Generally, in the TIG welding of stainless steel piping or closure weld seam of any vessel extensive purging is required before welding, and backing gas during welding, to avoid heat tint brought about by oxidation, which if happened, will result in loss of corrosion resistance.
(Heat tint formed is a thicker chromium oxide scale with a mixture of iron, nickel and other oxides. The thin layer beneath this surface is chromium-depleted layer. If heat tint is not removed, corrosion may start from this chromium-depleted region.)
This flux cored TIG rods contains metal powders and slag formers inside the core which produces slag to protect the reverse side of the root pass. This allows root pass welding without the use of purging gas. Thus, it is possible to eliminate gas purging downtime and save the costs of expensive purging gases before and during welding.
Formation of key-hole during welding is very important in order to supply slag onto reverse side bead.
Watch Video demonstration of this filler rods by Welding alloys here, https://www.youtube.com/watch?v=X4L81c7IdZQ
Reference: Welding Alloys literature, KOBELKO literature
Keep reading, Happy welding
Thank you,
KP Bhatt
weldknowledge 
why some time tig for stainless dont use purging gas? ang how the result its.? thanks
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Any type of shielding is required when welding stainless steel especially for root pass and second pass. If shielding is not given then weld will be oxides which may lead to loss of corrosion resistance.
So shielding in the form of purging gas, I. e. Inert gas is must for any root pass. Other than gas, one may also use solar Flux, fcaw tig filler rods which acts as shielding to the weld.
So without using purging you may find black oxidized weld for stainless steel.
Hope you get your answer…
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