WO2009145168A1 - Manufacturing method for machine parts having superior rolling-contact fatigue life - Google Patents

Manufacturing method for machine parts having superior rolling-contact fatigue life Download PDF

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WO2009145168A1
WO2009145168A1 PCT/JP2009/059573 JP2009059573W WO2009145168A1 WO 2009145168 A1 WO2009145168 A1 WO 2009145168A1 JP 2009059573 W JP2009059573 W JP 2009059573W WO 2009145168 A1 WO2009145168 A1 WO 2009145168A1
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steel
plastic working
subjected
present
condition
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PCT/JP2009/059573
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French (fr)
Japanese (ja)
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和弥 橋本
威史 藤松
典正 常陰
和彦 平岡
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山陽特殊製鋼株式会社
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Priority claimed from JP2008-138774 external-priority
Priority claimed from JP2008138776A external-priority patent/JP5403946B2/en
Priority claimed from JP2008138775A external-priority patent/JP5473249B2/en
Priority claimed from JP2008138774A external-priority patent/JP5403945B2/en
Application filed by 山陽特殊製鋼株式会社 filed Critical 山陽特殊製鋼株式会社
Priority to SE1051359A priority Critical patent/SE536953C2/en
Priority to CN2009801292273A priority patent/CN102105604B/en
Publication of WO2009145168A1 publication Critical patent/WO2009145168A1/en

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16CSHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30Parts of ball or roller bearings
    • F16C33/58Raceways; Race rings
    • F16C33/64Special methods of manufacture
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26Methods of annealing
    • C21D1/32Soft annealing, e.g. spheroidising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00Heat treatment of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium

Abstract

Provided is a manufacturing method for machine parts having a surface hardness of at least 58 HRC, in which a superior stable rolling-contact fatigue life is achieved even if there is no reduction in nonmetallic inclusions or decrease in size thereof when the steel is manufactured, compared to steel material for which there is a reduction in nonmetallic inclusions and a decrease in size thereof when the steel is manufactured. In addition to a process for imparting to steel for mechanical structures the steel shape or a process for imparting the subsequent machine part shape, the method includes a process in which the steel is worked in the previous process, the steel is heated to at least 780°C, and a hydrostatic pressure of at least 80 MPa is applied to create very close contact at the interface between the nonmetallic inclusions in the steel and the steel, which is the parent phase, after which some or all of the steel is quenched and tempered.

Description

転動疲労寿命に優れた機械部品の製造方法Manufacturing method of machine parts with excellent rolling fatigue life 関連出願の相互参照Cross-reference of related applications
 この出願は、2008年5月27日に出願された日本国特許出願2008-138774号、2008年5月27日に出願された日本国特許出願2008-138775号、および2008年5月27日に出願された日本国特許出願2008-138776号の優先権を主張するものであり、これらの全体の開示内容が参照により本明細書に組み込まれる。 This application includes Japanese Patent Application No. 2008-138774 filed on May 27, 2008, Japanese Patent Application No. 2008-138775 filed on May 27, 2008, and May 27, 2008. It claims the priority of the Japanese Patent Application No. 2008-138776 filed, the entire disclosure content of which is incorporated herein by reference.
 本発明は、軸受、ギア、ハブユニット、無段変速機、等速ジョイント、ピストンピンなどの、非金属介在物や空洞が破損起点である転動疲労寿命が求められ、表面硬さが58HRC以上に硬化されて使用される鋼材からなる機械部品の製造方法に関するものである。 The present invention requires a rolling fatigue life in which non-metallic inclusions and cavities such as bearings, gears, hub units, continuously variable transmissions, constant velocity joints, piston pins, etc. are damaged, and has a surface hardness of 58 HRC or more. The present invention relates to a method for manufacturing a machine part made of a steel material that is used after being hardened.
 近年、各種の機械装置の高性能化にともない、転動疲労寿命が求められる機械部品や装置の使用環境は非常に厳しくなり、寿命の向上ならびに信頼性の向上が強く求められている。このような要求に対し、鋼材の面からの対策としては、鋼成分の適正化や不純物元素の低減化が行われている。 In recent years, with the improvement in performance of various mechanical devices, the use environment of mechanical parts and devices that require a rolling fatigue life has become extremely severe, and there is a strong demand for improved life and improved reliability. In response to such demands, as countermeasures from the aspect of steel materials, optimization of steel components and reduction of impurity elements are performed.
 鋼成分の不純物元素のうち、酸素、窒素、硫黄はそれぞれAl23、MnS、TiNといった非金属介在物を形成し鋼部品の破損の起点となるため、特に有害であることが知られている。さらに、非金属介在物の径が大きいほど、鋼部品の転がり疲労寿命は短くなることが知られている。そのため非金属介在物量を少なく、すなわち、鋼の清浄度が高く、介在物径が20μm以上の大型の酸化物系非金属介在物の極めて少ない高清浄度鋼が種々提案されている(例えば、特開2006-63402号公報および特開平6-192790号公報参照)。 Among the impurity elements of steel components, oxygen, nitrogen, and sulfur are known to be particularly harmful because they form non-metallic inclusions such as Al 2 O 3 , MnS, and TiN, respectively, and cause damage to steel parts. Yes. Furthermore, it is known that the rolling fatigue life of a steel part becomes shorter as the diameter of the nonmetallic inclusion is larger. For this reason, various types of high cleanliness steels having a small amount of nonmetallic inclusions, that is, high cleanliness of the steel and extremely large oxide nonmetallic inclusions having an inclusion diameter of 20 μm or more have been proposed (for example, special features (See Kaikai 2006-63402 and JP-A-6-192790).
 このような高清浄度鋼からなる鋼材を用いても、短寿命で破損することを十分には抑制することができていない。そのため、鋼材中の非金属介在物を低減し、さらに該非金属介在物を小径化しようとする開発が盛んに行なわれている。 Even if such a steel material made of high cleanliness steel is used, it is not possible to sufficiently prevent breakage with a short life. For this reason, development has been actively conducted to reduce non-metallic inclusions in steel materials and to further reduce the diameter of the non-metallic inclusions.
 本発明者らは、今般、鋼の製造時に非金属介在物の低減および非金属介在物の小径化を図らなくても、鋼中の非金属介在物と母相である鋼との隙間を無くした状態の鋼材とすることで、該鋼材からなる表面硬さが58HRC以上で、かつ、剥離を抑制し、転動疲労寿命に優れた機械用部品を得ることができるとの知見を得た。 The present inventors have now eliminated the gap between the nonmetallic inclusions in the steel and the parent steel, without reducing the nonmetallic inclusions and reducing the diameter of the nonmetallic inclusions during the production of the steel. It was found that by using the steel material in the state, the surface hardness of the steel material is 58 HRC or more, and peeling can be suppressed and a machine part excellent in rolling fatigue life can be obtained.
 すなわち、軸受その他の機械部品において転動疲労寿命を改善するためには、これらの機械部品用鋼材から、非金属介在物を少なくすることが重要である。さらに軸受その他の機械部品の転走面下に大きな非金属介在物が存在すれば、該機械部品に剥離を発生させ、破損に至らせることから、軸受その他の機械部品の転走面下の危険部位に出現する非金属介在物を小さくすることが軸受その他の機械部品の寿命向上に対して特に重要であることが知られている。そこで、量産の製造工程において、非金属介在物を小径化する方策が多く発明されているが、安定して非金属介在物を小径化することは難しかった。 That is, in order to improve the rolling fatigue life of bearings and other machine parts, it is important to reduce non-metallic inclusions from these machine part steels. Furthermore, if there are large non-metallic inclusions under the rolling surface of bearings and other machine parts, the machine parts will be peeled off, leading to damage. It is known that reducing non-metallic inclusions appearing at the site is particularly important for improving the life of bearings and other machine parts. Thus, many measures have been invented to reduce the diameter of nonmetallic inclusions in mass production processes, but it has been difficult to stably reduce the diameter of nonmetallic inclusions.
 本発明者らは、転動疲労における破損すなわち剥離に至る過程について、人工欠陥材を用いて亀裂観察を行なうことで鋭意詳細に検討した。非金属介在物から亀裂発生および進展して剥離に至る過程において、非金属介在物の周囲への応力集中効果により、亀裂が変位する初期亀裂(以下「開口型の初期亀裂」という)過程を経ることを見出した。その後、せん断応力による亀裂の伝播を経て破損に至ることは従来の知見通りである。このことは、本発明者らが見出した開口型の初期亀裂が起こらなければ、その後の亀裂伝播や破損が起こらないことを意味する。また開口型の初期亀裂は非金属介在物と母相との界面に物理的な隙間すなわち空洞が生じていることを前提として起こるのであり、物理的な隙間が生じていなければ、開口型の亀裂は生じないことも応力計算により検証している(参照により本明細書に組み込まれる、鉄と鋼、94(2008)、p.13および平成20年度兵庫県立大学学位論文、平岡和彦(2008年1月)を参照)。 The present inventors diligently examined the process leading to breakage in rolling fatigue, that is, peeling, by observing cracks using an artificial defect material. In the process of crack initiation and debonding from non-metallic inclusions, it undergoes an initial crack (hereinafter referred to as “opening-type initial crack”) process in which the crack is displaced by the stress concentration effect around the non-metallic inclusions. I found out. After that, it is a conventional knowledge that the crack is propagated by the propagation of the crack due to the shear stress. This means that if the opening-type initial crack found by the present inventors does not occur, subsequent crack propagation and breakage will not occur. In addition, the opening-type initial crack occurs on the premise that there is a physical gap, that is, a cavity, at the interface between the nonmetallic inclusion and the parent phase. If there is no physical gap, the opening-type crack It has also been verified by stress calculation (Iron and Steel, 94 (2008), p. 13 and 2008 Hyogo Prefectural University Doctoral Dissertation, Kazuhiko Hiraoka (2008 1 Month)).
 さらに物理的な隙間は、鋼材の製造過程、部材に成形していく過程において必ず行なわれる何らかの塑性加工、すなわち、熱間圧延、冷間圧延、熱間鍛造、温間鍛造、冷間鍛造、ローリング鍛造、冷間転造、冷間ヘッダー加工ならびに引抜き加工などによって生じることも見出した。図1に熱間圧延鋼材から切り出し、イオンミリングを行った後に、走査電子顕微鏡(FE-SEM)にて非金属介在物1周囲の空洞有無を観察した影像を概念図にて示す。図1において、符号の2はAl23であり、符号の3は空洞である。特に機械構造用鋼では、通常Alによる脱酸が行なわれる。その際に生成するAl23系非金属介在物は母材との変形能の違いや形状から特に母相との界面に空洞が生成しやすいことを確認している。本発明は以上の新たに得た知見に基づきなされたものである。 Furthermore, the physical gap is any plastic processing that is always performed in the manufacturing process of steel materials and in the process of forming into members, that is, hot rolling, cold rolling, hot forging, warm forging, cold forging, rolling. It has also been found that it is caused by forging, cold rolling, cold header processing and drawing. FIG. 1 is a conceptual diagram showing an image obtained by observing the presence or absence of cavities around a nonmetallic inclusion 1 with a scanning electron microscope (FE-SEM) after being cut out from a hot rolled steel material and subjected to ion milling. In FIG. 1, reference numeral 2 is Al 2 O 3 and reference numeral 3 is a cavity. In particular, in machine structural steel, deoxidation with Al is usually performed. It has been confirmed that the Al 2 O 3 -based non-metallic inclusions generated at that time tend to generate cavities, particularly at the interface with the parent phase, due to the difference in deformability and shape from the parent material. The present invention has been made based on the above newly obtained knowledge.
 したがって、本発明の目的は、鋼の製造時に非金属介在物の低減およびその小径化を図らなくても、鋼材中に含有する非金属介在物と母相である鋼との界面状態を改善した鋼材とすることで、鋼の製造時に非金属介在物の低減およびその小径化を図った鋼材に比べて、優れた転動疲労寿命が安定して得られる機械用部品の製造方法を提供することにある。 Therefore, the object of the present invention is to improve the interface state between the non-metallic inclusions contained in the steel and the steel as the parent phase without reducing the non-metallic inclusions and reducing the diameter during the production of the steel. To provide a method of manufacturing a machine part that can stably obtain a superior rolling fatigue life compared to a steel material in which non-metallic inclusions are reduced and the diameter thereof is reduced when steel is manufactured. It is in.
 本発明によれば、機械構造用鋼の一部もしくは全体を焼入焼戻し処理により転動疲労寿命に優れた表面硬さ58HRC以上の機械部品を製造する方法であって、
 機械構造用鋼を、鋼材形状を付与するための工程またはその後の機械部品形状を付与するための工程に付し、該工程中で該鋼に塑性加工を施し、
 該塑性加工が施された鋼を780℃以上に加熱して80MPa以上の静水圧を付与し、それにより、該鋼中に含有する非金属介在物と母相である鋼との界面を密着させ、その後、
 該鋼の一部もしくは全体を焼入焼戻し処理に付する
工程を含んでなる方法が提供される。
According to the present invention, a method of manufacturing a machine part having a surface hardness of 58 HRC or more excellent in rolling fatigue life by quenching and tempering a part or the whole of a structural structural steel,
Machine structural steel is subjected to a step for imparting a steel material shape or a subsequent step for imparting a machine part shape, and the steel is subjected to plastic working in the step,
The steel subjected to the plastic working is heated to 780 ° C. or more to give a hydrostatic pressure of 80 MPa or more, thereby bringing the interface between the nonmetallic inclusions contained in the steel and the steel as the parent phase into close contact. ,afterwards,
There is provided a method comprising the step of subjecting part or all of the steel to a quenching and tempering treatment.
 本発明の第一の好ましい態様によれば、前記加熱が800℃以上で行われ、前記静水圧が100MPa以上である、上記製造方法が提供される。 According to a first preferred embodiment of the present invention, there is provided the above production method, wherein the heating is performed at 800 ° C. or higher and the hydrostatic pressure is 100 MPa or higher.
 本発明の第二の好ましい態様によれば、前記塑性加工を受ける機械構造用鋼が、通常のAlに加えてSiを含む脱酸剤を添加して、あるいは、Alからなる脱酸剤を添加することなく、脱酸されたものである、上記製造方法が提供される。 According to a second preferred embodiment of the present invention, the mechanical structural steel subjected to the plastic working is added with a deoxidizer containing Si in addition to normal Al, or a deoxidizer composed of Al is added. The above production method is provided without deoxidization.
 本発明の第三の好ましい態様によれば、前記塑性加工を受ける機械構造用鋼が、通常のAlに加えてCaを含む脱酸剤を添加して脱酸されたものである、上記製造方法が提供される。 According to a third preferred aspect of the present invention, the mechanical structural steel subjected to the plastic working is deoxidized by adding a deoxidizing agent containing Ca in addition to normal Al. Is provided.
 本発明の機械用部品の製造方法によれば、鋼材の製造時に非金属介在物の低減および小径化を図らなくても、何らかの塑性加工により鋼中に含有する非金属介在物と母相である鋼との界面に生じた物理的な隙間すなわち空洞を消滅させ、これらからなる界面を密着させうるならば、非金属介在物を破壊起点とする転動疲労による剥離が回避され、その結果、大幅に寿命が向上すると見込まれる。 According to the method for manufacturing a machine part of the present invention, it is a non-metallic inclusion and a parent phase contained in steel by some plastic working without reducing non-metallic inclusions and reducing the diameter when manufacturing a steel material. If the physical gaps or cavities generated at the interface with the steel can be eliminated and the interface consisting of these can be adhered, peeling due to rolling fatigue starting from non-metallic inclusions can be avoided. Life expectancy is expected to improve.
熱間圧延した鋼材から試料を切り出し、イオンミリングを行なった後に、走査電子顕微鏡(FE-SEM)にて非金属介在物周囲の空洞有無を観察した影像を示す概念図である。FIG. 5 is a conceptual diagram showing an image obtained by observing the presence or absence of cavities around non-metallic inclusions with a scanning electron microscope (FE-SEM) after cutting out a sample from hot-rolled steel and performing ion milling.
 本発明における機械構造用鋼は、軸受、ギア、ハブユニット、無段変速機、等速ジョイント、ピストンピンなどの機械部品に求められる鋼を広く包含する。具体的には、このような機械構造用鋼としては、一般的にJIS G 4805に規定されている高炭素クロム軸受鋼鋼材、JIS G 4051に規定されている機械構造用炭素鋼鋼材、JIS G 4052に規定されている焼入れ性を保証した構造用鋼鋼材(H鋼)、JIS G 4053に規定されている機械構造用合金鋼鋼材、JIS G 3441に規定されている機械構造用合金鋼鋼管、JIS G 3445に規定されている機械構造用炭素鋼鋼管、JIS G 3507-1に規定されている冷間圧造用炭素鋼-第1部:線材、JIS G 3507-2に規定されている冷間圧造用炭素鋼-第2部:線、JIS G 3509-1に規定されている冷間圧造用合金鋼-第1部:線材、JIS G 3509-2に規定されている冷間圧造用合金鋼-第2部:線、およびそれぞれの関連外国規格鋼、さらにそれぞれの成分類似鋼と成分改良鋼が使用されており、これらのJIS規格の記載は参照により本明細書に組み込まれる。本発明における機械構造用鋼とは上記JIS規格に記載の化学成分を満足する鋼材を包含する。 The steel for machine structure in the present invention widely includes steels required for machine parts such as bearings, gears, hub units, continuously variable transmissions, constant velocity joints, piston pins and the like. Specifically, as such machine structural steel, high carbon chromium bearing steel generally defined in JIS G 4805, carbon steel for mechanical structure defined in JIS G 4051, JIS G Steel steel for structural use (H steel) that guarantees the hardenability specified in 4052, alloy steel for machine structure specified in JIS G 4053, alloy steel pipe for machine structure specified in JIS G 3441, Carbon steel pipe for machine structure specified in JIS G 3445, Carbon steel for cold heading specified in JIS G 3507-1-Part 1: Wire, Cold specified in JIS G 3507-2 Carbon steel for forging-Part 2: Wire, alloy steel for cold forging specified in JIS G 3509-1-Part 1: Wire, specified in JIS G 3509-2 Alloy steels for cold heading-Part 2: Wires and their related foreign standard steels, as well as their respective component-similar steels and component-modified steels, are described in this specification by reference. Embedded in the book. The steel for machine structure in the present invention includes steel materials that satisfy the chemical components described in the JIS standard.
 本発明における機械構造用鋼の好ましい組成の数値範囲(質量%)は、以下の通りである。
     好ましい範囲    より好ましい範囲   更に好ましい範囲 
C   0.10~1.10  0.95~1.10  0.95~1.10
Si  2.0以下      0.15~0.70  0.15~0.35
Mn  3.0以下      1.15以下     0.50以下
P   0.025以下    0.025以下    0.025以下
S   0.100以下    0.025以下    0.025以下
Cr  15.0以下     0.90~1.60  1.30~1.60
Mo  2.0以下      0.25以下     0.08以下
Ni  5.0以下      0.25以下     0.25以下
Cu  0.25以下     0.25以下     0.25以下
残部  Fe及び不可避不純物  Fe及び不可避不純物  Fe及び不可避不純物
備考            JIS G 4805  JIS G 4805
              SUJ1~5     SUJ2     
 なお、不可避不純物には脱酸剤としてのAl、Caも含まれてよい。
The numerical range (mass%) of the preferable composition of the steel for machine structure in the present invention is as follows.
Preferred range More preferred range More preferred range
C 0.10 to 1.10 0.95 to 1.10 0.95 to 1.10.
Si 2.0 or less 0.15-0.70 0.15-0.35
Mn 3.0 or less 1.15 or less 0.50 or less P 0.025 or less 0.025 or less 0.025 or less S 0.100 or less 0.025 or less 0.025 or less Cr 15.0 or less 0.90 to 1. 60 1.30 to 1.60
Mo 2.0 or less 0.25 or less 0.08 or less Ni 5.0 or less 0.25 or less 0.25 or less Cu 0.25 or less 0.25 or less 0.25 or less
Remaining Fe and unavoidable impurities Fe and unavoidable impurities Fe and unavoidable impurities <br/> Remarks JIS G 4805 JIS G 4805
SUJ1 ~ 5 SUJ2
Inevitable impurities may also include Al and Ca as deoxidizers.
 このような機械構造用鋼は、一般的に、1)アーク溶解炉または転炉による溶鋼の酸化精錬、2)取鍋精錬炉(LF)による還元精錬、3)還流式真空脱ガス装置(RH)による還流真空脱ガス処理(RH処理)、4)連続鋳造または一般造塊による鋼塊の鋳造および5)鋼塊の熱間圧延あるいは熱間での圧鍛および冷間圧延あるいは冷間での圧鍛による塑性加工工程を経て、鋼材が製造される。本発明における鋼材形状を得るための工程とは上記の工程を指し、鋼材形状とは形鋼、棒鋼、管材、線材、鋼板、鋼帯を指す。 Such mechanical structural steels generally have 1) oxidation refining of molten steel by an arc melting furnace or converter, 2) reductive refining by a ladle refining furnace (LF), and 3) a reflux-type vacuum degassing apparatus (RH). ) Refluxing vacuum degassing treatment (RH treatment) by 4) Casting of steel ingot by continuous casting or general ingot and 5) Hot rolling or hot forging of steel ingot and cold rolling or cold rolling A steel material is manufactured through a plastic working process by pressure forging. The process for obtaining the steel material shape in the present invention refers to the above-described process, and the steel material shape refers to a shape steel, a steel bar, a pipe, a wire, a steel plate, and a steel strip.
 次いで、鋼材は、熱間鍛造、亜熱間鍛造、温間鍛造、冷間鍛造、ローリング鍛造、冷間転造、冷間ヘッダー加工ならびに引抜き加工、場合によっては引抜きと冷間ヘッダー加工、上記の組合せの塑性加工と、必要に応じて軟化や組織調整を目的とした熱処理あるいは旋削を行なって所望の部材に成形される。本発明における機械部品形状を得るための工程とは上記の工程を指す。 The steel is then hot forged, sub-hot forged, warm forged, cold forged, rolling forged, cold rolled, cold header processed and drawn, sometimes drawn and cold header processed, as described above. A desired plastic member is formed by performing combined plastic working and, if necessary, heat treatment or turning for the purpose of softening or microstructure adjustment. The process for obtaining the machine part shape in the present invention refers to the above process.
 なお、本発明における熱間塑性加工の熱間とは該鋼の再結晶温度以上を指し、温間塑性加工の温間とは室温以上、再結晶温度以下を指し、冷間塑性加工の冷間とは室温およびその近辺を指す。 In the present invention, the hot of the hot plastic working refers to a temperature higher than the recrystallization temperature of the steel, the warm of the hot plastic working refers to a temperature higher than the room temperature and lower than the recrystallization temperature, the cold of the cold plastic working. Refers to room temperature and its vicinity.
 一般的には、塑性加工が施された鋼は、次いで、表面硬さ58HRC以上を得るために全体焼入れ(ズブ焼入れ)、浸炭焼入れ、浸炭窒化焼入れ、窒化焼入れ、浸炭浸窒焼入れ、高周波焼入れなどの焼入焼戻し処理が鋼材や用途に応じて施されて、研磨や研削などの仕上げ処理を経て、本発明が対象とする機械部品が製造される。本発明における焼入焼戻し処理とは上記の処理を指す。 Generally, the steel subjected to plastic working is then subjected to overall quenching (sub-quenching), carburizing quenching, carbonitriding quenching, nitriding quenching, carburizing and nitrogen quenching, induction quenching, etc. to obtain a surface hardness of 58 HRC or more. The quenching and tempering treatment is applied according to the steel material and the application, and after finishing treatment such as polishing and grinding, the machine part targeted by the present invention is manufactured. The quenching and tempering treatment in the present invention refers to the above treatment.
 しかしながら、本発明の効果を得るためには、機械部品に焼入焼戻しを行って表面硬さ58HRC以上を得る前の段階で、強制的に酸化物系非金属介在物と母相との界面に存在する空洞を消滅させるための工程を経る必要がある。その手段としては、780℃以上に加熱した後に80MPa以上の静水圧付与が可能な工法が良い。例えば、その工法として熱間等方圧プレス(HIP)法、ホットプレス法、完全閉塞あるいは完全密閉による熱間鍛造法が良い。 However, in order to obtain the effect of the present invention, the mechanical parts are forcibly tempered at the interface between the non-metallic oxide inclusions and the matrix phase before obtaining a surface hardness of 58 HRC or higher by quenching and tempering the machine parts. It is necessary to go through a process for eliminating the existing cavities. As the means, a method that can apply a hydrostatic pressure of 80 MPa or higher after heating to 780 ° C. or higher is preferable. For example, a hot isostatic pressing (HIP) method, a hot pressing method, or a hot forging method with complete closure or complete sealing is preferable.
 なお、金型に完全密閉されていない熱間鍛造、亜熱間鍛造、温間鍛造、冷間鍛造、ローリング鍛造、冷間転造、冷間ヘッダー加工ならびに引抜き加工では、全鋼材部分に静水圧が付与できないか、もしくはある方向に材料が連続的に延伸されるために、本発明の効果が得られない。 In hot forging, sub-hot forging, warm forging, cold forging, rolling forging, cold rolling, cold header processing, and drawing processing that are not completely sealed in the mold, all steel parts are subjected to hydrostatic pressure. Can not be imparted, or the material is continuously stretched in a certain direction, so the effects of the present invention cannot be obtained.
 780℃以上に加熱した後に80MPa以上の静水圧付与を行う理由は次の通りである。すなわち、鋼材の加熱温度が高いほど、鋼材は変形し易くなる。従って、鋼材の加熱温度が高いほど、酸化物系非金属介在物と母相との界面に存在する隙間すなわち空洞を消滅させるために必要な静水圧は低くすることができる。本発明者らが鋭意検討した結果、780℃以上に加熱して、かつ80MPa以上の静水圧が付与できれば、本発明の効果が得られる。なお、本発明の第一の好ましい態様によれば、上記加熱が800℃以上で行われ、上記静水圧が100MPa以上であるのが好ましい。 The reason for applying a hydrostatic pressure of 80 MPa or higher after heating to 780 ° C. or higher is as follows. That is, the higher the heating temperature of the steel material, the easier it is for the steel material to deform. Therefore, the higher the heating temperature of the steel material, the lower the hydrostatic pressure required to eliminate gaps or cavities existing at the interface between the oxide-based nonmetallic inclusions and the parent phase. As a result of intensive studies by the present inventors, the effect of the present invention can be obtained if heating is performed at 780 ° C. or higher and a hydrostatic pressure of 80 MPa or higher can be applied. In addition, according to the 1st preferable aspect of this invention, it is preferable that the said heating is performed at 800 degreeC or more, and the said hydrostatic pressure is 100 Mpa or more.
 本発明の第二の好ましい態様によれば、塑性加工を受ける機械構造用鋼が、通常のAlに加えてSiを含む脱酸剤を添加して、あるいは、Alからなる脱酸剤を添加することなく、脱酸されたものである。一般的に、機械構造用鋼はAlによる脱酸が行なわれている。そのために生成する酸化物系非金属介在物は、Al23系が主体となる。Al23系は、硬質の介在物であり、かつ精錬以降に凝集し、ASTM E 45に規定されているタイプBの形状をとり易いという問題から、静水圧を付与した際に、酸化物系非金属介在物と母相との界面に存在する空洞を完全に消滅させるには、最適な静水圧付与時の条件範囲が限られる。そこで、酸化物系非金属介在物の形態を制御すれば、静水圧を付与した際に、酸化物系非金属介在物と母相との界面に存在する空洞を完全に消滅させるための効果は増す。その手段として、通常のAlに加えてSiを含む脱酸剤を添加して、あるいは、Alからなる脱酸材を添加することなく、脱酸することにより、生成する酸化物系非金属介在物を軟質化させて、母相との変形能の差を小さくするのが好ましい。 According to the second preferred embodiment of the present invention, the mechanical structural steel subjected to plastic working is added with a deoxidizer containing Si in addition to normal Al, or a deoxidizer composed of Al is added. Without deoxidation. Generally, mechanical structural steel is deoxidized with Al. For this purpose, the oxide-based non-metallic inclusions produced are mainly Al 2 O 3 -based. The Al 2 O 3 system is a hard inclusion, aggregates after refining, and easily takes the shape of type B defined in ASTM E 45. In order to completely eliminate the cavity existing at the interface between the system nonmetallic inclusion and the parent phase, the condition range at the time of applying the optimum hydrostatic pressure is limited. Therefore, if the form of the oxide-based nonmetallic inclusions is controlled, the effect of completely eliminating the cavities existing at the interface between the oxide-based nonmetallic inclusions and the parent phase when hydrostatic pressure is applied is Increase. As the means, oxide-based nonmetallic inclusions produced by adding a deoxidizing agent containing Si in addition to normal Al or by deoxidizing without adding a deoxidizing material made of Al. It is preferable to reduce the difference in deformability from the parent phase by softening.
 本発明の第三の好ましい態様によれば、塑性加工を受ける機械構造用鋼が、通常のAlに加えてCaを含む脱酸剤を添加して脱酸されたものである。一般的に、機械構造用鋼はAlによる脱酸が行なわれている。そのために生成する酸化物系非金属介在物は、Al23系が主体となる。Al23系は、硬質の介在物であり、かつ精錬以降に凝集し、ASTM E 45に規定されているタイプBの形状をとり易いという問題から、静水圧を付与した際に、酸化物系非金属介在物と母相との界面に存在する空洞を完全に消滅させるには、最適な静水圧付与時の条件範囲が限られる。そこで、酸化物系非金属介在物の形態を制御すれば、静水圧を付与した際に、酸化物系非金属介在物と母相との界面に存在する空洞を完全に消滅させるための効果は増す。その手段として、通常のAlに加えてCaを含む脱酸剤を添加して脱酸することにより、生成する酸化物系非金属介在物をASTM E 45に規定されているタイプDの形状(粒状)に制御することにより、非金属介在物の周囲に均一な静水圧が付与できるようにするのが好ましい。 According to the third preferred embodiment of the present invention, the steel for mechanical structure subjected to plastic working is deoxidized by adding a deoxidizer containing Ca in addition to normal Al. Generally, mechanical structural steel is deoxidized with Al. For this reason, the oxide-based nonmetallic inclusions produced are mainly Al 2 O 3 -based. The Al 2 O 3 system is a hard inclusion, aggregates after refining, and easily takes the shape of type B defined in ASTM E 45. In order to completely eliminate the cavity existing at the interface between the system nonmetallic inclusion and the parent phase, the condition range when applying the optimum hydrostatic pressure is limited. Therefore, if the form of oxide-based nonmetallic inclusions is controlled, the effect of completely eliminating cavities existing at the interface between the oxide-based nonmetallic inclusions and the parent phase when hydrostatic pressure is applied is Increase. As a means for this, by adding a deoxidizer containing Ca in addition to ordinary Al to deoxidize, the oxide-based non-metallic inclusions to be generated are shaped into the type D shape (granularity) defined in ASTM E45. It is preferable that a uniform hydrostatic pressure can be applied around the nonmetallic inclusions.
 なお、上述した第一、第二ないし第三の好ましい態様を任意に組み合わせて本発明を実施してもよいことは言うまでもない。 Needless to say, the present invention may be implemented by arbitrarily combining the first, second to third preferred embodiments described above.
 本発明の第一の態様の実施条件と得られた効果について具体的に説明する。先ず、表1に供試材の成分組成を示す。本供試材はJIS G 4805の組成を満足する鋼であるSUJ2鋼に基づくものである。アーク溶解炉にて溶鋼を酸化精錬し、取鍋精錬炉(LF)にて還元精錬し、還流式真空脱ガス装置(RH)にて還流真空脱ガス処理(RH処理)し、連続鋳造にて鋼塊を鋳造し、鋼塊を熱間圧延して鋼材を作製した。次に800℃にて球状化焼なましを施した。 The implementation conditions and the obtained effects of the first aspect of the present invention will be specifically described. First, Table 1 shows the component composition of the test materials. This sample material is based on SUJ2 steel, which is a steel satisfying the composition of JIS G 4805. Oxidation refining of molten steel in an arc melting furnace, reduction refining in a ladle refining furnace (LF), recirculation vacuum degassing treatment (RH treatment) in a recirculation type vacuum degassing device (RH), and continuous casting A steel ingot was cast, and the steel ingot was hot-rolled to produce a steel material. Next, spheroidizing annealing was performed at 800 ° C.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
 さらに、上記の球状化焼なましした鋼材を以下に示す工程条件1~3のいずれかに従って加工した。
 工程条件1:鋼材をスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件2:鋼材を、室温以上で再結晶温度以下である温間、600℃に加熱して据え込みを行なった後に、スラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件3:鋼材を、冷間据え込みを行なった後に、スラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
Furthermore, the above spheroidized steel was processed according to any one of the following process conditions 1 to 3.
Process condition 1: A steel material was cut into a washer shape which is a member of a thrust type rolling bearing.
Process condition 2: The steel material was heated to 600 ° C. at a temperature not lower than the room temperature and not higher than the recrystallization temperature, and after that, the steel material was cut into a bearing disc shape which is a member of a thrust type rolling bearing.
Process condition 3: After the steel material was cold upset, the steel material was cut into a bearing disc shape which is a member of a thrust type rolling bearing.
 得られた軌道盤形状品にそれぞれ熱間等方圧プレス(HIP)処理を施した。この処理条件を表2に示す。プレス条件Aとプレス条件Bは本発明の加熱温度条件および静水圧条件を満足する。プレス条件Cとプレス条件Dはプレス条件で、プレス条件EはHIP処理を行なわないもので、これらは本発明の加熱温度条件および静水圧条件を満足しないものである。これらプレス条件Aとプレス条件Bの軌道盤形状品を835℃で20分保持した後、油冷により焼入れし、次いで170℃で90分の焼戻し処理を行い、所望の58HRC以上の硬さを得た。さらに研磨を施して、スラスト型の転がり軸受に仕上げて、転動疲労寿命評価を行なった。なお、転動体は市販のスラスト型の転がり軸受用ボールを使用した。 Each of the obtained washer-shaped products was subjected to hot isostatic pressing (HIP) treatment. Table 2 shows the processing conditions. Press condition A and press condition B satisfy the heating temperature condition and the hydrostatic pressure condition of the present invention. The pressing condition C and the pressing condition D are pressing conditions, and the pressing condition E does not perform the HIP treatment, and these do not satisfy the heating temperature condition and the hydrostatic pressure condition of the present invention. These press condition A and press condition B washer-shaped products were held at 835 ° C. for 20 minutes, then quenched by oil cooling, and then subjected to tempering at 170 ° C. for 90 minutes to obtain a desired hardness of 58 HRC or higher. It was. Furthermore, it was ground and finished into a thrust type rolling bearing, and the rolling fatigue life was evaluated. The rolling element used was a commercially available thrust type rolling bearing ball.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
 スラスト型転がり疲労試験は5292MPaの最大ヘルツ応力Pmaxで行い、上記の各プレス条件につきそれぞれ10回ずつ行なった。その結果から、ワイブル分布関数に基づき、短寿命側から10%の試験片に剥離が生じるまでの総回転数を求め、これをL10寿命とした。これらの焼入・焼戻し後の表面硬さとスラスト型転がり疲労試験を行った各条件の10枚の試験片の寿命から評価したL10寿命を表3に示す。なお、各条件の試験片は試験の都合で1×108cycleに到達した時点で、剥離に至らなくても中止した。 The thrust type rolling fatigue test was performed at a maximum hertz stress Pmax of 5292 MPa, and was performed 10 times for each of the above pressing conditions. From the result, based on the Weibull distribution function, the total number of revolutions until the 10% specimen was peeled from the short life side was obtained, and this was defined as the L 10 life. Table 3 shows the L 10 life evaluated from the surface hardness after quenching and tempering and the life of 10 test pieces under each condition in which the thrust type rolling fatigue test was conducted. In addition, the test piece of each condition was stopped when it reached 1 × 10 8 cycles for the convenience of the test even if it did not come off.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
 なお、表3のL10寿命における→は1×108cycleで、剥離しなかったことを意味する。表3において、本発明の加熱温度条件および静水圧条件を満足するプレス条件Aとプレス条件Bは表面硬さが58HRC以上である。また、本発明の加熱温度条件および静水圧条件を満足しないプレス条件C~Eは表面硬さが58HRC以上である。しかし、本発明のプレス条件Aおよびプレス条件Bの発明例は、最終が熱間塑性加工、温間塑性加工、冷間塑性加工に関わらずプレス条件C~Eの比較例に比べて、転がり疲れ寿命が格段に優れている。 Incidentally, → is the L 10 life of Table 3 at 1 × 10 8 cycle, meaning that did not peel off. In Table 3, press conditions A and B satisfying the heating temperature condition and the hydrostatic pressure condition of the present invention have a surface hardness of 58 HRC or more. The pressing conditions C to E that do not satisfy the heating temperature condition and the hydrostatic pressure condition of the present invention have a surface hardness of 58 HRC or more. However, the invention examples of the press condition A and the press condition B according to the present invention are less in rolling fatigue than the comparative examples of the press conditions C to E regardless of whether the final is hot plastic working, warm plastic working, or cold plastic working. Life is much better.
 本発明の第二の態様の実施条件と得られた効果について具体的に説明する。先ず、表4に供試材の成分組成を示す。この供試材である鋼種AおよびBは、全てJIS G 4805の組成を満足する鋼であるSUJ2鋼に基づくものである。アーク溶解炉にて溶鋼を酸化精錬し、取鍋精錬炉(LF)にて還元精錬し、還流式真空脱ガス装置(RH)にて還流真空脱ガス処理(RH処理)し、連続鋳造にて鋼塊を鋳造し、鋼塊を熱間圧延して鋼材を作製した。なお、供試材の鋼種Aは脱酸時にAlを添加することなく、SiとMnで脱酸を行なったもので、表4に示すAlの0.003%は不可避不純物として含有されているものである。鋼種Bは一般的に行なわれているAlによる脱酸を行なった。熱間圧延して得た鋼材に800℃にて球状化焼なましを施した。 The implementation conditions and the obtained effects of the second aspect of the present invention will be specifically described. First, Table 4 shows the component composition of the test material. Steel types A and B which are the test materials are all based on SUJ2 steel which is a steel satisfying the composition of JIS G 4805. Oxidation refining of molten steel in an arc melting furnace, reduction refining in a ladle refining furnace (LF), recirculation vacuum degassing treatment (RH treatment) in a recirculation type vacuum degassing device (RH), and continuous casting A steel ingot was cast, and the steel ingot was hot-rolled to produce a steel material. Steel type A of the test material was deoxidized with Si and Mn without adding Al during deoxidation, and 0.003% of Al shown in Table 4 is contained as an inevitable impurity. It is. Steel type B was generally deoxidized with Al. The steel material obtained by hot rolling was subjected to spheroidizing annealing at 800 ° C.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
 さらに、上記の球状化焼なましした鋼材を以下に示す工程条件1~3のいずれかに従って加工した。
 工程条件1:鋼材をスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件2:鋼材を、室温以上で再結晶温度以下である温間、600℃に加熱して据え込みを行なった後にスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件3:鋼材を、冷間据え込みを行なった後にスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
Furthermore, the above spheroidized steel was processed according to any one of the following process conditions 1 to 3.
Process condition 1: A steel material was cut into a washer shape which is a member of a thrust type rolling bearing.
Process condition 2: The steel material was heated to 600 ° C. at a temperature not lower than the room temperature and not higher than the recrystallization temperature, and then the steel material was cut into a bearing disk shape which is a member of a thrust type rolling bearing.
Process condition 3: After the steel material was cold upset, it was cut into the shape of a washer which is a member of a thrust type rolling bearing.
 得られた軌道盤形状品にそれぞれ熱間等方圧プレス(HIP)処理もしくはホットプレス処理を施した。この処理条件を表5に示す。プレス条件(1)はホットプレス処理によるもので、プレス条件(2)~(4)はHIP処理によるものである。プレス条件(1)~(3)は本発明の加熱温度条件および静水圧条件を満足する本発明例である。これらに対してプレス条件(4)は加熱温度が700℃と本発明のHIP処理の加熱条件よりも低く本発明の条件を満足しないもので、比較例である。さらにプレス条件(5)はプレス無しの比較例である。この軌道盤形状品を835℃で20分保持した後、油冷により焼入れし、次いで170℃で90分の焼戻し処理を行い、所望の58HRC以上の硬さを得た。さらに研磨を施して、スラスト型の転がり軸受に仕上げて、転動疲労寿命評価を行なった。なお、転動体は市販のスラスト型の転がり軸受用ボールを使用した。 Each of the obtained washer-shaped products was subjected to hot isostatic pressing (HIP) processing or hot pressing processing. Table 5 shows the processing conditions. The pressing condition (1) is based on hot pressing, and the pressing conditions (2) to (4) are based on HIP processing. The pressing conditions (1) to (3) are examples of the present invention that satisfy the heating temperature condition and the hydrostatic pressure condition of the present invention. On the other hand, press condition (4) is a comparative example in which the heating temperature is 700 ° C. which is lower than the heating condition of the HIP treatment of the present invention and does not satisfy the conditions of the present invention. Furthermore, the pressing condition (5) is a comparative example without pressing. The washer-shaped product was held at 835 ° C. for 20 minutes, then quenched by oil cooling, and then tempered at 170 ° C. for 90 minutes to obtain a desired hardness of 58 HRC or higher. Furthermore, it was ground and finished into a thrust type rolling bearing, and the rolling fatigue life was evaluated. The rolling element used was a commercially available thrust type rolling bearing ball.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
 スラスト型転がり疲労試験は5292MPaの最大ヘルツ応力Pmaxで行い、上記の各プレス条件につき10回ずつ行なった。その結果から、ワイブル分布関数に基づき、短寿命側から10%の試験片に剥離が生じるまでの総回転数を求め、これをL10寿命とした。さらに、これらの焼入焼戻し後の表面硬さとスラスト型転がり疲労試験を行った各条件の10枚の試験片の寿命から評価したL10寿命を鋼種Aは表6に、鋼種Bは表7に示す。なお、各試験片は試験の都合で1×108cycleに到達した時点で、剥離に至らなくても中止した。 The thrust type rolling fatigue test was performed at a maximum hertz stress Pmax of 5292 MPa, and was performed 10 times for each of the above pressing conditions. From the result, based on the Weibull distribution function, the total number of revolutions until the 10% specimen was peeled from the short life side was obtained, and this was defined as the L 10 life. Further, Table 10 shows the L 10 life and Table 7 shows the steel 10 for the L 10 life evaluated based on the surface hardness after quenching and tempering and the life of 10 test pieces under the conditions of the thrust type rolling fatigue test. Show. Each test piece was stopped when it reached 1 × 10 8 cycles for the sake of the test, even if it did not come off.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
 表6における本発明の構成を満足する鋼である鋼種Aと表7における鋼種Bは、表面硬さが58HRC以上であり、本発明の加熱温度条件および静水圧条件を満足するプレス条件(1)~(3)は、本発明の条件を満足しない比較例である条件(4)および(5)に比べて、転がり疲れ寿命に優れている。さらに、鋼種Aと鋼種Bは、鋼種Cに比べて、本発明の条件を満足するプレス条件の条件(1)~(3)において、最適な静水圧付与時の条件範囲を広げることが可能で優れている。 Steel type A which is a steel satisfying the constitution of the present invention in Table 6 and Steel type B in Table 7 have a surface hardness of 58 HRC or more, and press conditions (1) which satisfy the heating temperature condition and hydrostatic pressure condition of the present invention. (3) to (3) are excellent in rolling fatigue life as compared with conditions (4) and (5) which are comparative examples not satisfying the conditions of the present invention. Furthermore, steel type A and steel type B, compared with steel type C, can expand the range of conditions for applying the optimum hydrostatic pressure in conditions (1) to (3) of the press conditions that satisfy the conditions of the present invention. Are better.
 本発明の第三の態様の実施条件と得られた効果について具体的に説明する。先ず、表8に供試材の成分組成を示す。この供試材である鋼種AおよびBは、全てJIS G 4805の組成を満足する鋼であるSUJ2鋼に基づくものである。アーク溶解炉にて溶鋼を酸化精錬し、取鍋精錬炉(LF)にて還元精錬し、還流式真空脱ガス装置(RH)にて還流真空脱ガス処理(RH処理)し、連続鋳造にて鋼塊を鋳造し、鋼塊を熱間圧延して鋼材を作製した。なお、供試材の鋼種AはAl脱酸を基本として、LF終了後にCaを添加した。鋼種Bは一般的に行なわれているAlによる脱酸を行なった。熱間圧延して得た鋼材に800℃にて球状化焼なましを施した。 The implementation conditions and the obtained effects of the third aspect of the present invention will be specifically described. First, Table 8 shows the component composition of the test material. Steel types A and B which are the test materials are all based on SUJ2 steel which is a steel satisfying the composition of JIS G 4805. Oxidation refining of molten steel in an arc melting furnace, reduction refining in a ladle refining furnace (LF), recirculation vacuum degassing treatment (RH treatment) in a recirculation type vacuum degassing device (RH), and continuous casting A steel ingot was cast, and the steel ingot was hot-rolled to produce a steel material. In addition, the steel type A of the test material was based on Al deoxidation, and Ca was added after the end of LF. Steel type B was generally deoxidized with Al. The steel material obtained by hot rolling was subjected to spheroidizing annealing at 800 ° C.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
 さらに、上記の球状化焼なましした鋼材を以下に示す工程条件1~3のいずれかに従って加工した。
 工程条件1:鋼材をスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件2:鋼材を、室温以上で再結晶温度以下である温間、600℃に加熱して据え込みを行なった後にスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
 工程条件3:鋼材を、冷間据え込みを行なった後にスラスト型の転がり軸受の部材である軌道盤形状に切削加工した。
Furthermore, the above spheroidized steel was processed according to any one of the following process conditions 1 to 3.
Process condition 1: A steel material was cut into a washer shape which is a member of a thrust type rolling bearing.
Process condition 2: The steel material was heated to 600 ° C. at a temperature not lower than the room temperature and not higher than the recrystallization temperature, and then the steel material was cut into a bearing disk shape which is a member of a thrust type rolling bearing.
Process condition 3: After the steel material was cold upset, it was cut into the shape of a washer which is a member of a thrust type rolling bearing.
 得られた軌道盤形状品にそれぞれ熱間等方圧プレス(HIP)処理もしくはホットプレス処理を施した。この処理条件を表9に示す。プレス条件(1)はホットプレス処理によるもので、プレス条件(2)~(4)はHIP処理によるものである。プレス条件(1)~(3)は本発明における加熱温度条件と静水圧条件を満足する本発明例である。これらに対してプレス条件(4)は加熱温度が700℃と本発明のHIP処理の加熱条件よりも低く本発明の条件を満足しないもので、比較例である。さらにプレス条件(5)はプレス無しの比較例である。この軌道盤形状品を835℃で20分保持した後、油冷により焼入れし、次いで170℃で90分の焼戻し処理を行い、所望の58HRC以上の硬さを得た。さらに研磨を施して、スラスト型の転がり軸受に仕上げて、転動疲労寿命評価を行なった。なお、転動体は市販のスラスト型の転がり軸受用ボールを使用した。 Each of the obtained washer-shaped products was subjected to hot isostatic pressing (HIP) processing or hot pressing processing. Table 9 shows the processing conditions. The pressing condition (1) is based on hot pressing, and the pressing conditions (2) to (4) are based on HIP processing. The pressing conditions (1) to (3) are examples of the present invention that satisfy the heating temperature condition and the hydrostatic pressure condition in the present invention. On the other hand, press condition (4) is a comparative example in which the heating temperature is 700 ° C. which is lower than the heating condition of the HIP treatment of the present invention and does not satisfy the conditions of the present invention. Furthermore, the pressing condition (5) is a comparative example without pressing. The washer-shaped product was held at 835 ° C. for 20 minutes, then quenched by oil cooling, and then tempered at 170 ° C. for 90 minutes to obtain a desired hardness of 58 HRC or higher. Furthermore, it was ground and finished into a thrust type rolling bearing, and the rolling fatigue life was evaluated. The rolling element used was a commercially available thrust type rolling bearing ball.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
 スラスト型転がり疲労試験は5292MPaの最大ヘルツ応力Pmaxで行い、上記の各プレス条件につき10回ずつ行なった。その結果から、ワイブル分布関数に基づき、短寿命側から10%の試験片に剥離が生じるまでの総回転数を求め、これをL10寿命とした。さらに、これらの焼入焼戻し後の表面硬さとスラスト型転がり疲労試験を行った各条件の10枚の試験片の寿命から評価したL10寿命を鋼種Aは表10に、鋼種Bは表11に示す。なお、各試験片は試験の都合で1×108cycleに到達した時点で、剥離に至らなくても中止した。 The thrust type rolling fatigue test was performed at a maximum Hertz stress Pmax of 5292 MPa, and was performed 10 times for each of the above pressing conditions. From the result, based on the Weibull distribution function, the total number of revolutions until the 10% specimen was peeled from the short life side was obtained, and this was defined as the L 10 life. Further, Table 10 shows steel L and Table 11 shows L 10 life evaluated based on the surface hardness after quenching and tempering and the life of 10 test pieces under the respective conditions of the thrust type rolling fatigue test. Show. Each test piece was stopped when it reached 1 × 10 8 cycles for the convenience of the test even if it did not come off.
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000010
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000011
 表10において、本発明の構成を満足する鋼である鋼種Aは、表面硬さが58HRC以上であり、本発明の加熱温度条件および静水圧条件を満足するプレス条件(1)~(3)は、本発明の条件を満足しない比較例であるプレス条件(4)および(5)に比べて、転がり疲れ寿命に優れている。さらに、鋼種Aは、表11における鋼種Bに比べて、本発明の条件を満足するプレス条件のプレス条件(1)~(3)において、最適な静水圧付与時の条件範囲を広げることが可能で優れている。 In Table 10, steel type A, which is a steel that satisfies the constitution of the present invention, has a surface hardness of 58 HRC or more, and pressing conditions (1) to (3) that satisfy the heating temperature condition and hydrostatic pressure condition of the present invention are as follows. Compared with press conditions (4) and (5) which are comparative examples not satisfying the conditions of the present invention, the rolling fatigue life is excellent. Furthermore, compared with steel type B in Table 11, steel type A can expand the range of conditions for applying the optimum hydrostatic pressure in the pressing conditions (1) to (3) that satisfy the conditions of the present invention. Is excellent.

Claims (7)

  1.  機械構造用鋼の一部もしくは全体を焼入焼戻し処理により転動疲労寿命に優れた表面硬さ58HRC以上の機械部品を製造する方法であって、
     機械構造用鋼を、鋼材形状を付与するための工程またはその後の機械部品形状を付与するための工程に付し、該工程中で該鋼に塑性加工を施し、
     該塑性加工が施された鋼を780℃以上に加熱して80MPa以上の静水圧を付与し、それにより、該鋼中に含有する非金属介在物と母相である鋼との界面を密着させ、その後、
     該鋼の一部もしくは全体を焼入焼戻し処理に付する
    工程を含んでなる方法。
    A method of manufacturing a machine part having a surface hardness of 58 HRC or more excellent in rolling fatigue life by quenching and tempering a part or the whole of a machine structural steel,
    Machine structural steel is subjected to a step for imparting a steel material shape or a subsequent step for imparting a machine part shape, and the steel is subjected to plastic working in the step,
    The steel subjected to the plastic working is heated to 780 ° C. or more to give a hydrostatic pressure of 80 MPa or more, thereby bringing the interface between the nonmetallic inclusions contained in the steel and the steel as the parent phase into close contact. ,afterwards,
    A method comprising a step of subjecting part or all of the steel to a quenching and tempering treatment.
  2.  前記加熱が800℃以上で行われ、前記静水圧が100MPa以上である、請求項1に記載の方法。 The method according to claim 1, wherein the heating is performed at 800 ° C or more and the hydrostatic pressure is 100 MPa or more.
  3.  前記塑性加工を受ける機械構造用鋼が、通常のAlに加えてSiを含む脱酸剤を添加して、あるいは、Alからなる脱酸剤を添加することなく、脱酸されたものである、請求項1または2に記載の方法。 The steel for mechanical structure subjected to the plastic working is deoxidized by adding a deoxidizer containing Si in addition to normal Al or without adding a deoxidizer composed of Al. The method according to claim 1 or 2.
  4.  前記塑性加工を受ける機械構造用鋼が、通常のAlに加えてCaを含む脱酸剤を添加して脱酸されたものである、請求項1または2に記載の方法。 The method according to claim 1 or 2, wherein the mechanical structural steel subjected to the plastic working is deoxidized by adding a deoxidizer containing Ca in addition to normal Al.
  5.  前記塑性加工が複数回行われ、該複数回の中の最後の塑性加工が熱間塑性加工である、請求項1~4のいずれか一項に記載の方法。 The method according to any one of claims 1 to 4, wherein the plastic working is performed a plurality of times, and the last plastic working in the plurality of times is a hot plastic working.
  6.  前記塑性加工が複数回行われ、該複数回の中の最後の塑性加工が温間塑性加工である、請求項1~4のいずれか一項に記載の方法。 The method according to any one of claims 1 to 4, wherein the plastic working is performed a plurality of times, and the last plastic working in the plurality of times is a warm plastic working.
  7.  前記塑性加工が複数回行われ、該複数回の中の最後の塑性加工が冷間塑性加工である、請求項1~4のいずれか一項に記載の方法。 The method according to any one of claims 1 to 4, wherein the plastic working is performed a plurality of times, and the last plastic working in the plurality of times is a cold plastic working.
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