JP2007224371A - METHOD FOR PRODUCING Cr-CONTAINING NICKEL-BASED ALLOY TUBE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively and uniformly form a chromium oxide film on the inside face of a Cr-containing nickel-based alloy tube. <P>SOLUTION: The method for producing a Cr-containing nickel-based alloy tube includes: a step (1) (Fig. 1(a)) where an atmospheric gas composed of gaseous carbon dioxide is fed to the inside of a workpiece tube 1b before being charged to a continuous heat treatment furnace 5 from the tip side of the progressing direction thereof using a gas feed device 4b and gas introduction tubes 3 arranged so as to pierce the inside of the continuous heat treatment furnace 5; a step (2) (Fig. 1(b)) where the workpiece tube 1b is charged inside the continuous heat treatment furnace 5 as an atmospheric gas composed of gaseous carbon dioxide is fed to the inside thereof; and a step (3) (Fig. 1(c)) where, after the tip of the workpiece tube 1b reaches the outlet side of a heating zone 5a in the continuous heat treatment furnace 5, the feeding of the atmospheric gas composed of gaseous carbon dioxide to the inside of the workpiece tube 1b is switched to the feeding from the other gas feed device 4a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a Cr-containing nickel-base alloy tube with little Ni elution even when used for a long period of time in a high-temperature water environment, and in particular, a Cr-containing nickel-base alloy suitable for applications such as nuclear plant components. The present invention relates to a method for manufacturing a pipe.

  Nickel base alloys are used as various members because of their excellent mechanical properties. In particular, since the members of the nuclear reactor are exposed to high-temperature water, nickel-based alloys having excellent corrosion resistance are used. For example, a 60% Ni-30% Cr-10% Fe alloy is used for a steam generator of a pressurized water reactor (PWR).

  These members will be used in the environment of high-temperature water at around 300 ° C., which is the reactor water environment for several years to several decades. Nickel-based alloys are excellent in corrosion resistance and have a slow corrosion rate, but a trace amount of Ni elutes from the base material after long-term use.

  The eluted Ni is transported to the core in the process of circulating the reactor water and irradiated with neutrons in the vicinity of the fuel. When Ni is irradiated with neutron, it is converted to radioactive Co by nuclear reaction. Since this radioactive Co has a very long half-life, it continues to emit radiation for a long time. Therefore, when the amount of Ni elution increases, the exposure dose of workers who perform periodic inspections and the like increases.

  Reducing the exposure dose is a very important issue for long-term use of light water reactors. Therefore, measures have been taken to prevent elution of Ni in the nickel-base alloy by improving the corrosion resistance on the material side and controlling the water quality of the reactor water.

In Patent Document 1, a nickel-base alloy heat transfer tube is annealed in a temperature range of 400 to 750 ° C. in an atmosphere of a vacuum degree of 10 ⁻² to 10 ⁻⁴ Torr to form an oxide film mainly composed of chromium oxide. A method for improving the overall corrosion resistance is disclosed.

In Patent Document 2, after a solution treatment of a nickel-base precipitation strengthened alloy, a heat treatment is performed in an oxidizing atmosphere under air of 10 ⁻³ Torr to atmospheric pressure to perform at least a part of an age hardening treatment and an oxide film formation treatment. A method for manufacturing a member for a nuclear power plant is disclosed.

  Patent Document 3 discloses a method for producing a nickel-based alloy product in which a nickel-based alloy product is heat-treated in a mixed atmosphere of hydrogen or hydrogen and argon having a dew point of −60 ° C. to + 20 ° C.

  Patent Document 4 discloses a method of forming a chromium-enriched layer by exposing an alloy workpiece containing Ni and Cr to a gas mixture of water vapor and at least one non-oxidizing gas.

  Patent Document 5 discloses a continuous heat treatment furnace as a heat treatment method for reliably and efficiently generating a two-layered oxide film that suppresses elution of Ni in a high-temperature water environment on the inner surface of a nickel-based alloy tube. At least two gas supply devices are provided on the outlet, or one gas supply device is provided on each of the outlet side and the inlet side, and one of these gas supply devices and a gas introduction pipe penetrating the inside of the furnace are used. Then, an atmosphere gas composed of hydrogen or a mixed gas of hydrogen and argon having a dew point in the range of −60 ° C. to + 20 ° C. from the front end side in the traveling direction is introduced into the work tube before charging into the heat treatment furnace. When supplying the tube to the furnace while supplying it and holding it at 650 to 1200 ° C. for 1 to 1200 minutes, after the tip of the tube reaches the exit side of the furnace, the supply of the atmospheric gas to the inside of the tube Repeated operation to switch to supply from supply device The heat treatment method is disclosed.

JP-A-64-55366 JP-A-8-29571 Japanese Patent Laid-Open No. 2002-121630 JP 2002-322553 A Japanese Patent Laid-Open No. 2003-239060

  Since the film formed by the method disclosed in Patent Document 1 is insufficient in thickness, there is a problem that the elution prevention effect is lost due to damage of the film due to long-term use.

  The method disclosed in Patent Document 2 has a problem in that oxidized Ni is easily taken into the film, and this Ni is eluted during use.

  Then, as in the methods disclosed in Patent Documents 3 and 4, a method of controlling the amount of water vapor (dew point) to form an oxide film, and as in the method disclosed in Patent Document 5, hydrogen having a dew point controlled as an atmospheric gas. In the heat treatment method using gas or hydrogen and argon gas, it is difficult to form a uniform oxide film on the inlet side and the outlet side of water vapor. This is due to the following reasons.

For example, in the case of continuous processing such as an oxide film on a long tube, the thickness of the oxide film to be generated is determined not only by the oxygen potential but also by the diffusivity through the concentration boundary layer of the oxidizing gas on the surface of the material to be processed. Is done. Here, the concentration boundary layer refers to the boundary layer of the gas concentration distribution at the surface of the material to be processed and at a position away from the surface (for example, near the central axis inside the tube). This diffusivity is affected by physical properties such as gas diffusion coefficient and kinematic viscosity coefficient, and oxidation treatment conditions such as gas concentration and flow velocity. Since water vapor (H ₂ O) has a higher diffusivity than other oxidizing gases such as CO ₂ , when performing an oxidation treatment in an atmosphere in which no oxidizing gas other than water vapor exists, It becomes difficult to form a uniform oxide film on the side and the exit side.

  The present invention has been made to solve these problems, and is inexpensive and can produce a chromium-containing nickel-based alloy tube that can uniformly form chromium oxide on the surface of the Cr-containing nickel-based alloy tube. It aims to provide a method.

  The gist of the present invention is a method for producing a Cr-containing nickel-base alloy tube shown in the following (A) to (K).

(A) At least two gas supply devices provided on the outlet side of the continuous heat treatment furnace so as to be movable in the advancing direction of the work tube while heating and holding the work tube made of a Cr-containing nickel-based alloy in a continuous heat treatment furnace A method for producing a Cr-containing nickel-base alloy tube in which an atmospheric gas is supplied to the inside of a work tube to form a chromium oxide film on the inner surface of the work tube, comprising the following steps (1) to (3): A method for producing a Cr-containing nickel-base alloy tube, comprising:
(1) Progress using a gas supply device and a gas introduction pipe arranged so as to penetrate through the inside of the work pipe before charging into the continuous heat treatment furnace Supplying an atmospheric gas composed of carbon dioxide gas from the leading end in the direction;
(2) A step of charging the work tube into a continuous heat treatment furnace while supplying an atmospheric gas composed of carbon dioxide gas therein,
(3) Step of switching the supply of the atmospheric gas made of carbon dioxide gas to the inside of the work tube to the supply from another gas supply device after the tip of the work tube reaches the exit side of the heating zone of the continuous heat treatment furnace .

(B) A gas supply device that is provided so as to be movable in the moving direction of the work tube on each of the entrance side and the exit side of the continuous heat treatment furnace while heating and holding the work tube made of a Cr-containing nickel-based alloy in the continuous heat treatment furnace Is a method for producing a Cr-containing nickel-based alloy tube in which an atmospheric gas is supplied to the inside of the work tube to form a chromium oxide coating on the inner surface of the work tube, the following steps (1) to (3) A method for producing a Cr-containing nickel-base alloy tube, comprising:
(1) Inside the work tube before charging into the continuous heat treatment furnace, a gas supply device provided on the entry side of the continuous heat treatment furnace, and longer than the work tube and passing through the continuous heat treatment furnace The step of supplying carbon dioxide gas atmosphere gas from the leading end side in the traveling direction using the gas introduction pipe disposed,
(2) A step of charging the work tube into a continuous heat treatment furnace while supplying an atmospheric gas composed of carbon dioxide gas therein,
(3) Gas in which an atmosphere gas consisting of carbon dioxide gas is supplied to the inside of the work tube on the exit side of the continuous heat treatment furnace after the tip of the work tube reaches the exit side of the heating zone of the continuous heat treatment furnace The process of switching to the supply from a supply apparatus.

  (C) The production of a Cr-containing nickel-based alloy tube according to (A) or (B) above, wherein the atmospheric gas contains 5 vol.% Or less of oxygen gas instead of part of the carbon dioxide gas Method.

  (D) The Cr-containing nickel-based alloy tube according to any one of (A) to (C) above, wherein the atmospheric gas contains a non-oxidizing gas instead of a part of the carbon dioxide gas Production method.

  (E) The non-oxidizing gas is composed of hydrogen gas, rare gas, carbon monoxide gas, nitrogen gas or hydrocarbon gas, or a mixture thereof. Manufacturing method.

  (F) The method for producing a Cr-containing nickel-based alloy tube according to any one of (A) to (E) above, wherein the concentration of carbon dioxide gas in the atmospheric gas is 50 Vol.% Or less.

  (G) Cr-containing nickel-base alloy tube in mass%, C: 0.15% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 10.0-40.0 %, Fe: 15.0% or less, Ti: 0.5% or less, Cu: 0.50% or less, and Al: 2.00% or less, with the balance being Ni and impurities, (A) to (F) above A method for producing a Cr-containing nickel-base alloy tube according to any one of the above.

  (H) The above-mentioned (G), wherein the Cr-containing nickel-base alloy tube contains Nb and / or Ta alone or in a total of 3.15 to 4.15% by mass% instead of a part of Ni A method for producing a Cr-containing nickel-base alloy tube as described in 1.

  (I) Cr-containing nickel-containing alloy as described in (G) or (H) above, wherein the Cr-containing nickel-based alloy tube contains 8 to 10% of Mo in mass% instead of part of Ni Manufacturing method of base alloy tube.

  (J) The method for producing a Cr-containing nickel-based alloy tube according to any one of (A) to (I), wherein the Cr-containing nickel-based alloy tube is used as a member for a nuclear power plant.

The “chromium oxide film” means an oxide film mainly composed of Cr ₂ O ₃ , and an oxide other than Cr ₂ O ₃ , for example, MnCr ₂ O ₄ , TiO ₂ , Al ₂ O ₃ , SiO ₂ An oxide such as ₂ may be included. In addition, if the Cr-containing nickel-based alloy has an oxide film made of chromium oxide, another oxide layer is formed on the upper layer (outer layer) and / or lower layer (inner layer) of the chromium oxide layer. It may be formed.

  According to the present invention, a chromium oxide film can be uniformly and inexpensively formed on the inner surface of a Cr-containing nickel-based alloy tube. The Cr-containing nickel-base alloy tube produced by the method of the present invention has a very low elution of Ni even when used for a long time in a high-temperature water environment, for example, a high-temperature water environment in a nuclear power plant. It is most suitable for members used in high-temperature water such as generator tubing, especially for nuclear power plants.

1. 1. About supply method of atmospheric gas 1-1. FIG. 1 is a plan view showing an example of an embodiment of a method for producing a Cr-containing nickel-base alloy tube according to the first invention (inside the furnace part) It is a plan view in the furnace). FIG. 1A shows a supply mode of atmospheric gas to the inside of the pipe for the workpiece tube group 1a during the preceding heat treatment and the workpiece tube group 1b before the subsequent heat treatment. FIG. 1B shows a supply mode of atmospheric gas to the inside of the pipes for the preceding work tube group 1a and the subsequent work tube group 1b during the heat treatment. FIG. 1C shows a mode of switching the supply of atmospheric gas to the inside of the tube for the subsequent workpiece tube group 1b during the heat treatment. FIG. 2 is an enlarged plan view showing the gas introduction pipe and the header in FIG.

  In FIG. 1, a continuous heat treatment furnace (hereinafter simply referred to as a heat treatment furnace) 5 includes a heating zone 5a and a cooling zone 5b. The furnace atmosphere of the heat treatment furnace 5 is a hydrogen gas atmosphere, and is set to a furnace pressure slightly higher than the atmospheric pressure so that air does not flow in.

  Two gas supply devices 4 a and 4 b are provided on the exit side (right side in the drawing) of the heat treatment furnace 5. Each of the gas supply devices 4a and 4b is provided so as to be able to advance and retreat in the same direction as the workpiece tube groups 1a and 1b conveyed in the direction of the white arrow. Note that the gas supply devices 4a and 4b in the illustrated example are arranged with their positions shifted in a direction perpendicular to the paper surface so as not to interfere.

  As shown in the enlarged plan view of FIG. 2, the leading work tube group 1a and the succeeding work tube group 1b are each provided with a tip portion of a tapered nozzle 2a of a header 2 in which a gas introduction tube 3 is arranged in parallel. Plugged in. Here, the header 2 and the gas introduction pipe 3 are not electrically connected.

  In the method shown in FIG. 1, the atmospheric gas is supplied from the gas supply device 4a to the inside of the pipe of the preceding work tube group 1a during the heat treatment, and inside the pipe of the subsequent work tube group 1b before the heat treatment. The gas is supplied from the gas supply device 4b through the gas introduction pipe 3 provided alongside the header 2 of the preceding work pipe group 1a (see FIG. 5A).

  Next, while maintaining the above state, the preceding workpiece tube group 1a and the succeeding workpiece tube group 1b are transported in the direction of the white arrow and charged into the heat treatment furnace 5 to heat treat the workpiece tubes of both groups. (Refer to (b) in the figure).

  And after the front-end | tip of the subsequent workpiece tube group 1b arrives at the exit side of the heating zone 5a of the heat treatment furnace 5, the supply of the atmospheric gas into the workpiece tube is switched to the supply from another gas supply device. That is, the following operations (1) to (5) are performed.

(1) Release the connection between the header 2 of the preceding work tube group 1a and the gas supply device 4a.
(2) Release the connection between the gas introduction pipe 3 of the preceding work pipe group 1a and the header 2 of the subsequent work pipe group 1b.
(3) Connect the header 2 of the subsequent work tube group 1b and the gas supply device 4a. That is, the connection of the subsequent work tube group 1b is switched from the gas supply device 4b to the gas supply device 4a.
(4) Release the connection between the gas introduction pipe 3 and the gas supply device 4b of the preceding work pipe group 1a.
(5) In order to supply the atmospheric gas into the tube of the next succeeding work tube group 1c, the gas supply device 4b is put on standby to be connected to the gas introduction tube 3 of the work tube group 1c (see FIG. 5C). ).

1-2. FIG. 3 is a plan view showing an example of an embodiment of a method for producing a Cr-containing nickel-based alloy tube according to the second invention (the furnace interior portion is a furnace). It is a plan view inside). FIG. 3 (a) shows the supply mode of the atmospheric gas to the inside of the pipe with respect to the preceding work pipe group 1a before the heat treatment. FIG. 3B shows an aspect of switching the supply of the atmospheric gas into the pipes of the preceding work tube group 1a during the heat treatment. FIG. 3 (c) shows an aspect of supplying atmospheric gas into the pipes of the preceding work tube group 1a and the subsequent work tube group 1b during the heat treatment. FIG. 4 is an enlarged plan view showing the gas introduction pipe and the header in FIG. In FIG. 3, the heat treatment furnace 5 is the same as that in FIG.

  In this method, unlike the case of FIG. 1, gas supply devices 4a and 4b are provided on the entry side (left side in the figure) and the exit side (right side in the figure) of the heat treatment furnace 5, respectively. As in the case of FIG. 1, the gas supply devices 4a and 4b are provided so as to be able to advance and retreat in the same direction as the work tube groups 1a and 1b conveyed in the direction of the white arrow.

  As shown in FIG. 4, the preceding work tube group 1a and the subsequent work tube group 1b before the heat treatment are both provided at the center in the longitudinal direction, and a plug body 2b that can be opened and closed is attached to the right end thereof. The tip portion is inserted into the tapered nozzle 2a of the header 2 having the protruding portion 2c. Further, the gas introduction pipe 3 has a tip end inserted into a tapered nozzle 2 a located at the center in the longitudinal direction of the header 2. Here, a check valve (not shown) that allows only the gas flow in the direction of the arrow may be mounted inside the left end portion of the gas introduction pipe 3. However, the check valve may not be provided.

  In the method shown in FIG. 3, the same as described above from the gas supply device (gas supply device provided on the inlet side of the continuous heat treatment furnace) 4a through the header 2 closed by the gas introduction pipe 3 and the plug 2b. Atmospheric gas is supplied to the inside of the tube of the preceding workpiece tube group 1a before the heat treatment (see FIG. 5A).

  Next, while maintaining the supply of the atmospheric gas by the gas supply device 4a, the preceding work tube group 1a is transported in the direction of the white arrow, charged in the heat treatment furnace 5, and heat-treated. And after the front-end | tip of the workpiece tube group 1a arrives at the exit side of the heating zone 5a of the heat treatment furnace 5, the atmosphere gas supply to the inside of the tube is made from the entrance side gas supply device 4a to the exit side gas supply device 4b. The inlet side gas supply device 4a is provided for supplying atmospheric gas to the inside of the tube of the subsequent work tube group (see FIG. 5B). At this time, the plug 2b attached to the right end of the protrusion 2c of the header 2 is naturally “open”.

  In FIG. 3C, as described above, the subsequent work tube group 1b that has received the atmospheric gas supply from the inlet side gas supply device 4a and the atmospheric gas supply from the outlet side gas supply device 4b are received. The simultaneous heat treatment mode with the preceding work tube group 1a is shown.

  In the method shown in FIGS. 1 and 3, when the length of the work pipe is extremely short, two or more work pipes are connected using a joint member in which the pipe end is fitted, and the length of the work pipe is long. It is good also as each work pipe | tube which comprises the work pipe | tube group 1a (1b, 1c) by lengthening.

  In the method shown in FIGS. 1 and 3, it goes without saying that the set of the header 2 and the gas introduction pipe 3 is circulated. Moreover, the shape of the header 2 may be configured to flow into each work pipe through a plurality of pipes branched from the gas supply device as shown in FIGS. The header 2 may have a BOX shape so that the gas can be supplied at a uniform flow rate.

  As described above, the air inside the pipe is purged by flowing the atmospheric gas into the work pipe before entering the heat treatment furnace. Therefore, a target Cr oxide film is formed on the inner surface of the tube during the heat treatment. Since the atmospheric gas is always supplied from the front end side in the traveling direction of the work tube, it flows in the tube in the direction opposite to the traveling direction of the tube even in the heat treatment furnace. As a result, the tube inner surface residue after the cleaning and before the heat treatment is vaporized at the high temperature portion of the heat treatment and discharged outside the tube.

  The vaporized pipe inner surface residue is moved by the gas flow in the pipe and recondensed when it reaches the unheated part, and may reattach to the pipe inner surface. By doing so, even if it is reattached, the temperature is raised and then re-vaporized, so that everything is finally discharged from the pipe. As a result, a uniform oxide film having a desired performance can be formed on the inner surface of the EP tube without the need for prior electrolytic polishing or the like.

2. Regarding the atmosphere gas supplied into the tube In the method for producing a Cr-containing nickel-based alloy tube of the present invention, the Cr-containing nickel-based alloy tube is replaced with an atmosphere gas composed of carbon dioxide gas, or an oxygen gas of 5 vol. The greatest feature is that a chromium oxide film is formed on the inner surface of the Cr-containing nickel-based alloy tube by heating with an atmospheric gas containing an oxidizing gas.

  If carbon dioxide is contained even in a trace amount, it forms a chromium oxide, and therefore there is no particular lower limit. However, the effect becomes remarkable when 0.0001 vol. Preferably it is 0.01 Vol% or more, More preferably, it is 0.1% Vol% or more. The upper limit of the concentration of carbon dioxide gas is not particularly limited, but is preferably 50 Vol.% Or less, and more preferably 10 Vol.% Or less, from the viewpoint of reducing manufacturing costs. Furthermore, 4Vol% or less is more preferable for forming a thin dense film. In this case, a part of the carbon dioxide gas may be replaced with a non-oxidizing gas.

Carbon dioxide gas has a function of forming a chromium oxide film on the inner surface of the Cr-containing nickel-base alloy tube in a high temperature environment. That is, in an atmosphere composed of carbon dioxide gas, as shown in the following reaction formula, CO ₂ is adsorbed on the Cr-containing nickel-based alloy tube (M), and O (oxygen) is directly taken into the Ni-based alloy from CO _2. As a result, chromium oxide is formed.
CO ₂ + M → CO + MO

  Here, since carbon dioxide has a lower diffusivity than water vapor, the thickness of the formed chromium oxide film is not easily affected by the oxidation treatment conditions such as the gas concentration and flow rate to be supplied. For this reason, a more uniform oxide film can be formed on the inner surface of the tube than in the conventional oxidation treatment performed in a water vapor atmosphere. An advantage of using carbon dioxide gas is that a desired oxidation treatment atmosphere can be created at a lower cost than a method in which the moisture concentration is controlled by a conventional dew point generator.

  Oxygen gas, like carbon dioxide gas, forms chromium oxide, so it may be contained in the atmospheric gas instead of part of carbon dioxide gas. However, when a large amount of oxygen gas is contained, the formation of a chromium oxide film is promoted, the Cr concentration in the base material is lowered, and the corrosion resistance is deteriorated. For this reason, when oxygen gas is contained, the concentration is preferably 5% by volume or less. If oxygen is contained even in a trace amount, the above-described effect is obtained. Therefore, the lower limit is not particularly set, but the effect becomes remarkable when 0.0001 Vol.% Or more is contained.

  In addition, when oxygen gas is contained instead of part of the carbon dioxide gas, a non-oxidizing gas is preferably contained as necessary.

  Thus, in the present invention, an atmospheric gas composed of carbon dioxide gas or an atmospheric gas further containing oxygen gas is supplied to perform oxidation treatment in the Cr-containing nickel-based alloy tube, and the carbon dioxide gas or further oxygen gas is Cr. Oxygen adsorbed by the nickel-base alloy and taken into the Cr-containing nickel-base alloy directly produces Cr oxide.

  The atmospheric gas may contain a non-oxidizing gas that does not contribute to the formation of Cr oxide in order to adjust the concentration of carbon dioxide gas or further the concentration of oxygen gas. Examples of the non-oxidizing gas include hydrogen gas, rare gas (Ar, He, etc.), carbon monoxide gas, nitrogen gas, hydrocarbon gas, and the like. Among these non-oxidizing gases, when carbon monoxide gas, nitrogen gas, or hydrocarbon gas is used, there is a concern of carburizing or nitriding, and therefore it is preferable that at least one of hydrogen gas and rare gas is included. . By adjusting the gas concentration of these non-oxidizing gases, the concentration of carbon dioxide gas or further oxygen gas can be appropriately adjusted.

  Note that hydrogen gas is often used industrially as an atmosphere gas for heat treatment, and if it is used for dilution of carbon dioxide gas, the production cost can be reduced. Therefore, it is most preferable to perform the heat treatment with the atmosphere gas as a gas atmosphere composed of carbon dioxide gas and hydrogen gas.

  In addition, as for the atmospheric gas, when oxygen gas is mixed with hydrogen gas or hydrocarbon gas, it is necessary to consider from the viewpoint of safety so that no explosion occurs. Therefore, when hydrogen gas or hydrocarbon gas is used, it is desirable to perform heat treatment in a mixed gas atmosphere of carbon dioxide gas or further non-oxidizing gas.

3. Heat treatment temperature and heat treatment time Heating temperature: 500-1250 ° C
The heating temperature only needs to be within a range where appropriate thickness and composition of the oxide film and strength characteristics of the alloy can be obtained. Specifically, when the heating temperature is less than 500 ° C., the oxidation of chromium may be insufficient, but when it exceeds 1250 ° C., the strength of the Cr-containing nickel-based alloy material may not be ensured. Therefore, the heating temperature is preferably in the range of 500 to 1250 ° C.

Heating time: 10 seconds to 35 hours The heating time may be set within a range in which an appropriate oxide film thickness and composition can be obtained. That is, in order to form an oxide film mainly composed of chromium oxide, it is desirable to heat for 10 seconds or more. However, even if it is heated for more than 35 hours, the oxide film hardly forms. Therefore, the heating time is desirably in the range of 10 seconds to 35 hours.

  Since the heating time can be shortened as the heating temperature increases, for example, when the heating temperature is in the range of 1000 to 1200 ° C., the heating time may be in the range of 10 seconds to 60 minutes.

  As described above, the thickness and composition of the coating can be adjusted by appropriately adjusting the heating temperature, heating time, and gas concentration conditions.

4). Regarding chemical composition of element tube of Cr-containing nickel-based alloy As a chemical composition of element tube of Cr-containing nickel-based alloy used in the production method of the present invention, for example, by mass, C: 0.15% or less, Si: 1.00 %: Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 10.0-40.0%, Fe: 15.0% or less, Ti: 0.5% or less, Cu: 0.50% or less, and Al: 2.00% It contains the following, and the balance consists of Ni and impurities. The reasons for limiting each element are as follows. In the following description, “%” for the content means “% by mass”.

C: 0.15% or less If C exceeds 0.15%, the stress corrosion cracking resistance may deteriorate. Therefore, when C is contained, the content is desirably 0.15% or less. More desirable is 0.06% or less. C has the effect of increasing the grain boundary strength of the alloy. In order to obtain this effect, the C content is desirably 0.01% or more.

Si: 1.00% or less
Si is used as a deoxidizer during smelting and remains as an impurity in the alloy. At this time, it is necessary to limit to 1.00% or less. If the content exceeds 0.50%, the cleanliness of the alloy may decrease, so it is desirable to limit the Si content to 0.50% or less.

Mn: 2.0% or less
If Mn exceeds 2.0%, the corrosion resistance of the alloy is lowered, so it is desirable to make it 2.0% or less. Mn has a lower free energy of formation of oxide than Cr and precipitates as MnCr ₂ O ₄ by heating. Further, since the diffusion rate is relatively fast, usually, Cr ₂ O ₃ is preferentially generated in the vicinity of the base material by heating, and MnCr ₂ O ₄ is formed as an upper layer outside thereof. If the MnCr ₂ O ₄ layer is present, the Cr ₂ O ₃ layer is protected in the use environment, and even if the Cr ₂ O ₃ layer is destroyed for some reason, the MnCr ₂ O ₄ repairs the Cr ₂ O ₃ Is promoted. Such an effect becomes remarkable when the content is 0.1% or more. Therefore, the desirable Mn content is 0.1 to 2.0%, and more desirably 0.1 to 1.0%.

P: 0.030% or less P is an element present as an impurity in the alloy. If its content exceeds 0.030%, corrosion resistance may be adversely affected. Therefore, it is desirable to limit the P content to 0.030% or less.

S: 0.030% or less S is an element present as an impurity in the alloy. If its content exceeds 0.030%, corrosion resistance may be adversely affected. Therefore, it is desirable to limit the S content to 0.030% or less.

Cr: 10.0-40.0%
Cr is an element necessary for generating an oxide film made of chromium oxide. In order to form such an oxide film on the alloy surface, it is desirable to contain 10.0% or more. However, if it exceeds 40.0%, the Ni content is relatively reduced, which may reduce the corrosion resistance of the alloy. Accordingly, the Cr content is desirably 10.0 to 40.0%. In particular, when Cr is contained in 14.0 to 17.0%, it is excellent in corrosion resistance in an environment containing chloride, and in the case where Cr is contained in 27.0 to 31.0%, it is further excellent in corrosion resistance in pure water and alkaline environments at high temperatures. .

Fe: 15.0% or less
If Fe exceeds 15.0%, the corrosion resistance of the Cr-containing nickel-base alloy may be impaired. Therefore, it shall be 15.0% or less. Further, since it is an element that can be used in place of a part of expensive Ni dissolved in Ni, it is desirable to contain 4.0% or more. The Fe content may be determined from the balance between Ni and Cr. If the Cr content is 14.0 to 17.0%, the content is 6.0 to 10.0%. If the Cr content is 27.0 to 31.0%, the content is 7.0 to 11.0%. Is desirable.

Ti: 0.5% or less
If the Ti content exceeds 0.5%, the cleanliness of the alloy may be deteriorated, so the content is desirably 0.5% or less. More desirable is 0.4% or less. However, from the viewpoint of improving the workability of the alloy and suppressing grain growth during welding, it is desirable to contain 0.1% or more.

Cu: 0.50% or less
Cu is an element present as an impurity in the alloy. If the content exceeds 0.50%, the corrosion resistance of the alloy may be lowered. Therefore, it is desirable to limit the Cu content to 0.50% or less.

Al: 2.00% or less
Al is used as a deoxidizer during steelmaking and remains as an impurity in the alloy. The remaining Al becomes oxide inclusions in the alloy, which deteriorates the cleanliness of the alloy and may adversely affect the corrosion resistance and mechanical properties of the alloy. Therefore, it is desirable to limit the Al content to 2.00% or less.

  The above-mentioned Cr-containing nickel-based alloy may contain any of the above-mentioned elements, and the balance may be made of Ni and impurities. For the purpose of improving performance such as corrosion resistance and strength, an appropriate amount of Nb, Ta, and Mo is added. May be.

Nb and / or Ta: 3.15 to 4.15% either alone or in total
Nb and Ta are effective in improving the strength of the alloy because they easily form carbides. Moreover, since C in the alloy is fixed, there is an effect of suppressing Cr deficiency at the grain boundary and improving the corrosion resistance of the grain boundary. Accordingly, one or both of these elements may be contained. The above effect becomes significant when the content of one element is contained when any one element is contained, and when the total content is 3.15% or more when both elements are contained.

  However, when the content of Nb and / or Ta is excessive, hot workability and cold workability may be impaired and sensitivity to heat embrittlement may be increased. Therefore, when either one element is contained, the content of the single element is desirable, and when both elements are contained, the total content is desirably 4.15% or less. Therefore, the content when one or both of Nb and Ta is contained is desirably 3.15 to 4.15% as a single substance or in total.

Mo: 8-10%
Mo has an effect of improving pitting corrosion resistance, and may be contained as necessary. The above effect becomes remarkable at 8% or more, but when it exceeds 10%, an intermetallic compound may be precipitated and the corrosion resistance may be deteriorated. Therefore, the content when Mo is contained is desirably 8 to 10%.

  The following two types are typical as the composition of the raw tube of the Cr-containing nickel base alloy.

  (a) C: 0.15% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 14.0 to 17.0%, Fe: 6.0 to 10.0%, Ti: 0.5 %, Cu: 0.50% or less, and Al: 2.00% or less, the balance being nickel-containing Cr-containing alloy consisting of Ni and impurities.

  (b) C: 0.06% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 27.0-31.0%, Fe: 7.0-11.0%, Ti: 0.5 %, Cu: 0.50% or less, and Al: 2.00% or less, the balance being nickel-containing Cr-containing alloy consisting of Ni and impurities.

  The alloy (a) contains 14.0 to 17.0% of Cr and contains about 75% of Ni, so that it has excellent corrosion resistance in an environment containing chloride. In this alloy, the content of Fe is preferably 6.0 to 10.0% from the viewpoint of the balance between the Ni content and the Cr content.

  The alloy (b) contains 27.0 to 31.0% of Cr and contains about 60% of Ni, so that it is excellent in corrosion resistance in high-temperature pure water or alkaline environments in addition to chloride-containing environments. In this alloy as well, the Fe content is preferably 7.0 to 11.0% from the viewpoint of the balance between the Ni content and the Cr content.

6). Method for Producing Cr-containing Nickel-Base Alloy Tube The method for producing a Cr-containing nickel-base alloy tube targeted by the present invention is to melt a Cr-containing nickel-base alloy having a predetermined chemical composition into an ingot. Usually, it is manufactured by a hot working-annealing process or a hot working-cold working-annealing process. Furthermore, in order to improve the corrosion resistance of the base material, a special heat treatment called TT treatment (Thermal Treatment) may be performed.

  The heat treatment method of the present invention may be performed after the above-mentioned annealing or may be performed also as annealing. If annealing is performed, it is not necessary to add a heat treatment process for forming an oxide film in addition to the conventional manufacturing process, and the manufacturing cost is not increased. Further, as described above, when the TT treatment is performed after annealing, this may be performed in combination with the heat treatment for forming the oxide film. Furthermore, both the annealing and the TT treatment may be used as the oxide film formation treatment.

  The raw tube used for the experiment was manufactured by the following manufacturing method. First, an alloy having a chemical composition shown in Table 1 was melted and cast in a vacuum to obtain an ingot. This ingot was hot forged into a billet and then formed into a tube by a hot extrusion tube manufacturing method. The tube thus obtained was cold-rolled with a cold pilger mill to have an outer diameter of 23.0 mm and a wall thickness of 1.4 mm. Next, after the cold-rolled tube was annealed in a hydrogen atmosphere at 1100 ° C., the product dimensions were 16.0 mm in outer diameter, 1.0 mm in thickness, and 18000 mm in length by the cold drawing method (section reduction rate = 50). %) Tube. Thereafter, the inner and outer surfaces of each tube were washed with an alkaline degreasing solution and rinse water, and the inner surface was further washed with acetone. The base tube thus obtained was subjected to heat treatment under the conditions shown in Table 2.

The atmosphere gas was supplied into the tube by the method shown in FIG. 3 (21 simultaneous processing). However, for Nos. 16, 18, 20, and 22, the header 2 was installed on the rear end side (that is, the side opposite to the method of the present invention) with respect to the direction of travel of the pipe, and atmospheric gas was supplied. The supply amount of the atmospheric gas was 7 Nm ³ / h in total in each case with respect to 21 tubes.

When both ends of the tube after the heat treatment were cut out and the coating composition was investigated by EDX (Energy Dispersive X-ray micro-analyzer), it was found that an oxide coating made of chromium oxide was formed. The thickness of observing with; (Scanning Electron Microscope SEM) to measure the thickness of the oxide film, the thickness of the oxide film of the gas upstream t _in, the gas downstream of the oxidation film that the cross-sectional scanning electron microscope as t _out, it was to evaluate the variation of both the thickness as _{│t in -t out │ / t in} . In Table 2, “◎” indicates a case of 0.50 or less, “◯” indicates a value greater than 0.50 and 1.00 or less, and “x” indicates a value exceeding 1.00.

Moreover, the test piece was extract | collected from each tube after heat processing, and it used for the elution test. In the dissolution test, an autoclave was used to measure the dissolution amount of Ni ions in the reactor primary system simulated water. At that time, the reactor primary system simulated water was contained on the inner surface of the test piece using a Ti lock, thereby preventing the test solution from being contaminated by ions eluted from the jig or the like. The test temperature was 320 ° C., and the mixture was immersed in 500 ppm B + ₂ ppm Li + 30 cc H ₂ / kgH ₂ O (STP), which is a primary reactor simulated water for 1000 hours. Immediately after completion of the test, the solution was analyzed by high-frequency plasma dissolution (ICP) to examine the elution amount of Ni ions. The above results are also shown in Table 2. The case of 0.05 ppm or less is indicated by “◎”, the case of greater than 0.05 ppm and 0.30 ppm or less is indicated by “◯”, and the case of exceeding 0.30 ppm is indicated by “X”.

  As shown in Table 2, in Nos. 1 to 13, 17, 19 and 21 in which heat treatment was performed by a method satisfying the conditions defined in the present invention, the chromium oxide coating was formed on the inner surface of the tube in the longitudinal direction of the tube. The variation in the oxide film thickness is small, and the Ni elution amount is small in the range of 0.30 ppm or less.

  In contrast, No. 14 and 15 using only water vapor as the oxidizing gas, and the atmospheric gas satisfy the conditions defined in the present invention, but the supply direction of the atmospheric gas is the reverse of the present invention No. 16 18, 20, and 22, there was a large variation in the oxide film thickness in the longitudinal direction of the tube, and the Ni elution amount exceeded 0.30 ppm.

  According to the present invention, a chromium oxide film can be uniformly and inexpensively formed on the inner surface of a Cr-containing nickel-based alloy tube. The Cr-containing nickel-base alloy tube produced by the method of the present invention has a very low elution of Ni even when used for a long time in a high-temperature water environment, for example, a high-temperature water environment in a nuclear power plant. It is most suitable for members used in high-temperature water such as generator tubing, especially for nuclear power plants.

It is a top view which shows the example of one embodiment of the manufacturing method of the Cr containing nickel base alloy pipe concerning the 1st invention (the part in a furnace is a top view in a furnace). (A) shows the supply mode of the atmospheric gas to the inside of the pipe for the workpiece tube group 1a during the preceding heat treatment and the workpiece tube group 1b before the subsequent heat treatment. (B) shows the supply mode of the atmospheric gas to the inside of the pipe for the preceding work tube group 1a and the subsequent work tube group 1b during the heat treatment. (C) shows the supply switching mode of the atmospheric gas to the inside of the tube for the subsequent work tube group 1b during the heat treatment. FIG. 2 is an enlarged plan view showing a gas introduction pipe and a header in FIG. 1. It is a top view which shows the example of one embodiment of the manufacturing method of the Cr containing nickel base alloy pipe of the 2nd invention (the inside of a furnace is a top view in a furnace). (A) shows the supply mode of the atmospheric gas to the inside of the pipe for the preceding work pipe group 1a before the heat treatment. (B) shows the supply switching mode of the atmospheric gas into the tube of the preceding workpiece tube group 1a during the heat treatment. (C) shows the supply mode of the atmospheric gas into the pipes of the preceding work tube group 1a and the subsequent work tube group 1b during the heat treatment. FIG. 4 is an enlarged plan view showing a gas introduction pipe and a header in FIG. 3.

Explanation of symbols

1a, 1b, 1c: Work tube (Cr-containing nickel-based alloy tube) group,
2: Header,
2a: nozzle,
2b: plug body,
2c: protrusion,
3: Gas introduction pipe,
4a, 4b: gas supply device,
5: Continuous heat treatment furnace,
5a: heating zone,
5b: cooling zone,

Claims (10)

A work tube made of Cr-containing nickel-base alloy is heated and held in a continuous heat treatment furnace, and at least two gas supply devices are provided on the outlet side of the continuous heat treatment furnace so as to be movable in the moving direction of the work tube. Is a method for producing a Cr-containing nickel-base alloy tube in which an atmosphere gas is supplied to form a chromium oxide film on the inner surface of the workpiece tube, and includes the following steps (1) to (3): A method for producing a Cr-containing nickel-base alloy tube.
(1) Progress using a gas supply device and a gas introduction pipe arranged so as to penetrate through the inside of the work pipe before charging into the continuous heat treatment furnace Supplying an atmospheric gas composed of carbon dioxide gas from the leading end in the direction;
(2) A step of charging the work tube into a continuous heat treatment furnace while supplying an atmospheric gas composed of carbon dioxide gas therein,
(3) Step of switching the supply of the atmospheric gas made of carbon dioxide gas to the inside of the work tube to the supply from another gas supply device after the tip of the work tube reaches the exit side of the heating zone of the continuous heat treatment furnace . The work tube made of a Cr-containing nickel-base alloy is heated and held in a continuous heat treatment furnace, while the work supply is provided on each of the inlet side and the outlet side of the continuous heat treatment furnace by a gas supply device that is movable in the moving direction of the work tube. A method for producing a Cr-containing nickel-based alloy tube in which an atmospheric gas is supplied to the inside of the tube to form a chromium oxide film on the inner surface of the work tube, and the method includes the following steps (1) to (3) A method for producing a Cr-containing nickel-base alloy tube characterized by
(1) Inside the work tube before charging into the continuous heat treatment furnace, a gas supply device provided on the entry side of the continuous heat treatment furnace, and longer than the work tube and passing through the continuous heat treatment furnace A step of supplying an atmospheric gas composed of carbon dioxide gas from the leading end side in the traveling direction using the gas introduction pipe disposed;
(2) A step of charging the work tube into a continuous heat treatment furnace while supplying an atmospheric gas composed of carbon dioxide gas therein,
(3) Gas in which an atmosphere gas consisting of carbon dioxide gas is supplied to the inside of the work tube on the exit side of the continuous heat treatment furnace after the tip of the work tube reaches the exit side of the heating zone of the continuous heat treatment furnace The process of switching to the supply from a supply apparatus.   The method for producing a Cr-containing nickel-based alloy pipe according to claim 1 or 2, wherein the atmospheric gas contains 5 vol.% Or less of oxygen gas in place of part of the carbon dioxide gas.   The method for producing a Cr-containing nickel-based alloy pipe according to any one of claims 1 to 3, wherein the atmospheric gas contains a non-oxidizing gas instead of a part of the carbon dioxide gas.   The method for producing a Cr-containing nickel-based alloy pipe according to claim 4, wherein the non-oxidizing gas is made of hydrogen gas, rare gas, carbon monoxide gas, nitrogen gas or hydrocarbon gas, or a mixture thereof.   The method for producing a Cr-containing nickel-based alloy pipe according to any one of claims 1 to 5, wherein the concentration of carbon dioxide gas in the atmospheric gas is 50 Vol.% Or less.   Cr-containing nickel-base alloy tube is mass%, C: 0.15% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 10.0-40.0%, Fe : 15.0% or less, Ti: 0.5% or less, Cu: 0.50% or less, and Al: 2.00% or less, with the balance consisting of Ni and impurities. A method for producing a Cr-containing nickel-base alloy tube as described.   The Cr-containing nickel-based alloy tube contains 3.15 to 4.15% of Nb and / or Ta alone or in total, in mass%, instead of a part of Ni. Manufacturing method of Cr nickel base alloy tube.   The Cr-containing nickel-based alloy tube according to claim 7 or 8, wherein the Cr-containing nickel-based alloy tube contains 8 to 10% of Mo in mass% instead of a part of Ni. Production method. The method for producing a Cr-containing nickel-based alloy pipe according to any one of claims 1 to 9, wherein the Cr-containing nickel-based alloy pipe is used as a member for a nuclear power plant.

Images