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Vacuum Sintering Furnace

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How does the vacuum sintering furnace work

Vacuum sintering furnace refers to a furnace that performs protective sintering of heated items in a vacuum environment. It has many heating methods. So, how does a vacuum sintering furnace operate?

Vacuum sintering furnace operation process

1.Inspection before powering on

Before turning on the power, check whether each switch is in the (off) position, the heating mode is “manual”, and the power adjustment is turned counterclockwise to the end (low). After confirmation, start the mechanical pump and diffusion pump in the order required by the process.

2.Measure the vacuum in the furnace

According to the operation of the vacuum gauge, heating can only occur when the required vacuum degree is reached.

3.Vacuum

Close all vacuum valves and start the mechanical pump. After it operates normally, open the low vacuum valve leading to the furnace body and evacuate the furnace body in advance. This valve should be opened slowly to avoid oil at the exhaust port of the mechanical pump. squirt.

4.Open the vacuum valve

While the furnace is being evacuated, open the vacuum valve and evacuate the diffusion pump. When the vacuum reaches 15Pa, first turn on the cooling water on the diffusion pump, and then heat the diffusion pump. Generally, after about 45 minutes, the diffusion pump takes effect. You can close the vacuum valve leading to the furnace body and open the vacuum valve. The vacuum degree will soon reach more than 1.33×10-1Pa, and the electric furnace can be heated.

5.Heating

Because there is a lot of outgassing during the primary heating, the vacuum degree is easy to drop. In addition, the workpiece is heated and outgassed, which also causes the vacuum to drop. Therefore, it is necessary to slowly increase the temperature and stop heating when the vacuum degree drops to 1.5 Pa. Wait until the vacuum degree rises to above 0.5 Pa before heating slowly again. Because the diffusion pump cannot work when it is lower than 20 Pa, and the diffusion pump oil is easily oxidized under too low a vacuum, causing the diffusion pump to fail to function. You can also heat and degas under low vacuum, wait until the degassing is basically completed, and then turn on high vacuum. In addition, the electric furnace should be stored in a vacuum state when not in use so that it can be evacuated faster next time. To stop vacuuming, first close the high vacuum valve, then stop heating. After one and a half hours, close the low vacuum valve and stop the mechanical pump. Only after the diffusion pump has cooled down, cut off its cooling water supply.

6.Manual heating

When the furnace temperature is below 200°C, first raise the temperature manually, otherwise the temperature control will be inaccurate. Press the heating start button in the vacuum state and slowly adjust the manual power (clockwise) to make the current rise slowly. It is forbidden to exceed the sub-rated current 1100A, and the temperature of the electric furnace will rise accordingly. 1000-2000℃, infrared can be used to automatically control the furnace temperature.

7.Cool down

The cooling can be controlled according to a preset program, or the heating can be turned off directly to allow it to cool down on its own. However, water is not allowed to be stopped during the cooling process, otherwise the sealing ring of the furnace body will burn out.

Precautions for operating vacuum sintering furnace

1.The appearance of the electric furnace should always be kept clean, and the vacuum should be kept when not in use, otherwise the vacuuming rate will be reduced next time it is used.

2.Vacuum sealing grease should be added to the axial sealing parts of the vacuum furnace and vacuum system after about half a year of use. The axial sealing refers to the observation window baffle seat, pneumatic vacuum butterfly valve and other parts.

3.After half a year of use of the automatic inlet and outlet thermocouple system, the thermocouple holder should be unscrewed and the diffusion pump oil should be added.

4.The observation window glass of the vacuum furnace should be removed and cleaned after using the furnace.