Cool down for about 150 seconds. 8-10MM glass is heated for about 500 seconds at a high temperature of 700 degrees, and cooled for about 300 seconds. In short, according to the thickness of the glass, the time for heating and cooling is also different). After tempering, uniform compressive stress is formed on the surface of the glass, while tensile stress is formed inside, which improves the bending and impact strength of the glass, and its strength is about four times that of ordinary annealed glass. The tempered glass that has been tempered cannot be cut, ground, etc. or damaged, otherwise it will be "shattered" due to the destruction of the uniform compressive stress balance.

Category Edit Broadcast

By shape

1. Tempered glass is divided into flat tempered glass and curved tempered glass according to shape.

Generally, the thickness of flat tempered glass is 11, 12, 15, 19mm, etc.; the thickness of curved tempered glass is 11, 15, 19mm, etc., and the specific thickness after processing depends on the equipment and technology of each manufacturer. But curved (ie curved tempered) tempered glass has a maximum arc limit for each thickness. That is to say, R R is the radius.

2. Tempered glass is divided into flat tempered and curved tempered according to its appearance.

3. Tempered glass is divided into: superior products and qualified products according to its flatness. High-quality tempered glass is used for car windshields; qualified products are used for architectural decoration.

By process

⒈ Physical tempered glass is also called quenched tempered glass. It heats ordinary flat glass in a heating furnace to a temperature close to the softening temperature of glass (600°C), eliminates the internal stress through its own deformation, then removes the glass from the heating furnace, and then uses a multi-head nozzle to blow high-pressure cold air to the glass. Tempered glass can be obtained by cooling it quickly and evenly to room temperature on both sides. This kind of glass is in a stress state of internal tension and external compression. Once local damage occurs, the stress will be released, and the glass will be broken into countless small pieces. These small pieces have no sharp edges and corners and are not easy to hurt people.

⒉Chemical tempered glass is to improve the strength of glass by changing the chemical composition of the surface of the glass, generally by applying ion exchange method for tempering. The method is to immerse the silicate glass containing alkali metal ions into the molten lithium (Li+) salt, so that the Na+ or K+ ions on the surface of the glass are exchanged with Li+ ions, and a Li+ ion exchange layer is formed on the surface. The expansion coefficient is smaller than the Na+ and K+ ions, so that the outer layer shrinks less and the inner layer shrinks more during the cooling process. When cooled to room temperature, the glass is also in a state where the inner layer is pulled and the outer layer is compressed. Similar to physical tempered glass.

According to the degree of toughness

⒈Tempered glass: degree of tempering=2~4N/cm, surface stress of tempered glass of glass curtain wall α≥95Mpa;

⒉Semi-tempered glass: degree of tempering=2N/cm, surface stress of semi-tempered glass of glass curtain wall 24Mpa≤α≤69Mpa;

⒊Super-strength tempered glass: degree of tempering>4N/cm.

Product application editor broadcast

Flat tempered and curved tempered glass are safety glass. Widely used in high-rise building doors and windows, glass curtain walls, indoor partition glass, lighting ceilings, sightseeing elevator passages, furniture, glass guardrails, etc. Usually tempered glass can be used in the following industries:

⒈Architecture, building formwork, decoration industry (eg: doors and windows, curtain walls, interior decoration, etc.)

⒉Furniture manufacturing industry (glass coffee table, furniture matching, etc.)

⒊Home appliance manufacturing industry (TVs, ovens, air conditioners, refrigerators and other products)

⒋Electronics, instrument industry (mobile phones, MP3, MP4, clocks and other digital products)

⒌Automotive manufacturing industry (automobile window glass, etc.)

⒍Daily products industry (glass cutting board, etc.)

⒎Special industry (military glass)

Since tempered glass is broken, the fragments will be broken into small uniform particles and there is no sharp corners like glass knives, so it is called safety glass and is widely used in automobiles, interior decoration, and high-rise windows that open to the outside.

Emergency methods edit broadcast

quality

Tempered glass is obtained by cutting ordinary annealed glass to the required size, heating it to a near softening point, and then rapidly and uniformly cooling it. After tempering, uniform compressive stress is formed on the surface of the glass, while tensile stress is formed inside, which greatly improves the performance of the glass. The tensile strength is more than 3 times that of the latter, and the impact resistance is more than 5 times that of the latter.

It is also this feature that the stress characteristic has become an important symbol for identifying real and fake tempered glass, that is, tempered glass can see colored stripes on the edge of the glass through the polarizer, and when observed on the surface of the glass, you can see black and white. Alternating spots. Polarizers can be found in camera lenses or glasses. Pay attention to the adjustment of the light source when observing, so that it is easier to observe.

Self-destruction

The automatic explosion of tempered glass without direct mechanical external force is called self-explosion of tempered glass. According to industry experience, the self-explosion rate of ordinary tempered glass is about 1~3‰. Self-explosion is one of the inherent characteristics of tempered glass.

There are many reasons for the expansion of self-explosion, which can be briefly summarized as follows:

①Influence of glass quality defects

A. There are stones, impurities and bubbles in the glass: impurities in the glass are the weak point of the tempered glass and the place where the stress is concentrated. In particular, if the stone is in the tensile stress area of the tempered glass, it is an important factor leading to the explosion.

Stones exist in glass and have a different coefficient of expansion than the vitreous body. The stress concentration in the crack area around the stone increases exponentially after glass tempering. When the expansion coefficient of the stone is smaller than that of the glass, the tangential stress around the stone is in tension. Crack propagation that accompanies stones is highly susceptible.

B. The glass contains nickel sulfide crystals

Nickel sulfide inclusions generally exist as small crystalline spheres with a diameter of 0.1-2mm. The appearance is metallic, and these miscellaneous inclusions are Ni3S2, Ni7S6 and Ni-XS, where X=0-0.07. Only Ni1-XS phase is the main reason for the spontaneous explosion of tempered glass.

The theoretical NIS is known at 379. There is a phase transition process at C, from the α-NiS hexagonal system in the high temperature state to the β-NiS trigonal system in the low temperature state, accompanied by a volume expansion of 2.38%. This structure is preserved at room temperature. If the glass is heated later, the α-β state transition may occur rapidly. If these impurities are inside the tempered glass under tensile stress, the volume expansion will cause spontaneous bursting. If a-NIS exists at room temperature, it will slowly transform to the β state after several years and months, and the slow increase in volume during this phase transition does not necessarily cause internal rupture.

C. Due to improper processing or operation, the glass surface has defects such as scratches, cracks, deep cracks, etc., which are easy to cause stress concentration or self-explosion of tempered glass.

②The stress distribution in tempered glass is uneven and offset

When the glass is heated or cooled, the temperature gradient along the thickness of the glass is not uniform and asymmetric. The tempered products have a tendency to self-explode, and some produce "wind explosion" when they are chilled. If the tensile stress area is shifted to one side of the product or shifted to the surface, the tempered glass will self-explode.

③Influence of the degree of tempering, experiments have shown that when the degree of tempering increases to level 1/cm, the number of self-explosions reaches 20% to 25%. It can be seen that the greater the stress, the higher the degree of tempering and the greater the amount of self-explosion.

Development history editing broadcast

The development of tempered glass can be traced back to the middle of the 17th century. A Prince of Rhine named Robert once did an interesting experiment. He put a drop of molten glass in icy cold water and made a kind of glass. Very hard glass. The high-strength, granular glass resembles water droplets with long, curved tails called "Prince Robert Grains." However, when the tail of the granule was bent and broken, it was strange that the whole granule suddenly collapsed violently and even became a fine powder. The above approach is very similar to the quenching of metal, but this is the quenching of glass. This quenching does not change the composition of the glass, so it is also called physical tempered, so tempered glass is called tempered glass.

The first patent for glass tempering was obtained by the French in 1874. The tempering method is to heat the glass to a temperature close to the softening temperature, and then immediately put it into a liquid tank with a relatively low temperature to increase the surface stress. This method is the early liquid tempering method. Frederick Siemens of Germany received a patent in 1875, and Geovge E. Rogens of Massachusetts, USA, applied the tempering method to wine glasses and lampposts in 1876. That same year, Hugh O'heill of New Jersey was granted a patent.

In the 1930s, Saint-Gobain in France, Triplex in the United States, and Pilkington in the United Kingdom all began to produce large-area flat tempered glass for automobile windshields. In the 1930s, Japan also successively carried out the industrial production of tempered glass. Since then, the world has begun the era of mass production of tempered glass.

After 1970, the British company Triplex succeeded in tempering glass with a thickness of 0.75~1.5mm in liquid medium, ending the history that physical tempering could not temper thin glass, which was a major breakthrough in tempered glass technology.

The history of tempered glass in China first started in 1955, when Shanghai Yaohua Glass Factory started trial production, and in 1958 Qinhuangdao City tempered glass factory successfully started trial production. In 1965, Qinhuangdao Yaohua Glass Factory began to produce tempered glass for military industry. In the 1970s, Luoyang Glass Factory was the first to introduce Belgian tempering equipment. During the same period, the chemical tempered glass of Shenyang Glass Factory was put into production.

Since the 1970s, tempered glass technology has been comprehensively promoted and popularized around the world, and tempered glass has been used in the fields of automobiles, construction, aviation, electronics, etc., especially in construction and automobiles.


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