Apparatus and Method for Imparting Selected Topographies to Aluminum Sheet Metal

Abstract

A method for surface treating work rolls to produce isotropic textured aluminum sheet features indenting the surface of the working rolls that produce the sheet with spherical media such as steel ball bearings having the requisite properties to avoid fracture and resulting in a smooth surface lacking facets. The spherical media can be introduced into a nip between two rolls and indent by compression, but ultrasonic peening or knurling. The aluminum sheet produced by the roll has properties that facilitate mechanical forming, such as when the sheet is processed by forming tools.

We claim: 
     
         1 . A method for surfacing a work roll for rolling aluminum sheet, comprising the following steps:
 indenting a surface of the work roll with spherical media, producing a surface 60% to 100% covered by the indentations, the indentations lacking facets.   
     
     
         2 . The method of  claim 1 , wherein the indentations have a depressed central area relative to a mean height of the surface and a raised, smooth peripheral lip having a greater height at an apex thereof than the mean height of the surface. 
     
     
         3 . The method of  claim 2 , wherein the indentations have a diameter in the range of 200 μm to 400 μm and a depth relative to the apex of the peripheral lip in the range of 0.5 μm to 2.0 μm. 
     
     
         4 . The method of  claim 1 , wherein the spherical media used for indenting is steel ball bearings. 
     
     
         5 . The method of  claim 4 , wherein the ball bearings have a diameter ≦0.125 inches and a hardness Rc≧60. 
     
     
         6 . The method of  claim 1 , wherein the spherical media used for indenting is ceramic balls. 
     
     
         7 . A work roll for rolling aluminum sheet metal surfaced by the method of  claim 1 . 
     
     
         8 . Aluminum sheet metal having a surface texture imparted by the work roll of  claim 7 . 
     
     
         9 . A work roll for rolling aluminum sheet metal surfaced by the method of  claim 3 . 
     
     
         10 . Aluminum sheet metal having a surface texture imparted by the work roll of  claim 9 . 
     
     
         11 . The method of  claim 1 , further comprising the steps of:
 installing the surfaced work roll in a rolling mill; and   rolling the aluminum sheet to reduce the aluminum sheet from a given initial thickness to a selected thickness and simultaneously imparting a texture from the work roll onto the surface of the aluminum.   
     
     
         12 . The method of  claim 11 , wherein the indentations have a depressed central area relative to a mean height of the surface and a raised, smooth peripheral lip having a greater height at an apex thereof than the mean height of the surface the indentations having a diameter in the range of 200 μm to 400 μm and a depth relative to the apex of the peripheral lip in the range of 0.5 μm to 2.0 μm and wherein the reduction in thickness of the aluminum sheet is in the range of 10 to 60% of the initial thickness. 
     
     
         13 . The method of  claim 12 , further comprising the step of pre-grinding the work roll prior to step of surfacing, the step of pre-grinding imparting a first surface texture on the roll, the step of surfacing imparting a second surface texture on the roll at least partially over-struck on the first surface texture and incompletely eradicating the first surface texture, such that a composite surface texture is formed. 
     
     
         14 . The method of  claim 12 , wherein the step of indenting is by shot peening, which may be conducted at an adjustable pressure to control media velocity and momentum when the media impacts the roll, the media and the velocity thereof corresponding to a media impression depth, width and shape on the surface of the roll and further comprising the step of adjusting the pressure at which shot peening is conducted to achieve a given surface texture. 
     
     
         15 . The method of  claim 14 , wherein the dwell time of shot peening of the roll surface is adjustable to control the number of impacts of the media on the surface of the roll and the consequential % coverage of media impressions on the surface of the roll and further comprising the step of adjusting the dwell time to achieve a given surface texture. 
     
     
         16 . The method of  claim 14 , wherein the surface texture of the roll is optically diffuse and specular. 
     
     
         17 . The method of  claim 16 , further comprising the steps of rolling a plurality of sheets of aluminum, the sheets differing in width and at least one variation in width resulting in rolling a narrower sheet followed by rolling a wider sheet. 
     
     
         18 . The method of  claim 16 , wherein the adjustment of the velocity of the media is determined at least partially based upon the hardness of the roll. 
     
     
         19 . The method of  claim 16 , wherein the adjustment of the velocity of the media is determined at least partially by the initial surface texture of the roll prior to shot-peening. 
     
     
         20 . A method for surfacing a work roll for rolling aluminum sheet, comprising the steps of:
 (A) positioning the work roll parallel another roll with a gap therebetween;   (B) turning at least one of the work roll and the another roll;   (C) feeding surfacing media into the gap, the media bridging the gap and being drawn through the gap by the turning work roll and creating impressions on the surface of the work roll.   
     
     
         21 . The method of  claim 20 , wherein the media has discrete units having a dimension larger than the gap, such that a mechanical interference exists when the units pass through the gap. 
     
     
         22 . The method of  claim 21 , wherein the units are spherical and the impressions are smooth indentations. 
     
     
         23 . The method of  claim 22 , wherein the units are ball bearings. 
     
     
         24 . The method of  claim 22 , wherein units are joined to a sheet of flexible material. 
     
     
         25 . The method of  claim 20 , wherein the surfacing media is a metal shim having a texture on at least one side. 
     
     
         26 . The method of  claim 25 , wherein the shim is produced using photolithography. 
     
     
         27 . A method for surfacing a work roll for rolling aluminum sheet, comprising the steps of:
 (A) positioning an ultrasonic ball peening apparatus proximate the work roll;   (B) peening the work roll until the surface is 60% to 100% covered by indentations lacking facets, the indentations having a depressed central area relative to a mean height of the surface and a raised, smooth peripheral lip having a greater height at an apex thereof than the mean height of the surface, the indentations having a diameter in the range of 200 μm to 400 μm and a depth relative to the apex of the peripheral lip in the range of 0.5 μm to 2.0 μm.   
     
     
         28 . A method for surfacing a work roll for rolling aluminum sheet, comprising the steps of:
 (A) pressing a rotatable knurling wheel with a peripheral surface texture against a side surface of the work roll;   (B) turning the work roll, inducing the knurling wheel to turn and impressing the peripheral surface texture into the side surface of the work roll until the side surface of the work roll is 60% to 100% covered by indentations lacking facets, the indentations having a depressed central area relative to a mean height of the surface and a raised, smooth peripheral lip having a greater height at an apex thereof than the mean height of the surface, the indentations have a diameter in the range of 200 μm to 400 μm and a depth relative to the apex of the peripheral lip in the range of 0.5 μm to 2.0 μm.