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About glass

Home > About glass > Content
Introduction of tempered glass
Mar 21, 2017

characteristic

safety

When the glass by external damage, the debris will be similar to the honeycomb obtuse broken small particles, not easy to cause serious harm to the human body.

high strength

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

Thermal stability

Tempered glass has good thermal stability, can withstand the temperature difference is 3 times the ordinary glass, can withstand 300 ℃ temperature difference.

advantage

The first is the strength than ordinary glass to improve several times, bending.

The second is the use of safety, its carrying capacity increased to improve the fragile nature, even if the destruction of tempered glass was no small angle of small pieces, the damage to the human body greatly reduced. Tempered quenching and cooling properties of tempered glass than ordinary glass has 3 to 5 times the increase, generally can withstand more than 250 degrees of temperature changes, to prevent the thermal cracking has a significant effect. Is a kind of safety glass. For the protection of high-rise buildings to provide qualified materials for security.

Disadvantages

Tempered glass defects:

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

Although the strength of tempered glass is stronger than that of ordinary glass, but the tempered glass has blew its own rupture, and there is no possibility that ordinary glass is blew.

3. The surface of the tempered glass will be uneven (wind spot), with a slight thickness thinning. The reason for the thinning is because the glass in the hot-melt softening, after a strong wind to make it quickly cooling, so that the glass inside the crystal gap becomes smaller, the pressure becomes larger, so the glass after the steel than in the steel before the thin. Under normal circumstances 4 ~ 6mm glass in the steel after thinning 0.2 ~ 0.8mm, 8 ~ 20mm glass in the steel after the thinning 0.9 ~ 1.8mm. The specific extent to be determined according to the equipment, which is tempered glass can not do the mirror of the reasons.

4. Through the steel furnace (physical steel) after the construction of flat glass, there will be a deformation, the degree of deformation by the equipment and technical staff process decision. To a certain extent, affecting the decorative effect (except for special needs).

preparation

Tempered glass is the ordinary annealing glass first cut into the required size, and then heated to close to the softening point of about 700 degrees, and then quickly and evenly cooled and get (usually 5-6MM glass at 700 degrees high temperature heating about 240 seconds, Cooling about 150 seconds .8-10MM glass at 700 degrees high temperature heating about 500 seconds, about 300 seconds in short, in short, according to the different thickness of the glass, choose to heat the cooling time is also different). After the steel treatment of the glass surface to form a uniform compressive stress, while the internal formation of tensile stress, so that the glass bending and impact strength can be improved, the strength is about four times more than ordinary annealing glass. Has been treated with a good tempered glass, can not be any cutting, grinding and other processing or damaged, otherwise it will be due to damage evenly compress the stress and "broken bone."



classification

By shape

The tempered glass is divided into flat tempered glass and curved tempered glass by shape.

General flat tempered glass thickness of 11,12,15,19 mm and other 12 kinds of surface tempered glass thickness of 11,15,19 mm and other eight kinds of specific processing after the thickness depends on the manufacturers of equipment and technology. But the curved surface (ie, curved steel) tempered glass has a maximum curvature limit for each thickness. That is usually R R is a radius.

2. Tempered glass according to its appearance is divided into flat steel and bending steel.

3. Tempered glass according to its flatness is divided into: excellent products, qualified products. Exquisite goods tempered glass for automotive windshields; qualified products for architectural decoration.

By craft

⒈ physical tempered glass, also known as quenched tempered glass. It is the ordinary flat glass in the heating furnace heated to close to the glass softening temperature (600 ℃), through its own deformation to eliminate the internal stress, and then remove the glass from the furnace, and then the long nozzle to high-pressure cold air blowing glass Both sides, so that it quickly and evenly cooled to room temperature, you can produce tempered glass. The glass is in the internal tension, the external stress state of stress, once the local damage occurs, there will be stress release, the glass was broken into numerous pieces, these small pieces without sharp edges and corners, not easy to hurt.

⒉ chemical tempered glass is by changing the chemical composition of the glass surface to improve the strength of the glass, the general application of ion exchange method for steel. The Li + ion exchange layer is formed on the surface by Li + ion exchange layer, and the Li + ion exchange layer is formed on the surface of the Li + ion exchange layer by adding the Na + or K + ions of the glass surface layer to the Li + ions in the lithium (Li +) salt in the molten state, The expansion coefficient is less than Na +, K + ions, which in the cooling process caused by the outer shrinkage of small inner shrinkage larger, when cooled to room temperature, the glass will be in the inner layer of tension, the outer pressure state, its effect Similar to physical tempered glass.

According to the degree of steel

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

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

⒊ super fortified glass: degree of steel> 4N / cm.

Applications

Flat steel, curved glass is a safety glass. Widely used in high-rise building doors and windows, glass curtain wall, indoor partition glass, lighting ceiling, sightseeing elevator channel, furniture, glass fence and so on. Usually tempered glass can be used in the following industries:

⒈ construction, building templates, decoration industry (example: doors and windows, curtain walls, interior decoration, etc.)

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

⒊ appliance manufacturing industry (TV, oven, air conditioning, refrigerator and other products)

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

⒌ automobile manufacturing industry (car windshield, etc.)

⒍ daily necessities industry (glass cutting board, etc.)

⒎ special industry (military use of glass)

As the tempered glass is broken, the debris will break into even small particles and there is no universal glass-like sharp corners, which are known as safety glass and are widely used in cars, interior decoration, and high-rise windows.

Emergency method

quality

Tempered glass is the ordinary annealing glass first cut into the required size, and then heated to close to the softening point, and then quickly and evenly cooled to get. After the steel treatment of the glass surface to form a uniform compressive stress, while the internal formation of tensile stress, so that the performance of the glass can be greatly improved, the tensile strength is more than 3 times the latter, the impact is more than 5 times the latter.

It is this feature, the stress characteristics of the identification of genuine and fake glass is an important symbol, that is, tempered glass can be through the polarized light in the glass side of the edge to see the color stripes, and in the glass surface observation, you can see the black and white Interspecies spots. Polarizers can be found in the camera lens or glasses, observe the adjustment of the light source, so easier to observe.

Each piece of tempered glass has a 3C certification mark.

Blew defects

Tempered glass in the absence of direct mechanical external force occurred under the automatic burst is called tempered glass blew, according to industry experience, ordinary tempered glass blasting rate of 1 to 3 ‰ or so. Blew is one of the inherent characteristics of tempered glass.

Expansion of the causes of blew a lot, simply summed up the following:

① the impact of glass quality defects

A, there are stones in the glass, impurities, bubbles: glass impurities are tempered glass is weak, but also stress concentration. In particular, if the stone in the tempered glass tensile area is an important factor leading to burst.

Stone is present in the glass and has a different coefficient of expansion from the glass body. The stress concentration in the crack area around the stone after the glass is increased exponentially. When the stone expansion coefficient is less than the glass, tangential stress around the stone in the state of tension. Crack propagation that accompanies stones is likely to occur.

B, the glass contains nickel sulfide crystals

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

Known theoretical NIS at 379. C, there is a phase transition process, from the high temperature state of α-NiS hexagonal system into low temperature state β-NiS tripartite system process, accompanied by 2.38% volume expansion. This structure is preserved at room temperature. If the glass is heated later, the α-β state transition may occur rapidly. If these debris in the tempered glass by the internal stress, the volume expansion will cause spontaneous burst. If there is a-NIS at room temperature, after several years, several months will slowly change to the β state, in this phase change process slowly increase the volume may not cause internal rupture.

C, the glass surface due to processing or improper operation caused by scratches, fried mouth, deep burst edge and other defects, easy to cause stress concentration or lead to tempered glass blew.

② uneven distribution of stress in the tempered glass, offset

The temperature gradient of the glass in the direction of the thickness of the glass during heating or cooling is not uniform and asymmetrical. So that the tendency of blooming products, and some in the cold when the "wind burst." If the tensile zone is offset to one side of the article or offset to the surface, the tempered glass is blew.

③ the degree of steel, the experiment proved that when the degree of steel to 1 / cm when the number of self-explosion up to 20% to 25%. This shows that the greater the stress the greater the degree of taper, the greater the amount of self-explosion.

Development History

The development of tempered glass dates back to the mid-17th century, and one of the princes of the Rhine, Robert, has done an interesting experiment. He put a drop of molten glass in icy water and made a Extremely hard glass. This kind of high-strength granular glass is like water droplets, dragging long and curved tails, called "Robert prince small grain". But when the tail of the small particles is bent and broken, it is surprising that the whole small particles so suddenly violent collapse, and even became a fine powder. The above practice, much like metal quenching, which is the quenching of glass. This quenching does not make any change in the composition of the glass, so it is called physical quenching (physical tempered), so the tempered glass called tempered glass (tempered glass).

The first patent for glass glazing was obtained by the French in 1874 by heating the glass to near softening temperatures and immediately putting a relatively low temperature in the liquid tank to increase the surface stress. This method is the early liquid steel method. Germany's Frederick Siemens received a patent in 1875, Geovge E. Rogens, Massachusetts, USA, applied the glass method to glass glasses and lampposts in 1876. In the same year, HughO'heill of New Jersey won a patent.

In the 1930s, Saint-Gobain and the United States of America Treprex, as well as the United Kingdom's Pilkington companies began to produce large-scale flat tempered glass for automotive use. Japan in the 20th century, 30 years have also carried out the production of glass industry. From the world began a large-scale production of tempered glass era.

After 1970, the United Kingdom Triplex company with liquid medium steel thickness of 0.75 ~ 1.5mm glass to be successful, the end of the physical steel can not be tempered glass history, which is a major breakthrough in glass technology.

China's history of glass began in 1955, Shanghai Yaohua glass factory began trial production, in 1958 Qinhuangdao City, glass factory trial production success. 1965 Qinhuangdao Yaohua glass factory began to produce military use of tempered glass, the 20th century, 70 years, the first introduction of Luoyang glass factory in Belgium steel equipment. Shenyang glass factory chemical glass production in the same period.

The 20th century, 70 years began to strengthen the glass technology in the world has been a comprehensive promotion and popularization, glass in the automotive, construction, aviation, electronics and other fields began to use, especially in the construction and automotive development of the fastest.

Blew the solution

Reduce the stress value

The distribution of stress in the tempered glass is that the two surfaces of the tempered glass are compressive stress, the core layer is in tensile stress, and the stress distribution on the glass is similar to that of the parabola. The center of the glass thickness is the apex of the parabola, that is, the maximum tensile stress; the two sides close to the glass surface is the compressive stress; zero stress plane is about 1/3 of the thickness. By analyzing the physical process of quenching and tempering, it can be seen that the surface tension of the tempered glass and the maximum tensile stress in the interior are roughly proportional to the value, that is, the tensile stress is 1/2 ~ 1/3 of the compressive stress. Domestic manufacturers generally tempered glass surface tension set at 100MPa or so, the actual situation may be higher. Tempered glass itself tensile stress of about 32MPa ~ 46MPa, glass tensile strength is 59MPa ~ 62MPa, as long as the expansion of nickel sulfide tension at 30MPa, is sufficient to trigger blew. If the surface stress is reduced, the tensile stress of the tempered glass itself is reduced, thereby contributing to the reduction of bleed-out.

The US standard ASTMC1048 specifies that the surface stress of the tempered glass is greater than 69 MPa; the semi-steel (heat-strengthened) glass is 24 MPa to 52 MPa. Curtain wall glass standard BG17841 is specified as semi-steel stress range 24 <; δ ≤ 69MPa. China's implementation of the new national standard GB15763.2-2005 "Building safety glass Part 2: Tempered glass" requires its surface stress should not be less than 90MPa. This is lower than the 95MPa specified in the old standard 5MPa, is conducive to reduce the blew.

Stress uniformity

Tempered glass uneven stress, will significantly increase the rate of self-blasting, has been to the extent that can not be ignored. Unevenness caused by uneven stress is sometimes very concentrated, especially the bending of a specific batch of tempered glass burst rate will reach a shocking severity, and may occur continuously blew. The main reason is the local stress uneven and tension layer in the thickness of the direction of the deviation, the quality of the original glass itself has a certain impact. Stress unevenness will significantly reduce the strength of the glass, to a certain extent, the equivalent of increasing the internal tensile stress, so the rate of self-explosion increased. If you can make the stress of the tempered glass evenly distributed, you can effectively reduce the rate of self-blasting.