High-strength titanium-free maraging steel for large machine parts

A relationship between the changes in the structure and mechanical properties of titanium-free Fe15% Ni-Co-Mo-V-based maraging steels was established. The strengthening of these maraging steels upon martensite aging was shown to be caused by the precipitation of intermetallics of Ni3V and Fe2Mo types. The titanium-free iron-nickel-vanadium maraging steels are remarkable for their combination of high strength, plasticity, ductility, and high resistances to heat embrittlement and delayed brittle fracture. The steel has the following mechanical properties: sigma (u) = 2300 N/mm(2), sigma (0.2) = 2200 N/mm(2), delta = 9%, psi = 50%, KCU = 40 J/cm(2), and K-Ic = 90 MPa m(1/2). A method of the industrial manufacture of large forged disks (430 mm in diameter and 110 mm in height) from the steel was developed. The full-scale tests of high-speed flywheels for mechanical energy storage (n = 15000 rpm) showed that the titanium-free maraging steels are promising For heavy-loaded large-scale machine parts.