E. T. WANDERER
ANNUAL REVIEW
Aluminum Alloy and temper development, fabrication and processes, and applications outline this year’s review of the aluminum industry
rimary aluminum production in the United States p i n 1967 increased 10.2% (301,375 tons) over the previous year to 3,269,759 tons. The year represented a relative plateau for aluminum industry shipments (a decline of less than 1% to 4,480,000 tons) because of a severe and lengthy inventory reduction through most of the year, and because of weakness in such volume markets as automobiles, homes, and major appliances. Forecasts for 1968 indicate sales gains in all major market areas. Major developments reported during the past 12 months appear in the following pages.
Alloy and Tepper Development A pilot program to produce high-performance castings from aluminum alloy KO-1 has been established. A limited number of U. S. foundries are working to develop new applications for the high-strength casting alloy, which reportedly exhibits 60,000 psi ultimate strength, 50,000 psi yield strength, and 5% elongation
@A). Manufacturers in the U. S. now can employ special corrosion-inhibiting T73 thermal treatment without entering into a license agreement with the patent holder. T h e treatment was developed for use with high-strength alloy 7075. I t produces high resistance to stress corrosion cracking, and has received wide use in aerospace and defense applications ( 5 A ) . An improved high-strength alloy for seamless cans and easy-open tops has been developed. Designated alloy X5182, the new sheet alloy is reported to be 10% stronger than stock previously used for aluminum cans and ends (44). A new high-strength alloy designed for aircraft castings has been introduced. Designated Arcast 67, the new alloy reports an ultimate tensile strength of 67,000 psi, yield strength of 57,000 psi, and elongation of 70/,. T h e alloy is said to exhibit good castability, is heat treatable, and contains no silver ( 3 A ) . Development of a new aluminum sheet alloy for porcelain enameling that is said to exhibit twice the yield strength of other porcelainizing alloys has been reported. Major use of the new sheet product will be for porcelain enameled cookware (ZA). A new low-temperature aluminum brazing alloy specially suited for parts to be plated or anodized has been developed. Alloy 601 is produced in 15-in. extruded rods with diameters of l / ~ o , 3/a?, and l/s inch ( I A ) . VOL. 6 0
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Fabrication and Processes Development of a new process for the manufacture of impact-extruded beverage cans has been announced. The method starts with impact extrusion slugs made by powder metallurgy. Standard can-making machinery and ordinary aluminum metalworking lubricants are used. The average strength of the container wall was 31,600 psi ultimate tensile strength; average burst strength was 170 psi gauge pressure; containers produced were impacted, drawn, and ironed to a height of 5 in. with a wall thickness of 0.005 in. (73B). Improvements in explosive bonding techniques appear to have made it the best joining method for metals, including aluminum, used under extreme conditions of stress, temperature, and atmosphere. The chief advantages of explosive bonding reported are formation of a high-strength metallurgical bond between similar metals and between dissimilar metals considered incompatible for fusion and diffusion bonding; bonds can be formed without disturbing the effects of mechanical or thermal treatments; the energy source is self-contained and often can be portable; bonding can be achieved quickly ( I S B ) . A study of the effects of varying electrode shape on arc, operations, and weld quality in aluminum alloy 2014-T6 indicates substantially different performance between fine electrode tips and tips with larger included angles or larger truncations. Results show that within the range of normal experience, variations in the tip can change the penetration current by more than 12 amp, move the position of the electrode from 0.50 in. below the plate surface to 0.030 in. above it, and affect the strength of the first weld pass by 5000 psi. Finer tipped electrodes did not produce welds as strong as the bluntest tips studied (3B). Alloys for complex welded aluminum structures are selected to meet various design criteria, high strength, stiffness,and resistance to corrosion. The most economical weldment will necessitate welded joints between dissimilar aluminum alloys. When specifying dissimilar alloy joints, the welding engineer should specify filler metals that do not shift-weld metal composition toward peak-cracking values. A welded joint between two different aluminum alloys will have five different engineering materials; two base metals, their heat-affected zones, and the hybrid weld metal alloy. I n the ideal joint, tensile fracture would occur in the heat-affected zone of the weaker base metal. Mechanical properties of welds for 158 combinations of aluminum base and filler metal alloys are listed (BB). Vacuum brazing-gas quenching of aluminum alloy 6061 has been found feasible for production quantities of complex and simple items. The investigation described was to develop a process or method for producing helium leak-tight containers with a high level of compatibility. The concept evolved around combining vacuum brazing and gas quenching into one operation. The advantages are such that possible applications include automotive radiators and various types of thermal conditioning sandwich panels and heat exchangers. Brazing flux is 64
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now used which provides a significant cost reduction and eliminates the danger of trapped flux residues. Post cleaning of assemblies is eliminated, and aluminum tooling can be used instead of expensive stainless steel and nickel alloy tooling (I5B). Plating methods combine the high strength/weight ratio of aluminum with the surface characteristics of other metals. Papers presented at a finishing seminar examine continuous coil plating, new barrel-plating methods, economics of plated aluminum us. bare copper, and trends to large captive plating plants (78B). An aluminum wire processing system that reportedly improves product dependability and speeds production has been developed. The unit is placed in the wire line after the let-off and before the extruder. Wire is annealed to required UL tensile strength, and rejects that occur with the more common batch annealing techniques are eliminated. The system can help solve difficulties for wire firms contemplating switching from copper to aluminum (72B). The latest finishing methods and materials developed for buffing and polishing aluminum are presented. Architectural anodized finishes are discussed ; characteristics of integral color-anodizing processes are explained ; and factors affecting appearance are examined. Plant layout, material, and equipment-systems recommendations for anodizing lines are detailed (ZB). Special article on finishing aluminum includes discussion of surface preparation for painting; types of conversion coatings and methods of application are described; and special alloy considerations and treatments are presented. Techniques for applying single and multiple color anodized finishes are detailed as well as colorants, appearance matching, and trouble shooting. The advantages and major uses of porcelain finishes are discussed ; porcelainizing methods, materials, and equipment are presented; and quality control tips, testing techniques, and commercial porcelain enameling practice are given (74B). Structural adhesive bonding has replaced or supplemented welding in the production of electronics equipment cabinets by one manufacturer. A 50% reduction in assembly costs, closer dimension tolerances, improved pressure tightness, and a more attractive appearance are among the advantages reported. T h e cabinets house radio and power supplies used in naval vessels and military aircraft ( I 7B). A comprehensive review presents the newest developments in techniques, materials, and equipment for cleaning and finishing aluminum. Formulations and controls for alkaline and acid baths that produce decorative or functional finishes are discussed. A growing number of applications obtain the appearance and corrosion resistance of anodized aluminum by using preanodized AUTHOR E. T. Wanderer is Development Manager, M a chinery and Equipment Section, Application Engineering f o r Aluminum Co. of America. M Y . Wanderer has authored the last two year’s reviews; engineers from A h a have authored this review since 7961.
coiled sheet. The advantages of the prefinished product and how they are being used are reviewed. The operational fundamentals and limitations of each major painting method are described (43). A new forming process called pierce forging makes parts from molten aluminum that are stronger and less expensive than screw machine parts. Testing has shown that tensile strength is increased by as much as 2OyG,and production costs are reduced 58Oj, when a part is pierce-forged rather than made on a screw machine. The new method is said to be competitive with impact extrusion, forging, casting, screw machining, and powder metal forming (IOB). A need for stronger aluminum weldments in aerospace, transportation, ordnance, and structural applications has focused attention on the higher strength but harder-toweld alloys. The problems, procedures, equipment, and filler alloys involved in welding the high-strength 2000 and 7000 series aluminum alloys are discussed by a welding expert (I7B). A new metal inert gas welding process identified as “pulse arc welding” joins thin aluminum with thick wire. A two-part power source is employed that provides good welds in sheet as thin as l/Ie-in. without backing bars or back chipping. Product applications include road and rail transport bodies, containers, and beer barrels (9B). Great interest in the possible use of nuclear power for aluminum reduction is being evidenced because of high power demands in the near future and the advantages of locating reduction plants in the large market areas. Nuclear power appears to be an appropriate energy source for close integration with aluminum production facilities ; however, careful consideration Must be given to reliability required and to adequate reserve capacity. For the most economical power, the size of nuclear power units appears best to be in the range of 500 to 1000
MW (6B). Quenching light-gauge aluminum in cold water usually guarantees good strength and corrosion resistance. I t also is certain to cause distortion which must be treated by hand straightening. Engineers have discovered that quenching thin-gauge aluminum in polyalkylene glycolwater solutions very nearly eliminates distortion and effects substantial savings in straightening costs (7B). The advantages of circulating aluminum in a melting or holding furnace are: improved control of alloy composition, increased melting rate, and reduced fuel consumption. Tests show that molten aluminum can be circulated by an electromagnetic pump. I n one case, a pump transferred more than 500 million pounds of alloys at an average rate of 20,000 pounds per minute. A magnetic field inside the pump acts as an impeller, and no moving parts contact the molten aluminum. Flow rate is controlled by changing the strength of the magnetic field (7B). Matching mold materials with alloys obtains certain characteristics in the finished casting. The product, designated a premium-engineered casting, offers minim u m tensile properties as high as 60,000 psi tensile strength, 50,000 psi yield strength, and 5% elongation;
tight dimensional accuracy down to plus or minus 0.005 in.; surface finishes in the range of 60 to 125 rms; ultrathin wall castings; uniform quality guaranteed in the part; and substantial savings over wrought parts that require extensive machining (5B). Applications The wave of construction of formaldehyde plants has focused attention on building materials. Materials specification for these plants remains a complex problem, and no single material can be recommended throughout the process. Five materials including aluminum are being used. Factors are discussed which affect the choice among these materials, particularly in matching them to the operating conditions of individual processes
(IC). The ocean has a great potential for the economic future of the chemical process industries and the country. Many new materials of construction-such as highstrength steels, improved titanium and aluminum alloys, and reinforced plastics-are being developed to withstand the ocean’s environment. Their properties and characteristics also are quite promising for service in the chemical process industries. The state of the art and the problems existing are highlighted, and advances in new materials are reviewed (ZC). Expansion joints in steel highway bridges have long been a problem but now a joint made of three interlocking aluminum extrusions seems to offer a solution. I t provides for bridge deck expansion and contraction created by temperature changes and normal displacement caused by deflection. I t is an effective water seal and has low maintenance requirements. While designed for highway bridge use, the joint can have important industrial applications where provision must be made for relatively small but predictable movement (26C). One of the world’s highest (altitude) transmission lines, Colorado’s 115-kv Shoshone to Leadville line, had been plagued by numerous outages caused by lightning. The original lightning protection had been removed during re-conductoring in 1940. The problem of restoring protection without completely rebuilding the line was solved by the use of a unique aluminum bayonet-type superstructure, specially designed for the lightweight towers, to carry static lines. Although built in 190708, the 63-mile line has been upgraded several times and still serves as a vital link in Colorado’s power grid (6C). Difficult problems are encountered in constructing transmission lines across the marshes and swamps of Louisiana’s coastal areas. Specially designed guyed-Y aluminum towers combined with helicopter erection techniques have helped provide a solution. I n the construction of a portion of a 500-kv line through Louisiana swampland, the installation of guyed-Y towers was found to be only two-thirds the cost of standard self-supporting towers through the same terrain. Once the foundation development and preliminary testing phases were completed, the cost was very little more than conventional dry land installation (5C). VOL. 6 0
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The largest ocean-going aluminum ship now is plying between Miami and San Juan with a cargo of 40 highway trailers. Approximately 760,000 pounds of aluminum were required to build the 226-foot SACAL BORINCANO, the first light metal vessel designed specifically as a trailer-ship. Described by the aluminum industry as the largest floating aluminum weldment, the ship represents the first entry in a new application where the strength, light weight, and corrosion resistance of aluminum can be used to good advantage (28C). A new standardized cargo container that can be disassembled and repaired with ordinary tools in a short time has passed all performance tests by the American Standards Association for Group I demountable containers. The 8-ft by 20-ft cargo container has a heavy-duty aluminum framework and is designed for transporting by truck, rail, marine, or air shipment. Containerization has developed into a major market area for the aluminum industry ( 7 0 2 ) . An all-new train based on aerodynamic design principles is described as far superior to all other railroad equipment available in terms of passenger appeal, . operating efficiency, and return on investment. The 14-car aluminum train weighs only one fourth as much as a conventional train of similar passenger-carrying capacity and will run at up to 120 mph on conventional track at one-third less cost. The train represents an economic as well as technological breakthrough, regarded as imperative if passenger trains are to survive (27C). Houseboats are becoming a leading growth segment of one of the aluminum industry’s expanding marketspleasure boats. All-welded aluminum construction makes the waterborne dwellings sturdy, speedy, and economical KO operate and maintain. Shipments have increased from approximately 500 units in 1965 K O an estimated 1500 for 1968. Houseboats now are sturdy, often luxurious craft with conveniences and appointments that virtually place them in the housing rather than transportation category (2jc). Approximately three miles of aluminum median barrier has been erected on a major highway in Florida. I t marks the first such installation of aluminum designed to improve highway safety. The barrier is designed to prevent a car from crossing the median strip and to redirect it on a parallel course. The aluminum system “gives” under impact sufficiently to bring a car to a stop without bouncing it back into the traffic lanes (23C). Aluminum rivets coated with tiny capsules of zinc chromate primer or a polysulfide sealer are designed for aircraft applications to reduce corrosion problems and production costs. Tl’hen the rivet is clinched, primer capsules rupture to apply a protective coating to the hole wall and fastener shank. The film thus protects the areas left bare by drilling, eliminating corrosion possibilities (247). I n the irrigation industry, aluminum pipe with a strengthening inner sleeve has been developed to combat damage to coupling ends. The new pipe features an inverted connecting end which holds the inner liner and 66
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virtually eliminates pipe buckling or damage at the connection (27C). A new aluminum I-bar grating has been introduced for such industrial uses as catwalks, bridge sidewalks, machinery safety guards, racks and shelving, scaffolding and railroad car flooring. Fabricated of aluminum extrusions, the symmetrically shaped panels are reversible permitting double duty. The unpainted light metal grating is said to be acid-resistant, nonmagnetic, and requires little maintenance (ZZC). Two new aluminum military products have reduced assembly time and effected substantial cost savings in production of the U. S. Army’s new M551 General Sheridan recounaisance vehicle. Forged aluminum armor and ballistic quality aluminum castings are employed in the vehicle which is designed for airborne transport, amphibious capability, and high-speed maneuverability over many t>-pesof terrain (2OC). A switch from copper to plastic-insulated aluminum underground cable by the telephone industry could open a multimillion ton market for the light metal. Several installations of the new cable design now are being tested. I t employs a protective plastic cable sheath: new splicing techniques, and a new stripping tool specially engineered to remove insulation from aluminum. A major factor in the success of the aluminum cable will be the skill with which telephone employees in local areas handle it (78C). Massive bulkheads built of aluminum place and extrusions have been used to hold back the Ohio River while repairs were made on a series of locks and dams. Aluminum was selected by the Army Corps of Engineers because its high strength/iveight ratio permits use of smaller and less expensive cranes and associated handling equipment (79C). Copper-clad aluminum sheet and wire display cost, engineering, and production advantages that promise new appliCatiOnS for nonferrous metals in building products, automobiles, appliances, and electronics. Potential uses include heat exchangers, cookware, and architectural and a variety of electronic and electrical applications (76C). The Apollo/Saturn moon rocket which has proved its capabilities in a successful unmanned flight is sheathed in high-strength aluminum allo)-s. I n all, the 363-ft tall spacecraft utilizes more than 500 tons of aluminum in its three stages. Major construction material in the first stage is alloy 2219, and the second and third stages are constructed primarily of alloy 2014 (77C). An 85-year-old vehicle bridge in Pittsburgh’s downtown area has been given a new lease on life by new deck design techniques employing aluminum panels. The renovation not only saved a landmark span but also gave it a higher load-bearing capacity. T h e lightweight bridge floor panels have increased the former 10-ton load limit to 20 tons (75C). Six welded aluminum truck bodies hauling bauxite in South America are paying for themselves in greater payloads, longer service life, and substantial reduction in operating costs. The rugged truck bodies are constructed of aluminum plate reinforced with extruded
aluminum structural shapes. Each has a capacity of 24 cu yd or 3 5 tons (74C). Investigations indicate that when properly applied, aluminum can provide a corrosion-resistant coating with possibilities for extensive applications. High-purity aluminum as a coating provides stability in service to 900 O F , is compatible with aluminum alloys, and has a very low evaporation-loss rate under hard vacuum conditions. Three vapor phase methods of aluminum plating are evaluated for ease of deposition, coating quality, and corrosion protection (82). Naval defense and exploration systems will require small, light propulsion systems capable of operating at great depths and providing high speeds. For many applications the exhaust must be nondetectable from the surface. A simple method is described in which amalgamated aluminum is readily reacted with water at moderate temperatures (100 to 500 OF). The reaction concept is reported as practical, and the reaction has been shown to be controllable. Hydrogen and sicam produced by the reaction can be expanded through a prime mover to produce power in applications where noncondensable hydrogen is acceptable. The concept has been designed into practical underwater power systems that utilize all reaction products permitting large reductions in system volumes and weights (9C). Backbone of the Boeing 747 are huge metal shapes, including the largest aluminum extrusions and plate ever produced. Implementing plans, tools, and techniques to fabricate the giant finished parts required unique solutions to a variety of engineering challenges (73C). Aluminum-to-stainless steel transition joints are required in most cryogenic equipment, and connections must be sound and leaktight. Welding produces a brittle interface, and brazed joints, while not brittle, may have insufficient strength or be sensitive to thermal shock and mechanical loadings. Threaded, flanged, and bolted connections can leak excessively. One solution appears to be friction-welded or roll-bonded transition joints. Test results show that the transition pieces will produce sound, leakfree seams (72C). Impact-extruded aluminum parts have accurate dimensions, smooth and clean surfaces, and high strength. These advantages have been employed by impact users to obtain better, less costly parts, all of which has led to a steadily growing number of applications for impact extrusions. Engineered parts include hose fittings, dehydrator tanks, and inlet tubes for automobile air conditioners; shaped containers for electronic components; and small motor housings, fuse bodies, and tube and fitting combinations ( 7 IC). Automotive design is following such motivations as contemporary design and handling, the feel of luxury and power, and the sheer joy of owning a magnificent machine. These ideas have been interpreted in terms of aluminum as seen for the functional stylish automobiles of the 1970's (7C). The characteristics and properties of competing materials are presented to help designers solve the problem of abundance. Many materials can satisfy specific design
requirements for a particular part. Detailed discussion of available alternatives is intended to help designers determine the best material for a specified job ( 4 C ) . An all-aluminum desalination system converts salty, brackish, or alkali waters into an ultrapure product by employing available waste industrial heat. The new system accomplishes this at '/z to '/a the cost of conventional water desalination methods. The lower costs are achieved in part by the aluminum-construction and simple-design concept. The system performs at far below the 250 "F of current water reclamation units and is designed to operate on streams of waste hot water available at chemical process and electric-generating plants where large volumes of water are used for cooling purposes. I t also can run on sun-warmed sea water (3C). REFERENCES Alloy a n d Temper Development (1A) M o d . Metals, 23 (7), 106 (1967). (2A) Ibid., p. 115. (3A) Zbzd., (9), p. 8 8 . (4A) Ibid., 24 (2), 79 (1968). (SA) Ibid., (3), p. 90. (6A) Ibzd., (4), p. 87. Fabrication a n d Processes (1B) Baker, R. S., MetalProgr., 92 (5), 133, 134 (1968). (2B) Ben, M., Bushey, A. H., Kissin, G . H., and Turner, T. A , , M o d . Metals, 24 (3), 57, 61 (1968). (3B) Chihoski, R. A., Weldin! J., 47 (5), 2104, 2 2 2 4 (1968). (4B) Drewes F. W., Kirchdorfer, H. N., McChesney W. S Detrisac, M. A . Spring S. 'Sanford B. L., Gault, F., Holmes, C., and hlitner,'h. C . , Mod. Metals, 24 (1),'331 6 9 (196e). (5B) Gardner, G. R., Steel, 162 ( 2 2 ) , 64, 66 (1968). (OB) Kaestle, F. L., Marsh, W. D., and Bigge, W. B., Light Metal Age, 26 (3, 4), 18, 22 (1968). (7B) Lauderdale, R . H., MetalProgr., 92 (6), 79, 81 (1967). (8B) Liptak, J.A., andBaysinger, F. R., Wddirig J., 47 (4), 173-S, 1 8 0 4 (1968). (9B) M o d . Metals, 23 (4), 47, 52 (1968). (10B) Ibid., 24 (l),80, 81. (1iB) Ibid., (2), p. 78. (12B) Ibid., (41, p. 96. (13B) Precirion M e t a l Molding, 25 (lo), 62, 63 (1967). (14B) Reeves, R. F., Newhard, N.J., Montie, E. J., Goodman, R., Hubbell, D. S., and Bryant, E. E., M o d . Metals 24 ( Z ) , 45, 70 (1968). (15B) Schwartz, M. M., Gurtner, F. B., and Shutt, P. K., Welding J., 46 (5), 423, 431 (1967). (16B) Space Aeronautics 48 (6), 94, 96 (1967). (17B) Waite, M. J., M o d . Metals, 23 (9), 77, 85 (1967). (18B) Wyman, S. B., and McFadden, M. F., M o d . Metals, 24 (4), 61, 81 (1968). Applications (1C) Chem. Engr., 75 (Z), 182, 188 (1968). (2C) Zbid., (12), pp. 105, 112. (3C) Design Newr, 23 (9), 15 (1968). (4C) Ibid., (lo), pp. 49, 60. (5C) Electric Light and Power, 46 (41, 70 (1968). (6C) Ibid., (5), pp. 92, 93. (7C) Herrman, G. E., Automotive Znd., 138 ( l l ) , 55, 56 (1968). (8C) Machine Design, 40 (l), 132, 134 (1968). (9C) Ibid., pp. 134, 135. (1OC) Marine Engr./Log, 72 (4), 55 (1967). ( i i C ) Metal Progr., 92 (4), 152, 155 (1968). (12C) Ibid., (S), 157, 162. (13C) Michaelson, G., Mdol Progr., 93 (31, 59, 61 (1968). (14C) Mod. M e l d s , 23 (7), 103 (1967). (15C) Ibid., (9), p. 86. (16C) Ibid., (111, pp. 28, 39. (17C) Ibid., p. 98. (l8C) Ibid., (12), 60, 64 (1968). (19C) Zbid., p. 80. (2OC) Zbid., 24 (l), 102, 103. (21C) Ibid., (2), p. 82. (22C) Ibid., p. 84. (23C) Ibid., (3), p. 90. (24C) Zbid., p. 98. (25C) Ibid., (4), pp. 35, 43. (26C) Precision Metal A4olding, 25 (71, 52 (1967). (27C) Roberts, R., Mod. Railroads, 22 ( l l ) , 68, 70 (1967). (28C) Rukin, J. B., Marine Engr./Log, 72 (8), 43, 46 (1967).
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