Method for manufacturing flat steel products from a steel forming a complex phase microstructure

Abstract

A method, which allows high-tensile flat steel products to be manufactured with less effort, includes a steel that forms a complex phase microstructure and contains (in wt. %) C: 0.08-0.11%, Mn: 1.00-1.30%, P: ≦0.030%, S: ≦0.004%, Si: 0.60-0.80%, Al: ≦0.05%, N: ≦0.0060%, Cr: 0.30-0.80%, Ti: 0.060-0.120%, remainder iron and unavoidable impurities, being cast into a cast strip having a thickness of 1-4 mm. The cast strip is hot-rolled in-line into a hot-rolled strip having a thickness of 0.5-3.2 mm in a continuous process at a final hot-rolling temperature ranging from 900 to 1100° C., the deformation degree being greater than 20%. The hot-rolled strip is coiled at a coiling temperature ranging from 550 to 620° C., so as to obtain a hot-rolled strip, which has a minimum tensile strength R m of 800 MPa at a minimum breaking elongation A 80 of 10%.

1 . Method for manufacturing flat steel products,
 wherein a steel that forms a complex phase microstructure with the following composition (in wt. %)   C: 0.08-0.11%   Mn: 1.00-1.30%   P: ≦0.030%   S: ≦0.004%   Si: 0.60-0.80%   Al: ≦0.05%   N: ≦0.0060%   Cr: 0.30-0.80%   Ti: 0.060-0.120%   remainder iron and unavoidable impurities   is cast into a cast strip having a thickness of 1-4 mm,
 wherein the cast strip is hot-rolled in-line into a hot-rolled strip having a thickness ranging from 0.5 to 3.2 mm in a continuous process at a final hot-rolling temperature ranging from 900 to 1100° C., the deformation degree being greater than 20%, and 
 wherein the hot-rolled strip is coiled at a coiling temperature ranging from 550 to 620° C., 
 so as to obtain a hot-rolled strip, which has a minimum tensile strength R m  of 800 MPa at a minimum breaking elongation A 80  of 10%. 
   
   
   
       2 . Method according to  claim 1 , wherein the width of the hot-rolled strip is greater than 1,200 mm. 
   
   
       3 . Method according to  claim 1 , wherein the thickness of the hot-rolled strip is 1.5 mm at most. 
   
   
       4 . Method according to  claim 1 , wherein the hot-rolled strip is cold-rolled into cold-rolled strip having a thickness of 0.5-1.4 mm. 
   
   
       5 . Method according to  claim 4 , wherein the cold-rolled strip is annealed at an annealing temperature of 750-850° C. 
   
   
       6 . Method according to  claim 4 , wherein the minimum tensile strength of the cold-rolled strip is 800 MPa. 
   
   
       7 . Method according to  claim 4 , wherein the cold-rolled strip has a minimum breaking elongation A 50  of 10%. 
   
   
       8 . Method according to  claim 1 , wherein the hot-rolled strip or cold rolled strip is provided with a metallic coating. 
   
   
       9 . Method according to  claim 8 , wherein the metallic coating is a zinc coating. 
   
   
       10 . Method according to  claim 4 , wherein the cold-rolled strip is provided with a metallic coating. 
   
   
       11 . Method according to  claim 10 , wherein the metallic coating is a zinc coating.