Steel sheet and plated steel sheet
When a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10 −3 , a Y value is an average crystal misorientation (°) in the grain, a metallic phase 1 is a metallic phase the K value of which is less than 4.000, a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0, a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, there is provided a steel sheet that has a predetermined chemical composition and includes a microstructure including, in area percent, a metallic phase 1: 1.0% or more and less than 35.0%, a metallic phase 2: 30.0% or more and 80.0% or less, a metallic phase 3: 5.0% or more and 50.0% or less, and a metallic phase 4: 5.0% or less. The steel sheet has a strength as high as 590 MPa or more (further, 780 MPa or more) in terms of tensile strength and has an excellent hole-expansion property.
1. A steel sheet comprising
a chemical composition consisting of, in mass percent:
C: 0.01 to 0.20%;
Si: 0.005 to 0.10%;
Mn: 0.60 to 4.00%;
Al: 0.55 to 3.00%;
P: 0.10% or less;
S: 0.03% or less;
N: 0.01% or less;
O: 0.01% or less;
Ti: 0 to 2.00%;
Nb: 0 to 2.00%;
V: 0 to 0.30%;
Cu: 0 to 2.00%;
Ni: 0 to 2.00%;
Mo: 0 to 1.00%;
Cr: 0 to 2.00%;
B: 0 to 0.01%;
Ca: 0 to 0.010%;
Mg: 0 to 0.010%;
Zr: 0 to 0.050%;
REM: 0 to 0.1%;
Sb: 0 to 0.10%;
Sn: 0 to 0.10%; and
As: 0 to 0.5%,
with the balance: Fe and impurities, and comprising
a microstructure that includes,
when a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when
a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10 −3 ,
a Y value is an average crystal misorientation (°) in the grain,
a metallic phase 1 is a metallic phase the K value of which is less than 4.000,
a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0,
a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and
a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, and the metallic phase 4 comprises at least one of upper bainite, lower bainite, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
2. The steel sheet according to claim 1 , comprising a microstructure in which the metallic phase 4 is 0%.
3. The steel sheet according to claim 1 , wherein 60.0% or more of boundaries of the metallic phase 1 with other metallic phases is a boundary of the metallic phase 1 with the metallic phase 2.
4. The steel sheet according to claim 3 , wherein a thickness of the steel sheet is 0.8 to 3.6 mm.
5. The steel sheet according to claim 4 , wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.
6. The steel sheet according to claim 4 , wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
7. The steel sheet according to claim 3 , wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.
8. The steel sheet according to claim 3 , wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
9. The steel sheet according to claim 1 , wherein a thickness of the steel sheet is 0.8 to 3.6 mm.
10. The steel sheet according to claim 9 , wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.
11. The steel sheet according to claim 9 , wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
12. The steel sheet according to claim 1 , wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.
13. The steel sheet according to claim 1 , wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
14. A plated steel sheet comprising a galvanized layer on a surface of the steel sheet according to claim 1 .
15. A plated steel sheet comprising a galvannealed layer on a surface of the steel sheet according to claim 1 .
16. A steel sheet comprising
a chemical composition comprising, in mass percent:
C: 0.01 to 0.20%;
Si: 0.005 to 0.10%;
Mn: 0.60 to 4.00%;
Al: 0.55 to 3.00%;
P: 0.10% or less;
S: 0.03% or less;
N: 0.01% or less;
O: 0.01% or less;
Ti: 0 to 2.00%;
Nb: 0 to 2.00%;
V: 0 to 0.30%;
Cu: 0 to 2.00%;
Ni: 0 to 2.00%;
Mo: 0 to 1.00%;
Cr: 0 to 2.00%;
B: 0 to 0.01%;
Ca: 0 to 0.010%;
Mg: 0 to 0.010%;
Zr: 0 to 0.050%;
REM: 0 to 0.1%;
Sb: 0 to 0.10%;
Sn: 0 to 0.10%; and
As: 0 to 0.5%,
with the balance: Fe and impurities, and comprising
a microstructure that includes,
when a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when
a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10 −3 ,
a Y value is an average crystal misorientation (°) in the grain,
a metallic phase 1 is a metallic phase the K value of which is less than 4.000,
a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0,
a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and
a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, and the metallic phase 4 comprises at least one of upper bainite, lower bainite, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.
17. The steel sheet according to claim 16 , comprising a microstructure in which the metallic phase 4 is 0%.
18. The steel sheet according to claim 16 , wherein
60.0% or more of boundaries of the metallic phase 1 with other metallic phases is a boundary of the metallic phase 1 with the metallic phase 2.
19. The steel sheet according to claim 16 , wherein a thickness of the steel sheet is 0.8 to 3.6 mm.