Only if you spend too much time on it. You do have to wet your tip more frequently when you are using high temp with flux core. However, I end up with shiny, w

Only if you spend too much time on it. You do have to wet your tip more frequently when you are using high temp with flux core. However, I end up with shiny, well made joints 99% of the time. If I burn off the flux, I typically will wick it up and re-apply, or just swipe the solder off the joint and add more solder (depending on what I am working on).