Patent GB-958753-A (GB)
Title: Method and arrangement for the electric resistance flash-butt welding of steels
IPC: B23K11/04
Filed: 1962-06-07
Abstract: 958,753. Welding by pressure. BRATISLAVSKE ELEKTROTECHNICKE ZAVODY NARODNI PODNIK. June 7, 1962 [June 14, 1961], No. 22003/62. Heading B3R. In a method of flask butt welding particularly suitable for chromium and molybdenum alloy steels, the weld parts are preheated by being repeatedly brought into contact with each other while carrying current, and the duration of preheating is controlled by regulation of the abutting force, and the number of successive cycles of preheating. The apparatus comprises two work clamping jaws 3, 6 and their associated electrodes 2, 4, 7, 8. The righthand jaw assembly is moved by a piston 11 and cylinder 12. Attached to the movable electrode assembly is a rod 42 which controls the movement of a piston 50 of a blocking valve 27. Movement of the main ram 11 is controlled by a 4-way valve 15 which is in turn controlled by two solenoids 16, 17. A pump 19 supplies fluid to the system at either of two pressures determined by pressure relief valves 22, 25. A ratchet-operated counter 40 is actuated each time a single preheat cycle is completed, and it is controlled by a reversing cylinder 31. The four positions of the 4-way valve 15 correspond respectively to moving piston to right, moving piston to left, piston stationary, and piston moving to left at variable speed under throttled discharge from the reflux side of the piston 13. In operation, the 4-way valve is moved to position 2, thus feeding pressure fluid to the main cylinder 12 at a pressure controlled by the relief valve 25. At this stage, the blocking valve 27 is in its closed position, thus isolating the reverse valve 31. As the main piston 11 moves forward, the rod 42 opens the blocking valve 27 and a switch 48 which de-energizes a solenoid 38 to engage the pawls 35, 37 of the counter 40. The workpieces will be abutted under a pressure determined by the relief valve 25. The time of abutment prior to reversal of ram pressure is controlled by the setting of throttling valve 29 situated in the flow line connecting the main cylinder 12 and reverse valve 30 through the blocking valve 27. Pressure fluid forces piston 32 upward against a spring 33 and opens a switch 34, and simultaneously indexes the counter 40. Opening of the switch 34 de-energizes the solenoids 16, 17 and the 4-way valve 15 returns to position 1, thus moving the piston 13 to the right, and opening the side 13 of the main piston to the sump 20. Drainage of the reverse valve 31 will not take place along the route which actuates it due to the presence of a non-return valve 26. Pressure is released from the reverse valve 31 through a throttling valve 30, pipe b, and after the blocking valve piston 50 has moved sufficiently to the right, through outlet pipe e to the sump 20. Thus the time lapse prior to closing of the switch 34 to commence a second preheating cycle is controlled by the throttling valve 30 and is independent of the main cylinder pressures. The preheating cycles continue until the number of cycles set on the counter 40 have been completed, after which the counter 40 closes a switch 41; and this moves the 4-way valve to position 4, in which pressure fluid exhausted from the reflux side 14 of the main cylinder is throttled by the 4-way valve 15. The infeed rate of the main piston 11 is controlled by a pre-set cam 21. Arcing and fusion take place at an increasing rate and the cam 21 controls the correspondingly increasing speed of infeed, until a switch (not shown) closes to energize solenoids 16, 17 which moves the 4-way valve to position 2 and moves valve 23 to the right to inactivate the low pressure relief valve 25. Thus after a suitable number of preheating cycles, followed by a single feed flasking period, the main piston is moved to the left with a force corresponding to the high pressure relief valve 22 setting until the weld is completed. The number of presetting pulses may be determined by setting the arm 40 for a single pulse and then isolating the counter indexing pawls 35, 37 by closing a switch 47. The preheating cycles will continue as already described and on the workpieces reaching the required temperature, the switch 47 is opened, after which one further cycle will take place before flasking and welding. Thus if a number of identical parts are to be welded, the machine is used in conjunction with temperature measuring equipment and independent counter, and the machine counter subsequently set to the ascertained number of pulses.