High-Strength, Lightweight Austenitic-Martensitic Steel and the Use Thereof

Abstract

The invention relates to a high-strength, lightweight austenitic-martensitic steel and the use thereof. The inventive lightweight steel is characterized by a chrome content of more than 0.5% and less than 18%, a silicon content of more than 1% and less than 4%, a manganese content of more than 2.5% and less than 30% and an aluminum content of more than 0.05 to 4% and lies within an alloy range that is determined by the coordinates of four points (Cr equ =2; Ni equ =2), (Cr equ =2; Ni equ =24), (Cr equ =20; Ni equ =10) and (Cr equ =20; Ni equ =6.5), whereby the chrome and nickel equivalent is calculated from the chemical composition of the steel using the relations (1) and (2): Cr equ =% Cr equ +% Mo+1.5% Si+0.5% W+0.9% Nb+4% Al+4% Ti+1.5% Ni eqe =% Ni+30% C+18% N+0.5% Mn+0.3% Co+0.2% Cu−0.2% AI (2). The indications are in weight percent and remainder substantially consists of iron and other elements usually present in steel (P. S). The inventive steel can be cold-formed, and is suitable for use as a material for hot- and cold-rolled sheets, strips and tubes, for non-flat semifinished products and non-flat products and retaining elements, for crash-relevant components and reinforcing structural components in the automobile industry, for expendable parts and as a material for weatherproof, corrosion resisting and stainless parts.

1 . High-strength austenitic-martensitic lightweight steel having a tensile strength greater than 800 to 1.200 MPa and an elongation at break greater than 25%, characterized in that the steel has a chromium content of greater than 0.5% and less than 18%, a silicon content of greater than 1% and less than 4%, a manganese content greater than 2.5% and less than 30%, and an aluminum content greater than 0.05% to 4%, and is within an alloying range that is determined by the coordinates of four points (Cr equ =2; Ni equ =2), (Cr equ =2; Ni equ =24), (Cr equ =20; Ni equ =10), and (Cr equ =20; Ni equ =6.5), wherein the chromium and nickel equivalents are calculated with the relationships 1 and 2
   Cr equ =% Cr+% Mo+1.5% Si+0.5% W+0.9% Nb+4% Al+4% Ti+1.5% V   (1)     Ni equ =% Ni+30% Cr+18% N+0.5% Mn+0.3% Co+0.2% Cu−0.2% Al   (2)   
       based on the chemical composition of the steel, wherein the values are to be applied in % by weight and wherein the remainder is essentially iron and other accompanying elements (P, S) of steel and is coldformable. 
     
     
         2 . Lightweight steel according to  claim 1 , characterized in that
 the nickel content is from 0 to 10%,   the niobium content is from 0 to 1.2%,   the carbon content is from 0.01 to 0.2%,   the nitrogen content is from 0 to 0.1%,   the copper content is from 0 to 4%,   the cobalt content is from 0 to 1%,   the molybdenum content is from 0 to 4%,   the tungsten content is from 0 to 3%,   the titanium content is from 0 to 1%, and   the vanadium content is from 0 to 0.15%,   the oxygen content dissolved in the steel is less than 0.003%, and the remainder is essentially iron.   
     
     
         3 . Lightweight steel according to  claim 1 , characterized in that
 the carbon content is 0.03%,   the chromium content is 14.1%,   the silicon content is 1.23%,   the nickel content is 6.3%,   the manganese content is 7.94%,   the aluminum content is 0.051%,   the niobium content is 0.5%, and   
       the remainder is essentially iron. 
     
     
         4 . Lightweight steel according to  claim 1 , characterized in that
 the carbon content is 0.04%,   the chromium content is 0.52%,   the silicon content is 1.5%,   the nickel content is 2.1%,   the manganese content is 11.5%, and   the aluminum content is 0.051%, and   
       the remainder is essentially iron. 
     
     
         5 . The lightweight steel according to  claim 1  as a material for hot-rolled and/or cold-rolled sheet steel, bands, and pipes. 
     
     
         6 . The lightweight steel according to  claim 1  as a material for non-flat products, non-flat semi-finished products, wire, cold massive formed parts and fasting elements. 
     
     
         7 . The lightweight steel according to  claim 1  as a material for crash-loaded components and reinforcing structural components. 
     
     
         8 . The lightweight steel according to  claim 1  as a material for wear parts. 
     
     
         9 . The lightweight steel according to  claim 3  wherein the material is subjected to a heat treatment before being coldformed. 
     
     
         10 . The lightweight steel according to  claim 1  as a material for rustproof parts. 
     
     
         11 . The lightweight steel according to  claim 1  as a material for weather-resistant and corrosion-resistant parts.