JPH0196354A - Steel for high strength bolt having excellent delayed fracture resistance characteristic - Google Patents
Steel for high strength bolt having excellent delayed fracture resistance characteristicInfo
- Publication number
- JPH0196354A JPH0196354A JP25168187A JP25168187A JPH0196354A JP H0196354 A JPH0196354 A JP H0196354A JP 25168187 A JP25168187 A JP 25168187A JP 25168187 A JP25168187 A JP 25168187A JP H0196354 A JPH0196354 A JP H0196354A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- delayed fracture
- fracture resistance
- hydrogen
- strength
- 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
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 24
- 230000003111 delayed effect Effects 0.000 title claims abstract description 24
- 239000010959 steel Substances 0.000 title claims abstract description 24
- 229910052804 chromium Inorganic materials 0.000 claims abstract 5
- 229910052720 vanadium Inorganic materials 0.000 claims abstract 4
- 239000012535 impurity Substances 0.000 claims abstract 3
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract 3
- 229910052758 niobium Inorganic materials 0.000 claims abstract 2
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 22
- 239000001257 hydrogen Substances 0.000 abstract description 22
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 21
- 229910052710 silicon Inorganic materials 0.000 abstract 3
- 229910052799 carbon Inorganic materials 0.000 abstract 2
- 229910052742 iron Inorganic materials 0.000 abstract 2
- 229910052748 manganese Inorganic materials 0.000 abstract 2
- 238000012360 testing method Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 6
- 238000005496 tempering Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000002076 thermal analysis method Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Landscapes
- Joining Of Building Structures In Genera (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、１４０〜１６０ ｋｇ ｆ ／ｍａｌの引張
強さを有する耐遅れ破壊特性の優れた高強度ボルトに適
用する鋼である。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a steel applicable to high-strength bolts having a tensile strength of 140 to 160 kg f /mal and excellent delayed fracture resistance.
［従来の技術］
高強度ボルト（以下、ボルトという）は、機械、自動車
、橋、建物に多く使用されている。ボルトの強度が１２
５ ｋｇ ｆ ／ ｍａｌを越えると遅れ破壊の危険性
が高まることはよく知られており、現在使用されている
ボルトの強度は９０ｋｇ ｆ ／ ａ＋４あるいは１１
０ｋｇ ｆ ／−級のものが主体となっている。[Prior Art] High-strength bolts (hereinafter referred to as bolts) are often used in machines, automobiles, bridges, and buildings. Bolt strength is 12
It is well known that the risk of delayed fracture increases when the strength exceeds 5 kg f/mal, and the strength of the bolts currently used is 90 kg f/a+4 or 11
The main type is 0 kg f/- class.
［発明が解決しようとする問題点］
しかしながら近年の構造物はますます大型化の傾向にあ
り、継手効率を高めるためあるいは軽量化の目的から、
ボルトをより高強度にしたい要求が強い。そこで、強度
が１２５）ｃｇｆ／−を越えるボルトの遅れ破壊の問題
を解決させなければならない。[Problems to be solved by the invention] However, in recent years, structures have become increasingly larger, and in order to increase joint efficiency or reduce weight,
There is a strong demand for higher strength bolts. Therefore, it is necessary to solve the problem of delayed fracture of bolts whose strength exceeds 125) cgf/-.
ボルトの遅れ破壊は、ボルト中の水素が原因していると
言われている。遅れ破壊に関わる水素は、鋼中組織間を
常温で容易に動きうる格子間隙または転位、あるいは結
晶粒界等に存在するいわゆる拡散性水素（以下、拡散性
水素という）である。The delayed fracture of bolts is said to be caused by hydrogen in the bolts. Hydrogen involved in delayed fracture is so-called diffusible hydrogen (hereinafter referred to as diffusible hydrogen) that exists in lattice gaps, dislocations, grain boundaries, etc. that can easily move between structures in steel at room temperature.
より高強度のボルトを使用する場合、水素特に拡散性水
素に対する抵抗力のある鋼でなければならない。If higher strength bolts are used, the steel must be resistant to hydrogen, especially diffusible hydrogen.
［問題点を解決するための手段、作用コ本発明者らは、
鋼の化学成分の調整、特にＳｌ。[Means and effects for solving the problem] The inventors have
Adjustment of chemical composition of steel, especially Sl.
Ｃ「を高めることにより、遅れ破壊に至らない限界の拡
散性水素（以下、限界拡散性水素という）が増加できる
ことが可能であるとの知見を得て、上記問題点を解決す
ることができたのである。We were able to solve the above problem by obtaining the knowledge that it is possible to increase the limit diffusible hydrogen that does not lead to delayed fracture (hereinafter referred to as "limit diffusible hydrogen") by increasing C. It is.
本発明は、以上の知見にもとづいてなされたものであり
、熱処理を施すことにより、１４０ｋｇｆ／−〜１６０
ｋｇｆ／−の高強度において、従来鋼より高い限界拡散
性水素を示すことを特徴とする耐遅れ破壊特性の優れた
高強度ボルト用鋼に関わるものである。The present invention was made based on the above knowledge, and by applying heat treatment, it is possible to
The present invention relates to a steel for high-strength bolts with excellent delayed fracture resistance, which is characterized by exhibiting a higher limit diffusivity of hydrogen than conventional steels at a high strength of kgf/-.
本発明者らは、耐遅れ破壊特性に及ぼす合金元素の影響
を調べたところ、従来のボルト用鋼に採用されているも
のと比べて、ＳｉＨの増加、特に、Ｃｒの増加が有効で
あることを見い出した。The present inventors investigated the influence of alloying elements on delayed fracture resistance and found that an increase in SiH, especially an increase in Cr, is effective compared to those used in conventional steel for bolts. I found out.
即ち、本発明のボルト用鋼の合金成分の範囲は、・次の
理由で決定した。That is, the range of alloy components of the steel for bolts of the present invention was determined for the following reasons.
Ｃは、焼入れ一焼戻しにより高強度を得るためには、０
．１８％以上必要とし、一方、０，３５％を超えるとじ
ん性および耐遅れ破壊特性が低下し、高強度ボルトの特
性を満足しえないことから、０，１８〜０．３５％とし
た。C should be 0 in order to obtain high strength through quenching and tempering.
．． On the other hand, if it exceeds 0.35%, the toughness and delayed fracture resistance will deteriorate and the characteristics of a high-strength bolt cannot be satisfied, so it is set at 0.18 to 0.35%.
Ｓｉは、元来脱酸に必要であるが、ここでは特に鋼の耐
遅れ破壊特性を向上させる。しかし、その効果を十分に
発揮せしめるには、０．５０％超必要であるが、一方こ
の増加による鋼のしん性の低下にもとづいて上限１．５
０％とした。Si is originally necessary for deoxidation, but here it particularly improves the delayed fracture resistance of steel. However, in order to fully demonstrate its effect, it is necessary to exceed 0.50%, but on the other hand, based on the decrease in the toughness of steel due to this increase, the upper limit is 1.5%.
It was set to 0%.
Ｍｎは、脱酸及び脱硫に必要であり、焼入性の確保のた
めにも０．２０％以上必要であるが、０．６０％を超え
ると遅れ破壊特性が低下するため、０．２０〜０．６０
％とした。Mn is necessary for deoxidation and desulfurization, and 0.20% or more is also required to ensure hardenability, but if it exceeds 0.60%, delayed fracture properties will deteriorate, so 0.60
%.
Ｃｒは、前述のとおり、かつ焼入性の確保のために１．
５０％超必要とした。また、１４０ｋｇｆ／−以上の強
度を得るための焼戻温度を高める働きが有り、一般に、
遅れ破壊特性は、焼戻温度が高い方が優れている。しか
し、多量に添加しても効果が飽和するので上限を３．５
０％とした。As mentioned above, Cr is added in 1. to ensure hardenability.
More than 50% was required. It also has the function of increasing the tempering temperature to obtain a strength of 140 kgf/- or more, and generally,
The higher the tempering temperature, the better the delayed fracture characteristics. However, even if a large amount is added, the effect will be saturated, so the upper limit is set at 3.5
It was set to 0%.
Ｍｏは、鋼の強じん性を高めるに非常に有効な元素であ
って、この場合の必要量は０．１０％以上である。しか
し、高価な元素であるため、その有効性を勘案して上限
を０．５０％とした。Mo is a very effective element for increasing the toughness of steel, and the required amount in this case is 0.10% or more. However, since it is an expensive element, the upper limit was set at 0.50% in consideration of its effectiveness.
■は、その炭窒化物の析出硬化により、鋼の強度を高め
るに有効な元素であって、その活用に０．０５％以上を
必要とする。しかし、その量が多くなるとじん性が低下
するので、０．２０％を上限とした。(2) is an element effective in increasing the strength of steel through precipitation hardening of its carbonitrides, and requires 0.05% or more for its utilization. However, as the amount increases, the toughness decreases, so the upper limit was set at 0.20%.
上述の基本成分の材料に対して、更に、鋼の高強度化お
よび細粒化のために０．００５〜０．０３０％のＮｂ或
は”ＩＮを一種以上添加することができる。In order to increase the strength of the steel and make the grains finer, one or more types of Nb or "IN" can be added in an amount of 0.005 to 0.030% to the above-mentioned basic component material.
これらは、添加効果が飽和する量で上限とした。The upper limit was determined by the amount at which the added effect was saturated.
［実 施 例］
共試鋼の化学成分を表１に示す。（Ａ） 、 （Ｉ３）
、 （Ｃ） 。[Example] The chemical composition of the joint test steel is shown in Table 1. (A), (I3)
, (C).
（Ｄ）、（Ｅ）および（Ｆ）は本発明のボルト用鋼に従
ったものであり、（Ｇ） 、 （Ｈ） 、および（１）
は比較のために用意した既存の鋼であり、これらのφ２
０１ＩＩ＋１の棒鋼を用イテ、引張強さが１４０ｋｇｒ
／ ｍｆｆ１〜１６０ｋｇｆ／ ｍａｉを目標に熱処理
（焼入れ一焼戻し）を行った。この時の熱処理条件およ
び引張性質を表２に示す。(D), (E) and (F) are according to the bolt steel of the present invention, (G), (H) and (1)
are existing steels prepared for comparison, and these φ2
Uses 01II+1 steel bar, tensile strength is 140kgr
Heat treatment (quenching and tempering) was performed with the goal of / mff1 to 160 kgf/mai. Table 2 shows the heat treatment conditions and tensile properties at this time.
これらの鋼が、遅れ破壊に対し、どれだけの拡散性水素
を許容しうるかを調べる。すなわち各欄の限界水素ユを
求める。We will investigate how much diffusible hydrogen these steels can tolerate against delayed fracture. In other words, find the limit hydrogen for each column.
次に限界水素量を求める方法について述べる。Next, we will discuss how to determine the limit amount of hydrogen.
第１図に示したＭＩＯボルトで軸部に２ｍｍＶの円周ノ
ツチを設けた試験片を作り、２本を組にして、水素を富
化するために、２０％ＨＣ１溶液に２０分間浸漬した後
大気中に放置し、その放置時間を種々変えることにより
、試験片中の水素量を変化させる。A test piece with a circumferential notch of 2 mmV on the shaft part was made using the MIO bolt shown in Figure 1, and two pieces were put together and immersed in a 20% HC1 solution for 20 minutes to enrich hydrogen. The amount of hydrogen in the test piece is varied by leaving it in the atmosphere and varying the length of time it is left in the atmosphere.
こうしてそのうちの１本は、熱的分析法により水素を測
定し、もう１本は、第２図に示した試験機で遅れ破壊を
行う。図において１は試験片、２はバランスウェイト、
３は支点を示す。In this way, one of the tubes measures hydrogen using a thermal analysis method, and the other tube undergoes delayed destruction using the testing machine shown in FIG. In the figure, 1 is a test piece, 2 is a balance weight,
3 indicates the fulcrum.
なお、試験片を２０％ＨＣΩ溶液に２０分間浸漬しても
水素侵入量が少ない場合は、浸漬時間およびＨＣｉｌ溶
液の濃度によって水素量を調整している。Note that if the amount of hydrogen penetrating is small even after immersing the test piece in a 20% HCΩ solution for 20 minutes, the amount of hydrogen is adjusted by the immersion time and the concentration of the HCil solution.
また、遅れ破壊試験における試験荷重は、ＨＣ，９溶液
に浸漬する前の各試験片の破断荷重の７０％と一定にし
た。Further, the test load in the delayed fracture test was kept constant at 70% of the fracture load of each test piece before being immersed in the HC,9 solution.
そして、浸漬時間および放置時間を種々変えた時の拡散
性水素量と、遅れ破壊試験における破断時間との関係を
表３に示す。Table 3 shows the relationship between the amount of diffusible hydrogen and the rupture time in the delayed fracture test when the immersion time and standing time were varied.
同表から、各欄の遅れ破壊を起こさない上限の拡散性水
素量、すなわち、限界拡散性水素量を推定すると表４の
ようになる。From the same table, the upper limit diffusible hydrogen amount that does not cause delayed fracture in each column, that is, the limit diffusible hydrogen amount, is estimated as shown in Table 4.
これより、本発明の範囲にある（Ａ） 、 （Ｂ） 、
（Ｃ） 。From this, (A), (B), which are within the scope of the present invention,
(C).
（Ｄ） 、 （Ｅ） 、および（Ｐ）は、比較材である
（Ｇ） 、 （＋１） 、および（１）に比べて限界水
素量が高く、遅れ破壊しにくいことを示している。(D), (E), and (P) have a higher limit hydrogen content than the comparative materials (G), (+1), and (1), indicating that they are less susceptible to delayed fracture.
表 ４
［発明の効果］
本発明によって、１４０ ｋｇ ｆ ／ ｍ＋ａ〜１６
０ｋｇｆ／ｍｊの強度を有する耐遅れ破壊特性の優れた
ボルトが期待できる。これによって、ボルトの継手効率
を高めることができ、自動車等の軽量化に寄与し、工業
的効果は大きい。Table 4 [Effect of the invention] According to the present invention, 140 kg f / m + a ~ 16
A bolt with a strength of 0 kgf/mj and excellent delayed fracture resistance can be expected. As a result, the efficiency of bolt joints can be increased, contributing to weight reduction of automobiles, etc., and the industrial effect is large.
第１図は試験片の形状の説明図、第２図は遅れ破壊試験
装置の説明図である。FIG. 1 is an explanatory diagram of the shape of a test piece, and FIG. 2 is an explanatory diagram of a delayed fracture test device.
Claims (1)
特性の優れた高強度ボルト用鋼。（２）重量％で Ｃ：０．１８〜０．３５％、 Ｓｉ：０．５０超１．５０％、 Ｍｎ：０．２０〜０．６０％、 Ｃｒ：１．５０超３．５０％、 Ｍｏ：０．１０〜０．５０％、 Ｖ：０．１０〜０．２０％を含みかつ０．００５〜０．
０３０％のＮｂあるいはＴｉを一種以上含有し、残Ｆｅ
及び不純物からなることを特徴とする耐遅れ破壊特性の
優れた高強度ボルト用鋼。(1) C: 0.18 to 0.35% by weight, Si: 1.50% over 0.50, Mn: 0.20 to 0.60%, Cr: 3.50% over 1.50, A high-strength steel for bolts with excellent delayed fracture resistance, characterized by comprising Mo: 0.10-0.50%, V: 0.05-0.20%, remaining Fe and impurities. (2) C: 0.18 to 0.35% by weight, Si: 1.50% over 0.50, Mn: 0.20 to 0.60%, Cr: 3.50% over 1.50, Contains Mo: 0.10-0.50%, V: 0.10-0.20%, and 0.005-0.
Contains at least 30% of Nb or Ti, with the remainder of Fe
A high-strength steel for bolts with excellent delayed fracture resistance, which is characterized by being composed of and impurities.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25168187A JPH0196354A (en) | 1987-10-07 | 1987-10-07 | Steel for high strength bolt having excellent delayed fracture resistance characteristic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25168187A JPH0196354A (en) | 1987-10-07 | 1987-10-07 | Steel for high strength bolt having excellent delayed fracture resistance characteristic |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0196354A true JPH0196354A (en) | 1989-04-14 |
Family
ID=17226427
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25168187A Pending JPH0196354A (en) | 1987-10-07 | 1987-10-07 | Steel for high strength bolt having excellent delayed fracture resistance characteristic |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0196354A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009173245A (en) * | 2008-01-28 | 2009-08-06 | Nishikawa Rubber Co Ltd | Opening trim |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5594463A (en) * | 1979-01-12 | 1980-07-17 | Nippon Steel Corp | Petrochemical plant or high tensile bolt steel having hydrogen penetration preventing effect |
| JPS57161050A (en) * | 1981-03-31 | 1982-10-04 | Daido Steel Co Ltd | High-strength bolt steel |
| JPS58117856A (en) * | 1982-01-06 | 1983-07-13 | Daido Steel Co Ltd | High-strength bolt steel |
| JPS596358A (en) * | 1982-06-30 | 1984-01-13 | Daido Steel Co Ltd | High strength bolt |
-
1987
- 1987-10-07 JP JP25168187A patent/JPH0196354A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5594463A (en) * | 1979-01-12 | 1980-07-17 | Nippon Steel Corp | Petrochemical plant or high tensile bolt steel having hydrogen penetration preventing effect |
| JPS57161050A (en) * | 1981-03-31 | 1982-10-04 | Daido Steel Co Ltd | High-strength bolt steel |
| JPS58117856A (en) * | 1982-01-06 | 1983-07-13 | Daido Steel Co Ltd | High-strength bolt steel |
| JPS596358A (en) * | 1982-06-30 | 1984-01-13 | Daido Steel Co Ltd | High strength bolt |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009173245A (en) * | 2008-01-28 | 2009-08-06 | Nishikawa Rubber Co Ltd | Opening trim |
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