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  • popspipes
    replied
    Yes they are, none of the welds pictured have any filler used. I do use some filler on the ends of the seam welds to tie it in to the coupler etc.

    It is hard to get a picture of the inner weld as these fittings are only 7/8" diameter, this one is a bit better quality.

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  • Scott76
    replied
    Pops those look great. Are those all fusion welds? Looks like it to my newbie eyes.

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  • popspipes
    replied
    These are a few pics of the fittings, maybe give you an idea of what a steel tube fitting purge weld looks like, I have some better pics but I havent found them yet. If you are interested I will look for them.


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  • popspipes
    replied
    I guess because I like a nice weld on steel tube as well, or I have been a dairy welder for too many years ha!
    I do it because some of the sheetmetal parts of these pipes are .020 thick and when welding them the atmospheric air gets into the steel from the backside of the tube and degrades the weld (porosity), so I purge them to get around that problem and get a nice 100% weld in the process. This may not happen on thicker material I dont really know, most of my welding career was on stainless tubing in food plants, there purging is a necessity.

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  • wronghand
    replied
    Same reason as stainless-- Keep out the O2. Mild steel can be prone to the same problems as any other metal when you heat it above it's reactive temperature (ie. fusion welding). The back side of the weld will be less prone to embrittlement and cracking AND not have any silicon islands if you use a back-purge, even on mild steel tubing. It's not always considered necessary but a lot of guys swear by it for thin wall mild steel headers, roll cages etc.

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  • Scott76
    replied
    Care to shed a little light on that? I've never heard of people purging mild steel tube. What's the reasoning?

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  • popspipes
    replied
    I use argon to purge the steel tube as well.

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  • Scott76
    replied
    Argon purge is only for stainless though, right?

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  • popspipes
    replied
    Originally posted by Scott76 View Post
    I'm 1/3 of the way through a TIG class I'm taking at the local CC. Today one of the jobs was butt welds on 16ga coupons, both with filler rod and fusion welds. While doing the fusion weld I remember a motorcycle exhaust system I had that is advertised as having 'low resistance welds'. Going back and looking at pictures of it, it almost looks as though the pipes were fusion welded. Is this possible, or in any way a good idea? Would the purpose be to minimize the amount of penetrated weldment on the inside of the pipe?

    Part of my reason for taking the class would be so I could make some basic motorcycle exhaust systems for myself. When fitting up 16ga mild steel tube, should the two pieces be touching each other or should I include a 1/16" gap like on the butt weld I did in class? I assume no edge bevel is necessary either, as my instructor has stated that butt joints done with material less than 1/8" do no require it. He has been very helpful, but I do not want to bother him with questoins that are not related to the class at this point.

    Any answers or help would be much appreciated, I'd like to practice some of this at home when I can.
    Cut the two pieces (chop saw cold saw etc) , remove the burs, and butt them together (no gap), tack together, purge the inside with argon and weld it up. It can be done with mild steel or stainless.
    Food industries use this autogenous or fusion process all the time on stainless tube.
    16 gage tube 48 amps dc, puddle width about 5/32", adjust your travel rate to get this and practice untill it goes thru 100%, the inner weld usually looks as good as or better than the outer weld if done correctly.
    I am now doing steel welds on thinwall tube fittings and steel stampings, same procedure.
    Last edited by popspipes; 03-09-2011, 03:38 PM. Reason: info

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  • Scott76
    started a topic Exhaust welding questions

    Exhaust welding questions

    I'm 1/3 of the way through a TIG class I'm taking at the local CC. Today one of the jobs was butt welds on 16ga coupons, both with filler rod and fusion welds. While doing the fusion weld I remember a motorcycle exhaust system I had that is advertised as having 'low resistance welds'. Going back and looking at pictures of it, it almost looks as though the pipes were fusion welded. Is this possible, or in any way a good idea? Would the purpose be to minimize the amount of penetrated weldment on the inside of the pipe?

    Part of my reason for taking the class would be so I could make some basic motorcycle exhaust systems for myself. When fitting up 16ga mild steel tube, should the two pieces be touching each other or should I include a 1/16" gap like on the butt weld I did in class? I assume no edge bevel is necessary either, as my instructor has stated that butt joints done with material less than 1/8" do no require it. He has been very helpful, but I do not want to bother him with questoins that are not related to the class at this point.

    Any answers or help would be much appreciated, I'd like to practice some of this at home when I can.
    Last edited by Scott76; 03-09-2011, 01:08 PM.
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