Abstract
In order to obtain a new age-hardening steel, a study was carried out to modify the strong and tough matrix of 18Ni maraging steel by reducing Ni content, addition of Cr, etc. It was proved that the Ni-Cr matrix steels with Ni content as low as 6 to 10% and Cr content of over 4% exhibited massive martensite structure similar to the high Ni steel, and promising mechanical properties. Then it was studied to strengthen this matrix by the addition of various elements which are expected to give precipitation hardening. It was shown that the most effective strengthening was obtained by the combined addition of Mo and Co, and a composition of ultra-low carbon 8Ni-6Cr-9Co-6Mo was finally obtained to give 180 kg/mm2 as ultimate tensile strength. This steel exhibited mechanical properties no inferior to those of 18Ni maraging steel and, showed better corrosive properties.
