The exhaust manifold of an automobile is exposed to thermal cycles by high temperature exhaust gas. Thermal fatigue resistance is one of the most important properties for an automotive exhaust manifold. In this study, we investigated changes in the microstructure, the crack propagation and the hysteresis loop during the thermal fatigue of Type 429 ferritic stainless steel. In addition, we compared Type 429 and Type 444 in order to evaluate the effect of high temperature strength on the thermal fatigue life. The following results were obtained. (1) During the thermal fatigue process, some wrinkles occurred on the surface of the material, and some cracks progressed in the direction of thickness. (2) During the thermal fatigue process of Type 429 in the temperature range from 200 deg C to 800 deg C, the material was softened by the reduction of the amount of solute Nb, and the dynamic recovery and recrystallization. (3) The form of hysteresis loop changed with the increase in cycles. By considering the softening of the material by heat treatment, the change in the form could be predicted to some extent. (4) Type 444 with high temperature strength had a longer thermal fatigue life than Type 429. The thermal fatigue behavior and life were related to high temperature strength, and increase in high temperature strength was effective in improving the thermal fatigue life.
Thermal fatigue behavior of ferritic stainless steel for automotive exhaust system
Thermisches Ermüdungsverhalten ferritischer nichtrostender Stähle im Fahrzeugabgassystem
2008
6 Seiten, 10 Bilder, 1 Tabelle, 17 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
ferritischer nichtrostender Stahl , chemische Zusammensetzung , Anwendung im Fahrzeugbau , Abgassystem , Temperaturverhalten , Temperaturwechselbeanspruchung , Hystereseschleife , Mikrostruktur , Feinkorngefüge , Rekristallisation , Niobcarbid , Niobnitrid , mechanische Eigenschaft , thermische Ermüdung
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