JPH09300002A - Rolled metallic product with gloss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve deep drawability, and also to give excellent gloss by forming a prow structure on a sheet surface, using rolls with fine bowl shaped recessing patterns when rolling an aluminum sheet for an automobile panel. SOLUTION: A rolling mill to be used must be a 4 high rolling mill. On the surface 14 of the work roll of the 4 high rolling mill, almost circular recesses 16 with 50.5 to 255μm in diameter and 0.4 to 10.0μm in depth are formed. The recesses 16 must be formed by laser beam or electron beam working. After the working, an annular rise occurred on the periphery of the recess 16 is removed by a machine or chemical grinding, etc. At the time of rolling, rolling mill lubricating oil is used. Cold rolling is performed with an about 70% draft, and by partially pushing backward the sheet material 12 into the bowl shaped recessed part 16 on the surface of the roll to give an action, and the prow 28 is formed. In addition, a rough surface with lots of these prows can be made on either of one surface of the sheet 12 or both surfaces. Also, at the time of press working, these projections must be easily leveled, and after painting, even their traces must be hard to detect.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a textured surface texture of working rolls in one final stand of a rolling mill, which is greater than, for example, the working rate achievable with directionally polished rolls in multiple stands. TECHNICAL FIELD The present invention relates to a metal thin plate product for constructing a car body of an automobile, which uses a processing rate of a thin plate thickness that can be achieved. This provided metal sheet has functional properties for the subsequent manufacturing process, such as formability in the press, spot weldability, galling or adhesive metal transfer from the sheet surface to the tool surface in a press for forming a member from the sheet. Resistance to abrasion, and the appearance of the thin plate surface before and after coating or coating are improved.

[0002]

BACKGROUND OF THE INVENTION The description of Applicants' earlier U.S. Pat. No. 5,025,547, issued June 25, 1991, is hereby incorporated by reference. This patent pertains to micro-engineered surface textures for both working and backup rolls on each stand of a rolling mill, where each stand is tuned to specific rolling conditions with lubrication, wear and traction. Thus, the final stand of the rolling mill embosses the surface of the sheet product by the textured surface of the work roll, rolling and reducing the thickness of the strip or sheet. This is described from line 63 at the bottom of column 3 of that patent publication. The uneven skin structure on the surface of the processing roll in the final stand of the rolling process is shown in the micrograph of FIG. 5 of the patent drawing of US Pat. It should be noted that the uneven surface structure formed on the strip surface in all the stands other than the final stand is generally removed from the thin plate surface by the action of the working roll in the latter stand of the rolling mill.

In addition, the working roll of the final stand in Applicants' above-mentioned patent is a continuous helical as described at the top of column 4 of that patent publication.
A groove can be provided. Such a surface texture skin structure forms the sheet surface shown in FIG. 29 of Applicant's drawing. The uneven skin structure of the continuous helical groove is anisotropic (directivity), and the uneven skin structure of the obtained thin plate is also made directional as shown in FIG. 29 of the present application. With such a textured surface structure, it is difficult to significantly reduce the thin plate thickness, that is, to roll at a working rate of 55% or more. The purpose of the grooved uneven skin structure is to remove the lubricant by narrowing the lubricant into the channels (grooves) of the roll surface uneven skin structure. Therefore, the sheet / work roll interface is not sufficiently lubricated to provide a large thickness reduction at the final stand of the cold roll process. The spiral groove texture is designed for rolling process with reduced thickness intended to produce sheets and products that are rolled at high speed to produce very shiny, i.e. improved specular gloss. .

Such a large reduction in thickness cannot be predicted even by the surface uneven surface structure with craters shown in FIG. 5 of the above-mentioned patent. The purpose of the patent is that the thin surface uneven surface of the working roll before exiting the rolling mill. This is because the structure is to emboss the surface of the sheet to form an isotropic and non-directional surface of the final sheet product. Any significant thickness reduction results in substantial smearing of the sheet surface, as will be described in detail below. In the patents mentioned above, the reduction is in the range of 15% to 54%, which range is substantially above that during temper rolling with a reduction in sheet thickness of the order of 3 to 10%. Including thickness reduction.

Steel and aluminum sheet are products made on rolling mills that use work rolls to engage the sheet during the thickness reduction process. The polished surface of the processing roll is provided with different textured skin structures using finishing techniques such as sandblasting, electrical discharge textured texture formation (EDT), CO ₂ laser textured texture formation and electron beam textured texture formation. be able to. These methods are based on fine craters (as shown in FIG. 3 of the drawings herein) placed individually along the work roll surface, to irregular irregularities with highly random elements (see FIG. 14). (As shown)
In the range up to, various fine surface roughness (roughness) surface morphologies are given. While laser and electron beam techniques can create a deterministic crater pattern on the work roll surface, the crater pattern provided by the electrical discharge machine has substantially random elements as shown in FIG. These techniques are generally described in "Iron and Steel Engineers" Vol. 68, No. 8, August 1991, and in the applicant's paper "Converged Energy Beam Machining Roll Surface Convex Skin Structure Formation Science and. Technology "Journal of
Materials Processing and Manufacturing Science, Volume 2, June 1993.

The uneven surface structure of the working roll surface formed by the above-described technique embosses the thin plate surface during rolling (for example, typically less than 5% reduction) to reduce the thin plate thickness with a slight reduction in thickness. Used to A processing roll surface having a crater uneven skin structure similar to that shown in FIG. 3 is shown in FIG.
Imprint the thin plate surface as shown in. This is a thin plate,
An array of annular recesses surrounding the plateau portion (plateau-like portion) is formed, and the surface of the plateau portion represents the polishing finish of the processing roll before the formation of the uneven skin structure.

At present, the working roll surface having such an uneven skin structure is generally used for a thin plate for an automobile body.
However, a number of significant rolling related problems continue to exist for the reasons explained below. These problems tend to be exacerbated by rolling thin sheet thickness during rolling, thereby preventing the use of the attached textured skin structure of FIG. 3 over some light reduction.

For example, the reduction of the thin plate thickness that can be achieved by the directional polishing roll is because the thickness of the thin plate bottoms with a relatively small roll gap force and a roll torque, as will be described later in detail.

Similarly, small reductions in sheet thickness (eg, typically less than 3%) in cold rolling at relatively low speeds without lubrication (eg, 150 meters (500 feet) per minute) The surface morphology (topography) of the processing roll surface is imprinted, ie, embossed, only partially on the thin plate surface because the formation of the uneven texture structure on the surface of the processing roll is incomplete. Such incomplete surface uneven skin structure formation is caused by irregular absorption of beam energy by various alloying agents of the working roll steel, which may result in an incomplete uneven texture structure of the working roll surface. FIG. 5 of the accompanying drawings is an example of an incomplete surface uneven skin structure formation, and FIG. 5 shows an example of an annular crater uneven skin structure (similar to that shown in FIG. 3) of a processing roll formed by an electron beam technique. The line drawing (stylus) which shows the form of the typical area part of the steel thin plate surface which shows perfect embossing is shown.

The surface roughness of the embossed sheet typically meets the functional requirements of automotive sheet,
It is possible to have a coated surface that is better than the appearance of a conventional sheet surface rolled by a processing roll having a substantially anisotropic surface roughness (roughness) in directional polishing.
However, the clarity of the painted surface image of a sheet texture with individual surface roughness (roughness) depends on the background surface roughness provided by the polished portion of the roll surface (as seen in Figure 4 of the accompanying drawings). Is not optimized for, and by the textured texture itself, which can be shown through the paint finish.

The generation of wear debris during rolling of a thin metal sheet is C
This is one of the most important rolling problems related to the roll surface uneven texture structure formed by the surface uneven texture structure forming device by O ₂ , electron beam, and discharge. In order to better understand the characteristics of this wear mechanism, some explanation of the textured topography made with these devices is desirable. For CO ₂ laser and electron beam devices, the generated surface roughness in these devices one of the elements known as "crater" is sufficient average energy density (which is the beam intensity and the pulse operation time Is produced by melting one of the microscopic quantities of the work roll surface with one or more pulses, which in the case of a CO ₂ laser is composed of electromagnetic radiation, or an electron beam. In the case of a device, it is composed of accelerated electrons. Each crater is composed of a substantially annular rim which is raised relative to the average surface roughness of the roll surface and which typically has depressions, referred to as depressions, formed in the roll surface as shown in FIG. It The rim of the crater is generally inclined with respect to the average roll surface roughness, and the inclination angle is just steep (for example, 15 ° to 50 °).
By pulse beam to adjust the angle of the fast gas adjunct to a position impinging on the roll surface, CO ₂ will impose a form of one of the raised "hump (plow)" and asymmetric craters comprised of one recess. FIG. 11 is a line drawing showing the form of such a raised hump. The slope of any one hump relative to the average roll surface roughness is also quite large.

The textured structure on the embossed sheet surface obtained by light rolling of thin sheet thickness due to the textured structure of the processing roll formed by the electric discharge technique (EDT) has a series of plateau portions and depressions in a distinguishable row. Is typically composed of parts, which are dielectric (ie initially non-conductive)
Is formed on the work roll surface (reverse state) by multiple sparks of the discharge electrode passing through the fluid medium of. The plateau edge is also very steep and jagged. This is seen in Figure 14 of the accompanying drawings. FIG. 14 is a line drawing showing the morphology of the 2008 aluminum alloy thin plate surface, and the steep and jagged surface is due to the marking of the processing roll surface having the uneven skin structure formed by the discharge device.

Therefore, the mechanism of fine cutting wear is
It shows a tendency to become a dominant mode in which abrasion debris is generated in a roll bite (biting) of a processing roll having an uneven skin structure. For example, according to processing rolls used for rolling automotive sheet metal, the average crater rim height or the average height of the asymmetric "hump" is typical of the average processing roll background surface roughness produced during roll polishing operations. Exceed.
As the crater rim or asymmetric "hump" plows the sheet surface and separates the small pieces from the sheet surface, there is some fine cutting. The total amount of wear debris generated on a roll bite when rolling with a roll having an uneven surface structure is proportional to the sliding distance between the work roll and the thin plate surface. This sliding distance is a function of the thin plate gauge wall thickness, the wall thickness processing rate (thickness reduction rate), and the processing roll diameter. Another factor affecting wear debris produced in textured roll bites is the average slope of the crater rim or asymmetric "hump" with respect to average roll background surface roughness. Generally, if this gradient exceeds 20 °,
Higher levels of wear debris can be predicted in the rolling process for thin plate thicknesses above%.

Excessive wear debris therefore poses aesthetic problems to the final sheet product. This is because the debris is rolled into a sheet or moves to the work roll surface where it acts like a sharp cutting edge that further damages the sheet surface. For this reason, the use of the uneven skin structure forming roll is generally limited to rolling the thin plate thickness at a small working rate because the slip between the working roll surface and the thin plate surface is relatively small. Such a low processing rate tends not to generate a substantial amount of waste.

Temper rolling is sometimes carried out on rolling mills with four stages, ie two backup rolls and two working rolls. In this case, the contact stress between the working roll and the backup roll is significantly higher than the contact stress at the boundary between the strip and the working roll. The reason for this is due to the fact that the width of the part where the backup roll surface and the working roll surface are brought into contact is considerably smaller than the width of the contact part between the working roll surface and the thin plate surface. Also, the sheet is typically subjected to tensile stress, which acts to reduce the normal contact stress required to achieve the desired conversion. Therefore, the crater rim (in the case of laser or electron beam technology) or the sharp cutting edge (in the case of electric discharge technology) repeatedly forms recesses in the backup roll surface during the rolling process, resulting in wear of the backup roll surface and its final result. Severe damage occurs.

The steel material of the working roll is generally harder than that of the backup roll steel. Therefore, the working roll surface having the uneven surface structure is eroded into the backup roll at a high place, and small steel pieces are generated and a recess is formed on the backup roll surface. Bring According to some simple techniques, at least in the case of the annular crater morphology of FIG.
In the case of the asymmetric "hump" form, the surface texture of the processing roll is actually the formation of depressions on the backup roll surface under the rolling process commonly found in the aluminum industry. Is possible. To do this, first estimate the lubricating film thickness between the processing roll surface and the backup roll surface, and determine whether the lubricating film separates these two surfaces, or whether the height of the uneven skin structure is the average of this film. It is necessary to determine if the thickness is exceeded. Next, under the condition that the uneven surface structure of the processing roll surface does not actually contact the backup roll surface, the related contact stress generated along the contact portion between the processing roll and the backup roll promotes the damage of the backup roll surface. It is necessary to determine whether or not the size is large enough. The following developments are limited to the annular crater configuration as shown in FIG. 3, but can be extended to the hump configuration of FIG.

Lubricating film thickness between working and backup rolls, as found in Dee Dowson and G. R. Higginson, "Elastohydrodynamic Lubrication," Pergamon Press, London, 1966, This can be inferred using the well known Dowson and Higginson formula for isotherm contacts using the following equation: That is,

[Equation 1]

[Equation 2]

The following material and process parameters, which are representative of many 4-rolled shapes in the aluminum industry, are substituted into equation 1: That is, u _W = u _b = 7.64 m / sec y _i = 0.001 m E _W = E _b = 207 GPa L _SW = 0.0254 m L _Wb = 0.0254 m R _W = 0.27 m R _b = 0.64 m β = 0.03 γ = 14.5 GPa ⁻¹ μ _o = 2.7 × 10 ⁻³ Pa · sec v _W = v _b = 0.33 σ _y = 1.4 × 10 ⁸ Pa (related to aluminum alloy 2008) , The contact lengths L _SW and L _Wb have been chosen for illustrative purposes only. The processing rate for thin plate thickness is simply β × 1
It should be noted that 00, ie 3% in this situation.

The calculated values are as follows. That is, a _SW = 0.0028 m w = 1.0 × 10 ⁴ NE ′ = 232 GPa G = 3364 R ′ = 0.19 m U = 4.7 × 10 ⁻¹³ W = 8.9 × 10 ⁻⁶ Here, suitable unit displays on "Newtons / meter ^2" is "Pascal", prefix notation "G" represents a Giga, which indicates a multiple of "10 ^9".

If the above values are used for the equations 1 and 2, the equations 1 and 2 between the backup roll and the processing roll are used.
The lubricating film thickness given by

It is clear that the h _min = 0.43 μm crater rim supports most of the load. This is because the film thickness h _min is significantly smaller than the typical crater rim height (for example, 3.0 μm to 10.0 μm) formed by either laser or electron beam technology. Therefore, most of the craters on the work roll come into direct contact with the backup roll surface. Since Equations 1 and 2 is appropriate with respect isotherm contact guess h _{mi n,} the thermal effect on the viscosity of the lubricant (plastic heating of the thin plate, such as by interfacial friction) may be smaller due.

An estimate of the total pressure supported by the crater rim, ie the normal contact stress, is therefore necessary to investigate the possibility of biting of the working roll texture skin structure into the backup roll surface. First of all, it is necessary to calculate the width a _Wb of the rectangular contact area between the working roll surface and the backup roll surface as shown in FIG. This was accomplished using the classical Hertzian contact theory, an explanation of which is given by K. L. Johnson in "Contact Mechanics", Cambridge University Press, New York, 1985. Found in. For two elastic cylinders contacting under a normal load w per unit axial length, the resulting surface contact area has a width of a _Wb along the rolling direction. Therefore,

(Equation 4) Here, the numerical values are obtained from the previous list of invalid residence parameters and material properties.

In the hexagonal crater pattern shown in FIG. 3 (given by the electron beam uneven skin structure forming technique) and in the schematic view of FIG. 7, the unit cells are parallelograms. Within each unit cell is one complete crater. The part of the parallelogram A _p is given by the following equation. That is,

(Equation 5) Here, C _s is the center-to-center distance between adjacent craters in one cell of the hexagonal pattern shown in FIG. 7. Therefore, the percentage of the area portion covered by the crater rim in one unit cell, that is,% A _cr is expressed by the following equation. Ie

(Equation 6) Where r _o and r _i are the outer and inner radii of the crater, respectively. A typical crater made by an electron beam roll uneven skin structure forming device is 76.
It has an outer radius r _{o of} 2 μm, a rim width of 25.4 μm and thus an inner radius r _{i of} 50.8 μm. A typical center-to-center distance C _s is 203 μm. The area of the crater rim is therefore 10.1 × 10 ^-9 m ² , and the area Ap of the parallelogram of the unit cell is 35.6 × 10 ^-9.
m ² and the area percentage% A _cr of the parallelogram covered by the crater rim is 28%. Processing roll /
0.025m long along the contact area of the backup roll
The number of craters "N" in a small rectangular area (along the roll axis and thus perpendicular to the rolling direction) and width a _wb = 204.2 μm (similar to the contact width in the rolling direction calculated above).
Is given by the following equation. Ie

(Equation 7) Here, N was rounded to the nearest integer value.

The total area _AT covered by all the crater rims along the unit length is then given by: Ie

(Equation 8)

Therefore, the average pressure P _A distributed across the crater rim along the sheet / work roll interface is given by: Ie

[Equation 9]

It is appropriate to assume that the pressure P _A is transmitted to the work roll / backup roll interface and therefore to the crater rim at that interface. The yield strength of the backup roll can be as high as 1.0 GPa. Therefore, the estimation of the bite pressure of the backup roll is 2.6 GPa. This is because this biting pressure is 2.6 times the yield strength of the material of the backup roll. Obviously, the pressure of 7.4 GPa against the crater rim is 2.
The biting pressure of 6 GPa is exceeded. Therefore, it is possible for the crater rim to bite into the backup roll surface, and the true area of contact is the thin plate thickness processing rate of 3
Even in the situation of%, it spreads over the entire area covered by craters. Over time, this causes severe damage to the backup roll surface. Such damage can only be stopped by replacing the backup roll, which results in downtime, increased process intensity, manpower and cost.

When the protruding rim or cutting edge of the working roll surface separates from the working roll surface during rolling, substantial surface wear of the working roll having the uneven skin structure occurs.
For example, in the case of an annular crater formed by the impact of a CO ₂ laser beam, the crater rim is formed by rapidly promoting a very small pool of molten metal in the polishing surface portion of the roll surrounding the central recess. The solidified metal on the roll surface (ie, the crater rim) adheres to the local roll surface roughness, which is typically polished. This bond strength is determined by the adhesive force of the solidified metal to the roll surface. This bond is extremely weak in nature. This is because the molten metal does not “fill” the surface roughness (roughness) of the polishing roll sufficiently. Therefore, the crater rim falls off from the work roll surface when subjected to repeated contact pressure in the roll bite. This causes deterioration of the work roll surface having the textured surface structure, which ultimately requires re-correction of the roll. The problem related to the adhesion of the molten material that solidifies to form the annular crater rim during the formation of the uneven skin structure of the processing roll by the CO ₂ laser was reported on February 21, 1989 by Braga.
rd) et al., U.S. Pat. No. 4,806,731.

There is no possibility to form rimless crater depressions. The reason is that the molten metal below the impinging beam flows radially out of the resulting depression and the outward flow velocity of the molten material is a surface that extends mainly along the surface of the pool of molten material formed by the beam. This is because it is induced by the spatial gradient of tension. This gradient is the product of the change in surface tension with temperature and the spatial gradient of surface temperature. Changes in surface tension result in shear stresses that accelerate the surface of the molten material. Shear stress σ is related to the spatial gradient of surface tension by the relationship:

(Equation 10) Where ξ'is the change in surface tension with temperature. The energy distribution in the beam pulse typically decreases radially outward from the center of the pulse and the local work roll surface temperature decreases radially outward from the point of impact of the beam. This equation causes the surface tension to increase radially outward from the point of impact. Therefore, the shear stress on the molten metal layer is quite enough to displace the molten metal into the walls of the depression, and the rapidity of the heating process overlaps with the subsurface fluid motion,
Thus, more material is carried radially outward than replaces the circulating flow beneath the outwardly flowing layer of molten work roll face material. Material build-up occurs, followed by rapid solidification of the material, where an annular lip or rim is formed around the recess. A description of surface melting and shearing effects during laser and electron beam treatment of materials can be found in A.
Published by SME Publishing Bureau (1987), S.M. K. Samantha (S
amanta), R.A. Conduri et al., Interdisciplinary Publications in Material Processing and Manufacturing
inary Issues) pp. 541-558, M.A. M. Chen "Thermocapillary Convection in Material Processing (Thermocapillary Convection)
Ion) ”.

The melting and surface shearing steps occur with or without gas assistance, but the gas assisted steps alter the maximum height of the molten fluid that will eventually form a solidified lip. If the rate of gas assistance is too high, crater lips will still form because the surface shear will occur as soon as a pool of molten material forms below the beam. In addition, the aid of high velocity gas expels the molten material and develops craters below the beam. A part of the melted material that has been expelled re-precipitates on the surface of the work roll, resulting in many sharp cutting edges. The cutting edges of the reprecipitated material generate wear debris during the rolling process where the sheet thickness reduction rate is high.

Another problem arises from the relative spacing of the craters along the work roll surface. In the rolling process, the working roll surface moves at a speed faster than the sheet surface in front of the neutral plane where the roll and the sheet surface have the same speed. After the sheet surface element passes through the neutral surface, the surface element moves at a faster speed than the work roll surface. (This phenomenon is discussed in detail in Applicants' previous patent specification and is hereby incorporated by reference.) If the overall reduction is less than about 5%, then between the sheet and roll surface Relative rubbing action is minimized and almost complete transfer of the roll surface texture skin structure to the sheet surface is obtained. When the thickness reduction is large, the craters on the surface of the work roll mark the sheet surface, and the sheet surface is rubbed in the rolling direction before the sheet surface element reaches the neutral plane, and the rubbed track (orbit) Part) is formed on the surface of the sheet. After the sheet surface element has passed through the neutral surface, the same effect is repeated, but in the opposite direction (backward scraping) because the sheet surface velocity exceeds the roll surface velocity due to volume conservation of plastic deformation. The overall effect of the back and front rubbing action is to create short and narrow "tracks" (passage tracks) on the seat surface, which significantly deforms the seat surface texture.

FIGS. 9 and (FIG. 10) show the surface morphology of two sheets of aluminum alloy 2008, each of which has a surface morphology of 3 under different identical rolling conditions.
Rolled to a surface similar to the 5% and 60% asymmetric raised surface texture shown in FIG. In either case,
The formed sheet surface does not faithfully represent the transfer of the surface structure of the processing roll. This is especially apparent in FIG. 10, where the sheet surface texture is simply an imprint of the work roll ridges, as in the case of the less thick rolling step formed on the sheet surface shown in FIG. Rather, because of imprinting and engraving, it represents a nearly directional element. Thus, the thinning of large sheets tends to prolong the crater impressions on the sheet surface, where long crater tracks are formed because the craters generally follow the spiral path at the work roll surface. When the sheet thickness reduction rate increases, the tracks are connected to each other by adjacent craters or ridges because the average length of a single track with a single structural element increases with increasing thickness reduction. If there is an external interruption of the continuous wave beam, there is little control over the crater position or the entire crater pattern on the roll surface during CO ₂ laser forming. This creates a groove in the surface of the sheet that creates an anisotropic roughness throughout.
Thus, it is possible to start with a substantially non-directional textured surface texture (as shown in FIG. 3) of the work roll surface and finish with a roughness of the rolled surface with considerable directional elements.

The action of these tracks is on the seat surface,
It can have a directional appearance, such as that found in a polished surface finish, or the appearance of the grid-like surface texture skin structure shown in FIG. Such surfaces, in some cases, are less likely to be from the customer's point of view, especially if the optical properties of such surface depend on the direction in which the sheet surface is viewed by the human eye, and such Not desirable when a quasi-isotropic sheet surface is desired because the surface tends to retain the lubricant by allowing it to flow freely during the molding cycle.

In general, the surface texture skin structure obtained by the CO ₂ laser forming process may be used in aluminum rolling processes at large thickness reductions (ie, thickness reductions equal to or greater than 15% of the thickness). You can conclude that there is no. The reason is as follows.
(1) A large sheet thickness reduction rate causes a large roll separating force. This promotes the tendency of the crater rim (or ridge in the case of the asymmetrical configuration shown in FIG. 11) to damage the backup roll surface by the contact stress mechanism, where premature wear of the crater rim occurs.
(2) If the annular craters are too close together (ie along the circumferential direction on the work roll surface), a 15% reduction in thickness of the sheet creates discontinuous scratch tracks,
If it contains a thickness significantly larger than 15%,
The scraping tracks connect to form a continuous track on the surface of the sheet. The connected tracks form a "coarse band",
On the other hand, a smoother and narrower band appears by the polishing process on the peripheral surface of the sheet rubbed by the relatively flat area of the roll (the portion having the textured surface structure). FIG. 12 shows a 40% reduction rolled 2008 aluminum alloy sheet surface due to the annular crater roll surface morphology generated by CO ₂ laser forming. The crater center-to-center distance is short enough to form a trajectory on the sheet surface. (3) Controlling the position of one crater relative to the adjacent craters, ie forming hexagonal or square cells, because the CO ₂ laser beam is mechanically interrupted by serrated (serrated) disks. Is impossible. This is currently only possible by electron beam technology, since this technology is printed by rotogravure printing with internal pulses CO _{2 in} which the active elements of the laser resonator are modulated by a radio frequency device. . For a more detailed description of the application of electron beam technology to rotogravure printing, see Optics, Vol. 77, No. 2 (1987) No. 83-.
92, W. It is described in "A rapid electron beam engraving method for engraving a metal cylinder" by Boppel. (4) CO ₂ lips or ridges which are produced by laser forming process generates a prohibitively high level of wear debris between the large thickness reduction rolling process. Excessive wear debris adds more load to the rolling mill's oil filtration housing and ultimately ends the rolling process. Similar problems can occur with electron beam structures.

The painted appearance of metal sheets rolled by laser forming rolls is often unacceptable to sheet metal manufacturers in the automotive industry. The annular crater roll surface uneven skin structure causes an annular recess on the sheet surface, and the raised structure causes a substantially circular recess on the sheet surface. In either case,
The depressions on the sheet surface are surrounded by flat areas, which act as support areas where the load from the forming tool is transferred to the sheet. The distortion from the pressing operation is not great enough to completely hide the recesses in the sheet from the sheet surface. Thus, the embossed sheet surface textured structure is observed through the painted finish that paints the background structure. This is often the reason for rejection of molded sheet elements, especially for high-end automobiles. For a discussion of the structure remaining after stamping,
(1988, published by Springer) "Optimieru
ng der Oberflachenminikroge
ometri von Aluminumfeinb
lech fur das Karosserezie
hen ", chapter 5. In English, the title is "Optimization of surface microstructure of aluminum sheet for automobile body panel drawing work" (written by R. Barbach).

The present invention takes advantage of the disadvantages of temper rolling processes, which allow only a small reduction in thickness of less than 5% at low rolling speeds, in the production of automobile body sheets at about 66 minutes per minute.
7 m (2000 ft), or in the production of can sheets, at a single final stand of a rolling mill that transfers sheets at about 1667 m (5000 ft) per minute, at high speed and with a sufficiently large reduction in thickness (ie 55% or more It is overcome by allowing the sheet to be thinned with a large reduction rate. This then eliminates any wear debris, substantially eliminates damage to the backup roll surface in the rolling contours of the backup roll, and avoids slippage along the intermediate plane, so that the sheet and work roll intermediate surfaces and This is achieved while maintaining the required level of pulling force on the intermediate surface between the work roll and the backup roll. This means that the roughness is 0.007μ.
a substantially smooth working roll surface in the range of m to 0.25 μm, as well as a solid rim removed from the roll surface,
Bowl type with almost smooth entrance area or mouth
This is achieved by a definitive pattern of micron-sized craters that leave depressions. The textured surface structure of this processing roll is best shown in the line drawing topographies of FIG.

The craters are preferably formed on the surface of the work roll by the melting and shearing action by a pulse laser or an electron beam device. The beam of those devices forms indentations in the work roll surface, and the lip or rim around each indentation is, in the present invention, any one or all of honing, lapping, belt polishing, grinding and chemical polishing. Substantially removed by one or more of the known polishing techniques, such as In this way, work roll material that would otherwise generate wear debris on the roll bite is removed before the work roll is used. Otherwise, wear debris is embedded in the sheet surface during rolling, making the rolled product extremely dirty to the extent that it is not desired by the manufacturer's customers. It is not possible to cut the crater rim with standard diamond tip tools, because diamond tips chemically degrade the steel during cutting. After the rim is removed, the roll surface can be coated with a dense, hard material such as chrome.

In the apparatus for greatly reducing the thickness of the sheet of the present invention, the material of the sheet is pressed into a bowl-shaped recess provided on the surface of the work roll as compared with the apparatus for reducing the thickness of the sheet by annealing or rolling. Partially pushed. While the sheet is being pushed in, the sheet is abraded by the difference in surface speed of the sheet and the work roll. Simultaneous pushing and rubbing within the roll bites results in the instantaneous and very temporary formation of fine raised structures on the sheet surface, formally called "prows". While the tip is being formed, any excess lubricant trapped in the dents on the roll surface is pushed out of the dents by the sheet material being pressed. Therefore, excess lubricant flows into the interface between the sheet and the roll, improving the frictional properties of the interface. As will be described in detail below, a small posterior plow remains on the seat surface even after the temporary tip disappears from the seat surface. When the sheet is used in secondary operations such as deep drawing, the remaining plow acts as a lubricant retainer as well as a lubricant barrier at the interface between the sheet and the die.
The plow improves friction characteristics of the secondary sheet forming process by minimizing undesired galling or adhesive metal transfer effects because metal-to-metal contact is substantially minimized.

Sheet base between remaining plows
The surface is also rubbed by the smooth working roll surface existing between the depressions of the working roll surface in the above-described high-thickness reduction step, and becomes a substantially smooth glossy sheet surface during the plow. The number and spacing of roll craters depend on the hardness and alloy of the material to be rolled, the amount of reduction performed, the speed at which the material is rolled, the amount and type of coolant and lubricant supplied, and the secondary forming process. Depends on the nature of (drawing or stamping). Traction between the work roll and backup roll surfaces is ensured by shearing the lubricant film and momentary partial filling of the soft roll material into the recesses in the work roll surface. The filling process is due to elastic deformation of the backup roll surface. Processing roll surface bowl (bowl-shaped part)
These areas of the back-up roll surface that partially fill the surface act as lips that support traction between the work roll and the back-up roll surface. The plows left on the rolled sheet surface are abraded and finally flattened during the pressing operation, because they are from the tool or die to the sheet surface during all stages of the forming process. This is because it is not possible to support the orthogonal force transmitted to the. Therefore, the textured surface structure remaining on the surface of the sheet after the pressing operation becomes less visible by the paint finish than the textured surface structure in the form of craters or ridges.

Therefore, it is an object of the present invention to obtain a bright sheet product both before and after painting by greatly reducing the thickness in the final stand of the rolling mill. Another object of the present invention is such that a significant reduction in the thickness of the rolled sheet is carried out by rolling in a single stand of the rolling mill without the outbreak and embedding of particulate debris on the surface of the rolled sheet. , To obtain a processing roll surface that significantly reduces the occurrence of wear debris. Still another object of the present invention is to achieve cold rolling without damaging the backup roll used with the working roll having the structure of the present invention, and to improve the life of the working roll surface and the backup roll surface. To obtain a working roll surface structure that extends.

Yet another object of the present invention is that in a single stand of the rolling process, it may not otherwise be provided with polishing roll surface finish or annular craters or asymmetric raised surface textures, and It is to obtain a textured surface structure of a processing roll capable of a large percentage of sheet thickness reduction leading to failure. Yet another object of the present invention is not only to support the lubricant on the intermediate surface of the sheet and tool as occurs during stamping operations, but also to form a film of lubricant on that surface, which is described in detail below. As described in Section 1., there is a barrier effect to obtain a structure that helps carry out later steps of the process. Yet another object of the present invention is to obtain an automobile body sheet product in which the image obtained by the specular reflection of the large amount of light from the substantially smooth back surface of the sheet is extremely sharp. Another object of the present invention is to easily see through or otherwise under the paint finish applied to the surface of the part by the automobile manufacturer after the sheet has been formed into the part by several secondary forming steps. To obtain a non-oriented sheet surface structure that is impossible. The objects and advantages of the present invention may be better understood based on the following detailed description and drawings.

Referring now to FIG. 1 of the drawings, there is shown an upper roll 10 and a lower roll 11 (other parts are not shown) of a rolling mill in the step of reducing the thickness of the thin plate 12. The upper roll 10 has a working surface 14 with a number of spaced micron-sized bowl-shaped recesses 16. Two of the indentations 16 are shown in FIG. 2 of the drawings, and these indentations 16 are also shown greatly enlarged for purposes of illustration. Dent 16
Before the surface 14 of one or more work rolls 10 and / or work rolls 11 is provided with
Is prepared in such a manner that it has a very smooth finish, for example, a finish of the order of 0.007 μm to 0.2 μm Ra (roughness of arithmetic mean). A measurement according to the ISO roughness standard is suitable. The surface roughness standard is L.E. in Hommelberg, Germany, issued in 1990. It is discussed in a paper entitled "Analysis of Skin Surface Texture-Handbook" by Mameli. Such a surface provides a metallic material of reduced thickness upon biting of the roll of Figure 1 having a substantially smooth surface. The result is an esthetically rolled product having a glossy surface with some smearing on the surface during rolling which enhances the overall brightness of the product as perceived by the human eye. To be

Discussed below and in FIGS. 3, 7 and 8
As shown in FIG.
When it collides with the crater 18 and forms a crater 18,
6 are formed. Crater 18 includes a raised rim material 20 surrounding each recess 16. Since the path of the energy beam is aligned with the axis of the roll, the energy beam is incident on the surface of the roll at a normal incident.
collision).

FIG. 2 shows the interface between one working roll of the invention and one surface of the thin sheet rolled by the working roll during a large-scale thin rolling operation of the thin sheet, and FIG. It is shown in an enlarged cross section of the area indicated by the small "box". The presence of bowl-shaped depressions on the surface of the work roll, along with the kinematics of the roll loading and the vertical loads exerted by the work roll surface on the thin plate surface during the large-scale reduction rolling process of the thin plate, together with the kinematics of the roll's entrainment. Undergoes a series of changes within the roll bite before it exits the roll bite. The front protrusion 22 is shown in FIG. The protrusions 22 are microscopic crescent shaped ridges of sheet metal surface material and are formed in the interfacial region preceding near the neutral plane of the roll bite. The neutral plane is shown at 24 in the figure. A mound 26 is formed on the surface of the sheet near the neutral plane. In the exit area,
A rear protrusion 28 is formed on the surface of the sheet and remains on the sheet as the final sheet surface texture. The transient nature of the surface of the sheet shown in FIG. 2 is similar to that of the sheet topology shown in FIG. 4 and the applicant's previously mentioned patent of the present invention.
It is not due to the surface texture of the processing roll that embosses the thin plate surface. Rather, the microscopic amount of sheet material is extruded backwards into the bowl (due to the right-angle loading exerted by the work roll surface on the sheet surface) and the large thickness reduction rolling of the sheet. It is subjected to a combination of abrasion of the material extruded rearward due to significant relative movement between the surface of the work roll and the surface of the lamella which occurs in between.

A laser or electron beam device (not shown) is used to form craters 18 (see FIGS. 3 and 8) on the surface of the work roll, each crater 18 having a central recess 16 and And a raised annular rim 20 surrounding the recess. The beam of such a device causes each crater 18 to be carried on the surface of the roll by the amount of thickness reduction performed, the alloy of the sheet 12 being thinned and the temper, the cooling used in the thickness reduction process. Precise positioning at size and frequency determined by the type and temperature of materials and lubricants and the rate at which the thickness reduction occurs. A typical depth of the recess in the surface of the processing roll is generally 50.0 μm to 25 μm.
It is in the range of 0.4 μm to 10.0 μm for a generally circular depression with an outer diameter in the range of 5 μm.

When a pulsed laser beam having a Gaussian intensity distribution around the center of the beam or a beam having a Gaussian current density emitted by an electron beam device strikes the orthogonal roll surface forming the crater 18, the energy of the beam. Since the density is significantly sufficient to melt the roll material, the rim 20 of roll material is recessed 16
Formed around (below the beam). Due to such melting, a subsequent rapid movement of a portion of the molten metal around the recess 16 occurs due to surface shear resulting from variations in the melt pool surface tension with temperature, as described above. In order to prevent such rim material from leaving the roll surface during rolling, which contributes to the above-mentioned wear debris problem, the rim material is removed, so that
The surface topology of the processing roll shown in FIG. 13 is obtained,
Therefore, the roll surface is preferably coated with a hard, dense material, such as chrome, to provide a durable, long-lasting wear surface. For example, abrasive removal of the rim material results in a substantially smooth surface finish (FIG. 13) around the indentations 16 in the surface of the work roll. The entrance area to the recess 16 shown in FIG. 13 is also smooth, so that the surface material of the sheet is extruded at the same time during the large thickness reduction of the sheet and rubs against the inner area of the depression. Cutting edge for producing debris due to wear on the
It is especially important not to act as s). The background working roll surface finish 30 is also substantially smooth, as previously described, so rolling with a working roll having such an uneven texture results in a glossy strip or sheet product. If the sheet thickness reduction ratio is large, the resulting smearing
The step g) enhances the brightness of the rolled product as described above. If the material of the rim 20 is not removed, as described above, abrasion may cause debris and damage to the backup roll. In addition, the work roll surface crater configuration (FIG. 3) produces elongated parallel tracks 32 on the surface of the sheet as the sheet is significantly thinned. The track 32 substantially follows the rolling direction, as shown in FIGS. 9, 10, and 12. Such surfaces are not aesthetically pleasing surfaces and products, and have tribological properties that enhance sheet formation during secondary forming processes such as drawing and stamping. As such, it is typically not desired by automotive sheet metal customers.

In contrast, removing the rim material 20 and forming curved protrusions or raised mounds on the sheet during the rolling process involving a large percentage sheet reduction ratio as described below. By doing, a thin plate product that is substantially free of debris due to abrasion is manufactured,
And the surface life of the backup and processing rolls is substantially extended while at the same time producing the plate or sheet product desired by the customer.

FIGS. 15, 17, 19 and 21 to 23 show a thin plate rolled by the work roll surface texture structure shown in FIG. 13 during a large-scale thin rolling operation of the thin plate in the final stand. It tracks microscopic parts of the surface. These figures show that the depression 16 exits from the inlet region at the roll bite as well as the influence of the right angle load of the working roll on the plate as it passes through the roll bite and the kinematics of the roll bite. The same two recesses (16a and 16
identified as b) shows the most significant or significant changes that occur on the sheet surface at three selected times. 16, FIG. 18, and FIG.
FIG. 20 is a photomicrograph of a representative portion of the thin plate surface showing changes in the uneven skin structure of the surface of the thin plate that occur at these stages of the rolling process shown in FIG. 5, FIG. 17 and FIG. 19. FIG. 21, FIG.
2 and 23 are topographical diagrams drawn by the needles of a sheet surface uneven skin structure element similar to the sheet surface uneven skin structure element shown in FIGS. 16, 18 and 20, respectively. FIG.
5 to 23 capture the highly transient nature of the sheet surface roughness as it passes through the roll bite. Upon roll biting, at least one work roll surface texture is exposed by microscopic indentations (FIG. 13) and is finished using the method of the present invention.

In FIG. 15, before the indentations 16a and 16b in the surface of the two rolls raised according to the invention reach the neutral plane 24 inside the roll bite,
At (first time t ₁ ), a load P _A perpendicular to the surface of the thin plate 12 is applied. This neutral plane is also indicated by the vertically oriented dash line 24 drawn on the far right in FIG. The leading edge of the bank of recesses 16b, shown as LB _{2 in} FIG.
It is at a distance d ₁ from the neutral surface 24. The bank of indentations 16 is defined as a mouse, ie a surface turning ring with a small width just below the entrance area of the indentations 16. This area is the area where contact with any extruded sheet metal surface material is likely to occur. The contact area between the bank of indentations and the extruded sheet metal surface material can be thought of as approximating a fan or solid triangle with a sum of angles of 180 °. The diameter of each indentation 16 is indicated by a "D" in FIG. 15, although in practice, due to the various conditions that exist during the time the roll is textured, There may be a slight distribution of diameters within the array of depressions. They are,
Pulse energy density forming the beam, beam focusing,
Vibration of machine tools, alloying agent inside roll surface (all
This includes irregular absorption of beam energy by oying agents and variations in associated control electronics used to texture the work roll.
As described above, the normal load and the change in speed between the work roll and the thin plate surface cause a small amount of the thin plate surface material to be indented.
It partially flows into a and 16b, ie is extruded into these depressions. The two front protrusions 22a and 22b are the result of the action of a right angle pressure and due to the fact that the speed of the sheet surface is slower than that of the roll surface.
Are formed along the rear region of the banks of the recesses 16a and 16b. These banks are labeled TB ₁ and T in FIG.
This is indicated by B ₂ .

A simple understanding of the formation of protrusions can be obtained by the following analogy. Point M of recess 16a in FIG.
Are arranged on the rear part of the bank of the recesses 16a. This sloping bank resembles the more familiar slopes of water skis. However, the surface of the water ski lacks the lateral curvature of the bank of depressions. When a person is riding on a water ski, the ski typically has a small angle of inclination with respect to the water surface in front of the skier, which tilts with the forward speed of the skier and below the skier's ski. Accumulate or produce crests. If the skier follows the movement of the skier and follows this crest over time, the skier knows that this wave is simply a traveling wave. The strength of this wave is enhanced if the skier hits a water surface area. In the water area, the speed of water is strongly opposite to the direction of skier movement, which may occur, for example, when the boat is running parallel to the direction of skier movement. On the other hand, if the skier hits a water surface area where the water is vigorously moving in the direction of the skier's movement, the wave strength may be reduced. Therefore, each protrusion has a solid or plastic wave formed by partially extruding a microscopic portion of the sheet metal surface material back into the depression of the roll surface. I can think. Such extrusion occurs predominantly along the trailing edge of a bank of depressions that have not yet reached the neutral plane. Please refer to FIG. 15 again. The sheet metal surface material that partially fills the depressions rubs in the rolling direction as the material is extruded. This is due to the relative surface movement between the roll and the sheet surface before the time for the partially filled depressions to pass through the neutral plane.

FIG. 16 is a photomicrograph at a magnification of 425 × showing the structure of the protrusions on the surface of the 2008 aluminum alloy thin plate. Such extrusion is obtained from the partially rearward extrusion mechanism shown in FIG. 15 and 16 show two front protrusions 22a and 22b. Each protrusion, as can be seen from FIG.
It has the form of a "crescent". The distance between the edges of the protrusions corresponds to the center-to-center separation between the two depressions 16a and 16b on the surface of the roll on which the protrusions (FIG. 15) are formed. The protruding edge of the protruding portion faces the rolling direction. Therefore, the inner edge of the projection, i.e. the concave edge, faces the entry point of the roll bite. There is a beveled end of material that is raised to form the tongue of the protrusion. Therefore, if one leans from the left side to the right side along this slope, that is, from the left side to the right side along the front protrusion in FIG. 16, the two sides forming a right angle to each lateral direction, that is, the rolling direction. It will curve in one direction and will tend to a slope that falls rapidly along the tongue of the protrusion. This is best shown in FIG. 21, which is a stylized topographical map of a representative area of the surface shown in FIG. The protrusions resemble waves on the surface of the ocean.
Also, the lateral curvature of the protrusion is clearly visible. The height of the protrusion is in the range of 0.25 μm to 3.0 μm. The accumulation of metal forming the protrusions is due to the scraping of the extruded sheet material by the fan-shaped region at the trailing edge of the recessed bank. The crescent shape of the protrusion in FIG. 21, which appears to face the shape of the depression, is obtained from the following two elements. That is, (a) the metal is extruded only partially into the depression, forming a plastic wave that is stationary with respect to the depression. (B) The maximum "pushing force" that the metal senses as it flows into the recess is obtained from the trailing edge of the bank of recesses.

At the subsequent time t ₂ > t ₁ , that is, in FIG. 17, the thin plate and the processing roll surface including the interface shown in FIG.
Move toward. However, the sheet and work roll surfaces reach near the neutral plane at slightly different times due to the above-described rubbing action which causes the sheet surface to slide over the roll surface. Therefore, the protrusions 22a and 22b
Is then the untextured area 30 on the roll surface.
Are rubbed towards the exit area and finally flattened into the lamella surface before the time when the lamella surface reaches near the neutral plane. The velocity of the lamina and the velocity of the roll surface are approximately the same, that is, near the neutral plane 24 there is a small area surrounding the neutral plane. Therefore, an observer riding when the roll surface is near the indentations 16a and 16b, at his own speed,
Or one would observe the surface of the sheet at a velocity close to that velocity. In these conditions, the relative scraping of the sheet surface is negligible, thereby leaving only the effect of normal pressure on the sheet applied through the work roll surface. This right-angled pressure is then exactly the same way the notary seal embosses a legal document,
The thin plate is recessed 16a in the form of mounds 26a and 26b.
And substantially forced into 16b. Theoretical calculations of right-angle loads during rolling predict that the right-angle loads on the surface of the sheet are highest near the neutral plane. This is why the sheet material near the neutral plane "partially fills" the depressions more uniformly and then forms the mound. Calculation of right-angle loads during rolling is described in McGraw-Hill (1987) pages 551-574, Chapter 7, Jay. It is discussed in a paper by Chakraberty entitled Theory of Plasticity.

FIG. 18 shows a set of microscopic mounds 42 on the sheet surface formed by the process described in FIG.
It is a microscope photograph of 5 times magnification. FIG. 22 is a topographical diagram drawn with a needle in a typical region of the surface in FIG.

Depressions 16a and 16b on the surface of the processing roll
After passing through the neutral plane 24 of FIG. 17, the velocity of the sheet surface begins to exceed the velocity of the roll surface due to the constant amount of plastic deformation, resulting in mounds 26a and 2
6b is flattened back into the sheet surface. Therefore, the mound of the sheet surface formed when the sheet passes near the neutral plane and near the exit area is recessed 16
a and 16b respectively banks LB ₁ and LB ₂
17 is abraded by the trailing edge of the
When the lamella 12 moves faster than the roll 10, the mound is then flattened.

Depressions 16a and 16b on the surface of the processing roll
Moves toward the exit area and reaches the vicinity of the exit area shown in FIG. 19 immediately after the portion of the thin plate shown in FIG. 19 reaches the exit area, the rear protrusion (plow) 28a
And 28b are formed on the sheet surface shown in FIG. FIG. 20 shows a surface of an aluminum sheet having rear projections 28a and 28b formed by the mechanism of FIG.
It is a microscope photograph of 25X magnification. The convex edge of each front protrusion faces the neutral plane, and thus the concave edge of each front protrusion faces the rightmost roll bite exit plane in FIG.

FIG. 23 is a topographical view drawn by the needle of a representative region of the surface shown in FIG. 20 including front protrusions (plows) 22a and 22b formed by the mechanism shown in FIG. FIG. 24 is a needle topographic map of a sheet surface rolled by the method of the present invention with the rolling process interrupted. A mound formed on the sheet surface near the neutral plane is shown with a front projection formed on the sheet surface as the sheet enters near the exit region. FIG. 24 further demonstrates the transient nature of the sheet topography during large scale thin rolling of the sheet. The texture of at least one work roll is provided by the topographical diagram of FIG.

Therefore, when the surface of the thin plate comes out of the biting of the roll, the surface of the thin plate has the uneven structure of the front plow portion shown in FIGS. 23 and 24.

FIG. 25 shows an aluminum alloy 200 using a milled work roll in a single mill stand.
Figure 8 shows roll force versus percentage sheet thickness reduction ratio recorded during 0-8F four-high rolling. As the percentage sheet thickness reduction ratio increases, the roll force increases non-linearly until the mill capacity (ie 100 kilopounds) reaches 45%. At this point, a reduction of more than 45% could not be achieved, so the rolling process had to be terminated.

FIG. 26 shows the change in roll force with respect to the percentage thin plate thickness reduction ratio under the same conditions as in FIG. 25, but under the condition that the working roll has the bowl structure of the present invention shown in FIG. The roll force increases at a slightly slower rate than the roll force shown in FIG. 25, which shows more favorable tribological conditions when the textured structure of the present invention is used. The rolling force capability of this rolling mill is not reached until a percentage sheet thickness reduction ratio of the order of 70% is achieved. Ejection of all or part of the lubricant at the sheet / working roll interface when a microscopic amount of sheet surface material is extruded into the bowl 16 in the manner shown in FIGS. 2, 15, 17 and 19. With the uneven surface structure of the bowl that conveys the lubricant to the bite of the roll, the textured processed roll surface is not subjected to substantial rolling and grinding, so excessive friction during roll biting is minimized. It has been limited to.

27 and 28 are similar to FIGS.
6 shows a comparison of changes in roll torque with respect to a percentage thin plate thickness reduction ratio when rolled using a grinding roll as well as a textured roll according to the present invention under the conditions quoted in FIG. Also, the torque capability of the stand (3000 foot pounds) when rolling with textured work rolls until a 70% reduction is achieved.
(Fig. 28), the grinding roll (Fig. 2
Since the rolling process using 7) had to be interrupted at approximately 2700 foot pounds when a reduction ratio of 45% was achieved, textured work rolls were rolled in a single rolling stand. The process capability can be extended well beyond the capability achievable with grinding rolls. FIG.
5 to 28 show the ability of the rolling mill to artificially impose on the rolling mill for the surface finishing of the research work roll when rolling with the work roll textured by the method of the present invention in a single stand. Clearly demonstrating that it is possible to extend well beyond these limits, and therefore
The rolling mill production capacity can be further increased.

In addition to the above-described improvement of the rolling process ability due to the uneven surface structure of the working roll of the present invention, the structure 2 of the rear side protruding portion which remains on the surface of the thin plate when the rolling roll comes out of the biting
8a and 28b enhance lubrication and metal flow during subsequent metal forming operations, such as pressing the body fenders through two important mechanisms. In the first mechanism, the rear projections 28a and 28b can provide lubricant into the lamella / machine tool interface due to the crescent-shaped configuration. In the second mechanism,
The rear protrusion acts as a "barrier" to impede the flow of lubricant along the sheet metal / machine tool interface. Since the lubricant does not flow freely in and out of the unhindered interface, the lubricant film is used continuously in later stages of the molding process. This reduces galling, minimizes premature damage to the sheet due to tearing, and protects the machine tool surface. A discussion of lubricant hindrance at lubricated interfaces is given in Part 1 of Volume 100 of the ASME Journal of Lubricating Tribology.
Pages 2 to 17 Patia and Etch, S. Shen in a paper entitled "Average Flow Model for Determining the Effect of Three-Dimensional Roughness on Partial Hydrodynamic Lubricants".

It should also be noted that skidding between the sheet and the surface of the roll does not even occur in the extreme case of textured "mirror finish" working rolls when using the method of the present invention. Should be. This is due to the fact that the protrusion / mound formation is the main traction mechanism in the meshing of the rolls, hence the "sideslip" is the rolling mill in which the large percentage of thin sheet reduction mentioned above is adopted. Does not occur during rolling in a single stand. According to the method of the present invention, skidding is independent of background roll roughness, although background roughness in the form of directional grinding can contribute to overall traction between the sheet and roll surface.

Further, it should be noted that the method of the present invention produces a sheet texture that is completely different from the surface texture of sheets produced by common roll texturing techniques, such as laser and electron beam texturing. is there. The crater rims 20 (FIG. 8) or asymmetric humps (FIG. 11) produced in the above melting and surface shearing processes due to the energy pulses of these techniques are typically in place along the roll surface. Left in
There is no replacement for the crater rim and hump.
Therefore, these rims are on the surface of the sheet metal (Figs. 4 and 5).
Embossing, i.e. indenting, microscopic depressions inside. Such a recess is arranged below the surface of the thin plate. As the shape of castle plateaus and valley depressions where an annular rim on the work roll surface forms a valley moat on the sheet surface, which is then filled with lubricant before the stamping operation. You can think of the embossed annular crater of Figure 4 and the castle plateau
In essence, it is a flat area that is kept to a nominal roll surface roughness and that has no essential effect on enhancing the lubrication effect in the subsequent laminating step. However, the method of the present invention is just the opposite effect, because by this method, when the thin plate flows out from the final stand of the rolling mill, a microscopic protrusion as the final thin plate surface uneven skin structure is obtained. Cause The protrusions are raised relative to the average roughness of the sheet. Also, the protrusions serve the dual function of enhancing lubrication at the lamella / machine tool interface instead of trapping a single lubricant done in the form of an annular crater. The protrusions not only carry the lubricant into the interface of the sheet metal / machine tool, for example the interface formed in the pressing operation, but also in the path of the lubricant flow along such interface. It acts as an obstacle and therefore sends the lubricant along the interface into the later stages of the laminating step to maintain the lubricating function persistently.
Moreover, since the lubricant is not generally confined by the individual protrusions, the lubricant carried into the interface by the protrusions is easily distributed at the sheet metal / machine tool interface during the pressing operation. . This does not occur frequently in the case of annular crater textures embossed on the surface of the sheet during small scale rolling. The reason is that a small amount of lubricant may remain inside the remainder of the annular "valley" region on the sheet after the sheet forming process is complete.

The protrusions of the present invention are substantially smaller in overall size than the annular crater and hump configurations described above with reference to FIGS. 3 and 11. In general, automobile manufacturers do not want the texture of the lamellae to be visible through the coating layer, and this problem has been associated with the latter two texture morphologies. Therefore, the protrusion (plow) is made so that the constituent parts of the automobile cannot be seen through the paint finish portion.

[Brief description of drawings]

FIG. 1 is a diagrammatic view of two rotary working rolls of a rolling mill that thins the thickness of a metal material in the middle.

2 is an enlarged partial cross-sectional view of the intermediate surface between the working roll of FIG. 1 and a metal material, the surface of the upper roll having a minute, shallow, bowl-shaped recess in which the sheet surface material A small amount is extruded.

FIG. 3 is a line drawing topography of a portion of a work roll surface displaying a hexagonally arranged annular crater structure by an electron beam shaping device.

FIG. 4 is a line drawing topography of an aluminum sheet surface embossed with a crater structure on the surface of a work roll during a small thickness reduction step.

FIG. 5: Line drawing topography of an iron sheet surface imperfectly embossed with crater structures on the work roll surface.

FIG. 6 is a diagram showing a contact width of a Hertz wire between a backup roll and a processing roll of a rolling mill.

FIG. 7 is a diagram of a hexagonal crater pattern (as shown in FIG. 3) provided on the surface of a work roll by an electron beam device, the basic unit of which is a parallelogram.

FIG. 8 is a line drawing topography of a single annular crater formed on the face of a working roll by the double pulse of an electron beam shaping device.

9 is an asymmetric "hump" (raised) C shown in FIG.
The O ₂ laser forming, shows 35% to be rolled to thickness decreasing the two rubbing surfaces of the aluminum sheet.

10 is an asymmetric "hump" (raised) shown in FIG.
The CO ₂ laser forming, shows the rubbing surfaces of the two aluminum sheets rolled with the thickness decreasing to 60%.

FIG. 11: Mechanically interrupted CO ₂ laser and to Bragard et al., 1989.
Line drawing topography of a portion of a work roll surface having an asymmetric hump structure produced by the use of a suitable gas according to the method described in U.S. Pat. No. 4,806,731, issued Feb. 21, 2014. .

12 is a micrograph (magnified 200 times) of a 2008 aluminum alloy sheet that has been reduced by 40% using the surface of a work roll having the annular crater morphology shown in FIG.

FIG. 13: To create a smooth entrance area to the bowl,
Smooth, bowl-shaped line drawing topography of steel work roll surface with crater rim removed.

FIG. 14 is a line drawing topography of a surface of a 2008 aluminum alloy sheet rolled by a reduced thickness rolling method with a working roll formed by an electric discharge method.

FIG. 15 shows in more detail anterior plow formation (prior to reaching the partial roll neutral surface) using the method of the present invention (post-plow formation later).
FIG. 3 is an enlarged partial sectional view of an intermediate surface between the processing roll and the sheet surface of FIGS. 1 and 2.

16 is a photomicrograph of the anterior plow of FIG. 15 magnified 425 times.

FIG. 17 shows the first two work roll surface recesses shown in FIG. 15 with the plows shown in FIGS. 15 and 16 being abraded and flattened by the sheet surface material into the two recesses on the work roll surface. FIG. 7 is an enlarged partial cross-sectional view of the intermediate surface between the processing roll and the sheet surface after further performing plastic deformation in the partially filling step and moving to near the stacking neutral surface.

FIG. 18 is a photomicrograph at 425 × magnification of a stack of metals formed as the sheet passes through the neutral plane.

FIG. 19: The recesses in the first two work roll surfaces shown in FIG. 15 have moved to near the exit face of the roll bite to flatten the loading of FIGS. 17 and 18 and the sheet surface material to the work roll surface. Of the seat surface at a position beyond the neutral plane in roll engagement after the plastic plow is further performed in the step of partially filling the two recesses of FIG.

FIG. 20 is a micrograph of the posterior plow material illustrated in FIG.

FIG. 21 is a line drawing topography of an exemplary sheet surface area including the anterior plow shown in FIGS. 15 and 16.

FIG. 22 is a line drawing topography of a representative sheet surface area with the same loading as shown in FIGS. 15 and 16.

FIG. 23 is a line drawing topography of a representative sheet surface area with the same posterior plow shown in FIGS. 19 and 20.

FIG. 24 shows the loading formed on the part of the sheet surface in the area of the neutral plane of the roll bite and the adjacent cross section of the same sheet surface which intersects the neutral plane but has not yet reached the exit plane. The figure which shows the relative size with the formed back plow.

FIG. 25 is a diagram showing a change in rolling force with respect to a sheet thickness reduction ratio that can be achieved by a polishing roll in a four-stage rolling process.

FIG. 26 is a diagram showing a change in rolling force with respect to a sheet thickness reduction rate, which can be achieved by the work roll structure of the present invention in a four-stage rolling process.

FIG. 27 is a diagram showing a change in rolling torque with respect to a sheet thickness reduction rate that can be achieved by a polishing roll in a four-stage rolling process.

FIG. 28 is a diagram showing a change in rolling torque with respect to a sheet thickness reduction ratio that can be achieved by the work roll structure of the present invention in a four-stage rolling process.

FIG. 29. Rolled 5 by the work roll weave described in our US Pat. No. 4,996,113.
Line drawing topography of 182 aluminum alloy sheet.

[Explanation of symbols]

 10 Upper Roll 11 Lower Roll 12 Metal Sheet 14 Surface 16 Center Recess 18 Crater 20 Annular Rim 22 Front Plow 24 Neutral Surface 26 Loading 28 Rear Plow 30 Roll Surface Finish 32 Parallel Tracks

Continuation of the front page (72) Inventor Lewis G. Hector, Jr., USA, Alcoa Center, Pennsylvania, Technical Drive 100, Alcoa Technical Center

Claims (7)

[Claims] 1. A large reduction in strip thickness in a rolling mill is achieved by the partial back-extrusion of the strip material into a smooth inlet bowl-shaped recess formed in the roll surface. A rolled bright metal product having a large number of fine plows formed on at least one side by the abrasion of the strip surface material due to the relative speed of the strip and the roll that occurs when smashed. 2. The strip material is aluminum,
A lustrous product having microplows used to make a vehicle body member, the plow acting as a carrier for a lubricant and as a barrier for the controlled lubrication of a tool used to make the body member. Rolled bright metal product according to. 3. A surface plow which is easily flattened on the surface of a thin sheet product by a tool used in a pressing operation for producing a metal part from the product, and the finished part has a glossy surface and is directional. Adds a textured surface structure that is substantially free of textured textures and is capable of substantially mitigating any traces of surface textured surface of any sheet by the paint finish applied to the shiny side of the part. Thin plate products. 4. A mirror-reflecting surface formed of an isotropic surface and a mirror-finishing surface of the rolling mill, which is deterministically formed by a working roll of a rolling mill, which definitively has individual smooth inlet bowl-shaped recesses. It has a textured surface structure consisting of a reflective surface part with a plow, and when the material of the aluminum sheet is extruded into the recess, and when a large thickness reduction is performed at the final stand of the rolling mill, it is processed. A rolled aluminum product, which is rubbed by the action of the relative speed of a roll and a thin metal plate to form a rolled aluminum product. 5. Having at least one isotropic textured surface of the micron-sized plow located in the reflective surface portion of the rolled product, the following steps: The roll is passed between two lubricated and rotating working rolls, which are rolls having a textured textured surface configured with deterministically arranged minute smooth inlet bowl-shaped recesses, the aluminum material Is compressed between the rotating working rolls for processing at a working rate of about 70%, a movable (temporary) plow on at least one side of the aluminum material, and the material after the aluminum material exits the working roll. A rolled aluminum product formed by the steps of using the compressing step to form a plow that remains on one side of the. 6. At least one isotropic textured surface forming surface of the micron-sized plow disposed on the reflective surface portion of the rolled product, the following steps: 408 kgm (3000 foot pounds) of aluminum material. With a degree of torque capacity of the stand, at least one roll of the stand of the rolling mill is a roll having an uneven skin structure surface having a minute smooth inlet bowl-shaped recess in which is definitely arranged. Through a lubricated, rotating working roll, compressing the aluminum material between the two lubricated, rotating working rolls, and a movable (temporary) plow on at least one side of the aluminum material, and the aluminum. Formed by the steps of using the compression step to form a plow such that the material remains on the one side after exiting the work roll Rolled aluminum products. 7. A specular reflection surface having a reflecting surface portion and a microscopic plow arranged on the reflecting surface portion and having a substantially isotropic uneven skin structure. It has an isotropic textured surface structure and has consistent dimensions in a pre-determined, adjusted micron size range, with mirror-finished features and individual smooth inlet bowl-shaped recesses. A bowl-shaped recess, which is adapted to be formed by the working rolls of a rolling mill having an aluminum material forming the sheet product and into which the sheet product material enters the recess when a large reduction in the wall thickness of the sheet is applied. An aluminum sheet product in which an aluminum material penetrates into the inside to form a plow and an isotropic plow texture structure.