JP3293378B2 - Method for producing high-strength extra-thick rolled H-section steel for construction with a flange thickness of 80 mm or more that has fire resistance, excellent weldability, and little change in strength in the thickness direction - Google Patents

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【産業上の利用分野】本発明は、建築用鋼材として要求
される低降伏比、狭ＹＰレンジ、及び耐火性を有し、引
張強度が５７０ＭＰａ以上の高強度鋼のうち、フランジ
厚さが８０ｍｍ以上の柱材に用いられる極厚圧延Ｈ形鋼
の製造方法に関する。BACKGROUND OF THE INVENTION The present invention relates to a high-strength steel having a low yield ratio, a narrow YP range, and fire resistance required for building steel materials and a tensile strength of 570 MPa or more, and a flange thickness of 80 mm. The present invention relates to a method for producing an extra-thick rolled H-section steel used for the above-mentioned column material.

【０００２】[0002]

【従来の技術】鉄骨構造の高層建物の柱材には、耐震設
計の観点から低降伏比の鋼材が用いられている。また耐
火設計の見直しにより、高温強度に優れた耐火鋼材を用
いて耐火被覆を減らすことにより、工期の短縮、工事費
の削減、建築物内の有効面積を拡張する設計も盛んにな
ってきている。2. Description of the Related Art Steel columns having a low yield ratio are used for columns of high-rise buildings having a steel structure from the viewpoint of seismic design. In addition, due to the review of fire-resistant design, the use of fire-resistant steel with excellent high-temperature strength to reduce the amount of fire-resistant coating has shortened the construction period, reduced construction costs, and expanded the design of the effective area in buildings. .

【０００３】上記のような設計手法を用いた高層建築物
に用いられる柱材には、各方向毎の断面係数の変化が少
ないボックス柱、鋼管を用いた円柱、あるいは温間また
は冷間で加工されたコラム柱が用いられている。[0003] Column materials used in high-rise buildings using the above-described design techniques include box columns, steel columns, or warm or cold columns having little change in section modulus in each direction. Column columns are used.

【０００４】しかし、円柱の場合は梁材と接続するため
の仕口部の加工が複雑になること、ボックス柱の場合は
角溶接の施工に技術が要求されること、高層建築物に用
いられる厚肉コラム柱の場合はコーナー部の低降伏比を
満足するような成形を行なうための成形コストが高いこ
と等の欠点を有している。従って材料費、施工費等を含
めたトータルとしてのコストを削減できる柱材が求めら
れている。[0004] However, in the case of a cylindrical column, the processing of the joint for connecting to the beam material is complicated, and in the case of a box column, the technique is required for the square welding, and it is used for a high-rise building. In the case of a thick column, there is a drawback such as a high forming cost for forming to satisfy a low yield ratio of a corner portion. Therefore, there is a need for a pillar material that can reduce the total cost including the material cost and the construction cost.

【０００５】ところで、Ｈ形鋼は、断面係数はＨ方向と
Ｉ方向で異なるが、複雑な曲げ加工、溶接施工を行なわ
ずに柱を製作できること、梁材を取り付ける仕口部が炭
酸ガス溶接のみで簡便に施工できること等の利点が多
い。また断面係数の違いは設計段階で考慮できることは
良く知られている。[0005] By the way, although the section modulus of the H-section steel is different between the H direction and the I direction, the column can be manufactured without performing complicated bending and welding work, and the connection portion for attaching the beam is only carbon dioxide welding. There are many advantages such as simple construction. It is well known that differences in section modulus can be considered at the design stage.

【０００６】以上の点から低降伏比と耐火性を満たし、
溶接性に優れ、板厚方向の均質性を有する極厚圧延高強
度Ｈ形鋼の製造を可能とすることにより、今後の高層建
築物における柱材として多くの需要が見込まれる。[0006] From the above points, satisfying a low yield ratio and fire resistance,
By enabling the production of an ultra-thick rolled high-strength H-section steel having excellent weldability and uniformity in the thickness direction, much demand is expected as a pillar material for future high-rise buildings.

【０００７】高層建築物に用いられる低降伏比と耐火性
を兼ね備えた鋼材については、溶接施工することにより
柱材、梁材に適用できる厚鋼板、およびフランジ厚さの
薄い梁材に用いられるＨ形鋼の分野で、特開平２−１６
３３４１号公報、特開平４−２６３０１２号公報、特開
平４−８３８２１号公報等に種々の提案がなされてい
る。[0007] For steel materials having both a low yield ratio and fire resistance used for high-rise buildings, thick steel plates applicable to columns and beams by welding, and H steels used for beams with thin flanges are used. In the field of shaped steel,
Various proposals have been made in JP-A No. 3341, JP-A-4-263012, JP-A-4-83821 and the like.

【０００８】[0008]

【発明が解決しようとする課題】上記公報に記載された
技術は、いずれもＴＭＣＰ（Thermomechanical Control
Process ）技術を駆使することが可能な厚鋼板、および
製造条件のコントロールが比較的容易なフランジ厚さが
薄い梁材用のＨ形鋼に適用されている。The techniques described in the above publications are all disclosed in TMCP (Thermomechanical Control).
Process) is applied to thick steel plates that can make full use of technology, and H-beams for beams with small flange thickness, which makes it relatively easy to control manufacturing conditions.

【０００９】しかしフランジ厚さが８０ｍｍを超える柱
材に適した極厚圧延Ｈ形鋼の分野では、圧延条件は主と
してＨ形状を整えるため、および寸法精度を満足するた
めに決定されていることから、材質の観点に基づいて圧
延条件を変更することは困難である。However, in the field of extremely thick rolled H-section steel suitable for a column having a flange thickness of more than 80 mm, the rolling conditions are determined mainly for adjusting the H shape and satisfying the dimensional accuracy. It is difficult to change the rolling conditions from the viewpoint of the material.

【００１０】このような柱材向け極厚圧延Ｈ形鋼におけ
るＴＭＣＰ技術の適用に関しては、特開昭６０−２３６
６号公報に、合金成分と加速冷却を用いた製造条件を規
定することにより高強度化を図る技術が、特開昭６０−
７７９２４号公報には加速冷却条件を規定した技術が開
示されているが、建築向けの柱材として要求される低降
伏比、耐火性、溶接性及び板厚方向の均質性を兼ね備え
た鋼材の製造方法に関しては全く提案されていない。Regarding the application of the TMCP technique to such an extremely thick rolled H-section steel for column materials, see JP-A-60-236.
Japanese Unexamined Patent Publication No. 60-1985 discloses a technique for increasing the strength by specifying the manufacturing conditions using alloy components and accelerated cooling.
Japanese Patent Application Laid-Open No. 77924 discloses a technique in which accelerated cooling conditions are specified. However, the production of a steel material having a low yield ratio, fire resistance, weldability, and thickness direction homogeneity required for a column material for construction is disclosed. No method has been proposed.

【００１１】また耐火性を有する鋼材に関しては、特開
平４−８３８２１号公報に成分と製造条件を規定した技
術が開示されているが、この技術は８０ｍｍ以上の板厚
の鋼材に対する制御冷却については考慮しておらず、ま
た溶接性および板厚方向の均質性を兼ね備えた鋼材の製
造方法に関しては全く考慮していない。Regarding fire-resistant steel, Japanese Patent Application Laid-Open No. 4-83821 discloses a technique in which the components and production conditions are specified. However, this technique is not applicable to controlled cooling of steel having a thickness of 80 mm or more. No consideration is given, and no consideration is given to a method of manufacturing a steel material having both weldability and uniformity in the thickness direction.

【００１２】本発明者らは、このような低降伏比、耐火
性、溶接性及び板厚方向の均質性を兼ね備えた高強度
（ＴＳ≧５７０ＭＰａ）のフランジ厚さ８０ｍｍ以上の
極厚Ｈ形鋼を、圧延により製造するための方法を検討し
てきた。The present inventors have developed a high-strength (TS ≧ 570 MPa) ultra-thick H-section steel having a flange thickness of 80 mm or more and having such a low yield ratio, fire resistance, weldability, and homogeneity in the thickness direction. Have been studied for producing the same by rolling.

【００１３】各種合金元素を多量に添加することによ
り、圧延のままで高強度化できることは自明であるが、
建築構造用鋼材は溶接性を考慮する必要がある。すなわ
ちＪＩＳの溶接用構造用圧延鋼材の規格（ＳＭ、ＳＮ）
に規定されているように、炭素当量を０．４４％以下と
する必要があり多量の合金元素の添加は困難である。ま
た上述したように極厚圧延Ｈ形鋼の圧延においては、圧
延荷重と寸法精度の点から圧延温度を低くすることは困
難なため、制御圧延による細粒化強化、転位強度は難し
い。It is obvious that the strength can be increased as it is rolled by adding a large amount of various alloying elements.
It is necessary to consider the weldability of steel for building structures. That is, JIS standard for rolled steel for structural welding (SM, SN)
, The carbon equivalent needs to be 0.44% or less, and it is difficult to add a large amount of alloying elements. Further, as described above, in the rolling of an extremely thick rolled H-section steel, it is difficult to lower the rolling temperature from the viewpoint of rolling load and dimensional accuracy, so that refinement of grain size and dislocation strength by controlled rolling are difficult.

【００１４】以上の点からフランジ厚さ８０ｍｍ以上の
極厚圧延Ｈ形鋼の場合、高強度化のためには圧延後の制
御冷却が必要となる。制御冷却に関しては、８０ｍｍ程
度の板厚の場合、理想的な水冷においても冷却速度は板
厚中央部において４℃／ｓ程度であるため、この程度の
冷却速度で高強度を得る必要がある。また、板厚中央部
で４℃／ｓ程度の冷却速度であっても、板厚方向には大
きな冷却速度分布が生じているため、表層付近の冷却速
度は非常に速くなっている。建築構造用鋼材としては板
厚方向に均質な特性であることが望ましいため、冷却速
度によらず強度が一定となるような成分系とする必要が
ある。In view of the above, in the case of an extremely thick rolled H-section steel having a flange thickness of 80 mm or more, controlled cooling after rolling is necessary to increase the strength. Regarding controlled cooling, in the case of a sheet thickness of about 80 mm, even in ideal water cooling, the cooling rate is about 4 ° C./s at the central part of the sheet thickness. Therefore, it is necessary to obtain high strength at such a cooling rate. Even at a cooling rate of about 4 ° C./s at the center of the sheet thickness, a large cooling rate distribution occurs in the sheet thickness direction, so that the cooling rate near the surface layer is extremely high. Since it is desirable that the steel material for a building structure has uniform properties in the thickness direction, it is necessary to use a component system having a constant strength regardless of the cooling rate.

【００１５】本発明はかかる事情に鑑みてなされたもの
であって、低降伏比、耐火性、優れた溶接性を兼ね備
え、板厚方向に強度変化の少ない、引張強度が５７０Ｍ
Ｐａ以上の高強度極厚Ｈ形鋼の製造方法を提供すること
を目的とする。The present invention has been made in view of the above circumstances, and has a low yield ratio, fire resistance, excellent weldability, a small change in strength in the thickness direction, and a tensile strength of 570M.
An object of the present invention is to provide a method for producing a high-strength ultra-thick H-section steel of Pa or more.

【００１６】[0016]

【課題を解決するための手段および作用】フランジ厚さ
８０ｍｍ以上の極厚圧延Ｈ形鋼は、形状の安定性、寸法
精度、及び圧縮機への負荷荷重の低減の観点から、加熱
温度・圧延仕上温度を高くしているため、細粒化強化が
適用できない。また単量が大きいこと、断面形状が複雑
であることから圧延後に形鋼熱処理炉等を用いたオフラ
インの熱処理を行うことは困難である。そこで本発明者
らは、溶接性の観点から炭素当量を０．４４％以下に抑
えた条件下において化学組成を最適化すること、および
圧延直後のオンライン型の制御冷却の実施により、常温
での降伏比が低くかつ耐火性を有し、溶接性にも優れ、
板厚方向に均質な特性を有する引張強度が５７０ＭＰａ
以上の、建築向け高強度極厚Ｈ形鋼（フランジ厚さ８０
ｍｍ以上）が得られることを見出した。Means and Action for Solving the Problems In the case of an extremely thick rolled H-section steel having a flange thickness of 80 mm or more, from the viewpoints of shape stability, dimensional accuracy, and reduction of the load applied to the compressor, the heating temperature and rolling Due to the high finishing temperature, grain refinement cannot be applied. In addition, it is difficult to perform off-line heat treatment using a shaped steel heat treatment furnace or the like after rolling because of a large single substance and a complicated cross-sectional shape. Therefore, the present inventors optimized the chemical composition under the condition that the carbon equivalent was suppressed to 0.44% or less from the viewpoint of weldability, and performed on-line controlled cooling immediately after rolling, so as to achieve a normal temperature. Low yield ratio, fire resistance, excellent weldability,
Tensile strength with uniform properties in the thickness direction is 570 MPa
The above high-strength ultra-thick H-section steel for construction (flange thickness 80
mm or more).

【００１７】本発明はこのような知見に基づいてなされ
たものであって、第１に、重量％で、Ｃ：０．０５〜
０．２０％、Ｓｉ：０．０５〜０．５０％、Ｍｎ：０．
８０〜１．２０％、Ｍｏ：０．２〜０．５％、Ｖ：０．
０３〜０．１３％、Ｔｉ：０．００３〜０．０１０％を
含有し、炭素当量０．４４％以下の鋼を、１３５０℃以
下に加熱し、８００℃以上１１００℃以下でＨ形鋼に圧
延終了後、ただちにフランジ板厚中央部において０．５
℃／ｓ以上３．５℃／ｓ以下の冷却速度で制御冷却を行
い、４５０℃以上６００℃以下で制御冷却を停止し、そ
の後放冷することを特徴とする、低降伏比と耐火性を有
し、溶接性に優れ、板厚方向の強度変化の少ないフラン
ジ厚さ８０ｍｍ以上の建築向け高強度極厚圧延Ｈ形鋼の
製造方法を提供するものである。The present invention has been made on the basis of such findings. First, C: 0.05 to 0.05% by weight.
0.20%, Si: 0.05 to 0.50%, Mn: 0.
80-1.20%, Mo: 0.2-0.5%, V: 0.
A steel containing 0.3 to 0.13% and Ti: 0.003 to 0.010% and having a carbon equivalent of 0.44% or less is heated to 1350 ° C or less , and turned into an H-shaped steel at 800 ° C or more and 1100 ° C or less. Immediately after the completion of rolling, 0.5 mm at the center of the flange plate thickness
Controlled cooling is performed at a cooling rate of not less than 450 ° C./s and not more than 3.5 ° C./s, controlled cooling is stopped at a temperature of not less than 450 ° C. and not more than 600 ° C., and then allowed to cool. Furan with excellent weldability and little change in strength in the thickness direction
An object of the present invention is to provide a method for manufacturing a high-strength extra- thickness rolled H-section steel for construction having a thickness of 80 mm or more .

【００１８】第２に、さらにＮｂ：０．０１〜０．０７
％を含有することを特徴とする、第１に記載の、低降伏
比と耐火性を有し、溶接性に優れ、板厚方向の強度変化
の少ないフランジ厚さ８０ｍｍ以上の建築向け高強度極
厚圧延Ｈ形鋼の製造方法を提供する。Second, Nb: 0.01 to 0.07
%, Characterized in that it has a low yield ratio and fire resistance, has excellent weldability, has little change in strength in the plate thickness direction, and has a flange thickness of 80 mm or more. Provided is a method for manufacturing a thick rolled H-section steel.

【００１９】第３に、さらにＣｕ：０．０５から０．５
％、Ｎｉ：０．０５〜０．５％、Ｃｒ：０．０５〜０．
５％の一種又は二種以上を含有することを特徴とする第
１または第２に記載の低降伏比と耐火性を有し、溶接性
に優れ、板厚方向の強度変化の少ないフランジ厚さ８０
ｍｍ以上の建築向け高強度極厚圧延Ｈ形鋼の製造方法を
提供する。Third, Cu: 0.05 to 0.5
%, Ni: 0.05-0.5%, Cr: 0.05-0.
Flange thickness having low yield ratio and fire resistance, excellent weldability, and little change in strength in the thickness direction according to the first or second aspect, characterized by containing one or more kinds of 5%. 80
Provided is a method for producing a high-strength extra-thick rolled H-section steel for buildings of not less than mm .

【００２０】以下、本発明について詳細に説明する。ま
ず、本発明の根拠となる実験例について説明する。図１
に、表１に成分範囲を示す炭素当量０．４４％以下でＶ
添加量を変化させた鋼を用い、１２８０℃に加熱し、９
５０℃仕上げで板厚８５ｍｍに圧延終了後、ただちに板
厚中央部の冷却速度を２．８℃／ｓとした制御冷却を行
い、板厚中央部が５５０℃となった時点で放冷した場合
のＶ添加量に伴う板厚中央部の室温強度並びに６００℃
における高温強度の変化を示す。Hereinafter, the present invention will be described in detail. First, an experimental example serving as a basis of the present invention will be described. FIG.
Table 1 shows the component ranges shown in Table 1.
Using steel with varying amounts of addition, heating to 1280 ° C.
After finishing rolling to a thickness of 85 mm by finishing at 50 ° C, immediately perform controlled cooling at a cooling rate of 2.8 ° C / s at the center of the thickness, and allow to cool when the center of the thickness reaches 550 ° C. Room temperature strength at the center of the sheet thickness and 600 ° C with the addition of V
3 shows the change in high-temperature strength in the above.

【００２１】[0021]

【表１】 [Table 1]

【００２２】図１から明らかなように、Ｖ添加量が０．
０３％未満の場合、室温のＴＳは５７０ＭＰａ以上を満
足しているが、室温の降伏応力（以下、ＹＳと記す）
（≧４３０ＭＰａ）及び６００℃におけるＹＳ（≧２８
７ＭＰａ）を満足しない。一方、Ｖ添加量が０．１３％
を超えた場合は室温における降伏比が８０％を超えるた
め、建築用鋼材として必要な規格を満足しなくなる。従
って、低降伏比を得る観点からはＶ添加量は０．０３〜
０．１３％の範囲とする必要がある。As is clear from FIG.
When it is less than 03%, the room temperature TS satisfies 570 MPa or more, but the room temperature yield stress (hereinafter referred to as YS).
(≧ 430 MPa) and YS at 600 ° C. (≧ 28
7 MPa) is not satisfied. On the other hand, the V addition amount is 0.13%
If the ratio exceeds 80%, the yield ratio at room temperature exceeds 80%, so that the standard required for building steel cannot be satisfied. Therefore, from the viewpoint of obtaining a low yield ratio, the amount of V added is from 0.03 to
Must be in the range of 0.13%.

【００２３】図２に、表２に示す鋼を１２３０℃加熱９
５０℃仕上で板厚８５ｍｍに圧延終了後、ただちに板厚
中央部の冷却速度が２．３℃／ｓとなるように制御冷却
を行い、板厚中央部の温度が５２０℃となった時点で空
冷とした場合のＭｏ添加量に伴う板厚１／４ｔ、１／２
ｔの位置での室温強度、および厚さ１／２ｔの位置での
高温強度変化を示す。In FIG. 2, the steel shown in Table 2 was heated at 1230.degree.
Immediately after the completion of rolling to a plate thickness of 85 mm by finishing at 50 ° C., control cooling was performed so that the cooling rate at the central portion of the plate became 2.3 ° C./s, and when the temperature at the central portion became 520 ° C. Sheet thickness 1 / 4t, 1/2 with Mo addition amount when air cooled
The room temperature strength at the position t and the high temperature strength change at the thickness 1 / 2t are shown.

【００２４】[0024]

【表２】 [Table 2]

【００２５】図２から明らかなように、Ｍｏ添加量が
０．２％以下の鋼２−１，２−２は高温強度が目標値に
達しておらず、またＭｏ添加量が０．５％を超える鋼２
−６，２−７は１／４ｔ，１／２ｔの室温強度の差が大
きく、板厚方向の均質性が損なわれている。一方、Ｍｏ
量が０．２〜０．５％の範囲を満たす鋼２−３，２−
４，２−５は１／４ｔ，１／２ｔにおける室温強度の差
が小さく板厚方向の均質性を満足しており、かつ高温強
度も目標値を満たしている。As is apparent from FIG. 2, the steels 2-1 and 2-2 having the Mo content of 0.2% or less do not have the high-temperature strength reaching the target value and have the Mo content of 0.5% or less. More than steel 2
-6 and 2-7 have a large difference in room temperature strength between 1 / 4t and 1 / 2t, impairing the homogeneity in the thickness direction. On the other hand, Mo
Steel 2-3,2- which satisfies the range of 0.2-0.5%
Nos. 4, 2-5 have a small difference in room temperature strength between 1 / 4t and 1 / 2t, satisfy the homogeneity in the thickness direction, and also have a high temperature strength that satisfies the target value.

【００２６】図３は、表３に示す鋼を１２６０℃加熱９
００℃仕上で板厚９０ｍｍに圧延終了後、ただちに板厚
中央部の冷却速度が３．５℃／ｓとなるように制御冷却
し、板厚中央部が５００℃となった時点で放冷した場合
の板厚方向の硬さ変化を示す。FIG. 3 shows that the steel shown in Table 3 was heated at 1260 ° C.
Immediately after the completion of rolling to a plate thickness of 90 mm in the finish at 00 ° C., control cooling was performed so that the cooling rate at the plate thickness central portion became 3.5 ° C./s, and the plate was allowed to cool when the plate thickness central portion reached 500 ° C. 5 shows a change in hardness in the thickness direction in the case.

【００２７】[0027]

【表３】 [Table 3]

【００２８】図３から明らかなように、Ｃを０．２１％
含有している鋼３−１、Ｍｎを１．６５％含有している
鋼３−２、Ｍｏを０．７％含有している鋼３−３、Ｃｒ
を０．７％含有している鋼３−４は、位置により硬さが
大きく変化しており、板厚方向に均質な特性は得られて
いない。一方、これら添加元素を減じて本発明の範囲内
を満足するレベルにした鋼３−５，３−６は、いずれの
位置においても板厚中央部との硬さ変化が少なく、冷却
速度感受性が低い。As is apparent from FIG. 3, C is 0.21%
Steel 3-1 containing, steel 3-2 containing 1.65% Mn, steel 3-3 containing 0.7% Mo, Cr
In steel 3-4 containing 0.7%, the hardness greatly changes depending on the position, and uniform characteristics in the thickness direction are not obtained. On the other hand, in steels 3-5 and 3-6 in which these additional elements are reduced to a level that satisfies the range of the present invention, there is little change in hardness from the center of the sheet thickness at any position, and the cooling rate sensitivity is low. Low.

【００２９】図４は、表４に示す鋼を１２３０℃加熱８
８０℃仕上で板厚９０ｍｍに圧延終了後、ただちに板厚
中央部における冷却速度を３．０℃／ｓとして制御冷却
し、冷却停止温度を室温から７００℃まで変化させた場
合の冷却停止温度と機械的性質の関係を示す。FIG. 4 shows that the steel shown in Table 4 was heated at 1230 ° C.
Immediately after the completion of rolling to a sheet thickness of 90 mm in the 80 ° C. finish, the cooling rate at the central part of the sheet thickness was controlled and cooled at 3.0 ° C./s, and the cooling stop temperature when the cooling stop temperature was changed from room temperature to 700 ° C. The relationship between mechanical properties is shown.

【００３０】[0030]

【表４】 [Table 4]

【００３１】図４から明らかなように、冷却停止温度が
６００℃を超える場合、十分な強度が得られない。一方
冷却停止温度が４５０℃未満の場合には強度が高くなり
過ぎ、また板厚方向の均質性が損なわれている。従っ
て、冷却停止温度は４５０℃〜６００℃の範囲とする必
要がある。As apparent from FIG. 4, when the cooling stop temperature exceeds 600 ° C., sufficient strength cannot be obtained. On the other hand, when the cooling stop temperature is lower than 450 ° C., the strength becomes too high, and the homogeneity in the thickness direction is impaired. Therefore, the cooling stop temperature needs to be in the range of 450 ° C to 600 ° C.

【００３２】次に、本発明の構成要件である化学成分、
加熱温度、圧延仕上温度、冷却速度、冷却停止温度につ
いて詳細に説明する。まず、化学成分の限定理由につい
て説明する。Next, a chemical component which is a constituent element of the present invention,
The heating temperature, rolling finish temperature, cooling rate, and cooling stop temperature will be described in detail. First, the reasons for limiting the chemical components will be described.

【００３３】Ｃ：０．０５〜０．２０％ Ｃは鋼の強度を安定して確保するために有効な元素であ
る。しかし、０．０５％未満では必要とする強度を得る
のが困難であり、また０．２０％を超えると溶接性が劣
化する。従って、Ｃ含有量を０．０５〜０．２０％の範
囲とした。C: 0.05 to 0.20% C is an effective element for stably securing the strength of steel. However, if it is less than 0.05%, it is difficult to obtain the required strength, and if it exceeds 0.20%, the weldability deteriorates. Therefore, the C content is set in the range of 0.05 to 0.20%.

【００３４】Ｓｉ：０．０５〜０．５０％ Ｓｉは脱酸、強度上昇に有効な元素であり、そのために
は０．０５％以上の添加が必要であるが、０．５０％を
超えて添加すると溶接性を損なう。従ってＳｉ含有量を
０．０５％〜０．５０％の範囲とした。Si: 0.05 to 0.50% Si is an element effective for deoxidation and increasing the strength. For that purpose, it is necessary to add 0.05% or more of Si. Addition impairs weldability. Therefore, the Si content is set in the range of 0.05% to 0.50%.

【００３５】Ｍｎ：０．８０〜１．２０％ Ｍｎは強度確保の上で有効な元素であり、特に高強度化
のためには０．８０％以上の添加が必要である。一方、
１．２０％を超えて添加すると溶接性を損なうだけでな
く制御冷却により偏析部が著しく硬化するため板厚方向
の強度の均質性を損なう。従ってＭｎ含有量を０．８０
％〜１．２０％の範囲とした。Mn: 0.80 to 1.20% Mn is an effective element for securing the strength. In particular, it is necessary to add 0.80% or more for increasing the strength. on the other hand,
When added in excess of 1.20%, not only does the weldability deteriorate, but also the segregated portion is significantly hardened by controlled cooling, thereby impairing the strength uniformity in the thickness direction. Therefore, the Mn content is set to 0.80
% To 1.20%.

【００３６】Ｍｏ：０．２〜０．５％ Ｍｏは焼入性の向上、析出強化等により鋼の高強度化に
効果があり、特に中・高温強度に対して有効である。こ
のような効果を発揮するためには０．２％以上の添加が
必要であるが、０．５％を超える添加は特に板厚方向の
強度の均質性を損なうだけでなく、コスト上昇を招くと
共に溶接性の劣化を生じる。従ってＭｏ含有量を０．２
〜０．５％の範囲とした。Mo: 0.2-0.5% Mo is effective for increasing the strength of steel by improving hardenability, precipitation strengthening, etc., and is particularly effective for medium and high temperature strength. In order to exhibit such an effect, addition of 0.2% or more is necessary. However, addition of more than 0.5% not only impairs the homogeneity of the strength particularly in the thickness direction, but also increases the cost. At the same time, the weldability deteriorates. Therefore, when the Mo content is 0.2
-0.5%.

【００３７】Ｖ：０．０３〜０．１３％ Ｖは微量添加により常温・高温強度の上昇に有効であ
り、特に本発明のような極厚圧延Ｈ形鋼のＹＳを高める
ためには０．０３％以上の添加が必要である。一方０．
１３％を超える添加は溶接性を劣化させ、また建築用鋼
として要求されている常温で低降伏比であることも満足
しなくなる。従ってＶ含有量を０．０３〜０．１３％の
範囲とした。V: 0.03 to 0.13% V is effective in increasing the strength at room temperature and high temperature by adding a small amount of V. In particular, in order to increase the YS of the extremely thick rolled H-section steel as in the present invention, V is set to 0.1%. Addition of at least 03% is required. On the other hand, 0.
Addition of more than 13% deteriorates the weldability and also makes it unsatisfactory that the low yield ratio at room temperature, which is required for building steel, is not satisfied. Therefore, the V content is set in the range of 0.03 to 0.13%.

【００３８】Ｔｉ：０．００３〜０．０１０％ ＴｉはＴｉＮを形成し、加熱時のオーステナイト粒を微
細化する効果を有し、靭性向上に効果がある。この効果
を発揮するには０．００３％以上の添加が必要である
が、０．０１０％を超えて添加するとＴｉＣを形成し、
常温における降伏比を上昇させてしまう。従ってＴｉ含
有量を０．００３〜０．０１０％の範囲とした。Ti: 0.003 to 0.010% Ti forms TiN, has the effect of miniaturizing austenite grains during heating, and has the effect of improving toughness. In order to exhibit this effect, 0.003% or more of addition is necessary. However, if it exceeds 0.010%, TiC is formed,
It increases the yield ratio at room temperature. Therefore, the Ti content is set in the range of 0.003 to 0.010%.

【００３９】本発明では以上の基本成分に加えて、必要
に応じて以下に示すＮｂ、さらにはＣｕ、Ｎｉ、Ｃｒの
内一種又は二種以上を添加することができる。 Ｎｂ：０．０１〜０．０７％ Ｎｂは微量添加により常温・高温強度を著しく上昇させ
るため、本発明のような極厚圧延Ｈ形鋼の高強度比には
有効であり、そのためには０．０１％以上の添加が有効
である。しかし、引張強度（以下、ＴＳと記す）に比べ
てＹＳの上昇率が高いことから、建築向けの低降伏比鋼
として要求される特性を満たすには添加量を０．０７％
以下とすることが必要である。従ってＮｂを添加する場
合には、その含有量を０．０１〜０．０７％の範囲とす
る。In the present invention, in addition to the above basic components, one or two or more of the following Nb and Cu, Ni and Cr can be added as required. Nb: 0.01 to 0.07% Nb significantly increases the room temperature / high temperature strength by adding a small amount, and is effective for the high strength ratio of the extremely thick rolled H-section steel as in the present invention. Addition of 0.01% or more is effective. However, since the increase rate of YS is higher than the tensile strength (hereinafter, referred to as TS), the amount of addition is 0.07% to satisfy the characteristics required as a low yield ratio steel for construction.
It is necessary to: Therefore, when adding Nb, its content is made into the range of 0.01 to 0.07%.

【００４０】Ｃｕ：０．０５〜０．５％ Ｃｕは強度上昇に有効な元素であり、そのためには０．
０５％以上の添加が必要である。一方、０．５％を超え
る添加はコスト上昇に加え、板厚方向の強度の不均質
性、表面疵の問題がある。従ってＣｕを添加する場合に
は、その含有量を０．０５〜０．５％の範囲とする。Cu: 0.05-0.5% Cu is an element effective for increasing the strength.
Addition of at least 05% is required. On the other hand, if the addition exceeds 0.5%, in addition to the cost increase, there is a problem of inhomogeneity of strength in the thickness direction and surface flaws. Therefore, when Cu is added, its content is in the range of 0.05 to 0.5%.

【００４１】Ｎｉ：０．０５〜０．５％ Ｎｉは強度上昇に有効であると共に靭性の向上にも効果
があるが、そのためには０．０５％以上の添加が必要で
ある。一方、０．５％以上の添加は溶接性を損ない、コ
ストの上昇にもつながる。従ってＮｉを添加する場合に
は、その含有量を０．０５〜０．５％の範囲とする。Ni: 0.05-0.5% Ni is effective not only for increasing the strength but also for improving the toughness. For this purpose, 0.05% or more must be added. On the other hand, addition of 0.5% or more impairs weldability and leads to an increase in cost. Therefore, when Ni is added, its content is in the range of 0.05 to 0.5%.

【００４２】Ｃｒ：０．０５〜０．５％ Ｃｒは常温及び高温強度の上昇に有効であり、そのため
には０．０５％以上の添加が必要である。一方、０．５
％を超える添加は溶接性の劣化、板厚方向の強度の不均
質性の原因となる。従ってＣｒを添加する場合には、
０．０５〜０．５％の範囲とする。Cr: 0.05-0.5% Cr is effective for increasing the strength at room temperature and high temperature, and for that purpose, it is necessary to add 0.05% or more. On the other hand, 0.5
% Causes the deterioration of weldability and the inhomogeneity of strength in the thickness direction. Therefore, when adding Cr,
The range is 0.05 to 0.5%.

【００４３】次に製造条件の限定理由を示す。 （１）加熱温度：１３５０℃以下 極厚圧延Ｈ形鋼を製造する場合には、寸法精度の観点か
ら比較的高温域で圧延を終了するようなパススケジュー
ルが用いられている。そのため加熱温度も高温にするこ
とが必要となるが、１３５０℃を超える高温に加熱する
ことは加熱時のオーステナイト粒径が著しく粗大化し、
建築向け鋼材として必要となる母材靭性の劣化を生じさ
せるばかりでなく、加熱炉の炉体の損傷にもつながる。
このため加熱温度を１３５０℃以下とした。Next, the reasons for limiting the manufacturing conditions will be described. (1) Heating temperature: 1350 ° C. or less When producing an extremely thick rolled H-section steel, a pass schedule that ends rolling in a relatively high temperature range is used from the viewpoint of dimensional accuracy. Therefore, it is necessary to increase the heating temperature, but heating to a temperature higher than 1350 ° C. significantly increases the austenite particle size during heating,
Not only does the base material toughness required for building steel deteriorate, but it also leads to damage to the furnace body of the heating furnace.
Therefore, the heating temperature was set to 1350 ° C. or less.

【００４４】 （２）圧延終了温度：８００℃以上１１００℃以下 圧延終了温度はミクロ組織に影響を与える因子であり、
８００℃未満ではオーステナイト粒に歪が残存し、ミク
ロ組織が細粒化される。細粒化は鋼の強化機構として有
効な手段であるが、極厚圧延Ｈ形鋼の場合８００℃未満
の低温圧延では圧延荷重が著しく高くなり、圧延機に負
荷がかかるだけでなく圧延材の寸法精度の向上が難しい
こと、ＴＳに比べてＹＳの上昇率が高いことから建築向
けの低降伏比鋼には不利であるため、圧延終了温度は８
００℃以上とする必要がある。一方圧延仕上温度が１１
００℃以上の高温の場合、圧延により再結晶したミクロ
組織がただちに粒成長により粗大化し、結果として得ら
れる組織が非常に粗くなり靭性が著しく劣化する。従っ
て圧延終了温度を８００℃以上１１００℃以下の範囲に
規定した。(2) Rolling end temperature: 800 ° C. or higher and 1100 ° C. or lower The rolling end temperature is a factor that affects the microstructure.
If the temperature is lower than 800 ° C., strain remains in the austenite grains, and the microstructure is refined. Although grain refinement is an effective means as a mechanism for strengthening steel, in the case of extremely thick rolled H-section steel, rolling at a low temperature of less than 800 ° C. significantly increases the rolling load, which not only places a load on the rolling mill but also reduces the rolling material. Since the dimensional accuracy is difficult to improve and the YS rise rate is higher than that of TS, it is disadvantageous for low yield ratio steel for construction.
It is necessary to be at least 00 ° C. On the other hand, when the rolling finish temperature is 11
At a high temperature of 00 ° C. or higher, the microstructure recrystallized by rolling immediately becomes coarse due to grain growth, and the resulting structure becomes very coarse and the toughness is significantly deteriorated. Therefore, the rolling end temperature is specified in the range of 800 ° C. or more and 1100 ° C. or less.

【００４５】（３）冷却速度：板厚中央部で０．５℃／
ｓ以上３．５℃／ｓ以下 フランジ板厚８０ｍｍの場合、理想的な水冷における板
厚中央部の冷却速度は約４℃／ｓである。本発明ではフ
ランジ板厚８０ｍｍ以上のＨ形鋼を対象としているこ
と、および実際の冷却の場合は必ずしも理想的な冷却と
はならないことから、最大冷却速度は実質的には３．５
℃／ｓ程度である。一方、本発明の成分組成では０．５
℃／ｓ未満の冷却速度では十分な強度が得られない。従
って冷却速度を板厚中央部で０．５℃／ｓ以上３．５℃
／ｓ以下に規定した。(3) Cooling rate: 0.5 ° C. /
s or more and 3.5 ° C./s or less When the flange plate thickness is 80 mm, the cooling rate at the center of the plate thickness in ideal water cooling is about 4 ° C./s. The maximum cooling rate is substantially 3.5 since the present invention is intended for an H-section steel having a flange plate thickness of 80 mm or more, and in the case of actual cooling, is not always ideal cooling.
C./s. On the other hand, in the component composition of the present invention, 0.5
If the cooling rate is lower than ℃ / s, sufficient strength cannot be obtained. Therefore, the cooling rate should be 0.5 ° C / s or more and 3.5 ° C at the center of the plate thickness.
/ S or less.

【００４６】 （４）冷却停止温度：４５０℃以上６００℃以下 冷却停止温度は、制御冷却時の変態により生じ、かつ母
材靭性に悪影響を与える残留オーステナイト（ＭＡ）の
分解、および制御冷却により得られる変態組織の回復に
重要な因子となっている。停止温度４５０℃未満ではＭ
Ａの分解が十分に行われず、建築構造用鋼として必要な
靭性が確保できない。一方停止温度が６００℃を超える
と、ミクロ組織として粗大なフェライトが生成し強度の
低下を招く。従って冷却停止温度を４５０℃以上６００
℃以下と規定した。(4) Cooling stop temperature: 450 ° C. or more and 600 ° C. or less The cooling stop temperature is obtained by decomposition of residual austenite (MA) which is generated by transformation during controlled cooling and adversely affects base metal toughness, and is obtained by controlled cooling. It is an important factor in the recovery of metamorphosis. If the stop temperature is less than 450 ° C, M
A is not sufficiently decomposed, and the toughness required for building structural steel cannot be secured. On the other hand, when the stop temperature exceeds 600 ° C., coarse ferrite is generated as a microstructure, which causes a decrease in strength. Therefore, the cooling stop temperature should be 450 ° C. or more and 600 ° C.
° C or less.

【００４７】[0047]

【実施例】以下、本発明の実施例について説明する。 （実施例１）表５に示す化学組成を有する鋼１〜１２を
用い、１２７０℃加熱８００℃仕上でフランジ幅４００
ｍｍ、ウェブ高さ４００ｍｍ、フランジ板厚８０ｍｍの
極厚圧延Ｈ形鋼を熱間圧延し、板厚中央部で３．０℃／
ｓの冷却速度になるように制御冷却を行ない、板厚中央
部の温度が５５０℃となった時点で放冷した。その際の
フランジ板厚中央部及び板厚１／４ｔにおける室温強
度、板厚中央部の６００℃における高温強度、ｙ割れ試
験による予熱温度を表６に示す。Embodiments of the present invention will be described below. (Example 1) Using steels 1 to 12 having the chemical compositions shown in Table 5, heating at 1270 ° C and finishing at 800 ° C, flange width 400
mm, a web height of 400 mm, and a flange thickness of 80 mm, hot rolled H-shaped steel is hot rolled, and 3.0 ° C /
Control cooling was carried out at a cooling rate of s. When the temperature at the central part of the sheet thickness became 550 ° C., cooling was performed. Table 6 shows the room temperature strength at the center of the flange plate thickness and the plate thickness of 板 t, the high temperature strength at 600 ° C. of the center of the plate thickness, and the preheating temperature by the y crack test.

【００４８】[0048]

【表５】 [Table 5]

【００４９】[0049]

【表６】 [Table 6]

【００５０】これらの表に示すように、化学組成が本発
明の範囲から外れる、鋼１，２，５，７，９，１１，１
２は本発明で要求する特性のいずれかを満足していな
い。すなわち、Ｃが高い鋼１は予熱温度が１００℃と高
い。一方Ｃが０．０４％と低い鋼２は、他の化学成分を
本発明の範囲内に制限しているため、板厚中央部の室温
強度及び高温強度が不足している。Ｍｎの高い鋼３、Ｍ
ｏの高い鋼５、Ｃｒの高い鋼７、Ｎｉの高い鋼９はフラ
ンジ板厚中央部と板厚１／４ｔとの間の強度差が大き
く、板厚方向の均質性に劣る。Ｖの低い鋼１１はＹＳが
低く建築向けＨＴ５７０の規格を満足しない。またＶの
高い鋼１２は著しい析出強化によりＹＳの上昇量が多
く、室温における低降伏比を満足しない。As shown in these tables, steels 1,2,5,7,9,11,1 whose chemical compositions fall outside the scope of the present invention.
No. 2 does not satisfy any of the characteristics required in the present invention. That is, the steel 1 having a high C has a high preheating temperature of 100 ° C. On the other hand, the steel 2 having a low C of 0.04% has insufficient room temperature strength and high temperature strength at the center of the plate thickness because other chemical components are restricted within the scope of the present invention. High Mn steel 3, M
Steel 5 with high o, steel 7 with high Cr, and steel 9 with high Ni have a large difference in strength between the central part of the flange plate thickness and the plate thickness of 1 / 4t, and are inferior in the plate thickness direction homogeneity. Steel 11 with a low V has a low YS and does not satisfy the standard of HT570 for construction. Further, the steel 12 with a high V has a large amount of increase in YS due to remarkable precipitation strengthening, and does not satisfy the low yield ratio at room temperature.

【００５１】一方、化学組成が本発明の範囲内である鋼
４、６、８、１０はＨＴ５７０の室温強度、６００℃の
高温強度を満足するだけでなく、板厚方向の強度差が小
さく、ｙ割れ試験における予熱温度も２５℃と低い。On the other hand, steels 4, 6, 8, and 10 having a chemical composition within the range of the present invention not only satisfy the room temperature strength of HT570 and the high temperature strength of 600 ° C., but also have a small strength difference in the thickness direction. The preheating temperature in the y crack test is also as low as 25 ° C.

【００５２】（実施例２）表７に示す化学組成を有する
鋼１３を用い、表８に示すように加熱温度、仕上温度、
板厚中央部の冷却速度、冷却停止温度を変化させた。そ
の場合の板厚中央部および板厚１／４ｔにおける室温強
度、板厚中央部の６００℃における高温強度、−５℃に
おけるシャルピー衝撃試験の吸収エネルギーを表９に示
す。(Example 2) A steel 13 having a chemical composition shown in Table 7 was used.
The cooling speed and cooling stop temperature at the center of the plate thickness were changed. Table 9 shows the room temperature strength at the plate thickness center and the plate thickness １ ／ t, the high temperature strength at 600 ° C. of the plate thickness center, and the absorbed energy of the Charpy impact test at −5 ° C. in that case.

【００５３】[0053]

【表７】 [Table 7]

【００５４】[0054]

【表８】 [Table 8]

【００５５】[0055]

【表９】 [Table 9]

【００５６】これらの表に示すように、製造条件が本発
明から外れるＡ、Ｃ、Ｅ、Ｇ、Ｉ、Ｋは、本発明で要求
する特性のいずれかを満足していない。すなわち、加熱
温度が１４００℃と高いＡは降伏比は低いが靭性の劣化
も著しく、建築用鋼材としては不適当な特性であった。
圧延仕上温度が１２００℃と高いＣについてもＡと同様
に低に靭性を示している。圧延仕上温度が７００℃と低
いＥは、室温における低降伏比を満足しない。板厚中央
部の冷却速度が０．２℃／ｓｅｃと低いＧは低降伏比は
満足しているものの室温のＴＳ及び６００℃におけるＹ
Ｓが目標値を満足しない。冷却停止温度が６５０℃と高
いＩは、十分な室温強度および高温強度を示さない。一
方冷却停止温度が２００℃と著しく低いＫは、室温のＴ
Ｓが目標とするレンジを超えた値を示し、靭性も劣化し
ている。As shown in these tables, A, C, E, G, I, and K whose production conditions deviate from the present invention do not satisfy any of the characteristics required in the present invention. That is, A having a high heating temperature of 1400 ° C. had a low yield ratio but markedly deteriorated toughness, and had unsuitable characteristics as a building steel material.
C, which has a high rolling finish temperature of 1200 ° C., shows low toughness similarly to A. E having a low rolling finish temperature of 700 ° C. does not satisfy the low yield ratio at room temperature. G, which has a low cooling rate of 0.2 ° C./sec at the center of the sheet thickness, satisfies a low yield ratio, but TS at room temperature and Y at 600 ° C.
S does not satisfy the target value. I having a high cooling stop temperature of 650 ° C. does not exhibit sufficient room-temperature strength and high-temperature strength. On the other hand, K whose cooling stop temperature is extremely low at 200 ° C.
S shows a value exceeding the target range, and the toughness is also deteriorated.

【００５７】これに対して、加熱温度、仕上温度、板厚
中央部の冷却速度、冷却停止温度がすべて本発明の範囲
内であるＢ、Ｄ、Ｆ、Ｈ、Ｊはいずれの特性も満たす優
れた特性を有している。On the other hand, B, D, F, H, and J, in which the heating temperature, the finishing temperature, the cooling rate at the center of the sheet thickness, and the cooling stop temperature are all within the range of the present invention, are excellent in satisfying all the characteristics. It has characteristics.

【００５８】（実施例３）表１０に示す化学組成を有す
る鋼１４〜２３を用い、表１１に示すように加熱温度、
仕上温度、板厚中央部の冷却速度、冷却停止温度を変化
させた。その場合の板厚中央部および板厚１／４ｔにお
ける室温強度、板厚中央部の６００℃における高温強
度、−５℃におけるシャルピー衝撃試験の吸収エネルギ
ーを表１２に示す。Example 3 Steels 14 to 23 having the chemical compositions shown in Table 10 were used.
The finishing temperature, the cooling rate at the center of the sheet thickness, and the cooling stop temperature were changed. Table 12 shows the room temperature strength at the center of the sheet thickness and 1 / 4t of the sheet thickness, the high-temperature strength at 600 ° C of the center of the sheet thickness, and the absorbed energy of the Charpy impact test at -5 ° C in this case.

【００５９】[0059]

【表１０】 [Table 10]

【００６０】[0060]

【表１１】 [Table 11]

【００６１】[0061]

【表１２】 [Table 12]

【００６２】これらの表に示すように、化学組成が本発
明の範囲から外れる、鋼１４〜１９は製造条件によら
ず、本発明で要求する特性のいずれかを満足していな
い。すなわち、Ｍｏ含有量が本発明の範囲を超えた０．
６％の鋼１４は、板厚中央部と板厚１／４ｔとの強度差
が大きく、板厚方向の均質性を損なっている。Ｖ含有量
が０．５％と多い鋼１５は、加熱温度・仕上温度が本発
明の範囲より高い場合、焼き入れ性が高いため圧延後の
制御冷却により強度が著しく増加し、目標強度を満足し
なくなる。また、圧延温度が本発明の範囲内もしくはそ
れよりも低い場合、Ｖの析出により特に降伏点が上昇
し、降伏比が著しく上昇するため建築用鋼材として要求
される規格を満たさない。Ｎｂを０．１％まで含有して
いる鋼１６は、仕上温度が７１０℃と低い場合ばかりで
なく、すべての製造条件が本発明の範囲を満たしている
場合にも常温における降伏比が高く、建築用鋼材として
は不適当な特性である。Ｃｕ添加量２．０％の鋼１７、
Ｎｉ添加量１．５％の鋼１８、Ｃｒ添加量１．２％の鋼
１９はいずれも請求範囲を超える合金元素を添加してい
ることから常温強度が目標の上限値を超えており、かつ
板厚中央部と板厚１／４ｔ部の強度の均質性が悪い。As shown in these tables, steels 14 to 19 whose chemical compositions are out of the range of the present invention do not satisfy any of the properties required in the present invention regardless of the production conditions. That is, when the Mo content exceeds the range of the present invention.
6% of the steel 14 has a large difference in strength between the central part of the sheet thickness and 1 / 4t of the sheet thickness, impairing the homogeneity in the sheet thickness direction. When the heating temperature / finish temperature is higher than the range of the present invention, the steel 15 having a high V content of 0.5% has a high hardenability, so that the strength is significantly increased by controlled cooling after rolling, and the target strength is satisfied. No longer. Further, when the rolling temperature is within the range of the present invention or lower than the range, the yield point is particularly increased by the precipitation of V, and the yield ratio is significantly increased, so that the standard required for building steel is not satisfied. Steel 16 containing up to 0.1% Nb has a high yield ratio at room temperature, not only when the finishing temperature is as low as 710 ° C., but also when all manufacturing conditions satisfy the range of the present invention. It is an unsuitable property for building steel. Steel 17 with 2.0% Cu added,
Since the steel 18 with 1.5% Ni addition and the steel 19 with 1.2% Cr addition contain alloying elements exceeding the claimed range, the room temperature strength exceeds the target upper limit, and Poor homogeneity of strength between the central part of the sheet thickness and the 1 / 4t part of the sheet thickness.

【００６３】これに対して化学組成が本発明の範囲内で
ある鋼２０、２１、２２の場合、製造条件が本発明の範
囲を満足しない条件３Ａ、３Ｄでは室温強度、降伏比が
目標値を満足しないが、製造条件についても請求範囲を
満足している条件３Ｂ、３Ｃ、３Ｅでは全ての特性につ
いて目標値を満足している。On the other hand, in the case of the steels 20, 21, and 22 whose chemical composition is within the range of the present invention, the room temperature strength and the yield ratio are less than the target values under the conditions 3A and 3D where the manufacturing conditions do not satisfy the range of the present invention. Under the conditions 3B, 3C, and 3E, which do not satisfy, but also satisfy the claims with respect to the manufacturing conditions, all the characteristics satisfy the target values.

【００６４】[0064]

【発明の効果】以上のように、本発明によれば、炭素当
量を０．４４％以下に抑えて化学組成を最適化し、加熱
温度を寸法精度及び加熱粒径の観点から規定し、圧延仕
上温度を低降伏比及び母材靭性の観点から規定し、冷却
速度を母材強度および理想的水冷条件の観点から規定
し、冷却停止温度を強度および靭性の観点から規定する
ことにより、フランジ厚さが８０ｍｍ以上と厚く、低降
伏比、耐火性、優れた溶接性を兼ね備え、板厚方向に強
度変化の少ない、引張強度が５７０ＭＰａ以上の高強度
極厚Ｈ形鋼を製造することが可能となる。As described above, according to the present invention, the chemical composition is optimized by suppressing the carbon equivalent to 0.44% or less, the heating temperature is specified from the viewpoint of the dimensional accuracy and the heated particle size, and the rolling finish is determined. By defining the temperature from the viewpoint of low yield ratio and base metal toughness, specifying the cooling rate from the viewpoint of base metal strength and ideal water cooling conditions, and specifying the cooling stop temperature from the viewpoint of strength and toughness, the flange thickness Has a thickness of 80 mm or more, has a low yield ratio, fire resistance, and excellent weldability, has a small strength change in the thickness direction, and can produce a high-strength ultra-thick H-section steel having a tensile strength of 570 MPa or more. .

【図面の簡単な説明】[Brief description of the drawings]

【図１】Ｖ添加量と、室温および６００℃における機械
的性質との関係を示すグラフ。FIG. 1 is a graph showing the relationship between the amount of V added and mechanical properties at room temperature and 600 ° C.

【図２】Ｍｏ添加量と、板厚１／４ｔ、１／２ｔの室温
強度および１／２ｔの高温強度との関係を示すグラフ。FIG. 2 is a graph showing the relationship between the amount of Mo added and the room-temperature strength of 板 t and ｔ t of the sheet thickness and the high-temperature strength of ｔ t.

【図３】極厚Ｈ形鋼の各組成における、フランジ板厚方
向の硬さの変化を示すグラフ。FIG. 3 is a graph showing a change in hardness in a flange plate thickness direction in each composition of an extremely thick H-section steel.

【図４】冷却停止温度とＴＳとの関係を示すグラフ。FIG. 4 is a graph showing a relationship between a cooling stop temperature and TS.

Claims (3)

(57)【特許請求の範囲】(57) [Claims] 【請求項１】 重量％で、Ｃ：０．０５〜０．２０％、
Ｓｉ：０．０５〜０．５０％、Ｍｎ：０．８０〜１．２
０％、Ｍｏ：０．２〜０．５％、Ｖ：０．０３〜０．１
３％、Ｔｉ：０．００３〜０．０１０％を含有し、炭素
当量０．４４％以下の鋼を、１３５０℃以下に加熱し、
８００℃以上１１００℃以下でＨ形鋼に圧延終了後、た
だちにフランジ板厚中央部において０．５℃／ｓ以上
３．５℃／ｓ以下の冷却速度で制御冷却を行い、４５０
℃以上６００℃以下で制御冷却を停止し、その後放冷す
ることを特徴とする、低降伏比と耐火性を有し、溶接性
に優れ、板厚方向の強度変化の少ないフランジ厚さ８０
ｍｍ以上の建築向け高強度極厚圧延Ｈ形鋼の製造方法。(1) C: 0.05 to 0.20% by weight,
Si: 0.05 to 0.50%, Mn: 0.80 to 1.2
0%, Mo: 0.2 to 0.5%, V: 0.03 to 0.1
3%, Ti: 0.003-0.010%, carbon
A steel having an equivalent of 0.44% or less is heated to 1350 ° C or less,
Immediately after the end of rolling into an H-shaped steel at 800 ° C or higher and 1100 ° C or lower, control cooling is performed at a cooling rate of 0.5 ° C / s or higher and 3.5 ° C / s or lower at the center of the flange plate thickness , and 450
Controlled cooling is stopped at a temperature of not less than 600 ° C and not more than 600 ° C, and then the material is allowed to cool. It has a low yield ratio and fire resistance, has excellent weldability, and has a small flange thickness 80 with little change in strength in the thickness direction.
Production method of high-strength extra-thick rolled H-section steel for buildings of mm or more . 【請求項２】 さらにＮｂ：０．０１〜０．０７％を含
有することを特徴とする、請求項１に記載の、低降伏比
と耐火性を有し、溶接性に優れ、板厚方向の強度変化の
少ないフランジ厚さ８０ｍｍ以上の建築向け高強度極厚
圧延Ｈ形鋼の製造方法。2. The composition according to claim 1, further comprising Nb: 0.01 to 0.07%, having a low yield ratio and fire resistance, excellent weldability, and thickness direction. A method for producing a high-strength extra-thick rolled H-section steel for construction having a flange thickness of 80 mm or more with little change in strength. 【請求項３】 さらにＣｕ：０．０５から０．５％、Ｎ
ｉ：０．０５〜０．５％、Ｃｒ：０．０５〜０．５％の
一種又は二種以上を含有することを特徴とする請求項１
または請求項２に記載の低降伏比と耐火性を有し、溶接
性に優れ、板厚方向の強度変化の少ないフランジ厚さ８
０ｍｍ以上の建築向け高強度極厚圧延Ｈ形鋼の製造方
法。3. Cu: 0.05 to 0.5%, N
2. The composition according to claim 1, wherein one or more of i: 0.05 to 0.5% and Cr: 0.05 to 0.5% are contained.
Or a flange thickness 8 having a low yield ratio and fire resistance, excellent weldability, and little change in strength in the thickness direction according to claim 2.
Method for producing high-strength extra-thick rolled H-section steel for buildings of 0 mm or more .