Talk:Cryogenic cold-forming

Some additional info and sources
Here are some additional info and sources for improving this article in the future, when it becomes more than just the REDIRECT it was recently created to be.


 * Austenitic stainless steel remains ductile at cryogenic temperatures because they "maintain an austenitic microstructure at all temperatures from the cryogenic region to the melting point. Thus austenitic stainless steels are not hardenable by heat treatment since they possess the same microstructure at all temperatures."(that quote from https://en.wikipedia.org/wiki/Stainless_steel#Austenitic_stainless_steel, today). Thus, cryogenic cold-forming is very unlike the cryogenic hardening possible with other alloys of stainless steel where the cryo process is designed to increase the amount of martensite in the steel's crystal structure, increasing hardness.

Here is an early NASA technical report on cryogenic cold-forming of Austenitic stainless steel (all 300-series stainless steels are austenitic face-centered cubic crystal formations; and this paper is about "301") Tensile Coupon Tests of Cryoformed AISI 301 Stainless Steel Pressure Vessels at Cryogenic Temperatures, Thomas W. Orange, NASA Lewis Research Center, 1964.

FWIW, 300-series stainless steels, including new alloys that have been developed in R&D by SpaceX in the 2010s, are planned to play a role in the structure and pressure vessel/tanks of the new Starship, the reusable upper stage of the SpaceX next-generation launch vehicle, the BFR. Cheers. N2e (talk) 20:31, 26 December 2018 (UTC)


 * Another Cyroforming Paper. High-Strength Stainless Steel by Deformation at Low Temperatures Author Information: S. Floreen (Supervisor, Iron-Nickel Alloys Section, Research Laboratory, The International Nickel Co., Inc., Bayonne, N.J.) and J. Mihalisin - Advances in the Technology of Stainless Steels, ASTM, 1965.  N2e (talk) 12:38, 5 January 2019 (UTC)

"Abstract: 'A series of nickel-chromium stainless alloys made by air and vacuum melting were rolled 20 or 40 per cent at temperatures ranging from —320 to 400 F. Smooth and sharp-notched sheet-tensile properties were measured after heat treating the cold-rolled pieces for 24 hr at 800 F. Yield strengths up to 260 ksi were obtained. Hardening resulted primarily from martensite formation, and also from work hardening of the austenite prior to transformation. The yield strengths were correlated in terms of composition." "'Lowering the silicon content to 0.1 per cent significantly raised the toughness. Over the ranges studied none of the remaining elements had effects comparable to silicon. The toughness at a given strength level also depended upon the rolling conditions, but not upon the per cent martensite." "'Tests at −320 F with a low-silicon alloy showed a notch-tensile ratio of 1.0 at 297 ksi ultimate tensile strength. The results suggest that a low-silicon 301-type composition would have good cryogenic properties.'"


 * and another: HIGH-STRENGTH STAINLESS STEEL BY DEFORMATION AT LOW TEMPERATURES by S. FLOEEEN' AND J. R. MIHALISIN, with a graf from the paper here. N2e (talk) 02:15, 10 January 2019 (UTC)


 * and another paper, this one from 1977. The effects of cryoforming and aging on the structure and mechanical properties of an austenitic stainless steel alloy, Jason Opoku, Iowa State University, 1977.  N2e (talk) 00:10, 2 February 2019 (UTC)
 * Some bits:
 * "2. Martensite transformation can enhance the low temperature ductility of both annealed and thermomechanically treated austenitie stainless steels. An optimum rate of transformation exists for the ductility improvements. 3. The combined effects of cryoforming and aging can produce a cryogenic yield strength in excess of 2000 MPa, with good ductility. Extensive room temperature deformation produces yield strengths of only up to 1300 MPa. 4. The stability of strain-induced martensite increased with an increasing amount of deformation and decreasing deformation temperature. 5. Short-time room temperature exposure produces an upper yield point phenomenon due to dislocation pinning by carbon atoms. 6. Artificial aging of the c^oformed material causes precipitation of (FeCrJggC^ carbides. 7. The factors affecting the strength are» a. Strain-induced martensitic transformation b. Strain hardening of retained austenite and freshly formed martensite c. Processes occurring during aging* i. Precipitation of iron-chromium carbides ii. Growth and coalescence of the precipitates iii. Depletion of carbide-forming elements from the matrix iv. Austenite reversion. 8. The major strengthening mechanisms in the naturally aged specimens are strain-induced martensite and work hardening of martensite and retained austenite. The yield strength at -196°C is related to the volume fraction of martensite as follows: For specimens cryoformed at -196°C* Sy = 756 + 1326 For specimens cryoformed at -73°Ci Sy = 756 + 1002 9. Precipitates alone can contribute between 225 and 650 MPa to the yield strength of the artificially aged specimens. The net effect of aging on the strength is the sum of the strengthening contribution due to precipitates, and the weakening due to matrix depletion, austenite reversion, and dislocation annihilation. 10. Aging the cryoformed material for 1 hr between 400°C and 450°C is sufficient to produce optimum mechanical properties. Aging for up to 12 hrs has no significant advantage over aging for 1 hr. 11. The mechanical properties are rate independent within the testing range of 0.05 min'^ to 0.5 min'^. 12. The temperature of the alloy is lower than 25°C but higher than -73°C. Mg is lower than -196°C."