Welding Tips and Tricks

Just doing some reading online the other day about headers and car stuff. There are people that swear by back purging mild steel. I don't see a reason for it, but wondering if there is some good reason some people swear by it for pipe and tube welding

Easier to weld when root is wetted and cooled quicker by root gas. Also no slag is formed inside root.

Any sense to use? Perhaps, but usually benefits are so small that it don't make sense to pay for argon you use during root shielding.

I agree with Markus.

The benefit is too small to justify the cost. If your customer insists on a back-purge, nitrogen will do fine for a fraction of the cost of argon, with no ill effects.

Steve S

There is a few chassis builders that back purge 4130. I owned a back purged chassis I will say it did not break or crack on any weld or haz when it got destroyed. Seen other chassis come apart in wrecks that where not as hard as this one was wrecked. Not sure if purged helped or not though. Other factors could be individual welder, tubing quality, etc. Take it as you want.

dirtmidget33 wrote:There is a few chassis builders that back purge 4130. I owned a back purged chassis I will say it did not break or crack on any weld or haz when it got destroyed. Seen other chassis come apart in wrecks that where not as hard as this one was wrecked. Not sure if purged helped or not though. Other factors could be individual welder, tubing quality, etc. Take it as you want.

For a critical weld, like 4130 chassis or airframe, I'd be happy to spend the extra.

The OP was discussing exhaust pipe/tube, in a presumably milder alloy.

Steve S

Hell I know I guy that welded exhausts for porsche cup teams all around the weld and refused to back purge the stainless because they wrecked them too fast and the exhaust broke before a weld ever failed lol.

When I'm building gas and oil tanks for motorcycles, I almost always back purge them. I just use my torch and pump it in there pre and post. Heat builds up and on the post flow you can really feel just how hot it gets inside a tank. I imagine it would help anything with in enclosed space where heat builds up and can't really escape. THANKS Jack