| CPC C21D 9/46 (2013.01) [B21D 22/022 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 8/0273 (2013.01); C22C 21/02 (2013.01); C22C 38/04 (2013.01); C23C 2/12 (2013.01); C23C 2/40 (2013.01); C21D 2211/008 (2013.01)] | 8 Claims |
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1. A shaped sheet metal article, formed from a flat steel product made by a process comprising the following steps:
a) providing a slab or a thin slab consisting of a steel having 0.1-3% by weight of Mn and up to 0.01% by weight of B;
b) through-heating the slab or thin slab at a temperature (T1) of 1000-1400° C.;
c) pre-rolling the through-heated slab or thin slab to give an intermediate product having an intermediate product temperature (T2) of 1000-1200° C.;
d) hot rolling to give a hot-rolled flat steel product, where a final rolling temperature (T3) is 750-1000° C.;
e) winding the hot-rolled flat steel product, wherein a winding temperature (T4) is not more than 700° C.;
f) descaling the hot-rolled flat steel product;
g) cold rolling the flat steel product, wherein a degree of cold rolling is at least 30%;
h) annealing the flat steel product at an annealing temperature (T5) of 650-900° C.;
i) cooling the flat steel product to a dipping temperature (T6) of 650-800° C.;
j) coating the flat steel product that has been cooled to the dipping temperature with a coating having an applied layer weight of 15-30 g/m2 by
i. dipping it into a melt bath having a melting temperature (T7) of 670-710° C.;
ii. blowing the flat steel product dry after it has exited from the melt bath by means of a gas stream with a flow pressure of 200-750 mbar;
k) cooling the coated flat steel product to room temperature including cooling through a first cooling time tmT and a second cooling time tnT, where the first cooling time tmT in a temperature range between 600° C. and 450° C. is more than 14 s, and the second cooling time tnT in a temperature range between 400° C. and 300° C. is more than 12 s;
l) skin pass rolling the coated flat steel product;
wherein the shaped sheet metal article comprises:
A) steel substrate consisting of a steel having 0.1-3% by weight of Mn and up to 0.01% by weight of B and
B) an aluminium-based coating disposed on at least one side of the steel substrate, wherein the coating has an applied layer weight of 15-30 g/m2 and consists of 1-15% by weight of Si, 15-35% by weight of Fe, 0.1-5% by weight of alkali metals or alkaline earth metals, and further constituents, the contents of which are limited to a total of not more than 2.0% by weight, and aluminium as the balance.
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