Method for the production of cast steel strip

Abstract

A method for the production of cast steel strip in a continuous procedure includes casting a steel melt into a casting gap having longitudinal sides of which are formed by walls that move during the casting process, to form the steel strip, and holding the steel melt, which is present above the casting gap in a melt pool, under an atmosphere containing nitrogen and hydrogen. This method allows the production of high-quality steel strips having a significantly improved surface composition compared to the prior art in that the hydrogen content of the atmosphere is greater than 0 mol % to 10 mol %, and the Cr, Mo, Nb, Si, Ti, Ni, Mn, C or N contents of the cast steel melt, which are selectively present in each case for adjusting the characteristics of the steel strip, are in each case selected so that a ratio Cr eq /Ni eq ≧1.7.

1 . A method for the production of cast steel strip in a continuous procedure comprises casting a steel melt into a casting gap having longitudinal sides of which are formed by walls that move during the casting process, to form the steel strip, and holding the steel melt, which is present above the casting gap in a melt pool, under an atmosphere containing nitrogen and hydrogen, wherein the hydrogen content of the atmosphere is greater than 0 mol % to 10 mol %, and the Cr, Mo, Nb, Si, Ti, Ni, Mn, C or N contents of the cast steel melt, which are selectively present in each case for adjusting the characteristics of the steel strip, are in each case selected in such a way that for the ratio Cr eq /Ni eq  formed from the Cr equivalent Cr eq  and the Ni equivalent Ni eq , the following applies:  
       Cr eq /Ni eq ≧1.7,  
     wherein Cr eq =% Cr+1.37% Mo+2% Nb+1.5% Si+3% Ti, 
 Ni eq =% Ni+0.31% Mn+22% C+14% N+% Cu,  
 % Cr=respective Cr content,  
 % Mo=respective Mo content,  
 % Nb=respective Nb content,  
 % Si=respective Si content,  
 % Ti=respective Ti content,  
 % Ni=respective Ni content,  
 % Mn=respective Mn content,  
 % C=respective C content,  
 % N=respective N content.  
 
   
   
       2 . The method according to  claim 1 , wherein the casting gap is formed between two casting rollers, which rotate in opposite directions, are cooled during the casting operation and delimit the longitudinal sides of the casting gap.  
   
   
       3 . The method according to  claim 1 , wherein the hydrogen content of the atmosphere is at least 0.5 mol %.  
   
   
       4 . The method according to  claim 1 , wherein the hydrogen content of the atmosphere is no greater than 7.5 mol %.  
   
   
       5 . The method according to  claim 1 , wherein the atmosphere additionally contains a noble gas.  
   
   
       6 . The method according to  claim 5 , wherein the noble gas is argon.  
   
   
       7 . The method according to  claim 1 , wherein the nitrogen content of the atmosphere is at least 30 mol %.  
   
   
       8 . The method according to  claim 1 , wherein for the ratio Cr eq /Ni eq , the following applies:  
       Cr eq /Ni eq ≧1.8.  
   
   
       9 . The method according to  claim 2 , wherein the casting rollers have a stochastic unevenness distribution.