DE1253839B - Method and device for arc welding - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
Display day:

B 23 k

German class: 21h -30/14

F 40159 VIII d / 9pm

5th July 1963

November 9, 1967

The invention relates to a method and an apparatus for shielding gas arc welding of pipes by means of an inner round seam using a non-consumable electrode.

It often happens that butt welding of pipes to other pipes or manifolds or Tube plates cannot be carried out in the conventional way or only with difficulty from the outside. That is particularly the case with heat exchangers od. Like. For nuclear power plants, where to increase the Exchange surface as large a number of tubes as possible are provided, but on the top plate are arranged so closely that welding from the outside is no longer possible. It it is then necessary to weld from the inside out.

Since there are strict safety regulations, especially in the case of nuclear power plants, the weld seams must meet the most extreme quality requirements. However, straight inner circular seams are particularly sensitive to inexact work, especially since the weld seam cannot be checked from the outside due to the tightness of the pipes and, of course, the pipe diameters used cannot be checked from the inside and corrected if necessary »5 .

The welding machines that are used today to produce internal welds are made of an electrode holder to be inserted into one of the parts to be welded together can and then must be rotated in this part. The devices for rotating the holder but often lead to difficulties that should be avoided.

There are currently already known magnetic devices that rotate or continue a welding arc. However, they are tools for drawing an outer seam on the face of a pipe or the outside of a pipe butt joint. For the production of pure internal circular seams are magnetic However, turned arcs have not yet been used, obviously because this way of working with the given quality requirements and the existing sensitivity as too was considered risky, so that the effort of a mechanically rotated welding electrode in Purchase was taken.

In contrast, it has been found that by using a magnetically guided arc it is surprisingly and unexpectedly possible to produce close-fitting tubes with relatively small diameters through internal seams of extreme quality and method and device
for arc welding

Applicant:

Foster Wheeler Limited, London

Representative:

Dr. KR Eikenberg, patent attorney,
Hanover, Schackstr. 1

Named as inventor:

Lindon Cyrill Laming, Redhill, Surrey;

Kenneth Stevens, Shenn Road, Richmond;

Alan Ernest Stevens, Stoneleigh, Ewell, Surrey

(Great Britain)

Claimed priority:

Great Britain 11 July 1962 (26 691)

butt-weld even at a relatively high welding speed.

The invention uses this knowledge in that the between the electrode and the pipe inner wall passing arc driven magnetically in a manner known per se on an annular track will. The device for carrying out the method according to the invention provides that the electrode Disc-like, held stationary on a holder within the tubes to be welded and is provided with a magnetic device.

The word »pipes« is not only intended to designate pure pipes, but also cylindrical ones that are to be welded Objects that are processed in this way or other types of manifolds or tube plates that represent tubes in themselves.

In an advantageous development of the invention, the magnet device contains two magnets between in which the electrode is sandwiched. Here are the electrode holder and the electrode by means of a cylindrical insert body, which consists of insulating material and with a snug fit in the one of the pipes to be welded can be used in which the pipe is held in the correct position.

This allows the device to be arranged so that the electrode is in the plane of the connection points between the pipe and the pipe plate or

709 «87/331

Claims (4)

the collecting tube, and the welding is carried out by supplying current to the electrode, so that an arc passes between the electrode and the connection point at which the weld is to be formed. Due to the magnetic field which the magnets generate, the arc runs around the electrode at high speed, so that the welding process is carried out in a very short time. An embodiment of the device according to the invention is shown in the drawing and is described in detail in the description that follows. The drawing shows a pipe 10 which is to be butt-welded to a pipe plate 12 which is provided with a pipe stub 14 in the vicinity of the welding point. The welding device comprises a cylindrical body 16 of insulating material which fits snugly into the bore of the tubesheet. A tubular electrode holder 18, which carries an electrode 20 and two magnets 22 at its upper end, is arranged within ao of the cylindrical body and protruding from it. The electrode has the shape of a disk, the outer surface of which is bevelled and lies opposite the connection point between the pipe 10 and the pipe stub 14 on which the weld seam is to be produced. At the other end of the cylindrical body 16, a housing made of insulating material is attached. This housing is provided with an inlet 26 for cooling water which flows through the tube 28 in the electrode holder to the vicinity of the electrode when it has entered the housing 24 and then through the annular space between the tube 28 and the holder to the housing outlet 30 back. The welding current is supplied via a conductor 32 which passes through the water inlet conduit 26 and which supplies the current to the electrode via a block 34 in the housing and tube 18. The housing also has an inlet 36 for an inert protective gas which flows into the vicinity of the electrode through the annular space in the cylindrical body 16 and through the channels 38 to the front end of the cylindrical body. It should be noted that the parts from which the welding device is constructed are all stationary parts. To carry out the welding it is only necessary to insert the welding device into the bores of the tubes and the tube plate, as shown in the drawing, so that the electrode is in the corresponding plane, and then to switch on the current. The arc that passes between the electrode and the pipe runs very quickly around the axis of the welding device and carries out the welding in a very short time. The speed at which the weld is carried out is of great importance because it provides security against possible cracks and distortions in the metal to be welded. These distortions can occur if an electrode is provided which rotates within the tube so that the arc travels around the axis of the tube. It can be advantageous to prevent the shielding gas from flowing through the arc rotating at high speed. This can be done by narrowing the space above the electrode through which the gas is to flow, or by bringing the gas close to the weld through a tube which passes up through the cylindrical body 16 and has an outlet opening which is above the level of the electrode. If desired, the latter configuration can be used in addition to the upward flow shown in the drawing. It can be seen from the drawing that a certain heat distribution from the electrode to the electrode holder 18 can also take place on the part that is touched by the cooling water. This heat distribution can be promoted by increasing the mass of the holder 18 if it is made of a material of high thermal conductivity, for example copper. The cylindrical body 16 must of course fit into the tube and tube of the tubesheet. It is therefore detachably connected to the housing 24 so that it and the electrode, the magnets and the holder can be replaced by another arrangement which has a body whose diameter corresponds to the pipe to be welded. The electrode should be fairly precisely aligned with the junction of the pipes that are to be welded. This can be achieved by using washers surrounding the cylindrical body and resting on the flange formed at the lower end thereof. The magnets 22 can, as shown, be permanent magnets or also electromagnets, which has the advantage that the field can be adjusted, whereby the speed at which the arc moves around the electrode can be adjusted. It will be understood that the correct penetration depth of the weld is a matter of adjusting the welding current as a function of the speed of the arc. Although the invention is illustrated in terms of the butt welding of tubes having a circular cross-section, because the electrode is stationary it can also be used to weld tubes which are not circular; the electrode would then have to be adapted accordingly to the cross-section of the tubes. Patent claims: 1. Process for gas-shielded arc welding of pipes by means of an internal circular seam using a non-consumable electrode, characterized in that that the arc passing between the electrode and the inner wall of the pipe in on is magnetically driven in a known manner on a ring track. 2. Apparatus for carrying out the method according to claim 1, characterized in that the electrode (20) is disk-like on a holder (18) held stationary within the tubes (10, 14) to be welded and is provided with a magnetic device (22). 3. Apparatus according to claim 2, characterized in that the magnetic device has two Contains magnets between which the electrode is sandwiched. 4. Apparatus according to claim 3, characterized in that the magnets (22) are permanent magnets are.