This memorandum summarizes the Fourth Maraging-Steel Project Review which was held on June 9 to 11, 1964, in Dayton Ohio. During the sessions, twenty-one scheduled and several unscheduled presentations were made by representatives of Government agencies, industrial concerns, and universities. Abstracts of these presentations are included in this memorandum preceded by a summary of the highlights of the various technical developments. Session I dealt with the mechanical properties of maraging-steels. The remaining four sessions dealt with general maraging steel evaluations, mechanical properties of welds and fabrication of 18 per cent nickel maraging-steels, fabrication and characteristics of maraging-steels, and alternate motor-case materials. During the past year, considerable effort has been expended to resolve certain technical problems relating primarily to 18 per cent nickel maraging-steel plate which has been under consideration for large booster cases. Among these problems have been banding and the resultant low short-transverse mechanical properties, associated with mill processing variables. The results of the research programs presented at this meeting shed much light on these and other problems and indicate that considerable progress has been made toward overcoming the production and fabrication problems of the maraging steels and other high-strength steels.

This memorandum briefly discusses the physical metallurgy, heat treatment, mechanical properties, stress-corrosion properties, and fabrication of the 9Ni-4Co-XC steels. This family of steels was developed specifically to meet the requirements of the aircraft and aerospace industries for materials possessing high strength and high toughness. By varying the composition and heat treatment, the 9Ni-4Co-xC steels can develop strengths in the 200 to 300 ksi tensile-strength range and reportedly possess high toughness. The lower carbon grades have excellent weldability, developing strength in the 180 to 200 ksi range with high toughness without the need for preheat or postweld-heat treatment. (Author).