Device and method for heat treatment of steels, including a wet cooling

Abstract

The invention relates to a method and a device for rapidly cooling a metal strip and removing residues present on the strip after this cooling, wherein the residues are formed during a cooling of said metal strip by a non-oxidizing liquid solution for the metal strip and a stripping liquid solution for the oxides present on the surface of the strip, or by a mixture of this liquid solution and a gas.

1 . Method for rapid cooling of a metal strip travelling in a continuous line, performed in a section of said line, and for removing residues formed during said rapid cooling in a section of said line, characterized in that it comprises a first step of water cooling, or cooling using a mixture of water and a gas, followed by a second step of cooling using a liquid solution that is non-oxidizing for the strip and is stripping for the oxides present at the surface of the strip, or using a mixture of said liquid solution and a gas, said second step leading to the presence of residues at the surface of the strip, followed by a step of removing said residues obtained by reduction of said residues by means of hydrogen. 
     
     
         2 . Method according to  claim 1 , wherein the first step of cooling cools the strip to a temperature of greater than or equal to the Leidenfrost temperature. 
     
     
         3 . Method according to  claim 1 , wherein the second step of cooling cools the strip from a temperature of less than or equal to the Leidenfrost temperature. 
     
     
         4 . Method according to  claim 1 , wherein the step of removing residues is performed when the metal strip is at a temperature of between 50° C. and 600° C., and for a period of between 15 seconds and 300 seconds. 
     
     
         5 . Method according to  claim 1 , wherein the step of removing residues is performed when the metal strip is in an atmosphere of which the hydrogen content is between 5% and 100% by volume, and preferably greater than or equal to 10%. 
     
     
         6 . Method according to  claim 1 , further comprising a step of pre-oxidation, or of selective internal oxidation, of the surface of the metal strip, performed in a preheating section of the strip or a heating section of the strip, or a temperature maintenance section of the strip, said section being arranged upstream of the section of rapid cooling of the strip, according to the direction of travel of the strip. 
     
     
         7 . Method according to  claim 1 , implemented on a continuous line having a section for dip coating of a metal strip in a molten bath, further comprising, after the step of removing residues, a step of heating of the strip or a step of cooling of the strip, in order to bring the strip to a temperature close to the temperature of the bath. 
     
     
         8 . Continuous treatment line for a metal strip, comprising a section for rapid cooling of the strip and a section for removing residues formed during the cooling of the strip using a liquid solution that is non-oxidizing for the strip and is stripping for the oxides present at the surface of the strip, or using a mixture of said liquid solution and a gas, said rapid cooling and residue removal sections being capable of implementing a method for cooling and for removing residues according to  claim 1 . 
     
     
         9 . Line according to  claim 8 , wherein the section for removing residues comprises, at the inlet in the direction of travel of the strip, a rapid heating device for bringing the strip to a temperature close or equal to a predetermined temperature at which chemical reactions for reducing residues start. 
     
     
         10 . Line according to  claim 8 , wherein the section for removing residues forms part of an overaging section. 
     
     
         11 . Line according to  claim 8 , wherein the section for removing residues comprises a means for blowing hydrogen, or a hydrogenated atmosphere, onto the metal strip. 
     
     
         12 . Line according to  claim 11 , further comprising a chamber for pre-oxidation, or selective internal oxidation, of the surface of the strip arranged in a preheating section, a heating section, or a temperature maintenance section, of the metal strip, said section being positioned upstream of the section of rapid cooling, in the direction of travel of the strip. 
     
     
         13 . Computer program comprising instructions which lead a continuous treatment line to execute the steps of a method according to  claim 1 ;
 wherein the continuous treatment line comprises a section for rapid cooling of the strip and a section for removing residues formed during the cooling of the strip using a liquid solution that is non-oxidizing for the strip and is stripping for the oxides present at the surface of the strip, or using a mixture of said liquid solution and a gas, said rapid cooling and residue removal sections being capable of implementing a method for cooling and for removing residues.