If I Die Before I Wake by windsryer
I'm looking for a specific fic where Steve is being tortured, and the team is helpless to do anything but watch. Steve manages to take it, thinking that he's not as important to the team as they are to him, and he tells Tony to take care of them all as he thinks he's going to die. I know that at one point the bad guy leaves a serretted knife (or some thing similar) in Steve overnight, and the serum means that his body is constantly healing around the blade, and then tearing open again.
The fic ends with Coulson saving the day, and Steve walking up in someone's lap, where he gets scolded (?) because he is worrying over Natasha's hurt hand, instead of being concerned about the fact that he was just tortured.
It wasn't on ff.net or AO3, but I can't remember if that means it was on DW or LJ.
It was definitely gen.
It's not You Got a Friend in Me, this fic definitely had Steve already being tortured, rather than him offering himself up.