Soldering heavy gauge wire is more about having thermal mass in the iron tip than high temperature. That is part of why you can buy different tips - selecting t

Soldering heavy gauge wire is more about having thermal mass in the iron tip than high temperature. That is part of why you can buy different tips - selecting the tip with the right thermal mass will allow you to quickly get the workpiece up to temp without overheating anything nearby. You can hack it by just turning the temperature way up, but there are a number of drawbacks to doing so. It's better to use the right tip.