Ultrahigh-Strength Steels

It is possible to design a hydrostatic test in such a way that it probably will be a proof test of the vessel. This usually requires, among other things, that the test be run at a temperature as low as and preferably lower than the minimum operating temperature of the vessel. Proof tests of this type are run on vessels built of ultrahigh-strength steel to operate at cryogenic temperatures. 

Baker, A. J., Lauta, E. J., and Wei, R. P., Relationships Between Microstructure and Toughness in Quenched and Tempered Ultrahigh-Strength Steels, ASTM STP 370 (1965), 3. 

Spitzig, W. A., and Wei, R. P., A Fractographic Investigation of the Effect of Environment on Fatigue-Crack Propagation in an Ultrahigh-Strength Steel, Trans. ASM, 60 (1967), 279. 

Fig. 20 Comparison of fracture toughness K c) and K scc for ultrahigh-strength steels [169], K scc was measured in 3.5% NaCl. The numbers by the bars are the tensile strengths (MPa) of the steels as tested. (Reprinted with permission from ASM international.)...

K. Yamazki, K. Sato, and Y. Tokunaga, Stahc and Fahgue Strength of Spot Welded Joint in Ultrahigh-Strength, Cold-Rolled Steel Sheets, Weld. Int, Vol 14 (No. 7), 2000, p 533-541... 

Maraging steels are a particular class of extra-low-carbon (i.e., < 0.03 wt.% C) and nickel-rich (i.e., 18 wt.% < Ni < 22 wt.%) iron alloys having an ultrahigh strength. Nickel is the major alloying element followed by cobalt, which is added up to 12 wt.% to accelerate precipitation reactions, molybdenum, and, to a lesser extent, titanium, aluminum, and copper. A typical example of a maraging steel is an iron alloy with the following composition 17 to 19 wt.% Ni, 7 to 9 wt.% Co, 4.5 to 5.0 wt.% Mo, and 0.6 to 0.9 wt.% Ti. Alloys of this type are... 

Polymer fibres are rather different in that they can be thought of as aligned molecules. Many polymer fibres, such as Kevlar, carbon fibre and ultrahigh-molecular-weight polythene have tensile strengths comparable to or better than steel. Rigid polymers, such as methyl methacrylate, polycarbonate, or many thermoplastics and elastomers at low temperatures, behave in a brittle fashion. 

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