JP3901504B2 - Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability - Google Patents
Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability Download PDFInfo
- Publication number
- JP3901504B2 JP3901504B2 JP2001382099A JP2001382099A JP3901504B2 JP 3901504 B2 JP3901504 B2 JP 3901504B2 JP 2001382099 A JP2001382099 A JP 2001382099A JP 2001382099 A JP2001382099 A JP 2001382099A JP 3901504 B2 JP3901504 B2 JP 3901504B2
- Authority
- JP
- Japan
- Prior art keywords
- case
- hardenability
- hardened steel
- steel
- cold workability
- 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.)
- Expired - Lifetime
Links
Images
Description
【０００１】
【発明の属する技術分野】
本発明は，冷間加工性および焼入れ性に優れた肌焼鋼，肌焼鋼鋼材および機械構造部品に関する。
【０００２】
【従来の技術】
従来，自動車，産業機械等における各種機械構造部品，特にシャフト，歯車等の表面硬化部品は，肌焼鋼を素材として用い，球状化焼鈍−伸線または伸線−球状化焼鈍−スキンパスによる鋼線の製造，冷間鍛造および機械加工を経て所定の形状に形成され，次いで浸炭，焼入れおよび焼戻しの各処理を順次行うことによって製造されており，これにより，疲労強度，耐摩耗性等の特性を改善された前記部品を得ていた。この場合，球状化焼鈍処理を省略することができれば，部品製造コストの低減を図る上で有利であることから，その球状化焼鈍処理を省略することを可能にすべく，Ｂ（ボロン）を含む肌焼鋼が提案されている（例えば，特開平９−２９６２５１号公報参照）。
【０００３】
【発明が解決しようとする課題】
しかしながら従来のＢを含む肌焼鋼は，Ｂの焼入れ性向上効果により部品芯部硬さは確保できるものの，浸炭部の焼入れ性が不十分であることから，浸炭硬化層にトルースタイト等の不完全焼入れ組織が発生し易い。浸炭硬化層におけるトルースタイトの面積率が大きくなると，歯車やシャフト等の疲労強度や耐摩耗性に悪影響をおよぼすことになる。また，トルースタイトを低減すべく，浸炭焼入れ時に，焼入れ能を向上し得る水焼入れを行った場合，焼割れや，部品のひずみ増大による部品精度の悪化に配慮することも必要になる。
【０００４】
【課題を解決するための手段】
本発明は，化学成分を調整することによって，鋼線の製造工程での球状化焼鈍の省略を可能にした，冷間加工性および焼入れ性に優れた肌焼鋼および肌焼鋼鋼材を提供することを目的とする。
【０００５】
前記目的を達成するため本発明によれば，必須化学成分として，質量％で，０．０５≦Ｃ≦０．３０，Ｓｉ≦０．１５，０．１５≦Ｍｎ≦０．８０，０．００１≦Ｓ≦０．０７０，１．２５≦Ｃｒ≦２．５０，Ｍｏ≦０．１５，Ｎ≦０．０１００および０．０００５≦Ｂ≦０．００５０を含有し，また選択化学成分として，０．００５≦Ｔｉ≦０．１５０，０．００５≦Ｎｂ≦０．１００および０．００５≦Ｖ≦０．１００から選択される少なくとも一種を含有し，残部がＦｅおよび不可避不純物からなる肌焼鋼であって，Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０である，冷間加工性および焼入れ性に優れた肌焼鋼が提供される。
【０００６】
また本発明によれば，必須化学成分として，質量％で，０．０５≦Ｃ≦０．３０，Ｓｉ≦０．１５，０．１５≦Ｍｎ≦０．８０，０．００１≦Ｓ≦０．０７０，１．２５≦Ｃｒ≦２．５０，Ｍｏ≦０．１５，Ｎ≦０．０１００および０．０００５≦Ｂ≦０．００５０を含有し，また選択化学成分として，０．００５≦Ｔｉ≦０．１５０，０．００５≦Ｎｂ≦０．１００および０．００５≦Ｖ≦０．１００から選択される少なくとも一種を含有し，残部がＦｅおよび不可避不純物からなる肌焼鋼鋼材であって，Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０であり，圧延後の硬さＨＲ（ＨＲ：ロックウエル硬さ，以下同じ）がＨＲ≦１００ＨＲＢである，冷間加工性および焼入れ性に優れた肌焼鋼鋼材が提供される。
【０００７】
前記のようにＢ添加を採用すると，肌焼鋼および肌焼鋼鋼材においてその焼入れ性を向上させ，またその他の合金元素の添加量を減少させることができ，結果的に鋼および鋼材の硬さを低減することができる。また，Ｃ，Ｓｉ，Ｍｎ，Ｃｒ，Ｍｏ，Ｓについては，パラメータＸ１をＸ１≦０．７５に管理することによって，圧延後の鋼材の硬さＨＲをＨＲ≦１００ＨＲＢに抑制することが可能である。これにより球状化焼鈍を行わなくても冷間加工に支障のない鋼および鋼材を提供することができる。前記硬さＨＲがＨＲ＞１００ＨＲＢでは冷間における変形抵抗が高く，例えば冷間鍛造時の鍛造荷重が高くなり，金型等の寿命が劣化するだけでなく，工具や鍛造機械の剛性が不足すること等により鍛造後の被鍛材における寸法精度劣化等を招く。したがって，圧延後球状化焼鈍を行わないと冷間加工を支障無く行うことができず，生産性が悪化する。
【０００８】
また，浸炭焼入れ後の芯部硬さを確保するためには，前記と逆に合金元素量を高目に設定する必要がある。そこで，Ｂ添加を前提として，パラメータＸ２をＸ２≧８０とすることによって芯部硬さＨＲをＨＲ≧２５ＨＲＣにすることができる。前記硬さＨＲがＨＲ＜２５ＨＲＣでは機械構造部品において，その強度が不足する。
【０００９】
浸炭硬化層中のトルースタイトは部品表面における疲労強度や耐摩耗性を低下させる原因となるもので，その量を抑制するためには，焼入れ時の冷却速度を上げて上部臨界冷却速度以上とする必要がある。しかしながら，焼入れ設備上の制約や，焼入れ後のひずみの問題から，冷却速度の向上には限界がある。そこで，Ｓｉ，Ｍｎ，Ｃｒ，Ｍｏに関するパラメータＸ３をＸ３≧１０に管理するもので，これにより上部臨界冷却速度を下げて，浸炭硬化層におけるトルースタイト面積率ＡをＡ≦５％に抑えることができる。これは，機械構造部品表面における疲労強度および耐摩耗性の低下を抑制してその部品の延命を図る上に有効である。
【００１０】
各化学成分の添加理由等は次の通りである。
【００１１】
Ｃ： Ｃは母材の強度を確保するために添加される。ただし，Ｃ含有量がＣ＜０．０５では添加効果が乏しく，一方，Ｃ＞０．３０では母材の靱性が低下する。そこで，Ｃ含有量は０．０５≦Ｃ≦０．３０に設定される。
【００１２】
Ｓｉ： Ｓｉは不純物であり，Ｓｉ含有量がＳｉ＞０．１５では鋼材の冷間鍛造性が低下するため，Ｓｉ含有量はＳｉ≦０．１５に設定される。
【００１３】
Ｍｎ： Ｍｎは母材の焼入れ性を向上させる効果を有する。ただし，Ｍｎ含有量がＭｎ＜０．１５では十分な焼入れ性を得ることができず，一方，Ｍｎ＞０．８０では熱間加工性が著しく低下する。そこで，Ｍｎ含有量は０．１５≦Ｍｎ≦０．８０に設定される。
【００１４】
Ｓ：Ｓは母材の被削性を向上させる効果を有する。ただし，Ｓ含有量がＳ＞０．０７０では鍛造性の低下，表面硬化層の靱性劣化等が起こり，一方，Ｓ＜０．００１では添加効果が乏しく，被削性の改善がみられない。そこで，Ｓ含有量は０．００１≦Ｓ≦０．０７０に設定される。
【００１５】
Ｃｒ：浸炭硬化層中のトルースタイト生成量を抑制するためには，Ｃｒ含有量をＣｒ≧１．２５に設定することが必要であり，好ましくは，Ｃｒ≧１．５０である。一方，Ｃｒ＞２．５０では靱性が劣化する。そこで，Ｃｒ含有量は１．２５≦Ｃｒ≦２．５０に設定される。
【００１６】
Ｍｏ： Ｍｏは母材の焼入れ性および芯部硬さを向上させる効果を有するが，過剰に添加すると冷間加工性が低下するため，Ｍｏ含有量はＭｏ≦０．１５に設定される。
【００１７】
Ｎ： Ｎは不純物であって，Ｂと反応してＢＮを形成し易い。ＢＮを形成したＢは母材の焼入れ性向上に寄与しないのでＮの含有量は極力低くする必要がある。そこで，Ｎ含有量はＮ≦０．０１００に設定される。
【００１８】
Ｂ： Ｂは母材の焼入れ性向上のために有効な元素である。ただし，Ｂ含有量がＢ＜０．０００５では焼入れ性の向上が十分でなく，一方，Ｂ＞０．００５０ではその効果が飽和する。そこで，Ｂ含有量は０．０００５≦Ｂ≦０．００５０に設定される。
【００１９】
Ｔｉ，Ｎｂ，Ｖ： Ｂを含む肌焼鋼では，粒界にＢが偏析することにより焼入れ性の向上が図られる反面，加熱時に結晶粒が粗大化し易いという欠点がある。粗粒化抑制のためには微細析出物による粒界のピン留めが有効であり，これにはＴｉ，ＮｂおよびＶから選択され少なくとも一種により炭窒化物を形成するのが有利である。これらの化学成分の添加量が少ないと粒成長抑制効果が乏しく，一方，過剰に添加されると圧延後の鋼材の硬さが上昇して冷間鍛造性が悪化する。そこで，Ｔｉ含有量は０．００５≦Ｔｉ≦０．１５０，Ｎｂ含有量は０．００５≦Ｎｂ≦０．１００，Ｖ含有量は０．００５≦Ｖ≦０．１００にそれぞれ設定される。
【００２０】
前記肌焼鋼および肌焼鋼鋼材に，ＰｂおよびＣａから選択される少なくとも一種を含有させることは，それらの被削性を良好にして，部品の生産性の向上を図り，その生産コストを低減する上で有効である。ただし，ＰｂおよびＣａ含有量がそれぞれＰｂ＞０．３５であるか，Ｃａ＞０．００５０であると，被削性向上効果が飽和し，添加コストが上昇する。一方，Ｐｂ＜０．０１であるか，Ｃａ＜０．０００５では添加効果が乏しく，被削性の改善がみられない。そこで，それらの含有量は０．０１≦Ｐｂ≦０．３５および０．０００５≦Ｃａ≦０．００５０にそれぞれ設定される。
【００２１】
本発明は，化学成分を調整することによって，浸炭焼入れ後の芯部硬さを確保し，且つ，化学成分と浸炭硬化層におけるトルースタイト面積率との関係を明らかにすることによって疲労強度や耐摩耗性の低下を抑制された，ひずみの少ない，肌焼鋼鋼材よりなる機械構造部品を提供することを目的とする。
【００２２】
前記目的を達成するため本発明によれば，必須化学成分として，質量％で，０．０５≦Ｃ≦０．３０，Ｓｉ≦０．１５，０．１５≦Ｍｎ≦０．８０，０．００１≦Ｓ≦０．０７０，１．２５≦Ｃｒ≦２．５０，Ｍｏ≦０．１５，Ｎ≦０．０１００および０．０００５≦Ｂ≦０．００５０を含有し，また選択化学成分として，０．００５≦Ｔｉ≦０．１５０，０．００５≦Ｎｂ≦０．１００および０．００５≦Ｖ≦０．１００から選択される少なくとも一種を含有し，残部がＦｅおよび不可避不純物からなる肌焼鋼鋼材であって，Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５に，Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０に，Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０に，圧延後の硬さＨＲをＨＲ≦１００ＨＲＢにそれぞれ設定された鋼材を用いて得られたものであり，浸炭焼入れ後の芯部硬さＨＲがＨＲ≧２５ＨＲＣであり，また浸炭硬化層におけるトルースタイト面積率ＡがＡ≦５％である，冷間加工性および焼入れ性に優れた肌焼鋼よりなる機械構造部品が提供される。
【００２３】
前記のように構成することによって，球状化焼鈍が省略可能な優れた冷間加工性と，良好な焼入れ性を有する肌焼鋼鋼材を素材として，表面の疲労強度や耐摩耗性を低下させることなく低ひずみで製造コストの低減を実現させた機械構造部品を提供することができる。このような機械構造部品が得られる理由は前記の通りである。
【００２４】
浸炭処理後の焼入れ処理時における冷却媒体温度Ｔは８０℃≦Ｔ≦２５０℃に設定される。一般に冷却媒体温度の低い方が焼入れ能が高いが，低すぎると焼割れやひずみ等の問題が生じるため冷却媒体温度はＴ≧８０℃に設定される。一方，冷却媒体温度ＴがＴ＞２５０℃では不完全焼入れを抑制するのに充分な冷却速度が得られないので，上限温度ＴはＴ＝２５０℃に設定される。
【００２５】
本発明によれば，浸炭焼入れ後の芯部硬さＨＲがＨＲ≧２５ＨＲＣであり，また浸炭硬化層におけるトルースタイト面積率ＡがＡ≦５％である機械構造部品を得るための肌焼鋼鋼材であって，必須化学成分として，質量％で，０．０５≦Ｃ≦０．３０，Ｓｉ≦０．１５，０．１５≦Ｍｎ≦０．８０，０．００１≦Ｓ≦０．０７０，１．２５≦Ｃｒ≦２．５０，Ｍｏ≦０．１５，Ｎ≦０．０１００および０．０００５≦Ｂ≦０．００５０を含有し，また選択化学成分として，０．００５≦Ｔｉ≦０．１５０，０．００５≦Ｎｂ≦０．１００および０．００５≦Ｖ≦０．１００から選択される少なくとも一種を含有し，残部がＦｅおよび不可避不純物からなり，Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０であり，圧延後の硬さＨＲがＨＲ≦１００ＨＲＢである，冷間加工性および焼入れ性に優れた肌焼鋼鋼材も提供される。
【００２６】
【発明の実施の形態】
表１，表２は，各種肌焼鋼鋼材（１）〜（２０），（２１）〜（３８）に関する化学成分を示し，また表３，表４は，各種肌焼鋼鋼材（１）〜（２０），（２１）〜（３８）に関するパラメータＸ１〜Ｘ３を示す。
【００２７】
【表１】
【表２】
【表３】
【表４】
鋼材（１）〜（２０），（２１）〜（３８）に熱間圧延を施して線材を製造した。これらの線材に断面減少率２０％以下の伸線加工を施して鋼線を製造し，その後，これらの鋼線に冷間鍛造を施して直径３０mmのシャフト素材を製造した。これらのシャフト素材に，９３０℃，１４０分間，カーボンポテンシャル０．８％の条件でのガス浸炭処理，焼入れ開始温度８３０℃までの降温，１２０℃の油中への焼入れ（冷却媒体温度Ｔ＝１２０℃）および１８０℃，９０分間の焼戻し，を順次行って機械構造部品であるシャフト（１）〜（２０），（２１）〜（３８）を得た。便宜上，これらのシャフトの符号は，使用された鋼材と同一にした。上記条件は，一般的な浸炭焼入れの例を示したものであり，この例によって本発明が制限されるものではなく，本発明の合致する範囲での変更を加え実施することは可能である。
【００３２】
表５，表６は各シャフト（１）〜（２０），（２１）〜（３８）に関する圧延材の硬さ（ＨＲＢ）と，シャフトにおける浸炭焼入れ後の芯部の硬さ（ＨＲＣ）および浸炭硬化層におけるトルースタイト面積率Ａとを示す。
【００３３】
【表５】
【表６】
表１〜表４および表５，表６から明らかなように，シャフト（１）〜（２０）は本発明における各種要件を満足していることから実施例に該当する。シャフト（２１）〜（３８）は，前記各種要件の一部を欠如しており，したがって比較例に該当する。
【００３６】
表７，表８は実施例に係るシャフト（１）〜（２０）および比較例に係るシャフト（２１）〜（３８）に関する結晶粒度Ｇc と切削性を示す。結晶粒度Ｇc は，シャフト断面における浸炭硬化層の旧オーステナイト粒径をＪＩＳ Ｇ０５５１に則って測定したものである。また切削性については，シャフト断面の中心に，直径１０mmのドリルを用いて，送り速度６０mm／min ，回転数６００rpm ，穴深さ７０mmの条件で穴あけを行い，３００個以上の穴あけが可能であった場合を「◎」とし，また１００個以上の穴あけが可能であった場合を「○」とし，さらに穴あけが１００個未満であった場合を「×」とした。
【００３７】
【表７】
【表８】
表７，表８から，特定量のＮｂ，Ｔｉ，Ｖの作用で結晶粒の成長が抑制されていることが判る。シャフト（３７）はＮｂ等の含有量が少ないため結晶粒の一部が粗大化しており，実用には供し得ない。また特定量のＳ，Ｐｂ，Ｃａの作用で切削性の向上が図られていることが判る。シャフト（２５）はＳの含有量が少なく，またＰｂおよびＣａを含まないことから切削性が著しく低下しており，実用には供し得ない。
【００４０】
表９は，鋼材（１）を使用したシャフト（１）において，前記浸炭焼入れ条件の冷却媒体温度Ｔを変化させた場合の，冷却媒体温度Ｔと，浸炭硬化層におけるトルースタイト面積率Ａおよびひずみとの関係を示す。
【００４１】
【表９】
焼入れ液は，冷却媒体温度ＴがＴ＝２０℃の場合は水を，また冷却媒体温度Ｔが６０℃≦Ｔ≦１８０℃の場合は油を，それを超える温度Ｔの場合はソルトをそれぞれ使用した。ひずみについては，図１に示すように，シャフト（１）から直径３０mm，長さ４００mmの試験片１を作製し，その試験片１を３００mmの間隔に置いた２つのＶブロック２上に載せて回転させ，二等分位置ｈの変位を測定した。冷却媒体温度Ｔを８０℃≦Ｔ≦２５０℃の範囲内に設定すると，浸炭硬化層におけるトルースタイト面積率ＡをＡ≦５％に保持しつつひずみを抑制することができる。
【００４３】
【発明の効果】
本発明によれば前記のように構成することによって，球状化焼鈍が省略可能な優れた冷間加工性と，良好な焼入れ性を有する肌焼鋼および肌焼鋼鋼材を提供することができると共に，その鋼材を素材として，疲労強度や耐摩耗性を低下させることなく低ひずみで製造コストの低減を実現させた機械構造部品を提供することができる。
【図面の簡単な説明】
【図１】ひずみ測定方法を示す説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a case hardening steel, a case hardening steel material, and a machine structural component that are excellent in cold workability and hardenability.
[0002]
[Prior art]
Conventionally, various machine structural parts in automobiles, industrial machines, etc., especially hardened parts such as shafts, gears, etc., use case-hardened steel as a raw material, and steel wire by spheroidizing annealing-drawing or drawing-sphering annealing-skin pass After being manufactured, cold forging, and machining, it is formed into a predetermined shape, and then manufactured by sequentially performing carburizing, quenching, and tempering treatments, thereby improving characteristics such as fatigue strength and wear resistance. Obtained improved parts. In this case, if the spheroidizing annealing process can be omitted, it is advantageous in reducing the manufacturing cost of the parts. Therefore, B (boron) is included to enable the spheroidizing annealing process to be omitted. Case-hardened steel has been proposed (for example, see JP-A-9-296251).
[0003]
[Problems to be solved by the invention]
However, the conventional case hardening steel containing B can ensure the hardness of the core of the part due to the effect of improving the hardenability of B. However, since the hardenability of the carburized part is inadequate, the carburized hardened layer is not resistant to such as troostite. Fully quenched structure is likely to occur. If the area ratio of troostite in the carburized hardened layer increases, it will adversely affect the fatigue strength and wear resistance of gears and shafts. In addition, in order to reduce troostite, when carburizing and quenching with water, which can improve the quenching ability, it is necessary to consider the deterioration of component accuracy due to quench cracking and increased component distortion.
[0004]
[Means for Solving the Problems]
The present invention provides a case-hardening steel and a case-hardening steel material excellent in cold workability and hardenability, which can omit the spheroidizing annealing in the manufacturing process of the steel wire by adjusting the chemical composition. For the purpose.
[0005]
In order to achieve the above object, according to the present invention, as essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001. ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050. A case-hardened steel containing at least one selected from 005 ≦ Ti ≦ 0.150, 0.005 ≦ Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, with the balance being Fe and inevitable impurities. X1 is changed to X1 = [C] + (1/10) [Si] + (1/5) [Mn] + (5/22) [Cr] + (1/3) [Mo] − (5 / 7) [S] (where [C] means the C content value, which is the same for other chemical components) ), X1 ≦ 0.75, and X2 is set to X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr] ) When (1 + 3.14 [Mo]), X2 ≧ 80, and when X3 is X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10 A case-hardened steel excellent in cold workability and hardenability is provided.
[0006]
Further, according to the present invention, as essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0. 070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and 0.005 ≦ Ti ≦ 0 as selective chemical components 150, 0.005 ≦ Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, containing at least one selected from the group consisting of Fe and inevitable impurities, , X1 = [C] + (1/10) [Si] + (1/5) [Mn] + (5/22) [Cr] + (1/3) [Mo] − (5/7) [S ] (However, [C] means the value of C content, which is the same for other chemical components) X1 ≦ 0.75, and X2 is set to X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3.14 [Mo]), X2 ≧ 80, and when X3 = X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10, after rolling A case-hardened steel with excellent cold workability and hardenability is provided in which the hardness HR (HR: Rockwell hardness, hereinafter the same) is HR ≦ 100HRB.
[0007]
When B addition is employed as described above, the hardenability can be improved in case-hardened steel and case-hardened steel, and the amount of other alloy elements added can be reduced, resulting in the hardness of steel and steel. Can be reduced. Further, for C, Si, Mn, Cr, Mo, and S, the hardness HR of the steel material after rolling can be suppressed to HR ≦ 100HRB by managing the parameter X1 to X1 ≦ 0.75. . As a result, it is possible to provide a steel and a steel material that do not hinder the cold working without performing spheroidizing annealing. When the hardness HR is HR> 100HRB, the deformation resistance in the cold is high, for example, the forging load at the time of cold forging becomes high, and not only the life of the die and the like is deteriorated but also the rigidity of the tool and the forging machine is insufficient. This causes deterioration of dimensional accuracy in the forged material after forging. Therefore, if spheroidizing annealing is not performed after rolling, cold working cannot be performed without hindrance, and productivity deteriorates.
[0008]
Also, in order to ensure the core hardness after carburizing and quenching, it is necessary to set the amount of alloying elements at a high level, contrary to the above. Therefore, assuming that B is added, the core hardness HR can be set to HR ≧ 25HRC by setting the parameter X2 to X2 ≧ 80. When the hardness HR is HR <25HRC, the mechanical structural component has insufficient strength.
[0009]
The troostite in the carburized hardened layer causes a decrease in fatigue strength and wear resistance on the part surface. In order to suppress the amount, the cooling rate during quenching is increased so that it exceeds the upper critical cooling rate. There is a need. However, there are limits to improving the cooling rate due to limitations on the quenching equipment and distortion problems after quenching. Therefore, the parameter X3 related to Si, Mn, Cr, and Mo is managed so that X3 ≧ 10, thereby lowering the upper critical cooling rate and suppressing the troostite area ratio A in the carburized hardened layer to A ≦ 5%. it can. This is effective in preventing the deterioration of fatigue strength and wear resistance on the surface of machine structural parts and prolonging the life of the parts.
[0010]
The reason for adding each chemical component is as follows.
[0011]
C: C is added to ensure the strength of the base material. However, when the C content is C <0.05, the effect of addition is poor, while when C> 0.30, the toughness of the base material is lowered. Therefore, the C content is set to 0.05 ≦ C ≦ 0.30.
[0012]
Si: Si is an impurity, and when the Si content is Si> 0.15, the cold forgeability of the steel material decreases, so the Si content is set to Si ≦ 0.15.
[0013]
Mn: Mn has the effect of improving the hardenability of the base material. However, when the Mn content is Mn <0.15, sufficient hardenability cannot be obtained. On the other hand, when Mn> 0.80, hot workability is remarkably lowered. Therefore, the Mn content is set to 0.15 ≦ Mn ≦ 0.80.
[0014]
S: S has the effect of improving the machinability of the base material. However, when the S content is S> 0.070, the forgeability is reduced and the toughness of the surface hardened layer is deteriorated. On the other hand, when S <0.001, the effect of addition is poor and the machinability is not improved. Therefore, the S content is set to 0.001 ≦ S ≦ 0.070.
[0015]
Cr: In order to suppress the production amount of troostite in the carburized hardened layer, it is necessary to set the Cr content to Cr ≧ 1.25, and preferably Cr ≧ 1.50. On the other hand, if Cr> 2.50, the toughness deteriorates. Therefore, the Cr content is set to 1.25 ≦ Cr ≦ 2.50.
[0016]
Mo: Mo has the effect of improving the hardenability and core hardness of the base material, but if added excessively, the cold workability is lowered, so the Mo content is set to Mo ≦ 0.15.
[0017]
N: N is an impurity and tends to react with B to form BN. Since B forming BN does not contribute to the improvement of the hardenability of the base material, the N content needs to be made as low as possible. Therefore, the N content is set to N ≦ 0.0100.
[0018]
B: B is an effective element for improving the hardenability of the base material. However, when the B content is B <0.0005, the hardenability is not sufficiently improved, while when B> 0.0050, the effect is saturated. Therefore, the B content is set to 0.0005 ≦ B ≦ 0.0050.
[0019]
In case hardening steel containing Ti, Nb, V: B, segregation of B at the grain boundary improves the hardenability, but there is a drawback that the crystal grains are likely to be coarsened during heating. In order to suppress the coarsening, pinning of grain boundaries by fine precipitates is effective, and it is advantageous to form carbonitride by at least one selected from Ti, Nb and V. If the addition amount of these chemical components is small, the effect of suppressing grain growth is poor. On the other hand, if added excessively, the hardness of the steel material after rolling increases and the cold forgeability deteriorates. Therefore, the Ti content is set to 0.005 ≦ Ti ≦ 0.150, the Nb content is set to 0.005 ≦ Nb ≦ 0.100, and the V content is set to 0.005 ≦ V ≦ 0.100.
[0020]
Inclusion of at least one selected from Pb and Ca in the case-hardened steel and case-hardened steel material improves their machinability, improves the productivity of parts, and reduces the production cost. It is effective in doing. However, if the Pb and Ca contents are respectively Pb> 0.35 or Ca> 0.0050, the machinability improving effect is saturated and the addition cost is increased. On the other hand, when Pb <0.01 or Ca <0.0005, the effect of addition is poor and machinability is not improved. Therefore, their contents are set to 0.01 ≦ Pb ≦ 0.35 and 0.0005 ≦ Ca ≦ 0.0050, respectively.
[0021]
The present invention ensures the hardness of the core after carburizing and quenching by adjusting the chemical composition, and clarifies the relationship between the chemical composition and the troostite area ratio in the carburized hardened layer, thereby improving the fatigue strength and resistance. The object is to provide a machine structural part made of case-hardened steel with reduced wear and reduced distortion.
[0022]
In order to achieve the above object, according to the present invention, as essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001. ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050. A case-hardened steel material containing at least one selected from 005 ≦ Ti ≦ 0.150, 0.005 ≦ Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, with the balance being Fe and inevitable impurities. X1 is represented by X1 = [C] + (1/10) [Si] + (1/5) [Mn] + (5/22) [Cr] + (1/3) [Mo] − (5 / 7) [S] (However, [C] means the value of C content, which is the same for other chemical components. When X1 ≦ 0.75, X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr] ) When (1 + 3.14 [Mo]), X2 ≧ 80 and when X3 = X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10 , The hardness HR after rolling is obtained using steel materials each set to HR ≦ 100HRB, the core hardness HR after carburizing and quenching is HR ≧ 25HRC, and the troustite in the carburized hardened layer There is provided a machine structural component made of case-hardened steel having an area ratio A of A ≦ 5% and excellent in cold workability and hardenability.
[0023]
By configuring as described above, the surface fatigue strength and wear resistance are reduced by using a case-hardened steel material having excellent cold workability that can omit spheroidizing annealing and good hardenability. In addition, it is possible to provide a machine structural component that realizes a reduction in manufacturing cost with low distortion. The reason why such a mechanical structural part is obtained is as described above.
[0024]
The cooling medium temperature T during the quenching process after the carburizing process is set to 80 ° C. ≦ T ≦ 250 ° C. In general, the lower the cooling medium temperature, the higher the quenching ability, but if it is too low, problems such as cracking and distortion occur, so the cooling medium temperature is set to T ≧ 80 ° C. On the other hand, when the cooling medium temperature T is T> 250 ° C., a cooling rate sufficient to suppress incomplete quenching cannot be obtained, so the upper limit temperature T is set to T = 250 ° C.
[0025]
According to the present invention, the case-hardened steel for obtaining a machine structural part having a core hardness HR after carburizing and quenching HR ≧ 25HRC and a troostite area ratio A in the carburized hardened layer A ≦ 5%. As essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0.070,1 .25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and 0.005 ≦ Ti ≦ 0.150 as a selective chemical component, It contains at least one selected from 0.005 ≦ Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, the balance is made of Fe and inevitable impurities, and X1 is expressed as X1 = [C] + (1 / 10) [Si] + (1/5) [Mn] + (5/22) Cr] + (1/3) [Mo] − (5/7) [S] (where [C] means the C content value, which is the same for other chemical components) , X1 ≦ 0.75, and X2 is set to X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3. 14 [Mo]), X2 ≧ 80, and when X3 = X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10, and rolling There is also provided a case-hardened steel material having a later hardness HR of HR ≦ 100HRB and excellent in cold workability and hardenability.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Tables 1 and 2 show chemical components related to various case-hardened steel materials (1) to (20) and (21) to (38), and Tables 3 and 4 show various case-hardened steel materials (1) to (1) to Parameters X1 to X3 related to (20) and (21) to (38) are shown.
[0027]
[Table 1]
[Table 2]
[Table 3]
[Table 4]
The steel materials (1) to (20) and (21) to (38) were hot-rolled to produce a wire. These wires were subjected to wire drawing with a cross-section reduction rate of 20% or less to produce steel wires, and then these steel wires were subjected to cold forging to produce a shaft material having a diameter of 30 mm. These shaft materials were subjected to gas carburizing treatment under conditions of 930 ° C. for 140 minutes and a carbon potential of 0.8%, cooling to a quenching start temperature of 830 ° C., quenching in oil at 120 ° C. (cooling medium temperature T = 120 And shafts (1) to (20) and (21) to (38), which are mechanical structural parts, were obtained by sequentially performing tempering for 90 minutes. For convenience, the code for these shafts was the same as the steel used. The above conditions show an example of general carburizing and quenching, and the present invention is not limited by this example. It is possible to carry out the present invention with modifications within the scope of the present invention.
[0032]
Tables 5 and 6 show the hardness (HRB) of the rolled material with respect to the shafts (1) to (20) and (21) to (38), the hardness of the core after carburizing and quenching in the shaft (HRC), and carburizing. The troostite area ratio A in a hardened layer is shown.
[0033]
[Table 5]
[Table 6]
As is clear from Tables 1 to 4 and Tables 5 and 6, the shafts (1) to (20) correspond to the examples because they satisfy various requirements in the present invention. The shafts (21) to (38) lack some of the various requirements, and thus correspond to comparative examples.
[0036]
Tables 7 and 8 show the crystal grain size Gc and the machinability of the shafts (1) to (20) according to the examples and the shafts (21) to (38) according to the comparative examples. The crystal grain size G c is obtained by measuring the prior austenite grain size of the carburized hardened layer in the shaft cross section in accordance with JIS G0551. In addition, with regard to machinability, a drill with a diameter of 10 mm was used in the center of the shaft cross section, drilling was performed at a feed rate of 60 mm / min, a rotation speed of 600 rpm, and a hole depth of 70 mm, and 300 or more holes could be drilled. In this case, “◎” was assigned, “◯” was assigned when 100 or more holes were possible, and “x” was assigned when less than 100 holes were made.
[0037]
[Table 7]
[Table 8]
From Tables 7 and 8, it can be seen that the growth of crystal grains is suppressed by the action of specific amounts of Nb, Ti, and V. Since the shaft (37) has a small content of Nb or the like, some of the crystal grains are coarsened and cannot be put to practical use. It can also be seen that the machinability is improved by the action of specific amounts of S, Pb, and Ca. The shaft (25) has a low content of S and does not contain Pb and Ca, so that the machinability is remarkably lowered and cannot be put to practical use.
[0040]
Table 9 shows the cooling medium temperature T in the shaft (1) using the steel material (1) when the cooling medium temperature T under the above carburizing and quenching conditions is changed, and the troostite area ratio A and strain in the carburized hardened layer. Shows the relationship.
[0041]
[Table 9]
The quenching liquid uses water when the cooling medium temperature T is T = 20 ° C., uses oil when the cooling medium temperature T is 60 ° C ≦ T ≦ 180 ° C., and uses salt when the temperature T exceeds the cooling medium temperature T. did. As for the strain, as shown in FIG. 1, a test piece 1 having a diameter of 30 mm and a length of 400 mm is prepared from the shaft (1), and the test piece 1 is placed on two
[0043]
【The invention's effect】
According to the present invention, it is possible to provide a case-hardening steel and a case-hardening steel material having excellent cold workability that can omit the spheroidizing annealing and good hardenability by being configured as described above. , By using the steel as a raw material, it is possible to provide a machine structural component that realizes a reduction in manufacturing cost with low strain without reducing fatigue strength and wear resistance.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a strain measuring method.
Claims (9)
Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］
＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，
Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，
Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０である
ことを特徴とする，冷間加工性および焼入れ性に優れた肌焼鋼。As essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and as selective chemical components, 0.005 ≦ Ti ≦ 0.150, 0.005 ≦ A case-hardening steel containing at least one selected from Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, the balance being Fe and inevitable impurities,
X1 is changed to X1 = [C] + (1/10) [Si] + (1/5) [Mn]
+ (5/22) [Cr] + (1/3) [Mo] − (5/7) [S] (where [C] means the value of the C content, and this is for other chemical components. X1 ≦ 0.75, and
When X2 is X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3.14 [Mo]) X2 ≧ 80,
X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo] When X3 ≧ 10, the skin excellent in cold workability and hardenability Burnt steel.
Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］
＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，
Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，
Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０であり，
圧延後の硬さＨＲがＨＲ≦１００ＨＲＢである
ことを特徴とする，冷間加工性および焼入れ性に優れた肌焼鋼鋼材。As essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and as selective chemical components, 0.005 ≦ Ti ≦ 0.150, 0.005 ≦ A case-hardened steel material containing at least one selected from Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, the balance being Fe and inevitable impurities,
X1 is changed to X1 = [C] + (1/10) [Si] + (1/5) [Mn]
+ (5/22) [Cr] + (1/3) [Mo] − (5/7) [S] (where [C] means the value of the C content, and this is for other chemical components. X1 ≦ 0.75, and
When X2 is X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3.14 [Mo]) X2 ≧ 80,
When X3 is X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10,
A case-hardened steel with excellent cold workability and hardenability, characterized in that the hardness HR after rolling is HR ≦ 100HRB.
Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］
＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５であり，
Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０であり，
Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０であり，
圧延後の硬さＨＲがＨＲ≦１００ＨＲＢである
ことを特徴とする，冷間加工性および焼入れ性に優れた肌焼鋼鋼材。A case-hardened steel for obtaining a machine structural part having a core hardness HR of HR ≧ 25HRC after carburizing and quenching and a troostite area ratio A in a carburized hardened layer of A ≦ 5% As components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2 .50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and 0.005 ≦ Ti ≦ 0.150, 0.005 ≦ Nb ≦ Containing at least one selected from 0.100 and 0.005 ≦ V ≦ 0.100, with the balance consisting of Fe and inevitable impurities,
X1 is changed to X1 = [C] + (1/10) [Si] + (1/5) [Mn]
+ (5/22) [Cr] + (1/3) [Mo] − (5/7) [S] (where [C] means the value of the C content, and this is for other chemical components. X1 ≦ 0.75, and
When X2 is X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3.14 [Mo]) X2 ≧ 80,
When X3 is X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10,
A case-hardened steel with excellent cold workability and hardenability, characterized in that the hardness HR after rolling is HR ≦ 100HRB.
Ｘ１を，Ｘ１＝［Ｃ］＋（１／１０）［Ｓｉ］＋（１／５）［Ｍｎ］
＋（５／２２）［Ｃｒ］＋（１／３）［Ｍｏ］−（５／７）［Ｓ］（但し，［Ｃ］はＣ含有量の数値を意味し，これは他の化学成分について同じである）としたとき，Ｘ１≦０．７５に，
Ｘ２を，Ｘ２＝１５．２５（√［Ｃ］）（１＋０．６４［Ｓｉ］）（１＋４．１［Ｍｎ］）（１＋２．３３［Ｃｒ］）（１＋３．１４［Ｍｏ］）としたとき，Ｘ２≧８０に，
Ｘ３を，Ｘ３＝［Ｓｉ］＋０．５［Ｍｎ］＋８［Ｃｒ］＋０．５［Ｍｏ］としたとき，Ｘ３≧１０に，
圧延後の硬さＨＲをＨＲ≦１００ＨＲＢに
それぞれ設定された鋼材を用いて得られたものであり，浸炭焼入れ後の芯部硬さＨＲがＨＲ≧２５ＨＲＣであり，また浸炭硬化層におけるトルースタイト面積率ＡがＡ≦５％であることを特徴とする，冷間加工性および焼入れ性に優れた肌焼鋼鋼材よりなる機械構造部品。As essential chemical components, by mass%, 0.05 ≦ C ≦ 0.30, Si ≦ 0.15, 0.15 ≦ Mn ≦ 0.80, 0.001 ≦ S ≦ 0.070, 1.25 ≦ Cr ≦ 2.50, Mo ≦ 0.15, N ≦ 0.0100 and 0.0005 ≦ B ≦ 0.0050, and as selective chemical components, 0.005 ≦ Ti ≦ 0.150, 0.005 ≦ A case-hardened steel material containing at least one selected from Nb ≦ 0.100 and 0.005 ≦ V ≦ 0.100, the balance being Fe and inevitable impurities,
X1 is changed to X1 = [C] + (1/10) [Si] + (1/5) [Mn]
+ (5/22) [Cr] + (1/3) [Mo] − (5/7) [S] (where [C] means the value of the C content, and this is for other chemical components. X1 ≦ 0.75,
When X2 is X2 = 15.25 (√ [C]) (1 + 0.64 [Si]) (1 + 4.1 [Mn]) (1 + 2.33 [Cr]) (1 + 3.14 [Mo]) X2 ≧ 80,
When X3 is X3 = [Si] +0.5 [Mn] +8 [Cr] +0.5 [Mo], X3 ≧ 10,
The hardness HR after rolling was obtained by using steel materials each set to HR ≦ 100HRB, the core hardness HR after carburizing and quenching was HR ≧ 25HRC, and the area of truastite in the carburized hardened layer A machine structural part made of case-hardened steel with excellent cold workability and hardenability, characterized in that the rate A is A ≦ 5%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001382099A JP3901504B2 (en) | 2001-12-14 | 2001-12-14 | Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001382099A JP3901504B2 (en) | 2001-12-14 | 2001-12-14 | Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2003183773A JP2003183773A (en) | 2003-07-03 |
| JP3901504B2 true JP3901504B2 (en) | 2007-04-04 |
Family
ID=27592579
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2001382099A Expired - Lifetime JP3901504B2 (en) | 2001-12-14 | 2001-12-14 | Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3901504B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107406943A (en) * | 2015-03-31 | 2017-11-28 | 新日铁住金株式会社 | Surface hardened layer steel part |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4964060B2 (en) * | 2007-08-17 | 2012-06-27 | 株式会社神戸製鋼所 | Mechanical structural steel and mechanical structural parts with excellent strength anisotropy and machinability |
| JP5458048B2 (en) | 2011-03-29 | 2014-04-02 | 株式会社神戸製鋼所 | Case-hardened steel, its manufacturing method, and machine structural parts using case-hardened steel |
| JP6094180B2 (en) * | 2012-11-30 | 2017-03-15 | Ｊｆｅスチール株式会社 | Machine structural steel with excellent cold forgeability and toughness |
| JP5790693B2 (en) * | 2013-03-29 | 2015-10-07 | Ｊｆｅスチール株式会社 | Case-hardened steel for cold forging |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05263183A (en) * | 1992-03-19 | 1993-10-12 | Sumitomo Metal Ind Ltd | Carburizing case hardening steel excellent in delayed fracture resistance |
| JPH07310118A (en) * | 1994-05-16 | 1995-11-28 | Daido Steel Co Ltd | Production of case hardening steel suitable for cold-working |
| JPH0892690A (en) * | 1994-09-27 | 1996-04-09 | Sumitomo Metal Ind Ltd | Carburized parts excellent in fatigue resistance and its production |
| JP3269374B2 (en) * | 1996-03-06 | 2002-03-25 | 住友金属工業株式会社 | Carburized gear |
| JP3329177B2 (en) * | 1996-03-21 | 2002-09-30 | 住友金属工業株式会社 | Carburized parts with excellent bending strength and impact properties |
-
2001
- 2001-12-14 JP JP2001382099A patent/JP3901504B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107406943A (en) * | 2015-03-31 | 2017-11-28 | 新日铁住金株式会社 | Surface hardened layer steel part |
| CN107406943B (en) * | 2015-03-31 | 2019-06-07 | 新日铁住金株式会社 | Surface hardened layer steel part |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2003183773A (en) | 2003-07-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4725401B2 (en) | Steel parts and manufacturing method thereof | |
| US10202677B2 (en) | Production method of carburized steel component and carburized steel component | |
| JP6610808B2 (en) | Soft nitriding steel and parts | |
| JP4464862B2 (en) | Case-hardening steel with excellent grain coarsening resistance and cold workability that can be omitted for soft annealing. | |
| JP5260460B2 (en) | Case-hardened steel parts and manufacturing method thereof | |
| JP5258458B2 (en) | Gears with excellent surface pressure resistance | |
| JP6225965B2 (en) | Soft nitriding steel and parts, and methods for producing them | |
| JP5370073B2 (en) | Alloy steel for machine structural use | |
| JP3915710B2 (en) | Carburized differential gear with excellent low cycle impact fatigue resistance | |
| JP4464861B2 (en) | Case hardening steel with excellent grain coarsening resistance and cold workability | |
| JP3901504B2 (en) | Case-hardened steel, case-hardened steel and machine structural parts with excellent cold workability and hardenability | |
| JP6431456B2 (en) | Soft nitriding steel and parts, and methods for producing them | |
| JP2002212672A (en) | Steel member | |
| JP4536327B2 (en) | Nb-containing case-hardened steel with excellent carburizing properties in a short time | |
| JP7263796B2 (en) | RING GEAR FOR AUTOMOBILE TRANSMISSION AND MANUFACTURING METHOD THEREOF | |
| JP3236883B2 (en) | Case hardening steel and method for manufacturing steel pipe using the same | |
| JP3849296B2 (en) | Method of manufacturing steel for nitrocarburizing and nitrocarburized component using the steel | |
| JPH05239602A (en) | High bearing pressure parts | |
| JP2001032037A (en) | Low distortion steel for gear, excellent in pitting resistance, and manufacture of gear using the steel | |
| JP2009235562A (en) | Steel for cold press die excellent in machinability, heat treatment dimensional change characteristic and impact characteristic, and press die | |
| JP4821582B2 (en) | Steel for vacuum carburized gear | |
| JP4506374B2 (en) | Manufacturing method of gear material for high speed dry cutting and manufacturing method of gear using the gear material | |
| JP2706940B2 (en) | Manufacturing method of non-heat treated steel for nitriding | |
| CN107532252B (en) | Case hardening steel | |
| JP2021028414A (en) | Steel for carburized gear, carburized gear, and manufacturing method of carburized gear |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20040713 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20040818 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20061213 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20061226 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 3901504 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100112 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20100112 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110112 Year of fee payment: 4 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110112 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20110112 Year of fee payment: 4 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120112 Year of fee payment: 5 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120112 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120112 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20120112 Year of fee payment: 5 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130112 Year of fee payment: 6 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313115 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130112 Year of fee payment: 6 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130112 Year of fee payment: 6 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313115 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140112 Year of fee payment: 7 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313117 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| EXPY | Cancellation because of completion of term |