metal founding modern perspective - saimm · 2009-08-26 · respect both to problems and prospects....

Metal founding - a modern perspectiveby P. R. BEELEY*, B. Met., Ph. D., F.I.M., F.I.B.F. (Visitor)

SYNOPSIS

The recent development of metal founding is reviewed in the context of basic requirements for the successfulmanufacture of cil;5ti,ngs.Progress has been related to the two interdependent fields of process technology andproduct characteristics. .

After a brief revi~w of the growth of the traditional industry. various features of the modern industry are dis-cussed. Reference IS made to current trends in process technology and to the introduction of new tech-niques affecting prod~ction engi~eering, product quality. and the general nature of the industry. Metallurgicalaspects of metal founding are considered, and modern techniques for the control of casting conditions are examined.These aspects are related to the structure and quality of cast metal and to the development of newer types of castmaterial and product.

SAMEVATTING

Die onlangse ontwikkeling van metaalgietery word in oenskou geneem in die jig van die basiese vereistes vir diegeslaagde vervaardiging van gietstukke. Die vordering is in verband gebring met die twee onderling afhankliketerreine van prosestegnologie en produkeienskappe.

~a 'n kort oorsig oor die groei van die tradisionele nywerheid word verskillende aspekte van die moderne nywer-held. bespreek. Daar ~ord ?ok ~erwys na die huidige tenden~e in prosestegnologie en die invoering van nuwet~gnleke wat produksle- ~n Ingenleurswese produkgehalte en die algemene aard van die nywerheid raak. Metallur-glese as~ekt~ van metaalglet~ry word oorwee~ en moderne tegnieke vir die beheer oor giettoestande word onder-soek. Hlerdle aspekte staan In verband met die struktuur en die ontwikkeling van nuwer soorte gietmateriaal en-produkte.

Introduction

The object is to review some recent process andproduct developments in metal founding, with particularreference to the situation in the United Kingdom,although much of the background is international withrespect both to problems and prospects. Most processdevelopments in the casting field are concerned with thestructure of manufacturing operations, involving pro-gressive changes in existing techniques and the adventof new systems of production. The primary emphasisin this area is on minimizing production costs, althoughthere can be incidental benefits to product quality andto working and environmental conditions. Other de-velopments, in cast materials and products, involvemetallurgical quality or new types of product: theyextend the design capability of castings relative to otherforms.

The past growth of metal founding has beencharacterized by innovations that have become pro-gressively closer together towards recent times. A briefsurvey of the most important of these will enable recentchanges to be seen in better perspective.

Despite its ancient origins, the true industrial develop-ment of metal founding can be ascribed to the eighteenthcentury, with the successful smelting of iron with coke byAbraham Darby in Shropshire, England. The principle,in widespread application by 1775, was one importantcomponent of the Industrial Revolution, and providedbulk supplies of cast iron as well as the foundation forthe later development of a massive steel industry.

The cupola was developed by Wilkinson in 1794 andenabled cold pig to become the main resource for anindustry that rapidly spread its geographical base. It isinteresting to reflect that the counterflow principle isstill accepted as the best basis for the economical use of afuel for melting, that the' cupola retains its competitive

*Department of Metallurgy, University of Leeds, England.

place in the foundry, and that a gas-fired cupola is evenseen as one approach to modem melting.

The next major development was that of steel castings,in which the main obstacle to be overcome was theachievement of temperatures approaching 1600°0,required for pouring and mould filling. The first com-mercial success with steel castings has been attributed toFischer at Schaffhausen, who used crucible steel tomanufacture horseshoes around 18421. Small openhearths and the combination of the cupola with smallconverters later became the main sources of moltenmetal in steel foundries, until they were superseded byelectric-arc furnaces.

Further innovations included the appearance of lightalloys, the widening of the range of copper alloys, andthe die casting of zinc. On the moulding side, machinesbegan to replace manual labour and skills for a pro-portion of the industry's output; many mouldingmachines were in use by 1900, and the sandslinger arrivedin 1912.

The second World War produced rapid progress incertain fields, including extensive use of radiographicand other non-destructive techniques of inspection,whilst a notable metallurgical development was theacceptance of castings in vital situations in aircraft.The long-known principle of investment casting alsobegan to find industrial application on a small scale,and Croning's shell-moulding process not only broughta new approach to bonding but provided the first breakin the traditional concept of a mould as a cavity in a solidblock of material. The shell process heralded the recentchanges of emphasis in the industry and its products,and represented the first application of sophisticatedchemical technology to metal founding.

Modern Process DevelopmentsThe moulding and coremaking field offers the most

dramatic picture of recent change; so much so, that it isdifficult to predict what the stable state will be. The

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY SEPTEMBER 1976 23

emergence of a range of different approaches to bondinghas been accompanied by the introduction of a varietyof new machines for compacting and handling mouldsand cores. One common consequence is a reduction inthe craft element in moulding, often accompanied by anincreasing need for skilled maintenance operatives.

The possibilities are most varied in the field of lightand medium castings required on a repetition basis. Thenow traditional high-throughput greensand mouldingsystem is still cost-competitive but has itself seen somenotable changes. There has been a trend towardsheavier, more rigid, and more accurate moulding boxesand pattern plates, and the use of the latter even injobbing applications. Higher squeeze pressures, used insome cases with contoured or multiple squeeze heads foruniform compaction, reduce the need for jolting and socontribute to noise reduction in the foundry.

There is increased automation throughout mouldproduction, and standardization of box size is pursuedeven at the expense of greater sand-to-metal ratios.In these circumstances, segment pattern systems canincrease box utilization and provide flexibility to meetvaried quantity requirements. A cardinal modernfeature is the capacity for rapid pattern change toaccommodate modest orders: this enhances the case forthe provision of mounted patterns irrespective ofquantity.

A major steelfoundry in the U.K. recently installed aline incorporating many of the above principles and hasdemonstrated the ability to achieve low costs even in a

Fig. I-Mould storage and pouring lines in the Cattonautomated steelfoundry2 (by courtesy of Foundry Trade Journal)

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Fig. 2-Rotary Y.fork unit facilitating pattern changes within the time cycle of the moulding machine2(by courtesy of Foundry Trade Journal)

24 SEPTEMBER 1976 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

field in whIch productIon runs tend to be short. Thesystem, at Catton & Co Ltd2, has a nominal capacity of220 t of castings weekly, with an approximate averagemass of 50 kg and a simultaneous manning of only16 direct operatives and 6 engineers; yet it is able todovetail one-off and sample castings into the sameproduction line. An impression of the production line isshown in Fig. 1, and the vital system of pattern changein Fig. 2.

At the lighter end of the product range, other mouldingsystems come into the picture, exemplified in theDisamatic machine, in which highly compacted boxlessblock moulds are produced by a blow-squeeze sequenceat a rate of several hundred units per hour, and in whichthe vertically jointed moulds are packed together forpouring without the need for individual clamping orweighting (Fig. 3). Some 540 such machines are in usefor the mass production of small components, including20 in the U.K. and 14 in South Mrica. Whilst mostapplication'! are in the repetition grey iron field, otheralloys are feasible and one U.K. foundry is successfullyproducing steel castings of up to 27 kg. The system isseen to best advantage in applications with minimalcoring.

Developments based on the newer moulding materialswere led by the shell process, which combined modestproduction costs with high standards of accuracy andfinish. Automatic machines now facilitate rapid outputrates, although the process is most often chosen wherethe castings offer some specific quality advantage overgreensand products.

The thermally cured shell principle has since foundwide application in general foundry coremaking. Mostother developments in chemical hardening were initiallydeployed in the coremaking context, although largelyapplicable to block- or box-mould production as well.The bonding systems are variously based on organiccompounds and on silicates. A valuable common featureof the systems is the capacity to stabilize shape bypartial setting whilst in contact with the pattern.

The use of heated metal core boxes was extended fromshell to wet mixes in the hot box process, based on fast-curing resin-catalyst combinations offering lower costsand more rapid production. This system is now widelyapplied where quantity requirements warrant the highinitial core box outlay. Cold-set coremaking was originallymost suitable for relatively heavy cores, since the needfor bench life was incompatible with rapid box turn-round. The advent of mixer-dispenser systems largelyeliminated this need, but, for smaller cores, the cold-setprinciple is being revolutionized by rapid cure systemsfor the mass production of blown cores. In the Fascoldprocess3, catalyst and resin are contained in separatesands blended in high-velocity streams and blown intothe core box, where setting occurs immediately. In theAshland process4, resin, hardener, and sand are premixedand blown, but the cure is completed in the ventedcore box by an amine catalyst va,pour, which is subse-quently purged from the box. Both processes offerrapid production and the ability to use wood or plasticcoreboxes.

Wide application of silicate bonding followed the

Fig. 3-Continuous mould string""'from Disamatic machine(by courtesy of Disa-Dansk Industri Syndikat AjS)

introduction of the versatile CO2 process, which rapidlyassumed a major role in coremaking and which was soonalso adopted for block moulding and mould facing.Progress has since followed with self-hardening silicates,in which catalysts are added at mixing to producecontrolled setting and stripping times, within the hour ifrequired, so avoiding the difficulty of gassing largemasses. One notable silicate development is the fluid-sand system, in which a pouring consistency is obtainedfrom foaming agents.

With the development of so large a range of bondingand forming systems for moulds and cores, selectionbetween them must, in the long run, depend uponcomparative costs and the availability of the varioussynthetic constituents, as well as upon their foundrycharacteristics.

No discussion of moulding developments would becomplete without reference to what could become themost significant foundry development of our time, theadvent of unbonded sand systems. The principle of theunbonded mould was first discussed in the context of thespecialized full-mould process, involving volatile patternsof low-density polymer, coupled later with a magneticgranular moulding material held in form in a magneticfield. The recent development of the V processs, 6 has,however, attracted much more attention, and operatinglicences are rapidly being acquired. The process, illus-trated in Fig. 4, relies on the suction forming of a thinplastic film against the pattern plate and the subsequentsealing of unbonded sand within the flask by a secondplastic film. On evacuation of the flask, the sand is heldunder compression and the mould cavity retains thepattern shape on stripping; mould hardness values of90 are obtained. Vacuum is maintained in cope and dragunits throughout closing and casting, so that knockout


merely requires vacuum release. The process is suitablefor both automated and jobbing production and for allnormal alloys. Current applications include baths,tractor sprockets, manhole covers, and steel castings forshipbuilding: the vast potential of so clean and simple aprocess is self-evident.

The main process development in the precision castingfield in recent years has been the establishment of lostwax ceramic shell as the dominant system. Theseproducts are at the forefront of casting design capability,and the growing importance of the precision castingsector is indicated by the fact that the U.K. turnoverhad already reached £35 million per annum in 1970, avalue equivalent to that for zinc-base diecastings andover 40 per cent of those for steel and aluminium alloy

~~1. Set pattern on hollow carrier plate.The pattern has IWmerous vent holes.These help the plastic ftlm to conformwhen vacuum is applied.

~~~4. Flask is set on the film 'coated pat-tern. Note that flask has a suction pipeat right. This set -up could also be ver-tical, with flask on both sides of pattern.

~

'7. Apply vacuum to flask. Atmosphericpressure hardens the sand which retainsthe pattern form. Release vacuum onpatiern carrier plate and mould stripseasily.

castings. Automatic line installations are in operation atsome of the larger producers.

Moulding developments have been consideredprimarily in relation to refractory mould systems, butthe diecasting sector too is important; progress in thisfield will be mentioned in a later section dealing withmore specialized products.

Progress in other areas of foundry production has beenless dramatic, although certain trends can be seen,especially in metal melting, where changes in rawmaterial costs, metallurgical requirements, and en.vironmentallegislation are influencing plant selection.

In the cast-iron field, the cupola so far retains themajor role for melting. Its moderate capital cost andflexibility have been combined in recent years with

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'3. Softened film drapes over the patternand 200 to 400 mm Hg vacuum suctIOnacts through the vents to draw it downso it adheres closely to the pattern.

5. Flask is filled with dry sand (tWo-screen: 70 mesh and 270 mesh. for max-imum compaction). Slight vibrationquickly compacts the sand to peakdensity.

8. Cope and drag (or left and right forvertical moulding) assembled. forming asprued, plastic-lined cavity. Duringpouring, moulds are kept under vacuum.

6. Form the sprue cup. Level the mouldCover the sprue opening with plastic filmand lay on plastic backing film to overlapflask.

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9. After cooling, release vacuum andfree-flowing sand drops away. leavinga clean casting. There are no lumps,no burn-on. Sand is cooled for re-use.

26 SEPTEMBER 1976

Fig. 4-The=V-process principle of unbonded sand moulding7

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

Improved control and performance. One recent develop-ment has been the introduction of the twin or dividedblast system, in which tuyeres at two separate levelsincrease thermal efficiency and melting rate: metaltemperature can be raised by 40 to 50°C or coke con-sumption reduced by up to 30 per cent. Many existingcupolas are being converted to this system. Oxygeninjection, too, is being employed to reduce raw materialcosts.

The use of high proportions of low-cost scrap oftenrequires further carburization of the melt, and there isconsiderable use of post treatments, including powderinjection and mixing induced by porous plug or shakingladle systems, both for this purpose and for de-sulphurizing.

The cupola is significantly affected by recent clean-airlegislation, which will entail heavy expenditure: a wetarrestor system, even for a small cupola, costs severalthousand pounds, whilst a large cupola installation cancost upwards of £100 000. The impact of environmentallngislation on the U.K. industry will be discussed later.

There has been a recent marked upturn in the instal-lation of electric furnaces in iron foundries in the U.K. Inthe past, the high capital cost restricted their use, butnew induction furnaces are now rapidly coming intoservice both for melting and holding. This arises fromtheir suitability for charges containing high proportionsof borings and scrap, low melting losses, ease of control,and reduced pollution problems. Both coreless andchannel furnaces are being installed; new developmentsin the latter include interchangeable inductors to reducedowntime for lining wear. Large coreless inductionfurnaces are also finding application in the copper alloyfoundry.

In the steelfoundry, the principal developments havebeen within the electric-arc steelmaking process andinclude fumeless refining, involving injection of ironoxides as distinct from oxygen lancing. Ancillary de-velopments in the melting field range from the slidegatenozzle for controlled metal dispensing to the increasinguse of computer facilities as an aid to analytical control.

In fettling, the main area of progress has been inhandling and in amelioration of working conditions, butthe widespread adoption of the air-carbon arc padwashing system is also worthy of note.

Some Developments in Cast Materials andProducts

The next step will be to review some recent develop-ments that are primarily aimed at increasing the qualityand range of cast products available to the designer, andthat can involve either metallurgical or shape character-istics.

Progress in the metallurgical category has arisenpartly from increased understanding of solidificationand its effects on soundness and structure, and partlyfrom developments in non-destructive testing, feedingtechniques, and molten-metal processing. Among newerdevelopments in the last area, much interest currentlycentres on filtration and baffle systems in the productionof light alloys. An in-line combined degassing andcleansing system recently proposed for shaped castingsinvolves a divided vessel in which the alloy is first

agitated with nitrogen under liquid flux and then passedthrough a column of flux-coated alumina balls forseparation of entrained flux and residual oxidesB, 9. Afurther aspect of metallurgical progress is the intro-duction of improved techniques for the assessment ofmelt quality.

Interest in the control of cast structure has developedto a considerable degree in recent years, particularly inrelation to applications requiring special propertycharacteristics. Structure control involves such featuresas grain size, grain shape, phase morphology, and den-drite arm spacing, whilst the control parameters includemelt superheat and pouring temperature, the additionof small amounts of inoculants and nucleants to theliquid, and the manipulation of cooling rates andtemperature gradients in the mould.

Chemical treatments of liquid metals are long estab-lished, but techniques of application are still undergoingdevelopment. Apart from ladle operations, variousmould treatments have been introduced in recent years,reducing the risk of fading before the critical stage. Oneexample of in-mould treatment for the production ofS.G. iron employs a reaction chamber embodied in thegating systemlO, whilst nucleant mould coatings arenow well established for the refining of super-alloyinvestment castingsll and of white iron castings destinedfor malleablizing12.

Much current interest is also focused on dynamic

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Fig. 6-Cast gas-turbine blade with columnar structure (bycourtesy of Pratt

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refining techniques. A recent development in this fieldinvolves the continuous mechanical agitation of solidify-ing metal to achieve fine spherical grains13. It has beendemonstrated that vigorous motion can delay theonset of solid cohesion to surprisingly high fractionssolid and that thixotropic behaviour is obtained, pro-ducing a slurry suitable for shaping by pressure-castingtechniques. This retention of mobility is demonstrated inFig. 5: it should enable product accuracy to be increasedowing to the reduction in the casting temperaturerequired, with beneficial effects on die distortion andcasting shrinkage.

Whilst the size factor is frequently manipulated incast structures, increased attention has recently beengiven to grain shape and orientation. In some cases,foundry conditions can be controlled to suppressnucleation and to promote columnar structures byunidirectional solidification under steep temperaturegradients. A general improvement in mechanicalproperties often results, since microporosity is reducedby conditions highly favourable to feeding: this approachhas been used for premium high-strength steel castings.Of greater interest, however, are cases in which align-ment and anisotropy can be exploited in engineeringdesign. Some gas-turbine blades are now being producedwith columnar structures (Fig. 6), in which the absenceof transverse grain boundaries enhances stress rupturelife and ductility. The unidirectional freezing is broughtabout by end chilling coupled with induction heating

28

from a furnace coil: the heat source is progressivelywithdrawn to produce the high GIR ratio required in thesolidification zone.

This principle has since been extended to the develop-ment of single-crystal blade castings of predeterminedorientation: selective growth of a single grain is inducedby provision of a mould passage system shaped tosuppress the continued growth of unwanted grains bysuccessive changes in the growth direction (Fig. 7).

Fig. 7-Technique for the production of a single-crystal gas-turbine blade by controlled solidification: upward growth

from base chill 15

SEPTEMBER 1976 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

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TIMEFig. 8-Comparison of creep properties of a cast high-temperature alloy: a orthodox structure, b

columnar structure, c single crystal'.

Typical improvements in high-temperature propertiesare illustrated in Fig. 8.

An older process that has found renewed impetus inrecent years is centrifugal casting. Tubes are nowproduced in a wider range of alloys, and the processhas found an important role in the manufacture of gasreformer plant and other modern applications. Onerecently commissioned plant in the U.K. has beendesigned for the vertical spinning of heavy dual-metalrolls at a rate of four per shift and embodies advancedcontrol features17. Pouring is currently preprogrammedto a graphical schedule, but this will eventually giveway to metal delivery from a servo-controlled ladle withsliding gates operated through a digital computer.

The diecasting sector, too, is making a vital con-tribution to the modern foundry industry18. Bothgravity and pressure processes are highly developed inthe U.K. and already predominate in non-ferrousfounding. There are numerous developments in controland automation, especially in the use of sophisticatedhydraulic circuitry in pressure diecasting, enablingplunger travel to respond to the needs of the successivephases of mould filling, whilst metal transfer andmetering systems are still undergoing development.Modern ideas attracting interest include the use ofenlarged gates, low velocity fill, and concentric plungersto produce sounder castings. Die mechanization is beingincreasingly used in the gravity field.

The most notable development, however, has been theextension of pressure die casting to steel on a com-mercial basis: low-carbon and stainless-steel componentsare now being regularly produced in masses up to1,5 kg, and examples are shown in Fig. 919. Nickel- andcobalt-based castings are also in production. Resistanceto thermal shock is obtained by the use of molybdenum-base alloy die and shot sleeve inserts. Single shot charges

are melted in less than one minute in self-tappinginduction furnaces. Porosity levels of 1 to 3 per cent arecurrently obtained in the products.

The low-pressure diecasting process is finding someapplication in the production of aluminium alloys, butthis principle has by no means reached its full potential.A critical look at past and present approaches to foundingshows that the most unsatisfactory feature appears at thecrucial stage of mould filling, during which control islargely lost: the metal stream undergoes free fall, isexposed to oxidation, and is subject to turbulent flow inthe mould cavity. The low-pressure process (Fig. 10)offers an elegant solution to these problems, providingupward fill at controlled rates under totally enclosedconditions. The system has many possibilities, althoughnumerous problems remain to be overcome for theprinciple to be extended to other alloys and other typesof mould. An existing diecast product is shown in Fig. 11.

Other developments in cast products include thecontinuous evolution of high-temperature nickel-basealloys designed for optimum properties in the cast form,and the introduction of additional high-strength caststeels of both orthodox and maraging types. Premium-grade titanium-base castings are also being successfullyproduced and are already finding structural applicationin aircraft21 (Fig. 12). Advanced techniques employed intitanium founding include skull melting, centrifugalcasting in vacuum, and highly specialized reaction-inhibitive moulds. This field has also seen the systematicevaluation of critical defect size relative to the specifiedperformance conditions of the individual cast component,using the concepts of fracture mechanics.

The present review of technical progress will be mostappropriately concluded wi&h.a cast product that com-bines three modern innovations and that aptly demon-strates the capability of the foundryman to meet the


Fig. 9-Examples of pressure diecastings in steel (by courtesy of G.K.N. Castings Ltd)

designer's challenge. The casting illustrated in Fig. 13 isa nickel-alloy gas-turbine blade manufactured by theRolls Royce casting facility. This gas-cooled blade, acomponent of the RB211 engine, is produced by theceramic shell process. The cooling passages are formedby fused-silica core flatsAocated in the original dieassembly and retained in the wax pattern, as shown onthe left of the illustration. The mould cavity is coatedwith a cobalt compound grain refiner, applied as aconstituent of the investment precoat. After casting, thecores are leached out with a caustic solvent, leaving thefinal blade as shown, an example both of structurecontrol and of shaping facility in a single advancedproduct.

Future Perspectives in FoundingThis paper has been devoted principally to individual

developments in processes and products of recent years,some well established and others still in embryo. Itwould be appropriate to conclude with a more generallook at the industry.

Problems facing the British industry were highlightedin a report published recently by the National EconomicDevelopment Office22; some of its findings are relevantwell beyond the ferrous castings industry, to which the

study was confined, and are mirrored in many othercountries. In the industry as a whole, there has beeninsufficient investment for the exploitation of newideas and the replacement of obsolete plant. Althoughthe U.K. industry had a 1974 output valued at £775million and employed 105000 people, both outputtonnage and employment have been falling. for someyears: there are 40000 fewer employees than formerly.The nature of the employment, too, is changing, withreduced emphasis on moulders as distinct from mainten-ance operatives; this is as well since there is aninsufficient flow of apprentices into the traditionalskills. The past image of the industry is also felt to havehad an adverse influence on the recruitment of mana-gerial and technical staff.

The decline in demand has produced many closures,but detailed examination indicates, more encouragingly,that much of the contraction is in traditional heavyproducts with low added value, owing to such factors assubstitution by plastics in domestic applications of castiron and by concrete in soil pipes, as well as by weld-ments in engineering. Part of the fall in tonnage alsoarises from technical progress that enables engineeringspecifications to be met by light, accurate castings of


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Fig. I I-A Iow-pressure diecast cylinder block in aluminiumalloy (by courtesy of Alumasc Ltd)

high quality: to quote one example, 64 per cent of the1974 output of pressure pipes was in S.G. iron, a pro-portion still rapidly increasing.

The more modern product types require greaterinvestment in advanced moulding and coremakingtechniques and in facilities for the control of melt andquality. A further area requiring heavy investment ispollution control: to meet stringent laws, it is estimatedthat £90 million will be required over the next fiveyears, representing roughly one-third of all foundryinvestment. Thus, to modernize in respect of bothtechnical developments and conditions in the industry,investment will need to be around 60 to 80 per centabove current rates. It has been concluded that there islittle chance of financing such investment from cashflow, especially in small foundries. Larger foundries canshow greater benefit from technical and mechanicaldevelopments, and now have more flexibility to under-take small batches so that more polarization seemsprobable: the largest 16 per cent of iron foundriesalready produce 78 per cent of the U.K. output, whilstthe smallest 59 per cent produce only 6 per cent. Inthese circumstances, there is already anxiety for futurejobbing capacity for more specialized castings.

A scheme has recently been introduced for the in-injection of £25 million of public funds to assist inmodernization. This will be used to provide up to 25 percent of the capital for approved schemes, but onlya limited proportion will be allowed for environmentalcontrol. This represents only a fraction of the totalinvestment required for the industry fully to exploitthe technical advances reviewed earlier. These areheavily concentrated in the most efficient sector, whichis giving a superb lead with competitive products ofhigh quality. Building on this lead, it seems probablethat a more streamlined industry will centre on thenumerous innovations devised by chemists, metal-lurgists, and plant engineers in recent years.

In conclusion, it might reasonably be asked of thepresent author what contribution can be expected fromthe universities to these objectives. Without belittlingpast achievements, perhaps their most valuable futurerole could lie in the development of further educationalpatterns specific to the needs of the managers andtechnologists who will be exploiting the newer foundryprocesses to the full.

References1. JACKSON, J. M. A history of steel casting. Br. Foundrym.,

vo!. 60. 1967. p. 305.2. Catton's Knowsthorpe Foundry. Fndry. Trade J., vo!. 139.

14th Aug., 1975. p. 197.3. GODDING, R. G., MCCORMACK,W., LEMON, P. H. R. B., and

EDWARDS, A. A high production rate cold coremakingprocess. Br. Foundrym., vo!. 64. 1971. p. 309.

4. GREGORY, A. H. Ashland cold box process. Proc. 1972Annual Conference of S.C.R.A.T.A., Paper 5, p. 1.

5. KONO, R., and MIURA, T. "Ftuidamental techniques of thevacuum sealed moulding process. Br. Foundrym., vo!. 67.1974. p. 319.

6. KONO, R., and MIURA, T. Accuracy of iron castings producedby the V-process. Br. Foundrym., vo!. 68. 1975. p. 70.

7. Progress in automatic moulding plant. Notes on B.C.I.R.A.Conference; Metals and Materials, 1974, vo!. 8, no. 2. p. 11.

8. EMLEY, E. F. The cleansing and degassing of light metals.Conference on Alloy Composition and Microstructure Control

.JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY SEPTEMBER 1976 31

1,5c 1ft.

l hOit> }

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Fig. 82-Titanium alloy casting for use in aircraft: engine hoist tube and arrestor hook bracket21 (bycourtesy of TiTech International Inc.)

Fig. IJ-Stages in the manufacture of gas-turbine blade casting with cored cooling passages: wax pattern with fused silicacore rods; sectioned ceramic shell mould; casting (by courtesy of Rolls Royce (1978) Ltd)


in Relation to Processing. London, Metals Society, 1975.(To be published.)

9. BRANT, M. V., BoNE, D. C., and EMLEY, E. F. Fumelessin-line degassing and cleaning ofliquid aluminium. J. Metals,vo!. 23. 1971. p. 48.

10. MCCAULEY, J. L. Production of nodular-graphite ironcastings by the Inmould process. Frulry. Trade J., vo!. 130.1971. p. 327.

11. RAPOPORT, D. B. Aerofoil investment castings for theMach 3 engine. Frulry. Trade J., vo!. 116. 1964. p. 169.

12. BRYANT, M. D., and MOORE, A. Mould coatings of zinc!ground coke or cobalt to prevent hot checking in malleableiron castings. Br. Fourulrym., vo!. 64. 1971. p. 215.

13. FLEMINGS, M. C., and MEHRABIAN, R. Casting semi-solidmetals. Trans. Am. Frulrym. Soc., vo!. 81. 1973.

14. SPENCER, D. B., MEHRABIAN, R., and FLEMINGS, M. C.Rheological behaviour of Sn-15PctPb in the crystallizationrange. Metall. Trans., vo!. 3. 1972. p. 1925.

15. VERSNYDER, F. L., and SHANK, M. E. The development ofcolumnar grain and single crystal high temperature materials

through directional solidification. Mat. Sci. Engng, vo!. 6.1970. p. 213.

16. VERSNYDER, F. L., BARROW, R. B., PIEARCEY, B. J., andSINK, L. W. Precision casting of alloy single crystal gasturbine parts. Trans. Am. Frulrym. Soc., vo!. 77. 1969. p. 10.

17. PAGE, M. L. Vertical centrifugal casting raises bi-metal rolllife. Metals Mats., Feb. 1975. p. 47.

18. BATEs, A. P. Recent developments in die casting. Progressin Cast Metals. London, Institution of Metallurgists, 1971.p. 3.31.

19. LEATHAM,A. G., CARVER,B. G., and SELLORS,R. G. R. Thehigh pressure diecasting of ferrous and other high meltingrange alloys. Conference on Alloy Composition and Micro-structure Control in relation to Processing. London, MetalsSociety, 1975. (To be published.)

20. WOODWARD,R. R. An examination of the relative theories ofgravity, high- and low-pressure die casting of aluminiumalloys. Br. Foundrym., vo!. 58. 1965. p. 148.

21. Proceedings of First International Titanium Casting Seminar,London, 1974.

22. Iron and steel castings: industrial review to 1977. London,National Economic Development Office, 1974.

Company AffiliatesThe following members have beenadmitted to the Institute as Com-pany Affiliates.

AE & Cl Limited.AfroxjDowson and Dobson Limited.Amalgamated Collieries ofS.A. Limit-

ed.Apex Mines Limited.Associated Manganese Mines of S.A.

Limited.Blackwood Hodge (S.A.) Limited.Blyvo()ruitzicht G.M. Co. Ltd.Boart International LimitedBracken Mines Limited.Buffelsfontein G.M. Co. Limited.Cape Asbestos South Africa (Pty) Ltd.Compair S.A. (Pty) Limited.Consolidated Murchison (Tvl) Gold-

fields & Development Co. Limited.Deelkraal Gold Mining Co. Ltd.Doornfontein G.M. Co. Limited.Durban Roodepoort Deep limited.East Driefontein G.M. Co. Limited.East Rand Prop. Mines Limited.Envirotech (Pty) Ltd.Free State SaaiplaasG.M. Co. Limited.Fraser & Chalmers S.A. (Pty) Limited.

Gardner-Denver Co. Africa (Pty) Ltd.Goldfields of S.A. Limited.The Grootvlei (Pty) Mines Limited.Harmony Gold Mining Co. Limited.Hartebeesfontein G.M. Co. Limited.Highveld Steel and Vanadium Corpo-

ration Limited.Hubert Davies Heavy Equipment(Pty) LtdImpala Platinum Limited.IngersqIJ Rand Co. S.A. (Pty) Ltd.Kinross Mines Limited.Kloof Gold Mining Co. Limited.Lennings Holdings Limited.Leslie G.M. Limited.Libanon G.M. Co. Limited.Lonrho S.A. Limited.Loraine Gold Mines Limited.Marievale Consolidated Mines LimitedMatte Smelters (Pty) Limited.Northern Lime Co. Limited.O'okiep Copper Company Limited.Palabora Mining Co. Limited.Placer Development S.A. (Pty) Ltd.President Stern G.M. Co. Limited.Pretoria Portland Cement Co. Limit-

ed.Prieska Copper Mines (Pty) Limited.Rand Mines Limited.

Rooiberg Minerals Development Co.Limited.

Rustenburg Platinum Mines Limited(Union Section).

Rustenburg Platinum Mines Limited(Rustenburg Section}.

St. Helena Gold Mines Limited.Shaft Sinkers (Pty) LImited.S.A. Land Exploration Co. LImited.Stilfontein G.M. Co. Limited.The Griqualand Exploration and Fi-

nance Co. LImited.The Messina (Transvaal) Develop-

ment Co. Limited.The Steel Engineering Co. Ltd.Trans-Natal Coal Corporation Limic-

ed.Tvl Cons. Land & Exploration Co.Tsumeb Corporation Limited.Union Corporation LImited.Vaal Reefs Exploration & Mining Co.

Limited.Venterspost G.M. Co. Limited.Vergenoeg MiningCo. (Pty) Limited.Vlakfontein G.M. Co. Limited.Welkom Gold Mining Co. Limited.West Driefontein G.M. Co. Limited.Western Deep Levels Limited.Western Holdings Limited.Winkelhaak Mines Limited.


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