Patent GB-495696-A (GB)
Title: Improvements in or relating to a method of welding together metal members at least one of which is tubular
IPC: B23K11/00
Filed: 1937-02-16
Abstract: 495,696. Welding tubes; making milling cutters. STEVENS, A. H. (Steel & Tubes, Inc.) Feb. 16, 1937, No. 4662. [A Specification was laid open to inspection under Sect. 91 of the Acts, Sept. 14, 1937.] [Classes 83 (ii) and 83 (iv)] Forging dies.-In electrically welding the end of a circular, elliptical, or square or other polygonal tube of low, medium or high carbon steel, stainless steel or aluminium or aluminium alloy, to another part such as a cross tube the end of the tube is provided with two radially spaced circumferential edges shaped to fit the other part but with one edge engaging the other part and the other edge spaced therefrom, and is pressed against the other part while a practically instantaneous . current is passed therebetween so as to effect the weld and bring the spaced edge into contact with the other parts without fiash. The duration of the current may be ¢ a second or less. The contact area is produced either by upsetting or machining. Light gauge tubes are first thickened either during the upsetting operation or by inserting liners and then welding the liners to the tubes, and simultaneously upsetting the end. The liners may be first expanded into the tubes. The liners may be placed where required in both tubes, which may be slightly oversize and fixed by hammering or pressing the tube which also reduces the tube to the desired size. A length of tube with several liners may be then cut on a transverse or angular straight or curved line in the centre of the liner. The liners or tubes may be knurled or otherwise roughened to form a good mechanical and electric contact. The other ends of the liners may be tapered or slotted so that they yield slightly and prevent localization of stresses at the tube joint and also lessen heat transfer between the insert and tube at this point. Localization of the stresses at the joint in the case of thickened tube may be similarly prevented by making the upset of varying thickness. The tube ends may be upset by placing between the jaws 15, 16 of the electrode clamp of a resistance welding machine, which have a die-cavity 18 and pressing thereon a spring pressed electrode with a cavity 19 so as to form a bevelled annular ridge on the tube end. In a modification the tube end may be upset to form two bevelled lugs 22 as shown in Fig. 5, or four lugs, projecting from a base 23. The ends alternatively may be machined so that the edge 62, Fig. 17, engages the cross tube 64, leaving a gap at the edge 63 which is closed during the welding operation. Machining may be effected by a milling cutter so shaped that the smallest diameter is greater than the diameter of the cross tube. This may be effected for a 90‹ joint by making a pattern 81, Figs. 22, 26 and 28 from a cylindrical rod in two diameters, the larger of which is equal to the outer diameter of the tube 61 and the smaller equal to the inner diameter of this tube. The ends of the pattern are then shaped by a cylindrical milling cutter of diameter equal to that of the cross tube. The feather edges 83 on the large end of the pattern are then removed and a cutter dummy 80, Fig. 20, made by first turning from a bar to a shape which fits the smaller end of the pattern, Fig. 26. The dummy is then shaped mainly at the corners 84 until it fits the larger end of the pattern as shown in Fig. 28. For making a milling cutter for a joint between tubes at an angle say of 70‹, a pattern is similarly formed by a cylindrical cutter at an angle of 70‹ with the axis of the pattern and the dummy then shaped to register with the pattern arranged at 70‹ to the axis thereof. In either case the tube may be clamped in jaws 88, Fig. 30, formed with projections and cut away partions of the shape of the pattern, so as to deform the parts containing the feather edges, which are thus removed during milling. Alternatively the end may be milled without deforming and the feather edges subsequently removed by a belt grinder. Welding may be effected by damping the tube 10 in a two part electrode 30, 31, Figs. 31, 32, and using a spring pressed electrode with a shoe 33 engaging the inside of a cross tube 29 of larger diameter. For tubes of the same diameter electrodes such as 48, 45, Fig. 33, may be used. For tubes of 1 inch outside diameter welding may be effected with a pressure of from 2000-4000 lb. and current of the order of one hundred to several hundred kilovolt amperes applied at a voltage of about 8 for a period of from ¢ a cycle of a sixty cycle current up to half a second. The movement of the parts towards each other is thus stopped before the outer edge 63 is materially disturbed and outward extrusion of the weld is thus avoided. The weld is in the nature of a surface weld, heating of the parts extending only a few hundredths of an inch from the surface. Tubes of high carbon or alloy steels such as stainless steel, which are stated to be resistance welded with difficulty may have liners of mild steel so that welding is effected mainly to the liner. The liner may be case hardened by cyaniding prior to insertion.