Tempered glass

What is tempered glass?

Tempered glass ,also called toughened glass, as a kind safety glass, is to heat the float glass to a temperature close to its softening temperature, and then use the wind to quickly cool the glass surface to form a compressive stress (inward) on the glass surface and a tensile stress inside (outward), thereby improving the load-bearing capacity and impact resistance.

Relying on advanced tempered glass production line ,mature production technology and production experience, GOFAI GLASS provides customers with high-quality tempered glass products in architecture, electrical appliances, PV modules fields，etc.

GOFAI tempered glass substrates: float glass, reflective glass, patterned glass, Low-E glass, acid-etched glass, fused glass, silk printed glass, digital printed glass, semi-processed glass, etc.

Thickness：2mm,3mm,4mm,5mm,6mm,8mm,10mm,12mm,15mm,19mm,22mm,25mm

Max size:3660*18000mm

Min size:50*320mm

Classification of GOFAI tempered glass

(1)According to the shape, it is divided into: flat tempered glass and curved tempered glass.

(2)According to the process, it is divided into physical tempering and chemical tempering. Our main application is physical tempering.

(3)According to the degree of toughening, it is divided into:  tempered glass and semi-tempered glass. The surface stress of tempered glass is α≥95Mpa, and the surface stress of semi-tempered glass is 24Mpa≤α≤69Mpa.

What is Semi-tempered glass?

Semi-tempered glass is also called thermally strengthened glass. Semi-tempered glass is between ordinary float glass and tempered glass. It has some of the advantages of tempered glass. For example, the strength is higher than ordinary float glass, which is twice that of ordinary float glass, while avoiding the flatness of tempered glass. Poor, prone to self-explosion, once broken, it will be crushed as a whole. When semi-tempered glass is broken, it will crack radially along the crack source and is not easy to fall off. Although most of the fragments do not have sharp corners, they will still hurt people and are not safety glass. Semi-tempered glass will not spontaneous breakage.

GOFAI tempered glass features:

(1)Safety: After being broken into small particles, it is not easy to cause harm to people.

(2)High strength: impact resistance is 3-5 times that of ordinary glass

(3)Thermal stability: Tempered glass has good thermal stability, can withstand a temperature difference of 3 times that of ordinary glass, and can withstand a temperature difference of 300°C.

(4)Spontaneous breakage: the automatic explosion of tempered glass without direct mechanical external force is called the spontaneous explosion of tempered glass. The Spontaneous breakage rate of ordinary tempered glass is about 1~3‰. Spontaneous breakage is one of the inherent characteristics of tempered glass.

Reasons for the spontaneous breakage of tempered glass:

①The effect of glass quality

A、Stones and impurities in the glass, especially when the stones are in the tensile stress zone of the tempered glass, are important factors leading to blasting.

The reason is: The stones exist in the glass and have a different expansion coefficient from the glass body. The stress concentration around the stones increases exponentially after glass tempering. When the expansion coefficient of the stone is less than the expansion coefficient of the glass, the stress around the stone is in a state of tension, causing the glass to spontaneous breakage.

B、Nickel sulfide in glass

During the transition of nickel sulfide from a high temperature state to a low temperature state, a volume expansion of 2.38% will be accompanied. If nickel sulfide is inside the tensile stress of tempered glass, volume expansion will cause spontaneous breakage.

C、Due to the processing process, improper installation or operation of the glass surface, the tempered glass can easily be spontaneous breakage.

②The stress distribution in tempered glass is uneven and offset

When the glass is heated or cooled, the temperature is uneven and asymmetrical along the thickness direction of the glass, which makes the tempered glass have a tendency to explode. If the tensile stress zone deviates to a certain side of the glass or deviates to the surface, the tempered glass will be spontaneous breakage.

③The influence of the degree of toughening, the higher the degree of toughening, the greater the amount of spontaneous breakage.

The solution to the spontaneous breakage of tempered glass

(1)Before tempering, carefully check whether the original glass sheet has quality problems such as firmness and impurities.

(2)Using GOFAI's Asia's longest tempered glass heat soak furnace（2440*13000mm）, the spontaneous breakage rate of the heat soaked tempered glass is reduced to less than 1/100000.

Possible problems with tempered glass

1.Rainbow speckle

(1) The tempered glass will form permanent compressive stress on the surface layer and permanent tensile stress inside the glass, and there is a difference in density. When light passes through the tempered glass, due to the density difference inside the glass, this beam of light will be decomposed into two beams of light with different propagation speeds, one beam with a relatively fast propagation speed, and the other with a relatively slow propagation speed. Light. When the two beams of light formed at a certain point intersect, the two beams of light will interfere at the intersection point. When the amplitude of the two beams of light is in the same direction, the light is strengthened, and a bright field of view, that is, rainbow speckles, is visually produced. Therefore, the more uneven the stress distribution of the tempered glass, the more obvious the rainbow markings.

(2) When the float glass is formed, SnO penetrates into the contact surface with the tin liquid, which is oxidized to SnO2 during the tempering process, and its volume expands, so the glass surface is pressed and there are micro wrinkles, causing the light to produce interference colors.

2.Poor flatness

(1)Since the glass is still at the softening point of the glass when it just enters the air-cooling section, the unbalance of the upper and lower wind pressures when the glass is blown will cause the glass to bend upward or downward, and the glass will face the side with less wind pressure. bending. On the other hand, during the cooling process of glass, due to the inconsistent cooling rate of the upper and lower glass surfaces, the compressive stress generated by the glass surface with a fast cooling rate will be greater than that on the surface with a slow cooling rate. It will cause the glass to bend toward the side with less compressive stress.

(2)Poor glass flatness caused by improper heating temperature control,There is a temperature difference between the upper and lower surfaces when the glass is heated.

①The tempered glass plate is bent upwards

After the glass is heated in the heating furnace, if the temperature of the upper surface of the glass is higher than the temperature of the lower surface, during the cooling process,When the cooling temperature and wind pressure of the upper and lower surfaces of the glass are the same, because the temperature of the upper surface of the glass is high, the upper surface of the glass will be displayed after cooling.The shrinkage of the surface is greater than that of the lower surface, and the phenomenon of bending and deformation of the glass plate facing upward will occur.

②The tempered glass plate is bent downward. The reason is the same as above.

3.Watermark

Possible reasons for the watermark: the tempered glass watermark is mainly produced in the edging stage.

(1)The water quality of the edging machine is too dirty.

(2)The cleaning performance of the brush of the edging machine is not enough.

(3)The generation of watermarks is also related to temperature.

Application: doors and windows, curtain walls, partitions, stairs, shower rooms,electrical appliances,PV modules,etc.

GOFAI GLASS, customer-oriented, serves the world.