JP2779449B2 - Manufacturing method of large diameter bolt - Google Patents
Manufacturing method of large diameter boltInfo
- Publication number
- JP2779449B2 JP2779449B2 JP31936288A JP31936288A JP2779449B2 JP 2779449 B2 JP2779449 B2 JP 2779449B2 JP 31936288 A JP31936288 A JP 31936288A JP 31936288 A JP31936288 A JP 31936288A JP 2779449 B2 JP2779449 B2 JP 2779449B2
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Description
【発明の詳細な説明】 「発明の目的」 （産業上の利用分野） この発明は、太径ボルトの製造方法に関するものであ
る。The present invention relates to a method for manufacturing a large-diameter bolt.
（従来の技術） 焼入れ、焼戻し後の強度が75kgf/mm2以上のボルト用
鋼として25φ以下の用途ではSWRCH35Kが広く用いられて
いる。然し、該鋼は焼き入れ性が低く、水焼き入れを行
なっても太径になると中心部の硬度が低いため、最高25
mmφまでの径のものにしか適用できない。そのため25mm
φ以上の太径のボルト用鋼としては、SCR440等の合金鋼
が使用されてきた。然し、該合金鋼の場合は圧延ままで
の強度が高いため、そのまま冷間鍛造に供することはで
きず、鍛造前に焼鈍を行なうと云う余分な工程を必要と
していた。又、焼入れ性向上の元素としてはＢが広く知
られているが、焼入れ性の安定性の再現性に若干問題の
あるところから、利用分野によってＢ含有鋼の使用を躊
躇するところがあるのが現状である。(Conventional technology) SWRCH35K is widely used as a steel for bolts having a strength after quenching and tempering of 75 kgf / mm 2 or more and a diameter of 25 φ or less. However, the steel has low hardenability, and even if it is water-quenched, the hardness of the central part is low when the diameter becomes large, so that the maximum of 25
Applicable only to diameters up to mmφ. So 25mm
Alloy steel such as SCR440 has been used as steel for bolts having a diameter larger than φ. However, in the case of the alloy steel, since the strength as rolled is high, it cannot be subjected to cold forging as it is, and an extra step of annealing before forging is required. B is widely known as an element for improving hardenability. However, there is a slight problem in reproducibility of stability of hardenability. It is.
（発明が解決しようとする課題） 本発明は、上述したような太径ボルト製造業界の現状
に鑑み創案されたものであって、Ｂを添加することな
く、而も軟化焼鈍なしで、冷間鍛造が可能であり、水焼
入れ、焼戻しにより強度75kgf/mm2以上の高強度を有す
る太径ボルトの製造方法を提供することを目的とする。(Problems to be Solved by the Invention) The present invention was conceived in view of the current situation in the large-diameter bolt manufacturing industry as described above. An object of the present invention is to provide a method for manufacturing a large-diameter bolt which can be forged, has high strength of 75 kgf / mm 2 or more by water quenching and tempering.
「発明の構成」 （課題を解決するための手段） 前述の目的を達成するために、本発明者等は、 （１） 重量％で、 C:0.28〜0.38％、Si:0.10％以下、Mn:0.60〜1.20％、C
r:0.20〜0.60％、を含み、下式により計算されるDI値が
30〜45を満足する残部鉄および不可避的不純物からなる
鋼線材から、冷間鍛造によりねじ部の外径25〜40mmのボ
ルトを成型し、次いで加熱し、水焼入れ、焼戻しを行な
うことを特徴とする太径ボルトの製造方法。"Constitution of the Invention" (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors (1) by weight%: C: 0.28 to 0.38%, Si: 0.10% or less, Mn : 0.60 to 1.20%, C
r: 0.20 to 0.60%, include, D I value calculated by the following formula
From steel wire consisting of the balance iron and unavoidable impurities satisfying 30 to 45, a bolt with an outer diameter of 25 to 40 mm of the screw part is formed by cold forging, and then heated, water-quenched, and tempered. To manufacture large diameter bolts.
但し、式中元素名は該元素含有重量％値で計算する。 However, the name of the element in the formula is calculated by the value of the element content% by weight.
（２） 重量％で、 C:0.28〜0.38％、Si:0.10％以下、Mn:0.60〜1.20％、C
r:0.20〜0.60％、を含み、更にTi、Zr、Nb、の内の１種
もしくは２種以上を0.005〜0.050％を含有し、下式によ
り計算されるDI値が30〜45を満足する残部鉄及び不可避
的不純物からなる鋼線材から、冷間鍛造によりねじ部の
外径25〜40mmのボルトを成型し、次いで加熱し、水焼入
れ、焼戻しを行なうことを特徴とする太径ボルトの製造
方法。(2) By weight%, C: 0.28 to 0.38%, Si: 0.10% or less, Mn: 0.60 to 1.20%, C
r: 0.20 to 0.60% wherein the further Ti, Zr, Nb, one or two or more of the containing 0.005 to 0.050 percent, satisfy D I value 30-45, which is calculated by the following equation From the steel wire consisting of the remaining iron and unavoidable impurities, a bolt with an outer diameter of the thread of 25 to 40 mm is formed by cold forging, then heated, water-quenched, and tempered. Production method.
但し、式中元素名は該元素含有重量％値で計算する。 However, the name of the element in the formula is calculated by the value of the element content% by weight.
を茲に提案する。本発明方法により太径ボルトを製造す
る場合には、高価な合金元素の添加を本質的には必要と
せず、又、従来のSCR440等のような軟化焼鈍の工程を必
要とすることなく、強度75kgf/mm2以上の太径ボルトを
得ることができる。Is proposed here. When a large diameter bolt is manufactured by the method of the present invention, the addition of expensive alloy elements is essentially unnecessary, and the strength of the bolt is reduced without the need for a soft annealing step such as the conventional SCR440. A large diameter bolt of 75 kgf / mm 2 or more can be obtained.
（作用） 本発明方法は下記に述べる化学組成、DI値、熱処理条
件により特定されるものであるが、主たる特徴は、少量
のCrの添加と、固溶Ｎを固定する元素の添加により圧延
まま鋼線材の強度を上げないことに成功したことであ
り、ボルト成型後の通常の熱処理により、高強度ボルト
を簡単に製造することを可能にしたことである。(Operation) The present invention method is the chemical composition described below, D I value, but those specified by heat treatment conditions, the main feature is rolling and the addition of a small amount of Cr, the addition of the element for fixing the solute N This means that the strength of the steel wire rod has not been increased as it is, and that high-strength bolts can be easily manufactured by ordinary heat treatment after bolt forming.
先ず、化学的組成について各元素の機能並びに数値限
定の理由について述べる。First, the function of each element in the chemical composition and the reason for limiting the numerical values will be described.
C:0.28〜0.38％ 鋼の強度を確保するのに重要な元素である。然し、0.
28％未満では所望の強度が得られず、一方0.38％を超え
て添加する場合には、冷間鍛造性が低下し、ボルトに加
工する際に軟化焼鈍を必要とするのでこの範囲とした。C: 0.28-0.38% It is an important element to secure the strength of steel. But 0.
If it is less than 28%, the desired strength cannot be obtained, while if it exceeds 0.38%, the cold forgeability deteriorates and softening annealing is required when working into bolts.
Si:0.10％以下 フェライトに固溶して鋼を強化し、鋼の変形能を低下
させるが、0.10％を超えて添加すると冷間鍛造時に割れ
が発生する危険性を増すので0.10％を上限とする。Si: 0.10% or less Solid solution in ferrite strengthens the steel and reduces the deformability of the steel. However, adding more than 0.10% increases the risk of cracking during cold forging, so the upper limit is 0.10%. I do.
Mn:0.60〜1.20％ 焼き入れ性を向上せしめる重要な元素である。然し、
0.60％未満ではその効果は少なく、一方1.20％を超えて
添加する場合には加工性の低下が著しいので、0.60〜1.
20％の範囲とした。Mn: 0.60 to 1.20% An important element that improves hardenability. But
If it is less than 0.60%, the effect is small, while if it exceeds 1.20%, the workability is significantly reduced.
The range was 20%.
Cr:0.20〜0.60％ Mnと同様に焼き入れ性を向上せしめる重要な元素であ
る。然し、0.20％未満ではその効果は小さく、一方0.60
％超えて添加すると鋼の強度は増大するが加工性は低下
するので、0.20〜0.60％の範囲とした。Cr: 0.20 to 0.60% Like Mn, it is an important element that improves hardenability. However, below 0.20%, the effect is small, while 0.60%
%, The strength of the steel increases, but the workability decreases. Therefore, the content is set in the range of 0.20 to 0.60%.
DI:30〜45 焼き入れ、焼き戻し後のボルトの強度を85kgf/mm2、
即ちロックウェルＣ硬さ25目標とした場合、焼き入れま
までの中心硬度はロックウェルC40を必要とする。25mm
φ棒の中心部の冷却速度は水冷の場合、ジョミニー試験
における端からの距離が5mm位置の冷却速度に相当す
る。同様に40mmφの場合には8mmに相当する。即ち25mm
φの場合はジョミニー端5mm（J5）で硬さ40となる焼き
入れ性、40mmφの場合はJ8で硬さ40となる焼き入れ性を
必要とする。D I : 30-45 The strength of the bolt after quenching and tempering is 85 kgf / mm 2 ,
That is, when the target of the Rockwell C hardness is 25, the center hardness as quenched requires the Rockwell C40. 25mm
In the case of water cooling, the cooling rate at the center of the φ rod corresponds to the cooling rate at a position 5 mm away from the end in the Jominy test. Similarly, in the case of 40 mmφ, it corresponds to 8 mm. That is, 25mm
hardenability as a hardness 40 Jominy end 5 mm (J 5) In the case of phi, in the case of 40mmφ require hardenability as the hardness 40 J 8.
そこでGrossmannによって与えられたジョミニー距離
と理想臨界直径DIの関係を式にすると、DI＝6.251×Ｊ
−0.0990×J2＋0.0007905×J3となる。ここのＪに５を
入れて計算したDI値は28.9mm、Ｊ＝８のときは44.7mmと
なる。即ち必要DIは28.9〜44.7となる。以上の理由によ
りDIの限定範囲を30〜45とした。DI値の計算は広く使わ
れている係数を用いた下式による。Therefore, the relationship between the Jominy distance given by Grossmann and the ideal critical diameter D I is expressed as D I = 6.251 × J
−0.0990 × J 2 + 0.0007905 × J 3 D I value calculated taking the 5 here of J becomes 44.7mm when 28.9Mm, the J = 8. That is necessary D I will be 28.9 to 44.7. And 30 to 45 of the limited range of D I above reasons. By the following equation using the coefficient calculation widely used of D I value.
但し、式中元素名は該元素含有重量％値で計算する。 However, the name of the element in the formula is calculated by the value of the element content% by weight.
選択元素:Ti、Zr、Nb、のうち１種もしくは２種以上0.0
05〜0.050％ これらの３元素は、Ｎとの親和力が強く、固溶してい
るＮを窒化物として固定し無害化するのに有効である。
然し、その１種もしくは２種以上の合計量が、0.005％
未満ではその効果が小さく、一方0.050％を超えて添加
しても、その効果は飽和してくると共に、鋼の清浄性は
低下することとなるので、0.005〜0.050％の範囲とし
た。Selective element: One, two or more of Ti, Zr and Nb 0.0
05 to 0.050% These three elements have a strong affinity for N, and are effective for fixing solid solution N as a nitride and rendering it harmless.
However, the total amount of one or more of them is 0.005%
If it is less than 0.050%, the effect is small. On the other hand, if it exceeds 0.050%, the effect will be saturated and the cleanliness of the steel will decrease. Therefore, the range is 0.005 to 0.050%.
尚、鋼中の全Ｎ量を安定して40ppm未満に抑えること
ができる場合には、歪み時効による硬化は小さく、冷間
鍛造性に与える影響も小さいので、これらの元素は添加
しなくてもよい。但し、一般的には鋼中には、40〜100p
pmが含まれており、冷間鍛造中に歪時効を起こして加工
性を低下せしめている。If the total amount of N in the steel can be stably suppressed to less than 40 ppm, the hardening due to strain aging is small and the influence on the cold forgeability is small. Good. However, in general, in steel, 40-100p
pm, which causes strain aging during cold forging and reduces workability.
次いで、冷間鍛造により成型するボルトの直径をねじ
部の外径25〜40mmの範囲に限定したのは、ねじ部の外径
25mm未満の小径では化学組成を特に厳密に規定しなくて
も、焼入れ、焼戻し後の強度が比較的簡単に得られ、一
方ねじ部の外径40mmを超える場合には特殊な合金元素の
添加もしくは熱処理条件を必要とするので、本願発明の
範囲外としたのがその理由である。Next, the diameter of the bolt formed by cold forging was limited to the range of the outer diameter of the threaded portion of 25 to 40 mm.
With a small diameter of less than 25 mm, the strength after quenching and tempering can be obtained relatively easily, even if the chemical composition is not strictly specified.On the other hand, if the outer diameter of the thread exceeds 40 mm, addition of a special alloy element or Since heat treatment conditions are required, the reason for this is that the present invention is out of the scope of the present invention.
最後に熱処理条件であるが、化学的組成、DI値等のよ
うな数値限定の必要はなく、通常の加熱、水焼入れ、焼
戻し条件で充分である。Is a last heat treatment conditions, chemical composition, it is not necessary numerical limitations such as D I values and the like, is sufficient conventional heating, water quenching, tempering conditions.
加熱温度はオーステナイト化するに充分な温度で、且
つ加熱によってオーステナイト粒の粗大化を起こさない
温度、即ちA3＋50℃程度の温度に加熱する。加熱時間は
60〜90分が一般的である。The heating temperature is a temperature sufficient for austenitization and heating to a temperature at which the austenite grains are not coarsened by heating, that is, a temperature of about A 3 + 50 ° C. The heating time is
60-90 minutes is common.
水焼入れ温度の水温は常温（約５〜25℃）が用いられ
る。水槽は冷却むらの発生を防止するため十分に撹拌す
る。A normal temperature (about 5 to 25 ° C.) is used as the water temperature of the water quenching temperature. The water tank is sufficiently stirred to prevent generation of uneven cooling.
焼戻し温度は430〜600℃の範囲内で60〜120分焼戻
す。焼戻し後は焼戻し脆性を防止するためできるだけ速
い速度で冷却する。Tempering temperature is in the range of 430-600 ° C for 60-120 minutes. After tempering, cooling is performed at a rate as fast as possible to prevent temper brittleness.
（実施例） 第１表に供試鋼としての本発明鋼（本発明方法により
得られた鋼）、従来鋼、比較鋼（化学組成の何れかを本
発明の範囲外とした鋼）の化学組成とDI値を示した。熱
処理の条件は下記の通りである。860℃で60分間加熱後2
5℃の水中に入れて焼入れを行ない、500℃で70分間加熱
して焼戻し後、25℃の水中に入れて冷却した。(Examples) Chemical properties of steels of the present invention (steels obtained by the method of the present invention), conventional steels, and comparative steels (steels having any chemical composition outside the scope of the present invention) as test steels in Table 1. It showed composition and D I value. The conditions of the heat treatment are as follows. After heating at 860 ° C for 60 minutes 2
It was quenched in water at 5 ° C., heated at 500 ° C. for 70 minutes, tempered, and then cooled in water at 25 ° C.
第２表は第１表の供試鋼に関する試験結果を示すもの
である。 Table 2 shows the test results for the test steels in Table 1.
No.1、No.2は本発明鋼である。圧延ままでの強度が低
いため、ボルト加工時の割れもなく、熱処理後も充分な
強度を有している。No.1はＮ固定元素としてTiを添加
し、No.2はNbは添加した例である。No.3はMnの含有量を
やや高くした場合の本発明鋼であり、ボルト加工時の割
れもなく熱処理後も充分な強度を有しており、Ｎ固定元
素としてはZrを用いた例である。No.4も本発明鋼の例で
あるが、Ｎ固定元素とし、Ti、Nbの２種類の元素を適量
添加したものであり、勿論、加工時の割れ発生もなく、
焼入れ焼戻し後の引張強さは90kgf/mm2にも達してい
る。No.5はＮの含有量が低いために、Ti、Zr、Nb等を添
加しなかった本発明の例であるが、焼入れ焼戻し後の引
張強さは91kgf/mm2の高い値が得られている。No. 1 and No. 2 are steels of the present invention. Since the strength as it is rolled is low, there is no cracking at the time of bolting, and it has sufficient strength after heat treatment. No. 1 is an example in which Ti was added as an N fixing element, and No. 2 was an example in which Nb was added. No. 3 is a steel of the present invention when the content of Mn is slightly increased, has no cracks during bolting, has sufficient strength even after heat treatment, and is an example using Zr as an N fixing element. is there. No. 4 is also an example of the steel of the present invention, but as an N-fixing element, an appropriate amount of two kinds of elements, Ti and Nb, was added.
The tensile strength after quenching and tempering has reached 90 kgf / mm 2 . No.5 is due to the low content of N, Ti, Zr, is an example of the present invention without addition of Nb or the like, the tensile strength after quenching and tempering is obtained a high value of 91kgf / mm 2 ing.
No.6の従来鋼としては、SWRCH35Kを用いたものである
が、72kgf/mm2の強度しか得られていない。No.7はDI値
が不足している比較鋼であるが、74kgf/mm2の強度しか
得られていない。No.8はSi、Crの含有量が多過ぎる例で
あり、このため圧延材の絞り値が低くボルト加工時に割
れを生じた比較例である。No.9はＣ、Mnが低く、DI値が
不足していることによりボルトの強度が低い比較例。N
o.10はＣ量が高いため延性が不足しボルト加工時は割れ
を発生した比較例である。No.11は組成的には本発明鋼N
o.3に近いものであるが、Ｎ固定元素としてTiが少ない
ため、冷間鍛造時に固溶Ｎに起因する歪み時効硬化を起
し割れを発生している。No.12はＮ固定用のTiの添加量
が過剰のため延性が低下し、割れが発生した例である。
最後のNo.13は、Mn量が過剰のため延性不足のためボル
ト加工時に割れを発生した比較鋼である。As No. 6 conventional steel, SWRCH35K was used, but only a strength of 72 kgf / mm 2 was obtained. No.7 is a comparative steel D I value is insufficient, not only obtained the strength of 74kgf / mm 2. No. 8 is an example in which the contents of Si and Cr are too large, and is a comparative example in which the reduced value of the rolled material is low and cracks occur during bolt working. No. 9 is a comparative example in which the strength of the bolt is low due to low C and Mn and insufficient DI value. N
o.10 is a comparative example in which ductility was insufficient due to a high C content and cracks occurred during bolting. No. 11 is steel N of the present invention in composition.
Although close to o.3, since Ti is a small N-fixing element, strain age hardening due to solid solution N occurs during cold forging and cracks occur. No. 12 is an example in which the addition of Ti for fixing N was excessive, resulting in a decrease in ductility and cracking.
Finally, No. 13 is a comparative steel in which cracks occurred during bolting due to insufficient ductility due to an excessive amount of Mn.
この第１〜２表から本願発明方法により得られた鋼材
を使用する場合には、ボルト加工時に割れを発生するこ
となく、而も焼入れ焼戻し後の引張強度が悉く80kgf/mm
2を超えていることが判る。From Tables 1 and 2, when using the steel material obtained by the method of the present invention, the tensile strength after quenching and tempering was 80 kgf / mm without cracking during bolting.
It turns out that it exceeds 2 .
「発明の効果」 以上詳述したように、本発明方法により得られた鋼材
を用い、ボルトねじ部外径25〜40mmのボルトを製造する
場合には、軟化焼鈍を必要とせず、直接冷間鍛造が可能
であり、而も充分な焼入れ性を有しているから、ボルト
加工時に割れを発生することなく、焼入れ、焼き戻し後
の引張強度75kgf/mm2以上のボルトを安価に製造するこ
とができる。SCR440等の低合金鋼を使用する場合と異な
り、軟化焼鈍を必要としないので生産性に寄与するとこ
ろが頗る大きい。 "Effects of the Invention" As described in detail above, in the case of manufacturing a bolt having an outer diameter of 25 to 40 mm using a steel material obtained by the method of the present invention, it is not necessary to perform soft annealing, forging are possible, because Thus, also have sufficient hardenability, without generating cracks at the time of bolt machining, quenching, be produced at a low cost tensile strength 75 kgf / mm 2 or more bolts after tempering Can be. Unlike the case where a low alloy steel such as SCR440 is used, softening annealing is not required, which greatly contributes to productivity.
Claims (2)
r:0.20〜0.60％、を含み、下式により計算されるDI値が
30〜45を満足する残部鉄および不可避的不純物からなる
鋼線材から、冷間鍛造によりねじ部の外径25〜40mmのボ
ルトを成型し、次いで加熱し、水焼入れ、焼戻しを行な
うことを特徴とする太径ボルトの製造方法。 但し、式中元素名は該元素含有重量％値で計算する。C .: 0.28 to 0.38%, Si: 0.10% or less, Mn: 0.60 to 1.20%, C
r: 0.20 to 0.60%, include, D I value calculated by the following formula
From steel wire consisting of the balance iron and unavoidable impurities satisfying 30 to 45, a bolt with an outer diameter of 25 to 40 mm of the screw part is formed by cold forging, and then heated, water-quenched, and tempered. To manufacture large diameter bolts. However, the name of the element in the formula is calculated by the value of the element content% by weight.
r:0.20〜0.60％、を含み、更にTi、Zr、Nb、の内の１種
もしくは２種以上を0.005〜0.050％を含有し、下式によ
り計算されるDI値が30〜45を満足する残部鉄及び不可避
的不純物からなる鋼線材から、冷間鍛造によりねじ部の
外径25〜40mmのボルトを成型し、次いで加熱し、水焼入
れ、焼戻しを行なうことを特徴とする太径ボルトの製造
方法。 但し、式中元素名は該元素含有重量％値で計算する。2. In% by weight, C: 0.28 to 0.38%, Si: 0.10% or less, Mn: 0.60 to 1.20%, C:
r: 0.20 to 0.60% wherein the further Ti, Zr, Nb, one or two or more of the containing 0.005 to 0.050 percent, satisfy D I value 30-45, which is calculated by the following equation From the steel wire consisting of the remaining iron and unavoidable impurities, a bolt with an outer diameter of the thread of 25 to 40 mm is formed by cold forging, then heated, water-quenched, and tempered. Production method. However, the name of the element in the formula is calculated by the value of the element content% by weight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31936288A JP2779449B2 (en) | 1988-12-20 | 1988-12-20 | Manufacturing method of large diameter bolt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31936288A JP2779449B2 (en) | 1988-12-20 | 1988-12-20 | Manufacturing method of large diameter bolt |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH02166231A JPH02166231A (en) | 1990-06-26 |
| JP2779449B2 true JP2779449B2 (en) | 1998-07-23 |
Family
ID=18109305
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31936288A Expired - Fee Related JP2779449B2 (en) | 1988-12-20 | 1988-12-20 | Manufacturing method of large diameter bolt |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2779449B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3315626B1 (en) * | 2015-06-29 | 2020-12-23 | Nippon Steel Corporation | Bolt |
-
1988
- 1988-12-20 JP JP31936288A patent/JP2779449B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH02166231A (en) | 1990-06-26 |
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