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Aviation History
1961
1961 - 0920.PDF
20 FLIGHT, 6 July 1961 SPECIALIST-ALLOY FACILITY... plant has grown steadily. Today its covered area is 28 acres, or1,219,680 sq ft, and employment has reached over 2,000. Current expansion may be gauged by the fact that building expenditure wasapproximately £3m last year and will be at least £4m in 1961. Completion of present programmes is scheduled for mid-1964,by which time employment should lie between 3,500 and 3,700. No longer is the Hereford works devoted solely to aircraft pro-ducts. Only about one-fifth of the total tonnage of raw material sent out from the plant is now destined for aircraft gas turbines; andeven excluding the vast output of nickel anodes, the proportion is less than one-third. The chief products are now nickel anodes,Inconel and Monel sheet and strip, and Nimonic 75, 80A and 90, which although originally gas-turbine alloys are now used in manyforms in a wide variety of commercial applications. These materials together account for some 75 per cent of the tonnage produced. Essentially, the Hereford factory is a jobbing unit, for although some basic materials and forms are churned out for years on end,Henry Wiggin & Co would be quite happy to produce 4oz of gold- plated nickel wire—provided the customer was prepared to pay.The range of products is tremendous. Even at the input end of the plant there are 72 basic raw-material stocks for melting and eightfor powder metallurgy, in addition to nickel itself. At the output end may be found several hundred specialist materials, in the formof sheet, strip, forged bar, extrusions or wire. In aircraft gas turbines Wiggin nickel alloys are found almostentirely in the hottest portions, where they may well claim to be the ruling structural material. It would be ludicrous to attempt todescribe all the bits and pieces of modern engines made from Nimonic or Inconel alloys, but some of the more noteworthyprocesses may be briefly referred to. In particular, it is clear that the company have been very bold in investing heavily in the extru-sion process at a time when the extrusion of most of the more difficult materials had yet to be accomplished. For example, much of the carcase of a modern engine is heldtogether or reinforced by circular rings having a variety of flanged sections. During recent years it has been found possible to fabri-cate these rings much more cheaply than hitherto by extruding a section very near to that required and then producing each ring byflash butt-welding. A process that is still in some respects a trade secret (though it was described in our sister-journal Aircraft Produc-tion over seven years ago) is the production of such rings by the Ugine Sejournet method, in which glass is used to lubricate thesteel or Nimonic alloy passing through the die. Using this process, the Hereford plant can squeeze out ring stock in remarkable lengths(plain nickel anode bars are extruded 80ft at a time), and the finished ring sections in Nimonic 75, 80A or 90 cost roughly halfas much as when they were rolled from an upset slug of metal. Incidentally, there is practically no difference in u.t.s. between theoriginal bar and the welded ring. Extrusion and rolling is also the common method for producing Brute force, but no ignorance: left, glass-lubricated extrusion from a hot billet by the 5,000-ton Loewy press; above, feeding sheet from a furnace to one of the hot sheet finishing stands bar stock for turbine rotor blades, and the number of Nimonicturbine blades must now be many million. Moreover, airline engines subject to intensive utilization are likely to require rebladingat least once a year, and Hereford's output of bar stock for Dart blades is much greater than that needed to support Rolls-Royce'soutput of new engines alone. It is pertinent to note that many of the latest Rolls-Royce engines, including the Avon, Tyne, DartRDa.10, Conway, RB.141 and Spey, incorporate air-cooled turbine blading; but although tens of thousands of such blades are inservice with many air forces and airlines, no details may be given of their fabrication. International Nickel and Henry Wiggin spend large sums everyyear in their quest for ever-better rotor-blade alloys. One of the first to go into production was Nimonic 80, and this is still ingreat demand for relatively mild applications. First-stage blading was successively produced in Nimonic 90, 95, 100 and 105, andthe visitor to Hereford can now see production quantities of Nimonic 115 as the latest blade material. Each of these alloysrepresents a sustained effort by numerous metallurgists, physi- cists, engineers and other staffs over a period of many years; andeven when the alloy is in production in one form, it may still require extensive research before it can be produced in another (for example,Nimonic 90 wire is now being drawn, after three years' intensive development). Throughout, the aim is to produce a material better able to with-stand physical deformation at elevated temperatures, and so it follows that each new blade material is more difficult to fabricatethan its predecessor. Some alloys are workable over a range of only a few degrees, and may require many trips into a furnace and outagain between successive operations. Actual blade-manufacture is handled by companies specializing in such work, or by the enginemanufacturer concerned; some material makes several trips between Hereford and the fabricator before being built into an engine, andHenry Wiggin & Co follow its progress throughout. Moreover every blade in every engine—be it installed in an Italian Caravelle,an American Friendship or a Peruvian Hunter—can be traced right back to a particular furnace or pot and to a particular heat, and thelog-sheet on the melt concerned is kept as a record. Improved blade material must be reflected in improved turbinediscs, and those of the latest engines run so hot that they will be forged in material even better than Nimonic 90. A vast excava-tion in a new bay at Hereford is steadily being filled with the under- ground workings of a 1,500-ton Bliss forging press, surrounded by itsown furnaces, which will be employed chiefly upon the production of "cheeses" for the manufacture of discs. New procedures havebeen devised for producing massive ingots for disc manufacture, and on a recent visit to the plant we noticed one of Nimonic 90with a weight of well over 5,0001b chalked on it. Such an ingot is worth about £7,000. Process heating throughout the works involves the consumptionof huge amounts of butane, supplied from a tank farm on the eastern perimeter of the facility, and steam is fed into the plant bya battery of oil-fired boilers of advanced design. Nearing comple- tion are new process laboratories; and there is a canteen for theneeds of the eventual 3,700 employees. The civil-engineering work is in hand on further plant extensions, included in which are addi-tional melting, hot strip mill, and rod and wire mill facilities. Eventually, the original Wiggin Street plant will shut down entirely.
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