Originally Posted by
Going Boeing
It’s claimed that the Collins class submarines are constructed of a lighter, yet stronger steel than the HY100 steel used in the Virginia class.
Steel doesn't get appreciably lighter. What you end up doing is using higher strength steel which allows you to reduce thickness and hence weight of structure. However, that's only if the fracture toughness properties allow it to absorb the fatigue damage the boat will see, allow for welding imperfections/flaws and resist both crack growth and high strain-rate loading. Plus be able to be formed and welded with acceptable levels of pre-heating etc, etc.
Tricky stuff submarine steel.