Method for producing steel sheets, steel sheet and use thereof

Abstract

A method for producing steel sheets, in particular for body shell sheets of vehicles, in which a steel alloy of a desired composition is melted, poured, and then rolled into sheet form, the steel alloy being an “interstitial free” steel (IF steel) and the steel sheet being annealed after the rolling and subsequently provided with a metallic anti-corrosion coating and then dressed, wherein in order to achieve a low Wsa value with the narrowest possible spread, a niobium content of >0.01% by weight, preferably >0.011% by weight, is added to the alloy.

1 . A method for producing steel sheets, in particular for body shell sheets of vehicles, comprising:
 melting an interstitial free steel (IF steel) alloy of a desired composition;   adding a niobium content of >0.01% by weight to the steel alloy in order to achieve a low Wsa value with a narrowest possible spread:   pouring the steel alloy, and rolling tire steel alloy into sheet form;   annealing the steel sheet after the rolling, and subsequently providing the steel sheet with a metallic anti-corrosion coating and then dressing the steel sheet.   
     
     
         2 . The method according to  claim 1 , wherein the IF steel has the following analysis in % by weight:
 C 0.001 to 0.020   Si 0.01 to 0.7   Mn 0.02 to 1.5   P max. 0.15   S max. 0.05   Al 0.015 to 1.0   Nb 0.011 to 0.15   Ti 0.01 to 0.2   optionally containing one or more of the following elements,   up to max. 100 ppm boron and/or   up to 0.4% by weight vanadium and/or   up to 0.4% by weight zirconium,   a remainder composed of iron and smelting-dictated impurities.   
     
     
         3 . The method according to  claim 1 ,
 wherein the IF steel has the following analysis in % by weight:   C 0.001 to 0.020   Si 0 01 to 0.7   Mn  0 . 02  to 1.5   P max. 0.15   S max. 0.05   Al 0.015 to 1.0   Nb 0.02 to 0.15   Ti 0.01 to 0.2   optionally containing one or more of the following elements:   up to max. 100 ppm boron and/or   up to 0.4% by weight vanadium and/or   up to 0.4% by weight zirconium, and/or   up to 0.5% by weight hafnium, and/or   up to 0.5% by weight tungsten, and/or   up to 0.5% by weight tantalum;   a remainder composed of iron and smelting-dictated impurities.   
     
     
         4 . The method according to  claim 1 , comprising applying the metallic anti-corrosion coating to the steel sheet while molten, wherein the coating is selected from the group consisting of: a zinc coating, a zinc-magnesium coating, a zinc-aluminum coating, a zinc-aluminum-magnesium coating, an aluminum-zinc coating, and an aluminum-silicon coating. 
     
     
         5 . The method according to  claim 4 , wherein the coating, in addition to zinc, contains 0.2-8% by weight magnesium and/or aluminum 
     
     
         6 . The method according to  claim 5 , wherein the coating contains 2-2.5% by weight aluminum and 1.5-2% by weight magnesium. 
     
     
         7 . The method according to  claim 1 , comprising using skin-pass rolls with a roughness (Ra) of 1.6 to 3.3 μm. 
     
     
         8 . The method according to  claim 1 , wherein a degree of dressing is between 0.85 and 1.7%. 
     
     
         9 . The method according to  claim 1 , wherein the alloy fulfills the following condition: N*(Ti+Nb)*S*10{circumflex over ( )}6, the product being greater than 1 in zinc coatings and greater than 2 in ZM coatings. 
     
     
         10 . The method according to  claim 1 , comprising annealing the steel sheet at a hearing rate between 8 K/s and 30 K/s. 
     
     
         11 . A steel sheet produced according to the method of  claim 2 . 
     
     
         12 . A method of using the steel sheet according to  claim 11  comprising using the steel sheet to form for body shell components of motor vehicles and/or buildings.  13 . A steel sheet produced according to the method of  claim 3 .  14 . A method of using the steel sheet according to claim  13 , comprising using the steel sheet to form body shell components of motor vehicles and/or buildings.