JP2000192141A - Production of hot rolled steel for structural purpose low in yield strength and narrow in its varing range - Google Patents
Production of hot rolled steel for structural purpose low in yield strength and narrow in its varing rangeInfo
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- JP2000192141A JP2000192141A JP10370388A JP37038898A JP2000192141A JP 2000192141 A JP2000192141 A JP 2000192141A JP 10370388 A JP10370388 A JP 10370388A JP 37038898 A JP37038898 A JP 37038898A JP 2000192141 A JP2000192141 A JP 2000192141A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、建築、土木などの
分野において、ブレース材、良加工材などの構造物とし
て用いて好適な、降伏強さが低い構造用熱延鋼材の製造
方法に関し、特に降伏強さの変動範囲が狭く、安定した
材質を得ることができる、構造用熱延鋼材の製造方法に
関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot-rolled structural steel material having a low yield strength, which is suitable for use as a structure such as a brace material or a well-processed material in the fields of construction and civil engineering. In particular, the present invention relates to a method for manufacturing a hot-rolled steel material for a structure, in which a fluctuation range of yield strength is narrow and a stable material can be obtained.
【０００２】[0002]
【従来の技術】建築、土木用の鋼管、カラムなどの素材
として用いられる鋼材で、これらが特に良好な加工性が
求められる場合や、耐震構造の建築構造物に用いられる
場合などのときには、降伏強さが低い構造用鋼材が必要
となる。このような降伏強さが低い材料として、まず、
添加元素を極力低減した高純度の純鉄が挙げられる。し
かし、この材料の場合でも、鋼中のＣ、Ｎなどの微量の
残留元素が転位の移動を妨げ、降伏応力を十分に低くす
ることができないという問題がある。これに対処するも
のとして、特開平５−320763号公報、特開平５−214442
号公報、特開平８−157947号公報に、Ti、Nb、Ｖ等のＣ
やＮとの間に金属間化合物を生成する元素を適量添加す
ることにより、固溶Ｃ，Ｎを固定し、降伏応力を低くす
る方法が提案されている。2. Description of the Related Art Steel materials used as materials for construction, civil engineering steel pipes, columns, and the like. When these materials require particularly good workability or when they are used for building structures having earthquake-resistant structures, yielding occurs. Structural steel with low strength is required. As such a material with low yield strength,
High-purity pure iron in which the added elements are reduced as much as possible can be used. However, even in the case of this material, there is a problem that trace amounts of residual elements such as C and N in the steel hinder the movement of dislocations, so that the yield stress cannot be sufficiently reduced. To cope with this, Japanese Patent Application Laid-Open Nos. Hei 5-320763 and Hei 5-214442
JP-A-8-157947, Ti, Nb, V, etc.
There has been proposed a method in which solid solution C and N are fixed and yield stress is reduced by adding an appropriate amount of an element which forms an intermetallic compound with N and N.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、これら
公報に開示の技術では、YSの実績値が75〜100MPaの下限
近傍にあり、しかも、熱処理条件などの製造要因の少し
の変化で降伏強さが大きく変動しやすく、安定した低降
伏強さを得ることができないという問題があった。本発
明の目的は、強度の変動が少なく、降伏強さの低い材質
を安定して達成できる構造用熱延鋼材の製造技術を提案
することにある。そして本発明の具体的目標は、降伏強
さの変動範囲を標準偏差で５N/mm2 以下に抑えて、降伏
強さ（0.2％耐力）90〜120N/mm2の鋼材を安定して製造
することにある。なお、本発明で主に対象とする鋼材は
板厚６〜50mmの熱延鋼板である。However, according to the techniques disclosed in these publications, the actual value of YS is near the lower limit of 75 to 100 MPa, and the yield strength can be reduced by slight changes in manufacturing factors such as heat treatment conditions. There has been a problem that it is easily fluctuated greatly and a stable low yield strength cannot be obtained. An object of the present invention is to propose a manufacturing technique of a structural hot-rolled steel material capable of stably achieving a material having a small variation in strength and a low yield strength. The specific goals of the present invention, the variation range of yield strength is suppressed to 5N / mm 2 or less in standard deviation, to stably produce a yield strength (0.2% proof stress) of 90~120N / mm 2 steel It is in. The steel material mainly used in the present invention is a hot-rolled steel sheet having a thickness of 6 to 50 mm.
【０００４】[0004]
【課題を解決するための手段】上記目的を達成すべく、
幾多の実験と検討を重ねた結果、極低Ｃをベースとした
鋼にTi, Nb, Ｖの１種以上を添加した鋼素材を用いて、
熱間圧延条件および焼きなまし条件を適正に制御し、そ
の後さらにレベラー圧下による加工歪みを加えて降伏応
力を調整すれば、所期の目的が達成できるとの知見を得
て、本発明を完成するに到った。In order to achieve the above object,
As a result of repeated experiments and studies, using a steel material containing one or more of Ti, Nb, and V added to a steel based on extremely low C,
Appropriately controlling the hot rolling conditions and the annealing conditions, and further adjusting the yield stress by further applying processing strain due to leveler reduction, gained the knowledge that the intended purpose can be achieved, and completed the present invention. It has arrived.
【０００５】すなわち本発明は、Ｃ：0.005 mass％以
下、Si：0.05mass％以下、Mn：0.25mass％以下、Al：0.
10mass％以下、Ｎ：0.005 mass％以下を含み、かつTi：
0.02〜0.10mass％、Nb：0.02〜0.10mass％およびＶ：0.
01〜0.10mass％のうちから選ばれるいずれか１種または
２種以上を含有し、残部がFeおよび不可避的不純物より
なる組成の鋼素材を、1100〜1270℃に加熱し、仕上温度
700 ℃〜1100℃で熱間圧延したのち、700 ℃〜900 ℃の
範囲で焼きなましし、その後レベラー圧下による加工歪
みを加えて降伏応力を調整することを特徴とする、降伏
強さが低く、その変動範囲が狭い構造用熱延鋼材の製造
方法である。That is, in the present invention, C: 0.005 mass% or less, Si: 0.05 mass% or less, Mn: 0.25 mass% or less, Al: 0.
10 mass% or less, N: 0.005 mass% or less, and Ti:
0.02 to 0.10 mass%, Nb: 0.02 to 0.10 mass% and V: 0.
A steel material containing one or more selected from 01 to 0.10 mass%, the balance being Fe and unavoidable impurities, is heated to 1100 to 1270 ° C, and the finishing temperature is increased.
After hot rolling at 700 ° C to 1100 ° C, annealing in the range of 700 ° C to 900 ° C, and then adjusting the yield stress by applying processing strain under the leveler pressure, the yield strength is low. This is a method of manufacturing a hot-rolled structural steel material having a narrow range of variation.
【０００６】[0006]
【発明の実施の形態】次に、本発明において、化学成分
組成および製造条件などを上記の範囲に限定した理由に
ついて述べる。 Ｃ：0.005 mass％以下 Ｃは、鋼中に固溶状態で存在すると、転位を固着し、鋼
の降伏強さを高めるので、極微量とする必要がある。こ
の影響は0.005 mass％を超えると顕著にあらわれるの
で、0.005 mass％以下に制限する。Next, the reasons for limiting the chemical composition and the production conditions to the above ranges in the present invention will be described. C: 0.005 mass% or less If C exists in a solid solution state in steel, it fixes dislocations and increases the yield strength of the steel. This effect becomes remarkable when it exceeds 0.005 mass%, so it is limited to 0.005 mass% or less.
【０００７】Si：0.05mass％以下 Siは、固溶強化作用により降伏強さを増大させる元素で
あり、極力低下することが必要である。このようなSiの
影響は0.05mass％を超えた場合に顕著になるので0.05ma
ss％以下に制限する。Si: 0.05 mass% or less Si is an element that increases the yield strength by the solid solution strengthening action, and it is necessary to reduce it as much as possible. Since the influence of such Si becomes remarkable when it exceeds 0.05 mass%,
Restrict to ss% or less.
【０００８】Mn：0.25mass％以下 MnもSiと同様に、固溶強化作用により降伏強さを増大さ
せる元素であり、極力低下させることが必要である。こ
のようなMnの影響は0.25mass％を超えた場合に顕著にな
るので0.25mass％以下に制限する。Mn: 0.25 mass% or less Mn, like Si, is an element that increases the yield strength by a solid solution strengthening action, and must be reduced as much as possible. Such an effect of Mn becomes remarkable when it exceeds 0.25 mass%, so it is limited to 0.25 mass% or less.
【０００９】Al：0.10mass％以下 Alは、鋼の脱酸に必要な元素であるが、0.10mass％を超
えて多量に添加すると結晶粒径の微細化をもたらし、低
い降伏強さ確保する上で不利となる。このため、Alの含
有量は0.10mass％以下とする。Al: 0.10 mass% or less Al is an element necessary for deoxidation of steel. However, if it is added in a large amount exceeding 0.10 mass%, the grain size becomes finer, and a low yield strength is secured. At a disadvantage. Therefore, the content of Al is set to 0.10 mass% or less.
【００１０】Ｎ：0.005 mass％以下 Ｎは、Ｃと同様に、鋼中に固溶状態で存在すると、転位
を固着し降伏強さを高めるので、極微量とする必要があ
る。この影響は0.005 mass％を超えると顕著にあらわれ
るので、0.005 mass％以下に制限する。N: 0.005 mass% or less N, like C, if present in a solid solution state in steel, dislocations are fixed and yield strength is increased. This effect becomes remarkable when it exceeds 0.005 mass%, so it is limited to 0.005 mass% or less.
【００１１】Ti：0.02〜0.10mass％，Nb：0.02〜0.10ma
ss％，Ｖ：0.01〜0.10mass％ Ti, NbおよびＶは、ＣやＮとの間で金属間化合物を形成
するために必要な元素であるが、これら元素の添加量が
過多になると、経済的でないばかりか、析出物の粗大化
による鋼の靱性劣化を招くので好ましくない。従って、
これら元素は、それぞれ上記の、添加効果があらわれ始
める量を下限とし、悪影響がでる量を上限として添加す
る。なお、これらTi, Nb, Ｖは単独添加のほか、複合添
加することも可能であり、その際の効果も単独に添加し
た場合と変わらない。Ti: 0.02 to 0.10 mass%, Nb: 0.02 to 0.10 ma
ss%, V: 0.01 to 0.10 mass% Ti, Nb, and V are elements necessary for forming an intermetallic compound with C and N. However, if the addition amount of these elements becomes excessive, economical Not only is this not desirable, but also the toughness of the steel deteriorates due to coarsening of the precipitates, which is not preferable. Therefore,
These elements are added with the lower limit of the amount at which the effect of the addition starts to appear and the upper limit of the amount at which the effect is exerted. Note that these Ti, Nb, and V can be added alone or in combination, and the effect at that time is not different from the case where they are added alone.
【００１２】次に、本発明における製造条件について説
明する。 ・加熱温度：1100〜1270℃ 熱延鋼板の靱性を高めるには、高温加熱により、炭化物
を一旦完全に固溶させてからTi, Nb, Ｖ等の炭化物を鋼
中に均一にかつ微細に分散させることが必要である。ま
た圧延仕上温度を高温域に維持し、初期γ粒径を十分に
大きくし低い降伏応力を得るためにも、高い加熱温度が
必要である。一方、加熱温度があまりに高くなると、経
済的でないばかりか極端な結晶粒の粗大化による靱性劣
化を招くことになる。したがって、加熱温度は1100〜12
70℃の範囲に限定する。Next, the manufacturing conditions in the present invention will be described.・ Heating temperature: 1100 to 1270 ° C To increase the toughness of hot-rolled steel sheet, carbides such as Ti, Nb, V, etc. are uniformly and finely dispersed in the steel after the carbides are completely dissolved by high-temperature heating. It is necessary to let Also, a high heating temperature is required to maintain the rolling finish temperature in a high temperature range, sufficiently increase the initial γ grain size, and obtain a low yield stress. On the other hand, if the heating temperature is too high, not only is it not economical but also the toughness deteriorates due to extreme coarsening of crystal grains. Therefore, the heating temperature is 1100-12
Limit to 70 ° C range.
【００１３】・仕上温度：700 ℃〜1100℃ 仕上温度を下げすぎると強度が上がりすぎ、目的の低降
伏応力が得られないため700 ℃を仕上温度の下限とす
る。また上限温度としては、圧延後に鋼板表面にスケー
ルが発生しない範囲とし1100℃とする。Finish temperature: 700 ° C. to 1100 ° C. If the finish temperature is too low, the strength is too high and the desired low yield stress cannot be obtained, so 700 ° C. is the lower limit of the finish temperature. The upper limit temperature is set to 1100 ° C. in a range in which no scale is generated on the steel sheet surface after rolling.
【００１４】・焼きなまし：700 ℃〜 900℃ 上記熱間圧延において、制御圧延を実施し加工歪みを付
与し、その後再加熱して、Ａc3以下の温度で焼鈍を行う
ことにより粒成長を促進させ、その後のレベラー圧下に
より目標の低耐力を達成する。焼鈍温度が900 ℃を超え
るとＡc3温度を超えるため、上限を900 ℃とする。ま
た、焼鈍温度が700 ℃を下回ると焼鈍時の粒成長が起こ
りにくくなるため、下限の温度を700 ℃とする。Annealing: 700 ° C. to 900 ° C. In the above hot rolling, controlled rolling is performed to impart a processing strain, and then reheated, and annealing is performed at a temperature of Ac 3 or less to promote grain growth. The target low yield strength is achieved by the subsequent leveler reduction. If the annealing temperature exceeds 900 ° C., the temperature will exceed the Ac 3 temperature, so the upper limit is made 900 ° C. If the annealing temperature is lower than 700 ° C., the grain growth during the annealing becomes difficult to occur, so the lower limit temperature is set to 700 ° C.
【００１５】・レベラー圧下 本発明では焼きなまし後のレベラー圧下により降伏応力
を調整することが重要である。焼きなましを行ったまま
の鋼板では、降伏応力にはばらつきが大きく、安定した
降伏強さが得られない。このばらつきを極力少なくする
ため、レベラー圧下を行う。レベラー圧下を付与するこ
とにより、引張強さ、伸びを変化させることなく、降伏
応力を上昇させるとともにばらつきを低下させることが
でき、降伏応力を90〜120N/mm2の非常に狭い範囲内に保
つことが可能となる。レベラーでの圧下は、本対象材の
降伏応力が100N/mm2程度の極軟鋼であり加工の影響を受
けやすく、さらに平坦な板に歪を付加するため形状が悪
化することを考慮して、１パス目で上反りさせ、２パス
目で平坦な板形状にする２パス圧下のパターンで行えば
よい。このときの具体的な圧下率範囲は３〜10％であ
る。In the present invention, it is important to control the yield stress by reducing the leveler after annealing. In the as-annealed steel sheet, the yield stress varies widely, and a stable yield strength cannot be obtained. In order to minimize this variation, leveler reduction is performed. By applying a leveler reduction, tensile strength, without changing the elongation, yield stress can reduce the variation with increasing and maintaining the yield stress within a very narrow range of 90~120N / mm 2 It becomes possible. Reduction in leveler, considering that the yield stress of the target material susceptible to machining a pole mild steel of about 100 N / mm 2, the shape for adding the distortion to the more flat plate deteriorates, What is necessary is just to perform it by the pattern under two-pass pressure which makes it warp in the 1st pass and makes a flat plate shape in the 2nd pass. The specific rolling reduction range at this time is 3 to 10%.
【００１６】[0016]
【実施例】表１に示す種々の成分組成の鋼を転炉により
溶製して、ＲＨ脱ガス処理を経てスラブとした後、同表
に示す条件で熱間圧延し、一旦冷却してから、焼きなま
しを行い、さらにレベラー圧下を加えて各種板厚の熱延
鋼板を製造した。また比較のために、焼きなましを行わ
ない条件、レベラーによる圧下を加えない条件でも熱延
鋼板を製造した。得られた熱延鋼板の中心から、板厚20
mm以下の鋼板ではJIS ５号試験片、板厚20mm超えの鋼板
ではJIS ４号試験片（板厚1/4tの位置）を採取し、引張
試験による材料特性を調査した。なお、降伏強さは0.2
％耐力から求めた。以上の圧延実験をｎ数＝３０回行
い、それぞれの降伏強さを測定し、これらの平均と変動
量（標準偏差）を求めた。その結果を表１に併せて示
す。EXAMPLES Steels having various component compositions shown in Table 1 were melted by a converter, made into slabs through RH degassing treatment, then hot-rolled under the conditions shown in the table, and once cooled, Then, annealing was performed, and a leveler was further reduced to produce hot-rolled steel sheets of various thicknesses. For comparison, a hot-rolled steel sheet was produced under the condition that annealing was not performed and the condition that rolling by a leveler was not applied. From the center of the obtained hot rolled steel sheet,
A JIS No. 5 test piece was sampled for a steel sheet having a thickness of not more than 20 mm, and a JIS No. 4 test piece (at a position of 1/4 t in thickness) was sampled for a steel sheet having a thickness of more than 20 mm, and the material properties were examined by a tensile test. The yield strength is 0.2
% Yield strength. The above rolling experiment was performed n times = 30 times, the yield strength of each was measured, and their average and variation (standard deviation) were determined. The results are shown in Table 1.
【００１７】[0017]
【表１】 [Table 1]
【００１８】表１において、鋼No, A1、C1、D1は発明例
であり、いずれもその降伏強さは90〜120N/mm2にあると
ともに、その標準偏差が５N/mm2 以下で降伏強さの変動
も極めて少ない。これに対して、成分、加熱圧延、焼な
まし、レベラー圧下のうち少なくとも一つの条件が発明
範囲を外れている比較例は、降伏強さの変動が大きく、
また降伏強さの値も90〜120N/mm2の範囲を外れており目
標を達成していない。In Table 1, steel Nos. A1, A1, C1, and D1 are examples of the invention, all of which have a yield strength of 90 to 120 N / mm 2 and a standard deviation of 5 N / mm 2 or less. The fluctuation of the height is extremely small. On the other hand, the composition, the hot rolling, the annealing, the comparative example in which at least one of the conditions under the leveler pressure is out of the range of the invention has a large variation in the yield strength,
Also not achieved the yield strength values are also outside the scope of 90~120N / mm 2 goal.
【００１９】[0019]
【発明の効果】以上説明したように、本発明によれば、
降伏強さの変動が少なく、鋼材の低降伏化が可能にな
り、降伏強さ90〜120N/mm2の鋼材を安定して供給するこ
とができる。As described above, according to the present invention,
The variation in yield strength is small, the yield of steel material can be reduced, and a steel material with a yield strength of 90 to 120 N / mm 2 can be supplied stably.
Claims (1)
または２種以上を含有し、残部がFeおよび不可避的不純
物よりなる組成の鋼素材を、1100〜1270℃に加熱し、仕
上温度700 ℃〜1100℃で熱間圧延したのち、700 ℃〜90
0 ℃の範囲で焼きなましし、その後レベラー圧下による
加工歪みを加えて降伏応力を調整することを特徴とす
る、降伏強さが低く、その変動範囲が狭い構造用熱延鋼
材の製造方法。C: 0.005 mass% or less Si: 0.05 mass% or less Mn: 0.25 mass% or less Al: 0.10 mass% or less N: 0.005 mass% or less, and Ti: 0.02 to 0.10 mass% Nb: 0.02 to 0.10 mass% and V: A steel material containing at least one selected from 0.01 to 0.10 mass% and having a balance of Fe and unavoidable impurities is heated to 1100 to 1270 ° C. After hot rolling at a finishing temperature of 700 ° C to 1100 ° C, 700 ° C to 90 ° C
A method for producing a hot-rolled structural steel material having a low yield strength and a narrow range of variation, characterized by annealing at a temperature of 0 ° C. and then adjusting the yield stress by applying a processing strain under a leveler pressure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10370388A JP2000192141A (en) | 1998-12-25 | 1998-12-25 | Production of hot rolled steel for structural purpose low in yield strength and narrow in its varing range |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10370388A JP2000192141A (en) | 1998-12-25 | 1998-12-25 | Production of hot rolled steel for structural purpose low in yield strength and narrow in its varing range |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000192141A true JP2000192141A (en) | 2000-07-11 |
Family
ID=18496785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10370388A Pending JP2000192141A (en) | 1998-12-25 | 1998-12-25 | Production of hot rolled steel for structural purpose low in yield strength and narrow in its varing range |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000192141A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007146220A (en) * | 2005-11-28 | 2007-06-14 | Nippon Steel Corp | Method for producing thick steel plate excellent in toughness |
| CN106987771A (en) * | 2017-04-20 | 2017-07-28 | 唐山钢铁集团有限责任公司 | A kind of extremely low yield strength steel plate and its production method |
-
1998
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007146220A (en) * | 2005-11-28 | 2007-06-14 | Nippon Steel Corp | Method for producing thick steel plate excellent in toughness |
| JP4660363B2 (en) * | 2005-11-28 | 2011-03-30 | 新日本製鐵株式会社 | Manufacturing method of thick steel plate with excellent toughness |
| CN106987771A (en) * | 2017-04-20 | 2017-07-28 | 唐山钢铁集团有限责任公司 | A kind of extremely low yield strength steel plate and its production method |
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