1. Whether the annealing temperature has reached the specified temperature. The heat treatment of stainless steel square tubes generally adopts solid solution heat treatment, which is commonly known as "annealing", with a temperature range of 1040~1120 ℃ (Japanese standard). You can also observe through the observation hole of the annealing furnace, and the square tube in the annealing area should be in an incandescent state, but there should be no softening or sagging.
2. Annealing atmosphere. Generally, pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is preferably above 99.99%. If the other part of the atmosphere is an inert gas, the purity can also be lower, but it must not contain too much oxygen or water vapor.
3. Sealing of furnace body. The bright annealing furnace should be closed and isolated from external air; When hydrogen gas is used as a protective gas, only one exhaust port is open (used to ignite the discharged hydrogen gas). The method of inspection can be to wipe the gaps in various joints of the annealing furnace with soapy water to see if there is any air leakage; The places where gas is most likely to escape are the places where the annealing furnace enters and exits the pipes. The sealing rings in this area are particularly prone to wear and tear, and should be inspected and replaced frequently.
4. Protective gas pressure. In order to prevent micro leakage, the protective gas inside the furnace should maintain a certain positive pressure. If it is hydrogen protective gas, it is generally required to be above 20kBar.
5. Water vapor in the furnace. On the one hand, check whether the furnace material is dry. For the first furnace installation, the furnace material must be dried; The second issue is whether there are too many water stains left on the square tube entering the furnace, especially if there are holes on the tube, do not let water leak in, otherwise it will completely damage the atmosphere of the furnace.
