I have been practicing welding stainless. I am doing 2mm thick stainless and my trouble is that the thing will always warp, and other than tacks, it never comes out looking good.
I mean the weld is strong but I can't help but feel I won't be passing any tests...
I'm using Andeli CT-520D welder (Chinese, does TIG/Stick/plasma), 60 amps, trying to keep as short of an arc as I can, and using 1.2mm filler rods. Using 2.4mm tungsten, #12 gas lens (not Furrick or anything, just standard), WP26 torch.
also my big problem is my tacks look good but as soon as I start trying to introduce filler rods things get hairy. I can't move fast enough to not create a huge swath of red hot steel (that ends up warping like crazy).
The picture is a right angle joint, tested the weld by bending it, appears to be strong but doesn't look as good as I like it to.
How much argon are you flowing? With a #12 cup, you need to be pushing up near 25-30 CFH.
Once you put 2 tacks down, the material is hot enough that 60 amps is probably too high, or very near too high. Stainless tends to warp no matter the thickness. You could try using some chill blocks behind (thick aluminum blocks) to suck some heat out while you weld. Even go so far as to clamp the stainless to the blocks, weld, let cool completely, and you might escape severe warpage.
cj737 wrote:How much argon are you flowing? With a #12 cup, you need to be pushing up near 25-30 CFH.
Once you put 2 tacks down, the material is hot enough that 60 amps is probably too high, or very near too high. Stainless tends to warp no matter the thickness. You could try using some chill blocks behind (thick aluminum blocks) to suck some heat out while you weld. Even go so far as to clamp the stainless to the blocks, weld, let cool completely, and you might escape severe warpage.
I've done that... and it eliminated warpage, however my gas flow is about 5 liters per minute (I have no idea what that is in CFH, I'm guessing about 10?)
I will try your suggestion and see how that turns out.
Edit: Sorry I meant by done that is I clamped aluminum chill blocks all around a joint and it did eliminate warpage. But as a rule I weld with the pieces on top of an aluminum block.
I tried 15 liters per minute, welds are looking better, however I tried 40 amps without pulsing, and it takes forever for a puddle to form. Honestly I feel like I can go lower because I'm using gas like crazy...
But I am still having trouble with the weld being all blue, and not the beautiful welds I keep seeing on those videos. Are furrick cup and back purge really necessary?
Rule of thumb is cup size x2 equals gas flow. #12 cup = 25 CFH (you'll have to do the liters per conversion.
Back purge always helps eliminate the sugaring. Blue is fine. Gold is better. Promptly after welding, take a clean stainless brush and scrub the weld. They will return to shiny silver.
If you use a chill block, you may need more amps since the chill block is pulling heat out of the weldment. If 40 takes too long to puddle, increase your amps. Easier to feather off the pedal once your puddle is established.
cj737 wrote:Rule of thumb is cup size x2 equals gas flow. #12 cup = 25 CFH (you'll have to do the liters per conversion.
Back purge always helps eliminate the sugaring. Blue is fine. Gold is better. Promptly after welding, take a clean stainless brush and scrub the weld. They will return to shiny silver.
If you use a chill block, you may need more amps since the chill block is pulling heat out of the weldment. If 40 takes too long to puddle, increase your amps. Easier to feather off the pedal once your puddle is established.
I don't have a foot pedal and my welder does not take pedals. Unless there's a way to make a DIY pedal and somehow hook it up to the machine so that it would recognize it, I'm stuck using the on off switch on my torch.
Besides a lot of situations require welding without foot pedals so it would help to learn to do without...
Fair enough. Then you must learn to use the filler rod to chill your puddle and snap out of the weld intermittently.
Thin stainless won't take prolonged welds. The material heat soaks too quickly. Weld an inch, wait, weld an inch. Wait some more.
I did a job welding a stainless paddock for food service. Large, industrial scale. Even the thick pieces and pipes, I had to stop frequently, weld an opposite side to prevent distortion. A 12' tall, sectioned pipe took me days to weld. Every welded inch pulled the thing out of plumb. Weld. Stop. Move. Check. Weld. Stop. Move. Check. I consumed more rubber off my boots than filler wire.
first thing is use a thicker filler rod. the rough rule of thumb for thin stainless is use a rod the same thickness as the metal.
that cools the puddle and avoids you having to shove filler in which helps keep the speed up. i would be using at least 1.6mm filler.
stainless is a lot more prone to warpage. you just have to clamp what you can, move around as much as you can.
I’m beginning to understand why vast majority of stainless fixtures are tacked on. It’s so much easier to tack stainless and get a colorless weld. I never realized it’s ok to have it blue and sandblast it later. Probably a lot of exhausts are done this way or they backpurge everything.
Sandblasting stainless is not recommended. It embeds particles into the metal. You simply brush the weld, or chemically passivate it to remove coloring.
When you see stainless welds online and the color is perfect (straw yellow to gold) it has been welded by an experienced guy and very likely purged. Controlling the color is all about controlling the heat input. Time, practice, experience will teach you how to do this. No shortcuts to bend this learning curve.
taiwanluthiers wrote:I’m beginning to understand why vast majority of stainless fixtures are tacked on. It’s so much easier to tack stainless and get a colorless weld. I never realized it’s ok to have it blue and sandblast it later. Probably a lot of exhausts are done this way or they backpurge everything.
your color is not horrific. looks like a lot of mine (stainless kicks my arse). however thats not a big deal for a lot of applications. all that heat tint and color will disappear when you pickle/passivate it, which you need to do otherwise it will rust. even if you brush all the color off it will rust a short while later.
after you pickle it it will be nice and shiny.
Yea I seen some TIG welders that have the passivating function. How do you passivate it? Do I dip it in hydrochloric acid? The passivating function seems to use some kind of a chemical and the machine applies a current or something.
taiwanluthiers wrote:Yea I seen some TIG welders that have the passivating function. How do you passivate it? Do I dip it in hydrochloric acid? The passivating function seems to use some kind of a chemical and the machine applies a current or something.
basic way is buy an acid mix. you put it on for a certain length of time then neutralise and wash it off. this removes all the heat tint and reacts with any iron thats on the surface which would otherwise rust later on. also can put an oxide layer on top which helps protect the metal.
the machine version uses electricity and a weak acid solution to do the same thing, but generally its a whole lot faster.
however the kit is usually expensive.
i just use the acid mix. a lot of guys will just wash it straight off. i use the neutralising solution as well just to make handling a lot easier. you don't want to drop something thats covered in acid onto you or other things which may react badly with it.
So passivating is essentially applying a DC current to an acidic mixture and putting one electrode in the acidic mix and clamp the piece.
Or do what I did and have a clamp and a copper or metal wand which is soldered onto the other polarity, put a green scotchbrite on it and dip IT in acid and then rub the weld with that. It works really well, if the polarity is opposite, you'll push the metal of the wand onto the metal so gotta watch that.
The idea with passivation is to pull all the iron in the top off and leave only chrome, electricity helps with that, I don't think pickling will do it alone, but it might.
Any color is fine, really, all it shows is the chromium has built up a new oxide layer and depending on it's temp, the color will be different, I don't think gold or pink, purple or blue really matters, I tend to get all of those or just pure gold but I know if it's gray, it's probably toast.
S.S warps like a mofo, no way around it, stitch welding is the way to go, it's just the nature of the beast. Fat filler helps too as it cools the weld puddle, it'll almost seem like the puddle is spazzing when you dip into it as you cool it so fast.
Olivero wrote:So passivating is essentially applying a DC current to an acidic mixture and putting one electrode in the acidic mix and clamp the piece.
Or do what I did and have a clamp and a copper or metal wand which is soldered onto the other polarity, put a green scotchbrite on it and dip IT in acid and then rub the weld with that. It works really well, if the polarity is opposite, you'll push the metal of the wand onto the metal so gotta watch that.
The idea with passivation is to pull all the iron in the top off and leave only chrome, electricity helps with that, I don't think pickling will do it alone, but it might.
Any color is fine, really, all it shows is the chromium has built up a new oxide layer and depending on it's temp, the color will be different, I don't think gold or pink, purple or blue really matters, I tend to get all of those or just pure gold but I know if it's gray, it's probably toast.
S.S warps like a mofo, no way around it, stitch welding is the way to go, it's just the nature of the beast. Fat filler helps too as it cools the weld puddle, it'll almost seem like the puddle is spazzing when you dip into it as you cool it so fast.
Yea I had the current in which it took a while to form a puddle and I tried dipping rod into that too, and sometimes (like every 2 dabs) the rod wants to freeze in the puddle. I got better welds this way but if I used a higher current so that the puddle forms faster, the stainless would overheat but too much time to form a puddle = same thing. I can see why I don't see many fully welded stainless steel anything. They are almost always tacked every 2 or so inches. And tacked weld looks better (and I can easily achieve no coloration).
My understanding (and I'm far from an expert, so take it FWIW which ain't much) is that passivation only helps so much, and there's still the problem of carbide precipitation at the intergranular boundaries, and the only way to minimize that is to minimize the amount of time that the material is hot...in other words, go in fast and hot and get out as fast as possible to minimize the total heat input, because the longer the SS is at a temperature where the carbides will precipitate, the more precipitaton will occur, causing problems down the road with rust, corrosion and changes in the mechanical properties of the SS...
The point is that stainless warps like a mofo, you CAN weld it all, I've done plenty of fully welded, watertight welding and it's just patience.
Doing 1" or so stitch welds along something, skipping a 6" or so section, depending on the size, then doing that all along, letting it cool and coming back and doing the same again, then do that until it's full, then you can run a sealer pass which is just fusion welding the already welded parts to make sure the welds tie in properly.
That's A way to do it and there's more.
Shock cooling also will warp it, so keep it cool and be patient, that's how stainless is done.
You don't want to freeze the rod as the weld won't be good but then use smaller filler, you only need so much penetration and the more heat you pump into it, the bigger the tungsten electrode, the further away you are, the more heat and so the larger puddle.
Olivero wrote:So passivating is essentially applying a DC current to an acidic mixture and putting one electrode in the acidic mix and clamp the piece.
keep in mind you can still passivate with chemicals (and no power).
you don't have to have an electric setup to pasivate stainless.
for hobby or small shop guys, using chems is cheaper.
for commercial work where you do lots of it, an electric setup is a lot faster and save you a lot of labour.
Olivero wrote:So passivating is essentially applying a DC current to an acidic mixture and putting one electrode in the acidic mix and clamp the piece.
keep in mind you can still passivate with chemicals (and no power).
you don't have to have an electric setup to pasivate stainless.
for hobby or small shop guys, using chems is cheaper.
for commercial work where you do lots of it, an electric setup is a lot faster and save you a lot of labour.
hmm. I was under the illusion it required electricity.
Olivero wrote:
hmm. I was under the illusion it required electricity.
But I've been wrong before.
i think thats called electro polishing which does the same job.
passivating is done with weaker acids than pickling to form an oxide layer.
afaik pickling with strong acids to remove tint, scale etc, then pickle with weaker oxidizing acids to make the protective coating.
electro polishing does both at once in seconds.
Olivero wrote:
hmm. I was under the illusion it required electricity.
But I've been wrong before.
i think thats called electro polishing which does the same job.
passivating is done with weaker acids than pickling to form an oxide layer.
afaik pickling with strong acids to remove tint, scale etc, then pickle with weaker oxidizing acids to make the protective coating.
electro polishing does both at once in seconds.
I did this practice piece... I feel I still have heat affected zone but I did this at 45 amps, because at 40 amps it takes forever to get any puddle unless the arc length is about .001" or something. I guess this is what we're aiming for right?
I'm still having problems with right angle joints... it's really hard to not get excess heat.
