A comment from a member of our “Weld Purging Best Practices” group on LinkedIn, reads as follows:
“I have used solar flux in place of purging where purging was too difficult and the weld quality was not high purity. The result was Ok at best and only good for one pass.
Once the second pass was produced the solar flux burned away leaving a root pass contaminated.
I am very hesitant to use anything other than high purity shielding gas purging in conjunction with my Weld Purge Monitor®.
After welding for 40 years I have found that working conditions, welding procedures and purity acceptance criteria may dictate what you are permitted to use.
In addition to this a new filler metal that eliminates the need for back purging may work fine in controlled environment but if it is not part of the accepted filler metal grouping recorded in the welding procedure PQR.
The welding procedure must be re-certified before this new wire can be used for any production weld.”
There has been quite a deal of discussion about fluxed wires, rods and pastes in our “Weld Purging Best Practices” group.
From my experience, I have to agree with Dave.
If you have to make 'Critical' joints, then don't go the flux route.
Better to TIG/GTAW the root with a good gas purge and keep the Weld Purging System in place for the next two passes as well and ensure that the interpass temperature has dropped below 150ºC (302ºF) before turning the gas off and removing the weld purge system.
