High-strength duplex/triplex steel for lightweight construction and use thereof

Abstract

The invention concerns a steel for lightweight construction, consisting of a multiphase structure. In the case of a duplex steel, it consists of mixed ferrite (α) and austenite (γ) crystals. In the case of a triplex steel, it comprises, additioally to said two phases, martensitic (ε) and/or (κ) phases. The volumetric weight of the inventive steel is low as a result of the high proportion of light alloys A1, Si Mn, Mg, Ga and Be. The inventive alloys have a volumetric weight of less than 7b/cm 3 .

1 - 10 . (canceled)  
   
   
       11 . A high-strength α/γ duplex or α/γ/ε triplex lightweight structural steel, characterized by the following composition (contents in % by weight): 
 18 to 35% of Mn,    8 to 12% of Al,    3 to 6% of Si, with Al+Si>12%,    0.5 to 2% of C,    at most 0.05% of B,    at most 3% of Ti,    at least one of the elements Mg, Ga, Be in an amount of in each case 0.3% to 3%,    remainder mainly iron including standard steel minor constituents.    
   
   
       12 . The high-strength lightweight structural steel as claimed in  claim 11 , wherein said Ti content is from 0.03 to 2%.  
   
   
       13 . The high-strength lightweight structural steel as claimed in  claim 11 , comprising the following contents of further alloying elements 
 up to 0.3% of N    up to 0.5% of Nb    up to 0.5% of V.    
   
   
       14 . The high-strength lightweight structural steel as claimed in  claim 11 , characterized by a fine-grained two-phase α/γ duplex microstructure or three-phase α/γ/ε triplex microstructure with an equiaxial morphology in the cold-rolled and recrystallized state.  
   
   
       15 . The high-strength lightweight structural steel as claimed in  claim 11 , characterized by a planar isotropy with r=1.  
   
   
       16 . The high-strength lightweight structural steel as claimed in  claim 11 , characterized by a steel which in the plane of the metal sheet has virtually isotropic mechanical properties in terms of strength and elongation.  
   
   
       17 . A high-strength lightweight structural steel article, 
 wherein said article is formed by a casting process, and    wherein said steel is A high-strength α/γ duplex or α/γ/ε triplex lightweight structural steel, characterized by the following composition (contents in % by weight):    18 to 35% of Mn,    8 to 12% of Al,    3 to 6% of Si, with Al+Si>12%,    0.5 to 2% of C,    at most 0.05% of B,    at most 3% of Ti,    at least one of the elements Mg, Ga, Be in an amount of in each case 0.3% to 3%,    remainder mainly iron including standard steel minor constituents.    
   
   
       18 . A lightweight structural steel article, wherein said article is selected from the group consisting of bodyshell and bodywork components, integral beams, chassis structures and space frames in vehicles, and wherein said steel is a high-strength α/γ duplex or α/γ/ε triplex lightweight structural steel, characterized by the following composition (contents in % by weight): 
 18 to 35% of Mn,    8 to 12% of Al,    3 to 6% of Si, with Al+Si>12%,    0.5 to 2% of C,    at most 0.05% of B,    at most 3% of Ti,    at least one of the elements Mg, Ga, Be in an amount of in each case 0.3% to 3%,    remainder mainly iron including standard steel minor constituents.    
   
   
       19 . A lightweight structural steel article, wherein said article is selected from the group consisting of building materials, conveying installations, metallurgy applications and guard rails and sheet pile walls, and wherein said steel is a high-strength α/γ duplex or α/γ/ε triplex lightweight structural steel, characterized by the following composition (contents in % by weight): 
 18 to 35% of Mn,    8 to 12% of Al,    3 to 6% of Si, with Al+Si>12%,    0.5 to 2% of C,    at most 0.05% of B,    at most 3% of Ti,    at least one of the elements Mg, Ga, Be in an amount of in each case 0.3% to 3%,    remainder mainly iron including standard steel minor constituents.