is stainless welding much harder?

[e9999]

you guys are way over my head with all this, clearly. To put this better in context, this would not be for any critical structural applications of course -I would not do those myself anyway-, I'm thinking light brackets, frames for storage boxes, supports for trailer covers, stuff like that where corrosion would not be a big issue and failure would not result in damage or injury.

Anyway, am committed now, got the tubes...

 

[fabriwelder]

Wow!

Forums are great for controversy....

Anyway, he is talking about stainless tubing. Tubing is awfully hard to back gouge. Hence the purge.

I am a boilermaker and I deal with this stuff on the daily. I believe stick WOULD be easier. It is not difficult to learn. Some are better than others, but it is all just welding. Some people have it and some don't. I will never be able to paint the "Mona Lisa" no matter how hard I try and how much practice I have, I am not a painter. I am a welder. If you are a decent welder you can pick it up easy enough. A few pointers here and there are all a guy needs, but these need to be accurate and informative pointers.

At the same time try not to overload a guy asking a simple question with too much technical stuff. If he asks a simple question he deserves a simple answer. If he then wants to know why, well then by all means elaborate......

Yes opinions are like assholes, but when someone asks for yours.......

There is some good information here and some cool debate also. It looks like we have a CWI among us? Nice to know.

Anyway, I stick by my original statement.

Stick Weld

 

[e9999]

so, do I have to worry about backpurging if it's for non-critical applications -both tubes and flats-?

 

[Pin_Head]

You can use Solar Flux instead. It works.

 

[steffan]

To me, it sounds like your looking for someone to confirm that welding stainless with methods other than the prescribed industry standards will give you positive results. There is no way to know that. If you over build your project enough, even substandard welds will be fine - most everyone has seen examples of that. There's only one way to find out if your project is going to work out: do it, see what happens and learn from it.

 

[e9999]

To me, it sounds like your looking for someone to confirm that welding stainless with methods other than the prescribed industry standards will give you positive results. snip

No. I'm asking. Since I don't know what the Industry standards are and there seems to have been some variances in opinion in the comments above, I'm simply trying to ascertain whether the backpurging mentioned above is indeed something that should be done routinely, or -on the contrary- is some subtlety pertaining more to people doing code pipe welding on nuclear subs than to those of us doing a ham radio bracket in the garage with a flux MIG welder. Furthermore, rust -if that's the main worry- is not an issue for my applications. Neither is SS for that matter, it's just that I could get a bunch from scrap and thought it could be put to good use.

 

[brian]

you do not need to purge or back purge stainless......every time you weld it. you also do not need to worry about getting 100% penetration on every joint you fit.
you do need to mind your heat setting though. as well as travel speed.
if you run a bead, and the back side of the joint is grey, black and has a bunch of sugaring, you are too hot or moving to slow.
as long as you just have a nice rainbow effect your heat and travel speed is good.
everything mentioned about purging above is correct, but does not need to apply to you.

basically as long as you avoid sugaring the back side, your beads will be just fine.....so long as all your machine settings are jiving with your travel speed, material thickness, blah blah blah. as long as you use stainless wire(not 309) your stuff shouldn't rust*, and it won't just break one day for no apparent reason

i'm a millwright, that deals with the food industry on an almost daily schedule, in addition to being just as at home in boiler and mechanical rooms.....doing inspected work.

did you score pipe or tubing?

*stainless is funny stuff.
if you use grinding wheels, sanding discs ect that have been used on carbon steel, on stainless steel you get rust in those areas.
if you grind or sand carbon steel, and blow the sparks on to your stainless, it will get rust.
if you drag a piece of carbon steel across your ss and scratch the ss, that gouge will get rusty.
if you have a stainless wire brush, that you used on carbon steel, than use it to brush off a stainless bead, that bead will rust.


neat trick:
if you have a clean stainless brush. run a bead with tig or stainless mig wire, while the bead is still hot, but not smoking hot. wire brush it, the color will brush right off leaving a shiney silvery bead.

 

[machinisttx]

Cutting stainless is no different than cutting any other material. Surface feet/minute differs between stainless alloys just as it does between carbon steel alloys.

I can put two pieces of stainless side by side next to a lathe, then tell you to turn them both down .300" with the same feed/speed settings. One will cut like butter and the other will be a royal PITA, if you can even get any material off of it. I can do the same with carbon steel.

 

[ojaij40]

I can't help it.. I deleted my previous post but, I must comment on this one.

I have to disagree Brian...

If I'm looking at a GTAW/TIG weld that lost its purge on a SS weld or was welded without a purge... It's a reject, plain and simple, no questions asked. Purge on GTAW/TIG is an essential variable on 100% of any WPS/PQR I have ever reviewed. I’ve never seen a GTAW/TIG procedure that didn't require/call out an argon purge/cover on GTAW/TIG for SS.

Reason for rejection is that the "Sugar" / "Drywashing" effect is simply... S**T...and if a welder thinks it's OK, I'll jerk his certs and kick his A** down the road (It’s a quality and experience issue) and #2 is:

Two things happen when you overheat SS (THIS IS WHAT SUGARING AND DRYWASHING IS/CAUSES) by not using a purge/cover on SS:

1) The carbon combines with the chromium to make carbides.. This basically robs the surface of the chromium that forms the chromium oxide that creates the stainless' quality.

2) The other thing is that the iron, chromium, and everything else gets badly oxidized and forms scale and there will be a loss of corrosion resistance due to the chromium carbide you have created.

You may think that if you watch your heat you can do without a purge/cover (For a newb... IMPOSSIBLE) however, argon is a "Cold Gas" and therefore that is why it is the most common cover/shield/purge gas used and for a very good reason... I don't care if you talk to a metallurgist, welding engineer, CWI, SCWI, etc.. etc... we will all agree on this. Argon shields/protects the weldment and keeps the chromium safe/cool in its composition to maintain its integrity and corrosion resistance. Heat treated SS (which is basically what has been created without the purge/cover) will crack within days once introduced to an adverse ambient condition/sour gas/extreme cold and/or fluctuating pressures... list can go on for sometime...........

You can "back yard' a SS GTAW/TIG weld all day long.. this is true.. But, with the deletion of the purge/cover gas on SS... you are certainly going to have rust issues (due to #1 and #2 above) within a week and over time the weldment will become brittle/crack and lead to failure.

As far as stick welding SS.. I agree with you.... an average guy in the garage will have to spend some serious time practicing with this or it will be an absolute nightmare.

Boilermakers/etc.. use this everyday to weld CS/SS or SS/SS on SCR's, catalyst bays, etc.. You need to burn this hot, fast and pay attention to create a good quality weld. I've inspected 1000's of them inside power houses over the years. I've seen all qualities of SS stick welds...... I'll leave SS stick welding at that...

As with any welding... practice makes perfect..period...

J

You will "pull his certs" and "kick his ass down the road" ??
Do you give him a video of you explaining how smart you are also?

 

[TRAIL TAILOR]

You will "pull his certs" and "kick his ass down the road" ??
Do you give him a video of you explaining how smart you are also?

ojai40, I'm speaking in terms of code work/testing. All my welders on site are individually given a book of WPS', PQR's, and quality requirements specific to the project. I also, give one to their sup's and foreman for them to give their men support. However, 90% of the time a welder will make a weld to how he has made it for the past ?? years etc... never once looking at the new requirements.

If they don't read the information, know their process, and can't make a quality weld to the requirements of the project.. well.. enough said.

A video, no. However that's a good idea for some I've known. I actually do a one on one and explain why they are done in private and have a Q&A time during that sit down as well.

My statement above was based on a welder thinking a bad weld was acceptable.. If a welder isn't sure and comes and asks questions or needs help, I'll stay with him all day long and the next if that's what they need.

Yes, I'm smart, but I know several that will run circles around me. You might be one of them. But, I'm absolutely done with guys that half ass work because that's what they've done/gotten by with their previous QC, CWI, CPWI, AI, etc... I have a high standard for the quality of my projects welding. Yes, I'm a hard ass when it comes to any weld in my industry.

Reason why...I want to know that a week or 10 or more years down the road from now that the men working next to those welds are safe. That my welders and I did the work to the best of our abilities. Whether that be you walking to do VT on a weld or its the men who walk by it everyday on their way to their work area. Quality and safety are #1 in my book. I hope they are in yours too.

J