Hi!
Yes! A 30W iron is way to weak.
I recommend a 50W-75W Automatic temperature controlled sweat soldering iron, like the one I have (50W Weller, 30 years old). These professional soldering irons use iron plated tips that never oxidizes and get worn out.
I also recommend that you get the Great Planes sweat solder, with acid, this stuff is also called Stay-Brite and is superior to any ordinary sweat solder, much stronger and much easier to use as you don't have to clean the piano wire before hand...just pour the acid on and solder.
Don't use it for electronic soldering though!

Regards!
Jan K
Sweden