JP2009138261A - Heat-treatment method for columnar component - Google Patents

Heat-treatment method for columnar component Download PDF

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JP2009138261A
JP2009138261A JP2008260347A JP2008260347A JP2009138261A JP 2009138261 A JP2009138261 A JP 2009138261A JP 2008260347 A JP2008260347 A JP 2008260347A JP 2008260347 A JP2008260347 A JP 2008260347A JP 2009138261 A JP2009138261 A JP 2009138261A
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quenching
pin
heating
outer peripheral
peripheral surface
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JP5371084B2 (en
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Moriharu Setsu
衛 東 薛
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Topy Industries Ltd
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Topy Industries Ltd
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Priority to JP2008260347A priority Critical patent/JP5371084B2/en
Application filed by Topy Industries Ltd filed Critical Topy Industries Ltd
Priority to PCT/JP2008/069724 priority patent/WO2009063753A1/en
Priority to EP08849643.5A priority patent/EP2224021A4/en
Priority to US12/741,556 priority patent/US9303297B2/en
Priority to CN201310541169.3A priority patent/CN103773937B/en
Priority to CN200880115603.9A priority patent/CN101855372B/en
Priority to EP14160659.0A priority patent/EP2746411A3/en
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-treatment method for a columnar component, by which the productivity and the quality can be improved and the cost can be reduced in comparison with the conventional method. <P>SOLUTION: This heat-treatment method is provided with a quenching step S1 and a tempering step S2 subsequent to the quenching step S1, and the above quenching step S1 includes a first step S11 and a second step S12 subsequent to the first step S11, and in the first step S11, the quenching is performed by heating the columnar component 3 over the entire region thereof from the outer curcumferential surface to the core part at the temperature above the Ac<SB>3</SB>transformation temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、円柱状部品、とりわけ、大型（大径）の円柱状部品の熱処理方法に関する。ここで、「円柱状部品」には、例えば建設機械の無限軌道帯（履帯）の構成部品であるピンが含まれる。ただし、「円柱状部品」はピンに限るものではなく、また、大型の部品（ピンであれば大径のピン）に限定されるものでもない。   The present invention relates to a heat treatment method for a cylindrical part, in particular, a large (large diameter) cylindrical part. Here, the “cylindrical component” includes, for example, a pin that is a component of an endless track (crawler belt) of a construction machine. However, the “cylindrical component” is not limited to a pin, and is not limited to a large component (a large-diameter pin if it is a pin).

油圧ショベルやブルドーザー等の建設機械に用いられる履帯１０（図８参照）は、図９に示すように、リンク１、履板２、ピン３、ブッシュ４を有している。
図１０において、履帯用のピン３のような円柱状部品では、外周表面部（外周表面およびその近傍）３１には曲げ応力とねじれ応力に耐えるための強度および耐摩耗性が要求され、芯部３２にはせん断応力に耐えるための強度および靭性が要求される。 A crawler belt 10 (see FIG. 8) used in a construction machine such as a hydraulic excavator or a bulldozer has a link 1, a crawler plate 2, a pin 3, and a bush 4 as shown in FIG.
In FIG. 10, in the cylindrical part such as the crawler belt pin 3, the outer peripheral surface portion (the outer peripheral surface and its vicinity) 31 is required to have strength and wear resistance to withstand bending stress and torsional stress. 32 requires strength and toughness to withstand shear stress.

これらの要求品質をすべて満足させるための履帯用ピンの熱処理方法として、従来から種々の方法が提案されている。
例えば、低炭素合金鋼を素材とし、「浸炭焼入れ」を行い、次に「低温焼もどし」を施す方法が存在する。係る方法（浸炭焼入れ方法）によれば、ＳＣＭ４１５またはＳＣＭ４２０等の低炭素合金鋼を素材とし、これに浸炭を施して外周表面部のみ高炭素合金鋼とし、その後、焼入れおよび低温焼もどしを施している。
しかし、浸炭焼入れ方法によれば、ピンの耐摩耗性および強度を向上するためには浸炭硬化層を深く、浸炭時間を長くする必要があり、コストが嵩むという問題がある。それと共に、浸炭ガスの大量使用等も、コスト高騰を惹起する。 Conventionally, various methods have been proposed as a heat treatment method for crawler belt pins to satisfy all of these required qualities.
For example, there is a method in which low carbon alloy steel is used as a raw material, “carburizing and quenching” is performed, and then “low temperature tempering” is performed. According to such a method (carburizing and quenching method), a low carbon alloy steel such as SCM415 or SCM420 is used as a raw material, and this is carburized to form a high carbon alloy steel only on the outer peripheral surface, and then subjected to quenching and low temperature tempering. Yes.
However, according to the carburizing and quenching method, in order to improve the wear resistance and strength of the pin, it is necessary to deepen the carburized hardened layer and lengthen the carburizing time, which increases the cost. At the same time, the use of a large amount of carburizing gas causes a rise in costs.

また、中炭素合金鋼を素材とし、「全体加熱焼入れ」を行い、次に「低温焼もどし」を施す方法が存在する。詳細には、炭素含有量が０．３〜０．５質量％の中炭素合金鋼を素材とし、ピンの外周表面から芯部までの全体をＡｃ３変態点以上の温度に加熱し、急冷して焼入れし、その後、低温焼もどしを施している。
しかし、係る従来技術では、ピンの硬化層深さは、素材の焼入れ性やピンの直径等によって決まってしまうので、焼入れ性の低い素材を使用すると、必要な耐摩耗性および強度が得られなくなる。一方、焼入れ性の高い素材を使用すると、硬化層深さが深くなりすぎ、外周表面の圧縮残留応力が低くなり、ピンの破壊靭性および疲労強度が低くなるという問題がある。 In addition, there is a method in which medium carbon alloy steel is used as a raw material, and “overall heat quenching” is performed, followed by “low temperature tempering”. Specifically, medium carbon alloy steel having a carbon content of 0.3 to 0.5% by mass is used as a raw material, and the entire surface from the outer peripheral surface of the pin to the core is heated to a temperature equal to or higher than the Ac 3 transformation point and rapidly cooled. And then quenching, followed by low-temperature tempering.
However, in the related art, the depth of the hardened layer of the pin is determined by the hardenability of the material, the diameter of the pin, etc. Therefore, if a material with low hardenability is used, the necessary wear resistance and strength cannot be obtained. . On the other hand, when a material with high hardenability is used, there is a problem that the hardened layer depth becomes too deep, the compressive residual stress on the outer peripheral surface is lowered, and the fracture toughness and fatigue strength of the pin are lowered.

履帯用ピンの熱処理方法の従来技術として、さらに、中炭素合金鋼を素材とし、「全体加熱焼入れ」を行い、「全体加熱高温焼もどし」を行い、「外周表面部の高周波焼入れ」を行い、最後に「低温焼もどし」を施す方法が存在する。詳細には、炭素含有量が０．３〜０．５質量％の中炭素合金鋼を素材とし、ピンの外周表面から芯部までの全体をＡｃ３変態点以上の温度に加熱し、急冷して焼入れした後、ピンの外周表面から芯部までの全体を高温焼もどしして、ピン全体のミクロ組織をソルバイト組織にする。その後、ピンの外周表面部に高周波焼入れを施し、そして、低温焼もどしを施す。
ここで、「全体加熱焼入れ」と「全体加熱高温焼もどし」の２工程を合わせて「素地調質（工程）」という。大型のピン（大径のピン：直径が概ね５０ｍｍ以上のピン）は、この方法によって熱処理が行われている。 As a conventional technology for heat treatment of crawler belt pins, further, using medium carbon alloy steel as a raw material, `` overall heating quenching '', `` overall heating high temperature tempering '', `` high frequency quenching of the outer peripheral surface part '', Finally, there is a method of applying “low temperature tempering”. Specifically, medium carbon alloy steel having a carbon content of 0.3 to 0.5% by mass is used as a raw material, and the entire surface from the outer peripheral surface of the pin to the core is heated to a temperature equal to or higher than the Ac 3 transformation point and rapidly cooled. After quenching, the entire structure from the outer peripheral surface of the pin to the core is tempered at a high temperature to make the microstructure of the entire pin a sorbite structure. Thereafter, induction hardening is performed on the outer peripheral surface portion of the pin, and low temperature tempering is performed.
Here, the two processes of “overall heating quenching” and “overall heating high temperature tempering” are collectively referred to as “base tempering (process)”. Large pins (large diameter pins: pins having a diameter of approximately 50 mm or more) are heat-treated by this method.

図１１は、中炭素合金鋼の一例であるＳＣＭ４４０の組成（質量％）を表として示している。
以下、ＳＣＭ４４０を素材とするピンを「ピンＡ」と表現する。なお、ピンＡの長さは３７０ｍｍ、直径は７０ｍｍである。 FIG. 11 shows the composition (mass%) of SCM440, which is an example of medium carbon alloy steel, as a table.
Hereinafter, a pin made of SCM440 is expressed as “pin A”. The pin A has a length of 370 mm and a diameter of 70 mm.

図１２〜図１５は、ピンＡに、前記従来技術（全体加熱焼入れ、全体加熱高温焼もどし、高周波焼入れ、低温焼もどしを行う従来技術）を施した場合において、各熱処理工程におけるピンの断面における硬さ分布（外周表面から中心部までの硬さ分布）を示している。
図１２〜図１５において、横軸はピンＡの外周表面からの距離を示し、縦軸はロックウェル硬さを示している。 12 to 15 are cross-sectional views of the pin in each heat treatment process when the conventional technology (conventional technology for performing overall heating and quenching, overall heating and high-temperature quenching, induction quenching and low-temperature quenching) is applied to the pin A. The hardness distribution (the hardness distribution from the outer peripheral surface to the center) is shown.
12 to 15, the horizontal axis indicates the distance from the outer peripheral surface of the pin A, and the vertical axis indicates the Rockwell hardness.

図１２は、全体加熱焼入れ工程の後における硬さ分布を示している。図１２で示すように、全体加熱焼入れ工程の後、ピンの外周表面部（外周表面近傍）の硬さはＨＲＣ５５程度で、芯部（ピンの中心近傍の領域：ピンの中心から半径方向所定距離の範囲）では、ＨＲＣ５０程度である。
図１３は、全体加熱高温焼もどし工程の後における硬さ分布を示している。図１３では、高温焼もどしによってピンの外周表面部の硬さはＨＲＣ４０程度まで低下する。また、中心を含む芯部では、ＨＲＣ３０程度となっている。 FIG. 12 shows the hardness distribution after the overall heating and quenching process. As shown in FIG. 12, the hardness of the outer peripheral surface portion (near the outer peripheral surface) of the pin is about HRC55 after the entire heating and quenching process, and the core portion (region near the center of the pin: a predetermined distance in the radial direction from the center of the pin) In the range) is about HRC50.
FIG. 13 shows the hardness distribution after the overall heating high temperature tempering step. In FIG. 13, the hardness of the outer peripheral surface portion of the pin is reduced to about HRC40 by high temperature tempering. Moreover, in the core part including a center, it is about HRC30.

図１４は、高周波焼入れ工程後の硬さ分布を示している。図１４において、ピンの外周表面部の硬さは、高周波焼入れのためＨＲＣ６０程度に上昇している。ピンの芯部ではＨＲＣ３０程度のままである。そして、ピンの外周表面部と芯部との間の領域で、急激に硬さが低下する領域Ｂ２が存在している。
図１５は、低温焼もどし工程の後における硬さ分布を示している。図１５で示すように、低温焼もどしのために外周表面部の硬さがやや下がり、ＨＲＣ５５程度となる。 FIG. 14 shows the hardness distribution after the induction hardening process. In FIG. 14, the hardness of the outer peripheral surface portion of the pin is increased to about HRC60 due to induction hardening. At the core of the pin, it remains around HRC30. And in the area | region between the outer peripheral surface part and core part of a pin, area | region B2 where hardness falls rapidly exists.
FIG. 15 shows the hardness distribution after the low temperature tempering step. As shown in FIG. 15, the hardness of the outer peripheral surface portion is slightly lowered due to low temperature tempering and becomes about HRC55.

全体加熱焼入れ、全体加熱高温焼もどし、高周波焼入れ、低温焼もどしを行う上述の従来技術は、４工程を行うため、リードタイムが長くなり、全体の処理時間が長くなるという問題がある。
また、必要な芯部硬さ（素地硬さ）を確保するためには焼入れ性の高い素材を使用する必要があり、そのような素材は価格が高いので、コストアップにつながってしまう。
さらに、必要な芯部硬さ（素地硬さ）が得られないと、過大なせん断応力が負荷された際に、折損する可能性がある。 The above-described conventional technique that performs whole heating quenching, whole heating high temperature quenching, induction quenching, and low temperature quenching has four problems, and thus has a problem that the lead time becomes longer and the entire processing time becomes longer.
Moreover, in order to ensure the required core hardness (base hardness), it is necessary to use a material with high hardenability, and such a material is expensive, leading to an increase in cost.
Furthermore, if the required core hardness (base hardness) is not obtained, there is a possibility of breakage when an excessive shear stress is applied.

その他の従来技術として、所定の配合の鋼材に高周波焼入れを２回施す熱処理方法が提案されている（特許文献１参照）。
しかし、係る従来技術（特許文献１）では、二次焼入れ硬化層深さが０．５ｍｍ〜０．７ｍｍ程度であり、履帯用ピンに要求される耐摩耗性を充足させることができない、という問題が存在する。
特開平７−１１８７９１号公報 As another conventional technique, a heat treatment method in which induction hardening is performed twice on a steel material having a predetermined composition has been proposed (see Patent Document 1).
However, in the related art (Patent Document 1), the depth of the secondary quench hardened layer is about 0.5 mm to 0.7 mm, and the problem that the wear resistance required for the crawler pin cannot be satisfied. Exists.
Japanese Patent Laid-Open No. 7-118791

本発明は上述したような従来技術の問題点に鑑みて提案されたものであり、円柱状部品、とりわけ、大型（大径）の円柱状部品の熱処理方法であって、従来の方法に比較して、生産性が高く、コストを低減することができ、品質の向上を可能にする円柱状部品の熱処理方法の提供を目的としている。   The present invention has been proposed in view of the above-mentioned problems of the prior art, and is a heat treatment method for a cylindrical part, particularly a large (large diameter) cylindrical part, which is compared with the conventional method. Therefore, it is an object of the present invention to provide a heat treatment method for a cylindrical part that has high productivity, can reduce costs, and can improve quality.

本発明の円柱状部品の熱処理方法は、中炭素合金鋼から成る円柱状部品（３：ピン）の熱処理方法であって、該熱処理方法は焼入れ工程（Ｓ1）と、該焼入れ工程の後に施される焼もどし工程（Ｓ２）とを有し、前記焼入れ工程（Ｓ１）は、焼入れ第１工程（Ｓ１１）と、焼入れ第１工程の後に施される焼入れ第２工程（Ｓ１２）とを有し、前記焼入れ第１工程（Ｓ１１）は前記円柱状部品（３）の外周表面（３１ｆ）から芯部（３２）までの前記円柱状部品（３）の全体をＡｃ３変態点以上の温度に加熱して焼入れする工程であり、前記焼入れ第２工程（Ｓ１２）は前記焼入れ第１工程（Ｓ１１）で焼入れされた前記円柱状部品（３）の外周表面部（３１）のみをＡｃ３変態点以上の温度に誘導加熱して焼入れする工程であり、前記焼もどし工程（Ｓ２）は、前記焼入れ工程（Ｓ１）で焼入れされた前記円柱状部品（３）を低温焼もどしする工程であることを特徴としている（請求項１）。 The heat treatment method for a cylindrical part according to the present invention is a heat treatment method for a cylindrical part (3: pin) made of medium carbon alloy steel, and the heat treatment method is performed after the quenching step (S1) and the quenching step. Tempering step (S2), the quenching step (S1) includes a quenching first step (S11) and a quenching second step (S12) applied after the quenching first step, In the first quenching step (S11), the entire cylindrical part (3) from the outer peripheral surface (31f) to the core part (32) of the cylindrical part (3) is heated to a temperature equal to or higher than the Ac 3 transformation point. In the second quenching step (S12), only the outer peripheral surface portion (31) of the cylindrical part (3) quenched in the first quenching step (S11) has an Ac 3 transformation point or higher. A process of induction heating to temperature and quenching, Step (S2) is characterized in that the said cylindrical component which is hardened by quenching step (S1) (3) a step of returning low temperature co (claim 1).

ここで、前記焼入れ第２工程（Ｓ１２）における「外周表面部（３１）」とは、円柱状部品（３）の外周表面（３１ｆ）のみならず、外周表面（３１ｆ）から半径方向内方（深さ方向）の一定の領域を含んでいる。換言すれば、外周表面（３１ｆ）から有効硬化層深さ（ｔ）だけ半径方向内方の領域が、「外周表面部」（３１）である。
「有効硬化層深さ（ｔ）」とは、有効硬化層の厚さ（深さ：半径方向寸法）であり、円柱状部品（３）の「外周表面」（３１ｆ）から「有効硬さ位置」（３１ｆｆ）までの距離である。
「有効硬化層」は、焼入れ第２工程後に有効硬さ以上になる領域（範囲）である。「有効硬さ」は、硬化した（焼入れされた）とみなされる硬さであり、本明細書では、「８０％マルテンサイト硬さ（ＨＲＣ４５）を以って硬化した（焼入れされた）とみなしている。
「有効硬さ位置」（３１ｆｆ）は、「有効硬さ（ＨＲＣ４５）」になる位置（外周表面３１ｆからの深さ）である。
有効硬化層深さ（ｔ）は、必要な耐摩耗性を確保するために、３ｍｍ以上であるのが望ましい。 Here, the “outer peripheral surface portion (31)” in the second quenching step (S12) means not only the outer peripheral surface (31f) of the cylindrical part (3) but also the radially inner side from the outer peripheral surface (31f) ( A certain region in the depth direction). In other words, the region radially inward from the outer peripheral surface (31f) by the effective hardened layer depth (t) is the “outer peripheral surface portion” (31).
“Effective hardened layer depth (t)” is the thickness (depth: radial dimension) of the effective hardened layer, and the “effective hardness position” from the “outer peripheral surface” (31f) of the cylindrical part (3). ”(31 ff).
The “effective hardened layer” is a region (range) that becomes equal to or higher than the effective hardness after the second quenching step. “Effective hardness” is the hardness that is considered hardened (quenched), and is herein considered “hardened (quenched) with 80% martensite hardness (HRC45)”. ing.
The “effective hardness position” (31ff) is a position (depth from the outer peripheral surface 31f) that becomes the “effective hardness (HRC45)”.
The effective hardened layer depth (t) is desirably 3 mm or more in order to ensure necessary wear resistance.

ここで、前記焼入れ第１工程（Ｓ１１）の加熱は誘導加熱であるのが好ましい（請求項２）。
あるいは、前記焼入れ第１工程（Ｓ１１）の加熱は炉中加熱であるのが好ましい（請求項３）。 Here, it is preferable that the heating in the first quenching step (S11) is induction heating.
Alternatively, the heating in the first quenching step (S11) is preferably in-furnace heating (Claim 3).

そして、前記焼入れ第２工程（Ｓ１２）における外周表面部（３１）の深さ（ｔ：有効硬化層深さ）は、円柱状部品（３）の半径（Ｒ）の１／１０以上で、円柱状部品（３）の半径（Ｒ）の１／２以下であるのが好ましい（請求項４）。
すなわち、 １／１０≦ｔ／Ｒ≦１／２ であるのが好ましい。 The depth (t: effective hardened layer depth) of the outer peripheral surface portion (31) in the second quenching step (S12) is 1/10 or more of the radius (R) of the cylindrical part (3), It is preferable that it is 1/2 or less of the radius (R) of the columnar part (3).
That is, it is preferable that 1/10 ≦ t / R ≦ 1/2.

本発明において、前記円柱状部品（３）は無限軌道帯用ピンであるのが好ましい（請求項５）。   In the present invention, the cylindrical part (3) is preferably an endless track band pin (Claim 5).

そして、前記円柱状部品（３）の直径は５０ｍｍ以上であるのが好ましい。
但し、前記円柱状部品（３）の直径が５０ｍｍ未満であっても、本発明を適用することが可能である。 And it is preferable that the diameter of the said cylindrical component (3) is 50 mm or more.
However, the present invention can be applied even if the diameter of the cylindrical part (3) is less than 50 mm.

上述する構成を具備する本発明によれば、円柱状部品（３）の熱処理が４工程から３工程に削減されるので、生産性が向上し、製造コストが低減する。
また、第２工程（Ｓ１２）では外周表面部（３１）のみが焼入れ硬化するので、外周表面部（３１）に高い圧縮の残留応力が付与され、円柱状部品（３）の疲労強度が向上する。
さらに、従来の方法によるものと比べて、ピンの横断面における最大せん断応力となる位置近傍の硬さが高くなるので、過大なせん断応力が負荷されても折損を防止することができる。そのため、必要な芯部硬さ（素地硬さ）を確保するために焼入れ性の高い素材を使用する必要がなくなり、使用するべき素材として合金元素の添加（量）が少ない素材の使用が可能になり、素材調達のコストが低減する。 According to the present invention having the above-described configuration, the heat treatment of the cylindrical part (3) is reduced from four steps to three steps, so that productivity is improved and manufacturing costs are reduced.
In the second step (S12), only the outer peripheral surface portion (31) is hardened and hardened, so that high compressive residual stress is applied to the outer peripheral surface portion (31), and the fatigue strength of the cylindrical part (3) is improved. .
Further, since the hardness in the vicinity of the position where the maximum shear stress is obtained in the cross section of the pin is increased as compared with the conventional method, breakage can be prevented even if an excessive shear stress is applied. Therefore, it is not necessary to use a material with high hardenability in order to secure the necessary core hardness (base hardness), and it is possible to use a material with less addition (amount) of alloying elements as the material to be used. As a result, the cost of material procurement is reduced.

本発明において、前記焼入れ第１工程（Ｓ１１）の加熱が誘導加熱であれば（請求項２）、焼入れ工程（Ｓ１）の連続化が可能になる。
一方、本発明において、前記焼入れ第１工程（Ｓ１１）の加熱が炉中加熱であれば（請求項３）、焼入れ第１工程（Ｓ１１）の加熱に関するコストが低減する。 In the present invention, if the heating in the first quenching step (S11) is induction heating (Claim 2), the quenching step (S1) can be continued.
On the other hand, in the present invention, if the heating in the first quenching step (S11) is heating in the furnace (Claim 3), the cost related to the heating in the first quenching step (S11) is reduced.

また本発明において、前記焼入れ第２工程（Ｓ１２）における外周表面部（３１）の深さ（ｔ：有効硬化層深さ）が円柱状部品（３）の半径（Ｒ）の１／１０以上で、円柱状部品（３）の半径（Ｒ）の１／２以下に設定すれば（請求項４）、有効硬化層深さ（ｔ）が小さ過ぎてピン（３）が早期に摩耗することがなく、有効硬化層深さ（ｔ）が大き過ぎて、ピン（３）外周表面の圧縮残留応力が小さくなってしまうこともない。   Moreover, in this invention, the depth (t: effective hardening layer depth) of the outer peripheral surface part (31) in the said hardening 2nd process (S12) is 1/10 or more of the radius (R) of a cylindrical component (3). If the radius is set to ½ or less of the radius (R) of the cylindrical part (3) (Claim 4), the effective hardened layer depth (t) is too small, and the pin (3) may be worn early. In addition, the effective hardened layer depth (t) is not too large, and the compressive residual stress on the outer peripheral surface of the pin (3) is not reduced.

なお本発明において、製造される円柱状部品（３）が、たとえば、無限軌道帯用ピンであってもよいし、無限軌道帯用ピン以外の部品にも適用できる。
加えて、本発明によれば、製造される無限軌道帯用ピン（３）の直径が５０ｍｍ以上への適用を推奨するが、無限軌道帯用ピン（３）の直径は５０ｍｍ未満のものにも適用可能である。 In the present invention, the manufactured cylindrical part (3) may be, for example, an endless track band pin, or may be applied to parts other than the endless track band pin.
In addition, according to the present invention, it is recommended that the diameter of the endless track band pin (3) to be manufactured is 50 mm or more, but the diameter of the endless track band pin (3) is less than 50 mm. Applicable.

以下、添付図面を参照して、本発明の実施形態を説明する。
本発明に係る円柱状部品の熱処理方法の実施形態を説明するため、円柱状部品として、例えば、油圧ショベルやブルドーザー等の建設機械の無限軌道帯（履帯）１０（図８参照）の構成部品である履帯用ピンを例示して、説明する。ただし、円柱状部品は、履帯用ピン（以下、「ピン」と記載する。）に限るものではない。 Embodiments of the present invention will be described below with reference to the accompanying drawings.
In order to describe an embodiment of the heat treatment method for a cylindrical part according to the present invention, the cylindrical part is, for example, a component part of an endless track (crawler belt) 10 (see FIG. 8) of a construction machine such as a hydraulic excavator or a bulldozer. A crawler belt pin will be described as an example. However, the cylindrical part is not limited to a crawler belt pin (hereinafter referred to as “pin”).

また、本願発明の方法では直径が５０ｍｍ以上の大型ピンを例示しているが、本願発明の方法に係る円柱状部品の熱処理方法は、小型、中型のピンにも適用することが可能である。
ここで、小型ピンとは直径が３０ｍｍ未満のものを意味しており、中型ピンとは直径が３０ｍｍ以上で５０ｍｍ未満のものを意味しており、大型ピンとは直径が５０ｍｍ以上のものを意味している。 In the method of the present invention, a large pin having a diameter of 50 mm or more is illustrated. However, the heat treatment method for a cylindrical part according to the method of the present invention can be applied to small and medium pins.
Here, the small pin means a pin having a diameter of less than 30 mm, the medium pin means a pin having a diameter of 30 mm or more and less than 50 mm, and the large pin means a pin having a diameter of 50 mm or more. .

上述したように、建設機械の履帯１０（図８）は、図９に示すように、１対のリンク１、履板２、ピン３、ブッシュ４から成るユニットが、連続的に連結されて構成されている。
そして、履帯用のピン３（図１０参照）において、外周表面部（外周表面３１ｆから有効硬さ位置３１ｆｆまでの深さがｔの範囲）３１には、曲げ応力とねじれ応力に耐えるための強度および耐摩耗性、すなわち、硬さが要求される。一方、芯部（外周表面部３１を除く部分）３２には、せん断応力に耐えるための強度および靭性が要求される。
本願発明の方法では、外周表面部３１に要求される硬さと、芯部３２に要求されるせん断強度および靭性を熱処理によって獲得するために、中炭素合金鋼から成る素材に熱処理を施すのである。 As described above, as shown in FIG. 9, the crawler belt 10 (FIG. 8) of the construction machine is constructed by continuously connecting units each including a pair of links 1, a crawler plate 2, a pin 3, and a bush 4. Has been.
In the crawler belt pin 3 (see FIG. 10), the outer peripheral surface portion (the depth t from the outer peripheral surface 31f to the effective hardness position 31ff is 31) has a strength to withstand bending stress and torsional stress. In addition, wear resistance, that is, hardness is required. On the other hand, the core portion (portion excluding the outer peripheral surface portion 31) 32 is required to have strength and toughness to withstand shear stress.
In the method of the present invention, in order to obtain the hardness required for the outer peripheral surface portion 31 and the shear strength and toughness required for the core portion 32 by heat treatment, the material made of medium carbon alloy steel is subjected to heat treatment.

ここで、中炭素合金鋼とは、中炭素鋼にＭｎ、Ｂ、Ｃｒ、Ｍｏ、Ｎｉ等の合金元素を添加したものをいう。これらの合金元素の添加目的は、焼入れ性向上、耐摩耗性向上、靭性向上等である。
また、中炭素鋼とは、炭素含有量が質量％で０．３０以上０．５０以下のものを言う。ちなみに、低炭素鋼とは、炭素含有量が質量％で０．３０未満のものを言い、高炭素鋼とは、炭素含有量が質量％で０．５０を超えるものを言う。 Here, the medium carbon alloy steel refers to a medium carbon steel added with an alloy element such as Mn, B, Cr, Mo, or Ni. The purpose of adding these alloy elements is to improve hardenability, wear resistance, and toughness.
In addition, the medium carbon steel is one having a carbon content of 0.30 or more and 0.50 or less in mass%. Incidentally, a low carbon steel means a carbon content of less than 0.30 by mass%, and a high carbon steel means a carbon content of more than 0.50 by mass%.

本願発明の方法では、大型ピン３は、機械加工完了後、図１に示す工程に従って製造される。
図２は、本願発明の方法を、図１２〜図１５を参照して説明した従来技術（全体加熱焼入れ、全体加熱高温焼もどし、高周波焼入れ、低温焼もどしを行う従来技術）に対比させて示している。より詳細には、図２では、本願発明の方法における各工程（製造プロセス）における断面の金属組織を、図１２〜図１５の従来技術における断面の金属組織と比較して模式的に示している。
それと共に図２では、図３〜図５および図１２〜図１５を参照することにより、図示の実施形態における各工程（製造プロセス）における断面の硬さ分布と、図１２〜図１５の従来技術における断面の硬さ分布とを比較することを企図している。 In the method of the present invention, the large pin 3 is manufactured according to the process shown in FIG.
FIG. 2 shows the method of the present invention in comparison with the prior art described with reference to FIG. 12 to FIG. 15 (prior art that performs overall heating quenching, overall heating high temperature quenching, induction quenching, and low temperature quenching). ing. In more detail, in FIG. 2, the metal structure of the cross section in each process (manufacturing process) in the method of this invention is typically shown compared with the metal structure of the cross section in the prior art of FIGS. .
In addition, in FIG. 2, by referring to FIGS. 3 to 5 and FIGS. 12 to 15, the cross-sectional hardness distribution in each step (manufacturing process) in the illustrated embodiment and the prior art of FIGS. 12 to 15. It is intended to compare the hardness distribution of the cross-section at.

図１において、「機械加工完了品」なる文言で示す工程では、中炭素合金鋼から成る素材（棒鋼）に機械加工等を施して、大型ピン３に成形する。ピン３の素材はＳＣＭ４４０であり、前記したように、その成分（質量％）は図１１で示されている。   In FIG. 1, in the process indicated by the term “machine finished product”, a material (bar steel) made of medium carbon alloy steel is subjected to machining or the like to form a large pin 3. The material of the pin 3 is SCM440, and as described above, its component (mass%) is shown in FIG.

次に、ピン３を全体焼入れ装置２０に搬入し、ピン３に対して焼入れ第１工程Ｓ１１を施す。明確には図示されていないが、全体焼入れ装置２０は、加熱手段（加熱炉あるいは誘導加熱装置）と冷却装置とを有している。先ず、全体焼入れ装置２０の加熱手段により、ピン３の全体（図１０における外周表面３１ｆから芯部３２に至る全ての領域）を、Ａｃ３変態点以上の温度に加熱する。
全体焼入れ装置２０による加熱は誘導加熱によって行なってもよいし、加熱炉内で行なってもよい。
加熱を加熱炉内で行う場合には、その加熱源（エネルギー）として、重油、軽油、灯油等の化石燃料または電気が用いられる。 Next, the pin 3 is carried into the entire quenching apparatus 20 and the first quenching step S <b> 11 is performed on the pin 3. Although not clearly shown, the entire quenching device 20 has a heating means (a heating furnace or an induction heating device) and a cooling device. First, the heating means of the entire hardening apparatus 20, the whole of the pin 3 (all region extending to the core portion 32 from the outer circumferential surface 31f in FIG. 10), is heated to Ac 3 transformation point or above the temperature.
Heating by the entire quenching apparatus 20 may be performed by induction heating or in a heating furnace.
When heating is performed in a heating furnace, fossil fuels such as heavy oil, light oil, kerosene or electricity are used as the heating source (energy).

ワークのＡｃ３変態点（特定の温度）は、ワークの化学成分によって決まり、概略、次式で示される。
Ａｃ３（℃）＝９０８−２２４×Ｃ（％）＋３０×Ｓｉ（％）
−３４×Ｍｎ（％）＋４３９×Ｐ（％）−２３×Ｎｉ（％）
中炭素合金鋼では、Ａｃ３変態点は、加熱炉内での加熱の場合、概略８００℃程度（７８０〜８２０℃）である。図示しない誘導加熱（急速加熱）の場合には、Ａｃ３変態点は、加熱炉内での加熱の場合よりも１００℃程度高くなる。 The Ac 3 transformation point (specific temperature) of the workpiece is determined by the chemical component of the workpiece and is roughly represented by the following formula.
Ac 3 (° C.) = 908-224 × C (%) + 30 × Si (%)
−34 × Mn (%) + 439 × P (%) − 23 × Ni (%)
In the medium carbon alloy steel, the Ac 3 transformation point is about 800 ° C. (780 to 820 ° C.) in the case of heating in a heating furnace. In the case of induction heating (rapid heating) (not shown), the Ac 3 transformation point is about 100 ° C. higher than that in the case of heating in the heating furnace.

焼入れ第１工程Ｓ１１を誘導加熱装置によって加熱する場合、ワークの外周表面３１ｆから芯部３２に至るすべての領域がＡｃ３変態点以上の温度に加熱されるように、図示しない発振機の周波数を選定する必要がある。
ここで、周波数ｆ（ｋＨｚ）と加熱深さｄ（ｍｍ）との間には、
ｄ＝（２５０／ｆ）１／２
なる関係がある。係る関係に従って、周波数ｆを適宜設定することにより、ピン３の断面全領域をＡｃ３変態点以上の温度に加熱することができる。 When heating the quenching first step S11 by the induction heating device, so that all region from the outer peripheral surface 31f of the work to the core portion 32 is heated to the Ac 3 transformation point or above the temperature, the frequency of the oscillator (not shown) It is necessary to select.
Here, between the frequency f (kHz) and the heating depth d (mm),
d = (250 / f) 1/2
There is a relationship. By appropriately setting the frequency f in accordance with such a relationship, the entire cross-sectional area of the pin 3 can be heated to a temperature equal to or higher than the Ac 3 transformation point.

全体加熱焼入れ装置２０によりピン３の全体がＡｃ３変態点以上の温度に加熱されたならば、加熱を停止し、ワークの外周表面３１ｆの温度がＡｒ３変態点まで下がる前に、全体焼入れ装置２０の図示しない冷却装置により冷却を開始して焼入れする。
Ａｒ３変態点は、中炭素合金鋼の場合、Ａｃ３変態点より１００℃程度低い温度になる。
焼入れの際に使用する冷却液（冷却手段）としては、水、水溶性焼入れ液、油等がある。コスト面、環境面を考慮すると、冷却液として水を使用することが望ましい。 If the entire pin 3 is heated to a temperature equal to or higher than the Ac 3 transformation point by the overall heating and quenching device 20, the heating is stopped, and before the temperature of the outer peripheral surface 31f of the work is lowered to the Ar 3 transformation point, the overall quenching device The cooling is started by a cooling device (not shown) 20 and quenched.
In the case of medium carbon alloy steel, the Ar 3 transformation point is about 100 ° C. lower than the Ac 3 transformation point.
Examples of the cooling liquid (cooling means) used during quenching include water, water-soluble quenching liquid, and oil. In view of cost and environment, it is desirable to use water as the coolant.

全体加熱焼入れ装置２０によりピン３を焼入れし、焼入れ第１工程Ｓ１１が完了したならば、部分加熱焼入れ装置３０に搬入する。明確には図示されていないが、部分加熱焼入れ装置３０は、誘導加熱装置と冷却装置とを有している。そして、ピン３に高周波焼入れ工程（焼入れ第２工程）Ｓ１２を施す。
この高周波焼入れ工程（焼入れ第２工程）Ｓ１２では、焼入れ第１工程Ｓ１１で焼入れされたピン３の外周表面部３１のみを、Ａｃ３変態点以上の温度に誘導加熱する。換言すれば、焼入れ第１工程Ｓ１１ではピン３の断面全領域をＡｃ３変態点以上の温度に加熱したが、焼入れ第２工程Ｓ１２ではピン３の外周表面部３１のみをＡｃ３変態点以上の温度に加熱する。
焼入れ第１工程Ｓ１１の加熱は全体加熱であるのに対し、焼入れ第２工程Ｓ１２の加熱は、外周表面部３１のみを加熱するので、いわゆる部分加熱である。外周表面部３１のみの加熱（いわゆる部分加熱）を行うために、焼入れ第２工程Ｓ１２における加熱は、誘導加熱（例えば高周波誘導電源による加熱）によらなければならない。 When the pin 3 is quenched by the overall heating and quenching apparatus 20 and the first quenching step S <b> 11 is completed, it is carried into the partial heating and quenching apparatus 30. Although not clearly shown, the partial heating and quenching device 30 includes an induction heating device and a cooling device. Then, the pin 3 is subjected to induction hardening step (quenching second step) S12.
In the induction hardening step (hardening second step) S12, only the outer peripheral surface portion 31 of the pin 3, which is hardened by quenching the first step S11, induction heating to Ac 3 transformation point or above the temperature. In other words, the entire region of the cross section of the pin 3 was heated to a temperature equal to or higher than the Ac 3 transformation point in the first quenching step S11. However, in the second quenching step S12, only the outer peripheral surface portion 31 of the pin 3 was higher than the Ac 3 transformation point. Heat to temperature.
The heating in the first quenching step S11 is the entire heating, whereas the heating in the second quenching step S12 is a so-called partial heating because only the outer peripheral surface portion 31 is heated. In order to heat only the outer peripheral surface portion 31 (so-called partial heating), the heating in the second quenching step S12 must be based on induction heating (for example, heating by a high frequency induction power source).

ここで、外周表面部３１とは、図１０に示すように、ピン３の外周表面３１ｆのみならず、その近傍をも含む一定の深さｔ（有効硬化層深さ）を有する領域である。
「有効硬化層深さｔ」は「有効硬化層の厚さ（深さ：半径方向寸法）」であり、図１０における円柱状部品３の外周表面３１ｆから有効硬さ位置３１ｆｆまでの距離である。さらに、「有効硬化層」は、焼入れ第２工程後に有効硬さ以上になる領域（範囲）であり、「有効硬さ」は、硬化した（焼入れされた）とみなされる硬さであり、本願発明の方法では、「８０％マルテンサイト硬さ（ＨＲＣ４５）」を以って、「硬化した（焼入れされた）」とみなしている。そして、「有効硬さ位置３１ｆｆ」は、「有効硬さ（ＨＲＣ４５）」になる位置である。 Here, as shown in FIG. 10, the outer peripheral surface portion 31 is a region having a certain depth t (effective hardened layer depth) including not only the outer peripheral surface 31f of the pin 3 but also the vicinity thereof.
“Effective hardened layer depth t” is “effective hardened layer thickness (depth: radial dimension)” and is the distance from the outer peripheral surface 31f of the cylindrical part 3 to the effective hardness position 31ff in FIG. . Furthermore, the “effective hardened layer” is a region (range) that becomes equal to or higher than the effective hardness after the second quenching step, and the “effective hardness” is the hardness that is considered to be hardened (quenched). In the method of the invention, it is regarded as “cured (quenched)” with “80% martensite hardness (HRC45)”. The “effective hardness position 31ff” is a position that becomes “effective hardness (HRC45)”.

有効硬化層深さｔは、ピン３の半径Ｒの１／１０以上で、ピン３の半径Ｒの１／２以下であることが好ましい。すなわち、外周表面３１ｆからの有効硬化層深さｔは、ピンの半径をＲとすれば、Ｒ／１０≦ｔ≦Ｒ／２であるのが望ましい。
有効硬化層深さｔがＲ／１０よりも小さいと、ピン３が早期に摩耗してしまう。一方、有効硬化層深さｔがＲ／２よりも大きいと、ピン３の外周表面の圧縮残留応力が小さくなり、後述する効果（ピンに作用する引張応力を下げる効果）が得られないからである。 The effective hardened layer depth t is preferably 1/10 or more of the radius R of the pin 3 and 1/2 or less of the radius R of the pin 3. That is, the effective hardened layer depth t from the outer peripheral surface 31f is preferably R / 10 ≦ t ≦ R / 2, where R is the radius of the pin.
If the effective hardened layer depth t is smaller than R / 10, the pin 3 is worn early. On the other hand, if the effective hardened layer depth t is larger than R / 2, the compressive residual stress on the outer peripheral surface of the pin 3 becomes small, and the effect described later (the effect of reducing the tensile stress acting on the pin) cannot be obtained. is there.

これに加えて、必要な耐摩耗性を確保するために、有効硬化層深さｔは、３ｍｍ以上であることが望ましい。
有効硬化層深さｔが Ｒ／１０≦ｔ≦Ｒ／２（Ｒはピン３の半径）であり、かつ、有効硬化層深さｔが３ｍｍ以上となるように、ピン３の外周表面部３１がＡｃ３変態点以上の温度に加熱されるように、誘導加熱による加熱深さｄを決定し、周波数ｆ（ｋＨｚ）と加熱深さｄ（ｍｍ）との関係式 ｄ＝（２５０／ｆ）１／２ に従って、周波数を決定するのである。
ここで、焼入れ第１工程Ｓ１１が誘導加熱装置によって加熱される場合、焼入れ第２工程Ｓ１２の誘導加熱装置の周波数は、焼入れ第１工程Ｓ１１の誘導加熱装置と同一の周波数を使用してもよい。この際、加熱時間や電流密度などの調整によって、必要な加熱深さを得る。 In addition to this, it is desirable that the effective hardened layer depth t is 3 mm or more in order to ensure necessary wear resistance.
The outer peripheral surface portion 31 of the pin 3 so that the effective hardened layer depth t is R / 10 ≦ t ≦ R / 2 (R is the radius of the pin 3) and the effective hardened layer depth t is 3 mm or more. Is heated to a temperature equal to or higher than the Ac 3 transformation point, the heating depth d by induction heating is determined, and the relational expression between the frequency f (kHz) and the heating depth d (mm) d = (250 / f) The frequency is determined according to 1/2 .
Here, when the first quenching step S11 is heated by the induction heating device, the frequency of the induction heating device in the second quenching step S12 may use the same frequency as the induction heating device in the first quenching step S11. . At this time, the necessary heating depth is obtained by adjusting the heating time and the current density.

ピン３の外周表面部３１のみを誘導加熱することにより、ピン３の外周表面３１ｆから芯部３２にかけて温度勾配が生じる。外周表面部ではＡｃ３変態点以上であるが、芯部側すなわち半径方向内方に向かって温度は低下する。
外周表面部３１の芯部側近傍では４００〜７００℃（高温焼もどし温度に相当）となり、さらに芯部側（半径方向内方）の領域では１５０〜２５０℃（低温焼もどし温度に相当）となる。 By induction heating only the outer peripheral surface portion 31 of the pin 3, a temperature gradient is generated from the outer peripheral surface 31 f of the pin 3 to the core portion 32. Although the outer peripheral surface portion is Ac 3 transformation point or more, the temperature is lowered toward the core side or radially inward.
400 to 700 ° C. (corresponding to the high temperature tempering temperature) in the vicinity of the core portion side of the outer peripheral surface portion 31, and 150 to 250 ° C. (corresponding to the low temperature tempering temperature) in the region on the core portion side (inward in the radial direction). Become.

ピン３の外周表面部３１がＡｃ３変態点以上の温度に加熱されたならば、加熱を停止し、ピン３を図示しない誘導加熱装置から取り出し、ピン３の外周表面３１ｆの温度がＡｒ３変態点まで下がる以前の段階で、部分加熱焼入れ装置３０の図示しない冷却装置により冷却を開始して焼入れする。
上述した通り、Ａｒ３変態点は、中炭素合金鋼の場合、Ａｃ３変態点より約１００℃低い温度になる。
高周波焼入れ工程（焼入れ第２工程）Ｓ１２においても、焼入れ第１工程Ｓ１１と同様に、焼入れの際に用いられる冷却液（冷却手段）としては、コスト面、環境面からは水を使用することが望ましい。但し、水溶性焼入れ液、油等を用いてもよい。 If the outer peripheral surface portion 31 of the pin 3 is heated to a temperature equal to or higher than the Ac 3 transformation point, the heating is stopped, the pin 3 is taken out from an induction heating device (not shown), and the temperature of the outer peripheral surface 31f of the pin 3 is changed to the Ar 3 transformation. In the stage before the point is lowered to the point, cooling is started by a cooling device (not shown) of the partial heating and quenching device 30 and quenching is performed.
As described above, the Ar 3 transformation point is about 100 ° C. lower than the Ac 3 transformation point in the case of medium carbon alloy steel.
In the induction hardening step (quenching second step) S12, as in the quenching first step S11, water is used as the cooling liquid (cooling means) used during quenching from the cost and environmental viewpoints. desirable. However, a water-soluble quenching liquid or oil may be used.

高周波焼入れ工程（焼入れ第２工程）Ｓ１２において、ピン３の外周表面部３１は、再度、焼入れされる。
また、ピン３の芯部３２における外周表面部３１近傍の領域では、高周波焼入れの際に４００〜７００℃に加熱されるため、高温焼もどしが施される。
さらに、芯部３２側の中心側（半径方向内方）領域では、高周波焼入れの際に１５０〜２５０℃に加熱されるので、低温焼もどしが施される。 In the induction hardening step (quenching second step) S12, the outer peripheral surface portion 31 of the pin 3 is quenched again.
Moreover, in the area | region near the outer peripheral surface part 31 in the core part 32 of the pin 3, since it heats at 400-700 degreeC in the case of induction hardening, high temperature tempering is given.
Furthermore, in the center side (radially inward) region on the core portion 32 side, since it is heated to 150 to 250 ° C. during induction hardening, low temperature tempering is performed.

これに対して、図１２〜図１５で説明した従来技術（全体加熱焼入れ、全体加熱高温焼もどし、高周波焼入れ、低温焼もどしを行う従来技術）では、本願発明の方法における焼入れ第１工程Ｓ１１と高周波焼入れ工程（焼入れ第２工程）Ｓ１２との間に、すでに、素地高温焼もどし（図１３参照）が施されている。そのため、図１２〜図１５の従来技術における図１４の高周波焼入れ工程（本願発明の方法における焼入れ第２工程：Ｓ１２に相当する工程）では、芯部３２に対する焼もどしは行われない。   On the other hand, in the conventional techniques described in FIGS. 12 to 15 (conventional techniques for performing overall heating quenching, overall heating high temperature quenching, induction quenching, and low temperature quenching), the first quenching step S11 in the method of the present invention and Between the induction quenching step (second quenching step) S12, the substrate high-temperature tempering (see FIG. 13) has already been performed. Therefore, in the induction hardening step of FIG. 14 in the prior art of FIGS. 12 to 15 (second step of quenching in the method of the present invention: step corresponding to S12), the core portion 32 is not tempered.

換言すれば、図１２〜図１５で説明した従来技術（全体加熱焼入れ、全体加熱高温焼もどし、高周波焼入れ、低温焼もどしを行う従来技術）では、単に外周表面部のみの高周波焼入れを行っているのに対して、図示の実施形態における高周波焼入れ工程（焼入れ第２工程）Ｓ１２では、３種類の熱処理、具体的には外周表面部３１における高周波焼入れと、芯部３２の外周表面部３１側（半径方向外方）領域における高温焼もどしと、芯部３２の中心側（半径方向内方）領域における低温焼もどしを、同時に行っている。   In other words, in the conventional technology described in FIGS. 12 to 15 (conventional technology in which global heating quenching, global heating high temperature quenching, induction quenching, and low temperature quenching), only induction hardening is performed on only the outer peripheral surface portion. In contrast, in the induction hardening step (quenching second step) S12 in the illustrated embodiment, three types of heat treatment, specifically, induction hardening in the outer peripheral surface portion 31, and the outer peripheral surface portion 31 side of the core portion 32 ( High-temperature tempering in the (radially outward) region and low-temperature tempering in the central side (radially inward) region of the core portion 32 are performed simultaneously.

高周波焼入れ工程（焼入れ第２工程）Ｓ１２の後、ピン３を低温焼もどし装置４０に搬入して、ピン３に低温焼もどし（Ｓ２）を施す。
この低温焼もどし工程（Ｓ２）においても、加熱は加熱炉（低温焼もどし炉）内で行ってもよく、図示しない誘導加熱装置によってもよい。
加熱炉内で低温焼もどしを行う場合は、１５０〜２５０℃にて加熱される。加熱源（エネルギー）としては、電気または重油、軽油、灯油等の化石燃料が用いられる。 After the induction hardening step (second hardening step) S12, the pin 3 is carried into the low temperature tempering device 40, and the pin 3 is subjected to low temperature tempering (S2).
Also in this low temperature tempering step (S2), the heating may be performed in a heating furnace (low temperature tempering furnace) or by an induction heating device (not shown).
When performing low temperature tempering in a heating furnace, it is heated at 150 to 250 ° C. As the heating source (energy), fossil fuels such as electricity or heavy oil, light oil, kerosene and the like are used.

一方、誘導加熱装置で低温焼もどし工程Ｓ２を行う場合には、誘導加熱が急速加熱であるため、加熱温度は加熱炉内で行う場合よりも若干高くなる。ピン３の少なくとも外周表面部３１が低温焼もどし温度に加熱されるように、上述した周波数ｆ（ｋＨｚ）と加熱深さｄ（ｍｍ）との関係式 ｄ＝（２５０／ｆ）１／２ に基いて、図示しない発振機の周波数を選定する必要がある。
加熱後の冷却は、自然放冷でもよい。あるいは、低温焼もどし装置４０に冷却装置を設けて、強制冷却を行ってもよい。
以上により、ピン３の熱処理が完了する。 On the other hand, when the low temperature tempering step S2 is performed by the induction heating apparatus, the heating temperature is slightly higher than that performed in the heating furnace because the induction heating is rapid heating. In order that at least the outer peripheral surface portion 31 of the pin 3 is heated to the low temperature tempering temperature, the relational expression d = (250 / f) 1/2 between the frequency f (kHz) and the heating depth d (mm) described above. Therefore, it is necessary to select the frequency of an oscillator (not shown).
The cooling after heating may be natural cooling. Alternatively, a cooling device may be provided in the low temperature tempering device 40 to perform forced cooling.
Thus, the heat treatment of the pin 3 is completed.

次に、図２〜図７を参照して、図示の実施形態の作用効果を説明する。
図示の実施形態の熱処理方法は、図２でも明らかなように、従来技術に対して、円柱状部品の素地高温焼もどしの工程を省略（廃止）している。すなわち、従来の４工程からなる熱処理工程を、３工程に削減している。
この工程削減は、円柱状部品の製造時間の短縮のみならず、従来あった素地高温焼もどし工程に費やされていた熱エネルギーを不要とし、製造コストの大幅な削減につながる。 Next, with reference to FIGS. 2-7, the effect of embodiment shown is demonstrated.
As is apparent from FIG. 2, the heat treatment method of the illustrated embodiment omits (eliminates) the high-temperature tempering process of the cylindrical part as compared with the prior art. That is, the conventional heat treatment process consisting of 4 processes is reduced to 3 processes.
This process reduction not only shortens the manufacturing time of the cylindrical part, but also eliminates the heat energy that has been spent in the conventional high-temperature tempering process, leading to a significant reduction in manufacturing cost.

図３〜図５において、横軸にピンの外周表面から中心位置までの距離をとり、縦軸に硬さをとって、ピンの断面における硬さ分布を示している。図３〜図５の左端がピンの外周表面で、右端がピンの中心を示している。
図３〜図５は、それぞれ、本願発明の方法における素地焼入れ（焼入れ第１工程）後のピンの断面における硬さ分布（図３）、表面部焼入れ（焼入れ第２工程、すなわち図２における「高周波焼入れ＋焼もどし」）後のピンの断面における硬さ分布（図４）、低温焼もどし後のピンの断面における硬さ分布（図５）を示している。 3 to 5, the horizontal axis represents the distance from the outer peripheral surface of the pin to the center position, and the vertical axis represents the hardness, and the hardness distribution in the cross section of the pin is shown. 3 to 5, the left end is the outer peripheral surface of the pin, and the right end is the center of the pin.
3 to 5 show the hardness distribution (FIG. 3) in the cross section of the pin after the base quenching (quenching first step) in the method of the present invention, and the surface portion quenching (quenching second step, that is, “ The hardness distribution (FIG. 4) in the cross section of the pin after induction hardening + tempering ”) and the hardness distribution (FIG. 5) in the cross section of the pin after low temperature tempering are shown.

低温焼もどし工程後のピンの断面における硬さ分布については、従来技術（図２の下欄に示す従来技術：図１２〜図１５で説明した従来技術）では、境界部分Ｂ２（硬さが急激に低下している部分）と中心との間の領域における硬さが、ＨＲＣ３０程度である（図１５参照）。これに対して、本願発明の方法では（図５参照）、芯部３２（図２のＴ：低温焼もどし層）において、外周表面部３１との境界部分Ｂ１（硬さが急激に低下している部分）と中心との間の領域における硬さが、ＨＲＣ３２〜４０程度であり、明らかに硬さが高くなっている。
同様に、従来技術における表面部焼入れ（図２の「高周波焼入れ」）後のピンの断面における硬さ分布は（図１４、図１５参照）、境界部分Ｂ２（硬さが急激に低下している部分）と中心との間の領域における硬さがＨＲＣ３０程度であるのに対して、本願発明の方法における表面部焼入れ（図２における「高周波焼入れ＋焼もどし」）後のピンの断面における硬さ分布では（図４、図５参照）、境界部分Ｂ１（硬さが急激に低下している部分）と中心との間の領域における硬さが、ＨＲＣ３２〜４０程度であり、従来技術に比較して硬くなっている。 Regarding the hardness distribution in the cross-section of the pin after the low-temperature tempering process, the boundary portion B2 (the hardness is abrupt in the conventional technique (the conventional technique shown in the lower column of FIG. 2: the conventional technique described in FIGS. 12 to 15)). The hardness in the region between the center and the center is about HRC30 (see FIG. 15). On the other hand, in the method of the present invention (see FIG. 5), in the core portion 32 (T: low-temperature tempered layer in FIG. 2), the boundary portion B1 (hardness sharply decreases) with the outer peripheral surface portion 31. The hardness in the region between the center) and the center is about HRC 32 to 40, and the hardness is clearly high.
Similarly, the hardness distribution in the cross section of the pin after surface portion quenching ("high frequency quenching" in FIG. 2) in the prior art (see FIGS. 14 and 15), the boundary portion B2 (hardness is drastically decreased). Hardness in the cross section of the pin after surface portion quenching ("induction quenching + tempering" in FIG. 2) in the method of the present invention, whereas the hardness in the region between the part) and the center is about HRC30 In the distribution (see FIG. 4 and FIG. 5), the hardness in the region between the boundary portion B1 (the portion where the hardness sharply decreases) and the center is about HRC32 to 40, which is compared with the conventional technology. It is hard.

ここで、外周表面部３１との境界部分（硬さが急激に低下している部分：図４、図５におけるＢ１：図１４、図１５におけるＢ２）と中心との間の領域は、ピン３への負荷による最大せん断応力が作用する領域でもある。係る領域における硬さが増加することは、最大せん断応力に対する強度が増加したことを意味している。すなわち、従来の方法によるものと比べて、図示の実施形態により製造されたピン３は、過大な負荷が作用しても折損し難いのである。
また、必要な芯部硬さ（素地硬さ）を確保するために焼入れ性の高い素材を使用する必要がなくなり、高価な素材を必要としなくなるため、素材調達に係るコストが低減する。
なお、図２の高周波焼入れにおける符号Ｑは、高周波焼入れによって形成された（外周）表面硬化層を示している。 Here, the region between the boundary portion with the outer peripheral surface portion 31 (the portion where the hardness is rapidly decreased: B1 in FIGS. 4 and 5: B2 in FIGS. 14 and 15) and the center is the pin 3. It is also the region where the maximum shear stress due to the load on the layer acts. An increase in hardness in such a region means that the strength against the maximum shear stress has increased. That is, the pin 3 manufactured according to the illustrated embodiment is less likely to break even when an excessive load is applied, as compared with the conventional method.
In addition, it is not necessary to use a material with high hardenability in order to secure the necessary core hardness (base hardness), and an expensive material is not required, so the cost for material procurement is reduced.
In addition, the code | symbol Q in the induction hardening of FIG. 2 has shown the surface hardening layer (outer periphery) formed by induction hardening.

図６は、本願発明の方法により製造されたピン３の表面残留応力の測定結果を、従来技術で製造されたピンと比較して示している。図６の横軸は、円周方向の残留応力の測定値を示し、縦軸は軸方向の残留応力の測定値を示している。ここで、負の値は圧縮応力を意味している。したがって、絶対値が大きいほど圧縮残留応力が大きいということになる。
図６から明らかなように、本願発明の方法で製造されたピンの表面圧縮残留応力は、従来技術で製造されたピンに比べて、円周方向においては同程度であるが、軸方向においては大きくなった。すなわち、本発明の方法で製造されたピンにおいては、軸方向の圧縮残留応力が大きくなるという作用効果を奏する。 FIG. 6 shows the measurement result of the surface residual stress of the pin 3 manufactured by the method of the present invention in comparison with the pin manufactured by the prior art. The horizontal axis of FIG. 6 shows the measured value of the residual stress in the circumferential direction, and the vertical axis shows the measured value of the residual stress in the axial direction. Here, a negative value means a compressive stress. Therefore, the larger the absolute value, the greater the compressive residual stress.
As is apparent from FIG. 6, the surface compressive residual stress of the pin manufactured by the method of the present invention is comparable in the circumferential direction as compared to the pin manufactured by the prior art, but in the axial direction. It became bigger. That is, in the pin manufactured by the method of the present invention, there is an effect that the compressive residual stress in the axial direction increases.

外周表面の圧縮残留応力の増加は、ピン３の外周表面３１ｆに、例えば、ショットピーニングや、ショットブラスト等を施したのと同等の効果が得られる。
そのため、ピン３に過大な負荷が作用して、その表面に引張応力が生じても、従来技術で製造されたピンに比較して、増加した圧縮残留応力の分だけ当該引張応力は減少する。 An increase in the compressive residual stress on the outer peripheral surface provides the same effect as that obtained when, for example, shot peening or shot blasting is performed on the outer peripheral surface 31f of the pin 3.
Therefore, even if an excessive load acts on the pin 3 and a tensile stress is generated on the surface thereof, the tensile stress is reduced by an amount corresponding to the increased compressive residual stress as compared with the pin manufactured by the prior art.

図７は、本願発明の方法により製造されたピン３の曲げ試験結果を、従来の方法で製造されたピンと比較して示している。図７の横軸はたわみの最大値を示し、縦軸は曲げ荷重の最大値を示している。
図７から明らかなように、本願発明の方法で製造されたピンの曲げ強度（図７では曲げ荷重）は、従来の方法で製造されたピンに比べて高くなっている。 FIG. 7 shows the bending test result of the pin 3 manufactured by the method of the present invention in comparison with the pin manufactured by the conventional method. The horizontal axis in FIG. 7 indicates the maximum value of deflection, and the vertical axis indicates the maximum value of bending load.
As is clear from FIG. 7, the bending strength (bending load in FIG. 7) of the pin manufactured by the method of the present invention is higher than that of the pin manufactured by the conventional method.

図６および図７から明らかなように、本願発明の方法によれば、素材をより安価なものに変更することが可能であり、あるいは、従来と同等の強度を有する素材であれば、ピンの小型化が可能となる。   As is apparent from FIGS. 6 and 7, according to the method of the present invention, the material can be changed to a cheaper one, or if the material has the same strength as the conventional one, Miniaturization is possible.

明確には図示されていないが、図示の実施形態において、焼入れ第１工程Ｓ１１の加熱を誘導加熱とすれば、焼入れ第２工程Ｓ１２も誘導加熱であるので、いわゆる「焼入れ工程のインライン化」が可能になる。
あるいは、焼入れ第１工程Ｓ１１の加熱を炉中加熱とすれば、誘導加熱炉に比べ、投入するエネルギーが削減でき、焼入れ第１工程Ｓ１１の加熱のコストが低減する。 Although not clearly illustrated, in the illustrated embodiment, if the heating in the first quenching step S11 is induction heating, the second quenching step S12 is also induction heating. It becomes possible.
Alternatively, if the heating in the first quenching step S11 is heating in the furnace, the energy to be charged can be reduced as compared with the induction heating furnace, and the heating cost in the first quenching step S11 is reduced.

図示の実施形態はあくまでも例示であり、本発明の技術範囲を限定する趣旨の記述ではないことを付記する。
例えば、図示の実施形態では、建設機械の無限軌道帯用１０の大型ピン３を例にとって図示の実施形態を説明したが、小型、中型のピンにも適用することが可能である。さらには、無限軌道帯用ピン以外の円柱状部品の熱処理にも適用することが可能である。 It should be noted that the illustrated embodiment is merely an example, and is not a description that limits the technical scope of the present invention.
For example, in the illustrated embodiment, the illustrated embodiment has been described by taking the large pin 3 for the endless track zone 10 of the construction machine as an example, but it can also be applied to small and medium pins. Further, it can be applied to heat treatment of cylindrical parts other than the endless track band pins.

本発明の実施形態に係る円柱状部品の熱処理の工程図。Process drawing of the heat processing of the cylindrical component which concerns on embodiment of this invention. 本発明の実施形態における各工程（製造プロセス）における金属組織や硬さ分布を、従来技術に対比させて模式的に示した比較図。The comparison figure which showed typically the metal structure and hardness distribution in each process (manufacturing process) in embodiment of this invention in contrast with the prior art. 本発明の実施形態で焼入れ第１工程を施されたピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin which gave the hardening 1st process in embodiment of this invention. 本発明の実施形態で焼入れ第２工程を施されたピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin which gave the hardening 2nd process in embodiment of this invention. 本発明の実施形態で低温焼もどし工程を施されたピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin in which the low temperature tempering process was given in embodiment of this invention. 本発明の実施形態と従来技術の熱処理工程後におけるピンの表面残留応力の測定結果を比較して示す図。The figure which compares and shows the measurement result of the surface residual stress of the pin after the heat processing process of embodiment of this invention, and a prior art. 本発明の実施形態と従来技術の熱処理工程後におけるピンの曲げ強度の測定結果を比較して示す図。The figure which compares and shows the measurement result of the bending strength of the pin after the heat processing process of embodiment of this invention, and a prior art. 建設機械の無限軌道帯（履帯）の斜視図。The perspective view of the endless track (crawler belt) of a construction machine. 建設機械の無限軌道帯（履帯）の構成要素の分解斜視図。The disassembled perspective view of the component of the endless track (crawler belt) of a construction machine. 無限軌道帯（履帯）のピンの斜視図。The perspective view of the pin of an endless track (crawler belt). 熱処理の対象であるピンの素材の組成表の一例を示す図。The figure which shows an example of the composition table | surface of the raw material of the pin which is the object of heat processing. 従来技術における素地調質焼入れ後のピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin after the base material temper hardening in a prior art. 従来技術における素地調質高温焼もどし後のピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin after the base-tempering high temperature tempering in a prior art. 従来技術における高周波焼入れ後のピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin after induction hardening in a prior art. 従来技術における低温焼もどし後のピンの断面における硬さ分布を示す図。The figure which shows the hardness distribution in the cross section of the pin after the low temperature tempering in a prior art.

符号の説明Explanation of symbols

１・・・リンク
２・・・履板
３・・・円柱状部材（履帯用ピン）
４・・・ブッシュ
２０・・・全体加熱焼入れ装置
３０・・・部分加熱焼入れ装置
３１・・・外周表面部
３１ｆ・・・外周表面
３２・・・芯部
４０・・・低温焼もどし装置 DESCRIPTION OF SYMBOLS 1 ... Link 2 ... Track board 3 ... Cylindrical member (crawler belt pin)
4 ... Bush 20 ... Whole heating and quenching device 30 ... Partial heating and quenching device 31 ... Outer peripheral surface portion 31f ... Outer peripheral surface 32 ... Core portion 40 ... Low temperature quenching device

Claims (5)

中炭素合金鋼から成る円柱状部品（３）の熱処理方法であって、該熱処理方法は焼入れ工程（Ｓ１）と、該焼入れ工程の後に施される焼もどし工程（Ｓ２）とを有し、前記焼入れ工程（Ｓ１）は、焼入れ第１工程（Ｓ１１）と、焼入れ第１工程の後に施される焼入れ第２工程（Ｓ１２）とを有し、前記焼入れ第１工程（Ｓ１１）は前記円柱状部品（３）の外周表面（３１ｆ）から芯部（３２）までの前記円柱状部品（３）の全体をＡｃ３変態点以上の温度に加熱して焼入れする工程であり、前記焼入れ第２工程（Ｓ１２）は前記焼入れ第１工程（Ｓ１１）で焼入れされた前記円柱状部品（３）の外周表面部（３１）のみをＡｃ３変態点以上の温度に誘導加熱して焼入れする工程であり、前記焼もどし工程（Ｓ２）は、前記焼入れ工程で（Ｓ１）焼入れされた前記円柱状部品（３）を低温焼もどしする工程であることを特徴とする円柱状部品の熱処理方法。 A heat treatment method for a cylindrical part (3) made of medium carbon alloy steel, the heat treatment method comprising a quenching step (S1) and a tempering step (S2) applied after the quenching step, The quenching step (S1) has a quenching first step (S11) and a quenching second step (S12) applied after the quenching first step, and the quenching first step (S11) is the columnar part. It is a step of heating and quenching the entire cylindrical part (3) from the outer peripheral surface (31f) to the core portion (32) of (3) at a temperature equal to or higher than the Ac 3 transformation point, and the second quenching step ( S12) is a step of quenching by induction heating only the outer peripheral surface portion (31) of the cylindrical part (3) quenched in the first quenching step (S11) to a temperature equal to or higher than the Ac 3 transformation point, The tempering step (S2) is the quenching step (S ) Hardened by heat treatment method of the cylindrical part, characterized in that the cylindrical part (3) is a step of returning low temperature co. 前記焼入れ第１工程（Ｓ１１）の加熱が誘導加熱である請求項１の円柱状部品の熱処理方法。 The heat treatment method for a cylindrical part according to claim 1, wherein the heating in the first quenching step (S11) is induction heating. 前記焼入れ第１工程（Ｓ１１）の加熱が炉中加熱である請求項１の円柱状部品の熱処理方法。 The heat treatment method for a cylindrical part according to claim 1, wherein the heating in the first quenching step (S11) is heating in a furnace. 前記焼入れ第２工程（Ｓ１２）における外周表面部（３１）の深さ（ｔ）が、円柱状部品の半径（Ｒ）の１／１０以上で、円柱状部品の半径（Ｒ）の１／２以下である請求項１〜３の何れか１項の円柱状部品の熱処理方法。 The depth (t) of the outer peripheral surface portion (31) in the second quenching step (S12) is 1/10 or more of the radius (R) of the cylindrical part, and 1/2 of the radius (R) of the cylindrical part. The heat treatment method for a cylindrical part according to any one of claims 1 to 3. 前記円柱状部品（３）が無限軌道帯用ピンである請求項１〜４の何れか１項の円柱状部品の熱処理方法。 The method for heat treatment of a cylindrical part according to any one of claims 1 to 4, wherein the cylindrical part (3) is an endless track band pin.
JP2008260347A 2007-11-12 2008-10-07 Heat treatment method for cylindrical parts Active JP5371084B2 (en)

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Application Number Priority Date Filing Date Title
JP2008260347A JP5371084B2 (en) 2007-11-12 2008-10-07 Heat treatment method for cylindrical parts
EP08849643.5A EP2224021A4 (en) 2007-11-12 2008-10-30 Method for heat treatment of columnar component
US12/741,556 US9303297B2 (en) 2007-11-12 2008-10-30 Heat treatment method of pin for endless track
CN201310541169.3A CN103773937B (en) 2007-11-12 2008-10-30 The heat treating method of columnar component
PCT/JP2008/069724 WO2009063753A1 (en) 2007-11-12 2008-10-30 Method for heat treatment of columnar component
CN200880115603.9A CN101855372B (en) 2007-11-12 2008-10-30 Method for heat treatment of columnar component
EP14160659.0A EP2746411A3 (en) 2007-11-12 2008-10-30 Method for heat treatment of columnar work

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Publication number Priority date Publication date Assignee Title
KR101746089B1 (en) * 2016-01-06 2017-06-12 주식회사 흥국 Excavator's lower roller with quenching tempering
KR101746091B1 (en) * 2016-01-06 2017-06-12 주식회사 흥국 Excavator's lower roller menufacturing method with quenching tempering
CN107523678A (en) * 2017-09-08 2017-12-29 常熟市瑞思知识产权服务有限公司 A kind of Technology for Heating Processing of collet
JP2019137890A (en) * 2018-02-09 2019-08-22 トピー工業株式会社 Pin for endless track belt

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JPH0452247A (en) * 1990-06-19 1992-02-20 Topy Ind Ltd Pin for track assembly and its manufacture
JPH1096010A (en) * 1996-09-20 1998-04-14 Hitachi Constr Mach Co Ltd Heat treatment member, heat treatment method, and heat treatment apparatus
JPH11279647A (en) * 1998-03-27 1999-10-12 Topy Ind Ltd Method for tempering cylindrical work
JP2000239744A (en) * 1998-01-29 2000-09-05 Topy Ind Ltd Heat treatment method for hollow cylindrical work
JP2006009145A (en) * 2004-05-24 2006-01-12 Komatsu Ltd Rolling member and production method thereof

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JPH0452247A (en) * 1990-06-19 1992-02-20 Topy Ind Ltd Pin for track assembly and its manufacture
JPH1096010A (en) * 1996-09-20 1998-04-14 Hitachi Constr Mach Co Ltd Heat treatment member, heat treatment method, and heat treatment apparatus
JP2000239744A (en) * 1998-01-29 2000-09-05 Topy Ind Ltd Heat treatment method for hollow cylindrical work
JPH11279647A (en) * 1998-03-27 1999-10-12 Topy Ind Ltd Method for tempering cylindrical work
JP2006009145A (en) * 2004-05-24 2006-01-12 Komatsu Ltd Rolling member and production method thereof

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101746089B1 (en) * 2016-01-06 2017-06-12 주식회사 흥국 Excavator's lower roller with quenching tempering
KR101746091B1 (en) * 2016-01-06 2017-06-12 주식회사 흥국 Excavator's lower roller menufacturing method with quenching tempering
CN107523678A (en) * 2017-09-08 2017-12-29 常熟市瑞思知识产权服务有限公司 A kind of Technology for Heating Processing of collet
JP2019137890A (en) * 2018-02-09 2019-08-22 トピー工業株式会社 Pin for endless track belt
JP7075233B2 (en) 2018-02-09 2022-05-25 トピー工業株式会社 Track pin

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