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The Basics of Bright Annealing

Bright Annealed Strip

Bright annealing, commonly known as bright annealing, is mainly used for heating and annealing in a closed space, allowing the temperature to slowly cool down at least 500 degrees in a closed space, and then naturally cooling, so that there will be brightness without causing decarburization.

Oxidation and decarburization occur during heating and cooling during ordinary annealing, so the heat-treated steel undergoes additional processing, which increases the loss and cost of metal, so bright annealing is often used.

The hot-rolled stainless steel coil is first annealed and pickled, and then rolled in a cold rolling mill. The required rolling passes are determined according to the thickness of the finished product. The rolled stainless steel strip should be chemically degreased to remove the surface of the strip. The residual rolling oil in the rolling process is then entered into a bright annealing furnace with protective gas for bright annealing and finally delivered as a finished BA sheet.

According to the chemical reaction between furnace gas and steel and its change law, a protective atmosphere is prepared and applied, and the conditions for preventing oxidation and decarburization are determined.

advantage

  1. Eliminate work hardening and obtain satisfactory metallographic structure. When the performance requirements are different, the requirements for the metallographic structure after bright annealing are different, and the process of bright heat treatment is also different.
  2. Obtain an oxidation-free bright surface with good corrosion resistance. Since bright annealing is a heat treatment of strip steel in a mixed gas protective atmosphere of hydrogen and nitrogen, a bright surface without oxidation is obtained by strictly controlling the protective atmosphere in the furnace, especially the purity, residual oxygen and dew point. Compared with the surface obtained by ordinary annealing and pickling, since there is no oxidation process, the phenomenon of poor chromium on the surface of the strip is reduced, and its corrosion resistance is better than that of the 2B plate after polishing.
  3. Bright treatment maintains the smoothness of the rolling surface, and a bright surface can be obtained without post-processing. After bright annealing, the surface of the steel strip retains the original metallic luster, and a bright surface close to the mirror surface has been obtained. Under general requirements, the surface can be directly used without processing.
  4. Strip steel with a special rolling pattern surface can be developed. Since the surface of the steel strip is not changed during the annealing process, the rolling surface pattern can be completely retained, and the cold-rolled special pattern strip can be easily developed.
  5. There is no pollution problem caused by ordinary pickling methods. The annealed strip does not need pickling or similar treatment, various media such as acid are not used, and there is no pollution problem caused by pickling.
  6. Realize the control of the shape of the plate. Since the bright annealing furnace design allows segmental adjustment along the width direction of the strip, the cooling rate in the width direction of the strip can be adjusted by airflow diversion to achieve online control of the shape of the strip.
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