Metal fusion bonding – Process – Using dynamic frictional energy
Patent
1994-08-01
1995-10-24
Heinrich, Samuel M.
Metal fusion bonding
Process
Using dynamic frictional energy
2281145, 228119, B23K 2012
Patent
active
054603170
DESCRIPTION:
BRIEF SUMMARY
The invention relates to friction welding, for joining two workpieces or for operating on a workpiece, for example to repair a crack or join a member to a workpiece.
Friction welding has been known for many years and typically involves causing relative movement between a pair of workpieces while they are urged together so as to generate a plasticised region, stopping the relative movement and allowing the plasticised region to solidify thereby joining the workpieces.
It has also been proposed in the past to join workpieces by making use of a "non-consumable" member which does not form part of the finished joint. An example of this approach is shown in U.S. Pat. No. 4,144,110 in which the two workpieces are urged together about a rotating wheel which causes the plasticised region to be generated. The two workpieces are also translated relative to the wheel so that they are welded together along a joint region. Similar techniques for welding straight-seamed metal pipes are disclosed in SU-A-1433522 and SU-A-1362593. The problem in all these cases is that the zone which is heated is displaced from the point at which the workpieces or sides of the pipe are urged together with the result that such techniques would need to be carried out in carefully controlled atmospheres to prevent oxidation of the plasticised region in for example aluminum.
JP-A-61176484 discloses a technique using "consumable" spinning plugs which are positioned between opposed faces of the workpieces and cause the generation of plasticised regions within the workpieces and within themselves so that as the workpieces are urged together the spinning plugs are accumulated into the plasticised region and thereby form part of the resulting joint. This is a complex procedure requiring the ability to rotate a multitude of spinning plugs and to ensure that the plug material is compatible with the material of the workpieces.
In accordance with one aspect of the present invention, a method of operating on a workpiece comprises offering a probe of material harder than the workpiece material to a continuous or substantially continuous surface of the workpiece; causing relative cyclic movement between the probe and the workpiece while urging the probe and workpiece together whereby frictional heat is generated as the probe enters the workpiece so as to create a plasticised region in the workpiece material around the probe; stopping the relative cyclic movement; and allowing the plasticised material to solidify around the probe.
This new technique, which we refer to as "friction plunge welding" provides a very simple method of joining a probe to a workpiece. The method can be used for repairing cracks and the like within a workpiece or for joining members, such as studs or bushes, to a workpiece.
Preferably, at least part of the probe which enters the workpiece is shaped, for example tapered, so as to key into the solidified material.
This technique can be extended more generally to the joining of workpieces or the joining of opposed sides of a workpiece in for example pipes and cracked materials and the like. Thus, in accordance with a second aspect of the present invention, a method of joining workpieces defining a joint region therebetween comprises causing a probe of material harder than the workpiece material to enter the joint region and opposed portions of the workpieces on either side of the joint region while causing relative cyclic movement between the probe and the workpieces whereby frictional heat is generated to cause the opposed portions to take up a plasticised condition; removing the probe; and allowing the plasticised portions to solidify and join the workpieces together.
This technique, which we refer to as "friction stir butt welding" enables a wide variety of workpieces to be joined using a "non-consumable" probe without the problems of the prior art mentioned above. In particular, the workpieces will not normally be urged towards each other but simply restrained against movement away from the joint region during passage of the probe
REFERENCES:
patent: 3949896 (1976-04-01), Luc
patent: 4144110 (1979-03-01), Luc
Patent Abstracts of Japan, vol. 6, No. 253 (M-178), Dec. 11, 1982, 57149082.
Patent Abstracts of Japan, vol. 10, No. 388 (M-549), Dec. 26, 1986, 61176484.
Derwent Publications, 89-199319/27, 16 Aug. '89, SU 1433-522A.
Derwent Publication, 88-203819/29, 23 Jun. '88, SU 1362 593A.
Dawes Christopher J.
Murch Michael G.
Needham James C.
Nicholas Edward D.
Temple-Smith Peter
Heinrich Samuel M.
Novack Martin M.
The Welding Institute
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