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The reverse transformation mechanism of martensite to austenite and the volume fraction of retained austenite have been studied in an Fe ± 3Si ± 13Cr ± 7Ni (wt-%) martensitic stainless steel by means of dilatometry, transmission electron microscopy and X-ray diffraction. Below a heating rate of 10 K s 1 , the reverse transformation of a' to c occurs by diffusion, whereas it occurs by a diffusionless shear mechanism above 10 K s 1 . After reversion treatment at low temperatures, ® lmlike retained austenite is observed along a' lath boundaries, while reversion treatment at high temperatures produces granular retained austenite inside the a' laths in addition to ® lmlike retained austenite. The volume fraction of retained austenite at room temperature increases with increasing reversion treatment temperature, exhibiting a maximum at~625°C, above which it decreases with increasing reversion temperature. MST/5353Professor Lee (yklee@yonsei.ac.kr) is in the

Nucleation and growth process of sticking particle in ferritic stainless steels was investigated using a twodisk type hot rolling simulator. The sticking behavior was strongly dependent on the surface roughness of a high speed steel roll (HSS) and the oxidation resistance of the ferritic stainless steels. A sticking occurrence was more sensitive for the steels containing higher chromium. There was a critical value which was found to be 3mm of scale thickness in the suppression of the sticking phenomenon. It was also illustrated that the initial sticking particles were nucleated at the scratches formed on the roll surface and were served as the sticking growth sites. As rolling proceeded, the sticking particles grew by the process that the previous sticking particles provided the sticking growth sites.KEY WORDS: ferritic stainless steel; sticking behavior; hot rolling; high speed steel roll.

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Fig. 4-Electron micrographs of the alloy aged at 823 K for 20 min: (a) BF (b ) An SADP taken from an area covering (␣ ϩ B2) particle and -carbide lamella. The foil normals of the ␣ and -carbide are [001] ␣ and [011] , respectively (hkl ϭ ␣, hkl ϭ B2, and (hkl) ϭ carbide). (c) and ( d ) 100carbide and 100 B2 DF images, respectively. 15. T.