JP2007146233A - Method for manufacturing structural parts for automobile made from steel - Google Patents

Method for manufacturing structural parts for automobile made from steel Download PDF

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JP2007146233A
JP2007146233A JP2005342583A JP2005342583A JP2007146233A JP 2007146233 A JP2007146233 A JP 2007146233A JP 2005342583 A JP2005342583 A JP 2005342583A JP 2005342583 A JP2005342583 A JP 2005342583A JP 2007146233 A JP2007146233 A JP 2007146233A
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steel
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Makoto Okonogi
真 小此木
Kenichiro Naito
賢一郎 内藤
Yoshiki Mizuno
孝樹 水野
Hideki Matsuda
英樹 松田
Seiji Kobayashi
誠司 小林
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Honda Motor Co Ltd
Nippon Steel Corp
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Nippon Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing structural parts for an automobile made from steel, which have fatigue strength equivalent to that of a nitrocarburized product or an induction-hardened product, even when machined while skipping a heat treatment step after a hot forging step. <P>SOLUTION: This manufacturing method comprises the steps of: hot-forging a steel material into a formed workpiece; cooling it to room temperature into a hot-forged workpiece having a micro metal structure in which an austenite structure occupies 50% or more by an area rate; machining the hot-forged workpiece; and then, cold-working only a portion in which the fatigue strength is desired to be improved to impart a strain with a true strain of 0.10 or more to the portion. The manufacturing method further comprises subjecting the cold-worked workpiece to tempering treatment at 400 to 650°C, or sub-zero treatment at minus 196°C or higher but lower than 0°C, as needed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、熱間鍛造後に調質処理及び焼ならし等の熱処理を施さずに切削等の機械加工を行う鋼製自動車用構造部品の製造方法に関し、特に、熱間鍛造にて成型加工されるクランクシャフト及びコンロッド等の自動車用構造部品を製造する際に好適な鋼製自動車用構造部品の製造方法に関する。   The present invention relates to a method for manufacturing a steel automobile structural part that performs machining such as cutting without performing heat treatment such as tempering and normalizing after hot forging, and in particular, is formed by hot forging. The present invention relates to a method of manufacturing a steel automotive structural component suitable for manufacturing automotive structural components such as crankshafts and connecting rods.

一般に、自動車のエンジンに使用されるクランクシャフト等の構造部品は、ＪＩＳ Ｇ４０５１に規定されているＳ４５Ｃ等の機械構造用炭素鋼材を熱間鍛造によって成形し、その後、調質及び焼ならし等の熱処理を施し、更に仕上げの切削等の機械加工をして製造される。また、このような機械部品の中でも特に疲労強度及び耐摩耗性が要求される部品は、通常、最終工程において上述の処理に加えて、更に軟窒化処理及び高周波焼入れ処理等の表面硬化熱処理が施される。しかしながら、これらの表面硬化熱処理は、例えば軟窒化炉及び高周波焼入れ設備等の専用の設備を必要とするため、設備コストが嵩むという問題点がある。   In general, structural parts such as crankshafts used in automobile engines are formed by hot forging a carbon steel material for mechanical structures such as S45C specified in JIS G4051, and then subjected to tempering and normalization. Manufactured by heat treatment and machining such as finishing cutting. Among such mechanical parts, especially those parts that require fatigue strength and wear resistance are usually subjected to surface hardening heat treatment such as soft nitriding treatment and induction hardening treatment in addition to the above treatment in the final process. Is done. However, since these surface hardening heat treatments require dedicated equipment such as a soft nitriding furnace and induction hardening equipment, there is a problem that equipment costs increase.

そこで、従来、コスト削減及び生産性向上のために、熱間鍛造後の調質又は焼ならしを省略して軟窒化処理しても、疲労強度等の機械的性質及び曲げ矯正性等の加工性を改善することができる鋼材が提案されている（例えば、特許文献１〜３参照。）。例えば、特許文献１に記載の軟窒化用非調質鋼は、Ｃ、Ｍｎ、Ｃｒ、ｓ−Ａｌ、Ｔｉ及びＯの含有量を適正化することにより、強度、窒化性及び疲労強度の改善を図ると共に、Ｏ含有量とＴｉ含有量との関係及びＯ含有量とＮ含有量との関係を適正化することにより、熱間鍛造時の旧オーステナイト粒の成長を抑制して、曲げ矯正性の向上を図っている。   Therefore, conventionally, in order to reduce costs and improve productivity, processing such as mechanical properties such as fatigue strength and bend straightening can be performed even if soft nitriding is performed by omitting tempering or normalizing after hot forging. Steel materials capable of improving the properties have been proposed (see, for example, Patent Documents 1 to 3). For example, the non-tempered steel for soft nitriding described in Patent Document 1 can improve strength, nitriding properties and fatigue strength by optimizing the contents of C, Mn, Cr, s-Al, Ti and O. At the same time, by optimizing the relationship between the O content and the Ti content and the relationship between the O content and the N content, the growth of the prior austenite grains during hot forging is suppressed, and the bending straightening property is improved. We are trying to improve.

また、特許文献２の非調質軟窒化鋼部品においては、調質又は焼ならしを施さずに軟窒化処理を行っても、焼ならしを施したものと同等以上の疲労強度を得るために、加工前の鋼素材の組成について、Ｃ、Ｓｉ、Ｍｎ、Ｐ、Ｃｒ、Ｔｉ、Ｖ、Ｎ、Ａｌ、Ｐｂ、Ｓ及びＣａの含有量を規定すると共に、Ｃ、Ｍｎ及びＮの含有量から求められるＦｎ1〜Ｆｎ３の値の範囲を規定している。更に、特許文献３には、Ｃ、Ｓｉ、Ｍｎ、Ｔｉ、Ａｌ、Ｎ、Ｓ、Ｃａ、Ｐ、Ｃｒ及びＶの含有量を適正化した組成の鋼素材を使用した非調質クランク軸が開示されている。   In addition, in the non-tempered soft nitrided steel part of Patent Document 2, in order to obtain a fatigue strength equal to or higher than that obtained by normalizing even if the soft nitriding treatment is performed without tempering or normalizing. In addition, regarding the composition of the steel material before processing, the contents of C, Si, Mn, P, Cr, Ti, V, N, Al, Pb, S and Ca are defined, and the contents of C, Mn and N Defines the range of values of Fn1 to Fn3 obtained from Further, Patent Document 3 discloses a non-tempered crankshaft using a steel material having a composition in which the contents of C, Si, Mn, Ti, Al, N, S, Ca, P, Cr and V are optimized. Has been.

一方、例えばフィレットロールと呼ばれる圧下設備を使用して、クランクシャフトにおける疲労破壊が発生し易い部位、即ち、フィレット部に冷間加工を施し、クランクシャフトの疲労強度、ひいては耐久寿命を向上させる方法が提案されている（例えば、特許文献４及び５参照。）。具体的には、特許文献４に記載のクランクシャフトの製造方法では、フィレットＲ部に対して高周波加熱後急冷する焼き入れ処理を施した後、クランクシャフト全体に対して低温焼戻し処理をし、その後フェレットＲ部をロール加工している。また、特許文献５に記載のクランクシャフトの製造方法においては、クランクシャフトのフィレット領域等の強化要請部位に、ロール加工等により加工硬化処理を施した後、この部分に直接又は間接的に熱を与える加熱処理を施している。   On the other hand, there is a method for improving the fatigue strength of the crankshaft, and consequently the durability life, by subjecting the crankshaft to a portion where fatigue failure is likely to occur, that is, using a reduction equipment called a fillet roll, that is, the cold treatment is applied to the fillet portion. It has been proposed (for example, see Patent Documents 4 and 5). Specifically, in the crankshaft manufacturing method described in Patent Document 4, the fillet R part is subjected to a quenching process of rapid cooling after high-frequency heating, and then a low-temperature tempering process is performed on the entire crankshaft. The ferret R part is rolled. Further, in the crankshaft manufacturing method described in Patent Document 5, after a work hardening treatment is applied to a strengthening request portion such as a fillet region of the crankshaft by roll processing or the like, heat is directly or indirectly applied to this portion. Heat treatment is given.

特開２００２−２２６９３９号公報JP 2002-226939 A 特開２００１−１３１６８７号公報JP 2001-131687 A 特開平１１−６２９４３号公報JP 11-62943 A 特開平１０−３１７０６２号公報Japanese Patent Laid-Open No. 10-317062 特開２０００−３３７３４５号公報JP 2000-337345 A

しかしながら、前述の特許文献１〜３に記載の従来の技術は、鋼素材の組成を適正化しているだけであり、また、これらの技術は軟窒化処理を行っているものの、加工性向上の制約から肝心の疲労強度については、ＪＩＳ Ｇ４０５１に規定されているＳ４５Ｃ〜４８Ｃの機械構造用炭素鋼材と同等か、又はこれらの鋼材よりも１０〜２０％高い程度しか得られないという問題点がある。   However, the conventional techniques described in Patent Documents 1 to 3 described above only optimize the composition of the steel material, and these techniques perform soft nitriding, but are limited in improving workability. Therefore, there is a problem that the essential fatigue strength is equivalent to the carbon steel materials for mechanical structures of S45C to 48C specified in JIS G4051 or only 10 to 20% higher than these steel materials.

また、特許文献４及び５に記載の技術を、ＪＩＳ Ｇ４０５１に規定されているＳ４５Ｃ等の機械構造用炭素鋼材を使用したクランクシャフトに適用した場合、疲労強度は、未処理のものと比べると１０％程度向上させることができるが、軟窒化処理又は高周波焼き入れ処理を施したものと比べると、大幅に低いという問題点がある。   In addition, when the techniques described in Patent Documents 4 and 5 are applied to a crankshaft using a carbon steel material for mechanical structure such as S45C specified in JIS G4051, the fatigue strength is 10 compared to that of an untreated one. %, But there is a problem that it is significantly lower than those subjected to soft nitriding or induction hardening.

本発明は、上述した問題点に鑑みて案出されたものであり、熱間鍛造後に熱処理を省略して機械加工しても、軟窒化処理品又は高周波焼入れ品と同等の疲労強度が得られる鋼製自動車用構造部品の製造方法を提供することを目的とする。   The present invention has been devised in view of the above-mentioned problems, and even after machining by omitting heat treatment after hot forging, fatigue strength equivalent to that of a soft nitriding product or an induction-hardened product can be obtained. It aims at providing the manufacturing method of the structural parts for steel automobiles.

本発明に係る鋼製自動車用構造部品の製造方法は、鋼材を熱間鍛造にて成形した後、室温まで冷却し、ミクロ金属組織中のオーステナイト組織の面積率が５０％以上の熱間鍛造品を得る工程と、前記熱間鍛造品を切削加工した後、疲労強度が必要な部分に真歪み０．１０以上の歪を付与する冷間加工を行う工程と、を有することを特徴とする。   The method for manufacturing a steel automobile structural component according to the present invention is a hot forged product in which a steel material is formed by hot forging and then cooled to room temperature, and the area ratio of the austenite structure in the micro metal structure is 50% or more. And a step of performing cold working to give a strain having a true strain of 0.10 or more to a portion requiring fatigue strength after cutting the hot forged product.

本発明においては、熱間鍛造品のミクロ金属組織中のオーステナイト組織の面積率を５０％以上とし、更に、この熱間鍛造品を切削加工した後、冷間加工により疲労強度を向上させたい部分に真歪み０．１０以上の歪を付与しているため、冷間加工を施した部分に加工誘起変態が生じ、硬さ及び圧縮残留応力が増加する。これにより、熱間鍛造後に調質処理及び焼ならし等の熱処理を行わなくても、疲労強度が高い鋼製自動車用構造部品が得られる。また、疲労強度が必要な部分にのみ冷間加工を施すことにより、局所的に疲労強度を向上させることができる。   In the present invention, the area ratio of the austenite structure in the micro metal structure of the hot forged product is set to 50% or more, and after the hot forged product is cut, the portion where the fatigue strength is desired to be improved by cold working Since a true strain of 0.10 or more is imparted to the steel, a work-induced transformation occurs in the cold-worked portion, and the hardness and compressive residual stress increase. Thereby, even if it does not perform heat processing, such as a tempering process and normalization, after hot forging, the structural parts for steel automobiles with high fatigue strength are obtained. Further, the fatigue strength can be locally improved by performing the cold working only on the portion requiring the fatigue strength.

この鋼製自動車用構造部品の製造方法では、更に、前記冷間加工の後に、４００〜６５０℃の温度条件下で焼戻し処理を行ってもよい。これにより、靭性を向上させることができる   In this method of manufacturing a steel automobile structural component, after the cold working, a tempering treatment may be performed under a temperature condition of 400 to 650 ° C. Thereby, toughness can be improved.

又は、前記冷間加工の後に、−１９６℃以上で且つ０℃未満の温度条件下でサブゼロ処理を行うこともできる。これにより、剛性を向上させることができる。   Alternatively, after the cold working, sub-zero treatment can be performed under a temperature condition of −196 ° C. or more and less than 0 ° C. Thereby, rigidity can be improved.

また、前記鋼材としては、例えば、Ｃ、Ｍｎ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎ及びＳｉを含有し、Ｃ含有量（質量％）を［Ｃ］、Ｍｎ含有量（質量％）を［Ｍｎ］、Ｎｉ含有量（質量％）を［Ｎｉ］、Ｃｒ含有量（質量％）を［Ｃｒ］、Ｍｏ含有量（質量％）を［Ｍｏ］、Ｎ含有量（質量％）を［Ｎ］、Ｓｉ含有量（質量％）を［Ｓｉ］としたとき、下記数式（１）で定義されるＭｓの値が５０以下であり、且つ下記数式（２）で定義されるＭｄの値が２０以上である組成のものを使用することができる。   Moreover, as said steel material, for example, C, Mn, Ni, Cr, Mo, N and Si are contained, C content (mass%) is [C], Mn content (mass%) is [Mn], Ni content (mass%) is [Ni], Cr content (mass%) is [Cr], Mo content (mass%) is [Mo], N content (mass%) is [N], Si content When the amount (mass%) is [Si], the composition is such that the Ms value defined by the following formula (1) is 50 or less and the Md value defined by the following formula (2) is 20 or more. Can be used.

Figure 2007146233
Figure 2007146233

Figure 2007146233
Figure 2007146233

本発明によれば、ミクロ金属組織中のオーステナイト組織の面積率が５０％以上の熱間鍛造品を切削加工した後、冷間加工により疲労強度が必要な部分に真歪み０．１０以上の歪を付与しているため、高周波焼入れ処理又は軟窒化処理等の表面硬化熱処理を行わなくても、疲労強度が高い鋼製自動車用構造部品を製造することができると共に、疲労強度を向上させたい部分を選択して、局所的に疲労強度を向上させることができる。   According to the present invention, a hot forged product having an area ratio of an austenite structure in a micro metal structure of 50% or more is machined, and then a strain having a true strain of 0.10 or more is applied to a portion requiring fatigue strength by cold working. Therefore, it is possible to manufacture steel automotive structural parts with high fatigue strength without performing surface hardening heat treatment such as induction hardening or soft nitriding, and to improve fatigue strength. The fatigue strength can be locally improved by selecting.

以下、本発明を実施するための最良の形態について、詳細に説明する。本発明者等は、上述した問題点を解決するために鋭意検討を重ねた結果、以下に示す知見を得た。   Hereinafter, the best mode for carrying out the present invention will be described in detail. As a result of intensive studies to solve the above-described problems, the present inventors have obtained the following knowledge.

（１）フィレットロールを使用して疲労強度が必要な部分を冷間加工する従来の方法の機構は、表層を局部的に冷間加工することにより、表面の硬さが増加して圧縮残留応力が付与されることが主要因である。しかしながら、特許文献４及び５に記載の技術では、冷間加工している材料がフェライト−パーライト組織により構成されているため、このような処理を行っても硬さの増加量はＨＶ３０〜５０程度であり、処理した部分に付与される残留応力は５０〜１００ＭＰａ程度に過ぎない。   (1) The mechanism of the conventional method of cold-working a portion that requires fatigue strength using a fillet roll has a surface hardness increased by locally cold-working the surface layer, resulting in a compressive residual stress. Is the main factor. However, in the techniques described in Patent Documents 4 and 5, since the material being cold worked is composed of a ferrite-pearlite structure, the amount of increase in hardness is about HV 30 to 50 even if such treatment is performed. The residual stress applied to the treated part is only about 50 to 100 MPa.

（２）残留オーステナイトを多量に含む金属組織を有する材料に冷間加工を施すと、加工誘起変態が起こり、硬さが著しく増加し、更に圧縮残留応力も、前述したフェライト−パーライト組織により構成されている材料に比べて、５〜１０倍程度増加する。これにより、材料の疲労強度を飛躍的に向上させることができる。   (2) When a material having a metal structure containing a large amount of retained austenite is cold worked, a work-induced transformation occurs, the hardness increases remarkably, and the compressive residual stress is also composed of the ferrite-pearlite structure described above. It increases about 5 to 10 times compared to the material. Thereby, the fatigue strength of the material can be dramatically improved.

（３）熱間鍛造部品に加工誘起変態を生じさせると、衝撃特性及び剛性が低下するという問題点がある。しかしながら、冷間加工後の部品に対して、４００〜６５０℃の温度条件下で焼戻し処理を行うと衝撃特性が回復し、また、サブゼロ処理を行うと剛性が回復する。従って、冷間加工後に、これらの処理を行うことにより、衝撃特性及び剛性を低下させずに鋼製自動車用構造部品の疲労強度を向上させることができる。   (3) When work-induced transformation is caused in a hot forged part, there is a problem that impact characteristics and rigidity are lowered. However, the impact characteristics are restored when a tempering process is performed on a cold-worked part under a temperature condition of 400 to 650 ° C., and the rigidity is restored when a sub-zero process is performed. Therefore, by performing these treatments after cold working, the fatigue strength of steel structural parts for automobiles can be improved without deteriorating impact characteristics and rigidity.

発明は、上記知見に基づき完成されたものであり、その特徴は、鋼材を熱間鍛造にて成形した後、室温まで冷却し、ミクロ金属組織中のオーステナイト組織の面積率を５０％以上にした熱間鍛造品に対して、切削加工を施し、その後、疲労強度を向上させる部分に真歪み０．１０以上の歪を付与する冷間加工を行うことにある。   The invention has been completed based on the above knowledge, and the feature is that after forming the steel material by hot forging, the steel material is cooled to room temperature, and the area ratio of the austenite structure in the micro metal structure is 50% or more. The hot forging product is subjected to a cutting process, and then a cold process is performed in which a strain having a true strain of 0.10 or more is applied to a portion where the fatigue strength is improved.

以下、本発明の鋼製自動車用構造部品の製造方法において、各種因子を上述の範囲に限定した理由について説明する。   Hereinafter, the reason why various factors are limited to the above-described range in the method for manufacturing a steel automobile structural component of the present invention will be described.

ミクロ金属組織中のオーステナイト組織の面積率：５０％以上
熱間鍛造品のミクロ金属組織は本発明の主要項目であり、オーステナイト組織を、面積率で５０％以上含有する必要がある。熱間鍛造品のミクロ金属組織中のオーステナイト組織の面積率が５０％未満の場合、局部的な冷間加工により加工誘起変態を生じさせて、硬さ及び圧縮残留応力を増加させても、疲労強度を顕著に向上させることができない。よって、熱間鍛造品のミクロ金属組織中のオーステナイト組織の面積率は５０％以上とする。なお、オーステナイト組織の面積率を５０％以上にする方法としては、例えば、鍛造後に衝風冷却、及び後述するＭｓの値が５０以下となる鋼材成分にする等の方法がある。 Area ratio of austenite structure in the micro metal structure: 50% or more The micro metal structure of the hot forged product is a main item of the present invention, and it is necessary to contain the austenite structure in an area ratio of 50% or more. When the area ratio of the austenite structure in the micro metal structure of the hot forged product is less than 50%, fatigue is caused even if the work-induced transformation is caused by local cold working and the hardness and compressive residual stress are increased. The strength cannot be improved significantly. Therefore, the area ratio of the austenite structure in the micro metal structure of the hot forged product is set to 50% or more. In addition, as a method of making the area ratio of an austenite structure 50% or more, for example, there are methods such as blast cooling after forging and a steel material component having an Ms value of 50 or less described later.

冷間加工により付加する歪量：真歪で０．１０以上
本発明の鋼製自動車用構造部品の製造方法においては、熱間鍛造品を切削加工した後、疲労強度が必要な部分に対して冷間加工を行う。このとき、付与される歪量が真歪みで０．１０未満の場合、疲労強度を顕著に向上させることができない。よって、切削後の冷間加工により付加する歪量は、真歪で０．１０以上とする。これにより、鋼材の種類によっては、冷間加工しないものに比べて疲労強度を１．５倍以上できるものもある。なお、冷間加工により歪を付与する方法は、特に限定されるものではないが、例えば、硬質ローラーによる圧迫及びリング状のポンチの押付け等であれば、真歪で０．１０以上の歪を付与することができる。 Strain applied by cold working: 0.10 or more in true strain In the method of manufacturing a steel automotive structural component of the present invention, after cutting a hot forged product, a portion requiring fatigue strength Perform cold working. At this time, if the applied strain is true strain and less than 0.10, the fatigue strength cannot be significantly improved. Therefore, the amount of strain applied by cold working after cutting is 0.10 or more in true strain. Thereby, depending on the type of steel material, there is a steel material that can increase the fatigue strength by 1.5 times or more compared to a steel material that is not cold worked. Note that the method of applying strain by cold working is not particularly limited. For example, in the case of compression by a hard roller and pressing of a ring-shaped punch, a strain of 0.10 or more is obtained as a true strain. Can be granted.

また、本発明の鋼製自動車用構造部品の製造方法においては、靭性が要求される部品を製造する場合には、必要に応じて、前述の冷間加工の後に、更に４００〜６５０℃で焼戻し処理してもよい。これにより、疲労強度のばらつきを少なくすることができ、疲労強度を安定的に向上させることができると共に、衝撃特性を改善することができる。しかしながら、焼戻し処理温度が６５０℃を超えると、加工誘起変態したマルテンサイトが再びオーステナイト組織に変態し、強度が低下する。一方、焼戻し処理温度が４００℃未満の場合、冷間加工により低下した衝撃特性が十分に回復しない。よって、冷間加工後に焼戻し処理をする場合には、処理温度を４００〜６５０℃にする。   In the method for manufacturing a steel automobile structural component of the present invention, when manufacturing a component requiring toughness, it is further tempered at 400 to 650 ° C. after the aforementioned cold working, if necessary. It may be processed. Thereby, variation in fatigue strength can be reduced, the fatigue strength can be stably improved, and impact characteristics can be improved. However, when the tempering temperature exceeds 650 ° C., the martensite that has undergone work-induced transformation is transformed again into an austenite structure, and the strength is lowered. On the other hand, when the tempering treatment temperature is less than 400 ° C., the impact characteristics lowered by cold working are not sufficiently recovered. Therefore, when tempering is performed after cold working, the processing temperature is set to 400 to 650 ° C.

更に、本発明の鋼製自動車用構造部品の製造方法においては、疲労強度に加えて剛性が要求される部品を製造する場合には、必要に応じて、前述の冷間加工の後に、低温下で一定時間保持するサブゼロ処理を行ってもよい。このとき、サブゼロ処理温度が０℃以上の場合、未変態のオーステナイト組織をマルテンサイト組織に変態させる効果が小さくなる。一方、サブゼロ処理温度が−１９６℃未満の場合、冷却コストが増加する。よって、冷間加工後にサブゼロ処理をする場合には、処理温度を−１９６℃以上で且つ０℃未満にする。   Furthermore, in the method for manufacturing a steel automobile structural component according to the present invention, when manufacturing a component that requires rigidity in addition to fatigue strength, if necessary, after the cold working described above, Sub-zero processing that holds for a certain period of time may be performed. At this time, when the subzero treatment temperature is 0 ° C. or higher, the effect of transforming the untransformed austenite structure into the martensite structure becomes small. On the other hand, when the sub-zero treatment temperature is less than -196 ° C, the cooling cost increases. Therefore, when the sub-zero treatment is performed after the cold working, the treatment temperature is set to −196 ° C. or higher and lower than 0 ° C.

次に、本発明において使用する鋼材の組成について説明する。なお、以下の説明においては、鋼材に含まれる各成分の含有量を示す質量％は、単に％と記載する。本発明の鋼製自動車用構造部品の製造方法においては、熱間鍛造品のミクロ金属組織中のオーステナイト組織の面積率が５０％以上であることが重要であって、鋼材に含まれる各元素の含有量については特に限定されるものではないが、工業生産的には、Ｃ：０．０２〜０．７０％、Ｓｉ：０．１〜２．０％、Ｍｎ：０．５０〜２０．０％、Ｃｒ：０．１〜２０．０％、Ｎｉ：０〜１０．０％、Ｍｏ：０〜５．０％、Ｎ：０．００３〜０．３％を含有し、残部がＦｅ及び不可避的不純物である鋼材を使用することが望ましい。なお、本発明において使用する鋼材には、上記各成分に加えて、切削性向上のために、Ｐｂ、Ｓ及びＣａ等の快削性元素が添加されていてもよく、その場合でも同様の効果が得られる。   Next, the composition of the steel material used in the present invention will be described. In the following description, mass% indicating the content of each component contained in the steel material is simply described as%. In the method for manufacturing a steel automobile structural component of the present invention, it is important that the area ratio of the austenite structure in the micro metal structure of the hot forged product is 50% or more, and each element contained in the steel material Although it does not specifically limit about content, From industrial production, C: 0.02-0.70%, Si: 0.1-2.0%, Mn: 0.50-20.0 %, Cr: 0.1 to 20.0%, Ni: 0 to 10.0%, Mo: 0 to 5.0%, N: 0.003 to 0.3%, the balance being Fe and inevitable It is desirable to use steel materials that are mechanical impurities. In addition to the above components, free cutting elements such as Pb, S and Ca may be added to the steel material used in the present invention in order to improve the machinability. Is obtained.

更に、本発明において使用する鋼材は、Ｃ含有量（％）を［Ｃ］、Ｍｎ含有量（％）を［Ｍｎ］、Ｎｉ含有量（％）を［Ｎｉ］、Ｃｒ含有量（％）を［Ｃｒ］、Ｍｏ含有量（％）を［Ｍｏ］、Ｎ含有量（％）を［Ｎ］、Ｓｉ含有量（％）を［Ｓｉ］としたとき、下記数式（３）で定義されるＭｓの値が５０以下であり、且つ下記数式（４）で定義されるＭｄの値が２０以上であることが好ましい。   Furthermore, the steel material used in the present invention has a C content (%) of [C], an Mn content (%) of [Mn], an Ni content (%) of [Ni], and a Cr content of (%). When [Cr], Mo content (%) is [Mo], N content (%) is [N], and Si content (%) is [Si], Ms defined by the following formula (3) Is preferably 50 or less, and the Md value defined by the following mathematical formula (4) is preferably 20 or more.

Figure 2007146233
Figure 2007146233

Figure 2007146233
Figure 2007146233

上記数式（３）で定義されるＭｓの値が５０を超えると、熱間鍛造後に室温まで冷却した際に、オーステナイトが主体の組織が得られにくくなる。よって、本発明においては、上記数式（３）で定義されるＭｓの値の好ましい範囲を５０以下とする。また、上記数式（４）で定義されるＭｄの値が２０未満の場合、冷間加工により歪みを付与しても、その部分が十分に強化されず、疲労強度を向上させる効果が得られにくい。よって、本発明においては、上記数式（４）で定義されるＭｄ値の好ましい範囲を２０以上とする。   When the value of Ms defined by the above formula (3) exceeds 50, it becomes difficult to obtain a structure mainly composed of austenite when cooled to room temperature after hot forging. Therefore, in the present invention, the preferable range of the value of Ms defined by the above mathematical formula (3) is set to 50 or less. In addition, when the value of Md defined by the above formula (4) is less than 20, even if distortion is applied by cold working, the portion is not sufficiently strengthened, and it is difficult to obtain the effect of improving fatigue strength. . Therefore, in the present invention, the preferable range of the Md value defined by the above mathematical formula (4) is 20 or more.

以上、詳述したように、本発明の鋼製自動車用構造部品の製造方法においては、ミクロ金属組織中のオーステナイト組織の面積率を５０％以上にした熱間鍛造品を、切削加工した後、冷間加工により疲労強度を向上させたい部分に真歪み０．１０以上の歪を付与しているため、冷間加工を施した部分に加工誘起変態が生じ、硬さ及び圧縮残留応力を増加するため、熱間鍛造後に調質処理及び焼ならし等の熱処理を行わなくても、鋼製自動車用構造部品の疲労強度を大幅に向上させることができる。また、局所的に冷間加工を施すことができるため、疲労強度を高めたい部分のみ、局所的に疲労強度を向上させることもできる。   As described above in detail, in the method for manufacturing a steel automobile structural component of the present invention, after hot forging products in which the area ratio of the austenite structure in the micro metal structure is 50% or more, cutting, Since a strain with a true strain of 0.10 or more is imparted to the part where the fatigue strength is to be improved by cold working, a work-induced transformation occurs in the cold-worked part, increasing the hardness and compressive residual stress. Therefore, the fatigue strength of steel structural parts for automobiles can be greatly improved without performing heat treatment such as tempering and normalizing after hot forging. Further, since cold working can be performed locally, the fatigue strength can be locally improved only in the portion where the fatigue strength is desired to be increased.

次に、実施例及び比較例を挙げて、本発明の効果について具体的に説明する。本実施例においては、先ず、下記表１に示す組成の鋼を真空溶解炉にて溶製した後、熱間圧延して直径が９０ｍｍの熱間圧延棒鋼を作製した。次に、各熱間圧延棒鋼を、１２５０℃に加熱した後、熱間鍛造により直径が５０ｍｍになるように加工して、大気中放冷により室温まで冷却した。その際、熱電対にて測温した中心部の冷却速度は約０．７℃／秒であった。そして、冷却後の熱間鍛造品について、ミクロ金属組織観察を行うと共に、Ｘ線回折により組織中のオーステナイト組織の面積率（％）を求めた。また、マイクロビッカース硬さ試験機を使用して、冷却後の熱間鍛造品のビッカース硬さを測定した。更に、冷却後の熱間鍛造品からＪＩＳ Ｚ２２０１に規定されている１０号試験片を作製し、Ｎｏ．１〜１０，１２〜１４の試料は、引張試験機により所定の歪みを付与した。その後、Ｎｏ．３〜５の試料には焼戻し処理を施し、Ｎｏ．６，８の試料にはサブゼロ処理を施した。   Next, the effects of the present invention will be specifically described with reference to examples and comparative examples. In this example, first, steels having the compositions shown in Table 1 below were melted in a vacuum melting furnace, and then hot-rolled to produce hot-rolled steel bars having a diameter of 90 mm. Next, each hot-rolled steel bar was heated to 1250 ° C., then processed by hot forging so as to have a diameter of 50 mm, and cooled to room temperature by cooling in the air. At that time, the cooling rate of the central portion measured with a thermocouple was about 0.7 ° C./second. And about the hot forging after cooling, while performing micro metal structure observation, the area ratio (%) of the austenite structure in a structure | tissue was calculated | required by X-ray diffraction. Moreover, the Vickers hardness of the hot forged product after cooling was measured using a micro Vickers hardness tester. Furthermore, No. 10 test piece prescribed in JIS Z2201 was produced from the hot forged product after cooling. Samples 1 to 10 and 12 to 14 were given a predetermined strain by a tensile tester. Then, no. The samples 3 to 5 were subjected to tempering treatment. The samples 6 and 8 were subjected to sub-zero treatment.

Figure 2007146233
Figure 2007146233

次に、上述の方法で作製した実施例及び比較例の試料について、ビッカース硬さを測定した。また、ＪＩＳ Ｚ２２７４に基づき、実施例及び比較例の試料から夫々平行部の直径が８ｍｍの回転曲げ疲労試験片を作製して疲労試験を行って、１×１０７回で破断しない最大の応力を疲労限度σｗ（ＭＰａ）として評価した。また、Ｎｏ．２〜５の試料については、ＪＩＳ Ｚ２２０２に規定されているＶノッチの衝撃試験片を作製し、ＪＩＳ Ｚ２２４２に規定されている方法で衝撃試験を行い、室温にて衝撃値を測定した。更に、Ｎｏ．６〜８の試料については、ＪＩＳ Ｚ２２４１に基づき引張試験を行い、応力−歪線図により弾性係数を求めた。 Next, Vickers hardness was measured about the sample of the Example and comparative example which were produced with the above-mentioned method. Moreover, based on JIS Z2274, the rotation bending fatigue test piece whose diameter of a parallel part is 8 mm is produced from the sample of an Example and a comparative example, respectively, and a fatigue test is conducted, and the maximum stress which does not fracture by 1 × 10 7 times. The fatigue limit σ w (MPa) was evaluated. No. For the samples 2 to 5, V-notch impact test pieces defined in JIS Z2202 were prepared, impact tests were performed by the method defined in JIS Z2242, and impact values were measured at room temperature. Furthermore, no. About the samples of 6-8, the tension test was done based on JISZ2241 and the elastic modulus was calculated | required with the stress-strain diagram.

次に、従来例としてフェレットロール加工により試料を作製した。図１はロール加工試験片の形状を示す側面図であり、図２（ａ）及び（ｂ）はロール加工方法を模式的に示す図である。本従来例においては、上記表１に示す鋼種Ｅを使用して作製した熱間圧延棒鋼を１２５０℃に加熱した後、熱間鍛造により直径が５０ｍｍになるように加工し、大気中放冷により室温まで冷却した。次に、冷却後の熱間鍛造品から、図１に示す形状の試験片１を作製し、フィレットロール加工を模して、図２（ａ）及び（ｂ）に示すように、ロール２とバックアップロール３ａ，３ｂとにより、試験片１のノッチ部にロール加工を行い、Ｎｏ．１６の試料を作製した。このとき、荷重印加方向４はロール２から試験片１に向かう方向とし、荷重は４．９０ｋＮ（５００ｋｇｆ）とした。また、比較のため、Ｎｏ．１６と同様の方法で作製した熱間鍛造品から、図１に示す形状の試験片１を作製し、ロール加工を施さずにＮｏ．１５の試料とした。そして、Ｎｏ．１５，１６の試料について、ロール加工部位のビッカース硬さ及び残留応力を測定した。なお、残留応力の測定には、Ｘ線回折法を使用した。更に、Ｎｏ．１５，１６の試料については、前述の実施例及び比較例の試料と同様の方法で、回転曲げ疲労試験を行い、１×１０７回で破断しない疲労限度σｗ（ＭＰａ）を評価した。 Next, the sample was produced by the ferret roll process as a prior art example. FIG. 1 is a side view showing the shape of a roll processing test piece, and FIGS. 2A and 2B are diagrams schematically showing a roll processing method. In this conventional example, a hot rolled steel bar produced using the steel type E shown in Table 1 above is heated to 1250 ° C., then processed to a diameter of 50 mm by hot forging, and then allowed to cool in the atmosphere. Cooled to room temperature. Next, from the hot forged product after cooling, the test piece 1 having the shape shown in FIG. 1 is produced, imitating fillet roll processing, and as shown in FIGS. 2 (a) and 2 (b), With the backup rolls 3a and 3b, roll processing was performed on the notch portion of the test piece 1, Sixteen samples were prepared. At this time, the load application direction 4 was a direction from the roll 2 toward the test piece 1, and the load was 4.90 kN (500 kgf). For comparison, no. 16 was produced from the hot forged product produced in the same manner as in No. 16, and the test piece 1 having the shape shown in FIG. There were 15 samples. And No. About the 15 and 16 samples, the Vickers hardness and the residual stress of the roll processing part were measured. In addition, the X-ray diffraction method was used for the measurement of residual stress. Furthermore, no. For the 15 and 16 samples, a rotating bending fatigue test was performed in the same manner as the samples of the above-described examples and comparative examples, and the fatigue limit σ w (MPa) that did not break at 1 × 10 7 times was evaluated.

以上の評価結果を下記表２にまとめて示す。なお、下記表２には、サブゼロ処理及び焼戻し処理における処理温度も併せて示す。また、下記表２に示す熱間鍛造品のミクロ金属組織においては、Ａはオーステナイト、Ｍはマルテンサイト、Ｆはフェライト、Ｐはパーライトを示す。   The above evaluation results are summarized in Table 2 below. Table 2 below also shows treatment temperatures in the sub-zero treatment and the tempering treatment. Moreover, in the micro metal structure of the hot forged product shown in Table 2 below, A represents austenite, M represents martensite, F represents ferrite, and P represents pearlite.

Figure 2007146233
Figure 2007146233

上記表２に示すように、Ｎｏ．１〜３，６〜１０，１４の試料は、本発明の範囲内で作製した実施例であり、Ｎｏ．４，５，１１〜１３の試料は本発明の範囲から外れる比較例であり、Ｎｏ．１５，１６の試料は、フィレットロール加工により作製した従来例である。これらのうち、Ｎｏ．１０〜１２の試料は、歪みの影響を評価したものである。付与した真歪みが本発明の範囲を満たす実施例Ｎｏ．１０の試料は、加工強化ΔＨＶが１５６であった。これに対して、付与した真歪みが本発明の範囲よりも低いＮｏ．１２の試料は、加工強化ΔＨＶが５７と低かった。また、疲労限度σｗに関しては、実施例Ｎｏ．１０の試料は７１０ＭＰａであったのに対して、冷間加工を実施していない、即ち、歪みを付与していない比較例Ｎｏ．１１の試料は４７０ＭＰａであり、また付与した真歪みが本発明の範囲よりも低い比較例Ｎｏ．１２の試料は５００ＭＰａであり、いずれも実施例Ｎｏ．１０の試料に比べて著しく低かった。この結果から、本発明の範囲内で作製した実施例Ｎｏ．１０の試料は、冷間加工を行わなかった比較例Ｎｏ．１１の試料に比べて疲労限度σｗが５０％程度向上することが確認された。 As shown in Table 2 above, no. Samples 1 to 3, 6 to 10 and 14 are examples prepared within the scope of the present invention. Samples Nos. 4, 5, and 11 to 13 are comparative examples out of the scope of the present invention. Samples 15 and 16 are conventional examples manufactured by fillet roll processing. Of these, No. Samples 10 to 12 were evaluated for the influence of distortion. Example No. in which the applied true strain satisfies the scope of the present invention. Ten samples had a processing enhancement ΔHV of 156. On the other hand, the applied true strain is lower than the range of the present invention. The 12 samples had a low processing enhancement ΔHV of 57. Regarding the fatigue limit σ w , Example No. While the sample of No. 10 was 710 MPa, it was not subjected to cold working, that is, Comparative Example No. to which no strain was applied. Sample No. 11 has a pressure of 470 MPa, and the applied true strain is lower than the range of the present invention. Sample No. 12 is 500 MPa, and all of Examples No. It was significantly lower than 10 samples. From this result, Example No. produced within the scope of the present invention was obtained. Sample No. 10 was comparative example No. which was not cold worked. It was confirmed that the fatigue limit σ w was improved by about 50% compared to the 11 samples.

また、Ｎｏ．１３の試料は、ミクロ金属組織中のオーステナイトの面積率が本発明の範囲よりも低い比較例である。この比較例Ｎｏ．１３の試料の加工強化ΔＨＶと、サブゼロ処理又は焼戻し処理を実施していない実施例の試料の加工強化ΔＨＶとを比較すると、オーステナイトの面積率が本発明の範囲内である実施例Ｎｏ.１，２，７，１０，１４の試料は、いずれもΔＨＶが８４〜２２７であったのに対して、比較例Ｎｏ．１３の試料はΔＨＶが３２と著しく低かった。その結果、冷間加工前の熱間鍛造品の硬さに対して、冷間加工後の試料の疲労限度σｗが著しく低くなっていた。図３は横軸に熱間鍛造品のビッカース硬さをとり、縦軸に疲労限度σｗをとって、冷間加工前の硬さと冷間加工後の疲労限度との関係を示すグラフ図である。なお、図３においては、サブゼロ処理又は焼戻し処理を行った実施例及び比較例は除外している。図３に示すように、本発明の実施例の試料は、冷間加工前は軟質であり切削等の加工性が優れており、また、冷間加工後には高い疲労強度が得られることがわかる。 No. Sample 13 is a comparative example in which the area ratio of austenite in the micro metal structure is lower than the range of the present invention. This Comparative Example No. Comparing the processing strengthening ΔHV of the 13 samples with the processing strengthening ΔHV of the samples of the examples in which the sub-zero treatment or the tempering treatment was not performed, Example No. 1 in which the area ratio of austenite is within the scope of the present invention The samples 2, 7, 10, and 14 all had ΔHV of 84 to 227, whereas the comparative example No. The 13 samples had an extremely low ΔHV of 32. As a result, the fatigue limit σ w of the sample after cold working was significantly lower than the hardness of the hot forged product before cold working. Figure 3 takes a Vickers hardness of hot forging on the horizontal axis and the vertical axis represents the fatigue limit sigma w, a graph showing the relationship between hardness and cold fatigue limit after processing before cold working is there. In addition, in FIG. 3, the Example and comparative example which performed the subzero process or the tempering process are excluded. As shown in FIG. 3, the sample of the example of the present invention is soft before cold working and has excellent workability such as cutting, and high fatigue strength can be obtained after cold working. .

更に、Ｎｏ．３〜５の試料は、焼戻し温度の影響を比較するためのものである。焼戻しは、本発明の製造方法を衝撃特性が要求される部品に適用する場合、必要に応じて行う処理である。焼戻し温度が本発明の範囲を満たす実施例Ｎｏ．３の試料は、衝撃値が１６．２Ｊ／ｃｍ２であったのに対して、本発明の範囲から外れる比較例Ｎｏ．４の試料は１２．９Ｊ／ｃｍ２、比較例Ｎｏ．５の試料は１０．３Ｊ／ｃｍ２であり、衝撃値が著しく低いことが確認された。 Furthermore, no. Samples 3 to 5 are for comparing the effects of the tempering temperature. Tempering is a treatment that is performed as necessary when the manufacturing method of the present invention is applied to a part that requires impact characteristics. Example No. tempering temperature satisfying the scope of the present invention. The sample of No. 3 had an impact value of 16.2 J / cm 2 , whereas the comparative example No. 3 deviated from the scope of the present invention. The sample of No. 4 is 12.9 J / cm 2 , Comparative Example No. The sample of No. 5 was 10.3 J / cm 2 , and it was confirmed that the impact value was extremely low.

更にまた、Ｎｏ．６〜８の試料は、サブゼロ処理の影響を比較するためのものである。サブゼロ処理は、本発明の製造方法を剛性が要求される部品に適用する場合、必要に応じて行う処理である。サブゼロ処理を行わなかった実施例Ｎｏ．７の試料は、弾性係数が２０３ＧＰａであったのに対して、本発明の範囲内の条件でサブゼロ処理を行った実施例Ｎｏ．６及びＮｏ．８の試料の弾性係数は、夫々２１２ＧＰａ及び２１１ＧＰａとなっていた。その結果、サブゼロ処理を行うことにより、弾性係数が向上することが確認された。   Furthermore, no. Samples 6-8 are for comparing the effects of sub-zero treatment. The sub-zero process is a process performed as necessary when the manufacturing method of the present invention is applied to a part that requires rigidity. Example No. in which sub-zero treatment was not performed. The sample of No. 7 had an elastic modulus of 203 GPa, whereas the sample of Example No. 6 and no. The elastic modulus of the sample No. 8 was 212 GPa and 211 GPa, respectively. As a result, it was confirmed that the elastic modulus was improved by performing the sub-zero treatment.

更にまた、従来例Ｎｏ．１５及び１６の試料の冷却後のミクロ金属組織は、約２％のオーステナイトを含んでいるが、フェライト−パーライトを主体とする組織となっており、オーステナイト組織の面積率が本発明の範囲を満たしていなかった。また、ロール加工を施した従来例Ｎｏ．１６の試料は、ΔＨＶ２３程度の加工強化が得られ、約９０ＭＰａの圧縮応力が付与されていた。更に、疲労強度に関しては、従来例Ｎｏ．１６の試料が４６０ＭＰａであり、ロール加工していない従来例Ｎｏ．１５の試料が４２０ＭＰａであった。この結果から、従来のロール加工による方法では、疲労強度の向上は１０％程度に過ぎないことが確認された。   Furthermore, the conventional example No. The micro-metallic structure after cooling of the samples 15 and 16 contains about 2% austenite, but has a structure mainly composed of ferrite-pearlite, and the area ratio of the austenite structure satisfies the scope of the present invention. It wasn't. Moreover, the conventional example No. which gave the roll process. In the 16 samples, a processing strengthening of about ΔHV23 was obtained, and a compressive stress of about 90 MPa was applied. Furthermore, regarding fatigue strength, the conventional example No. No. 16 sample is 460 MPa, and rolls are not processed. Fifteen samples were 420 MPa. From this result, it was confirmed that the fatigue strength was improved only by about 10% by the conventional roll processing method.

上述の如く、本発明の鋼製自動車用構造部品の製造方法によれば、疲労強度の高い鋼製自動車用機械部品を製造することができる。   As described above, according to the method for manufacturing a steel automotive structural component of the present invention, a steel automotive mechanical component having high fatigue strength can be manufactured.

ロール加工試験片の形状を示す側面図である。It is a side view which shows the shape of a roll processing test piece. （ａ）及び（ｂ）はロール加工方法を模式的に示す図である。(A) And (b) is a figure which shows a roll processing method typically. 横軸に熱間鍛造品のビッカース硬さをとり、縦軸に疲労限度σｗをとって、冷間加工前の硬さと冷間加工後の疲労限度との関係を示すグラフ図である。It is a graph which shows the relationship between the hardness before cold work, and the fatigue limit after cold work, taking the Vickers hardness of the hot forged product on the horizontal axis and taking the fatigue limit σ w on the vertical axis.

符号の説明Explanation of symbols

１ 試験片
２ ロール
３ａ、３ｂ バックアップロール
４ 荷重印加方向 1 Test piece 2 Roll 3a, 3b Backup roll 4 Load application direction

Claims (4)

鋼材を熱間鍛造にて成形した後、室温まで冷却し、ミクロ金属組織中のオーステナイト組織の面積率が５０％以上の熱間鍛造品を得る工程と、
前記熱間鍛造品を切削加工した後、疲労強度が必要な部分に真歪み０．１０以上の歪を付与する冷間加工を行う工程と、を有することを特徴とする鋼製自動車用構造部品の製造方法。 After forming the steel material by hot forging, cooling to room temperature, obtaining a hot forged product with an area ratio of the austenite structure in the micro metal structure of 50% or more,
And a step of performing cold working to give a strain having a true strain of 0.10 or more to a portion requiring fatigue strength after cutting the hot forged product. Manufacturing method. 更に、前記冷間加工の後に、４００〜６５０℃の温度条件下で焼戻し処理することを特徴とする請求項１に記載の鋼製自動車用構造部品の製造方法。   Furthermore, after the said cold work, the tempering process is carried out on 400-650 degreeC temperature conditions, The manufacturing method of the steel steel structural components of Claim 1 characterized by the above-mentioned. 更に、前記冷間加工の後に、−１９６℃以上で且つ０℃未満の温度条件下でサブゼロ処理を行うことを特徴とする請求項１に記載の鋼製自動車用構造部品の製造方法。   Furthermore, after the said cold work, a subzero process is performed on the temperature conditions which are -196 degreeC or more and less than 0 degreeC, The manufacturing method of the structural parts for steel automobiles of Claim 1 characterized by the above-mentioned. 前記鋼材は、Ｃ、Ｍｎ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎ及びＳｉを含有し、Ｃ含有量（質量％）を［Ｃ］、Ｍｎ含有量（質量％）を［Ｍｎ］、Ｎｉ含有量（質量％）を［Ｎｉ］、Ｃｒ含有量（質量％）を［Ｃｒ］、Ｍｏ含有量（質量％）を［Ｍｏ］、Ｎ含有量（質量％）を［Ｎ］、Ｓｉ含有量（質量％）を［Ｓｉ］としたとき、下記数式（１）で定義されるＭｓの値が５０以下であり、且つ下記数式（２）で定義されるＭｄの値が２０以上であることを特徴とする請求項１〜３のいずれか１項に記載の鋼製自動車用構造部品の製造方法。
Figure 2007146233
The steel material contains C, Mn, Ni, Cr, Mo, N and Si, the C content (mass%) is [C], the Mn content (mass%) is [Mn], and the Ni content (mass). %) [Ni], Cr content (% by mass) [Cr], Mo content (% by mass) [Mo], N content (% by mass) [N], Si content (% by mass) The value of Ms defined by the following mathematical formula (1) is 50 or less, and the value of Md defined by the following mathematical formula (2) is 20 or more, where is [Si]. Item 4. A method for manufacturing a steel automotive structural component according to any one of Items 1 to 3.
Figure 2007146233
JP2005342583A 2005-11-28 2005-11-28 Method for manufacturing structural parts for automobile made from steel Withdrawn JP2007146233A (en)

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WO2010052751A1 (en) * 2008-11-05 2010-05-14 Honda Motor Co., Ltd. High-strength steel sheet and the method for production therefor
JP2010248540A (en) * 2009-04-10 2010-11-04 Kobe Steel Ltd Integrated crankshaft and method for manufacturing the same
WO2016166932A1 (en) * 2015-04-16 2016-10-20 本田技研工業株式会社 Connecting rod and manufacturing method therefor
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Cited By (9)

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WO2010052751A1 (en) * 2008-11-05 2010-05-14 Honda Motor Co., Ltd. High-strength steel sheet and the method for production therefor
JP2012507620A (en) * 2008-11-05 2012-03-29 本田技研工業株式会社 High strength steel plate and manufacturing method thereof
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US9267193B2 (en) 2008-11-05 2016-02-23 Honda Motor Co., Ltd High-strength steel sheet and the method for production therefor
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US10161439B2 (en) 2015-04-16 2018-12-25 Honda Motor Co., Ltd. Connecting rod and manufacturing method thereof
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