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Re: Mig Welding Guys-Running a bead
[Re: Stanton]
#288888
04/20/09 09:40 AM
04/20/09 09:40 AM
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Joined: Apr 2009
Posts: 183
Canada
Mofopar
member
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member
Joined: Apr 2009
Posts: 183
Canada
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Quote:
They are inert gases used to sheild from impurities during the cooling of the weld. It really doesn't even do any cooling (put your hand oven the nozzle and tell me if you think the little that come out would have any cooling effect!). The gas does absolutely noting as far as "cleaning". Running argon over a surface before tig welding is a waste of gas. I find it hard to believe that someone who knows how to tig would even think this !! Different mig gases will have an effect on a mig weld.
Shield gases keep the filler and base mat'l from oxidizing - that all.
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Re: Mig Welding Guys-Running a bead
[Re: Stanton]
#288889
04/20/09 01:53 PM
04/20/09 01:53 PM
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Joined: Sep 2005
Posts: 6,516
Santa Cruz, California
Lefty
master
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master
Joined: Sep 2005
Posts: 6,516
Santa Cruz, California
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Quote:
Maybe you should take a welding course instead of just making assumptions from what you're seeing.
Enough is enough and too much is too much. There is such a thing as too much heat and too much penetration and the result is a weak joint. Done properly there is absolutely no reason to stop and go with a mig weld. If you think you're getting better penetration with that method then you haven't got your unit set up properly. It's as simple as that. As for documentation, how about YOU open ANY welding book and show me where they encourage stop and go mig welding.
 The instructor who taught my welding class didn't have a problem with it. But, he was only a AWS/ASME certified welder with 20+ years in the iron workers union.
BTW, changing direction in a zig zag pattern is no different than what i'm talking about as you have to stop to change direction. Maybe I should rephrase. I'm talking about forming a puddle then advance to the far edge of the puddle until the next puddle is formed and then repeating the distance of the bead. If you watch the puddle you can see when it flattens and it's time to advance. I do agree zig zag is only for joints that are wider than optimum. 
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Re: Mig Welding Guys-Running a bead
[Re: Fishmarket]
#288891
04/20/09 05:53 PM
04/20/09 05:53 PM
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Joined: Oct 2005
Posts: 8,918
Ontario, Canada
Stanton
Don't question me!
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Don't question me!
Joined: Oct 2005
Posts: 8,918
Ontario, Canada
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Quote:
Going over the mat'l first with the torch etches the metal. Do me a favour, the next time you are TIG welding contaminate your electrode by touching the metal while welding. Now go regrind your electrode and go over the dirty mess left by the contaminated weld. Where does all the nastiness go? I'm no scientist but maybe the impurities on the surface (ie:oils, oxides)are changed to gases and are then shielded from the area to be welded. All I know is that it works.
First of all, TIG is more susceptible to contamination than any other form of welding. That said, its critical that the surfaces be cleaned BEFORE any welding begins. And not by running your torch over the area !
Second, what you're doing is burning the contaminants with heat - the gas itself is doing nothing to "clean" the area. You may think you're "etching" the metal but in reality you're just contaminating the area by melting the surface and allowing the dirt into the molten metal (as minute as that may be). The heat generated by the TIG is about as hot as the sun so its stands to reason that just about any oil will burn of but oxidation doesn't melt so it flows right into the molten metal. Aluminum is a great example as it oxidizes almost instantly. If you don't clean it well and weld it right away it will be contaminated. Running your torch over it prior to welding wouldn't do squat to improve the final weld.
Quote:
The instructor who taught my welding class didn't have a problem with it. But, he was only a AWS/ASME certified welder with 20+ years in the iron workers union
I know welding technologists that don't have a problem with it. The point is that there's no advantage to it. No additional strength, just additional time and materials. Learn to weld properly - particularly if you want to make any money at it !
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Re: Mig Welding Guys-Running a bead
[Re: Stanton]
#288892
04/20/09 08:29 PM
04/20/09 08:29 PM
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Joined: Jul 2006
Posts: 383
Essex, Ont., Canada
Fishmarket
enthusiast
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enthusiast
Joined: Jul 2006
Posts: 383
Essex, Ont., Canada
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Well stanton, I TIG weld every day for a living. I will conceed that it was poor wording for me to say that the ARGON is doing the cleaning, even though I believe the it plays a large part in keeping contaminates out of the weld, even stuff that is left on the metal post cleaning. My teachers taught me that going over the weld prior to actually laying a bead, can help keep contaminants from the weld. I do not heat up the area enough to puddle just quickly go over it and then usually grab a wire brush and clean again. Many times the heat will draw oils to the surface (especially in cracks). I'll keep doing it that way because it works for me. I weld tool steel mostly that have been run in a stamping environment. We do our best to clean the steel before welding, however cracks etc. hoard oils and dirt that we can't get. I'm very familiar with cantaminated welds, and have on occasion had to grind it out and redo it. Also, try welding aluminum with AC. Then you'll have the natural CLEANING effect of alternating positive and negative ions. 
1972 Plymouth Cuda 340 4 speed
1971 Plymouth Road Runner 383 Auto
1970 Plymouth Duster /6 Auto
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