GB1427329A - Welding process - Google Patents

Abstract

1427329 Welding by fusion; rotary cutter heads; work holders; rolling CRC-CROSE INTERNATIONAL Inc 1 Oct 1973 [29 June 1972 17 July 1972 12 Dec 1972] 30609/72 33368/72 and 57202/72 Headings B3R B3B B3T and B3M In butt-joining together, end-to-end, cylindrical workpiece such as pipes 11, 12, the adjacent workpiece ends are each formed with inner and outer bevel surfaces and an intermediate plane land, the workpiece ends are brought into substantial abutment thereby providing a weld preparation having an internal and an external V, and a root pass is effected from outside the pipes 12 by rotary arc welding in which a consumable electrode wire is fed into the external V and the plane lands are fused through so that the internal V is at least partially filled with weld metal. The welding may be effected in the dip-transfer (shortcircuiting) mode, and the electrode may be transversely oscillated. The weld preparations are effected, or buffed to a bright finish, just before welding. In Figs. 13, 14B, the weld preparation bevels and land are produced on a machine wherein a pipe 11 is held fixed by shoes 913 radially movable by cams or, as shown, toggle members 923 acted on as by a ram 910, and cutters 975 (e.g. three) are rotatable by an electric motor 940, via gearing 938, 936 and fed towards the workpiece by rams 890. The cutters are mounted on outwardly sprung arms 950 pivoted at 952 and carrying workpiece internal surface engaging rollers 954 maintaining the cutters in a predetermined relationship with said internal surface. The rollers each have a lead-in end bevel 980 and also a hardened metal bevel 982 which latter, on part withdrawal from the workpiece, cold rolls the workpiece to produce a shallow inner bevel 829 and, Fig. 15 (not shown), small feather projections (993), respectively permitting use of a flush fitting backing bar and serving to retain molten metal. In Fig. 3 (not shown), thick pipe walls have a weld preparation including steep additional outer bevel surfaces. The workpieces are held aligned by clamping shoes 62F, 62R actuated by pressure rams 63F, 63R via toggle members 64F, 64R. A welding head 55 is carried on a carriage 53 guided on an endless track 51 tensioned about one workpiece. Consumable electrode wire from a spool 835 is fed, by drive rolls at 836, through the head 55 which, together with a follow wheel 833, is mounted on a plate 830 pivoted at 832 on the carriage. An acruate backing and/or cooling bar body 846 is adjustably spring pressed at 824 against the back of the joint and is carried via slots 822 engaging pins (821) on the clamping shoes 62F. The body 846 carries an insert 823 (e.g. copper) which may be plain (Fig. 11B, not shown) for use with the abovementioned weld preparation provided with the shallow inner bevels 829, recessed (Fig 11A, not shown) to provide an inwardly projecting root, or waffle surfaced (Figs. 12A, 12B, not shown). The bead engaging surface of the insert may be coated with anti-stick powder or have permanently bonded thereto a ceramic coating. Welding is effected from 12 o'clock to 6 through 3, and 12 to 6 through 9. To stabilize the molten pool, the electrode is introduced to the pool at an inclination (15-45 degrees) to the workpiece radius, particularly at or near the 12 and 6 o'clock position. The inclination angle may be fixed (preferably at 30 degrees) or variable (Fig. 6, not shown). Welding penetration may be assisted by directing inert gas (e.g. CO 2 ) at high velocity (via a closely set nozzle, Fig. 1, not shown) in opposition to the gravitational flow of the metal. Contact tube-to-workpiece distance may be varied (i.e. increased for reduced penetation at 12 and 6 o'clock) about the workpiece periphery by a control knob 837 on the carriage or by cams 810 which are frictionally held by leaf springs 811 between the endless track and its mounting workpiece, located by track stand-off acorns 841 and engaged by the follower wheel 833 movable with the welding head.