JP2019026899A - Carburization component and carbonitride component - Google Patents
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Abstract
Description
この発明は浸炭部品および浸炭窒化部品に関し、詳しくは歯車等の動力伝達部品として好適なものに関する。 The present invention relates to a carburized component and a carbonitrided component, and more particularly to a component suitable as a power transmission component such as a gear.
歯車等の動力伝達部品は、曲げ疲労強度に加え、高いピッチング疲労強度が要求される。このような部品の材料としては、従来ＪＩＳ ＳＣＲ４２０などが用いられ、そこに種々の表面処理による高強度化が施されてきた。 Power transmission parts such as gears are required to have high pitting fatigue strength in addition to bending fatigue strength. Conventionally, JIS SCR420 or the like has been used as a material for such parts, and the strength has been increased by various surface treatments.
歯車等におけるピッチングの現象は、歯面と歯面とが擦れ合うことによって発生する高い応力により亀裂発生、亀裂進行及び剥離する現象である。このとき歯面等の接触面には高い面圧が負荷され、さらに繰返し摩擦を受けるため、３００℃程度まで温度上昇を引き起こす。よって、歯面強度（ピッチング疲労強度）は軟化抵抗性（高温に保持した時の軟化のしにくさ）と相関がある。 The phenomenon of pitching in a gear or the like is a phenomenon in which cracks are generated, crack progresses, and peels off due to high stress generated by rubbing between tooth surfaces. At this time, a high contact pressure is applied to the contact surface such as the tooth surface, and the friction surface is repeatedly subjected to friction, so that the temperature rises to about 300 ° C. Therefore, tooth surface strength (pitching fatigue strength) is correlated with softening resistance (hardness of softening when held at high temperature).
ピッチング疲労強度の向上策としては、浸炭窒化処理や高濃度浸炭処理が知られている。浸炭窒化処理は処理材の表層に炭素とともに窒素を導入して、焼戻し軟化抵抗を向上させる処理である。一方、高濃度浸炭処理は処理材の表層への炭素供給を増加させ、表層に硬質の炭化物を分散析出させ焼戻し軟化抵抗を向上させる処理である。 As measures for improving the pitching fatigue strength, carbonitriding and high-concentration carburizing are known. The carbonitriding process is a process for improving the temper softening resistance by introducing nitrogen into the surface layer of the treatment material together with carbon. On the other hand, the high-concentration carburizing treatment is a treatment for increasing the carbon supply to the surface layer of the treatment material and dispersing and precipitating hard carbides on the surface layer to improve the temper softening resistance.
また、ピッチング疲労強度の向上策として、上記の浸炭窒化及び高濃度浸炭を組合せた高濃度浸炭窒化処理も提案されている（下記特許文献１参照）。高濃度浸炭窒化処理は、処理材の表層におけるＮ量や析出炭化物を制御することで焼戻し軟化抵抗の向上を図るものである。
しかしながら、高濃度浸炭処理ではＣが、また高濃度浸炭窒化処理ではＣ及びＮが、鋼材の表層に多く固溶するため、焼入れ後に多量の残留オーステナイト（以下、残留γとする）が生成し易い。多量の残留γが発生すると局所的に表層の硬度が低下して、負荷荷重に耐えられず曲げ疲労強度等が低下してしまう問題があり、高濃度浸炭処理が施された浸炭部品や高濃度浸炭窒化処理が施された浸炭窒化部品については、ピッチング疲労強度及び曲げ疲労強度の両立が図られておらず未だ改善の余地があった。
Further, as a measure for improving the pitching fatigue strength, a high-concentration carbonitriding process combining the above carbonitriding and high-concentration carburization has also been proposed (see Patent Document 1 below). High concentration carbonitriding is intended to improve the temper softening resistance by controlling the amount of N in the surface layer of the treated material and the precipitated carbide.
However, a large amount of residual austenite (hereinafter referred to as residual γ) is likely to be formed after quenching because C is dissolved in the high concentration carburizing process and C and N are dissolved in the surface layer of the steel material in the high concentration carbonitriding process. . When a large amount of residual γ occurs, the hardness of the surface layer locally decreases, and there is a problem that bending fatigue strength etc. is not able to withstand load load, carburized parts that have been subjected to high concentration carburizing treatment and high concentration The carbonitrided parts that have been subjected to carbonitriding have not yet been able to achieve both pitting fatigue strength and bending fatigue strength, and there is still room for improvement.
本発明は以上のような事情を背景とし、浸炭層や浸炭窒化層における残留γの多量生成を抑制して、以てピッチング疲労強度及び曲げ疲労強度を高めた浸炭部品および浸炭窒化部品を提供することを目的としてなされたものである。 The present invention provides a carburized part and a carbonitrided part that have increased pitching fatigue strength and bending fatigue strength by suppressing the formation of a large amount of residual γ in the carburized layer and the carbonitrided layer in the background as described above. It was made for the purpose.
而して請求項１は浸炭部品に関するもので、質量％で、Ｃ：０．１４〜０．３８％、Ｓｉ：０．０１〜１．５０％、Ｍｎ：０．２０〜２．０％、Ｃｕ：０．５％以下、Ｎｉ：０．８％以下、Ｃｒ：０．５０〜４．５％、Ｍｏ：０．８％以下、Ａｌ：０．０１０〜０．０６０％、Ｎ：０．００５〜０．０３０％、を含有し、残部Ｆｅ及び不可避的不純物の組成を有し且つ下記式（１）を満たす鋼からなり、
浸炭層を表層に有し、該表層は、炭化物面積率が５〜４０％で、更に残留γ量が４０％未満であることを特徴とする。
−0.19＞−0.102［Si］−0.03［Cu］−0.01［Ni］−0.135［Cr］ ・・・式（１）
（但し式（１）中各元素記号は含有質量％を表す）
Thus, Claim 1 relates to a carburized part, and in terms of mass%, C: 0.14 to 0.38%, Si: 0.01 to 1.50%, Mn: 0.20 to 2.0%, Cu: 0.5% or less, Ni: 0.8% or less, Cr: 0.50 to 4.5%, Mo: 0.8% or less, Al: 0.010 to 0.060%, N: 0.00. 005 to 0.030%, made of steel having the composition of the balance Fe and inevitable impurities and satisfying the following formula (1),
The surface layer has a carburized layer, and the surface layer has a carbide area ratio of 5 to 40% and a residual γ amount of less than 40%.
−0.19> −0.102 [Si] −0.03 [Cu] −0.01 [Ni] −0.135 [Cr] (1)
(However, each element symbol in the formula (1) represents mass%)
請求項２のものは、請求項１において、前記鋼の合金成分として質量％で、Ｎｂ：０．１％以下を更に含有することを特徴とする。 According to a second aspect of the present invention, in the first aspect, the alloy component of the steel further includes Nb: 0.1% or less by mass%.
請求項３は浸炭窒化部品に関するもので、質量％で、Ｃ：０．１４〜０．３８％、Ｓｉ：０．０１〜１．５０％以下、Ｍｎ：０．２０〜２．０％、Ｃｕ：０．５％以下、Ｎｉ：０．８％以下、Ｃｒ：０．５０〜４．５％、Ｍｏ：０．８％以下、Ａｌ：０．０１０〜０．０６０％、Ｎ：０．００５〜０．０３０％、を含有し、残部Ｆｅ及び不可避的不純物の組成を有し且つ下記式（１）を満たす鋼からなり、
浸炭窒化層を表層に有し、該表層は、Ｎ濃度が質量％で０．０５〜０．５％、炭化物面積率が５〜４０％で、更に残留γ量が４０％未満であることを特徴とする。
−0.19＞−0.102［Si］−0.03［Cu］−0.01［Ni］−0.135［Cr］ ・・・式（１）
（但し式（１）中各元素記号は含有質量％を表す）
Claim 3 relates to carbonitrided parts, and in mass%, C: 0.14 to 0.38%, Si: 0.01 to 1.50% or less, Mn: 0.20 to 2.0%, Cu : 0.5% or less, Ni: 0.8% or less, Cr: 0.50 to 4.5%, Mo: 0.8% or less, Al: 0.010 to 0.060%, N: 0.005 -0.030%, comprising the balance Fe and inevitable impurities and satisfying the following formula (1),
It has a carbonitriding layer as a surface layer, and the surface layer has an N concentration of 0.05 to 0.5% by mass, a carbide area ratio of 5 to 40%, and a residual γ amount of less than 40%. Features.
−0.19> −0.102 [Si] −0.03 [Cu] −0.01 [Ni] −0.135 [Cr] (1)
(However, each element symbol in the formula (1) represents mass%)
請求項４のものは、請求項３において、前記鋼の合金成分として質量％で、Ｎｂ：０．１％以下を更に含有することを特徴とする。 According to a fourth aspect of the present invention, in the third aspect of the present invention, the alloy component of the steel further includes Nb: 0.1% or less by mass%.
高濃度浸炭処理や高濃度浸炭窒化処理は、例えば図１に示すような処理パターンで行われる。先ず１次浸炭・焼入れを実施した後、処理材を再度昇温して炭化物を析出させる。その後、再度浸炭（２次浸炭）を行い炭化物を成長させ、その後、焼入れを行なう。
なお、高濃度浸炭処理では、２次浸炭の際にアセチレン等の浸炭ガスを導入するのに対し、高濃度浸炭窒化処理では、２次浸炭の際に浸炭ガスと窒化のためのアンモニアガスとを交互に導入し、浸炭とともに窒化を行なう。
The high-concentration carburizing process or the high-concentration carbonitriding process is performed with a processing pattern as shown in FIG. First, after performing primary carburization and quenching, the temperature of the treated material is increased again to precipitate carbide. Thereafter, carburization (secondary carburization) is performed again to grow carbides, and then quenching is performed.
In the high-concentration carburizing process, a carburizing gas such as acetylene is introduced in the secondary carburizing process, whereas in the high-concentrating carbonitriding process, the carburizing gas and the ammonia gas for nitriding are used in the secondary carburizing process. Introduce alternately and perform nitriding with carburizing.
ところで２次浸炭後の焼入れ時における固溶Ｃ濃度は、状態図におけるＡｃｍ点の濃度にほぼ対応する。一般に、固溶Ｃ濃度が過剰になると、焼入れ後の残留γが多くなり硬さが低下すること、また固溶Ｃに加えて固溶Ｎが多くなれば更に残留γが増加することが知られている。
本発明者らは、従来の浸炭処理に比べて鋼材の表層におけるＣ濃度が高くなる高濃度浸炭処理や、Ｃ濃度およびＮ濃度が高くなる高濃度浸炭窒化処理における残留γの生成を抑制すべく、ＳＣＲ４２０材をベースとして各合金元素の添加量を変化させ、８５０℃における固溶Ｃ濃度の変化を調査及び研究したところ、固溶Ｃ濃度に対しては、特にＳｉ量及びＣｒ量の影響が大きいことを見出した。
By the way, the solute C concentration at the time of quenching after the secondary carburizing substantially corresponds to the concentration at the Acm point in the phase diagram. In general, it is known that when the concentration of solute C is excessive, residual γ after quenching increases and hardness decreases, and when solute N increases in addition to solute C, the residual γ increases further. ing.
In order to suppress the generation of residual γ in the high-concentration carburizing process in which the C concentration in the surface layer of the steel material is higher than in the conventional carburizing process and in the high-concentration carbonitriding process in which the C concentration and the N concentration are increased, The amount of each alloying element was changed based on the SCR420 material, and the change in the solid solution C concentration at 850 ° C. was investigated and studied. In particular, the effect of the Si amount and the Cr amount on the solid solution C concentration. I found it big.
本発明はこのような知見に基づくものであり、鋼中に固溶Ｃ濃度の抑制効果の大きいＳｉ，Ｃｒを積極添加するとともに、その他の成分を固溶Ｃ濃度抑制に対する寄与率に応じて含有させることで焼入れ後の残留γ量の抑制を図ったものである。高濃度浸炭処理において残留γ量を抑制するには、２次浸炭温度である８５０℃付近における固溶Ｃ濃度（即ち、Ａｃｍ点）を０．９０％以下とすることが望ましく、本発明では固溶Ｃ濃度に影響を与える合金元素を、上記式（１）を満たすように鋼中に含有させることで８５０℃における固溶Ｃ濃度を０．９０％以下に低下させ、焼入れ後に残留γが多量生成する問題の解決を図ったものである。 The present invention is based on such knowledge, and actively adds Si and Cr, which have a large effect of suppressing solute C concentration, to the steel and contains other components according to the contribution ratio to solute C concentration suppression. This is intended to suppress the amount of residual γ after quenching. In order to suppress the residual γ amount in the high-concentration carburizing treatment, it is desirable that the solid solution C concentration (that is, the Acm point) around 850 ° C., which is the secondary carburizing temperature, is 0.90% or less. By containing an alloy element that affects the dissolved C concentration in the steel so as to satisfy the above formula (1), the solid solution C concentration at 850 ° C. is reduced to 0.90% or less, and a large amount of residual γ after quenching. It is intended to solve the problem to be generated.
即ち、本発明の浸炭部品は、上記式（１）を満たすように成分調整された鋼からなり、部品表層に形成された浸炭層の、炭化物面積率を５〜４０％とし、更に残留γ量を４０％未満としたもので、本発明の浸炭部品によれば、残留γの多量生成に起因する強度低下を防止してピッチング疲労強度及び曲げ疲労強度を共に高めることができる。本発明の浸炭部品は、特に高いピッチング疲労強度及び曲げ疲労強度が要求される歯車等の耐高面圧部品に適用して特に好適なものである。 That is, the carburized component of the present invention is made of steel whose components are adjusted so as to satisfy the above formula (1), the carbide area ratio of the carburized layer formed on the component surface layer is 5 to 40%, and the residual γ amount Therefore, according to the carburized component of the present invention, it is possible to prevent the strength from being reduced due to a large amount of residual γ and to increase both the pitching fatigue strength and the bending fatigue strength. The carburized parts of the present invention are particularly suitable when applied to high surface pressure resistant parts such as gears that require particularly high pitching fatigue strength and bending fatigue strength.
また本発明の浸炭窒化部品は、上記式（１）を満たすように成分調整された鋼からなり、部品表層に形成された浸炭窒化層の、炭化物面積率を５〜４０％，残留γ量を４０％未満とし、更にＮ濃度を質量％で０．０５〜０．５％としたものである。浸炭窒化部品の場合、表層でのＮ濃度の増加は、焼戻し軟化抵抗の向上に有効であるが、残留γ量が増加してしまう。このため本発明の浸炭窒化部品では、浸炭窒化層のＮ濃度を０．０５〜０．５％に規定し、残留γ量を４０％未満に抑制する。 The carbonitrided component of the present invention is made of steel whose components are adjusted so as to satisfy the above formula (1). The carbonitrided layer formed on the component surface layer has a carbide area ratio of 5 to 40% and a residual γ amount. It is less than 40%, and the N concentration is 0.05 to 0.5% by mass%. In the case of carbonitrided parts, an increase in the N concentration in the surface layer is effective in improving the temper softening resistance, but the residual γ amount increases. For this reason, in the carbonitrided component of the present invention, the N concentration of the carbonitrided layer is regulated to 0.05 to 0.5%, and the residual γ amount is suppressed to less than 40%.
次に本発明における各化学成分の限定理由を以下に説明する。
Ｃ：０．１４〜０．３８％
Ｃは、強度を確保する上で必要な元素であり、部品の芯部硬さを確保するために０．１４％以上含有させる。但し、含有量が多くなり過ぎると芯部の靭性が低下し、また冷間鍛造性等の加工性が低下するため、上限を０．３８％とする。
Next, the reasons for limiting each chemical component in the present invention will be described below.
C: 0.14-0.38%
C is an element necessary for ensuring the strength, and is contained in an amount of 0.14% or more in order to ensure the core hardness of the component. However, if the content is too large, the toughness of the core part is lowered, and workability such as cold forgeability is lowered, so the upper limit is made 0.38%.
Ｓｉ：０．０１〜１．５０％以下
Ｓｉは、浸炭焼入時の固溶Ｃ濃度を低下させる効果が大きく、０．０１％以上含有させる。但し、含有量が過大になると靭性及び被削性が低下するため、含有量を１．５０％以下とする。
Si: 0.01 to 1.50% or less Si has a great effect of reducing the concentration of dissolved C during carburizing and quenching, and is contained by 0.01% or more. However, if the content is excessive, the toughness and machinability deteriorate, so the content is made 1.50% or less.
Ｍｎ：０．２０〜２．０％
Ｍｎは、芯部の焼入れ性を確保する上で有用な成分であり、その働きのために０．２０％以上含有させる。但し、含有量が多くなり過ぎると被削性の低下が懸念されるため、上限を２．０％とする。
Mn: 0.20 to 2.0%
Mn is a component useful for securing the hardenability of the core, and is contained in an amount of 0.20% or more for its function. However, if the content is too large, there is a concern about deterioration of machinability, so the upper limit is made 2.0%.
Ｃｕ：０．５０％以下
Ｃｕは、焼入れ性を向上させる働きがある。但し、含有量が過大になると熱間鍛造性が低下するため、含有量を０．５０％以下とする。
Cu: 0.50% or less Cu has a function of improving hardenability. However, if the content is excessive, the hot forgeability decreases, so the content is made 0.50% or less.
Ｎｉ：０．８％以下
Ｎｉは、焼入れ性を向上させる働きがある。但し、含有量が過大になると残留γが増加し、また加工性が低下するため、含有量を０．８％以下とする。
Ni: 0.8% or less Ni has a function of improving hardenability. However, if the content is excessive, the residual γ increases and the workability decreases, so the content is made 0.8% or less.
Ｃｒ：０．５０〜４．５％
Ｃｒは、焼入れ性を確保する上で有用な成分である。また、Ｓｉとともに浸炭焼入時の固溶Ｃ濃度を低下させる効果が大きい。このため０．５０％以上含有させる。但し、含有量が多くなり過ぎると加工性、特に被削性が低下する。また焼入れ性が大きくなりすぎ、焼入歪みの増大が懸念されるため、上限を４．５％とする。
Cr: 0.50 to 4.5%
Cr is a useful component for ensuring hardenability. Moreover, the effect of reducing the solid solution C concentration at the time of carburizing and quenching with Si is great. For this reason, 0.50% or more is contained. However, if the content is too large, workability, particularly machinability, is lowered. Moreover, since hardenability becomes too large and there is a concern about increase in quenching distortion, the upper limit is made 4.5%.
Ｍｏ：０．８％以下
Ｍｏは、焼入れ性を向上させ、焼戻し軟化抵抗を高める。但し、多量に添加すると加工性、特に被削性が低下するため、上限を０．８％とする。
Mo: 0.8% or less Mo improves hardenability and increases temper softening resistance. However, if added in a large amount, the workability, particularly machinability, decreases, so the upper limit is made 0.8%.
Ａｌ：０．０１０〜０．０６０％
Ａｌは、結晶粒の粗大化を抑制するピン止めの働きがあり、このピン止め効果を得るために０．０１０％以上含有させる。但し、含有量が多くなり過ぎると鋼中にＡｌ2Ｏ3系介在物が形成され強度の低下を招くため、上限を０．０６０％とする。
Al: 0.010 to 0.060%
Al has a function of pinning to suppress coarsening of crystal grains, and is contained in an amount of 0.010% or more in order to obtain this pinning effect. However, if the content is too large, Al 2 O 3 inclusions are formed in the steel and the strength is lowered, so the upper limit is made 0.060%.
Ｎ：０．００５〜０．０３０％
Ｎは、結晶粒の粗大化を抑制するピン止めの働きがあり、このピン止め効果を得るために０．００５％以上含有させる。一方、鋳造時におけるブロー発生を防止するため、上限を０．０３０％とする。
N: 0.005-0.030%
N has a function of pinning to suppress coarsening of crystal grains, and is contained in an amount of 0.005% or more in order to obtain this pinning effect. On the other hand, the upper limit is made 0.030% in order to prevent blow during casting.
Ｎｂ：０．１％以下
Ｎｂは、Ａｌと同様に結晶粒の粗大化を抑制するピン止めの働きがあり選択元素としてさらに含有させることができる（請求項２，４）。但し、含有量が多くなり過ぎると加工性を劣化させたり、粗大な窒化物を生成するため、上限を０．１％とする。
Nb: 0.1% or less Nb, like Al, has a function of pinning to suppress coarsening of crystal grains and can be further contained as a selective element (claims 2 and 4). However, if the content is too large, the workability is deteriorated or coarse nitrides are formed, so the upper limit is made 0.1%.
−0.19＞−0.102［Si］−0.03［Cu］−0.01［Ni］−0.135［Cr］ ・・・式（１）
Ｓｉ，Ｃｕ，Ｎｉ，Ｃｒは、浸炭時の固溶Ｃ量を低下させる効果がある。式(１)中Ｓｉ，Ｃｕ，Ｎｉ，Ｃｒの係数は、それぞれ固溶Ｃ量低下に対する寄与度を表している。本発明者らの調査によれば、式(１)の右辺の値が−０．１９を下回るように（換言すれば、右辺の値の絶対値が０．１９よりも大きくなるように）成分調整することで、８５０℃での固溶Ｃ濃度（Ａｃｍ点）が０．９０％以下に抑えられ、焼入れ後の残留γを減少させることができる。なお、Ｃｕ，Ｎｉ量が不純物レベルである場合は、Ｃｕ，Ｎｉの項は除外して計算すればよい。
−0.19> −0.102 [Si] −0.03 [Cu] −0.01 [Ni] −0.135 [Cr] (1)
Si, Cu, Ni, and Cr have the effect of reducing the amount of solute C during carburizing. In formula (1), the coefficients of Si, Cu, Ni, and Cr represent the degree of contribution to the decrease in the amount of dissolved C, respectively. According to the investigation by the present inventors, the component so that the value on the right side of Equation (1) is less than −0.19 (in other words, the absolute value of the value on the right side is greater than 0.19). By adjusting, the solid solution C concentration (Acm point) at 850 ° C. is suppressed to 0.90% or less, and the residual γ after quenching can be reduced. When the amount of Cu and Ni is at the impurity level, the calculation may be performed excluding the terms of Cu and Ni.
表層の炭化物面積率が５〜４０％
部品表層に析出する炭化物の面積率を５％以上とすることで、焼戻し軟化抵抗を向上させることができる。但し、面積率が過大になると粗大な炭化物が網状に発生し易くなり疲労強度の低下が懸念されるため、上限を４０％とする。
The carbide area ratio of the surface layer is 5 to 40%
The temper softening resistance can be improved by setting the area ratio of the carbide deposited on the component surface layer to 5% or more. However, if the area ratio is excessive, coarse carbides are likely to be generated in a net shape and there is concern about a decrease in fatigue strength, so the upper limit is made 40%.
表層の残留γ量が４０％未満
表層に多量の残留γが発生すると、表層の硬さが低下し、特に曲げ疲労強度が低下するため、本発明では表層の残留γ量を４０％未満とする。
The amount of residual γ in the surface layer is less than 40% If a large amount of residual γ is generated in the surface layer, the hardness of the surface layer is lowered, especially the bending fatigue strength is lowered. Therefore, in the present invention, the amount of residual γ in the surface layer is made less than 40%. .
表層のＮ濃度が０．０５〜０．５％
浸炭窒化部品の場合は、部品表層（浸炭窒化層）におけるＮ濃度を０．０５％以上とすることで焼戻し軟化抵抗を向上させることができる。但し、Ｎ濃度が過大になると残留γが増加して硬さが低下してしまうため、上限を０．５％とする。
N concentration of the surface layer is 0.05 to 0.5%
In the case of carbonitrided parts, temper softening resistance can be improved by setting the N concentration in the component surface layer (carbonitrided layer) to 0.05% or more. However, if the N concentration becomes excessive, the residual γ increases and the hardness decreases, so the upper limit is made 0.5%.
以上のような本発明によれば、表層における残留γの多量生成を抑制して、以てピッチング疲労強度及び曲げ疲労強度を共に高めた浸炭部品および浸炭窒化部品を提供することができる。 According to the present invention as described above, it is possible to provide a carburized part and a carbonitrided part in which the generation of a large amount of residual γ in the surface layer is suppressed, thereby increasing both the pitching fatigue strength and the bending fatigue strength.
次に本発明の実施例を以下に詳述する。
表１に示す化学組成を有する鋼を１５０ｋｇ高周波誘導炉にて溶製した。得られた鋼塊は、直径Φ９０ｍｍの丸棒に圧延あるいは熱間鍛造し、さらにΦ２２〜３２ｍｍの棒鋼に熱間鍛造して試験用の素材とし、表２に示す各種項目について評価した。
尚、表１において、鋼種ａ〜ｐ，ｘ（計１５種）は本発明の成分範囲の要件を満たす。一方、鋼種ｑ〜ｗ，ｙ（８種）は本発明の成分範囲の要件を満たしていない。具体的には少なくとも式（１）の要件を満たしていない。
Next, examples of the present invention will be described in detail below.
Steel having the chemical composition shown in Table 1 was melted in a 150 kg induction furnace. The obtained steel ingot was rolled or hot forged into a round bar having a diameter of Φ90 mm, and further hot forged into a bar steel having a diameter of Φ22 to 32 mm as a test material, and various items shown in Table 2 were evaluated.
In Table 1, steel types a to p and x (15 types in total) satisfy the requirements of the component range of the present invention. On the other hand, steel types q to w, y (8 types) do not satisfy the requirements of the component range of the present invention. Specifically, at least the requirement of formula (1) is not satisfied.
＜固溶Ｃ濃度＞
表１に示す２２鋼種（鋼種ａ〜ｘ）について、８５０℃における固溶Ｃ濃度を評価した。詳しくは、上記の試験用の素材よりΦ１５×１００Ｌの丸棒試験片を作成し、８５０℃にて真空浸炭処理を実施した。真空浸炭処理は、試験片の表層Ｃ濃度が１．５％となるように実施し表層に炭化物を析出させた。そして処理後の試験片を断面で切断し、試験片の表面から所定の深さまで、ＥＰＭＡ線分析を実施した。かかるＥＰＭＡ線分析では、炭化物に分析ビームが当たると高い値が検出される一方、マトリックス部分では低い値が検出される。このため得られたＣ濃度曲線は、炭化物が析出する表層付近で上下にはげしくばらつくが、炭化物がなくなりＣが固溶している部分になると曲線の大きな乱れが収まる。ここではこの境界の濃度を８５０℃における固溶Ｃ濃度（Ａｃｍ点）とした。結果は表２に示す通りである。
<Solution C concentration>
About 22 steel types (steel types ax) shown in Table 1, the solid solution C density | concentration in 850 degreeC was evaluated. Specifically, a Φ15 × 100 L round bar test piece was prepared from the above test material and vacuum carburized at 850 ° C. The vacuum carburization treatment was performed such that the surface layer C concentration of the test piece was 1.5%, and carbides were deposited on the surface layer. And the test piece after a process was cut | disconnected in the cross section, and the EPMA line analysis was implemented from the surface of the test piece to the predetermined depth. In such EPMA line analysis, a high value is detected when an analysis beam hits the carbide, whereas a low value is detected in the matrix portion. For this reason, the obtained C concentration curve varies greatly up and down in the vicinity of the surface layer where the carbide precipitates, but when the carbide disappears and C becomes a solid solution portion, the large disturbance of the curve is settled. Here, the concentration at this boundary was defined as a solid solution C concentration (Acm point) at 850 ° C. The results are as shown in Table 2.
表２に示すように、８５０℃における固溶Ｃ濃度は、鋼種の組成が本発明の要件を満たしていない（具体的には式（１）右辺の値が−０．１９よりも大きい）比較例３〜９において、残留γが増加する目安である０．９０％を超えている。これに対し、鋼種の組成が本発明の要件を満たしている実施例１〜１４、比較例１，２，１０では、８５０℃における固溶Ｃ濃度が何れも０．９０％よりも低くなっており、式（１）を満たす組成において固溶Ｃ濃度低下の効果が認められた。 As shown in Table 2, the solid solution C concentration at 850 ° C. is a comparison in which the composition of the steel type does not satisfy the requirements of the present invention (specifically, the value on the right side of the formula (1) is larger than −0.19). In Examples 3 to 9, the residual γ exceeds 0.90%, which is a standard for increasing the residual γ. In contrast, in Examples 1 to 14 and Comparative Examples 1, 2 and 10 in which the composition of the steel type satisfies the requirements of the present invention, the solute C concentration at 850 ° C. is lower than 0.90%. In the composition satisfying the formula (1), the effect of decreasing the solute C concentration was recognized.
次に、上記の試験用の素材よりΦ１５×１００Ｌの丸棒試験片を作製し、以下に示す高濃度浸炭処理を施し、表層Ｃ濃度，残留γ量，炭化物面積率及び表層硬さの評価を行った。また、上記の試験用の素材を所定形状に加工した後、高濃度浸炭処理を施した試験片を用いて曲げ疲労強度およびピッチング疲労強度を評価した。
なお、一部の試験片については、高濃度浸炭処理に代えて高濃度浸炭窒化処理を施し、上記評価項目に加えて表層Ｎ濃度の測定を行った。
Next, a Φ15 × 100L round bar test piece is prepared from the above test materials, and subjected to the following high-concentration carburizing treatment to evaluate the surface layer C concentration, residual γ amount, carbide area ratio, and surface layer hardness. went. Moreover, after processing the said test raw material into a predetermined shape, the bending fatigue strength and the pitching fatigue strength were evaluated using the test piece which performed the high concentration carburizing process.
In addition, about some test pieces, it replaced with the high concentration carburizing process, the high concentration carbonitriding process was performed, and in addition to the said evaluation item, the surface layer N density | concentration was measured.
＜高濃度浸炭処理／高濃度浸炭窒化処理＞
高濃度浸炭処理は、真空浸炭炉を用い、浸炭ガスとしてアセチレンを使用し、図１に示すような処理パターンで、１次浸炭処理および２次浸炭処理を行った。
１次浸炭処理は、最表面のＣ濃度が１．１％程度となるように、１０５０℃で７０分間浸炭処理を行った後、５００℃以下の温度域までガス冷却によって急冷し、炭化物が析出しない程度の高濃度域までＣを鋼中に侵入させた。
２次浸炭処理は、８５０℃の温度で保持して炭化物の析出処理を行った後、そのままの温度を保持して目標のＣ濃度に応じて３０〜９０分の間、浸炭処理を実施して浸炭層に析出した炭化物を成長させ、その後油焼入れを行った。そして焼入れ後には１８０℃×１２０分の焼戻し処理を実施した。
<High concentration carburizing treatment / High concentration carbonitriding>
In the high-concentration carburizing treatment, a primary carburizing treatment and a secondary carburizing treatment were performed using a vacuum carburizing furnace, using acetylene as a carburizing gas, and with a treatment pattern as shown in FIG.
In the primary carburizing process, the carburizing process is performed at 1050 ° C. for 70 minutes so that the C concentration on the outermost surface is about 1.1%, and then rapidly cooled by gas cooling to a temperature range of 500 ° C. or lower to precipitate carbide. C was allowed to penetrate into the steel to such a high concentration range as not to occur.
The secondary carburizing process is performed at a temperature of 850 ° C. to perform carbide precipitation, and then the carburizing process is performed for 30 to 90 minutes depending on the target C concentration while maintaining the temperature as it is. The carbide precipitated in the carburized layer was grown and then oil quenching was performed. And after quenching, a tempering treatment of 180 ° C. × 120 minutes was performed.
尚、表２における比較例１１は、ＪＩＳ ＳＣＲ４２０相当の鋼を用い、表面のＣ濃度を共析組成とし真空浸炭処理を施した例であり、比較例１１については上記の高濃度浸炭処理を行なっていない。 In addition, Comparative Example 11 in Table 2 is an example in which steel corresponding to JIS SCR420 was used and the surface C concentration was a eutectoid composition and vacuum carburized, and Comparative Example 11 was subjected to the above high concentration carburizing. Not.
一方、高濃度浸炭窒化処理では、上記高濃度浸炭処理の場合と同様の１次浸炭処理を実施した後、２次浸炭窒化処理を実施した。２次浸炭窒化処理では、上記高濃度浸炭処理の２次浸炭処理と同じ温度・時間の条件の下、浸炭のためのアセチレンガスと、窒化のためのアンモニアガスとを交互に流し、表層に浸炭窒化層を形成した。 On the other hand, in the high-concentration carbonitriding process, after performing the same primary carburizing process as in the case of the high-concentration carburizing process, the secondary carbonitriding process was performed. In the secondary carbonitriding process, acetylene gas for carburizing and ammonia gas for nitriding are alternately flowed under the same temperature and time conditions as the secondary carburizing process of the high-concentration carburizing process, and carburizing is performed on the surface layer. A nitride layer was formed.
＜表層Ｃ濃度＞
上記高濃度浸炭処理後もしくは高濃度浸炭窒化処理後の試験片を用いて、試験片表面から０．０５ｍｍまでの深さのダライ粉を採取しＣ濃度（質量％）をガス分析にて測定した。
<Concentration of surface layer C>
Using the test piece after the above high-concentration carburizing treatment or after the high-concentration carbonitriding treatment, dairy powder having a depth of 0.05 mm from the surface of the test piece was collected, and the C concentration (mass%) was measured by gas analysis. .
＜表層Ｎ濃度＞
上記高濃度浸炭窒化処理後の試験片を用いて、試験片表面から０．０５ｍｍまでの深さのダライ粉を採取しＮ濃度（質量％）をガス分析にて測定した。
<Surface N concentration>
Using the test piece after the high-concentration carbonitriding treatment, dairy powder having a depth of 0.05 mm from the surface of the test piece was collected, and N concentration (mass%) was measured by gas analysis.
＜残留γ量＞
上記高濃度浸炭処理後もしくは高濃度浸炭窒化処理後の試験片の最表面をＸＲＤにより測定し、残留γ量を求めた。
<Residual γ amount>
The outermost surface of the test piece after the high concentration carburizing treatment or after the high concentration carbonitriding treatment was measured by XRD, and the residual γ amount was obtained.
＜炭化物面積率＞
上記高濃度浸炭処理後もしくは高濃度浸炭窒化処理後の試験片の横断面を切断、研磨後、ピクラールで腐食し、最表面〜０．０５ｍｍの位置内部をＳＥＭで写真撮影し、画像解析をすることにより炭化物の面積率の測定を行った。
<Carbide area ratio>
The cross section of the test piece after the above high-concentration carburizing treatment or after the high-concentration carbonitriding treatment is cut, polished, corroded with picral, and the inside of the position of the outermost surface to 0.05 mm is photographed with SEM and image analysis is performed. Thus, the area ratio of the carbide was measured.
＜表層硬さ＞
上記高濃度浸炭処理後もしくは高濃度浸炭窒化処理後の試験片の断面部分を切断して埋め込み、硬さ測定用の試験片を作成した。測定にはビッカース硬さ試験機を用い、ＪＩＳ Ｚ２２４４に規定された試験方法により、表面下０．０５ｍｍの位置の硬さの５点平均を表層硬さとした。また、高濃度浸炭処理後もしくは高濃度浸炭窒化処理後の試験片に３００℃で３時間の焼戻し処理を施し、表層の焼戻し硬さの測定を行った。尚、試験荷重は３００ｇとした。
<Surface hardness>
The test piece after the high concentration carburizing treatment or after the high concentration carbonitriding treatment was cut and embedded to prepare a test piece for hardness measurement. A Vickers hardness tester was used for the measurement, and the five-point average of the hardness at a position of 0.05 mm below the surface was defined as the surface layer hardness by the test method specified in JIS Z2244. Further, the test piece after the high-concentration carburizing treatment or the high-concentration carbonitriding treatment was tempered at 300 ° C. for 3 hours, and the tempering hardness of the surface layer was measured. The test load was 300 g.
＜曲げ疲労強度＞
曲げ疲労強度は、ＪＩＳ Ｚ２２７４に準拠した小野式回転曲げ疲労試験にて評価した。上記の試験用の素材を、図２（Ａ）に示す半径ｒ＝１ｍｍの環状切欠を有する丸棒形状の小野式回転曲げ疲労試験片１０に加工した後、上記高濃度浸炭処理もしくは高濃度浸炭窒化処理を施し、試験に供した。試験条件は回転数３５００ｒｐｍ、試験温度は室温とした。曲げ疲労強度は１０7サイクルで破断しない最大応力とした。また、ＪＩＳ ＳＣＲ４２０の真空浸炭材（比較例１１）の曲げ疲労強度を１として、ぞれぞれの試験片での曲げ疲労強度向上率を％で表した。
<Bending fatigue strength>
The bending fatigue strength was evaluated by an Ono type rotating bending fatigue test based on JIS Z2274. The above test material is processed into a round bar-shaped Ono-type rotating bending
＜ピッチング疲労強度＞
ピッチング疲労強度は、ローラピッチング試験にて評価した。上記の試験用の素材を、図２（Ｂ）に示すように、接触部１２ａの直径φ２６ｍｍ，その両側の小径部１２ｂの直径φ２３ｍｍ，接触部１２ａの幅２８ｍｍの小ローラの試験片１２に機械加工した後、上記高濃度浸炭処理もしくは高濃度浸炭窒化処理を施し、試験に供した。
<Pitting fatigue strength>
The pitching fatigue strength was evaluated by a roller pitching test. As shown in FIG. 2B, the test material is machined into a small
試験片１２の相手側となる大ローラは、材質がＳＵＪ２でＨＲＣ６１となるように焼入れ焼戻し処理を実施した。尚、大ローラの曲率半径は１５０Ｒとした。
ローラピッチング試験では、試験片１２と相手側大ローラとを２．０〜４．０ＧＰａの種々の面圧で、回転数（試験片１２）：１５００ｒｐｍで接触させ、ローラピッチング試験機を用いてそれらを滑り率：−６０％で回転させ、１０7サイクルでピッチングを生じない負荷応力を面疲労強度（ピッチング疲労強度）とした。そしてＪＩＳ ＳＣＲ４２０の真空浸炭材（比較例１１）の面疲労強度を１として、ぞれぞれの試験片での面疲労強度向上率を％で表した。
これらの評価結果を上記表２および図３、図４に示す。
The large roller on the other side of the
In the roller pitching test, the
The evaluation results are shown in Table 2 above and FIGS.
表２に示すように、高濃度浸炭処理もしくは高濃度浸炭窒化処理が施された実施例１〜１４、比較例１〜１０は、何れも３００℃焼戻し硬さが比較例１１（ＳＣＲ４２０の真空浸炭材）よりも高く維持され、面疲労強度（ピッチング疲労強度）は図４（Ａ）に示すように従来の真空浸炭材（比較例１１）よりも良好な値であった。全体として高濃度浸炭処理もしくは高濃度浸炭窒化処理を施したことによる効果が得られている。 As shown in Table 2, each of Examples 1 to 14 and Comparative Examples 1 to 10 subjected to high-concentration carburizing treatment or high-concentration carbonitriding treatment has a tempering hardness of 300 ° C. in Comparative Example 11 (vacuum carburizing of SCR420). The surface fatigue strength (pitting fatigue strength) was a better value than the conventional vacuum carburized material (Comparative Example 11) as shown in FIG. 4 (A). The effect by having performed high concentration carburizing process or high concentration carbonitriding process as a whole is acquired.
しかしながら比較例１は、表層の炭化物面積率が本発明の下限値５％を下回っており、３００℃焼戻しにおける硬さの低下が７４７ＨＶ→６４５ＨＶと著しく、焼戻し軟化抵抗を向上させる効果が他の例と比較して十分でない。
一方、比較例２は、表層の炭化物面積率が本発明の上限値４０％を上回っている。この比較例２は、表層硬さが７９６ＨＶと高いにも拘らず、図３（Ａ）に示すように曲げ疲労強度が、従来の真空浸炭材（比較例１１）よりも低下しており、ピッチング疲労強度と曲げ疲労強度の両立は図られていない。炭化物面積率が過度に大きい比較例２では、炭化物が粗大化するとともにその形状が球状から網状に変化したため、曲げ疲労強度が悪化したものと推測される。
However, in Comparative Example 1, the carbide area ratio of the surface layer is lower than the lower limit of 5% of the present invention, and the decrease in hardness in tempering at 300 ° C. is markedly 747 HV → 645 HV, and the effect of improving the temper softening resistance is another example. Not enough.
On the other hand, in Comparative Example 2, the carbide area ratio of the surface layer exceeds the upper limit of 40% of the present invention. Although the comparative example 2 has a high surface hardness of 796 HV, the bending fatigue strength is lower than that of the conventional vacuum carburized material (Comparative Example 11) as shown in FIG. Fatigue strength and bending fatigue strength are not compatible. In Comparative Example 2 in which the carbide area ratio is excessively large, it is presumed that the bending fatigue strength deteriorated because the carbide coarsened and the shape changed from a spherical shape to a net shape.
他方、比較例３〜８は、表層の炭化物面積率が本発明の規定範囲内であったが、残留γ量は４０％以上で本発明の規定値を超えている。このため図３（Ａ）に示すように曲げ疲労強度が、従来の真空浸炭材（比較例１１）よりも低下しており、ピッチング疲労強度と曲げ疲労強度との両立は図られていない。残留γ量が４０％以上であった比較例３〜８は、見かけ上表層硬さは高いものの、多量の残留γ量が発生しているため局所的に硬さが低下し、曲げ疲労強度が悪化したものと推測される。 On the other hand, in Comparative Examples 3 to 8, the carbide area ratio of the surface layer was within the specified range of the present invention, but the residual γ amount was 40% or more and exceeded the specified value of the present invention. For this reason, as shown in FIG. 3A, the bending fatigue strength is lower than that of the conventional vacuum carburized material (Comparative Example 11), and the coexistence of the pitching fatigue strength and the bending fatigue strength is not achieved. In Comparative Examples 3 to 8, in which the residual γ amount was 40% or more, the surface hardness was apparently high, but since a large amount of residual γ amount was generated, the hardness decreased locally and the bending fatigue strength was low. Presumed to have deteriorated.
高濃度浸炭窒化処理が施された比較例９，１０は、表層の炭化物面積率およびＮ濃度が本発明の規定範囲内であったが、残留γ量が４０％以上で本発明の規定値を超えていたため、図３（Ａ）に示すように曲げ疲労強度が、従来の真空浸炭材（比較例１１）よりも低下しており、ピッチング疲労強度と曲げ疲労強度との両立は図られていない。 In Comparative Examples 9 and 10 subjected to high-concentration carbonitriding, the surface area carbide area ratio and N concentration were within the specified range of the present invention, but the residual γ amount was 40% or more and the specified value of the present invention was exceeded. Therefore, the bending fatigue strength is lower than that of the conventional vacuum carburized material (Comparative Example 11) as shown in FIG. 3 (A), and the coexistence between the pitching fatigue strength and the bending fatigue strength is not achieved. .
これに対し高濃度浸炭処理が施された実施例１〜１２は、上記式（１）を満たすように成分調整された鋼からなり、浸炭層の炭化物面積率および残留γ量も本発明の規定範囲内である。これら実施例１〜１２は、表２，図４（Ｂ）に示すように、何れも３００℃焼戻し硬さが比較例１１（ＳＣＲ４２０の真空浸炭材）よりも高く、面疲労強度（ピッチング疲労強度）は、図４（Ａ）に示すように従来の真空浸炭材（比較例１１）よりも良好な結果が得られている。
加えて曲げ疲労強度についても、図３（Ａ）に示すように、従来の真空浸炭材（比較例１１）に対して１．０〜６．５％の向上が認められた。即ち、高濃度浸炭処理が施された実施例１〜１２は、従来の真空浸炭材（比較例１１）に対してピッチング疲労強度と曲げ疲労強度を共に高めることができている。
On the other hand, Examples 1 to 12 subjected to high-concentration carburizing treatment are made of steel whose components are adjusted so as to satisfy the above formula (1), and the carbide area ratio and residual γ amount of the carburized layer are also defined in the present invention. Within range. In Examples 1 to 12, as shown in Table 2 and FIG. 4 (B), the 300 ° C. tempering hardness is higher than that of Comparative Example 11 (SCR carburized material of SCR420), and surface fatigue strength (pitting fatigue strength). As shown in FIG. 4 (A), a better result than that of the conventional vacuum carburized material (Comparative Example 11) is obtained.
In addition, as shown in FIG. 3A, the bending fatigue strength was also improved by 1.0 to 6.5% with respect to the conventional vacuum carburized material (Comparative Example 11). That is, Examples 1-12 in which the high-concentration carburizing treatment was performed can increase both the pitching fatigue strength and the bending fatigue strength with respect to the conventional vacuum carburized material (Comparative Example 11).
また高濃度浸炭窒化処理が施された実施例１３，１４は、上記式（１）を満たすように成分調整された鋼からなり、浸炭窒化層の炭化物面積率，残留γ量およびＮ濃度が本発明の規定範囲内である。これら実施例１３，１４は、何れも３００℃焼戻し硬さが比較例１１（ＳＣＲ４２０の真空浸炭材）よりも高く維持されている。そのため、面疲労強度（ピッチング疲労強度）については、図４（Ａ）に示すように従来の真空浸炭材（比較例１１）よりも良好な結果が得られている。
加えて曲げ疲労強度についても、図３（Ａ）に示すように、従来の真空浸炭材に対して１．３〜２．６％の向上が認められた。即ち、高濃度浸炭窒化処理が施された実施例１３，１４においても、従来の真空浸炭材（比較例１１）に対してピッチング疲労強度と曲げ疲労強度を共に高めることができている。
Further, Examples 13 and 14 subjected to high-concentration carbonitriding treatment are made of steel whose components are adjusted so as to satisfy the above formula (1), and the carbide area ratio, residual γ amount and N concentration of the carbonitriding layer are present. It is within the specified range of the invention. In these Examples 13 and 14, the 300 ° C. tempering hardness is maintained higher than that of Comparative Example 11 (the SCR420 vacuum carburized material). Therefore, the surface fatigue strength (pitching fatigue strength) is better than that of the conventional vacuum carburized material (Comparative Example 11) as shown in FIG.
In addition, as shown in FIG. 3A, the bending fatigue strength was also improved by 1.3 to 2.6% with respect to the conventional vacuum carburized material. That is, also in Examples 13 and 14 where the high-concentration carbonitriding treatment was performed, both the pitching fatigue strength and the bending fatigue strength can be increased compared to the conventional vacuum carburized material (Comparative Example 11).
以上本発明の実施例を詳述したがこれはあくまで一例示であり、本発明はその趣旨を逸脱しない範囲において種々変更を加えた態様で実施可能である。 Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be implemented in various modifications without departing from the spirit of the present invention.
Claims (4)
Ｃ：０．１４〜０．３８％
Ｓｉ：０．０１〜１．５０％
Ｍｎ：０．２０〜２．０％
Ｃｕ：０．５％以下
Ｎｉ：０．８％以下
Ｃｒ：０．５０〜４．５％
Ｍｏ：０．８％以下
Ａｌ：０．０１０〜０．０６０％
Ｎ：０．００５〜０．０３０％
を含有し、残部Ｆｅ及び不可避的不純物の組成を有し且つ下記式（１）を満たす鋼からなり、
浸炭層を表層に有し、該表層は、炭化物面積率が５〜４０％で、更に残留γ量が４０％未満であることを特徴とする浸炭部品。
−0.19＞−0.102［Si］−0.03［Cu］−0.01［Ni］−0.135［Cr］ ・・・式（１）
（但し式（１）中各元素記号は含有質量％を表す） In mass% C: 0.14-0.38%
Si: 0.01-1.50%
Mn: 0.20 to 2.0%
Cu: 0.5% or less Ni: 0.8% or less Cr: 0.50 to 4.5%
Mo: 0.8% or less Al: 0.010-0.060%
N: 0.005-0.030%
Comprising the balance Fe and inevitable impurities and satisfying the following formula (1),
A carburized part having a carburized layer as a surface layer, the surface layer having a carbide area ratio of 5 to 40% and a residual γ content of less than 40%.
−0.19> −0.102 [Si] −0.03 [Cu] −0.01 [Ni] −0.135 [Cr] (1)
(However, each element symbol in the formula (1) represents mass%)
Ｎｂ：０．１％以下
を更に含有することを特徴とする浸炭部品。 The carburized part according to claim 1, further comprising Nb: 0.1% or less by mass% as an alloy component of the steel.
Ｃ：０．１４〜０．３８％
Ｓｉ：０．０１〜１．５０％
Ｍｎ：０．２０〜２．０％
Ｃｕ：０．５％以下
Ｎｉ：０．８％以下
Ｃｒ：０．５０〜４．５％
Ｍｏ：０．８％以下
Ａｌ：０．０１０〜０．０６０％
Ｎ：０．００５〜０．０３０％
を含有し、残部Ｆｅ及び不可避的不純物の組成を有し且つ下記式（１）を満たす鋼からなり、
浸炭窒化層を表層に有し、該表層は、Ｎ濃度が質量％で０．０５〜０．５％、炭化物面積率が５〜４０％で、更に残留γ量が４０％未満であることを特徴とする浸炭窒化部品。
−0.19＞−0.102［Si］−0.03［Cu］−0.01［Ni］−0.135［Cr］ ・・・式（１）
（但し式（１）中各元素記号は含有質量％を表す） In mass% C: 0.14-0.38%
Si: 0.01-1.50%
Mn: 0.20 to 2.0%
Cu: 0.5% or less Ni: 0.8% or less Cr: 0.50 to 4.5%
Mo: 0.8% or less Al: 0.010-0.060%
N: 0.005-0.030%
Comprising the balance Fe and inevitable impurities and satisfying the following formula (1),
It has a carbonitriding layer as a surface layer, and the surface layer has an N concentration of 0.05 to 0.5% by mass, a carbide area ratio of 5 to 40%, and a residual γ amount of less than 40%. Carbonitriding parts featured.
−0.19> −0.102 [Si] −0.03 [Cu] −0.01 [Ni] −0.135 [Cr] (1)
(However, each element symbol in the formula (1) represents mass%)
Ｎｂ：０．１％以下
を更に含有することを特徴とする浸炭窒化部品。 The carbonitriding component according to claim 3, further comprising Nb: 0.1% or less by mass% as an alloy component of the steel.
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| JPH0625823A (en) * | 1992-07-10 | 1994-02-01 | Kobe Steel Ltd | Parts made of carburized steel excellent in pitting resistance |
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| JP2021109982A (en) * | 2020-01-06 | 2021-08-02 | 日産自動車株式会社 | Method for producing carburized and hardened component |
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