BRUCE H. W Y M A
USES OF A L U M I N U M A L L O Y S E X P A N D Light weight and corrosion-resistant properties continue to be exploited, particularly f o r large storage tanks, shipping containers, and chemical equipment
ast year, aluminum production was down slightly11,000 short tons-from a record total of 2,014,498 short tons in 1960 to 1,903,711 tons in 1961. Yet in spite of this decline, which was shared by much of industry, primary capacity increased by 1 5,000 tons, making the total (2,483,750 tons) more than double that of 10 years ago. Such optimism and confidence on the part of the aluminum industry seem well founded, because fresh signs of increased emphasis on aluminum are apparent in all facets of our economy. This article covers major developments described in the literature during the last 18 months.
L
Alloy Development
Duranel, a stainless steel-clad aluminum sheet developed by the Aluminum Co. of America combines the virtues of steel and aluminum. I t is particularly useful for making cooking utensils, but should have other valuable industrial uses as well. A 0.010-inch layer of Type 304 stainless steel is metallurgically bonded to 3004 aluminum alloy to form sheets 0.050 to 0.375 inch thick. Several methods for joining Duranel have been developed, and already some are used in production. A new aluminum casting alloy ( 2 A ) can be machined a t high speeds without cutting fluids, and its machining characteristics are excellent at low cutting speeds. The alloy can be run down a machine line tooled for cast iron with no change in tooling and without installing coolant or cutting lubricants. Alloy 221 9, initially introduced as an aircraft forging alloy for highly stressed parts operating at high temperatures, has demonstrated other outstanding characteristics-e.g., high strength, good weldability ( I A ) , and resistance to stress-corrosion cracking ( 3 A ) . Thus, it should be useful in the transportation, missile, and chemical process industries. 46
INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY
Industrial Applications
Architectural and Construction. The Alcoa-Hico, a new adjustable shoring beam, is saving contractors u p to 40% on forming concrete slabs. It consists of an I-beam telescoped inside a box section, and weighs u p to 60y0 less than comparable adjustable steel beams. The Alretic Division of McGraw-Edision Co. has developed the Dynabeam truss, a new box-type structural beam. Made from aluminum plate and extrusions, it is connected by a mechanical joint system which requires no M-elding or riveting and eliminates bolt holes and diagonal lacing. Various sizes can be stocked, then cut to suit a particular application and assembled on the spot with only a handsaw and a wrench. I n recent years, there has been a marked trend toward use of aluminum in the structures which house power stations (4B). Walls are normally very high, and, in time, masonry walls supporting the roof gave way to the more economical masonry curtain wall on steel frames. Lightweight, durable aluminum can do the job as well and at less cost. The size of foundations and certain components of the steel frames can be reduced, and advantages of high reflectivity can be gained in both hot and cold climates. Two new laminates have been developed, which should have significant architectural potential. U. S. Plywood Corp. is producing a new industrial material, metal-backed Flexwood, by bonding flexible plywood to aluminum sheet. Alcoa’s new vinyl-aluminum laminate, Vinylate, also has a large spectrum of uses. Both materials can be fabricated by conventional metalworking equipment. Atomic Energy. Yankee Atomic Electric Co.’s 485,000 thermal kw. reactor now is in commercial operation. Three large aluminum tanks, fabricated from alloy 5052, help guard water purity. The units
For mixing chemicals in polystyrene foam production: are a 135,000-gallon primary water storage tank, a 125,000-gallon safety injection (cavity water) tank, and a 30,000-gallon demineralized water tank. The vessels, which resist attack by carbon dioxide and ammonia carried over froin the steam system, are reported to be virtually maintenance-free. Aluminum also preserves water quality by eliminating pickup of heavy metal particles. Aluminum powder metallurgy alloys are espccially suitable for cladding and structural materials for organic cooled and moderated reactor fuel elements. Fabrication techniques include methods such as conventional forging, rolling, and extrusion processes (4B). Strengths of two flash-welded -4PM alloys ( 6 B ) are evaluated-XAP001 (formerly M257) up to 600” F. and M486 up to 800’ F. Average joint efficiencies, in terms of tensile strength, rverc about 95% for both alloys. Chemical. For years, aluniinum tapcred sheet and plate have been provided for the aircraft industry. Through its use, large field-erected storage tanks are now being built cheaper and faster. The tapered panels form thick walls a t the tank bottom, ivhere hydrostatic pressure is greatest, and progressively thinner walls to the top T \ v o courses of tapered plate rvere used in a liquid-i‘wtilizer storage tank, 70 feet in diameter and 4s fecct high, with a savings of 7000 pounds of aluminum and 260 feet of weld length. Many types of fertilizers are satisfactorily handled in nluminum. African Explosives and Chemical Industries, Ltd., have completed a new urea plant and inodifications of a n existing ammonia plant. All tanks and pipe in the dressing room, where urea solution and granulated products are processed, are sheathed in aluminum. It has been used to roof and clad the steam plant, bagged products store, air separation plant, and carbonization plant. Aluminum is used extensively for duct work in the bulk store, sheathing of pipes a t tanks in the carbon dioxide purification plant, and lagging for piping around the carbamate reactors. I n making many plastics, aluminum is used extensively for reaction vessels, storage tanks, piping, heat exchangers, and polymerization equipment. I t does not discolor the product. The world’s largest polypropylcne plant, constructed for Avisun, includes a 42,500-cubic foot aluminum granular storage structure. The top dcck is a 20-foot diameter conical vessel leading down to a 40-foot diameter aluminum tank. As a material of construction for chemical equipment, properties of aluminum are compared with those of stecl ( T I ? ) , using the price parameter for strength and for stability, the thermal stress parameter, and the strength-density parameter. Cryogenics. At low temperatures, where many steels and other materials become brittle and prone to 48
INDUSTRIAL AND
ENGINEERING C H E M I S T R Y
A 10,000-gallon
rupture, aluminum retains its ductility and irnpact resistance and actually becomes stronger. It is resistant to corrosion, light weight, and does not have to be stress-relieved after welding. This makes fabrication easier and reduces cost (9B). Therchrc aluminum alloys are being used widely in cr) ogcnics, including handling of liquid helium at -425’ F. In 1961, Air Products, Inc., began delivering to the U. S. Air Force the first 4000-gallon units of all-aluminum tank trailers for the road transport of liquid oxygen. Carrying capacity was increased 40y0 by using aluminum instead of steel. An aluminum tsnk for holding 90,000 gallons of liquid hydrogen w a s fitted into a steel sphere a t Douglas Aircraft’s SacraIncnto field station. I t will be used to store fuels for the Saturn space vehicle program. Some other cryogenically processed products handled in aluminum include nitrogen, deuterium, argon, propylene, anhydrous ammonia, dry ice, propane, and methane. One interesting technique of storing liquid natural gas in a frozen hole (7B) \vas employed by Conch International Methane, Ltd., and Constock Pritchard Corp. Thc storage pit was capped by an insulated aluminum roof. Recent development of aluminum-to-stainless stecl transition joints, which facilitate the joining of aluminum pipe to other materials in cryogenic installations is reported ( 9 B ) . Such joints also simplify the inclusion of thermal darns in vacuum insulated vessels. A 1961 report ( S B ) notes, . . . . the tensile strengths of all the aluminum alloys in the melded and unwelded conditions ;ncrease as the temperature is lowered from room temperature to -423” I?. They do not, for example, reveal a transition from ductile to brittle beha.i-ior as the test temperature is lowered .” The report presents data on the 5000 Series aluminum plate alloys at the temperature of liquid hydrogen and states one conclusion, “ I n general, the yield strengthto-density ratios of the 5000 Series aluminum allo)s, both welded and not melded, u e r e higher than those of the Type 304 stainless steel a t room temperatures.”
