WO2023145423A1 - Precipitation-hardening-type austenitic alloy steel material and method for manufacturing same, and precipitation-hardening-type austenitic alloy heat-treated steel material and method for manufacturing same - Google Patents

Precipitation-hardening-type austenitic alloy steel material and method for manufacturing same, and precipitation-hardening-type austenitic alloy heat-treated steel material and method for manufacturing same Download PDF

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WO2023145423A1
WO2023145423A1 PCT/JP2023/000383 JP2023000383W WO2023145423A1 WO 2023145423 A1 WO2023145423 A1 WO 2023145423A1 JP 2023000383 W JP2023000383 W JP 2023000383W WO 2023145423 A1 WO2023145423 A1 WO 2023145423A1
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steel material
austenitic alloy
forging
precipitation
heat
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PCT/JP2023/000383
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French (fr)
Japanese (ja)
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優 藤吉
修 多久和
隆司 竹原
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株式会社プロテリアル
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/04—Shaping in the rough solely by forging or pressing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon

Definitions

  • the present invention relates to a method for producing a precipitation hardening austenitic alloy steel, a method for producing a heat treated precipitation hardening austenitic alloy steel, a precipitation hardening austenitic alloy steel, and a heat treated precipitation hardening austenitic alloy steel.
  • Precipitation hardening austenitic alloys such as SUH660 have good strength characteristics over a wide range of temperatures and are excellent in hydrogen embrittlement resistance in a hydrogen environment, so they are known as members suitable for hydrogen station (hydrogen station) applications.
  • Patent Document 1 describes obtaining a forged product by forging an A286 alloy (equivalent to SUH660) suitable for hydrogen energy equipment at a total forging ratio of 5:1.
  • Non-Patent Document 1 describes that when a precipitation-strengthened A286 test piece is charged with hydrogen, properties such as tensile strength of the test piece decrease as the amount of hydrogen increases. against this background, even precipitation hardening austenitic alloys are required to have higher strength materials.
  • Non-Patent Document 2 describes that the composition of the A286 alloy is improved to increase the strength in order to suppress the precipitation of the ⁇ layer that increases the susceptibility to hydrogen embrittlement.
  • Non-Patent Document 2 The method described in Non-Patent Document 2 is effective for improving mechanical properties of high-temperature strength, but there is concern that ductility such as elongation will decrease as strength improves.
  • a relatively large amount of W is contained in order to improve the characteristics, but W is one of the expensive raw materials, so it is one of the raw materials that should be avoided as much as possible in industrial products. . Therefore, the object of the present invention is to provide a precipitation hardening austenitic alloy steel material and a precipitation hardening austenitic steel material that can improve mechanical properties without improving the composition of the steel material and can be expected to extend the life of parts in a high-pressure hydrogen environment.
  • Another object of the present invention is to provide a method for producing a heat-treated steel material based on a series alloy.
  • a forging material having a composition of a precipitation hardening austenitic alloy is prepared, hot forged multiple times so that the total forging forming ratio is 30 or more, and a columnar shape and perpendicular to the axis are formed.
  • a method for producing a precipitation hardening austenitic alloy steel including a hot forging step to obtain a forged material having an area equivalent circle diameter of 100 mm or more in a directional cross section.
  • Another aspect of the present invention is a method for producing a precipitation hardening type austenitic alloy heat-treated steel material, including a heat treatment step of obtaining a heat-treated material by further performing solution treatment and aging treatment using the forged material.
  • Another aspect of the present invention has a crystal grain having a GOS (Grain Orientation Spread) value of 1.0° or more in an area ratio of 50% or more, and has a columnar shape and an area circle equivalent diameter of a cross section in the direction perpendicular to the axis of 100 mm.
  • GOS Gram Orientation Spread
  • the grain size number is at a depth of D/4 and a depth of D/2 from the surface of the heat-treated steel.
  • a precipitation hardening austenitic alloy steel material and a precipitation hardening austenitic alloy heat-treated steel material that can further improve mechanical properties and can be expected to have a long life in a high-pressure hydrogen environment.
  • FIG. 4 is a schematic diagram showing the sample collection position for mechanical property measurement in the example.
  • FIG. 4 is a schematic diagram showing EBSD sample collection positions in the example.
  • the present invention is directed to a precipitation hardening austenitic alloy steel material.
  • This precipitation hardening type austenitic alloy steel refers to SUH309, SUH310, SUH330, SUH660, SUH661 and their improved materials described in JIS-G-4311. Specifically, it is preferable that Ni: 10 to 40% and Cr: 10 to 30% be included in mass %, and that Fe+Ni+Cr be 95% or more in mass %.
  • Ni 10 to 40%, Cr: 10 to 30%, and the balance may be Fe and unavoidable impurities.
  • a more preferable lower limit of the Ni amount is 20% by mass, and a more preferable upper limit of the Ni amount is 30% by mass.
  • a more preferable upper limit of Cr is 20% by mass.
  • one or more elements of V, Si, Mn, Al, B, Ta, W, Ti, Mo, and Nb are added in a total of up to 5% by mass. It may be contained up to .0%.
  • Other impurity elements that are inevitably included include, for example, C, S, P, and O, and the upper limit of each of these elements is preferably set to 0.1%.
  • a forging material having a precipitation hardening austenitic alloy composition is prepared.
  • This forging material is preferably a steel ingot that can be obtained by casting.
  • a steel ingot is subjected to hot plastic working such as hot pressing or hot rolling, and then homogenized heat treatment is applied to a steel billet (billet, bloom, etc.) machined into a round or square bar shape,
  • the billet may be used as a forging material.
  • remelting may be performed for the purpose of reducing component segregation and non-metallic inclusions.
  • the prepared forging material is heated in a heating furnace and hot forged a plurality of times to obtain a precipitation hardening austenitic alloy steel material.
  • forging is performed so that the total forging forming ratio (hereinafter also referred to as the total forging ratio) is 30 or more.
  • the "total forging forming ratio (total forging ratio)" in the present invention is derived using the forging forming ratio of actual forging described in JIS-G-0701.
  • S 0 , S 1 , S 2 . . . S n-1 , S n are cross-sectional areas.
  • the total forging ratio exceeds 30
  • the material forging is performed from 100 mm in diameter to 50 mm in diameter, and 50 mm in diameter to 18 mm in diameter.
  • the ratio becomes 30.8, satisfying the requirements of the present invention.
  • a preferred lower limit for the total forging ratio is 35, and a more preferred lower limit for the total forging ratio is 40.
  • the upper limit of the total forging ratio is not particularly limited, but since the manufacturing cost increases as the number of forgings increases, it is realistic to set it to 200, and it may be set to 150, for example.
  • the working strain imparted by actual forging tends to mainly contribute to the improvement of mechanical properties.
  • the forging forming ratio upsetting ratio
  • the temperature of the heating furnace during forging is preferably 800 to 1300° C., and the surface temperature of the material at the end of forging is preferably 600° C. or higher.
  • the "hot forging" in the present invention may include hot free forging in which a workpiece is placed on an anvil with a flat or curved surface and the material is processed with a hammer with a flat or curved surface. It is preferable from the viewpoint of the degree of freedom of the shape to be processed.
  • die forging using a die may be performed, and a forged material is obtained by pressing the material from four directions over the entire length of the material while rotating the material in the circumferential direction. Radial forging may be performed, or a combination thereof may be applied. Further, processing combining blooming rolling and hot forging may be applied.
  • the cross-sectional area before rolling and the cross-sectional area after rolling may be measured and applied to the formula for deriving the forging ratio of the physical forging described above to obtain the total forging ratio. Further, in order to achieve the above-described total forging ratio of the present embodiment, it is preferable to perform the actual forging at least three times. This is because the deformation resistance of precipitation hardening austenitic alloy steel is high, and therefore the smaller the working rate per forging, the more stable the working. Further, the number of upset forgings is preferably at least two or more because processing strain is introduced to the inside of a large forged product having an area equivalent circle diameter of 100 mm or more.
  • a forged product (precipitation hardening austenitic alloy steel material) obtained by a hot forging process is subjected to solution treatment and aging treatment to obtain a precipitation hardening austenitic alloy heat treated steel material.
  • a preferred solution treatment temperature is 850 to 1050°C, more preferably 900 to 1000°C.
  • the aging treatment temperature is preferably 650 to 800°C, more preferably 700 to 760°C.
  • the precipitation hardening austenitic alloy steel material of the present invention which can be obtained by the manufacturing method of the present invention, will be described.
  • the precipitation hardening austenitic alloy steel material of the present invention has crystal grains having a GOS (Grain Orientation Spread) value of 1.0° or more in an area ratio of 50% or more. A preferable area ratio is 60% or more.
  • This GOS value can be measured by the conventionally known "SEM-EBSD method (electron beam backscatter diffraction method)", and can be derived by calculating the misorientation of points (pixels) constituting the crystal grain. can.
  • the crystal orientation difference obtained by the GOS value is an index that indicates the strain imparted to the alloy by working.
  • the GOS values of this embodiment are obtained by taking samples at positions D/4 and D/2 in depth from the surface of the forging in the axial direction (D is the distance between the surfaces passing through the axis. equivalent), which can be derived by measurement.
  • the area ratio of the crystal grains is 50% or more.
  • the GOS value in the present invention is measured by taking a sample from the forged material (before solution treatment and aging treatment).
  • the area ratio of crystal grains having a GOS value of 1.0° or more after solution heat treatment and aging heat treatment tends to be a low value of less than 50% because strain due to forging is released.
  • the GOS value described above in this embodiment is the direction shown in FIG. and D/2.
  • the position of depth D/2 corresponds to the center of the steel material, and strain is least likely to occur, so it is preferable that the test piece taken from the position of depth D/2 also satisfies the characteristics specified in the present invention.
  • the precipitation hardening austenitic alloy steel material of the present invention is a steel material having a columnar shape and an area circle equivalent diameter of a cross section in the direction perpendicular to the axis of 100 mm or more.
  • the steel material of the present invention obtained by the manufacturing method of the present invention described above has an area circle equivalent diameter of 100 mm or more (preferably 200 mm or more, 300 mm or more, or 400 mm or more). Processing strain is introduced up to
  • the “columnar shape” refers to, for example, a columnar shape or a prismatic shape, and may be tapered in the axial direction.
  • the area circle equivalent diameter of the cross section perpendicular to the axis of the present invention can be obtained by measuring the cross section perpendicular to the axis at the position of L/2, where L is the length of the steel material.
  • the precipitation hardening type austenitic alloy heat-treated steel material of the present invention (material subjected to solution heat treatment and aging treatment) obtained by the production method of the present invention preferably has a grain size number of 4.0 or more.
  • the precipitation hardening austenitic alloy steel material before solution heat treatment and aging treatment has crystal grains with a GOS value of 1.0° or more in an area ratio of 50% or more. Coarse non-recrystallized grains are less likely to be formed later, and a uniform fine grain structure tends to be easily obtained.
  • precipitation hardened austenite having good mechanical properties such as 0.2% proof stress of 590 MPa or more, tensile strength of 900 MPa or more, and elongation of 15% or more system alloy steel can be obtained.
  • the 0.2% proof stress is preferably 600 MPa or more, more preferably 630 MPa or more, and still more preferably 660 MPa or more.
  • a preferable tensile strength is 950 MPa or more, and a more preferable tensile strength is 980 MPa or more.
  • the preferable lower limit of elongation is 20%, and the preferable upper limit of elongation is 30%.
  • the upper limit of the crystal grain size number is not particularly limited, but in order to make the crystal grains excessively fine, the forging ratio must be set too high, making manufacturing difficult.
  • a preferable upper limit of the grain size number is 8.0, and a more preferable upper limit of the grain size number is 7.0.
  • the 0.2% proof stress is affected by the grain size and tends to decrease due to the presence of coarse unrecrystallized grains to which sufficient processing strain has not been applied. With the steel material of the present invention, it is possible to obtain a good value without lowering the 0.2% yield strength. Note that the grain size, 0.2% yield strength, tensile strength, and elongation described above in this embodiment are measured in the axial direction from the surface of the obtained forging material in the direction shown in FIG.
  • a test piece is taken from the position of depth D/4 (D: the diameter of the equivalent circle diameter) and the position of D/2 and measured.
  • D the diameter of the equivalent circle diameter
  • D/2 the position of depth D/2 corresponds to the center of the steel material, and strain is most difficult to enter, so it is difficult to obtain a uniform microstructure. It is preferable to meet the regulations.
  • Example 1 Steel ingots (equivalent to SUH660) having the compositions shown in Table 1 were prepared as raw materials for columnar forgings for the examples of the present invention and the comparative examples, and hot forging was applied to each of them.
  • the forging material was subjected to multiple forgings and upset forgings so that the total forging ratio was 101, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 470 mm was obtained.
  • the forging material was subjected to multiple forgings and upset forgings so that the total forging ratio was 26, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 620 mm was obtained. From the surface of the forged material obtained after that, in the direction shown in FIG. , A test piece (13 x 13 x 100 mm) was taken in the axial direction from the position of D/2, subjected to solution treatment and aging treatment to obtain a heat-treated material, and various mechanical properties and grain size numbers were measured.
  • test piece defined by JISZ2241 was used as the test piece used for measuring various mechanical properties, and the test was performed based on the JISZ2241 metal material tensile test method.
  • the grain size number was determined according to JIS-G-0551 with a grain size standard chart plate 1.
  • Table 2 shows the results of heat treatment conditions, various mechanical properties, and grain size numbers. From Table 2, it was confirmed that the samples of the invention examples all had higher 0.2% proof stress and tensile strength than the comparative examples, had the same level of elongation, and had excellent mechanical properties. In addition, it was confirmed that the crystal grain size of the sample of the invention example was finer than that of the comparative example, and the variation of the crystal grain size was also smaller than that of the comparative example.
  • the test piece was measured from the position of depth D/4 and the position of D/2 in the axial direction from the surface in the direction shown in FIG. was sampled in the direction perpendicular to the axis, subjected to solution treatment and aging treatment to obtain a heat-treated material, and then various mechanical properties were sampled.
  • Table 3 shows the heat treatment conditions and the results of various mechanical properties. From Table 3, it can be seen that the various mechanical properties of the samples sampled in the direction perpendicular to the axis of the present invention are excellent at the same level as those obtained in the axial direction. It was confirmed that
  • Example 3 A steel ingot (equivalent to SUH660) having the composition shown in Table 7 was prepared, used as a material for columnar forging of the present invention example, and subjected to hot forging.
  • the forging material for forging was subjected to multiple forgings and upsetting forgings so that the total forging ratio was 63, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 200 mm was obtained. .
  • a test piece was taken in the axial direction from the position of depth D/4 from the surface of the forged material subjected to solution treatment and aging treatment, and various mechanical properties and grain size numbers were measured.

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Abstract

Provided is a method for manufacturing an austenitic alloy steel material with which it is possible to improve mechanical properties even without improving the steel composition and to expect an increase in the service life of a component in a high-pressure hydrogen environment.　A method for manufacturing a precipitation-hardening-type austenitic alloy steel material including a hot forging step for preparing a forging material having a composition of a precipitation-hardening-type austenitic alloy steel material, and performing hot forging a plurality of times so that the total forging ratio is 30 or above to obtain a forged material. The method preferably includes a heat treatment step for further performing a solution heat treatment and an aging treatment on the forged material to obtain a heat-treated steel material.

Description

析出硬化型オーステナイト系合金鋼材およびその製造方法、ならびに析出硬化型オーステナイト系合金熱処理鋼材およびその製造方法Precipitation Hardening Austenitic Alloy Steel Material and Manufacturing Method Thereof, Precipitation Hardening Austenitic Alloy Heat Treated Steel Material and Manufacturing Method Thereof
　本発明は、析出硬化型オーステナイト系合金鋼材の製造方法、析出硬化型オーステナイト系合金熱処理鋼材の製造方法、析出硬化型オーステナイト系合金鋼材、および析出硬化型オーステナイト系合金熱処理鋼材に関するものである。 The present invention relates to a method for producing a precipitation hardening austenitic alloy steel, a method for producing a heat treated precipitation hardening austenitic alloy steel, a precipitation hardening austenitic alloy steel, and a heat treated precipitation hardening austenitic alloy steel.
　ＳＵＨ６６０等の析出硬化型オーステナイト系合金は、幅広い温度で良好な強度特性を有し、水素環境下における耐水素脆性にも優れることから、水素ステーション（水素スタンド）用途に適する部材として知られている。例えば特許文献１には、水素エネルギー設備に適するＡ２８６合金（ＳＵＨ６６０相当材）について、総鍛造比５：１で鍛造して鍛造品を得ることが記載されている。 Precipitation hardening austenitic alloys such as SUH660 have good strength characteristics over a wide range of temperatures and are excellent in hydrogen embrittlement resistance in a hydrogen environment, so they are known as members suitable for hydrogen station (hydrogen station) applications. . For example, Patent Document 1 describes obtaining a forged product by forging an A286 alloy (equivalent to SUH660) suitable for hydrogen energy equipment at a total forging ratio of 5:1.
　上述したような析出硬化型オーステナイト系合金は耐水素脆性に優れるが、高温環境下や高圧水素ガス中においては水素の存在で塑性変形に伴う変形の局所化が生じ、積層欠陥が形成され易い。そのような欠陥はき裂の発生原因になり易く、大気中よりも引張強度等の機械特性が低下する傾向にある。例えば非特許文献１には、析出強化したＡ２８６試験片に水素チャージを施したところ、試験片の引張強度等の特性が水素量の増加に伴い低下していることについて記載されている。そのような背景から、析出硬化型オーステナイト系合金においても材料のさらなる高強度化が要求されている。非特許文献２では、水素脆化感受性を増加させるη層の析出を抑制するためにＡ２８６合金の組成を改良して高強度化する旨が記載されている。 Although precipitation hardening austenitic alloys such as those described above are excellent in resistance to hydrogen embrittlement, the presence of hydrogen causes localization of plastic deformation due to the presence of hydrogen, and stacking faults are likely to form. Such defects tend to cause cracks, and mechanical properties such as tensile strength tend to be lower than in air. For example, Non-Patent Document 1 describes that when a precipitation-strengthened A286 test piece is charged with hydrogen, properties such as tensile strength of the test piece decrease as the amount of hydrogen increases. Against this background, even precipitation hardening austenitic alloys are required to have higher strength materials. Non-Patent Document 2 describes that the composition of the A286 alloy is improved to increase the strength in order to suppress the precipitation of the η layer that increases the susceptibility to hydrogen embrittlement.
中国特許出願公開第１１３５４９８２号明細書Chinese Patent Application Publication No. 11354982
　非特許文献２に記載の方法は高温強度の機械特性向上に有効であるが、強度の向上に伴って伸び等の延性低下が懸念される。また非特許文献２では特性改善のためにＷを比較的多めに含有させているが、Ｗは高価な原料のひとつであるので、産業用途製品では出来る限り使用を控えたい原料の一つである。そこで本発明の目的は、鋼材の組成改良を行わなくても機械特性を向上させることができ、高圧水素環境下における部品の長寿命化が期待できる析出硬化型オーステナイト系合金鋼材および析出硬化型オーステナイト系合金熱処理鋼材の製造方法を提供することである。 The method described in Non-Patent Document 2 is effective for improving mechanical properties of high-temperature strength, but there is concern that ductility such as elongation will decrease as strength improves. In addition, in Non-Patent Document 2, a relatively large amount of W is contained in order to improve the characteristics, but W is one of the expensive raw materials, so it is one of the raw materials that should be avoided as much as possible in industrial products. . Therefore, the object of the present invention is to provide a precipitation hardening austenitic alloy steel material and a precipitation hardening austenitic steel material that can improve mechanical properties without improving the composition of the steel material and can be expected to extend the life of parts in a high-pressure hydrogen environment. Another object of the present invention is to provide a method for producing a heat-treated steel material based on a series alloy.
　本発明は上述した課題に鑑みてなされたものである。
　すなわち本発明の一態様は、析出硬化型オーステナイト系合金の組成を有する鍛造用素材を準備し、総鍛錬成形比が３０以上となるように複数回の熱間鍛造を行い、柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である鍛造材とする熱間鍛造工程を含む、析出硬化型オーステナイト系合金鋼材の製造方法である。 The present invention has been made in view of the problems described above.
That is, in one aspect of the present invention, a forging material having a composition of a precipitation hardening austenitic alloy is prepared, hot forged multiple times so that the total forging forming ratio is 30 or more, and a columnar shape and perpendicular to the axis are formed. A method for producing a precipitation hardening austenitic alloy steel including a hot forging step to obtain a forged material having an area equivalent circle diameter of 100 mm or more in a directional cross section.
　本発明の他の一態様は、前記鍛造材を用いて、更に溶体化処理及び時効処理を行って熱処理材を得る熱処理工程を含む、析出硬化型オーステナイト系合金熱処理鋼材の製造方法である。 Another aspect of the present invention is a method for producing a precipitation hardening type austenitic alloy heat-treated steel material, including a heat treatment step of obtaining a heat-treated material by further performing solution treatment and aging treatment using the forged material.
　本発明の他の一態様は、ＧＯＳ（Ｇｒａｉｎ　Ｏｒｉｅｎｔａｔｉｏｎ　Ｓｐｒｅａｄ）値が１．０°以上となる結晶粒を面積比率で５０％以上有し、柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である、析出硬化型オーステナイト系合金鋼材である。 Another aspect of the present invention has a crystal grain having a GOS (Grain Orientation Spread) value of 1.0° or more in an area ratio of 50% or more, and has a columnar shape and an area circle equivalent diameter of a cross section in the direction perpendicular to the axis of 100 mm. The above is the precipitation hardening type austenitic alloy steel material.
　本発明の他の一態様は、熱処理鋼材の軸直角断面における面積円相当径をＤとしたとき、熱処理鋼材の表面からＤ／４の深さおよびＤ／２の深さにおいて、結晶粒度番号が４．０以上、０．２％耐力が５９０ＭＰａ以上、引張強さが９００ＭＰａ以上、伸びが１５％以上であり、
　柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である、析出硬化型オーステナイト系合金熱処理鋼材である。 In another aspect of the present invention, when the equivalent circle diameter in the axis-perpendicular cross section of the heat-treated steel is D, the grain size number is at a depth of D/4 and a depth of D/2 from the surface of the heat-treated steel. 4.0 or more, 0.2% yield strength of 590 MPa or more, tensile strength of 900 MPa or more, elongation of 15% or more,
It is a precipitation hardening type austenitic alloy heat-treated steel material having a columnar shape and an area-equivalent circle diameter of a cross section in the direction perpendicular to the axis of 100 mm or more.
　本発明によれば、機械特性をさらに向上でき、高圧水素環境下における長寿命化が期待できる析出硬化型オーステナイト系合金鋼材および析出硬化型オーステナイト系合金熱処理鋼材を製造することができる。 According to the present invention, it is possible to manufacture a precipitation hardening austenitic alloy steel material and a precipitation hardening austenitic alloy heat-treated steel material that can further improve mechanical properties and can be expected to have a long life in a high-pressure hydrogen environment.
鍛錬成形比を説明するための模式図である。It is a schematic diagram for demonstrating a forging molding ratio. 他の鍛錬成形比を説明するための模式図である。It is a schematic diagram for demonstrating other forging molding ratios. 実施例における機械特性測定用試料採取位置を示す模式図である。FIG. 4 is a schematic diagram showing the sample collection position for mechanical property measurement in the example. 実施例におけるＥＢＳＤ用試料採取位置を示す模式図である。FIG. 4 is a schematic diagram showing EBSD sample collection positions in the example.
　以下、本発明を詳細に説明する。ただし、本発明は、ここで取り挙げた実施形態に限定されるものではなく、その発明の技術的思想を逸脱しない範囲で適宜組み合わせや改良が可能である。本発明は析出硬化型オーステナイト系合金鋼材を対象とする。この析出硬化型オーステナイト系合金鋼材とは、ＪＩＳ－Ｇ－４３１１に記載されているＳＵＨ３０９、ＳＵＨ３１０、ＳＵＨ３３０、ＳＵＨ６６０、ＳＵＨ６６１、およびこれらの改良材を示す。具体的には、質量％でＮｉ：１０～４０％、Ｃｒ：１０～３０％を含み、Ｆｅ＋Ｎｉ＋Ｃｒが質量％で９５％以上であることが好ましい。または、Ｎｉ：１０～４０％、Ｃｒ：１０～３０％を含み、残部Ｆｅおよび不可避的不純物とすることができる。
　より好ましいＮｉ量の下限は質量％で２０％であり、より好ましいＮｉ量の上限は質量％で３０％である。また、より好ましいＣｒの上限は質量％で２０％である。さらに、硬さや高温強度等を向上させるために、Ｖ、Ｓｉ、Ｍｎ、Ａｌ、Ｂ、Ｔａ、Ｗ、Ｔｉ、Ｍｏ、Ｎｂの一種または二種以上の元素を、質量％にて合計で最大５．０％まで含有しても良い。その他、不可避的に含まれる不純物元素として、例えばＣ、Ｓ、Ｐ、Ｏが挙げられ、例えばそのそれぞれの上限を０．１％とすることが好ましい。 The present invention will be described in detail below. However, the present invention is not limited to the embodiments mentioned here, and appropriate combinations and improvements are possible without departing from the technical idea of the invention. The present invention is directed to a precipitation hardening austenitic alloy steel material. This precipitation hardening type austenitic alloy steel refers to SUH309, SUH310, SUH330, SUH660, SUH661 and their improved materials described in JIS-G-4311. Specifically, it is preferable that Ni: 10 to 40% and Cr: 10 to 30% be included in mass %, and that Fe+Ni+Cr be 95% or more in mass %. Alternatively, it may contain Ni: 10 to 40%, Cr: 10 to 30%, and the balance may be Fe and unavoidable impurities.
A more preferable lower limit of the Ni amount is 20% by mass, and a more preferable upper limit of the Ni amount is 30% by mass. A more preferable upper limit of Cr is 20% by mass. Furthermore, in order to improve hardness, high-temperature strength, etc., one or more elements of V, Si, Mn, Al, B, Ta, W, Ti, Mo, and Nb are added in a total of up to 5% by mass. It may be contained up to .0%. Other impurity elements that are inevitably included include, for example, C, S, P, and O, and the upper limit of each of these elements is preferably set to 0.1%.
　本実施形態の製造方法では、まず析出硬化型オーステナイト系合金組成を有する鍛造用素材を準備する。この鍛造用素材は、鋳造によって得ることができる鋼塊とすることが好ましい。また鋼塊に熱間プレスや熱間圧延等の熱間塑性加工を行ったのち、丸棒または角棒の形状に機械加工した鋼片（ビレット、ブルーム等）へ均質化熱処理を施した場合、本鋼片を鍛造用素材としてもよい。鋼塊を製造する際には成分偏析や非金属介在物を低減させる目的で再溶解を施してもよい。 In the manufacturing method of this embodiment, first, a forging material having a precipitation hardening austenitic alloy composition is prepared. This forging material is preferably a steel ingot that can be obtained by casting. In addition, when a steel ingot is subjected to hot plastic working such as hot pressing or hot rolling, and then homogenized heat treatment is applied to a steel billet (billet, bloom, etc.) machined into a round or square bar shape, The billet may be used as a forging material. When producing a steel ingot, remelting may be performed for the purpose of reducing component segregation and non-metallic inclusions.
　続いて準備した上記鍛造用素材を加熱炉で加熱して、複数回の熱間鍛造を行い、析出硬化型オーステナイト系合金鋼材を得る。本発明ではこの熱間鍛造の際、総鍛錬成形比（以下、総鍛造比とも記載する）が３０以上となるように鍛造する。これにより、鍛造材の中心部まで加工歪みを導入することができ、動的再結晶に伴う再結晶化が生じることで鍛造材の機械特性を向上させることができる。なお本発明における「総鍛錬成形比（総鍛造比）」とは、ＪＩＳ－Ｇ－０７０１に記載されている実体鍛錬の鍛錬成形比を用いて導出する。例えば図１に示す熱間鍛造を実施した場合、（（Ｓ０／Ｓ１）×(Ｓ１／Ｓ２)×・・・・・×(Ｓｎ－１／Ｓｎ)）の式が総鍛錬成形比となる。なお上記の式において、Ｓ０、Ｓ１、Ｓ２・・・・・Ｓｎ－１、Ｓｎは断面積である。総鍛造比が３０を超える加工例としては、直径１００ｍｍの丸棒を鍛造用素材とした場合、直径１００ｍｍ→直径５０ｍｍへ実体鍛錬、直径５０ｍｍ→直径１８ｍｍへ実体鍛錬を実施する場合、総鍛錬成形比は３０．８となり、本発明の要件を満たす。好ましい総鍛造比の下限は３５であり、より好ましい総鍛造比の下限は４０である。総鍛造比の上限については特に制限しないが、鍛造回数が多いほど製造コストがかかるため、例えば２００とすることが現実的であり、１５０とすることもできる。 Subsequently, the prepared forging material is heated in a heating furnace and hot forged a plurality of times to obtain a precipitation hardening austenitic alloy steel material. In the present invention, during this hot forging, forging is performed so that the total forging forming ratio (hereinafter also referred to as the total forging ratio) is 30 or more. As a result, it is possible to introduce working strain to the central part of the forged material, and recrystallization due to dynamic recrystallization occurs, thereby improving the mechanical properties of the forged material. The "total forging forming ratio (total forging ratio)" in the present invention is derived using the forging forming ratio of actual forging described in JIS-G-0701. For example , when the hot forging shown in FIG . It becomes the forging molding ratio. In the above equations, S 0 , S 1 , S 2 . . . S n-1 , S n are cross-sectional areas. As an example of processing in which the total forging ratio exceeds 30, when a round bar with a diameter of 100 mm is used as a forging material, the material forging is performed from 100 mm in diameter to 50 mm in diameter, and 50 mm in diameter to 18 mm in diameter. The ratio becomes 30.8, satisfying the requirements of the present invention. A preferred lower limit for the total forging ratio is 35, and a more preferred lower limit for the total forging ratio is 40. The upper limit of the total forging ratio is not particularly limited, but since the manufacturing cost increases as the number of forgings increases, it is realistic to set it to 200, and it may be set to 150, for example.
　本実施形態では、鍛造材のサイズを極端に落とさずに総鍛造比を大きくするため、据え込み鍛錬を少なくとも一回以上実施することが好ましい。なお本実施形態では実体鍛錬によって付与される加工歪みが機械特性の向上に主体的に寄与している傾向にあるため、据え込み鍛錬を実施する際、本実施形態では総鍛造比の計算時に、据え込み鍛錬時の鍛錬成形比（据込比）を含めずに計算する。例えば図２に示す熱間鍛造を実施した場合（Ｓ１－Ｓ２間が据え込み鍛錬）、（（Ｓ０／Ｓ１）×(Ｓ２／Ｓ３)×・・・・・×(Ｓｎ－１／Ｓｎ)）の式が総鍛錬成形比となる。据え込み鍛造を組み合わせることで、面積円相当径が１００ｍｍ以上といった大型の鍛造品に関しても十分な加工歪みを導入させることができる。なお鍛造時の加熱炉の温度は８００～１３００℃であることが好ましく、鍛造終了時の素材の表面温度は６００℃以上であることが好ましい。 In this embodiment, in order to increase the total forging ratio without drastically reducing the size of the forged material, it is preferable to perform upset forging at least once. In the present embodiment, the working strain imparted by actual forging tends to mainly contribute to the improvement of mechanical properties. Calculate without including the forging forming ratio (upsetting ratio) at the time of upsetting forging. For example, when the hot forging shown in FIG. 2 is performed (S 1 -S 2 is upset forging), ((S 0 /S 1 ) × (S 2 /S 3 ) × . n−1 /S n )) is the total forging ratio. By combining upset forging, it is possible to introduce a sufficient amount of processing strain even in a large forged product having an area equivalent circle diameter of 100 mm or more. The temperature of the heating furnace during forging is preferably 800 to 1300° C., and the surface temperature of the material at the end of forging is preferably 600° C. or higher.
　本発明における「熱間鍛造」は表面が平面または曲面である金敷の上に被加工材を載置し、同じく表面が平面または曲面であるハンマーにより材料を加工する熱間自由鍛造を含むことが加工する形状の自由度の点から好ましい。勿論、複雑な形状へ加工する場合には金型を用いた型入鍛造を実施してもよく、素材を周方向に回転しつつ、素材の全長にわたって４方向から押圧することで鍛造材を得るラジアル鍛造を実施してもよく、またそれらを組み合わせた加工を施してもよい。また分塊圧延と熱間鍛造を組み合わせた加工を施してもよい。分塊圧延を実施する際は、圧延前の断面積と圧延後の断面積を測定して上述した実体鍛錬の鍛錬成形比を導出する式に当てはめ、総鍛錬成形比を求めても良い。
　また、上述した本実施形態の総鍛造比を達成するために、実体鍛錬は少なくとも三回以上行うことが好ましい。これは析出硬化型オーステナイト系合金鋼材の変形抵抗が大きいため、鍛造一回あたりの加工率は小さいほうが安定加工できるためである。また据え込み鍛造の回数は、面積円相当径が１００ｍｍ以上といった大型鍛造品においても内部まで加工歪を導入するため、少なくとも二回以上行うことが好ましい。 The "hot forging" in the present invention may include hot free forging in which a workpiece is placed on an anvil with a flat or curved surface and the material is processed with a hammer with a flat or curved surface. It is preferable from the viewpoint of the degree of freedom of the shape to be processed. Of course, when processing into a complicated shape, die forging using a die may be performed, and a forged material is obtained by pressing the material from four directions over the entire length of the material while rotating the material in the circumferential direction. Radial forging may be performed, or a combination thereof may be applied. Further, processing combining blooming rolling and hot forging may be applied. When blooming is performed, the cross-sectional area before rolling and the cross-sectional area after rolling may be measured and applied to the formula for deriving the forging ratio of the physical forging described above to obtain the total forging ratio.
Further, in order to achieve the above-described total forging ratio of the present embodiment, it is preferable to perform the actual forging at least three times. This is because the deformation resistance of precipitation hardening austenitic alloy steel is high, and therefore the smaller the working rate per forging, the more stable the working. Further, the number of upset forgings is preferably at least two or more because processing strain is introduced to the inside of a large forged product having an area equivalent circle diameter of 100 mm or more.
　本実施形態では、熱間鍛造工程により得られた鍛造品（析出硬化型オーステナイト系合金鋼材）に対して溶体化処理および時効処理を行い、析出硬化型オーステナイト系合金熱処理鋼材を得る。これにより鋼材の結晶粒度ばらつきを抑制して均一な細粒組織とし、製品の機械的強度をさらに向上させることができる。好ましい溶体化処理温度は８５０～１０５０℃であり、より好ましくは９００～１０００℃である。また好ましい時効処理温度は６５０～８００℃であり、より好ましくは７００～７６０℃である。 In the present embodiment, a forged product (precipitation hardening austenitic alloy steel material) obtained by a hot forging process is subjected to solution treatment and aging treatment to obtain a precipitation hardening austenitic alloy heat treated steel material. As a result, it is possible to suppress variations in the grain size of the steel material and obtain a uniform fine-grained structure, thereby further improving the mechanical strength of the product. A preferred solution treatment temperature is 850 to 1050°C, more preferably 900 to 1000°C. Also, the aging treatment temperature is preferably 650 to 800°C, more preferably 700 to 760°C.
　続いて、本発明の製造方法により得ることができる、本発明の析出硬化型オーステナイト系合金鋼材について説明する。本発明の析出硬化型オーステナイト系合金鋼材は、ＧＯＳ（Ｇｒａｉｎ　Ｏｒｉｅｎｔａｔｉｏｎ　Ｓｐｒｅａｄ）値が１．０°以上となる結晶粒を面積比率で５０％以上有する。好ましい面積比率は６０％以上である。このＧＯＳ値は、従来知られる「ＳＥＭ－ＥＢＳＤ法（電子線後方散乱回折法）」によって測定することができ、結晶粒を構成する点（ピクセル）の方位差を計算することで導出することができる。ＧＯＳ値により得られる結晶方位差は加工によって合金中に付与される歪みを示す指標であり、ＧＯＳ値が１．０°以上となる結晶粒を面積比率で５０％以上有する場合、溶体化処理後に結晶粒度のばらつきが少ない、均一な細粒組織を得やすい傾向にある。また加工歪が付与されていない粗大な未再結晶粒が少なく、機械特性、特に０．２％耐力を向上させることができる傾向にある。ＧＯＳ値が１．０°以上となる結晶粒の面積比率が５０％未満の場合、上述した粗大な未再結晶粒が増加し、０．２％耐力等の機械特性を低下させる惧れがある。本実施形態のＧＯＳ値は、鍛造材の表面から軸心方向に深さのＤ／４およびＤ／２の位置において試料を採取し（Ｄは軸心を通る表面間の距離。例えば、直径に相当）、測定することにより導出することができる。また、面積比率を観察する断面は、軸直角方向断面と軸方向断面もあるが、棒材の軸直角方向断面および軸方向断面で観察した場合の両方において、ＧＯＳ値が１．０°以上となる結晶粒の面積比率が５０％以上であることが好ましい。なお、本発明におけるＧＯＳ値は、鍛造材（溶体化処理および時効処理前）から試料を採取して測定したものである。また、溶体化熱処理および時効熱処理後のＧＯＳ値が１．０°以上となる結晶粒の面積比率は、鍛造による歪みが開放されるため、５０％未満と低い値となる傾向にある。なお本実施形態において上述したＧＯＳ値は、得られた鍛造材の表面から、図３に示すような方向で、軸心方向に深さＤ／４（Ｄ：面積円相当径の直径）の位置およびＤ／２の位置より試験片を採取して測定すればよい。特に深さＤ／２の位置は鋼材の中心に相当し、歪みが最も入りにくいため、この深さＤ／２の位置から採取した試験片においても本発明に規定する特性を満たすことが好ましい。 Next, the precipitation hardening austenitic alloy steel material of the present invention, which can be obtained by the manufacturing method of the present invention, will be described. The precipitation hardening austenitic alloy steel material of the present invention has crystal grains having a GOS (Grain Orientation Spread) value of 1.0° or more in an area ratio of 50% or more. A preferable area ratio is 60% or more. This GOS value can be measured by the conventionally known "SEM-EBSD method (electron beam backscatter diffraction method)", and can be derived by calculating the misorientation of points (pixels) constituting the crystal grain. can. The crystal orientation difference obtained by the GOS value is an index that indicates the strain imparted to the alloy by working. There is a tendency to easily obtain a uniform fine-grained structure with little variation in grain size. In addition, the number of coarse unrecrystallized grains to which processing strain is not imparted is small, and there is a tendency that mechanical properties, particularly 0.2% yield strength, can be improved. If the area ratio of crystal grains with a GOS value of 1.0° or more is less than 50%, the above-mentioned coarse non-recrystallized grains increase, and there is a risk of deteriorating mechanical properties such as 0.2% yield strength. . The GOS values of this embodiment are obtained by taking samples at positions D/4 and D/2 in depth from the surface of the forging in the axial direction (D is the distance between the surfaces passing through the axis. equivalent), which can be derived by measurement. In addition, there are cross sections in the direction perpendicular to the axis and cross sections in the axial direction for observing the area ratio. It is preferable that the area ratio of the crystal grains is 50% or more. The GOS value in the present invention is measured by taking a sample from the forged material (before solution treatment and aging treatment). In addition, the area ratio of crystal grains having a GOS value of 1.0° or more after solution heat treatment and aging heat treatment tends to be a low value of less than 50% because strain due to forging is released. It should be noted that the GOS value described above in this embodiment is the direction shown in FIG. and D/2. In particular, the position of depth D/2 corresponds to the center of the steel material, and strain is least likely to occur, so it is preferable that the test piece taken from the position of depth D/2 also satisfies the characteristics specified in the present invention.
　本発明の析出硬化型オーステナイト系合金鋼材は、柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上の鋼材を対象とする。前述した本発明の製造方法により得られた本発明の鋼材は、面積円相当径が１００ｍｍ以上(好ましくは２００ｍｍ以上であり、３００ｍｍ以上であり、４００ｍｍ以上)と大型な鋼材においても、材料中心部まで加工歪が導入されている。ここで「柱状形状」とは、例えば、円柱状、角柱状を指し、軸方向にテーパーが形成されていてもよい。なおテーパーが形成されている場合、本発明軸直角方向断面の面積円相当径は、鋼材の長さをＬとした場合、Ｌ／２の位置における軸直角断面を測定すればよい。 The precipitation hardening austenitic alloy steel material of the present invention is a steel material having a columnar shape and an area circle equivalent diameter of a cross section in the direction perpendicular to the axis of 100 mm or more. The steel material of the present invention obtained by the manufacturing method of the present invention described above has an area circle equivalent diameter of 100 mm or more (preferably 200 mm or more, 300 mm or more, or 400 mm or more). Processing strain is introduced up to Here, the “columnar shape” refers to, for example, a columnar shape or a prismatic shape, and may be tapered in the axial direction. When a taper is formed, the area circle equivalent diameter of the cross section perpendicular to the axis of the present invention can be obtained by measuring the cross section perpendicular to the axis at the position of L/2, where L is the length of the steel material.
　本発明の製造方法により得られた本発明の析出硬化型オーステナイト系合金熱処理鋼材（溶体化熱処理および時効処理を施した材料）は、結晶粒度番号が４．０以上であることが好ましい。前述したように、溶体化熱処理および時効処理前の析出硬化型オーステナイト系合金鋼材は、ＧＯＳ値が１．０°以上となる結晶粒を面積比率で５０％以上有するため、溶体化熱処理および時効処理後に粗大な未再結晶粒が形成されにくく、均一な細粒組織を得やすい傾向にある。そしてこの結晶粒度番号を４．０以上に保つことによって、０．２％耐力が５９０ＭＰａ以上、引張強さが９００ＭＰａ以上、伸びが１５％以上である、良好な機械特性を有した析出硬化型オーステナイト系合金鋼材を得ることができる。好ましい０．２％耐力は６００ＭＰａ以上であり、より好ましい０．２％耐力は６３０ＭＰａ以上であり、さらに好ましい０．２％耐力は６６０ＭＰａ以上である。好ましい引張強さは９５０ＭＰａ以上であり、より好ましい引張強さは９８０ＭＰａ以上である。また好ましい伸びの下限２０％であり、好ましい伸びの上限は３０％である。結晶粒度番号の上限は特に限定しないが、過剰に微細な結晶粒とするためには鍛造比も過大に設定しなければならず、製造が困難となるため、例えば上限を１０．０と設定してもよい。好ましい結晶粒度番号の上限は８．０、より好ましい結晶粒度番号の上限は７．０である。特に０．２％耐力は結晶粒サイズに影響を受け、十分な加工歪が付与されていない粗大な未再結晶粒があることで低下しやすい傾向にあるが、本発明の製法により得られた本発明の鋼材であれば、０．２％耐力を低下させることなく良好な値とすることが可能である。なお本実施形態において上述した結晶粒度、０．２％耐力、引張強さ、伸びは、ＧＯＳ値と同様、得られた鍛造材の表面から、図３に示すような方向で、軸心方向に深さＤ／４（Ｄ：面積円相当径の直径）の位置およびＤ／２の位置より試験片を採取して測定する。特に深さＤ／２の位置は鋼材の中心に相当し、歪みが最も入りにくいことから均一微細組織が得られにくいため、この深さＤ／２の位置から採取した試験片においても本発明の規定を満たすことが好ましい。 The precipitation hardening type austenitic alloy heat-treated steel material of the present invention (material subjected to solution heat treatment and aging treatment) obtained by the production method of the present invention preferably has a grain size number of 4.0 or more. As described above, the precipitation hardening austenitic alloy steel material before solution heat treatment and aging treatment has crystal grains with a GOS value of 1.0° or more in an area ratio of 50% or more. Coarse non-recrystallized grains are less likely to be formed later, and a uniform fine grain structure tends to be easily obtained. By keeping this grain size number at 4.0 or more, precipitation hardened austenite having good mechanical properties such as 0.2% proof stress of 590 MPa or more, tensile strength of 900 MPa or more, and elongation of 15% or more system alloy steel can be obtained. The 0.2% proof stress is preferably 600 MPa or more, more preferably 630 MPa or more, and still more preferably 660 MPa or more. A preferable tensile strength is 950 MPa or more, and a more preferable tensile strength is 980 MPa or more. The preferable lower limit of elongation is 20%, and the preferable upper limit of elongation is 30%. The upper limit of the crystal grain size number is not particularly limited, but in order to make the crystal grains excessively fine, the forging ratio must be set too high, making manufacturing difficult. may A preferable upper limit of the grain size number is 8.0, and a more preferable upper limit of the grain size number is 7.0. In particular, the 0.2% proof stress is affected by the grain size and tends to decrease due to the presence of coarse unrecrystallized grains to which sufficient processing strain has not been applied. With the steel material of the present invention, it is possible to obtain a good value without lowering the 0.2% yield strength. Note that the grain size, 0.2% yield strength, tensile strength, and elongation described above in this embodiment are measured in the axial direction from the surface of the obtained forging material in the direction shown in FIG. A test piece is taken from the position of depth D/4 (D: the diameter of the equivalent circle diameter) and the position of D/2 and measured. In particular, the position of depth D/2 corresponds to the center of the steel material, and strain is most difficult to enter, so it is difficult to obtain a uniform microstructure. It is preferable to meet the regulations.
　以下の実施例で本発明を更に詳しく説明する。
（実施例１）
　表１に示す組成を有する鋼塊（ＳＵＨ６６０相当材）を準備して本発明例および比較例用の柱状鍛造用素材とし、それぞれに熱間鍛造を施した。本発明例は、鍛造用素材に総鍛造比１０１となるように実体鍛造と据え込み鍛造を複数回実施し、柱状素材の軸直角断面の面積円相当径で４７０ｍｍである鍛造材を得た。比較例は、鍛造用素材に総鍛造比２６となるように実体鍛造と据え込み鍛造を複数回実施し柱状素材の軸直角断面の面積円相当径で６２０ｍｍである鍛造材を得た。その後得られた鍛造材の表面から、図３の「軸方向より採取する素材」に示すような方向で、軸心方向に深さＤ／４（Ｄ：面積円相当径の直径）の位置と、Ｄ／２の位置より試験片（１３×１３×１００ｍｍ）を軸方向にて採取し、溶体化処理、時効処理を施して熱処理材とした後、各種機械特性と結晶粒度番号を測定した。各種機械特性測定に用いた試験片はＪＩＳＺ２２４１で定められるＪＩＳ１４Ａ号試験片を使用し、ＪＩＳＺ２２４１の金属材料引張試験方法に基づいて実施した。結晶粒度番号は、ＪＩＳ－Ｇ－０５５１に則り、結晶粒度標準図プレート１にて粒度番号を判定した。熱処理条件と各種機械特性と結晶粒度番号の結果を表２に示す。
　表２より、本発明例の試料はいずれも比較例よりも０．２％耐力、引張強さが高く、伸びも同水準であり、優れた機械特性を有することが確認できた。また、本発明例の試料の結晶粒度は比較例よりも細粒であり、結晶粒度のバラつきも、比較例より小さいことも確認できた。 The following examples further illustrate the invention.
(Example 1)
Steel ingots (equivalent to SUH660) having the compositions shown in Table 1 were prepared as raw materials for columnar forgings for the examples of the present invention and the comparative examples, and hot forging was applied to each of them. In the example of the present invention, the forging material was subjected to multiple forgings and upset forgings so that the total forging ratio was 101, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 470 mm was obtained. In the comparative example, the forging material was subjected to multiple forgings and upset forgings so that the total forging ratio was 26, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 620 mm was obtained. From the surface of the forged material obtained after that, in the direction shown in FIG. , A test piece (13 x 13 x 100 mm) was taken in the axial direction from the position of D/2, subjected to solution treatment and aging treatment to obtain a heat-treated material, and various mechanical properties and grain size numbers were measured. A JIS No. 14A test piece defined by JISZ2241 was used as the test piece used for measuring various mechanical properties, and the test was performed based on the JISZ2241 metal material tensile test method. The grain size number was determined according to JIS-G-0551 with a grain size standard chart plate 1. Table 2 shows the results of heat treatment conditions, various mechanical properties, and grain size numbers.
From Table 2, it was confirmed that the samples of the invention examples all had higher 0.2% proof stress and tensile strength than the comparative examples, had the same level of elongation, and had excellent mechanical properties. In addition, it was confirmed that the crystal grain size of the sample of the invention example was finer than that of the comparative example, and the variation of the crystal grain size was also smaller than that of the comparative example.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　また本発明例の鍛造材について、図３の「軸直角方向より採取する素材」に示すような方向で表面から軸心方向に深さＤ／４の位置と、Ｄ／２の位置より試験片を軸直角方向にて採取し、溶体化処理、時効処理を施して熱処理材とした後、各種機械特性を採取した。熱処理条件と各種機械特性の結果を表３に示す。表３より、本発明例の軸直角方向から採取した試料の各種機械的特性は、軸方向で得られたものと同水準の優れた機械特性　
であることが確認できた。 Further, regarding the forged material of the present invention example, the test piece was measured from the position of depth D/4 and the position of D/2 in the axial direction from the surface in the direction shown in FIG. was sampled in the direction perpendicular to the axis, subjected to solution treatment and aging treatment to obtain a heat-treated material, and then various mechanical properties were sampled. Table 3 shows the heat treatment conditions and the results of various mechanical properties. From Table 3, it can be seen that the various mechanical properties of the samples sampled in the direction perpendicular to the axis of the present invention are excellent at the same level as those obtained in the axial direction.
It was confirmed that
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　続いて、本発明例と比較例で得られた鍛造材（熱処理前）の表面から軸心方向に深さＤ／４位置とＤ／２位置より軸方向と軸直角方向の２種類の試料を採取し、それぞれの試料についてＧＯＳ値を確認した。ＧＯＳ値は、ＺＥＩＳＳ製の電界放射型走査電子顕微鏡とＴＳＬ社製のＥＢＳＤ測定・解析システムＯＩＭ(Ｏｒｉｅｎｔａｔｉｏｎ－Ｉｍａｇｉｎｇ－Ｍｉｃｒｏｇｒａｐｈ)とを用い、試料の縦断面(軸方向断面)と横断面(軸直角方向断面)を観察し、図４に示すようにそれぞれの断面から測定用試料（１１×１０×５ｍｍ）を採取した。測定面は１１×１０ｍｍとし、測定視野は１５００μｍ×１５００μｍであり、隣接するピクセル間のステップ距離は３．０μｍとした。また、隣接するピクセル間の方位差が５°以上の境界を結晶粒界と判別する条件で観察を行い、得られたＧＯＳ値のマップから、ＧＯＳ値が１．０°以上の結晶粒が占める観察視野全体に対する面積率を求めた。表４に観察結果を示す。表４の結果より、本発明例は縦断面および横断面においてもＧＯＳ値１．０°以上の占有率が５０％以上であり、結晶粒度のバラつきも小さく、熱処理後における軸方向と軸直角方向の０．２％耐力、引張強さ、伸びのいずれも良好となる結果であった。 Subsequently, from the surface of the forged material (before heat treatment) obtained in the present invention example and the comparative example, two types of samples were taken in the axial direction and the axial direction from the depth D / 4 position and D / 2 position in the axial direction. A sample was taken and the GOS value was confirmed for each sample. The GOS value is obtained by using a field emission scanning electron microscope manufactured by ZEISS and an EBSD measurement and analysis system OIM (Orientation-Imaging-Micrograph) manufactured by TSL. 4, and samples for measurement (11×10×5 mm) were taken from each cross section as shown in FIG. The measurement surface was 11×10 mm, the measurement field was 1500 μm×1500 μm, and the step distance between adjacent pixels was 3.0 μm. Observation was performed under the condition that a boundary with an orientation difference of 5° or more between adjacent pixels was determined to be a grain boundary. From the obtained GOS value map, crystal grains with a GOS value of 1.0° or more occupied. The area ratio with respect to the entire observation field was obtained. Table 4 shows the observation results. From the results in Table 4, in the examples of the present invention, the occupancy rate of GOS values of 1.0° or more is 50% or more in both the longitudinal and cross sections, the variation in crystal grain size is small, and the axial direction and the axis-perpendicular direction after heat treatment. 0.2% yield strength, tensile strength, and elongation were all good results.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
（実施例２）
　表５に示す組成を有する鋼塊(ＳＵＨ６６０相当材)を準備して本発明例の柱状鍛造用素材とし、熱間鍛造を施した。本発明例は、鍛造用素材に総鍛造比が３８または５０となるように実体鍛造とすえ込鍛造を複数回実施し、柱状素材の軸直角断面の面積円相当径で５００ｍｍと４４０ｍｍである鍛造材を得た。その後、溶体化処理、時効処理を施した鍛造材の表面から軸心方向に深さＤ／４の位置より軸方向にて試験片を採取し、各種機械特性と結晶粒度番号を測定した。各種機械特性と結晶粒度番号の結果を表６に示す。ここで、本発明である試料Ｎｏ．１５およびＮｏ．１６で測定した耐力は、歪が０．１％時点での耐力（０．１％耐力）であることから、０．２％耐力はＮｏ．１５で６０５ＭＰａ以上、Ｎｏ．１６で６００ＭＰａ以上であることが示唆される。本発明例の試料は実施例１の比較例よりも０.２％耐力および引張強さが高く、優れた機械特性を有することが確認できた。 (Example 2)
A steel ingot (equivalent to SUH660) having the composition shown in Table 5 was prepared and used as a material for columnar forging of the present invention example, and subjected to hot forging. In the example of the present invention, the forging material was subjected to multiple times of solid forging and upsetting so that the total forging ratio was 38 or 50. got the wood. After that, a test piece was taken in the axial direction from a position of depth D/4 in the axial direction from the surface of the forged material subjected to solution treatment and aging treatment, and various mechanical properties and grain size numbers were measured. Table 6 shows the results of various mechanical properties and grain size numbers. Here, sample no. 15 and no. The yield strength measured in No. 16 is the yield strength when the strain is 0.1% (0.1% yield strength). 605 MPa or more at No. 15; 16 is 600 MPa or more. It was confirmed that the samples of the present invention had higher 0.2% proof stress and tensile strength than the comparative example of Example 1, and had excellent mechanical properties.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
（実施例３）
　表７に示す組成を有する鋼塊(ＳＵＨ６６０相当材)を準備して、本発明例の柱状鍛造用素材とし、熱間鍛造を施した。本発明例は、鍛造用素材に総鍛造比が６３となるように実体鍛造とすえ込鍛造を複数回実施し、柱状素材の軸直角断面の面積円相当径で２００ｍｍである鍛造材を得た。その後、溶体化処理、時効処理を施した鍛造材の表面から深さＤ／４の位置より軸方向にて試験片を採取し、各種機械特性と結晶粒度番号を測定した。各種機械特性と結晶粒度番号の結果を表８に示す。本発明である試料Ｎｏ．１７で測定した耐力は、歪が０．１％時点での耐力（０．１％耐力）であることから、０．２％耐力はＮｏ．１７で６４４ＭＰａ以上であることが示唆される。本発明例の試料は実施例１の比較例よりも０．２％耐力および引張強さが高く、優れた機械特性を有することが確認できた。 (Example 3)
A steel ingot (equivalent to SUH660) having the composition shown in Table 7 was prepared, used as a material for columnar forging of the present invention example, and subjected to hot forging. In the example of the present invention, the forging material for forging was subjected to multiple forgings and upsetting forgings so that the total forging ratio was 63, and a forged material having an area circle equivalent diameter of a cross section perpendicular to the axis of the columnar material of 200 mm was obtained. . After that, a test piece was taken in the axial direction from the position of depth D/4 from the surface of the forged material subjected to solution treatment and aging treatment, and various mechanical properties and grain size numbers were measured. Table 8 shows the results of various mechanical properties and grain size numbers. Sample No. of the present invention. The yield strength measured in No. 17 is the yield strength when the strain is 0.1% (0.1% yield strength). 17 is 644 MPa or more. It was confirmed that the sample of the present invention had higher 0.2% proof stress and tensile strength than the comparative example of Example 1, and had excellent mechanical properties.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000008
 
Figure JPOXMLDOC01-appb-T000008
 

Claims (4)

  1. 　析出硬化型オーステナイト系合金の組成を有する鍛造用素材を準備し、総鍛錬成形比が３０以上となるように複数回の熱間鍛造を行い、柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である鍛造材とする熱間鍛造工程を含む、析出硬化型オーステナイト系合金鋼材の製造方法。
          A forging material having a composition of a precipitation hardening austenitic alloy is prepared, and hot forging is performed multiple times so that the total forging forming ratio is 30 or more, and the area circle equivalent diameter of the columnar shape and the cross section in the direction perpendicular to the axis is A method for producing a precipitation hardening austenitic alloy steel material, including a hot forging step to obtain a forged material having a thickness of 100 mm or more.
  2. 　請求項１に記載の析出硬化型オーステナイト系合金鋼材に、更に溶体化処理及び時効処理を行って熱処理鋼材を得る熱処理工程を含む、析出硬化型オーステナイト系合金熱処理鋼材の製造方法。
          A method for producing a heat treated precipitation hardening austenitic alloy steel material, comprising a heat treatment step of further subjecting the precipitation hardening austenitic alloy steel material according to claim 1 to solution treatment and aging treatment to obtain a heat treated steel material.
  3. 　ＧＯＳ（Ｇｒａｉｎ　Ｏｒｉｅｎｔａｔｉｏｎ　Ｓｐｒｅａｄ）値が１．０°以上となる結晶粒を面積比率で５０％以上有し、
    　柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である、析出硬化型オーステナイト系合金鋼材。
          Crystal grains having a GOS (Grain Orientation Spread) value of 1.0° or more have an area ratio of 50% or more,
    A precipitation hardening austenitic alloy steel material having a columnar shape and an equivalent circle diameter of 100 mm or more in a cross section perpendicular to the axis.
  4. 　熱処理鋼材の軸直角断面における面積円相当径をＤとしたとき、熱処理鋼材の表面からＤ／４の深さおよびＤ／２の深さにおいて、結晶粒度番号が４．０以上、０．２％耐力が５９０ＭＰａ以上、引張強さが９００ＭＰａ以上、伸びが１５％以上であり、
    　柱状形状かつ軸直角方向断面の面積円相当径が１００ｍｍ以上である、析出硬化型オーステナイト系合金熱処理鋼材。

          When the equivalent circle diameter in the cross section perpendicular to the axis of the heat-treated steel is D, the grain size number is 4.0 or more and 0.2% at a depth of D/4 and a depth of D/2 from the surface of the heat-treated steel. Yield stress of 590 MPa or more, tensile strength of 900 MPa or more, elongation of 15% or more,
    A precipitation-hardening austenitic alloy heat-treated steel material having a columnar shape and an equivalent circle diameter of a cross section perpendicular to the axis of 100 mm or more.
PCT/JP2023/000383 2022-01-31 2023-01-11 Precipitation-hardening-type austenitic alloy steel material and method for manufacturing same, and precipitation-hardening-type austenitic alloy heat-treated steel material and method for manufacturing same WO2023145423A1 (en)

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JP2006334607A (en) * 2005-05-31 2006-12-14 Sumitomo Metal Ind Ltd Forging method for hard-to-work material
JP2016074946A (en) * 2014-10-06 2016-05-12 山陽特殊製鋼株式会社 Austenitic stainless steel excellent in wire drawing
WO2016152985A1 (en) * 2015-03-25 2016-09-29 日立金属株式会社 Ni-BASED SUPER HEAT-RESISTANT ALLOY AND TURBINE DISK USING SAME
JP2017036477A (en) * 2015-08-10 2017-02-16 新日鐵住金株式会社 Austenitic heat resistant alloy member and manufacturing method therefor
CN111235434A (en) * 2020-03-02 2020-06-05 北京钢研高纳科技股份有限公司 Preparation method of nickel-based deformed superalloy wheel disc forging used at high temperature

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006334607A (en) * 2005-05-31 2006-12-14 Sumitomo Metal Ind Ltd Forging method for hard-to-work material
JP2016074946A (en) * 2014-10-06 2016-05-12 山陽特殊製鋼株式会社 Austenitic stainless steel excellent in wire drawing
WO2016152985A1 (en) * 2015-03-25 2016-09-29 日立金属株式会社 Ni-BASED SUPER HEAT-RESISTANT ALLOY AND TURBINE DISK USING SAME
JP2017036477A (en) * 2015-08-10 2017-02-16 新日鐵住金株式会社 Austenitic heat resistant alloy member and manufacturing method therefor
CN111235434A (en) * 2020-03-02 2020-06-05 北京钢研高纳科技股份有限公司 Preparation method of nickel-based deformed superalloy wheel disc forging used at high temperature

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