US3882648A

US3882648A - Method for improving the stainless steel surface finish on a composite metal laminate

Info

Publication number: US3882648A
Application number: US307708A
Authority: US
Inventors: Joseph J Buchinski; Thaddeus Smietana
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 1972-11-17
Filing date: 1972-11-17
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

The stainless steel surface of a strip of composite, rollbonded, stainless steel-aluminum laminate material is characterized by a matte finish and by considerable surface roughness but is shown to be provided with a high quality surface finish in an economical manner by advancing the metal laminate over spaced supporting rolls under substantial tension, by providing a series of buffing rolls formed of fabrics of moderate abrading properties and by rotating these buffing rolls in the direction of advance of the laminate on roll axes disposed normal to said direction of advance while oscillating the buffing rolls to a controlled limited extent along the roll axes and while pressing the buffing rolls against the stainless steel surface between the support rolls with substantial force for obtaining a selected degree of wrap of the laminate against surfaces of the buffing rolls to provide a substantial area of buffing engagement between the strip surface and the rolls, and by intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in excess of 600 psi, substantially radially onto surfaces of the buffing rolls for penetrating the buffing rolls with the abrasive particles to a significant extent so that the abrasive particles are carried by the buffing rolls over the entire area of buffing engagement between the strip surface and the rolls, thereby to obtain an extensive degree of a moderate type of surface abrasion for achieving the desired high quality surface finish while using only limited quantities of expendable buffing and abrasive materials.

Description

States Buchinski et a1.

atent 1 METHOD FOR IMPROVING THE STAINLESS STEEL SURFACE FINISH ON A COMPOSITE METAL LAMINATE [75] Inventors: Joseph J. Buchinski, Wrentham;

Thaddeus Smietana, Attleboro, both of Mass.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Nov. 17, 1972 [21] Appl. No.: 307,708

[52] US. Cl 51/328; 51/292 [51] Int. Cl. B24b 1/00 [58] Field of Search 51/292, 281 R, 317, 318, 51/263, 264, 328. 39, 78

[56] References Cited UNITED STATES PATENTS 783,850 2/1905 Zucker 51/263 1,998,770 4/1935 Schulte 51/324 X 3,277,609 10/1966 Horie 51/281 R X 3,434,240 3/1969 Phelps... 51/39 X 3,581,439 6/1971 Jensen 51/328 X 3,701,222 10/1972 Testolin 51/292 X [57] ABSTRACT The stainless steel surface of a strip of composite, rollbonded, stainless steel-aluminum laminate material is characterized by a matte finish and by considerable surface roughness but is shown to be provided with a high quality surface finish in an economical manner by advancing the metal laminate over spaced supporting rolls under substantial tension, by providing a series of buffing rolls formed of fabrics of moderate abrading properties and by rotating these buffing rolls in the direction ofadvance 0f the laminate on roll axes disposed normal to said direction of advance while oscillating the buffing rolls to a controlled limited extent along the roll axes and while pressing the buffing rolls against the stainless steel surface between the support rolls with substantial force for obtaining a selected degree of wrap of the laminate against surfaces of the buffing rolls to provide a substantial area of buffing engagement between the strip surface and the rolls, and by intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in excess of 600 psi, substantially radially onto surfaces of the buffing rolls for penetrating the buffing rolls with the abrasive particles to a significant extent so that the abrasive particles are carried by the buffing rolls over the entire area of buffing engagement between the strip surface and the rolls, thereby to obtain an extensive degree of a moderate type of surface abrasion for achieving the desired high quality surface finish while using only limited quantities of expendable buffing and abrasive materials.

4 Claims, 2 Drawing Figures 1 METHOD FOR IMPROVING THE STAINLESS STEEL SURFACE FINISH ON A COMPOSITE METAL LAMINATE In the past, the automotive industry had used stain less steel strip materials in making automotive trim and, for these purposes, had required that the strip materials display a high quality surface finish corresponding to AISI Finish No. 8 (a root mean square surface roughness of about 0.5 to 1.5 R.M.S.). The unit of measurement of surface roughness as described herein is the microinch as established by the American Standards Association, ASA B46. This quality of surface finish is easily obtained in solid stainless steel strip materials at very low cost by use of conventional rolling mill processes. However, the automotive industry is now making automotive trim from roll-bonded, composite, stainless steel-aluminum strip material so that the aluminum component of the trim will provide galvanic corrosion protection for automotive bodies at the trim locations on the bodies. It is found that the stainless steel surface of such roll-bonded laminate material is characterized by a matte finish and by a surface roughness on the order of 20 R.M.S. and very substantial buffing has been required to provide the laminate withthe high quality stainless steel surface finish required for automotive trim purposes. The'costs associated with providing this high quality finish on the laminate by conventional buffing methods have been almost prohibitive.

It is an object of this invention to provide novel and improved methods for providing a composite, rollbonded stainless steel-aluminum laminate material with a high quality surface finish suitable for automotive trim purposes; and to provide such methods which are convenient and economical to perform.

Other objects, advantages and details of the methods of this invention appear in the following detailed description of preferrred embodiments of the invention, the detailed description referring to the drawings in which:

FIG. 1 is a diagrammatic view illustrating the method of this invention; and

FIG. 2 is a partial section view to enlarged scale along line 22 of FIG. 1.

In accordance with the present invention, it has now been recognized that, although the stainless steel surface of a roll-bonded, composite, stainless steelaluminum laminate strip material is normally characterized by a matte finish and by a surface roughness on the order of 20 R.M.S., the stainless steel surface of the laminate material is substantially free of major surface defects. Accordingly, it has been found that the high quality surface finish required for automotive trim purposes is obtained on the stainless steel surface with suitable economy where a relatively moderate type of sur face abrasion is used but where this moderate type of abrasion is carried out to an extensive degree while employing novel and advantageous procedures for minimizing use of expendable abrading materials such as buffing pads and abrasive compounds to keep the surface finishing costs low.

Referring now to the drawings, 10 in FIGS. 1 and 2 indicates a strip of composite, roll-bonded stainless steel-aluminum laminate material as conventionally used in the manufacture of automotive trim. As will be understood, such laminate material is usually formed in a strip about 24 inches wide and in 40-60 percentage ratio typically having a total composite thickness of about 0.022 inches embodying a layer of stainless steel about 0.009 inches thick and a layer of aluminum about 0.013 inches thick, these layer materials being metallurgically bonded together throughout the interfaces between the layer materials. For example, the stainless steel material usually comprises 434 Stainless Steel and the aluminum layer is formed of 5052 Alloy Aluminum. Alternately the aluminum layer of the composite may comprise several different aluminum materials metallurgically bonded together. As roll-bonded, the stainless steel layer of the laminate typically has a matte finish and has a surface roughness of about 20 R.M.S. but is substantially free of major surface defects of a depth greater than about 30 microinches. As will be understood, references herein to the depth of major surface defects refers to the measurement from the highest point at the edge of the defect to the level of the lowest portion of the defect area. As roll-bonded, the stainless steel layer of the laminate is usually in almost soft or annealed condition having undergone only slight workhardening during roll-bonding of the stainless 1 steel material to the aluminum layer of the laminate.

As shown in the drawings, the laminate material 10 is advanced from a pay-off reel 12 between a pair of pass line or guide rolls 14, over a series of supporting rolls 16, and between additional guide rolls 18 and is then coiled on a take-up reel 20, the take-up reel being driven with sufficient force relative to the drag imposed on the strip material 10 by the pay-off reel 12 to establish a substantial tension in the strip material. In a preferred embodiment of the method of this invention, for example, the strip material is advanced at a speed from about 10 to feet per minute and is subjected to a tensile force of about 6000 pounds (about 1 1,000 psi for a strip of the noted cross-sectional dimensions) for drawing the strip 10 tautly over the supporting rolls 16. The stainless steel surface 22 of the strip 10 is disposed in an upwardly facing direction as viewed in FIGS. 1 and 2.

In accordance with this invention, the strip 10 may be advanced from the guide rolls 14 between a pair of pressing pads 24 which have relatively soft fabric surfaces 26 held lightly against the strip for wiping extraneous materials such as dust and dirt from the strip surfaces. However, these pads may be omitted where the strip material is substantially free of such extraneous matter. The strip 10 is then advanced beneath six buffing rolls 28, 30, 32, 34, 36 and 38 each of which is located between a pair of supporting rolls l6 and each of which is pressed against the stainless steel surface of the strip 10 with sufficient force so that the strip 10 wraps against a substantial surface area of each of the buffing rolls as shown in FIG. 2 to provide a substantial area of buffing engagement between the strip and buffing rolls. Typically, for example, where the buffing rolls have a diameter of about 18 inches and a lateral length of engagement with the strip 10 of about 24 inches, and where the strip 10 is tensioned as described in the example set forth above, the buffing rolls are pressed against the strip 10 with a force of at least about 1000 pounds so that the strip wraps an arc of between 20 and 40, and preferably wraps an arc of at least about 5, on the surface of each of at least the buffing rolls 28, 30, 32 and 34.

as is indicated by the arrow 40 in FIG. 2. In addition, 7

each of the buffing rolls is oscillated along the axes of the buffing rolls by any conventional means (not shown) as is indicated by the arrows 42 in FIG. 1, these buffing roll axes each being disposed normal to the di-' rection of movement of the strip 110 as is illustrated in FIG. 1. The buffing rolls are rotated at a sufficient speed to achieve a relative speed or linear speed of engagement between the buffing roll surface and the stainless steel surface of the strip it), the relative speed of the buffing roll and strip surfaces therefore being equal to about 141 feet per second less the speed of advance of the strip 10 on the order of 100 to 150 feet per second. Typically, for example, where the buffing rolls have a diameter of about 18 inches, the buffing rolls are rotated at a speed of about l800'rpm to achieve a linear surface speed of about l4l feet per second at the area of engagement with the strip 10. The speed of rotation of the buffing rolls may be adjusted during wear of the buffing rolls to substantially maintain this surface speed. Most importantly, in the process ofthis invention, the oscillation of the buffing rolls is controlled to be selectively limited in extent relative to the frequency of the oscillation so that, with the relatively extensive degree of moderate abrasion utilized in the process of this invention, no visible buffing patterns are formed on the stainless steel surface of the strip by the buffing roll oscillation. It is found, for example, that the oscillation of the buffing rolls should be at least about one-fourth inches (as measured between extreme limits of movement of such oscillation) but should be limited to about three-fourths inches in length and at a frequency from 50 to 200oscillations per minute. Typically, for example, the buffing rolls are oscillated one-half inches at a frequency of 180 oscillations per minute.

In accordance with the method of this invention, the materials employed in the buffing rolls 28, 3t), 32, 34, 36 and 38 are characterized as displaying moderate abrading properties. That is, the materials of the buffing rolls are selected such that they are adapted to cut the stainless steel surface of the strip 10 to a depth of as much as 10 microinches but are not adaptedto cut this stainless steel surface to a depth greater than about 20 to microinches. Typically, for example, the buffing rolls 28 and 30 are each made up by round buffing pads each comprising a layer of sisal fabric between two layers of cotton fabric, the sisal fabric embodying natural fibers loosely woven with five to seven groups of fibers per inch in each of two directions, the fabric being bias cut in conventional manner to dispose fiber ends obliquely to the circumference of the buffing rolls, each of the fabrics having an original sheet diameter greater than 18 inches with a large center opening but being shirred or drawn in to form a pad of about 18 inches outer diameter and several inches inside diameter. The sheet of cotton fabric used is about to inches in diameter with a large center opening and is shirred to form a pad of the same final diameter as the sisal fabric, the cotton fabric having 80 to fibers per inch in each direction over the fabric and having a weight 2.50 (2.5 square yards per pound), these cotton pad fabrics also preferably being bias cut as noted above. In this arrangement, where the strip 10 is about 24 inches wide, about 40 to 50 0f the noted three layer A. buffingpadsare stacked inside-by-side relation in each of the buffing rolls 28 and 30 to form a hard-packed buffing roll. Typically, theibuffing rolls 32, 34, Zip and 38 are then each made up of about 40 toSO 4-layer pads where each. layer of the pad comprises a layer of cotton fabric as above-described shirred and hardpacked in the buffing roll.

In accordance with this invention, moderateabrasive compounds are also used :in conjunction with the buffing rolls described above. That is, the abrasive compounds include chromium oxide and aluminum oxide abrasive particles of about minus 325 mesh size, the. W most abrasive compound utilized in this invention com prising what is commonly called a cut and color compound embodying abrasive particles consisting of'abo ut one halfchromium oxide andone half aluminum oxide particles. I i

In addition, the method ofthis invention also utilizes a less abrasive compound commonly called a color compound embodying a major proportion of chromium oxide particles and a substantially smaller portion of aluminum oxide particles, the abrasive particles in this I g latter compound also being about minus 325 mesh size.

' Typically, for example, these abrasive compounds'have of gaseous carrier mediums substantiallyradially onto 7 the buffing rolls so that the abrasive compounds penea composition, by weight, of about 50 percent water, about 15 percent fatty acids to serve as a compound binder and lubricant, and about 35 percent of the noted abrasive particles.

In an important part of this invention, the abovenoted moderate abrasive compounds are supplied to selected buffing rolls by projecting the abrasive c'ompounds with very substantial force and without the use trate the buffing roll materials to a significant extent. For example, in a preferred embodiment of this invention, the abrasive compounds are projected by a "conventional airless spray mechanisrntnot shown).-at.pres sures in the range from about 600 to 1200 'psi.-from nozzles closely spaced with respect to the buffingrolls;

the abrasive compound preferably being projected in;

termittently to minimize use of the abrasive compound. Typically, for example, the abrasive compound described above as a cut and color compound is projected; from a pair of nozzles 44 spaced 8 to 12 inches away from each ofthe buffing rolls 28 and 30, theQnozzles being directed radially toward the buffing roll surfaces but being adapted to face out the abrasive compound 46 so that the compound projected by two nozzles 44 covers the full width of each of the buffing rolls'28 and 7 3t) and so that the buffing compound is directedinto a typical embodiment of this invention as thus far described above, the nozzles 44 and 48 are regulated by any conventional means (not shown) to direct the I noted abrasive compounds into the buffing rolls intermittently for durations on the order of 0.005 to 0.015 seconds and at a frequency of 2 to 3 times per minute.

As illustrated in FIG. 1, abrasive compounds are preferably not projected onto the buffing rolls 36 and 38 which perform a final polishing of the stainless steel surface of the strip 10.

In accordance with this invention, the strip is finally advanced between a pair of pressure pads 52 which have soft fabric surfaces (not shown) thereon for wiping all abrasive compounds from the strip before coiling of the strip on the take-up reel 20.

Where the above-described buffing method has been utilized as described, roll-bonded composite stainless steel-aluminum strip material has been provided with a very high quality surface finish at very low cost. For example, where the laminate material having a stainless steel surface 24 inches wide characterized by a matte finish and by a surface roughness of R.M.S. was buffed using the buffing rolls and abrasive compounds described above as being preferred, where the two rolls were 18 inches in diameter, were rotated at 1800 rpm., and were oscillated for a distance of one-half inch 180 times per minute, and where the rolls were pressed against the stainless steel surface with a force of 1000 pounds and were penetrated to a depth of about onehalf inch with the noted abrasive compounds projected at pressures of about 900 psi., the surface finish pro-- vided on the stainless steel surface exceeded the surface quality required for automotive purposes even though the cost of performing the method was as little as one-quarter the cost of providing this surface finish by conventional methods. In this arrangement, the substantial buffing pressures and speeds and substantial areas of buffing engagement utilized with the moderately abrasive materials was fully effective to achieve the desired surface improvements. The disposition of the buffing rolls normal to the direction of advance of the strip materials, the prescribed limited degree of oscillation of the buffing rolls and the substantial area of buffing engagement cooperate to avoid formation of buffing patterns even though substantial buffing forces are used, thereby avoiding the development of surface defects that would require additional buffing to remove, Further, the airless spray projection of the abrasive compounds avoids wide dispersal and waste of the abrasive compounds; the projection of the abrasive compounds at high pressures to penetrate the buffing rolls to a significant extent assures that the abrasive compound is carried by the buffing rolls throughout the area of buffing engagement and assures most effective utilization of the abrasive compounds; the penetration of the pads with the abrasive particles effects maximum buffing results with minimum wear of the buffing pad materials. In this way, by accomplishing the desired surface improvement while maximizing effective utilization of expendable buffing pad and abrasive compound materials, the total cost of performing the buffing process has been significantly improved.

It should be understood that although particular embodiments of the methods of this invention have been described in detail by way of illustrating this invention, this invention includes all modifications and equivalents of the disclosed embodiments falling within the scope of the appended claims.

We claim:

1. Method for providing a high quality surface finish corresponding to MS] Surface Finish No. 8 on the stainless steel surface of a composite roll-bonded stainless-steel-aluminum-laminate strip material where said stainless steel surface is characterized by a matte finish and by a root mean square surface roughness of about 20 R.M.S. and is substantially free of surface defects of a depth greater than about 30 microinches, said method comprising the steps of advancing said strip material over a series of spaced supporting rolls under substantial tension with said stainless steel surface facing away from said supporting rolls, rotating a series of fabric buffing rolls of moderate abrading properties in the direction of advance of said strip material on axes disposed normal to said direction of advance while oscillating said buffing rolls to a controlled limited extent along said buffing roll axes and while pressing said buffing rolls against said stainless steel surface with sufficient force between respective pairs of said supporting rolls for obtaining a wrap of an arc of between 20 and 40 of said tensioned strip material against the peripheral surfaces of each of said buffing rolls to provide substantial areas of buffing engagement between said stainless steel surface and said buffing rolls, and intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in excess of about 600 pounds per square inch substantially radially onto respective surfaces of said fabric buffing rolls to penetrate said buffing rolls to a significant extent with said abrasive particles for assuring that said abrasive particles are carried by said buffing rolls throughout said areas of buffing engagement.

2. A method as set forth in claim 1 wherein said buffing rolls are oscillated on said buffing roll axes for a dis tance in the range from one-fourth to three-fourths inches at a frequency in the range from about 50 to 200 oscillations per minute.

3. A method as set forth in claim 1 wherein said buffing rolls are rotated at a speed selected with respect to the speed of advance of said strip material to provide a linear speed of engagement between the buffing rolls and said stainless steel surface in the range from about to feet per second.

4. Method for providing a high quality surface finish corresponding to AlSl Surface Finish No. 8 on the stainless steel surface of a composite 24 inch wide rollbonded stainless-steel-aluminum-laminate strip material where said stainless steel surface is characterized by a matte finish and by a root mean square surface roughness of about 20 R.M.S. and is substantially free of surface defects of a depth greater than about 30 microinches, said method comprising the steps of advancing the said strip material over a series of spaced supporting rolls under substantial tension on the order of 1 1,000 pounds per square inch with said stainless steel surface facing away from said supporting rolls, rotating a series of fabric buffing rolls of moderate abrading properties at a selected surface speed in the range from 100 to 150 feet per second in the direction of advance of said strip material on axes disposed normal to said direction of advance while oscillating said buffing rolls to a controlled limited extent in the range from onefourth to three-fourths inches at a frequency of 50 to 200 oscillations per minute along said buffing roll axes and while pressing said buffing rolls against said stainless steel surface with sufficient force between respective pairs of said supporting rolls for obtaining a selected degree of wrap of an arc of at least about 20 of said tensioned strip material against the peripheral surfaces of each of said buffing rolls to provide substantial areas of buffing engagement between said stainless to a significant extent of at least about one-half inch l with said abrasive particles for assuring that said abrasive particles are carried by said buffing rolls through: I

out said areas of buffing engagement.

Claims

1. Method for providing a high quality surface finish corresponding to AISI Surface Finish No. 8 on the stainless steel surface of a composite roll-bonded stainless-steel-aluminumlaminate strip material where said stainless steel surface is characterized by a matte finish and by a root mean square surface roughness of about 20 R.M.S. and is substantially free of surface defects of a depth greater than about 30 microinches, said method comprising the steps of advancing said strip material over a series of spaced supporting rolls under substantial tension with said stainless steel surface facing away from said supporting rolls, rotating a series of fabric buffing rolls of moderate abrading properties in the direction of advance of said strip material on axes disposed normal to said direction of advance while oscillating said buffing rolls to a controlled limited extent along said buffing roll axes and while pressing said buffing rolls against said stainless steel surface with sufficient force between respective pairs of said supporting rolls for obtaining a wrap of an arc of between 20* and 40* of said tensioned strip material against the peripheral surfaces of each of said buffing rolls to provide substantial areas of buffing engagement between said stainless steel surface and said buffing rolls, and intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in excess of about 600 pounds per square inch substantially radially onto respective surfaces of said fabric buffing rolls to penetrate said buffing rolls to a significant extent with said abrasive particles for assuring that said abrasive particles are carried by said buffing rolls throughout said areas of buffing engagement.

2. A method as set forth in claim 1 wherein said buffing rolls are oscillated on said buffing roll axes for a distance in the range from one-fourth to three-fourths inches at a frequency in the range from about 50 to 200 oscillations per minute.

3. A method as set forth in claim 1 wherein said buffing rolls are rotated at a speed selected with respect to the speed of advance of said strip material to provide a linear speed of engagement between the buffing rolls and said stainless steel surface in the range from about 100 to 150 feet per second.

4. Method for providing a high quality surface finish corresponding to AISI Surface Finish No. 8 on the stainless steel surface of a composite 24 inch wide roll-bonded stainless-steel-aluminum-laminate strip material where said stainless steel surface is characterized by a matte finish and by a root mean square surface roughness of about 20 R.M.S. and is substantially free of surface defects of a depth greater than about 30 microinches, said method comprising the steps of advancing the said strip material over a series of spaced supporting rolls under substantial tension on the order of 11,000 pounds per square inch with said stainless steel surface facing away from said supporting rolls, rotating a series of fabric buffing rolls of moderate abrading properties at a selected surface speed in the range from 100 to 150 feet per second in the direction of advance of said strip material on axes disposed normal to said direction of advance while oscillating said buffing rolls to a controlled limited extent in the range from one-fourth to three-fourths inches at a frequency of 50 to 200 oscillations per minute along said buffing roll axes and while pressing said buffing rolls against said stainless steel surface with sufficient force between respective pairs of said supporting rolls for obtaining a selected degree of wrap of an arc of at least about 20* of said tensioned strip material against the peripheral surfaces of each of said buffing rolls to provide substantial areas of buffing engagement betweEn said stainless steel surface and said buffing rolls, and intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in the range from about 600 to 1200 pounds per square inch substantially radially onto respective surfaces of said fabric buffing rolls to penetrate said buffing rolls to a significant extent of at least about one-half inch with said abrasive particles for assuring that said abrasive particles are carried by said buffing rolls throughout said areas of buffing engagement.