When you're done soldering, cover the soldering iron tip in solder, and store it covered in solder. This prevents it from oxidizing when you're not using it
When I say explode, I mean the tip shot bits in a 1-2 inch radius after I put pressure on a thick copper wire. It nearly hit my non-dominant hand which was holding the circuit board on the floor tile I used to isolate my soldering shit from the now singed table
Would it help you to know it was the soldering iron my dad got when he finished his electrician apprenticeship in the early 80s, which was probably a decade old at that point
This kind of sounds like whatever was on the tip had oxidized severely over the intervening 40 years. So when you applied heat it couldn't conduct very well, so it got hotter and hotter until it had an uncontrolled thermal expansion. This just comes down to especially with older equipment, making sure the device is clean, and if you apply heat be careful especially on the first startup.