AlおよびAl-Ti添加17Crフェライト系ステンレス鋼の熱間圧延時の再結晶挙動

抄録

To investigate the recrystallization behaviour of Al and Al-Ti containing 17Cr ferritic stainless steel during hot rolling, the precipitation behaviour of AlN and Ti(C, N) in heated east slab was examined, and then wedge shaped specimens taken from the slab were hot rolled at 1173K to 1453K in single pass manner and hardness test and optical microscopic observation were conducted. The results are as follows.
When heating the slab of Al containing steel, AlN precipitates most easily at about 1273K; this gives the nose in precipitation behaviour.
With Al-Ti containing steel, almost all of Ti precipitated as Ti (C, N) in the as-solidified state, and this prevented precipitation of AlN.
The Al containing steel hot rolled at relatively lower heating temperature near 1173K exhibited deformation structure with deformation bands. The deformation band initiated at ferrite grain boundaries and dispersed AlN precipitates. The deformation structure changed into partial recrystallization structure with raising heating temperature to 1273K and increasing rolling reduction. In relatively higher heating temperature, recovery structure which contained many fine sub-boundaries was attained. Therefore the nose in recrystallization behaviour existed at near 1273K. It is considered that recrystallization structure is statically formed after hot rolling and recovery structure is dynamically formed in hot rolling.
Nearly the same results were obtained in Al-Ti containing steel. A peculiarity was found of the Al-Ti containing steel in structural changes during hot rolling, that is relatively coarse recrystallized grains existed in the recovered structure. This is considered attributable to dynamical recrystallization.