JP2741222B2 - Method for manufacturing a nitrided steel member - Google Patents
Method for manufacturing a nitrided steel memberInfo
- Publication number
- JP2741222B2 JP2741222B2 JP30444788A JP30444788A JP2741222B2 JP 2741222 B2 JP2741222 B2 JP 2741222B2 JP 30444788 A JP30444788 A JP 30444788A JP 30444788 A JP30444788 A JP 30444788A JP 2741222 B2 JP2741222 B2 JP 2741222B2
- Authority
- JP
- Japan
- Prior art keywords
- steel member
- shot
- treatment
- bainite
- steel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Heat Treatment Of Steel (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は窒化処理した鋼部材の製造方法に関し、特に
鋼部材に窒化処理とショットピーニング処理を施し疲労
寿命に優れる鋼部材を製造する方法に関する。Description: TECHNICAL FIELD The present invention relates to a method for producing a steel member subjected to a nitriding treatment, and more particularly to a method for producing a steel member having an excellent fatigue life by subjecting a steel member to a nitriding treatment and a shot peening treatment. .
従来、鋼部材を用いて疲労強度に優れる歯車などの鋼
部材を製造する技術として、鋼部材に浸炭処理を施す技
術と、鋼部材に窒化処理や軟窒化処理を施す技術が広く
実用化されている。Conventionally, as a technology for manufacturing a steel member such as a gear having excellent fatigue strength using a steel member, a technology of carburizing a steel member and a technology of nitriding or nitrocarburizing a steel member have been widely put into practical use. I have.
上記窒化処理や軟窒化処理を施すと、鋼部材の表層に
窒化鉄(Fe2N、Fe3N、Fe4N)からなる高硬度の窒化物被
膜が形成され、同時に鋼部材の内部にも窒化物(拡散硬
化層)が形成され、疲労寿命が著しく向上する。When the above nitriding or nitrocarburizing treatment is performed, a high hardness nitride coating made of iron nitride (Fe 2 N, Fe 3 N, Fe 4 N) is formed on the surface layer of the steel member, and at the same time, the inside of the steel member is also formed. A nitride (diffusion hardened layer) is formed, and the fatigue life is significantly improved.
上記表層の窒化物被膜の内側の拡散硬化層を極力深く
形成することが重要であるとの観点から、窒化処理に際
し鋼組織を最適化し、金属組織をフェライト+パーライ
ト組織にすることも提案されている。(特公昭61−3118
4号公報参照)。From the viewpoint that it is important to form the diffusion hardened layer inside the above-mentioned nitride coating as deeply as possible, it has been proposed to optimize the steel structure during the nitriding treatment and change the metal structure to a ferrite + pearlite structure. I have. (Japanese Patent Publication No. 61-3118
No. 4).
一方、鋼部材の疲労寿命を高める技術として、ショッ
トピーニング処理により鋼部材の表層部及び内部に圧縮
残留応力を付与し且つ加工硬化によりマルテンサイト組
織とする技術も広く実用化されている。On the other hand, as a technique for increasing the fatigue life of a steel member, a technique of imparting a compressive residual stress to the surface layer portion and the inside of the steel member by shot peening treatment and forming a martensite structure by work hardening has been widely used.
歯車などの鋼部材では、上記浸炭処理後の鋼部材にシ
ョットピーニング処理を施すことにより疲労寿命を更に
改善する技術も実用化されているけれども、窒化処理や
軟窒化処理を施した鋼部材にショットピーニング処理を
施すと、高硬度で脆い窒化物に多数のクラックが発生し
て窒化処理や軟窒化処理の効果が失なわれてしまうの
で、窒化処理や軟窒化処理とショットピーニング処理を
併用する技術は実用化されていない。For steel members such as gears, a technique for further improving the fatigue life by performing shot peening treatment on the steel member after the carburizing treatment has been put to practical use. When peening is performed, many cracks are generated in brittle nitride with high hardness and the effect of nitriding or nitrocarburizing is lost, so a technique that combines shot peening with nitriding or nitrocarburizing is used. Has not been put to practical use.
但し、エンジンのバルブスプリングなどに関しては、
鋼部材を窒化処理後、電解研磨処理などによって表層の
窒化物被膜を除去してからショットピーニング処理を施
す技術も実用化されているが、このようにすると窒化物
被膜を除去してしまうので窒化処理の効果が大幅に減殺
されてしまう。However, for engine valve springs, etc.
A technique of removing the surface nitride film by electrolytic polishing or the like after nitriding the steel member and then performing shot peening has also been put to practical use, but this method removes the nitride film. The effect of the treatment is greatly reduced.
上記窒化処理や軟窒化処理を施した鋼部材にショット
ピーニング処理を施した場合に、窒化物に多数のクラッ
クが発生する原因について考察してみると、次の3点が
考えられる。The following three points are considered when considering the cause of the generation of many cracks in nitride when a shot peening treatment is applied to a steel member subjected to the nitriding treatment or the nitrocarburizing treatment.
(1)窒化鉄(Fe2N、Fe3N、Fe4N)からなる窒化物被膜
が本質的に高硬度で脆いこと、 (2)鋼部材の窒化物被膜下の基材の靱性が十分でな
く、ショットピーニングの打撃力によって降伏状態とな
り、窒化物被膜を基材の内部より支持する支持作用が失
われること、 (3)窒化処理や軟窒化処理した鋼部材に対するショッ
トピーニング処理条件が適正でないこと、 などの原因が考えられる。(1) that iron nitride (Fe 2 N, Fe 3 N , Fe 4 N) nitride film composed of the brittle essentially high hardness, (2) the toughness of the base material of the nitride subcapsular steel member is sufficiently Instead, the steel sheet is yielded by the impact force of shot peening, and loses the support function of supporting the nitride film from the inside of the base material. (3) The shot peening condition for the steel member subjected to the nitriding treatment or the nitrocarburizing treatment is appropriate. Is not possible, and other causes.
上記公報に記載のように、フェライト+パーライト組
織の鋼部材に窒化処理を施し、且つショットピーニング
を施す場合には、フェライト+パーライト組織は余り硬
度が高くないことから、上記(2)の原因により窒化物
被膜へのクラックの発生は避けられず、実用に適さな
い。As described in the above publication, when a steel member having a ferrite + pearlite structure is subjected to nitriding treatment and shot peening, the ferrite + pearlite structure does not have too high hardness. The generation of cracks in the nitride film is unavoidable and is not suitable for practical use.
本発明の目的は、上記(2)と(3)の原因を除去
し、窒化処理や軟窒化処理を施した鋼部材にショットピ
ーニングを施す技術を確立して疲労寿命を大幅に改善し
た鋼部材の製造方法を提供することである。An object of the present invention is to eliminate the causes of the above (2) and (3), establish a technique for performing shot peening on a steel member subjected to nitriding or nitrocarburizing treatment, and significantly improve the fatigue life. Is to provide a method of manufacturing the same.
請求項1に係る窒化処理した鋼部材の製造方法は、鋼
部材を、熱間鍛造後冷却するか或いはオーステナイト化
温度以上に加熱した後冷却して、ベイナイトを主体とす
る金属組織とし、次にこの鋼部材に窒化処理又は軟窒化
処理を施し、次にこの鋼部材に、ショット径/窒化化合
物膜厚=15〜60、ショットのロックウェル硬さ=45〜6
0、ショット速度=50〜120m/secの条件にてショットピ
ーニング処理を施すものである。請求項2に係る鋼部材
の製造方法は、請求項1の方法において、上記鋼部材の
鋼材料として、重量%にてCが0.15〜0.35、Siが0.50以
下、Mnが0.50〜1.20、Crが0.80〜1.20、Vが0.05〜0.2
0、Moが0.05〜0.50を含んだ鋼材料を用いることを特徴
とするものである。In the method for producing a nitrided steel member according to claim 1, the steel member is cooled after hot forging or after being heated to an austenitizing temperature or higher, and cooled to obtain a metal structure mainly composed of bainite. This steel member is subjected to a nitriding treatment or a nitrocarburizing treatment. Then, the shot member / nitride compound film thickness is 15 to 60, and the Rockwell hardness of the shot is 45 to 6.
The shot peening process is performed under the condition of 0, shot speed = 50 to 120 m / sec. The method for producing a steel member according to claim 2 is the method according to claim 1, wherein, as a steel material of the steel member, C is 0.15 to 0.35, Si is 0.50 or less, Mn is 0.50 to 1.20, and Cr is 0.80-1.20, V 0.05-0.2
0, Mo is characterized by using a steel material containing 0.05 to 0.50.
請求項1に係る窒化処理した鋼部材の製造方法におい
ては、先ず、鋼部材を熱間鍛造後冷却するか或いはオー
ステナイト化温度以上に加熱した後冷却して、ベイナイ
トを主体とする金属組織とする。ベイナイトの金属組織
は、マルテンサイトよりは低硬度であるものの非常に硬
度が高く、フェライト+パーライト組織よりも硬く靱性
も高いので、ショットピーニング処理を施したときにも
鋼部材の内部が降伏状態とならずに表層の窒化物被膜を
内部より支持する支持作用を維持することになる。上記
ベイナイト組織は窒化化合物を生成し易いので、ベイナ
イト組織とすることは有利であるが、ベイナイト組織の
面積率は50%以上であることが望ましい。残りはフェラ
イト、パーライト、ソルバイト(焼戻しマルテンサイ
ト)である。In the method for manufacturing a nitrided steel member according to the first aspect, first, the steel member is cooled after hot forging or is heated to an austenitizing temperature or higher, and then cooled to obtain a metal structure mainly composed of bainite. . Although the metal structure of bainite is lower than martensite, it is very hard, and it is harder and tougher than ferrite + pearlite structure. Instead, the support function of supporting the surface nitride coating from the inside is maintained. Since the above-mentioned bainite structure easily generates a nitride compound, it is advantageous to use a bainite structure, but the area ratio of the bainite structure is desirably 50% or more. The remainder is ferrite, pearlite, and sorbite (tempered martensite).
次に、上記鋼部材に窒化処理又は軟窒化処理を施す
と、鋼部材の表層には約10μm程度乃至数10μmの膜厚
の窒化鉄(Fe2N、Fe3N、Fe4N)の窒化化合物の被膜が形
成されるとともに、内部にも窒素原子が拡散して窒化鉄
が形成される。Next, when the above steel member is subjected to nitriding treatment or soft nitriding treatment, nitriding of iron nitride (Fe 2 N, Fe 3 N, Fe 4 N) having a thickness of about 10 μm to several tens μm is performed on the surface layer of the steel member. While a film of the compound is formed, nitrogen atoms are diffused inside to form iron nitride.
次に、上記鋼部材にショットピーニング処理を施すの
であるが、そのショットピーニングが、ショット径/窒
化化合物膜厚(D/t)=15〜60、ショットのロックウェ
ル硬さ(HRC)=45〜60、ショット速度(V)=50〜120
m/secのショットピーニング条件で施される。Then, although subjected to a shot peening treatment to the steel member, the shot peening, shot size / nitride compound film thickness (D / t) = 15~60, shot Rockwell hardness (H R C) = 45-60, shot speed (V) = 50-120
It is performed under shot peening conditions of m / sec.
ここで、D/t<15では、窒化化合物の被膜下の金属組
織にショットピーニングの作用がおよばず、残留応力の
形成が不十分となり、ショットピーニングによる疲労寿
命の改善を図り得ない。一方、D/t>60では、ショット
の打撃力が過大となって窒化化合物の被膜下の金属組織
が降伏状態となり、上記被膜にクラックが発生する。Here, when D / t <15, the effect of shot peening does not reach the metal structure under the nitride compound film, the formation of residual stress becomes insufficient, and the fatigue life due to shot peening cannot be improved. On the other hand, when D / t> 60, the impact strength of the shot becomes excessive, and the metal structure under the nitride compound film becomes a yield state, and cracks occur in the film.
HRC<45では、ショットピーニングの加工力に乏しい
ため、被膜下の金属組織中の残留圧縮応力の形成が不十
分となる。また、HRC>60では、ショットが硬すぎて被
膜にクラックが発生する。V<50m/secでは、ショット
の運動エネルギが十分でなく、加工力が不足し、またV
>120m/secでは、ショットの運動エネルギが過大となる
ため被膜にクラックが発生する。In H R C <45, since poor working force of the shot peening, the formation of residual compressive stress in the subcapsular metal structure is insufficient. If H R C> 60, the shot is too hard and cracks occur in the coating. When V <50 m / sec, the kinetic energy of the shot is not sufficient, the machining force is insufficient, and V
At> 120 m / sec, the kinetic energy of the shot becomes excessive and cracks occur in the coating.
上記のようにして窒化処理した鋼部材を製造すると、
鋼部材の金属組織は硬く靱性に優れ、その表層には窒化
化合物の被膜が形成されるとともに内部金属組織中にも
拡散により拡散窒化物層が形成されて硬度並びに疲労寿
命が改善され、且つショットピーニング処理によって、
窒化化合物被膜にクラックを発生させることなく、窒化
化合物被膜下の金属組織に適正に残留圧縮応力が形成さ
れ、この残留圧縮応力の作用により疲労寿命が改善され
る。請求項2に係る鋼部材の製造方法においては、基本
的に請求項1と同様の作用を奏するが、上記鋼部材の鋼
材料として、重量%にてCが0.15〜0.35、Siが0.50以
下、Mnが0.50〜1.20、Crが0.80〜1.20、Vが0.05〜0.2
0、Moが0.05〜0.50を含んだ鋼部材を用い、この鋼部材
は焼入れ性向上元素であるMoとMnとCrとを適量含んでい
るため、熱間鍛造後連続的な調整冷却するか或いはオー
ステナイト化温度以上に加熱した後連続的な調整冷却し
て、ベイナイトを主体とする金属組織にすることができ
る。When manufacturing a steel member that has been nitridated as described above,
The metal structure of the steel member is hard and excellent in toughness. A nitride compound film is formed on the surface layer, and a diffusion nitride layer is formed by diffusion in the internal metal structure, so that the hardness and fatigue life are improved. By peening process,
Residual compressive stress is appropriately formed in the metal structure under the nitride compound film without causing cracks in the nitride compound film, and the fatigue life is improved by the action of the residual compressive stress. In the method of manufacturing a steel member according to claim 2, basically the same operation as in claim 1 is achieved, but as a steel material of the steel member, C is 0.15 to 0.35, Si is 0.50 or less by weight%, Mn is 0.50 to 1.20, Cr is 0.80 to 1.20, V is 0.05 to 0.2
0, Mo uses a steel member containing 0.05 to 0.50, and since this steel member contains an appropriate amount of Mo, Mn, and Cr, which are quenchability improving elements, it may be continuously adjusted and cooled after hot forging or After heating to an austenitizing temperature or higher, continuous adjustment and cooling can be performed to obtain a metal structure mainly composed of bainite.
請求項1に係る窒化処理した鋼部材の製造方法によれ
ば、上記〔作用〕の項で説明したように、鋼部材の金属
組織をベイナイトを主体とする組織にし、窒化処理又は
軟窒化処理を施し、前記所定の条件でショットピーニン
グ処理を施す、というプロセスによって、窒化化合物の
被膜を破壊することなく、窒化処理又は軟窒化処理した
鋼部材にショットピーニング処理を施すことが可能とな
る。これにより、窒化処理又は軟窒化処理した鋼部材で
あって疲労寿命が飛躍的に向上した鋼部材を製造するこ
とが可能となる。請求項2に係る鋼部材の製造方法によ
れば、基本的に請求項1と同様の効果を奏するが、上記
鋼部材の鋼材料として、重量%にてCが0.15〜0.35、Si
が0.50以下、Mnが0.50〜1.20、Crが0.80〜1.20、Vが0.
05〜0.20、Moが0.05〜0.50を含んだ鋼材料を用い、この
鋼材料は焼入れ性向上元素であるMoとMnとCrとを適量含
んでいるため、熱間鍛造後連続的な調整冷却するか或い
はオーステナイト化温度以上に加熱した後連続的な調整
冷却して、ベイナイトを主体とする金属組織にすること
ができる。According to the method for producing a nitrided steel member according to claim 1, the metal structure of the steel member is changed to a structure mainly composed of bainite, and the nitriding treatment or the nitrocarburizing treatment is performed. By applying the shot peening process under the above-described predetermined conditions, it is possible to perform the shot peening process on the nitrided or soft-nitrided steel member without destroying the nitride compound film. This makes it possible to manufacture a steel member that has been subjected to nitriding treatment or nitrocarburizing treatment and has a significantly improved fatigue life. According to the method of manufacturing a steel member according to the second aspect, basically the same effects as in the first aspect are achieved, but as a steel material of the steel member, C is 0.15 to 0.35 by weight%,
Is 0.50 or less, Mn is 0.50 to 1.20, Cr is 0.80 to 1.20, and V is 0.
05-0.20, Mo used 0.05-0.50 steel material.Since this steel material contains Mo, Mn and Cr which are hardenability improving elements, it is continuously adjusted and cooled after hot forging. Alternatively, after heating to an austenitizing temperature or higher, continuous adjustment and cooling can be performed to obtain a metal structure mainly composed of bainite.
以下、本発明の実施例について図面を参照して説明す
る。Hereinafter, embodiments of the present invention will be described with reference to the drawings.
本実施例に係る窒化処理した鋼部材の製造方法につい
て、第1図に基いて説明しておく。A method for manufacturing a steel member subjected to a nitriding treatment according to the present embodiment will be described with reference to FIG.
本願の製造方法を適用するのに適した鋼材料として
は、重量%にてCが0.15〜0.35、Siが0.50以下、Mnが0.
50〜1.20、Crが0.80〜1.20、Vが0.05〜0.20、Moが0.05
〜0.50を含んだ鋼であることが望ましい。As a steel material suitable for applying the production method of the present application, C is 0.15 to 0.35, Si is 0.50 or less, and Mn is 0.
50-1.20, Cr 0.80-1.20, V 0.05-0.20, Mo 0.05
Desirably, the steel contains up to 0.50.
先ず、鋼材を熱間鍛造に供するのに適した形状に切断
し、次にその鋼材を熱間鍛造して所定の形状の鋼部材と
する。但し、この熱間鍛造するときの温度はオーステナ
イト化温度(約730℃)よりも高い。First, a steel material is cut into a shape suitable for hot forging, and then the steel material is hot forged to obtain a steel member having a predetermined shape. However, the temperature at the time of the hot forging is higher than the austenitizing temperature (about 730 ° C.).
次に、上記熱間鍛造されオーステナイト化温度よりも
高温の鋼部材を0.4〜4.0℃/secの冷却速度で調整冷却に
より鋼部材の金属組織をベイナイトを主体とする組織に
する。或いは、熱間鍛造後冷却してから再びオーステナ
イト化温度以上に加熱後調整冷却により鋼部材の金属組
織をベイナイトを主体とする組織にする。上記ベイナイ
トを主体とする組織にするのに従来周知の恒温冷却によ
り行なってもよいが、上記のような鋼材料を用いる場合
には、焼入れ性向上元素であるMoとMnとCrとを適当に添
加してあるので上記のように連続的な調整冷却によって
ベイナイト組織とすることが出来る。上記ベイナイトを
主体とする金属組織は、フェライト+パーライト組織で
あってもよいが、面積率で50%以上のベイナイトを含む
ことが望ましい。Next, the hot forged steel member having a temperature higher than the austenitizing temperature is adjusted and cooled at a cooling rate of 0.4 to 4.0 ° C./sec to change the metal structure of the steel member into a structure mainly composed of bainite. Alternatively, the metal structure of the steel member is changed to a structure mainly composed of bainite by cooling after hot forging and then heating again to the austenitizing temperature or higher and then adjusting and cooling. The bainite-based structure may be formed by conventional well-known constant temperature cooling.However, when the above steel material is used, Mo, Mn, and Cr, which are quenchability improving elements, are appropriately Since it has been added, a bainite structure can be obtained by continuous adjustment cooling as described above. The metal structure mainly composed of bainite may be a ferrite + pearlite structure, but preferably contains bainite in an area ratio of 50% or more.
次に、上記ベイナイトを主体とする金属組織の鋼部材
を機械加工し、或いは必要に応じて焼戻し処理を施して
から機械加工して機械部品の形状にする。この場合、フ
ェライト+ベイナイト+ソルバイト(焼戻しマルテンサ
イト)の金属組織となるが、面積率で50%以上のベイナ
イトを含むことが望ましい。Next, the steel member having a metal structure mainly composed of bainite is machined or, if necessary, subjected to a tempering treatment and then machined into a shape of a machine part. In this case, a metal structure of ferrite + bainite + sorbite (tempered martensite) is obtained, and it is desirable to include bainite in an area ratio of 50% or more.
次に、上記鋼部材に窒化処理又は軟窒化処理を施し、
鋼部材の表層に約10μm程度の窒化鉄(Fe2N、Fe3N、Fe
4N)の被膜を形成するとともに内部には拡散窒化層を形
成する。上記窒化処理や軟窒化処理の技術は公知のもの
なので詳しい説明は省略する。Next, the steel member is subjected to a nitriding treatment or a nitrocarburizing treatment,
About 10μm iron nitride (Fe 2 N, Fe 3 N, Fe
Inside form a diffusion nitrided layer to form a coating of 4 N). Since the techniques of the nitriding treatment and the nitrocarburizing treatment are known, detailed description is omitted.
次に、上記鋼部材に、ショット径(D)/窒化鉄被膜
厚(t)=15〜60、ショットのロックウェル硬さ(H
RC)=45〜60、ショット速度(V)=50〜120m/secの条
件にてショットピーニング処理を施す。但し、ショット
径(D)と膜厚(t)は何れも同じ単位(例えばμm)
での値を用いる。Next, a shot diameter (D) / iron nitride coating thickness (t) = 15 to 60 and a Rockwell hardness (H
R C) = 45~60, subjected to shot peening at a shot speed (V) = 50~120m / sec condition. However, the shot diameter (D) and the film thickness (t) are the same unit (for example, μm).
Use the value at.
上記の製造方法により得られる鋼部材は、ベイナイト
組織の利点(高硬度で靱性が高いこと)に加えて、窒化
処理による利点(高硬度の窒化鉄被膜及び拡散窒化層を
有し、疲労寿命に優れること)と、ショットピーニング
処理による利点(内部の金属組織に残留圧縮応力が形成
されて疲労寿命に優れること)と兼備したものとなる。The steel member obtained by the above manufacturing method has the advantage of nitriding treatment (high hardness iron nitride coating and diffusion nitrided layer) in addition to the advantage of bainite structure (high hardness and high toughness), and reduces the fatigue life. Excellent) and the advantage of the shot peening treatment (residual compressive stress is formed in the internal metal structure and the fatigue life is excellent).
次に、ショットピーニング処理の処理条件と疲労寿命
の向上との相関関係を調べる為に実際に行なった実験例
Iと実験例IIについて説明する。Next, a description will be given of Experimental Examples I and II actually performed to examine the correlation between the processing conditions of the shot peening processing and the improvement of the fatigue life.
〈実験例I〉 使用した鋼材の組成を次の第1表に示す。<Experimental Example I> The composition of the steel material used is shown in Table 1 below.
(1)試験片の作成 上記組成の鋼材を熱間鍛造後900℃に加熱し、次に1.0
℃/secの冷却速度で冷却しオーステンパー処理して、フ
ェライト+ベイナイト組織(ベイナイトの面積率70%)
の試験片を製作した。 (1) Preparation of test piece After hot forging a steel material with the above composition, it was heated to 900 ° C,
Ferrite + bainite structure (area ratio of bainite 70%) after cooling at a cooling rate of ° C / sec and austempering
Was manufactured.
次に上記試験片を機械加工して直径=10mm、切欠R=
1.0mmの疲労試験片を作成した。Next, the test piece was machined to have a diameter of 10 mm and a notch R =
A 1.0 mm fatigue test piece was prepared.
(2)窒化処理 次に、上記試験片に、570℃×3Hr、NH3/RX=50/50の
条件にてガス軟窒化処理を施した。この窒化処理により
表面に形成された窒化鉄被膜の膜厚は10μmであった。
尚、上記RXは吸熱型変性ガスである。(2) Nitriding Treatment Next, the test piece was subjected to a gas soft nitriding treatment under the conditions of 570 ° C. × 3 H r , NH 3 / RX = 50/50. The film thickness of the iron nitride film formed on the surface by this nitriding treatment was 10 μm.
Note that RX is an endothermic modified gas.
(3)ショットピーニング処理 上記疲労試験片に種々の径のスチールショットを用い
てショットピーニング処理を施してから疲労試験片を疲
労試験に供した。(3) Shot peening treatment The above-mentioned fatigue test pieces were subjected to a shot peening treatment using steel shots of various diameters, and then subjected to a fatigue test.
ショットピーニングの条件は、ショットのロックウェ
ル硬さ(HRC)=48、ショット速度(V)=80m/sec、疲
労試験応力=45Kgf/mm2であった。Conditions of the shot peening, shot Rockwell hardness (H R C) = 48, shot velocity (V) = 80m / sec, was fatigue test stress = 45Kgf / mm 2.
(4)疲労試験結果 疲労試験結果をショット径(D)、窒化鉄被膜の膜厚
(t)とし、D/tのパラメータを横軸に、また疲労寿命
比を縦軸にして整理すると第1図のような結果が得られ
た。ここで、疲労寿命比=1.0は窒化処理したままでシ
ョットピーニング処理を施さない試験片の場合である。(4) Fatigue test results The fatigue test results are shown as shot diameter (D) and iron nitride film thickness (t). The D / t parameter is plotted on the horizontal axis, and the fatigue life ratio is plotted on the vertical axis. The result as shown in the figure was obtained. Here, the fatigue life ratio = 1.0 is the case of the test piece which is not subjected to the shot peening treatment while being subjected to the nitriding treatment.
第1図から判るように、D/t=15〜60の範囲のときに
疲労寿命が4倍以上向上した。As can be seen from FIG. 1, the fatigue life was improved by a factor of 4 or more when D / t = 15 to 60.
D/t<15では、ショット径(D)が小さく或いは被膜
の膜厚(t)が大きいために、ショットによるヘルツの
接触応力が表層部に発生し、窒化鉄被膜下にショットピ
ーニングの影響が及ばず、残留圧縮応力の形成が不十分
となることから、疲労寿命の向上が不十分となる。When D / t <15, the shot diameter (D) is small or the film thickness (t) is large, so that Hertz contact stress due to the shot is generated in the surface layer, and the effect of shot peening under the iron nitride film is reduced. Because the formation of the residual compressive stress is insufficient, the improvement of the fatigue life is insufficient.
D/t>60では、ショットの打撃力が過大で且つヘルツ
の接触応力が内部に及び、内部の鋼材料が降伏状態とな
って表層の窒化鉄被膜を内側から支持する支持作用が不
十分となり、窒化鉄被膜にクラックが発生しやすくなる
ことから、疲労寿命の向上が不十分となる。At D / t> 60, the impact strength of the shot is excessive and the Hertzian contact stress extends to the inside, and the steel material inside yields and the supporting action to support the surface iron nitride coating from the inside becomes insufficient. In addition, cracks are easily generated in the iron nitride coating, and the improvement of the fatigue life is insufficient.
〈実験例II〉 上記実験例Iと同様に製作した試験片にショット径
(D)0.4mm、つまりD/t=40で且つショットの硬さとシ
ョット速度を変えてショットピーニング処理を施し、疲
労試験(疲労試験応力=45Kgf/mm2)に供した。<Experimental Example II> A test piece manufactured in the same manner as in Experimental Example I above was subjected to a shot peening treatment with a shot diameter (D) of 0.4 mm, that is, D / t = 40, and with different shot hardness and shot speed, and a fatigue test. (Fatigue test stress = 45 kgf / mm 2 ).
その結果、次の第2表のような結果となり、それを図
示すると第3図のようになった。As a result, the results were as shown in Table 2 below, and the results are shown in FIG.
第2表及び第3図から判るように、ショットのロック
ウェル硬さ(HRC)=45〜60、ショット速度(V)=50
〜120m/secの範囲のときに疲労寿命が4倍以上に向上す
る。 As can be seen from Table 2 and FIG. 3, the shot of Rockwell hardness (H R C) = 45~60, shot velocity (V) = 50
When it is in the range of ~ 120 m / sec, the fatigue life is improved four times or more.
HRC<45では、ショットの加工力が小さく、残留圧縮
応力の形成が不十分となることから、疲労寿命の向上が
十分でない。In H R C <45, the working force of the shot is small, since the formation of the residual compressive stress is insufficient, is not sufficient improvement in fatigue life.
HRC>60では、ショットの硬さが過大で、窒化鉄被膜
にクラックが発生することから、疲労寿命の向上が十分
でない。In H R C> 60, excessive hardness of the shot, the generation of cracks in the iron nitride coating is not sufficient improvement in fatigue life.
また、ショット速度(V)<50m/secでは、ショット
の運動エネルギが不十分で、加工力が不足するため疲労
寿命の向上が十分でない。ショット速度(V)>120m/s
ecでは、ショットの加工力が過大となるため疲労寿命の
向上が十分でない。When the shot speed (V) is less than 50 m / sec, the kinetic energy of the shot is insufficient and the working force is insufficient, so that the fatigue life is not sufficiently improved. Shot speed (V)> 120m / s
In the case of ec, the improvement of the fatigue life is not sufficient because the processing power of the shot becomes excessive.
上記実験例Iと実験例IIの結果を総合すると、結局最
も望ましいショットピーニング処理の条件は次のように
なる。When the results of Experimental Examples I and II are combined, the most desirable conditions of the shot peening process are as follows.
(i)ショット径(D)/窒化鉄被膜の膜厚(t)=15
〜60、 (ii)ショットのロックウェル硬さ(HRC)=45〜60、 (iii)ショット速度(V)=50〜120m/sec 上記のように、鋼部材をベイナイトを主体とする金属
組織とし、その鋼部材に窒化処理や軟窒化処理を施し、
その後上記の条件でショットピーニング処理を施すと、
前述の如くベイナイトの特性と窒化処理により得られる
特性とショットピーニング処理により得られる特性とを
兼備した鋼部材を製造することが出来る。(I) Shot diameter (D) / Film thickness of iron nitride coating (t) = 15
To 60, (ii) available for Rockwell hardness (H R C) = 45~60, as (iii) Shot velocity (V) = 50~120m / sec above, metal steel member composed mainly of bainite The steel member is subjected to nitriding or soft nitriding,
After that, when the shot peening process is performed under the above conditions,
As described above, it is possible to manufacture a steel member having both the characteristics of bainite, the characteristics obtained by nitriding, and the characteristics obtained by shot peening.
図面は本発明の実施例に係るもので、第1図は本実施例
に係る窒化処理した鋼部材の製造方法の製造工程図、第
2図は実験例Iで得られたショット径/窒化鉄被膜の膜
厚と疲労寿命比の関係を示す線図、第3図は実験例IIで
得られたショットのロックウェル硬さとショット速度の
疲労寿命比の関係を示す図である。The drawings relate to an embodiment of the present invention. FIG. 1 is a manufacturing process diagram of a method for manufacturing a steel member subjected to nitriding treatment according to the present embodiment, and FIG. 2 is a shot diameter / iron nitride obtained in Experimental Example I. FIG. 3 is a diagram showing the relationship between the film thickness of the coating and the fatigue life ratio, and FIG. 3 is a diagram showing the relationship between the Rockwell hardness of the shot obtained in Experimental Example II and the fatigue life ratio of the shot speed.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 FI // C22C 38/00 301 C22C 38/00 301Z 38/24 38/24 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 6 Identification symbol FI // C22C 38/00 301 C22C 38/00 301Z 38/24 38/24
Claims (2)
ーステナイト化温度以上に加熱した後冷却して、ベイナ
イトを主体とする金属組織とし、 次にこの鋼部材に窒化処理又は軟窒化処理を施し、 次にこの鋼部材に、ショット径/窒化化合物膜厚=15〜
60、ショットのロックウェル硬さ=45〜60、ショット速
度=50〜120m/secの条件にてショットピーニング処理を
施すことを特徴とする窒化処理した鋼部材の製造方法。The steel member is cooled after hot forging or is heated to an austenitizing temperature or higher and then cooled to obtain a metal structure mainly composed of bainite. Then, the shot diameter / nitride compound film thickness = 15 to
60. A method for producing a nitrided steel member, wherein a shot peening treatment is performed under the conditions of a Rockwell hardness of a shot = 45 to 60 and a shot speed = 50 to 120 m / sec.
が0.15〜0.35、Siが0.50以下、Mnが0.50〜1.20、Crが0.
80〜1.20、Vが0.05〜0.20、Moが0.05〜0.50を含んだ鋼
材料を用いることを特徴とする請求項1に記載の鋼部材
の製造方法。2. The steel material of the steel member is C in weight%.
Is 0.15 to 0.35, Si is 0.50 or less, Mn is 0.50 to 1.20, and Cr is 0.
The method according to claim 1, wherein a steel material containing 80 to 1.20, V of 0.05 to 0.20, and Mo of 0.05 to 0.50 is used.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP30444788A JP2741222B2 (en) | 1988-11-30 | 1988-11-30 | Method for manufacturing a nitrided steel member |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP30444788A JP2741222B2 (en) | 1988-11-30 | 1988-11-30 | Method for manufacturing a nitrided steel member |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH02149616A JPH02149616A (en) | 1990-06-08 |
JP2741222B2 true JP2741222B2 (en) | 1998-04-15 |
Family
ID=17933121
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JP30444788A Expired - Fee Related JP2741222B2 (en) | 1988-11-30 | 1988-11-30 | Method for manufacturing a nitrided steel member |
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JP2005256870A (en) * | 2004-03-09 | 2005-09-22 | Toyota Motor Corp | Method for manufacturing endless metal belt |
JP2006291310A (en) * | 2005-04-12 | 2006-10-26 | Daido Steel Co Ltd | Crankshaft and producing method therefor |
JP4752635B2 (en) * | 2006-06-15 | 2011-08-17 | 住友金属工業株式会社 | Method for manufacturing soft nitrided parts |
JP5025666B2 (en) * | 2009-01-09 | 2012-09-12 | 住友金属工業株式会社 | Nitrided steel |
JP5601990B2 (en) * | 2010-11-24 | 2014-10-08 | 株式会社ヴァレオジャパン | Swash plate compressor and swash plate surface treatment method for swash plate compressor |
WO2012115135A1 (en) * | 2011-02-23 | 2012-08-30 | Dowaサーモテック株式会社 | Nitrided steel member and method for producing same |
JP7365773B2 (en) * | 2019-02-13 | 2023-10-20 | 株式会社日立製作所 | Soft magnetic material and its manufacturing method, and electric motor using soft magnetic material |
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