JPH09239563A - Manufacture of heat exchanging metal tube with projection in inner surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently form a projection and to improve material soundness by irradiating the outside surface of a metal tube held horizontally with an electronic beam to heat and melt the irradiated part up to the inner surface side, swelling the molten metal in a projecting shape in the inner surface side and solidifying it. SOLUTION: A metal tube 1 is horizontally held, an electronic beam gun G is directed to the outside surface of the metal tube 1 from the upward of the metal tube 1. The outside surface of the metal tube 1 is irradiated with the electronic beam B from the electronic beam gun G, and the irradiated part of the metal tube 1 is heated and molten up to the inner surface side. The molten metal in the molten part M is subjected to a suspending condition swelling to the inside space from the inside surface I3 of the tube in a projecting shape due to the balance between the self-weight and the surface tension, and solidified in that condition to form the projection 2. Therefore, the time required for working is largely reduced compared with a welding method by cladding and moreover the operation for inserting a welding torch into the tube is unnecessitated, whereby this method is applied even to the tube having an extremely small diameter regardless of the size of the tube.

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 metal tube for heat exchange, which has a projection on the inner surface of the tube and has a high heat exchange property and is useful as, for example, a reaction tube for ethylene production.

[0002]

2. Description of the Related Art In a pyrolysis furnace for producing ethylene, a mixed fluid containing hydrocarbons (naphtha, natural gas, ethane, etc.) is supplied into a reaction tube, and while the fluid is flowing at high speed, heat is supplied from the outside of the tube. The decomposition reaction is performed to obtain an olefin such as ethylene or propylene as a thermal decomposition reaction product. In the pyrolysis operation, it is required to efficiently perform heat transfer to the fluid flowing at a high speed in the tube and to quickly heat and raise the temperature to a predetermined reaction temperature range. As a measure to enhance the heat transfer property of the reaction tube, a projection (protrusion height of about 2 to 1
It is effective to form a film of about 5 mm (Japanese Patent Laid-Open No. 6-1).
09392). This means that the projection functions as a stirring element for the fluid in the pipe, and as a turbulent flow forming effect, the fluid in the pipe can be rapidly heated to the required temperature up to the central portion of the cross section of the pipe. The effect of improving heat transfer performance by the projection is to greatly reduce the length of the pipe line, downsize the device, simplify operation management, increase the feed rate of the fluid in the pipe, increase the production capacity, etc. Bring

[0003]

As described in the above publication, the method for forming the projection on the inner surface of the tube is as follows.
Examples include powder plasma welding method, melt polarity inert gas arc welding, non-melt polarity inert gas arc welding, etc., but the present invention is capable of forming the protrusions more efficiently and improving material soundness. It is intended to provide an excellent method for manufacturing a metal tube with a protrusion.

[0004]

According to the method of manufacturing a metal tube for heat exchange with an inner surface projection of the present invention, an outer side surface of a metal tube held horizontally is irradiated with an electron beam so that the irradiation portion extends to the inner surface side. It is characterized in that the molten metal is heated and melted, and the molten metal is bulged in the shape of a protrusion on the inner surface side to be solidified.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION By accelerating an electron beam, squeezing it with a converging lens and irradiating it on the surface of a metal tube, the irradiated portion can be melted as an effect of heat generation by impact. Electron beam welding is known as a method for heating and melting a metal material by electron beam irradiation. The projection formation of the metal tube of the present invention can be performed under the same operating conditions as those in electron beam welding. In forming the protrusions of the present invention, the outer surface of the tubular body is irradiated with an electron beam, and the entire wall thickness of the tubular body is heated and fused to the inner side surface of the tubular body to form a fused portion.
Due to the balance between its own weight and surface tension, the molten metal bulges and hangs like a protrusion into the inner space of the tube. By cooling and solidifying in the expanded state, a protrusion is formed on the inner surface of the tube. The electron beam irradiation operation for forming the protrusions is carried out in an air atmosphere, and optionally in a vacuum or an inert gas atmosphere. Since the projection formation by electron beam irradiation of the present invention is performed by heating and melting and cooling the base material tube, unlike the method of forming the projection as the buildup layer by welding, the base material and the buildup layer are different from each other. The base material tube body and the projection have a completely integrated structure without causing defects such as poor fusion of the interface.

FIG. 1 schematically shows an electron beam irradiation process for forming projections on the inner surface of the tube. (1) is a metal tube,
(G) is an electron beam gun. The metal tube is held horizontally, and the electron beam gun (G) is directed from above the metal tube (1) to the outer surface of the metal tube (1). The electron beam (B) is irradiated from the electron beam gun (G) to the outer surface of the metal tube to heat and melt the irradiated metal tube to the inner surface side. The molten metal in the molten portion (M) has a suspended state in which it is bulged like a protrusion from the inner surface (1 ₃ ) of the tube to the inner space due to the balance between its own weight and surface tension, and solidifies in that state to produce a protrusion ( 2)
Is formed. When electron beam irradiation is performed by arranging a plurality of electron beam guns (G), it is possible to simultaneously form protrusions at a plurality of locations.

The distribution form of the projections on the inner surface of the tube can be arbitrarily designed according to the electron beam irradiation construction procedure.
A projection that extends in a desired direction in a streak shape by irradiating an electron beam while rotating the metal tube about the tube axis or moving the metal tube and the electron beam gun relative to each other in the tube axis direction. Are formed, and by intermittently operating the irradiation of the electron beam, an intermittent distribution pattern can be given to the formed projections.

FIG. 2 shows a sectional shape of a protrusion formed on the inner surface of the tube. Height of protrusion from inner surface of tube (2 _H )
The width, width (2 _W ), and distribution pattern are set as appropriate according to the application of the metal tube, conditions of use, tube size, etc. These are determined by the electron beam irradiation acceleration voltage, beam current, beam diameter, etc.
Regardless of the wall thickness of the tubular body, it can be controlled easily and accurately. For example, a reaction tube for ethylene production (tube inner diameter of about 30 to 150 mm) has a protrusion height (2 _H ) of about 2 to 15 mm,
The width (2 _W ) is about 3 to 10 mm, the adjoining protrusions (2) and the protrusions (2) and the distance (D ₁ ) are about 3 to 400 mm, and FIG.
When the protrusions (2) are formed intermittently, the break point (D ₂ ) between the protrusions is about 1 to 50 mm, and the protrusion length (2 _L )
Is about 3 to 100 mm.

The metal tube (1) is made of a single metal material type (single layer tube), and as shown in FIG. 3, an outer layer (1 ₁ ) and an inner layer (1 ₂ ) having different metal material types. As shown in the figure, the inner layer (1 ₂ ) is used as the surface layer by performing projection formation by electron beam irradiation on a two-layer pipe (centrifugal casting pipe, two-layer pipe, etc.) stacked concentrically A protrusion (2) is formed. The use of such a laminated tube is effective when special material properties are required on the inner surface of the body, as described later. Further, the region where the protrusion (2) is formed on the inner surface of the metal tube is appropriately set depending on the application and usage of the metal tube. In the case of an ethylene production reaction tube, as shown in FIG. It is formed over the area near the entrance side (A ₁ ), the central area (A ₂ ) of the conduit, the area near the exit side (A ₃ ), or the entire area from the entrance end to the exit end.

6 to 11 show examples of distribution patterns of protrusions on the inner surface of the pipe. FIG. 6 shows an example in which a protrusion (2) extending in a stripe shape on the pipe inner surface (1 ₃ ) is formed in a direction orthogonal to the pipe axis (x). The protrusion (2) horizontally mounts the metal tube (1) on a rotating device such as a rotation driving roller, and performs continuous rotational movement around the tube axis while continuously carrying out along the outer surface of the tube. It is formed by performing electron beam irradiation.
Further, when electron beam irradiation is performed while rotating the metal tube (1) and moving the electron beam gun (G) in the tube axis direction (the electron beam gun may be fixed and the metal tube may be moved), rotation is performed. As a combined effect of the movement and the movement in the tube axis direction, a protrusion (2) having a spiral shape as shown in FIG. 7 is formed. The inclination angle of the spiral protrusion (2) with respect to the tube axis (x) can be arbitrarily adjusted by the rotation speed of the metal tube and the relative movement speed of the electron beam gun (G). On the other hand, when electron beam irradiation is performed while moving the electron beam gun (G) in a direction parallel to the tube axis (the electron beam gun may be fixed and the metal tube may be moved) while the rotational movement of the metal tube is stopped. As shown in FIG. 8, a metal tube having a ridge-shaped projection (2) extending in a direction parallel to the tube axis (x) is obtained.

When the electron beam gun (G) is subjected to a swinging motion in a direction orthogonal to the forming direction of the protrusion (2) in the protrusion forming step, a wavy protrusion can be formed. FIG. 9 shows an example thereof. This figure shows an example of wavy protrusions formed when a swinging motion is applied to the electron beam gun (G) in the process of forming protrusions parallel to the tube axis (x) of FIG. When the electron beam gun (G) is subjected to oscillating motion in the process of forming the projection extending in a stripe shape in the direction orthogonal to the tube axis (x) of FIG. 6, the tube inner surface (1 ₃ ) is repeated wavy. A protrusion that goes around
If the electron beam gun (G) is subjected to a swinging motion in the process of forming the spiral projection of FIG. 7, a spiral projection that is spirally wound along the inner surface (1 ₃ ) of the tube is formed while repeating wavy meandering.

Further, in the step of forming projections, the heating and melting portion (M) is intermittently formed by irradiation with an electron beam to form intermittent projections (2) as shown in FIGS. 10 and 11. can do. 10 shows an intermittent pattern of the protrusions (2) formed when the electron beam irradiation is intermittently performed in the process of forming the spiral protrusions of FIG. 7, and FIG. 11 shows the tube axis of FIG. The intermittent pattern of the protrusions formed when the electron beam irradiation is intermittently performed in the step of forming the parallel protrusions is shown.
The intermittent distribution form of the protrusions is not limited to this, and the intermittent form of the wavy meandering protrusions can be imparted by intermittently performing electron beam irradiation in the step of forming the wavy meandering protrusions (for example, FIG. 9). I can do it. In addition, formation of protrusions having a periodic or random scattered point distribution pattern can be arbitrarily performed.

The material type of the metal tube is arbitrarily selected depending on the application and use conditions. For reaction tubes for ethylene production,
When forming protrusions, the metal tube is made of heat-resistant alloy steel, such as AS
TM HK 40 material (0.4C-20Ni-25Cr-Fe), HP material (0.5C-35Ni-25C)
r-Fe), or 0.5C-45Ni-30Cr-Fe, 0.5C-35Ni-25C
Examples of the tubular body include r and incoloy alloy (45Cr-Ni type). In addition, in the reaction tube for ethylene production, solid carbon is deposited from the reaction system during the pyrolysis operation and adheres and deposits on the inner surface of the tube, so-called coking phenomenon (adhesion of solid carbon accelerates material deterioration due to carburization of the pipe body. If the solid carbon adhesion and deposition on the surface of the protrusion or in the vicinity thereof is promoted due to the formation of the protrusion (2) on the inner surface of the pipe, the caulking resistance A metal tube formed of a material having high carburization resistance, or a tube body having a two-layer structure as shown in FIG. 3, and an inner layer (1 ₂ ) (layer thickness is, for example, 0.3 to
It is possible to apply an alloy grade having high caulking resistance and carburization resistance to 5 mm) and use a metal pipe (centrifugal casting pipe, etc.) formed of general heat-resistant alloy steel for the outer layer ( ₁₁ ).

As an example of the above-mentioned tube material having improved caulking resistance and carburization resistance, C: 0.1 to 0.6%, Si: 4.0%
Hereinafter, Mn: 5.0% or less, Ni: 30.0 to 50.0% (Ni may replace 20% or less with Co), Cr: 20.0 to 5%
0.0%, Al: 4.0% or less, if desired, W: 10% or less, Ca: 0.5% or less, Hf: 1.0% or less, Y: 1.0% or less, and one or more elements selected from the group, and / Or Nb: 4.0% or less, Mo: 5.0% or less, Ti: 1.0% or less, Zr: 1.0% or less, rare earth element: 0.5% or less, B: 0.5%
A heat-resistant alloy containing one or more elements selected from the following group and the balance being substantially Fe, C: 0.02 to 0.
6%, Si: 4.0% or less, Mn: 5.0% or less, Cr: 40.0 ~
52.0%, if desired, Al: 4.0% or less, W: 10.0% or less, Ca: 0.5% or less, Hf: 1.0% or less, Y: 1.0% or less, and one or more elements selected from the group, and / Or Nb: 0.4% or less, Mo: 5.0% or less, Ti: 1.0% or less, Zr: 1.0% or less, rare earth element: 0.5% or less, B: 0.5%
It contains one or more elements selected from the following groups, and the balance is substantially Ni (a part of Ni is 20% or less of Co.
May be substituted).

[0015]

EXAMPLE A metal tube is horizontally placed on a rotary drive roller, and while being rotated about the tube axis, electron beam irradiation (atmosphere atmosphere) shown in Table 1 is performed to form a ring-shaped projection in a direction orthogonal to the tube axis. Was formed. Metal tube: Heat-resistant alloy steel single layer tube (centrifugal casting material) Tube type: C 0.5, Si 1.7, Mn 0.8, Ni 35, Cr 25, Fe Ba
l, wt% (HP equivalent material) Tube size: 98 outer diameter, 81.5 inner diameter, 250 (mm) length

[Table 1] Beam current value Acceleration voltage Feed rate Example 1 60 mA 70 KV 1500 m / min Example 2 90 mA 70 KV 2000 m / min Example 3 90 mA 70 KV 1500 m / min Either of the above conditions Projection height (2 _H ) 1 to 1.5 m
A ring-shaped protrusion with a width of m and a protrusion width (2 _W ) of about 2 mm was formed.

[0016]

According to the present invention, since the projections on the inner wall surface of the pipe are formed by electron beam irradiation, the construction time can be greatly shortened as compared with the welding method in which the build-up of beads is formed as the weld build-up.
Moreover, since the operation of inserting the welding torch inside the pipe is not required, even if the pipe diameter is extremely small, it can be carried out without being restricted by the pipe diameter. Further, in the case of a protrusion formed as a weld overlay bead, a defect such as poor fusion may occur at the interface between the base metal tube and the protrusion, but such a defect may occur in the present invention. Absent. The metal tube with protrusions manufactured by the present invention requires high heat exchange performance such as a steam generation boiler tube, a power generation super heater tube for a municipal waste incinerator, and a radiant tube for a heat treatment furnace as a reaction tube for ethylene production. It is useful as a method for producing a metal tube.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the axial direction of a tube schematically showing the formation of protrusions on the inner surface of the tube by electron beam irradiation according to the present invention.

FIG. 2 is an explanatory cross-sectional view of a protrusion shape on the inner surface of the tube.

FIG. 3 is an explanatory cross-sectional view of a protrusion shape on the inner surface of the tube.

FIG. 4 is an explanatory plan view of an intermittent distribution of protrusions on the inner surface of the tube.

FIG. 5 is an explanatory diagram of a protrusion formation region on the inner surface of the tube.

FIG. 6 is a tube axial direction sectional view showing an example of a distribution form of protrusions.

FIG. 7 is a sectional view in the tube axis direction showing an example of a distribution form of protrusions.

FIG. 8 is a tube axial direction sectional view showing an example of a distribution form of protrusions.

FIG. 9 is a sectional view in the tube axis direction showing an example of a distribution form of protrusions.

FIG. 10 is a sectional view in the tube axis direction showing an example of a distribution form of protrusions.

FIG. 11 is a cross-sectional view in the tube axis direction showing an example of distribution form of protrusions.

[Explanation of symbols]

1: metal pipe 1 _1: external layer 1 _2: inner layer 1 _3: inner surface 2 ,: projections G: Electronic beam gun B: electron beam M: heat-melting section

Front page continued (72) Inventor Kaoru Hamada 1-1-1, Nakamiya Oike, Hirakata-shi, Osaka Prefecture Kubota Hirakata Factory

Claims (6)

[Claims] 1. An outer surface of a horizontally held metal tube is irradiated with an electron beam to heat and melt the irradiated portion to the inner surface side,
A method for producing a metal tube for heat exchange with an inner surface protrusion, characterized in that molten metal is bulged in the shape of a protrusion toward the inner surface to solidify. 2. A metal tube is irradiated with an electron beam while rotating the metal tube about the tube axis and / or performing relative movement of the metal tube and the electron beam gun in the tube axis direction. The method for manufacturing a metal tube for heat exchange according to claim 1, wherein protrusions distributed in a stripe shape are formed on the inner surface. 3. By intermittently irradiating an electron beam while rotating the metal tube about the tube axis and / or performing relative movement of the metal tube and the electron beam gun in the tube axis direction, The method for producing a metal tube for heat exchange according to claim 1, wherein projections that are intermittently distributed are formed on the inner surface of the metal tube. 4. The method for producing a metal tube for heat exchange according to claim 1, wherein the metal tube is made of a heat resistant alloy. 5. The metal tube is a two-layer tube in which an outer layer and an inner layer made of two kinds of heat-resistant alloys having different alloy compositions are concentrically laminated, and the metal tube is a two-layer tube. 2. A method for manufacturing a metal tube for heat exchange according to item 1. 6. The method for producing a metal tube for heat exchange according to claim 1, wherein the reaction tube is an ethylene production reaction tube.