JP2011012305A5

JP2011012305A5 -

Info

Publication number: JP2011012305A5
Application number: JP2009157083A
Authority: JP
Filing date: 2009-07-01
Publication date: 2012-08-16
Anticipated expiration: 2029-07-01

Description

本発明は、上記知見に基づいてなされたもので、合金元素を含む鉄鋼部材を窒化処理することにより得られた窒化部材であって、窒素化合物層を表層部に有し、該表層部の表面部に、内部よりも合金元素の濃度が低い厚さ０．１〜５μｍの合金元素低濃度領域を有することを特徴としている。また、本発明の窒化部材の製造方法は、鉄鋼部材に酸化処理を行って表面に厚さ０．１〜５μｍの酸化皮膜を形成し、次いで窒化処理を行うことを特徴としている。 The present invention has been made based on the above knowledge, and is a nitriding member obtained by nitriding a steel member containing an alloy element, having a nitrogen compound layer in a surface layer portion, and a surface of the surface layer portion The portion is characterized by having an alloy element low concentration region having a thickness of 0.1 to 5 μm, which is lower in concentration of the alloy element than the inside. The method for producing a nitrided member according to the present invention is characterized in that an oxidation treatment is performed on a steel member to form an oxide film having a thickness of 0.1 to 5 μm on the surface, and then a nitriding treatment is performed.

上記のような酸化処理後の鉄鋼部材に窒化処理を行うと窒化が促進され、酸化処理を行わない場合と比べて窒素化合物層と窒素拡散層の深さは５％程度増加する。その理由は以下のように考えられる。すなわち、鉄と窒素が結び付いて窒化鉄が生成されるよりも、酸化鉄の方が窒化鉄になり易いため、窒素化合物が容易に生成される。この点について、本発明者等が窒化鉄の反応生成系における熱力学計算を行ったところ、Ｆｅ_２Ｎの４００〜７００℃における生成自由エネルギーは、Ｆｅ、ＦｅＯ、Ｆｅ_３Ｏ_４、Ｆｅ_２Ｏ_３の順番で低くなることを確認した。したがって、鉄よりも酸化鉄の方が窒化され易く、また、酸化鉄の中でも酸素の原子比が高い方が窒化され易い。そして、上記のようにして生成された窒化鉄の下層には、酸化処理を行わない鉄鋼部材と同様に、鉄と窒素が結び付いて窒化鉄が生成されるから、結果として厚い窒化鉄層が生成される。また、窒化鉄層の下層に形成される窒素の拡散層も厚くなる。 When nitriding is performed on the steel member after the oxidation treatment as described above, nitriding is promoted, and the depths of the nitrogen compound layer and the nitrogen diffusion layer are increased by about 5% as compared with the case where the oxidation treatment is not performed. The reason is considered as follows. That is, since iron oxide is more likely to be iron nitride than iron and nitrogen are combined to generate iron nitride, a nitrogen compound is easily generated. In this regard, the present inventors or the like was carried out thermodynamic calculations in the reaction system for generating the iron nitride, free energy at 400 to 700 ° C. of Fe ₂ N _{_{is, Fe, FeO, Fe 3 O}} 4, Fe 2 O It confirmed that it became low in order of ₃ . Therefore, iron oxide is more easily nitrided than iron, and among iron oxides, the one having a higher oxygen atomic ratio is more easily nitrided. And, in the lower layer of iron nitride generated as described above, iron nitride is combined with iron and nitrogen, as in the case of steel members not subjected to oxidation treatment, resulting in the formation of a thick iron nitride layer. Is done. Further, the nitrogen diffusion layer formed under the iron nitride layer is also thickened.

窒化処理では、炉内を所定温度まで昇温して均熱で保持した後、炉内に例えばＮ_２ガス、ＮＨ_３ガス、およびＣＯ_２ガスからなる窒化ガスを導入し、所定時間保持した後に冷却する。この場合、炉内温度は５００〜６００℃であり、保持時間は１００〜３００分である。この窒化処理により、酸化皮膜であった部分に合金元素低濃度領域が形成される。合金元素低濃度領域の合金元素の濃度は、合金元素の総含有量に対して総量で０〜６０％が望ましく、また、合金元素低濃度領域の厚さは、０．１〜０．５μｍである。 In the nitriding treatment, after raising the temperature in the furnace to a predetermined temperature and keeping it soaked, a nitriding gas composed of, for example, N ₂ gas, NH ₃ gas, and CO ₂ gas is introduced into the furnace and held for a predetermined time. Cooling. In this case, the furnace temperature is 500 to 600 ° C., and the holding time is 100 to 300 minutes. By this nitriding treatment, a low concentration region of the alloy element is formed in the portion that was the oxide film. The concentration of the alloy element in the low concentration region of the alloy element is preferably 0 to 60% in total with respect to the total content of the alloy element, and the thickness of the low concentration region of the alloy element is 0.1 to 0.5 μm. Oh Ru.

Claims

A nitrided member obtained by nitriding a steel member containing an alloy element,
A nitriding member comprising a nitrogen compound layer in a surface layer portion, and a surface portion of the surface layer portion having an alloy element low concentration region having a thickness of 0.1 to 5 [mu] m in which the concentration of the alloy element is lower than the inside.

2. The nitrided member according to claim 1, wherein the concentration of the alloy element in the alloy element low concentration region is 0 to 60% in total with respect to the total content of alloy elements.

A method for producing a nitrided member, comprising subjecting a steel member to an oxidation treatment to form an oxide film having a thickness of 0.1 to 5 μm on the surface, followed by nitriding treatment.

4. The method for producing a nitride member according to claim 3, wherein a low concentration region of 0.1 to 5 μm in thickness of the alloy element having a lower concentration of the alloy element than the inside is formed in the oxide film by the nitriding treatment.