JP6032881B2 - Hot mold steel - Google Patents
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Description
この発明は、熱間鍛造、熱間押出、ダイカストその他の鋳造などに用いる熱間金型用鋼に関する。 The present invention relates to hot die steel used for hot forging, hot extrusion, die casting and other casting.
従来、熱間金型用鋼として、ＪＩＳのＧ４４０４には、合金工具鋼鋼材の一部として、ＳＫＤ４、ＳＫＤ５、ＳＫＤ６、ＳＫＤ６１、ＳＫＤ６２、ＳＫＤ７、ＳＫＤ８、ＳＫＴ３、ＳＫＴ４、ＳＫＴ６が規定されている。これらの熱間金型用鋼の用途例として、ＳＫＤ４、ＳＫＤ５、ＳＫＤ６、ＳＫＤ６１はプレス型、ダイカスト型、押出工具、シャーブレードが例示され、ＳＫＤ６２及びＳＫＤ７はプレス型、押出工具が例示され、ＳＫＤ８はプレス型、ダイカスト型、押出工具が例示され、さらにＳＫＴ３、ＳＫＴ４及びＳＫＴ６は鍛造型、プレス型及び押出工具が例示されている。 Conventionally, SKD4, SKD5, SKD6, SKD61, SKD62, SKD7, SKD8, SKT3, SKT4, and SKT6 are prescribed as part of alloy tool steel in JIS G4404 as hot mold steel. Examples of applications of these hot mold steels include SKD4, SKD5, SKD6, and SKD61 as press dies, die casting dies, extrusion tools, shear blades, SKD62 and SKD7 as press dies, extrusion tools, and SKD8. Is exemplified by a press die, a die-casting die, and an extrusion tool, and SKT3, SKT4, and SKT6 are exemplified by a forging die, a press die, and an extrusion tool.
ところで、熱間加工工具鋼の鋼材として、重量％で次に示す値からなる合金組成を有することを特徴とする、熱間加工工具鋼の鋼材であって、Ｃ：０．３〜０．４、Ｍｎ：０．２〜０．８、Ｃｒ：４〜６％、Ｍｏ：１．８〜３、Ｖ：０．４〜０．６、バランス：鉄及び不可避の金属不純物及び不可避の非金属不純物からなり、該非金属不純物は、次に示す最高量で存在できるシリコン、窒素、酸素、リン及び硫黄を含む：Ｓｉ：ｍａｘ．０．２５重量％、Ｎ：ｍａｘ．０．０１０重量％、Ｏ：ｍａｘ．１０ｐｐｍ、Ｓ：ｍａｘ．０．０００８重量％、該鋼材は、１０００〜１０８０℃の温度におけるオーステナイト化および５５０〜６５０℃の焼戻しによって４５ＨＲＣを超える硬度を得ることができる、熱間加工工具用の鋼材が提案されている（例えば、特許文献１参照。）。 By the way, it is a steel material of hot work tool steel characterized by having the alloy composition which consists of the value shown below by weight% as steel material of hot work tool steel, Comprising: C: 0.3-0.4 , Mn: 0.2 to 0.8, Cr: 4 to 6%, Mo: 1.8 to 3, V: 0.4 to 0.6, balance: iron and unavoidable metal impurities and unavoidable nonmetallic impurities And the non-metallic impurities include silicon, nitrogen, oxygen, phosphorus and sulfur that can be present in the highest amounts: Si: max. 0.25 wt%, N: max. 0.010% by weight, O: max. 10 ppm, S: max. 0.0008% by weight of the steel material has been proposed as a steel material for a hot working tool capable of obtaining a hardness exceeding 45 HRC by austenitizing at a temperature of 1000 to 1080 ° C. and tempering at 550 to 650 ° C. ( For example, see Patent Document 1.)
さらに、ダイカスト用金型鋼として、質量％で、０．３２〜０．４２％のＣを含む鋼に、Ｃｒ、Ｓｉ、Ｍｎ及びＶの必須添加元素、少なくともいずれかを含み得るＭｏ及びＷの準必須添加元素、及び、任意に含み得る任意添加元素添加したダイカスト金型鋼であって、前記任意添加元素において、Ｃｕを１．０％以下、Ｎｉを０．５％以下、Ｃｏを１．０％以下、Ｂを０．０１％以下、Ｓｅを０．０５％以下、Ｔｅを０．０５％以下、Ｐｂを０．０５％以下、Ｂｉを０．０１％以下、Ｃａを０．０１％以下、Ｎｂを０．１％以下、Ｔａを０．１％以下、Ｔｉを０．１％以下、Ｚｒを０．１％以下、ＲＥＭを０．１％以下、Ｍｇを０．１％以下で任意に含みうるとともに、前記必須添加元素において、質量％で、Ｃｒを４．０〜６．０％の範囲内、Ｓｉを０．０５〜０．２％の範囲内、Ｍｎを０．３〜１．５％の範囲内、及び、Ｖを０．２〜０．７％の範囲内で添加し、前記準必須添加元素において、質量％で、Ｍｏ及び／又はＷを、０．８≦Ｍｏ＋１／２Ｗ≦２．０となるように添加し３０Ｗ／（ｍ・Ｋ）以上の熱伝導率を与えたことを特徴とするダイカスト金型鋼が提案されている（例えば、特許文献２参照。）。 Further, as die metal for die casting, steel containing 0.32 to 0.42% by mass in mass%, and a quasi of Mo and W which may contain at least one of essential elements of Cr, Si, Mn and V A die-cast die steel to which an optional additive element and an optional additive element that can optionally be added are added, and in the optional additive element, Cu is 1.0% or less, Ni is 0.5% or less, and Co is 1.0%. Hereinafter, B is 0.01% or less, Se is 0.05% or less, Te is 0.05% or less, Pb is 0.05% or less, Bi is 0.01% or less, Ca is 0.01% or less, Nb is 0.1% or less, Ta is 0.1% or less, Ti is 0.1% or less, Zr is 0.1% or less, REM is 0.1% or less, and Mg is 0.1% or less. In the essential additive element, Cr is contained in the range of 4.0 to 6.0% by mass%. Si is added in a range of 0.05 to 0.2%, Mn is added in a range of 0.3 to 1.5%, and V is added in a range of 0.2 to 0.7%. As an essential additive element, Mo and / or W was added in mass% so that 0.8 ≦ Mo + 1 / 2W ≦ 2.0, and a thermal conductivity of 30 W / (m · K) or more was given. A characteristic die-cast die steel has been proposed (for example, see Patent Document 2).
熱間金型用鋼として高靭性及び高強度を両立させるには、合金元素の添加量に加えて、生成する炭化物の組成の制御が重要であり、また、焼入性を高めて靭性を向上させるために、Ｃｒ及びＭｏの添加は有効であるが、Ｃｒ及びＭｏのバランスを考慮しなければ、析出する炭化物としてＭＸやＭ2Ｃが少なくなり、高温強度が不十分になる問題がある。 In order to achieve both high toughness and high strength as a steel for hot molds, it is important to control the composition of the resulting carbide in addition to the amount of alloying elements added, and to improve toughness by improving hardenability. Therefore, the addition of Cr and Mo is effective, but unless the balance between Cr and Mo is taken into account, there is a problem that MX and M 2 C are reduced as precipitated carbides and the high-temperature strength is insufficient.
本発明が解決しようとする課題は、上記の問題を解消して、高靭性かつ高強度な熱間金型用鋼を提供することである。 The problem to be solved by the present invention is to solve the above-mentioned problems and provide a steel for hot molds having high toughness and high strength.
上記の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：０．３０〜０．５０％、Ｓｉ：０．１０〜０．５０％、Ｍｎ：０．１０〜１．００％、Ｃｒ：４．１１〜５．１２％、Ｍｏ：１．４０〜２．６０％、Ｖ：０．２０〜０．８０％、Ｔｉ：０．００３０％以下、Ｎ：０．０１１６％以下を含有し、残部Ｆｅおよび不可避不純物からなる熱間金型用鋼である。この熱間金型用鋼における［％Ｍｏ］と［％Ｃｒ］のバランスは、質量％で、０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足する。さらに、靱性がシャルピー衝撃試験値で５０．３〜８６．６Ｊ／ｃｍ 2 であり、かつ、焼入焼戻しによる調質前の初期硬さのＨＲＣと焼入焼戻しによる調質後のＨＲＣとの差であるΔＨＲＣが７．３〜１１．１である。このように本発明の第１の手段は、高靭性及び高強度な熱間金型用鋼である。 The means of the present invention for solving the above-mentioned problems is, in the first means, in mass%, C: 0.30 to 0.50%, Si: 0.10 to 0.50%, Mn: 0.00. 10 to 1.00%, Cr: 4.11 to 5.12%, Mo: 1.40 to 2.60%, V: 0.20 to 0.80%, Ti: 0.0030% or less, N: It is a steel for hot molds containing 0.0116% or less and the balance being Fe and inevitable impurities. The balance between [% Mo] and [% Cr] in this hot mold steel is 0.33 × [% Cr] −0.37 <[% Mo] <4.45−0.44 in mass%. X [% Cr] is satisfied. Furthermore, the toughness is 50.3 to 86.6 J / cm 2 in Charpy impact test value, and the difference between the HRC of the initial hardness before tempering by quenching and tempering and the HRC after tempering by quenching and tempering ΔHRC is 7.3 to 11.1. Thus, the first means of the present invention is a steel for hot molds having high toughness and high strength.
第２の手段では、質量％で、Ｃ：０．３０〜０．５０％、Ｓｉ：０．１０〜０．５０％、Ｍｎ：０．１０〜１．００％、Ｃｒ：４．１１〜５．１２％、Ｍｏ：１．４０〜２．６０％、Ｖ：０．２０〜０．８０％、Ｔｉ：０．００３０以下、Ｎ：０．０１１６％以下を含有し、さらにＮｉ：０．２〜１．５％及びＣｏ：１．２％以下のいずれか１種又は２種を含有し、残部Ｆｅおよび不可避不純物からなる熱間金型用鋼である。この熱間金型用鋼における［％Ｍｏ］と［％Ｃｒ］のバランスは、質量％で、０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足する。さらに、靱性がシャルピー衝撃試験値で５０．３〜８６．６Ｊ／ｃｍ 2 であり、かつ、焼入焼戻しによる調質前の初期硬さのＨＲＣと焼入焼戻しによる調質後のＨＲＣとの差であるΔＨＲＣが７．３〜１１．１である。このように本発明の第２の手段は、高靭性及び高強度な熱間金型用鋼である。 In the second means, in mass%, C: 0.30 to 0.50%, Si: 0.10 to 0.50%, Mn: 0.10 to 1.00%, Cr: 4.11 to 5 .12%, Mo: 1.40 to 2.60%, V: 0.20 to 0.80%, Ti: 0.0030 or less, N: 0.0116% or less, and Ni: 0.2 It is steel for hot molds which contains any 1 type or 2 types of -1.5% and Co: 1.2% or less, and consists of remainder Fe and an unavoidable impurity. The balance between [% Mo] and [% Cr] in this hot mold steel is 0.33 × [% Cr] −0.37 <[% Mo] <4.45−0.44 in mass%. X [% Cr] is satisfied. Furthermore, the toughness is 50.3 to 86.6 J / cm 2 in Charpy impact test value, and the difference between the HRC of the initial hardness before tempering by quenching and tempering and the HRC after tempering by quenching and tempering ΔHRC is 7.3 to 11.1. Thus, the second means of the present invention is a steel for hot molds having high toughness and high strength.
第３の手段では、質量％で、Ｃ：０．３０〜０．５０％、Ｓｉ：０．１０〜０．５０％、Ｍｎ：０．１０〜１．００％、Ｃｒ：４．１１〜５．１２％、Ｍｏ：１．４０〜２．６０％、Ｖ：０．２０〜０．８０％、Ｔｉ：０．００３０％以下、Ｎ：０．０１１６％以下を含有し、さらにＮｂ：０．３０％以下を含有し、なお、さらにＮｉ：０．２〜１．５％及びＣｏ：１．２％以下のいずれか１種又は２種を含有し、残部Ｆｅおよび不可避不純物からなる熱間金型用鋼である。この熱間金型用鋼における［％Ｍｏ］と［％Ｃｒ］のバランスは、質量％で、０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足する。さらに、靱性がシャルピー衝撃試験値で５０．３〜８６．６Ｊ／ｃｍ 2 であり、かつ、焼入焼戻しによる調質前の初期硬さのＨＲＣと焼入焼戻しによる調質後のＨＲＣとの差であるΔＨＲＣが７．３〜１１．１である。このように本発明の第３の手段は、高靭性及び高強度な熱間金型用鋼である。 In the third means, by mass%, C: 0.30 to 0.50%, Si: 0.10 to 0.50%, Mn: 0.10 to 1.00%, Cr: 4.11 to 5 .12%, Mo: 1.40 to 2.60%, V: 0.20 to 0.80%, Ti: 0.0030% or less, N: 0.0116% or less, and Nb: 0.0. Hot gold containing 30% or less, and further containing any one or two of Ni: 0.2 to 1.5% and Co: 1.2% or less, the balance being Fe and inevitable impurities Mold steel. The balance between [% Mo] and [% Cr] in this hot mold steel is 0.33 × [% Cr] −0.37 <[% Mo] <4.45−0.44 in mass%. X [% Cr] is satisfied. Furthermore, the toughness is 50.3 to 86.6 J / cm 2 in Charpy impact test value, and the difference between the HRC of the initial hardness before tempering by quenching and tempering and the HRC after tempering by quenching and tempering ΔHRC is 7.3 to 11.1. Thus, the third means of the present invention is hot mold steel for high toughness and strength.
ここで、本願の上記の手段に係る発明と特許文献１の発明及び特許文献２の発明との関係について以下に説明する。 Here, the relationship between the invention according to the above means of the present application and the invention of Patent Document 1 and the invention of Patent Document 2 will be described below.
特許文献１に係る発明における合金成分の添加量の範囲は本願の上記の手段の発明と重複している。しかしながら、特許文献１の発明は、本願発明の重要な技術である、焼入焼戻し状態の炭化物組成に関する見解が論じられておらず知見されていない。かつ、当該特許文献１の段落０００８に示される合金組成では、Ｍｏの添加量は１．８〜３％、好ましくは１．８〜２．５％、好適には２．２〜２．４％であり、標準では２．３％である。この特許文献１のＭｏの含有量はいずれも本願発明が規定する０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の範囲外であることから、特許文献１の発明は、本願の上記の手段の発明とは異なる、別の発明である。 The range of the addition amount of the alloy component in the invention according to Patent Document 1 overlaps with the above-described means of the present invention. However, the invention of Patent Document 1 does not discuss or know the view regarding the carbide composition in the quenched and tempered state, which is an important technique of the present invention. And in the alloy composition shown by the paragraph 0008 of the said patent document 1, the addition amount of Mo is 1.8 to 3%, Preferably it is 1.8 to 2.5%, Suitably 2.2 to 2.4% The standard is 2.3%. The content of Mo in Patent Document 1 is outside the range of 0.33 × [% Cr] −0.37 <[% Mo] <4.45−0.44 × [% Cr] defined by the present invention. Therefore, the invention of Patent Document 1 is another invention different from the invention of the above means of the present application.
特許文献２に係る発明における合金成分の添加量の範囲は本願の上記の手段の発明と重複しているが、特許文献２の発明は、本願発明の重要な技術の一つである、Ｎの規定がされておらず、靭性が不十分になる可能性を払拭できないものである。さらに、特許文献２の発明は、本願手段の発明の別の重要な技術である、焼入焼戻し状態の炭化物組成に関する見解が論じられていない。また、特許文献２の発明に示される実施例の中には、本願手段の発明が規定する１．４０＜［％Ｍｏ］＜２．６０かつ０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の範囲外であり、さらにＮが規定されていないものであることから、特許文献２の発明も、本願の上記の手段の発明とは異なる、別の発明である。 Although the range of the addition amount of the alloy component in the invention according to Patent Document 2 overlaps with the invention of the above means of the present application, the invention of Patent Document 2 is one of the important techniques of the present invention, N It is not stipulated and cannot eliminate the possibility of insufficient toughness. Further, the invention of Patent Document 2 does not discuss the view regarding the carbide composition in the quenched and tempered state, which is another important technique of the present invention. In addition, in the embodiments shown in the invention of Patent Document 2, 1.40 <[% Mo] <2.60 and 0.33 × [% Cr] −0.37 < Since it is outside the range of [% Mo] <4.45−0.44 × [% Cr] and N is not defined, the invention of Patent Document 2 is also the invention of the above means of the present application. This is a different invention.
本願の熱間金型用鋼は上記の手段からなる発明であり、鋼成分として含有されるＣｒ及びＭｏの量のバランスが適切であり、かつ、含有される炭化物の組成の制御が適切とされたことで、析出する炭化物としてのＭＸやＭ2Ｃが適量であり、熱間鍛造、熱間押出、鋳造あるいはダイカストなどに適応した際に、靱性が５０．３〜８６．６Ｊ／ｃｍ 2 であり、かつ、焼入焼戻しによる調質前の初期硬さのＨＲＣと焼入焼戻しによる調質後のＨＲＣとの差であるΔＨＲＣが７．３〜１１．１であり、高強度及び高靭性で従来の熱間金型用鋼に見られない優れた効果を奏する鋼材である。 The hot die steel of the present application is an invention comprising the above means, and the balance of the amount of Cr and Mo contained as steel components is appropriate, and the composition of the contained carbide is appropriately controlled. It was that, MX or M 2 C as carbides precipitated is an appropriate amount, hot forging, hot extrusion, upon adapted such as casting or die casting, toughness at 50.3~86.6J / cm 2 And ΔHRC, which is the difference between the HRC of the initial hardness before tempering by quenching and tempering and the HRC after tempering by quenching and tempering, is 7.3 to 11.1, with high strength and high toughness. It is a steel material that exhibits an excellent effect not seen in conventional hot metal mold steels.
本願の発明を実施するための形態を説明するに先立って、先ず、本願発明の熱間金型用鋼の鋼組成である化学成分の限定理由を以下に説明する。なお、％は質量％である。 Prior to describing the mode for carrying out the invention of the present application, first, the reasons for limiting the chemical components that are the steel composition of the steel for hot molds of the present invention will be described below. In addition,% is the mass%.
Ｃ：０．３０〜０．５０％
Ｃは、十分な焼入性を確保し、炭化物を形成させることで、耐摩耗性や高温強度を得るための元素である。Ｃが０．３０％未満では、十分な高温強度及び耐摩耗性が得られず、Ｃが０．５０％を超えると凝固偏析を助長し、靭性を阻害する。そこで、Ｃは０．３０〜０．５０％とする。
C: 0.30 to 0.50%
C is an element for obtaining wear resistance and high-temperature strength by ensuring sufficient hardenability and forming carbides. If C is less than 0.30%, sufficient high-temperature strength and wear resistance cannot be obtained. If C exceeds 0.50%, solidification segregation is promoted and toughness is inhibited. Therefore, C is set to 0.30 to 0.50%.
Ｓｉ：０．１０〜０．５０％
Ｓｉは、製鋼における脱酸の効果及び被削性並びに焼入性の確保に必要な元素である。Ｓｉが０．１０％未満であると脱酸の効果及び焼入性の確保は発揮できず、また、被削性を悪化させる。Ｓｉが０．５０％より多すぎると靭性を低下させ、また、熱間工具鋼として重要な物性値である熱伝導率を低下させる。そこで、Ｓｉは０．１０〜０．５０％とする。
Si: 0.10 to 0.50%
Si is an element necessary for ensuring the effect of deoxidation and machinability and hardenability in steelmaking. If Si is less than 0.10%, the effect of deoxidation and securing of hardenability cannot be exhibited, and the machinability is deteriorated. When Si is more than 0.50%, the toughness is lowered, and the thermal conductivity, which is an important physical property value for hot work tool steel, is lowered. Therefore, Si is set to 0.10 to 0.50%.
Ｍｎ：０．１０〜１．００％
Ｍｎは、焼入性を確保する元素である。Ｍｎが０．１０％未満では焼入性の確保は不十分である。一方、Ｍｎが１．００％を超えると加工性を低下させる。そこで、Ｍｎは０．１０〜１．００％とする。
Mn: 0.10 to 1.00%
Mn is an element that ensures hardenability. If Mn is less than 0.10%, ensuring of hardenability is insufficient. On the other hand, when Mn exceeds 1.00%, workability is reduced. Therefore, Mn is set to 0.10 to 1.00%.
Ｃｒ：４．１１〜５．１２％
Ｃｒは焼入性を改善する元素である。Ｃｒが４．００％未満では焼入性が不十分である。一方、Ｃｒが６．００％を超えると、焼入焼戻し時にＣｒ系の炭化物が過多に形成されて、高温強度及び軟化抵抗性を低下させる。そこで、Ｃｒは以上の範囲内において、実施例である補正後の表１の記載に基づき、Ｃｒは４．１１〜５．１２％とする。
Cr: 4.11 to 5.12%
Cr is an element that improves hardenability. If Cr is less than 4.00%, the hardenability is insufficient. On the other hand, if Cr exceeds 6.00%, excessive Cr-based carbides are formed during quenching and tempering, and the high temperature strength and softening resistance are lowered. Therefore, Cr is set to 4.11 to 5.12% in the above range based on the description in Table 1 after correction as an example .
Ｍｏ：１．４０〜２．６０％
Ｍｏは、焼入性と二次硬化、耐摩耗性、高温強度に寄与する析出炭化物を得るために必要な元素であり、また、焼入れ時に未固溶となった微細なＭｏ炭化物が結晶粒の粗大化を抑制する元素であるが、Ｍｏが１．４０％より少ないとそれらの効果が得られない。一方、Ｍｏは、２．６０％より過剰に添加しても効果が飽和するばかりか、Ｍｏ炭化物が粗大となって凝集することにより靭性を低下させ、また、Ｍｏの２．６０％より過剰の添加はコスト高となる。そこで、Ｍｏは１．４０〜２．６０％とする。
Mo: 1.40 to 2.60%
Mo is an element necessary for obtaining precipitated carbides that contribute to hardenability, secondary hardening, wear resistance, and high-temperature strength. In addition, fine Mo carbides that have become insoluble during quenching are composed of crystal grains. Although it is an element which suppresses coarsening, those effects cannot be obtained if Mo is less than 1.40%. On the other hand, even if Mo is added in excess of 2.60%, the effect is not only saturated, but Mo carbide is coarsened and aggregated to reduce toughness, and more than 2.60% of Mo. Addition is costly. Therefore, Mo is set to 1.40 to 2.60%.
Ｖ：０．２０〜０．８０％
Ｖは、焼戻時に微細で硬質なＶの炭化物や炭窒化物を析出し、高温強度や耐摩耗性に寄与する元素である。また、焼入れ時にはＶの微細な炭化物や炭窒化物が結晶粒の粗大化を抑制し、靭性の低下を抑制する効果を有するが、Ｖが０．２０％より少ないとそれらの効果が得られない。一方、Ｖが０．８０％より多すぎると、凝固時に粗大なＭＸ型の炭窒化物を晶出し、靭性を阻害する。また、Ｖの０．８０％より過剰の添加はコスト高となる。そこで、Ｖは０．２０〜０．８０％とする。
V: 0.20 to 0.80%
V is an element that precipitates fine and hard V carbides and carbonitrides during tempering and contributes to high-temperature strength and wear resistance. In addition, fine carbides and carbonitrides of V have an effect of suppressing coarsening of crystal grains and suppressing a decrease in toughness at the time of quenching, but if V is less than 0.20%, those effects cannot be obtained. . On the other hand, if V is more than 0.80%, coarse MX-type carbonitrides are crystallized during solidification, thereby inhibiting toughness. Moreover, addition exceeding 0.80% of V will become expensive. Therefore, V is set to 0.20 to 0.80%.
Ｔｉ：０．００３０％以下
Ｔｉは、Ｎとともに凝固時に晶出するＭＸ型炭窒化物に混入し、固溶温度を上昇させる。その結果、均質化熱処理での固溶が不足し、靭性を阻害する。また、十分に固溶させるためには、均質化熱処理の高温化や長時間化が必要となり、コストおよび環境負荷を増大させる。そこでＴｉは０．００３０％以下、望ましくは０．００２０％以下とする。
Ti: 0.0030 % or less Ti is mixed with MX type carbonitride which is crystallized during solidification together with N, and raises the solid solution temperature. As a result, the solid solution in the homogenization heat treatment is insufficient and the toughness is hindered. Moreover, in order to make it fully dissolve, it is necessary to increase the temperature and time of the homogenization heat treatment, thereby increasing the cost and environmental load. Therefore, Ti is made 0.0030% or less, preferably 0.0020% or less.
Ｎ：０．０１１６％以下
Ｎは、Ｔｉとともに凝固時に晶出するＭＸ型炭窒化物に混入し、固溶温度を上昇させる。その結果、均質化熱処理での固溶が不足し、靭性を阻害する。また、十分に固溶させるためには、均質化熱処理の高温化や長時間化が必要となり、コストおよび環境負荷を増大させる。そこでＮは実施例である補正後の表１本発明鋼に基づいて０．０１１６％以下とする。
N: 0.0116 % or less N mixes with MX type carbonitride that crystallizes during solidification together with Ti, and raises the solid solution temperature. As a result, the solid solution in the homogenization heat treatment is insufficient and the toughness is hindered. Moreover, in order to make it fully dissolve, it is necessary to increase the temperature and time of the homogenization heat treatment, thereby increasing the cost and environmental load. Therefore, N is set to 0.0116% or less based on Table 1 steel of the present invention after correction as an example .
Ｎｂ：０．３０％以下
Ｎｂは、焼戻時に微細で硬質なＮｂの炭化物や炭窒化物を析出し、高温強度や耐摩耗性に寄与する元素である。また、焼入れ時にはＮｂの微細な炭化物や炭窒化物が結晶粒の粗大化を抑制し、靭性の低下を抑制する効果を有するが、Ｎｂが０．３０％より多すぎると、凝固時に粗大なＭＸ型の炭窒化物を晶出し、靭性を阻害する。また、Ｎｂの０．３０％より過剰の添加はコスト高となる。そこで、Ｎｂは０．３０％以下とする。
Nb: 0.30% or less Nb is an element that precipitates fine and hard Nb carbides and carbonitrides during tempering and contributes to high-temperature strength and wear resistance. In addition, fine carbides and carbonitrides of Nb have the effect of suppressing the coarsening of crystal grains and suppressing the decrease in toughness during quenching, but if Nb is more than 0.30%, coarse MX during solidification Crystallize type carbonitride, impair toughness. Further, if Nb is added in excess of 0.30%, the cost becomes high. Therefore, Nb is set to 0.30% or less .
Ｎｉ：０．２〜１．５％
Ｎｉは焼入性と靭性を改善する元素である。しかし、Ｎｉが０．２％未満であるとその改善する効果が無い。一方、Ｎｉを２．０％より過多に添加すると高温強度及び被削性を阻害し、コストも嵩む。ところで、実施例の補正後の表１の本発明鋼に基づいてＮｉの上限を１．５％とする。そこで、Ｎｉは０．２〜１．５％とする。
Ni: 0.2~ 1.5%
Ni is an element that improves hardenability and toughness. However, when Ni is less than 0.2%, there is no effect to improve the Ni. On the other hand, if Ni is added in excess of 2.0%, the high temperature strength and machinability are hindered, and the cost increases. By the way, the upper limit of Ni is set to 1.5% based on the steel of the present invention in Table 1 after correction of the example. Therefore, Ni is set to 0.2 to 1.5 %.
Ｃｏ：２．０％以下
Ｃｏは基地を強化し高温強度を改善する元素である。しかし、Ｃｏが２．０％より過多に添加すると靭性を阻害し、コストも嵩む。そこで、Ｃｏは２．０％以下とする。
なお、上記のＮｉ及びＣｏは選択的にいずれか１種を若しくは２種を請求項１に係る発明の化学成分に加えて、補正後の請求項２又は請求項３に係る発明としている。
Co: 2.0% or less Co is an element that strengthens the matrix and improves high-temperature strength. However, if Co is added in excess of 2.0%, the toughness is hindered and the cost increases. Therefore, Co is set to 2.0% or less.
In addition, the above-described Ni or Co is selectively added to the chemical component of the invention according to claim 1 in addition to any one or two of them, and the invention according to claim 2 or claim 3 after correction is made.
熱間金型用鋼の化学成分は、質量％で、Ｍｏは１．４〜２．６％、かつ、０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］である理由
熱間金型用鋼においては、Ｃｒ、Ｍｏ、Ｖ、ＮｂおよびＴｉなどは、ＣやＮと結合して、炭化物および／または炭窒化物を形成する。炭化物および／または炭窒化物は、溶鋼からの凝固時に液相から晶出したり、各種の熱処理を経由して鋼の基地組織から析出したりする。また、炭化物および／または炭窒化物は、Ｍ3Ｃ、Ｍ7Ｃ3、Ｍ23Ｃ6、Ｍ6Ｃ、Ｍ2Ｃ、ＭＸ（Ｍ：Ｆｅ、Ｃｒ、Ｍｏ、Ｖ、ＮｂおよびＴｉなど。Ｘ：ＣおよびＮ。ここで、ＭＸにはＶ4Ｃ3も含む）などの結晶構造を成すが、合金元素添加量のバランスによって安定となる組成や結晶構造は異なる。
The chemical composition of the steel for hot die is mass%, Mo is 1.4 to 2.6%, and 0.33 × [% Cr] −0.37 <[% Mo] <4.45−. Reason for 0.44 × [% Cr] In hot mold steel, Cr, Mo, V, Nb, Ti and the like combine with C and N to form carbide and / or carbonitride. . Carbides and / or carbonitrides crystallize from the liquid phase during solidification from molten steel, or precipitate from the base structure of the steel via various heat treatments. The carbides and / or carbonitrides include M 3 C, M 7 C 3 , M 23 C 6 , M 6 C, M 2 C, MX (M: Fe, Cr, Mo, V, Nb, Ti, and the like). X: C and N. Here, MX includes V 4 C 3 ), but the composition and crystal structure that are stable differ depending on the balance of the amount of alloying elements added.
本願技術分野である熱間鍛造、熱間押出、ダイカストその他鋳造に用いられる熱間金型用鋼は、焼入焼戻しにより４０〜５０ＨＲＣの硬度に調質されて利用されるのが一般であり、焼入焼戻し組織中では、Ｍ23Ｃ6、Ｍ6Ｃ、Ｍ2Ｃ、およびＭＸが熱力学的に安定になり得る。ところで、炭化物および／または炭窒化物は硬質な物質であるが、その構造により硬度が異なり、Ｍ2ＣやＭＸは他の構造を呈する炭化物よりも高硬度である。ゆえに、熱間金型においては、Ｍ2ＣやＭＸが多く存在する方が高温環境下における硬度・強度を維持し易く、摩耗および／またはヒートチェックと呼ばれる熱疲労の抑制に有効である。熱間金型中のＭ2ＣやＭＸを増加させるためには、それらを形成する主成分であるＭｏ、ＶとＣおよび／またはＮを増量すれば良いが、過剰に添加すると炭化物および／または炭窒化物の総量が多くなり、また偏析を助長して炭化物および／または炭窒化物の凝集粗大化を招くことにより、別の重要な特性である靭性を低下させる。したがって、高い水準の高温強度と靭性を兼備させるためには、Ｍ2ＣやＭＸが安定になりやすく、かつ、炭化物および／または炭窒化物が過剰にならないようにする必要がある。 Hot die steel used for hot forging, hot extrusion, die casting and other castings that are the technical fields of the present application is generally used after being tempered to a hardness of 40 to 50 HRC by quenching and tempering, In the quenched and tempered structure, M 23 C 6 , M 6 C, M 2 C, and MX can be thermodynamically stable. By the way, carbides and / or carbonitrides are hard substances, but their hardness varies depending on their structures, and M 2 C and MX have higher hardness than carbides exhibiting other structures. Therefore, in a hot metal mold, the presence of a large amount of M 2 C and MX tends to maintain the hardness and strength in a high temperature environment, and is effective in suppressing thermal fatigue called wear and / or heat check. In order to increase M 2 C and MX in the hot mold, Mo, V and C and / or N, which are the main components forming them, may be increased, but if added excessively, carbide and / or The total amount of carbonitride increases, and segregation is promoted to cause agglomeration and coarsening of the carbide and / or carbonitride, thereby reducing toughness, which is another important characteristic. Therefore, in order to combine a high level of high-temperature strength and toughness, it is necessary to make M 2 C and MX easy to be stable and to prevent excessive carbides and / or carbonitrides.
ここで、前述の如く、優れた靭性を発揮させる為に本願発明で規定した、Ｃ、ＶおよびＮの範囲において、各種の炭化物および／または炭窒化物の構成元素と成り得るＭｏについて研究を重ねた結果、ＭｏとＣｒの含有量バランスによって、安定する炭化物および／または炭窒化物が変化することを見出した。即ち、Ｍｏの質量含有量［％Ｍｏ］が、０．３３×［％Ｃｒ］−０．３７よりも小さい場合は、焼入焼戻し時にＭ2ＣやＭＸよりも先んじて析出するＭ23Ｃ6の形成に大部分が消費されるため、高温強度に有効なＭ2ＣやＭＸの量が不十分となる。一方、［％Ｍｏ］が、４．４５−０．４４×［％Ｃｒ］より大きい場合は、焼入焼戻し時および／または高温環境下での炭化物反応によりＭ2ＣよりもＭ6Ｃが安定となり、高温強度への効果が弱まることを発見するに至った。そこで、Ｍｏは１．４〜２．６％で、かつ、０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］を満足するものとする。 Here, as described above, in order to exhibit excellent toughness, research was repeated on Mo which can be a constituent element of various carbides and / or carbonitrides in the range of C, V and N defined in the present invention. As a result, it has been found that the stable carbide and / or carbonitride changes depending on the content balance of Mo and Cr. That is, when the mass content [% Mo] of Mo is smaller than 0.33 × [% Cr] −0.37, M 23 C 6 precipitated prior to M 2 C and MX during quenching and tempering. As a result, the amount of M 2 C and MX effective for high-temperature strength becomes insufficient. On the other hand, when [% Mo] is larger than 4.45-0.44 × [% Cr], M 6 C is more stable than M 2 C due to carbide reaction during quenching and tempering and / or in a high temperature environment. It came to discover that the effect on high-temperature strength weakens. Therefore, Mo is 1.4 to 2.6% and satisfies 0.33 × [% Cr] −0.37 <[% Mo] <4.45−0.44 × [% Cr]. And
表１に示す化学成分と、残部がＦｅ及び不可避不純物からなる熱間金型用鋼を、１トン真空溶解炉を用いて溶製して、インゴットを造塊し、当該インゴットを１２５０℃で１６時間保持して均質化熱処理を施した後に、鍛錬成形比が凡そ６Ｓとなる直径１４０ｍｍに、熱間鍛造して鋼材を製造した。 Hot mold steel consisting of the chemical components shown in Table 1 and the balance consisting of Fe and inevitable impurities is melted using a 1 ton vacuum melting furnace to ingot an ingot. The steel material was manufactured by hot forging to a diameter of 140 mm at which the forging ratio was about 6S after the time-holding and homogenizing heat treatment.
表１において、※１のＱは、０．３３×［％Ｃｒ］−０．３７の値を示し、※２のＲは４．４５−０．４４×［％Ｃｒ］の値を示す。
さらに、表１において、本願発明鋼のＭｏの含有量は、質量％で、１．４％≦［％Ｍｏ］≦２．６％であり、かつ、Ｑ＜［％Ｍｏ］＜Ｒを満たすものである。
In Table 1, Q in * 1 indicates a value of 0.33 × [% Cr] −0.37, and R in * 2 indicates a value of 4.45−0.44 × [% Cr].
Further, in Table 1, the Mo content in the steel of the present invention is, in mass%, 1.4% ≦ [% Mo] ≦ 2.6% and satisfies Q <[% Mo] <R. It is.
表２において、※３の高温強度は、各鋼材の中周部から各辺１５ｍｍのブロック状供試材を割出し、焼入焼戻しにより４４〜４６ＨＲＣに調質し（供試材の表面にあるスケール層を除去した後ロックウェル硬度計にて測定し初期硬さとする）、該供試材を６５０℃にて５０時間保持し、これらの鋼材を空冷した後、再び鋼材の表面にあるスケール層を除去した後ロックウェル硬度計にて測定し、初期硬さとの差、すなわち硬度低下度であるΔＨＲＣにより評価した。さらに、※４の靭性は、シャルピー衝撃試験により破壊に要したエネルギーで評価した。これらに用いた試験片は、直径１４０ｍｍ鍛造材の中心部の圧延方向と垂直方向から採取した。さらに、これらの試験片は、焼入焼戻しにより４４〜４６ＨＲＣに調質し、ＪＩＳ Ｚ ２２４２に規定する深さ２ｍｍのＵノッチを圧延方向に垂直となる面に加工したものである。 In Table 2, the high-temperature strength of * 3 is determined by indexing a block-shaped specimen with a side of 15 mm from the middle part of each steel material and tempering to 44-46 HRC by quenching and tempering (on the surface of the specimen) After removing the scale layer, the initial hardness is measured with a Rockwell hardness meter), the specimen is held at 650 ° C. for 50 hours, and these steels are air-cooled, and then the scale layer on the surface of the steel again. After removal, the film was measured with a Rockwell hardness meter and evaluated by a difference from the initial hardness, that is, ΔHRC, which is a degree of hardness reduction. Furthermore, the toughness of * 4 was evaluated by the energy required for fracture by the Charpy impact test. The test pieces used for these were taken from the direction perpendicular to the rolling direction at the center of the forged material having a diameter of 140 mm. Further, these test pieces were tempered to 44 to 46 HRC by quenching and tempering, and a U-notch having a depth of 2 mm defined in JIS Z 2242 was processed into a surface perpendicular to the rolling direction.
表１及び表２における本発明鋼について説明する。
表１に示す本発明鋼のＡ〜Ｃ、Ｅ〜Ｆの化学成分は本発明の請求項１の手段の鋼のＦｅ及び不可避不純物以外の化学成分のＣ、Ｓｉ、Ｍｎ、Ｃｒ、Ｍｏ、Ｖ、Ｔｉ及びＮを示し、本発明鋼のＨの化学成分は本発明の請求項２の手段のＦｅ及び不可避不純物以外の化学成分のＣ、Ｓｉ、Ｍｎ、Ｃｒ、Ｍｏ、Ｖ、Ｔｉ、Ｎ、Ｎｂ及びＮｉを示し、本発明鋼のＩの化学成分は本発明の請求項３の手段のＦｅ及び不可避不純物以外の化学成分のＣ、Ｓｉ、Ｍｎ、Ｃｒ、Ｍｏ、Ｖ、Ｔｉ、Ｎ及びＣｏを示している。これらの化学成分は、いずれも本願発明の各化学成分として規定する範囲内にある。また、Ｑの値は［％Ｍｏ］の値より小さく、かつ［％Ｍｏ］の値はＲの値より大きい。すなわち、本発明鋼の、質量％で示す、Ｍｏ含有量は、１．４％≦［％Ｍｏ］≦２．６％であり、かつＱ＜［％Ｍｏ］＜Ｒを満足している。
The steels of the present invention in Tables 1 and 2 will be described.
The chemical components of A to C and E to F of the steel of the present invention shown in Table 1 are C, Si, Mn, Cr, Mo, V of chemical components other than Fe and unavoidable impurities of the steel of the means of claim 1 of the present invention. represents Ti and N, the chemical components of the H of the present invention steel chemical components other than Fe and unavoidable impurities means according to claim 2 of the present invention C, Si, Mn, Cr, Mo, V, Ti, N, Nb and Ni are shown, and the chemical component of I of the steel of the present invention is C, Si, Mn, Cr, Mo, V, Ti, N and Co of chemical components other than Fe and inevitable impurities of the means of claim 3 of the present invention Is shown. These chemical components are all within the range defined as each chemical component of the present invention. Further, the value of Q is smaller than the value of [% Mo], and the value of [% Mo] is larger than the value of R. That is, the Mo content of the steel of the present invention, expressed as mass%, satisfies 1.4% ≦ [% Mo] ≦ 2.6% and satisfies Q <[% Mo] <R.
次いで、表１及び表２における比較鋼について説明する。
比較鋼のｆ１は、本発明鋼Ｆ相当の鋼であるが、Ｃ添加量が本発明鋼Ｆよりも多過ぎるため、凝固偏析が顕著で、かつ、過剰な炭化物析出が生じたことで、表２にみられるように、靭性※４が３６．３Ｊ／ｃｍ 2 であり、本発明鋼のＦの７７．５Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ 2 よりもさらに小さいので、比較鋼のｆ１は本発明鋼Ｆやその他の本発明鋼より靱性が劣っている。
Next, the comparative steels in Tables 1 and 2 will be described.
F1 comparison steels is the present invention steels F equivalent steel, for C addition amount is too large than the present invention steels F, solidification segregation is remarkable, and that excessive carbide precipitation occurs, the table As shown in FIG. 2, the toughness * 4 is 36.3 J / cm 2, which is smaller than 77.5 J / cm 2 of F of the steel of the present invention, and 50.3 J / cm, which is the lowest toughness of the steel of the present invention. Since it is smaller than cm 2 , f1 of the comparative steel is inferior in toughness to the steel F of the present invention and other steels of the present invention .
比較鋼のｃ１は、本発明鋼Ｃ相当の鋼であるが、Ｃ添加量が本発明鋼Ｃよりも少なすぎるため、必要な量の炭化物析出が得られず、表２にみられるように、高温強度※３のΔＨＲＣが１４．５で本発明鋼のＣの高温強度※３のΔＨＲＣの８．１より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣ最高値の１１．１よりもさらに大きいので、本発明鋼よりも初期硬さとの硬度低下の差が大きく、比較鋼のｃ１は本発明鋼Ｃやその他の本発明鋼より高温強度が劣っている。 C1 of the comparative steel is a steel equivalent to the steel C of the present invention, but since the amount of C added is too small compared to the steel C of the present invention, a necessary amount of carbide precipitation cannot be obtained, and as shown in Table 2, ΔHRC of high-temperature strength * 3 is 14.5, which is larger than 8.1 of ΔHRC of high-temperature strength * 3 of steel of the present invention, and higher than 11.1 of ΔHRC maximum value of high-temperature strength * 3 of steel of the present invention. Since it is larger, the difference in hardness reduction from the initial hardness is larger than that of the steel of the present invention, and the comparative steel c1 is inferior in high temperature strength to the steel C of the present invention and other steels of the present invention .
比較鋼のｅ１は、本発明鋼Ｅ相当の鋼であるが、本発明鋼ＥよりもＳｉ添加量が多すぎるため、基地組織の延性が低下し、表２にみられるように、靭性※４が４２．２Ｊ／ｃｍ 2 であり、本発明鋼のＥの７０．３Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ 2 よりもさらに小さいので、比較鋼のｅ１は本発明鋼Ｅやその他の本発明鋼より靱性が劣っている。 The comparative steel e1 is a steel equivalent to the steel E of the present invention. However, since the amount of Si added is larger than that of the steel E of the present invention, the ductility of the base structure is reduced, and as shown in Table 2, toughness * 4 Is 42.2 J / cm 2, which is smaller than 70.3 J / cm 2 of E of the steel of the present invention and further smaller than 50.3 J / cm 2 of the lowest toughness of the steel of the present invention. The e1 of the present invention is inferior in toughness to the steel E of the present invention and other steels of the present invention .
比較鋼のｂ１は、本発明鋼Ｂ相当の鋼であるが、本発明鋼ＢよりもＭｎ添加量が少なく、したがって焼入性が不足することで、表２にみられるように、靭性※４が４１．９Ｊ／ｃｍ 2 であり、本発明鋼のＢの６７．４Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ 2 よりもさらに小さいので、比較鋼のｂ１は本発明鋼Ｂやその他の本発明鋼よりも靱性が低下している。 B1 of the comparative steel is a steel equivalent to the steel B of the present invention. However, the amount of Mn added is smaller than that of the steel B of the present invention, and therefore the hardenability is insufficient. As shown in Table 2, toughness * 4 since There was 41.9J / cm 2, less than 67.4J / cm 2 of the present invention steels B, and, even smaller than 50.3J / cm 2 of the lowest value of the toughness of the steel of the present invention, comparative steels B1 has lower toughness than the steel B of the present invention and other steels of the present invention .
比較鋼のｅ２は、本発明鋼Ｅ相当の鋼であるが、本発明鋼ＥよりもＣｒ添加量が少なく、十分な焼入性が得られないため、表２にみられるように、靭性※４が３８．１Ｊ／ｃｍ 2 であり、本発明鋼のＥの７０．３Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ 2 よりもさらに小さいので、比較鋼のｅ２は本発明鋼Ｅやその他の本発明鋼より靱性が低下している。 E2 comparison steels is the present invention steels E equivalent steel, for the present invention steel small amount of Cr added than E, no sufficient hardenability can be obtained, as seen in Table 2, toughness ※ 4 is 38.1 J / cm 2, which is smaller than 70.3 J / cm 2 of E of the steel of the present invention and further smaller than 50.3 J / cm 2 of the lowest toughness of the steel of the present invention. The e2 of steel has lower toughness than the steel E of the present invention and other steels of the present invention .
比較鋼のｆ２は、本発明鋼のＦ相当の鋼であるが、本発明鋼ＦよりもＣｒ添加量が多すぎるため、より有効なＭＸやＭ2Ｃの析出が少なくなり、表２にみられるように、高温強度※３のΔＨＲＣが１５．２で本発明鋼のＦの高温強度※３のΔＨＲＣの７．５より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣ最高値の１１．１よりもさらに大きいので、本発明鋼よりも初期硬さとの硬度低下の差が大きく、比較鋼のｆ２は本発明鋼Ｆやその他の本発明鋼より高温強度が大きく低下している。 F2 of Comparative Steel is a F corresponds steel of the steel of the present invention, since the amount of Cr added than the present invention steels F is too large, it more effective MX and M 2 C precipitation of less seen in Table 2 As shown in the figure, the ΔHRC of the high temperature strength * 3 is 15.2, which is greater than 7.5 of the ΔHRC of the high temperature strength * 3 of F of the steel of the present invention, and 11 of the maximum ΔHRC of the high temperature strength * 3 of the steel of the present invention. The difference in hardness from the initial hardness is larger than that of the steel of the present invention , and the high-temperature strength of f2 of the comparative steel is significantly lower than that of the steel F of the present invention and other steels of the present invention .
比較鋼のｆ３は、本発明鋼Ｆ相当の鋼であるが、ｆ３のＣｒ添加量は本発明鋼Ｆと全く同一である。ところで、ｆ３の［％Ｍｏ］の値は２．４５であるが、表１のｆ３のＲ※２の値すなわち４．４５−０．４４×［％Ｃｒ］は２．２１であり、これは本願発明の［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足しないものである。したがって、本発明鋼ＦよりもＭｏ添加量がやや多く、表２に見られるように、ｆ３は高温強度※３のΔＨＲＣが１３．４で本発明鋼のＦの高温強度※３のΔＨＲＣの７．５より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣ最高値の１１．１よりもさらに大きいので、本発明鋼よりも初期硬さからの硬度低下が大きく十分な高温強度が得られていない。このように比較鋼のｆ３は本発明の適正範囲内のＭｏ量を添加しても、優れた強度は得られない。 The comparative steel f3 is equivalent to the steel F of the present invention, but the amount of Cr added to the f3 is exactly the same as that of the steel F of the present invention. By the way, the value of [% Mo] of f3 is 2.45, but the value of R3 of f3 in Table 1, that is, 4.45−0.44 × [% Cr] is 2.21, which is This does not satisfy the relational expression [% Mo] <4.45−0.44 × [% Cr] of the present invention. Accordingly, the amount of Mo added is slightly higher than that of the steel F of the present invention, and as shown in Table 2, the ΔHRC of the high temperature strength * 3 is 13.4 and f3 is 7 of the ΔHRC of the high temperature strength * 3 of the steel F of the present invention. .5 and higher than the highest ΔHRC value 11.1 of the high-temperature strength * 3 of the steel of the present invention, the hardness decrease from the initial hardness is larger than that of the steel of the present invention, and sufficient high-temperature strength can be obtained. Not. Thus, even if the amount of Mo within the appropriate range of the present invention is added to f3 of the comparative steel , an excellent strength cannot be obtained.
比較鋼のａ２は、本発明鋼Ａ相当の鋼であるが、ａ２のＣｒ添加量は本発明鋼Ａと略同一でやや多い。ところで、ａ２の［％Ｍｏ］の値は２．５５であるが、表１のａ２のＲ※２の値すなわち４．４５−０．４４×［％Ｃｒ］は２．４７であり、これは本願発明の［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足しないものである。したがって、本願発明鋼ＡよりもＭｏ添加量がやや多く、表２に見られるように、ａ２は高温強度※３のΔＨＲＣが１３．０で本発明鋼のＡの高温強度※３のΔＨＲＣの７．３より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣの最高値である１１．１よりもさらに大きな値であるので、本発明鋼よりも初期硬さからの硬度低下が大きい。したがって、ａ２は、高温強度が低く、十分な高温強度が得られていない。このように比較鋼のａ２は本発明の適正範囲内のＭｏ量を添加しても、優れた強度は得られない。 A2 of the comparative steel is a steel equivalent to the steel A of the present invention, but the amount of Cr added in a2 is substantially the same as the steel A of the present invention and is slightly higher. By the way, the value of [% Mo] of a2 is 2.55, but the value of R * 2 of a2 in Table 1, that is, 4.45-0.44 × [% Cr] is 2.47, which is This does not satisfy the relational expression [% Mo] <4.45−0.44 × [% Cr] of the present invention. Accordingly, the amount of Mo added is slightly higher than that of the present invention steel A, and as shown in Table 2, a2 has a ΔHRC of the high temperature strength * 3 of 13.0, and the AHR of the present invention steel 7 has a ΔHRC of the high temperature strength * 3 of 7 .3 and a value larger than 11.1 which is the maximum value of ΔHRC of the high-temperature strength * 3 of the steel of the present invention, so that the hardness decrease from the initial hardness is larger than that of the steel of the present invention. Therefore, a2 has a low high temperature strength, and a sufficient high temperature strength is not obtained. Thus, even if the a2 of the comparative steel is added with an Mo amount within the proper range of the present invention, an excellent strength cannot be obtained.
比較鋼のｈ１は、本発明鋼Ｈ相当の鋼であるが、ｈ１のＣｒ添加量は本発明鋼Ｈと略同一でやや多い。ところで、ｈ１の［％Ｍｏ］の値は１．４３であるが、ｈ１の表１のＱ※１の値すなわち０．３３×［％Ｃｒ］−０．３７は１．４７であり、これは本願発明の０．３３×［％Ｃｒ］−０．３７＜［％Ｍｏ］の関係式を満足しないものである。したがって、本発明鋼ＨよりもＭｏ添加量がやや少なく、表２にみられるように、ｈ１は高温強度※３のΔＨＲＣが１４．１で本発明鋼のＨの高温強度※３のΔＨＲＣの１１．１より大きく、かつ、本発明鋼のＨの高温強度※３のΔＨＲＣは本発明鋼の最高値であることから、本発明鋼よりも初期硬さからの硬度低下が大きく十分な高温強度が得られていない。このように比較鋼のｈ１は本発明の適正範囲内のＭｏ量を添加しても、優れた強度は得られない。 The comparative steel h1 is a steel equivalent to the steel H of the present invention, but the Cr addition amount of h1 is substantially the same as the steel H of the present invention and is slightly higher. By the way, the value of [% Mo] of h1 is 1.43, but the value of Q * 1 in Table 1 of h1, that is, 0.33 × [% Cr] −0.37 is 1.47. This does not satisfy the relational expression of 0.33 × [% Cr] −0.37 <[% Mo] of the present invention. Accordingly, the amount of Mo added is slightly smaller than that of the steel H of the present invention, and as shown in Table 2, h1 has a ΔHRC of high temperature strength * 3 of 14.1 and 11 of ΔHRC of the high temperature strength * 3 of H of the steel of the present invention. .DELTA.HRC of H of the invention steel is the highest value of the steel of the present invention, and the hardness decrease from the initial hardness is larger than that of the steel of the present invention. Not obtained. Thus, even if the h1 of the comparative steel is added with an Mo amount within the appropriate range of the present invention, an excellent strength cannot be obtained.
比較鋼のｃ２は、本発明鋼Ｃ相当の鋼であるが、ｃ２のＣｒ添加量は本発明鋼Ｃと略同一である。しかし、ｃ２の［％Ｍｏ］の値は２．７０であり、これは本発明鋼Ｃの［％Ｍｏ］の値の２．５１を超えており、このため、これ等の値は本願発明の［％Ｍｏ］＜４．４５−０．４４×［％Ｃｒ］の関係式を満足しないものである。したがって、表２に見られるように、ｃ２は靭性※４が４０．８Ｊ／ｃｍ 2 であり、本発明鋼のＣの５０．３Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼のＣの５０．３Ｊ／ｃｍ 2 は本発明鋼の靱性の最低値であることから、比較鋼のｃ２は本発明鋼Ｃやその他の本発明鋼の靱性に比して劣っている。 The comparative steel c2 is a steel equivalent to the steel C of the present invention, but the Cr addition amount of c2 is substantially the same as that of the steel C of the present invention. However, the value of [% Mo] of c2 is 2.70, which exceeds 2.51 of the value of [% Mo] of the steel C of the present invention . Therefore , these values are those of the present invention. The relational expression [% Mo] <4.45-0.44 × [% Cr] is not satisfied. Therefore, as shown in Table 2, c2 has a toughness * 4 of 40.8 J / cm 2, which is smaller than 50.3 J / cm 2 of C of the steel of the present invention, and 50. Since 3 J / cm 2 is the lowest toughness of the steel of the present invention, c2 of the comparative steel is inferior to the toughness of the steel C of the present invention and other steels of the present invention .
比較鋼のｅ３は、本発明鋼Ｅ相当の鋼であるが、本発明鋼ＥよりもＭｏ添加量が少なく、表２にみられるように、高温強度※３のΔＨＲＣが１５．９で本発明鋼のＥの高温強度※３のΔＨＲＣの９．６より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣ最高値の１１．１よりもさらに大きいので、本発明鋼よりも初期硬さからの硬度低下が大きく、比較鋼のｅ３は本発明鋼Ｅやその他の本発明鋼より高温強度が大きく低下し、十分な高温強度が得られない。 The comparative steel e3 is a steel equivalent to the steel E of the present invention. However, the amount of Mo added is smaller than that of the steel E of the present invention, and as shown in Table 2, the ΔHRC of the high temperature strength * 3 is 15.9. Since the high temperature strength of steel E * 3 is greater than the ΔHRC of 9.6, and is higher than the highest ΔHRC value of 11.1 of the high temperature strength * 3 of the steel of the present invention, the initial hardness is higher than that of the steel of the present invention. The comparative steel e3 has a large decrease in hardness, and the high temperature strength of the comparative steel e3 is significantly lower than that of the steel E of the present invention and other steels of the present invention , and sufficient high temperature strength cannot be obtained.
比較鋼のａ３は、本発明鋼Ａ相当の鋼であるが、本発明鋼ＡよりもＶ添加量が０．１６％と少なく、表２にみられるように、高温強度※３のΔＨＲＣが１３．８で本発明鋼のＡの高温強度※３のΔＨＲＣの７．３より大きく、かつ、本発明鋼の高温強度※３のΔＨＲＣ最高値の１１．１よりもさらに大きいので、本発明鋼よりも初期硬さからの硬度低下が大きく、比較鋼のａ３は本発明鋼Ａやその他の本発明鋼より高温強度が大きく低下し、十分な高温強度が得られない。 A3 comparison steels is the present invention steels A substantial steel less V addition amount is 0.16% higher than the present invention steels A, as seen in Table 2, high-temperature strength ※ 3 of ΔHRC 13 .8 is larger than 7.3 of ΔHRC of A high temperature strength * 3 of the steel of the present invention and is further larger than 11.1 of ΔHRC maximum value of high temperature strength * 3 of the steel of the present invention. However, the hardness decrease from the initial hardness is large, and the a3 of the comparative steel has a high temperature strength significantly lower than that of the steel A of the present invention and other steels of the present invention , and a sufficient high temperature strength cannot be obtained.
比較鋼のｂ２は、本発明鋼Ｂ相当の鋼であるが、本発明鋼ＢよりもＶ添加量が過剰で、凝固時に粗大な炭窒化物を晶出し、比較鋼のｂ２は本発明鋼Ｂやその他の本発明鋼より靱性が阻害されて低下しており、表２に見られるように、靭性※４が３１．１Ｊ／ｃｍ 2 であり、本発明鋼のＢの６７．４Ｊ／ｃｍ 2 より小さく、かつ、本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ 2 よりもさらに小さい。 B2 of comparative steel is the present invention steels B equivalent steel, V addition amount is in excess of the present invention steels B, crystallized coarse carbonitrides during the solidification, b2 of comparative steel steel of the present invention B and other and toughness than the present invention steels is lowered is inhibited, as seen in Table 2, a toughness ※ 4 is 31.1J / cm 2, of the present invention steels B 67.4J / cm 2 It is smaller and is even smaller than 50.3 J / cm 2, which is the minimum value of the toughness of the steel of the present invention .
比較鋼のｃ３又は比較鋼のｂ３は、同順で本発明鋼Ｃ相当鋼又は本発明鋼Ｂ相当鋼であるが、ｃ３は本発明鋼ＣよりもＴｉ含有量が多く、又ｂ３は本発明鋼ＢよりもＮ含有量が多く、凝固時に晶出した炭窒化物の固溶温度が上昇したため、均質化熱処理での固溶が不十分となり、表２にみられるように、靭性※４がｃ３では３４．８Ｊ／ｃｍ 2 で本発明鋼Ｃの５０．３Ｊ／ｃｍ 2 より低下しており、ｂ３では３７．７Ｊ／ｃｍ 2 で本発明鋼Ｂの６７．４Ｊ／ｃｍ 2 より靱性が低下している。さらに、比較鋼のｃ３と比較鋼のｂ３の靱性※４は本発明鋼の靱性の最低値の５０．３Ｊ／ｃｍ2よりもさらに小さい。 C3 of the comparative steel or b3 of the comparative steel is steel C equivalent steel of the present invention or steel equivalent to steel B of the present invention in the same order, but c3 has a Ti content higher than steel C of the present invention, and b3 is the present invention. As N content is higher than that of steel B and the solid solution temperature of carbonitrides crystallized during solidification has increased, the solid solution in the homogenization heat treatment becomes insufficient, and as shown in Table 2, the toughness * 4 is in c3 in 34.8J / cm 2 and lower than 50.3J / cm 2 of the present invention steels C, decreases toughness than 67.4J / cm 2 of the present invention steels B in b3 in 37.7J / cm 2 doing. Furthermore, the toughness * 4 of the comparative steel c3 and the comparative steel b3 is even smaller than the minimum toughness value 50.3 J / cm 2 of the steel of the present invention .
表２の本発明鋼が有する特性は、補正後の表２の本発明鋼における、高温強度※３のΔＨＲＣが７．３〜１１．１であり、かつ、靱性※４が５０．３〜８６．６Ｊ／ｃｍThe characteristics of the steel of the present invention shown in Table 2 are as follows: ΔHRC of the high temperature strength * 3 is 7.3 to 11.1 and toughness * 4 is 50.3 to 86 in the steel of the present invention after correction. .6J / cm 22 である評価である。一方、表２の比較鋼が有する特性では、比較鋼のｃ１、ｆ２、ｆ３、ａ２、ｈ１、ｅ３、ａ３の高温強度※３のΔＨＲＣが本発明鋼の高温強度※３のΔＨＲＣの１１．１より大きく、したがって、これらの比較鋼のものに比して本発明鋼は高温強度および靱性において優れており、さらに比較鋼のｆ１、ｅ１、ｂ１、ｅ２、ｃ２、ｃ３、ｂ３の靱性※４が本発明鋼の靱性の５０．３Ｊ／ｃｍIs an evaluation. On the other hand, in the properties of the comparative steels in Table 2, ΔHRC of the high temperature strength * 3 of the comparative steels c1, f2, f3, a2, h1, e3, and a3 is 11.1 of ΔHRC of the high temperature strength * 3 of the steel of the present invention. Therefore, the steel of the present invention is superior in high-temperature strength and toughness as compared with those of these comparative steels, and the toughness * 4 of the comparative steels f1, e1, b1, e2, c2, c3, b3 is further increased. 50.3 J / cm of toughness of the steel of the present invention 22 よりも低い。したがって、比較鋼は全てのものにおいて、高温強度、靱性のいずれかの特性が本発明鋼よりも劣っている結果となっている。このことから、本発明鋼は高温強度及び靱性に優れた鋼である。Lower than. Therefore, in all the comparative steels, either high temperature strength or toughness is inferior to the steel of the present invention. For this reason, the steel of the present invention is a steel excellent in high-temperature strength and toughness.
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| JP6366326B2 (en) * | 2014-03-31 | 2018-08-01 | 山陽特殊製鋼株式会社 | High toughness hot work tool steel and manufacturing method thereof |
| JP6647771B2 (en) * | 2014-05-23 | 2020-02-14 | 大同特殊鋼株式会社 | Mold steel and mold |
| JP2015224363A (en) * | 2014-05-27 | 2015-12-14 | 大同特殊鋼株式会社 | Steel for metallic mold and metallic mold |
| JP5744300B1 (en) | 2014-11-11 | 2015-07-08 | 日本高周波鋼業株式会社 | Hot work tool steel |
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| JP6925781B2 (en) * | 2016-03-03 | 2021-08-25 | 山陽特殊製鋼株式会社 | Hot tool steel with excellent high temperature strength and toughness |
| CN106086688A (en) * | 2016-08-29 | 2016-11-09 | 营口市特殊钢锻造有限责任公司 | A kind of Cr3 series hot die steel and heat treatment method thereof |
| CN108018499A (en) * | 2017-11-29 | 2018-05-11 | 无锡透平叶片有限公司 | A kind of mold materials and preparation method thereof |
| JP7144717B2 (en) * | 2018-04-02 | 2022-09-30 | 大同特殊鋼株式会社 | Mold steel and mold |
| US20210262071A1 (en) * | 2018-10-05 | 2021-08-26 | Hitachi Metals, Ltd. | Hot work tool steel and hot work tool |
| CN109468538A (en) * | 2018-12-25 | 2019-03-15 | 上海合毓模具技术有限公司 | A kind of high-performance die-casting die steel DIEMAX and preparation method thereof |
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| CN111621695A (en) * | 2020-01-10 | 2020-09-04 | 宝鼎科技股份有限公司 | HC166 high-alloy die steel forging and manufacturing method thereof |
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