INDUSTRIAL AND ENGINEERING CHEMISTRY
2130
(39) Graham, Robert D., Oregon Forest Products Lab., Progr. Rept. 7, 1953. (40) Harrow, K. K., New Zealand J . S c i . Technol., 32B, N o . 4, 28-31, (1951). (41) Ibid., 33B, No. 5, 385-92 (1952). (42) Heicks, Ray E., Am. Wood-Preserters' Assoc. Proc., 48, 53-80 (1952). (43) Heicks, Ray E., Blum, Samuel E., and Burch, Joseph E., I b i d . , 49, 18-37 (1953). (44) Holsschutzmittel Prufung und Forschung I11 Rirsenschaftlich -4bhandlungen der Deutschen llateralprufungsaustalten, Berlin-Dahlem, I1 Folge, Heft 7, Springer-Verlag Berlin, 1950. (45) Hudson, M. S., Am. Wood-Preserzers' Assoc. Proc., 49, 146-68 (1953). (46) Hudson, 11.S., J . Forest Products Research Soc., 3, 177-82, 230-2 (1953). (47) Hunt, George M.,and Garratt, George A., "Wood Preservation," 2nd ed., McGraw-Hill, New York, 1953. (48) Hunt. George AI., and Snyder, Thomas E., Am. Wood-Presewers' Assoc. Proc., 48, 314-27 (1952). (49) Jelley, Joseph F., Ibid., 49, 215-28 (1953). (50) Kuenael, J. G., Poletika, K. V., and McIiean, H. B., J . Forest Products Research Soc., 3, 35 (1953). (51) Lindgren, Ralph bl., Am. Wood-Preservers' Assoc. Proc., 48,15868 (1952). (52) Lindgren, Ralph I f . , and Harvey, George 1I.,J . Forest P T O ~ U C ~ S Research Soc., 2, 250-6 (1952). (53) Lumsden, George Q., Am. Wood-Preserzers' Assoc. Proc., 48, 2 7 4 8 (1952). (54) McGehee, H. T., and Van Allen, R. G., Ibid., 48, 224-39 (1952). (55) hlacleau. J. D.. Ibid.. 47. 155 (1951). (56) Ibzd., 49, 88 (1953) (57) XacLean, J. D., "Preservative Treatment of Wood by Pressure Processes," U. S. Dept. of Agr. Handbook 40, 1952. (58) hIarra, A. A., Forest Products Research SOC.Proc., 5 , 256 (1951). (59) Nartinez, Jose Benito, "Conservation des Maderas en sus Aspectos Teorico, Industrial, y Economico," Vol. 1, Inst. Forestal d Investigaciones y Experiencios, Ministerio d Agric. Madrid, 1952. The (60) blayfield, P. B., Am. Wood-Pieselzers' Assoc. PTOC., 47, 62-85
Vol. 46, No. 10
Llayfield, P. B., J . Forest P r o i h c t s Research Soc.. 4, 52-5 (1954). LIitchell, R. L., Seborg, R. AI., and hlillett, M. A., Ibid., 3, 38 (1953). Phinney. H . K., Forest Products Research Soc. Proc., 5 , 268, (1951). Raphael, Harold J., and Graham, Robert D., Am. W o o d Preserrers' Assoe. Proc., 47, 173-5 (1951). Richards. -4. P., I b i d . , 48,15-24 (1952). Roche, J. N., J . Forest Products Research Soc., 2, 75-9 (1952). Rogers, R. T., Am. W o o d - P r e s e r w s ' Assoc. Proc., 49, 40-7 (1953). Scheffer. Theodore C., J . Forest Products Research SOC.,3, 72-7 (1953). Schnell, Robert L., Ibid.,2, 80-4 (1952). Seborg, R. M.,Tarkow, H., and Stamm, A . J., Ibid., 3, 59 (1953). Seborg, R. M., and Vallier, -4.E., Ibid., 4 (1954). Sedsiak. Henry, Ibid.,2, 260-8 (1952). Selbo, 31. L., and Olson, W.Z., Ibid., 3, 50 (1953). Snoke, Lloyd R., I b i d . , 4, 515-17 (1954). Snyder, F. H., and Plisky, C. J.. Ibid., 1, 3 (1951). Stanley, G. W., Jr., Forest Products SOC.Proc., 5 , 280 (1951). Steer, Henry B., Bm. Wood-PreseTaers' h s o c . Proc., 49, 291330 (1953). Tarkow, H., and Stamm, A. J., J . Forest Products Research Soc., 3, 33 (1953). Tigelaar, J. H., Ibid., 3, 41 (1953). Truax, T. R., Blew, J. Oscar, and Selbo, AI. L., Am. WoodPreservers' Assoc. Proc., 49, 113-120 (1953). Van Groenow, H. Broese, Rischen, H. W. L., and Van der Berge, J. "Food Preservation during the Last 50 Years," A. IT, Sijthoff, Leiden, Holland, 1951. Verrall, A. F., J . Forest Products Research Soc., 3, 54-60 (1953). Volkening, B. V., I b i d . , 3, 72-7 (1953). Walters, C. S., Ibid., 3, 61-6, 74-5 (1953). West, Richard F., Ibid., 2 , 85-8 (1952). Yavorsky, J. M., Forest Products Research SOC.Proc., 5 , 285 (1951). Yavorsky, J. >I., J . Forest Prodztcts Research Soc., 4, 36 (1954).
U. S. Forest Products Laboratory is maintained a t hIadison, Wis., in cooperation with t h e University of Wisconsin.
(1951).
e
tals
W. R. BEKEBREDE ASD L. F. YNTERIA Fansteel .Metallurgical G o r p . , lYorth Chicago, Ill. This review of the past year's literature on the less common metals as materials of construction is divided into sections on titanium, zirconium, molybdenum, and tantalum.
T
HE past year's literature reveals a sustained interest in
titanium in spite of the fact t h a t during the first part of 1951 the supply of this metal exceeded the demand. This situation was attributed to rapid increases in sponge capacity and should be only temporary. The industrial uses of titanium are still quite small, awaiting a price reduction and improvements in oxidation and corrosion resistance. Considerable attention n-as paid during the past year to surface treatments and welding procedures. Also investigated were the corrosion resistance of titanium, its reactions with gases, and improved melting and casting methods, T h e zirconium literature x a s concerned with a n electrolytic method of production, the corrosion of zirconium in liquid metals, and its reactions with gases and refractories. .4n electrolytic process was also investigated for molybdenum. Information appeared on its corrosion behavior in liquid metals, and on a method of protecting molybdenum against Oxidation. T h e tantalum literature discussed corrosion in liquid metals and high pressure oxidation.
TITANIUM
-4double arc-melting method vias designed by Van Thyne and associates (33)to overcome the segregation normally encountered in commercial titanium-base alloy ingots. T h e first melting is done in a nonconsumable electrode furnace. The resulting ingot is forged to rod, which is used as the consumable electrode in thcl second melting. Homogeneity of ingots produced in this manner was checked b y chemical analysis, and the results iridicatrd that a good degree of homogeneity was achieved. Recent research at Battelle Memorial Institute for the Frankford Arsenal (3)revealed a possible method of using inexpensive and expendable materials for casting titanium. Interesting results xere obtained by using a zirconium oxychloride wash on silica shell molds. A mixture was prepared consisting of a saturated aqueous solution of zirconium oxychloride and a small amount of ethanol. This was brushed on the molding faces of silica shell molds t h a t were then baked a t 232" C. for 1 hour. The titanium m-as prepared in a skull-melting furnace under ar-
October 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
gon. The finished castings were compared with titanium from unwashed molds and molds coated with other washes. While the over-all depth of contamination was not decreased by the zirconium oxychloride wash, the degree of surface contamination was reduced. Also, the metal had a much improved surface with much less pinholing than was found in the other castings. Straumanis and Gill (52) investigated the rate of dissolution and the passivation of titanium in acids with ammonium fluoride added. They found that the resistance of titanium to the action of acids breaks down if soluble fluorides are added to the acidic solutions. The hydrogen fluoride liberated by the acids partially dissolves the protective film which is always present on the surface of titanium. This is confirmed by the fact that the rate of dissolution of titanium increases only slightly with increased cowentration of strong acid a t a constant concentration of ammonium fluoride, but it increases greatly with increased concentration of ammonium fluoride a t a constant concentration of the strong acid. However, when the concentration of ammonium fluoride in the solution exceeded 4M, the rate of dissolution dropped quickly. This passivation was explained by the formation of a partial salt film on the surface of the dissolving titanium, and by an increase of hydrogen overvoltage on local cathodes because of the ammonium fluoride present. The oxidation of titanium was investigated in the temperature range 600" to 925" C., a t an oxygen pressure of 700 mm. of mercury, by Jenkins (16). Test specimens were cut from strips of titanium refined by the iodide process in the Philips Laboratories, Eindhoven, and commercial titanium produced by the Kroll process a t the Boulder City plant of the U. S. Bureau of Mines. The oxidation process was followed by determining the gain in weight of separate specimens after various periods. In agreement with past investigations, the oxidation rate below about 650" C. continually decreased, whereas in the range 650' to 925" C. it became constant after a short initial period. At low temperatures a thin, dense, slate-gray scale formed which was replaced a t high temperatures by a thick, porous, yellowbrown scale. Investigation of the structure of the titanium core after oxidation showed that oxygen had entered the surface layers of the core during the reaction. Furthermore, when the supply of oxygen was withdrawn, the metal redissolved the oxide scale. In general the refined titanium showed a greater oxygen absorption than the co.nmercia1 grade. The difference in total oxygen absorption was never more than 30%, and appeared to be negligible in the vicinity of 850' C. Richardson and Grant (28) reported that titanium follows parabolic rate laws in its reactions with oxygen and nitrogen between 700" and 1050' C. They listed the activation energies for the oxygen and nitrogen reactions, respectively, as 47,400 Gal. per mole (above 700' C.) and 45,400 cal. per mole (above about 800" C.). The reaction rate of titanium with oxygen was nearly 50 times larger than with nitrogen. X-ray studies of the surfaces of the specimens reacted with oxygen showed the presence of TiOg (rutile), TiO, and Ti. Presumably any coating of Ti203 was too thin to yield a diffraction pattern. Only the patterns of Ti and T i N were found on the nitrogen specimens. Economos and Kingery (9) studied the interfacial reactions a t elevated temperatures of various metals with dense oxide specimens. Their results indicated that four general types of behavior may be observed, corresponding to varying degrees of reaction. The first consists of the formation of a definite new phase a t the interface Titanium showed this type of reaction with MgO a t 1800" C. where MgTiOo was the new phase. Only alight reaction occurred a t 1600' and 1400' C. The second-type reaction is the corrosion of the oxide interface by the metal. In order for a reaction of this type t o proceed, it is necessary that the reaction products be removed from the interface as they are formed. This second type of behavior occurred in the systems Ti-BeO, Ti-AlgOa, Ti-ZrOp, Ti-MgO a t 1800' C., and in the syetem Ti-Ti02 a t 1600' C. The third-type reaction is charac-
2131
Lap Welding Tantalum Sheet Under Water
terized by penetration along the grain boundaries of the oxide and darkening of the oxide grains. This was observed for the systems Ti--0, Ti-,41203, Ti-ZrOz, Ti-hlgO, and Ti-ThOz. The fourth-type behavior is one where no apparent alteration of the interface or new phase is observed. The system Ti-Tho2 behaved in this way. Pray and associates (65) reported that a fluoride-phosphate bath has been developed for coating titanium by simple immersion of the metal. I t can be operated a t room temperature and will coat in a 1 to 2 minute immersion. Wire-drawing evaluations showed that by the prior use of this bath, commercial Ti-75 A can be continuously cold drawn t o a total reduction of 94% without an intermediate anneal. An investigation of the surface hardening methods for titanium was conducted by Wyatt and Grant (34). The use of ammonia was the best means of commercially producing a suitable case on titanium. Liquid cyaniding resulted in serious corrosion and was not effective in producing a hard case. Pack carburizing developed only an embrittled oxidized skin, and while gas produced a carbide surface, it would not harden sufficiently. Nitrogen nitriding, although less effective than ammonia, can, with certain limitations, be used for hardening titanium. The three major variables which were found to be the controlling factors in the ammonia nitriding process were temperature, time of exposure, and purity of the gas. Case depths to 0.004 inch and hardness to 1700 Knoop were obtained. In a subsequent investigation (%), ammonia nitriding improved the creep-rupture properties of titanium and its alloys in the 540' to 650" C. range, the oxidation resistance a t 650" C., and the corrosion resistance to boiling sulfuric acid and hydrochloric acid. The corrosion tests were performed in 10% solutions of these acids. As long as the case was intact, nitrided titanium corroded approximately one sixth as fast as untreated titanium. Once pitting occurred, the cor-
2132
INDUSTRIAL AND ENGINEERING CHEMISTRY
rosion was higher for nitrided specimens, indicating a chemical potential between the highly stressed case and t.he core. This subject was also iiivest,igated a t the -4rmour Research Foundation, Chicago. Hanael ( I S ) reported t h a t of the four elements investigated-oxygen, nitrogen, carbon, and boron-nitrogen produced the most satisfactory surface. Unalloyed titaiiiuni, several special titanium-base alloys, and several commercial alloys were treated wit,li purified nitrogen, and hard, adherent cases developed hetween 815' and 980" C. Their properties appeared to be adequate for a practical surface hardening process. The average surface hardness developed mas Vickers 800, with case depth ranging between 0.0024 and 0.0028 inch. Amnionia nitriding mas being studied a t ilrmour but had not yet been completely evaluated. T h e titanium-base vanadium and boron alloys developed optimuni hard adherent cases z t 650" C. Ivhen t,reated in purified nitrogen. With these exceptions, none of the special alloys yielded case properties superior to those of unalloyed titanium a t this temperature. Colner and associates ( 7 ) investigated the conditions under tvliich adherent electroplates can be obtained on titanium. The hulk of the experiments were carried out with commercially pure titanium sheet. The test specimens n-ere cathodically ?leaned (when required) in a solution of 20 grams per liter of sodium orthosilicate a t 70" C. This n'as followed by pickling in a solution containing 185 cc. per liter of 48y0 hydrofluoric acid and 8.00 cc. per liter of 707, nitric acid unt.il the specimens looked clean. The inveetiga,tion revealed that fully adherent copper electroplates (to 0.005-inch thick) mag be obtained if the titanium is anodically etched, prior to plating, in a solution based on ethylene glycol and hydrofluoric acid. A typical coinposition would be 15% by w i g h t hydrofluoric acid, 6% vater, and i070ethylene glycol. The bath should be operated a t 55" to 60" C. and a current density of 50 amp. per sq. ft. or slightly less. The required etching time was 15 t o 30 minutes. RIetallographic examination indicated that the bond hetween plate arid basis metal was a mechanical one, due to interlocking between the etched surface of the tit,anium and the plated metal, n-hioh appeared t o "thron." well into the cavities created by the etch. Baldwin ( 1 ) reported that the hcnding properties of titaiiiuiii rtrip can be sharply improved by removing a few thousandths of an inch of surface niet,al which was embrittled in annealing or hot rolling. Pickling in 10% hydrofluoric acid was found to be a n effective method of removing from 0,001 to 0.002 inch per side of met.al, although bend properties were also improved !Then surface metal n-as ground. Embrittlenient results from oxygen and nitrogen absorption rather than the formation of a highly oriented surface layer during rolling. Hutchinson and associates (15) described a new, weldable titanium alloy recently introduced b y Rem-Cru Titanium, Inc. It was designated Item-Cru 9-110 AT and has a nominal coinposition of 5% aluminum, 2.5% tin, with a total interstitial content of about 0.2%. It is the first commercial alpha-type titanium alloy and possesses the high toughness, hot streIlgth, and weldability expected of alpha alloys. The tensile properties of 0.100- t o 0.125-inch sheet averages 110,000 pounds per square inch yield strength, 116,000 pounds per square inch tensile strength, 18% elongation, and 40yo reduction of area a t room temperature. With rising temperatures the strength drops steadily t o about 55,000 pounds per square inch yield strength at 315" C. and to 25,000 pounds per square inch a t 650' C. Elongation and reduction of area remain fairly constant up t o 540" C. after which both increase rapidly. D a t a are also given for bend ductility, fatigue properties, notch sensitivity, stress rupture and creep, and for properties of welded joints. -4 new way t o provide inert gas-shielding when welding titanium was developed b y the I.T.E. Circuit Breaker Co. (30). 9 &eel chamber is used t h a t closely resembles a hospital incubator. Shoulder-length rubber gloves are sealed to the walls of chamher permitting the xvelding operator t o manipulate the
Vol. 46, No. 10
work and welding t'oolp froin the outside. Windom? niatfe of ultraviolet absorhing Plexiglas serve as viewing ports for the operator. Torch, cables, and hoses are introduced to the (rlimiber t,hrough gas-tight connections, and a double seal gas lock is provided for inserting or removing small parts and tools ivitliout breaking the seal. The entire chamber is sealed t o t,he table of a conventional welding positioner. The inert gas is introtlucwl nt the top of the chamber and displaces the air through a purging valve a t the base. This method is said to provide advantag(+ when more intricate melds are being made. The effects of alloying elements on t.he weldability of t8itaniuin sheet mere investigated by RIeyer and Rostoker (81). Eleven alloy compositions were studied from the systems Ti--U, Ti-Mo, and Ti-Cr, these three belonging respectively to the t,hree iiiajor titanium alloy systems, stabilized alpha, stabilized beta, and eutectoid systems. Three Ti-AI alloys containing 3, 5, and 8% slumiiium, respectively, v-ere studied. The 3 and 5% a l l o y werr found to be nonlieat-treatable ivelding alloys providing tensile strengths dictated by alloy content. On the basis of preliniinary experiments it was concluded t h a t the 8% alloy may \)e either fundamentally brittle or more euscept,ible t,o ernbrittlemerit b y atmospheric contaminants. Four chromium alloys were studied containing 2, 5 , 7, and 15% chromium, resyec~ively. The most significant point conccrning these alloys is the except'ional brittleness of the niediuni alloy contents in the as-~veldod state. While it was demonstrated that ductilit,ies could he restored by postheat treatment, tliere is danger of r i d d e d assemblies in handling or on heating. For the authors warn against their u-e if alternative materials arc> available. The 15% alloy gave a ductile meld but vas harclly superior in strength t o v h a t might be obtained in a po;ttrent,ed 2 t o 4% chromium alloy. Four Ti-Mo alloys were studied containing 3, 6, 10, and 30% molybdenum, respectively. Thcw alloys, in contrast with the chromium alloys, produced duc:t,iIr welds iyithout postheat treatment in the medium alloy i'airge. Posttreatment increased the strength of the 6% alloy a t soi~ie sacriSce in ductility. Llost of the alloys were capablcx of t ~ ~ i i s i i l crable strengthening by heat treat3inent. An investigation was conducted by Holt and associate$ ( 1 4 )into t,lie spot welding of three grades of titanium eheet, i~oiit;iiriii~g 0.1, 0.4, and 0.6% carbon, respectively, and in sheet tiiickrii of 0.038 t o 0.047 inch. All welds were made using a stand::rti, single phase, a.c. combination spot and projection xveldiiig niiichine with the electrodes mounted in platen-type boldera t o minimize deflection and skidding. The following conclu were draTvn from the st,udy: 1. The surface contact resistance of t,he "as received'' tifaniuni is sufficiently low and uniform t o permit reasonably good weld consistency. 2. Contact resistance is appreciably lowered and iiictlc niow uniform by mechanical or chemical cleaning with att enthtrit, iinprovement in m-eld strength consistency. 3. Hydride cleaning requires further study to avoid high contact resistance and possible impairment of weld ductility. 4. There is no apparent interaction between cleaning mrtiiotl an: carbon content. o. Weld strength is not affected b y the direction i i i w!iicIi the sheet is rolled. 6. Welding causes slight increase in hardness in the \ \ < , I ( l nugget and heat-affected zone.
Faulkner and associates ( I O ) studied the effects of the p~iiii~i~i:il beta-stablizing elements (iron, manganese, chromium, a n d molytidenum) now being used in commercial titanium alloys on w.iJldc(l joints in titanium. Four series of experimental binary alloy^ were used in the tests. Their compositions covered a range j t i which useful alloys were expected to fall. Inert g:is-shieltlwi tungsten arc welds were made in >/2- and I/*-inch plates of t,hr alloys, and the melded joints were investigated t o determiiir their mechanical and metallurgical properties. T h e bend tluctility of welds in the alpha-beta alloys decreased rapidly with iii-
October 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
creasing alloy content', becoming very low when the alloy content approached 3 t o 6%. Postweld heat treatments may generally be used to improve the bend ductility in alloys having 6 % alloy content. Welds with very good bend ductility in the asivelded condition were made in the 13y0metastable-beta chromium alloy, but the welds were embrittled by heat treatment. Welds in the other high alpha-beta and metastable-bet,a alloys had very low ductility in bot,h the as-welded and heat-treated conditions. An extensive invest.igation of the brazing of titanium was made hy DeCecco and Parks (8). Particular consideration was given to the selection of metals most likely t o be suitable as brazing alloys; to the development of fluxes; and to an evaluation of three methods for brazing commercially pure titanium-with an oxyacetylene torch, with electric resistance heating, and in an inert gas atmosphere furnace. Of the metals studied only silver proved significant. A strong ductile joint mas produced with ailver, and this was attributed to the formation of a ductile intermetallic phase having the composition TiAg. This compound was prepared and studied and it was the only compound in the t,itanium binary systems discovered thus far that had good ductility at room temperature. A new principle was applied to flux development', namely, electrochemical deposition of a metalprotecting film. Silver chloride, in conjunction with lithium salts, proved t o be the best metal-depositing flux reagent for silver brazing with an oxyacetylene torch. MnClz and CulClz were poor metal-depositing reagents for torch brazing but were quite successful in inert atmospheres. Harrett and associates ( 2 ) studied the effect of gaseous oontamiiiants on the properties of arc welds in t,itanium. The tests were performed on commercially pure titanium sheet, '/8-inch thick, and on commercially pure Ti wire, 0.1 inch in diameter. The test welds were made in a pure helium atmosphere to which was added controlled amounts of water vapor, nitrogen, oxygen, and hydrogen. The results showed that the relative humidity of the helium atmosphere should be lower than 5% for the welds to be comparable with those made in pure helium. Helium atmospheres containing nitrogen or oxygen must contain considerably less than 1% by volume of these gases singly. Hydrogen is not as detrimental to meld tensile and bend properties as is oxygen or nitrogen, since a weld made in a 1% hydrogen-99% helium atmosphere showed properties nearly comparable to those of welds made in pure helium. An increase in hydrogen to 10% resulted in no drastic lowering of the tensile and bend properties. Baughman ( 4 ) described a series of tests that showed that 1K 130B is satisfactory for bolting applications. The test specimens were 7/16 inch in diameter and had 20 threads per inch. Tensile tests made at both room temperature and at 260" C. showed that the tensile strength of the bolts was comparable to the original material. In stress-rupture tests at 260" C. the bolts all successfully withstood a load of 13,800 pounds for a 4hour period. ZIRCONIUM
Further study on the electrolytic production of zirconium was reported by Steinberg, Sibert, and Wainer (31 ). They developed a practical electrolytic process involving the electrolysis of JilZrFe in molten sodium chloride under a protective argon atmosphere. The metal is produced in the form of coarse crystalline dendrites t h a t may be consolidated by standard arc melting or powder metallurgy techniques. The process may be run on a semicontinuous basis, a number of runs being made on the same salt bath simply by charging fresh KzZrFe t o the electrolyte. The bath life is limited only by the build-up of sodium fluoride and potassium fluoride in the salt system, making it more refractory and less conductive. Although the bath may be run from 790" t o 1000' C., maximum efficiency is obtained from 800" to 850" C. Voltages over 2.0 to 2.5 volts must be used t o obtain
2133
a satisfactory deposit. Current density has little effect within fairly large limits; however, it should not exceed 500 amp. per sq. dm. Beyond this value metal is produced, but particle size diminishes, and the metal is more difficult t o recover from the deposit. The zirconium produced by this process contained, on the average, 99.6 t o 99.9% zirconium and hydrogen fluoride with small quantities of nitrogen (0.002 t o 0.004%), carbon (0.04 to 0.06%), and oxygen (0.04 to 0.08%). It had a hardness of 80 to 85 on the Rockwell B scale. Koenig (18) discussed the corrosion of zirconium in various liquid metals. The following table summarizes the presentlv available information on this subject in a qualitative way for static, isothermal conditions: Liquid hIetal Bi Bi-In-Sn Bi-Pb Bi-Pb-In Bi-Pb-Sn Gll Hg
Li
M g
300 Unknown Cnknomn Good Unknown
Good Limited Poor Good
N a , K, or N a K Good Pb Good fJ A t its melting point, G51° C . b At its melting point, 327O C.
Temperature, 600 Poor Poor Limited Poor Limited Poor Poor Limited Poora
Goo?
Limited
C
_-sno. Puor 7Jnlinon.n Unknowii >;nknomn L, nknoivri Cnhnown Unknown Limited Unknown Li 111it ed
The information in this report was taken from a variety of sources, mostly unpublished data and private communications. Belle and Mallett (6) studied t,he rate of oxidation of low hafnium (0.01 wt. %) zirconium in the temperature range from 575" t o 950' C. a t 1-atmosphere pressure. The data can be fitted to a cubic law, and the rate constant in (ml. per sq. cm.)3 per where sec. has been calculated t o be K = 3.9 X 106ee-47:200'RT 47,200 & 1000 cal. per mole is the activation energy for the reaction. This work appears to be the first experimental evidence that the cubic growth law can prevail over a wide temperature range. The rate of reaction of nitrogen with high purity (0.015% hafnium) zirconium was determined for the temperature range of 975' t o 1640' C. a t 1 atmosphere by Mallett, Bclle, and Clelaiid ( 1 9 ) . Test specimens were machined from iodide crystal t,ar produced by the de Boer process. The reaction followed a parabolic law and the parabolic rate constant in (ml. per sq. cm.)' per where 48,000 see. was calculated to be K = 5.0 X 103e-48~000'RT i 1500 cal. per mole is the activation energy for the reaction. It is interesting to compare the latter value with the value of 52,000 cal. per mole ohtained earlier for high-hafnium zirconium. The solubilityin weight per cent nitrogen in zirconium over the ternperature range 920" to 1640" C. is given by log co = - (2810/2') 1.42. The heat of solution for nitrogen in zirconium obtained from this equation is AH = 12,900 & 500 cal. per mole. The role of oxide films, pretreatments, and occluded gases on i,he rate of reaction of hydrogen with zirconium wtts studied by Gulbransen and Andrew (fa). High purity zirconium containing the room temperature equilibrium oxide film reacts very slowly with hydrogen a t 150' C. and 24 mm. of mercury pressure, arid in a self-accelerating manner. Similar specimens preheated in high vacuum a t temperatures above 500" C. for 1 hour react very rapidly with hydrogen a t 150" C. and 24 mm. of mercury pressure without an induction period. The ratio of the rate reaction for the preheated specimens relative to those not preheated was 7700 or greater. These results were interpreted in terms of an oxide film limiting the rat,e of reaction, this film dissolving in the metal as the temperature of aunealing was raised. Furtliermore, the nature of the oxide film was very important in its resistance t o hydrogen, room temperature equilibrium films bring more resistant than thicker oxide films formed at higher tempera,tures. Small amounts of dissolved oxygen and nitrogen t o 0.1 wt. yo have only a minor effect on the rate of hydriding :it 150" C
+
INDUSTRIAL AND ENGINEERING CHEMISTRY
2134
Economos and Hingery (9j studied the interfacial reactions at elevated temperatures of various metals with dense oxide specimens. Their results indicated that four general Q-pes of behavior may be observed, corresponding t o varying degrees of reaction. T h e first consists of the formation of a definite new phase at the interface. Zirconium did not react in this R-ay with any of the oxides tested. The second-type reaction is the corrosion of the oxide interface b y the metal. I n order for a reaction of this type to proceed, it is necessary that the reaction products be removed from the interface as t'hey are formed. This second type of behavior occurred in t'he systems Zr-Al,O, and Zr-MgO a t 1800" C. a n d in the system Zr-TiO,. a t 1600' C. The third-type reaction is characterized by penetration along the grain boundaries of the oxide and darkening of t'he oxide grains. This was observed for the systems Zr-BeO, Zr-hl,O,, Zr-ZrOl, and Zr-ThOn. T h e fourth type of behavior is one where no apparent alteration of the interface or new phase is observed. The systems Zr-ZrOz and Zr-Tho, behaved in this way. The creep properties of annealed, unalloyed zirconium were investigated by Manjoine and Mudge (20). Test specimens ?yere prepared from tn.0 double arc-melted ingots of iodide crystal bar, and t,he t,ests were run in spring-loaded autographic creeprupture machines and lever arm machines. The creep properties depend on the state of anneal. T o 315" C. the plast'ic flow on loading is so much larger than the creep strain for 1000 hours that creep can be neglected in design for such lives. Bbove 31.5' C., creep plays an increasingly important role and must be taken into account. Paasche and Killin (25) described the fabrication of a zirconium-lined reaction vessel a t the U. S.Bureau of Mines st'ation at Albany, Ore. The lining \vas 0.050-inch t,hick zirconium sheet, a n d a number of additional parts were also made of zirconium. These included the cover flange on the vessel itself, outlet pipe and flange, inlet pipes, manhole and stud bolts. The welding techniques employed were discussed. MOLYBDENUM
Senderoff and Brenner ( 2 9 ) investigated the electrolytic production of molybdenum from fused salts. They were interested not only in the production of pure molybdenum powders but also in the possibility of obtaining coherent molybdenum electrodeposits. The latter would provide a means of bypassing the rather complicated powder metallurgy techniques now used for producing molybdenum objects. A solution of potassium hexachloromolybdate(II1) dissolved in a mixture of alkali halides can be electrolyzed in an inert atmosphere t o produce deposits of pure molybdenum a t the cathode. The recommended compositions and operating conditions for the deposition are: Bath 8 , Grams
Bath B, 600' t o QOOa C., Grams
50 50 33
54.5 45.5 33
9000
KC1 NaCl KJMoC16
c.,
Reed (26) investigated the corrosion properties of molybdenum in molten sodium, bismuth, and tin. No corrosion was observed in sodium and very little in bismuth, but in tin at 1000" C. for 338 hours there was a pronounced solution effect. The specimens were mottled, and 1.69% molybdenum was found in the tin. A patent was granted t o Garrison and Lovett ( 1 2 ) for a process for providing molybdenum with a protective silicide coating. A slip is first prepared of finely divided glass and silica in alcohol. A coating of this slip is applied t o the molybdenum, either by spraying or dipping, and the coated piece is heated above 1300" C. in a hydrogen atmosphere. The temperature must be high enough t o generate hydrogen silicide and cause it t o react with t h e surface of the molybdenum. This treatment produces an outer coating of silica about 0.004-inch thick superimposed on a
Vol. 46. No. 10
coating of molybdenum silicide about 0.008-inch thick. The coating increases the hardness about 20 on the Rockwell B scale over the normal hardness of the molybdenum itself. This hardness increase should improve the resistance t o abrasion. Little, if any, volatilization of the coating occurred t o about 1000" C. Rendall, Johnstone, and Carrington ( 2 7 ) studied the forgeability. creep strength, and ductility of molybdenum a itli Icgard to the effects on these propertie5 of alloying additions 2nd processing variables. Their results are summarized.
1. Nearly all alloying additions have an adverse e? eot on forgeabilitg; the effect is greater the larger the difference in atomic diameter between the alloying element and molybdenum. 2. The creep strength of forgeable alloys a t 1000" C. is not very much greater than that of molybdenum. 3. T h e effects of processing variables on the ductility of molybdenum are very inconsistent, but increases in oxygen content, grain size, and porosity decrease the ductility of sintered molybdenum. 4. All alloying additions, except carbon, aluminum, and titanium, decrease the ductility of molybdenum. The improvement brought about by these elements is not large and is probaiily due to the resulting reduction of oxygen content. I
Bechtold ( 5 )determined the effects of temperature, strain, and rate of strain on the flow and fracture strengths of molybdenum above, through, and below the ductile-to-brittle transition. X sample of annealed molybdenum was studied between - 195" and +970' C. by tension tests a t a constant rate of extension of 2.8 X 10-4 sec.-1 This temperature range can be divided into four zones:
1. A brittle zone below -75" C., characterized b y a lack of measurable ductility and bright t'ransgranular cleavage-type fractures. 2. A transition zone extending from about -75' t o i l 5 0 " C. characterized by a rapid increase in yield strength, a simultancous decrease in ductility with decreased test temperature and a change from bright transgranular fracture t o a dull fibrous fracture. 3. A ductile zone extending from about 150" t o about 900" C. characterized b y low yield strength, excellent duct'ility, and a dull, fibrous fracture. 4. An unstable zone above 900" C. due to thermal instability of the microstructure.
lloss (26) found that commercial sintered molybdenum sheet can be pressure welded, using impact loading, a t temperatures as low as 690' C. in atmospheres of oxygen-free argon or hydrogen. The latter is preferred as appreciably less deformation is required, the time interval between cleaning and welding id not critical, and the surface finish of the faying surfaces does not appear t o influence the weldability. The temperature and amount of deformation to produce a weld can be reduced considerably by using insert materials between the faying surfaces. This effect was produced with a wide range of materials, including niobium and tantalum. The latter produced a sound weld in argon a t 1000" C. with only 23% deformation, using a 0.002-inch thick tantalum insert, whereas a weld a t 1000a C. without an insert required a t least 46% deformation. By electroplating molybdenum with chromium it was possible t o pressure-n7eld chromium to chromium interfaces a t low deforming pressures. Commercial molybdenum can be readily welded by conventional resistance and inert gas-shielded melding procedures, but the welds are brittle at room temperature. Kearns and associates ( 1 7 ) reported t h a t ductile velds may be obtained by using extremely pure molybdenum and resistance upset welding. The faying surfaces must be cleaned very carefully, preferably by electropohshing, and the welding must be done in high vacuum (about 0.1 micron), Two methods for preparing molybdenum of sufficient purity were developed. One was multiple vacuum arc melting; the other was heating above 1930" C . for long periods in high vacuum.
October 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY TANTALUM
Peterson and associates ( 2 4 ) studied the temperature and pressure dependence of the reaction of tantalum in oxygen from 500' t o 1000' C. a t pressures from 10 mm. of mercury t o 600 pounds per square inch total oxygen pressure. Tantalum was found t o oxidize linearly under these conditions. Three distinct regions of temperature dependence were found with different energies of activation. From500" t o 600" C. the rate of oxidation was essentially independent of the oxygen pressure. From 600' t o 800" C. the oxidation rate increased rapidly with an increase of pressure. Reed (26) investigated the corrosion properties of tantalum in liquid sodium, bismuth, and tin. I n sodium at 900" C. for 168 hours tantalum experienced essentially no corrosion, although some of the samples were darkened. The specimen weight I n bismuth a t 1000' C. changes varied from --0.09 t o +O.Ol%. for 227 hours, tantalum suffered pronounced intergranular attack, and 0.11% tantalum was found in the bismuth. I n tin at 1740' C. the solution of tantalum was evident after 1 hour, and 0.33% tantalum was found in the tin. LITERATURE CITED
Baldwin, W.&I.,Jr., Iron Age, 172, 165-7 (Dec. 3, 1953). Barrett, J. C., Lane, I. R., Jr., and Huber, R. W., Welding J., 32, 283s-91s (1953). Battelle Tech. Rev., 3, 9 (January 1954). Baughman, R. A., Materials & Methods, 39, 98-9 (March 1954). Bechtold, J. H., J . Metals, 5, 1469-75 (1953). Belle, Jack, and Mallett, If.W., J . Electrochem. Sac., 101, 33942 (1954). Colner, William H., and associates, Ibid., 100, 485-9 (1953). DeCecco, N. A., and Parks, John M., Welding J., 32, 1071-81 (1953). Economos, G., and Kingery, W. D., J . Am. Ceram. Sac., 36, 403-9 (1953).
2135
Faulkner, G. E., Grable, G. B., and Voldrick, C. B., Welding J., 32, 4819-497s (1953). Garrison, John W., and Lovett, Albert B. (to Westinghouse Electric Corp.), U. S. Patent 2,650,903 (Sept. 1, 1953). Gulbransen, E. A., and Andrew, K. F., J . Electrochem. Soc., 101, 348-53 (1954). Hanael, R. W., Metal Progr., 65, 89-96 (March 1954). Holt, E. F., Vandenburgh, F. H., and NcClymounds, N. L., Welding J., 32, 1057-66 (1953). Hutchinson, G. E., and associates, Materials & Methods, 39, 91-3 (April 1954). Jenkins, A. E., J . Inst. Metals, 82, 213-21 (1954). Kearns, W. H., Goodmin, H. B., Eichen, E., and Martin, D. C., Welding J., 32, 1082-8 (1953). Koenig, R. F., Nuclear Sci.Abstr., 8 , 1079 (Feb. 28, 1954). Mallett, A I . W., Belle, Jack, and Cleland, B. B., J . Electrochem. SOC.,101, 1-5 (1954). hIanjoine, M. J., and Nudge, W. L., Jr., ASTM, Preprint 106a (1954). Illeyer, H. M., and Rostoker, W., Welding J., 33, 173s-186s (19.54).
iM&-i.. R., J . Inst. Metals, 82, 374-8 (1954). Paasche, 0. G., and Killin, A. J., Welding J., 33, 115-18 (1954). Peterson, Robert C., and associates, ;Vuclear Sei. Abstr., 8 ,
1096 (Feb. 28, 1954). Pray, H. A,, and associates, Ibid., 8, 825 (Feb. 15, 1954). Reed, E. L., J . Am. Ceram. SOC.,37, 146-53 (1954). Rendall, J. H., and associates, J . Inst. Metals, 82, 345-60 (1954). Richardson, Lee S., and Grant, Nicholas J., J . Metals. 6, 69-70 (1954). Senderoff, Seymour, and Brenner, Abner, J . Electrochem. Sac., 101, 16-27 (1954). Steel, 134, 114-15 (March 1954). Steinberg, M. A., Sibert, M. E., and Wainer, E., J . Electrochem. SOC.,101, 63-78 (1954). Straumanis, hl. E., and Gill, C. B., Ibad., 101, 10-15 (1954). Van Thyne, R. J., and associates, Iron Age, 172, 146-8 (Aug. 6 , 1953). Wyatt, J. L., and Grant, X. J., Ibid., 173, 112-15 (Jan. 14 1954). Ibid., pp. 124-7 (Jan. 28, 1954).
PLASTICS RAYMOND B. SEYMOUR Atlas Mineral Products Co., Mertatown, Pa.
In spite of recent business fluctuations, the trend toward the increased utilization of plastics as materials of construction has continued. While this phase represents but a small segment of the billion dollar plastics industry, it has been well publicized during the past year. For example, approximately $1,000,000 have been invested in advertising programs promoting the use of unplasticized polyvinyl chloride although the dollar volume of such resins last year was considerably less than that amount.
T
HE almost universal acknodedgment of plastics' potential
role as materials of construction for the chemical process industry has not been limited t o the promotion of vinyl resins. All available commercial plastics have been evaluated both empirically ( 1 4 A ) and technically ( I d A ) . Two symposia on plastic materials of construction were held in this country, and a series of meetings with the same objective were held a t the University of Birmingham in England. Papers on the use of plastics as materials of construction for the chemical industry were presented by Bruner ($A), Eifflaender ( 5 A ) , Seymour ( I O A ) , and Shepard (15A). Discussions on the use of plastics as construction materials were also published ( 6 A ,8A, 9 A ) . Annual reviews on plastics were published b y Kline and Stanley ( 7 A . 17A), and a n international plastics organization was pro-
posed a t the International Dinner of the Society of Plastics Industry, Cleveland, Ohio, June 8, 1954. Another forward step was the adoption of a statement of principles in a n attempt t o bring t o the plastics industry and the public alike all the benefits, economies, and satisfaction inherent in these versatile engineering and construction materials (16.4). Almost 500 individual firms in the plastics industry have formally subscribed t o these principles ( S A ) . Many technical committees are attempting to establish standards for plastic materials of construction. The Thermoplastic Pipe, Thermoplastic Structures, and Reinforced Plastics Divisions of the Society of the Plastics Industry are establishing standards for pipe, thermoplastic structures, and reinforced plastics, respectively. The Thermoplastic Pipe Division has sponsored a research project at Battelle Memorial Institute in order t o develop testing methods and physical data for thermoplastic pipe. A similar program is under consideration by the Reinforced Plastics Division. A project at the National Sanitation Foundation a t the University of Michigan has proved that many
