JP4593510B2 - High strength bearing joint parts excellent in delayed fracture resistance, manufacturing method thereof, and steel for high strength bearing joint parts - Google Patents

High strength bearing joint parts excellent in delayed fracture resistance, manufacturing method thereof, and steel for high strength bearing joint parts Download PDF

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JP4593510B2
JP4593510B2 JP2006098555A JP2006098555A JP4593510B2 JP 4593510 B2 JP4593510 B2 JP 4593510B2 JP 2006098555 A JP2006098555 A JP 2006098555A JP 2006098555 A JP2006098555 A JP 2006098555A JP 4593510 B2 JP4593510 B2 JP 4593510B2
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delayed fracture
strength bearing
fracture resistance
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徹志 千田
学 久保田
敏三 樽井
清三郎 東
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新日本製鐵株式会社
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本発明は、土木、建築、自動車、各種産業機械等の接合部に使用されるボルト、ピン等の接合部品及びその製造方法、並びに接合部品の素材である鋼材に関する。   The present invention relates to a joining part such as a bolt and a pin used for joining parts of civil engineering, architecture, automobiles, various industrial machines and the like, a manufacturing method thereof, and a steel material as a material of the joining part.
従来の接合部品、例えば、ボルトによる接合部は、主として、ボルトに引張応力が負荷される摩擦接合や引張接合である。この場合、ボルトによる接合部の強化や、接合部のコンパクト化等のために、引張強さが1200MPaを超える高力ボルトを使用すると、遅れ破壊が発生する可能性が高くなる。   Conventional joint parts, for example, joints by bolts, are mainly friction joints and tensile joints in which tensile stress is applied to the bolts. In this case, if a high-strength bolt with a tensile strength exceeding 1200 MPa is used for strengthening the joint with bolts or making the joint compact, the possibility of delayed fracture increases.
一方、鋼構造物の設計で、大地震に対する耐力を考慮してボルト本数を決定する場合には、引張応力及び剪断応力に対する接合部の耐力の強化が求められる。この課題に対して、本発明者らの一部は、支圧接合又は支圧接合と摩擦接合を組み合わせた接合部に、引張強さ1700〜2600MPaの高強度接合部品を使用し、ボルト本数の低減、接合部のコンパクト化を図る方法を提案した(例えば、特許文献1、2、参照)。   On the other hand, when the number of bolts is determined in consideration of the strength against a large earthquake in the design of a steel structure, strengthening of the strength of the joint against tensile stress and shear stress is required. In response to this problem, some of the present inventors use a high-strength joint component having a tensile strength of 1700 to 2600 MPa in a joint portion that is a support joint or a combination of a support joint and a friction joint. A method for reducing the size and reducing the size of the joint has been proposed (see, for example, Patent Documents 1 and 2).
これらの方法によれば、高強度接合部品に、常時、高張力を導入することなく、接合部の耐力を十分に確保することが可能であり、引張応力による高強度接合部品の遅れ破壊を防止することができる。また、接合形態を支圧接合とした場合、導入張力に起因する引張応力に対する遅れ破壊は排除できる。更に、接合部の耐久性を高めるためには、ボルトに高い剪断応力が作用した場合の剪断応力による遅れ破壊を考慮することが望ましい。   According to these methods, it is possible to ensure sufficient strength of the joint without constantly introducing high tension to the high-strength joint parts, and prevent delayed fracture of the high-strength joint parts due to tensile stress. can do. Further, when the joining form is a support bearing, delayed fracture with respect to the tensile stress caused by the introduced tension can be eliminated. Furthermore, in order to increase the durability of the joint, it is desirable to consider delayed fracture due to shear stress when high shear stress is applied to the bolt.
これまでに、引張方向に張力が導入された条件での遅れ破壊特性を向上させる技術として、例えば、特許文献3〜6には、合金元素や、熱処理時に析出する炭化物や、旧オーステナイト粒のアスペクト比に着目した、耐遅れ破壊特性向上技術が開示されている。しかし、剪断応力負荷条件における耐遅れ破壊特性を向上させる技術は明確にされていない。   So far, as techniques for improving delayed fracture characteristics under the condition where tension is introduced in the tensile direction, for example, Patent Documents 3 to 6 include alloy elements, carbides precipitated during heat treatment, and aspects of prior austenite grains. A technique for improving delayed fracture resistance focusing on the ratio is disclosed. However, a technique for improving delayed fracture resistance under shear stress loading conditions has not been clarified.
特願2005−184699号Japanese Patent Application No. 2005-184699 特願2005−271859号Japanese Patent Application No. 2005-271859 特開平7−70695号公報Japanese Patent Laid-Open No. 7-70695 特開平11−236617号公報Japanese Patent Laid-Open No. 11-236617 特開2001−32044号公報JP 2001-32044 A 特開2002−97551号公報JP 2002-97551 A
本発明は、剪断応力負荷条件における耐遅れ破壊特性に優れた支圧接合部品及びその製造方法並びに支圧接合部品の素材である鋼材を提供するものである。   The present invention provides a bearing member having excellent delayed fracture resistance under shear stress loading conditions, a method for manufacturing the bearing member, and a steel material as a material for the bearing member.
本発明者らは、(i)剪断応力負荷条件における耐遅れ破壊特性の向上には、適正量のSi及びAlを添加してFe炭化物を微細化させることが有効であること、及び、(ii)靭性の確保には、旧オーステナイト粒の微細化、即ち、旧オーステナイトの粒度番号を大きくすることが有効であることを見出した。   In order to improve the delayed fracture resistance under shear stress loading conditions, the present inventors are effective to refine Fe carbide by adding an appropriate amount of Si and Al, and (ii) It has been found that to secure toughness, it is effective to refine the prior austenite grains, that is, to increase the grain number of the prior austenite.
本発明は、このような知見に基づいてなされたものであり、その要旨とするところは、以下のとおりである。   This invention is made | formed based on such knowledge, The place made into the summary is as follows.
(1) 質量%で、C:0.5〜0.8%、Mn:0.1〜2%、Cr:0.1〜1.5%を含有し、Si:0.05〜3%、Al:0.01〜1%の双方を、(Si+1.3×Al):0.08〜3.5%を満たすように含有し、残部がFe及び不可避不純物からなり、金属組織が面積率90%以上の焼戻しマルテンサイトと7%以下の残留オーステナイトからなり、かつ、前記焼戻しマルテンサイトが粒径50nm以下のFe炭化物を有し、旧オーステナイトの結晶粒度がJIS G 0551の粒度番号6以上であり、引張強さが1800MPa以上であることを特徴とする耐遅れ破壊特性に優れた高強度支圧接合部品。 (1) By mass%, C: 0.5 to 0.8%, Mn: 0.1 to 2%, Cr: 0.1 to 1.5%, Si: 0.05 to 3%, Al: 0.01 to 1% of both are contained so as to satisfy (Si + 1.3 × Al): 0.08 to 3.5%, the balance is made of Fe and inevitable impurities, and the metal structure has an area ratio. 90% or more of tempered martensite and 7% or less of retained austenite , the tempered martensite has Fe carbide having a particle size of 50 nm or less, and the crystal grain size of the prior austenite is JIS G 0551 grain size number 6 or more Ah is, the tensile strength of high-strength bearing capacity bonding component which is excellent in delayed fracture resistance, characterized in der Rukoto least 1800 MPa.
) 前記高強度支圧接合部品において、剪断遅れ破壊限界拡散性水素量が0.4ppm以上であることを特徴とする上記(1)に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 2 ) The high strength bearing pressure excellent in delayed fracture resistance according to (1) above, wherein the high strength bearing joint part has a shear delay fracture limit diffusible hydrogen content of 0.4 ppm or more. Joined parts.
) 前記高強度支圧接合部品において、JIS Z 2242のノッチ深さ2mmのUノッチ5mmサブサイズ試験片を用いたシャルピー衝撃試験による吸収エネルギーが10J以上であることを特徴とする上記(1)又は(2)に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 3 ) In the high-strength bearing member, the energy absorbed by a Charpy impact test using a U-notch 5 mm sub-size test piece having a notch depth of 2 mm according to JIS Z 2242 is 10 J or more (1 ) Or high strength bearing joint parts excellent in delayed fracture resistance as described in (2) .
) 前記高強度支圧接合部品において、初期水素含有量が0.4ppm未満であることを特徴とする上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 4 ) In the high-strength bearing member, the initial hydrogen content is less than 0.4 ppm, and the high resistance to delayed fracture resistance according to any one of (1) to ( 3 ) above Strength bearing parts.
) 前記高強度支圧接合部品において、更に、質量%で、P:0.015%以下、S:0.01%以下に制限することを特徴とする上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 5 ) In the high-strength bearing member, the mass content is further limited to P: 0.015% or less and S: 0.01% or less, in the above (1) to ( 4 ) High-strength bearing parts with excellent delayed fracture resistance as described in any of the above.
) 前記高強度支圧接合部品において、更に、質量%で、Mo:0.05〜2%、W:0.05〜1%、B:0.0001〜0.005%の1種又は2種以上を含有することを特徴とする上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 6 ) In the high-strength bearing member, in addition, by mass%, Mo: 0.05-2%, W: 0.05-1%, B: 0.0001-0.005% or The high strength bearing joint having excellent delayed fracture resistance according to any one of the above (1) to ( 5 ), comprising two or more kinds.
) 前記高強度支圧接合部品において、更に、質量%で、V:0.05〜1%、Ti:0.001〜0.05%、Nb:0.001〜0.05%、の1種又は2種以上を含有することを特徴とする上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 ( 7 ) In the high-strength bearing member, the mass% is V: 0.05 to 1%, Ti: 0.001 to 0.05%, Nb: 0.001 to 0.05%. The high strength bearing joint having excellent delayed fracture resistance according to any one of the above (1) to ( 6 ), comprising one or more kinds.
) 上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、質量%で、C:0.5〜0.8%、Mn:0.1〜2%、Cr:0.1〜1.5%を含有し、Si:0.05〜3%、Al:0.01〜1%の双方を、(Si+1.3×Al):0.08〜3.5%を満たすように含有し、残部がFe及び不可避不純物からなる耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材( 8 ) A material for manufacturing a high-strength bearing member having excellent delayed fracture resistance according to any one of (1) to ( 4 ) above by molding and heat treatment , %, C: 0.5-0.8%, Mn: 0.1-2%, Cr: 0.1-1.5%, Si: 0.05-3%, Al: 0. High strength bearing with excellent delayed fracture resistance including both 01 to 1% so as to satisfy (Si + 1.3 × Al): 0.08 to 3.5%, the balance being Fe and inevitable impurities Steel material for joining parts.
) 上記()に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、P:0.015%以下、S:0.01%以下に制限することを特徴とする上記()に記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材( 9 ) A material for producing a high-strength bearing member having excellent delayed fracture resistance as described in ( 5 ) above by molding and heat-treating , and further in mass%, P: The steel material for high-strength bearing members with excellent delayed fracture resistance according to ( 8 ) above, which is limited to 0.015% or less and S: 0.01% or less.
10) 上記()に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、Mo:0.05〜2%、W:0.05〜1%、B:0.0001〜0.005%の1種又は2種以上を含有することを特徴とする上記()又は()に記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材( 10 ) A material for producing a high-strength bearing member having excellent delayed fracture resistance as described in ( 6 ) above by molding and heat-treating , and further, in mass%, Mo: ( 8 ) or ( 9 ) above, characterized by containing one or more of 0.05-2%, W: 0.05-1%, B: 0.0001-0.005% Steel material for high strength bearing parts with excellent delayed fracture resistance as described.
11) 上記()に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、V:0.05〜1%、Ti:0.001〜0.05%、Nb:0.001〜0.05%の1種又は2種以上を含有することを特徴とする上記()〜(10)の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材( 11 ) A material for producing a high-strength bearing member having excellent delayed fracture resistance as described in ( 7 ) above by molding and heat-treating , and further in mass%, V: The above ( 8 ) to ( 10 ) characterized by containing one or more of 0.05 to 1%, Ti: 0.001 to 0.05%, Nb: 0.001 to 0.05%. The steel material for high-strength bearing parts with excellent delayed fracture resistance as described in any of the above.
12) 上記(1)〜()の何れかに記載の耐遅れ破壊特性に優れた高強度支圧接合部品の製造方法であって、上記()〜(11)の何れかに記載の鋼を成形加工し、850〜1000℃に加熱して焼入れ処理を行った後、加熱速度を10℃/s以上とし、焼戻温度T[℃]を200〜450℃の範囲とし、焼戻時間t[s]を1〜7200sの範囲とし、下記式(1)で定義される焼戻しパラメータPを6000〜12000として、焼戻し処理を行うことを特徴とする高強度支圧接合部品の製造方法。
P=(T+273){log(t/3600)+21.3−5.8C
−(Si+1.3Al)} ・・・(1)
ここで、C、Si、Alは成分の含有量[質量%]である。
( 12 ) A method for producing a high-strength bearing member having excellent delayed fracture resistance according to any one of (1) to ( 7 ), which is described in any one of ( 8 ) to ( 11 ) above After the steel was molded and heated to 850 to 1000 ° C. and subjected to quenching treatment, the heating rate was set to 10 ° C./s or more, the tempering temperature T [° C.] was set to the range of 200 to 450 ° C., and tempered. A method for producing a high-strength bearing member, characterized in that the tempering treatment is performed with the time t [s] in the range of 1 to 7200 s and the tempering parameter P defined by the following formula (1) as 6000 to 12000.
P = (T + 273) {log (t / 3600) + 21.3-5.8C
-(Si + 1.3Al)} (1)
Here, C, Si, and Al are component contents [% by mass].
本発明によれば、剪断応力に対する耐遅れ破壊特性に優れた高強度支圧接合部品及びその製造方法並びに高強度支圧接合部品用鋼を提供することができ、産業上の貢献が顕著である。   ADVANTAGE OF THE INVENTION According to this invention, the high strength bearing joint component excellent in the delayed fracture resistance with respect to a shear stress, its manufacturing method, and the steel for high strength bearing joint components can be provided, and industrial contribution is remarkable. .
本発明は、支圧接合、更に必要に応じて、摩擦接合、引張接合の一方又は双方との組み合わせによって鋼構造物を構築する場合に使用される支圧接合部品及びその製造方法、並びに接合部品の素材である鋼材である。   The present invention relates to a support joint, a manufacturing method thereof, and a joining component used when constructing a steel structure by bearing joint, and if necessary, a combination of one or both of friction joining and tensile joining. This is a steel material.
摩擦接合とは、図3(a)に示すように、接合部品、例えば、ボルトで継手部材を締め付け、部材間に生じる摩擦力によって応力を伝達する接合法であり、支圧接合とは、図3(b)に示すように、軸部の剪断、部材の支圧によって応力を伝達する接合法である。   As shown in FIG. 3A, friction bonding is a bonding method in which a joint member, for example, a joint member is tightened with a bolt, and stress is transmitted by friction force generated between the members. As shown in FIG. 3 (b), this is a joining method in which stress is transmitted by shearing the shaft portion and supporting pressure of the member.
摩擦接合と支圧接合は、接合部で伝達する応力がボルト軸と直角方向である点で外観上は似ているが、応力伝達形態が全く異なっており、力学的な原理において、両者は全く別の接合形式である。また、引張接合とは、例えば、図4に示すフランジ付き鋼管の接合部のように、接合部品、例えば、ボルトの軸方向の応力を伝達する接合方法であり、ボルトを締め付けて得られる部材間の圧縮力を利用して応力を伝達するものである。   Friction welding and bearing welding are similar in appearance in that the stress transmitted at the joint is in the direction perpendicular to the bolt axis, but the stress transmission forms are completely different. Another joining type. In addition, tensile joining is a joining method that transmits stress in the axial direction of a joined part, for example, a bolt, such as a joined part of a flanged steel pipe shown in FIG. 4, and between members obtained by tightening the bolt. The stress is transmitted using the compression force.
本発明者らは、支圧接合部の接合部品に負荷される剪断応力下において遅れ破壊が発生しない限界拡散性水素量、即ち、剪断遅れ破壊限界拡散性水素量に及ぼす鋼の組織、析出物の影響を評価した。   The inventors of the present invention have proposed that the critical diffusible hydrogen amount at which delayed fracture does not occur under the shear stress applied to the joint component of the bearing joint, that is, the steel structure and precipitates that affect the shear delayed fracture critical diffusible hydrogen amount. The impact of.
まず、焼入れ処理及び焼戻し処理によって製造した種々の強度を有する鋼材から採取した試料に、電解水素チャージによって水素を吸蔵させ、カドミウムめっきを施すことによって、試験中の水素の放出を防止した。カドミウムめっき後に、図1に示す試験装置により、剪断遅れ破壊試験を行い、剪断引張強さの90%の剪断応力を負荷し、図2に示すように、遅れ破壊が発生しなくなる剪断遅れ破壊限界拡散性水素量を求めた。   First, hydrogen sampled from steel materials having various strengths produced by quenching and tempering were occluded by electrolytic hydrogen charging and cadmium plating was performed to prevent hydrogen release during the test. After the cadmium plating, a shear delayed fracture test is performed using the test apparatus shown in FIG. 1, and a shear stress of 90% of the shear tensile strength is applied. As shown in FIG. The amount of diffusible hydrogen was determined.
図1に示す冶具1、2を、試験片挿入穴4、5が一致するようにセットし、試験片挿入穴4、5に試験片3を貫通させる。その後、引張試験機によって冶具1、2に一定の引張応力を負荷し、試験片3に一定の剪断応力を負荷して破断時間を測定した。なお、剪断引張強さは、図1に示す冶具を用いて求めた、剪断応力の最大値である。   The jigs 1 and 2 shown in FIG. 1 are set so that the test piece insertion holes 4 and 5 coincide with each other, and the test piece 3 is passed through the test piece insertion holes 4 and 5. Thereafter, a constant tensile stress was applied to the jigs 1 and 2 with a tensile tester, and a constant shear stress was applied to the test piece 3 to measure the rupture time. The shear tensile strength is the maximum value of the shear stress obtained using the jig shown in FIG.
また、試験後、試験片からめっきを除去した後にガスクロマトグラフを用いた昇温分析にて各試験片の拡散性水素量を求めた。なお、めっき除去後から拡散性水素量の測定までは、ドライアイスによって試験片を冷却し、水素の放散を防止した。本発明において、拡散性水素量は、100℃/hrで昇温したときに、室温から300℃までの間に放出する水素量とした。   In addition, after the test, after removing the plating from the test piece, the amount of diffusible hydrogen in each test piece was determined by temperature rising analysis using a gas chromatograph. In addition, the test piece was cooled with dry ice until the measurement of the amount of diffusible hydrogen after removing the plating to prevent the hydrogen from being diffused. In the present invention, the amount of diffusible hydrogen is the amount of hydrogen released between room temperature and 300 ° C. when the temperature is raised at 100 ° C./hr.
図2に、拡散性水素量[ppm]と遅れ破壊に至るまでの破断時間[分]の関係について解析した一例を示す。図中の右向きの矢印は、破断していないことを意味する。試料中に含まれる拡散性水素量が少なくなるほど遅れ破壊に至るまでの時間が長くなり、拡散性水素量がある値以下では遅れ破壊が発生しなくなる。   FIG. 2 shows an example in which the relationship between the amount of diffusible hydrogen [ppm] and the fracture time [min] until delayed fracture is analyzed. A right-pointing arrow in the figure means that it is not broken. The smaller the amount of diffusible hydrogen contained in the sample, the longer the time until delayed fracture occurs.
6000分で遅れ破壊しない水素量の上限を、剪断遅れ破壊限界拡散性水素量HCSと定義し、この値によって、遅れ破壊特性を評価した。その結果、(Si+1.3×Al)を0.08〜3.5%とすることにより、焼戻し時におけるFe炭化物が微細に分散し、剪断応力下における耐遅れ破壊特性が向上することがわかった。 The upper limit of the amount of hydrogen that does not cause delayed fracture at 6000 minutes was defined as the shear delayed fracture limit diffusible hydrogen amount HCS, and the delayed fracture characteristics were evaluated based on this value. As a result, it was found that by setting (Si + 1.3 × Al) to 0.08 to 3.5%, Fe carbides are finely dispersed during tempering, and delayed fracture resistance under shear stress is improved. .
本発明において、Fe炭化物とは、セメンタイトとイプシロン炭化物の総称である。   In the present invention, Fe carbide is a general term for cementite and epsilon carbide.
また、剪断応力下においては、曲げ応力に起因するき裂も発生する。したがって、支圧接合部材には遅れ破壊特性と共に曲げ応力下でのき裂の発生し難くさ、即ち、靭性も必要であり、旧オーステナイト粒の微細化が有効であるという知見を得た。   In addition, cracks due to bending stress also occur under shear stress. Therefore, it has been found that the bearing member is required to have a delayed fracture characteristic and hardly cause cracking under bending stress, that is, toughness, and that refinement of prior austenite grains is effective.
まず、本発明の対象とする鋼の成分組成の限定理由について述べる。   First, the reasons for limiting the component composition of steel as the object of the present invention will be described.
Cは、鋼材の強度を確保する上で必須の元素であるが、0.5%未満では、所定の焼戻し温度範囲では所要の強度が得られず、一方、0.8%を超えると、靭性を劣化させ、残留オーステナイトが増加するため、0.5〜0.8%の範囲に制限した。   C is an essential element for securing the strength of the steel material, but if it is less than 0.5%, the required strength cannot be obtained within a predetermined tempering temperature range, while if it exceeds 0.8%, toughness is obtained. And the retained austenite increases, so the content was limited to 0.5 to 0.8%.
Mnは、焼入れ性を向上させるのに有効な成分であるとともに、脱酸や脱硫についても効果がある。0.1%未満では、上記の効果が得られず、一方、2%を超えると、偏析を助長するため、0.1〜2%の範囲に制限した。   Mn is an effective component for improving hardenability, and is also effective for deoxidation and desulfurization. If it is less than 0.1%, the above effect cannot be obtained. On the other hand, if it exceeds 2%, segregation is promoted, so the content is limited to a range of 0.1 to 2%.
Crは、焼入れ性及び焼戻し軟化抵抗を高める元素であるが、0.1%未満では、その効果が得られず、一方、1.5%超を含有すると、未溶解炭化物が増加する傾向にあるので、0.1〜1.5%の範囲に限定した。   Cr is an element that enhances hardenability and temper softening resistance, but if it is less than 0.1%, the effect cannot be obtained, while if it contains more than 1.5%, undissolved carbide tends to increase. Therefore, it was limited to the range of 0.1 to 1.5%.
Siは、焼戻し軟化抵抗を高め、セメンタイトの粗大化を防止するが、0.05%未満では、その効果が得られず、一方、3%を超えて添加すると、靭性が劣化するので、0.05〜3%の範囲に制限した。更に、優れた遅れ破壊特性を得る観点から、好ましい下限は、0.1%である。   Si increases temper softening resistance and prevents coarsening of cementite, but if less than 0.05%, the effect cannot be obtained, while if added over 3%, the toughness deteriorates. Limited to a range of 05-3%. Furthermore, from the viewpoint of obtaining excellent delayed fracture characteristics, the preferred lower limit is 0.1%.
Alは、脱酸及び熱処理時においてAlNを形成することにより、オーステナイト粒の粗大化を防止する効果がある。また、微細なAlNは、微細なセメンタイトの粒内析出の核となるため、セメンタイトの微細分散に対して有効である。Al量が0.01%未満では、これらの効果が不十分である。一方、1%超のAlを含有すると、Al23介在物による靭性の劣化が生じるため、0.01〜1%の範囲に限定した。特に、Al23介在物を減らしたいときは、上限を0.5%以下とすることが好ましい。 Al has the effect of preventing austenite grains from coarsening by forming AlN during deoxidation and heat treatment. Further, fine AlN is effective for fine dispersion of cementite because it becomes a nucleus of intra-particle precipitation of fine cementite. If the Al content is less than 0.01%, these effects are insufficient. On the other hand, if containing more than 1% Al, deterioration of toughness due to Al 2 O 3 inclusions occurs, so it was limited to the range of 0.01 to 1%. In particular, when it is desired to reduce Al 2 O 3 inclusions, the upper limit is preferably 0.5% or less.
本発明では、更に、Siの含有量とAlの含有量を特定の関係を満足することが必要であり、(Si+1.3×Al)を0.08〜3.5%の範囲に限定している。下限を0.08%とするのは、焼戻し時におけるFe炭化物の微細分散を達成するためであり、上限を3.5%とするのは、靭性確保のためである。更に、より微細なFe炭化物を得る観点から、好適範囲は0.1〜3%である。   In the present invention, it is further necessary to satisfy the specific relationship between the Si content and the Al content, and (Si + 1.3 × Al) is limited to a range of 0.08 to 3.5%. Yes. The lower limit is set to 0.08% in order to achieve fine dispersion of Fe carbides during tempering, and the upper limit is set to 3.5% to ensure toughness. Furthermore, from the viewpoint of obtaining finer Fe carbide, the preferred range is 0.1 to 3%.
P及びSは不純物であり、含有量を制限することが好ましい。   P and S are impurities, and the content is preferably limited.
Pは、旧オーステナイト粒界に偏析して粒界を脆化させ、耐遅れ破壊特性を低下させる効果があるので、0.015%以下に抑えることにより、より優れた耐遅れ破壊特性を得ることができる。   P segregates at the prior austenite grain boundaries, embrittles the grain boundaries, and lowers the delayed fracture resistance. Therefore, by suppressing the content to 0.015% or less, better delayed fracture resistance can be obtained. Can do.
Sも、Pと同様の効果があるため、0.01%以下に抑えることにより、より優れた耐遅れ破壊特性を得ることができる。   Since S has the same effect as P, by suppressing it to 0.01% or less, more excellent delayed fracture resistance can be obtained.
更に、Mo、W、Bの1種又は2種以上を含有してもよい。   Furthermore, you may contain 1 type, or 2 or more types of Mo, W, and B.
Moは、焼入れ性向上に有効な元素であり、かつ、焼戻し時に微細な炭化物として析出することによって鋼に強度を与えるため、0.05%以上添加することが好ましい。一方、2%を超えて添加しても、その効果は飽和するため、0.05〜2%の範囲とすることが好ましい。   Mo is an element effective for improving the hardenability and is added as 0.05% or more in order to give strength to the steel by being precipitated as fine carbides during tempering. On the other hand, even if added in excess of 2%, the effect is saturated.
Wは、焼入れ性向上に有効な元素であり、かつ、焼戻し時に微細な炭化物として析出することによって鋼に強度を与えるため、0.05%以上添加することが好ましい。一方、1%を超えて添加しても、その効果は飽和するため、0.05%〜1%の範囲とすることが好ましい。   W is an element effective for improving hardenability, and is added as 0.05% or more in order to give strength to the steel by precipitating as fine carbides during tempering. On the other hand, even if added in excess of 1%, the effect is saturated, so it is preferable that the content be in the range of 0.05% to 1%.
Bは、微量の添加で焼入れ性向上に効果があり、効果を得るためには0.0001%以上の添加が好ましい。一方、0.005%を超えて添加しても、その効果は飽和するため、0.0001〜0.005%の範囲とすることが好ましい。   B is effective for improving the hardenability when added in a small amount, and 0.0001% or more is preferable for obtaining the effect. On the other hand, even if added over 0.005%, the effect is saturated, so it is preferable that the content be in the range of 0.0001 to 0.005%.
更に、V、Ti、Nbの1種又は2種以上を含有してもよい。   Furthermore, you may contain 1 type, or 2 or more types of V, Ti, and Nb.
Vは、旧オーステナイト粒を微細にし、かつ焼戻し時に微細な炭化物として析出することによって鋼に強度を与えるため、0.05%以上添加することが好ましい。一方、1%を超えて添加しても、その効果は飽和するため、0.05〜1%の範囲とすることが好ましい。   V imparts strength to the steel by making the prior austenite grains fine and precipitating as fine carbides during tempering, so 0.05% or more is preferably added. On the other hand, even if added in excess of 1%, the effect is saturated.
Tiも、旧オーステナイト粒の微細化に有効な元素であるため、0.001%以上添加することが好ましい。一方、0.05%超えて添加しても、その効果は飽和するため、0.001〜0.05%の範囲とすることが好ましい。   Since Ti is also an element effective for refinement of prior austenite grains, 0.001% or more is preferably added. On the other hand, even if added over 0.05%, the effect is saturated, so it is preferable to set the content within the range of 0.001 to 0.05%.
Nbは、Tiと同様の効果があるため、0.001%以上添加することが好ましい。一方、0.05%超えて添加しても、その効果は飽和するため、0.001〜0.05%の範囲とすることが好ましい。   Nb has the same effect as Ti, so 0.001% or more is preferably added. On the other hand, even if added over 0.05%, the effect is saturated, so it is preferable to set the content within the range of 0.001 to 0.05%.
本発明において、不純物であるN及びOの含有量は特に制限しないが、N及びOは、それぞれ0.01%超を含有すると、窒化物等及び酸化物等の介在物が生成しやすくなるため、それぞれ、0.01%以下とすることが好ましい。   In the present invention, the contents of N and O which are impurities are not particularly limited, but if N and O each contain more than 0.01%, inclusions such as nitrides and oxides are likely to be generated. , Each is preferably 0.01% or less.
次に、本発明の対象とする接合部品の組織について述べる。   Next, the structure of the joined part which is the subject of the present invention will be described.
本発明における接合部品の組織として、十分な強度が有し、かつ、靭性及び耐遅れ破壊特性を備えるためには、面積率で90%以上を焼戻しマルテンサイトとすることが必要である。焼戻しマルテンサイトの残部は、残留オーステナイト、ベイナイト、フェライト、パーライトの1種若しくは2種以上又は全部からなる。   In order to have sufficient strength and toughness and delayed fracture resistance as the structure of the joined part in the present invention, it is necessary that 90% or more of the area ratio is tempered martensite. The balance of the tempered martensite is composed of one or more or all of retained austenite, bainite, ferrite and pearlite.
焼戻しマルテンサイトの面積率は、焼入れ後、焼戻す前の組織を光学顕微鏡により観察し、撮影した組織写真から求める。この理由は、焼戻し後の組織では、焼戻しマルテンサイトと焼戻しベイナイトの判別が難しいためである。また、焼入れ後に生成したマルテンサイトは、焼戻しによってそのまま焼戻しマルテンサイトとなるため、焼戻しマルテンサイトの量は、焼戻し前のマルテンサイトの量と同等である。   The area ratio of tempered martensite is determined from a photograph of the structure taken by observing the structure before quenching and before tempering with an optical microscope. This is because it is difficult to distinguish between tempered martensite and tempered bainite in the structure after tempering. Moreover, since the martensite produced | generated after hardening becomes tempered martensite as it is by tempering, the quantity of tempered martensite is equivalent to the quantity of martensite before tempering.
焼戻しマルテンサイトの面積率は、焼入れままの接合部品から組織観察用の試料を採取し、鏡面研磨後、ナイタールでエッチングし、光学顕微鏡によって任意の10視野を500倍で観察して写真を撮影し、その視野内を画像解析し、残留オーステナイト、ベイナイト、フェライト、パーライトを除いた部分の面積率を焼戻しマルテンサイトの量として求める。   The area ratio of tempered martensite was obtained by taking a sample for observing the structure from as-quenched bonded parts, mirror polishing, etching with nital, and observing any 10 fields of view with an optical microscope at 500 times and taking a photograph. Then, the inside of the visual field is subjected to image analysis, and the area ratio of the portion excluding residual austenite, bainite, ferrite and pearlite is obtained as the amount of tempered martensite.
残留オーステナイト量は、光学顕微鏡組織写真から求めることもできるが、少量であるため、X線回折法によって測定することが好ましい。   The amount of retained austenite can be determined from an optical micrograph, but since it is a small amount, it is preferably measured by an X-ray diffraction method.
残留オーステナイトは、耐遅れ破壊特性を低下させる加工誘起マルテンサイト生成の原因となるため、7%以下とすることが好ましい。   Residual austenite causes generation of work-induced martensite that degrades delayed fracture resistance, and is therefore preferably 7% or less.
更に、曲げ応力に対する靭性向上の観点から旧オーステナイト粒の微細化が必要である。したがって、本発明では、旧オーステナイトの結晶粒度を、JIS G 0551の粒度番号6以上に限定した。   Furthermore, refinement of prior austenite grains is necessary from the viewpoint of improving toughness against bending stress. Therefore, in the present invention, the crystal grain size of prior austenite is limited to grain size number 6 or more of JIS G 0551.
また、高強度接合部品において、十分な剪断応力に対する耐遅れ破壊特性を確保するため、Fe炭化物の粒径が50nm以下であることが好ましい。Fe炭化物の粒径は、走査型電子顕微鏡(canning lectron icroscope、SEMという。)によって任意の20視野を10000倍で観察して写真を撮影し、その視野内における最大の粒径とする。 Moreover, in a high-strength joint component, in order to ensure the delayed fracture resistance with respect to sufficient shear stress, it is preferable that the particle size of Fe carbide is 50 nm or less. The particle size of the Fe carbides, scanning electron microscope and photographed and observed by 10000 times any 20 fields by (S canning E lectron M icroscope, called. SEM), the maximum particle size within its field of view .
なお、SEM観察の際には、試料のエッチングを非水溶媒系電解液による定電位電解腐食法によって行う。Fe炭化物の平均粒径は小さいほど好ましいが、25nmよりも微細になるとSEMによる判別は困難である。   In the SEM observation, the sample is etched by a constant potential electrolytic corrosion method using a non-aqueous solvent electrolyte. The average particle size of Fe carbide is preferably as small as possible, but when it becomes finer than 25 nm, discrimination by SEM is difficult.
次に、本発明の高強度支圧接合部品の特性について述べる。   Next, the characteristics of the high strength bearing joint part of the present invention will be described.
剪断遅れ破壊限界拡散性水素量が0.4ppm未満では、腐食などが原因で鋼材中に侵入する水素によって、遅れ破壊が発生する可能性が高いため、下限を0.4ppmとすることが好ましい。鋼の成分、組織を上記の範囲とすれば、剪断遅れ破壊限界拡散性水素量は0.4ppm以上となる。   If the amount of shear delay fracture limit diffusible hydrogen is less than 0.4 ppm, there is a high possibility that delayed fracture will occur due to hydrogen entering the steel material due to corrosion or the like, so the lower limit is preferably set to 0.4 ppm. If the composition and structure of the steel are within the above ranges, the shear lag fracture limit diffusible hydrogen content is 0.4 ppm or more.
引張強度は1800MPa以上であることが好ましい。これは、引張強度が1800MPa以上の接合部品を使用すると、支圧接合する場合に必要なボルト本数を著しく減少させることができるという、本発明者らの試算結果に基づくものである。なお、現状の技術では、引張強度を2600MPa超とすることは困難である。   The tensile strength is preferably 1800 MPa or more. This is based on the results of calculations by the present inventors that the number of bolts necessary for bearing support can be significantly reduced when a joining part having a tensile strength of 1800 MPa or more is used. In the current technology, it is difficult to make the tensile strength exceed 2600 MPa.
JIS Z 2242のノッチ深さ2mmのUノッチ5mmサブサイズ試験片を用いたシャルピー衝撃試験による吸収エネルギーが10J未満では、侵入した水素量が増加すると、曲げ応力によるき裂が発生する可能性が高いため、下限を10Jとすることが好ましい。本発明の成分、組織を満足する鋼材であれば、吸収エネルギーが10J以上となる。   If the absorbed energy by the Charpy impact test using a JIS Z 2242 notch depth 2 mm U-notch 5 mm sub-size test piece is less than 10 J, there is a high possibility that a crack due to bending stress will occur if the amount of hydrogen that has penetrated increases. Therefore, the lower limit is preferably 10J. If the steel material satisfies the components and structures of the present invention, the absorbed energy is 10 J or more.
使用前の高強度支圧接合部品の初期水素含有量が剪断遅れ破壊限界拡散性水素量を超えると、使用中に剪断応力による遅れ破壊を生じ易くなる。そのため、高強度支圧接合部品の初期水素含有量は0.4ppm未満であることが好ましい。本発明において、初期水素含有量は、製造後、使用前の高強度支圧接合部品から試料を採取し、100℃/hrの昇温分析で室温から300℃の間に放出した水素量とする。   If the initial hydrogen content of the high-strength bearing member before use exceeds the shear lag fracture limit diffusible hydrogen content, delayed fracture due to shear stress is likely to occur during use. For this reason, the initial hydrogen content of the high-strength bearing member is preferably less than 0.4 ppm. In the present invention, the initial hydrogen content is the amount of hydrogen released between room temperature and 300 ° C. in a temperature rising analysis at 100 ° C./hr after taking a sample from a high strength bearing member before use after production. .
本発明の高強度支圧接合部品の素材である鋼材は、質量%で、C:0.5〜0.8%、Mn:0.1〜2%、Cr:0.1〜1.5%を含有し、Si:0.05〜3%、Al:0.01〜1%の双方を、(Si+1.3×Al):0.08〜3.5%を満たすように含有し、残部がFe及び不可避不純物からなる鋼である。   The steel material which is the material of the high strength bearing joint part of the present invention is in mass%, C: 0.5 to 0.8%, Mn: 0.1 to 2%, Cr: 0.1 to 1.5% Si: 0.05 to 3%, Al: 0.01 to 1% are included so as to satisfy (Si + 1.3 × Al): 0.08 to 3.5%, and the balance is Steel made of Fe and inevitable impurities.
鋼の成分組成は、P:0.015%以下、S:0.01%以下に制限することが好ましい。また、Mo:0.05〜2%、W:0.05〜1%、B:0.0001〜0.005%の1種又は2種以上を含有しても良く、V:0.05〜1%、Ti:0.001〜0.05%、Nb:0.001〜0.05%の1種又は2種以上を含有してもよい。鋼材の成分組成を限定する理由は、上述の高強度支圧接合部品の成分を限定した理由と同様である。   The component composition of steel is preferably limited to P: 0.015% or less and S: 0.01% or less. Moreover, you may contain 1 type (s) or 2 or more types, Mo: 0.05-2%, W: 0.05-1%, B: 0.0001-0.005%, V: 0.05- You may contain 1 type, Ti: 0.001-0.05%, Nb: 0.001-0.05% 1 type (s) or 2 or more types. The reason for limiting the component composition of the steel material is the same as the reason for limiting the components of the high-strength bearing member.
これらの成分からなる鋼を、溶製後、鋳造又は鍛造により鋳片又は鋼片とし、再加熱して、熱間圧延する。支圧接合部品がボルト、ピン等である場合は、鋼材も線材であることが好ましいが、支圧接合部品の形状によっては熱延板でもよい。加熱温度は、100〜1250℃とし、線材圧延の減面率、板圧延の圧下率は、50%以上、好ましくは80%以上、更に好ましくは90%とすれば良い。   After melting, the steel composed of these components is cast or forged by casting or forging, reheated and hot-rolled. When the bearing member is a bolt, a pin or the like, the steel material is also preferably a wire, but depending on the shape of the bearing member, it may be a hot-rolled sheet. The heating temperature may be 100 to 1250 ° C., and the area reduction rate of the wire rod rolling and the rolling reduction of the plate rolling may be 50% or more, preferably 80% or more, and more preferably 90%.
本発明の支圧接合部品の製造方法について説明する。   The manufacturing method of the bearing support joining component of this invention is demonstrated.
鋼材を、必要に応じて焼鈍し、熱間鍛造、冷間鍛造、引抜加工、転造、切削加工を適宜組み合わせて所定の形状、即ち軸力導入をしない支圧形高力ボルト、高力リベット、高力ピン、孔を明けない形式のセルフドリルビスや打込み鋲等の剪断抵抗体に成形加工した後、焼入れ処理、浸炭焼入れ処理又は高周波焼入れ処理を行い、焼戻し処理を施す。本発明においては、焼入れ処理及び焼戻し処理が重要である。   Steel is annealed as necessary, and hot forging, cold forging, drawing, rolling, and cutting are combined as appropriate to achieve a specific shape, that is, a bearing-type high-strength bolt and high-strength rivet that do not introduce axial force. After forming into a high resistance pin, a shearing resistance body such as a self-drilling screw or a driving rod that does not open a hole, a quenching process, a carburizing quenching process, or an induction quenching process is performed, and a tempering process is performed. In the present invention, quenching and tempering are important.
焼入れ処理における鋼の加熱温度は、焼入れ処理前の組織をオーステナイトとするため、850℃以上とすることが必要である。一方、加熱温度が1000℃を超えるとオーステナイト粒が粗大化し、旧オーステナイトの結晶粒度が6未満となる。この温度範囲に加熱した鋼を焼入れ処理すると、面積率が90%以上のマルテンサイト組織を得ることができる。焼入れ処理は、水焼入れ、油焼入れでよい。   The heating temperature of the steel in the quenching process needs to be 850 ° C. or higher in order to make the structure before the quenching process austenite. On the other hand, if the heating temperature exceeds 1000 ° C., the austenite grains become coarse, and the crystal grain size of the prior austenite becomes less than 6. When the steel heated to this temperature range is quenched, a martensite structure with an area ratio of 90% or more can be obtained. The quenching process may be water quenching or oil quenching.
その後の焼戻し処理が、本発明において最も重要であり、この条件を適正な範囲とすることで、微細なFe炭化物を析出させ、鋼材に靭性や耐遅れ破壊特性に優れた特徴を付与することができる。   Subsequent tempering is the most important in the present invention, and by setting this condition in an appropriate range, fine Fe carbides can be precipitated, and the steel material can be imparted with characteristics excellent in toughness and delayed fracture resistance. it can.
本発明の焼戻し処理は、高温かつ短時間とするために、高周波誘導加熱に代表される急速加熱機を用いる。この場合、焼戻し処理の加熱速度が10℃/s未満では、正確に焼戻しを制御できないため、10℃/s以上とする。加熱速度の上限は規定しないが、300℃/s超とすることは、現状の技術では困難である。   The tempering treatment of the present invention uses a rapid heater represented by high-frequency induction heating in order to achieve a high temperature and a short time. In this case, if the heating rate of the tempering treatment is less than 10 ° C./s, the tempering cannot be accurately controlled, so that it is 10 ° C./s or more. Although the upper limit of the heating rate is not specified, it is difficult to make it higher than 300 ° C./s with the current technology.
焼戻し温度が200℃未満、焼戻し時間が1s未満では、靭性が不十分になる。また、焼戻し温度が450℃超、焼戻し時間が7200s超になると強度が低下し、また、Fe炭化物が粗大になる。したがって、焼戻し温度は200〜450℃の範囲内、焼戻し時間は1〜7200sの範囲内とすることが必要である。   If the tempering temperature is less than 200 ° C. and the tempering time is less than 1 s, the toughness becomes insufficient. Further, when the tempering temperature exceeds 450 ° C. and the tempering time exceeds 7200 s, the strength decreases and the Fe carbide becomes coarse. Therefore, it is necessary that the tempering temperature is in the range of 200 to 450 ° C. and the tempering time is in the range of 1 to 7200 s.
更に、焼戻温度T[℃]、焼戻時間t[s]、C、Si、Al(各成分の含有量[質量%])により、下記式(1)で定義される焼戻しパラメータPを6000〜12000とすることが必要である。   Furthermore, the tempering parameter P defined by the following formula (1) is set to 6000 by the tempering temperature T [° C.], the tempering time t [s], C, Si, and Al (content of each component [% by mass]). ˜12000 is required.
焼戻しパラメータPが12000を超えると、必要とする強度が得らず、6000未満であると焼戻しが不十分であり、Fe炭化物が十分に析出しないため、剪断応力負荷条件における耐遅れ破壊特性が低下する。なお、焼戻しパラメータPが6000より小さいと、支圧接合部品の初期水素含有量が0.4ppm以上になることがある。   When the tempering parameter P exceeds 12000, the required strength cannot be obtained. When the tempering parameter P is less than 6000, tempering is insufficient, and Fe carbide is not sufficiently precipitated. To do. If the tempering parameter P is smaller than 6000, the initial hydrogen content of the bearing joint may be 0.4 ppm or more.
P=(T+273){log(t/3600)+21.3−5.8C
−(Si+1.3Al)} ・・・(1)
P = (T + 273) {log (t / 3600) + 21.3-5.8C
-(Si + 1.3Al)} (1)
表1に示す化学成分を有する鋼を溶製し、鋳造し、1000〜1250℃に再加熱して、99%の減面率で直径16mmの線材形状に熱間圧延した。表1において、空欄は各成分の含有量が検出限界未満であったことを意味し、下線は本発明の範囲外であるものに付した。ボルト形状に加工後、表2に示す加熱温度から焼入れし、一部のボルトからは組織観察用の試料を採取し、その他のボルトには、表2示す条件(温度、時間)で焼戻しを行った。   Steel having chemical components shown in Table 1 was melted, cast, reheated to 1000 to 1250 ° C., and hot-rolled into a wire rod shape having a diameter of 16 mm with a reduction in area of 99%. In Table 1, a blank means that the content of each component was less than the detection limit, and an underline is attached to what is outside the scope of the present invention. After processing into bolt shape, quenching from the heating temperature shown in Table 2, taking samples for structure observation from some bolts, and tempering other bolts under the conditions (temperature, time) shown in Table 2 It was.
ボルトの軸部から径が6mmのJIS Z 2201の2号の丸棒引張試験片を採取し、引張試験をJIS Z 2241に準拠して行った。シャルピー衝撃試験は、JIS Z 2242のノッチ深さ2mmであるUノッチ5mmサブサイズ試験片を用いて室温で行った。   A No. 2 round bar tensile test piece of JIS Z 2201 having a diameter of 6 mm was taken from the shaft portion of the bolt, and a tensile test was performed in accordance with JIS Z 2241. The Charpy impact test was performed at room temperature using a U-notch 5 mm sub-size test piece having a notch depth of 2 mm according to JIS Z 2242.
剪断遅れ破壊限界拡散性水素量HCSは、図1に示す試験機によって、水素チャージ及びカドミウムめっきを施した5φ×6mmの試験片を用いて測定した。また、一部の試験片には水素チャージを行わずに、初期水素含有量を測定した。 The shear delay fracture limit diffusible hydrogen amount H CS was measured by using a test piece of 5φ × 6 mm subjected to hydrogen charging and cadmium plating by the test machine shown in FIG. Moreover, initial hydrogen content was measured without performing hydrogen charge to some test pieces.
焼戻しマルテンサイト量は焼入れ後、焼戻し前のボルトから試料を採取し、鏡面研磨、エッチングを行い、光学顕微鏡によって任意の10視野を500倍で観察して写真を撮影し、その組織写真から求めた。また、JIS G 0551に準拠して、旧オーステナイトの粒度番号を測定した。   The amount of tempered martensite was obtained from a microstructure photograph of a sample taken from a bolt before quenching, sampled from a bolt before tempering, mirror-polished and etched, observed with an optical microscope at an arbitrary 10 field of view at 500 times. . Moreover, based on JIS G 0551, the particle size number of the prior austenite was measured.
Fe炭化物の粒径は、試料を非水溶媒系電解液による定電位電解腐食法によってエッチングし、SEMを用いて任意の20視野について10000倍の写真を撮影し、視野内における最大サイズのものを採用した。残留オーステナイト量はX線回折による定量分析より求めた。   The particle size of Fe carbide was determined by etching the sample by a constant-potential electrolytic corrosion method using a non-aqueous solvent electrolyte, taking 10,000 times a photo of any 20 fields of view using the SEM, and measuring the maximum size within the field of view. Adopted. The amount of retained austenite was determined by quantitative analysis by X-ray diffraction.
No.1〜14は、本発明例であり、表2に示すとおり、剪断応力の限界拡散性水素量HCSは0.4ppm以上であり、引張強さが1800MPa以上と高強度であり、剪断応力に対する耐遅れ破壊特性も優れている。 No. 1-14 are examples of the present invention, as shown in Table 2, the critical diffusible hydrogen amount H CS shear stress is at least 0.4 ppm, the tensile strength is high strength and more 1800 MPa, to shear stress Excellent delayed fracture resistance.
一方、No.15は、C量が本発明の下限よりも少なく、引張強さが1800MPaを下回っている。No.21は、Mnが、No.23は、Crが、それぞれ本発明の下限よりも少なく、焼入れが不十分であり、又は、焼戻し軟化抵抗が不足しているため、引張強さが1800MPaに達していない。   On the other hand, no. No. 15, the amount of C is less than the lower limit of the present invention, and the tensile strength is below 1800 MPa. No. No. 21 is Mn. In No. 23, Cr is less than the lower limit of the present invention, respectively, and quenching is insufficient or resistance to temper softening is insufficient, so that the tensile strength does not reach 1800 MPa.
また、No.21は、Alの添加量も本発明の下限未満であり、旧オーステナイトの結晶粒度が小さく、Fe炭化物が粗大化しているため、引張強さが低いにもかかわらず、剪断応力に対する耐遅れ破壊特性が劣っている。   No. No. 21 is an additive amount of Al less than the lower limit of the present invention, the grain size of the prior austenite is small, and the Fe carbides are coarsened, so that the delayed fracture resistance to shear stress despite low tensile strength. Is inferior.
また、No.16〜20は、HCS0.4ppm以上を達成できず、剪断応力に対する耐遅れ破壊特性が不十分であった例である。比較例のNo.16は、C量が、No.19は、Al量が、No.20は、Siが、それぞれ、本発明の上限を超えており、吸収エネルギーも低いことから、曲げ応力によるき裂の発生が原因でHCSが低下している。 No. Nos. 16 to 20 are examples in which H CS 0.4 ppm or more could not be achieved and delayed fracture resistance against shear stress was insufficient. Comparative Example No. No. 16 has a C amount of No. 16. No. 19 has an Al content of No. 19. 20, Si, respectively, exceeds the upper limit of the present invention, since the absorption energy is low, H CS occurs because of crack due to bending stress is reduced.
No.17は、Si量及びSi+1.3Alが本発明の下限よりも低いために、Fe炭化物の粒径が50nmを超え、HCSが低下している。 No. 17, Si content and Si + 1.3Al is to lower than the lower limit of the present invention, the particle size of Fe carbides exceeds the 50 nm, H CS is reduced.
No.22は、Mnが、No.24は、Crが、それぞれ、本発明の上限を超えており、偏析や未溶解炭化物の存在によって吸収エネルギーが低下し、曲げ応力によるき裂の発生により、HCSが低下したと考えられる。 No. No. 22 is Mn. 24, Cr, respectively, exceeds the upper limit of the present invention, the absorption energy decreases by the presence of segregation and undissolved carbides, due to the occurrence of crack due to bending stress is considered that H CS is lowered.
また、No.18は、Si+1.3Alが本発明の範囲よりも高く、更に、P値も6000より低くなり、HCSは著しく低下し、初期水素含有量も0.4ppm以上である。 No. 18, Si + 1.3Al is higher than the range of the present invention, further, P value becomes lower than 6000, H CS is significantly reduced, the initial hydrogen content be 0.4ppm or more.
No.26は、P値が6000より低い例であり、HCSが著しく低下し、初期水素含有量も0.4ppm以上である。一方、P値が12000より高いNo.25は、引張強さが低下している。 No. No. 26 is an example in which the P value is lower than 6000, the HCS is remarkably lowered, and the initial hydrogen content is 0.4 ppm or more. On the other hand, the P value is higher than 12000. No. 25 has a reduced tensile strength.
剪断遅れ破壊試験装置を模式的に示す図である。It is a figure which shows typically a shear delay fracture test apparatus. 拡散性水素量[ppm]と遅れ破壊に至るまでの破断時間[分]の関係の一例を示す図である。It is a figure which shows an example of the relationship between the amount of diffusible hydrogen [ppm] and the fracture | rupture time [min] until it leads to a delayed fracture. 接合態様を示す図である(a)は、摩擦接合の態様を示し、(b)は、支圧接合の態様を示す図である。(A) which shows a joining aspect shows the aspect of friction joining, (b) is a figure which shows the aspect of bearing support joining. 引張接合の態様を示す図である。It is a figure which shows the aspect of tension joining.
符号の説明Explanation of symbols
1 冶具
2 冶具
3 試験片
4 冶具1試験片挿入穴
5 冶具2試験片挿入穴
DESCRIPTION OF SYMBOLS 1 Jig 2 Jig 3 Test piece 4 Jig 1 Test piece insertion hole 5 Jig 2 Test piece insertion hole

Claims (12)

  1. 質量%で、
    C :0.5〜0.8%、
    Mn:0.1〜2%、
    Cr:0.1〜1.5%
    を含有し、
    Si:0.05〜3%、
    Al:0.01〜1%
    の双方を、
    (Si+1.3×Al):0.08〜3.5%
    を満たすように含有し、残部がFe及び不可避不純物からなり、金属組織が面積率90%以上の焼戻しマルテンサイトと7%以下の残留オーステナイトからなり、かつ、前記焼戻しマルテンサイトが粒径50nm以下のFe炭化物を有し、旧オーステナイトの結晶粒度がJIS G 0551の粒度番号6以上であり、引張強さが1800MPa以上であることを特徴とする耐遅れ破壊特性に優れた高強度支圧接合部品。
    % By mass
    C: 0.5-0.8%
    Mn: 0.1 to 2%,
    Cr: 0.1 to 1.5%
    Containing
    Si: 0.05-3%,
    Al: 0.01 to 1%
    Both
    (Si + 1.3 × Al): 0.08 to 3.5%
    The balance is composed of Fe and inevitable impurities, the metal structure is composed of tempered martensite with an area ratio of 90% or more and residual austenite of 7% or less , and the tempered martensite has a particle size of 50 nm or less. has a Fe carbide, high-strength Bearing grain size of prior austenite is Ri der size number 6 or more JIS G 0551, tensile strength excellent in delayed fracture resistance, characterized in der Rukoto than 1800MPa Joined parts.
  2. 前記高強度支圧接合部品において、剪断遅れ破壊限界拡散性水素量が0.4ppm以上であることを特徴とする請求項1に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 2. The high strength bearing joint having excellent delayed fracture resistance according to claim 1, wherein the high strength bearing joint has a shear delay fracture limit diffusible hydrogen content of 0.4 ppm or more.
  3. 前記高強度支圧接合部品において、JIS Z 2242のノッチ深さ2mmのUノッチ5mmサブサイズ試験片を用いたシャルピー衝撃試験による吸収エネルギーが10J以上であることを特徴とする請求項1又は2に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 3. The absorbed energy by Charpy impact test using a U-notch 5 mm sub-size test piece having a notch depth of 2 mm according to JIS Z 2242 is 10 J or more in the high-strength bearing member. High strength bearing joints with excellent delayed fracture resistance as described.
  4. 前記高強度支圧接合部品において、初期水素含有量が0.4ppm未満であることを特徴とする請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。 In the high-strength bearing capacity bonding component, high strength Bearing joint which is excellent in delayed fracture resistance as set forth in any one of claim 1 to 3, wherein the initial hydrogen content of less than 0.4ppm parts.
  5. 前記高強度支圧接合部品において、更に、質量%で、
    P:0.015%以下、
    S:0.01%以下
    に制限することを特徴とする請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。
    In the high-strength bearing member, further in mass%,
    P: 0.015% or less,
    The high strength bearing joint having excellent delayed fracture resistance according to any one of claims 1 to 4 , wherein S is limited to 0.01% or less.
  6. 前記高強度支圧接合部品において、更に、質量%で、
    Mo:0.05〜2%、
    W :0.05〜1%、
    B :0.0001〜0.005%
    の1種又は2種以上を含有することを特徴とする請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。
    In the high-strength bearing member, further in mass%,
    Mo: 0.05-2%,
    W: 0.05 to 1%
    B: 0.0001 to 0.005%
    The high strength bearing joint part excellent in delayed fracture resistance according to any one of claims 1 to 5 , characterized by containing one or more of the following.
  7. 前記高強度支圧接合部品において、更に、質量%で、
    V :0.05〜1%、
    Ti:0.001〜0.05%、
    Nb:0.001〜0.05%
    の1種又は2種以上を含有することを特徴とする請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品。
    In the high-strength bearing member, further in mass%,
    V: 0.05 to 1%
    Ti: 0.001 to 0.05%,
    Nb: 0.001 to 0.05%
    1 or 2 types or more of these are included, The high strength bearing joint components excellent in the delayed fracture resistance of any one of Claims 1-6 characterized by the above-mentioned.
  8. 請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、質量%で、
    C :0.5〜0.8%、
    Mn:0.1〜2%、
    Cr:0.1〜1.5%
    を含有し、
    Si:0.05〜3%、
    Al:0.01〜1%
    の双方を、
    (Si+1.3×Al):0.08〜3.5%
    を満たすように含有し、残部がFe及び不可避不純物からなることを特徴とする高強度支圧接合部品用鋼素材
    A high-strength bearing member having excellent delayed fracture resistance according to any one of claims 1 to 4 , which is a material for manufacturing by molding and heat treatment , and in mass%,
    C: 0.5-0.8%
    Mn: 0.1 to 2%,
    Cr: 0.1 to 1.5%
    Containing
    Si: 0.05-3%,
    Al: 0.01 to 1%
    Both
    (Si + 1.3 × Al): 0.08 to 3.5%
    A steel material for a high-strength bearing member having a balance of Fe and inevitable impurities.
  9. 請求項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、
    P:0.015%以下、
    S:0.01%以下
    に制限することを特徴とする請求項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材
    A material for producing a high-strength bearing member excellent in delayed fracture resistance according to claim 5 by molding and heat-treating , further, in mass%,
    P: 0.015% or less,
    S: Restricted to 0.01% or less, The steel material for high-strength bearing members with excellent delayed fracture resistance according to claim 8 .
  10. 請求項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、
    Mo:0.05〜2%、
    W :0.05〜1%、
    B :0.0001〜0.005%
    の1種又は2種以上を含有することを特徴とする請求項8又は9に記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材
    A high-strength bearing member having excellent delayed fracture resistance according to claim 6 , a material for manufacturing by molding and heat treatment ,
    Mo: 0.05-2%,
    W: 0.05 to 1%
    B: 0.0001 to 0.005%
    The steel material for high-strength bearing members with excellent delayed fracture resistance according to claim 8 or 9 , characterized by containing one or more of the following.
  11. 請求項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品を、成形加工し、熱処理することにより製造するための素材であって、更に、質量%で、
    V :0.05〜1%、
    Ti:0.001〜0.05%、
    Nb:0.001〜0.05%
    の1種又は2種以上を含有することを特徴とする請求項8〜10の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品用鋼素材
    A high-strength bearing member having excellent delayed fracture resistance according to claim 7 , a material for manufacturing by molding and heat-treating , and further, in mass%,
    V: 0.05 to 1%
    Ti: 0.001 to 0.05%,
    Nb: 0.001 to 0.05%
    1 or 2 types or more of these are contained, The steel material for high strength bearing joint parts excellent in the delayed fracture resistance of any one of Claims 8-10 characterized by the above-mentioned.
  12. 請求項1〜の何れか1項に記載の耐遅れ破壊特性に優れた高強度支圧接合部品の製造方法であって、請求項8〜11の何れか1項に記載の鋼を成形加工し、850〜1000℃に加熱して焼入れ処理を行った後、加熱速度を10℃/s以上とし、焼戻温度T[℃]を200〜450℃の範囲とし、焼戻時間t[s]を1〜7200sの範囲とし、下記式(1)で定義される焼戻しパラメータPを6000〜12000として、焼戻し処理を行うことを特徴とする高強度支圧接合部品の製造方法。
    P=(T+273){log(t/3600)+21.3−5.8C
    −(Si+1.3Al)} ・・・(1)
    ここで、C、Si、Alは成分の含有量[質量%]である。
    A claim 1-7 High Strength Bearing joining component manufacturing method having excellent delayed fracture resistance as set forth in any one of molding a steel according to any one of claims 8 to 11 After heating to 850 to 1000 ° C. and quenching treatment, the heating rate is set to 10 ° C./s or more, the tempering temperature T [° C.] is set to 200 to 450 ° C., and the tempering time t [s]. Is a range of 1 to 7200 s, a tempering parameter P defined by the following formula (1) is set to 6000 to 12000, and a tempering process is performed.
    P = (T + 273) {log (t / 3600) + 21.3-5.8C
    -(Si + 1.3Al)} (1)
    Here, C, Si, and Al are component contents [% by mass].
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