Cold-Rolled Flat Steel Product for Deep Drawing Applications and Method for Production Thereof

Patent metadata

Field	Value
Publication number	US-2016017467-A1
Application number	US-201414767741-A
Country	US
Kind code	A1
Filing date	Feb 13, 2014
Priority date	Feb 14, 2013
Publication date	Jan 21, 2016
Grant date	—

Abstract

A cold-rolled flat steel product for deep drawing applications is disclosed, composed of a steel which, in addition to Fe and unavoidable impurities (in % by weight) contains C: 0.008%-0.1%, Al: 6.5%-12%, Nb: 0.1%-0.2%, Ti: 0.15-0.5%, P: <0.1%, S: <0.03%, N: <0.1% and optionally one or more elements from the group of “Mn, Si, REM, Mo, Cr, Zr, V, W, Co, Ni, B, Cu, Ca, N”, provided that Mn: <1%, REM: <0.2%, Si: <2%, Zr: <1%, V: <1%, W: <1%, Mo: <1%, Cr: <3%, Co: <1%, Ni: <2%, B: <0.1%, Cu: <3%, Ca: <0.015%. The ratio is 2.5 ≧% Ti/% Nb ≧1.5, %Ti=Ti content and % Nb=Nb content. For production of such a flat steel product, a steel of appropriate composition is cast to give a pre-product, which is then hot-rolled to hot strip at a hot rolling end temperature of 820-1000° C. The latter is subsequently wound at a winding temperature of up to 750° C., after winding annealed at an annealing temperature of >650-1200° C. for 1-50 h, then cold-rolled in one or more stages with a total cold rolling level of ≧65% to give the cold-rolled flat steel product and finally annealed at 650-850° C.

First claim

1 . A cold-rolled flat steel product for deep drawing applications, consisting of a steel containing, in addition to iron and unavoidable impurities (in % by weight):
C: 0.008%-0.1%, Al: 6.5%-12%, Nb: 0.1%-0.2%, Ti: 0.15%-0.5%, P: up to 0.1%, S: up to 0.03%, N: up to 0.1% and optionally one or more elements from the group of “Mn, Si, rare earth metals, Mo, Cr, Zr, V, W, Co, Ni, B, Cu, Ca, N”, provided that Mn: up to 1%, rare earth metals: up to 0.2%, Si: up to 2%, Zr: up to 1%, V: up to 1%, W: up to 1%, Mo: up to 1%, Cr: up to 3%, Co: up to 1%, Ni: up to 2%, B: up to 0.1%, Cu: up to 3%, Ca: up to 0.015%, where the % Ti/% Nb ratio of the Ti content % Ti and the Nb content % Nb is 2.5≧% Ti/% Nb ≧1.5.

2 . The flat steel product as claimed in claim 1 , wherein the Al content thereof is 6.5%-10% by weight.

3 . The flat steel product as claimed in claim 1 , wherein the Al content thereof is more than 6.8% by weight.

4 . The flat steel product as claimed in claim 1 , wherein the C content thereof is not more than 0.05% by weight.

5 . The flat steel product as claimed in claim 1 , wherein the Nb content thereof is 0.1%-0.15% by weight.

6 . The flat steel product as claimed in claim 1 , wherein the Ti content thereof is 0.15%-0.3% by weight.

7 . The flat steel product as claimed in claim 1 , wherein its microstructure contains 0% to 0.1% by volume of κ-carbides.

8 . The flat steel product as claimed in claim 1 , wherein its r value is at least 1.3.

9 . The flat steel product as claimed in claim 1 , wherein the grains in its microstructure have a ratio of grain lengths in rolling direction to the grain width in transverse direction of the flat steel product of <1.5.

10 . A method for producing a cold-rolled flat steel product intended for deep drawing applications, comprising the steps of:
melting a steel melt containing, in addition to iron and unavoidable impurities (in % by weight): C: 0.008%-0.1%, Al: 6.5%-12%, Nb: 0.1%-0.2%, Ti: 0.15%-0.5%, P: up to 0.1%, S: up to 0.03%, N: up to 0.1% and optionally one or more elements from the group of “Mn, Si, rare earth metals, Mo, Cr, Zr, V, W, Co, Ni, B, Cu, Ca, N”, provided that Mn: up to 1%, rare earth metals: up to 0.2%, Si: up to 2%, Zr: up to 1%, V: up to 1%, W: up to 1%, Mo: up to 1%, Cr: up to 3%, Co: up to 1%, Ni: up to 2%, B: up to 0.1%, Cu: up to 3%, Ca: up to 0.015%, wherein the % Ti/% Nb ratio of the Ti content % Ti and the Nb content % Nb is 2.5% Ti/% Nb 1.5; casting the steel melt to give a pre-product; optionally heating or holding the pre-product at a preheating temperature of 1000-1300° C.; hot-rolling the pre-product to give a hot strip, the hot-rolling end temperature being 820-1000° C.; winding the hot strip to give a coil, the winding temperature being in the range from room temperature to 750° C.; annealing the hot strip at an annealing temperature of more than 650° C. and up to 1200° C. over an annealing time of 1-50 h; optionally pickling the hot strip; cold-rolling the annealed and optionally pickled hot strip to give a cold-rolled flat steel product in one or more stages having a total cold-rolling level of at least 65%; and finally annealing the cold-rolled flat steel product at a final annealing temperature of 650-850° C.

11 . The method as claimed in claim 10 , wherein the pre-product is a cast strip.

12 . The method as claimed in claim 10 , wherein the hot rolling end temperature is 830-960° C.

13 . The method as claimed in claim 10 , wherein the winding temperature is 450-750° C.

14 . The method as claimed in claim 10 , wherein the hot strip annealing is conducted as a bell annealing.

15 . The method as claimed in claim 10 , wherein the cold rolling is conducted in two or more stages and intermediate annealing is effected between the cold-rolling stages.

Assignees

• Thyssenkrupp Steel Europe Ag

Inventors

• Balichev Evgeny
• Hofmann Harald
• Jimenez Jose

Classifications

• C21D8/04 Primary

  to produce plates or strips for drawing, e.g. for deep-drawing · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/06

  containing aluminium · CPC title

• C21D1/26

  Methods of annealing · CPC title