Control method for improving EDT roller texturing efficiency and high-surface automobile aluminum plate oil storage amount

Abstract

The invention relates to a control method for improving EDT roller texturing efficiency and high-surface automobile aluminum plate oil storage amount. The control method comprises the steps that (1) a single-rack cold rolling mill is adopted; (2) carrying out roller surface treatment by adopting an electrode electric spark roller grinder, wherein the roughness Ra of a working roller before roughening is less than or equal to 0.4 mu m; the roughness Ra after EDT roughening is equal to 1.95 to 2.2 [mu] m; (3) a single-rack cold rolling mill is adopted for production, the rolling oil temperature is 35 + / -5 DEG C, and the rolling oil pressure is 6.0-9.0 bar; (4) an air cushion type continuous annealing line is adopted for cleaning and solid solution aging treatment; (5) carrying out surface appearance and pit size measurement on the prepared aluminum plate by adopting a 3D optical microscope; and (6) the manufactured aluminum plate is measured through a 3D non-contact optical contourgraph. By means of the method, the requirements for the surface roughness Ra and Rpc of the automobile sheet can be met, the downstream stamping cracking risk and the corrosion spot defect caused by the too large surface pit diameter are reduced, the better high-surface automobile sheet, the higher aluminum sheet surface oil storage amount and the lower friction coefficient can be obtained, and the EDT roller texturing working time can be saved.

Description

Technical Field

[0001] This invention relates to a method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets. Background Technology

[0002] With the increasing demand for lightweighting and energy conservation in the domestic automotive industry, the production of aluminum body panels is constantly increasing. Aluminum alloys are lightweight, corrosion-resistant, have high specific strength, and are easy to process. In the development of automotive body panel rolling technology, hot-rolled billets are used for billet supply. 6-series aluminum alloys are used, with billet thickness of 3.0-8.0 mm and width of 950-2150 mm. The finished product thickness is 0.8-4.0 mm. The main production process route is: melting and casting - sawing - milling - ingot heat treatment - 1+3 hot rolling - cold rolling - intermediate annealing - intermediate cold rolling - finished product cold rolling EDT rolling - continuous annealing - aging - surface passivation treatment - packaging. High-surface-quality automotive aluminum sheets used for car body exteriors require painting. Downstream processes include: aluminum coil – blanking – stamping – car body assembly – phosphating / silanizing – electrophoretic painting – baking. Automotive aluminum sheets typically have a surface roughened using work rollers and grinding wheels, known as a MF (Metallurgical Fabrication) surface. Another surface roughening method is EDT (Electro-Discharge Textured) surface, achieved using work rollers. Lower MF surface roughness results in a lower coefficient of friction, making it easier for the sheets to slip and scratch during slitting. Therefore, most automotive exterior panels use an EDT surface. During the production of automotive aluminum coils, oil is applied to the aluminum sheet surface to prevent surface damage and corrosion during transportation and to provide lubrication during stamping.

[0003] However, due to its low surface roughness, the surface has limited oil storage capacity, and the grinding of the MF surface along the rolling direction is directional, with large differences in roughness between the transverse and longitudinal directions, resulting in insufficient oil storage and uniformity. The EDT surface has better uniform friction performance, making it less prone to slippage during sheet separation. At the same time, the pits on the EDT surface can act as oil storage. Typically, the surface roughness Ra of automotive sheet EDT strips should meet the following requirements: peak number Rpc ≥ 50 / cm (for example, see the method for controlling the peak number of high roughness on the surface of automotive sheet EDT of a six-roll aluminum cold rolling mill disclosed in Chinese Patent Publication No. CN116393523B). However, during the stamping process, it was found that insufficient oil storage on the surface of the strip EDT (under-lubrication) leads to stamping cracks, while excessive oil storage (over-lubrication) causes wrinkles during stamping. Large pits on the surface of the EDT strip can easily cause corrosion points during phosphating treatment after stamping. Summary of the Invention

[0004] The present invention addresses the problems existing in the prior art, namely, the technical problem to be solved by the present invention is to provide a method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a method for controlling the texturing efficiency of EDT rolls and the oil storage capacity of high-surface-area automotive aluminum sheets, comprising the following steps: (1) A single-stand cold rolling mill is adopted, with the working roll diameter ranging from Ф400 to Ф480 mm and the roll surface width of 2050 mm; the intermediate roll diameter ranging from Ф490 to 560 mm and the roll surface width of 2050 mm; and the support roll diameter ranging from Ф1150 to 1400 mm and the roll surface width of 2000 mm. (2) The surface treatment of the roll is carried out by an electrode electric spark roll grinding machine. The electrode type is copper electrode. The roughness Ra of the work roll before roughening is ≤0.4μm; the roughness Ra after EDT roughening is 1.95-2.2μm. (3) Cold rolling mill and rolling process parameters: The single-stand cold rolling mill is used for production. The additive and base oil weight ratio is 8.5-10.0%; the roll diameter is 400-480mm, the work roll type is flat roll; the rolling oil temperature is 35±5℃, the rolling oil flow rate is 3000-4500L / min, and the rolling oil pressure is 6.0-9.0bar; (4) Cleaning, solution treatment and aging are carried out using an air cushion continuous annealing line, and the sharp points on the strip and the strip surface are treated using a straightening machine. The solution temperature is 530-560℃ and the time is 20-30s. The straightening elongation rate is 0.2-0.5% to eliminate the sharp peaks on the strip surface and reduce the friction during strip stamping. The amount of oil applied to the electrostatic oiling surface is controlled at 1.0±0.2g / m2 / side. (5) The surface morphology and pit size of the aluminum plate were measured by a 3D optical microscope. The pit diameter was controlled at 45-65μm by the surface roughness of the roll and the rolling reduction. The surface roughness of the aluminum plate was high and the rolling texture was not obvious after the rough pit was covered. (6) The prepared aluminum plate was measured using a 3D non-contact optical profilometer. The surface roughness Sa of the aluminum plate ranged from 0.75 to 1.0 μm, the sharpness Sku < 3.0 μm, the maximum valley depth Sv ranged from 3.5 to 5.0 μm, and the void volume Vvc and solid volume Vmc of the central part ranged from 1.0 to 2.0 μm. 3 / um 2 Quantify the oil storage capacity of aluminum plate surfaces using data; (7) The friction coefficient test method of metal materials is adopted. Under test temperature conditions, the friction coefficient is measured at a sliding speed of 20 mm / s under pressure of 5MPa and 10MPa, which is convenient for guiding the optimization of EDM process parameters.

[0006] Furthermore, in step (2), the roughening process parameters are: current 12A, on / off time 11 / 15us, electrode travel speed 24mm / min, electrode and roll gap position 3.6 / 3.0mm, roll speed 18mm / min, electrode gain 10, roughening pass number 2, and roughening time 150min.

[0007] Furthermore, in step (3), light white oil 110# base oil is used, and the additive is an alcohol additive.

[0008] Furthermore, in step (3), 6-series aluminum alloy is used for production, with the following chemical composition by mass fraction: Si: 0.10-1.0%; Fe: 0.1-0.30%; Cu: 0.02-0.10%; Mn: 0.1-0.15%; Mg: 0.2-0.6%; Ti: 0.01-0.03%; hot-rolled billet 2.5-6.0mm, final rolling temperature 270~310℃; hot-rolled strip crown range 0-0.3%.

[0009] Furthermore, the rolling process is carried out in 1 to 3 passes to the thickness of the intermediate annealing pass. After the initial rolling and intermediate annealing, the work rolls are rolled with a roughness of Ra=0.2 to 0.6μm by grinding with a grinding wheel. The total processing rate after cold rolling and intermediate annealing is 45-65%. After intermediate annealing, the production is carried out in two passes. The rolls used in the finished product pass are the rolls with electrical discharge machining treatment used in step (2). The processing rate of the finished product pass is controlled at 3.5 to 5.0%.

[0010] Furthermore, in step (4), when applying oil electrostatically, the oil type is Hobton 6130 lubricating oil.

[0011] Furthermore, in step (7), the YS / T4286 test method for friction coefficient of metallic materials is adopted.

[0012] Furthermore, in step (2), the electrode type is PB102 copper electrode.

[0013] Compared with the prior art, the present invention has the following effects: The present invention is reasonably designed and can meet the surface roughness Ra and Rpc requirements of automotive sheet, reduce the risk of downstream stamping cracking and corrosion point defects caused by excessive surface pit diameter, and can obtain better high surface automotive sheet, higher aluminum sheet surface oil storage capacity, lower friction coefficient and save EDT roll texturing time. Attached Figure Description

[0014] Figure 1 In contrast, in Comparative Solution 1 of this invention, long strip rolling marks are visible on the surface of the strip. Figure 2 The strip surface of comparative embodiment 2 in this invention features strip-shaped rolling texture. Figure 3 In contrast, no rolling marks were observed on the surface microstructure of the strip in Comparative Scheme 3 of this invention. Figure 4 It is a function graph of the load area ratio of the separation center and the prominent peak, and the load area ratio of the separation center and the prominent valley. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0016] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0017] This invention provides a control method for improving the texturing efficiency of EDT rolls and the oil storage capacity of high-surface-area automotive aluminum sheets. It saves approximately 150 minutes of processing time per EDT roll, significantly reducing production costs and improving production efficiency. This is a reliable, low-cost, simple, and easily promoted control method, which specifically includes the following steps.

[0018] (1) A single-stand cold rolling mill is adopted, with the working roll diameter ranging from Ф400 to Ф480 mm and the roll surface width of 2050 mm; the intermediate roll diameter ranging from Ф490 to 560 mm and the roll surface width of 2050 mm; and the support roll diameter ranging from Ф1150 to 1400 mm and the roll surface width of 2000 mm.

[0019] (2) The surface treatment of the roll was carried out by Sarclad 12 electrode EDM roll grinding machine (i.e., EDT: Electro-Disharge Textured). The electrode type was PB102 copper electrode. The roughness Ra of the work roll before roughening was ≤0.4μm; the roughness Ra after EDT roughening was 1.95-2.2μm. The roughening process parameters were as follows: current 12A, on / off time 11 / 15us, electrode travel speed 24mm / min, electrode and roll gap position 3.6 / 3.0mm, roll speed 18mm / min, electrode gain 10, roughening pass number 2, and roughening time 150min.

[0020] (3) Rolling process parameters: Cold rolling mill and rolling process parameters: A single-stand cold rolling mill is used for production, using light white oil 110# base oil and alcohol additives. The weight ratio of additives to base oil is 8.5-10.0%; the roll diameter is 400-480mm, and the work roll type is flat roll; the rolling oil temperature is 35±5℃, the rolling oil flow rate is 3000-4500L / min, and the rolling oil pressure is 6.0-9.0bar; 6-series aluminum alloy is used for production, and the chemical composition mass fraction % is: Si: 0.10-1.0%; Fe: 0.1-0.30%; Cu: 0.02-0.10%; Mn: 0.1-0.15%; Mg: 0.2-0.6%; Ti: 0.01-0.03%; hot-rolled billet 2.5-6.0mm, final rolling temperature 270~310℃; hot-rolled strip crown range 0-0.3%; rolled to the thickness of the intermediate annealing pass through 1-3 passes, and the roughness of the work rolls Ra=0.2~0.6μm is achieved by grinding with a grinding wheel in the passes after billet opening and intermediate annealing; the total processing rate after cold rolling intermediate annealing is 45-65%, and two passes are used for production after intermediate annealing. The rolls used in the finished product pass are the rolls with electrical discharge texturing treatment used in step (2), and the processing rate of the finished product pass is controlled at 3.5~5.0% (for other operation methods, see the control method of high peak value of surface roughness of six-roll aluminum cold rolling mill EDT automotive sheet disclosed in Chinese Patent Publication No. CN116393523B).

[0021] (4) Cleaning, solution treatment and aging are carried out using an air cushion continuous annealing line, and the sharp points on the strip and the strip surface are treated using a straightening machine. The solution temperature is 530-560℃ and the time is 20-30s. The straightening elongation rate is 0.2-0.5% to eliminate the sharp peaks on the strip surface and reduce the friction during strip stamping. The amount of oil applied to the electrostatic oiling surface is controlled at 1.0±0.2g / m2 / side, and the oil type is Hobton 6130 lubricating oil.

[0022] (5) The surface morphology and pit size of the aluminum plate were measured using an Olympus 3D optical microscope. The pit diameter was controlled to be 45-65μm by adjusting the surface roughness of the rolls and the rolling reduction. The surface roughness of the aluminum plate was high and the rolling texture was not obvious after the rough pits were covered.

[0023] (6) The prepared aluminum plate was measured using a Sensofar 3D non-contact optical profilometer. The surface roughness Sa of the aluminum plate ranged from 0.75 to 1.0 μm, the sharpness Sku < 3.0 μm, the maximum valley depth Sv ranged from 3.5 to 5.0 μm, and the void volume Vvc and solid volume Vmc of the central part ranged from 1.0 to 2.0 μm. 3 / um 2The oil storage capacity of aluminum plate surfaces is quantified using data.

[0024] (7) The friction coefficient of metallic materials was tested using YS / T4286. The friction coefficient was measured using a Bruker TriboLab friction tester at room temperature with a sliding speed of 20 mm / s under pressures of 5 MPa and 10 MPa. The friction coefficient was used to guide the optimization of EDM process parameters.

[0025] It should be noted that (Vvc represents the difference between the void volume at a load area ratio of p% and the void volume at a load area ratio of q%. Vmc represents the difference between the solid volume at a load area ratio of q% and the solid volume at a load area ratio of p%. Vmc represents the volume of the central part, Vvc represents the spatial volume of the central part, and Vvv represents the spatial volume of the protruding valley. When using volume parameters, the load area ratio separating the central part from the protruding peak and the load area ratio separating the central part from the protruding valley must be specified; the default values ​​are 10% and 80%, respectively. A schematic diagram is shown below.) Figure 4 As shown.

[0026] By implementing the above methods, the surface roughness Ra and Rpc requirements of automotive panels can be met, and the risk of downstream stamping cracking and corrosion point defects caused by excessively large surface pit diameters can be reduced. This results in higher surface roughness automotive panels, higher oil storage capacity on aluminum plate surfaces, lower friction coefficients, and reduced EDT roll texturing time.

[0027] To better illustrate the practicality of this control method, the following comparative schemes are listed: EDT texturing parameter scheme 1 (comparison scheme 1): Ra=1.55-1.65μm, Rpc=110-120pecak / cm: .

[0028] EDT texturing parameter scheme 2 (comparison scheme 2): Ra=1.95-2.05μm, Rpc=100-110pecak / cm: .

[0029] EDT texturing parameter scheme 3 (comparison scheme 3): Ra=1.95-2.2μm, Rpc=100-110pecak / cm: .

[0030] The case study solutions are compared below: .

[0031] Compared with the production process used in Scheme 1, the roughening pit diameter is smaller and the roughness is lower. The aluminum plate produced by pure drawing mode has a larger surface sharpness, the depth of the roughening pit and the volume of the central solid part are smaller, the oil storage capacity is smaller, and the friction coefficient is better than that of Scheme 2.

[0032] Compared with the production process of Scheme 2, the diameter of the roughening pits is larger than that of Scheme 1. The aluminum plate produced by pure drawing mode has a larger surface sharpness, higher roughness, larger pit depth and central solid volume, larger oil storage capacity, and a larger coefficient of friction than Scheme 1.

[0033] Compared with the production process of Scheme 3, the diameter of the roughening pit is similar to that of this embodiment. The aluminum plate produced by the roller straightening mode has a smaller surface sharpness, higher roughness, larger pit depth and central solid volume, larger oil storage capacity, better friction coefficient and higher production efficiency than the previous two comparative schemes.

[0034] The surface morphology and pit size were measured using an Olympus 3D optical microscope (Japan). The pit diameter was controlled within the range of 45-65 μm by adjusting the roll surface roughness and rolling reduction. The aluminum plate surface exhibited high saturation of rolling texture, and no obvious rolling marks were observed on the surface microstructure after the pits were covered. Figure 1-3 As shown, the surface morphology was examined using an optical microscope. It can be seen that compared to scheme 3, the saturation is better and the coefficient of friction is smaller. This shows that using the pure stretching mode and the roll straightening mode have a significant impact on the sharpness of the strip surface.

[0035] This invention utilizes 3D microscopes and 3D profilometers to measure and analyze the surface morphology, roughness, oil retention, and friction coefficient of aluminum plates. While ensuring downstream stamping and phosphating processes, it can also be used to improve EDT process parameters. This invention saves approximately 150 minutes of processing time per EDT roll, significantly reducing production costs and improving efficiency. It is a reliable, low-cost, simple, and easily implemented control method. This invention reduces EDM working time while achieving automotive sheet roughness Ra and Rpc that meet customer requirements, reducing quality defects in downstream stamping and surface treatment, and giving the company's automotive sheet products a better market prospect and competitiveness.

[0036] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a fixed connection that can be detached (e.g., using bolts or screws), or a fixed connection that cannot be detached (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0037] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0038] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets, characterized in that: Includes the following steps: (1) A single-stand cold rolling mill is adopted, with the working roll diameter ranging from Ф400 to Ф480 mm and the roll surface width of 2050 mm; the intermediate roll diameter ranging from Ф490 to 560 mm and the roll surface width of 2050 mm; and the support roll diameter ranging from Ф1150 to 1400 mm and the roll surface width of 2000 mm. (2) The surface treatment of the roll is carried out by an electrode electric spark roll grinding machine. The electrode type is copper electrode. The roughness Ra of the work roll before roughening is ≤0.4μm; the roughness Ra after EDT roughening is 1.95-2.2μm. (3) Cold rolling mill and rolling process parameters: The single-stand cold rolling mill is used for production. The additive and base oil weight ratio is 8.5-10.0%; the roll diameter is 400-480mm, the work roll type is flat roll; the rolling oil temperature is 35±5℃, the rolling oil flow rate is 3000-4500L / min, and the rolling oil pressure is 6.0-9.0bar; (4) Cleaning, solution treatment and aging are carried out using an air cushion continuous annealing line, and the sharp points on the strip and the strip surface are treated using a straightening machine. The solution temperature is 530-560℃ and the time is 20-30s. The straightening elongation rate is 0.2-0.5% to eliminate the sharp peaks on the strip surface and reduce the friction during strip stamping. The amount of oil applied to the electrostatic oiling surface is controlled at 1.0±0.2g / m2 / side. (5) The surface morphology and pit size of the aluminum plate were measured by a 3D optical microscope. The pit diameter was controlled at 45-65μm by the surface roughness of the roll and the rolling reduction. The surface roughness of the aluminum plate was high and the rolling texture was not obvious after the rough pit was covered. (6) The prepared aluminum plate was measured using a 3D non-contact optical profilometer. The surface roughness Sa of the aluminum plate ranged from 0.75 to 1.0 μm, the sharpness Sku < 3.0 μm, the maximum valley depth Sv ranged from 3.5 to 5.0 μm, and the void volume Vvc and solid volume Vmc of the central part ranged from 1.0 to 2.0 μm. 3 / um 2 Quantify the oil storage capacity of aluminum plate surfaces using data; (7) The friction coefficient test method of metal materials is adopted. Under room temperature conditions, the friction coefficient is measured at a sliding speed of 20 mm / s with pressure of 5 MPa and 10 MPa. This is convenient for guiding the optimization of EDM process parameters.

2. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (2), the roughening process parameters are: current 12A, on / off time 11 / 15us, electrode travel speed 24mm / min, electrode and roll gap position 3.6 / 3.0mm, roll speed 18mm / min, electrode gain 10, roughening pass number 2, and roughening time 150min.

3. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (3), light white oil 110# base oil is used, and the additive is an alcohol additive.

4. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (3), 6-series aluminum alloy is used for production, with the following composition by mass fraction: Si: 0.10-1.0%; Fe:0.1-0.30%;Cu:0.02-0.10%,Mn:0.1-0.15%; Mg: 0.2-0.6%; Ti: 0.01-0.03%; hot-rolled billet 2.5-6.0mm, final rolling temperature 270~310℃; hot-rolled strip crown range 0-0.3%.

5. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1 or 4, characterized in that: Rolling is carried out in 1 to 3 passes to the thickness of the intermediate annealing pass. After the initial rolling and intermediate annealing passes, the work rolls are rolled with a roughness of Ra=0.2 to 0.6μm by grinding with a grinding wheel. The total processing rate after cold rolling and intermediate annealing is 45-65%. After intermediate annealing, two passes are used for production. The rolls used in the finished product pass are the rolls with electrical discharge machining treatment used in step (2). The processing rate of the finished product pass is controlled at 3.5 to 5.0%.

6. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (4), when applying oil using electrostatic methods, the oil type is Hobton 6130 lubricating oil.

7. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (7), the YS / T4286 test method for friction coefficient of metallic materials is adopted.

8. The method for improving the texturing efficiency of EDT rolls and controlling the oil storage capacity of high-surface-area automotive aluminum sheets according to claim 1, characterized in that: In step (2), the electrode type is PB102 copper electrode.

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