Coil Design of Hot Strip in Steel Plant

One of the important indicators to measure the quality of hot-rolled strip steel is the coil shape of the strip steel coil. The coil shape of the strip steel coil needs to moderately control the tension during the hot rolling process. The tension control is reasonable and the coil shape is beautiful. Applicable and good quality. In the production of hot-rolled strip steel, the material of the steel is also related to the control of the opening of the coiling side guide plate.
【Key words】hot rolling; strip steel; coiling; control

With the development of economy, my country's iron and steel industry began to take off. In people's production and life, the demand for steel is gradually increasing, the requirements for steel materials are increasing day by day, and the demand and quality requirements for hot-rolled strip steel are more stringent. An important index to measure the quality of hot-rolled strip steel is to look at the coil shape of the strip steel coil. The coil shape needs to be moderately controlled during the hot rolling process. Only when the coil shape is controlled reasonably can it be beautiful, suitable and of good quality. In addition, the material of the steel is related to the control of the opening of the side guide plate, and the higher the control accuracy, the better the material. The author will elaborate on the moderate control of the coiling tension and the control of the opening of the side guide plate during the hot rolling process. It is hoped that this article has reference value for the design improvement and production application of the coiler.
1. Problems and causes of coiling machine in production
The down coiler ( Down Coiler ) of the hot-rolled strip steel plant often has piled steel accidents and tower-shaped steel coils after commissioning and production. Coiler ( Down Coiler ) , the equipment used to coil the rolled finished hot-rolled steel strip into steel coils, is used in hot strip rolling lines, thin slab continuous casting and rolling lines, and medium slab continuous casting and rolling lines. It is used in the production line of the steckel rolling mill. The downcoiler is constantly developing, and its performance tends to be improved day by day. This paper analyzes the current situation of the coiler design theoretically, in order to make the further design of the downcoiler more rational.

The coil shape in the production process is related to the quality of the material in coiling. According to the production and a large number of sales history records of our factory, it can be concluded that: the tower-shaped steel coil is in the production line - walking beam, often in the transportation process There will be a rollover phenomenon. The cause of the accident has been analyzed to be that the steel coil cannot be aligned accurately, which will cause the center of gravity of the steel coil to deviate. The root cause is this serious "tower shape". This "tower shape" will also cause a lot of trouble when the clamp is lifted. For example, the clamp will cause damage and scratches to the edge of the irregular strip steel coil, and even make the clamp unable to clamp the strip steel at all. in the inner circle of the circle. In the process of transshipment, because the "tower shape" is too large, it is very inconvenient to load. The main reason is that the packing belt often cracks and loosens. Of course, in order to save production costs, it is impossible to use the finishing machine to go to the volume again. There are mainly three types of tower shapes: inner tower shape, interlayer tower shape, and outer tower shape.
(1) Inner tower shape. It is within the range of 5 to 10 circles of the inner ring of the steel ring that the strip steel just appears to deviate to one side. The reason is that when the lead head enters the coiler, it deviates from the center line, and then the side guide is alert and forced to correct the deviation, so that the steel belt returns to the center line, so that a "tower shape" will appear on the head . , which requires timely error correction of the side guides to avoid quality problems in the tower shape. If the error correction is not timely, the head may loosen.
(2) Interlayer tower shape. The main reason is that the steel strip in the middle of the steel ring deviates to both sides. It can be seen from the side that the entire steel ring is uneven. The reason is that the steel belt vibrates up and down or left and right during the traveling process. This generally occurs when the tension between the F7 frame and the reel is not appropriate. Due to the back and forth vibration, the side guide plate is severely worn , the control of the position is no longer accurate, and the pressure of the pinch roller is out of control, forming a tower shape between the layers of the loose roll.
( 3) Outer tower shape. Occurs between 15 and 20 circles of the outer ring, similar to the inner tower shape, with a large deviation towards one side, and a tower shape appears on the outer ring, also known as "tail tower shape"
2. Estimated coiling tension ( tension control AJC ) When setting the coiling tension, the tension setting must be appropriate. The advantage of high coiling tension is that the coil is tight, but if the tension is too high, the performance of the strip will be affected due to stretching. If the tension is too small and the coil is too loose, flat coils will appear, which will have a serious impact on the next step of cold rolling uncoiling, resulting in sharp fluctuations in the tension of cold rolling uncoiling, and will also cause scratches due to the misalignment between layers of steel coils. Especially with carbon steel, a constant tension is required.
The speed regulator outputs the limit value, and the tension value depends on the values of tension moment, friction moment, bending moment, acceleration and deceleration moment.
Coil diameter calculation: Calculated according to the value displayed by the pulse generator, and at the same time check and filter processing, steel coil diameter = 2 times strip length / rotation arc
Calculation of strip tension moment: Tension moment = preset tension setting value (variable) x coil diameter /2 times transmission ratio
Bending moment = Yield coefficient X strip width x strip thickness square /4
Coiler acceleration moment = acceleration x fixed part moment of inertia coefficient X1 / steel coil diameter + strip width x (coil diameter moment of inertia coefficient x steel coil diameter cube - coil diameter moment of inertia coefficient x 1 / steel coil path)
The moment of inertia of the steel coil = the calculation correction factor of the moment of inertia x (the width of the steel strip x the specific gravity of the steel x n ) / ( 32 x the square of the reduction ratio) x (the 4th power of the diameter of the coil - The 4th power of the expansion diameter of the reel )
Friction torque is a non-linear function of velocity.

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