Method for producing a cold rolled strip that is cold formed with low degrees of deformation

Abstract

The invention pertains to a method for manufacturing a recrystallization-annealed cold strip, in which an input stock, e.g., a slab, a thin slab or a cast strip, that is produced from a steel containing (in wt. %) ≦0.2% C, ≦1.0% Si, ≦1.0% Mn, ≦0.2% P, ≦0.2% S, ≦0.2% Al, ≦0.02% N, ≦0.2% Ti, ≦0.2% V, ≦0.2% Nb and ≦0.01% B, the remainder being iron and unavoidable impurities, is hot-rolled into a hot strip, wherein the hot strip is cold-rolled into a cold strip, wherein the cold strip is subjected to a crystal regeneration-annealing process at an annealing temperature that is lower than the recrystallization temperature, wherein the cold strip that was subjected to the crystal regeneration annealing process is cold-worked with low degrees of deformation, and wherein the cold-worked cold strip is subjected to a recrystallization annealing process. The method according to the invention makes it possible to manufacture recrystallization-annealed, cold-worked cold strips consisting of mild steels of conventional composition without risking the formation of coarse grain.

1 . A method for manufacturing a recrystallization-annealed cold strip, 
 wherein an input stock, e.g., a slab, a thin slab or a cast strip, that is produced from a steel containing 
 no more than 0.2 wt. % C,  
 no more than 1.0 wt. % Si,  
 no more than 1.0 wt. % Mn,  
 no more than 0.2 wt. % P,  
 no more than 0.2 wt. % S,  
 no more than 0.2 wt. % Al,  
 no more than 0.02 wt. % N,  
 no more than 0.2 wt. % Ti,  
 no more than 0.2 wt. % V,  
 no more than 0.2 wt. % Nb and  
 no more than 0.01 wt. % B,  
 the remainder being iron and unavoidable impurities, is hot-rolled into a hot strip,  
   wherein the hot strip is cold-rolled into a cold strip,    wherein the cold strip is subjected to a crystal regeneration annealing process at an annealing temperature that is lower than the recrystallization temperature,    wherein the cold strip that was subjected to the crystal regeneration annealing process is cold-worked with low degrees of deformation,    and wherein the cold-worked cold strip is subjected to a second recrystallization annealing process.    
     
     
         2 . The method according to  claim 1 , characterized by the fact that the steel consists of a mild steel, and by the fact that the annealing temperature during the crystal regeneration annealing process lies at no less than 450° C. and no more than 550° C.  
     
     
         3 . The method according to  claim 1 , characterized by the fact that the steel consists of an IF-Steel, and by the fact that the annealing temperature during the crystal regeneration annealing process lies at no less than 550° C. and no more than 650° C.  
     
     
         4 . The method according to one of the preceding claims, characterized by the fact that the cold strip is recrystallized by no more than 90% after the crystal regeneration annealing process.  
     
     
         5 . The method according to-one of the preceding claims, characterized by the fact that the annealing temperature during the recrystallization annealing process lies at no less than 650° C. and no more than 850° C.  
     
     
         6 . The method according to one of the preceding claims, characterized by the fact that the degree of deformation achieved during the course of the cold-working amounts to no more than 40%.  
     
     
         7 . The method according to one of the preceding claims, characterized by the fact that the cold-working is carried out in the form of a flexible rolling process.  
     
     
         8 . The method according to one of the preceding claims, characterized by the fact that the microstructure of the obtained cold strip has a grain size of no more than 6 ASTM.