TWIP steel sheet having an austenitic matrix
A TWIP steel sheet is provided having an austenitic matrix including by weight: 0.1≤C≤1.2%, 13.0≤Mn<25.0%, 0.1≤Si≤3.0%, 0.1≤Cu≤5.0%, S≤0.030%, P≤0.080%, N≤0.1%, 0.1≤Al≤4.0% and 0.1≤V≤2.50% in such way that:—when the amount of Al<2.0%, the weight ratio Al/V is between 0.2 and 8 or—when the amount of Al≥2.0%, the amount of V>0.25%, and on a purely optional basis, one or more of Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.40%, Ni≤1.0%, Ti≤0.5%, and/or 0.06≤Sn≤0.2%, the remainder of the composition being made of iron and inevitable impurities resulting from elaboration.
1 . A cold rolled and recovered TWIP steel sheet having an austenitic matrix comprising by weight:
0.1≤C≤1.2%,
13.0≤Mn<25.0%,
0.1≤Si≤3.0%,
0.1≤Cu≤5.0%,
S≤0.030%,
P≤0.080%,
N≤0.1%,
0.1≤Al≤4.0% and
0.1≤V≤2.50% in such way that:
when the amount of Al<2.0%, the weight ratio Al/V is between 0.2 and 8 or
when the amount of Al≥2.0%, the amount of V>0.25%,
and optionally one or more of the following elements: Nb≤0.5%,
B≤0.005%,
Cr≤1.0%,
Mo≤0.40%,
Ni≤1.0%,
Ti≤0.5%, and
0.06≤Sn≤0.2%;
the remainder of the composition being made of iron and inevitable impurities resulting from elaboration, the steel sheet having a microstructure with a recovered fraction greater than a recrystallized fraction.
2 . The steel sheet according to claim 1 , wherein the austenitic matrix further comprises one or more of
Nb≤0.5%,
B≤0.005%,
Cr≤1.0%,
Mo≤0.40%,
Ni≤1.0%,
Ti≤0.5%, and
0.06≤Sn≤0.2%.
3 . The steel sheet according to claim 1 , wherein the amount of V is between 0.1 and 1.0% by weight.
4 . The steel sheet according to claim 1 , wherein the amount of Al is below or equal to 2.0% by weight.
5 . The steel sheet according to claim 1 , wherein at least one vanadium element under the form of nitrides, carbides or carbonitrides is present in the steel sheet.
6 . The steel sheet according to claim 1 , wherein the amount of Cu is below 2.0% by weight.
7 . The steel sheet according to claim 1 , wherein the amount of Nb is between 0.070 and 0.50% by weight.
8 . The steel sheet according to claim 1 , wherein the amount of Si is below or equal to 0.6% by weight.
9 . The steel sheet according to claim 1 , wherein the amount of Al, V, C, Mn, Si, Cu and Nb by weight satisfies the following equation:
105.1*Al %−358.1*V %≤279.67*C %−11*Mn %+30*Si %−69.02*Cu %+78.3*Nb %+144.
10 . The steel sheet according to claim 1 , wherein the steel sheet is covered by an aluminum-based coating.
11 . The steel sheet according to claim 1 , wherein the steel sheet is covered by a zinc-based coating.
12 . The steel sheet according to claim 10 , wherein the aluminium-based coating comprises less than 15% Si, less than 5.0% Fe, optionally 0.1 to 8.0% Mg and optionally 0.1 to 30.0% Zn, and the remainder being Al.
13 . The steel sheet according to claim 11 , wherein the zinc-based coating comprises 0.01-8.0% Al, optionally 0.2-8.0% Mg, and the remainder being Zn.
14 . The steel sheet according to claim 1 , wherein the composition includes Sn by weight in an amount 0.06≤Sn≤0.2%.
15 . The steel sheet according to claim 1 , further comprising a coating, the coating being a hot-dip metallic coating.
16 . The steel sheet according to claim 1 , wherein the recovered fraction is above 75%.
17 . The steel sheet according to claim 1 , wherein the recovered fraction is above 90%.
18 . The method according to claim 15 , preparing a surface of the steel sheet for coating deposition in a continuous annealing followed by the dipping the steel sheet in a molten metallic bath having a temperature between 410 and 700 °C.
19 . The method according to claim 18 , wherein during the preparation of surface, the steel sheet is heated from ambient temperature to the temperature of the molten bath.
20 . The method according to claim 18 , wherein the bath is aluminum-based and comprises less than 15% Si, less than 5.0% Fe, optionally 0.1 to 8.0% Mg and optionally 0.1 to 30.0% Zn, the remainder being Al.
21 . The method according to claim 18 , wherein the bath is zinc-based and comprises 0.01-8.0% A1, optionally 0.2-8.0% Mg, the remainder being Zn.
22 . The method according to claims 15 , wherein the recovery heat treatment is performed during 1 second to 30 minutes.
23 . The method according to claim 22 , wherein the recovery heat treatment is performed during 30 seconds to 10 minutes.
24 . The steel sheet according to claim 1 , further comprising a coating, the coating being a hot-dip metallic coating.
25 . The steel sheet according to claim 1 , wherein the recovered fraction is above 75%.
26 . The steel sheet according to claim 1 , wherein the recovered fraction is above 90%.