Products and solutions, 2000-06-13, 02:00 AM
Krupp VDM wins Steel Innovation Prize for new catalytic converter material
Krupp VDM GmbH has been awarded the 2000 Steel Innovation Prize in the Research and Development category for a newly developed metallic catalytic converter substrate which allows a further significant reduction in exhaust emissions. "In this way steel creates the conditions for environment-friendly auto-mobiles" was the jury's verdict in awarding first prize to Krupp VDM.
This was the fifth year in which the Steel Innovation Prize was awarded by Stahl-Informations-Zentrum, a joint organization of the German steel industry, this time under the patronage of Germany's education and research minister Edelgard Bulmahn. In all, 369 entries were received in the categories Innovative Steel Products, Research and Development, Steel in Housing Construction, and Steel Design. The new material from Krupp VDM was selected from 43 projects submitted in the category Research and Development.
Catalytic converters comprise a honeycomb-like substrate on whose surface noble metals such as platinum or rhodium act as the actual catalysts. In metallic-substrate converters the substrate is made from corrugated and wound metal foils. With conventional catalytic converters, 70 percent of the pollutants still emitted are produced during the start-up phase, before the exhaust gases have heated the converter to the required operating temperature.
The new Krupp VDM material shortens the start-up phase and thus reduces emissions. It allows substrate foils to be manufactured which at 25 µm are only half as thick as previously used foils and thus heat up more quickly to the required operating temperature. Moreover the alloy has electrical resistance of 1.6 ohms per square millimeter and meter, allowing the catalytic converter to be electrically preheated.
Foils of conventional material cannot be used in such low gages due to their inadequate heat resistance. Exhaust temperatures of up to 1,100 degrees cen-tigrade would quickly destroy the substrate if the foil thickness were reduced to 30 µm or less. The new material is designated Aluchrom 7Al YHf and was developed under the lead of Krupp VDM GmbH in a research and development project sponsored by the German education and research ministry. Also involved in the project were the Fraunhofer Institute for Applied Materials Research in Bremen, the university of Wuppertal and Emitec GmbH, Lohmar.
The improved heat resistance of the new alloy is achieved by raising the aluminum content (two percent higher than in conventional materials) and adding the reactive elements yttrium and hafnium. The aluminum prevents the destruction of the foil by oxidizing under the effect of heat and thus producing a slow-growing protective layer of aluminum oxide on the foil surface. However, the aluminum in the alloy is gradually used up in this way. The reactive elements yttrium and hafnium have been added to slow down the aluminum depletion process. As a result, the 25µm thick foils have the same lifetime as 50µm foils made of conventional material.
In parallel with the development of the material, Krupp VDM GmbH also devel-oped a cost-efficient process to manufacture the thin Aluchrom foils, in which a chromium steel strip is passed through a bath of molten aluminum. Subsequent heat treatment and annealing ensure intimate bonding.
Metallic-substrate catalytic converters using the newly developed substrate foil already satisfy the limits that will apply Europe-wide in 2005 under the "EURO Level IV" standard.