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Technical Paper

Development and Application of Enhanced Compacted Graphite Iron for the Bedplate of the New Chrysler 4.7 Liter V-8 Engine

For the new 4.7 L, V-8 engine, which was introduced in the all new 1999 Jeep Grand Cherokee, Chrysler product engineers found they needed a bedplate material that was significantly stronger and stiffer than gray iron to help meet engine weight requirements. The material also had to provide good NVH characteristics, be cost effective, and machinable. Intermet Corporation, the casting supplier, wanted a material that was significantly tougher than gray iron, would cast sound in complex sections, and which could be reliably produced on a cost effective basis. This paper presents an overview of the development, properties, casting practices, and engine validation of enhanced compacted graphite iron, a material specifically developed and tailored for the bedplate of the new 4.7 liter engine.
Technical Paper

Reliability Analysis of Ductile Iron Chassis Components

Reliability predictions have become a standard practice for ductile iron safety components and this paper shows how reliability analysis has been used to verify process changes. Examples of reliability and survival probability analysis applied to fully machined and assembled components to evaluate tooling and material changes are presented. These examples demonstrated how the casting industry is “protecting the customer”.
Technical Paper

Effect of Liquid Environments on the Tensile Properties of Ductile Iron

The open literature suggests that high strength ductile irons (Q&T or ADI with hardnesses over 250 BHN) in contact with liquids, such as water or motor oil, may show a loss of ductility in the standard tensile test. This study determined the effect of water and various automotive fluids (mineral oil, motor oil, gear oil, brake fluid, power steering fluid and diesel fuel) on the tensile properties of various low and high strength grades of ductile iron (D-4512, N&T, Q&T, Grade 1 ADI and MADITM). The low strength grade of ductile iron (D-4512), the low strength grade of MADI™ and the high strength quenched & tempered ductile iron showed no loss of ductility when in contact with water or automotive liquids but the industry standard high strength grade of ductile iron (Grade 1 ADI) showed significant degradation.
Technical Paper

Component Testing and Materials Properties of Ductile Iron Brake Anchors

During product development and production, product testing is often desirable to improve design robustness and verify consistent product performance. However, product testing is very complicated, requires highly specialized and trained personnel and utilizes expensive, dedicated equipment and facilities. This paper describes two brake anchor component tests (pull and impact) and the use of strain gaged components to determine the characteristics of the component during loading. Data for two brake anchor designs are presented and the component properties are then correlated with material properties and design. The combined effect of material properties and component design on performance is demonstrated. The data also demonstrates that apparently identical tests on different component designs can lead to misleading conclusions.
Technical Paper

Induction Hardened Ductile Iron Camshafts

The General Motors L850 world engine uses an induction hardened, ductile iron, camshaft. Unlike most induction hardened camshafts that are machined first and then hardened, this camshaft is deep hardened first and then machined. Using this process, the beneficial compressive surface residual stresses are extremely high. During the development of the L850 camshaft, the casting process was optimized to produce material of sufficient quality to resist quench cracking during the hardening process and to resist mechanical cracking during the machining process. Retained austenite content, residual stress profiles, hardness, microstructure and chemical composition were all characterized and optimized. This paper reviews the material and process development for this unique automotive application.
Technical Paper

Statistical Analysis of the Mechanical Properties of Thin Walled Ductile Iron Castings

Ductile iron castings have long been used in the automotive market. Ductile iron is inexpensive to produce and has desirable fracture resistance and mechanical properties. However, the weight of ductile iron is driving an effort to reduce wall thickness in order to increase fuel economy. Traditionally, cast iron has been cast into thick, bulky shapes. Reducing the section size of cast iron can be done, but pushes foundry practice into new areas. A consortium of foundries, foundry suppliers, and automotive manufacturers has been pursuing the use of thin walled ductile cast iron. This paper investigates the mechanical behavior of three experimental heats of thin-wall castings in order to evaluate property trends and limits. Castings as thin as 1.7 mm (0.07 in) have been successfully cast.