Reducing Fuel Consumption
Hollow engine valves made of nickel alloy wins top prize for innovation. By Virginia Heffernan
THE MAGAZINE DEVOTED TO NICKEL AND ITS APPLICATIONS
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ENGINE VALVES typically open and close 30 times a second. This creates extreme thermal and mechanical
stresses on the valves which have to operate in a very corrosive environment.
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IF THEY ARE MADE of nickel alloy N06601, engine valves can be hollow (as shown), thus saving weight
and therefore reducing fuel consumption and exhaust emissions.
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THE 2003 "STEEL IN RESEARCH AND DEVELOPMENT" award presented by the German stainless steel
industry, went to Mahle Ventiltrieb GmbH for the design of the above lightweight engine
valve.
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Nickel magazine, March, 2004 --A lightweight valve made from a nickel alloy has won first prize in the "Steel in Research and Development" category of the 2003 Steel Innovation Prize.
The annual award was introduced by the German steel industry in 1989 to promote innovative applications and ideas involving steel. Last year, there were 678 contestants but only 12 winners in various categories including: products made of steel; research and development; steel for the construction industry; and design.
The award-winning valve, made from N06601, containing 60% nickel, was designed by Stuttgart-based Mahle Ventiltrieb to meet the demand for a lightweight, cost-effective valve in combustion engines.
The choice of material was based on several, often conflicting, requirements, says project manager Marcus Abele. The material had to be suitable for cold forming and laser beam welding while being able to withstand extreme thermal and mechanical stresses within the corrosive atmosphere of the engine. At average engine speeds, these valves open and close 30 times a second at temperatures up to 950°C.
The new valve is 30-50% lighter than conventional valves, reducing the mass that must be moved in the valve actuating mechanism and, in turn, creating less frictional drag within the engine. Less friction and lower weight translates into less fuel consumption, fewer exhaust emissions, a higher allowable engine speed and reduced wear on the engine.
"Customers are already showing interest in the lightweight valve," says Abele. "The first products are to go into volume production in 2005."
In the past, attempts to develop a lighter valve involved ceramics, titanium or titanium aluminide. But Abele says ceramics are prone to cracking under high loads, while titanium materials must be coated in order to be tribologically compatible with the other components in the valve. High material costs and/or expensive manufacturing and testing discouraged further development of these materials.
Another difference between the new valve and conventional valves is the structure. The Mahle valve has a hollow structure with a high-precision N06601 tube shaft. The valve ball and plate are manufactured by a multi-stage forming process using N06601 sheet with a thickness of 0.8-1.8 mm. The individual components are connected to each other by laser beam welding and the hollow areas of the exhaust valves, which must be able to withstand high thermal stress, are filled with sodium to ensure thermal conductivity.
By using high-precision components, the amount of mechanical processing required is about a quarter of that required for a valve manufactured by forging.
Demand for a suitable, reasonably-priced valve for combustion engines triggered the development of the prize-winning valve in 1998. The key innovation, says Abele, was the use of sheet metal parts. After developing a prototype, Mahle filed patent applications for the valve, both in Germany and internationally, then began a rigourous design and testing program, including a successful vehicle test covering more than 50,000 miles.
In 2001, Mahle presented the new valve to the industry at the SAE World Congress in Detroit and the Engine
Symposium in Vienna.
Virginia Heffernan is a Toronto-based freelance writer.
PHOTOS: MAHLE Ventiltrieb GmbH
Marcus Abele |
