Refrigerations question about brazing

[Skyline_GT]

I have a question about brazing copper tubing for A/C, is it true it's better to blow a constant amount of nitrogen when brazing the lines ?

[rmuntz]

This is true but "blow" is probably not a good term. You push 1-2 psi max through the piping. What this does is replace the oxygen that is inside the piping with an inert gas so there is no oxidation (black stuff) inside the pipe when welding