When welding stainless steel (or one of the high nickel alloys (Inconel, Monel, etc.), the shielding gas or the flux in the electrode only protects the FRONT of the weld. You must use something on the BACK of the weld to keep the oxygen out, float out the oxides and dissipate the heat. This can be accomplished either by purging with an inert gas, usually argon, or by the use of SOLAR FLUX. Failure to protect the back of the weld by one method or the other will result in a sugary, porous weld, burn-through; and the weld will not be of x-ray quality.
Isn’t the weld pictured above beautiful? From the front it looks perfect, doesn’t it?
But, when you turn it over…
…it becomes very evident that proper backing, either purging or SOLAR FLUX, is needed if you hope to get a good weld.
In the above test coupon, the left half of the joint was protected with SOLAR FLUX while the right half was left unprotected.
A similar result would have been obtained if an argon purge had been used.
SOLAR FLUX has been protecting the backs of welds, keeping the oxygen off, dissipating heat and unwanted oxides, and producing x-ray quality welds for over 70 years. It is often preferred over inert gas purging because it is easier, faster, simpler, less expensive to use, and yet yields the same x-ray quality weld.