HY-100 is a high-tensile, high yield strength, low alloy steel. It was developed for use in naval applications, specifically the development of pressure hulls for the US nuclear submarine program and is still currently used in many naval applications and used extensively in petrochemical applications due to its strength to weight ratio.

The “HY” steels are designed to possess a high yield strength (strength in resisting permanent deformation). The alloy measures high-tensile strength with a minimum of 100ksi. HY 100 is generally considered unweldable. HY-100 also offers exceptionally high impact strength as well. This combination makes HY 100 unique among steels. This material is Available to the MIL-S-16216 & NAVSEA Technical Publication T9074-BD-GIB-010/0300.