The high wire laying machine of Taiyuan Iron and Steel No. 3 Rolling Plant adopts the original Demark technology and is manufactured by Taiyuan Mining Machinery Factory. The laying head is one of the key production equipment on the wire rod production line. It is located between the water cooling section of the control cooling line after the finishing mill and the roll table of the unwinding conveyor. Its axis is inclined downward by 10° relative to the rolling line. The outgoing wire forms a continuous spiral coil and automatically falls on the air-cooled and loose-coiled transport roller table. After passing through the air-cooled and loose-coiled transport roller table, it falls onto the winding machine. The winding machine is turned over 90° and enters the P-F line.
1. Working principle
The laying machine is mainly composed of a transmission device, a hollow shaft, a laying tube, a laying disc and a bearing seat. After the wire rod is rolled out from the high-speed finishing mill, it is fed into the hollow shaft of the laying machine from the pinch rolls in front of the laying machine through the conduit. The motor drives the hollow shaft to rotate through the speed-increasing mechanism, and the hollow shaft drives the spinning tube and spinning disc fixed on the hollow shaft to rotate, so that the wire entering the hollow shaft is spit out along the tangential direction of the circumference through the spinning tube, and is spit out by its own weight. On the loose roll transport roller table.
2. There is a problem
(1) When rolling the wire rod with the specifications of d 5.5 mm ~ d 6.5 mm, due to the high rolling speed, which is 65 m/s and 55 m/s respectively, the coil of the wire falls on the air-cooled transport roller table is an Oval shape, stuck on the winding mandrel and forced to interrupt production. The production workers used tools such as crowbars to force the coil down, which seriously affected the quality of the roll shape and surface quality, and even affected the baler not being able to punch normally. Bales (there have been many problems with damage to the baler plain bearing housing).
(2) When rolling d5.5 mm ~ d6.5 mm wire rod, the wire laying is relatively dense. When the wire rod falls into the air-cooled roller table, the tail of the previous circle is pushed back by the tail of the previous circle, resulting in the laying machine At the export, the coil was wound and piled up, and the production was forced to be interrupted to replace the laying tube. It took at least 1.5 hours to replace a laying tube. At least 2 rolls of scrap, about 2 t.
(3) When rolling wire rods with specifications of d16 mm to d20 mm, the spinning tail of the laying machine is small and cannot go up and down on the set reel, resulting in interruption of production. As a last resort, the tail of the coil was cut off with an oxygen gun, which greatly reduced the yield.
The above problems seriously restrict and affect the smooth progress of production and the appearance quality of products.
3. Reason analysis
(1) When the laying machine is working, a certain speed is given to the laying tube, and the steel slides relatively in the laying tube. Under the action of centrifugal force, relative motion inertial force, and the frictional force generated by the sliding in the laying tube, the wire rod moves linearly. Bend gradually to achieve the required curvature at the exit of the laying tube.
The theoretical requirements of the high wire laying machine: the acceleration value at the entrance and exit of the laying tube is zero, the exit speed is zero, and the steel forms a stationary ring after passing through the laying machine.
f1 model: r=t-sin(2π) vr=[1-cos(2π)]αr=2πsin(2π)
The laying tube curve model is as follows: f2 model: z=t-sin(π) vz=[1+cos(π)]αz=sin(π)
According to the principle of equal flow per second, the spindle speed of the laying tube and the steel speed should satisfy: n=60 V/πD
In the formula, n is the rotating speed of the laying head, r/min; V is the rolling speed of the steel, m/s; D is the diameter of the coil, mm.
The technological parameters of the spinning machine used in our factory are as follows: motor power P=90 kW, D=1 050 mm, V=65 m/s.
It can be seen from the above formula:
First, if the angle of the nozzle of the laying tube is not suitable and V is not zero or too large, the coil will not fall into the roller table through the tray when the coil will leave the laying machine after spinning. However, it falls directly on the air-cooled roller and falls flat to form an ellipse, which makes it difficult for the coil to fall on the collecting drum. Second, when V increases, D must increase. Therefore, when rolling large-sized wire rods above d16.0 mm, the end of the wire rod is passed out of the finishing mill to increase the speed of the wire rod tail through the pinch rollers to increase the speed and ensure the tail coil. normal shape.
(2) Due to the centrifugal force of the wire in the laying tube, the error of the shape of the parts and the error caused by the assembly of the laying tube, the main inertia axis of the rotor center of gravity does not coincide with the axis, and the spinning machine must be tested for dynamic balance.
The allowable unbalance amount is generally: M=1/2·em
In the formula, e is the allowable eccentricity, and m is the mass of the rotating part.
Because the spinning motor balance requires high precision, for this reason, the pipe clamps of the spinning pipe must be closely matched with the spinning pipe, one at an interval of 150 mm, and there are firm and reliable limit pipe clamps in the axial direction to avoid causing Sudden coiling caused by tube deformation and movement.
(3) When the laying tube is simmered on the simmering machine, the correct shape is ensured by the thermal process, especially during the cooling process of the laying tube, the curve on the simmering machine is guaranteed to be in close contact with the laying tube by fixing the clip to prevent the tube Warp of the head to avoid changes in the shape of the spinning wire.
(4) The laying tube is divided into three sections: straight section, deformation section, and forming section. Through the segmental anatomy of the cross-section of the used laying tube, it is found that the motion trajectories of different specifications and different speeds are basically the same between the straight section and the deformed section; while between the deformed section and the forming section, different speeds have different trajectories. In fact, during rolling, when there are many large-gauge wires, the track grooves between the deformed section and the forming section have deep wear. rule.
4. Measures and countermeasures
(1) In view of the current situation that the nozzle of the laying tube in the original design is not conducive to adjustment, a top wire is added on the first clip of the nozzle of the laying machine to perform cold adjustment during the process, which has changed the adjustment of no nozzle on the laying machine in the past. of insufficiency. When rolling small-sized wire rods of d5.5 mm ~ d6.5 mm, by adjusting the angle of the nozzle, that is, the forward stroke speed, ensure that the distance between the center line of the nozzle and the laying disc is between 37 mm and 42 mm. The effect is the best, and it can meet the large-scale circle shape while meeting the small-size circle shape.
(2) In view of the lack of an adjustable device on the lower tray of the original laying machine, an adjustable transition plate is added to the lower tray of the laying machine, so that the coil does not fall directly on the roller table after laying, but is adjusted to cooperate with the nozzle. , so that the quality of the ring shape is greatly improved.
(3) Improve the assembly quality of the laying tube, so that the tube clamp and the laying tube are closely matched, and the deformation of the laying tube and the resulting disorder caused by the centrifugal force caused by the large gap between the laying tube and the tube clip are eliminated. roll.
(4) Strengthen the process management, and use different laying tubes when rolling small-sized and medium-sized, and large-sized wire rods to ensure the quality of the ring.
After nearly 3 years of on-site use, the results have been remarkable.
In 1999, it was recorded in the data that the laying tube was replaced for 96 hours during the year, and the scrap steel was 100 t. Based on the steel price of 2,000 yuan/t at that time, the direct loss was about 200,000 yuan. As calculated by producing 30 t of steel per hour, at least 2 940 t of steel will be produced less in one year.
After taking targeted measures, the quality of the circle has improved year by year. According to the records, in 2001, the normal production hours were affected by the replacement of the laying tube and the adjustment test, the maximum was only 22 hours, and the scrap steel was 15 t. After that, it decreased year by year. While greatly improving the high wire yield, it effectively reduced the downtime and the labor intensity of workers.