Grain Refinement and Tensile Properties of 17.5Ni Maraging Steels with High Strength

Abstract

Solution-treatment temperature and the refinement of austenite grains by solution-treatment after cold working have been investigated for 17.5Ni-12.5Co-Mo maraging steels with and without titanium. Titanium contents were 1.7 and 2%, and molybdenum content varied from 3.9 to 6.5%.
Optimum solution-treatment temperature rises with the increase in molybdenum or titanium content. When the solution-treatment after cold working is applied to the maraging steels which were previously solution-treated at relatively low temperatures, austenite grains are possible to be refined considerably.
Tensile properties after maraging in the temperature range 500° to 560°C have also been investigated for 17.5Ni-12.5Co-5.4Mo-2Ti and 17.5Ni-12.5Co-6.2Mo-1.7Ti maraging steels, the austenite grains of which were refined by solution-treatment after cold working. Maximum tensile strengths obtained are about 280 kgf/mm² for the 17.5Ni-12.5Co-5.4Mo-2Ti steel and about 270 kgf/mm² for the 17.5Ni-12.5Co-6.2Mo-1.7Ti steel. Because of fine austenite grains, the materials are ductile even in high strength level.