Method for Continuous Casting of a Metal with Improved Mechanical Strength and Product Obtained by Said Method

Abstract

The invention concerns a method for continuous casting of a metal in the form of a hollow jet into a nozzle arranged between a pouring ladle or a tundish and a continuous casting ingot mold, said nozzle including in its upper part a dispensing member capable of deflecting at least part of the liquid metal reaching the nozzle inlet towards an inner wall of the nozzle before it penetrates into the ingot mold. Said method includes injecting into an inner volume of the hollow jet finely-divided solid material, characterized in that the finely-divided solid material comprises technical ceramic nanoparticles, of characteristic size less than 200 nm and preferably less than 100 nm.

1 - 18 . (canceled) 
   
   
       19 . Method for the continuous casting of metal in the form of a hollow jet in a nozzle positioned between a ladle or a tundish and a continuous casting ingot mould, said nozzle comprising in its upper part a distribution device capable of diverting at least part of the molten metal arriving at the inlet of the nozzle towards an inner wall of the nozzle before it enters the ingot mould, said method comprises the injection into an internal volume of the hollow jet of finely divided solid material comprising nanoparticles of technical ceramic with a characteristic size lower than 200 nm, said nanoparticles being conglomerated prior to their injection into the nozzle into microparticles of a size between 10 and 1,000 microns, characterised in that said nanoparticles are conglomerated into microparticles in a metal matrix. 
   
   
       20 . Method according to  claim 19 , characterised in that the characteristic size of the nanoparticles is lower than 100 nm. 
   
   
       21 . Method according to  claim 20 , characterised in that the size of the nanoparticles is between 10 and 100 nm. 
   
   
       22 . Method according to  claim 19 , characterised in that the size of the microparticles is between 100 and 200 microns. 
   
   
       23 . Method according to  claim 19 , characterised in that the metal matrix is made of the same metal as the cast metal. 
   
   
       24 . Method according to  claim 19 , characterised in that the nanoparticles of technical ceramic comprise nanoparticles of oxides, nitrides, carbides, borides, silicides and/or compounds thereof. 
   
   
       25 . Method according to  claim 24 , characterised in that the oxides are Al 2 O 3 , TiO 2 , SiO 2 , MgO, ZrO 2  or Y 2 O 3 . 
   
   
       26 . Method according to  claim 19 , characterised in that the quantity of nanoparticles incorporated into the molten metal is between 0.1 and 1% by weight of the cast metal. 
   
   
       27 . Method according to  claim 19 , characterised in that the conglomerated ceramic nanoparticles injected into the inner volume of the hollow jet of the nozzle are in suspension in a non-oxidising gas, said gas being at a slightly higher pressure relative to atmospheric pressure and at most equal to the static pressure of the cast metal upon its entry into the ingot mould. 
   
   
       28 . Method according to  claim 19 , characterised in that the conglomerated ceramic nanoparticles are injected into the inner volume of the hollow jet of the nozzle by means of a mechanical conveyance device. 
   
   
       29 . Method according to  claim 19 , characterised in that the cast metal is molten steel and the metal matrix is an iron matrix. 
   
   
       30 . Method according to  claim 29 , characterised in that the metal matrix comprises an alloy metal other than iron. 
   
   
       31 . Method according to  claim 29 , characterised in that the conglomeration of the nanoparticles is obtained by mixing ceramic nanoparticles with micrometric iron particles, i.e. with a size greater than 10 microns. 
   
   
       32 . Method according to  claim 31 , characterised in that said micrometric iron particles have a size lower than 20 microns. 
   
   
       33 . Method according to  claim 31 , characterised in that said mixture is produced by a premix in a slurry, followed by drying, crushing, isostatic pressing and re-crushing. 
   
   
       34 . Method according to  claim 31 , characterised in that said mixture is produced by high-energy tapping to ensure that the ceramics are incorporated into the iron matrix. 
   
   
       35 . Method according to  claim 19 , characterised in that the hollow jet nozzle used is of the rotary jet type, i.e. it comprises a vertical conduit having a distribution device with a dome in its upper part, whose function is to divert the molten metal entering the nozzle towards the inner surface of said conduit and which comprises a series of arms symmetrically arranged in a star pattern relative to the axis of the nozzle and canted relative to the horizontal, said arms being arranged to impart a helicoidal rotary motion to the molten steel along the internal wall of the nozzle. 
   
   
       36 . Method according to  claim 19 , characterised in that the hollow jet nozzle used comprises in its upper part a distribution device with a dome designed to separate the molten metal into two streams, an inner stream and an outer stream, in two physically well-separated zones, the injection of ceramic nanoparticles under the dome in the inner zone allowing the formation of a metal with a different chemical composition to that of the basic metal, cast in the outer zone. 
   
   
       37 . Method according to  claim 36 , characterised in that the injection of ceramic nanoparticles is alternatively produced in the outer zone. 
   
   
       38 . Metal with great mechanical strength having the form after casting of a ingot in a continuous sheet upon exit from a continuous casting ingot mould, which may be obtained by means of the method according to claim  1 , comprising less than one percent by weight of technical ceramic homogeneously distributed in at least one part of the ingot.