Factors Affecting Bright Annealing of Stainless Steel Tubes

  • By:Bonnie Auyeung
  • Date:2023/06/01


Stainless steel pipe is now widely used in the market, in all walks of life have its figure, and play an important role. Compared with decorative pipe, stainless steel industrial pipe has higher added value, and is becoming an important breakthrough point for the industry to high-end transformation. But the stainless steel pipe wants to meet the standards of industrial pipe is very strict. It is usually necessary to reduce hardness, improve plasticity, refine grains and eliminate internal stress, which requires annealing. In addition, the advantages of bright annealing are as follows: keep the stainless steel tube bright outer surface, to meet the industrial needs for the automobile tube, food fluid tube and other high requirements for the bright external surface. Bright annealing of stainless steel does not need pickling, the process is more environmentally friendly.

There are many influencing factors, the main factors affecting the bright annealing quality of stainless steel are: gas composition and purity protection, heating and cooling system.

1. Whether the annealing temperature reaches the specified temperature

The heat treatment of stainless steel is usually the solid solution heat treatment, which is commonly known as annealing. Bright annealing equipment is used for stainless steel pipe on-line heated to 1050 ℃, then rapid cooling below 100 ℃ under hydrogen protection of special equipment. Temperature is an important influencing factor, and the temperature needs to reach the range of 1040 to 1120℃.

2.  The annealing atmosphere

BA used in the production of protective gas composition and purity are bright annealing the first condition. Generally, pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is best above 99.99%. If another part of the atmosphere is inert gas, the purity can also be a little lower, but absolutely must not contain excessive oxygen vapor.

3. The bright annealing furnace should be closed and isolated from the outside air

Sealing properties of the annealing furnace. The bright annealing furnace shall be closed and isolated from the outside air; only one vent is open (used to ignite the discharged hydrogen gas). The inspection method is to use soapy water on the joints of the annealing furnace, to see whether the leakage; the most likely to leak is the place into the pipe and the pipe, the sealing ring in this place is easy to wear, so often check and change.

4. Gas pressure for protecting the gas

In order to prevent trace leakage, the protective gas in the furnace should maintain a certain positive pressure. If it is hydrogen protection gas, it is generally required to be above 20 kBar.

5. Check whether the furnace charge is dry

The first loading of the furnace must be dry. Secondly, whether the stainless steel pipe into the furnace remains too much moisture, especially there are holes in the pipe, do not leak in, otherwise it will destroy the atmosphere of the stove.

Hangao Tech bright annealing furance: On-Line Fixing & Fusing (Anealing) equipment can heat the stainless steel welded pipeto 1050°C then cool it to the temperature lower than 100 °C under the protection of hydrogen.The heating power supply of the intermediate ferquency induction is the newest DSP+IGBT structure.With DSP digital control system,there are self protection and self diagnostic functions.With small volume,it heats pipes rapidly and efficiently with energy-saving and low-waste features.The especially developed inducer designed according to the features of stainless steel can save 15%-20% energy in contrast of other products of the same class. Using hydrongen as of gas every minute.




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