Method For Producing High Strength Steel Strips or Sheets With Twip Properties, Method For Producing a Component and High-Strength Steel Strip or Sheet

Abstract

A method for producing cold-formable, high-strength steel strips or sheets with TWIP properties, wherein in successive working steps are carried out without interruption, uses a molten material of the following composition (mass %): C: 0.003-1.50%, Mn: 18.00-30.00%, Ni: ≦10.00%, Si: ≦8.00%, Al: ≦10.00%, Cr: ≦10.00%, N: ≦0.60%, Cu: ≦3.00%, P: ≦0.40%, S: ≦0.15%, selectively one or more components from the Se, Te, V, Ti, Nb, B, REM, Mo, W, Co, Ca and Mg group provided that the total content of Se, Te is ≦0.25%, the total content of V, Ti, Nb, B, REM is ≦4.00%, the total content of Mo, W, Co is ≦1.50% and the total content of Ca, Mg is ≦0.50%, the rest being iron and melting conditioned impurities, wherein the content of Sn, Sb, Zr, Ta and As, whose total content is equal to or less than 0.30% is included in said impurities.

1 . A method for producing cold-formable, high-strength steel strips or sheets with TWIP properties, wherein in successive working steps carried out without interruption
 a molten material of the following composition (mass %):   C: 0.003-1.50%,   Mn: 18.00-30.00%,   Ni: ≦10.00%,   Si: ≦8.00%,   Al: ≦10.00%,   Cr: ≦10.00%,   N: ≦0.60%,   Cu: ≦3.00%,   P: ≦0.40%,   S: ≦0.15%,   selectively one or more components from the Se, Te, V, Ti, Nb, B, REM, Mo, W, Co, Ca and Mg group provided that   the total content of Se, Te is ≦0.25%,   the total content of V, Ti, Nb, B, REM is ≦4.00%,   the total content of Mo, W, Co is ≦1.50% and   the total content of Ca, Mg is ≦0.50%,   the rest being iron and melting conditioned impurities, wherein the content of Sn, Sb, Zr, Ta and As, whose total content is equal to or less than 0.30% is included in said impurities, is applied to a conveyor and is cooled thereon, until it is solidified into a pre-strip,   the pre-strip is removed from the conveyor belt,   the removed pre-strip is exposed if required to heat treatment,   the pre-strip is heat-rolled at a hot-rolling temperature of at least 700° C. into a hot strip with a completely re-crystallized structure,   
     and
 the hot strip is wound at a winding temperature of up to 750° C. 
 
   
   
       2 . The method according to  claim 1 , wherein the C content of the molten material is 0.2-0.8 mass %. 
   
   
       3 . The method according to  claim 1 , wherein the Mn content of the molten material is at least 20 mass %. 
   
   
       4 . The method according to  claim 1 , wherein the total Se and Te contents of the molten material are at least 0.01 mass %. 
   
   
       5 . The method according to  claim 1 , wherein the total V, Ti, Nb and REM contents of the molten material are at least 0.01 mass %. 
   
   
       6 . The method according to  claim 1 , wherein the B content of the molten material is at least 0.001 mass %. 
   
   
       7 . The method according to  claim 1 , wherein the total Mo, W and Co contents are at least 0.01 mass %. 
   
   
       8 . The method according to  claim 1 , wherein the total Ca and Mg contents are at least 0.001 mass %. 
   
   
       9 . The method according to  claim 1 , wherein the pre-strip is cooled down during the heat treatment carried out if required. 
   
   
       10 . The method according to  claim 1 , wherein the pre-strip is heated up during the heat treatment, carried out if required, to a hot-rolling start temperature. 
   
   
       11 . The method according to  claim 1 , wherein the thickness of the hot strip obtained is ≦3 mm. 
   
   
       12 . The method according to  claim 1 , wherein the winding temperature is at least 450° C. 
   
   
       13 . The method according to  claim 1 , wherein the hot strip is cold-rolled after winding. 
   
   
       14 . The method according to  claim 13 , wherein the thickness of the cold strip obtained is ≦0.8 mm. 
   
   
       15 . The method according to  claim 13 , wherein the cold strip is subjected to annealing at an annealing temperature of 600 20  C.-1,100° C. 
   
   
       16 . The method for producing a component, wherein by using the method in accordance with  claim 1 , a hot or cold strip is produced wherein a pre-product is produced from the hot or cold strip obtained and wherein the pre-product is afterwards finally cold-formed into the component. 
   
   
       17 . The method according to  claim 16 , wherein the cold-forming of the blank is carried out by flow-turning. 
   
   
       18 . A steel strip or sheet with TWIP properties, produced by the method in accordance with  claim 1  with a brittle/ductile transition temperature T ue  of ≦−40° C. 
   
   
       19 . The steel strip or sheet according to  claim 18 , wherein its average r-value r m  is 1.0+/−0.15 and its Δr value is −0.20 to +0.20.