GTAW TECHNIQUE FOR STAINLESS NEEDED

By jon20013 (*****)

Date 12-15-2005 13:49

You might try straight Argon to see if the appearance improves. What is the gas flow? What are you using for purge?

By regis.hgs Date 12-15-2005 15:24

The flow I was using was 45 cfh. For purge (20 cfh), I was using pure argon, but with the root it was everything ok.

By Lawrence (*****)

Date 12-15-2005 15:04

The first step in testing for weld surface color would be to just strike a low amperage arc with your torch angle exactly perpendicular and create a small puddle with no melt thru. Do not progress forward, only melt the metal directly under the electrode. After the puddle is established begin to slowly tail off your amperage until you see the puddle shrink and refreeze. (This should take less than 10 seconds). After the puddle is frozen and gone continue to reduce amps until the arc is out. With your postflow set for 10-15 seconds keep your electrode directly over the weld area until the gas stops.

Do you have acceptable color in this condition?
If Yes we can move on to technique and cup size

If no. Check for bad gas flow connections.
If Yes repair connections and retry.
If no replace gas supply and do trial with gas known to be pure.

The Hydrogen mix is not all that common in the U.S. but should have no effect on the surface color of the finished weld. It should however produce nicer wetting at the toes and slightly better penetration and higher travel speeds when compared to Argon 100%

With a small dia cup the flow rate must be small also. a 1/4 inch nozzel requires about 7-10 cfh as the size increases so does the gas demand. A larger cup provides better coverage and allows for longer stickout. A cup of about 1/2 inch dia. may draw about 15 CFH in a standard cup and collet and slightly more with a gas lens arrangement.

Torch angle must also be considered. If you lean your electrode too far in the direction of travel the result will be that the shield gas envelop will not sufficiently cover the weld as it cools. It will also make your puddle oblong rather than round and reduce penetration.

Let us know more and I'm sure more advice will come.

By regis.hgs Date 12-15-2005 15:33

I checked the connections and there were leaks indeed. But how can this bring problems, if the gas is going out through the leak ? After repairing, the results were better. But then I tried Argon 100 %, the results were even better. Could you please suggest me a current (and gas flow and stick out for cup number 8) for a butt joint in 1/8 thick sheets ?

Thank you.

By SWP

Date 12-15-2005 17:21

It is counter-intuitive but gas leaks will allow air to enter your shield gas system. You must ensure there are no leaks! Also, event the type of hose can make a difference, only use a high quality impermeable hose material, do not use the cheap rubber hose.

I agree with Lawrence completely, on all the points he made.
Your 45 cfh flow is way too high, more is not better in this case, it will create turbulence that mixes in surrounding air.
Use a gas lens! If you want to overkill it, try a "Monster Lens", see http://www.arc-zone.com
As for your question on stick out, if your still having shielding problems, keep stick out to a minimum.

By regis.hgs Date 12-15-2005 19:27

The test you suggested responded well. Would you have further advice when adding filler metal ? Without filler metal the result is far better, but I need to add material.

By ridesideways (*)

Date 12-16-2005 01:27

Again, start super-simple to diagnose the problem. You are getting good results now without filler material, so you might try the same simple test suggested earlier, except now with filler: make a low-amperage puddle with the electrode perpendicular to the work, dip the filler once, and then extinguish the arc slowly and allow post-flow to complete. Is this test result any better?

If so, then perhaps your filler manipulation technique can be examined, i.e. are oxides/contamination forming on the filler metal because it's not within the gas envelope at all times, etc.

By regis.hgs Date 12-16-2005 12:32

Thanks a lot. And what filler manipulation technique would you suggest me ?

By SWP

Date 12-16-2005 15:25

Don't know if it makes much difference with stainless, but I've heard it recommended for critical aluminum welds, you should try to keep the end of the filler wire within the shield gas envelope as you dip and retract. When you dip the wire, then retract out of the shielding, hot end of the wire oxidizes, then you deposit that contamination on your next dip.

By medicinehawk (**)

Date 12-17-2005 15:48

What diameter stainless steel rod are you using???? If you are welding 1/8" Thk plate and are using 3/32" wire.....then this could be your trouble.
If you are welding 1/8" thick plate, try using 1/16" ss wire or better yet: .045 wire. While it seems you are getting good gas coverage by fusing (No wire) but then you are getting blackened welds with wire, then you maybe using too large a wire for what you are welding.
It has been my experience that it works better (cosmetically) to use a smaller diameter wire (when you have to have it) because you with stainless steel, you need to minimize the heat input on the HAZ. You can do this in 2 ways: 1) increase your travel speed or 2) use less amperage.
With a smaller diameter rod, you are decreasing heat input by needing less heat to melt the filler wire. If you are using a gas lense and the flow rate (regardless of pure argon or H mix) then you should be able to crank it up to 35-45 CFH. This can be expensive if you are paying for the gas so I would stay with the minimum (20-25 cfh) if that is the case.
If you lean the torch away from the direction of travel (30-40 degrees) you might get better results with gas coverage then holding the torch perfectly perpenticular to the work. Also, keep the wire in the gas cloud and you will know if you are doing this correctly by examining the welding rod after making a weld. Does the wire need to be clipped because it is black on the end???? Or is the rod end clean and shiny like the bead you just put down??? Sometimes copper colour indicated you are keeping it in the argon shield pretty well.
Anyway, you are getting good feed back from others and we all want to know how you are doing so ,please, keep us informed.
Be well.

Hawk

By regis.hgs Date 12-21-2005 21:07

Thanks a lot. Well, actually, I got better results when changing from .045" wire to 1/16" mm wire. The fusion tests suggested by the others worked well, even with wire feeding. While feeding material, I am not pulling the wire tip out of the gas envelope. But I think that with the suggested gas lens I could achieve better results. I will let you know when I test it.

By welder5354 (**)

Date 12-17-2005 21:45

Butt welding with GTAW. It looks like the pros have given you some good advise. One more piece of advice-Use a stainless steel wire brush. The key to wirer brushing stainless steel is to start wire brushing about 4 to 5 minutes after you stop welding that particular area. Wire brush slightly and continue until the weld becomes the same color as the base metal. (Don't wire brush immediately after welding because the base metal and filler metal is still too hot.)