JP4117114B2

JP4117114B2 - Manufacturing method of welded closed high strength shear reinforcement

Info

Publication number: JP4117114B2
Application number: JP2001129521A
Authority: JP
Inventors: 健 ▲高▼濱; 雅光武井; 岩本　　隆
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 2001-04-26
Filing date: 2001-04-26
Publication date: 2008-07-16
Anticipated expiration: 2021-04-26
Also published as: JP2002327242A

Description

【０００１】
【発明の属する技術分野】
本発明は、溶接閉鎖高強度せん断補強筋に関する。
【０００２】
【従来の技術】
鉄筋コンクリート構造又はプレストレストコンクリート構造の柱又は梁等の部材では、曲げ剛性を高めるために、長手方向の主筋の周囲を囲繞するせん断補強筋が用いられる。従来のせん断補強筋は、両端部にフックを設けたもので、全体形状が角形、日の字形、目の字形、田の字形、囲の字形又はこれらを組み合わせた形状を有し、主筋を取り巻き、フックを主筋に係止して剪断力に対して抵抗するようになっていた。このフックを両端部に設ける代わりに両端部を相互に溶接接合してループを形成した閉鎖せん断補強筋とすることもあった。このような閉鎖せん断補強筋は、主筋の位置とは無関係に任意の位置で溶接接合することができるので、製造上の制約、取付け作業時の制約等がなく、またフックがなく、連続したせん断補強筋として賞用されている。しかし、溶接を施すことが困難な材質を用いることができない問題があった。また、特に引張強さが高く、耐力が大きい高強度せん断補強筋では、接合部や溶接熱影響境界部が母材に比べて低強度となったり、引張破損しやすいなどの問題があった。このため、優れた高強度の母材を用いても、溶接部の特性により制約されるという問題があった。
【０００３】
【発明が解決しようとする課題】
本発明は上記実情に鑑みてなされたもので、高強度、高耐力で溶接部の特性が母材部に比べて遜色のない、むしろ優れた特性を有する溶接閉鎖せん断補強筋を提供することを目的とする。
【０００４】
【課題を解決するための手段】
本発明は、上記目的を達成するために開発されたものであって、その技術的手段は、次の通りである。
【０００５】
Ｃ：０．１５〜０．４０質量％、
Ｓｉ：０．８〜２．０質量％、
Ｍｎ：０．８〜２．０質量％、
Ａｌ：０．００５〜０．０５０質量％、
Ｎｂ：０．００５〜０．１５０質量％、
Ｎ：０．００１５〜０．０１５０質量％
を含み、さらに、
Ｃｒ：０．０５〜２．００質量％、
Ｍｏ：０・０５〜１．００質量％、
Ｖ：０．０５〜１．００質量％、
の１種または２種以上を（Ｃｒ＋Ｍｏ＋Ｖ）≧０．５質量％含有し、残部がＦｅ及び不可避的不純物からなる鋼材を線棒状に熱間圧延を行った後徐冷を行い、硬度がＨＭＶ５００以下とした線棒材に、伸線及びまたは異形加工を行い、所定の焼入れを実施後、焼戻温度４００〜６００℃で焼戻しを行い、切断し、曲げ加工を行った後、その両端部をコブ状増径部を有しない形状に溶接し、その後焼鈍をすることなしに引張強さが１４２０Ｎ／ｍｍ^２以上、０．２％耐力が１２７５Ｎ／ｍｍ^２以上、破断後つき合わせ伸びが５％以上である溶接閉鎖高強度せん断補強筋とすることを特徴とする溶接閉鎖高強度せん断補強筋の製造方法を提供する。ＨＭＶはマイクロビッカース硬度である。
【０００６】
上記成分にさらに
Ｔｉ：０．００１〜０．１００質量％、
Ｂ：０．００３〜０．０１０質量％、
を１種または２種を含有すると好適である。
【０００７】
また、上記溶接閉鎖高強度せん断補強筋の製造方法においては、溶接熱影響境界部の硬度が母材部の硬度の９０％以上となる。さらに、母材部を含む引張破断が接合部以外で起こるものとすることができ、溶接熱影響部の形状がコブ状増径部を有しないものにおいても、引張強さが１４２０Ｎ／ｍｍ^２以上、０．２％耐力が１２７５Ｎ／ｍｍ^２以上、破断後つき合わせ伸びが５％以上である。本発明において、コブ状増径部とは、圧接溶接により溶接金属が接合部の外周部に盛り上がり接合部の外径が大きくなっている部分を言う。さらに、この溶接閉鎖高強度せん断補強筋において、溶接熱影響部を含む溶接個所を４６０〜６００℃で焼戻しを行い、接合部及び溶接熱影響部の硬度がＨＭＶ５５０以下とし、接合部及び溶接熱影響部と母材部の硬度との差が２０％以内とすると、好適である。
【０００８】
【発明の実施の形態】
以下、本発明の成分限定理由及び加工条件について説明する。
【０００９】
Ｃ：０．１５〜０．４０質量％、
Ｃは鋼の強度を上げるために必須の成分で、Ｃが高いと溶接熱影響境界部の強度低下が著しく、さらに溶接熱影響部の硬度が高くなり熱影響境界部との硬度の差が非常に大きくなる。本発明はＣ含有量を下げると共に合金成分を加え、強度の向上と溶接部の上記欠点をカバーすることとした。Ｃが、０．１５質量％を下回ると他の合金成分を加えても強度が不足するので０．１５質量％以上と規定する。一方Ｃが０．４０質量％を越えると、強度向上は得易いが溶接熱影響部と溶接熱影響境界部の差が大きくなり、曲げ加工性も劣化するので、特に溶接熱影響境界部の強度低下を抑えるために対熱軟化性の高い合金成分を加えると共にＣの上限を０．４０質量％とした。
【００１０】
Ｓｉ：０．８〜２．０質量％、
Ｓｉは、０．８質量％未満では０．２％耐力が不足すると共に脱酸能力が不十分となる。２．０質量％を越えて含有させると伸びや曲げ加工性が低下し、また強度上昇効果が飽和し効果がなくなるので上限を２．０質量％とした。
【００１１】
Ｍｎ：０．８〜２．０質量％、
Ｍｎは、脱酸、脱硫作用のために添加するもので、強度向上にも寄与する成分で、０．８質量％未満では効果が乏しく、２．０質量％を越える量を含有すると、溶接性、曲げ加工性に悪影響があり、強度向上も飽和するので２．０質量％を上限とする。
【００１２】
Ａｌ：０．００５〜０．０５０質量％、
Ａｌは、結晶粒を微粒化にすることができ、延性や曲げ性を向上させる。Ａｌは０．００５質量％以上必要である。しかし多く含有しすぎると粒大な酸化物を生成して延性に悪影響を及ぼすので、０．０５０質量％までに限定した。
【００１３】
Ｎｂ：０．００５〜０．１５０質量％
Ｎｂは、析出硬化による焼戻し後の強度を上昇させるとともに、組織の微細化にも有効な成分であるため、鋼材の焼入れ焼戻し後の強度の向上に有効である。Ｎｂ量が０．００５質量％未満では必要な効果が得られず、一方、０．１５０質量％を超えて添加しても効果が飽和して経済的でないので、０．００５〜０．１５０質量％の範囲で添加するものとした。
【００１４】
Ｎ：０．００１５〜０．０１５０質量％
Ｎは、ＡｌやＮｂと結合して組織を微細化させる成分であるとともに、鋼中の固溶Ｎ自身も焼入れ焼戻し後の組織の微細化に有効である。Ｎ量が０．００１５質量％に満たないと十分な効果が得られない。一方、０．０１５０質量％を超えて含有させると効果が飽和し、脆化のおそれもあるため、０．００１５〜０．０１５０質量％とした。
【００１５】
Ｃｒ：０．０５〜２．００質量％
Ｃｒは、焼入れ性を向上させるとともに、焼戻し時の炭窒化物析出により強度を上昇させ、鋼の焼戻し軟化抵抗を上昇させ溶接時の熱影響境界部での硬度低下を押さえることに有効な成分である。Ｃｒ量が０．０５質量％未満では必要な効果が得られず、２．００質量％を超えて添加しても効果が飽和するばかりか、経済的でないので、０．０５〜２．００質量％の添加とした。
【００１６】
Ｍｏ：０．０５〜１．００質量％、Ｖ：０．０５〜１．００質量％
Ｍｏ及びＶは、析出硬化により焼戻し後の強度を上昇させ、Ｃｒ同様に組織の微細化にも有効に作用することで、焼入れ焼戻し後の強度を向上させるのに極めて有効な成分である。これらの成分量が０．０５質量％未満では必要な効果がえられず、一方、１．００質量％を超えて添加しても効果が飽和するばかりか経済的でないので、それぞれ０．０５〜１．００質量％の添加とした。
【００１７】
（Ｃｒ＋Ｍｏ＋Ｖ）≧０．５質量％
上述したＣｒ、Ｍｏ及びＶは、単独添加、あるいは２種以上の複合添加のいずれでも構わないが、これらの成分の添加量の総量が０．５質量％に満たない場合には、焼入れ焼戻し後に必要な強度を得ることができないそのため、Ｃｒ、Ｍｏ及びＶの添加量は、それぞれ上記の範囲でかつ、（Ｃｒ＋Ｍｏ＋Ｖ）≧０．５質量％を満たすことを必要とする。
【００１８】
Ｔｉ：０．００１〜０．１００質量％、
Ｔｉは、結晶粒を微粒化にすることができ、延性や曲げ性を向上させる。Ｔｉは０．００１質量％未満では添加の効果が乏しく、０．１００質量％を超えて含有させても効果が飽和し、更に多くなると延性に悪影響を及ぼすので、０．００１質量％〜０．１００質量％に限定した。
【００１９】
Ｂ：０．０００３〜０．０１００質量％、
Ｂは微量添加で焼入性を大幅向上させ、組織改善に寄与する元素である。０．０００３質量％以上必要であり、一方、０．０１００質量％を越えても効果が飽和し更に靭性が低下するので不可である。
【００２０】
次に、処理条件について説明する。
【００２１】
この鋼は線棒状に熱間圧延を行った後、硬度がＨＭＶ５００以下となるように徐冷する。硬度がＨＭＶ５００を超えるものでは伸線、異形加工などの後工程での加工性が著しく低下するため好ましくない。
【００２２】
焼戻し温度は４００〜６００℃の範囲とした。これは熱軟化抵性の高い合金元素を多く含んでいるため規格強度と伸びのバランスを両立できる温度範囲が高めとなったためである。４００℃未満では伸びが規格に満たないので不可であり、６００℃を超えると規格強度を割るので限定した。
【００２３】
溶接閉鎖高強度せん断補強筋によって、溶接熱影響境界部の硬度の低下が少なく母材部の硬度の９０％以上ある溶接閉鎖高強度せん断補強筋が得られる。熱影響境界部が母材部の硬度の９０％を下回ると、引張試験時にたとえ狭い範囲の境界部といえども境界部から破断する。又引張強さが１４２０Ｎ／ｍｍ²以上、０．２％耐力が１２７５Ｎ／ｍｍ²以上、破断後つき合わせ伸びが５％以上であることを満足させることができない。
【００２４】
溶接閉鎖高強度せん断補強筋は、接合部及び熱影響部と母材部を含めて引張試験を行ったとき接合部で破断しない。接合部で破断した際には引張強さが１４２０Ｎ／ｍｍ²以上、０．２％耐力が１２７５Ｎ／ｍｍ²以上、破断後つき合わせ伸びが５％以上であることを満足させることができないこと、また接合部で破断することそれ自体が溶接継ぎ手性能を満足させることができないため接合部で破断しないとした。
【００２５】
溶接閉鎖高強度せん断補強筋において、図３に示すように、母材１を接合部で突き合わせ溶接したとき、溶接部２の形状がコブ状増径部６を有するもの（参考例）がある。また、このコブ状増径部を有しないものがある。両方とも性能を満足する。コブ状増径部を有しないものにおいては溶接部の増径の為だけにコンクリートのかぶり量を増やす必要が無いため設計上の自由度が向上し、施工上有利に働く。
【００２６】
溶接閉鎖高強度せん断補強筋において溶接熱影響部を含む溶接個所を４６０〜６００℃で焼戻しを行うことにより、接合部及び熱影響部硬度がＨＭＶ５５０以下で、母材部との高度差が２０％以内となる。これに関して、溶接閉鎖高強度せん断補強筋は溶接個所の焼戻しをすることなく十分に性能を満足することはできるが、焼戻しを行い溶接熱影響部の硬度をＨＭＶ５５０以下にすることにより、使用中に継続して荷重がかかったときの遅れ破壊などの問題に対してより有利になる。
【００２７】
【実施例】
表１に本発明の実施例の開発鋼Ｎｏ．１〜６及び比較鋼Ｎｏ．７〜１２の成分及びこれらを冷却速度２℃／ｓｅｃで冷却した圧延ままの特性を示した。開発鋼Ｎｏ．１〜６では、適正な引張強さ、耐力、耐力比、伸び及び硬度特性を示している。比較鋼Ｎｏ．７では、Ｓｉ、Ｍｎが低く、合金成分を加えても引張強さ、耐力共に低い。比較鋼Ｎｏ．８ではＣが高く、（Ｃｒ＋Ｍｏ＋Ｖ）を含まないので、引張強さは大きいが、耐力が劣り、伸びもやや小さい。比較鋼９〜１１は合金成分の添加量が少なく、所望の特性を得られない。比較鋼１２では、Ｃが低すぎ、合金成分の効果が乏しい。
【００２８】
以上の鋼材を突き合わせ溶接により接合した。図４は、表２に示す溶接条件の説明図で、母材１に電極７を装着し、接合部２を突き合わせて矢印１０で示すように押圧して圧接する。圧接直前の電極７同士の電極間隔８は、圧接時に電極移動量９だけ移動する。この左右の電極移動量９の和が押込量である。以上の鋼材のコブ状増径部を有するもの（参考例）と有しないものの双方の溶接条件を表２に示した。表３に溶接材（溶接後）の機械的性質を示した。開発鋼Ｎｏ．１〜６では、コブ状増径部を有する参考例でも、コブ状増径部を有しない実施例でも、引張強さ（Ｔｓ）、耐力（Ｙｓ）、伸びが良好であり、破断箇所はすべて母材であった。また、溶接熱影響境界部の硬度が適切であり、母材の硬度との比が９０％超であった。これに比し比較鋼７〜１２では、引張強さ、耐力、伸びが小さく、破断箇所はすべて溶接熱影響境界部であり、溶接熱影響境界部の硬度が低下し、母材の硬度との比が９０％を下回っている。表４は、開発鋼Ｎｏ．１〜６の溶接ままのものと、４６０℃で焼戻ししたもの（参考例）とについて、溶接部＋溶接熱影響部の硬度を示した。また母材部硬度を併せて示し、母材部と４６０℃焼戻し後の硬度との硬度差を母材部比％で示した。この硬度差は最大でも１３．１％であり２０％を下回っている。
【００２９】
また、図１に溶接まま材と４６０℃焼戻し材の溶接熱影響部及び母材部の硬度の分布の例を示した。図２はこの硬度を測定した測定位置を示すもので、接合部２から溶接熱影響部３の溶接熱影響境界部４を越えて母材１まで、測定点５に示すように、０．５ｍｍ間隔で測定したものである。接合部及び溶接熱影響部の硬度は４６０℃焼戻しにより、ＨＭＶ５５０以下となり、母材部の硬度との差異が明らかに２０％以下となっている。
【００３０】
【表１】

【００３１】
【表２】

【００３２】
【表３】

【００３３】
【表４】

【００３４】
【発明の効果】
以上、説明したように、本発明によれば、高強度、高耐力で溶接部の特性が母材部に比べて遜色のない、むしろ優れた特性を有する溶接閉鎖せん断補強筋を得ることができた。
【図面の簡単な説明】
【図１】実施例の溶接部の硬度分布を示すグラフである。
【図２】実施例の硬度測定点を示す平面図である。
【図３】コブ状増径部を有する溶接部の側面図である。
【図４】溶接条件の説明図である。
【符号の説明】
１母材
２接合部
３溶接熱影響部
４溶接熱影響境界部
５硬度測定点
６コブ状増径部
７電極
８電極間隔
９押し込み量
１０矢印[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a welded closed high strength shear reinforcement.
[0002]
[Prior art]
In a member such as a column or beam of a reinforced concrete structure or a prestressed concrete structure, a shear reinforcement bar that surrounds the periphery of the main bar in the longitudinal direction is used to increase bending rigidity. Conventional shear reinforcement bars are provided with hooks at both ends, and the overall shape has a square shape, a Japanese character shape, an eye shape, a rice field shape, a square shape, or a combination of these, and surrounds the main reinforcement. The hook is locked to the main muscle to resist the shearing force. Instead of providing the hooks at both ends, both ends may be welded together to form a closed shear reinforcement that forms a loop. Such a closed shear reinforcement bar can be welded at any position regardless of the position of the main bar, so there are no manufacturing restrictions, restrictions during installation, etc., and there are no hooks and continuous shearing. It is used as a reinforcement. However, there is a problem that a material that is difficult to weld cannot be used. In particular, a high strength shear reinforcement with high tensile strength and high yield strength has problems such as the joint and the weld heat-affected boundary have a lower strength than the base metal and are easily damaged by tension. For this reason, even if an excellent high-strength base material is used, there is a problem that it is restricted by the characteristics of the welded portion.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and provides a welded closed shear reinforcing bar having high strength, high proof stress, and the characteristics of a welded part comparable to that of a base metal part, but having rather excellent characteristics. Objective.
[0004]
[Means for Solving the Problems]
The present invention has been developed to achieve the above object, and technical means thereof are as follows.
[0005]
C: 0.15-0.40 mass%,
Si: 0.8 to 2.0 mass%,
Mn: 0.8 to 2.0% by mass,
Al: 0.005 to 0.050 mass%,
Nb: 0.005 to 0.150 mass%,
N: 0.0015 to 0.0150 mass%
Including,
Cr: 0.05 to 2.00% by mass,
Mo: 0.05-1.00 mass%,
V: 0.05-1.00 mass%,
1 or 2 types or more of (Cr + Mo + V) ≧ 0.5% by mass, the steel material comprising the balance Fe and inevitable impurities is hot-rolled into a wire rod shape and then annealed, and the hardness is HV500 or less line bars which was, performed wire drawing and or profile processing, after performing a predetermined hardening, carried out tempering at tempering temperature 400 to 600 ° C., and cut, after the bending, Cobb both ends thereof welded Jo increase diameter portion having no shape, then annealing without the pull ChoTsutomu is possible to have 1420N / mm ² or more, a 0.2% proof stress 1275 N / mm ² or more, elongation combined per post breaking least 5% be welded closed high strength shear reinforcements is to provide a manufacturing method of weld closing high strength shear reinforcement according to claim. HMV is micro Vickers hardness.
[0006]
In addition to the above components, Ti: 0.001 to 0.100 mass%,
B: 0.003-0.010 mass%,
It is preferable to contain 1 type or 2 types.
[0007]
Moreover, in the manufacturing method of the said weld closure high strength shear reinforcement, the hardness of a weld heat influence boundary part becomes 90% or more of the hardness of a base material part. Furthermore, the tensile including base metal rupture can be those with be Rukoto occurring outside the junction, in which the shape of the weld heat affected zone has no nodular increase diameter also a tensile strength 1420N / mm ² As described above, the 0.2% proof stress is 1275 N / mm ² or more, and the elongation after breaking is 5% or more. In the present invention, the bump-shaped increased diameter portion refers to a portion where the weld metal rises to the outer peripheral portion of the joint portion by pressure welding and the outer diameter of the joint portion increases. Further, in this welded closed high-strength shear reinforcement, the welded portion including the weld heat affected zone is tempered at 460 to 600 ° C., and the hardness of the weld zone and weld heat affected zone is set to HV550 or less. It is preferable that the difference between the hardness of the affected part and the base material part is within 20%.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the reasons for limiting the components of the present invention and the processing conditions will be described.
[0009]
C: 0.15-0.40 mass%,
C is an indispensable component for increasing the strength of steel. If C is high, the strength of the weld heat-affected zone decreases significantly, and the hardness of the weld heat-affected zone increases, resulting in a very large difference in hardness from the heat-affected zone. Become bigger. In the present invention, the C content is reduced and an alloy component is added to improve the strength and cover the above-mentioned defects of the welded portion. If C is less than 0.15% by mass, the strength is insufficient even if other alloy components are added, so it is defined as 0.15% by mass or more. On the other hand, when C exceeds 0.40% by mass, it is easy to improve the strength, but the difference between the weld heat affected zone and the weld heat affected zone becomes large and the bending workability deteriorates. In order to suppress the decrease, an alloy component having high heat softening property was added, and the upper limit of C was set to 0.40% by mass.
[0010]
Si: 0.8 to 2.0 mass%,
If Si is less than 0.8% by mass, the 0.2% yield strength is insufficient and the deoxidizing ability is insufficient. If the content exceeds 2.0% by mass, the elongation and bending workability deteriorate, and the effect of increasing the strength is saturated and the effect is lost. Therefore, the upper limit is set to 2.0% by mass.
[0011]
Mn: 0.8 to 2.0% by mass,
Mn is added for deoxidation and desulfurization and contributes to strength improvement. Less than 0.8% by mass is less effective, and if it contains more than 2.0% by mass, weldability In addition, the bending workability is adversely affected and the improvement in strength is saturated, so 2.0 mass% is the upper limit.
[0012]
Al: 0.005 to 0.050 mass%,
Al can make crystal grains fine and improve ductility and bendability. Al is required to be 0.005% by mass or more. However, if the content is too large, a large oxide is formed and the ductility is adversely affected, so the content is limited to 0.050% by mass.
[0013]
Nb: 0.005-0.150 mass%
Nb is an effective component for increasing the strength after tempering by precipitation hardening and also effective for refining the structure, and is effective in improving the strength after quenching and tempering of the steel material. If the amount of Nb is less than 0.005% by mass, the necessary effect cannot be obtained. On the other hand, even if added over 0.150% by mass, the effect is saturated and not economical, so 0.005 to 0.150% by mass. % In the range.
[0014]
N: 0.0015 to 0.0150 mass%
N is a component that combines with Al and Nb to refine the structure, and solid solution N itself in the steel is also effective in refining the structure after quenching and tempering. If the N amount is less than 0.0015% by mass, a sufficient effect cannot be obtained. On the other hand, when the content exceeds 0.0150% by mass, the effect is saturated and there is a possibility of embrittlement, so 0.0015 to 0.0150% by mass was set.
[0015]
Cr: 0.05-2.00 mass%
Cr is an effective component for improving the hardenability, increasing the strength by precipitation of carbonitride during tempering, increasing the temper softening resistance of steel, and suppressing the decrease in hardness at the heat-affected boundary during welding. is there. If the amount of Cr is less than 0.05% by mass, the necessary effect cannot be obtained, and even if added over 2.00% by mass, the effect is saturated and is not economical, so 0.05 to 2.00% by mass % Addition.
[0016]
Mo: 0.05-1.00 mass%, V: 0.05-1.00 mass%
Mo and V are extremely effective components for improving the strength after quenching and tempering by increasing the strength after tempering by precipitation hardening and acting effectively on the refinement of the structure in the same manner as Cr. If the amount of these components is less than 0.05% by mass, the necessary effect cannot be obtained. On the other hand, adding more than 1.00% by mass not only saturates the effect but also is not economical. The addition amount was 1.00% by mass.
[0017]
(Cr + Mo + V) ≧ 0.5 mass%
The above-mentioned Cr, Mo and V may be added alone or in combination of two or more, but if the total amount of these components added is less than 0.5% by mass, after quenching and tempering Therefore, the required strength cannot be obtained. Therefore, the addition amounts of Cr, Mo, and V need to satisfy the above ranges and satisfy (Cr + Mo + V) ≧ 0.5 mass%.
[0018]
Ti: 0.001 to 0.100% by mass,
Ti can make crystal grains fine and improves ductility and bendability. When Ti is less than 0.001% by mass, the effect of addition is poor, and even if contained over 0.100% by mass, the effect is saturated, and when it is further increased, the ductility is adversely affected, so 0.001% by mass to 0.00%. It was limited to 100% by mass.
[0019]
B: 0.0003 to 0.0100 mass%,
B is an element that greatly improves the hardenability by adding a small amount and contributes to the improvement of the structure. 0.0003 mass% or more is necessary. On the other hand, exceeding 0.0100 mass% is not possible because the effect is saturated and the toughness is further lowered.
[0020]
Next, processing conditions will be described.
[0021]
This steel is hot-rolled into a wire rod shape and then slowly cooled so that the hardness is HV500 or less. When the hardness exceeds HMV500, the workability in the subsequent process such as wire drawing or deforming process is remarkably lowered, which is not preferable.
[0022]
The tempering temperature was in the range of 400 to 600 ° C. This is because the temperature range in which the balance between the standard strength and the elongation is compatible is increased because the alloy element contains a high thermal softening resistance. If the temperature is lower than 400 ° C., the elongation is less than the standard.
[0023]
The weld-closed high-strength shear reinforcing bar provides a weld-closed high-strength shear bar that has a low decrease in hardness at the weld heat-affected boundary and is 90% or more of the hardness of the base metal part. If the heat-affected boundary is less than 90% of the hardness of the base metal part, even a narrow boundary part breaks from the boundary part during a tensile test. Further, it cannot be satisfied that the tensile strength is 1420 N / mm ² or more, the 0.2% proof stress is 1275 N / mm ² or more, and the lap elongation after breaking is 5% or more.
[0024]
The welded closed high strength shear reinforcement does not break at the joint when a tensile test is performed including the joint, the heat affected zone and the base metal. When it breaks at the joint, it cannot be satisfied that the tensile strength is 1420 N / mm ² or more, the 0.2% proof stress is 1275 N / mm ² or more, and the lap elongation after breaking is 5% or more, Moreover, since it cannot satisfy the welded joint performance itself by rupturing at the joint portion, it is assumed that it does not break at the joint portion.
[0025]
In the welded closed high strength shear reinforcement, as shown in FIG. 3, when the base material 1 is butt welded at the joint portion, there is one in which the shape of the weld portion 2 has a bump-shaped increased diameter portion 6 (reference example) . Moreover, there is a thing which does not have this bump-shaped enlarged diameter part. Both satisfy performance . In those without a hump-like increase diameter portion is improved degree of freedom in design since it is not necessary to only increase the amount of fog concrete for increasing the diameter of the weld, construction on favors.
[0026]
By tempering the welded portion including the weld heat affected zone in the welded closed high strength shear reinforcement at 460 to 600 ° C., the hardness of the joint and the heat affected zone is HV550 or less, and the altitude difference from the base metal portion is 20 Within%. In this regard, the welded closed high-strength shear reinforcement can sufficiently satisfy the performance without tempering the welded part, but by tempering the welded heat-affected zone to a hardness of HV550 or less, It becomes more advantageous for problems such as delayed fracture when a load is continuously applied.
[0027]
【Example】
Table 1 shows developed steel Nos. Of Examples of the present invention. 1-6 and Comparative Steel No. 1 The components of 7 to 12 and the properties as-rolled when these were cooled at a cooling rate of 2 ° C./sec were shown. Development steel No. 1 to 6 show appropriate tensile strength, yield strength, yield ratio, elongation and hardness characteristics. Comparative steel No. In No. 7, Si and Mn are low, and even if an alloy component is added, both tensile strength and proof stress are low. Comparative steel No. In No. 8, since C is high and does not contain (Cr + Mo + V), the tensile strength is large, but the proof stress is inferior and the elongation is slightly small. The comparative steels 9 to 11 have a small amount of alloy components added and cannot obtain desired characteristics. In the comparative steel 12, C is too low and the effect of the alloy component is poor.
[0028]
The above steel materials were joined by butt welding. FIG. 4 is an explanatory diagram of the welding conditions shown in Table 2. The electrode 7 is attached to the base material 1, the joint portion 2 is abutted and pressed as shown by an arrow 10 and pressed. The electrode interval 8 between the electrodes 7 immediately before the press contact is moved by the electrode movement amount 9 at the time of the press contact. The sum of the left and right electrode movement amounts 9 is the pushing amount. Table 2 shows the welding conditions of both the steel material having the bump-shaped increased diameter portion (reference example) and the steel material having no bump portion. Table 3 shows the mechanical properties of the welding material (after welding). Development steel No. Nos. 1 to 6 have good tensile strength (Ts), proof stress (Ys) and elongation both in the reference example having the bump-shaped enlarged portion and in the example not having the bump-shaped enlarged portion , and all the broken portions are It was a base material. Moreover, the hardness of the weld heat-affected boundary was appropriate, and the ratio to the hardness of the base material was more than 90%. In comparison steels 7 to 12, the tensile strength, proof stress, and elongation are small, and the fracture points are all weld heat-affected boundary portions, and the hardness of the weld heat-affected boundary portion is reduced. The ratio is below 90%. Table 4 shows the development steel No. For as the as welded 1-6, those tempered at 460 ° C. and (Reference Example), showing the hardness of the weld + HAZ. The base material part hardness is also shown, and the difference in hardness between the base material part and the hardness after tempering at 460 ° C. is shown in base material part ratio%. This hardness difference is 13.1% at maximum and is less than 20%.
[0029]
FIG. 1 shows an example of the hardness distribution of the weld heat-affected zone and the base metal zone of the as-welded material and the 460 ° C. tempered material. FIG. 2 shows the measurement position at which this hardness was measured. From the joint 2 to the base metal 1 beyond the weld heat affected zone 4 of the weld heat affected zone 3, 0.5 mm as shown at the measurement point 5. Measured at intervals. The hardness of the joint and the weld heat affected zone is HV550 or less by tempering at 460 ° C., and the difference from the hardness of the base material is clearly 20% or less.
[0030]
[Table 1]

[0031]
[Table 2]

[0032]
[Table 3]

[0033]
[Table 4]

[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a welded closed shear reinforcement having high strength, high proof stress, and the characteristics of a welded part comparable to that of a base material part, but rather excellent characteristics. It was.
[Brief description of the drawings]
FIG. 1 is a graph showing the hardness distribution of a welded part of an example.
FIG. 2 is a plan view showing hardness measurement points of an example.
FIG. 3 is a side view of a welded portion having a bump-shaped increased diameter portion.
FIG. 4 is an explanatory diagram of welding conditions.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base material 2 Junction part 3 Welding heat influence part 4 Welding heat influence boundary part 5 Hardness measuring point 6 Hump-shaped enlarged diameter part 7 Electrode 8 Electrode space | interval 9 Push amount 10 Arrow

Claims

C: 0.15-0.40 mass%,
Si: 0.8 to 2.0 mass%,
Mn: 0.8 to 2.0% by mass,
Al: 0.005 to 0.050 mass%,
Nb: 0.005 to 0.150 mass%,
N: 0.0015 to 0.0150 mass%
Including,
Cr: 0.05 to 2.00% by mass,
Mo: 0.05-1.00 mass%,
V: 0.05-1.00 mass%,
1 or 2 types of (Cr + Mo + V) ≧ 0.5% by mass, and the steel material comprising the balance Fe and inevitable impurities is hot-rolled into a wire rod shape and then gradually cooled, and the hardness is HV500 or less line bars which was, performed wire drawing and or profile processing, carried out tempering at a predetermined after performing quenching tempering temperature 400 to 600 ° C., cut, after the bending, nodular both ends thereof welded to no shape increased diameter, then annealed without the pull ChoTsutomu it is possible to have 1420N / mm ² or more, a 0.2% proof stress 1275 N / mm ² or more, elongation combined per post breaking least 5% manufacturing method of weld closing high strength shear reinforcement, characterized in that the weld closing high strength shear reinforcement is.

further
Ti: 0.001 to 0.100% by mass,
B: 0.0003 to 0.0100 mass%,
The method for producing a welded closed high-strength shear reinforcement according to claim 1, comprising: 1 type or 2 types.

Further, the welded portion including the weld heat affected zone is tempered at 460 to 600 ° C., the hardness of the joint and the weld affected zone is set to HMV550 or less, and the difference between the hardness of the welded zone and the weld affected zone and the base material is 20 The method for producing a welded closed high-strength shear reinforcement according to claim 1 or 2 , wherein the ratio is within% .