Heat Resistant Ferritic Steel and Ferritic Heat Transfer Member
This invention provides a ferritic heat transfer member and a heat resistant ferritic steel which are excellent in heat transfer characteristics and steam oxidation resistance properties. The heat resistant ferritic steel includes a base material, and an oxidized layer A on the surface of the base material. The base material has a chemical composition containing, in mass %: C: 0.01 to 0.3%, Si: 0.01 to 2.0%, Mn: 0.01 to 2.0%, Cr: 7.0 to 14.0%, N: 0.005 to 0.15%, and sol. Al: 0.001 to 0.3%, and one or more types of element selected from the specific oxidized layer forming elements of 0.5 to 7.0%, with the balance being Fe and impurities. An oxidized layer A includes a chemical composition containing, in mass %: Cr and Mn in a total amount of 20 to 45%, and one or more types of element selected from the specific oxidized layer forming elements of 0.5 to 10%.
1 . A heat resistant ferritic steel comprising:
a base material, and
an oxidized layer A on a surface of the base material;
wherein:
the base material has a chemical composition consisting of, in mass %:
C: 0.01 to 0.3%,
Si: 0.01 to 2.0%,
Mn: 0.01 to 2.0%,
P: 0.10% or less,
S: 0.03% or less,
Cr: 7.0 to 14.0%,
N: 0.005 to 0.15%,
sol. Al: 0.001 to 0.3%,
one or more types of element selected from the group consisting of Mo: 0 to 5.0%, Ta: 0 to 5.0%, W: 0 to 5.0% and Re: 0 to 5.0%: 0.5 to 7.0% in total,
Cu: 0 to 5.0%,
Ni: 0 to 5.0%,
Co: 0 to 5.0%,
Ti: 0 to 1.0%,
V: 0 to 1.0%,
Nb: 0 to 1.0%,
Hf: 0 to 1.0%,
Ca: 0 to 0.1%,
Mg: 0 to 0.1%,
Zr: 0 to 0.1%,
B: 0 to 0.1%, and
rare earth metal: 0 to 0.1%,
with the balance being Fe and impurities; and
the oxidized layer A has a chemical composition containing, in mass %:
Cr and Mn: 20 to 45% in total, and
one or more types of element selected from the group consisting of Mo, Ta, W and Re: 0.5 to 10% in total.
2 . The heat resistant ferritic steel according to claim 1 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Cu: 0.005 to 5.0%,
Ni: 0.005 to 5.0%, and
Co: 0.005 to 5.0%.
3 . The heat resistant ferritic steel according to claim 1 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ti: 0.01 to 1.0%,
V: 0.01 to 1.0%,
Nb: 0.01 to 1.0%, and
Hf: 0.01 to 1.0%.
4 . The heat resistant ferritic steel according to claim 1 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ca: 0.0015 to 0.1%,
Mg: 0.0015 to 0.1%,
Zr: 0.0015 to 0.1%,
B: 0.0015 to 0.1%, and
rare earth metal: 0.0015 to 0.1%.
5 . A ferritic heat transfer member, comprising:
a base material having a chemical composition according to claim 1 , and
an oxide film on a surface of the base material;
wherein:
the oxide film comprises:
an oxidized layer B containing Fe 3 O 4 and Fe 2 O 3 in a total amount of 80% or more in vol %, and
an oxidized layer C that is disposed between the oxidized layer B and the base material; and
a chemical composition of the oxidized layer C contains, in mass %:
Cr and Mn: more than 5% to 30% in total, and
one or more types of element selected from the group consisting of Mo, Ta, W and Re: 1 to 15% in total.
6 . The ferritic heat transfer member according to claim 5 , wherein a chemical composition of the oxidized layer B contains, in mass %:
Cr and Mn: 5% or less in total.
7 . The ferritic heat transfer member according to claim 5 , wherein the oxidized layer C contains, in vol %, 5% or less of Cr 2 O 3 .
8 . The heat resistant ferritic steel according to claim 2 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ti: 0.01 to 1.0%,
V: 0.01 to 1.0%,
Nb: 0.01 to 1.0%, and
Hf: 0.01 to 1.0%.
9 . The heat resistant ferritic steel according to claim 2 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ca: 0.0015 to 0.1%,
Mg: 0.0015 to 0.1%,
Zr: 0.0015 to 0.1%,
B: 0.0015 to 0.1%, and
rare earth metal: 0.0015 to 0.1%.
10 . The heat resistant ferritic steel according to claim 3 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ca: 0.0015 to 0.1%,
Mg: 0.0015 to 0.1%,
Zr: 0.0015 to 0.1%,
B: 0.0015 to 0.1%, and
rare earth metal: 0.0015 to 0.1%.
11 . The heat resistant ferritic steel according to claim 8 , wherein the chemical composition of the base material contains one or more types of element selected from the group consisting of:
Ca: 0.0015 to 0.1%,
Mg: 0.0015 to 0.1%,
Zr: 0.0015 to 0.1%,
B: 0.0015 to 0.1%, and
rare earth metal: 0.0015 to 0.1%.
12 . The ferritic heat transfer member according to claim 6 , wherein the oxidized layer C contains, in vol %, 5% or less of Cr 2 O 3 .