Document 2qYKJDJx6NYo597G2Kb4e6zNL

in t 664 CHAPTER 62 C. Deschan: Assembling parts by tmnV fittings {Ma~ terials and Methods, VoL 29, May 1949, p. 64). J. L. Everhart: How cold treatments unprove performance of materials {Materials and Methods, Vol. 37, February 1953, p. 115). S. G. Fletcher. B. L. Averbach, and M. Cohen; Tim dimensional stability of steel, Part T1 further experiments on subatmospheric transformations {American Society for Metals Transactions, VoL 40, 1948, p. 703). 8. G. Fletcher and M. Cohen: The dimensional stability of steel Part l.subatmospberic transformation of retained austenite {American Bocietyfor Metals Transactions, Vol. 34, 1945, p. 216). L. E. Gippert, and G. M. Butler, Jr.: Changes in size ana tough ness of bign carbon high chromium steels due to subzero treat ments (American Society for Metals Transactions, Vol. 39, 1947, p. 649). G. P. Gordon and M. Cohen: -Transformations of retained austenite in high speed steel at subatmospheric temperatures {American Societyfor Metals Transactions Vol. 30, 1942, p. 569). A. Gulyaev: Transformation of retained austenite at subzero temperatures with high speed steel {Metallurgy, VoL 14, 1939, p. 64). (Russian) R. 8. Jamison: Sub-Zero treatment of metals for stabilization {Metal Treating, Vol. 4, January-February 1953, p. 4). H. A. Knight: Subzero stabilizing of steel gages and parts {Metals and AUoys, VoL 19, March 1944, p. 610). 1962 Guide And Data Book I. R. Kramer: Mercury patterns make ceramic shell nv^ (American Foundryman, February 1955, p. 38). M. W. Marshall, D. C. Perry, and N. R. Harpster: Enhanced properties in 17-7 PH stainless {Metal Progress, VoL 70, Julv 1956, p. 94). W. H. Miller: Low temperature treatments improve products and processes {Iron Age, VoL 171, May 28, 1953, p. 121). J. G. Morrison: An appraisal of subzero hardening of high speed steels {Iron Age, July 26, 1945, p. 54, August 2,1945, p. 64). W. I. Neimeyer: Precision casting with frozen mercury pat. ' terns {Iron Age, March 17, 1949, p. 94). P. Payson and C. H. Savage: Martensite reactions in alloy steels {American Society for Metals Transactions, Vol. 33, 1&44. P- 261). " ^ C. T. Post: Cold treatment in gage stabilization {Iron Age March 15, 1945, p. 52). ' G. A. Roberts and J. P. Gill: Some effects of subzero cooling on the tempering of high speed steel {Iron Age, March 23, 1944. o 52). B. Sainati: Cold treatment improves accuracy, life of v-blocks {Iron Age, VoL 174, October 14,1954, p. 136). N. A. Ziegler and P. H. Brace: Hardening of austenitic stainless steels by mechanical working at subzero temperatures (American Society for Testing Materials Proceedings, Vol. 50, 1950, p. 861). CHAPTER 63 PROPERTIES OF METALS AT LOW TEMPERATURES Tensile Strength, Ductility, Notch Bar impact, Nonferrous Alloys, Steels, Tests, Selection of Materials, Specifications, Physical Constants THIS chapter describes bow low temperatures affect the Tensile strength, however, is not a particularly good cri properties of pure metal* and commercial alloys and terion for determining the suitability of a material for low also the criteria used for selecting metals for low temperature temperature service as most failures result from embrittle applications or metals subjected to low temperature environ ment. Ductility values obtained from the static tensile test ments. may give some clue to the degree of embrittlement, but the Few general deductions can be made except that with de notched bar impact test is generally preferred as it is con crease in temperature there is an increase in hardness, strength sidered to give a better indication of how the material per and modulus of elasticity. The effect of low temperatures on forms under dynamic loading, and the reaction to complex ductility and toughness varies considerably among the multi-directional stress. metals and alloys; the ductility of some metals increases with decrease in temperature, while others show increase in ductil DUCTILITY ity to some limiting low temperature followed by a decrease at lower temperatures, and still others show decrease in toughness and ductility as the temperature is decreased below that normally encountered in the atmosphere. Ductility, as measured by percentage of elongation in the tensile test, is shown in relation to temperature for several of the frequently used metals (Fig. 2). Of particular note are the curves for copper, nickel, aluminum, and lead which show that TENSILE STRENGTH ductility of all these metals increase as the temperature is lowered. The three metals iron, zinc, and magnesium show a In fig. 1 the relation of tensile strength to temperature is decided decrease in ductility with decrease in temperature, shown for metals generally selected .for structural com and at the temperature of liquid air, all of these metals rup ponents. It will be noted that the slope of the curves indicat ture with little plastic deformation, even when tested under ing increase in strength with decrease in temperature, varies static loading. among the different metals. NOTCH BAR IMPACT When these metals are compared on the basis of notched bar impact properties, the same trends may be noted, al though the order of magnitude may differ appreciably from that when comparison was made on hn^is of ductility. For instance, lead has a high order of ductility when detennined by the static tensile test, but the resistance to impact is ^9- 1 .... Relation of Temperature to Tensile Strength of Several Metals1 665 Fig. 2 ,,.. Relation of Temperature to Elongation of Several Metals*