Ferritic-austenitic two-phase stainless steel material and method for manufacturing same

Patent metadata

Field	Value
Publication number	US-10793930-B2
Application number	US-201715998964-A
Country	US
Kind code	B2
Filing date	Feb 14, 2017
Priority date	Feb 17, 2016
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

A steel material contains, in mass %, C: 0.005 to 0.050, N: 0.05 to 0.30, Si: 0.1 to 1.5, Mn: 0.1 to 7.0, P: 0.005 to 0.100, S: 0.0001 to 0.0200, Cr: 18.0 to 28.0, Cu: 0.1 to 3.0, Ni: 0.1 to 8.0, Mo: 0.1 to 5.0, Al: 0.001 to 0.050, B: 0.0001 to 0.0200, and Ca: 0.0001 to 0.0100. An area ratio of an austenitic phase ranges from 30% to 70% and formulae (I) and (II) below are satisfied.

1.03≤[% Cr*F]/[% Cr]≤1.40  Formula (I)

1.05≤[% Mn*A]/[% Mn]≤1.80  Formula (II)

[% symbol of an element]: a content of the element in the steel

[% symbol of an element*F]: a content of the element in a ferrite phase

[% symbol of element*A]: a content of the element in the austenitic phase

First claim

The invention claimed is:

1. A ferritic-austenitic duplex stainless steel material comprising, in mass %,
C: 0.005% to 0.050%,
N: 0.05% to 0.30%,
Si: 0.1% to 1.5%,
Mn: 0.1% to 7.0%,
P: 0.005% to 0.100%,
S: 0.0001% to 0.0200%,
Cr: 18.0% to 28.0%,
Cu: 0.1% to 3.0%,
Ni: 0.1% to 8.0%,
Mo: 0.1% to 5.0%,
Al: 0.001% to 0.050%,
B: 0.0001% to 0.0200%,
Ca: 0.0001% to 0.0100%, and
a balance consisting of Fe and inevitable impurities, wherein
an austenitic phase has an area ratio ranging from 30% to 70%, and
formulae (I) and (II) below are satisfied,
1.03≤[% Cr*F]/[% Cr]≤1.40  Formula (I)

1.05≤[% Mn*A]/[% Mn]≤1.80  Formula (II)

where [% symbol of an element] indicates a content (mass %) of the element in the steel, [% symbol of an element*F] indicates a content (mass %) of the element in a ferrite phase, and [% symbol of an element*A] indicates a content (mass %) of the element in the austenitic phase.

2. The ferritic-austenitic duplex stainless steel material according to claim 1 , further comprising, in mass %, one of or two or more of
V: 0.001% to 0.5%,
Ti: 0.001% to 0.5%,
Nb: 0.001% to 0.5%,
Zr: 0.001% to 0.5%,
Hf: 0.001% to 0.5%,
W: 0.1% to 3.0%,
Sn: 0.01% to 1.0%,
Co: 0.01% to 1.0%,
Sb: 0.005% to 0.3%,
Ta: 0.001% to 1.0%,
Ga: 0.0002% to 0.3%,
Mg: 0.0002% to 0.01%,
Bi: 0.001% to 1.0%, and
REM: 0.001% to 0.2%.

3. The ferritic-austenitic duplex stainless steel material according to claim 1 or 2 , wherein the ferritic-austenitic duplex stainless steel material is used for an in-vehicle channel part having a material temperature of 400 degrees C. or less in use and a part to be joined to the channel part.

4. The ferritic-austenitic duplex stainless steel material according to claim 1 or 2 , wherein the ferritic-austenitic duplex stainless steel material is used for a to-be-brazed part.

5. The ferritic-austenitic duplex stainless steel material according to claim 1 or 2 , wherein the steel material is in a form of a steel sheet or a steel pipe.

6. A vehicle part made of a material comprising the ferritic-austenitic duplex stainless steel material according to claim 1 or 2 .

7. A heat exchanger made of a material comprising the ferritic-austenitic duplex stainless steel material according to claim 1 or 2 .

8. A pipe made of a material comprising the ferritic-austenitic duplex stainless steel material according to claim 1 or 2 .

9. A channel structure made of a material comprising the ferritic-austenitic duplex stainless steel material according to claim 1 or 2 .

10. A method of producing the ferritic-austenitic duplex stainless steel material according to claim 1 or 2 , the method comprising final annealing performed at a temperature of 1200 degrees C. or less, wherein
in a temperature-rise process, a time Tu (sec) for a range of 500 degrees C. to 900 degrees C. is 5 seconds to 100 seconds and a time Th (sec) for a range of 900 degrees C. or more is 30 seconds or more,
in a cooling process, a time Td (sec) for a range of 900 degrees C. or 500 degrees C. is 1 second to 400 seconds, and
a formula (III) below is satisfied,
0.20≤( Tu+Td )/ Th≤ 10.00  Formula (III).

11. The ferritic-austenitic duplex stainless steel material according to claim 3 , wherein the ferritic-austenitic duplex stainless steel material is used for a to-be-brazed part.

12. The ferritic-austenitic duplex stainless steel material according to claim 3 , wherein the steel material is in a form of a steel sheet or a steel pipe.

13. The ferritic-austenitic duplex stainless steel material according to claim 4 , wherein the steel material is in a form of a steel sheet or a steel pipe.

14. A method of producing the ferritic-austenitic duplex stainless steel material according to claim 3 , the method comprising final annealing performed at a temperature of 1200 degrees C. or less, wherein
in a temperature-rise process, a time Tu (sec) for a range of 500 degrees C. to 900 degrees C. is 5 seconds to 100 seconds and a time Th (sec) for a range of 900 degrees C. or more is 30 seconds or more,
in a cooling process, a time Td (sec) for a range of 900 degrees C. or 500 degrees C. is 1 second to 400 seconds, and
a formula (III) below is satisfied,
0.20≤( Tu+Td )/ Th≤ 10.00  Formula (III).

15. A method of producing the ferritic-austenitic duplex stainless steel material according to claim 4 , the method comprising final annealing performed at a temperature of 1200 degrees C. or less, wherein
in a temperature-rise process, a time Tu (sec) for a range of 500 degrees C. to 900 degrees C. is 5 seconds to 100 seconds and a time Th (sec) for a range of 900 degrees C. or more is 30 seconds or more,
in a cooling process, a time Td (sec) for a range of 900 degrees C. or 500 degrees C. is 1 second to 400 seconds, and
a formula (III) below is satisfied,
0.20≤( Tu+Td )/ Th≤ 10.00  Formula (III).

16. A method of producing the ferritic-austenitic duplex stainless steel material according to claim 5 , the method comprising final annealing performed at a temperature of 1200 degrees C. or less, wherein
in a temperature-rise process, a time Tu (sec) for a range of 500 degrees C. to 900 degrees C. is 5 seconds to 100 seconds and a time Th (sec) for a range of 900 degrees C. or more is 30 seconds or more,
in a cooling process, a time Td (sec) for a range of 900 degrees C. or 500 degrees C. is 1 second to 400 seconds, and
a formula (III) below is satisfied,
0.20≤( Tu+Td )/ Th≤ 10.00  Formula (III).

Assignees

• Nippon Steel & Sumikin Sst

Inventors

• HAYASHI Atsutaka
• Hiraide Nobuhiko
• Hamada Junichi

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• B23K35/302

  Cu as the principal constituent · CPC title

• B23K35/3033

  Ni as the principal constituent · CPC title

• C21D9/0068

  for particular articles not mentioned below · CPC title

• B23K2101/14

  Heat exchangers · CPC title