Machinery's Handbook, 31st Edition
Pipe Welding 1617 1) First pass, weld from the 7 to the 4 o’clock position. Start with a slight forehand nozzle angle. At the 4 o’clock position, the gun should be at the same angle as the pipe. 2) Second pass, weld from the 10 to the 1 o’clock position, then grind all stops and start again at the 1-inch (25 mm) position. FCAW 5G (Non-rotated) Welding of Thin-Walled Carbon Steel Pipes, Procedure for Root, Fill and Cover Pass Welding.— This procedure can be applied to most common pipe sizes, and should be given special consideration for 5G (non-rotated) welding of carbon steel pipe with wall thicknesses up to 3 ∕ 8 inch (10 mm). Pipe and Weld Data Electrode for root weld = 0.035 inch diameter, E70S-6 flux cored Gas = argon with 15–25% CO 2 Gas flow rates = 30 to 40 cubic ft/hr Root Welding Procedure for 5G Welds: Use root welding data from Root Welding Procedures for FCAW 5G Pipe Welds , above. Fill and Cover Pass Procedures for 5G Welds: Use MIG short-circuit, vertical-up for fill and cover passes. Electrode wire and gas, same as for root weld. Weld vertical-up. If the vertical-up fill pass can be made in two passes, weld from the 7 to the 1 o’clock position, to avoid starting and finishing on the root tacks. Starting just past 6 o’clock ensures that optimum weld energy is achieved as the first pass welds over the initial 6 o’clock root tack location. Feather 1 inch (25 mm) of the weld start and stop on the first pass with the grinder before applying the second vertical-up weld pass. Use a slight weave action. Use MIG short-circuit wire feed, 200–230 in/min 125–135 amps, 19–22 volts. Start at optimum 210 in/min (10 o’clock on the wire feeder) for 130 amps, 21–22 volts. Fine tune voltage by listening to arc sound to obtain a consistent rapid crackle sound. Electrode sticks out 1 ∕ 2 to 5 ∕ 8 inch, contact tip flush with nozzle end. Remove MIG surface slag islands between weld passes. No fill pass should be thicker than 1 ∕ 8 inch (3 mm). Use straight weave across the root face. At the bevel, use a slight upward motion with the gun. The motion should be no greater than the wire diameter. Then use a slight back step for added bevel fusion and to avoid possibility of undercut. For the cover pass, leave 1 ∕ 32 to 1 ∕ 16 inch of the groove depth for the optimum cover pass profile. The bevel edge will act as a guide for the cover pass weld. If more weld fusion is required after the root is complete and between fill passes, pre- heat pipe to 200–400 ° F (93–204 ° C). For pipe diameters on which more than two passes are required for the circumference the weld sequence is: 3) Third pass, weld from the 4 to the 1 o’clock position. 4) Fourth pass, weld from the 7 to the 10 o’clock position. 1) First pass, weld from the 7 to the 4 o’clock position. Start with a slight forehand nozzle angle. At the 4 o’clock position the gun should point straight at the joint; 2) Second pass, weld from the 10 to the 1 o’clock position, then grind all stops and starts for at least 1 inch (25 mm); 3) Third pass, weld from the 4 to the 1 o’clock position; and 4) Fourth pass, weld from the 7 to the 10 o’clock position.
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