Could We Temper The Tempered Glass Again?

1. What is tempered glass?

Tempered glass is a highly reinforced type of glass that has been heated and rapidly cooled to become hard and durable. The manufacturing process of tempered glass involves heating standard glass to a temperature close to its softening point, and then rapidly cooling it. This process can put the glass surface under pressure, greatly improving the overall strength and impact resistance of the glass.

2. Can tempered glass be re tempered?

According to the characteristics of tempered glass, it is theoretically possible to undergo secondary tempering. However, in reality, few glass factories adopt this process. The main reasons are as follows:

1. High cost: The tempering process requires the use of large, high energy consuming glass tempering furnaces, and secondary tempering requires similar equipment and energy investment, resulting in high costs.

2. High technical difficulty: Secondary tempering requires a higher temperature and faster heating and cooling process, which requires higher technical level and experience.

3. The effect is not obvious: One tempering treatment can already make the glass have good strength and hardness, and the benefits of secondary treatment are not very high, which is not worth investing a lot of resources and time.

3. How to temper the tempered glass again?

Set the speed of glass entering the furnace to below 300MM/S. Excessive speed will make tempered glass more susceptible to damage when entering the tempering furnace.

If the secondary tempering is carried out due to excessive bending, we need to manually block the glass induction eye on the loading table, because excessive bending of the glass will make the eye unable to sense the glass and collide with the furnace door, causing the glass to break.

Attention: Tempered glass should not be subjected to secondary tempering as much as possible to avoid damage and unnecessary losses caused by the glass in the heating furnace.

4. Why not recommend tempering tempered glass again?

Glass that has already been tempered cannot be tempered again because it has reached its physical limit.

Tempered glass is made by heating the glass to 400-700 ℃ and rapidly cooling it at high temperatures. After tempered glass is made, it cannot be further heated or processed because a compression zone with high stress is formed on the surface of tempered glass, while the glass below the surface is a tensile stress zone. This internal stress difference can provide strength for glass and cause it to break into small particles when subjected to external impact, reducing damage. However, if tempered glass is heated, internal stress differences can cause cracks in the glass, leading to the finished product being drilled or ruptured.

In addition, the special structure and hardness of tempered glass make it very difficult to process and drill holes. If drilling is required, a specialized drill bit can be considered, but it is also difficult to achieve the desired effect.

5. Application of re-tempered Glass

Although secondary tempering is not common, it is still possible to use this process in some special circumstances.

5.1. Effective utilization of glass: In the glass coated with pure silver reflective film, tempering treatment can be carried out again to achieve energy conservation, consumption reduction, and effective utilization of glass.

5.2. Dyed glass secondary tempering: Dyed glass, as a special purpose glass, has a relatively special manufacturing process. During the dyeing process, a certain thickness of colored substance layer will form on the glass surface, which will significantly reduce the hardness of the glass surface. To compensate for this decrease in hardness, secondary tempering treatment can be carried out.

6. Precautions

When using tempered glass, attention should be paid to avoiding sharp objects colliding and surface abrasion to prevent breakage. In addition, tempered glass should also avoid excessive bending, especially for thicker glass.

7. Summary

Although tempered glass can theoretically undergo secondary tempering, it is rarely used in practical production. This is because the cost and difficulty of secondary treatment are high, and the effect is not as obvious as that of primary tempering. Only in certain specific circumstances can secondary tempering be adopted.