Metal Sheet Component, Manufactured by Hot Forming a Flat Steel Product and Method for Its Manufacture

Abstract

A metal sheet component including (in % by weight) C: up to 0.5%, Si: 0.05-1%, Mn: 4-12%, Cr: 0.1-4%, Al: up to 3.5%, N: up to 0.05%, P: up to 0.5%, S: up to 0.01%, Cu, Ni: in total up to 2%, Ti, Nb, V: in total up to 0.5%, rare earth metals: up to 0.1%, and as a remainder, Fe and unavoidable impurities, wherein the content % C of C and the content % Cr of Cr meet the following condition: (10×% C)+% Cr<5.5%. In order to manufacture a metal sheet component, a flat steel product is heated to a heating temperature, which is at least 200° C. and at most 800° C., and then formed into the component by hot forming the flat steel product heated to the heating temperature, with the structure of the hot-formed metal sheet component having 5-50% by volume austenite and, as the remainder, martensite, tempered martensite and/or ferrite, wherein the ferrite proportion can also be 0, and the average grain diameter of the structure is less than 5 μm.

1 . A metal sheet component, manufactured by hot forming a flat steel product, consisting (in % by weight)
 C: up to 0.5%,   Si: 0.05-1%,   Mn: 4-12%,   Cr: 0.1-4%,   Al: up to 3.5%,   N: up to 0.05%,   P: up to 0.05%,   S: up to 0.01%,   Cu, Ni: in total up to 2%,   Ti, Nb, V: in total up to 0.5%,   Rare earth metals: up to 0.1%,   and a remainder, Fe and unavoidable impurities,   wherein the content % C of C and the content % Cr of Cr meet the following condition:
   (10×% C)+% Cr<5.5%,
 
   wherein the flat steel product after forming into the metal sheet component has a bending angle of more than 60°,   wherein a structure of the hot-formed metal sheet component comprises 5-50% by volume austenite and as a remainder, martensite, tempered martensite, and/or ferrite,   wherein the ferrite proportion can be 0, and   wherein an average grain diameter of the structure is less than 5 μm.   
     
     
         2 . The metal sheet component according to  claim 1 , wherein the C content is at least 0.02% by weight. 
     
     
         3 . The metal sheet component according to  claim 1 , wherein the C content is up to 0.3% by weight. 
     
     
         4 . The metal sheet component according to  claim 1 , wherein the Cr content is at least 2.2% by weight. 
     
     
         5 . The metal sheet component according to  claim 1 , wherein the average grain diameter is below 2 μm. 
     
     
         6 . The metal sheet component according to  claim 1 , wherein the bending angle is more than 80°. 
     
     
         7 . The metal sheet component according to  claim 1 , wherein after the hot forming tensile strength Rm of the flat steel product is at least 1000 MPa, elongation at break A80 of the flat steel product is more than 10%, and a product Rm*A80 formed of the tensile strength Rm and the elongation at break A80 of the flat steel product is more than 13000 MPa %. 
     
     
         8 . The metal sheet component according to  claim 1 , wherein the metal sheet component is provided with a metallic protective coating. 
     
     
         9 . A method for manufacturing a metal sheet component, comprising the following steps:
 a) providing a flat steel product made of a steel, comprising (in %—by weight):   C: up to 0.5%,   Si: 0.05-1%,   Mn: 4-12%,   Cr: 0.1-4%,   Al: up to 3.5%,   N: up to 0.05%,   P: up to 0.05%,   S: up to 0.01%,   in total up to 2% Cu or Ni,   in total up to 0.5% of Ti, Nb or V,   REM: up to 0.1%,   and as a remainder, Fe and unavoidable impurities,   wherein the content % C of C and the content % Cr of Cr meet the following condition:
   (10×% C)+% Cr<5.5%
 
   b) heating the flat steel product to a heating temperature which is at least 200° C. and at most equal to the Ac3 temperature +60° C. of the flat steel product; and   c) hot forming the flat steel product heated to the heating temperature into the component.   
     
     
         10 . The method according to  claim 9 , wherein the heating temperature is at most 800° C. 
     
     
         11 . The method according to  claim 9 , wherein the heating temperature is above the Ac1 temperature and below the Ac3 temperature of the flat steel product. 
     
     
         12 . The method according to  claim 9 , wherein the heating temperature is below the Ac1 temperature of the flat steel product, and wherein austenite setting takes place in an annealing step before the hot forming step. 
     
     
         13 . The method according to  claim 9 , wherein the flat steel product provided in step a) has a metallic corrosion protection layer. 
     
     
         14 . The method according to  claim 9 , wherein the heating in step b) is carried out by a conductively or inductively acting heating method.