Apparatus and method for rolling metal

Abstract

An apparatus and method for rolling sheet with reduced yield strength at elevated temperatures using textured rolls. Texture rolling is used to repair defects at various stages of rolling and smooth subsequent rolling stages.

Description

Technical Field

[0001] <Cross - Reference to Related Applications> This application claims the benefit of U.S. Provisional Patent Application No. 61 / 991,973, filed May 12, 2014, "Apparatus and Method for Rolling Aluminum," which is incorporated herein by reference in its entirety. <Field> The present invention relates to the production of sheet materials, and more particularly, to methods and apparatus for rolling metals such as aluminum and aluminum alloys into sheets to produce sheet materials having desired surface and subsurface characteristics.

Background Art

[0002] <Background> Various methods are known for rolling aluminum and imparting a predetermined surface texture to the resulting rolled sheet. The surface texture can be applied to the sheet surface by a roll, which may be textured by processes such as electrical discharge machining (EDT), roll grinding, cross-hatch grinding, ball or shot peening. In the art, a "texture roll" is typically defined as a roll having an isotropic or directional pattern of random or repeating peaks and valleys on its surface, with average height and spacing for aesthetic or functional purposes. Texture on textured rolls is usually applied to aluminum, steel, and other metal surfaces after the cold rolling process, typically with a low reduction (3-10%). In the case of automotive sheets with EDT texture, the texture is usually formed as the final pass of the skin pass (temper) mill. Applying texture after cold rolling in a skin pass or cold mill is often limited due to the cold working characteristics of the product, the roll size, and the low reduction amount of rolling, which restrict the transfer of the roll surface texture to the sheet. In this case, the incoming surface becomes a surface that is not completely removed or covered by the roll surface texture. This is particularly undesirable when features such as scratches or metal sliver from upstream processes are present. The term sliver is defined as "a thin, elongated piece rolled onto the surface of a base metal, with only one end attached" [McGraw-Hill Dictionary of Scientific and Technical Terms, 3rd edition, p. 1491]. Sliver can also be defined as "a thin piece of aluminum that is part of the material but is only partially attached" [Visual Quantity Attributes of Aluminum Sheet and Plate, Al Assoc., 1994]. In cold rolling, if the reduction by the EDT roll is large, a large amount of debris is generated, which reduces the cleanliness of the sheet produced as the final product or as an intermediate product that will undergo further processing.

[0003] Furthermore, the skin pass after cold rolling adds an additional step to the process, increasing the cost of the product. Therefore, improvements and / or alternatives to methods and apparatus for imparting desired surface textures to aluminum sheets are still desired. [Overview of the project]

[0004] <Summary of the Invention> The disclosed subject matter relates to a method for achieving a second state by rolling a metal sheet provided in a first state, which includes rolling the metal sheet with a texture roll when the metal sheet is at a temperature that exhibits a yield strength lower than the yield strength of the metal sheet at ambient temperature.

[0005] In another aspect of this disclosure, the metal is aluminum, and the temperature at which the metal sheet is rolled by the texture roll is 250 to 970 degrees Fahrenheit.

[0006] In another embodiment, the texture roll has a surface roughness in the range of 1 micrometer to 50 micrometers.

[0007] In another embodiment, the thickness reduction of the metal sheet in the rolling step is in the range of 0% to 30%.

[0008] In another embodiment, the thickness reduction is in the range of 0% to 70%.

[0009] In another embodiment, the texture transfer in the rolling step covers 60% to 100% of the surface of the metal sheet.

[0010] In another embodiment, the step of rolling with a texture roll is a first rolling step, further comprising a second rolling step performed on the metal sheet following the first rolling step.

[0011] In another embodiment, the second step is a second texture rolling step.

[0012] In another embodiment, the first rolling step is carried out using a texture roll having a coarser texture than the texture roll used in the second rolling step.

[0013] In another embodiment, the first rolling step and the second rolling step reduce the crystal size of the metal sheet.

[0014] In another embodiment, the second rolling step is carried out by cold rolling.

[0015] In another embodiment, the second rolling step is carried out by hot reduction rolling.

[0016] In another embodiment, the first rolling step is to form a surface shape on the metal sheet that can contain a lubricant within the metal sheet.

[0017] In another embodiment, the method further includes multiple rolling steps, the first step of rolling with a texture roll, which reduces the number of rolling steps required to achieve the final target state of the metal sheet.

[0018] In another embodiment, the first step of rolling facilitates the second step of rolling.

[0019] In another embodiment, the first step of rolling repairs defects present in the metal sheet that are not repaired by the second step of rolling.

[0020] In another embodiment, the wear of the texture rolls that occurs in a rolling step at a temperature in which the metal sheet exhibits a low yield strength is less than the wear of the texture rolls that occurs when the rolling is performed at a lower temperature.

[0021] In another embodiment, reduced wear on the texture roll corresponds to an extended lifespan for the texture roll.

[0022] In another aspect, the first step of rolling reduces the transfer of the metal sheet during the second step of rolling.

[0023] In another aspect, the rolling step when the metal sheet exhibits a low yield strength removes surface defects present in the metal sheet.

[0024] In another aspect, the rolling step when the metal sheet exhibits a low yield strength reduces subsurface defects present in the metal sheet.

[0025] In another aspect, the rolling step when the metal sheet exhibits a low yield strength redistributes the metal in the metal sheet by deforming it.

[0026] In another aspect, the rolling step when the metal sheet exhibits a low yield strength is performed as the final rolling step before the metal sheet is wound into a coil.

[0027] In another aspect, the surface defects removed by the rolling step range from 10 μm to 1 mm.

[0028] In another aspect, the rolling step involves at least one of once-through lubrication, evaporative roll cooling, roll surface coating, or high-pressure water blasting.

[0029] In another aspect, the temperature of the metal sheet is the temperature due to the residual heat that persists in the metal sheet from its pre-treatment state.

[0030] In another aspect, the temperature of the metal sheet is the temperature due to the heat applied to the metal sheet by a heat source.

[0031] In another aspect, the texture of the textured roll is imparted to the textured roll by at least one of EDT, ball peening, shot peening, grinding, or cross-hatch grinding.

[0032] In another embodiment, the texture of the texture roll has a discernable pattern.

[0033] In another embodiment, the texture of the texture roll does not have a recognizable pattern.

[0034] In another embodiment, the step of forming the metal sheet into an automotive panel is further included after the rolling step.

[0035] In another embodiment, the automotive panel is a closure panel.

[0036] In another embodiment, the molding step further includes the steps of fabricating a plurality of closure panels and joining the plurality of closure panels.

[0037] In another embodiment, the invention further includes integrating automotive panels into a body-in-white.

[0038] In another embodiment, the sheet is supplied in a first state by Micromill®.

[0039] In another embodiment, the step of rolling with a textured roll makes surface defects in the sheet that are visible to the human eye less noticeable.

[0040] In another embodiment, the defects are on the scale of 10 μm to 200 μm.

[0041] In another embodiment, the texture of the texture roll is in the range of 600 μin to 1200 μin, and the reduction ratio is in the range of 5% to 25%.

[0042] In another aspect, the defect is completely invisible to the human eye.

[0043] In another embodiment, the defect is at least one of a scratch or a sliver.

[0044] In another embodiment, the defects form a recognizable pattern.

[0045] In another embodiment, the pattern is a repeating pattern.

[0046] In another embodiment, the defect is made less noticeable by reducing the average distance from the peak to the valley floor.

[0047] In another embodiment, the defect is made less noticeable by bringing the area of ​​the defect closer to the roughness Ra of the background surface near the defect.

[0048] In another embodiment, the sheet, after being rolled on a textured roll, is perceived as having a uniform isotropic texture by human vision at a distance of 0.1 to 5 feet.

[0049] In another embodiment, a rolling mill for rolling a metal to produce a metal sheet has a textured roll, the textured roll is positioned at a temperature at which the temperature of the metal sheet exhibits a yield strength lower than the yield strength at ambient temperature.

[0050] In another embodiment, the rolling mill has a heating device that heats the metal in front of the texture rolls.

[0051] In another embodiment, the rolling mill has a casting machine, and metal castings coming out of the casting machine are rolled by the rolling mill.

[0052] In another aspect, the casting machine is a micromill.

[0053] In another embodiment, the temperature range in which the metal sheet exhibits a low yield strength is approximately 250–970°F.

[0054] In another embodiment, the textured roll has a surface roughness Ra in the range of 1 micrometer to 50 micrometers.

[0055] In another embodiment, the reduction in texture rolls is in the range of 0% to 70%.

[0056] In another embodiment, the rolling mill has an additional rolling station after the texture rolls.

[0057] In another embodiment, the additional rolling station includes a texture rolling station.

[0058] In another embodiment, the additional texture rolling station has a finer surface texture than the texture roll. [Brief explanation of the drawing]

[0059] For a more complete understanding of this disclosure, the following accompanying drawings are provided for further consideration in connection with the description of exemplary embodiments.

[0060] [Figure 1] Figure 1 is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0061] [Figure 2] Figure 2 is a graph showing the roll roughness against the roughness transferred to the sheet, expressed as a percentage when reduced by 3% and 9% at 200, 400, and 600°F.

[0062] [Figure 3A] Figure 3A is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0063] [Figure 3B] Figure 3B is a perspective view of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0064] [Figure 4] Figure 4 is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0065] [Figure 5] Figure 5 is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0066] [Figure 6] Figure 6 is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0067] [Figure 7] Figure 7 is a schematic diagram of an apparatus and method for manufacturing a sheet material according to one embodiment of the present disclosure.

[0068] [Figure 8] Figure 8 is a schematic diagram of surface scratch patterns with different depths and orientations within the sheet.

[0069] [Figure 9A] Figure 9A is an optical image of the first scratch pattern on the surface. [Figure 9B] Figure 9B shows topography images of the first scratch pattern on the surface. [Figure 9C] Figure 9C is an optical image of the second scratch pattern on the surface. [Figure 9D] Figure 9D is a topographic image of the second scratch pattern on the surface.

[0070] [Figure 10] Figure 10 shows an optical image of surface slivers present on the surface of a metal sheet or slab, which are formed when metal adheres to the surface during rolling or is pressed into the surface of the metal sheet or slab.

[0071] [Figure 11] Figure 11 shows the results of a series of surface topography scans for five examples of sheet aluminum manufactured according to one embodiment of the present disclosure, with different reduction rates on the EDT roll. [Figure 11-1] Figure 11 shows the results of a series of surface topography scans for five examples of sheet aluminum manufactured according to one embodiment of the present disclosure, with different reduction rates on the EDT roll.

[0072] [Figure 12] Figure 12 shows a series of surface topography maps and line profiles for five examples of sheet aluminum manufactured according to one embodiment of the present disclosure, with different reduction ratios on the cross-hatch roll. [Figure 12-1] Figure 12 shows a series of surface topography maps and line profiles for five examples of sheet aluminum manufactured according to one embodiment of the present disclosure, with different reduction ratios on the cross-hatch roll.

[0073] [Figure 13A] Figure 13A shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 5% using an EDT roll with an Ra of 600 μin. [Figure 13B] Figure 13B shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 10% using an EDT roll with an Ra of 600 μin. [Figure 13C]Figure 13C shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 20% using an EDT roll with an Ra of 600 μin.

[0074] [Figure 14A] Figure 14A shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 5% using an EDT roll with an Ra of 1200 μin. [Figure 14B] Figure 14B shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 10% using an EDT roll with an Ra of 1200 μin. [Figure 14C] Figure 14C shows a series of optical images, topographic images, and line profiles of a sheet sample with surface scratches, before and after rolling at a temperature of 850°F with a reduction ratio of 20% using an EDT roll with an Ra of 1200 μin.

[0075] [Figure 15] Figure 15 is a graph showing the percentage reduction in scratch depth after rolling with an EDT textured roll for different scratch depths.

[0076] [Figure 16] Figure 16 shows an apparatus for measuring light scattering from a surface.

[0077] [Figure 17A] Figure 17A shows a series of optical images and light scatter signatures of a metal surface of a sample with an EDT finish after 10% reduction. [Figure 17B]Figure 17B shows a series of optical images and light scattering signatures of a metal surface of a sample with a milled finish after 10% reduction. [Figure 17C] Figure 17C shows a series of optical images and light scattering signatures of the metal surface of a sample with an EDT finish after 25% reduction. [Figure 17D] Figure 17D shows a series of optical images and light scattering signatures of a metal surface of a sample with a milled finish after 25% reduction.

[0078] [Figure 18A] Figure 18A shows a series of light scattering signatures for a metal surface of a sample with a milled finish after reduction by 5%, 10%, 15%, and 25%. [Figure 18B] Figure 18B shows a series of light scattering signatures for the metal surface of a sample with an EDT finish after reduction by 5%, 10%, 15%, and 25%.

[0079] [Figure 19A] Figure 19A shows the texture data signature of the milled surface. [Figure 19B] Figure 19B shows the texture data signature of a surface textured with EDT. [Modes for carrying out the invention]

[0080] The aspects of this disclosure have the following effects: Surface texturing is performed when the sheet to be textured is at a high temperature, for example, 250-970°F, and the roll pressure is reduced to facilitate transfer. Texturing is used to repair or improve surface and subsurface damage present in the sheet or caused in upstream processes (e.g., scratches, slivers, and dents that cannot be favorably affected by conventional cold texturing), and to improve surface quality by removing surface features or patterns transferred by casting or rolling processes. Texturing can be applied as an intermediate step in rolling, improving and facilitating subsequent rolling passes in later stages, such as reduction rolling with hot or cold rolls. The "rough" texture imparted by a texture roll with a "rough" surface is useful for repairing surface defects, creating sheets for further processing, and manufacturing sheets with beneficial properties. Texturing can be performed simultaneously with reduction if carried out at high temperatures. This surface texturing can be performed over a range of reduction amounts and can remove or cover features such as scratches and slivers with little or no adverse effect on the cleanliness of the surface. These and other aspects of the present disclosure are further described below.

[0081] Figure 1 shows an apparatus 10 for manufacturing sheet material 12 such as an aluminum sheet. The apparatus 10 may include an upstream source 14 of aluminum metal that will ultimately be formed into the sheet 12. Various sources 14 can be used in the apparatus and processes of this disclosure, and to represent this diversity, the sources are enclosed by dotted rectangles. For example, the source 14 may include an outlet 15 from a reservoir of molten aluminum for continuously casting and rolling the aluminum sheet 12, and this outlet may be, for example, the outlet of a pusher furnace that extrudes a hot slab ingot, the nozzle outlet of a casting box, the outlet of a coil winder, the outlet of a roll or slab casting machine, or the outlet of a micromill. The micromill and process are described in U.S. Patent No. 6,672,368 owned by Alcoa, Inc. In one embodiment, the apparatus 10 is a hot coiling mill modified in accordance with this disclosure for inline texture application. In state S1, the aluminum sheet 12 exhibits a predetermined temperature (e.g., 950-1100°F), solidification / hardness state, temper, dimensions, surface texture, surface integrity, and subsurface structure. Optionally, for example, in the case of the micromill outlet 15, the aluminum sheet 12 can be passed through one or more sets of rolling rolls 18A, 18B that reduce the thickness of the aluminum sheet 12. As a result, the sheet 12 enters a second state S2 having a predetermined temperature, solidification state, hardness, temper, dimensions, surface texture, surface integrity, and subsurface structure. Since the aluminum sheet 12 extends from the supply source 14, it can be cooled or heated by exposure to the ambient environment E. As the aluminum sheet 12 moves through the apparatus 10, its state differs in terms of hardness / yield strength / plasticity, etc., in addition to temperature, resulting in states S1, S2...S5. In addition to the stepwise changes in state due to temperature changes, the dimensions of the aluminum sheet 12 change as it moves through the apparatus 10. For example, the aluminum sheet 12 in state S2 is optionally reduced in thickness by rolls 20A and 20B to state S3, and then again to state S4 by rolls 22A and 22B.In one embodiment of the present disclosure, when the sheet 12 is at a high temperature, for example, 250 to 970°F, the aluminum sheet 12 can be surface-treated / textured by texturing rolls 24A, 24B. This particular temperature range of the sheet 12 can be achieved, for example, by the residual thermal energy that the sheet 12 possesses after casting, or the sheet 12 may be heated before being textured by the texturing rolls 24A, 24B. The texturing rolls 24A, 24B can have their surfaces pre-formed by electrical discharge texturing (EDT) to impart a desired texture to the sheet 12, or they can have a desired texture formed by ball or shot peening, grinding, cross-grinding, etc. Textured rolls are produced, for example, by EDT, grinding, blasting, laser beam texturing, or electron beam texturing, and have random combinations of peaks and valleys, where, for example, the height between peaks and valleys is in the range of Ra 0.5 μm to 50 μm or greater, which is desired for the surface features being transferred. These features generally do not have a preferred orientation based on the process used. Textured rolls can be oriented or may exhibit a preferred orientation in points where there are definitive features produced using processes such as grinding, belt polishing, laser, or electron beam texturing. The size and orientation of these features can be designed and controlled by these processes, for example, producing a surface where the height from peak to valley when measured laterally is Ra 0.1 μm to 25 μm. Grinding produces topography with lengths from 0.5 mm to several centimeters in the longitudinal direction at angles of 1 to 45 degrees or greater, depending on the ratio of abrasive to part rotation / travel speed.

[0082] When texturing with rolls 24A and 24B is performed at a high temperature, for example, 250 to 970°F, the yield strength decreases due to the high temperature, allowing for greater topographic transfer at a lower roll pressure level with a smaller reduction amount compared to texturing at room temperature. One aspect of this disclosure allows texturing of sheet 12 at a high temperature, low roll pressure level, and low reduction amount to repair surface and subsurface defects present in the sheet before texturing, such as defects such as sliver caused by the transfer of adhesive metal to rolls at stations prior to texturing rolls 24A and 24B, for example, rolls 20A, 20B and / or 22A and 22B. When high-temperature texturing is performed, the temperature range of 250 to 970°F for sheet 12 is the temperature of the outer layer, and since the sheet has a temperature gradient from the outside to the inside, the inner portion is either hotter or colder than the outer portion. The sheet temperature changes over time and can also be adjusted by heating or cooling the sheet 12. Therefore, the temperature of the outer portion of the sheet 12 can be measured and controlled so that a selected temperature range is achieved immediately before texturing with the texturing rolls 24A and 24B suitable for obtaining the desired texture.

[0083] The texturing rolls 24A and 24B can be driven by frictional interaction with the sheet 12, which is pulled by rotating a coiled sheet 12E of a coil winding machine (not shown). This sheet drive can be used to reduce forward sliding that adversely affects the surface of the sheet 12, i.e., sliding of the sheet 12 on the surface of the texturing rolls 24A and 24B, or to reduce other asynchronous movements of the sheet relative to the rolls 24A and 24B. Since texturing is performed at a high temperature, the texturing of the sheet 12 by the texturing rolls 24A and 24B can be easily performed with lower roll pressure than in the case of conventional texturing performed at low temperatures.

[0084] In one embodiment, the texturing rolls 24A and 24B can have a surface roughness Ra of approximately 1 to 10 μm. When the temperature of the aluminum sheet 12 in state S4 is 250°F to 970°F, pressing the texturing rolls 24A and 24B onto the sheet 12 achieves a thickness reduction of approximately 1 to 30% or more as needed, and in state S5, the surface texture of the texturing rolls 24A and 24B is transferred to approximately 60 to 100% of the surface of the sheet 12C and 12D. Since the aluminum sheet 12 in state S4 is more malleable, it can accept the impressions of the texturing rolls 24A and 24B more easily than an aluminum sheet that has been cooled and tempered, so the texturing can be transferred more faithfully to the surface texture of the texturing rolls 24A and 24B with less pressure, and the wear of the rolls 24A and 24B is reduced, and less debris is generated. Synchronized texturing (rotation speed of texture rolls 24A and 24B relative to the sheet extrusion rate) improves texture transfer, resulting in a more consistent sheet 12 surface with fewer scratches. The reduction in roll pressure associated with high-temperature texture rolling can reduce wear on the texture rolls 24A and 24B, which means less roll variation is required to process a given amount of sheet 12.

[0085] One aspect of this disclosure allows for high-temperature surface treatment of an aluminum sheet 12 by texturing it with texturing rolls 24A and 24B that have been surface-treated by electrical discharge texturing (EDT). Alternatively, the rolls 24A and 24B can be textured by ball or shot peening, plating, grinding, or other surface treatments, and can be used to surface treat the aluminum sheet 12 when it is at a high temperature, for example, 250 to 970°F. In the aforementioned temperature range, the aluminum sheet 12 is softer, and an aluminum sheet with a low yield strength of <10kSi in its untempered state can be more easily formed by the action of the texturing / surface treatment rolls. Furthermore, if the aluminum sheet 12 is surface-treated before cold working in a cold rolling mill or the like, the surface treatment can be easily performed because the aluminum sheet 12 has not been mechanically tempered and hardened by cold working. The aforementioned advantages can be achieved by integrating the texturing rolls 24A and 24B into a rolling mill line, for example, a high-temperature coiling mill line that manufactures aluminum sheets 12 from a molten material, thereby utilizing the heat inherently present in the aluminum sheets 12 during manufacturing by the mill and performing surface treatment while the aluminum sheets 12 are still hot before coil winding. In this way, aluminum sheets can be manufactured efficiently, minimizing or eliminating subsequent surface treatment and rolling processes before and after coil winding. In another embodiment, as described below, the cooled sheet 12 can be heated before surface treatment by the texturing rolls.

[0086] Each roll 18A, 18B, 20A, 20B, 22A, 22B, 24A, 24B and the environment E can be temperature-controlled by, for example, insulation provided by an enclosed structure such as a tunnel, and / or by heating, for example, by natural gas combustion, electric resistance heating, or induction heating. The temperature of the aluminum sheet 12 during texturing / surface treatment can be controlled by saving the thermal energy present in the aluminum sheet 12 by casting, and / or by exposing it to a heating medium such as air in the environment, radiation, or flame, or by applying thermal energy to the sheet 12 by bringing it into contact with a heated surface such as, for example, rolls 20A, 20B, 22A, 22B, casting rolls 18A, 18B, and / or texturing rolls 24A, 24B.

[0087] To achieve state S5, after surface treatment of the aluminum sheet 12 by texturing rolls 24A, 24B, the aluminum sheet 12 is subjected to heat treatment, cooling, hardening and / or tempering by exposure to a medium such as radiation and / or air or water at temperature T. For example, the sheet 12 may be exposed to the environment E, or actively cooled or heated by water quenching at a selected temperature, for example by passing it through a bath or spray station, a heated tunnel, or exposed to cooled or heated air via a blower or the like. In one aspect of the present disclosure, the surface treatment of the aluminum sheet 12 may be performed before cooling, final heat treatment, tempering and / or hardening. If necessary, after the desired treatment, the aluminum sheet 12 can be wound into a coil 12E and stored and transported in the conventional manner.

[0088] This disclosure describes a texturing process performed at high temperatures, which can impart a "rougher" surface (e.g., surface topography Ra of 50 μm) compared to conventional tempering / skin-pass processes performed at room temperature. (In this art, units of roughness are generally used interchangeably, with micrometers (μm) and microinches (μin) being used, where 1 μm = 39.37 μin. For example, in the United States, when a texturing roll is described as a 600 or 1200 EDT roll, this means an average surface roughness Ra of 600 μin or 1200 μin, corresponding to an EDT roll with an average surface roughness Ra of 15.20 μm or 30.48 μm.) Higher temperatures reduce yield strength, allowing for higher topographic transfer at lower roll pressures and lower reductions. Typically, a "rougher" surface topography, large reductions, and high temperatures damage the subsurface of the sheet, as this promotes the transfer of adhesive metals. The method of this disclosure allows rolling with low load and small reduction, and since there is little to no forward sliding, the transfer of sticky metals and subsurface damage are significantly reduced. According to the method of this disclosure, a texture is formed on the sheet 12, and numerous depressions are formed on the sheet surface. These depressions imparted to the sheet 12 by high-temperature texture rolling are beneficial in that they can contain lubricant, facilitate rolling, and in some cases have the ability to eliminate cold rolling passes. Another aspect of this disclosure is that it is possible to roll a sheet having an isotropic matte finish with less damage than before. When rolling a rough texture with the sheet 12, this roughness Ra increases the friction per wrap-to-wrap, reducing the risk of coil collapse. The texturing according to this disclosure is performed to a disturbing depth below the surface of the sheet, resulting in a better finish on the final product of the sheet 12. More specifically, by analyzing the sheet 12 from a predetermined source, the scale and distribution of typical surface and subsurface defects can be confirmed. A texture with an appropriate surface roughness Ra is selected and applied to the texturing rolls 24A and 24B.As a result, the depth and resolution (interval) of the impression formed by the texturing rolls 24A and 24B are such that, for example, when the material is in a softened state during high-temperature texturing, surface defects and subsurface defects present in the sheet are removed by the redistribution of the material. In another embodiment of this disclosure, the EDT roll texture removes the non-uniform surface generated during the rolling process to produce an isotropic surface signature. This isotropic surface signature can be measured with optical or topographic measurement systems such as Optimap® (Rhopoint Instruments), Scatterscope® (Scatterworks), or a 3D interferometer or confocal microscope. In another embodiment, the surface signature can be traced through the texture rolling process and the standard rolling process and can be highlighted by surface coating or surface treatment.

[0089] One aspect of this disclosure is that, as the sheet 12 passes through each successive stage in the apparatus 10, the conformity of the state and the changes forged within the sheet 12 depend on the previous state, in particular, the surface texture and integrity, as well as the subsurface structure. Compared to conventional processing conditions, the changes in state in successive stages of rolling, texturing, or other processing are carried out gradually to control the surface progression, so that the processing at each stage of the sheet 12 is appropriate in terms of scale and pattern, as described below.

[0090] For the most successful replication from the original roll surface texture to the sheet surface, it is crucial to prevent metal deposition on the roll surface texture. The methods disclosed herein can improve / enable this prevention through once-through lubrication, evaporative roll cooling, and the use of roll surface coating and high-pressure water blasting or similar roll cleaning. These methods address the need to maintain the roll clean and at a desired temperature while controlling friction (by sheet lubrication) while preserving surface quality.

[0091] Figure 2 is a graph showing roll roughness relative to sheet roughness transfer at reduction ratios of 3% and 9% at temperatures of 200, 400, and 600°F. The method and apparatus of this disclosure enable high percentage topographic transfer at low reduction ratios and mill loads. In comparison, the transfer rate of cold-rolled EDT is significantly lower, for example, 60%.

[0092] Figures 3A and 3B illustrate alternative embodiments of the present disclosure, in which texturing rolls 124A, 124B are positioned before warm rolling rolls 120A, 120B for pretexturing the slab before rolling, for example, in a high-temperature tandem mill. More specifically, the apparatus 110 may include a source 114 of aluminum metal for forming the sheet 112 in a first state S7 of temperature, solidification / hardness, temper, and dimensions. As described above with respect to the source 14, there are many sources such as a minimill, a previously formed coil, etc. Therefore, the source 114 is comprehensively shown by a dotted rectangle. The aluminum sheet 112 in state S7 has a temperature of 250-970°F due to its heat retention or heat supplied from a heater such as a natural gas or electric induction heater. The texturing rolls 124A and 124B may be surface-treated by, for example, electrical discharge texturing (EDT), grinding, or other methods, and act on the sheet 112 to impart a selected texture to the sheet 112, creating state S8. In one embodiment, high-temperature texturing is performed with a "coarse" texture, for example, with a roughness of Ra 1 μm to 50 μm Ra. The texture takes the form of a regular pattern, such as rows, grids, or a series of dots, and acts on the surface to more uniformly redistribute the metal within the sheet 112, creating a flat sheet with less residual stress. The resulting sheet has visible surface defects such as lines, scratches, or slab marks caused by the table rolls, as well as subsurface defects such as voids, which are disturbed and made less noticeable. This texturing and repair effect is used to prepare the sheet 112 for further processing at a different scale or "resolution" by subsequent mill stands, such as rolls 120A, 120B, 122A, and 122B. These defects cannot be removed at the scale / resolution level that texture rolls 124A and 124B can eliminate.

[0093] For example, surface and subsurface defects in sheet 112 in state S7 are on the first scale, while the surface texture of the hot rolling rolls is on the second scale. The second scale is twice as large or twice as small when pressed against the sheet, for example, at a reduction ratio of 30%. When sheet 112 in state S7 is textured at the first scale by textured rolls 124A and 124B, which have surface textures, and pressed into the sheet at a reduction ratio of 5-10%, the first scale defects present in state S7 are removed. However, since the hot rolling rolls apply texture at a different scale, these defects cannot be substantially removed by the hot rolling rolls. From the perspective of a continuous process of surface progression by rolling in a continuous rolling stand, using high-temperature texturing allows for the development of a texture specifically designed to pre-treat the surface of sheet 112, enabling differentiation of the hot rolling process by passing the sheet 112 through an optimal surface for the next set of rolls having predetermined characteristics and functions. One aspect of this disclosure describes how rolling equipment and processes between a metal in an initial condition or state (with respect to a given temperature, thickness, width, surface texture, subsurface properties, temper, etc.) and a metal in a finishing condition or state (with respect to a target temperature, thickness, width, surface texture, subsurface properties, temper, etc.) can be optimized by using rolling texture at various stages of the rolling operation. More specifically, the rolling process can be improved not only in terms of the final properties (quality) of the product, but also by minimizing the time, energy, equipment, and space required to achieve the target product, for example, by reducing the number of rolling stages, the roll pressure at a given stage, etc., and by selectively using high-temperature texture rolling at various points in the roll line, which can be used to assist in surface progression. This disclosure considers the initial state of the sheet, the state at each stage of the rolling process (before and after the texture rolling station), and the final target state of the sheet in order to achieve efficient and effective progression of the sheet and its properties with respect to surface and subsurface hardness / temper.

[0094] After the sheet passes through texturing rolls 124A, 124B, it is then subjected to one or more stages of low-reduction hot rolling, such as hot rolls 120A, 120B, 122A, 122B. The texturing step can remove slab damage from the table rolls as a preparatory step before finally achieving an isotropic surface free of visible defects. Texturing can reduce the rolling force required by rolls 120A, 120B by trapping lubricant in the irregularities of the sheet surface when the texturized sheet is in state S8. This means that the desired target thickness and surface texture can be obtained by improving reduction capacity, reducing the rolling load, and / or reducing the number of times the roll stand passes. The texturing step can also increase the “bite” or friction grip of rolls 120A, 120B on the sheet 112. The increased gripping is distributed more evenly (in the width direction) across the surface of sheet 112, so that sheet 112 passes more straight between rolls 120A, 120B, 122A, and 122B. The stabilization of the frictional interaction between sheet 112 and rolls 120A, 120B, 122A, and 122B allows the sheet to pass through rolls 120A, 120B, 122A, and 122B at a steady pace. When the material flow between stands is uneven (for example, when the speed of sheet 112 passing through rolls 120A and 120B is faster than the speed of sheet 112 passing through rolls 122A and 122B), corrugations (cobbles) (bent sections) are formed in the sheet, but this formation can be avoided by maintaining a balance in the sheet flow between stands. By texturing the sheet 112 with texture rolls 124A and 124B, the reduction in rolls 120A, 120B, 122A, and 122B can be increased. The effect of texturing with rolls 124A and 124B is that it can reduce the number of cold rolling passes required to repair damage to the sheet 112 that occurs even when hot rolling with a low reduction, enabling casting at thinner gauges and producing products with better surfaces, such as isotropic surfaces suitable for anodizing.

[0095] As shown in Figure 3B, in state S7, the incoming sheet 112 has surface defects 112D and subsurface defects 112SSD, but this sheet 112 undergoes substantial improvement and progress before the next stage, for example, the warm rolls 120A, 120B and 122A, 122B. As previously mentioned, the aluminum sheet 112 in state S7 is malleable and can more easily accept the impression of the surface rolls 124A, 124B than sheet aluminum that allows cooling and tempering. As a result, the surface treatment can be more faithful to the surface texture of the rolls 124A, 124B with less pressure, and the wear of the rolls 124A, 124B is reduced, as well as exhibiting the aforementioned properties of high-temperature texturing.

[0096] Figure 4 shows an alternative embodiment of the present disclosure, for example, in a scenario where texturing is applied in-line to a cold rolling mill, with texturing rolls 224A, 224B positioned after the cold rolling rolls 220A, 220B and 222A, 222B. The cold rolling rolls 220A, 220B reduce the thickness of the sheet to state S11, producing the sheet 212 to state S12. The rolls 222A, 222B further reduce the thickness of the sheet 212 to form state S13. In one embodiment, the sheet 212 can be reduced in thickness by about 50% by the rolls 220A, 220B, and then by a further 50% by the rolls 222A, 222B. The sheet 212 is then heated by heaters 230, which are positioned on opposing portions 230A, 230B on both sides of the sheet 212. The heater may be of various types, including electrical resistance, induction heating, or natural gas. Cold working of the sheet 212 with the cold rolling rolls 220A, 220B and 222A, 222B increases the residual stress of the sheet 212 in stages S12 and S13, increasing the yield strength of the sheet and making rolling in the subsequent stand more difficult. Heater 230 heats the sheet to a temperature of 250-970°F, thereby reducing the yield strength of the sheet 212 in state S14, facilitating rolling by the texture rolls 224A, 224B and enabling greater topographic transfer with lower roll forces. As described above, the heat penetration depth into the sheet 212 can be selected / adjusted so as to provide sufficient heat penetration depth and softening to enable texturing at a given reduction amount and pressure.

[0097] Due to the high-temperature texture rolling, the residual stress in sheet 212 in state S15 is less than the residual stress in S14. This reduction in residual stress is reflected in a flatter sheet. That is, the sheet exhibits relatively superior flatness when in a free state without tension applied to the apparatus 210. The flatness of sheet 212 is also favorably influenced by texturing by rolls 224A and 224B. The texturing can be selected to have a texture suitable for the finished roll product having the texture provided by the texture rolls 224A and 224B.

[0098] The aluminum sheet 212 in state S14 is reduced in thickness by texture rolls 224A and 224B to state S15. The texture rolls may be pre-surfaced by, for example, electrical discharge texturing (EDT) or other processes. When the sheet 212 in state S14 has a temperature of 250 to 970°F, the thickness is reduced by approximately 0 to 30% by pressing the texturing rolls 224A and 224B, which have a surface roughness Ra of 1 μm to 10 μm, against the sheet 212 with a pressure of 1 klbs / in to 10 klbs / in, and the surface texture of the rolls 224A and 224B is transferred to approximately 60 to 100% of the surface 212H and 212I of the sheet 212 in state S15.

[0099] The high-temperature texturing method of this disclosure enables a "rougher" surface topology, e.g., a Ra 5 μm surface topology, compared to conventional temper skim pass processing at room temperature. High temperature reduces yield strength, allowing for greater topographic transfer at lower roll pressure and lower reduction. Generally, "rough" surface topography, high reduction, and high temperature promote the transfer of sticky metals, and therefore accelerate subsurface damage to the sheet. The method of this disclosure significantly reduces the transfer of sticky metals and subsurface damage by texturing with low load, low reduction, and with little or no forward sliding. The method of this disclosure is made possible by once-through lubrication, evaporative roll cooling, and the use of roll surface coating and high-pressure water blasting or similar roll cleaning. The aforementioned measures address the need to maintain surface quality while keeping the roll clean and at the desired temperature, and controlling friction (by sheet lubrication).

[0100] According to the method of this disclosure, the texture applied to the sheet 212 can, in some cases, be converted into the ability to remove rolling passes in hot or cold rolling. In another embodiment of this disclosure, the required tonnage of the mill is reduced, energy consumption is reduced, and the reduction amount is reduced, resulting in less residue generation. Less residue results in a cleaner sheet 212. The reduction in rolling force and the reduction in residue generation correspond to reduced wear on the texturing rolls 224A and 224B, resulting in longer roll life and fewer roll replacements. Since the number of roll replacements is reduced due to the reduced wear on the roll topography, the variation in Ra of the sheet surface roughness from one coil 212E to the next coil is reduced. For example, this variation occurs between a coil of sheet 212 manufactured using the last texturing rolls 224A and 224B and a coil manufactured using newly textured rolls 224A and 224B. High-temperature texture rolling can reduce the cost of the textured sheet 212E by, for example, reducing the number of rolling passes, making the texturing process applicable to a wider range of products. Reducing the number of rolling passes also reduces the amount of rolls used in the rolling mill, thereby increasing the mill's output capacity over a given period.

[0101] Figure 5 shows an apparatus 310 for manufacturing a sheet material 312 such as an aluminum sheet. The apparatus 310 has two sets of texture rolls 324A, 324B and 340A, 340B, which are arranged continuously in the flow direction of the sheet 312. The sheet 312 is fed to the texture rolls from an arbitrary source, e.g., a leading roll of a rolling mill or casting mill, cooled or heated to a high temperature of, for example, 250-970°F in state S16, and high-temperature texturing is performed by the texture rolls 324A, 324B and 340A, 340B. This high-temperature texturing has all the features and characteristics described above. The texture rolls 324A, 324B may be large-diameter rolls, and the sheet 312 may have little or no thickness reduction in the pass. The texture rolls 340A, 340B may have a smaller diameter, and the thickness reduction of the sheet 312 may be greater. In another embodiment, the working roll stand of the hot rolling mill can be texturized to produce textured rolls 340A, 340B. As described above, high-temperature texturization can be used to modify the surface of the sheet 312 in preparation for subsequent processing by the subsequent roll stand. In the apparatus 310, the surface can be progressively advanced by sequentially or auxiliaryly texturizing the sheet 312 through texture rolling by the roll sets 324A, 324B and 340A, 340B. In one embodiment, the first set of textured rolls 324A, 324B have a surface roughness of 1 to 10 Ra, and the second set of 340A, 340B have a surface roughness of 1 to 5 Ra. The first set of texture rolls 324A and 324B act more heavily on the surface and subsurface to impart a texture with a greater roughness Ra, and then the second set of texture rolls 340A and 340B, which have a less rough texture, partially remove the pattern formed by the first set of texture rolls 324A and 324B. High-temperature texturing can also be used to create a sheet for subsequent rolling with hot rolls (e.g., 320A and 320B) or cold rolls.

[0102] The sequential texturing described above can be used to reduce the size of the crystal grains and break down the surface of the sheet 312, reducing the "orange peel"-like uneven surface of the sheet 312 in stage S19, and producing a cleaner surface with superior isotropy, especially when anodized. The isotropic topography of the slab formed by high-temperature texturing reduces the rolling force in subsequent roll stands (e.g., 320A, 320B), promotes tracking, reduces folds, reduces rolling passes with large reductions, allows casting at thinner gauges, reduces the number of cold rolling passes to repair damage within the sheet 312, and improves surface quality. The sequential texturing method shown in Figure 5 improves the ability to produce diverse sheet 312 textures, as multiple consecutive texture rolling passes are represented in the final rolled sheet 312 in stage S19. The aforementioned high-temperature continuous texturing can be facilitated by once-through lubrication, evaporative roll cooling, and the use of roll surface coating and high-pressure water blasting or similar roll cleaning.

[0103] Figure 6 shows an apparatus 410 for manufacturing sheet material 412 such as an aluminum sheet. The apparatus 410 has a heater 430 for raising the temperature of the sheet 412 being transported, and the sheet is fed from various sources such as a cold rolling mill stand or a casting mill. The heater 430 raises the temperature of the sheet 412 in state S20 to 250-970°F in state S21, enabling high-temperature texturing by texture rolls 424A and 424B. This high-temperature texturing has all the features and properties described above, and by texturing with a rough topographic surface, it acts on the surface of the sheet 412 to more evenly redistribute the metal and improve surface quality before further processing. High-temperature texturing can be performed with low load and low reduction ratio, so there is little to no forward sliding and the tendency to cause subsurface damage is reduced. As the sheet 412 softens upon heating and its yield strength decreases, the pressure on the texture rolls 424A and 424B decreases, enabling advanced topographic transfer. After passing through the texturing rolls 424A and 424B, the sheet can then be rolled by cold roll sets 420A and 420B to state S23, and then rolled by cold rolls 422A and 422B. In apparatus 410, a high-temperature pre-textured sheet 412 is produced before cold rolling. As described above, high-temperature texturing can be used to modify the surface of the sheet 412 in preparation for subsequent processing by the roll sets. In apparatus 410, the surface can be progressively textured by sequentially or auxiliaryly applying texture to the sheet 412 through texture rolling by roll sets 424A, 424B and 420A and 420B. In one embodiment, the texture rolls 424A and 424B have a surface roughness of Ra 1 μm to 50 μm, and the first set of cold rolls 420A and 420B have a surface roughness of Ra 1 μm to 5 μm. The texture rolls 424A and 424B impart texture with a higher roughness Ra, exerting a greater effect on the surface and subsurface.Next, the first set of cold rolls 420A, 420B, which have a finer texture, partially remove the pattern formed by the texture rolls 424A, 424B, substantially reducing the thickness. The second set of cold rolls 422A, 422B further reduce the thickness of the sheet and / or impart additional texture to the sheet 412. The effect of the texturing rolls 424A, 424B is to improve and accelerate the cold rolling by the rolls 420A, 420B and 422A, 422B by forming pockets in the sheet 412 in state S22 that can hold lubricant. The improvement in cold rolling allows for the elimination of cold rolling passes, resulting in a sheet in state S24 with fewer scratches and an isotropic matte finish. High-temperature texturing improves texture transfer, and the sheet 412 in state S24 has a more uniform surface. The above-described high-temperature texturing and subsequent cold rolling can be facilitated by once-through lubrication, evaporative roll cooling, and the use of roll surface coating and high-pressure water blasting or similar roll cleaning.

[0104] Figure 7 shows an apparatus 510 for manufacturing sheet material 512 such as an aluminum sheet. The apparatus 510 has a heater 530 for raising the temperature of the sheet 512 being transported, and the sheet is fed from various sources such as a cold rolling mill stand or a casting mill. The heater 530 raises the temperature of the sheet 512 in state S25 to 250-970°F in state S26, enabling high-temperature texturing by texture rolls 524A and 524B. This high-temperature texturing has all the features and properties described above, and by texturing with a rough surface topography, it acts on the surface of the sheet 512 to more evenly redistribute the metal and improve the surface quality before further processing. High-temperature texturing can be performed with low load and low reduction ratio, so there is little to no forward sliding and the tendency to cause subsurface damage is reduced. The sheet 512 softens upon heating, reducing its yield strength and decreasing the pressure on the texture rolls 524A and 524B, but still, a high degree of topographic transfer of the sheet 512 in state S27 is achieved. After passing through the texturing rolls 524A and 524B, the sheet is then rolled by a second set of texturing rolls 540A and 540B to state S28, and then rolled by cold rolls 520A and 520B to produce the sheet 512 in state S29. In apparatus 510, a high-temperature pretextured sheet 512 is produced in two texturing passes before cold rolling. The texture rolls 524A and 524B are large-diameter rolls and pass through the sheet 512 with a low reduction. The texture rolls 540A and 540B are small-diameter rolls and apply a large reduction to the sheet 512. In another embodiment, the working roll stand of the hot mill can be texturized to produce textured rolls 540A, 540B. As described above, high-temperature texturization can be used to modify the surface of the sheet 512 in preparation for subsequent processing by the subsequent roll stand. In the apparatus 510, the surface can be progressively developed by sequentially or auxiliaryly texturing the sheet 512 through texture rolling by the roll sets 524A, 524B and 540A, 540B.In one embodiment, the first set of texture rolls 524A and 524B have a surface roughness of Ra 1 μm to 50 μm, and the second set of rolls 540A and 540B have a surface roughness of Ra 1 μm to 5 μm. The first set of rolls imparts texture with a higher roughness Ra and has a greater effect on the surface and subsurface. Then, the second set of texture rolls 540A and 540B, which have a lower roughness texture, partially remove the pattern formed by the texture rolls 524A and 524B. Sequential high-temperature texturing can be used to prepare a sheet for subsequent enhanced rolling by cold rolls (e.g., 520A and 520B).

[0105] As described above, high-temperature texturing can be used to modify the surface of the sheet 312 in preparation for subsequent processing by a subsequent roll stand. In the apparatus 510, the surface can be progressively advanced by sequentially or auxiliaryly applying texture to the sheet 512 by texture rolling with roll sets 524A, 524B and 540A, 540B. In one embodiment, the first set of texture rolls 524A, 524B have a surface roughness of Ra 1 μm to 50 μm, and the second set of 540A, 540B have a surface roughness of Ra 1 μm to 5 μm. The texture rolls 524A, 524B act more strongly on the surface and subsurface to impart a texture with a greater roughness Ra, and then the second set of texture rolls 540A, 540B, which have a texture with a lower roughness, partially remove the pattern formed by the texture rolls 524A, 524B, substantially reducing the thickness. The cold rolls 520A and 520B further reduce the thickness of the sheet and / or impart additional texture to the sheet 512. The effect of the texturing rolls 524A, 524B and 540A and 540B is to improve and accelerate cold rolling by the rolls 520A and 520B, for example, by forming pockets in the sheet 512 in state S28 that can hold lubricant. The improved cold rolling allows for the elimination of cold rolling passes, resulting in a sheet with fewer scratches and an isotropic matte finish in state S29. High-temperature texturing improves texture transfer, resulting in a more consistent surface on the sheet 512 in states S27 and S28. The above high-temperature texturing and subsequent cold rolling can be accelerated by once-through lubrication, evaporative roll cooling, and the use of roll surface coating and high-pressure water blasting or similar roll cleaning. After condition S29 is achieved, the aluminum sheet 512 can be heat-treated, quenched and / or tempered. The aluminum sheet 512 can then be wound into a coil 512E and stored and transported in the conventional manner.

[0106] According to aspects of this disclosure, adding texture to the sheet at the end of the continuous casting process significantly reduces costs when implemented in-line. Additional winding and unwinding are not required, the cast and rolled F-temper characteristics are low, and topographic transfer can be improved. The latter, due to improved topographic transfer, allows for smaller reduction, longer roll life, and the achievement of topography similar to conventional textures or newly differentiated surfaces. Reduced reduction also reduces debris generation, minimizing the need to clean some textures such as EDT. Surface quality issues arising from processes such as casting and heat treatment can be addressed after texturing with each standard heat treatment. Adding texture to the continuously cast product in an additional step allows for further control of topographic transfer depending on the desired product characteristics (e.g., F, O, or T temper). Additional post-texturing heat treatments may also be added as needed. Another potential advantage of adding texture in-line or at-line to the surface of continuously cast products is that it creates a uniform surface, minimizing surface characteristics after casting or rolling.

[0107] EDT is used in finish rolling to produce matte-finish, non-oriented sheets to improve appearance and formability. Other texturing processes that can produce similar results include abrasive rolls, sandblasted rolls, cross-angle grinding rolls, inclined-angle grinding rolls, laser or electron beam textured rolls, rolls deposited with nodular chromium plating by TopoCrom® or other high-nodule chromium processes, ball peening rolls, and shot peening rolls.

[0108] Potential advantages in aspects of this disclosure include extended texture roll life, unique textures due to improved topographic transfer, cost reduction by minimizing coil winding and unwinding operations in inline applications, consistent surface, improved recovery by reducing surface artifacts from casting and rolling, and reduced mill load. When EDT or similar textures are used in hot roll mills (HRMs), two further advantages are obtained: with the right combination of lubricant and texture, mis-engagement does not occur even at larger reductions, and the number of passes can be reduced. This is important because it eliminates the need for kerosene bite assistance.

[0109] The advantage of adding texture in-line or at-line to the surface of a continuously cast product is that a uniform surface can be formed, minimizing surface features caused by casting or rolling. By texturing (at low cost and with low load equipment) immediately after a continuous casting machine, Micromill®, roll coating machine, or slab casting machine, features that would be unacceptable in critical surface applications can be redistributed, removed, and masked. For example, topography created by Micromill leaves undesirable features and / or patterns on the surface of the cast metal. By using the teachings of this disclosure on a textured surface in a hot rolling process, appearance problems in the subsequent anodized surface can be reduced or eliminated. This method allows for the low-cost production of sheets for applications where surface performance is more critical.

[0110] In the process of using the method and apparatus of this disclosure, a lubricant such as a hot rolling dispersant was applied to the sheet before it entered the nip between the hot rolling work rolls of the first stand. Although high-pressure roll coating was expected due to the "coarse" nature of EDT topography, contrary to expectations, very low-pressure roll coating was performed. It should also be noted that rolling in the two stand mills was significantly improved. Firstly, the "stability" of roll engagement was greatly improved, the steering of the sheet was much improved, and the rolling process was facilitated. This improved stability resulted in greater reduction than expected at low loads. It was expected that higher friction of the EDT work rolls in stand 1 would result in greater load forces and limit the reduction capacity, but this phenomenon was not observed. Under standard rolling conditions, the reduction in stand 1 was 57%, but the load force from the EDT rolls was not greater than the load force from the standard grinding rolls. Using an EDT roll in stand 1 allowed for a reduction capacity improvement of up to 70% without significantly increasing the load force. This was not possible with ground topography. Furthermore, when feeding the sheet from stand 1 to stand 2 using the EDT texture, the load force was significantly reduced. The apparatus and method of this disclosure resulted in lower loads, greater reduction, and less residue and surface degradation than expected.

[0111] EDT is used in finish rolling to produce matte-finish, non-oriented sheets for improved appearance and formability, but other texturing methods can be used to manufacture texturing rolls (e.g., 24A, 24B) for use in the apparatus of this disclosure. For example, EDT suppliers do not currently have the equipment to handle all sizes in terms of dimensions and weights for hot-rolling work rolls. Other texturing processes that can produce similar results to EDT include, for example, sandblasted rolls, cross-ground rolls, rolls produced by TopoCrom or other high-nodule chromium processes, ball-peening rolls, and shot-peening rolls.

[0112] As described above, the sources of aluminum metal (14, 114, etc.) are diverse, and it may be cast from a molten material into ingots, which are then rolled to a thickness of, for example, 0.125 to 0.250 inches, or it may be cast by a continuous casting method. The advantage of this disclosure is that it eliminates characteristics that adversely affect surface quality in the processing to the completion of the sheet product, and reduces the amount of work and energy required to achieve the objective.

[0113] Figure 8 shows a number of planned virtual surface scratches 612D1, 612D2, 612D3, 612D4, 612D5A, 612D6, 612D7, 612D8, 612D9, 612D10, and 512D11 on a virtual sheet 612. The virtual scratches 612D5A are multiple and parallel to each other, forming a subpattern 612D5, while the other virtual scratches, e.g., 612D1, 612D2, and 612D3, are arranged in close proximity to each other, and these scratches can be associated by an observer with a single pattern, e.g., an incomplete triangle 612DT1. If scratches or other defects 612D5 can communicate a perceptible pattern, the observer can observe more of them than scratches or defects that do not have a perceptible pattern and are perceived as random. Similarly, since scratch 612D4 is recognized as existing in the background 612B or in an area of ​​sheet 612 that does not have similar optical properties, scratch 612D4 is recognized as a local area having different optical properties from the background 612B. If we describe a scratch, for example, 612D1 which is a local area lower than the surface of the background 612B, it should be understood that the methods and apparatus of this disclosure are effective in correcting other types of surface defects, such as defects resulting from defects protruding above the background surface 612B, or defects that oscillate up and down the background surface 612B, or defects having different optical properties such as different reflective properties from the background surface 612B. It is understood that when inspection is performed at sufficiently high magnification, any surface will be observed as "rough" or highly variable, and furthermore, if the magnification is sufficiently large that the defect itself occupies the field of view, the recognition of the defect will be impaired. One method is to specify the size or scale of the defects of interest, which can be defined as those recognizable at magnifications from 1x to 100x. Alternatively, it can be defined as a defect of interest that is observable with normal human vision (with the naked eye) at a distance of 0.1 to 5 feet. In a further alternative example, the range of roughness Ra considered to be a background surface with undetectable defects is 0.1 μmRa to 2 μmRa.Any feature adjacent to the background surface that exceeds this roughness Ra is considered a surface defect. In one embodiment of this disclosure, the apparatus and method described above can partially or completely conceal or eliminate recognizable defects on the surface of the sheet, as well as defects on the virtual sheet 612. This will be illustrated in the embodiments described below.

[0114] Figure 9A is an optical image of sheet 812 of type 3XXX aluminum alloy, showing the edges of scratches 812D1 and 812D2 on the background surface 812B, the scratches being approximately 10 μm deep, 400 μm wide, and 50 mm long. These scratches were created using a TABER® linear abrader, which has an adjustable mechanism that allows the user to select and set the speed, stroke length, and test load. Different test loads were used to create scratches on the test specimen. Figure 9B shows a topographic image of scratch 812D1 obtained by a white light phase-shift interferometer.

[0115] Figure 9C is an optical image of a sheet 912 made of type 3XXX aluminum alloy, with the edges of scratches 912D1 and 912D2 shown on the background surface 912B. The scratches are approximately 200 μm deep, 1000 μm wide, and 50 mm long. These scratches were created using a TABER linear abrader, which has an adjustable mechanism that allows the user to select and set the speed, stroke length, and test load. These test specimens were subjected to a larger test load than those in Figure 9A in order to create deeper scratches than those in Figure 9A. Figure 9D shows a topographic image of scratch 912D1 obtained by a white light phase-shift interferometer.

[0116] Figure 10 shows an optical image of surface sliver 1012D1 present on the background surface 1012B of a metal sheet or slab 1012. This type of surface defect is observed as a result of rolling, where metal adheres to the roll and is rolled, embedding itself into the surface of the slab / sheet.

[0117] Figure 11 shows a series of surface topography scan results 112S1 to 112S5 of aluminum sheets 12 (Figure 1) rolled at five different reduction ratios using EDT rolls 18A and 18B with a surface roughness Ra of 5 μm, on 5XXX sheet aluminum manufactured according to one embodiment of the present disclosure. The sheet aluminum is reduced in thickness by 2.5%, 4.2%, 12.7%, 23.7%, and 28% using an apparatus such as apparatus 10 shown in Figure 1. The aluminum sheet supply source 15 (Figure 1) is a Micromill or a mill described in any of the following U.S. Patents [Nos. 5515908, 5655593, 5894879, 5772799, 5772802, 6045632, 5769972, 6102102, 6391127, 6623797, 6672368, 7089993, 7503377, 7125612, 6581675, 7182825, 8403027, 7846554, 8697248, 8381796, or 8956472]. These patents are incorporated herein by reference. The texturing rolls 24A and 24B used were textured by EDT. Reduction of the sheet was performed when the sheet was 930°F, and topographic scanning was performed after quenching on the roll line. As can be understood, the surface topographic scanning results show that the peaks and valleys become more uniform with increasing reduction, replicating the EDT topography. As can be understood, the sheet output of the Micromill varies depending on the operating parameters of the Micromill, which include surface quality, output temperature, thickness, and alloy composition. The operating parameters of the high-temperature texture rolling disclosed herein can be adjusted with respect to temperature, reduction rate, and roughness Ra to suit the specific output characteristics of the sheet obtained by the Micromill in order to achieve the advantages described herein. In one embodiment, the temperature of the sheet output from the Micromill is in the range of 1100 to 1000°F.After leaving the micromill and being exposed to ambient temperature and handling equipment (such as casting machines and / or conveyor belts), the sheet is cooled and solidified to a temperature at which rolling and / or high-temperature texture rolling is possible, as taught in this disclosure. This can be done at temperatures above 970°F, if the cooling between the mill output and the initial rolling stand can be increased by casting conditions (e.g., throughput rate, solidification state and alloy composition) or by performing other steps, thereby increasing the distance between them or decreasing the throughput rate.

[0118] Figure 12 shows a series of surface topography scan maps 1212M1-1212M5 and line profiles 1212S1-1212S5 of aluminum sheets 12 rolled at five different reduction rates using cross-hatch rolls 24A and 24B with a surface roughness Ra of 5 μm, on a sheet aluminum of 5XXX manufactured according to one embodiment of the present disclosure. The sheet aluminum was reduced in thickness by 2.5%, 5.5%, 9.3%, 15.7%, and 22% using an apparatus such as apparatus 10 shown in Figure 1. The texturing rolls 24A and 24B used were textured by cross-hatch grinding. Reduction of the sheets was performed when the sheets were at 930°F, and the topography scans were performed after quenching at the roll line. As can be seen, the surface topography scan results show undesirable surface features, with large variations in peaks and valleys, some deep valleys, and retained features of the ground cross-hatch rolls.

[0119] Figure 13A shows a series of optical images 1312AO, a topographic image 1312AT, and a line profile 1312AP of a sheet sample 1312A with a background surface 1312AB that has surface defects 1312AD (scratches) after being rolled at a temperature of 850°F using an EDT with a thickness of 600 μin (15 μm) Ra to reduce its thickness by 8%. The sheet sample before the thickness reduction rolling had a background surface roughness Ra of 1 μm and a scratch depth of approximately 1000 μm, as shown in Figures 9C and 9D. As can be seen from Figure 13A, the visibility of the scratch 1312AD was reduced in the sample that was reduced by 5% with the EDT texture roll compared to the sample shown in Figures 9C and 9D. As shown by the topographic image 1312AT and line profile 1312AP, this reduction in the visual perceptibility of the scratch 1312AD is observed in the change in surface dimensions, where the average difference between the peaks and valleys is 45% less than in the sheet before rolling. When the reduction ratio increases to 10% in Figure 13B, the scratch depth decreases by 70%, and when it increases to 20% in Figure 13C, the scratch depth decreases by 80%.

[0120] Figure 14A shows a series of optical images 1512AO, a topographic image 1512AT, and a line profile 1512AP of a sheet sample 1512A with a background surface 1512AB and surface defects 1512AD (scratch) after being rolled at a temperature of 850°F using an EDT with a thickness of 1200 μin (30 μm) to reduce its thickness by 5%. The sheet sample before the thickness reduction rolling had a background surface roughness Ra of 1 μm and a scratch depth of approximately 1000 μm, as shown in Figures 9C and 9D. As can be seen from Figure 14A, the visibility of the scratch 1512AD was reduced in the sample reduced by 5% with the EDT texture roll compared to the sample shown in Figures 9C and 9D. As shown by the topographic image 1512AT and line profile 1512AP, this reduction in the visual recognizability of the scratch 1512AD is observed in the change in surface dimensions, where the average difference between the peaks and valleys is 65% less than in the sheet before rolling. When the reduction ratio increases to 10% in Figure 14B, the scratch depth decreases by 80%, and when it increases to 20% in Figure 14C, the scratch depth decreases by 100%.

[0121] Figure 15 shows graphs of the reduction ratio at different scratch depths for shallow scratches (approximately 10 μm deep, 200 μm wide), medium scratches (approximately 100 μm deep, 500 μm wide), and deep scratches (approximately 200 μm deep, 1000 μm wide) after rolling with EDT texture rolls having either 600 EDT (Ra600 μin) or 1200 EDT (Ra1200 μin) textures. The rolling apparatus used is the same as that shown in Figure 7, and the measurements for creating the graphs in Figure 15 were taken in state S27. State S27 is an intermediate state, which is after rolling with texture rolls 524A and 524B (having either an EDT texture of Ra600 μin or Ra1200 μin) and before rolling with texture rolls 540A and 540B. It should be noted that shallow and moderate depth scratches were completely or nearly completely eliminated with a 10% reduction using a 1200 EDT roll, and with a 20% reduction, all other scratches were eliminated except for deep scratches with a 20% reduction using a 600 EDT roll, and 80% of the deep scratches were eliminated with a 20% reduction using a 600 EDT roll.

[0122] Figure 16 shows an apparatus 1740 that utilizes a computer 1742 and a scanning device 1744 for measuring light scattered from a surface 1712. The computer 1742 displays an image 1742I that models the light scattering of the surface 1712. The computer software for programming the scanning device and the computer 1742 may be ScatterScope®, obtained from The Scatter Works, Inc. of Tucson, Arizona.

[0123] Figure 17A shows an optical image 1812O of an aluminum sheet 1812 processed according to this disclosure, which was reduced by 10% using an apparatus 10 (shown in Figure 1) equipped with texturing rolls 20A and 20B having an EDT texture of Ra 200 μin (5 μm) Ra. The light scattering signature 1812S was taken from the surface of sample 1812. Figure 17B shows an optical image 1912O of an aluminum sheet 1912 with a milled finish reduced by 10% using a conventional mill, and the light scattering signature 1912S taken from the surface of sample 1912. While the sheet 1912 with a conventional milled finish has a directional signature 1912S, the light scattering 1812S from the EDT rolls exhibits isotropic light scattering with more uniform light intensity in the X and Y directions (approximating a more circular pattern).

[0124] Figure 17C shows an optical image 2012O of an aluminum sheet 2012 processed according to this disclosure, which was reduced by 25% in an apparatus 10 (shown in Figure 1) equipped with Ra200μin (5μm) texturing rolls 20A and 20B. The light scattering signature 2012S was taken from the surface of sample 2012. Figure 17D shows an optical image 2112O of an aluminum sheet 2112 reduced by 25% in a conventional mill, and the light scattering signature 2112S taken from the surface of sample 2112. The directionality of the light intensity in the X and Y directions of the light scattering 2012S is greater than that of the light scattering 1812S of sheet 1812 at 10% reduction, but still much smaller than that of the light scattering 2112S of milled sheet 2112 at 25% reduction.

[0125] Figure 18A shows a series of light scattering signatures for an aluminum sheet sample with a milled finish, rolled using a milled finish roll with Ra 50 μin (1 μm). 2212S1 is the result of a 5% reduction, 2212S2 of 10% reduction, 2212S3 of 15% reduction, and 2212S4 of 25% reduction.

[0126] Figure 18B shows a series of light scattering signatures for aluminum sheet samples with an EDT finish rolled with an Ra200μin (5μm) EDT roll, where 2312S1 is 5% reduced, 2312S2 is 10% reduced, 2312S3 is 15% reduced, and 2312S4 is 25% reduced. Comparing the light scattering signatures of Figure 18A and Figure 18B, it can be concluded that the EDT finish exhibits less directionality than the mill finish at all reduction ratios.

[0127] Figure 19A shows the texture data signature 2412DS obtained by an Optimap® PSD apparatus for a milled surface, illustrating the directional texture quantified by the characteristics of the apparatus and the process used.

[0128] Figure 19B shows the texture data signature 2512DS obtained by an Optimap PSD instrument for an EDT-textured surface, indicating low directionality as quantified by the characteristics of this instrument and the process used. The images shown in Figures 19A and 19B represent a sample surface area of ​​approximately 95 mm × 70 mm. The light scattering signatures 2312S1 to 2312S4 show that although the test area of ​​the sample is circular with a diameter of approximately 5 mm, the non-directionality clearly continues over a large area of ​​the sheet, indicating that the entire sheet surface is non-directional. EDT roll texture removes non-uniform surfaces introduced during the rolling process, generating an isotropic surface signature that can be measured with optical or topographic measurement systems such as Optimap (Rhopoint Instruments), Scatterscope (Scatterworks), 3D interferometers, or confocal microscopes. The surface signature is traceable by the texture rolling process and the standard rolling process and can be enhanced by surface coatings or treatments.

[0129] In the above-described embodiment, high-temperature, low-yield-strength texture rolling was used at a relatively low reduction ratio (e.g., 0% to 30%) to remove surface defects such as scratches having a depth of 10 μm to 200 μm. However, a larger reduction ratio can be applied to remove larger surface defects. For example, an EDT roll with a surface roughness of Ra 600 μin or 1200 μin can be reduced by up to 70% to remove scratches and other surface defects with a depth of 1 mm.

[0130] One aspect of the present disclosure is the manufacture of a metal sheet suitable for forming automobile body panels using the techniques described above. In one embodiment, the metal sheet manufactured by the embodiment of the present disclosure is used to form a closing panel (for example, metal panels joined together to form a car door or hood structure). In another embodiment, the metal sheet manufactured by the method of the present disclosure can be used to form at least a portion of a white body. The term "white body" is used to describe a sheet metal assembly for a car body before painting, i.e., before the installation of glass, trim and movable parts (suspension, power transmission, etc.).

[0131] The embodiments described herein are merely illustrative, and those skilled in the art will understand that many variations and modifications can be made without departing from the spirit and scope of the subject matter set forth in the claims. For example, the rolling temperature and reduction ratio can be adjusted to suit different aluminum alloys. All such changes and modifications are included in this disclosure and the claims.

Claims

1. 1. A method for rolling an aluminum alloy metal sheet provided in a first state with an EDT texture roll to achieve a second state, comprising: The first state is that the surface of the aluminum alloy metal sheet has a surface defect having a depth of 10 μm to 1 mm; The surface of the EDT texture roll is formed with a random pattern of peaks and valleys having an average height and spacing or a repeating pattern of peaks and valleys having an average height and spacing, and has a surface roughness Ra of 1 μm to 50 μm. texture rolling the aluminum alloy metal sheet with an EDT texture roll while the aluminum alloy metal sheet is at a temperature of 250-970°F (121.1-521.1°C), a temperature at which the aluminum alloy metal sheet exhibits a reduced yield strength compared to its yield strength at room temperature; said texture rolling comprising contacting a surface of said aluminum alloy metal sheet provided in said first state with said EDT texture roll; said texture rolling including imparting a texture of said EDT texture roll to a surface of said aluminum alloy metal sheet to reduce the thickness of said aluminum alloy metal sheet by 5-25% to achieve said second condition; the surface of the aluminum alloy metal sheet in the second condition achieved by said texture rolling has a background surface roughness that is considered an imperceptible surface defect; The method wherein said background surface roughness is between 0.1 μm Ra and 2 μm Ra.

2. 2. The method of claim 1, wherein the texture transfer by said texture rolling is 60% to 100% of the surface of the aluminum alloy metal sheet.

3. 10. The method of claim 1, wherein said texture rolling is a final rolling step before coiling the aluminum alloy metal sheet.

4. 2. The method of claim 1, wherein the texture rolling involves keeping the EDT texture roll clean and at temperature and / or controlling friction by at least one of once-through lubrication, evaporative roll cooling, roll surface coating, or high pressure water blasting.

5. 1. A rolling mill for rolling metal to produce an aluminum alloy metal sheet, comprising: The aluminum alloy metal sheet has a surface defect having a depth of 10 μm to 1 mm, the rolling mill comprising an EDT texture roll positioned at a position where the temperature of the aluminum alloy metal sheet is between 250 and 970°F (121.1 and 521.1°C); The surface of the EDT texture roll is formed with a random pattern of peaks and valleys having an average height and spacing or a repeating pattern of peaks and valleys having an average height and spacing, and has a surface roughness Ra of 1 μm to 50 μm. the EDT texture roll is configured to directly contact a surface of the aluminum alloy metal sheet having a temperature of 250 to 970°F (121.1 to 521.1°C) to perform rolling to reduce the thickness of the aluminum alloy metal sheet by 5 to 25%, A rolling mill, wherein the surface of the aluminum alloy metal sheet rolled by said EDT texture roll has a background surface roughness that is considered an imperceptible surface defect, said background surface roughness being between 0.1 μm Ra and 2 μm Ra.

6. 6. The rolling mill of claim 5 further comprising an additional rolling station after the EDT texture roll.

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