We can assume that in the 1912 Titanic wreckage the sea water temperature wasn't 60ºF or 15ºC, because there were icebergs floating around. Icebergs would quickly melt down at a water temperature of 60ºF.
A few years ago I read an article on a magazine whose name I don't remember. The article said that a piece of the Titanic's hull plate was cut and took to a lab to analyze it. The chemical analysis revealed that the steel could be considered as being SAE 1020. Mechanical tests were also run, but they weren't considered valid because the long time under sea could have changed the mechanical properties of the steel.
Giovanni S. Crisi