HY-80 and HY-100 names can outlast alloy changes

Have U.S. submarines used essentially the same HY-80 and HY-100 alloys since the late 1960s?

The alloys have evolved under the same designations, although the specific changes are not disclosed.

A familiar steel designation does not establish that the material has remained unchanged. HY-80 and HY-100 are described as having evolved despite retaining their names. The answer relies on personal technical knowledge and does not provide alloy recipes or a specification comparison. The claim therefore concerns continuing development, with its details left unstated.