first time with stainless...

[Eric Baker]

Hi fellow sculptors,

I've been working in mild steel for a while now, but have accepted a commission for a substantial stainless steel piece.

Having committed to the work without any real knowledge or understanding of the materials has been a challenge, but there's nothing like hands-on learning.

The work will be of 1/4" 304L stainless, has already been laser-cut and rolled, and is now waiting for me to weld it all together.

My questions thus far:

1. I've heard so many different versions of what should be used as a shield gas that I am so confused. Info on the web conflicts, info from gas suppliers varies, etc.--so much that I'm not sure what type of gas to use for my Lincoln MIG welder. 100% argon; or 98% argon--2% CO2 (recommended by this guy on the web: Ed Craig, weldreality.com); or even variations of a tri-mix (the previously mentioned guy abhors the tri-mixes...)

I'll be combining 1/4" thick 304L stainless for most of the piece, with the exception of a 1/2" thick disc to be welded to a 1-1/2" thick disc for part of the base.

Any recommendations and real world experience for shield gases, and/or wire (and sizes 0.030, 0.035, etc.) would be appreciated.

I'm a self-taught individual with limited experience, but am willing to learn new materials and their pros/cons. (I'm using a lincoln mig welder (model pro-175)

2. Additionally, I've learned that the piece will need to be 'passivated' after all the cutting, bending, welding, etc. to avoid the formation of rust. The finished piece will stand about 7' tall and will be 3'-4' in width. Are there companies/industries that I could search out locally that can help me with the process of passivation of a such a large piece?

Thanks for any and all help,

Eric

[raspero]

I gas weld my stainless so I can't help you about arc welding, but I do know something about the second part of your question.

If stainless is kept between about 600 F and 1400 F for more than around two minutes, the chromium precipitates out of the alloy and you no longer have stainless steel. When welding pieces of the thickness you describe, this will certainly happen unless you take measures, as stainless doesn't transfer heat as quickly as plain steel; it holds the heat. You need to cool it every couple of minutes, then continue welding. I recommend a paper Lincoln Welding Co. published on welding stainless:

http://content.lincolnelectric.com/p...ure/c64000.pdf

I was in communication with a sculptor in North Carolina who made a large gate of stainless for a pricey condo project there. Gorgeous thing. Big. Fancy. The damned thing is rusting, and the condo developers are wanting him to fix it. How do you put two twenty foot long gates into a heat treating oven to re-alloy the stainless? Big problem.

Do your homework before you mess with stainless.

R

[PTsideshow]

Derustit/Passivating
Another maker of liquid for passivation

also good source of info on the subject.

[Eric Baker]

Hi Raspero,

Thanks for the link, and the cautionary tale. I'll read up...

Forgive my ignorance, but when you say 'gas welding', do you mean with a TIG, or with a torch?

I feel for the guy with the gates. Fixing problems later sure is harder, and most often is costly...

Thanks for the tips,

Eric

[PTsideshow]

This is the place for metal coating and finishing questions

This is a real old school bulletin board style forum. It does take a day or two to get answers or longer some times. This a world wide site with platers and finishers form around the world get answers.
They also have info on shops and finishers around the world. once you figure out how to navigate it is a wealth of info!

Under the heading preparation 1b. is the section on passivating etc.

[Eric Baker]

Hi Glen,

Thanks for those links also.

So do you passivate yourself, or do you outsource the work? I'm intimidated by anything 'acid', especially if it involves hazardous waste disposal, etc. The citric acid link sounds interesting, but is it as effective as the nitric?

all the best,

Eric

[Ries]

I have been making relatively large sculptures from stainless for over ten years now- so I, at least, know how little I know.

First- Mig is a bad idea. For a lot of reasons. It can work, and I have done it, but for a small piece like you are talking about, I sure would Tig it.
Stainless warps a lot more than mild steel, for the same heat input. This is a problem in general, as you must be better and smarter about clamps, jigs, strongbacks, weld sizes and welding order, taking your time to let things cool, and finally, ways to bend it back into shape after it does warp.
(mine include the hossfeld bender, brake and rolls, hydraulic press, and porta-powers)
But its more of a problem with mig, which comparatively, puts more heat into the weld. Mig welds in stainless warp. Period.

Mig also spatters a huge amount on stainless, and the spatter sticks really well. So lots more time in cleanup. Which, in stainless, is not easy or cheap.

I generally figure that materials in stainless, versus mild steel, run about 5 times the amount, and general costs are at least double- labor, tools, consumables, and so on. Many sanding discs and grinding wheels either dont work at all on stainless, or wear out twice as fast. So I use almost exclusively alumina zirconia sanding consumables- which cost more. I like Klingspor CS411 for this- in sanding belts, disc sanders, and flap discs.

I have used tri-mix, which is the recommended sheild gas for migging stainless, and I have used straight argon. For 1/4" I dont think tri-mix is worth the added cost- the additional heat it allows for wont be visible or usable at such low amperages- its more for really big stuff.

As for passivation- Stainless rusts not from some mysterious de-alloying process- it rusts where you have either burnt off the chromium, by welding it too hot, or when you contaminate it with mild steel.

This is yet another reason to tig- its much easier to keep welding temps in control. Most properly tig welded joints wont rust, even if you just wire brush em as a final finish.
Also, tig welding is much less likely to produce Hexevalant Chromium, while stick and mig welding do- and Hex Chrome fumes are the ones that kill you. If you do mig, wear a respirator AND use a fan for fume exhaust.
New laws for industry for migging stainless are very strict- this is a real problem.

So- use only brand new stainless steel wire brushes, brand new grinding and sanding discs and belts. Never use these on mild steel. Mark em, we write "SS" on em all with sharpies, and keep em separate. Saws and drill bits are okay, but abrasives are very easy to pick up mild steel dust, and then embed it in the stainless. Thats what rusts.
Fork lift tines, crowbars, even hammers can leave invisible bits of mild, which will rust a week or two after you install. Use wood blocks, blankets, and other padding when using steel tools of force.

I have all my stainless electropolished- this is one step up from passivation. Passivation is just an acid dip. Electropolishing is acid PLUS electricity- the reverse current flow of plating, it strips off all the nasties, and leaves a nice, shiny, rust free stainless piece.

Its expensive, and almost nobody does it. Call platers in your area, and ask if they do it, or know who does. If you are lucky, you may find someone with a small tank. Maybe in Wichita- aerospace uses it a lot.
My guys are unusual- they have a 4'x4' x8' tank- so I make my sculptures in sections, have them electropolished, then weld them together. Then, I site electropolish the welds, with a small hand held unit. Which is also expensive, fussy, and hard to find.

Passivation is more commonly available, especially with larger tanks. But often not "local". Passivation will not polish the work, in fact it usually dulls the finish a small bit, but it should etch out all the tiny bits of mild steel, meaning it is less likely to rust spot.

Stainless is great stuff- but it aint easy or cheap. You need bigger, more expensive tools, more time, more swear words, and more benjamins in your budget.

[PTsideshow]

First I have to say that when it comes to "Stainless" Ries is the man to listen to. I haven't did any in a number of years and then it was small items that were oxy acetylene welded. So no real help for you!.

[The Forge]

They used the wrong grade of stainless to start with. To maintain the corrosion resistance of the stainless even after welding, you need to use type 316 or 316L with the same filler rod.

[Ries]

316 is great- its food grade, and it is no harder to fabricate than 304, and electropolishes swell.

But- it costs more, is harder to find in all the shapes and sizes that 304 is, and for most landbased sculpture, is not worth the additional money, in my opinion.

I have probably close to 20 tons of stainless fabbed into various railings, fences, sculptures, and building parts in the last 10 years. NONE of it is rusting.
So to say that you MUST use 316- well, I just cant agree.

Certainly you CAN use 316, and most maritime shops use 316, it is definitely more corrosion resistant. But for sculpture, on land, not right on a salt water beach, 304 stainless will outlive you or me by several lifetimes.

[Eric Baker]

Hey everybody,

thanks for all the replies and info.

Ries, I do have access to a stick welder. Would that be a better route to getting the piece welded than the mig route? (I don't have the immediate funds for a TIG, but I'm working on that...)

It's not a high end cracker-box, in fact I can't even remember the amp rating, but I do have access to one... And I'll make sure I'm wearing a respirator during welding and grinding...

Regarding passivation versus electropolishing:
I want to use discs/wire cups to put some texture into the surface. I know (and appreciate your warning about separating the stainless tools from those that touch mild steel) that after all the work is done, either of the processes will have to be done to the work, but I've heard that electropolishing will eliminate most of any textural work put into the surface.

Do you mind sharing your experience of passivation versus electropolishing?

And any recommendations for a TIG welder? I checked this afternoon with a local welding shop and they sell a Lincoln Precision 225 for $2200. It's limit is right near 1/4". There's a big jump in price to go for a machine with more capacity, and even the $2200 is out of my price-ballpark right now...

Thanks for sharing the insights--I checked out your website; nice work!

have a great Friday,

Eric

[Ries]

No, Mig is probably better than stick. Just tack everything first, then jump around a lot, trying to equalize the heat input in different areas. The worst thing you could do would be to weld long seams all at once.

As for Electropolishing getting rid of detail- nope, it doesnt do that.
This gun, for example, is 304, milled, forged, needlescaled, and otherwise textured like crazy. The electropolishing makes it all pop, and look even better.

As for tig machines- depends if you need AC for aluminum or not- DC only is gonna be cheaper. Lincoln or Miller, they are both good. I am a fan of inverter machines, myself, like the little Maxstar 150- which wont do 1/4", but has big brothers that will.
But often, you can find a good deal on a used tig machine, especially big beasts of older transformer style rigs.

More amps is always better- my two tigs are 250 amps, and 300 amps, nominal, and both will actually put out more than that. On non-ferrous, like aluminum, and especially copper, I have had both of em completely maxxed out, putting out 300 amps, and close to 400 amps, and still could have used more.

[evaldart]

1/4" plate plus those two really heavy discs for the base? Nice, but Ries is right about the amperage. If you go tig you're gonna need a big machine.

When stainless comes through my studio I use the 250 mig and the tri-mix. I've gone as heavy as 5/8 with no problem. But that machine is about 2500 bucks. If you're really in a budget jamb and just need to get the thing done an AC- DC stick welder (500 bucks) will work - but its kinda messy (the sputter, splatter and slag stick like crazy, but I guess thats why god made grinders). Find the appropriate electrode and get after it.

If it turned out that I was going to be doing alot of this I would simply buy the tig. Because in the big picture you'll need to be getting significantly more money for your work and the price of a good machine (the RIGHT machine), in proportion to the take-home pay, will be less than the other options.

Good luck.

Maybe Aaron Schroeder will pipe-in. He's sure to have an alternative take on this whole thing.

[Aaron Schroeder]

When this thread came up I abstained from commenting because I figured Reis would jump in with another well written post. And he did because he is so good that way. Ya'll listen to Reis, he is the master of all things stainless.

My alternative take... would involve establishing expectations with my client. If you don't know what you're doing and you're going to be employing limited technology ......your best bet is to establish lowered expectations and/or find an artful way to exploit the limited knowledge and tools that you have. Not always an option and too late for Eric but a good policy.

A clever artist can find a way to make rusty stainless desirable and charge more for it in the process. One can weld stainless with non stainless wire and even flux core ( they also make a stainless flux core ). On the first pass the wire alloys with the parent metals and effectively becomes a stainless weld. It'll be a different color but that can be exploited. Heck, an artist could go crazy with the application of wrong welding practices and people would love it.

If I were to enter a competition with Reis to design a stainless sculpture, my only hope would be to design something that would exploit my lack of tools, knowledge and experience.....a sculpture that would be charmingly warped and artfully rusting in all the right places. I'd try to shift expectations to a different set of parameters and celebrate that. Make my liabilities....assets. That or humbly step aside and let my superiors take over.

[Zophia]

remember not to contaminate your grinding disks by using them on mild steel also. I made my mail box out of stainless and ground swirlies in it which rusted later. I liked the effect but that may not work on other projects. I also heard of this guy who built a sculpture in mount dora of a heron, he didn't use the right filler and it rusted. I spent probably 100 hours plus learning how to TIG weld stainless. If you don't have time you may want to hire a welder to weld it for you and put the time in to learn the process later. Stainless is a beautiful metal to weld the way it flows together and makes an array of colors but it can also come out grey, bumpy and ugly if you don't know how it flows. It will probably save you alot of time and money.

Z

[Eric Baker]

Thanks to you all. I'm sure I'll have a few more questions as the project moves ahead, but I appreciate all that's been said so far.

Thanks,

Eric

[arcdawg]

Mig it.....end of story.

Too thick to Tig (as far as it would take way way way too much time. Stick welding would be fine if you know how to stick weld, However I can only imagine how much a 50lb box of S.S. rod would cost.

Change the liner in your mig gun as the new stainless wire will get all the crap from the steel wire you ran through it in the past and it will contaiminate the stainless wire = rust. Make sure to bevel all of your joints too.

[andyvoytko]

I agree with MIGging it. TIG welding 1/4" plate would take a long time. My problem here is that your piece is going to be heavy. Are you able to move the piece around to get a good welding position? Or, are you going to have to weld everything in place. Welding overhead is not fun and not easy for someone with no or little experience. I've got quite a few burns on my arms from spatter raining down on me while welding. But, it's how I pay the bills so I live with it. Also, grinding sucks plain and simple. The better the weld the less you have to grind. My advice hire it out. Practice on something other than a customers piece.