Bright annealing involves heating stainless steel to the target temperature (typically 1000-1150°C) in a controlled protective atmosphere, holding for sufficient time to achieve full recrystallization or solution treatment, then rapidly cooling under protective atmosphere to obtain an oxidation-free, bright surface.

Typical Process Flow:

1. Pre-Treatment (Degreasing & Cleaning) – Removes rolling oil, lubricants, and other contaminants from the stainless steel strip or tube surface to prevent carbon deposits or discoloration after annealing.
2. Heating Zone – Stainless steel is heated to target annealing temperature in protective atmosphere (H2+N2 or pure H2) for grain recrystallization or complete carbide solution.
3. Holding Zone – Maintained at target temperature for sufficient time to ensure uniform temperature across material section and complete microstructural transformation.
4. Cooling Zone – Rapid cooling (water cooling + air cooling) under protective atmosphere prevents oxidation and discoloration during cooling.
5. Post-Treatment (Optional) – Leveling, tension leveling, or slitting according to product requirements.

Different stainless steel grades require different annealing temperatures and protective atmospheres. Parameters must be precisely adjusted according to material characteristics.

1. Continuous Bright Annealing for Strip/Coil – Applicable to stainless steel strip or coil with thickness 0.2-3.0mm and width 50-650mm. Uses continuous horizontal through-type furnace with line speed 1-12 m/min. Finished surface achieves mirror-level brightness (Ra<0.1μm), ready for decorative and deep drawing applications.

2. In-Line Bright Annealing for Tube – Applicable to stainless steel tube with diameter Φ6-100mm. Uses continuous through-type furnace or induction annealing equipment with line speed 1-6 m/min. Both inner and outer surfaces of finished tube are bright and oxidation-free, ready for decorative tube and heat exchanger tube applications.

3. Sink Bright Annealing – Applicable to stainless steel sinks after deep drawing forming. Uses batch-type bright annealing furnace to eliminate work hardening stress, restore corrosion resistance, and achieve bright, uniform surface.

1. Unwinding stand / pay-off
2. Degreasing and cleaning section
3. Bright annealing furnace (heating + holding + cooling zones)
4. Tension control system
5. Recoiling / cutting station
6. Ammonia cracker and atmosphere control system

Surface Brightness Control:
- Post-annealing surface: silver-white or mirror-like
- No oxidation color (yellow, blue, gray)
- Surface roughness: Ra ≤ 0.1μm (mirror grade)

Mechanical Property Control:

Atmosphere Purity Control:

- Hydrogen content: ≥75%
- Dew point: ≤-40°C
- Residual oxygen: ≤50 ppm
- Positive furnace pressure to prevent air infiltration

Cooling Effect Control – Cooling rate must be fast enough to prevent carbide precipitation. Outlet water temperature ≤40°C to prevent oxidation and discoloration.

Bright annealing of stainless steel strip and tube is a core process for achieving high surface quality and excellent performance. As downstream industries demand higher surface quality and performance from stainless steel, continuous bright annealing technology will continue to develop toward wider widths, higher efficiency, greater intelligence, and greener manufacturing.

Rexin China factory provides complete continuous bright annealing production lines for stainless steel strip, tube, sink, and other applications, including degreasing cleaning, annealing furnace, ammonia cracker, and control systems, supporting wholesale supply and custom manufacturing. Contact our engineering team for more information or to request a quote.