RESEARCH IN THE ALUMINUM INDUSTRY
FATIGUE TESTING MACHINES
A
FRANCIS C. FRARY with the necessity of competing with NY business, to live, must make a all the other commercial materials, from profit, if not this year, a t least Aluminum Research Laboratories, paper to steel, and wresting from them most years, and certainly on the New Kensington, Pa. piecemeal various Dortions of their a v e r a g e . over a series of v e a r s . markets. Without a- real market the I n some years many businesses fail to aluminum industry could not make a profit, and without a do this, and some of them manage to linger on for a while in profit it could not exist. this profitless condition. Unless, however, they can sell out In order to displace any other material, this new metal must to someone who can do better or reorganize “under new offer to the consumer a sufficient advantage to justify changmanagement,” the sheriff will eventually get them. Their ing from the old and tried material to the new and untried one. employees will be out of a job and the owners will lose most or It must offer either distinctly better utility a t the same cost all of their investment. This need of profits must necessarily or a satisfactory utility a t a decided saving. A manufacturer, control the actions of all of the departments of a company. with a plant and process operating with reasonable satisfacResearch is no exception; the company must make a profit on tion and profit on a given material, cannot afford to risk the stockholders’ money which it spends on research and dechanges unless the prospects of additional profits are suffivelopment. The problems and services of the research orciently tempting to justify taking the chance of some loss in ganization depend, therefore, upon the technical and comcase his judgment is faulty. mercial situation in the industry. Research is naturally most It is apparent that the result of this competition between productive when backed by the resources and “know how” of metals depends on the properties and cost of the finished an integrated industry with a field of activity extending from fabricated article delivered to the ultimate consumer, althe production of the raw material to the fabrication of the though the actual competitive material may be a semifinished product. This might well be termed “straight-line” fabricated product such as sheet, rod, tubing, castings, etc., research, to borrow a phrase from the automobile industry. which is sold to the manufacturer of the finished article. Therefore, while the problem of producing maximum utility Recent Commercial Development of Aluminum of the finished product a t a minimum cost is the fundamental one, the solution of it may turn upon the properties and cost The aluminum industry differs from the other metal indusof the semifabricated commodities which are in direct competries in that its commercial development has taken place tition with similar items made of other materials. I n general, within the last fifty years; therefore aluminum has no tradionly the maker of semifabricated products can use the crude tions of long service and widely known virtues to aid it in metal; if he is already successfully fabricating other maprocuring or holding markets. When aluminum became an terials, such as brass, copper, lead, tin, zinc, paper, cork, etc., article or commerce a t a price which enabled it to leave the he usually sees little or no reason for spending time and money jewelry business and go into more humble lines, it was faced “
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metal. Each of these groups contains some problems which a t first glance do not seem to be obviously related to it, as well as the more obvious type of problems.
Improving UtiIity
TESTIXG AN ALUMINUM COLUMN IN COMPRESSION
and taking a risk in order to find out whether he could profitably use aluminum instead of his present raw material. It was this situation which stared the original producers of aluminum in the face when they finally had their process working and had a few tons of the metal for sale, and which forced them to invest time and money in the development of fabricating plants and processes in order to convert their metal into a salable form. The only other method which has been successful in rapidly expanding the use of aluminum in the metal-fabricating industry is the modern German one. For economic reasons the use in Germany of certain competing materials has been either forbidden completely or so hedged about with restrictions and difficulties that the industry has been compelled by governmental pressure to substitute the aluminum produced by government-owned plants for other metals which must be imported. This competitive situation is also the reason why most of the advances in fabricating methods and technique, new alloys, finishing processes, etc., and fruitful investigations of the basic problems of the industry have been accomplished by the companies which produce the crude metal, with occasional contributions by scientific laboratories operating under government auspices. If research were conducted by companies which only fabricate and do not produce the crude metal, they would work a t a decided disadvantage. They would be unable to determine whether anything done to the metal prior to their receipt of it was involved in their difficulties, or what could be done by the metal producers to simplify their problems or facilitate their solution. The problems in research and development in the aluminum industry, therefore, divide themselves into two groups: (a) improving the utility of the final product t o the ultimate consumer and (b) reducing the cost of this finished product by reducing the costs of both producing and fabricating the
I n general, the utility of the final product to the consumer depends upon its properties and form. Thus, we have facing us the problem of modifying and improving the properties of the metal itself by surface treatment, mechanical working, alloying, annealing, and heat treating, so as to produce a wide range of finish, hardness, strength, ductility, electrical and thermal conductivity, etc. From the results, the particular combination most suitable to the purposes of an individual customer must then be selected, in the hope that it may present adequate advantages to induce the customer to use it. Historically, the problems of mechanical working and annealing and control of impurities to produce arange of properties were the first to be attacked and partially Eolved. When the properties thus obtained were found inadequate for many uses, alloying was begun for the production of both cast and wrought articles. Almost all of the alloy development work has been accomplished within the last thirty years. Thus, of the twenty-seven standard aluminum casting alloys now employed in large tonnages in this country, only four were in use in 1915; of the nearly twenty standard wrought products, only pure aluminum and an aluminummanganese alloy were then in use. The heat treatment of certain types of aluminum alloys was also discovered about thirty years ago, and its development has gone hand in hand with the development of alloying knowledge and practice. Upon the original requirements of castability and high strength, experience superposed the requirement of high stability under corrosive conditions, so that the zinc-bearing alloys originally employed have gradually passed out of the picture to a great extent and been replaced by alloys containing copper, silicon, and magnesium. Special finishes, such as oxide coatings, have been a more recent but important development, adding resistance to corrosion and abrasion, luster, reflectivity, and even color to the finished article. The original-semifabricated products were sheet and sand castings; they were soon supplemented by wire and rod; later other semifabricated forms, such as foil, permanent-mold castings, die castings, forgings, bronze powder, and extrusions were added to the list, If aluminum was to be used, therefore, the customer found himself faced with a choice from among a variety of alloy compositions and tempers, as well as a variety of semifabricated forms in which these alloys could be furnished t o him. Obviously, the chance of being able to persuade him to use aluminum instead of some other material could be greatly increased. However, it was necessary that the salesman or engineer who had this job be adequately informed of the properties, virtues, and costs of these different products, and be able to select and sell the one which would best serve the individual customer without being prejudiced or limited by the possibility that his company could not furnish the particular article. The development of these varied products under one management with the incentive of not only keeping the specialized fabricating plants busy, but also providing an outlet for the metal, and thus keeping mines, alumina plants, and
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INDUSTRIAL AND ENGINEERING CHEMISTRY
reduction plants busy, was undoubtedly the reason why the United States early became the world’s greatest consumer and producer of aluminum and aluminum products and still retains this position. A less obvious but important group of problems in this class involves the development of technical information to help the consumer to use the products of the industry more economically and satisfactorily. This includes the accurate determination of all the physical properties of all the different commercial alloys in all their commercial forms and tempers, and the effects of variations in composition and fabricating practice upon such properties; it also involves a complete study of the principles of engineering design applicable to the use of aluminum structural products. Structural and machine design information for steel has been available in handbooks for years. Although the tensile properties of some of the aluminum alloys are comparable with those of steel, there is a large difference between them in the modulus of elasticity-a figure which appears in most of the design formulas. In view of this difference in a property which is so important in steel design, much experimental work was necessary to determine what formulas would represent good practice with aluminum alloys. The higher cost of the aluminum structural members introduced a pressure for economy in their use which made a complete study of stress distributions in structures and the refinement of structural design imperative. Practical experience showed that the principal reason for employing aluminum in structural work was to reduce weight. Only by taking advantage of the maximum weight reduction consistent with safety and adequate performance could the higher cost per pound of the aluminum structure often be justified and the final result be a net profit to the user, American producers have pioneered in the experimental study of the elements of structural design in aluminum and, as a result, have been able to publish a comprehensive structural aluminum handbook. Its two hundred pages of information on the design of aluminum structures are based on the experimental investigation of
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stress distributions and load-carrying ability, and the correlation of experimental results with modified design formulas. The resulting information on design refinement and the stimulation of the demand for light and yet strong construction, together with the alloy and fabricating developments of the aluminum industry, have naturally reacted on the other metal industries to stimulate them to similar competitive developments-all to serve the ultimate consumer better. Along a still different line, the problem of increasing the sale of aluminum in pigment form has involved years of research on the properties of the resulting paint as a function of the character of both the pigment and the vehicle. As a result, the paint manufacturer can now produce such paints and vehicles and the consumer can purchase them with assurance of excellent results. Here again the manufacturer of the finished product had little incentive to develop aluminum pigment or its use, and only the broad policy of developing to the full all outlets for aluminum could justify the continuous heavy experimental expenditures necessary to develop aluminum paint properly and demonstrate its advantages to the customer, in competition with well-established paints made from a variety of other pigments.
Reducing Costs No matter what the merits of an aluminum product, its sale is handicapped unless its price is competitive with that of the material it seeks to replace. Since market expansion thus depends upon costs, it is obvious that an important part of the research and development work must be directed towards reduction of the cost of both producing and fabricating the metal, in the face of steadily increasing labor and tax rates. Naturally, the first point of attack is the rich ore, bauxite. Although it occurs in tremendous quantities in subtropical areas, local conditions are not usually favorable to the extraction of the pure aluminum oxide from it or the conversion of the oxide into the metal on the spot, Southern France is probably the only notable exception, where bauxite, coal, and water power occur relatively close together. The expense of transporting 4 tons of bauxite per ton of metal produced has naturally focused research on processes of beneficiating the bauxite a t the mine so as to reduce the amount of impurities; such methods have been worked out and are employed. The common world-wide occurrence of clays and other rocks containing from one-fourth to three-fourths as much alumina as bauxite has been the incentive for a tremendous amount of investigation, both inside and outside the industry, in an attempt to reduce the cost of alumina by extracting it from these leaner ores. Technological difficulties in chemically extracting alumina of the necessary high purity from such materials, a t a cost which will compete with that of alumina extracted from bauxite by the relatively simple Bayer process, have thus far prevented the accomplishment of any saving in this direction. The possibility of using somewhat lower grade material by a smelting process, to produce fused alumina and a ferrosilicon type of alloy as a by-product, was unsuccessfully investigated here nearly forty years ago by Charles M. Hall and again much more exhaustively by others about ten years ago. Also the possibility of directly smelting more or less pure alumina with carbon to form the metal or an alloy which could be subsequently refined has been exhaustively studied on a smalI and a large scale; the electrolytic refining of aluminum alloys in a molten cryolite bath was actually accomplished commercially more than ten years ago. While the refining process was important as a source of high-purity metal, no other combination has yet been discovered which can produce commercial aluminum a t as low a cost as the
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Bayer process of alumina extraction and the Hall electrolytic reduction of the oxide in a fused cryolite bath. The only exception to this statement is the Pedersen alumina process, where ferruginous bauxite is smelted with limestone to form calcium aluminate and iron, and the alumina is extracted from the slag with sodium carbonate and then reduced to metal by the usual electrolytic process. This seems to be commercially successful under Norwegian conditions and possibly under some conditions in Russia.
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tice, have gone a long way towards reducing and controlling the amount of this scrap and eliminating the unexpected features of its occurrence in a given lot of metal. Without this development some of the present important commercial alloys could not have been produced a t all, and others would be too costly to meet competition in the market so that a good share of the present market never would have been obtained. The design, building, and installation of new, improved, and larger furnaces, molds, mills, presses, etc., by the engi-
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TENSILE STRENGTH YIELD STRENGTH
ELO ON OAT ION
50 000
w
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RANGEOF TENSILEAND YIELD STREN5THS 0% TYPICAL COMMERCIAL ALUMINUM ALLOYS Temper designations: 0 = annealed. H = hard-rolled; W = given solution he& treatment but not aged. T = heat-treated and aged. 2s is comdercially pure (99+ per cent) aluminum. 39 45 and 62s are nonheattreatable alloys: 53’5, i7S, 24S, and 145 are heat-treatable alloys.
ALLOY-
25
3s
45
525
53s
I7 5
It should not be thought, however, that the commercial processes have remained in a stationary condition technologically. This is far from being true. Continuous study and experimentation have steadily improved both processes, increasing yields and permitting the use of larger and more economical equipment, so that the world price of aluminum has shown a steady and considerable decrease over the last twenty years. In most fabricated or semifabricated aluminum products, the fabricating cost represents a large item, and a considerable part of this cost is bound up with the problem of scrap production. In the earlier days (for example, even after the war) unknown and therefore uncontrollable factors produced large and varying amounts of finished and semifabricated products which were unsalable and had to be scrapped because of fabricating defects. Slivers and blisters in sheet, tubing, etc., and porosity, shrinkage cracks, and other defects in castings took a large toll, not only in expense but in customer good will; the industry did not know, when a given amount of metal was put into process to fill a certain order, how much of it would come out several weeks later in a form which would be accepted by the customer. The introduction of the stronger alloys into the processes of fabricating wrought materials caused tremendously increased scrap losses because of the cracking of these alloys under the fabricating stresses a t various points in the process. Surface cracks which rolled out into slivers, edge cracking of slabs and sheet (which required continual edge shearing, perhaps to the point where the finished sheet was too narrow to meet the customer’s specifications), “alligatoring” and splitting of the strong alloy ingots in the initial stages of rolling, and the unexpected and uncontrollable appearance of blisters when the partially or completely fabricated wrought products were annealed or heat-treated, caused scrap losses which might sometimes run as high as 90 per cent of the ingot weight. These resulted in delays in shipment and clogging of the mill with scrap a,nd additional material which must be rolled to replace thc scrap, Fundamental research on alloy compositions and the influence of minor ingredients, on segregation, gas absorption, fabricating temperatures and other conditions, and on the development of improved melting, casting, and rolling prac-
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neering and development organizations in the fabricating plants have been a continuous process that has been of great importance in bringing strong aluminum alloys into their present competitive position with respect to steel, brass, bronze, etc. Therefore today there is no difficulty in obtaining a satisfactory yield of finished strong alloy sheets or plates weighing as much as a thousand pounds apiece from correspondingly large ingots. It is obvious that as the size and weight of the finished semifabricated articles increase, the risk of expense involved in the occurrence of fabricating defects which may cause rejection of the finished article increases tremendously; and hence an excellent control of the fabricating processes and metal quality from beginning to end is indispensable to the economical production of such articles. Thus, it is clear that the research and development organization is an agency neither of the sales department nor of the operating organization; it is a staff group under the control of the general company management and must serve both the sales and operating departments, as well as the management itself. Upon its shoulders rests much of the responsibility for the future of the industry. It must understand and evaluate the importance and the ramifications of changes and improvements in practice anywhere in the company, and keep in mind in its investigations the whole picture of the operations of the industry and the requirements of present and potential customers. Improvements in competing materials must be watched and matched with corresponding improvements in the aluminum base materials, if markets are to be retained. Kew and improved fabricated and semifabricated forms must be continually developed in order to enter new markets in competition with older and established materials. Retaining and expanding present markets and acquiring new ones are the fundamental problem of the aluminum industry and hence the fundamental problem of research in that industry. It is evident that this problem can be most efficiently attacked when the research organization is backed by the knowledge, experience, and resources of all branches of the industry, from the mining of the ore to the fabrication of finished products. R E C E I Y ~August D 18, 1938. Presented before the meeting of the Pittsburgh Local Section of the American Chemioal Society, September 15, 1938.
