Welding Tips and Tricks

I need to get a certification for groove welding stainless steel(SS) to carbon steel(CS). I have taken, and failed, the exam three times!!! The problem is on the CS. Every bend test shows a hairline crack along the root pass and sometimes on the face pass where the weld metal meets the CS. What am I not doing right? I am using 309L 3/32 filler wire. I am using 1/8" electrode 2% thorated. The electrodes are filed to a sharp point. I wonder if it is just a finesse thing that comes with practice.

I know SS takes about 1/3 less heat than carbon. I also realize this means I need to focus more heat on the CS than the stainless side. I am trying to do that. However, I keep failing the darn test.

Any suggestions would be appreciated.

Thanks,
Taz

I'm really very Sorry,
The reason of being sorry of mine is i can't gave you any suggestion because i'm also suffering the very same thing so i'll pray for both of us to got the answer of this Metal....

Yes I need to know what TIG welding and Stick welding definition ? mY HUSBAND HAS A TEST TO MARROW...PLEASE HELP !!!!!
Thanks
ShannonW

Shannon, what exactly are you asking here? To me, it looks like you are asking for a "definition" for "TIG" and "Stick" welding?
I'm probably reading this wrong, but here goes just in case this is what you are asking.
TIG = Tungsten Inert Gas welding, but is properly known as GTAW = Gas Tungsten Arc Welding GTAW uses a non - consumable tungsten electrode to produce an arc and the filler rod is added manually.
"Stick" welding is properly known as SMAW or Shielded Metal Arc Welding. It is a consumable flux covered electrode rod that creates an arc, and melts into the weld pool to add filler material.
If I am totally out to lunch, please ask again!

As for the OP question, sorry i can't help, but would love to know the answer!

What is the parent metal thickness?
Also how deep are you back gouging? Any test i have taken (not that its been alot, but mostly TIG) i always back gouge into my root pass to the point that when i weld it I almost
melt thru. If there is a "crack" opposed to "no fusion" then possibly a pre-heat of the metal is necessary. Also cool down is important as well, doing a second pass to early could
pose a problem as well.

Im not saying any of this is correct just my opinion.

To TIG weld Stainless to Carbon steel with no cracks you need to use Hastelloy W filler rod. It is a very stretchy metal and will bond to both metals with out cracking. Welds like a dream. The only bad thing is it is very expensive!

Hastelloy is probably not an option. If he's taking a test, he'll have to use whatever the WPS specifies for the test, thus the 309/309L/309LSi type rod.

My suggestion would be more heat on the CS side, to allow 1) more diffusion of the carbon between the parent metal and the filler, and 2) a slower quench (cool down) of the HAZ on the carbon side.

Does the WPS allow a PWHT? If so, you can anneal the HAZ and reduce the brittleness.

My two cents. Your mileage may vary.

Steve

I've never had a test like that, but I've had to weld a lot of CS Hydraulic lines to SS or unknown Alloy fittings. Usually we have to watch for hot cracking from the different materials shrinking at different rates. I've found that it helps to really feed the rod to it to keep the torch moving faster at as low an overall temp I can maintain while still getting good penetration/ dilution. But I also try to keep the heat about as steady as possible minimizing rapid temp changes per each material. When all else fails, my coworkers bring this stuff to me, and so far using these methods I've been pretty successful. Let us know what you find though.

This topic is from last October, and is the OP's only post on the forum. I doubt we'll hear any more about it.

Otto Nobedder wrote:This topic is from last October, and is the OP's only post on the forum. I doubt we'll hear any more about it.

Thanks! Regardless, it's still good discussion.

Try siiting longer and add more filler wire especially on the root. Suck back is minimal. Better root beads