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Analysis and control measures of coil shape of spinning machine
Abstract: the reeling machine is the key equipment for high-speed wire rod production. Starting with the reeling principle of the reeling machine, this paper analyzes the main factors affecting the coil shape in the reeling process, and puts forward the measures to control the coil shape.
[Key words]: spinning machine, spinning tube, pinch roll
1、 Foreword
In 1970s, 450 cantilever high-speed torsion free wire rod mill and Steyr friction controlled cooling line appeared in wire rod production. The application of these two new technologies and their continuous improvement in the future have greatly improved the output and quality of wire rod and brought about great changes in production. After the wire is rolled, it is spun into a circle by the wire drawing machine, which turns the high-speed linear wire into a coil with stable circle shape and uniform spacing. With the improvement of wire rolling speed and output, the requirements for wire drawing machine are becoming higher and higher. Therefore, many high-speed wire rod production enterprises will have unstable wire drawing circle in production, which will affect the product quality and smooth production.
2、 Structure and spinning process of spinning machine
(1) Structure of spinning machine. The wire drawing machine of high-speed wire rod in the rolling operation area of Laiwu Iron and steel Xinjiang company of Shandong Iron and Steel Group is a horizontal structure, which is located between the water-cooling box and the cold control roller table of the control cooling line behind the finishing mill. The spinning machine is composed of transmission device, hollow shaft, spinning disc, spinning tube, bevel gear, etc. The reeling machine is driven by a motor, which drives the hollow shaft to rotate through the meshing of a pair of bevel gears in the gear box. The reeling pipe is installed on the reeling disc, which is connected with the hollow shaft through bolts.
(2) Analysis of spinning process of spinning machine. When the reeling machine is working, it is fed into the hollow shaft of the reeling machine through the pinch roll in front of the reeling machine through the inlet conduit of the reeling machine. The hollow shaft drives the reeling disc and reeling tube to rotate together, so that the wire entering the hollow shaft will be discharged out of the coil along the tangential direction of the exit circumference of the reeling tube through the rotating reeling tube, and smoothly dumped on the air-cooled roller table to form a continuous coil.
When the wire passes through the high-speed spinning tube, under the action of the positive pressure of the tube wall, the sliding friction, the thrust of the finishing mill and pinch roll, and its own centrifugal force, the wire will gradually bend and deform with the shape of the spinning tube, gradually bend from the linear motion, and reach the required curvature at the outlet of the spinning tube to form a spiral coil, which will be uniformly and stably discharged in circles.
3、 Main parameters of spinning machine
According to the analysis of the principle of the wire drawing machine, it can be known that the factors affecting the coil drawing quality of the wire drawing machine mainly include the curve of the wire drawing pipe and the speed matching of the finishing mill, pinch roll and wire drawing machine.
(1) Space curve of spinning tube.
The drawing pipe curve can be divided into three parts:
1. lead in part: to ensure that the wire can fully enter the threading tube before entering the deformed part of the threading tube, and reduce the track offset caused by deformation force.
2. deformation area: the middle section of the spinning tube is expanded according to the Archimedes spiral. The helix starts from the direction of the rotation axis, and the included angle with the normal plane of the rotation axis gradually decreases from 90 ° to the outlet of the threading pipe at the end of the helix α= 1.6 ° ~ 1.9 °, the distance from each point on the axis of the threading pipe to the rotation axis, that is, the rotation radius r of this point gradually increases, and R ~ R0 within a certain range of the outlet section. The reeling tube rotates in the opposite direction of the wire. Since it only makes the circular motion of the fixed axis, the tangential speed of each point on the reeling tube is y=r (R is the turning radius of the corresponding points and the turning angular speed of the reeling machine).
(2) Speed matching of finishing mill, wire rod and wire drawing machine.
According to e Fink's forward slip formula, the wire speed is greater than the linear speed of the exit roll of the finishing mill, and the actual situation is complex, such as the change of steel temperature, friction, roll diameter and tension will cause the change of forward slip value. Therefore, in order to achieve the most stable wire drawing, it is necessary to ensure that the speed of the wire drawing machine is slightly higher than that of the finishing mill and slightly lower than the actual speed of the wire rod, so as to meet the consistency of the speed calculation results. The change of the lead coefficient of the reeling machine will directly cause the change of the coil diameter and the coil bias. If the spinning coefficient is too large, the diameter of the spinning coil will be smaller and the coil will be left along the spinning direction of the spinning machine; On the contrary, the coil diameter is too large, and the coil deviates to the right along the rotation direction of the spinning machine. Too large setting deviation of wire drawing coefficient will cause the coil to be unbalanced and laterally erected at the moment of wire drawing, seriously deviate from the axis line of wire drawing, and the coil shape is poor, or even unable to be rolled. According to different specifications and rolling speed, the lead factor of the wire drawing machine is generally taken as 2% ~ 10%.
4、 Factors influencing the coil shape of spinning machine and control measures
(1) Influence of threading pipe and measures:
1. poor forming of the threading tube during processing or improper installation position will cause changes in the space curve of the threading tube and the running track of the wire rod, and the speed and force of the wire rod in the threading tube will change, which will greatly reduce the service life of the threading tube; Select well processed threading pipe, and ensure the correct position of threading pipe during installation; 2. the wear on the inner wall of the reeling tube changes the running track of the wire in the reeling tube, resulting in poor ring deformation. In serious cases, it will also increase the vibration value of the eccentric reeling machine of the reeling disc. After the use of the reeling tube reaches the standard production capacity, the reeling tube shall be replaced in time to ensure that the reeling ring type is normal; 3. there is iron oxide scale accumulation in the wire feeding pipe, which hinders the operation of the wire rod and leads to disordered wire feeding circle; Use the maintenance downtime to clean the threading pipe in time.
(2) Influence and measures of process parameters matching between pinch roll and spinning machine
The speed matching requirements of finishing mill, pinch roll and wire drawing machine are high. If the process parameters of pinch roll or wire drawing machine are not set properly, the shape of steel stacking or wire drawing ring is often poor. As far as the pinch roll and the wire drawing machine are concerned, it can be seen that the pinch roll should slightly exceed the wire drawing machine by 0.04% to ensure the stable working state of the wire drawing machine, so the pinch roll should be 0.94% ~ 8.4% ahead of the finishing mill. There are three control states for the linear speed of pinch roll:
1. maintain the status. In order to avoid the speed increase of pinch roll due to the disappearance of the tension of rolled piece, resulting in the increase of the diameter of the last few rounds of wire rod, after the tail of rolled piece leaves the finishing mill, the linear speed of pinch roll is given to be reduced to the linear speed of finishing mill outlet minus a lag amount of rolled piece tail. When the lag speed setting value is 1, the rolled piece will maintain the original linear speed after the tail of rolled piece leaves the finishing mill;
2. tail deceleration. When rolling small wire rod, in order to reduce the coil diameter of the last few rounds, so as to avoid winding at the end of the wire in the collecting drum and facilitate the collection of coils, after the end of the rolled piece leaves the finishing mill, the linear speed of the pinch roll is reduced to the outlet linear speed of the finishing mill minus a lag at the end of the rolled piece. When the hysteresis speed setting value is not equal to zero, the linear speed of the rolled piece will be lower than the outlet speed of the finishing mill after the tail of the rolled piece leaves the finishing mill.
3. tail growth rate. When rolling large specifications, the rolling speed is low, and the wire rod needs to add a power to pass through the wire drawing machine. Therefore, after the tail of the rolled piece leaves the finishing mill, the linear speed of the pinch roll is set to increase to the outlet linear speed of the finishing mill plus a lag at the tail of the rolled piece, so that the linear speed of the rolled piece will be lower than the outlet speed of the finishing mill after the tail of the rolled piece leaves the finishing mill. During the production process, it is necessary to regularly check the limiting current value when the pinch roll clamps the steel. Only when the limiting current value is stable and the speed drops by 30 ~ 50rpm can it be considered as normal, otherwise it must be adjusted accordingly. The normal clamping pressure of pinch roll is generally set at about 2bar, and the high-pressure clamping pressure at the tail is generally 3 ~ 4bar.
5、 Concluding remarks
Wire rod production has a high requirement for the shape of the spinning circle, and the spinning quality directly affects the production rhythm. The reeling process of the reeling machine is complex. When the reeling condition is bad, it is necessary to carefully observe the displayed condition, carefully check, detect and carefully make adjustment records. Through the understanding of the reeling process, find out the causes and timely adjust and deal with them.
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15358968703
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15358968703