JP5743382B2 - Steel material for earthquake-resistant structure and manufacturing method thereof - Google Patents
Steel material for earthquake-resistant structure and manufacturing method thereof Download PDFInfo
- Publication number
- JP5743382B2 JP5743382B2 JP2009067318A JP2009067318A JP5743382B2 JP 5743382 B2 JP5743382 B2 JP 5743382B2 JP 2009067318 A JP2009067318 A JP 2009067318A JP 2009067318 A JP2009067318 A JP 2009067318A JP 5743382 B2 JP5743382 B2 JP 5743382B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel
- rolling
- steel material
- earthquake
- 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.)
- Active
Links
- 229910000831 Steel Inorganic materials 0.000 title claims description 77
- 239000010959 steel Substances 0.000 title claims description 77
- 239000000463 material Substances 0.000 title claims description 39
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 238000005096 rolling process Methods 0.000 claims description 29
- 239000000203 mixture Substances 0.000 claims description 17
- 238000005098 hot rolling Methods 0.000 claims description 15
- 238000001816 cooling Methods 0.000 claims description 11
- 230000007704 transition Effects 0.000 claims description 8
- 229910001035 Soft ferrite Inorganic materials 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910001563 bainite Inorganic materials 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000012467 final product Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910001562 pearlite Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 238000009826 distribution Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 229910052726 zirconium Inorganic materials 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims 2
- 230000000694 effects Effects 0.000 description 11
- 239000000047 product Substances 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 5
- 230000006378 damage Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000009749 continuous casting Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000001066 destructive effect Effects 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
本発明は、耐震性構造物用鋼材及びその製造方法に係り、特に高層建築物、橋梁、ラインパイプなど地震による被害を受けやすい鋼構造物の構築に用いられる鋼材及びその製造法に関する。 The present invention relates to a steel material for an earthquake-resistant structure and a manufacturing method thereof, and more particularly to a steel material used for construction of a steel structure that is easily damaged by an earthquake such as a high-rise building, a bridge, a line pipe, and the manufacturing method thereof.
高層建築物、橋梁、ラインパイプなどの構築に用いられる鋼材は、大地震時を想定した変形にあっても、倒壊や落下或いは破裂などの決定的な破壊から免れるようにするために、通常求められる高強度や高靭性の他に、延性の大きいことが求められている。 Steel materials used for construction of high-rise buildings, bridges, line pipes, etc. are usually sought in order to avoid destructive destruction such as collapse, fall, or rupture even in the case of deformation assuming a large earthquake. In addition to high strength and high toughness, high ductility is required.
このような延性は、一般に、鋼材の降伏点を低くすることによって塑性変形能を高めること、具体的には、特許文献1に記載されているように、鋼材の機械的特性のうち、一様伸びを高めることによって達成される。また、いわゆる強度−延性バランス、強度×均一伸びを向上させることが必要なことも知られている(特許文献2参照)。 Such ductility generally increases the plastic deformability by lowering the yield point of the steel material. Specifically, as described in Patent Document 1, it is uniform among the mechanical properties of the steel material. This is achieved by increasing the elongation. It is also known that it is necessary to improve the so-called strength-ductility balance, strength × uniform elongation (see Patent Document 2).
また、かかる鋼材の組成についても、例えば、特許文献3には、微量のCrを添加することによって低降伏化を達成できるとして、「mass%でC:0.10〜0.18%、Si:0.05〜0.50%,Mn:0.6〜1.3%,Cr:0.1〜1.0%、P:0.020%以下、S:0.005%以下、Al:0.1%以下、N:0.0060%以下、0.38≦Ceq≦0.43、残部Feおよび不可避的不純物の組成とフェライト−パーライトを主相とする金属組織を有する低降伏比鋼板。
Ceq=C+Si/24+Mn/6+Ni/40+Cr/5+Mo/4+V/14
但し、C、Si、Mn、Ni、Cr、Mo、V:各元素の含有量(mass%)」が提案されている。
Also, regarding the composition of such steel materials, for example, in Patent Document 3, it is possible to achieve low yield by adding a small amount of Cr, “mass% C: 0.10 to 0.18%, Si: 0.05 to 0.50%, Mn: 0.6 to 1.3%, Cr: 0.1 to 1.0%, P: 0.020% or less, S: 0.005% or less, Al: 0 .1% or less, N: 0.0060% or less, 0.38.ltoreq.Ceq.ltoreq.0.43, composition of balance Fe and inevitable impurities, and low yield ratio steel sheet having a metal structure mainly composed of ferrite-pearlite.
Ceq = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14
However, “C, Si, Mn, Ni, Cr, Mo, V: content of each element (mass%)” has been proposed.
上記特許文献1,2に示されているように、一様伸びを向上させることにより耐震性を向上させることが可能になる。この場合において、鋼材が建築物などの強度部材として使用される場合、地震波に起因する応力は鋼材のL方向のみならずC方向にもかかるので、上記一様伸び値の向上は当然、C方向についても行われなければならない。 As shown in Patent Documents 1 and 2, it is possible to improve the earthquake resistance by improving the uniform elongation. In this case, when the steel material is used as a strength member such as a building, the stress caused by the seismic wave is applied not only to the L direction of the steel material but also to the C direction. Must also be done.
また、地震波に起因する致命的な破壊を回避するためには、一様伸びの他に全伸び、すなわち、「一様伸び+局部伸び」の値が大きいことが要求される。さらに、鋼材の使用環境を考慮すれば、破面遷移温度(vTrs)によって代表される靭性が高いことが要求され、これについても異方性が小さいことが必要である。特許文献3には、降伏比を低下させる手段が示されているが、異方性を小さくする手段については示されていない。 Further, in order to avoid a fatal destruction caused by seismic waves, it is required that the total elongation, that is, the value of “uniform elongation + local elongation” is large in addition to uniform elongation. Furthermore, considering the use environment of the steel material, it is required that the toughness represented by the fracture surface transition temperature (vTrs) is high, and it is also necessary for this to have low anisotropy. Patent Document 3 shows means for reducing the yield ratio, but does not show means for reducing the anisotropy.
しかしながら、特許文献1〜3に記載の手段による場合、硬質第二相の分布状態によっては、上記耐震性構造物用鋼材に要求される諸特性が満たされない場合がある。例えば、特許文献1、2に記載の一様伸び値は、鋼材の圧延方向(L方向)の値であって、C方向の値は不明である。同様に、特許文献3に記載の手段も同様である。特に、一様伸び及び破面遷移温度の異方性を小さくすることは重要であるにもかかわらず、そのための具体的手段については検討がなされていない。 However, when the means described in Patent Documents 1 to 3 are used, depending on the distribution state of the hard second phase, various characteristics required for the steel material for an earthquake-resistant structure may not be satisfied. For example, the uniform elongation values described in Patent Documents 1 and 2 are values in the rolling direction (L direction) of the steel material, and the values in the C direction are unknown. Similarly, the means described in Patent Document 3 is the same. In particular, although it is important to reduce the anisotropy of the uniform elongation and the fracture surface transition temperature, no specific means for that purpose has been studied.
本発明は、耐震性構造物用鋼材に要求される諸特性について検討し、一様伸び、全伸び及び破面遷移温度によって代表される靭性が高く、かつ、これらの異方性が小さく、一様伸び(以下uELという)及び破面遷移温度(以下vTrsという)のL方向、C方向の差がそれぞれ0.7%以下及び8℃以下である耐震性構造物用鋼材である。本発明は、従来技術より改善した耐震性構造物用鋼材及びその製造方法を提供することを目的とする。 The present invention examined various properties required for earthquake resistance structure steel material, uniform elongation, high toughness typified by total elongation and fracture appearance transition temperature, and these anisotropy rather small, It is a steel material for earthquake-resistant structures in which the difference in the L direction and C direction of uniform elongation (hereinafter referred to as uEL) and fracture surface transition temperature (hereinafter referred to as vTrs) is 0.7% or less and 8 ° C. or less, respectively. An object of this invention is to provide the steel material for earthquake-resistant structures improved from the prior art , and its manufacturing method.
本発明は、鋼組成においてMn含有量を低くとり、かつ、これに少量のCrを含有させるときは、軟質フェライト相中に硬質第二相がランダムに分布するようになるとの知見を得て完成されたものであり、その具体的構成は、下記のとおりである。 The present invention is completed with the knowledge that when the Mn content is low in the steel composition and a small amount of Cr is contained in the steel composition, the hard second phase is randomly distributed in the soft ferrite phase. The specific configuration is as follows.
本発明に係る耐震性構造物用鋼材は、鋼組成が質量%で、C:0.01〜0.2%、Si:0.01〜1.0%、Mn:0.5%未満、P:0.030%以下、S:0.030%以下、Al:0.1%以下、Cr:1.28〜3.0%、Ti:0.001〜0.030%、残部Fe及び不可避的不純物からなり、金属組織が軟質フェライト相中に硬質第二相がランダムに分布しているという特徴を有する。 The steel material for earthquake-resistant structures according to the present invention has a steel composition of mass%, C: 0.01 to 0.2%, Si: 0.01 to 1.0%, Mn: less than 0.5%, P : 0.030% or less, S: 0.030% or less, Al: 0.1% or less, Cr: 1.28 to 3.0%, Ti: 0.001 to 0.030%, balance Fe and inevitable It consists of impurities, and has a feature that the metal structure has a hard second phase randomly distributed in the soft ferrite phase.
上記発明において、硬質第二相の平均アスペクト比が圧延方向断面及び圧延直角方向断面においてともに5.0以下であることが好ましい。 In the said invention, it is preferable that the average aspect-ratio of a hard 2nd phase is 5.0 or less in a rolling direction cross section and a rolling perpendicular direction cross section.
上記発明において、鋼組成を、さらに、Cu:1%以下、Ni:1%以下及びMo:1%以下から選ばれる1種又は2種以上を含有するものとすることができる。また、V:0.1%以下及びNb:0.05%以下から選ばれる1種又は2種を含有するものとすることができ、さらに、Ca:0.0005〜0.005%、REM:0.001〜0.020%、Mg:0.0005〜0,005%及びZr:0.0005〜0.0030%から選ばれる1種又は2種以上を含するものとすることができる。 In the above invention, the steel composition may further contain one or more selected from Cu: 1% or less, Ni: 1% or less, and Mo: 1% or less. Moreover, it can contain 1 type or 2 types chosen from V: 0.1% or less and Nb: 0.05% or less, Furthermore, Ca: 0.0005-0.005%, REM: One or more selected from 0.001 to 0.020%, Mg: 0.0005 to 0.005%, and Zr: 0.0005 to 0.0030% may be included.
上記耐震性構造物用鋼材は、上記に記載の何れかの鋼組成を有する素材を1000〜1350℃に加熱後、熱間圧延を施して最終製品形状に成形するに当たり、前記熱間圧延の最終圧延温度をAr3〜Ar3+150℃の範囲とするとともに、熱間圧延の終了後500℃までの範囲を放冷することによって製造することができる。また、前記熱間圧延の終了後、Ar3−50℃以下の温度から500℃までの温度範囲を1〜80℃/sの速度で加速冷却することによって製造することができる。 The steel material for an earthquake-resistant structure is heated at 1000 to 1350 ° C. after being heated to 1000 to 1350 ° C. and then formed into a final product shape. the rolling temperature Ar 3 as well as a range of ~Ar 3 + 150 ℃, can be prepared by cooling a range of up to 500 ° C. after completion of the hot rolling. Can also be produced by accelerated cooling the rear end of the hot rolling, the temperature range of Ar 3 -50 ° C. from the temperature to 500 ° C. at a rate of 1 to 80 ° C. / s.
なお、本発明に係る耐震性構造物用鋼材は、いわゆる「圧延まま」の状態で製造することができる。 In addition, the steel material for earthquake-resistant structures according to the present invention can be manufactured in a so-called “as-rolled” state.
本発明により提供される耐震性構造物用鋼材を、一様伸び、全伸び及び破面遷移温度によって代表される靭性を十分高くとりながら、異方性が小さいという特性を有する。これにより、大地震時を想定した変形にあっても高層建築物、橋梁、ラインパイプなどを倒壊や落下或いは破裂などの決定的な破壊から免れるようにすることが一層確実になる。 The steel material for earthquake-resistant structures provided by the present invention has a characteristic that the anisotropy is small while taking sufficiently high toughness represented by uniform elongation, total elongation and fracture surface transition temperature. This makes it even more reliable to avoid high-rise buildings, bridges, line pipes, etc. from destructive destruction such as collapse, fall, or rupture even in the case of deformation assuming a large earthquake.
本発明に係る耐震性構造物用鋼材は、下記の組成を有する。 The steel material for earthquake-resistant structures according to the present invention has the following composition.
C:0.01〜0.2%
Cは硬質第二相の硬さとその量を支配する基本的な元素であり、所定の強度を得るために0.01%(質量比:以下同様)を必要とする。しかし、その含有量が0.2%を超えると溶接性を損なう。したがって、C含有量は0.01〜0.2%、好ましくは、0.05〜0.18%に制限される。
C: 0.01 to 0.2%
C is a basic element that governs the hardness and amount of the hard second phase, and requires 0.01% (mass ratio: the same applies hereinafter) in order to obtain a predetermined strength. However, if the content exceeds 0.2%, weldability is impaired. Therefore, the C content is limited to 0.01 to 0.2%, preferably 0.05 to 0.18%.
Si:0.01〜1.0%
Siは鋼中に固溶して鋼強度を向上させる基本的な元素であり、その目的を達成するためには0.01%以上の添加が必要であるが、過度の添加は溶接熱影響部の靭性を損なうため、上限が1%に、好ましくは0.6%に制限される。
Si: 0.01 to 1.0%
Si is a basic element that improves the strength of steel by solid solution in steel. To achieve the purpose, addition of 0.01% or more is necessary. In order to impair the toughness, the upper limit is limited to 1%, preferably 0.6%.
Mn:0.5%未満
Mnは、本発明においては、0.5%未満に制限される。通常の溶接構造用鋼においては、Mnは高強度化のため1%以上含有する。しかしながら、かかる含有量をとるときには、素材の連続鋳造過程において生ずるMnの正負ミクロ偏析の拡大によって熱間圧延後の製品組織に硬質第二相がバンド状に分布するようになり、鋼材の幅方向や板厚方向の一様伸びを著しく低下させる原因になる。かかる問題を回避するため、本発明においてはMn含有量を0.5%未満、好ましくは0.01〜0.4%に制限する。
Mn: less than 0.5% Mn is limited to less than 0.5% in the present invention. In ordinary welded structural steel, Mn is contained in an amount of 1% or more for high strength. However, when such a content is taken, the hard second phase is distributed in a band shape in the product structure after hot rolling due to the expansion of positive and negative microsegregation of Mn that occurs in the continuous casting process of the material, and the width direction of the steel material Or the uniform elongation in the plate thickness direction is significantly reduced. In order to avoid such a problem, in the present invention, the Mn content is limited to less than 0.5%, preferably 0.01 to 0.4%.
P:0.030%以下
Pは硬質第二相がバンド状に分布する傾向を助長する元素であり、その含有量は極力少ないことが望ましい。しかしながら、その過度の低減は製造コストの上昇を招く。これらの事情を勘案してPの含有量は0.030%以下、好ましくは、0.025%以下とする。
P: 0.030% or less P is an element that promotes the tendency of the hard second phase to be distributed in a band shape, and its content is preferably as small as possible. However, the excessive reduction leads to an increase in manufacturing cost. Considering these circumstances, the P content is 0.030% or less, preferably 0.025% or less.
S:0.030%以下
Sは、鋼中において第二相のバンド状析出を助長する元素である反面、溶接熱影響部において析出するMnSがフェライト変態核として機能し、溶接熱影響部靭性(HAZ靭性)を向上させる効果を奏する。かかる観点からS含有量は特にMn含有量との関係において適正に調整されなければならない。本発明におけるMn含有量0.5%未満においてはS含有量は0.030%以下、好ましくは0.002〜0.015%の範囲とする。
S: 0.030% or less S is an element that promotes band-like precipitation of the second phase in the steel, but MnS precipitated in the weld heat affected zone functions as a ferrite transformation nucleus, and weld heat affected zone toughness ( There is an effect of improving HAZ toughness). From this point of view, the S content must be properly adjusted, particularly in relation to the Mn content. In the present invention, when the Mn content is less than 0.5%, the S content is 0.030% or less, preferably 0.002 to 0.015%.
Al:0.1%以下
Alは、脱酸元素として機能し、鋼中の酸化物系介在物を低減して鋼材の靭性及び延性の向上に寄与する。しかしながら、その添加量(鋼中存在量)が0.1%を超えると、上記効果が飽和するばかりか、アルミナクラスタの増加により靭性、延性の低下をもたらす。したがって、Alの添加量は0.1%以下、好ましくは、0.005%〜0.1%とする。
Al: 0.1% or less Al functions as a deoxidizing element and contributes to the improvement of the toughness and ductility of the steel material by reducing oxide inclusions in the steel. However, when the addition amount (abundance in steel) exceeds 0.1%, the above effect is saturated, and toughness and ductility are reduced due to an increase in alumina clusters. Therefore, the amount of Al added is 0.1% or less, preferably 0.005% to 0.1%.
Cr:0.1〜3.0%
Crは、フェライト相を強化し、高強度化に寄与する。また、その添加により、素材の連続鋳造過程において正負ミクロ偏析の拡大を生ずることがなく、したがって、バンド状組織の生成が助長されることがなく、かえって、軟質フェライト相中に硬質第二相をランダムに分布させ、異方性を軽減させる効果がある。このような効果は、0.1%以上の添加で顕著に認められるようになる。しかしながら、3%を超える添加は溶接性を損なうため好ましくない。かかる観点から本発明においてはCrの添加量は0.1〜3.0%、好ましくは、0.3〜2.5%の範囲とする。
Cr: 0.1-3.0%
Cr strengthens the ferrite phase and contributes to high strength. In addition, the addition does not cause the expansion of positive and negative microsegregation in the continuous casting process of the material, and therefore the formation of a band-like structure is not promoted. Instead, a hard second phase is added in the soft ferrite phase. It is distributed at random and has the effect of reducing anisotropy. Such an effect becomes noticeable when 0.1% or more is added. However, addition exceeding 3% is not preferable because it deteriorates weldability. From this point of view, in the present invention, the amount of Cr added is in the range of 0.1 to 3.0%, preferably 0.3 to 2.5%.
Ti:0.001〜0.030%
Tiは、鋼中の鋼中のNと結合してTiNを形成し、Nを固定して鋼の靭性向上や溶接熱影響部靭性向上に寄与する。その効果は0.001%以上で顕著になるが、0.030%を超えるとTiCの析出に伴う脆化が生ずる。したがって、Tiは0.001〜0.030%の範囲で添加される。
Ti: 0.001 to 0.030%
Ti combines with N in the steel in the steel to form TiN, and fixes N to contribute to improving the toughness of the steel and improving the weld heat affected zone toughness. The effect becomes remarkable at 0.001% or more, but when it exceeds 0.030%, embrittlement accompanying precipitation of TiC occurs. Therefore, Ti is added in the range of 0.001 to 0.030%.
本発明では、上記の成分のほか、下記の成分を任意に添加することができる。 In the present invention, in addition to the above components, the following components can be optionally added.
Cu:1%以下、Ni:1%以下及びMo:1%以下から選ばれる1種又は2種以上
これらの元素は、軟質フェライトを固溶強化することにより鋼の強度を向上させる効果がある。このうち、Cuは、Crと同様に、軟質フェライト相中に硬質第二相をランダムに分布させ、異方性を軽減させる効果があり、この効果を得るために添加する場合には、0.05%以上とすること好ましい。しかしながら、Cuは、1.0%を超えて添加するとCuの析出による脆化の原因になるので、Cuの添加量は1%以下でなければならない。Niは、靭性を低下させることなく強度を向上させる元素であり、この効果を得るために添加する場合には0.05%以上とすることが好ましい。しかし、過度の添加は、硬質第二相をバンド状に析出させる原因となるので、上限を1%に制限する。また、Moは軟質フェライト相中に硬質第二相をランダムに分布させ、異方性を軽減させる効果があり、鋼の高強度化に有用である。この効果を得るためには添加する場合は、0.05%以上とすることが好ましい。しかし、過剰の添加は溶接性を低下させるため、上限を1%とした。なお、これらの元素は、上記範囲でそれぞれ独立して添加可能である。
Cu: 1% or less, Ni: 1% or less, and Mo: 1% or more selected from 1% or less These elements have an effect of improving the strength of the steel by solid-solution strengthening soft ferrite. Among these, Cu, like Cr, has the effect of randomly distributing the hard second phase in the soft ferrite phase and reducing the anisotropy. It is preferable to set it to 05% or more. However, if Cu is added in excess of 1.0%, it causes embrittlement due to precipitation of Cu, so the added amount of Cu must be 1% or less. Ni is an element that improves the strength without reducing toughness, and is preferably 0.05% or more when added to obtain this effect. However, excessive addition causes the hard second phase to precipitate in a band shape, so the upper limit is limited to 1%. Mo has the effect of randomly distributing the hard second phase in the soft ferrite phase to reduce anisotropy, and is useful for increasing the strength of steel. In order to acquire this effect, when adding, it is preferable to set it as 0.05% or more. However, excessive addition reduces weldability, so the upper limit was made 1%. These elements can be added independently within the above range.
V:0.1%以下及びNb:0.05以下から選ばれる1種又は2種
Nbは結晶粒の微細化及び炭化物等の析出強化により、Vは炭化物等の析出強化により鋼の強度を向上させる効果がある。しかしながら、Nbはオーステナイトの未再結晶温度域を高温側に移動させ、異方性を助長するのでその添加量が0.05%以下に制限される。また、Vはその添加量が0.1%を超えるとHAZ靭性を低下させる原因になるので上限を0.1%とする。これらの元素についても、上記範囲でそれぞれ独立して添加可能である。
1 or 2 types selected from V: 0.1% or less and Nb: 0.05 or less Nb improves the strength of steel by refining crystal grains and strengthening precipitation of carbides, etc. V improves precipitation strength of carbides, etc. There is an effect to make. However, Nb moves the non-recrystallization temperature range of austenite to the high temperature side and promotes anisotropy, so that the addition amount is limited to 0.05% or less. Further, if V is added in an amount exceeding 0.1%, the HAZ toughness is lowered, so the upper limit is made 0.1%. These elements can also be added independently within the above range.
Ca:0.0005〜0.005%、REM:0.001〜0.020%、Mg:0.0005〜0,005%及びZr:0.0005〜0.0030%から選ばれる1種又は2種以上
これらの元素は、いずれも溶接熱影響部の靭性を向上させるために有効な元素であり、鋼材に対して適用される溶接法に応じてその下限値以上の量においてかつ、鋼の清浄度を害さない限度において添加することができる。これらの元素についても、上記範囲でそれぞれ独立して添加可能である。
One or two selected from Ca: 0.0005 to 0.005%, REM: 0.001 to 0.020%, Mg: 0.0005 to 0.005%, and Zr: 0.0005 to 0.0030% More than seeds These elements are all effective elements to improve the toughness of the heat-affected zone of the weld. It can be added to the extent that it does not harm the degree. These elements can also be added independently within the above range.
上記組成を有する鋼は、そのミクロ組織における硬質第二相の平均アスペクト比が圧延方向断面及び圧延直角方向断面においてともに5.0以下であるものとすることによって一層確実に本発明の目的を達することができるようになる。これは、圧延方向断面(以下「L方向断面」と称する)及び圧延直角方向断面(以下「C方向断面」と称する)における硬質第二相の平均アスペクト比がともに5.0以下とした場合は、硬質第二相の存在形態が従来鋼の如きバンド状ではなくランダム状となり、一様伸び、全伸び及び靭性の異方性が低減されるからである。 The steel having the above composition achieves the object of the present invention more reliably by setting the average aspect ratio of the hard second phase in the microstructure to 5.0 or less in both the cross section in the rolling direction and the cross section in the direction perpendicular to the rolling direction. Will be able to. When the average aspect ratio of the hard second phase in the rolling direction cross section (hereinafter referred to as “L direction cross section”) and the rolling perpendicular cross section (hereinafter referred to as “C direction cross section”) is 5.0 or less, This is because the existence form of the hard second phase is not a band shape as in the conventional steel, but a random shape, and uniform elongation, total elongation, and anisotropy of toughness are reduced.
上記硬質第二相の平均アスペクト比は、以下のようにして決定される。すなわち、製造された鋼材から顕微鏡観察用の小サンプルを採取し、前記L方向及びC方向の各断面についてナイタール腐食によるミクロ組織を観察し、パーライトなどを硬質第二相としてその個々のアスペクト比(長径/短径)を画像処理により求め、これらの平均値を平均アスペクト比とするものである。なお、ミクロ組織の観察にあたっては、観察すべき硬質第二相の大きさに応じて、観察倍率を×200〜×500の範囲で選択するとともに視野数を3視野程度(観察面積0.4〜1mm2)とする。そして、上記により観察された各視野において認められるパーライトやベイナイトなどを硬質第二相としてその平均アスペクト比が求められるのである。上記のうち、L方向断面について求められた値がL方向平均アスペクト比であり、C方向断面について求められた値がC方向平均アスペクト比である。このような平均アスペクト比を有する硬質第二相は、前記のとおり鋼組成を適正化するとともに、さらに、以下のとおり圧延、熱処理条件を適正化することによって得ることができる。 The average aspect ratio of the hard second phase is determined as follows. That is, a small sample for microscopic observation is collected from the manufactured steel material, the microstructure due to the nital corrosion is observed for each cross section in the L direction and the C direction, and the individual aspect ratio ( (Major axis / minor axis) is obtained by image processing, and the average of these values is taken as the average aspect ratio. In the observation of the microstructure, the observation magnification is selected in the range of × 200 to × 500 according to the size of the hard second phase to be observed, and the number of fields of view is about 3 (viewing area of 0.4 to 1 mm 2 ). And the average aspect-ratio is calculated | required by making pearlite, bainite, etc. which are recognized in each visual field observed by the above into a hard 2nd phase. Among the above, the value obtained for the L-direction section is the L-direction average aspect ratio, and the value obtained for the C-direction section is the C-direction average aspect ratio. The hard second phase having such an average aspect ratio can be obtained by optimizing the steel composition as described above and further by optimizing the rolling and heat treatment conditions as follows.
上記に説明した耐震性構造物用鋼は、前述のとおり特定された鋼組成を有する素材を1000〜1350℃に加熱後、熱間圧延を施して最終製品形状に成形するに当たり、前記熱間圧延の最終圧延温度をAr3〜Ar3+150℃の範囲とするとともに、熱間圧延の終了後500℃までの範囲を放冷すること、又は熱間圧延の終了後Ar3−50℃以下の温度から500℃までの温度範囲を1〜80℃/sの速度で加速冷却することによって製造することができる。 When the steel having the steel composition specified as described above is heated to 1000 to 1350 ° C. and then subjected to hot rolling to form a final product shape, the above-described hot rolling the final rolling temperature with the range of Ar 3 ~Ar 3 + 150 ℃, allowed to cool to the range to the end after 500 ° C. hot rolling, or after completion of Ar 3 -50 ° C. below the temperature of the hot rolling To 500 ° C. can be produced by accelerated cooling at a rate of 1 to 80 ° C./s.
上記圧延プロセスにおいて、鋼素材の加熱温度を1000〜1350℃に限定するのは、加熱温度が1000℃未満の場合、素材である連続鋳造鋳片内に存在するミクロ偏析の溶体化処理が不十分となり、製品に硬質第二相がバンド状に現れるのを防止し得ないからである。一方、加熱温度が1300℃を超えるときには、初期γ相が粗大化し、これに伴って製品フェライト粒が粗大化して、製品の低温靭性を低下させる結果を招くからである。 In the rolling process, the heating temperature of the steel material is limited to 1000 to 1350 ° C. When the heating temperature is less than 1000 ° C., the solution treatment of microsegregation existing in the continuous cast slab as the material is insufficient. This is because the hard second phase cannot be prevented from appearing in a band shape in the product. On the other hand, when the heating temperature exceeds 1300 ° C., the initial γ phase becomes coarse, and as a result, the product ferrite grains become coarse, resulting in a decrease in the low temperature toughness of the product.
本発明においては、熱間圧延における最終圧延温度がAr3〜Ar3+150℃の範囲に限定される。熱間圧延温度がAr3未満では、圧延の際に圧延集合組織が発達するために、製品の一様伸び、特にC方向一様伸びが低下し、異方性が大きくなるからである。反対に、最終圧延温度がAr3+150℃より高いときには、硬質第二相のサイズが粗大化し、製品の強度や衝撃値を低下させる。 In the present invention, the final rolling temperature in hot rolling is limited to the range of Ar 3 to Ar 3 + 150 ° C. This is because, when the hot rolling temperature is less than Ar 3 , a rolling texture develops during rolling, so that the uniform elongation of the product, in particular, the uniform elongation in the C direction decreases, and the anisotropy increases. On the other hand, when the final rolling temperature is higher than Ar 3 + 150 ° C., the size of the hard second phase becomes coarse, and the strength and impact value of the product are reduced.
上記の温度で熱間圧延を終えた鋼材は、熱間圧延終了後500℃までの温度範囲を放冷され、これによって主な硬質第二相としてパーライトがランダムに分布した組織が得られる。なお、この場合において、放冷とは、熱延終了後500℃までの温度区間を加速冷却せず、冷却床の上で自然放冷(空冷)されることをいう。 The steel material that has been hot-rolled at the above temperature is allowed to cool to a temperature range of up to 500 ° C. after the hot rolling is completed, thereby obtaining a structure in which pearlite is randomly distributed as the main hard second phase. In this case, the term “cooling” means that the temperature section up to 500 ° C. after the end of hot rolling is not cooled at an accelerated rate, but is naturally cooled (air cooled) on the cooling floor.
一方、熱間圧延を終えた鋼材を、Ar3−50℃以下の温度から500℃までの温度範囲を1〜80℃/sの速度で加速冷却することもできる。この場合は、主な硬質第二相がベイナイトやその微細分散物がランダムに分布した組織を得ることができる。この場合は、硬質第二相の強化及びその微細分散化によって強度を高めることができる。なお、加速冷却開始温度をAr3−50℃以下とするのは、上記ベイナイトなどの中間段階変態相の析出を確実にするためである。なお、500℃未満まで加速冷却を行うと延性が低下するために、加速冷却停止温度の下限は500℃以上とすることが好ましい。 On the other hand, the steel material that has been hot-rolled can be accelerated and cooled at a rate of 1 to 80 ° C./s in a temperature range from a temperature of Ar 3 −50 ° C. or lower to 500 ° C. In this case, it is possible to obtain a structure in which the main hard second phase is bainite and its fine dispersion are randomly distributed. In this case, the strength can be increased by strengthening the hard second phase and finely dispersing the hard second phase. The reason why the accelerated cooling start temperature is Ar 3 -50 ° C. or lower is to ensure the precipitation of the intermediate stage transformation phase such as bainite. In addition, since ductility will fall when accelerated cooling to less than 500 degreeC, it is preferable that the minimum of accelerated cooling stop temperature shall be 500 degreeC or more.
表1に示す組成の溶鋼を転炉により溶製し、連続鋳造法により厚さ:210mmのスラブに鋳造した。得られたスラブを厚板圧延機により板厚:12〜25mmの厚鋼板に圧延した。この際のスラブ加熱温度及び圧延仕上温度を表2に示す。また、仕上圧延後の冷却条件についても表2に示す。 Molten steel having the composition shown in Table 1 was melted by a converter and cast into a slab having a thickness of 210 mm by a continuous casting method. The obtained slab was rolled into a thick steel plate having a thickness of 12 to 25 mm by a thick plate rolling machine. Table 2 shows the slab heating temperature and rolling finishing temperature at this time. Table 2 also shows the cooling conditions after finish rolling.
得られた製品の板厚中心より、L方向及びC方向に沿って、平行部直径6mm、標点距離25mmの丸棒試験片、ミクロ組織観察用試験片及び2mmVノッチシャルピー衝撃試験片を切出し、強度(下降伏点(LYP)及び引張強さ(TS))、延性(一様伸び(uEL)及び全伸び(tEL))、靭性(破面遷移温度(vTrs))を測定した。なお、一様伸び(uEL)は、引張試験において引張荷重が最大となったときの試験片の伸び量を標点距離(25mm)で除した値である。 From the thickness center of the obtained product, along the L direction and the C direction, cut out a round bar test piece having a parallel part diameter of 6 mm and a gauge distance of 25 mm, a microstructure observation test piece, and a 2 mm V notch Charpy impact test piece, Strength (falling yield point (LYP) and tensile strength (TS)), ductility (uniform elongation (uEL) and total elongation (tEL)), and toughness (fracture surface transition temperature (vTrs)) were measured. The uniform elongation (uEL) is a value obtained by dividing the amount of elongation of the test piece when the tensile load becomes maximum in the tensile test by the gauge distance (25 mm).
試験結果を表3に示す。また、本発明例に係る鋼板と比較例に係る鋼板のL方向断面及びC方向断面のミクロ組織の代表例として、鋼B(圧延番号B1)及び鋼I(圧延番号I1)に係るものをそれぞれ図1及び図2に示す。なお、硬質第二相のアスペクト比は、前記のとおり、製造された鋼材から顕微鏡観察用の小サンプルを採取し、前記L方向及びC方向の各断面についてナイタール腐食によるミクロ組織を観察し、パーライトなどを硬質第二相としてその個々のアスペクト比(長径/短径)を画像処理により求め、これらの平均値を平均アスペクト比としたものである。
表3には、L方向及びC方向の硬質第2相のアスペクト比が4.8以下で、vTrsが−39℃以下、uEL及びvTrsのL方向、C方向の差がそれぞれ0.7%以下及び8℃以下である、本発明例の耐震性構造物用鋼材が示される。
The test results are shown in Table 3. Moreover, as a representative example of the microstructure of the L direction cross section and the C direction cross section of the steel plate according to the present invention and the steel plate according to the comparative example, those related to steel B (rolling number B1) and steel I (rolling number I1), respectively. It shows in FIG.1 and FIG.2. As described above, the aspect ratio of the hard second phase was obtained by taking a small sample for microscopic observation from the manufactured steel material, observing the microstructure due to nital corrosion for each cross section in the L direction and the C direction, And the like as a hard second phase, the individual aspect ratio (major axis / minor axis) is obtained by image processing, and the average value of these is defined as the average aspect ratio.
Table 3 shows that the aspect ratio of the hard second phase in the L direction and the C direction is 4.8 or less, the vTrs is −39 ° C. or less, and the difference between the L direction and the C direction of uEL and vTrs is 0.7% or less, respectively. And the steel material for earthquake-resistant structures of the example of this invention which is 8 degrees C or less is shown.
上記実施例から明らかなように、本発明により得られた鋼材は、一様伸び、全伸び及び破面遷移温度によって代表される靭性が高く、かつ、これらの異方性が小さいという特性を有する。これは図1及び図2に示すように本発明例ではミクロ組織において、L方向においても、C方向においても硬質第二相の分布がランダムになっていることに由来する。これに対し、鋼I(圧延No.I1)、鋼J(圧延No.J1)、鋼K(圧延No.K1)の場合は、Mn含有量が高すぎるため、異方性が大きくなった。また、鋼L(圧延No.L1)は、機械的特性は、異方性を含めて良好であったが、Cr含有量が高すぎるため、溶接性が悪かった。また、鋼M(圧延No.M1)は、Cr含有量が低すぎるため、強度が低かった。圧延番号A3に係るものは、組成条件は本発明範囲内にあるが、熱間圧延温度がAr3未満であるため組織がバンド状組織となり、機械的性質の異方性が大きくなった。 As is clear from the above examples, the steel material obtained by the present invention has the characteristics that the toughness represented by uniform elongation, total elongation and fracture surface transition temperature is high and these anisotropies are small. . As shown in FIGS. 1 and 2, this is because the distribution of the hard second phase is random both in the L direction and in the C direction in the microstructure of the present invention example. On the other hand, in the case of steel I (rolling No. I1), steel J (rolling No. J1), and steel K (rolling No. K1), the anisotropy was increased because the Mn content was too high. Steel L (Rolled No. L1) had good mechanical properties including anisotropy, but its weldability was poor because the Cr content was too high. Steel M (rolling No. M1) had a low strength because the Cr content was too low. In the case of rolling number A3, the composition conditions are within the scope of the present invention, but since the hot rolling temperature is less than Ar 3 , the structure becomes a band-like structure, and the anisotropy of mechanical properties is increased.
上記から明らかなように、本発明に係る鋼は、大地震時を想定した変形にあっても高層建築物、橋梁、ラインパイプなどを倒壊や落下或いは破裂などの決定的な破壊から免れるようにすることが一層確実になることが期待できる。 As is clear from the above, the steel according to the present invention is free from decisive destruction such as collapse, fall or rupture of high-rise buildings, bridges, line pipes, etc. even in deformation assuming a large earthquake. It can be expected to be even more certain.
Claims (7)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009067318A JP5743382B2 (en) | 2009-03-19 | 2009-03-19 | Steel material for earthquake-resistant structure and manufacturing method thereof |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2009067318A JP5743382B2 (en) | 2009-03-19 | 2009-03-19 | Steel material for earthquake-resistant structure and manufacturing method thereof |
Publications (2)
Publication Number | Publication Date |
---|---|
JP2010215996A JP2010215996A (en) | 2010-09-30 |
JP5743382B2 true JP5743382B2 (en) | 2015-07-01 |
Family
ID=42975127
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP2009067318A Active JP5743382B2 (en) | 2009-03-19 | 2009-03-19 | Steel material for earthquake-resistant structure and manufacturing method thereof |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP5743382B2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP7194592B2 (en) | 2016-04-07 | 2022-12-22 | マテリオン コーポレイション | Beryllium oxide integrated resistance heater |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5994819B2 (en) * | 2014-05-30 | 2016-09-21 | 新日鐵住金株式会社 | Steel plate with excellent impact resistance and method for producing the same |
CN115976408B (en) * | 2022-12-15 | 2024-08-09 | 芜湖新兴铸管有限责任公司 | Low-alloy corrosion-resistant and earthquake-resistant steel bar and production method thereof |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0756044B2 (en) * | 1990-02-15 | 1995-06-14 | 新日本製鐵株式会社 | Method for producing low yield ratio H-section steel with excellent fire resistance |
JP4864297B2 (en) * | 2004-07-21 | 2012-02-01 | 新日本製鐵株式会社 | 490 MPa class high strength steel for welded structure excellent in high temperature strength and method for producing the same |
JP4752441B2 (en) * | 2005-10-17 | 2011-08-17 | Jfeスチール株式会社 | Steel material with excellent fatigue crack propagation resistance |
JP4998708B2 (en) * | 2007-02-26 | 2012-08-15 | Jfeスチール株式会社 | Steel material with small material anisotropy and excellent fatigue crack propagation characteristics and method for producing the same |
-
2009
- 2009-03-19 JP JP2009067318A patent/JP5743382B2/en active Active
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP7194592B2 (en) | 2016-04-07 | 2022-12-22 | マテリオン コーポレイション | Beryllium oxide integrated resistance heater |
Also Published As
Publication number | Publication date |
---|---|
JP2010215996A (en) | 2010-09-30 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP3042976B1 (en) | Steel sheet for thick-walled high-strength line pipe having exceptional corrosion resistance, crush resistance properties, and low-temperature ductility, and line pipe | |
EP2264205B1 (en) | High-strength steel plate excellent in low-temperature toughness, steel pipe, and processes for production of both | |
KR101492753B1 (en) | High strength hot rolled steel sheet having excellent fatigue resistance and method for manufacturing the same | |
JP5776398B2 (en) | Low yield ratio high strength hot rolled steel sheet with excellent low temperature toughness and method for producing the same | |
US7914629B2 (en) | High strength thick steel plate superior in crack arrestability | |
JP5679114B2 (en) | Low yield ratio high strength hot rolled steel sheet with excellent low temperature toughness and method for producing the same | |
KR100799421B1 (en) | Cold-formed steel pipe and tube having excellent in weldability with 490MPa-class of low yield ratio, and manufacturing process thereof | |
JP6146358B2 (en) | High strength hot rolled steel sheet and method for producing the same | |
KR20080085739A (en) | High tension steel material having excellent weldability and plastic deformability, and cole-formed steel tube | |
JP6070642B2 (en) | Hot-rolled steel sheet having high strength and excellent low-temperature toughness and method for producing the same | |
JP6788589B2 (en) | High-strength steel with excellent brittle crack propagation resistance and its manufacturing method | |
JP3790135B2 (en) | High-strength hot-rolled steel sheet with excellent stretch flangeability and manufacturing method thereof | |
JP5082667B2 (en) | High-strength thick steel plate with excellent arrest properties and method for producing the same | |
JP6519024B2 (en) | Method of manufacturing low yield ratio high strength hot rolled steel sheet excellent in low temperature toughness | |
JPH08188847A (en) | Steel plate with composite structure, excellent in fatigue characteristic, and its production | |
JP2007177326A (en) | High tensile strength thin steel sheet having low yield ratio and its production method | |
JP4502272B2 (en) | Hot-rolled steel sheet excellent in workability and fatigue characteristics and casting method thereof | |
JP3849244B2 (en) | Steel material excellent in ductile crack growth resistance under repeated large deformation and its manufacturing method | |
JPH10306316A (en) | Production of low yield ratio high tensile-strength steel excellent in low temperature toughness | |
JPWO2020202333A1 (en) | Electric pipe and its manufacturing method, and steel pipe pile | |
WO2019180957A1 (en) | Rolled h-shaped steel and method for manufacturing same | |
JP5743382B2 (en) | Steel material for earthquake-resistant structure and manufacturing method thereof | |
JP6390813B2 (en) | Low-temperature H-section steel and its manufacturing method | |
JP4008378B2 (en) | Low yield ratio high strength steel with excellent toughness and weldability | |
JP6400517B2 (en) | High strength steel material with excellent fatigue crack propagation resistance and method for producing the same |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A821 Effective date: 20100716 |
|
RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20100716 |
|
A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20120223 |
|
A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20130807 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20130813 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20131011 |
|
A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20131210 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20140306 |
|
A911 | Transfer to examiner for re-examination before appeal (zenchi) |
Free format text: JAPANESE INTERMEDIATE CODE: A911 Effective date: 20140409 |
|
A912 | Re-examination (zenchi) completed and case transferred to appeal board |
Free format text: JAPANESE INTERMEDIATE CODE: A912 Effective date: 20140606 |
|
A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20150304 |
|
A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20150428 |
|
R150 | Certificate of patent or registration of utility model |
Ref document number: 5743382 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |