U.S. patent application number 14/238959 was filed with the patent office on 2014-07-31 for first layer or upper layer welding section of high cr steel turbine rotor, overlay welding material for welding section, and method for manufacturing overlay welding section.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.). The applicant listed for this patent is Yuta Honma, Rinzo Kayano, Mikihiro Sakata, Ken Yamashita. Invention is credited to Yuta Honma, Rinzo Kayano, Mikihiro Sakata, Ken Yamashita.
Application Number | 20140212323 14/238959 |
Document ID | / |
Family ID | 47715216 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140212323 |
Kind Code |
A1 |
Honma; Yuta ; et
al. |
July 31, 2014 |
FIRST LAYER OR UPPER LAYER WELDING SECTION OF HIGH Cr STEEL TURBINE
ROTOR, OVERLAY WELDING MATERIAL FOR WELDING SECTION, AND METHOD FOR
MANUFACTURING OVERLAY WELDING SECTION
Abstract
The present invention relates to a multilayer overlay welding
section in which a first layer of an overlay welding section to be
formed on the bearing contact surface of a high Cr steel turbine
rotor includes C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5% with a remainder including Fe
and unavoidable impurities, a multilayer overlay welding section in
which, in addition to the above layer, an upper layer welding
section includes C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 2.5%,
Cr: 1.0 to 4.0%, and Mo: 0.5 to 1.5%, and a welding material
therefor and a process for producing the multilayer overlay welding
section.
Inventors: |
Honma; Yuta; (Hokkaido,
JP) ; Kayano; Rinzo; (Hokkaido, JP) ; Sakata;
Mikihiro; (Kanagawa, JP) ; Yamashita; Ken;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Honma; Yuta
Kayano; Rinzo
Sakata; Mikihiro
Yamashita; Ken |
Hokkaido
Hokkaido
Kanagawa
Kanagawa |
|
JP
JP
JP
JP |
|
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO SHO
(KOBE STEEL, LTD.)
Hyogo
JP
THE JAPAN STEEL WORKS, LTD.
Tokyo
JP
|
Family ID: |
47715216 |
Appl. No.: |
14/238959 |
Filed: |
August 17, 2012 |
PCT Filed: |
August 17, 2012 |
PCT NO: |
PCT/JP2012/070923 |
371 Date: |
February 14, 2014 |
Current U.S.
Class: |
420/91 |
Current CPC
Class: |
C22C 38/24 20130101;
C22C 38/105 20130101; C22C 38/12 20130101; C22C 38/16 20130101;
C22C 38/20 20130101; C22C 38/52 20130101; C22C 38/22 20130101; B23K
9/04 20130101; B23K 35/3053 20130101; C22C 38/001 20130101; B23K
35/3093 20130101; C22C 38/32 20130101; C22C 38/08 20130101; B23K
35/308 20130101; B23K 2101/001 20180801; C22C 38/00 20130101; B23K
35/30 20130101; C22C 38/46 20130101; B23K 35/3086 20130101; C22C
38/54 20130101; C22C 38/30 20130101; C22C 38/44 20130101; C22C
38/04 20130101; C22C 38/40 20130101; C22C 38/42 20130101; C22C
38/48 20130101; C22C 38/02 20130101 |
Class at
Publication: |
420/91 |
International
Class: |
C22C 38/02 20060101
C22C038/02; C22C 38/08 20060101 C22C038/08; C22C 38/10 20060101
C22C038/10; C22C 38/12 20060101 C22C038/12; C22C 38/40 20060101
C22C038/40; C22C 38/20 20060101 C22C038/20; C22C 38/22 20060101
C22C038/22; C22C 38/24 20060101 C22C038/24; C22C 38/30 20060101
C22C038/30; C22C 38/32 20060101 C22C038/32; C22C 38/04 20060101
C22C038/04; C22C 38/16 20060101 C22C038/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2011 |
JP |
2011-178628 |
Claims
1. A first layer welding section of a high Cr steel turbine rotor,
which is a first layer welding section among a multilayer overlay
welding section formed on a bearing contact surface of the high Cr
steel turbine rotor, the first layer welding section comprising, in
terms of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
1.5%, Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, V: 0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B:
0.005% or less, W: 1.5% or less, and Nb: 0.07% or less in terms of
% by weight based on the first layer welding section.
2. The first layer welding section of the high Cr steel turbine
rotor according to claim 1, which satisfies an expression (1):
Pcr(1)=(a Cr amount in the first layer welding
section).times.0.65-(a Cr amount of the high Cr steel turbine
rotor-the Cr amount in the first layer welding
section).times.0.35>0.7 (1).
3. An overlay welding material for a first layer welding section of
a high Cr steel turbine rotor, which is a welding material for
obtaining the first layer welding section according to claim 1
among the multilayer overlay welding section formed on the bearing
contact surface of the high Cr steel turbine rotor, the welding
material comprising, in terms of % by weight: C: 0.03 to 0.2%, Si:
0.1 to 1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%,
with a remainder including Fe and unavoidable impurities, in which
the unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the welding
material.
4. An upper layer welding section of a high Cr steel turbine rotor,
which is an upper layer welding section formed on the first layer
welding section according to claim 1, among the multilayer overlay
welding section formed on the bearing contact surface of the high
Cr steel turbine rotor, the upper layer welding section comprising,
in terms of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3
to 2.5%, Cr: 1.0 to 4.0%, and Mo: 0.5 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, V: 0.15% or less, Ni: 0.3% or less, and Nb: 0.07% or less
in terms of % by weight based on the upper layer welding
section.
5. The upper layer welding section of the high Cr steel turbine
rotor according to claim 4, wherein an amount of V contained in the
upper layer welding section is smaller than an amount of V
contained in the first layer welding section.
6. The upper layer welding section of the high Cr steel turbine
rotor according to claim 4, which satisfies an expression (2):
Pcr(n)=(a Cr amount in the upper layer welding section at n-th
layer).times.0.65-{a Cr amount in the upper layer welding section
at (n-1)-th layer-the Cr amount in the upper layer welding section
at the n-th layer}.times.0.35>0.7 (2), in which when N
represents the number of layers constituting the multilayer overlay
welding section, 2.ltoreq.n.ltoreq.N.
7. An overlay welding material for an upper layer welding section
of a high Cr steel turbine rotor, which is a welding material for
obtaining the upper layer welding section according to claim 4
formed on the first layer welding section of the multilayer overlay
welding section formed on the bearing contact surface of the high
Cr steel turbine rotor, the welding material comprising, in terms
of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 3.0%,
Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, and
V: 0.1% or less, and a sum of one or more kinds selected from the
group consisting of Ni, Nb and Ti is 0.2% or less in terms of % by
weight based on the welding material.
8. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 4 on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section comprising, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
9. The upper layer welding section of the high Cr steel turbine
rotor according to claim 5, which satisfies an expression (2):
Pcr(n)=(a Cr amount in the upper layer welding section at n-th
layer).times.0.65-{a Cr amount in the upper layer welding section
at (n-1)-th layer-the Cr amount in the upper layer welding section
at the n-th layer}.times.0.35>0.7 (2), in which when N
represents the number of layers constituting the multilayer overlay
welding section, 2.ltoreq.n.ltoreq.N.
10. An overlay welding material for an upper layer welding section
of a high Cr steel turbine rotor, which is a welding material for
obtaining the upper layer welding section according to claim 5
formed on the first layer welding section of the multilayer overlay
welding section formed on the bearing contact surface of the high
Cr steel turbine rotor, the welding material comprising, in terms
of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 3.0%,
Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, and
V: 0.1% or less, and a sum of one or more kinds selected from the
group consisting of Ni, Nb and Ti is 0.2% or less in terms of % by
weight based on the welding material.
11. An overlay welding material for an upper layer welding section
of a high Cr steel turbine rotor, which is a welding material for
obtaining the upper layer welding section according to claim 6
formed on the first layer welding section of the multilayer overlay
welding section formed on the bearing contact surface of the high
Cr steel turbine rotor, the welding material comprising, in terms
of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 3.0%,
Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, and
V: 0.1% or less, and a sum of one or more kinds selected from the
group consisting of Ni, Nb and Ti is 0.2% or less in terms of % by
weight based on the welding material.
12. An overlay welding material for an upper layer welding section
of a high Cr steel turbine rotor, which is a welding material for
obtaining the upper layer welding section according to claim 9
formed on the first layer welding section of the multilayer overlay
welding section formed on the bearing contact surface of the high
Cr steel turbine rotor, the welding material comprising, in terms
of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 3.0%,
Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, and
V: 0.1% or less, and a sum of one or more kinds selected from the
group consisting of Ni, Nb and Ti is 0.2% or less in terms of % by
weight based on the welding material.
13. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 5 on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section comprising, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
14. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 6 on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section comprising, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
15. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 9 on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section comprising, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
16. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 7 on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section comprising, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
17. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 10 on an upper layer of
the thus-formed first layer welding section by welding using an
overlay welding material for the upper layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the upper layer welding section.
18. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 11 on an upper layer of
the thus-formed first layer welding section by welding using an
overlay welding material for the upper layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the upper layer welding section.
19. A process for producing a multilayer overlay welding section of
a high Cr steel turbine rotor, the process comprising: forming a
first layer welding section of a high Cr steel turbine rotor, which
is a first layer welding section among a multilayer overlay welding
section formed on a bearing contact surface of the high Cr steel
turbine rotor, the first layer welding section comprising, in terms
of % by weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%,
Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5%, with a remainder including Fe
and unavoidable impurities, in which the unavoidable impurities
contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V:
0.2% or less, Ni: 0.3% or less, Co: 1.5% or less, B: 0.005% or
less, W: 1.5% or less, and Nb: 0.07% or less in terms of % by
weight based on the first layer welding section, on the bearing
contact surface of the high Cr steel turbine rotor by welding using
an overlay welding material for the first layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section, and forming the upper
layer welding section according to claim 12 on an upper layer of
the thus-formed first layer welding section by welding using an
overlay welding material for the upper layer welding section
comprising, in terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to
1.0%, Mn: 0.3 to 3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a
remainder including Fe and unavoidable impurities, in which the
unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the upper layer welding section.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multilayer overlay for
forming a Cr-containing steel overlay on a surface with which
bearings of a high Cr steel turbine rotor come into contact.
BACKGROUND ART
[0002] Since a high Cr steel is excellent in high-temperature
strength and low-temperature toughness, the steel has been
increasingly used as a material for high-pressure and
medium-pressure turbine rotors of generators. However, the contact
surface with the bearings of the high Cr steel turbine rotor is
prone to develop seizure at the bearings during its use, so that
there is a concern of inviting damage. Therefore, there has been
proposed a method for preventing the generation of seizure by
overlay welding a low alloy steel on the bearing part of the rotor
(e.g., see Patent Document 1).
[0003] Heretofore, with regard to such a kind of overlay welding,
mainly welding materials and welding methods for submerge arc
welding have been developed.
[0004] For example, Patent Document 2 proposes a welding material
to be applied to a journal part of a turbine rotor and, in
consideration of weld residual stress, discloses one using a
welding material having low strength and large linear expansion
coefficient as a first layer welding material as compared with a
low alloy steel of an upper layer and a rotor substrate.
[0005] Moreover, in the invention described in Patent Document 3,
it is intended to reduce a difference in the level of strength for
the purpose of an increase in fatigue strength. Patent Document 4
discloses intention of an improvement in fatigue strength by using
a welding material having a high Cr content as a first layer.
BACKGROUND ART DOCUMENT
Patent Document
[0006] Patent Document 1: JP-A-57-137456 [0007] Patent Document 2:
JP-A-6-272503 [0008] Patent Document 3: JP-A-9-76091 [0009] Patent
Document 4: JP-A-9-066388
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0010] However, since the welding material used in the first layer
welding material described in Patent Document 2 contains no Cr,
accumulation of strain occurs in the first layer at shape
discontinuous parts such as a thrust part during stress relief
annealing and there is a possibility of generation of defects such
as cracks in some cases, depending on the strength of the upper
layer.
[0011] Also, in the execution with the welding material having a Cr
amount of 1.0% for the first layer defined in the invention
described in Patent Document 3, there is a concern that the Cr
content of the welding section decreases and further there is a
concern that diffusion of C and the like occurs and the strength at
the welding metal side decreases due to the difference in the Cr
amount between the base material and the welding metal during the
stress relief annealing after welding.
[0012] As above, in the conventional technologies, since the Cr
content of the welding material which comes into contact with the
rotor substrate is low and strength balance among the rotor
substrate, the first layer, and the upper layer is not considered,
the residual stress induced by welding is high. Also, in the shape
discontinuous parts such as the thrust part at which stress
concentration is prone to occur due to the shape, there is a
concern of occurrence of defects. In Patent Document 4, although a
welding material having a high Cr content is used for the first
layer, it is supposed that stress relief annealing crack
susceptibility increases through component dilution by welding
depending on the components of the rotor base material, so that
there is room for improvement.
[0013] Accordingly, an object of the present invention is to
provide a combination of overlay welding materials for the first
layer or the upper layer and a first layer or upper layer welding
section obtained therefrom, and a process for producing a
multilayer overlay welding section, which satisfy the strength and
toughness required for a high Cr steel turbine rotor bearing part
and are used for avoiding cracks during the stress relief
annealing.
Means for Solving the Problems
[0014] Namely, a first invention relates to a first layer welding
section among a multilayer overlay welding section formed on a
bearing contact surface of a high Cr steel turbine rotor, and the
first layer welding section includes, in terms of % by weight: C:
0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.5%, Cr: 4.0 to 7.7%,
and Mo: 0.5 to 1.5%, with a remainder including Fe and unavoidable
impurities, in which the unavoidable impurities contain P: 0.015%
or less, S: 0.015% or less, Cu: 0.2% or less, V: 0.2% or less, Ni:
0.3% or less, Co: 1.5% or less, B: 0.005% or less, W: 1.5% or less,
and Nb: 0.07% or less in terms of % by weight based on the first
layer welding section.
[0015] A second invention relates to the first layer welding
section among the multilayer overlay welding section formed on the
bearing contact surface of the high Cr steel turbine rotor, and in
the first invention, the following expression (1) is satisfied:
Pcr(1)=(a Cr amount in the first layer welding
section).times.0.65-(a Cr amount of the high Cr steel turbine
rotor-the Cr amount in the first layer welding
section).times.0.35>0.7 (1).
[0016] A third invention relates to an overlay welding material for
a first layer welding section for obtaining the first layer welding
section according to the first or second invention, among the
multilayer overlay welding section formed on the bearing contact
surface of the high Cr steel turbine rotor, and the welding
material includes, in terms of % by weight: C: 0.03 to 0.2%, Si:
0.1 to 1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo: 0.1 to 1.5%,
with a remainder including Fe and unavoidable impurities, in which
the unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the first layer welding section.
[0017] A fourth invention relates to an upper layer welding section
formed on the first layer welding section according to the first or
second invention, among the multilayer overlay welding section
formed on the bearing contact surface of the high Cr steel turbine
rotor, the upper layer welding section includes, in terms of % by
weight: C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 2.5%, Cr: 1.0
to 4.0%, and Mo: 0.5 to 1.5%, with a remainder including Fe and
unavoidable impurities, in which the unavoidable impurities contain
P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V: 0.15% or
less, Ni: 0.3% or less, and Nb: 0.07% or less in terms of % by
weight based on the upper layer welding section.
[0018] A fifth invention relates to the upper layer welding section
of the high Cr steel turbine rotor, and in the fourth invention, an
amount of V contained in the upper layer welding section is smaller
than an amount of V contained in the first layer welding section
according to the first or second invention.
[0019] A sixth invention relates to the upper layer welding section
of the high Cr steel turbine rotor, and in the fourth or fifth
invention, the following expression (2) is satisfied:
Per(n)=(a Cr amount in the upper layer welding section at n-th
layer).times.0.65-{a Cr amount in the upper layer welding section
at (n-1)-th layer-the Cr amount in the upper layer welding section
at the n-th layer}.times.0.35>0.7 (2),
in which when N represents the number of layers constituting the
multilayer overlay welding section, 2.ltoreq.n.ltoreq.N.
[0020] A seventh invention relates to an overlay welding material
for an upper layer welding section for obtaining the upper layer
welding section according to any one of the fourth to sixth
inventions formed on the first layer welding section of the
multilayer overlay welding section formed on the bearing contact
surface of the high Cr steel turbine rotor, and the welding
material includes, in terms of % by weight: C: 0.03 to 0.2%, Si:
0.1 to 1.0%, Mn: 0.3 to 3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%,
with a remainder including Fe and unavoidable impurities, in which
the unavoidable impurities contain P: 0.015% or less, S: 0.015% or
less, Cu: 0.2% or less, and V: 0.1% or less, and a sum of one or
more kinds selected from the group consisting of Ni, Nb and Ti is
0.2% or less in terms of % by weight based on the overlay welding
material for the upper layer welding section.
[0021] A eighth invention relates to a process for producing a
multilayer overlay welding section of a high Cr steel turbine
rotor, the process including:
[0022] forming the first layer welding section according to the
first or second invention on the bearing contact surface of the
high Cr steel turbine rotor by welding using an overlay welding
material for the first layer welding section including, in terms of
% by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.2%, Cr:
2.0 to 5.5%, and Mo: 0.1 to 1.5%, with a remainder including Fe and
unavoidable impurities, in which the unavoidable impurities contain
P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less, and V: 0.1%
or less, and a sum of one or more kinds selected from the group
consisting of Ni, Nb and Ti is 0.2% or less in terms of % by weight
based on the overlay welding material for the first layer welding
section, and
[0023] forming the upper layer welding section according to any one
of the fourth to sixth inventions on an upper layer of the
thus-formed first layer welding section by welding using an overlay
welding material for the upper layer welding section including, in
terms of % by weight: C: 0.03 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5%, with a remainder
including Fe and unavoidable impurities, in which the unavoidable
impurities contain P: 0.015% or less, S: 0.015% or less, Cu: 0.2%
or less, and V: 0.1% or less, and a sum of one or more kinds
selected from the group consisting of Ni, Nb and Ti is 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section.
Advantage of the Invention
[0024] According to the upper layer welding section of the present
invention, ferrite is not formed at the boundary part between the
first layer and the upper layer, also it is possible to suppress
stress relief annealing cracks, and bearings can be prevented from
seizing with satisfying strength and toughness required for the
bearing part.
[0025] Furthermore, the strength balance among the base material,
the first layer, and the upper layer is made most suitable by
combining the first layer welding section according to the first
invention and the second invention as mentioned above with the
upper layer welding section, so that the strain concentration to
the first layer can be prevented during stress relief annealing.
Thereby, the execution becomes possible without generating stress
relief annealing cracks even for the welding of the thrust part
which may develop large residual stress at welding. Also, by
considering the difference in the Cr amount in each layer, an
overlay-strengthened high Cr steel turbine rotor having stable
quality can be provided with preventing the formation of
pro-eutectoid ferrite.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a side view showing an outline of a high Cr steel
turbine rotor in the invention.
[0027] FIG. 2 is a schematic view showing an analysis portion to be
measured at the time of property evaluation of inside of a first
layer welding section or an upper layer welding section and a
sampling position of a test piece for a high-temperature low strain
rate tensile test.
[0028] FIG. 3 is a graph showing a relationship between the Cr
amount and reduction of area at a high-temperature low strain rate
tensile test using Cr variation materials.
[0029] FIGS. 4(a) to 4(d) are schematic views showing a ring crack
test piece for evaluating stress relief annealing crack
susceptibility at the first layer welding section. FIG. 4(a) is a
drawing showing a sampling position of the test piece for use in
the test. FIG. 4(b) is a side view of the test piece. FIG. 4(c) is
a front view of the test piece. FIG. 4(d) is an enlarged view of
the A part in FIG. 4(c). The unit of values of the sizes in FIGS.
4(a) to 4(d) is "mm".
[0030] FIG. 5 is a schematic view showing a step of imparting
tensile residual stress to a U notch bottom part at the time of
conducting the ring crack test.
[0031] FIG. 6 is a schematic view showing the shape of the test
piece for a high-temperature low strain rate tensile test. The unit
of values of the sizes in FIG. 6 is "mm".
MODE FOR CARRYING OUT THE INVENTION
[0032] The following will describe embodiments of the present
invention in detail but the invention is not limited thereto and
can be implemented in any variations.
<First Layer Welding Section>
[0033] The components of the first layer welding section according
to the invention contain C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3
to 1.5%, Cr: 4.0 to 7.7%, and Mo: 0.5 to 1.5% in terms of % by
weight and a remainder includes Fe and unavoidable impurities. The
following will describe the meanings of these components and, when
the first layer welding section has the above-mentioned
composition, a difference in the level of strength among the base
material and the overlay first layer or subsequent overlay layers
can be suppressed to a degree at which problems do not practically
arise and thus stress relief annealing cracks in the first layer
can be suppressed. The contents in the following are all shown in
terms of % by weight.
C: 0.05 to 0.2%
[0034] Since C is a necessary additive element from the viewpoint
of securing the tensile strength of the welding section, a lower
limit thereof is set to 0.05%. On the other hand, in view of a
decrease in an impact value and an increase in weld crack
susceptibility, an upper limit thereof is set to 0.2%.
Si: 0.1 to 1.0%
[0035] Since Si is an element necessary as a deoxidizer or for
securing strength, a lower limit thereof is set to 0.1%. However,
since an excessive content of Si promotes cracks such as stress
relief annealing cracks and invites a decrease in toughness, an
upper limit thereof is set to 1.0%. For the same reason, the lower
limit thereof is preferably set to 0.25% and the upper limit is
desirably set to 0.7%.
Mn: 0.3 to 1.5%
[0036] Since Mn is an element necessary as a deoxidizer or for
securing strength similarly to Si, a lower limit thereof is set to
0.3%. However, since an excessive content of Mn invites a decrease
in toughness, an upper limit thereof is set to 1.5%. For the same
reason, the upper limit is set to desirably 1.2%, more desirably
1.0%.
Cr: 4.0 to 7.7%
[0037] Cr is an important element for securing strength and
toughness. In order to suppress the strain concentration to the
first layer, suppress the difference in Cr from the base material,
and prevent the formation of ferrite, a lower limit thereof is set
to 4.0%. However, since an excessive content of Cr increases
hardenability and enhances weld crack susceptibility, an upper
limit thereof is set to 7.7%. For the same reason, the upper limit
is desirably set to 6.7%.
Mo: 0.5 to 1.5%
[0038] Since Mo precipitates as a carbide during the stress relief
annealing and enhances temper softening resistance, it is an
important element for obtaining strength after the stress relief
annealing. In order to suppress the strain concentration during the
stress relief annealing, a lower limit thereof is set to 0.5%.
However, since an excessive content of Mo enhances cracking ability
and invites a decrease in toughness, an upper limit thereof is set
to 1.5%. For the same reason, the upper limit is desirably set to
1.0%.
[0039] The essential constituting elements of the first layer
welding section are as mentioned above. Also, the remainder
substantially contains Fe and unavoidable impurities resulting from
dilution from the base material. As the unavoidable impurities, the
first layer welding section may contain P: 0.015% or less, S:
0.015% or less, Cu: 0.2% or less, V: 0.2% or less, Ni: 0.3% or
less, Co: 1.5% or less, B: 0.005% or less, W: 1.5% or less, and Nb:
0.07% or less in terms of % by weight based on the whole first
layer welding section. The following will describe reasons
thereof.
P: 0.015% or less
[0040] P is an impurity element that mixes in from a raw material
during the smelting of a metal material. Since P has a possibility
of decreasing toughness, it is desirable to reduce it as far as
possible. Therefore, the content of P is set to 0.015% or less.
S: 0.015% or less
[0041] Similarly to P, S is an impurity element that mixes in from
a raw material during the smelting of a metal material. Since S has
a possibility of decreasing toughness, it is desirable to reduce it
as far as possible. Therefore, the content of S is set to 0.015% or
less.
Cu: 0.2% or less
[0042] Since Cu has a possibility of decreasing the toughness of
the welding section, an upper limit of the content is set to 0.2%
or less.
V: 0.2% or less
[0043] V is known as an element for increasing the temper softening
resistance to obtain strength after stress relief annealing.
However, from the studies of the present inventors, it has been
found that V extremely elevates the stress relief annealing crack
susceptibility. Therefore, the content of V is limited to 0.2%,
preferably 0.1% at most.
Ni: 0.3% or less
[0044] Since an excessive content of Ni has a possibility of
causing temper embrittlement, the content of Ni is limited to 0.3%
at most.
Co: 1.5% or less
[0045] In the case where the base material contains Co, the content
of Co should be suppressed to an increase by dilution/fusion from
the base material during welding and is limited to 1.5% at
most.
B: 0.005% or less W: 1.5% or less Nb: 0.07% or less
[0046] These elements are generally known as elements that improve
temper softening resistance during the stress relief annealing and
secure room-temperature strength. However, from the studies of the
present inventors, it has been found that an excessive content of
each element decreases toughness and also degrades welding ability.
Therefore, in the invention, as for the contents of these
components, upper limits are determined to the above values,
respectively.
[0047] The Cr amount contained in the first layer welding section
according to the invention preferably satisfies the following
expression (1):
Pcr(1)=(Cr amount in first layer welding section).times.0.65-(Cr
amount in high Cr steel turbine rotor-Cr amount in first layer
welding section).times.0.35>0.7 (1)
[0048] With an increase in the Cr content of the first layer
welding section and a decrease in the difference from the Cr amount
in the high Cr steel turbine rotor, the ferrite formation during
the stress relief annealing is suppressed. When the Pcr (1) value
represented by the above expression (1) is a value exceeding 0.7,
the ferrite formation is suppressed at the boundary between the
base material and the first layer welding section and an
overlay-strengthened high Cr steel turbine rotor having stable
quality can be obtained. Incidentally, the Cr amounts in the above
expression (1) are all represented in terms of % by weight.
<Welding Material for First Layer Welding Section>
[0049] In the welding material for obtaining the above first layer
welding section, the dilution of the components occurs with the
base material during the overlay welding on the base material and
also the dilution of the components occurs with the upper layer to
be welded on the upper layer. The dilution of the components occurs
through the fusion of a part of the neighboring layers during
welding and the migration of the components from a layer having
high concentration of the components to a layer having low
concentration thereof. It is generally sufficient that the base
material is a high Cr steel to be commonly used as a turbine rotor
for thermal power generation and particularly, the material thereof
is preferably 12Cr steel, more preferably one so-called new 12Cr
steel in which W, Co, and B are added thereto.
[0050] With considering the aforementioned dilution, the welding
material for the first layer welding section is defined for
obtaining the above composition of the first layer welding section.
Thereby, the action and effect of the first layer welding section
can be exhibited.
[0051] By using the welding material for the first layer welding
section as an overlay first layer in the high Cr rotor substrate, a
difference in the level of strength between the base material and
the overlay first layer or subsequent overlay layers can be
suppressed to a degree at which no problem arises practically and
the stress relief annealing cracks can be suppressed in the first
layer. Moreover, for the welding material, by suppressing the
difference in the Cr content between the base material and the
first layer welding metal so that the first layer welding section
satisfies the above expression (1), the formation of ferrite can be
suppressed.
[0052] Specifically, the welding material for the first layer
welding section according to the invention includes C: 0.03 to
0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.2%, Cr: 2.0 to 5.5%, and Mo:
0.1 to 1.5% in terms of % by weight, and the remainder includes Fe
and unavoidable impurities. The unavoidable impurities are
desirably P: 0.015% or less, S: 0.015% or less, Cu: 0.2% or less,
and V: 0.1% or less, and the sum of one or more kinds selected from
the group consisting of Ni, Nb, and Ti is 0.2% or less in terms of
% by weight based on the welding material for the first layer
welding section.
[0053] The following will specifically describe individual
components.
C: 0.03 to 0.2%
[0054] The C content of the first layer welding section according
to the invention ranges from 0.05 to 0.2% and there is a case where
the base material component exceeds the upper limit of the C
content range of the first layer welding section. In consideration
of the dilution/fusion with the base material component during
welding, it is desirable that a lower limit of the C content in the
welding material is set to 0.03% and an upper limit thereof is set
to 0.2% in view of welding workability and the like, for making the
C content of the first layer welding section fall within the above
range.
Si: 0.1 to 1.0%
[0055] The Si content of the first layer welding section according
to the invention ranges from 0.1 to 1.0%. In consideration of the
dilution/fusion with the base material component during welding,
the Si content in the welding material desirably ranges from 0.1 to
1.0%, for making the Si content of the first layer welding section
fall within the above range.
Mn: 0.3 to 1.2%
[0056] The Mn content of the first layer welding section according
to the invention ranges from 0.3 to 1.5% and there is a case where
the base material component exceeds the upper limit of the Mn
content range of the first layer welding section. In consideration
of the dilution/fusion with the base material component during
welding, it is desirable that a lower limit of the Mn content in
the welding material is 0.3% for assuring the effect as a
deoxidizer and an upper limit thereof is 1.2% so as not to exceed
the upper limit of the component range of the first layer welding
section.
Cr: 2.0 to 5.5%
[0057] The Cr content of the first layer welding section according
to the invention ranges from 4.0 to 7.7%. In consideration of the
dilution/fusion with the base material component during welding,
the Cr content in the welding material desirably ranges from 2.0 to
5.5% for obtaining the component range of the first layer welding
section.
Mo: 0.1 to 1.5%
[0058] The Mo content of the first layer welding section according
to the invention ranges from 0.5 to 1.5%. In consideration of the
dilution/fusion with the base material component during welding,
the Mo content in the welding material desirably ranges from 0.5 to
1.5% for obtaining the component range of the first layer welding
section.
[0059] As the impurities contained in the welding material, there
may be mentioned P, S, Cu, V, Ni, Nb, Ti, W, Co, B, and the
like.
[0060] As the impurities of the first layer welding section defined
in the invention, the following are allowed: P: 0.015% or less, S:
0.015% or less, and Cu: 0.2% or less. These are components that
deteriorate mechanical properties and welding ability of both the
welding section and base material and, also in the welding material
for the first layer, the same component range is desirable as that
of the first layer welding section.
V: 0.1% or less
[0061] V is a component contained in the base material. For
obtaining the range, i.e., 0.2% or less, of the first layer welding
section according to the invention, the V content in the welding
material is desirably 0.1% or less in consideration of the
dilution/fusion during welding.
The sum of one or more kinds selected from the group consisting of
Ni, Nb, and Ti being 0.2% or less
[0062] Ni and Nb are elements contained in the base material. For
obtaining Ni: 0.3% or less and Nb: 0.07% or less that are the
ranges of the first layer welding section according to the
invention, the contents thereof in the welding material are
desirably as low as possible in consideration of the
dilution/fusion during welding.
[0063] Moreover, Ti is an element that is usually hardly contained
in the base material. However, since Ti increases the formation of
non-metal inclusion when remains, the content thereof in the
welding material is desirably as low as possible. Therefore, the
sum of one or more kinds selected from the group consisting of Ni,
Nb, and Ti is desirably 0.2% or less.
[0064] W, Co, and B are components that may be contained in the
base material. For obtaining W: 1.5% or less, Co: 1.5% or less, and
B: 0.005% or less that are the ranges of the first layer welding
section according to the invention, the contents thereof are
desirably as low as possible within the ranges unavoidably
contained by a usual process for producing the welding
material.
<Upper Layer Welding Section>
[0065] The components constituting the upper layer according to the
invention contain C: 0.05 to 0.2%, Si: 0.1 to 1.0%, Mn: 0.3 to
2.5%, Cr: 1.0 to 4.0%, and Mo: 0.5 to 1.5% in terms of % by weight
and the remainder includes Fe and unavoidable impurities.
[0066] The following will describe reasons for defining the
components of the upper layer welding section of the invention.
Incidentally, the contents in the following are all represented in
terms of % by weight.
C: 0.05 to 0.2%
[0067] Since C is a necessary additive element for imparting a
necessary strength to the bearing surface, a lower limit thereof is
set to 0.05%. However, since the impact value is lowered and the
weld crack susceptibility becomes high when the content thereof
exceeds 0.2%, an upper limit thereof is set to 0.2%.
Si: 0.1 to 1.0%
[0068] Since Si is an element necessary as a deoxidizer or for
securing strength as shown in the first layer overlay welding
metal, the content thereof is limited to 0.1% at least. However,
since an excessive content of Si promotes cracks such as stress
relief annealing cracks and invites a decrease in toughness, an
upper limit thereof is set to 1.0%. For the same reason, the lower
limit is desirably set to 0.3% and the upper limit is desirably set
to 0.7%.
Mn: 0.3 to 2.5%
[0069] Since Mn is an element necessary as a deoxidizer or for
securing strength similarly to Si, a lower limit thereof is set to
0.3%. However, since an excessive content of Mn invites a decrease
in toughness, an upper limit thereof is set to 2.5%. For the same
reason, the lower limit is desirably set to 0.7% and the upper
limit is desirably set to 2.0%, and further, the lower limit is
more desirably set to 1.0%.
Cr: 1.0 to 4.0%
[0070] Cr is an important element for securing strength and
toughness. In order to suppress the difference in Cr from the first
layer and prevent the formation of ferrite, a lower limit thereof
is set to 1.0%. However, since strain is concentrated to the first
layer owing to too high strength when the content exceeds 4.0% and
a crack may be generated in some cases during the stress relief
annealing, an upper limit thereof is set to 4.0%.
Mo: 0.5 to 1.5%
[0071] Since Mo precipitates as a carbide during the stress relief
annealing and enhances temper softening resistance, it is an
important element for obtaining strength after the stress relief
annealing. In order to suppress the strain concentration during the
stress relief annealing, a lower limit thereof is set to 0.5%.
However, an excessive content thereof enhances the stress relief
annealing crack susceptibility and invites a decrease in toughness,
an upper limit thereof is set to 1.5%.
[0072] The essential constituting elements of the upper layer
welding section are as mentioned above and the remainder
substantially contains Fe. However, minute amounts of unavoidable
impurities such as S, P, and Ni may be further contained in the
range where the above properties are not inhibited. Seizure
resistance can be made excellent by using the above upper layer
welding section as an upper layer in the high Cr steel turbine
rotor substrate, and the formation of ferrite can be suppressed by
suppressing the difference in the Cr content between the first
layer and the upper layer welding section.
[0073] As the unavoidable impurities, there may be contained P:
0.015% or less, S: 0.015% or less, Cu: 0.2% or less, V: 0.15% or
less, Ni: 0.3% or less, and Nb: 0.07% or less in terms of % by
weight based on the upper layer welding section. The following will
describe details.
P: 0.015% or less
[0074] P is an impurity element that mixes in from a raw material
during the smelting of a metal material. Since P has a possibility
of decreasing toughness, it is desirable to reduce it as far as
possible. Therefore, the content of P is set to 0.015% or less.
S: 0.015% or less
[0075] S is also an impurity element that mixes in from a raw
material during the smelting of a metal material. Since S has a
possibility of decreasing toughness, it is desirable to reduce it
as far as possible. Therefore, the content of S is set to 0.015% or
less.
Cu: 0.2% or less
[0076] Since Cu has a possibility of decreasing the toughness of
the welding section, an upper limit thereof is set to 0.2% or
less.
V: 0.15% or less
[0077] V is an element for increasing the temper softening
resistance to obtain strength after the stress relief annealing. On
the other hand, in the case of considering that the prevention of
the stress annealing crack is important, the content of V is
limited. Since V improves the temper softening resistance, the
strain concentration to the first layer occurs and thus a crack may
be generated during the stress annealing in some cases. In order to
avoid it, the V content is limited to 0.15% or less.
[0078] Incidentally, a welding material containing more than 0.15%
of V may be used in combination, for example, with avoiding the
stress annealing cracks by controlling the V content of the welding
section to 0.15% or less using a welding material having a low V
content as the first layer of the upper layer and with controlling
the V content of the welding section of each of the second and
subsequent layers or at least the product surface layer part that
is the outermost surface of the upper layer to 0.15 to 0.3%. In
that case, the Cr content of welding section of the product surface
layer part is desirably 2.5% or less for preventing seizure.
Although a mechanism between the Cr amount and the generation of
seizure is not solved, it is empirically well known for one of
ordinary skill in the art that a risk of the generation of seizure
becomes high when the Cr amount exceeds 2.5%.
[0079] Moreover, the amount of V contained in the upper layer
welding section is preferably smaller than the amount of V
contained in the first layer welding section from the viewpoint of
no occurrence of excessive stress concentration to the first
layer.
Ni: 0.3% or less
[0080] Since an excessive content of Ni has a possibility of
causing temper embrittlement, the content thereof is limited to
0.3% at most.
Nb: 0.07% or less
[0081] Nb improves the temper softening resistance during the
stress relief annealing and secures the room-temperature strength.
However, since an excessive content thereof may decrease toughness
and also degrade welding ability, an upper limit thereof is defined
to be 0.07% in the invention.
[0082] The Cr amount contained in the upper layer welding section
preferably satisfies the following expression (2):
Pcr(n)=(Cr amount in upper layer welding section at n-th
layer).times.0.65-{Cr amount of upper layer welding section at
(n-1)-th layer-Cr amount of upper layer welding section at n-th
layer}.times.0.35>0.7 (2),
in which when N represents the number of layers constituting the
multilayer overlay welding section, 2.ltoreq.n.ltoreq.N.
[0083] By controlling Pcr (n) represented by the above expression
(2) to a value exceeding 0.7 with considering the difference
between the Cr amount of the upper layer welding section at the
n-th layer and the Cr amount of the upper layer welding section at
the (n-1)-th layer, the ferrite formation at the boundaries of
individual layers is suppressed. In this regard, Per (2) means a
calculation value satisfying the expression (2) of an upper layer
that is the 2nd layer (the 1st layer of the upper layer) on the
first layer welding section that is the 1st layer. In this case, in
the expression (2), the upper layer welding section at the (n-1)-th
layer corresponds the first layer welding section. Incidentally,
the Cr amounts in the above expression are all represented in terms
of % by weight.
<Overlay Welding Material for Upper Layer Welding
Section>
[0084] With considering composition variation by the occurrence of
dilution of the components with the first layer welding section
during the overlay welding on the first layer welding section, the
overlay welding material for obtaining the above upper layer
welding section is defined for obtaining the above composition of
the upper layer welding section. By the welding using the overlay
welding material, the above upper layer welding section can be
obtained, and the action and effect of satisfying strength and
toughness and avoiding cracks during the stress relief annealing
can be exhibited.
[0085] Specifically, the overlay welding material for the upper
layer welding section contains C: 0.03 to 0.2%, Si: 0.1 to 1.0%,
Mn: 0.3 to 3.0%, Cr: 1.0 to 2.5%, and Mo: 0.1 to 1.5% in terms of %
by weight, with the remainder including Fe and unavoidable
impurities. The unavoidable impurities desirably contains P: 0.015%
or less, S: 0.015% or less, Cu: 0.2% or less, and V: 0.1% or less,
and the sum of one or more kinds selected from the group consisting
of Ni, Nb, and Ti is 0.2% or less in terms of % by weight based on
the overlay welding material for the upper layer welding
section.
[0086] The following will specifically describe the above
components.
C: 0.03 to 0.2%
[0087] The C content of the upper layer welding section according
to the invention ranges from 0.05 to 0.2%. In consideration of the
dilution/fusion with C contained in the first layer welding section
according to the invention, it is desirable that a lower limit of
the C content in the welding material is set to 0.03% and an upper
limit thereof is set to 0.2% in view of welding workability, in
order not to exceed the upper limit of the C component range of the
upper layer welding section.
Si: 0.1 to 1.0%
[0088] The Si content of the upper layer welding section according
to the invention ranges from 0.1 to 1.0%. In consideration of the
dilution/fusion with Si contained in the first layer welding
section according to the invention, the Si content in the welding
material desirably ranges from 0.1 to 1.0% for obtaining the Si
component range of the upper layer welding section.
Mn: 0.3 to 3.0%
[0089] The Mn content of the upper layer welding section according
to the invention ranges from 0.3 to 2.5%. In consideration of the
dilution/fusion with Mn contained in the first layer welding
section according to the invention, the Mn content in the welding
material is desirably ranges from 0.3% to 3.0% for obtaining the Mn
component range of the upper layer welding section.
Cr: 1.0 to 2.5%
[0090] The Cr content of the upper layer welding section according
to the invention ranges from 1.0 to 4.0%. In consideration of the
dilution/fusion with Cr contained in the first layer welding
section according to the invention, a lower limit of the Cr content
in the welding material is desirably 1.0% so as not to be lower
than the lower limit of the Cr content of the upper layer welding
section. An upper limit thereof is desirably 2.5% so as not to
exceed the upper limit of the Cr content of the upper layer welding
section.
[0091] Moreover, the Cr content of the upper welding section as the
product surface layer part that is the outermost surface of the
upper layer is also desirably 2.5% or less for preventing seizure.
Similarly, an upper limit of the overlay welding material for the
upper layer welding section as the product surface layer part is
also desirably 2.5%.
Mo: 0.1 to 1.5%
[0092] The Mo content of the upper layer welding section according
to the invention ranges from 0.5 to 1.5%. In consideration of the
dilution/fusion with Mo contained in the first layer welding
section according to the invention, the Mo content in the welding
material desirably ranges from 0.1 to 1.5% for obtaining the
component range of the upper layer welding section.
Unavoidable impurities: P, S, Cu, V, Ni, Nb, Ti, W, Co, B
[0093] As the impurities contained in the upper layer overlay
welding material according to the invention, the following are
allowed: P: 0.015% or less, S: 0.015% or less, and Cu: 0.2% or less
in terms of % by weight based on the overlay welding material for
the upper layer welding section. These are components deteriorating
mechanical properties and welding ability, and the same component
ranges are desirable as those of the upper layer welding section
according to the invention.
V: 0.1% or less
[0094] As for V, 0.2% or less of V may be contained in the first
layer welding section by the dilution/fusion from the base
material. Therefore, for obtaining 0.15% or less as the range of
the V content of the upper layer welding section according to the
invention, the V content in the welding material is desirably 0.1%
or less in consideration of the dilution/fusion during binding.
The sum of one or more kinds selected from the group consisting of
Ni, Nb, and Ti being 0.2% or less
[0095] Ni and Nb are elements that may be contained in the base
material. For obtaining Ni: 0.3% or less and Nb: 0.07% or less that
are the ranges of the upper layer welding section defined in the
invention, the contents thereof in the welding material are
desirably as low as possible.
[0096] Moreover, Ti is usually hardly contained in the base
material but, since Ti increases the formation of non-metal
inclusion when remains in the welding section, the content in the
welding material is also desirably as low as possible. Therefore,
the sum of one or more kinds selected from the group consisting of
Ni, Nb, and Ti is desirably 0.2% or less.
[0097] W, Co, and B may be contained in the ranges of W: 1.5% or
less, Co: 1.5% or less, and B: 0.005% or less in the first layer
welding section by the dilution/fusion from the base material.
However, the upper layer welding section does not necessarily
contain these components and, in view of costs, it is sufficient
that the contents fall within the ranges unavoidably contained by a
usual process for producing the welding material.
[0098] With regard to the composition of the welding section, since
the material to be welded is generally melted to a degree of 20 to
40% and is diluted/fused with the welding material during welding,
the elemental composition of the welding material may be determined
with taking the dilution/fusion into account.
<High Cr Steel Turbine Rotor>
[0099] In the invention of the present application, a high Cr steel
turbine rotor is a target of the overlay welding. The high Cr steel
turbine rotor is constituted by a high Cr steel and, for example, a
steel containing 8 to 13% of Cr is exemplified. The composition of
the turbine rotor in the invention is not limited to specific one
and a high Cr steel capable of being used as the turbine rotor is
sufficient.
[0100] The following will exemplify a typical turbine rotor
composition (% by weight).
[0101] C: 0.05 to 0.25%,
[0102] Si: 1.0% or less,
[0103] Mn: 1.5% or less,
[0104] Ni: 1.0% or less,
[0105] Cr: 8 to 13%,
[0106] Mo: 2.0% or less,
[0107] V: 0.05 to 0.4%,
[0108] Nb: 0.01 to 0.1%,
[0109] N: 0.01 to 0.05%,
[0110] W: 0.05 to 5.0%,
[0111] Co: 0.05 to 5.0%, and
[0112] B: 0.015% or less,
with the remainder being Fe and unavoidable impurities.
[0113] FIG. 1 is a schematic view showing a side surface of a high
Cr steel turbine rotor to which the overlay welding material
according to the invention is applied. For example, a steel
containing 8 to 13% by weight of Cr is exemplified.
[0114] A high Cr steel turbine rotor 1 has a journal part 2 and a
thrust part 3 as bearing parts, and the overlay welding section can
be formed by welding to one or both of the journal part 2 and the
thrust part 3 using the welding material according to the
invention.
[0115] At the formation of the overlay welding section, it is
desirable to form the first layer welding section according to the
invention and then to form the upper layer welding section thereon
using the welding material according to the invention. In the
formation of the above first layer and upper layer welding
sections, it is desirable to perform the welding by TIG (Tungsten
Inert Gas) welding, submerge arc welding, or the like. The welding
method and welding conditions in the welding are not particularly
limited in the invention and a known method can be conducted under
known conditions.
[0116] At the welding of an under layer, it is desirable to
determine the Cr content of the first layer so as to satisfy the
following expression (1).
Pcr(1)=(Cr content in first layer welding section).times.0.65-(Cr
content of high Cr steel turbine rotor-Cr content in first layer
welding section).times.0.35>0.7 (1)
[0117] Also, at the welding of overlaying, it is desirable to
determine the Cr content of the upper layer so as to satisfy the
following expression (2).
Pcr(n)=(Cr content in upper layer welding section at n-th
layer).times.0.65-{Cr content in upper layer welding section at
(n-1)-th layer-Cr content in upper layer welding section at n-th
layer}.times.0.35>0.7 (2),
in which when N represents the number of layers constituting the
multilayer overlay welding section, 2.ltoreq.n.ltoreq.N.
EXAMPLES
[0118] The following will describe Examples of the invention.
[0119] Using a 12Cr rotor substrate having a component composition
(the remainder being Fe and unavoidable impurities) shown in Table
1 on the supposition of a high Cr steel turbine rotor, overlay
welding wires each having the component composition (the remainder
being Fe and unavoidable impurities) shown in Table 2 were used as
welding materials for first layer welding sections of Examples or
Comparative Examples and further, overlay welding wires each having
the component composition (the remainder being Fe and unavoidable
impurities) shown in Table 3 were used as overlay welding materials
for upper layer welding sections of Examples or Comparative
Examples.
[0120] The component analysis of the rotor substrate was conducted
in accordance with the prescription of JIS G 1253 (2010) after a
test piece was sampled from an arbitrary portion. The component
analysis of the overlay welding wires as the overlay welding
materials for the first layer welding section or for the upper
layer welding object was conducted in accordance with the
prescription of JIS Z 3317 (2010).
[0121] Using each of the above welding materials, the first layer
and the upper layer was overlay-welded by TIG welding under the
welding conditions shown in Table 4. Thereafter, a test piece was
sampled from the check analysis position 20 shown in FIG. 2 and the
component analysis (check analysis; the remainder being Fe and
unavoidable impurities) of the first layer and upper layer welding
sections was conducted. The component analysis of individual
welding sections was conducted in accordance with the prescription
of JIS G 1253 (2010).
[0122] Furthermore, as shown by .alpha. in FIG. 2, a tensile test
piece was sampled from each test piece so that the first layer
welding metal became central. After the piece was held at a
temperature of 660.degree. C. for 30 minutes to homogenize the
temperature, which simulates a stress relief annealing process, a
high-temperature low strain rate tensile test was performed at a
strain rate of 6.7.times.10.sup.-6/s. A value of reduction in area
(%) was used for evaluation.
TABLE-US-00001 TABLE 1 12Cr rotor substrate composition (% by
weight) C Si Mn P S Ni Cr Cu Mo V Nb N W Co B 0.10 0.07 0.08 0.010
0.0014 0.22 9.71 0.03 0.60 0.20 0.05 0.0145 1.80 3.00 0.010
TABLE-US-00002 TABLE 2 Overlay welding wire for first layer (% by
weight) Wire Ni + No. C Si Mn P S Cu Ni Cr Mo V Nb Ti Nb + Ti 1
0.10 0.76 1.40 0.012 0.012 0.24 0.01 0.02 <0.01 -- -- -- 0.01 2
0.01 0.02 0.44 0.012 0.008 -- -- -- -- -- -- -- -- 3 0.10 0.36 0.77
0.006 0.009 0.19 0.06 2.29 1.11 0.01 -- 0.002 0.06 4 0.04 0.51 1.06
0.005 0.010 0.11 0.02 2.36 1.05 -- -- -- 0.02 5 0.12 0.17 0.41
0.003 0.006 0.16 0.02 2.31 1.06 0.27 0.036 -- 0.06 6 0.08 0.40 0.52
0.010 0.006 0.17 0.03 5.47 0.58 -- -- -- 0.03
TABLE-US-00003 TABLE 3 Overlay welding wire for overlaying (% by
weight) Wire Ni + No. C Si Mn P S Cu Ni Cr Mo V Nb Ti Nb + Ti 3
0.10 0.36 0.77 0.006 0.009 0.19 0.06 2.29 1.11 0.01 -- 0.002 0.06 7
0.12 0.17 0.41 0.003 0.006 0.16 0.02 2.31 1.06 0.27 0.04 -- 0.06 8
0.12 0.53 1.86 0.003 0.002 0.16 0.19 1.45 0.56 0.01 0.01 --
0.20
TABLE-US-00004 TABLE 4 Test Temperature between material Number of
Wire preheating and path Current Voltage Rate Tungsten No.
Lamination layers No. (aim) (.degree. C.) (A) (V) (mm/min) aim (mm)
TP-1 first layer 1 1 200 230 14 155 lap 1.5 TP-2 220 220 14 155 toe
aim TP-3 280 250 14 155 toe aim All overlaying until 20 mm 8
200-300 240 14 155 toe aim Residual 8 200-300 200-240 20-27 120-230
-- layer (10 mm)
[0123] Then, in order to evaluate the stress relief annealing crack
susceptibility with the Cr amount, a high-temperature low strain
rate tensile test was conducted at a strain rate of
6.7.times.10.sup.-6/s using Cr variation materials in which the Cr
content was varied by changing welding conditions. A value of
reduction in area (%) was used for the evaluation.
[0124] Table 5 shows results of check analysis of the first layer
and FIG. 3 shows correlation between the Cr amount and the
reduction in area obtained as a result of the high-temperature low
strain rate tensile test. With an increase in the Cr amount of the
first layer welding section, the reduction in area increases and
the reduction in area was saturated at about 4.0% of the Cr amount.
From the result, it was revealed that 4.0% or more is necessary as
the Cr amount of the first layer welding section.
TABLE-US-00005 TABLE 5 Wire First Upper Results of check analysis
(% by weight) No. layer No. layer No. C Si Mn P S Ni Cr Cu Mo V
TP-1 1 7 0.11 0.42 0.68 0.011 0.008 0.13 4.99 0.14 0.30 0.10 TP-2
0.10 0.32 0.63 0.006 0.008 0.06 2.65 0.17 0.68 0.19 TP-3 0.10 0.67
1.06 0.012 0.012 0.07 1.92 0.22 0.12 0.04
[0125] Next, Table 6 shows results of check analysis of the first
layer welding section after overlay welding (the remainder being Fe
and unavoidable impurities) and Table 7 shows results of check
analysis of the upper layer welding section (the remainder being Fe
and unavoidable impurities). Moreover, Table 8 shows weld
combinations with which the high-temperature low strain rate
tensile test was performed and test results thereof.
[0126] The check analysis and the high-temperature low strain rate
tensile test were performed in the same manner as mentioned
above.
[0127] From Table 6, Cr contained in the first layer welding
sections according to the invention is from 4.0 to 7.7% by weight
but the contents of Cr are small in the first layer wires Nos. 1,
2, and 5 and thus the contents fall out of the above range.
Moreover, as compared with the range of the Si content contained in
the first layer welding sections according to the invention, the
content is small in the first layer wire No. 2 and, as compared
with the range of the V content, the content is large in the first
layer wire No. 5.
[0128] In Table 8, since the accumulation of strain into the first
layer is thought to be a cause of generation of the stress relief
annealing cracks, the case where a test piece was broken at the
first layer and the reduction in area at break is 10% or less is
shown as (x), the case where a test piece was broken at the first
layer and the reduction in area at break is more than 10% and less
than 30% is shown as (.DELTA.), and the case where a test piece was
broken at the upper layer and the reduction in area at break is 30%
or more is shown as (0). As is apparent also from Table 8, with
wires of Examples which satisfy the requirements of the invention,
test pieces are broken at the upper layer welding metal or the
reduction in area at break exceeds 10% even when they are broken at
the first layer section, so that no accumulation of strain into the
first layer is observed or a sufficient reduction in area at break
is exhibited even when the accumulation of strain into the first
layer is observed.
TABLE-US-00006 TABLE 6 Wire Results of check analysis of first
layer welding section (% by weight) No. C Si Mn P S Cu Ni Cr Mo V
Nb W Co B 1 0.10 0.56 0.99 0.012 0.009 0.18 0.09 2.76 0.17 0.06
0.013 0.50 0.84 0.0023 2 0.05 0.04 0.36 0.005 <0.003 0.14 0.09
3.42 0.21 0.07 0.020 0.62 1.04 0.0026 3 0.11 0.27 0.54 0.007 0.008
0.13 0.11 4.46 0.93 0.06 0.019 0.52 0.87 0.0022 4 0.05 0.40 0.79
0.006 0.008 0.09 0.09 4.27 0.94 0.05 0.020 0.46 0.76 0.0019 5 0.11
0.14 0.34 0.005 0.006 0.14 0.09 3.89 0.93 0.27 0.046 0.38 0.64
0.0017 6 0.09 0.32 0.38 0.007 0.006 0.15 0.08 6.53 0.57 0.05 0.015
0.41 0.71 0.0015
TABLE-US-00007 TABLE 7 Wire Results of check analysis of upper
layer welding section (% by weight) No. C Si Mn P S Cu Ni Cr Mo V
Nb Ti 3 0.10 0.36 0.75 0.006 0.007 0.19 0.06 3.56 1.09 0.02
<0.005 0.002 7 0.10 0.1 0.40 0.005 0.006 0.16 0.04 2.27 1.03
0.29 0.04 -- 8 0.11 0.54 1.91 0.007 0.004 0.16 0.26 1.41 0.54
<0.01 <0.005 --
TABLE-US-00008 TABLE 8 Second and Results of high- First layer of
subsequent temperature low strain Cr amount of V amount First layer
upper layer layers of upper rate tensile test second layer*2 Pcr(2)
(% by wire No. wire No. layer wire No. (reduction in area, %)*1 (%
by weight) value Ferrite weight) 1 7 7 x (4.9).sup. 2.42 1.45
.smallcircle. (absence) 0.27 2 x (6.2).sup. 2.62 1.42 .smallcircle.
(absence) 0.27 3 .DELTA. (14.4) 2.93 1.37 .smallcircle. (absence)
0.27 4 .DELTA. (13.5) 2.87 1.38 .smallcircle. (absence) 0.27 5
.smallcircle. (48.5) 2.76 1.40 .smallcircle. (absence) 0.27 1 8 8
.smallcircle. (84.0) 1.82 0.85 .smallcircle. (absence) 0.02 3
.smallcircle. (82.4) 2.33 0.77 .smallcircle. (absence) 0.02 4
.smallcircle. (82.0) 2.27 0.77 .smallcircle. (absence) 0.02 5
.smallcircle. (83.1) 2.15 0.79 .smallcircle. (absence) 0.10 6
.smallcircle. (81.5) 2.95 0.66 .DELTA. (minute) 0.02 6 3 8
.smallcircle. (83.4) 3.56 1.27 .smallcircle. (absence) 0.02
*1.smallcircle.: reduction in area .gtoreq. 30%, .DELTA.: 30% >
reduction in area > 10%, x: reduction in area .ltoreq. 10% *2in
case where dilution amount from first layer is regarded as 30% Pcr
(2) value: calculation value of first layer of upper layer
[0129] In the case where the difference in the Cr amount contained
is large as in the case of the first layer welding metal (first
layer wire No. 6) and the upper layer welding metal (upper layer
wire No. 8), Pcr (2) was 0.66 in the following expression and
minute ferrite was formed at the boundary of the welding sections.
Since ferrite induces a local decrease in strength and there is a
possibility of concentration of strain during the stress relief
annealing treatment. Therefore, it is preferable to prevent the
ferrite formation, so that the Cr amount of each layer desirably
satisfies a value larger than 0.7 in the expression shown below.
Moreover, from the following expression (1), the precipitation of
ferrite at the boundary between the base material and the first
layer can be prevented when the Cr amount of the first layer
welding section is 4.1% or more.
Pcr(n)=(Cr amount in metal at n-th layer).times.0.65-{Cr amount in
metal at (n-1)-th layer-Cr amount in metal at n-th
layer}.times.0.35>0.7 (1),
in which n=0 represents the base material and n=1 represents the
first layer. [0088]
[0130] After welding was performed with a welding material for the
first layer welding section where the welding material was selected
from Table 2 based on the results in Table 8, a ring crack test was
conducted, which is a test for evaluating the stress relief
annealing crack susceptibility of the first layer welding section.
FIG. 4 shows a shape of a ring crack test piece and a sampling
position of the test piece.
[0131] In FIG. 4(a), 10 is a 12Cr rotor substrate, 11 is a first
layer welding section, and 12 is a ring crack test piece.
[0132] FIG. 4(b) shows a side view of the ring crack test piece 12
and FIG. 4(c) shows a front view of the ring crack test piece 12.
FIG. 4(d) is an enlarged view of the A part in FIG. 4(c).
[0133] The ring crack test piece 12 has a cylindrical shape having
an inner diameter of 5 mm, an outer diameter of 10 mm, and a length
of 20 mm and a slit 12a running through in a diameter direction and
having a gap of 0.3 mm is formed along an axis direction in the
side wall. Also, on the outer peripheral wall at the opposite side
of the slit 12a, a U notch 12b having a width of 0.4 mm, a depth of
0.5 mm, and a bottom part whose cross-sectional shape is a curved
shape having a curvature of 0.2 mm is formed along an axis
direction.
[0134] In order to exclude the influence of the welding thermal
cycle, after one layer is build up on the base material with an
arbitrary welding material, the ring crack test piece 12 is sampled
with adjustment so that the U notch comes to an unaffected zone, in
a welded state without further treatment (FIG. 4(a)).
[0135] By imparting a force to the sampled test piece in arrowed
directions as shown in FIG. 5, the slit 12a was caulked and
gathered and then subjected to TIG welding and restrained, so that
tensile residual stress was imparted to the bottom part of the U
notch 12b.
[0136] After the restrained and welded ring crack test piece 121
was subjected to a stress relief annealing treatment at 630.degree.
C..times.10 hours, the presence of cracks was evaluated using two
test pieces (N-1, N-2) by observing three cross-sections per one
test piece, i.e., six cross-sections in total. Table 9 shows the
results. Also, the Pcr(1) value was calculated based on the
expression (1) and shown in Table 9.
[0137] The case where no crack is generated was shown as "O" and
the case where crack(s) were generated was shown as "x".
[0138] Here, the compositions of elements constituting the wires
Nos. 3, 4, and 6 fall within the range of the first layer welding
section according to the invention and the wires Nos. 1 and 5 have
compositions falling outside the range of the first layer welding
section according to the invention.
[0139] From the results in Table 9, the stress relief annealing
crack susceptibility varied depending on the Cr content and the
stress relief annealing crack susceptibility decreased in the case
of a high Cr material.
TABLE-US-00009 TABLE 9 0.3 mm slit N-1 N-2 Wire Cross-section
Cross-section Cross-section Cross-section Cross-section
Cross-section Pcr(1) No. A B C A B C value 1 x x x x x x -0.63 3
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 1.06 4 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 0.88 5
.smallcircle. x x .smallcircle. .smallcircle. .smallcircle. 0.49 6
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. 3.13 .smallcircle.: no crack is
generated, x: crack(s) were generated
[0140] Table 10 shows results collecting the above Examples. In the
over-all evaluation, it was evaluated so that the case where all
the individual evaluation items were shown as "O" was marked "OO",
the case where ".DELTA." was present was marked "O", and the case
where "x" was present in any item was marked "x". The case where
the over-all evaluation is marked "OO" can be judged to be
sufficiently usable and the case where the over-all evaluation is
marked "O" can be judged to be usable.
[0141] From the results, the welding sections and welding materials
according to the invention exhibit low stress relief annealing
crack susceptibility of the first layer and no accumulation of
strain in the first layer was observed in the high-temperature low
strain rate tensile test, so that breakage occurs at the upper
layer welding metal. Furthermore, by considering Cr in the base
material, the first layer, and the upper layer, the precipitation
of ferrite can be also suppressed.
TABLE-US-00010 TABLE 10 Second and Result of high- Result of ring
First layer First layer of subsequent layers temperature low crack
test of welding upper layer of upper layer strain rate first layer
Presence of Overall Symbol wire No. welding wire No. welding wire
No. tensile test welding metal ferrite evaluation Example 1 3 8 8
.smallcircle. .smallcircle. .smallcircle.
.smallcircle..smallcircle. 2 4 8 8 .smallcircle. .smallcircle.
.smallcircle. .smallcircle..smallcircle. 3 6 8 8 .smallcircle.
.smallcircle. .DELTA. .smallcircle. 4 6 3 8 .smallcircle.
.smallcircle. .smallcircle. .smallcircle..smallcircle. 5 3 7 7
.DELTA. .smallcircle. .smallcircle. .smallcircle. 6 4 7 7 .DELTA.
.smallcircle. .smallcircle. .smallcircle. Comparative 1 1 7 7 x x
.smallcircle. x Example 2 2 7 7 x -- .smallcircle. x 3 5 7 7
.smallcircle. x .smallcircle. x 4 1 8 8 .smallcircle. x
.smallcircle. x 5 5 8 8 .smallcircle. x .smallcircle. x
[0142] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
[0143] The present application is based on Japanese Patent
Application No. 2011-178628 filed on Aug. 17, 2011, and the
contents are incorporated herein by reference.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0144] 1: High Cr steel turbine rotor [0145] 2: Journal part [0146]
3: Thrust part [0147] 10: 12Cr rotor substrate [0148] 11: First
layer welding section [0149] 12: Ring crack test piece [0150] 12a:
Slit [0151] 12b: U Notch [0152] 13: Upper layer welding section
[0153] 14: Base material [0154] 20: Check analysis position [0155]
100: Restraint welding section (TIG welding/non-filler) [0156] 121:
Restrained and welded ring crack test piece
* * * * *