Electromagnetic agitation method for continuous casting of metal products having an elongate section

Abstract

A stirring method provides overall stirring of metal over a metallurgical length, thereby ensuring both thermal and chemical uniformity between a top and bottom of a liquid pool without correspondingly being deprived of beneficial effects specific to stirring in a mold and in a secondary cooling zone respectively, and without disturbing, but rather stabilizing, local flow mode in the mold. During a continuous slab casting operation, in which molten metal is introduced into a mold via a submerged nozzle having lateral discharge outlets opening towards narrow faces, a stirring uses moving magnetic fields that act, in pairs, at least in a secondary cooling zone of a casting plant, by travelling collinearly between them in opposite directions so as to forcibly establish a middle longitudinal circulation in the liquid pool as two opposing collinear streams, which produce a global movement in the form of a “four-leaf clover”, the upper lobes of which extend into the mold to near discharge jets coming from outlets of the nozzle, brake the jets or accelerate them, as required.

1 - 10 . (canceled)  
   
   
       11 . A method of electromagnetic stirring in a secondary cooling zone of a plant for continuous casting of metal products of elongate cross section, a mold of which is provided with a submerged casting nozzle having lateral discharge outlets directed towards narrow faces of the mold, and utilizing travelling magnetic fields generated by multiphase inductors placed near the cast metal, the method comprising: 
 for promoting liquid metal exchange within the liquid pool between a secondary cooling zone and the mold, forcibly establishing a longitudinal metal flow in the secondary cooling zone, the metal flow being localized in a middle region of the cast product as two opposing collinear streams, and providing circulation of the liquid metal as a four-leaf clover configuration design having two upper lobes and two lower lobes, the upper lobes extending into the mold right up to a level of jets coming out from the discharge outlets of the submerged casting nozzle.    
   
   
       12 . A stirring method according to  claim 11 , wherein the longitudinal opposing collinear streams in the middle region of the cast product, which move away from each other, are created such that the two upper lobes that extend into the mold right up to the level of the jets coming out from the discharge outlets of the casting nozzle merge concurrently with the jets to reinforce the jets.  
   
   
       13 . A stirring method according to  claim 11 , wherein the longitudinal opposing collinear streams in the middle region of the cast product, which converge on each other, are created such that the two upper lobes that extend into the mold up to the level of the jets emanating from the discharge outlets of the casting nozzle are superposed counter-currently on the jets to slow the jets down.  
   
   
       14 . A stirring method according to  claim 11 , wherein the location of the longitudinal flow in the secondary is shifted laterally towards one or other of the small sides of cast product.  
   
   
       15 . A stirring method according to  claim 11 , wherein the longitudinal metal flow is created as the two opposing collinear streams by collinear moving magnetic fields that travel longitudinally in the central region, either coming closer together, or further apart.  
   
   
       16 . A stirring method according to  claim 12 , wherein the longitudinal metal flow is created as the two opposing collinear streams by collinear moving magnetic fields that travel transversely over the width of the cast product, either coming closer together from an edge towards the center of the cast product, or moving further apart from the center towards the edge of the cast product.  
   
   
       17 . A stirring method according to  claim 11 , wherein the travelling magnetic fields are generated by multiphase linear inductors placed facing large faces of the cast product.  
   
   
       18 . A stirring method according to  claim 17 , wherein the inductors are supplied with electric currents of different intensities.  
   
   
       19 . A stirring method according to  claim 11 , wherein other travelling magnetic fields are also used that act directly in the mold on the jets of metal discharging from the outlets of the nozzle.  
   
   
       20 . A flat metal product obtained from a continuous casting plant, the secondary cooling zone of which being the location of an electromagnetic stirring operation according to that defined in  claim 11.