Investigation of the efficacy of a water-cooled chill on enhancing heat transfer at the casting-chill interface in a sand-cast A319 engine block

• Published in: Journal of materials processing technology Vol. 286; p. 116789
• Main Authors: Farhang Mehr, Farzaneh, Cockcroft, Steve, Reilly, Carl, Maijer, Daan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2020; Elsevier BV
• Subjects: A319 alloy; Aluminum base alloys; Automobile industry; Automotive engines; Casting; Chill; Chill casting; Chills; Cooling rate; Cylinder heads; Dendrite arm spacing; Engine block casting; Engine blocks; Fatigue life; Fatigue strength; Fuel economy; Heat transfer; Heat treating; Interface gap; Interfacial heat transfer; Liquid cooling; Machining; Microstructure; Permanent molds; Precision Sand Casting; Sand; Sand casting; Solidification; Thermocouples; Transducers; Water cooled chill; Weight reduction; Dendrite arm spacing; Water cooled chill; Interfacial heat transfer; Chill; Cooling rate; Interface gap; Precision Sand Casting; Engine block casting; Microstructure; A319 alloy; Heat transfer; Solidification
• ISSN: 0924-0136; 1873-4774
• DOI: 10.1016/j.jmatprotec.2020.116789

•The evolution of the casting-chill interface gap plays a significant role in the heat extraction ability of the chill.•Watercooling the chill helps to maintain better physical contact between the casting and the chill.•Using a water-cooled chill increases the cooling rate in the casting, thus can potentially improve its fatigue properties. In the recent years, the automotive industry has increased the production of small, high-power gas engines as part of several strategies to attain the new “Corporate Average Fuel Economy” (CAFE) standards, while meeting consumer demand for increased performance at the same time. This trend necessitates an improvement in the thermal and mechanical fatigue strength of the aluminium alloys used in manufacturing cylinder heads and engine blocks in these engines. In the absence of changing alloy chemistry, which potentially has important implications for downstream operations such as heat treating and machining, one feasible way to improve fatigue life is to reduce the length-scales of the microstructural constituents arising from solidification that limit fatigue resistance. This, in turn, may be accomplished by increasing the cooling rate during solidification (reducing the solidification time). Conventionally, solid chills are employed in the industry to achieve this goal. A potential tactic for improving the efficacy of these chills is to incorporate water cooling. In order to assess the effectiveness of this technique, a water-cooled chill was designed and installed in a bonded-sand engine block mould package (quarter section). Twelve experiments were conducted with a conventional solid chill and a water-cooled chill (with and without delay in water cooling). The moulds were instrumented with “Linear Variable Displacement Transducers” (LVDTs) to measure the gap formation at the casting-chill interface, and thermocouples to measure the evolution of temperature at key locations in the casting and the chill. Overall, the results show that the adoption of water-cooled chill technology, if implemented carefully, has the potential to improve the cast microstructure, therefore, increase the fatigue durability of the engine blocks.