In order to make oceanographic research activity more extensive, deep submergence research vehicle diving to the depth of 6000 m is being required in these days.
A pressure hull of the vehicle requires the material of high strength/weight ratio and good ability of manufacturing. In this point, 10 Ni-8 Co steel with the yield strength of 120 kgf/ mm2 can be said the most promising candidate for the pressure hull at present.
To give 10 Ni-8 Co steel enough strength and toughness, heat treatment (double-quenching and tempering) is indispensable.
From this respect, the authors conducted experimentally heat-treatment of 10 Ni-8 Co spherical shell using a full scale model.
The report presents the description on the heat-treatment procedure, including the experimental results, which are necessary to establish the whole manufacturing procedure of a pressure hull being combined with the welding procedure already established.
