The function of the current limit value adjustment of the pinch roller
By adjusting the current limit value of the pinch roller, the working state of the pinch roller and the clamping ability of the pinch roller during the clamping process can be changed. The generated clamping force should be controlled to be less than the product of the pressing force and the coefficient of friction, so as to accurately match the peripheral speed of the pinch roller and the wire speed, thereby ensuring good spinning quality.
Speed setting of pinch roller and its technical requirements
The speed of the pinch roll generally exceeds 3% to 5% of the exit speed of the finishing mill, and can be increased further when the rolling speed is very high, but generally should not exceed 10%. The speed of the pinch roll is set by manually inputting the diameter of the pinch roll to the computer, and then the computer calculates the speed calculation value of the pinch roll according to the rolling speed and the pinch roll overspeed coefficient, which is the pinch roll speed reference value.
The technical requirements for pinch rollers are as follows:
The setting range of the pinch roll gap is 0.2~2mm, which can be adjusted according to different specifications and steel grades; the working pressure of the pinch roll cylinder is 0.2~0.35MPa, which can be adjusted according to different specifications and steel grades; the installation of the pinch roll guides The alignment is more strict. The import guide should be aligned with the clamping groove, push it in place, and then clamp and fix it. The exit guide and the pinch roller surface maintain a micro gap and are clamped and fixed
The main reasons for the pile-up accident of the pinch roll laying machine are:
(1) The detection signal of the photocell in front of the pinch roller fails, so that the pinch roller cannot be opened/closed on time, resulting in stacking of steel;
(2) The hole grooves of the pinch rolls do not match the rolling specifications, or the upper and lower rolls are dislocated, causing the steel pile to be blocked;
(3) The guide guard is installed incorrectly, the guide guard and the roller ring are seriously worn, or there are foreign objects in the guide guard, which leads to the pile of steel;
(4) There are foreign objects in the laying pipe, deformation of the laying pipe, perforation or serious wear of the laying pipe, which cause steel piles;
(5) The unreasonable setting of the pinch roll gap or the working pressure of the cylinder causes the steel to be stacked or broken;
(6) The unreasonable speed coordination of the finishing mill, pinch roll and laying machine causes steel stacking;
(7) The tension between the finishing mill and the pinch roll is too large, causing the pull to break;
(8) Internal quality defects of wire rods (smelting defects) or rolling defects (severe folding) cause piled steel
The role of pinch roll speed increase in rolling large-size and high-wire products
When rolling large-scale wire rod products at low speed, due to the large size and low speed, after the tail of the rolling piece leaves the sizing machine, due to factors such as the resistance of the water-cooling section, the spinning circle at the end of the coil will be small or twisted, and it cannot be spun out. The silk forms a circle and stays in the spinning tube, causing an accident. Therefore, when the rolling speed is lower than about 22m/s, it is necessary to use the control method of the pinch roll and the laying machine to increase the speed when the tail of the rolling piece leaves the sizing machine. The acceleration ensures that the tail of the rolling piece completes spinning at a speed of about 22m/s.
The main reasons for the poor loop formation of the wire at the exit of the laying machine are as follows:
(1) The tension between the rolling mills is too large, and the speed fluctuations of the finishing mill and the reducing and sizing mill are too large;
(2) The deviation of the centering adjustment in the water cooling section, the wear and corrosion of the nozzle guide tube cause the unstable operation of the rolling stock;
(3) The pinch roller clamping force is inappropriate due to the wear of the pinch roller ring or the failure of the cylinder linkage mechanism;
(4) Deviation of the bending curve of the laying tube, serious wear and tear of the laying tube, adhesion of the iron oxide scale of the laying tube, and poor loop formation caused by the dynamic imbalance of the laying tube;
(5) Improper speed configuration of reducing and sizing machine, pinch roll and laying machine, serious speed fluctuation of rolling mill, causing the speed of rolling stock to be faster or slower, resulting in uneven coil size;
(6) The roller table after the laying machine is not high enough. When the temperature of the rolling piece is high, the coil is too soft, and the coil falls on the receiving platform, which will become an ellipse or a random circle.
Influence of the lead coefficient of the laying machine on the laying state of the coil
The change of the lead coefficient of the laying machine will directly cause the change of the diameter of the coil and the direction of the cloth ring, which will have a certain impact on the subsequent winding. If the laying coefficient is too large, the diameter of the laying coil will be too small, and the coil will deviate to the left along the rotation direction of the laying machine; If the setting deviation of the spinning coefficient is too large, the spinning of the coil will be instantly unbalanced and sideways, seriously deviate from the spinning axis, and the shape of the coil will be poor, and even the coil cannot be collected. According to different specifications and rolling speeds, the lead factor of the laying machine is generally between 2% and 10%.
The method of avoiding steel jamming on laying machine during rolling of large-size rolling stock
To avoid the laying machine jamming during the rolling of large-size rolled products, first of all, it is necessary to ensure the control ability of the pinch roll to the spinning tail of the large-size wire rod, which is based on the correct roll gap, pressure, lead, torque, Based on the current limit setting, so that the tail of the rolling stock can be spit out smoothly. Secondly, due to the small side pressing angle and relatively small roll gap of the large-size finished product, the appearance of flash ears of the finished product at any time must be strictly controlled under the guarantee of the basic rolling conditions, which is to ensure the large-size product. The key to the wire rod head and the middle of the laying machine is that there is no steel jam accident.
The main reasons for the vibration of the laying machine and the solutions are:
(1) The large fluctuation of the motor speed causes the vibration of the body, and the motor should be optimized or the rolling process should be optimized;
(2) If the coupling is misaligned or the bolts are loosened to cause vibration, the alignment should be re-aligned, and the radial deviation should not exceed 0.1mm;
(2) The bearing in the gearbox is damaged or the clearance is too large to cause vibration, and the bearing clearance should be disassembled every year to check whether the bearing clearance meets the standard; (4) The bevel gear in the gearbox is improperly adjusted, and the meshing difference causes vibration, and the tooth backlash should be guaranteed to be 0.2 ~ 0.4mm , the meshing surface is greater than 20%;
(5) If the tap plate is cracked or the dynamic imbalance causes vibration, it is necessary to regularly check whether the tap is cracked and whether the dynamic balance block is lost, and the spinning tube and the spinning disc are installed and then dynamically balanced;
(6) Vibration caused by excessive clearance between the tap, spinning disc and the coaming disc. When the clearance is less than 2mm, the spinning disc and coaming disc will be rubbed due to the heating of the tapping tap, and the coaming disc should be repaired. , which will cause steel to be stuck in the gap, resulting in damage to the tap and the body;
(7) The dynamic unbalance of the laying pipe causes vibration, the weight, material and wall thickness of the laying pipe are not standardized, the bending curve of the laying pipe is not standardized, the installation of the pipe clamp of the laying pipe is not standardized, the laying pipe is seriously worn or the iron oxide scale is sticking. If it is connected, it will cause dynamic imbalance, so the laying tube should be replaced in time.
The role of the blowing gas in the laying machine
Due to the high-speed rolling of the high-speed wire rod mill, a horizontal laying head designed with a certain inclination (the angle between its axis and the horizontal is 10° to 20°) is widely used. “Scratch” on the inner wall of the laying tube. A high-pressure air purging nozzle is installed at the inlet end of the laying tube, which is used to purge the laying tube, which is beneficial to slow down the wear of the laying tube, enhance the heat dissipation performance of the laying tube, and prolong the service life of the laying tube . The air supply can be released before the end of the wire leaves the finishing mill or reducing sizing machine, or the purge time can be determined by the operator, or it can be purged continuously.