HSLA-100 steel is a steel developed by the United States for a new aircraft carrier shell and an advanced attack-type nuclear submarine (non-pressure-resistant shell). Its performance has reached the level of HY-100 steel, and its thickness can reach 100mm. Its military specification ML-S-24645A has been developed and its welding material is the same as that of HY-100 steel. The first order for HSLA-100 steel was for the nuclear-powered aircraft carrier "Stannis" (CVN-74). HSLA-115 steel has a yield strength of approximately 800 MPa, which is higher than HSLA-100 steel (yield strength is approximately 690 MPa). The US Navy used the latter as the flight deck steel for the future aircraft carrier CVN-78, and developed HSLA-115 steel for weight reduction and center of gravity reduction. The US Navy conducted a study on the “High-performance HSLA-115 Steel Evaluation and Implementation Phase II” project from February 28, 2007 to February 22, 2010. Through the new heat treatment, the yield strength of the current high-strength low-alloy steel HSLA-100 is increased to 115ksi (794MPa) (code HSLA-115), and the thickness of the steel plate is reduced, so that the weight of the hull can be reduced under the premise of meeting the performance requirements