JPH06279810A - Production of corrosion-and wear resistant double pipes - Google Patents

Abstract

PURPOSE:To produce the double pipes to be used as the furnace wall pipes of boilers for business, industrial and other purposes in such a manner that the double pipes can be furnished at a lower cost than that in the past. CONSTITUTION:Metallic powder 2 of an outside layer material is packed by arranging this powder with a slight deviation from a metallic blank material 3 which is an inside layer material in such a manner that respective axial centers 4, 5 are not aligned at the time of arranging this metallic blank material 3 into a capsule 1 and thereafter, the capsule is canned in the case of production of the double PIPES by an HIP + hot extrusion process. As a result, such double pipes having the thickness of the outside layer material changing over a circumferential direction are produced. The part where the thickness of the outside layer material is smallest eventually faces the wall side where corrosion is of no problem by using the double pipes by directing the part where the thickness of the outside layer material is largest toward the furnace side if the place where the corrosion is of problem is only the furnace side like, for example, the furnace wall pipe. The amt. of the expensive outside layer material to be used is, therefore saved as compared with the double pipes by the prior art having the specified thickness of the outside layer material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing 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.

With such movement, boiler steel pipes 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.
-190007 and Japanese Patent Laid-Open No. 61-190008.
In the gazette, powder is filled and sealed in a capsule composed of a malleable metal cylinder having a thick wall and a thin metal cylinder having a diameter different from that of the cylinder, and this is applied by cold isostatic pressure. Press to compress the powder into a billet, which is hot extruded, and a malleable cylindrical metal material in a rubber or similar container with inner and outer double-walled concentric cylinders. While accommodating in close contact with one container wall, the powder material is filled and sealed between the other container wall and the cylindrical material, which is pressed by cold isostatic pressure.
A method of hot extruding a material taken out of the container as a billet has been proposed. On the other hand, as a method capable of selecting a wider range of combinations of the base material and the laminated material, Japanese Patent Publication No. 3-75601 discloses that a powder of another metal is fixed on the surface of a metal material. There has been proposed a method of forming a coating layer by a hot isostatic press which applies gas pressure at a temperature below the phase line temperature, followed by hot working and stretching.

However, when half of the wall tube is used by being embedded in the wall side like a furnace wall tube, 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.
The purpose is to manufacture in 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 use of expensive anti-corrosion material 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 In order to manufacture a double pipe having such a shape, in the method according to Japanese Patent Publication No. 3-75601, when a columnar or cylindrical metal material as an inner layer material is placed in a cylindrical capsule, Place them slightly offset so that the axes of
It has been found that it is sufficient to fill the gap between the metal material and the capsule with metal powder to be the outer layer material, perform hot isostatic pressing, and then perform hot working and stretching.

The present invention has been made on the basis of the above findings. The gist of the present invention is that the powder of another kind of metal is formed on the surface of a cylindrical or cylindrical metallic material and the gap between the metallic material and the cylindrical capsule is made. In a method of forming a coating layer by hot isostatic pressing in which a gas pressure is applied below the solidus temperature of the other metal, and then performing hot working to draw the metal material into a cylinder. A capsule-shaped capsule is arranged so that the respective axial cores do not coincide with each other.

Here, the kinds 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, and the like. On the other hand, the outer layer material may be selected from the functions such as corrosion resistance, high temperature corrosion resistance, oxidation resistance, and wear resistance, depending on the required function, for example, Hastelloy, Stellite, Ni.
-Cr alloys, stainless steel, Fe-based superalloys, nickel and nickel alloys, cobalt and cobalt alloys, titanium and titanium alloys, and the like can be mentioned.

The present invention will be described in detail below.

[0012]

In the present invention, first, a columnar or cylindrical metal material serving as an inner layer material of a double pipe is arranged in a cylindrical capsule.
As shown in (a) and (b), the capsule and the metal material are arranged so that their axes are slightly displaced from each other. Further, in the case of a cylindrical metal material, as shown in FIGS. 2 (a) and 2 (b), the axis of the inner cavity of the cylindrical metal material is slightly deviated from the axis of the metal material itself. Create something and arrange the capsule and the metal material so that the axis of the capsule and the axis of the cavity coincide with each other. Next, the gap between the capsule and the metal material is filled with powder of another metal serving as the outer layer material of the double pipe and vacuum-sealed. At that time, in the case of a cylindrical metal material, by marking etc. at the position corresponding to the axis of the capsule,
Make a mark. Next, hot isostatic pressing is performed to form another kind of metal powder as an outer layer, and at the same time, the outer layer and the inner layer are metal-bonded to each other so that the bonding interface has sufficient strength. Thereafter, as shown in FIGS. 1 (c) and 2 (c), the capsule portion is removed by mechanical grinding, and in the case of a cylindrical metal material, the material central portion is perforated. At this time, in the case of a cylindrical metal material, the inner and outer surfaces of the double-tube material should be concentric with the mark that was placed before hot isostatic pressing as the center, and the cylindrical metal material In this case, the axis of the outer surface of the double pipe material and the axis of the cavity are aligned with each other with reference to the axis of the cavity. That is, a cylindrical tube of equal thickness is used. By stretching the double-tube material produced in this manner, for example, by hot extrusion, the outer layer thickness gradually changes depending on the location, and the region where the outer layer thickness is maximum and the region where the outer layer thickness is minimum are mutually different. It is possible to manufacture double tubing such that it is located opposite the center of the tubing.

When this double tube is used as a furnace wall tube, if the part with the maximum outer layer thickness is directed to the flame side where the highest corrosion resistance is required, the part with the smallest outer layer thickness is inevitably found. It will face the wall where corrosion resistance is not 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 pipe in which the outer layer thickness is constant at any part.

In the double pipe of the present invention, the corrosion resistance is required on the outer surface of the pipe, and the corrosion resistance is a problem.
It can be applied in the usage environment of all steel pipes where the parts where corrosion resistance is not a problem are located on opposite sides of the center of the pipe, for example, as a superheater pipe or evaporation pipe depending on the corrosive environment. However, it is not limited to the use as a furnace wall tube.

Examples of the present invention will be described below.

[0016]

[Examples] SUS310S steel was selected as the outer layer material that is a food-resistant material, and carbon steel was selected as the inner layer material. The outer diameter, the diameter of the circle forming the boundary between the outer layer and the inner layer, the inner diameter, and the boundary between the outer layer and the inner layer are shown in Table 1. The distance between the center of the circle forming the and the center of the double tube,
A double tube having a slab was manufactured by the process of hot isostatic pressing + hot extrusion. The maximum wall thickness of the food material obtained at that time,
Table 1 also shows the minimum wall thickness and the saving ratio of the food material. Here, No. Nos. 1 to 3 are examples produced by the method according to the present invention, No. Nos. 4 and 5 are examples of conventional double pipes manufactured by a normal hot isostatic pressing + hot extrusion process. 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. It shows how much 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 by what percentage.

As is clear from Table 1, the double pipe according to the present invention can save 32 to 37% of the food material resistance as compared with the conventional double pipe.

[0018]

[Table 1]

[0019]

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]

1A and 1B are views showing the arrangement of an inner layer metal material in a capsule and the filling procedure of an outer layer metal powder when hot isostatic pressing is performed when a columnar metal material is used. is there. (C) is a figure which shows the processing point of the double pipe | tube raw material after performing a hot isostatic pressing when using a cylindrical metal raw material.

2 (a) and 2 (b) are views showing the arrangement of the inner layer metal material in the capsule and the filling procedure of the outer layer metal powder when hot isostatic pressing is performed using a cylindrical metal material. is there. (C) is a figure which shows the processing point of the double pipe | tube material after hot isostatic pressing is performed when a cylindrical metal material is used.

[Explanation of symbols]

 1 Cylindrical capsule 2 Other metal powder as outer layer material 3 Cylindrical metal material as inner layer material 4 Cylindrical capsule shaft core 5 Cylindrical metal material shaft core 6 Cylindrical capsule 7 Other metal powder as outer layer material 8 Cylindrical Metal Material as Inner Layer Material 9 Cylindrical Metal Material Cavity 10 Cylindrical Capsule and Cavity Shaft Center 11 Cylindrical Metal Material Shaft Center

Claims (1)

[Claims] 1. A surface of a cylindrical or cylindrical metal material is filled with a powder of another metal in a gap between the metal material and a cylindrical capsule, and a gas pressure is applied at a temperature below the solidus temperature of the other metal. After forming as a coating layer by hot isostatic pressing, in the method of performing hot working and stretching, the metal material is arranged in a cylindrical capsule so that respective axial cores do not match. A method of manufacturing a corrosion- and wear-resistant double pipe.