Components that are directly connected to the engine of automobiles, such as the exhaust manifold, have to sustain high temperatures, thermo-mechanical load as well as corrosive environment. Ferritic stainless steel grades are preferred for this implementation, since they exhibit good thermo-mechanical and cyclic oxidation behaviour while the production is economical. However, meeting the recent European directives in terms of exhaust gas and particle emissions, the exhaust gas temperature of automobiles is getting up to 950 °C. This extreme condition cannot be covered by existing ferritic grades. Hence, a new ferritic stainless steel grade has been developed in this study, which exhibits improved properties for application in an exhaust manifold compared to the state of the art steel grade, 1.4509. To improve the high temperature properties, defined amounts of Cu and Mo were added to a 1.4509 lab heat. Sheet material of the new grade and of the reference grade was tested in various test methods. To achieve a reliable evaluation of the new grade, test methods were adapted to real conditions in automotive exhaust manifolds. This paper presents the obtained outcomes of high cycle fatigue tests up to 700 °C and high temperature tensile as well as ageing tests up to 950 °C. As final point of the material evaluation, prototype tests with the new and the reference grade are displayed. The influence of the new chemical composition was clarified by means of microstructure investigations. It was found that the additions of Cu and Mo lead to enhanced properties for manifold application compared to grade 1.4509.
New ferritic stainless steel grade for exhaust manifold application
Neue nichtrostende ferritische Stahlgüten für Abgasrohrkrümmer
2014
8 Seiten, 9 Bilder, 6 Quellen
Conference paper
English
nichtrostender ferritischer Stahl , Abgasrohrkrümmer , Anwendung im Fahrzeugbau , thermomechanische Eigenschaft , Korrosionsverhalten , Motorabgas , Umweltbelastung , Temperatureinfluss , Werkstoffentwicklung , Hochtemperatureigenschaft , Mikrostruktur , Kupferzusatz , Molybdänzusatz , Ermüdung bei hohen Lastspielzahlen , Prototypentwicklung , Abgastemperatur , Temperaturverteilung , Warmauslagern , mechanische Eigenschaft , Warmzugversuch , Warmzugfestigkeit , Werkstoffvergleich , Dauerschwingprüfung , Temperaturwechselbeständigkeit , Ausscheidungsprodukt
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