Steel and method for producing an intermediate product

Abstract

The present invention relates to a steel, in particular for tools exposed to corrosion, of the following composition (in mass-%): C: min. 0.02 and max. 0.12%; Si: max. 1.5%; Mn: more than 1.0-2.50%; P: max. 0.035%; S: min. 0.04% and less than 0.15%; Cr: more than 8.0% and less than 12%; Mo: more than 0.0% and max. 0.20%; V: more than 0.0% and max. 0.25%; Nb: more than 0.1% and max. 0.5%; N: at least 0.02% and max. 0.12%; Ni: max. 0.5%; B: max. 0.005%; Cu: max. 0.3%; Al: max. 0.035%; Sn: max. 0.035%; As: max. 0.02%; at least one of the elements Ca, Mg or Ce, wherein the sum of the contents of these elements is at least 0.0002% and max. 0.015%; with the remainder being iron and unavoidable impurities.

1 . A steel, in particular for tools exposed to corrosion, of the following composition (in mass-%): 
 C: min. 0.02 and max. 0.12%;    Si: max. 1.5%;    Mn: more than 1.0-2.50%;    P: max. 0.035%;    S: min. 0.04% and less than 0.15%;    Cr: more than 8.0% and less than 12%;    Mo: more than 0.0% and max. 0.20%;    V: more than 0.0% and max. 0.25%;    Nb: more than 0.1% and max. 0.5%;    N: at least 0.02% and max. 0.12%;    Ni: max. 0.5%;    B: max. 0.005%;    Cu: max. 0.3%;    Al: max. 0.035%;    Sn: max. 0.035%;    As: max. 0.02%;    at least one of the element Ca, Mg or Ce, wherein the sum of the contents of these elements is more than 0.0002% and max. 0.015%;    with the remainder being iron and unavoidable impurities.    
     
     
         2 . The steel according to  claim 1 , characterised in that it contains 0.001-0.009 mass-% of Ca.  
     
     
         3 . The steel according to one of claims  1  or  2 , characterised in that its hardness factor H f  meets the following condition: 
         0.047   <H   f <0.095, wherein     H   f =0.11−% Nb/ 7.14   with %Nb designating the respective Nb content of the steel.    
     
     
         4 . The steel according to one of the preceding claims, characterised in that its weld factor S f  meets the following condition: 
         S   f <3.99, wherein S f =%C+5x%B+2x%Cu+(%P+%S)/2+(%Mo+%Cr)/4+%Mn/10    and wherein %C, %B, %Cu, %P, %S, %Mo, %Cr, %Mn designate the respective contents of C, B, Cu, P, S, Mo, Cr and Mn of the steel.    
     
     
         5 . The steel according to one of the preceding claims, characterised in that its embrittlement factor KG f  meets the following condition: 
         KG   f <1.07; wherein     KG   f =2.97 x % Cu+ 3.2 x (% Sn +% As )+0.55 x % Al+ 5.42 x % P+ 0.98% N     with %Cu, %Sn, %As, %Al, %P and %N designating the respective contents of Cu, Sn, As, Al, P and N of the steel.    
     
     
         6 . The steel according to any one of the preceding claims, characterised in that it comprises at least 0.05 mass-% of sulphur.  
     
     
         7 . The steel according to any one of the preceding claims, characterised in that it comprises at least 0.07 mass-% of sulphur.  
     
     
         8 . A method for producing an intermediate product for the production of components, in particular for the production of tools exposed to corrosion, made from a steel with a composition according to any one of  claims 1  to  7 , comprising the following steps: 
 melting the steel;  
 casting the steel to form a raw material such as ingots, slabs, continuous-cast bars, thin slabs or cast strip;  
 diffusion annealing of the raw material at a temperature between 1200 and 1280° C.; and  
 hot forming the annealed raw material to form the intermediate product.  
 
     
     
         9 . The method according to  claim 8 , characterised in that hot forming is carried out by way of forging.  
     
     
         10 . The method according to  claim 8 , characterised in that hot forming is carried out by way of hot rolling.  
     
     
         11 . The method according to any one of  claims 7  to  10 , characterised in that following hot forming, the intermediate product is held where it is exposed to air.  
     
     
         12 . The method according to any one of  claims 7  to  11 , characterised in that hot forming takes place at temperatures between 850° C. and 1150° C.  
     
     
         13 . The method according to any one of  claims 7  to  12 , characterised in that following hot forming, the intermediate product is heat treated at temperatures between 850° C. and 1050° C. and after heat treatment is subjected to controlled cooling with the use of a cooling medium such as air, oil, water or a polymer.  
     
     
         14 . The method according to  claim 13 , characterised in that after cooling, tempering at temperatures between 400° C. and 650° C. is carried out.  
     
     
         15 . The use of a steel with a composition according to any one of  claims 1  to  6  for the production of tools for plastics processing.