JP2020132891A - Mold steel having excellent thermal conductivity - Google Patents
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 68
- 239000010959 steel Substances 0.000 title claims abstract description 68
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 21
- 239000012535 impurity Substances 0.000 claims abstract description 18
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 17
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 9
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 9
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 8
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 8
- 229910052802 copper Inorganic materials 0.000 claims abstract description 6
- 229910000734 martensite Inorganic materials 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
- 238000004512 die casting Methods 0.000 abstract description 9
- 238000010791 quenching Methods 0.000 description 29
- 230000000171 quenching effect Effects 0.000 description 29
- 238000005496 tempering Methods 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 15
- 229910001563 bainite Inorganic materials 0.000 description 11
- 239000011159 matrix material Substances 0.000 description 11
- 230000007423 decrease Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 238000001816 cooling Methods 0.000 description 5
- 150000001247 metal acetylides Chemical class 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 238000005242 forging Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910001315 Tool steel Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052735 hafnium Inorganic materials 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 229910052715 tantalum Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229910000760 Hardened steel Inorganic materials 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
- 229910052787 antimony Inorganic materials 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000011835 investigation 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
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052714 tellurium Inorganic materials 0.000 description 1
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Abstract
Description
この発明は、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、高温環境下で使用される金型用鋼に関する。 The present invention relates to mold steels, especially 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加工ピッチの短縮化から、ダイカスト用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、硬度や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、高硬度が求められている。 In recent years, in the field of die casting, the mechanical and thermal load on die casting dies has been increased 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. Is increasing. As a result, the mold is liable to have 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.
さらに、ダイカスト用金型やホットスタンピング用金型は内部に冷却回路が配されており、冷却回路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要請されている。 Further, the die casting mold and the hot stamping mold are provided with a cooling circuit inside, and the cooling efficiency by the cooling water flowing through the cooling 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.
こうした背景から、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が提案されている（たとえば特許文献１参照。）。
しかし、上記のものは、Ｃｕを含有しておらず、不完全焼入れ相であるベイナイトが形成されやすいことから、靱性が不足することとなる。
Against this background, in terms of 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: less than 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: Containing 0.080% or less, consisting of the balance Fe and unavoidable impurities, TC = 68.0-6.5Mn-5.7Cr-3.1V-4.4Mo-2.2W-24.7C-21 A hot tool steel having excellent thermal conductivity has been proposed, which is characterized by satisfying .2N-6.5Ni-1.7Si + 3.2A ≧ 32.5 (see, for example, Patent Document 1).
However, the above-mentioned ones do not contain Cu and tend to form bainite, which is an incompletely hardened phase, so that the toughness is insufficient.
また、質量％で、Ｃ：０．３０〜０．５０％、Ｓｉ：０．１０〜０．５０％、Ｍｎ：０．１〜１．０％、Ｃｒ：４．５〜５．４％、Ｍｏ：１．４〜２．４％、Ｗ：１．０％以下、かつＭｏ＋Ｗ／２：１．７〜２．４％、Ｖ：０．３０〜０．７０％を含有し、さらに、残部Ｆｅおよび不可避不純物からなる鋼で、焼入焼戻し後に観察される残留炭化物の種類や割合がＭ23Ｃ6、Ｍ6Ｃ、Ｍ2Ｃ、ＭＣからなる全炭化物中に占めるＭ6Ｃ、Ｍ2Ｃ、ＭＣからなる炭化物の割合が５．０％以上、さらに全炭化物面積率が断面積０．０１ｍｍ2辺り２％以下、シャルピー衝撃値が３０Ｊ／ｃｍ2以上、軟化量（ΔＨＲＣ）が１３ＨＲＣ以下であることを特徴とする優れた高温強度および靱性を有する熱間金型用鋼が提案されている（たとえば特許文献２参照。）。
しかし、上記のものは、Ｃｕを含有しておらず、不完全焼入れ相であるベイナイトが形成されやすいことから、靱性が不足することとなる。また、Ｃｒ量が過多であり、熱伝導率が不足する。
Further, in terms of mass%, C: 0.30 to 0.50%, Si: 0.10 to 0.50%, Mn: 0.1 to 1.0%, Cr: 4.5 to 5.4%, Mo: 1.4 to 2.4%, W: 1.0% or less, and Mo + W / 2: 1.7 to 2.4%, V: 0.30 to 0.70%, and the balance steel consisting of Fe and unavoidable impurities, quenching the type and proportion of residual carbides observed after tempering is M 23 C 6, M 6 C , M 2 C, M 6 in the whole carbides consisting MC C, M 2 The ratio of carbides consisting of C and MC is 5.0% or more, the total carbide area ratio is 2% or less per 0.01 mm 2 cross-sectional area, the Charpy impact value is 30 J / cm 2 or more, and the softening amount (ΔHRC) is 13 HRC or less. A hot mold steel having excellent high temperature strength and toughness has been proposed (see, for example, Patent Document 2).
However, the above-mentioned ones do not contain Cu and tend to form bainite, which is an incompletely hardened phase, so that the toughness is insufficient. In addition, the amount of Cr is excessive and the thermal conductivity is insufficient.
また、０．２５＜Ｃ＜０．３８、０．０１＜Ｓｉ＜０．３０、０．９２＜Ｍｎ＜１．８０、０．８＜Ｃｒ＜２．２、０．８＜Ｍｏ＜１．４、０．２５＜Ｖ＜０．５８、残部Ｆｅ及び不可避的不純物からなる金型用鋼が提案されている（たとえば特許文献３参照。）。
しかし、上記のものは、Ｍｎ量が過多であって、Ｍｎの過剰添加によって熱伝導率が低下する。
Further, 0.25 <C <0.38, 0.01 <Si <0.30, 0.92 <Mn <1.80, 0.8 <Cr <2.2, 0.8 <Mo <1. A mold steel composed of 4, 0.25 <V <0.58, the balance Fe and unavoidable impurities has been proposed (see, for example, Patent Document 3).
However, in the above-mentioned one, the amount of Mn is excessive, and the thermal conductivity decreases due to the excessive addition of Mn.
また、Ｃ：０．４５超〜０．６０％、Ｓｉ：０．０５〜０．２０％、Ｍｎ：０．
３〜０．７％、Ｎｉ：０．２〜０．５％、Ｃｒ：０．２〜０．５％、Ｖ：０．０３〜０．
１％、Ａｌ：０．０１〜０．０３％、Ｓ：０．０１０％未満、Ｏ：０．００３０以下、Ｎ
：０．０２％以下を含有し、残部がＦｅおよび不可避不純物からなり、かつ不可避不純物
中でＰ：０．０１５％以下、Ｃｕ：０．３０％以下、Ｍｏ：０．２０％以下に規制した組
成を有することを特徴とする熱伝導性に優れたプラスチック成形金型用鋼が提案されている（たとえば特許文献４参照。）。
しかし、上記のものは、Ｖ量が過小であり、焼入焼戻し硬さが不足する。
Further, C: more than 0.45 to 0.60%, Si: 0.05 to 0.20%, Mn: 0.
3 to 0.7%, Ni: 0.2 to 0.5%, Cr: 0.2 to 0.5%, V: 0.03 to 0.
1%, Al: 0.01 to 0.03%, S: less than 0.010%, O: 0.0030 or less, N
: 0.02% or less, the balance is composed of Fe and unavoidable impurities, and P: 0.015% or less, Cu: 0.30% or less, Mo: 0.20% or less among the unavoidable impurities. A steel for plastic molding dies having a composition and excellent thermal conductivity has been proposed (see, for example, Patent Document 4).
However, the above-mentioned one has an excessively small amount of V, and the quenching and tempering hardness is insufficient.
さらに、質量％で、０．１５＜Ｃ＜０．４３、０．２０＜Ｓｉ＜０．５２、４．００＜Ｃｒ＜５．７２、−０．０５８１４×［Ｃｒ］＋０．４３２６＜Ｍｎ＜−０．２９０７×［Ｃｒ］＋２．４６２８・・式（１）、（但し式（１）中［Ｃｒ］はＣｒの含有量％を表す）、０．７２＜Ｍｏ＜１．６０、０．２０＜Ｖ＜０．６１、残部がＦｅ及び不可避的不純物の組成を有する金型用鋼が提案されている（例えば、特許文献５参照。）。
しかし、この金型用鋼は、Ｃｒ量が過剰であって、熱伝導率が低下することとなる。
Further, in mass%, 0.15 <C <0.43, 0.20 <Si <0.52, 4.00 <Cr <5.72, -0.05814 × [Cr] +0.4326 <Mn < −0.2907 × [Cr] +2.4628 .. Equation (1), (wherein [Cr] in equation (1) represents% of Cr content), 0.72 <Mo <1.60, 0. Mold steels having a composition of 20 <V <0.61, the balance of Fe and unavoidable impurities have been proposed (see, for example, Patent Document 5).
However, the amount of Cr in this mold steel is excessive, and the thermal conductivity is lowered.
さらに、質量％でＣ：０．１５〜０．３５％、Ｓｉ：０．０５〜０．２０％未満、Ｍｎ：０．０５〜１．５０％、Ｐ：０．０２０％以下、Ｓ：０．０１３％以下、Ｃｕ：０．１０％以下、Ｎｉ：０．２０％以下、Ｃｒ：０．２０〜２．５０％、Ｍｏ：０．５０〜３．００％、Ｖ＋Ｎｂ：０．０５〜０．３０％、Ａｌ:０．０２０〜０．０４０％、Ｏ：０．００３％以下、Ｎ：０．０１０〜０．０２０％、残部が実質的にＦｅからなり、３０ＨＲＣ以上４０ＨＲＣ以下のロックウェル硬さを有するダイカスト金型用プリハードン鋼が提案されている（たとえば特許文献６参照。）。
しかし、上記のものは、Ｃ量が過小であって、焼入焼戻し硬さが不足する。
Further, in terms of mass%, C: 0.15 to 0.35%, Si: 0.05 to less than 0.20%, Mn: 0.05 to 1.50%, P: 0.020% or less, S: 0 .013% or less, Cu: 0.10% or less, Ni: 0.20% or less, Cr: 0.25 to 2.50%, Mo: 0.50 to 3.00%, V + Nb: 0.05 to 0 .30%, Al: 0.020 to 0.040%, O: 0.003% or less, N: 0.010 to 0.020%, the balance is substantially Fe, and the rockwell is 30 HRC or more and 40 HRC or less. A pre-hardened steel for a die-casting mold having hardness has been proposed (see, for example, Patent Document 6).
However, in the above case, the amount of C is too small, and the quenching and tempering hardness is insufficient.
また、０．２６〜０．５５重量％のＣ、＜２重量％のＣｒ、０〜１０
重量％のＭｏ、０〜１５重量％のＷ、但しＷとＭｏとの含有量は合計で１．８〜１５重量
％となる、単独または合計で０〜３重量％の含有量を有する炭化物形成元素Ｔｉ，Ｚｒ，
Ｈｆ，Ｎｂ，Ｔａ、０〜４重量％のＶ、０〜６重量％のＣｏ、０〜１．６重量％のＳｉ、
０〜２重量％のＭｎ、０〜２．９９重量％のＮｉ、０〜１重量％のＳ、ならびに残り：鉄
および不可避の不純物、を有する工具鋼、特に熱間加工鋼が提案されている（たとえば特許文献７参照。）。
しかし、上記のものは、本発明でいうＭｏ＋５／６Ｗが過大であって、ＭｏまたはＷの過剰添加によって熱伝導率が低下する。
Further, 0.26 to 0.55% by weight of C, <2% by weight of Cr, 0 to 10
Carbide formation with 100% by weight Mo, 0-15% by weight W, where the total content of W and Mo is 1.8-15% by weight, either alone or with a total content of 0-3% by weight. Elements Ti, Zr,
Hf, Nb, Ta, 0-4% by weight V, 0-6% by weight Co, 0-1.6% by weight Si,
Tool steels with 0-2 wt% Mn, 0-2.99 wt% Ni, 0-1 wt% S, and the rest: iron and unavoidable impurities, especially hot-worked steels, have been proposed. (See, for example, Patent Document 7.).
However, in the above, Mo + 5 / 6W referred to in the present invention is excessive, and the thermal conductivity decreases due to the excessive addition of Mo or W.
また、％Ｃｅｑ：０．２０−１．２、％Ｃ：０．２０−１．２、％Ｎ：０−１、％Ｂ：０−１、％Ｃｒ＜１．５、％Ｎｉ＝１．０−９、％Ｓｉ＜０．４、％Ｍｎ：０−３、％Ａｌ：０−２．５、％Ｍｏ：０−１０、％Ｗ：０−１５、％Ｔｉ：０−３、％Ｔａ：０−３，％Ｚｒ：０−３、％Ｈｆ：０−３、％Ｖ：０−４、％Ｎｂ：０−３、％Ｃｕ：０−４、％Ｃｏ：０−６、％Ｓ：０−１，％Ｓｅ：０−１、％Ｔｅ：０−１、％Ｂｉ：０−１、％Ａｓ：０−１，％Ｓｂ：０−１，％Ｃａ：０−１を有し、残部が鉄及び不可避不純物からなり、％Ｃｅｑ：％Ｃ＋０．８６×％Ｎ＋１．２×％Ｂ、％Ｍｏ＋１／２・％Ｗ＞１．２を満たす熱間工具鋼が提案されている（たとえば特許文献８参照。）。
しかし、上記のものは、Ｎｉ量が過多であって、Ｎｉの過剰添加によって熱伝導率が低下する。
Further,% Ceq: 0.20-1.2,% C: 0.20-1.2,% N: 0-1 and% B: 0-1.,% Cr <1.5,% Ni = 1. 0-9,% Si <0.4,% Mn: 0-3,% Al: 0-2.5,% Mo: 0-10,% W: 0-15,% Ti: 0-3,% Ta : 0-3,% Zr: 0-3,% Hf: 0-3,% V: 0-4,% Nb: 0-3,% Cu: 0-4,% Co: 0-6,% S: It has 0-1 and% Se: 0-1 and% Te: 0-1 and% Bi: 0-1 and% As: 0-1 and% Sb: 0-1 and% Ca: 0-1 and the balance. Is composed of iron and unavoidable impurities, and hot tool steels satisfying% Ceq:% C + 0.86 ×% N + 1.2 ×% B and% Mo + 1/2 ·% W> 1.2 have been proposed (for example, Patent Documents). 8).
However, in the above-mentioned products, the amount of Ni is excessive, and the thermal conductivity decreases due to the excessive addition of Ni.
本願の発明が解決しようとする課題は、高熱伝導率、高硬度、高靭性を兼ね備えており、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 invention of the present application is to provide a mold steel which has high thermal conductivity, high hardness, and high toughness 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、以下の各手段に記載の合金成分、組織状態とすることで、高硬度、高靭性、高熱伝導率を兼備した金型用鋼が得られることを見出した。
なお、本発明でいう高硬度とは４５ＨＲＣ以上であること、高靱性とは焼入焼戻し後のシャルピー衝撃値が３０Ｊ／ｃｍ2以上であること、高熱伝導率とは２５．０Ｗ／ｍ・Ｋ以上であることをいう。
As a result of diligent development, the inventors have found that mold steel having high hardness, high toughness, and high thermal conductivity can be obtained by using the alloy components and microstructures described in the following means. It was.
The high hardness in the present invention means 45 HRC or more, the high toughness means that the Charpy impact value after quenching and tempering is 30 J / cm 2 or more, and the high thermal conductivity means 25.0 W / m · K. That is all.
上記の課題を解決するための本発明の第１の手段は、質量％で、Ｃ：０．３５超〜０．６３％、Ｓｉ：０．０１〜１．２０％、Ｍｎ：０．０１〜０．９２％、Ｃｒ：０．４０〜４．００％、Ｃｕ：０．０５〜２．８５％、Ｖ：０．１０超〜０．４５％未満を含有し、
またＭｏとＷのうち少なくとも一種以上をＭｏ：１．５０％未満かつＷ：１．８０％未満かつ（Ｍｏ＋５／６Ｗ）：０．４０〜１．５０未満の範囲で含有し、
さらに残部がＦｅと不可避的不純物からなる金型用鋼である。
The first means of the present invention for solving the above problems is, in mass%, C: more than 0.35 to 0.63%, Si: 0.01 to 1.20%, Mn: 0.01 to. It contains 0.92%, Cr: 0.40 to 4.00%, Cu: 0.05 to 2.85%, V: more than 0.10 to less than 0.45%.
Further, at least one or more of Mo and W are contained in the range of Mo: less than 1.50%, W: less than 1.80%, and (Mo + 5 / 6W): 0.40 to less than 1.50.
Further, the balance is mold steel composed 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、Ｎｉ：０．０１〜２．９９％を含有し、さらに残部がＦｅと不可避的不純物からなる金型用鋼である。 The second means is a mold steel containing Ni: 0.01 to 2.99% in addition to the chemical components described in the first means, and the balance is Fe and unavoidable impurities. ..
その第３の手段は、第１又は第２の手段に記載の化学成分に加えて、Ｎ：０．００１〜０．０４０％を含有し、さらに残部がＦｅと不可避的不純物からなる金型用鋼である。 The third means is for molds containing N: 0.001 to 0.040% in addition to the chemical components described in the first or second means, and the balance is Fe and unavoidable impurities. It is steel.
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、Ａｌ：０．００１〜０．３００％を含有し、さらに残部がＦｅと不可避的不純物からなる金型用鋼である。 The fourth means contains Al: 0.001 to 0.300% in addition to the chemical components described in any one of the first to third means, and the balance is from Fe and unavoidable impurities. It is a steel for molds.
その第５の手段は、第１から第４の手段のいずれか１項に記載の鋼が、焼入れ焼戻しされた状態であることを特徴とする金型用鋼である。 The fifth means is a mold steel characterized in that the steel according to any one of the first to fourth means is in a state of being hardened and tempered.
その第６の手段は、第５の手段に記載の金型用鋼が、マルテンサイト単相組織であることを特徴とする金型用鋼である。 The sixth means is a mold steel according to the fifth means, characterized in that the mold steel has a martensite single-phase structure.
本発明の上記の手段による金型用鋼は、焼入焼戻し後の室温での熱伝導率が２５．０Ｗ／ｍ・Ｋ以上と高熱伝導率であり、焼入焼戻し後の硬度が４５．０ＨＲＣ以上の高硬度であり、さらに焼入焼戻し後のシャルピー衝撃値が３０Ｊ／ｃｍ2以上の高靭性であるなど、高熱伝導率、高硬度および高靭性の熱間工具鋼である。高硬度、高靱性、高熱伝導率を兼ね備えるものであるから、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として優れた特性を発揮する。 The mold steel by the above means of the present invention has a high thermal conductivity of 25.0 W / m · K or more at room temperature after quenching and tempering, and a hardness of 45.0 HRC after quenching and tempering. It is a hot tool steel with high thermal conductivity, high hardness and high toughness, such as the above high hardness and high toughness with a charpy impact value of 30 J / cm 2 or more after quenching and tempering. Since it has high hardness, high toughness, and high thermal conductivity, it exhibits excellent characteristics as mold steel used in high temperature environments such as die casting and hot stamping.
本発明の実施の形態の説明に先立って、本願発明における化学成分等の限定理由を説明する。なお、説明における記載中の％は、質量％である。 Prior to the description of the embodiment of the present invention, the reasons for limiting the chemical components and the like in the present invention will be described. In addition,% in the description is mass%.
Ｃ：０．３５超〜０．６３％
Ｃは、鋼中に固溶することで、マトリックスを強化し、また炭化物を形成することで析出強化を促す元素である。Ｃは０．３５％以下であると十分な焼入焼戻し硬さが得られない。一方、Ｃは０．６３％より多いと偏析を助長し、靭性を低下させる。そこで、Ｃは０．３５超〜０．６３％とする。より好ましくは０．４０〜０．６０％である。
C: Over 0.35 to 0.63%
C is an element that strengthens the matrix by solid solution in steel and promotes precipitation strengthening by forming carbides. If C is 0.35% or less, sufficient quenching and tempering hardness cannot be obtained. On the other hand, if C is more than 0.63%, segregation is promoted and toughness is lowered. Therefore, C is set to more than 0.35 to 0.63%. More preferably, it is 0.40 to 0.60%.
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。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もあるが、Ｓｉは０．０１％より少ないと十分に脱酸されない。一方、Ｓｉは１．２０％より多いと、Ｓｉ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大きく低下させる。そこで、Ｓｉは０．０１〜１．２０％とする。より好ましくは、０．０５〜１．００％とする。
Si: 0.01 to 1.20%
Si is an element required as a deoxidizer during steelmaking. Si is also an element that improves hardness by being dissolved in the matrix, but if Si is less than 0.01%, it is not sufficiently deoxidized. On the other hand, if the amount of Si is more than 1.20%, it dissolves in the matrix without forming Si carbides and significantly lowers the thermal conductivity. Therefore, Si is set to 0.01 to 1.20%. More preferably, it is 0.05 to 1.00%.
Ｍｎ：０．０１〜０．９２％
Ｍｎは、製鋼時の脱酸剤として必要な元素である。Ｍｎは０．０１％より少ないと十分に脱酸されない。一方、Ｍｎは、０．９２％より多すぎると、マトリックスに固溶して鋼の熱伝導率を低下させる。そこで、Ｍｎは０．０１〜０．９２％とし、好ましくは、０．１０〜０．８５％とする。
Mn: 0.01 to 0.92%
Mn is an element required as a deoxidizer during steelmaking. If Mn is less than 0.01%, it will not be sufficiently deoxidized. On the other hand, if Mn is more than 0.92%, it dissolves in the matrix and lowers the thermal conductivity of the steel. Therefore, Mn is set to 0.01 to 0.92%, preferably 0.10 to 0.85%.
Ｃｒ：０．４０〜４．００％
Ｃｒは、鋼の焼入性を向上させ、ベイナイト形成による靭性の低下を抑制するために必要な元素である。Ｃｒが０．４０％より少ないと十分な靭性が得られない。一方、Ｃｒは４．００％より多いと、マトリックスに固溶して鋼の熱伝導率を低下させる。そこで、Ｃｒは０．４０〜４．００％とする。より好ましくは、０．６０〜３．００％とする。
Cr: 0.40 to 4.00%
Cr is an element necessary for improving the hardenability of steel and suppressing the decrease in toughness due to the formation of bainite. If Cr is less than 0.40%, 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 of the steel. Therefore, Cr is set to 0.40 to 4.00%. More preferably, it is 0.60 to 3.00%.
Ｃｕ：０．０５〜２．８５％
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のに必要な元素である。Ｃｕが０．０５％より少ないと、十分な靱性が得られない。一方、Ｃｕが２．８５％より多すぎると、マトリックスに固溶して鋼の熱伝導率を低下させる。そこで、Ｃｕは０．０５〜２．８５％とする。より好ましくは、０．１０〜２．６０％とする。
Cu: 0.05 to 2.85%
Cu is an element necessary for improving hardenability and suppressing a decrease in toughness due to bainite formation. If the amount of Cu is less than 0.05%, sufficient toughness cannot be obtained. On the other hand, if Cu is more than 2.85%, it dissolves in the matrix and lowers the thermal conductivity of the steel. Therefore, Cu is set to 0.05 to 2.85%. More preferably, it is 0.10 to 2.60%.
Ｖ：０．１０超〜０．４５％未満
Ｖは、鋼の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。Ｖは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は０．４５％以上だ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〜０．４５％未満とする。より好ましくは０．２５〜０．４５％未満とする。
V: More than 0.10 to less than 0.45% V is an element that promotes secondary hardening during tempering of steel and enhances quenching and tempering hardness. If V is 0.10 or less, sufficient quenching and tempering hardness cannot be obtained. On the other hand, when V is 0.45% or more, V remaining in the matrix increases and the thermal conductivity decreases. Therefore, V is set to more than 0.10 to less than 0.45%. More preferably, it is less than 0.25 to 0.45%.
（選択的必須成分について）
ＭｏとＷのうち少なくともいずれか１種以上を含有し、Ｍｏ：１．５０％未満、Ｗ：１．８０％未満、（Ｍｏ＋５／６Ｗ）：０．４０〜１．５０未満
ＭｏとＷは、鋼の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。そこで、本発明では、ＭｏとＷは少なくともいずれか１種以上をＭｏ：１．５０％未満、Ｗ：１．８０％未満で含有するもの（すなわち、ＭｏとＷのいずれか一方あるいは双方を含有するもの）であって、さらにＭｏ＋５／６Ｗで０．４０％〜１．５０未満である。
Ｍｏ＋５／６Ｗが０．４０％より少ないと十分な焼入焼戻し硬さが得られないので０．４０％以上とする。より好ましくは、０．４５％以上とする。
一方、Ｍｏ：１．５０％以上、Ｗ：１．８０％以上、あるいはＭｏ＋５／６Ｗが１．５０以上であると、すなわちＭｏやＷが多すぎると、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ので、Ｍｏ：１．５０％未満、Ｗ：１．８０％未満、（Ｍｏ＋５／６Ｗ）：０．４０〜１．５０未満とする。より好ましくは、０．４５以上〜１．４５以下である。
(About selective essential ingredients)
Contains at least one or more of Mo and W, Mo: less than 1.50%, W: less than 1.80%, (Mo + 5 / 6W): less than 0.40-1.50 Mo and W are It is an element that promotes secondary hardening during tempering of steel and enhances quenching and tempering hardness. Therefore, in the present invention, Mo and W contain at least one or more of Mo: less than 1.50% and W: less than 1.80% (that is, one or both of Mo and W are contained. Further, it is 0.40% to less than 1.50 at Mo + 5 / 6W.
If Mo + 5 / 6W is less than 0.40%, sufficient quenching and tempering hardness cannot be obtained, so the content is set to 0.40% or more. More preferably, it is 0.45% or more.
On the other hand, if Mo: 1.50% or more, W: 1.80% or more, or Mo + 5 / 6W is 1.50 or more, that is, if there are too many Mo and W, the Mo and W remaining in the matrix will increase. Since the thermal conductivity is lowered, Mo: less than 1.50%, W: less than 1.80%, (Mo + 5 / 6W): less than 0.40 to 1.50. More preferably, it is 0.45 or more and 1.45 or less.
（付加的成分について）
Ｎｉ：０．０１〜２．９９％
Ｎｉは、必ずしも添加する必要はないが、Ｃｒと同様に、鋼の焼入性を向上させ、ベイナイト形成による靱性低下を抑制する元素であることから、必要に応じて添加する。一方、Ｎｉは２．９９％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、Ｎｉは０．０１〜２．９９％とする。好ましくは、０．０１〜２．００％とする。
(About additional ingredients)
Ni: 0.01 to 2.99%
Ni does not necessarily have to be added, but like Cr, it is an element that improves the hardenability of steel and suppresses the decrease in toughness due to bainite formation, so it is added as necessary. On the other hand, if Ni is more than 2.99%, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Ni is set to 0.01 to 2.99%. Preferably, it is 0.01 to 2.00%.
Ｎ：０．００１〜０．０４０％
Ｎは、必ずしも添加する必要はないが、Ｃと同様に、鋼の焼入焼戻し硬さを大きくするのに有効な元素であり、必要に応じて、添加する。一方、Ｎは、０．０４０％より多く添加すると、過剰添加によって精錬の時間およびコストの上昇を招くこととなる。そこで、Ｎは０．００１〜０．０４０％とし、好ましくは、０．００１〜０．０３０％とする。
N: 0.001 to 0.040%
N is not necessarily added, but like C, it is an element effective for increasing the quenching and tempering hardness of steel, and is added as necessary. On the other hand, if N is added in an amount of more than 0.040%, the time and cost of refining will increase due to excessive addition. Therefore, N is 0.001 to 0.040%, preferably 0.001 to 0.030%.
Ａｌ：０．００１〜０．３００％
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り、必要に応じて添加することができる。一方、Ａｌが多すぎると、マトリックスに固溶して熱伝導率を低下させる。そこで、Ａｌは０．００１〜０．０３０％とし、好ましくは、０．００５〜０．１５０％とする。
Al: 0.001 to 0.300%
Al is an element that does not necessarily need to be added, but is an element that dissolves in a matrix to improve hardness, and can be added as needed. On the other hand, if the amount of Al is too large, it dissolves in the matrix and lowers the thermal conductivity. Therefore, Al is 0.001 to 0.030%, preferably 0.005 to 0.150%.
焼入焼戻し状態での組織：マルテンサイト単相
焼入焼戻し状態での鋼の組織をマルテンサイト単相組織とするのは、不完全焼入れ相であるベイナイトが存在すると靭性が大幅に低下することから、ホットスタンピング・ダイカスト金型として使われた際に、十分な金型寿命が得られなくなるためである。そこで、焼入焼戻し状態での組織は、マルテンサイト単相が好ましく、マルテンサイト相とベイナイト相の混合組織は靱性が低いので望ましくない。
Structure in quenching and tempering state: Martensite single phase The structure of steel in the quenching and tempering state is martensite single phase structure because the toughness is significantly reduced in the presence of baynite, which is an incompletely hardened phase. This is because when used as a hot stamping die-casting mold, a sufficient mold life cannot be obtained. Therefore, the structure in the quenching and tempering state is preferably a martensite single phase, and a mixed structure of a martensite phase and a bainite phase is not desirable because it has low toughness.
次に、発明の実施の形態について、以下に記載する。
まず、表１の本願の発明鋼のＮｏ．１〜２７および表２のＮｏ．２８〜４８、及び表３の比較鋼のＮｏ．４９〜６４に記載の各化学成分と残部Ｆｅおよび不可避不純物からなる鋼を真空誘導溶解炉にて溶製し、それぞれ１００ｋｇの鋼塊を得た。得られた各鋼塊を、幅６５ｍｍ、高さ３０ｍｍのブロックに熱間鍛伸した。
Next, embodiments of the invention will be described below.
First, No. 1 of the invention steel of the present application in Table 1. Nos. 1-27 and Table 2 Nos. 28 to 48 and the comparative steels in Table 3 Steel composed of each of the chemical components described in 49 to 64, the balance Fe, and unavoidable impurities was melted in a vacuum induction melting furnace to obtain 100 kg of each steel ingot. Each of the obtained ingots was hot forged into a block having a width of 65 mm and a height of 30 mm.
次いでこの鍛伸材を８７０℃から焼なましした後、ブロックの表面と中心の中間となる位置から、直径１６ｍｍ、長さ１６０ｍｍの丸棒を採取した。これらの丸棒は１０３０℃に保持した後、空冷によって焼入れを行ない、さらに５７０〜６７０℃で２回焼戻しを行った後、組織観察と各特性の調査を実施した。それらの結果を、表４〜６に示す。 Next, this forged material was annealed from 870 ° C., and then a round bar having a diameter of 16 mm and a length of 160 mm was collected from a position intermediate between the surface and the center of the block. These round bars were held at 1030 ° C., then quenched by air cooling, and then tempered twice at 570 to 670 ° C., and then microstructure observation and investigation of each characteristic were carried out. The results are shown in Tables 4-6.
なお、組織観察には、走査型電子顕微鏡を用いた。焼入焼戻し後の試料の鍛伸方向に平行な面を鏡面になるまで研磨し、ナイタールで腐食した後、観察を行った。組織観察により、ベイナイト組織の有無を確認し、ベイナイト組織が確認できずマルテンサイト単相であった場合は「Ｍ」と、マルテンサイト組織ベイナイト組織の混合組織の場合を「Ｍ＋Ｂ」として記録した。 A scanning electron microscope was used for tissue observation. The surface parallel to the forging direction of the sample after quenching and tempering was polished until it became a mirror surface, corroded with nital, and then observed. The presence or absence of bainite tissue was confirmed by tissue observation, and the case where the bainite structure could not be confirmed and the martensite structure was monophasic was recorded as "M", and the case of a mixed structure of martensite structure bainite structure was recorded as "M + B".
これら試験片の鍛伸材の焼入焼戻された鋼の特性について、熱伝導率、焼入焼戻し硬さおよびシャルピー衝撃値を測定し、その結果を、発明鋼Ｎｏ．１〜４８については表４、表５に示し、比較鋼のＮｏ．４９〜６４については、表６に示した。 Regarding the characteristics of the tempered and tempered steel of the forged material of these test pieces, the thermal conductivity, the quenching and tempering hardness, and the Charpy impact value were measured, and the results were obtained as the invention steel No. Nos. 1 to 48 are shown in Tables 4 and 5, and the comparative steel Nos. 49 to 64 are shown in Table 6.
熱伝導率の測定には、レーザフラッシュ法を用いた。焼入焼戻し後の試料を直径１０ｍｍ×１ｍｍの円柱形状に仕上げ加工し、試験に供した。パルス・レーザーを円板の片面に照射して厚さ方向の熱拡散率を得て、定圧比熱と密度を乗じて焼入焼戻し後の室温での熱伝導率を得て、表４〜６の熱伝導率とした。この焼入焼戻し後の室温での熱伝導率が２５．０Ｗ／ｍ・Ｋ以上を高熱伝導率という。 The laser flash method was used to measure the thermal conductivity. The sample after quenching and tempering was finished into a cylindrical shape having a diameter of 10 mm × 1 mm and subjected to a test. Irradiate one side of the disk with a pulsed laser to obtain the thermal diffusivity in the thickness direction, and multiply it by the constant pressure specific heat and density to obtain the thermal conductivity at room temperature after quenching and quenching. It was defined as thermal conductivity. A thermal conductivity of 25.0 W / m · K or more at room temperature after quenching and tempering is called high thermal conductivity.
焼入焼戻し硬さはロックウェル硬さ試験機で測定した。焼入焼戻状態の試料の鍛伸方向に垂直な面を硬さ測定した。この焼入焼戻し後の硬さが４５．０ＨＲＣ以上を高硬度であると評価する。 The quenching and tempering hardness was measured with a Rockwell hardness tester. The hardness of the surface perpendicular to the forging direction of the sample in the quenched and tempered state was measured. A hardness of 45.0 HRC or more after quenching and tempering is evaluated as high hardness.
靭性は、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。この焼入焼戻し後のシャルピー衝撃値が３０Ｊ／ｃｍ2以上を高靭性であると評価する。 The toughness was evaluated by the Charpy impact test. The test piece was prepared from a sample 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. A Charpy impact value of 30 J / cm 2 or more after quenching and tempering is evaluated as having high toughness.
表３の比較鋼のＮｏ．４９はＣの含有量が０．３３％と本発明の範囲より低い。すると、表６の焼入焼戻し硬さが４３．０ＨＲＣと本発明で得られる４５．０ＨＲＣ以上のものよりも硬さが低いものとなった。 No. of comparative steel in Table 3 49 has a C content of 0.33%, which is lower than the range of the present invention. Then, the quenching and tempering hardness in Table 6 was 43.0 HRC, which was lower than the hardness of 45.0 HRC or more obtained in the present invention.
表３の比較鋼のＮｏ．５０はＣの含有量が０．６５％と本発明の範囲より高い。すると、表６のシャルピー衝撃値が２３．４Ｊ／ｃｍ2と本発明で得られる３０．０Ｊ／ｃｍ2以上のものよりも靱性が低いものとなった。 No. of comparative steel in Table 3 50 has a C content of 0.65%, which is higher than the range of the present invention. Then, the Charpy impact value in Table 6 was 23.4 J / cm 2, which was lower than that obtained in the present invention at 30.0 J / cm 2 or more.
表３の比較鋼のＮｏ．５１はＳｉの含有量が１．２３％と本発明の範囲より高い。すると、表６の熱伝導率が２２．６Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 51 has a Si content of 1.23%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 22.6 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５２はＭｎの含有量が０．９５％と本発明の範囲より高い。すると、表６の熱伝導率が２４．４Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 The Mn content of 52 is 0.95%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 24.4 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５３はＣｒの含有量が０．３７％と本発明の範囲より低く、ベイナイト組織が形成されている。すると、表６のシャルピー衝撃値が２１．６Ｊ／ｃｍ2と本発明で得られる３０．０Ｊ／ｃｍ2以上のものよりも靱性が低いものとなった。 No. of comparative steel in Table 3 In 53, the Cr content is 0.37%, which is lower than the range of the present invention, and a bainite structure is formed. Then, the Charpy impact value in Table 6 was 21.6 J / cm 2, which was lower than that obtained in the present invention at 30.0 J / cm 2 or more.
表３の比較鋼のＮｏ．５４はＣｒの含有量が４．１２％と本発明の範囲より高い。すると、表６の熱伝導率が２３．９Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 54 has a Cr content of 4.12%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 23.9 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５５はＣｕの含有量が０．０４％と本発明の範囲より低く、ベイナイト組織が形成されている。すると、表６のシャルピー衝撃値が２０．８Ｊ／ｃｍ2と本発明で得られる３０．０Ｊ／ｃｍ2以上のものよりも靱性が低いものとなった。 No. of comparative steel in Table 3 55 has a Cu content of 0.04%, which is lower than the range of the present invention, and a bainite structure is formed. Then, the Charpy impact value in Table 6 was 20.8 J / cm 2, which was lower than that obtained in the present invention at 30.0 J / cm 2 or more.
表３の比較鋼のＮｏ．５６はＣｕの含有量が２．８８％と本発明の範囲より高い。すると、表６の熱伝導率が２４．９Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 56 has a Cu content of 2.88%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 24.9 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５７はＭｏの含有量が１．５５％と本発明の範囲より高い。また、Ｍｏ＋５／６Ｗの値も１．５５％と本発明の範囲よりも高い。すると、表６の熱伝導率が２４．１Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 57 has a Mo content of 1.55%, which is higher than the range of the present invention. The value of Mo + 5 / 6W is also 1.55%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 24.1 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５８はＷの含有量が１．８６％と本発明の範囲より高い。また、Ｍｏ＋５／６Ｗの値も１．５５％と本発明の範囲よりも高い。すると、表６の熱伝導率が２４．４Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 58 has a W content of 1.86%, which is higher than the range of the present invention. The value of Mo + 5 / 6W is also 1.55%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 24.4 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．５９はＭｏ＋５／６Ｗの値が１．５４％と本発明の範囲よりも高い。すると、表６の熱伝導率が２４．０Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 In 59, the value of Mo + 5 / 6W is 1.54%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 24.0 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．６０はＭｏ＋５／６Ｗの値が０．３３％と本発明の範囲より低い。すると、表６の焼入焼戻し硬さが４４．１ＨＲＣと本発明で得られる４５．０ＨＲＣ以上のものよりも硬さが低いものとなった。 No. of comparative steel in Table 3 In 60, the value of Mo + 5 / 6W is 0.33%, which is lower than the range of the present invention. Then, the quenching and tempering hardness in Table 6 was 44.1 HRC, which was lower than the hardness of 45.0 HRC or more obtained in the present invention.
表３の比較鋼のＮｏ．６１はＶの含有量が０．１０％と本発明の範囲より低い。すると、表６の焼入焼戻し硬さが４４．４ＨＲＣと本発明で得られる４５．０ＨＲＣ以上のものよりも硬さが低いものとなった。 No. of comparative steel in Table 3 61 has a V content of 0.10%, which is lower than the range of the present invention. Then, the quenching and tempering hardness in Table 6 was 44.4 HRC, which was lower than the hardness of 45.0 HRC or more obtained in the present invention.
表３の比較鋼のＮｏ．６２はＶの含有量が０．４８％と本発明の範囲より高い。すると、表６の熱伝導率が２３．８Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 62 has a V content of 0.48%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 23.8 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．６３はＮｉの含有量が３．０２％と本発明の範囲より高い。すると、表６の熱伝導率が２３．８Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 63 has a Ni content of 3.02%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 23.8 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
表３の比較鋼のＮｏ．６４はＡｌの含有量が０．３１１％と本発明の範囲より高い。すると、表６の熱伝導率が２３．４Ｗ／ｍ・Ｋと、本発明で得られる２５．０Ｗ／ｍ・Ｋ以上のものよりも熱伝導率が劣るものとなった。 No. of comparative steel in Table 3 64 has an Al content of 0.311%, which is higher than the range of the present invention. Then, the thermal conductivity in Table 6 was 23.4 W / m · K, which was inferior to that obtained in the present invention at 25.0 W / m · K or higher.
Claims (6)
またＭｏとＷのうち少なくとも一種以上をＭｏ：１．５０％未満かつＷ：１．８０％未満かつ（Ｍｏ＋５／６Ｗ）：０．４０〜１．５０未満の範囲で含有し、
さらに残部がＦｅと不可避的不純物からなる金型用鋼。 By mass%, C: more than 0.35 to 0.63%, Si: 0.01 to 1.20%, Mn: 0.01 to 0.92%, Cr: 0.40 to 4.00%, Cu : 0.05 to 2.85%, V: more than 0.10 to less than 0.45%,
Further, at least one or more of Mo and W are contained in the range of Mo: less than 1.50%, W: less than 1.80%, and (Mo + 5 / 6W): 0.40 to less than 1.50.
Furthermore, the mold steel whose balance consists of Fe and unavoidable impurities.
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