The causes and control methods of unevenness in tempered glass made by glass tempering furnace?

The deformation of tempered glass directly affects the quality of tempered glass, and there are many factors that affect the flatness of tempered glass. It is not solely dependent on the horizontal control of glass tempering furnace equipment. Below, glass tempering furnace manufacturers will explain the reasons for the unevenness of tempered glass? And how to control the flatness of tempered glass.

1. The reasons for the unevenness of tempered glass

1.1. Tempered glass bends upwards or downwards

When the glass enters the air-cooled section, it is still at the softening point. This is because when there is an inconsistency in the upper and lower wind pressure during blowing, it will cause the tempered glass to bend towards the side with lower wind pressure; During the cooling process of glass, the cooling speed of the upper and lower surfaces of the glass is inconsistent, causing the side with the faster cooling speed to generate greater pressure than the side with the slower cooling speed, resulting in uneven internal pressure of the glass and causing the side with the lower compressive stress to bend.

1.2. Deformation of ceramic rollers in the heating section of the tempering furnace

The ceramic rollers selected for the heating section of the tempering furnace have lower quality and uneven distribution of internal microstructure, which leads to thermal deformation of the roller conveyor at high temperatures and surface deformation when carrying the transmission glass.

1.3. Uneven random temperature distribution

Due to damage to the heating wire of the glass tempering furnace, improper placement of glass on the roller conveyor, and changes or distortions in the position of temperature sensors, the random temperature distribution is uneven, resulting in uneven heating on the surface of the glass after heating. During cooling, irregular shrinkage occurs in this area, resulting in poor local flatness of the glass surface.

1.4. There is a temperature difference between the middle and the edge during heating

After being heated in a heating furnace, the temperature at the edges of the glass is higher than that in the middle. During the cooling process, the shrinkage of the higher temperature edges will be greater than that of the lower temperature middle. When the glass is completely cooled to room temperature, it will cause the size of the glass edges to be larger than that of the middle, resulting in significant compressive stress at the glass edges and causing the glass edges to bend upwards. On the contrary, the same applies when the temperature in the middle is higher than the temperature at the edges.

2. Methods for controlling the flatness of tempered glass

2.1. A solution to the upward or downward bending of tempered glass

When the glass is bent due to inconsistent wind pressure or temperature difference on the upper and lower surfaces, when the glass is bent upwards, it indicates that the temperature on the upper surface of the glass is high. The temperature on the upper surface should be lowered to lower the temperature at the bottom of the heating furnace and reduce the temperature difference between the upper and lower surfaces of the glass; When the glass is bent downwards, the temperature on the lower surface is higher than that on the upper surface, reducing the temperature on the lower surface while increasing the temperature on the upper surface. Extending or reducing the heating time can also be adopted to reduce the factors affecting the quality of tempered glass.

2.2. Solution to the deformation of ceramic rollers in the heating section of the tempering furnace

Preheat the roller conveyor in advance to evenly heat the inside, eliminate stress, and reduce stress deformation of the rollers.

2.3. Solution to Uneven Random Temperature Distribution

The glass tempering furnace should be repaired in a timely manner, and the equipment should be regularly maintained to avoid poor condition. The glass slag near the temperature sensor should be cleaned regularly to ensure that the temperature sensor can perceive the furnace temperature normally. A reasonable equipment maintenance and loading system should be established to solve the problem.

2.4. Solution to the temperature difference between the middle and edge during heating

When the glass bends upwards at the edges, it is due to the low temperature setting at the edges or insufficient insulation of the furnace body, and the edge temperature setting needs to be adjusted. When tempered glass has a situation where the middle part is higher than the edge part, it can be operated empty first to ensure uniform temperature distribution in the furnace before being coated.

The above is a complete introduction to the causes and control methods of unevenness in tempered glass, hoping to be helpful to everyone. Only by clearly understanding the causes of tempered glass deformation can we grasp the correct response methods