JPH06304646A - Manufacture of double pipe having resistance to wear and corrosion - Google Patents

Abstract

PURPOSE:To manufacture in an inexpensive shape a double pipe that is used for a large furnace wall pipe or the like. CONSTITUTION:In the center of a cylindrical metallic base material 1, a cylindrical air space is provided which does not coincide axially with the base material, in the cylindrical air space, a cylindrical capsule is provided whose axial center is coincident with the axial center 5 of the cylindrical base material, a powder 3 of a different kind of metal is filled in the space between the cylindrical base material and the capsule, the inside surface of the cylindrical base material is covered by means of a hot hydrostatic press, and a double pipe is manufactured and stretched whose thickness of the inner layer material is likely to vary over the circumferential direction. For example, in the case of using the pipe as a sediment transporting pipe, the material to be used is saved by using the thick part underneath.

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 fluidized sand transport pipe for a fluidized bed 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.

Further, in the fluidized sand transport pipe, since high temperature sandy silica passes through the inner surface, a double pipe having a material having excellent wear resistance as an inner pipe has been used. As a manufacturing method of the double pipe, for example, Japanese Patent Laid-Open Nos. 61-190007 and 61-190008 disclose a thick-walled malleable metal cylinder and a thin-walled metal cylinder having a different diameter. Fill the capsule with the powder and seal it, press it with cold isostatic pressure, compress the powder into a billet, and hot extrude it. A malleable metal cylindrical material is housed in close contact with one container wall in a rubber or similar substance container having inner and outer double walls, and a powder material is provided between the other container wall and the cylindrical material. There is proposed a method in which the material is filled and sealed, the material is taken out from this container as a billet and hot extruded as a billet by pressurizing it with cold isostatic pressure. 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.

[0005] However, when a sandy substance having high abradability such as a fluidized sand transport pipe passes through the inner surface of the pipe, the places to be worn are concentrated on a certain side of the inner surface of the pipe, and wear is less problematic on the opposite side. In many cases it does not. However, in the conventional double pipe, since the wall thickness of the inner layer portion is uniform, a large amount of waste occurs due to the inner layer material on the side where wear is not a problem.
A material excellent in erosion / corrosion resistance such as used as an inner layer material is usually very expensive,
It is very uneconomical to use a conventional double pipe for a fluidized sand transport pipe, and urgent improvement is required from the standpoint of effectively using limited resources.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to manufacture a double pipe used as a fluidized sand transport pipe of a fluidized bed boiler in a shape that can be provided at a lower cost than conventional ones. Is.

[0007]

Means for Solving the Problems As a result of various experiments and studies to achieve the above object, the present inventors have found that the thickness of the inner layer material on the side where wear does not pose a problem It was found that if the thickness of the inner layer material on the side is made thinner, the amount of the expensive wear resistant material as the inner layer material used decreases. Furthermore, in order to manufacture a double pipe in which the thickness of the inner layer material on the side where wear is not a problem is smaller than the thickness of the inner layer material on the side where wear is a problem, the center of the inner layer of the double pipe and the double pipe It was found that the center of the body should not be aligned. And, in order to manufacture a double pipe having such a shape, Japanese Patent Publication No.
In the method according to Japanese Patent No. 75601, a cylindrical cavity having an axial center that does not coincide with the axial center of the columnar metal material is opened in the central portion of the cylindrical metal material serving as the outer layer material in the axial direction of the columnar metal material. A cylindrical capsule is placed in the cavity so that the axis of the cylindrical metal material and the axis of the cylindrical capsule coincide with each other, and thereafter, the cavity wall of the cylindrical metal material and the cylinder. It has been found that a powder of a metal to be an inner layer material may be filled between the capsule and the capsule, hot isostatic pressing may be performed, and then hot working may be performed for stretching.

The present invention has been made on the basis of the above findings. The gist of the present invention is to apply a powder of another metal to the surface of a metal material at a gas pressure below the solidus temperature of the other metal. After forming as a coating layer by hot isostatic pressing under load, in the method of performing hot working and stretching,
A cylindrical cavity whose axial center does not coincide with that of the metal material is opened in the central portion of the cylindrical metal material, and a cylindrical capsule is provided inside the cylindrical cavity, and the axis of the cylindrical capsule is the cylindrical metal material. Manufacture of a corrosion-resistant and wear-resistant double pipe, characterized in that it is arranged so as to coincide with the axis and a powder of another metal is filled in the gap between the inner wall of the cavity of the cylindrical metal material and the capsule. On the way.

Here, the kinds of the metal material serving as the outer layer and the metal material serving as the inner layer are not particularly limited, and examples of the outer layer material include carbon steel, low alloy steel, stainless steel, nickel and nickel alloys, and cobalt. And cobalt alloys, titanium and titanium alloys, and the like. On the other hand, as the inner layer material, corrosion resistance, high temperature corrosion resistance, oxidation resistance,
Of the functions such as wear resistance, it may be selected according to 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.

[0011]

In the present invention, first, a cylindrical cavity is formed in the central portion of the cylindrical metal material as the outer layer material in the axial direction of the cylindrical metal material. Shift them slightly so that the axes of the cavities are not aligned. Next, a cylindrical capsule is arranged in the cylindrical cavity. At that time, as shown in FIGS. 1a and 1b, the cylindrical metal material and the cylindrical capsule are arranged so that their axes coincide with each other. . Next, the gap between the cavity wall of the cylindrical metal material and the cylindrical capsule is filled with a powder of another metal serving as the inner layer material of the double pipe and vacuum-sealed. At that time, the position of the axis of the cylindrical metal material is marked by marking or the like. Next, hot isostatic pressing is performed to form another kind of metal powder as an inner 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. Then, as shown in FIG. 1c, the cylindrical capsule portion and the outer surface layer portion of the cylindrical metal material are removed by mechanical grinding, in which case the inner and outer surfaces of the double tube material are subjected to hot isostatic pressing. Make a concentric circle centered on the mark that was previously attached. By stretching the double-tube material produced in this way, for example, by hot extrusion, the inner layer wall thickness gradually changes depending on the location, and the region where the inner layer wall thickness is maximum and the region where the inner layer wall thickness is minimum are mutually connected. It is possible to manufacture a double tube such that it is located opposite to the center of the tube.

When the double pipe thus obtained is used as a fluidized sand transport pipe, the inner layer inevitably becomes inevitable by directing the part having the maximum inner layer thickness to the side where the most abrasion resistance is required. The part where the wall thickness is the minimum will face the side where wear resistance does not matter so much, and the inner layer is generally more expensive than the case of a normal double pipe where the wall thickness is constant at any part. The amount of wood used can be reduced.

In the double pipe of the present invention, it is the inner surface of the pipe that is required to have corrosion resistance and wear resistance, and a portion where corrosion resistance and wear resistance is a problem and a portion where corrosion resistance and wear resistance is not a problem. However, the present invention can be applied in any usage environment of steel pipes in which the positions are opposite to each other with respect to the center of the pipe, and is not particularly limited to use as a fluidized sand transport pipe.

Examples of the present invention will be described below.

[0015]

[Examples] 25Cr3C steel was selected as the inner layer material, which is a wear resistant material, and carbon steel was selected as the outer layer material, and 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 as shown in Table 1 were selected. 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 according to the method of the present invention. Table 1 also shows the maximum thickness of the wear-resistant material, the minimum thickness, and the saving ratio of the wear-resistant material obtained at that time.

Here, No. Nos. 1 to 3 are examples produced by the method according to the present invention, No. 4 and 5 are normal hot isostatic press +
1 is an example of a conventional double tube manufactured by a hot extrusion process. Further, the saving ratio of the wear resistant material, the amount of the wear resistant material required for any double tube of the present invention has the same outer diameter, inner diameter as the double tube of the present invention, the thickness of the wear resistant material over the entire circumference. It shows how much the wear resistance of the conventional double pipe is reduced by the percentage of the wear resistance of the double pipe of the present invention.

As is clear from Table 1, the double pipe according to the present invention can save 27 to 40% of wear resistant material 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 the same corrosion resistance and wear resistance effect as the conventional one, at a much lower cost than the conventional one, and to develop the industry. It is extremely large that it contributes to.

[Brief description of drawings]

1A and 1B are views showing the arrangement of a cylindrical outer layer metal material and a cylindrical capsule and a filling procedure of an inner layer metal powder when hot isostatic pressing is performed, and c is a hot isostatic press. It is a figure which shows the processing point of the double pipe | tube raw material after it bent.

[Explanation of symbols]

 1 Cylindrical metal material which is an outer layer material 2 Cylindrical cavity 3 Other metal powder which is an inner layer material 4 Axial core of cylindrical cavity 5 Cylindrical metal material and axial center of cylindrical capsule 6 Cylindrical capsule and its lid

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B30B 11/00 E 9347-4E F16L 9/02 7123-3J

Claims (1)

[Claims] 1. A hot working is carried out after forming a powder of another metal on the surface of a metal material as a coating layer by a hot isostatic press applying a gas pressure below the solidus temperature of the other metal. In the method of subjecting to stretching, a cylindrical cavity whose axial center does not coincide with the metal material is opened in the central part of the cylindrical metal material, and a cylindrical capsule is provided inside the cylindrical cavity. Corrosion resistance, characterized in that the core is arranged so as to coincide with the axis of the cylindrical metal material, and a powder of another metal is filled in the gap between the inner wall of the cavity of the cylindrical metal material and the capsule. Method for manufacturing wear-resistant double pipe.