Development strategies for exhaust gas systems have been strongly influenced in the recent years by the advancing legislation that imposed the use of catalytic converters. This factor together with the increasing guarantee of durability caused a strong increase in the use of high-performance stainless steels. The main requirements for such materials are weldability, formability and resistance to the working environment. Regarding the last point, resistance to high-temperature oxidation and resistance to high-temperature mechanical stresses are particularly needed for the hot end, while for cold end resistance to corrosion by exhaust gas condensate and by atmospheric agents is particularly required. The present work reviews the possible alternatives presently offered on the market for the different components of the car exhaust gas system and critically examines possible future evolutions. Hot end components were tested to determine creep resistance by means of the SAG test, consisting in maintaining in a furnace at 900 deg C a prism-shaped specimen suspended by wires for 100 hours and measuring the curvature resulting due to the effect of its own weigh. Static and dynamic oxidation resistance tests were conducted as well as hot corrosion resistance tests in presence of chlorides. This last test is intended to verify the in-service material behaviour in presence of ice-melting salts. In particular, 409 steel is suitable for applications up to 850 deg C, 430NbTi up to 900 - 950 deg C, while 3212 and the ferritic 441 show good resistance to oxidation up to 1000 deg C. The above mentioned steels are applied for manifold and front pipes. Presently carbon steel and cast iron for manifold are rather common in Europe, but there is the tendency to increase the gas temperature in order to improve the efficiency of catalyst, and ferritic stainless steels will be extensively used. The transition to stainless steel is almost completed in the muffler, so the stainless steel consumption is expected to increase proportionally to the automotive production.


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    Title :

    Gli acciai inossidabili nei sistemi di scarico degli autoveicoli


    Additional title:

    Nichtrostende Stähle für die Auspuffsysteme von Kraftfahrzeugen
    Stainless steels in car exhaust gas systems


    Contributors:
    Barteri, M. (author) / Fazio, F. (author) / Fortunati, S. (author)

    Published in:

    Metallurgia Italiana ; 91 , 5 ; 31-36


    Publication date :

    1999


    Size :

    6 Seiten, 9 Bilder, 2 Tabellen, 4 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    Italian




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