Advanced and ultra high-strength steels (AHSS and UHSS) require more complex heating and cooling cycles for continuous annealing and galvanizing lines. High cooling rates combined with uniform temperature distribution keep the strip in proper shape during the cooling stage. It is key to producing AHSS and UHSS grades, such as those required in automotive steel processing. Fives has designed a range of FlashCooling® technologies for vertical annealing and galvanizing furnaces to cover any cooling rate, from 50˚C/sec up to 1000˚C/sec.
FlashCooling® technologies for wet and dry processes have been developed to meet this need, providing very fast cooling in vertical Stein Digiflex® furnace:
- 50 to 200°C/sec (1 mm thick) in dry condition (5 to 75% H2)
- Up to 1000°C/sec to process latest AHSS grades (MS, Q&P, etc.)
- 8 patents in application
- More than 40 units operating
History of FlashCooling® technology development
Fives has developed the FlashCooling® technology at its own test centre by building several scale 1 test benches. The research works were conducted together with renowned institutes specializing in aerodynamics (Institut Aérotechnique, Saint-Cyr-l'École, France) and fluid flow thermal transfer (Brno University of Technology, Czech Republic). The new technology was tested and optimized in a pilot bench facility before being introduced to the market for hot dip galvanizing lines operating wet or dry processes.
Fives implemented its first high H2 rapid cooling system in 1998 for the vertical furnace in a 1 million t/y continuous annealing line in Europe. The FlashCooling® technology is now in operation in about 40 continuous annealing and galvanizing lines worldwide.
Dry FlashCooling® technology
The Dry FlashCooling® system is Fives' patented technology. It has come to be the standard for continuous galvanizing lines (CGL). The first dry FlashCooling® system was installed at British Steel (now Tata Steel) in Port Talbot, Wales (UK) in 1999. It operated with 50% hydrogen to increase the cooling capacity. Today, installations with up to 75% hydrogen and cooling rates of 200˚C/sec are not uncommon.
Dry FlashCooling® benefits
- High operation flexibility with atmosphere gas blowing 5-75% H2
- Full lengthways and crosswise control of cooling rate
- Symmetrical blowing and rear central exhaust for perfect strip stability
- Design and control features to avoid strip cool buckling and mistracking
- Approved safety
Wet FlashCooling® technology
The Wet FlashCooling® system is Fives' patented technology. Nitrogen is blown with water mist, which offers greater flexibility in operation in terms of cooling rate control, temperature cycle control and uniformity of cooling. This modern technology has replaced the more conventional method involving water quenching of the strip. It was introduced on the continuous annealing line at POSCO’s Gwangyang Steelworks in 2008.
Wet FlashCooling® benefits
- Very high cooling rate in a controlled manner up to 1,000˚C/sec
- High cooling rate flexibility: range 1 – 10
- Unique capability to control all process parameters including exit strip temperature (600˚C to 100˚C)
- State-of-the-art control system for crosswise temperature uniformity and buckling prevention
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