The ultra higher steel grade GL F550 shipbuilding steel plate are used abnormally owning to its high cost and substitutability.With the minimum yield point at 550 Mpa,and tensile strength within 670-835 Mpa,steel plate GL F550 can bear the higher strength and used to some steel structure parts in ships.At current,Xinsteel is cooperating with Wuyang steel mill about starting rolling the heavy shipbuilding steel plate GL F550 with the unit weight about 30 tons.This rolling should be from steel ingots and normally the plate rolling yield should be above 72 percentage.