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How To Control The Temperature In The Production Process Of Tempered Glass?
Jan 18, 2018

Temperature control is the core part of the steel glass production process. It has an extremely important impact on the quality of the product.

At present, most of our manufacturers have adopted horizontal steel furnaces for the production of tempered glass. So focused on horizontal tempering furnace to talk about the process of temperature control method to achieve high quality steel products.

In the case of temperature control, there are two basic requirements: Glass must be rapidly heated to the desired temperature; The temperature of each part of the glass surface cannot be too different which means uniform heating.

1. The heating temperature of the glass. 

When tempered, the temperature will have a series of effects on the quality of tempered glass. Such as glass broken pieces too large, glass bending, glass roller trace, glass surface white road, glass surface jute, glass in the cooling of the broken. 

How to get the glass to reach the required temperature quickly, In the process of heating, we should pay attention to the following aspects:

  1.1 Avoid the overload of the electric furnace. Electric furnace overload is not the area of glass in the furnace, but the thickness of glass. 

Under normal circumstances, in the heating area of the electric furnace, there is always the glass in the heat absorption, and there is always glass in this area of the electric furnace. 

If the heat consumption of an area in the electric furnace exceeds the heating effect, the temperature in this area starts to go down, down to the temperature equilibrium. 

Therefore, when the electric furnace is overloaded, it will cause the glass to break in the cooling section.

The different thickness of glass requires different heating temperatures.

The thinner the tempered glass, the higher the heating temperature is required.

The thicker the glass, the lower the heating temperature is required.

The operator should understand the relationship between the furnace temperature and the heating time and the temperature of the electric furnace varies with the thickness of the glass.

So in the case of tempered glass, You can't specify which temperature is better. The choice of temperature depends on the quality of the original glass and the process parameters adjusted by the operator. 

The glass tempered temperature of 5mm-15mm is between 680 and 720. In actual production, the adjustment of heating temperature is mainly achieved by adjusting the heating time to control the heating temperature.

The basic calculation method of heating time should be mastered by each operator. The basic calculation is about 40 to 50 seconds per millimeter of glass. 

If there are holes, holes and grooves in the glass, the heating time should be increased by 1.5-2.5% on this basis. 

In addition, the larger the surface of the glass, the longer the heating time should be. On the other hand, Decrease accordingly.

2. Uniform Heating.

The Tempered of glass is mainly determined by the lower temperature of the glass plate. To temper the glass, you must first reach the temperature. So you have to do the uniform heating of the various parts of the glass surface.

Glass in electric furnace heating mainly include: conduction, radiation and convection three ways. 

Conduction heating is the process of the heat to the glass from the ceramic roll in a horizontal steel furnace. Conduction heating occurs only on the under surface of the glass. The under surface of glass has one more way to gain the heat than upper surface of glass. It's going to create a temperature difference between the tow surface of the glass.

Convection heating is the heat transfer process of the hot air to the glass surface by the heat balance of the electric furnace.

Radiant heating refers to the heat generated by electric heating wire in a steel furnace, direct radiation to the glass surface or transfer heat to the radiant panel then radiates to the glass that wants to be heated.

After understanding the heating method in the furnace, in the actual production, we can use different temperature control strategies at different stages of heating. How to make the glass as uniform as possible, we should pay attention to the following aspects:

When the glass has just entered the furnace, the original thermal equilibrium state in the furnace is broken, which will cause the furnace temperature to drop. Drop between 20 ~ 100 ℃. So in the first half of the glass heating, the glass is heating up. It is easy to see the uneven temperature rise. Now if you increase convection heating, open the upper and lower heat balance, through the high temperature and temperature system in the furnace let the hot air circulate in the furnace. Can solve the problem of glass each point temperature difference.

In the second half of the heating, as the glass heats up, the furnace temperature is also gradually tending to set the value, the temperature difference of each point of glass is not obvious. The heating rate should be increased, you can turn off the heat balance, Until the glass temperature is consistent with the set temperature,The heating process is over.

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