Alloying element-saving hot rolled duplex stainless steel material, clad steel plate having duplex stainless steel as cladding material therefor, and production method for same

Patent metadata

Field	Value
Publication number	US-9862168-B2
Application number	US-201213978743-A
Country	US
Kind code	B2
Filing date	Jan 26, 2012
Priority date	Jan 27, 2011
Publication date	Jan 9, 2018
Grant date	Jan 9, 2018

Abstract

This alloying element-saving hot rolled duplex stainless steel material contains, by mass %, C: 0.03% or less, Si: 0.05% to 1.0%, Mn: 0.5% to 7.0%, P: 0.05% or less, S: 0.010% or less, Ni: 0.1% to 5.0%, Cr: 18.0% to 25.0%, N: 0.05% to 0.30% and Al: 0.001% to 0.05%, with a remainder being Fe and inevitable impurities, wherein the alloying element-saving hot rolled duplex stainless steel material is produced by hot rolling, a chromium nitride precipitation temperature TN is in a range of 960° C. or lower, a yield strength is 50 MPa or more higher than that of a hot rolled steel material which is subjected to a solution heat treatment, and the alloying element-saving hot rolled duplex stainless steel material is as hot rolled state, and is not subjected to a solution heat treatment. This clad steel plate includes a duplex stainless steel as a cladding material, the duplex stainless steel has the above composition, and the chromium nitride precipitation temperature TN is in a range of 800° C. to 970° C.

First claim

The invention claimed is:

1. An alloying element-saving hot rolled duplex stainless steel material comprising, by mass %:
C: 0.03% or less;
Si: 0.05% to 1.0%;
Mn: 0.5% to 7.0%;
P: 0.05% or less;
S: 0.010% or less;
Ni: 0.1% to 5.0%;
Cr: 18.0% to 25.0%;
N: 0.05% to 0.30%; and
Al: 0.001% to 0.05%,
with a remainder being Fe and inevitable impurities,
wherein:
said alloying element-saving hot rolled duplex stainless steel material is produced by hot rolling,
said alloying element-saving hot rolled duplex stainless steel material is not subjected to a solution heat treatment,
a chromium nitride precipitation temperature TN, which is an index regarding precipitation of chromium nitrides during the hot rolling, is in a range of 960° C. or lower,
a yield strength of said alloying element-saving hot rolled duplex stainless steel material is 50 MPa or more higher than that of a solution heat-treated hot rolled steel material having the same composition as the alloying element-saving hot rolled duplex stainless steel material, the solution treatment including soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature,
an impact value at −20° C. is 50 J/cm 2 or more,
a difference between a potential of said alloying element-saving hot rolled duplex stainless steel material, which is not subjected to a solution heat treatment, and a potential of the solution heat-treated hot rolled steel material is 0.05V or less, the solution treatment including soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature, the potential being measured by a method specified in JIS G0577, and the potential being a potential at which a current density corresponds to 100 μA/cm 2 , and
the chromium nitride precipitation temperature TN is obtained by a measuring method including: a step in which the solution treatment of the solution heat-treated hot rolled steel material includes soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature; a step in which the solution heat-treated hot rolled steel material is subjected to soaking at a temperature of 800° C. to 1000° C. for 20 minutes, and then water cooling is conducted after a time of 5 seconds or less is passed; a subsequent step in which a precipitation amount of chromium nitrides in the cooled steel material is measured by an electroextraction residue analyzing method of non-metallic inclusions; and a step in which among soaking temperatures at which a Cr residue amount becomes in a range of 0.01% or less, the lowest temperature is used as the chromium nitride precipitation temperature TN.

2. An alloying element-saving hot rolled duplex stainless steel material comprising, by mass %:
C: 0.03% or less;
Si: 0.05% to 1.0%;
Mn: 0.5% to 7.0%;
P: 0.05% or less;
S: 0.010% or less;
Ni: 0.1% to 5.0%;
Cr: 18.0% to 25.0%;
N: 0.05% to 0.30%; and
Al: 0.001% to 0.05%, and further comprising one or more selected from:
V: 0.05% to 0.5%;
Nb: 0.01% to 0.20%; and
Ti: 0.003% to 0.05%,
with a remainder being Fe and inevitable impurities,
wherein:
said alloying element-saving hot rolled duplex stainless steel material is produced by hot rolling,
said alloying element-saving hot rolled duplex stainless steel material is not subjected to a solution heat treatment,
a chromium nitride precipitation temperature TN2, which is a second index regarding precipitation of chromium nitrides during the hot rolling, is in a range of 960° C. or lower,
a yield strength of said alloying element-saving hot rolled duplex stainless steel material is 50 MPa or more higher than that of a solution heat-treated hot rolled steel material having the same composition as the alloying element-saving hot rolled duplex stainless steel material, the solution treatment including soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature,
an impact value at −20° C. is 50 J/cm 2 or more,
a difference between a potential of said alloying element-saving hot rolled duplex stainless steel material, which is not subjected to a solution heat treatment, and a potential of the solution heat-treated hot rolled steel material is 0.05V or less, the solution treatment including soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature, the potential being measured by a method specified in JIS G0577, and the potential being a potential at which a current density corresponds to 100 μA/cm 2 , and
the chromium nitride precipitation temperature TN2 is obtained by a measuring method including: a step in which the solution treatment of the solution heat-treated hot rolled steel material includes soaking at a temperature of 1000° C. for 5 minutes and subsequent water cooling to room temperature; a step in which the solution heat-treated hot rolled steel material is subjected to soaking at a temperature of 800° C. to 1000° C. for 20 minutes, and then water cooling is conducted after a time of 5 seconds or less is passed; a subsequent step in which a precipitation amount of chromium nitrides in the cooled steel material is measured by an electroextraction residue analyzing method of non-metallic inclusions; and a step in which among soaking temperatures at which a Cr residue amount becomes in a range of 0.03% or less, the lowest temperature is used as the chromium nitride precipitation temperature TN2.

3. The alloying element-saving hot rolled duplex stainless steel material which is not subjected to a solution heat treatment according to claim 1 or 2 , which further comprises one or more elements selected from:
Mo: 1.5% or less;
Cu: 2.0% or less;
W: 1.0% or less;
Co: 2.0% or less;
B: 0.0050% or less;
Ca: 0.0050% or less;
Mg: 0.0030% or less; and
REM: 0.10% or less.

4. A method for producing the alloying element-saving hot rolled duplex stainless steel material which is not subjected to a solution heat treatment according to claim 1 or 2 , the method comprising:
subjecting a billet having the chemical composition according to claim 1 or 2 to hot rolling; and
subsequently cooling a hot rolled steel material,
wherein in the case where V, Nb and Ti, which are selective components, are not contained, an input side temperature TF of a final finishing rolling pass of the hot rolling is adjusted so as to fulfill the following formula (1), in the case where the selective components are contained, the input side temperature TF of the final finishing rolling pass of the hot rolling is adjusted so as to fulfill the following formula (2),
the hot rolled steel material is cooled in a temperature range from the input side temperature TF of the final finishing rolling pass of the hot rolling to 600° C. for a time of 5 minutes or less, and
the method does not include a solution heat treatment,
TF≧TN− 30  (1)

TF≧TN 2−30  (2).

5. The method for producing the alloying element-saving hot rolled duplex stainless steel material according to claim 4 ,
wherein a plate thickness exceeds 20 mm, and
in the case where V, Nb and Ti, which are the selective components, are not contained, accelerated cooling is initiated from an accelerated cooling initiation temperature TC after an end of the hot rolling, that fulfills the following formula (3), and, in the case where the selective components are contained, accelerated cooling is initiated from an accelerated cooling initiation temperature TC after the end of the hot rolling that fulfills the following formula (4), and thereby, the hot rolled steel material is cooled in a temperature range from the input side temperature TF of the final finishing rolling pass of the hot rolling to 600° C. for a time of 5 minutes or less,
TN− 200≦ TC≦TN+ 50 (here, TF≧TC

Assignees

• Tsuge Shinji
• Oikawa Yuusuke
• Yamamoto Yoichi
• Kajimura Haruhiko
• Ishida Kazuhiko
• Nippon Steel & Sumikin Sst

Inventors

• Tsuge Shinji
• Oikawa Yuusuke
• Yamamoto Yoichi
• Kajimura Haruhiko
• Ishida Kazuhiko

Classifications

• C22C38/46

  with vanadium · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C22C38/54

  with boron · CPC title