What steel is used in US submarines?

Answer 1

HY80 steel and variants, a flexible steel alloy, has for decades been used on modern U.S. and Allied submarines. Its flexible properties are what makes it an asset - it contracts and expands as sea pressure increases/decreases with submerged operations. Internal submarine decks are not actually attached to the hull - they're actually hanging from from suspended cables and the decks are several inches from the sides of the hull to allow for the contraction as the boat goes deep.

About 25 years ago, there was a lot of controversy about the Russian ALFA class Fast-Attack and her known Titanium hull, able to reach depths near 3000'. Many in Congress wanted to know why the U.S. didn't have something similar. Fortunately, idiots remain in Congress and Engineers design Nuclear Submarines.

Titanium is extremely strong, but it is not flexible - sure, the ALFA can dive deep, but each time it puts stress on the hull when it deep-dives it becomes more brittle over time. It's like putting increased pressure on an eggshell - eventually it'll crack. This doesn't happen with HY80. It remains flexible over decades and hundreds of dives and surfaces.

Also, you don't need a submarine that can go to 3000'. All you need is a weapon that'll go to 3000'. At that depth, even minimal damage to the pressure hull would result in a major casualty and likely loss of the boat.

Answer 2

American submarines are constructed with a flexible steel known as HY-100. Although the chemical composition and rolling methods are classified, HY-100 enables America's Fast Attack and Ballistic submarines to operate at depths exceeding 1,000'.