Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Technical Discussions / The finer points of welding stainless...
- - By T0M (*) Date 03-15-2005 00:00
I am fabricating some stainless steel turbo headers for a V6.


I can weld stainless to a functional extent, but I am not as confident in my stainless welds as I am steel and aluminum.


My main concern is my weld appearance, after welding, the welds are always sort of a brown tinge. when I polish it it comes out all nice and shiny...but I am really trying to get a cosmetic effect of how the heat affected zone changes colors. so rather than polishing the stainless afterwards.. I am polishing the stainless before hand. this way the heat affected zone is not polished out.. for this reason I need my weld to be just as clean and healthy as the area surrounding it.

My main issue is getting a brilliant weld. the weld always comes out looking brown. but i have seen many sstainless manifolds floating around the internet that you can tell they are getting a brilliant finish in their welds.

http://www.full-race.com/images/products/products/fullsize/manifolds/006.jpg
http://www.full-race.com/catalog/images/supra%202.jpg

any tips on getting a similar brilliant weld finish? any particular shielding gas or welding rod?.. i am using argon and er 308 for reference sake.

i havent actually been able to completely shield the backside to my satisfaction yet, I only have one argon tank and have tried purging the backside with my torches tank by sharing with an argon Y but what I run into is poor flow control on either my torch or the purge side... so scrap that. I am gonna rent an aditional argon tank and buy another regulator tommorrow hopefully ill get better results.

in the meantime I have also tried solar flux. That doesnt seem like a good thing to be using on turbo manifolds because of the possibility of unremoved flux particles entering the turbo. so thats out...


Also I cant seem to get the weld puddles to lay predictably like aluminum... they kinda lay unevenly. I tried beveling the tubing.. its only 16 gauge but I figured it would help to center the puddles, howver they still kinda lay however they want any tips for this?




My choice of material was 304, and it was only after I purchased and began mocking my manifolds that I discovered that 321 would have been a better idea. any of you guys out there fabricating turbo headers that could lend suggestions feel free to.

Thanks
Parent - - By DGXL (***) Date 03-15-2005 01:24
TOM:
1.) Nice looking welds for a novice.

2.) The welds appear large in the photo if they (parts) are 0.060" in thickness.
*Try to maintain a smaller puddle which will also help with puddle control issue you mentioned. < heat input.

3.) Stop weaving on that thin stuff. The welds look nice, but you are creating a lot of stress where you don't want it. QC should be part of your service to your customers
*Large welds can break early in service on these types of applications. These weave beads also equate to more heat input and anything but shiny silvery (base metal colored) beads.

4.) Use a smaller dia. filler metal to help reduce weld size. It will also require more skill on your end in the weld appearance.
*You will have to feed more wire - faster.

5.) Try using a larger cup or gas lense.
*If your going to keep weaving this is a real good idea.

6.) Nice looking welds.
*I will be training/testing a welder this week in SS sheet for aerospace (D17.1). Your not far from your goal. Good luck and post photos of your progress please.
Parent - - By T0M (*) Date 03-15-2005 01:58
thanks for your input. I should clarify that those welds pictured arent mine but rather an example of the finish I am looking for. I believe that guy is using 8 gauge stainless and that would explain the larger filler rod / puddle size.


I read somewhere that the stringer bead is best for stainless beacuse it doesnt heat up the metal as much as the weave style..so thats what i am trying out.

for reference, I am using 16 gauge 304 ss tubing with 1/16" filler rod, and sharpening my tungsten to a fine point. my amperage is around 37- 40 amps. I notice that stainless minds well on a fillet weld but not on a tubing weld. so I have been beveling the 16 gauge to sorta mimic the scenario, but the weld still lays all funny and crooked. I am holding my torch angle dead still at a 10 -15 degree angle yet i am getting the same results . I may have a problem with feeding my rod correctly

so is that guy (pictured above) using a weave pattern to get the welds to lay down so uniformly?

Thanks
Tom
Parent - By DGXL (***) Date 03-15-2005 03:39
Tom:
The welds at the tube intersection are definitely weaved. The welds at the flange simply looked too large for 16 ga. material. Now that I know the fotos are not yours, help yourself and maybe post actual work your concerned about.

There lot's of TIG-type people that hang out in here who can help you out, but the doctor needs to see your scratch...

;-]
Parent - - By T0M (*) Date 03-15-2005 20:41
here are some pics of my welds. please excuse the abrupt stop/start as I was just running a quick bead to show what I am talking about.

this is 16 ga 304 with 308 filler rod. 100% argon shield gas a 20 scfms and 100% argon purge with 10 scfms


this is immediately after welding.
http://www.photodump.org/stored/weld4.jpg
http://www.photodump.org/stored/weld3.jpg
http://www.photodump.org/stored/weld2.jpg
http://www.photodump.org/stored/weld.jpg

any comments or suggestions?
Parent - - By medicinehawk (**) Date 03-16-2005 08:53
Your welds are alright for "free hand" tig , but if you learn to "walk-the-cup" you wouldn't believe how consistent you can be, plus your welds would always be gold or when you brushed them up...there would be no black spots at all.
You might have shown us what the inside of the welds looked like unless you had no purge going(argon) while you welded it.
Parent - - By T0M (*) Date 03-17-2005 01:10
i am having trouble understanding how to properly walk the cup on 16 gauge material.

from what i read, walking the cup is when you lay your cup against the weld and inch the cup along the weld by rotating your wrist left and right. In every application I have seen or read about this, it has been in a heavy pipe welding application where you are a 1/4" deep in the middle of a v groove and making multiple passes.

but it seems to me on 16 gauge stainless any left or right rotation of the torch will cause the weld profile to go way off. are there different ways to do it?

thanks
tom


Parent - - By DGXL (***) Date 03-18-2005 02:45
Tom:
You do not want to walk the cup on "thin" gage SS. You are correct in that the bead profile will be excessive for the material thickness.

P - R - A - C - T - I - C - E . . .
Parent - By medicinehawk (**) Date 04-30-2005 18:42
You absolutely can walk the cup on thin-wall stainless steel. I do it all the time. It does take some practice to get good at it, but that's welding is ALL about.
Most all large breweries have miles of thin wall stainless steel (304L-1/16" Thick) where it is all hand-welded using TIG welding. They don't care if you walk the cup (there) but put a weld side by side with one which is "free-handed" and one which is (cup-walked) and it is like night and day as to which is better.
You ALL might be interested to note that there is NO QA/QC standard in brewerys, so drink it up!
Parent - - By awill4wd (**) Date 03-16-2005 10:05
Tom, your best bet to keep in mind is "gas lens, gas lens, gas lens." and preferably the largest you can get. I use one which is more likely seen on titanium welding and has an orifice of approximately 19mm (3/4") It helps prevent the oxidisation which causes the change of colour. I've seen these new "monster" ones on the net which look really interesting and would love to give them a try as well. Have a look at
http://www.arc-zone.com/catalog/web_store.cgi?page=monster.html
Regards Andrew.
Parent - By Lawrence (*****) Date 03-16-2005 12:28


Andrew!


Those are nice.

Thanks for the find. I just happen to have a few budget dollars left to try one out.
Parent - - By T0M (*) Date 03-16-2005 13:48
I was using a 1/16" gas lens. but I am guesssing thats not sufficient for welding metals like stainless and titanium.

what is the proper gas flow for your torch when doing stainless?

I have heard people say 14 all the way to 35.


thanks for the link to the gas nozzle. I was also looking at getting this one made by CK (the large gas saver at the bottom)
http://www.ckworldwide.com/Gas_saver.html




Thanks
Tom





Parent - By DGXL (***) Date 03-16-2005 16:02
Tom:
I knew you would get some replies with your actual photos.

You can accomplish the weld quality and appearance you desire without the monster nozles. We used to make those out of torch nozzles from automatic machines and glue (an industrial AMS adhesive) a standard collet body the the reversed larger nozzle. Then stuff with stainless steel wool as a difusser and put a screen to retain the wool.

Many welders can perform the welds like you want without any special aids. They perform this task everyday using standard welding supplies and equipment. After looking at your photos I think Tom simply needs more practice. Keep in mind those large nozzles severly restrict your line of sight, particularly with the part geometry you encounter welding those tubes together.

With a number 4/5 nozzle you should be around 15cfh gas flow rate. Too much gas will result in a vortex around the nozzle and defeat the purpose of "more is better". Too much gas can be as bad as not enough as well as not being very efficient (<$) for you as a manufacturer.

Good Luck with your practice.
Parent - - By - Date 03-18-2005 14:27
First of all, when weldiing stainless steel, the "color" you are seeing is a chromium depleted oxide layer. Stainless steel is protected by an impervious, invisible layer of chromium. When you weld, you burn that protective layer away, leaving a chromium depleted oxide layer. Using a mild pickling procedure will enhance the appearance, plus return the stainless steel to it's natural anti-corrosive state. By removing this oxide layer, the natural oxidation in the atmosphere will allow the stainless to "heal" itself and return to a corrosion protective surface.
Also, when welding thin gauge stainless, using a 308LSi TIG wire will allow better fluidity and give a better weld bead appearance than a straight 308 or 308L. The "brown tinge" you see is directly related to your shielding, travel speed, and heat input.
Your choice for using a 304 material for your headers is acceptable if they are not going to be subjected to a high heat environment. If that is the case, you will encounter sigma phase after a certain time frame. If high heat is encountered, then certainly a 321 base metal is a good choice. For that, you will need to use a 347 fillet metal. The niobium and higher carbon content will counter the sigma occurrance.
Your inability to fully shield the back of the root bead will definitely compromise the corossion protection and will weaken the weld due to the oxidation of the root pass. Solar flux is an option but has not proven to be as good as an inert shielding gas.
Parent - - By T0M (*) Date 03-22-2005 05:25
thanks for the info..

quick question.. will using a chop saw to cut the tubing also affect weld quality? I am using a chop saw for the cuts .. then beveling the pipe with a carbide bit to remover any chop saw material as well as making a groove for th e weld. is this acceptable?


Thanks
Parent - - By - Date 03-22-2005 12:11
Using a chop saw to cut the stainless is OK, but make sure it doesn't have any residual carbon steel left on it from another job. The carbon can become impregnated in the stainless and cause premature rusting. Also, a 304 grade stainless is not designed for extreme heat, if this is the case, because of the formation of sigma. Just make sure there is no carbon contamination after your cuts and bevels. Good luck..

CM
Parent - - By rodofgod (**) Date 03-24-2005 01:50


Hi Tom!

You've stated that these headers are for a 'Turbo' V6,given the higher temps. involved with turbo exhaust systems, then 304 S/S is not an ideal choice of material!

The pictures of the 'weld quality' that you are trying to achieve are not that good, welding wise. In fact,apart from the 'gas coverage' in yours, I think your welds are at least on par with those in your pictures.
One thing I noticed on your practice photo's, is that you are welding 'small' pieces of pipe onto 'big' pieces of pipe. In my experience, this is rarely given to perfect color match in the 'as welded' state.There's nowhere for the heat to go, in the short piece of pipe!

Always use a gas lense when welding stainless! Keep the torch as near 90› as possible.Don't forget to turn up the gas flow when using a gas lense!

Regards

Parent - - By - Date 03-24-2005 02:37
Rod,
As stated earlier, and we both agree, that 304 stainless is not the "ideal" material for high heat applications. Now, it this 304 is an "H" grade, or high carbon grade, the scenario is different, but sigma is still possible. The better choice would be a 310 stainless, which is pure austenitic material that contains no ferrite which causes sigma to form. Using a 310, he would not have the sigma, or embrittlement and loss of corrosion protection. But, ya know, for headers, is he really that concerned???

CM
Parent - - By rodofgod (**) Date 03-25-2005 05:58

Hi All!

cmeadows, who mentioned 310 s/s? Before you say anything, I agree with you! For a fairly simple job like Toms (exhaust headers), We don't need to be exploring 'ideal' materials too much!

However, regards the welding of whatever material, then I think that anyone posting a question on this forum deserves the 'BEST' knowledge available, from everyone who responds!

Thats all I was doing!

Tom, Your welding is not far off from being acceptable, if your sort out your 'back' purging problems, it will improve 100%. Can you 'pulse' weld with your welding set? If so, then You will see a further improvement in your welding.

Use a 'gas lense', gas flow really depends on the size but should be in the order of 15 to 25 Lt/p/m! depending on size! Travel rate should be as slow as you can manage, with a LOW heat input. This lets the 'weld' cool under a 'gas' shield! Keep your welding angle as near to vertical as possible!

Joint design has alot to do with it as well! Typically, fillet welds and 'groove' joints will have 'good' gas coverage because of the design of the joint (gas is 'trapped' in the joint!).

When you stop welding, don't move the torch away from the weld until it has 'cooled' under the shielding gas,'cause next time you start on the same 'place, your gunna pick up contamination from the oxidized steel!

Hope this helps!


Regards

Parent - - By - Date 03-25-2005 14:23
Hi Rod,
Please re-read my last sentence. Regardless, I disagree with you in stating that the post should not be given the "ideal" material because he might learn that there is better metals out there for his job and want to change. That is how we all learn, then it should be up to us to consider the options and make our decision. Please do not consider this disrespectful in any sense. Thank you for your responding to my response to Tom.

CM
Parent - - By rodofgod (**) Date 03-29-2005 21:42
Hi All!

cm, I think we got crossed wires here! Must be a 'Transatlantic' breakdown!

Quote:
" But, ya know, for headers, is he really that concerned??? "

I must have read your last sentence wrong! Apologies Mate, looks like we are in agreement, because if you re-read my answer, I, too, am all for exploring alternative materials for best applications!

Regards
Parent - By - Date 03-29-2005 21:58
Rod,
No problem, my friend. Us Texas boys don't always have our mind and mouth working in conjunction all the time. <smile> We were totally on the same page the whole time, though. Thanks for your e-mail. Have a great day!!!

Chuck
Parent - - By T0M (*) Date 04-09-2005 18:32
hello,

My welder is capable of pulsing, though it didnt occur to me to use it because I thought pulsing was mainly for aluminum.
Ill definately try it to see if there is any improvements.



I have been practicing the walk the cup method a couple of members above have mentioned but dont seem to be too savvy to the process.

I am finding more luck by locking my wrist, welding really slow with very little amperage and stopping and repositioning the work when my torch starts to angle(given that my wrist is as stationary as possible)

thanks for the help

Tom
Parent - By medicinehawk (**) Date 04-30-2005 19:18
You should be using a "backing purge" on the tubes you are welding and really, 304L .035-.065 (wall) will not need any filler wire. I don't know about 327 material or whatever, but I DO know about thin walled stainless joining in General. Assuming your weld joints are "faced" square with a belt sander, and there is no gap when you "dry-fit" the parts to be joined, then you can "Fusion weld" the joint with out adding wire with 304L 0R 316L SS. The parts must be CLEAN, meaning no oil or grease or sanding particles. Straight alcohol (from walmart) works well and a rag which doesn't leave particles helps as well. Weld prep here IS important!
The process requires a balance between the inner purge (with Argon) and the heat input and ofcourse Good gas coverage. I have taught welding of stainless steel pipe (Schedule 10-40) and I started the students off with thin-wall stainless to learn to "walk the cup".
I would give them a 2 or 3 foot length of 2"-.065-316L material, show them how to set up the purge and have them "score" lines around the tube using a tubing cutter. Spacing the lines about 4 or 5 inches apart. First, I would give them a demo, and then I'd leave them alone. I did not care whether they got penetration or not, but it was a good exercise until they had figured out the technique well enough to place a tig wire in their hands.
I totally agree that stainless has to be welded cold, that is, using just "enough" amps to achieve penetration. Having a rheostat is essential and the ability to use a pulser....even better!
If you look back thru the archives(on this web site), you'll find a detailed post about how to walk the cup which explains every thing in detail or send me an e-mail and I'll send you the information. The trick (so-called) in walking the cup is to minimize the width of occillation while still being able to Travel along the tube.
Never let anyone say it can't be done, because that it the first thing the assures that you won't succeed. Practice is everything!
Parent - - By T0M (*) Date 04-09-2005 18:34
I wasnty aware of the carbide precipation problems that occur with 304 at the time I purchased the material, however i recently acquired some 321 that i am hoping well be better suited to the job.


this 321 stuff doesnt polish very well at all tho....
Parent - - By - Date 04-10-2005 13:09
Tom,
Not a bad choice by any means. Using a 347 filler metal (which is used to weld 321) will give you the resistance to elevated temperatures to virtually eliminate the sigma phase. Very wise choice.

Chuck
Parent - - By T0M (*) Date 04-11-2005 19:26
Any problem with using 1/16" 347 filler on 16 gauge 321 tubing?

after scouring the earth I finally found a shop that would order me some 1/16" 347, then shortly after I read an article on burns stainless suggesting .031 or .035 filler for 16 gauge tubing.

Id hate to even have to ask the shop to change my order but after checking on the price of .035 ($24 a lb...10lb minimum) im not sure id want too anyways!!


not sure why they suggest such a small filler but I hope its not too relevant.


thanks again
tom


Parent - By Lawrence (*****) Date 04-11-2005 21:43
Unless your trying to obtain a very small weld bead profile the 1/16 filler will be just fine.

The rule of thumb (for sheet metal) is as follows;

The filler wire should be close to the thickness of the sheet. So the 16 gauge (0.062) is just about a technical perfect match for the 1/16 (0.063) filler wire.

For sheet below 16 gauge such as 0.032 (22ga.) the step down to 0.035 wire reduces the amps/heat required to melt the filler, which can be important in heat sensitive alloys. Fillers less than 0.035 are pretty hard to hand feed.

Conversly, welding 16 gauge or thicker with 0.035 filler can be problematic, it is slower, filling gaps if any is more difficult, wire feeding is less accurate as larger "pushing dips" may be required.
Parent - - By MBSims (****) Date 04-10-2005 04:27
Here is a link to a helpful book on welding of stainless steels that should help:

http://content.lincolnelectric.com/pdfs/products/literature/c64000.pdf

Parent - By pro-weld Date 04-29-2005 01:41
tom, if the people that are making those headers are using 8 ga. tubing, i believe thats what you said, then thats the reason he can get that clean colorful look. i've welded a lot of stainless over the years, most of it on guys toys ,and looks meant everything to them. anyway, between the the thick walled tube and those hefty flanges hes using, its pretty easy to get what you are looking for, because the material is not overheating, overheating is what is causing your problem.
If you have to use 16 ga. then like someone mentioned, try pulsing, either with the pulse on the machine or manually with your pedal or finger control. i use a finger slider amptrol, it works well for me. also, move as fast as you can, and still weld good. try cooling your part prior to welding, i used dry ice before, it worked well, and kept distortion down also

i hope this helps, mike















Up Topic Welding Industry / Technical Discussions / The finer points of welding stainless...

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill