Back Shielding Stainless Tube

[Gusmann]

Andy/welders,

I’m helping a buddy weld some stainless steel headers and inlet pipes for a turbocharger install on a Mustang. I’d like to get the interior of the pipe (backside of the weld) to look better. After welding it has a fair amount of ugly back nuggies inside the tubes. I’m aware that we could back-shield by damming the tube and filling it with argon. Will CO2 work of this purpose? Also I recall seeing some type of paste to shield the back of stainless welds without the secondary gas inside the tube. Have you seen this product, what is it called, and where can I get some.

Thank You

Gus

[rpm]

I don't think CO2 would work as a back shield, you can get
solarflux B from Burns stainless steel,I don't know if there are
any other fluxes that work as well.Perhaps Andy Knows.

[ROCK]

GUSMAN.........RPM IS CORRECT CO 2 WON'T WORK... BACK FILLING WITH ARGON WILL HELP....... THE ONLY PASTE I'M FAMILURE WITH IS THE HEAT ABSORBING TYPE........ PERHAPS IF YOU TRY IT WITH SOME ANTI SPLATTER COMPOUND MAY HELP......... THIS IS NOTHING MORE THAN CONTAMINATION FROM NO GAS ON THE BACK SIDE.........TO IMPROVE AIRFLOW INTERNALLY CAN YOU REACH IT WITH A DREMMEL............. ANYTHING WE CAN DO TO HELP DECREASE AIR RIPPLE WILL HELP.....................ALSO WHAT TYPE OF STAINLESS STEEL IS IT..........ROCK..........
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[Kevin Disney]

Gus,

The proper way to weld stainless steel tubing is with a backing or purge gas (100% Argon), this will prevent "sugaring" or as you stated "ugly black nuggies". When using a purge, you need to have a flow of Argon through the piece to be welded prior to starting, typically this is a 6 volume change. This is to insure that nearly all of the Oxygen is displaced. An oxygen analyzer can be used to check the oxygen concentration (2% or less) prior to welding. Typical flowrate would be 5 to 15 cu.ft/hr, depending on size and configuration of the piece.

[ASKANDY]

Great answer Kevin!
He is correct. Back purge with Argon. I use an Argon purge with a Argon/Hydrogen mix weld gas and a 347 filler.
Good luck

A-