This question was posed to me in an interview.
This is a very interesting question from Advantages and Applications of Steel topic in division Steel and its Alloys of Aerospace Materials & Processes
To explain I would say: S.A.E 4037 is molybdenum steel. This can be used as a replacement for nickel steel in manufacturing several parts like bolts, pins, terminals and several other kinds of components. It is heated to obtain certain tensile strength.