Stainless Tubing Help

[Injected65]

I am working on my first project using 304 Stainless tubing. The tubing that I am working with varies in diameter from 1.75" to 3.5". All of the tubing is around .065" thick. Most of the joints are butt welds and I have been trying real hard to keep the fit up tight. The problem I am having is the welds end up with little to no color. They look grey and dull. During my many hours of practice, the only time I seem to be able to get a nice looking weld is when fusion welding the tubing. As soon as I add filler the weld turns grey.


200DX welder
#8 Gas Lens
Tried 30-70 amps with the sweet spot around 50 it seems
Also tried with pulse and without.
Gas flow around 7-10 L
Tried with back purge and without back purge with no noticeable change
Tried 1/16 tungsten and 3/32 tungsten. 3/32 seems to have a more stable arc
Tried 2% Ceriated, 2% Thoriated and bought but haven't tried Lanthaniated Tungsten.
Have been using .045" 316L filler rod


I'm just getting frustrated with the lack of improvement on the welds. I have had no problem with steel or aluminum, but this Stainless is kicking my butt. I really would like to be able to get a nice looking strong weld. I forgot to grab my camera from home. I will post up some examples of the welds tonight.

Thanks for the help,
Chris

[Paul Moir]

Grey is the result of too much temperature when the weld moves out of your gas shield. That's easier to achieve when fusing because you're moving faster and using less heat. (I also suspect that you get some from the rod itself by moving it out of the shield.) Doing tubing is particularly difficult because maintaining your torch angle & back shielding is harder. And I have noticed that 316l filler seems to be more difficult to keep pretty than 308.

But really I don't care. Grey doesn't make your welds weak since it's just the surface that's affected, and I pickle my welds so the colour is gone anyway (and the corrosion resistance lost is regained; the free iron is removed from the surface).

EDIT: it's hard to loose heat out of your stainless because it's such a good insulator compared to steel (about 3x!) or esp. aluminum.

EDIT 2: If pretty colours is part of the spec, think big cups, lots of gas, short welds with lots of cool down and/or some way of soaking the heat out of the stainless.

[sportbike]

Not sure what you are stating with, "The problem I am having is the welds end up with little to no color." The welds aren't supposed to have color. Color is the result of oxidation.

If you aren't seeing any difference with back purge or no back purge, something may not be correct. When welding thin wall stainless tube, a sugary "clumping" will apear if you don't back purge or otherwise protect the backside from oxidation.

This is an odd question, but are you sure it is in fact stainless and not plain steel?

[Injected65]

By color I mean this nice golden hue to the weld. Similar to these pictures I found on the net.





The back purging does make a difference on whether or not I get sugaring on the backside, but it does not seem to effect the color or look of the weld its self on the front side. I've made the move from a regular style cup to the gas lens and then moved up from a #5 to a #6 to a #8 to make sure I have adequate gas coverage. I've also had the gas as low as 5L and up to 15L before and it didn't seem to change anything. Torch angle has been anywhere from straight 90* to the work piece to 45*. I've made sure to not pull the filler out of the gas flow as well. To give you a reference, I've gone through most of a 250cf tank of gas as well as nearly 1# of filler rod testing out different variables trying to get not only a strong joint but a visually nice one as well.

Sportbike - Yes the tubing is definitely 304. It has the spec printed right on the tubing. The filler rod came out of a brand new box at the LWS.


Thanks for the help guys. I'm sure the problem is something I am not doing right. I'm just looking for ideas on other things to try to see what is happening here.

[jerky]

i also suggest using 308L filler. this is a better match for 304L.

[jakeru]

Paul Moir has nailed it. Grey welds are from the metal being too hot when they leave the inert environment.

You should be able to easily eliminate the dull grey at least at the end of your weld, just by increasing your post-flow and/or by not pulling away from torch from the weld area so fast. Keep the gas flowing as long as it takes for the metal to cool down.

As for getting the whole weld bead to not be dull grey, you might need to develop better torch and filler feeding coordination. Using the right torch angle is also important. Specifically, try to use less torch angle (closer to perpendicular with the surface your welding) to push the inert gas backwards over the hot metal. If you angle it too far, the inert gas won't get pushed backwards enough. Another fact is that Argon is heavier than atmosphere and sinks, so you may get better results in some positions than others. (e.g., flat welding easier than vertical welding.)

Check out the video in this thread if you haven't already, it shows .065" stainless exhaust tubing being welded with great technique and results:
http://www.everlastgenerators.com/fo...-Welding-Video

[Injected65]

Great video. A couple of things I noticed were that the tungsten in that video was ground with a bunch more taper than what I have been doing. I'm going to watch that video again tonight and try it again with reground tungsten, greater post flow time and I am also going to work on the purge setup to let it purge longer before starting my weld. Hopefully this is the key to getting a nicer looking weld.

[Injected65]

I figured I would give an update. Yesterday a friend of mine came up from Wichita KS. He is an aircraft parts welder at a fab shop. He welds everything from Aluminum to stainless to titanium 8+ hours a day. He brought with him the gas lens/cup setup he welds with daily. He uses a standard small diameter gas lens with a 10 cup that has another small screen at the very end of the cup. I couldn't find a 10 cup for the small diameter gas lens so he is going to find out where his shop buys them. The small screen in the end they make in house so he is going to see about buying a few extra for me. He made some small gas flow adjustments and then he got to welding. The cup change definitely helped. He also pointed out that I was trying to move too fast with too much heat. He showed me to slow down and use less amps and the results definitely improved from that. The last thing he mentioned was that the weld puddle was "dancing around" a bit. He said he see's it here and there and its usually related to material that isn't 100% pure stainless. The 321 that they normally use he said welds nicer, but obviously on this project it was out of the budget.

In the end he made some incredible looking welds and my welds weld from functional but butt ugly to functional and presentable. I'm still in need of more practice to make them really start looking pretty.

[225]

pics? i would like to see..

[sportbike]

I figured I would give an update. Yesterday a friend of mine came up from Wichita KS. He is an aircraft parts welder at a fab shop. He welds everything from Aluminum to stainless to titanium 8+ hours a day. He brought with him the gas lens/cup setup he welds with daily. He uses a standard small diameter gas lens with a 10 cup that has another small screen at the very end of the cup. I couldn't find a 10 cup for the small diameter gas lens so he is going to find out where his shop buys them. The small screen in the end they make in house so he is going to see about buying a few extra for me. He made some small gas flow adjustments and then he got to welding. The cup change definitely helped. He also pointed out that I was trying to move too fast with too much heat. He showed me to slow down and use less amps and the results definitely improved from that. The last thing he mentioned was that the weld puddle was "dancing around" a bit. He said he see's it here and there and its usually related to material that isn't 100% pure stainless. The 321 that they normally use he said welds nicer, but obviously on this project it was out of the budget.

In the end he made some incredible looking welds and my welds weld from functional but butt ugly to functional and presentable. I'm still in need of more practice to make them really start looking pretty.

glad to see you're making some progress. It is always amazing to see what someone who really knows how to use a certain tool or another can do with the same tools you have.

It's kind of like racing.
most of the performance is in teh driver and crew setup, then the little bit left is in the actual tool / vehicle.

A great operator can do beautiful work with sub-par equipment, but it seldom works the other way around.

[Rodsmachineshop]

yes pics would be nice hey when things go wrong with me i walk away grab a beer sit down and blame it all on my exwifes

[Injected65]

I'll try and remember to post some before/after pictures when I get home tonight.

[Injected65]

Sorry, keep forgetting to download the pictures. Here is a video I found on welding tips and tricks that shows what my buddy was doing (except for he used a #10 cup instead of a #12 cup in the video). I am still waiting on confirmation from my buddy on the brand of the cups he is using, but it looks like this place might have some of the larger gas lens cups. http://www.ceramicnozzles.com

[Injected65]

Here are the tig cups he was using. I ordered them in for myself and a few friends. They are pricey as all get out, but seem to be worth the money.

[jakeru]

Jody gave these a mention a while back, in one of his web pages or videos. When I contacted the manufacturer about them, I was turned off by the cost, so didn't give one a try.

Let us know how it works.

[Injected65]

Here are a couple more pictures of those cups along with a #10 cup and the little brass screens that my buddy uses at work with the cups. Unfortunately I have not had an opportunity to use the cups yet. I have a set of SS headers coming up for my 65 Mustang, but it will probably be 2-3 months until I am at a point to build those. If I can find a little bit of free time I might grab some SS scraps and try them out though.





Chris

[Injected65]

Here is something else I want to try. Not saying that it will fix anything, but I can't see it hurting anything either.

http://www.weldingtipsandtricks.com/...gas-dryer.html

[jakeru]

Injected65 - I think I'd try and recess those screens behind the opening of the cup a comfortable amount, to help ensure that the arc won't go through the screen. If an arc goes through the screen, it could mess the screen up in the short blink of an eye.

[Injected65]

I will experiment around with the screen positions. Thankfully he gave me 5-6 extra screens of each size.