JP3462182B2 - Method for producing chromium-containing oxide dispersion strengthened ferritic iron alloy tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant material, and more particularly to a method for producing an oxide dispersion strengthened ferritic iron alloy tube containing chromium which is used under high temperature neutron irradiation environment.

[0002]

2. Description of the Related Art Conventionally, austenitic stainless steels such as SUS316 and its improved steels have been studied as a core constituent member of a fast breeder reactor of a nuclear reactor for power generation. However, austenitic stainless steel has excellent high temperature strength,
There is a limit to swelling resistance and creep resistance under fast neutron irradiation at 400 to 700 ℃, and it is not always sufficient as a core constituent member for practical fast breeder reactors. On the other hand, ferritic stainless steels or ferritic high chromium iron alloys have better resistance to fast neutron irradiation deterioration than austenitic stainless steels, but their high temperature creep strength or high temperature strength is inferior. Therefore, development of oxide-dispersion-strengthened ferritic high-chromium iron alloys in which fine particles of oxides are dispersed in a matrix to improve high-temperature strength is under way, and its application for fuel cladding is being studied. There is. Furthermore, ferritic stainless steel or ferritic iron alloy has the advantage that it has a smaller coefficient of thermal expansion and better thermal conductivity than austenitic stainless steel, and if high temperature strength can be improved, it can be used as a heat-resistant material such as high-temperature members for thermal power generation. Can also be expected to be utilized.

With such a ferritic high chromium iron alloy
In the amount of 11% to 15% of Cr in mass%
To some extent, for example (a) Fe-14% Cr-1% Ti-0.3
% Mo-0.25% Y_TwoO_ThreeAlloy (MA957 alloy: US Patent No. 4
075010) and (b) Fe-13% Cr-3% (Mo + W)
-0.5% Ti-0.1% C-0.35% Y_TwoO_ThreeAlloy (UK patent
Published application specification GB2219004A) and the like. these
Is the essential Cr and high temperature strength for corrosion resistance and oxidation resistance.
In order to secure the iron alloy containing Mo and W, Ti and
Y as oxide_TwoO_ThreeIs an alloy to which is added. T
i is added to Y _TwoO_ThreeReact with
It has the effect of finely dispersing it in the matrix.

When the oxide is finely dispersed, high temperature clear
The reason why the strength at high temperature or the high temperature strength greatly increases is because the finely dispersed oxide particles strongly restrain the dislocations and the movement of grain boundaries due to the deformation. The effect of the finely dispersed particles is generally greater as the abundance of the particles is larger, and is larger as the content is the same and the diameter is smaller and the particles are uniformly dispersed. However, the presence of fine particles increases the deformation resistance when molding a tube or the like, deteriorates the deformability and deteriorates the workability, and makes it difficult to soften the work-hardened material by annealing.

In the case of producing a fuel cladding tube for a nuclear reactor, first, in order to obtain an oxide dispersion type alloy, the alloy powder and the oxide powder are sufficiently pulverized and mixed in a ball mill or the like, and after so-called mechanical alloying, for example, a cylinder is used. It is encapsulated in a shaped mild steel capsule, which is hot extruded and solidified into a raw tube. This raw pipe is cold-rolled using a two-roll type Pilger mill or a three-roll type HPTR mill, and produced into a required size. Since the fuel cladding tube, which is strictly required to have dimensional accuracy, has a small diameter and thin wall, it must be cold-worked with a high degree of workability.

However, in the case of an alloy in which fine oxide particles are dispersed, the fibrous structure elongated in the working direction due to the strong cold rolling remains strongly even after annealing, and as a result, the stress in the length direction is reduced. Although it has high strength, the tube is extremely weak against stress in the direction orthogonal to it. Since the internal pressure creep strength is required for the fuel cladding tube, the improvement of the strength in the radial direction or the circumferential direction of the tube is a major issue for practical use.

On the other hand, when the heat treatment after the working is sufficiently performed to coarsen the crystal grains to form a recrystallized structure in which the grains grow in the direction perpendicular to the working direction, the strength in the radial direction is long. It is known that the creep strength of internal pressure improves as it approaches the direction (Ukai, et al .: "Materia" vol.39).
(2000), No.1, p78). Further, in Japanese Patent Laid-Open No. 8-225891 , Y of the oxide-dispersed ferrite high chromium iron alloy is disclosed.
_By setting the content of ₂ O ₃ to 0.3% or less and additionally limiting the amount of excess oxygen, the temperature for coarsening the crystal grains is set to 13
The invention is disclosed in which the temperature is set to 00 ° C. or lower, and in the examples, 1200
The results of annealing at ° C are shown.

[0008] However, when an oxide-dispersion-strengthened ferritic high chromium iron alloy is used to manufacture a fuel clad pipe of an actual size, it is possible to obtain a pipe having an internal pressure creep strength or a high temperature strength in the circumferential direction. Getting stable is not always easy. In particular, in order to sufficiently obtain the effect of strengthening the dispersion of the oxide, the strength difference between the length direction and the circumferential direction increases as the content is increased and the dispersion is improved, and it is considered that further improvement of the manufacturing conditions is required. It was

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxide dispersion strengthened ferritic high chromium iron alloy pipe manufactured by repeating rolling and annealing, which is perpendicular to the rolling length direction. It is to provide a method for reducing the anisotropy of strength with respect to the circumferential direction and improving the level of internal pressure creep strength.

[0010]

SUMMARY OF THE INVENTION The inventors of the present invention have found that mainly chromium is 11 to 15% by mass, and the sum of W and Mo is 4%.
%, Ti less than 1%, and enhanced performance by dispersion of fine oxide particles containing Y ₂ O ₃ ; improvement of performance of reactor fuel cladding tube by dispersion strengthening ferritic high chromium iron alloy, especially tube In order to stably improve the high temperature strength in the circumferential direction, the manufacturing conditions were examined.

First, an alloy tube was produced by performing cold rolling at about 50% and annealing at various temperatures twice twice using a raw tube obtained by hot extrusion to prepare an alloy tube in the length direction. The creep strength, which is perpendicular to the direction of increasing the inner diameter of the tube, was investigated. As a result, by lowering the temperature of the first annealing, that is, the intermediate annealing between rolling, and increasing the temperature of the second annealing, that is, the final annealing, the strength in the direction orthogonal to this length direction is increased. It was confirmed that the tendency of remarkably inferiority was improved and that the metallographic structure became a structure with large crystal grains.

Generally, creep deformation at a high temperature is caused by the sliding of crystal grain boundaries. Therefore, the smaller the number of crystal grain boundaries crossing the direction in which stress is applied, the better the high temperature strength. Therefore, it is considered that the metal structure in which the crystal grains are grown large has brought more preferable results even in the circumferential direction of the tube finely grained by cold working.

Since an actual reactor fuel cladding tube is thin and thin, it is necessary to repeat cold rolling and intermediate annealing for softening 2-3 times or more from a raw tube obtained by hot extrusion. , Final cold rolling and annealing must be performed. Therefore, based on the conditions considered to be preferable in the above-described two cold rolling and annealing experiments,
When manufacturing was performed by selecting the annealing conditions, etc., the internal pressure creep strength of the manufactured pipe was not always sufficiently stable and could not be obtained.

In order to clarify the cause of this, as a result of investigating the metallographic structure of the longitudinal section parallel to the length direction of the pipe manufactured by repeating cold rolling and annealing at least three times in total, the following results were obtained. I found out.

The optical microscope structure of the cross section parallel to the length direction of the tube after annealing has a typical structure as shown in FIG.
Two tissues were observed. (A) is an example that is often seen when the annealing temperature is slightly low, and the hardness is lower than that in the processed state, but there is almost no difference from the as-processed state by observation with an optical microscope. The tube of this structure has large anisotropy of strength and poor internal creep strength. On the other hand, (c) shows an example in which the annealing temperature is sufficiently high. In many cases, this tube having a structure composed of coarse grains has excellent anisotropy of strength and excellent high-temperature internal pressure creep strength. .

The structure of the tube annealed after rolling is shown in FIG.
Large crystal grains that are supposed to correspond to the coarse grains of the structure of (c) may be observed in the fine structure as shown in FIG. This is a phenomenon generally observed in the process of non-uniform grain growth that occurs when grain boundary movement of grain growth during recrystallization is strongly restrained by fine precipitates, and the whole of these coarse grains is observed. The structure of (c) which is presumed to have become the only one shows that it is a so-called secondary recrystallization structure.

Usually, in the state where the metal is cold worked and hardened, the working structure is stretched in the working direction. When it is heated to soften it, the strain, dislocation movement and rearrangement caused by processing, that is, recovery, recrystallization nucleation, growth,
A recrystallization phenomenon called recrystallization texture formation progresses. Such progress of the recrystallization process can be detected as a change in mechanical properties such as hardness, and at the same time, a change in metal structure can be observed by an optical microscope.

However, in the case of an alloy in which fine particles are dispersedly present, dislocations and movements of crystal grain boundaries are largely hindered by the fine particles, so that the above recrystallization process does not easily proceed,
Moreover, even if a recrystallization phenomenon occurs in the usual sense,
The difference with the processed structure can hardly be distinguished by observation with an optical microscope. Even if there is no difference by optical microscope observation, the hardness is lowered, and the ductility is restored to a state in which further processing is possible, so it is presumed that recrystallization is in progress.

When the temperature is further increased, only specific grains grow out of the fine structure, which eclipse the surrounding fine structure to form coarse grains, and eventually the whole becomes coarse grain structure. This is a phenomenon generally called secondary recrystallization or abnormal grain growth, and in the above oxide dispersion type alloy, a microstructural change cannot be detected by optical microscope observation until this stage.

Therefore, here, this secondary recrystallization is recrystallized, the resulting structure (c) is recrystallized, and the softened recrystallized state before the secondary recrystallization, that is, generally the primary recrystallization is performed. The structure in the state (a) called a crystal is called a recovery structure. Therefore, the structure as shown in (b) is a partially recrystallized structure, but this structure has a large anisotropy of strength and a poor internal pressure creep strength as in (a).

In the observed structure, as shown in (d), the part where the deformation band remains and the part which is in the state of being processed or in the state close to the recovered structure are stretched in a band shape and adjacent to each other. There is something. Even if the annealing temperature is increased, this state cannot be easily resolved. Further investigation of this revealed that the intermediate re-annealing resulted in a coarse recrystallized structure, which was subsequently cold-rolled and finally annealed. It is considered that the coarse grains before rolling are stretched, and the parts corresponding to the original individual coarse grains show the same behavior, and remain in the deformed state after annealing or have progressed to the recovery state. In the processing after the coarse grain structure is obtained, sufficient deformation is not accumulated mainly due to slip deformation within the grain, and normal recrystallization does not proceed, and the recrystallization referred to in the present invention as secondary recrystallization. It is presumed that crystals have disappeared. The tube having such a structure has low internal pressure creep strength and large strength anisotropy.

When this recrystallized structure is obtained after the intermediate annealing, it may be the same structure as the recrystallized structure by further cold rolling and annealing, but such a tube has low strength and large anisotropy. Show a trend.

Even if coarse grains do not appear in the first cold rolling and annealing of the blank, if reannealed under the same conditions after the subsequent cold rolling, a recrystallized structure may be formed. When rolling and intermediate annealing are repeated, sufficient care must be taken in selecting the annealing temperature.
It is considered that this is because by repeating rolling and annealing, fine oxide particles aggregate and coarsen, and the effect of inhibiting dislocation and movement of crystal grain boundaries diminishes.

From the above investigation results, when a recrystallized structure or a partial recrystallized structure appeared in the intermediate annealing stage, it was obtained even if the recrystallized structure was shown after the final cold rolling and annealing. It was found that the internal pressure creep strength of the pipe was low. That is, in the annealing during rolling, the condition must be such that it can be sufficiently softened, but it is not good to allow coarse grains to appear.

The intermediate annealing is carried out in order to recover the workability of the work-hardened material to be rolled, but it is desirable not to raise the temperature as described above. However, the lowering of the annealing temperature causes insufficient softening, which makes the rolling process in the next step difficult. On the other hand, it was confirmed that it is important to make the cold rolling workability as large as possible in order to sufficiently soften even at a low temperature.

The above-mentioned investigations are mainly conducted on chromium.
The target was a ferritic iron alloy containing 11 to 15% and Y ₂ O ₃ of about 0.2%, but when more chromium was contained or when the finely dispersed oxide was other than Y ₂ O _3. As a result of the examination, similar results were found in these alloys. That is, when a ferritic iron alloy containing chromium in which oxides are finely dispersed is used for the purpose of heat resistance, and cold-working and annealing are repeated many times to produce a tube of a required size, annealing during rolling is performed. That is, the intermediate annealing lowers the temperature to less than 1100 ° C. to prevent the recrystallization structure as described above from occurring, and the final annealing increases the temperature to 1100 ° C. or more to obtain the recrystallization structure having a large crystal grain size. By doing so, it was found that an alloy pipe having sufficient strength not only in the rolled length direction but also in the circumferential direction perpendicular to the rolling can be stably obtained.

Based on the above findings, the present invention was completed by further confirming the limiting conditions. The gist of the present invention is as follows.

(1) Cr: 11 to 15%, Ti: 0.
1-1% and _Y 2 _{O 3:} oxide dispersion containing from 0.15 to 0.35%
A method of manufacturing a reinforced ferritic iron alloy tube, which comprises producing a material by mixing and sintering metal powder and oxide powder, and repeating cold rolling and annealing at least three times to obtain a tube having a required shape. In this case, the rolling ratio of each cold rolling is 30% or more, the annealing during rolling is less than 1100 ° C, and the final annealing is performed at 1100 ° C or more. Method for manufacturing alloy pipe.

(2) Cr: 11 to 15%, Ti: 0.1% by mass
~ 1%, the sum of one or two of W and Mo: 0.1 to 4
%, And Y ₂ O ₃ : oxide dispersion containing 0.15 to 0.35%
A method of manufacturing a reinforced ferritic iron alloy tube, which comprises producing a material by mixing and sintering metal powder and oxide powder, and repeating cold rolling and annealing at least three times to obtain a tube having a required shape. In this case, the rolling ratio of each cold rolling is 30% or more, the annealing during rolling is less than 1100 ° C, and the final annealing is performed at 1100 ° C or more. Method for manufacturing alloy pipe.

[0030]

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention is applied to the production of a ferrite-based iron alloy tube dispersion-strengthened with an oxide. In order to uniformly disperse oxide fine particles, such alloy pipes are made by mixing and sintering metal powder and oxide powder to form a raw pipe, which is repeatedly cold-rolled and annealed to form the required shape. To do. In this manufacturing process, cold rolling and annealing are repeated three times or more in total to form a pipe having a required shape. At that time, the rolling ratio of each cold rolling is 30% or more, and the annealing in the middle of rolling is performed. Is below 1100 ° C, and the final annealing is above 1100 ° C.

In the production of the raw tube, for example, first, a metal powder and an oxide powder having a required composition are sufficiently pulverized and mixed by a so-called mechanical alloying method using a ball mill or the like. Next, this powder is enclosed in a mild steel capsule or the like, and is integrally sintered by heat extrusion to produce a cold-rolling base pipe. If necessary, this is further annealed by heating to obtain a material for cold working. The manufacturing up to this stage may be performed according to a conventionally practiced technique.

For the cold rolling of the blank, it is desirable to use a Pilger rolling machine or an HPTR rolling machine. This is because a relatively hard material can be processed cold or warm with a large forming ratio. Cold rolling reduction rate (area reduction rate)
Needs more than 30%. Here, the rolling ratio of the cold rolling, starting the rolling from the raw tube or the softened state after annealing,
It is the total rolling ratio of rolling until the intermediate annealing or the final annealing for the next softening, and the rolling may be 30% or more in one pass, or 30 in two passes, three passes or multiple passes.
% Or more may be used.

The cold rolling with a rolling ratio of 30% or more can lower the heating temperature of softening annealing during rolling, that is, the intermediate annealing, and also the heating temperature for forming a recrystallized structure after the final rolling. This is because it can be lowered.
In order to obtain the effect of lowering the annealing temperature more stably, it is desirable that the rolling ratio of this cold rolling be 40% or more.

The intermediate annealing during the rolling process is performed at a temperature of less than 1100 ° C. This is because a temperature of 1100 ° C. or higher may cause a recrystallized structure or a partial recrystallized structure, and in particular, if rolling and softening annealing are repeated, the risk increases. However, if the annealing heating temperature is too low, the softening becomes insufficient and it becomes difficult to roll more than 30% thereafter.

The final annealing was performed to obtain a recrystallized structure.
Heating above 00 ℃ is required. If it is less than 1100 ° C, the recrystallized structure is not sufficiently formed, and the anisotropy of strength may not be reduced. However, heating above 1250 ° C may lower the creep strength even if the anisotropy can be reduced, and it is desirable to set the temperature in the range of 1150 to 1250 ° C.

The heating time of each of the above annealings, whether it is the softening annealing in the middle or the final annealing, can be sufficiently achieved by maintaining the temperature for 10 minutes or more and 2 hours.

The rolling and annealing conditions of the method of the present invention are particularly effective when rolling and intermediate and final annealing are repeated a total of three times or more. In the case of twice, even if the intermediate annealing is not performed at less than 1100 ° C as described above, the recrystallized structure often does not appear at this stage. However, in the case of a fuel clad tube, rolling and annealing must be repeated three times or more due to its small diameter and thin wall, and if the number of rolling and annealing is increased, there is a risk that a recrystallized structure will appear before the final rolling. Is increasing.

The tube to which the present invention is applied is made by mixing and sintering alloy powder and oxide powder, and Cr: 11-15%
And Ti: 0.1 to 1%, or even 1 of W and Mo
Made of a ferritic heat-resistant iron alloy containing 0.1 to 4% of a total of 0.1 to 4% and reinforced by dispersing an oxide.
It The fine oxide particles dispersed in the alloy include Y
₂ O ₃ : It contains 0.15 to 0.35%. Others, Mg
_{O, Al 2 O 3, MgAl} 2 O 4, ThO 2, Ti O 2
It is those and including one or more of Zr _{O 2}
May be . In order to improve the high temperature strength of the alloy tube by using any of the oxide fine particles dispersed therein, the application of the method of the present invention is effective in improving the strength and reducing the anisotropy of the strength.

One of the most effective alloy pipes to which the manufacturing method of the present invention is applied is that Cr is 11 to 15% (hereinafter, all are mass%), Ti is 0.1 to 1%, and Y ₂ O ₃ is 0.15. An oxide dispersion strengthened ferritic iron alloy tube containing ~ 0.35%. In addition to these components, the alloy may contain other alloy components added to the ferritic iron alloy.

In this case, if the Cr content is less than 11%, the oxidation resistance and corrosion resistance are insufficient, and if it exceeds 15%, embrittlement due to neutron irradiation or the like tends to occur. Good. Ti has a function of refining oxide particles such as Y ₂ O _3, and is preferably contained in the range of 0.1 to 1%. This is less than 0.1%, the effect is small, 1%
If it exceeds, the effect will be saturated.

As the oxide to be dispersed, Y ₂ O ₃ of 0.
Although it is contained in an amount of 15 to 0.35%, Y ₂ O ₃ is an oxide that is extremely effective for easily finely dispersing and improving high temperature strength. If the content is less than 0.15%, a recrystallized structure is likely to occur during the softening process during rolling, and as a result, the strength anisotropy tends to be large after the final annealing. However, if the content exceeds 0.35%, the annealing temperature required to obtain the recrystallized structure becomes high and the working becomes difficult. Therefore, the content of Y ₂ O ₃ is 0.15 to 0.35%
Is good. However, 0.20 to 0.35% is desirable in order to obtain a tube having high strength at high temperature within a range where strength anisotropy does not increase.

W and M are used as elements for improving the high temperature strength of the above-mentioned ferritic iron alloy tube without causing significant deterioration of workability and anisotropy unlike the dispersion of oxide fine particles.
One or two kinds of o may be contained in a total amount of 0.1 to 4%. In this case, if it is less than 0.1%, there is no effect of addition, and if it exceeds 4%, the workability deteriorates.

[0044]

[Examples] Y ₂ O ₃ powder was mixed with iron-based alloy powder, and pulverized and mixed in an argon atmosphere with an attritor ball mill,
The obtained powder was enclosed in a mild steel capsule and heated to 1150 ° C. to produce an alloy rod having an extrusion ratio of 7 and an outer diameter of about 20 mm.
From this, a blank pipe having an outer diameter of 18 mm and a wall thickness of 3 mm was machined out and annealed at 1250 ° C. for 30 minutes to obtain a cold-rolled blank pipe. Table 1 shows the chemical compositions of the three types of prepared tube.

[0045]

[Table 1]

Using these raw tubes, in the process shown in FIG. 2, the cold rolling and annealing of are repeated to obtain an outer diameter of 7.1 mm,
An alloy tube with a wall thickness of 0.53 mm was produced. For cold rolling, a Pilger rolling machine was used to perform 45 to 48% processing in one pass.
The three intermediate anneals performed during the rolling process are repeated at the same temperature for rolling one pipe, and 1050 ℃, 1100 ℃, 11
Four temperatures of 50 ° C or 1200 ° C were used. 1 for final annealing
It is 150 ℃. The soaking time for each of these annealings was 30 minutes. After each annealing, a test piece was cut out from the tube end and the microscopic structure of the longitudinal section was observed.

These microscopic structures show (a) recovered structure, (b) partial recrystallized structure, (c) recrystallized structure or (d) deformation recovered structure, examples of which are shown in FIG. The relationship with the annealing temperature is summarized in FIG. Figure 3
Shows the measurement results of hardness (HV) together with the tissue.

As shown here, when a tube is manufactured by repeating cold rolling and intermediate annealing, alloy A having a small content of Y ₂ O ₃ has a high intermediate annealing temperature of 1100 ° C. or higher. A recrystallized structure is generated during repeated cold rolling and annealing, and further a deformation recovery structure is generated. If the intermediate annealing temperature is high, the recrystallized structure can be finally obtained even if the deformation recovery structure is formed in the middle of rolling. Thus, even if a recrystallized structure is likely to occur in the stage of intermediate annealing, if the intermediate annealing is performed at 1050 ° C, which is lower than 1100 ° C, the recrystallized structure does not occur at this stage, and the recrystallized structure is not regenerated after the final annealing. A crystalline structure can appear. However, with alloy A having a small amount of oxide, the improvement in high temperature strength is not significant, and the purpose of strengthening cannot be achieved sufficiently.

Even in alloys B and C containing a large amount of oxides, at an intermediate annealing temperature of 1100 ° C. or higher, a recrystallization structure is generated during rolling, and after the final annealing, a deformation recovery structure having a large anisotropy of strength is formed. turn into. On the other hand, the temperature of the intermediate annealing is set to 1050 ° C, which is less than 1100 ° C, and the final annealing
By setting the temperature to 1150 ° C. or higher, a tube having a recrystallized structure with small strength anisotropy and having sufficient strength can be obtained.

Intermediate annealing made of the above alloy B has 10
An internal pressure creep rupture test was carried out using two types of tubes, a tube having a recrystallized structure by final annealing at 50 ° C and a tube having a deformation recovery structure at 1150 ° C. Test temperature 70
FIG. 4 shows the results of measuring the time until fracture at 0 ° C. with various internal pressures.

As is apparent from the above, a tube having a recrystallized structure by the method of the present invention has a fracture time 10 times longer than that of a tube having a recovered deformed structure for the same internal pressure. This is an effect obtained by forming a recrystallized structure in the final annealing without generating a recrystallized structure during rolling.

[0052]

According to the manufacturing method of the present invention, in an oxide dispersion strengthened ferritic high chromium iron alloy pipe manufactured by repeating rolling and annealing, the strength in the length direction and the circumferential direction orthogonal thereto is increased. It is possible to reduce the anisotropy of the thickness and improve the strength. If this alloy tube is used for a fuel cladding tube of a fast reactor used under high temperature and strong neutron irradiation environment, it will be excellent in high temperature strength, especially internal pressure creep strength, and will be put to practical use in a fast reactor. The effect of contributing to is great.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a microstructure of a cross section in a rolling direction of a tube obtained by annealing after cold rolling.

FIG. 2 is a diagram illustrating a rolling process of an alloy pipe.

FIG. 3 is a view showing a change in microstructure of an alloy tube after intermediate annealing or final annealing.

FIG. 4 is a diagram showing a creep rupture test result at 700 ° C. of a tube having a recrystallization structure or a tube having a recovery deformation structure.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22C 38/28 C22C 38/28 G21C 3/07 GDF B22F 3/20 B 3/30 G21C 3/06 GDFP // B22F 3/20 3/30 V (72) Inventor Shigeharu Ukai 4002 Narita-cho, Oarai-cho, Higashi-Ibaraki, Ibaraki Prefecture Oarai Engineering Center, Nuclear Fuel Cycle Development Organization (72) Inventor Jusumi Kobayashi 1 Nishino-cho, Higashimukaijima, Amagasaki-shi, Hyogo Sumitomo Kin Genus Technology Co., Ltd. Kansai Plant (72) Inventor Takanari Okuda 13-1 Chofu Minatomachi, Shimonoseki City, Yamaguchi Prefecture Shinko Special Steel Tube Co., Ltd. (72) Inventor Yuyuki Fujiwara 1-5 Wakihamacho, Chuo-ku, Kobe-shi, Hyogo Prefecture No. 8 Kobelco Research Institute Co., Ltd. (56) Reference JP-A-9-53141 (JP, A) JP-A-8-225891 (JP, A) JP-A-2001-49335 (JP, A) Open 2000-282101 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) C21D 8/10 B22F 3/24 C22C 33 / 02,38 / 00 - 38/60

Claims (2)

(57) [Claims] 1. Cr: 11-15%, Ti: 0.1-1 by mass%
% And Y ₂ O ₃ : 0.15 to 0.35% containing oxide dispersion strengthening
A method for manufacturing a type ferritic iron alloy tube, wherein a raw material is prepared by mixing and sintering metal powder and oxide powder, and a total of 3
When cold rolling and annealing are repeated more than once to form a tube with the required shape, the rolling ratio of each cold rolling is 30% or more, the annealing during rolling is less than 1100 ° C, and the final annealing is performed at 1100 ° C or more. A method for producing an oxide dispersion strengthened ferritic iron alloy tube containing chromium. 2. Cr: 11-15%, Ti: 0.1-1 in mass%
%, The total of one or two of W and Mo: 0.1 to 4%,
And _Y 2 _{O 3:} ODS containing 0.15 to 0.35%
A method for manufacturing a type ferritic iron alloy tube, wherein a raw material is prepared by mixing and sintering metal powder and oxide powder, and a total of 3
When cold rolling and annealing are repeated more than once to form a tube with the required shape, the rolling ratio of each cold rolling is 30% or more, the annealing during rolling is less than 1100 ° C, and the final annealing is performed at 1100 ° C or more. A method for producing an oxide dispersion strengthened ferritic iron alloy tube containing chromium.