Patent GB-853471-A (GB)
Title: An improved method of pressure welding and an improved machine for uniting members by pressure welding
Inventor: HARRIS HERBERT
IPC: B23K13/00
Filed: 1956-03-16
Abstract: 853,471. Welding by pressure. BABCOCK & WILCOX Ltd. March 15, 1957 [March 16, 1956], No. 8341/56. Class 83 (4). In welding steel tubular members end to end the ends of the members are heated to welding temperature by induction, the temperature being maintained substantially constant until welding is complete, and the members are pressed together at a pressure of at least 0.15 tons per square inch, but not substantially greater than one ton per square inch. If mild or low alloy steel members are to be welded the pressure employed may be 0.15-0.85 tons per square inch with a welding temperature of 1460-1380‹ C. and if the members are of austenitic steel 0.15-0.55 tons per square inch and 1420-1340‹ C. are appropriate. In an embodiment, relatively-movable tube clamps 2, 3 are provided in a machine 1. The clamp 2 comprises a block 4, Fig. 2, on a support 8 secured in a frame 9, the lower end of which is mounted on an eccentric 10. The frame is adjustable in a plane transverse to the longitudinal axis of the machine by a hand wheel 11 which rotates the eccentric through chain gearing and by a hand wheel 16 which rotates the frame about the eccentric by a link 14. Mounted in the frame is an hydraulic piston-and-cylinder means 21 which supports a member 6 having arms 7 sliding in the member 8 on opposite sides of the block 4. A similar block 4 on the clamp 3 is mounted on a bridge 23, Fig. 3, secured to guide-bars 24 running in bearings 15 and the bridge is connected to a piston-and-cylinder hydraulic device 26 for longitudinal movement. A similar member 6 with arms 7 is provided for the block 4 and is actuated by an hydraulic piston-and-cylinder device 27. The lower hollow copper water-cooled half 44 of an induction heater ring 45 is arranged between the clamps 2, 3. The machine is normally in a lowered position in relation to a work-table 47 and is raised into operating position by a crank and lever means 30 operated by an hydraulic piston and cylinder. In operation, tube lengths 101, 102, Fig. 6, are placed on the work-table and the machine is raised to operating level until the blocks 4 engage the lengths and the ends of the lengths are in contact at the central plane of the induction ring half 44. An upper clamp block 51 is placed on each length and secured by a cross-piece 53 engaging the arms 7 and the hydraulic means 21, 27 are operated to clamp the lengths. An abutment 56 on one of the guide members 24 is set a predetermined distance from a switch 55 in the supply circuit to the induction coil. The-lengths are pressed together at 0.15- 0.85 tons per square inch by the means 26 and with a high-frequency current supplied on the ring half 45, the upper ring half 54 is lowered on to the lower half and the ends heat up. A radiation pyrometer 61 interrupts the supply to the inductor if the temperature rises above a value in the range 1380-1460‹ C. The switch 55 cuts off the supply to the inductor when sufficient upset has occurred. It is stated that an internal-induction coil may in addition be used, and according to the Provisional Specification electromagnetic tube clamping means may be employed.