Method for improving grinding accuracy of backing bearing of twenty-roller mill

Abstract

The application provides a method for improving the grinding precision of a twenty-roller mill backing bearing, wherein each size of the backing bearing is analyzed, key sizes needing to be controlled are found out, a double top is used to fix a grinding clamp, a top force is controlled between 1300-1400 N, a pressure is controlled between 34-40 Pa, and the bearing clearance is reduced to 0 through an inflatable sleeve to avoid the influence of the bearing clearance on the grinding precision in the grinding process; when clamping, a micrometer gauge is arranged on the two positions of the back bearing, the difference between the two position micrometer gauges is controlled to be within 2 mu m, and the clamping precision is improved; in the grinding process, the manual adjustment of the allowance grinding according to the grinding roller type measurement precision can efficiently grind the backing bearing meeting the high size precision, and ensures that the repaired backing bearing can meet the working performance and product quality requirements of the rolling mill.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of backing bearing repair, in particular to a method for improving the grinding precision of backing bearings of a 20-roller mill. BACKGROUND

[0002] The backing support roller is assembled by a backing bearing, a mandrel and a saddle. The backing support roller is a key component for bearing and transmission of the 20-roller mill, and belongs to a high-precision mechanical component. The outer diameter surface of the backing bearing outer ring directly contacts the intermediate roller. The backing bearing outer ring rotates while bearing the rolling force. Therefore, the outer ring not only has sufficient rigidity and fatigue strength through special heat treatment, but also is subjected to high-precision fillet machining. The six backing bearings on the same backing support roller are matched according to the wall thickness control. The wall thickness difference between the adjacent two bearings is ≤0.002 mm, and the wall thickness difference of the single backing support roller is ≤0.006 mm, which is high in the middle and low on both sides. Once the error is too large, the forces on the backing bearings of the column support roller during rolling will be extremely unbalanced. The outer diameter surface of the backing bearing outer ring directly contacts the intermediate roller. The backing bearing outer ring rotates while bearing the rolling force. In long-term use, due to factors such as wear and fatigue, the bearing is prone to have defects such as precision reduction and surface indentation, which will seriously affect the working performance of the rolling mill and the product quality. After the backing bearing has the above defects, the outer ring of the bearing is usually ground to remove the above defects, so that the surface reaches the required dimensional accuracy before being put into use. However, the grinding method of the existing grinding machine cannot meet the high precision requirement of the backing support roller. The backing bearing repaired by the method of the existing technology cannot guarantee the working performance of the rolling mill and the product quality. SUMMARY

[0003] In order to solve the problem that the backing bearing repaired by the grinding method of the existing grinding machine cannot meet the high precision requirement of the backing support roller, the present application provides a method for improving the grinding precision of the backing bearings of a 20-roller mill.

[0004] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0005] A method for improving the grinding precision of the backing bearings of a 20-roller mill, comprising the following steps:

[0006] S1, clamping the backing bearing: clamping the backing bearing to be machined on the grinding machine through a grinding clamp, the grinding clamp can make the bearing outer ring rotate and the bearing inner ring fixed during grinding machining, the double centers of the grinding machine are used to fix the grinding clamp during clamping, and the bearing clearance is reduced to 0 during clamping;

[0007] S2, editing the grinding machining program according to the size of the backing bearing:

[0008] S3, adopt the edited grinding processing program to grind the backing bearing on the grinding fixture, in this process, the following method is used to control the machining precision, so that the wall thickness difference of the adjacent two backing bearings is ≤0.002mm, the roll type precision of a single backing bearing is controlled to be ≤0.002mm, the circular runout is ≤0.002mm, and 25*15mm curve chamfers are added at both ends of the backing bearing:

[0009] Diameter machining precision control: for the 6 backing bearings in the backing support roller, first check the wear condition of the backing bearing surface after taking out, grind the most seriously damaged backing bearing first, take the diameter of the first ground backing bearing ±0.006mm as the target, and grind the remaining 5 backing bearings;

[0010] Roll type machining precision control: in the grinding process, the roll type precision is controlled by repeatedly measuring and manually adjusting the installation error value, and the adjustment method is as follows: click "manual installation error" in the grinding program, then click "installation error", input the adjusted installation error value and press enter to confirm; The adjusted installation error value = the diameter of the headstock after grinding - the diameter of the tailstock after grinding + the current error value.

[0011] Further, the grinding processing program includes an outer circle flat roller grinding program and a curve chamfering program, the outer diameter surface of the backing bearing is ground by using the outer circle flat roller grinding program during grinding processing, and chamfers are machined at both ends of the backing bearing by using the curve chamfering program.

[0012] Further, the outer circle flat roller grinding program includes four processes, process one, process two, process three and process four, the parameter setting of process one is: grinding wheel linear speed 20m / s, headstock speed 14r / min, support plate speed 800mm / min, continuous feed 0mm / min, periodic feed 0.0030mm; The parameter setting of process two is: grinding wheel linear speed 18m / s, headstock speed 15r / min, support plate speed 600mm / min, continuous feed 0mm / min, periodic feed 0.0020mm; The parameter setting of process three is: grinding wheel linear speed 16m / s, headstock speed 15r / min, support plate speed 400mm / min, continuous feed 0mm / min, periodic feed 0.0010mm; The parameter setting of process four is: grinding wheel linear speed 14m / s, headstock speed 16r / min, support plate speed 300mm / min, continuous feed 0mm / min, periodic feed 0.0000mm.

[0013] Further, the parameter setting of the curve chamfering program is: grinding wheel linear speed 22m / s, headstock speed 24r / min, support plate speed 200mm / min, continuous feed 0mm / min, periodic feed 0.0050mm, support plate reversal delay 2s.

[0014] Furthermore, the grinding fixture includes a shaft body, an expandable sleeve, two clamping members, a hydraulic connector, an oil pipe, and a manual pressure pump. The shaft body has an oil inlet channel, one end of which passes through the outer peripheral wall of the shaft body to form an oil inlet. The expandable sleeve is fitted onto the shaft body, and the expandable sleeve has an oil cavity communicating with the end of the oil inlet channel away from the oil inlet. The two clamping members are located at opposite ends of the expandable sleeve and are both fitted onto the shaft body. At least one clamping member is detachably connected to the shaft body. Each clamping member includes an inner clamping disc fitted onto the shaft body and an outer clamping disc rotatably wrapped around the outer peripheral surface of the inner clamping disc. One end of the oil pipe is connected to the oil inlet through the hydraulic connector, and the manual pressure pump is installed at the other end of the oil pipe.

[0015] Further, step S1 includes the following steps:

[0016] S11, remove one of the clamping members from the shaft body, put the backing bearing to be ground onto the expandable sleeve, and then install the removed clamping member onto the shaft body, so that the two clamping members are located at opposite ends of the backing bearing to be ground.

[0017] S12, the grinding fixture equipped with the backing bearing is hoisted to the grinding machine, and the two centers of the grinding machine are used to press the opposite ends of the shaft body respectively to ensure that the pressing force of the centers on the shaft body is between 1300-1400N.

[0018] S13, connect one end of the oil pipe to the oil inlet through the oil pressure connector, and install dial indicators on the upper busbar and side busbar of the backing bearing respectively;

[0019] S14, Connect a manual hydraulic pump to the other end of the oil pipe, pressurize the hydraulic oil in the oil chamber with the help of the manual hydraulic pump, causing the expandable sleeve to expand. After the expandable sleeve expands, it drives the inner ring of the backing bearing to expand. During this process, by tapping and rotating the outer diameter surface of the backing bearing, the inner ring of the bearing expands evenly, thereby making the bearing clearance become 0.

[0020] S15, lock the two clamping members in the axial direction so that the centers of the two clamping members match. After locking, the inner clamping discs of the two clamping members clamp the opposite ends of the inner ring of the backing bearing, and the outer clamping discs of the two clamping members clamp the opposite ends of the outer ring of the backing bearing.

[0021] S16, the outer disk of the fixture and the headstock of the grinding machine are connected by a plug bar. Then, the headstock of the grinding machine drives the outer disk of the fixture and the outer ring of the bearing of the backing bearing to rotate. The micrometer readings at the upper and side busbar positions are read, and the difference between the two values ​​is controlled within 2μm.

[0022] Furthermore, in step S16, if the difference between the dial gauge readings at the upper busbar and the side busbar is greater than 2μm, the clamping member is adjusted so that the backing bearing can rotate relative to the expandable sleeve. After rotating the backing bearing to adjust its angle, the clamping member is re-locked until the difference between the two readings is controlled within 2μm.

[0023] Furthermore, a pressure gauge is installed at the connection between the manual hydraulic pump and the oil pipe to detect the pressure inside the oil pipe and ensure that the pressure inside the oil pipe is maintained between 34-40 Pa during the bearing clearance adjustment process.

[0024] By adopting the above technical solution, the present invention has the following beneficial effects:

[0025] The method for improving the grinding accuracy of backing bearings in a 20-roll mill according to the present invention analyzes the dimensions of the backing bearings to identify the key dimensions that need to be controlled. Experiments show that the accuracy of each backing bearing in the backing support roll is extremely important. The wall thickness difference between two adjacent bearings should be ≤0.002mm, the roll shape accuracy of a single backing bearing should be controlled to ≤0.002mm, and the circular runout should be ≤0.002mm. Furthermore, adding 25*15mm curved chamfers at both ends of the backing bearings can better prevent concentrated loads at the ends from damaging the intermediate rolls. To achieve this grinding accuracy, the method for improving the grinding accuracy of backing bearings in a 20-roll mill according to the present invention uses double centers for fixing. The grinding fixture is fixed, with the top force controlled between 1300-1400N and the pressure controlled between 34-40Pa. The bearing clearance is reduced to zero by pressurizing with an expandable sleeve, so as to avoid the bearing clearance affecting the grinding accuracy during the grinding process. When clamping, dial indicators are set at two positions, the upper generatrix and the side generatrix of the backing bearing. By setting dial indicators at two positions, the runout difference is controlled within 2μm, which improves the clamping accuracy. During the grinding process, the tolerance is manually adjusted according to the grinding roll type measurement accuracy. This allows for efficient grinding of backing bearings that meet the above-mentioned high dimensional accuracy, ensuring that the repaired backing bearings can meet the working performance and product quality requirements of the rolling mill. Attached Figure Description

[0026] Figure 1 This is a flowchart of a preferred embodiment of the method for improving the grinding accuracy of the backing bearing of a 20-roll mill according to the present invention.

[0027] Figure 2 A structural diagram of the grinding fixture used in the method for improving the grinding accuracy of the backing bearing of a 20-roll mill, which is a preferred embodiment of the present invention;

[0028] Figure 3 for Figure 2 Sectional view along line AA;

[0029] Explanation of main component symbols

[0030] 10. Backing bearing; 11. Inner ring of bearing; 12. Outer ring of bearing; 20. Grinding fixture; 21. Shaft body; 210. Oil inlet channel; 211. Oil inlet; 22. Expandable sleeve; 220. Oil cavity; 23. Clamping component; 231. Inner plate of fixture; 232. Outer plate of fixture. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Please see Figures 1 to 3 A preferred embodiment of the present invention provides a method for improving the grinding accuracy of backing bearings in a 20-roll mill, comprising the following steps:

[0035] S1, clamping the backing bearing: The backing bearing 10 to be processed is clamped on the grinding machine (not shown) through a grinding fixture 20. The grinding fixture 20 enables the outer ring 12 of the backing bearing 10 to rotate while the inner ring 11 of the bearing remains stationary during grinding. The grinding fixture 20 is fixed by the double centers of the grinding machine (not shown) during clamping, and the bearing clearance is reduced to 0 during clamping.

[0036] In this embodiment, the grinding fixture 20 includes a shaft body 21, an expandable sleeve 22, two clamping members 23, a hydraulic connector (not shown), an oil pipe (not shown), and a manual pressure pump (not shown). The shaft body 21 has an oil inlet channel 210, one end of which penetrates the outer peripheral wall of the shaft body 21 to form an oil inlet 211. The expandable sleeve 22 is fitted onto the shaft body 21, and has an oil cavity 220 communicating with the end of the oil inlet channel 210 away from the oil inlet 211. The two clamping members 23 are located at opposite ends of the expandable sleeve 22 and are both fitted onto the shaft body 21, with at least one clamping member 23 being detachably connected to the shaft body 21. Each clamping member 23 includes an inner clamping disc 231 fitted onto the shaft body 21 and an outer clamping disc 232 rotatably wrapped around the inner clamping disc 231. Specifically, at least one clamping member 23's inner clamping disc 231 is detachably connected to the shaft body 21 via threads. One end of the oil pipe is connected to the oil inlet 211 via a hydraulic connector, and a manual pressure pump is installed at the other end of the oil pipe. The following steps are included when using this grinding fixture to clamp the backing bearing:

[0037] S11, remove one of the clamping parts 23 from the shaft body 21, put the backing bearing 10 to be ground onto the expandable sleeve 21, and then install the removed clamping part 23 onto the shaft body 21, so that the two clamping parts 23 are located at opposite ends of the backing bearing 10 to be ground.

[0038] S12, the grinding fixture 20 equipped with the backing bearing 10 is hoisted to the grinding machine, and the two centers of the grinding machine are used to press the opposite ends of the shaft body 21 to ensure that the pressing force of the centers on the shaft body 21 is between 1300-1400N.

[0039] S13, connect one end of the oil pipe to the oil inlet 211 through the oil pressure connector, and install dial indicators (not shown) on the upper busbar and side busbar of the backing bearing 10 respectively.

[0040] S14, a manual hydraulic pump is connected to the other end of the oil pipe. The hydraulic oil in the oil chamber 220 is pressurized by the manual hydraulic pump, which causes the expandable sleeve 22 to expand. After the expandable sleeve 22 expands, it drives the inner ring 11 of the backing bearing 10 to expand. During this process, the outer diameter surface of the backing bearing 10 is tapped and rotated to make the inner ring 11 of the bearing expand evenly, thereby reducing the bearing clearance to 0 and avoiding the impact of clearance on the grinding accuracy of the backing bearing 10.

[0041] In this embodiment, a pressure gauge (not shown) is also installed at the connection between the manual hydraulic pump and the oil pipe to detect the pressure in the oil pipe and ensure that the pressure in the oil pipe is maintained between 34-40 Pa during the bearing clearance adjustment process to prevent damage to the expandable sleeve 22.

[0042] S15, the two clamping members 23 are locked axially along the shaft body 21 to securely hold the backing bearing 10. Specifically, the clamping members 23 can be rotated to bring them closer together, thereby locking the backing bearing 10. After locking, the inner clamping discs 231 of the two clamping members 23 are respectively clamped at the opposite ends of the inner ring 11 of the backing bearing 10, and the outer clamping discs 232 of the two clamping members 23 are respectively clamped at the opposite ends of the outer ring 12 of the backing bearing 10.

[0043] S16, the clamping outer disk 232 of the clamping member 23 and the headstock of the grinding machine (not shown) are connected via a plunger (not shown). The headstock of the grinding machine drives the clamping outer disk 232 and the outer ring 12 of the backing bearing 10 to rotate. The runout values ​​of the dial indicator at the upper and side generatrices are read. The clamping is completed when the difference between the two values ​​is controlled within 2μm. If the difference between the dial indicator values ​​at the upper and side generatrices is greater than 2μm, the clamping member 23 is adjusted so that the backing bearing 10 can rotate relative to the expandable sleeve 22. After rotating the backing bearing 10 to adjust the bearing angle, the clamping member 23 is re-locked until the difference between the two values ​​is controlled within 2μm.

[0044] In this embodiment, the insert bar is connected to the outer disk 232 of the clamping member 23, which is located away from the oil inlet 211. Specifically, the outer disk 232 and the headstock of the grinding machine are respectively provided with slots, and the two ends of the insert bar are respectively inserted into the slots on the outer disk 232 and the headstock of the grinding machine. Since the insert bar is connected to the outer disk 232 of the clamping member 23, which is located away from the oil inlet 211, the movement of the insert bar is prevented from being obstructed by the oil pipe during the rotation of the outer disk 232. Furthermore, the inner diameter surface and side surface of the backing bearing 10 must be thoroughly cleaned before clamping to prevent impurities from reducing the clamping accuracy.

[0045] S2, edit the grinding program according to the backing bearing size.

[0046] In this embodiment, the grinding process includes an external cylindrical flat roller grinding process and a curve chamfering process. During grinding, the external cylindrical flat roller grinding process is used to grind the outer diameter surface of the backing bearing 10, and the curve chamfering process is used to machine chamfers at both ends of the backing bearing 10. Specifically, the external cylindrical flat roller grinding process includes four processes: process one, process two, process three, and process four. The parameters for process one are set as follows: grinding wheel linear speed 20 m / s, headstock speed 14 rpm, pallet speed 800 mm / min, continuous feed 0 mm / min, and periodic feed 0.0030 mm. The parameters for process two are set as follows: grinding wheel linear speed 18 m / s, headstock speed 15 rpm, pallet speed 600 mm / min, and continuous feed 0 mm / min. The cycle feed is 0.0020 mm; the parameters for process three are: grinding wheel linear speed 16 m / s, headstock speed 15 rpm, pallet speed 400 mm / min, continuous feed 0 mm / min, and cycle feed 0.0010 mm; the parameters for process four are: grinding wheel linear speed 14 m / s, headstock speed 16 rpm, pallet speed 300 mm / min, continuous feed 0 mm / min, and cycle feed 0.0000 mm. See Table 1 for details.

[0047] Table 1

[0048] Parameters Process 1 Process 2 Process 3 Process 4 Wheel linear speed (m / s) 20 18 16 14 Headstock speed (rpm) 14 15 15 16 Table speed (mm / min) 800 600 400 300 Continuous feed (mm / min) 0.0000 0.0000 0.0000 0.0000 Periodic feed (mm) 0.0030 0.0020 0.0010 0.0000

[0049] In this embodiment, the parameters of the curve chamfering program are set as follows: grinding wheel linear speed 22 m / s, headstock speed 24 rpm, pallet speed 200 mm / min, continuous feed 0 mm / min, periodic feed 0.0050 mm, and pallet reversal delay 2 seconds. See Table 2 for details.

[0050] Table 2

[0051] Parameters Process Wheel linear speed (m / s) 22 Headstock speed (rpm) 24 Table speed (mm / min) 200 Continuous feed (mm / min) 0.0000 Periodic feed (mm) 0.0050 Table reversal delay (s) 2

[0052] S3. The backing bearing 10 on the grinding fixture 20 is ground using the edited grinding program. During this process, the machining accuracy is controlled by the following methods to ensure that the wall thickness difference between two adjacent backing bearings is ≤0.002mm, the roll shape accuracy of a single backing bearing is controlled to ≤0.002mm, the circular runout is ≤0.002mm, and a 25*15mm curved chamfer is added to both ends of the backing bearing.

[0053] Diameter machining accuracy control: For the six backing bearings 10 in the backing support roller, after the machine is off, the wear condition of the backing bearing 10 surface is first checked. The backing bearing 10 with the most severe damage is ground first. With the diameter of the first ground backing bearing 10 being ±0.006mm as the target, the remaining five backing bearings 10 are ground.

[0054] Control of roller profile machining accuracy: During the grinding process, the roller profile accuracy is controlled by repeatedly measuring and manually adjusting the installation error value. The adjustment method is as follows: Click "Manual tolerance" in the grinding program, then click "Installation error", enter the adjusted tolerance value and press Enter to confirm; the adjusted tolerance value = headstock diameter after grinding - tailstock diameter after grinding + current error value.

[0055] For example: after grinding, the headstock diameter (299.904mm) - after grinding, the tailstock diameter (299.915mm) + the current error value (0.010mm) = the adjusted tolerance value (-0.001mm). Then, enter the adjusted tolerance value -0.001 in the "Installation Error" column and press Enter to confirm. Click "Y" on the measurement results interface to continue grinding.

[0056] The method for improving the grinding accuracy of backing bearings in a 20-roll mill according to the present invention analyzes the dimensions of each backing bearing 10 to identify the key dimensions that need to be controlled. Experiments show that the accuracy of each backing bearing 10 in the backing support roll is extremely important. The wall thickness difference between two adjacent bearings should be ≤0.002mm, the roll shape accuracy of a single backing bearing should be controlled to ≤0.002mm, and the circular runout should be ≤0.002mm. Furthermore, adding 25*15mm curved chamfers at both ends of the backing bearing can better prevent concentrated loads at the ends from damaging the intermediate roll. To achieve this... The present invention improves the grinding accuracy of the backing bearing of a 20-roll mill by employing a double-center method to fix the grinding fixture 20. The center force is controlled between 1300-1400N, and the pressure is controlled between 34-40Pa. Pressure is applied through an expandable sleeve 22 to reduce the bearing clearance to zero, preventing the bearing clearance from affecting the grinding accuracy during the grinding process. During clamping, dial indicators are placed at two positions: the upper generatrix and the side generatrix of the backing bearing 10. The difference in runout between these two positions is controlled to be within 2μm, improving clamping accuracy. During the grinding process, manual adjustment of the tolerance after measuring the grinding roll type allows for efficient grinding of the backing bearing 10 to meet the aforementioned high dimensional accuracy requirements, ensuring that the repaired backing bearing 10 meets the working performance and product quality requirements of the mill.

[0057] In summary, by effectively reducing the internal clearance of the bearing to zero through grinding with a grinding fixture, and by using the double centers of the grinding machine, manual tolerance adjustment, and the grinding fixture, the roller profile accuracy of the backing bearing ≤0.002mm and the circular runout ≤0.002mm can be effectively controlled, providing an accurate guarantee for the fitting accuracy of the backing support roller and the dimensional accuracy of the backing bearing itself.

[0058] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for improving the grinding accuracy of backing bearings in a 20-roll mill, characterized in that: Includes the following steps: S1, clamping the backing bearing: clamp the backing bearing to be processed onto the grinding machine using a grinding fixture. The grinding fixture enables the outer ring of the bearing to rotate while the inner ring of the bearing remains stationary during grinding. The grinding fixture is fixed by the double centers of the grinding machine during clamping, and the bearing clearance is reduced to 0 during clamping. S2, Edit the grinding program according to the dimensions of the backing bearing: S3. The backing bearings on the grinding fixture are ground using the edited grinding program. During this process, the following methods are used to control the machining accuracy so that the wall thickness difference between two adjacent backing bearings is ≤0.002mm, the roll profile accuracy of a single backing bearing is controlled to ≤0.002mm, the circular runout is ≤0.002mm, and a 25*15mm curved chamfer is added to both ends of the backing bearings: Diameter machining accuracy control: For the six backing bearings in the backing support roller, after the machine is off, the wear condition of the backing bearing surface is first checked. The backing bearing with the most severe damage is ground first. The diameter of the first ground backing bearing is ±0.006mm as the target, and the remaining five backing bearings are ground. Control of roller profile machining accuracy: During the grinding process, the roller profile accuracy is controlled by repeatedly measuring and manually adjusting the installation error value. The adjustment method is as follows: Click "Manual tolerance" in the grinding program, then click "Installation error", enter the adjusted tolerance value and press Enter to confirm; the adjusted tolerance value = headstock diameter after grinding - tailstock diameter after grinding + current error value.

2. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 1, characterized in that: The grinding process includes an outer cylindrical flat roller grinding process and a curve chamfering process. During the grinding process, the outer cylindrical flat roller grinding process is used to grind the outer diameter surface of the backing bearing, and the curve chamfering process is used to process chamfers at both ends of the backing bearing.

3. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 2, characterized in that: The external cylindrical flat roller grinding program includes four processes: process one, process two, process three, and process four. The parameters for process one are set as follows: grinding wheel linear speed 20 m / s, headstock speed 14 rpm, pallet speed 800 mm / min, continuous feed 0 mm / min, and periodic feed 0.0030 mm. The parameters for process two are set as follows: grinding wheel linear speed 18 m / s, headstock speed 15 rpm, pallet speed 600 mm / min, continuous feed 0 mm / min, and periodic feed 0.0020 mm. The parameters for process three are set as follows: grinding wheel linear speed 16 m / s, headstock speed 15 rpm, pallet speed 400 mm / min, continuous feed 0 mm / min, and periodic feed 0.0010 mm. The parameters for process four are set as follows: grinding wheel linear speed 14 m / s, headstock speed 16 rpm, pallet speed 300 mm / min, continuous feed 0 mm / min, and periodic feed 0.0000 mm.

4. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 2, characterized in that: The parameters of the curve chamfering program are set as follows: grinding wheel linear speed 22 m / s, headstock speed 24 rpm, pallet speed 200 mm / min, continuous feed 0 mm / min, periodic feed 0.0050 mm, and pallet reversal delay 2 seconds.

5. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 1, characterized in that: The grinding fixture includes a shaft body, an expandable sleeve, two clamping members, a hydraulic connector, an oil pipe, and a manual pressure pump. The shaft body has an oil inlet channel, one end of which passes through the outer peripheral wall of the shaft body to form an oil inlet. The expandable sleeve is fitted onto the shaft body and has an oil cavity inside that communicates with the end of the oil inlet channel away from the oil inlet. The two clamping members are located at opposite ends of the expandable sleeve and are both fitted onto the shaft body. At least one clamping member is detachably connected to the shaft body. Each clamping member includes an inner clamping disc fitted onto the shaft body and an outer clamping disc rotatably wrapped around the outer peripheral surface of the inner clamping disc. One end of the oil pipe is connected to the oil inlet through the hydraulic connector, and the manual pressure pump is installed at the other end of the oil pipe.

6. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 5, characterized in that: Step S1 includes the following steps: S11, remove one of the clamping members from the shaft body, put the backing bearing to be ground onto the expandable sleeve, and then install the removed clamping member onto the shaft body, so that the two clamping members are located at opposite ends of the backing bearing to be ground. S12, the grinding fixture equipped with the backing bearing is hoisted to the grinding machine, and the two centers of the grinding machine are used to press the opposite ends of the shaft body respectively to ensure that the pressing force of the centers on the shaft body is between 1300-1400N. S13, connect one end of the oil pipe to the oil inlet through the oil pressure connector, and install dial indicators on the upper busbar and side busbar of the backing bearing respectively; S14, Connect a manual hydraulic pump to the other end of the oil pipe, pressurize the hydraulic oil in the oil chamber with the help of the manual hydraulic pump, causing the expandable sleeve to expand. After the expandable sleeve expands, it drives the inner ring of the backing bearing to expand. During this process, by tapping and rotating the outer diameter surface of the backing bearing, the inner ring of the bearing expands evenly, thereby making the bearing clearance become 0. S15, lock the two clamping members in the axial direction so that the centers of the two clamping members match. After locking, the inner clamping discs of the two clamping members clamp the opposite ends of the inner ring of the backing bearing, and the outer clamping discs of the two clamping members clamp the opposite ends of the outer ring of the backing bearing. S16, the outer disk of the fixture and the headstock of the grinding machine are connected by a plug bar. Then, the headstock of the grinding machine drives the outer disk of the fixture and the outer ring of the bearing of the backing bearing to rotate. The micrometer readings at the upper and side busbar positions are read, and the difference between the two values ​​is controlled within 2μm.

7. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 6, characterized in that: In step S16, if the difference between the dial gauge readings at the upper busbar and the side busbar is greater than 2μm, the clamping device is adjusted so that the backing bearing can rotate relative to the expandable sleeve. After rotating the backing bearing to adjust its angle, the clamping device is re-locked until the difference between the two readings is controlled within 2μm.

8. The method for improving the grinding accuracy of the backing bearing of a 20-roll mill as described in claim 6, characterized in that: A pressure gauge is also installed at the connection between the manual hydraulic pump and the oil pipe to detect the pressure inside the oil pipe and ensure that the pressure inside the oil pipe is maintained between 34-40 Pa during the bearing clearance adjustment process.

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