Why Is It More Difficult To Temper Glass That Is Closer To A Square?

Why is it more difficult to temper glass that is closer to a square?

During the tempering process of glass, it must be heated first and then cooled to achieve the tempering effect. Under normal circumstances, the heat absorption process of glass in the heating furnace is gradually transferred from the edges of the glass to the middle. If the tempering time is short, the middle part of the glass will not absorb enough heat, resulting in the tempered glass bursting or cracking after tempering. The result of glass bending into a spherical shape.

When tempering nearly square glass, when heating, because the four sides are easy to heat, it is difficult to heat closer to the middle, so low-temperature and long-term heating is usually used. When cooling, the heat dissipation speeds between the edges and the middle are inconsistent. The closer to the edges, the faster the heat dissipation, and the heat dissipation is slower in the middle. It is difficult to achieve uniform heat dissipation. The glass will easily affect the flatness due to thermal expansion and contraction.

In actual production, most ordinary doors and windows are rectangular, and it is easier to achieve qualified flatness when tempered. But for glass above 2.5 meters, the closer it is to a square, the more difficult it is to temper. Because heating and cooling cannot be completely uniform, which affects the flatness of tempered glass.

Of course, in order to be able to temper a qualified square piece of glass, we can make adjustments mechanically and technologically. Both traditional radiation furnaces and double-chambers heating furnaces can achieve this.