Low density steels: phase structures

Hájek Jiří - COMTES FHT a.s. (Czech Republic)

The paper deals with low-density steels based on Fe – Al – C combination. The aim was to obtain steels with a density close to 7.0 g.cm-3. The specific chemical composition design is based on calculations performed using JMatPro software and analytical techniques. The experimental material was prepared by casting 50kg ingots of 110mm diameter and 500mm length using a vacuum induction furnace.
Metallographic analyses were carried out in the cast and as-formed conditions as part of the experiment. Dilatometric analysis was supplemented by LM, SEM, EDS, and X-ray diffraction analysis.
The reduction in specific gravity was up to 11% for the heat with 7wt% Al. The very strong effect of ferrite-forming elements is evident in the experiments, especially aluminium and chromium. We come to the significant conclusion that even at very high austenitisation temperatures exceeding 1100 °C, it is impossible to leave the two-phase structure of ferrite and austenite. The amount of ferrite is 30 to 50% of the total volume.

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