Ferritic stainless steel for biofuel supply system part, biofuel supply system part, ferritic stainless steel for exhaust heat recovery unit, and exhaust heat recovery unit

• US 9,611,525 B2
• Filed: 03/28/2012
• Issued: 04/04/2017
• Est. Priority Date: 03/29/2011
• Status: Active Grant

• Current Assignee: Nippon Steel Stainless Steel Corporation (Nippon Steel Corporation)
• Original Assignee: Nippon Steel & Sumikin Stainless Steel Corporation (Nippon Steel Corporation)
• Inventors: Fudanoki, Fumio, Hiraide, Nobuhiko, Sakamoto, Shunji
• Primary Examiner(s): King, Roy
• Assistant Examiner(s): KIECHLE, CAITLIN ANNE
• Application Number:
  US14/007,807
• Publication Number:
  US 20140069619A1
• Time in Patent Office: 1,833 Days
• CPC Class Codes: C21D 2211/005 Ferrite
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/004 Very low carbon steels, i.e. having a carbon content of less than 0,01%
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22C 38/008 containing tin
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/24 with vanadium
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/30 with cobalt
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/42 with copper
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 with vanadium
• CPC Class Codes: C22C 38/48 with niobium or tantalum
• CPC Class Codes: C22C 38/50 with titanium or zirconium
• CPC Class Codes: C22C 38/52 : with cobalt
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: F02M 37/0011 : Constructional details; Manufacturing or assembly of elements of fuel systems; Materials therefor
• CPC Class Codes: F28D 21/0003 : the heat being recuperated from exhaust gases F28D21/0014 takes precedence
• CPC Class Codes: F28F 19/02 : by using coatings, e.g. vitreous or enamel coatings
• CPC Class Codes: F28F 21/083 : from stainless steel

Abstract

An aspect of a ferritic stainless steel contains, by mass %: C: 0.03% or less; N: 0.03% or less; Si: more than 0.1% to 1% or less; Mn: 0.02% to 1.2%; Cr: 15% to 23%; Al: 0.002% to 0.5%; and either one or both of Nb and Ti, with the remainder being Fe and unavoidable impurities, wherein Expression (1) and Expression (2) illustrated below are satisfied, an oxide film is formed on a surface thereof, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 30% or more,
8(C+N)+0.03≦Nb+Ti≦0.6  (1)
Si+Cr+Al+{Nb+Ti−8(C+N)}≧15.5  (2).

Claims

1. A ferritic stainless steel for a biofuel supply system part comprising, by mass %:

C;

0.03% or less;

N;

0.03% or less;

Si;

more than 0.1% to 1% or less;

Mn;

0.02% to 1.2%;

Cr;

15% to 23%;

Al;

0.002% to 0.5%; and

either one or both of Nb and Ti,

with the remainder being Fe and unavoidable impurities,

wherein Expression (1) and Expression (2) illustrated below are satisfied, and

wherein an oxide film is formed on a surface thereof and carbonitrides containing either one or both Nb and Ti are produced on the surface by heat treatment in a vacuum atmosphere containing N₂ with a vacuum of 10<sup>−

2</sup> torr to 1 torr, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 30% or more and Cr in a cationic fraction of 20% or more,

8(C+N)+0.03≦

Nb+Ti≦

0.6 

 

(1)

Si+Cr+Al+{Nb+Ti−

8(C+N)}≦

15.5 

 

(2)

each element symbol represents the content (mass %) of the element in Expression (1) and Expression (2).

2. The ferritic stainless steel for a biofuel supply system part according to claim 1, further comprising, by mass %:

one or more elements selected from a group consisting of Ni;

2% or less, Cu;

1.5% or less, Mo;

3% or less, Sn;

0.5% or less, V;

1% or less, W;

1% or less, B;

0.005% or less, Zr;

0.5% or less, Co;

0.2% or less, Mg;

0.002% or less, Ca;

0.002% or less, and REM;

0.01% or less.

3. A biofuel supply system part made of the ferrtic stainless steel for a biofuel supply system part according to claim 1.

4. A biofuel supply system part made of the ferrtic stainless steel for a biofuel supply system part according to claim 2.

5. A ferritic stainless steel for an exhaust heat recovery unit comprising, by mass %:

C;

0.03% or less;

N;

0.05% or less;

Si;

more than 0.1% to 1% or less;

Mn;

0.02% to 1.2%;

Cr;

17% to 23%;

Al;

0.002% to 0.5%;

either one or both of Nb and Ti; and

two or three elements selected from a group consisting of Ni;

0.25% to 1.5%, Cu;

0.25% to 1%, and Mo;

0.5% to 2%,

with the remainder being Fe and unavoidable impurities,

wherein Expression (3) and Expression (4) illustrated below are satisfied, and

wherein an oxide film is formed on a surface thereof and (Nb, Ti) carbonitrides containing either one or both Nb and Ti are produced on the surface by heat treatment in a vacuum atmosphere containing N₂ with a vacuum of 10<sup>−

2</sup> torr to 1 torr, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 40% or more and Cr in a cationic fraction of 20% or more,

8(C+N)+0.03≦

Nb+Ti≦

0.6 

 

(3)

Si+Cr+Al+{Nb+Ti−

8(C+N)}≧

17.5 

 

(4)

each element symbol represents the content (mass %) of the element in Expression (3) and Expression (4), and in addition, the value of Nb+Ti−

8(C+N) is equal to or greater than 0 in Expression (4).

6. The ferritic stainless steel for an exhaust heat recovery unit according to claim 5, further comprising, by mass %:

one or more elements selected from a group consisting of V;

0.5% or less, W;

1% or less, B;

0.005% or less, Zr;

0.5% or less, Sn;

0.5% or less, Co;

0.2% or less, Mg;

0.002% or less, Ca;

0.002% or less, and REM;

0.01% or less.

7. An exhaust heat recovery unit comprising:

a heat exchange section of which members are fabricated by brazing,

wherein the heat exchange section is made of a ferritic stainless steel,

wherein the ferritic stainless steel comprises, by mass %;

C;

0.03% or less;

N;

0.05% or less;

Si;

more than 0.1% to 1% or less;

Mn;

0.02% to 1.2%;

Cr;

17% to 23%;

Al;

0.002% to 0.5%;

either one or both of Nb and Ti; and

two or three elements selected from a group consisting of Ni;

0.25% to 1.5%, Cu;

0.25% to 1% and Mo;

0.5% to 2%, with the remainder being Fe and unavoidable impurities,

wherein Expression (3) and Expression (4) illustrated below are satisfied, and

wherein an oxide film is formed on a surface thereof and (Nb, Ti) carbonitrides containing either one or both Nb and Ti are produced on the surface by heat treatment in a vacuum atmosphere containing N₂ with a vacuum of 10<sup>−

2</sup> torr to 1 torr, and the oxide film contains Cr, Si, Nb, Ti and Al in a total cationic fraction of 40% or more and Cr in a cationic fraction of 20% or more,

8(C+N)+0.03≦

Nb+Ti≦

0.6 

 

(3)

Si+Cr+Al+{Nb+Ti−

8(C+N)}≧

17.5 

 

(4)

each element symbol represents the content (mass %) of the element in Expression (3) and Expression (4), and the value of Nb+Ti−

8(C+N) is equal to or greater than 0 in Expression (4).

8. The exhaust heat recovery unit according to claim 7,

wherein the ferritic stainless steel further comprises one or more elements selected from a group consisting of, by mass %, V:

0.5% or less, W;

1% or less, B;

0.005% or less, Zr;

0.5% or less, Sn;

0.5% or less, Co;

0.2% or less, Mg;

0.002% or less, Ca;

0.002% or less, and REM;

0.01% or less.