Research and Application of Aspect Ratio of Slitting Steel Coil

The slitting line of a finishing branch of a hot rolling mill is a multi-purpose coiling unit with the functions of slitting strips, slitting and recoiling. With the advancement of the company's integration process, the proportion of slitting coils in the internal supply has gradually increased, and at the same time it has brought new production requirements, that is, individual strips are required to be bundled into bundles after slitting. The problem of overturning in the storage and transportation of finished products has been brought about. In this paper, by studying the principle of object tipping, the author determines the width-to-height ratio of steel coils in combination with the actual situation, and according to the different needs of users, determines the production organization plan to solve the problem of overturning storage and transportation of slitting belts.
1. The principle of object tipping
According to the principles of physics, if an object or a system wants to maintain a balanced state, it must satisfy the conservation principle of physics, that is, the balance (stationary or uniform motion) under the action of a common point force, then there is work F 20; there is fixed rotation For the balance of the object on the axis, then there is M = 0; if the object does not have a fixed axis of rotation, and it is not acted by a common point force, but to maintain balance, then there are F20 and M = 0 .
When the object is on an inclined plane, to maintain its static balance, F = 0 must be satisfied .
According to the mechanical decomposition diagram (Figure 1 ) , the resultant force of support force N and gravity G should be equal in magnitude to static friction force, but opposite in direction, that is, f ' = G sin ^ = f . And N = G cos a , and f 2 " N , so you end up with " =tg a . Since tg a is monotonous between 0 and 90°

When the inclined plane angle increases, the monotonically increasing function tg a also increases. When tg a is greater than the coefficient of static friction , the static equilibrium state of the object on the slope is broken, and the object begins to slide. Since the dynamic friction coefficient is smaller than the static friction coefficient, the object that breaks the static equilibrium state is in a state of uniform acceleration and decline.
When the object on the slope breaks the state of static equilibrium and is in the state of uniform acceleration and slide, the force F H0, the gravity G is greater than the resultant force G' of the support force N and the dynamic friction force f , that is to say, there is a magnitude in the direction of the vertical line of the center of gravity is the resultant force of G - G ', direction downward. If the vertical line of the center of gravity deviates from the geometric shape of the object at this time, that is, to the left of point A as shown in Figure 2 , then M = ( G - G ') L H0, and the object rotates counterclockwise around point A And cause an overturn. If the vertical line of the center of gravity does not deviate from the geometric shape of the object at this time, then IM = 0, and the object is still in the state of uniform acceleration and descent.

Although the vertical line of the center of gravity does not deviate from the geometric shape of the object, the object can maintain a state of uniform acceleration and decline. But if an obstacle is encountered at this time, two situations will occur. As shown in Figure 3 , the height of the obstacle is lower than the center of gravity L. At this time , the resultant force F of the gravity G and the support force N is greater than the dynamic friction force f , then M = ( F - f ) L H0, and the object rotates counterclockwise around point B And overturned. If the height of the obstacle is higher than the center of gravity, then IM = 0, the object will not overturn, but other motions may occur (such as stop, deceleration, or reverse motion due to excessive momentum, etc.).

A simple static overturning process is that the object tilts above the arctg " angle, the static balance is broken, the object accelerates down, and finally overturns.
The finished steel coil produced by slitting is a homogeneous object with regular geometric shape, so its center of gravity is at the center of the geometric shape. According to the previous mechanical analysis, when the inclination angle is greater than the arctg angle, the static balance of the object is broken, and there is a possibility of overturning. The key depends on whether the work M at this time is 0. Therefore, the author uses the critical angle arctg to break the equilibrium state " For tipping critical point, to determine the aspect ratio of steel coil. The coefficient of static friction between steel and steel is 0.7 , combined with Figure 1 and Figure 2, the aspect ratio of the critical point is equal to tg a , which is the coefficient of static friction " , so the aspect ratio of the steel coil is 7:10 .
2. Application of aspect ratio

1. Cold-rolled sheet materials. The specifications of the materials (steel for magnetic shielding and shadow mask strip) used in the cold-rolled sheet plant are usually 2.5X700 L. Due to the limitation of loopers, the length of the strip steel is expected to be more than 300 m . Taking 300m as an example, through the mass formula m = 〃v , the calculated unit weight of the bale should be more than 4.2t , and the outer diameter should be more than 1120mm . This fails to meet the 7:10 aspect ratio requirement.

Combined with the reality, the author starts from the requirements of the next process, and takes the minimum limit to ensure the requirements of the next process, so as to minimize the value of manpower M when tipping may occur . Then, even when the tipping limit is reached, due to the external force provided by the fixed rope during loading, the IM value can still ensure that no tipping will occur when the tipping limit is reached.
In order to enable the front-line operators to operate more intuitively, the quality of the feeding slab is usually limited to about 25t , and the finishing only needs to be organized according to two two-cut production, that is, four bales can be formed after finishing and slitting In this way, after removing the cut damage, etc., the weight of each genuine package is about 5t , that is, the outer diameter is about 1180mm .

1. ERW materials. Also limited by the looper , ERW hopes to use large rolls, that is, only strips are cut without cutting. For this reason, the author designs a special saddle for transport vehicles, and uses a special saddle structure in an internal transport vehicle.

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