The engine is the single most important part of the automobile. Without it, the car simply will not move. It is important that the cylinder or engine block is built to withstand the high temperatures and pressures that are put into it and it is equally important that the engine block is built to last. Over the years, materials used for making engine blocks have changed and materials sciences have matured enough to find the best possible materials to build engine blocks. Common materials used for engine blocks include Grey Cast Iron, aluminum and Compacted Graphite Iron (CGI).
In the early years of building engine blocks, grey cast iron was the only material used. The process of using alloys was non-existent and aluminum was a new material which few people were familiar with. At the time, however, grey cast iron worked very well. The carbon, present as flakes of graphite, in grey cast iron gives the material good resistance to wear and also provides good corrosion resistance and lubrication characteristics which gives it exceptional machinability. The Carbon also provides good strength and toughness and has a high melting point which allows it to handle more heat under intense driving conditions.
The composition of the grey cast iron is 3. 5% carbon, 2. 5% silicon and . 65% manganese. Cast Iron engine blocks are still very common to this day in larger vehicles such as trucks and SUV’s. The advantage of cast iron is that it is much cheaper and easier to produce than aluminum and it has high tensile and fatigue strength at room and elevated temperatures. The disadvantages of cast iron are its high specific gravity and higher casting and solidification temperatures which causes poor surface quality and poor dimensional accuracy.
That is the reason why manufacturers began to experiment with aluminum. The question still remains, which material is best for manufacturing engine blocks? Many variables should be brought into consideration when deciding which the best is. Each material has its advantages and disadvantages. At this point in time, the need for making automobiles as fuel efficient as possible is becoming more and more necessary. Aluminum alloys are possibly the best solution for reducing weight in engine blocks. Cast Iron is a great way to make engine blocks strong and durable at the lowest price.
CGI is perhaps the best material for making engine blocks when looking at it from a mechanical stand point because it is stronger and lighter than cast iron. However, its greatest advantage is also its greatest weakness and that is its grain structure. It makes the material very strong but also makes it very difficult to machine. If not for the complicated machining processes and necessity for advanced machinery and tooling, I believe that the majority of engine blocks would be made from Compacted Graphite Iron.
Sources
- Georgiou, George. Iron engines may be in your future; compacted graphite iron is top prospect. (automotive). ” Tooling & Production. Nelson Publishing. 2003. AccessMyLibrary. 28 Nov. 2009 .
- Moore, C. M. ; K. Rohrig,; R. Deike,. “Automotive aluminum castings: are they really cost effective? ” Foundry Management & Technology. Penton Media, Inc. 1999. AccessMyLibrary. 28 Nov. 2009 .
- Satyanarayana, Ashwin. “Automobile Engine Constructional Details. ” 08 Sep 2008: n. pag. Web. 28 Nov 2009.
- Woodruff, David. “Why Compact Graphite Iron? “Competitive Production. 2009. Makino Inc. , Web. 29 Nov 2009.
