The thing is not going to blow up in your face if used with a correctly rated stepdown transformer
What exactly does "correctly rated" mean? I have 3 step down auto transformers. One of them can even be regulated according to input voltage for 188-212v, 212-238v or 238-260v. Given Portugal's mains voltage to be 245v (don't know why, supposed to be 230v), I can have the TX output 105v, 120v or 130v.
No . 50Hz and 60Hz
All 50Hz equipment works fine with 60Hz but not vice versa.
I don't think a soldering iron is going to be so heavily loaded that the extra losses incurred by the use of 50Hz will be a real problem,unless the internal transformer is very poorly specified.
A lot of North American & Japanese origin stuff is in use in 50Hz countries,without having been specially designed for that frequency in the first place.
High power stuff,like,for instance Ham Linear amplifiers,is sometimes offered with the option of US 240v 60Hz.or
Aus/Europe,etc, 240v 50Hz transformers,but small stuff seldom will be a problem.