Process Improvements to Reduce Bonding Gap between Aluminum Cylinder Block and Cast-In Liner and Evaluation through Non-Destructive Techniques

Abstract

<div class="section abstract"><div class="htmlview paragraph">Light weight technologies are inevitable in the automotive industry to increase fuel efficiency and meet emission norms. An engine cylinder block is one of the major elements contributing approximately 3-4 % of the automobile weight. Aluminum cylinder block with cast-in liner is almost 40-55 % lighter than a conventional cast iron block [<span class="xref">1</span>] and hence the manufacturing processes and challenges associated with them are of high interest. A heterogeneous cast-in liner of gray cast iron in cast aluminum offers a low cost option, but the mechanical bond created between the liner and aluminum interface is prone to gap formation which affects the engine in terms of in-effective heat transfer, distortion and higher blow-by, and thereby high oil consumption & higher emissions. This study aims at reducing this interface bonding gap by in-depth study of critical process parameters involved in manufacturing of cylinder blocks.</div><div class="htmlview paragraph">The study involved a single cylinder petrol engine block manufactured using High Pressure Die Casting (HPDC) process. Using detailed cause and effect analysis, various stages of HPDC like die design, including gating & cooling system were studied & improved using mold flow analysis. Die casting process parameters like die temperature, warm up shots, and biscuit thickness were optimized. Evaluation of bonding gap was carried out using non- destructive techniques like Immersion Ultrasonic Testing & Computed Tomography Testing and a comparative analysis with experimental results of both methods are discussed. Considering initial investment, testing cost, testing time, sensitivity & resolution, a feasible method may be selected for implementation.</div></div>