welding 4130 tubing

[hunter1151]

Have been tig welding 4130 tubing lately and my welds seem to be too hot. They are gray when I am finished. I have good fit up and this is not my first rodeo but I did change welders. I have a Dynasty 350. The thickest I weld is
.095 and the thinnest wall is about .049. I have tried 4130 rod and the ER's, different tungsten and different cups. Nothing seems to help..........am I just losing my touch or what?

 

[USMCdodge]

Sounds like the machine is welding a little hotter than your other one causing the while puddle to reach the inside of the pipe where the steel is oxidizing possibly due to lack of shielding gas. then the nasty oxidation gets sucked up into your beautiful dime stack. are you filling the pipe with backup gas?

 

[t100]

unlike mild steel, 4130 is very clean metal, probably only contamination problem is from cutting oil when they were cut/notched.

if your machine is set up correctly, you can also try speed up the torch welding a bit faster.

ER rods are just fine.

 

[GaryRoushkolb]

er 70 s2 is the rod you need, don't use 4310 without heat treatment. I think you need just to turn the amps down and slow down where you can control the heat better. if everything is clean "thats removing the surface down to shiney metal" with good argon flow you should be able to weld this ok. I assume your not using the pulse on the dynasty. Some cases it works great on 4130 tube but that's after you get the problem of "too hot" welds taken care of.
If this were mine I would run some test beads on a flat until I get the sweet spot on amperage.

 

[hunter1151]

Thanks guys..........I'll give it a whirl

 

[hunter1151]

Sounds like the machine is welding a little hotter than your other one causing the while puddle to reach the inside of the pipe where the steel is oxidizing possibly due to lack of shielding gas. then the nasty oxidation gets sucked up into your beautiful dime stack. are you filling the pipe with backup gas?

No I am not back purging the tube but that will be my next thing to try. Thanks
Tubes have machined fit up with consistant thickness and cleaned before I start down to shiney metal. Then cleaned with acetone........

 

[USMCdodge]

No I am not back purging the tube but that will be my next thing to try. Thanks
Tubes have machined fit up with consistant thickness and cleaned before I start down to shiney metal. Then cleaned with acetone........

Sound like everything is right to me. set yourself up with some backup gas and try again. I seal it up with some metal tape and let it fill for maybe 5-10 min. also make sure the flow of argon coming out of the torch isn't too high or low. i set mine up for 20-30...psi? cant remember what that unit of measurement is...

 

[1967lemans]

Sound like everything is right to me. set yourself up with some backup gas and try again. I seal it up with some metal tape and let it fill for maybe 5-10 min. also make sure the flow of argon coming out of the torch isn't too high or low. i set mine up for 20-30...psi? cant remember what that unit of measurement is...

If it is a flow meter, its SCFH

 

[NASTYZEN]

Pic's of the welds would help a little in finding out whats wrong.
One thing I noticed with cro-moly tubing is that the coating when sucked into the puddle makes it harder to control and seems to be a little hotter than I want it. I also wire brush the edges and the interior lip of the tubing with a bench grinder prior to welding.
You don't want to use too small a cup ether , drags in too much air and cools the welds too rapidly. A nice 10 to 12 cfh of Argon, is what I use.
Purging the interior of the tube is best as others have stated make sure you leave a small hole at the other end so pressure won't build up and blow a hole (UP)thru your weld.
May I ask what your building? That also determines the method.

 

[hunter1151]

I'll get some pic's

 

[Gary Anderson]

Tungsten - use 1/16" 2% (or equal in something non radioactive).
Grind tungsten to a pencil like sharp tip with the grind marks PARALLEL to the tungsten

Machine - rough setting approx 1 amp per .001 of material thickness
DCSP, High frequency on START ONLY.
100% Argon set at 15-18 CFM
I like a gas lens, but you can use whatever you want.
#6 or 7 cup
ER70s2 1/16" filler rod
I like to do a test piece to make sure of my settings.

Weld approx. 3/4" then go to the opposite side , do the same , then go 90*, do the same.

I use the foot peddle a LOT to regulate my heat

I clean the ends to be welded with a 3M surface conditioning disc, (I don't grind the ends clean, it removes too much material.) then clean with acetone.

I also do an AIR TIGHT FIT, way better weld.

You don't need any back gas, pre heat or any other B.S.

Just a CLEAN TIGHT fit.

If the weld is grayish , too much heat.
Turn the heat down or use less throttle (peddle).

I have taught welding at the college level.

The examples are 304 .065" Stainless welded to a mild steel flange
using 1/16"309 rod , all the other settings are the same as stated.

Your Pal, Gary

 

[Britt]

Gary, I agree with everything you said...except the purge part...without knowing what he is welding...I have welded on some 4130 chassis, that purge was necessary...and you can't do this without purge either.. (316L Stainless, one pass)

Welding is how I make a Living.

 

[hunter1151]

Nice Britt........ Thanks Gary I will try the settings you suggest. Still trying to get pictures loaded