Electric heating – Metal heating – For deposition welding
Patent
1991-10-07
1993-09-14
Shaw, Clifford C.
Electric heating
Metal heating
For deposition welding
B23K 904
Patent
active
052451534
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to the deposition of metal onto a surface using a spraying process. The invention is especially useful in spraying onto internal cylindrical surfaces, and a typical example of such a surface is the internal surface of an internal combustion engine cylinder. The invention is however equally applicable to other cylindrical bores and to other surfaces.
2. Description of the Prior Art
Both plasma spray and arc spray processes are known for depositing metal onto a surface. The plasma spray process uses a powder feed, whereas in the arc spray process the material to be deposited is supplied in the form of wire. Plasma deposition has the advantage of a hot, short flame giving high molten particle velocities and dense deposits but arc spray equipment has the advantages that it is cheaper than plasma and that the rate of deposition is higher.
For use in the coating of cylindrical surfaces, arc spray would be the method of choice, but there are formidable difficulties in designing a rotating twin-wire spray gun for cylindrical surfaces because of the need to rotate two heavy spools of feed wire each occupying a large amount of space. This is particularly complicated when the cylinder bores of a combustion engine are to be coated, because in this application it is desirable to be able to simultaneously coat a number of adjacent, parallel, cylindrical bores.
SUMMARY OF THE INVENTION
According to the invention, there is provided a method of depositing metal onto a surface using an arc spraying process with a consumable electrode and a non-consumable electrode, characterised in that the surface is an internal cylindrical surface, the non-consumable electrode rotates about a first axis, the consumable electrode is fed in a direction generally parallel to the first axis but does not rotate about its own axis, an arc is struck between the electrodes and atomising gas is directed through the arc at an angle to the first axis to atomise molten metal in the arc and to carry it towards and deposit it on the surface.
The non-consumable electrode preferably describes a circle when it rotates about the first axis and the consumable electrode can be fed axially within the circle described by the non-consumable electrode.
The consumable electrode is moved in an axial direction as it is consumed. Apart from this axial movement, the consumable electrode can either describe a circle about the first axis, or can lie at all times on the first axis. Whichever alternative is used however, it is important to note that the consumable electrode will not rotate about its own axis.
In a preferred embodiment, the non-consumable electrode rotates about the consumable electrode, and the consumable electrode lies on the first axis whilst the non-consumable electrode rotates around the first axis.
An additive can be introduced into the atomised molten metal before the atomised metal is deposited on the surface.
The invention also provides apparatus for depositing metal onto a surface using an arc spraying process, the apparatus comprising a consumable electrode and a non-consumable electrode, characterised in that the surface is an internal cylindrical surface and the non-consumable electrode is mounted for rotation about a first axis, the apparatus also including a feed mechanism for feeding the consumable electrode in a direction generally parallel to the first axis, means for striking an arc between the electrodes and means for directing atomising gas through the arc at an angle to the first axis towards the surface.
The non-consumable electrode is preferably of tungsten, is water-cooled at its base and is shrouded by an inert gas. The electrode can be mounted in a head and directed towards the centre of the surface, the head being mounted for rotation such that the electrode maintains its direction towards the centre as it rotates. The head can include gas passages for directing the atomising gas through the arc towards the surface.
The apparatus may include means for fee
REFERENCES:
patent: 2982845 (1961-05-01), Yenni et al.
patent: 2998922 (1961-09-01), Gibson
patent: 3013528 (1961-12-01), Bland
patent: 3064114 (1962-11-01), Cresswell et al.
patent: 4019011 (1977-04-01), Cape
patent: 4160895 (1979-07-01), Hopper
patent: 4547391 (1985-10-01), Jenkins
Davies Gordon I.
Roche Allen D.
Singer Alfred R. E.
Ford Motor Company
Malleck Joseph W.
May Roger L.
Shaw Clifford C.
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