JPH06106237A - Corrosion resistant and wear resistant double pipe - Google Patents

Abstract

PURPOSE:To give a shape of a double pipe used as a furnace wall pipe of a boiler for enterprise, industry, etc., so that the pipe can be provided at a low cost. CONSTITUTION:Concerning the cross section shape vertical to the pipe axis of the double pipe, the center 6 of a circle making the boundary between an outer layer and an inner layer is made displaced from the axial center 5 of the double pipe, and the thickness of a clad material is changed in the entire peripheral direction, for example, a part thinnest in the thickness of the clad material is positioned in such a direction that a corrosive atmosphere is mild like the wall side of the furnace wall pipe. As a result, the usage of the expensive clad material can be saved and the double pipe can be manufactured at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corrosion- and wear-resistant double pipe used as a furnace wall pipe of a commercial or industrial boiler.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of effective use of energy in power generation boilers, power generation methods with higher thermal efficiency such as super-supercritical pressure of steam conditions and pressurized fluidized bed boiler combined power generation have been pointed out. In addition, municipal waste and industrial waste that have been simply incinerated in the past have also been reviewed as one of the new fuels. In addition, from the viewpoint of resource depletion, orinocotar and low-grade coal will have to be used as fuel in the future.

In accordance with such movements, steel pipes for boilers have come to be used in increasingly severe environments. For example, steel pipes are required to have high high-temperature strength for super-supercritical pressure under steam conditions, high-temperature erosion resistance for fluidized-bed boilers, and high-temperature corrosion resistance for waste power generation and low-grade fuel. However, there are only a limited number of materials that are compatible with high-temperature strength and corrosion resistance, and even if there are any, they are very expensive. Double pipes can solve this problem.Currently, double pipes that use a material with excellent high temperature strength as the inner pipe and a material with excellent high temperature erosion / corrosion resistance as the outer pipe are superheater pipe materials and furnace wall pipe materials. Is used as.

Particularly in a furnace wall tube, since water passes through the inner surface, high temperature water stress corrosion cracking becomes a problem, so that stainless steel cannot be used, and carbon steel or low alloy steel containing Cr or Mo is used. However, when the outer surface of the pipe is exposed to a severe corrosive environment, a protector and a built-up deposit are indispensable, and double pipes are being promoted as alternatives.

A method of manufacturing a double tube is disclosed in, for example, Japanese Patent Laid-Open No. 61-61.
In Japanese Patent Laid-Open No. 190007 and Japanese Patent Laid-Open No. 61-190008, powder is filled and sealed in a capsule composed of a thick-walled malleable metal cylinder and a thin-walled metal cylinder having a different diameter. , A method of pressurizing this by cold isostatic pressure to form a billet by compressing powder and hot extruding this, and a container of rubber or similar substance having concentric cylindrical inner and outer double walls Inside, the cylindrical material of malleable metal is housed in close contact with one container wall,
A method is proposed in which a powder material is filled between the other container wall and the cylindrical material and hermetically sealed, and this is pressurized by cold isostatic pressure, and the material taken out from this container is hot extruded as a billet. Has been done.

[0006] However, when half of a furnace wall tube is used by being embedded in the wall side, the problem of corrosion is on the flame side, and the wall side is in a milder corrosive environment than the flame side. Therefore, the outer layer on the wall side does not need to be thicker than the outer layer on the flame side. However, in the conventional double pipe, since the outer layer portion has a uniform wall thickness, a large amount of waste occurs due to the outer layer material on the wall side. Materials with excellent erosion / corrosion resistance, such as those used as outer layer materials, are usually very expensive, so it is very uneconomical to use conventional double pipes for furnace wall pipes, and limited resources are used. Immediate improvement is required from the standpoint of effective use of the.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a double pipe used as a furnace wall pipe of a boiler for business use, industrial use, etc.
It is intended to have a shape that can be provided at a lower cost than conventional ones.

[0008]

As a result of various experiments and studies to achieve the above object, the present inventors have found that the outer layer material on the wall side is thinner than the outer layer material on the flame side. if,
It has been found that it is possible to reduce the amount of expensive anti-corrosion material used as the outer layer material. Further, in order to manufacture a double pipe in which the thickness of the outer layer material on the wall side is thinner than the thickness of the outer layer material on the flame side, the center of the inner layer of the double tube and the center of the double tube body should not be aligned. I found that

The present invention has been made on the basis of the above findings, and the gist of the invention is a double pipe, in which the center of the circle that forms the boundary between the outer layer and the inner layer in a cross section perpendicular to the pipe axis is The corrosion resistant and wear resistant double pipe is characterized in that it does not coincide with the axis of the double pipe. Here, the types of the metal material as the inner layer and the metal material as the outer layer are not particularly limited, and examples of the inner layer material include carbon steel, low alloy steel, stainless steel, nickel and nickel alloys, cobalt and cobalt alloys. , Titanium and titanium alloys. On the other hand, as the outer layer material, among the functions such as corrosion resistance, high temperature corrosion resistance, oxidation resistance, and wear resistance, it may be selected according to the necessary function, for example, Hastelloy, stellite, Ni-Cr alloy, stainless steel, Fe-based superalloys, nickel and nickel alloys, cobalt and cobalt alloys,
Examples thereof include titanium and titanium alloys.

[0010]

The present invention will be described in detail below. First, the cross-sectional shape of the double pipe of the present invention is shown in FIG. In this case, the outer layer portion of the double pipe is resistant to food. As shown in FIG. 1, by slightly shifting the center of the double pipe body and the center of the circle that forms the boundary between the outer layer and the inner layer, the wall thickness of the outer layer portion of the double pipe can be gradually changed depending on the location. . Moreover, the part where the outer layer thickness is maximum and the part where the outer layer thickness is minimum are located on opposite sides of the center of the pipe. Therefore, if the part with the maximum outer layer thickness is directed to the flame side that requires the most corrosion resistance, the part with the minimum outer layer thickness will inevitably face the wall side where corrosion resistance is less of a problem. The amount of the outer layer material, which is generally expensive, can be reduced as compared with the case of a normal double tube in which the thickness is constant at any part.

In the double pipe of the present invention, the environment where all steel pipes are used is such that the portion where corrosion resistance is a problem and the portion where corrosion resistance is not a problem are located on opposite sides of the center of the pipe. Applicable in, for example, superheater tubes,
It can also be used as an evaporation tube depending on the corrosive environment,
In particular, the application as a furnace wall tube is not limited.

[0012] Corrosion resistance is required on the inner surface of the pipe, and a portion where corrosion resistance is a problem and a portion where corrosion resistance is not a problem are located on opposite sides of the center of the pipe. In such a case, for example, in the case of a fluidized sand transport pipe in a fluidized bed boiler, the inner layer may have a cross-sectional shape such as that shown in FIG. There is no difference from the case where the part to be laid is the outer surface of the tube.

Embodiments of the present invention will be described below.

[0014]

EXAMPLE As shown in Table 1, the outer diameter, the diameter of the circle that bounds the outer layer and the inner layer, the inner diameter, and the distance between the center of the circle that bounds the outer layer and the inner layer and the center of the double pipe are set. HIP the heavy pipe
Manufactured by a hot pressing process. Table 1 also shows the maximum and minimum thicknesses of food materials and the savings ratio of food materials obtained at that time.
Are also shown. Here, No. Nos. 1 to 3 of the present invention in which the outer layer is made of a food-resistant material, No. Nos. 4 to 6 are examples of the present invention in which the inner layer is made of a food-resistant material, No. Reference numerals 7 and 8 are conventional double tubes which are comparative examples. Further, the saving ratio of the food-resistant material means that the amount of the food-resistant material required for any double tube of the present invention has an outer diameter and an inner diameter equal to those of the double tube of the present invention, and the thickness of the food material is all over the circumference. FIG. 7 shows how much the amount of the food material required for the conventional double pipe, which is equal to the maximum food material thickness of the double pipe of the present invention, is reduced.

As can be seen from Table 1, the double pipe according to the present invention can save 25-40% of the food material in comparison with the conventional double pipe.

[0016]

[Table 1]

[0017]

As described above, according to the present invention, it is possible to manufacture a double pipe having a corrosion resistance equivalent to that of the conventional one at a much lower cost than the conventional one, and contribute to the industrial development. It is extremely large.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a double pipe of the present invention when a food-resistant material is used as an outer layer.

FIG. 2 is a cross-sectional view of the double pipe of the present invention when the food material is the inner layer.

[Explanation of symbols]

 1 Outer layer material (foodstuff) 2 Inner layer material 3 Outer layer material 4 Inner layer material (foodstuff) 5 Center of double pipe 6 Center of circle that forms boundary between outer layer and inner layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Ogawa 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division

Claims (1)

[Claims] 1. A double pipe, characterized in that the center of a circle forming the boundary between the outer layer and the inner layer in a cross section perpendicular to the pipe axis does not coincide with the axis of the double pipe. Wearable double tube.