A method for calculating the roll change elevation of a four-high rolling mill

Abstract

This invention belongs to the field of steel rolling production, specifically a method for calculating the roll change elevation of a four-high rolling mill. Through calculation, the distance H between the actual roll change elevation and the reference surface is obtained, thus yielding the actual roll change elevation. Based on the difference between the actual and theoretical roll change elevations, a suitable support roll under-mount pad is selected for correction to meet production requirements. The reference surface is selected on the roll shifting fixing block. This invention offers high correction accuracy, effectively improving rolling stability, ensuring smooth roll change operations, reducing unplanned downtime, extending equipment lifespan, and lowering maintenance costs. The method is simple, practical, and easy to implement, and also provides a data foundation for intelligent operation and maintenance. It is suitable for calculating the roll change elevation of four-high rolling mills, especially older mills with long production histories and some equipment wear.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling production, specifically a method for calculating the roll change elevation of a four-roll mill. Background Technology

[0002] In hot-rolled coil production, changing the rolls is a fundamental operation. A four-high mill typically consists of two support rolls (upper and lower) and two work rolls (upper and lower) located between the support rolls, with a gap between the work rolls for the workpiece to pass through. The spatial height position of the upper surface of the lower work roll (work roll surface elevation) is called the roll change elevation. The work roll has a smaller diameter and is in direct contact with the workpiece, resulting in faster wear. The support roll has a larger diameter and is in contact with the work roll, resulting in slower wear. As the rolls wear, the roll surface becomes uneven, affecting the workpiece processing quality. Offline turning and grinding are necessary; after surface grinding to a smooth finish, the rolls can be reused online. Generally, work rolls are replaced according to the number of kilometers rolled, with a replacement cycle of approximately ten hours. Replacing a set of support rolls (for the entire mill) is called a "roll service cycle," which is approximately 10-15 days. The "roll service life" specifies the maximum and minimum roll diameter range of the work rolls. When the work rolls have been re-grinded several times within a service life and approach the minimum roll diameter within the range, the next roll service life plan must be carried out, and the support rolls must be replaced, also known as roll replacement. The "roll service life" is related to the number of work rolls used, the amount of steel processed on the work rolls, the support roll bearings, the wear of the support rolls, the rolling specifications, and the product quality requirements. Each company has its own "roll service life" applicable to its own conditions.

[0003] Since the replacement of the support roll and work roll results in a change in roll diameter, the change in roll replacement elevation caused by this change in roll diameter is compensated by the combined pad under the support roll. Figure 1 As shown, the spatial height position of the upper roller surface of the lower working roller 7 is called the roller changing elevation 11. The lower support roller combination pad 2 includes several pads of different thicknesses. After calculation based on the roller diameters of the lower working roller 7 and the lower support roller 5, pads of different specifications are selected to form a support roller combination pad 2 that meets the requirements for compensation, thus satisfying the requirements of normal roller changing and production operations.

[0004] However, with increasing production years, wear or deformation of roller system accessories such as lifting tracks, work roll bearing housing paddle wheels, and roll sliding blocks can cause deviations between the actual rolling position (roll change elevation) and the standard value (the roll change elevation calculated based on the diameters of the work roll and support roll). This leads to rolling instability, and in severe cases, abnormal situations such as roll rubbing or failure to install rolls can occur during roll change operations. Especially after changing the work roll, leveling is difficult to guarantee, posing risks to the start of rolling and easily causing accidents such as workpiece misalignment and jamming. Therefore, after the workshop equipment has been in operation for a long time, there is an urgent need for a method to calculate the roll change elevation, to correct the increasingly deviating roll change data, and thus verify the roll change elevation to ensure rolling stability. Summary of the Invention

[0005] To address the aforementioned shortcomings in the existing technology, this invention aims to provide a method for calculating the roll change elevation of a four-roll mill, thereby achieving the goal of accurately measuring the actual roll change elevation.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: A method for calculating the roll change elevation of a four-high rolling mill, wherein the distance H between the actual roll change elevation and the reference surface is calculated, thereby obtaining the actual roll change elevation; based on the difference between the actual roll change elevation and the theoretical roll change elevation, a suitable support roll under-mount pad is selected for correction to meet production requirements; the formula for calculating H is:

[0007]

[0008] In the formula, d represents the diameter of the work roll, in mm.

[0009] D - Diameter of the support roller, in mm;

[0010] H1 - Distance between the reference plane and the edge platform area of ​​the lower support roller bearing seat, in mm;

[0011] H2 - The distance between the edge platform area of ​​the lower support roller bearing housing and the center of the lower support roller bearing housing, in mm;

[0012] The reference plane is selected on the roller fixing block.

[0013] As a limitation of the present invention: the reference surface is the lower edge of the roller fixing block and does not contact the roller sliding block.

[0014] As a limitation of the present invention, it includes the following steps:

[0015] S1: Obtain the distance H2 between the edge platform area of ​​the lower support roller bearing seat and the center of the lower support roller bearing seat;

[0016] S2: Obtain the working roll diameter d and the support roll diameter D;

[0017] S3: Measure the distance H1 between the reference plane and the platform area on the side of the lower support roller bearing seat;

[0018] S4: Calculate the distance H between the roll change elevation and the reference surface to obtain the actual roll change elevation;

[0019] S5: Calculate the theoretical roll change elevation and correct the lower combination pad based on the difference between the actual roll change elevation and the theoretical roll change elevation.

[0020] As a limitation of the present invention: if the actual roller change elevation obtained is lower than the standard value, the lower combination pad needs to be corrected by increasing the thickness of the support roller lower combination pad; if the actual roller change elevation obtained is higher than the standard value, the lower combination pad needs to be corrected by decreasing the thickness of the support roller lower combination pad.

[0021] As a limitation of the present invention, it also includes the following steps:

[0022] S6: After correcting the lower combination pad, install the lower support roller according to the normal roller changing process;

[0023] S7: Measure the H1 value again. If the corrected H1 value is within ±2.5mm of the standard value, the correction is valid. If it exceeds ±2.5mm, repeat steps S1 to S6 until the correction is valid.

[0024] As a limitation of the present invention: after the lower combination pad is modified, the lower combination pad is replaced and adjusted according to the modified lower combination pad value.

[0025] As a limitation of the present invention: the lower half of the roll system that affects the roll change elevation includes the mill stand, lower pad box, lower support roll assembly pad, lower support roll bearing seat, lower support roll fixing pad, lower support roll, lower work roll, lower work roll bearing seat, roll shifting fixing block and roll shifting sliding block.

[0026] As a limitation of the present invention: the lower combination pad includes several pad bodies with thicknesses of 5mm, 10mm, 20mm and 50mm respectively.

[0027] By adopting the above technical solution, the beneficial effects achieved by the present invention compared with the prior art are as follows:

[0028] (1) This invention abandons the traditional method of simply relying on theoretical roll diameter to calculate the elevation. By introducing a reference surface, the distance H between the actual roll change elevation and the reference surface is calculated to calculate the actual roll change elevation. This value comprehensively reflects the real wear or deformation of the rolling mill roll system and accessories (such as lifting rails, bearing seat small wheel pairs, etc.) after long-term use. Based on this, the combination pad under the support roll is selected, which can accurately correct the increasingly deviated roll change elevation data. This fundamentally eliminates the rolling line fluctuation caused by elevation deviation, significantly improves the stability of the rolling process, and effectively prevents production accidents such as workpiece deviation and steel jamming.

[0029] (2) By using the roll changing elevation verified by this method, the roll changing operation can be carried out to ensure that the work roll and the support roll are in the expected spatial position, effectively avoiding abnormal situations such as roll rubbing or failure to install rolls during the roll removal and installation process, making the roll changing operation smoother and more efficient. At the same time, the leveling state of the rolling mill is guaranteed after the roll changing, reducing the risk of starting rolling, reducing unplanned downtime caused by improper adjustment or handling accidents, and improving equipment operating rate and production efficiency;

[0030] (3) The method of the present invention can compensate for the elevation changes caused by equipment wear in a timely manner, so that the rolling mill can operate in the best process state, reduce the abnormal stress, vibration and impact of the equipment caused by inaccurate elevation, and help protect the roller system, bearing seat and other related components, delay their wear rate, thereby extending the overall service life of the equipment to a certain extent and reducing the long-term maintenance and spare parts replacement costs.

[0031] (4) The calculation method is logically clear and the steps are well-defined. It does not require complex modifications to the existing rolling mill equipment. It only requires the acquisition of key data through conventional measuring tools to complete the calculation and verification. It is easy to operate and can be mastered and implemented by on-site operators and technicians. It has good applicability and scalability. It is especially suitable for old rolling mill workshops with long production years and certain wear and tear on the equipment. It has high practical application value.

[0032] (5) By periodically implementing this method, a large amount of real elevation data reflecting the actual status of the equipment can be accumulated. These data can be used to analyze the wear trend of the equipment, provide solid data support for predictive maintenance and intelligent monitoring of the rolling mill status, and promote the development of production management towards a more refined and intelligent direction.

[0033] In summary, this invention offers high correction accuracy, effectively improves rolling stability, ensures smooth roll changing operations, reduces unplanned downtime, extends equipment lifespan, lowers maintenance costs, and is simple, practical, and easy to promote and implement. It also provides a data foundation for intelligent operation and maintenance, and is suitable for calculating roll changing elevations in four-high rolling mills, especially for older rolling mills with long production years and some wear. Attached Figure Description

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0035] Figure 1 This is a schematic diagram of the roller changing elevation in the background art;

[0036] Figure 2 This is a schematic diagram showing the positions of various parameters on the rolling mill in the calculation method for the roll change elevation of a four-roll rolling mill according to an embodiment of the present invention.

[0037] In the diagram: 1-Lower support box, 2-Lower support roll combination pad, 3-Lower support roll fixing pad, 4-Lower support roll bearing seat, 5-Lower support roll, 6-Lower work roll, 7-Lower work roll bearing seat, 8-Roller fixing block, 9-Roller sliding block, 10-Mill stand, 11-Roll changing elevation, 12-Reference surface. Detailed Implementation

[0038] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the method for calculating the roll change elevation of a four-high rolling mill described herein is a preferred embodiment and is only used for illustration and explanation of the present invention, and does not constitute a limitation thereof.

[0039] The directional terms or positional relationships used in this invention, such as "up," "down," "left," and "right," are based on the positional relationships in the accompanying drawings of this invention. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or component must have a specific orientation, or that it must be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the content protected by this invention.

[0040] This embodiment describes a method for calculating the roll change elevation in a four-high rolling mill. It is used to calculate the actual roll change elevation 11. It should be noted that in a multi-high rolling mill, the elevation of the lower work roll surface is the rolling elevation, and the roll change elevation is also based on the rolling elevation; that is, the roll change elevation is determined by the lower rolling system. The upper rolling system is used for adjusting the roll gap and setting the reduction rate. Simultaneously, the upper rolling system must also perform real-time leveling and stability control during rolling. The roll change elevation 11 is not within its scope of implementation. Correspondingly, due to the characteristics of the rolled product, the upper rolling system also has an upper pad compensation system to compensate for insufficient stroke of the reduction cylinder, which is not discussed in this article. Therefore, this embodiment focuses on the lower rolling system structure.

[0041] The initial design intent of this embodiment is to perform a "calculation" before the start of a new roll service cycle, after the installation of the new support rolls and before the installation of the work rolls. This calculation measures the actual error of the roll change plan (theoretical value), meaning it is performed during the roll change process. In essence, this process can be considered part of the actual roll change operation. Of course, after a period of operation, this calculation can also be repeated during downtime, depending on site requirements or downtime arrangements.

[0042] like Figure 2 As shown, the spatial height position of the upper roll surface of the lower work roll 6 is called the roll changing elevation 11. The lower half of the roll system that affects the roll changing elevation 11 includes the mill archway 10, the lower pad box 1 which is slidably set at the center of the archway corresponding to the operating side and the drive side of the roll changing support trolley (not shown in the figure), the lower pad box 1 can move along the roll axis with the roll changing support trolley to switch the roll changing position and the rolling position of the roll system, and also includes the lower support roll 5 combination pad 2 placed in the lower pad box 1. The lower support roll 5 combination pad 2 has thicknesses of 5mm, 10mm, 20mm and 50mm respectively. The pads of the above specifications are combined to form the lower support roller 5 combined pad 2 according to the process requirements. It also includes a lower support roller bearing seat 4 and a lower support roller 5 fixing pad 3 fixed between the lower support roller bearing seat 4 and the lower support roller 5 combined pad 2. The lower support roller 5 fixing pad 3 and the lower support roller 5 are hoisted into the support roller changing trolley as a whole to ensure that the specifications of the lower support roller 5 fixing pad 3 and the lower combined pad are exactly the same on the transmission side and the operation side. It also includes a lower support roller 5, a lower working roller 6, a lower working roller bearing seat 7, a roller shifting fixing block 8 and a roller shifting sliding block 9.

[0043] Since the actual roll change elevation 11 is difficult to measure directly, this application introduces the concept of a reference surface 12. The actual roll change elevation 11 is calculated by determining the distance H between the actual roll change elevation 11 and the reference surface 12. The key point lies in the selection of the reference surface 12: the reference surface 12 must have minimal wear, no positional change, and be easy to measure. For example... Figure 2 As shown, in this embodiment, the reference surface 12 is selected as the lower edge of the roll-shifting fixing block 8, a position that does not contact the roll-shifting sliding block 9. Firstly, this location does not contact any other parts, ensuring the accuracy of its shape and dimensions. Secondly, the space around this location is relatively large, making measurement easy. Furthermore, this surface is part of the roll-shifting fixing block 8, which is directly fixed to the mill stand 10, resulting in minimal positional error. A suitable selection of the reference surface 12 ensures that the form and position tolerances fully meet the elevation ±2.5mm requirement. In other embodiments, the reference surface 12 can also be selected at other locations on the roll-shifting fixing block 8, but positions that do not contact other parts should be avoided.

[0044] Key dimensions: Working roller diameter d (mm); Support roller diameter D (mm); Lower assembly pad thickness h 组合The units are mm; the distance H between the roll change elevation 11 and the reference surface 12 is mm; the distance H1 between the reference surface 12 and the edge platform area of ​​the lower support roll bearing seat 4 is mm; the distance H2 between the edge platform area of ​​the lower support roll bearing seat 4 and the center of the lower support roll bearing seat 4 is mm. It should be noted that when a new roll system is put into operation, the minimum roll diameter must be used for theoretical calculations (as agreed upon). Therefore, the working roll diameter d here needs to be substituted with the "minimum working roll diameter within this roll change cycle".

[0045] Among the above parameters, the working roll diameter d and the support roll diameter D are measured when the grinding machine completes the rolling and grinding process. The distance H2 between the edge platform area of ​​the lower support roll bearing seat 4 and the center of the lower support roll bearing seat 4 is the equipment dimension, that is, the dimension of the spare part itself. For equipment from the same manufacturer, this dimension is fixed (the bearing seat housing is a whole piece, cast and precision machined). Even if it is replaced with an aftermarket product, it can be accurately measured in advance. That is, the working roll diameter d, the support roll diameter D, and the distance H2 between the edge platform area of ​​the lower support roll bearing seat 4 and the center of the lower support roll bearing seat 4 can all be obtained in advance.

[0046] Accounting principle:

[0047] Elevation constant A = d + D / 2 + distance from bearing housing center to under the fixing pad + h 组合

[0048] Elevation constant B = H1 + H2 + distance from bearing housing center to under the fixing pad + h 组合

[0049] Combining the above two equations, we get:

[0050] The distance H between the elevation and the reference plane = elevation constant A - elevation constant B, that is:

[0051] (Formula 1)

[0052] Therefore, the calculation method for the roll change elevation of a four-high rolling mill includes the following steps:

[0053] S1: Obtain the distance H2 between the edge platform area of ​​the lower support roller bearing seat 4 and the center of the lower support roller bearing seat 4. Under normal circumstances, H2 is a constant.

[0054] S2: Obtain the working roll diameter d and the support roll diameter D.

[0055] S3: Measure the distance H1 between the reference plane 12 and the platform area on the side of the lower support roller bearing seat 4.

[0056] S4: Calculate the distance H between the actual roll change elevation 11 and the reference surface 12 according to Formula 1 to obtain the actual roll change elevation 11. Adjust the lower combination pad according to the actual roll change elevation to meet production requirements. If the obtained actual roll change elevation is lower than the standard value, the lower combination pad needs to be corrected by increasing its thickness. If the obtained actual roll change elevation is higher than the standard value, the lower combination pad needs to be corrected by decreasing its thickness.

[0057] S5: After correcting the lower combination pad, install the lower support roller 5 according to the normal roller changing process.

[0058] S6: Measure the H1 value again. If the corrected H1 value is within ±2.5mm of the standard value, the correction is valid. If it exceeds ±2.5mm, repeat steps S1 to S5 until the correction is valid.

[0059] After correcting the lower assembly pad, replace and adjust the lower assembly pad according to the corrected values.

[0060] Since the working roll diameter d, the support roll diameter D, and the distance H2 between the edge platform area of ​​the lower support roll bearing seat 4 and the center of the lower support roll bearing seat 4 can all be obtained in advance, only the distance H1 between the reference surface 12 and the edge platform area of ​​the lower support roll bearing seat 4 needs to be measured online, and only this data needs to be measured, the online operation time can be greatly shortened and the efficiency improved.

[0061] One possible implementation of the method for calculating the roll change elevation of a four-high rolling mill, taking an old four-high rolling mill as an example.

[0062] The actual roll change elevation of the rolling mill has deviated, and it is now necessary to calculate the actual roll change elevation.

[0063] The results were obtained through verification of the drawings and on-site measurements:

[0064] H2=525mm (unchanged before and after roller replacement);

[0065] d=538mm (after roller change), d=541mm (before roller change);

[0066] D=1170.79mm (after roller change), D=1216.62mm (before roller change).

[0067] h 组合 =125mm (before changing rollers)

[0068] Before the measurement, the thickness h of the lower combined pad after the roller change needs to be calculated. 组合 Theoretical value:

[0069] According to the formula: Elevation constant A = d + D / 2 + (center of bearing housing to below the fixing pad) + h组合

[0070] Substitute the data of the new roll system after the roll change into the above formula:

[0071] Elevation constant A = 538 + 1170.79 / 2 + (center of bearing housing to underside of fixed pad) + h 组合 (After changing the roller)

[0072] Substitute the data of the old roll system before the roll replacement into the above formula:

[0073] Elevation constant A = 541 + 1216.62 / 2 + (center of bearing housing to underside of mounting pad) + 125

[0074] Combining the above two formulas:

[0075] h 组合 (After changing the rollers) = (541-538) + (1216.62-1170.79) / 2 + 125

[0076] =3 + 22.9 + 125 = 150.9 mm

[0077] Note: The distance from the center of the bearing housing to the bottom of the mounting pad is a fixed value of 930mm, including the lower half of the bearing housing and the frame mounting pad. Since this can be eliminated during calculation, it was not substituted into the calculation. The above calculation process actually uses the change in roller diameter before and after roller replacement to deduce the theoretical value of the lower combined pad thickness, which is the existing conventional calculation method.

[0078] The theoretical lower pad under the current roller configuration is 150.9mm, which is rounded to 151mm. The minimum unit of the lower pad combination is 5mm, so the final pad should be 150mm. The actual pad combinations used on site are 50mm×2, 20mm×2, and 10mm×1.

[0079] Clean all contact surfaces, place the new support roller, and double-check the roller box number and roller diameter.

[0080] The theoretical distance between the roller changing elevation 11 and the reference plane 12 was calculated and determined as follows:

[0081] H=93.5mm;

[0082] On-site measurements yielded the following results:

[0083] H1 = 508.5 mm;

[0084] Substitute into Formula 1:

[0085]

[0086] =538+1170.79 / 2-508.5-525

[0087] =89.9mm

[0088] The actual distance H between the actual roller change elevation 11 and the reference surface 12 was calculated to be 89.9 mm.

[0089] The difference between the two is 89.9-93.5=-3.6mm, which exceeds the process requirement of ±2.5mm and needs to be corrected. The correction value is: +3.6.

[0090] The actual on-site padding was then adjusted as follows:

[0091] 50mm×2+20mm×2+10mm×1+5mm×1=155mm

[0092] After correcting the lower assembly pad, install the lower support roller 5 according to the normal roller replacement process. Measure the distance H1 between the reference surface 12 and the edge platform area of ​​the lower support roller bearing housing 4 again. The measured value is 504.2. Substitute this value into formula 1.

[0093]

[0094] =538+1170.79 / 2-504.2-525

[0095] =94.2mm

[0096] The error is 94.2 - 93.5 = 0.7 mm.

[0097] The corrected H value has an error of 0.7 compared to the standard value, which is within ±2.5 mm, indicating that the correction is effective.

Claims

1. A method for calculating the roll change elevation of a four-high rolling mill, characterized in that, Through calculation, the distance H between the actual roll changing elevation and the datum plane is obtained, and then the actual roll changing elevation is obtained. According to the difference between the actual roll changing elevation and the theoretical roll changing elevation, the appropriate lower supporting roll combined pad is selected for correction to meet the production requirements. The calculation formula of H is: In the formula, d is the diameter of the work roll, in mm; D is the diameter of the supporting roll, in mm; H1 is the distance between the datum plane and the edge platform area of the lower supporting roll bearing seat, in mm; H2 is the distance between the edge platform area of the lower supporting roll bearing seat and the center of the lower supporting roll bearing seat, in mm; The datum plane is selected on the roll shifting fixed block; the datum plane is the lower edge of the roll shifting fixed block and does not contact the roll shifting sliding block; The accounting method comprises the following steps, S1: obtaining the distance H2 between the edge platform area of the lower supporting roll bearing seat and the center of the lower supporting roll bearing seat; S2: obtaining the diameter d of the work roll and the diameter D of the supporting roll; S3: measuring the distance H1 between the datum plane and the edge platform area of the lower supporting roll bearing seat; S4: calculating the distance H between the roll changing elevation and the datum plane to obtain the actual roll changing elevation; S5: calculating the theoretical roll changing elevation, and correcting the lower combined pad according to the difference between the actual roll changing elevation and the theoretical roll changing elevation; S6: after the correction of the lower combined pad, the lower supporting roll is installed according to the normal roll changing process; S7: the value of H1 is measured again. If the corrected value of H1 is within the range of ±2.5 mm from the standard value, the correction is effective. If the value of H1 exceeds the range of ±2.5 mm, steps S1 to S6 are repeated until the correction is effective; In step S5, if the obtained actual roll changing elevation is lower than the standard value, the lower combined pad needs to be corrected by increasing the thickness of the lower supporting roll combined pad. If the obtained actual roll changing elevation is higher than the standard value, the lower combined pad needs to be corrected by reducing the thickness of the lower supporting roll combined pad; After the correction of the lower combined pad, the lower combined pad is replaced and adjusted according to the corrected value of the lower combined pad.

2. The method according to claim 1, characterized in that, The lower half of the roll system that affects the roll changing elevation includes the rolling mill housing, the lower pad box, the lower supporting roll combined pad, the lower supporting roll bearing seat, the lower supporting roll fixed pad, the lower supporting roll, the lower work roll, the lower work roll bearing seat, the roll shifting fixed block and the roll shifting sliding block.

3. The method according to claim 2, characterized in that, The lower combined pad comprises a plurality of pad bodies with thicknesses of 5 mm, 10 mm, 20 mm and 50 mm.

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