Ignoring the flux during regular PCB soldering, I was curious as to whether core in the solder wire is required to properly wet the iron tip. I saw someone saying that for drag soldering the solid-core wire was better, but in that case there is no flux when you wet the tip or deposit solder onto the tip. The flux must do something to the tip right? Although, I have heard that active flux does shorten tip life, I am not sure if it does anything beneficial for the tip.