Austenite stainless steel material, method for producing same, and plate spring
An austenitic stainless steel material comprises, on a mass basis, 0.200% or less of C, 4.00% or less of Si, 5.00% or less of Mn, 4.00 to 10.00% of Ni, 12.00 to 18.00% of Cr, 3.50% or less of Cu, 1.00 to 5.00% of Mo, and 0.200% or less of N, a total amount of C and N of 0.100% or more, and the balance being Fe and impurities; wherein the austenitic stainless steel material has a value of Md 30 of −40.0 to 0° C., wherein the value of Md 30 is represented by the following equation (1): Md 30 =551−462(C+N)−9.2Si−8.1Mn−29(Ni+Cu)−13.7Cr−18.5Mo (1) in which the symbols of the elements each represents a content (% by mass) of each element.
1 . An austenitic stainless steel plate,
wherein the austenitic stainless steel plate comprises, on a mass basis, 0.200% or less of C, 4.00% or less of Si, 5.00% or less of Mn, 4.00 to 10.00% of Ni, 12.00 to 18.00% of Cr, 3.50% or less of Cu, 1.00 to 5.00% of Mo, and 0.200% or less of N, a total amount of C and N of 0.100% or more, and the balance being Fe and impurities;
wherein the austenitic stainless steel plate has a value of Md 30 of −40.0 to 0° C., the value of Md 30 being represented by the following equation (1):
Md
30
=
551
-
462
(
C
+
N
)
-
9.2
Si
-
8.1
Mn
-
29
(
Ni
+
Cu
)
-
13.7
Cr
-
18.5
Mo
(
1
)
in which the symbols of the elements in equation (1) each represents a content % by mass of each element;
wherein the austenitic stainless steel plate has a metallographic structure having a dislocation density of a strain-induced martensite phase of 8.0×10 16 m −2 or less, a dislocation density of a retained austenite phase of 1.5×10 16 to 6.0×10 16 m −2 , and a content of the strain-induced martensite phase of 20 to 55% by volume; and
wherein the austenitic stainless steel plate has a thickness of 0.20 mm or less.
2 . The austenitic stainless steel plate according to claim 1 , further comprising, on a mass basis, one or more selected from 0.100% or less of Al, 0.010% or less of O, 0.0001 to 0.500% of V, and 0.0001 to 0.0150% of B.
3 . The austenitic stainless steel plate according to claim 1 , further comprising, on a mass basis, one or more selected from 0.0001 to 0.500% of Ti, 0.010 to 0.500% of Co, 0.010 to 0.100% of Zr, 0.010 to 0.100% of Nb, 0.0005 to 0.0030% of Mg, 0.0003 to 0.0030% of Ca, 0.010 to 0.200% of Y, 0.001 to 0.100% of lanthanoids, 0.001 to 0.500% of Sn, 0.001 to 0.500% of Sb, 0.010 to 0.100% of Pb, and 0.010 to 0.500% of W.
4 . The austenitic stainless steel plate according to claim 1 , wherein the austenitic stainless steel plate has a tensile strength (TS) of 1400 MPa or more and an elongation at break (EL) of 2.0% or more.
5 . The austenitic stainless steel plate according to claim 1 , wherein the austenitic stainless steel plate has a stress relaxation percentage of 1.00% or less, the stress relaxation percentage being represented by the following equation (2):
stress
relaxation
percentage
=
(
σ
1
-
σ
2
)
/
σ
1
(
2
)
in which σ1 is a stress less than 0.2% yield strength, and σ2 is a stress on 180 seconds after applying the stress of σ1.
6 . The austenitic stainless steel plate according to claim 2 , further comprising, on a mass basis, one or more selected from 0.0001 to 0.500% of Ti, 0.010 to 0.500% of Co, 0.010 to 0.100% of Zr, 0.010 to 0.100% of Nb, 0.0005 to 0.0030% of Mg, 0.0003 to 0.0030% of Ca, 0.010 to 0.200% of Y, 0.001 to 0.100% of lanthanoids, 0.001 to 0.500% of Sn, 0.001 to 0.500% of Sb, 0.010 to 0.100% of Pb, and 0.010 to 0.500% of W.
7 . A plate spring, comprising the austenitic stainless steel plate according to claim 1 .
8 . A plate spring, comprising the austenitic stainless steel plate according to claim 2 .