JPH10141341A - High strength bolt excellent in delayed fracture - Google Patents
High strength bolt excellent in delayed fractureInfo
- Publication number
- JPH10141341A JPH10141341A JP30169596A JP30169596A JPH10141341A JP H10141341 A JPH10141341 A JP H10141341A JP 30169596 A JP30169596 A JP 30169596A JP 30169596 A JP30169596 A JP 30169596A JP H10141341 A JPH10141341 A JP H10141341A
- Authority
- JP
- Japan
- Prior art keywords
- delayed fracture
- strength
- bolt
- hardness
- surface hardness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、遅れ破壊特性に優
れた高強度ボルトに関する。[0001] The present invention relates to a high-strength bolt excellent in delayed fracture characteristics.
【０００２】[0002]
【従来の技術】高強度ボルトはJIS Ｂ 1186 「摩擦接合
用高力六角ボルト・六角ナット・平座金のセット」やJI
S Ｂ 1051 「鋼製のボルト・小ねじの機械的性質」で強
度が規格化されているが、遅れ破壊が問題となるため、
１２００Ｎ／ｍｍ2 級までの強度となっている。一方
で、自動車の軽量化や建築物の高層化に対応し、更なる
高強度化が要望されているが、１２００Ｎ／ｍｍ2 以上
の強度の鋼は未だ確立されていない。遅れ破壊の起点は
表面であり、表面を軟化し、遅れ破壊感受性に優れた鋼
あるいはボルトを造る考え方がある。軟化法では一般的
に脱炭が考えられるが、この思想で出されたものとし
て、特開昭61-79015号公報、特開昭61-82014号公報及び
特開昭62-267420 号公報がある。[Prior art] High-strength bolts are JIS B 1186 "Set of high-strength hexagon bolts, hexagon nuts and flat washers for friction welding" and JI
SB 1051 The strength is standardized in “Mechanical properties of steel bolts and small screws”, but delayed fracture is a problem.
And it has a strength of up to 1200N / mm 2 class. On the other hand, in order to cope with the reduction in the weight of automobiles and the height of buildings, further strengthening is demanded, but steel having a strength of 1200 N / mm 2 or more has not yet been established. The starting point of delayed fracture is the surface, and there is a concept of softening the surface and producing steel or bolt having excellent delayed fracture sensitivity. In the softening method, decarburization is generally considered, and as a result of this idea, there are JP-A-61-79015, JP-A-61-82014 and JP-A-62-267420. .
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、特開昭
61-79015号公報では脱炭を用いるとは言っても、表面硬
さがＨＶ２９５〜３８３と比較的高い上、脱炭深さの規
定がなく、遅れ破壊の完全な防止は難しい。特開昭61-8
2014号公報も表面硬さがＨＶ２５０〜３５０と比較的高
く、脱炭深さを規定しているものの０．０１〜０．１ｍ
ｍと浅いため、遅れ破壊の完全な防止は難しい。特開昭
62-267420 号公報は高Ｓｉ添加鋼を用い、直接焼入れし
たものであり、ボルトへの適用は難しい。本発明の目的
は、上記した問題点を解決し、遅れ破壊特性に優れた引
張強さ：１４２０Ｎ／ｍｍ2 超えの高強度ボルトを提供
することにある。SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
In Japanese Patent Application Laid-Open No. 61-79015, although decarburization is used, the surface hardness is relatively high at HV 295 to 383, and the decarburization depth is not specified, so that it is difficult to completely prevent delayed fracture. JP-A-61-8
No. 2014 also has a relatively high surface hardness of HV250 to 350 and defines the decarburization depth, but it is 0.01 to 0.1 m.
m, it is difficult to completely prevent delayed fracture. JP
JP-A-62-267420 uses high Si-added steel and is directly quenched, and is difficult to apply to bolts. An object of the present invention is to solve the above-mentioned problems and to provide a high-strength bolt excellent in delayed fracture characteristics and having a tensile strength of more than 1420 N / mm 2 .
【０００４】[0004]
【課題を解決するための手段】前記課題を解決し目的を
達成するために、本発明は以下に示す手段を用いてい
る。 （１）本発明のボルトは、重量％（以下％は重量％を示
す）で、Ｃ＞０．３％を含有する鋼を用いたボルトであ
って、内部硬さ：ＨＶ＞４３０、表面硬さ：ＨＶ＜２５
０及び０．１ｍｍ＜脱炭深さ≦０．３ｍｍを満たすこと
を特徴とする引張強さ：１４２０Ｎ／ｍｍ2 超えの遅れ
破壊特性に優れた高強度ボルトである。In order to solve the above problems and achieve the object, the present invention uses the following means. (1) The bolt of the present invention is a bolt using steel containing C> 0.3% by weight (hereinafter,% indicates weight%), and has an internal hardness: HV> 430 and a surface hardness. Sa: HV <25
It is a high-strength bolt excellent in delayed fracture characteristics with a tensile strength of more than 1420 N / mm 2 characterized by satisfying 0 and 0.1 mm <decarburization depth ≦ 0.3 mm.
【０００５】[0005]
【発明の実施の形態】本発明者は、１４２０Ｎ／ｍｍ2
超えの高強度ボルトにおいて、脱炭による遅れ破壊特性
の向上を確実なものにするよう、鋭意研究を重ねた。そ
の結果、１４２０Ｎ／ｍｍ2 超えの高強度ボルトにおい
て、脱炭による遅れ破壊特性を確実に向上させるために
は、ボルトの内部硬さ、表面硬さ及び脱炭深さを最適化
することが有効であるという知見を得た。DETAILED DESCRIPTION OF THE INVENTION The present inventors have, 1420N / mm 2
For high-strength bolts exceeding that, we have conducted intensive studies to ensure the improvement of delayed fracture characteristics by decarburization. As a result, the high-strength bolts exceeding 1420N / mm 2, in order to reliably improve the delayed fracture due to decarburization, the internal hardness of the bolt, effective to optimize the surface hardness and decarburization depth Was obtained.
【０００６】この知見に基づき、本発明者は、高強度ボ
ルトの内部硬さ、表面硬さ及び脱炭深さを一定範囲内に
制限するようにして、遅れ破壊特性に優れた引張強さ：
１４２０Ｎ／ｍｍ2 超えの本発明の高強度ボルトを見出
し、本発明を完成させた。すなわち、本発明は鋼組成及
びボルトの内部硬さ、表面硬さ及び脱炭深さを下記範囲
に限定することにより、遅れ破壊特性に優れた引張強
さ：１４２０Ｎ／ｍｍ2 超えの高強度ボルトを提供する
ことができる。[0006] Based on this finding, the present inventors have limited the internal hardness, surface hardness and decarburization depth of the high-strength bolt to certain ranges, and have a tensile strength excellent in delayed fracture characteristics:
A high-strength bolt of the present invention exceeding 1420 N / mm 2 was found, and the present invention was completed. That is, the present invention limits the steel composition and the internal hardness, surface hardness and decarburization depth of the bolt to the following ranges, thereby providing a tensile strength excellent in delayed fracture characteristics: a high-strength bolt exceeding 1420 N / mm 2. Can be provided.
【０００７】以下に本発明の成分添加理由、成分限定理
由、ボルトの内部硬さ、表面硬さ及び脱炭深さの限定理
由について説明する。 （１）成分組成範囲 Ｃ＞０．３％ Ｃは焼入れ焼戻し処理により引張強度を確保するために
必要であり、０．３％以下では所望の引張強度が得られ
ない。従って、Ｃ量は０．３％超えである。The reasons for adding the components of the present invention, the reasons for limiting the components, and the reasons for limiting the internal hardness, surface hardness and decarburization depth of the bolt will be described. (1) Component composition range C> 0.3% C is necessary to secure tensile strength by quenching and tempering, and if it is 0.3% or less, a desired tensile strength cannot be obtained. Therefore, the C amount exceeds 0.3%.
【０００８】また、Ｓｉ，Ｐ，Ｓ，は本発明の効果を阻
害しない範囲で、それぞれ０．５％、０．０１５％、
０．０１５％の混入は許容される。また、必要に応じて
Ｍｎ，Ｃｒ，Ｍｏ，Ｎｉを、それぞれ、＜２％、＜２
％、＜０．５％、＜２％添加することも可能である。 （２）ボルトの内部硬さ、表面硬さ及び脱炭深さの範囲 内部硬さ＞ＨＶ４３０ 内部硬さがＨＶ４３０以下では所望の引張強度を確保で
きない。従って、ＨＶ４３０超えである。Further, Si, P, S, are 0.5%, 0.015%, and 0.5%, respectively, within a range not to impair the effects of the present invention.
A mixing of 0.015% is acceptable. If necessary, Mn, Cr, Mo, and Ni may be set to <2% and <2%, respectively.
%, <0.5%, <2%. (2) Range of internal hardness, surface hardness and decarburization depth of bolt Internal hardness> HV430 If the internal hardness is HV430 or less, a desired tensile strength cannot be secured. Therefore, it exceeds HV430.
【０００９】表面硬さ＜ＨＶ２５０ 表面硬さがＨＶ２５０以上では遅れ破壊感受性が高い。
従って、ＨＶ２５０未満である。 ０．１ｍｍ＜脱炭深さ≦０．３ｍｍ 脱炭深さが０．１ｍｍ以下では表面硬さが低くても遅れ
破壊抑制の効果がない。また、０．３ｍｍを超えるとボ
ルト実体での強度にばらつきが出やすい。従って、０．
１ｍｍ超えで０．３ｍｍ以下である。Surface hardness <HV250 When the surface hardness is HV250 or more, the delayed fracture sensitivity is high.
Therefore, it is less than HV250. 0.1 mm <decarburization depth ≦ 0.3 mm When the decarburization depth is 0.1 mm or less, there is no effect of suppressing delayed fracture even if the surface hardness is low. On the other hand, if it exceeds 0.3 mm, the strength of the bolt body tends to vary. Therefore, 0.
More than 1 mm and 0.3 mm or less.
【００１０】なお、上記（２）の範囲に調整するための
鋼の熱処理条件については、本発明では特に規定しない
が、焼入れ温度を７５０〜９００℃に制御することが好
ましい。The conditions for heat treatment of the steel for adjusting to the range of the above (2) are not particularly defined in the present invention, but it is preferable to control the quenching temperature to 750 to 900 ° C.
【００１１】９００℃を超えて焼入れした場合、結晶粒
の粗大化により靭性が低下するため、上限を９００℃と
するのが好ましい。一方、７５０℃未満ではフェライト
分率が増え、必要な強度が出ないため、また脱炭深さが
浅いため、下限を７５０℃とするのが好ましい。When quenching is performed at a temperature exceeding 900 ° C., the toughness is reduced due to coarsening of crystal grains. Therefore, the upper limit is preferably set to 900 ° C. On the other hand, if the temperature is lower than 750 ° C, the lower limit is preferably set to 750 ° C because the ferrite fraction increases and the required strength is not obtained and the decarburization depth is shallow.
【００１２】上記の鋼成分範囲及びボルトの内部硬さ、
表面硬さ及び脱炭深さの範囲に調整することにより、遅
れ破壊特性に優れた引張強さ：１４２０Ｎ／ｍｍ2 超え
の高強度ボルトを得ることが可能である。以下に本発明
の実施例を挙げ、本発明の効果を立証する。[0012] The above steel composition range and the internal hardness of the bolt,
By adjusting the surface hardness and the decarburization depth within the ranges, it is possible to obtain a high-strength bolt excellent in delayed fracture characteristics and having a tensile strength of more than 1420 N / mm 2 . Hereinafter, examples of the present invention will be described to demonstrate the effects of the present invention.
【００１３】[0013]
（実施例１）ＳＣＭ４３５（Ｃ：0.35％，Ｓｉ：0.23
％，Ｍｎ：0.77％，Ｐ：0.009 ％，Ｓ：0.008 ％，Ｃ
ｒ：1.06％，Ｍｏ：0.15％）のＭ２２ボルトを用い、焼
入れ焼き戻しを行い、所定の強度を付与した。この際、
雰囲気制御を行い、脱炭性とし、焼入れ温度を７５０〜
９００℃に制御し、内部硬さ、表面硬さ及び脱炭深さを
変化させた。熱処理後、ボルト軸部を切断し研磨後、硬
さをマイクロビッカース硬度計で測定した。(Example 1) SCM435 (C: 0.35%, Si: 0.23
%, Mn: 0.77%, P: 0.009%, S: 0.008%, C
(r: 1.06%, Mo: 0.15%), quenching and tempering were performed using M22 bolts to give a predetermined strength. On this occasion,
Atmosphere control, decarburization, quenching temperature 750 ~
The temperature was controlled at 900 ° C., and the internal hardness, surface hardness, and decarburization depth were changed. After the heat treatment, the bolt shaft was cut and polished, and the hardness was measured with a micro Vickers hardness meter.
【００１４】硬さは表面から０．０２５ｍｍ間隔で０．
５ｍｍまで測定し、内部は１ｍｍ間隔で測定した。表面
硬さは表面から０．０２５ｍｍの硬さ、内部硬さは表面
から０．５ｍｍより内部の硬さの平均値とした。脱炭深
さは表面硬さが内部硬さと同等になる位置とした。強度
はボルト実体で引張試験を行い、評価した。The hardness is 0.1 at an interval of 0.025 mm from the surface.
The measurement was performed up to 5 mm, and the inside was measured at 1 mm intervals. The surface hardness was a hardness of 0.025 mm from the surface, and the internal hardness was an average value of the internal hardness from 0.5 mm from the surface. The decarburization depth was set at a position where the surface hardness was equal to the internal hardness. The strength was evaluated by performing a tensile test on a bolt body.
【００１５】遅れ破壊試験は溝付きの２枚重ねの鋼板に
耐力点締め付けを行った供試ボルト１００本を３．５％
食塩水中で乾湿繰り返し（１日浸漬、１日乾燥で６カ月
間）を行い、破断本数で評価した。In the delayed fracture test, 3.5% of 100 test bolts tightened at a proof stress point on a two-ply grooved steel plate were used.
The samples were repeatedly dried and wet in a saline solution (immersion for 1 day, drying for 1 day for 6 months) and evaluated by the number of breaks.
【００１６】結果を表１に示す。Ｎｏ．１〜３は本発明
例であり、Ｎｏ．４〜６は比較例である。本発明例のＮ
ｏ．１〜３は、それぞれ１００本の試験を行い、１本の
破断もなかった。The results are shown in Table 1. No. Nos. 1 to 3 are examples of the present invention. 4 to 6 are comparative examples. N of the present invention example
o. In each of Nos. 1 to 3, 100 tests were performed, and there was no breakage.
【００１７】これに対して、比較例のＮｏ．４は表面硬
さが高く、Ｎｏ．５は脱炭深さが浅く、それぞれ本発明
の範囲から外れており、いずれも遅れ破壊特性に劣る。
また、Ｎｏ．６は脱炭をしない通常のボルトでこの場合
は全数破断してしまった。On the other hand, the comparative example No. No. 4 has a high surface hardness. No. 5 has a shallow decarburization depth, which is out of the range of the present invention, and all have poor delayed fracture characteristics.
In addition, No. Reference numeral 6 denotes a normal bolt which is not decarburized. In this case, all bolts are broken.
【００１８】[0018]
【表１】 [Table 1]
【００１９】（実施例２）Ｓ４５Ｃ（Ｃ：0.44％，Ｓ
ｉ：0.26％，Ｍｎ：0.81％，Ｐ：0.009 ％，Ｓ：0.007
％，Ｃｒ：0.16％）のＭ１２ボルトを用い、実施例１と
同様の試験を行った。(Example 2) S45C (C: 0.44%, S
i: 0.26%, Mn: 0.81%, P: 0.009%, S: 0.007
%, Cr: 0.16%), and the same test as in Example 1 was performed.
【００２０】結果を表２に示す。Ｎｏ．１〜３は本発明
例であり、Ｎｏ．４〜６は比較例である。本発明例のＮ
ｏ．１〜３は、それぞれ１００本の試験を行い、１本の
破断もなかった。The results are shown in Table 2. No. Nos. 1 to 3 are examples of the present invention. 4 to 6 are comparative examples. N of the present invention example
o. In each of Nos. 1 to 3, 100 tests were performed, and there was no breakage.
【００２１】これに対して、比較例のＮｏ．４は表面硬
さが高く、Ｎｏ．５は脱炭深さが浅く、それぞれ本発明
の範囲から外れており、いずれも遅れ破壊特性に劣る。
また、Ｎｏ．６は脱炭をしない通常のボルトでこの場合
は全数破断してしまった。On the other hand, the comparative example No. No. 4 has a high surface hardness. No. 5 has a shallow decarburization depth, which is out of the range of the present invention, and all have poor delayed fracture characteristics.
In addition, No. Reference numeral 6 denotes a normal bolt which is not decarburized. In this case, all bolts are broken.
【００２２】[0022]
【表２】 [Table 2]
【００２３】[0023]
【発明の効果】本発明によれば、鋼組成及びボルトの内
部硬さ、表面硬さ及び脱炭深さを特定することにより、
１４２０Ｎ／ｍｍ2 超えの強度を有する高強度ボルトで
あっても、遅れ破壊を生じない遅れ破壊特性に優れた高
強度ボルトを提供することができる。また、この技術は
高強度ボルト以外にもＰＣ鋼棒他の高強度鋼においても
適用できるなど、産業上極めて有用な効果をもたらすも
のである。According to the present invention, by specifying the steel composition and the internal hardness, surface hardness and decarburization depth of the bolt,
Even with a high-strength bolt having a strength exceeding 1420 N / mm 2, it is possible to provide a high-strength bolt excellent in delayed fracture characteristics that does not cause delayed fracture. In addition, this technique has an industrially very useful effect, for example, it can be applied to high-strength steels such as PC steel bars in addition to high-strength bolts.
Claims (1)
用いたボルトであって、内部硬さ：ＨＶ＞４３０、表面
硬さ：ＨＶ＜２５０及び０．１ｍｍ＜脱炭深さ≦０．３
ｍｍを満たすことを特徴とする引張強さ：１４２０Ｎ／
ｍｍ2 超えの遅れ破壊特性に優れた高強度ボルト。1. A bolt made of steel containing C> 0.3% by weight, wherein the internal hardness is HV> 430 and the surface hardness is HV <250 and 0.1 mm <decarburization depth. S ≦ 0.3
mm, tensile strength: 1420 N /
mm 2 over delayed fracture properties in excellent high-strength bolts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30169596A JPH10141341A (en) | 1996-11-13 | 1996-11-13 | High strength bolt excellent in delayed fracture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30169596A JPH10141341A (en) | 1996-11-13 | 1996-11-13 | High strength bolt excellent in delayed fracture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH10141341A true JPH10141341A (en) | 1998-05-26 |
Family
ID=17900044
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30169596A Pending JPH10141341A (en) | 1996-11-13 | 1996-11-13 | High strength bolt excellent in delayed fracture |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH10141341A (en) |
Cited By (5)
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|---|---|---|---|---|
| WO2009123227A1 (en) * | 2008-03-31 | 2009-10-08 | 高周波熱錬株式会社 | Steel material, process for producing steel material, and apparatus for producing steel material |
| WO2011030853A1 (en) * | 2009-09-10 | 2011-03-17 | 独立行政法人物質・材料研究機構 | High-strength bolt |
| WO2011111872A1 (en) * | 2010-03-11 | 2011-09-15 | 新日本製鐵株式会社 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| WO2011111873A1 (en) * | 2010-03-11 | 2011-09-15 | 新日本製鐵株式会社 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| WO2019150434A1 (en) * | 2018-01-30 | 2019-08-08 | 日産自動車株式会社 | Bolt |
-
1996
- 1996-11-13 JP JP30169596A patent/JPH10141341A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009123227A1 (en) * | 2008-03-31 | 2009-10-08 | 高周波熱錬株式会社 | Steel material, process for producing steel material, and apparatus for producing steel material |
| CN102597543A (en) * | 2009-09-10 | 2012-07-18 | 独立行政法人物质·材料研究机构 | High-strength bolt |
| WO2011030853A1 (en) * | 2009-09-10 | 2011-03-17 | 独立行政法人物質・材料研究機構 | High-strength bolt |
| US8876451B2 (en) | 2009-09-10 | 2014-11-04 | National Institute For Materials Science | High-strength bolt |
| KR101322534B1 (en) * | 2010-03-11 | 2013-10-28 | 신닛테츠스미킨 카부시키카이샤 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| EP2546380A1 (en) * | 2010-03-11 | 2013-01-16 | Nippon Steel Corporation | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| JP5135557B2 (en) * | 2010-03-11 | 2013-02-06 | 新日鐵住金株式会社 | High-strength steel material and high-strength bolt excellent in delayed fracture resistance |
| JP5177323B2 (en) * | 2010-03-11 | 2013-04-03 | 新日鐵住金株式会社 | High-strength steel material and high-strength bolt excellent in delayed fracture resistance |
| WO2011111873A1 (en) * | 2010-03-11 | 2011-09-15 | 新日本製鐵株式会社 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| EP2546380A4 (en) * | 2010-03-11 | 2013-12-25 | Nippon Steel & Sumitomo Metal Corp | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| KR101366375B1 (en) * | 2010-03-11 | 2014-02-24 | 신닛테츠스미킨 카부시키카이샤 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| WO2011111872A1 (en) * | 2010-03-11 | 2011-09-15 | 新日本製鐵株式会社 | High-strength steel and high-strength bolt with excellent resistance to delayed fracture, and manufacturing method therefor |
| US8951365B2 (en) | 2010-03-11 | 2015-02-10 | Nippon Steel & Sumitomo Metal Corporation | High strength steel and high strength bolt excellent in delayed fracture resistance and methods of production of same |
| WO2019150434A1 (en) * | 2018-01-30 | 2019-08-08 | 日産自動車株式会社 | Bolt |
| JPWO2019150434A1 (en) * | 2018-01-30 | 2021-01-14 | 日産自動車株式会社 | bolt |
| US11333189B2 (en) | 2018-01-30 | 2022-05-17 | Nissan Motor Co., Ltd. | Bolt |
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