JP2021017623A - Tool steel for hot work, excellent in thermal conductivity - Google Patents
Tool steel for hot work, excellent in thermal conductivity Download PDFInfo
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- 229910001315 Tool steel Inorganic materials 0.000 title claims abstract description 41
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 37
- 239000010959 steel Substances 0.000 claims abstract description 37
- 239000012535 impurity Substances 0.000 claims abstract description 17
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 14
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 13
- 239000000203 mixture Substances 0.000 claims abstract description 11
- 229910000734 martensite Inorganic materials 0.000 claims description 20
- 239000000126 substance Substances 0.000 claims description 18
- 229910001563 bainite Inorganic materials 0.000 claims description 12
- 229910052802 copper Inorganic materials 0.000 abstract description 3
- 229910052742 iron Inorganic materials 0.000 abstract description 2
- 229910052751 metal Inorganic materials 0.000 abstract description 2
- 239000002184 metal Substances 0.000 abstract description 2
- 229910052804 chromium Inorganic materials 0.000 abstract 1
- 229910052748 manganese Inorganic materials 0.000 abstract 1
- 229910052720 vanadium Inorganic materials 0.000 abstract 1
- 238000010791 quenching Methods 0.000 description 33
- 230000000171 quenching effect Effects 0.000 description 33
- 238000005496 tempering Methods 0.000 description 32
- 150000001247 metal acetylides Chemical class 0.000 description 20
- 239000000463 material Substances 0.000 description 12
- 239000011159 matrix material Substances 0.000 description 12
- 238000004512 die casting Methods 0.000 description 8
- -1 C 6 carbides Chemical class 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 238000005242 forging Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000009628 steelmaking Methods 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical group [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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Abstract
Description
本発明は、熱伝導率に優れる熱間工具鋼に関する。特に熱間工具鋼のうち、ダイカストやホットスタンピングなどの、高温環境下で使用される金型用鋼に関する。 The present invention relates to a hot tool steel having excellent thermal conductivity. In particular, among hot tool steels, it relates to mold steels used in high temperature environments such as die casting and hot stamping.
近年、ダイカスト分野において、自動車の軽量化を目的としたアルミ部品の高強度化や生産性向上を目的とした部品成形の加工ピッチの短縮化から、ダイカスト金型への機械的及び熱的負荷が増大している。その結果、金型には、摩耗、大割れ、ヒートチェックといった問題が生じやすくなっている。これらの問題に対応するため、金型材料には、硬度・靭性に優れる材料が求められている。また、ホットスタンピングでは、被加工材である鋼板の表面に発生したスケールによる金型の摩耗が問題となっており、金型材料には、高い硬度及び軟化抵抗性が求められている。 In recent years, in the die-casting field, the mechanical and thermal load on the die-casting die has increased due to the increase in the strength of aluminum parts for the purpose of reducing the weight of automobiles and the shortening of the processing pitch of parts molding for the purpose of improving productivity. It is increasing. As a result, the mold is prone to problems such as wear, large cracks, and heat check. In order to deal with these problems, the mold material is required to have excellent hardness and toughness. Further, in hot stamping, wear of the mold due to the scale generated on the surface of the steel plate as the work material has become a problem, and the mold material is required to have high hardness and softening resistance.
さらに、ダイカストやホットスタンピング用の金型は、内部に冷却回路が作製されており、ここを流れる冷却水による冷却効率が生産サイクルスピードに大きく影響する。冷却効率を高める方法としては、金型の高熱伝導率化がある。そのため、前述した生産性向上を目的とした、生産サイクルスピードの向上に対する要求に応えるためには、材料の特性として、高い熱伝導率が必要である。 Further, the mold for die casting and hot stamping has a cooling circuit formed inside, and the cooling efficiency by the cooling water flowing through the circuit greatly affects the production cycle speed. As a method of increasing the cooling efficiency, there is a method of increasing the thermal conductivity of the mold. Therefore, in order to meet the above-mentioned demand for improvement of production cycle speed for the purpose of improving productivity, high thermal conductivity is required as a characteristic of the material.
特許文献１〜特許文献９には、上記要請の改善を試みる従来技術が提案されている。
まず、ＣｕやＢを考慮していないダイカスト金型用鋼が提案されている（例えば特許文献１参照。）。もっとも、言及のないＣｕやＢは不可避不純物の範囲に留まっているので、不完全焼入れ相であるベイナイトが形成しやすく、靱性が不足する問題がある。
Patent Documents 1 to 9 propose conventional techniques for attempting to improve the above requirements.
First, a die-casting die steel that does not consider Cu and B has been proposed (see, for example, Patent Document 1). However, since Cu and B, which are not mentioned, remain in the range of unavoidable impurities, there is a problem that bainite, which is an incompletely hardened phase, is easily formed and the toughness is insufficient.
また、熱間鍛造時に表面割れ現象が発生して鍛造性を減少させるので、Ｃｕを０．０２％以下とする熱間金型鋼が提案されている（例えば、特許文献２参照。）。もっとも、Ｃｕが少ないので不完全焼入れ相であるベイナイトが形成されて、靭性が不足する問題がある。 Further, since a surface cracking phenomenon occurs during hot forging and the forgeability is reduced, a hot shaped steel having Cu of 0.02% or less has been proposed (see, for example, Patent Document 2). However, since the amount of Cu is small, there is a problem that bainite, which is an incompletely hardened phase, is formed and the toughness is insufficient.
また、焼入れ性確保のためにＭｎが１．５０％より多く含有されている金型用鋼が提案されている（例えば、特許文献３参照。）。しかし、このようにＭｎが過剰添加されると熱伝導率が低下する問題がある。 Further, in order to ensure hardenability, a mold steel containing Mn in an amount of more than 1.50% has been proposed (see, for example, Patent Document 3). However, there is a problem that the thermal conductivity is lowered when Mn is excessively added in this way.
また、被削性確保のためにＶが０．１％以下で含有されている金型用鋼が提案されている（例えば、特許文献４参照。）。しかし、このようにＶが少ないと、焼入焼戻し硬さが不足する問題がある。 Further, in order to ensure machinability, a mold steel containing V of 0.1% or less has been proposed (see, for example, Patent Document 4). However, when V is small in this way, there is a problem that the quenching and tempering hardness is insufficient.
また、焼入れ時のγ結晶粒粗大化抑制のため、Ｖが０．５５％より多く含有されている金型用鋼を用いた成形具が提案されている（例えば、特許文献５参照。）。しかし、このようにＶが過剰に添加されると、熱伝導率が低下する問題がある。 Further, in order to suppress the coarsening of γ crystal grains at the time of quenching, a molding tool using a mold steel containing more than 0.55% of V has been proposed (see, for example, Patent Document 5). However, when V is excessively added in this way, there is a problem that the thermal conductivity is lowered.
また、耐食性確保のためにＣｒが４．００％以上と多く含有されている金型用鋼が提案されている（例えば、特許文献６参照。）。しかし、Ｃｒの過剰添加によって、熱伝導率が低下する問題がある。 Further, in order to ensure corrosion resistance, a mold steel containing a large amount of Cr of 4.00% or more has been proposed (see, for example, Patent Document 6). However, there is a problem that the thermal conductivity is lowered due to the excessive addition of Cr.
溶接割れ抑制のためＣが０．３５％以下と少なく含有されているダイカスト金型用プリハードン鋼が提案されている（例えば、特許文献７参照。）しかし、このようにＣ量が少ないと、焼入焼戻し硬さが不足する問題がある。 A pre-hardened steel for die casting dies containing a small amount of C of 0.35% or less has been proposed in order to suppress welding cracks (see, for example, Patent Document 7). However, if the amount of C is small in this way, quenching There is a problem that the quenching and tempering hardness is insufficient.
また、Ｍｏ＋１／２・Ｗが３．０％より大きい熱間工具鋼が提案されている（例えば、特許文献８参照。）。しかし、ＭｏまたはＷの過剰添加によって、熱伝導率が低下する問題がある。 Further, a hot tool steel having Mo + 1/2 · W greater than 3.0% has been proposed (see, for example, Patent Document 8). However, there is a problem that the thermal conductivity is lowered due to the excessive addition of Mo or W.
また、Ｎｉが３％以上含有されている熱間工具鋼が提案されている（例えば、特許文献９参照。）。この文献の請求項や実施例に記載の鋼は、Ｎｉを３％より多く含有している。しかし、３％以上では、Ｎｉの過剰添加によって熱伝導率が低下する問題がある。 Further, a hot tool steel containing 3% or more of Ni has been proposed (see, for example, Patent Document 9). The steels described in the claims and examples of this document contain more than 3% Ni. However, if it is 3% or more, there is a problem that the thermal conductivity is lowered due to the excessive addition of Ni.
本発明が解決しようとする課題は、高い熱伝導率、高い硬度、優れた軟化抵抗性、高い靭性を兼ね備えた、ダイカストやホットスタンピングなどに適用可能な金型用鋼である熱間工具鋼を提供することである。熱間工具鋼とは、熱間温度域の被加工物を加工する工具として用いられる工具鋼のことである。 The problem to be solved by the present invention is to obtain hot tool steel, which is a mold steel suitable for die casting, hot stamping, etc., which has high thermal conductivity, high hardness, excellent softening resistance, and high toughness. Is to provide. Hot tool steel is tool steel used as a tool for machining workpieces in the hot temperature range.
発明者は鋭意開発を進めた結果、合金成分を特定の範囲に規定し、さらには鋼の組織、炭化物状態を特定することで、高い熱伝導率、高い硬度、軟化抵抗性に優れ、および高い靭性を兼備した熱間工具鋼が得られることを見出した。 As a result of diligent development, the inventor has defined the alloy composition in a specific range, and further specified the structure and carbide state of the steel, resulting in high thermal conductivity, high hardness, excellent softening resistance, and high We have found that hot tool steel with toughness can be obtained.
課題を解決するための第１の手段は、質量％で、
Ｃ：０．３５超〜０．７０％、
Ｓｉ：０．０１〜１．２０％、
Ｍｎ：０．０１〜１．５０％、
Ｃｒ：０．３０〜４．００％、
Ｃｕ：０．０５〜３．５０％、
ＭｏとＷのうちの１種類または２種類であって、Ｍｏ：３．００％以下、Ｗ：６．００％以下で、かつ、Ｍｏ＋１／２・Ｗ：０．５０％〜３．００％であり、
Ｖ：０．１０超〜０．５５％、
Ｂ：０．０００１〜０．０１００％
を有し、残部はＦｅおよび不可避的不純物からなることを特徴とする熱間工具鋼である。
The first means to solve the problem is by mass%
C: Over 0.35 to 0.70%,
Si: 0.01 to 1.20%,
Mn: 0.01 to 1.50%,
Cr: 0.30 to 4.00%,
Cu: 0.05 to 3.50%,
One or two types of Mo and W, Mo: 3.00% or less, W: 6.00% or less, and Mo + 1/2 · W: 0.50% to 3.00%. Yes,
V: Over 0.10 to 0.55%,
B: 0.0001 to 0.0100%
The balance is a hot tool steel characterized by consisting of Fe and unavoidable impurities.
その第２の手段は、第１の手段に記載の化学成分に加えて、質量％でＮｉ：０．０１〜２．９９％を有し、残部：Ｆｅおよび不可避的不純物からなることを特徴とする熱間工具鋼である。 The second means is characterized in that, in addition to the chemical components described in the first means, it has Ni: 0.01 to 2.99% by mass, and the balance: Fe and unavoidable impurities. Hot tool steel.
その第３の手段は、第１または第２のいずれか１の手段に記載の化学成分に加えて、質量％でＮ：０．０００１〜０．０４００％を有し、残部：Ｆｅおよび不可避的不純物からなることを特徴とする熱間工具鋼である。 The third means has N: 0.0001 to 0.0400% by mass in addition to the chemical composition described in either the first or second means, the balance: Fe and inevitable. It is a hot tool steel characterized by being composed of impurities.
その第４の手段は、第１から第３のいずれか１の手段に記載の化学成分に加えて、質量％でＴｉ：０．００１〜０．０１５０％を有し、残部：Ｆｅおよび不可避的不純物からなることを特徴とする熱間工具鋼である。 The fourth means has Ti: 0.001 to 0.0150% by mass in addition to the chemical composition according to any one of the first to third means, with the balance: Fe and inevitable. It is a hot tool steel characterized by being composed of impurities.
その第５の手段は、第１から第４のいずれか１の手段に記載の化学成分に加えて、質量％で、Ａｌ：０．００１〜１．０００％を有し、残部はＦｅおよび不可避的不純物からなることを特徴とする熱間工具鋼である。 The fifth means has Al: 0.001 to 1.000% in mass% in addition to the chemical components according to any one of the first to fourth means, and the balance is Fe and unavoidable. It is a hot tool steel characterized by being composed of target impurities.
その第６の手段は、第１から第５のいずれか１の手段に記載の化学成分を有し、残部はＦｅおよび可避的不純物から熱間工具鋼は、マルテンサイト単相組織、あるいはマルテンサイトとベイナイトの混合組織であって該混合組織のマルテンサイトの割合は８０％以上であること、を特徴とする熱間工具鋼である。 The sixth means has the chemical composition according to any one of the first to fifth means, the balance is from Fe and unavoidable impurities, and the hot tool steel is martensite single-phase structure or martensite. It is a hot tool steel having a mixed structure of sight and bainite, wherein the ratio of martensite in the mixed structure is 80% or more.
その第７の手段は、第１から第５のいずれか１の手段に記載の化学成分を有し、残部は不可避的不純物からなる熱間工具鋼であって、鋼中のＭ23Ｃ6炭化物、Ｍ6Ｃ炭化物、Ｍ7Ｃ3炭化物、Ｍ3Ｃ炭化物、Ｍ2Ｃ炭化物およびＭＣ炭化物の全炭化物中に占める、Ｍ23Ｃ6炭化物及びＭ6Ｃ炭化物の割合が９０％以下であることを特徴とする熱間工具鋼である。 The seventh means is a hot tool steel having the chemical composition according to any one of the first to fifth means, the balance of which is unavoidable impurities, and M 23 C 6 carbides in the steel. , M 6 C Carbide, M 7 C 3 Carbide, M 3 C Carbide, M 2 C Carbide and MC Carbide in the total carbide, the ratio of M 23 C 6 Carbide and M 6 C Carbide is 90% or less. It is a hot tool steel characterized by.
その第８の手段は、第６の手段に記載の熱間工具鋼であって、さらに、鋼中のＭ23Ｃ6炭化物、Ｍ6Ｃ炭化物、Ｍ7Ｃ3炭化物、Ｍ3Ｃ炭化物、Ｍ2Ｃ炭化物およびＭＣ炭化物の全炭化物中に占める、Ｍ23Ｃ6炭化物及びＭ6Ｃ炭化物の割合が９０％以下であることを特徴とする熱間工具鋼である。 The eighth means is the hot tool steel according to the sixth means, and further, M 23 C 6 carbide, M 6 C carbide, M 7 C 3 carbide, M 3 C carbide, M in the steel. It is a hot tool steel characterized in that the ratio of M 23 C 6 carbide and M 6 C carbide to the total carbide of 2 C carbide and MC carbide is 90% or less.
さて、上記の本発明の各手段の熱間工具鋼は、これを焼入焼戻しされた状態で、室温での熱伝導率が２５．０Ｗ／ｍ・Ｋ以上の高熱伝導率となり、室温での硬さが４８．０ＨＲＣ以上の高硬度となり、焼入焼戻し後に６００℃で１００時間保持した後の室温での硬さが３２．０ＨＲＣ以上の高軟化抵抗性を示し、室温でのシャルピー衝撃値が２０Ｊ／ｃｍ2以上の高靭性となる。そこで、本発明の各手段の熱間工具鋼を用いると、金型用鋼として好適な、高熱伝導率、高硬度、高軟化抵抗性、高靱性を兼備するものとできる。 By the way, the hot tool steel of each means of the present invention described above has a high thermal conductivity of 25.0 W / m · K or more at room temperature in a state of being quenched and tempered, and at room temperature. The hardness is as high as 48.0 HRC or more, the hardness at room temperature after quenching and tempering at 600 ° C for 100 hours shows high softening resistance of 32.0 HRC or more, and the Charpy impact value at room temperature is High toughness of 20 J / cm 2 or more. Therefore, when the hot tool steel of each means of the present invention is used, it is possible to have high thermal conductivity, high hardness, high softening resistance, and high toughness suitable for mold steel.
なお、本発明において、
高熱伝導率とは：焼入焼戻し後の室温での熱伝導率が２５．０Ｗ／ｍ・Ｋ以上、
高硬度とは：焼入焼戻し後の室温での硬さが４８．０ＨＲＣ以上、
高靱性とは：焼入焼戻し後の室温でのシャルピー衝撃値が２０Ｊ／ｃｍ2以上、
高軟化抵抗性とは：焼入焼戻し後に６００℃で１００ｈ保持後の室温での硬さが３２．０ＨＲＣ以上のことをいう。
In addition, in this invention
What is high thermal conductivity: Thermal conductivity at room temperature after quenching and tempering is 25.0 W / m · K or more,
What is high hardness: Hardness at room temperature after quenching and tempering is 48.0 HRC or more,
What is high toughness: Charpy impact value at room temperature after quenching and tempering is 20 J / cm 2 or more,
High softening resistance: Hardness at room temperature of 32.0 HRC or more after holding at 600 ° C. for 100 hours after quenching and tempering.
まず、本発明の課題を解決するための手段の熱間工具鋼における化学成分の規定理由と、この熱間工具鋼の組織および炭化物の状態について規定する理由を以下に説明する。 First, the reason for defining the chemical composition in the hot tool steel of the means for solving the problem of the present invention and the reason for defining the structure and the state of carbides of the hot tool steel will be described below.
Ｃ：０．３５超〜０．７０％
Ｃは、固溶することでマトリックスを強化し、また、炭化物を形成すること析出強化を促す元素である。ところで、Ｃが０．３５％以下と少ない場合には、十分な焼入焼戻し硬さが得られない。一方、Ｃが０．７０％を超えて過多となると、偏析を助長し、靭性を低下させる。そこでＣは０．３５％超から０．７０％以下とし、望ましくは、Ｃは０．５５％超から０．７０％以下とする。
C: Over 0.35 to 0.70%
C is an element that strengthens the matrix by solid solution and promotes precipitation strengthening by forming carbides. By the way, when C is as small as 0.35% or less, sufficient quenching and tempering hardness cannot be obtained. On the other hand, when C exceeds 0.70% and becomes excessive, segregation is promoted and toughness is lowered. Therefore, C is set to more than 0.35% to 0.70% or less, and preferably C is set to more than 0.55% to 0.70% or less.
Ｓｉ：０．０１〜１．２０％
Ｓｉは、製鋼時の脱酸剤として必要な元素である。ところで、Ｓｉが０．０１％より少ないと、製鋼時に十分に脱酸されない。一方、Ｓｉは１．２０％より多過ぎると、炭化物を形成することなくマトリックスに固溶して熱伝導率を低下させる。そこで、Ｓｉは０．０１％以上１．２０％以下とする。しかし、Ｓｉは０．０５％以上であるときは、マトリックスに固溶することで硬さを向上させる効果があるので、望ましくは、Ｓｉは０．０５％以上１．００％以下とする。
Si: 0.01 to 1.20%
Si is an element required as a deoxidizer during steelmaking. By the way, if Si is less than 0.01%, it is not sufficiently deoxidized during steelmaking. On the other hand, if the amount of Si is more than 1.20%, it dissolves in the matrix without forming carbides and lowers the thermal conductivity. Therefore, Si is set to 0.01% or more and 1.20% or less. However, when Si is 0.05% or more, it has an effect of improving the hardness by being dissolved in the matrix, so it is desirable that Si is 0.05% or more and 1.00% or less.
Ｍｎ：０．０１〜１．５０％
Ｍｎは、製鋼時の脱酸剤として必要な元素である。ところで、Ｍｎが０．０１％より少ないと、十分に脱酸されない。一方、Ｍｎが１．５０％より多すぎると、マトリックスに固溶して熱伝導率を低下させる。そこで、Ｍｎは０．０１％以上１．５０％以下とし、望ましくはＭｎは０．０５％以上０．９２％未満とし、より望ましくはＭｎは０．１０％以上０．５０％未満とする。
Mn: 0.01 to 1.50%
Mn is an element required as a deoxidizer during steelmaking. By the way, if Mn is less than 0.01%, it is not sufficiently deoxidized. On the other hand, if Mn is more than 1.50%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Mn is 0.01% or more and 1.50% or less, preferably Mn is 0.05% or more and less than 0.92%, and more preferably Mn is 0.10% or more and less than 0.50%.
Ｃｒ：０．３０％〜４．００％
Ｃｒは、焼入れ性を向上させ、ベイナイト形成による靱性の低下を抑制するのに必要な元素である。ところで、Ｃｒが０．３０％より少ないと、十分な靭性が得られない。一方、Ｃｒが４．００％より過多であると、マトリックスに固溶して熱伝導率を低下させる。また、Ｃｒが多すぎると、焼戻し時に高温で粗大化しやすいＭ23Ｃ6炭化物が析出し、軟化抵抗性が低下する。そこで、Ｃｒは０．３０％以上４．００％以下とし、望ましくは、Ｃｒは０．４０％以上２．６０％未満とし、より望ましくは、Ｃｒは０．５０％以上２．１０％未満とする。
Cr: 0.30% to 4.00%
Cr is an element necessary for improving hardenability and suppressing a decrease in toughness due to bainite formation. By the way, if Cr is less than 0.30%, sufficient toughness cannot be obtained. On the other hand, if Cr is more than 4.00%, it dissolves in the matrix and lowers the thermal conductivity. Further, if the amount of Cr is too large, M 23 C 6 carbides that tend to be coarsened at a high temperature are precipitated during tempering, and the softening resistance is lowered. Therefore, Cr is 0.30% or more and 4.00% or less, preferably Cr is 0.40% or more and less than 2.60%, and more preferably Cr is 0.50% or more and less than 2.10%. To do.
Ｃｕ：０．０５％〜３．５０％
Ｃｕは、焼入れ性を向上させ、ベイナイト形成による靱性の低下を抑制するために必要な元素である。ところで、Ｃｕは０．０５％より少ないと、十分な靭性が得られない。一方、Ｃｕは３．５０％より多過ぎると、マトリックスに固溶して熱伝導率を低下させる。そこで、Ｃｕは０．０５％以上３．５０％以下とし、望ましくは、Ｃｕは０．１０％以上３．００％以下とする。
Cu: 0.05% to 3.50%
Cu is an element necessary for improving hardenability and suppressing a decrease in toughness due to bainite formation. By the way, if Cu is less than 0.05%, sufficient toughness cannot be obtained. On the other hand, if Cu is more than 3.50%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Cu is 0.05% or more and 3.50% or less, and preferably Cu is 0.10% or more and 3.00% or less.
ＭｏまたはＷのいずれか１種または２種を含有し、
Ｍｏ：３．００％以下、
Ｗ：６．００％以下、
Ｍｏ＋１／２・Ｗ：０．５０〜３．００％であること
ＭｏとＷは、焼戻し時の二次硬化を促進し、焼入焼戻し硬さを高めるために必用な元素である。ＭｏやＷは、多すぎると、マトリックスに残存するＭｏやＷが増加し、熱伝導率を低下させる。そこで、Ｍｏ＋１／２・Ｗが３．００％以下であって、Ｍｏ：３．００％以下、Ｗ：６．００％以下とする。
他方、ＭｏやＷが少なすぎると、十分な焼入焼戻し硬さがえられない。Ｍｏ＋１／２・Ｗが０．５０％未満で少なすぎると、十分な焼入焼戻し硬さが得られない。そこで、Ｍｏ、Ｗは１種又は２種を含有するものとし、Ｍｏは３．００％以下、Ｗは６．００％以下、Ｍｏ＋１／２・Ｗは０．５０％以上３．００％以下とし、望ましくはＭｏ＋１／２・Ｗは１．５０％以上３．００％以下とする。
Contains one or two of either Mo or W,
Mo: 3.00% or less,
W: 6.00% or less,
Mo + 1/2 · W: 0.50 to 3.00%
Mo and W are elements necessary for promoting secondary curing during tempering and increasing quenching and tempering hardness. If the amount of Mo or W is too large, the amount of Mo or W remaining in the matrix will increase and the thermal conductivity will decrease. Therefore, Mo + 1/2 · W is 3.00% or less, Mo: 3.00% or less, and W: 6.00% or less.
On the other hand, if Mo and W are too small, sufficient quenching and tempering hardness cannot be obtained. If Mo + 1/2 · W is less than 0.50% and too small, sufficient quenching and tempering hardness cannot be obtained. Therefore, Mo and W are assumed to contain one or two types, Mo is 3.00% or less, W is 6.00% or less, and Mo + 1/2 · W is 0.50% or more and 3.00% or less. Desirably, Mo + 1/2 · W is 1.50% or more and 3.00% or less.
Ｖ：０．１０超〜０．５５％
Ｖは、焼戻し時の二次硬化を促進し、焼入焼戻し硬さを高める元素である。ところが、Ｖが０．１０％以下であると、十分な焼入焼戻し硬さが得られない。一方、Ｖが０．５５％より多すぎると、マトリックスに残存するＶが増加し、熱伝導率を低下させる。そこで、Ｖは０．１０％超から０．５５％以下とし、望ましくは、Ｖは０．２５％以上０４５％未満とする。
V: Over 0.10 to 0.55%
V is an element that promotes secondary curing during tempering and enhances quenching and tempering hardness. However, when V is 0.10% or less, sufficient quenching and tempering hardness cannot be obtained. On the other hand, if V is more than 0.55%, the V remaining in the matrix increases and the thermal conductivity decreases. Therefore, V is set to more than 0.10% to 0.55% or less, and preferably V is set to 0.25% or more and less than 045%.
Ｂ：０．０００１〜０．０１００％
Ｂは、微量添加により、焼入性を向上させ、ベイナイト形成による靱性の低下を抑制するのに必要な元素である。ところで、Ｂが０．０００１％より少ないと、十分な靭性が得られない。一方、Ｂが０．０１００％より多すぎると焼戻し時に粗大な炭化物を形成し、靭性が低下する。そこで、Ｂは０．０００１％以上０．０１００％以下とし、望ましくは、Ｂは０．０００５％以上０．００７５％以下とする。
B: 0.0001 to 0.0100%
B is an element necessary for improving hardenability by adding a small amount and suppressing a decrease in toughness due to bainite formation. By the way, if B is less than 0.0001%, sufficient toughness cannot be obtained. On the other hand, if B is more than 0.0100%, coarse carbides are formed during tempering and the toughness is lowered. Therefore, B is 0.0001% or more and 0.0100% or less, and preferably B is 0.0005% or more and 0.0075% or less.
Ｎｉ：０．０１〜２．９９％
Ｎｉは、必ずしも添加する必要はない元素であるが、Ｃｒと同様に、焼入れ性を向上させ、ベイナイト形成による靱性の低下を抑制する元素である。ところで、Ｎｉは２．９９％より多く含有されると、マトリックスに固溶して熱伝導率を低下させる。そこで、Ｎｉは０．０１％以上２．９９％以下とし、望ましくは、Ｎｉは０．０１％以上２．００％以下とする。
Ni: 0.01 to 2.99%
Ni is an element that does not necessarily need to be added, but like Cr, it is an element that improves hardenability and suppresses a decrease in toughness due to bainite formation. By the way, when Ni is contained in an amount of more than 2.99%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Ni is 0.01% or more and 2.99% or less, and preferably Ni is 0.01% or more and 2.00% or less.
Ｎ：０．０００１〜０．０４００％
Ｎは、必ずしも添加する必要はないが、Ｃと同様に焼入焼戻硬さを大きくするのに有効な元素である。ところで、Ｎが０．０４００％より過剰に添加されると、製錬の際に時間を要するので、製錬時のコストの上昇を招く。そこで、Ｎは０．０００１％以上０．０４００％以下とし、望ましくは、Ｎは０．０００１％以上０．０３００％以下とする。
N: 0.0001 to 0.0400%
N is not necessarily added, but is an element effective for increasing the quenching and quenching hardness like C. By the way, if N is added in excess of 0.0400%, it takes time for smelting, which causes an increase in cost during smelting. Therefore, N is 0.0001% or more and 0.0400% or less, and preferably N is 0.0001% or more and 0.0300% or less.
Ｔｉ：０．１５０％以下
Ｔｉは、必ずしも添加する必要はないが、Ｂによる焼入性向上を促進する効果を有する元素である。焼入れの際にＮがＴｉと化合物化することによって、固溶Ｂ量が増加し、焼入性が向上する。ところが、Ｔｉが０．１５０％より多く添加されると、粗大なＴｉＮを形成し、靭性が低下する。そこで、Ｔｉは０．１５０％以下とし、望ましくは、Ｔｉは０．１００％以下とする。
Ti: 0.150% or less Ti is an element that does not necessarily have to be added, but has an effect of promoting the improvement of hardenability by B. When N is compounded with Ti during quenching, the amount of solid solution B increases and the quenchability is improved. However, when more than 0.150% of Ti is added, coarse TiN is formed and the toughness is lowered. Therefore, Ti is set to 0.150% or less, and preferably Ti is set to 0.100% or less.
Ａｌ：０．００１〜１．０００％
Ａｌは、必ずしも添加する必要はないが、マトリクスに固溶して硬さを向上する元素である。ところで、Ａｌが０．００１％未満であると、マトリックスに固溶して硬さが向上されない。一方、Ａｌが１．０００％より多いと、マトリックスに固溶して熱伝導率を低下させる。そこで、Ａｌは０．００１％以上１．０００％以下とし、望ましくは、Ａｌは０．００５％以上０．７００％以下とする。
Al: 0.001 to 1.000%
Al is an element that does not necessarily need to be added, but dissolves in a matrix to improve hardness. By the way, if Al is less than 0.001%, it dissolves in the matrix and the hardness is not improved. On the other hand, if Al is more than 1.000%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Al is 0.001% or more and 1.000% or less, and preferably Al is 0.005% or more and 0.700% or less.
次に熱間工具鋼の組織について説明する。
焼入焼戻し状態での組織：マルテンサイト単相（マルテンサイトの割合（Ｍ率）：１００％）、もしくはマルテンサイトとベイナイトの混合組織であって混合組織中のマルテンサイトの割合：８０％以上
焼入焼戻し状態の組織中に不完全焼入れ相であるベイナイトが多く存在すると、靭性が大幅に低下し、ホットスタンピング・ダイカスト金型として使う際に、十分な金型寿命が得られないこととなる。そこで、焼入焼戻し状態の組織は、マルテンサイト単相のみの組織（すなわち、マルテンサイトの割合のＭ率は１００％である。）か、あるいは、焼入焼戻し状態での組織がマルテンサイトとベイナイトの混合組織の場合には、該混合組織中におけるマルテンサイトの割合のＭ率は８０％以上である。
Next, the structure of the hot tool steel will be described.
Structure in the tempered state: Martensite single phase (ratio of martensite (M ratio): 100%), or a mixed structure of martensite and bainite, and the ratio of martensite in the mixed structure: 80% or more If a large amount of baynite, which is an incompletely hardened phase, is present in the tempered structure, the toughness is significantly reduced, and a sufficient mold life cannot be obtained when used as a hot stamping die casting mold. Therefore, the structure in the quenching and tempering state is a structure having only a single phase of martensite (that is, the M ratio of the ratio of martensite is 100%), or the structure in the quenching and tempering state is martensite and baynite. In the case of the mixed structure of, the M rate of the ratio of martensite in the mixed structure is 80% or more.
焼入焼戻しされた状態の熱間工具鋼の特定の炭化物の割合について
鋼材中の全炭化物に占めるＭ23Ｃ6炭化物及びＭ6Ｃ炭化物の割合：９０％以下
焼入焼戻し状態で、鋼材中の全炭化物（すなわち、Ｍ23Ｃ6炭化物、Ｍ6Ｃ炭化物、Ｍ7Ｃ3炭化物、Ｍ3Ｃ炭化物、Ｍ2Ｃ炭化物、ＭＣ炭化物）に占めるＭ23Ｃ6炭化物及びＭ6Ｃの炭化物の割合を９０％以下とする。なぜなら、高温で粗大化しやすい炭化物であるＭ23Ｃ6炭化物とＭ6Ｃ炭化物が焼入焼戻し状態で鋼材中に９０％より多く存在すると、鋼材の軟化抵抗性が低下するからである。
About the ratio of specific carbides in hot tool steel in the hardened and tempered state Ratio of M 23 C 6 carbides and M 6 C carbides in the total carbides in the steel material: 90% or less In the hardened and tempered state, in the steel material Percentage of M 23 C 6 carbides and M 6 C carbides in total carbides (ie, M 23 C 6 carbides, M 6 C carbides, M 7 C 3 carbides, M 3 C carbides, M 2 C carbides, MC carbides) Is 90% or less. This is because if more than 90% of M 23 C 6 carbide and M 6 C carbide, which are carbides that tend to be coarsened at high temperature, are present in the steel material in the state of quenching and tempering, the softening resistance of the steel material is lowered.
次いで、本発明の実施の形態について、適宜、表を参照しながら順次説明する。 Next, embodiments of the present invention will be sequentially described with reference to the table as appropriate.
本発明の実施例として、以下の表１および表２に、発明鋼Ｎｏ．１〜Ｎｏ．７８の化学成分を示す。また、表３にＮｏ．７９〜９７の比較鋼の化学成分を示す。なお、残部はＦｅおよび不可避的不純物である。
これらの化学成分のＮｏ．１〜８３の発明鋼ならびに比較鋼は、それぞれ、真空誘導溶解炉にて溶製して、得られた各Ｎｏ．の１００ｋｇの鋼塊を、それぞれ幅６５ｍｍで高さ３０ｍｍのブロックに熱間鍛伸により鍛伸材とした。次いで、これらの各Ｎｏ．の鍛伸材を８７０℃で焼なましを行った後、それらの表面と中心との中間位置から、直径２０ｍｍで長さ１６０ｍｍの丸棒をそれぞれ採取した。
さらに、これらの各丸棒を１０３０℃に保持して均熱化した後、空冷によって焼入れを行ない、次いで５７０〜６７０℃で２回の焼戻しを行った。その後、焼入焼戻しされた状態の各鋼材の組織、析出炭化物を観察し、また表４〜表６に示す各種の特性についての調査を実施した。
As an example of the present invention, the following Tables 1 and 2 show the invention steel No. 1-No. 78 chemical components are shown. In addition, Table 3 shows No. The chemical composition of the comparative steels of 79 to 97 is shown. The balance is Fe and unavoidable impurities.
No. of these chemical components The invention steels 1 to 83 and the comparative steels were each obtained by melting in a vacuum induction melting furnace, and each No. 100 kg of steel ingots were formed into blocks having a width of 65 mm and a height of 30 mm by hot forging. Then, each of these Nos. After annealing the forged materials of No. 1 at 870 ° C., round bars having a diameter of 20 mm and a length of 160 mm were collected from intermediate positions between their surfaces and the center.
Further, each of these round bars was kept at 1030 ° C. to equalize the heat, then quenched by air cooling, and then tempered twice at 570 to 670 ° C. After that, the structure and precipitated carbides of each steel material in the state of quenching and tempering were observed, and various characteristics shown in Tables 4 to 6 were investigated.
上記の各種の特性とは、熱伝導率（Ｗ／ｍ・Ｋ）、焼入焼戻し硬さ（ＨＲＣ）、靭性を示すシャルピー衝撃値（Ｊ／ｃｍ2）および高温保持後の硬さ（ＨＲＣ）すなわち軟化抵抗性である。 The above-mentioned various characteristics include thermal conductivity (W / m · K), quenching and tempering hardness (HRC), Charpy impact value (J / cm 2 ) indicating toughness, and hardness after high temperature holding (HRC). That is, it is softening resistant.
１）組織観察は、焼入焼戻しされた状態の各試料について、その鍛伸方向に平行な面を、鏡面になるまで研磨して、ナイタールで腐食した後、走査型電子顕微鏡（ＳＥＭ）を用いて行った。総面積５００００μｍ2の領域において、ベイナイトの有無を確認し、ベイナイトが確認された場合には、画像解析を用いて、面積率の算出を百分率で行った。 1) For microstructure observation, for each sample in the quenched and tempered state, the surface parallel to the forging direction is polished to a mirror surface, corroded with nital, and then a scanning electron microscope (SEM) is used. I went. The presence or absence of bainite was confirmed in a region having a total area of 50,000 μm 2 , and if bainite was confirmed, the area ratio was calculated as a percentage using image analysis.
２）炭化物観察用の試験片は、焼入焼戻しした状態の各試料の鍛伸方向に平行な面を研磨し、抽出レプリカ法により作成した。この試験片を、透過型電子顕微鏡の明視野像を用いて、総面積５００μｍ2の領域において観察した。炭化物種は、電子線回折の結果と炭化物の形状から判断した。撮影した写真を画像解析し、全炭化物中に占めるＭ23Ｃ6炭化物、Ｍ6Ｃ炭化物の合計面積率を百分率で算出した。 2) The test piece for observing carbides was prepared by the extraction replica method by polishing the surface parallel to the forging direction of each sample in the quenched and tempered state. This test piece was observed in a region having a total area of 500 μm 2 using a bright field image of a transmission electron microscope. The carbide species was determined from the result of electron diffraction and the shape of the carbide. The photograph taken was image-analyzed, and the total area ratio of M 23 C 6 carbide and M 6 C carbide in the total carbide was calculated as a percentage.
３）熱伝導率の測定には、レーザフラッシュ法を用いた。焼入焼戻しされた状態の各試料を直径１０ｍｍ×１ｍｍの円柱形状に仕上げ加工して、試験に供した。熱伝導率は、室温で測定した。 3) The laser flash method was used for the measurement of thermal conductivity. Each sample in the state of quenching and tempering was finished into a cylindrical shape having a diameter of 10 mm × 1 mm and subjected to a test. Thermal conductivity was measured at room temperature.
４）焼入焼戻し硬さは、ロックウェル硬さ試験機により室温で測定した。焼入焼戻しされた状態の各試料について、その鍛伸方向に垂直な面の硬さを測定した。 4) Quenching and tempering hardness was measured at room temperature by a Rockwell hardness tester. For each sample in the quenched and tempered state, the hardness of the surface perpendicular to the forging direction was measured.
５）靭性は、室温でのシャルピー衝撃試験により評価を実施した。試験片は、焼入焼戻し後の鋼材の試料から作製した。試験片形状は２ｍｍＵノッチシャルピー試験片であり、ノッチ方向は鍛伸方向に対して垂直な方向とした。 5) The toughness was evaluated by a Charpy impact test at room temperature. The test piece was prepared from a sample of steel material after quenching and tempering. The shape of the test piece was a 2 mm U notch Charpy test piece, and the notch direction was perpendicular to the forging direction.
６）軟化抵抗性は、焼入焼戻し後の鋼材の試料を６００℃で１００時間保持して空冷した後、室温での硬さをロックウェル硬さ試験機で測定することで評価した。 6) The softening resistance was evaluated by holding the sample of the steel material after quenching and tempering at 600 ° C. for 100 hours, air-cooling it, and then measuring the hardness at room temperature with a Rockwell hardness tester.
上記の１）の組織および２）の炭化物の状態については、表１〜３に示した。表中の組織のＭ率とは、組織中におけるマルテンサイトの面積比を百分率で示した値である。また、全炭化物中のＭ6Ｃ炭化物及びＭ23Ｃ6炭化物の合計面積率を百分率で示している。 The structure of 1) and the state of carbides of 2) are shown in Tables 1 to 3. The M ratio of the tissue in the table is a value indicating the area ratio of martensite in the tissue as a percentage. In addition, the total area ratio of M 6 C carbide and M 23 C 6 carbide in total carbide is shown as a percentage.
上記の３）で測定した熱伝導率、４）で測定した焼入焼戻し硬さ、５）で測定したシャルピー衝撃値（靭性）、および６）で測定した高温保持後の硬さ（軟化抵抗性）、について、以下の表４および表５で発明鋼について示し、さらに以下の表６で比較鋼について示した。 Thermal conductivity measured in 3) above, quenching and tempering hardness measured in 4), Charpy impact value (toughness) measured in 5), and hardness (softening resistance) after high temperature holding measured in 6). ), The invention steel is shown in Tables 4 and 5 below, and the comparative steel is shown in Table 6 below.
本願の発明鋼は、表１および表２の各Ｎｏ．１〜７８の化学成分を有し、８０％以上のマルテンサイトの面積率であって、全炭化物中のＭ6Ｃ炭化物及びＭ23Ｃ6炭化物の合計面積率を９０％以下としている。それらの発明鋼は、表４および表５の各Ｎｏ．１〜７８において示すように、熱伝導率が２５．０Ｗ／ｍ・Ｋ以上、焼入焼戻し硬さが４８．０ＨＲＣ以上、シャルピー衝撃値が２０Ｊ／ｃｍ2以上、高温保持後の硬さが３２．０ＨＲＣ以上であった。このように、本願の熱間工具鋼は、成分組成、組織、炭化物に着目することで、焼入焼戻した状態のときに、高熱伝導率、高硬度、高軟化抵抗性および高靭性を兼備する熱間工具鋼として、金型用鋼等に好適に適用しうるものとなる。 The steels of the present invention are the Nos. Nos. 1 and 2 in Table 1. It has 1 to 78 chemical components and has an area ratio of martensite of 80% or more, and the total area ratio of M 6 C carbide and M 23 C 6 carbide in total carbide is 90% or less. The steels of those inventions are No. 1 in Tables 4 and 5. As shown in 1 to 78, the thermal conductivity is 25.0 W / m · K or more, the quenching tempering hardness is 48.0 HRC or more, the Charpy impact value is 20 J / cm 2 or more, and the hardness after high temperature holding is 32. It was 0.0 HRC or higher. As described above, the hot tool steel of the present application has high thermal conductivity, high hardness, high softening resistance and high toughness in the state of quenching and tempering by paying attention to the composition, structure and carbides. As hot tool steel, it can be suitably applied to mold steel and the like.
これに対して、比較鋼では、表３の各Ｎｏ．７９〜９７における化学成分には、本願の規定する成分範囲から一部が外れている。また、組織がマルテンサイトとベイナイトの混合組織であってマルテンサイトの面積率が低いもの、Ｍ6Ｃ炭化物及びＭ23Ｃ6炭化物の合計面積率の割合が高すぎるものが含まれている。
そして、これら比較鋼の特性については、表６の各Ｎｏ．７９〜９７に示すとおり、熱伝導率、硬度、軟化抵抗性、靭性のいずれかの特性が本願の熱間工具鋼よりも劣るものとなった。
On the other hand, in the comparative steel, each No. in Table 3 Some of the chemical components in 79 to 97 are out of the component range specified in the present application. In addition, the structure is a mixed structure of martensite and bainite, and the area ratio of martensite is low, and the ratio of the total area ratio of M 6 C carbide and M 23 C 6 carbide is too high.
The characteristics of these comparative steels are described in Table 6 No. As shown in 79 to 97, any of the properties of thermal conductivity, hardness, softening resistance, and toughness is inferior to that of the hot tool steel of the present application.
比較例について、さらに以下に詳述する。
Ｎｏ．７９では、表３に示すように、Ｃが０．３３％で規定より少なく、表６に示すように、焼入れ焼戻し硬さが４６．４ＨＲＣで規定より低い。
Ｎｏ．８０では、表３に示すように、Ｃが０．７３％で規定より多く、表６に示すように、シャルピー衝撃値が１４．２Ｊ／ｃｍ2で規定より低い。
Ｎｏ．８１では、表３に示すように、Ｓｉが１．２７％で規定より多く、表６に示すように、熱伝導率が２３．５Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．８２では、表３に示すように、Ｍｏが１．５４％で規定より多く、表６に示すように、熱伝導率が２３．８Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．８３では、表３に示すように、Ｃｒが０．２３％で規定より少なく、さらにマルテンサイトの割合であるＭ率が７４％と低く、表６に示すように、シャルピー衝撃値が１５．５Ｊ／ｃｍ2で規定より低い。
Ｎｏ．８４では、表３に示すように、Ｃｒが４．１２％で規定より多く、さらに全金属炭化物中のＭ6Ｃ炭化物及びＭ23Ｃ6炭化物の合計面積率が９１％でやや高く、表６に示すように、熱伝導率が２２．９Ｗ／ｍ・Ｋで規定より低く、さらに高温保持後の硬さが３１．６ＨＲＣで規定より低い。
Ｎｏ．８５では、表３に示すように、Ｎｉが３．１２％で規定より多く、表６に示すように、熱伝導率が２３．１Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．８６では、表３に示すように、Ｃｕが０．０３％で規定より少なく、さらにマルテンサイトの割合であるＭ率が７８％とやや低く、表６に示すように、シャルピー衝撃値が１５．４Ｊ／ｃｍ2で規定より低い。
Ｎｏ．８７では、Ｃｕが３．６２％で規定よりやや多く、表６に示すように、Ｎｏ．７５では、熱伝導率が２２．７Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．８８では、表３に示すように、Ｍｏが３．１２％で規定より少なく、さらにＭｏ＋１／２・Ｗが３．１２％で規定より多く、表６に示すように、熱伝導率が２２．８Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．８９では、表３に示すように、Ｗが６．４７％で規定より多く、さらにＭｏ＋１／２・Ｗが３．２４％で規定より多く、表６に示すように、熱伝導率が２４．２Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．９０では、表３に示すように、Ｍｏ＋１／２・Ｗが３．４６％で規定より多く、表６に示すように、熱伝導率が２４．２Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．９１では、表３に示すように、Ｍｏ＋１／２・Ｗが０．４１％で規定より少なく、表６に示すように、焼入れ焼戻し硬さが４６．６ＨＲＣで規定より低い。
Ｎｏ．９２では、表３に示すように、Ｖが０．０８％で規定より少なく、表６に示すように、焼入れ焼戻し硬さが４２．３ＨＲＣで規定より低い。
Ｎｏ．９３では、表３に示すように、Ｖが０．６１％で規定より多く、表６に示すように、熱伝導率が２４．２Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．９４では、表３に示すように、Ｖが０．６１％で規定より多く、表６に示すように、熱伝導率が２４．２Ｗ／ｍ・Ｋで規定より低い。
Ｎｏ．９５では、表３に示すように、Ｂが０．０１２％で規定より多く、表６に示すように、シャルピー衝撃値が１７．２Ｊ／ｃｍ2で規定より低い。
Ｎｏ．９６では、表３に示すように、Ｔｉが０．１６２％で規定より多く、表６に示すように、シャルピー衝撃値が１６．０Ｊ／ｃｍ2で規定より低い。
Ｎｏ．９７では、表３に示すように、Ａｌが１．２１０％で規定より多く、表６に示すように、熱伝導率が２２．５Ｗ／ｍ・Ｋで規定より低い。
A comparative example will be described in more detail below.
No. In 79, as shown in Table 3, C was 0.33%, which was less than the specified value, and as shown in Table 6, the quenching and tempering hardness was 46.4 HRC, which was lower than the specified value.
No. In 80, as shown in Table 3, C was 0.73%, which was higher than the specified value, and as shown in Table 6, the Charpy impact value was 14.2 J / cm 2, which was lower than the specified value.
No. In 81, as shown in Table 3, Si was 1.27%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 23.5 W / m · K, which was lower than the specified value.
No. In 82, as shown in Table 3, Mo was 1.54%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 23.8 W / m · K, which was lower than the specified value.
No. In 83, as shown in Table 3, Cr was 0.23%, which was less than the specified value, and the M ratio, which is the proportion of martensite, was as low as 74%. As shown in Table 6, the Charpy impact value was 15.5J. / Cm 2 is lower than specified.
No. In 84, as shown in Table 3, Cr was 4.12%, which was higher than the specified value, and the total area ratio of M 6 C carbides and M 23 C 6 carbides in the total metal carbides was 91%, which was slightly higher. As shown in the above, the thermal conductivity is 22.9 W / m · K, which is lower than the specified value, and the hardness after holding at a high temperature is 31.6 HRC, which is lower than the specified value.
No. In 85, as shown in Table 3, Ni was 3.12%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 23.1 W / m · K, which was lower than the specified value.
No. In 86, as shown in Table 3, Cu was 0.03%, which was less than the specified value, and M ratio, which is the ratio of martensite, was slightly low, 78%. As shown in Table 6, the Charpy impact value was 15. 4 J / cm 2 is lower than specified.
No. In 87, Cu was 3.62%, which was slightly higher than the specified value, and as shown in Table 6, No. At 75, the thermal conductivity is 22.7 W / m · K, which is lower than the specified value.
No. In 88, as shown in Table 3, Mo was 3.12%, which was less than the specified value, and Mo + 1/2 · W was 3.12%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 22. It is lower than the regulation at 8 W / m · K.
No. In 89, as shown in Table 3, W was 6.47%, which was more than specified, and Mo + 1/2 · W was 3.24%, which was more than specified, and as shown in Table 6, the thermal conductivity was 24. It is lower than the regulation at 2 W / m · K.
No. In 90, as shown in Table 3, Mo + 1/2 · W was 3.46%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 24.2 W / m · K, which was lower than the specified value.
No. In 91, as shown in Table 3, Mo + 1/2 · W was 0.41%, which was less than the specified value, and as shown in Table 6, the quenching and tempering hardness was 46.6 HRC, which was lower than the specified value.
No. In 92, as shown in Table 3, V was 0.08%, which was less than the specified value, and as shown in Table 6, the quenching and tempering hardness was 42.3 HRC, which was lower than the specified value.
No. In 93, as shown in Table 3, V was 0.61%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 24.2 W / m · K, which was lower than the specified value.
No. In 94, as shown in Table 3, V is 0.61%, which is higher than the specified value, and as shown in Table 6, the thermal conductivity is 24.2 W / m · K, which is lower than the specified value.
No. In 95, as shown in Table 3, B was 0.012%, which was higher than the specified value, and as shown in Table 6, the Charpy impact value was 17.2 J / cm 2, which was lower than the specified value.
No. In 96, as shown in Table 3, Ti was 0.162%, which was higher than the specified value, and as shown in Table 6, the Charpy impact value was 16.0 J / cm 2, which was lower than the specified value.
No. In 97, as shown in Table 3, Al was 1.210%, which was higher than the specified value, and as shown in Table 6, the thermal conductivity was 22.5 W / m · K, which was lower than the specified value.
Claims (8)
Ｃ：０．３５超〜０．７０％、
Ｓｉ：０．０１〜１．２０％、
Ｍｎ：０．０１〜１．５０％、
Ｃｒ：０．３０〜４．００％、
Ｃｕ：０．０５〜３．５０％、
ＭｏとＷのうちの１種類または２種類であって、Ｍｏ：３．００％以下、Ｗ：６．００％以下で、かつ、Ｍｏ＋１／２・Ｗ：０．５０％〜３．００％であり、
Ｖ：０．１０超〜０．５５％、
Ｂ：０．０００１〜０．０１００％、
を有し、残部はＦｅおよび不可避的不純物からなることを特徴とする熱間工具鋼。 By mass%
C: Over 0.35 to 0.70%,
Si: 0.01 to 1.20%,
Mn: 0.01 to 1.50%,
Cr: 0.30 to 4.00%,
Cu: 0.05 to 3.50%,
One or two types of Mo and W, Mo: 3.00% or less, W: 6.00% or less, and Mo + 1/2 · W: 0.50% to 3.00%. Yes,
V: Over 0.10 to 0.55%,
B: 0.0001 to 0.0100%,
Hot tool steel characterized in that the balance consists of Fe and unavoidable impurities.
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