ATI C-200TM, ATI C-250TM, and ATI C-350TM alloys (18% nickel maraging steels) are divided into two broad classes depending on the primary strengthening element in the chemical analysis. The original maraging steels, introduced in the early 1960s, depend on cobalt (7-12% cobalt depending on grade) as their strengthening agent; they are cobalt strengthened 18% nickel maraging steels. In the early 1980s, ATI introduced a new type of maraging steel which contains no cobalt and has titanium as a primary strengthening agent; they are titanium-strengthened 18% nickel maraging steels. Cobalt-strengthened grades, or "C-type 18 Ni maraging", are designated by the letter "C" in the grade identification (example: ATI C-250). Titanium-strengthened grades, or "T-type 18Ni maraging", are designated by the letter "T" in the grade identification (example: ATI T-250).

APPLICATIONS
ATI produces the maraging steel alloys in a full range of "long" mill product forms including billet, bar, rod, rod coil, and wire.
Extensive laboratory and field testing, plus numerous production applications of ATI C-250, have proven that this family of maraging steels is equivalent to, or slightly better than, the cobalt-bearing grades. Typical applications for the maraging steels are missile and rocket motor cases, wind tunnel models, recoil springs, flexures, actuators, landing gear components, high performance shafting, gears, and fasteners. The alloys are used in extrusion tooling, and in the die casting industry for long-run dies and also as core pins.