JPH1053834A - Steel for high strength bolt and high strength bolt - Google Patents
Steel for high strength bolt and high strength boltInfo
- Publication number
- JPH1053834A JPH1053834A JP20741596A JP20741596A JPH1053834A JP H1053834 A JPH1053834 A JP H1053834A JP 20741596 A JP20741596 A JP 20741596A JP 20741596 A JP20741596 A JP 20741596A JP H1053834 A JPH1053834 A JP H1053834A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車や各種産業
機械等に用いられるボルト用鋼および該ボルト用鋼を用
いて得られるボルトに関する。詳細には、引張強度が７
８５Ｎ／ｍｍ2 を超えると共に、オーステナイト結晶粒
度番号が５以上であるボルトを製造するのに有用な高強
度ボルト用鋼に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to steel for bolts used in automobiles and various industrial machines, and to a bolt obtained by using the steel for bolts. Specifically, the tensile strength is 7
The present invention relates to a high-strength bolt steel that is useful for producing a bolt having an austenite crystal grain size number of 5 or more while having a strength exceeding 85 N / mm 2 .
【０００２】[0002]
【従来の技術】従来、引張強度が７８５〜１１７５Ｎ／
ｍｍ2 の高強度ボルトを製造するには、ＳＣＭ４３５に
代表される低合金鋼が使用されていたが、近年における
コスト低減化の要請に伴い、Ｂ添加による焼入性向上効
果を利用したＢ添加鋼が用いられつつある。しかしなが
らＢ添加鋼は、焼入れ加熱時にオーステナイトの結晶粒
度が粗大化しやすいという問題がある。特に、冷間加工
を施した材料については、焼入れ・焼鈍時にオーステナ
イト結晶粒度が粗大化しやすくなる。そこで、オーステ
ナイト結晶粒の粗大化を抑制することを目的として、特
に焼入れ加熱時、或いは焼入れ加熱前における加熱速度
を制御した種々の方法が提案されている。2. Description of the Related Art Conventionally, a tensile strength of 785 to 1175 N /
In order to manufacture high-strength bolts of mm 2 , low alloy steels represented by SCM435 have been used. However, with the recent demand for cost reduction, B-addition utilizing the hardenability improvement effect of B-addition has been used. Steel is being used. However, the B-added steel has a problem that the grain size of austenite tends to become coarse during quenching and heating. In particular, for a material that has been subjected to cold working, the austenite crystal grain size tends to become coarse during quenching and annealing. For the purpose of suppressing coarsening of austenite crystal grains, various methods have been proposed in which the heating rate is controlled particularly during quenching heating or before quenching heating.
【０００３】例えば特開平５７−７９１１６号は焼入れ
時の加熱速度を３〜５０℃／ｓｅｃに制御する方法であ
るが、通常のボルト焼入れ時の加熱速度（０．１〜０．
８℃／ｓｅｃ）とは異なり急速加熱処理を施す必要があ
り、適用範囲が限定されてしまうという問題がある。For example, Japanese Patent Application Laid-Open No. 57-79116 discloses a method of controlling the heating rate at the time of quenching to 3 to 50 ° C./sec.
(8 ° C./sec), it is necessary to perform a rapid heating treatment, and there is a problem that the applicable range is limited.
【０００４】また特公昭５６−１３７６８号では、焼入
れ時の加熱速度を３℃／ｍｉｎ以下と、通常の焼入加熱
速度に比べて非常に遅くする方法であるが、加熱手段は
誘導加熱法を前提としており、通常のボルト焼入れ・焼
鈍処理で繁用される電気炉加熱は利用しにくいという不
都合がある。更にこの方法によれば、オーステナイトの
結晶粒度を調整するために、鋼の焼入れ処理前に熱間加
工または９５０℃以上１０００℃以下の加熱処理を行う
ことが前提となっており、工程が煩雑となりコストの上
昇を招く等の問題も伴っている。Japanese Patent Publication No. 56-13768 discloses a method in which the heating rate during quenching is set to 3 ° C./min or less, which is much lower than the normal quenching heating rate. As a premise, there is an inconvenience that electric furnace heating often used in ordinary bolt quenching and annealing treatment is difficult to use. Furthermore, according to this method, in order to adjust the grain size of austenite, it is premised that hot working or heat treatment at 950 ° C. or more and 1000 ° C. or less is performed before quenching the steel, which makes the process complicated. There are also problems such as an increase in cost.
【０００５】更に、特開平３−４７９１８号には、Ｔｉ
Ｎを微細析出させることによって焼入れ時のオーステナ
イト結晶粒の粗大化を防止する方法が開示されている。
即ち、連続鋳造時にＴｉＮを微細析出させると共に、そ
の後の圧延工程においても、ＴｉＮの凝集を阻止すると
いう観点から従来の加熱温度（１０００〜１２５０℃）
よりも低い加熱温度（８００〜９５０℃）で加熱処理す
る方法である。しかしながら、この方法では鋳造時の凝
固速度を速くする必要があり、従って、ブルーム連続鋳
造や造塊鋳造等の如く凝固速度の遅い鋳造方法を採用し
た場合には、オーステナイト結晶粒度の粗大化を防止す
ることはできない。Further, Japanese Patent Application Laid-Open No. 3-47918 discloses that Ti
A method for preventing coarsening of austenite crystal grains during quenching by precipitating N finely is disclosed.
That is, the conventional heating temperature (1000 to 1250 ° C.) is used from the viewpoint of precipitating TiN finely during continuous casting and also preventing aggregation of TiN in the subsequent rolling step.
This is a method of performing heat treatment at a lower heating temperature (800 to 950 ° C.). However, in this method, it is necessary to increase the solidification rate during casting, and therefore, when a casting method having a low solidification rate such as bloom continuous casting or ingot casting is employed, coarsening of the austenite grain size is prevented. I can't.
【０００６】[0006]
【発明が解決しようとする課題】本発明はこうした事情
に着目してなされたものであって、その目的は、焼入れ
加熱前における加熱速度や加熱温度等を制御しなくと
も、オーステナイト結晶粒度番号が５以上の微細結晶粒
を含有し且つ引張強度が７８５Ｎ／ｍｍ2を超える高強
度ボルトを製造するのに有用な高強度ボルト用鋼を提供
することにある。SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to control the austenite grain size number without controlling the heating rate and heating temperature before quenching heating. An object of the present invention is to provide a high-strength bolt steel containing five or more fine crystal grains and having a tensile strength exceeding 785 N / mm 2 and useful for producing a high-strength bolt.
【０００７】[0007]
【課題を解決するための手段】上記目的を達成し得た本
発明の高強度ボルト用鋼とは、鋼の化学成分がＢ：0.00
08〜0.004％（質量％の意味、以下同じ），Ｃ：0.4％以
下（０％を含まない），Ｔｉ：0.025 〜0.06％，Ｎ：0.
006 ％以下（０％を含まない），残部：Ｆｅおよび不可
避不純物であると共に、［ＴｉＮを除くＴｉ化合物の合
計量／ＦＧｃ1/2］×1000で規定されるＧ値（ＦＧｃは
鋼を熱間圧延したときのフェライト結晶粒度を意味す
る。以下、単にＧ値と呼ぶ場合がある）が下式（１）ま
たは（２）を満足するところに要旨を有するものであ
る。The steel for high-strength bolts of the present invention, which has achieved the above object, has a chemical composition of B: 0.00
08 to 0.004% (meaning by mass%, the same applies hereinafter), C: 0.4% or less (excluding 0%), Ti: 0.025 to 0.06%, N: 0.
006% or less (excluding 0%), balance: Fe and unavoidable impurities, and a G value defined by [total amount of Ti compounds excluding TiN / FGc 1/2 ] × 1000 (FGc is heat (Hereinafter, simply referred to as a G value) when satisfying the following expression (1) or (2).
【０００８】 Ｇ値≧（Ｙ−７７５）／７０ … （１） ｛式中、Ｙ：焼入温度（℃）を意味する｝ Ｇ値≧３ … （２） 上記鋼において、更にＳｉ：0.35 ％以下（０％を含ま
ない），Ｍｎ：2％以下（０％を含まない），Ａｌ：0.1
％以下（０％を含まない）の少なくとも一種を含有す
るものは本発明の好ましい実施態様である。G value ≧ (Y−775) / 70 (1) {where, Y: quenching temperature (° C.)} G value ≧ 3 (2) In the above steel, Si: 0.35% Or less (excluding 0%), Mn: 2% or less (excluding 0%), Al: 0.1
% Or less (not including 0%) is a preferred embodiment of the present invention.
【０００９】また、上記ボルト用鋼を用いて得られる高
強度ボルトも本発明の範囲内に包含される。[0009] High-strength bolts obtained using the above-mentioned bolt steel are also included in the scope of the present invention.
【００１０】[0010]
【発明の実施の形態】本発明者らは、高強度ボルト用鋼
として有用なＢ添加鋼における上述した問題点、即ち焼
入れ時におけるオーステナイト結晶粒の粗大化を防止す
ることを目的として鋭意検討を行った。その結果、オ
ーステナイト結晶粒の粗大化を防止するには、ＴｉＮを
除くＴｉ化合物を微細析出させることが有効であるこ
と、及びオーステナイト結晶粒の粗大化は鋼材のフェ
ライト結晶粒にも依存することが分かった。従って、鋼
材のフェライト結晶粒度および焼入温度に見合った量
の、ＴｉＮを除くＴｉ化合物を微細析出させることがで
きれば上記課題を解決し得ることを見出し、本発明を完
成したのである。BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies for the purpose of preventing the above-mentioned problems in the B-added steel useful as high-strength steel for bolts, that is, to prevent austenite crystal grains from becoming coarse during quenching. went. As a result, in order to prevent austenite crystal grains from coarsening, it is effective to finely precipitate Ti compounds other than TiN, and that austenite crystal grains are also dependent on ferrite crystal grains of steel. Do you get it. Therefore, the present inventors have found that the above-mentioned problems can be solved if a Ti compound other than TiN can be finely precipitated in an amount corresponding to the ferrite crystal grain size and the quenching temperature of the steel material, and the present invention has been completed.
【００１１】以下、本発明を特徴付ける各要件について
説明する。Hereinafter, each requirement that characterizes the present invention will be described.
【００１２】Ｃ：0.4％以下（０％を含まない） Ｃは鋼の焼入性と強度確保のために有用な元素である
が、過剰に添加すると；焼入れ後の靭性が低下すると共
に、割れが発生する等の問題を招くので、その上限を0.
4％とした。好ましい上限値は0.35％である。また、上
記作用を有効に発揮させるには、0.15％以上の添加が好
ましい。C: 0.4% or less (excluding 0%) C is an element useful for securing the hardenability and strength of steel, but if added excessively; the toughness after quenching is reduced and cracking occurs. Cause an issue such as the occurrence of
4%. A preferred upper limit is 0.35%. In order to effectively exert the above-mentioned effects, it is preferable to add 0.15% or more.
【００１３】Ｔｉ：0.025 〜0.06％ Ｔｉは鋼中のＮをＴｉＮの形で固定し、Ｂ添加による焼
入効果を発揮させるのに非常に有用である。特に、Ｔｉ
化合物の形成は焼入れ後のオーステナイト結晶粒の粗大
化防止に非常に有用である。この様な作用を有効に発揮
させるには0.025％以上の添加が必要である。好ましい
下限値は0.030％であり、より好ましいのは0.040％であ
る。しかしながら、0.06％以上添加してもその効果は飽
和するので、その上限を0.06％とした。Ti: 0.025-0.06% Ti is very useful for fixing N in steel in the form of TiN and exerting a quenching effect by adding B. In particular, Ti
The formation of the compound is very useful for preventing coarsening of austenite crystal grains after quenching. To exert such an effect effectively, it is necessary to add 0.025% or more. A preferred lower limit is 0.030%, more preferably 0.040%. However, the effect is saturated even if 0.06% or more is added, so the upper limit is set to 0.06%.
【００１４】Ｎ：0.006 ％以下（０％を含まない） Ｎは、ＡｌＮやＴｉＮの形成によって焼入れ後のオース
テナイト結晶粒の粗大か防止に寄与する元素である。し
かしながら、過剰に添加するとＡｌやＴｉの添加によっ
ても全てを捕捉することはできず、余剰のＮがＢＮを形
成するため、Ｂによる焼入性を確保できないと共に、焼
入れ後のオーステナイト結晶粒の粗大化防止に大きく寄
与するＴｉＮを除くＴｉ化合物の析出量が少なくなるた
め、その上限値を0.006％にした。好ましい上限値は0.0
050％であり、より好ましいのは0.0040％である。N: 0.006% or less (excluding 0%) N is an element contributing to the prevention of austenite crystal grains after quenching due to the formation of AlN or TiN. However, if added excessively, not all can be trapped even by the addition of Al or Ti, and since excess N forms BN, hardenability by B cannot be ensured and coarse austenite crystal grains after quenching. Since the amount of precipitation of Ti compounds other than TiN, which greatly contributes to prevention of oxidization, is reduced, the upper limit is set to 0.006%. The preferred upper limit is 0.0
050%, more preferably 0.0040%.
【００１５】Ｂ：0.0008〜0.004％ Ｂは粒界に偏析することにより鋼の焼入性を向上させる
元素である。その効果を有効に発揮させるためには0.00
08％以上の添加が必要である。好ましい下限値は0.0010
％であり、より好ましいのは0.0015％である。しかしな
がら過剰に添加すると、かえって延性を阻害するので、
その上限を0.004％とした。好ましい上限値は0.0035％
であり、より好ましいのは0.0030％である。B: 0.0008 to 0.004% B is an element that segregates at the grain boundaries to improve the hardenability of steel. 0.00 for effective use
08% or more must be added. The preferred lower limit is 0.0010
%, More preferably 0.0015%. However, if added in excess, it will rather inhibit ductility,
The upper limit was made 0.004%. Preferred upper limit is 0.0035%
And more preferably 0.0030%.
【００１６】本発明の鋼は、上記元素を必須成分とし、
残部：Ｆｅおよび不可避不純物からなるが、その他に、
以下の選択的許容成分を少なくとも１種積極的に添加す
ることができる。The steel of the present invention contains the above elements as essential components,
The balance is composed of Fe and unavoidable impurities.
At least one of the following optional components can be positively added.
【００１７】Ｓｉ：0.35 ％以下（０％を含まない） Ｓｉは脱酸剤として有用な元素であり、好ましい下限値
は0.035％である。しかしながら、その添加量が増大す
るにつれて冷間鍛造性が低下するので、その上限を0.35
％以下とした。好ましい上限値は0.030％であり、より
好ましいのは0.025％である。Si: 0.35% or less (excluding 0%) Si is an element useful as a deoxidizing agent, and a preferable lower limit is 0.035%. However, as the addition amount increases, the cold forgeability decreases, so the upper limit is 0.35.
% Or less. A preferred upper limit is 0.030%, more preferably 0.025%.
【００１８】Ｍｎ：2 ％以下（０％を含まない） Ｍｎは焼入性向上元素として使用され、高強度を付与す
るのに有用である。しかしながら、Ｍｎの添加量が多す
ぎると、圧延後に過冷組織が生成し、冷間鍛造性が低下
する他、ボルトの寿命低下をもたらす。好ましい上限値
は1.5％であり、より好ましいのは1.2％である。Mn: 2% or less (excluding 0%) Mn is used as a hardenability improving element and is useful for imparting high strength. However, if the added amount of Mn is too large, a supercooled structure is generated after rolling, and the cold forgeability is reduced, and the life of the bolt is reduced. A preferred upper limit is 1.5%, more preferably 1.2%.
【００１９】Ａｌ：0.1 ％以下（０％を含まない） Ａｌは脱酸剤として使用され、鋼中のＮを固定してＡｌ
Ｎを形成して結晶粒を微細化することによって頭飛び特
性の向上に寄与する元素である。この様な作用を有効に
発揮させるには0.005％以上の添加が好ましい。より好
ましい下限値は0.010％であり、更により好ましいのは
0.020％である。しかしながら多過ぎると酸化物系介在
物が生成することによって冷間鍛造性が低下するので、
その上限を0.1％とした。好ましい上限値は0.08％であ
り、より好ましいのは0.06％である。Al: 0.1% or less (excluding 0%) Al is used as a deoxidizing agent and fixes N in steel to fix Al.
It is an element that contributes to the improvement of head jump characteristics by forming N to refine crystal grains. In order to effectively exhibit such an effect, it is preferable to add 0.005% or more. A more preferred lower limit is 0.010%, and an even more preferred lower limit is
0.020%. However, when the content is too large, the cold forgeability decreases due to generation of oxide-based inclusions.
The upper limit was set to 0.1%. A preferred upper limit is 0.08%, more preferably 0.06%.
【００２０】その他、必要に応じてＣｒ：2.0％以下お
よび／またはＭｏ：1.0 ％以下（これらの元素は全て０
％を含まない）を添加することは、焼入性を改善して強
度を高めるという観点から非常に有用である。In addition, if necessary, Cr: 2.0% or less and / or Mo: 1.0% or less (all of these elements are 0% or less).
%) Is very useful from the viewpoint of improving hardenability and increasing strength.
【００２１】更に、本発明の高強度ボルト用鋼は、本発
明で規定する前記Ｇ値について、上記式（１）または
（２）を満足しなければならない。Further, the steel for high-strength bolts of the present invention must satisfy the above formula (1) or (2) for the G value specified in the present invention.
【００２２】上述した様に、焼入れ後のオーステナイト
結晶粒の粗大化はＴｉＮを除くＴｉ化合物量および鋼材
のフェライト結晶粒度に依存し、焼入れ後のオーステナ
イト結晶粒の粗大化を防止するには、上記Ｇ値が式
（１）または（２）の関係を満足することが必要であ
る。尚、本発明において「ＴｉＮを除くＴｉ化合物」と
は、例えばＴｉＣ、Ｔｉ4Ｃ2Ｓ2、ＴｉＳ等のＴｉ化合
物を意味する。As described above, the coarsening of the austenite crystal grains after quenching depends on the amount of the Ti compound excluding TiN and the ferrite crystal grain size of the steel material. It is necessary that the G value satisfies the relationship of equation (1) or (2). In the present invention, the “Ti compound excluding TiN” means a Ti compound such as TiC, Ti 4 C 2 S 2 , and TiS.
【００２３】このうち式（１）は、Ｇ値を焼入温度
（Ｙ）との関係で規定したものである。図１に、後記す
る実施例において、Ｇ値や焼入温度（Ｙ）を種々変化さ
せた場合におけるＭ１０ボルトのオーステナイト結晶粒
粗大化の有無をグラフ化したものを示す。図中、ＧＧと
はオーステナイト結晶粒の粗大化を示す。同図から明ら
かな様に、式（１）の関係を満たすものは、焼入温度
（Ｙ）を変化させてもオーステナイト結晶粒の粗大化は
全く生じないことが分かる。好ましい焼入温度は８００
〜１０００℃であり、より好ましくは８５０〜９４０℃
である。Equation (1) defines the G value in relation to the quenching temperature (Y). FIG. 1 is a graph showing the presence or absence of austenite crystal grain coarsening of M10 volts when the G value and the quenching temperature (Y) are variously changed in Examples described later. In the figure, GG indicates coarsening of austenite crystal grains. As is clear from the figure, in the case of the one satisfying the relationship of the formula (1), even if the quenching temperature (Y) is changed, the austenite crystal grains are not coarsened at all. The preferred quenching temperature is 800
~ 1000 ° C, more preferably 850-940 ° C
It is.
【００２４】一方、式（２）は、焼入温度（Ｙ）とは関
係なくＧ値のみによって規定されるものである。即ち、
Ｇ値が３以上である鋼を用いれば、その後の製造条件に
拘わらず、焼入れ加熱前における加熱速度や加熱温度等
を制御しなくとも、オーステナイト結晶粒の粗大化は生
じないのである。Ｇ値の好ましい下限値は４である。On the other hand, the expression (2) is defined only by the G value regardless of the quenching temperature (Y). That is,
If steel having a G value of 3 or more is used, coarsening of austenite crystal grains does not occur without controlling the heating speed, heating temperature, and the like before quenching heating, regardless of the subsequent manufacturing conditions. A preferred lower limit of the G value is 4.
【００２５】尚、その上限値は特に規定されないが、Ｔ
ｉ化合物が多量に生成すると鋼の清浄化が低下する等の
点を考慮すれば、６以下が好ましい。Although the upper limit is not specified, T
Considering, for example, that if a large amount of the i-compound is produced, the cleaning of the steel is reduced, it is preferably 6 or less.
【００２６】本発明のボルト用鋼は、この様に鋼の化学
組成およびＧ値を制御した点に特徴があり、この様な鋼
を用いれば、オーステナイト結晶粒度番号が５以上の高
強度ボルトを効率よく製造することができる。従って、
本発明鋼を用いてボルトを製造するに当たっては、鋼片
の加熱温度や加熱処理後の焼入れ・焼鈍条件、ボルト製
造時における冷間加工条件、溶製条件等については特に
制御されず、本発明の作用を損なわない範囲で、適宜好
ましい条件を選択することができる。The steel for bolts according to the present invention is characterized in that the chemical composition and the G value of the steel are controlled as described above. If such steel is used, a high-strength bolt having an austenite grain size number of 5 or more can be obtained. It can be manufactured efficiently. Therefore,
In producing a bolt using the steel of the present invention, the heating temperature of the steel slab, the quenching and annealing conditions after the heat treatment, the cold working conditions during the production of the bolt, the melting conditions, etc. are not particularly controlled. Preferred conditions can be appropriately selected within a range that does not impair the effect of the above.
【００２７】以下実施例を挙げて本発明をさらに詳細に
説明するが、下記実施例は本発明を制限するものではな
く、前・後記の趣旨を逸脱しない範囲で変更実施するこ
とは全て本発明の技術的範囲に包含される。Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and all changes and implementations without departing from the spirit of the present invention will be described. Within the technical scope of
【００２８】[0028]
実施例１ 表１に示す化学成分を有する各種鋼を連続鋳造法（３０
０×４３０ｍｍブルーム連鋳機）または造塊法にて溶製
した後、圧延加熱温度および圧延仕上温度を変化させる
ことにより１０．３ｍｍφの線材に熱間圧延した。後記
する表２中、圧延加熱条件における低温加熱とは約８５
０℃の加熱を、高温加熱とは約１０５０℃の加熱を夫々
意味し、一方、圧延仕上温度条件における低温仕上とは
約７５０℃の仕上温度を、高温仕上とは約９００℃の仕
上温度で処理することを夫々意味する。Example 1 Various steels having the chemical components shown in Table 1 were continuously cast (30
(0 × 430 mm bloom continuous caster) or ingot casting method, and then hot-rolled into a 10.3 mmφ wire rod by changing the rolling heating temperature and the rolling finishing temperature. In Table 2 described below, low-temperature heating under rolling heating conditions is about 85
The heating at 0 ° C. and the high-temperature heating mean heating at about 1050 ° C., respectively, while the low-temperature finishing under the rolling finishing temperature condition has a finishing temperature of about 750 ° C. and the high-temperature finishing has a finishing temperature of about 900 ° C. Means to process.
【００２９】この線材のフェライト結晶粒度およびＴｉ
Ｎを除くＴｉ化合物の合計量を測定した後、９．０ｍｍ
φに冷間伸線し、冷間加工を施すことによりＭ１０ボル
トを作製した。このＭ１０ボルトを更に８５０〜９４０
℃で加熱した後、焼入処理を施し、オーステナイト結晶
粒の粗大化の有無を調べた。The ferrite grain size and Ti
After measuring the total amount of Ti compounds excluding N, 9.0 mm
An M10 bolt was prepared by cold drawing to φ and performing cold working. This M10 bolt is further increased to 850 to 940
After heating at ℃, quenching treatment was performed, and the presence or absence of coarsening of austenite crystal grains was examined.
【００３０】尚、１０．３ｍｍφ線材のフェライト結晶
粒度およびＴｉＮを除くＴｉ化合物量、並びにＭ１０ボ
ルトのオーステナイト結晶粒度は、夫々、下記の方法で
測定した。The ferrite grain size and the amount of the Ti compound excluding TiN of the 10.3 mmφ wire and the austenite grain size of M10 volts were measured by the following methods, respectively.
【００３１】［フェライト結晶粒度］ＪＩＳ Ｇ ０５
５２に準拠して測定した。[Ferrite grain size] JIS G05
52.
【００３２】［ＴｉＮを除くＴｉ化合物量］ドリル
（５．０ｍｍφ）を用い、１０．３ｍｍφの線材から切
粉を採取し、以下の手順によりＴｉ化合物を組成別に分
離して分析した。[Amount of Ti Compound Excluding TiN] Using a drill (5.0 mmφ), a chip was collected from a 10.3 mmφ wire, and the Ti compound was separated according to composition according to the following procedure and analyzed.
【００３３】上記切粉を１０％ＡＡ系電解法および４
％ＭＳ系電解法にて溶解し、０．１μｍのフィルターを
用いて残渣を抽出した（１次分離）。The above-mentioned chips were subjected to a 10% AA electrolysis method and
% MS-based electrolysis, and the residue was extracted using a 0.1 μm filter (primary separation).
【００３４】１次分離で得られた残渣をＨＣｌ（ＨＣ
ｌ：Ｈ2Ｏ＝１：１）で溶解した後、超音波処理を行
い、０．１μｍのフィルターを用いて残渣を抽出した
（２次分離）。The residue obtained in the first separation is separated from HCl (HC
1: H 2 O = 1: 1), followed by sonication, and the residue was extracted using a 0.1 μm filter (secondary separation).
【００３５】２次分離で得られた残渣を、５％Ｂｒ2
−メタノールと１４％Ｉ2−メタノールの混液中に加
え、６０℃×５ｍｉｎの条件で溶解した後、超音波処理
を行い、０．１μｍのフィルターを用いて残渣を抽出し
た（３次分離）。The residue obtained in the second separation is separated from 5% Br 2
-Methanol and 14% I 2 -Methanol were added, and dissolved under the conditions of 60 ° C. × 5 min, followed by ultrasonic treatment, and the residue was extracted using a 0.1 μm filter (third separation).
【００３６】３次分離で得られた溶液を蒸発乾固させ
た後、ＨＣｌ（ＨＣｌ：Ｈ2Ｏ＝１：１）とＨ2Ｏ2の混
液で溶解してからＩＣＰ法でＴｉＳを定量した。……
（１） また、溶液については灼熱・灰化した後、Ｎａ2Ｏ3及び
Ｎａ2Ｂ4Ｏ7で融解し、更にＨＣｌ，Ｈ2Ｏ2及びＨ2Ｏの
混液で溶解してから、ＩＣＰ分析法で［Ｔｉ＋Ｔｉ4Ｃ2
Ｓ2＋ＴｉＣ］を分析した。……（２） 上記（１）＋（２）を、ＴｉＮを除くＴｉ化合物量とし
て算出した。After evaporating the solution obtained by the tertiary separation to dryness, it was dissolved in a mixed solution of HCl (HCl: H 2 O = 1: 1) and H 2 O 2 , and TiS was quantified by the ICP method. . ......
(1) Further, after the solution was scorched and incinerated, it was melted with Na 2 O 3 and Na 2 B 4 O 7 , further dissolved with a mixed solution of HCl, H 2 O 2 and H 2 O, and then subjected to ICP. [Ti + Ti 4 C 2
[S 2 + TiC] was analyzed. (2) The above (1) + (2) was calculated as the amount of Ti compound excluding TiN.
【００３７】［オーステナイト結晶粒度］ＪＩＳ Ｇ
０５５１に準拠して測定し、オーステナイト結晶粒度Ｎ
o.が５番未満か、或いはオーステナイト結晶粒度が３番
以上離れたものをオーステナイト結晶粒の粗大化発生有
りと判定した。[Austenite grain size] JIS G
Austenitic grain size N
When o. was less than 5 or the austenite grain size was 3 or more away, it was judged that the austenite grains were coarsened.
【００３８】各鋼種の圧延加熱条件・圧延仕上条件、１
０．３ｍｍφ線材のフェライト結晶粒度、ＴｉＮを除く
Ｔｉ化合物量およびＧ値を表２に併記する。更に、図１
には、Ｇ値や焼入温度を種々変化させた場合におけるＭ
１０ボルトのオーステナイト結晶粒の粗大化状況をグラ
フ化して表す。Rolling heating conditions and rolling finishing conditions for each steel type, 1
Table 2 also shows the ferrite crystal grain size, the amount of Ti compound excluding TiN, and the G value of the 0.3 mmφ wire. Further, FIG.
In the case where G value and quenching temperature are variously changed, M
The graph shows the state of coarsening of austenite crystal grains of 10 volts.
【００３９】[0039]
【表１】 [Table 1]
【００４０】[0040]
【表２】 [Table 2]
【００４１】表および図の結果より次の様に考察するこ
とができる。The following can be considered from the results of the tables and figures.
【００４２】Ｎo.１〜８，１１，１２，１７，１８…本
発明で規定する化学組成およびＧ値を満足する鋼を用い
た例であり、連続鋳造法、造塊法のいずれの溶製法を採
用しようとも、焼入加熱温度（圧延加熱条件、圧延仕上
条件）に関係なく、オーステナイト結晶粒の粗大化は見
られなかった。Nos. 1 to 8, 11, 12, 17, 18 ... These are examples using steel satisfying the chemical composition and G value specified in the present invention. No austenitic crystal grains were coarsened regardless of the quenching heating temperature (rolling heating conditions and rolling finishing conditions).
【００４３】Ｎo.９，１０，１５，１６…化学組成は本
発明の要件を満足しており、式（１）を満足する範囲内
ではオーステナイト結晶粒の粗大化は認められなかっ
た。No. 9, 10, 15, 16 ... The chemical composition satisfies the requirements of the present invention, and no coarsening of austenite crystal grains was observed within the range satisfying the formula (1).
【００４４】Ｎo.１３，１４…Ｔｉ量が少なく且つＧ値
が規定外の鋼を用いた例であり、焼入加熱温度を種々変
えてもオーステナイト結晶粒の粗大化が見られた。No. 13, 14,... This is an example of using a steel with a small Ti content and a G value outside the specified range, and coarsening of austenite crystal grains was observed even when the quenching heating temperature was variously changed.
【００４５】Ｎo.１７，１８…Ｔｉ量の多い鋼を用いた
例であり、オーステナイト結晶粒の粗大化効果が飽和し
ている。Nos. 17, 18,... Are examples using steel with a large amount of Ti, and the effect of coarsening austenite crystal grains is saturated.
【００４６】[0046]
【発明の効果】本発明鋼は上記の様に構成されているの
で、焼入れ加熱前における加熱速度や加熱温度等を制御
しなくとも、オーステナイト結晶粒度番号が５以上の微
細結晶粒を含有し、且つ引張強度が７８５Ｎ／ｍｍ2を
超える高強度ボルトを効率よく製造することができる。Since the steel of the present invention is constituted as described above, even if the heating rate and the heating temperature before quenching and heating are not controlled, the steel contains fine crystal grains having an austenite grain size number of 5 or more, In addition, a high-strength bolt having a tensile strength exceeding 785 N / mm 2 can be efficiently manufactured.
【図１】Ｇ値と焼入温度を種々変化させた場合における
ボルトのオーステナイト結晶粒の粗大化状況を示すグラ
フ。FIG. 1 is a graph showing a state of coarsening of austenite crystal grains of a bolt when G value and quenching temperature are variously changed.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 並村 裕一 神戸市灘区灘浜東町２番地 株式会社神戸 製鋼所神戸製鉄所内 (72)発明者 長谷川 豊文 神戸市灘区灘浜東町２番地 株式会社神戸 製鋼所神戸製鉄所内 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Namimura 2nd Nadahama Higashicho, Nada-ku, Kobe Kobe Steel Works, Ltd. Inside Kobe Works (72) Inventor Toyofumi Hasegawa 2nd Nadahama-Higashicho, Nada-ku, Kobe Kobe Steel, Ltd. In Kobe Works
Claims (4)
高強度ボルト用鋼。 ［ＴｉＮを除くＴｉ化合物の合計量／ＦＧｃ1/2］×1000 ≧（Ｙ−７７５）／７０ …… （１） （式中、ＦＧｃ：鋼を熱間圧延したときのフェライト結
晶粒度，Ｙ：焼入温度（℃）を夫々意味する）1. The chemical composition of steel is B: 0.0008 to 0.004% (meaning by mass%, the same applies hereinafter), C: 0.4% or less (excluding 0%), Ti: 0.025 to 0.06%, N: 0.006% The following (excluding 0%), balance: Fe and inevitable impurities, and satisfy the following formula (1). [Total amount of Ti compounds excluding TiN / FGc 1/2 ] × 1000 ≧ (Y−775) / 70 (1) (wherein, FGc: ferrite grain size when steel is hot-rolled, Y: Quenching temperature (℃) means each)
高強度ボルト用鋼。 ［ＴｉＮを除くＴｉ化合物の合計量／ＦＧｃ1/2］×1000 ≧３ …… （２） （式中、ＦＧｃは前と同じ意味）2. The chemical composition of steel is B: 0.0008 to 0.004%, C: 0.4% or less (excluding 0%), Ti: 0.025 to 0.06%, N: 0.006% or less (excluding 0%), The balance: Fe and unavoidable impurities, and a high-strength bolt steel satisfying the following expression (2). [Total amount of Ti compounds excluding TiN / FGc 1/2 ] × 1000 ≧ 3 (2) (in the formula, FGc has the same meaning as before)
２に記載の高強度ボルト用鋼。3. The steel further comprises at least: Si: 0.35% or less (excluding 0%), Mn: 2% or less (excluding 0%), Al: 0.1% or less (excluding 0%). The high-strength steel for bolts according to claim 1, wherein the steel contains one kind.
用鋼を用いて得られる高強度ボルト。4. A high-strength bolt obtained by using the steel for bolts according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20741596A JP3507626B2 (en) | 1996-08-06 | 1996-08-06 | Steel for high strength bolts and high strength bolts |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20741596A JP3507626B2 (en) | 1996-08-06 | 1996-08-06 | Steel for high strength bolts and high strength bolts |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1053834A true JPH1053834A (en) | 1998-02-24 |
| JP3507626B2 JP3507626B2 (en) | 2004-03-15 |
Family
ID=16539379
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20741596A Expired - Lifetime JP3507626B2 (en) | 1996-08-06 | 1996-08-06 | Steel for high strength bolts and high strength bolts |
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| Country | Link |
|---|---|
| JP (1) | JP3507626B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004360022A (en) * | 2003-06-05 | 2004-12-24 | Nippon Steel Corp | HIGH-STRENGTH Al-PLATED WIRE OR BOLT EXCELLENT IN DELAYED FRACTURE RESISTANCE AND METHOD FOR PRODUCING THE SAME |
| WO2015083599A1 (en) | 2013-12-02 | 2015-06-11 | 株式会社神戸製鋼所 | Steel wire for bolt, bolt, and production method therefor |
| WO2017094487A1 (en) | 2015-12-04 | 2017-06-08 | 新日鐵住金株式会社 | High-strength bolt |
| US10669604B2 (en) | 2015-06-29 | 2020-06-02 | Nippon Steel Corporation | Bolt |
-
1996
- 1996-08-06 JP JP20741596A patent/JP3507626B2/en not_active Expired - Lifetime
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004360022A (en) * | 2003-06-05 | 2004-12-24 | Nippon Steel Corp | HIGH-STRENGTH Al-PLATED WIRE OR BOLT EXCELLENT IN DELAYED FRACTURE RESISTANCE AND METHOD FOR PRODUCING THE SAME |
| WO2015083599A1 (en) | 2013-12-02 | 2015-06-11 | 株式会社神戸製鋼所 | Steel wire for bolt, bolt, and production method therefor |
| KR20160088372A (en) | 2013-12-02 | 2016-07-25 | 가부시키가이샤 고베 세이코쇼 | Steel wire for bolt, bolt, and production method therefor |
| US10669604B2 (en) | 2015-06-29 | 2020-06-02 | Nippon Steel Corporation | Bolt |
| WO2017094487A1 (en) | 2015-12-04 | 2017-06-08 | 新日鐵住金株式会社 | High-strength bolt |
| KR20180082543A (en) | 2015-12-04 | 2018-07-18 | 신닛테츠스미킨 카부시키카이샤 | High strength bolt |
| US10487372B2 (en) | 2015-12-04 | 2019-11-26 | Nippon Steel Corporation | High-strength bolt |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3507626B2 (en) | 2004-03-15 |
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