The thick rubber purge plugs enable a little quantity of argon to flow out to prevent pipe pressure from blowing the weld. To pump argon straight into the pipe, one hole requires a tiny hose connected to the argon tank. If you can imagine water filling up a pipe, that’s how heavy argon is; the tube blowing in the argon will always end up at the bottom of said pipe, even if the seam is on a flat pipe.
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What Is Purge Welding?
When welding corrosion-resistant materials like titanium, stainless, and others, a proper welding environment is essential. It is needed for corrosion resistance. If unprotected, the hot weld seam oxidizes. Avoid or fix this oxidation. Purging methods and equipment help welding.
Oxygen purging follows pipe stabilization. Purge gasses might be argon, helium, or a combination. Argon is cheaper than helium. Helium transports arc heat better. Helium helps thick welds penetrate. Heat speeds up work.
Welding stainless steel using carbon dioxide might produce complications. Read more about carbon dioxide here, if you would like. The joint will be carbon steel instead of stainless. Avoid CO2—it is worse than sugaring. Some purge mixtures include 5–10% hydrogen. Before the oxygen can combine with the stainless steel, the hydrogen interacts with what little is left of it to generate water. Most food-grade stainless is 200 and 300 grade, which benefits from hydrogen purge gas.
If you are just purging a little, employ the shielding gas. Use the second gas bottle hose as a purge line by installing a Y-fitting. To accommodate the second line, increase gas flow from the bottle. Start gas flow by connecting your purge line to the purge dam inflow fitting. Forty cubic feet of purge gas per hour is normal (CFH). Time the cleansing and the oxygen meters can confirm whether the oxygen level is low enough to weld.
Purging takes time, so practice your welding. This is crucial when welding pipes into a bigger system. Torch angles might be uncomfortable if the weld is hard to reach. Torch control causes poor welds. You now have time to plan the weld and ensure that you can appropriately maintain the control of the torch.
Weld after the purge gas fills the chamber. Weld without air entering the purge zone by keeping the purge gas flowing. After the weld has been completed, the gas supply may be turned off, and any seals or dams that were placed on the pipe can be removed. Welding is the simplest part. Arc and bead the junction. TIG welding works as usual. Dab the torch in a puddle and move it. Dab and move around the pipe until the weld are finished.
Welding flat material may need sugaring protection. You can shield the rear of a flat weld without sealing it like a pipe.
Flux protects metal while welding. Stick and MIG welders use flux-filled rods. A blacksmith weld using powdered flux. A stainless-steel joint may be protected against sugaring by applying powdered flux on the back. Stainless welding fluxes exist.
Liquid, gel, or powder stainless steel fluxes exist. Apply flux per package instructions after cleaning and prepping the joint. Flux may be corrosive, so avoid getting it on your skin. After welding, remove the flux from the rear. It is easier using an angle grinder. Scrubbing it off with a wire brush takes time.
In real life, the welder should strive for enough flow to progressively drive out the oxygen and maintain a little greater force within the purge chamber than outside it. This action prevents new air from flowing into the purged zone when welding via the weld surface, decreasing friction that might damage the welding arc.
Weld purge time is another common question. Welders may use many methods to determine the correct purging time, in addition to expertise.
Why Is Welding Purged?
Metal reacts with airborne oxygen during welding due to tremendous heat. Oxidation weakens and degrades the weld. Welders use inert gas to keep the weld heated. The weld is unaffected by the inert gas (https://en.wikipedia.org/wiki/Inert_gas), which removes oxygen from the weld.
Unprotected TIG welds fracture and splatter. The bead will also be covered with black oxidation muck. Unprotected welds are weaker and may rip and fracture. Welding requires shield gas. Purging works well when welding copper, steel, aluminum, and other metals. It is bad for stainless steel. Because chromium in the alloy melts both sides of the weld. The weld joint’s backside will discolor and become covered with rough particles if this happens. Welders call this “sugaring”.
This purge weld checklist is short. Purge welding requires a welding helmet, power source, argon, purge plugs for a saw, and a file. These materials guarantee a neat, appealing weld that passes inspection.
Before welding, cut the pipe. Read the blueprint’s cutting instructions. Never guess. Bad cuts, fit up, and waste welds come from poor cuts. Measure twice, cut once is ideal. This will improve cutting and welding.
- The Pipe
Welding and fitting pipes are crucial, so you need to secure the pipe. Pipe sawing leaves minor burns and it is a sign that if left on the pipe, the weld will get diseased, forcing the welder to rip it out and start again. Pipe filling improves fit-up. Because the saw burrs and flaws are wiped off, the surface is smooth and beautiful, making it simple to fit.
- Purge Plugs
To prevent purge plugs from slipping out, insert and tap them in the opposite pipes. Purge plugs, thick rubber parts like those at https://www.techsouthinc.com/purge-plug-equipment/, release a little quantity of argon to prevent pipe stress from bursting the weld.
Right-flowing argon fills the pipe. 2 PSI is recommended (psi). Argon travels slowly, so weld the pipe after a second. Wait until air pressure leaves the gaping hole.
Fit the pipes now that argon is flowing. The fit-up is more important than the weld since a defective fit-up will result in a bad weld.
Fire welding is fun next. Freehanding or walking the cup during welding is crucial.
Review the welded pipe. Welding inspection is necessary because ignoring faults may cause welding failure, wasting time and money.