WO2023238851A1 - Austenitic stainless alloy material - Google Patents

Austenitic stainless alloy material Download PDF

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Publication number
WO2023238851A1
WO2023238851A1 PCT/JP2023/020959 JP2023020959W WO2023238851A1 WO 2023238851 A1 WO2023238851 A1 WO 2023238851A1 JP 2023020959 W JP2023020959 W JP 2023020959W WO 2023238851 A1 WO2023238851 A1 WO 2023238851A1
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Prior art keywords
alloy material
content
austenitic stainless
less
precipitates
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PCT/JP2023/020959
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French (fr)
Japanese (ja)
Inventor
奈央 大瀧
友彰 浜口
孝裕 小薄
克樹 田中
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日本製鉄株式会社
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies

Definitions

  • the present disclosure relates to alloy materials, and more specifically to austenitic stainless steel alloy materials.
  • the austenitic stainless steel alloy material disclosed in Patent Document 2 has, in mass%, C: 0.03 to 0.12%, Si: 0.2 to 2%, Mn: 0.1 to 3%, P: 0.03% or less, S: 0.01% or less, Ni: more than 18% and less than 25%, Cr: more than 22% and less than 30%, Co: 0.04 to 0.8%, Ti: 0.002 % or more and less than 0.01%, Nb: 0.1 to 1%, V: 0.01 to 1%, B: more than 0.0005% and less than 0.2%, sol. It contains Al: 0.0005% or more and less than 0.03%, N: 0.1 to 0.35%, O (oxygen): 0.001 to 0.008%, and the remainder consists of Fe and impurities.
  • the alloy material disclosed in this document contains Ti, Nb, and V to generate precipitates when used in a high-temperature environment, thereby increasing creep strength.
  • the austenitic stainless steel alloy material according to the present disclosure is In mass%, C: 0.03-0.12%, Si: 0.05-2.00%, Mn: 0.05-3.00%, P: 0.03% or less, S: 0.010% or less, Ni: 18.0 to less than 25.0%, Cr: less than 22.0 to 30.0%, Co: 0.04-0.80%, Ti: 0.002 to 0.010%, Nb: 0.1-1.0%, V: 0.01-1.00%, Al: 0.001 to less than 0.030%, N: 0.10-0.35%, Mo: 0-1.00%, W: 0-1.00%, B: 0 to 0.010%, and Contains Ca: 0 to 0.0100%, the remainder consists of Fe and impurities, The number density of precipitates with an equivalent circle diameter of 0.5 to 2.0 ⁇ m is 5000 pieces/mm 2 or more.
  • the present inventors investigated an austenitic stainless steel alloy material that can have both excellent creep strength and excellent stress relaxation cracking resistance.
  • the present inventors attempted to achieve both excellent creep strength and excellent stress relaxation cracking resistance from the viewpoint of chemical composition.
  • C 0.03 to 0.12%
  • Si 0.05 to 2.00%
  • Mn 0.05 to 3.00%
  • P 0.03% or less
  • S 0.010% or less
  • Ni 18.0 to less than 25.0%
  • Cr 22.0 to less than 30.0%
  • Co 0.04 to 0.80%
  • Nb 0.1 to 1.0%
  • V 0.01 to 1.00%
  • Al 0.01 to less than 0.030%
  • N 0.10 to 0.35%
  • Mo 0 -1.00%
  • W 0-1.00%
  • B 0-0.010%
  • Ca 0-0.0100%
  • the balance is Fe and impurities.
  • the present inventors intentionally removed the fine precipitates from the austenitic stainless steel alloy material. We thought that by pre-existing it in stainless steel alloy materials, it would be possible to increase not only creep strength but also stress relaxation cracking resistance.
  • the present inventors have developed a method that can be used in high-temperature environments by reducing the amount of precipitates in the alloy material as much as possible, like the conventional austenitic stainless steel alloy materials such as Patent Document 1 and Patent Document 2.
  • a method that can be used in high-temperature environments by reducing the amount of precipitates in the alloy material as much as possible, like the conventional austenitic stainless steel alloy materials such as Patent Document 1 and Patent Document 2.
  • Patent Document 1 and Patent Document 2 We have discovered that it is possible to achieve both excellent creep strength and excellent stress relaxation cracking resistance by deliberately allowing 5000 or more fine precipitates/ mm2 to exist in the austenitic stainless steel alloy material, rather than increasing the creep strength of the material.
  • the austenitic stainless steel alloy material of this embodiment was completed.
  • the austenitic stainless steel alloy material of this embodiment which was completed based on the above technical idea, has the following configuration.
  • S 0.010% or less Sulfur (S) is unavoidably contained.
  • the S content is over 0%. S segregates at the grain boundaries of the alloy material. If the S content exceeds 0.010%, even if the contents of other elements are within the ranges of this embodiment, the above-mentioned segregation occurs and stress relaxation cracking resistance decreases. Therefore, the S content is 0.010% or less. It is preferable that the S content is as low as possible. However, excessive reduction in S content increases the manufacturing cost of the alloy material. Therefore, considering normal industrial production, the preferable lower limit of the S content is 0.001%. A preferable upper limit of the S content is 0.008%, more preferably 0.006%, still more preferably 0.004%, and still more preferably 0.003%.
  • a preferable upper limit of the Cr content is 29.9%, more preferably 29.8%, even more preferably 29.5%, still more preferably 29.0%, and even more preferably 28.5%. %, more preferably 28.0%, still more preferably 27.5%, even more preferably 27.0%.
  • the chemical composition of the austenitic stainless steel alloy material of this embodiment may further contain one or more selected from the group consisting of Mo and W in place of a part of Fe. These elements are optional elements, and all of them increase the creep strength of the austenitic stainless alloy material.
  • the preferable lower limit of the B content is more than 0%, more preferably 0.001%, and still more preferably 0.002%.
  • a preferable upper limit of the B content is 0.009%, more preferably 0.008%, still more preferably 0.007%, and still more preferably 0.006%.
  • the austenitic stainless steel alloy material of this embodiment may further contain Ca.
  • Ca 0 ⁇ 0.0100%
  • Calcium (Ca) is an optional element and may not be included. That is, the Ca content may be 0%.
  • Ca When Ca is contained, that is, when the Ca content is more than 0%, Ca fixes O (oxygen) and S (sulfur) as inclusions and improves the hot workability of the alloy material. If even a small amount of Ca is contained, the above effects can be obtained to some extent. However, if the Ca content exceeds 0.0100%, even if the contents of other elements are within the range of this embodiment, the cleanliness of the alloy material will decrease and the hot workability of the alloy material will decrease. . Therefore, the Ca content is 0 to 0.0100%, and if contained, the Ca content is 0.0100% or less.
  • fine precipitates With an equivalent circle diameter of 0.5 to 2.0 ⁇ m are defined as "fine precipitates".
  • the fine precipitates keep the crystal grains of the austenitic stainless alloy material fine due to the pinning effect. As a result, the grain boundary area of the austenitic stainless steel alloy material increases, and stress relaxation cracking resistance increases. Furthermore, fine precipitates with an equivalent circle diameter of 0.5 to 2.0 ⁇ m exhibit a precipitation-strengthening function during use in a high-temperature environment, increasing the creep strength of the austenitic stainless alloy material.
  • the preferable lower limit of the number density ND of fine precipitates is 5200 pieces/mm 2 , more preferably 5500 pieces/mm 2 , even more preferably 6000 pieces/mm 2 , and still more preferably 6200 pieces/mm 2 be.
  • the number density ND of fine precipitates can be determined by the following method.
  • a test piece is taken from an austenitic stainless steel alloy material. If the austenitic stainless steel alloy material is an alloy tube, collect a test piece including the thick center part. Among the surfaces of the test pieces, the surface that is a cross section perpendicular to the tube axis direction of the alloy tube and that includes the central part of the wall thickness is used as the observation surface, and the central part of the wall thickness is used as the observation field of view.
  • the austenitic stainless steel alloy material is an alloy plate
  • the surface that is a cross section perpendicular to the rolling direction of the alloy plate and includes the central part of the plate thickness is used as the observation surface, and the central part of the plate thickness is used as the observation field of view.
  • the observation surface After mirror-polishing the observation surface, use an optical microscope to obtain a microstructure photograph of the observation field in the mirror-polished observation surface at a magnification of 500 times.
  • the area of the observation field is 140 ⁇ m ⁇ 160 ⁇ m.
  • the equivalent circle diameter of the particles in the observation field is determined.
  • the equivalent circle diameter means the diameter of a circle having the same area as the particle area.
  • the equivalent circle diameter can be determined by well-known image processing. Particles during visual field observation can be easily identified by contrast. Particles with an equivalent circle diameter of 0.5 to 2.0 ⁇ m are recognized as precipitates (fine precipitates).
  • the number density (number/mm 2 ) of fine precipitates is determined based on the number of all fine precipitates in the observation field and the area of the observation field. Note that the fine precipitates are, for example, one or more of Ti precipitates containing Ti, Nb precipitates containing Nb, and V precipitates containing V.
  • the austenitic stainless steel alloy material of this embodiment satisfies Feature 1 and Feature 2.
  • the austenitic stainless alloy material of this embodiment can have both excellent creep strength and excellent stress relaxation cracking resistance.
  • microstructure of austenitic stainless steel alloy material The microstructure of the alloy material of this embodiment consists of austenite.
  • the shape of the austenitic stainless alloy material of this embodiment is not particularly limited.
  • the austenitic stainless steel alloy material may be an alloy tube or an alloy plate.
  • the austenitic stainless steel alloy material may be a bar material.
  • the austenitic stainless alloy material of this embodiment is an alloy tube.
  • the manufacturing method described below is an example of the manufacturing method of the austenitic stainless alloy material of this embodiment. Therefore, the austenitic stainless steel alloy material of this embodiment may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferable example of the manufacturing method of the austenitic stainless alloy material of this embodiment.
  • the method for manufacturing an alloy material of this embodiment includes the following steps.
  • Step 1) Preparation step (Step 2) Hot working step (Step 3) High temperature holding step (Step 4) Cold working step (Step 5) Precipitation heat treatment step
  • the holding temperature in the high temperature holding step is defined as T1 (°C)
  • the holding time at the holding temperature T1 is defined as t1 (minutes)
  • the heat treatment temperature in the precipitation heat treatment step is T2 (°C).
  • a material having a chemical composition that satisfies the above feature 1 is prepared.
  • Materials may be supplied or manufactured by a third party.
  • the material may be an ingot, a slab, a bloom, or a billet.
  • a molten alloy having a chemical composition that satisfies feature 1 above is produced.
  • an ingot is produced by an ingot-forming method.
  • a slab, bloom, or billet may be produced by a continuous casting method.
  • a billet may be manufactured by hot working the manufactured ingot, slab, or bloom.
  • an ingot may be hot forged to produce a cylindrical billet, and this billet may be used as the raw material.
  • the temperature of the material immediately before the start of hot forging is not particularly limited, but is, for example, 1100 to 1300°C.
  • the method for cooling the material after hot forging is not particularly limited.
  • Step 2 Hot processing step hot working is performed on the material prepared in the preparation step to produce an intermediate alloy material.
  • the intermediate alloy material may be, for example, an alloy tube, an alloy plate, or an alloy bar.
  • the intermediate alloy material is an alloy tube
  • the following processing is performed in the hot processing step.
  • the heating temperature is not particularly limited, but is, for example, 1100 to 1300°C.
  • the alloy tube may be manufactured by performing piercing rolling using the Mannesmann method.
  • the cylindrical material is heated.
  • the heating temperature is not particularly limited, but is, for example, 1100 to 1300°C.
  • the heated cylindrical material is punched and rolled using a punching machine to form a hollow tube.
  • the hollow tube is further subjected to elongation rolling or sizing rolling using a mandrel mill, reducer, sizing mill, etc. to produce an intermediate alloy material (alloy tube).
  • the hot working step uses, for example, one or more rolling mills equipped with a pair of work rolls.
  • the material such as a slab is heated.
  • the heating temperature is not particularly limited, but is, for example, 1100 to 1300°C.
  • the heated material is hot rolled using a rolling mill to produce an intermediate alloy material (alloy plate).
  • the hot working step uses, for example, a blooming mill and/or a continuous rolling mill in which a plurality of rolling mills are arranged in a row.
  • the material is heated.
  • the heating temperature is not particularly limited, but is, for example, 1100 to 1300°C.
  • the heated material is hot rolled using a blooming mill and/or a continuous rolling mill to produce an intermediate alloy material (alloy bar material).
  • Step 3 High temperature holding step
  • the intermediate alloy material produced in the hot working step is held at a high temperature to sufficiently dissolve precipitates in the intermediate alloy material.
  • the holding temperature T1 (° C.) and the holding time t1 (minutes) at the holding temperature T1 in the high temperature holding step are adjusted to the range shown below.
  • the intermediate alloy material cooled to room temperature in the hot working step may be heated to a holding temperature T1 and held at the holding temperature T1 for a holding time t1. Further, the intermediate alloy material immediately after the hot working step (that is, the intermediate alloy material that has not been cooled to room temperature) may be held at the holding temperature T1 for a holding time t1. After the holding time t1 has elapsed, the intermediate alloy material is rapidly cooled.
  • the rapid cooling may be water cooling or oil cooling.
  • Step 4 Cold working step
  • the intermediate alloy material is pickled and then cold worked.
  • the cold working is, for example, cold drawing.
  • the intermediate alloy material is an alloy plate
  • the cold working is, for example, cold rolling.
  • the area reduction rate in the cold working process is not particularly limited, but is, for example, 10 to 90%.
  • Step 5 Precipitation heat treatment step
  • the intermediate alloy material after the cold working step is heat treated to generate fine precipitates in the intermediate alloy material.
  • the heat treatment temperature T2 (° C.) in the precipitation heat treatment step and the holding time t2 (minutes) at the heat treatment temperature T2 are adjusted within the following ranges.
  • the rapid cooling method may be water cooling or oil cooling.
  • F1 is a conditional expression for sufficiently dissolving precipitates (Nb precipitates, Ti precipitates, V precipitates, etc.) in the intermediate alloy material in the high temperature holding step.
  • the austenitic stainless steel alloy material of this embodiment has a high N content of 0.10 to 0.35%. In such a case where the N content is high, in order to sufficiently dissolve the Ti precipitates, an amount of heat corresponding to the Ti content in the alloy material is required. Similarly, in order to sufficiently dissolve Nb precipitates and V precipitates, an amount of heat corresponding to the Nb content and V content of the alloy material is required.
  • the Nb content, Ti content, and V content are arranged in the denominator. That is, F1 is adjusted according to the Nb content, Ti content, and V content in the alloy material. As described above, the austenitic stainless alloy material of this embodiment has a high N content. Therefore, among Nb precipitates, Ti precipitates, and V precipitates, Ti, which has a strong bond with N, is the most difficult to dissolve. Therefore, the coefficient of Ti in F1 is large.
  • F1 is 4100 or more, sufficient heat is applied to the intermediate alloy material in the high temperature holding step to melt Nb precipitates, Ti precipitates, and V precipitates in the intermediate alloy material. Therefore, the precipitates present in the intermediate alloy material can be sufficiently dissolved.
  • a preferable lower limit of F1 is 4200, more preferably 4300.
  • F2 (T2+t2) ⁇ (Nb+50Ti+20V).
  • F2 is a conditional expression for setting the number density ND of fine precipitates to 5000 pieces/mm 2 or more. If F2 is 1000 or more, the number density of fine precipitates will be 5000 pieces/mm 2 or more on the premise that formulas (A) and (B) are satisfied.
  • a preferable lower limit of F2 is 1020, more preferably 1100, and still more preferably 1200.
  • an austenitic stainless steel alloy material that satisfies Features 1 and 2 can be produced.
  • the method for manufacturing the austenitic stainless alloy material of this embodiment is not limited to the above-described manufacturing method. Other manufacturing methods may be used as long as an austenitic stainless steel alloy material that satisfies Features 1 and 2 can be produced.
  • the austenitic stainless alloy material of this embodiment will be explained in more detail with reference to Examples.
  • the conditions in the following examples are examples of conditions adopted to confirm the feasibility and effects of the austenitic stainless alloy material of this embodiment. Therefore, the austenitic stainless alloy material of this embodiment is not limited to this one example condition.
  • the produced ingot was hot forged to produce a cylindrical material with a diameter of 180 mm.
  • the heating temperature of the ingot during hot forging was 1100 to 1300°C.
  • a hot working process was performed on the manufactured cylindrical material. Specifically, the material was heated in a heating furnace. The heating temperature in the hot working step was 1100 to 1300°C. Hot extrusion was performed on the heated cylindrical material to produce a blank pipe.
  • Cold working was performed on the raw tube after the high temperature holding process. Specifically, cold drawing was performed on the raw pipe. Note that the area reduction rate during cold working was 20 to 70%.
  • a precipitation heat treatment process was performed on the raw pipe after the cold working process.
  • the heat treatment temperature T2 (° C.) in the precipitation heat treatment step and the holding time t2 (minutes) at the heat treatment temperature T2 were as shown in Table 2.
  • the F1 value is shown in the "F1” column in Table 2.
  • T (Ture) indicates that the holding temperature T1 was greater than or equal to the heat treatment temperature T2
  • F (False) indicates that the holding temperature T1 was less than the heat treatment temperature T2. shows.
  • the F2 value is shown in the "F2" column.
  • an austenitic stainless steel alloy material (alloy tube) was manufactured.
  • a creep test in accordance with JIS Z2271:2010 was conducted using the collected creep rupture test piece. Specifically, a creep rupture test piece was heated to 700°C. Thereafter, a creep rupture test was conducted. The test stress was 80 MPa. In the test, creep rupture time (hours) was determined.
  • the creep strength was evaluated as follows according to the obtained creep rupture time. Evaluation E (Excellent): Creep rupture time is 1500 hours or more Evaluation B (Bad): Creep rupture time is less than 1500 hours In the case of evaluation E, it was determined that excellent creep strength was obtained. The evaluation results are shown in the "Creep strength" column in Table 2.
  • a C-ring type restrained weld crack test piece shown in FIG. 1 was prepared from the center of the wall thickness of the alloy material (alloy tube) of each test number.
  • the situation was As shown in FIG. 1, a gap G of 1.5 mm was formed in the opening.
  • a notch portion was formed at a position 180° from the opening with respect to the central axis of the C-ring type restrained weld crack test piece when viewed in the tube axis direction.
  • the width NW of the notch portion was 0.4 mm
  • the depth NOD was 0.5 mm
  • the radius of curvature R of the bottom portion was 0.2 mm.
  • the tanned C-ring type restrained weld crack test piece was heat treated at 650° C. for 500 hours. After the heat treatment, the number of cracks occurring at the notch bottom of the C-ring restraint weld crack test piece was counted. Specifically, crack observation test pieces including the notch bottom of the C-ring type restrained weld crack test piece and a cross section perpendicular to the pipe axis direction of the C-ring type restrained weld crack test piece were collected at three locations in the pipe axis direction. did. The surface corresponding to the above-mentioned cross section of each crack observation test piece was taken as the observation surface. After the observation surface was mirror polished, it was etched with a 10% oxalic acid aqueous solution.
  • the stress relaxation cracking resistance was evaluated according to the obtained cracking incidence as follows. Evaluation E: The cracking incidence is 30% or less. Evaluation B: The cracking incidence is more than 30%. In the case of evaluation E, it was determined that excellent stress relaxation cracking resistance was obtained. The evaluation results are shown in Table 2.
  • test numbers 13 and 14 F1 was too low and did not satisfy formula (A). Therefore, in the austenitic stainless steel alloy materials having these test numbers, the number density ND of fine precipitates was less than 5000 pieces/mm 2 . As a result, sufficient stress relaxation cracking resistance could not be obtained.
  • test numbers 18 and 19 F2 was too low and did not satisfy formula (C). Therefore, in the austenitic stainless steel alloy materials having these test numbers, the number density ND of fine precipitates was less than 5000 pieces/mm 2 . As a result, sufficient creep strength could not be obtained. Furthermore, sufficient stress relaxation cracking resistance could not be obtained.

Abstract

The present invention provides an austenitic stainless alloy material which has excellent creep strength and excellent stress relaxation cracking resistance. An austenitic stainless alloy material according to the present disclosure contains, in mass%, 0.03% to 0.12% of C, 0.05% to 2.00% of Si, 0.05% to 3.00% of Mn, 0.03% or less of P, 0.010% or less of S, not less than 18.0% but less than 25.0% of Ni, not less than 22.0% but less than 30.0% of Cr, 0.04% to 0.80% of Co, 0.002% to 0.010% of Ti, 0.1% to 1.0% of Nb, 0.01% to 1.00% of V, not less than 0.001% but less than 0.030% of Al and 0.10% to 0.35% of N, while having a number density of precipitates having a circle-equivalent diameter of 0.5 µm to 2.0 µm of 5,000 per mm2 or more.

Description

オーステナイト系ステンレス合金材Austenitic stainless steel alloy material
　本開示は、合金材に関し、さらに詳しくは、オーステナイト系ステンレス合金材に関する。 The present disclosure relates to alloy materials, and more specifically to austenitic stainless steel alloy materials.
　石炭火力ボイラ、バイオマスボイラ、及び、ＨＲＳＧ（Ｈｅａｔ　Ｒｅｃｏｖｅｒｙ　Ｓｔｅａｍ　Ｇｅｎｅｒａｔｏｒ）等のボイラ用途の材料として、オーステナイト系ステンレス合金材が用いられている。これらのボイラ用途に用いられる材料では、高温環境での優れたクリープ強度が求められる。 Austenitic stainless steel alloy materials are used as materials for boilers such as coal-fired boilers, biomass boilers, and HRSG (Heat Recovery Steam Generator). Materials used in these boiler applications are required to have excellent creep strength in high-temperature environments.
　クリープ強度を高めたオーステナイト系ステンレス合金材が、国際公開第２００９／０４４７９６号（特許文献１）及び特開２００４－２５０７８３号公報（特許文献２）に提案されている。 Austenitic stainless steel alloy materials with increased creep strength are proposed in International Publication No. 2009/044796 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-250783 (Patent Document 2).
　特許文献１に開示されているオーステナイト系ステンレス合金材は、質量％で、Ｃ：０．０４～０．１８％、Ｓｉ：１．５％以下、Ｍｎ：２．０％以下、Ｎｉ：６～３０％、Ｃｒ：１５～３０％、Ｎ：０．０３～０．３５％、ｓｏｌ．Ａｌ：０．０３％以下を含有し、さらに、Ｎｂ：１．０％以下、Ｖ：０．５％以下及びＴｉ：０．５％以下のうちの１種又は２種以上を含有し、残部がＦｅ及び不純物からなる。この合金材はさらに、Ｐ１（＝Ｓ＋｛（Ｐ＋Ｓｎ）／２｝＋｛（Ａｓ＋Ｚｎ＋Ｐｂ＋Ｓｂ）／５｝）が０．０６以下であり、Ｐ２（＝Ｎｂ＋２（Ｖ＋Ｔｉ））が０．２～１．７－１０×Ｐ１である。この文献に開示された合金材では、Ｎｂ、Ｖ、及び、Ｔｉの指標であるＰ２を０．２以上とすることにより、高温環境での使用時に析出物を生成して、クリープ強度を高めている。 The austenitic stainless steel alloy material disclosed in Patent Document 1 has C: 0.04 to 0.18%, Si: 1.5% or less, Mn: 2.0% or less, and Ni: 6 to 6% by mass. 30%, Cr: 15-30%, N: 0.03-0.35%, sol. Contains Al: 0.03% or less, further contains one or more of Nb: 1.0% or less, V: 0.5% or less, and Ti: 0.5% or less, with the balance consists of Fe and impurities. Furthermore, this alloy material has P1 (=S+{(P+Sn)/2}+{(As+Zn+Pb+Sb)/5}) of 0.06 or less, and P2 (=Nb+2(V+Ti)) of 0.2 to 1.7. -10×P1. In the alloy material disclosed in this document, by setting P2, which is an index of Nb, V, and Ti, to 0.2 or more, precipitates are generated when used in a high-temperature environment and the creep strength is increased. There is.
　特許文献２に開示されているオーステナイト系ステンレス合金材は、質量％で、Ｃ：０．０３～０．１２％、Ｓｉ：０．２～２％、Ｍｎ：０．１～３％、Ｐ：０．０３％以下、Ｓ：０．０１％以下、Ｎｉ：１８％を超え２５％未満、Ｃｒ：２２％を超え３０％未満、Ｃｏ：０．０４～０．８％、Ｔｉ：０．００２％以上で０．０１％未満、Ｎｂ：０．１～１％、Ｖ：０．０１～１％、Ｂ：０．０００５％を超え０．２％以下、ｓｏｌ．Ａｌ：０．０００５％以上で０．０３％未満、Ｎ：０．１～０．３５％、Ｏ（酸素）：０．００１～０．００８％を含有し、残部はＦｅ及び不純物からなる。この文献に開示された合金材では、Ｔｉ、Ｎｂ、及び、Ｖを含有することにより、高温環境での使用時に析出物を生成して、クリープ強度を高めている。 The austenitic stainless steel alloy material disclosed in Patent Document 2 has, in mass%, C: 0.03 to 0.12%, Si: 0.2 to 2%, Mn: 0.1 to 3%, P: 0.03% or less, S: 0.01% or less, Ni: more than 18% and less than 25%, Cr: more than 22% and less than 30%, Co: 0.04 to 0.8%, Ti: 0.002 % or more and less than 0.01%, Nb: 0.1 to 1%, V: 0.01 to 1%, B: more than 0.0005% and less than 0.2%, sol. It contains Al: 0.0005% or more and less than 0.03%, N: 0.1 to 0.35%, O (oxygen): 0.001 to 0.008%, and the remainder consists of Fe and impurities. The alloy material disclosed in this document contains Ti, Nb, and V to generate precipitates when used in a high-temperature environment, thereby increasing creep strength.
国際公開第２００９／０４４７９６号International Publication No. 2009/044796 特開２００４－２５０７８３号公報Japanese Patent Application Publication No. 2004-250783
　ところで、ボイラ用途のオーステナイト系ステンレス合金材は、ボイラに適用される場合に溶接されたり、曲げ加工が施されたりする。ボイラに適用されたオーステナイト系ステンレス合金材は、５００～７５０℃の高温域で長時間使用される。その際、オーステナイト系ステンレス合金材の溶接部や、曲げ加工を受けた部分では、残留応力の緩和が生じる。残留応力の緩和により、結晶粒内に析出物が生成して粒内が硬化する。そのため、粒界にクリープ歪が蓄積して、粒界で割れが生じる場合がある。このような割れを応力緩和割れという。 By the way, austenitic stainless alloy materials for boiler use are welded or bent when used in boilers. Austenitic stainless steel alloy materials used in boilers are used for long periods of time in the high temperature range of 500 to 750°C. At this time, residual stress is relaxed in the welded parts of the austenitic stainless alloy material and in the parts that have undergone bending. Due to the relaxation of residual stress, precipitates are generated within the crystal grains and the insides of the grains are hardened. Therefore, creep strain may accumulate at the grain boundaries and cracks may occur at the grain boundaries. Such cracks are called stress relaxation cracks.
　ボイラ用途のオーステナイト系ステンレス合金材では、優れたクリープ強度だけでなく、優れた耐応力緩和割れ性も求められる。上述の特許文献では、クリープ強度に関する検討はされているものの、耐応力緩和割れ性に関する検討はされていない。 Austenitic stainless steel alloy materials for boiler applications require not only excellent creep strength but also excellent stress relaxation cracking resistance. In the above-mentioned patent documents, although creep strength has been studied, stress relaxation cracking resistance has not been studied.
　本開示の目的は、優れたクリープ強度及び優れた耐応力緩和割れ性を有するオーステナイト系ステンレス合金材を提供することである。 An object of the present disclosure is to provide an austenitic stainless steel alloy material having excellent creep strength and excellent stress relaxation cracking resistance.
　本開示によるオーステナイト系ステンレス合金材は、
　質量％で、
　Ｃ：０．０３～０．１２％、
　Ｓｉ：０．０５～２．００％、
　Ｍｎ：０．０５～３．００％、
　Ｐ：０．０３％以下、
　Ｓ：０．０１０％以下、
　Ｎｉ：１８．０～２５．０％未満、
　Ｃｒ：２２．０～３０．０％未満、
　Ｃｏ：０．０４～０．８０％、
　Ｔｉ：０．００２～０．０１０％、
　Ｎｂ：０．１～１．０％、
　Ｖ：０．０１～１．００％、
　Ａｌ：０．００１～０．０３０％未満、
　Ｎ：０．１０～０．３５％、
　Ｍｏ：０～１．００％、
　Ｗ：０～１．００％、
　Ｂ：０～０．０１０％、及び、
　Ｃａ：０～０．０１００％、を含有し、残部がＦｅ及び不純物からなり、
　円相当径が０．５～２．０μｍの析出物の個数密度が５０００個／ｍｍ２以上である。 The austenitic stainless steel alloy material according to the present disclosure is
In mass%,
C: 0.03-0.12%,
Si: 0.05-2.00%,
Mn: 0.05-3.00%,
P: 0.03% or less,
S: 0.010% or less,
Ni: 18.0 to less than 25.0%,
Cr: less than 22.0 to 30.0%,
Co: 0.04-0.80%,
Ti: 0.002 to 0.010%,
Nb: 0.1-1.0%,
V: 0.01-1.00%,
Al: 0.001 to less than 0.030%,
N: 0.10-0.35%,
Mo: 0-1.00%,
W: 0-1.00%,
B: 0 to 0.010%, and
Contains Ca: 0 to 0.0100%, the remainder consists of Fe and impurities,
The number density of precipitates with an equivalent circle diameter of 0.5 to 2.0 μm is 5000 pieces/mm 2 or more.
　本開示のオーステナイト系ステンレス合金材は、優れたクリープ強度及び優れた耐応力緩和割れ性を有する。 The austenitic stainless steel alloy material of the present disclosure has excellent creep strength and excellent stress relaxation cracking resistance.
図１は、耐応力緩和割れ性評価試験に用いる、Ｃリング型拘束溶接割れ試験片の斜視図である。FIG. 1 is a perspective view of a C-ring type restrained weld cracking test piece used in the stress relaxation cracking resistance evaluation test. 図２は、図１に示すＣリング型拘束溶接割れ試験片を用いた耐応力緩和割れ性評価試験の方法を説明するための模式図である。FIG. 2 is a schematic diagram for explaining the method of stress relaxation cracking resistance evaluation test using the C-ring type restrained weld cracking test piece shown in FIG. 図３は、実施例中の耐応力緩和割れ性評価試験において、Ｃリング型拘束溶接割れ試験片の管軸方向に垂直な断面でのノッチ底近傍部分の拡大図である。FIG. 3 is an enlarged view of a portion near the notch bottom in a cross section perpendicular to the tube axis direction of a C-ring type restrained weld cracking test piece in the stress relaxation cracking resistance evaluation test in Examples.
　本発明者らは、優れたクリープ強度及び優れた耐応力緩和割れ性を両立可能なオーステナイト系ステンレス合金材について検討を行った。初めに、本発明者らは、化学組成の観点から、優れたクリープ強度及び優れた耐応力緩和割れ性の両立を試みた。その結果、質量％で、Ｃ：０．０３～０．１２％、Ｓｉ：０．０５～２．００％、Ｍｎ：０．０５～３．００％、Ｐ：０．０３％以下、Ｓ：０．０１０％以下、Ｎｉ：１８．０～２５．０％未満、Ｃｒ：２２．０～３０．０％未満、Ｃｏ：０．０４～０．８０％、Ｔｉ：０．００２～０．０１０％、Ｎｂ：０．１～１．０％、Ｖ：０．０１～１．００％、Ａｌ：０．００１～０．０３０％未満、Ｎ：０．１０～０．３５％、Ｍｏ：０～１．００％、Ｗ：０～１．００％、Ｂ：０～０．０１０％、Ｃａ：０～０．０１００％を含有し、残部がＦｅ及び不純物からなる化学組成であれば、優れたクリープ強度及び優れた耐応力緩和割れ性を両立できる可能性があると考えた。 The present inventors investigated an austenitic stainless steel alloy material that can have both excellent creep strength and excellent stress relaxation cracking resistance. First, the present inventors attempted to achieve both excellent creep strength and excellent stress relaxation cracking resistance from the viewpoint of chemical composition. As a result, in mass%, C: 0.03 to 0.12%, Si: 0.05 to 2.00%, Mn: 0.05 to 3.00%, P: 0.03% or less, S: 0.010% or less, Ni: 18.0 to less than 25.0%, Cr: 22.0 to less than 30.0%, Co: 0.04 to 0.80%, Ti: 0.002 to 0.010 %, Nb: 0.1 to 1.0%, V: 0.01 to 1.00%, Al: 0.001 to less than 0.030%, N: 0.10 to 0.35%, Mo: 0 -1.00%, W: 0-1.00%, B: 0-0.010%, Ca: 0-0.0100%, and the balance is Fe and impurities. We believe that it is possible to achieve both high creep strength and excellent stress relaxation cracking resistance.
　そこで、本発明者らは、上述の化学組成を満たすオーステナイト系ステンレス合金材においてさらに、ミクロ組織の観点から、優れたクリープ強度及び優れた耐応力緩和割れ性の両立を検討した。 Therefore, the present inventors further investigated how to achieve both excellent creep strength and excellent stress relaxation cracking resistance from the viewpoint of the microstructure in an austenitic stainless steel alloy material that satisfies the above-mentioned chemical composition.
　通常、ボイラ用途のオーステナイト系ステンレス合金材では、高温環境での使用中に、Ｔｉ析出物、Ｎｂ析出物、及び、Ｖ析出物といった微細な析出物を生成し、これらの析出物の析出強化により、クリープ強度を高めている。そのため、特許文献１や特許文献２に開示されたオーステナイト系ステンレス合金材では、製造工程の最終段階で熱処理（溶体化処理）を実施する。これにより、オーステナイト系ステンレス合金材中の析出物をなるべく溶解して、Ｔｉ、Ｎｂ、Ｖを固溶状態としておく。オーステナイト系ステンレス合金材を高温環境で使用中に、これらの固溶元素で微細析出物を形成してクリープ強度を高めるためである。 Normally, in austenitic stainless steel alloy materials for boiler applications, fine precipitates such as Ti precipitates, Nb precipitates, and V precipitates are generated during use in high-temperature environments, and due to precipitation strengthening of these precipitates, , increasing creep strength. Therefore, in the austenitic stainless steel alloy materials disclosed in Patent Document 1 and Patent Document 2, heat treatment (solution treatment) is performed at the final stage of the manufacturing process. Thereby, the precipitates in the austenitic stainless alloy material are dissolved as much as possible, and Ti, Nb, and V are kept in a solid solution state. This is to increase creep strength by forming fine precipitates with these solid solution elements while the austenitic stainless alloy material is used in a high-temperature environment.
　しかしながら、本発明者らは、従前のようにオーステナイト系ステンレス合金材中の析出物をなるべく少なくして、Ｔｉ、Ｎｂ及びＶを固溶状態としておくのではなく、敢えて、微細な析出物をオーステナイト系ステンレス合金材中に予め存在させておくことで、クリープ強度だけでなく、耐応力緩和割れ性も高めることができるのではと考えた。 However, instead of reducing the precipitates in the austenitic stainless alloy material as much as possible and keeping Ti, Nb, and V in a solid solution state as in the past, the present inventors intentionally removed the fine precipitates from the austenitic stainless steel alloy material. We thought that by pre-existing it in stainless steel alloy materials, it would be possible to increase not only creep strength but also stress relaxation cracking resistance.
　オーステナイト系ステンレス合金材に予め存在する微細な析出物のピン止め効果により、オーステナイト系ステンレス合金材の結晶粒を微細に維持できる。この場合、合金材中の粒界面積は増大する。粒界面積の増大により、耐応力緩和割れ性を高めることができる。 The crystal grains of the austenitic stainless alloy material can be maintained fine due to the pinning effect of the fine precipitates that already exist in the austenitic stainless steel alloy material. In this case, the grain boundary area in the alloy material increases. By increasing the grain boundary area, stress relaxation cracking resistance can be improved.
　一方で、オーステナイト系ステンレス合金材に予め析出物が存在している場合、高温環境での使用中に新たな微細析出物が生成しにくい。さらに、高温環境中での使用中に、既存の析出物が粗大化することも考えられる。この場合、十分なクリープ強度が得られない可能性もあり得る。しかしながら、本発明者らの検討の結果、ボイラ用途に使用する前の上記化学組成を有するオーステナイト系ステンレス合金材において、円相当径が０．５～２．０μｍの析出物が５０００個／ｍｍ２以上存在していれば、高温環境での使用中においても、十分なクリープ強度が得られることが判明した。 On the other hand, if precipitates already exist in the austenitic stainless steel alloy material, new fine precipitates are less likely to be generated during use in a high-temperature environment. Furthermore, existing precipitates may become coarse during use in a high-temperature environment. In this case, there is a possibility that sufficient creep strength cannot be obtained. However, as a result of studies by the present inventors, in the austenitic stainless steel alloy material having the above chemical composition before use in boiler applications, the number of precipitates with an equivalent circle diameter of 0.5 to 2.0 μm is 5000/mm 2 It has been found that if the above is present, sufficient creep strength can be obtained even during use in a high temperature environment.
　以上の知見に基づいて、本発明者らは、特許文献１及び特許文献２のような従来のオーステナイト系ステンレス合金材のように、合金材中の析出物をなるべく少なくすることにより、高温環境でのクリープ強度を高めるのではなく、オーステナイト系ステンレス合金材中に敢えて微細な析出物を５０００個／ｍｍ２以上存在させることにより、優れたクリープ強度及び優れた耐応力緩和割れを両立できることを見出し、本実施形態のオーステナイト系ステンレス合金材を完成させた。 Based on the above findings, the present inventors have developed a method that can be used in high-temperature environments by reducing the amount of precipitates in the alloy material as much as possible, like the conventional austenitic stainless steel alloy materials such as Patent Document 1 and Patent Document 2. We have discovered that it is possible to achieve both excellent creep strength and excellent stress relaxation cracking resistance by deliberately allowing 5000 or more fine precipitates/ mm2 to exist in the austenitic stainless steel alloy material, rather than increasing the creep strength of the material. The austenitic stainless steel alloy material of this embodiment was completed.
　以上の技術思想に基づいて完成した本実施形態のオーステナイト系ステンレス合金材は、次の構成を有する。 The austenitic stainless steel alloy material of this embodiment, which was completed based on the above technical idea, has the following configuration.
　［１］
　質量％で、
　Ｃ：０．０３～０．１２％、
　Ｓｉ：０．０５～２．００％、
　Ｍｎ：０．０５～３．００％、
　Ｐ：０．０３％以下、
　Ｓ：０．０１０％以下、
　Ｎｉ：１８．０～２５．０％未満、
　Ｃｒ：２２．０～３０．０％未満、
　Ｃｏ：０．０４～０．８０％、
　Ｔｉ：０．００２～０．０１０％、
　Ｎｂ：０．１～１．０％、
　Ｖ：０．０１～１．００％、
　Ａｌ：０．００１～０．０３０％未満、
　Ｎ：０．１０～０．３５％、
　Ｍｏ：０～１．００％、
　Ｗ：０～１．００％、
　Ｂ：０～０．０１０％、及び、
　Ｃａ：０～０．０１００％、を含有し、残部がＦｅ及び不純物からなり、
　円相当径が０．５～２．０μｍの析出物の個数密度が５０００個／ｍｍ２以上である、
　オーステナイト系ステンレス合金材。 [1]
In mass%,
C: 0.03-0.12%,
Si: 0.05-2.00%,
Mn: 0.05-3.00%,
P: 0.03% or less,
S: 0.010% or less,
Ni: 18.0 to less than 25.0%,
Cr: less than 22.0 to 30.0%,
Co: 0.04-0.80%,
Ti: 0.002 to 0.010%,
Nb: 0.1-1.0%,
V: 0.01-1.00%,
Al: 0.001 to less than 0.030%,
N: 0.10-0.35%,
Mo: 0-1.00%,
W: 0-1.00%,
B: 0 to 0.010%, and
Contains Ca: 0 to 0.0100%, the remainder consists of Fe and impurities,
The number density of precipitates with a circular equivalent diameter of 0.5 to 2.0 μm is 5000 pieces/mm 2 or more,
Austenitic stainless steel alloy material.
　［２］
　［１］に記載のオーステナイト系ステンレス合金材であって、
　Ｍｏ：０．０１～１．００％、
　Ｗ：０．０１～１．００％、
　Ｂ：０．００１～０．０１０％、及び、
　Ｃａ：０．０００１～０．０１００％、からなる群から選択される１種以上を含有する、
　オーステナイト系ステンレス合金材。 [2]
The austenitic stainless steel alloy material according to [1],
Mo: 0.01-1.00%,
W: 0.01-1.00%,
B: 0.001 to 0.010%, and
Containing one or more selected from the group consisting of Ca: 0.0001 to 0.0100%,
Austenitic stainless steel alloy material.
　以下、本実施形態のオーステナイト系ステンレス合金材について詳述する。 Hereinafter, the austenitic stainless alloy material of this embodiment will be described in detail.
　［本実施形態の合金材の特徴］
　本実施形態のオーステナイト系ステンレス合金材は、次の特徴１及び特徴２を満たす。
　（特徴１）
　化学組成が、質量％で、Ｃ：０．０３～０．１２％、Ｓｉ：０．０５～２．００％、Ｍｎ：０．０５～３．００％、Ｐ：０．０３％以下、Ｓ：０．０１０％以下、Ｎｉ：１８．０～２５．０％未満、Ｃｒ：２２．０～３０．０％未満、Ｃｏ：０．０４～０．８０％、Ｔｉ：０．００２～０．０１０％、Ｎｂ：０．１～１．０％、Ｖ：０．０１～１．００％、Ａｌ：０．００１～０．０３０％未満、Ｎ：０．１０～０．３５％、Ｍｏ：０～１．００％、Ｗ：０～１．００％、Ｂ：０～０．０１０％、Ｃａ：０～０．０１００％を含有し、残部がＦｅ及び不純物からなる。
　（特徴２）
　円相当径が０．５～２．０μｍの析出物の個数密度が５０００個／ｍｍ２以上である。 [Characteristics of the alloy material of this embodiment]
The austenitic stainless steel alloy material of this embodiment satisfies the following characteristics 1 and 2.
(Feature 1)
The chemical composition is in mass%, C: 0.03 to 0.12%, Si: 0.05 to 2.00%, Mn: 0.05 to 3.00%, P: 0.03% or less, S : 0.010% or less, Ni: 18.0 to less than 25.0%, Cr: 22.0 to less than 30.0%, Co: 0.04 to 0.80%, Ti: 0.002 to 0.0%. 010%, Nb: 0.1 to 1.0%, V: 0.01 to 1.00%, Al: 0.001 to less than 0.030%, N: 0.10 to 0.35%, Mo: 0 to 1.00%, W: 0 to 1.00%, B: 0 to 0.010%, Ca: 0 to 0.0100%, and the remainder consists of Fe and impurities.
(Feature 2)
The number density of precipitates with an equivalent circle diameter of 0.5 to 2.0 μm is 5000 pieces/mm 2 or more.
　以下、特徴１及び特徴２について説明する。 Feature 1 and Feature 2 will be explained below.
　［（特徴１）化学組成について］
　［必須元素（Ｅｓｓｅｎｔｉａｌ　Ｅｌｅｍｅｎｔｓ）について］
　本実施形態のオーステナイト系ステンレス合金材の化学組成は、次の元素を含有する。 [(Feature 1) Regarding chemical composition]
[About Essential Elements]
The chemical composition of the austenitic stainless steel alloy material of this embodiment contains the following elements.
　Ｃ：０．０３～０．１２％
　炭素（Ｃ）は高温環境での合金材のクリープ強度を高める。Ｃ含有量が０．０３％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｃ含有量が０．１２％を超えれば、他の元素含有量が本実施形態の範囲内であっても、粒界にＭ２３Ｃ６型のＣｒ炭化物が生成する。この場合、粒界にＣｒ欠乏領域が生成する。そのため、合金材の耐応力緩和割れ性が低下する。
　したがって、Ｃ含有量は０．０３～０．１２％である。
　Ｃ含有量の好ましい下限は０．０３％超であり、さらに好ましくは０．０４％であり、さらに好ましくは０．０５％である。
　Ｃ含有量の好ましい上限は０．１１％であり、さらに好ましくは０．１０％であり、さらに好ましくは０．０９％である。 C: 0.03-0.12%
Carbon (C) increases the creep strength of alloy materials in high-temperature environments. If the C content is less than 0.03%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the C content exceeds 0.12%, M 23 C 6 type Cr carbides are generated at the grain boundaries even if the contents of other elements are within the range of this embodiment. In this case, Cr-deficient regions are generated at grain boundaries. Therefore, the stress relaxation cracking resistance of the alloy material decreases.
Therefore, the C content is 0.03-0.12%.
The preferable lower limit of the C content is more than 0.03%, more preferably 0.04%, and still more preferably 0.05%.
A preferable upper limit of the C content is 0.11%, more preferably 0.10%, and still more preferably 0.09%.
　Ｓｉ：０．０５～２．００％
　シリコン（Ｓｉ）は、製鋼工程において、合金を脱酸する。Ｓｉはさらに、高温環境で合金材の耐酸化性を高める。Ｓｉ含有量が０．０５％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｓｉ含有量が２．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、耐溶接高温割れ性が低下する。
　したがって、Ｓｉ含有量は０．０５～２．００％である。
　Ｓｉ含有量の好ましい下限は０．１０％であり、さらに好ましくは０．１５％であり、さらに好ましくは０．１８％であり、さらに好ましくは０．２０％である。
　Ｓｉ含有量の好ましい上限は１．８０％であり、さらに好ましくは１．６０％であり、さらに好ましくは１．４０％であり、さらに好ましくは１．３０％であり、さらに好ましくは１．２５％である。 Si: 0.05-2.00%
Silicon (Si) deoxidizes the alloy in the steel manufacturing process. Si further increases the oxidation resistance of the alloy material in high temperature environments. If the Si content is less than 0.05%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Si content exceeds 2.00%, the weld hot cracking resistance will decrease even if the contents of other elements are within the range of this embodiment.
Therefore, the Si content is 0.05 to 2.00%.
The preferable lower limit of the Si content is 0.10%, more preferably 0.15%, even more preferably 0.18%, and still more preferably 0.20%.
The preferable upper limit of the Si content is 1.80%, more preferably 1.60%, even more preferably 1.40%, still more preferably 1.30%, and still more preferably 1.25%. %.
　Ｍｎ：０．０５～３．００％
　マンガン（Ｍｎ）は、溶接施工時において合金材の溶接部を脱酸する。Ｍｎはさらに、オーステナイトを安定化する。Ｍｎが０．０５％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｍｎ含有量が３．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、高温環境での使用時において、シグマ相（σ相）が生成しやすくなる。σ相は、高温環境での合金材の靱性及びクリープ延性を低下する。
　したがって、Ｍｎ含有量は０．０５～３．００％である。
　Ｍｎ含有量の好ましい下限は０．１０％であり、さらに好ましくは０．１５％であり、さらに好ましくは０．２０％であり、さらに好ましくは０．３０％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．４５％である。
　Ｍｎ含有量の好ましい上限は３．００％未満であり、さらに好ましくは２．９９％であり、さらに好ましくは２．９５％であり、さらに好ましくは２．９０％であり、さらに好ましくは２．８０％であり、さらに好ましくは２．６０％であり、さらに好ましくは２．４０％であり、さらに好ましくは２．３５％であり、さらに好ましくは２．２０％であり、さらに好ましくは２．００％である。 Mn: 0.05-3.00%
Manganese (Mn) deoxidizes the welded part of the alloy material during welding work. Mn further stabilizes austenite. If Mn is less than 0.05%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Mn content exceeds 3.00%, even if the contents of other elements are within the range of this embodiment, sigma phase (σ phase) is likely to be generated when used in a high temperature environment. . The σ phase reduces the toughness and creep ductility of the alloy material in a high temperature environment.
Therefore, the Mn content is 0.05-3.00%.
The preferable lower limit of the Mn content is 0.10%, more preferably 0.15%, even more preferably 0.20%, still more preferably 0.30%, and even more preferably 0.40%. %, more preferably 0.45%.
A preferable upper limit of the Mn content is less than 3.00%, more preferably 2.99%, even more preferably 2.95%, still more preferably 2.90%, and still more preferably 2.99%. 80%, more preferably 2.60%, still more preferably 2.40%, still more preferably 2.35%, even more preferably 2.20%, even more preferably 2. It is 00%.
　Ｐ：０．０３％以下
　りん（Ｐ）は不可避に含有される。つまり、Ｐ含有量は０％超である。
　Ｐは、合金材の粒界に偏析する。Ｐ含有量が０．０３％を超えれば、他の元素含有量が本実施形態の範囲内であっても、上述の偏析が生じて、耐応力緩和割れ性が低下する。
　したがって、Ｐ含有量は０．０３％以下である。
　Ｐ含有量はなるべく低い方が好ましい。しかしながら、Ｐ含有量の過度の低減は、合金材の製造コストを引き上げる。したがって、通常の工業生産を考慮すれば、Ｐ含有量の好ましい下限は０．０１％である。
　Ｐ含有量の好ましい上限は０．０２％である。 P: 0.03% or less Phosphorus (P) is unavoidably contained. In other words, the P content is over 0%.
P segregates at the grain boundaries of the alloy material. If the P content exceeds 0.03%, even if the contents of other elements are within the ranges of this embodiment, the above-mentioned segregation occurs and stress relaxation cracking resistance decreases.
Therefore, the P content is 0.03% or less.
It is preferable that the P content is as low as possible. However, excessive reduction in P content increases the manufacturing cost of the alloy material. Therefore, in consideration of normal industrial production, the preferable lower limit of the P content is 0.01%.
A preferable upper limit of the P content is 0.02%.
　Ｓ：０．０１０％以下
　硫黄（Ｓ）は不可避に含有される。つまり、Ｓ含有量は０％超である。
　Ｓは、合金材の粒界に偏析する。Ｓ含有量が０．０１０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、上述の偏析が生じて、耐応力緩和割れ性が低下する。
　したがって、Ｓ含有量は０．０１０％以下である。
　Ｓ含有量はなるべく低い方が好ましい。しかしながら、Ｓ含有量の過度の低減は、合金材の製造コストを引き上げる。したがって、通常の工業生産を考慮すれば、Ｓ含有量の好ましい下限は０．００１％である。
　Ｓ含有量の好ましい上限は０．００８％であり、さらに好ましくは０．００６％であり、さらに好ましくは０．００４％であり、さらに好ましくは０．００３％である。 S: 0.010% or less Sulfur (S) is unavoidably contained. In other words, the S content is over 0%.
S segregates at the grain boundaries of the alloy material. If the S content exceeds 0.010%, even if the contents of other elements are within the ranges of this embodiment, the above-mentioned segregation occurs and stress relaxation cracking resistance decreases.
Therefore, the S content is 0.010% or less.
It is preferable that the S content is as low as possible. However, excessive reduction in S content increases the manufacturing cost of the alloy material. Therefore, considering normal industrial production, the preferable lower limit of the S content is 0.001%.
A preferable upper limit of the S content is 0.008%, more preferably 0.006%, still more preferably 0.004%, and still more preferably 0.003%.
　Ｎｉ：１８．０～２５．０％未満
　ニッケル（Ｎｉ）はオーステナイトを安定化して、高温環境での合金材のクリープ強度を高める。Ｎｉ含有量が１８．０％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｎｉ含有量が２５．０％以上であれば、上記効果が飽和する。さらに、製造コストが高くなる。
　したがって、Ｎｉ含有量は１８．０～２５．０％未満である。
　Ｎｉ含有量の好ましい下限は、１８．４％であり、さらに好ましくは１８．８％であり、さらに好ましくは１９．２％であり、さらに好ましくは１９．５％である。
　Ｎｉ含有量の好ましい上限は２４．９％であり、さらに好ましくは２４．８％であり、さらに好ましくは２４．４％であり、さらに好ましくは２４．０％であり、さらに好ましくは２３．６％である。 Ni: 18.0% to less than 25.0% Nickel (Ni) stabilizes austenite and increases the creep strength of the alloy material in a high temperature environment. If the Ni content is less than 18.0%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Ni content is 25.0% or more, the above effects are saturated. Furthermore, manufacturing costs are increased.
Therefore, the Ni content is less than 18.0-25.0%.
The preferable lower limit of the Ni content is 18.4%, more preferably 18.8%, even more preferably 19.2%, and still more preferably 19.5%.
A preferable upper limit of the Ni content is 24.9%, more preferably 24.8%, even more preferably 24.4%, still more preferably 24.0%, and even more preferably 23.6%. %.
　Ｃｒ：２２．０～３０．０％未満
　クロム（Ｃｒ）は、高温環境での合金材の耐食性を高める。Ｃｒ含有量が２２．０％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｃｒ含有量が３０．０％以上であれば、他の元素含有量が本実施形態の範囲内であっても、高温環境でオーステナイトの安定性が低下する。この場合、合金材のクリープ強度が低下する。
　したがって、Ｃｒ含有量は２２．０～３０．０％未満である。
　Ｃｒ含有量の好ましい下限は２２．５％であり、さらに好ましくは２３．０％であり、さらに好ましくは２３．５％である。
　Ｃｒ含有量の好ましい上限は２９．９％であり、さらに好ましくは２９．８％であり、さらに好ましくは２９．５％であり、さらに好ましくは２９．０％であり、さらに好ましくは２８．５％であり、さらに好ましくは２８．０％であり、さらに好ましくは２７．５％であり、さらに好ましくは２７．０％である。 Cr: 22.0% to less than 30.0% Chromium (Cr) increases the corrosion resistance of alloy materials in high-temperature environments. If the Cr content is less than 22.0%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Cr content is 30.0% or more, the stability of austenite decreases in a high-temperature environment even if the contents of other elements are within the ranges of this embodiment. In this case, the creep strength of the alloy material decreases.
Therefore, the Cr content is less than 22.0-30.0%.
The preferable lower limit of the Cr content is 22.5%, more preferably 23.0%, and still more preferably 23.5%.
A preferable upper limit of the Cr content is 29.9%, more preferably 29.8%, even more preferably 29.5%, still more preferably 29.0%, and even more preferably 28.5%. %, more preferably 28.0%, still more preferably 27.5%, even more preferably 27.0%.
　Ｃｏ：０．０４～０．８０％
　コバルト（Ｃｏ）はオーステナイトを安定化して、高温環境での合金材のクリープ強度を高める。Ｃｏ含有量が０．０４％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｃｏ含有量が０．８０％を超えれば、原料コストが高くなる。
　したがって、Ｃｏ含有量は０．０４～０．８０％である。
　Ｃｏ含有量の好ましい下限は０．０５％であり、さらに好ましくは０．０６％であり、さらに好ましくは０．０８％である。
　Ｃｏ含有量の好ましい上限は０．７０％であり、さらに好ましくは０．６０％であり、さらに好ましくは０．５５％であり、さらに好ましくは０．５０％である。 Co:0.04~0.80%
Cobalt (Co) stabilizes austenite and increases the creep strength of alloy materials in high-temperature environments. If the Co content is less than 0.04%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Co content exceeds 0.80%, the raw material cost will increase.
Therefore, the Co content is 0.04-0.80%.
The preferable lower limit of the Co content is 0.05%, more preferably 0.06%, and still more preferably 0.08%.
A preferable upper limit of the Co content is 0.70%, more preferably 0.60%, still more preferably 0.55%, and still more preferably 0.50%.
　Ｔｉ：０．００２～０．０１０％
　チタニウム（Ｔｉ）は、Ｔｉ析出物を形成して高温環境での合金材のクリープ強度を高める。Ｔｉはさらに、Ｔｉ析出物の形成により、合金材の耐応力緩和割れ性を高める。Ｔｉ含有量が０．００２％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｔｉ含有量が０．０１０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、粗大なＴｉ析出物が生成する。この場合、溶接施工時に、合金材に形成される溶接熱影響部の耐溶接高温割れ性が低下する。
　したがって、Ｔｉ含有量は０．００２～０．０１０％である。
　Ｔｉ含有量の好ましい下限は０．００３％であり、さらに好ましくは０．００４％である。
　Ｔｉ含有量の好ましい上限は０．００９％であり、さらに好ましくは０．００８％である。 Ti: 0.002-0.010%
Titanium (Ti) forms Ti precipitates to increase the creep strength of the alloy material in a high temperature environment. Ti further increases the stress relaxation cracking resistance of the alloy material through the formation of Ti precipitates. If the Ti content is less than 0.002%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Ti content exceeds 0.010%, coarse Ti precipitates will be formed even if the contents of other elements are within the range of this embodiment. In this case, the weld hot cracking resistance of the weld heat affected zone formed in the alloy material during welding is reduced.
Therefore, the Ti content is 0.002 to 0.010%.
The lower limit of the Ti content is preferably 0.003%, more preferably 0.004%.
A preferable upper limit of the Ti content is 0.009%, more preferably 0.008%.
　Ｎｂ：０．１～１．０％
　ニオブ（Ｎｂ）は、Ｎｂ析出物を形成して高温環境での合金材のクリープ強度を高める。Ｎｂはさらに、Ｎｂ析出物の形成により、合金材の耐応力緩和割れ性を高める。Ｎｂ含有量が０．１％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｎｂ含有量が１．０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の溶接施工時に、合金材の溶接熱影響部において耐溶接高温割れ性が低下する。
　したがって、Ｎｂ含有量は０．１～１．０％である。
　Ｎｂ含有量の好ましい下限は０．２％であり、さらに好ましくは０．３％であり、さらに好ましくは０．４％である。
　Ｎｂ含有量の好ましい上限は０．９％であり、さらに好ましくは０．８％であり、さらに好ましくは０．７％である。 Nb: 0.1-1.0%
Niobium (Nb) forms Nb precipitates to increase the creep strength of alloy materials in high temperature environments. Nb further improves the stress relaxation cracking resistance of the alloy material through the formation of Nb precipitates. If the Nb content is less than 0.1%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Nb content exceeds 1.0%, even if the content of other elements is within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding of the alloy material. Sexuality decreases.
Therefore, the Nb content is 0.1-1.0%.
The lower limit of the Nb content is preferably 0.2%, more preferably 0.3%, and still more preferably 0.4%.
A preferable upper limit of the Nb content is 0.9%, more preferably 0.8%, and still more preferably 0.7%.
　Ｖ：０．０１～１．００％
　バナジウム（Ｖ）は、Ｖ析出物を形成して高温環境での合金材のクリープ強度を高める。Ｖはさらに、Ｖ析出物の形成により、合金材の耐応力緩和割れ性を高める。Ｖ含有量が０．０１％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｖ含有量が１．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の溶接施工時に、合金材の溶接熱影響部において耐溶接高温割れ性が低下する。
　したがって、Ｖ含有量は０．０１～１．００％である。
　Ｖ含有量の好ましい下限は０．０２％であり、さらに好ましくは０．０３％であり、さらに好ましくは、０．０４％である。
　Ｖ含有量の好ましい上限は０．８０％であり、さらに好ましくは０．７５％であり、さらに好ましくは０．７０％であり、さらに好ましくは０．６５％であり、さらに好ましくは０．６０％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．３５％であり、さらに好ましくは０．２５％である。 V:0.01~1.00%
Vanadium (V) forms V precipitates to increase the creep strength of alloy materials in high temperature environments. V further increases stress relaxation cracking resistance of the alloy material through the formation of V precipitates. If the V content is less than 0.01%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the V content exceeds 1.00%, even if the contents of other elements are within the range of this embodiment, the welding heat-affected zone of the alloy material will be resistant to welding hot cracking during welding of the alloy material. Sexuality decreases.
Therefore, the V content is 0.01-1.00%.
The lower limit of the V content is preferably 0.02%, more preferably 0.03%, and still more preferably 0.04%.
A preferable upper limit of the V content is 0.80%, more preferably 0.75%, even more preferably 0.70%, still more preferably 0.65%, and even more preferably 0.60%. %, more preferably 0.40%, still more preferably 0.35%, even more preferably 0.25%.
　Ａｌ：０．００１～０．０３０％未満
　アルミニウム（Ａｌ）は、製鋼工程において、合金を脱酸する。Ａｌはさらに、高温環境での合金材の耐酸化性を高める。Ａｌ含有量が０．００１％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ａｌ含有量が０．０３０％以上であれば、他の元素含有量が本実施形態の範囲内であっても、合金材の熱間加工性が低下する。
　したがって、Ａｌ含有量は０．００１～０．０３０％未満である。
　Ａｌ含有量の好ましい下限は０．００２％であり、さらに好ましくは０．００３％であり、さらに好ましくは０．００５％である。
　Ａｌ含有量の好ましい上限は０．０２９％であり、さらに好ましくは０．０２８％であり、さらに好ましくは０．０２７％であり、さらに好ましくは０．０２６％であり、さらに好ましくは０．０２５％である。
　なお、Ａｌ含有量は、酸可溶Ａｌ（ｓｏｌ．Ａｌ）の含有量（質量％）である。 Al: 0.001% to less than 0.030% Aluminum (Al) deoxidizes the alloy in the steelmaking process. Al further increases the oxidation resistance of the alloy material in high temperature environments. If the Al content is less than 0.001%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the Al content is 0.030% or more, the hot workability of the alloy material will decrease even if the contents of other elements are within the range of this embodiment.
Therefore, the Al content is less than 0.001% to 0.030%.
The preferable lower limit of the Al content is 0.002%, more preferably 0.003%, and still more preferably 0.005%.
A preferable upper limit of the Al content is 0.029%, more preferably 0.028%, even more preferably 0.027%, still more preferably 0.026%, and even more preferably 0.025%. %.
Note that the Al content is the content (% by mass) of acid-soluble Al (sol.Al).
　Ｎ：０．１０～０．３５％
　窒素（Ｎ）は、マトリクス（母相）に固溶してオーステナイトを安定化する。固溶Ｎはさらに、高温環境での使用中において、合金材中に微細な窒化物を形成する。微細な窒化物はＣｒ欠乏領域を強化する。そのため、合金材の耐応力緩和割れ性が高まる。高温環境での使用中に生成した微細な窒化物はさらに、析出強化により合金材のクリープ強度を高める。Ｎ含有量が０．１０％未満であれば、他の元素含有量が本実施形態の範囲内であっても、上記効果が十分に得られない。
　一方、Ｎ含有量が０．３５％を超えれば、他の元素含有量が本実施形態の範囲内であっても、粗大な窒化物が生成する。粗大な窒化物は合金材の靱性を低下する。
　したがって、Ｎ含有量は０．１０～０．３５％である。
　Ｎ含有量の好ましい下限は０．１１％であり、さらに好ましくは０．１２％であり、さらに好ましくは０．１４％であり、さらに好ましくは０．１６％である。
　Ｎ含有量の好ましい上限は０．３３％であり、さらに好ましくは０．３１％であり、さらに好ましくは０．２９％である。 N: 0.10-0.35%
Nitrogen (N) stabilizes austenite by forming a solid solution in the matrix (mother phase). Solid solution N further forms fine nitrides in the alloy material during use in a high temperature environment. The fine nitride strengthens the Cr-depleted region. Therefore, the stress relaxation cracking resistance of the alloy material increases. The fine nitrides generated during use in high-temperature environments further increase the creep strength of the alloy material through precipitation strengthening. If the N content is less than 0.10%, the above effects cannot be sufficiently obtained even if the contents of other elements are within the range of this embodiment.
On the other hand, if the N content exceeds 0.35%, coarse nitrides will be produced even if the contents of other elements are within the range of this embodiment. Coarse nitrides reduce the toughness of the alloy material.
Therefore, the N content is between 0.10 and 0.35%.
The preferable lower limit of the N content is 0.11%, more preferably 0.12%, still more preferably 0.14%, and still more preferably 0.16%.
A preferable upper limit of the N content is 0.33%, more preferably 0.31%, and still more preferably 0.29%.
　本実施形態によるオーステナイト系ステンレス合金材の化学組成の残部は、Ｆｅ及び不純物からなる。ここで、不純物とは、オーステナイト系ステンレス合金材を工業的に製造する際に、原料としての鉱石、スクラップ、又は製造環境などから混入されるものであって、意図的に含有されるものではなく、本実施形態のオーステナイト系ステンレス合金材に悪影響を与えない範囲で許容されるものを意味する。 The remainder of the chemical composition of the austenitic stainless steel alloy material according to this embodiment consists of Fe and impurities. Here, impurities are those that are mixed in from ores used as raw materials, scraps, or the manufacturing environment when industrially manufacturing austenitic stainless steel alloy materials, and are not intentionally contained. , means an acceptable value within a range that does not adversely affect the austenitic stainless alloy material of this embodiment.
　［任意元素（Ｏｐｔｉｏｎａｌ　Ｅｌｅｍｅｎｔｓ）について］
　本実施形態のオーステナイト系ステンレス合金材の化学組成はさらに、Ｆｅの一部に代えて、
　Ｍｏ：０～１．００％、
　Ｗ：０～１．００％、
　Ｂ：０～０．０１０％、及び、
　Ｃａ：０～０．０１００％、からなる群から選択される１種以上を含有してもよい。
　これらの元素はいずれも任意元素であり、含有されなくてもよい。以下、これらの任意元素について説明する。 [About Optional Elements]
The chemical composition of the austenitic stainless steel alloy material of this embodiment further includes, in place of a part of Fe,
Mo: 0-1.00%,
W: 0-1.00%,
B: 0 to 0.010%, and
It may contain one or more selected from the group consisting of Ca: 0 to 0.0100%.
All of these elements are optional elements and may not be included. These arbitrary elements will be explained below.
　［（第１群）Ｍｏ及びＷについて］
　本実施形態のオーステナイト系ステンレス合金材の化学組成はさらに、Ｆｅの一部に代えて、Ｍｏ及びＷからなる群から選択される１種以上を含有してもよい。これらの元素は任意元素であり、いずれも、オーステナイト系ステンレス合金材のクリープ強度を高める。 [(First group) Regarding Mo and W]
The chemical composition of the austenitic stainless steel alloy material of this embodiment may further contain one or more selected from the group consisting of Mo and W in place of a part of Fe. These elements are optional elements, and all of them increase the creep strength of the austenitic stainless alloy material.
　Ｍｏ：０～１．００％
　モリブデン（Ｍｏ）は任意元素であり、含有されなくてもよい。つまりＭｏ含有量は０％であってもよい。
　Ｍｏが含有される場合、つまり、Ｍｏ含有量が０％超である場合、Ｍｏは高温環境での使用中において、固溶強化により、合金材のクリープ強度を高める。Ｍｏが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｍｏ含有量が１．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、結晶粒内において、ＬＡＶＥＳ相等の金属間化合物が生成する。この場合、二次誘起析出硬化が増加して、結晶粒内と結晶粒界との強度差が大きくなる。そのため、耐応力緩和割れ性が低下する。
　したがって、Ｍｏ含有量は０～１．００％であり、含有される場合、Ｍｏ含有量は１．００％以下である。
　Ｍｏ含有量の好ましい下限は０％超であり、さらに好ましくは０．０１％であり、さらに好ましくは０．０３％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．０８％である。
　Ｍｏ含有量の好ましい上限は０．９０％であり、さらに好ましくは０．８５％であり、さらに好ましくは０．８０％であり、さらに好ましくは０．７０％であり、さらに好ましくは０．６０％であり、さらに好ましくは０．５０％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．３０％である。 Mo: 0-1.00%
Molybdenum (Mo) is an optional element and may not be included. That is, the Mo content may be 0%.
When Mo is contained, that is, when the Mo content is more than 0%, Mo increases the creep strength of the alloy material through solid solution strengthening during use in a high-temperature environment. If even a small amount of Mo is contained, the above effects can be obtained to some extent.
However, if the Mo content exceeds 1.00%, intermetallic compounds such as the LAVES phase are generated within the crystal grains even if the contents of other elements are within the ranges of this embodiment. In this case, secondary induced precipitation hardening increases and the difference in strength between the inside of the grain and the grain boundary increases. Therefore, stress relaxation cracking resistance decreases.
Therefore, the Mo content is 0 to 1.00%, and if contained, the Mo content is 1.00% or less.
The lower limit of the Mo content is preferably more than 0%, more preferably 0.01%, even more preferably 0.03%, even more preferably 0.05%, and even more preferably 0.08%. It is.
The preferable upper limit of the Mo content is 0.90%, more preferably 0.85%, even more preferably 0.80%, still more preferably 0.70%, and still more preferably 0.60%. %, more preferably 0.50%, still more preferably 0.40%, still more preferably 0.30%.
　Ｗ：０～１．００％
　タングステン（Ｗ）は任意元素であり、含有されなくてもよい。つまりＷ含有量は０％であってもよい。
　Ｗが含有される場合、つまり、Ｗ含有量が０％超である場合、Ｗは高温環境での合金材の使用中において、固溶強化により、合金材のクリープ強度を高める。Ｗが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｗ含有量が１．００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、結晶粒内において、ＬＡＶＥＳ相等の金属間化合物が生成する。この場合、二次誘起析出硬化が増加して、結晶粒内と結晶粒界との強度差が大きくなる。そのため、耐応力緩和割れ性が低下する。
　したがって、Ｗ含有量は０～１．００％であり、含有される場合、Ｗ含有量は１．００％以下である。
　Ｗ含有量の好ましい下限は０％超であり、さらに好ましくは０．０１％であり、さらに好ましくは０．０３％であり、さらに好ましくは０．０５％であり、さらに好ましくは０．１０％である。
　Ｗ含有量の好ましい上限は０．９０％であり、さらに好ましくは０．８０％であり、さらに好ましくは０．７０％であり、さらに好ましくは０．６０％であり、さらに好ましくは０．５０％であり、さらに好ましくは０．４０％であり、さらに好ましくは０．３５％であり、さらに好ましくは０．３０％である。 W: 0-1.00%
Tungsten (W) is an optional element and may not be included. That is, the W content may be 0%.
When W is contained, that is, when the W content is more than 0%, W increases the creep strength of the alloy material through solid solution strengthening during use of the alloy material in a high-temperature environment. If even a small amount of W is contained, the above effects can be obtained to some extent.
However, if the W content exceeds 1.00%, intermetallic compounds such as the LAVES phase are generated within the crystal grains even if the contents of other elements are within the ranges of this embodiment. In this case, secondary induced precipitation hardening increases and the difference in strength between the inside of the grain and the grain boundary increases. Therefore, stress relaxation cracking resistance decreases.
Therefore, the W content is 0 to 1.00%, and when included, the W content is 1.00% or less.
The lower limit of the W content is preferably more than 0%, more preferably 0.01%, even more preferably 0.03%, even more preferably 0.05%, and even more preferably 0.10%. It is.
The upper limit of the W content is preferably 0.90%, more preferably 0.80%, even more preferably 0.70%, even more preferably 0.60%, and still more preferably 0.50%. %, more preferably 0.40%, still more preferably 0.35%, even more preferably 0.30%.
　［（第２群）Ｂについて］
　本実施形態のオーステナイト系ステンレス合金材はさらに、Ｂを含有してもよい。 [(2nd group) Regarding B]
The austenitic stainless steel alloy material of this embodiment may further contain B.
　Ｂ：０～０．０１０％
　ボロン（Ｂ）は任意元素であり、含有されなくてもよい。つまり、Ｂ含有量は０％であってもよい。
　Ｂが含有される場合、つまり、Ｂ含有量が０％超である場合、Ｂは高温環境で粒界に偏析し、粒界強度を高める。そのため、合金材の耐応力緩和割れ性が高まる。Ｂが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｂ含有量が０．０１０％を超えれば、他の元素含有量が本実施形態の範囲内であっても、Ｂが粒界でのＣｒ炭化物の生成を促進する。この場合、合金材の耐応力緩和割れ性が低下する。
　したがって、Ｂ含有量は０～０．０１０％であり、含有される場合、Ｂ含有量は０．０１０％以下である。
　Ｂ含有量の好ましい下限は０％超であり、さらに好ましくは０．００１％であり、さらに好ましくは０．００２％である。
　Ｂ含有量の好ましい上限は０．００９％であり、さらに好ましくは０．００８％であり、さらに好ましくは０．００７％であり、さらに好ましくは０．００６％である。 B: 0-0.010%
Boron (B) is an optional element and may not be included. That is, the B content may be 0%.
When B is contained, that is, when the B content is more than 0%, B segregates at grain boundaries in a high-temperature environment and increases grain boundary strength. Therefore, the stress relaxation cracking resistance of the alloy material increases. If even a small amount of B is contained, the above effects can be obtained to some extent.
However, if the B content exceeds 0.010%, B promotes the formation of Cr carbides at grain boundaries even if the contents of other elements are within the range of this embodiment. In this case, the stress relaxation cracking resistance of the alloy material decreases.
Therefore, the B content is 0 to 0.010%, and when contained, the B content is 0.010% or less.
The preferable lower limit of the B content is more than 0%, more preferably 0.001%, and still more preferably 0.002%.
A preferable upper limit of the B content is 0.009%, more preferably 0.008%, still more preferably 0.007%, and still more preferably 0.006%.
　［（第３群）Ｃａについて］
　本実施形態のオーステナイト系ステンレス合金材はさらに、Ｃａを含有してもよい。 [(Group 3) About Ca]
The austenitic stainless steel alloy material of this embodiment may further contain Ca.
　Ｃａ：０～０．０１００％
　カルシウム（Ｃａ）は任意元素であり、含有されなくてもよい。つまり、Ｃａ含有量は０％であってもよい。
　Ｃａが含有される場合、つまり、Ｃａ含有量が０％超である場合、Ｃａは、Ｏ（酸素）及びＳ（硫黄）を介在物として固定し、合金材の熱間加工性を高める。Ｃａが少しでも含有されれば、上記効果がある程度得られる。
　しかしながら、Ｃａ含有量が０．０１００％を超えれば、他の元素含有量が本実施形態の範囲内であっても、合金材の清浄性が低下し、合金材の熱間加工性が低下する。
　したがって、Ｃａ含有量は０～０．０１００％であり、含有される場合、Ｃａ含有量は０．０１００％以下である。
　Ｃａ含有量の好ましい下限は０％超であり、さらに好ましくは０．０００１％であり、さらに好ましくは０．０００３％であり、さらに好ましくは０．０００５％であり、さらに好ましくは０．０００８％であり、さらに好ましくは０．００１０％である。
　Ｃａ含有量の好ましい上限は０．００９０％であり、さらに好ましくは０．００８０％であり、さらに好ましくは０．００７０％であり、さらに好ましくは０．００６０％であり、さらに好ましくは０．００５０％であり、さらに好ましくは０．００４５％である。 Ca: 0~0.0100%
Calcium (Ca) is an optional element and may not be included. That is, the Ca content may be 0%.
When Ca is contained, that is, when the Ca content is more than 0%, Ca fixes O (oxygen) and S (sulfur) as inclusions and improves the hot workability of the alloy material. If even a small amount of Ca is contained, the above effects can be obtained to some extent.
However, if the Ca content exceeds 0.0100%, even if the contents of other elements are within the range of this embodiment, the cleanliness of the alloy material will decrease and the hot workability of the alloy material will decrease. .
Therefore, the Ca content is 0 to 0.0100%, and if contained, the Ca content is 0.0100% or less.
The lower limit of the Ca content is preferably more than 0%, more preferably 0.0001%, even more preferably 0.0003%, even more preferably 0.0005%, and even more preferably 0.0008%. and more preferably 0.0010%.
The preferable upper limit of the Ca content is 0.0090%, more preferably 0.0080%, even more preferably 0.0070%, still more preferably 0.0060%, and even more preferably 0.0050%. %, more preferably 0.0045%.
　［（特徴２）微細析出物の個数密度ＮＤ（Ｎｕｍｂｅｒ　Ｄｅｎｓｉｔｙ）について］
　本実施形態のオーステナイト系ステンレス合金材ではさらに、円相当径が０．５～２．０μｍの析出物の個数密度ＮＤが５０００個／ｍｍ２以上である。 [(Feature 2) About the number density ND (Number Density) of fine precipitates]
Further, in the austenitic stainless steel alloy material of the present embodiment, the number density ND of precipitates having an equivalent circle diameter of 0.5 to 2.0 μm is 5000 pieces/mm 2 or more.
　上述のとおり、従来のオーステナイト系ステンレス合金材では、溶体化処理を実施することにより、合金材中の析出物をなるべく低減する。しかしながら、本実施形態のオーステナイト系ステンレス合金材では、特定のサイズの析出物を合金材中に積極的に存在させることにより、優れたクリープ強度と優れた耐応力緩和割れ性とを両立させる。 As mentioned above, conventional austenitic stainless steel alloy materials are subjected to solution treatment to reduce the amount of precipitates in the alloy material as much as possible. However, in the austenitic stainless steel alloy material of the present embodiment, by proactively allowing precipitates of a specific size to exist in the alloy material, excellent creep strength and excellent stress relaxation cracking resistance are both achieved.
　ここで、円相当径が０．５～２．０μｍの析出物を、「微細析出物」と定義する。微細析出物は、ピン止め効果により、オーステナイト系ステンレス合金材の結晶粒を微細に維持する。これにより、オーステナイト系ステンレス合金材の粒界面積が増加し、耐応力緩和割れ性が高まる。さらに、円相当径が０．５～２．０μｍの微細析出物は、高温環境下での使用中において析出強化機能を発現し、オーステナイト系ステンレス合金材のクリープ強度を高める。 Here, precipitates with an equivalent circle diameter of 0.5 to 2.0 μm are defined as "fine precipitates". The fine precipitates keep the crystal grains of the austenitic stainless alloy material fine due to the pinning effect. As a result, the grain boundary area of the austenitic stainless steel alloy material increases, and stress relaxation cracking resistance increases. Furthermore, fine precipitates with an equivalent circle diameter of 0.5 to 2.0 μm exhibit a precipitation-strengthening function during use in a high-temperature environment, increasing the creep strength of the austenitic stainless alloy material.
　特徴１を満たすオーステナイト系ステンレス合金材において、微細析出物の個数密度ＮＤが５０００個／ｍｍ２以上であれば、優れたクリープ強度と優れた耐応力緩和割れ性とを両立させることができる。 In the austenitic stainless steel alloy material that satisfies Feature 1, if the number density ND of fine precipitates is 5000 pieces/mm 2 or more, it is possible to achieve both excellent creep strength and excellent stress relaxation cracking resistance.
　微細析出物の個数密度ＮＤの好ましい下限は５２００個／ｍｍ２であり、さらに好ましくは５５００個／ｍｍ２であり、さらに好ましくは６０００個／ｍｍ２であり、さらに好ましくは６２００個／ｍｍ２である。 The preferable lower limit of the number density ND of fine precipitates is 5200 pieces/mm 2 , more preferably 5500 pieces/mm 2 , even more preferably 6000 pieces/mm 2 , and still more preferably 6200 pieces/mm 2 be.
　微細析出物の個数密度ＮＤの上限は特に限定されない。オーステナイト系ステンレス合金材が特徴１を満たす場合、微細析出物の個数密度ＮＤの上限は例えば、２００００個／ｍｍ２であり、例えば、１８０００個／ｍｍ２であり、例えば、１５０００個／ｍｍ２である。 The upper limit of the number density ND of fine precipitates is not particularly limited. When the austenitic stainless alloy material satisfies characteristic 1, the upper limit of the number density ND of fine precipitates is, for example, 20,000 pieces/ mm2 , for example, 18,000 pieces/ mm2 , and, for example, 15,000 pieces/ mm2 . be.
　［微細析出物の個数密度ＮＤの測定方法］
　微細析出物の個数密度ＮＤは、次の方法で求めることができる。 [Method for measuring number density ND of fine precipitates]
The number density ND of fine precipitates can be determined by the following method.
　初めに、オーステナイト系ステンレス合金材から試験片を採取する。オーステナイト系ステンレス合金材が合金管である場合、肉厚中央部を含む試験片を採取する。試験片の表面のうち、合金管の管軸方向に垂直な断面であって、かつ、肉厚中央部を含む表面を観察面とし、肉厚中央部を観察視野とする。 First, a test piece is taken from an austenitic stainless steel alloy material. If the austenitic stainless steel alloy material is an alloy tube, collect a test piece including the thick center part. Among the surfaces of the test pieces, the surface that is a cross section perpendicular to the tube axis direction of the alloy tube and that includes the central part of the wall thickness is used as the observation surface, and the central part of the wall thickness is used as the observation field of view.
　オーステナイト系ステンレス合金材が合金板である場合、板厚中央部を含む試験片を採取する。試験片の表面のうち、合金板の圧延方向に垂直な断面であって、板厚中央部を含む表面を観察面とし、板厚中央部を観察視野とする。 If the austenitic stainless steel alloy material is an alloy plate, collect a test piece including the central part of the plate thickness. Among the surfaces of the test pieces, the surface that is a cross section perpendicular to the rolling direction of the alloy plate and includes the central part of the plate thickness is used as the observation surface, and the central part of the plate thickness is used as the observation field of view.
　オーステナイト系ステンレス合金材が棒材である場合、Ｒ／２部を含む試験片を採取する。ここで、Ｒとは、棒材の軸方向に垂直な断面の半径を意味する。Ｒ／２部とは、上述の断面における半径の中央部を意味する。試験片の表面のうち、棒材の長手方向に垂直な断面であって、Ｒ／２部を含む表面を観察面とし、Ｒ／２部を観察視野とする。 If the austenitic stainless steel alloy material is a bar, a test piece containing part R/2 is taken. Here, R means the radius of the cross section perpendicular to the axial direction of the bar. The R/2 portion means the center portion of the radius in the above-mentioned cross section. Among the surfaces of the test pieces, the surface that is a cross section perpendicular to the longitudinal direction of the bar and that includes the R/2 part is the observation surface, and the R/2 part is the observation field.
　観察面を鏡面研磨した後、光学顕微鏡を用いて、５００倍の倍率で鏡面研磨後の観察面中の観察視野のミクロ組織写真を得る。観察視野の面積は１４０μｍ×１６０μｍとする。 After mirror-polishing the observation surface, use an optical microscope to obtain a microstructure photograph of the observation field in the mirror-polished observation surface at a magnification of 500 times. The area of the observation field is 140 μm×160 μm.
　光学顕微鏡観察により得られたミクロ組織写真を用いて、観察視野中の粒子の円相当径を求める。ここで、円相当径とは、粒子の面積と同じ面積の円の直径を意味する。円相当径は周知の画像処理により求めることができる。視野観察中の粒子は、コントラストにより容易に特定できる。円相当径が０．５～２．０μｍの粒子を、析出物（微細析出物）と認定する。観察視野中の全ての微細析出物の個数と、観察視野の面積とに基づいて、微細析出物の個数密度（個／ｍｍ２）を求める。なお、微細析出物は例えば、Ｔｉを含有するＴｉ析出物、Ｎｂを含有するＮｂ析出物、及び、Ｖを含有するＶ析出物のいずれか１種以上である。 Using a microstructure photograph obtained by optical microscopic observation, the equivalent circle diameter of the particles in the observation field is determined. Here, the equivalent circle diameter means the diameter of a circle having the same area as the particle area. The equivalent circle diameter can be determined by well-known image processing. Particles during visual field observation can be easily identified by contrast. Particles with an equivalent circle diameter of 0.5 to 2.0 μm are recognized as precipitates (fine precipitates). The number density (number/mm 2 ) of fine precipitates is determined based on the number of all fine precipitates in the observation field and the area of the observation field. Note that the fine precipitates are, for example, one or more of Ti precipitates containing Ti, Nb precipitates containing Nb, and V precipitates containing V.
　［オーステナイト系ステンレス合金材の効果］
　本実施形態のオーステナイト系ステンレス合金材は、特徴１及び特徴２を満たす。その結果、本実施形態のオーステナイト系ステンレス合金材は、優れたクリープ強度と優れた耐応力緩和割れ性とを両立できる。 [Effects of austenitic stainless steel alloy materials]
The austenitic stainless steel alloy material of this embodiment satisfies Feature 1 and Feature 2. As a result, the austenitic stainless alloy material of this embodiment can have both excellent creep strength and excellent stress relaxation cracking resistance.
　［オーステナイト系ステンレス合金材のミクロ組織］
　本実施形態の合金材のミクロ組織は、オーステナイトからなる。 [Microstructure of austenitic stainless steel alloy material]
The microstructure of the alloy material of this embodiment consists of austenite.
　［オーステナイト系ステンレス合金材の形状］
　本実施形態のオーステナイト系ステンレス合金材の形状は特に限定されない。オーステナイト系ステンレス合金材は合金管であってもよいし、合金板であってもよい。オーステナイト系ステンレス合金材は棒材であってもよい。好ましくは、本実施形態のオーステナイト系ステンレス合金材は、合金管である。 [Shape of austenitic stainless alloy material]
The shape of the austenitic stainless alloy material of this embodiment is not particularly limited. The austenitic stainless steel alloy material may be an alloy tube or an alloy plate. The austenitic stainless steel alloy material may be a bar material. Preferably, the austenitic stainless alloy material of this embodiment is an alloy tube.
　［オーステナイト系ステンレス合金材の製造方法］
　本実施形態のオーステナイト系ステンレス合金材の製造方法を説明する。
　以降に説明する製造方法は、本実施形態のオーステナイト系ステンレス合金材の製造方法の一例である。したがって、本実施形態のオーステナイト系ステンレス合金材は、以降に説明する製造方法以外の他の製造方法により製造されてもよい。しかしながら、以降に説明する製造方法は、本実施形態のオーステナイト系ステンレス合金材の製造方法の好ましい一例である。 [Production method of austenitic stainless steel alloy material]
A method for manufacturing the austenitic stainless alloy material of this embodiment will be described.
The manufacturing method described below is an example of the manufacturing method of the austenitic stainless alloy material of this embodiment. Therefore, the austenitic stainless steel alloy material of this embodiment may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferable example of the manufacturing method of the austenitic stainless alloy material of this embodiment.
　本実施形態の合金材の製造方法は、次の工程を含む。
　（工程１）準備工程
　（工程２）熱間加工工程
　（工程３）高温保持工程
　（工程４）冷間加工工程
　（工程５）析出熱処理工程 The method for manufacturing an alloy material of this embodiment includes the following steps.
(Step 1) Preparation step (Step 2) Hot working step (Step 3) High temperature holding step (Step 4) Cold working step (Step 5) Precipitation heat treatment step
　上記製造工程において、高温保持工程での保持温度をＴ１（℃）と定義し、保持温度Ｔ１での保持時間をｔ１（分）と定義し、析出熱処理工程での熱処理温度をＴ２（℃）と定義し、熱処理温度Ｔ２での保持時間をｔ２（分）と定義したとき、次の式（Ａ）～式（Ｃ）を満たす。
　（１／２０）×｛（Ｔ１－７００）２＋ｔ１｝／（５Ｎｂ＋３０Ｔｉ＋５Ｖ）≧４１００　（Ａ）
　Ｔ１≧Ｔ２　（Ｂ）
　（Ｔ２＋ｔ２）×（Ｎｂ＋５０Ｔｉ＋２０Ｖ）≧１０００　（Ｃ）
　ここで、式（Ａ）及び式（Ｃ）中の元素記号には、対応する元素の質量％での含有量が代入される。
　以下、各工程について説明する。 In the above manufacturing process, the holding temperature in the high temperature holding step is defined as T1 (℃), the holding time at the holding temperature T1 is defined as t1 (minutes), and the heat treatment temperature in the precipitation heat treatment step is T2 (℃). When the holding time at the heat treatment temperature T2 is defined as t2 (minutes), the following formulas (A) to (C) are satisfied.
(1/20)×{(T1-700) 2 +t1}/(5Nb+30Ti+5V)≧4100 (A)
T1≧T2 (B)
(T2+t2)×(Nb+50Ti+20V)≧1000 (C)
Here, the content in mass % of the corresponding element is substituted for the element symbol in formula (A) and formula (C).
Each step will be explained below.
　［（工程１）準備工程］
　準備工程では、上述の特徴１を満たす化学組成を有する素材を準備する。素材は第三者から供給されてもよいし、製造してもよい。素材はインゴットであってもよいし、スラブ、ブルーム、又は、ビレットであってもよい。 [(Process 1) Preparation process]
In the preparation step, a material having a chemical composition that satisfies the above feature 1 is prepared. Materials may be supplied or manufactured by a third party. The material may be an ingot, a slab, a bloom, or a billet.
　素材を製造する場合、次の方法により、素材を製造する。上述の特徴１を満たす化学組成を有する溶融合金を製造する。製造された溶融合金を用いて、造塊法によりインゴットを製造する。製造された溶融合金を用いて、連続鋳造法によりスラブ、ブルーム、又は、ビレットを製造してもよい。製造されたインゴット、スラブ、ブルームに対して熱間加工を実施して、ビレットを製造してもよい。例えば、インゴットに対して熱間鍛造を実施して、円柱状のビレットを製造し、このビレットを素材としてもよい。この場合、熱間鍛造開始直前の素材の温度は特に限定されないが、例えば、１１００～１３００℃である。熱間鍛造後の素材の冷却方法は特に限定されない。 When manufacturing the material, use the following method to manufacture the material. A molten alloy having a chemical composition that satisfies feature 1 above is produced. Using the produced molten alloy, an ingot is produced by an ingot-forming method. Using the produced molten alloy, a slab, bloom, or billet may be produced by a continuous casting method. A billet may be manufactured by hot working the manufactured ingot, slab, or bloom. For example, an ingot may be hot forged to produce a cylindrical billet, and this billet may be used as the raw material. In this case, the temperature of the material immediately before the start of hot forging is not particularly limited, but is, for example, 1100 to 1300°C. The method for cooling the material after hot forging is not particularly limited.
　［（工程２）熱間加工工程］
　熱間加工工程では、準備工程において準備された素材に対して熱間加工を実施して、中間合金材を製造する。中間合金材は例えば、合金管であってもよいし、合金板であってもよいし、合金棒材であってもよい。 [(Step 2) Hot processing step]
In the hot working step, hot working is performed on the material prepared in the preparation step to produce an intermediate alloy material. The intermediate alloy material may be, for example, an alloy tube, an alloy plate, or an alloy bar.
　中間合金材が合金管である場合、熱間加工工程では、次の加工を実施する。初めに、円柱素材を準備する。機械加工により、円柱素材の中心軸に沿った貫通孔を形成する。貫通孔が形成された円柱素材を加熱する。加熱された円柱素材に対して、ユジーンセジュルネ法に代表される熱間押出を実施して、中間合金材（合金管）を製造する。熱間押出法に代えて、熱間押抜き製管法を実施してもよい。加熱温度は特に限定されないが、例えば、１１００～１３００℃である。 When the intermediate alloy material is an alloy tube, the following processing is performed in the hot processing step. First, prepare the cylinder material. Through machining, a through hole is formed along the central axis of the cylindrical material. A cylindrical material with through holes formed therein is heated. The heated cylindrical material is subjected to hot extrusion, typically the Eugene-Séjournet method, to produce an intermediate alloy material (alloy tube). Instead of the hot extrusion method, a hot extrusion tube manufacturing method may be used. The heating temperature is not particularly limited, but is, for example, 1100 to 1300°C.
　また、熱間押出に代えて、マンネスマン法による穿孔圧延を実施して、合金管を製造してもよい。この場合、円柱素材を加熱する。加熱温度は特に限定されないが、例えば、１１００～１３００℃である。加熱された円柱素材に対して、穿孔機による穿孔圧延を実施して、中空素管とする。中空素管に対してさらに、マンドレルミル、レデューサ、サイジングミル等により延伸圧延又は定径圧延を実施して、中間合金材（合金管）を製造する。 Furthermore, instead of hot extrusion, the alloy tube may be manufactured by performing piercing rolling using the Mannesmann method. In this case, the cylindrical material is heated. The heating temperature is not particularly limited, but is, for example, 1100 to 1300°C. The heated cylindrical material is punched and rolled using a punching machine to form a hollow tube. The hollow tube is further subjected to elongation rolling or sizing rolling using a mandrel mill, reducer, sizing mill, etc. to produce an intermediate alloy material (alloy tube).
　中間合金材が合金板である場合、熱間加工工程は例えば、一対のワークロールを備える１又は複数の圧延機を用いる。この場合、スラブ等の素材を加熱する。加熱温度は特に限定されないが、例えば、１１００～１３００℃である。加熱された素材に対して圧延機を用いて熱間圧延を実施して、中間合金材（合金板）を製造する。 When the intermediate alloy material is an alloy plate, the hot working step uses, for example, one or more rolling mills equipped with a pair of work rolls. In this case, the material such as a slab is heated. The heating temperature is not particularly limited, but is, for example, 1100 to 1300°C. The heated material is hot rolled using a rolling mill to produce an intermediate alloy material (alloy plate).
　中間合金材が合金棒材である場合、熱間加工工程は例えば、分塊圧延機、及び／又は、複数の圧延機が一列に並んだ連続圧延機を用いる。この場合、素材を加熱する。加熱温度は特に限定されないが、例えば、１１００～１３００℃である。加熱された素材に対して、分塊圧延機及び／又は連続圧延機を用いて熱間圧延を実施して、中間合金材（合金棒材）を製造する。 When the intermediate alloy material is an alloy bar, the hot working step uses, for example, a blooming mill and/or a continuous rolling mill in which a plurality of rolling mills are arranged in a row. In this case, the material is heated. The heating temperature is not particularly limited, but is, for example, 1100 to 1300°C. The heated material is hot rolled using a blooming mill and/or a continuous rolling mill to produce an intermediate alloy material (alloy bar material).
　［（工程３）高温保持工程］
　高温保持工程では、熱間加工工程で製造された中間合金材を高温で保持して、中間合金材中の析出物を十分に溶解させる。高温保持工程での保持温度Ｔ１（℃）及び保持温度Ｔ１での保持時間ｔ１（分）は以下に示す範囲に調整する。
　保持温度Ｔ１：１１００～１３５０℃
　保持時間ｔ１：２～４０分 [(Step 3) High temperature holding step]
In the high temperature holding step, the intermediate alloy material produced in the hot working step is held at a high temperature to sufficiently dissolve precipitates in the intermediate alloy material. The holding temperature T1 (° C.) and the holding time t1 (minutes) at the holding temperature T1 in the high temperature holding step are adjusted to the range shown below.
Holding temperature T1: 1100-1350℃
Holding time t1: 2-40 minutes
　高温保持工程では、熱間加工工程で常温まで冷却された中間合金材を保持温度Ｔ１に加熱して、保持温度Ｔ１で保持時間ｔ１保持してもよい。また、熱間加工工程直後の中間合金材（つまり、常温まで冷却されていない中間合金材）を、保持温度Ｔ１で保持時間ｔ１保持してもよい。保持時間ｔ１経過後、中間合金材を急冷する。急冷は水冷であってもよいし、油冷であってもよい。 In the high temperature holding step, the intermediate alloy material cooled to room temperature in the hot working step may be heated to a holding temperature T1 and held at the holding temperature T1 for a holding time t1. Further, the intermediate alloy material immediately after the hot working step (that is, the intermediate alloy material that has not been cooled to room temperature) may be held at the holding temperature T1 for a holding time t1. After the holding time t1 has elapsed, the intermediate alloy material is rapidly cooled. The rapid cooling may be water cooling or oil cooling.
　［（工程４）冷間加工工程］
　冷間加工工程では、中間合金材に対して、酸洗処理を実施した後、冷間加工を実施する。中間合金材が合金管又は合金棒材である場合、冷間加工は例えば、冷間抽伸である。中間合金材が合金板である場合、冷間加工は例えば、冷間圧延である。冷間加工工程を実施することにより、次工程の析出熱処理工程において、再結晶による結晶粒の微細化を行うことができる。冷間加工工程における減面率は特に限定されないが、例えば、１０～９０％である。 [(Step 4) Cold working step]
In the cold working step, the intermediate alloy material is pickled and then cold worked. When the intermediate alloy material is an alloy tube or an alloy bar, the cold working is, for example, cold drawing. When the intermediate alloy material is an alloy plate, the cold working is, for example, cold rolling. By performing the cold working step, crystal grains can be refined by recrystallization in the next precipitation heat treatment step. The area reduction rate in the cold working process is not particularly limited, but is, for example, 10 to 90%.
　［（工程５）析出熱処理工程］
　析出熱処理工程では、冷間加工工程後の中間合金材に対して熱処理を実施して、中間合金材中に微細析出物を生成する。析出熱処理工程での熱処理温度Ｔ２（℃）、及び、熱処理温度Ｔ２での保持時間ｔ２（分）は以下の範囲に調整する。
　熱処理温度Ｔ２：１０００～１３５０℃
　保持時間ｔ２　：１～３０分
　保持時間ｔ２経過後の中間合金材を急冷する。急冷方法は水冷であってもよいし、油冷であってもよい。 [(Step 5) Precipitation heat treatment step]
In the precipitation heat treatment step, the intermediate alloy material after the cold working step is heat treated to generate fine precipitates in the intermediate alloy material. The heat treatment temperature T2 (° C.) in the precipitation heat treatment step and the holding time t2 (minutes) at the heat treatment temperature T2 are adjusted within the following ranges.
Heat treatment temperature T2: 1000-1350℃
Holding time t2: 1 to 30 minutes After the holding time t2 has elapsed, the intermediate alloy material is rapidly cooled. The rapid cooling method may be water cooling or oil cooling.
　［式（Ａ）～式（Ｃ）について］
　上記製造工程ではさらに、高温保持工程及び析出熱処理工程での、保持温度Ｔ１（℃）、保持時間ｔ１（分）、熱処理温度Ｔ２（℃）、及び、保持時間ｔ２（分）が、式（Ａ）～式（Ｃ）を満たす。
　（１／２０）×｛（Ｔ１－７００）２＋ｔ１｝／（５Ｎｂ＋３０Ｔｉ＋５Ｖ）≧４１００　（Ａ）
　Ｔ１≧Ｔ２　（Ｂ）
　（Ｔ２＋ｔ２）×（Ｎｂ＋５０Ｔｉ＋２０Ｖ）≧１０００　（Ｃ）
　ここで、式（Ａ）及び式（Ｃ）中の元素記号には、対応する元素の質量％での含有量が代入される。 [About formulas (A) to (C)]
In the above manufacturing process, the holding temperature T1 (°C), holding time t1 (minutes), heat treatment temperature T2 (°C), and holding time t2 (minutes) in the high temperature holding step and the precipitation heat treatment step are calculated by the formula (A ) ~ satisfies formula (C).
(1/20)×{(T1-700) 2 +t1}/(5Nb+30Ti+5V)≧4100 (A)
T1≧T2 (B)
(T2+t2)×(Nb+50Ti+20V)≧1000 (C)
Here, the content in mass % of the corresponding element is substituted for the element symbol in formula (A) and formula (C).
　［式（Ａ）について］
　Ｆ１＝（１／２０）×｛（Ｔ１－７００）２＋ｔ１｝／（５Ｎｂ＋３０Ｔｉ＋５Ｖ）と定義する。Ｆ１は、高温保持工程において、中間合金材中の析出物（Ｎｂ析出物、Ｔｉ析出物、Ｖ析出物等）を十分に溶解させるための条件式である。本実施形態のオーステナイト系ステンレス合金材では、Ｎ含有量が０．１０～０．３５％と高い。このようにＮ含有量が高い場合において、Ｔｉ析出物を十分に溶解させるためには、合金材中のＴｉ含有量に応じた熱量が必要となる。同様に、Ｎｂ析出物及びＶ析出物について、これらの析出物を十分に溶解させるためには、合金材のＮｂ含有量、Ｖ含有量に応じた熱量が必要となる。 [About formula (A)]
It is defined as F1=(1/20)×{(T1-700) 2 +t1}/(5Nb+30Ti+5V). F1 is a conditional expression for sufficiently dissolving precipitates (Nb precipitates, Ti precipitates, V precipitates, etc.) in the intermediate alloy material in the high temperature holding step. The austenitic stainless steel alloy material of this embodiment has a high N content of 0.10 to 0.35%. In such a case where the N content is high, in order to sufficiently dissolve the Ti precipitates, an amount of heat corresponding to the Ti content in the alloy material is required. Similarly, in order to sufficiently dissolve Nb precipitates and V precipitates, an amount of heat corresponding to the Nb content and V content of the alloy material is required.
　Ｆ１では、Ｎｂ含有量、Ｔｉ含有量、及び、Ｖ含有量が分母に配置される。つまり、Ｆ１は合金材中のＮｂ含有量、Ｔｉ含有量、及び、Ｖ含有量に応じて調整される。上述のとおり、本実施形態のオーステナイト系ステンレス合金材ではＮ含有量が高い。そのため、Ｎｂ析出物、Ｔｉ析出物、及び、Ｖ析出物のうち、Ｎとの結びつきが強いＴｉが最も溶解しにくい。そのため、Ｆ１中でのＴｉの係数が大きい。 In F1, the Nb content, Ti content, and V content are arranged in the denominator. That is, F1 is adjusted according to the Nb content, Ti content, and V content in the alloy material. As described above, the austenitic stainless alloy material of this embodiment has a high N content. Therefore, among Nb precipitates, Ti precipitates, and V precipitates, Ti, which has a strong bond with N, is the most difficult to dissolve. Therefore, the coefficient of Ti in F1 is large.
　Ｆ１が４１００以上であれば、高温保持工程において、中間合金材中のＮｂ析出物、Ｔｉ析出物、及び、Ｖ析出物を溶解するのに十分な熱量が、中間合金材に付与される。そのため、中間合金材中に存在している析出物を十分に溶解することができる。 If F1 is 4100 or more, sufficient heat is applied to the intermediate alloy material in the high temperature holding step to melt Nb precipitates, Ti precipitates, and V precipitates in the intermediate alloy material. Therefore, the precipitates present in the intermediate alloy material can be sufficiently dissolved.
　Ｆ１の好ましい下限は４２００であり、さらに好ましくは４３００である。 A preferable lower limit of F1 is 4200, more preferably 4300.
　［式（Ｂ）について］
　上述の製造工程では、高温保持工程で中間合金材中の析出物をほぼ溶解した後、析出熱処理工程で中間合金材中に微細析出物を生成する。熱処理温度Ｔ２が保持温度Ｔ１よりも高ければ、析出熱処理工程において、中間合金材中に微細析出物が十分に生成しない。したがって、保持温度Ｔ１を熱処理温度Ｔ２以上とする。 [About formula (B)]
In the above manufacturing process, after most of the precipitates in the intermediate alloy material are dissolved in the high temperature holding step, fine precipitates are generated in the intermediate alloy material in the precipitation heat treatment step. If the heat treatment temperature T2 is higher than the holding temperature T1, fine precipitates will not be sufficiently generated in the intermediate alloy material in the precipitation heat treatment step. Therefore, the holding temperature T1 is set to be equal to or higher than the heat treatment temperature T2.
　［式（Ｃ）について］
　析出熱処理工程では、高温保持工程により析出物が十分に溶解した中間合金材に対して、円相当径が０．５～２．０μｍの微細析出物を生成する。微細析出物の個数密度ＮＤを５０００個／ｍｍ２以上とするためには、中間合金材中のＮｂ含有量、Ｔｉ含有量、及び、Ｖ含有量に応じた熱量を中間合金材に付与する必要がある。 [About formula (C)]
In the precipitation heat treatment step, fine precipitates with an equivalent circle diameter of 0.5 to 2.0 μm are generated on the intermediate alloy material in which the precipitates have been sufficiently dissolved in the high temperature holding step. In order to make the number density ND of fine precipitates 5000 pieces/mm2 or more, it is necessary to provide the intermediate alloy material with an amount of heat corresponding to the Nb content, Ti content, and V content in the intermediate alloy material. There is.
　Ｆ２＝（Ｔ２＋ｔ２）×（Ｎｂ＋５０Ｔｉ＋２０Ｖ）と定義する。Ｆ２は、微細析出物の個数密度ＮＤを５０００個／ｍｍ２以上とするための条件式である。Ｆ２が１０００以上であれば、式（Ａ）及び式（Ｂ）を満たすことを前提として、微細析出物の個数密度が５０００個／ｍｍ２以上となる。 Define F2=(T2+t2)×(Nb+50Ti+20V). F2 is a conditional expression for setting the number density ND of fine precipitates to 5000 pieces/mm 2 or more. If F2 is 1000 or more, the number density of fine precipitates will be 5000 pieces/mm 2 or more on the premise that formulas (A) and (B) are satisfied.
　Ｆ２の好ましい下限は１０２０であり、さらに好ましくは１１００であり、さらに好ましくは１２００である。 A preferable lower limit of F2 is 1020, more preferably 1100, and still more preferably 1200.
　以上の製造工程により、特徴１及び特徴２を満たすオーステナイト系ステンレス合金材を製造できる。なお、本実施形態のオーステナイト系ステンレス合金材の製造方法は、上述の製造方法に限定されない。特徴１及び特徴２を満たすオーステナイト系ステンレス合金材を製造できれば、他の製造方法で製造されてもよい。 Through the above manufacturing process, an austenitic stainless steel alloy material that satisfies Features 1 and 2 can be produced. Note that the method for manufacturing the austenitic stainless alloy material of this embodiment is not limited to the above-described manufacturing method. Other manufacturing methods may be used as long as an austenitic stainless steel alloy material that satisfies Features 1 and 2 can be produced.
　以下、実施例により本実施形態のオーステナイト系ステンレス合金材の効果をさらに具体的に説明する。以下の実施例での条件は、本実施形態のオーステナイト系ステンレス合金材の実施可能性及び効果を確認するために採用した一条件例である。したがって、本実施形態のオーステナイト系ステンレス合金材はこの一条件例に限定されない。 Hereinafter, the effects of the austenitic stainless alloy material of this embodiment will be explained in more detail with reference to Examples. The conditions in the following examples are examples of conditions adopted to confirm the feasibility and effects of the austenitic stainless alloy material of this embodiment. Therefore, the austenitic stainless alloy material of this embodiment is not limited to this one example condition.
　［合金材の製造］
　表１－１及び表１－２に示す化学組成を有するインゴットを製造した。 [Manufacture of alloy materials]
Ingots having the chemical compositions shown in Tables 1-1 and 1-2 were produced.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　製造されたインゴットに対して熱間鍛造を実施して、直径１８０ｍｍの円柱素材を製造した。熱間鍛造でのインゴットの加熱温度は、１１００～１３００℃であった。製造された円柱素材に対して、熱間加工工程を実施した。具体的には、素材を加熱炉で加熱した。熱間加工工程での加熱温度は１１００～１３００℃であった。加熱後の円柱素材に対して熱間押出しを実施して、素管を製造した。 The produced ingot was hot forged to produce a cylindrical material with a diameter of 180 mm. The heating temperature of the ingot during hot forging was 1100 to 1300°C. A hot working process was performed on the manufactured cylindrical material. Specifically, the material was heated in a heating furnace. The heating temperature in the hot working step was 1100 to 1300°C. Hot extrusion was performed on the heated cylindrical material to produce a blank pipe.
　製造された素管に対して、高温保持工程を実施した。高温保持工程での保持温度Ｔ１（℃）、及び、保持時間ｔ１（分）は表２に示すとおりであった。 A high temperature holding process was carried out on the manufactured raw pipe. The holding temperature T1 (° C.) and holding time t1 (minutes) in the high temperature holding step were as shown in Table 2.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　高温保持工程後の素管に対して、冷間加工を実施した。具体的には、素管に対して冷間抽伸を実施した。なお、冷間加工での減面率は２０～７０％であった。 Cold working was performed on the raw tube after the high temperature holding process. Specifically, cold drawing was performed on the raw pipe. Note that the area reduction rate during cold working was 20 to 70%.
　冷間加工工程後の素管に関して、析出熱処理工程を実施した。析出熱処理工程での熱処理温度Ｔ２（℃）、及び、熱処理温度Ｔ２での保持時間ｔ２（分）は、表２に示すとおりであった。なお、表２中の「Ｆ１」欄にＦ１値を示す。「Ｔ１≧Ｔ２？」欄において、「Ｔ（Ｔｕｒｅ）」は保持温度Ｔ１が熱処理温度Ｔ２以上であったことを示し、「Ｆ（Ｆａｌｓｅ）」は保持温度Ｔ１が熱処理温度Ｔ２未満であったことを示す。「Ｆ２」欄にＦ２値を示す。 A precipitation heat treatment process was performed on the raw pipe after the cold working process. The heat treatment temperature T2 (° C.) in the precipitation heat treatment step and the holding time t2 (minutes) at the heat treatment temperature T2 were as shown in Table 2. Note that the F1 value is shown in the "F1" column in Table 2. In the "T1≧T2?" column, "T (Ture)" indicates that the holding temperature T1 was greater than or equal to the heat treatment temperature T2, and "F (False)" indicates that the holding temperature T1 was less than the heat treatment temperature T2. shows. The F2 value is shown in the "F2" column.
　以上の製造工程により、オーステナイト系ステンレス合金材（合金管）を製造した。 Through the above manufacturing process, an austenitic stainless steel alloy material (alloy tube) was manufactured.
　［評価試験］
　製造された合金材を用いて、次の評価試験を実施した。
　（試験１）微細析出物の個数密度ＮＤ測定試験
　（試験２）クリープ強度評価試験
　（試験３）耐応力緩和割れ性評価試験
　以下、各評価試験について説明する。 [Evaluation test]
The following evaluation test was conducted using the manufactured alloy material.
(Test 1) Fine precipitate number density ND measurement test (Test 2) Creep strength evaluation test (Test 3) Stress relaxation cracking resistance evaluation test Each evaluation test will be explained below.
　［（試験１）微細析出物の個数密度ＮＤ測定試験］
　各試験番号のオーステナイト系ステンレス合金材に対して、［微細析出物の個数密度ＮＤの測定方法］に記載の方法により、微細析出物の個数密度（個／ｍｍ２）を測定した。得られた微細析出物の個数密度ＮＤを、表２中の「個数密度ＮＤ（個／ｍｍ２）」欄に示す。 [(Test 1) Fine precipitate number density ND measurement test]
For the austenitic stainless steel alloy material of each test number, the number density of fine precipitates (pieces/mm 2 ) was measured by the method described in [Method for measuring number density ND of fine precipitates]. The number density ND of the obtained fine precipitates is shown in the "number density ND (pieces/mm 2 )" column in Table 2.
　［（試験２）クリープ強度評価試験］
　各試験番号の合金材（合金管）に対して、次のクリープ強度評価試験を実施した。
　各試験番号の合金材（合金管）の肉厚中央部から、ＪＩＳ　Ｚ２２７１：２０１０に準拠したクリープ破断試験片を採取した。クリープ破断試験片の平行部の軸方向に垂直な断面は円形であった。平行部の外径は６ｍｍであり、長さは３０ｍｍであった。クリープ破断試験片の長手方向は、合金管の管軸方向と平行であった。 [(Test 2) Creep strength evaluation test]
The following creep strength evaluation test was conducted on the alloy material (alloy pipe) of each test number.
A creep rupture test piece conforming to JIS Z2271:2010 was taken from the center of the wall thickness of the alloy material (alloy tube) of each test number. The cross section of the parallel part of the creep rupture test piece perpendicular to the axial direction was circular. The outer diameter of the parallel portion was 6 mm and the length was 30 mm. The longitudinal direction of the creep rupture test piece was parallel to the tube axis direction of the alloy tube.
　採取したクリープ破断試験片を用いて、ＪＩＳ　Ｚ２２７１：２０１０に準拠したクリープ試験を実施した。具体的には、クリープ破断試験片を７００℃に加熱した。その後、クリープ破断試験を実施した。試験応力は８０ＭＰａとした。試験では、クリープ破断時間（時間）を求めた。 A creep test in accordance with JIS Z2271:2010 was conducted using the collected creep rupture test piece. Specifically, a creep rupture test piece was heated to 700°C. Thereafter, a creep rupture test was conducted. The test stress was 80 MPa. In the test, creep rupture time (hours) was determined.
　得られたクリープ破断時間に応じて、クリープ強度を次のとおり評価した。
　評価Ｅ（Ｅｘｃｅｌｌｅｎｔ）：クリープ破断時間が１５００時間以上である
　評価Ｂ（Ｂａｄ）　　　　　　：クリープ破断時間が１５００時間未満である
　評価Ｅの場合、優れたクリープ強度が得られたと判断した。評価結果を表２中の「クリープ強度」欄に示す。 The creep strength was evaluated as follows according to the obtained creep rupture time.
Evaluation E (Excellent): Creep rupture time is 1500 hours or more Evaluation B (Bad): Creep rupture time is less than 1500 hours In the case of evaluation E, it was determined that excellent creep strength was obtained. The evaluation results are shown in the "Creep strength" column in Table 2.
　［（試験３）耐応力緩和割れ性評価試験］
　各試験番号の合金材（合金管）の肉厚中央部から、図１に示すＣリング型拘束溶接割れ試験片を作製した。Ｃリング型拘束溶接割れ試験片は、外径ＯＤ＝６ｍｍ、内径ＩＤ＝４ｍｍ、長さＬ＝２０ｍｍの試験片であって、試験片の管軸方向に垂直な断面は一部が開口したリング状であった。図１に示すとおり、開口部には１．５ｍｍの隙間Ｇを形成した。Ｃリング型拘束溶接割れ試験片を管軸方向に見て、試験片の中心軸に対して開口部と１８０°の位置に、ノッチ部を形成した。ノッチ部の幅ＮＷは０．４ｍｍ、深さＮＯＤは０．５ｍｍとし、底部の曲率半径Ｒを０．２ｍｍとした。 [(Test 3) Stress relaxation cracking resistance evaluation test]
A C-ring type restrained weld crack test piece shown in FIG. 1 was prepared from the center of the wall thickness of the alloy material (alloy tube) of each test number. The C-ring type restrained weld cracking test piece is a test piece with an outer diameter OD = 6 mm, an inner diameter ID = 4 mm, and a length L = 20 mm, and the cross section perpendicular to the tube axis direction of the test piece is a partially open ring. The situation was As shown in FIG. 1, a gap G of 1.5 mm was formed in the opening. A notch portion was formed at a position 180° from the opening with respect to the central axis of the C-ring type restrained weld crack test piece when viewed in the tube axis direction. The width NW of the notch portion was 0.4 mm, the depth NOD was 0.5 mm, and the radius of curvature R of the bottom portion was 0.2 mm.
　図２に示すとおり、Ｃリング型拘束溶接割れ試験片を管軸方向に見て、開口部に対して９０°及び２７０°の位置を両側から外力Ｐで拘束して、開口部の端部同士を付き合わせた。そして、付き合わせた部分の外周面側を、ＴＩＧ（Ｔｕｎｇｓｔｅｎ　Ｉｎｅｒｔ　Ｇａｓ）溶接によりなめ付けした。より具体的には、ＴＩＧ溶接により、Ｃリング型拘束溶接割れ試験片の管軸方向の全長をなめ付けした。なめ付けにより、ノッチ部に拘束応力を発生させた。ＴＩＧ溶接の条件は、いずれの試験番号でも同じとした。 As shown in Figure 2, when looking at the C-ring restraint weld crack test piece in the tube axis direction, the ends of the opening were restrained by external force P from both sides at 90° and 270° positions with respect to the opening. We dated. Then, the outer peripheral surface side of the mated portion was tanned by TIG (Tungsten Inert Gas) welding. More specifically, the entire length of the C-ring type restrained weld crack test piece in the tube axis direction was tanned by TIG welding. By tanning, a restraining stress was generated in the notch part. The TIG welding conditions were the same for all test numbers.
　なめ付けされたＣリング型拘束溶接割れ試験片に対して、６５０℃で５００時間保持する熱処理を実施した。熱処理後、Ｃリング型拘束溶接割れ試験片のノッチ底に発生している割れ数をカウントした。具体的には、Ｃリング型拘束溶接割れ試験片のノッチ底を含み、Ｃリング型拘束溶接割れ試験片の管軸方向に垂直な断面を含む割れ観察試験片を、管軸方向に３箇所採取した。各割れ観察試験片の上記断面に相当する表面を観察面とした。観察面を鏡面研磨した後、１０％しゅう酸水溶液でエッチングした。エッチング後、図３に示すとおり、観察面において、幅ＮＷのノッチ底ＮＢに含まれる結晶粒の数をカウントした（図３では結晶粒数が２９個）。さらに、観察面において、ノッチ底ＮＢから伝播している割れの個数をカウントした。３つの試験片のノッチ底ＮＢに含まれる結晶粒の総数と、３つの試験片のノッチ底ＮＢから伝播している割れの総数とを用いて、次の式に基づいて、割れ発生率を求めた。
　割れ発生率＝割れの総数／ノッチ底ＮＢに含まれる結晶粒の総数×１００ The tanned C-ring type restrained weld crack test piece was heat treated at 650° C. for 500 hours. After the heat treatment, the number of cracks occurring at the notch bottom of the C-ring restraint weld crack test piece was counted. Specifically, crack observation test pieces including the notch bottom of the C-ring type restrained weld crack test piece and a cross section perpendicular to the pipe axis direction of the C-ring type restrained weld crack test piece were collected at three locations in the pipe axis direction. did. The surface corresponding to the above-mentioned cross section of each crack observation test piece was taken as the observation surface. After the observation surface was mirror polished, it was etched with a 10% oxalic acid aqueous solution. After etching, as shown in FIG. 3, the number of crystal grains included in the notch bottom NB having the width NW was counted on the observation surface (the number of crystal grains was 29 in FIG. 3). Furthermore, on the observation surface, the number of cracks propagating from the notch bottom NB was counted. Using the total number of crystal grains included in the notch bottom NB of the three test pieces and the total number of cracks propagating from the notch bottom NB of the three test pieces, calculate the crack occurrence rate based on the following formula. Ta.
Crack occurrence rate = total number of cracks/total number of crystal grains included in notch bottom NB x 100
　得られた割れ発生率に応じて、耐応力緩和割れ性を次のとおり評価した。
　評価Ｅ：割れ発生率が３０％以下である
　評価Ｂ：割れ発生率が３０％超である
　評価Ｅの場合、優れた耐応力緩和割れ性が得られたと判断した。評価結果を表２に示す。 The stress relaxation cracking resistance was evaluated according to the obtained cracking incidence as follows.
Evaluation E: The cracking incidence is 30% or less. Evaluation B: The cracking incidence is more than 30%. In the case of evaluation E, it was determined that excellent stress relaxation cracking resistance was obtained. The evaluation results are shown in Table 2.
　［試験結果］
　表１－１、表１－２及び表２を参照して、試験番号１～１２では、合金材が特徴１及び特徴２を満たした。そのため、高温環境において、十分なクリープ強度が得られた。さらに、優れた耐応力緩和割れ性が得られた。 [Test results]
Referring to Tables 1-1, 1-2, and 2, in test numbers 1 to 12, the alloy materials satisfied Feature 1 and Feature 2. Therefore, sufficient creep strength was obtained in a high-temperature environment. Furthermore, excellent stress relaxation cracking resistance was obtained.
　一方、試験番号１３及び１４では、Ｆ１が低すぎ、式（Ａ）を満たさなかった。そのため、これらの試験番号のオーステナイト系ステンレス合金材では、微細析出物の個数密度ＮＤが５０００個／ｍｍ２未満となった。その結果、十分な耐応力緩和割れ性が得られなかった。 On the other hand, in test numbers 13 and 14, F1 was too low and did not satisfy formula (A). Therefore, in the austenitic stainless steel alloy materials having these test numbers, the number density ND of fine precipitates was less than 5000 pieces/mm 2 . As a result, sufficient stress relaxation cracking resistance could not be obtained.
　試験番号１５～１７では、保持温度Ｔ１が熱処理温度Ｔ２よりも低く、式（Ｂ）を満たさなかった。そのため、これらの試験番号のオーステナイト系ステンレス合金材では、微細析出物の個数密度ＮＤが５０００個／ｍｍ２未満となった。その結果、十分な耐応力緩和割れ性が得られなかった。 In test numbers 15 to 17, the holding temperature T1 was lower than the heat treatment temperature T2, and formula (B) was not satisfied. Therefore, in the austenitic stainless steel alloy materials having these test numbers, the number density ND of fine precipitates was less than 5000 pieces/mm 2 . As a result, sufficient stress relaxation cracking resistance could not be obtained.
　試験番号１８及び１９では、Ｆ２が低すぎ、式（Ｃ）を満たさなかった。そのため、これらの試験番号のオーステナイト系ステンレス合金材では、微細析出物の個数密度ＮＤが５０００個／ｍｍ２未満となった。その結果、十分なクリープ強度が得られなかった。さらに、十分な耐応力緩和割れ性が得られなかった。 In test numbers 18 and 19, F2 was too low and did not satisfy formula (C). Therefore, in the austenitic stainless steel alloy materials having these test numbers, the number density ND of fine precipitates was less than 5000 pieces/mm 2 . As a result, sufficient creep strength could not be obtained. Furthermore, sufficient stress relaxation cracking resistance could not be obtained.
　以上、本発明の実施の形態を説明した。しかしながら、上述した実施の形態は本発明を実施するための例示に過ぎない。したがって、本発明は上述した実施の形態に限定されることなく、その趣旨を逸脱しない範囲内で上述した実施の形態を適宜変更して実施することができる。 The embodiments of the present invention have been described above. However, the embodiments described above are merely examples for implementing the present invention. Therefore, the present invention is not limited to the embodiments described above, and can be implemented by appropriately modifying the embodiments described above without departing from the spirit thereof.

Claims (2)

  1. 　質量％で、
    　Ｃ：０．０３～０．１２％、
    　Ｓｉ：０．０５～２．００％、
    　Ｍｎ：０．０５～３．００％、
    　Ｐ：０．０３％以下、
    　Ｓ：０．０１０％以下、
    　Ｎｉ：１８．０～２５．０％未満、
    　Ｃｒ：２２．０～３０．０％未満、
    　Ｃｏ：０．０４～０．８０％、
    　Ｔｉ：０．００２～０．０１０％、
    　Ｎｂ：０．１～１．０％、
    　Ｖ：０．０１～１．００％、
    　Ａｌ：０．００１～０．０３０％未満、
    　Ｎ：０．１０～０．３５％、
    　Ｍｏ：０～１．００％、
    　Ｗ：０～１．００％、
    　Ｂ：０～０．０１０％、及び、
    　Ｃａ：０～０．０１００％、を含有し、残部がＦｅ及び不純物からなり、
    　円相当径が０．５～２．０μｍの析出物の個数密度が５０００個／ｍｍ２以上である、
    　オーステナイト系ステンレス合金材。     In mass%,
    C: 0.03-0.12%,
    Si: 0.05-2.00%,
    Mn: 0.05-3.00%,
    P: 0.03% or less,
    S: 0.010% or less,
    Ni: 18.0 to less than 25.0%,
    Cr: less than 22.0 to 30.0%,
    Co: 0.04-0.80%,
    Ti: 0.002 to 0.010%,
    Nb: 0.1-1.0%,
    V: 0.01-1.00%,
    Al: 0.001 to less than 0.030%,
    N: 0.10-0.35%,
    Mo: 0-1.00%,
    W: 0-1.00%,
    B: 0 to 0.010%, and
    Contains Ca: 0 to 0.0100%, the remainder consists of Fe and impurities,
    The number density of precipitates with a circular equivalent diameter of 0.5 to 2.0 μm is 5000 pieces/mm 2 or more,
    Austenitic stainless steel alloy material.
  2. 　請求項１に記載のオーステナイト系ステンレス合金材であって、
    　Ｍｏ：０．０１～１．００％、
    　Ｗ：０．０１～１．００％、
    　Ｂ：０．００１～０．０１０％、及び、
    　Ｃａ：０．０００１～０．０１００％、からなる群から選択される１種以上を含有する、
    　オーステナイト系ステンレス合金材。     The austenitic stainless steel alloy material according to claim 1,
    Mo: 0.01-1.00%,
    W: 0.01-1.00%,
    B: 0.001 to 0.010%, and
    Containing one or more selected from the group consisting of Ca: 0.0001 to 0.0100%,
    Austenitic stainless steel alloy material.
PCT/JP2023/020959 2022-06-07 2023-06-06 Austenitic stainless alloy material WO2023238851A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020164919A (en) * 2019-03-29 2020-10-08 日本製鉄株式会社 Austenitic heat-resistant steel
JP2021021093A (en) * 2019-07-25 2021-02-18 日本製鉄株式会社 Austenite stainless steel
WO2021141107A1 (en) * 2020-01-10 2021-07-15 日本製鉄株式会社 Austenitic stainless steel material
US20210348248A1 (en) * 2018-11-13 2021-11-11 Korea Advanced Institute Of Science And Technology Austenitic stainless steel containing niobium and manufacturing method of the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20210348248A1 (en) * 2018-11-13 2021-11-11 Korea Advanced Institute Of Science And Technology Austenitic stainless steel containing niobium and manufacturing method of the same
JP2020164919A (en) * 2019-03-29 2020-10-08 日本製鉄株式会社 Austenitic heat-resistant steel
JP2021021093A (en) * 2019-07-25 2021-02-18 日本製鉄株式会社 Austenite stainless steel
WO2021141107A1 (en) * 2020-01-10 2021-07-15 日本製鉄株式会社 Austenitic stainless steel material

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