Help again... welding

[thecheat]

Hey, well... I went to a local fabricator's shop and picked up some STAINLESS.

Now, I got a couple different sizes, but, one small sheet of 20 gauge. I'm working on cutting all the pieces out for another mini thermojet, and am basically trying to get some experience with stainless before moving up to bigger projects.

Here's the problem. I'm having one heck of a time welding my piece of stainless! I tried it out the first time, and welded two small pieces of stainless pipe together with little problem. A little later I tried to weld one of the intakes for the PJ. Total disaster. the welds were wrinkled and look like crap.



I don't know what my problem is! perhaps stainless just welds ugly... I really don't know. (I'm using a TIG by the way)

my power, no matter how I fiddle with it, too low to melt it, or too high to control it, can't get it to look good! (besides the fact I ruined a good piece of piping...)

power's at 30-50Amps
2% thoriated tungsten electrodes
(no filler metal)
argon at 20cfh flow rate
electrode sharp
well grounded
well cleaned
as far as I know it's 304 stainless (here's the label, I don't know how to read it...)



any guesses why it looks like it does? this is all a learning experience for me, and I really want to get good at this stuff!

[hinote]

any guesses why it looks like it does? this is all a learning experience for me, and I really want to get good at this stuff!

Check your PM

[Dave_G]

perhaps stainless just welds ugly... I really don't know.

'Cheat' : Stainless welds beautifully...just takes a little practice -- See attached photo of 180 degree U-bend made from two 90 degree sections of 304SS. It was TIG-welded without filler.

Lots of people can give you dozens of tips, but there's no substitute for experience. You're burning through. Turn the heat UP, and try to weld faster. Stainless likes high heat and fast welds -- completely the opposite of Aluminum. There's a saying when welding stainless: "Get in, make your weld, and get out FAST" If you take your time with the puddle like you would when welding Aluminum, you're going to burn through. Try to target a travel speed of 1/4 to 1/2 inch per second.

**

Bill: Good to see you posting again. Welcome back!! Your expertise and informative posts were greatly missed!

Dave

[hinote]

Bill: Good to see you posting again. Welcome back!! Your expertise and informative posts were greatly missed!

Dave

Please DON'T consider that a post--just an alert.

I'm sticking to my decision not to post on the Forums.

[El-Kablooey]

With SS, prep is everything. It needs to be absolutlely clean, I want to use the word sterile. With thin SS sheet, you need a perfect fitup, no gaps anywhere. You need to be backpurging. Not doing so will cause "sugar" really bad on the backside of your welds, and with thin stuff it will cause you to burn through every time. You can also use Solarflux-B on the backsides of weld areas instead of backpurging. Solarflux works well, I use it often for places that are a pain to backpurge.

You are in the right range for amps, Try 35-40 for starter. Like Dave said, set it up to puddle quickly and weld fast. Keep your welds short for now, only try to travel for 1/2" or so before you stop and skip to another location while that bead cools.

When you get the prep right, SS is fun to weld. I would rather weld stainless than anything, especially thicker stuff. It flows nicer, and makes some beautiful welds.

In the pictures you posted, the top piece that had been welded has alot of problems too... The bead should be very shiney, and the only color should be a little pink and purple hue here and there and around the HAZ.

[El-Kablooey]

Bill: Good to see you posting again. Welcome back!! Your expertise and informative posts were greatly missed!

Dave

Please DON'T consider that a post--just an alert.

I'm sticking to my decision not to post on the Forums.

Was that one a post?



Seriously Bill, if you have something to share... Well that IS what this place is for ya know. It's a shame to send helpful tips in a PM.

[Dave_G]

Cheat: Just an FYI...That U-bend I made in the photo shown above is the same wall thickness as the tubing shown in your second photo; about 0.065".

I made that weld at 75 amps. Anything below 50 and you'll risk burning through, because you'll have to go too slow. I admit that 75 is a little high, but I like to weld fast -- saves on Argon ;-)

It just takes practice. Set up on some scrap and get your procedure dialed in to where you're making good welds BEFORE you tackle your semi-finished parts for your engine. If you change material thickness, or weld type, setup again, and don't weld your good parts until you're making good welds on your scrap pieces.

El-Kablooey's right, "stitch" welds will introduce less distortion into your part and make it a easier to weld. You can also use the 'backstep' technique. That's where you make a short stitch -- say half an inch -- Then 'backstep' and make the following stitch so it terminates at the beginning of the previous one. Make sure the part is fully tack welded first. Backstepping can help to reduce distortion in parts, without having to move the part around so much.

Hope this helps.

Dave

[thecheat]

Thanks for the tips! All this is helping, and I'm very glad for the help!

Here's what I've got down.

use argon
use electricity
welder must be plugged in
you must use tungsten (preferably sharpened)
molten metal is hot

:D

So my main problem is, I'm slow. So, turn it up and speed it up! (I guess like a mig...)

Back flushing will be an interesting problem for me to work with... how do you guys do that?

Also, what should my argon flow rate be? I've got one of those nice flow meters with the bubble that tell the rate (that's what so far is universally recommended to me). I've been draining my tank pretty fast... (20CFH on an 80CF tank)

Anyways, thanks all for the help, if you've got more, lump it on me!

PS: why is stainless so different to weld than steel? my movements are the same for the steel as the stainless but the stainless looks like crap... guess I'd better go practice! And roll another intake...

[larry cottrill]

PS: why is stainless so different to weld than steel? my movements are the same for the steel as the stainless but the stainless looks like crap... guess I'd better go practice! And roll another intake...

Basically, there are two main problems with stainless:
- The metal burns in air at welding temperature
- The metal is a very POOR heat conductor

Understanding these two factors explains all the hints and tips you're getting. You MUST shield the back side of what you're welding, not just the front side where you're applying your heat. In fact, in acetylene welding (the way I've done it), a flux on the BACK side is much more important than protecting the front side (which is bathed in flame, not air). You could do that by flowing a little argon through a tube at one end of your intake tube as you weld - that will use a lot of gas, though.

The poor conductivity is the reason for moving quickly - the heat buildup in the local area of the weld is very rapid. It also is the reason that welded areas can end up "wavy" - the metal heats and buckles up (or down) as you're working. Naturally, it usually doesn't buckle equally on both pieces, so you can get some serious local misalignment, i.e. "waviness". Experienced SS weldors will start out by tack welding at very close intervals, say every 3/4 inch or 1 inch, along the seam before doing the finish weld, just to hold reasonable alignment between the parts (buckling is much less troublesome when performing the small tack welds).

In acetylene welding, I actually used a lower heat than I would with similar thickness steel. It was surprising how quickly the metal would be ready to weld, because of the heat retention, and once you were there, you still had to move the weld quickly along!

The conductivity of SS is so poor that I actually found I could handle the pieces at the other end, 16 inches from the weld, FAR longer with bare hands than I would ever think of doing with plain steel of the same weight and geometry. It is VERY different.

L Cottrill

[thecheat]

Ok, I took some of your tips and ran with them!

tried welding the pipe with 50Amps of power... UGLY weld, whether I moved fast or not.

tried with around 30Amps welding was controllable, and fast. (I don't know how good my penetration is... hard to see on the inside of a pipe.

Here are two pictures, Without cleaning, and then, with cleaning. Please note the middle two welds are the ones I just preformed.




I did NOT use any zigzag pattern, I just welded straight along the crack, this is how I am supposed to do this, correct?

PS: Larry, thanks for contributing! It makes sense now why shielding is so important on the BACK. I didn't know the metal burns at that temperature, but, it makes sense.

Any more donations of knowledge?

[El-Kablooey]

Try backing your argon flow rate down to around 10-12 CFH, and make sure there is no wind, or fans blowing in your welding area. Backpurging or fluxing will be a huge help.

What diameter tungsten are you using? What size gas cup are you using?

[thecheat]

ok, will do!

No wind or fans...

I guess I'll have to wait to find some of the flux (are there any alternatives to solarflux?) Backpurging isn't going to happen.

tungsten, 1/16ths

gas cup, I was using what was labeled as "4" just changed to a bigger "6" just to experiment. (don't know if that helps... I can't seem to find my ruler...)

[anguz]

http://www.millerwelds.com/education/bo ... hlets.html

you can do worse than reading the stuff on the above link

[El-Kablooey]

You aren't going to have much luck until you backpurge or solarflux. Your local welding shop should have solarflux. It's kinda expensive, about $40.00 for a 1lb can. That can will last you a very long time though.

[jerry marra]

cheat,

why are you using just high flow of 20?,back it down to 10,tha's all you need,otherwise you are creating a turbulance and sucking in outside air.

Kablu is right ,make sure there is no outside air movement and the parts need to be realy realy clean,use a brush thats dedicated just for Stainless.

Also double check your ground.

jerry
pulsereactor