MIL-S-24371 is a specification covering HY-130 Steel. MILITARY SPECIFICATION: STEEL PLATE, STRUCTURAL, HIGH YIELD STRENGTH (HY-130)

HY-130 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. It is valued for its strength to weight ratio

The “HY” steels are designed to possess a high yield strength (strength in resisting permanent plastic deformation). HY-130 yield strength in ksi is 130,000 psi. HY-130 is generally considered unweldable. Available to the MIL-S-24371 which has now been superseded by NAVSEA Technical Publication T9074-BD-GIB-010/0300.