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, entitled "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 material, and more particularly to methods and apparatus for rolling metals, such as aluminum and aluminum alloys, into sheets to produce sheet material having desired surface and subsurface properties. [Background technology]

[0002] <Background> Various methods are known for rolling aluminum and imparting a desired surface texture to the resulting rolled sheet. The surface texture can be imparted to the sheet surface by rolls, the surfaces of which have been textured by processes such as electrical discharge machining (EDT), roll grinding, crosshatch grinding, ball or shot peening. When used in A "texture roll" is typically It is defined as follows: Random Pattern Or repeating putts hmm, isotropic (Isotropic) Pattern Orientation (directional) Pattern and the surface is made up of peaks and valleys; For aesthetic or functional purposes , defined Have average height and spacing rollTextured roll textures are applied to aluminum, steel and other metal surfaces, usually after the cold rolling process, with low reductions (3-10%). For automotive sheets with EDT texture, the texture is usually applied as the last pass of a skin pass (temper) mill. Applying the texture after cold rolling in a skin pass or cold mill often limits the transfer of the roll surface texture to the sheet due to the cold working characteristics of the product, the size of the rolls and the low reduction of the rolls. In this case, the incoming surface is one that is not completely removed or covered by the roll surface texture. This is especially undesirable when features such as scratches or metal slivers from upstream processes are present. The term sliver is defined as "a thin, elongated piece of metal rolled onto the surface of the parent metal with only one end attached" [McGraw-Hill Dictionary Of Scientific And Technical Terms, 3rd Edition, p.1491]. Slivers can also be defined as "thin pieces of aluminum that are part of the material but only partially attached" [Visual Quantity Attributes of Aluminum Sheet and Plate, Al Assoc., 1994]. In cold rolling, high reduction by EDT rolls leads to high debris generation, which reduces the cleanliness of the sheet produced as a final product or as an intermediate product undergoing further processing.

[0003] Additionally, the skin pass after cold rolling adds an additional step to the process, increasing the cost of the product. Therefore, improvements and / or alternative methods and apparatus for imparting a desired surface texture to aluminum sheet remain desirable. Summary of the Invention

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

[0005] In another embodiment of the present disclosure, the metal is aluminum and the temperature at which the metal sheet is rolled by the texture roll is between 250 and 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 ranges from 0% to 30%.

[0008] In another embodiment, the reduction in thickness ranges from 0% to 70%.

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

[0010] In another embodiment, the rolling with the texture roll is a first rolling step and further comprises a second rolling step performed on the metal sheet subsequent to said 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 performed with a textured roll having a coarser texture than the textured roll used in the second rolling step.

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

[0014] In another embodiment, the second rolling step is performed by cold reduction rolling.

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

[0016] In another embodiment, the first rolling step creates surface features in the metal sheet that can accommodate a lubricant in the metal sheet.

[0017] In another embodiment, the method further includes multiple rolling steps, where the first step of rolling with a textured roll reduces the number of rolling steps required to achieve the final target condition 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 aspect, the rolling step at a temperature at which the metal sheet exhibits a low yield strength results in less wear of the textured roll than would occur if the rolling were performed at a lower temperature.

[0021] In another aspect, reduced wear of the texture roll corresponds to an increased lifespan of the texture roll.

[0022] In another embodiment, 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 removes surface defects present in the metal sheet when the metal sheet exhibits a low yield strength.

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

[0025] In another aspect, the rolling step when the metal sheet exhibits a low yield strength redistributes the metal within 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 a final rolling step before the metal sheet is wound into a coil.

[0027] In another embodiment, the surface defects removed by the rolling step are in the range of 10 μm to 1 mm.

[0028] In another embodiment, 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 embodiment, the temperature of the metal sheet is due to residual heat remaining in the metal sheet from a pre-treatment state.

[0030] In another embodiment, the temperature of the metal sheet is a result of heat imparted to the metal sheet by a heat source.

[0031] In another embodiment, the texture of the texture roll is imparted to the texture roll by at least one of EDT, ball peening, shot peening, grinding, or crosshatch 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 has no discernible pattern.

[0034] In another aspect, the method further comprises forming the metal sheet into an automotive panel after the rolling step.

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

[0036] In another aspect, the molding step further comprises creating a plurality of closure panels and joining the plurality of closure panels.

[0037] In another embodiment, the method further comprises incorporating the automotive panel into a body-in-white.

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

[0039] In another aspect, rolling with a textured roll reduces the appearance of surface defects in the sheet that are visible to the human eye.

[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 rolling reduction is in the range of 5% to 25%.

[0042] In another embodiment, the defects are 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 discernible pattern.

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

[0046] In another embodiment, defects are made less noticeable by decreasing the average peak to valley distance.

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

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

[0049] In another aspect, a rolling mill for rolling metal to produce a metal sheet has a textured roll disposed in a position where the temperature of the metal sheet is at a temperature that results in a yield strength that is lower than the yield strength at ambient temperature.

[0050] In another embodiment, the rolling mill has a heating device that heats the metal prior to the texture roll.

[0051] In another embodiment, the rolling mill includes a casting mill, and the metal casting leaving the casting mill is rolled by the rolling mill.

[0052] In another embodiment, the casting machine is a Micromill.

[0053] In another embodiment, the temperature at which the metal sheet exhibits low yield strength is in the range of about 250-970°F.

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

[0055] In another embodiment, the reduction in the texture roll ranges from 0% to 70%.

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

[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 description of the drawings]

[0059] For a more complete understanding of the present disclosure, the detailed description of the illustrative embodiments should be considered in conjunction with the accompanying drawings, in which:

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

[0061] [Diagram 2] FIG. 2 is a graph showing roll roughness versus transferred sheet roughness expressed as a percentage at 3% and 9% reduction at 200, 400, and 600° F.

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

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

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

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

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

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

[0068] [Figure 8] FIG. 8 is a schematic illustration of patterns of surface scratches with different depths and orientations in a sheet.

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

[0070] [Figure 10] FIG. 10 is an optical image of a surface sliver that is present on the surface of a metal sheet or slab due to metal being deposited or pressed into the surface of the metal sheet or slab during rolling.

[0071] [Figure 11] FIG. 11 shows a series of surface topography scans for five different EDT roll reduction examples of sheet aluminum produced in accordance with an embodiment of the present disclosure. [Figure 11-1]FIG. 11 shows a series of surface topography scans for five different EDT roll reduction examples of sheet aluminum produced in accordance with an embodiment of the present disclosure.

[0072] [Figure 12] FIG. 12 shows a series of surface topography maps and line profiles for five different crosshatch roll reduction examples of sheet aluminum produced in accordance with an embodiment of the present disclosure. [Figure 12-1] FIG. 12 shows a series of surface topography maps and line profiles for five different crosshatch roll reduction examples of sheet aluminum produced in accordance with an embodiment of the present disclosure.

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

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

[0075] [Figure 15] FIG. 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] FIG. 16 shows an apparatus for measuring light scattering from a surface.

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

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

[0079] [Figure 19A] FIG. 19A shows the texture data signature of a mill-finished surface. [Figure 19B] FIG. 19B shows the texture data signature of a surface textured with EDT. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0080] The aspects of the present disclosure have the following advantages. Surface texturing is done when the sheet to be textured is hot, e.g., 250-970°F, to reduce roll pressure and facilitate transfer. Texturing is used to repair or enhance surface and subsurface damage present in the sheet or caused by upstream processes (e.g. scratches, slivers, dents, etc. that cannot be beneficially affected by conventional cold texturing) and improves surface quality by removing surface features or patterns transferred by the casting or rolling processes. Texturing can be applied as an intermediate stage in rolling, with subsequent rolling passes at a later stage to enhance and facilitate the next step in the rolling process, 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, preparing the sheet for further processing, and producing a sheet with beneficial properties. Texturing can be performed simultaneously with reduction if carried out at elevated 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 described further below.

[0081] FIG. 1 shows an apparatus 10 for producing sheet material 12, such as aluminum sheet. The apparatus 10 can include an upstream source 14 of aluminum metal that will ultimately be formed into the sheet 12. A variety of sources 14 can be utilized in the apparatus and process of the present disclosure, and the sources are enclosed in dotted rectangles to represent this variety. For example, the source 14 can include an outlet 15 from a reservoir of molten aluminum for continuously casting and rolling the aluminum sheet 12, such as an outlet of a pusher furnace that extrudes hot slab ingots, a nozzle outlet of a casting box, an outlet of a coil unwinder, an outlet of a roll or slab caster, or an outlet of a micromill, the micromill and process of which 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 the present disclosure to apply texture in-line. The aluminum sheet 12 in state S1 exhibits a predetermined temperature (e.g., 950-1100°F), state of solidification / hardness, temper, dimensions, surface texture, surface integrity, and subsurface structure. Optionally, for example, at the exit 15 of the micromill, the aluminum sheet 12 can pass 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 is in a second state S2 having a predetermined temperature, state of solidification, hardness, temper, dimensions, surface texture, surface integrity, and subsurface structure. As the aluminum sheet 12 extends from the source 14, it can be exposed to the ambient environment E to cool or heat the aluminum sheet 12. As the aluminum sheet 12 progresses through the apparatus 10, it is in different states, e.g., with respect to temperature, hardness / yield strength / plasticity, etc., and in states S1, S2 ... S5. In addition to the gradual change in state with temperature change, the aluminum sheet 12 also changes dimensions as it progresses through the apparatus 10. For example, aluminum sheet 12 in state S2 is optionally reduced in thickness by rolls 20A, 20B to state S3, and then again by rolls 22A, 22B to state S4.In one embodiment of the present disclosure, the aluminum sheet 12 can be surface treated / textured by the texturing rolls 24A, 24B when the sheet 12 is at a high temperature, e.g., 250-970°F. This particular temperature range of the sheet 12 can be achieved by residual heat energy retained by the sheet 12 after casting, for example, or the sheet 12 can be heated before being textured by the texturing rolls 24A, 24B. The texturing rolls 24A, 24B can be pre-formed by electric discharge texturing (EDT) to impart the desired texture to the sheet 12, or the desired texture can be formed by ball or shot peening, grinding, cross-grinding, etc. Textured rolls are produced, for example, by EDT, grinding, blasting, laser beam texturing, e-beam texturing, and have a random combination of peaks and valleys, e.g., peak-to-valley heights in the range of Ra 0.5 μm to 50 μm or more, as desired for the transferred surface features. These features generally do not have a preferred orientation based on the process used. Texture rolls can be oriented or exhibit preferred orientation in that they have defining features produced using processes such as grinding, belt sanding, laser or e-beam texturing. The size and orientation of these features can be designed and controlled by these processes, e.g., producing surfaces with peak-to-valley heights of Ra 0.1 μm to 25 μm as measured laterally. Grinding produces topographies with lengths of 0.5 mm to several centimeters in the longitudinal direction at angles of 1 degree to 45 degrees or more, depending on the ratio of the abrasive to the part rotation / travel speed.

[0082] When texturing with rolls 24A, 24B is performed at elevated temperatures, e.g., 250-970°F, greater topography transfer is possible at lower roll pressure levels with less roll reduction compared to room temperature texturing, due to the lower yield strength caused by the high temperature. One aspect of the present disclosure is that texturing of sheet 12 at elevated temperatures with lower roll pressure levels and reductions can be used to repair surface and subsurface defects present in the sheet prior to texturing, such as slivers caused by transfer of adhesive metal to rolls at stations prior to texture rolls 24A, 24B, e.g., rolls 20A, 20B and / or 22A, 22B. When performing high temperature texture rolling, the temperature range of 250-970°F for sheet 12 is the temperature at the outer layer, and the sheet has a temperature gradient from the outside to the inside, such that the inner portions are hotter or cooler than the outer portions. Because the temperature of the sheet changes over time and can be adjusted by heating or cooling the sheet 12, the temperature can be measured and controlled so that a selected temperature range is achieved on the outer portions of the sheet 12 just prior to texturing with the appropriate texturing rolls 24A, 24B to obtain the desired texture.

[0083] The texturing rolls 24A, 24B can be driven by frictional interaction with the sheet 12, which is pulled by rotating the coiled sheet 12E of a coil winder (not shown). This sheet drive can be used to reduce forward sliding, which adversely affects the surface of the sheet 12, i.e., sliding of the sheet 12 on the surface of the texture rolls 24A, 24B, or to reduce other asynchronous movement of the sheet relative to the rolls 24A, 24B. Because the texturing is performed at high temperatures, the texturing rolls 24A, 24B can easily impart texture to the sheet 12 with lower roll pressures than is the case for conventional texturing performed at lower temperatures.

[0084] In one embodiment, the texturing rolls 24A, 24B can have a surface roughness Ra of about 1-10 μm. When the temperature of the aluminum sheet 12 in state S4 is between 250° F. and 970° F., pressing the texturing rolls 24A, 24B against the sheet 12 achieves a thickness reduction of about 1-30% or more, as needed, to transfer the surface texture of the texturing rolls 24A, 24B to about 60-100% of the surface of the surfaces 12C, 12D of the sheet 12 in state S5. Because the aluminum sheet 12 in state S4 is more malleable and therefore more easily able to accept the impressions of the texturing rolls 24A, 24B than an aluminum sheet that has been cooled and tempered, the texturing can be transferred more faithfully to the surface texture of the texturing rolls 24A, 24B with less pressure and with less wear and less debris on the rolls 24A, 24B. Synchronous texturing (rotational speed of the texture rolls 24A, 24B relative to the sheet throughput rate) improves texture transfer resulting in a more consistent sheet 12 surface with fewer imperfections. The reduced roll pressure associated with hot texture rolling can reduce wear on the texture rolls 24A, 24B, meaning fewer roll changes are required to process a given amount of sheet 12.

[0085] In one embodiment of the present disclosure, high temperature surface treatment of the aluminum sheet 12 can be achieved by texturing the aluminum sheet 12 with texturing rolls 24A, 24B that have been surface treated by electrical discharge texturing (EDT). Alternatively, the rolls 24A, 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 the sheet 12 is at an elevated temperature, e.g., 250-970°F. In the aforementioned temperature range, the aluminum sheet 12 is softer and aluminum sheets having low yield strengths, e.g., <10 kSi in the untempered state, are more easily formed by the action of the texturing / surface treatment rolls. Also, if the aluminum sheet 12 is surface treated prior to cold working, such as in a cold rolling mill, the surface treatment can be easily performed since the aluminum sheet 12 has not been mechanically tempered and hardened by the cold working. The aforementioned advantages can be realized by incorporating the texturing rolls 24A, 24B into a rolling mill line, such as a hot coiling mill that produces the aluminum sheet 12 from the melt, to take advantage of the heat inherently present in the aluminum sheet 12 during production by the mill and apply the surface treatment to the aluminum sheet 12 while it is still hot and before coiling. In this way, the aluminum sheet can be produced efficiently and subsequent surface and rolling treatments before and after coiling can be minimized or eliminated. As described below, in another embodiment, the cooled sheet 12 can be heated prior to surface treatment by the texturing rolls.

[0086] Each of the rolls 18A, 18B, 20A, 20B, 22A, 22B, 24A, 24B and the environment E can be temperature controlled by insulation provided, for example, by an enclosing structure such as a tunnel, and / or by heating, for example, by natural gas combustion or electrical resistance or induction heating. The temperature of the aluminum sheet 12 during texturing / surface treatment can be controlled by storing the thermal energy present in the aluminum sheet 12 from casting, and / or by applying thermal energy to the sheet 12 by exposure to a heating medium, for example, air, radiation, flame, etc. in the environment, or by contact with heated surfaces, for example, of the rolls 20A, 20B, 22A, 22B, the casting rolls 18A, 18B, and / or the texturing rolls 24A, 24B.

[0087] After surface treatment of the aluminum sheet 12 by the texturing rolls 24A, 24B to achieve state S5, the aluminum sheet 12 is exposed to radiation and / or a medium such as air or water at a temperature T to heat treat, cool, harden and / or temper. For example, the sheet 12 may be exposed to the environment E, or may be actively cooled or heated, for example, by passing through a bath or spray station, a heated tunnel, water quenched at a selected temperature, or exposed to cooled or heated air via a blower or the like. In one embodiment 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 performing the desired treatment, the aluminum sheet 12 may be wound into a coil 12E and stored and transported in a conventional manner.

[0088] The present disclosure provides for texturing at elevated temperatures, which can provide a "rougher" surface (e.g., surface topography Ra of 50 μm) compared to conventional temper / skin pass treatments at room temperature (roughness units are commonly used interchangeably in the art as micrometers (μm) and microinches (μin) with 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, which corresponds to an EDT roll with an average surface roughness Ra of 15.20 μm or 30.48 μm). High temperatures reduce yield strength, allowing for higher topography transfer with lower roll pressures and lower reductions. Typically, a "rough" surface topography, large reductions, and high temperatures promote the transfer of sticky metal, thus damaging the subsurface of the sheet. The disclosed method allows for rolling with low loads and reductions with little or no forward sliding, significantly reducing sticky metal transfer and subsurface damage. According to the disclosed method, a texture is formed in the sheet 12, forming numerous depressions in the sheet surface. These depressions imparted to the sheet 12 by hot texture rolling are beneficial in that they can contain lubricants, making rolling easier and potentially eliminating cold rolling passes. Another aspect of the present disclosure is that the sheet can be rolled with an isotropic matte finish with less scratches than ever before. When rolling a rough texture into the sheet 12, the roughness Ra increases wrap-to-wrap friction and reduces the risk of coil collapse. The texturing according to the present disclosure is done to a depth that disturbs the surface of the sheet, resulting in a better finish for the final product of the sheet 12. More specifically, by analyzing the sheet 12 from a given source, the scale and distribution of typical surface and subsurface defects can be ascertained. A texture having an appropriate magnitude of surface roughness Ra is selected and applied to the texturing rolls 24A, 24B.As a result, the depth and resolution (spacing) of the impressions made by the texturing rolls 24A, 24B, for example, when in the softened state during hot texturing, removes surface and subsurface defects present in the sheet due to material redistribution. In another aspect of the present disclosure, the EDT roll texture removes the uneven surface caused by the rolling operation to produce an isotropic surface signature. This isotropic surface signature can be measured with optical or topographical measurement systems such as Optimap® (Rhopoint Instruments), Scatterscope® (Scatterworks) or 3D interferometer or confocal microscopes. In another aspect, the surface signature can be tracked through the texture rolling process and the standard rolling process and can be highlighted by surface coatings or surface treatments.

[0089] One aspect of the present disclosure is that the conformability and changes engineered within sheet 12 as it passes through each successive stage in apparatus 10 depend on the previous condition, particularly the surface texture and integrity, and subsurface structure. The changes in condition at each successive stage of rolling, texturing, or other processing are gradual and provide control over the evolution of the surface, such that the processing at each stage of sheet 12 has the appropriate scale and pattern, as compared to conventional processing conditions, as described below.

[0090] For optimal replication of the original roll surface texture to the sheet surface, it is important to prevent metal deposition on the roll surface texture. The methods of the present disclosure can enhance / enable this prevention by once-through lubrication, evaporative roll cooling, and by the use of roll surface coatings and high pressure water blasting or similar roll cleaning. These methods address the need to keep the roll clean and at a desired temperature, and to control friction (by sheet lubrication), while maintaining surface quality.

[0091] 2 is a graph showing roll roughness versus sheet roughness transfer at temperatures of 200, 400, and 600° F. and reductions of 3% and 9%. The disclosed method and apparatus allows for a high percentage of topography transfer at low reductions and mill loads. In comparison, cold rolled EDT transfers significantly less, e.g., 60%.

[0092] 3A and 3B show an alternative embodiment of the present disclosure in which texturing rolls 124A, 124B are positioned in front of warm mill rolls 120A, 120B for pre-texturing the slab prior to rolling, for example, in a hot tandem mill. More specifically, the apparatus 110 can include a source 114 of aluminum metal forming a sheet 112 in a first state S7 of temperature, solidification / hardness, temper and dimensions. As discussed above with respect to source 14, there are many sources such as mini mills, pre-formed coils, etc. Thus, the source 114 is generally shown by a dotted rectangle. The aluminum sheet 112 in state S7 has a temperature between 250°F and 970°F due to retained heat or heat applied from a heater such as a natural gas or electric induction heater. The texturing rolls 124A, 124B may be surface treated, for example, by electrodischarge 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 Ra of 1 μm to 50 μmRa. The texture may be a regular pattern. It can be in the form of a regular pattern. , e.g., column (rows) ,grid (a grid) , a series of dots (a series of dots) etc. and the sheet surface Disturbing and Redistributing the metal more evenly within the sheet 112 Potentially, Residual stress More Few Faster, faster Flat sheet It can be used to manufacture Lines, scratches or slabs caused by cable rolls loss Visible surface scratches etc. of Defects and 、 void (voids) Subsurface defects Disturbing the pitfalls / Unobtrusive Can be used to 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, 122B, which cannot eliminate defects at the scale / resolution that the texture rolls 124A, 124B can remove.

[0093] For example, the surface and subsurface defects of the sheet 112 in state S7 are at a first scale, and the surface texture of the hot rolling rolls is at a second scale. The second scale is twice as large or twice as small when pressed into the sheet with, for example, a 30% reduction. When the sheet 112 in state S7 is textured by the texture rolls 124A, 124B with the surface texture at the first scale and pressed into the sheet 112 with a reduction of 5-10%, the defects of the first scale present in state S7 are removed. It should be noted that the defects cannot be substantially removed by the hot rolling rolls, since the texture is imparted at a different scale in the hot rolling rolls. In terms of a continuous process of surface evolution by rolling in successive rolling stands, high temperature texturing allows the development of textures specifically designed to pretreat the surface of the sheet 112, allowing differentiation of the hot rolling process by passing the optimal surface through the next set of rolls with the desired properties and functions for the sheet 112. One aspect of the present disclosure is that the rolling equipment and process that exists between the metal at a starting condition or state (for a given temperature, thickness, width, surface texture, subsurface properties, temper, etc.) and the metal at a finishing condition or state (for a target temperature, thickness, width, surface texture, subsurface properties, temper, etc.) can be optimized by using rolled texture at various stages of the rolling operation. More specifically, the rolling process can be improved not only with respect to the final properties (quality) of the product, but also minimize the time, energy, equipment and space required to achieve the target product, for example, by reducing the number of rolling stages, roll pressure at a given stage, etc., and by selectively using hot texture rolling at various points in the rolling line, which can be used to aid in the development of the surface. The present 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 to achieve efficient and effective development of the sheet and its properties with respect to surface and subsurface hardness / temper.

[0094] After passing through the texturing rolls 124A, 124B, the sheet is then hot rolled with low reduction in one or more stages 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 without visible defects. Texturing can reduce the rolling force required by the rolls 120A, 120B by trapping lubricant in the asperities of the sheet surface when the textured sheet is in state S8. This means that the desired target thickness and surface texture can be achieved with improved reduction capacity, reduced rolling load, and / or fewer passes through the roll stands. The texturing step can also increase the "bite" or frictional grip of the rolls 120A, 120B on the sheet 112. The increased bite is distributed evenly across the surface of the sheet 112, so that the sheet 112 passes straighter between the rolls 120A, 120B, 122A, 122B. The stabilization of the frictional interaction between the sheet 112 and the rolls 120A, 120B, 122A, 122B allows the sheet to pass through the rolls 120A, 120B, 122A, 122B at a steady pace. When the material flow between the stands is uneven (e.g., when the speed of the sheet 112 passing through the rolls 120A, 120B is faster than the speed of the sheet 112 passing through the rolls 122A, 122B), cobbles (folds) form in the sheet, but this can be avoided by balancing the sheet flow between the stands. Texturing the sheet 112 with the texture rolls 124A, 124B allows for larger reductions in the rolls 120A, 120B, 122A, 122B. The effect of texturing with the rolls 124A, 124B is to reduce the number of cold rolling passes required to repair damage to the sheet 112 that occurs even when hot rolling with low reductions, to allow casting at thinner gauges, and to produce products with better surfaces, e.g., isotropic surfaces suitable for anodizing.

[0095] 3B, in condition S7, the incoming sheet 112 has surface defects 112D and subsurface defects 112SSD, but the sheet 112 can undergo substantial improvement and progress prior to the next stage, e.g., warm rolling 120A, 120B and 122A, 122B. As previously discussed, aluminum sheet 112 in condition S7 is malleable and can more easily accept the impression of the surface rolls 124A, 124B than sheet aluminum that has been allowed to cool and temper. As a result, the surface treatment can be more faithful to the surface texture of the rolls 124A, 124B with less pressure, and with less wear on the rolls 124A, 124B, among other previously discussed attributes of hot texturing.

[0096] 4 illustrates an alternative embodiment of the present disclosure, for example in an in-line texturing situation in a cold rolling mill, where texturing rolls 224A, 224B are positioned after cold rolling rolls 220A, 220B and 222A, 222B. Cold rolls 220A, 220B reduce the thickness of the sheet in state S11 to produce sheet 212 in state S12. Rolls 222A, 222B further reduce the thickness of sheet 212 to form state S13. In one embodiment, sheet 212 can be reduced in thickness by about 50% by rolls 220A, 220B and then reduced another 50% by rolls 222A, 222B. Sheet 212 is then heated by heaters 230, which are positioned on opposing portions 230A, 230B on either side of sheet 212. The heaters can be of various types including electrical resistance, induction heating or natural gas. Cold working the sheet 212 by the cold rolling rolls 220A, 220B and 222A, 222B increases the residual stresses in the sheet 212 in stages S12 and S13, increasing the yield strength of the sheet and making rolling in subsequent stands more difficult. The heater 230 heats the sheet to a temperature of 250-970°F, which reduces the yield strength of the sheet 212 in state S14, facilitating rolling by the texture rolls 224A, 224B and allowing greater topography transfer with lower roll forces. As discussed above, the heat penetration depth into the sheet 212 can be selected / adjusted to provide sufficient heat penetration depth and softening to allow texturing at a given reduction and pressure.

[0097] Texture rolling at elevated temperatures results in less residual stress in sheet 212 at state S15 than at S14. This reduction in residual stress is reflected in a flatter sheet, i.e., the sheet exhibits relatively better flatness when in a free state with no tension applied by apparatus 210. The flatness of sheet 212 is also beneficially affected by the texturing provided by rolls 224A, 224B, which can be selected to have a texture suitable for the finished roll product having the texture provided by texture rolls 224A, 224B.

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

[0099] The disclosed method of high temperature texturing allows for a "rougher" surface topology, e.g., Ra 5 μm, compared to conventional room temperature temper skim pass processing. High temperatures reduce yield strength and allow for greater topography transfer with lower roll pressure and lower roll reduction. In general, "rougher" surface topography, larger roll reductions and higher temperatures promote sticky metal transfer and therefore sheet subsurface damage. The disclosed method significantly reduces sticky metal transfer and subsurface damage by texturing with low loads, low roll reductions and little or no forward sliding. The disclosed method is made possible by once-through lubrication, evaporative roll cooling, and by the use of roll surface coatings and high pressure water blasting or similar roll cleaning. The aforementioned measures address the need to keep the roll clean and at the desired temperature and to control friction (by sheet lubrication) while maintaining surface quality.

[0100] According to the techniques of the present disclosure, the texture applied to the sheet 212 can translate into the ability to eliminate roll passes in hot or cold rolling, as the case may be. In another aspect of the present disclosure, a smaller mill tonnage is required, reducing energy consumption, and a smaller roll reduction, generating less debris. Less debris results in a cleaner sheet 212. The reduced rolling force and reduced debris generation corresponds to reduced wear on the texturing rolls 224A, 224B, resulting in longer roll life and fewer roll changes. The reduced wear on the roll topography reduces the number of roll changes, resulting in less variation in the sheet surface roughness Ra from one coil 212E to the next, for example, between a coil of sheet 212 produced with the last texturing rolls 224A, 224B and a coil produced with a new textured roll 224A, 224B. Hot texture rolling can reduce the cost of the textured sheet 212E due to cost savings such as reduced rolling passes, allowing the texturing process to be utilized for more products. Reduction in rolling passes can reduce the usage of rolls in the rolling mill, thus expanding the output capacity of the mill over a given period of time.

[0101] FIG. 5 shows an apparatus 310 for producing 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 successively in the flow direction of the sheet 312. The sheet 312 is fed to the texture rolls from any source, for example, a preceding roll in a rolling mill or casting mill, and cooled or heated to a high temperature, for example 250-970° F., in state S16, by the texture rolls 324A, 324B and 340A, 340B, which are subjected to high temperature texturing. This high temperature texturing has all the characteristics and properties described above. The texture rolls 324A, 324B may be large diameter rolls, and the sheet 312 has little or no thickness reduction in the pass. The texture rolls 340A, 340B may be smaller in diameter, and the thickness reduction of the sheet 312 may be greater. In another embodiment, the working roll stands of the hot rolling mill can be textured to produce texture rolls 340A, 340B. As described above, hot texturing can be used to modify the surface of the sheet 312 in preparation for subsequent processing by subsequent roll stands. In the apparatus 310, the texture rolling by roll sets 324A, 324B and 340A, 340B can provide a stepwise surface development by sequentially or sequentially texture the sheet 312. In one embodiment, the first set of texture rolls 324A, 324B has a surface roughness of 1-10 Ra and the second set 340A, 340B has a surface roughness of 1-5 Ra. A first set of texture rolls 324A, 324B acts more on the surface and subsurface to impart a texture with a higher roughness Ra, and then a second set of texture rolls 340A, 340B with a less rough texture only partially removes the pattern formed by the first set of texture rolls 324A, 324B. Subsequent hot texturing can also be used to prepare the sheet for subsequent rolling by hot rolls (e.g., 320A, 320B) or cold rolls.

[0102] Sequential texturing as described above can be used to reduce grain size and break up the surface of the sheet 312, reducing the "orange peel" surface irregularities of the sheet 312 in state S19, and producing a cleaner, more isotropic surface, especially when anodized. The isotropic topography of the slab produced by hot texturing reduces rolling forces in subsequent roll stands (e.g., 320A, 320B), promotes tracking, reduces folds, requires fewer high reduction roll passes, casts at thinner gauges, reduces the number of cold roll passes to repair damage in the sheet 312, and improves surface quality. The sequential texturing method illustrated in FIG. 5 improves the ability to produce a variety of sheet 312 textures, in that multiple successive texture rolling passes are represented in the final rolled sheet 312 in stage S19. Such high temperature continuous texturing can be facilitated by once-through lubrication, evaporative roll cooling, and by the use of roll surface coatings and high pressure water blasting or similar roll cleaning.

[0103] FIG. 6 shows an apparatus 410 for producing sheet material 412, such as aluminum sheet. The apparatus 410 includes a heater 430 for increasing the temperature of the conveyed sheet 412, which may come from a variety of sources, such as cold rolling mill stands, casting mills, etc. The heater 430 increases the temperature of the sheet 412 from state S20 to state S21, 250-970°F, for hot texturing by texture rolls 424A, 424B. This hot texturing has all the characteristics and properties described above, and can affect the surface of the sheet 412 by texturing with a rough topographical surface to more evenly redistribute the metal and improve the surface quality before further processing. Hot texturing can be done with low loads and reductions, resulting in little or no forward sliding and reduced tendency to cause damage to the subsurface. As the sheet 412 softens with heat and its yield strength decreases, the pressure on the texture rolls 424A, 424B is reduced, and a high degree of topography transfer can be achieved. After passing through the texturing rolls 424A, 424B, the sheet can then be rolled by the cold roll set 420A, 420B to state S23, and then rolled by the cold rolls 422A, 422B. In the apparatus 410, a hot pre-textured sheet 412 is produced before cold rolling. As mentioned above, hot texturing can be used to modify the surface of the sheet 412 in preparation for subsequent processing by the subsequent roll stands. In the apparatus 410, the texture rolling by the roll sets 424A, 424B and 420A, 420B can be used to sequentially or sub-texture the sheet 412, thereby developing the surface in stages. In one embodiment, the texture rolls 424A, 424B have a surface roughness Ra of 1 μm to 50 μm, the first set of cold rolls 420A, 420B have a surface roughness Ra of 1 μm to 5 μm, and the texture rolls 424A, 424B impart texture with a larger roughness Ra to have a greater effect on the surface and subsurface.The first set of cold rolls 420A, 420B, which have a less rough texture, then only partially removes the pattern formed by the texture rolls 424A, 424B, substantially reducing the thickness. The second set of cold rolls 422A, 422B further reduces the thickness of the sheet and / or imparts additional texture to the sheet 412. The effect of the texturing rolls 424A, 424B is to enhance and facilitate cold rolling by the rolls 420A, 420B and 422A, 422B, for example, by forming pockets in the sheet 412 in state S22 that can hold lubricant. The enhanced cold rolling allows for the elimination of cold rolling passes to produce a sheet in state S24 with fewer flaws and an isotropic matte finish. The hot texturing enhances the transfer of the texture, and the sheet 412 in state S24 has a more consistent surface. The above hot texturing and subsequent cold rolling can be enhanced by once-through lubrication, evaporative roll cooling, and by the use of roll surface coatings and high pressure water blasting or similar roll cleaning.

[0104] FIG. 7 shows an apparatus 510 for producing sheet material 512, such as aluminum sheet. The apparatus 510 includes a heater 530 for increasing the temperature of the conveyed sheet 512, which may come from a variety of sources, such as cold rolling mill stands, casting mills, etc. The heater 530 increases the temperature of the sheet 512, in state S25, to 250-970°F, in state S26, for hot texturing by texture rolls 524A, 524B. This hot texturing has all the characteristics and properties described above, and can affect the surface of the sheet 512 by texturing with a rough surface topography to redistribute the metal more evenly and improve the surface quality before further processing. Hot texturing can be performed with low loads and reductions, resulting in little or no forward sliding and reduced tendency to cause subsurface damage. Heating softens the sheet 512, reducing its yield strength and the pressure against the texture rolls 524A, 524B, but still achieves a high degree of topography transfer of the sheet 512 in state S27. After passing through the texturing rolls 524A, 524B, the sheet is then rolled by a second set of texturing rolls 540A, 540B to state S28, and then by cold rolls 520A, 520B to produce the sheet 512 in state S29. In the apparatus 510, two texturing passes before cold rolling produce the hot pre-textured sheet 512. The texture rolls 524A, 524B are large diameter rolls that apply a low reduction to the sheet 512. The texture rolls 540A, 540B are small diameter rolls that apply a high reduction to the sheet 512. In another embodiment, the working roll stands of the hot mill can be textured to produce texture rolls 540A, 540B. As described above, hot texturing can be used to modify the surface of the sheet 512 in preparation for subsequent processing by subsequent roll stands. In the apparatus 510, the texture rolling by roll sets 524A, 524B and 540A, 540B can provide a step-by-step surface development by sequentially or sequentially applying texture to the sheet 512.In one embodiment, the first set of texture rolls 524A, 524B has a surface roughness of Ra 1 μm to 50 μm, and the second set of rolls 540A, 540B has a surface roughness of 1 μm to 5 μm Ra, where the first set of rolls imparts a texture with a larger roughness Ra and affects more the surface and subsurface. The second set of texture rolls 540A, 540B, which has a less rough texture, then only partially removes the pattern formed by the texture rolls 524A, 524B. Sequential hot texturing can be used to prepare the sheet for subsequent enhanced rolling by cold rolls (e.g., 520A, 520B).

[0105] As mentioned above, hot texturing can be used to modify the surface of the sheet 312 in preparation for subsequent processing by the subsequent roll stands. In the apparatus 510, the texture rolling by the roll sets 524A, 524B and 540A, 540B can be used to sequentially or sub-sequently texture the sheet 512 to achieve a step-by-step surface development. In one embodiment, the first set of texture rolls 524A, 524B has a surface roughness of Ra 1 μm to 50 μm, and the second set 540A, 540B has a surface roughness of Ra 1 μm to 5 μm. The texture rolls 524A, 524B act more on the surface and subsurface to impart a texture with a larger roughness Ra, and then the second set of texture rolls 540A, 540B with a smaller texture only partially removes the pattern formed by the texture rolls 524A, 524B to substantially reduce the thickness. The cold rolls 520A, 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, 540B is to enhance and facilitate cold rolling by the rolls 520A, 520B, for example, by forming pockets in the sheet 512 at state S28 that can retain lubricant. The enhanced cold rolling allows for the elimination of cold rolling passes to produce a sheet at state S29 with fewer flaws and an isotropic matte finish. The hot texturing enhances the transfer of texture, providing a more consistent surface to the sheet 512 at states S27 and S28. The hot texturing and subsequent cold rolling can be enhanced by once-through lubrication, evaporative roll cooling, and by the use of roll surface coatings and high pressure water blasting or similar roll cleaning. After state S29 is achieved, the aluminum sheet 512 may be heat treated, quenched and / or tempered. The aluminum sheet 512 may then be wound into a coil 512E and stored and transported in a conventional manner.

[0106] According to aspects of the present disclosure, adding texture to the sheet at the end of the continuous casting process significantly reduces costs when added in-line. No additional winding and unwinding is required, and the as-cast and rolled F-temper characteristics can be improved with improved topography transfer. The latter allows for smaller reductions and longer roll life with improved topography transfer to achieve topographies similar to traditional textures or newly differentiated surfaces. Lower reductions also reduce debris generation, minimizing the need for some texture cleaning such as EDT. Surface quality issues caused by processes such as casters, heat treatments, etc. can be performed after texturing per standard heat treatment. Adding texture to the continuously cast product in an additional step allows for further control of topography transfer depending on the desired product characteristics (e.g. F, O or T temper). Post-texture heat treatments can also be added as needed. Another potential advantage of adding in-line or at-line texture to a continuously cast product surface is the ability to create a uniform surface with minimal surface features after casting or rolling.

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

[0108] Potential benefits of embodiments of the present disclosure include longer texture roll life, unique texture with improved topography transfer, cost savings from minimizing coiling and uncoiling operations if in-line, improved recovery due to consistent surface, reduced surface artifacts from casting and rolling, and reduced mill load. When EDT or similar textures are used in hot roll mills (HRM), two additional benefits are gained; with the right combination of lubricant and texture, larger reductions can be achieved without jamming, allowing for reduced passes. This is important in that it can eliminate the need for kerosene bite assistance.

[0109] The advantage of the in-line or at-line texture addition embodiment to the surface of a continuous cast product is that it creates a uniform surface and minimizes surface features due to casting or rolling. Texturing (with low-cost, low-load equipment) immediately after the continuous caster, Micromill®, roll coater, or slab caster can redistribute, remove, or mask features that would prohibit use in critical surface applications. For example, the topography created by the Micromill leaves undesirable features and / or patterns on the surface of the cast metal. Using the teachings of the present disclosure to texture surfaces in the hot rolling process can reduce or eliminate appearance issues in the subsequent anodized surface. This method can be used to produce sheet at a low cost for applications where surface performance is more important.

[0110] In the course of utilizing the disclosed method and apparatus, a lubricant, such as a hot rolling dispersant, was applied to the sheet prior to entering the nip between the hot rolling work rolls of the first stand. Contrary to expectations, very low pressure roll coating was performed, despite the "rough" nature of the EDT topography. It should also be noted that rolling in the two stand mill was significantly improved. First, the "stability" of the roll bite was significantly improved, resulting in much better steering of the sheet and facilitating the rolling process. This improved stability resulted in a larger reduction than expected, at a lower load. It was expected that higher friction in the EDT work rolls of stand 1 would result in a larger load force, limiting the reduction capacity, but this phenomenon was not observed. Although the reduction in stand 1 is 57% under standard rolling conditions, the load force from the EDT rolls was not greater than that from the standard grinding rolls. Using the EDT rolls in stand 1, it was possible to increase the reduction capacity by up to 70% without a significant increase in load force, something that was not possible with the ground topography. Also, the load force was significantly reduced when the sheet was sent from stand 1 with the EDT texture to stand 2. The disclosed apparatus and method had lower loads, higher reductions, and less debris and surface degradation than expected.

[0111] EDT is used in the finish mill to produce a matte finish non-oriented sheet for improved appearance and formability, but other texturing methods can be used to manufacture the textured rolls (e.g., 24A, 24B) for use in the apparatus of the present disclosure. For example, EDT suppliers are not currently equipped to handle all sizes of hot rolling work rolls for their dimensions and weights. Other texturing processes that can produce similar results to EDT include, for example, sandblasted rolls, cross ground rolls, rolls from TopoCrom and other high nodule chrome processes, ball peened rolls, and shot peened rolls.

[0112] As mentioned above, the source of aluminum metal (14, 114, etc.) can vary and can be cast from a melt into an ingot that is then rolled to a thickness of, for example, 0.125 to 0.250 inches, or cast by a continuous casting process. An advantage of the present disclosure is that it eliminates features that adversely affect the surface quality of the processed sheet product, reducing the amount of labor and energy required to accomplish the goal.

[0113] 8 shows a number of virtual surface scratches 612D1, 612D2, 612D3, 612D4, 612D5A, 612D6, 612D7, 612D8, 612D9, 612D10, 512D11 planned in a virtual sheet 612. The virtual scratches 612D5A are multiple and parallel to each other, forming a sub-pattern 612D5, while others of the virtual scratches, e.g. 612D1, 612D2, 612D3, are aligned close to each other and can be associated by an observer with a pattern, e.g. an incomplete triangle 612DT1. If the scratches or other defects 612D5 can convey a perceptible pattern, the observer can see more than scratches or defects that do not have a perceptible pattern and are perceived as random. Similarly, the scratch 612D4 is perceived to be present in the background 612B or in an area of ​​the sheet 612 that does not have similar optical properties, and therefore the scratch 612D4 is perceived as a localized area having different optical properties than the background 612B. Having described a scratch, e.g., 612D1, which is a localized area below the surface of the background 612B, it should be understood that the disclosed method and apparatus is useful for correcting other types of surface defects, e.g., defects resulting from defects that protrude above the background surface 612B, or defects that wobble up and down the background surface 612B, or defects that have optical properties, such as reflective properties, that are different from the background surface 612B. It is understood that any surface will be observed to be "rough" or highly variable when inspected at a sufficiently high magnification, and further, that if the magnification is large enough that the defect itself occupies the field of view, the perception of the defect will be impaired. One way is to specify the size or scale of the defects of interest, which can be defined as being perceptible at magnifications between 1x and 100x. Alternatively, it may be defined as defects of interest that are observable to normal human vision (the naked eye) at a distance of 0.1 to 5 feet. In a further alternative, the range of roughness Ra that is considered a background surface with non-perceptible defects is 0.1 μmRa to 2 μmRa.Any feature aligned adjacent to the background surface that exceeds this roughness Ra is considered a surface defect. In one aspect of the present disclosure, the above-described apparatus and method can partially or completely mask or obscure perceptible defects in the surface of the sheet, as well as defects in the virtual sheet 612, as will be illustrated in the examples provided below.

[0114] FIG. 9A is an optical image of a sheet 812 of type 3XXX aluminum alloy showing the edges of scratches 812D1 and 812D2 in a background surface 812B, the scratches being approximately 10 μm deep, 400 μm wide, and 50 mm long. The scratches were created using a TABER® linear abrader, which has user-selectable adjustments for speed, stroke length, and test load. Different test loads were used to create scratches in the test specimens. Different test loads were used to create flaws in the test samples. FIG. 9B shows a topographic image of scratch 812D1 obtained by white light phase-shifting interferometry.

[0115] FIG. 9C is an optical image of a sheet 912 of type 3XXX aluminum alloy showing the edges of scratches 912D1 and 912D2 in a background surface 912B, the scratches being approximately 200 μm deep, approximately 1000 μm wide, and 50 mm long. The scratches were made using a TABER linear abrader, which has user adjustable settings for speed, stroke length, and test load. These test specimens used a higher test load than that of FIG. 9A to create deeper scratches than the specimen of FIG. 9A. FIG. 9D shows a topographic image of scratch 912D1 obtained by white light phase shifting interferometry.

[0116] 10 shows an optical image of a 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 sticks to the rolls and is rolled into the surface of the slab / sheet.

[0117] 11 shows a series of surface topography scans 112S1-112S5 of aluminum sheet 12 (FIG. 1) rolled at five different reductions using EDT rolls 18A, 18B with a surface roughness Ra of 5 μm for 5XXX sheet aluminum produced in accordance with one embodiment of the present disclosure. The sheet aluminum was reduced in thickness by 2.5%, 4.2%, 12.7%, 23.7%, and 28% using an apparatus such as apparatus 10 shown in FIG. The source of aluminum sheet 15 (FIG. 1) is a Micromill or a mill described in any of the following U.S. patents: [5,515,908; 5,655,593; 5,894,879; 5,772,799; 5,772,802; 6,045,632; 5,769,972; 6,102,102; 6,391,127; 6,623,797; 6,672,368; 7,089,993; 7,503,377; 7,125,612; 6,581,675; 7,182,825; 8,403,027; 7,846,554; 8,697,248; 8,381,796; or 8,956,472]. These patents are incorporated herein by reference. The texturing rolls 24A, 24B used were textured by EDT. Reduction of the sheet was performed when the sheet was at 930°F and the topography scan was performed at a stage after quenching on the roll line. As can be seen, the surface topography scan shows that with increasing reduction, the peaks and valleys become more uniform and replicate the EDT topography. As can be seen, the sheet output of the Micromill varies with the operating parameters of the Micromill, including surface quality, output temperature, thickness and alloy composition. The operating parameters of the hot texture rolling disclosed herein can be adjusted to match the particular output characteristics of the sheet obtained by the Micromill in terms of temperature, reduction and roughness Ra to achieve the advantages described herein. In one embodiment, the temperature of the sheet output from the Micromill ranges from 1100 to 1000°F.After exiting the Micromill and exposure to ambient temperatures and handling equipment (such as a caster and / or conveyor belts), the sheet is cooled and solidified to a temperature that allows for rolling and / or hot texture rolling as taught in this disclosure. This can be done at temperatures above 970°F if the casting conditions (e.g., throughput rate, solidification state, and alloy composition) or other steps can be taken to increase the cooling between the output of the mill and the first rolling stand, increasing the distance between them or decreasing the throughput rate.

[0118] FIG. 12 shows a series of surface topography scan maps 1212M1-1212M5 and line profiles 1212S1-1212S5 of aluminum sheet 12 rolled at five different reductions using crosshatch rolls 24A, 24B with a surface roughness Ra of 5 μm for 5XXX sheet aluminum produced 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 the apparatus 10 shown in FIG. 1. The texturing rolls 24A, 24B used were textured by crosshatch grinding. The reduction on the sheet was performed when the sheet was at 930° F. and the topography scans were taken at a stage after quenching on the roll line. As can be seen, the surface topography scans show a large variation in peaks and valleys, some of the valleys are deep, and undesirable surface features remaining from the ground crosshatch rolls.

[0119] FIG. 13A shows a plate rolled at 850°F using an EDT with a Ra of 600 μin (15 μm). 59C and 9D show a series of optical images 1312AO, topographic images 1312AT, and line profiles 1312AP of a sheet sample 1312A having surface defects 1312AD (scratches) on the background surface 1312AB after a thickness reduction of 10%. The sheet sample before thickness reduction had a background surface roughness Ra of 1 μm and a scratch depth of about 1000 μm, as shown in FIGS. 9C and 9D. As can be seen from FIG. 13A, a 5% reduction with the EDT texture roll reduces the perceptibility of the scratches 1312AD compared to those shown in FIGS. 9C and 9D. This reduction in visual perceptibility of the scratches 1312AD is observed in the change in surface dimensions, as shown by the topographic images 1312AT and line profiles 1312AP, where the average peak-to-valley difference is 45% less than for the sheet before rolling. When the reduction rate is increased to 10% in FIG. 13B, the scratch depth is reduced by 70%, and when the reduction rate is increased to 20% in FIG. 13C, the scratch depth is reduced by 80%.

[0120] FIG. 14A shows a series of optical images 1512AO, topographic images 1512AT, and line profiles 1512AP of a sheet sample 1512A having a surface defect 1512AD (scratch) in the background surface 1512AB after rolling to a 5% thickness reduction at a temperature of 850° F. with an EDT of 1200 μin (30 μm) Ra. The sheet sample prior to thickness reduction rolling had a background surface roughness Ra of 1 μm and a scratch depth of about 1000 μm, as shown in FIG. 9C and FIG. 9D. As can be seen from FIG. 14A, the 5% reduction with the EDT texture roll reduced the perceptibility of the scratch 1512AD compared to that shown in FIG. 9C and FIG. 9D. This reduction in visual perceptibility of the scratches 1512AD is observed in the change in surface dimensions, as shown by the topographic image 1512AT and line profile 1512AP, where the average peak-to-valley difference is 65% less than for the sheet before rolling. As the reduction ratio increases to 10% in FIG. 14B, the scratch depth decreases by 80%, and as the reduction ratio increases to 20% in FIG. 14C, the scratch depth decreases by 100%.

[0121] FIG. 15 shows a graph of the reduction in scratch depth for shallow scratches (depth about 10 μm, width about 200 μm), medium scratches (depth about 100 μm, width about 500 μm) and deep scratches (depth about 200 μm, width about 1000 μm) after rolling with EDT textured rolls having either a 600 EDT (Ra 600 μin) or 1200 EDT (Ra 1200 μin) texture. The rolling apparatus used was similar to that shown in FIG. 7 and the measurements to generate the graph in FIG. 15 were taken in state S27. State S27 is an intermediate state, which is after rolling with textured rolls 524A, 524B (having an EDT texture of either Ra 600 μin or Ra 1200 μin) and before rolling with textured rolls 540A, 540B. It should be noted that the shallow and medium depth scratches disappeared completely or almost completely under 10% pressure with the 1200 EDT roll, and all other scratches disappeared under 20% pressure with the 600 EDT roll except for the deep scratches under 20% pressure with the 600 EDT roll, and the deep scratches disappeared by 80% under 20% pressure with the 600 EDT roll.

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

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

[0124] FIG. 17C shows an optical image 2012O of an aluminum sheet 2012 processed according to the present disclosure, which was reduced by 25% in an apparatus 10 (shown in FIG. 1) with Ra 200 μin (5 μm) texturing rolls 20A, 20B. A light scattering signature 2012S was taken from the surface of the sample 2012. FIG. 17D shows an optical image 2112O of an aluminum sheet 2112 reduced by 25% in a conventional mill, and a light scattering signature 2112S taken from the surface of the sample 2112. The directionality of light intensity in the X and Y directions of the light scattering 2012S is greater than the light scattering 1812S of the sheet 1812 under 10% reduction, but is still much less than the light scattering 2112S of the mill finish 2112 under 25% reduction.

[0125] FIG. 18A shows a series of light scattering signatures for aluminum sheet samples having a mill finish rolled with Ra 50 μin (1 μm) mill finish rolls, with 2212S1 being 5% reduction, 2212S2 being 10% reduction, 2212S3 being 15% reduction, and 2212S4 being 25% reduction.

[0126] Figure 18B shows a series of light scattering signatures for aluminum sheet samples with EDT finishes rolled with Ra 200 μin (5 μm) EDT rolls, 2312S1 with 5% reduction, 2312S2 with 10% reduction, 2312S3 with 15% reduction, and 2312S4 with 25% reduction. Comparing the light scattering signatures of Figures 18A and 18B, it can be concluded that the EDT finish is less directional than the mill finish at all reductions.

[0127] FIG. 19A is a texture data signature 2412DS obtained by an Optimap® PSD instrument for a mill-finished surface, showing the directional texture quantified with characteristics of the instrument and process used.

[0128] FIG. 19B is a texture data signature 2512DS obtained by the Optimap PSD instrument for an EDT textured surface, showing less directional quantification with this instrument and characteristic of the process used. The images shown in FIG. 19A and FIG. 19B show a surface area of ​​the sample of approximately 95 mm×70 mm. The light scattering signatures 2312S1-2312S4 show that while the test area of ​​the sample is circular with a diameter of approximately 5 mm, the non-directionality continues over a large area of ​​the sheet, indicating that the entire sheet surface is non-directional. The EDT roll texture removes the non-uniform surface that comes in during the rolling operation, producing an isotropic surface signature that can be measured with optical or topographical measurement systems such as Optimap (Rhopoint Instruments), Scatterscope (Scatterworks), 3D interferometers or confocal microscopes. The surface signature is traceable through texture rolling and standard rolling processes and can be enhanced by surface coatings or treatments.

[0129] In the above examples, high temperature, low yield strength texture rolling was used with relatively low reduction (e.g., 0%-30%) to remove surface defects such as scratches having a depth of 10 μm-200 μm, but even larger reductions can be applied to remove larger surface defects. For example, EDT rolls with surface roughnesses of Ra 600 μin or 1200 μin can use reductions of up to 70% to remove scratches and other surface defects having a depth of 1 mm.

[0130] One aspect of the present disclosure is the use of the techniques described above to produce metal sheets suitable for forming automotive body panels. In one embodiment, metal sheets produced by the disclosed embodiments are used to form closure panels (e.g., metal panels that are joined together to form an automotive door or hood structure). In another embodiment, metal sheets produced by the disclosed methods can be used to form at least a portion of a body-in-white, the term body-in-white being used to describe the sheet metal assembly for the body of a vehicle before painting, i.e., before the installation of glass, trim, and moving parts (suspension, driveline, etc.).

[0131] It should be understood that the embodiments described herein are merely exemplary, and that those skilled in the art may make many variations and modifications without departing from the spirit and scope of the claimed subject matter. For example, rolling temperatures and reductions may be adjusted to accommodate different aluminum alloys. All such variations and modifications are intended to be within the scope of 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.

Images