Rolling mill roll assembly
Rolling mill roll
The material of the roll should be selected according to the different conditions of the rolled material and the size of the rolling force. This rolling mill uses nickel-chromium-molybdenum infinitely cold-hardened ductile iron. The fillet of the roll journal should be processed according to the size required by the drawing, with a finish of Ra1.6 or above to avoid stress concentration. When turning the hole profile, the outer diameter of the inner ring of the bearing sleeved on the journal should be used as the reference (as the reference surface) to ensure the best concentricity between the hole profile and the journal. The position of the hole groove should be measured from the end of the fixed end of the roll body to ensure that the spacing between the hole profiles of each roll is the same.
Bearings
Four-row cylindrical roller bearings are used at both ends of the roll. The inner and outer rings can be separated. The outer diameter of the inner ring is φ312mm. It is installed on the roll shaft neck after preheating to 100℃. It is fixed on the roll shaft neck until the roll is scrapped. The four-row cylindrical roller bearing is wide and cannot be self-positioned. In order to make the four-row rollers evenly stressed, the roll box should be able to self-position. For this reason, the roll box transmits the force to the pull rod through the spherical end face of the pressing nut and the matching spherical pad. At the same time, the guide surface of the guide groove formed by the support seat and the pressure plate fixed on the support seat and the roll box is inlaid with a balancing block. The contact surface of the balancing block is spherical, so that the roll box can tilt slightly after being stressed.
Before assembling the inner ring of the bearing, pay attention to the following two points:
First, put the shoulder retaining ring on the shaft neck;
–Measure the size of the roll shaft neck and the size of the inner ring of the bearing. The interference ——should be between 0.06 and 0.09 mm.
When installing the inner ring of the bearing, it must be required to fit tightly with the moving labyrinth (I) and the shoulder of the roller. For this reason, during the cooling process after the inner ring is installed, it must be knocked along the circumference with a copper rod to make it close, or an axial force must be applied to make it close until it cools to room temperature.
In order to ensure the axial rigidity of the rolling mill, the fixed end of the roller adopts a bidirectional thrust tapered roller bearing. The axial clearance of this bearing must be guaranteed to be within the range of 0.10-0.15mm on this rolling mill. If the bearing clearance is found to be too large, it should be adjusted or replaced in time. When ordering bearings, the clearance must be required to be within the range of 0.10-0.15mm.
At the floating end, the roller meets the requirements of roller thermal expansion through the sliding between the inner sleeve of the four-row cylindrical roller bearing and its rollers, and the roller box is fixed axially.
Before assembly, all parts in the roller box should be cleaned with kerosene and the bearings should be cleaned with gasoline.
During assembly, the cavity of the roller box should be kept clean, and special attention should be paid to the lubrication of the bidirectional thrust tapered roller bearing, threaded sleeve, worm wheel and worm gear of the inner end cover of the fixed end.
After each roll change, it should be checked carefully. The four-row cylindrical roller bearing and the bidirectional thrust tapered roller bearing are lubricated with oil and gas. In order to avoid re-adjusting the axial clearance, the bidirectional thrust tapered roller bearing should be left in the roller box when changing the roller, and the fixing bolts should not be loosened. The bearing 829736 is not subjected to radial force.
When tightening the bolts of the fixed end flange, roller box and end cover, they should be staggered with each other, and the final tightening torque should not be less than 120Nm. The adjustment gasket must be made of thin iron sheet or other metal sheet (aluminum or copper), and shall not be replaced by rubber asbestos sheet or other non-metallic materials. During rolling, attention should be paid to the temperature rise of the roll itself (water should be poured at the roll pass to cool it) so that the working temperature rise of the bearing is not greater than 80℃.
Bearing seals
The seal of the four-row cylindrical roller bearing adopts the single-lip oil seal with inner skeleton produced by Guangzhou Mechanical Science Research Institute. The O-rings and dust rings used in other places are made of fluororubber. When changing the roller, pay attention to check the seal and replace it in time if it is damaged.
Axial adjustment of the rolls
The four roll boxes of the roll system are fixed. To align the hole type, the upper roll box at the fixed end is equipped with an axial adjustment device for the roll. When adjusting the axial direction, the worm is rotated, and the worm wheel is driven to rotate and move axially through the worm, thereby driving the bidirectional thrust tapered roller bearing installed in the external thread sleeve I to move the roll axially. The left and right rotation angles of the external thread sleeve I do not exceed 360°, the thread is M340×4, the axial adjustment amount is ±5mm, and only the upper roll can be adjusted.
Press down the nut and tie rod
The press-down nut and the tie rod are installed in the roller box and the support seat respectively. The tie rod is first installed in the support seat. The deadweight of the tie rod and the roller system are transmitted to the support seat by the tie rod’s shaft shoulder through the copper sleeve installed on the support seat.
After the upper and lower roller boxes are installed on the tie rod, in order to ensure that the four roller boxes are parallel to each other, 8 equal-height pads of equal height are made between the roller box and the support seat, and then the press-down nut is screwed onto the tie rod (before this, parts such as spherical pads should be put in first).
The press-down nut is made of bronze, and its end is matched with the spherical pad. The spherical pad is a quenched steel part, and the contact area of the two spheres should be ensured to be not less than 75%.
The press-down nut does not rotate when adjusting the mill opening, so after installation and adjustment, it needs to be equipped as a fixing pin between the roller box and the nut.
In order to ensure symmetrical adjustment of the opening of the upper and lower rollers, the four tie rods are all right-handed on the top and left-handed on the bottom.
The thread is a trapezoidal tooth with a sixth-grade precision. The force-bearing part of the thread has about ten pitches. In order to ensure that the bearing is evenly loaded, the roll box should be allowed to tilt with the bending of the roll. Therefore, there is a gap between the press-down nut and the roll box.
When assembling, pay attention to fill all the gaps around the press-down nut with grease. When changing the rolls at ordinary times, use a manual dry oil gun and aim at the lubrication point to add oil (at this time, the tie rod should be turned to bring the lubricating oil to the thread of the nut). Every time it is overhauled (at least once a year), it should be completely disassembled, cleaned, and re-oiled.
mill rolls balancing
Eight springs on the upper and lower sides are placed through the tie rod between the end cover and the balance nut to eliminate the thread gap between the press-down nut and the tie rod.
After the balance nut is installed on the column, a cylindrical pin pins it together with the press-down nut. When the opening changes, the balance nut does not rotate, but moves up and down with the roll box, so that the elastic force of the balance spring on it does not change with the change of the mill opening.
During assembly, attention should be paid to maintaining the distance between the balance nut and the press-down nut. Any hole on the balance nut is aligned with the pin hole on the press-down nut, and the internal thread cylindrical pin is inserted. The thread on the pin is used to pull out the pin.
The balancing force is about 1.2-1.4 times the weight to be balanced. The purpose is to eliminate all the gaps between the roll neck and the press-down nut. The balancing force can be determined by the height of the pre-loaded balancing spring.
Be careful not to increase the load of the press-down mechanism due to excessive balancing force. Compared with other balancing methods (hydraulic balancing, colloid balancing), the spring balancing method has the characteristics of low cost and easy use.
Mill Roll gap adjustment device
The roll gap adjustment device of the rolling mill includes two worm gear boxes, each with a pair of worm gear pairs and a gear shaft (one) driving the transmission system of two gear shafts (two) on both sides. The gear shafts (two) on both sides are connected to the two tie rods of the roll system by inner and outer spline sleeves. The hydraulic motor drives a pair of worm gear pairs to drive the gear shaft (one), and the gear shaft (one) drives the tie rod through the gear shafts (two) on both sides, so that the left and right tie rods rotate in the same direction to complete the roll gap adjustment.
If the roll gap adjustment device on one side needs to be adjusted separately, the mandrel in the worm (II) is rotated, and the cylindrical pin on the shaft rotates outward in the wheel groove of the worm (II) and is stuck. The retaining spring installed at the end of the shaft moves to one side with the spline sleeve, and the left and right worms are separated. One side is adjusted monotonically. After adjustment, the mandrel is reversed and closed. The two sides are connected as one and can be adjusted synchronously.
The hydraulic motor is installed on the housing of the roll gap adjustment device through a sleeve, and the flat key on the motor head is inserted into the connecting sleeve at the end of the worm. Using a hydraulic motor to adjust the roll gap in a large range is convenient and labor-saving.
When the roll gap adjustment device is working, the worm rotates one circle, and the roll opening changes by 0.2516 mm. In order to smoothly cover the roll gap adjustment device on the spline at the upper end of the tie rod, the gear shaft in the roll gap adjustment device has an internal spline sleeve. The gear shaft and tie rod on one side can be installed first, and the gear shaft and tie rod on the other side can be assembled after rotating the angle according to the actual requirements. During assembly, the housing of the roll gap adjustment device should be filled with lubricating grease, and the worm gear, gears and bearings are all grease-lubricated. Pay attention to refueling during maintenance.
When changing the roller, slide the spline sleeve on the transmission shaft in the same way as on one side to separate the left and right boxes and change the roller. Do the reverse operation to connect the left and right boxes.
