How To Solve Problem of Yellowing or Blackening of Stainless Steel Tubes After Bright Annealing?

At present, the application of stainless steel pipe in the market is very extensive, and it has a very important role in many industries. In order to reduce the hardness and improve the plasticity; to refine the grains and eliminate the internal stress, annealing is necessary.

However, many users report that the yellow or blue stainless steel tube after annealing always fails to achieve the expected bright effect, so how to solve this problem?

1. The yellowing of the surface may be caused by unstable heating temperature. The surface temperature is high and the temperature is low. The cause is the annealing temperature control or the design of the annealing furnace temperature zone. This is currently on the market. Annealing furnaces are mixed, and prices vary greatly. It is difficult for users to distinguish good from bad.

2. Find the reason from the process flow and technology, which is related to the user's temperature setting, the surface cleanliness of the stainless steel pipe, and the material of the stainless steel pipe.

To solve the above problems, make the stainless steel tube bright after annealing:

1. The air tightness of the muffle tube is the key factor for the brightness of the stainless steel tube.

2. Whether the structure of the annealing furnace, the distribution of temperature zones, and the thermal field of the annealing furnace are reasonable, this directly affects the heating uniformity of the stainless steel tube. The stainless steel tube must be heated to incandescent condition without softening and sagging.

3. The stainless steel pipe itself has too much oil or water stains, so the atmosphere in the furnace is destroyed and the purity of the protective gas cannot be reached.

4. Ensure that the atmosphere in the furnace has a slight positive pressure, so that the air will not be sucked back into the furnace. If it is ammonia decomposition mixed gas, it usually requires more than 20kBar.

Here recommended you to consider Hangao Tech heat preservation type induction heating bright annealing heat treating machine. With single and continuous type, it could prevent the heated pipes from the oxygen in the air, with excellent air sealing performance, to guarantee the brightness of the finished pipes.

Just feel free to contact us for consulting.