JPH10147834A - 590mpa class rolled shape steel and its production - Google Patents
590mpa class rolled shape steel and its productionInfo
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- JPH10147834A JPH10147834A JP30448696A JP30448696A JPH10147834A JP H10147834 A JPH10147834 A JP H10147834A JP 30448696 A JP30448696 A JP 30448696A JP 30448696 A JP30448696 A JP 30448696A JP H10147834 A JPH10147834 A JP H10147834A
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は、建造物の構造部材
として用いられる靭性の優れた高張力圧延形鋼およびそ
の製造方法に係わるものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-tensile-rolled section steel having excellent toughness used as a structural member of a building and a method for producing the same.
【0002】[0002]
【従来の技術】建築物の超高層化、安全規準の厳格化な
どから、柱用に用いられる鋼材、例えば特に板厚の大き
なサイズのH形鋼(以下、極厚H形鋼と称す)には、一
層の高強度化、高靭性化、低降伏比化が求められてい
る。このような要求特性を満たすために、従来は圧延終
了後に焼準処理などの熱処理を施すことが行われた。熱
処理の付加は熱処理コストと生産効率の低下など大幅な
コスト上昇を招き、経済性に問題があった。この問題を
解決するために、圧延ままで高性能の材質特性が得られ
るような新しい合金設計による鋳片と製造法の開発が必
要となった。2. Description of the Related Art Due to the increase in height of buildings and stricter safety standards, steel materials used for pillars, for example, H-beams having a particularly large thickness (hereinafter referred to as extra-thick H-beams) have been developed. There is a demand for higher strength, higher toughness, and lower yield ratio. In order to satisfy such required characteristics, conventionally, a heat treatment such as a normalizing process has been performed after the completion of rolling. The addition of heat treatment causes a significant increase in cost, such as a decrease in heat treatment cost and production efficiency, and has a problem in economy. In order to solve this problem, it is necessary to develop a slab and a manufacturing method by a new alloy design that can obtain high-performance material properties as rolled.
【0003】一般に、フランジを有する形鋼、例えばH
形鋼をユニバーサル圧延により製造すると、圧延造形上
からの圧延条件(温度、圧下率)の制限およびその形状
の特異性からウエブ、フランジ、フィレットの各部位で
圧延仕上げ温度、圧下率、冷却速度に差を生じる。その
結果、部位間に強度、延性、靭性のバラツキが発生し、
例えば溶接構造用圧延鋼材(JIS G3106) 等の規準に満た
ない部位が生じる。特に極厚H形鋼を連続鋳造鋳片を素
材とし圧延製造する場合には、連続鋳造設備での製造可
能な鋳片最大厚みに限界があり、造形に必要な十分な鋳
片断面積が得られないため、その圧延は低圧下比圧延と
なる。さらに、圧延造形により製品の寸法精度を得るた
めに高温圧延を指向するので板厚の厚いフランジ部は高
温圧延となり、圧延終了後の鋼材冷却も徐冷となる。そ
の結果、ミクロ組織は粗粒化し、強度・靭性が低下す
る。Generally, a section steel having a flange, for example, H
When a section steel is manufactured by universal rolling, the rolling conditions (temperature, rolling reduction) from the roll molding and the uniqueness of the shape limit the rolling finish temperature, rolling reduction, and cooling rate at each part of the web, flange, and fillet. Make a difference. As a result, variations in strength, ductility and toughness occur between the parts,
For example, there are portions that do not meet the standards such as rolled steel materials for welded structures (JIS G3106). In particular, when rolling an extremely thick H-beam using a continuous cast slab as a raw material, there is a limit to the maximum thickness of a slab that can be produced by a continuous casting facility, and a sufficient slab cross-sectional area required for molding can be obtained. Therefore, the rolling is a low reduction ratio rolling. Furthermore, since high-temperature rolling is performed in order to obtain the dimensional accuracy of the product by rolling molding, the flange portion having a large thickness is subjected to high-temperature rolling, and the steel material after rolling is also gradually cooled. As a result, the microstructure becomes coarse and the strength and toughness are reduced.
【0004】圧延プロセスでの組織微細化法として、T
MCP(Thermo-Mechanical-Controll Process)がある
が、形鋼圧延では、圧延条件に制限があるので、鋼板で
のTMCPのような低温・大圧下圧延の適用は困難であ
る。また、厚鋼板分野ではVNの析出効果を利用し高強
度・高靭性鋼を製造する、例えば特公昭62−5054
8号公報、特公昭62−54862号公報の技術が提案
されている。しかし、この方法を590MPa 級の製造に
適用した場合には、高濃度の固溶Nを含有することか
ら、生成するベイナイト組織内に高炭素島状マルテンサ
イト(以降M*と称する)を生成し、靭性が著しく低下
して規格値をクリアーすることは困難であるという問題
があった。As a method of refining the structure in the rolling process, T
Although there is MCP (Thermo-Mechanical-Controll Process), since rolling conditions are limited in section steel rolling, it is difficult to apply low-temperature, large-reduction rolling such as TMCP to a steel sheet. In the field of thick steel plates, high strength and high toughness steels are produced by utilizing the effect of precipitation of VN, for example, Japanese Patent Publication No. Sho 62-5054.
No. 8 and Japanese Patent Publication No. Sho 62-54862 have been proposed. However, when this method is applied to the production of a 590 MPa class, since high concentration of solute N is contained, high carbon island-like martensite (hereinafter referred to as M *) is generated in the bainite structure. In addition, there is a problem that it is difficult to clear the standard value because the toughness is significantly reduced.
【0005】[0005]
【発明が解決しようとする課題】前記の問題を解決する
ためには、形鋼圧延ままでM*生成量の少ない低炭素ベ
イナイトを生成させ組織を微細化する必要がある。それ
には圧延加熱時のγ粒径を細粒化するために製鋼過程に
おいて、鋳片中に予めMgOを微細晶出させ、これを核
にTiNを微細析出させ、加えて、低炭素化するため
に、微量で高強度が得られるマイクロアロイの微量添加
した鋳片を製造する必要がある。また、H形鋼のフラン
ジとウェブの結合部のフィレット部はCC鋳片の中心偏
析帯と一致し、この偏析帯内のMnSは圧延により著し
く延伸する。ここでの高濃度の元素偏析帯と延伸MnS
は板厚方向の絞り値・靭性を著しく低下させ、さらに溶
接時にラメラテイ ア割れを生じさせる場合もあり、この
有害な作用を持つMnSの生成を阻止することも大きな
課題である。このように従来の技術では目的の信頼性の
高い高強度・高靭性の圧延形鋼をオンラインで製造し安
価に提供することは困難である。In order to solve the above-mentioned problems, it is necessary to form a low-carbon bainite with a small amount of M * generated as it is in the form of rolled steel to refine the structure. In order to reduce the γ grain size at the time of rolling and heating, in the steelmaking process, MgO is finely crystallized in advance in the slab, TiN is finely precipitated in the nucleus, and in order to reduce the carbon, In addition, it is necessary to produce a slab to which a small amount of microalloy that can obtain a high strength in a small amount is added. The fillet at the joint between the flange of the H-section steel and the web coincides with the central segregation zone of the CC slab, and MnS in this segregation zone is significantly elongated by rolling. Here, high concentration elemental segregation zone and stretched MnS
The steel sheet significantly reduces the drawing value and toughness in the sheet thickness direction, and may cause lamella tearing at the time of welding. Therefore, it is also a major problem to prevent the production of MnS having this harmful effect. As described above, it is difficult for the conventional technology to manufacture a rolled section steel having high reliability and high strength with high reliability on-line and to provide it at low cost.
【0006】本発明は、従来の焼準処理などの熱処理を
施すことなく、低コストで(圧延ままで)高張力圧延形
鋼の製造を可能とし、建造物の構造部材に用いる高強度
で靭性の優れた590MPa 級圧延形鋼およびその製造方
法を提供すること目的とする。The present invention makes it possible to produce high-strength rolled steel at low cost (as it is rolled) without performing conventional heat treatment such as normalizing treatment, and to provide high strength and toughness for structural members of buildings. It is an object of the present invention to provide a 590 MPa class rolled section steel excellent in the above and a method for producing the same.
【0007】[0007]
【課題を解決するための手段】本発明の特徴は従来の発
想とは異なり、Mgを添加し、これにより生成させた微
細酸化物とTiNの微細分散およびマイクロアロイの添
加による低炭素ベイナイト組織の生成とによる組織の微
細化により高強度でかつ高靭性の圧延形鋼を実現した点
にある。SUMMARY OF THE INVENTION The feature of the present invention is different from the conventional idea, in that Mg is added, a fine oxide and a fine dispersion of TiN formed by this are added, and a low carbon bainite structure is formed by adding a microalloy. The point is that a rolled section steel with high strength and high toughness has been realized by making the structure finer due to its formation.
【0008】加えて採用したTMCPの特徴は厚鋼板で
実施されている大圧下圧延に代わる形鋼圧延での軽圧下
の熱間圧延においても効率的に組織の細粒化が可能なよ
うに圧延パス間で水冷し、圧延と水冷を繰り返す方法に
ある。本発明は、圧延ままで、M*含有量の少ない低炭
素ベイナイトの微細組織が得られる鋳片を鋳造し、この
鋳片を用い、形鋼圧延において効率的なTMCPを行い
高強度かつ高靭性を有する形鋼を製造することを特徴と
している。In addition, the feature of the TMCP adopted is that the structure can be efficiently refined even in the hot rolling under light pressure in the shape steel rolling in place of the large rolling under pressure performed in a thick steel plate. There is a method of cooling with water between passes and repeating rolling and water cooling. The present invention casts a slab that can obtain a microstructure of low-carbon bainite with a low M * content as it is rolled, and uses this slab to perform efficient TMCP in rolling a section steel to achieve high strength and high toughness. It is characterized by producing a shaped steel having
【0009】その鋳片は、製鋼過程において、圧延加熱
時のγ細粒化を目的に、鋳片内にMg添加により微細M
gOの晶出とTi添加によりTiNを微細分散させ、加
えて、圧延後の組織内のM*低減を狙い、合金元素を微
量のNb、V、Mo添加で代替し、さらに極低B化を行
ない製造する。次いで、この鋳片を圧延造形し形鋼を製
造するが、この圧延形鋼圧延プロセスでは、熱間圧延パ
ス間で鋼材を水冷することにより、鋼材の表層部と内部
に温度差を与え、軽圧下条件下においても、より高温の
鋼材内部への圧下浸透を高め、γ粒内でのベイナイト生
成核となる加工転位を導入し、その生成核を増加させ
る。加えて、圧延後のγ/α変態温度域を冷却制御する
ことにより、その核生成させたベイナイトの成長を抑制
する方法によればミクロ組織の微細化ができ、高能率で
製造コストの安価な制御圧延形鋼の製造が可能であると
言う知見に基づき前記課題を解決したもので、その要旨
とするところは、以下のとおりである。[0009] In the steelmaking process, the slab is made to have a fine M content by adding Mg into the slab for the purpose of refining γ during rolling and heating.
Finely disperse TiN by crystallization of gO and addition of Ti. In addition, aiming to reduce M * in the structure after rolling, substitute a small amount of Nb, V, and Mo for the alloying element, and further reduce the ultra-low B. Conduct and manufacture. Next, the cast slab is roll-formed to produce a shaped steel.In the rolled shaped steel rolling process, the steel material is water-cooled between hot rolling passes to provide a temperature difference between the surface layer portion and the inside of the steel material, thereby reducing the lightness. Even under the rolling condition, the rolling penetration into the steel material at a higher temperature is enhanced, and the working dislocations serving as bainite forming nuclei in the γ grains are introduced to increase the formed nuclei. In addition, by controlling the cooling of the γ / α transformation temperature region after rolling, the microstructure can be refined according to the method of suppressing the growth of the nucleated bainite, and the production cost can be reduced with high efficiency. The object of the present invention is to solve the above-mentioned problem based on the knowledge that the production of a controlled rolled steel is possible, and the gist thereof is as follows.
【0010】重量% で、C:0.02〜0.06% 、Si:0.05 〜0.
25% 、Mn:0.8〜1.6%、Ti:0.005〜0.025%、Mg:0.0005 〜
0.0050% 、Nb:0.04 〜0.10% 、V :0.01 〜0.10% 、Mo:
0.05〜0.40% 、N :0.002〜0.006%、およびO:0.003 〜0.
006%を含み、残部がFeおよび不可避不純物からなり、該
不可避不純物のうち B含有量を0.0003% 以下およびAl含
有量を0.005%以下に制限した化学組成を有し、かつベイ
ナイトの面積率が50〜90%で、残部がフェライト・
パーライトおよび高炭素島状マルテンサイトから成り、
該高炭素島状マルテンサイトの面積率が5%以下であっ
て、熱間圧延完了後の旧γ粒径が40μm以下であるミ
クロ組織を有することを特徴とする590MPa 級圧延形
鋼。[0010] By weight%, C: 0.02 to 0.06%, Si: 0.05 to 0.
25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to
0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo:
0.05-0.40%, N: 0.002-0.006%, and O: 0.003--0.
006%, the balance being Fe and unavoidable impurities, the unavoidable impurities having a chemical composition in which the B content was limited to 0.0003% or less and the Al content to 0.005% or less, and the area ratio of bainite was 50%. ~ 90%, with the balance being ferrite
Consisting of perlite and high carbon island martensite,
590 MPa class rolled section steel having a microstructure in which the area ratio of the high carbon island martensite is 5% or less and the prior γ grain size after completion of hot rolling is 40 μm or less.
【0011】重量% で、C:0.02〜0.06% 、Si:0.05 〜0.
25% 、Mn:0.8〜1.6%、Ti:0.005〜0.025%、Mg:0.0005 〜
0.0050% 、Nb:0.04 〜0.10% 、V :0.01 〜0.10% 、Mo:
0.05〜0.40% 、N :0.002〜0.006%、O:0.003 〜0.006%、
およびCr:0.1〜1.0%、Ni:0.1〜1.0%およびCu:0.1〜1.0%
のうちの少なくとも1種を含み、残部がFeおよび不可避
不純物からなり、該不可避不純物のうち B含有量を0.00
03% 以下およびAl含有量を0.005%以下に制限した化学組
成を有し、かつベイナイトの面積率が50〜90%で、
残部がフェライト・パーライトおよび高炭素島状マルテ
ンサイトから成り、該高炭素島状マルテンサイトの面積
率が5%以下であって、熱間圧延完了後の旧γ粒径が4
0μm以下であるミクロ組織を有することを特徴とする
590MPa 級圧延形鋼。In weight%, C: 0.02-0.06%, Si: 0.05-0.
25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to
0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo:
0.05-0.40%, N: 0.002-0.006%, O: 0.003-0.006%,
And Cr: 0.1-1.0%, Ni: 0.1-1.0% and Cu: 0.1-1.0%
And the balance consists of Fe and inevitable impurities, and the B content of the inevitable impurities is 0.00
It has a chemical composition of not more than 03% and an Al content of not more than 0.005%, and the area ratio of bainite is 50 to 90%,
The balance consists of ferrite pearlite and high carbon island martensite, the area ratio of the high carbon island martensite is 5% or less, and the old γ grain size after completion of hot rolling is 4%.
590 MPa class rolled section steel having a microstructure of 0 μm or less.
【0012】重量% で、C:0.02〜0.06% 、Si:0.05 〜0.
25% 、Mn:0.8〜1.6%、Ti:0.005〜0.025%、Mg:0.0005 〜
0.0050% 、Nb:0.04 〜0.10% 、V :0.01 〜0.10% 、Mo:
0.05〜0.40% 、N :0.002〜0.006%、およびO:0.003 〜0.
006%を含み、残部がFeおよび不可避不純物からなり、該
不可避不純物のうち B含有量を0.0003% 以下およびAl含
有量を0.005%以下に制限した鋳片を1200〜1300℃の温度
域に加熱した後に圧延を開始し、圧延工程で形鋼のフラ
ンジ表面を700 ℃以下にまで水冷し復熱過程で圧延する
水冷・圧延サイクルを一回以上行い、圧延終了後に0.5
〜10℃/sの冷却速度で700 〜400 ℃の温度域に冷却した
後に放冷することを特徴とする590MPa 級圧延形鋼の
製造方法。C: 0.02-0.06% by weight, Si: 0.05-0.
25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to
0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo:
0.05-0.40%, N: 0.002-0.006%, and O: 0.003--0.
006%, the balance consisting of Fe and unavoidable impurities, the slab of which the B content was limited to 0.0003% or less and the Al content was limited to 0.005% or less among the inevitable impurities was heated to a temperature range of 1200 to 1300 ° C. Rolling is started later, and at least one water-cooling / rolling cycle in which the flange surface of the section steel is water-cooled to 700 ° C or less in the rolling process and rolled during the recuperation process,
A method for producing a 590 MPa class rolled section steel, comprising cooling to a temperature range of 700 to 400 ° C. at a cooling rate of 10 to 10 ° C./s and then allowing it to cool.
【0013】重量% で、C:0.02〜0.06% 、Si:0.05 〜0.
25% 、Mn:0.8〜1.6%、Ti:0.005〜0.025%、Mg:0.0005 〜
0.0050% 、Nb:0.04 〜0.10% 、V :0.01 〜0.10% 、Mo:
0.05〜0.40% 、N :0.002〜0.006%、O:0.003 〜0.006%、
およびCr:0.1〜1.0%、Ni:0.1〜1.0%およびCu:0.1〜1.0%
のうちの少なくとも1種を含み、残部がFeおよび不可避
不純物からなり、該不可避不純物のうち B含有量を0.00
03% 以下およびAl含有量を0.005%以下に制限した鋳片を
1200〜1300℃の温度域に加熱した後に圧延を開始し、圧
延工程で形鋼のフランジ表面を700 ℃以下にまで水冷し
復熱過程で圧延する水冷・圧延サイクルを一回以上行
い、圧延終了後に0.5 〜10℃/sの冷却速度で700 〜400
℃の温度域に冷却した後に放冷することを特徴とする5
90MPa 級圧延形鋼の製造方法。In weight%, C: 0.02-0.06%, Si: 0.05-0.
25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to
0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo:
0.05-0.40%, N: 0.002-0.006%, O: 0.003-0.006%,
And Cr: 0.1-1.0%, Ni: 0.1-1.0% and Cu: 0.1-1.0%
And the balance consists of Fe and inevitable impurities, and the B content of the inevitable impurities is 0.00
Cast slabs with an Al content of not more than 03% and 0.005% or less
Rolling is started after heating to a temperature range of 1200 to 1300 ° C, and at least one water-cooling / rolling cycle is performed, in which the flange surface of the section steel is water-cooled to 700 ° C or less in the rolling process and rolled in the reheating process. 700-400 at a cooling rate of 0.5-10 ° C / s later
5. Cooling to a temperature range of ° C. followed by cooling
Manufacturing method of 90MPa grade rolled section steel.
【0014】[0014]
【発明の実施の形態】以下、本発明について詳細に説明
する。鋼の高強度化はフェライト結晶の微細化、合
金元素による固溶体強化、硬化相による分散強化、微
細析出物による析出強化等によって達成される。また、
高靭性化は、結晶の微細化、母相(フェライト)の
固溶N、Cの低減、破壊の発生起点となる硬化相の高
炭素マルテンサイト及び粗大な酸化物、析出物の低減と
微小化等により達成される。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Strengthening of steel is achieved by refinement of ferrite crystals, solid solution strengthening by alloying elements, dispersion strengthening by hardened phases, precipitation strengthening by fine precipitates, and the like. Also,
Higher toughness is achieved by miniaturization of crystal, reduction of solid solution N and C of mother phase (ferrite), reduction and miniaturization of high carbon martensite and coarse oxides and precipitates of hardened phase which is a starting point of fracture. And so on.
【0015】一般的には鋼の高強度化により靭性は低下
し、高強度化と高靭性化は相反する対処が必要である。
両者を同時に満たす冶金因子は唯一、結晶の微細化であ
る。本発明の特徴は、製鋼工程における、Mg添加によ
る微細Mg酸化物とTiNの分散およびマイクロアロイ
ング合金設計に基づく低炭素ベイナイト組織化による組
織微細化により高強度・高靭性化を達成するものであ
る。In general, the toughness is reduced by increasing the strength of steel, and it is necessary to contradict high strength and toughness.
The only metallurgical factor that satisfies both at the same time is crystal refinement. The feature of the present invention is to achieve high strength and high toughness by dispersing fine Mg oxide and TiN by adding Mg in the steel making process and by refining the structure by forming low carbon bainite based on the microalloying alloy design. is there.
【0016】加えて本発明では、熱間圧延工程におい
て、熱間圧延パス間でフランジ表面を水冷し、その復熱
時に圧延する工程を繰り返すことによりフランジの板厚
中心部に圧下浸透効果を付与し、この部位においてもT
MCPによる組織微細化効果を高め、この組織微細化に
よりH形鋼の各部位における母材の機械特性を向上させ
るとともにバラツキを低減し均質化を達成するものであ
る。In addition, according to the present invention, in the hot rolling step, the flange surface is water-cooled between hot rolling passes, and the rolling step is repeated at the time of reheating to impart a rolling reduction effect to the center portion of the flange in the thickness direction. And T
The effect of refining the structure by the MCP is enhanced, and the refining of the structure improves the mechanical properties of the base material in each part of the H-section steel, and reduces the variation to achieve homogenization.
【0017】以下に本発明形鋼の成分範囲、ミクロ組織
および制御条件の限定理由について述べる。まず、Cは
鋼を強化するために添加するもので、0.02% 未満では構
造用鋼として必要な強度が得られず。また、0.06% を超
える添加では、母材靭性、耐溶接割れ性、溶接熱影響部
(以下HAZと略記)靭性などを著しく低下させるの
で、下限を0.02% 、上限を0.06% とした。The reasons for limiting the composition range, microstructure, and control conditions of the shaped steel according to the present invention will be described below. First, C is added to strengthen the steel. If it is less than 0.02%, the strength required for structural steel cannot be obtained. Further, if the addition exceeds 0.06%, the base metal toughness, the resistance to weld cracking, the weld heat affected zone (hereinafter abbreviated as HAZ) toughness, etc. are significantly reduced, so the lower limit was made 0.02% and the upper limit was made 0.06%.
【0018】次に、Siは母材の強度確保、溶鋼の予備
脱酸などに必要であるが、0.25% を超えると母材および
HAZの硬化組織中に高炭素島状マルテンサイトを生成
し、母材および溶接継手部靭性を著しく低下させる。ま
た、0.05% 未満では溶鋼の予備脱酸が十分にできないた
めSi含有量を0.05〜0.25% の範囲に限定した。Mnは
母材の強度確保には0.8%以上の添加が必要であるが、母
材および溶接部の靭性、割れ性などに対する許容濃度か
ら上限を1.6%とした。Next, Si is necessary for securing the strength of the base material, pre-deoxidizing the molten steel, etc. If it exceeds 0.25%, high-carbon island-like martensite is formed in the hardened structure of the base material and HAZ, It significantly reduces the toughness of the base metal and the welded joint. If the content is less than 0.05%, the preliminary deoxidation of the molten steel cannot be sufficiently performed, so the Si content is limited to the range of 0.05 to 0.25%. Mn must be added at 0.8% or more to secure the strength of the base material, but the upper limit is set to 1.6% from the allowable concentration for the toughness, cracking, and the like of the base material and the welded portion.
【0019】TiはTiNを析出し、固溶Nを低減する
ことによりM*の生成を抑制する。また、微細析出した
TiNはγ相の細粒化にも寄与する。これらのTiの作
用により組織を微細化し強度・靭性を向上させる。従っ
て、0.005%未満ではTiNの析出量が不足し、これらの
効果を発現し得ないためTi量の下限値を0.005%とし
た。しかし0.025%を超えると過剰なTiはTiCを析出
し、その析出硬化により母材および溶接熱影響部の靭性
を劣化させるため0.025%以下に制限した。Ti suppresses generation of M * by precipitating TiN and reducing solid solution N. The finely precipitated TiN also contributes to the refinement of the γ phase. By the action of these Tis, the structure is refined and the strength and toughness are improved. Therefore, if the content is less than 0.005%, the amount of TiN deposited is insufficient, and these effects cannot be exhibited. Therefore, the lower limit of the Ti content is set to 0.005%. However, if the content exceeds 0.025%, excessive Ti precipitates TiC, and the precipitation hardening deteriorates the toughness of the base material and the heat affected zone by welding, so that the content is limited to 0.025% or less.
【0020】Mgは、Mg系酸化物による粒界ピンニン
グ作用により、熱間圧延直後のγ粒径を40μm以下に
微細化するために必要である。Mg添加に使用するMg合
金はSi-Mg-Al及びNi-Mg が好ましい。Mg合金を用いた
理由は合金化によりMg含有濃度を低減し、溶鋼への添
加時の脱酸反応を抑制し、添加時の安全性の確保とMg
の歩留を向上させるためである。Mgを0.0005〜0.005%
に限定するのは、Mgも強力な脱酸元素であり、晶出し
たMg酸化物は溶鋼中で容易に浮上分離されるため0.00
5%を超えて添加しても、これ以上は歩留まらないため上
限を0.005%とした。また、0.0005% 未満ではγ粒径微細
化のためのMg系酸化物の分散密度が不足するため下限
を0.0005% とした。なお、ここでのMg系酸化物は、主
にMgOと表記しているが、電子顕微鏡解析などによる
と、この酸化物はTi、微量のAlおよび不純物として
含まれているCaなどとの複合酸化物を形成している。Mg is necessary for reducing the γ grain size immediately after hot rolling to 40 μm or less by the grain boundary pinning action of the Mg-based oxide. The Mg alloy used for adding Mg is preferably Si-Mg-Al or Ni-Mg. The reason for using Mg alloy is to reduce the Mg content by alloying, suppress the deoxidation reaction when adding to molten steel, secure the safety when adding, and
This is to improve the yield. 0.0005-0.005% Mg
Mg is also a strong deoxidizing element, and the crystallized Mg oxide is easily floated and separated in molten steel.
Even if it is added in excess of 5%, the yield is not further increased, so the upper limit was made 0.005%. On the other hand, if the content is less than 0.0005%, the dispersion density of the Mg-based oxide for reducing the γ particle size becomes insufficient, so the lower limit is made 0.0005%. Here, the Mg-based oxide is mainly described as MgO, but according to electron microscopic analysis and the like, this oxide is a complex oxide of Ti, a trace amount of Al, and Ca contained as an impurity. Is forming an object.
【0021】Nbは焼入性を上昇させ強度を増加させる
目的で添加している。この効果の発現には、Nb含有量
は0.04% 以上が必要である。しかし0.10% 超では、Nb
炭窒化物の析出量が増加し固溶Nbとしての効果が飽和
するので0.10% 以下に制限した。Vは微量添加により圧
延組織を微細化でき、バナジン炭窒化物の析出により強
化することから低合金化でき溶接特性を向上できる。こ
の効果の発現には、V含有量は0.01% 以上が必要であ
る。しかしながら、Vの過剰な添加は溶接部の硬化や、
母材の高降伏点化をもたらすので、含有量の上限をV:0.
10% とした。Nb is added for the purpose of increasing hardenability and increasing strength. To achieve this effect, the Nb content needs to be 0.04% or more. However, if it exceeds 0.10%, Nb
Since the amount of precipitated carbonitride increases and the effect as solid solution Nb saturates, the content is limited to 0.10% or less. The addition of a small amount of V can make the rolling structure finer and strengthening it by precipitation of vanadium carbonitride, so that a lower alloy can be obtained and welding characteristics can be improved. To achieve this effect, the V content must be 0.01% or more. However, excessive addition of V hardens the weld and
Since the base material has a high yield point, the upper limit of the content is set to V: 0.
10%.
【0022】Moは母材強度の確保に有効な元素であ
る。この効果の発現には、Mo含有量は0.05% 以上が必
要である。しかし0.4%超では、Mo炭化物(Mo2 C)
を析出し固溶Moとしての焼入性向上効果が飽和するの
で0.4%以下に制限した。Nはα中に固溶し、強度を上昇
させるが、上部ベイナイト組織では、M*を生成し、靭
性を劣化させるので、固溶Nはできるだけ低減する必要
がある。しかし、本発明でのNはTiと化合させ鋼中に
TiNを微細析出させ、固溶Nを低減させた上で、Ti
Nによる結晶の粒成長を抑制し組織微細化効果を発揮さ
せる目的で添加している。従って、この効果の発現に
は、N量が0.002%未満ではTiNの析出量が不足し、0.
006%超では析出量は十分となるが、固溶Nが増加し、靭
性を損ねるのでN:0.002 〜0.006%に限定した。Mo is an element effective for securing the strength of the base material. In order to achieve this effect, the Mo content needs to be 0.05% or more. However, if it exceeds 0.4%, Mo carbide (Mo2C)
Was precipitated, and the effect of improving the hardenability as solid solution Mo was saturated, so the content was limited to 0.4% or less. N forms a solid solution in α and increases the strength, but in the upper bainite structure, M * is generated and the toughness is deteriorated. Therefore, it is necessary to reduce the solute N as much as possible. However, N in the present invention is combined with Ti to cause fine precipitation of TiN in the steel and to reduce solid-solution N,
It is added for the purpose of suppressing the crystal grain growth due to N and exhibiting the structure refinement effect. Therefore, in order to achieve this effect, if the N content is less than 0.002%, the amount of TiN deposited is insufficient, and the amount of TiN is not sufficient.
If it exceeds 006%, the amount of precipitation will be sufficient, but the solute N will increase and the toughness will be impaired, so N is limited to 0.002 to 0.006%.
【0023】Bは微量添加で焼入性を上昇させ強度増加
に寄与する。しかし、0.0003% 超のBを含有すると上部
ベイナイト組織中にM*を生成し靭性を著しく低下させ
ることが判明したので、Bはむしろ不純物として0.0003
% 以下に制限した。Alを0.005%以下としたのは、Al
は強力な脱酸元素であり、0.005%超の含有では、M gO
の生成が阻害され、微細な分散ができないため、Alも
不純物として0.005%以下に制限した。B increases hardenability by adding a small amount and contributes to an increase in strength. However, it has been found that when B is contained in excess of 0.0003%, M * is formed in the upper bainite structure and the toughness is significantly reduced.
%. The reason why the content of Al is set to 0.005% or less is that Al
Is a strong deoxidizing element, and if its content exceeds 0.005%, MgO
Since the formation of Al was inhibited and fine dispersion was not possible, Al was also limited to 0.005% or less as an impurity.
【0024】O(酸素)はMg−Oの生成に不可欠であ
り、それには0.003 %以上の含有が必要であるが、0.00
6%を超えて含有すると、生成するMg−O粒子は粗大化
し、靭性を低下させるため、O含有量を 0.003〜0.006%
に限定した。不可避不純物として含有するP、Sについ
ては、それらの量を特に限定しないが凝固偏析による溶
接割れ、靭性低下の原因となるので、極力低減すべきで
ありP、S量はそれぞれ0.02% 未満に制限することが望
ましい。O (oxygen) is indispensable for the production of Mg—O, and it needs to contain 0.003% or more.
When the content exceeds 6%, the generated Mg-O particles are coarsened and the toughness is reduced, so the O content is 0.003 to 0.006%.
Limited to. The amounts of P and S contained as unavoidable impurities are not particularly limited, but may cause welding cracks and decrease in toughness due to solidification segregation. Therefore, P and S contents should be reduced as much as possible, and the contents of P and S are each limited to less than 0.02%. It is desirable to do.
【0025】以上の元素に加えて、母材強度の上昇、お
よび母材の靭性向上の目的で、Cr、NiおよびCuの
うちの少なくとも1種を含有することができる。Crは
焼入性の向上により、母材の強化に有効である。この効
果の発現にはCr含有量は0.1%以上が必要である。しか
し1.0%を超える過剰の添加は、靭性および硬化性の観点
から有害となるため、上限を1.0%とした。In addition to the above elements, at least one of Cr, Ni and Cu can be contained for the purpose of increasing the strength of the base material and improving the toughness of the base material. Cr is effective in strengthening the base material by improving the hardenability. In order to achieve this effect, the Cr content must be 0.1% or more. However, an excessive addition exceeding 1.0% is harmful from the viewpoint of toughness and curability, so the upper limit was made 1.0%.
【0026】Niは母材の強靭性を高める極めて有効な
元素である。この効果の発現にはNi含有量は0.1%以上
が必要である。しかし、1.0%を超える添加は合金コスト
を増加させ経済的でないので上限を1.0%とした。Cuは
母材の強靱性を高める元素であり、この効果の発現には
Cu含有量0.1%以上が必要である。しかし、1.0 %を
超えて添加すると鋳片に表面割れを発生させるなど、高
温延性を低下させるのでCu:0.1〜1.0%に限定した。Ni is an extremely effective element for increasing the toughness of the base material. To achieve this effect, the Ni content must be 0.1% or more. However, the addition of more than 1.0% increases the alloy cost and is not economical, so the upper limit was made 1.0%. Cu is an element that enhances the toughness of the base material, and a Cu content of 0.1% or more is required to exhibit this effect. However, if added in excess of 1.0%, the high-temperature ductility is reduced, such as the occurrence of surface cracks in the slab, so Cu was limited to 0.1-1.0%.
【0027】本発明の圧延形鋼は、590MPa (60kg
f/mm2)級の引張強さと靱性とを同時に確保するために、
ベイナイトの面積率が50〜90%で、残部がフェライ
ト・パーライトおよび高炭素島状マルテンサイトから成
り、該高炭素島状マルテンサイトの面積率が5%以下で
あって、熱間圧延完了後のγ粒径が40μm以下である
ミクロ組織を有することが必要である。The rolled section steel of the present invention has a capacity of 590 MPa (60 kg).
f / mm 2 ) class tensile strength and toughness at the same time,
The area ratio of bainite is 50 to 90%, and the balance is composed of ferrite / pearlite and high carbon island martensite, and the area ratio of the high carbon island martensite is 5% or less, and after completion of hot rolling. It is necessary to have a microstructure having a γ particle size of 40 μm or less.
【0028】また、本発明の590MPa 級圧延形鋼は、
梁材として用いる際のボルト穴を開けるために、表面か
ら深さ3mm以内の表層硬さがHv250以下であるこ
とが望ましい。上記のミクロ組織および表層硬さは、本
発明の方法によって実現できる。すなわち、上記の化学
組成を有する鋳片を1200〜1300℃の温度域に再
加熱する。この温度域に再加熱温度を限定したのは、熱
間加工による形鋼の製造には塑性変形を容易にするため
1200℃以上の加熱が必要であり、且つV、Nbなど
の元素を十分に固溶させる必要があるため再加熱温度の
下限を1200℃とした。その上限は加熱炉の性能、経
済性から1300℃とした。Further, the 590 MPa class rolled section steel of the present invention is:
In order to form a bolt hole when used as a beam material, the surface hardness within a depth of 3 mm from the surface is desirably Hv250 or less. The above microstructure and surface hardness can be achieved by the method of the present invention. That is, the slab having the above chemical composition is reheated to a temperature range of 1200 to 1300 ° C. The reason for limiting the reheating temperature to this temperature range is that the production of a section steel by hot working requires heating at 1200 ° C. or higher to facilitate plastic deformation, and sufficiently removes elements such as V and Nb. Since it is necessary to form a solid solution, the lower limit of the reheating temperature was set to 1200 ° C. The upper limit was set to 1300 ° C. in view of the performance and economy of the heating furnace.
【0029】熱間圧延のパス間で水冷し、圧延中に、フ
ランジ表面温度を700℃以下に冷却し、次の圧延パス
間の復熱過程で圧延する水冷・圧延サイクルを1回以上
行うとしたのは、圧延パス間の水冷により、フランジの
表層部と内部とに温度差を付与し、軽圧下条件において
も内部への加工歪みを浸透させるためと、水冷により短
時間で低温圧延を実現させTMCPを効率的に行うため
である。Water-cooling between hot rolling passes, the surface temperature of the flange is cooled to 700 ° C. or less during rolling, and a water-cooling / rolling cycle of rolling in the reheating process between the next rolling passes is performed at least once. Water cooling between the rolling passes gives a temperature difference between the surface layer and the inside of the flange to penetrate the processing strain into the interior even under light rolling conditions. This is for performing the TMCP efficiently.
【0030】フランジ表面温度を700℃以下に冷却し
た後、復熱過程で圧延するのは、仕上げ圧延後の加速冷
却による表面の焼入れ硬化を抑制し軟化させるために行
うものである。その理由はフランジ表面温度を700℃
以下に冷却すれば一旦γ/α変態温度を切り、次の圧延
までに表層部は復熱昇温し、圧延はγ/αの二相共存温
度域での加工となり、γ細粒化と加工された微細αとの
混合組織を形成する。これにより表層部の焼入性を著し
く低減でき、加速冷却により生じる表面層の硬化を防止
できるからである。Rolling in the recuperation process after the flange surface temperature is cooled to 700 ° C. or lower is performed to suppress and soften the surface by quenching and hardening due to accelerated cooling after finish rolling. The reason is that the flange surface temperature is 700 ° C
Once cooled, the γ / α transformation temperature is temporarily cut off, and the surface layer is reheated and heated by the next rolling. Rolling is performed in the γ / α two-phase coexisting temperature range. A mixed structure with the fine α thus formed is formed. Thereby, the hardenability of the surface layer can be significantly reduced, and the hardening of the surface layer caused by accelerated cooling can be prevented.
【0031】また、圧延終了後、引続き、0.5 〜10℃/s
の冷却速度で700〜400℃まで冷却し放冷するとし
たのは、加速冷却によりベイナイトの粒成長を抑制し、
ベイナイト組織を微細化して、高強度・高靭性を付与す
るためである。次いで、加速冷却を700〜400℃で
停止するのは、700℃を超える温度で停止した場合に
は、表層部の一部がAr1 点以上となりγ相を残存し、こ
のγ相が、共存するフェライトを核にフェライト変態
し、さらにフェライトが成長し粗粒化するため加速冷却
の停止温度を700℃以下とした。また、400℃未満
の冷却では、その後の放冷中にベイナイト相のラス間に
生成する高炭素マルテンサイトが、冷却中にセメンタイ
トを析出することにより分解できず、硬化相として存在
することになる。この高炭素マルテンサイトは脆性破壊
の起点として作用し、靭性低下の原因となる。これらの
理由により、加速冷却の停止温度を700〜400℃に
限定した。After the end of the rolling, the temperature is continuously maintained at 0.5 to 10 ° C./s.
The reason for cooling to 700 to 400 ° C. at a cooling rate of and allowing it to cool is to suppress grain growth of bainite by accelerated cooling,
This is because the bainite structure is refined to provide high strength and high toughness. Next, the reason why the accelerated cooling is stopped at 700 to 400 ° C. is that, when the temperature is stopped at a temperature exceeding 700 ° C., a part of the surface layer becomes an Ar1 point or more and a γ phase remains, and this γ phase coexists Since the ferrite is transformed into a ferrite core and the ferrite grows and becomes coarse, the stop temperature of the accelerated cooling is set to 700 ° C. or less. In addition, when the cooling is performed at a temperature lower than 400 ° C., high carbon martensite generated between laths of the bainite phase during the subsequent cooling is not decomposed due to precipitation of cementite during cooling, and exists as a hardened phase. . This high carbon martensite acts as a starting point of brittle fracture and causes a decrease in toughness. For these reasons, the stop temperature of the accelerated cooling was limited to 700 to 400 ° C.
【0032】[0032]
【実施例】試作形鋼は転炉溶製し、合金を添加後、予備
脱酸処理を行い、溶鋼の酸素濃度を調整後、Ti、Mg
合金を順次添加し、連続鋳造により250 〜300mm 厚鋳片
に鋳造した。鋳片の冷却はモールド下方の二次冷却帯の
水量と鋳片の引き抜き速度の選択により制御した。該鋳
片を加熱し、粗圧延工程の図示は省略するが、図1に示
す、ユニバーサル圧延装置列でH形鋼に圧延した。圧延
パス間水冷は中間ユニバーサル圧延機4の前後に水冷装
置5aを設け、フランジ外側面のスプレー冷却とリバー
ス圧延の繰り返しにより行い、圧延後の加速冷却は仕上
げユニバーサル圧延機6で圧延終了後にその後面に設置
した冷却装置5bでフランジ外側面をスプレー冷却し
た。EXAMPLE A prototype steel was melted in a converter, an alloy was added, preliminary deoxidation was performed, and the oxygen concentration of the molten steel was adjusted.
Alloys were sequentially added and cast into 250-300 mm thick slabs by continuous casting. The cooling of the slab was controlled by selecting the amount of water in the secondary cooling zone below the mold and the speed of drawing the slab. The slab was heated and rolled into an H-beam by a universal rolling mill row shown in FIG. 1, although illustration of the rough rolling step was omitted. Water cooling between rolling passes is provided with a water cooling device 5a before and after the intermediate universal rolling mill 4, and spray cooling and reverse rolling are repeated on the outer surface of the flange. Accelerated cooling after rolling is performed after finishing rolling by the finishing universal rolling mill 6. The outer surface of the flange was spray-cooled by the cooling device 5b installed in the above.
【0033】機械特性は図2に示す、フランジ2の板厚
t2 の中心部(1/2t2 )でフランジ幅全長(B) の1/4,1/
2 幅(1/4B,1/2B) から、採集した試験片を用い求めた。
なお、これらの箇所についての特性を求めたのは、フラ
ンジ1/4F部はH形鋼の平均的な機械特性を示し、フラン
ジ1/2F部はその特性が最も低下するので、これらの2箇
所によりH形鋼の機械試験特性を代表できると判断した
ためである。The mechanical characteristics are shown in FIG. 2 at the center (1 / 2t2) of the thickness t2 of the flange 2 at 1 / 4,1 / of the overall flange width (B).
2 From the width (1 / 4B, 1 / 2B), it was determined using test specimens collected.
The properties of these parts were determined as follows: The flange 1 / 4F shows the average mechanical properties of the H-section steel, and the flange 1 / 2F has the lowest properties. This is because it was judged that the mechanical test characteristics of the H-section steel could be represented by the above.
【0034】表1、表3には、本発明鋼及び比較鋼の化
学成分値を、表2、表4には、それらの鋼のTi添加前
の溶鋼の酸素濃度およびMg系酸化物とその酸化物とT
iNの複合体の個数を、表5、表6には、圧延・加速冷
却条件を示す。次いで表7、表8には、それらのH形鋼
の機械試験特性値、フランジ側面の表面硬さおよびベイ
ナイト、M*の面積率及び圧延後の旧γ粒径を示す。な
お、圧延加熱温度を1300℃に揃えたのは、一般的に
加熱温度の低下によりγ粒は細粒化し、機械試験特性を
向上させることは周知であり、高温加熱条件では機械特
性の最低値を示すと推定され、この値がそれ以下の加熱
温度での機械試験特性を代表できると判断したためであ
る。また、各表中で下線を付した数値は本発明の範囲外
である。Tables 1 and 3 show the chemical composition values of the steels of the present invention and the comparative steels. Tables 2 and 4 show the oxygen concentrations and the Mg-based oxides of the molten steels of these steels before adding Ti. Oxide and T
Tables 5 and 6 show the number of the iN composites and the rolling / accelerated cooling conditions. Next, Tables 7 and 8 show the mechanical test characteristic values of these H-section steels, the surface hardness of the flange side surface, bainite, the area ratio of M *, and the prior γ grain size after rolling. It is well known that the rolling heating temperature is adjusted to 1300 ° C. because it is generally known that, by lowering the heating temperature, γ grains are refined to improve mechanical test characteristics. This is because it was determined that this value could represent the mechanical test characteristics at a lower heating temperature. The underlined numerical values in each table are outside the scope of the present invention.
【0035】表7,8に示すように、本発明によるH形
鋼1〜5、H形鋼A1〜A3では、降伏強度、抗張力と
もに590MPa級鋼でのJIS規格値を満たしてい
る。すなわち降伏強度はその下限値の445MPaを超
え、拡張力も590MPaを超えており、またこれらの
降伏比(YS/TS)は0.8 以下の低YR値を満たして
いる。シャルピー衝撃値についても−10℃で47
(J)を超えておりJIS規格値を十分に満たしてい
る。As shown in Tables 7 and 8, the H-section steels 1 to 5 and the H-section steels A1 to A3 according to the present invention both satisfy the JIS standard values of the 590 MPa class steel in both yield strength and tensile strength. That is, the yield strength exceeds the lower limit of 445 MPa, the expansion force also exceeds 590 MPa, and their yield ratio (YS / TS) satisfies the low YR value of 0.8 or less. The Charpy impact value is 47 at -10 ° C.
It exceeds (J) and satisfies the JIS standard value sufficiently.
【0036】一方、H形鋼6ではSiとMo含有量が、
H形鋼7では炭素含有量が、H形鋼8ではTiとN含有
量が、H形鋼9ではボロンとA1含有量が、H形鋼10
ではNb含有量が、各々の上限値を超え、靱性を劣化さ
せるM*面積率が5%を超えるために、−10℃でのシ
ャルピー吸収エネルギー値が、目標の47J以上をクリ
アできない。加えてH形鋼7では、Mg含有量が下限値
未満であり、H形鋼9ではA1含有量が上限値を超える
ために、Mg系酸化物の分散個数が不足し、圧延後のγ
粒径を40μm以下に細粒化できないために、組織が粗
大化し靱性値をクリアーできない。また、H形鋼6およ
びH形鋼9では、焼入性が上昇し、フランジ表面硬さが
Hv250を超える。On the other hand, in the H-section steel 6, the content of Si and Mo is
The H-section steel 7 has a carbon content, the H-section steel 8 has a Ti and N content, the H-section steel 9 has a boron and A1 content, and the H-section steel 10
In this case, since the Nb content exceeds the respective upper limit values and the M * area ratio that deteriorates toughness exceeds 5%, the Charpy absorbed energy value at −10 ° C. cannot exceed the target of 47 J or more. In addition, in the H-section steel 7, the Mg content is less than the lower limit, and in the H-section steel 9, since the A1 content exceeds the upper limit, the number of dispersed Mg-based oxides is insufficient, and γ after rolling is reduced.
Since the grain size cannot be reduced to 40 μm or less, the structure becomes coarse and the toughness value cannot be cleared. Further, in the H-section steel 6 and the H-section steel 9, the hardenability increases, and the flange surface hardness exceeds Hv250.
【0037】H形鋼A4では、Ti添加前の溶鋼の酸素
濃度が低く、酸素含有量の下限値未満であるので、Mg
系酸化物の生成個数が減少するため、γ粒径を細粒化で
きず、組織が粗大化して靱性が低下し、目標のシャルピ
ー吸収エネルギー値をクリアできない。これに反して、
H形鋼A5では、酸素含有量が上限値を超えたために、
Mg系酸化物の粗大化が生じ、これにより靱性値がクリ
アできない。次いで、H形鋼A6では、圧延中の水冷お
よび圧延後の冷却速度の要件を満たしていないために、
強度の目標値をクリアできない。In the H-section steel A4, the oxygen concentration of the molten steel before the addition of Ti is low and less than the lower limit of the oxygen content.
Since the number of generated system oxides decreases, the γ particle size cannot be reduced, the structure becomes coarse and the toughness decreases, and the target Charpy absorption energy value cannot be cleared. On the contrary,
In the H-section steel A5, since the oxygen content exceeded the upper limit,
Mg-based oxides are coarsened, so that the toughness value cannot be cleared. Next, since the H-section steel A6 does not satisfy the requirements of water cooling during rolling and cooling rate after rolling,
The strength target value cannot be cleared.
【0038】すなわち、本発明の製造法の要件が総て満
たされた時に、表7,8に示されるH形鋼1〜5、A1
〜A3のように、圧延形鋼の機械試験特性の最も保証し
にくいフランジ板厚1/2、幅1/2部においても十分
な強度、低温靱性を有する、高張力圧延形鋼の生産が可
能になる。なお、本発明が対象とする圧延形鋼は上記実
施例のH形鋼に限らずI形鋼、山形鋼、溝形鋼、不等辺
不等厚山形鋼等のフランジを有する形鋼にも適用できる
ことは勿論である。That is, when all the requirements of the production method of the present invention are satisfied, H-section steels 1 to 5 and A1 shown in Tables 7 and 8 are obtained.
As in A3, it is possible to produce high tensile rolled steel with sufficient strength and low-temperature toughness even in 1/2 flange width and 1/2 width width where mechanical test characteristics of rolled steel are the least guaranteed. become. The rolled section steel to which the present invention is applied is not limited to the H section steel of the above embodiment, but is also applicable to section steels having flanges such as I section steel, angle steel, channel steel, and unequal thickness angle steel. Of course, you can.
【0039】[0039]
【表1】 [Table 1]
【0040】[0040]
【表2】 [Table 2]
【0041】[0041]
【表3】 [Table 3]
【0042】[0042]
【表4】 [Table 4]
【0043】[0043]
【表5】 [Table 5]
【0044】[0044]
【表6】 [Table 6]
【0045】[0045]
【表7】 [Table 7]
【0046】[0046]
【表8】 [Table 8]
【0047】[0047]
【発明の効果】本発明による合金設計された鋳片と制御
圧延法を適用した圧延形鋼は機械試験特性の最も保証し
にくいフランジ板厚1/2、幅1/2部においても十分
な強度を有し、優れた靭性を持つ形鋼の製造が圧延まま
で可能となり、大型鋼構造物の信頼性の向上、安全性の
確保、経済性等の産業上の効果は極めて顕著なものであ
る。According to the present invention, the alloy-designed cast slab and the rolled section steel to which the controlled rolling method is applied have sufficient strength even in a flange plate thickness 1/2 and a width 1/2 part where mechanical test characteristics are hardly guaranteed. The production of shaped steel with excellent toughness becomes possible as it is rolled, and the industrial effects such as improvement of reliability, safety and economical efficiency of large steel structures are extremely remarkable. .
【図1】図1は、本発明法を実施する装置配置例の略図
である。FIG. 1 is a schematic view of an example of an apparatus arrangement for performing the method of the present invention.
【図2】図2は、H形鋼の断面形状および機械試験片の
採取位置を示す図である。FIG. 2 is a diagram illustrating a cross-sectional shape of an H-section steel and a sampling position of a mechanical test piece.
1…H形鋼 2…フランジ 3…ウェブ 4…中間圧延機 5a…中間圧延機前後面の水冷装置 5b…仕上げ圧延機後面冷却装置 6…仕上げ圧延機 DESCRIPTION OF SYMBOLS 1 ... H-shaped steel 2 ... Flange 3 ... Web 4 ... Intermediate rolling mill 5a ... Water cooling device of the front and rear surface of an intermediate rolling mill 5b ... Finishing rolling machine rear surface cooling device 6 ... Finishing rolling mill
Claims (6)
避不純物のうち B含有量を0.0003% 以下およびAl含有量
を0.005%以下に制限した化学組成を有し、かつベイナイ
トの面積率が50〜90%で、残部がフェライト・パー
ライトおよび高炭素島状マルテンサイトから成り、該高
炭素島状マルテンサイトの面積率が5%以下であって、
熱間圧延完了後の旧γ粒径が40μm以下であるミクロ
組織を有することを特徴とする590MPa 級圧延形鋼。1% by weight C: 0.02 to 0.06%, Si: 0.05 to 0.25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to 0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo: 0.05 to 0.40%, N: 0.002 to 0.006%, and O: 0.003 to 0.006%, with the balance being Fe and inevitable impurities, and the B content of the inevitable impurities. It has a chemical composition of not more than 0.0003% and an Al content of not more than 0.005%, and has an area ratio of bainite of 50 to 90%, and the balance consists of ferrite pearlite and high carbon island martensite. The area ratio of the island-like martensite is 5% or less,
590 MPa class rolled section steel having a microstructure in which the prior γ grain size after completion of hot rolling is 40 μm or less.
v250以下であることを特徴とする請求項1記載の5
90MPa 級圧延形鋼。2. The hardness of the surface layer within a depth of 3 mm from the surface is H.
5. The method according to claim 1, wherein the value of v is not more than 250.
90MPa class rolled section steel.
の少なくとも1種、を含み、残部がFeおよび不可避不純
物からなり、該不可避不純物のうち B含有量を0.0003%
以下およびAl含有量を0.005%以下に制限した化学組成を
有し、かつベイナイトの面積率が50〜90%で、残部
がフェライト・パーライトおよび高炭素島状マルテンサ
イトから成り、該高炭素島状マルテンサイトの面積率が
5%以下であって、熱間圧延完了後の旧γ粒径が40μ
m以下であるミクロ組織を有することを特徴とする59
0MPa 級圧延形鋼。3% by weight C: 0.02 to 0.06%, Si: 0.05 to 0.25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to 0.0050%, Nb: 0.04 to 0.10%, V: 0.01-0.10%, Mo: 0.05-0.40%, N: 0.002-0.006%, O: 0.003-0.006%, and Cr: 0.1-1.0%, Ni: 0.1-1.0% and Cu: 0.1-1.0% At least one of them, and the balance consists of Fe and inevitable impurities, and the B content of the inevitable impurities is 0.0003%.
And a chemical composition in which the Al content is limited to 0.005% or less, the area ratio of bainite is 50 to 90%, and the balance is composed of ferrite / pearlite and high carbon island martensite. The area ratio of martensite is 5% or less, and the old γ grain size after completion of hot rolling is 40 μm.
m having a microstructure of not more than m
0MPa class rolled section steel.
v250以下であることを特徴とする請求項3記載の5
90MPa 級圧延形鋼。4. The hardness of the surface layer within a depth of 3 mm from the surface is H.
5. The method according to claim 3, wherein the value is not more than v250.
90MPa class rolled section steel.
避不純物のうち B含有量を0.0003% 以下およびAl含有量
を0.005%以下に制限した鋳片を1200〜1300℃の温度域に
加熱した後に圧延を開始し、圧延工程で形鋼のフランジ
表面を700 ℃以下にまで水冷し復熱過程で圧延する水冷
・圧延サイクルを一回以上行い、圧延終了後に0.5 〜10
℃/sの冷却速度で700 〜400 ℃の温度域に冷却した後に
放冷することを特徴とする590MPa 級圧延形鋼の製造
方法。5% by weight C: 0.02 to 0.06%, Si: 0.05 to 0.25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to 0.0050%, Nb: 0.04 to 0.10%, V: 0.01 to 0.10%, Mo: 0.05 to 0.40%, N: 0.002 to 0.006%, and O: 0.003 to 0.006%, with the balance being Fe and inevitable impurities, and the B content of the inevitable impurities. Rolling is started after heating the slabs with the content of 0.0003% or less and the content of Al to 0.005% or less to the temperature range of 1200 to 1300 ° C, and the flange surface of the section steel is water-cooled to 700 ° C or less in the rolling process and then restored. Perform a water-cooling / rolling cycle at least once for rolling in the heat process, and after rolling is completed
A method for producing a 590 MPa class rolled section steel, which is cooled at a cooling rate of 700C / s to a temperature range of 700 to 400C and then left to cool.
の少なくとも1種、を含み、残部がFeおよび不可避不純
物からなり、該不可避不純物のうち B含有量を0.0003%
以下およびAl含有量を0.005%以下に制限した鋳片を1200
〜1300℃の温度域に加熱した後に圧延を開始し、圧延工
程で形鋼のフランジ表面を700 ℃以下にまで水冷し復熱
過程で圧延する水冷・圧延サイクルを一回以上行い、圧
延終了後に0.5 〜10℃/sの冷却速度で700 〜400 ℃の温
度域に冷却した後に放冷することを特徴とする590MP
a 級圧延形鋼の製造方法。6% by weight C: 0.02 to 0.06%, Si: 0.05 to 0.25%, Mn: 0.8 to 1.6%, Ti: 0.005 to 0.025%, Mg: 0.0005 to 0.0050%, Nb: 0.04 to 0.10%, V: 0.01-0.10%, Mo: 0.05-0.40%, N: 0.002-0.006%, O: 0.003-0.006%, and Cr: 0.1-1.0%, Ni: 0.1-1.0% and Cu: 0.1-1.0% At least one of them, and the balance consists of Fe and inevitable impurities, and the B content of the inevitable impurities is 0.0003%.
Below and the slab with the Al content limited to 0.005% or less is 1200
Rolling is started after heating to a temperature range of ~ 1300 ° C, and at least one water-cooling / rolling cycle is performed, in which the flange surface of the section steel is water-cooled to 700 ° C or less in the rolling process and rolled in the recuperation process. 590MP, characterized by cooling to a temperature range of 700-400 ° C at a cooling rate of 0.5-10 ° C / s and then allowing to cool
Production method for a-grade rolled steel bars.
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