INOCAST layman report

Transcription

1 INOCAST layman report About cars and the engines that make them run There are currently about 700 million motor vehicles being driven on the streets of earth. Every motor vehicle has an engine and at the core of each engine is the engine block, usually made from cast iron or aluminium. An engine block accounts for about 3-4% of an average vehicle s total weight. As customer demands for more power, more safety and more on-board luxury increase, the pressures on the engines become higher and higher. The easiest way to solve this would be to simply build ever bigger and heavier engines, preferably with high-grade cast iron blocks. However, more weight means heavier vehicles and higher fuel consumption, not to mention higher wear & tear on things like tyres, brake-discs etc. All this would result in more environmental pollution. This is not what car manufacturers want: because of climate change effects - a substantial part of which is attributed to motor vehicles - they now put strong emphasis on building environmentally friendly (thus lighter) cars. Car manufacturers now face the problem of having to square ever higher customer demands with the need to be more fuel and emission efficient. A small part of the problem is solved by using aluminium instead of cast iron as resource a resource for engine blocks. Aluminium is lighter than cast iron and aluminium engine blocks have a high weight reduction potential: a 100kg weight reduction reduces fuel consumption by 0.7L per 100 km. However, aluminium also tends to be a softer material than cast iron. This means that when you increase the power output (in terms of horsepower and/or torque) of a motor engine, the stress levels put on aluminium blocks will be higher relative to cast iron blocks. This does not have to be a problem. Nowadays it is possible to squeeze even 200 break horsepower out of a 1.4 litre engine cast from aluminium. The point here is, that for environmental reasons aluminium engine blocks have a clear advantage, but require careful and intensive pre-production testing in order to guarantee their functionality, endurance and wear & tear. Keep this in mind as we first move to explain the production process for aluminium engine blocks.

2 How an engine block is cast The production of an aluminium engine block is heavy stuff. Some car manufacturers produce engine block in-house, others have dedicated casting companies do this work for them. Hydro Dillingen is a dedicated casting centre for the production of engine blocks and cylinder heads. At the Hydro Dillingen plant about 800 people work in three production facilities. Each production street is about 150 meters long and divided into several sections. The first main section concerns the production of so-called sand-cores. The sand cores will later hold the liquid aluminium which makes the engine block. The current process used at Hydro Dillingen is called the Core Package System or CPS. It s a bit like building a sand castle: first a sand mould is produced under high pressure. The sand is held together through the use of so-called organic binders. These binders act like glue between individual sand grains. The tools to form the mould are either heated (called hot box procedure) or cool (called cold box procedure). Most aluminium producers (in Germany: 75%) within the automotive industry currently use cold box, as hot box requires much higher energy consumption because of the need to heat up the tools and moulding templates. When pressed into shape, the sand mould itself mirrors all the parts and openings of the final engine block in your car. Once the mould is treated and cooled off, it moves on to the second section where the liquid aluminium flows into it. At this stage casting fumes appear, some of which can be environmentally harmful if not treated properly. The fumes are led through filters and after treatment they are emitted into the air. Again the block is cooled down before entering the third section where the mould and cast are heat treated. This is important for tempering the cast (making it stronger and last longer) as well as for burning off the organic binder which holds together the sand core. Heat treatment is very expensive: usually between 40% and 60% of all electricity used in a casting plant will go to the heat treatment section. Once the binder is burned of, the sand grains let go off the casting and fall onto a conveyor belt. About 98% of the sand can then be used again for producing the next mould. The aluminium castings then go continues through a further cleaning and inspection stage. Then they are ready for transport to a car manufacturer who will final machine and assemble the block into a proper car engine. So what is the problem? One problem with casting engine blocks as described above is that it is potentially not very environmentally friendly: first you have the organic compounds (among which phenol resins and amines) within the binder which have to be burned off the cast. Then there is the casting moment at which time substantial amounts of toxic fumes (aromatic amines, furan, benzopyrene and other organic materials) escape into the partially closed production room, creating a health risk for employees. The fumes are led into an extensive post-combustion and filtering system to avoid spontaneous production and emission. Finally there is the thermal heat treatment, which uses a lot of energy. The heat treatment and thermal sand recycling procedure at Dillingen is responsible for about 56% of total energy consumption of the plant ( MWh; data 2005). It takes a lot of energy to make the sand disintegrate from the casting and also to burn off the binder from each individual sand grain so it may be re-used. The described production method is in different variations widely accepted within the industry. Emissions stay within regulatory boundaries and electricity can be bought according to requirement. Having said this, casting companies are under constant pressure from car manufacturers to cut cost and be more competitive. Hydro Dillingen is no exception to that. But where to cut cost? Why the Inocast project? The answer is relatively simple, even if the implementation certainly is not. The best place to cut cost (making the most impact) can be found in the thermal heat treatment and sand reclamation section. After all, 56% of the plant s total energy consumption is located here. But then the question is how to remove both the sand on the cast and the organic binder from the sand?

3 In 2004 the Hydro Research facility in Bonn and leading minerals supplier Minelco came up with a possible answer after extensive tests with so-called inorganic binders. These binders have the advantage that they are based on water glass and can form natural binder bridges between sand grains. This only works if the mould is formed with warm moulding tools ( warm box as opposed to cold box and hot box ) to allow subsequent dehydration of the binder. REM Picture of AWB binder bridge Hydro was not the first to experiment with water glass binder, but the innovation lies in how to make the chemical adherence of the binder to the sand grains reversible. This is important, because otherwise the sand (in cold box 98% of the sand re-used to build new cores) would be useless after just one production cycle. The expectation was that due to its neutral properties it would not need to be burned off the sand grains after casting in order to retrieve the sand for reuse. Instead, the mould should be easily removable from the casting through hammering or beating, after which a quick sand wash would remove any last trace of the binder. The result would be that the thermal heating section would become superfluous and could be shut off. Result: a substantial drop in energy costs. The added bonus was the removal of the relatively expensive organic compounds (phenols, resins etc) and amines from the production process. To top it up, the researchers at Hydro and Minelco wanted to further improve the adherence and reversibility properties of the inorganic binder further through the use of synthetic sand instead of traditional quartz sand. Synthetic sand has a more regular shape and provides more/better surfaces for building the desired binder bridges. Also, by using synthetic sand the risk of employees contracting silicosis could be fully banned. So far, so good. Lab tests showed that the new process - called AWB-CPS - could work. But here is the problem: for Hydro the only reason for changing its production system to AWB would be if a car manufacturer agreed to have a series engine block built in this manner. Now, car manufacturers tend to be fairly conservative, and rightly so. They require that engine blocks undergo very rigorous testing before production can start. Standard cold box and hot box core building and casting methods using organic binders at least provide the relative certainty that a widely established knowledge base is available on all kinds of quality aspects and technical risks when building sand core packages. The challenge for Hydro was to find a manufacturer who not only wanted to have a high-powered aluminium series engine with a hypereutectic block built by Hydro (which in itself involves a large investment and involves certain risks at the development stage), but on top of that would allow the engine block to be built in a completely novel and as yet untried production method. At this point Hydro Dillingen and Minelco decided to go for a demonstration of AWB: they wanted to build at least 300 core packages and about 30 good quality engine blocks which could be handed over to an innovative car manufacturer who would validate the quality of the blocks in a properly built car engine. Quality tests, wear & tear and endurance of the engine block should be

4 checked both at test stands as well as on the road. This would convince car manufacturers that high performance demands, AWB and aluminium were a good match. At this point the Audi engine factory at Györ in Hungary came in. Audi were willing to perform the validation tests by comparing AWB-produced blocks against a standard cold-box produced block of the same type and model. Demonstrating the quality aspects of the engine provided Hydro also with the opportunity to test its assumptions on reduction of emissions, electricity consumption and resources. The result of the discussions between the organisations led to the submission of the Inocast project to the EU LIFE-programme in January Inocast project results Inocast finished in March The technical and environmental results have met the original expectations. Inorganic binders are able to produce high quality moulds and excellent casts. Thermal heating is no longer a requirement and emissions are (practically) non-existent [g carbon]] AWB Inotec 4110 Inotec 4044 Cold-Box Quantitative FID analysis by TÜV Saarland The inorganic core production is running on modified series machines with electrical heated tools. A new production system covers the extended core drying times and assures high productivity and economic production. The core package assembly takes place with existing robot and gripper systems. Today visually inorganic cores are distinguishable from cold box cores only by real experts. Inorganic core package and side core of a core package with glued inner oil drain cores

5 The produced engine blocks meet highest demands on mechanical properties, complex geometries in sand casting process, surface roughness and accurate microstructure of the castings: I4 aluminium engine block in AWB CPS Section of inner oil drains Where at the start the leading binder manufacturers did not take the inorganic initiative seriously, they are now in advanced stages of development of production-ready inorganic binders. In fact, it appears the inorganic CPS-system has good application potential in other markets too, like iron casting, casting of fittings and plastics moulding. The success did not come without its share of difficulties. The intended validation tests in proper car engines did not take place. For internal business reasons manufacturer Audi decided not to continue testing with the already existing engine model and it was too soon to start testing with a new model. A replacement was sought and found, but this took time. The original AWB binder and synthetic sand did in the end not meet technical requirements (but further research is still taking place and looks promising). Instead quality tests on core packages were performed with a different type of inorganic binder and the use of quartz sand. This in turn did require the development of a separate and larger sand washing installation. All in all, the result thus far is that particularly for large (outer) core packages, the inorganic CPS system has a very promising future. Once validation tests are finished, it is likely that car manufacturers will come to accept inorganic CPS as a standard. Apart from achieving the quality standards, inorganic CPS also meets production cycle times and tact frequencies. Moulds can indeed be easily de-cored and with the use of the new washing installation, sand regeneration levels getting near to the levels achieved in cold box. Inorganic CPS is currently being improved to meet quality standards for small and inner cores in the package. Finally and most importantly from the perspective of the EU-LIFE programme - the environmental aims and targets have been met. When the warm box technology would be introduced for all casting lines, the total electricity consumption of the Dillingen plant would gone down by 37%. Measurements and analysis by a recognised independent institute confirm that

6 emissions are below measurable levels. In other words: inorganic CPS is an environmentally friendly casting method. The future of engine block casting The Inocast project is now finished. As a result of the transfer of the Dillingen plant from Norsk Hydro to Nemak, the results from the project are currently being integrated into several merged business processes. Project partner Minelco will continue to actively market the project results throughout the world and will showcase AWB at the upcoming GIFA 2007 fair in Dusseldorf (June). More information on the Inocast project and further inorganic CPS casting can be found at: and The project partners would like to thank all involved in this project for their enthusiasm and support. On behalf of the project team members, Joachim Kahn