Flat Steel Product and Method for the Production Thereof

Abstract

The invention provides a reliably manufacturable flat steel product based on a Fe 3 Al alloy and a method that allows the production of such flat steel products. For this purpose, the flat steel product is made of a steel which comprises (in % by weight) Al: 12-20%, Ti: 0.2-2%, B: 0.1-0.6%, in each case at least one element from the group “Cr, C, Mn, Si, Nb, Ta, W, Zr, V, Mo, Ni, Cu, Ca, rare earth metals, and Co” unavoidable impurities. The method according to the invention specifies that a molten steel with the stated composition is cast as a precursor in the form of a slab, thin slab or a cast strip, the precursor is then hot rolled into a hot strip.

1 . A flat steel product made from a steel that comprises (in % by weight):
 Al: 12-20%   Ti: 0.2-2%   B: 0.1-0.6%,   as well as optionally one or more elements selected from the group consisting of Cr, C, Mn, Si, Nb, Ta, W, Zr, V, Mo, Ni, Cu, Ca, rare earth metals, and Co at the following levels:   N: up to 0.1%   Cr: up to 7%   C: up to 0.15%   Mn: up to 2%   Si: 0.05-5%   Nb, Ta, W: up to 0.2% in total   Zr: up to 1%   V: up to 1%   Mo: up to 1%   Ni: up to 2%   Cu: up to 3%   Ca: up to 0.015%   Rare earth metals: up to 0.2%   Co: up to 1%   remainder iron and unavoidable impurities, wherein S levels of up to 0.03% by weight and P levels of up to 0.1% by weight can be attributable to the unavoidable impurities,   and   wherein the ratio % Ti/% B formed from the Ti levels % Ti and the B levels % B of the steel is
   0.33≤% Ti/% B≤3.75
 
   and a microstructure of the flat steel product comprises 0.3-5% by volume TiB 2  precipitates that are embedded in a structural matrix made up of at least 80% by volume Fe 3 Al.   
     
     
         2 . The flat steel product according to  claim 1 , wherein the % Ti/% B ratio is
   0.5≤% Ti/% B≤3.75,
   
     
     
         3 . The flat steel product according to  claim 2 , wherein the % Ti/% B ratio is
   1.0≤% Ti/% B≤3.75.
   
     
     
         4 . The flat steel product according to  claim 1 , wherein a grain size of the Fe 3 Al in the structural matrix is a maximum of 500 μm. 
     
     
         5 . Thee flat steel product according to  claim 4 , wherein the grain size of the Fe 3 Al in the structural matrix is maximum of 100 μm. 
     
     
         6 . The flat steel product according to  claim 1 , wherein at least 70% of the TiB 2  precipitates in the structural matrix have a mean particle diameter of 0.5-10 μm. 
     
     
         7 . The flat steel product according to  claim 1 , wherein the sum of Nb, Ta, and W is up to 0.1% by weight. 
     
     
         8 . The flat steel product according to  claim 1 , wherein Cr is at least 0.3% by weight. 
     
     
         9 . The flat steel product according to  claim 1 , wherein the microstructure of the flat steel product comprises at least 0.5% by volume TiB 2  precipitates. 
     
     
         10 . The flat steel product according to  claim 1 , wherein the microstructure of the flat steel product comprises a maximum of 3% by volume TiB 2  precipitates. 
     
     
         11 . A method for producing the flat steel product according to  claim 1 , comprising:
 a) melting a steel that comprises (in % by weight):   Al: 12-20%   Ti: 0.2-2%   B: 0.10-0.6%,   as well as optionally one or more elements selected from the group consisting of Cr, C, Mn, Si, Nb, Ta, W, Zr, V, Mo, Ni, Cu, Ca, rare earth metals, and Co at the following levels:   N: up to 0.1%   Cr: up to 7%   C: up to 0.15%   Mn: up to 2%   Si: 0.05-5%   Nb, Ta, W: up to 0.2% in total   Zr: up to 1%   V: up to 1%   Mo: up to 1%   Ni: up to 2%   Cu: up to 3%   Ca: up to 0.015%   Rare earth metals: up to 0.2%   Co: up to 1%   remainder iron and unavoidable impurities, wherein S levels of up to 0.03% by weight and P levels of up to 0.1% by weight can be attributed to the unavoidable impurities, and wherein the ratio % Ti/% B formed from the Ti levels % Ti and the B levels % B of the steel is 0.33≤% Ti/% B≤3.75;   b) casting the steel melt into a precursor in a form of a slab, thin slab or cast strip;   c) hot rolling the precursor into a hot-rolled hot strip, wherein the precursor has a hot rolling start temperature of 1000-1300° C. at the start of the hot rolling process, and has a hot rolling end temperature of at least 850° C.; and   d) coiling the hot strip at a coiling temperature between room temperature and 750° C.   
     
     
         12 . The method according to  claim 11 , wherein the hot strip obtained after coiling (step d)) is annealed at an annealing temperature of 200-1000° C. over an annealing period of 1-200 hours. 
     
     
         13 . The method according to  claim 11 , wherein the precursor is heated to the hot rolling start temperature over a heating time of 15-1500 min between steps b) and c). 
     
     
         14 . The method according to  claim 11 , wherein the coiling temperature is at least 400° C. 
     
     
         15 . (canceled) 
     
     
         16 . Components for plant construction comprising the flat steel product of  claim 1 . 
     
     
         17 . Components for gas turbines comprising the flat steel product of  claim 1 . 
     
     
         18 . Heat-resistant components for the automotive industry comprising the flat steel product of  claim 1 . 
     
     
         19 . Components for plants that are operated in the low-temperature range comprising the flat steel product of  claim 1 . 
     
     
         20 . Hot formed component comprising the flat steel product of  claim 1 .