Einfluss der Herstellparameter auf die Korrosionseigenschaften des thermomechanisch hergestellten, austenitischen Stahles Alloy 926

Translated title of the contribution: The influence of production parameters on the corrosion properties of the thermomechanically rolled, austenitic stainless steel Alloy 926

Tanja Wernig

Research output: ThesisDiploma Thesis

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Abstract

Plated sheets are a composite material and exhibit a metallurgical bonding between a conventional carbon steel and a highly alloyed, stainless plating material. The requested strength of the sheets is achieved by means of a thermomechanical rolling process. However, the applied process route could cause sensitisation in the plating material. In this study the austenitic stainless steel Alloy 926 was investigated in cooperation with the company voestalpine Grobblech GmbH. The main focus of this study was to figure out the ideal rolling process, to achieve the requested strength of the conventional carbon steel on the one hand and to retain excellent corrosion resistance of the plating material on the other hand. To prolong the leading position of company voestalpine Grobblech GmbH in the field of cladding materials in Europe, rolling process parameters as end rolling temperature and cooling rate were varied. One test series was additionally quenched and tempered (Q+T) subsequent the rolling process. The impact of the prescribed parameters on corrosion properties and microstructure was examined and discussed. Different thermomechanical (TM) treatments lead to different microstructures. High-resolution investigations were carried out in the scanning electron microscope (SEM) as well as in the transmission electron microscope (TEM) to analyse the microstructure in detail. Considerable differences between samples with a different cooling rate were obtained. Also the corrosion properties were considerably influenced by the applied heat treatment. This was verified by electrochemical and standard immersion tests. Furthermore, by means of investigations on the TEM the size and the extent of the chromium / molybdenum-depleted zone adjacent the precipitations was determined. The sample 950_W (which means an end rolling temperature of 950 °C with subsequent water cooling) passed all performed types of corrosion testing (EPR, Streicher, CPT, current density - potential - curve) as the best one. Its performance was equivalent to the solution annealed reference sample LG. Therefore, this process route should be applied to achieve best corrosion properties of the plating material Alloy 926L. A quenching and tempering treatment (at least with the applied Q+T - parameters of this study) should be avoided, because it decreases the corrosion resistance of the material dramatically.
Translated title of the contributionThe influence of production parameters on the corrosion properties of the thermomechanically rolled, austenitic stainless steel Alloy 926
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Mori, Gregor Karl, Supervisor (internal)
Award date26 Mar 2010
Publication statusPublished - 2010

Bibliographical note

embargoed until null

Keywords

  • Intergranular corrosion
  • Alloy 926
  • Thermomechanical rolling process

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