Zinc die-casting alloys

Titanium and Titanium Alloys Tungsten and Tungsten Alloys Zinc Alloy Die Castings... 

The first plastic to be metallized on a commercial scale was ABS, which is used as a replacement for the much heavier zinc alloy die castings widely used in the motor industry. Many other polymers are now coated not only for decorative purposes such as bathroom fittings but also for the production of objects where the specific properties of metals such as electrical conductivity, high reflectivity and good barrier properties are combined with those of polymers such as toughness, flexibility, corrosion resistance and low cost. The techniques used to produce highly adherent metal deposits may be divided into two major groups, dry methods and wet methods. 

American Society for Testing and Materials. (1961). Report of Subcommittee V, Committee B-6, on Atmospheric Exposure Tests of Zinc Alloy Die Castings. Proc. ASTM, 61, 273-281. 

BNFMRA. (circa 1960). The corrosion of zinc alloy die castings in hot and boiling solutions of. some commercial detergents. Typescript, 3 pp. (Unpublished copy in ZDA library, London). 

Lodder, L. A. J., and Baumgarten, S. (1951). Corrosion tests with zinc alloy die castings in damp gypsum plaster. Metallurgia, 43, 273-279. 

Zinc alloy die castings may contain nickel, chromium, silicon, and manganese in amounts of. 02,. 02,. 035, and. 5% respectively. No harmful effects have ever been noted due to the presence of these elements in these concentrations and therefore, analyses are not required for these elements. 

HYDROCARBON FUELS AND LUBRICANTS In the absence of moisture, zinc alloy die castings are strongly resistant to attack by acid-free hydrocarbons. In the presence of water some corrosion takes place which, while not seriously detrimental to the strength of the casting may, in the case of fuel handling devices, create some binding or clogging effect. 

ALCOHOL While pure ethyl and methyl alcohol are considerably less corrosive to zinc than water, mixtures of alcohol and water are more corrosive than water alone. This fact, combined with the probable presence of iron rust, makes undesirable the use of zinc alloy die castings in automobile cooling systems except in the presence of a suitable inhibitor. 

Alcohol-water mixtures represented by beverages are a special case, as the use of zinc alloy die castings in direct contact with potable alcoholic mixtures is not recommended. 

GLYCERINE Pure glycerine produces a smooth, light etch on the surface of the Zamak alloys. There is evidence, however, that glycerine-operated door checks and similar devices can be satisfactorily made of zinc alloy die castings. 

INSECTICIDES In dry form insecticides have relatively little action on zinc. In water solution, those materials which contain copper, arsenic or lead tend to accelerate the corrosion of zinc by electro-chemical replacement. It is not recommended that zinc alloy die castings be used in insecticide spray devices. 

TRICHLORETHYLENE - CARBON TETRACHLORIDE In short periods of exposure necessary for degreasing prior to electropiating, neither trichiorethylene nor carbon tetrachioride will have any visible effect on zinc alloy die castings. Dry carbon tetrachloride has no visible effect on continued exposure of much longer duration. Dry trichiorethylene over a period of four months shows a very slight etching action. 

Fig. 8.17 Typical die castings (a) hot-chamber zinc alloy die castings (from Ref 2, p. 177) (6) cold-chamber ahiminium alloy die castings of an automobile part, shown with slug and runner attached (from Ref. 2,p. 100) (c) low-pressure aluminium alloy casting of a cyhnder head (from Ref. 2, P- 166).

Forming-Die Alloys. The tonnage of slab zinc used in this appHcation is small. The use of zinc alloy dies started in the aircraft industry during World War II (119). Zinc-based alloys cast in sand and plaster molds continue to be used for short-mn dies for steel and aluminum stampings in the automotive and aircraft industries (120). Considerable cost savings are realized with these low melting zinc-based alloys which are easy to poHsh, machine, weld, and remelt. 

Dry methyl chloride may be contained in such common metals as steel, iron, copper, and bronze, but it has a corrosive action on zinc, aluminum, die castings, and possibly magnesium alloys. Methyl chloride must not be used with aluminum, since in the presence of moisture it forms spontaneously flammable methyl aluminum compounds upon contact with that metal. No reaction occurs, however, with the drying agent, activated alumina. 

Large quantities of zinc are used to produce die castings, which are used extensively by the automotive, electrical, and hardware industries. An alloy called Prestal(R), consisting of 78 percent zinc and 22 percent aluminum, is reported to be almost as strong as steel and as easy to mold as plastic. The alloy said to be so moldable that it can be molded into form using inexpensive ceramics or cement die casts. 

Tungsten has Htde effect on recrystallization temperature or the high temperature properties of molybdenum. However, the Mo—30% W alloy is recognized as a standard commercial alloy for stirrers, pipes, and other equipment that is required to be in contact with molten zinc during processing of the metal and in galvanizing and die casting operations. 

Zinc consumption is categorized in five semifabricating markets (see Table 15). Galvanizing was the main market for zinc in the 1970s followed by zinc-base casting alloys and brass and bronze. Depressed constmction and automotive industries caused a decline from 1979 to 1980 of ca 18%, and the die-casting business declined 34% and galvanizing 24%. 

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