How to vacuum and pass protective atmosphere in vacuum atmosphere furnace
In the high-temperature heat treatment process, some workpieces need to be vacuumed and pass protective atmosphere to conduct experiments, then this process must use a vacuum atmosphere furnace. But do you know how the atmosphere furnace is evacuated and the atmosphere is ventilated? Let me tell you the following:
1. Vacuuming. Vacuuming can be divided into low vacuum and high vacuum. The specific methods are as follows:
1. Low vacuum: close all vacuum valves tightly, start the mechanical pump, wait for it to run normally (about 1-2min), open the low vacuum valve that leads to the furnace body of the vacuum atmosphere furnace, namely the upper disc valve, and align the furnace body in advance Low vacuum.
2. High vacuum: Open the lower disc and pump the diffusion pump. When the vacuum reaches 15 Pa or less, turn on the diffusion pump for preheating. Generally, after about 45 minutes, the diffusion pump starts its function, and then the upper disc valve can be closed. At the same time, open the main barrier valve and wait until the vacuum degree is selected to 1.33×10 to the -1 power Pa or more, then the heating button can be turned on to heat the sample. The vacuum gauge has two ranges, low vacuum range 1.0×10 to the 5th power -1.0×10 to the -1 power; high vacuum range 1.0×10 to the -1 power to 1.0×10 to the -5 power, general Start to switch the range at 2Pa. Note that the vacuum gauge switch should be turned off before filling the atmosphere to prevent the vacuum gauge from aging.
When pumping a vacuum, please note that the upper disc valve and the main blocking valve of the vacuum atmosphere furnace cannot be opened at the same time.
Two, through protective atmosphere
1. Open the upper gas path control valve and make the button arrow point to the “open” position.
2. Adjust the flowmeter knob to make the reading at 20ml/min.
3. Open the air inlet valve of the vacuum atmosphere furnace until the barometer reads zero. And open the outlet valve on the protective atmosphere gas path.
The manufacturer of the vacuum atmosphere furnace reminds that the vacuum atmosphere furnace can only be heated after the protective atmosphere has been passed for ten minutes.