The Melting Point of Solder
The melting point of solder depends on its particular formulation. In the case of eutectic tin-lead solder, the melting temperature is somewhere around 360 degrees Fahrenheit. The temperature becomes a bit higher with different formulations of solder, for example 60/40 tin-lead may need 10 degrees higher. Higher temperatures can also be required for lead-free versions of solder, and that may change the temperature at which you’d want to use for your soldering iron.
Your soldering iron obviously is hotter than the material you’re trying to melt. The heat has to flow from the tip to the work piece so that it can melt the material. So we typically have a setting of temperature that is hundreds of degrees hotter, so that the material can heat rapidly, melt efficiently, and proceed very quickly.
As to typical solder work, the temperature between 650 and 700 degrees Fahrenheit is a good choice. You may expect hotter temperatures for very heavy or large work pieces, and perhaps higher temperatures for lead-free solders.