JP2005163177A - Waste-gas duct - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a duct superior in durability/workability in a gas atmosphere in a metal-smelting furnace (a converter or an electric furnace) or an ash-melting furnace. <P>SOLUTION: The waste-gas duct has a structure made by welding a steel for the waste-gas duct, of which the face to be contacted with the gas in a waste-gas passage comprises, by mass%, 0.1-1% Cu, 0.01-0.5% Ni, 3.5-9.0% Cr, and 0.01-0.2% Sb, further one or two elements of 0.005-0.5% Mo and 0.005-0.5% W, and the balance being Fe with unavoidable impurities, with an austenitic welding material. Alternatively, the waste-gas duct has a structure made by welding the surface layer of a bilayer steel material having the above chemical composition on the surface side, with the austenitic welding material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas duct that exhibits excellent durability in an exhaust gas environment of a converter or an electromelting furnace in metal refining of steel or the like, and is excellent in workability, repairability, and economy.

  Hereinafter, the background art will be described by taking a smelting furnace (converter, electric furnace, etc.) for producing steel as an example.

  Since the exhaust gas from the metal smelting furnace contains corrosive gas components and metal dust, the exhaust gas flow path suffers severe wear in the smoke exhaust system. In general, the temperature of the exhaust gas reaches 1200 ° C. In some furnaces, combustible gas is burned in a combustion tower and then vented to a smoke exhausting facility.

  In general, the flue gas duct is a double-tube structure with a carbon steel plate welded structure, a case in which exhaust gas is passed through the inner cylinder and cooling water is passed between the inner cylinder and the outer cylinder, and a water-cooled tube panel with steel pipes arranged on the inner surface of the duct Is used, and cooling water is passed inside. Hereinafter, these are referred to as a flue gas cooling duct.

  In recent years, the exhaust of the flue gas water cooling duct has become prominent. Up to the first half of the 1990s, carbon steel inner cylinders with a plate thickness of 9 mm had a durability of 5 years or more, but recently, even if the plate thickness is increased to 12 mm, there is a case where wear occurs in half a year to a year. Increasingly, routine repairs and replacement work were performed. Further, in the converter exhaust gas (OG) treatment apparatus, recently, the endurance life of the flue gas cooling duct has been shortened to less than half compared with the conventional one.

  Possible causes of wear include wear due to collision of solid particles, molten salt corrosion due to dust, and wet corrosion due to the formation of concentrated electrolyte due to moisture absorption, but it has been clarified which factor is the dominant process of wear. There was no problem.

  In the prior art for preventing wear and tear of the flue gas water cooling duct, a method for ensuring durability by changing the material of the surface in contact with the exhaust gas has been proposed. This method can be classified into a method of modifying the surface in contact with the exhaust gas and a method of changing the material of the member itself constituting the duct.

  Examples of methods for modifying the surface in contact with the exhaust gas include 1) lining with heat-resistant and refractory bricks, 2) lining with inorganic casters, 3) applying a build-up sprayed layer, 4) high alloy steel on the surface A method such as adopting clad steel is considered, and some have already been proposed.

  For example, a method of forming a thermal spray coating of a stainless steel alloy as shown in (Patent Literature 1) or a thermal spray coating layer of an alloy of an alloy that forms an oxide at 800 ° C. as shown in (Patent Literature 2). Furthermore, coating with a self-fluxing sprayed alloy represented by Ni-Cr-Mo-B system shown in (Patent Document 3) (metal coating for forming an alloy layer with a base material and a sprayed metal) and the like can be mentioned. .

  In addition, as a method of changing the material of the member constituting the duct itself, it is easily considered to use a structural material having excellent durability, heat resistant stainless steel such as steel SUS310S, etc., instead of carbon steel.

  Brick lining, metal spraying, inorganic lining, and high alloy lining all have an extremely high material and construction cost in the exhaust gas duct that has been used bare carbon steel, and the thermal expansion coefficient with carbon steel is high. Since it is inevitably different, there is a problem that it is difficult to ensure adhesion over a long period of time in an environment where a high temperature of about 1000 ° C. and a thermal cycle near room temperature are received once a hour.

  In addition, when bricks or inorganic linings are used, 1) the exhaust gas cooling rate becomes slow, so it is necessary to extend the exhaust gas duct in order to send the exhaust gas to the dust collector at a predetermined temperature or lower, and 2) If the cooling rate is too low, the generation of dioxins cannot be sufficiently suppressed, and 3) the weight of the exhaust gas duct increases.

  When high alloy steel such as stainless steel is used instead of carbon steel, there is a problem that the material and the construction cost become extremely high. Further, even with stainless steel such as SUS316L and SUS310S, there is a problem that durability corresponding to economic efficiency is not necessarily obtained.

  As described above, an exhaust gas duct in which one surface of carbon steel is a surface in contact with exhaust gas (gas contact surface) and the remaining surface is a refrigerant surface is extremely excellent in material cost, workability, repairability, and economy. Accordingly, there has been a strong demand for an exhaust gas duct that is equivalent in construction work and repairability to the carbon steel exhaust gas duct, and that has excellent gas contact surface durability and is economically consistent.

Japanese Patent Publication No. 4-80089 Japanese Patent No. 2565727 Japanese Patent Laid-Open No. 2003-231909

  The present invention has been made by overcoming the above-mentioned problems. In particular, the durability, workability, and workability in an exhaust gas environment such as a converter or an electric furnace or an ash melting furnace in a smelting facility such as steel are improved. An object is to provide an excellent exhaust gas duct.

  As a result of examining in detail the wear mechanism of the water-cooled exhaust gas duct of the steel melting furnace and ash melting furnace, the present inventors have shown that the steel satisfying a specific chemical composition exhibits excellent durability in the environment, and It has been found that it has workability and workability comparable to carbon steel.

  In addition, it is possible to obtain an exhaust gas duct with a construction efficiency equivalent to the production of a carbon steel exhaust gas duct by combining the above-mentioned steel satisfying a specific chemical composition as a gas contact surface and combining it with a specific known welding material. I found out.

  The present invention is configured based on the above findings, and the gist thereof is as follows.

(1) The gas contact surface of the exhaust gas flow path in the exhaust gas duct is mass%,
C: 0.001 to 0.2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 9.0%,
Sb: 0.01-0.2%
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
An exhaust gas duct comprising a steel containing one or two of the above, the balance being Fe and inevitable impurities, welded together with an austenitic welding material.

(2) The gas contact surface of the exhaust gas flow path in the exhaust gas duct is mass%,
C: 0.001 to 0.2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 9.0%,
Sb: 0.01-0.2%
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
A surface layer portion of a multilayer steel material containing one or two types of the above, the balance being steel composed of Fe and unavoidable impurities in the surface layer is formed by welding and joining with an austenitic welding material Exhaust gas duct.

(3) Both the steel and weld metal on the gas contact surface of the exhaust gas flow path in the exhaust gas duct are in mass%.
C: 0.001 to 0.2%,
Si: 0.01 to 0.5%
Mn: 0.1 to 2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 6.0%,
Sb: 0.01-0.2%
P: 0.05% or less,
S: 0.005 to 0.02%,
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
An exhaust gas duct comprising one or two of the following, the balance being made of steel and weld metal made of Fe and inevitable impurities.

  (4) The exhaust gas duct is a double-cylinder water-cooled exhaust gas duct, which is composed of a metal outer cylinder and a metal inner cylinder, and an inner side of the inner cylinder serves as an exhaust gas flow path. The exhaust gas duct according to any one of (1) to (3), characterized in that a gap is provided as a refrigerant flow path.

  (5) The exhaust gas duct is an exhaust gas duct in which a plurality of pipes are joined and disposed on a surface opposite to the gas contact surface of the exhaust gas flow path, and has a function of allowing a refrigerant to pass through the pipes. The exhaust gas duct according to any one of (1) to (3).

  The exhaust gas duct of the present invention exhibits excellent durability in a flue gas environment of a metal melting furnace and an ash melting furnace, and also has workability, repairability, and economic efficiency comparable to a carbon steel duct. Yes.

  Hereinafter, the present invention will be described in detail. Hereinafter,% means mass%.

  The essence of the present invention is that, first, in an exhaust gas duct structure having a forced cooling mechanism comprising an exhaust gas channel and a cooling medium channel, the gas contact surface is made of low C—Cr—Cu—Ni— (Mo, W, Mo + W). ) -Sb steel, one side of which is water-cooled. Second, the exhaust gas duct uses a steel plate having the above-described composition using an austenitic welding material or a ferritic welding material of the same component system as steel. This is the point to be welded.

  In general, the gas contact surface of the flue gas treatment facility deteriorates due to wear (thickness reduction) due to the interaction between the exhaust gas and the material. In the wear and tear, a chemical corrosion phenomenon, a physical wear phenomenon, etc. act in a complex manner. In the present invention, the phenomenon that causes a reduction in the thickness of the member surface in contact with gas in the flue gas treatment facility is referred to as wear.

  First, the influence of the alloy composition on the wear behavior will be described. FIG. 1 is a result of a test using a steel material in which the amount of Cr was changed using the comparative example A3 shown in Table 1 as a basic component. This shows the effect of the amount added.

  From FIG. 1, it can be seen that 4.0% or more of Cr is necessary to obtain a sufficient effect at the average wear rate. It can also be seen that the maximum wear depth is not sufficiently reduced by adding Cr alone. Therefore, in the case of 4.0% or more Cr-added steel, it is necessary to improve the wear resistance by composite addition of the third element.

  As a result of studying the effect of composite additive elements on the wear resistance of 4.0% or more Cr-containing steel, the present inventors have found that low C, Si, Cu, Ni, Mo, It has been found that the addition of W, Sb, Sn, and Pb is effective. Furthermore, it has been found that a remarkable effect of improving wear resistance can be obtained by the combined addition of Cu—Ni— (Mo, W, Mo + W) —Sb.

  FIG. 2 shows the effect of combined addition of Cu, Ni, Mo, Sb to 5% Cr steel on the wear environment in the exhaust gas duct. It can be seen that when Cu—Ni—Mo—Sb is added to the Cr-added steel, the wear resistance is drastically improved.

Next, the limiting requirements of the present invention will be described in detail.
[Chemical composition]
First, as the steel used for the gas contact surface of the exhaust gas passage, the chemical composition of the steel in the surface layer portion of the steel that is welded and joined by the austenitic welding material or the multilayer steel material that is welded and joined by the austenitic welding material is limited. The reason is described below. In addition,% means the mass%.

  From the viewpoint of wear resistance in an exhaust gas duct environment, the amount of C is preferably as small as possible. However, since 0.001% or more of addition is necessary to ensure strength, the lower limit is set to 0.001%. It was. If it exceeds 0.2%, wear resistance, cold workability, and weldability are impaired, so 0.001 to 0.2% was set as a limited range. In particular, when workability is required, 0.01 to 0.06% is preferable.

  In order to suppress local wear, Cu needs to be added in an amount of 0.1% or more together with Ni, (one or more of Mo and W), and Sb. If added over 1%, an excessive increase in strength and a decrease in manufacturability and cold workability are caused, so 0.1 to 1% was made the limited range. Preferably, the addition of 0.2 to 0.5% is excellent in the balance between cold workability and wear resistance.

  Ni is added in an amount of 0.01% or more together with Cu, Mo and Sb for the purpose of suppressing local wear, but since 0.5% is sufficient for the effect, 0.01 to 0.5% is limited. It was.

  In order to ensure wear resistance, Cr needs to be added by 4.0% or more. Even if added over 9.0%, the wear resistance is saturated, so 4.0-9.0% was made the limited range. Due to the combined effect of 4.0 to 9.0% Cr—Cu—Ni—Sb— (Mo, W, or Mo + W), the wear resistance is higher than that of the 4.0 to 9.0% Cr single additive system. And dramatically improved.

  Moreover, if it exceeds 6.0%, even if Si is restricted, the cutting property by an endothermic gas such as acetylene tends to be lowered. Therefore, the limited range is preferably 4.0 to 6.0%. In consideration of workability and wear resistance, 4.5 to 5.5% is more preferable.

  Sb is added in an amount of 0.01% or more together with Cu, Ni, (one or more of Mo and W) for the purpose of suppressing local wear. Since saturation occurs, 0.01 to 0.2% is set as a limited range. From the viewpoint of hot workability, 0.05 to 0.15% is more preferable.

  Mo and W are added in an amount of 0.005% or more together with Cu, Ni and Sb for the purpose of suppressing local wear, but if over 0.5%, conversely, weldability and Since wear resistance is inhibited, 0.005 to 0.5% is set as a limited range. From the viewpoint of wear resistance, economy, and weldability, 0.01 to 0.1% is preferable.

  Other components are as follows.

  Si is an indispensable element for ensuring gas cutting properties by adding 0.01% or more for deoxidation and reducing gas components to reduce blowholes. However, it exceeds 0.5%. And the heat-affected zone (HAZ) toughness deteriorates, so 0.01 to 0.5% is preferable. In order to achieve both wear resistance and good gas cutting properties, addition of 0.01 to 0.3% is more preferable. When considering the manufacturability and weldability of steel, 0.1 to 0.3% is more preferable.

  Mn needs to be added in an amount of 0.1% or more for securing the strength of the steel and deoxidizing, but excessive addition impairs the strength and cold workability, so 0.1 to 2% is preferable.

  P is an impurity element, and if it exceeds 0.05%, weldability and wear resistance deteriorate, so 0.05% or less is preferable. In addition, since the effect becomes so favorable that there is little P, 0.02% or less is more preferable. The lower limit value includes 0%.

  S is an impurity element, and if it exceeds 0.02%, the lamellar resistance is reduced, so 0.02% or less is preferable. When S is less than 0.005%, wear resistance decreases, so 0.005 to 0.02% is preferable.

  Al can be added in an amount of 0.005% or more as a deoxidizing element, if necessary. The wear resistance is improved as the Al content is increased, but excessive addition impairs the gas cutting property, so 0.005 to 0.5% is preferable.

  Furthermore, the steel on the gas contact surface is added with one or more of Co, Ti, Nb, V, Ta, Zr, B, Mg, Ca, Y, La, Ce, Sn, and Pb as required. However, the effect of the present invention is not lost.

  Next, when both the steel used for the gas contact surface of the exhaust gas flow path and the welding material are steels having the same chemical composition, that is, when using a metal alloy welding material, the chemical composition of the steel is limited. The reason for doing this will be described below.

  About C, Cu, Ni, Sb, Mo, W, the case where the above-mentioned austenitic welding material is used and the limitation range and the limitation reason are the same.

  However, the upper limit value of Cr is different between Cr when an austenitic welding material is used and when a common metal welding material is used.

  That is, when using a metal alloy welding material, it is necessary to add 4.0% or more in order to ensure wear resistance. However, if over 6.0% is added, preheating at a relatively high temperature and post-heat treatment become indispensable, and welding workability deteriorates, so 4.0 to 6.0% was made the limited range. In consideration of welding workability, workability and wear resistance, 4.0 to 5.5% is more preferable.

  Furthermore, with respect to Si, Mn, P, and S, when using a common metal welding material, it is different from using an austenitic welding material that these are essential components. However, the limitation ranges and reasons for limiting Si, Mn, P, and S are basically the same as in the case of using the austenitic welding material described above.

  The steel used in the exhaust gas duct of the present invention is made by melting steel in a melting furnace such as a converter or an electric furnace, and if necessary, subjecting it to secondary refining in a degassing device, a ladle, etc. After making into a component, this molten steel is made into a steel piece by continuous casting or after making it into a steel ingot, and then into pieces.

  Then, this steel slab can be hot-rolled with or without heating to be a hot-rolled thin steel plate or a thick steel plate, and further cold-rolled to be used as a steel plate such as a cold-rolled thin steel plate. It can be used in various forms as a corrosion-resistant steel member such as a shape steel, steel bar, wire rod or steel pipe by hot rolling.

  In general, since the exhaust gas duct of the flue gas treatment facility is composed of a welded structure of steel material, the steel material is required to have welding workability in addition to the required characteristics. Therefore, the alloy composition of the weld metal is important in order to prevent the selective wear of the weld metal and to ensure the weldability comparable to that of carbon steel in the present invention.

  Austenitic welding material with increased content of Cr, Ni, Cu, Mo, etc. effective for wear resistance, or low C—Cr—Cu—Ni— (Mo, W, Mo + W) —Sb as in the base material It is preferable to use a ferrite-based welding material. As an austenitic welding material, a known technique may be used, and it is a common practice to use an austenitic stainless steel, such as SUS309L.

  As the material of the gas contact surface of the exhaust gas passage, in the case of a multilayer steel material, it is important that the surface layer is a wear resistant layer and is a steel component having the chemical composition of the present invention. From the viewpoint of durability, the wear-resistant layer is preferably 3 mm or more, but steel having the chemical composition defined in the present invention is more preferable than the multilayer steel.

  As the structure of the exhaust gas duct, an exhaust gas duct composed of a water-cooled double structure or a water-cooled steel tube panel is preferable as follows. This is because, in the case of a water-cooled double structure, even if the exhaust gas is at a high temperature exceeding 300 ° C., the metal surface temperature of the duct is at most several tens of degrees C. This is because wear can be avoided.

[Exhaust duct with water-cooled double structure]
An example of the structure of a water-cooled dual structure exhaust gas duct is shown in FIG. Inner cylinder 2 and carbon composed of a welded portion of an austenitic welding material (for example, SUS309L), whose base layer is a clad steel whose surface layer on the gas contact surface has the characteristic composition of the present invention or a steel having the specific composition of the present invention. It is a double-structured exhaust gas duct composed of a steel outer cylinder 1. In FIG. 3, 3 is a flow path for cooling water, and 4 is a flow path for exhaust gas.

  FIG. 4 shows an example of the structure of an inner cylinder composed of clad steel coated with steel having a specific composition of the present invention on a base material 6 to form a wear-resistant layer 5 and a welded portion 7 made of an austenitic welding material. In FIG. 4, 8 is a surface in contact with the exhaust gas.

  The temperature of the refrigerant is preferably 100 ° C. or less, and water is preferred as the refrigerant. The plate thickness of the inner cylinder is preferably 6 mm or more, more preferably 9 to 16 mm from the viewpoint of durability. The manufacturing method of the inner cylinder may be any method such as plate winding, steel pipe, spiral processing and welding. If necessary, the gas contact surface layer may be coated with a limited range heat and wear resistant material of the present invention.

[Exhaust gas duct composed of water-cooled steel pipe panel]
An example of the structure of an exhaust gas duct composed of water-cooled steel pipe panels is shown in FIG. A plurality of water-cooled tubes 9 are usually arranged in parallel on the surface opposite to the surface in contact with the exhaust gas (gas contact surface), and are welded to the panel. A steel plate having a composition limited in the present invention is welded and joined with an austenitic welding material as a gas contact face plate on a panel on which carbon steel pipes are arranged. If necessary, the gas contact surface layer may be coated with a heat and wear resistant material.

(Example 1)
A steel plate (1000 mm × 500 mm × 12 mm) having an alloy composition shown in Table 1 is divided into two in the longitudinal direction, joined by butt welding, and then cold-bended to the inner cylinder diameter. A window into which the test steel plate was fitted in advance was cut into the exhaust gas duct inner cylinder (site 1) and the water cooling duct (site 2) of the converter OG exhaust gas treatment facility, and the test steel plate was welded and attached.

  The welding was performed by arc welding with a heat input of about 20 kJ / cm, and an austenitic stainless steel (SUS309L) coated arc welding rod was used as the welding material.

  Preheating and post heat treatment were not performed. All the specimens had sufficient weldability and were comparable to carbon steel. After 6 months, cut the section of the duct with the test steel plate with gas, cut out each test piece, measure the thickness after pickling, determine the average wear rate and the local maximum wear rate, and wear resistance Evaluated.

  Table 2 shows the above-described in-duct exposure test results.

  A1, which is a comparative example, is a commercially available general welded steel (JIS G 3141 SS400), and A2 is a low alloy steel, both of which have low wear resistance. A3 is a low carbon steel to which 4.9% Cr is added alone, and the average wear rate is comparable to A1 and A2, but the maximum wear rate is the same as A2, and the effect of adding Cr is not recognized. .

  A4, A5, A6, and A7 contain 5.1% Cr, and Si, Cu, Ni, Mo, and Sb are added in combination. A4 is Cu, A5 is Ni, and A6 is Mo. , A7 has insufficient Sb, so that the maximum wear rate is not sufficiently suppressed.

  In addition, since A8 has a low Cr content of 3.0%, the suppression of the average and maximum wear rate by composite addition is not sufficient.

  On the other hand, B1-B5 which is an example of this invention exists in the steel composition range which this application prescribes, and it turns out that it is excellent in wear resistance.

(Example 2)
A steel plate (300 mm × 300 mm × 12 mm) having an alloy composition shown in Table 3 was butt welded with a trial welded ferrite alloy welding rod, and the weldability and weld crack sensitivity were investigated.

  The welding rod was adjusted to the alloy composition shown in Table 4 so that the composition in the weld metal of Cr—Cu—Ni—Mo—Sb, which is important for ensuring wear resistance, was comparable to the chemical composition of the steel plate. The welding was arc welding with heat input of about 20 kJ / cm.

  As a result, in a welded joint (hereinafter referred to as a welded joint C2) in which the steel plate C2 of the comparative example was butt welded with a welding rod having a composition of the weld metal WM2, low temperature cracking was observed in the weld metal. On the other hand, the welded joints (hereinafter referred to as welded joints C1, C3, and C4, respectively) having the steel plates C1, C3, and C4 as the base materials and the welded metals of WM1, WM3, and WM4, respectively, have weldability and crack sensitivity. Was good.

  Therefore, the welded joints C1, C3, and C4, excluding the welded joint C2, were attached to the gas contact surface of the flue gas double water-cooled duct of the steel refining electric furnace in the same manner as in Example 1. After cutting the section of the installed duct with gas, each test piece was cut out, the plate thickness was measured after pickling, the average wear rate and the local maximum wear rate were determined, and the wear resistance was evaluated.

  Table 5 shows the above-mentioned in-duct exposure test results.

  Since the weld joint C1 of the comparative example has a Cr amount equal to or less than the lower limit value of the Cr amount defined in the invention of (3) for both the base metal and the weld metal, the wear resistance is higher than that of the inventive examples C3 and C4. It turns out that it is inferior. As described above, the weld joint C2 of the comparative example has sufficient weldability because the Cr amount exceeds the upper limit value of the Cr amount defined in the invention of (3) for both the base metal and the weld metal. I can't understand.

  From the above results, both the base metal and the weld metal have excellent wear resistance and welding performance even when a ferrite-based welding material is used, provided that the Cr content is in the Cr content range specified in the invention of (3). It can be seen that it is possible to achieve compatibility with gas cutting properties.

  The exhaust gas duct of the present invention is a steelmaking electric furnace, an exhaust gas treatment device for a steelmaking converter, an exhaust gas treatment device for an ash melting furnace, an exhaust gas treatment device for an incineration facility such as waste or sludge, for example, a duct, a heat exchanger casing, If it is used for casings of electrostatic precipitators and bag filters, casings of cooling towers, chimney inner cylinders, etc., the same maintenance and repair methods as conventional carbon steel can be continued while extending the equipment life due to excellent durability. Its industrial value is extremely high.

It is a figure which shows the influence of the amount of Cr which has on the maximum and average wear rate of the steel with single Cr addition in the water cooling duct inner cylinder of the steel melting electric furnace. It is a figure which shows the effect of combined addition of Cu, Ni, and Sb which has on the wear rate of 5% Cr steel in the inner cylinder environment of a water-cooled exhaust gas duct. It is a figure which shows the structural example of a double water cooling duct. It is a figure which shows the structural example of the inner cylinder of a double water cooling duct. It is a figure which shows the structural example of the duct comprised with a water cooling panel. (A) shows the cross section of a duct, (b) is an enlarged view of the cross section of a water-cooled tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer cylinder 2 Inner cylinder 3 Cooling water flow path 4 Exhaust gas flow path 5 Wear-resistant layer 6 Base material 7 Welded part by austenitic welding material 8 Surface in contact with exhaust gas 9 Water-cooled pipe 10 Duct skirt 11 Fin

Claims (5)

The gas contact surface of the exhaust gas passage in the exhaust gas duct is mass%,
C: 0.001 to 0.2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 9.0%,
Sb: 0.01-0.2%
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
An exhaust gas duct comprising a steel containing one or two of the above, the balance being Fe and inevitable impurities, welded together with an austenitic welding material. The gas contact surface of the exhaust gas passage in the exhaust gas duct is mass%,
C: 0.001 to 0.2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 9.0%,
Sb: 0.01-0.2%
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
A surface layer portion of a multilayer steel material containing one or two types of the above, the balance being steel composed of Fe and unavoidable impurities in the surface layer is formed by welding and joining with an austenitic welding material Exhaust gas duct. Both the steel and weld metal on the gas contact surface of the exhaust gas flow path in the exhaust gas duct are in% by mass.
C: 0.001 to 0.2%,
Si: 0.01 to 0.5%,
Mn: 0.1 to 2%,
Cu: 0.1 to 1%,
Ni: 0.01 to 0.5%,
Cr: 4.0% to 6.0%,
Sb: 0.01-0.2%
P: 0.05% or less,
S: 0.005 to 0.02%,
Containing, and
Mo: 0.005 to 0.5%,
W: 0.005-0.5%
An exhaust gas duct comprising one or two of the following, the balance being made of steel and weld metal made of Fe and inevitable impurities.   The exhaust gas duct is a double-cylinder type water-cooled exhaust gas duct, and is composed of a metal outer cylinder and a metal inner cylinder. The inside of the inner cylinder serves as an exhaust gas flow path, and a refrigerant is provided between the outer cylinder and the inner cylinder. It is set as a flow path, The exhaust gas duct of any one of Claims 1-3 characterized by the above-mentioned.   The exhaust gas duct is an exhaust gas duct in which a plurality of pipes are joined to a surface opposite to a gas contact surface of an exhaust gas flow path, and has a function of allowing a refrigerant to pass through the pipes. The exhaust gas duct according to any one of 1 to 3.

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