Metal fusion bonding – Process – Using dynamic frictional energy
Patent
1993-03-16
1994-05-24
Ramsey, Kenneth J.
Metal fusion bonding
Process
Using dynamic frictional energy
228114, 228189, 22826244, B23K 2012
Patent
active
053141067
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for joining blanks or structural components of steel to those of aluminum alloy or titanium alloy, and it comprises turbochargers obtained by the method.
2. Discussion of Background
The joining of different materials plays a considerable part in the highly developed fabrication technology, since frequently different properties are demanded within one arrangement, which properties cannot be obtained by a single material so that, depending on the manufacture and operating function, different materials are used for individual elements of a component or of a structure, in order to arrive at an optimum of economical manufacture and mechanical property.
Thus, for example, according to European Patent Specification 0,129,311, aluminum or aluminum alloy is used, for reasons of manufacturing technology, for the compressor rotor of a turbocharger and, because of the good mechanical properties such as strength and toughness, tool steel is provided for the shaft to be fitted on or for the fixing component for the latter, and these are to be joined to one another by friction-welding.
Some difficulties arise, however, in following this recommendation since, although aluminum can be joined to steel by friction-welding under certain conditions, making a welded joint between steel and hardenable aluminum alloys causes great difficulties.
Likewise, friction-welded joints, capable of being loaded, between steel and titanium alloys have hitherto not been achieved.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to develop a novel method, by means of which blanks or structural components of steel can be joined to those of aluminum alloys or titanium alloys by friction-welding.
The method according to the invention, developed for this purpose, comprises joining the blanks or components to one another with insertion of at least one transition layer of a ductile subgroup metal by friction weld-joining of the individual contact surfaces.
Owing to the use of ductile pure metal layers, thermal strains between the partners of the joint can be compensated. The material systems on the joint surfaces remain clear, and especially the formation of brittle phases in the boundary region is suppressed. Of course, attention is paid, here to the metallurgical compatibility of the partners of the joint and to the suitability for friction-welding.
The joining of steel to a titanium alloy is carried out especially by applying a copper layer to the steel by friction-welding and applying a vanadium layer to the titanium alloy by friction-welding and then joining the copper and vanadium surfaces, after weld bead removal, to one another by friction-welding.
The friction welds are advantageously made with exclusion of the ambient air under an inert gas, in vacuo or especially under a liquid such as, for example, a petroleum/mineral oil mixture, such as is used for spark-erosion machining.
For the joining, conventional friction-welding machines can be used which run at fixed speeds of rotation or with infinite adjustment of the speed of rotation. Friction for a certain time or to a certain depth are possible modes of operation.
In the method according to the invention, conventional speeds of rotation in the region of 500 -2000 rpm, especially in the range around 1000 rpm, and forging pressures up to about 500 kN, especially in the range 100-200 kN, can be applied.
The interlayers in the finished joint are as thin as possible; their thickness is advantageously within the mm range.
Before the friction-welding, the surface is carefully prepared; especially, the freshly turned surface is degreased in an ultrasonic bath, rinsed with alcohol and dried.
In order to avoid high starting torques, a conical joining surface can be provided on one joining partner but, for reasons of the loading capacity of the joint, flat joining surfaces are preferred.
Roughnesses of the surfaces to be joined of 30-300 .mu.m, especially about 100 .mu.m, are appropriate.
REFERENCES:
patent: 3121948 (1964-02-01), Hollander et al.
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patent: 3421201 (1969-01-01), Oberle et al.
patent: 4333671 (1982-06-01), Holko
patent: 4514470 (1985-04-01), Rosenthal et al.
patent: 4765530 (1988-08-01), Dang et al.
patent: 5064112 (1991-11-01), Isobe et al.
Sassani et al. Welding Journal (supplement) American Welding Society Issue of Nov. 1988 pp. 264s-270s.
Ambroziak Andrzej
Lison Rudolf
Ricanek Rudolf
Asea Brown Boveri AG
Ramsey Kenneth J.
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