New High-strength Nickel-alloy Steel
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SCIENT1STS of the International Nickel Co., Inc., Bayonne, N.J., U.S.A. have developed a new 18-per-cent. nickel-alloy steel which is claimed to have unmatched toughness" at the highest strength levels of traditional alloy steels. It is stated to be the only known material which can achieve a yield strength in excess of 250,000. p.s.i., while maintaining a nil ductility temperature below —80°F.
Another outstanding characteristic is the notched tensile strength which exceeds 400,000 p.s.i. (with a notch radius 0.0005 in.). Tests have shown that this new alloy possesses a remarkable resistance to delayed cracking when exposed to a severely corrosive atmosphere in a highly stressed condition. The new steel develops its high strength while maintaining unmatched ductility and toughness because of a fairly simple heat-treatment process involving age-hardening of martensite. This treatment has been given the abbreviated description of " mar-aging."
This treatment is noteworthy because of its simplicity, and consists merely of holding for about three hours at 900°F. and air cooling, subsequent to normal mill procedure. Quenching is not required.
The new steel has a nominal composition of 18 per cent, nickel, 7 per cent. cobalt, 5 per cent, molybdenum, and less than 0.5 per cent, titanium with a maximum of 0.05 per cent. carbon. The steel can easily be welded by either manual or automatic methods. A patent application covering the alloy has been tiled with the U.S. Patent Office. The British company associated with the American concern responsible for this development is the International Nickel Co. (Mond), Ltd., Thames House, Millbank, London, S.W.I.