JPH07102348A - Corrosion resistant metallic material for trash incineration treating equipment - Google Patents

Abstract

PURPOSE:To produce a corrosion resistant metallic material for trash incineration treating equipment (such as a fire grate and a boiler tube) capable of showing excellent corrosion resistance even in the case of being exposed to a very severe high temp. corrosive environment by using relatively inexpensive metallic stock. CONSTITUTION:This metallic material essentially contains an Fe-Al series binary alloy having 20 to 45 atomic % Al content. This Fe-Al series binary alloy is constituted of an Fe-Al series intermetallic compound and/or an FeAl series intermetallic compound, and it shows excellent applicability for, in particular, the stock for the fire grate and boiler tube of an incinerator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a waste incineration facility (including a refuse incinerator and a waste power generation facility) exposed to a very severe corrosive environment, and is a high temperature corrosion resistant metal mainly composed of an Fe-Al alloy. This metal material is useful as a grate of an incinerator, a pipe material for a heat exchanger of a waste power generation facility, and the like.

[0002]

2. Description of the Related Art The amount of municipal waste generated has increased rapidly over the last few years, and the amount of incinerated waste has also increased along with the difficulty of securing landfill sites. On the other hand, research on utilizing the incineration energy of these wastes for power generation has been actively pursued, and power generation facilities using wastes as fuel have been constructed one after another since the 1970s and are operating on a practical scale. It is clear that the amount of waste generated will increase in the future, and waste is positioned as an important energy source in the future.

By the way, garbage contains a large amount of plastics containing chlorine and various metal salts and heavy metal salts. Therefore, the grate of an incinerator and the boiler pipe of a power generation facility are corrosive gas and medium. It is exposed to a very severe corrosive environment, including dust and adhered ash. That is, the combustion atmosphere forms a severe corrosive environment containing a large amount of oxidizing air, high-concentration HCl, SO _x , NO _x , water and the like, and further sulfate and chloride. It is considered that the combustion atmosphere basically constitutes a severe corrosive environment in which molten salt corrosion due to an alkali metal salt and acid gas corrosion mainly containing HCl combine with a high temperature to bring about a synergistic action.

Considering such corrosive environmental conditions, SCH13 (Fe is a conventional material for the grate of refuse incinerators.
-26% Cr-12% Ni-0.35% C) and SCH1
Corrosion resistant alloy steel materials such as 1 (Fe-26% Cr-5% Ni-0.4% or less C) have been used. However, in recent years as hypoxia incineration in view of prevention of air pollution as a NO _x reduction measures begins to be adopted, has become as a problem of the high temperature corrosion in the above such heat resistant alloy steel is pointed out.

[0005] In particular, grate is hot and usually at a temperature of 50 due to direct exposure to combustion gases and direct contact with falling combustion residues.
As it undergoes temperature fluctuations of about -80 ° C, alloy steel materials repeatedly expand and contract under these influences, causing corrosion products (scale) to break and peel off, and the corrosion resistance of alloy steel bases depleted of Cr. It is considered that erosion due to corrosive gas progresses at an accelerated rate. Therefore, the use of a heat-resistant alloy steel containing no Ni such as SCH2 was examined as a measure for preventing high-temperature corrosion, but satisfactory high-temperature corrosion resistance has not been obtained.

On the other hand, STB35 (carbon steel pipe) is currently mainly used as a boiler pipe for refuse power generation equipment, but these also rapidly corrode under the high temperature corrosive environment as described above. The rate of corrosion progress is temperature 4
It has been confirmed that it becomes noticeable when the temperature exceeds 00 ° C. Therefore, in actual operation, the temperature of the boiler tube should be 400 ° C.
The control operation is performed at a temperature below about 300 ° C (steam temperature below 300 ° C).

However, since it is obvious that the above-mentioned control operation is disadvantageous in improving the energy efficiency of power generation, the steam temperature is set to 50 to improve the energy efficiency.
There is a movement to raise the temperature to about 0 ° C or higher, and research and development of high temperature corrosion resistant materials that can withstand such temperature conditions are also underway. Although there is a stainless steel material as a general-purpose corrosion resistant metal material, the high temperature corrosion resistance in the severe corrosive environment as described above is insufficient. At present, the most promising are Alloy 825 (22% Cr-42% Ni-3%
Mo) and Alloy 625 (22% Cr-62% Ni-
Ni-based alloys such as 9% Mo), but these Ni-based alloys are very expensive and not suitable for practical use. Further, it is possible to use stellite (Co-Cr-WC alloy), 50% Cr-50% Ni, etc. by utilizing the general tendency that the high-temperature corrosion resistance is improved by increasing the Cr or Ni content. It is pointed out that these are also very expensive and have extremely poor workability.

On the other hand, an inexpensive carbon steel is used as a material, and its surface is coated with Al by a dipping method as a measure for improving high temperature corrosion resistance, and the Al coating layer is changed to an Al oxide film in a high temperature oxidizing atmosphere during use. Although a method (alma processing method) for imparting high temperature corrosion resistance is also known by this method, this method also causes the Al oxide film to peel off under high temperature conditions exceeding about 400 ° C. It cannot be applied to boiler boiler tubes.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to expose a relatively inexpensive metal material to the above-mentioned severe high temperature corrosive environment. The present invention intends to provide a corrosion-resistant metal material for a refuse incineration facility, which can exhibit excellent corrosion resistance even in the case of the above.

[0010]

Means for Solving the Problems The structure of the corrosion-resistant metal material for refuse incineration equipment according to the present invention, which has been able to solve the above-mentioned problems, has an Fe content of 20 to 45 atomic%.
It has a gist that it contains a binary alloy as a main component, and this Fe-Al based binary alloy is F
e ₃ Al-based intermetallic compound and / or FeAl-based intermetallic compound, wherein the corrosion-resistant metallic material is
In particular, it exhibits excellent suitability as a material for incinerator grate and boiler tubes. Also, when using it as a boiler tube, the Al content on the outer surface side exposed to severe corrosive environment is 2
If it is composed of an alloy containing 0 to 45 atomic% of Fe-Al binary alloy as the main component and the inner surface is composed of ordinary carbon steel that can withstand high temperature steam, the material cost of the boiler tube will be much lower. It can be anything.

[0011]

As is well known, many intermetallic compounds, such as Ni, are used.
It has been confirmed that Al, CoAl, FeAl, MoSi _2, etc. exhibit excellent corrosion resistance in a high temperature oxidizing atmosphere.
However, the degree of corrosion resistance of these intermetallic compounds in a severe corrosive environment in which a corrosive metal salt (incineration residue) coexists, including high-temperature HCl gas, such as the grate and boiler pipe of the refuse incineration facility. It has not been clarified at present whether it will work.

On the other hand, it is also known that intermetallic compounds generally have poor ductility and very poor moldability. Therefore, in order to make these intermetallic compounds practicable as materials for grate and boiler tubes, it is necessary to thoroughly study the formability.

In view of the above, various intermetallic compounds are taken into consideration in consideration of corrosion resistance and molding processability in a corrosive environment in which a high temperature corrosive gas and a corrosive metal salt coexist, and also the price. We pursued its applicability as a corrosion-resistant metal material for refuse incineration equipment.

As a result, among the Fe-Al alloys which are cheaper than the conventional high-temperature corrosion resistant Ni-based alloys, the Fe-contents of which the Al content is 20 to 45 atom%, particularly 25 to 40 atom%.
Al-based binary alloys have high-temperature corrosion resistance comparable to Ni-based alloys, and are relatively easy to process into plates, rods, and tubes, and high-temperature corrosion-resistant metals for grate and boiler tubes in refuse incineration facilities. It was confirmed that an excellent effect as a material can be exhibited.

Al content in Fe-Al binary alloy
The specific basis for determining the range of 20 to 45 atom% is described later.
The details will be described with reference to the following examples.
Fe-Al binary alloys containing
l-based intermetallic compound single phase, Fe ₃ Al-based intermetallic compound
Phase, or a mixture of these phases,
Fe-Al binary alloys with similar phase structure have excellent high temperature corrosion resistance.
And moldability.

By the way, the high temperature corrosion resistance and the formability of the Fe-Al binary alloy are significantly changed depending on the Al content and the phase structure which changes with it, and the Al content is 1 or less.
If it is less than 0 atomic%, excellent moldability is exhibited, but with this composition, an intermetallic compound is not formed and the high temperature corrosion resistance becomes poor. Further, although the high temperature corrosion resistance is improved in the composition range where the Al content is 10 to 20 atomic%, the high temperature corrosion resistance under severe corrosion conditions when applied for incineration facilities is insufficient, and thus, for the purpose of the present invention. It will not fit.

On the other hand, when the Al content is 20 atomic% or more, the phase structure is mainly Fe ₃ Al-based intermetallic compound, and as the Al content increases, the ratio of the FeAl-based intermetallic compound increases, and the Al content increases. rate but is exceeds 35 atomic% FeAl intermetallic compound single-phase, these Fe ₃
Al-based single phase, two-phase coexistence of Fe ₃ Al and FeAl-based or FeAl-based single phase shows high temperature corrosion resistance comparable to or exceeding Ni-based alloys and excellent workability, and grate and boiler tube. Hot-working to etc. can also be performed relatively easily. However, when Al content exceeds 45 atomic%, next 2 phases coexist FeAl ₂ system together with FeAl system, such as those containing FeAl ₂ intermetallic compound is poor in hot workability, processing into tubular such Because it becomes difficult, it lacks practicality.

As described above, the corrosion-resistant metal material of the present invention is made of Al
Content is 20 to 45 atom%, more preferably 25 to 40
The atomic percentage is mainly Fe ₃ Al-based and / or FeAl-based intermetallic compounds, but if necessary, a small amount (total 20% or less) of alloying elements (Cr, Ni, etc.) may be included. ) Is also effective.

By the way, when the above corrosion-resistant metal material is used as a boiler pipe for a refuse incineration facility, all of the above-mentioned pipe material can be the above-mentioned corrosion-resistant metal material. However, considering the corrosion conditions of the boiler tube, its outer surface side is exposed to the severe high temperature corrosive environment as described above, but its inner surface side is only in contact with high temperature steam, so that not so much corrosion resistance is required. Therefore, in consideration of these differences in corrosion conditions, it is necessary and sufficient to use a double pipe structure made of carbon steel on the outer surface side of the boiler tube and the inner surface side of carbon steel showing sufficient corrosion resistance to high temperature steam. This is advantageous because the material cost as a whole can be reduced while ensuring high temperature corrosion resistance.

A boiler tube having such a double tube structure is manufactured by a coextrusion molding method, an Osprey method, or a method of coating the above-mentioned FeAl intermetallic compound on the outer surface side of a carbon steel tube by thermal spraying or overlaying. do it.

[0021]

EXAMPLES Next, examples of the present invention will be shown, but the present invention is not limited by the following examples, and may be carried out with appropriate modifications within a range compatible with the gist of the preceding and following description. Of course, it is possible, and all of them are included in the technical scope of the present invention.

Example 1: Trial manufacture of Fe-Al binary alloy and atmospheric oxidation test Five kinds of Fe-Al binary alloys made of Fe-10, 20, 30, 40, 50 Al (atomic%, hereinafter omitted) About 50kg ingot by vacuum high frequency melting,
After homogenizing treatment under the conditions of 00 ° C. × 24 h, a 25 mmφ round bar was manufactured by hot extrusion. The extrusion conditions are a heating temperature of 1200 ° C. and an extrusion ratio of 6 and 1000 ° C. × 1 after extrusion.
The heat treatment was performed under the conditions of h and air cooling.

In this round bar trial experiment, Fe-10
With 40Al, sound extruded round bars were obtained, but F
With e-50Al, severe intergranular cracking occurred. I couldn't make a round bar. As a result of X-ray diffraction, Fe
-40Al had a single phase of FeAl-based intermetallic compound, but Fe-50Al had _two phases of FeAl and FeAl ₂ .
Since it is a phase alloy, it has been clarified that the hot workability is extremely reduced due to the presence of the FeAl ₂ phase. According to the state diagram, when the Al content is about 48% or less, FeAl
It has been shown to be monophasic.

Further, the above-mentioned five types of extruded round bar heat-treated materials were subjected to an atmospheric oxidation test. Test conditions are 800,900,1
3 kinds of continuous oxidation in air at 000 ° C x 1000h
The results are shown in Table 1.

[0025]

[Table 1]

As is clear from Table 1, the oxidation resistance is Al
It greatly fluctuates depending on the amount, and becomes extremely bad especially in the case of Fe-10Al. However, Fe-30,40Al shows good oxidation resistance not only in SUS304 but also in Ni-based alloy Alloy 718. Oxidation resistance is a basic property that must be cleared when used as a high temperature material. According to the state diagram, the amount of Al is about 20.
If it is more than 100%, Fe ₃ Al-based intermetallic compounds are generated. Therefore, it is considered that the reason why the oxidation resistance of Fe-10Al is extremely deteriorated is that the composition is not an intermetallic compound phase.

When other elements are added to the Fe-Al system, A
It is considered that the appropriate range (upper limit and lower limit) of the amount of 1 is slightly changed, but basically, the Al content is set in the range of 20 to 45%, and most of the matrix is Fe ₃ Al phase or FeA.
By adopting the 1-phase single phase or the two-phase coexisting system of Fe ₃ Al + FeAl, it is possible to obtain a material having both excellent workability and high temperature corrosion resistance.

[0028] Example 2: the Fe-28Al is Fe ₃ atmospheric oxidation test Al alloy Fe ₃ Al-based binary alloy and the Cr which are said to improve the room temperature ductility was added 5% Fe
-28Al-5Cr is 5 by vacuum high frequency melting.
A 0 kg ingot was melted, homogenized at 1200 ° C. for 24 hours, and then forged repeatedly to produce a 25 mmφ round bar. The heating temperature at the time of forging was 1150 ° C., and the forging was performed by repeating the heating a plurality of times. The heat treatment condition after forging was 800 ° C. × 1 h.

About these two kinds of alloys, 1000 ° C. ×
The results of the continuous oxidation test in the air for 200 hours are shown in Table 2, and it is clear that the deterioration of the oxidation resistance due to the presence or absence of the addition of Cr is hardly recognized, and that the excellent oxidation resistance is obtained. is there.

[0030]

[Table 2]

Example 3: Corrosion test of Fe ₃ Al based alloy in high temperature gas containing HCl Fe-28Al and F obtained in the same manner as in Example 2 above.
Using e-28Al-5Cr as a test material, a corrosion test was conducted in the following atmosphere gas simulating the exhaust gas of a refuse incinerator and a waste power generation facility.

Atmospheric gas composition: HCl (0.24 V
ol%) + H ₂ O (relative humidity: 30%) + Air (remaining) ・ Temperature: 700 ° C. ・ Time: 120 h ・ Atmospheric gas flow rate: 0.7 liter / min The results are as shown in Table 3, Fe ₃ Al It can be confirmed that the system alloy exhibits corrosion resistance comparable to or higher than that of the Ni-based alloy (Alloy 625), which is considered to be the most promising at present, even in the extremely severe corrosive atmosphere as described above.

[0033]

[Table 3]

Example 4 Prototype Experiment of Fe ₃ Al Alloy Tube and Double Tube For two kinds of alloys Fe-28Al and Fe-28Al-5Cr, 50 kg ingot was melted by vacuum high frequency melting, and 1200 ° C. After homogenizing treatment under the condition of 3h,
A 80 mmφ round bar was manufactured by heat forging at 1150 ° C. and 850 ° C. This round bar has an outer diameter of 70 mm and an inner diameter of 35 m.
After processing into an extruded billet of m, a tube having an outer diameter of 33 mm and an inner diameter of 28 mm (extrusion ratio: 12) was manufactured by the hot isostatic pressing method at a temperature of 900 ° C. At this time, the glass material was prevented from being oxidized when the billet was heated. By using the material and performing sufficient glass lubrication during extrusion, a sound extruded tube was obtained for both of the above two alloys.

For Fe-28Al-5Cr, an outer diameter of 31.5 was obtained by using an as-extruded tube (without heat treatment).
Cold drawing was carried out up to mm without a mandrel, but there was no particular problem and it was confirmed that finish drawing was possible.

In the double pipe trial manufacture, carbon steel (S
TB35) and Fe-28Al-5Cr on the outer surface side, and the same hot isostatic extrusion method as described above was applied. The billet size is the same as above, but the outer surface Fe-28Al-5Cr has a total thickness of 17.5.
It was set to 4.5 mm out of mm. Therefore, the thickness of the Fe-28Al-5Cr layer on the outer surface side of the double pipe after extrusion is about 0.8.
mm (total wall thickness 2.5 mm). It was confirmed that this double pipe could also be subjected to finish drawing by performing cold drawing without heat treatment after extrusion.

[0037]

The present invention is constituted as described above, and F
The Al content in the e-Al based alloy is specified, and the main phase constitution is Fe ₃ Al based intermetallic compound and / or FeA.
By using an l-based intermetallic compound, it is possible to provide a metal material that exhibits excellent corrosion resistance even in a severe corrosive environment at high temperature and has excellent suitability as a grate or boiler pipe for refuse incineration equipment. became.

Claims (5)

[Claims] 1. An Fe-containing material having an Al content of 20 to 45 atomic%.
A corrosion-resistant metal material for a refuse incineration facility, which contains an Al-based binary alloy as a main component. 2. The corrosion-resistant metal material according to claim 1, wherein the Fe-Al binary alloy comprises an Fe ₃ Al intermetallic compound and / or an FeAl intermetallic compound. 3. The corrosion resistant metal material according to claim 1, which is used for a grate of a refuse incinerator. 4. The corrosion-resistant metal material according to claim 1, which is used for a boiler pipe in a refuse incineration facility. 5. The outer surface side is made of an alloy containing a Fe--Al binary alloy having an Al content of 20 to 45 atomic% as a main component, and the inner surface side is made of carbon steel.
Corrosion resistant metal material described.