Measures for Improving Coiling Quality of Strip Steel

Starting from the influence of the expansion and contraction hydraulic system and the tension control hydraulic system of the coiler on the coiling quality of the strip, by improving the expansion and contraction hydraulic system and the tension control hydraulic system , the coiler of the cold rolling processing line is solved. Frequently occurring problems such as slipping of the head on the reel , failure to establish tension, overflow of the inner ring of the steel coil, wrinkles and stem marks during strip coiling .
Keywords Coiler Drum Expansion and Shrinkage Tension Control

1. Current status overview

The coiler is one of the necessary equipment for the continuous cold rolling mill. In order to ensure the smooth coiling of the steel strip by the coiler , the coiler is generally equipped with auxiliary devices such as a coiler . When the steel strip starts to be coiled on the coiler , the coiler is used to press the strip head to prevent the misalignment of the strip head and the coiler drum. In recent years , in order to improve productivity and shorten the auxiliary operation time , the coilers in the cold-rolled thin plate units generally do not use jaw biting heads for coiling, but generally use belt coilers. Coiler and coiler structure .

A coiler with a belt coiler on a strip steel cold rolling processing line frequently occurs when the strip head slips on the coil , the tension cannot be established, the inner ring of the steel coil overflows, wrinkles and stem marks and other issues. In the previous production process , when the coiler coiled the steel coil, the first few laps of the strip steel at the beginning of coiling slipped on the coil , which caused the coiling tension to not be established, and the calculation of the coil diameter was caused by the slipping. No, it is difficult to unwind the steel coil trolley, the coiling speed at the exit section has not reached the design speed, and the coils coiled all have inner ring overflow, thin strip steel coil inner ring wrinkles and thick strip steel coils. These problems seriously affect the production capacity of the continuous annealing unit and also affect the quality of the product .

1. Cause Analysis

Through many observations and analyzes on site , the main problems and causes in the coiling process are as follows :
1 ) The strip steel slips on the reel in the first few turns of coiling : the main reason for this problem is that the belt steel cannot tightly wrap the rubber sleeve during the coiling process . The friction generated between the steel and rubber sleeve is less than the coiling tension.
2 ) There is an overflow edge in the inner ring of the rolled steel coil : the overflow of the inner ring is also caused by the slippage between the strip steel and the reel . Because the steel is tightly wrapped on the reel, it cannot move laterally with the reel, resulting in the overflow of the inner ring cannot be effectively controlled ;

1. Wrinkles on the inner ring of the strip steel coil with a thickness of less than 0.6mm : This problem is mainly because the original design of the coiling belt has only one tension mode, which cannot be automatically adjusted for different thicknesses of strip steel . It is necessary to use a larger belt winding force to ensure that the strip steel does not slip on the reel , but when the thin strip steel is coiled at the same tension, the inner ring will be wrinkled, the belt threading will not be smooth, and the belt head will be folded . Or the traces of the edge of the belt are printed on the strip steel in the inner ring of the steel coil .
2. are about 40 rings of the inner ring of the steel coil with a thickness greater than 1. 5mm . There are stem marks : the inner ring of the strip steel has always existed, but the degree is different. Because the tape head is not effectively embedded in the rubber sleeve during the coiling , the tension increases after the coiling , and the tape head continues to produce indentations on the steel coil .

The first circle of the inner circle has the most serious stem marks , especially when the thick strip is coiled, the influence of the inner circle stem marks reaches about 40 circles.

1. Improvement measures

3.1 Modify the hydraulic control circuit of the reel to solve the slipping of the inner ring and the stem mark of the inner ring . The original design of the hydraulic circuit uses a simple two-position four-way valve and a hydraulic lock controlled by an electromagnetic auxiliary valve to control the three positions of the reel. Due to the unavoidable internal leakage of the expansion and contraction cylinder and the rotary oiler itself, the unloading position ( " 590 ) often loses the unloading position ( " 590 ) . Because the original design is open -loop control, there is no position loss The compensation mechanism causes frequent interruptions in the roll -down process , requiring human intervention.
After modifying the hydraulic circuit [ 1 ] , the main valve is replaced by a proportional valve to realize the closed-loop control of the position of the reel. By detecting the position of the expansion and contraction cylinder, the control of multiple positions of the reel can be realized. After the circuit is reformed, the pre-tensioning function ( " 608 ) of the reel can be realized, so as to effectively solve the problem of inner ring slippage and reduce stem marks. The principle of solving the inner ring slippage is : when the first three turns of the coil are taken , the roll The cartridge only expands to

" 608 , after the roll-assist belt is returned , it immediately rises to " 610 , so that the strip steel is tightened again on the rubber sleeve , which improves the force of the strip steel pressing the sleeve and increases the frictional force, thus avoiding the belt The steel slips ; in the process of tightening again , the strip steel head is embedded in a part of the rubber sleeve during the first turn , thereby reducing the influence of stem marks.
3 for the schematic diagrams before and after the modification of the coil expansion and contraction hydraulic system .
3.2 Modify the hydraulic control circuit of the belt roll to eliminate inner ring folds [ 2 ] .
the coiling belt The original designed hydraulic circuit can only provide one working tension, which cannot satisfy the smooth coiling of the thin strip while satisfying the high tension of the thick strip . According to the characteristics of the original circuit , the The decompression valve is replaced with a two-stage pressure control, and different tension controls are implemented for strip steel with a thickness of M l. 2mm and < 1.2mm , which can eliminate inner ring folds while satisfying the high tension of thick strip steel wrinkle phenomenon.

conclusion

1. The reel expansion and contraction hydraulic system of the coiler replaces the main valve with a proportional valve, which can realize the closed-loop control of the reel position . By detecting the position of the expansion and contraction cylinder, the control of multiple positions of the reel can be realized , and the coil The pre-expansion function of the barrel can effectively solve the problem of inner ring slippage and reduce the generation of stem marks .
2. tension control hydraulic system of the belt assist coil replaces the pressure reducing valve with a two-stage pressure control valve, which can realize different tension control for strip steel with different thickness , and can meet the demand for high tension of thick strip steel , and can effectively eliminate Inner ring wrinkles produced by strip coiling .
3. The above-mentioned problems of the coiler with belt coiler have been puzzling the designer and the manufacturer , and its partial improvement has greatly improved the coiling quality of the strip .

The improvement method above can be extended to other places where similar problems need to be solved, and can be used as a reference for the design unit to improve the design .

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