APPARATUS AND METHOD FOR EXTRUDING WIDE PROFILES

Abstract

An apparatus for extruding a material, the apparatus comprising: a block which includes two or more extrusion containers composed of heat resisting material, the containers being arranged to receive billets of the extruding material; a die set arranged downstream of the block including the two or more extrusion containers; and one or more rams, wherein the one or more rams are aligned with the axes of the extrusion containers and are arranged to push the billets of material through the extrusion containers into the die set; wherein the die set includes an upper die including two or more extrusion channels for extruding material from each of the extrusion containers, and a lower die incorporating a welding chamber, wherein two or more extruded billets from each of the extrusion channels are welded together and passed out through the exit of the die set.

Claims

1. An apparatus for extruding a material, the apparatus comprising: a block which includes two or more extrusion containers composed of heat resisting material, said containers being arranged to receive billets of the extruding material; a die set arranged downstream of the block including the two or more extrusion containers; and one or more rams, wherein the one or more rams are aligned with the axes of the extrusion containers and are arranged to push the billets of material through the extrusion containers into the die set; wherein the die set includes an upper die including two or more extrusion channels for extruding material from each of said extrusion containers, and a lower die incorporating a welding chamber, wherein two or more extruded billets from each of said extrusion channels are welded together and passed out through the exit of the die set.

2. An apparatus as claimed in claim 1, in which the extrusion containers are cylindrical.

3. An apparatus as claimed in claim 1, in which the axes of the extrusion containers are parallel to each other.

4. An apparatus as claimed in claim 1, in which the block comprises two or more independent containers which are held in position by bolsters.

5. An apparatus as claimed in claim 1, in which the block comprises a block extruder incorporating the two or more independent containers, the block extruder being held between bolsters.

6. An apparatus as claimed in claim 4, in which the bolsters are held by use of hydraulic pressure or other means.

7. An apparatus as claimed in claim 1, in which the containers or block extruder are made from hot extrusion tool material and the bolsters are made from cast iron or steel.

8. An apparatus as claimed in claim 1, in which the exit of the die set is arranged to be at an angle between 0 and 90? to the plane of the container axes.

9. An apparatus as claimed in claim 1, further comprising rolling stands downstream of the exit of the die set, in order to receive the extruded material and reduce the extruded thickness by hot rolling.

10. An apparatus as claimed in claim 9, further comprising one or more quenching baths downstream of the rolling stands.

11. An apparatus as claimed in claim 10, further comprising further rolling stands downstream of the quenching bath for further processing of the extruded material by cold rolling.

12. An apparatus as claimed in claim 1, in which the material to be extruded is selected from metals and alloys, in particular aluminium alloys, magnesium alloys, and steels.

13. An apparatus as claimed in claim 1, in which two or more blocks comprising extrusion containers, and associated rams are arranged to feed into the same die set.

14. A method of extruding a sheet of material using the apparatus as claimed in claim 1, the method comprising: pre-heating two or more billets of material; transferring the pre-heated billets of material to the two or more extrusion containers; pushing the billets through the containers using the rams, such that the material is forced through the extrusion channels in the upper die; welding the extruded material in the welding chamber; and passing the welded material out through the exit of the die set.

15. A method as claimed in claim 14, further comprising a step of passing the extruded material through a set of rollers while hot to further reduce the thickness of the sheet.

16. A method as claimed in claim 15, further comprising quenching the rolled material.

17. A method as claimed in claim 16, further comprising cold rolling the quenched rolled material.

18. A method as claimed in claim 14, further comprising cold or hot stamping the extruded product.

19. A method as claimed in claim 14, in which two or more blocks comprising extrusion containers are arranged around a common die set and material is fed to each extrusion container and several billets of material are extruded simultaneously to increase productivity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 shows a schematic example of an apparatus according to the present invention comprising an extruder with multiple close-spaced containers in a block arranged to produce wide sheet material;

[0015] FIG. 2 shows a schematic example of two units according to the present invention arranged sideways, each comprising multiple containers;

[0016] FIGS. 3a and 3b show schematic representations of block configurations according to the present invention;

[0017] FIG. 4 is a graph showing the comparison of the applied force requirement between an apparatus according to the present invention and a conventional extruder when extruding a sheet of AA6061 material with a width, w=700 mm, and a thickness, t=5 mm;

[0018] FIG. 5 shows schematically the die set as used in an example of the present invention; and

[0019] FIG. 6 shows schematically an exploded view of the dies set as used in an example of the present invention.

DETAILED DESCRIPTION

[0020] The present invention processes raw material in the form of cylindrical billets which could be acquired by casting or other alloy agglomerating processes. The number of billets is the same as the number of extrusion containers within the apparatus. Prior to insertion into the apparatus of the present invention, the billets are heated in preparation for extrusion. For aluminium alloys, for example, the preheating might be in the range of 400-580? C. depending on the alloy. This would generally be around the solution heat treatment temperature. The heated billets are then placed into each one of the containers within the apparatus and simultaneously pushed by hydraulic system through the extrusion die set and formed into wide sheets/components. The container block and the die set can be used in cold state or hot state using internal and/or external heating.

[0021] Wide components which are not very thin could be formed directly by extrusion. To form very thin wide metal sheet, the hot extruded wide sheet can be hot rolled, to further reduce thickness and quenched for subsequent cold forming, if required. The hot rolled and quenched sheets could be further cold rolled for surface refinement and finally cut to size and shape. Alternatively, according to the production requirement, the quenched material could be cold or hot stamped to form contoured panel components.

[0022] An example of an apparatus according to the present invention to produce wide sheets/components by extrusion is shown in FIG. 1. The extrusion unit is designed as a block with multiple, close-spaced containers made of heat-resisting material. Each billet 2 of raw material is pushed by a ram 1 through the containers in block 3 into a die set 4. The multiple billets are extruded through the first part of die set 4 and then welded in the second part of die set 4 and pushed out to extrude the billets into a wide sheet or component 5. The welding chamber design and strength check of die set 4 is similar to conventional porthole die. The exit of die set 4 could be at any angle, 0 to 90? to the plane of the container axes, in order to increase the level of deformation strain within the extruded product. To further reduce extruded thickness in order to produce wide sheet, the extrusion may be transferred to rolling stands 6 for further thickness reduction.

[0023] The containers may be manufactured as cylindrical circular holes through the block, and the strength of the container is guaranteed by dispersing the internal stress generated by extrusion throughout the block 3. The axes of the containers are parallel and can be in one plane or in different planes depending on whether the extruded product is to be a flat sheet or have another final product shape. If the final product is not to be a flat sheet then it may be that the axes of the containers are in different planes, but the axes would still be parallel to each other. The arrangement of block 3 can be changed according to different cross-section and size of the product. FIG. 1 shows the situation that the axes of the containers are parallel and in one plane, but this could be varied depending on the required characteristics of the product.

[0024] FIG. 1 show only one extrusion unit, but multiple extrusion units also can be used for higher productivity. Referring to FIG. 2, extrusion units 7 and 9 work simultaneously in opposite directions, to push billets into the common die set 8. This technique can have a higher production efficiency compared with single extrusion unit. More extrusion units (more than two) can be assembled around the common die set to further raise the productivity by allowing a higher rate of extrusion through the multiple extrusion units. The number of containers in each block is sufficient to enable the correct width of product to be formed.

[0025] Referring to FIG. 3 (a), a schematic representation of a first configuration of the block according to an embodiment of the present invention is shown. In this configuration, the individual containers comprise separate cylinders. The block of the extrusion unit consists of several parallel close-spaced cylinders 11 which are enclosed, located and supported under load, by upper and lower bolsters 10. The containers 11 are made of hot extrusion tool material, and the bolsters could be made of cheaper material such as cast iron or steel, as they do not suffer from wear. The bolsters 10 can be held by squeezing them together over the cylinders 11 using hydraulic pressure or other means.

[0026] Referring to FIG. 3 (b), another configuration of the block according to an embodiment of the present invention is shown. In this configuration the extrusion container chambers are machined into a single hot work tool steel block, 12. The block is reinforced against extrusion pressure by being clamped between two bolsters 13 made of cheaper material.

[0027] Referring to FIGS. 5 and 6, further detail of the die set 4 as shown in FIG. 1 is given. As shown in FIG. 6, for sheet extrusion, the die set usually includes two parts, which are the deflector (also considered as upper die) and the lower die. The welding chamber is a critical area located in lower die, where multiple billets are forced to be welded together. It has huge influence on metal flow and weld quality. In the embodiment of FIG. 1, a die set 4 as shown in FIG. 5 would be used with the billet 2 of raw material being forced through the containers of the block 3 into the upper die of die set 4 and extruded out through the upper die into the welding chamber where the extruded billets are welded together and extruded out through the exit of the die set. In the embodiment of FIG. 3 with multiple extrusion units there would be an upper die associated with each of the blocks, each leading to a common welding chamber in the lower die and, in operation, each block would simultaneously push through the billets into the welding chamber resulting in a faster overall production rate.

[0028] Referring to FIG. 4, there is shown a comparison of the present invention with a conventional wide extrusion apparatus. The apparatus and method of the present invention substantially extends the width range of the product which can be produced due to reduced extrusion force for producing a wide product when compared with a conventional single container extrusion product. The effect of the number of containers n, on the force required for operating an extruder according to the present invention (F.sub.nd) and the force required for conventional large container (FD) is shown in FIG. 4, when extruding AA6061 sheet material with a width (w) of 700 mm and thickness (t) of 5 mm. This is a simplified calculation to show the difference between the apparatus of the present invention and a conventional apparatus and the actual forces and dimensions of the product may differ slightly, but this shows the effect of the present invention. The diameter sum of all containers for the apparatus of the present invention is assumed to equal to the extrudate width, i.e., w=D=n.Math.d, where d and D are the container diameter for each container in the apparatus of the present invention with n multiple small containers and the conventional extruder with a single large container, respectively. As shown in FIG. 4, when using two small containers, the force required for the apparatus of the present invention is halved compared with the conventional design, i.e. F.sub.nd=6?10.sup.5 kN. When using five small containers, the force required for the proposed design is less than a fifth that for the conventional design, i.e. F.sub.nd=2?10.sup.5 kN, and it keeps decreasing with increasing number of small containers.

[0029] The number of containers within the block is determined by the maximum extrusion force and the possible minimum size of extrusion container, which is related to the instability of the extruders, the amount of materials to be extruded, the length of cylinders, etc. The equipment space also has limitation on the number of containers. The number of containers cannot increase infinitely since there is a minimum size of each container. For the same extrusion product, more containers can decrease extrusion force but mean the size of container needs to be smaller. If the size of container is too small, then the corresponding extrusion stem feeding in to the welding chamber will be too thin to handle the extrusion force and the quality of extrusion welding could be affected due to low welding pressures.

[0030] An additional process of hot rolling-quenching and cold rolling could be performed after extrusion to further reduce thickness and/or to acquire a smoother surface finish, if required. These would be using conventional rolling and quenching techniques and are not described in further detail here. Alternatively, or in addition, in order to produce specific 3-D profiles, after hot rolling and quenching, cold or hot stamping, Hot Form Quenching (HFQ) could be utilised. Again, this would be done in a conventional manner and is not described in further detail here.

[0031] As will be clear from looking at the figures, and in particular by looking at FIGS. 3 and 4, the apparatus of the present invention is very flexible in that it is straightforward to change the number of containers within the block, whether in the form of a single block or as individual containers enclosed by upper and lower bolsters. It is therefore simple to extrude metal or alloy material of a range of widths, from small (for example 100 mm wide) up to large wide sheets (for example, up to 5000 mm wide or even wider). Similarly, a range of thicknesses of extruded sheet can be produced by the apparatus and method of the present invention, for example from thin sheets of 1 mm thickness or less up to thick plate type shapes of 25 mm or more can be produced.

[0032] While cylindrical containers and billets are preferred, the present invention could also use containers and billets of different shapes, for example triangular, cuboid, pentagonal, hexagonal, heptagonal, octagonal or star shaped. Such shapes are less preferred as they have higher tooling and manufacturing costs and have a shorter lifetime as the non-uniform stress concentration weakens the container more quickly than for a cylindrical container.