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Old 28-06-2010, 10:04   #301
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Well, ya' know, I'm not sure why a person would want to use helium! Argon does a better job and is cheaper. Argon is heavier than air, so it tends to stay down on the weld, where helium floats away. I don't see where it would do you much good with any ferrous metal. It does increase splatter as well, so I don't have a good answer for you. To be honest, I've always used argon/CO2 with aluminum and stainless and straight CO2 with mild steel on occasion. Maybe some here who knows more than I do can answer the helium question.

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Old 28-06-2010, 10:22   #302
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There is a well written section here that seems to explain the whole argon/helium point. Don't have time to read it all right now but you can indulge and give your thoughts.

Gas metal arc welding - Wikipedia, the free encyclopedia
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Old 28-06-2010, 10:39   #303
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LOL which pretty much says what I just said! LOL

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Old 28-06-2010, 10:56   #304
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Y66 ummmm not quite

"A helium concentration of 50%–75% raises the required voltage and increases the heat in the arc, due to helium's higher ionization temperature. "

and

"Other mixtures add a small amount of helium to argon-oxygen combinations, these mixtures are claimed to allow higher arc voltages and welding speed. Helium is also sometimes used as the base gas, with small amounts of argon and carbon dioxide added. "

so apparently temp increases. Looking at my class notes, have a line in there about this triple mix for stainless steel welds in MIG vs TIG, but wasn't sure the specifics.
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Old 28-06-2010, 11:00   #305
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Read it again Monkey. We were addressing the use of small amounts of He, not the use of He as the primary gas. Different use altogether.

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Old 28-06-2010, 11:04   #306
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Read post #301. You had no idea why. Don't deflect.
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Old 28-06-2010, 11:08   #307
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Actually I won't. Trying to enlighten someone who thinks he knows it all is....well.....not very interesting.

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Old 28-06-2010, 11:26   #308
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BTW I ran the paint up well above the welds on my toe rail and that seemed to help a bit.

Thomas
That will of course keep the mild steel and weld protected from the ellements nicely (as long as that all important paint layer is kept up but the fact that the two materials are joined means that the more noble stainless sitting out there in the weather doing it's stainless thing will slowly rob electrons from the less noble mild steel. At least it's above the saltwater and not accelerated by bieng imersed in an electrolite. On my aluminum boat everywhere stainless bolts have been used the aluminum is crusting a bit under the paint- being sacraficial. Needless to say, aluminum is slightly farther than mild steel is from stainlesses on the galvanic scale but not much. They'll all be replaced with galvinized. I'd rather deal with a few rusty bolts than loose my hull thickness. Theorhetically your zincs should work better than mine as they are further away from your parrent material than mine on the galvanic scale. The scary thing is when you see how fast dissimilar metals can dissappear when electrical current is added to the mix (electroplating..). Keeping all electric totally isolated-no grounding to the hull- seems to be the best practice as far as the boat is concerned. (Which, according to the autorities, isn't the best practice as far as people are concerned...but it's easy and cheap to make people-expensive to make a boat!)....
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Old 28-06-2010, 11:35   #309
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The only aluminum boat I've ever owned was a small motor boat and that was on a fresh water lake, so I can't speak from experience. All the stainless on my Roberts was well above the waterline, except for the 316 crash plate which wrapped around the bow, and it was well painted. The toe rail was painted only from the deck up about 2". It had holes punched in it for the snatch blocks, which turned out to be a great idea. The paint was out of harms way and held up well (Ameron 235). If there was any electrolysis going on it was not apparent. That darn 304 though would get some rust spots on it. Not serious, but to me unsightly. A little elbow grease and a scots pad took care of the problem most times. Still, I'd never use 304 on a boat after that experience even if it does cost a lot less. Now my stern arch was aluminum and I had mylar pads between the aluminum base and steel deck with stainless bolts passing through the aluminum, but those were backed by nylon washers. I experienced no real problems with this arrangement.

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Thomas
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Old 28-06-2010, 11:48   #310
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I guess the same point could be made in reverse. What's the point of using stainless wire to weld stainless to non stainless? There is an interface in iether situation (and a physical and electrical connection which some want to avoid). However your point is good for other reasons, primarily that most wires have a higher carbon content than the mild steel that is being welded and the higher carbon content wants to rust more. Certainly where one is welding stainless to stainless it would make no sense whatsoever but I believe Haidan was speaking of welding stainless to mild steel on corners and such as trim where paint easily wears off.

The idea is to keep the point where the metal will start to rust as far away from the wear area where it'll get the paint scratched off. Mostly on my boat the wear areas are covered with 1/2" sch 40 pipe. 304 316 309 doesn't really seem to matter much, I welded it all with 309L rod, (yes even stainless to stainless, oh my) after the wire-spatter debockle, again doesn't seem to matter I'm not sailing a nuclear powerplant.
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Old 28-06-2010, 12:13   #311
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Now my stern arch was aluminum and I had mylar pads between the aluminum base and steel deck with stainless bolts passing through the aluminum, but those were backed by nylon washers. I experienced no real problems with this arrangement.

Regards,

Thomas
Aluminum and mild steel are quite close and you shouldn't experience much problem because of dissimilarity. Where water can sit in a crack though, the potential for poltice or crevasse corrossion exhists with aluminum. If you take it appart you will probably see some white powdery stuff and possible some pits. But ussually the stauff is thick enough to loose planty and not have a problem. Stainless is also very prone to crevasse corrossion. Stainless bolts especially when used under water will show the erossion where they are not exposed to o2 even when no dissimilar metals are in the mix.
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Old 28-06-2010, 12:16   #312
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Actually I did take it apart and I was rather amazed at how little there was. They combination of nylon washers and mylar pad seems to have done the trick in this case.

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Thomas
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Old 28-06-2010, 12:22   #313
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again doesn't seem to matter I'm not sailing a nuclear powerplant.
Nope! And it's a bit of a tank anyway. Plenty of thickness for some sacrifice! Seriously a real bennefit to the design to be able to have thick plating with steel. I was seriously considering an aluminum one because of the increadible potential strength that could be achieved by using twice as thick material and still having a weight savings. Would have ended up like the A-10 sort of- Now that's a thought...anyone want to build one out of titanium?
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Old 28-06-2010, 12:32   #314
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I had the great pleasure of watching part of a new wing being built at Cedars-Sinai hospital. My son was in the hospital for 15 days as they were welding the framework together. BIG "I" beams, like 18" X 24" X 3/4" thick. I automatically assumed that they would be stick welding but they were not. In fact, they were mig welding the entire frame. They used flux core mig because it was too difficult and dangerous to haul gas bottles around. The mig wire was quite large as I recall, about 1/8" in diameter. I use .023 wire in my racecar building business, sometimes .035. They would lay a 12" X 36" X 36" fiberglass blanket over the joint to be welded and clamp a huge rosebud torch tip under the joint and heat it to 350 degrees before they started welding.
One of the welders was kind enough to spend his lunch break with me a couple of times explaining to me how they did everything.
One interesting part of it all was that when the joint was done they would drill and grind a 1 1/2" hole right through the middle of the thickest part of the joint and weld it up from the center out to be certain that they had complete penetration throughout.
He said that there was about 10 hours of welding per joint. Not counting cutting, fitting, heating, chipping, or grinding. 10 hours of the welder running.
Besides the part where my kid survived, he was the bright spot of the 2 weeks at the hospital far from home.
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Old 28-06-2010, 12:39   #315
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BTW, I've read a couple of anchor test reviews. They're not all good at all. There are about (IIRC) 50% of the commercially available anchors that are absolute crap. Either they failed to do their job well or they failed structurally. I'll be all for trying to make my own anchor when I get to that point. It seems that if I test it one time that will be more testing than many manufactured anchors received.
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