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Old 04-07-2012, 03:56 AM   #2656
David R
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You do have lots of questions. You are learning the same things I did about stainless.

Fusing stainless is OK. You end up with a good joint.

TRY IT, Weld a piece with filler and fuse a piece. Then destroy them to break the welds. Have fun doing it, get your frustrations out.

If you can leave a little extra base metal and fuse, its a perfect weld.

For the amps thing yes it takes more amps if you add filler because it cools the puddle.

If you truly and correctly purge your exhaust you will get NO sugaring. It can be a full pen weld.

Using a large gas lens and large cup help a lot on the front side. Are you using a foot pedal?

Keep at it. I would cut those cupons and weld them again. Note the warpage. Stainless warps like crazy.

I have pictures if you need them, but it looks like you are going in the right direction. Seat time is what it takes.

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Old 04-07-2012, 08:52 AM   #2657
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stainless

Quote:
Originally Posted by sakurama View Post
i'm using a 1/16 2% tungsten, i started with 1/16" filler but it seemed to need more heat and so i was getting sugar. I decided to swap to the next smaller size which was .035 and that seemed to make a big difference. I should shoot the back of those welds but most of them show sugar through the back when i was up over 40-45 amps. Lower and i was just getting the rainbow on the back but no full pen. These are butt welds on probably .050-.065 stainless sheet. Gregor
fwiw, i don't weld stainless much but have been versed in its use for the bicycle industry. So take my advice with a grain of salt until someone who's a real welder chimes in and tells you that i'm all wrong.

My understanding is that you should treat it as if it were titanium, which means that the three most important things to welding it are cleaning, cleaning and purging (to keep it clean). It looks like the stainless sheet wasn't cleaned with abrasives before you welded it. Use a flap wheel, a wire wheel or even scotchbrite to clean the area to be welded and then about 1" back into the haz on both sides of the coupon. Wipe it down with acetone or denatured alcohol after you abrade it. At a minimum, wipe down your filler with a solvent too. I tend to scrub my filler with scotchbrite and then wipe it. This will help with some of the discoloration.

Also, check your torch setup. You should have a gas lens in there with an appropriate cup size for the amount of heat you're putting into it. Try a #10 to start, maybe a #8 will be enough. Also check your argon flow...20-30 cfh uses up some gas, but goes a long way to keep your surface clean.

You're going to have to use enough heat to get a proper joint. For a full pen joint with a good (aesthetically) filler flow you're going to get the sugaring on the back unless you back purge it. I have a tool you can borrow while you're welding these coupons. I hardly ever use it so you're welcome to it for a while.

Quote:
Originally Posted by sakurama View Post
my impression is that the control needed is way finer than i would have guessed. I would have thought you'd have a window of 10-15 amps where you could weld but it seems more like 2-3 amps. Is this really the case? How the hell do you get that nice golden weld when it seems like that temp is just barely on the verge of melting the stainless? Why does it seem that adding filler, at the same amperage, makes the weld hotter? I can fuse at 45 amps but add filler and 45 amps seems to cook it and i end up with gray dull welds. Gregor
the amperage you use is going to depend highly on your travel speed. You can get away with a lot more heat if you're going fast. Most beginners go very slow because they're too worried about blowing holes in the material. Blow some holes in it. Learning to fill the gaps is a very valuable exercise.

Do you have any photos of fusion only passes? That might help diagnose the issue. My guess goes back to the prep procedure. If you fuse dirty metal, then try to add filler on top of it, you're going to have a tough go of it. In an ideal world, you'll see no color change after your fusion pass. If you do, breakout the stainless brush.

Quote:
Originally Posted by sakurama View Post
another question: I've always thought you wanted full penetration but my instructor was saying that full pen on the back of stainless will give you sugar and you've cooked the chromium out of it and weakened it. Are you going for something like 90-95% penetration? On my headers i have an argon purge set up but should i be trying to not fully penetrate? There was a sample in the classroom of a flawless stainless weld of a pipe to a flange and there was only the hint of color on the back with a tiny felt bump where the weld would be but no real distortion and certainly no penetration to the other side. Is that what i'm going for? Gregor
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Old 04-07-2012, 09:37 PM   #2658
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Sean and David - thanks for the help.

My fusion weld was perfect or at least that's what the instructor said. Golden with a small rainbow HAZ and a perfect, slightly concave, bead. Since it was just on the verge, but not fully penetrated my instructor thought we should test it and she said that if we hammered it from the back it should break but it didn't. In the group shot it's the one at 90°. I don't know why but I thought I had to add filler. It didn't occur to me that I could do my exhaust without filler. Of course I would now have to break my tacks and make perfect fit ups instead of the merely good ones I have...

It's funny you mention cleaning Sean as when I pulled the stainless out of the bin I asked the instructor if they used acetone or alcohol to clean the metal and the filler and she said, oh, they don't bother with that. That was my first clue that I might not be dealing with someone who tigs at a high level. Hopefully I'll find the person there who really knows their stuff.

So, yes, the coupons were probably not clean and of course I had nothing to clean them with. I was taught to keep various brushes designated for each metal, to clean with alcohol and to scuff all metal around the weld before starting. All things I didn't do. I also was using a borrowed helmet and thicker than I care for Tig gloves. I plan to get my shit together for my next session and I'll bring my own alcohol, scotchbrite, helmet and gloves.

I also got a big glass diffusion for lens my Dynasty that I've not tried. The instructor gave me her diffusion lens but it necked down to about a 6 or so. I'd never seen anything like it. I was using a 6 or 7 cup before that and the argon was at 15 which is what I would normally have it set to. I'll crank that up next time - it's their argon, not mine.

Yes, my best weld was at a real snails pace. Not the super fast dip and move that I've seen others weld. My instructor said to pick up my pace to see if it helped but it didn't.

I've got to head out of town for work this week and then to Italy for a week (tough I know) and then I'll try to get better prepared for my next session. I'd love to stop by and watch you put down a few beads Sean as I think getting the chance to watch someone really good will answer a lot of questions. Don't argue - I've seen your frames.

If I can I'll do some practice when I'm in NYC next week as well.

Thanks for the tips and I'll post an update.

G
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Old 04-08-2012, 04:26 AM   #2659
David R
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Laugh gas lens

This is the gas cone I used on a counter top I did a few weeks ago. I ran the flow at about 15 to 20 cfh for a FLAT counter top with almost perfect fit up. #17 air cooled torch with a .040 tungsten. If it was a round part or different conditions, I may have used more cfh. With a gas lens, its supposed to be able to use 1/2 the flow because its a laminar flow or nice and smooth. If you turn the gas up too high, it can cause turbulence which can draw air into the stream by the venturi effect.



If you can go back, un tack and make better fit up, you will not regret it.

When I fuse, I move the torch ahead and back about 1/4". This encourages the weld to move together. It also preheats the joint in front of the weld.

3 or 4 amps is a difference of 10% at 30 or 40 amps, so yes just a few amps makes a difference. You are doing great that you can tell how much is too much. When doing these silly counter tops I use the bare minimum of heat I can get away with and still get a weld.

Best of luck and keep at it. If you can weld a few inches perfect, keep at it and you will get all the inches perfect. It took me a long time to get the hang of tig. Like 5 years.

Could you post a pic of your exhaust when done?

David

Edit, the tungsten is discolored because I turned the valve off too soon. Job was at the customer.
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Old 04-08-2012, 10:11 AM   #2660
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Quote:
Originally Posted by sakurama View Post
Sean and David - thanks for the help.

My fusion weld was perfect or at least that's what the instructor said. Golden with a small rainbow HAZ and a perfect, slightly concave, bead. Since it was just on the verge, but not fully penetrated my instructor thought we should test it and she said that if we hammered it from the back it should break but it didn't. In the group shot it's the one at 90°. I don't know why but I thought I had to add filler. It didn't occur to me that I could do my exhaust without filler. Of course I would now have to break my tacks and make perfect fit ups instead of the merely good ones I have...

It's funny you mention cleaning Sean as when I pulled the stainless out of the bin I asked the instructor if they used acetone or alcohol to clean the metal and the filler and she said, oh, they don't bother with that. That was my first clue that I might not be dealing with someone who tigs at a high level. Hopefully I'll find the person there who really knows their stuff.

So, yes, the coupons were probably not clean and of course I had nothing to clean them with. I was taught to keep various brushes designated for each metal, to clean with alcohol and to scuff all metal around the weld before starting. All things I didn't do. I also was using a borrowed helmet and thicker than I care for Tig gloves. I plan to get my shit together for my next session and I'll bring my own alcohol, scotchbrite, helmet and gloves.

I also got a big glass diffusion for lens my Dynasty that I've not tried. The instructor gave me her diffusion lens but it necked down to about a 6 or so. I'd never seen anything like it. I was using a 6 or 7 cup before that and the argon was at 15 which is what I would normally have it set to. I'll crank that up next time - it's their argon, not mine.

Yes, my best weld was at a real snails pace. Not the super fast dip and move that I've seen others weld. My instructor said to pick up my pace to see if it helped but it didn't.

I've got to head out of town for work this week and then to Italy for a week (tough I know) and then I'll try to get better prepared for my next session. I'd love to stop by and watch you put down a few beads Sean as I think getting the chance to watch someone really good will answer a lot of questions. Don't argue - I've seen your frames.

If I can I'll do some practice when I'm in NYC next week as well.

Thanks for the tips and I'll post an update.

G
A few more things...

Experiment with 3/32 tungsten too. I prefer it actually but mostly for cosmetic reasons. It spreads the cone a bit and makes the bead "wash" better into the parent material...for me.

I've had some friends who have had less than stellar experiences with those Pyrex nozzles. If you're still not getting good results when you switch, keep that in mind. I definitely had a few dud welding setups that were supposed to be the shit for welding ti. In the end I have a plain jane gas lens and nozzles from #8-#12 that work perfectly.

If your machine at school has a pulser, experiment with that too. Using a pulser can really help reduce the total heat input into the piece and can reduce distortion. Especially when you're dealing with sheet, there are some tricks you can use to limit the distortion. I've played around with pulse frequencies from 250 down to 1.5. I've found that I can move much faster when I use a high pulse rate BUT when I go back to add filler, I can't see the joint well enough.

You can also "cheat" with a pulser to make a much nicer looking bead. Some refer to this as gutter welding...where you essentially spring load the filler into the joint and let the arc consume it as you move along. It can work very successfully if done right but you have to be careful around acute angle joints especially as it's very possible to leave voids under the filler if you get lazy with your torch angle.

About gloves - It seems that everyone uses leather gloves. Grab a set (or I can give you a set) of tight fitting kevlar gloves to see if you like them as much or better. IMO, you get better dexterity and it's easier to cool off your hand if you do something stupid.

One for the experts...if one were to merely fuse the entire exhaust, would the thickness of the tubing at the weld be sufficient to hold up under use over the long term?
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Old 04-10-2012, 06:21 PM   #2661
KTM640Dakar OP
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Quote:
Originally Posted by VertigoCycles View Post
A few more things...


...if one were to merely fuse the entire exhaust, would the thickness of the tubing at the weld be sufficient to hold up under use over the long term?

Welding without using filler is called autogenous TIG welding. As you would expect the area that you weld will be slightly thinner than the parent tubes. You see many custom exhausts welded without filler. I guess as long as the reduction in cross section at the welds is stronger than the forces that the pipe will see than your golden.
You will need the parts to fit up perfectly. So I wouldnt be without a cut length in your hand just in case you need to add a little filler to keep the gap filled.


A good two stroke pipe can look like a piece of art.
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Old 04-11-2012, 08:59 AM   #2662
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Stainless Steel......

You don't have to be as careful about pre-cleaning as you do with aluminum, getting rid of any oily residue on the surface is what is most important. SS doesn't get the oxides on the surface that aluminum does that contaminate the welds.

Go for full penetration and purge the back side. This will be really important on your pipe. Once you get it down, a newbie will have a hard time determining which was the backside.
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Old 04-14-2012, 05:59 AM   #2663
sakurama
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Hi guys,

Thanks for the help so far. I got back to east for work and found a little time to get to my shop to practice with my own gear. I had been using a 3/32 tungsten but I had a pyrex diffusion lens I'd ordered but never tried so I put that on and it uses a 1/16" tungsten.



Here's some early practice.



The weld on the right is from two weeks ago - now I can see it's obviously scorching the shit out of the material. The others are my practice over the last day.



Now after a few hours of practice I'm to here. The top one is my last weld last night before I went home. I think the middle looks a little cold but on the back I'm just getting full penetration. This is 35amps for .065 wall with 1/16" tungsten and .035 308 filler. Gas is 20 cfh with the lens. Towards the end I was trying to ride the peddle with the machine set a bit higher than I thought it needed (35 amps) so I could work on my manual control.

I feel that I now have a good feel for the heat and puddle and I just need a few miles of bead under my belt to be consistent. It's much harder to weld tube than flat stock. I seem to be able to only do about 1/2" at a time so I'm trying to tie my welds together so it looks better but following the tube around and keeping the torch angle is tough. I need to brace my hand on something and that limits my ability to freely follow the tube.

One funny thing I noticed: I really want to see the weld puddle so I get my helmet really close and it felt like I was spacing out or couldn't hold my concentration. It took a moment to realize that I was trying to look from 6" away and that, for the first time in my life, it was my eyes. I need to wear reading glasses I guess. I tried welding from father away which was fine but I really want to be super close to see.

Anyway, feel free to offer some criticism.

Gregor
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Old 04-14-2012, 06:45 AM   #2664
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Get some cheater lenses for your welding hood. And wear reading glasses too if you need to. I am in the same boat. If you can see you will weld much better.
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Old 04-14-2012, 07:33 AM   #2665
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How are you bracing your torch? Your welds are wildly inconsistent in places. Are you using your middle finger to brace? In your class was she teaching you to walk the cup or freehand?

I think-- and I'm a pipefitter, not an exhaust fabricator-- that a full pen, open butt weld with filler would be better than a fusion weld. Lots of guys can make excellent stainless welds, not so many can freehand a fusion weld.

Of course you'll need a double flow metre for the argon tank and some hose, but you can plug the one end and fill from the other and use foil tape over the joint. Peel it back as you progress up the weld.

I have very little experience welding something so thin. When we do .065 or .049 stainless it's usually done by an orbital machine unless it cannot.

I flapper wheel on an end grinder will do all the cleaning you need.

Make sure you get some cheaters. Any welding shop will sell them. Get two or three (they don't cost much) in differnt powers. If you can't see, you can't weld. Period. This isn't like a carbon stick weld when you can hear/feel it in.
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Old 04-14-2012, 10:04 AM   #2666
David R
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Sakurama, your welds are getting better. You are not overcooking the filler as much. Doing beads on the pipe is good, now its time to cut the pipe and do it again. It will take less heat because the edges burn back real easy with stainless.

Practice on butt joints and you will find out fit up is MOST important.

Tack in 4 places, don't stop or start on tacks.

Have fun!

David
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Old 04-14-2012, 11:59 AM   #2667
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You don't want him to tie into his tacks?

I suppose I could see running over his tacks in this case...

had to think about it for a second
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Old 04-14-2012, 07:12 PM   #2668
David R
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Laugh

I try to weld through the corners and weld through the tacks. stops and starts should be planned. If I am building something that has to be air or water tight, I make as few starts and stops as I can. Those and tacks are where I could get leaks.

David
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Old 04-14-2012, 07:19 PM   #2669
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Instead of restarting where you stopped backup about a 1/4" or so fireup and everything will nice an hot when you come to where you stopped.
By starting on a tac, rather than between tacs, you eliminate the number of tie ins' that need to be made.
If you are using a fill wire fuse the wire to the side near the tac then without breaking the arc backup about 1/4" or so and start a puddle then when you come to where the wire is fused everything will be good and hot and flowing. The same method can be used if multiple passes are required to fill the joint.
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Old 04-15-2012, 06:28 PM   #2670
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Tank ? I have a small tank 7"x 24" on my welder and a large 7"x 48" tank for Nitrogen, are they the same? I would like to make the larger one my welding tank and the smaller one my Nitrogen.
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