A method for determining the cause of vibration marks on an aluminum cold rolling mill from a mechanical point of view

Abstract

The present application relates to a kind of methods for determining the cause of aluminum cold rolling mill vibration mark from mechanical angle, by grinding roll grinding, calculation and analysis of roll system bearing rolling body fault frequency, universal joint shaft mating clearance and dynamic balance, process lubrication parameter change, main transmission reduction gearbox gear meshing frequency etc., reasonably use the method such as elimination, frequency calculation and analysis, dynamic balance precision calculation, material ratio adjustment to carry out analysis and judgment, systematically study the mechanism of aluminum cold rolling mill vibration mark from mechanical angle and its relationship with equipment, process lubrication etc., the method for determining the cause of aluminum cold rolling mill vibration mark is proposed, without time-consuming and labor-consuming way of trial and error to check various factors affecting quality defects, it is beneficial to more complete clear rolling mill vibration mark comprehensive reason, and reasonable scheme for inhibiting or eliminating vibration mark is proposed, guarantee the stability of rolling strip quality.The present application method principle is scientific, method is simple and easy to operate, and effect is good.

Description

Technical Field

[0001] This invention relates to a method for determining the cause of vibration marks in aluminum cold rolling mills from a mechanical perspective, belonging to the field of aluminum and aluminum alloy processing. Background Technology

[0002] During the aluminum strip rolling process, stripes of alternating light and dark color, perpendicular to the direction of strip movement, often appear on the surface of the strip. This surface defect is called vibration pattern.

[0003] As a key process in the production of cold-rolled strip for aluminum processing enterprises, the stability of the rolled strip quality is the primary goal pursued in aluminum cold rolling mill production. The generation of vibration marks has three main adverse effects on aluminum rolling production: first, it is difficult to meet the user's requirements for strip surface quality; second, it increases the frequency of roll changing or reduces the rolling speed, resulting in low production efficiency; and third, the vibration of the rolling mill during the rolling process seriously affects the life of the rolling mill, and if measures are not taken in time, rolling accidents such as strip breakage are likely to occur.

[0004] Vibration marks are a widespread problem worldwide, and many non-ferrous metal producers have been or are currently troubled by this issue. However, due to the complexity of the problem, there is still no universally feasible method to suppress vibration marks. The only solution is to investigate the causes one by one through trial and error, making vibration marks a significant issue affecting the surface quality of strip materials. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a method for determining the cause of vibration marks in aluminum cold rolling mills from a mechanical perspective.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for determining the cause of vibration marks in aluminum cold rolling mills from a mechanical perspective, characterized by comprising the following steps:

[0007] S1: Use the process of elimination to investigate, and provide the rolls to different rolling mills using the same grinding machine that grinds the same pair of rolls with identical grinding parameters:

[0008] If vibration marks appear in different rolling mills, it indicates that grinding marks have appeared in the grinding machine. The accuracy of the grinding machine needs to be checked, including the accuracy of the track, the accuracy of the grinding wheel spindle, the measurement accuracy, the accuracy of the center, and the grinding program. In subsequent grinding processes, real-time monitoring of the roll surface quality should be strengthened. For grinding machines with large vibrations, damping vibration dampers should be installed to reduce the impact of grinding machine vibration on roll grinding vibration.

[0009] If no vibration marks appear on other rolling mills, the vibration marks on the roll surface caused by grinding can be ruled out. The cause of abnormal vibration of the rolling mill can be attributed to other equipment or process reasons, and proceed to step 2.

[0010] S2: By calculating the failure frequency of the rolling elements of the roller bearing, it is possible to check whether the vibration marks are caused by bearing issues.

[0011] The calculated comparison between rolling element failure frequency and vibration crack frequency is as follows:

[0012] The relationship between vibration marks and mill chatter is as follows:

[0013]

[0014] In the formula, ω is the groove pitch in mm, d is the roll diameter in mm, n is the roll speed in r / min, and f is the vibration frequency in Hz;

[0015] Based on the commonly used on-site rolling speed V=πdn, the actual measured gap ω of the vibration marks is used for calculation:

[0016] According to equation (1), the vibration frequency is obtained:

[0017] Then, according to the formula for the failure frequency of bearing rolling elements:

[0018]

[0019] In the formula, F is the rolling element failure frequency (Hz), n is the roll speed (r / min), and A is the number of rolling elements per row of the bearing.

[0020] Under the same conditions, i.e., the rolling speed V = πdn, calculate the rotational speed of each roll. Based on the known roll diameter, calculate the rotational speed of each roll.

[0021] Based on the above roll speed values ​​and equation (2), we can obtain:

[0022]

[0023] Based on the above calculation results, compare the vibration pattern frequency with the failure frequency of each rolling element of the roll bearing. If they are integer multiples, it indicates that the vibration pattern is related to the bearing damage frequency, and the bearing damage needs to be inspected and replaced. If they are not integer multiples, the vibration pattern caused by the failure of the rolling element of the roll bearing can be ruled out, and proceed to step 3.

[0024] S3: Check the design dimensions of the work roll shaft head and the design dimensions of the coupling that mates with it. This mating dimension is suitable for mating with very small clearances, allowing for a certain amount of relative movement, not requiring free rotation, but allowing for precise positioning. The clearance adjustment is divided into two levels: the first level is 0.06-0.09mm, and the second level is 0.15-0.2mm. Test under the same rolling conditions: if one level has a vibration mark and the other does not, then the mating dimension between the work roll and the flat head may produce vibration marks. The vibration frequency is generated by this clearance, or is the vibration frequency of the rolling mill work roll or an integer multiple of the work roll vibration frequency. The clearance needs to be adjusted to the first level where no vibration marks are produced. If vibration marks are produced in both clearance levels, it means that the clearance has no effect on the vibration marks, and proceed to step 4.

[0025] S4: Perform dynamic balancing tests and reweighting on existing universal joints. The simplified calculation of the allowable residual imbalance is as follows:

[0026]

[0027] in:

[0028] M --- Mass of the universal joint shaft, in kg;

[0029] G---Universal joint shaft balance accuracy grade, requiring G6.3;

[0030] r---Universal coupling shaft correction radius, in mm;

[0031] n --- the operating speed of the universal joint shaft, in rpm;

[0032] m --- the allowable residual imbalance, in grams;

[0033] If the vibration marks disappear after the universal joint is used for rolling after adjusting the counterweight, it indicates that the vibration marks were caused by the dynamic imbalance of the universal joint. If the vibration marks still exist, it is considered that the vibration marks are not caused by the universal joint and proceed to step 5.

[0034] S5:

[0035] S51: Adjusting the rolling oil ratio also affects the performance of the rolling oil and the coefficient of friction. The content of the rolling oil additive is set to 7.5% and 9% respectively. By adjusting the rolling oil ratio, the coefficient of friction between the workpiece and the roll is changed, thereby changing the rolling pressure. If the vibration marks disappear, it means that the periodic fluctuation of the system stiffness is caused by the rolling oil ratio, which triggers the self-excited vibration of the mill and produces vibration marks. If the vibration marks do not disappear or only the severity of the marks changes, proceed to S52.

[0036] S52: Adjust the pressure and flow rate parameters of the zoned cooling spray. It is recommended to test the pressure in three levels: 6 bar, 8 bar, and 10 bar, and the flow rate in three levels: 3000 L / min, 4000 L / min, and 6000 L / min. If the vibration pattern disappears, it indicates that the vibration pattern is caused by the rolling oil lubrication. If the vibration pattern still exists or only varies in severity and there is no pattern, proceed to step 6.

[0037] S6: By calculating the gear meshing frequency, check whether the vibration pattern is caused by the gears in the main drive reduction gearbox; the gear meshing frequency is calculated as follows:

[0038] Based on the design drawings of the main drive reducer, the low-speed reduction ratio, the number of teeth on the output shaft Z1, and the number of teeth on the input shaft Z2 are obtained.

[0039] And the high-speed reduction ratio, the number of teeth on the output shaft is Z3, and the number of teeth on the input shaft is Z4;

[0040] Simultaneously, using the known working roll diameter d WR And the commonly used rolling speed V,

[0041] Calculate the output shaft speed of the main gearbox:

[0042] achievable

[0043] Output shaft rotation frequency

[0044] According to the meshing frequency formula:

[0045] f m =f 转频 ×Z(3)

[0046] In the formula, f m f is the gear meshing frequency. 转频 Z represents the rotational frequency of the input or output shaft, and Z represents the number of teeth on the corresponding input or output shaft.

[0047] According to equation (3), we can obtain that

[0048] High-speed gear meshing frequency f m-高速 =f 输出 ×Z3

[0049] meshing frequency f at low speed m-低速 =f 输出 ×Z1

[0050] According to equation (1), substituting f m-高速 and f m-低速 We can obtain them separately.

[0051]

[0052] The above calculations can be used to determine ω. 低速 With ω 高速 Comparing the calculated values ​​with the measured spacing of vibration marks on the strip surface, if they are close or match, it indicates that the meshing frequency of the helical gears in the main drive reduction gearbox of the rolling mill is similar to or equal to the frequency of the vibration marks. Therefore, it can be determined that the impact generated by the gears excites the vibration of the rolling mill, thereby leading to the formation of vibration marks on the strip surface. This further confirms that the impact vibration generated by the main drive line due to equipment wear excites the vibration of the rolling mill, resulting in vibration marks.

[0053] Compared with existing technologies, this invention has the following advantages: By analyzing the grinding of mill rolls, calculating and analyzing the failure frequency of rolling elements in roller bearings, the fit clearance and dynamic balance of universal joints, changes in process lubrication parameters, and the gear meshing frequency of the main drive reduction gearbox, this invention systematically studies the mechanism of vibration marks in aluminum cold rolling mills and its relationship with equipment and process lubrication from a mechanical perspective, and proposes a method for determining the causes of vibration marks in aluminum cold rolling mills. The determination method provided by this invention is scientifically sound, simple to implement, and has good analytical results. Aluminum cold rolling mills that have been determined and adjusted using this method have achieved the goal of eliminating vibration mark defects on the plate surface and ensuring the stability of the rolled strip material quality.

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0055] Figure 1 A schematic diagram showing vibration marks still appearing on an 1850mm six-roll irreversible aluminum cold rolling mill.

[0056] Figure 2 This is a schematic diagram showing that no vibration marks appeared on other 1850mm six-roll aluminum cold rolling mills.

[0057] Figure 3 This is a schematic diagram of the vibration pattern before the process lubrication parameters were adjusted.

[0058] Figure 4 This is a schematic diagram of the vibration pattern after adjusting the process lubrication parameters.

[0059] Figure 5 This is a schematic diagram showing that the tooth surface of a helical gear has a certain degree of wear. Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0061] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, 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 application pertains.

[0062] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0063] like Figures 1-5 As shown, this embodiment provides a method for determining the cause of vibration marks in aluminum cold rolling mills from a mechanical perspective, characterized by the following steps:

[0064] S1: Use the process of elimination to investigate, and provide the same pair of rolls to different rolling mills using the same grinding machine and with identical grinding parameters:

[0065] If vibration marks appear in different rolling mills, it indicates that grinding marks have appeared in the grinding machine. The accuracy of the grinding machine needs to be checked, including the accuracy of the track, grinding wheel spindle, measurement accuracy, center accuracy, grinding program, etc. In subsequent grinding processes, real-time monitoring of the roll surface quality can be strengthened. For grinding machines with large vibrations, damping vibration dampers can be installed to reduce the impact of grinding machine vibration on roll grinding vibration.

[0066] If no vibration marks appear on other rolling mills, the vibration marks on the roll surface caused by grinding can be basically ruled out. The cause of abnormal vibration of the rolling mill can be attributed to other equipment or process reasons, and we can proceed to step 2.

[0067] S2: By calculating the failure frequency of the rolling elements of the roller system (work roll, intermediate roll, and support roll respectively), check whether the vibration marks are caused by bearing issues.

[0068] The calculated comparison between rolling element failure frequency and vibration crack frequency is as follows:

[0069] The relationship between vibration marks and mill chatter is as follows:

[0070]

[0071] In the formula, ω is the groove pitch in mm, d is the roll diameter in mm, n is the roll speed in r / min, and f is the vibration frequency in Hz;

[0072] Based on the commonly used on-site rolling speed V=πdn, the actual measured gap ω of the vibration marks is used for calculation:

[0073] According to equation (1), the vibration frequency is obtained:

[0074] Then, according to the formula for the failure frequency of bearing rolling elements:

[0075]

[0076] In the formula, F is the rolling element failure frequency (Hz), n is the roll speed (r / min), and A is the number of rolling elements per row of the bearing.

[0077] Under the same conditions, i.e., the rolling speed V = πdn, calculate the rotational speed of each roll. Based on the known roll diameter, calculate the rotational speed of each roll.

[0078] Based on the above roll speed values ​​and equation (2), we can obtain:

[0079]

[0080] Based on the above calculation results, compare the vibration pattern frequency with the failure frequency of each rolling element of the roll bearing. If they are integer multiples, it indicates that the vibration pattern is related to the bearing damage frequency, and the bearing damage needs to be inspected and replaced. If they are not integer multiples, the vibration pattern caused by the failure of the rolling element of the roll bearing can be ruled out, and you can proceed to step 3.

[0081] S3: Check the design dimensions of the work roll shaft head and the design dimensions of the coupling that mates with it. This mating dimension is suitable for mating with very small gaps, allowing for a certain amount of relative movement, not requiring free rotation, but allowing for precise positioning. The gap adjustment is divided into two levels: the first level gap is 0.06~0.09mm, and the second level gap is 0.15~0.2mm. Test under the same rolling conditions: if one level has a gap and the other does not, then the mating dimension between the work roll and the flat head may produce vibration marks. The vibration frequency is generated by this gap, or is the vibration frequency of the rolling mill work roll or an integer multiple of the work roll vibration frequency. The gap needs to be adjusted to the first level where no vibration marks are produced. If vibration marks are produced in both gap levels, it means that the gap has no effect on the vibration marks, and you can proceed to step 4.

[0082] S4: Perform dynamic balancing tests and reweighting on existing universal joints. The simplified calculation of the allowable residual imbalance is as follows:

[0083]

[0084] in:

[0085] M --- Mass of the universal joint shaft, in kg;

[0086] G---Universal joint shaft balance accuracy grade, requiring G6.3;

[0087] r---Universal coupling shaft correction radius, in mm;

[0088] n --- the operating speed of the universal joint shaft, in rpm;

[0089] m --- the allowable residual imbalance, in grams;

[0090] If the vibration marks disappear after the universal joint is used for rolling after adjusting the counterweight, it indicates that the vibration marks were caused by the dynamic imbalance of the universal joint. If the vibration marks still exist, it is considered that the vibration marks are not caused by the universal joint and proceed to step 5.

[0091] S5:

[0092] S51: Adjusting the rolling oil ratio also affects the performance of the rolling oil and the coefficient of friction. The content of the rolling oil additive is set to 7.5% and 9% respectively. By adjusting the rolling oil ratio, the coefficient of friction between the workpiece and the roll is changed, thereby changing the rolling pressure. If the vibration marks disappear, it means that the periodic fluctuation of the system stiffness is caused by the rolling oil ratio, which triggers the self-excited vibration of the mill and produces vibration marks. If the vibration marks do not disappear or only the severity of the marks changes, proceed to S52.

[0093] S52: Adjust the pressure and flow rate parameters of the zoned cooling spray. It is recommended to test the pressure in three levels: 6 bar, 8 bar, and 10 bar, and the flow rate in three levels: 3000 L / min, 4000 L / min, and 6000 L / min. If the vibration pattern disappears, it indicates that the vibration pattern is caused by the rolling oil lubrication. If the vibration pattern still exists or only varies in severity and there is no pattern, proceed to step 6.

[0094] S6: By calculating the gear meshing frequency, check whether the vibration pattern is caused by the gears in the main drive reduction gearbox; the gear meshing frequency is calculated as follows:

[0095] Based on the design drawings of the main drive reducer, the low-speed reduction ratio, the number of teeth on the output shaft Z1, and the number of teeth on the input shaft Z2 are obtained.

[0096] And the high-speed reduction ratio, the number of teeth on the output shaft is Z3, and the number of teeth on the input shaft is Z4;

[0097] Simultaneously, using the known working roll diameter d WR And the commonly used rolling speed V,

[0098] Calculate the output shaft speed of the main gearbox:

[0099] achievable

[0100] Output shaft rotation frequency

[0101] According to the meshing frequency formula:

[0102] f m =f 转频 ×Z(3)

[0103] In the formula, f m f is the gear meshing frequency. 转频 Z represents the rotational frequency of the input or output shaft, and Z represents the number of teeth on the corresponding input or output shaft.

[0104] According to equation (3), we can obtain that

[0105] High-speed gear meshing frequency f m-高速 =f 输出 ×Z3

[0106] meshing frequency f at low speed m-低速 =f 输出 ×Z1

[0107] According to equation (1), substituting f m-高速 and f m-低速 We can obtain them separately.

[0108]

[0109] The above calculations can be used to determine ω. 低速 With ω 高速 Comparing the calculated values ​​with the measured spacing of vibration marks on the strip surface, if they are close or match, it indicates that the meshing frequency of the helical gears in the main drive reduction gearbox of the rolling mill is similar to or equal to the frequency of the vibration marks. Therefore, it can be determined that the impact generated by the gears excites the vibration of the rolling mill, thereby leading to the formation of vibration marks on the strip surface. This further confirms that the impact vibration generated by the main drive line due to equipment wear excites the vibration of the rolling mill, resulting in vibration marks.

[0110] Based on the above assessment, the gear fit can be readjusted by grinding and replacing some worn gears, adjusting the gear bearing clearance, etc.

[0111] By following the above six steps, the causes of vibration marks in aluminum cold rolling mills can be determined systematically from a mechanical perspective.

[0112] During aluminum strip rolling, alternating light and dark stripes perpendicular to the strip's movement direction frequently appear on the strip surface; this surface defect is called vibration marks. As a crucial process in aluminum processing enterprises producing cold-rolled strip, the stability of the rolled strip quality is the primary goal of aluminum cold rolling mill production. Vibration marks have three main adverse effects on aluminum rolling production: first, they make it difficult to meet user requirements for strip surface quality; second, they increase the frequency of roll changes or reduce rolling speed, leading to low production efficiency; and third, severe vibration during rolling significantly affects the mill's lifespan, and if measures are not taken promptly, rolling accidents such as strip breakage can easily occur. This invention, by studying the mechanism of vibration mark generation in aluminum cold rolling mills from a mechanical perspective and its relationship with equipment, process lubrication, etc., proposes a method for determining the causes of vibration marks in aluminum cold rolling mills. This eliminates the need for time-consuming and laborious trial-and-error methods to investigate various factors affecting quality defects, facilitating a more comprehensive understanding of the comprehensive causes of mill vibration marks and proposing reasonable solutions to suppress or eliminate vibration marks, thus ensuring the stability of rolled strip quality.

[0113] Specific implementation process: Example 1:

[0114] Taking a company's 1850mm six-roll irreversible aluminum cold rolling mill as an example, vibration marks were found on the surface of the strip during the rolling process. The vibration marks were distributed on the entire coil of strip. When observed from the head, middle and tail of the strip, the spacing of the vibration marks was uniform, perpendicular to the rolling direction, and the period was about 28mm.

[0115] In view of the above, the process of vibration pattern investigation was continuously tracked and analyzed. Based on the causes of vibration pattern generation, and through field practice and data analysis, vibration pattern suppression measures were proposed, as follows:

[0116] 1. Roll grinding machine and rolls

[0117] On-site measurements of multiple strip coils showed that the spacing ω of the vibration marks on the surface of each coil was approximately 28mm. Given the possibility that the vibration marks from the rolls themselves might be affecting the strip, an elimination method was used. The same pair of rolls were ground on the same grinding machine with identical grinding parameters and supplied to different rolling mills. The 1850mm six-roll irreversible aluminum cold rolling mill still exhibited vibration marks, while other 1850mm six-roll aluminum cold rolling mills did not. Figure 1 , Figure 2 As shown:

[0118] Therefore, the vibration marks on the roll surface caused by grinding can be basically ruled out. The abnormal vibration of the rolling mill can be attributed to other equipment or process reasons, namely, the impact vibration caused by the wear and tear of the rolling mill equipment or the vibration caused by the rolling lubrication.

[0119] In the subsequent grinding process, strengthening real-time monitoring of the roll surface quality and taking measures such as installing damping vibration dampers for grinding machines with large vibrations can reduce the impact of grinding machine vibration on roll grinding vibration.

[0120] 2. Roll bearings

[0121] On-site inspection of the inner and outer rings of the roller bearings revealed no obvious defects. The failure frequency of the rolling elements was calculated to determine if bearing-related issues were causing the vibration patterns. A comparison of the calculated rolling element failure frequency and vibration pattern frequency is shown below:

[0122] The relationship between vibration marks and mill chatter is as follows:

[0123]

[0124] In the formula, ω is the groove spacing (mm), d is the roll diameter (mm), n is the roll rotation speed (r / min), and f is the vibration frequency (Hz).

[0125] Based on the commonly used on-site production process, the rolling speed V = πdn = 500 m / min, and taking the actual measured gap of the vibration marks as 28 mm, the calculation is performed as follows:

[0126] According to equation (1), we get:

[0127] According to the formula for bearing rolling element failure frequency:

[0128]

[0129] In the formula, F is the rolling element failure frequency (Hz), n is the roll speed (r / min), and A is the number of rolling elements per row.

[0130] According to the drawings, each row of tapered roller bearings for the work rolls has 40 rolling elements, i.e., A. WR =40; the intermediate roller tapered roller bearing has 40 rolling elements per row, i.e., A IMR =40; the support roller tapered roller bearing has 35 rolling elements per row, i.e., A BUR =35.

[0131] Under the same conditions, i.e., a rolling speed of V = πdn = 500 m / min, calculate the rotational speed of each roll, and take the diameter d of the work roll in the field. WR =420mm, intermediate roller diameter d IMR =500mm, support roller diameter d BUR =1190mm, the rotational speeds of each roll are as follows:

[0132]

[0133] Based on the above roll speed values ​​and equation (2), we can obtain that

[0134]

[0135] Based on the above calculation results, it can be seen that the vibration pattern frequency (297.6Hz) is not an integer multiple of the failure frequencies of the rolling elements of each roll bearing (933.4Hz, 2534.5Hz, 3020.6Hz), which basically eliminates the possibility that the vibration pattern is caused by the failure of the rolling elements of the roll bearing.

[0136] Going forward, we can introduce bearing (damaged) frequency detection equipment and spectrum comparison to verify whether the vibration is caused by the bearing. At the same time, we can clean the bearing regularly, check and adjust the bearing precision, and strengthen the daily maintenance of the equipment.

[0137] 3. Main drive universal joint shaft

[0138] Roller head design dimensions: diameter of the roller head arc surface (flat head size) The coupling designed to work with it has a circular arc surface of 230H7 (0~+0.046).

[0139] H7

[0140] The g6 fit is suitable for fits with very small gaps, allowing for some relative movement, not requiring free rotation, but requiring precise positioning. Based on the above design theory, the maximum fit gap is 0.09mm. However, according to actual field conditions, a 0.09mm gap would cause difficulties in pushing and pulling the rolls. During production, the fit is adjusted to 0.15–0.2mm based on field experience. Tests under the same rolling conditions showed that both fit gaps had no effect on vibration patterns.

[0141] Further research can be conducted on the permissible range of the working roll and flat head mating dimensions. Vibration marks may occur outside this range, and their vibration frequency may be the working roll vibration frequency of the rolling mill or an integer multiple of the working roll vibration frequency.

[0142] Universal joint dynamic balancing: A decrease in dynamic balancing accuracy may cause the universal joint to impact the roller system when rotating at high speed, thereby exciting the natural frequency vibration.

[0143] A. On-site dynamic balancing test and reweighting of the existing universal joint shaft, as shown in the table below (balancing accuracy grade G6.3; because the dynamic imbalance exceeds 5000g, the manufacturer specifies that the balancing machine test speed cannot exceed 400rpm, so only the dynamic balancing accuracy test is performed at 400rpm):

[0144] The simplified calculation of the allowable residual imbalance is as follows:

[0145]

[0146] Where M---rotor mass, unit (kg), this universal joint has a mass of 1611kg;

[0147] G---Balance accuracy grade; this universal joint requires G6.3.

[0148] r---Correction radius, unit (mm), this universal joint has a value of 195mm;

[0149] n---Working speed of the workpiece, in rpm, test speed limit 400 rpm;

[0150] m --- Permissible residual imbalance, in grams (g)

[0151]

[0152] B. Re-machine a pair of universal joint shafts with a balancing accuracy of G6.3 and a dynamic balancing speed of 900 rpm;

[0153] The two pairs of universal joints were replaced on-site, but the vibration pattern still existed, only to varying degrees. Therefore, it was determined that the vibration pattern was not caused by the universal joints.

[0154] Further research can be conducted on the relationship between the failure frequency of the transmission shaft bearing and the dynamic imbalance exceeding the allowable unbalance and the vibration pattern. The vibration frequency may be the vibration frequency of the rolling mill work roll or an integer multiple of the work roll vibration frequency.

[0155] At the same time, equipment maintenance should be strengthened, the main drive system should be optimized, the internal clearance of the connecting shaft components and the fitting clearance between the flat head of the working roller and the bushing should be strictly controlled, and the dynamic balance accuracy should be checked regularly to ensure normal operation of the equipment.

[0156] 4. Process lubrication parameters

[0157] During strip rolling, the rolls require rolling oil for lubrication and cooling. The lubricating oil film in the roll gap of the rolling mill can play a certain damping role for the vertical movement of the rolling mill system. At the same time, if the rolling oil temperature is too low, the viscosity will increase, the friction coefficient of the rolling oil will decrease, and the damping effect of the oil film will be weaker, resulting in a decrease in the stability of the rolling mill system. In addition, the rolling oil ratio will also affect the performance of the rolling oil and affect the friction coefficient. Changes in the friction coefficient cause changes in the rolling pressure, resulting in periodic fluctuations in the system stiffness, thereby triggering self-excited vibration of the rolling mill.

[0158] Comparison table of usage results for adjusting the ratio of rolling oil additives

[0159]

[0160]

[0161] Furthermore, even after adjusting the zoned cooling spray curves, spray pressure, and flow rate, vibration patterns still persisted, varying in severity and exhibiting no discernible pattern.

[0162] like Figure 3 , Figure 4 As shown, by adjusting the content of rolling oil additives and parameters such as injection pressure and flow rate, the vibration marks showed signs of reduction in certain specific situations, but the marks still existed, only differing in degree. Therefore, it is believed that the vibration marks were not caused by the lubrication of the rolling oil.

[0163] 5. Main drive reduction gearbox

[0164] After the main drive gearbox has been running for a long time, the helical gear teeth inside the gearbox will wear and the positioning clearance of the fixed meshing gears will be out of tolerance. This will cause a gap in the gear meshing, which will cause a significant increase in the impact amplitude when the gears mesh, resulting in vibration. This vibration will eventually act on the surface of the strip and produce vibration marks.

[0165] The main drive reduction gearbox was disassembled on-site, and inspection revealed a certain degree of wear on the helical gear teeth. Figure 5 :

[0166] By calculating the gear meshing frequency, we can check whether the vibration pattern is caused by the gears in the main drive reduction gearbox. The gear meshing frequency is calculated as follows:

[0167] Given: Low gear reduction ratio 1:2.03, number of teeth on output shaft Z1 = 63, number of teeth on input shaft Z2 = 31;

[0168] The high-speed reduction ratio is 1:1, the number of teeth on the output shaft is Z3=47, and the number of teeth on the input shaft is Z4=47.

[0169] Take the diameter d of the working roller WR =420mm, the commonly used on-site rolling speed is V=500m / min.

[0170] Calculate the output shaft speed of the main gearbox:

[0171] achievable

[0172] Output shaft rotation frequency

[0173] According to the meshing frequency formula:

[0174] f m =f 转频 ×Z(3)

[0175] In the formula, fm is the gear meshing frequency, f is the input shaft or output shaft rotation frequency, and Z is the number of teeth of the corresponding input shaft or output shaft;

[0176] According to equation (3), we can obtain that

[0177] High-speed gear meshing frequency f m-高速 =f 输出 ×Z3=6.3×47=296.1Hz

[0178] meshing frequency f at low speed m-低速 =f 输出 ×Z1=6.3×63=396.9Hz

[0179] According to equation (1), substituting f m-高速 and f m-低速 We can obtain them separately.

[0180]

[0181] From the above calculations, we can see that ω 低速 With ω 高速 The calculated values ​​are close to or match the measured strip surface vibration pattern spacing of 28 mm, indicating that the meshing frequency of the helical gears in the main drive reduction gearbox of the rolling mill is similar to or equal to the vibration pattern frequency. Therefore, it can be preliminarily determined that the impact generated by the helical gears excites the rolling mill vibration, thus leading to the formation of vibration patterns on the strip surface. This further confirms that the main drive line can generate impact vibration due to equipment wear, which excites the rolling mill vibration and causes vibration patterns.

[0182] Based on the above assessment, the company readjusted the gear fit by grinding and replacing some worn gears, and adjusting the gear bearing clearance. Because the helical gear's helix angle is relative to the gear axis, the gear pair generates an axial thrust while transmitting torque. This causes meshing impact during engagement due to excessive axial clearance in the gear bearing. The axial clearance of the bearing was measured and adjusted from 0.95mm (when vibration marks appeared) to 0.4mm. The gear and its bearing were also axially positioned. After re-production, no vibration marks were found.

[0183] The company subsequently strengthened its point inspections and regular maintenance of all components in the main drive line, strictly and regularly inspected and adjusted the clearance of gear transmission components, and improved the gears and their meshing accuracy to prevent vibration from recurring.

[0184] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for determining the cause of vibration marks in aluminum cold rolling mills from a mechanical perspective, characterized in that: Includes the following steps: S1: Use the process of elimination to investigate, and provide the rolls to different rolling mills using the same grinding machine that grinds the same pair of rolls with identical grinding parameters: If vibration marks appear in different rolling mills, it indicates that grinding marks have appeared in the grinding machine. The accuracy of the grinding machine needs to be checked, including the accuracy of the track, the accuracy of the grinding wheel spindle, the measurement accuracy, the accuracy of the center, and the grinding program. In subsequent grinding processes, real-time monitoring of the roll surface quality should be strengthened. For grinding machines with large vibrations, damping vibration dampers should be installed to reduce the impact of grinding machine vibration on roll grinding vibration. If no vibration marks appear on other rolling mills, the vibration marks on the roll surface caused by grinding can be ruled out. The cause of abnormal vibration of the rolling mill can be attributed to other equipment or process reasons, and proceed to step 2. S2: By calculating the failure frequency of the rolling elements of the roller bearing, it is possible to check whether the vibration marks are caused by bearing issues. The calculated comparison between rolling element failure frequency and vibration crack frequency is as follows: The relationship between vibration marks and mill chatter is as follows: In the formula, ω is the groove pitch in mm, d is the roll diameter in mm, n is the roll speed in r / min, and f is the vibration frequency in Hz; Based on the commonly used on-site rolling speed V=πdn, the actual measured gap ω of the vibration marks is used for calculation: According to equation (1), the vibration frequency is obtained: Then, according to the formula for the failure frequency of bearing rolling elements: In the formula, F is the rolling element failure frequency (Hz), n is the roll speed (r / min), and A is the number of rolling elements per row of the bearing. Under the same conditions, i.e., the rolling speed V = πdn, calculate the rotational speed of each roll. Based on the known roll diameter, calculate the rotational speed of each roll. Based on the above roll speed values ​​and equation (2), we can obtain: Based on the above calculation results, compare the vibration pattern frequency with the failure frequency of each rolling element of the roll bearing. If they are integer multiples, it indicates that the vibration pattern is related to the bearing damage frequency, and the bearing damage needs to be inspected and replaced. If they are not integer multiples, the vibration pattern caused by the failure of the rolling element of the roll bearing can be ruled out, and proceed to step 3. S3: Check the design dimensions of the work roll shaft head and the design dimensions of the coupling that mates with it. This mating dimension is suitable for mating with very small clearances, allowing for a certain amount of relative movement, not requiring free rotation, but allowing for precise positioning. The clearance adjustment is divided into two levels: the first level is 0.06-0.09mm, and the second level is 0.15-0.2mm. Test under the same rolling conditions: if one level has a vibration mark and the other does not, then the mating dimension between the work roll and the flat head may produce vibration marks. The vibration frequency is generated by this clearance, or is the vibration frequency of the rolling mill work roll or an integer multiple of the work roll vibration frequency. The clearance needs to be adjusted to the first level where no vibration marks are produced. If vibration marks are produced in both clearance levels, it means that the clearance has no effect on the vibration marks, and proceed to step 4. S4: Perform dynamic balancing tests and reweighting on existing universal joints. The simplified calculation of the allowable residual imbalance is as follows: in: M --- Mass of the universal joint shaft, in kg; G---Universal joint shaft balance accuracy grade, requiring G6.3; r---Universal coupling shaft correction radius, in mm; n --- the operating speed of the universal joint shaft, in rpm; m --- the allowable residual imbalance, in grams; If the vibration marks disappear after the universal joint is used for rolling after adjusting the counterweight, it indicates that the vibration marks were caused by the dynamic imbalance of the universal joint. If the vibration marks still exist, it is considered that the vibration marks are not caused by the universal joint and proceed to step 5. S5： S51: Adjusting the rolling oil ratio also affects the performance of the rolling oil and the coefficient of friction. The content of the rolling oil additive is set to 7.5% and 9% respectively. By adjusting the rolling oil ratio, the coefficient of friction between the workpiece and the roll is changed, thereby changing the rolling pressure. If the vibration marks disappear, it means that the periodic fluctuation of the system stiffness is caused by the rolling oil ratio, which triggers the self-excited vibration of the mill and produces vibration marks. If the vibration marks do not disappear or only the severity of the marks changes, proceed to S52. S52: Adjust the pressure and flow rate parameters of the zoned cooling spray. It is recommended to test the pressure in three levels: 6 bar, 8 bar, and 10 bar, and the flow rate in three levels: 3000 L / min, 4000 L / min, and 6000 L / min. If the vibration pattern disappears, it indicates that the vibration pattern is caused by the rolling oil lubrication. If the vibration pattern still exists or only varies in severity and there is no pattern, proceed to step 6. S6: By calculating the gear meshing frequency, check whether the vibration pattern is caused by the gears in the main drive reduction gearbox; the gear meshing frequency is calculated as follows: Based on the design drawings of the main drive reducer, the low-speed reduction ratio, the number of teeth on the output shaft Z1, and the number of teeth on the input shaft Z2 are obtained. And the high-speed reduction ratio, the number of teeth on the output shaft Z3, and the number of teeth on the input shaft Z4; Simultaneously, using the known working roll diameter d WR And the commonly used rolling speed V, Calculate the output shaft speed of the main gearbox: achievable Output shaft rotation frequency According to the meshing frequency formula: f m =f 转频 ×Z (3) In the formula, f m f is the gear meshing frequency. 转频 Z represents the rotational frequency of the input or output shaft, and Z represents the number of teeth on the corresponding input or output shaft. According to equation (3), we can obtain that High-speed gear meshing frequency f m-高速 =f 输出 ×Z3 meshing frequency f at low speed m-低速 =f 输出 ×Z1 According to equation (1), substituting f m-高速 and f m-低速 We can obtain them separately. The above calculations can be used to determine ω. 低速 With ω 高速 Comparing the calculated values ​​with the measured spacing of vibration marks on the strip surface, if they are close or match, it indicates that the meshing frequency of the helical gears in the main drive reduction gearbox of the rolling mill is similar to or equal to the frequency of the vibration marks. Therefore, it can be determined that the impact generated by the gears excites the vibration of the rolling mill, thereby leading to the formation of vibration marks on the strip surface. This further confirms that the impact vibration generated by the main drive line due to equipment wear excites the vibration of the rolling mill, resulting in vibration marks.

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