US2015027597A1PendingUtilityA1
High strength bake-hardenable low density steel and method for producing said steel
Assignee: TATA STEEL NEDERLAND TECHNOLOGY BVPriority: Feb 20, 2012Filed: Feb 19, 2013Published: Jan 29, 2015
Est. expiryFeb 20, 2032(~5.6 yrs left)· nominal 20-yr term from priority
C23C 2/02C21D 8/0263C22C 38/04C21D 8/0284C22C 38/14C21D 2211/005C22C 38/06C22C 38/12C22C 38/004C22C 38/001C23C 2/022C23C 2/024C23C 2/0224C22C 38/02Y10T29/49991
46
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Claims
Abstract
This invention relates to a high strength bake-hardenable low density steel and to a method for producing said the steel.
Claims
exact text as granted — not AI-modified1 . A ferritic steel strip or sheet comprising, in weight percent,
up to 0.01% C_total; up to 0.5% Si; 0.1 to 1.0 % Mn; 5 to 10 % Al; up to 0.010% N; up to 0.01% S; up to 0.1% P; at least one of
0.005 to 0.019% Ti;
0.008 to 0.08% Nb;
0.002 to 0.1% V;
0.004 to 0.1% Zr;
optionally between 5 and 50 ppm B; remainder iron and inevitable impurities; wherein C_solute=C_total
Minimum[X,Y]
Maximum[Z,0]
(12/93)*Nb
(12/91)*Zr
(12/51)*V;
wherein
X
=
2
·
(
12
2
·
32
)
·
S
Y
=
2
·
(
12
4
·
48
)
·
(
Ti
-
(
(
48
14
)
·
N
)
)
Z
=
(
12
48
)
·
(
Ti
-
(
(
48
14
)
·
N
)
-
(
4
·
48
(
2
·
32
)
·
S
)
)
wherein
Minimum[X,Y]=lower value of X and Y and Minimum[X,Y]=zero if Y is negative;
Maximum[Z,0]=higher value of zero and Z;
and wherein C_solute is at least 0.0005 (5 ppm).
2 . The steel according to claim 1 1 wherein C_solute is at most 0.0050 (50 ppm).
3 . The steel according to claim 1 , wherein Mn is at least 0.1%.
4 . The steel according to claim 1 , wherein Al is at least 6% and/or at most 9%.
5 . The steel according to claim 1 , wherein C_total is at least 0.0010% (10 ppm).
6 . The steel according to claim 1 , wherein C_solute is at least 0.0010% (10 ppm) and/or at most 0.0040% (40 ppm).
7 . The steel according to claim 1 , wherein N is at most 0.005% (50 ppm).
8 . The steel according to claim 1 , wherein Si is at most 0.2%.
9 . The steel according to claim 1 , wherein the specific density of the steel is between 6800 and 7300 kg/m3.
10 . A method for producing a ferritic steel strip according to claim 1 comprising the steps of:
providing a steel slab or thick strip by:
continuous casting, or
by thin slab casting, or
by belt casting, or
by strip casting;
optionally followed by reheating the steel slab or strip at a reheating temperature of at most 1250° C.;
hot rolling the slab or thick strip and finishing the hot-rolling process at a hot rolling finishing temperature of at least 850° C. to form a hot rolled ferritic strip;
coiling the hot-rolled strip at a coiling temperature of between 550 and 750° C.
11 . The method according to claim 10 , wherein the hot-rolled strip carbon is reheated in:
a continuous annealing step, optionally followed by hot-dip galvanising followed by fast cooling, or a heat-to-coat step, followed by hot-dip galvanising and fast cooling.
12 . A method for producing the ferritic steel strip comprising the steps of
cold-rolling the hot rolled ferritic steel strip of claim 10 at a cold-rolling reduction of from 40 to 90% to produce a cold-rolled strip; annealing the cold-rolled strip in a continuous annealing process with a peak metal temperature of between 700 and 900° C.; optionally galvanising the annealed strip in a hot-dip galvanising or electro-galvanising or a heat-to-coat process.
13 . The method according to claim 12 , wherein the peak metal temperature in the continuous annealing process is at least 750° C.
14 . The method according to claim 11 , wherein the cold rolling reduction is at least 50%.
15 . The method according to claim 10 , wherein the thickness of the hot-rolled strip is between 1 and 5 mm and/or wherein the thickness of the cold-rolled strip is between 0.4 and 2 mm.
16 . The steel according to claim 1 , wherein Al is at least 6% and/or at most 8%.
17 . The steel according to claim 1 , wherein C_solute is at least 0.0010% (10 ppm) and/or at most 0.0030% (30 ppm).
18 . The method according to claim 12 , wherein the peak metal temperature in the continuous annealing process is at least 800° C.Join the waitlist — get patent alerts
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