Copper saute pan metal lining is melting?
You overheated it, tin melts at 450 F . It may have a few per-cent of other metals in the tin that would raise the melt temperature slightly.It should be fine now except if the surface is now rough ,it will be difficult to clean. The tin can be remelted and smoothed. Unfortunately that requires some skill/experience. I have retinned at least one, I added some pure tin (not commonly available- no solder is pure tin.). I managed to get an OK result, not as good as the original very smooth surface.