US2024229183A9PendingUtilityA9
Coiling temperature influenced cold rolled strip or steel
Est. expiryDec 23, 2040(~14.4 yrs left)· nominal 20-yr term from priority
C21D 8/02C22C 38/38C22C 38/06C22C 38/04C22C 38/02C22C 38/001C21D 2211/008C21D 2211/002C21D 2211/001C21D 8/0278C21D 8/0263C21D 8/0236C21D 8/0226C21D 6/008C21D 6/005C21D 6/002C21D 1/84C21D 1/18C23C 2/40C22C 38/18C21D 9/46C23C 2/06C22C 38/24C22C 38/22C22C 38/28C22C 38/26C22C 38/34C21D 1/26C21D 8/0247C21D 9/52C21D 8/0205C21D 8/0463
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Claims
Abstract
A cold roll strip or sheet includes in (wt %) C 0.08-0.28; Mn 1.4-4.5; Cr 0.01-0.5; Si 0.01-2.5; Al 0.01-0.6; Si+Al≥0.1; Si+Al+Cr≥0.4; Nb≤0.008; Ti≤0.02; Mo≤0.08; Ca≤0.005; V≤0.02; balance Fe apart from impurities. The steel is within the area defined by the coordinates A, B, C, D, where Ri/t (y-axle) is plotted vs TS(MPa)/YR (x-axle), and where A is [1200, 2), B is [2000, 4], C is [2000, 3], and D is [1200, 1].
Claims
exact text as granted — not AI-modified1 . A cold rolled steel strip or sheet
a) having a composition consisting of in wt. %:
C
0.08-0.28
Mn
1.4-4.5
Cr
0.01-0.5
Si
0.01-2.5
Al
0.01-0.6
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.1
Ti
≤0.1
Mo
≤0.5
Ca
≤0.05
V
≤0.1
Cu
≤0.06%
Ni
≤0.08%
B
≤0.0006%
P
≤0.02%
S
≤0.005%
As
≤0.010%
Zr
≤0.006%
Sn
≤0.015%
O
≤0.0003
H
≤0.0020
N
≤0.015%
balance Fe apart from impurities;
b) fulfilling the following conditions:
TS tensile strength (R m )
950-1550 MPa
YS yield strength (R p0.2 )
550-1400 MPa
YR yield ratio (R p0.2 /R m )
≥0.50
bendability (Ri/t)
≤5;
c) being within the area defined by the coordinates A, B, C, D, where Ri/t y-axle is plotted vs TS(MPa)/YR x-axle, and where A is [1200, 2), B is [2000, 4], C is [2000, 3], and D is [1200, 1];
d) having a multiphase microstructure comprising in vol %
tempered martensite +
≥50
bainite
fresh martensite
≤10
retained austenite
2-20
polygonal ferrite
≤1;
e) wherein the amount of retained austenite was measured by means of the saturation magnetization method described in detail in Proc. Int. Conf. on TRIP-aided high strength ferrous alloys (2002), Ghent, Belgium, p. 61-64;
f) wherein the bendability Ri/t is determined in accordance with JIS Z2248, where Ri is the limiting bending radius and t is the sheet thickness;
g) wherein the yield strength and tensile strength are determined according to the European norm EN 10002 Part 1; and
h) the steel does not contain other kind of ferrite than polygonal ferrite
2 . The cold roll strip or sheet according to claim 1 , wherein the composition comprising in wt %:
C
0.1-0.25
Mn
1.4-3
Cr
0.01-0.5
Si
0.1-1
Al
0.01-0.1
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.008
Ti
≤0.02
Mo
≤0.08
Ca
≤0.005
V
≤0.02
balance Fe apart from impurities.
3 . The cold roll strip or sheet according to claim 1 wherein the composition fulfilling at least one of the following requirements:
Si
≥0.4
Si + Al
≥0.8
Al
≤0.1
Mn + Cr
1.7-5.0.
4 . The cold roll strip or sheet according to claim 3 fulfilling all of the requirements.
5 . The cold roll strip or sheet according to claim 1 wherein the microstructure fulfils at least one of the following requirements:
tempered martensite +
≥60
bainite
fresh martensite
1-10
retained austenite
5-15.
6 . The cold roll strip or sheet according to claim 1 , wherein the yield ratio is ≥0.70.
7 . The cold roll strip or sheet according to claim 1 ,
a) having a composition comprising of in wt. %:
C
0.08-0.16
Mn
2.0-3.0
Cr
0.1-0.5
Si
0.5-1.2
Al
0.01-0.5
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.1
Ti
≤0.1
Mo
≤0.5
Ca
≤0.05
V
≤0.1
balance Fe apart from impurities; and
a) fulfilling at least one of the following conditions:
TS tensile strength (R m )
950-1150 MPa
YS yield strength (R p0.2 )
750-1000 MPa
YR yield ratio (R p0.2 /R m )
≥0.70
bendability (Ri/t)
≤2.
8 . The cold roll strip or sheet according to claim 1 ,
a) having a composition comprising of in wt. %:
C
0.15-0.25
Mn
1.0-2.0
Cr
0.1-0.5
Si
0.1-0.5
Al
0.01-0.5
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.1
Ti
≤0.1
Mo
≤0.5
Ca
≤0.05
V
≤0.1
balance Fe apart from impurities; and
b) fulfilling at least one of the following conditions:
TS tensile strength (R m )
1300-1550 MPa
YS yield strength (R p0.2 )
1000-1300 MPa
YR yield ratio (R p0.2 /R m )
≥0.70
bendability (Ri/t)
≤4.
9 . The cold roll strip or sheet according to claim 1 ,
a) having a composition comprising of in wt. %:
C
0.15-0.25
Mn
2.0-3.0
Cr
0.1-0.5
Si
1-2.0
Al
0.01-0.5
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.1
Ti
≤0.1
Mo
≤0.5
Ca
≤0.05
V
≤0.1
balance Fe apart from impurities; and
b) fulfilling at least one of the following conditions:
TS tensile strength (R m )
1100-1300 MPa
YS yield strength (R p0.2 )
900-1100 MPa
YR yield ratio (R p0.2 /R m )
≥0.70
bendability (Ri/t)
≤3.
10 . The cold roll strip or sheet according to claim 1 ,
a) having a composition comprising of in wt. %:
C
0.10-0.20
Mn
2.0-3.0
Cr
0.1-0.5
Si
0.2-0.9
Al
0.01-0.5
Si + Al
≥0.1
Si + Al + Cr
≥0.4
Nb
≤0.1
Ti
≤0.1
Mo
≤0.5
Ca
≤0.05
V
≤0.1
balance Fe apart from impurities; and
b) fulfilling at least one of the following conditions:
TS tensile strength (R m )
900-1100 MPa
YS yield strength (R p0.2 )
600-800 MPa
YR yield ratio (R p0.2 /R m )
≥0.65
bendability (Ri/t)
≤2.5.
11 . The cold roll strip or sheet according to claim 1 , wherein
Al≤0.1.
12 . A method of manufacturing of a cold rolled steel strip or sheet according to claim 1 , comprising the following steps:
a) providing a steel slab; b) hot rolling the slab in the austenitic range to a hot rolled strip, wherein the hot rolling finishing temperature is greater than or equal to 850° C.; c) coiling the hot rolled strip at a coiling temperature in the range of 500-540° C.; d) optionally performing scale removal process on the coiled steel strip; e) batch annealing the coiled strip at a temperature in the range of 500-650° C. for a duration of 5-30 h; f) cold rolling the annealed steel strip with a reduction rate between 35 and 90%; g) further treating the cold rolled steel strip in a Continuously Annealing Line or in a Hot Dip Galvanizing Line, in which the soaking temperature is 800-1000° C., and a holding temperature is 200-500° C. for a time of 150 to 1000 s; and h) further cooling the steel strip down to room temperature.
13 . The method according to claim 12 , fulfilling at least one of the following conditions:
in step b) reheating the slab to a temperature between 1000° C. and 1280° C.; in step e) batch annealing in the range of 550-650° C.; and in step g) the holding temperature is 350-450° C.
14 . The method according to claim 12 , wherein the soaking temperature in step g) is in the range of 830-900° C.
15 . The method according to claim 12 , wherein the soaking temperature in step g) is above A c3 as defined by: A c3 =910-203*C 1/2 −15.2 Ni−30 Mn+44.7 Si+104 V+31.5 Mo+13.1 W.
16 . The method according claim 15 , wherein the soaking temperature in step g) is above A c3 +20° C.
17 . The method according claim 15 , wherein the soaking temperature in step g) is above A c3 +30° C.Cited by (0)
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