JP2019019397A - Preharden hot tool steel excellent in machinability - Google Patents
Preharden hot tool steel excellent in machinability Download PDFInfo
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- 229910001315 Tool steel Inorganic materials 0.000 title claims abstract description 23
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 46
- 239000010959 steel Substances 0.000 claims abstract description 46
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 4
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 3
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 3
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 3
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 3
- 150000001247 metal acetylides Chemical class 0.000 claims description 30
- 238000005242 forging Methods 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 238000005520 cutting process Methods 0.000 description 25
- 230000000052 comparative effect Effects 0.000 description 17
- 230000000694 effects Effects 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 239000002436 steel type Substances 0.000 description 7
- 238000011156 evaluation Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 229910000760 Hardened steel Inorganic materials 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000010730 cutting oil Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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Abstract
Description
本発明は、特に熱間で使用されるハンマー型鍛造用の金型において、プリハードン後の被削性に優れた高靭性の熱間工具鋼に関する。 The present invention relates to a high toughness hot tool steel excellent in machinability after pre-hardening, particularly in a hammer die forging die used hot.
熱間で使用されるハンマー型鍛造用などの金型には、衝撃に耐えうる靭性が必要とされている。そこで、このための熱間工具鋼としては、これまでＪＩＳ鋼種のＳＫＴ３やＳＫＴ４などの高靭性のプリハードン鋼が用いられている。ところで、これらの鋼種を使用する場合、３６〜４２ＨＲＣ程度の硬度に調質されているので、金型ユーザーは熱処理することなく加工して使用することができ、鋼材をそのままで所望の金型形状に削り出して使用するのが一般的である。しかし、これらの鋼種は、高硬度であるので、金型形状に削り出す被削性が十分に良好であるとはいえなかった。 Metal molds for forging hammer dies that are used hot are required to have toughness that can withstand impacts. Thus, as hot tool steel for this purpose, high-toughness pre-hardened steel such as JIS steel types SKT3 and SKT4 has been used so far. By the way, when these steel types are used, since they are tempered to a hardness of about 36 to 42 HRC, the mold user can process and use them without heat treatment. It is common to cut and use it. However, since these steel types have high hardness, it cannot be said that the machinability to be machined into a mold shape is sufficiently good.
そこで、熱間工具鋼の合金の化学成分を、式を用いて規定することで当該合金の化学成分の量を最適化し、鋼中における炭化物などの偏析を低減させることによって、被削性を向上させようとする熱間工具鋼が提案されている（例えば、特許文献１参照。）。もっとも、この特許文献１の熱間工具鋼では、析出している炭化物の量や形態については考慮されていないので、被削性が悪く急に削れなくなることが生じてしまい、被削性を制御しきれていない場面があった。 Therefore, by defining the chemical composition of the alloy of the hot tool steel using an equation, the amount of the chemical composition of the alloy is optimized and the segregation of carbides in the steel is reduced, thereby improving the machinability. There has been proposed a hot work tool steel (see, for example, Patent Document 1). However, in the hot work tool steel of Patent Document 1, since the amount and form of precipitated carbides are not taken into consideration, the machinability is poor and it becomes impossible to sharply cut, and the machinability is controlled. There was an unsatisfactory scene.
さらに、断面積が３μｍ2以上の炭化物量と炭化物の総量とを一定範囲に抑制して介在物を制御することで、被削性を著しく改善した低合金工具鋼が提案されている（例えば、特許文献２参照。）。しかし、この低合金工具鋼は、介在物の量を一定の範囲に規定して有しているため、靭性が低くならざるを得ないものとなってしまう。また、炭化物の量がこの文献に規定の範囲を満足している場合であっても、被削性が良好でない場合があった。 Furthermore, a low alloy tool steel has been proposed in which the amount of carbide having a cross-sectional area of 3 μm 2 or more and the total amount of carbides are controlled within a certain range to control inclusions, thereby significantly improving machinability (for example, (See Patent Document 2). However, since this low alloy tool steel has the amount of inclusions defined within a certain range, the toughness must be lowered. Even when the amount of carbide satisfies the range specified in this document, the machinability may not be good.
上述したように、熱間で使用されるハンマー型鍛造用などの金型には、衝撃に耐えうる高い靭性が必要とされることから、これらの熱間工具鋼の鋼種として、従前はＪＩＳ鋼種のＳＫＴ３やＳＫＴ４などの高靭性のプリハードン鋼が用いられている。しかし、これらの鋼種は、３６〜４２ＨＲＣ程度の高硬度に調質された鋼であるので、鋼材そのままの状態で金型の形状に削り出して使用するには、被削性が十分良いとはいえなかった。そこで、本願の発明が解決しようとする課題は、高硬度に調質された状態でも容易に切削できることで熱間で使用されるハンマー型鍛造用などの金型の製造コストをより低減し得るような、高靭性でかつ被削性の良好なプリハードンの熱間工具鋼を提供することである。 As described above, since a high-toughness that can withstand impact is required for a die for hammer die forging that is used hot, as a steel type of these hot tool steels, the JIS steel type has been used in the past. High-toughness prehardened steel such as SKT3 and SKT4 is used. However, since these steel types are steel tempered to a high hardness of about 36 to 42 HRC, the machinability is sufficiently good to be used by cutting out into the shape of a mold as it is. I couldn't. Accordingly, the problem to be solved by the invention of the present application is that it can be easily cut even in a state of being tempered with high hardness, so that the manufacturing cost of a die for forging a hammer die used hot can be further reduced. Another object of the present invention is to provide a pre-hardened hot tool steel having high toughness and good machinability.
本発明の課題を解決するため、発明者は、高靱性な熱間工具鋼を所望の形状に削りだす際に、切削工具の切削性を悪化させてしまう原因を解明すべく鋭意研究を進めた結果、これまでと異なる原因を見出した。すなわち、従前の理解としては、切削工具の切削性が悪化するのは、被削対象物の鋼材中に析出している硬質の炭化物が工具の表面を傷付けることで切削工具自体が摩耗することによると考えられていた。しかし、発明者は、切削工具の切削性が悪化する主な原因は、被削対象物の鋼材中の、特定の形状をした炭化物を切断しながら切削していくときに断続切削が起こりやすいことに起因しており、このために切削工具に微細な欠けが発生したり、欠けが促進される結果、切削工具の切削性が悪化してしまうことを見出した。そしてさらに、本願発明の構成要件である合金成分範囲および、特定の炭化物の形状と量を調整することにより、Ｓなどの快削成分を添加しなくても良好に切削される、高靱性でかつ被削性の良好なプリハードンの熱間工具鋼が得られることを見出した。 In order to solve the problems of the present invention, the inventor has conducted extensive research to elucidate the cause of the deterioration of the cutting performance of a cutting tool when cutting a tough hot tool steel into a desired shape. As a result, we found a different cause. That is, as a conventional understanding, the cutting performance of the cutting tool is deteriorated because the hard carbide precipitated in the steel material to be cut damages the surface of the tool so that the cutting tool itself is worn. It was thought. However, the main reason for the inventor's deterioration of the cutting performance of the cutting tool is that intermittent cutting is likely to occur when cutting a specific shape of carbide in the steel material to be cut. For this reason, it has been found that the cutting tool is deteriorated due to the occurrence of fine chipping or the promotion of chipping. Furthermore, by adjusting the alloy component range and the shape and amount of a specific carbide that are constituent elements of the present invention, the toughness can be cut well without adding a free-cutting component such as S, and It has been found that a pre-hardened hot tool steel with good machinability can be obtained.
すなわち、本発明の課題を解決するための手段は、第１の手段では、質量％で、Ｃ：０．３５〜０．６０％、Ｓｉ：≦０．３％、Ｍｎ：０．６〜１．２％、Ｎｉ：０．７〜１．６％、Ｃｒ：１．６〜２．２％、Ｍｏ＋Ｗ／２：０．４〜１．８％、Ｖ＋Ｎｂ／２：≦０．３％を含有し、残部Ｆｅおよび不可避不純物からなる鋼である。この鋼はプリハードン状態であり、そのプリハードン状態における鋼の１００μｍ2中に観測される、断面積が０．０１μｍ2以上の炭化物の数が１２０個以下であり、かつ炭化物の面積率が３０％以下であることを特徴とする被削性に優れたプリハードンの熱間工具鋼である。 That is, the means for solving the problems of the present invention is that in the first means, in mass%, C: 0.35 to 0.60%, Si: ≦ 0.3%, Mn: 0.6 to 1 0.2%, Ni: 0.7-1.6%, Cr: 1.6-2.2%, Mo + W / 2: 0.4-1.8%, V + Nb / 2: ≤0.3% And it is steel which consists of remainder Fe and inevitable impurities. This steel is in a pre-hardened state, and the number of carbides having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 of the steel in the pre-hardened state is 120 or less, and the area ratio of carbides is 30% or less. It is a pre-hardened hot work tool steel with excellent machinability.
第２の手段では、炭化物は、縦横比が３以上である炭化物の占める割合が７０％以下であることを特徴とする第１の手段に記載の被削性に優れたプリハードンの熱間工具鋼である。 In the second means, the pre-hardened hot tool steel having excellent machinability according to the first means, wherein the carbide occupies 70% or less of the carbide having an aspect ratio of 3 or more. It is.
上記の手段とすることで、第１の手段に係る発明は、熱間で使用されるハンマー型鍛造用の金型における、プリハードン状態における熱間工具鋼の１００μｍ2中に観測される、断面積が０．０１μｍ2以上の炭化物の数が１２０個以下でかつ炭化物の面積率が３０％以下であり、粗大な炭化物がない、被削性が良好な高靱性のプリハードン熱間工具鋼となっている。さらに、第２の手段に係る発明は、第１の手段に係る発明の効果に加えて、プリハードン状態における熱間工具鋼の１００μｍ2中に観測される、縦横比が３以上の炭化物の割合が７０％以下であるので、切削工具の微細な刃の欠けや摩耗を生じることのない、被削性が良好な高靱性のプリハードン熱間工具鋼となっている。 By using the above means, the invention according to the first means is the cross-sectional area observed in 100 μm 2 of the hot tool steel in the pre-hardened state in the die for hammer die forging used hot. Is a high-toughness pre-hardened hot tool steel with good machinability, having no carbides and having an area ratio of carbides of 30% or less, with a number of carbides of 0.01 μm 2 or more. Yes. Furthermore, in the invention according to the second means, in addition to the effect of the invention according to the first means, the ratio of carbide having an aspect ratio of 3 or more observed in 100 μm 2 of the hot tool steel in the pre-hardened state is Since it is 70% or less, it is a high-toughness pre-hardened hot tool steel with good machinability that does not cause chipping or wear of fine blades of the cutting tool.
本願発明の実施の形態を説明するに先立って、本願の手段の工具鋼における化学成分、およびプリハードン状態にある熱間工具鋼（以下「プリハードン鋼」という。）における炭化物の特性などの限定理由について説明する。なお、以下の化学成分は質量％である。 Prior to describing the embodiment of the present invention, the reasons for limitation such as the chemical composition of the tool steel of the means of the present application and the characteristics of carbide in the hot tool steel in a prehardened state (hereinafter referred to as “prehardened steel”). explain. In addition, the following chemical components are mass%.
Ｃ：０．３５〜０．６０％、望ましくは、０．３５〜０．５０％
Ｃは、硬質炭化物を形成し、硬さおよび耐摩耗性を向上させるとともに焼入性を高める元素である。これらの効果を得るためには、Ｃは０．３５％以上が必要である。しかし、Ｃは０．６０％を超えて含有されると、鋼中に粗大な炭化物を形成して、靭性および被削性が悪化する。そこで、Ｃは０．３５〜０．６０％、望ましくは、０．３５〜０．５０％とする。
C: 0.35-0.60%, desirably 0.35-0.50%
C is an element that forms hard carbides, improves hardness and wear resistance, and increases hardenability. In order to obtain these effects, C needs to be 0.35% or more. However, if C is contained in excess of 0.60%, coarse carbides are formed in the steel, and the toughness and machinability deteriorate. Therefore, C is 0.35 to 0.60%, preferably 0.35 to 0.50%.
Ｓｉ：≦０．３％
Ｓｉは、脱酸剤として作用し、基地の硬さを得るために必要であり、かつ鋼材の切削時に工具表面に付着して酸化皮膜を形成し、工具の焼付きを抑制する効果を有する元素である。しかし、Ｓｉは０．３％より多く含有されると、固溶強化が進む結果、靭性が悪化する。そこで、Ｓｉは０．３％以下とする。
Si: ≦ 0.3%
Si acts as a deoxidizer and is necessary to obtain the hardness of the base, and is an element that has the effect of suppressing the seizure of the tool by forming an oxide film by adhering to the tool surface when cutting steel. It is. However, if Si is contained in an amount of more than 0.3%, solid solution strengthening proceeds, resulting in poor toughness. Therefore, Si is set to 0.3% or less.
Ｍｎ：０．６〜１．２％
Ｍｎは、脱酸剤および焼入性を得るために必要な元素である。これらの効果を得るためには、Ｍｎは０．６％以上が必要である。しかし、Ｍｎは１．２％を超えて含有されるとマトリックスを脆化させて靱性が悪化する。そこで、Ｍｎは０．６〜１．２％とする。
Mn: 0.6 to 1.2%
Mn is an element necessary for obtaining a deoxidizer and hardenability. In order to obtain these effects, Mn needs to be 0.6% or more. However, if Mn exceeds 1.2%, the matrix becomes brittle and the toughness deteriorates. Therefore, Mn is set to 0.6 to 1.2%.
Ｎｉ：０．７〜１．６％
Ｎｉは、焼入性および靭性を得るために必要な元素である。これらの効果を得るためには、Ｎｉは０．７％以上が必要である。しかし、Ｎｉは１．６％を超えて含有されると焼なましがされ難くなり、焼なまし時にミクロ組織が部分的にフェライトと球状炭化物からなる組織とベイナイトとの混晶組織になることで、合金元素の分布が不均一となり、被削性が低下する。そこで、Ｎｉは０．７〜１．６％とする。
Ni: 0.7-1.6%
Ni is an element necessary for obtaining hardenability and toughness. In order to obtain these effects, Ni needs to be 0.7% or more. However, if Ni exceeds 1.6%, it becomes difficult to anneal, and the microstructure becomes a mixed crystal structure of bainite and a structure partially composed of ferrite and spherical carbide during annealing. Thus, the distribution of the alloy elements becomes non-uniform, and the machinability decreases. Therefore, Ni is set to 0.7 to 1.6%.
Ｃｒ：１．６〜２．２％
Ｃｒは、硬質炭化物を形成し、硬さおよび耐摩耗性を向上させるとともに焼入性を高める元素である。これらの効果を得るためには、Ｃｒは１．６％以上が必要である。しかし、Ｃｒは２．２％を超えて含有されると、粗大な炭化物が形成され、靭性および被削性が悪化する。そこで、Ｃｒは１．６〜２．２％とする。
Cr: 1.6-2.2%
Cr is an element that forms hard carbides, improves hardness and wear resistance, and improves hardenability. In order to obtain these effects, Cr needs to be 1.6% or more. However, if the Cr content exceeds 2.2%, coarse carbides are formed, and the toughness and machinability deteriorate. Therefore, Cr is set to 1.6 to 2.2%.
（Ｍｏ＋Ｗ／２）：０．４〜１．８％
（Ｍｏ＋Ｗ／２）は、硬質炭化物を形成して、硬さおよび耐摩耗性を向上させるとともに焼入性および焼戻し軟化抵抗性を高める元素成分である。これらの効果を得るためには、（Ｍｏ＋Ｗ／２）は０．４％以上が必要である。しかし、（Ｍｏ＋Ｗ／２）は１．８％を超えて含有されると、粗大な炭化物が形成されて、靭性および被削性が悪化する。そこで、（Ｍｏ＋Ｗ／２）は０．４〜１．８％とする。
(Mo + W / 2): 0.4 to 1.8%
(Mo + W / 2) is an elemental component that forms hard carbides to improve hardness and wear resistance, and to increase hardenability and temper softening resistance. In order to obtain these effects, (Mo + W / 2) needs to be 0.4% or more. However, if (Mo + W / 2) exceeds 1.8%, coarse carbides are formed, and the toughness and machinability deteriorate. Therefore, (Mo + W / 2) is set to 0.4 to 1.8%.
（Ｖ＋Ｎｂ／２）：≦０．３％、望ましくは、０．１〜０．２％
（Ｖ＋Ｎｂ／２）は、硬質炭化物を形成して、硬さおよび耐摩耗性を向上させるとともに焼入れ時の結晶粒の粗大化を抑制して靭性を向上させる元素成分である。これらの効果を得るためには、（Ｖ＋Ｎｂ／２）は０．３％以下とする必要がある。しかし、（Ｖ＋Ｎｂ／２）は、０．３％を超えて含有されると、粗大な炭窒化物が形成されて、靭性および被削性が悪化する。そこで、（Ｖ＋Ｎｂ／２）は０．３％以下、望ましくは、０．１〜０．２％とする。
(V + Nb / 2): ≦ 0.3%, preferably 0.1-0.2%
(V + Nb / 2) is an elemental component that forms hard carbides, improves hardness and wear resistance, and suppresses coarsening of crystal grains during quenching to improve toughness. In order to obtain these effects, (V + Nb / 2) needs to be 0.3% or less. However, if (V + Nb / 2) is contained in excess of 0.3%, coarse carbonitrides are formed, and toughness and machinability deteriorate. Therefore, (V + Nb / 2) is 0.3% or less, preferably 0.1 to 0.2%.
プリハードン鋼の１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の数：≦１２０個、同炭化物の面積率：≦３０％
炭化物は硬質であるため切削工具の摩耗が起きやすい。そこで、プリハードン鋼の１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の数は１２０個以下、同炭化物の面積率は３０％以下と限定する。
Number of carbides having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 of prehardened steel: ≦ 120, area ratio of the carbides: ≦ 30%
Since carbide is hard, wear of the cutting tool is likely to occur. Therefore, the number of carbides having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 of prehardened steel is limited to 120 or less, and the area ratio of the carbides is limited to 30% or less.
プリハードン鋼の炭化物のうち、縦横比３以上である炭化物が占める割合：≦７０％
プリハードン鋼の炭化物のうち、縦横比３以上の炭化物が占める割合が７０％を超えると、切削中に断続切削が起こりやすくなって、切削工具の摩耗が促進される。そこで、プリハードン鋼の炭化物のうち、縦横比３以上である炭化物が占める割合は７０％以下とする。
Ratio of pre-hardened steel carbides with aspect ratio of 3 or more: ≦ 70%
If the proportion of carbide in the pre-hardened steel is more than 70%, the intermittent cutting is likely to occur during cutting and the wear of the cutting tool is promoted. Accordingly, the proportion of prehardened steel carbides having an aspect ratio of 3 or more is 70% or less.
ここで、本願発明の実施の形態を以下に説明する。まず、表１に示す本願の発明例であるＮｏ．１〜１６の発明鋼とそれらの比較例であるＮｏ．１７〜２９の比較鋼について、各Ｎｏ．の化学元素の成分量とその残部のＦｅおよび不可避不純物からなる、各鋼の１００ｋｇを真空誘導溶解炉にて溶製して鋼とし、得られた各鋼を縦６０ｍｍ、横６０ｍｍに鍛伸して角材とした。これらの縦横６０ｍｍの角材を８７０℃に３０分加熱した後、油冷にて焼入れを行った。その後、これらの角材を５００〜６５０℃の温度範囲で１時間加熱して空冷する、焼戻し処理を２回繰り返して硬さ３８ＨＲＣに調質し、プリハードン状態とし、以下に記載の評価をそれぞれ行った。 Here, an embodiment of the present invention will be described below. First, No. 1 which is an invention example of the present application shown in Table 1. Nos. 1 to 16 of the invention steels and comparative examples thereof. For comparative steels 17-29, each No. 100kg of each steel consisting of the chemical element component and the balance Fe and inevitable impurities is melted in a vacuum induction melting furnace to make steel, and the obtained steel is forged to 60mm length and 60mm width. And used as a square. These 60 mm vertical and horizontal squares were heated to 870 ° C. for 30 minutes and then quenched with oil cooling. Then, these squares were heated in the temperature range of 500 to 650 ° C. for 1 hour and air-cooled. The tempering treatment was repeated twice to adjust the hardness to 38 HRC to obtain a pre-hardened state, and the following evaluations were performed. .
以下、各供試材である発明鋼およびその比較鋼のＦｅおよび不可避不純物を除く化学成分、ならびに１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の個数および面積率、ならびに鋼中の炭化物の中で縦横比３以上である炭化物の割合の計算結果を、それぞれ表１に示す。この場合、表１において、比較鋼に見られるように、１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の数が１２０個を超えるものにはその個数に下線を付し、同じく１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の面積率が３０％を超えるものにはその面積率に下線を付し、また、炭化物のうち縦横比３以上である炭化物の占める割合が７０％を超えるものにはその割合の箇所に下線を付して表示した。 Hereinafter, the chemical composition excluding Fe and unavoidable impurities of the invention steel and its comparative steel as test materials, and the number and area ratio of carbides having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 , Table 1 shows the calculation results of the ratio of carbides having an aspect ratio of 3 or more among the carbides in steel. In this case, in Table 1, the number of carbides with a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 is underlined when the number of carbides exceeding 120 is observed in 100 μm 2 . Similarly, when the area ratio of carbide having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 exceeds 30%, the area ratio is underlined, and among the carbides, the aspect ratio is 3 In the case where the ratio of the above-described carbide exceeds 70%, the portion of the ratio is underlined and displayed.
上記で調質した角材の中心部から、縦横各１０ｍｍで長さ５５ｍｍのシャルピー衝撃試験片を鍛伸方向（以下、「Ｌ方向」と示す。）より割出し、２ｍｍＵノッチの試験片に加工して、常温でシャルピー衝撃値を測定して、靱性を評価した。一般に熱間鍛造に使用される工具鋼のＪＩＳ鋼種であるＳＫＴ４は、硬さ３８ＨＲＣで５０Ｊ／ｃｍ2の衝撃値が得られる。このことから、シャルピー衝撃値が６０Ｊ／ｃｍ2以上であれば、表２において、良いと評価して○と表示した。シャルピー衝撃値が６０Ｊ／ｃｍ2未満であれば、悪いと評価して×と表示した。 A Charpy impact test piece of 10 mm in length and width and 55 mm in length is indexed from the forging direction (hereinafter referred to as “L direction”) from the center part of the tempered slab, and processed into a 2 mm U notch test piece. Then, the Charpy impact value was measured at room temperature to evaluate toughness. In general, SKT4, which is a JIS steel type of tool steel used for hot forging, can obtain an impact value of 50 J / cm 2 at a hardness of 38 HRC. From this, when the Charpy impact value was 60 J / cm 2 or more, it was evaluated as good in Table 2 and indicated as ◯. If the Charpy impact value was less than 60 J / cm 2, the Charpy impact value was evaluated as bad and indicated as x.
被削性試験の評価は、上記で調質した角材の表面をフライス加工し、刃の欠けや摩耗量（ｍｍ）で評価した。すなわち、フライス加工は、φ１００ｍｍの５枚刃のカッターを用意し、チップはＡＣＰ２００とした。フライス加工は、回転数を２００ｒｐｍ、送りを２５０ｍｍ／ｍｉｎ、切込を１．３ｍｍ、切込幅を６４ｍｍとし、切削油を使用することなく、エアブローのみの条件で行った。切削距離は３０ｍとした。切削後に発生している刃の逃げ面の欠けや摩耗の幅の測定を５枚のチップの全てで行って、一番大きい幅で被削性を評価した。ＪＩＳ鋼種のＳＫＴ４で試験を行った際に、０．４ｍｍの刃の欠けや摩耗量が生じていた。このことから、刃の欠けや摩耗量が０．２ｍｍ以下であれば、表２において、被削性が良いと評価して○と表示した。一方、刃の欠けや摩耗量が０．３ｍｍ以上であれば、同じく表２において、被削性が悪いと評価して×と表示した。 In the evaluation of the machinability test, the surface of the tempered slab was milled and evaluated by chipping of the blade and the amount of wear (mm). That is, for milling, a φ100 mm 5-blade cutter was prepared, and the tip was ACP200. The milling was performed under the conditions of air blow only, without using cutting oil, with a rotational speed of 200 rpm, a feed of 250 mm / min, a cutting depth of 1.3 mm, and a cutting width of 64 mm. The cutting distance was 30 m. The cutting of the flank face of the blade generated after the cutting and the width of wear were measured with all the five chips, and the machinability was evaluated with the largest width. When the test was conducted with SKT4 of JIS steel grade, a 0.4 mm blade chip and an abrasion amount were generated. From this, if the chip of the blade and the amount of wear were 0.2 mm or less, in Table 2, it was evaluated that the machinability was good and indicated as “◯”. On the other hand, if the chip of the blade and the amount of wear were 0.3 mm or more, in Table 2, it was evaluated that the machinability was bad and indicated as x.
表２に見られるように、本願のプリハードン状態の発明鋼のＮｏ．１〜１６のシャルピー衝撃値は、Ｎｏ．１２の６０Ｊ／ｃｍ2以上であるので、いずれもシャルピー衝撃値は良いと評価して○と表示した。さらに、本願のプリハードン状態の発明鋼のＮｏ．１〜１６の工具の刃の欠けや摩耗量は０．２ｍｍ以下であるので、いずれも被削性は良いと評価して○と表示した。 As seen in Table 2, No. of the pre-hardened state steel of the present application. The Charpy impact values of 1 to 16 are No. Since it was 12 60 J / cm 2 or more, the Charpy impact value was evaluated as good and indicated as ◯. Furthermore, No. of the invention steel of the prehardened state of this application. Since the chip and the amount of wear of the tools 1 to 16 were 0.2 mm or less, all were evaluated as good machinability and indicated as “◯”.
一方、プリハードン状態の比較鋼のＮｏ．１７〜２９については以下に順次説明する。 On the other hand, No. of comparative steel in the pre-hardened state. 17 to 29 will be sequentially described below.
比較鋼のＮｏ．１７は、表１に示すように、プリハードン状態の鋼の１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物面積率が３０％より高い３９％であり、表２に示すように、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．４ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 17 is 39% in which the carbide area ratio of the cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 of the prehardened steel is 39% higher than 30%, as shown in Table 1. As described above, since the chipping or wear amount of the tool blade is 0.4 mm, which is larger than 0.2 mm of the present invention, it is evaluated that the machinability is low, and x is displayed.
比較鋼のＮｏ．１８は、表１に示すように、プリハードン状態の鋼の１００μｍ2中に観測される断面積０．０１μｍ2以上の大きさの炭化物の数は１２０個より多い１２２個であり、表２に示すように、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. No. 18, as shown in Table 1, the number of carbides having a cross-sectional area of 0.01 μm 2 or more observed in 100 μm 2 of the prehardened steel is 122 more than 120, and shown in Table 2. As described above, since the chipping and the amount of wear of the tool blade were 0.3 mm larger than 0.2 mm of the present invention, the machinability was evaluated to be low and indicated as x.
比較鋼のＮｏ．１９は、表１に示すように、炭化物のうち縦横比３以上の炭化物が占める割合が７０％より多く、表２に示すように、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. As shown in Table 1, the ratio of carbide with an aspect ratio of 3 or more occupies more than 70% as shown in Table 1. As shown in Table 2, the cutting edge of the tool and the amount of wear are 0.2 mm of the present invention. Since it was larger than 0.3 mm, it was evaluated that the machinability was low, and x was displayed.
比較鋼のＮｏ．２０は、表１に示すように、Ｓｉの含有量が１．０％と本願発明の最低値の０．３％よりも高Ｓｉであるため、靭性が低く、表２に示すように、シャルピー衝撃値が４０Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示した。 No. of comparative steel. No. 20 has a Si content of 1.0% as shown in Table 1 and higher Si than the lowest value of 0.3% of the present invention, so the toughness is low. The impact value was 40 J / cm 2 , which was evaluated to be lower than 60 J / cm 2, the lowest Charpy impact value of the present invention, and indicated as “x”.
比較鋼のＮｏ．２１は、表１に示すように、Ｃの含有量が０．８０％と本願発明の最高値の０．６０％よりも高Ｃであるため、粗大炭化物が増えて炭化物面積率が４８％と本願発明の３０％よりも多く、靭性が低く、表２に示すように、シャルピー衝撃値が３５Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示し、さらに、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が悪いと評価して×と表示した。 No. of comparative steel. No. 21, as shown in Table 1, since the C content is 0.80%, which is higher than the maximum value of 0.60% of the present invention, coarse carbide increases and the carbide area ratio is 48%. More than 30% of the present invention, toughness is low, and as shown in Table 2, the Charpy impact value is 35 J / cm 2 , which is evaluated to be lower than the lowest Charpy impact value of the present invention, 60 J / cm 2. In addition, since the chipping or wear amount of the tool blade was 0.3 mm, which was larger than 0.2 mm of the present invention, it was evaluated that the machinability was bad and indicated as x.
比較鋼のＮｏ．２２は、表１に示すように、Ｍｎの含有量が１．７％と本願発明の最高値の１．２％よりも高Ｍｎであるため、靭性が低く、表２に示すように、シャルピー衝撃値が４２Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示した。 No. of comparative steel. No. 22 has a Mn content of 1.7% as shown in Table 1 and a Mn higher than the maximum value of 1.2% of the present invention, so the toughness is low. As shown in Table 2, Charpy impact value is 42J / cm 2, was designated × evaluate lower than 60 J / cm 2 of the lowest value of the Charpy impact value of the present invention.
比較鋼のＮｏ．２３は、表１に示すように、Ｎｉの含有量が０．４％と本願発明の最低値の０．７％よりも低Ｎｉであるため、靭性が低く、表２に示すように、シャルピー衝撃値が５５Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示した。 No. of comparative steel. 23, as shown in Table 1, since the Ni content is 0.4%, which is lower than 0.7% of the lowest value of the present invention, the toughness is low. As shown in Table 2, Charpy is used. impact value is 55 J / cm 2, was designated × evaluate lower than 60 J / cm 2 of the lowest value of the Charpy impact value of the present invention.
比較鋼のＮｏ．２４は、表１に示すように、Ｎｉの含有量が２．０％と本願発明の最高値の１．６％よりも高Ｎｉであるため、不均一な合金成分となって、表２に示すように、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 24, as shown in Table 1, since the Ni content is 2.0%, which is higher than 1.6% of the maximum value of the present invention, it becomes a non-uniform alloy component. As shown, since the chipping and wear amount of the tool blade is 0.3 mm, which is larger than 0.2 mm of the present invention, the machinability is evaluated to be low and indicated as x.
比較鋼のＮｏ．２５は、表１に示すように、Ｃｒの含有量が４．０％と、本願発明の最高値の２．２％よりも高Ｃｒであるため、粗大炭化物が増えて炭化物面積率が３６％と本願発明の３０％よりも多くなり、靭性が低く、表２に示すように、シャルピー衝撃値が４４Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示し、さらに、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 25, as shown in Table 1, since the Cr content is 4.0%, which is higher than the maximum value of 2.2% of the present invention, the coarse carbide increases and the carbide area ratio is 36%. and the more than 30 percent of the present invention, low toughness, as shown in Table 2, a Charpy impact value 44J / cm 2, less than 60 J / cm 2 of the lowest value of the Charpy impact value of the present invention Was evaluated, and x was displayed. Furthermore, since the chipping or wear amount of the tool blade was 0.3 mm larger than 0.2 mm of the present invention, it was evaluated that the machinability was low, and x was displayed.
比較鋼のＮｏ．２６は、表１に示すように、Ｍｏの含有量が２．５％で本願発明の最高値の１．８％よりも高Ｍｏのため、粗大炭化物が増えて炭化物面積率が３８％と本願発明の３０％よりも多くなり、靭性が低く、表２に示すように、シャルピー衝撃値が３４Ｊ／ｃｍ2であり、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示し、さらに、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．４ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 26, as shown in Table 1, because the Mo content is 2.5% and Mo is higher than the maximum value of 1.8% of the present invention, coarse carbide increases and the carbide area ratio is 38%. becomes greater than 30% of the invention, low toughness, as shown in Table 2, the Charpy impact value was 34 J / cm 2, minimum value lower evaluation than 60 J / cm 2 of the Charpy impact value of the present invention In addition, since the chipping and wear amount of the tool blade is 0.4 mm, which is larger than 0.2 mm of the present invention, the machinability is evaluated as low and displayed as x.
比較鋼のＮｏ．２７は、表１に示すように、Ｖの含有量が１．０％と本願発明の最高値の０．３％よりも高Ｖのため、粗大炭化物が増えて炭化物面積率が３５％と本願発明の３０％よりも多くなり、靭性が低く、表２に示すように、シャルピー衝撃値が３７Ｊ／ｃｍ2であるので、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示し、さらに、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 27, as shown in Table 1, since the V content is 1.0%, which is higher than the maximum value of 0.3% of the present invention, coarse carbide increases and the carbide area ratio is 35%. More than 30% of the invention, toughness is low, and as shown in Table 2, the Charpy impact value is 37 J / cm 2 , so if it is lower than the lowest value of the Charpy impact value of the present invention, 60 J / cm 2 The evaluation was indicated as x, and further, since the chipping and wear amount of the tool were 0.3 mm larger than 0.2 mm of the present invention, the machinability was evaluated as low and indicated as x.
比較鋼のＮｏ．２８は、表１に示すように、Ｓｉが未添加であるため、表２に示すように、工具の刃の欠けや摩耗量が本願発明の０．２ｍｍよりも大きい０．３ｍｍであるので、被削性が低いと評価して×と表示した。 No. of comparative steel. 28, as shown in Table 1, since Si is not added, as shown in Table 2, since the chipping and wear amount of the tool blade is 0.3 mm larger than 0.2 mm of the present invention, Evaluation was made that the machinability was low, and x was displayed.
比較鋼のＮｏ．２９は、表１に示すように、Ｖが未添加であり、さらに表２に示すように、シャルピー衝撃値が４１Ｊ／ｃｍ2であるので、本願発明のシャルピー衝撃値の最低値の６０Ｊ／ｃｍ2よりも低いと評価して×と表示した。 No. of comparative steel. No. 29 has no added V as shown in Table 1, and further has a Charpy impact value of 41 J / cm 2 as shown in Table 2. Therefore, the lowest Charpy impact value of the present invention is 60 J / cm 2. It evaluated that it was lower than 2, and displayed x.
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| CN112853201A (en) * | 2019-11-28 | 2021-05-28 | 武汉昆伦特钢装备科技开发有限公司 | Ultrahigh-strength high-hardness wear-resistant impact-resistant corrosion-resistant alloy steel and manufacturing process thereof |
| WO2023008413A1 (en) * | 2021-07-27 | 2023-02-02 | 山陽特殊製鋼株式会社 | Hot work tool steel having excellent high-temperature strength and toughness |
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Cited By (7)
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| WO2021095831A1 (en) * | 2019-11-14 | 2021-05-20 | 山陽特殊製鋼株式会社 | Hot-work tool steel having exceptional high-temperature strength and toughness |
| JP2021080492A (en) * | 2019-11-14 | 2021-05-27 | 山陽特殊製鋼株式会社 | Hot work tool steel excellent in high-temperature strength and toughness |
| JP7149250B2 (en) | 2019-11-14 | 2022-10-06 | 山陽特殊製鋼株式会社 | Hot work tool steel with excellent high temperature strength and toughness |
| CN112853201A (en) * | 2019-11-28 | 2021-05-28 | 武汉昆伦特钢装备科技开发有限公司 | Ultrahigh-strength high-hardness wear-resistant impact-resistant corrosion-resistant alloy steel and manufacturing process thereof |
| WO2023008413A1 (en) * | 2021-07-27 | 2023-02-02 | 山陽特殊製鋼株式会社 | Hot work tool steel having excellent high-temperature strength and toughness |
| JP7220750B1 (en) | 2021-07-27 | 2023-02-10 | 山陽特殊製鋼株式会社 | Hot work tool steel with excellent high-temperature strength and toughness |
| JP2023024893A (en) * | 2021-07-27 | 2023-02-20 | 山陽特殊製鋼株式会社 | Hot work tool steel having excellent high-temperature strength and toughness |
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