APPARATUS AND METHOD FOR EXTRUDING WIDE PROFILES
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.
Embodiments described herein relate to an apparatus and method for extruding wide profiles, in particular wide sheets of metal or alloy material for use in various industries, e.g. the transportation industry.
BACKGROUNDLightweight materials, such as aluminium and magnesium alloys, are in high demand for their use in modern transportation industries as construction components, especially in the automobile and aerospace industries in metal sheet or plate form.
An existing method for producing metal sheet or plate from a metal stock is rolling, which may employ multiple rolling passes with intermediate heating. Rolling techniques can be used to produce wide metal sheet for use in the automobile industry, such as aluminium alloy sheets with a width of 2200 mm or more, however, the multiple passes and heating often required in these rolling processes in order to make the sheet or plate wide enough make them energy intensive and therefore costly. For magnesium alloy, the cost is higher than for aluminium since the hexagonal close packed (HCP) crystal structure of magnesium is hard to deform by rolling. To overcome these drawbacks, a new manufacturing technique with fewer processing steps and reduced cost is desired.
Extrusion processes offer an alternative to rolling for producing metal sheet or plate and can also be used to manufacture straight lengths of a chosen complex-shaped cross-section. In contrast to rolling, extrusion is a one-step process and therefore requires no intermediate heating.
An existing extrusion method for producing metal sheet or plate involves extruding a thin curved profile (e.g. in a U-shape or W-shape) and then flattening the profile to produce a large flat sheet. Such a process may, for example, be that described in U.S. Pat. No. 2,681,734. The extrusion ratio to produce a wide sheet or plate via such extrusion methods from, e.g. cylindrical metal billets, would be very large and this results in large extrusion forces and pressures. Flattening the curved profile into a flat sheet or plate entails multiple rolling resulting in added costs and possible inconsistencies in mechanical properties across the sheet or plate where initially curved regions have been flattened. In practice, this kind of extrusion process is used to make sheet or plate extrusions with a width of up to around 1500 mm.
Another existing extrusion method for producing wide metal sheet or plate is called expanding extrusion which involves extruding a cylindrical billet through a rectangular orifice and allowing the extrudate to expand sideways before it is forced through a thinner slightly shorter rectangular die to form a thin sheet. Large extrusion forces are required for expanding extrusion due to the friction at the workpiece-tool contact surfaces. Also, edge quality of the sheet or plate is hard to control since if the extrudate material does not fill the expanding die well, extruded edges will have saw-tooth features. This would then require further downstream processing. Additionally, in practice, expanding extrusion can only produce profiles with a width less than 1.5 times the diameter of an extrusion container, because if the size of the expanding die is too large, it is difficult for the material in the die to flow to the positions far away from the centre of the die. Further, the rectangular section and profile dies would be expensive to build and maintain. In practice, this kind of extrusion process is usually used to make sheet or plate extrusions with a maximum width of up to around 800 mm.
In general, the smallness in cross-sectional area of sheet or plate (its maximum width and minimum thickness) extruded from cylindrical billet is limited by the associated high extrusion ratio and hence high load and pressure required to produce it within an extruder. There is a need for new extrusion apparatus and methods obtaining the benefits of extrusion and capable of producing wide metal sheet or plate in an efficient and cost-effective way, e.g. a sheet wide enough for use in the automotive industry (2200 mm or wider).
The present disclosure seeks to alleviate, at least to a certain degree, the problems and/or address at least to a certain extent, the difficulties associated with the prior art.
SUMMARYAspects and features of the invention are set out in the appended claims.
According to one aspect of the present disclosure, there is provided 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 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.
According to another aspect of the present invention there is provided a method of extruding a sheet of material using the apparatus as set out above, 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.
The present invention uses multiple small containers to replace the single conventional large container, which can hugely decrease the effective extrusion ratio for wide extrusion and therefore the load requirement and cost are decreased, compared with the conventional single container extrusion. Load requirement in the present invention is decreased significantly with the increase of the number of the small containers. The process enables manufacture, with a low applied force, of a wide, metal material that could be used in the automobile industry and other industries, (for example, a width of more than 2200 mm). The apparatus and method of the present invention applies primarily to processing aluminium and magnesium alloy material, but in certain circumstances, it could also be used to manufacture other metal materials such as steel and titanium alloys, and the shape of extrusion could be complex and of wide profile, especially useful for aircraft, train, bus, truck and construction applications.
Other optional and preferred features of the apparatus and method of the present invention are set out below in the detailed description and follow in the claims.
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.
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.
An example of an apparatus according to the present invention to produce wide sheets/components by extrusion is shown in
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.
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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.
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.
As will be clear from looking at the figures, and in particular by looking at
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.
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.
Type: Application
Filed: Jul 14, 2022
Publication Date: Oct 17, 2024
Inventors: Weishu LI (London), Jiaxin LV (London), Junquan YU (London), Zhusheng SHI (London), Jianguo LIN (London)
Application Number: 18/579,683