Yes, but only with good proper threads on both parts.
I hear what you are saying too Chris, but unless this is a last ditch effort to get the car one way home, I would never suggest welding parts that way on a hydraulic system.
My lines from Technafit were custom made to my spec, and they fit flawlessly into the threaded portions and lock up at the appropriate depth due to design. That is how it has to be.
Also, no rubber washer style parts can be used if actually attempting to seal fluid from coming out. The threads on a pipe style threaded fitting or the tapered seat (watch the angles there too) do all the sealing of fluid/pressure.
An O-ring/washer has no place on these two styles of systems.