Metal deforming – By extruding through orifice – Container and/or support therefor
Reexamination Certificate
2002-06-04
2003-10-28
Tolan, Ed (Department: 3725)
Metal deforming
By extruding through orifice
Container and/or support therefor
C072S257000, C072S271000, C072S342100, C072S364000
Reexamination Certificate
active
06637250
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a extrusion press device for manufacturing a profile from an extrusion block of a material that is at least in part metallic, whereby the extrusion press device contains a container with a container bore for acommo-dating the extrusion block, a stem, a shaping chamber and/or die and a heating facility situated between the container bore and the die or shaping chamber, and relates also to a process for manufacturing a metal profile.
The production of metal profiles via the extrusion process is a technology known to experts in the field, whereby however the production of large profiles made of aluminum alloys and having a breadth of more than 700 mm is associated with many technical problems.
Further, it is hardly possible to produce profile wall thicknessess smaller than 2 mm using state-of-the-art extrusion technology. In view of the savings in weight and costs, however, it is highly desirable to be able to reduce the wall thickness of profiles i.e. while maintaining the normal geometric tolerances of the profile to achieve wall thickness of less than 1 mm. Limited extrusion force and limited possibilities of achieving uniform distribution of metal due to temperature distribution and flow rates are the esential factors that oppose the production of very thin walled profiles using present day technology.
With current extrusion technology, however, production of profiles of medium and smaller breadth is also to a certain extent limited in terms of the material employed and cross-sectional dimensions. For example, high strength aluminum alloys can hardly be extruded, or if so only with great difficulty, with the extrusion forces avail-able in conventional extrusion presses. These limitations apply in particular for extrusion of hollow profiles, especially multi-chamber hollow profiles. In addition, failure to meet dimensional tolerances and poor distribution of metal are problems frequently encountered and are due to insufficient filling of the die in parts of the profile with small cross-sectional dimensions.
Using the extrusion method as a way for processing metal-based, particle-reinforced composites containing particles or non-metallic, high melting point fibres dispersed in the metal matrix, results in problems comparable to those described above when processing high strength alloys. In the publications WO-A-87/06624, WO-A-91/02098 and WO-A-92/01821 a detailed description is provided of the production of these so-called “metal matrix composites”. Thereby, the particles to be embedded in the metal matrix are first stirred homogeneously into an alloy melt. The molten composite material is then cast e.g. continuously cast into a format suitable for further processing by extrusion.
In WO98/19803, as a solution to the above mentioned problem, an extrusion process is proposed in which the extrusion block in the part-solid/part-liquid state is shaped into a profile. In order to reach a part-solid/part-liquid state, prior to extrusion, the extrusion block is pressed through the through-flow channels of a heating element for the purpose of being heated. However, pressing the initially still solid block material through the through-flow channels requires very large extrusion forces, and there is a marked reduction in pressure in the region of these through-flow channels. Apart from the large extrusion forces that are necessary, the control of the extrusion process is made considerably more difficult as a result of the local drop in pressure. Further, the distribution of the fluid fraction of the block, after passing through the heating element in the semi-solid state, is difficult to control and is as a rule inhomogeneous.
The object of the present invention is to improve the above mentioned process and to reduce the reduction in pressure in the heating element. Further, the extrusion of blocks of thixotropic alloys in the part-solid/part-liquid state should be simplified while achieving as homogeneous as possible distribution of the liquid fraction.
SUMMARY OF THE INVENTION
The foregoing object is achieved by way of the invention in that the heating facility contains a heating chamber which is in the form of a hollow body arranged, with respect to the direction of extrusion, after or immediately following the container and features at least a first and a second heating section with heating chamber walls and means for heating the heating chamber walls, and the first heating section exhibits a larger cross-sectional diameter than the subsequent, with respect to the direction of extrusion x, second heating chamber section.
The heating chamber contains preferably less than five sections, advantageously less than four sections, and in particular two sections. At least one of the heating sections, preferably all heating sections, are of larger cross-sectional diameter than the heating section that follows immediately in the direction of extrusion x, this of course with the exception of the first section of the heating chamber. The transition zone between two heating sections of different diameter is characterised by way of a sudden, complete or partial narrowing in cross-section. In a particularly preferred version of the invention the narrowing in cross-section is in the form of a ledge or step extending over the whole periphery or a part of the periphery of the heating chamber cross-section. If several sections of heating chamber are provided, then a sudden narrowing in cross-section, e.g. in the form of a ledge or step, may be provided in all or several transition zones between two heating sections, whereby as described above the narrowing takes place in the direction of extrusion x.
The narrowing may also run continuously e.g. tapered and if desired exhibit a roughness pattern. Further, the narrowing of the cross-section may be made in several steps.
The narrowing in cross-section amounts preferably to around 5 to 40%, advantageously 15 to 30%, in particular 20 to 30% of the cross-sectional diameter of the aforegoing heating chamber section. Advantageously, the overall length of the heating chamber amounts to 2-4 times the length of the extrusion block, in particular 2.5-3.5 times that length.
The cross-sectional shape and diameter of the first section of the heating chamber immediately following the container is essentially, preferably exactly the cross-sectional shape and diameter of the container bore. The extrusion block is prefer-ably in the form of a billet, whereby the cross-sectional shape of the container bore and the neighbouring first heating section that follows the container bore are cylindrical in shape. The subsequent heating sections are preferably likewise cylindrical in shape. The cross-sectional shape of the heating sections, in particular the heating chamber sections near the die may be differently shaped e.g. elliptical in shape.
In a special version of the invention the shape of the heating sections may approach that of the cross-section of the profile in question. In a preferred version a first section of the heating chamber corresponds in cross-sectional shape and diameter of to that of the container bore and the following sections of the heating chamber, in particular the section or sections of the heating chamber next to the die approach the cross-sectional shape and cross-sectional diameter of the profile, this in a stepwise manner in the direction of extrusion x. By making the shape of the extrusion block approach the shape of the profile cross-section before the actual shaping in the die, there is a reduction in the amount of force required at the die to shape-form the block. If a heating chamber section does not exhibit a cylindrical cross-section, then by cross-sectional diameter is to be understood the mean cross-sectional diameter.
The heating chamber of an extrusion device according to the invention for manufacturing a rectangular profile may e.g. exhibit a first cylindrical heating section next to the container core and a elliptical shaped heating section that approaches the shape of the pr
Arnold Grégoire
Bagnoud Christophe
Bolliger Martin
Plata Miroslaw
Alcan Technology & Management Ltd
Bachman & LaPointe P.C.
Tolan Ed
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