Sheet-metal formed component and method for the production of the sheet-metal formed component

Abstract

The invention relates to a sheet-metal formed component and a method or producing the sheet-metal formed component, produced by hot-working and press-quenching from a quenchable, unitary and materially uniform steel alloy, wherein the sheet-metal formed component has multiple superposed martensite layers, wherein a respectively outer martensite layer of the sheet-metal formed component has higher ductility than an underlying martensite layer.

1 - 10 . (canceled) 
     
     
         11 . A sheet-metal formed component, produced by hot-working and press-quenching from a quenchable, unitary and materially uniform steel alloy, the sheet-metal formed component comprising:
 a plurality of superposed martensite layers,   wherein   one of the plurality of superposed martensite layers is an outer martensite layer and another one of the plurality of superposed martensite layers is an underlying martensite layer underlying the outer martensite layer, the outer martensite layer having higher ductility than the underlying martensite layer,   the sheet-metal formed component has a tensile strength of greater than 1200 MPa, and   the sheet-metal formed component has a bending angle of greater than 60° for a wall thickness of 0.5 to 1.5 mm or a bending angle of greater than 45° for a wall thickness of 1.5 to 2.5 mm.   
     
     
         12 . The sheet-metal formed component according to  claim 11 , wherein
 the plurality of superposed martensite layers comprises at least three martensite layers between two opposite surfaces of the sheet-metal formed component over the wall thickness, and the outer martensite layer has a thickness of 4 μm to 140 μm.   
     
     
         13 . The sheet-metal formed component according to  claim 11 , wherein
 the plurality of superposed martensite layers is superposed between two opposite surfaces of the sheet-metal formed component, and   both of the surfaces are surface-decarburized layers comprising an ferritic material structure.   
     
     
         14 . The sheet-metal formed component according to  claim 11 , wherein the plurality of superposed martensite layers is produced from a semi-finished product having an outer ferrite layer with an underlying pearlite layer. 
     
     
         15 . The sheet-metal formed component according to  claim 11 , wherein the quenchable steel alloy comprises a manganese boron steel having a proportion by weight of 0.5 to 1.7% (inclusive) of manganese and 0.0008 to 0.005% (inclusive) of boron. 
     
     
         16 . The sheet-metal formed component according to  claim 11 , wherein certain area regions of the sheet-metal formed component have at least one of
 different strengths, or   different wall thicknesses.   
     
     
         17 . A method of producing a sheet-metal formed component, the method comprising:
 hot-rolling a quenchable steel alloy to obtain a hot-rolled product,   generating, on a surface of the hot-rolled product, a ferrite-pearlite lamination with a ferrite layer over an entire strip breadth of the product,   individualizing the product to obtain blanks,   rapid heating of the blanks at a heating rate of greater than 30 K/s from ambient temperature to above an austenizing temperature, and   hot-working and press-quenching each of the rapid heated blanks into a sheet-metal formed component,   wherein   the sheet-metal formed component comprises a plurality of superposed martensite layers,   one of the plurality of superposed martensite layers is an outer martensite layer and another one of the plurality of superposed martensite layers is an underlying martensite layer underlying the outer martensite layer, the outer martensite layer having higher ductility than the underlying martensite layer,   the sheet-metal formed component has a tensile strength of greater than 1200 MPa, and   the sheet-metal formed component has a bending angle of greater than 60° for a wall thickness of 0.5 to 1.5 mm or a bending angle of greater than 45° for a wall thickness of 1.5 to 2.5 mm.   
     
     
         18 . A method of producing a metal semi-finished product from a quenchable steel alloy for further processing into a sheet-metal formed component, the method comprising:
 hot-rolling the quenchable steel alloy to obtain a hot-rolled product,   generating an outer ferrite layer and an underlying pearlite layer on both of opposite surfaces of the hot-rolled product, over an entire strip breadth of the product, and   individualizing the product to obtain blanks each of which is a metal semi-finished product to be further processed into a sheet-metal formed component,   wherein   the sheet-metal formed component comprises a plurality of superposed martensite layers,   one of the plurality of superposed martensite layers is an outer martensite layer and another one of the plurality of superposed martensite layers is an underlying martensite layer underlying the outer martensite layer, the outer martensite layer having higher ductility than the underlying martensite layer,   the sheet-metal formed component has a tensile strength of greater than 1200 MPa, and   the sheet-metal formed component has a bending angle of greater than 60° for a wall thickness of 0.5 to 1.5 mm or a bending angle of greater than 45° for a wall thickness of 1.5 to 2.5 mm.   
     
     
         19 . The method according to  claim 17 , wherein the hot-rolling comprises:
 heating a slab of the quenchable steel alloy to a core temperature of above 1200° C. for a time of greater than 60 s,   rolling the heated slab first to a preliminary strip thickness of between 45 and 55 mm, and then to a strip thickness of 13 to 25 mm to obtain a rolled steel strip, wherein a rolling end temperature of the rolled steel strip is 860 to 920° C., and a rolling end velocity is 3-12 m/s, and   after the rolling, cooling the rolled steel strip over a path of 65 to 80 m at a cooling rate of 15 to 30 K/s until reaching a reel temperature of 650 to 800° C. to obtain the hot-rolled product.   
     
     
         20 . The method according to  claim 17 , wherein the rapid heating is carried out by contact heating at a heating rate of greater than 50 K/s. 
     
     
         21 . The sheet-metal formed component of  claim 11 , wherein the sheet-metal formed component has a tensile strength of greater than 1350 MPa. 
     
     
         22 . The sheet-metal formed component according to  claim 11 , wherein
 the plurality of superposed martensite layers comprises at least five martensite layers between two opposite surfaces of the sheet-metal formed component over the wall thickness, and   the outer martensite layer has a thickness of 4 μm to 140 μm.   
     
     
         23 . The sheet-metal formed component according to  claim 11 , wherein
 the plurality of superposed martensite layers comprises at least seven martensite layers between two opposite surfaces of the sheet-metal formed component over the wall thickness, and   the outer martensite layer has a thickness of 4 μm to 140 μm.   
     
     
         24 . The sheet-metal formed component according to  claim 11 , wherein
 the plurality of superposed martensite layers comprises two outermost martensite layers at two opposite surfaces of the sheet-metal formed component, respectively, and   the two outermost martensite layers are surface-decarburized layers having an essentially ferritic material structure.   
     
     
         25 . The sheet-metal formed component according to  claim 14 , wherein the semi-finished product has further underlying alternating ferrite layers and pearlite layers. 
     
     
         26 . The method according to  claim 17 , wherein the rapid heating is carried out by contact heating at a heating rate of greater than 80 K/s. 
     
     
         27 . The method according to  claim 17 , wherein the rapid heating of the blanks is carried out at a heating rate of greater than 50 K/s, from ambient temperature to above the austenizing temperature.