JP2012219317A - Iron-based material and method for producing the same - Google Patents
Iron-based material and method for producing the same Download PDFInfo
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Abstract
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本発明は、産業機械や自動車等の機械部品に好適に用いられる機械構造用鉄系材料に関し、特に一部あるいは全体に硬質相を具え、優れた強度を有する鉄系材料に関する。 The present invention relates to an iron-based material for machine structure that is suitably used for machine parts such as industrial machines and automobiles, and particularly relates to an iron-based material having a hard phase partially or entirely and having excellent strength.
産業機械や自動車等の機械部品は一般的に、鋼材を切削または塑性加工、あるいはこれらの併用により所定の形状に加工した後、焼入れ焼戻し処理を施すことにより所望の特性を確保する方法により製造される。このような機械部品に用いられる鋼材は、機械部品として必要な強度を満足するために、通常0.4〜0.6mass％程度のＣおよびMn、Cr、Mo等の合金元素を含有する。しかしながら、鋼材中に含有されるCおよび合金元素は鋼材の硬度上昇に寄与するため、切削、鍛造などの冷間加工を著しく困難にする。また、Ｃ含有鋼の焼入れ焼戻しにより得られる、焼戻しマルテンサイトは、常温で高い強度を有するものの、150℃程度を超える高温に長時間曝されると強度が低下するため、使用環境がこのような温度に達する用途には必ずしも適合しない。 Machine parts such as industrial machines and automobiles are generally manufactured by a method of securing desired characteristics by applying a quenching and tempering treatment after processing a steel material into a predetermined shape by cutting or plastic working or a combination thereof. The Steel materials used for such machine parts usually contain about 0.4 to 0.6 mass% of alloy elements such as C and Mn, Cr, Mo, etc. in order to satisfy the required strength as machine parts. However, since C and alloy elements contained in the steel contribute to an increase in the hardness of the steel, cold working such as cutting and forging becomes extremely difficult. In addition, tempered martensite obtained by quenching and tempering C-containing steel has high strength at room temperature, but the strength decreases when exposed to high temperatures exceeding about 150 ° C. for a long time. It is not always suitable for applications that reach temperatures.
機械部品を所定の形状に加工する際の冷間加工性と機械部品に要求される強度という、相反する特性を共に満足させる方法として、低Ｃ鋼素材に冷間加工を施して所望の形状とした後、浸炭焼入れする方法が従前行われている。しかしながら、浸炭にてＣ濃度を上昇させるといえども、やはり焼戻しマルテンサイトの強度を利用する上記方法では、依然として高温環境下での強度低下に関する問題は未解決のままであった。 As a method of satisfying both of the conflicting properties of cold workability when machining a machine part into a predetermined shape and strength required for the machine part, a low C steel material is cold worked to obtain a desired shape. After that, carburizing and quenching has been performed in the past. However, even if the C concentration is increased by carburizing, the above-described method that utilizes the strength of tempered martensite still remains a problem regarding strength reduction under a high temperature environment.
また、上記浸炭焼入れに代えて、窒化処理により表面硬化層を形成する方法も知られている。窒化処理では、処理温度が比較的低温である上、焼入れ工程を必要としないため、発生する熱処理歪も小さい。そのため、寸法精度が要求される機械部品の強度を確保する方法としては極めて有効である。 A method of forming a hardened surface layer by nitriding treatment instead of the carburizing and quenching is also known. In the nitriding treatment, the treatment temperature is relatively low and a quenching step is not required, so that the generated heat treatment strain is small. Therefore, it is extremely effective as a method for ensuring the strength of mechanical parts that require dimensional accuracy.
しかしながら、多量の合金元素を添加しない鉄系材料に、従前の窒化処理を施した機械部品では、表面硬化層の硬度が不十分であった。例えば、特許文献１〜４には、鋼板を所望の形状に加工した後、窒化処理を施して表面硬化層を形成した機械部品について開示されているが、何れの文献に開示された機械部品においても、その表面硬化層の硬度は最大でもHV400程度である。特許文献５には硬度がHV803の表面硬化層を得る製法が記載されているが、硬化層の厚さが３〜１５μｍと薄く、面圧の高い部品への適用には課題があった。 However, the hardness of the surface hardened layer is insufficient in a machine part obtained by performing a conventional nitriding treatment on an iron-based material to which a large amount of alloy elements are not added. For example, Patent Documents 1 to 4 disclose a machine part in which a steel sheet is processed into a desired shape and then subjected to nitriding treatment to form a hardened surface layer. However, the hardness of the hardened surface layer is at most about HV400. Patent Document 5 describes a production method for obtaining a surface hardened layer having a hardness of HV803, but there is a problem in application to parts having a high surface pressure, with the hardened layer being as thin as 3 to 15 μm.
一方で、鋼表層部にHV700を超える高い硬度を付与する為に、窒化時にAlやTi等の硬質窒化物を形成させる方法が従前行われているが、鋼中にAlやTi等の窒化物形成元素を多量に含有させる必要があり、鋼素材の製造コストを上昇させる等の問題を残していた。 On the other hand, in order to give the steel surface layer a high hardness exceeding HV700, a method of forming hard nitrides such as Al and Ti at the time of nitriding has been performed in the past, but nitrides such as Al and Ti in steel It was necessary to contain a large amount of forming elements, which left problems such as an increase in the manufacturing cost of steel materials.
本発明は、上記現状を鑑みなされたものであり、鋼中に高濃度のＣおよび合金元素を必ずしも含有させることなく、冷間加工性と最終部品強度を兼備し、更には高温使用環境における強度特性にも優れた機械部品が得られる機械構造用鉄系材料の提供を目的とする。 The present invention has been made in view of the above-mentioned present situation, and does not necessarily contain a high concentration of C and alloy elements in steel, and has both cold workability and final part strength, and further, strength in a high temperature use environment. The object is to provide an iron-based material for machine structure that can provide machine parts with excellent characteristics.
上記目的を達成すべく、本発明者らは冷間加工性に加え、最終的に高強度を有する機械部品が製造可能である、機械構造用材料を得るための方途について鋭意検討を進めた。その結果、特定範囲量のＣを含有する鉄系材料に窒化処理を施すことにより、鉄系材料の少なくとも表層部にオーステナイト形成元素であるＮを高濃度に含有させ、Ｎ高濃度領域をオーステナイト組織とし、窒化処理後に急冷して窒化処理時に形成させた上記オーステナイト組織を500℃以下の温度域まで残留させ、これを100〜500℃の温度域に加熱保持して、上記オーステナイト組織をα（フェライト）中に微細なγ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ）が分散した組織に変化させることにより、HV700以上の高い硬質相が得られ、なおかつ高温に長時間曝された後も高い硬度を維持し得ることを知見した。さらに、窒化による硬質層（以下、窒化層とも言う）の性状についても、窒化層中に空隙が少なく、より強靭な窒化層が得られることが明らかとなった。 In order to achieve the above object, the present inventors have intensively studied a method for obtaining a material for machine structure that can finally produce a machine part having high strength in addition to cold workability. As a result, by nitriding an iron-based material containing a specific amount of C, at least the surface layer portion of the iron-based material contains N as an austenite-forming element at a high concentration, and the N high-concentration region has an austenite structure. The austenite structure formed at the time of nitriding by rapid cooling after nitriding is left to a temperature range of 500 ° C. or lower, and this is heated and held in a temperature range of 100 to 500 ° C. ) Is changed to a structure in which fine γ ′ (Fe 4 N and / or Fe 4 (C, N) is dispersed, and a hard phase higher than HV700 is obtained and after being exposed to a high temperature for a long time. It was also found that the hardness of the hard layer by nitriding (hereinafter also referred to as the nitrided layer) is less cavities in the nitrided layer and a tougher nitrided layer can be obtained. It became one.
本発明は上記知見に基づきなされたものであり、その要旨構成は次のとおりである。
（１）Ｃ：0.1mass％以上1.5mass％以下を含有し、残部Feおよび不可避的不純物からなる材料の表層または全体を窒化して得た硬質相を有し、該硬質相は、Ｎ：（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下を含有し、かつ硬さがHV700以上であることを特徴とする鉄系材料。
ただし、［Ｃ］は材料中のＣ含有量（at％）
This invention is made | formed based on the said knowledge, The summary structure is as follows.
(1) C: has a hard phase obtained by nitriding the surface layer or the whole of the material containing 0.1 mass% to 1.5 mass% and the balance Fe and inevitable impurities, and the hard phase is N :( An iron-based material containing 8- [C]) at% or more and (11- [C]) at% or less and having a hardness of HV700 or more.
However, [C] is the C content in the material (at%)
（２）上記（１）に記載の鉄系材料が、更に、
Cr：0.05 mass％以上2.0 mass％以下、
Al：0.005 mass％以上0.5 mass％以下、
Ti：0.0005 mass％以上0.5 mass％以下、
Nb：0.005 mass％以上0.1 mass％以下、
Ｖ：0.02 mass％以上1.0 mass％以下、
Mo：0.02 mass％以上1.0 mass％以下、
Mn：0.02 mass％以上2.0 mass％以下、
Si：0.02 mass％以上2.0 mass％以下、
Ni：0.02 mass％以上2.0 mass％以下、
Cu：0.02 mass％以上2.0 mass％以下および
Co：0.02 mass％以上2.0 mass％以下
の中から選択される少なくとも一種以上を含有することを特徴とする鉄系材料。
(2) The iron-based material described in (1) above is further
Cr: 0.05 mass% or more and 2.0 mass% or less,
Al: 0.005 mass% or more and 0.5 mass% or less,
Ti: 0.0005 mass% or more and 0.5 mass% or less,
Nb: 0.005 mass% or more and 0.1 mass% or less,
V: 0.02 mass% or more and 1.0 mass% or less,
Mo: 0.02 mass% or more and 1.0 mass% or less,
Mn: 0.02 mass% or more and 2.0 mass% or less,
Si: 0.02 mass% or more and 2.0 mass% or less,
Ni: 0.02 mass% or more and 2.0 mass% or less,
Cu: 0.02 mass% to 2.0 mass%
Co: An iron-based material containing at least one selected from 0.02 mass% to 2.0 mass%.
（３）Ｃ：0.1mass％以上1.5mass％以下を含有し、残部Feおよび不可避的不純物からなる材料に590℃以上の温度で窒化処理を施して該材料の一部または全体にＮ：（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下を含有させた後、500℃以下の温度域まで１℃／ｓ以上の速度で冷却し、その後100〜500℃の温度域に保持してHV700以上の硬質相を形成することを特徴とする鉄系材料の製造方法。
ただし、［Ｃ］は材料中のＣ含有量（at％）
(3) C: 0.1 mass% or more and 1.5 mass% or less, and a material comprising the balance Fe and inevitable impurities is subjected to nitriding treatment at a temperature of 590 ° C. or more, and a part or all of the material is N: (8 -After containing [C]) at% or more and (11- [C]) at% or less, it is cooled to a temperature range of 500 ° C or less at a rate of 1 ° C / s or more, and then a temperature range of 100 to 500 ° C. And producing a hard phase of HV700 or higher by holding the steel.
However, [C] is the C content in the material (at%)
（４）上記（３）に記載の鉄系材料が、更に、
Cr：0.05 mass％以上2.0 mass％以下、
Al：0.005 mass％以上0.5 mass％以下、
Ti：0.0005 mass％以上0.5 mass％以下、
Nb：0.005 mass％以上0.1 mass％以下、
Ｖ：0.02 mass％以上1.0 mass％以下、
Mo：0.02 mass％以上1.0 mass％以下、
Mn：0.02 mass％以上2.0 mass％以下、
Si：0.02 mass％以上2.0 mass％以下、
Ni：0.02 mass％以上2.0 mass％以下、
Cu：0.02 mass％以上2.0 mass％以下および
Co：0.02 mass％以上2.0 mass％以下
の中から選択される少なくとも一種以上を含有することを特徴とする鉄系材料の製造方法。
(4) The iron-based material described in (3) above is further
Cr: 0.05 mass% or more and 2.0 mass% or less,
Al: 0.005 mass% or more and 0.5 mass% or less,
Ti: 0.0005 mass% or more and 0.5 mass% or less,
Nb: 0.005 mass% or more and 0.1 mass% or less,
V: 0.02 mass% or more and 1.0 mass% or less,
Mo: 0.02 mass% or more and 1.0 mass% or less,
Mn: 0.02 mass% or more and 2.0 mass% or less,
Si: 0.02 mass% or more and 2.0 mass% or less,
Ni: 0.02 mass% or more and 2.0 mass% or less,
Cu: 0.02 mass% to 2.0 mass%
Co: A method for producing an iron-based material comprising at least one selected from 0.02 mass% to 2.0 mass%.
産業機械や自動車等の機械部品に好適に用いられる機械構造用鉄系材料であって、優れた冷間加工性を有し、HV700以上という従来に無い硬質相を有する鉄系材料が得られる。 An iron-based material for machine structure that is suitably used for machine parts such as industrial machines and automobiles, and has an excellent cold workability and an iron-based material having an unprecedented hard phase of HV700 or higher.
以下、本発明について具体的に説明する。
（組成の限定理由）
窒化による硬質相中のＮ含有量：（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下
Ｎは、本発明の硬質相を形成する上で必須の元素である。先述の通り、本発明の鉄系材料においては、窒化処理による窒化層が形成され、この窒化層について、α（フェライト）中に微細なγ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））が分散した組織とすることにより硬質相を形成する。そのため、本発明の鉄系材料においては、硬質相を形成すべき部分に、γ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））の構成元素であるＮを含有させる必要がある。硬質相のＮ含有量が（８−［Ｃ］）at％未満では、Ｍｓ点が室温よりも高く、室温でオーステナイト組織を得ることが出来ず、また窒化冷却後の保持時に十分な量のα−Fe中に微細γ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））が分散した組織が得られないため、HV700以上の硬化層を形成することができない。一方、Ｎ含有量が（１１−［Ｃ］）at％を超えると、窒化を目的とした加熱保持中の組織がオーステナイト単相とならず、材料中に過剰なε窒化物を形成する。このε窒化物はその後の硬化熱処理後も残留して、硬化熱処理後のミクロ組織中に多量の空孔を形成し、最終部品の強度および靭性を著しく劣化させる。したがって、Ｎ含有量は（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下に規定する。なお、［Ｃ］は材料中のＣ含有量（at%）であり、後述する鉄系材料中のＣ量0.1mass％〜1.5mass％をat％に換算した値（0.46〜6.6at％）の範囲内の値となる。
Hereinafter, the present invention will be specifically described.
(Reason for limitation of composition)
N content in hard phase by nitriding: (8- [C]) at% or more and (11- [C]) at% or less N is an essential element for forming the hard phase of the present invention. As described above, in the iron-based material of the present invention, a nitrided layer is formed by nitriding treatment, and this nitrided layer has a fine γ ′ (Fe 4 N and / or Fe 4 (C, N) in α (ferrite). )) Is dispersed to form a hard phase. Therefore, in the iron-based material of the present invention, it is necessary to contain N which is a constituent element of γ ′ (Fe 4 N and / or Fe 4 (C, N)) in a portion where a hard phase is to be formed. When the N content of the hard phase is less than (8- [C]) at%, the Ms point is higher than room temperature, an austenite structure cannot be obtained at room temperature, and a sufficient amount of α is maintained during holding after nitriding cooling. Since a structure in which fine γ ′ (Fe 4 N and / or Fe 4 (C, N)) is dispersed in Fe cannot be obtained, a hardened layer of HV700 or higher cannot be formed. On the other hand, when the N content exceeds (11- [C]) at%, the structure being heated and held for nitriding does not become an austenite single phase, and excessive ε nitride is formed in the material. This ε-nitride remains after the subsequent hardening heat treatment, and a large amount of voids are formed in the microstructure after the hardening heat treatment, so that the strength and toughness of the final part are significantly deteriorated. Therefore, the N content is defined as (8- [C]) at% or more and (11- [C]) at% or less. In addition, [C] is the C content (at%) in the material, and is a value (0.46 to 6.6 at%) obtained by converting the C content in the iron-based material described later from 0.1 mass% to 1.5 mass% into at%. The value is within the range.
鉄系材料中のＣ含有量：0.1mass％以上1.5mass％以下
Ｃは、オーステナイト安定化元素であり、材料にＣを添加した場合、窒化処理によりＮを含有させる際に、Ｃの含有量（at％）分だけ低いＮ量でオーステナイトが形成するようになる。このオーステナイト組織を急冷して、オーステナイト組織を500℃以下の温度域まで残留させ、これを100〜500℃の温度域に加熱保持すると、ＣはＮとともに鉄化合物γ´（Fe4（Ｃ，Ｎ））を形成し、α（フェライト）中に硬質のγ´（Fe4（Ｃ，Ｎ））が分散した組織が得られる。
C content in iron-based material: 0.1 mass% or more and 1.5 mass% or less C is an austenite stabilizing element, and when C is added to the material, the content of C ( Austenite is formed with an amount of N lower by at%). When this austenite structure is rapidly cooled to leave the austenite structure to a temperature range of 500 ° C. or less, and this is heated and held in a temperature range of 100 to 500 ° C., C and iron compound γ ′ (Fe 4 (C, N )) To form a structure in which hard γ ′ (Fe 4 (C, N)) is dispersed in α (ferrite).
また、Ｃを添加した場合、Ｃが添加されていない場合に比較して、窒化処理の際により低いＮ量でオーステナイトが形成するようになる。すなわち、Ｃが添加されていない場合には、オーステナイトを形成させるためには８〜１１at％の窒素が必要となるが、Ｃを上記の範囲で添加している場合は、（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下の範囲でオーステナイトが形成するので、Ｃの添加量分だけ窒化により導入するＮの量を低く抑えることができる。そのため、窒化層でのＮ２ガス分子の生成を抑制でき、これにより、窒化層中の空隙率が低下し、より強靭な窒化層が得られる。具体的には、硬質相における空隙率は１０％以下とすることができる。空隙率が１０％を超える場合、硬質相が脆化するので、硬質相の剥離が起こりやすくなり最終部品の強度および靭性が劣化するが、本発明の鉄系材料では、剥離が生じにくいため、窒化層を形成させた最終部品の強度および靭性を確保することができる。 Further, when C is added, austenite is formed with a lower amount of N during nitriding as compared with the case where C is not added. That is, when C is not added, 8 to 11 at% nitrogen is required to form austenite, but when C is added in the above range, (8- [C] ) Since austenite is formed in the range of at% or more and (11- [C]) at% or less, the amount of N introduced by nitriding can be kept low by the amount of addition of C. Therefore, the generation of N 2 gas molecules in the nitride layer can be suppressed, whereby the porosity in the nitride layer is reduced and a tougher nitride layer can be obtained. Specifically, the porosity in the hard phase can be 10% or less. When the porosity exceeds 10%, the hard phase becomes brittle, so that the hard phase is easily peeled off and the strength and toughness of the final part is deteriorated. The strength and toughness of the final part on which the nitride layer is formed can be ensured.
また、Ｃは特に本発明においてHV700以上の硬質相を鉄系材料の表層のみに形成する場合、鉄系材料の表層部以外の強度を確保する上で有効な元素でもある。 Further, C is an element effective in securing strength other than the surface layer portion of the iron-based material, particularly when the hard phase of HV700 or more is formed only on the surface layer of the iron-based material in the present invention.
このため、本発明においては鉄系材料中のＣは0.1mass％以上添加する。0.1mass％未満の場合、空隙率が著しく増加し、最終部品の強度および靭性が劣化する。一方、1.5mass％を超えると、機械部品の寸法精度や冷間加工性に悪影響を及ぼすため、1.5mass％以下とする。より好ましいＣ含有量は、0.16mass％以上1.1mass％未満である。 For this reason, in the present invention, C in the iron-based material is added by 0.1 mass% or more. When it is less than 0.1 mass%, the porosity is remarkably increased, and the strength and toughness of the final part are deteriorated. On the other hand, if it exceeds 1.5 mass%, the dimensional accuracy and cold workability of machine parts will be adversely affected. More preferable C content is 0.16 mass% or more and less than 1.1 mass%.
さらに、本発明においては必要に応じて、Cr：0.05 mass％以上2.0 mass％以下、Al：0.005 mass％以上0.5 mass％以下、Ti：0.0005 mass％以上0.5 mass％以下、Nb：0.005 mass％以上0.1 mass％以下、Ｖ：0.02 mass％以上1.0 mass％以下、Mo：0.02 mass％以上1.0 mass％以下、Mn：0.02 mass％以上2.0 mass％以下、Si：0.02 mass％以上2.0 mass％以下、Ni：0.02 mass％以上2.0 mass％以下、Cu：0.02 mass％以上2.0 mass％以下およびCo：0.02 mass％以上2.0 mass％以下の中から選択される少なくとも１種以上を含有することができる。 Furthermore, in the present invention, Cr: 0.05 mass% to 2.0 mass%, Al: 0.005 mass% to 0.5 mass%, Ti: 0.0005 mass% to 0.5 mass%, Nb: 0.005 mass% or more as necessary 0.1 mass% or less, V: 0.02 mass% to 1.0 mass%, Mo: 0.02 mass% to 1.0 mass%, Mn: 0.02 mass% to 2.0 mass%, Si: 0.02 mass% to 2.0 mass%, Ni : 0.02 mass% or more and 2.0 mass% or less, Cu: 0.02 mass% or more and 2.0 mass% or less, and Co: 0.02 mass% or more and 2.0 mass% or less can be contained.
Cr、Al、Ti、Nb、ＶおよびMoは、いずれも鉄系材料中の窒素と結合して硬質な窒化物を形成し、主に表層において耐摩耗性を向上する作用を有するため、必要に応じて含有させる。含有量が各々の下限値に満たない場合にはその効果が不十分である。一方、各々の上限値を超えて含有してもその効果が飽和するとともに、過剰な窒化物が析出して体積変化をもたらし寸法精度に悪影響を及ぼす。また、体積変化が生じることにより空隙を含むミクロ組織が形成されるため、鉄系材料の強度が劣化する。 Cr, Al, Ti, Nb, V, and Mo all combine with nitrogen in the iron-based material to form a hard nitride, which has the effect of improving wear resistance mainly in the surface layer, so it is necessary Depending on the content. When the content is less than each lower limit, the effect is insufficient. On the other hand, even if the content exceeds each upper limit value, the effect is saturated and excessive nitride precipitates to cause a volume change, which adversely affects the dimensional accuracy. Moreover, since the microstructure containing voids is formed due to the volume change, the strength of the iron-based material is deteriorated.
Mn、Si、Ni、CuおよびCoは、本発明の鉄系材料を製造する上で必要となる低温でのオーステナイト組織の形成に効果的に作用するため、必要に応じて含有する。含有量が各々の下限値に満たない場合にはその効果が不十分であり、一方、各々の上限値を超えて含有すると最終的な所望の組織、すなわち、α（フェライト）中に微細なγ´（Fe4Ｎ）が分散した組織の形成に悪影響を及ぼす。 Mn, Si, Ni, Cu and Co are contained as necessary because they effectively act to form an austenite structure at a low temperature necessary for producing the iron-based material of the present invention. When the content is less than each lower limit, the effect is insufficient. On the other hand, when the content exceeds each upper limit, the final desired structure, that is, fine γ in α (ferrite) ′ (Fe 4 N) adversely affects the formation of a dispersed structure.
本発明における硬質相は、硬さがHV700以上であるものとする。HV700以上の硬質相は、構成ミクロ組織がα−Fe（フェライト）とγ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）からなるか、あるいは、これに上述した合金元素の窒化物が析出したものであり、かつ、γ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）が微細に分散した形態となることで達成できる。γ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）は、面積率で25〜60％であることが必要である。すなわち、γ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）は面積率が25％に満たないと、HV700以上の硬さの確保が困難となる。また、γ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）は面積率が60％超で生成させようとすると、ε（Fe3Ｎ）の析出回避が困難となり、この場合もHV700以上の硬さの確保が困難になる。 The hard phase in the present invention has a hardness of HV700 or more. The hard phase of HV700 or higher is composed of α-Fe (ferrite) and γ ′ (Fe 4 N and / or Fe 4 (C, N)) or a nitride of the above-described alloy element. And γ ′ (Fe 4 N and / or Fe 4 (C, N)) is finely dispersed. γ ′ (Fe 4 N and / or Fe 4 (C, N)) needs to be 25 to 60% in terms of area ratio. That is, if γ ′ (Fe 4 N and / or Fe 4 (C, N)) has an area ratio of less than 25%, it is difficult to secure a hardness of HV700 or higher. In addition, if γ ′ (Fe 4 N and / or Fe 4 (C, N)) is generated with an area ratio exceeding 60%, it is difficult to avoid precipitation of ε (Fe 3 N). It becomes difficult to ensure the above hardness.
また、生成したγ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）は、サイズが300nm以下のγ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）が分散した形態となっている必要がある。γ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）のサイズがこれより大きい場合にも、HV700以上の硬さの確保が困難になる。なお、析出物観察は後述する実施例に示したように透過電子顕微鏡（ＴＥＭ）にて行い、これで観察可能な１ｎｍ以上の析出物について観察して、300nm以下のγ´（Fe4Ｎおよび／またはFe4(Ｃ，Ｎ)）の分散の有無が確認できる。
また、本発明において、硬さHVは、荷重25ｇf（0.245Ｎ）、荷重保持時間15ｓの条件にて測定したビッカース硬さを意味する。
Further, the generated gamma prime (Fe 4 N and / or Fe 4 (C, N)) is a form gamma prime size is below 300 nm (Fe 4 N and / or Fe 4 of (C, N)) is dispersed It needs to be. Even when the size of γ ′ (Fe 4 N and / or Fe 4 (C, N)) is larger than this, it is difficult to ensure the hardness of HV700 or more. The precipitates were observed with a transmission electron microscope (TEM) as shown in the examples described later, and observable for precipitates of 1 nm or more that can be observed with this, and γ ′ (Fe 4 N and 300 nm or less). / Or Fe 4 (C, N)) can be confirmed.
In the present invention, the hardness HV means Vickers hardness measured under conditions of a load of 25 gf (0.245 N) and a load holding time of 15 s.
次に、本発明の鉄系材料の製造方法について説明する。
本発明の鉄系材料は、所定の組成を有する鉄系素材に、590℃以上の温度で窒化処理を施して該鉄系素材の一部または全体にＮ：（８−［Ｃ］）at％以上（11−［Ｃ］）at％以下を含有させた後、500℃以下の温度域まで1℃/s以上の速度で冷却し、その後、100〜500℃の温度域に加熱保持してHV700以上の硬質相を形成する方法により好適に製造することができる。
Next, the manufacturing method of the iron-type material of this invention is demonstrated.
The iron-based material of the present invention is obtained by subjecting an iron-based material having a predetermined composition to nitriding treatment at a temperature of 590 ° C. or higher, and N: (8- [C]) at% in part or all of the iron-based material After containing (11- [C]) at% or less, it is cooled to a temperature range of 500 ° C. or less at a rate of 1 ° C./s or more, and then heated and maintained in a temperature range of 100 to 500 ° C. It can manufacture suitably by the method of forming the above hard phase.
（窒化処理条件）
窒化処理温度を590℃以上とすることにより、鉄系素材中への十分な窒素の拡散速度を
得ることが可能になるとともに、窒化処理中に安定なオーステナイト相を得ることができ、オーステナイト相厚さの確保が可能となる。これによりその後の硬質相形成処理で硬化層厚さの確保が可能となる。ただし、窒化温度を極端に高くすると、窒化処理中の窒化進行速度の制御が困難になるとともに、窒化処理中に組織のオーステナイト粒の粗大化を引き起こし、窒化処理後の鉄系材料の延性および靱性に悪影響を及ぼす。そのため、窒化処理温度は1000℃以下にすることが好ましい。
(Nitriding conditions)
By setting the nitriding temperature to 590 ° C or higher, it becomes possible to obtain a sufficient diffusion rate of nitrogen into the iron-based material, and a stable austenite phase can be obtained during the nitriding treatment, and the austenite phase thickness It is possible to ensure the thickness. This makes it possible to ensure the thickness of the hardened layer in the subsequent hard phase forming process. However, if the nitriding temperature is extremely high, it becomes difficult to control the nitriding progress rate during the nitriding treatment, and the austenite grains of the structure become coarse during the nitriding treatment, and the ductility and toughness of the iron-based material after the nitriding treatment Adversely affect. Therefore, the nitriding temperature is preferably 1000 ° C. or lower.
なお、上記窒化処理としては、ガス窒化法、ガス軟窒化法、プラズマ窒化法、塩浴窒化法等、公知の方法を適用することができるが、本発明の鉄系材料を製造する上では、特に、窒化ポテンシャルの制御が比較的容易でかつ処理コストが低廉な、ガス窒化法を適用することが好ましい。また、鉄系材料中の窒化濃度制御の観点から、窒化処理時間は60〜1000minとすることが好ましい。 As the nitriding treatment, known methods such as a gas nitriding method, a gas soft nitriding method, a plasma nitriding method, a salt bath nitriding method, etc. can be applied, but in producing the iron-based material of the present invention, In particular, it is preferable to apply a gas nitriding method, in which the control of the nitriding potential is relatively easy and the processing cost is low. Further, from the viewpoint of controlling the nitriding concentration in the iron-based material, the nitriding treatment time is preferably 60 to 1000 min.
（冷却条件）
上記条件で窒化処理を施した鉄系材料の少なくとも表層部は、Ｎ：（８−［Ｃ］）at％以上（１１−［Ｃ］）at％以下を含有するオーステナイト組織が形成される。本発明においては、これを１℃/s以上の冷却速度で500℃以下の温度まで冷却することにより、上記オーステナイト組織を室温近傍まで残留させる。冷却速度が１℃/s未満である場合には、冷却中にフェライト相が形成してしまい、冷却終了時点におけるオーステナイト含有量が減少するため、その後の熱処理により所望の硬度を有する硬質相が得られない。なお、冷却速度の上限値は特に限定しないが、簡易な冷却方法で達成するために、50℃/s以下とすることが好ましい。
(Cooling conditions)
An austenitic structure containing N: (8- [C]) at% or more and (11- [C]) at% or less is formed in at least the surface layer portion of the iron-based material subjected to nitriding treatment under the above conditions. In the present invention, the austenite structure is left to near room temperature by cooling it to a temperature of 500 ° C. or lower at a cooling rate of 1 ° C./s or higher. When the cooling rate is less than 1 ° C./s, a ferrite phase is formed during cooling, and the austenite content at the end of cooling is reduced, so that a hard phase having a desired hardness is obtained by subsequent heat treatment. I can't. The upper limit value of the cooling rate is not particularly limited, but is preferably 50 ° C./s or less in order to achieve a simple cooling method.
冷却停止温度が500℃超である場合には、冷却停止後の放冷時に組織中に粗大なフェライト相が形成されてしまい、冷却後のオーステナイト含有量が減少する。また、冷却速度が１℃/s以上の冷却は、−10℃以上の温度で停止することが望ましい。すなわち、冷却を−10℃未満の低温域まで行うと、オーステナイトの少なくとも一部にマルテンサイト変態が生じる。マルテンサイト自体は、硬質な組織であるが、その後の硬質化処理時および、高温使用環境に曝された場合、焼戻しが進行して硬度が低下し、所望の硬度を得ることが困難となるため、冷却停止温度は−10℃以上であることが好ましい。
なお、１℃/s以上の冷却速度での冷却は、500℃まで行えばよく、500℃に達した後の冷却速度は任意である。
When the cooling stop temperature is higher than 500 ° C., a coarse ferrite phase is formed in the structure at the time of cooling after cooling is stopped, and the austenite content after cooling is reduced. Moreover, it is desirable to stop the cooling at a cooling rate of 1 ° C./s or higher at a temperature of −10 ° C. or higher. That is, when cooling is performed to a low temperature range of less than −10 ° C., martensitic transformation occurs in at least a part of austenite. Martensite itself is a hard structure, but when it is subjected to subsequent hardening treatment and when exposed to a high temperature use environment, tempering proceeds and the hardness decreases, making it difficult to obtain the desired hardness. The cooling stop temperature is preferably −10 ° C. or higher.
The cooling at a cooling rate of 1 ° C./s or more may be performed up to 500 ° C., and the cooling rate after reaching 500 ° C. is arbitrary.
（硬質相形成処理条件）
上記冷却工程を経た鉄系材料は、少なくともその表層部に軟質なオーステナイト組織を有する。しかし、この鉄系材料を100〜500℃の温度域に保持することにより、上記オーステナイト組織がα（フェライト）中に微細なγ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））が分散した組織に変化し、HV700以上の硬質相が形成される。保持温度が100℃未満では上記の組織変化が不十分となり、所望の硬度を有する硬質相が形成されない。また、保持温度が500℃を超えると、形成される組織の粗大化を生じるとともに、表層部で脱窒が発生し、やはり硬質相の硬度が不十分となる。また、鉄系材料を所望の組織とするためには、上記温度における保持時間を60min以上とする。上記温度における保持時間を60min未満とすると、組織変化が不十分となり、HV700以上の硬質相が得られない。なお、60000minを超えて保持しても、それ以上の硬度の上昇は望めないため、60000min以下とすることが好ましい。
(Hard phase formation processing conditions)
The iron-based material that has undergone the cooling step has a soft austenite structure at least in the surface layer portion. However, by maintaining this iron-based material in a temperature range of 100 to 500 ° C., the austenite structure has fine γ ′ (Fe 4 N and / or Fe 4 (C, N)) in α (ferrite). It changes into a dispersed structure, and a hard phase of HV700 or higher is formed. When the holding temperature is less than 100 ° C., the above-described change in structure becomes insufficient, and a hard phase having a desired hardness is not formed. On the other hand, when the holding temperature exceeds 500 ° C., the formed structure is coarsened and denitrification occurs in the surface layer portion, and the hardness of the hard phase becomes insufficient. In order to make the iron-based material a desired structure, the holding time at the above temperature is set to 60 min or more. If the holding time at the above temperature is less than 60 min, the structure change becomes insufficient and a hard phase of HV700 or higher cannot be obtained. In addition, even if it is kept over 60000 min, no further increase in hardness can be expected, so 60000 min or less is preferable.
上記方法においては、フェライトとFe4Ｎおよび／またはFe4（Ｃ，Ｎ）すなわち熱的に安定な相により硬質な相が形成されているため、硬質相の形成のために保持された温度で長時間保持された後にも十分な強度を有している。そのため、本発明に係る鉄系材料を用いて機械部品を製造するに際しては、窒化処理前の鉄系素材は比較的軟質であるため、冷間加工を施す場合であっても容易に所望の形状に成形することができる。なお、一部に硬質相を形成する鉄系材料について、硬質相以外の部分に冷間加工を施す場合においては、硬質相形成後に冷間加工を施すことも可能である。さらに、比較的高温に曝される環境で長時間使用した後にも、十分な強度を有する部品を得ることが可能である。 In the above method, since a hard phase is formed by ferrite and Fe 4 N and / or Fe 4 (C, N), that is, a thermally stable phase, at a temperature maintained for the formation of the hard phase. It has sufficient strength even after being held for a long time. Therefore, when manufacturing machine parts using the iron-based material according to the present invention, since the iron-based material before nitriding is relatively soft, the desired shape can be easily obtained even when cold working is performed. Can be molded. In addition, about the iron-type material which forms a hard phase in part, when performing cold work on parts other than a hard phase, it is also possible to give cold work after hard phase formation. Furthermore, it is possible to obtain a component having sufficient strength even after being used for a long time in an environment exposed to a relatively high temperature.
表１に示す化学組成の鋼を転炉にて溶製し、連続鋳造によりブルームとした。次いで、ビレット圧延を経て、更に圧延によりφ35mmの棒材とし、これを素材とした。こうして得た素材のビッカース硬さを測定するとともに、以下に示す種々の熱処理に供し、特性を調査した。
すなわち、表２に示す条件にて、窒化処理、冷却、その後の硬化熱処理（硬質相形成処理)を行った。窒化処理後の鉄系材料および、硬化熱処理後の鉄系材料について、ＥＰＭＡを用いて、表面から深さ20μｍ近傍の窒素濃度(at％)を測定した。また、窒化処理後および、硬化熱処理後の鉄系材料について、表面から深さ20μｍ部を光学顕微鏡により観察し、構成ミクロ組織の判定を行うとともに、その部分のビッカース硬さを測定した。さらに、硬化熱処理後の鉄系材料については、20μｍ間隔で深さ方向にビッカース硬さ測定を行い、硬さがHV700を超える領域の厚さを測定した。
ここで、ビッカース硬さの測定はいずれも、荷重25ｇf（0.245Ｎ）、荷重保持時間15ｓの条件にて行った。
Steel having the chemical composition shown in Table 1 was melted in a converter and bloomed by continuous casting. Next, after billet rolling, it was further rolled into a φ35 mm bar, which was used as the material. While measuring the Vickers hardness of the material obtained in this way, it used for the various heat processing shown below, and investigated the characteristic.
That is, under the conditions shown in Table 2, nitriding treatment, cooling, and subsequent curing heat treatment (hard phase forming treatment) were performed. With respect to the iron-based material after the nitriding treatment and the iron-based material after the hardening heat treatment, the nitrogen concentration (at%) in the vicinity of a depth of 20 μm from the surface was measured using EPMA. Further, with respect to the iron-based material after the nitriding treatment and after the hardening heat treatment, a portion having a depth of 20 μm from the surface was observed with an optical microscope, the constituent microstructure was determined, and the Vickers hardness of the portion was measured. Furthermore, the iron-based material after the heat treatment was subjected to Vickers hardness measurement in the depth direction at intervals of 20 μm, and the thickness of the region where the hardness exceeded HV700 was measured.
Here, all the measurements of Vickers hardness were performed under conditions of a load of 25 gf (0.245 N) and a load holding time of 15 s.
さらにまた、薄膜TEM観察により硬化熱処理後の鉄系材料中に生成したγ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））のサイズおよび面積率の測定を行った。サイズ測定は、各実施例について30個以上のγ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））を測定し、サイズが300nm以下であったγ´相の個数の、全γ´相に対する個数比を微細γ´率として求めた。 Furthermore, the size and area ratio of γ ′ (Fe 4 N and / or Fe 4 (C, N)) formed in the iron-based material after the heat treatment for curing were measured by thin film TEM observation. For size measurement, 30 or more γ ′ (Fe 4 N and / or Fe 4 (C, N)) were measured for each example, and the total γ ′ of the number of γ ′ phases whose size was 300 nm or less. The number ratio to the phase was determined as the fine γ ′ rate.
なお、表１中の材料Ｌは、代表的な機械構造用鋼であるJIS−Ｓ53Ｃに相当する。当該
材料は、本発明との比較を目的として特性を調査したものであり、素材としての比較には、上記の通り35mmφの棒材とした後に、球状化焼なましを行ったものを用いた。さらに、表２に示すように、焼入れ焼戻しを行った材料について、表層から20μｍ部のビッカース硬さ、構成ミクロ組織、硬さがHV700を超える領域の厚さを測定した。
In addition, the material L in Table 1 corresponds to JIS-S53C, which is a typical steel for machine structural use. The material was investigated for the purpose of comparison with the present invention, and for the comparison as a material, after using a 35 mmφ bar as described above, a material subjected to spheroidizing annealing was used. . Further, as shown in Table 2, for the material subjected to quenching and tempering, the Vickers hardness, the constituent microstructure, and the thickness of the region where the hardness exceeds HV700 from the surface layer were measured.
本発明条件を満足する鉄系材料（実施例No.１およびNo.10〜22）は、いずれも、代表的機械構造用鋼であるJIS−Ｓ53Ｃの焼なまし材（No.24）よりも低い素材硬さを有しており、冷間加工性に優れている。また、これらの鉄系材料では、窒化→硬化熱処理後には、JIS−Ｓ53Ｃの焼入れ焼戻し材よりも優れた表層部の硬さを有している。 The iron-based materials satisfying the conditions of the present invention (Examples No. 1 and Nos. 10 to 22) are both more than JIS-S53C annealing material (No. 24), which is a typical steel for machine structural use. It has low material hardness and is excellent in cold workability. In addition, these iron-based materials have surface layer hardness superior to the JIS-S53C quenching and tempering material after nitriding → curing heat treatment.
一方、窒化あるいはその後の冷却の条件が適切でない場合（No.2〜6）には、窒化冷却後における表面から20μｍ部におけるオーステナイト（γ）組織の形成がなされず、その後の硬化熱処理によっても十分な硬さが得られなかった。すなわち、窒化処理温度が低いNo.2および窒化処理時間が短いNo.3は、窒化の進行が不十分であり、十分な窒素濃度が得られなかった。窒化処理温度が高いNo.4では、過剰な窒化の進行に伴い、窒素濃度が本発明範囲を超えてしまい、不適な窒化物（ε（Fe3N、Fe3(Ｃ，Ｎ)））が窒化処理段階で生成し、硬化処理後もこれが残留して硬さに悪影響を及ぼした。
窒化後冷却条件が不適なNo.5およびNo.6では、冷却途中または冷却完了後にフェライト（α）相が生じ、硬化熱処理後には微細γ´率が低くなって十分な硬さが得られなかった。
On the other hand, when the conditions for nitriding or subsequent cooling are not appropriate (No. 2 to 6), the austenite (γ) structure is not formed in the 20 μm portion from the surface after nitridation cooling, and the subsequent hardening heat treatment is sufficient. The hardness was not obtained. That is, No. 2 having a low nitriding temperature and No. 3 having a short nitriding time had insufficient nitriding progress, and a sufficient nitrogen concentration could not be obtained. In No. 4 where the nitriding temperature is high, as the excessive nitriding proceeds, the nitrogen concentration exceeds the range of the present invention, and inappropriate nitrides (ε (Fe 3 N, Fe 3 (C, N))) are generated. It was generated at the nitriding stage and remained after the curing process, which had an adverse effect on the hardness.
In No. 5 and No. 6 where the cooling conditions are not suitable after nitriding, a ferrite (α) phase is generated during cooling or after cooling is completed, and after the heat treatment, the fine γ ′ rate becomes low and sufficient hardness cannot be obtained. It was.
また、No.7およびNo.9は、窒化処理後の冷却によりオーステナイト（γ）組織が得られたが、No.7ではその後の硬化熱処理温度が低いため、また、No.9では硬化熱処理時間が短いため、窒化冷却処理で得られたオーステナイトからの組織変化が十分に進行せず、結果として硬化熱処理後の構成ミクロ組織がオーステナイトとなり、十分な硬さが得られなかった。 In No. 7 and No. 9, an austenite (γ) structure was obtained by cooling after nitriding treatment, but in No. 7, the subsequent curing heat treatment temperature was low. Therefore, the structural change from the austenite obtained by the nitriding cooling treatment did not sufficiently proceed, and as a result, the constituent microstructure after the hardening heat treatment became austenite, and sufficient hardness was not obtained.
さらに、No.8の場合、窒化冷却によりオーステナイト組織が得られているものの、その後の硬化熱処理温度が高いため、オーステナイト相からの組織変化によって形成されたフェライト（α）相、および、γ´（Fe4Ｎおよび／またはFe4（Ｃ，Ｎ））相が粗大化し、十分な硬さが得られなかった。 Further, in the case of No. 8, although the austenite structure is obtained by nitriding cooling, since the subsequent hardening heat treatment temperature is high, the ferrite (α) phase formed by the structure change from the austenite phase, and γ ′ ( The Fe 4 N and / or Fe 4 (C, N)) phase was coarsened, and sufficient hardness was not obtained.
また、Ｃ量が本発明範囲より低いNo.23では、窒化層の空隙率が高く、窒化層が脆化している。 In No. 23, in which the C content is lower than the range of the present invention, the porosity of the nitride layer is high, and the nitride layer is brittle.
産業機械や自動車等の機械部品に好適に用いられる機械構造用鉄系材料を提供する。 Provided is an iron-based material for machine structure that is suitably used for machine parts such as industrial machines and automobiles.
Claims (4)
ただし、［Ｃ］は材料中のＣ含有量（at％） C: has a hard phase obtained by nitriding the surface layer or the whole of the material containing 0.1 mass% or more and 1.5 mass% or less, and the balance Fe and inevitable impurities, and the hard phase is N: (8- [ C]) at least (11- [C]) at% or less and a hardness of HV700 or more.
However, [C] is the C content in the material (at%)
Cr：0.05 mass％以上2.0 mass％以下、
Al：0.005 mass％以上0.5 mass％以下、
Ti：0.0005 mass％以上0.5 mass％以下、
Nb：0.005 mass％以上0.1 mass％以下、
Ｖ：0.02 mass％以上1.0 mass％以下、
Mo：0.02 mass％以上1.0 mass％以下、
Mn：0.02 mass％以上2.0 mass％以下、
Si：0.02 mass％以上2.0 mass％以下、
Ni：0.02 mass％以上2.0 mass％以下、
Cu：0.02 mass％以上2.0 mass％以下および
Co：0.02 mass％以上2.0 mass％以下
の中から選択される少なくとも一種以上を含有することを特徴とする鉄系材料。 The iron-based material according to claim 1,
Cr: 0.05 mass% or more and 2.0 mass% or less,
Al: 0.005 mass% or more and 0.5 mass% or less,
Ti: 0.0005 mass% or more and 0.5 mass% or less,
Nb: 0.005 mass% or more and 0.1 mass% or less,
V: 0.02 mass% or more and 1.0 mass% or less,
Mo: 0.02 mass% or more and 1.0 mass% or less,
Mn: 0.02 mass% or more and 2.0 mass% or less,
Si: 0.02 mass% or more and 2.0 mass% or less,
Ni: 0.02 mass% or more and 2.0 mass% or less,
Cu: 0.02 mass% to 2.0 mass%
Co: An iron-based material containing at least one selected from 0.02 mass% to 2.0 mass%.
ただし、［Ｃ］は材料中のＣ含有量（at％） C: 0.1 mass% or more and 1.5 mass% or less, and a material comprising the balance Fe and inevitable impurities is subjected to nitriding treatment at a temperature of 590 ° C. or more, and a part or all of the material is subjected to N: (8- [C ]) After containing at% or more (11- [C]) at% or less, cool to a temperature range of 500 ° C. or less at a rate of 1 ° C./s or more, and then hold at a temperature range of 100 to 500 ° C. Forming a hard phase of HV700 or higher.
However, [C] is the C content in the material (at%)
Cr：0.05 mass％以上2.0 mass％以下、
Al：0.005 mass％以上0.5 mass％以下、
Ti：0.0005 mass％以上0.5 mass％以下、
Nb：0.005 mass％以上0.1 mass％以下、
Ｖ：0.02 mass％以上1.0 mass％以下、
Mo：0.02 mass％以上1.0 mass％以下、
Mn：0.02 mass％以上2.0 mass％以下、
Si：0.02 mass％以上2.0 mass％以下、
Ni：0.02 mass％以上2.0 mass％以下、
Cu：0.02 mass％以上2.0 mass％以下および
Co：0.02 mass％以上2.0 mass％以下
の中から選択される少なくとも一種以上を含有することを特徴とする鉄系材料の製造方法。
The iron-based material according to claim 3,
Cr: 0.05 mass% or more and 2.0 mass% or less,
Al: 0.005 mass% or more and 0.5 mass% or less,
Ti: 0.0005 mass% or more and 0.5 mass% or less,
Nb: 0.005 mass% or more and 0.1 mass% or less,
V: 0.02 mass% or more and 1.0 mass% or less,
Mo: 0.02 mass% or more and 1.0 mass% or less,
Mn: 0.02 mass% or more and 2.0 mass% or less,
Si: 0.02 mass% or more and 2.0 mass% or less,
Ni: 0.02 mass% or more and 2.0 mass% or less,
Cu: 0.02 mass% to 2.0 mass%
Co: A method for producing an iron-based material comprising at least one selected from 0.02 mass% to 2.0 mass%.
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| JP2013044036A (en) * | 2011-08-25 | 2013-03-04 | Jfe Steel Corp | Method for producing ferrous material |
| JP2014201812A (en) * | 2013-04-08 | 2014-10-27 | 株式会社神戸製鋼所 | Method for manufacturing cold forging steel material |
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|---|---|---|---|---|
| JPH06184727A (en) * | 1992-12-22 | 1994-07-05 | Parker Netsushiyori Kogyo Kk | Method for hardening surface of part made of steel |
| JP2005232543A (en) * | 2004-02-20 | 2005-09-02 | Nsk Ltd | Ball screw |
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| JPH06184727A (en) * | 1992-12-22 | 1994-07-05 | Parker Netsushiyori Kogyo Kk | Method for hardening surface of part made of steel |
| JP2005232543A (en) * | 2004-02-20 | 2005-09-02 | Nsk Ltd | Ball screw |
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| JP2014201812A (en) * | 2013-04-08 | 2014-10-27 | 株式会社神戸製鋼所 | Method for manufacturing cold forging steel material |
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