Welding 304 SS Warping

[johnplctech]

When welding 304 SS or other stainless steel structurals like tube and angle how do you keep the material from warping so bad. For example if I weld a "T" shape from 1" x 11ga square tube the top of the T will droop quite alot after the weld cools. I have tried welding in short bursts with some cool time but it still warps... I have tried GTAW and MIG welding. The MIG is the worst it splaters bad and is hard to get a small weld to look pretty. The GTAW is by far the easiest to control. Any tips???

Thanks
John

 

[IFRs]

Clamp the plate being welded into an inverse of the shape it takes when welded. Then weld and un-clamp.

 

[sayee1]

johnplctech
Did you try straight TIG or pulsed TIG? Maybe pulsing would help. Any chance of using a chill from second side. Just thinking out aloud! I see you have already tried intermittent welding to reduce heat.
What IFR posted as a method to minimise distortion ( Remember you can minimise distortion but not eliminate or avoid it completely)is called presetting.
Metalguy,
Can one use 100% CO2 for ss welding? I have used Ar(98%)+O2(2%), Ar+He and Ar+ He+CO2 mixtures.
Or did you mean a CO2 containing mixture?
Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!

 

[johnsford]

you can also try "stagger" welding, This will help prevent the build up of heat/metal expansion/warp. I have also had some luck on light gauge with increasing the root gap from start to finish,(minimal tacking)

 

[sayee1]

When you do stagger welding keep the direction of welding opposite to the overall welding direction.

2<------1*6<------5*4<------3*8<------7*

The length of 1-2,3-4 should be approx ~2&quot;. I still feel pulsing the TIG would help because you can then use a low background current as well as longer background duration to allow the base/weld metal to cool down before starting the next pass. Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!

 

[Seldom]

Hi Johnplctech,
IFRs has given you sound advice but there are a couple of more/other things to try.

1. Make sure you have a tight fit if you’re applying a fillet weld and the use the smallest gap you can stand if you are using a groove joint.
2. If you use a clamping system as IFRs suggested as I do also, chamfer the weldments if possible. That is, pre-stress the “T” when you clamp it down by putting something under it such as a shim. You’ll figure out the appropriate thickness of the shim by experimenting so you’ll have a straight “T” after the weld cools.

Understanding the principles of what your weld does when it cools will help you figure out the best way to minimize distortion. The first and most important thing to understand is that a weld cools from its edges to the center and when it cools, it contracts. It therefore contracts toward the center and pulls the ends of the “T” inward.
Seldom
&quot;There's no such thing as a welding problem, just welding puzzles of assorted sizes!&quot;

 

[johnplctech]

Thanks for all the great tips.

I'm guessing here that one would jig up the &quot;T&quot;, square everything up tack it well then put some pre-stress into the joint then weld....

I have a Miller Syncrowave 180 TIG welder. What is Pulse Welding? Is my machine pulse capable of that?

Thanks
John

 

[sayee1]

Miller Syncrowave 180 TIG is an AC/DC welding power source with &quot;Squarewave™ output with AC balance features adjustable penetration and cleaning action while increasing arc stability on various aluminum alloys, and helps eliminate tungsten spitting and arc rectification.&quot; This is not possible of giving a pulsed DC output if I remember correctly. In a pulsed mode, the output is still in DC mode but with pulsing. There are alternating short pulses of peak current for short periods and background current for short periods. The time duration/percentage of one cycle/frequencies for the background and peak currents as well as the current settings for both the peak and background can be independently set for such machines. The melting of the base metal as well as feeding of filler wire to weld pool is during the peak pulse, while the weld and base metal cools during the background current. The effective average current thus used for welding is much lower than the value that would be used in a straight DC mode. The heat input can be be controlled by changing the duration for background current as well as the background current itself

Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!

 

[sayee1]

I forgot, I still remember what one of my instructors compared pulsed GTAW welding to: he compared it with stiching, the energy given to the base metal and weld is in short bursts and in between bursts the metal cools down, so effectively reducing distortion especially for thin sheets Thanks and regards
Sayee Prasad R
Ph: 0097143968906
Mob: 00971507682668
End of all knowledge is the attainment of immortality!