JP2012130998A - Smelt spout, and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smelt spout improved in life thereof by restricting occurrence of cracks in an overlaying layer, and to provide a method of manufacturing the same.SOLUTION: The smelt spout 1 is formed with a cooling water passage 8 between an inner plate 2 having an overlaying layer 3 in the surface thereof and an outer plate 4. The smelt spout 1 is manufactured by mainly: an overlaying process for forming the overlaying layer 3 in the surface of a flat plate 20; an annealing process for annealing the flat plate 20 formed with the overlaying layer 3 in the surface thereof; a bending process for bending the annealed flat plate 20 so as to obtain the inner plate 2 curved to be recessed; and an outer plate fitting process for fitting the outer plate 4 to the inner plate 2 so that the cooling water passage 8 is formed between the outer plate 4 and the inner plate 2.

Description

  The present invention relates to a smelt spout used for, for example, a soda recovery boiler in a paper mill and a method for manufacturing the same.

In the paper manufacturing process, a waste liquid whose main component is Na ₂ SO ₄ , called black liquor, is generated. The black liquor is burned in a soda recovery boiler, discharges the melt (smelt) remaining after combustion, and collects the soda. At this time, a saddle member called a smelt spout is used to discharge the smelt to the outside of the soda recovery boiler.

The smelt discharged from the soda recovery boiler is about 800 ° C. or higher, and its main component is Na ₂ S. For this reason, the smelt spout is exposed to an extremely severe corrosive environment of high temperature and high alkali. Therefore, a smelt spout is known in which a coating layer made of a material excellent in heat resistance and corrosion resistance is provided on a portion exposed to smelt (the surface of the inner plate).

  For example, Patent Document 1 discloses a smelt in which a coating layer having a carbon content of 0.06 to 0.13% and a chromium content of 20 to 26% is provided on the surface of the first substrate (inner plate) by overlay welding. Spout is listed. It also describes cooling water flowing through the smelt spout (between the first base and the second base) to cool the smelt spout.

  Patent Document 2 discloses a smelt spout in which a portion directly exposed to smelt is made of a heat-resistant and corrosion-resistant Cr—Ni-based alloy so that it can withstand a corrosive environment of high temperature and high alkali without flowing cooling water inside. Is described. Specifically, a smelt spout composed entirely of a cast or forged product of a heat-resistant and corrosion-resistant Cr—Ni base alloy or a smelt spout whose surface is covered with a coating layer made of a heat-resistant and corrosion-resistant Cr—Ni based alloy is disclosed. ing.

Japanese Patent Laid-Open No. 2003-211287 JP-A-3-287890

  In the smelt spout described in Patent Document 1, cracks may occur in the coating layer (building overlay) provided by overlay welding, and the coating layer may deteriorate over time. The crack generated in the coating layer may progress to the inner plate as the base material, which may lead to a shortened life of the smelt spout.

It is thought that the crack which generate | occur | produces in the coating layer (building overlay layer) provided by overlay welding is partly due to the residual stress of the overlay welding layer at the time of manufacture.
In a conventional smelt spout, a structure having a basic structure of a smelt spout is prepared by attaching an outer plate to a concavely curved inner plate, and then a coating layer is formed on the surface of the inner plate of the structure by overlay welding. It was common. For this reason, the coating layer whose temperature has increased during overlay welding tends to shrink when it returns to room temperature, but the inner plate on which the coating layer is formed cannot be deformed because it is incorporated in the structure ( A large residual stress is generated in the coating layer. This residual stress cannot be completely removed even if annealing is performed after overlay welding. It is considered that cracking of the coating layer occurs due to this residual stress during manufacturing.
In addition, thermal stress at the time of use of a smelt spout can also be considered as another cause of the occurrence of cracks in the build-up weld layer (coating layer). That is, since the coating layer formed by overlay welding is located between the high-temperature smelt of about 800 ° C. and the inner plate cooled by the cooling water, thermal stress is generated in the coating layer when using the smelt spout. This occurs and cracks occur in the coating layer due to this thermal stress.
Actually, it is considered that cracks in the build-up weld layer occur due to the combination of the residual stress of the build-up weld layer during production and the thermal stress of the build-up weld layer during use of the smelt spout.

  Moreover, even in the smelt spout described in Patent Document 2, when the coating layer is provided by overlay welding, the coating layer may be cracked. The heat-resistant and corrosion-resistant Cr—Ni base alloy is expensive, and it is difficult to form the entire smelt spout with a heat-resistant and corrosion-resistant Cr—Ni base alloy by casting or forging.

  This invention is made | formed in view of the above-mentioned situation, and it aims at providing the smelt spout which suppressed the crack generation | occurrence | production of the overlay welding layer, and improved the lifetime, and its manufacturing method.

  A method for producing a smelt spout according to the present invention is a method for producing a smelt spout in which a cooling water channel is formed between an inner plate and an outer plate having a build-up weld layer on the surface, and is overlay-welded on the surface of a flat plate. An overlay welding step for forming a layer, an annealing step for annealing the flat plate on which the build-up weld layer is formed, and an annealed flat plate so as to obtain a concavely curved inner plate It is characterized by comprising a bending step for bending and an outer plate attaching step for attaching the outer plate to the inner plate so that the cooling water channel is formed between the inner plate and the inner plate.

  According to this smelt spout manufacturing method, overlay welding is performed on the surface of the flat plate before bending, so there is nothing to restrain the flat plate during overlay welding, and residual stress generated in the overlay weld layer. Can be reduced. Further, even if some residual stress is generated in the overlay weld layer, the residual stress is released by annealing. Therefore, the crack generation of the build-up weld layer due to the residual stress of the build-up weld layer during production can be suppressed, and the life of the smelt spout can be improved.

  It is preferable that the manufacturing method of the said smelt spout is further equipped with the convex part removal process of removing the convex part of the weld bead of the said build-up weld layer.

As described above, the direct cause of the cracking of the overlay weld layer is the residual stress of the overlay weld layer during production and the thermal stress of the overlay weld layer during use of the smelt spout. It is thought that the stress concentration on the convex part spurs the occurrence of cracks in the overlay weld layer.
Thus, by removing the convex portion of the weld bead of the build-up weld layer where stress tends to concentrate, it is possible to suppress the occurrence of cracks in the build-up weld layer due to residual stress and thermal stress. Therefore, the life of the smelt spout can be further improved.

  In this case, the convex portion removing step may be performed before the bending step, and the convex portion of the weld bead of the build-up weld layer on the surface of the flat plate may be removed.

  Thus, the convex part of the weld bead can be easily removed by machining (cutting or grinding) by performing the convex part removing step in the state of the flat plate before bending.

  The smelt spout according to the present invention is concavely curved, and is attached to the inner plate so that a cooling water channel is formed between the inner plate having an overlay weld layer on the surface and the inner plate. The inner plate is manufactured by forming the build-up weld layer on the surface of a flat plate, annealing the flat plate, and bending the flat plate.

  According to this smelt spout, build-up welding is performed in the state of the flat plate before bending during inner plate production, so there is nothing to restrain the flat plate during build-up welding, and residual stress occurs in the build-up weld layer. Hateful. Further, even if some residual stress is generated in the overlay weld layer, the residual stress is released by annealing. Therefore, the crack generation of the build-up weld layer due to the residual stress of the build-up weld layer during production can be suppressed, and the life of the smelt spout can be improved.

  In the smelt spout, the inner plate preferably has a convex portion of the weld bead of the build-up weld layer removed.

  Thus, by removing the convex part of the weld bead of the build-up weld layer where stress tends to concentrate, it is possible to suppress the occurrence of cracks in the build-up weld layer due to residual stress and thermal stress. Therefore, the life of the smelt spout can be further improved.

  According to the present invention, since overlay welding is performed on the surface of the flat plate before bending, there is nothing to restrain the flat plate during overlay welding, and residual stress is hardly generated in the overlay weld layer. Further, even if some residual stress is generated in the overlay weld layer, the residual stress is released by annealing. Therefore, the crack generation of the build-up weld layer due to the residual stress of the build-up weld layer during production can be suppressed, and the life of the smelt spout can be improved.

It is a perspective view which shows the structural example of a smelt spout. It is sectional drawing along the AA line in FIG. It is a figure which shows the procedure which produces the inner board in which the overlay welding layer was formed in the surface.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

[First Embodiment]
FIG. 1 is a perspective view showing a configuration example of a smelt spout. 2 is a cross-sectional view taken along line AA in FIG.

  As shown in FIGS. 1 and 2, the smelt spout 1 is mainly composed of an inner plate 2 and an outer plate 4 that are curved in a concave shape, and a cooling water pipe 6. The smelt spout 1 is a saddle member through which smelt (soda melt) discharged from a soda recovery boiler (not shown) flows, and the surface of the inner plate 2 exposed to the smelt is covered with a build-up weld layer 3. ing.

  Further, the space between the inner plate 2 and the outer plate 4 is partitioned by a partitioning portion 9 to form a cooling water channel 8. The cooling water channel 8 communicates with the cooling water pipe 6 through a communication hole (not shown) provided in the cooling water channel 6. Both ends of the cooling water pipe 6 form a cooling water inlet 10 and a cooling water outlet 12, respectively. The cooling water supplied from the cooling water inlet 10 flows into the cooling water channel 8 through the cooling water pipe 6, cools the smelt spout 1, and then is discharged from the cooling water outlet 12.

  The material of the overlay welding layer 3 is not particularly limited as long as it has heat resistance and corrosion resistance and can be formed by overlay welding. For example, high chromium steel such as 18Cr steel or 25Cr steel can be used. In addition, as described later, in the overlay weld layer 3, the convex portion of the weld bead is removed by machining.

  The smelt spout 1 having the above-described configuration is manufactured by producing a curved inner plate 2 having a build-up weld layer 3 formed on the surface, and attaching the outer plate 4 and the cooling water pipe 6 to the inner plate 2 by welding. . Hereinafter, after describing the manufacturing procedure of the inner plate 2, a process until the smelt spout 1 is manufactured using the inner plate 2 will be described.

  FIG. 3 is a diagram showing a procedure for producing the inner plate 2 having the build-up weld layer 3 formed on the surface.

First, as shown in FIG. 3A, the build-up weld layer 3 is formed on the surface of the flat plate 20 by a plurality of weld beads 22.
At this time, the weld bead 22 is preferably formed so as to partially overlap the weld bead 22 formed immediately before. For example, as shown in FIG. 3A, welding beads 22 may be formed in order from the left side to the right side, and welding may be performed so as to partially overlap the adjacent welding beads 22. Alternatively, the welding beads 22 may be formed in order from the right side to the left side, and welding may be performed so as to partially overlap the adjacent welding beads 22. Thus, by forming the weld bead 22 so as to partially overlap the weld bead 22 formed immediately before, the height of the weld bead 22 can be made uniform, and the weld bead 22 to be removed by machining, which will be described later. The amount of the convex part of is reduced.

Since the built-up weld layer 3 formed in this way has nothing to restrain the flat plate 20 at the time of build-up welding, residual stress is hardly generated. However, since the residual stress does not occur at all in the build-up weld layer 3, the flat plate 20 on which the build-up weld layer 3 is formed is annealed. Thereby, the some residual stress which has arisen in the overlay welding layer 3 is released.
In addition, when the build-up weld layer 3 is 18Cr steel or 25Cr steel, you may perform annealing of the flat plate 20 which has the build-up weld layer 3 on the conditions for 30 minutes at 675 degreeC, for example.

Thereafter, as shown in FIG. 3B, the convex portions of the weld beads 22 of the build-up weld layer 3 formed on the flat plate 20 are removed by machining (cutting or grinding). Thus, by removing the convex part of the weld bead 22 of the build-up weld layer 3 where stress tends to concentrate, it is possible to suppress the occurrence of cracks in the build-up weld layer 3. Moreover, machining (cutting or grinding) can be easily performed by removing the convex part of the weld bead 22 in the state of the flat plate 20 before bending.
In addition, it is preferable that the thickness of the build-up weld layer 3 after removing the convex part of the weld bead 22 is a predetermined value or less from the viewpoint of further reducing the residual stress of the build-up weld layer 3. The predetermined value here varies depending on the material of the build-up weld layer 3 and the shape of the inner plate 2, but may be about 3 mm, for example.

  Next, as shown in FIG.3 (c), the inner plate 2 is obtained by making the flat plate 20 which has the build-up welding layer 3 in which the convex part of the welding bead 22 was removed on the surface bend by bending.

On the other hand, in parallel with the production of the inner plate 2, the outer plate 4, the cooling water pipe 6 and other accessories are prepared.
The outer plate 4 is a plate member that is curved along the inner plate 2 and is obtained by bending the flat plate by bending. The cooling water pipe 6 is formed by bending the pipe material according to the outer shape of the inner plate 2 and the outer plate 4 by bending, and forming a communication hole to the cooling water channel 8 (see FIG. 2) by drilling the pipe material. can get. Further, as another accessory, a support metal for attaching the smelt spout 1 to the smelt discharge port of the soda recovery boiler is produced.
Finally, the outer plate 4, the cooling water pipe 6 and other accessories are attached to the inner plate 2 by welding. Thereby, the smelt spout 1 shown to FIG. 1 and 2 is obtained.

  As described above, in this embodiment, the smelt spout 1 in which the cooling water channel 8 is formed between the inner plate 2 and the outer plate 4 having the build-up weld layer 3 on the surface is mainly formed on the surface of the flat plate 20. It was annealed so as to obtain a build-up welding process for forming the build-up weld layer 3, an annealing process for annealing the flat plate 20 on which the build-up weld layer 3 was formed, and an inner plate 2 curved in a concave shape. It is manufactured by a bending process for bending the flat plate 20 and an outer plate attaching process for attaching the outer plate 4 to the inner plate 2 so that the cooling water channel 8 is formed between the inner plate 2 and the inner plate 2.

  According to the present embodiment, since the build-up welding is performed on the surface of the flat plate 20 before bending, there is nothing to restrain the flat plate 20 during the build-up welding, and residual stress is generated in the build-up weld layer 3. Hard to occur. Even if some residual stress is generated in the build-up weld layer 3, the residual stress is released by annealing. Therefore, the crack generation of the build-up weld layer 3 due to the residual stress of the build-up weld layer 3 during production can be suppressed, and the life of the smelt spout 1 can be improved.

  As mentioned above, although embodiment of this invention was described in detail, it cannot be overemphasized that this invention is not limited to this, In the range which does not deviate from the summary of this invention, various improvement and deformation | transformation may be performed.

  For example, in the above-described embodiment, the example in which the convex portion of the weld bead 22 of the build-up weld layer 3 formed on the flat plate 20 is removed by machining, but the surface of the flat plate 20 before bending is performed. By performing build-up welding, the residual stress of the build-up weld layer 3 may be reduced to sufficiently suppress the occurrence of cracks in the build-up weld layer 3, and it is not always necessary to remove the convex portion of the weld bead 22. Absent. That is, after the build-up weld layer 3 is formed on the flat plate 20 without removing the convex portion of the weld bead 22, the process may proceed to the bending process of the flat plate 20 as it is.

DESCRIPTION OF SYMBOLS 1 Smelt spout 2 Inner plate 3 Overlay welding layer 4 Outer plate 6 Cooling water pipe 8 Cooling water channel 9 Partition part 10 Cooling water inlet 12 Cooling water outlet 20 Flat plate 22 Weld bead

Claims (5)

A method for producing a smelt spout in which a cooling water channel is formed between an inner plate and an outer plate having an overlay weld layer on the surface,
Build-up welding process for forming a build-up weld layer on the surface of the flat plate;
An annealing step for annealing the flat plate on which the overlay weld layer is formed; and
A bending step of bending the annealed flat plate so as to obtain a concavely curved inner plate;
A method for producing a smelt spout, comprising: an outer plate attaching step of attaching the outer plate to the inner plate so that the cooling water channel is formed between the inner plate and the inner plate.   The method for producing a smelt spout according to claim 1, further comprising a convex portion removing step of removing a convex portion of the weld bead of the build-up weld layer.   3. The smelt spout according to claim 2, wherein the convex portion removing step is performed before the bending step, and the convex portion of the weld bead of the build-up weld layer on the surface of the flat plate is removed. Production method. An inner plate that is concavely curved and has a build-up weld layer on the surface;
An outer plate attached to the inner plate so that a cooling water channel is formed between the inner plate and the inner plate;
The inner plate is produced by forming the build-up weld layer on the surface of a flat plate, annealing the flat plate, and bending the smelt spout.   5. The smelt spout according to claim 4, wherein a convex portion of a weld bead of the build-up weld layer is removed from the inner plate.

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