GB715969A - Improvements in or relating to butt welding metal tubes - Google Patents

Abstract

715,969. Induction heating. COMBUSTION ENGINEERING - SUPER-HEATER, Inc. Jan. 15, 1952 [Jan. 18, 1951], No. 1133/52. Class 39 (3) [Also in Group XXII] Apparatus for butt welding the ends of metal tubes, including means for holding the tubes in aligned relationship initially separated by a small axial gap, has an inductor heating coil and plug like baffles inserted into the tube interiors to block substantial escape of non- oxidising gas therethrough. The coil C1, C2, comprises an assembly 32, 34 of magnetic material laminations flanking each side of the coil and serving to concentrate the magnetic flux therefrom into the extreme edge portions of the tubes, the laminations lying in planes radial to the tube axes, and means for pressing together the tube end edges to effect contact and welding thereof after the edges have been inductively heated. The laminated assemblies each comprise two parts, 32, 32<SP>1</SP>, 34, 34<SP>1</SP>, hinged on a pin 38 so that they may be placed around or removed from the tubes, the laminations of each part being held together by a weld 37, preferably of non-magnetic stainless steel. The coil comprises a single turn, preferably of copper, in halves C1, C2, joined on one side by a bar 12 welded to the upper half C1 and bolted to the lower half C2 to enable the coil to be removed from the tube after welding. The other ends of the coil halves are separated by insulation 9 and joined through a transformer 15 to a high frequency generator G. Each of the coil halves is provided with an inner hollow section 10 for the passage of cooling fluid and insulated from the laminated assemblies by insulation 42. After welding, the heating is continued for approximately 1¢ minutes, the temperature being maintained constant by an optical pyrometer sighted on the weld line.