Are shark teeth as hard as steel?

This is a poorly defined question, because the difficulty of biting through steel depends upon how thick the steel is, as well as the kind of steel (some steel alloys are much harder than others), and in addition, there are many different kinds of sharks, and some have stronger jaws than others. I will note that if the steel is sufficiently thin (steel foil) even we human beings can bite through it. I will also note that sharks do not normally encounter steel anyway, and they much prefer to bite fish and seals. That said, it is true that sharks have very strong jaws. That is probably what you are trying to find out.