JPH1150147A - Production of high strength reinforcing bag - Google Patents
Production of high strength reinforcing bagInfo
- Publication number
- JPH1150147A JPH1150147A JP20282597A JP20282597A JPH1150147A JP H1150147 A JPH1150147 A JP H1150147A JP 20282597 A JP20282597 A JP 20282597A JP 20282597 A JP20282597 A JP 20282597A JP H1150147 A JPH1150147 A JP H1150147A
- Authority
- JP
- Japan
- Prior art keywords
- elongation
- steel
- luders
- yield
- present
- 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.)
- Granted
Links
Landscapes
- Reinforcement Elements For Buildings (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、耐震性に優れた
高強度鉄筋に関するもので、従来法よりも安価に降伏棚
の伸びの大きい鉄筋を製造する技術に関するものであ
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength reinforcing bar having excellent seismic resistance, and more particularly to a technique for manufacturing a reinforcing bar having a larger yielding shelf at a lower cost than a conventional method.
【０００２】[0002]
【従来の技術】近年の建築構造物の大型化により、高強
度な鉄筋コンクリート用棒鋼が望まれている。鉄筋を高
強度化することにより、一方では棒鋼の重量を軽減する
こともでき、作業性も向上する。こうした、鉄筋用棒鋼
に対して近年では耐震性の面から降伏棚の伸び（降伏伸
び）の大きい棒鋼が要求されている。降伏棚の伸びと
は、図１に示す応力−歪み曲線において、規格降伏強度
の上限値である上限応力Ｆを通過するときの伸びの値の
ことをいう。例えば、強度６８５Ｎ／ｍｍ2 級の鉄筋で
は、降伏棚の伸び４が１．４％以上あることが必要であ
る。2. Description of the Related Art With the recent enlargement of building structures, high-strength steel bars for reinforced concrete have been desired. By increasing the strength of the rebar, on the other hand, the weight of the bar can be reduced, and the workability is improved. In recent years, for such steel bars for reinforcing bars, steel bars having a large elongation of the yield shelf (yield elongation) have been demanded from the viewpoint of earthquake resistance. The elongation of the yield shelf refers to the value of elongation when passing the upper limit stress F which is the upper limit of the specified yield strength in the stress-strain curve shown in FIG. For example, in the case of a reinforcing bar having a strength of 685 N / mm 2 , it is necessary that the elongation 4 of the yielding shelf is 1.4% or more.
【０００３】こうした要望に対して、例えば、特開平６
−１３６４４１号公報には、棒鋼を熱間圧延後に水冷
し、表層部を３５０℃以下に冷却してマルテンサイトを
生成させた後、内部の保有熱により自己焼戻しする方法
（先行技術１という）が開示されている。しかしなが
ら、この方法は３５０℃以下にまで冷却するのに数秒の
水冷時間を必要とし、今日の棒鋼製造における高速圧延
においては数１０ｍの長い水冷管を必要とし、更に、圧
延速度をも低下させなければならず、設備費や生産性に
おいてコスト高になる要因が大きな問題となる。[0003] In response to such a demand, for example, Japanese Unexamined Patent Publication No.
Japanese Patent Application Publication No. 136441 discloses a method in which a steel bar is hot-rolled, then water-cooled, a surface layer portion is cooled to 350 ° C. or lower to generate martensite, and then self-tempering is performed by internal retained heat (referred to as prior art 1). It has been disclosed. However, this method requires several seconds of water cooling time to cool to 350 ° C. or less, high speed rolling in steel bar production today requires a long water cooling tube of several tens of meters, and the rolling speed must be reduced. Factors that increase costs in equipment costs and productivity are a major problem.
【０００４】また、特開昭６１−１２４５２４号公報に
は、Ｍｎを１．８〜５．０wt.%として焼入れ性を高めた
鋼を、圧延後大気放冷した後、４５０〜７００℃に焼戻
しを行なう方法（先行技術２という）が開示されてい
る。しかしながら、この方法では焼戻しに当たって再加
熱をせねばならず、コスト高になってしまう。Japanese Unexamined Patent Publication (Kokai) No. 61-124524 discloses that a steel having an Mn content of 1.8 to 5.0 wt.% And having improved hardenability is rolled, air-cooled, and then tempered to 450 to 700 ° C. (Referred to as Prior Art 2). However, in this method, reheating must be performed at the time of tempering, which increases the cost.
【０００５】特開平４−５６７２７号公報には、Ｖ：
０．１５〜０．５wt.%に加え、Ｔｉ：０．１５〜０．４
wt.%を添加する方法（先行技術３という）が開示されて
いるが、Ｔｉは炭化物を形成して強度を下げるので、Ｖ
による強度向上の効果が相殺されてしまい、このため多
量の合金元素を必要とし、コスト高になってしまう。[0005] JP-A-4-56727 discloses that V:
0.15 to 0.5 wt.%, And Ti: 0.15 to 0.4
Although a method of adding wt.% (referred to as prior art 3) is disclosed, Ti forms carbides and lowers the strength.
The effect of improving the strength is canceled out, so that a large amount of alloying elements is required and the cost is increased.
【０００６】特開平６−２２８６３５号公報には、Ｖ：
０．０１〜０．３０wt.%に加え、Ｎｂ：０．０５〜０．
４０wt.%及びＴｉ：０．０５wt.%以上を添加した鋼を、
圧延終了温度６５０〜８５０℃で圧延する方法（先行技
術４という）が開示されている。しかしながら、Ｖの他
にＮｂ及びＴｉを添加することは、それだけでコスト高
になるのみならず、８５０℃より低い圧延終了温度を得
るには、圧延速度を現状よりも著しく低下させねばなら
ず、更にコスト高になってしまう。[0006] JP-A-6-228635 discloses that V:
In addition to 0.01 to 0.30 wt.%, Nb: 0.05 to 0.
Steel containing 40 wt.% And Ti: 0.05 wt.% Or more
A method of rolling at a rolling end temperature of 650 to 850 ° C. (referred to as prior art 4) is disclosed. However, the addition of Nb and Ti in addition to V not only increases the cost alone, but also in order to obtain a rolling end temperature lower than 850 ° C., the rolling speed must be significantly reduced from the current state. The cost is further increased.
【０００７】[0007]
【発明が解決しようとする課題】先行技術１〜４には、
上述したように、圧延後の材料冷却用の水冷管の増設や
圧延速度の低下が必要となったり、焼戻しのための再加
熱が必要になったり、フェライトを増やして伸びの値を
大きくするために添加したＴｉが炭化物を形成すること
により強度低下をもたらしたり、あるいは、材料の強度
向上元素であるＶ以外にコストのかかる合金元素の添加
を要する等の問題があり、設備投資、圧延能率低下ある
いは合金材コストの増加が避けられない。The prior arts 1 to 4 include:
As described above, it is necessary to add a water cooling tube for cooling the material after rolling or to reduce the rolling speed, or it is necessary to reheat for tempering, or to increase the ferrite to increase the elongation value. Or the addition of expensive alloying elements other than V, which is an element for improving the strength of the material, may cause problems such as a reduction in strength due to the formation of carbides by the Ti added to the steel. Alternatively, an increase in alloy material cost is inevitable.
【０００８】そこで、この発明においては、上記問題を
解決するために、降伏棚の伸びを大きくする方法とし
て、リューダース伸びを大きくすることが効果的である
ことに着眼し、高価な合金元素の添加量を抑制しつつ、
引張試験におけるリューダース伸びを増大させる高強度
鉄筋の製造方法を開発することを課題とした。こうし
て、この発明の目的は、設備増強、製造工程の増加ある
いは合金材コストを抑制することを前提とし、従来法に
よるよりも安価に、降伏棚の伸びの大きい、高強度鉄筋
を製造する方法を提供することにある。In order to solve the above-mentioned problem, the present invention focuses on the fact that it is effective to increase the Luders elongation as a method of increasing the elongation of the yield shelf. While controlling the amount of addition,
It is an object of the present invention to develop a method for manufacturing a high-strength rebar that increases Luders elongation in a tensile test. Thus, an object of the present invention is to provide a method of manufacturing a high-strength rebar at a lower cost than the conventional method, with a large elongation of the yielding shelf, on the assumption that the equipment is increased, the number of manufacturing steps is increased, or the alloy material cost is suppressed. To provide.
【０００９】[0009]
【課題を解決するための手段】先行技術１〜４の上述し
た問題点に鑑み、本発明者等は鋭意研究を重ねた。その
結果、降伏棚の伸びは３つの部分に分けることができ、
降伏棚の伸びの大きさを左右するのは、主としてリュー
ダース帯の発生に伴って生じるリューダース伸びである
ことを突き止めた。In view of the above-mentioned problems of the prior arts 1 to 4, the present inventors have intensively studied. As a result, the yield of the yield shelf can be divided into three parts,
It was determined that the size of the yielding shelf is largely determined by the Lüders elongation caused by the occurrence of the Lüders belt.
【００１０】図１に示した応力−歪み曲線において、Ｅ
は目標下限応力、Ｆは目標上限応力を示す。そして、Ａ
部分は弾性伸びであり、これは鋼の弾性率によって決ま
り、約０．４％であって一定であり、若干の成分組成の
違いによって大きく変化することはない。Ｂ部分はリュ
ーダース帯の発生によって応力の増加を伴わずに伸びる
リューダース伸びであり、この部分は鋼への添加元素の
種類やその量によって大きく変化する。また、Ｃ部分
は、加工硬化を伴って伸びる加工硬化伸びとも呼ぶべき
部分であるが、組織がフェライト＋パーライトの場合、
この部分も著しく変化することはない。従って、大きな
降伏棚の伸びＤ部分を得るためには、リューダース伸び
Ｂ部分を大きくしなければならない。In the stress-strain curve shown in FIG.
Indicates a target lower limit stress, and F indicates a target upper limit stress. And A
The portion is the elastic elongation, which is determined by the elastic modulus of the steel and is constant at about 0.4%, and does not significantly change due to a slight difference in component composition. Part B is a Ruders elongation that is extended without an increase in stress due to the generation of a Ruders band, and this part greatly changes depending on the type and amount of the element added to the steel. In addition, the C portion is a portion that should be called work hardening elongation that extends with work hardening, but when the structure is ferrite + pearlite,
This part also does not change significantly. Therefore, in order to obtain a large yield D portion of the yield shelf, the Luders elongation B portion must be increased.
【００１１】そして、リューダース伸びに及ぼす合金元
素の作用・効果として、下記点が重要であることを知見
した。 Ｖは、降伏応力を確保するのに必須の元素である
が、高価な元素であるので、必要最小限に抑えるべきで
ある。 Ｓｉは、降伏応力を高める効果は小さいが、リュー
ダース伸びを大きく向上させるので、積極的に利用すべ
きである。 Ｎは、転位を固着することによりリューダース伸び
を大きくする。また、降伏応力を高める効果が大きく、
また大気を混入させることによって安価にその量を高め
ることができるので、積極的に利用すべきである。 Ｔｉは、降伏棚の伸びを大きくするが、窒素と結合
して降伏応力を大きく低下させるので、添加すべきでな
い。It has been found that the following points are important as actions and effects of alloying elements on Luders elongation. V is an element indispensable for securing the yield stress, but it is an expensive element, so that it should be minimized. Although Si has a small effect of increasing the yield stress, it greatly enhances the Luders elongation, and therefore should be used positively. N increases the Luders elongation by fixing dislocations. In addition, the effect of increasing the yield stress is great,
In addition, since the amount can be increased at low cost by mixing with the atmosphere, it should be actively used. Ti increases the yield shelf extension but should not be added because it combines with nitrogen and greatly reduces yield stress.
【００１２】この発明は上記知見に基づきなされたもの
であり、その構成は下記の通りである。即ち、この発明
の高強度鉄筋の製造方法は、化学成分組成が、Ｃ：０．
２５〜０．５０wt.%、Ｓｉ：１．０〜２．０wt.%、Ｍ
ｎ：１．０〜２．０wt.%、Ｃｒ：０．０１〜０．５０w
t.%、Ｖ：０．１０〜０．３０wt.%、sol.Ａｌ：０．０
１０〜０．１００wt.%、Ｎ：０．００８〜０．０３０w
t.%、及び、Ｔｉ：０．０１０wt.%未満、但し、Ｔｉを
添加しない場合を含む、を含有し、残部Ｆｅ及び不可避
不純物よりなる鋼塊又は鋼片を調製する。得られた上記
鋼塊又は鋼片を、９００〜１０００℃の範囲内の温度に
加熱した後、８５０〜９５０℃の範囲内の仕上げ圧延温
度で圧延した後、空冷する。こうして得られる圧延鋼材
の降伏応力を６８５Ｎ／ｍｍ2 以上にし、且つリューダ
ース帯の伸びを０．６％以上にすることに特徴を有する
ものである。The present invention has been made based on the above findings, and has the following configuration. That is, in the method for producing a high-strength rebar according to the present invention, the chemical composition is C: 0.
25 to 0.50 wt.%, Si: 1.0 to 2.0 wt.%, M
n: 1.0 to 2.0 wt.%, Cr: 0.01 to 0.50 w
t.%, V: 0.10 to 0.30 wt.%, sol. Al: 0.0
10 to 0.100 wt.%, N: 0.008 to 0.030 w
% and Ti: less than 0.010 wt.%, including the case where Ti is not added, to prepare a steel ingot or a slab consisting of the balance of Fe and unavoidable impurities. The obtained steel ingot or slab is heated to a temperature in the range of 900 to 1000 ° C., rolled at a finish rolling temperature in the range of 850 to 950 ° C., and air-cooled. The rolled steel material thus obtained is characterized in that the yield stress is 685 N / mm 2 or more and the elongation of the Luders band is 0.6% or more.
【００１３】[0013]
【発明の実施の形態】この発明の実施の形態としては、
使用する鋼塊又は鋼片を、上述した所定の化学成分組成
となるように調製し、次いで、得られた鋼塊又は鋼片を
上述した条件で熱間圧延をし、そして空冷する。上記に
おいて、鋼塊又は鋼片の製造は、転炉及び電気炉等の製
鋼炉で精錬され、取鍋に出鋼され、次いで適宜ＲＨ脱ガ
ス装置等の２次精錬炉で処理された、上記化学成分組成
からなる溶鋼を連続鋳造法又は造塊法等で鋳造する。鋳
造された鋼塊又は鋳片を所定の加熱炉に装入し、上記加
熱温度に昇温する。次いで、これを熱間棒鋼圧延機に装
入し、上記仕上げ圧延温度で圧延して所定の寸法・形状
にし、空冷し、そして、得られる鋼材の降伏応力及びリ
ューダース帯の伸びをいずれも上述した所定値以上にす
る。こうして、所要の高強度鉄筋を製造する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention include:
The ingot or billet to be used is prepared so as to have the above-mentioned predetermined chemical composition, and then the obtained ingot or billet is hot-rolled under the above-mentioned conditions, and air-cooled. In the above, the production of steel ingots or billets is refined in steelmaking furnaces such as converters and electric furnaces, tapped into a ladle, and then appropriately processed in a secondary smelting furnace such as an RH degassing apparatus. A molten steel having a chemical composition is cast by a continuous casting method or an ingot casting method. The cast steel ingot or slab is charged into a predetermined heating furnace and heated to the above-mentioned heating temperature. Next, this was charged into a hot steel bar rolling mill, rolled at the above-mentioned finish rolling temperature to a predetermined size and shape, air-cooled, and the yield stress and elongation of the Ruders zone of the obtained steel material were all described above. Above the specified value. Thus, the required high-strength rebar is manufactured.
【００１４】次に、この発明において、鋼の化学成分組
成、熱間圧延条件、及び鉄筋用鋼材の機械的性質を上述
したように限定した理由について述べる。 〔化学成分組成〕 （１）Ｃ：０．２５〜０．５０wt.% Ｃは、鋼の強度を確保するのに必要な元素である。しか
し、０．２５wt.%未満では所要の強度を得ることができ
ない。一方、Ｃが０．５０wt.%を超えると、フェライト
の量が不足して、伸びを確保するのが困難になる。従っ
て、Ｃ含有率は、０．２５〜０．５０wt.%の範囲内に限
定する。Next, the reasons for limiting the chemical composition of the steel, the hot rolling conditions, and the mechanical properties of the steel for reinforcing steel as described above in the present invention will be described. [Chemical component composition] (1) C: 0.25 to 0.50 wt.% C is an element necessary to secure the strength of steel. However, if it is less than 0.25 wt.%, The required strength cannot be obtained. On the other hand, if C exceeds 0.50 wt.%, The amount of ferrite becomes insufficient and it becomes difficult to secure elongation. Therefore, the C content is limited to the range of 0.25 to 0.50 wt.%.
【００１５】（２）Ｓｉ：１．０〜２．０wt.% Ｓｉは、フェライトに固溶して降伏応力を高める。ま
た、Ｓｉはフェライト形成元素であり、鋼中の組織にフ
ェライトの量を多くして降伏棚の伸びを大きくする作用
を有する。この効果を十分に発揮させるためには、１．
０wt.%以上のＳｉ添加が必要であるが、一方、Ｓｉが
２．０wt.%を超えると、鋼中に非金属介在物の量が多く
なって鋼材の靱性が低下する。従って、Ｓｉ含有率は、
１．０〜２．０wt.%の範囲内に限定する。(2) Si: 1.0 to 2.0 wt.% Si forms a solid solution in ferrite and increases the yield stress. Si is a ferrite-forming element, and has an effect of increasing the amount of ferrite in the structure in steel to increase the elongation of the yield shelf. In order to fully exhibit this effect,
Addition of Si of 0 wt.% Or more is necessary. On the other hand, when Si exceeds 2.0 wt.%, The amount of nonmetallic inclusions in the steel increases, and the toughness of the steel material decreases. Therefore, the Si content is
It is limited to the range of 1.0 to 2.0 wt.%.
【００１６】（３）Ｍｎ：１．０〜２．０wt.% Ｍｎは、鋼の強度を高めるとともに、Ｓと結合してＭｎ
Ｓを形成し、鋼材の靱性を高める作用を有する。この効
果を十分に発揮させるためには、１．０wt.%以上のＭｎ
添加が必要であるが、一方、Ｍｎが２．０wt.%を超える
と、組織内にベイナイトが混入して伸びが低下する。従
って、Ｍｎ含有率は、１．０〜２．０wt.%の範囲内に限
定する。(3) Mn: 1.0 to 2.0 wt.% Mn increases the strength of steel and combines with S to form Mn.
It forms S and has the effect of increasing the toughness of the steel material. In order to fully exhibit this effect, Mn of 1.0 wt.
On the other hand, when Mn exceeds 2.0 wt.%, Bainite is mixed in the structure and elongation is reduced. Therefore, the Mn content is limited to the range of 1.0 to 2.0 wt.%.
【００１７】（４）sol.Ａｌ：０．０１０〜０．１００
wt.%、 Ａｌは、鋼の結晶粒を微細にして伸びを確保するのに重
要な元素である。この効果を十分に発揮させるために
は、酸可溶Ａｌであるsol.Ａｌとして０．０１０wt.%以
上の量が必要である。一方、sol.Ａｌが０．１００wt.%
を超えると、溶鋼中のＡｌ2 Ｏ3 介在物が増加し、連続
鋳造時にノズル詰まりの原因となる。従って、sol.Ａｌ
含有率は、０．０１０〜０．１００wt.%の範囲内に限定
する。(4) sol. Al: 0.010 to 0.100
wt.%, Al is an important element for refining the crystal grains of steel to secure elongation. In order to sufficiently exhibit this effect, the amount of sol. Al, which is acid-soluble Al, is required to be 0.010 wt.% Or more. On the other hand, sol.Al is 0.100wt.%
If it exceeds, Al 2 O 3 inclusions in the molten steel increase, causing nozzle clogging during continuous casting. Therefore, sol.Al
The content is limited to the range of 0.010 to 0.100 wt.%.
【００１８】（５）Ｎ：０．００８〜０．０３０wt.% Ｎは、鋼に固溶して降伏応力を高める。また、Ｖと結合
して窒化物を形成し、降伏応力を高める。Ｎは更に、結
晶粒を微細にするとともに、転位の回りにコットレル雰
囲気をつくり、このピン止め効果によりリューダース伸
びを大きくする作用・効果を有する。この作用・効果を
十分に発揮させるためには、０．００８wt.%以上のＮ添
加が必要である。一方、Ｎが０．０３０wt.%を超える
と、鋼中に気泡が形成されて鋼材の靱性が劣化する。従
って、Ｎ含有率は、０．００８〜０．０３０wt.%の範囲
内に限定する。(5) N: 0.008 to 0.030 wt.% N forms a solid solution in steel and increases the yield stress. Further, it combines with V to form a nitride, thereby increasing the yield stress. N further has the effect of making the crystal grains fine, creating a Cottrell atmosphere around the dislocations, and increasing the Luders elongation by this pinning effect. In order to sufficiently exhibit this function and effect, it is necessary to add 0.008 wt.% Or more of N. On the other hand, if N exceeds 0.030 wt.%, Bubbles are formed in the steel, and the toughness of the steel material deteriorates. Therefore, the N content is limited to the range of 0.008 to 0.030 wt.%.
【００１９】（６）Ｃｒ：０．０１〜０．５０wt.% Ｃｒは、Ｍｎと同様、鋼を強化する元素である。この効
果を十分発揮させるためには、０．０１wt.%以上のＣｒ
添加を必要とする。一方、Ｃｒが０．５０wt.%を超える
と、組織内にベイナイトが混入して伸びを低下させる。
従って、Ｃｒ含有率は、０．０１〜０．５０wt.%の範囲
内に限定する。(6) Cr: 0.01 to 0.50 wt.% Cr, like Mn, is an element that strengthens steel. In order to sufficiently exhibit this effect, it is necessary to use Cr of 0.01 wt.% Or more.
Requires addition. On the other hand, if Cr exceeds 0.50 wt.%, Bainite is mixed in the structure and the elongation is reduced.
Therefore, the Cr content is limited to the range of 0.01 to 0.50 wt.%.
【００２０】（７）Ｔｉ：０．０１０wt.%未満 Ｔｉは、Ｎと結合してＮの上述した重要な効果を弱め
る。従って、Ｔｉはこの発明の鋼材においては不純物で
あり、その混入量を０．０１０wt.%未満に抑えるべきで
ある。(7) Ti: less than 0.010 wt.% Ti combines with N to weaken the above-mentioned important effect of N. Therefore, Ti is an impurity in the steel material of the present invention, and its content should be suppressed to less than 0.010 wt.%.
【００２１】なお、鋼には通常、以上の元素の他にＰ、
Ｓ、Ｎｉ、Ｍｏ及びＳｎ等の不可避的に混入する元素が
含まれる。この発明においても、上記不可避不純物の不
可避的含有率の混入は差し支えない。Incidentally, steel usually contains P,
Elements that are unavoidably mixed such as S, Ni, Mo, and Sn are included. Also in the present invention, the inevitable content of the inevitable impurities may be mixed.
【００２２】〔熱間圧延条件〕 （１）加熱温度：９００〜１０００℃ 圧延前の加熱温度が９００℃未満では、圧延中の鋼材の
変形抵抗が大きくて、圧延機に過大な負荷がかかる。ま
た、所望の形状の棒が得られにくい。一方、加熱温度が
１０００℃を超えると、鋼材中ＡｌＮが固溶してオース
テナイト粒が粗大化し、圧延後に微細な結晶粒を得るの
が困難になる。従って、加熱温度は９００〜１０００℃
の範囲内に限定する。[Hot rolling conditions] (1) Heating temperature: 900 to 1000 ° C If the heating temperature before rolling is less than 900 ° C, the deformation resistance of the steel material during rolling is large, and an excessive load is applied to the rolling mill. Further, it is difficult to obtain a rod having a desired shape. On the other hand, when the heating temperature exceeds 1000 ° C., AlN in the steel material is dissolved and the austenite grains are coarsened, and it is difficult to obtain fine crystal grains after rolling. Therefore, the heating temperature is 900-1000 ° C.
Within the range.
【００２３】（２）仕上げ圧延温度：８５０〜９５０℃ 仕上げ圧延温度が８５０℃未満では、鋼材の変形能が低
下して表面疵の発生が多くなる。一方、仕上げ圧延温度
が９５０℃を超えると、ベイナイトが発生し易くなり、
降伏棚が発生しにくくなったり、降伏棚の伸びが小さく
なったりする。従って、仕上げ圧延温度は８５０〜９５
０℃の範囲内に限定する。(2) Finish rolling temperature: 850-950 ° C. If the finish rolling temperature is less than 850 ° C., the deformability of the steel material is reduced, and the number of surface flaws is increased. On the other hand, when the finish rolling temperature exceeds 950 ° C., bainite easily occurs,
Surrender shelves are less likely to occur, and the yield shelves are less elongated. Therefore, the finish rolling temperature is 850-95.
Limit within the range of 0 ° C.
【００２４】〔機械的性質〕 （１）降伏応力：６８５Ｎ／ｍｍ2 以上 高強度鉄筋として所望の強度を持たせるためには、降伏
応力が６８５Ｎ／ｍｍ 2 以上必要である。これは、図１
における目標下限応力Ｅが６８５Ｎ／ｍｍ2 であるとき
に相当する。なお、この発明においては、同図の目標上
限応力Ｆが７８５Ｎ／ｍｍ2 であることが望ましい。[Mechanical properties] (1) Yield stress: 685 N / mmTwoTo achieve the desired strength as a high-strength rebar,
Stress is 685 N / mm TwoIt is necessary. This is shown in FIG.
Target lower limit stress E at 685 N / mmTwoWhen
Is equivalent to In the present invention, the target shown in FIG.
Limiting stress F is 785 N / mmTwoIt is desirable that
【００２５】（２）リューダース帯の伸び：０．６％以
上 リューダース帯の伸びが０．６％未満では、所望とする
１．４％以上の降伏棚の伸びを得ることが困難になるの
で、リューダース帯の伸びは０．６％以上にすべきであ
る。(2) Elongation of the Luders zone: 0.6% or more If the elongation of the Luders zone is less than 0.6%, it becomes difficult to obtain the desired elongation of the yield shelf of 1.4% or more. Therefore, the growth of the Luders zone should be 0.6% or more.
【００２６】[0026]
【実施例】次に、この発明を、実施例に基づき更に説明
する。表１及び２に示す各種化学成分組成の供試鋼を溶
製し、次いで上記鋼を加熱温度及び仕上げ温度を本発明
の範囲内で種々変化させ、呼び名Ｄ２２の異径棒鋼に熱
間圧延した。仕上げ圧延温度の調整は、圧延速度の調節
及び圧延中の中間水冷の使用により行なった。そして、
降伏応力及びリューダース帯の伸びのそれぞれが本発明
の範囲内又は本発明の範囲外になるよう、析出物である
ＶＮの大きさと数、並びに、変態前のオーステナイト粒
の大きさ及び変態後のフェライト粒の大きさと数を、そ
れぞれ調整した。Next, the present invention will be further described based on embodiments. Test steels having various chemical component compositions shown in Tables 1 and 2 were melted, and then the above steels were hot-rolled into different-diameter steel bars having a nominal name of D22 while varying the heating temperature and the finishing temperature within the scope of the present invention. . Adjustment of the finish rolling temperature was performed by adjusting the rolling speed and using intermediate water cooling during rolling. And
The size and number of the precipitate VN, the size of the austenite grains before the transformation and the size after the transformation, so that the yield stress and the elongation of the Luders zone are within or outside the scope of the present invention, respectively. The size and number of ferrite grains were adjusted respectively.
【００２７】このようにして、本発明の範囲内の製造方
法である実施例１〜８、及び、本発明の範囲外の製造方
法である比較例１〜９により製造された鉄筋用棒鋼につ
いて引張試験により引張特性を評価した。また、ミクロ
組織試験をした。表１及び２に、上記試験結果を併記す
る。As described above, the steel bars for rebar produced by Examples 1 to 8 which are production methods within the scope of the present invention and Comparative Examples 1 to 9 which are production methods outside the scope of the present invention were subjected to tension. The test evaluated the tensile properties. A microstructure test was also performed. Tables 1 and 2 also show the above test results.
【００２８】[0028]
【表１】 [Table 1]
【００２９】[0029]
【表２】 [Table 2]
【００３０】表１及び２より、下記事項がわかる。実施
例１〜８は、高価な合金元素であるＶ含有量を０．１〜
０．３wt.%の低い範囲に抑えており、鋼の加熱温度、及
び圧延温度も適正であり、鉄筋として必要な引張特性を
有するものを得ることができた。これにより、従来より
も安価に鉄筋の製造が可能となった。Tables 1 and 2 show the following. In Examples 1 to 8, the content of V, which is an expensive alloy element, was set to 0.1 to 0.1.
It was suppressed to a low range of 0.3 wt.%, The heating temperature and the rolling temperature of the steel were also appropriate, and a steel bar having the necessary tensile properties could be obtained. This has made it possible to manufacture rebar at a lower cost than before.
【００３１】これに対して、比較例では、下記のように
問題点が必ずしも解決されていない。比較例１は、Ｓｉ
含有量が本発明の範囲より低いため、フェライトの面積
率が不足して、リューダース帯の伸びを十分に確保する
ことができず、従って、十分な降伏棚の伸びを得ること
ができなかった。On the other hand, in the comparative example, the problems are not necessarily solved as described below. Comparative Example 1 is composed of Si
Since the content is lower than the range of the present invention, the area ratio of ferrite is insufficient, it is not possible to sufficiently secure the elongation of the Luders zone, and therefore, it is not possible to obtain sufficient elongation of the yield shelf. .
【００３２】比較例２は逆にＳｉ含有量が本発明の範囲
より高い場合であり、非金属介在物が多量に混入したた
めにやはり降伏棚の伸びが小さい。比較例３は、本発明
の範囲より、Ｍｎ及びＮ含有量が低く、Ｔｉ含有量が高
いため、Ｍｎによる固溶強化、ＮによるＶＮの析出強化
が不足し、更に、ＣがＴｉと結合して鋼中のパーライト
量が少なくなってしまったため、所望の降伏強度を得る
ことはできなかった。Comparative Example 2 is a case where the Si content is higher than the range of the present invention, and the elongation of the yield shelf is also small because a large amount of nonmetallic inclusions are mixed. In Comparative Example 3, since the Mn and N contents were lower and the Ti content was higher than the range of the present invention, solid solution strengthening by Mn and precipitation strengthening of VN by N were insufficient, and C was bonded to Ti. Therefore, the desired yield strength could not be obtained because the amount of pearlite in the steel was reduced.
【００３３】比較例４は、本発明の範囲より、Ｍｎ及び
Ｃｒ含有量が高いため、組織がベイナイトになってしま
い、降伏点が発生していない。従って、リューダース伸
びを発生させることができなかった。In Comparative Example 4, since the contents of Mn and Cr were higher than those of the present invention, the structure became bainite, and no yield point was generated. Therefore, Luders elongation could not be generated.
【００３４】比較例５は、Ｖ含有量が本発明の範囲より
低いため、Ｖによる析出強化が不足して、所望の降伏強
度を得ることはできなかった。比較例６は、Ｖ及びＮ含
有量が本発明の範囲より高いため、強度が高過ぎて、十
分なリューダース伸びを得ることはできなかった。In Comparative Example 5, since the V content was lower than the range of the present invention, the precipitation strengthening by V was insufficient, and the desired yield strength could not be obtained. In Comparative Example 6, since the V and N contents were higher than the range of the present invention, the strength was too high and sufficient Luders elongation could not be obtained.
【００３５】比較例７は、Ｃ含有量が本発明の範囲より
低いため、必要な降伏強度を得ることができなかった。
また、sol.Ａｌが本発明の範囲より低いため、圧延後の
棒鋼にブローホール性の線状疵が多数見られた。In Comparative Example 7, the required yield strength could not be obtained because the C content was lower than the range of the present invention.
Further, since sol.Al was lower than the range of the present invention, a number of blowhole-like linear flaws were found in the rolled steel bar.
【００３６】比較例８は、Ｃ含有量が高すぎるため、フ
ェライト量が不足して、十分なリューダース伸びを得る
ことができなかった。比較例９は、sol.Ａｌ含有量が高
過ぎたために非金属介在物が多量に混じり、伸びが十分
でない。In Comparative Example 8, since the C content was too high, the amount of ferrite was insufficient and sufficient Luders elongation could not be obtained. In Comparative Example 9, since the sol.Al content was too high, a large amount of nonmetallic inclusions were mixed, and the elongation was insufficient.
【００３７】次に、化学成分組成が本発明の範囲内にあ
る一定の供試鋼を用い、加熱温度及び圧延仕上げ温度
を、本発明の範囲の内外に変化させて、前記試験と同様
の方法により呼び名Ｄ２２の異径棒鋼を製造した。この
ようにして得られた、本発明の範囲内の製造方法である
実施例９、及び、本発明の範囲外の製造方法である比較
例１０〜１２により製造された鉄筋用棒鋼について、引
張試験及びミクロ組織試験を行なった。Next, the same method as in the above test was carried out by using a certain test steel having a chemical composition within the range of the present invention and changing the heating temperature and the rolling finish temperature to within and outside the range of the present invention. Produced a steel bar having a different diameter of D22. Tensile tests were performed on the steel bars for reinforcing bars obtained in Example 9 which is the manufacturing method within the scope of the present invention and Comparative Examples 10 to 12 which were obtained outside the scope of the present invention. And a microstructure test.
【００３８】表３に、上記試験における供試鋼の化学成
分組成及び圧延条件、並びに、引張試験等の結果を示
す。Table 3 shows the chemical composition and rolling conditions of the test steel in the above test, and the results of a tensile test and the like.
【００３９】[0039]
【表３】 [Table 3]
【００４０】表３より、下記事項がわかる。実施例９
は、鉄筋として良好な特性を有するものを得ることがで
きた。これに対して、比較例１０〜１２では、下記のよ
うに問題点が必ずしも解決されていない。Table 3 shows the following. Example 9
Was able to obtain a steel bar having good characteristics. On the other hand, in Comparative Examples 10 to 12, the problems are not necessarily solved as described below.
【００４１】比較例１０は、成分組成は適正であるが、
加熱温度及び仕上げ温度とも高過ぎたため、ベイナイト
が発生して、降伏現象が起きていない。比較例１１は、
成分組成及び加熱温度は適正であるが、中間水冷を施さ
なかったため、仕上げ温度が本発明の範囲より高くなっ
てしまい、このためベイナイトが発生して、やはり降伏
現象を起こしていない。In Comparative Example 10, although the component composition was appropriate,
Since both the heating temperature and the finishing temperature were too high, bainite was generated and no yield phenomenon occurred. Comparative Example 11
Although the component composition and the heating temperature are appropriate, the intermediate temperature was not applied, so that the finishing temperature was higher than the range of the present invention, and bainite was generated, and the yield phenomenon did not occur.
【００４２】比較例１２は、成分組成は適正であるが、
加熱温度及び仕上げ温度とも低過ぎたため、鋼材の変形
能が不足して、多数の割れが発生した。In Comparative Example 12, although the component composition was appropriate,
Since both the heating temperature and the finishing temperature were too low, the deformability of the steel material was insufficient and many cracks occurred.
【００４３】[0043]
【発明の効果】以上述べたように、この発明によれば、
十分な延性を有する高強度鉄筋を、高価な合金元素資源
を節減しつつ、また、極端な低温圧延をしなくてもよい
ので生産性の低下をきたすということもなく、従って、
安価に製造することが可能となる。この発明は、このよ
うな高強度鉄筋の製造方法を提供することができ、工業
上有用な効果がもたらされる。As described above, according to the present invention,
A high-strength rebar having sufficient ductility, while saving expensive alloy element resources, and without having to perform extreme low-temperature rolling, without causing a decrease in productivity,
It can be manufactured at low cost. The present invention can provide a method for producing such a high-strength rebar, and has an industrially useful effect.
【図１】引張試験における応力−歪み曲線によりリュー
ダース伸びを説明する図である。FIG. 1 is a diagram illustrating Luders elongation based on a stress-strain curve in a tensile test.
Ａ：弾性伸び Ｂ：リューダース伸び Ｃ：加工硬化による伸び Ｄ：降伏棚の伸び Ｅ：目標下限応力 Ｆ：目標上限応力 A: elastic elongation B: Luders elongation C: elongation due to work hardening D: elongation of yield shelf E: target lower limit stress F: target upper limit stress
Claims (1)
合を含む、を含有し、残部Ｆｅ及び不可避不純物よりな
る化学成分組成の鋼塊又は鋼片を、９００〜１０００℃
の範囲内の温度に加熱した後、８５０〜９５０℃の範囲
内の仕上げ圧延温度で圧延し、空冷し、そして、得られ
る圧延鋼材の降伏応力を６８５Ｎ／ｍｍ2 以上で、且つ
リューダース帯の伸びを０．６％以上にすることを特徴
とする、高強度鉄筋の製造方法。1. C: 0.25 to 0.50 wt.%, Si: 1.0 to 2.0 wt.%, Mn: 1.0 to 2.0 wt.%, Cr: 0.01 to 0.50 wt. %, V: 0.10 to 0.30 wt.%, Sol. Al: 0.010 to 0.100 wt.%, N: 0.008 to 0.030 wt.%, And Ti: 0.010 wt.% Less than, including when not adding Ti, a steel ingot or a steel slab having a chemical composition composed of the balance of Fe and unavoidable impurities at 900 to 1000 ° C.
After being heated to a temperature in the range of 850 to 950 ° C., it is rolled at a finish rolling temperature in the range of 850 to 950 ° C., air-cooled, and the yield stress of the obtained rolled steel material is 685 N / mm 2 or more, and the A method for producing a high-strength rebar, wherein the elongation is 0.6% or more.
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|---|---|---|---|
| JP20282597A JP3756291B2 (en) | 1997-07-29 | 1997-07-29 | Manufacturing method of high strength rebar |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20282597A JP3756291B2 (en) | 1997-07-29 | 1997-07-29 | Manufacturing method of high strength rebar |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1150147A true JPH1150147A (en) | 1999-02-23 |
| JP3756291B2 JP3756291B2 (en) | 2006-03-15 |
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ID=16463819
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| Country | Link |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012067363A (en) * | 2010-09-24 | 2012-04-05 | Kobe Steel Ltd | High-strength reinforcing bar and manufacturing method therefor |
| CN111172459A (en) * | 2020-01-19 | 2020-05-19 | 江苏省沙钢钢铁研究院有限公司 | HRB600E vanadium-titanium microalloyed high-strength anti-seismic hot-rolled steel bar |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102796961B (en) * | 2012-09-14 | 2014-01-29 | 武钢集团昆明钢铁股份有限公司 | 600MPa high-performance fire-resistant aseismic reinforcing steel bar for concrete and production thereof |
| CN107385342A (en) * | 2017-08-02 | 2017-11-24 | 首钢水城钢铁（集团）有限责任公司 | A kind of large-specification high-intensity steel rod and its manufacturing process |
-
1997
- 1997-07-29 JP JP20282597A patent/JP3756291B2/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012067363A (en) * | 2010-09-24 | 2012-04-05 | Kobe Steel Ltd | High-strength reinforcing bar and manufacturing method therefor |
| CN111172459A (en) * | 2020-01-19 | 2020-05-19 | 江苏省沙钢钢铁研究院有限公司 | HRB600E vanadium-titanium microalloyed high-strength anti-seismic hot-rolled steel bar |
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