After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing t...After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing the moving strip through a furnace heated by combustion of natural gas with little air excess.Although the time at high temperature is short(<1 min),the formed surface oxide is thick enough to modify the surface aspect of the steel,making necessary subsequent chemical pickling.The present work explores the oxidation step of various stainless steels during final annealing in order to better understand the mechanisms involved and make further improvements in the pickling sequence.展开更多
This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(...This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(several cm/h).The method,valid far from stagnation points or detachments,is based on the properties of turbulent boundary layers,with a normal velocity of the liquid towards the solid/liquid interface due to solidification,that has the same effect as boundary layer suction in aeronautics.The transition between the diffusive regime(no segregation),and the convective regime(efficient segregation)occurs if the friction at the wall is greater than a threshold depending on the solidification rate.A chart is given to estimate the convecto-diffusive parameter from the ratio between stirring and solidification velocity,and the Reynolds number.展开更多
文摘After the cold rolling sequence of the production line,stainless steels strips present highly disordered structure and have to be annealed to recover their crystalline structure.This operation takes place by passing the moving strip through a furnace heated by combustion of natural gas with little air excess.Although the time at high temperature is short(<1 min),the formed surface oxide is thick enough to modify the surface aspect of the steel,making necessary subsequent chemical pickling.The present work explores the oxidation step of various stainless steels during final annealing in order to better understand the mechanisms involved and make further improvements in the pickling sequence.
基金Item Sponsored by the French Agency for Environment and Energy (ADEME) as Part of the ISOPEM Project and labelled by TENERRDIS (Rhone-Alpes Energy Cluster)
文摘This paper proposes an estimate of the stirring intensity needed to maintain an efficient segregation of impurities towards the liquid when crystallizing semiconductors such as silicon,with rapid solidification rates(several cm/h).The method,valid far from stagnation points or detachments,is based on the properties of turbulent boundary layers,with a normal velocity of the liquid towards the solid/liquid interface due to solidification,that has the same effect as boundary layer suction in aeronautics.The transition between the diffusive regime(no segregation),and the convective regime(efficient segregation)occurs if the friction at the wall is greater than a threshold depending on the solidification rate.A chart is given to estimate the convecto-diffusive parameter from the ratio between stirring and solidification velocity,and the Reynolds number.
