WO2015087869A1 - Cvt用リング部材及びその製造方法 - Google Patents
Cvt用リング部材及びその製造方法 Download PDFInfo
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- WO2015087869A1 WO2015087869A1 PCT/JP2014/082535 JP2014082535W WO2015087869A1 WO 2015087869 A1 WO2015087869 A1 WO 2015087869A1 JP 2014082535 W JP2014082535 W JP 2014082535W WO 2015087869 A1 WO2015087869 A1 WO 2015087869A1
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- Prior art keywords
- cvt
- ring member
- less
- ring
- nitriding
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16G—BELTS, CABLES, OR ROPES, PREDOMINANTLY USED FOR DRIVING PURPOSES; CHAINS; FITTINGS PREDOMINANTLY USED THEREFOR
- F16G5/00—V-belts, i.e. belts of tapered cross-section
- F16G5/16—V-belts, i.e. belts of tapered cross-section consisting of several parts
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B5/00—Extending closed shapes of metal bands by rolling
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/06—Surface hardening
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D53/00—Making other particular articles
- B21D53/14—Making other particular articles belts, e.g. machine-gun belts
Definitions
- This invention relates to the ring member which comprises the belt for power transmission used for CVT, ie, the ring member for CVT, and its manufacturing method.
- the power transmission belt used in the CVT is composed of a plurality of thin metal ring members stacked to form a set of CVT belts, and two sets of friction members called elements are assembled to the two sets of CVT belts. Has been.
- the CVT belt is not in direct contact with the pulley in the CVT, but rotates to transmit power in a state of constituting a power transmission belt assembled with the element, and repeatedly receives tension and bending stress during the rotation. Therefore, it is necessary to use a material having excellent fatigue strength as the material of the ring member constituting the CVT belt. Furthermore, with the recent increase in the performance of automobiles, the power transmission belt has been required to have higher strength than ever.
- maraging steel which is known as a high-strength material
- maraging steel contains a large amount of expensive Ni, Co, and Mo, and there is a problem that the material cost becomes very high. Therefore, as a technique for obtaining a high-strength material excellent in fatigue strength, for example, as shown in Patent Document 1, a technique for increasing the strength by making steel into a high alloy is known.
- Patent Document 2 discloses an excellent steel that has a much lower cost than maraging steel by reducing the content of expensive alloy elements and has fatigue strength characteristics equivalent to maraging steel. Is disclosed. However, the steel of Patent Document 2 may not be able to reach the required level when strength properties that are significantly higher than those of the conventional steel are required. Therefore, there is still room for improvement in the steel used for the ring member for CVT.
- the present invention intends to provide an inexpensive CVT ring member and a method for manufacturing the same, while ensuring suitable strength characteristics for a CVT belt.
- One aspect of the present invention is a ring member for CVT having a nitride layer on its surface,
- C 0.43 to 0.70%
- Si 2.50% or less
- Mn 1.00% or less
- Cr 1.50 to 4.00%
- Mo 0.50 to 3. 00%
- V 1.00% or less
- formula 1 159 ⁇ C (%) + 91 ⁇ Si (%) + 68 ⁇ Cr (%) + 198 ⁇ Mo (%) + 646 ⁇ 1000 is satisfied, the balance Has a chemical component consisting of Fe and inevitable impurities,
- the tensile strength is 1700 MPa or more
- the surface hardness of the nitride layer is HV800 to HV950. It is in the ring member for CVT.
- Another aspect of the present invention is, in mass%, C: 0.43 to 0.70%, Si: 2.50% or less, Mn: 1.00% or less, Cr: 1.50 to 4.00%, Mo: 0.50 to 3.00%, V: 1.00% or less, Formula 1: 159 ⁇ C (%) + 91 ⁇ Si (%) + 68 ⁇ Cr (%) + 198 ⁇ Mo (%) + 646 Prepare an ingot satisfying the relationship of ⁇ 1000, the balance being Fe and inevitable impurities, Add plastic processing to the ingot to make a plate material, Bending the plate material and welding the end faces together to form a rough ring material, The rough ring material is soft-annealed and then cold-rolled to obtain a ring material having a desired thickness.
- the ring material is subjected to a quenching treatment in which it is heated to a heating temperature T 1 of 850 ° C. to 1000 ° C. and then rapidly cooled, Thereafter, subjected to nitriding treatment to the ring material at the processing temperature T 2 of 400 ° C. ⁇ 500 ° C., It exists in the manufacturing method of the ring member for CVT.
- the CVT ring member has the specific chemical component and a nitride layer on the surface. And the tensile strength and the surface hardness of the nitride layer are adjusted to the said specific range. Thereby, since the said ring member for CVT does not contain a lot of expensive elements like maraging steel, satisfy
- C carbon: 0.43 to 0.70%; C is an element necessary for increasing the strength, and in order to sufficiently obtain the effect, it is necessary to contain 0.43% or more.
- the productivity is deteriorated, and further, coarse carbides are formed and the strength is lowered. Therefore, the upper limit of C addition is 0.70%.
- Si silicon: 2.50% or less; Si is an element necessary for increasing the strength, and the effect can be obtained even in a small amount, but it is preferable to add 0.10% or more. However, excessive addition of Si deteriorates manufacturability and inhibits nitriding properties, so the upper limit of Si addition is 2.50%.
- Mn manganese: 1.00% or less; Mn is an element necessary for increasing the strength, and the effect can be obtained even in a trace amount, but it is preferable to add 0.10% or more. However, excessive addition of Mn leads to a decrease in ductility, so the upper limit of Mn addition is 1.00%.
- Cr chromium: 1.50 to 4.00%; Cr is an element necessary for increasing the strength and ensuring nitriding properties, and in order to sufficiently obtain these effects, addition of 1.50% or more is necessary. However, if Cr is excessively added, coarse carbides are formed, the strength is lowered, and the cost is increased, so 4.00% is made the upper limit.
- Mo mobdenum
- Mo mobdenum
- V vanadium: 1.00% or less (excluding 0%) V is an element effective for securing high strength and nitride properties. However, excessive addition of V increases the cost, so the upper limit is made 1.00%.
- the tensile strength of the CVT ring member is 1700 MPa or more.
- the CVT ring member may be given a high tensile load during use. In order to obtain a ring member that cannot be broken by such a high load, a tensile strength of 1700 MPa or more is required. This mechanical property can be realized by applying the above manufacturing method.
- the surface hardness of the nitride layer of the CVT ring member is HV800 to HV950.
- the surface hardness of the nitride layer is less than HV800, the ring member may be worn by contact with the element.
- the surface hardness of the nitride layer exceeds HV950, the material becomes brittle, so that it is difficult to ensure the strength as a ring member. Therefore, the surface strength of the nitride layer is set within the above range. This characteristic can be ensured by applying the above manufacturing method.
- the manufacturing method first, an ingot having the specific chemical component is prepared, and plastic processing is applied to the ingot to obtain a plate material.
- plastic working for example, various known plastic working methods such as hot rolling, hot forging, cold rolling, and cold forging can be applied. Usually, after hot working is performed, cold working is performed to produce a plate material. In addition, it is preferable to remove the black skin (oxide film) generated on the plate material surface by the hot working before the cold working. The removal of the black skin can be performed by, for example, machining such as peeling or pickling.
- the bending process can be performed by, for example, a roll bending method after the plate material is cut into a predetermined size. Welding can be performed, for example, by plasma welding, laser welding, or the like with both end surfaces attached. It is effective for streamlining the process that the rough ring material is produced in a wide width including a plurality of ring materials and is cut to a desired width before the next step. In this case, it is preferable to deburr the cut surface by barrel polishing or the like after the width cutting.
- the rough ring material is subjected to soft annealing and then cold-rolled to obtain a ring material having a desired plate thickness. Thereafter, the ring material is subjected to a quenching process in which it is heated to a heating temperature T 1 in the range of 850 ° C. to 1000 ° C. and then rapidly cooled, and if necessary, a tempering process is performed after the quenching process.
- a heating temperature T 1 in the range of 850 ° C. to 1000 ° C. and then rapidly cooled, and if necessary, a tempering process is performed after the quenching process.
- the heating temperature T 1 for the quenching treatment is set to 850 ° C. or higher in order to dissolve C and ensure the internal hardness. However, if the heating temperature of the quenching process is too high, the crystal grains become coarse and the ductility is lowered, so 1000 ° C. is the upper limit. Further, the heating temperature T 1 at the time of quenching treatment is further expressed by the formula 2: 0.015 ⁇ C (%) ⁇ 0.014 ⁇ Cr (%) + 1.46 ⁇ V (%) ⁇ 0.81 ⁇ T 1 /1000+0.71 ⁇ 0.05 is preferably satisfied.
- V carbide (VC) having a pinning effect can be sufficiently secured, and it can be expected that the coarsening of crystal grains and the reduction in ductility are suppressed.
- the condition of Formula 2 when the condition of Formula 2 is satisfied, it becomes easy to control the crystal grains to 15 ⁇ m or less.
- the measuring method of a crystal grain is mentioned later.
- a tempering process can be added as necessary. Since the effect obtained by the tempering process is also obtained in the subsequent nitriding process, it is not necessary to perform it in a separate process before the nitriding process. However, when the time from the quenching process to the start of the nitriding process is very long, it is preferable to perform the tempering process after the quenching process.
- the treatment temperature when performing the tempering treatment is preferably in the range of 400 ° C. to 500 ° C. and not more than the nitriding treatment temperature. Thereby, embrittlement of material can be suppressed and the tensile strength of the cross-sectional center part of a ring material can be ensured more than a predetermined value. When the tempering temperature is higher than 500 ° C., the internal hardness is lowered, resulting in a decrease in tensile strength.
- correction processing is usually performed to remove distortion caused by these processes.
- This straightening process can also serve as a process for adjusting the circumference of the ring material.
- the ring material is nitrided at a processing temperature T 2 of 400 ° C. to 500 ° C.
- a processing temperature T 2 of 400 ° C. to 500 ° C.
- the treatment temperature T 2 of the nitriding treatment is too high becomes excessive nitriding, excessively high surface hardness, since become brittle, processing temperature T 2 is an upper limit of 500 ° C..
- nitriding treatment treatment methods such as soft nitriding, salt bath nitriding, plasma nitriding, etc. can be used in addition to gas nitriding performed in a nitrogen atmosphere or a mixed gas containing nitrogen.
- Example 1 Examples of the ring member for CVT and its manufacturing method will be described.
- CVT ring members samples 1 to 32
- the CVT ring member 1 produced in this example is formed by laminating a plurality of layers to constitute a CVT belt 2 and used by assembling two sets of CVT belts 2 to a plurality of continuous elements 3. Is.
- ingots having chemical components shown in Tables 1 and 2 were prepared. Specifically, melting and casting of the raw materials of each sample were performed using a 30 kg VIM (Vacuum Induction Melting) to obtain an ingot. The obtained ingot was subjected to forging as plastic working to produce a plate having approximate dimensions of 300 mm long ⁇ 155 mm wide ⁇ 7 mm thick. Further, after removing the black skin by machining, the obtained plate material was rolled by cold rolling to obtain a plate material having approximate dimensions of length 500 mm ⁇ width 200 mm ⁇ thickness 0.39 mm.
- VIM Vauum Induction Melting
- the obtained plate material was cut to a length of about 300 mm, subjected to a roll bending process, and then the end surfaces in the longitudinal direction were plasma welded to form a rough ring material, and then cut to a width of about 5 to 15 mm. Thereafter, the rough ring material was barrel-polished to remove burrs generated during cutting.
- the rough ring material was subjected to soft annealing that was held at 860 ° C. for 2 hours, then cold-rolled, and rolled to a thickness of 0.2 mm to obtain a ring material.
- the obtained ring material was quenched.
- a tempering process which is an optional process, was also performed on some samples. The quenching process was performed by heating to the temperatures shown in Tables 1 and 2 and holding for 60 minutes, followed by air cooling. The tempering treatment conditions were such that the tempering temperature was maintained at 425 ° C. for 1 hour.
- the circumference adjustment that doubles as the straightening process of the ring material was carried out. Specifically, the ring material was passed over the outer periphery of a pair of rollers (not shown), and the ring material was rotated while applying tension in the direction of expanding the gap between the rollers.
- nitriding treatment was performed in which the ring material was maintained at a nitriding temperature of 350 ° C. to 550 ° C. in a mixed gas of NH 3 and N 2 .
- the nitriding temperature was the temperature shown in Tables 1 and 2, respectively.
- Each ring member (Samples 1 to 32) that had undergone the nitriding treatment was evaluated as described later.
- the crystal grain size was measured by a so-called “cutting method” using a photograph taken with an optical microscope in an arbitrary cross section of the ring member after nitriding treatment.
- the cutting method is based on ASTM, and is a method of drawing a straight line of a known length on a photograph taken of a metal structure and calculating from the number of grains intersecting this.
- the surface not containing the nitrided layer obtained by etching an arbitrary cross section of the ring member with an aqueous picric acid hydrochloric acid solution containing a surfactant was observed with an optical microscope, and the magnification of 1000 times in any 10 fields of view was observed. Get a photo.
- the fatigue life has a plurality of rollers over which the ring member is wound, and a predetermined tension can be applied to the ring member between the rollers, and the bending stress is repeatedly applied to the ring member by rotating the roller. It was measured using a fatigue tester (not shown). The evaluation was performed with the average number of repetitions of fatigue life of 10 6 times as the standard number of times when the maraging steel (sample 19), which is the current product, was tested. ), The case of a result less than the standard number of times was regarded as rejected (x).
- Samples 1 to 18 have higher tensile strength (internal hardness) and equivalent or higher nitrided layer hardness (surface hardness) compared to maraging steel (Sample 19). In addition, the result was that the fatigue characteristics were equivalent or better.
- Sample 20 had a C content that was too low, resulting in poor tensile strength and fatigue properties. Since the sample 21 had too high C content and became too hard and could not be plastically processed into a ring shape, measurement was impossible. In Sample 22, the Si content was too high, the nitriding property deteriorated, and N hardly penetrated, resulting in a low nitrided layer hardness. Sample 23 had an excessively high Mn content, resulting in poor toughness due to reduced toughness.
- Sample 24 the Cr content was too low, the nitriding property deteriorated, and the hardness of the nitrided layer was low. In sample 25, the Cr content was too high, and a huge carbide was formed, resulting in early fracture in the fatigue life test. Sample 26 had a low Mo content and a low tensile strength.
- Sample 29 had a low nitrided layer hardness because the nitriding temperature at the time of manufacture was too low. Since the nitriding temperature at the time of manufacture of Sample 30 was too high, the hardness of the nitrided layer was too high, leading to a decrease in toughness, resulting in poor fatigue strength.
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Abstract
Description
質量%で、C:0.43~0.70%、Si:2.50%以下、Mn:1.00%以下、Cr:1.50~4.00%、Mo:0.50~3.00%、V:1.00%以下を含有し、式1:159×C(%)+91×Si(%)+68×Cr(%)+198×Mo(%)+646≧1000の関係を満たし、残部がFeおよび不可避的不純物よりなる化学成分を有し、
引張強さが1700MPa以上であり、
上記窒化層の表面硬度がHV800~HV950である、
CVT用リング部材にある。
該鋳塊に塑性加工を加えて板材とし、
該板材を曲げ加工すると共に端面同士を溶接して粗リング材とし、
該粗リング材を軟化焼鈍した後に冷間圧延して所望板厚のリング材とし、
該リング材に、850℃~1000℃の加熱温度T1に加熱した後急冷する焼き入れ処理を施し、
その後、400℃~500℃の処理温度T2で上記リング材に窒化処理を施す、
CVT用リング部材の製造方法にある。
Cは、高強度化に必要な元素であり、その効果を十分に得るためには0.43%以上含有させることが必要である。一方、Cを過剰添加すると、製造性が悪化し、さらには、粗大な炭化物が形成されて強度が低下してしまうため、Cの添加は0.70%を上限とする。
Siは、高強度化に必要な元素であり、その効果は微量でも得られるが、好ましくは、0.10%%以上添加するのがよい。ただし、Siを過剰添加すると、製造性が悪化すると共に窒化性の阻害要因となるため、Siの添加は2.50%を上限とする。
Mnは、高強度化に必要な元素であり、その効果は微量でも得られるが、好ましくは0.10%以上添加するのがよい。ただし、Mnを過剰添加すると延性低下につながるため、Mnの添加は1.00%を上限とする。
Crは、高強度化および窒化性確保のために必要な元素であり、これらの効果を十分に得るためには、1.50%以上の添加が必要である。ただし、Crを過剰添加すると、粗大な炭化物が形成されて強度が低下し、また、コストアップにもつながるため、4.00%を上限とする。
Moは、高強度化に必要な元素であり、その効果を十分に得るためには0.50%以上含有させることが必要である。ただし、Moを過剰添加するとコストアップになるため、3.00%を上限とする。
Vは、高強度化及び窒化物性を確保するのに有効な元素である。ただし、Vを過剰添加するとコストアップになるため、1.00%を上限とする。
上記化学成分が式1を満足することによって、疲労寿命が優れたものとなる。一方、式1を満足していない場合には、十分な疲労強度特性を確保することが困難となる。
上記製造方法では、まず、上記特定の化学成分を有する鋳塊を準備し、該鋳塊に塑性加工を加えて板材とする。塑性加工としては、例えば、熱間圧延、熱間鍛造、冷間圧延、冷間鍛造等の公知の種々の塑性加工方法を適用することが可能である。通常は、熱間加工を実施した後、冷間加工を施して板材を作製する。なお、熱間加工によって板材表面に生成した黒皮(酸化皮膜)は、冷間加工の前に除去することが好ましい。黒皮の除去は、例えば、ピーリング等の機械加工や酸洗によって実施することができる。
上記CVT用リング部材及びその製造法に係る実施例について説明する。本例では、表1及び2に示すごとく、複数種類の鋼材からなるCVT用のリング部材(試料1~32)を作製し、複数の項目について評価した。なお、本例で作製したCVT用リング部材1は、図1に示すごとく、複数層積層してCVTベルト2を構成し、2組のCVTベルト2を複数連なるエレメント3に組み付けられて使用されるものである。
引張強さは、一対のローラにリング部材を掛け渡し、一対のローラを介してリング部材を引っ張るという引張試験を行うことにより測定した。なお、引張強さは、上記引張試験においてリング部材が破断するまでの応力変化を測定し、最大応力をリング部材の断面積で割った値とした。
窒化層硬さは、窒化処理後のリング部材の表面において、マイクロビッカース(島津製)により測定した。
結晶粒径は、窒化処理後のリング部材の任意断面において、光学顕微鏡を用いて撮影した写真を用い、いわゆる「切断法」により測定した。切断法は、ASTMに準拠するものであり、金属組織を撮影した写真上に既知の長さの直線を引き、これと交わる粒の数から計算する方法である。具体的には、界面活性剤を入れた塩酸ピクリン酸水溶液によりリング部材の任意断面をエッチングして得られた窒化層を含まない面を光学顕微鏡によって観察し、任意の10視野における倍率1000倍の写真を得る。次に、各写真上に、任意の長さL(mm)の直線を引き、この直線と交わる結晶粒の数nを求める。直線の長さL(mm)の値は、実際のスケールを考慮して、L’(μm)に換算する。そして、L’/n(μm)を計算し、これを結晶粒径とする。そして、10枚の写真から得られた10個の結晶粒径の値の平均値を、最終的な結晶粒径の値として採用した。
疲労寿命は、リング部材を掛け渡す複数のローラを有し、そのローラ間でリング部材に対して定められたテンションをかけることができ、ローラを回転することによりリング部材に繰り返し曲げ応力をかけることのできる疲労試験機(図示略)を用いて測定した。評価は、現行品であるマルエージング鋼(試料19)を試験した場合の疲労寿命の平均繰り返し数である106回を基準回数として行い、基準回数以上の結果が得られた場合を合格(○)、基準回数未満の結果の場合を不合格(×)とした。
試料21は、C含有量が高すぎ、過剰に硬くなりすぎて、リング状に塑性加工ができなかったため、測定不能となった。
試料22は、Si含有量が高すぎ、窒化処理性が悪化してNが浸入しにくくなるため、窒化層硬さが低い結果となった。
試料23は、Mn含有量が高すぎ、靱性が低下して疲労特性に劣る結果となった。
試料25は、Cr含有量が高すぎ、巨大炭化物が形成され疲労寿命試験において、早期破断を招く結果となった。
試料26は、Mo含有量が低すぎ、引張強さが低い結果となった。
試料28は、製造時の焼き入れ処理における加熱温度が高すぎたため、旧オーステナイトの結晶粒が粗大化し、靱性が低下して疲労特性が劣る結果となった。
試料30は、製造時の窒化処理温度が高すぎたため、窒化層硬さが高くなりすぎて靱性の低下を招き、疲労強度に劣る結果となった。
試料32は、式2を満たしていないため、結晶粒が粗大化し、靱性(延性)が低下する結果となった。
Claims (5)
- 表面に窒化層を備えたCVT用リング部材であって、
質量%で、C:0.43~0.70%、Si:2.50%以下、Mn:1.00%以下、Cr:1.50~4.00%、Mo:0.50~3.00%、V:1.00%以下を含有し、式1:159×C(%)+91×Si(%)+68×Cr(%)+198×Mo(%)+646≧1000の関係を満たし、残部がFeおよび不可避的不純物よりなる化学成分を有し、
引張強さが1700MPa以上であり、
上記窒化層の表面硬度がHV800~HV950である、
CVT用リング部材。 - 結晶粒径が15μm以下である、請求項1に記載のCVT用リング部材。
- 質量%で、C:0.43~0.70%、Si:2.50%以下、Mn:1.00%以下、Cr:1.50~4.00%、Mo:0.50~3.00%、V:1.00%以下を含有し、式1:159×C(%)+91×Si(%)+68×Cr(%)+198×Mo(%)+646≧1000の関係を満たし、残部がFeおよび不可避的不純物よりなる鋳塊を準備し、
該鋳塊に塑性加工を加えて板材とし、
該板材を曲げ加工すると共に端面同士を溶接して粗リング材とし、
該粗リング材を軟化焼鈍した後に冷間圧延して所望板厚のリング材とし、
該リング材に、850℃~1000℃の加熱温度T1に加熱した後急冷する焼き入れ処理を施し、
その後、400℃~500℃の処理温度T2で上記リング材に窒化処理を施す、
CVT用リング部材の製造方法。 - 上記焼き入れ処理を施した後には、焼き戻し処理を施す、請求項3に記載のCVT用リング部材の製造方法。
- 上記焼き入れ処理時の上記加熱温度T1は、さらに、式2:0.015×C(%)-0.014×Cr(%)+1.46×V(%)-0.81×T1/1000+0.71≧0.05の関係を満たす、請求項3又は4に記載のCVT用リング部材の製造方法。
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US15/103,526 US10948046B2 (en) | 2013-12-12 | 2014-12-09 | CVT ring member and method for manufacturing the same |
CN201480067731.6A CN105814226B (zh) | 2013-12-12 | 2014-12-09 | Cvt用环部件及其制造方法 |
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WO2019112026A1 (ja) * | 2017-12-07 | 2019-06-13 | アイシン・エィ・ダブリュ株式会社 | 伝達ベルトおよび無段変速機並びにエレメントの設計方法、エレメントの製造方法 |
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