Method and apparatus for producing metal sheets

Abstract

Metal sheets (13) are produced from strand-shaped profiles (8) having a low thickness, made of magnesium or magnesium alloys by way of an extrusion system (1). The open or closed extruded profile (8) exiting the extrusion die (6-7) of an extrusion press (1) is shaped to obtain a flat metal sheet (13) and is then subjected to a defined shaping process by way of stretch-forming. The system for carrying out the method is essentially composed of an extrusion press (1) comprising a die plate generating the extruded profile and a shaping unit (5) following the die plate, wherein the shaping unit (5) is composed of a severing unit (2), a bending unit (3), and an unrolling unit (4).

Claims

1. A method for producing metal sheets from strand-shaped profiles having a low thickness made of magnesium or magnesium alloys, an extruded tubular profile being produced and cut corresponding to the length of the metal sheet to be produced in a preceding method step, the extruded tubular profile having a longitudinal opening along a peripheral surface line thereof, characterized in that in a first step, the longitudinal opening of the extruded tubular profile is pushed onto two displaceable angled gibs and bent open to obtain a U-shaped profile by moving the angled gibs apart; in a second step, the U-shaped profile is transferred into an unrolling unit, gripped by gripping elements on the longitudinal sides of the U-shaped profile, and shaped by outwardly moving the gripping elements to obtain a metal sheet; and in a third step, the metal sheets are subjected to defined shaping by lateral stretch-forming, wherein all steps of shaping the extruded profile to obtain the metal sheet take place in a temperature range above 200° C.

2. The method according to claim 1, characterized in that shaping of the U-shaped profile to obtain a metal sheet is additionally supported by a roller pair being moved into the U-shaped profile and each of the individual rollers being moved towards edge regions located on the longitudinal sides.

3. A method for producing magnesium or magnesium alloy metal sheets from tubular profiles, comprising: providing an extruded tubular profile made of magnesium or magnesium alloy having a length corresponding to the length of the metal sheet to be produced and a longitudinal opening along a peripheral surface line thereof; pushing the longitudinal opening of the extruded profile onto two displaceable angled gibs; moving the angled gibs apart to bend open the extruded profile and form a U-shaped profile; transferring the U-shaped profile into an unrolling unit; gripping longitudinal sides of the U-shaped profile by gripping elements and outwardly moving the gripping elements to form a metal sheet; and stretch-forming the metal sheets to obtain a defined shape, wherein all steps of shaping the extruded profile to obtain the metal sheet are performed at a temperature above 200° C.

4. A system for producing metal sheets from an extruded tubular profile, comprising: an extrusion press (1) comprising a die plate generating the extruded tubular profile; and a shaping unit (5) following the die plate, wherein the shaping unit (5) is composed of a severing unit (2) for cutting the extruded profile corresponding to the length of the metal sheet to be produced, a bending unit (3) for bending the extruded profile into a U-shaped profile by moving apart angled gibs, and an unrolling unit (4) having gripping elements in form of floating collets connected to hydraulic cylinders for unrolling the U-shaped profile into metal sheets and for stretch-forming the metal sheets.

5. The system according to claim 4, characterized in that the unrolling unit (4) in addition to the gripping elements comprises two movable rollers that can be moved into the U-shaped profile, wherein the individual rollers can be moved away from each other in the direction of the longitudinal edge regions.

Description

(1) The invention will be described in more detail based on one exemplary embodiment. In the drawings:

(2) FIG. 1 shows a composition of the system in terms of the principle thereof;

(3) FIG. 2 shows a tool concept;

(4) FIGS. 3a to b show variants of the profiled ends;

(5) FIG. 4 shows the expansion by way of rollers;

(6) FIGS. 5a to g show the tool concept for open profiles.

(7) FIG. 1 shows the composition of the system in terms of the principle thereof for carrying out the method for producing metal sheets from extruded profiles. The system is essentially composed of an extrusion press for producing an extruded profile and a forming unit 5. The forming unit is composed of a severing unit 2, a bending unit 3, and an unrolling unit 4.

(8) Using the extrusion press 1, a round billet made of a magnesium alloy is formed to obtain an extruded profile, for example a tubular profile. The extrusion press 1 is stopped when the tubular profile has reached the length that corresponds to the predefined length of the metal sheet. The tubular profile is cut to size by way of the severing unit 2.

(9) The severing unit 2 can be composed of a revolving jet nozzle, a laser, cutting rollers, or a co-rotating saw. If the severing of the tubular profile is carried out by way of metal-cutting, a suction device is provided so as to minimize a risk of fire from magnesium chips or magnesium dust. There is also the option to introduce a notch having a depth of 25% to 85% of the wall thickness at the separation point and to tear off the section of the tubular profile.

(10) The severed section of the tubular profile is then forwarded to the bending unit 3. Here, the section of the tubular profile is severed along a peripheral surface line and bent open to obtain a U-shaped profile by way of a slotted wedge and optionally several rollers. Contact with the tube occurs only in regions of the cut edges, which are later located in the waste region of the metal sheet. Severing can take place, for example, by way of a longitudinally displaceable suction jet nozzle, a laser cutting device or the like.

(11) After severing and bending open to obtain a U-shaped profile, the same is forwarded to the unrolling unit 4. This unit is composed of a flat base area and two movable gripping elements, wherein the gripping elements grip the longitudinal sides of the U-shaped profile and unroll the U-shaped profile to obtain a flat metal sheet.

(12) FIG. 2 shows a tool concept for a bridge die for extruding open tubular profiles 8. The bridge die is essentially composed of the die plate 6 and the mandrel part 7, between which a gap is formed that determines the wall thickness of the profile 8. Profiled ends 9 are provided at the bottom open end of the profile 8.

(13) FIGS. 3a and 3b show variants of the profiled ends 9. These can be designed to be angled or as thickened regions.

(14) After the open tubular profile 8 has left the extrusion press, it is expanded. In a first step, the profile 8 is cut to the appropriate length by way of a severing unit. The expanding may take place by way of forming rollers 10. As is shown in FIG. 4, these form a kind of rail guide and expand the tubular profile 8 to obtain a U-shaped profile 8.

(15) However, it is also possible to push the longitudinal opening of the severed open tubular profile 8 onto two displaceable angled gibs 11, or the open tubular profile can be pushed onto the displaceable angled gibs 11 immediately after leaving the press die (FIG. 5a). The open tubular profile 8 is bent open in a U-shaped manner by moving the angled gibs 11 apart (FIG. 5b).

(16) The U-shaped profile 8 is then forwarded to an unrolling unit 4. Here, the longitudinal sides of the profile 8 are gripped by way of the collets 12 (FIG. 5c, FIG. 5d) and unrolled to obtain a flat metal sheet 13 (FIG. 5e). The profiled ends 9 ensure secure gripping and holding of the profile 8.

(17) The collets 12 have a floating design and are connected on one side, or on both sides, to hydraulic cylinders, whereby an adaptation to the profiled ends 9 of the longitudinal edges of the profile 8 is achieved. Slightly concave or convex deflection at the profiled ends 9 on the longitudinal edges can thus be compensated for.

(18) Following the hydraulic chucking process, the unrolled profile 8 is stretch-formed linearly by way of the hydraulic cylinders. The overpolishing rotational movement of the collets 12 is carried out by way of the pivotable hydraulic cylinders. In this way, the stretch-formed material is free of interfering bending forces (FIG. 5f).

(19) During final stretch-forming, the floating collets 12 are oriented against fixed stops, whereby consistent stretch-forming across the entire sheet metal width is ensured. So as to minimize the heat dissipation via the collets 12, these are provided with a ceramic coating.

(20) After the stretch-forming operation, the collets 12 are opened, and the stretch-formed metal sheet 13 is pushed out in the longitudinal direction by way of a pneumatic cylinder. The stretch-formed metal sheet 13 can subsequently be forwarded to a metal-forming working operation, for example using pressing, stamping or the like. However, it is also possible to cut the stretch-formed metal sheets 13—removing the profiled ends—and to stack the metal sheets 13.

(21) A considerable advantage of the method and of the system is that stretch-forming of the metal sheet in the transverse direction can be carried out by way of the gripping elements. Stretch-forming in the transverse direction can be carried out in a range of 1% to 10%. As a result of stretch-forming the metal sheet, it is not only possible to decisively improve flatness, but also to achieve a thickness configuration for the metal sheet. It is also crucial that no surface defect-causing contact areas are present at what will later be the visible surfaces.

LISTS OF REFERENCE NUMERALS

(22) 1—extrusion press 2—severing unit 3—bending unit 4—unrolling unit 5—shaping unit 6—die plate 7—mandrel part 8—open profile 9—profiled ends 10—forming rollers 11—angled gibs 12—collets 13—metal sheet