Technological method for reducing aluminum plate cold rolling roll marks

Abstract

The invention relates to a process method for reducing cold rolling roll marks of an aluminum plate. The process method comprises the steps that S1, the plate shape of the aluminum plate is pre-adjusted; s2, an upper roller and a lower roller with a diameter difference value are selected for rolling, wherein the diameter of the lower roller is 1.0-1.5 mm larger than that of the upper roller; s3, the height delta of a cold rolling line is set according to the thickness h of the incoming aluminum plate, and the determination mode is shown in the table 1; s4, during rolling, the thickness of the aluminum plate, the cold rolling pass and the single-pass cold rolling machining rate meet the corresponding relation shown in the table 2; and meanwhile, in the rolling process, rolling oil with the viscosity of 7.5-12.0 mm < 2 > / s at the temperature of 40 DEG C is sprayed to the position, 12-20 cm away from the plate head, of the lower surface of the plate head. By systematically optimizing key parameters such as plate shape pre-adjustment, rolling line height setting, upper and lower roller diameter matching, cold rolling pass and machining rate control and rolling lubricating technology, the roller mark defect caused by head warping in the cold rolling process of the aluminum plate is effectively restrained, the surface quality of a finished plate is remarkably improved, the surface smoothness of the product is high, and the product quality is improved. And the strict requirements of high-end applications such as polishing, wire drawing, oxidation coloring and the like on chromatic aberration and consistency are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic working of aluminum materials, and particularly relates to a process method for reducing cold rolling imprint of aluminum plates. BACKGROUND

[0002] The rolling imprint defect generated in the cold rolling process of aluminum plates is a technical problem that has long plagued the aluminum material processing industry. The head warping deformation of the aluminum plate is the main cause of the rolling imprint defect on the surface of the aluminum plate. The warping is divided into head warping and head buckling, the upward bending is head warping, and the downward bending is head buckling. The cold rolling imprint has a relatively large impact on the plate quality, such as the thickness tolerance of the plate being out of tolerance, the uneven distribution of internal stress causing the flatness to be unqualified during sawing and processing deformation, and the inconsistent color difference of the polished wire drawing / oxidized coloring plate surface. SUMMARY

[0003] (I) Technical problem to be solved

[0004] In view of the above-mentioned defects and shortcomings of the prior art, the present application provides a process method for reducing the cold rolling imprint of aluminum plates. The process method of the present application is designed by deeply analyzing the causes of the filter plate warping combined with the production characteristics on site, so as to achieve the technical purpose of inhibiting the head warping problem of the aluminum plate in production (reducing warping or edge wave defects) and reducing the occurrence of cold rolling imprint defects.

[0005] (II) Technical scheme

[0006] In a first aspect, the present application provides a process method for reducing the cold rolling imprint of aluminum plates, which comprises the following steps:

[0007] S1, pre-adjusting the plate shape of the aluminum plate;

[0008] S2, selecting an upper roll and a lower roll with a diameter difference for rolling, wherein the diameter of the lower roll is 1.0-1.5mm larger than the diameter of the upper roll;

[0009] S3, setting the height δ of the cold rolling line according to the thickness h of the incoming aluminum plate, and the determination method is:

[0010] When 6≤h<12mm, -1.0mm≤δ<0mm;

[0011] When 12mm≤h<20mm, δ=0mm;

[0012] When 20mm≤h<40mm, 0≤δ<2.0mm;

[0013] When 40mm≤h<60mm, 2.0≤δ<5.0mm;

[0014] When 60mm≤h<100mm, 5.0≤δ<10.0mm;

[0015] 10.0≤δ<15mm when 100mm≤h<220mm;

[0016] S4, after rolling, the thickness of the aluminum plate, the number of cold rolling passes, and the single pass cold rolling reduction rate satisfy the following corresponding relationship:

[0017] when 6mm≤thickness h<15mm, the number of cold rolling passes is 1, and the reduction rate is 2.2-3.2%;

[0018] when 15mm≤thickness h<25mm, the number of cold rolling passes is 2, and the reduction rate is 2.0-3.0%;

[0019] when 25mm≤thickness h<40mm, the number of cold rolling passes is 3, and the reduction rate is 2.0-2.7%;

[0020] when 40mm≤thickness h<60mm, the number of cold rolling passes is 4, and the reduction rate is 1.8-2.5%;

[0021] when 60mm≤thickness h<100mm, the number of cold rolling passes is 6, and the reduction rate is 1.5-2.2%;

[0022] when 100mm≤thickness h<220mm, the number of cold rolling passes is 9, and the reduction rate is 1.0-1.5%; during rolling, 40℃ rolling oil with viscosity of 7.5-12.0mm / s is sprayed to the lower surface of the plate head at a distance of 12-20cm from the plate head. 2

[0023] In the above scheme, the rolling line height δ = the offset of the actual rolling center line relative to the theoretical center line (usually the + value is the downward offset, and the - value is the upward offset).

[0024] According to the preferred embodiment of the present application, step S1 includes pre-adjusting using a multi-roller straightening system, and combining with detecting the plate shape curvature using a special instrument to meet the following requirements:

[0025] the plate head of a plate with thickness h of 6mm≤h<12mm is warped upward by 0-30mm;

[0026] the plate head of a plate with thickness h of 12mm≤h<20mm is warped downward by 0-30mm;

[0027] the flatness of the plate head of a plate with thickness h≥20mm is within ±10mm.

[0028] ​According to the preferable embodiment of the present application, in step S1, the multi-roller straightening system is configured with 9-11 roller straightening machines for the plate with thickness h<20mm, and large span roller system for the plate with thickness h≥20mm; the diameter of the working roller is 200-350mm, and the roller diameter is designed in gradient, and the larger the thickness of the plate is, the larger the diameter of the roller is.

[0029] According to the preferable embodiment of the present application, in step S1, the pre-adjustment method is as follows:

[0030] The pre-adjustment method for the plate with thickness 6mm≤h<12mm is to establish a quadratic parabolic straightening curve: y=0.15x 2 , wherein x is the initial distance of the plate head, unit: m; the aluminum plate is preheated to 80-120℃, the third and fifth rollers are controlled to apply reverse bending moment, and the bending moment gradient is 15-20kN·m / m; the mechanical parameters are: straightening force 300-500kN, straightening speed 15-20m / min; the laser range finder is used to measure at 500mm of the plate head, and the plate is qualified when the warping amount is 0-3.75mm;

[0031] The pre-adjustment method for the plate with thickness 12mm≤h<20mm is: 50-80℃ hot air circulation heating, the first straightening roller is controlled to pre-set the down pressure 1.2-1.8mm, the pressure transition is started at 200mm of the plate tail, and the pressure decay rate is 2-3MPa / m; the mechanical parameters are: straightening force 500-800kN, straightening speed 10-15m / min, and straightening acceleration≤0.3m / s 2 ; online 3D profile instrument monitoring, and the plate is qualified when the predetermined warping height is reached;

[0032] The pre-adjustment method for the plate with thickness 20mm≤h is: preheated to 200-250℃, coarsely straightened at 800-1000kN, then cold straightened at room temperature by using double cross roller system at 1000-1200kN, the cross angle of the double cross roller system is 0.5-1.2°, and the straightening speed is 5-8m / min; online 3D profile instrument monitoring, and the plate is qualified when the predetermined flatness is reached.

[0033] According to the preferable embodiment of the present application, in S2, the diameter of the lower roller=diameter of the upper roller+(1.0-1.2)mm, preferably, the diameter of the lower roller=diameter of the upper roller+1.0mm.

[0034] According to the preferable embodiment of the present application, in S4, during the rolling process, the bite-in speed, the rolling acceleration and the maximum rolling speed of the aluminum plate satisfy: maximum rolling speed=18-22m / min, the bite-in speed is 1 / 4 of the maximum rolling speed, and the rolling acceleration is to ensure that the maximum rolling speed is reached in 6.5-7.5 seconds.

[0035] According to the preferred embodiment of the present application, in S4, the oil injection position is 150mm below the head lower surface from the head end, and the composition of the rolling oil is: kerosene 69.6-70.4%, base oil 23.3-23.7%, additive 6-6.4%, acid agent 0.2-0.4%, and the pH is 4-4.5.

[0036] According to the preferred embodiment of the present application, in S4, the composition of the rolling oil is: kerosene 70%, base oil 23.5%, additive 6.2%, acid agent 0.3%, and the pH is 4-4.5.

[0037] (III) Beneficial effects

[0038] The present application provides a process for reducing the cold rolling of aluminum plate roll marks, by systematically optimizing key parameters such as plate shape pre-adjustment, rolling line height setting, upper and lower roller diameter matching, cold rolling pass and processing rate control, and rolling lubrication process, effectively inhibiting the roll mark defects caused by head warping during cold rolling of aluminum plate, and significantly improving the surface quality and dimensional accuracy of finished plate. The specific technical effects are as follows:

[0039] 1. Significantly reduce the incidence of cold rolling marks: By implementing differentiated plate shape pre-straightening strategies for different thickness aluminum plates, the roll mark defect rate is reduced from the original 8.5% or more to 0.6% or less, especially in thick plate (≥20mm) rolling, the improvement effect is more obvious. Combined with segmented straightening process and temperature regulation, the flatness of the head of thick plate is controlled within ±10mm, significantly improving the stability of the initial stage of rolling.

[0040] 2. Inhibit head warping and improve bite stability: The rolling line height δ is reasonably set according to the thickness of the aluminum plate, and the lower roller diameter is slightly larger than the upper roller (1.0-1.2mm larger), forming a "micro wedge" entry zone that is beneficial to the stable bite of the head, avoiding the warping or buckling phenomenon caused by asymmetric stress on the upper and lower rollers.

[0041] 3. Optimize cold rolling deformation distribution and improve stress uniformity: Set reasonable cold rolling pass and processing rate range for different thickness intervals to avoid local stress concentration caused by excessive deformation in single pass. Multi-pass small reduction rolling is beneficial to the uniformization of metal flow, reducing residual internal stress, thereby reducing the warping and deformation risk in subsequent processing (such as sawing, tension leveling, heat treatment), and improving the final flatness of the plate.

[0042] 4. Improve surface quality and adaptability to subsequent processing: precisely control straightening force, speed and bending moment gradient, combined with gradient roll diameter design and hot-cold straightening composite process, to ensure full straightening of thick plates without damaging the surface. At the same time, use weakly acidic rolling oil (pH 4-4.5) with a specific formula, and spray it at a fixed point 150mm below the head of the plate, which effectively enhances the lubrication effect and cooling uniformity, prevents sticking and scratching, ensures surface smoothness, and meets the stringent requirements of color difference and consistency for high-end applications such as polishing, wire drawing, and oxidation coloring.

[0043] The process method of the present application is established through in-depth analysis of the causes of filter plate warping and based on actual production data and mechanical analysis, suitable for cold rolling production of various types of aluminum alloy plates in the thickness range of 6-220mm. Through multi-dimensional collaborative control means, the problem of roll marks caused by poor plate shape in the aluminum plate cold rolling process is fundamentally solved, not only improving the product pass rate and surface quality, but also enhancing the stability and economy of production, with significant technical advancement and industrial application value. DETAILED DESCRIPTION

[0044] In order to better explain the present application, the following specific embodiments are used to describe the present application in detail.

[0045] In the production process of aluminum and aluminum alloy medium-thick plate (thickness ≥ 6mm) by block method cold rolling (i.e. single sheet rolling, non-continuous rolling), although the generation of roll mark defects is directly related to the plate head warping, the deep reason thereof involves the complex coupling of multiple aspects such as material, process, equipment, lubrication and thermodynamics. The aluminum plate head is in a stressed free state, and the stress state thereof is the most complex, mainly in three-way stress distribution, and the stress distribution is most likely to be uneven, thereby causing the aluminum plate head to generate warping phenomenon such as warping head or buckling head (warping head for upward bending, buckling head for downward bending). In addition to the foregoing reasons, the inventors analyze the deep reason of roll mark generation from the mechanism level, which further includes (1) imbalance of friction coefficient caused by poor rolling lubrication, and the lubrication state directly affects the friction force distribution between the upper and lower rollers and the aluminum plate. If the oil supply of the upper and lower rollers is uneven, the nozzle is blocked or the rolling oil composition is unstable, the friction coefficient difference of the upper and lower interfaces will be caused. The asymmetric friction makes the metal flow speed of the upper and lower surfaces of the aluminum plate inconsistent, a shear stress gradient is generated, and the plate shape instability is induced. For example, when the upper roller is insufficiently lubricated, the upper surface friction is large, the metal flow is slow, and the buckling head is easily caused; on the contrary, the warping head is easily caused. This flow instability can cause local bulging or indentation, which is manifested as non-periodic roll marks. (2) Dynamic inertia effect caused by rolling speed change. In the biting, stable rolling and throwing stages, the rolling speed experiences acceleration, uniform speed and deceleration process. Especially in the low-speed biting stage, improper acceleration control will generate inertia torque. The plate head as a free end is extremely sensitive to acceleration. If the biting acceleration is too large or the acceleration gradient is not stable, a dynamic bending moment will be generated at the plate head, which will aggravate the warping trend. This transient impact may cause the plate head to instantaneously hit the edge of the roller or the supporting roller, causing local indentation or scratches, and forming the starting roll mark.

[0046] In order to eliminate or reduce the aluminum plate cold rolling roll mark, the technical scheme of the present application is as follows:

[0047] Step (1): First, the plate shape of the incoming aluminum plate is as follows:

[0048] The plate head of the 6-12mm thickness size is required to be upwardly warped by 0-30mm; the plate head of the 12-20mm thickness size is required to be downwardly warped by 0-30mm; and the plate head of the thickness of more than 20mm is required to be flat within ±10mm.

[0049] If the shape of the incoming aluminum plate can meet the above requirements, no pretreatment is needed, otherwise, the plate should be pre-adjusted and the special instrument should be used to detect the shape curvature to meet the above requirements. The pre-adjustment is to use the multi-roll straightening system for pre-straightening. Generally, the multi-roll straightening system is configured with 9-11 roll straightening machines, and the close-packed roller system is used for the plate with a thickness h < 20 mm, and the large-span roller system is used for the plate with a thickness h ≥ 20 mm; the work roll diameter is 200-350 mm, and the roll diameter is gradient designed, and the larger the plate thickness, the larger the diameter of the roll.

[0050] The multi-roll structure of the 9-11 roll straightening machines of the multi-roll straightening system can realize multiple repeated bending, so that each layer of the metal experiences sufficient elastic-plastic deformation, effectively releases residual stress, and compared with the few-roll straightening machine, can more thoroughly homogenize the internal stress and improve the plate shape consistency. The close-packed roller is mainly used for thin plate (h < 20 mm) to reduce the support span and prevent the thin plate from producing "bulging" or secondary warping during straightening due to insufficient stiffness. The large-span roller is mainly used for thick plate (h ≥ 20 mm) to consider the characteristics of high stiffness of thick plate and avoid surface indentation or tissue damage caused by excessive bending. Thick plate has high yield strength and large deformation resistance, and requires larger bending moment to effectively straighten. The large-diameter roller has higher bending stiffness and larger force arm, and can apply larger straightening force without being easily deformed, so the thick plate uses large-diameter roller and the thin plate uses small-diameter roller, which can effectively ensure the effective transmission of straightening force and avoid "slip" or "ineffective straightening".

[0051] Specifically, the pre-adjustment method for aluminum plates of different thicknesses is as follows:

[0052] The pre-adjustment method for the plate shape with a thickness of 6 mm ≤ thickness h < 12 mm is as follows:

[0053] The quadratic parabolic straightening curve y = 0.15x is established. 2 Wherein, x is the starting distance of the plate head, unit: m; first preheat the aluminum plate to 80-120℃ (temperature control accuracy ±5℃), control the third and fifth rollers to apply reverse bending moment, and the bending moment gradient is 15-20 kN·m / m.

[0054] Mechanical parameters: straightening force 300-500 kN, straightening speed 15-20 m / min.

[0055] Detection standard: use a laser range finder to measure at 500 mm from the plate head, and when the warping amount is 0-3.75 mm, it is qualified.

[0056] Thin and medium plates are prone to small radius warping in a free state, so a parabolic preset curvature is used, which is equivalent to pre-assigning the plate with a controllable "anti-warping" shape. When the rolling is bitten, this preset curvature can offset the natural warping tendency caused by the difference in upper and lower friction during rolling. According to y = 0.15x 2The straightening curve of the aluminum plate shows that the amount of warping increases with the square of the distance from the head of the plate (x = 0), forming a gently rising "upward warping" trend, which is suitable for the subsequent rolling entry conditions. The aluminum plate is preheated to 80-120°C, which can improve the plasticity of the material and reduce the yield strength, so that the straightening is easier and new residual stress is not easy to produce. Among them, the third and fifth rollers apply a reverse bending moment (15-20 kN·m / m) to realize "local reverse bending" and eliminate the original bending trend in the head area. By adjusting the warping amount measured at 500 mm to be within the range of 0-3.75 mm, a controllable upward warping entry shape can be established for thin medium plates to prevent excessive warping of the head during rolling, which can cause abnormal contact with the upper roller and produce indentation.

[0057] The pre-adjustment method for plates with a thickness of 12 mm≤h<20 mm is as follows:

[0058] The temperature difference between the core and the surface of the plate is ≤15°C under the hot air circulation heating at 50-80°C.

[0059] The preset down pressure of the first straightening roller is controlled to be 1.2-1.8 mm, and the pressure is gradually reduced at the tail of the plate for 200 mm, and the pressure decay rate is 2-3 MPa / m.

[0060] Mechanical parameters: straightening force 500-800 kN, straightening speed 10-15 m / min, straightening acceleration ≤0.3 m / s 2 .

[0061] Detection standard: online 3D profilometer monitoring, and the predetermined warping height is reached.

[0062] The temperature is moderate at 50-80°C, which softens the material and does not cause oxidation or changes in the structure, which is beneficial to straightening. The preset down pressure of the first straightening roller is 1.2-1.8 mm, which actively applies the initial pressure and forces the head of the plate to bend downward, forming a "buckling head" trend to resist the common "warping head" tendency during rolling. The pressure is gradually reduced at the tail of the plate for 200 mm, and the pressure decay rate is 2-3 MPa / m, which prevents uneven elastic rebound at the end of straightening due to sudden unloading, causing the tail to warp or wave. Low-speed straightening and low acceleration reduce the influence of dynamic inertia, ensuring that the straightening process is stable and controllable. This step establishes a controllable buckling head entry shape for medium plates, balances the deformation difference between the upper and lower surfaces during rolling, and suppresses the roll marks caused by warping the head.

[0063] The pre-adjustment method for plates with a thickness of 20 mm≤h is as follows:

[0064] Preheat to 200-250°C (eliminate 90% of the initial stress under hot state), coarse straightening at 800-1000 kN, and then cold straightening at room temperature using a double cross roller system at 1000-1200 kN, and the cross angle of the double cross roller system is 0.5-1.2°. In general, the greater the thickness of the aluminum plate, the greater the straightening force used.

[0065] Mechanical parameters: straightening speed v = 5-8 m / min. Preferably, a speed-force coupling control is used, with a control relationship of v = 8-0.03F, v in units of m / min, and F in units of kN.

[0066] Detection standard: online 3D profile monitoring, until the preset flatness is reached.

[0067] First, preheat to 200-250°C, significantly reduce the yield strength, facilitate the realization of full plastic deformation under large tonnage straightening force (800-1000 kN), release deep residual stress. The first stage is rough straightening, to remove macro bending at high temperature; the second stage is cold straightening, to realize fine adjustment of flatness at room temperature, avoiding high temperature springback error. Double cross roller system (cross angle 0.5-1.2°) mainly changes the transverse distribution of the roll gap by tilting the roll shaft, compensates for the common "middle wave" or "edge wave" of thick plates, and realizes the shape control in three-dimensional space. High straightening force (1000-1200 kN) + low speed (5-8 m / min) is used in cold straightening to match the high rigidity requirement of thick plates, to ensure effective deep straightening. This step realizes deep stress homogenization and high-precision flatness control of thick plates, fundamentally eliminating roll marks caused by poor initial plate shape.

[0068] The above pre-adjustment of plate shape of different thicknesses is a key pre-process to eliminate residual stress of incoming material, improve initial plate shape, and control warping tendency. If there are waves, side bends or warping in the incoming material, it will cause a sudden change in local contact pressure due to uneven stress when entering the cold rolling, forming a non-uniform deformation zone, which is prone to induce roll marks. This step actively applies controllable reverse stress through the straightening system to offset or reconstruct the original internal stress distribution, so that the plate is in a "low stress, high flatness" stable state before entering the rolling mill, avoiding instability-induced warping and roll marks in the initial stage of rolling.

[0069] Step (2): selecting an upper roller and a lower roller with a diameter difference for rolling, wherein the lower roller diameter is 1.0-1.5 mm larger than the upper roller diameter, preferably, the lower roller diameter = the upper roller diameter + (1.0-1.2) mm, further preferably, the lower roller diameter = the upper roller diameter + 1.0 mm. Wherein, the diameter difference between the upper and lower rollers of the cold rolling mill ensures that the lower roller speed is greater than the upper roller speed, so that the upward warping deformation height of the aluminum plate after passing through the roller is controlled within 0-300 mm. Wherein, the upper roller diameter can be 400-700 mm, and in general, the larger the plate thickness of the aluminum plate, the larger the diameter of the rolling roller used in cold rolling.

[0070] When the lower roller is slightly larger, the lower surface linear velocity is slightly higher than the upper surface, which will result in the lower surface metal flowing slightly faster, thus forming a slight "upward bending" trend at the head of the plate (i.e. preset "head warping"). This preset deformation can offset the actual "head warping" aggravation caused by greater friction of the upper roller during rolling, achieving dynamic balance. Preferably, the lower roller diameter = the upper roller diameter + 1.0 mm, further optimizing the difference between the lower roller and the upper roller diameter to avoid excessive difference causing new shear stress concentration or edge bulging.

[0071] This step can form a controllable difference between the upper and lower surface velocities and deformations, actively regulate the plate shape evolution path, suppress warping development, and reduce indentation caused by uneven contact between rollers.

[0072] Step (3): Set the height δ of the cold rolling line according to the thickness h of the incoming aluminum plate, and the corresponding relationship is shown in Table 1 to ensure that the aluminum plate is flat and not warped when it exits the roller.

[0073] Table 1: Corresponding relationship between cold rolling line height (δ) and aluminum plate thickness (h)

[0074]

[0075] wherein the rolling line height δ = the offset of the actual rolling center line relative to the theoretical center line (generally, the + value is the downward offset, and the - value is the upward offset). By adjusting the rolling center line position in sections, a "micro-wedge-shaped entry zone" that is beneficial to the stable biting of the plate head is constructed, avoiding the instability of warping caused by the sudden change of stress at the free end, thereby reducing the initial roller marks generated during the biting stage. Generally speaking, the larger the thickness of the aluminum plate, the higher the corresponding value selected within the interval.

[0076] Step (4): After selecting the cold rolling roller, cold rolling is performed. During cold rolling, the corresponding relationship between the thickness of the aluminum plate, the cold rolling pass, and the cold rolling reduction rate is shown in Table 2, which can prevent the generation of cold rolling marks. During rolling, 40°C rolling oil with a viscosity of 7.5-12.0 mm 2 / s is sprayed to the lower surface of the plate head at a distance of 12-20 cm from the plate head.

[0077] Table 2: Corresponding relationship between aluminum plate thickness, cold rolling pass, and single pass cold rolling reduction rate

[0078] Aluminum sheet thickness (mm) Cold rolling passes (passes) Single pass cold rolling reduction (%) 6 mm ≤ thickness h < 15 mm 1 2.2～3.2 15 mm ≤ thickness h < 25 mm 2 2.0～3.0 25 mm ≤ thickness h < 40 mm 3 2.0～2.7 40 mm ≤ thickness h < 60 mm 4 1.8～2.5 60 mm ≤ thickness h < 100 mm 6 1.5～2.2 100 mm ≤ thickness h < 220 mm 9 1.0～1.5

[0079] Wherein, thick plate single large reduction easily causes surface and core deformation uncoordinated, stress gradient steep increase, local yield instability. And multi-pass small reduction can realize deformation energy dispersion, stress partial release after each pass, more uniform metal flow, reduce cumulative residual stress and other effects. Wherein, with the greater the thickness of the aluminum plate, the more the cold rolling passes, the smaller the single pass deformation of the thicker plate, to control the stress increment in each pass within a safe range, prevent stress superposition exceeding the yield limit, thereby inhibit warping and bulging. For thick plate, use progressive, low stress accumulation rolling process, avoid local instability and roll imprint caused by severe deformation.

[0080] In addition, the rolling speed, including the bite speed, rolling acceleration, maximum rolling speed, etc. also affect the formation of cold rolling roll imprint. Therefore, during the rolling process, the bite speed, rolling acceleration, maximum rolling speed of the aluminum plate meet the following conditions:

[0081] ① The maximum rolling speed = 18-22 m / min, preferably 20 m ± 0.5 m / min. At this maximum rolling speed, the production efficiency and stability can be balanced. Too high is easy to cause vibration; too low will prolong the rolling time and increase the risk of uneven temperature rise.

[0082] ② The bite speed is 1 / 4 of the maximum rolling speed. Lower bite reduces impact and prevents the head of the plate from bending sharply or impacting the roll due to inertia.

[0083] ③ The rolling acceleration is to ensure that the maximum rolling speed is reached in 6.5-7.5 seconds. The acceleration is about 0.2-0.3 m / s 2 , to avoid excessive dynamic bending moment causing instantaneous warping of the head. By smooth acceleration transition, reduce the impact of dynamic load on the shape of the plate, prevent "start roll imprint".

[0084] Because the viscosity of the rolling oil for cold rolling and the position of the oil spray on the plate surface are different, the metal flow direction during deformation of the aluminum plate during cold rolling can be changed, thereby changing the warping direction of the aluminum plate when it exits the roll. Therefore, during the rolling process, the aluminum plate is sprayed with rolling oil, the oil spray position is the lower surface of the plate head 150 mm away from the end of the plate head, and the composition of the rolling oil is: kerosene 69.6-70.4%, base oil 23.3-23.7%, additives 6-6.4%, acid agent 0.2-0.4%, pH 4-4.5. Preferably, the composition of the rolling oil is: kerosene 70%, base oil 23.5%, additives 6.2%, acid agent 0.3%, pH 4-4.5.

[0085] Since the head of the plate is a free end, it is most prone to dry friction or local adhesion with the lower roller. Therefore, pre-lubrication on the lower surface can reduce the friction coefficient of the lower roller, reduce the flow resistance of the lower surface, help to form a slight "head-up" trend, and the roller diameter difference in step (2) cooperates. When spraying rolling oil, avoid spraying on the upper surface to prevent the upper surface from being too lubricated, which can cause "head buckling". By spraying rolling oil at a fixed position, directional lubrication controls the asymmetry of friction and actively guides the evolution direction of the plate shape.

[0086] The 40℃ viscosity of the rolling oil is 7.5-12.0mm 2 / s, which is mainly composed of kerosene as the main solvent (diluent), has moderate volatility (slow evaporation), and good cleanliness. The base oil is a deeply refined mineral lubricating oil or a synthetic hydrocarbon oil (such as poly-alpha olefin), and the kinematic viscosity (40℃) is 20-35mm 2 / s, which can provide a basic lubricating film. The additives are preferably extreme pressure additives (such as phosphate ester), antioxidants, and rust inhibitors to improve boundary lubrication performance. The acid agent mainly adjusts the pH, and a slightly acidic environment can slightly etch the aluminum plate surface oxide film to improve the wettability and adsorption capacity of the lubricant, enhance the adhesion of the oil film, and prevent the oil film from breaking down to cause local dry friction. The pH cannot be too low to avoid causing corrosion of the aluminum plate. By spraying rolling oil, a stable and high-strength lubricating film is formed at a specific position on the aluminum plate, reducing friction fluctuations, preventing aluminum sticking, scratching, and local indentation (i.e. chemical roller marks) caused by lubrication failure.

[0087] In the above scheme, step (1) regulates or pre-adjusts the plate shape of the incoming aluminum plate, eliminates initial stress (eliminates source defects), and controls warping. This process involves multi-stage straightening, thermal-mechanical coupling, and online detection, providing excellent sources for subsequent cold rolling; step (2) selects upper and lower rollers with a diameter difference, actively controls the flow rate difference between the upper and lower rollers, and uses the speed difference to induce controllable warping, which cooperates with the oil spraying position to adjust the friction; step (3) determines the rolling line δ to build a stable bite condition, which cooperates with step (2) to optimize the inlet shape to build an ideal bite and deformation path; step (4) sets the reduction passes and single-pass cold rolling reduction rate according to the thickness of the aluminum plate, disperses the deformation stress for thick plates, and reduces the single-pass stress peak to prevent cumulative instability. During cold rolling, the bite speed is controlled to suppress dynamic impact, and slow acceleration and low bite speed are used to protect the stability of the aluminum plate head. During rolling, the rolling oil is sprayed at a fixed position to control the symmetry of friction, and the lower surface is preferentially lubricated to form a positive feedback with the diameter difference.

[0088] The present application solves the problem of aluminum plate cold rolling imprint by pre-control, guidance, balancing, protection and other technical routes. The parameters set in the above steps are not set independently, but are optimized based on the coupling simulation and measured data of stress field, velocity field and lubrication field, have scientific basis and engineering practicability, can significantly reduce the occurrence rate of roll imprint, and improve the surface quality and yield of high-end aluminum plate.

[0089] The following embodiments are set according to different incoming aluminum plate thicknesses.

[0090] Example 1

[0091] Incoming material: 5052 aluminum alloy, plate width 1200mm, plate length 2500mm, thickness 8mm. The process steps are as follows:

[0092] (1) Plate pre-adjustment: 11-roll close-packed straightening machine (roll pitch 180mm) is used, and the working roll diameter is 220mm. The aluminum plate is heated to 100℃ (electric heating air circulation), and is straightened according to the straightening curve y=0.15x 2 (x is the distance from the plate head, unit m) to control the 3rd and 5th rolls to apply reverse bending moment, and the bending moment gradient is 18kN·m / m; the straightening force is set to 400kN, and the straightening speed is 18m / min. The laser range finder is used to measure at 500mm from the plate head, and the warping amount is controlled to be 2.5-2.6mm.

[0093] (2) Roll configuration: the upper working roll diameter is 480mm, and the lower roll diameter is 481.0mm.

[0094] (3) Rolling line height δ: set to -0.6mm (i.e. the rolling center line is moved up by 0.6mm).

[0095] (4) Rolling parameters: cold rolling pass is 1, processing rate is 2.8%, biting speed is 5m / min, maximum rolling speed is 20m / min, and the speed is ensured to reach within 7 seconds (acceleration is about 2.38m / s 2 ); the rolling oil is sprayed at the lower surface of the plate head 150mm from the end, and the composition of the rolling oil is: kerosene 70%, mineral lubricating oil 23.5%, additives 6.2%, acid agent 0.3%, pH=4.2, and 40℃ viscosity is 9.2±1.0mm 2 / s.

[0096] Cold rolling state and product detection: the plate head is smoothly bitten, the surface after rolling has no periodic or non-periodic roll imprint, and the flatness is <3I. 3I means that the maximum allowable fluctuation of the plate surface per meter length is 3mm.

[0097] Example 2

[0098] Material: 3003 aluminum alloy, plate width 1500 mm, plate length 3000 mm, thickness 16 mm. Process steps are as follows:

[0099] (1) Plate pre-adjustment: 10-roll close-spaced straightening machine is used, work roll diameter is 280 mm, hot air circulation heating to 65℃. The first straightening roll is preset to 1.5 mm, the pressure is reduced at the tail of 200 mm, and the pressure decay rate is 2.5 MPa / m. Straightening force: 650 kN, straightening speed 12 m / min, acceleration ≤0.3 m / s 2 . On-line 3D profile instrument monitoring, the height of the plate head is controlled at 22-23 mm.

[0100] (2) Roll configuration: the upper work roll diameter is 500 mm, and the lower roll diameter is 501.1 mm.

[0101] (3) Rolling line height δ: set to 0 mm (symmetric rolling line).

[0102] (4) Cold rolling parameters: 2 passes of cold rolling, single pass processing rate is 2.5%; bite-in speed 5.25 m / min, maximum rolling speed 21 m / min, rolling acceleration 7.5 s to speed. Spray rolling oil at the lower surface of the plate head 150 mm from the end, rolling oil composition: kerosene 70%, mineral lubricating oil 23.5%, additives 6.2%, acid agent 0.3%, pH = 4.2.

[0103] Cold rolling state and product detection: stable rolling process, good plate shape, no edge wave or middle indentation, 0% roll mark rate.

[0104] Example 3

[0105] Material: 6061-T6, plate width 1800 mm, plate length 2000 mm, thickness 30 mm. Process steps are as follows:

[0106] (1) Plate pre-adjustment: 9-roll large-span straightening machine (roll span 300 mm) is used, work roll diameter is 320 mm; the aluminum plate is preheated to 220℃ (resistance heating furnace), first high-temperature rough straightening is performed at 900 kN; then, after cooling to room temperature, cold straightening is performed using double cross roll system, cross angle 1.0°, cold straightening force 1100 kN, straightening speed 6 m / min. After pre-straightening, on-line 3D profile instrument detection, plate head flatness control within ±8 mm.

[0107] (2) Roll configuration: the upper work roll diameter is 550 mm, and the lower roll diameter is 551.0 mm.

[0108] (3) Rolling line height δ: set to 1.5 mm (rolling line moderately lowered).

[0109] (4) Cold rolling parameters: 3 passes, single pass reduction ratio 2.3%, bite speed 5 m / min, maximum rolling speed 20 m / min, ensure 7 seconds to reach speed. Spray rolling oil at the lower surface of the head 160 mm from the end, rolling oil composition: kerosene 70%, mineral lubricating oil 23.5%, additives 6.2%, acid agent 0.3%, pH = 4.2.

[0110] Cold rolling state and product detection: uniform deformation of plate thickness, symmetrical distribution of internal stress, no obvious warping or local bulging after rolling, no visible roll marks on the surface.

[0111] Example 4

[0112] Incoming material: 1060 pure aluminum, plate width 1600 mm, plate length 1800 mm, thickness 50 mm. The process steps are as follows:

[0113] (1) Plate pre-adjustment: 9-roll large-span straightening machine, work roll diameter 350 mm. Preheat the aluminum plate to 240°C (resistance heating furnace), first high-temperature rough straightening at 950 kN; then, after cooling to room temperature, cold straightening is carried out using double cross roller system, cross angle 1.1°, cold straightening force 1150 kN, straightening speed 5.5 m / min. After pre-straightening, online 3D profile instrument detection, plate head flatness control within ±9 mm.

[0114] (2) Rolling roller configuration: upper work roll diameter 600 mm, lower roll diameter 601.0 mm.

[0115] (3) Rolling line height δ: set to 3.8 mm (significantly lowered, forming a guide cone angle).

[0116] (4) Cold rolling parameters: 4 passes, single pass reduction ratio 2.1%, bite speed 4.75 m / min, maximum speed 19 m / min, acceleration control 6.5 seconds to reach speed. Spray oil position and oil product are the same as example 1.

[0117] Cold rolling state and product detection: the head is successfully bitten, the rolling force fluctuates little, and no initial roll marks caused by bite impact occur, the finished plate is flat.

[0118] Example 5

[0119] Incoming material: 5083 aluminum alloy, plate width 1400 mm, plate length 1500 mm, thickness 80 mm. The process steps are as follows:

[0120] (1) Plate pre-adjustment: 9-roller large span straightener was used, and the work roll diameter was 350 mm. The aluminum plate was preheated to 250 °C (resistance heating furnace), and high-temperature rough straightening was first performed at 1000 kN; then, after cooling to room temperature, cold straightening was performed using a double cross roller system, the cross angle was 1.2°, the cold straightening force was 1200 kN, and the straightening speed was 5 m / min. After pre-straightening, the on-line 3D profiler was detected, and the plate head flatness was controlled within ±7 mm.

[0121] (2) Roll configuration: the upper work roll diameter was 650 mm, and the lower roll diameter was 651.0 mm.

[0122] (3) Rolling line height δ: set to 7.5 mm (significantly lowered, forming a guide cone angle).

[0123] (4) Cold rolling parameters: the cold rolling pass was 6 times, and the single pass processing rate was 1.8%; the bite-in speed was 4.5 m / min, the maximum speed was 18 m / min; the acceleration control was 6.5 seconds to reach the speed. The oil injection position and oil product were the same as in Example 1.

[0124] Cold rolling state and product detection: the rolling process was smooth, and there was no bulge or shear band, and the surface quality was excellent.

[0125] Example 6

[0126] Incoming material: 7050 aluminum alloy, plate width 1200 mm, plate length 1200 mm, thickness 160 mm. The process steps are as follows:

[0127] (1) Plate pre-adjustment: a special 9-roller heavy straightener was used, and the work roll diameter was 350 mm. The aluminum plate was preheated to 250 °C, and high-temperature rough straightening was first performed at 1000 kN; then, after cooling to room temperature, cold straightening was performed using a double cross roller system, the cross angle was 1.0°, the cold straightening force was 1100 kN, and the straightening speed was 5 m / min. After pre-straightening, the on-line 3D profiler was detected, and the plate head flatness was controlled within ±6 mm.

[0128] (2) Roll configuration: the upper work roll diameter was 700 mm, and the lower roll diameter was 701.0 mm.

[0129] (3) Rolling line height δ: set to 12.0 mm (significantly lowered, forming a strong guide inlet).

[0130] (4) Cold rolling parameters: the cold rolling pass was 9 times, and the single pass processing rate was 1.2%; the bite-in speed was 5 m / min, the maximum speed was 20 m / min; the acceleration control was 7 seconds to reach the speed. The rolling oil was sprayed at the lower surface of the plate head 150 mm from the end, and the rolling oil composition was: kerosene 70%, mineral lubricating oil 23.5%, additives 6.2%, acid agent 0.3%, pH = 4.2.

[0131] Cold-rolled state and product detection: the very thick plate is rolled stably without obvious warping or local deformation concentration, and the finished product surface is smooth without roll mark defects.

[0132] Among them, Example 1 is a thinner aluminum plate, in the cold rolling process, by presetting the upward warping line, low delta and one-pass cold rolling to reduce roll marks, Example 2 is a medium thick plate, the aluminum plate buckle is adjusted in advance, and the roll mark is controlled by using the symmetric rolling line, and the thick aluminum plates of Examples 3-6 use high-temperature rough straightening, combined with cold straightening at room temperature, greatly reduce the rolling line height delta, and reduce the roll marks by multiple passes with small reduction rate.

[0133] Comparative Example 1

[0134] In this example, the incoming material is the same as Example 1. The rolling line height delta is set to be lowered by 0.8 mm. The plate shape is not pre-adjusted according to the thermal-mechanical coupled straightening, and the straightening method is: using a common 5-roll straightening machine for cold straightening, without heating and bending moment control, the straightening force is set to 200 kN, and the straightening speed is 18 m / min. After straightening, the plate head is upwardly warped by 65 mm. Steps (2) and (4) refer to Example 1.

[0135] Cold-rolled state and product detection: the plate head is severely warped, and hits the upper roller edge. Vibration occurs during the biting of the aluminum plate, and periodic indentation appears on the surface of the aluminum plate, and the surface roughness Ra increases from 0.4 μm in Example 1 to 1.2 μm.

[0136] Comparative Example 2

[0137] In this example, the incoming material is the same as Example 5. But the plate shape pre-adjustment method does not have high-temperature rough straightening, and the pre-adjustment method is: only using a common 9-roll straightening machine for straightening at room temperature. There is no preheating before straightening, and the straightening is first performed at room temperature with 1000 kN, without double cross roller system cold straightening. After pre-straightening, the in-line 3D profile instrument detects that the flatness of the plate head is ± 25 mm. During cold rolling, single-pass large reduction rate rolling is used, the single-pass processing rate is 10.8%, the biting speed is 5 m / min, and the maximum speed is 20 m / min.

[0138] The remaining conditions refer to Example 5

[0139] Cold-rolled state and product detection: the plate head is difficult to bite and needs to be tried many times; the rolled plate surface appears non-periodic bulge type roll marks, which are concentrated in the plate head and the middle part.

[0140] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements, or combinations of technical features in the above embodiments do not conflict with each other, and can be combined as recorded in the embodiments, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for reducing cold rolling roller marks on aluminum plates, characterized in that: The steps include: S1. Pre-adjust the shape of the aluminum plate; S2. Selecting an upper roll and a lower roll with a diameter difference for rolling, wherein the diameter of the lower roll is 1.0-1.5 mm larger than the diameter of the upper roll; S3. Set the height δ of the cold rolling line according to the thickness h of the incoming aluminum plate. The determination method is: When 6≤h<12mm, -1.0mm≤δ<0mm; When 12mm≤h<20mm, δ=0mm; When 20mm≤h<40mm, 0≤δ<2.0mm; When 40mm≤h<60mm, 2.0≤δ<5.0mm; When 60mm≤h<100mm, 5.0≤δ<10.0mm; When 100mm≤h<220mm, 10.0≤δ<15mm; S4. During the rolling process, the thickness of the aluminum plate, the number of cold rolling passes, and the single-pass cold rolling processing rate satisfy the following corresponding relationship: When 6mm≤thickness h<15mm, the cold rolling pass is 1 time and the processing rate is 2.2-3.2%; When 15mm≤thickness h<25mm, the number of cold rolling passes is 2 times and the processing rate is 2.0-3.0%; When 25mm≤thickness h<40mm, the number of cold rolling passes is 3 times and the processing rate is 2.0-2.7%; When 40mm≤thickness h<60mm, the number of cold rolling passes is 4 times and the processing rate is 1.8-2.5%; When 60mm≤thickness h<100mm, the number of cold rolling passes is 6 times and the processing rate is 1.5-2.2%; When 100mm≤thickness h<220mm, the number of cold rolling passes is 9 times and the processing rate is 1.0-1.5%; During the rolling process, spray a 40℃ viscosity of 7.5-12.0mm thick liquid on the lower surface of the plate head at a distance of 12-20cm from the plate head. 2 / s rolling oil.

2. The process according to claim 1, characterized in that: Step S1 includes: using a multi-roller straightening system for pre-adjustment, combined with the use of specialized instruments to detect the curvature of the plate to meet the following requirements: For plates with a thickness of 6mm≤h<12mm, the upward warping height of the plate head is 0-30mm; For plates with a thickness of 12mm≤h<20mm, the downward warping height of the plate head is 0-30mm; The straightness of the plate head with thickness h≥20mm is within the range of ±10mm.

3. The process according to claim 1, characterized in that: In step S1, the multi-roller straightening system is configured with 9 to 11 roller straightening machines, which use a close-packed roller system for plates with a thickness of h < 20 mm and a large-span roller system for plates with a thickness of h ≥ 20 mm; the working roller diameter is 200-350 mm, and the roller diameter is designed in a gradient manner. The thicker the plate, the larger the diameter of the roller.

4. The process according to claim 2, characterized in that: In step S1, the pre-adjustment method is as follows: The pre-adjustment method for plates with thickness of 6mm≤h<12mm is to establish a quadratic parabolic straightening curve: y=0.15x 2 , where x is the starting distance from the plate head, in meters. Preheat the aluminum plate to 80-120°C. Control the third and fifth rollers to apply reverse bending moment with a bending moment gradient of 15-20 kN·m / m. Mechanical parameters: straightening force 300-500 kN, straightening speed 15-20 m / min. Use a laser rangefinder to measure 500 mm from the plate head. A warpage of 0-3.75 mm is considered acceptable. The pre-adjustment method for plates with a thickness of 12mm≤h<20mm is as follows: 50-80℃ hot air circulation heating, control the preset downward pressure of the first straightening roller to 1.2-1.8mm, start the pressure reduction transition at 200mm from the plate tail, and the pressure decay rate is 2-3MPa / m; mechanical parameters: straightening force 500-800kN, straightening speed 10-15m / min, straightening acceleration ≤0.3m / s 2 ;Online 3D profilometer monitoring, reach the predetermined warping height; The pre-adjustment method for plates with a thickness of 20mm ≤ h is: preheat to 200-250℃, perform rough straightening at 800-1000kN, and then perform cold straightening at room temperature using a double-cross roller system at 1000-1200kN. The cross angle of the double-cross roller system is 0.5-1.2°, and the straightening speed is 5-8m / min. Monitor with an online 3D profiler to achieve the pre-inspected straightness.

5. The process according to claim 2, characterized in that: In S2, the lower roller diameter = the upper roller diameter + 1.0 mm.

6. The process according to claim 2, characterized in that: In S4, during the rolling process, the bite speed, rolling acceleration and maximum rolling speed of the aluminum plate meet the following requirements: maximum rolling speed = 18-22 m / min, the bite speed is 1 / 4 of the maximum rolling speed, and the rolling acceleration is to ensure that the maximum rolling speed is reached in 6.5-7.5 seconds.

7. The process according to claim 2, characterized in that: In S4, the oil injection position is 150 mm from the lower surface of the plate head to the end of the plate head, and the composition of the rolling oil is: kerosene 69.6-70.4%, base oil 23.3-23.7%, additive 6-6.4%, acid agent 0.2-0.4%, pH 4-4.

5.

8. The process according to claim 7, characterized in that: In S4, the composition of the rolling oil is: kerosene 70%, base oil 23.5%, additive 6.2%, acid agent 0.3%, and pH 4-4.5.

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