JP6800532B2 - Hot tool steel with excellent thermal conductivity - Google Patents
Hot tool steel with excellent thermal conductivity Download PDFInfo
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- JP6800532B2 JP6800532B2 JP2017010738A JP2017010738A JP6800532B2 JP 6800532 B2 JP6800532 B2 JP 6800532B2 JP 2017010738 A JP2017010738 A JP 2017010738A JP 2017010738 A JP2017010738 A JP 2017010738A JP 6800532 B2 JP6800532 B2 JP 6800532B2
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- 229910001315 Tool steel Inorganic materials 0.000 title claims description 16
- 229910000831 Steel Inorganic materials 0.000 claims description 27
- 239000010959 steel Substances 0.000 claims description 27
- 238000010791 quenching Methods 0.000 claims description 21
- 230000000171 quenching effect Effects 0.000 claims description 21
- 238000005496 tempering Methods 0.000 claims description 21
- 238000012360 testing method Methods 0.000 claims description 10
- 229910052721 tungsten Inorganic materials 0.000 claims description 10
- 150000001247 metal acetylides Chemical class 0.000 claims description 9
- 239000000470 constituent Substances 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 239000011159 matrix material Substances 0.000 description 12
- 230000007423 decrease Effects 0.000 description 10
- 238000004512 die casting Methods 0.000 description 8
- 238000000034 method Methods 0.000 description 6
- 229910052750 molybdenum Inorganic materials 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910001563 bainite Inorganic materials 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005275 alloying Methods 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
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000010137 moulding (plastic) Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- 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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
Description
本発明は、金型用鋼に関して、特にダイカストやホットスタンピングなどの、５００℃以上の熱環境下で使用される金型用鋼に関する。 The present invention relates to a mold steel, particularly a mold steel used in a thermal environment of 500 ° C. or higher, such as die casting or 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加工ピッチの短縮化から、ダイカスト金型への機械的およ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、硬度および靭性に優れる材料が求められている。また、ダイカスト・ホットプレス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。これらの点に着目した従来技術や類似技術として、以下の技術が挙げられる。本発明とは異なるものである。 In recent years, in the die casting field, mechanical and thermal loads on die casting dies have been increasing due to the increase in strength of aluminum parts for the purpose of reducing the weight of automobiles and the shortening of the parts molding processing pitch 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. In addition, a cooling circuit is manufactured inside the die-cast hot press die, and the cooling efficiency of the cooling water flowing through this 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. The following techniques can be mentioned as conventional techniques and similar techniques focusing on these points. It is different from the present invention.
従来技術として、金型用鋼として、質量％で、Ｃ：０．２５％超え０．３８％未満、Ｓｉ：０．０１％超え０．３０％未満、Ｍｎ：０．９２％超え１．８０％未満、Ｃｒ：０．８％超え２．２％未満、Ｍｏ：０．８％超え１．４％未満、Ｖ：０．２５％超え０．５８％未満を含有する金型用鋼が提案されている（例えば、特許文献１参照。）。しかし、この提案の金型用鋼は、Ｍｎ量が本願発明と異なり、Ｍｎの過剰添加によって熱伝導率が低下する問題がある。 As a conventional technique, as a mold steel, in terms of mass%, C: 0.25% or more and less than 0.38%, Si: 0.01% or more and less than 0.30%, Mn: 0.92% or more and 1.80. Proposed mold steel containing less than%, Cr: more than 0.8% and less than 2.2%, Mo: more than 0.8% and less than 1.4%, V: more than 0.25% and less than 0.58% (See, for example, Patent Document 1). However, the mold steel of this proposal has a problem that the amount of Mn is different from that of the present invention and the thermal conductivity is lowered due to excessive addition of Mn.
さらに、高い熱伝導率を有する金型用鋼が提案されている（例えば、特許文献２参照。）。しかし、この提案の金型用鋼は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 mold steel having a high thermal conductivity has been proposed (see, for example, Patent Document 2). However, the mold steel of this proposal has a problem that the thermal conductivity is lowered due to the excessive addition of Mo or W.
フェライト・パーライトの二相組織としたプラスチック成形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、Ｖ量が本発明と異なり、焼入焼戻し硬さが不足する問題がある。 Steels for plastic molding dies having a two-phase structure of ferrite and pearlite have been proposed (see, for example, Patent Document 3). However, the amount of V is different from that of the present invention, and there is a problem that the quenching and tempering hardness is insufficient.
焼入れ加熱時にオーステナイト結晶粒の粗粒化を防止して焼入れ焼戻し後の靱性を高くして得て、熱伝導性能が高い金型用鋼および金型の発明が提供されている（例えば、特許文献４参照。）。しかし、この発明はＶ量が本発明と異なり、Ｖの過剰添加によって熱伝導率が低下する問題がある。 Inventions of mold steels and dies having high thermal conductivity performance have been provided, which are obtained by preventing coarsening of austenite crystal grains during quenching and heating to increase toughness after quenching and tempering (for example, Patent Documents). See 4.). However, this invention has a problem that the amount of V is different from that of the present invention and the thermal conductivity is lowered due to excessive addition of V.
本願発明が解決しようとする課題は、高硬度、高靭性、高熱伝導率を兼ね備えており、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を提供することである。 An object to be solved by the present invention is to provide a mold steel which has high hardness, high toughness, and high thermal conductivity and can be applied to die casting, hot stamping, and the like.
発明者らは鋭意開発を進めた結果、本願の請求項に示す合金成分とし、かつ限定式を満たすことにより、高硬度、高靭性、高熱伝導率を兼備した熱間工具鋼が得られることを見出したことに基づくものである。 As a result of diligent development, the inventors have determined that a hot tool steel having high hardness, high toughness, and high thermal conductivity can be obtained by using the alloy component shown in the claims of the present application and satisfying the limited formula. It is based on what we have found.
課題を解決するための本発明の手段は、第１の手段では、質量％で、Ｃ：０．２０〜０．５０％、Ｓｉ：０．５０％以下、Ｍｎ：０．９２％以下、Ｃｒ：４．００％以下、Ｎｉ：２．００％以下、２Ｍｏ＋Ｗ：１．８０％未満（ただし、Ｍｏ：０．９０％未満、かつ、Ｗ：１．８０％未満）、Ｖ：０．１０超〜０．６１％、Ｎ：０．０４０％以下、Ａｌ：０．０８０％以下を含有し、残部Ｆｅおよび不可避不純物からなり、ＴＣ＝６８．０−６．５Ｍｎ−５．７Ｃｒ−３．１Ｖ−４．４Ｍｏ−２．２Ｗ−２４．７Ｃ−２１．２Ｎ−６．５Ｎｉ−１．７Ｓｉ＋３．２Ａ≧３２．５を満足することを特徴とする熱伝導率に優れた熱間工具鋼である。
ただし、ＴＣの式中の各元素記号は質量％を示し、かつ式中のＡは焼戻し状態での全炭化物の総面積率（％）を示す。
The means of the present invention for solving the problem is, in the first means, in terms of mass%, C: 0.20 to 0.50%, Si: 0.50% or less, Mn: 0.92% or less, Cr. : 4.00% or less, Ni: 2.00% or less, 2Mo + W: less than 1.80% (however, Mo: less than 0.90% and W: less than 1.80%), V: more than 0.10. It contains ~ 0.61%, N: 0.040% or less, Al: 0.080% or less, and consists of the balance Fe and unavoidable impurities. TC = 68.0-6.5Mn-5.7Cr-3.1V -4.4Mo-2.2W-24.7C-21.2N-6.5Ni-1.7Si + 3.2A ≧ 32.5 is a hot tool steel with excellent thermal conductivity. ..
However, each element symbol in the TC formula indicates mass%, and A in the formula indicates the total area ratio (%) of all carbides in the tempered state.
第２の手段では、第１の手段の熱間工具鋼の構成要件に加えて、該鋼の焼入焼戻し状態の室温における熱伝導率が３０．０（Ｗ／ｍ・Ｋ）以上であることを特徴とする熱伝導率に優れた熱間工具鋼である。 In the second means, in addition to the constituent requirements of the hot tool steel of the first means, the thermal conductivity of the steel in the quenched and tempered state at room temperature is 30.0 (W / m · K) or more. It is a hot tool steel with excellent thermal conductivity.
第３の手段では、第１の手段および第２の手段の熱間工具鋼の構成要件に加えて焼入焼戻し状態での硬さが４０.０ＨＲＣ以上であることを特徴とする熱伝導率に優れた熱間工具鋼である。 In the third means, in addition to the constituent requirements of the hot tool steel of the first means and the second means, the thermal conductivity in the quenched and tempered state is 40.0 HRC or more. Excellent hot tool steel.
第４の手段では、第１の手段、第２の手段および第３の手段の熱間工具鋼の構成要件に加えて焼入焼戻し状態での２ｍｍＵノッチ試験片でのシャルピー衝撃値が３０Ｊ／ｃｍ2以上であることを特徴とする熱伝導率に優れた熱間工具鋼である。 In the fourth means, in addition to the constituent requirements of the hot tool steel of the first means, the second means and the third means, the Charpy impact value of the 2 mm U notch test piece in the quenching and tempering state is 30 J / cm. It is a hot tool steel with excellent thermal conductivity, which is characterized by having 2 or more.
上記の手段とすることで、ダイカストやホットスタンピングなどに適用可能な５００℃以上の熱環境下で使用される４０.０ＨＲＣ以上の高硬度、シャルピー衝撃値が３０Ｊ／ｃｍ2以上の高靭性、３０．０Ｗ／ｍ・Ｋ以上の高熱伝導率を兼ね備えた金型用鋼を得ることができる。 By using the above means, high hardness of 40.0 HRC or more, high toughness of Charpy impact value of 30 J / cm 2 or more, used in a thermal environment of 500 ° C or more, which can be applied to die casting and hot stamping, 30 It is possible to obtain a mold steel having a high thermal conductivity of .0 W / m · K or more.
発明を実施するための形態の説明に先立って、本願の発明の手段における化学成分の限定理由および各特性の限定理由について説明する。なお、化学成分は質量％である。 Prior to the description of the embodiment for carrying out the invention, the reasons for limiting the chemical components and the reasons for limiting each property in the means of the present invention will be described. The chemical component is mass%.
Ｃ：０．２０〜０．５０％
Ｃは、固溶することでマトリックスを強化し、さらに、炭化物を形成し、析出効果を促進する元素である。Ｃが０．２０％より少ないと十分な焼入焼戻し硬さが得られない。一方、Ｃが０．５０％より多すぎるとミクロ偏析を助長し、靱性を低下させる。さらに、固溶Ｃ量が増加して鋼の熱伝導率を低下する。そこで、Ｃは０．２０〜０．５０％とする。望ましくは、Ｃは０．３５〜０．５０％とする。
C: 0.20 to 0.50%
C is an element that strengthens the matrix by solid solution, further forms carbides, and promotes the precipitation effect. If C is less than 0.20%, sufficient quenching and tempering hardness cannot be obtained. On the other hand, if C is more than 0.50%, microsegregation is promoted and toughness is lowered. Further, the amount of solid solution C increases and the thermal conductivity of the steel decreases. Therefore, C is set to 0.25 to 0.50%. Desirably, C is 0.35 to 0.50%.
Ｓｉ：０．５０％以下
Ｓｉは、マトリックスに固溶することで、硬さを向上させる元素である。ところで、Ｓｉが０．５０％より多いと、炭化物を形成することなくマトリックスに溶け込むため、熱伝導率を大きく低下させる。そこで、Ｓｉは０．５０％以下とし、望ましくは、０．３０％以下とする。
Si: 0.50% or less Si is an element that improves hardness by being dissolved in the matrix. By the way, when Si is more than 0.50%, it dissolves in the matrix without forming carbides, so that the thermal conductivity is greatly lowered. Therefore, Si is 0.50% or less, and preferably 0.30% or less.
Ｍｎ：０．９２％以下
Ｍｎは、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元素である。ところで、Ｍｎが０．９２％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０．９２％以下とし、望ましくは、０．８０％以下とする。
Mn: 0.92% or less Mn is an element that improves hardenability and suppresses a decrease in toughness due to bainite formation. By the way, if Mn is more than 0.92%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Mn is set to 0.92% or less, and preferably 0.80% or less.
Ｃｒ：４．００％以下
Ｃｒは、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元素である。ところで、Ｃｒが４．００％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、Ｃｒは４．００％以下とし、望ましくは、２．００％未満とする。
Cr: 4.00% or less Cr is an element that improves hardenability and suppresses a decrease in toughness due to bainite formation. By the way, if Cr is more than 4.00%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Cr is set to 4.00% or less, and preferably less than 2.00%.
Ｎｉ：２．００％以下
Ｎｉは、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元素である。
ところで、Ｎｉは炭化物を形成せずにマトリックスに固溶し、熱伝導率を低下させる。Ｎｉが２．００％より多いと、熱伝導率は大きく低下する。そこで、Ｎｉは２．００％以下とし、望ましくは１．５０％以下とする。
Ni: 2.00% or less Ni is an element that improves hardenability and suppresses a decrease in toughness due to bainite formation.
By the way, Ni dissolves in the matrix without forming carbides and lowers the thermal conductivity. If the amount of Ni is more than 2.00%, the thermal conductivity is greatly reduced. Therefore, Ni is set to 2.00% or less, preferably 1.50% or less.
Ｍｏ：０．９０％未満、かつＷ：１．８０％未満の範囲内で、２Ｍｏ＋Ｗ：１．８０％未満
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元素である。ところで、Ｍｏが０．９０％以上で多すぎる、またはＷが１．８０％以上で多すぎると、マトリックスに残存するＭｏやＷが増加し、熱伝導率を低下する。さらに、Ｍｏが０．９０％未満で、かつＷが１．８０％未満の範囲内でも、２Ｍｏ＋Ｗが１．８０％以上で多すぎると、マトリックスに残存するＭｏやＷが増加し、熱伝導率が低下する。そこで、Ｍｏは０．９０％未満、かつＷは１．８０％未満の範囲内で、２Ｍｏ＋Ｗは１．８０％未満とする。望ましくは、Ｍｏは０．８５％未満、かつＷは１．７０％未満の範囲内で、２Ｍｏ＋Ｗは１．７０％未満とする。
Mo: less than 0.90% and W: less than 1.80%, 2Mo + W: less than 1.80% Mo and W promote secondary hardening during tempering and increase quenching and tempering hardness. It is an element. By the way, if Mo is 0.90% or more and too much, or W is 1.80% or more and too much, Mo and W remaining in the matrix increase and the thermal conductivity decreases. Further, even if Mo is less than 0.90% and W is less than 1.80%, if 2Mo + W is 1.80% or more and too much, Mo and W remaining in the matrix increase and the thermal conductivity Decreases. Therefore, Mo is less than 0.90%, W is less than 1.80%, and 2Mo + W is less than 1.80%. Desirably, Mo is less than 0.85%, W is less than 1.70%, and 2Mo + W is less than 1.70%.
Ｖ：０．１０超〜０．６１％
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。ところでＶが０．６１％より多すぎると、マトリックスに残存するＶが増加し、熱伝導率が低下する。そこで、Ｖは０．１０超〜１．８０％とし、望ましくは０．２５〜０．４５％とする。
V: Over 0.10 to 0.61%
V is an element that promotes secondary curing during tempering and enhances quenching and tempering hardness. By the way, if V is more than 0.61%, V remaining in the matrix increases and the thermal conductivity decreases. Therefore, V is set to more than 0.10 to 1.80%, preferably 0.25 to 0.45%.
Ｎ：０．０４０％以下
Ｎは、固溶することでマトリックスを強化し、さらに窒化物を形成することで、析出硬化を促進し、焼入焼戻し硬さを大きくする元素である。ところで、Ｎは、０．０４０％より過剰に添加すると、マトリックス中のＮ量が増加し、熱伝導率を低下する。そこで、Ｎは０．０４０％以下とし、望ましくは０．０３０％以下とする。
N: 0.040% or less N is an element that strengthens the matrix by solid solution and further forms nitride to promote precipitation hardening and increase quenching and tempering hardness. By the way, when N is added in excess of 0.040%, the amount of N in the matrix increases and the thermal conductivity decreases. Therefore, N is 0.040% or less, and preferably 0.030% or less.
Ａｌ：０．０８０％以下
Ａｌは、窒化物を形成し焼入れにおける結晶粒の粗大化を抑制する元素である。ところで、Ａｌは０．０８０％よりも多く添加すると、過剰のＡｌ窒化物の形成により、靱性が低下する。そこで、Ａｌは０．０８０％以下とし、望ましくは０．０６０％以下とする。
Al: 0.080% or less Al is an element that forms a nitride and suppresses the coarsening of crystal grains during quenching. By the way, when Al is added in an amount of more than 0.080%, the toughness is lowered due to the formation of excess Al nitride. Therefore, Al is set to 0.080% or less, and preferably 0.060% or less.
ＴＣ（熱伝導率の指標）：３２．５以上
ＴＣは、請求項１の限定条件であり、３２．５未満であると、マトリックスに残存する合金元素量が増加し、熱伝導率を低下させる。そこで、ＴＣは３２．５以上とし、望ましくは３７．５以上とする。
なお、ＴＣ＝６８．０−６．５Ｍｎ−５．７Ｃｒ−３．１Ｖ−４．４Ｍｏ−２．２Ｗ−２４．７Ｃ−２１．２Ｎ−６．５Ｎｉ−１．７Ｓｉ＋３．２Ａとする。ここで、各元素記号は質量％を示す。Ａは焼戻し状態での全炭化物の総面積率を示す。このＴＣの式は熱伝導率の指標となるものであり、ＴＣが大きいほど熱伝導率は大きくなる。各元素の添加量が増加すると、ＴＣの値は小さくなり、炭化物量が大きくなるほどＴＣは大きくなる。
TC (Indicator of Thermal Conductivity): 32.5 or more TC is a limiting condition of claim 1, and if it is less than 32.5, the amount of alloying elements remaining in the matrix increases and the thermal conductivity decreases. .. Therefore, TC is set to 32.5 or more, and preferably 37.5 or more.
It should be noted that TC = 68.0-6.5Mn-5.7Cr-3.1V-4.4Mo-2.2W-24.7C-21.2N-6.5Ni-1.7Si + 3.2A. Here, each element symbol indicates mass%. A indicates the total area ratio of all carbides in the tempered state. This TC formula is an index of thermal conductivity, and the larger the TC, the larger the thermal conductivity. As the amount of each element added increases, the TC value decreases, and as the amount of carbide increases, the TC increases.
焼入焼戻し状態の室温の熱伝導率（請求項２の限定条件）：３０．０Ｗ／ｍ・Ｋ以上
焼入焼戻し状態の室温の熱伝導率は、ホットスタンピングやダイカスト工程における生産性に関係する値であり、これらの向上のためには、３０．０Ｗ／ｍ・Ｋ以上が必要であり、望ましくは３５．０Ｗ／ｍ・Ｋ以上が必要である。
Thermal conductivity at room temperature in the tempered and tempered state (limited condition of claim 2): 30.0 W / m · K or more The thermal conductivity at room temperature in the tempered and tempered state is related to productivity in the hot stamping and die casting processes. It is a value, and in order to improve these, 30.0 W / m · K or more is required, and preferably 35.0 W / m · K or more is required.
焼入焼戻し状態の硬さ（請求項３の限定条件）：４０.０ＨＲＣ以上
焼入焼戻し状態の硬さは、ホットスタンピングやダイカストの金型として使われる際に、十分な金型寿命を得るために必要な値であり、そのためには４０.０ＨＲＣ以上の硬さが必要であり、望ましくは４５.０ＨＲＣ以上が必要である。
Hardness in the tempered and tempered state (limited condition of claim 3): 40.0 HRC or more The hardness in the tempered and tempered state is to obtain a sufficient mold life when used as a mold for hot stamping or die casting. This is a value required for the above, and for that purpose, a hardness of 40.0 HRC or more is required, and preferably 45.0 HRC or more is required.
焼入焼戻し状態における２ｍｍＵノッチ試験片でのシャルピー衝撃値（請求項４の限定条件）：３０Ｊ／ｃｍ2以上
焼入焼戻し状態における２ｍｍＵノッチ試験片でのシャルピー衝撃値はホットスタンピングやダイカストの金型として使われる際に、十分な金型寿命を得るために必要な値であり、そのためには、シャルピー衝撃値は３０Ｊ／ｃｍ2以上が必要であり、望ましくは４０Ｊ／ｃｍ2以上が必要である。
Charpy impact value with 2 mm U notch test piece in quenching and tempering state (limited condition of claim 4): 30 J / cm 2 or more Charpy impact value with 2 mm U notch test piece in quenching and tempering state is hot stamping or die casting mold It is a value required to obtain a sufficient mold life when used as a charpy impact value of 30 J / cm 2 or more, and preferably 40 J / cm 2 or more. ..
ここで、本願の発明を実施するための形態について以下に説明する。 Here, a mode for carrying out the invention of the present application will be described below.
表１に示す本願の発明鋼の各Ｎｏ．の鋼および表２に示す比較鋼の各Ｎｏ．化学成分の鋼を、真空溶解炉で溶製し、得られた各１００ｋｇの鋼塊を、幅６５ｍｍ、高さ３０ｍｍのブロックに熱間鍛伸した。この鍛伸材を８７０℃で焼なまし後、表面と中心の中間位置から試料を採取した。これらの試料を１０３０℃で焼入れし、６００℃で２回の焼戻しを行った後、それらの鋼の炭化物面積率と特性を調査した。表１に本願の発明鋼の成分、炭化物面積率、ＴＣについて記載し、表２に比較鋼の成分、炭化物面積率、ＴＣについて示した。 Each No. 1 of the invention steel of the present application shown in Table 1. No. 1 of the steel and the comparative steel shown in Table 2. Steel having a chemical component was melted in a vacuum melting furnace, and the obtained steel ingots of 100 kg each were hot-stretched into blocks having a width of 65 mm and a height of 30 mm. After annealing this forged material at 870 ° C., a sample was taken from an intermediate position between the surface and the center. These samples were quenched at 1030 ° C. and tempered twice at 600 ° C., after which the carbide area ratio and properties of the steels were investigated. Table 1 describes the composition, carbide area ratio, and TC of the invention steel of the present application, and Table 2 shows the composition, carbide area ratio, and TC of the comparative steel.
この場合、炭化物の面積率は、焼入焼戻し状態の鍛伸方向に平行な面を研磨して炭化物面積率の測定用の試験片とした。これらの試験片を用いて、走査型電子顕微鏡の反射電子像から、総面積１００００μｍ2の領域における炭化物を観察した後、画像解析により面積率を算出した。 In this case, the area ratio of carbides was determined by polishing a surface parallel to the forging direction in the quenching and tempering state to obtain a test piece for measuring the area ratio of carbides. Using these test pieces, carbides in a region having a total area of 10000 μm 2 were observed from the reflected electron images of a scanning electron microscope, and then the area ratio was calculated by image analysis.
さらに、表３に本願の発明鋼の各Ｎｏ．の熱伝導率、焼入焼戻し硬さおよびシャルピー衝撃値を示し、表４に比較鋼の各Ｎｏ．の熱伝導率、焼入焼戻し硬さおよびシャルピー衝撃値を示した。 Further, Table 3 shows the No. 1 of the invention steel of the present application. The thermal conductivity, quenching and tempering hardness, and Charpy impact value of each of the comparative steels are shown in Table 4. The thermal conductivity, quenching and tempering hardness, and Charpy impact value were shown.
熱伝導率の測定には、レーザーフラッシュ法を用い、焼入焼戻し状態の試料を直径１０ｍｍで厚さ１ｍｍの円板形状に仕上げ加工し、試験に供した。 For the measurement of thermal conductivity, a laser flash method was used, and a sample in a quenched and tempered state was finished into a disk shape having a diameter of 10 mm and a thickness of 1 mm and subjected to a test.
焼入焼戻し硬さは、ロックウェル硬さ試験機で、焼入焼戻し状態の試料の鍛伸方向に垂直な面の硬さを測定した。 For the quenching and tempering hardness, the hardness of the surface perpendicular to the forging direction of the sample in the quenching and tempering state was measured with a Rockwell hardness tester.
靱性は、シャルピー衝撃値は靱性により評価を実施した。試験片は、焼入焼戻し状態の試料から作製した。試験片の形状は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。 The toughness was evaluated based on the Charpy impact value. The test piece was prepared from a sample in a quenched and tempered state. 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.
以上のように、表１および表３に示す本願の発明鋼のＮｏ．１〜２５は、ＴＣの値が３２．５以上であり熱伝導率がいずれも３０．０Ｗ／ｍ・Ｋ以上と大きく、焼入焼戻し硬さがいずれも４０．０ＨＲＣ以上であり、シャルピー衝撃値がいずれも３０Ｊ／ｃｍ2以上であり、優れた高熱伝導率、高硬度、高靱性の熱間工具鋼である。 As described above, No. 1 of the invention steel of the present application shown in Tables 1 and 3. 1 to 25 have a TC value of 32.5 or more, a large thermal conductivity of 30.0 W / m · K or more, a quenching and tempering hardness of 40.0 HRC or more, and a Charpy impact value. Is 30 J / cm 2 or more, and is a hot tool steel with excellent high thermal conductivity, high hardness, and high toughness.
一方、表２および表４に示す比較鋼のＮｏ．２６〜３９について以下に検討する。
表２のＮｏ．２６ではＣ量が０．１９％と０．２０％より少ないので、表４のＮｏ．２６の焼入焼戻し硬さが３９．１ＨＲＣと４０．０ＨＲＣより低い。
Ｎｏ．２７はＣ量が０．５３％と０．５０％より多いので、ＴＣの値が２９．５と３２．５より低くかつ表４の熱伝導率が２９．０Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．２８はＳｉ量が０．５２％と０．５０％より多いので、ＴＣの値が２９．４と３２．５より低くかつ表４の熱伝導率が２６．２Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．２９はＭｎ量が０．９４％と０．９２％より多いので、ＴＣの値が３２．２と３２．５より低くかつ表４の熱伝導率が２９．７Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３０はＣｒ量が４．１１％と４．００％より多いので、ＴＣの値が２８．４と３２．５より低くかつ表４の熱伝導率が２５．４Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３１はＮｉ量が２．０９％と２．００％より多いので、ＴＣの値が２６．８と３２．５より低くかつ表４の熱伝導率が２５．３Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３２はＭｏ量が０．９３％と０．９０％より多いので、２Ｍｏ＋Ｗの量が１．８９％と１．８０％より多くかつＴＣの値が２９．９と３２．５より低く、表４の熱伝導率が２９．５Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３３はＷ量が１．８２％と１．８０％より多いので、２Ｍｏ＋Ｗの量が１．８８％と１．８０％より多くかつＴＣの値が３１．０と３２．５より低く、表４の熱伝導率が２５．７Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３４は２Ｍｏ＋Ｗの量が１．８２％と１．８０％より多くかつＴＣの値が３０．５と３２．５より低く、表４の熱伝導率が２８．５Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３５はＶ量が０．０９％と０．１０％より少ないので、表４の焼入焼戻し硬さが３７．６ＨＲＣと４０．０より低い。
Ｎｏ．３６はＶ量が０．６２％と０．６１％より多いので、ＴＣの値が３２．３と３２．５より低くかつ表４の熱伝導率が２９．４Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３７はＮ量が０．０６１％と０．０４０％より多いので、ＴＣの値が２９．７と３２．５より低くかつ表４の熱伝導率が２９．１Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
Ｎｏ．３８はＡｌ量が０．０９３％と０．０８０％より多いので、表４のシャルピー衝撃値が２６Ｊ／ｃｍ2と３０Ｊ／ｃｍ2より低い。
Ｎｏ．３９は化学成分の量は規定の範囲内であるが、ＴＣの値が３２．２と３２．５より低いので、表４の熱伝導率が２９．４Ｗ／ｍＫと３０．０Ｗ／ｍＫより低い。
On the other hand, No. 1 of the comparative steels shown in Tables 2 and 4. 26-39 will be considered below.
No. in Table 2 In No. 26, the amount of C was 0.19%, which was less than 0.20%. The quenching and tempering hardness of 26 is lower than 39.1 HRC and 40.0 HRC.
No. Since the amount of C in 27 is 0.53% and more than 0.50%, the TC value is lower than 29.5 and 32.5 and the thermal conductivity in Table 4 is 29.0 W / mK and 30.0 W / mK. Lower.
No. Since the amount of Si in 28 is 0.52% and more than 0.50%, the TC value is lower than 29.4 and 32.5 and the thermal conductivity in Table 4 is 26.2 W / mK and 30.0 W / mK. Lower.
No. Since the amount of Mn of 29 is 0.94% and more than 0.92%, the TC value is lower than 32.2 and 32.5 and the thermal conductivity in Table 4 is 29.7 W / mK and 30.0 W / mK. Lower.
No. Since the amount of Cr in 30 is 4.11%, which is larger than 4.00%, the TC value is lower than 28.4 and 32.5, and the thermal conductivity in Table 4 is 25.4 W / mK and 30.0 W / mK. Lower.
No. Since the amount of Ni in 31 is 2.09%, which is higher than 2.00%, the TC value is lower than 26.8 and 32.5, and the thermal conductivity in Table 4 is 25.3 W / mK and 30.0 W / mK. Lower.
No. Since 32 has a Mo amount of 0.93% and more than 0.90%, the amount of 2Mo + W is 1.89% and more than 1.80% and the TC value is lower than 29.9 and 32.5, Table 4 The thermal conductivity of is 29.5 W / mK, which is lower than 30.0 W / mK.
No. Since 33 has a W amount of 1.82% and more than 1.80%, the amount of 2Mo + W is 1.88% and more than 1.80% and the TC value is lower than 31.0 and 32.5, Table 4 The thermal conductivity of is 25.7 W / mK, which is lower than 30.0 W / mK.
No. In 34, the amount of 2Mo + W is 1.82%, which is more than 1.80%, the TC value is lower than 30.5 and 32.5, and the thermal conductivity of Table 4 is 28.5 W / mK and 30.0 W / mK. Lower.
No. Since the amount of V of 35 is 0.09%, which is less than 0.10%, the quenching and tempering hardness in Table 4 is 37.6 HRC, which is lower than 40.0.
No. Since the V amount of 36 is 0.62%, which is larger than 0.61%, the TC value is lower than 32.3 and 32.5, and the thermal conductivity in Table 4 is 29.4 W / mK and 30.0 W / mK. Lower.
No. Since the amount of N in 37 is 0.061%, which is larger than 0.040%, the TC value is lower than 29.7 and 32.5, and the thermal conductivity in Table 4 is 29.1 W / mK and 30.0 W / mK. Lower.
No. Since the Al content of 38 is 0.093%, which is larger than 0.080%, the Charpy impact values in Table 4 are lower than 26 J / cm 2 and 30 J / cm 2 .
No. In 39, the amount of chemical components is within the specified range, but the TC value is lower than 32.2 and 32.5, so the thermal conductivity in Table 4 is lower than 29.4 W / mK and 30.0 W / mK. ..
Claims (4)
ただし、ＴＣの式中の各元素記号は質量％を示し、かつ式中のＡは焼戻し状態での全炭化物の総面積率（％）を示す。 By mass%, C: 0.25 to 0.50%, Si: 0.50% or less, Mn: 0.92% or less, Cr: 4.00% or less, Ni: 2.00% or less, 2Mo + W: 1 .80% (however, Mo: less than 0.90% and W: less than 1.80%), V: more than 0.10 to 0.61%, N: 0.040% or less, Al: 0. It contains 080% or less, and consists of the balance Fe and unavoidable impurities. TC = 68.0-6.5Mn-5.7Cr-3.1V-4.4Mo-2.2W-24.7C-21.2N-6 A hot tool steel having excellent thermal conductivity, which satisfies .5Ni-1.7Si + 3.2A ≧ 32.5.
However, each element symbol in the TC formula indicates mass%, and A in the formula indicates the total area ratio (%) of all carbides in the tempered state.
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