GB2136721A

GB2136721A - A metal electrode for use in underwater arc welding or cutting, and an apparatus therefore

Info

Publication number: GB2136721A
Application number: GB08407183A
Authority: GB
Inventors: Tapio Niinivaara
Original assignee: NIINIVAARA T
Current assignee: NIINIVAARA T
Priority date: 1983-03-22
Filing date: 1984-03-20
Publication date: 1984-09-26
Also published as: AU2509184A; FR2543038A1; NO841118L; DK106684A; JPS59179287A; ZA841627B; DK106684D0; GB8407183D0

Abstract

A consumable electrode comprises a rotatable disc (1) the periphery (11) of which is intended to be placed against the workpiece and to move along it. The electrode may comprise radial or tangential bars of metal filler material. Conduits for compressed air or oxygen may extend from the centre of the disc to its periphery. The conduits may be formed by a corrugated sheet which lies between two additional layers. The material forming the conduits may be thermite. Alternatively the electrode may be a net of metal filler material with an auxiliary material within its mesh. The electrode may comprise a reciprocating elongate disc or an elongate disc supporting an endless chain.

Description

SPECIFICATION A metal electrode for use in underwater arc welding or cutting, and an apparatus therefore The present invention relates to a metal electrode for use in underwater arc welding or arc cutting which is adapted to be connected to one of the poles of a source of current.

The present invention also relates to an underwater arc welding or arc cutting apparatus which has the above-mentioned metal electrode with optional auxiliary materials, means for moving the electrode in relation to the workpiece, and means for connecting the electrode to a source of electric current.

Welding is divided into two main categories, namely pressure welding and fusion welding. In fusion welding, the metal is in the molten state and the joining is effected without pressure or striking.

Fusion welding includes gas welding and arc welding. In arc welding, the source of heat is an electric arc struck between the electrode and the workpiece.

The electrode is connected to one of the poles in the source of current and the workpiece to its other pole.

The electrode used is a metal wire covered with an auxiliary material such as flux, and from this electrode the melting metal, which serves as a filler material, and the flux are transferred by the effect of the electric arc into the welded joint. Arc welding can also be carried out in a shield gas, in which case the electric arc is struck between an endless electrode and the workpiece. The molten area is protected from the effect of the atmosphere by directing to the welding point a suitable inert gas or a gas mixture.

Metals can also be cut by cutting methods related to welding, such as gas or arc cutting. In arc cutting the electric arc is used for cutting metals. The cutting by means of electricity can be carried out using a carbon or metal electrode. In order to improve the cutting effect, oxygen gas is used as an aid in connection with the electrode; the oxygen gas is blown to the cutting point via a specific nozzle or a hole drilled through the electrode. In oxygen arc cutting, the electric arc is thus used as a source of heat, and molten metal is removed by means of an oxygen gas jet. The cutting electrodes are usually tubular electrodes covered with a protective coating, and this cutting method is especially advantageous for carrying out underwater arc cutting.

The object of the present invention is thus to provide a metal electrode intended for use in underwater arc welding or arc cutting, an electrode by means of which underwater arc welding and arc cutting can be carried out more rapidly and more reliably than previously.

It is also the object of the present invention to provide an underwater arc welding or arc cutting apparatus fitted with the above-mentioned metal electrode, an apparatus which is simplerthan previously and suitable for welding in position, even under very difficult underwater conditions. The object of the present invention is thus to provide an arc welding or arc cutting apparatus for underwater welding and arc cutting. The operation of the apparatus is, furthermore, very easy and simple to automate.

The main characteristics of the invention are given in the accompanying claims.

In one aspect of the present invention the previously known rod-like electrode has been replaced by a rotatable disc which is consumed in the welding or cutting; the periphery of the disc is intended to be placed against the workpiece and to move along it as the disc rotates about its transverse axis.

In resistance welding, which is one of the pressure welding methods, it is previously known to use disc electrodes instead of rod electrodes, especially in spot welding. The welding is carried out using either continuous current and continuously rotating discs, or the current is cut off intermittently but the electrodes rotate continuously, or the movement of the electrodes may also be intermittent. Thus, in disc welding two discs are used as electrodes, the discs moving one on each side of the joint to be welded. In disc welding the discs serve only as current conductors by means of which the joint is heated. The joining itself is effected by pressure or by striking when the metal has been heated to a paste-like state.

In the present invention, on the other hand, the rotatable disc serves not only as a current conductor but also to form the melt and is thus consumed as the arc welding or arc cutting proceeds.

The electrode according to the present invention for use in arc welding may consist of an uninterrupted metal filler-material disc having at least on one side an auxiliary-material layer and a possible protective-material layer. Instead of an uninterrupted metal filler-material disc it is possible to use several radial or tangential filler-material bars, along which the electric current is conducted to the workpiece, in which case the auxiliary material can be between the bars. Metal bars may widen towards the periphery, as seen in the direction of the shaft, in which case the disc advantageously at the same time converges respectively towards the circumference so that the cross-sectional area of the bars remains constant.The electrode according to the present invention for use in underwater arc welding can also be composed of a net of a metal filler material and of an auxiliary material within the mesh, as well as of a possible protective layer. The metal filler material can also be in particulate form, in which case the disc is made up of a mix of a particulate filler material and an auxiliary material, possibly covered with a protective material.

A disc-like electrode according to the invention can also have conduits extending from the center of the disc to its periphery in order to direct shield gas, or the compressed air or oxygen used in arc cutting, to the workpiece along a conduit or conduits oriented towards it. In this case every second conduit may be shorter and connected to at least one adjacent conduit, in which case the shorter conduits end at the periphery of the disc. The conduits in the disc-like electrode can be formed from a corrugated sheet between two layers of additional material.

In a disc-like electrode suitable for underwater arc cutting, the conduits are made up at least in part of a mixture of aluminium and brass, as well as iron oxide; when burning, this mixture produces great heat, so-called thermit combustion. The hot gas and melt produced by the therm it combustion are blown to the work-piece along the conduits in the disc by means of compressed air.

In the underwater arc welding or arc cutting apparatus according to the invention, a disc-like electrode of the above-mentioned type is attached to a rotatable shaft, the shaft being attached to a motor which rotates it and to electric conducting means which connect the disc-like electrode to the source of electric current.

The invention is described below in greater detail with reference to the accompanying drawings, in which Figures land 2 depict an underwater arc welding or arc cutting apparatus according to the invention, in two different working positions, Figure 3 depicts a side view of a disc-like electrode according to the invention for use in underwater arc welding, Figure 4 is a cross section of the welding disc of Figure 3, Figure Sdepicts a side view of an alternative electrode according to the invention for use in underwater arc welding, Figure 6 depicts a front view of a welding disc according to Figure 5, the layers being shown apart, Figure 7 depicts two alternative embodiments of the electrode according to the invention for use in underwater arc welding, parts of the electrode shown cut off, the upper half depicting an embodiment different from the lower half, Figures 8- 14 depict front views of different electrodes according to Figure 7 for use in arc welding, the cross-sectional shape and positioning of the radial ortangential metal bars varying in them, Figure 15 depicts a cross section of the electrode according to Figure 7 for use in underwater arc welding, Figure 16 depicts four different alternative embodiments of a disc-like electrode according to the invention for use in underwater arc welding, each quarter sector depicting a different embodiment, Figures 17and 18 depict front views of some of the embodiments according to Figure 16.

Figure 19 depicts a side view of two electrodes according to the invention for use in underwater arc cutting, part of the electrode shown cut off, the upper half representing an embodiment different from the lower half, Figure 20 depicts a front view of the electrode according to Figure 19 for underwater arc cutting, Figure 21 depicts front views of two alternative electrodes for use in underwater arc cutting, the upper half depicting an embodiment different from the lower half, Figure 22 illustrates side and front views of a further embodiment of the present underwater arc cutting or welding apparatus, and Figure 23 illustrates side and front views of a preferred embodiment of the present underwater arc cutting apparatus.

As can be seen from Figures 1 and 2, the underwater arc welding or arc cutting apparatus according to the invention consists of a shaft 2 rotatable about its longitudinal axis, there being attached to the shaft a replaceable disc-like electrode 1 consumed at its periphery during the process of the welding or arc cutting, the shaft 2 and the replaceable electrode 1 attached to it being rotated by means of a motor 6 at one end of the shaft 2. In addition, there is attached to the shaft 2 a conductor 4, which is connected to one of the poles of the source of electric current (not shown in the Figure) in order to conduct electric current via the shaft 2 to the electrode 1 in order to strike an electric arc between the periphery 11 of the electrode 1 and the workpiece 8, the workpiece being connected to the opposite pole of the said source of current.Owing to the electric arc struck, the disc-like electrode 1 melts at its periphery 11, thereby filling the welding groove 9 with filler material. Correspondingly, the apparatus according to the invention can be used as an arc cutting apparatus, in which case the shaft 2 is hollow in order to direct compressed air or oxygen into the conduits, shown in greater detail in Figures 19-21, in the disc 1.

The shaft 2 with its electrode 1 and motor 6 is articulated to the frame of the underwater arc welding or arc cutting apparatus, the frame not being shown in detail in Figures 1 and 2. This frame can also be a trolley on wheels, capable of being moved forwards when the underwater welding or arc cutting proceeds, the shaft 2 being fitted to the trolley in such a way that it can be lowered as the periphery 11 of the electrode 1 is consumed.

The rotatable shaft 2 is preferably provided, over the part between the electrode 1 and the motor 6, with an articulated joint 5 made of plastic or some other electrically non-conductive material, the joint enabling welding in position to be carried out, as shown in Figure 2.

The underwater arc welding or arc cutting apparatus according to the invention can be easily adjusted for automatic operation. It is very rapid acting, for the welding groove can be filled in a single run even when thick materials are involved. Also, the disc according to the invention need not be replaced as often as needs a conventional welding rod. In arc cutting it is possible to achieve cutting efficiencies 60% greater than by conventional cutting methods.

Figures 3 and 4 depict a preferred embodiment of the disc-like electrode 1 according to the invention for use in underwater arc welding. It is seen that in the center of the disc 1 there is an opening 10 for fitting the shaft. Figure 4 shows in greater detail that the electrode is made up of an uninterrupted metal filler-material disc 12 having an auxiliary-material layer 13 on each side.

The electric current required for producing the electric arc is conducted via the opening 10 along the metal filler-material disc 12 to the periphery 11 of the disc-like electrode 1. The electric arc is struck between the periphery 11 of the disc-like electrode 1 and the workpiece, producing such great heat that the filler material disc 12 and the auxiliary-material layer 13 on its both sides melt in this area. The molten filler material fills the welding groove, and the auxiliary material forms a slag layer on the welded joint, which slows down the cooling of the melt and protects the welded joint from oxidation as well as absorbs detrimental gases from the joint.

The auxiliary-material layers 13 are preferably made up of an alkaline coating such as rutile, cellulose or iron oxide, and are possibly coated with a protective layer.

Figures 5 and 6 depict an alternative disc-like underwater arc welding electrode 1, which is assembled from several sheets, the central sheet 15 being of some material which retards combustion, the sheets 12 on its both sides being of metal fillermaterial, and the outermost sheets consisting of supporting sheets 14 coated with an auxiliarymaterial layer. When these sheets 12-15 are pressed together, they form an uninterrupted disc-like arc welding disc 1, in which the thickness of the filler material sheets 12 can be varied according to the welded joint to be filled.

Instead of an uninterrupted metal filler-material disc, the disc-like electrode used in underwater arc welding can be made from radial ortangential bars 12 of metal filler material, along which the electric current is conducted to the workpiece from the ring 10 in the center of the disc 1 to the periphery 11 of the disc. In Figure 7, the upper half represents an embodiment in which the bars 12 of a metal filler material have been fitted tangentially between the protective layers 16 of the disc 1, in which case the auxiliary material 13 is between the bars 12. In the lower half of Figure 7 the bars 12 of a metal filler material are radial. In the embodiment depicted in Figure 8 the filler-material bars 12 form a single layer, whereas in the embodiment depicted in Figure 9 the bars 12 have been fitted not only successively but also side by side inside the auxiliary material 13.

Instead of metal bars it is, of course, possible to use, for example, cylinders, which are easy to manufacture from hollow welding rods. The tangential orientation of the bars 12 depicted in the upper half of Figure 7, the orientation of the electric arc struck between the periphery of the disc 1 and the workpiece can be affected advantageously by means of the tangential orientation of the pins 12 shown in the upper half of Figure 7.

Figures 10-14 show various compositions of metal filler-material bars, and it can be seen that the shape and arrangement of the metal filler-material bars can vary, within very wide limits, according to the use.

Since the metal filler-material bars 12 widen towards the periphery 11 of the disc 1, as seen in the direction of the transverse axis of the disc, the cross-sectional area of the disc 1 advantageously converges respectively towards its periphery 11, as shown in Figure 15, and so the cross-sectional area of the metal filler-material bars 12 remains substantially constant over their entire length.

Figures 16-18 show various alternative embodiments of the disc-like electrode 1 for use in underwater arc welding; in this electrode the metal filler material is in the form of a net 12 which has been immersed in an auxiliary-material mix 13 and covered on each side with a protective layer 16.

It is evident that the thickness of the wire, and the mesh and the pattern of the net can vary greatly within the present invention, as seen in Figure 16.

Figure 16 shows four different net patterns, the upper left-hand quarter representing ordinary interlacing with one or several wires, the lower left-hand quarter representing interlacing with several wires, the upper right-hand quarter representing interlacing using a wavy wire, and the right-hand lower quarter representing a paraboloidal interlacing of wire.

As can be seen from Figures 17 and 18, the wires of the nets of different patterns appear in different shapes at the periphery 11 of the disc 1, and thus the welding result can be affected.

Figures 19-21 show different disc-like underwater arc cutting electrodes which are particularly suitable for arc cutting of underwater metal structures. Figure 19 shows two different embodiments, the lower half depicting an arc cutting disc having, between two layers 16 of protective material, a disc-like layer 18 of additional material, in which radial, bar-like conduits 17 have been formed which extend from the opening 10 in the center of the disc 1 to its periphery 11.

Between these radial conduits 17 it is possible to form shorter partial conduits 17', which connect with the adjacent conduits 17, as shown in the upper half of Figure 19.

The arc cutting disc is preferably thermitestructured, in which case part of it is aluminum or brass, in order to produce therm it combustion, which produces a very high temperature. The melt and hot gases thus produced are then blown, by means of compressed air or oxygen, along the conduits 17, 17' in the disc 1 to the workpiece to be cut.

The compressed air or oxygen is brought to the conduits 17, 17' along the hollow shaft of the disc 1 and is directed to those conduits 17, 17' which are oriented towards the workpiece at each given time.

Figures 20 and 21 depict various conduit shapes.

In the embodiment shown in the upper half of Figure 21,the conduits 17 have been formed by using a corrugated metal sheet 19, which has been fitted between the layers formed from the protective material 16 and the layer 18 formed from the additional material which forms the melt.

Figure 22 illustrates an apparatus for underwater arc welding or cutting having an elongated disc 102 with an endless chain 101 guided around the periphery thereof and a device 103 for supporting and moving the disc 102 in contact with a workpiece 104 and further to move the chain 101 along the periphery of the disc 102. If the chain 101 is made of some metal filler material, the apparatus can be used for welding otherwise it is used for underwater cutting and the continuously moving chain effectively removes all molten metal from the cutting area.

The device 103 further comprises means 105 for connecting the chain 101 and the workpiece 104 to a source 106 of electrical current.

Figure 23 illustrates an alternative embodiment for underwater cutting by means of a reciprocating elongated disc 201. The reciprocating movement of the peripheral position of the disc in contact with the workpiece 204 effectively removes all molten metal from the cutting area.

The disc-like members 101 and 201 in Figures 22 and 23 are effectively cooled by the surrounding water. Although not shown, it should be understood that the apparatus may further have means for feeding a protective jelly known perse to the cutting area for subsequent welding purposes.

The disclosed and claimed underwater arc cutting method is especially useful since no gas jet is required to remove molten metal from the cutting area but this is effected by the rotary or reciprocational movement of the electrode itself.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

1. A metal electrode for use in underwater arc welding or cutting which is adapted to be connected to one of the poles of a source of current and comprises a rotatable disc, the periphery of which is intended to be placed against a workpiece and to move along the workpiece as the disc rotates about its transverse axis.

2. An electrode according to claim 1 for use in underwater arc welding which comprises an uninterrupted metal filler-material disc and an auxiliarymaterial layer situated on at least one side of said disc.

3. An electrode according to claim 1 for use in underwater arc welding which comprises radial or tangential bars of a metal filler material, along which the electric current is conducted to the workpiece, and an auxiliary material located at least between the bars.

4. An electrode according to claim 3 for use in underwater arc welding in which the metal bars widen towards the periphery, as seen in the direction of the shaft.

5. An electrode according to claim 3 or 4 for use in underwater arc welding in which the disc converges towards the periphery.

6. An electrode according to claim 1 for use in underwater arc welding which comprises a net of metal filler material and an auxiliary material within its mesh.

7. An electrode according to any preceding claim for use in underwater arc welding which includes a protective layer on the disc.

8. An electrode according to claim 1 for use in underwater arc cutting in which conduits extend from the centre of the disc to its periphery which direct compressed air or oxygen towards the workpiece along at least one conduit which is oriented towards the workpiece

9. An electrode according to claim 8 for use in underwater arc cutting in which every second conduit is shorter than and connected to at least one adjacent conduit.

10. An electrode according to claim 8 for use in underwater arc cutting in which the conduits are formed from a corrugated sheet which lies between at least two additional - material layers.

11. An electrode according to claim 8,9 or 10 in which the material from which the conduits are formed is at least in part thermite-structu red.

12. An underwaterarcwelding or arc cutting apparatus comprising a metal electrode, means for moving the electrode in relation to a workpiece and means for connecting the electrode to a source of electric current in which the electrode is a substantially circular disc and the means for moving the electrode comprises a rotatable shaft, to which the disc can be attached, and a motor for rotating the shaft, the shaft being connected to the electrical connecting means.

13. An underwater arc welding or arc cutting apparatus according to claim 12 in which the metal electrode possesses auxiliary material.

14. An apparatus according to claim 12 or claim 13 in which the shaft is articulated.

15. An apparatus according to anyone of claims 12, 13 and 14 in which the shaft is hollow.

16. An underwater arc welding or arc cutting apparatus having a metal electrode, means for moving the electrode in relation to a workpiece and means for connecting the electrode to a source of electric current in which the electrode comprises an elongated disc and an endless chain supported on and guided by the periphery of said disc, said chain being electrically connected to one pole of the source of electric current and operationally to said means for moving the chain along the periphery of said disc and along the workpiece.

17. An underwater arc cutting apparatus having a metal electrode, means for moving the electrode in relation to a workpiece and means for connecting the electrode to a source of electric current, in which the electrode comprises an elongated disc, at least a peripheral portion of which is electrically connected to one pole of said source of electric current, said disc being operationally connected to said means for moving the periphery of the disc along the workpiece.

18. A method of underwater arc welding utilising a metal electrode which comprises the steps of connecting the electrode to one pole of a source of electric current and a workpiece to the other pole, moving the electrode in relation to the workpiece, the metal electrode having a continuous peripheral surface, and rotating said surface continuously to provide fresh welding material.

19. A method of underwater arc cutting utilising a metal electrode which comprises the steps of connecting the electrode to one pole of a source of electric current and a workpiece to the other pole, moving the electrode to maintain it in contact with the workpiece as it is cut, the electrode being an elongated disc, and moving the edge of the disc during cutting to remove molten metal from the cutting area.

20. A method according to claim 18 or 19 in which a protective jelly is fed to the welding or cutting area.

21. An electrode for use in underwater arc welding or arc cutting substantially as hereinbefore described and with reference to the accompanying drawings.

22. An underwater arc welding or arc cutting apparatus substantially as hereinbefore described and with reference to the accompanying drawings.

23. A method of underwater arc welding or arc cutting substantially as hereinbefore described with reference to the accompanying drawings.