I
R. W. HALE and R. L. CARMICHAEL Battelle Memorial Institute, Columbus 1 , Ohio
These metals are expensive now, but present demand is too low for predicting potential price reductions
WHY
ARE THE 10 metals discussed in this symposium classed as less common and how does this tie in with economics? -4re they less common because of limited availability in the earth’s crust? Is it because of inherent difficulty in separating the metal from natural materials and preparing high purity metal? Is it because the metals have properties so similar to those of other known metals that higher cost precludes their use in ordinary applications? O r is it because these metals have properties that have not been needed until recently? Are they less common because so little is known about them and their behavior under a variety of conditions? Are they less common because they are costly? O r are they costly because they are less common? All of these questions add u p to this: Do these metals represent a mature industry with a reasonably long history or. rather, should thev be classed as a Johnny-come-latel) group? I n delineating the scope of this discussion on economics, it is sufficient to sav that these 10 metals as a group have interesting properties such as higher melting points, inertness to certain environments, better strengths at elevated temperatures, and better nuclear properties than more common metals.
Niobium Although first identified in the early 18OO’s, it was not until 1929 that Balke
first produced metallic niobium (columbium) ( 3 ) . In the interim little was done with niobium metal until the last 10 years. Of course, ferroniobium for use as a carbide stabilizer in stainless steel was introduced in the early 1930’s. Availability of niobium ore has been tight during past times of emergencies, and yet today, it is considered potentially readily available. Kiobium is certainly no rare element compared with many accepted and known metals. Ac-
108
cording to the recent M.4B report ( Z ) ? the reserves of niobite in Nigeria and the Belgian Congo are ovcr 100,000 short tons of contained pentoxide that might be used to produce metal. There are additional pegmatitic sources, as yet undefined, that could constitute even more of a reserve. Recent discoveries of the pyrochlore ores have made niobium potentially as available as molybdenum, and perhaps even more so. Inferred and probable reserves of niobium in pyrochlores are estimated at close to 10,000,000 short tons of contained N b 2 0 j . A large fraction of this reserve is in one deposit in Brazil. Recent production of niobium metal has been as high as 65 tons a year. The United States’ production of ferroalloy has been some 400 to 500 tons of contained metal annually. Ob\-iously, production of the metal is not limited by raw material availability. At $36 per pound for powder in rondel form, niobium metal production in 1959 had a value of about $4.700.000. Tantalum Although identified in the early 1800’s: tantalum was not isolated in pure metallic form until 1903 ( 3 ) . Incidentally, tantalum was the first metallic lamp filament used on a commercial scale until replaced by tungsten. So tantalum has been used in metallic form for a t least 50 years. Known deposits of high-grade tantalite are not only small but are limited in potential productive capacity. The major known sources of tantalum are the tantalite-niobite ores. in the Belgian Congo and Nigeria. and certain other tin slags. Total estimated reserves are about 150,000 tons of contained pentoxide. Tantalum is definitely less common than many other metals from the ra\v material viewpoint. Tantalum metal production in 1959 is estimated a t about 125 tons, the year of peak output. Since very minor amounts of tantalum compounds a r e used for other purposes, the metal may be considered as representative of total commerce in tantalum. AI a base price of $30 a pound in powder form, tantalum metal business last year amounted to some $7,500,000. Sheet prices of tantalum are quoted a t $55 per pound ( 7 ) .
INDUSTRIAL AND ENGINEERINGCHEMISTRY
Molybdenum Molybdenum represents a quite different situation, having been recognized, although confused with lead, by the ancients. I t was first prepared in elemental form about 1790 ( 2 ) . hlolybdenum does not occur free in nature but usually as the sulfide in molybdenite and as a n oxide with lead in wulfenite. I t is widely distributed on all continents in granites and in pegmatites. A few large deposits of molybdenite are known, but almost 50% of our molybdenum is recovered as a by-product from the processing of porphyry coppers. Total estimated reserves of molybdenum are some 3 billion pounds as recoverable metal. About 70%) of these reserves are found in the Cnited States. Molybdenum metal powder production in 1959 was the highest-1250 tons. However, molybdenum in metal form is only a small fraction of the total conI n 1959, sumption of this element. metal production was about 7Yo of the total of about 18?000 tons. Oxide accounts for about two thirds of the total and ferroalloys about one fourth. Greatly increased consumption rates for all forms of molybdenum would not be limited by raw material availability. At prices of 93 to $4 per pound for powder. the metal would have a value of $7,500:000 to $10,000,000 in 1959. T h e Bureau or Mines estimates that in 1959, about 520 tons of powder were consumed in wire. rod, and sheet and 580 tons in forging billet (5). At average prices ($40 per pound for sheet and $8 for billet), these products would have a value of about $35,000,000 and $9,000,000, respectively. Tungsten Although known for centuries, tungsten metal was first produced in 1783 ( 3 ) . Commercial applications of tungsten metal were a reality in the early 1900’s, primarily as filament in electric light bulbs. Total world ore reserves are difficult to estimate because the large majority are in Communist countries and have not been fully explored. I t is estimated that total reserves in the United States are 71,370 tons of contained tungsten. iMost of these reserves should be considered definitely submarginal a t present prices for tungsten ore. Foreign reserves, excepting iron curtain countries, are estimated at
LESS C O M M O N E L E M E N T S 220,000 tons of contained tungsten. or about three times United States reserves. Reserves in China are probably a t least three times the total for the free world. The recent discovery of a large deposit in Canada has increased the North American reserves substantially. Tungsten metal production, exclusive of that used in carbides has been about 500 tons for a number of years. T h e Bureau of XIines reports that almost 700 tons of metal Lvere used in the form of wire. rod, and sheet during 1959 (5). This use has represented about 12 to 15% of the total amount of contained tungsten by all classes of manufacture for the past several years. Tungsten metal powder, hydrogen reduced, is quoted a t $3.35 to $4.25 per pound ( I ) . Chromium -4lthough identified before 1800, metallic chromium was not produced until 1857. During the past century, the use of chromium--primarily in ferroalloys, chemicals, and refractories-has grown until over 1.000.000 tons of ore are used anr,ually in the Cnited States. Chrome ore reserves are tremendous, although grade varies considerably. T h e best kno\vn and probably most extensive reserves are in the Transvaal, where certainly many tens of millions and probably hundreds of millions of tons of ore occur. Southern Rhodesia is second only to the Transvaal in known deposits. Turkey has been a large producer but the reserves here are not so well defined. An estimate often accepted is 10~000.000 tons of reserves. The known United States deposits are small, widely scattered. and of loiv grade. All are uneconomic to \mrk a t present ore prices. High purit!. chromium metal has comprised onl>- a minute portion of the total demand for chromium ores. \vhich has varied from 1.300.000 I O 1,800,000 tons annually. I n this report, only metal having much higher purity than commercial electrolytic chromium metal is considered. There a r r several laboratories making metal that falls in this class. O n this basis. perhaps a maximum of 1 ton of high purity metal \vas produced in 1959, T h e purest chromium metal available to date has been prepared by a n iodiderefining process starting with commercial electrolytic chromium as feed material. Total impurities are less than 100 p.p.m. and the price is about $100 per pound. Another product ivith about 400 p.p.ni. total impurities is available for about $30 per pound, Rhenium Truly a less common element. rhenium is recovered primarily from the molybdenite fraction of porphyry cop-
per deposits. .4lthough the metal is widely distributed in nature, no large deposits containing recoverable grade of ore are known. T h e metal was first prepared in the mid 1920’s and has remained almost a laboratory curiosity despite its unusual properties. Total reserves in the Cnited States are estimal.ed a t 1.000,OOO pounds, with world reserves estimated a t several million. Rhenium production is measured in pounds rather than tons. I t is estimated that perhaps 12,000 pounds per year could be recovered if all of the flue gases and dusts from the roasting of by-product molybdenum were treated. At present, probably not more than 10 to 15%, of this available material is being recovered. Rhenium powder is quoted a t about $600 a pound, and in rod or sheet form, it is about $1000 per pound. Zirconium First discovered in 1789, zirconium met.al was not prepared until 1914 ( 3 ) . Other forms of zirconium such as the oxide and silicate have been used to a reasonable extent for many years Commercial raw material sources of zirconium are found in the United States, Australia, Union of South Africa, Brazil, and India. United States reserves are estimated to be about 12,000,000 tons of 66% Z r O ? and world reserves are estimated a t about 33,OOO:OOO tons. Zirconium metal production, if estimates based on announced Atomic Energy Commission contracts are correct. is about 3250 tons per year. Capacity to produce is much greater-about t\vo times this rate. Ferroalloys containing zirconium also are produced. Recent estimates of ferroalloy production and consumption are around 500 tons as contained metal. TM.Ogrades of zirconium metal, commercial and reactor. are produced. Commercial-grade zirconium contains 1 to 37, of hafnium and is normally used except in nuclear applications. Reactor-grade zirconium is essentially hafnium-free and is someivhat more expensive than commercial grade. T h e government contract prices for zirconium vary from contract to contract. The present quoted price for commercial
zirconium sponge is about $5 per pound, and reactor-grade sponge is quoted a t about $7 per pound. Sheet, strip, and bars are quoted a t prices u p to $30. Hafnium Hafnium is recovered only as a byproduct from making reactor-grade zirconium. Therefore. its production is limited by the output of zirconium. This metal was first produced in the pure state about 10 years ago and has found limited use in reactors. Since from 1 to 3 pounds of hafnium are recovered for each 100 pounds of zirconium, a steady supply is available, even if it is limited. I t has been reported that some of the niobite-tantalite operations in Africa can recover a hafnium-bearing by-product that could be a new source, if a satisfactory and economical method for extraction could be achieved. If achieved, this might add a few hundred thousand pounds to the annual supply. Hafnium is definitely less common than many other metallic elements. Production of hafnium is in the neighborhood of 70>000pounds per year. In sheet form? it is quoted a t $40 a pound. Vanadium Although produced in impure metallic form in 1867, vanadium was not used because of the difficulty in preparing high purity metal. T h e Bureau of Rfines rates vanadium as eighth in abundance among the metals ( 1 ) . In this respect. it is more plentiful than many of the common metals but is not as readily recoverable. Total vanadium resources are described as very large, yet only rough and incomplete estimates of reserves have been made. I t does appear that there are at least 1.000,OOO tons of reserves. calculated as V2Oj. in the United States and close to 500.000 tons knoivn in the rest of the free Lvorld. Vanadium metal production has been almost exclusively for research and development uses, and it is reasonable to say that no more than a few hundred or perhaps a few thousand pounds are produced annually. Some small amounts of vanadium are used in ferroalloys and in chemical form. T h e price of VZO5 is
Although their potential supply is generally adequate, these metals are less common because:
b b b b
Quantities produced as fairly pure metal are small Experience in production methods and uses is limited Uses are uncommon and are still being developed
Much needs to be learned about them. They will remain less common until prices are lowered, and volume is increased VOL. 53, NO. 2
FEBRUARY 1961
109
MORE DATA WILL PROBABLY MEAN WIDER USAGE 1. R h e n i u m a n d hafnium definitely a r e limited as to r a w material availability, a n d it a p p e a r s t h a t the! mill b e less c o m m o n metals for t h e foreseeable future. T a n t a l u m is limited by o r e materials, b u t is i n a better position t h a n t h e first tivo. T h e remaining metals-niobium, molybdenum. tungsten, t i t a n i u m , zirconium, c h r o m i u m , a n d vanadium-are not limited by r a w material availability, even w h e n f u t u r e d e m a n d s a r e considered. 2. Commercial production of these metals varies widely; with t h e exception of tungsten a n d t a n t a l u m . use of t h e p u r e metals h a s not really been commercial except in t h e past 10 to 1 5 )ears. I n this respect, there is u n d e r s t a n d a b l y a strictly limited capacity for producing these metals a t present. But h e r e again, is this a t r u e limit t o keep t h e m classed as less c o m m o n ? C e r tainly there is sufficient capacity for foreseeable d e m a n d s for titanium, zirconium, tungsten, a n d mol\ b d e n u m . Productive capacity for n i o b i u m and t a n t a l u m is not too well known, b u t p r o b a b l y is a d e q u a t e for noiv. IVith t h e tremendous interest in niobium now evident, plus known activities being t a k e n b y various companies t o increase capacity, there seems t o be little d o u b t t h a t a d e q u a t e supplies of m e t a l will b e available. Production facilities for hafnium a r e d e e m e d a d e q u a t e , as related t o zirconium about $1.25 per pound and contains 56% vanadium. Vanadium metal, 90% pure, is quoted at $3.65. High puritv metal can be obtained a t $30 to $35. Titanium Estimated to he the ninth most abundant element in the earth’s crust, titanium metal was made first in 1910 but not commercially until 1946. The history of its growth and subsequent decline during the 1950’s is well known. Titanium minerals are widely scattered over the earth’s surface. but many of them are not in recoverable form. Resources are estimated to be in the neighborhood of 230,000.000 tons of contained TiO?. with about 25% of the total in the United States. Another 25% of the world supply ir found in Canada. Titanium ingot consumption has been as high as 21.700,OOO pounds in 1956 and was 11,600,000 pounds in 1959. From the raw material vielvpoint, many tinies more ore is used to produce Ti02 pigment (495.000 tons in 1959) than are needed for metal. Economic Factors I n general. these metals were prepared in metal form 50 to 100 years ago. However, most of them were extremely difficult to obtain in high purity form and so were not studied and their true properties substantiated. Because first attempts to make the metals produced impure materials whose properties were negatively influenced by the impurities
1 10
production, b u t could he increased. ,Also, it is conceivable t h a t m o r e t h a n o n e m e t a l could b e m a d e i n t h e s a m e e q u i p m e n t because of similar processing. V a n a d i u m , rhenium, a n d high puritb- c h r o m i u m a r e a different story. Facilities to p r o d u c e r h e n i u m a r e not being- built, a n d it is even doubtful if t h e by-product m o l y b d e n u m companies will install rec0:w-y e q u i p m e n t , since it does n o t a p p e a r realistic to d o so. Both vanad i u m and c h r o m i u m a r e being produced o n a laboratory scale for research a n d development purposes. So, if a terrific d e m a n d s h m l d arise, additional capacity would b e required immediately. 3 . Apparently, d e m a n d for these metals is insufficient t o require serious consideration of their availability. TVhen t h e m a r k e t d e m a n d grows, it c a n be assumed t h a t supplies will b e found. Two examples of this c a n he cited. I n t h e late 1940’s a n d early 1950’s: t h e sur%e i n d e m a n d for titanium was unlimited-capacity to prod u c e was built, which now is unused. D u r i n g t h e K o r e a n IVar, w h e n niobium was i n tight supply a n d u n d e r t h e aegis of t h e government stockpile a n d p r e m i u m prices, pyrochlore deposits were found a n d evaluated. T r u e , i n b o t h instances, a few years’ t i m e lapse occurred, b u t this was to be expected.
remaining. it \vas naturally assumed that the metals \- they were worked with for research-curiosity purposes. Because they had no apparent outstanding qualities, and had drawbacks, it was best for engineers and scientists to work with knoivn materials. HoIvever. during the past decade, and especially in the past 5 years: demands for metals to serve environmental extremes have risen sharply and the end is not yet in sight. Better strengths at elevated temperatures, nuclear environments, corrosion resistance, etc., have all stimulated a search for better materials. because it is recognized that our common metals fall short. This group of less common metals appears to offer some hope from a theoretical standpoint. Stimulated by government demand and backed by government funds, new methods of processing and techniques \vere developed, to prepare these metals in pure form for study. However, exaggrrated urgencies pushed developments too fast. \vith the consequent result of some costly mistakes. Also. another factor tended to keep these metals in the less common class. T h a t is. little work had been done with them. and little was knoivn about their properties, especially the influence of trace impurities on the properties. Little by little. these problems are being investigated, answers obtained, and considerable knowledge of the metals ac-
INDUSTRIAL AND ENGINEERING CHEMISTRY
cumulated. Each time an advance is made. the mrtals become more commonly known. C\’e are just nolv beginning to understand enough about good properties and ways of handling the drawbacks so that advantage can he taken of the inherent attractive properties of these metals. Thus. lack of knowledge has deterred these metals from becoming materials of commerce. Regarding preparation. these metals, by and large, are recovered by more highly specialized chemical processing rather than well-known conventional metallurgical processes. In so doing, many of them have been produced in batch operations and this is considered inherently more expensive than continuous production. This type of processing has been accepted because it allows for removal of impurities that cannot be obtained by standard techniques. Saturally, these methods have produced expensive metal but reasons for this are well known. The costs of research and development to perfect processes and equipment have to be paid for and so raise the price of the metai. The volume of production has been so low that amortization of capita; costs per pound has been terrific. It is anticipated, both at Battelle and among other groups, that costs of producing these metals \\,ill come down as volume rises, because of mirket demand and because of new and better processes. Of course, this is the circle that must be broken. IVhich comes first? Low cost from volume output to satisfy market de-
LESS COMMON E L E M E N T S mands, or market demand created by high volume output at low cost. Fabrication into useful shapes and mill forms has a very definite bearing on the economics of the less common metals. Aside from the relatively high cost of the starting material (as compared Lvith the more common metals), such problems and characteristics as lo\v volume of production, high strength a t elevated temperature. affinit! for the common gases a i elevated trmperature. and a number of others all contribute to the relatively high cost of mill forms. Most of the less common metals are produced as metal po\ver or sponge and must be consolidated into ingot or billet form before primary fabrication. Both porvder meta1lurg:- techniques and double consurnable-electrode vacuum melting processes are used. Electronbeam melting is another. more recent technique. In some instances. the ingot must be broken do\vn by forging or extrusion berore further \\-orking. Fairly rugged fabrication equipment is required. although in general. existing rolling mills can be used. A feiv of the metals. such as pure niobium and tantalum. can be cold-rolled directly rrom the ingot form, hut others, such as mol>-bdt.num and tungsten, must be worked at elevated temperatures. 4 1 1 of the refractory-reactive metals have a n affinity for the common gases (oxygen, nitrogen. hydrogen) a t elevated teniperarures. ivhich contributes to excessi\,e scaling and contamination during fabrication. \7ery small amounts of these gases may he deleterious: both to fabricability and to quality of the finished product. I-arious ways have been tried to get around the contamination problem. including grinding contaminated material off the surface of the mill shape. jacketing the material before fabrication. and fabricating in a vacuum or inert atmosphere. Obviously. any of these alternatives adds to the cost. These problems, are compounded by the fact that our experience in fabricating these metals is of relatively short duration and we still have much to learn about them. For example, with the possible exception of titanium. cast shapes cannot be considered commercially available as yet. As another example, the Ividths of sheet commercially available. again with the exception of titanium. d o not yet approach the widths available in? say, stainless steel o r aluminum. \\'idths available in tungsten measure but a few inches. For molybdenum. the maximum Xvidth readily and cornmercially available is about 36 inches. I n contrast, stainless steel sheets in common grades are available in tvidths of over 66 inches. Large sheets have been made in several of the less common metals. but the very
fact that these are put on display at the metal shows and receive wide publicity in the trade journals points up to the uniqueness of such fabrication. T h e nonavailability of certain shapes and sizes in many of the less common metals makes it difficult to compare the fabrication economics with more common metals.
Mill Product Prices Are Much Higher Than Those of Steel (Dollar\ Th.) SS" TRh Powder Ingot Sheet, 24 in. wide 0.1875in. thick 0.010in. thick a Type 301.
SIilh
35.00
3.15 7.82
0.55
49.30
21.34
0.74
55.83
49.50
0.24
ITnalloyed
Commercial-grade titanium sheet and strip sell for $6.75 to $13 and zirconium cold-rolled strip rangrs bet\veen S16 and $31 per pound. Thus. fabrication of mill products in the less common metals is relativel7. costly. I t is encouraging to note that remarkable strides have been taken in the past 2 or 3 years. I t is virtuall:. certain that as experience increases and more is learned about the rvorking of these metals. fabrication costs \vi11 decrease and quality will improve. However, certain problems are inherent and it is unlikely that mill product prices \vi11 approach those of stainless steel, for example. in the foreseeable future. Another economic factor that must be taken into account is government activities. because the present market and the great interest in these materials is based on government research and de\,elopment programs related to missiles. nuclear reactors. supersonic aircraft. and space vehicles. The vagaries of government action in this field may, as they have in the past, exert a great economic force. T h e case of titanium is well known. Huge capacity was built u p to supply the Air Force and then shut down because of the shift in equipment demands in manned aircraft LS. missiles. Now it js obvious that the titanium industry, after several years of scratching for a place to exist. and using this period to learn more about its products, is beginning to grow on a firm basis. This is a n example of trying to force a n industry to groiv u p too fast. Another part of this concerns not only government cancellations or changes in policies, but the fact that specifications are so severe, compared with civilian needs. that it is difficult to go immediately from government markets to com-
mercial markets. Time is often involved in obtaining performance data that \vi11 justify high costs for installation. LVe have no doubts That industry will adopt these metals to commercial applications when their performance is adequately proved. Price and price comparisons \vi11 ahvays be an important consideration, but life, maintenance, down time, and similar economic factors will play a n important part and will he considered in cost comparison of installed items. Certainly in ore beneficiation and estraction. economies \vi11 be realizcd. Preparation of the metals in pure form can stand a lot of improvement, especially if the metals can be produced by continuous rather than batch processing. Improvement in fabrication techniques \vith less generation of scrap, and increased recycling of scrap will be important. No doubt, new techniques and equipment will be required. Then, and last but not least, economics will be improved when volume output reaches the point ivhere amortization of research and development costs and capital expenditures are not such a burden on the unit pound sold. How can these things be accomplished? T h e prime ans\\z'er lies in hard work, backrd by sufficient quantity of research funds. Beyond some undetermined point. the new metals. industry has to mature over a period of time because a basic amount of information and knowledge mmst be obtained before the next step in a long series is taken. How and lvhen w7ill these things be realized!' I t is difficult to say that one metal should he singled out and emphasis placed on it. Insufficient kno\vledge exists today for such a stand to be taken. There is plenty of reason to believe that each metal will serve growing environmental demands most unique to its capabilities, so that all. or many of them, \vi11 share in the over-all growth. Therefore. in this race, several entrants must be backed, and we must be alert to change. Before too many years, these metals certainly will he removed from the less common list and placed among the materials readily available for engineering purposes. literature Cited (1) Amer. AMetai .liarket ( A u g . 26, 1960). ( 2 ) National Academy of Sciences, \.trashington. D. C.. Committee on Refractory hfetals, MAB154-M(1), October 19%. ( 3 ) Rare 5letals Handbook, Reinhold, Ne\v York, 1954. ( 4 ) U. S. Bureau of Mines, Washington 25, D. C., Bull. 5 8 5 , 1960. ( 5 ) Zbrd., Mineral Industry Surveys. RECEIVED for review September 15, 1960 ACCEPTED December 2, 1960 Division of Industrial and Engineering Chemistry. 138th Meeting, ACS: New York, N. Y., September 15, 1960. VOL. 53, NO. 2
FEBRUARY 1961
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