Vacuum heat treatment products abnormal color reasons

Vacuum furnace is the mainstream equipment in heat treatment industry at present. Its products are not only reliable in quality, but also environmentally friendly, without waste treatment. At the same time, energy consumption is significantly lower than traditional heat treatment equipment such as salt bath furnace. Therefore, it is widely used in aerospace, weapons, electronics, automotive, machinery industry and other fields. But it is often seen that the users of the vacuum furnace are posted on the Internet to ask about the wrong color of the heat treated products in the vacuum furnace. This problem is a common problem in the production of heat treatment. Then, what is the reason why it should be solved?

1 test whether the vacuum furnace equipment itself has air leakage
This can be determined by the pressure rise index of the vacuum furnace; it needs to be reminded that it is to be tested when the rate of lift is tested and then cooled to room temperature, instead of opening the furnace door and then taking a vacuum test.

2 check the air leakage in the intake pipe of the vacuum furnace
Sometimes we test the pressure rise rate of the vacuum furnace to be normal, but there is a leak in the intake pipe or valve in the vacuum furnace. The pressure in the intake pipe is gradient, the more the negative pressure is near the end of the furnace, which is one of the reasons for the color of the products treated by the vacuum furnace.

3. the purity of inert gas detected in vacuum furnace is not high.
When the purity of inert gas is not enough, the oxygen mixed in it will lead to oxidation and decarbonization of products, which will lead to discoloration of products. The purity of gas can be directly detected or compared with other equipment.

4. the moisture in the vacuum furnace is attached to the inner wall of the vacuum furnace or the heat exchanger.
This kind of wet gas is difficult to drain through the oven. When there are no above three problems in the vacuum furnace equipment, the color of the processed product is not due to this reason. At this time, we can lift the vacuum furnace equipment to the high temperature, stop the heating, and then enter the high purity inert gas into the furnace. Body, then start the fan circulation system, using the high temperature and hot air in the vacuum furnace to bake the moisture on the inner wall of the vacuum furnace and the heat exchanger to solve the problem.

5 cause of quenching oil
The author found in practice that a large part of the reason why the color of the vacuum oil quenched is not bright is due to the improper selection of quenching oil.