What are the reasons why the workpiece is not bright when annealed in a bright annealing furnace

The reason why the workpiece is not bright when annealed in a bright annealing furnace

1. Whether the annealing temperature reaches the specified temperature. Bright annealing furnace generally adopts solution heat treatment, which is called "annealing", and the temperature range is 1040~1120℃ (Japanese standard). It can be observed through the observation hole of the annealing furnace that the stainless steel tube in the annealing zone should be in an incandescent state, but there is no softening and sagging.

2. The 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 also be lower, but it must not contain too much oxygen and water vapor.

3. Furnace body tightness. The bright annealing furnace should be closed and isolated from the outside air; if hydrogen is used as a protective gas, only one exhaust port is open (used to ignite the discharged hydrogen). The method of inspection can be wiped with soapy water on the joints of the annealing furnace to see if it is out of gas; the easiest place to outgas is the place where the annealing furnace enters the pipe and the place where the pipe exits. The sealing ring in this place is particularly easy to wear. Always 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 hydrogen is used as the protective gas, it is generally required to be above 20kBar.

5. Water vapor in the furnace. On the one hand, check whether the furnace body material is dry. When installing the furnace for the first time, the furnace body material must be dried; second, whether the stainless steel pipe entering the furnace has excessive water stains, especially if there are holes on the pipe, do not leak water in. Otherwise, the atmosphere of the stove will be destroyed. If these types of problems do not occur, the stainless steel pipe that should be back about 20 meters after the furnace starts to shine.