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Technical Paper

Bearing Bronzes with Additions of Zinc, Phosphorus, Nickel and Antimony

SEVEN basic copper-tin-lead bearing-bronzes having high copper contents were studied by the application of various mechanical tests, such as Brinell hardness, resistance to impact, resistance to repeated pounding and resistance to wear. The effects of various additions were investigated by preparing test bearings of the same base alloys with additions of zinc, phosphorus, nickel and antimony, taken singly, and applying the same tests to these. The preparation of the test castings and the methods of testing are described in detail. The chemical analyses are given for the 40 different alloys tested; and the results of the various tests on each group of alloys are reported and discussed in detail, with the observations charted and tabulated for convenient reference. A tabulation of the specifications of 54 different bearing bronzes now in use is included in the paper. Dr. Dowdell presented and discussed∗ the paper for the authors.
Technical Paper

Heating, Ventilating, and Cooling of Passenger Cars

MANY question whether a complete job of air-conditioning passenger cars for all weather conditions can be done at a price which most car buyers care to pay and with assurance that dependable and acceptable results can be guaranteed, Mr. Chase reports in prefacing this paper, a comparative study of existing heating, ventilating, and cooling systems. Some 1939 and many more 1940 car models, he believes, yield greatly improved results in heating the entire car and ventilating it well with all windows closed, but, he points out, the design of such systems is still in a state of flux. Mr.
Technical Paper

The Use of Zinc and Zinc Alloys in the Automotive Industry

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.
Technical Paper

Die Castings for Automotive Parts

ADAPTABILITY of die castings to economical manufacture, to close dimensions, to complex shapes, and to thin sections is stressed. Die-casting alloys are reviewed, emphasizing the suitability of the zinc alloys in cost, physical properties, and die cost, along with their limitations as to temperature and otherwise. A discussion of applications to automotive grilles includes comparison with other methods of producing these parts and a description of the built-up type of die-cast grille. Steering-wheel applications considered include hubs, horn rings, and light switches. Windshield-frame parts, louvres, radio grilles, lamp mountings, body-interior parts, horn bodies, and a number of chassis applications also are discussed. A review of finishing processes and notes and suggestions on design conclude the paper.
Technical Paper

New Alloys And Plating Systems Through Zinc Research

Two new zinc casting alloys have been developed to add to the family of zinc alloys in use for decades. A zinc-copper-titanium alloy (ILZRO 14) offers a cold chamber casting alloy with excellent casting characteristics, low porosity and superior surface finish with very good creep resistance for supra-ambient temperature applications. A gravity casting zinc-12% Al alloy (ILZRO 12) provides outstanding performance for prototype production as well as for limited production runs when tooling costs prohibit the use of die castings. These developments linked to existing die casting and wrought zinc alloys, combined with superior plating systems now available, provide improved design and styling flexibility and outstanding service performance.
Technical Paper

Zinc Extrusion

The extrusion of zinc alloys, with special reference to zinc-titanium alloys, is described. Parameters for this process are defined. The excellent tensile and creep properties obtained in a typical extruded zinc-titanium alloy are presented. Extruded zinc with a quality copper-nickel-chrome plated finish offers a new approach to the production of automotive trim and of similar products.
Technical Paper

The Electron Probe Microanalyzer: Its Theory and Applications

The electron probe microanalyzer, made practical by Castaing, is a unique instrument which permits the qualitative and quantitative chemical analysis of samples as small as one micron in diameter. This is accomplished by using the specimen as a target for a focused high energy electron beam and measuring the characteristic X-rays excited. The instrument at General Motors Research Laboratories has been applied to a variety of metallurgical and automotive material problems such as the identification of deleterious inclusions in zinc alloys and steel, grain boundary precipitates, corrosion of anodized aluminum, the wetting of steel by solder, and many others.
Technical Paper

Corrosion Considerations In The Selection of Materials In Automotive Terminal Systems

The corrosion performance of alloys considered suitable for automotive terminal systems are examined. General corrosion is insignificant when copper alloys are used. The designer can avoid stress corrosion by choosing from a complete range of mechanical and electrical property combinations in less sensitive and even immune copper alloys. Crevice corrosion can be minimized chiefly by designing to eliminate crevices and also by choice of less susceptible alloys. Finally, dezincification can be overcome by using less susceptible modified brasses or inhibited brasses; lower zinc alloys or alloys not containing zinc may also be used.
Journal Article

Improving the Relationship between Processing and Properties of Zinc Die Casting: Developments in Creep and Ageing Correlations

Most creep studies are conducted to determine steady state creep rate and time to failure. However, the priority for the designer is to predict the amount of total creep, being the sum of primary and secondary creep elongations, for a given service life under given loads and temperatures, for example 0.5% elongation after 3000h. An assessment of total creep behavior of industrially important zinc alloys has been conducted, and correlation/prediction curves produced. Another important property, related to creep, is stability after ageing, both for unloaded and also loaded castings. Recently developed relationships between natural and artificial ageing, and the correlation of mechanical property changes for different periods of artificial ageing with natural ageing will be presented.
Technical Paper

Notched Bar Izod Impact Properties of Zinc Die Castings

Notched bar Izod impact testing of zinc die cast Alloy 3, Alloy 5, ZA-8, and AcuZinc 5 was performed at five temperatures between -40 °C and room temperature in accordance with ASTM E23 for impact testing of metallic materials. A direct comparison between ASTM D256 for impact testing of plastics and ASTM E23 was performed using continuously cast zinc specimens of Alloy 5 and ZA-8 at -40 °C and room temperature. There are differences in sample sizes, impact velocity, and striker geometry between the two tests. Bulk zinc tested according to ASTM E23 resulted in higher impact energies at -40 °C and lower impact energies at room temperature then did the same alloys when tested according to ASTM D256.
Technical Paper

Black passivation films without hexavalent chromium on top of electroplated layers of zinc and zinc alloys

Typical layers with cathodic corrosion protection for steel are zinc and zinc alloys. These layers are usually chromated and, for special applications, an additional organic or inorganic topcoat is applied. The most attractive finish is either black or clear. For aesthetic reasons, black coatings must be used for parts to be mounted in close vicinity of other black parts. Trivalent clear chromatings with good corrosion protection are nowadays well established in the production lines, but trivalent black chromatings are not. Development efforts were made to identify and overcome the problems and/or to find suitable workarounds. This paper will introduce a complete line of new products for producing black parts with high cathodic corrosion protection. This is: black chromiting on top of acid zinc and on top of alkaline Zn, Zn/Fe and Zn/Ni.
Technical Paper

“RoHS” Compliant Chrome - Free Conversion Coating for Aerospace Manufacturing

This paper presents, chemistry, test data and processing procedures on a non toxic and environmentally friendly chrome-free conversion coating alternative with the same level of adhesion and secondary corrosion resistance as that found in chrome containing conversion coating systems. Test data from military and independent sources will be presented on secondary coating adhesion, electrical conductivity, filiform and neutral salt-spray corrosion resistance as compared to chromate based systems .on magnesium, aluminum and zinc and their respective alloys. The European “RoSH” initiative will not allow for the presence of any hexavalent chromium on imported electrical components as of July first of 2006. Trivalent chromium based systems generate hexavalent chromium due to the oxidation of the trivalent chromium and as such will not be allowed.
Journal Article

Dissimilar Joining of Aluminum Alloy and Steel by Resistance Spot Welding

This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.
Technical Paper

Mechanical Study of Thixoforming Magnesium Parts

Nowadays the use of magnesium automotive engineering has become an essential way for weight reduction. The change from conventional materials, such as zinc alloys, to lighter weight materials, such as magnesium alloys, is realizable at commercially competitive rates. This requires lightweight solutions, optimized design and advanced manufacturing processes. The goal of this study is to validate the thixocasting process for a part of a wiper system. This paper summarizes the first mechanical tests carried out on a wiper part in AZ91 magnesium alloy by thixocasting and traditional casting process. The semi-solid die casting process enables to improve the mechanical behavior. To explain these results, the effects of microstructure on thermal properties are investigated and microstructural examination is also performed using optical microscope and scanning electronic microscope (SEM).
Technical Paper

Corrotect® Rust Prevention for Rolling Bearings and Precision Parts

Corrotect® is an ultra thin electroplating for rolling bearings and precision parts. Dimensions of non-plated components do not need to be considered and plated components do not need to be refinished. Due to the cathodic effect smaller non-plated locations keep protected as well. Characteristic ranges of application are corrosion prevention against moisture and neutral aqueous media. Corrotect® offers explicit advantages compared to other coatings and often is the only suitable solution. Corrotect® is composed of a zinc alloy with a yellow to iridescent or a black chromate passivation. For automotive applications a Chromium(VI)-free version of this plating becomes more and more important.
Technical Paper

Surface Treatments and Characterization of Electroplated and Hot Dip Galvanized Steel Sheets

Protection of surfaces is a critical factor in determining the extended service life of a structure in polluted and aggressive environments. In particular, a rapid growth of the technology for the protecting coating of cold rolled steel is experienced, for the use in transport, electric housewares, building and industrial plants. Numerous changes have taken place in the production of zinc coatings on steel in order to improve the corrosion resistance using zinc alloy platings. Our research group collected from the international production a number of selected galvanized steel samples, including electrodeposited zinc alloys, multilayer coatings, hot dip galvanized steels. On the selected materials we established and analyzed morphology, composition, crystal structure, impurity content and distribution, using many surface microanalysis techniques.
Technical Paper

High Performance Alternative to Hexavalent Chromium Passivation of Plated Zinc and Zinc Alloys

Hexavalent chrome passivates have been used for improving the corrosion resistance of sacrificial zinc and zinc alloy coatings on ferrous substrates for many years. However, forthcoming legislation and corporate policies are beginning to curtail the use of hexavalent chrome compounds and replacements are actively being sought. Comparative corrosion resistance data is presented here. The data shows that the corrosion resistance of the trivalent passivates do not significantly diminish after thermal shock, as is the case with hexavalent chromates. This makes it particularly suitable for components that are subjected to high ambient temperatures. No changes to the dimensional characteristics of the components occur. Recommended application areas include the engine compartment, brake components, fasteners of all sizes and fluid system components.
Technical Paper

New Applications for Zinc from a New Zinc Technology

Zinc, which has served the automotive industry for five decades, is reemerging as an engineering material and reenforcing its position as a decorative material. Ongoing research and development by the zinc industry is documenting the engineering properties of zinc alloys and placing this information within reach of the designer. This paper presents an overview of the progress in alloys, processes, and product development achieved by the industry in the last decade. Several new lightweight, cost effective applications, which are now possible with the new technology, are described.
Technical Paper

Corrosion Protection Fundamentals of Metal-Finished Steel Sheets for Automotive Applications

Corrosion protection mechanism was investigated on newly developed-metal-finished steel sheets for automobile applications. Such alloying elements to zinc as Ni, Co, Mn, Mg and Al retard oxygen reduction reaction because of their stabilizing effect of Zn(OH)2 films, leading to improved corrosion resistance. Wet adhesion of cathodic primed full painted system is governed by alkali-induced dissolution of phosphate and zinc coatings during electrocoating. Fe in coating layer improves wet adhesion because of its high alkali-resistance. Both Fe and Ni have a pore blocking effect on phosphate films, with resultant a superior paint performance. The factors affecting perforation of jointed panels were also discussed.
Technical Paper

Bolt-Load Retention Behavior of a Die Cast Magnesium-Rare Earth Alloy

The need for improved understanding of new magnesium alloys for the automotive industry continues to grow as the application for these lightweight alloys expands to more demanding environments, particularly in drivetrain components. Their use at elevated temperatures, such as in transmission cases, presents a challenge because magnesium alloys generally have lower creep resistance than aluminum alloys currently employed for such applications. In this study, a new die cast magnesium alloy, MEZ, containing rare earth (RE) elements and zinc as principal alloying constituents, was examined for its bolt-load retention (BLR) properties. Preloads varied from 14 to 28 kN and test temperatures ranged from 125 to 175°C. At all test temperatures and preloads, MEZ retained the greatest fraction of the initial imposed preload when compared to the magnesium alloys AZ91D, AE42, AM50, and the AM50+Ca series alloys.