Project Name: 160m/min Continuous Galvanizing Line for Strip Steel
Customer Name: Dong'e County Yike Steel Sheet Co., Ltd.
Project Nature: New Construction
Contracting Method: General Contracting by Jingjie Ruisi
Signing Date: April 7, 2011
Production Status: Under Construction
Operation Status: Good
I. Characteristics of the Unit
This unit is designed to produce high-quality hot-dip galvanized steel sheets and features functions such as annealing and reduction, galvanizing, tempering, tension leveling, and passivation. The raw material types are cold-rolled hard steel coils SPCC, SPCD, and SPCE, with specifications of 800-1250mm × 0.18-0.8mm. The designed maximum process speed of the unit is 160m/min. The main features of the unit are as follows:
(1) It adopts the most advanced and widely used United States Steel Corporation (US Steel) process in the world.
(2) The horizontal loop uses a four-roll mobile trolley, which shortens the full loop length and sets a deviation correction device at the fixed turning roller to ensure that the loop does not deviate when full.
(3) A steel strip cleaning section is set up, and considering the requirements of galvanizing, an advanced and practical chemical degreasing and electrolytic degreasing combined technology is adopted to enhance the degreasing effect and remove oil and iron powder from the surface of the steel strip.
(4) A reduction method bright horizontal annealing furnace is set up, and a new energy-saving radiant tube technology independently developed by Jingjie Ruisi Company is used for indirect heating. The heating is uniform, the control is simple, the plate shape is good, and it overcomes the disadvantage that most domestic units have difficulty in producing thin strips.
(5) The annealing furnace adopts a natural gas heating scheme and is equipped with a comprehensive waste heat recovery system independently developed by Jingjie Ruisi Company. This system can replace steam (or electricity) for heating the cleaning liquid and hot air drying throughout the line. It has good synchronization and can eliminate the investment in the system boiler. At the same time, according to general estimates, compared with the traditional steam heating and heat exchange method, it can save costs by more than one million yuan per year.
(6) The inner lining of the annealing furnace is made of lightweight fiber, which is fast to build and has small thermal inertia.
(7) The cooling of the steel strip inside the furnace uses a protective gas circulation spray cooling device, which is regulated by frequency conversion. The cooling speed of the steel strip is fast and uniform, meeting the accurate pot entry temperature requirements for galvanized steel strips. A special zinc nose structure is used to meet the requirements of galvanizing.
(8) An advanced air knife of the QD type independently developed by Jingjie Ruisi Company is adopted, ensuring good control of the coating weight and quality.
(9) A ceramic induction zinc pot is used to ensure the stability of the bath temperature and meet the requirements of galvanized products. The zinc pot is heated by a jet ceramic induction heating method, which has the advantages of fast heating, uniform temperature, long service life, and less zinc dross.
(10) A four-roll tempering machine is used to effectively improve the surface quality of the product, eliminate the yield platform, and enhance the cold forming performance of the product. A quick roll changing trolley is set up to reduce the roll changing time.
(11) A two-bend two-leveling tension leveling machine is used to effectively improve the plate shape and surface quality of the steel strip and enhance the competitiveness of the product.
(12) CPC and EPC systems are set up to ensure stable production of the unit.
(13) The electrical drive control system adopts the Siemens 6SE70 system, with AC variable frequency speed control transmission, achieving closed-loop control of tension and speed. The PLC is a powerful SIMATIC S7-400 device, with a good human-machine interface and simple equipment maintenance.
(14) The braking system throughout the line adopts electro-hydraulic brake control.
II. Basic Parameters:
Raw Materials:
Steel Type: SPCC, SPCD, SPCE
Steel Strip Thickness: 0.18-0.80 mm
Steel Strip Width: 800-1250mm
Steel Coil Inner Diameter: Φ508/Φ610mm
Steel Coil Outer Diameter: Φ1100mm - Φ2100mm
Steel Coil Weight: Max. 25t
Finished Products:
Comply with National Standard: GB/T2518-2008 Inner diameter of steel coil: Φ508/Φ610mm
Outer diameter of steel coil: Φ1100mm - Φ1500mm
Weight of steel coil: Max. 15t
Line speed: Entry and exit sections: 0 - 210m/min; Process section: 0 - 160m/min
Steel feeding speed: 30m/min
Annual production capacity: 180,000 tons (estimated). The specific production capacity is determined based on the product range.
Line layout: Looking from the operator side, the production line runs from left to right. The total length of the line is approximately 238m, with the highest point at 11.5m (excluding the cooling tower).
III. Process Flow of the Line
According to the functions of the line and the sequence of steel strip processing, the line can be divided into the entry section, process section and exit section. The entry section mainly includes uncoiling, shearing, welding and degreasing processes, continuously providing clean steel strips to the process section; the process section mainly includes annealing reduction, galvanizing, temper rolling, tension leveling, passivation, etc., completing the processing of the steel strip; the exit section completes the slitting and coiling of the steel strip. The process flow of the line is as follows:
Uncoiling → Uncoiling → Head shearing → Welding → Entry loop → Degreasing (alkali spray + alkali brushing + electrolytic cleaning + water brushing + water cleaning + fresh water spray) → Hot air drying → Annealing reduction → Protective gas cooling + Galvanizing → Air cooling → Water quenching cooling → Hot air drying → Tempering rolling → Tension leveling → Passivation → Hot air drying → Exit loop → Slitting → Coiling → Uncoiling → Packaging.
