WO2023167226A1 - Alloy tool steel for hot working - Google Patents
Alloy tool steel for hot working Download PDFInfo
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- WO2023167226A1 WO2023167226A1 PCT/JP2023/007504 JP2023007504W WO2023167226A1 WO 2023167226 A1 WO2023167226 A1 WO 2023167226A1 JP 2023007504 W JP2023007504 W JP 2023007504W WO 2023167226 A1 WO2023167226 A1 WO 2023167226A1
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- 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
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
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- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
-
- 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
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
Definitions
- This specification discloses an alloy steel suitable for tools used in hot plastic working such as hot forging.
- JIS standard SKD61 is used as alloy steel for hot molds. SKD61 is excellent in high temperature strength. SKT4 standardized by JIS is also used for hot forging dies. SKT4 has excellent toughness.
- Patent Document 1 Japanese Patent Application Laid-Open No. 2011-195917 discloses a hot work tool steel with an improved composition. This tool steel is intended to achieve both high temperature strength and toughness.
- Patent Document 2 Japanese Patent Application Laid-Open No. 2006-322071 discloses an alloy steel having an improved metal structure. The hardness of this alloy steel is great.
- JP 2011-195917 A Japanese Patent Application Laid-Open No. 2006-322071
- An object of the present invention is to provide an alloy tool steel for hot working that is excellent in both toughness and softening resistance.
- alloy tool steel for hot working according to the present invention (hereinafter sometimes referred to as “alloy tool steel according to the present invention") is C: 0.40% by mass or more and 0.60% by mass or less, Si: 0.10% by mass or more and 0.50% by mass or less, Mn: 0.20% by mass or more and 1.10% by mass or less, Ni: 0.20% by mass or more and 2.10% by mass or less, Cr: 0.50% by mass or more and 2.00% by mass or less, Mo: 0.10% by mass or more and 0.60% by mass or less, V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and N: Contains 0.020% by mass or less.
- the balance of the alloy tool steel according to the invention is Fe and impurities.
- the metal structure of the alloy tool steel according to the present invention is martensite or bainite.
- a metallographic structure according to the present invention includes blocks having a diameter of 2.0 ⁇ m or more and 6.0 ⁇ m or less.
- the alloy tool steel according to the present invention has a solute element parameter Q during quenching calculated by the following formula, which is 1.12 or more.
- the alloy tool steel for hot working according to the present invention is excellent in toughness and softening resistance.
- a mold whose material is the alloy tool steel according to the present invention is suitable for continuous use in a high temperature environment.
- the alloy tool steel for hot working according to the present invention is obtained through quenching and tempering which will be detailed later.
- the alloy tool steel according to the present invention is C: 0.40% by mass or more and 0.60% by mass or less, Si: 0.10% by mass or more and 0.50% by mass or less, Mn: 0.20% by mass or more and 1.10% by mass or less, Ni: 0.20% by mass or more and 2.10% by mass or less, Cr: 0.50% by mass or more and 2.00% by mass or less, Mo: 0.10% by mass or more and 0.60% by mass or less, V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and N: Contains 0.020% by mass or less.
- the balance of the alloy tool steel according to the invention is Fe and impurities (unavoidable impurities).
- the amount of alloying elements is relatively small. Therefore, the alloy tool steel according to the present invention has excellent toughness. As will be detailed later, the alloy tool steel according to the present invention has an appropriate metal structure and an appropriate solid-solution element parameter Q during quenching. Therefore, the alloy tool steel according to the present invention is excellent in softening resistance even though the amount of alloying elements is not large.
- [Carbon (C)] C contributes to the hardenability, hardness and strength of alloy tool steels. From these points of view, the C content is preferably 0.40% by mass or more, more preferably 0.45% by mass or more, and particularly preferably 0.49% by mass or more. Excess C impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the C content is preferably 0.60% by mass or less, more preferably 0.57% by mass or less, and particularly preferably 0.55% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- Si contributes to the hardenability and hardness of alloy tool steel. Si can further contribute to deoxidation during melting of the alloy. From these points of view, the Si content is preferably 0.10% by mass or more, more preferably 0.14% by mass or more, and particularly preferably 0.15% by mass or more. Excess Si impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Si content is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and particularly preferably 0.34% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- Mn contributes to the hardenability and hardness of alloy tool steel. Mn further dissolves in the matrix during quenching and promotes precipitation of carbide during tempering. From these points of view, the Mn content is preferably 0.20% by mass or more, more preferably 0.30% by mass or more, and particularly preferably 0.50% by mass or more. Excess Mn impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Mn content is preferably 1.10% by mass or less, more preferably 1.05% by mass or less, and particularly preferably 1.00% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- Nickel (Ni) forms a substitution solid solution in the matrix during heating for quenching and contributes to the hardenability of the alloy tool steel. Ni also contributes to the toughness of alloy tool steels. From these points of view, the Ni content is preferably 0.20% by mass or more, more preferably 0.59% by mass or more, and particularly preferably 1.00% by mass or more. Excessive Ni causes twinning due to an excessive decrease in the Ms point, impairing the toughness of the alloy tool steel. From the viewpoint of toughness, the Ni content is preferably 2.10% by mass or less, more preferably 1.94% by mass or less, and particularly preferably 1.61% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- Cr Cr contributes to the hardenability of alloy tool steel. Cr further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Cr content is preferably 0.50% by mass or more, more preferably 1.10% by mass or more, and particularly preferably 1.50% by mass or more. Excessive Cr causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Cr content is preferably 2.00% by mass or less, more preferably 1.95% by mass or less, and particularly preferably 1.90% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- Mo Mo contributes to the hardenability of alloy tool steel. Mo further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Mo content is preferably 0.10% by mass or more, more preferably 0.17% by mass or more, and particularly preferably 0.33% by mass or more. Excessive Mo causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Mo content is preferably 0.60% by mass or less, more preferably 0.55% by mass or less, and particularly preferably 0.50% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- V can precipitate carbides. V particularly precipitates as secondary carbides VC during tempering. From this point of view, the V content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.10% by mass or more. Excessive V causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the V content is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, and particularly preferably 0.20% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- the alloy tool steel according to the present invention contains either one or both of V and Nb. In the alloy tool steel according to the invention, V is not an essential element. Therefore, the V content may be substantially zero. In other words, the V content may be below the detection limit.
- Nb can precipitate carbides. Nb especially precipitates as a secondary carbide NbC during tempering. From this point of view, the Nb content is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and particularly preferably 0.03% by mass or more. Excessive Nb causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Nb content is preferably 0.30% by mass or less, more preferably 0.15% by mass or less, and particularly preferably 0.08% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- the alloy tool steel according to the present invention contains either one or both of V and Nb.
- Nb is not an essential element in the alloy tool steel according to the present invention. Therefore, the Nb content may be substantially zero. In other words, the Nb content may be less than the detection limit.
- the alloy tool steel according to the present invention contains either one or both of V and Nb.
- the total content of V and Nb is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.12% by mass or more.
- the total content of V and Nb is preferably 0.30% by mass or less, more preferably 0.27% by mass or less, and particularly preferably 0.24% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- N can combine with V or Nb to precipitate nitrides or carbonitrides.
- Each of these nitrides and carbonitrides can contribute to the toughness of alloy tool steels. From these points of view, the N content is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and particularly preferably 0.003% by mass or more.
- Nitrides and carbonitrides do not form a solid solution in the matrix during quenching and tend to remain. Alloy tool steels in which nitrides and carbonitrides are excessive have a small solute element parameter Q, which will be described later. In alloy tool steels with a small solute element parameter Q, the amount of secondary carbides after tempering is insufficient.
- Alloy tool steels with a small solute element parameter Q are inferior in softening resistance.
- the N content is preferably 0.020% by mass or less, more preferably 0.015% by mass or less, and particularly preferably 0.010% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
- N is not an essential element in the alloy tool steel according to the present invention. Therefore, the N content may be substantially zero. In other words, the N content may be less than the detection limit.
- the solid-solution element parameter Q during quenching is calculated by the following formula.
- Q (Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
- Cr1 Amount of Cr dissolved in austenite at quenching temperature (% by mass)
- Mo1 Amount of Mo dissolved in austenite at quenching temperature (% by mass)
- V1 Amount of V dissolved in austenite at quenching temperature (% by mass)
- Nb1 Amount of Nb dissolved in austenite at the quenching temperature (% by mass)
- Cr2 Amount of Cr dissolved in austenite at 800°C (% by mass)
- Mo2 Amount of Mo dissolved in austenite at 800°C (% by mass)
- V2 Amount of V dissolved in austenite at 800°C (% by mass)
- Nb2 Amount of Nb dissolved in austenite at 800°C (% by mass)
- (Cr1+Mo1+V1+Nb1) represents the total amount (% by mass) of Cr, Mo, V, and Nb dissolved in austenite (FCC_A1) at the quenching temperature applied to the alloy tool steel according to the present invention.
- (Cr2+Mo2+V2+Nb2) represents the total amount (% by mass) of Cr, Mo, V and Nb dissolved in austenite at 800°C.
- the quenching temperature applied to the alloy tool steel according to the present invention is, for example, 850°C or higher and 1050°C or lower, preferably 900°C or higher and 1020°C or lower.
- Thermo-calc is an integrated thermodynamic calculation software provided by Thermo-Calc Software AB. This software performs thermodynamic equilibrium calculations. The calculation conditions are as follows. Mode: Graphical Pressure: 1 ⁇ 10 5 Pa Total size: 1mol All phases that are automatically selected when selecting an element are taken into account in the calculation.
- the solute element parameter Q of the alloy tool steel according to the present invention is preferably 1.12 or more.
- Alloy tool steels with a solute element parameter Q of 1.12 or more have a large amount of secondary carbides after tempering. This secondary carbide inhibits recovery of dislocations when the alloy tool steel is used in a high temperature environment.
- An alloy tool having a solute element parameter Q of 1.12 or more is excellent in softening resistance.
- the parameter Q is more preferably 1.13 or more, particularly preferably 1.14 or more. From the viewpoint of softening resistance, the larger the parameter Q, the better.
- the parameter Q that can be achieved in real alloy tool steels is 1.70 or less.
- the alloy tool steel according to the present invention is obtained through quenching and tempering.
- the metal structure of the alloy tool steel according to the present invention is martensite or bainite. Alloy tool steels having this metallographic structure are excellent in toughness and softening resistance.
- the alloy tool steel according to the present invention can achieve both toughness and softening resistance at a higher level.
- An alloy tool steel having a bainite metallographic structure is preferable from the viewpoint that the diameter of the blocks described later is large and therefore the softening resistance is excellent.
- Martensite and bainite have packets, blocks and laths as substructures within the former austenite grains.
- a packet is a collection of laths having the same habit plane. The orientation difference in this packet is greater than or equal to 15°.
- a block is a structure that divides packets and is a group of laths having the same crystal orientation. The misorientation of this block is 15° or more.
- Lath is considered the smallest substructure of martensite. The orientation difference between the laths is about 2°.
- the inventors have found that dislocation recovery is suppressed in alloy tool steels with large block diameters.
- Alloy tool steels with large block diameters have excellent softening resistance.
- the block diameter is preferably 2.0 ⁇ m or more, more preferably 2.2 ⁇ m or more, and particularly preferably 2.4 ⁇ m or more.
- the block diameter is preferably 6.0 ⁇ m or less, more preferably 5.7 ⁇ m or less, and particularly preferably 5.5 ⁇ m or less. Each of these upper limits may be combined with any of the above lower limits.
- the block diameter is measured from the orientation map of ⁇ Fe obtained by the FESEM-EBSP method.
- the measurement conditions are as follows. Field of view: 50 ⁇ m ⁇ 50 ⁇ m Pitch: 0.05 ⁇ m
- a base material having the composition described above is obtained by melting.
- This base material is subjected to plastic working to obtain an intermediate.
- This intermediate is subjected to quenching.
- the quenching temperature is usually 850° C. or higher and 1050° C. or lower.
- the quenching temperature is preferably 900° C. or higher and 1020° C. or lower.
- the intermediate is quenched. Quenching causes a transformation in the intermediate.
- This intermediate is subjected to tempering.
- the tempering temperature is usually 550°C or higher and 700°C or lower. This tempering results in a product whose material is alloy tool steel.
- the metallographic structure of this alloy tool steel is martensite or bainite.
- a typical application of the alloyed tool steel according to the invention is in tools used for hot plastic working.
- a tool used for hot plastic working is also called a hot tool.
- the alloy tool steel according to the present invention is suitable for hot forging dies.
- hot forging dies include hammer dies and press dies.
- Hot tools such as dies for hot forging are, for example, for the purpose of improving workability, or for the purpose of controlling the structure to obtain desired properties after hot working. , the vicinity of the surface is exposed to a considerable temperature (for example, 180 to 1300° C.) due to heat transfer from the material to be processed.
- the present specification is also directed to hot forging dies.
- the material of the hot forging die according to the present invention is the alloy tool steel according to the present invention.
- the alloy tool steel according to the present invention is C: 0.40% by mass or more and 0.60% by mass or less, Si: 0.10% by mass or more and 0.50% by mass or less, Mn: 0.20% by mass or more and 1.10% by mass or less, Ni: 0.20% by mass or more and 2.10% by mass or less, Cr: 0.50% by mass or more and 2.00% by mass or less, Mo: 0.10% by mass or more and 0.60% by mass or less, V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and N: Contains 0.020% by mass or less.
- the balance of the alloy tool steel according to the invention is Fe and impurities.
- the metal structure of the alloy tool steel according to the present invention is martensite or bainite. This metallographic structure includes blocks whose diameter is 2.0 ⁇ m or more and 6.0 ⁇ m or less.
- the alloy tool steel according to the present invention has a solid solution element parameter Q during quenching of 1.12 or more.
- the hot forging die according to the present invention is excellent in toughness and softening resistance.
- the hot forging die according to the present invention has a long life.
- Example 1 The raw material was put into a vacuum melting furnace, melted, and cast into a mold having a diameter of 190 mm to obtain an ingot. This ingot was heated to 1100° C. and forged to obtain a rectangular bar having a size of 15 mm ⁇ 15 mm. After holding this square bar at a temperature of 900° C. for 30 minutes, it was quenched by oil cooling. As shown in Table 2, the quenching temperature was adjusted to 900°C. This square bar was heated to a predetermined temperature and tempered by air cooling to obtain the alloy tool steel for hot working according to Example 1. The tempering temperature was adjusted so that the hardness of the rectangular bar after tempering was 39 HRC to 41 HRC. The composition of this alloy tool steel is shown in Table 1 below.
- Example 2-6 and Comparative Example 1-10 Examples 2 to 6 and Comparative Example were prepared in the same manner as in Example 1 except that the composition was as shown in Table 1 and the quenching temperature was adjusted within the range of 850 ° C. to 1250 ° C. as shown in Table 2. 1-10 hot working alloy tool steels were obtained.
- the alloy tool steel for hot working according to each example is excellent in toughness and softening resistance. From these evaluation results, the superiority of the alloy tool steel according to the present invention is clear.
- the alloy tool steel for hot working described above is suitable for various metal products used in high-temperature environments.
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Abstract
The purpose of the present invention is to provide an alloy tool steel for hot working that has both excellent toughness and excellent softening resistance. Provided is an alloy tool steel for hot working, containing carbon, silicon, manganese, nickel, chromium, molybdenum, vanadium, niobium, and nitrogen, the remainder being iron and impurities, wherein: the metallographic structure of the alloy tool steel for hot working is martensite or bainite; the metallographic structure includes blocks with a diameter of 2.0–6.0 μm; and a solid solute element on quenching parameter Q, calculated on the basis of the formula Q = (Cr1 + Mo1 + V1 + Nb1) / (Cr2 + Mo2 + V2 + Nb2) [where (Cr1 + Mo1 + V1 + Nb1) represents the total amount of chromium, molybdenum, vanadium, and niobium in solid solution in austenite at the quenching temperature and (Cr2 + Mo2 + V2 + Nb2) represents the total amount of chromium, molybdenum, vanadium, and niobium in solid solution in austenite at 800°C], is at least 1.12.
Description
本明細書は、熱間鍛造等の熱間塑性加工に使用される工具に適した合金鋼を開示する。
This specification discloses an alloy steel suitable for tools used in hot plastic working such as hot forging.
熱間金型用合金鋼として、ＪＩＳに規格されたＳＫＤ６１が使用されている。ＳＫＤ６１は、高温強度に優れている。熱間鍛造用の型に、ＪＩＳに規格されたＳＫＴ４も使用されている。ＳＫＴ４は靱性に優れている。
JIS standard SKD61 is used as alloy steel for hot molds. SKD61 is excellent in high temperature strength. SKT4 standardized by JIS is also used for hot forging dies. SKT4 has excellent toughness.
特許文献１（特開２０１１－１９５９１７号公報）には、組成が改良された熱間工具鋼が開示されている。この工具鋼では、高温強度と靱性との両立が意図されている。
Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-195917) discloses a hot work tool steel with an improved composition. This tool steel is intended to achieve both high temperature strength and toughness.
特許文献２（特開２００６－３２２０７１号公報）には、改良された金属組織を有する合金鋼が開示されている。この合金鋼の硬度は大きい。
Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-322071) discloses an alloy steel having an improved metal structure. The hardness of this alloy steel is great.
従来の熱間鍛造型用の合金は、軟化抵抗性に劣り、高温環境下での継続的な使用には適していない。
Conventional alloys for hot forging dies have poor softening resistance and are not suitable for continuous use in high temperature environments.
本発明は、靱性及び軟化抵抗性の両方に優れた熱間加工用合金工具鋼を提供することを目的とする。
An object of the present invention is to provide an alloy tool steel for hot working that is excellent in both toughness and softening resistance.
本発明に係る熱間加工用合金工具鋼（以下「本発明に係る合金工具鋼」という場合がある。）は、
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物である。本発明に係る合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。本発明に係る金属組織は、その径が２．０μｍ以上６．０μｍ以下であるブロックを含む。本発明に係る合金工具鋼の、下記数式で算出される焼入時固溶元素パラメータＱは、１．１２以上である。
Ｑ＝（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）／（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）
［式中、
Ｃｒ１は焼入れ温度においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ１は焼入れ温度においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ１は焼入れ温度においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ１は焼入れ温度においてオーステナイトに固溶するＮｂの量（質量％）を表し、
Ｃｒ２は８００℃においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ２は８００℃においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ２は８００℃においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ２は８００℃においてオーステナイトに固溶するＮｂの量（質量％）を表す。］ The alloy tool steel for hot working according to the present invention (hereinafter sometimes referred to as "alloy tool steel according to the present invention") is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities. The metal structure of the alloy tool steel according to the present invention is martensite or bainite. A metallographic structure according to the present invention includes blocks having a diameter of 2.0 μm or more and 6.0 μm or less. The alloy tool steel according to the present invention has a solute element parameter Q during quenching calculated by the following formula, which is 1.12 or more.
Q=(Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
[In the formula,
Cr1 represents the amount (% by mass) of Cr dissolved in austenite at the quenching temperature,
Mo1 represents the amount (% by mass) of Mo dissolved in austenite at the quenching temperature,
V1 represents the amount (% by mass) of V dissolved in austenite at the quenching temperature,
Nb1 represents the amount (% by mass) of Nb dissolved in austenite at the quenching temperature,
Cr represents the amount (% by mass) of Cr dissolved in austenite at 800 ° C.,
Mo2 represents the amount (mass%) of Mo dissolved in austenite at 800 ° C.,
V2 represents the amount (% by mass) of V dissolved in austenite at 800 ° C.,
Nb2 represents the amount (% by mass) of Nb dissolved in austenite at 800°C. ]
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物である。本発明に係る合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。本発明に係る金属組織は、その径が２．０μｍ以上６．０μｍ以下であるブロックを含む。本発明に係る合金工具鋼の、下記数式で算出される焼入時固溶元素パラメータＱは、１．１２以上である。
Ｑ＝（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）／（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）
［式中、
Ｃｒ１は焼入れ温度においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ１は焼入れ温度においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ１は焼入れ温度においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ１は焼入れ温度においてオーステナイトに固溶するＮｂの量（質量％）を表し、
Ｃｒ２は８００℃においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ２は８００℃においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ２は８００℃においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ２は８００℃においてオーステナイトに固溶するＮｂの量（質量％）を表す。］ The alloy tool steel for hot working according to the present invention (hereinafter sometimes referred to as "alloy tool steel according to the present invention") is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities. The metal structure of the alloy tool steel according to the present invention is martensite or bainite. A metallographic structure according to the present invention includes blocks having a diameter of 2.0 μm or more and 6.0 μm or less. The alloy tool steel according to the present invention has a solute element parameter Q during quenching calculated by the following formula, which is 1.12 or more.
Q=(Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
[In the formula,
Cr1 represents the amount (% by mass) of Cr dissolved in austenite at the quenching temperature,
Mo1 represents the amount (% by mass) of Mo dissolved in austenite at the quenching temperature,
V1 represents the amount (% by mass) of V dissolved in austenite at the quenching temperature,
Nb1 represents the amount (% by mass) of Nb dissolved in austenite at the quenching temperature,
Cr represents the amount (% by mass) of Cr dissolved in austenite at 800 ° C.,
Mo2 represents the amount (mass%) of Mo dissolved in austenite at 800 ° C.,
V2 represents the amount (% by mass) of V dissolved in austenite at 800 ° C.,
Nb2 represents the amount (% by mass) of Nb dissolved in austenite at 800°C. ]
本発明に係る熱間加工用合金工具鋼は、靱性及び軟化抵抗性に優れている。その材質が本発明に係る合金工具鋼である型は、高温環境下での継続的な使用に適している。
The alloy tool steel for hot working according to the present invention is excellent in toughness and softening resistance. A mold whose material is the alloy tool steel according to the present invention is suitable for continuous use in a high temperature environment.
本発明に係る熱間加工用合金工具鋼は、後に詳説される焼入れ及び焼戻しを経て得られる。本発明に係る合金工具鋼は、
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物（不可避的不純物）である。 The alloy tool steel for hot working according to the present invention is obtained through quenching and tempering which will be detailed later. The alloy tool steel according to the present invention is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities (unavoidable impurities).
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物（不可避的不純物）である。 The alloy tool steel for hot working according to the present invention is obtained through quenching and tempering which will be detailed later. The alloy tool steel according to the present invention is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities (unavoidable impurities).
本発明に係る合金工具鋼では、合金元素の量は比較的少ない。従って、本発明に係る合金工具鋼は、靱性に優れている。後に詳説されるように、本発明に係る合金工具鋼では、金属組織が適正であり、かつ焼入時固溶元素パラメータＱが適正である。従って、本発明に係る合金工具鋼は、合金元素の量が多くないにもかかわらず、軟化抵抗性に優れている。
In the alloy tool steel according to the present invention, the amount of alloying elements is relatively small. Therefore, the alloy tool steel according to the present invention has excellent toughness. As will be detailed later, the alloy tool steel according to the present invention has an appropriate metal structure and an appropriate solid-solution element parameter Q during quenching. Therefore, the alloy tool steel according to the present invention is excellent in softening resistance even though the amount of alloying elements is not large.
以下、それぞれの元素が、詳説される。なお、「質量％」は、別段規定される場合を除き、本発明に係る合金工具鋼の質量を基準とする。
Each element is explained in detail below. "% by mass" is based on the mass of the alloy tool steel according to the present invention, unless otherwise specified.
［炭素（Ｃ）］
Ｃは、合金工具鋼の焼入れ性、硬さ及び強さに寄与する。これらの観点から、Ｃの含有率は０．４０質量％以上が好ましく、０．４５質量％以上がより好ましく、０．４９質量％以上が特に好ましい。過剰のＣは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｃの含有率は０．６０質量％以下が好ましく、０．５７質量％以下がより好ましく、０．５５質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Carbon (C)]
C contributes to the hardenability, hardness and strength of alloy tool steels. From these points of view, the C content is preferably 0.40% by mass or more, more preferably 0.45% by mass or more, and particularly preferably 0.49% by mass or more. Excess C impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the C content is preferably 0.60% by mass or less, more preferably 0.57% by mass or less, and particularly preferably 0.55% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｃは、合金工具鋼の焼入れ性、硬さ及び強さに寄与する。これらの観点から、Ｃの含有率は０．４０質量％以上が好ましく、０．４５質量％以上がより好ましく、０．４９質量％以上が特に好ましい。過剰のＣは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｃの含有率は０．６０質量％以下が好ましく、０．５７質量％以下がより好ましく、０．５５質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Carbon (C)]
C contributes to the hardenability, hardness and strength of alloy tool steels. From these points of view, the C content is preferably 0.40% by mass or more, more preferably 0.45% by mass or more, and particularly preferably 0.49% by mass or more. Excess C impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the C content is preferably 0.60% by mass or less, more preferably 0.57% by mass or less, and particularly preferably 0.55% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［ケイ素（Ｓｉ）］
Ｓｉは、合金工具鋼の焼入れ性及び硬さに寄与する。Ｓｉはさらに、合金の溶製時の脱酸に寄与しうる。これらの観点から、Ｓｉの含有率は０．１０質量％以上が好ましく、０．１４質量％以上がより好ましく、０．１５質量％以上が特に好ましい。過剰のＳｉは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｓｉの含有率は０．５０質量％以下が好ましく、０．４０質量％以下がより好ましく、０．３４質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Silicon (Si)]
Si contributes to the hardenability and hardness of alloy tool steel. Si can further contribute to deoxidation during melting of the alloy. From these points of view, the Si content is preferably 0.10% by mass or more, more preferably 0.14% by mass or more, and particularly preferably 0.15% by mass or more. Excess Si impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Si content is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and particularly preferably 0.34% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｓｉは、合金工具鋼の焼入れ性及び硬さに寄与する。Ｓｉはさらに、合金の溶製時の脱酸に寄与しうる。これらの観点から、Ｓｉの含有率は０．１０質量％以上が好ましく、０．１４質量％以上がより好ましく、０．１５質量％以上が特に好ましい。過剰のＳｉは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｓｉの含有率は０．５０質量％以下が好ましく、０．４０質量％以下がより好ましく、０．３４質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Silicon (Si)]
Si contributes to the hardenability and hardness of alloy tool steel. Si can further contribute to deoxidation during melting of the alloy. From these points of view, the Si content is preferably 0.10% by mass or more, more preferably 0.14% by mass or more, and particularly preferably 0.15% by mass or more. Excess Si impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Si content is preferably 0.50% by mass or less, more preferably 0.40% by mass or less, and particularly preferably 0.34% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［マンガン（Ｍｎ）］
Ｍｎは、合金工具鋼の焼入れ性及び硬さに寄与する。Ｍｎはさらに、焼入れ時にマトリクスに固溶し、焼戻し時に炭化物の析出を促す。これらの観点から、Ｍｎの含有率は０．２０質量％以上が好ましく、０．３０質量％以上がより好ましく、０．５０質量％以上が特に好ましい。過剰のＭｎは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｍｎの含有率は１．１０質量％以下が好ましく、１．０５質量％以下がより好ましく、１．００質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Manganese (Mn)]
Mn contributes to the hardenability and hardness of alloy tool steel. Mn further dissolves in the matrix during quenching and promotes precipitation of carbide during tempering. From these points of view, the Mn content is preferably 0.20% by mass or more, more preferably 0.30% by mass or more, and particularly preferably 0.50% by mass or more. Excess Mn impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Mn content is preferably 1.10% by mass or less, more preferably 1.05% by mass or less, and particularly preferably 1.00% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｍｎは、合金工具鋼の焼入れ性及び硬さに寄与する。Ｍｎはさらに、焼入れ時にマトリクスに固溶し、焼戻し時に炭化物の析出を促す。これらの観点から、Ｍｎの含有率は０．２０質量％以上が好ましく、０．３０質量％以上がより好ましく、０．５０質量％以上が特に好ましい。過剰のＭｎは、合金工具鋼の靱性を阻害する。靱性の観点から、Ｍｎの含有率は１．１０質量％以下が好ましく、１．０５質量％以下がより好ましく、１．００質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Manganese (Mn)]
Mn contributes to the hardenability and hardness of alloy tool steel. Mn further dissolves in the matrix during quenching and promotes precipitation of carbide during tempering. From these points of view, the Mn content is preferably 0.20% by mass or more, more preferably 0.30% by mass or more, and particularly preferably 0.50% by mass or more. Excess Mn impairs the toughness of alloyed tool steels. From the viewpoint of toughness, the Mn content is preferably 1.10% by mass or less, more preferably 1.05% by mass or less, and particularly preferably 1.00% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［ニッケル（Ｎｉ）］
Ｎｉは、焼入れの加熱時にマトリクスに置換固溶し、合金工具鋼の焼入れ性に寄与する。Ｎｉはさらに、合金工具鋼の靱性に寄与する。これらの観点から、Ｎｉの含有率は０．２０質量％以上が好ましく、０．５９質量％以上がより好ましく、１．００質量％以上が特に好ましい。過剰のＮｉは、Ｍｓ点の過度の低下に起因する双晶を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｎｉの含有率は２．１０質量％以下が好ましく、１．９４質量％以下がより好ましく、１．６１質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Nickel (Ni)]
Ni forms a substitution solid solution in the matrix during heating for quenching and contributes to the hardenability of the alloy tool steel. Ni also contributes to the toughness of alloy tool steels. From these points of view, the Ni content is preferably 0.20% by mass or more, more preferably 0.59% by mass or more, and particularly preferably 1.00% by mass or more. Excessive Ni causes twinning due to an excessive decrease in the Ms point, impairing the toughness of the alloy tool steel. From the viewpoint of toughness, the Ni content is preferably 2.10% by mass or less, more preferably 1.94% by mass or less, and particularly preferably 1.61% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｎｉは、焼入れの加熱時にマトリクスに置換固溶し、合金工具鋼の焼入れ性に寄与する。Ｎｉはさらに、合金工具鋼の靱性に寄与する。これらの観点から、Ｎｉの含有率は０．２０質量％以上が好ましく、０．５９質量％以上がより好ましく、１．００質量％以上が特に好ましい。過剰のＮｉは、Ｍｓ点の過度の低下に起因する双晶を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｎｉの含有率は２．１０質量％以下が好ましく、１．９４質量％以下がより好ましく、１．６１質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Nickel (Ni)]
Ni forms a substitution solid solution in the matrix during heating for quenching and contributes to the hardenability of the alloy tool steel. Ni also contributes to the toughness of alloy tool steels. From these points of view, the Ni content is preferably 0.20% by mass or more, more preferably 0.59% by mass or more, and particularly preferably 1.00% by mass or more. Excessive Ni causes twinning due to an excessive decrease in the Ms point, impairing the toughness of the alloy tool steel. From the viewpoint of toughness, the Ni content is preferably 2.10% by mass or less, more preferably 1.94% by mass or less, and particularly preferably 1.61% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［クロム（Ｃｒ）］
Ｃｒは、合金工具鋼の焼き入れ性に寄与する。Ｃｒはさらに、遷移金属Ｍの二次炭化物（Ｍ２Ｃ、ＭＣ等）に固溶し、これら二次炭化物の析出を促す。これらの観点から、Ｃｒの含有率は０．５０質量％以上が好ましく、１．１０質量％以上がより好ましく、１．５０質量％以上が特に好ましい。過剰のＣｒは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｃｒの含有率は２．００質量％以下が好ましく、１．９５質量％以下がより好ましく、１．９０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Chromium (Cr)]
Cr contributes to the hardenability of alloy tool steel. Cr further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Cr content is preferably 0.50% by mass or more, more preferably 1.10% by mass or more, and particularly preferably 1.50% by mass or more. Excessive Cr causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Cr content is preferably 2.00% by mass or less, more preferably 1.95% by mass or less, and particularly preferably 1.90% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｃｒは、合金工具鋼の焼き入れ性に寄与する。Ｃｒはさらに、遷移金属Ｍの二次炭化物（Ｍ２Ｃ、ＭＣ等）に固溶し、これら二次炭化物の析出を促す。これらの観点から、Ｃｒの含有率は０．５０質量％以上が好ましく、１．１０質量％以上がより好ましく、１．５０質量％以上が特に好ましい。過剰のＣｒは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｃｒの含有率は２．００質量％以下が好ましく、１．９５質量％以下がより好ましく、１．９０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Chromium (Cr)]
Cr contributes to the hardenability of alloy tool steel. Cr further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Cr content is preferably 0.50% by mass or more, more preferably 1.10% by mass or more, and particularly preferably 1.50% by mass or more. Excessive Cr causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Cr content is preferably 2.00% by mass or less, more preferably 1.95% by mass or less, and particularly preferably 1.90% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［モリブデン（Ｍｏ）］
Ｍｏは、合金工具鋼の焼き入れ性に寄与する。Ｍｏはさらに、遷移金属Ｍの二次炭化物（Ｍ２Ｃ、ＭＣ等）に固溶し、これら二次炭化物の析出を促す。これらの観点から、Ｍｏの含有率は０．１０質量％以上が好ましく、０．１７質量％以上がより好ましく、０．３３質量％以上が特に好ましい。過剰のＭｏは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｍｏの含有率は０．６０質量％以下が好ましく、０．５５質量％以下がより好ましく、０．５０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Molybdenum (Mo)]
Mo contributes to the hardenability of alloy tool steel. Mo further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Mo content is preferably 0.10% by mass or more, more preferably 0.17% by mass or more, and particularly preferably 0.33% by mass or more. Excessive Mo causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Mo content is preferably 0.60% by mass or less, more preferably 0.55% by mass or less, and particularly preferably 0.50% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
Ｍｏは、合金工具鋼の焼き入れ性に寄与する。Ｍｏはさらに、遷移金属Ｍの二次炭化物（Ｍ２Ｃ、ＭＣ等）に固溶し、これら二次炭化物の析出を促す。これらの観点から、Ｍｏの含有率は０．１０質量％以上が好ましく、０．１７質量％以上がより好ましく、０．３３質量％以上が特に好ましい。過剰のＭｏは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｍｏの含有率は０．６０質量％以下が好ましく、０．５５質量％以下がより好ましく、０．５０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [Molybdenum (Mo)]
Mo contributes to the hardenability of alloy tool steel. Mo further dissolves in secondary carbides (M2C, MC, etc.) of the transition metal M and promotes precipitation of these secondary carbides. From these points of view, the Mo content is preferably 0.10% by mass or more, more preferably 0.17% by mass or more, and particularly preferably 0.33% by mass or more. Excessive Mo causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Mo content is preferably 0.60% by mass or less, more preferably 0.55% by mass or less, and particularly preferably 0.50% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［バナジウム（Ｖ）］
Ｖは、炭化物を析出させうる。Ｖは特に、焼戻し時に二次炭化物ＶＣとして析出する。この観点から、Ｖの含有率は０．０１質量％以上が好ましく、０．０５質量％以上がより好ましく、０．１０質量％以上が特に好ましい。過剰のＶは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｖの含有率は０．３０質量％以下が好ましく、０．２５質量％以下がより好ましく、０．２０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。本発明に係る合金工具鋼において、Ｖは必須の元素ではない。従って、Ｖの含有率が実質的にゼロであってもよい。換言すれば、Ｖの含有率が、検出限界値未満であってもよい。 [Vanadium (V)]
V can precipitate carbides. V particularly precipitates as secondary carbides VC during tempering. From this point of view, the V content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.10% by mass or more. Excessive V causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the V content is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, and particularly preferably 0.20% by mass or less. Each of these upper limits may be combined with any of the above lower limits. The alloy tool steel according to the present invention contains either one or both of V and Nb. In the alloy tool steel according to the invention, V is not an essential element. Therefore, the V content may be substantially zero. In other words, the V content may be below the detection limit.
Ｖは、炭化物を析出させうる。Ｖは特に、焼戻し時に二次炭化物ＶＣとして析出する。この観点から、Ｖの含有率は０．０１質量％以上が好ましく、０．０５質量％以上がより好ましく、０．１０質量％以上が特に好ましい。過剰のＶは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｖの含有率は０．３０質量％以下が好ましく、０．２５質量％以下がより好ましく、０．２０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。本発明に係る合金工具鋼において、Ｖは必須の元素ではない。従って、Ｖの含有率が実質的にゼロであってもよい。換言すれば、Ｖの含有率が、検出限界値未満であってもよい。 [Vanadium (V)]
V can precipitate carbides. V particularly precipitates as secondary carbides VC during tempering. From this point of view, the V content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.10% by mass or more. Excessive V causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the V content is preferably 0.30% by mass or less, more preferably 0.25% by mass or less, and particularly preferably 0.20% by mass or less. Each of these upper limits may be combined with any of the above lower limits. The alloy tool steel according to the present invention contains either one or both of V and Nb. In the alloy tool steel according to the invention, V is not an essential element. Therefore, the V content may be substantially zero. In other words, the V content may be below the detection limit.
［ニオブ（Ｎｂ）］
Ｎｂは、炭化物を析出させうる。Ｎｂは特に、焼戻し時に二次炭化物ＮｂＣとして析出する。この観点から、Ｎｂの含有率は０．０１質量％以上が好ましく、０．０２質量％以上がより好ましく、０．０３質量％以上が特に好ましい。過剰のＮｂは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｎｂの含有率は０．３０質量％以下が好ましく、０．１５質量％以下がより好ましく、０．０８質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。前述の通り、本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。本発明に係る合金工具鋼において、Ｎｂは必須の元素ではない。従って、Ｎｂの含有率が実質的にゼロであってもよい。換言すれば、Ｎｂの含有率が、検出限界値未満であってもよい。 [Niobium (Nb)]
Nb can precipitate carbides. Nb especially precipitates as a secondary carbide NbC during tempering. From this point of view, the Nb content is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and particularly preferably 0.03% by mass or more. Excessive Nb causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Nb content is preferably 0.30% by mass or less, more preferably 0.15% by mass or less, and particularly preferably 0.08% by mass or less. Each of these upper limits may be combined with any of the above lower limits. As mentioned above, the alloy tool steel according to the present invention contains either one or both of V and Nb. Nb is not an essential element in the alloy tool steel according to the present invention. Therefore, the Nb content may be substantially zero. In other words, the Nb content may be less than the detection limit.
Ｎｂは、炭化物を析出させうる。Ｎｂは特に、焼戻し時に二次炭化物ＮｂＣとして析出する。この観点から、Ｎｂの含有率は０．０１質量％以上が好ましく、０．０２質量％以上がより好ましく、０．０３質量％以上が特に好ましい。過剰のＮｂは、焼入れ後の未固溶炭化物を招来し、合金工具鋼の靱性を阻害する。靱性の観点から、Ｎｂの含有率は０．３０質量％以下が好ましく、０．１５質量％以下がより好ましく、０．０８質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。前述の通り、本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。本発明に係る合金工具鋼において、Ｎｂは必須の元素ではない。従って、Ｎｂの含有率が実質的にゼロであってもよい。換言すれば、Ｎｂの含有率が、検出限界値未満であってもよい。 [Niobium (Nb)]
Nb can precipitate carbides. Nb especially precipitates as a secondary carbide NbC during tempering. From this point of view, the Nb content is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and particularly preferably 0.03% by mass or more. Excessive Nb causes undissolved carbides after quenching and impairs the toughness of the alloy tool steel. From the viewpoint of toughness, the Nb content is preferably 0.30% by mass or less, more preferably 0.15% by mass or less, and particularly preferably 0.08% by mass or less. Each of these upper limits may be combined with any of the above lower limits. As mentioned above, the alloy tool steel according to the present invention contains either one or both of V and Nb. Nb is not an essential element in the alloy tool steel according to the present invention. Therefore, the Nb content may be substantially zero. In other words, the Nb content may be less than the detection limit.
［Ｖ、Ｎｂ］
前述の通り、本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。二次炭化物の析出の観点から、Ｖ及びＮｂの合計含有率は０．０５質量％以上が好ましく、０．１０質量％以上がより好ましく、０．１２質量％以上が特に好ましい。靱性の観点から、Ｖ及びＮｂの合計含有率は０．３０質量％以下が好ましく、０．２７質量％以下がより好ましく、０．２４質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [V, Nb]
As mentioned above, the alloy tool steel according to the present invention contains either one or both of V and Nb. From the viewpoint of precipitation of secondary carbides, the total content of V and Nb is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.12% by mass or more. From the viewpoint of toughness, the total content of V and Nb is preferably 0.30% by mass or less, more preferably 0.27% by mass or less, and particularly preferably 0.24% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
前述の通り、本発明に係る合金工具鋼は、Ｖ及びＮｂのいずれか一方又は両方を含む。二次炭化物の析出の観点から、Ｖ及びＮｂの合計含有率は０．０５質量％以上が好ましく、０．１０質量％以上がより好ましく、０．１２質量％以上が特に好ましい。靱性の観点から、Ｖ及びＮｂの合計含有率は０．３０質量％以下が好ましく、０．２７質量％以下がより好ましく、０．２４質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。 [V, Nb]
As mentioned above, the alloy tool steel according to the present invention contains either one or both of V and Nb. From the viewpoint of precipitation of secondary carbides, the total content of V and Nb is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and particularly preferably 0.12% by mass or more. From the viewpoint of toughness, the total content of V and Nb is preferably 0.30% by mass or less, more preferably 0.27% by mass or less, and particularly preferably 0.24% by mass or less. Each of these upper limits may be combined with any of the above lower limits.
［窒素（Ｎ）］
Ｎは、Ｖ又はＮｂと結合し、窒化物又は炭窒化物を析出させうる。これらの窒化物及び炭窒化物は、それぞれ、合金工具鋼の靱性に寄与しうる。これらの観点から、Ｎの含有率は０．００１質量％以上が好ましく、０．００２質量％以上がより好ましく、０．００３質量％以上が特に好ましい。窒化物及び炭窒化物は、焼入れ時にマトリクスに固溶せず、残存しやすい。窒化物及び炭窒化物が過剰である合金工具鋼では、後述される固溶元素パラメータＱが小さい。固溶元素パラメータＱが小さい合金工具鋼では、焼戻し後の二次炭化物の量が不十分である。固溶元素パラメータＱが小さい合金工具鋼は、軟化抵抗性に劣る。軟化抵抗性の観点から、Ｎの含有率は０．０２０質量％以下が好ましく、０．０１５質量％以下がより好ましく、０．０１０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。本発明に係る合金工具鋼において、Ｎは必須の元素ではない。従って、Ｎの含有率が実質的にゼロであってもよい。換言すれば、Ｎの含有率が、検出限界値未満であってもよい。 [Nitrogen (N)]
N can combine with V or Nb to precipitate nitrides or carbonitrides. Each of these nitrides and carbonitrides can contribute to the toughness of alloy tool steels. From these points of view, the N content is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and particularly preferably 0.003% by mass or more. Nitrides and carbonitrides do not form a solid solution in the matrix during quenching and tend to remain. Alloy tool steels in which nitrides and carbonitrides are excessive have a small solute element parameter Q, which will be described later. In alloy tool steels with a small solute element parameter Q, the amount of secondary carbides after tempering is insufficient. Alloy tool steels with a small solute element parameter Q are inferior in softening resistance. From the viewpoint of softening resistance, the N content is preferably 0.020% by mass or less, more preferably 0.015% by mass or less, and particularly preferably 0.010% by mass or less. Each of these upper limits may be combined with any of the above lower limits. N is not an essential element in the alloy tool steel according to the present invention. Therefore, the N content may be substantially zero. In other words, the N content may be less than the detection limit.
Ｎは、Ｖ又はＮｂと結合し、窒化物又は炭窒化物を析出させうる。これらの窒化物及び炭窒化物は、それぞれ、合金工具鋼の靱性に寄与しうる。これらの観点から、Ｎの含有率は０．００１質量％以上が好ましく、０．００２質量％以上がより好ましく、０．００３質量％以上が特に好ましい。窒化物及び炭窒化物は、焼入れ時にマトリクスに固溶せず、残存しやすい。窒化物及び炭窒化物が過剰である合金工具鋼では、後述される固溶元素パラメータＱが小さい。固溶元素パラメータＱが小さい合金工具鋼では、焼戻し後の二次炭化物の量が不十分である。固溶元素パラメータＱが小さい合金工具鋼は、軟化抵抗性に劣る。軟化抵抗性の観点から、Ｎの含有率は０．０２０質量％以下が好ましく、０．０１５質量％以下がより好ましく、０．０１０質量％以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。本発明に係る合金工具鋼において、Ｎは必須の元素ではない。従って、Ｎの含有率が実質的にゼロであってもよい。換言すれば、Ｎの含有率が、検出限界値未満であってもよい。 [Nitrogen (N)]
N can combine with V or Nb to precipitate nitrides or carbonitrides. Each of these nitrides and carbonitrides can contribute to the toughness of alloy tool steels. From these points of view, the N content is preferably 0.001% by mass or more, more preferably 0.002% by mass or more, and particularly preferably 0.003% by mass or more. Nitrides and carbonitrides do not form a solid solution in the matrix during quenching and tend to remain. Alloy tool steels in which nitrides and carbonitrides are excessive have a small solute element parameter Q, which will be described later. In alloy tool steels with a small solute element parameter Q, the amount of secondary carbides after tempering is insufficient. Alloy tool steels with a small solute element parameter Q are inferior in softening resistance. From the viewpoint of softening resistance, the N content is preferably 0.020% by mass or less, more preferably 0.015% by mass or less, and particularly preferably 0.010% by mass or less. Each of these upper limits may be combined with any of the above lower limits. N is not an essential element in the alloy tool steel according to the present invention. Therefore, the N content may be substantially zero. In other words, the N content may be less than the detection limit.
［焼入時固溶元素パラメータＱ］
本明細書では、下記の数式により、焼入時固溶元素パラメータＱが算出される。
Ｑ＝（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）／（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）
Ｃｒ１：焼入れ温度においてオーステナイトに固溶するＣｒの量（質量％）
Ｍｏ１：焼入れ温度においてオーステナイトに固溶するＭｏの量（質量％）
Ｖ１：焼入れ温度においてオーステナイトに固溶するＶの量（質量％）
Ｎｂ１：焼入れ温度においてオーステナイトに固溶するＮｂの量（質量％）
Ｃｒ２：８００℃においてオーステナイトに固溶するＣｒの量（質量％）
Ｍｏ２：８００℃においてオーステナイトに固溶するＭｏの量（質量％）
Ｖ２：８００℃においてオーステナイトに固溶するＶの量（質量％）
Ｎｂ２：８００℃においてオーステナイトに固溶するＮｂの量（質量％） [Quenching solid solution element parameter Q]
In this specification, the solid-solution element parameter Q during quenching is calculated by the following formula.
Q=(Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
Cr1: Amount of Cr dissolved in austenite at quenching temperature (% by mass)
Mo1: Amount of Mo dissolved in austenite at quenching temperature (% by mass)
V1: Amount of V dissolved in austenite at quenching temperature (% by mass)
Nb1: Amount of Nb dissolved in austenite at the quenching temperature (% by mass)
Cr2: Amount of Cr dissolved in austenite at 800°C (% by mass)
Mo2: Amount of Mo dissolved in austenite at 800°C (% by mass)
V2: Amount of V dissolved in austenite at 800°C (% by mass)
Nb2: Amount of Nb dissolved in austenite at 800°C (% by mass)
本明細書では、下記の数式により、焼入時固溶元素パラメータＱが算出される。
Ｑ＝（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）／（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）
Ｃｒ１：焼入れ温度においてオーステナイトに固溶するＣｒの量（質量％）
Ｍｏ１：焼入れ温度においてオーステナイトに固溶するＭｏの量（質量％）
Ｖ１：焼入れ温度においてオーステナイトに固溶するＶの量（質量％）
Ｎｂ１：焼入れ温度においてオーステナイトに固溶するＮｂの量（質量％）
Ｃｒ２：８００℃においてオーステナイトに固溶するＣｒの量（質量％）
Ｍｏ２：８００℃においてオーステナイトに固溶するＭｏの量（質量％）
Ｖ２：８００℃においてオーステナイトに固溶するＶの量（質量％）
Ｎｂ２：８００℃においてオーステナイトに固溶するＮｂの量（質量％） [Quenching solid solution element parameter Q]
In this specification, the solid-solution element parameter Q during quenching is calculated by the following formula.
Q=(Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
Cr1: Amount of Cr dissolved in austenite at quenching temperature (% by mass)
Mo1: Amount of Mo dissolved in austenite at quenching temperature (% by mass)
V1: Amount of V dissolved in austenite at quenching temperature (% by mass)
Nb1: Amount of Nb dissolved in austenite at the quenching temperature (% by mass)
Cr2: Amount of Cr dissolved in austenite at 800°C (% by mass)
Mo2: Amount of Mo dissolved in austenite at 800°C (% by mass)
V2: Amount of V dissolved in austenite at 800°C (% by mass)
Nb2: Amount of Nb dissolved in austenite at 800°C (% by mass)
上記数式において（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）は、本発明に係る合金工具鋼に施された焼入れ温度においてオーステナイト（ＦＣＣ＿Ａ１）に固溶するＣｒ、Ｍｏ、Ｖ及びＮｂの合計量（質量％）を表す。上記数式において（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）は、８００℃においてオーステナイトに固溶するＣｒ、Ｍｏ、Ｖ及びＮｂの合計量（質量％）を表す。Ｎｂの含有率が０．０１質量％に満たない合金工具鋼における、固溶元素パラメータＱの算出においては、上記数式中のＮｂ１及びＮｂ２に、ゼロが代入される。本発明に係る合金工具鋼に施された焼入れ温度は、例えば８５０℃以上１０５０℃以下、好ましくは９００℃以上１０２０℃以下である。
In the above formula, (Cr1+Mo1+V1+Nb1) represents the total amount (% by mass) of Cr, Mo, V, and Nb dissolved in austenite (FCC_A1) at the quenching temperature applied to the alloy tool steel according to the present invention. In the above formula, (Cr2+Mo2+V2+Nb2) represents the total amount (% by mass) of Cr, Mo, V and Nb dissolved in austenite at 800°C. In calculating the solid-solution element parameter Q in an alloy tool steel with an Nb content of less than 0.01% by mass, zero is substituted for Nb1 and Nb2 in the above formula. The quenching temperature applied to the alloy tool steel according to the present invention is, for example, 850°C or higher and 1050°C or lower, preferably 900°C or higher and 1020°C or lower.
この固溶元素パラメータＱは、データベース「ＴＣＦＥ１０」が用いられ、ソフトウェア「Ｔｈｅｒｍｏ－ｃａｌｃ」によって算出される。Ｔｈｅｒｍｏ－ｃａｌｃは、Ｔｈｅｒｍｏ－Ｃａｌｃ Ｓｏｆｔｗａｒｅ ＡＢ社が提供する、統合型熱力学計算ソフトウェアである。このソフトウェアにより、熱力学平衡計算がなされる。計算の条件は、以下の通りである。
モード：グラフィカル
圧力：１×１０５Ｐａ
トータルサイズ：１ｍｏｌ
元素を選択した場合に自動的に選択される全ての相が考慮されて、計算がなされる。 This solute element parameter Q is calculated by the software "Thermo-calc" using the database "TCFE10". Thermo-calc is an integrated thermodynamic calculation software provided by Thermo-Calc Software AB. This software performs thermodynamic equilibrium calculations. The calculation conditions are as follows.
Mode: Graphical Pressure: 1×10 5 Pa
Total size: 1mol
All phases that are automatically selected when selecting an element are taken into account in the calculation.
モード：グラフィカル
圧力：１×１０５Ｐａ
トータルサイズ：１ｍｏｌ
元素を選択した場合に自動的に選択される全ての相が考慮されて、計算がなされる。 This solute element parameter Q is calculated by the software "Thermo-calc" using the database "TCFE10". Thermo-calc is an integrated thermodynamic calculation software provided by Thermo-Calc Software AB. This software performs thermodynamic equilibrium calculations. The calculation conditions are as follows.
Mode: Graphical Pressure: 1×10 5 Pa
Total size: 1mol
All phases that are automatically selected when selecting an element are taken into account in the calculation.
本発明に係る合金工具鋼の固溶元素パラメータＱは、１．１２以上が好ましい。固溶元素パラメータＱが１．１２以上である合金工具鋼では、焼戻し後の二次炭化物の量が多い。この二次炭化物は、合金工具鋼が高温環境で使用されたときの、転位の回復を抑制する。固溶元素パラメータＱが１．１２以上である合金工具は、軟化抵抗性に優れる。軟化抵抗性の観点から、このパラメータＱは１．１３以上がより好ましく、１．１４以上が特に好ましい。軟化抵抗性の観点からは、このパラメータＱは、大きいほど好ましい。現実の合金工具鋼において達成されうるパラメータＱは、１．７０以下である。
The solute element parameter Q of the alloy tool steel according to the present invention is preferably 1.12 or more. Alloy tool steels with a solute element parameter Q of 1.12 or more have a large amount of secondary carbides after tempering. This secondary carbide inhibits recovery of dislocations when the alloy tool steel is used in a high temperature environment. An alloy tool having a solute element parameter Q of 1.12 or more is excellent in softening resistance. From the viewpoint of softening resistance, the parameter Q is more preferably 1.13 or more, particularly preferably 1.14 or more. From the viewpoint of softening resistance, the larger the parameter Q, the better. The parameter Q that can be achieved in real alloy tool steels is 1.70 or less.
固溶元素パラメータＱが１．１２以上である合金工具鋼を得る手段として、
（１）Ｃｒ、Ｍｏ、Ｖ又はＮｂを比較的多く添加すること、
（２）Ｎの含有率を比較的少なくすること、及び、
（３）焼入れ温度を比較的高くすること
が例示される。 As means for obtaining an alloy tool steel having a solute element parameter Q of 1.12 or more,
(1) adding a relatively large amount of Cr, Mo, V or Nb;
(2) relatively low content of N, and
(3) Raising the quenching temperature relatively high is exemplified.
（１）Ｃｒ、Ｍｏ、Ｖ又はＮｂを比較的多く添加すること、
（２）Ｎの含有率を比較的少なくすること、及び、
（３）焼入れ温度を比較的高くすること
が例示される。 As means for obtaining an alloy tool steel having a solute element parameter Q of 1.12 or more,
(1) adding a relatively large amount of Cr, Mo, V or Nb;
(2) relatively low content of N, and
(3) Raising the quenching temperature relatively high is exemplified.
前述の通り、本発明に係る合金工具鋼は、焼入れ及び焼戻しを経て得られる。本発明に係る合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。この金属組織を有する合金工具鋼は、靱性及び軟化抵抗性に優れる。例えば焼鈍で得られるフェライト組織を有する合金鋼に比べると、本発明に係る合金工具鋼では、靱性及び軟化抵抗性がより高い次元で両立されうる。後述されるブロックの径が大きく、従ってより軟化抵抗性に優れるとの観点から、金属組織がベイナイトである合金工具鋼が好ましい。
As described above, the alloy tool steel according to the present invention is obtained through quenching and tempering. The metal structure of the alloy tool steel according to the present invention is martensite or bainite. Alloy tool steels having this metallographic structure are excellent in toughness and softening resistance. For example, compared with alloy steel having a ferrite structure obtained by annealing, the alloy tool steel according to the present invention can achieve both toughness and softening resistance at a higher level. An alloy tool steel having a bainite metallographic structure is preferable from the viewpoint that the diameter of the blocks described later is large and therefore the softening resistance is excellent.
マルテンサイト及びベイナイトは、旧オーステナイト粒内に、下部組織として、パケット、ブロック及びラスを有する。パケットは、同じ晶癖面を有するラスの集団である。このパケットにおける方位差は、１５°以上である。ブロックは、パケットを分断する組織であり、同じ結晶方位を有するラスの集団である。このブロックの方位差は、１５°以上である。ラスは、マルテンサイトの最も小さな下部組織と考えられている。ラス同士の方位差は、２°程度である。
Martensite and bainite have packets, blocks and laths as substructures within the former austenite grains. A packet is a collection of laths having the same habit plane. The orientation difference in this packet is greater than or equal to 15°. A block is a structure that divides packets and is a group of laths having the same crystal orientation. The misorientation of this block is 15° or more. Lath is considered the smallest substructure of martensite. The orientation difference between the laths is about 2°.
本発明者は、ブロックの径が大きい合金工具鋼において転位の回復が抑制されることを、見出した。ブロックの径が大きい合金工具鋼は、軟化抵抗性に優れる。軟化抵抗性の観点から、ブロックの径は２．０μｍ以上が好ましく、２．２μｍ以上がより好ましく、２．４μｍ以上が特に好ましい。靱性の観点から、ブロックの径は６．０μｍ以下が好ましく、５．７μｍ以下がより好ましく、５．５μｍ以下が特に好ましい。これらの上限はそれぞれ、上述の下限のいずれと組み合わせてもよい。
The inventors have found that dislocation recovery is suppressed in alloy tool steels with large block diameters. Alloy tool steels with large block diameters have excellent softening resistance. From the viewpoint of softening resistance, the block diameter is preferably 2.0 μm or more, more preferably 2.2 μm or more, and particularly preferably 2.4 μm or more. From the viewpoint of toughness, the block diameter is preferably 6.0 μm or less, more preferably 5.7 μm or less, and particularly preferably 5.5 μm or less. Each of these upper limits may be combined with any of the above lower limits.
ブロックの径は、ＦＥＳＥＭ－ＥＢＳＰ法により得られるαＦｅの方位マップから、測定される。測定条件は、以下の通りである。
視野：５０μｍ×５０μｍ
ピッチ：０．０５μｍ
ソフトウェア：ＯＩＭ－Ａｎａｌｙｓｉｓ（ＴＳＬソリューションズ）
隣接する結晶との方位差が１５°以上で囲まれる領域をブロックの一つとして扱い、求めたブロックの面積から円相当径を求める。求めた円相当径の面積荷重平均した値が、ブロック径と定義される。 The block diameter is measured from the orientation map of αFe obtained by the FESEM-EBSP method. The measurement conditions are as follows.
Field of view: 50 μm×50 μm
Pitch: 0.05 μm
Software: OIM-Analysis (TSL Solutions)
A region surrounded by an orientation difference of 15° or more with adjacent crystals is treated as one block, and the equivalent circle diameter is obtained from the obtained area of the block. The area-loaded average value of the obtained equivalent circle diameters is defined as the block diameter.
視野：５０μｍ×５０μｍ
ピッチ：０．０５μｍ
ソフトウェア：ＯＩＭ－Ａｎａｌｙｓｉｓ（ＴＳＬソリューションズ）
隣接する結晶との方位差が１５°以上で囲まれる領域をブロックの一つとして扱い、求めたブロックの面積から円相当径を求める。求めた円相当径の面積荷重平均した値が、ブロック径と定義される。 The block diameter is measured from the orientation map of αFe obtained by the FESEM-EBSP method. The measurement conditions are as follows.
Field of view: 50 μm×50 μm
Pitch: 0.05 μm
Software: OIM-Analysis (TSL Solutions)
A region surrounded by an orientation difference of 15° or more with adjacent crystals is treated as one block, and the equivalent circle diameter is obtained from the obtained area of the block. The area-loaded average value of the obtained equivalent circle diameters is defined as the block diameter.
ブロックの径が２．０μｍ以上６．０μｍ以下である合金工具鋼を得る手段として、
（１）焼入れ温度を比較的高くすること、
（２）焼入れ時の保持時間を比較的長くすること、及び、
（３）Ｖ及びＮｂの添加量を適正とすること
が例示される。 As means for obtaining an alloy tool steel having a block diameter of 2.0 μm or more and 6.0 μm or less,
(1) relatively high quenching temperature;
(2) relatively long holding time during quenching, and
(3) Appropriate addition amounts of V and Nb are exemplified.
（１）焼入れ温度を比較的高くすること、
（２）焼入れ時の保持時間を比較的長くすること、及び、
（３）Ｖ及びＮｂの添加量を適正とすること
が例示される。 As means for obtaining an alloy tool steel having a block diameter of 2.0 μm or more and 6.0 μm or less,
(1) relatively high quenching temperature;
(2) relatively long holding time during quenching, and
(3) Appropriate addition amounts of V and Nb are exemplified.
［製造方法］
以下、本発明に係る合金工具鋼の製造方法の一例が説明される。この製造方法では、まず、前述の組成を有する母材が溶製によって得られる。この母材に塑性加工が施され、中間体が得られる。この中間体が、焼入れに供される。焼入れの温度は、通常は、８５０℃以上１０５０℃以下である。焼入れの温度は、９００℃以上１０２０℃以下であることが好ましい。焼入れでは、中間体が急冷される。急冷により、中間体で変態が生じる。この中間体に、焼戻しが施される。焼戻しの温度は、通常は、５５０℃以上７００℃以下である。この焼戻しにより、その材質が合金工具鋼である製品が得られる。この合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。 [Production method]
An example of the method for producing an alloy tool steel according to the present invention will be described below. In this manufacturing method, first, a base material having the composition described above is obtained by melting. This base material is subjected to plastic working to obtain an intermediate. This intermediate is subjected to quenching. The quenching temperature is usually 850° C. or higher and 1050° C. or lower. The quenching temperature is preferably 900° C. or higher and 1020° C. or lower. In quenching, the intermediate is quenched. Quenching causes a transformation in the intermediate. This intermediate is subjected to tempering. The tempering temperature is usually 550°C or higher and 700°C or lower. This tempering results in a product whose material is alloy tool steel. The metallographic structure of this alloy tool steel is martensite or bainite.
以下、本発明に係る合金工具鋼の製造方法の一例が説明される。この製造方法では、まず、前述の組成を有する母材が溶製によって得られる。この母材に塑性加工が施され、中間体が得られる。この中間体が、焼入れに供される。焼入れの温度は、通常は、８５０℃以上１０５０℃以下である。焼入れの温度は、９００℃以上１０２０℃以下であることが好ましい。焼入れでは、中間体が急冷される。急冷により、中間体で変態が生じる。この中間体に、焼戻しが施される。焼戻しの温度は、通常は、５５０℃以上７００℃以下である。この焼戻しにより、その材質が合金工具鋼である製品が得られる。この合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。 [Production method]
An example of the method for producing an alloy tool steel according to the present invention will be described below. In this manufacturing method, first, a base material having the composition described above is obtained by melting. This base material is subjected to plastic working to obtain an intermediate. This intermediate is subjected to quenching. The quenching temperature is usually 850° C. or higher and 1050° C. or lower. The quenching temperature is preferably 900° C. or higher and 1020° C. or lower. In quenching, the intermediate is quenched. Quenching causes a transformation in the intermediate. This intermediate is subjected to tempering. The tempering temperature is usually 550°C or higher and 700°C or lower. This tempering results in a product whose material is alloy tool steel. The metallographic structure of this alloy tool steel is martensite or bainite.
［合金工具鋼の用途］
本発明に係る合金工具鋼の典型的な用途は、熱間塑性加工に使用される工具である。熱間塑性加工に使用される工具は、熱間工具とも呼ばれる。特に、熱間鍛造用の型に、本発明に係る合金工具鋼は適している。熱間鍛造用の型として、ハンマー型及びプレス型が例示される。熱間鍛造用の型等の熱間工具は、例えば、加工性向上を目的に、又は、熱間加工後に所望の特性を得るための組織制御等を目的に、高温に加熱された被加工材と接触するため、被加工材からの熱移動により表面近傍が相当の温度（例えば１８０～１３００℃）に曝されて使用される。 [Applications of alloy tool steel]
A typical application of the alloyed tool steel according to the invention is in tools used for hot plastic working. A tool used for hot plastic working is also called a hot tool. In particular, the alloy tool steel according to the present invention is suitable for hot forging dies. Examples of hot forging dies include hammer dies and press dies. Hot tools such as dies for hot forging are, for example, for the purpose of improving workability, or for the purpose of controlling the structure to obtain desired properties after hot working. , the vicinity of the surface is exposed to a considerable temperature (for example, 180 to 1300° C.) due to heat transfer from the material to be processed.
本発明に係る合金工具鋼の典型的な用途は、熱間塑性加工に使用される工具である。熱間塑性加工に使用される工具は、熱間工具とも呼ばれる。特に、熱間鍛造用の型に、本発明に係る合金工具鋼は適している。熱間鍛造用の型として、ハンマー型及びプレス型が例示される。熱間鍛造用の型等の熱間工具は、例えば、加工性向上を目的に、又は、熱間加工後に所望の特性を得るための組織制御等を目的に、高温に加熱された被加工材と接触するため、被加工材からの熱移動により表面近傍が相当の温度（例えば１８０～１３００℃）に曝されて使用される。 [Applications of alloy tool steel]
A typical application of the alloyed tool steel according to the invention is in tools used for hot plastic working. A tool used for hot plastic working is also called a hot tool. In particular, the alloy tool steel according to the present invention is suitable for hot forging dies. Examples of hot forging dies include hammer dies and press dies. Hot tools such as dies for hot forging are, for example, for the purpose of improving workability, or for the purpose of controlling the structure to obtain desired properties after hot working. , the vicinity of the surface is exposed to a considerable temperature (for example, 180 to 1300° C.) due to heat transfer from the material to be processed.
［熱間鍛造用型］
前述の通り、本明細書は、熱間鍛造用型にも向けられる。本発明に係る熱間鍛造用型の材質は、本発明に係る合金工具鋼である。本発明に係る合金工具鋼は、
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物である。本発明に係る合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。この金属組織は、その径が２．０μｍ以上６．０μｍ以下であるブロックを含む。本発明に係る合金工具鋼の、焼入時固溶元素パラメータＱは、１．１２以上である。本発明に係る熱間鍛造用型は、靱性及び軟化抵抗性に優れる。本発明に係る熱間鍛造用型は、長寿命である。 [Hot forging die]
As noted above, the present specification is also directed to hot forging dies. The material of the hot forging die according to the present invention is the alloy tool steel according to the present invention. The alloy tool steel according to the present invention is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities. The metal structure of the alloy tool steel according to the present invention is martensite or bainite. This metallographic structure includes blocks whose diameter is 2.0 μm or more and 6.0 μm or less. The alloy tool steel according to the present invention has a solid solution element parameter Q during quenching of 1.12 or more. The hot forging die according to the present invention is excellent in toughness and softening resistance. The hot forging die according to the present invention has a long life.
前述の通り、本明細書は、熱間鍛造用型にも向けられる。本発明に係る熱間鍛造用型の材質は、本発明に係る合金工具鋼である。本発明に係る合金工具鋼は、
Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有する。本発明に係る合金工具鋼の残部は、Ｆｅ及び不純物である。本発明に係る合金工具鋼の金属組織は、マルテンサイト又はベイナイトである。この金属組織は、その径が２．０μｍ以上６．０μｍ以下であるブロックを含む。本発明に係る合金工具鋼の、焼入時固溶元素パラメータＱは、１．１２以上である。本発明に係る熱間鍛造用型は、靱性及び軟化抵抗性に優れる。本発明に係る熱間鍛造用型は、長寿命である。 [Hot forging die]
As noted above, the present specification is also directed to hot forging dies. The material of the hot forging die according to the present invention is the alloy tool steel according to the present invention. The alloy tool steel according to the present invention is
C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
N: Contains 0.020% by mass or less. The balance of the alloy tool steel according to the invention is Fe and impurities. The metal structure of the alloy tool steel according to the present invention is martensite or bainite. This metallographic structure includes blocks whose diameter is 2.0 μm or more and 6.0 μm or less. The alloy tool steel according to the present invention has a solid solution element parameter Q during quenching of 1.12 or more. The hot forging die according to the present invention is excellent in toughness and softening resistance. The hot forging die according to the present invention has a long life.
以下、実施例に係る熱間加工用合金工具鋼の効果が明らかにされるが、実施例の記載に基づいて本明細書で開示された範囲が限定的に解釈されるべきではない。
Although the effects of the alloy tool steel for hot working according to the examples will be clarified below, the scope disclosed in the present specification should not be construed to be limited based on the description of the examples.
［実施例１］
原料を真空溶解炉に投入して溶融し、直径が１９０ｍｍである鋳型に鋳込み、インゴット得た。このインゴットを１１００℃に加熱し、鍛伸を施して、サイズが１５ｍｍ×１５ｍｍである角材を得た。この角材を、９００℃の温度下に３０分間保持した後、油冷による焼入れを施した。表２に示すように、焼入れ温度は９００℃に調整した。この角材を所定温度まで加熱し、空冷による焼戻しを施して、実施例１に係る熱間加工用合金工具鋼を得た。焼戻し後の角材の硬さが３９ＨＲＣから４１ＨＲＣとなるように、焼戻し温度を調整した。この合金工具鋼の組成が、下記の表１に示されている。 [Example 1]
The raw material was put into a vacuum melting furnace, melted, and cast into a mold having a diameter of 190 mm to obtain an ingot. This ingot was heated to 1100° C. and forged to obtain a rectangular bar having a size of 15 mm×15 mm. After holding this square bar at a temperature of 900° C. for 30 minutes, it was quenched by oil cooling. As shown in Table 2, the quenching temperature was adjusted to 900°C. This square bar was heated to a predetermined temperature and tempered by air cooling to obtain the alloy tool steel for hot working according to Example 1. The tempering temperature was adjusted so that the hardness of the rectangular bar after tempering was 39 HRC to 41 HRC. The composition of this alloy tool steel is shown in Table 1 below.
原料を真空溶解炉に投入して溶融し、直径が１９０ｍｍである鋳型に鋳込み、インゴット得た。このインゴットを１１００℃に加熱し、鍛伸を施して、サイズが１５ｍｍ×１５ｍｍである角材を得た。この角材を、９００℃の温度下に３０分間保持した後、油冷による焼入れを施した。表２に示すように、焼入れ温度は９００℃に調整した。この角材を所定温度まで加熱し、空冷による焼戻しを施して、実施例１に係る熱間加工用合金工具鋼を得た。焼戻し後の角材の硬さが３９ＨＲＣから４１ＨＲＣとなるように、焼戻し温度を調整した。この合金工具鋼の組成が、下記の表１に示されている。 [Example 1]
The raw material was put into a vacuum melting furnace, melted, and cast into a mold having a diameter of 190 mm to obtain an ingot. This ingot was heated to 1100° C. and forged to obtain a rectangular bar having a size of 15 mm×15 mm. After holding this square bar at a temperature of 900° C. for 30 minutes, it was quenched by oil cooling. As shown in Table 2, the quenching temperature was adjusted to 900°C. This square bar was heated to a predetermined temperature and tempered by air cooling to obtain the alloy tool steel for hot working according to Example 1. The tempering temperature was adjusted so that the hardness of the rectangular bar after tempering was 39 HRC to 41 HRC. The composition of this alloy tool steel is shown in Table 1 below.
［実施例２－６及び比較例１－１０］
組成を表１に示される通りとし、焼入れ温度を表２に示すように８５０℃以上１２５０℃の範囲内で調整した点を除き、実施例１と同様にして、実施例２－６及び比較例１－１０の熱間加工用合金工具鋼を得た。 [Example 2-6 and Comparative Example 1-10]
Examples 2 to 6 and Comparative Example were prepared in the same manner as in Example 1 except that the composition was as shown in Table 1 and the quenching temperature was adjusted within the range of 850 ° C. to 1250 ° C. as shown in Table 2. 1-10 hot working alloy tool steels were obtained.
組成を表１に示される通りとし、焼入れ温度を表２に示すように８５０℃以上１２５０℃の範囲内で調整した点を除き、実施例１と同様にして、実施例２－６及び比較例１－１０の熱間加工用合金工具鋼を得た。 [Example 2-6 and Comparative Example 1-10]
Examples 2 to 6 and Comparative Example were prepared in the same manner as in Example 1 except that the composition was as shown in Table 1 and the quenching temperature was adjusted within the range of 850 ° C. to 1250 ° C. as shown in Table 2. 1-10 hot working alloy tool steels were obtained.
［軟化抵抗試験］
前述の角材（焼戻し後）を、６２０℃の温度下に１００時間保持した。この角材を、空冷した。この角材の硬さを測定し、下記の基準に従って格付けした。
Ａ：硬さが２６ＨＲＣ以上である。
Ｂ：硬さが２６ＨＲＣ未満である。
この結果が、下記の表２に示されている。 [Softening resistance test]
The aforementioned rectangular bar (after tempering) was held at a temperature of 620° C. for 100 hours. This square bar was air-cooled. The hardness of this rectangular timber was measured and graded according to the following criteria.
A: Hardness is 26HRC or more.
B: Hardness is less than 26 HRC.
The results are shown in Table 2 below.
前述の角材（焼戻し後）を、６２０℃の温度下に１００時間保持した。この角材を、空冷した。この角材の硬さを測定し、下記の基準に従って格付けした。
Ａ：硬さが２６ＨＲＣ以上である。
Ｂ：硬さが２６ＨＲＣ未満である。
この結果が、下記の表２に示されている。 [Softening resistance test]
The aforementioned rectangular bar (after tempering) was held at a temperature of 620° C. for 100 hours. This square bar was air-cooled. The hardness of this rectangular timber was measured and graded according to the following criteria.
A: Hardness is 26HRC or more.
B: Hardness is less than 26 HRC.
The results are shown in Table 2 below.
［転位密度］
前述の軟化抵抗試験の後の角材に、下記の条件にて、Ｘ線回折測定を実施した。
Ｘ線源：Ｃｕ－Ｋα線
計数時間：２秒
ステップサイズ：０．０２°
測定範囲２θ：３５°から１４０°
得られたマルテンサイトからの回折ピークを用いて、Ｍｏｄｉｆｉｅｄ Ｗｉｌｌｉａｍｓｏｎ－Ｈａｌｌ／Ｍｏｄｉｆｉｅｄ Ｗａｒｒｅｎ－Ａｖｅｒｂａｃｈ法による転位密度の定量を実施した。装置起因のピーク広がりは、ＬａＢ６を用いて補正した。この転位密度を、下記の基準に従って格付けした。
Ａ：転位密度が１．０×１０１４以上である。
Ｂ：転位密度が１．０×１０１４未満である。
この結果が、下記の表２に示されている。 [Dislocation density]
X-ray diffraction measurement was performed on the rectangular timber after the above softening resistance test under the following conditions.
X-ray source: Cu-Kα ray Counting time: 2 seconds Step size: 0.02°
Measurement range 2θ: 35° to 140°
Using the obtained diffraction peak from martensite, the dislocation density was quantified by the Modified Williamson-Hall/Modified Warren-Averbach method. Instrument-induced peak broadening was corrected using LaB6. This dislocation density was rated according to the following criteria.
A: The dislocation density is 1.0×10 14 or more.
B: Dislocation density is less than 1.0×10 14 .
The results are shown in Table 2 below.
前述の軟化抵抗試験の後の角材に、下記の条件にて、Ｘ線回折測定を実施した。
Ｘ線源：Ｃｕ－Ｋα線
計数時間：２秒
ステップサイズ：０．０２°
測定範囲２θ：３５°から１４０°
得られたマルテンサイトからの回折ピークを用いて、Ｍｏｄｉｆｉｅｄ Ｗｉｌｌｉａｍｓｏｎ－Ｈａｌｌ／Ｍｏｄｉｆｉｅｄ Ｗａｒｒｅｎ－Ａｖｅｒｂａｃｈ法による転位密度の定量を実施した。装置起因のピーク広がりは、ＬａＢ６を用いて補正した。この転位密度を、下記の基準に従って格付けした。
Ａ：転位密度が１．０×１０１４以上である。
Ｂ：転位密度が１．０×１０１４未満である。
この結果が、下記の表２に示されている。 [Dislocation density]
X-ray diffraction measurement was performed on the rectangular timber after the above softening resistance test under the following conditions.
X-ray source: Cu-Kα ray Counting time: 2 seconds Step size: 0.02°
Measurement range 2θ: 35° to 140°
Using the obtained diffraction peak from martensite, the dislocation density was quantified by the Modified Williamson-Hall/Modified Warren-Averbach method. Instrument-induced peak broadening was corrected using LaB6. This dislocation density was rated according to the following criteria.
A: The dislocation density is 1.0×10 14 or more.
B: Dislocation density is less than 1.0×10 14 .
The results are shown in Table 2 below.
［靱性］
前述の角材（焼戻し後）に、「ＪＩＳ Ｚ ２２４２：２００５」の規定に準拠してシャルピー衝撃試験を施し、衝撃値を測定した。条件は、下記の通りである。
試験片：ＪＩＳ－３号 縦：１０ｍｍ、横：１０ｍｍ、長さ：５０ｍｍ
ノッチ：Ｕノッチ
温度：常温
この衝撃値を、下記の基準に従って格付けした。
Ａ：衝撃値が５０Ｊ／ｃｍ２以上である。
Ｂ：衝撃値が５０Ｊ／ｃｍ２以下である。
この結果が、下記の表２に示されている。 [Toughness]
A Charpy impact test was performed on the above-mentioned rectangular bar (after tempering) in accordance with the provisions of "JIS Z 2242:2005" to measure the impact value. The conditions are as follows.
Test piece: JIS-3 length: 10 mm, width: 10 mm, length: 50 mm
Notch: U notch Temperature: normal temperature This impact value was rated according to the following criteria.
A: The impact value is 50 J/cm 2 or more.
B: The impact value is 50 J/cm 2 or less.
The results are shown in Table 2 below.
前述の角材（焼戻し後）に、「ＪＩＳ Ｚ ２２４２：２００５」の規定に準拠してシャルピー衝撃試験を施し、衝撃値を測定した。条件は、下記の通りである。
試験片：ＪＩＳ－３号 縦：１０ｍｍ、横：１０ｍｍ、長さ：５０ｍｍ
ノッチ：Ｕノッチ
温度：常温
この衝撃値を、下記の基準に従って格付けした。
Ａ：衝撃値が５０Ｊ／ｃｍ２以上である。
Ｂ：衝撃値が５０Ｊ／ｃｍ２以下である。
この結果が、下記の表２に示されている。 [Toughness]
A Charpy impact test was performed on the above-mentioned rectangular bar (after tempering) in accordance with the provisions of "JIS Z 2242:2005" to measure the impact value. The conditions are as follows.
Test piece: JIS-3 length: 10 mm, width: 10 mm, length: 50 mm
Notch: U notch Temperature: normal temperature This impact value was rated according to the following criteria.
A: The impact value is 50 J/cm 2 or more.
B: The impact value is 50 J/cm 2 or less.
The results are shown in Table 2 below.
表１に示されたそれぞれの合金の残部は、Ｆｅ及び不可避的不純物である。
The balance of each alloy shown in Table 1 is Fe and unavoidable impurities.
表２に示される通り、各実施例に係る熱間加工用合金工具鋼は、靱性及び軟化抵抗性に優れている。これらの評価結果から、本発明に係る合金工具鋼の優位性は明らかである。
As shown in Table 2, the alloy tool steel for hot working according to each example is excellent in toughness and softening resistance. From these evaluation results, the superiority of the alloy tool steel according to the present invention is clear.
以上説明された熱間加工用合金工具鋼は、高温環境下にて使用される種々の金属製品に適している。
The alloy tool steel for hot working described above is suitable for various metal products used in high-temperature environments.
Claims (1)
- Ｃ：０．４０質量％以上０．６０質量％以下、
Ｓｉ：０．１０質量％以上０．５０質量％以下、
Ｍｎ：０．２０質量％以上１．１０質量％以下、
Ｎｉ：０．２０質量％以上２．１０質量％以下、
Ｃｒ：０．５０質量％以上２．００質量％以下、
Ｍｏ：０．１０質量％以上０．６０質量％以下、
Ｖ及び／又はＮｂ：合計で０．０５質量％以上０．３０質量％以下、並びに、
Ｎ：０．０２０質量％以下
を含有し、残部がＦｅ及び不純物である、熱間加工用合金工具鋼であって、
前記熱間加工用合金工具鋼の金属組織がマルテンサイト又はベイナイトであり、
前記金属組織が、その径が２．０μｍ以上６．０μｍ以下であるブロックを含んでおり、
下記数式：
Ｑ＝（Ｃｒ１＋Ｍｏ１＋Ｖ１＋Ｎｂ１）／（Ｃｒ２＋Ｍｏ２＋Ｖ２＋Ｎｂ２）
［式中、
Ｃｒ１は焼入れ温度においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ１は焼入れ温度においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ１は焼入れ温度においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ１は焼入れ温度においてオーステナイトに固溶するＮｂの量（質量％）を表し、
Ｃｒ２は８００℃においてオーステナイトに固溶するＣｒの量（質量％）を表し、
Ｍｏ２は８００℃においてオーステナイトに固溶するＭｏの量（質量％）を表し、
Ｖ２は８００℃においてオーステナイトに固溶するＶの量（質量％）を表し、
Ｎｂ２は８００℃においてオーステナイトに固溶するＮｂの量（質量％）を表す。］
で算出される焼入時固溶元素パラメータＱが１．１２以上である、熱間加工用合金工具鋼。 C: 0.40% by mass or more and 0.60% by mass or less,
Si: 0.10% by mass or more and 0.50% by mass or less,
Mn: 0.20% by mass or more and 1.10% by mass or less,
Ni: 0.20% by mass or more and 2.10% by mass or less,
Cr: 0.50% by mass or more and 2.00% by mass or less,
Mo: 0.10% by mass or more and 0.60% by mass or less,
V and/or Nb: 0.05% by mass or more and 0.30% by mass or less in total, and
An alloy tool steel for hot working containing N: 0.020% by mass or less, the balance being Fe and impurities,
The metal structure of the alloy tool steel for hot working is martensite or bainite,
the metallographic structure includes blocks having a diameter of 2.0 μm or more and 6.0 μm or less;
The formula below:
Q=(Cr1+Mo1+V1+Nb1)/(Cr2+Mo2+V2+Nb2)
[In the formula,
Cr1 represents the amount (% by mass) of Cr dissolved in austenite at the quenching temperature,
Mo1 represents the amount (% by mass) of Mo dissolved in austenite at the quenching temperature,
V1 represents the amount (% by mass) of V dissolved in austenite at the quenching temperature,
Nb1 represents the amount (% by mass) of Nb dissolved in austenite at the quenching temperature,
Cr represents the amount (% by mass) of Cr dissolved in austenite at 800 ° C.,
Mo2 represents the amount (% by mass) of Mo dissolved in austenite at 800 ° C.,
V2 represents the amount (% by mass) of V dissolved in austenite at 800 ° C.,
Nb2 represents the amount (% by mass) of Nb dissolved in austenite at 800°C. ]
An alloy tool steel for hot working, wherein the parameter Q of solute elements during quenching calculated by the formula is 1.12 or more.
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| JP2022-031584 | 2022-03-02 | ||
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001089826A (en) * | 1999-09-22 | 2001-04-03 | Sumitomo Metal Ind Ltd | Hot working tool steel excellent in wear resistance |
| JP2021017623A (en) * | 2019-07-19 | 2021-02-15 | 山陽特殊製鋼株式会社 | Tool steel for hot work, excellent in thermal conductivity |
| WO2021149676A1 (en) * | 2020-01-22 | 2021-07-29 | 日本製鉄株式会社 | Steel sheet and method for producing same |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001089826A (en) * | 1999-09-22 | 2001-04-03 | Sumitomo Metal Ind Ltd | Hot working tool steel excellent in wear resistance |
| JP2021017623A (en) * | 2019-07-19 | 2021-02-15 | 山陽特殊製鋼株式会社 | Tool steel for hot work, excellent in thermal conductivity |
| WO2021149676A1 (en) * | 2020-01-22 | 2021-07-29 | 日本製鉄株式会社 | Steel sheet and method for producing same |
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