The melting point of the lead wire is about 180 degrees, of course, the melting point is different according to the proportion of lead and tin in the wire. While the melting point of lead-free wire is generally about 230 degrees, the melting point is also different according to the different metal composition proportions.
There are exceptions, however, for lead-free solders, which also have low-temperature solders, which have a lower melting point than lead solders, but the low-temperature solders are quite expensive.
Of course, theoretically speaking, lead solder joints can also be soldered with lead-free soldering station because the temperature of the lead-free soldering station can reach the melting point of lead solder, but in fact, no one uses it to do that because once the lead solder is soldered by lead-free soldering station, lead-free soldering station would be contaminated and can no longer make lead-free environmentally friendly products.
In turn, it is not possible to solder lead-free solders with lead solders because the temperature of the lead soldering station cannot reach the melting temperature of the lead-free solders.