WVwelder,
Here is something I posted a while back - never did locate the original article,
Regards,
Shane
Hi all,
This has turned into an interesting subject (hopefully I am not hijacking the post) but I was initially in agreement with Lawrence and Jeff that the welds couldn't be performed successfully without backing purge but after a bit of research I am unsure.
If you read some of the literature below it appears STT is being used "successfully" without purging on s/s pipes.
Miller RMD
Potential to eliminate backing gas. The shielding gas coming out of the gun remains relatively undisturbed by the controlled metal transfer of the RMD Pro process. As a result, enough shielding gas gets pushed through the root opening to prevent sugaring (oxidation) on the backside of the weld. Some fabricators have qualified procedures to weld some of the 300 series stainless steels without a backing gas, improving productivity by up to 400 percent.
Fluor Corporation
http://files.aws.org/conferences/abstracts/2003/11e.pdfhttp://www.fiatech.org/pdfs/Roadmap2004/E4_FA4_P4.pdfThe original article written by Charles "Pat" Patrick would be very interesting reading especially if it has been re-released in the Welding Journal with some differences from the original.
Regards,
Shane