Improvement of Low Temperature Mechanical Properties of Ultrahish-strength Low-alloy Steels

Abstract

Ultrahigh-strength low-alloy steels with a medium carbon (0.25 to 0.50 mass%) content and various amounts of chromium, molybdenum, nickel, silicon, and vanadium have been needed for high-performance aerospace parts. The steels can be employed successfully at yield strengths of 1400 MPa or higher, but their commercial use is limited by their poor ductility and toughness at low ambient temperatures. Brittle fracture has to be given serious consideration at these levels. This review surveys improvement of the low temperature mechanical properties of ultrahigh-strength low-alloy steels. Particular emphasis is placed on improving the mechanical properties through mixed-structure control, thermomechanical treatments, and modification of non-metallic inclusions. The major microstructures controlling the mechanical properties are discussed for each of these techniques.