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LI/ECJMaterials of Construction Review
Tin and Its Alloys by R, M. Maelntosh, Tin Research Institute, Inc., Columbus I , Ohio
Preplating processes influence porosity of electrodeposits on steel Research on tin-nickel coatings opens door to new applications S I L V E R ALLOYS CONTAINING 2, 5, 7.5, and 10% tin were prepared by vacuum melting and casting, and after fabrication into wire, mechanical properties were determined. These alloys were not susceptible to age hardening. T h e room temperature electrical resistivity increased with increasing tin content from 1.6 microhms per cc. for unalloyed silver to 31.3 microhms per cc. for the 10% tin alloy. A similar technique produced wires of ductile titanium-tin-oxygen alloys. T h e tensile strength of titanium-0.3% oxygen alloy was increased from 98,000 to 140,000 p.s.i. by the addition of 10% tin. Both the binary and ternary alloys had elongations of 15 to 17%. Zones of distorted metal parallel to the surface of cold rolled steel were found to have a variable influence on the porosity of tin, tin-nickel, and other metal coatings electrodeposited on the surface. Removal of the outer zones by selective etching provided information that was helpful in selecting the proper undercoating for pore-free deposits. T h e superior bearing properties of steel-backed aluminum-tin alloys resulted in their increased use for big-end and main bearings in internal combustion engines. T h e dispersion of the tin in continuously cast metal was similar to that produced by working and annealing conventionally cast metal. Nickel-containing bronze castings have high tensile strength and adequate corrosion resistance to withstand immersion in corrosive waters for many years. A great deal of attention in basic research studies was given to alloys of tin with the less common and transition elements. This review of the literature published in 1960 covers the period ending Dec. 31.
General T h e 1960 annual report of the I n ternational T i n Research Council (8A) describes current research activities and lists 17 new publications. Silver-tin alloys prepared by vacuum melting and casting showed a progressive increase in tensile strength, hardness, and electrical resistivity with increasing tin content. T h e electrical and mechanical properties
of high-melting-point compounds of tin with titanium and the transition metals, in the form of single phase ingots, have been examined. Among the new alloy developments (70A) are gold-tin alloys with good oxidation and corrosion resistance, a lowmelting quaternary alloy useful for cryogenic circuits, and alloys with germanium or silicon as semiconductor contacts. Research studies on the powder metallurgy of titanium-tin alloys, using sodium-reduced sponge, indicated that this method is suitable for the fabrication of alloys which cannot be produced by conventional methods (76A). T h e removal of the extreme surface layer of steel influences the porosity of a n applied coating for better or worse according to the metal deposited and the conditions of deposition. Well chosen undercoatings offer the best method of reducing porosity (5A). A reappraisal of the heat stability of tin-nickel electrodeposits showed that the coating is structurally stable u p to a t least 500' C. (932' F.). This finding makes its use possible in applications requiring heat stability 400' F. higher than previous investigators had reported (77A). T i n over zinc-coated steel provides structural material resistant to weathering (4A). Advances in metallurgical practices have made possible a new material-thin tin coated steel 0.0045 inch thick. T h e material is cheaper and is produced in a wider variety of tempers than conventional tinned sheet (9.4, 7 5 4 78A). T h e production of tin products is simplified when fabricated in newly designed die-casting (ZA), extrusion (73A, 79A), and centrifugal casting equipment (77A). T h e British Standards Institution has issued their first specification for ingot tin (3A). A tentative classification (7A) of pig tin (B339-59T) was approved by the American Society for Testing Materials. Specifications are given for electroplating the threads of nuts, bolts, and screws ( 6 A ) . T h e properties, uses, and compounds of tin (72A) and the metallurgy of tin 17A) were reviewed. Production of tin powder by atomization, reduction, and electrolytic processes was described ( 7 4 4 .
Tinplate Improvements in the manufacture of tin-coated steel moved forward a t a rapid pace with a marked improvement in the quality of the product ( 7 4 3B, SB, 24B). Open coil annealing, with a spacer between raps, facilitates control of the carbon and nitrogen level and the temper of the steel base. Continuous strand annealing installations were added in a number of plants (4B, 75B, 78BZUB, 25B). Greater speeds and higher efficiencies were reported. Data accumulation systems have been developed which accept signals from sensing devices and provide a running record of imperfections (76B, 17B, 27B, 26B). Other production innovations were: increasing the degree of reduction on each of the five rolling stands instead of decreasing the degree of reduction (23B), using multinotched rolls in the temper mill (5B), using superheated steam io flow-brighten the tin (73B), and plating a n iron layer on one side of the sheet to aid in the identification of differential plate (72B, 28B). Studies on surface chemistry have continued to provide clues for the improvement of tinplate quality and corrosion resistance (7OB). Oxide films have been investigated. T h e kinetics of the irontin alloy (FeSnz) have been studied at temperatures below and above the melting point of tin (77B). Ten factors have been experimentally established that affect the formation of alternate bands of bright and dull tin (wood grain) on finished tinplate (74B). Grain size of the tin coating and its relationship to flow-brightening has been investigated (27B). Polarization and electrochemical studies of tin, iron-tin alloy, and steel in de-aerated acid media have resulted in a new theoretical approach to tinplate corrosion (2B, 6B-
8B, 22B). Joining Among developments in joining metals and coatings were suggestions on selection of solders and fluxes for nuclear service and electronics. Table I lists the studies of most interest. VOL. 53,
NO.
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NOVEMBER 1961
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Materials of Construction Review
Electrochemistry Shiny hard tin deposits are obtained by adding rosin oils to the tin plating bath (40,80). Xew concepts in immersion plating of tin on steel, copper, a n d aluminum were reported (20, 50, 7 7 0 ) . Various tinplating baths were tested for oxidation susceptibility ( 7 0 0 ) . Most of the activity in the field of tinalloy plating was centered on tin-nickel plating ( 7 0 , 30, 6D, 1 7 0 , 740, 750, 780, 2 0 0 ) . T h e outstanding advantages-corrosion resistance, brightness.
Table 1. Joining Subject Joining precoated metals Soft solder for nuclear service Solderability of coatings in electrical industry Importance of flux in solder Fluxes for soldering A1 Hydrazine flux Choosing solder flux Soft soldering process Seam-welding Zircaloy Seam-welding terneplate Brazing and soldering Be Joining A1 to stainless steel Fluxless welding of A1 with soft solders Soldering electrodes to semiconductor crystal elements Soldering of gray cast iron Solders containing Hg for higher shear strength Ag-bearing solder solves Cu piping problems Strength of soldered joints Furnace soldering in exothermic atmosphere Production of cored solder wire
II. Corrosion Subject Effect of irradiation on reactor fuel alloys Cause of bearing corrosion in turbines Effect of heat treatment on corrosion resistance of Zr-NbSn alloys Corrosion behavior of Sn alloy coatings Effect of metallic cations on corrosion of Fe and Sn Flame-sprayed Sn coating prevents rusting Protection of Mg by Sn plating Creep and corrosion resistance of Zircaloy in steam Effect of H2 on corrosion resistance of Zircaloy Corrosion of metals in molten Sn Film growth on Zircaloy-formation and mechanism of protection Coupled Zircaloy 2-Nb ; c3rrosion resistance Sn aids galvanizing for corrosion protection Coupling shift for Sn-steel couple Studies on corrosion control Protection of hot dip metallic coatings Table
91 0
throwing power, low coefficient of friction: and high reflectivity have justified its use in a \vide range of applications. Bronze plating is recommended for many finishing problems ( 9 0 , 730). Tin-zinc plating was selected on the basis of high corrosion resistance and good solderability for large scale use in the radio and television industry ( 7 9 0 ) . Tin-cobalt and tin-nickel-cobalt alloys have been deposited successfully from a (760). pyrophosphate electrolyte Standard and precious metals can be plated on missile components using the Dalic process (70). A ternary alloy of lead-tin-indium is applied to printed circuits by diffusing the indium into the tin-lead coating ( 7 2 0 ) .
Corrosion Studies pertaining to the corrosion resistance of tin coatings, alloys of tin, and factors affecting their use as construction materials are listed in Table 11. Bronze Xi-Vee bronze was selected on the basis of corrosion resistance and strength for sluice gate stems (EF, 17F). T h e 20-foot-long rods a r e used for holding, opening, and closing nine sluice gates. Studies have been made on the behavior of bronzes for p u m p bodies and centrifugal propellers in swiftly moving waters ( 7 F ) and under conditions of dry friction a t high temperatures ( 4 F ) . Vacuum Table 111.
Practical Developments Subject Ref. BaSnO3, CaSnOa, and Pb(15H) S n 0 3for insulators (PbH, 2 6 H ) Spark plug insulators containing SnO2 and A1203 Conducting S n O ? films ( 8 H , 14% Semiconductive bodies(11 H ) SnTe, Sn and GaAs Insulation of conductors with (24H) anodized Sn Electrical resistors containing (6H) SnOl and B z O ~ Porcelain capacitors contain(ISH) ing PbSn08 Assembling circuitry boards (2H) for airborne computers Friction resistant white metal (7H) parts for diesels, turbines Nonwetting components by (10H) compacting Sn with Tic, WC Effect of Sn on mechanical (21H ) properties of nodular iron Jobs for low-melting alloys UGH) Metal spraying improves cor(19H) rosion resistance Preventing metal whiskers W H ) Device for tinning terminals (6H) of electrical components Desulfurizing metals with Sn (SH) Wave soldering printed circuits (12H) Resistance welding terneplate (QH) Coloring of bronzes (%OH,2SHj Avoiding stress corrosion (4HI cracking of Ti-Sn Glass for light sensitive products (f8Hj Tinning electrical connectors (22H) Device for hot tinning strip (1 H )
I N D U S T R I A L A N 0 E N G I N E E R I N G CHEMISTRY
degassing of liquid bronze results in considerable reduction in gas content (72F). Mechanical properties and corrosion resistance are improved. Better quality centrifugal castings are obtained when iron molds are used ( 5 F ) . Correct risering and heading directions are given (7F, 76F). Age hardening and tensile properties of nickel-tin bronzes are affectad by impurities (327. 74F, 75F), and the electrical conductivities of sand-cast bronzes have been recorded ( 7 7 F ) . D a t a are given for the effect of time. temperature, grain size. and composition on the oxidation of molten red brass (73F). Intergranular corrosion cracking of bronze is reduced by alloy additions (927, 78F). Additions of small amounts of mercury; lithium, and zirconium to bronzes have been studied (70F). A patent has been issued on porous gun metal containing 1 to 1 6 7 , tin and 0.1 to lyGphosphorus which is suitable for self-lubricating bearings ( 6 F ) . A4method is given for electropolishing tin and beryllium-containing bronzes (ZF). Table
IV.
Alloy
Development Properties
Subject
and
Ref.
Creep in thin Pb-Sn wires Thermodynamic properties of liquid In-Sn alloys Structure of Au-Sn alloys Electrical resistance of Pb-Sn Constitution of Sn-TI alloys Reactions between Hg, Sn, Au Low-melting eutectics Electrical properties and structure of Sn-Bi alloys The system Hf-Sn The system Pd-Sn Evaluation of Ti-Sn alloys Co-rich ternary alloys with Sn, C Stress corrosion cracking of Ti-Al-Sn alloys The system Zr-Fe-Sn Structure of Ag-Cd-Sn alloys Microhardness of Sn-Na-A1 Constitution of Ag-Cu-Cd-Sn Table V. Basic Research on Tin Subject Ref. Transformation of gray Sn (urc single crystals isri) Elastic constants of p-Sn (1.W Electronic structure of Sn (13K) Dry friction coefficient of Sn (21I i ) Steady state creep of Sn (20K) Slip of Sn single crystals (010 Change in sound velocity (jro between Sn states (ibri) Zone refining Sn Solute diffusion in liquid Sn (far') Solution of sheet iron in Sn (1OJij Diffusion of Sn in Ti (610 Zn diffusion in Sn (1Iij Reaction of Sn with Fe-C alloys (18K) Fusion curves of Sn and In (SK) Behavior of Sn in refining Pb (rK) Oxidation of Sn (%IC, 1111) Wetting of oxides by Sn ( 16K) Electrical properties of SnOz films (8K) Solid solubility of Sb in Sn (410
a Bearings Aluminum-tin alloys containing 6 to 20% tin €or bearing applications have created considerable attention (7G). A series of continuously cast 6yo tinaluminum bearings was vastly superior to copper-lead bearings. Fatigue life at 4000 r.p.m. a n d 3 tons per sq. in. exceeded 150 hours compared with 25 hours €or copper-lead. T h e continuously cast material was twice as good as chill-cast material for big end bearings. A patent has been issued covering aluminum alloys containing 10 to 25% tin, 1 to 3y0 copper, 0 to 2% nickel, a n d 0.25 to 1% lead. In the as-cast condition they gave satisfactory service as bearings (4G). Wear resistance and microstructure of aluminum base bearing alloys containing silicon and tin have been assessed (3G, 6G, 8G). A method was described €or the white metal lining of steel tubing for camshaft bearings (5G). Proper selection of bearing composition a n d babbitting technique ensures top performance a n d reliable service (7G). A lead-base bearing metal resists elevated temperatures to a high degree (2G).
Practical Developments Tin, tin coatings, a n d tin chemicals are involved in miscellaneous production techniques a n d products. Significant examples are listed in Table 111.
Basic Research Studies Fundamental investigations of tin and its alloys of special interest are outlined in Tables IV a n d V.
Literature Cited General (1‘4) Am. SOC. Testing Materials, Philadelphia, Pa., “Non-Ferrous Metals,” Pt. 2, Supplement, 1959. (2A) Barton, H. K., Engrs. Digest 21, 75 126 (December 1960). (3A) Brit. Standards Inst., B. S. 3252, 1960. (4A) Britton, S. C., T i n and Its Uses No. 50, 6 (1960). (5A) Clarke, M., Britton, S. C., Trans. Inst. Metal Finishing 37, Pt. 3, 110 (August 1960). (6A) Fishlock, D., Metalworking Prod. 104, 77 (Oct. 19, 1960). (7A) Gonser, B. W., “McGraw-Hill Encyclopedia of Science and Technology,” p. 279, McGraw-Hill, New York, 1960. (8A) Intl. Tin Research Council, “Annual Report 1960,” Publ. 321, Tin Research Inst., Columbus, Ohio, 1960. (9A) Iron Steel Engr. 37, 207 (October 1960). (10A) Lcng, J. B., J . Metals 12, 964 (1960). (11A) McIntyre, J. B., Foundry Trade J . 110, 459 (April 13, 1961). (12A) MacIntosh, R. M., “McGraw-Hill Encyclopedia of Science and Technology,” p. 647, McGraw-Hill, New York, 1960. (13A) Mailliard, J., Zngrs. automobile 35, 79 (February 1961).
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(14A) Olep, W. A., Wisconsin Engr. 65, 14, 38 (October 1960). (15A) Polakowski, N. H..‘ Metal Proer. u ‘ 77; 130 (June 1960). (I6A) Smart, R. F.. Tin Research Inst. Publ. 305, 1960. (17A) Smart, R. F., Robins, D. A., Trans. Inst. Metal Finishing 37, 108 (1 ,-.960). -- . (18A) dtone, M. D., Iron Steel Engr. 38, 77 (February 1961). (19A) Wilcox, R. J., Whitton. P. W.. ‘ Mktal Znd. 98, 286 (April 14, 1961).
(11C) Keil, R. W., Hanks, G. S., Taub, J. M., Welding J . 39, 406s (September 1960). (12C) Keller, J. D., Metal Progr. 79, 111 (April 1961). (13C) Lemon, L. C. (to U. S. Atomic Energy Commission), U. S. Patent 2,937,438 (May 24, 1960). (14C) Manko, H. H., Prod. Eng. 31, 43 (June 13. 1960). (ISC) Moravek, O., Zuaranie 9, 362 (Decembrr 1960 (16C) Nippes, E. ., Savage, W. F., Wu, K . C., Welding J . 39, 97s (March 1960). Tinplate (17C) Sistiaga, J. M., Limpo, J. L., Ciencia y t k . soldadura (Madrid) 10, (IB) Arnold, J., Iron Steel Engr. 37, 91 No. 53, 1 (1960). (August 1960). (18C) Spengler, H., Metal1 13, 1130 (2B) Australasian M f r . 45, 84 (March 11, (1959). 1961). (l$C)- Thwaites, C. J., Wire Znd. 27, 165 (3B) Bauscher, J. A,, Iron Steel Engr. 37, (February 1960). 161 (September 1960). (20C) Thwaites, C. J., Elec. M f r . 5 , 6 (4B) Blast Furnace Steel Plant 48, 950 (December 1960). (September 1960). (21C) Werkstatt u. Betrieb 93, 514 (August (5B) Borovik, L. I., Grishko, A. G., 1960). Pimenov. A. F.. Stal’ 1960. D. 726. Electrodeposition (6B) Britton, S. C., Bright,’K,, Chem. &f Znd. (London) 1960. D. 158. (ID) Australasian M f r . 45, 77 (May 7, (7B) Bhtton,’S. C.:’Bright, K., T i n and 1960). Its U s e f N o . 50, 12 (1960). (2D) Balden, A. R. (to Chrysler Corp.), (8B) Cheftel, H., Corrosion et anticorrosion U. S. Patent 2,947,639 (Aug. 2, 1960). 7; 125 (April 1959). (3D) Fishlock, D., Metalworking Prod. 104, (9B) Engineer 210, 650 (Nov. 28, 1960). 74 (Oct. 5, 1960). (10B) Falkenhagen, M., Bode, J. D., J . f4D) Kovaleva. R. G.. Bruk. E. S.. Electrochem. SOC. 107, 178c (August SandigurskaGa, M. E., RUSH. Paten; 1960). 129,908 (July 1, 1960). (11B) Frankenthal, R. P., Loginow, A. N., (5D) Kozawa, A,, Takahashi, T., Kinzoku Zbid., 107, 920 (1960). Hyomen Gzjutsu 11, 301 (August 1960). (6D) Kudriautsev, H. T., Tutina, K . M., (12B) Gazard, J. F. S., Salt, F. W. (to British Iron & Steel Research Assoc.), Chvankin, I. v., Zavodskaya Lab. 26, Brit. Patent 844,932 (Aug. 17, 1960). 301 (1960). (13B) Hess. F.. U. S. Patent 2.933.425 (7D) LaFond, C. D., Missiles and Rockets ’ (Abril 19. 1960). 7, 44 (Nov. 28, 1960). (14Bj Higgs, R . ’ F., McCarthy, J. A., (8D) LaManna, F. J., Metal Finishing 58, Plating 47, 1255 (1960). 66 (October 1960). (15B) Znd. Heating 27, 319, 322 (1960). (9D) Lowenheim, F. A., Metal Progr. 77, (16B) Iron Age 185, 9 (Feb. 18, 1960). 126 (June 1960). (17B) Ibid., p, 104 (May 26, 1960). (10D) McCarthy, J. A., Plating 47, No. 7 , (18B) Ironsteel Ener. 37.159 (Mav 19601. 805 (1960). (l9B) Zbid., p. 18q(August 1960): (31D) Mayer, S. E. (to International (20B) Zbid., p. 209 (September 1960). Standard Electric Corp.), U. s. Patent (21B) Zbid., p. 185 (October 1960). 2,914,449 (Nov. 24, 1959). (22B) Kamm, G. G., Willey, A. R., (12D) Murray, W. S., Dyer, 3. R., Jr. Corrosion 17, 77t (February 1961). (to The Indium Corp. of America), (23B) Leychenko, M. A., Metallurg 1960, U. S. Patent 2,909,833 (Oct. 27, 1959). p. 25 (April). (13D) Price, J. W., Prod. Finishing (London) (24B Metal Progr. 78, 66 (August 1960). 13. No. 3. 65 (19601. (25Bi P act& Factory 101, 15 (August 1960). (14D\-Zbid.,’14, i 4 (April 1961). (26B) Steel 147, 138 (Sept. 12, 1960). (15D) Rau, R . L., Bailar, J. C., Jr., (27B) Thwaites. C. J., Metallurgia 61, J . Electrocheinical Soc. 107, 745 (1960). 113 (March 1960). (16D) Sree, V., RamaChar, T. L., Bull. (28B) Tin 1960, p. 146. ‘ Zndia Sect. Electrochem. Soc. 9, No. 1, 13 (1960). (17D) Streicher, M. A. (to E. I. du Pont Joining de Nemours & Co.), U. s. Patent (1C) Angus. H. T., “Physical & Engineer2,940,867 (June 14, 1960). ing Properties of Cast Iron,” p. 357, (18D) Taylor, R., Phillips, R. M. (to British Cast Iron Research Assoc., BirChrysler Corp.), Zbid., 2,926,124 (Feb. mingham, England, 1960. 23, 1960). (2C) Bastion, C., Welding Engr. 45, 60 (19D) Von Schwerzenbach, W., Galunno(October 1960). technik 51, No. 7, 327 (1960). (3C) Chapman, F., Raine, P. A. (to (20D) Watson, S. A., Galvano 30, 24 Johnson & Son, Ltd., and Whiffen & (January 1961). Sons, Ltd.), Brit. Patent 834,031 (May 4, Corrosion 1960). (1E) Corrosion Engr. 7, vi-vii (May 1960). (4C) Chem. Eng. 68, 106 (Feb. 20, 1961). (2E) Britton, S. C., T i n and Its Uses No. (5C) Greer, H. F., Begeman, M. L., Welding J . 39, 247s (June 1960). 50, 6 (1960). (3E) Buck, W. R., 111, Leidheiser, H., (6C) Iron Age 185, 148 (June 30, 1960). Jr., J . Electrochem. Soc. 108, 203 (1961). (7C) Jacobs, B. (to International Tele. phone and Telegraph Corp.), U. S. (4E) Campagnoni, R . E., Powers, M. A,, Patent 2,867,899 (Jan. 13, 1959). U. S. At. Enercrv Comm. KAPL-2079, p. 16, 1960. (8C) Kanevskiy, Y. M., Ztvest. Akad. N Q U ~ S.S.S.R. 1960, p. 146 (May ). (5E) Corrosion Technol. 7, 195 (July 1960). (9C) Kaufman, A. B., Materials in Design (6E) Cox, B., J . Electrochem. Soc. 108, 24 (1961). Eng. 51, 87 (February 1960). (7E) Dhgaard, S. B., At. Energy Can., (1OC) Kawasaki, T., Yositsu Gakkaishi 29, 122, 336, 340 (1960). Ltd., AECL-993, p. 23, 1960. *
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Arch. Hutnictwa 5, 281 (March 1960). (235) Vicentini, M., Paoletti A,, Xuor’o cimento 14, 4277 (1959). (245) Winterhager, H., Schlosser, il’., Metall 14, 396 (1960). Basic Research (1K) Britton, S . C., Clarke, M . , Trans. Inst. M e t a l Finishing 36, Pt. 6, 230 (1959). (2K) Boggs, W. F., J . Electrochem. Soc. ‘ 107, 17’& (August 1960). (3K) Dudlev, J. D., Hall, H. T.. Phvi. Ret. 118, i211 (1960). (4K) Eyre, B. L., J . Inst. Metals 88, Pt. 5, 223 (January 1960). (5K) Gibbons, D. F., Renton, C. A,, Phys. Rev. 114, 1257 (1959). (6K) Goold, D., J . Inst. M e t a l j 88, Pt. 10, 444 (June 1960\. (7K) Hadamovsky, H., Frezberger Forrchungsh. B53, 7 (1960). (8K) Imai, I.; J . Phys. Soc. Japan 15, 937 (1960). (9K) Ishii, K., Oyo Butsuri 30, 54 (1961). (1010 Koehergin, V. P., Cherdantseva. N. N., Plotnikova, N. I., Iruest. Vysshikh Ucheb. Zmedeniz’ Khim. i Khim. Tekhno:. 2, 734 (1959). (11K) Luner, C., Trans. Am. Inst. Mining. M i t . , Petrol. Engrs. 218, 572 (1960). (12K) Ma, C. H., Swalin, R. A., Acto Metallurgica 8, 388 (.June 1960). (13K Olsen, T., Phjls. Rev. 118,1007 (1960). (14K] R ayne, J. A,, Chandraskher, B. S., Phys. Rev. 120, 1658 (1960). (15K) Reich, R., Montariol, F., Compt. rend. 251,2350 (1960). (16K) Schatt, W., Planseeber. Pulvermetal. 8, 122 (December 1960). (17K) Smith, R. W., Can. J . Phys. 38, 588 (1960). (18K) Stadelelmaier, H. H., Hutter, L.. Hardy, W. K., Z. Melallk. 51, 210 (April 1960). (19K) Wolfson, R . G., Fine, M. E.. Ewald, A. W., J . Apjd. Phys. 31, 1973 (November 1960). (20K) Zama, W.A,, Lang, D. D., Brotzcn. F. R., J . Mech. and Phys. Solids 8, No. 1: 45 (1960). (21K) Zuev, A. M., Izvest. Vvsshikh Uchrb. Zauadenii Fiz. No. 2, 21 7 (1960). I
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