JP2007181841A - Composite metallic pipe for carburizing treatment having excellent carburizing resistance and excellent high temperature strength - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite metallic pipe for a carburizing treatment, which composite metallic pipe is excellent in both of carburizing resistance and high temperature strength, and also can be used as a small diameter pipe and a long pipe. <P>SOLUTION: The composite metallic pipe 10 for the carburizing treatment is configured by laminatedly forming a first building-up welding layer 14 on the outer surface of a base pipe 12, the first building-up welding layer 14 being made of an alloy, which has chemical composition different from that of the base pipe 12 and has the high carburizing resistance, and also by laminatedly forming a second building-up welding layer 16 on the outer surface of the first building-up welding layer 14, the second building-up welding layer 16 being made of an alloy, which has chemical composition different from those of the base pipe 12 and the first building-up welding layer 14 and has high temperature strength. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carburized metal composite pipe excellent in carburization resistance and high-temperature strength, and in particular, is disposed as a core tube inside a carburizing furnace, and is treated in a carburized atmosphere by flowing a carburizing gas inside. The present invention relates to a metal composite pipe suitable for use in a pipe for carburizing a metal wire as a material.

Conventionally, a carburizing pipe (hereinafter simply referred to as a pipe) is disposed as a core tube inside the carburizing furnace, and a carburizing gas such as ethylene gas is flowed into the carburizing atmosphere, and the pipe is treated. A metal wire as a material is continuously passed and carburized.
In the carburizing process using this pipe, the inside of the carburizing furnace is evacuated to a reduced pressure state, and the inside of the carburizing furnace is heated to a high temperature state by heating, and the carburizing gas is supplied into the pipe to continuously carburize the metal wire. To process.

Conventionally, pipes for this kind of application have not been provided, and it is conceivable to use pipes made of stainless steel such as JIS SUS310S having relatively good corrosion resistance.
However, pipes made of stainless steel have insufficient carburization resistance, and the pipe itself undergoes carburization during use, and carbon diffuses and penetrates from the pipe surface to the inside.
Thus, when such carburization occurs in the pipe itself, the pipe becomes brittle, or the corrosion resistance is lowered and the corrosion progresses. End up.
When the pipe reaches the end of its life, it needs to be replaced. However, the replacement takes a lot of labor and time, and during that time, the carburizing process must be interrupted.
Therefore, the pipe is required to have a long life.

The pipe is exposed to a high temperature of 850 ° C. or higher inside the carburizing furnace, but the stainless steel pipe does not have a high temperature strength that can withstand this, and there is a risk of bending during use due to insufficient high temperature strength. is there.
In this case, there arises a problem that the internal metal wire contacts the inner surface of the pipe.

As a countermeasure, it is conceivable that a stainless steel pipe is used as a mother pipe and an overlay weld layer made of an alloy having higher carburization resistance than the mother pipe is formed on the inner surface thereof.
Incidentally, the following points are disclosed in Patent Document 1, Patent Document 2, Patent Document 3, and the like regarding the formation of an overlay welding layer of an alloy having high carburization resistance on the inner surface of the mother pipe.
However, formation of the overlay weld layer on the inner surface of the mother pipe is possible when the inner diameter of the mother pipe is large, but in the case of a mother pipe with a small inner diameter (for example, a narrow pipe having an inner diameter of 40 mm or less), this is actually used. I can't do it.

The plasma powder welding method can be suitably used as a method for forming this build-up weld layer. However, in the case of the plasma powder welding method, a powder is used as a solubilizing material. Overlay welding on the inner surface is also possible for pipes.
However, the pipe used for carburizing treatment may be a thin tube having an inner diameter of 40 mm or less, and in this case, overlay welding on the inner surface cannot actually be performed even by such a plasma powder welding method.

In addition, the carburizing pipe may have a length of 1000 mm or more (for example, 10 m), and even if the inner diameter is large to some extent, it is built on the inner surface of such a long mother pipe. The welding itself is also extremely difficult.
Even if an overlay weld layer of an alloy having higher carburization resistance than that of the mother pipe can be formed, there still remains a problem that the high temperature strength is insufficient.

  Therefore, it is conceivable to use a commercially available heat-resistant pipe such as an HP material instead of the stainless steel mother pipe as the mother pipe. This heat-resistant pipe is a centrifugal cast pipe. It is difficult to produce small capillaries, and it is therefore difficult to achieve high heat resistance of the mother pipe itself.

JP 2001-113389 A JP 2003-001427 A JP 2004-149856 A

  The present invention has been made for the purpose of providing a metal composite pipe for carburizing treatment, which has good characteristics of carburization resistance and high-temperature strength and can be applied to a thin tube and a long tube. It is a thing.

  Thus, according to the first aspect of the present invention, a first build-up weld layer of a high carburization-resistant alloy having a chemical composition different from that of the mother pipe is laminated on the outer surface of the metal mother pipe. A further feature is that a second build-up weld layer of an alloy having a high temperature strength with a chemical composition different from those of the metal mother pipe and the first build-up weld layer is laminated on the outer surface of the weld layer.

  According to a second aspect of the present invention, in the first aspect, the first build-up weld layer and the second build-up weld layer are formed by a plasma powder welding method.

  According to a third aspect of the present invention, in the first or second aspect, the thin tube has an inner diameter of 40 mm or less.

  According to a fourth aspect of the present invention, in the first or second aspect, a long tube having a length of 1000 mm or more is provided.

Effects and effects of the invention

As described above, according to the present invention, the first build-up weld layer of an alloy having high carburization resistance is laminated on the outer surface of the metal mother pipe, and the second build-up weld layer of the alloy having high temperature strength is further formed on the outer surface. It is laminated to form a carburized metal composite pipe.
According to the present invention, it is possible to impart both carburization resistance and high-temperature strength properties to the carburized metal composite pipe.
As a result, the life of the carburizing pipe can be increased, the labor and time required for the replacement can be saved, and the interruption time of the carburizing operation can be reduced.

When carburizing treatment is performed using the metal composite pipe of the present invention, it is inevitable that the innermost layer of the main pipe undergoes carburization and gradually deteriorates.
However, since the first build-up weld layer having carburization resistance is formed on the outer surface, further carburization is prevented by the first build-up weld layer.
Moreover, although this carburization-resistant first build-up weld layer does not have the necessary high-temperature strength (a carburization-resistant material having high-temperature strength is not currently known), the high-temperature strength is the first build-up. Since it is secured by the second build-up weld layer on the outer surface of the weld layer, it is prevented that the metal composite pipe is bent even if it is exposed to high temperature for a long time, and the inner material to be treated contacts the inner surface of the metal composite pipe. It is possible to prevent the occurrence of problems such as
Note that the innermost mother pipe may be scraped off depending on circumstances.

In the present invention, the first build-up weld layer and the second build-up weld layer can be formed by a plasma powder welding method (claim 2).
Thus, by forming the first build-up weld layer and the second build-up weld layer by a plasma powder welding method using powder as a solubilizing material, each weld layer has an optimum component composition easily. Can be formed.

  The present invention is particularly effective when applied to a pipe made of a thin tube having an inner diameter of 40 mm or less (Claim 3), and to a metal composite pipe made of a long tube having a length of 1000 m or more. The effect is great (claim 4).

Next, embodiments of the present invention will be described in detail below.
In FIG. 1, 10 is a metal composite pipe for carburizing treatment of the present embodiment (hereinafter simply referred to as a metal composite pipe), 12 in the figure is a mother pipe, and its outer surface has a resistance to chemical composition different from that of the mother pipe 12. A first build-up weld layer 14 made of a highly carburizable alloy is laminated and further formed on the outer surface of the alloy having a high temperature strength with a chemical composition different from those of the mother pipe 12 and the first build-up weld layer 14. The build-up weld layer 16 is laminated.
In this embodiment, the metal composite pipe 10 is an inner diameter _{D 1} is 28.4 mm, in capillary outer diameter _{D 2} is 42mm, those length of 10 m.

Here, each of the first build-up weld layer 14 and the second build-up weld layer 16 is formed by a plasma powder welding method (PPW method).
In this plasma powder welding method, plasma with good heat concentration is used as a heat source, powder is supplied into the plasma as a solubilizate, melted, and sprayed onto the material to be welded to form a deposited metal film on the surface.

Here, the mother pipe 12 has an outer diameter of 34 mm and a wall thickness of 2.8 mm.
Various materials can be used as the material of the mother pipe 12, and carbon steel can be used in some cases.
However, in the case of carbon steel, when forming the first build-up weld layer 14, Fe of the mother pipe 12 enters the first build-up weld layer 14, and the resistance of the boundary portion with the mother pipe 12 in the first build-up weld layer 14. In order to lower the carburizing property, the mother pipe 12 is preferably made of stainless steel with a small amount of Fe, and particularly preferably made of SUS310S with a large amount of Cr and Ni and a small amount of Fe.
In this embodiment, SUS310S is used as the mother pipe 12.
This SUS310S contains 24 to 26% Cr (mass%, the same shall apply hereinafter) and 19 to 22% Ni.

For example, when the above-described carbon steel is used as the mother pipe 12, Fe increases at the boundary with the mother pipe 12 in the first build-up weld layer 14 and the carburization resistance is impaired. It is necessary to increase the thickness, and accordingly, the outer diameter of the metal composite pipe 10 is increased.
However, if SUS310S is used as the mother pipe 12, it is possible to suppress the penetration of Fe into the boundary portion between the first build-up weld layer 14 and the mother pipe 12, and therefore the boundary portion between the first build-up weld layer 14 and the mother pipe 12 is used. High carburization resistance can be maintained.
Therefore, the thickness of the first build-up weld layer 14 can be reduced, and as a result, an increase in the outer diameter of the metal composite pipe 10 can be prevented.

Here, the first build-up weld layer 14 is formed with a thickness of 2 mm.
The first build-up weld layer 14 is made of a Cr-containing Ni-based alloy.
As the material for the carburizing-resistant first build-up weld layer 14, a material containing 20 to 49% Cr and 35 to 80% Ni can be suitably used.
In particular, an alloy having a composition of 45Cr—Ni is used in this embodiment.

On the other hand, the second build-up weld layer 16 made of a high-temperature strength material is formed here with a thickness of 2 mm, like the first build-up weld layer 14.
In the case of the first build-up weld layer 14 made of a material having carburization resistance, since C is harmful to the corrosion resistance, its content is suppressed to, for example, 0.1% or less. As a result, the first build-up weld layer 14 is reduced. Becomes weak at high temperature.
Since the second build-up weld layer 16 is a layer responsible for high-temperature strength, a material having a higher C content than the first build-up weld layer 14 is used.
Various materials classified as heat-resistant steel can also be used for the second overlay weld layer 16 responsible for this high-temperature strength, but here HP-Nb material containing 0.35% C (0.35C-25Cr) -35Ni-Nb) is used.

According to the present embodiment as described above, both the carburization resistance and the high temperature strength characteristics can be imparted to the metal composite pipe 10.
As a result, the service life of the pipe for carburizing treatment can be increased, and the labor and time required for the replacement can be saved, and the interruption time of the carburizing operation during the replacement can be reduced. it can.

Although the embodiment of the present invention has been described in detail above, this is merely an example.
For example, the materials exemplified above as the mother pipe, the first build-up weld layer, and the second build-up weld layer are merely examples, and materials made of various other materials can be used for each.
Further, the above-described dimensions of the metal composite pipe 10 are also only examples, and the present invention can be variously modified without departing from the spirit of the present invention, such as being able to configure the metal composite pipe 10 with other various dimensions. Can be configured.

It is the figure which showed the metal composite pipe for carburizing process which is one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Metal composite pipe for carburizing process 12 Mother pipe 14 1st overlay welding layer 16 2nd overlay welding layer

Claims (4)

  A first build-up weld layer made of a highly carburized alloy having a chemical composition different from that of the mother pipe is laminated on the outer surface of the metal pipe, and the metal build-up is further formed on the outer surface of the first build-up weld layer. A carburizing metal excellent in carburization resistance and high-temperature strength, characterized in that it is formed by laminating a second build-up weld layer of an alloy having a high temperature strength with a chemical composition different from that of the pipe and the first build-up weld layer. Composite pipe.   2. The carburizing treatment having excellent carburization resistance and high temperature strength according to claim 1, wherein the first build-up weld layer and the second build-up weld layer are formed by a plasma powder welding method. Metal composite pipe.   The metal composite pipe for carburizing treatment having excellent carburization resistance and high-temperature strength according to claim 1 or 2, wherein the inner diameter is a thin tube of 40 mm or less.   The metal composite pipe for carburizing treatment having excellent carburization resistance and high-temperature strength according to claim 1 or 2, wherein the pipe is a long pipe having a length of 1000 mm or more.

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