深海船用耐力900MPa級極厚強靱鋼

抄録

A steel intended for use as the hull materials of deep submergible vehicles has been developed. The aimed properties of the steel were minimum proof stress of 900 MPa and high toughness.
The primary research was conducted on several steels containing nickel of a range from 2.5 to 5 percent with the emphasis on mechanical properties, heat treating characteristics and weldability. The optimum chemical composition of steel having the above-mentioned properties has been determined as 0.09C-5Ni-0.5Cr-0.5Mo-0.05 V with minimal impurities, especially, low sulfur content. Production heats of this steel were made. Electroslag remelting process was applied to make slabs of ultra low impurities and super cleanliness. Quenched and tempered steel plates of 65 mm thick exhibited proof stresses ranging from 931 to 960 MPa, and V-notch charpy shelf energy ranging from 172 to 209 J.
This steel plate was applied for the hull material of deep submergible vehicle ("Shinkai 2 000") operating in seas of 2 000 meters depth.