AMS6478B Steel, Bars and Forgings, 3.1Cr - 11.5Ni - 13.5Co - 1.2Mo (0.21 - 0.25C), Vacuum Melted, Annealed, Heat Treatable to 290 ksi (1999 MPa) Tensile Strength

This specification covers a premium aircraft-quality alloy steel in the form of bars, forgings, and forging stock.

These products have been used typically for parts requiring a combination of high strength, high toughness, and weldability, but usage is not limited to such applications. Product after proper heat treatment should attain a minimum tensile strength of 290 ksi (1999 MPa) and yield strength of 245 ksi (1689 MPa).