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Press-hardening steels get more and more popular for body in white applications as an approach to meet the demands of passenger safety and CO2 reduction. Unlike the larger part of the structure that is typically zinc coated, the majority of the PHS parts is either uncoated or aluminum silicon coated. This paper shall give an overview of press-hardening steels with zinc coatings with detailed results for corrosion resistance, weldability and mechanical properties for strength levels of 490 to 1800 MPa. Furthermore as for zinc coated material maintaining a robust press-hardening process is of even higher importance than for uncoated or AlSi coated material. A range of different processes including indirect and direct process are shown in detail. Especially the topic of micro-cracks, mechanisms and avoidance of micro-cracks in the direct process will be discussed. Results from industrial and semi industrial production are shown.

HOT-DIP galvanized steel sheets have been increasingly used in the automotive industry. However, two major problems occur during spot-welding because of the presence of zinc: 1/ Welding parameters differ from those used for bare sheets 2/ Electrodes life span often decreases. Two products have been thoroughly tested: 1/ Usinor MONOGAL® sheet 2/ Two-sides hot-dip galvanized sheet with various zinc-coating thicknesses. Welding parameters have been optimized by the determination of weldability lobes. Both products present a wide range of intensities, provided that weld current and electrode force are increased. The effect of an enventual variation of zinc-coating thickness is negligible. Electrodes life satisfies the FORD 2000 spot welds acceptance test. At last, temperature measurements inside the electrodes have shown the interest in increasing the electrodes tip diameter.

Interactions between a Zinc dialkyldithiophosphate (ZDP) and three different commercially available succinimide dispersants were observed through changes in solutions behavior, as determined by viscometry and Fourier Transform Infrared spectroscopy (FTIR), and four-ball tests. The viscometric response observed for two component blends of ZDP and succinimide dispersant in white oil changed as a function of the molar Zn to N ratio, indicative of specific interactions. The break in the viscometric response curve occurred at Zn:N=0.13 for all three succinimide dispersants. FTIR spectra of the same ZDP-dispersant blends were examined and similar Zn:N dependencies were observed. Four-ball tests measuring wear scar diameter, seizure load and weld load showed a dependence on the Zn to N ratio similar to that observed by viscometry. At very low Zn to N ratios wear and seizure load were decreased, while at higher ratios the seizure and weld loads were increased over that for ZDP alone.

Because of the drastic chilling involved in die casting and the fact that the solid solubilities of both aluminum and copper in zinc change with temperature, these alloys are subject to some aging changes, one of which is a dimensional change. Both of the alloys undergo a slight shrinkage after casting, which at room temperature is about two-thirds complete in five weeks. It is possible to accelerate this shrinkage by a stabilizing anneal, after which no further changes occur. The recommended stabilizing anneal is 3 to 6 h at 100 °C (212 °F), or 5 to 10 h at 85 °C (185 °F), or 10 to 20 h at 70 °C (158 °F). The time in each case is measured from the time at which the castings reach the annealing temperature. The parts may be air cooled after annealing. Such a treatment will cause a shrinkage (0.0004 in per in) of about two-thirds of the total, and the remaining shrinkage will occur at room temperature during the subsequent few weeks.

The role of zinc die castings in the materials marketplace has changed significantly in the last generation. In response to a shift in the available market, the industry has made major advances intended to improve competitiveness in both traditional and non-traditional areas. Better efficiency and performance have been achieved by the application of new methods and technologies. The ZA alloys, introduced to die casting during the last decade, have markedly expanded the capabilities of both zinc and the die casting process. This paper presents a review of several zinc die castings used in automatic applications.

Many papers have been written for SAE on electrochemical metallizing, a modern term for “selective” or “brush” plating. These papers have dealt primarily with the aerospace industry, including the use of non-embrittling cadmium LHE® coatings for corrosion protection on aircraft. Shadowed by 30 years of successes in the aerospace industry, electrochemical metallizing corrosion protection in the automotive industry is often overlooked. Specifically, the use of selectively applied zinc coatings for corrosion protection on wheel hubs during manufacture has proven integral at several European automotive manufacturers. In the past, environmental conditions have corroded both the hubs and wheels of automobiles. Quite often the corrosion is in the microscopic gap between the hub and the wheel, which over time causes the wheel to seize and prevents removal. This has been frustrating to both stranded motorists and shop mechanics.

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.

The critical component for maintaining uniform zinc phosphate coatings on aluminum is fluoride. The control of free fluoride is critical to the operation of the process, because aluminum is dissolved in a zinc phosphate bath as a step in the coating reaction. If the dissolved aluminum is not removed from the bath, it will inhibit the formation of coatings on all metals being treated. This paper presents the characteristics and composition of zinc phosphate coatings on aluminum and steel, and lists some practical considerations of the transition from steel to aluminum components. Some possible problem areas discussed are: galvanic corrosion, underpaint quality, surface finish, electro-painting, and new paint surfaces.

Copper and brass radiators have served the automobile industry for many years using traditional fabrication processes. Demand for newer and stronger radiators with lighter weight for the modern vehicles prompted investigation of alternate materials. Properties of zinc alloys and their compatibility with brass suggested these could be used for radiator manufacture. Many zinc alloy compositions were investigated in the initial studies, because a solder alloy has to have many positive attributes. The first screening studies evaluated the ability of the solder to spread over copper and brass surfaces, representing tube, fin, and header materials. The second most important feature was the melting range of the developed alloy. In order to retain the anneal resistance of the fin and temper in the tube it was desirable to have a zinc solder with a melting temperature at 800°F or less.

For over a decade, industry prognosticators have been predicting that the use of plastics by automakers would soon surpass the deployment of metals in automobiles, While there is no denying that plastics have made inroads, it recently has become apparent that metal will retain its position as the prime car material for the foreseeable future. One reason for the revised forecast is the development of improved zinc coatings for the automotive industry. Such material as electrogalvanized and Galfan™ are shaping up as steel's saviors when it comes to ensuring that metal will continue to play the major role on car assembly lines. Meanwhile on the other side of the equation, developments in zinc die casting technology have taken the edge off plastics' forward thrust into both functional and decorative car part applications.

A presentation on zinc demonstrating its versatile applications to the auto industry. A review of metal balances, domestic, world and major producing countries. The energy required to mine, smelt and refine zinc is compared to other metals. The value of recycling zinc is also considered. This paper concludes with a statement, supported with evidence, that today's automobile is a better buy than twenty years ago.

Zinc-coatings with a substantial Magnesium content have been in use for over 30 years by now. Unlike the well-established Zn-Al-Mg coatings originating from Japan which have significant higher alloying contents applied mainly for building applications, this Zinc Magnesium Aluminum coating (ZM) is also specifically designed to meet the requirements of car manufacturers. The ZM coating introduced by voestalpine, corrender, is in the upper range of ZM-alloying compositions, which was set by VDA (German Association of the Automotive Industry) and SAE to be within 1.0 to 2.0 wt. % Mg and 1.0 to 3.0 wt. % Al. The properties of these “European” Zinc-Magnesium coatings are well comparable within this range. Compared to GI and GA ZM coatings exhibit significant advantages in the press shops with its excellent formability and reduced galling and powdering respectively which is a significant advantage for the forming of outer panels.

Zinc-manganese alloy electroplated has been developed for automotive body panel applications. The product is manufactured on a conventional electrogalvanizing line using an electrolyte containing zinc sulfate, manganese sulfate and sodium citrate. Electroplated steel with an alloy content of 30-50% manganese exhibits excellent corrosion resistance both as-produced and after painting. Zinc-manganese coatings also show good workability and voidability. Accordingly, this product is suitable for both unexposed parts and the interior surfaces of exposed parts. Finally, zinc-manganese electroplated steel displays good wet adhesion and anti-cratering characteristics so that the product can also be used for exposed applications as automotive body panels.

In a 2-year program sponsored by SJAC, an aqueous electroplating process using alkaline Zn-Ni with trivalent chromium post treatment is under evaluation for high strength steel for aircraft application as an alternative to cadmium. Commercial Zn-15%Ni rack/barrel plating solutions are basis for plating aircraft parts or fasteners. Brightener was reduced from the original formula to form porous plating that enables bake-out of hydrogen to avoid hydrogen embrittlement condition. Properties of the deposit, such as appearance, adhesion, un-scribed corrosion resistance, and galvanic corrosion resistance in contact with Al alloy, were evaluated. Coefficient of friction was compared with Cd plating by torque-tension measurements. Evaluation of the plating for scribed corrosion resistance, primer adhesion, etc. will continue in FY2007.

To enable the tests required for development work to be performed with maximum efficiency, the Zwick Roell Group (ZwickRoell) – a global supplier of materials testing machines based out of Ulm, Germany – developed a materials testing machine that can be equipped with both a temperature chamber and a high-temperature furnace.

NEW WELDING processes are dropping costs while providing improvements in weld quality. This paper describes some of the more promising new developments in pressure and fusion welding and brazing. Included in the discussion are ultrasonic, high frequency resistance, foil seam, magnetic force, percussion, friction, and thermopressure welding and diffusion bonding. The description of adhesive bonding includes the development of glass or ceramic materials as structural adhesives.*

STRUCTURAL MATERIALS for Mach 3 jet transports pose difficult problems for the design engineer. Reasons for this problem are the incomplete information available on the many possible metals and the diversity of critical properties that are added by supersonic requirements. The material properties discussed in this paper include tensile strength, resistance to crack propagation, ease of fabrication, weldability, and thermal expansion. Cost factors are also considered. The structural configuration of the wing and fuselage is an example of the complexity of the material selection problem. The wing may be rigidity-critical, and the fuselage strength-critical; each requires diferent material properties to solve the problem.*

PEARLITIC malleable iron crankshafts are being used in the new Pontiac engine as a result of recent developments. This paper discusses the physical properties of pearlitic malleable iron such as elastic modulus, fatigue endurance, and tensile strength. According to the author, definite machining economies result from using pearlitic malleable iron crankshafts.

EXPERIMENTS have been conducted at Cambridge University which probed the sliding friction and wear of nonmetals, and the deformation of solids at high rates of strain. The author was particularly interested in the deformation and damage of metals and nonmetals under high-speed liquid impact. The findings will contribute to the development of materials that can withstand the friction of high-speed space flight. The author discusses the sliding friction and wear of wood, diamond, glass, rubber, and metallic carbides. In the last part of the paper, he describes the high-speed problems arising when solids are deformed very rapidly.

THE AIR FORCE has set up a program to evaluate the machining characteristics of the more commonly used high-strength thermal-resistant materials. This paper describes the test results to date. Four materials are being tested: SAE 4340 quenched and tempered to 50–55 Rockwell C, SAE designation H11 quenched and tempered to 50–55 Rockwell C, AM-350 solution treated and aged, and A-286 solution treated and aged. Machining tests include: turning milling, drilling, and tapping.*