Modelling of coagulation processes and removal of non-metallic inclusions at melt's inert gas flushing inside a ladle

Kaoma Mulenga Michou

Description

The present work is devoted to optimization based upon physical and mathematical modelling of calcium treatment processes for low-alloy steel grades in Ladle, using Steel Refining Unit (SRU). The widely applicable method of calcium injection into ladle on Steel Refining Unit by means of Flux-Cored Wire (FCW) or the method of silicocalcium blowing-in often requires significant flow rate of calcium containing alloys to ensure the necessary concentration of calcium and sulfur in the finished steel. Methods of mathematical modelling are widely applied for the purpose of improvement of calcium alloys injection modes into ladle. However, mainly heating processes in the ladle are taken into consideration in this connection; meanwhile hydrodynamic processes are accounted only partially. At the same time, interfacial reactions of the metal with steam bubbles play a significant role in the processes of interaction between calcium and supernatant liquid, whereby sulfur and oxygen that are dissolved in steel take part in the reactions described above. Nevertheless, only single quantitative estimates are known for kinetics of mass exchanging processes in the ladle. Finally, efficiency of calcium treatment depends on chemical composition of steel. Probability of low-melting calcium aluminates formation, which ensure improvement of pouring capacity, depends not only on the frequently used proportion of [Ca] to [Al], but also on conditions of steel oxidation and sulfur content in the steel. Therefore, optimization of injection modes for calcium containing alloys based on the thermodynamic and kinetic analysis of steel deoxidation and modification conditions, as well as on the mathematical modelling of mass exchanging processes, represents a crucial scientific and technical challenge of nowadays.

Sujets

• Sciences fondamentales
• Sciences et techniques

Informations

• Publié par: Connaissances & Savoirs
• Date de parution: 02 septembre 2016
• Nombre de lectures: 0
• EAN13: 9782342055221
• Langue: Français

Extrait

Modelling of coagulation processes and removal of non-metallic inclusions at melt's inert gas flushing inside a ladle
Kaoma Mulenga Michou
Connaissances & Savoirs

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Modelling of coagulation processes and removal of non-metallic inclusions at melt's inert gas flushing inside a ladle
 
 
 
 
Th e presen t w or k is devote d t o optim i zatio n base d upo n phys i ca l an d mathemat i ca l model l in g o f ca l c i u m treatment processe s fo r l o w -al l o y stee l grade s in Ladle , us i n g Stee l Ref i nin g U ni t (SRU) .
Th e w i del y app li cab le metho d o f ca l c i u m i nject i o n int o ladl e o n Stee l Refinin g Un it b y mean s o f F l ux-Core d Wir e (FCW ) o r th e metho d o f s ili coca l c i u m blowing- in ofte n requ i re s s i gn i f i can t f l o w rat e o f ca l ciu m con t a i nin g a ll oy s t o ensur e th e necessar y concen t rat i o n o f calc i u m an d su l fu r in th e f i n i she d steel .
Method s o f mathematica l mode l lin g ar e widel y appl i e d fo r th e purpos e o f improvemen t o f ca l c i u m al l oy s i nject i o n mode s i nt o l adle . H owever , ma i nl y hea ti n g processe s in th e l adl e ar e take n i nt o cons i deratio n in th is c onnect i on ; mean w h i l e hydrodynami c processe s ar e accounte d onl y par t ia ll y . A t th e sam e time , i nterfacia l react i on s o f th e me t a l w i t h stea m bubb l e s p l a y a s i gn i f i can t ro le i n th e processe s o f i nteract i o n bet w ee n ca l ciu m an d supernatan t li quid , w hereb y su l fu r an d oxyge n tha t ar e d i sso l ve d i n stee l t ak e par t in th e react i on s describe d above . Nevertheless , onl y s i ngl e quantitat i v e estimate s ar e kno wn fo r kinet i c s o f mas s exchangin g processe s in th e l adle .
F i na ll y , eff i c i enc y o f ca l c i u m t reatmen t depend s o n chemica l composit i o n o f steel . Probab il it y o f l ow-melt i n g ca l ciu m a l uminate s form a t i on , w h i c h ensur e improvemen t o f pourin g capacity , depend s no t onl y o n th e frequen t l y use d propor ti o n o f [Ca ] t o [A l ] , bu t a l s o o n cond i t i on s o f stee l ox i dat i o n an d su l fu r conten t in th e steel .
Therefore , optim i zat i o n o f i njectio n mode s fo r ca lci u m con t a i nin g al l oy s base d o n th e thermodynami c an d kinet ic ana l ysi s o f stee l deoxidatio n an d mod i ficat i o n cond iti ons , a s w el l a s o n th e mathemat i ca l mode ll in g o f mas s exchangin g processes , represent s a cruc i a l scien ti f ic an d techn i ca l cha l leng e o f nowadays .
Within th e spec i fie d l imi ts throug h optim i zatio n o f stee l ladl e t reatmen t mode s in term s o f i ntegrate d researc h o f processe s occurrin g in ladl e dur i n g ladl e t reatmen t o f steel .
I n thi s contex t, th e followin g task s w er e se t forw a r d an d solved :
-  Modelling of coagulation processes and removal of non-metallic inclusions at melts insert gas flushing inside a ladle a tundish :
-  Development and implementation of complex technology of steel refining and modification in a concaster tundish.
- Mixing and Mass Transfer by Bubbling in Treating Ferrocarbon Melts with Alkaline-Earth Metals
 
Principa l researc h m ethod s in th e presen t wor k ar e phys i ca l model l in g an d mathemat i ca l model l ing . Ca l cu l a ti on s accordin g t o mathemat i ca l model s w er e performe d o n basi s o f spec i f i ca l l y develope d softw a r e w i t h th e app li cat i o n o f numer i ca l methods .
Process i n g o f i ndus t ria l heat s fo r th e give n b l ock s wa s real i ze d w i t h th e app li catio n o f method s o f mathemat i ca l s t at i st i cs .
Ca l cu l a ti o n methods fo r averag e c i rcu l ator y flo w o f me t a l i n th e condit i on s o f s ili coca l c i u m blowing- in ar e develope d an d ver i f i e d base d o n resul ts o f phys i ca l mode lli ng ; thes e method s t ak e int o accoun t i ncreas e i n vo l um e frac t io n o f ga ...