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Recent growth in automotive applications of magnesium die cast alloys has made the refining and recycling of magnesium scrap a key issue for the automotive and magnesium industries, if growth is to continue. Today, with only a few exceptions, commercially refined and recycled alloy is produced using a variety of flux-based processes. However, fluxless refining, has been the focus of growing interest, particularly for the in-house refining of scrap by the die cast producers. This paper summarizes the results of a study conducted to better understand the behavior of non-metallic contaminants in scrap melts and the requirements for their separation, using argon sparging. Brightness measurements were used to experimentally determine the distribution of non-metallic contaminants within scrap melts both before and after argon treatment.

In 1998, approximately 57,000 Tonnes of plastic composites were utilized as body panels on cars and trucks in North America. Three material types, generically labeled SMC, RIM and Thermoplastic are vying to carve a market niche from steel which dominates the market place with an estimated volume of 1 million Tonnes per year. Since plastic body panels have higher material costs but lower tooling costs, they are primarily utilized when build volumes are less than 200,000 vehicles per year or specific composite performance capabilities are demanded. This paper reviews the various performance parameters required of a body panel material and the relative strengths of Aluminum, RIM, SMC, Steel and Thermoplastics to meet these demands. A decision making process is utilized which allows for a comparison between the different materials. Since cost is so critical, it is left as an independent variable.

Continued development of Reinforced Reaction Injection Molding (RRIM) polyurea polymers for toughness, blister resistance and large-part processing as exterior vertical body panels has launched ELPO-compatible exterior outers into automotive assembly-line operations. This allows automotive OEM design to take advantage of the unique molding shapes for side outers and fenders while reducing weight, assembly (DFA) and time/operations costs (DFM). Polyurea RRIM body panels have been successful in meeting the demanding auto industry requirement for lightweight, damage-resistant exterior outer panels as an economical alternative to steel. Design freedom advantages, low prototype cost and tooling savings through predictive modelling have allowed the commercial use of RRIM body panels. This high-temperature-resistant polyurea RRIM composite allows on-line painting, including passing through the steel corrosion protection primer (E-coat) cure environments.

The increase in instrument panel design and functional performance requirements has resulted in a variety of structural architectures that have been utilized in different passenger vehicles, vans, and light trucks. Each architecture can be designed and engineered to meet corporate and federal requirements using different levels of integration, functionality consolidation, and assembly simplification. The present paper reviews three basic IP design architectures, i.e., traditional, hybrid, and structural, and discusses the performance requirement-functionality matrix in each case. Emphasis is given at explaining the role components play in the different architectures, defining their contribution to static, dynamic and crash performance and their relation to the overall assembly process and sequence. Performance and functionality requirements are linked to basic material characteristics that guide material selection for achieving design targets.

The effect of non-metallic inclusions (NMIs) on the properties of die cast magnesium was investigated. NMI content was quantified by a newly developed light reflectance technique. The mechanical properties of optimized AM60B test bars were found to decrease at high inclusion levels. Low inclusion levels did not statistically reduce the mechanical properties of AM60B as compared to virgin metal. Argon-refined AM60B displayed mechanical properties that were indistinguishable from virgin alloy. AZ91D test plates were die cast at various cleanliness levels. After salt spray testing, it was found that the surface quality of the castings was slightly degraded at high NMI levels. The general corrosion performance was also affected, but paint adhesion was relatively unaffected. At high NMI levels, the corrosion performance was still better than 380 A. Machinability of the AZ91D test plates was quantified by measuring tool wear and cutting forces.

A fully-integrated thermoplastic structural instrument panel (IP) system will be implemented on Chrysler's Dodge Dakota Truck Platform. The structural IP consists of a three-piece monocoque thermoplastic injection molded structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs. Ribbed thermoplastic bolster systems have been incorporated as part of the energy management system. The structural IP provides the required stiffness to satisfy noise, vibration, and harshness (NVH) quality targets and the necessary strength and rigidity to effectively meet FMVSS No. 208 requirements for managing occupant and passenger air bag (PAB) deployment loading during 48 km/h (30 mph) frontal crashes.

Increased requirements for crash energy management in automotive interiors have led to increased application of magnesium alloy AM50A. Successful integration of this new alloy with hot chamber diecasting process technology requires substantial adjustment and attention to processes and practices. This paper details the conversion of magnesium AZ91D steering column diecastings to high ductility structural alloy. Description is given of the changes made to foundry practices, casting parameters, process compliance monitoring, and hot end component management. The resulting improvements allow production of components comparable to the traditional alloy in manufacturing process demands while offering improved ductility and impact strength.

The recycling of plastics from end of useful life durable goods continues to evolve as an issue. Recycle strategies need to be based on a careful understanding of sustainability for both the environmental and business domains. The definitions and processes utilized in a recycle program can dramatically affect the economic structure. These recycle programs need to be carefully constructed to minimize cash costs. There is an emerging industry, recyclers, who may become an important link in the recycle supply chain.

The opportunity for composites in engine closure systems such as valve covers, oil pans, and timing belt covers is expanding rapidly. The primary driving forces are lighter weight finished components, integrated designs, improved isolation of engine noise, improved materials systems, and matured manufacturing processes for composite materials. Thermoset-based composite materials, particularly those based on high-temperature resistant epoxy vinyl ester matrices, offer improved performance with respect to thermoplastic and thermoset polyester-based composites and can be manufactured using different processing methods. This paper presents the current state-of-the-art design, engineering and optimization techniques for engine closure systems. The performance requirements of different systems such as valve covers and oil pans are explained in detail. Techniques for long-term structural stiffness evaluation, vibration performance assessment and noise transmission estimation are described.

The market for composite engine oil sealing components, such as valve covers and oil pans, continues to expand, replacing traditional metal stamping and die casting materials. As the market for these composite components grows, so must the understanding of the material performance characteristics and the relationship of these characteristics to the design of the part. Unlike metals, composites are viscoelastic in nature, exhibiting time-temperature dependant properties. Therefore, the traditional design approach utilizing static property data to predict long-term performance under load and over a wide temperature range will not sufficiently characterize the nonlinear property response of polymeric-based composites. A robust composite sealing design requires complete materials characterization, including long-term creep performance as a function of temperature, loading, and cycling.

The use of low density reinforced Reaction Injection Molded (RIM) substrates for covered interior automotive articles continues to increase globally. Reduced party mass, consolidation of manufacturing steps (labor), and the use of aluminum tooling, instead of steel, are cited advantages that LD-RIM offers when compared to traditional wood based and thermoplastic materials. Two RIM processes are successfully being used to produce covered interior door panels. Low density structural RIM (LD-SRIM), utilizing conventional RIM equipment, involves the placement of a pre-cut fiberglass mat in the tool cavity prior to open-pour injection of the 2-stream liquid urethane components. Low density reinforced RIM (LD-RRIM), utilizing lance cylinder RIM equipment, incorporates reinforcing fibers, such as milled fiberglass or wollastonite, in the liquid resin component. The liquid resin containing reinforcing filler is injected with the isocyanate component into a closed mold.

The persistent occurrence of microporosity defects in AZ91 castings has made it difficult to consistently produce sound parts. Earlier work established that dissolved hydrogen gas causes microporosity defects in AZ91; however, the exact role of hydrogen in the nucleation and growth of microporosity was not determined. In this paper, the behavoir of dissolved hydrogen gas in elemental magnesium, AZ91 alloy, and liquid binary Mg/Al alloys was studied. The results show that during the last stages of solidification, hydrogen gas is rejected from the Mg17Al12 intermetallic compound to assist in the nucleation and/or growth of microporosity.

The relationship between hydrogen gas and microporosity in magnesium alloy AZ91 was quantified, refuting the belief that hydrogen levels less than the maximum solid solubility are of no detriment. Sand castings were made from melts containing measured levels of hydrogen gas, and the amount of porosity was determined by density measurements. At concentrations below the maximum solid solubility, it was established that the amount of microporosity is directly proportional to the gas content. This supports the premise that dissolved hydrogen gas provides nucleation sites for microporosity, and that it is useful to remove all gas to achieve porosity-free cast parts.

The American public's desire to recycle and the predictions of future recycle mandates are motivating automotive OEMs and plastic suppliers to address the recycling of plastic materials. As a result, the OEMs and plastic industry groups have asked resin suppliers, automotive dismantlers and reprocessors to assist them in studying and developing solutions for the recovery of post-consumer automotive plastics and recycling those materials back into automotive applications. The Dow Chemical Company has been a participant in plastic industry sponsored projects and has initiated numerous research and development activities involving the recycling of automotive thermoplastic and thermoset materials, as well.

A highly reflective polymeric sheet has been invented which has a metallic appearance but contains no metal. The material can appear chrome-like, or be designed to transmit and reflect light for novel lens applications. The absence of metal waste streams and volatile organic emissions gives this technology significant environmental advantages over competitive methods of bright work or reflector fabrication. This unique optical material is non-corroding, and has the low thermal and electrical conductance of plastic. It is produced by coextruding a large number of alternating layers of polymers having a refractive index difference. This technology offers new degrees of freedom for light control in many applications including lighting reflectors, lenses, display panels, decorative trims, and energy management.

Fast, accurate delivery of metal to the shot well is critical to the success of any cold chamber die casting operation. For some metals this is a simple problem to solve. Magnesium, however, requires more innovative thinking. Simplicity of design is essential for reliable operation in the environment of a magnesium die casting facility. Complex control is required to provide speed and accuracy of shot delivery. Blending these two ingredients to produce a viable system produces a truly innovative shot delivery system for magnesium. Construction details of a newly developed stand alone system for the auto ladling of magnesium will be presented. Data with regard to speed and accuracy will also be presented.

The magnesium alloy AE42 (nominally a 4 % aluminum, 2 % rare earth alloy of magnesium) is a developmental die cast alloy with good strength and creep resistance at elevated temperatures. Standard salt spray corrosion tests have been used with controlled purity AE42 die castings to define the critical iron, nickel and copper contaminant levels below which excellent corrosion performance can be obtained. As previously observed with the magnesium alloys AZ91, AM60, and AS41, the critical iron content is dependent upon the manganese content of the alloy. While the iron:manganese tolerance for AE42 is about the same as that of AM60, the tolerance for the nickel and copper contaminants is greater than that of AZ91. When each of these contaminants is less than the critical level, the salt spray performance was equal to or better than die cast 380 aluminum and cold rolled steel.

A method for refining magnesium scrap which produces consistent, high quality magnesium metal has been developed. High quality magnesium metal is defined in this paper as metal which has heavy metal contaminants controlled within high-purity ASTM chemical specification, and is relatively free of internal impurities such as non-metallic inclusions (oxides and flux) and dissolved gas. The refining process utilizes a protective gas atmosphere, inert gas sparging and filtration techniques, rather than salt based fluxes, to remove both non-metallic inclusions and dissolved gases. Experimentation results of this refining process indicate magnesium scrap can be remelted and refined to a quality equal to or better than virgin ingot, without the introduction of salt based fluxes or a large capital investment.

With the introduction of high purity corrosion resistant magnesium alloys and also the re-emphasis of quality products throughout the industrial world, the need for more accurate and more reproducible analysis between laboratories has become apparent. The availability of high quality analytical standards was one of the principle obstacles to achieving analytical agreement between laboratories. This presentation briefly reviews what until recently was available to the industry and their customers with respect to analytical methods and analytical standards and their limitations in today's quality conscious world. The development of a new series of die cast magnesium standards by The Dow Chemical Company is also described in this paper including their compositional design considerations relating to the selection of the modern direct reading emission spectrometer as the analytical instrument of choice.

New efforts to improve quality control through the use of Statistical Quality Control techniques were introduced to the Dow Magnesium Extraction Process. All the employees in the magnesium plants were trained in the Statistical Quality Control procedures. Successful application has lead to improved chemical purity and reduced variability in the feed process. These improvements were followed by better reduction cell operation, improvements in alloying and casting operations. Consistent quality, high purity magnesium alloys are now available for use in automotive applications.