How do you properly weld Stainless? Tips? Tricks? Advice? Techniques?

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sniper

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So I just started TIG welding some stainless together and at first i would try and fill the simple butt joint with rod. Well now iv seen that with simple heat control and motion i can get super flat nice looking welds with no need for filler rod. Welding like this makes it look nice, but is it strong? I will have pix of my work up soon,

So how do you weld your stainless joints? Any one have any basic tips, tricks, advice?
 
you dont want it to be concave. so just heat is a nono, you want it slightly convex, ie humed up just a bit. so find an amount of filler that just bairly fills the groove and bairly makes a hump.

im sure more experanced tig welders on this forum will add it more insightfull info.
 
There are a number of different things that need to be concidered when welding SS. Thin gauge need to be back side shielded for one either using solar flux or back gassing. You can fusion weld i.e. no filler on thin stuff as long as its not under a lot of stress, it is pretty stong but still better off using some some filler that is about half the thickness of the base metals if it is thin gauge. example would be 16ga. SS exhaust piping best bet is .035 (1mm) filler. This is for butt welds. If it is an overlap joint like one pipe slipped into another or a plate overlapping another, no filler is needed as long as the thickness is under 1/8" (3mm), thicker then that and you would want to use filler.

Stainless is kind of funny with heat settings and depositions rates Typically you will be fairly hot but have to be fast or you will overheat the joint and that causes other problems like cracking. And no, lower heat and slower deposition rates doesn't make it easier, this route will over heat the joint too.

Basically you want to just start to melt the base metals and then add filler quickly. This is why you want to use a really thin filler cause otherwise it takes to much to melt the filler and you are then adding to much heat into the joint itself.

One trick if you have a amprage control device like a foot peddle or thumb wheel and you are consistant with it is to turn up the heat to get everything to melt quickly into a single puddle, dab your filler, then quickly bring the heat back down to the point that the puddle solidifies, then move forward to the leading edge of that solidified puddle and repeat the process. This is a way of cheating get really pretty welds if you cant get the heat and deposition rate dialed in, but it is more time consuming.

In the end, you will know that you are doing something right when you get nice shiny silver to gold beads. You dont want gray color as that is way to hot. A bit redish in color is still ok, a little hot but ok. Basically it will go from silver to gold to red to gray as temp increases. On real heavy gauge material it is very common to have a silvery blue color bead or a bead that fades from blue to silver if the two parts are different thinknesses.
 
Sigh forum problems eating my posts!
What exactly are you welding??? Post your pics!

Use 1/16 and 3/32 filler until youre welding very thin metal. I preffer 3/32 on almost everything, but I can control it. Once you get use to thicker it's just easier. There's much less rod feeding to do with your off-hand and your skill increases alot I remember when I went from using 1/16 and mostly 3/32 at the house to 1/8, 5/32 and 5/16 rods. For an entire week I was lost. Once I got use to controlling it I got home and was a MUCH better welder.

Stainless welds almost exactly like MS once you get it. The only major differance is the chromium is sensative to the heat you're inputting, so you can't dilly dally all day like MS. The other differance (that I love) is that unlike MS. A stainless (within reason) will not run away and flow with gravity. It stays exactly how your arc orientates it.


Learn your electrode and filler angles.
One of the best first things you can do is google te electrode and filler angles for various positions and types of joints to be welded.

DITCH YOUR GAS CUPS FOR A GAS LENS SETUP
This will HALF the argon going through the torch, while allowing TREMENDOUS amounts of stick-out where you can see what you're doing. Also very helpful for doing restricted welds without a pencil torch. ;)




Here's the flat out easyest way to learn to do stainless pipe.
The slowest you can practically weld it (giving you the most time to see what you are doing) is in pulse.
Set your machine to GTAW-P (tig-P) mode.
40amps
Balance too 20% high amp 80% low amp
Pule Per Second to 6 or 8 PPS

Start your arc with the pedal floored.
When the puddle is the wanted size dip your filler the first time.
Advance your arc and drop your heat from 100% to 75-80%.
From here continue the weld dipping, or walk the cup.

If you don't want to run pulse, start with 30amps.

The earlier you learn to walk the cup the better off you are!

Remember you're not getting paid $25-55/h to make 6GR welds. Your life will be made easier by keeping all pipe to pipe welds uphill.

Stainless colors for two reasons. Chromium carbide precipitation, and poor shielding gas coverage. When you overheat stainless the chromium goes bye bye. Grossly overheated stainless is grey and is completely unacceptable. Mildly overheated are the pretty blue to purple tones. Poor gas coverage generally will be black.
It should seem obvious. Where there is color, there is a lack of chromium. The penalty for not brushing the "pretty ricer muffler colors" off is early rusting. All stainless exhaust welds need to be brushed clean after welding wth a stainless wire brush.

As he told you, a weld with nice gold bands around it lets you know that the heat is about right, and the gas coverage is good.


Now most manifold / exhaust welding is done between 18-gauge and Schedule-10 (.05-.109). This (and schedule-40) is fairly easly welded in one pass once you get the hang of it. I always one-pass with a correct root opening for my filler simply to save argon and stay in practice.
That being said 99% of people are there are going to two pass everything from 16 gauge and up by beveling the pipe, then running a cap pass. I suggest starting with that!


Stainless requires backpurging with argon, or solarflux-B. For yourown (or a buddies) work, no you do NOT have to backpurge even a turbo manifld. That being said do it when possible and NEVER sell non-backpurged welds. It's 2008; money welds get backpurged.

AFA the weld bead. Joining pipe to pipe with a butt or groove weld you want a flat, to convex profile (1/16". 1/8" max). Honestly... A nice bead will reinforce around 1/32" with all this thin pipe. With a fillet weld (say a slip joint, or weld to a flange) it CAN be concave, flat or convex PROVIDED the demensions from toe to toe and root to throat equal the thickness of the base material (or the smaller part)






The only real thing to grasp when you first weld anything beyond insensative mild steel is that heat isn't just amps. It's an average. It's an average of your arc's output VS the time it takes you to weld something.





One last thing. Clean the metal before welding. Check the filler and electrode for contamination BEFORE welding.
While you're welding the filler rod will cause impurities to float to the surface of the weld puddle. It'll be just a tiny dot that you carry along as you weld. If you keep it flowing around the middle of your puddle you travel speed (and hence your average heat input) is right on the money, and your angles are atleast fairly ballpark correct!











Alot of people ask how to walk the cup. And there's no really good way of telling people/grips without just showng them.
Theres an easy way to feed your filler rod and some grips on how to hold your torch to walk it.

When you walk the cup, you do not start by wlking the cup. You start by dipping th first dip or few then you transition into doing it to make it seamless. The electrode you simply run down the joint and hold pressure on it. Once you get the walking motion down pat it nearly welds itself.

th_toggrips2.jpg


th_toggrips2.jpg
 
About filler sizes. Cut your preffered rods down where you can easily use them. I cut 3/32 and 1/16ths in half. For the size weld puddles we generally carry around it may only take 1/8 of a 3/32" rod to do a weld. 1/4 of a 1/16" rod. And an entire stick of anything smaller.

Remember do not simply shove filler metal in and rop the heat. It's a normal tendancy, but its not right. When you add filler you are cooling the puddle alot. You're litterally throwing ice into boiling water. If you're having to add filler and drop the pedal at the same time, you're running too hot. Try to get your travel speed and dipping patterns down to where you do not need to varry your amp much, if at all. That's your sweet spot!

One more thing about dipping... Alot of people like to tell guys to make the C Z triangle motions with their arc when they are dip welding. This is incorrect so don't get in a habbit of doing it. The torch travels down the joint, and the filler is added to the leading edge of the puddle at the joint. If you want to work the torch, walk te cup ;)
 

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WOW. talk about a wealth of information!

I never welded without a gas lens as it was something i bought when i bought a tank. The color scale helps too. Iv been welding 304 with 308 filler rod, will that make the bead look dull? iv also had the welder at 125 amps with light petal and no pulse, but iv been at 40 now. I am also using the stock Red tungsten. I was using thick rod as the person who sold it to me he liked it better, but he wasn't a noob. So thick filler plus a welder set too hot led to all the welds being gray. I am going to start getting photos of everything once i get my camera back. Till then ill be using up gas and trying not to dig tungsten. again, thanks so much for your post,
 
308 is the correct filler for 304. Actually, you can use anything that is a higher number. But generally,
304 to 304 use 308 filler
304 to mild use 309 filler
 
Some great direction there Toysrme. You mentioned back purging. I wondered if it might be worth adding when I was taught to weld piping in stainless I was shown how to T off from my argon feed and used foam or foam tennis balls in either end of the pipe( as long as heat transmission allows) and in one end pass a thin argon feeding pipe through the foam into the pipe interior. This purges the pipe of oxygen and gives a clean weld on the internal surface with none of that greay furring.

Chris
 
That's a good way.
Personally I use slices of bread, no joke. Find something that's cheap, can take the heat if it's too close and will burn off so fast it wont exactly contaminate it!
 
That's a good way.
Personally I use slices of bread, no joke. Find something that's cheap, can take the heat if it's too close and will burn off so fast it wont exactly contaminate it!


LOL, your not the only one to use bread.... everyone used to look at me like I was crazy at work......... Glad to see someone else that does that.....
 


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