Forgeabilité des aciers inoxydables austéno-ferritiques

tel-00672279, version 1 - 21 Feb 2012
Chapter I. Introduction 17
(1) Continuous cast slabs are first reheated to 1280°C and kept at this temperature. The duration
of this stage is about 3h.
(2) The slabs are then rough rolled on a reversible mill in 5-7 rolling passes. With a very strong
thickness reduction, i.e. from 200mm to 30mm thickness.
(3) The rough rolled sheets are then hot rolled on 7 consecutive finishing mills to the final thick-
ness from 2 to 13mm. The temperature is around 800-1000°C at the end of the hot rolling
process.
(4) Cooling of the sheet on a specific table.
(5) Coiling at a temperature between 500 and 800°C. The final length coil can measure more than
100m.
I.2.3.2 Microstructures after the roughing-mill operations
The as-cast slabs are then reheated before to be rolled at high temperature. The microstructures after
the roughing-mill operations present an elongated austenite in the rolling direction, see Figure I.8.
D1
ND
RD
δ-ferrite
γ-austenite
a) b)
D2
ND
RD
δ-ferrite
γ-austenite
Figure I.8. Microstructures of the transfer bar, i.e. just after the roughing-mill operations; a) D1
grade; b) D2 grade; γ-austenite in white, δ-ferrite in grey.