The Use of Zinc and Zinc Alloys in the Automotive Industry 310043
THE PURPOSE of the paper is to discuss zinc as an engineering material. To this end the author reviews briefly the part that zinc and its alloys have played in the past and discusses recent development in zinc-base alloys which have greatly enlarged their field of use in the automotive industry.
Among the various specific subjects treated by the author are brass, nickel and silver, rolled zinc and rolled zinc-alloys, zinc wire, extruded zinc shapes and die-castings. He states that in the early days of die-casting, alloys composed principally of tin or lead were used almost exclusively, but that castings made of these alloys did not possess the necessary strength and their use was greatly restricted. Zinc was tried and found to have certain advantages and, finally, a special zinc-alloy was adopted. Shortly after this the so-called high-grade zinc was introduced.
After discussing die-cast zinc-alloy gears, the author treats the subjects of zinc alloys for body hardware and other equipment, recent improvements in zinc alloys, and zinc data on the zinc-aluminum-alloy system. Heat-treatment of zinc-base die-casting alloys, water-vapor tests, the disastrous effects of contamination and the physical tests that can be applied to die-casting alloys are considered in some detail. The use of inserts in zinc-alloy die-castings, plating methods, cleaning and other procedures, the nickel-plating process, enameling, japanning and lacquering are touched upon.
In conclusion, the author summarizes his paper by stating that metallic zinc is used in the automotive industry for electro-galvanizing; as a constituent of brass; as rolled sheet and strip for a variety of fabricated parts of which running-board molding heads the list; and in the production of a great number of die-cast parts. The marked improvement in both rolled zinc-alloys and zinc die-casting alloys has done much to stimulate added interest in this white non-ferrous metal, the price and properties of which lend themselves well to effect economy without jeopardizing quality.
Not only have improvements been made in the physical properties of the various zinc-alloys, but the application of attractive and durable plated finishes can now be accomplished without difficulty, according to the author. The number of parts on the automobile which are made of zinc or zinc alloys is increasing annually. Additional investigations are being undertaken to produce still other zinc alloys of suitable properties for use in a wider range of automotive parts.
Among the major points considered in the discussion* are included the maximum allowable stress in working particular metals, undesirable physical changes that occur at a temperature of 500 deg. fahr. and result in a decrease in strength, the purity of zinc and zinc-alloys, and further data on die-castings, including their use as bearing material.