From: Rabbi Moshe Sofer
To: Rabbi Meir
A frying pan previously used for dairy (no longer ben yomo) was subsequently used to fry meat. The Chasam Sofer rules that hagalah suffices without libun, since the absorbed substance is classified as heitera bala; for extra measure he recommends three rounds of hagalah. He further argues that concern about sharp foods reviving the weakened absorbed taste does not require libun, as hagalah sufficiently weakens the absorption beyond revival according to those who hold sharp foods can revive stale taste.
Source: Shu"t Chasam Sofer YD §110