Joined: Nov 2006
Posts: 19,810
Likes: 597
From: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...
As Tom explained it to me, high end steels like 531 are something like spring steel, can bend a great deal momentarily and come right back to where they started. But once the steel starts to deflect, it is permanently changed. You can bend it again; you can bend it more; you can bend it "back"; but you cannot unbend it. That's probably not really what he said; that's what I learned from talking to him.
From your photos, it's unclear whether your frame really bent at all. It clearly flexed enough to crack the paint; but it may have sprung back to where it started, in which case it has not deflected, and has not weakened. As I understand it.
Why not put a new fork on it, and ride it? You'll soon know whether it needs Kurt's attention.