Technical Field
[0001] The present invention relates to a boiler waterwall panel constituting a furnace
housing with cooling water passages.
[0002] This boiler waterwall panel is a plate-pipe composite panel to be used as an element
member at the time of forming a wall panel constituting a housing of a furnace (combustion
chamber-cum-heat exchanger) as the core of a water heating boiler. A plurality of
boiler waterwall panels are joined by welding vertically and horizontally to constitute
a furnace housing.
[0003] To improve the durability of the furnace housing inner surface, one surface of the
boiler waterwall panel is covered with an alloy, e.g. a self-fluxing alloy of nickel
series.
Background Art
[0004] A method for heating a water-cooling panel segment comprising a metal tubular portion
and a metal plate portion arranged alternately without causing heat strain is known
(see e.g., Japanese Unexamined Laid-open Patent Publication No.
2000-329304). The structure and production method of this water-cooling panel segment 20 (boiler
waterwall panel) will be explained with reference to figures. Fig. 3(a) is a side
view showing metal tubular members 21 and metal plate members 22; Fig. 3(b) is a cross-sectional
view thereof; and Fig. 3(c) is a cross-sectional view of a water-cooling panel segment
20. In this specification, the language "cross-section" denotes a cross-section perpendicular
to a tubular axial direction.
[0005] The metal tubular member 21 and the metal plate member 22 are separately produced
by the number required to constitute a panel by alternately arranging them. At the
time of the production, they are configured to have the same length (see Figs. 3(a)
and 3(b)). Then (see Fig. 3(c)), a first metal plate member 22 is placed on a first
metal tubular member 21 in a direction that the first metal plate member 22 extending
in the tubular axial direction. In this state, one long side of the metal plate member
22 is linearly joined by welding to the peripheral surface of the metal tubular member
21. Then, another metal plate member 22 is placed on the other peripheral side of
the first metal tubular member 21 in a direction that the metal plate member 22 extending
in the tubular axial direction. In this state, one long side of the metal plate member
22 is linearly joined by welding to the peripheral surface of the metal tubular member
21. Thereafter, another metal tubular member 21 is placed on the joined metal plate
member 22 and another long side of the metal plate member 22 and the peripheral surface
of the metal tubular member 21 are linearly joined by welding. The above welding connection
is repeatedly performed to obtain a panel member with cooling water passages which
is a panel body of the water-cooling panel segment 20.
[0006] Furthermore, every panel member with water passages, an alloy coating with self-fluxing
alloy, such as a Ni-Cr based, is formed on one side or both sides of each piece of
the panel bodies. Thus, a water-cooling panel segment 20 is provided. The coating
is formed by a thermal spraying with post fusing method. Concretely, a coating material
layer is formed on an external surface of the water-cooling panel segment 20 by a
thermal spraying method, and then a fusing treatment is performed.
[0007] Because of the aforementioned production method, in this water-cooling panel segment
20, the panel body has a welded structure in which the transition portion 23 ranging
from the metal tubular member 21 to the metal plate member 22, is formed by welding.
[0008] Another production methods and structures will be now explained. The following production
method is known (see e.g., Japanese Unexamined Laid-open Publication
2001-004101). In this production method, a protection coating of the alloy is formed on an external
surface of a finned tubular member in which metal plate vertical fins are provided
at peripheral opposite sides of a metal tube to obtain a unit member for a water-cooling
segment. Then, a plurality of the unit members are joined by welding at their vertical
fin tips thereby to obtain a water-cooling panel segment. This structure and production
method of the water-cooling panel segment 50 (boiler waterwall panel) will be explained
with reference to figures. Fig. 4(a) is a side view of a metal tube 31 and vertical
fins 32; Fig. 4(b) is a cross-sectional view thereof; Fig. 4(c) is a cross-sectional
view of a finned tubular member; Fig. 4(d) is a side view of a unit members 40 for
a water-cooling panel segment; Fig. 4(e) is a cross-sectional view thereof; and Fig.
4(f) is a cross-sectional view of a water-cooling panel segment 50.
[0009] Also in this case, one piece of the metal tube 31 to be served as a cooling water
passage and two sheets of the vertical fins 32 to be served as webs constitute one
set, but each of them is produced separately (see Figs. 4(a) and 4(b)). The number
of sets required to form a water-cooling panel segment 50 are configured to have the
same length. Then (see Fig. 4(c)), each set, a pair of vertical fins 32 are placed
on peripheral opposite sides of the metal tube 31 with the fins extending in the tubular
axis direction. One long side of each vertical fin 32 and the peripheral surface of
the metal tube 31 are linearly joined by welding. Thus, a finned tubular member 30
comprising a metal tube 31 and a pair of vertical fins 32 placed on both peripheral
sides and extending in the tubular axis direction can be produced. Thus, in such a
finned tubular member 30, it also has a welded structure in which the transition portion
33 ranging from the metal tube 31 to the vertical fin 32 is formed by welding.
[0010] Then (see Figs. 4(d) and 4(e)), each finned tubular member 30, a alloy coating 41
with of self-fluxing alloy, such as Ni-Cr based, is formed on one side surface of
the tubular member 30. Thus, a unit member 40 for a water-cooling panel segment is
produced. Although the coating is also formed by a thermal spraying with post fusing
method, the treating object is segmentalized. That is, the treatment is performed
not to the assembled water-cooling panel segment 50 but to the not-yet-assembled unit
member 40 of the water-cooling panel segment 50. Thereafter, (see Fig. 4(f)), a plurality
of such unit members 40 for a water-cooling panel segment 50 as units are joined by
welding at their tip ends of the vertical fins 32 as joint portions 51. Thus, the
water-cooling panel segment 50 is formed.
[0011] Other than the above, (although not illustrated here), technique of producing a boiler
furnace panel (e.g., Japanese Unexamined Laid-open Patent Publication No.
2005-274022) and a method of producing an alloy coated boiler panel (e.g., Japanese Unexamined
Laid-open Patent Publication No.
2005-337623) are also known. In the boiler furnace panel producing technique of the former, employing
not-yet-coated panel body of the aforementioned water-cooling panel segment 20 as
the substrate, then, at the time of forming a fusion-bonded coating of a corrosion
resistant alloy on one side surface of the panel body, a super alloy coating is formed
at the end (frame-like region including edge) portions to be joined to another panel
by a weld overlaying method, and a self-fluxing alloy coating is formed at the inner
side thereof by a thermal spraying with post fusing method. In the method of producing
the alloy coated boiler panel of the latter, deformation is corrected by controlling
displacement in the dual direction perpendicular to the longitudinal direction at
plural portions with a positional correction tool, while pulling the boiler panel
in the longitudinal direction with a pulling tool, during the heating in fusing treatment
after the thermal spraying. Also in these boiler waterwall panels, the transition
portion 23 ranging from the metal tubular portion 21 to the metal plate portion 22
is a welded structure formed by welding.
[0012] In the aforementioned conventional boiler waterwall panels however, since the transition
portion ranging from the tubular portion to the plate shaped fin portion is a welded
portion, the quality of the welding exerts a great influence on the quality of the
boiler waterwall panel. In detail, when a boiler is in use, although both the tubular
portion and the fin portion are exposed to a high temperature environment, the tubular
portion is cooled from the inside with water or steam, but the fin portion is not
cooled. Thus, a steep temperature gradient, i.e., a steep thermal strain driving force,
is generated at the transition portion. If the welding of the transition portion is
not perfect, e.g., if there is any welding defect such as, e.g. pinholes, unevenness,
blowholes, overlaps, undercuts, slag inclusions, weld cracks, sputters, and extremely
uneven weld bead configurations, such welding defects become notches, resulting in
a breakdown of the corrosion resistant alloy coating started from the welding defect.
As a result, corrosion of the substrate material occurs at an early stage.
[0013] Defects of the welded portion are hard to be found through visual examination and
therefore dye penetrant testing should be employed to find such weld defects. The
repair of the found welding defects requires troublesome works, such as, e.g. blasting
treatment and then TIG welding.
[0014] Furthermore, since the welding between the tubular member and the plate fin member
is harder than the butt welding of the fin tip ends each other, welding defects tend
to occur despite of spending much working hours, which bears a great burden of examination
and repair of welding defects after the welding, as well as welding operation.
[0015] Therefore, a technical object is to improve the construction/formation of the boiler
waterwall, panel to reduce the burden of welding operation at the time of producing
the boiler waterwall panel and to reduce the burden of maintaining a furnace housing
consist of the boiler waterwall panels thereby to improve the operating rate of the
boiler.
Disclosure of Invention
[0016] The boiler waterwall panel (claim 1) according to the present invention was made
to solve the aforementioned problems. A boiler waterwall panel comprises a metal panel
member with water passages as a panel body equipped with plural rows of tubular portions
to serve as cooling water passages, web portions connecting the rows of tubular portions,
and a pair of fin portions located at the outside of the outermost tubular portions
and extending in a tubular axial direction, at least one surface of the panel body
being covered with a fusion-bonded coating of a corrosion resistant alloy,
wherein the panel member with water passages as the panel body, comprises a plurality
of metal seamless finned single tubes as constituent units, each provided with a single
tubular portion and a pair of fin portions disposed at peripheral opposite sides of
the single tubular portion, the single tubular portion and the fin portions exist
sharing a common metal phase continuously extended, and
wherein the plurality of metal seamless finned single tubular portions are joined
by welding with each other at tip ends of the fin portions of the constituent units
so that a welded portion is located at a median line position of the web portion.
[0017] The boiler waterwall panel according to the present invention (claim 2) comprises
a metal panel member with water passages as a panel body equipped with a plurality
of rows of tubular portions to serve as cooling water passages, web portions connecting
the rows of tubular portions, and a pair of fin portions located at the outside of
the outermost tubular portions and extending in a tubular axial direction, at least
one surface of the panel body being covered with a fusion-bonded coating of a corrosion
resistant alloy,
wherein the panel member with water passages as the panel body comprises a plurality
of seamless metal finned tube-web assemblies as constituent units, each having a few
rows of tubular portions corresponding to a part of the plural rows of the tubular
portions, a web portion connecting said few rows of the tubular portions, and a pair
of fin portions provided at outer sides of the outermost tubular portions, the tubular
portions, the web portions and the fin portions exist sharing a common metal phase
continuously extended, and
wherein the plurality of metal seamless finned tube-web assemblies are joined by welding
with each other at tip ends of the fin portions of the constituent units so that a
welded portion is located at a median line position of the limited web portions.
[0018] The boiler waterwall panel according to the present invention (claim 3) comprises
a metal panel member with water passages as a panel body equipped with a plurality
of rows of tubular portions as cooling passages, web portions connecting the rows
of tubular portions, and a pair of fin portions located at the outside of the outermost
tubular portions and extending in a tubular axial direction, at least one surface
of the panel body being covered with a fusion-bonded coating of a corrosion resistant
alloy,
wherein the panel member with water passages as the panel body has a seamless integrated
structure in which an entirety of the panel member is constituted by a single metal
seamless finned tube-web assembly comprising the plurality of rows of the tubular
portions, the web portions connecting the rows of tubular portions, and the pair of
fin portions located at the outside of the outermost tubular portions, wherein the
tubular portions, the web portions and the fin portions exist sharing a common metal
phase continuously extended.
[0019] The boiler waterwall panel according to the present invention (claim 4) is the boiler
waterwall panel as recited in claims 1 to 3, wherein an external surface of a transition
portion ranging from the tubular portion to the fin portion or the web portion of
the panel member as the panel body is formed into a concave surface.
[0020] The boiler waterwall panel according to the present invention (claim 5) is the boiler
waterwall panel as recited in claims 1 to 4, wherein the seamless finned tubular member
or the seamless finned tube-web assembly, each being formed with the single common
metal phase, constituting the panel body, is produced by a seamless forming method
such as a hot extrusion method.
[0021] The boiler waterwall panel according to the present invention (claim 6) is the boiler
waterwall panel as recited in claims 1 to 5, wherein the corrosion resistant alloy
constituting the fusion-bonded coating is made of a Ni-rich Ni-Cr based alloy in which
an amount of boron is restricted to 0.1 mass % or below and an amount of silicon is
restricted to 0.5 mass % or less at a frame-like region including edge portions of
the panel.
Effects of the invention
[0022] According to the boiler waterwall panel of the present invention (claim 1), since
an integrally continued metal seamless finned single tube of an entire continuous
phase having a tubular portion and a pair of fin portions located at opposite peripheral
sides of the tubular portion and extending in the tubular axial direction capable
of being produced by a hot extrusion method is employed as a constituent unit, the
transition portion ranging from the tubular portion to the fin portion is not required
to be welded. Furthermore, the welding of the tip ends of the fin portions can be
performed more easily than the welding of the transition portion, and the welded portion
is higher in quality. This reduces the burden of the welding operation for producing
the boiler waterwall panel. As to the furnace housing using aforementioned boiler
waterwall panels, since no welded portion exists at the transition portion, the fusion-bonded
coating is free from the influence of the notch due to unevenness of the welding of
this portion. Furthermore, since the welded portion formed in the middle of the web
portion instead of the welded portion of the transition is high in quality, damages
of the fusion-bonded coating can be remarkably reduced, resulting in a remarkably
reduced necessity of the maintenance, which in turn results in stable operation and
an improved operation rate of the boiler with furnace housing.
[0023] According to the boiler waterwall panel of the present invention (claim 2), since
a seamless finned tube-web assembly, which is equivalent to the case in which a small
number of the aforementioned integrally continued seamless finned single tubes are
united with an entire continuous phase manner, then employed as a constituent unit,
the transition portion ranging from the tubular portion to the fin portion is not
required to be welded, too. Furthermore, the number of the welding operation for welding
the tip ends of the fin portions can be reduced. This reduces the burden of the welding
operation at the time of producing the boiler waterwall panel. In a furnace housing
in which the boiler waterwall panel is assembled, damages of the fusion-boned coating
can be further remarkably reduced.
[0024] Accordingly, in the present invention (claims 1 and 2), the burden of the welding
operation at the time of producing the boiler waterwall panel can be reduced, and
the operation rate of the boiler can be improved.
[0025] According to the boiler waterwall panel of the present invention (claim 3), since
a seamless finned tube-web assembly, which is equivalent to the case in which a plurality
of the aforementioned seamless finned single tubes are integrated into an entire continuous
phase, then constitutes an entirety of the panel member, the transition portion ranging
from the tubular portion to the fin portion is not required to be welded, too. Furthermore,
the welding of the tip ends of the fin portions is not required. This eliminates the
necessity of the welding operation at the time of producing the boiler waterwall panel.
In a furnace housing using the boiler waterwall panels, damages of the fusion-bonded
coating can be further remarkably reduced.
[0026] Accordingly, in the present invention (claim 3), not only the burden of the welding
operation at the time of producing the boiler waterwall panel can be eliminated, but
also in an improved operation rate of the boiler can be obtained, further remarkably.
[0027] According to the boiler waterwall panel of the present invention (claim 4), since
the external surface of the transition portion ranging from the tubular portion to
the fin portion or the web portion in the panel member is formed into a concave surface,
the stress concentration thereto can be reduced. Furthermore, since the cross-section
of this portion has a configuration gradually increasing in thickness towards the
basal portion, resulting in an enhanced rigidity of this portion, undesired effects
by the stress due to the aforementioned steep temperature gradient can be reduced,
which enhances the aforementioned preferable functions and results. Furthermore, the
concave surface can be easily formed by a seamless forming method, such as e.g., a
hot extrusion method, which in turn contributes a longer operating life of an extruding
die for use in a hot extrusion method, etc.
[0028] Here, it is preferable that the curvature radius of the concave surface to be formed
on the external surface of the transition portion ranging from the tubular portion
to the fin portion is set to 3 mm or more. With this, in a panel with a tubular portion
or a web portion a few mm in thickness, in most cases the stress concentration can
be sufficiently reduced and the rigidity can be remarkably increased. Furthermore,
the notch function against the fusion-bonded coating can be sufficiently reduced by
a radius of 3 mm or more. Although these effects increase as the radius increases,
it is preferable to set the radius up to 6 mm or so, in the light of the effect of
saturation and/or to avoid wasting material.
[0029] According to the boiler waterwall panel of the present invention (claim 5), since
the seamless finned single tube or finned tube-web assembly of a continuous phase
constituting the panel body is produced by a seamless forming method, such as e.g.,
a hot extrusion method, the integration as the continuous phase can be performed assuredly,
and the production can be performed efficiently.
[0030] In the meantime, currently, it is generally considered that a hot extrusion method
is the most suitable method of producing a seamless finned single tube or a seamless
finned tube-web assembly. However, it is possible to produce a seamless constituent
unit, etc., constituting the panel body, by another seamless forming method, such
as e.g., a powder sintering method, a casting method using a sand mold, or a centrifugal
casting method, so long as facility circumstances and cost allowed it.
[0031] According to the boiler waterwall panel of the present invention (claim 6), since
the amount of B and Si is minimized in the fusion-bonded coating of the frame-like
portion to be subjected to welding thereby, thermal shock crack sensitivity is remarkably
reduced than the coating with self-fluxing alloy material in which sufficient B and
Si is added, this said sensitivity is enhanced. Therefore, even if a furnace housing
is formed by welding the boiler waterwall panels, the problems of thermal shock crack
can be eliminated. As to the corrosion resistant alloy low in thermal shock crack
sensitivity, it is preferable to use the alloy as recited in claim 6, in terms of
the thermal shock crack-vs-cost performance or the availability. Depending on the
situation, however, another alloy (e.g., another group alloys defined by JIS 4901,
4902 or ISO 4955, 9723) can be used.
Brief Description of Drawings
[0032] Fig. 1 shows a structure and production method of a boiler waterwall panel according
to an embodiment of the present invention, wherein Fig. 1 (a) is a side view of a
finned tubular member (seamless finned single tube), Fig. 1 (b) is a cross-sectional
view thereof, Fig. 1 (c) is a side view of a panel body (panel member with water passages),
Fig. 1 (d) is a cross-sectional view thereof, Fig. 1 (e) is a side view of a boiler
waterwall panel, and Fig. 1 (f) is a cross-sectional view thereof.
[0033] Fig. 2 shows a structure and production method of a boiler waterwall panel according
to another embodiment of the present invention, wherein Fig. 2(a) is a side view showing
a seamless finned tube-web assembly, Fig. 2(b) is a cross-sectional view thereof,
Fig. 2(c) is a side view of a panel body (panel member with water passages), and Fig.
2(d) is a cross-sectional view thereof.
[0034] Fig. 3 shows an example of a conventional water cooling panel segment, wherein Fig.
3(a) is a side view showing metal tubular members and metal plate members, Fig. 3(b)
is a cross-sectional view thereof, Fig. 3(c) is a cross-sectional view of a water-cooling
panel segment.
[0035] Fig. 4 shows another example of a conventional water-cooling panel segment, wherein
Fig. 4(a) is a side view of a metal tube and vertical fins, Fig. 4(b) is a cross-sectional
view thereof, Fig. 4(c) is a cross-sectional view of a finned tubular member, Fig.
4(d) is a side view of unit members for a water-cooling panel segment, Fig. 4(e) is
a cross-sectional view thereof, and Fig. 4(f) is a cross-sectional view of the water-cooling
panel segment.
Brief Description of Reference Marks
[0036]
20...Water-cooling panel segment (boiler waterwall panel)
21...Metal tubular member
22...Metal plate member
23...Transition portion (welded)
30...Finned tubular member
31...Metal tube
32...Vertical fin
33...Transition portion (welded)
40...Water-cooling panel segment unit
41...Self-fluxing alloy series coating
50...Water-cooling panel segment (boiler watewall panel)
51...Joint (welded)
60...Finned tubular member (seamless finned single tube)
61...Tubular portion
62...Fin portion
63...Transition portion (integrally formed)
70...Panel body (panel member with water passages)
71...Joint (welded portion formed in the middle of the web)
80...Boiler waterwall panel
81...Frame-like portion fusion-bonded coating
82...Inner region fusion-bonded coating
90...Seamless finned tube-web assembly
91...Tubular portion
92...Web portion
93...Fin portion
94...Transition portion (integrally formed)
95...Panel body (panel member with water passages)
96...Joint (welded portion formed in the middle of the web)
Best Mode for Carrying Out the Invention
[0037] The structure and production method of a boiler waterwall panel according to an embodiment
of the present invention will be explained with reference to drawings. Fig. 1 (a)
is a side view of a finned tubular member 60, Fig. 1 (b) is a cross-sectional view
thereof, Fig. 1 (c) is a side view of a panel body 70, Fig. 1 (d) is a cross-sectional
view thereof, Fig. 2(e) is a side view of a boiler waterwall panel 80, and Fig. 1
(f) is a cross-sectional view thereof. The cross-section of each cross-sectional view
denotes a cross-section perpendicular to the axial direction of the tubular portion
61.
[0038] This boiler waterwall panel 80 is produced as follows. That is, initially, a tubular
member 60, which is a metal seamless finned pipe as the minimum constituent unit,
is integrally produced by a hot extrusion method (see Figs. 1 (a) and 1 (b)). A plurality
of finned tubular members 60 are aligned in length, and the tip ends of the fin portions
62 as joining portions are welded with each other to obtain a panel body 70 (see Figs.
1 (c) and 1 (d)). Thereafter, a fusion-bonded coating of a corrosion resistant alloy
is formed on one surface side of the panel body 70 as a treating surface. As the fusion-bonded
coating, thermal spraying with post-fusing method and weld overlaying method are mentioned
typically, other methods e.g. power-slurry coating with post-fusing method etc. can
be employed. That is to say, any method, in which a fusible alloy can be bonded on
a metallic substrate with mutual alloying through fusing step thereof, is available.
Thus, the boiler waterwall panel 80 is produced. The fusion-bonded coating of a corrosion
resistant alloy according to the boiler waterwall panel 80 is formed by the following
steps (see Figs. 1 (e) and 1 (f)). For example, an alloy having no thermal shock crack
sensitivity is applied to the frame-like region 81 including edge portion of the treating
surface by a weld overlaying method. Then, to the inner region 82 surrounded by the
frame-like region 81, an alloy good in workability, such as, e.g., Ni series (Ni-Cr
group, etc.) or Co series (Co-Cr group, etc.) self-fluxing alloy, or an alloy in which
WC is added to the above alloy, etc., are applied by a thermal spraying with post
fusing method.
[0039] The finned tubular member 60 (see Figs. 1 (a) and 1 (b)) is a metal elongated member
having a tubular portion 61 serving as a cooling water passage and a pair of fin portions
62 provided at peripheral opposite sides of the tubular portion so as to extend in
the tubular member axial direction. A transition portion 63 ranging from the tubular
portion 61 to the fin portion 62 is not a welded portion but an integral portion formed
by a hot extrusion method. The external surface of the transition portion 63 is formed
into a concave curve having a curvature radius of 3 mm to 6 mm at the minimum curvature
radius portion. The finned tubular member 60 is commonly made from a rolled member
of cheap carbon steel or low-alloy steel (e.g., Cr-Mo steel), but the material can
be stainless steel, casting material, or another metal. In the case of a common boiler
furnace panel, the dimensional data is, for example, about 60 to 80 mm in diameter
of the tubular portion 61, about 5 to 7 mm in thickness of the tubular portion 61,
about 10 to 20 mm in width of the fin portion 62, and about 5 to 7 mm in thickness
of the fin portion 62. As the hot extrusion method, the Ugine-Sejournet method using
glass as lubricant agent is popular, but any method can be employed.
[0040] The panel body 70 (see Figs. 1 (c) and (d)) is produced by welding a plurality of
the aforementioned finned tubular members 60. Concretely, for example, about 5 to
20 pieces of the finned tubular members 60 are arranged in parallel with the length
aligned, and the tip ends of the adjacent fin portions 62 are welded to obtain a flat
shaped member. In the case of a commonly used boiler furnace panel, a general size
of the panel body 70 is about 4,000 to 8,000 mm in length and about 400 to 1,200 mm
in width. The welding connection of the joint 71 in the panel body 70 is performed
by a common welding method, such as e.g., a CO
2 arc welding method or a TIG welding method. This welding is not performed in a state
in which a plate member and a tubular member are placed together, but can be simply
performed in a state in which edges of adjacent plate portions are placed in a mutually
butt state. This makes the welding easier and enhances the efficiency, and almost
no welding defects will be generated. In the panel body 70 produced as mentioned above
and having the aforementioned structure, the butt welded fin portions 62 and 62 constitute
a web portion connecting the tubular portions 61 and 61, and the joint 71 which is
a welded portion is located at the median line position of the web.
[0041] The boiler waterwall panel 80 (see Figs. 1 (e) and 1 (f)) is finished by forming
a frame-like portion fusion-bonded coating 81 and an inner region fusion-bonded coating
82 on the aforementioned panel body 70.
[0042] As a corrosion resistant alloy having no thermal shock crack sensitivity to be used
as the frame-like portion fusion-bonded coating 81, a Ni-rich Ni-Cr based alloy in
which the amount of boron B as a melting-point lowering element is restricted to 0.1
mass % or below and the amount of silicon Si as a melting-point lowering element is
restricted to 0.5 mass % or less can be exemplified. As the standard of defining such
alloy material, JIS G4901 for bar members, JIS G4902 for plate members can be exemplified
in Japan, and ISO 4955 or ISO 9723 can be exemplified in the International Standard.
The thickness of the frame-like portion fusion-bonded coating 81 is about 1 to 3 mm.
[0043] As to the frame-like portion of the panel body 70, it is important that the frame-like
portion has no thermal shock crack sensitivity because it is subjected to be welded
to another panel after it becomes a boiler waterwall panel 80. On the other hand,
as to the remaining inner region, the easiness and/or cost of the coating treatment
is given more importance since the region is not to be welded anymore.
[0044] As the corrosion resistant alloy to be used for the inner region fusion-bonded coating
82, a Ni-Cr group self-fluxing alloy can be exemplified because it is suitable to
the thermal spraying with post-fusing method and excellent in applicability. In the
material, although the Ni-rich Ni-Cr component occupies the predominant quantity,
the amount of B and that of Si are regulated to 1 to 5 mass %, respectively, so as
to provide an easy-to-melt nature, a self-fluxing function etc., preferable to a thermal
spraying treatment or a fusing treatment while avoiding excessive increase of brittleness.
As such alloy material, nickel self-fluxing alloy material defined by Japanese Industrial
Standard JIS H8303 or International Standard ISO 4920 can be exemplified. The thickness
of the inner region fusion-boned coating 82 is usually set to about 0.5 to 3.0 mm.
In the present invention structure, since the surface configuration of the tubular
member-fin/web transition portion and the welded portion of the panel body are smoothly
formed, the coating having a thickness of 0.2 mm or above can give sufficient corrosion
prevention.
[0045] In forming the inner region fusion-bonded coating 82, in the fusing treatment to
be performed after thermally spraying the inner region fusion-bonded coating 82 on
one surface of the panel body 70, it is more preferable to correct deformation of
the panel body 70 by regulating the displacements in the dual direction perpendicular
to the longitudinal direction at plural points with a positional correction tool while
pulling the panel body 70 in the longitudinal direction with a pulling tool during
the heating while heating the panel body 70 with a manner in which a partially heating
tool, e.g., an induction coil, being moved in the longitudinal direction.
[0046] The boiler waterwall panel 80 produced as mentioned above will be transported from
a panel production factory to a boiler installation site, and joined by welding to
another panel at frame-like portions to be fabricated in a furnace housing.
[0047] As to a structure and production method of a boiler waterwall panel according to
the present invention, another embodiment will be explained with reference to the
drawings. Fig. 2(a) is a side view showing seamless finned tube-web assembly 90, Fig.
2(b) is a cross-sectional view thereof, Fig. 2(c) is a side view of a panel body 95
(panel member with water passages), and Fig. 2(d) is a cross-sectional view thereof.
Here, the "cross-section" of each cross-sectional view denotes a cross-section perpendicular
to the axial direction of the tubular portion 91.
[0048] This boiler waterwall panel is different from the aforementioned boiler waterwall
panel 80 in that the constituent unit of the panel body 95 which is a panel member
with water passages as a panel body is constituted by seamless finned tube-web assemblies
90.
[0049] The seamless finned tube-web assembly 90 is equipped with a few rows of tubular portions
91, web portions 92 connecting the rows of tubular portions and a pair of fin portions
93 located at the outside of the outermost rows of the tubular portions 91, which
are connected as a continuous phase. Like the finned tubular member 60, the assembly
90 is integrally formed by a hot extrusion method. However, not like a single tube
such as the finned tubular member 60, a few tubular portions 91 are included in a
plane in a parallel arranged manner as if a part of the panel is previously assembled
by arranging the finned tubular members 60.
[0050] Partially, the tubular portion 91 to be served as a cooling water passage can be
the same as the aforementioned tubular portion 61, the fin portion 93 can be the same
as the fin portion 62, the web portion 92 can have a size almost equal to the size
corresponding to two fin portions 93, and the transition portion 94 ranging from the
tubular portion 91 to the web portion 92 or the fin portion 93 can be the same as
the transition portion 63.
[0051] The few rows of the tubular portions 91 contained in the seamless finned tube-web
assembly 90 correspond to a part of plural rows of the tubular portions 91 contained
in the panel body 95 or the boiler waterwall panel. In this embodiment, an assembly
having three rows of tubular portions is illustrated, but the number of rows of tubular
portions can be two, four, or more.
[0052] The panel body 95 can be formed by welding a plurality of seamless finned tube-web
assemblies 90 in the same manner as in the panel body 70. Concretely, tip ends of
the adjacent fin portions 93 are welded to be assembled into a flat panel. In the
web formed by welding the fin portions 93 and 93, the joint 96 which is a welded portion
is located at the median line position of the web. However, at the time of producing
the seamless finned tube-web assembly 90, since no joint 96 exists at the web portion
92 integrally formed together with the tubular portion 91, the panel body 95 has a
welding structure in which a welded portion is located at the median line positions
of some web portions among web portions connecting the plural rows of tubular portions
91 to be served as cooling passages. A pair of fin portions 93 are located at the
outside of the outermost tubular members.
[0053] In the same manner as in the aforementioned panel body 70, a frame-like portion fusion-bonded
coating 81 and inner region fusion-bonded coating 82 are formed on the panel body
95 having the aforementioned welding structure produced as mentioned above into a
boiler waterwall panel. The number of joints 96 in the panel body 95 is fewer than
the number of joints 71 in the panel body 70.
[0054] The boiler waterwall panel produced as mentioned above will also be transported from
a panel production factory to a boiler installation site, and joined by welding to
another panel at frame-like portions to be fabricated in a furnace housing.
[0055] A structure and production method of a boiler waterpanel according to still another
embodiment of the present invention will now be explained.
[0056] This embodiment is a deformation of the aforementioned second embodiment. If this
embodiment is explained using Fig. 2 showing the structure or the panel body according
to the second embodiment, this is an embodiment in which the joint 96 in the panel
body 95 is eliminated.
[0057] That is, in this embodiment, the number of rows of the tubular portions 91 in the
seamless finned tube-web assembly 90 which is a panel constituent unit of the second
embodiment is increased to the number of rows of the tubular portions 91 in the panel
body 95. Thus, the seamless finned tube-web assembly 90 constitutes not a panel constituent
unit but an entire panel structural member.
[0058] This embodiment is useful for the case in which the panel body 95 is relatively small
in width (e.g., 400 to 600 mm width /3 to 6 rows of tubular portions). Depending on
the improvement of assembly production technique such as a hot extrusion method, the
preferable applicable target will be expanded to a wider panel.
[Other]
[0059] In the above embodiments, the seamless finned single tube 60 and the seamless finned
tube-web assembly 90 are produced by a hot extrusion method. As a seamless member
production method of producing an integral member in which tubular members and fins
or webs extending in the tubular axial direction are united with a continuous metal
phase to be replaced with a hot extrusion method, a powder sintering method, a casting
method using a sand mold, and a centrifugal casting method can be exemplified.
[0060] In the aforementioned embodiments, the frame-like portion fusion-bonded coating 81
of a low thermal shock crack sensitivity alloy is formed by a weld overlaying method.
However, in cases where the coating can be formed by another method, such as e.g.,
a thermal spraying with post-fusing method, the frame-like portion fusion-bonded coating
81 can be formed by such a method.
Industrial Applicability
[0061] The boiler waterwall panel of the present invention can be applied to various boiler
furnace housings including the so-called super boiler. As an installation example
of a boiler, an incinerator can be exemplified. An incinerator of a garbage incineration
power generation equipment is also included in the installation example.