THE ROLE OF THE NATIONAL METALLURGICAL

LABORATORY IN RESEARCH AND DEVELOPMENT

OF LIGHT METAL INDUSTRY IN INDIA

B. R. N i jhawan

RESEARCH in metals and their alloys now presentsa wide spectrum ranging from experiments onlaboratory bench scale based on speculations

arising out of applied or fundamental hypothesesto organized pilot plant scale Investigations andheavily financed industrial prototype trials. Onone end of this spectrum lies a purely academicappeal answering human insatiable curiosity and onthe other end is research in applied fields and betweenthe two prevails a broad-based field in which the roleof a young industrial laboratory, such as the NationalMetallurgical Laboratory, covers diverse research anddevelopment fields in ferrous and non-ferrous metalsincluding light metals and their family of alloys ; suchdevelopment work in the latter fields has, of necessity,been pioneering in scope so far at the National Metal-lurgical Laboratory located in the Steel Town ofJamshedpur and yet considerable ground has beencovered. Whilst the metallurgy of heavier metals rapidlydeveloped with the recovery of those relatively easierto smelt, the lighter metals such as aluminium andmagnesium could he produced only in the 19th century.The Second World War in its train gave a tremendousstimulus to the development of light metals and theiralloys both in production targets and range of servicerequirements. In the case of India, if the hard core ofthe Second Five Year Plan has centred round thedevelopment of iron and steel industry, the industrialgrowth of light metals and their alloys may well claimthis place of pride during the Third Five Year Planwhose outlay has now been more or less fully for-mulated. In the field of aluminium, annual target capa-city of 82.500 tons by 1965-66 is expected to beachieved and it is now being discussed that it mayfurther be stepped up to over a lakh tons of aluminiumper annum. The production of magnesium -a metalas light as it is important in this supersonic age, doesnot yet figure in our Third Five Year Plan-a lacunawhich must be rectified at the earliest. The production

Dr. B. R. Nijhawan, Ph.D., F.I.M., F.N.I., Director, NationalMetallurgical Laboratory, Jamshedpur.

of other light metals such as titanium, lithium, etc.,despite their "classic" resources in India judged frommetallurgical quality standards and reserves established,also does not figure in our Third Five Year Plan, re-presenting gaps that have also to be bridged. Beryl-lium, another light metal, resources of which are abund-ant in India, is now attaining its place of pride in ourPlans, being indispensable in nuclear technology in itsapplications as a moderator and reflector of high velocityneutrons in nuclear atomic reactor, The same can besaid of zirconium with its rich indigenous resourceswherein valuable work has been done at the IndianAtomic Energy Commission on research into the pro-duction of hafnium-free zirconium for nuclear use as afuel canning material.

The scope of research and development work on lightmetals and their alloys has necessarily to be linked withour indigenous resources in respect of these metals. Toan Indian student of Metallurgy, the extent of suchresources and limitations imposed in respect of theirmetallurgical characteristics, would be well known. Thegeneral position in outline in respect of indigenous re-sources may he reviewed as follows and as shown in theaccompanying map (Fig. U.

Bauxite

Deposits of commercial importance of bauxite arelocated near Katni, Bilaspur, Mandla, Sarguja andJashpur in Madhya Pradesh and in Belgaum (Mysore),Thana. Koria and Kolhapur in Maharastra and GujratStates. Bauxite deposits in Ranchi and Singhbhumdistricts of Bihar are fairly large. The States of Kashmir,Madras (Salem) and Orissa also possess good depositsof bauxite. A rich belt of bauxite also occurs in theVindhya mountains from where the Hindustan Alumi-nium Corporation Limited will receive the supply ofbauxite for their 20,000 tons new smelter plant nowbeing installed at Pipri in U.P. The production ofbauxite in 1959 was 126,000 metric tons as against139,000 metric tons in 1958. During 1959, 67,000metric tons of bauxite were used in producing alumina

32

Fig. I.

M.u-ITE 4

lE RYA .

DOLOMtt -0

iLMf N^TE•• • S

•I JMINVM PL ANTS (tEIST NG/-•-^

•LUMINVM FL.Ni% (PNOPOSEO)•-•^

LIGHT METAL INDUSTRIES I RESOURCES-LOCATION IN INDIA

flG.i

33

as against 55.000 metric ions in 1958. The export.luring 1959 was 24,000 metric tons, an increase of'nearly 3,000 metric toils over the previous year. Thereserves of' all grades of bauxite in India have beenestimated at 250 million tons. 1-ligh grade bauxite depo-sit is estimated at 25 million tons 150' .'0 AI.,Oaand over).Indian hauxites present certain chemical peculiarities. InNorth and Si nth America. nearly all bauxites are tri-hydrates, i.e., with three molecules of water to onemolecule of alumina. In Europe. bauxites are generallyof monohvdrate type. generally high in iron oxide- InAfrica and Indonesia, hauxites are of' trihydrate type,similar to that in America. Although Indian bauxite ismainly of' trihydrate type. varying amounts of m0110-hydrates are often found mixed with Lrihydrate. Thislack of' uniformity applies to most of the constituents ofthe Indian bauxite. such as. water and iron oxide (whichvaries from 2 to 30 per cen(). titanium (which variesfrom 1.5 to 12 per cent), silica, etc. which also show awide variation. In relation to American hauxites. Indianbauxites require finer ,grinding. better and more concen-

325.000 metric tons in 1959. Birmitrapur and Panposhin Sundergarh district of Orissa accounted for 97 percent of the total output. Reserves of' rich dolomitedeposits of' Birmitrapur are estimated at 252 milliontons at a depth of' 150 ft and 84 million tons thereofare of' high grade stone. Apart from this, 5 million tonsat Sanlbalpur and 25 million tons in Durg district havebeen estinurted.

Titanium and rare-earthgroup of metals

in India, large quantities of' ilmcnitc occur in thebeach sands of' Kerala Stale. The production of iline-nite during 1959 was 303.000 metric tons. 95°,r, of' theoutput is recorded from Kerala State. Indian reservesof ilmcnitc in the form of beach sand alone totalbetween 300 and 350 million toils.

Typical analyses figures of Indian ilmenites are givenhelovv :

trated caustic soda solution to dissolve it, and three Quilon, Manavalakurichi,

times more filtering capacity per unit of alumina. As Travancore Travancore

the aluminium content 01' Indian bauxite is also less, SiO, .. 1'40 1'53bauxite needed per unit of aluminium is 25 per centhigher in India than in Canada or U.S.A. AI,O„ n.d. I' I I

Fe,O3 ... 24' 80 14' 17Magnesite FeO ... 9'70 26'71

In India. inagrlesitc deposits are known to occur in the Nino ... n.d. 0 38

Salem district of Madre, and I lassan district of Mysore. NIgO ... n. d. 1.01Sonic deposits are also reported in the Kurnool district Ca0 ... n.d. nilof' Andhra Pradesh, 'I irueltirapalIt district of Madras. Tit:) . 60'30 53'56Dungarpur in Rajasthan and Singbhum district ofBihar. Recently deposits of' nlagrtesite have been

.

Cr,O;,

...

... 0'14 0.09located at Alnnorah in Garlwxal area in U.P. The 0126 0'03production of magnesite was 157.957 metric tons in PO 0' 17 0'201959. As much as 98 per cent was reported frontSaleni district of Madras State. Estimated reserves ofmagnesite in Salem district of Madras are 82'5 trilliontons at a depth of 100 ft and 330 million torn at500 It. The reseres of' high grade magnesite in Almoradistrict are estimated at about 4 million tons.

The present world production of magnesite is of theorder of' 2 million Will, per annum- of which 30 per centcomes from U.S.A_

Dolomite

Dolomite deposits are known to occur in Orissa andMadhya Pradesh. In Orissa, dolomite deposits of-com-mereiat interest are found in Panposh and Birmitrapurin Sunderg . arlt district . Good deposits also occuraround Ciangpur , Amghat , Khatkurhahal . Lanjibernaand 13eldIIi . Dolomitic Iimestone deposita are found atPutada near Chaibasa in Singhhum district. InMadhya Pradesh , dolomitic deposits occur aroundBlialaghat . Gw.rir. Rupaund in .lahalpur district andnear Akaltara and Jairamnagar in 13ila,pur. Otherdeposits of' dolomite and dolomitic limestone are foundin Rajasthan . Andhra Pradesh . Mysore. Bombay. Kash-mir, tJ,P. and Punjah . The output of dolomite was

Rutile, the other important titanium mineral, isderived from Travancore beach sands and also foundin Punjab, Kadavur in Trichinopoly district. Madras,Singhhhum and Dhalbhum districts in Bihar. Titani-ferous magnetite is found in Singbhum and Mayur-bhanj districts containing up to28% TiO,. The aluniin-ous and ferruginous lateritcs of India contain highamounts of titanium. If aluminium is extracted fromthe aluminous laterite,. the sludge obtained duringrefining should provide a potential source of titaniluil.The most important deposits of titanium mineraIsworked in India lie in Travancore, on the South-westCoast, in five stretches along the coast, viz., Nindakara(north of (triton), Anjengo-Varkala (south of Quilon),Kovilam (south of' Trivandrum). Mitttam Pudur (nearColachel) and Cape Comorin-Liparum (on the easterncoast of Tinnevelly district). These beach sands ofTravancore are a mixture of' mineral sands With aspecific gravity varying from 2'3 of silica to 4 9 ofmonazite and contain quartz, monazite, rutilc. zircon,garnet and ilmenite. These sands are derived throughweathering of igneous rocks and in some regions haveyielded lateritcs, while in the other, sandstones, as at

34

Varkala. The mineralogical composition of the beachsands is given below :

Manavalalcurichi Nindakara

00/o^o

Ilmenite ... 75 - 80 80Zircon ... 4-6 4-6Sillimanite .. 2-4 3-5Rutile ... 3-5 4-5Garnet ... 3-5 less than 0'5Silica ... 5-7 4-5Monazite about 1 0'5 to 1Other minerals lessthan0'1

The analyses of pure monazite (India, Travancore)are given below :

India,Travancore

Thoria ThO2 ... 811Ceria Ceg03 ... 30.6Lanthanum oxide, La_O3 ... 15'7Praseodymium oxide, Pr2O3 ... 2'9Neodymium oxide, Nd,03 ... 10'5Europium, Gadolinium and terbium oxides 0.7Yttrium oxide, Yt2O3 ... 0'4Dysyprosium, holmium, erbium, ytterbium

and lutecium oxideLime, CaO

0'l

Alumina A1203 1.0Iron oxide, Fe2O3Uranium oxide , U3O„ ... 0'3Phosphoric acid, P205 ... 26'2Silica, SIO, ... 2'4Loss on ignition, H2O ... -

Beryl

In India, beryl is found in Ajmer-Merwara (Rajasthan).It is also found in the mica mines of Hazaribagh andNellore districts. The mica deposits of Udaipur alsoyield certain quantity of beryl.

India was once the world's only source of berylsupply. Production in India was 1'15 thousand metrictons in 1957.

Zircon

In India, zirconium ore is obtained as a by-productin ilmenite concentration process. Separate statisticsof production are not available. India is one of thelargest producers of zirconium in the world.

Naturally therefore, in consideration of our indige-nous resources of light metals, investigations at theNational Metallurgical Laboratory have related to andare projected to cover the treatment of Indian ores oflight metals through suitable pyro- and electro-metallur-gical techniques. Extensive work for the treatment andhandling of bauxite ore for the Rihand Project is beingplanned. Thus the general theme in logical sequencewould relate to extraction processes based on pyro- andelectro-metallurgical technique of these metals, to befollowed by methods of production of their optimum

alloys, in some cases incorporating micro-additions ofrare-earth group of metals in which Indian resources areabundant and ending with studies of fabrication charac-teristics and properties of such alloys. Whilst epoch-making discoveries are not claimed in these fields at theNational Metallurgical Laboratory, progress in diversefields has been very steady and rewarding, whilst muchmore remains to be accomplished in many fields. Oneof our main aims would be to further strengthen closeconnections between research and development activitiesof National Metallurgical Laboratory and Indian lightmetal industries now coming into their own during theThird Five Year Plan. In this connection, it may not beout of place to mention that whilst firm collaborativeassociations have been established between research,development and pilot-plant activities of the NationalMetallurgical Laboratory and the Indian ferrous metal-lurgical industries, the same is now taking shape in sofar as light metal industry in India is concerned. Underthe impact of our Five Year Plans these collaborativecontacts will be further consolidated and expanded tomutual technical advantage. At the same time, there islittle doubt that in the midst of a mass of data ondifferent problems that confront us needing allotment ofpriorities. treatment on the basis of "ominum gatherum"will result in an unmanageable collection of items. Assuch, efforts at the Laboratory have followed the oldadage choosing limited objectives in the present contextof our industrial development. At the same time, it willbe recognised that some of our mineral wealth is rela-tively of poor grade in respect of impurity contents andas such processes standard elsewhere cannot be adoptedad hoc under Indian conditions. At the same time,these objectives open new horizons before us in exploit-ing Indian resources of light metals to the maximumnational advantage. It is on such basis that projectedresearch and development work has accordingly beenaligned with a view to developing potential uses of rare-earth group of metals in different metallurgical fields,utilisation of titanium values contained in Indian ilme-nite and titaniferous magnetites, etc. It has to be con-ceded that the scope is as vast as it is complex both fromapplied as also fundamental angles-in the latter field.Concentrated attention will be devoted to dispersion-strenthened as also precipitation-hardened light alloysand study of age-hardening mechanism in these alloys.It will also be the aim to avoid duplication of work onlight metals and alloys of nuclear and atomic interestand applications which will be left to the purview ofresearch organisations of the Indian Atomic EnergyCommission. Work on purification and production ofsemi-conductor elements such as germanium, selenium,silicon, etc. may be left for immediate studies to oursister laboratories of the Council of Scientific and in-dustrial Research such as the National Physical Labora-tory and the National Chemical Laboratory. Studiesof pyro- and electro-metallurgical extraction techniqueson indigenous ores for light metals and alloys willloom largely in the immediate programme of our deve-lopment work. Some of the work in these directionsundertaken at the National Metallurgical Laboratorymay be now outlined.

35

Titanium

The addition of titanium to the family of light metalshas drawn much attention by virtue of its attractiveproperties such as excellent corrosion resistance, highstrength weight ratio and retention of strength atmoderately elevated temperatures. As a first stepconnected with the recovery of titanium. investigationswere taken up for the chlorination of ilneenite. Aprocess for the preferential chlorination of iron frontilmenite has been worked out. The process consistsin the removal of almost the entire amount of iron byselective chlorination with HCI ,as at 900 1.000Cleaving a titania-rich residue that can be chlorinatedwith chlorine and a reducing agent to produce titaniumtetra-chloride. It is expected that the process mayoffer scope for reduction in the cost of titanium tetra-chloride thus produced.

A systeniatic study on the production of titaniumsponge by reduction of titanium tetra-chloride withmagnesium was taken up and a unit producing one lbof metal was set up. The effect of rate of additionof titanium tetra-chloride to the nlagnesiurn andinfluence of using more nlagnesiunl than theoreticalneeds were studied. In order to stop even slighthydrolysis of titanium tetra-chloride from the distilla-tion assembly to the reduction set-up, the distillationassembly as made a part of the plain reduction unit.The apparatus worked satisfactorily. Titaniutll wasrecovered from the reaction mass by acid leaching.It is now proposed to extend this work using sodiumas a reducing agent and to set up a larger assemblycapable of producing I(1-15 lb of titanium per batch.It is expected that the requirements of' our researchdevelopment progranlnle may he thus met from thisunit.

Besides the chlorination of ilnlenite and the produc-tion of titanium, systematic studies have also beenundertaken on organu-metallic salts of titanium andtitanium tetra-iodide. It has been observed that thetitanium oxalate is unstable and from a solution oftitanic acid and oxalic acid, it precipitate of titanyloxalate is thrown down on addition of absolute alcohol.Various factors like temperature of solution, volumesolution, acid, etc. have been studied. It has beenobserved that on heating litany! oxalate in an inertatmosphere, sub-oxides of titanium are formed.

Titanium iodide is of interest for the production ofpure titanium metal by the decomposition of thetetra-iodide. In fact the dissociation of titanium iodidehas been used for purifying the crude titanium sponge.A process for the preparation of' titanium tetra-iodideusing titanium dioxide as a raw material has beendeveloped vOhich consists in heating alunliniunl powder,iodine and titanilun dioxide in a sealed, evacuatedglass bomb. The process gives a mixture of titaniumtetra-iodide and unreacted aluminium iodide and aftersubsequent purification. the titanium iodide could beused for making pure metal by Van Arkel's process.The process for slaking titanium iodide as a rawmaterial for producing high purity titanium may beconsidered an inlprovcnlent since much cheaper raw

material, i.e. titanium dioxide, is used instead of crudesponge.

Alumino-thermic reaction for the pro-duction of aluminium -titanium alloys

Reduction of titanium dioxide by aluminium inpresence of energisers yielding aluminium-titaniumalloys has also been studied. It was observed thatthe reduction of titanium dioxide with alunliniunl byusing preheated reactants in presence of cryolite pro-duces an aluminium-titaniumn alloy containing 19"titanium. It was not possible to attain higher titaniumconcentrations. Use of energisers such as bariumperoxide or potassium chlorate were made for theattainment of higher temperature and to increase thetitanium content in the alloy. Theoretical calculationswere made to get an idea of the amount of energisernecessary to obtain suitable temperature. A studyof factors Such as variation of aluminium and bariumperoxide additions and admixture of various amountsof calcium oxide and particle size of alunliniunl andrutile was made to ascertain the optimum conditionsfor the reduction of rutile. Presence of 55% bariumperoxide of the charge and admixture of 10",, calciumoxide were found to favour the reaction. Results ofthe experiments with decreasing amounts of aluminiumwith a view to increase the titanium content of alloyshowed that an alloy containing 62% titanium canhe prepared when aluminium addition was 70"0 ofthe rutile. Further decrease of aluminium in thecharge to below 65 of rutile resulted in a slagwithout any sell;lration of the alloy. Effect of differentparticle size of aluminium and rutile indicated thatoptinlunl results were obtained with 140 i 170 BSSmesh size.

Removal of aluminium from aluminium-titanium alloys by catalytic distillation

Gross's process for the production and refining ofaluminium by sub-halide formation may show thepossibility in as much as an alumino-thermic alloy oftitanium and aluminium may he used as a raw materialfor the production of titanium by removing thealuminium content of the titailiunl alloy by catalyticdistillation :

2 Al (in the alloy) ' AICI3- 3AICI.Aluminium trichloride reacts with aluminium in the

Al-Ti alloy, forming the nlonochloride which maydistil out and re-form as aluminium and trichloride atlower temperatures leaving behind the unreactedtitanium, Attempts are also being made to study thedisproportionate kinetics of lower halides of titaniumto study the feasibility of producing titanium fromscrap and alloys. An assembly has been set up tostudy the reaction between titanium tetra-chloridevapours at various patrial pressures and titanium metalkept at various temperatures using argon as a carriergas for titanium tetra-chloride.

Work on the production of aluminium powder ofhigh purity for different needs has progressed

36

successfully and detailed plans are being worked out toset up a larger unit. Investigations have also been takenup to produce aluminium powder suitable for alumino-thermic reactions by granulating and blowing. It hasbeen observed that the powder produced by blowingthe molten metal flowing through gravity yields thepowder suitable for alumino-thermic reactions. Asystematic study on the effect of rate of flow ofmetal. temperature of molten metal, the pressure ofair, etc. is under way.

Magnesium

In this era of "missiles". weight saving in alloysposes it problem of utmost importance. Magnesiumand its alloy have largely contributed towards fabrica-tion of light structural components for achievement ofspeed and fuel economy. Existing processes for theextraction of mannesium can be broadly classified intotwo groups, namely. electrolytic and direct reductionprocesses. The electrolytic processes are fundamentallysimilar except in the nature of the cell feed and thecell characteristics. The fused salt technique employsanhydrous magnesium chloride as its cell feed.

Direct reduction processes generally employ reduc-tants such as carbon, calcium carbide, ferro-silicon,aluminium-silicon, aluminium, etc. Among the directreduction processes, two basic processes, namely,Hansgrig's carbo-thermic process and Pidgeon's silico-thermic processes were placed on it commercial scaleduring World War 11. In the carbo-thermic process,the reaction between a mixture of magnesium oxideand carbon is carried out at 1,700"C in an arcfurnace when carbon monoxide and magnesiumvolatilise into a condensation chamber. The volatileproducts must be shock-cooled to avoid a reversalreaction which would result in the formation of carbonand magnesium oxide as follows :

MgO + C --:CO + MgThe magnesium so obtained is in a powder form and

is carefully remelted for further use. Silico-thermicprocess consists in the reduction of calcined dolomitewith ferro-silicon under a vacuum with the followingreaction taking place

2 (CaO. MgO) -i- Si=(CaO).,. SiO., --r- 2 MgIncreasing interest is now being evinced in the

development of suitable direct reduction processesin view of the operational advantages of theseprocesses. A few direct reduction processes runon a continuous basis are under development inGermany and in U.S.A. A recent development inthe field of silico-thermal reduction of dolomite whichshows promise in extraction metallurgy of magnesiumis the "Magnetherm process" patented by Le Magne-sium Thermique Magnetherm, France. The processconsists in the electro-thermal reduction of calcineddolomite with ferro-silicon under a vacuum in themiddle of a liquid pool constituting time, silica andalumina. In the light of the modern developmentstowards direct reduction processes and the inherentadvantages embodied therein, studies were undertakenat the National Metallurgical Laboratory for the

development of silico-thermal process utilising indige-nous resources. Advantages offered by Pidgeon'sprocess are that the raw materials do not requireelaborate proceseing and the magnesium metal obtainedis of high purity. In respect of raw materials also.India has vast resources of dolomite spread over itsvarious States and the best known occurrences arein Orissa with reserves of over 252 millions tons.Laboratory scale studies were undertaken at theNational Metallurgical Laboratory and the factors sofar studied include temperature of reduction, effectof particle size of' reactants, effect of catalysts onthe reaction kinetics, briquetting pressure, grade offerro-silicon, condensation characteristics of magnesiumvapours, etc. On the basis of these studies. a smallunit was designed and fabricated at the NationalMetallurgical Laboratory. A 6" dia, heat resistingalloy retort was employed embodying a condensationchamber with arrangements for deflecting alkaliesseparately into a different zone to eliminate firehazards. Magnesium metal obtained in a massivebright crystalline form analysed as follows :

Cd ... tracesMn ... 0.025%Cu 0.002%Al ... 01002%Zn ... 0'003%Mg ... Remainder

A pilot plant capable of producing 25 lb of magne-sium metal per day is now being established. A flow-sheet of the process is given below :

Dolomite

Calcination-Grinder(CaO.MgO)

Ferro- Catalystsilicon

Mixer

Residue

GBriquetting

IVacuum furnace

Magnesiumcrystals

The pilot plant will cover an area of 2,400 sq ft con-stituting the following principal equipment :

1. Kiln for dolomite calcination,Grinders for size reduction of calcined dolomite.ferro-silicon and catalyst,

3. Briquetting machine,4. Vacuum furnaces with accessories.Besides magnesium production, it is also proposed to

incorporate a magnesium powder making unit in thispilot plant. Magnesium metal has been successfullypowdered and different grades having bulk densitiesto rigid specifications have been prepared. It has

37

been observed that during the process of powder-making the oxidation of the surface to an extentcould not be ordinarily avoided. Therefore, powder-ing under an inert atmosphere to eliminate surfaceoxidation has to be undertaken. Development ofmagnesium production in the country should go along way in meeting the ever-increasing demands forthis light metal for multitudinous types of light alloys.

Work has also been taken up for the production ofmagnesium from sea-water magnesium chloride.Messrs Tata Chemicals Limited have been supplyingus the crude magnesium chloride for this purpose.The investigation has been divided into two parts

1. Dehydration of the hydrated magnesiumchloride.

I Electrolysis of dehydrated magnesium chloridein the electrolytic cell designed in thelaboratory.

Dehydration is carried out in shelf drier fitted withstirring rakes fabricated in the laboratory. Lumps ofhydrated magnesium chloride containing about 6-7molecules of water are broken up into small piecesand passed through a range of slowly rising tempera-ture in a current of hot air. The dried productcontains about 1'5 mols of water per molecule ofmagnesium Chloride.

Several experimental cells have been tried. The cellbody is used as cathode with ceramic hood to preventaction of chlorine on the metal produced. Initialdifficulties have been to a large extent overcome.Work is now directed to modification of cell design tomake continuous running ol- the cell possible forelectrolytic magnesium production.

Aluminium - magnesiumalloys

Alloys of aluminium with magnesium are characte-rised by their high resistance to corrosion, superiorhigh temperature properties and good machineability.These are extensively used for structural members inaircraft and marine vessels, brake shoes, etc. ButAl-Mg alloys with magnesium content higher thanabout 6°0 are not normally hot-workable, with theresult that the benefit of these excellent properties ofthe higher magnesium content alloys is not available inthe wrought form. Several authors have observed thatincorporation of cerium or misch metal in alumi-nium and magnesium and their alloys results in grainrefinement and improvement in their elevated tempera-ture properties. No tangible work has, however, itis understood, been reported on the alloys of the AI-Mgsystem. In view of expected and current requirementsof these alloys and utilisation of indigenous aluminiumand magnesium. it was felt that high magnesiumbinary Al-Mg alloys could be made readily hot-workable through making use of well-establishedeffects of addition of rare-earth group of metals tothese difficult alloys. A systematic study was, there-fore, initiated on the effects of the addition of ceriummisch-metal to binary Al-Mg alloys containing magne-sium contents of 7- 10°0.

Cerium misch-metal was added to these alloys up to501o and its effects on changes in their microstructure,tensile strength and workability have been studiedunder controlled conditions. It has been seen thatmicrostructure of both as cast and wrought specimensundergoes considerable changes with additions ofmisch-metal. The initial AI-Mg phase, present in theuntreated alloys, is replaced by a new cerium contain-ing phase which could be due to the formation ofeither AI44Ce or Mg9Ce (or both). With higher misch-metal contents the cerium phase predominates.

The tensile strength of these alloys was reduced atfirst till the misch-metal content rises to 2-3°';, afterwhich it again increased (as per Table 1 given below).The hot-workability of all the Al-Mg alloys (7-9°' Mg)was distinctly improved by additions of misch-metal,while in the case of AI-104- Mg alloy, considerableimprovement was observed in physical properties onlywhen 2-3°o misch-metal was added. The tensilestrength of wrought alloys was also distinctly improvedby increase in misch-metal contents as also hard-ness values apart from appreciable improvement inhot-workability.

TABLE I

Tensile strength of Al-Mg allots

SerialN o.

" Misch- As castmetaladded Mg -7%. Mg-S% Mg-9;o

tans/sq inch)

Wrought

Mg-10% Mg-7%

1 0 915 1010 10'5 10.6 23-52 1 7'7 9'1 8'9 7'7 25'43 2 6* 2 8'S 7'9 6'6 26.74 3 5-2 8-4 7'9 6'9 28.05 4 6'6 8'7 8'1 8.3 29.06 5 8'05 9'6 8'7 9.8 30.0

It is proposed to complete the work on the presentseries of alloys by studying their corrosion resistance(salt spray and atmospheric), as also other physicalproperties, such as, fatigue and high temperature creepresistance, etc. Fundamental studies will also becarried out on the crystal structure of the new phasesobserved, for their identification, and on the ageingcharacteristics of these alloys.

Aluminising of ferrous materials

Work under this head, although not falling distinctlyunder light metals and alloys, is referred to here inoutline on the possible opening for indigenousaluminium. Aluminising of ferrous materials is aimedat replacing galvanising which involves import of about30,000 tons of zinc for protection of ferrous materialsagainst atmospheric corrosion and also to impart acertain measure of oxidation resistance and resistanceto sulphurous atmospheres.

Of the various methods of coating steel withaluminium, the hot-dip process is the most versatilein its scope and applications. It consists in degreasingthe steel base with either alkaline or solvent degreasers,

38

pickling in sulphuric or hydrochloric acid, washing,drying and suitably fluxing prior to immersion in itbath of molten aluminium.

Work done at the National Metallurgical Laboratoryrelates to the use of different types of fluxes priorto aluminising. Pilot plant trials of the patentedprocess are now in progress. Initially work on hot-dip aluminising of wire has been undertaken. Fig. 2shows a general view of the Pilot Plant established atthe National Metallurgical Laboratory.

Pole line hardware for Posts and Telegraphs Depart-ment was aluminised and given field tests. Aluminisedhardware is superior to galvanised one with respect toits atmospheric corrosion resistance. Several miles ofaluminised steel wire has been supplied to the GeneralManager, Posts and Telegraphs workshops, Calcutta,for field trial on telephone lines. Fig. 3 shows coils ofaluminised wire. Tuts carried out at British Iron andSteel Research Association's Coating Research Labora-tory in U.K. on our aluminised wire samples are highlyencouraging. Their report indicates :

(a) effective preparation and prefluxing as there isno sign of failure in alloy layer

(h) wiping leaves it thin coating without decreasinglustre

(c) coating thickness of 0'6-l'5 mils is obtained(d) good wrapping properties are observed.

Coating weight

Representative 12" samples were tested for coatingweights as per ASTM A 428 58T Stripping test whereinit substantial weight of coating is dissolved in 201/),'sodium hydroxide solution at 90"C and finally in cone.hydrochloric acid in one to three cycles. Wiped coat-ings had 220 350 mgms, ft of aluminium on 10 SWGwire. Coatings obtained by use of sizing die had acoating weight of 330 400 mgms ft.

Salt spray corrosion test

Accelerated corrosion test as per ASTM BI17-54Tshows that an increase in coating weight from 220mgms; ft to 350 mgms; ft in wired coatings decreasescorrosion rate from 65 mgms ft 120 ltrs to 15 mgms ft120 hrs. Corrosion rate of coatings obtained by useof sizing die is only around 10 mgms, ft 20 hours.

Soundness tests

Coatings behaved N,,cll in Preece test withstanding fivedips and in 15%` HNO;; test wherein very little gas wasevolved in 5-6 hours.

Electrical resistance

Good aluminised steel wire has an electrical resistancearound 24 ohms mile and will he suitable for telephonelines.

Work on joint design and soldering of aluminisedwire is in hand to enable utilisation of this product byPosts and Telegraphs Department.

Fig. 2.

A view of the Pilot Plants set up at the National MetallurgicalLaboratory for hot- dip aluminising of ferrous materials.

Fig. 3.

Coils of aluminised wire according to National MetallurgicalLaboratory patented process on hot-dip aluminising

of ferrous materials.

39

Mechanical propertise

Tensile test results on M.S. wire in the uncoated,coated and drawn conditions are given below :--

Sample Dia. in. Max. stressT.S.I.

Elonga-Lion°,,

Uncoated annealedM.S. wire ... 0'125 30-93 18'75

Hot-dip aluminisedwire ... ... 0'123 33.82 12.5

Cold-drawn alumi-nised wire ... 0116 46.46 625

Al-Alloy bearing

Considerable work has of late been reported on solidaluminium hearings from many parts of the worldincluding U.S.S.R. and U.S.A. Typical aluminiumbearing alloys developed in General Motors Corpora-tion (by Alfred W. Sehulchter) consist of 0'5-5°^ Si ;0'2-2°%o Cd ; 01 0'15";, Zn, and the rest Al plus theusual impurities. The alloy is hardened at 482-565 Cfor 8-15 hrs. Bearings of the alloy are ductile andstable against shocks. need no supporting shell, donot seize. and arc stable against oil corrosion.

From it study of the ternary diagram of Zn-AI-Cu anapproximate composition of 60 : 34 : 0 was selectedwhich Was supposed to consist of two constituents.CuAIL an intermetallie compound and a solid solutionof zinc and alumrnrunm. A study was made on meltingin different kinds of furnaces. castability in sand andmetal mould, thermal treatment, anti-frictional pro-perty, wearing property. thermal conductivity andmicrostructure. Bonding characteristics with gun-metaland steel were also studied to find out its suitabilityfor backed hearing.

Electric pot frurnace was found very suitable formelting this alloy. The charge was covered withgraphite powder to protect the surface from the atmos-pheric oxidation. After the alloy had melted themolten bath was scavenged with dry nitrogen gas.

The alloy was poured in different types of cast ironmoulds. It produced very clean and flawless ingotsurface. In sand castings also, it produced equallyuniform surface. free of blow-holes. The alloy hadgood casting properties and could he sand cast givingit smooth surface equal to that of permanent mouldcasting.

The micro-structure of the chill-cast alloy consistedof two phases. The effects of annealing on the distri-bution of phases acre studied and it was found thatspecimen annealed at 400 C showed structure similarto the usual tin-base habbit metal. The micro-hardnessof the hard phase embedded in the grey matrix of asolid solution of zinc and aluminium showed thehardness of 380 V.P.N. and the matrix having ahardness of 67 V.P.N. The overall hardness of thealloy Was found to he 95 B.H.N. The alloy showedcomparatively loth wear and coellicient of frictionunder lubricated conditions.

Continuous casting of fight metals and alloys

Work on continuous casting of light alloys hasrecently been taken up at this Laboratory. A smallexperimental unit was designed and fabricated inthe Laboratory for casting I.," products. Mechanicaldrawing arrangement was provided. A double-walledwater cooled copper die (I I" I.D. by 2" long) wasdesigned and fabricated with the exit water fallingdirectly on the cast rod in the form of a spray. In thebeginning difficulties were experienced due to waterrising into the annular space around the semi-solidrod, with water circulating at it rate of 3,500 cc nunand a rod drawing rate of nearly 18 min. When Alwas poured in the graphite pot preheated to 350.0,the cast rod could be drawn continuously. Becauseof the inherent difliculties in the drawing arrangement.it is being redesigned for further experiments on thecontinuous casting of the light metal and alloys witha view to study their metallurgical characteristics,effects of rate of cooling, rate of drawing, etc.

Aluminium-silicon alloys

Alloys of al Lint ill unl-srliCOrl have today attainedconsiderable commercial importance in their ,side usefor multifarious applications and as much as 80"0 ofthe world's production of light alloy castings has beenestimated to belong to the family of these alloys.Comprehensive investigation was undertaken at theNational Metallurgical Laboratory on the preparationof aluminium-silicon alloys by the alunlino-therlnicreduction of quartz. Based on thereto-dynamical andexperimental data obtained. the reduction of quartzhas been observed to depend upon a number of' factors,the chief of which are particle size of quartz. amountof cryolite in the charge, temperature of the reactantsand holding time. Physical properties of the alloysexperimentally made by this method have been deter-mined and compared with the physical properties orcorresponding alloys produced experimentally hereby direct alloying of the two metals. This comparisonyielded identical results in the two cases. Referenceto the general economics of this process has also beenmade. It has finally been stressed that this methodcan he usefully exploited for commercial applicationsin countries dependent on silicon imports and richin bauxite and quartz, such as India. The processis simple and can he easily worked without anycomplicated prior treatment of raw materials. Thetemperature necessary for alumino-thermic reductionis easily attainable and therefore does not need anycostly equipment. The reduction and alloying of sili-con can be completed at one stage. It is, therefore,recommended that this process may advantageouslybe adopted under Indian conditions wherein foreignexchange has to he spent on import of metal silicon.Aluminium-silicon alloys are used for pistons in theinternal combustion engine and more recently for thecylinder block also. The high wear resistance, goodcasting properties, and high corrosion resistance makethis alloy suitable for these purposes. Aluminium has

40

very little solubility for silicon and so the micro-structure of these alloys consists of it matrix ofalunlinilnnl in which silicon is dispersed. Ordinarilysilicon exists as coarse particles and this adverselyaffects the resulting properties. To improve the distri-bution and size of silicon particles the alloy is modifiedwith sodium or phosphorus. Work is being done inthis Laboratory on modification of aluminium-siliconalloys by other elements and a process has been foundout which greatly improves the size and distributionof the silicon particles. The fluidity of the alloy wasalso greatly improved at the same time. This is shownin Figs. 4 and 5. Fig. 4 is the fluidity pattern obtainedwith an alloy modified with our nucleant and Fig. 5that obtained by the addition of phosphorus.

In this connection work on the production of`alunliniunl-silicon alloys by direct smelting of clays,etc. will also be taken up along lines indicated by workdone chiefly in the U.S.A. by 0. C. Fursman andL. H. Banning at the U.S. Bureau of Mines ; a widerange ol'crude Al-Si alloys (Al 15-55%) were produced bythe smelting of clays or similar Al-silicate raw materialsin a pit-type 3-phase C-lined are furnace. 1-loggedfuel or wood chips were used as the major source ofC in the charge. Suggested potential uses of the crudealloys are as hardeners for producing high Si-Al alloys,as reducing agents in the ferrous industries and asraw materials for aluminium production.

Beryllium

This brittle metal, difficult to extract economically--once called the "world's number-one metallurgicalheadache" owing to its high melting point coupled withits high vapour pressure at temperature little above themelting point and its apparent toxicity- --seemed to havereached its limit of application. Then sixteen years agoberyllium in the atonic energy field became the newdirective for research into industrial beryllium. Themetal was seen to be of great value in reactors, themost effective practical element of low atonic weightwhich could serve as moderator capable of "slowingdown" high-velocity neutrons. Moreover, berylliummetal is also superior to other materials as a reflectorof neutrons.

In India, Rajasthan produces very rich beryl orewhich contains as high as 12'5 to 13'5 per cent ofberyllium.

Beryllium is used industrially in the manufacture ofalloys, specially those of copper, nickel, cobalt and iron.Heat-treated copper-beryllium alloy (2'35;(, of beryllium)has it tensile strength about six times that of copperwithout any substantial decrease in its electrical conduc-tivity. This alloy can suitably replace phosphor-bronzesprings in electrical instruments. Beryllium-copperalloy is also used in the manufacture of wear resistingparts, viz., bushings, sleeves, rollers, etc. and also in themanufacture of tools, nickel-beryllium, iron-nickel-beryl-lium and iron-chronli.um-nickel-beryllium alloys findextensive application in industry. Beryllium-copperalloy, because of its special physical properties, suchas, high degree of fatigue endurance, non-sparking

Fig. 4.Aluminium -silicon alloy fluidity spiral with the addition

of our modifying agent.

Fig. 5.Aluminium -silicon alloy fluidity spiral without the use

of modifying agent.

quality and resistance to heat and corrosion, is one ofthe most valuable alloys and finds wide use in defenceand other industries. Likewise binary and ternaryalloys of beryllium with some non-ferrous metals likemagnesium, alunliniunl, nickel, cobalt and particularly

41

those with copper are unique in some of their propertiesand hence industrially very useful. In fact. it is claimedthat "beryllium is to copper what carbon is to iron".

Beryllium oxide is also an important ram material formanufacture of special types of refractory wares. Be-cause of its extraordinary resistance to thermal shocksand high electrical resistance even at high temperatures,it may rightly be called it 'super-refractory" which canhe used with great advantage for making crucibles,muffles. laboratory boats. electric furnace linings andvacuum tubes. It is also an important ingredient in"phosphor," for Iluore,cent lamps. By far the mostimportant is its use as moderator in nuclear reactorsand as an allovino agent for copper and nickel toproduce precipitation hardening alloys.

In view of the strategic importance of the metal.investigations were undertaken at the National Metal-lurgical Laboratory to prot'.uce heryllia. A suitablechemical method was developed which mas chosen fortrial on semi-pilot plant has is. The 11ow-sheet of theprocess is shown in f=ig. 6. On an average, an extrac-tion of 80 85",, of beryllium oxide from beryl wasobtained alone with it purity of product ranging from95 to 9"'

An electrolytic process was also developed at theNational Metallurgical Laboratory, the flow-sheet ofwhich is shown in Fig. 6. The electrolytic methoddeveloped consisted in electrolysing it solution ofsodium beryllium fluoride obtained by leaching withwater a sinter of beryl and sodium silico fluoride.The leach liquor containing the complex salts of beryl-lium formed the catholvte in (lie Outer vessel and a10 per cent sodium chloride solution contained in aporous pot placed at the centre of the vessel was theanolyte. On electrolysis of the solution, it slurrycontaining the beryllium hydroxide was obtained inthe cathode compartment which on washing, dryingand ignition gave the oxide.

The electrolytic process oilers advantages over theconventional chemical process in that the productis purer and the process is simpler and much cheaperwith a cost estimate of Re. O-N7 per lb instead ofRs. 6.50 per lb by the chemical process.

Based on the results obtained in course of our experi-ments oil semi-pilot plant basis of the fluoride process,as developed by its, a pilot plant scheme for productionof 2,400 lb of herylliunt oxide per annum waslater drawn up. But it was later considered thatfurther work connected with beryllium would he con-ducted at the Indian Department of Atomic Energy.

Zirconium

The metal zirconium is another metal like beryllium,which has assumed strategic importance since the lastWar. The field of application of this metal is alreadyvery wide. covering right from the nuclear reactordown to the surgeon 's gadgets and is expanding dailyin various directions . The use of zirconium metal andits alloys in the construction of nuclear reactors isof- outstanding importance today. Its superior mecha-nical properties and corrosion resistance even at very

high temperature coupled with its very low neutron ab-sorption cross-section snakes it almost all ideal construc-tional material for high temperature thermal reactors.

Zirconium in the form of silicon-zirconium andFerro-silicon-zirconium is used as an alloying addi-tion in the steel industry where it acts as it powerfuldeoxidiser and scavenger. Zirconium is an intensivegrain-refiner for magnesium-base alloys. Finer grainsize results in increase in strength and ductility ofthe alloys. Addition of zirconium to beryllium-copperalloys improves the strength at high temperature.Alloys of nickel containing 2-1011;, zirco;tiunl aresuitable for cutlery manufacture and those containingstill higher proportions of zirconium from 25 to 30°',,for high speed cutting tools High purity zirconiummetal is resistant to attack by hydrochloric acid evenat elevated temperatures. Hence it is used particularlyin U.S.A. for fabricating various parts of the hydro-chloric acid plant. It is an ideal material for spinnersfor spinning rayon fibres.

Zirconium silicate and zirconium dioxide are twouseful refractory materials which are used for the liningof electric furnaces and burning chambers, in glassindustry, for foundry work and electrical insulators.

In India, zircon occurs in the beach sand of Travan-core, mixed with monazite, ilmenite, rutile, etc. Itconstitutes about 6< of the sand and is recoveredits a by-product in the tailings after separation ofmonazite and ilmenite. In fact, 'India is one of the im-portant zircon-producing countries. Development workwas therefore undertaken at the National MetallurgicalLaboratory to explore (lie possibility of processingthis mineral for the in industries and a process wasdeveloped for obtaining zirconium dioxide from zircon.The flow-sheet of the process is shown in Fig. 7.As it first step for the production of zirconium dioxidean electrolytic method was developed consisting infusing the zircon sand with potassium silico-fluoride.The sintered product was leached and electrolysed.The sediment of the hydroxide was filtered, washedand ignited and a pure zirconium dioxide was obtained,The product could therefore he used for chlorination.High efficiency of extraction of the order of 85 95°;hasgenerally been obtained for the process. Thepurity of the product ranged from 93 to 96",,

Soderberg electrodes

Continuous self-baking electrodes of the Soderbergtype ar-, universally used in the eletrolytic extrac-tion of aluntiniunt and other light metals. They arealso employed in the smelting of pig iron and certainFerro-alloys. In India the main consumers of Soder-berg paste are the aluminium producers and manu-facturers of Ferro-manganese and ferro-silicon. Atpr,:sent the aluminium units are producing their ownpaste from petroleum coke of Digboi refinery. It waswith a view to conserve foreign exchange and exploreways and means of getting good service performancefrom indigenous pastes, that the National MetallurgicalLaboratory undertook a study on the production ofsuitable Soderberg paste from indigenous materials.

42

FLOW - SHEET FOR THE FLUORIDE PROCESS FOR BERYLLIUM OXIDE .

i[

11-FrAa'srio, CL zAaa7QAr[F

_

0 /

PA'£ C/P/ rA 71ON

fit TRA T/ON

DRY/NG

POwOE a-/w/G

".or/Ow

aq/EO FAKES

PosvO^/a

- ---- ---- -

.'VAS WED CAKES

O.IEO CAKES

P0.WDER

__ - J

TECHNICAL B eO .

Fig. 6.

Flow-sheet for the fluoride process for beryllium oxide and alternative process for beryllium oxide.

43

r

ALTERNATIVE PROCESS FOR-BERYLLIUM OXIDE,

SL IiA'RY C(O*.)

IMG d! (OM)s

L rLrl .9Arip/v

f

/YA, MIG I{

I f/L TRA r/ON

I

I

L _

DA Y/I.16

,V/,f c /"C,

FLOW SHEET OF THE PROCESS FOR 2rO2

POTASSIUMSIL ICOf LUOR IDES

WATER

AIR

ORE

: GRINDING

sCREFkING - OVERSIZE

MIXING

BRIQUE T T ING

ISINTERING

I

J

F GRWDING

SCREENING

LEACHING

OVERSIZE

FILTRATION MUD TO11 L_-WIn

WON REMOVAL

F

FEED TANK

1FILTR AT ION

F ELECTROLYSIS

FILTRATION FILTRATEJ

WET AKIES

IDRnNO CAL . C INING

12IRCONIUM DIOXIIJ> 1

Fig. 7.Flow-sheet of the process for ZrO.-.

The work so far done indicates that while calcinedpetroleum coke is being used for production of thispaste, consertine it into dense aggregate at a slightlyhigher cost makes the material more uniform in itsdensity as sell as conductivity and the electrodes canconsequently he expected to be stronger, more wearresistant and better conductors. Conversion of bitu-minous coals into dense aggregates will involve additionof low temperature char,. Kinetic Studies indicatethat it may be possible to conduct low temperaturecarbonisation so that a pre-determined quantity of

residual volatiles remain in the char. Conversion ofhituminous coals into dense aggregate is a pre-requisitefor their utilisation as raw materials of Soderbergpastes.

Laboratory scale experiments have established thatit is possible to obtain hard dense briquettes frompetroleum coke or low ash coal which can be usedas carbon grist in the Soderberg paste after crushingand grading (Fig. 8).

Results indicate that the paste composition tradeout of these carbon aggregates are very well com-parable with those of imported paste as shown inTables 11 and 111.

TattLE 11

Comparison bet R een the green and fired properties of theimported electrode pastes and the author's conipo.sitions.

Bendingstrength of

Physical characteristics of tampedpaste fired to 1,200 C.

Sample the greenpaste

Compressive Apparent Bulk densitythstren orosit

kg cmg

lb. sq. inchp y

0//u

gms cc

French paste 24'20 1,650 22-25 I'4Norwegianpaste ... 22'4 2,000 22-24 1'5Author'scompositions

1. 20.0 2.400 22-25 1'52. 14.0 1,500 22-24 1.5

T.a ut.t•: I I I

Electrical resistirities cif the author's compositions andFrench paste calcined at 1,200-C'

SampleBinder

CompositionElectrical Resistivity

ohms,, mm-, m

French paste - 175'0Author' s

1.compositions

Electrode pitchand tar 37.0

2. Hard pitch andtar 113.0

General

Investigations have also been undertaken on shortterm, long range and ad hoc basis on processing andmetallurgical problems for light metal industries.Technical data and advisory information have alsobeen freely furnished to different firms and plantsengaged in the production and processing of lightmetal alloy products, etc. Long-range service prob-lems have also been likewise undertaken for Govern-ment bodies and kindred organisations. A typicalexample may he the production of aluminium-bronzecontaining 12°, alurn1n1Um and less than 100 ironand manganese, the rest being copper, for theRailways. A typical industrial problem may he

44

1,

\^KROIL CRUSHER

1^ -CLASSIFIER

STORAGE SILO

ROAD TAR90°C HOT MIXER

1

SODERBERG ELECTRODE PASTE

QUALITATIVE LINE DIAGRAM

BRIQUETTING PRESS14,000 p, si.

uAGERS

COOLING BINS

DENSEAGGREGATE

c-1

CLASSIFIER

MEDIUM COARSE

ROAD TAR SOFT PITCH SILO SILO

(^pGRINDER

BALL

MILL

! -100 MESH

STORAGE SILO

BALL MILL

1 FINES

a

SIL

HOT MIXER

MOULDS

O

N. M.L.

Fig. 8.

Soderberg electrode paste qualitative line diagram.

45

Pilot Plant set - up at the National Metallurgical Laboratoryfor the recovery of vanadium pentoxide.

illustrated by ins estigations undertaken into cause,effect and remedial measures for ''dark brown spots"on aluminium sheet met With in a production unit.Elucidation of causes re,ponsible for such "dark brownspots" and remedial me rsures propose, after ad hocinvestigation of the problcin from fundamental andapplied angles have been furnished. Our investiga-tion in this field resealed that the Formation of `'darkbrown spots" appcared to he due to alternate condensa-tion and evaporation of moisture condensed in thecapillary spaces between the stacked sheets. It wassuggested that ambient temperature of the storageroom should not he allowed to fall below the dewpoint. Similarly an active corrosion station has beenestablished at the National MetaIlurgical Laboratoryfor corrosion studies under ''industrial atmospheric"conditions as are met with in Jamshedpur relating toIight alloys under development at the National NIetal-lurgical Laboratory as also of the hot-dip aluminisedsteel wire and strips, etc. Such corrosion tests haveextended over periods of se era I months to over 5 years'exposure under local atmospheric conditions. Investi-gations were also carried out in connection With the useof aluminium in distillation stills for essential oils [whichindicate that in the absence of phenol in the oil,aluminium is an excellent metal for fabrication ofthe distillation stills.

Other problems have related to the surface treatmentof light metals and alloys. Deselopnient work onsurface treatment of light metals and alloys is wideindeed and has cowered several aspects of electro-plat-ing of aluminium, chemical polishing of aluminium. etc.Electro-plating of aluminium permits the advantages ofits light weight to combine with specific properties oftht plated coating. This also includes chromium platingof aluminium-alloy pistons, etc. for imparting ade-quate wear resistance. In the particular case of alumi-nium. the adherence of the electroplated coating to the

base metal has been a serious problem, arising out ofthe strongly electro-positive character of aluminium andthe case with which it forms tenacious and protectiveoxide film which has to he removed before electro-plating. Nickel plating of aluminium has been deve-loped by using the modified "iron dip" method. Thealuminium sheet is degreased in a mild alkaline cleanercontaining trisodiurn phosphate and a washing soda3°o each, then dipped in 5" ,, NaOH solution andetched in 53 hydrofluoric acid solution followed by ashort dip in 70°o HNO3 solution and then an iron dipand nickel plating bath followed by stoving at 250Cfor 2 hours and polishing, etc. The adherence of thenickel plating on aluminium was excellent. It wasfurther experimentally established that plating ofchromium, gold, etc. can be done on the aluminiumsurface after the latter has been nickel plated as out-lined above.

Having given a general resume of the work underwayat the National Metallurgical Laboratory on lightmetals and their alloys, it will perhaps he not outof' place to state some of our projected activities inthese fields.

One of the most important light metals of interestfrom the indigenous angle is aluminium, whose worldproduction today stands at 3 million tons per annumand is likely to he doubled by 1965. Aluminiumcannot, however, rival steel since the minimum chemicalwork involved in extracting a ton of aluminium fromits oxide is about 7 times that involved for one tonof iron. Likewise, magnesium required during thelast World War as an incendiary is now being producedto the extent of 200.000 tons per year. Titaniumclaimed as a "wonder metal" has today a worldproduction figure of over 10,000 tons per annum andcosts less than £l per pound to produce.

We are rapidly moving in the world of supersonicjet flights, missiles, more and more powerful and fasterand complex machines. In this unabated race, re-sources of metals in general are getting depleted atan enormous rate ; for example proved world reservesof copper will barely last 30 years and if its produc-tion continues to multiply fourfold over 2-3 decades,we shall have to look around for metals of the "rare-earth group" of metals which today have relativelymuch smaller industrial scale uses but will be neededfar more abundantly in years to cone. It has now beenclearly shown that metals of the rare-earth group arevaluable alloying elements both in micro and macro-additions in the metallurgy of iron and steel, in highlyalloyed and stainless steels, in light alloys of aluminiumand magnesium. etc. Researches and developmentwork are actively being pursued all over the world inthese metals of the complex rare-earth group of whichIndia has enormous resources. Naturally, therefore,one of the most active themes under pursuit at theNational Metallurgical Laboratory is to study theeffects of relatively minor additions of rare-earth groupof metals to different ferrous and non-ferrous metalsincluding light metal and their family of alloys as alsoemploying the rare-earth group of metals as integralconstituent alloying elements in potential series of

46

alloys. The extraction of rare-earth minerals, despitetheir abundant resources, is highly complex and costly.The extraction techniques, however, are being steadilyimproved upon and the cost of production thereof isexpected to drop in course of time. Cerium. of veryhigh purity now being produced, has three times theelectrical conductivy of the commercial grade. It hasunique properties of readily absorbing impurity con-tents in other metals when molten. It will not,perhaps. be out of place to outline such applications onrare-earth group of metals in light alloys, represent-ing the fields on which projected research and develop-ment work at the National Metallurgical Laboratoryis being actively planned and intesified.

The use of rare-earth metals in light alloys hasaroused considerable interest during the last fewyears. Such metallurgical applications of rare-earthmay be classified in two broad headings

1. Applications in which rare-earths form analloy with some other metals e.g. with alumi-nium and magnesium.

2. Applications where rare-earths play it weakrole as alloying agents but function funda-mentally as purifying elements.

In each case, rare-earths are added in the form ofa mixture and not in their pure state. Two types ofmixtures are widely used, one of which is Lan-Ceramp(Lanthanum , cerium ) whose average analysis is asfollows :Lanthanum .. ... 30%Cerium ... ... 45 to 50%Mixture of neodymium ... ... 20 to 24%Praseodymium and Samarium and Iron 10",% nulx.The other mixture is "misch metal" which is derived

from monazite and contains 22 to 25°,0 lanthanum,50 to 55'%;, cerium, 15 to 17% neodymium, 8 to l0",,other rare-earth metals (varying according to originof monazite)`, and small amounts of iron. Ceriumis said to exercise beneficial influence in aluminiumproduction and to increase the toughness of purealuminium by reducing the silicon content. It isclaimed that an addition of 0'2", cerium will reducethe silicon content of 0'! "0 to 0'021;,. For thispurpose, cerium is added to the aluminium in thefused state, preferably in the form of a high ceriumcontaining alullllnlulll alloy, or in the form of ceriumfluoride to the electrolytic bath in which aluminiumis prepared.

Rare-earths are chiefly used in light alloys of alumi-nium and magnesium. 10 to 12% of the Lan-Cer-anlp or nlisch metal added to aluminium willconsiderably improve its mechanical resistance to heat.However, relative additions of rare-earths requiredfor magnesium are not so large. A few per cent ofrare-earths added to magnesium improves its mechani-cal resistance to heat, refines the grain structure andproduces a more easily workable material.

Leontis' has evaluated the specific effects of variousrare-earth metals at room and elevated temperatureson properties of magnesium. Alloys containingdidymium exhibited the highest tensile and compressivestrengths at room and elevated temperatures. All

Three- high reversing rolling mill installed at theNational Metallurgical Laboratory.

rare-earth metals increased the creep resistance ofextruded magnesium between 400 to 600 F, but theincrease depended on the temperature and concentra-tion of the added metal.

Magnesium rare-earth metal alloys were investigatedin Germany many years ago and the findings werepublished in Becks Technology of Magnesium in1939. Cast alloys of magnesium with rare-earthhave now become commercially available. They alluse zirconium as a second essential alloying elementbecause of its grain-refining effect, thus preventingcracking during freezing.

For aircraft applications, engineers and metallurgistshave sought alloys with high strength-weight ratio andability to withstand increasing stress at elevatedtemperatures. Patton' has described how by adding2 to 4"%, rare-earths to Mg-Zr alloys, Dow Chemicalshave obtained new alloys with outstanding hightemperature properties.

At 300 F and above, cast nlagnesium-zirconium alloyswith 2 to 4% additions of rare-earth metals, haveshown as much as five times the creep strength comparedto older nlagnesium-aluminium-zirconium type alloys.For aircraft engines which require outstanding elevatedtemperature properties and high strength-weight ratios,the properties exhibited by these alloys with rare-earthadditions are particularly useful. Several alloys havebeen developed e.g. the addition of 0,3 ',"0 rare-earthsto aluminium-copper-silicon piston alloys, the use of0'05 to 0'3% rare-earth metal in aluminium alloyscontaining manganese and the recent use of rare-earthzirconium alloys for jet engine parts. The latter alloyscontain 0'1 to 0'9°,, Zr and up to 4"0, rare-earths andsometimes I to 6% Th and 0'5 to 5";, Zr. The didy-mium metals, particularly neodymium, are especiallyinteresting in this application but their uses may be

47

Experimental set-up at the National Metallurgical Laboratoryfor the production of magnesium metal.

restricted due to limited availahility of neoLlyntiunt.Misch metal contents up to I I„ in an aluntiniunl alloycontaining silicon. copper, nickel. manganese and smallamounts olfchronliunl and titanium have been reconl-mended for high temperature aircralI engine service.

Tvvo nlagnesiurtl base alloys have recently been an-nounced by \lagnesium Flektonl Iu which thoriumand rare-carth metals are added : one being a wroughtalloy with 0'7 Th. O'S Zr, O'6 Zr-magnesiuIll availablein sheet. plate. e.x1rusio11s and forgings possessive goodproperties at elevated temperatures and the secondbeing a nutgnesiLI ill base casting 2-5Ag-2--rare-ea rtIt - 0.6Zr-alloy with a room-temperature proof stress com-parable \\ till high-strength aluntiniu,n alloys and hickhas very attractive creep properties at elevated tempera-ture, especially at 201) C.

For uses in cryogenics, the 4 \lg-\1n-Ti-aluminiumalloy B54S\l developed by Northern Aluminium Con1-pany is a serious rival to new nickel steels developedby International Nickel Company for pressure vesselsrequired for holding liquid nitrogen at temperatures aslaw as 200 U.

Another recent an nouneernent" a few months hackfrom France has indicated the development of as-castand heat-treatable aluminium-magnesium alloy contain-ing 1 1 % magnesium.

In this connection, the application of lithium inmetallurgy of light alDrys forms an interesting field ofapplication to he potentially developed. Resources ofIithiunl have been loe;tled in India such as. for example,ill considerable quarllities in northern Hazarihagli. inBastar in Madhya Pradesh and other places. Lithiumis an important dc-gassing agent and de-oxidiser inmetal refining, such as, of copper bronzes, grey iron,low carbon steel. etc. Considerable research has beenconducted in the :\rnlour Research institute on silver-lithium brazing aliovs. The Alumillinrn Company- ofAmerica has developed new aluminium alloys in which

11", lithium is an important alloying element besides

copper up to 4°(,. Likewise, nlagnesiunl-lithium alloysare also being developed containing 10-15";, lithium.It is proposed to study the scope of the applications oflithium under Indian conditions for the development of11ILunlilliLIIl1-Illannesium alloys.

There are several Other applications'' of substitutealuminium alloys, such as I lie development ofalu1111111L1111bronze for replacing tin-bronzes, used in worn gearsof trolley bus reducers. Considerable work in thisconnection has been done in Russia on the productionof aluminium-bronze for the above purpose whereincoarse granularity is overcome by the addition of 3-6°aFe and 2.5" o M n.

The Austrian Casting Institute` has all 110I.Inced tiledevelopment of a11unillil1111-1,11iCo11 alloys containing7 9"U Si. 5 I I"Zn. 0.2 05°;, Mg. This is an uttsualcomposition because alloys with Zn contents are notsuitable for casting. However, it is claimed to possessgood tensile. bending and hardness characteristics.This alloy known as "Durofondal" allows scrap zincalloys to he used in its production.

An a11.1111i111t1111-hase anti-friction alloy' containingSb 3'5- 4'5 Mg 0'3 0.7",, has been developed in theU.S.S.R. This anti-friction alloy is successfully appliedas a thin layer on a steel base and rolled at 350-450"Cfollowed by annealing at 460'C.

Yeshvvant P. Telang4, of the Ford Scientific Labora-tory's applied science department, has recently describedaluntiniuin 21";, silicon alloys with ultimate tensilestrengths approaching 50.000 pounds per square inch ata synlposiunl sponsored by the American Society furMetals during the 42nd National Metal Congress. Thenew alloys are claimed to possess unprecedented mecha-nical properties particularly for high silicon alloys, ine11cct higher than those of commercial automotivecasting or heavy-duty piston alloys currently in use. Inaddition to their high strength. the alloys are shown tohave excellent hardness, impact and anti-friction pro-perties, low density and lowvered thermal expansion Co-etlicients. Alloys of similar composition have been usedfor pistons in Europe for some time but their poorfoundry characteristics, excessive variation in propertiesand poor nlachineahility have caused them to he general-ly neglected in U.S.A. To achieve the superior proper-ties demonstrated by the Ford metallurgists. the alloyshave been modified to produce a material with the linestpossible microstructure. From the foundrynlan' s pointof view, the alloys possess the advantage of little or noloss in refinement during remelting, superheating orholding at elevated temperatures. It is proposed to fur-ther investigate development of similar alloys underIndian conditions considering that 50" of the lightalloy castings in U.S.A. fall in the aluminium-siliconfamily of alloys which claim S0° of the world's lightalloys.

Tremendous interest has been aroused recently by theannouncement of a basically new alunliniunl makingprocess to he used by Aluminium Limited at 4 milliondollars to he built at Arvida, Quebec. Designed as a pilotplant unit. it will have it production capacity of (t)00-i{000 tons of alu111illlLlln a year. The process is covered

4y

by patent right and some details are available . Thoughpower requirements remain almost the same, the newprocess of Aluminium Limited cuts the cost of produc-tion by fifty per cent reduction in capital cost . Impurealumina is partially reduced electrically, convertingabout 5010 of aluminium content to metal . Partly re-duced mass then contacts AICI,-vapour at over 1000°Cand at about 1 atm. Under these conditions, thealuminium in the converter reacts with vapour to formA1C1. This monohalide then flows to a condenser leav-ing behind impurities, such as, titanium,-aluminiumvapour cools by coming into contact with a violentlyagitated pool of molten aluminium when temperaturedrops and the initial reaction reverses , forming AIC13and Al. Product Al can be tapped continuously andthe AIC13 is recycled to the converter10 . Further detailsof this new process are available in several announce-ments on the subject.

From an appraisal of the developments in the field oflight metals and their family of alloys referred to in thispaper , it is obvious that tremendous scope for researchand development in these fields exists under Indianraw-materials and processing conditions . The NationalMetallurgical Laboratory will be actively engaged instudying such developments , both in the fields of metal-lurgy of light metals and in the development of lightalloys based on indigenous alloying elements includingthe rare - earth group of metals . Considerable ground inthese fields has been covered and good beginningsmade . In concluding , it may be stated that progress inresearch and development work in diverse fields of themetallurgy of light metals and their family of alloys atthe National Metallurgical Laboratory has been steadyand rewarding , placing a high premium on scientificingenuity and rationalised planning and yet far moreremains to be accomplished during successive Five Year

Extrusion press installed at the National Metallurgical Laboratory.

Plans of our country to which end , this young Labora-tory is fully geared today.

References

Trombe, F.-Metal Treatment and Drop Forging (1957), 24,421 -424Leon tis, T. E., Journal of Metals ( 1951), 3, 987 993.Patton, W. G., Iron Age (1952), 169, No. 21, 134-136.Engineering , February 12, 1960, p. 215.Revue de Aluminium V. 37, May 1960 , p. 585 -593.Yu. Yu. Gapanovich . Nauch . Trud. Khar ' kov Inst. Inst.Inzh. Kommun . Stroitel'stva, (6), 121-131, 1956.

7 The New Scientist ( England ) 5, No. 1 16, 285, Feb . 5, 1959.a Nauchno -Issledovatelskiy Traktornyi Institute NATIB and

Lipetskiy Traktornyi Zavod '•LTZ". U .S.S.R. Patent 107, 751.Publ. October 25, 1957.

• Publications : Engineering & Research , Ford Motor Com-

10pang, Dearborn , Michigan, Oct. 20, 1960.Fr. 1.2 10 , 068, 9 . P. 846, 189.Chem. Engg . Sept . 5, 1960 , p. 41, Light Metals , Sept. 1960,p. 230.

Mr. U. P. Mulliek, Institute of Consulting Engineers,Calcutta : Dr. Nijhawan in his paper has referredto various tests on aluminium coating on steelwires and the good anti-corrosive properties of thisprocess. I would like to know (i) whether the problemhas been considered taking into account the rates ofexpansion of steel and aluminium which are different,(ii) the extent of anti-corrosive properties of alumi-nising of thick mild-steel rods so that they can be usedin structural works like reinforced concrete works,(iii) whether the aluminised steel wire or rods will havesufficient adhesive strength and tensile strength, etc. and(iv) whether abrasive resistance of aluminised steel coat-ings will be comparable with galvanised coating, say, forwire, rod and tubes of %" diameter and larger sections.Dr. B. R. Nijhau'an (.4uthor) : Personally, I wouldnot advocate the use of aluminised steel rods for thepurpose of reinforced concrete at all. It is embeddedin the concrete and the corrosion resistance of steelrods vis-a-vis reinforced concrete is being separatelystudied at other laboratories of the Council of Scientific

and Industrial Research. I would not consider at allaluminising necessary for reinforced concrete structures.The coating of steel with the hot-dip aluminium shouldpossess certain minimum adhesion strength as there aretests specified to determine the adhesive properties ofthis bond and all attempts are directed towards reducingthe thickness of the intermetallic iron-aluminium com-pound. If the thickness of the intermetallic layer iswithin control and within specified limits, the coatingwill possess the requisite rigidity and adhesion strength.If the thickness of the intermetallic compound exceedsthese limits, spalling of the coating may result. Butfor certain conductivity uses, where we want to substi-tute copper conductor by this aluminised steel wire,we have suitably increased the thickness of the alumi-nium coating in comparison with what is normallyused for Posts and Telegraphs purposes, where we cur-rently employ galvanised wire. It is quite a complexsubject and I would invite Mr. Mullick to come anddiscuss with us the detailed investigation reports thatwe have prepared on the subject.

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