HP9-4-30 is a low alloy, high strength steel with nickel and cobalt additions. These additions increase the strength and provide excellent fracture toughness properties making it suitable for aerospace structural components, rocket motor cases, and other high toughness applications. It is typically used in the 220/240 ksi (1520/1655Mpa) tensile strength range. For optimum cleanliness, the alloy is produced by the consumable electrode vacuum arc remelting process.