What factors affect the brightness of stainless steel pipe fittings during annealing

Annealing is a heat treatment process in the processing of stainless steel pipe fittings, which slowly heats the pipe fittings to a certain temperature, maintains it for a sufficient time, and then cools them at an appropriate speed. If not handled properly, it will affect the brightness of stainless steel fittings. What are the specific factors that cause it?

1. Whether the annealing temperature reaches the specified temperature. Stainless steel pipe fittings are generally subjected to solution heat treatment, which is commonly known as "annealing", with a temperature range of 1040~1120 degrees (Japanese standard). It can also be observed through the observation hole of the annealing furnace. The stainless steel fittings in the annealing zone should be in an incandescent state, but there should be no softening or sagging of the lifting device.

2. The annealing atmosphere generally uses pure hydrogen as the annealing atmosphere, with a purity of 99.99% or higher. If another part of the atmosphere is an inert gas, the purity can also be lower, but it cannot contain too much oxygen or water vapor.

3. The furnace body sealing of the bright annealing furnace should be closed and isolated from the outside air; When using hydrogen as a protective gas, only one exhaust port is open (used to ignite the discharged hydrogen). The inspection method can be to apply soapy water to the joints and gaps of the annealing furnace to see if there is any gas leakage; The areas that are prone to gas leakage are the places where the annealing furnace enters and exits the pipes. The sealing rings in these areas are particularly prone to wear and need to be checked and replaced regularly.

4. To prevent micro leaks, 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. On the one hand, check whether the furnace material is dry when installing water vapor inside the furnace. For the first time, the furnace material must be dried; The second is whether there are too many water stains left on the stainless steel pipes entering the furnace, especially if there are holes on the pipes, do not let water leak in, otherwise it will completely destroy the atmosphere of the furnace. Generally, if it is normal, the stainless steel pipe that should be stepped back about 20 meters after opening the furnace will start to shine, shining so brightly that it reflects light.

The above are the factors that affect the brightness of stainless steel pipe fittings during annealing. If similar problems occur, you can find the cause from above. The annealing process directly affects the quality of stainless steel fittings, so attention should be paid to processing details, including control of annealing temperature, during operation.