JP4633748B2 - Method for producing highly corrosion-resistant boiler cladding for waste incinerator and powder cladding material used therefor - Google Patents

Description

  The present invention relates to a method for producing a highly corrosion-resistant boiler cladding for a waste incinerator and a powder cladding material used therefor.

  In recent years, in order to effectively use the heat generated by incineration of municipal waste, etc., a waste heat recovery boiler has been installed in conjunction with the waste incineration equipment, and a boiler pipe has been placed on the distribution path of the combustion exhaust gas generated by the waste incineration. However, the water circulating through the boiler tube is heated to steam and used for heat generation and other heat utilization.

For example, the following Patent Document 1 discloses an example of this type of facility.
FIG. 5 shows this.
In the figure, 200 is a waste incinerator, and 201 and 202 are an incinerator and a boiler part of the incinerator 200, respectively.
The boiler unit 202 has a boiler tube group on the flow path of the combustion exhaust gas from the incineration unit 201, and high-temperature and high-pressure steam is generated in the boiler tube by the heat of the combustion exhaust gas, and is used for other heat generation. The

  The combustion exhaust gas that has passed through the boiler tube group and has been absorbed by the heat is lowered in temperature by the temperature control tower 204, passes through the bag filter 206, is removed there, and is then discharged from the chimney 208.

By the way, incineration ash adheres to the boiler tube, and when the amount increases, the passage of the combustion exhaust gas is narrowed, and the efficiency of heat exchange decreases.
Therefore, steam (saturated steam or superheated steam) is periodically sprayed on the boiler pipe at a high pressure to remove the deposited incineration ash.

By the way, combustion exhaust gas and incineration ash are highly corrosive materials containing chloride and sulfide substances, and the boiler tube is exposed to the high temperature of the combustion exhaust gas. is there.
Conventionally, inexpensive JIS STB340S-C (C: ≤0.18%, Si: ≤0.35%, Mn: 0.30-0.60%, P: ≤0.035%, S: ≤0.035%) has been used as a boiler tube for waste incinerators. However, this is not sufficient in corrosion resistance, and the boiler tube is corroded in the above corrosive environment.
Further, the thinning of the boiler tube proceeds due to the progress of corrosion and the repeated spraying of steam to remove the incinerated ash onto the boiler tube.

For this reason, conventionally, a stainless steel plate or pipe having high corrosion resistance divided in the radial direction is covered with a boiler pipe as a protector, and is fixed by bolt fastening or welding to protect the boiler pipe.
However, in this case, the boiler tube and the protector made of stainless steel plate or tube are not in close contact with each other, and a gap is formed between them, and the protector is heated to a high temperature by the heat of the combustion exhaust gas due to the gap. End up.

The boiler pipe is cooled to some extent by the steam (saturated steam or superheated steam) flowing through the inside of the boiler pipe, but the protector that covers this through the gap is not sufficiently cooled by the steam. The temperature rises to a higher temperature.
Therefore, even if it is installed as such a protector made of stainless steel, the protector itself has been reduced in thickness due to corrosion and high-pressure steam spraying, so the service life is short, and it is necessary to replace it quickly. End up.
For this reason, instead of attaching a stainless steel protector to the boiler tube, it is proposed that the high corrosion resistant alloy is directly welded to the outer surface of the boiler tube, and the boiler tube is covered with the overlay layer. (For example, Patent Document 1 and Patent Document 2 below).

However, when overlay welding is directly performed on the outer surface of the boiler tube and the protector layer is formed by the overlay layer, another new problem arises.
For example, in order to form a JIS SUS310S corrosion-resistant layer as a build-up layer on the outer surface of a JIS STB340 carbon steel pipe as a mother pipe, a build-up material having the same composition as SUS310S is built-up. When welding is performed, the composition of the overlay layer differs from the original composition of the overlay material, and the corrosion resistance of the resulting overlay layer becomes insufficient.
This is because the components of the mother pipe diffuse into the build-up layer during welding, and the corrosion-resistant component (component that gives corrosion resistance) of the build-up layer is diluted by dilution.

  In addition, although the case where the layer of the composition of SUS310S is formed as the corrosion-resistant build-up layer is taken as an example, JIS STB340 is taken as an example of the mother pipe, but other materials are used as the mother pipe, and the composition of the build-up layer The situation is the same when other high corrosion resistance compositions are used.

Japanese Patent Laid-Open No. 10-30897 JP-A-8-103867

  The present invention is based on the above circumstances, and a method for producing a highly corrosion-resistant boiler overlay for a waste incinerator capable of easily forming a target highly corrosion-resistant build-up layer, and a build-up material used therefor It was made for the purpose of providing.

Thus, claim 1 relates to a method for manufacturing a boiler overlay pipe for a refuse incinerator, wherein a carbon steel steel pipe is used as a mother pipe, and a dilution component is estimated in anticipation of dilution of the ingredient by the mother pipe at the time of welding. Corrosion resistance of the target composition different from the composition of the overlay material before welding to the outer surface of the mother pipe by overlay welding the outer material of the mother pipe with the component adjusted so as to contain a large amount in advance of the cladding layer formed as a protector layer upon producing a high corrosion resistant boiler cladding tube for waste incinerators, with JIS STB340 as before Symbol substrate tube, the outer surface of said mother tube, by mass%, C: ≦ 0.08%, Si: ≦ 1.50 %, Mn: ≦ 2.00%, Ni: 19.0~22.0%, Cr: contains 24.0 to 26.0%, to form a cladding layer of the composition of the balance inevitable impurities and Fe and the As the overlay material for forming the overlay layer , C: ≦ 0.08%, Si: ≦ 1.50%, Mn: ≦ 2.00%, Ni: 19.5-32.0% in mass% , Cr: 24.7 to 38.0%, Ni and Cr as corrosion resistant components are included in excess of the overlay layer, and the balance material unavoidable impurities and Fe composition adjusted to the composition of Fe, using the overlay welding As a technique, plasma powder welding is used in which the powder material is supplied into a plasma arc and melted and welded by plasma heat .

Those claims 2 Oite to claim 1, wherein the forming the cladding layer thickness of less than the thickness 1.0mm or 3.5 mm.

Claim 3 relates to the build-up material. On the outer surface of the mother pipe of JIS STB340, in mass%, C: ≦ 0.08%, Si: ≦ 1.50%, Mn: ≦ 2.00%, Ni: 19.0-22.0%, Cr : 24.0 to 26.0%, powder build-up material for forming a built-up layer of the composition of the inevitable impurities and Fe as a protector layer by plasma powder welding , in mass%, C: ≦ 0.08%, Si: ≦ 1.50%, Mn: ≦ 2.00%, Ni: 19.5 to 32.0%, Cr: 24.7 to 38.0%, and containing Ni and Cr as corrosion-resistant components in excess of the overlay layer, and the remainder of inevitable impurities and Fe It has the composition of this.

Effects and effects of the invention

  As described above, the manufacturing method according to claim 1 uses a carbon steel steel pipe as a mother pipe when manufacturing a highly corrosion-resistant boiler overlay for a waste incinerator, and previously dilutes components by the mother pipe at the time of welding. A build-up material with the corrosion resistance component adjusted to a high concentration in anticipation is build-up welded to the outer surface of the mother pipe, thereby forming a corrosion-resistant build-up layer of the desired composition on the outer surface of the mother pipe According to the present invention, despite the dilution by the mother pipe during welding, it is possible to form a corrosion-resistant build-up layer having a desired proper composition on the outer surface of the mother pipe as a protector layer. It is possible to provide sufficient corrosion resistance.

In this case, in the present invention, JIS STB340 is used as the mother pipe, and JIS SUS310S equivalent material on the outer surface of the mother pipe, specifically, in mass%, C: ≦ 0.08%, Si: ≦ 1.50%, Mn: ≦ 2.00% , Ni: 19.0 to 22.0%, Cr: 24.0 to 26.0%, the remainder of the inevitable impurities and the composition of Fe is formed, and as a build-up material therefor, C: ≦ Containing 0.08%, Si: ≤1.50%, Mn: ≤2.00%, Ni: 19.5-32.0%, Cr: 24.7-38.0% and containing Ni and Cr as corrosion resistant components in excess of the overlay layer Ru used as adjusted.

Further, in the production method of the present invention, plasma powder welding (PTA) is used as a build-up welding technique, more specifically, a powder material is used as a build-up material, and the powder material is supplied into a plasma arc and melted by plasma heat. Plasma powder welding is used in which is welded to the material to be welded.

According to this plasma powder welding, it is possible to easily and freely adjust the composition of the powder material as the build-up material, and therefore it is possible to easily and inexpensively obtain the build-up material having a desired and appropriate composition.
In addition, in this plasma powder welding, a built-up layer up to a thickness of about 3.5 mm can be easily formed by one build-up welding, and conversely, a thin built-up layer of 1.5 mm or less can be formed well and easily. be able to.
For example, in the case of MIG welding, it is difficult to form a built-up layer with a thin thickness of 1.5 mm, and when the built-up layer is formed with this thickness, there is a possibility that a defect will occur in the built-up layer.
However, if plasma powder welding is used, a good build-up layer with few defects can be easily formed.
Moreover, if this plasma powder welding is used, it is also possible to form a 1 mm build-up layer having a thickness of 1.5 mm or less.

In addition, the reason for limitation of a component is as follows.
(Building layer components)
C: ≤ 0.08%
C is an austenite-forming element, and has the effect of improving the solidity of the matrix by solid solution strengthening. However, if it is contained in a large amount, it produces chromium carbide, which degrades corrosion resistance and oxidation resistance. %.

Si: ≦ 1.50%
Si is an element contributing to the improvement of oxidation resistance, and may be added as necessary. However, if added in a large amount, the parent phase becomes brittle and sufficient toughness cannot be obtained, so the upper limit was made 1.50%.

Mn: ≤2.00%
Mn is an austenite-forming element and contributes to the stabilization of the austenite structure of the parent phase. Therefore, Mn may be added as necessary. However, adding a large amount deteriorates corrosion resistance and oxidation resistance, so the upper limit is made 2.00%.

Ni: 19.0-22.0%
Ni is an austenite-forming element and contributes to stabilization of the austenite structure of the parent phase and improvement of heat resistance. If it is less than 19.0%, the austenite structure of the parent phase is not stable, and if it exceeds 22.0%, the cost increases. Therefore, the range is set to 19.0 to 22.0%.

Cr: 24.0-26.0%
Cr greatly contributes to the improvement of oxidation resistance and corrosion resistance by forming chromium oxide on the surface. If it is less than 24.0%, the oxidation resistance and corrosion resistance are not sufficiently improved. If it exceeds 26.0%, a delta ferrite phase is formed and the austenite structure becomes unstable, so the range is set to 24.0 to 26.0%.

(Ingredients for overlaying materials)
C: ≤ 0.08%
C is an austenite-forming element and has the effect of improving the hardness of the matrix phase by solid solution strengthening. If it is contained in a large amount, chromium carbide is formed and the corrosion resistance and oxidation resistance are deteriorated, so the upper limit is made 0.08%.

Si: ≦ 1.50%
Si is an element contributing to the improvement of oxidation resistance, and may be added as necessary. However, if added in a large amount, the parent phase becomes brittle and sufficient toughness cannot be obtained, so the upper limit was made 1.50%.

Mn: ≤2.00%
Mn is an austenite-forming element and contributes to the stabilization of the austenite structure of the parent phase. Therefore, Mn may be added as necessary. However, adding a large amount deteriorates corrosion resistance and oxidation resistance, so the upper limit is made 2.00%.

Ni: 19.5-32.0%
Ni is a main element that improves the heat resistance of the built-up layer, and it is necessary to improve the heat resistance more than the parent phase (parent pipe) part, so 19.5% or more of addition is necessary. On the other hand, considering the dilution of the content due to dissolution of the parent phase during PTA, a higher content than the parent phase is necessary, but if it exceeds 32.0%, the cost becomes too high, and boiler overlays are manufactured at low cost become unable.

Cr: 24.7-38.0%
Cr is a main element that improves the corrosion resistance and oxidation resistance of the built-up layer, and it is necessary to improve the corrosion resistance and oxidation resistance as compared with the parent phase (parent pipe) part, so addition of 24.00% or more is necessary. On the other hand, considering the dilution of the content due to the dissolution of the parent phase during plasma powder welding (PTA), a larger content than the parent phase is necessary. However, if it exceeds 38.0%, a delta ferrite phase is formed, and the austenite structure is Since it becomes unstable, the range is set to 24.7 to 38.0%.

The excess of Ni and Cr as corrosion-resistant components varies depending on the thickness of the overlay layer, but the excess should be 1.2 to 22% based on the composition of the overlay material (Ni and Cr in the overlay material). Is desirable.
If the excess is less than 1.2%, Ni and Cr cannot be contained in a sufficient amount in the build-up layer after build-up welding, resulting in low corrosion resistance.
On the other hand, even if it exceeds 22%, the effect is saturated and the cost is increased.

According to the present invention , an inexpensive carbon steel pipe is used as a mother pipe, and the build-up layer can also be made of a relatively inexpensive SUS310S equivalent material as a corrosion-resistant material, and the boiler build-up pipe is constructed at low cost. And its corrosion resistance can be sufficient.

In the present invention, it is desirable that the thickness of the built-up layer is 1.0 mm or more and 3.5 mm or less (claim 2 ).
Even if the thickness of the build-up layer is made thicker than 3.5 mm, the effect is thin, while the cost is increased.
In particular, when a built-up layer defined in the present invention is formed, the thickness is 1.0 mm, and the necessary corrosion resistance can be imparted.
In consideration of fluctuations in the build-up conditions, the thickness is preferably 1.0 mm and sufficient corrosion resistance can be provided.

In addition, when forming such a build-up layer by one build-up, a composition suitable as a build-up material changes with the magnitude of the thickness.
For example, in the case of forming a cladding layer of the present invention in the present invention by using a buildup material defining, suitable composition of the deposition material, such as, respectively, depending on the thickness of the deposition layer next (except corrosion component As Ni and Cr only). The excess of Ni and Cr are also shown below.
Overlay thickness Ni Cr excess
1.0mm 23-32% 29-38% 9-22%
1.5mm 21-30% 27-35% 5-17%
2.0mm 20-29% 25-34% 2-15%
3.5mm 19.5-27% 24.7-32% 1.2-11%

Therefore, when the thickness of the built-up layer is 1.0 to 1.5 mm, 1.5 to 2.0 mm, 2.0 to 3.5 mm, the following is preferable as the contents of Ni and Cr: Amount.
Overlay thickness Ni Cr excess
1.0-1.5mm 21-32% 27-38% (5-22%)
1.5 over 2.0mm 20-30% 25-35% (2-17%)
Over 2.0 to 3.5mm 19.5 to 29% 24.7 to 34% (1.2 to 15% )

To claim 3 Next, as a powder cladding material for a plasma powder welding used for production of high corrosion resistant boiler cladding tube for waste incinerators, C: ≦ 0.08%, Si : ≦ 1.50%, Mn: ≦ 2.00% , Ni: 19.5 to 32.0%, Cr: 24.7 to 38.0% are used. By using the powder build-up material according to claim 3 , the above manufacturing method can be suitably carried out.

Next, embodiments of the present invention will be described in detail below.
JIS STB340-SC is used as a mother pipe (outer diameter 38.1 mm × thickness 4 mm), and various cladding materials shown in Table 1 are MIG welded (No. 1) or plasma powder welding shown in FIG. (No. 2 and No. 3) were overlay welded (S in STB340-SC represents a seamless pipe, and C represents a cold finish).
In Table 1, No. 4 SUS310S and No. 5 STB340-SC were used as comparative materials for the corrosion resistance test. These No. 4 and No. 5 comparative materials are solid materials, not overlay welds.

In FIG. 1, 10 represents a plasma torch, 12 represents a tungsten electrode, and 14 represents a material to be welded (base pipe).
Reference numeral 16 denotes a plasma gas, 18 denotes a shielding gas, 20 denotes a powder build-up material, 22 denotes cooling water, and 24 denotes a plasma arc generated between the tungsten electrode 12 and the workpiece 14. ing.
In this plasma powder welding (PTA), a powder build-up material is supplied into a plasma arc 24 generated at the center, melted by plasma heat, and welded onto a material to be welded.
Here, Ar gas is used as the plasma gas, and an inert gas of Ar gas is also used as the shield gas 18.
In addition, the powder overlaying material was supplied to the plasma arc 24 using an inert gas flow of Ar gas as a carrier gas.

  As shown in Table 1, when the build-up layer formed by welding was analyzed with EPMA (electron beam microanalyzer), the No. 1 SUS310 wire material was used, and this was MIG-laid with a thickness of 2 mm. In some cases, the composition was diluted about 24% with 20.5% Cr and 16.0% Ni.

  In addition, when No. 2 SUS310SM (M represents a component adjusted with respect to SUS310S) and this was built up to a thickness of 2 mm by plasma powder welding, the Cr content was 25.8%. The Ni content was 22.4% and the dilution rate was about 15%.

  Furthermore, when SUS310SM is used as a powder build-up material and this is built up to a thickness of 1.5 mm, the Cr content of the build-up layer is 25.1%, and the Ni content is 22.0% and diluted by about 18%. It was.

  As can be seen from the results of No.2 and No.3, even when overlay welding is performed using the same powder overlay material, the dilution rate of Cr and Ni, which are corrosion resistant components, depends on the thickness of the overlay The dilution ratio is smaller as the thickness is larger.

When SUS310SM is used as the No. 2 material, that is, the powder build-up material and is built up with a thickness of 2 mm, the composition of the build-up layer after welding is a composition corresponding to SUS310S.
On the other hand, when SUS310S itself is used as the build-up material, the Cr and Ni contents are reduced as a result of the dilution of Cr and Ni, and the composition of the build-up layer deviates from the composition of SUS310S.

Next, No. 1 to No. 5 were subjected to a high temperature corrosion test.
This high temperature corrosion test was conducted as follows.
As shown in FIG. 2, a build-up layer 28 is formed on the carbon steel mother pipe 26 to obtain a build-up pipe 30 shown in (A) (a), and this is cut at a cutting position P to obtain (A) (b) ) And a test piece 32 shown in (A) and (C) was collected from the built-in tube 30A.
The direction of sampling of the test piece 32 is shown in (A) and (B).
Here, the dimension of the test piece 32 is 15 mm for the dimension a, 10 mm for the dimension b, and 1.8 mm for the thickness c.

Next, the test piece 32 was immersed in the incineration ash 34 produced | generated in the refuse incinerator, and the corrosion test was carried out in that state using the high temperature corrosion test apparatus 36 of FIG. 2 (B).
The composition of the incinerated ash used is shown in Table 2.
In the corrosion test using the high temperature corrosion test apparatus 36 of FIG. 2B, CO ₂ , O ₂ and N ₂ are supplied from the gas cylinder to the gas mixing apparatus 38, and this mixed gas and HCl are supplied in the humidity adjustment tank 40. It is adjusted to corrosive gas (8% CO ₂ + 8% O ₂ + 18% H ₂ O + 0.1% HCl + remaining N ₂ ), and the test piece 32 is set inside the incinerated ash 34 and set in the furnace 42. This state was kept at a temperature of 350 ° C. for 100 hours, and corrosion weight loss (corrosion rate) was determined.
In FIG. 2B, reference numeral 44 denotes an HCl absorption tank.

The result is shown in FIG. In FIG. 3, the corrosion degree is converted into the corrosion degree per year.
From the results of FIG. 3, it can be seen that the corrosion resistance is dramatically improved by overlay welding the corrosion-resistant powder overlay material to the outer surface of the STB340 mother pipe.

Figure 4 compares the difference in corrosion resistance between No. 2 SUS310SM powdered with 2 mm thickness and No. 3 1.5 mm thick with No. 1 results. It is shown.
As shown in the results of FIG. 4, the corrosion resistance is better when the No. 2 material, that is, when the powder overlaying material is built up to a thickness of 2 mm, compared to when the material is built up to a thickness of 1.5 mm. ing.

  When overlay welding is performed with a build-up thickness of 2 mm, the dilution rate of the Cr and Ni mother pipes is smaller than when overlay welding is performed with a build-up thickness of 1.5 mm. In the case where the build-up thickness is 2 mm, the composition of the build-up layer has a composition equivalent to SUS310S, so that the corrosion resistance of No. 2 is better than that of No. 3. It is good.

  Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be implemented in variously modified forms without departing from the spirit of the present invention.

It is explanatory drawing of the method of the plasma powder welding performed in embodiment of this invention. It is explanatory drawing of the method of a high temperature corrosion test. It is a figure showing the result of the high temperature corrosion test at 350 degreeC. It is the figure which showed the principal part of FIG. It is the figure which showed an example of the waste incineration plant.

Claims (3)

Using a steel pipe of carbon steel as the mother pipe, overlay welding is performed on the outer surface of the mother pipe with the component adjusted so as to contain a large amount of diluted components in anticipation of dilution of the components by the mother pipe during welding. Te, different from the composition of the meat Sheng material before welding to the outer surface of the mother tube, the built-up layers of corrosion resistance of the desired composition is formed as a protector layer high corrosion resistant boiler cladding tube for a waste incinerator In manufacturing,
With JIS STB340 as before Symbol substrate tube, the outer surface of said mother tube, in mass%
C: ≤ 0.08%
Si: ≦ 1.50%
Mn: ≤2.00%
Ni: 19.0-22.0%
Cr: 24.0-26.0%
As a build-up material for forming the build-up layer and forming the build-up layer of the composition of the inevitable impurities and Fe of the balance,
C: ≤ 0.08%
Si: ≦ 1.50%
Mn: ≤2.00%
Ni: 19.5-32.0%
Cr: 24.7-38.0%
In addition, Ni, Cr as an anticorrosive component is included in excess of the build-up layer, and the powder material adjusted to the composition of the remaining inevitable impurities and Fe is used as a method of build-up welding in the plasma arc. A method for producing a highly corrosion-resistant boiler overlay for a waste incinerator, characterized in that plasma powder welding is used in which powder material is supplied and melted and welded by plasma heat . Oite to claim 1, the high corrosion resistant boiler manufacturing method of cladding tubes for waste incinerator, characterized in that the cladding layer is formed with a thickness of a wall thickness less than 1.0mm 3.5 mm. On the outer surface of the mother pipe of JIS STB340,
C: ≤ 0.08%
Si: ≦ 1.50%
Mn: ≤2.00%
Ni: 19.0-22.0%
Cr: 24.0-26.0%
A powder build-up material for forming a built-up layer of the balance of inevitable impurities and Fe as a protector layer by plasma powder welding , and in mass%
C: ≤ 0.08%
Si: ≦ 1.50%
Mn: ≤2.00%
Ni: 19.5-32.0%
Cr: 24.7-38.0%
For the production of a highly corrosion-resistant boiler cladding for a refuse incinerator, which contains Ni and Cr as corrosion-resistant components in excess of the cladding layer and has the composition of the remaining inevitable impurities and Fe Powder overlay material to be used.

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