The tag iron is used 29 times. Out of these, 17 are tagged soldering iron which is definitely the wrong use of tags.
I suppose iron as in the material might be on-topic, when discussing various chemical aspects as in how well it conducts etc, but I kind of doubt we need a separate tag just for that. In-depth questions about the characteristics of iron should probably be posted at https://chemistry.stackexchange.com/ instead.
At the very least I propose that we remove the tag from the 17 incorrectly tagged solder iron questions.