Abstract
In order to obtain 3.5 GPa grade maraging steels, the chemical composition and the effect of thermo-mechanical treatments (TMT) including cold rolling have been investigated. From age-hardening experiments of various Mo-Co-Ni-Fe alloys, 14%Mo-(18 and 20)%Co-6%Ni alloys having superior hardness were selected. Tensile tests of these alloys bearing Ti and Al subjected to various TMT were carried out and the results were discussed observing the microstructures. Finally the materials having the hardness higher than Hv 950 (max. Hv 965) and tensile strength higher than 3.5 GPa (max. 3.70 GPa) were obtained by performing double direct quenchings after hot rolling from 1350°C inserted solution treatment at 1000°C for grain refinement, with subsequent cold rolling and aging.
