1. Whether the annealing temperature reaches the specified temperature. The heat treatment of stainless steel generally adopts solid solution heat treatment, which is what people usually call "annealing". The temperature range is 1040~1120℃. You can also observe through the observation hole of the annealing furnace. The stainless steel pipe in the annealing area should be in an incandescent state, but there should be no softening and sagging.
2. Annealing atmosphere. Generally, pure hydrogen is used as the annealing atmosphere. The purity of the atmosphere is preferably above 99.99%. If the other part of the atmosphere is an inert gas, the purity can be lower, but it must not contain too much oxygen or water vapor.
3. Furnace body sealing. The bright annealing furnace should be closed and isolated from the outside air; if hydrogen is used as the protective gas, only one exhaust port should be open (used to ignite the discharged hydrogen). The inspection method can be to apply soapy water on the joints of the annealing furnace to see if there is air leakage; the most likely places for air leakage are the places where the tubes enter and exit the annealing furnace. The sealing rings in this place are particularly easy to wear. Check and change frequently.
4. Protective gas pressure. In order to prevent micro-leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is hydrogen protective gas, it generally requires more than 20kBar.
5. Water vapor in the furnace. On the one hand, check whether the furnace material is dry. When installing the furnace for the first time, the furnace material must be dried; secondly, whether there are too many water stains on the stainless steel pipe entering the furnace. Especially if there are holes on the pipe, be sure not to allow water to leak in. Otherwise, the atmosphere of the furnace will be completely destroyed.
