Metal fusion bonding – Including means to provide heat by friction between...
Reexamination Certificate
2000-02-01
2001-07-24
Dunn, Tom (Department: 1725)
Metal fusion bonding
Including means to provide heat by friction between...
C228S112100
Reexamination Certificate
active
06264088
ABSTRACT:
The present invention relates to a welding assembly for joining together workpieces along a joint between said pieces by means of friction stir welding, said welding assembly comprising a welding probe intended to be advanced along said joint during the welding operation and comprising a body and a pin, the body being arranged to be pressed against the upper faces of the workpieces during the welding operation whereas the pin is arranged to be moved along said joint during the welding while being rotated and pressed against said workpieces.
The definition friction stir welding designates a welding method according to which the workpieces to be joined together are plasticized along their joint line by supply of frictional heat from a rotating welding probe, said probe being moved along the joint between the workpieces while at the same time being pressed against the workpieces. As described in WO93/10935 and WO95/26254 the welding probe should be manufactured from a material that is harder than that of the workpieces, and during the welding operation the workpieces should be securely fixed relative to one another and to the work-table. In this respect this technique differs from that of conventional friction welding according to which the frictional heat is generated by the relative motion of the workpieces as they are being pressed together, i.e. the frictional heat is generated only by the two components to be joined together. This friction stir welding technique according to the above-mentioned publications may be used for the welding of different materials, such as plastics, metals, etcetera in various fields of application, for example to join workpieces together, to repair cracks in a workpiece, and so on. The design of the welding probe is conditioned e.g. by the material to be welded and by the intended application.
One of the problems encountered in the implementation of the welding method described in the above patent specifications for joining together e.g. aluminium profile sections is that vertically, the welding probe in principle must extend through the entire joint between the workpieces to be welded together in order to ensure that the resulting weld will extend all the way from the top to the lower faces of the workpieces, i.e. that a complete-penetration weld is produced. The welding probes disclosed in the above patent specifications are in the form of a rotatable, essentially cylindrical body the upper part of which is connected to a drive unit and the lower part of which is provided with a co-rotating pin. The essential difference distinguishing the probe according to WO93/10935 from that of WO95/26254 is that according to the former the body and the pin of the probe form one integral piece whereas according to the latter they are two separate pieces. In accordance with the latter patent specification the body and the pin are, however, securely interconnected during the welding operation proper. Accordingly, the entire welding probe or at least the pin thereof must be exchanged according to the latter specification in order to allow workpieces of different thicknesses to be welded together.
An additional problem is that the thickness of the workpieces to be joined together may vary along the joint, and consequently the end product will not be formed with a weld that extends all the way through the joint, i.e. the joining-together operation will not result in an acceptable weld.
A further problem encountered in prior-art welding probes is the formation of an exit aperture at the point where the probe is lifted off the produced weld following completion of the welding operation.
Another problem is that presently existing welding probes precludes any supply of additional material during the welding operation proper, which supply is desirable when one wishes that the body be pressed against the top faces of the workpieces without the lower part of the body, i.e. its so called shoulder, entering into the workpieces.
One object of the present invention thus is to provide a welding assembly to be used for friction stir welding operations that in a convenient and rapid manner may be adapted to different thicknesses in the workpieces to be joined together or may adjust itself to thickness variations in the workpieces.
A further object of the present invention is to provide a welding assembly of the kind referred to which allows supply of additional material during the welding operation.
These objects are achieved in accordance with the present invention in a welding assembly for use in friction stir welding of the kind defined in the introduction, which probe is characterised in that the pin and the body are so arranged relative to one another as to be mutually movable, allowing said pin and body to perform different movement patterns relative to one another.
As a consequence of the probe of the welding assembly being constructed in the form of a pin and a body that are so disposed relative to one another as to be mutually movable, whereby they are allowed to perform mutually different movement patterns, any material that is plasticized during the welding operation will be safely retained below the lower part of the body, and consequently the position of the pin relative to the joint may be adjusted in a manner ensuring that a complete-penetration weld will be produced in the full extension of the joint.
Advantageous modified embodiments of this welding assembly are defined in the dependent claims.
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Burns Doane Swecker & Mathis L.L.P.
Cooke Colleen
Dunn Tom
Esab AB
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