GB1583515A - Method for welding a tube in a tube sheet - Google Patents

Description

(54) METHOD FOR WELDING A TUBE IN A TUBE SHEET (71) We, KONINliLIJKE MACHINEFAB RIEK STÒRK B.V., a Company incorporated in accordance with the laws of the Netherlands of Hengelo, The Netherlands, do hereby declare the invention, for which we pray that a patejit may be granted to us, and the method by which it is to be performed, to be particularly described in and by the- .foJlo-wing- statement:-- The invention relates to a method for welding a tube in a bore by means of the so-called internal bore welding, to which a tube is inserted over a given distance into a bore of a tube plate, whilst inside the bore and the tube a non-consumable welding electrode is provided, which performs a relative rotary movement with respect to the edge of the tube and of the bore.

In such a method the arc struck between the welding electrode and the tube plate operating as a counter-pole ensures melting down of the material. There is no need to supply additional welding material.

Such a method is employed for establishing welds that have to satisfy high requirements. If the tube exhibits differences in shape and/or other properties, amongst which also metallurgical properties, this welding method has, however, the disad vantage that the melt exhibits differences.

The present invention has for its object to provide a method in which the effect of the aforesaid differences is diminished.

According to the invention there is provided a method of welding a tube into a bore including inserting the tube into the bore, providing within the bore and the tube a non-consumable welding electrode and rotating the electrode with respect to the edge of the tube and of the bore to perform the welding and positively cooling the tube in the vicinity of the weld during welding.

The small differences in heat transfer due to the aforesaid differences in the tube will then no longer play any part with respect to the forced cooling. Thus completely uniform welds are obtained.

In a preferred form of the invention the positive cooling includes the introduction of a coolant, the temperature and flow rate of the coolant being adjusted to control the cooling. This enables the geometry and the mechanical properties- of the weld to be controlled. It can be ensured; for example, that the weld will not be smaller than the thickness of the tube wall. More over, -local sagging of the tube wall can be. - avoided, whilst the appearance of the welds is ensured to be the same.

Preferably an inert gas, particularly argon, or alternatively a gas mixture including CO2 can be supplied to the area of the cooled zone.

The invention will now be described by way of example with reference to the drawings. In the drawings: Fig. 1 is a sectional view of a device used in the method of the invention; Fig. 2 is a sectional view taken on the line II-II in Fig. 1, and Fig. 3 shows a detail of Fig. 1.

In the drawings, Fig. 1 shows a sheet 1 having a bore 2, into which the end 4 of a tube 3 is inserted. The end 4 of the tube is rolled outwardly to press against the inner wall of the bore 2. An electrode 5 is arranged inside the bore 2 and adjacent the end of the tube 3. Between the electrode 5 and the edge of the tube 3 and the edge of the bore 2 an arc can be struck so that the tube 3 is welded in the bore 2.

A cooling ring 6 is slipped around the tube 3. The cooling ring 6 is formed by two halves 7 and 8. The half 7 defines a cooling space 9 having an inlet 10 and an outlet 11 for coolant. In a similar manner the half 8 has a cooling space 12 having an inlet 13 and an outlet 14 for the coolant.

The two halves 7 and 8 can be secured to one another by fitting pins 15. The ring 7, 8 has at the short end an impact rim 16, which has recesses to provide for escape of gas. On the inner side, the ring has spacer rings 17 and 18 for holding the ring and the tube at a distance from one another. Through an inlet 19 an inert gas, for example, argon can be introduced, which is distributed via the channels 20 and the gap between the ring 7, 8 and the tube 3 in the space between the cooling ring and the sheet 1 and the tube 3. The ring 17 has a sealing function, whereas the ring 18 has passages for the inert gas.

In operation a cooling fluid is supplied through the connections 10 and 13 and conducted away through the connections 11 and 14. Since heat transfer from the tube to the coolant takes place in the ring 6, 7 irregularities in the melt behaviour of the tube wall will not affect the quality of the weld. Therefore, by means of the device shown, a weld of very high quality can be established.

Fig. 3 shows the finished weld.

WHAT WE CLAIM IS: - 1. A method of welding a tube into a bore including inserting the tube into the bore, providing within the bore and the tube a non-consumable welding electrode and rotating the electrode with respect to the edge of the tube and of the bore to perform the welding and positively cooling the tube in the vicinity of the weld during welding.

2. A method according to claim 1 wherein the positive cooling includes the introduction of a coolant, the temperature and flow rate of the coolant being adjusted to control the cooling.

3. A method as claimed in claim 1 or 2 wherein an inert gas, or a gas mixture including CO2 is introduced in the vicinity of the cooled zone.

4. A method substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. tube 3 in the space between the cooling ring and the sheet 1 and the tube 3. The ring 17 has a sealing function, whereas the ring 18 has passages for the inert gas. In operation a cooling fluid is supplied through the connections 10 and 13 and conducted away through the connections 11 and 14. Since heat transfer from the tube to the coolant takes place in the ring 6, 7 irregularities in the melt behaviour of the tube wall will not affect the quality of the weld. Therefore, by means of the device shown, a weld of very high quality can be established. Fig. 3 shows the finished weld. WHAT WE CLAIM IS: -

1. A method of welding a tube into a bore including inserting the tube into the bore, providing within the bore and the tube a non-consumable welding electrode and rotating the electrode with respect to the edge of the tube and of the bore to perform the welding and positively cooling the tube in the vicinity of the weld during welding.

2. A method according to claim 1 wherein the positive cooling includes the introduction of a coolant, the temperature and flow rate of the coolant being adjusted to control the cooling.

3. A method as claimed in claim 1 or 2 wherein an inert gas, or a gas mixture including CO2 is introduced in the vicinity of the cooled zone.

4. A method substantially as hereinbefore described with reference to the accompanying drawings.