JPH08197105A - Manufacture of extremely thick wide-flange steel excellent in strength, toughness and weldability - Google Patents
Manufacture of extremely thick wide-flange steel excellent in strength, toughness and weldabilityInfo
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- JPH08197105A JPH08197105A JP897595A JP897595A JPH08197105A JP H08197105 A JPH08197105 A JP H08197105A JP 897595 A JP897595 A JP 897595A JP 897595 A JP897595 A JP 897595A JP H08197105 A JPH08197105 A JP H08197105A
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- weight
- toughness
- strength
- cooling
- weldability
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- Metal Rolling (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、建築、土木構造物など
に用いられる板厚４０ｍｍ以上の強度、靭性及び溶接性
に優れた所謂極厚Ｈ形鋼の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a so-called extra-thick H-section steel having a plate thickness of 40 mm or more and having excellent strength, toughness and weldability, which is used for construction, civil engineering structures and the like.
【０００２】[0002]
【従来の技術】建築や土木などの分野では、ＪＩＳ Ｇ
３１０１で規定される一般構造用圧延鋼材やＪＩＳ
Ｇ ３１０６で規定される溶接構造用圧延鋼材を熱間圧
延したＨ形鋼が広く利用されている。一方、近年の構造
物大型化の要請に伴ない、大型構造物に使用されるＨ形
鋼は、厚肉化および高強度化の傾向にある。2. Description of the Related Art In the fields of architecture and civil engineering, JIS G
General structural rolled steel and JIS specified in 3101
The H-section steel obtained by hot-rolling the rolled steel material for welded structure specified by G 3106 is widely used. On the other hand, the H-section steel used for large-sized structures tends to be thicker and have higher strength in response to the recent demand for larger structures.
【０００３】しかしながら、板厚が４０ｍｍを超える極
厚Ｈ形鋼を、素材として引張強度（ＴＳ）が４９０ＭＰ
ａ以上の高張力鋼を用いて従来通りの熱間圧延法で製造
しようとすると、その製品の目標強度を確保するには、
素材のＣ当量を高くせざるを得なかった。その結果、該
製品の極厚Ｈ形鋼を溶接する際には、溶接割れが発生し
やすくなったり、溶接熱影響部（以下、ＨＡＺ部とい
う）の靭性が低くなる等の問題が生じた。[0003] However, the tensile strength (TS) is 490MP as a raw material of an extra-thick H-section steel having a plate thickness of more than 40 mm.
In order to secure the target strength of the product when trying to manufacture it by the conventional hot rolling method using high tensile steel of a or more,
I had no choice but to increase the C equivalent of the material. As a result, when the extremely thick H-section steel of the product is welded, problems such as easy occurrence of weld cracks and low toughness of the weld heat affected zone (hereinafter referred to as HAZ portion) have occurred.
【０００４】一方、極厚Ｈ形鋼で高強度と溶接性を確保
する方法としては、所謂ＴＭＣＰ（Ｔｈｅｒｍｏ Ｍｅ
ｃｈａｎｉｃａｌ Ｃｏｎｔｒｏｌｌｅｄ Ｐｒｏｃｅ
ｓｓ，水冷による加速冷却）を活用して、素材中のＣ当
量を低減する方法が知られている。例えば、特公昭５６
−３５７３４号公報は、Ｃ ０．０１〜０．３０％、Ｍ
ｎ ０．３０〜１．５０％を含有する鋼材をオーステナ
イト域でＨ形鋼に熱間加工し、そのフランジ温度をＡｒ
1 点〜Ｍｓ点の温度範囲に急冷した後、空冷して微細な
低温変態生成物を形成せしめるフランジ強化Ｈ形鋼の製
造方法を開示した。また、特公昭５８−１０４４２号公
報は、Ｃ ０．００５〜０．２％、Ｓｉ１．０％以下、
Ｎｂ，Ｖの１種又は２種を０．００５〜０．２％含有
し、残部が鉄及び不可避不純物からなる鋼材を１０００
〜１３００℃に加熱し、少なくとも９８０℃〜Ａｒ3 点
の温度範囲で減面率３０％以上加工してフェライトを析
出させた後、急冷によってフェライトとマルテンサイト
の２相層状組織とする加工性に優れた高靭性高張力鋼の
製造方法を提案している。On the other hand, as a method for ensuring high strength and weldability in an extremely thick H-section steel, so-called TMCP (Thermo Me
mechanical Controlled Proce
There is known a method of reducing C equivalent in the material by utilizing ss, accelerated cooling by water cooling). For example, Japanese Patent Publication Sho 56
-35734 gazette is C 0.01-0.30%, M
steel containing n 0.30 to 1.50% is hot worked into an H-section steel in the austenite region, and its flange temperature is set to Ar.
Disclosed is a method for producing a flange-reinforced H-section steel which is rapidly cooled to a temperature range of 1 point to Ms point and then air-cooled to form a fine low-temperature transformation product. Further, JP-B-58-10442 discloses that C 0.005 to 0.2%, Si 1.0% or less,
A steel material containing 0.005 to 0.2% of one or two of Nb and V and the balance of iron and inevitable impurities is 1000
~ 1300 ℃, at least 980 ℃ -Ar 3 points in the temperature range of 30% or more to reduce the surface area of the ferrite to precipitate ferrite, then by quenching to form a two-phase layered structure of ferrite and martensite workability It proposes a method for producing excellent high-toughness high-strength steel.
【０００５】しかしながら、これらの公報に記載の技術
は、熱間圧延後にフランジ外面側から急冷するため、フ
ランジの板厚断面で強度や靭性に差が生じたり、低温ま
で急冷することにより残留応力、歪が発生するなど、極
厚Ｈ形鋼の製造に適用した場合には、多くの問題が発生
した。However, since the techniques described in these publications are rapidly cooled from the outer surface side of the flange after hot rolling, there are differences in strength and toughness between the flange thickness sections, and residual stress due to rapid cooling to a low temperature, When applied to the production of extra-thick H-section steel, many problems have occurred, such as strain.
【０００６】[0006]
【発明が解決しようとする課題】本発明は、かかる事情
に鑑み、強度、靭性のばらつき及び残留応力、歪を発生
させることなく、強度、靭性及び溶接性に優れた極厚Ｈ
形鋼の製造方法を提供することを目的とする。SUMMARY OF THE INVENTION In view of such circumstances, the present invention has an extra-thickness H which is excellent in strength, toughness and weldability without causing variations in strength and toughness and residual stress and strain.
An object is to provide a method for manufacturing a shaped steel.
【０００７】[0007]
【課題を解決するための手段】発明者は、上記目的を達
成するために、種々の実験、研究を鋭意行った結果、以
下の新しい知見を得た。 １．Ｎｂ及びＶの炭窒化物析出による極厚Ｈ形鋼の強化
は、圧延冷却中の６００〜７００℃温度域で最大に起き
る。７００℃以上の高温域では、Ｎｂ及びＶの炭窒化物
が粗大析出し、また６００℃以下の低温域ではＮｂ及び
Ｖの炭窒化物の析出量が減少するためである。従って、
７００℃以上の高温域を０．２℃／ｓ以上で急冷すれ
ば、Ｎｂ及びＶの炭窒化物の粗大析出は防止できるの
で、その後の空冷中（７００〜６００℃）に起こる上記
Ｎｂ及びＶの析出強化を十分に発揮させることができ
る。 ２．７００℃以下の冷却は、空冷でもＮｂ及びＶの炭窒
化物を微細析出させることができ、Ｎｂ及びＶの析出強
化を十分に発揮させることができる。しかし、冷却停止
温度が６００℃以下になると、その後の空冷中にＮｂ及
びＶ炭窒化物が析出できないため、Ｎｂ及びＶの析出強
化が十分に発揮できない。また、６００℃以下を空冷す
ることによって、フランジの板厚断面での強度、靭性の
ばらつき及び残留応力、歪の発生はほぼ防止できる。 ３．上記（１）式のＣ当量を０．４０％以下になるよう
に合金成分を調整することによって、６００〜７００℃
温度域を急冷した場合にフェライト粒が微細化し良好な
母材靭性が得られるとともに、良好な溶接性が確保でき
る。 ４．Ｔｉ，ＲＥＭの添加により圧延加熱時のγ（オース
テナイト）結晶粒の粗大化を抑制し、さらにＴｉ，Ｂの
添加により圧延後のγ結晶粒からＴｉＮ及び析出ＢＮを
核としてフェライトを析出させるとともに、フェライト
の粗大化を抑制して細粒化することにより、通常の熱間
圧延条件でも極厚Ｈ形鋼に良好な靭性が得られる。 ５．溶接ＨＡＺ部も，ＴｉＮ、ＲＥＭ及びＢＮによる結
晶粒の微細化作用によって靭性が向上できる。The inventor has earnestly conducted various experiments and researches in order to achieve the above object, and has obtained the following new findings. 1. The strengthening of the extremely thick H-section steel by carbonitride precipitation of Nb and V occurs at the maximum in the temperature range of 600 to 700 ° C. during rolling cooling. This is because Nb and V carbonitrides are coarsely precipitated in a high temperature range of 700 ° C. or higher, and Nb and V carbonitrides are reduced in a low temperature range of 600 ° C. or lower. Therefore,
If a high temperature region of 700 ° C. or higher is rapidly cooled at 0.2 ° C./s or higher, coarse precipitation of carbonitrides of Nb and V can be prevented, so that Nb and V that occur during subsequent air cooling (700 to 600 ° C.) can be prevented. The precipitation strengthening of can be sufficiently exerted. 2. Cooling at 700 ° C. or lower can finely precipitate Nb and V carbonitrides even with air cooling, and can sufficiently exert precipitation strengthening of Nb and V. However, when the cooling stop temperature is 600 ° C. or lower, Nb and V carbonitrides cannot be precipitated during the subsequent air cooling, so that precipitation strengthening of Nb and V cannot be sufficiently exerted. Further, by air cooling at 600 ° C. or lower, it is possible to substantially prevent variations in strength, toughness, residual stress, and strain in the plate thickness section of the flange. 3. By adjusting the alloy components so that the C equivalent of the above formula (1) is 0.40% or less, 600 to 700 ° C.
When the temperature range is rapidly cooled, the ferrite grains become fine and good base metal toughness can be obtained, and good weldability can be secured. 4. The addition of Ti and REM suppresses the coarsening of γ (austenite) crystal grains during heating by rolling, and the addition of Ti and B causes ferrite to precipitate from the γ crystal grains after rolling by using TiN and precipitated BN as nuclei. By suppressing coarsening of ferrite and making it finer, good toughness can be obtained for extra-thick H-section steel even under normal hot rolling conditions. 5. The welded HAZ portion can also have improved toughness due to the grain refining action of TiN, REM and BN.
【０００８】本発明は、以上の知見に基づきなされたも
ので、具体的には、Ｃ：０．０５〜０．１５重量％，Ｓ
ｉ：０．２０重量％以下，Ｍｎ：１．００〜１．８０重
量％，Ａｌ：０．００５〜０．０５０重量％，Ｎｂ：
０．００３〜０．０１５重量％，Ｖ：０．０１０〜０．
０８０重量％，Ｎ：０．００２０〜０．００７０重量％
を含有し、且つ、上記（１）式で規定するＣ当量が０．
４０％以下で残部Ｆｅ及び不可避的不純物からなる鋼片
を、１２００〜１３５０℃に加熱し、１２００℃以下の
温度で４０％以上の累積圧下を与え、９５０〜１０５０
℃の温度で熱間圧延を終了した後、直ちにフランジの板
厚１／４ｔ部を内外面から０．２〜３．０℃／ｓの冷却
速度で７００〜６００℃まで急冷し、その後空冷するこ
とを特徴とする強度、靭性及び溶接性に優れた極厚Ｈ形
鋼の製造方法である。また、本発明は、上記鋼片が、Ｃ
ｕ：０．０５〜０．６０重量％，Ｎｉ：０．０５〜０．
６０重量％，Ｃｒ：０．０５〜０．５０重量％，Ｍｏ：
０．０２〜０．３０重量％，Ｃａ：０．００１０〜０．
０１００重量％，Ｔｉ：０．００５〜０．０２０重量
％，ＲＥＭ：０．００１０〜０．０２０重量％，Ｂ：
０．０００２〜０．００３重量％の１種または２種以上
を含有することを特徴とする強度、靭性及び溶接性に優
れた極厚Ｈ形鋼の製造方法でもある。The present invention has been made based on the above findings. Specifically, C: 0.05 to 0.15% by weight, S
i: 0.20 wt% or less, Mn: 1.00 to 1.80 wt%, Al: 0.005 to 0.050 wt%, Nb:
0.003 to 0.015% by weight, V: 0.010 to 0.
080% by weight, N: 0.0020 to 0.0070% by weight
And the C equivalent defined by the above formula (1) is 0.
A steel slab consisting of balance Fe and inevitable impurities at 40% or less is heated to 1200 to 1350 ° C., and a cumulative reduction of 40% or more is applied at a temperature of 1200 ° C. or less, and 950 to 1050.
Immediately after finishing the hot rolling at a temperature of ℃, the 1 / 4t thickness portion of the flange is rapidly cooled from the inner and outer surfaces to 700 to 600 ° C at a cooling rate of 0.2 to 3.0 ° C / s, and then air cooled. This is a method for producing an extremely thick H-section steel excellent in strength, toughness, and weldability. Further, in the present invention, the above steel slab is C
u: 0.05-0.60% by weight, Ni: 0.05-0.
60% by weight, Cr: 0.05 to 0.50% by weight, Mo:
0.02-0.30% by weight, Ca: 0.0010-0.
0100% by weight, Ti: 0.005 to 0.020% by weight, REM: 0.0010 to 0.020% by weight, B:
It is also a method for producing an extra-thick H-section steel excellent in strength, toughness and weldability, characterized by containing 0.0002 to 0.003% by weight of one kind or two or more kinds.
【０００９】[0009]
【作用】本発明では、Ｃ：０．０５〜０．１５重量％，
Ｓｉ：０．２０重量％以下，Ｍｎ：１．００〜１．８０
重量％，Ａｌ：０．００５〜０．０５０重量％，Ｎｂ：
０．００３〜０．０１５重量％，Ｖ：０．０１０〜０．
０８０重量％，Ｎ：０．００２０〜０．００７０重量％
を含有し、且つ、（１）式で規定するＣ当量が０．４０
％以下で残部Ｆｅ及び不可避的不純物からなる鋼片を、
１２００〜１３５０℃に加熱し、１２００℃以下の温度
で４０％以上の累積圧下を与え、９５０〜１０５０℃の
温度で熱間圧延を終了した後、直ちにフランジの板厚１
／４ｔ部を内外面から０．２〜３．０℃／ｓの冷却速度
で７００〜６００℃まで急冷し、その後空冷するように
したので、強度、靭性のばらつき及び残留応力、歪を発
生させることなく、強度、靭性及び溶接性に優れた極厚
Ｈ形鋼の製造が可能になる。また、本発明では、上記鋼
片が、Ｃｕ：０．０５〜０．６０重量％，Ｎｉ：０．０
５〜０．６０重量％，Ｃｒ：０．０５〜０．５０重量
％，Ｍｏ：０．０２〜０．３０重量％，Ｃａ：０．００
１０〜０．０１００重量％，Ｔｉ：０．００５〜０．０
２０重量％，ＲＥＭ：０．００１０〜０．０２０重量
％，Ｂ：０．０００２〜０．００３０重量％の１種また
は２種以上を含有するようにしたので、上記効果は確実
に達成できるようになる。In the present invention, C: 0.05 to 0.15% by weight,
Si: 0.20 wt% or less, Mn: 1.00 to 1.80
% By weight, Al: 0.005-0.050% by weight, Nb:
0.003 to 0.015% by weight, V: 0.010 to 0.
080% by weight, N: 0.0020 to 0.0070% by weight
And the C equivalent defined by the formula (1) is 0.40.
% Or less, a steel slab consisting of the balance Fe and inevitable impurities,
After heating to 1200 to 1350 ° C., a cumulative reduction of 40% or more is applied at a temperature of 1200 ° C. or less, and hot rolling is completed at a temperature of 950 to 1050 ° C., immediately after which the flange plate thickness 1
Since the / 4t portion is rapidly cooled from the inner and outer surfaces to 700 to 600 ° C at a cooling rate of 0.2 to 3.0 ° C / s and then air-cooled, variations in strength and toughness, residual stress, and strain are generated. It becomes possible to manufacture an extremely thick H-section steel excellent in strength, toughness, and weldability. Further, in the present invention, the steel slab has a Cu content of 0.05 to 0.60% by weight and a Ni content of 0.0.
5 to 0.60% by weight, Cr: 0.05 to 0.50% by weight, Mo: 0.02 to 0.30% by weight, Ca: 0.00
10-0.0100% by weight, Ti: 0.005-0.0
20% by weight, REM: 0.0010 to 0.020% by weight, B: 0.0002 to 0.0030% by weight, so as to contain one or more kinds, it is possible to surely achieve the above effect. become.
【００１０】以下に、本発明に係る製造方法における構
成要素の限定理由を説明する。まず、素材鋼片の化学組
成に関してであるが、Ｃは、母材（主にフランジ部）お
よび溶接部の強度を確保するために、０．０５重量％以
上必要であるが、０．１５重量％を超えると、母材靭性
および溶接性が劣化するので、０．０５〜０．１５重量
％の範囲に限定した。The reasons for limiting the constituent elements in the manufacturing method according to the present invention will be described below. First, regarding the chemical composition of the raw steel billet, C is required to be 0.05% by weight or more in order to secure the strength of the base material (mainly the flange portion) and the welded portion, but 0.15 weight% %, The base material toughness and weldability deteriorate, so the content is limited to the range of 0.05 to 0.15% by weight.
【００１１】Ｓｉは、上記強度の向上に有効な元素であ
るが、その量が多くなると製品の極厚Ｈ形鋼の溶接性お
よびＨＡＺ部靭性が悪くなるとともに、１２００℃以上
の圧延加熱において素材の酸化が顕著になり、圧延後の
該Ｈ形鋼の表面性状が悪くなるので、０．２０重量％を
上限とした。Ｍｎも、上記強度を確保する上で不可欠な
元素であり、その下限は１．００重量％とした。しか
し、その量が１．８０重量％を超えると製品の溶接性や
ＨＡＺ部靭性の劣化が大きくなるので、上限を１．８０
重量％とした。Si is an element effective for improving the above-mentioned strength, but when the amount thereof is large, the weldability and HAZ portion toughness of the extra-thick H-section steel of the product are deteriorated, and Si is a raw material in rolling heating at 1200 ° C. or higher. However, since the surface properties of the H-section steel after rolling deteriorate, the upper limit was 0.20% by weight. Mn is also an element essential for ensuring the above strength, and its lower limit is 1.00% by weight. However, if the amount exceeds 1.80% by weight, the weldability of the product and the toughness of the HAZ part deteriorate significantly, so the upper limit is 1.80.
It was set to% by weight.
【００１２】Ａｌは、素材の脱酸の為に通常０．００５
重量％以上必要であるが、０．０５０重量％を超えて必
要以上に添加しても該脱酸効果は向上しないので、上限
を０．０５０重量％とした。Ｎｂは、母材のγ（オース
テナイト）結晶粒中に固溶して、α（フェライト）変態
後のα地に析出して母材を強化する。これらの強化作用
を発揮させるためには、少なくとも０．００３重量％以
上の添加が必要であり、一方、その添加量が０．０１５
重量％を超えると、熱間圧延時の再結晶細粒化が起こり
難くなり、圧延冷却後に粗大ベイナイトが生成して靭性
を低下させるとともに、製品の溶接性およびＨＡＺ部靭
性を低下させるので、０．００３〜０．０１５重量％の
範囲とした。Al is usually 0.005 for deoxidizing the material.
The amount is required to be not less than wt%, but the deoxidizing effect is not improved even if added in excess of 0.050 wt%, so the upper limit was made 0.050 wt%. Nb forms a solid solution in the γ (austenite) crystal grains of the base material and precipitates in the α base after the α (ferrite) transformation to strengthen the base material. In order to exert these reinforcing effects, it is necessary to add at least 0.003% by weight, while the addition amount is 0.015%.
When the content is more than 10% by weight, recrystallization of fine grains during hot rolling becomes difficult to occur, coarse bainite is generated after rolling and cooling, and the toughness is lowered, and the weldability and HAZ part toughness of the product are lowered. The range was 0.003 to 0.015% by weight.
【００１３】Ｃｕ，Ｎｉ，Ｃｒ，Ｍｏは、いずれも焼入
性向上に有効な元素であり、熱間圧延後の空冷で製品強
度を高める。該強度向上にためには、それぞれ０．０５
重量％，０．０５重量％，０．０５重量％，０．０２重
量％以上が必要である。また、Ｃｕ，Ｎｉは製品の溶接
性をほとんど劣化させないが、Ｃｕは熱間加工性を劣化
させる欠点もある。Ｃｕのこの熱間加工性低下を抑制す
るにはほぼ等量のＮｉ添加を必要とするが、Ｎｉは０．
６０重量％を超えて添加すると、製造コストが高価とな
りすぎるため、Ｃｕ，Ｎｉの上限は０．６０重量％とし
た。Ｃｒ，Ｍｏは、それぞれ０．５０重量％，０．３０
重量％を超えると、製品の溶接性や低温靭性を損なうな
どの弊害をもたらすので、その数値を上限とした。Cu, Ni, Cr and Mo are all effective elements for improving hardenability, and enhance the product strength by air cooling after hot rolling. To improve the strength, 0.05
%, 0.05% by weight, 0.05% by weight, 0.02% by weight or more are required. Further, Cu and Ni hardly deteriorate the weldability of the product, but Cu has a defect that the hot workability is deteriorated. In order to suppress this deterioration of hot workability of Cu, it is necessary to add approximately the same amount of Ni, but Ni is less than 0.1%.
If it is added in an amount of more than 60% by weight, the manufacturing cost becomes too expensive. Therefore, the upper limits of Cu and Ni were set to 0.60% by weight. Cr and Mo are 0.50 wt% and 0.30, respectively.
When the content exceeds the weight%, the weldability of the product and the low temperature toughness may be impaired. Therefore, the value is set as the upper limit.
【００１４】Ｖは、所謂析出強化型の元素であり、空冷
後の母材強度を向上させる。特に、０．００３重量％以
上のＮｂを含む鋼にＶを添加した場合は大きな析出強化
が得られる。また、０．０１０重量％以下の添加ではそ
の効果がなく、０．０８０重量％を超えると、製品のＨ
ＡＺ部靭性を劣化させるので、０．０１０〜０．０８０
重量％の範囲に制限した。V is a so-called precipitation strengthening element and improves the strength of the base material after air cooling. In particular, when V is added to steel containing 0.003% by weight or more of Nb, a large precipitation strengthening is obtained. If it is added in an amount of 0.010% by weight or less, the effect is not obtained.
Since it deteriorates the toughness of the AZ part, it is 0.010 to 0.080.
It was limited to the range of% by weight.
【００１５】Ｃａは、母材中に生成したＭｎＳの形態を
制御し、とくに板厚方向の延性、靭性を向上させる。し
かし、０．００１０重量％以下では実用上効果がなく、
０．０１００重量％を超えると、ＣａＯあるいはＣａＳ
が多く生成し、かえって母材の清浄性や靭性を劣化させ
るので、Ｃａの添加範囲は０．００１０〜０．０１０重
量％とした。Ca controls the morphology of MnS formed in the base material, and particularly improves the ductility and toughness in the plate thickness direction. However, if it is less than 0.0010% by weight, there is no practical effect,
If it exceeds 0.0100% by weight, CaO or CaS
Therefore, the Ca addition range was set to 0.0010 to 0.010 wt%.
【００１６】Ｔｉは、熱間圧延したままでの極厚Ｈ形鋼
において良好な靭性を得るために有効な元素である。す
なわち、母材中にＴｉＮを形成して、１２００〜１３５
０℃加熱時のγ結晶粒の粗大化を抑制するとともに、γ
→α変態時のフェライト結晶粒の成長を抑制し、該フェ
ライト結晶粒を微粒化し、母材靭性を向上させる。ま
た、同様の理由でＨＡＺ部靭性も向上させる。そのため
には、Ｔｉは０．００５重量％以上の添加が必要である
が、０．０２０重量％を超えて添加すると、かえって母
材およびＨＡＺ部の靭性を劣化させる。Ti is an element effective for obtaining good toughness in the extremely thick H-section steel as hot-rolled. That is, by forming TiN in the base material,
It suppresses the coarsening of γ crystal grains during heating at 0 ° C, and
→ Suppresses the growth of ferrite crystal grains during the α transformation, atomizes the ferrite crystal grains, and improves the toughness of the base material. Further, the HAZ portion toughness is also improved for the same reason. For this purpose, Ti needs to be added in an amount of 0.005% by weight or more, but if added in excess of 0.020% by weight, the toughness of the base material and HAZ portion is rather deteriorated.
【００１７】Ｎは、母材中にＴｉＮを形成し、上記フェ
ライト結晶粒の微細化効果を得るためには、０．００２
０重量％以上必要であるが、０．００７０重量％を超え
ると、母材およびＨＡＺ部の靭性が劣化するので、０．
００２０〜０．００７０重量％の範囲に限定した。ＲＥ
Ｍは、高温においても安定でＴｉＮと同様に、フェライ
ト結晶粒の微細化に効果がある。この効果を発揮させる
には、０．００１０重量％以上の添加が必要であるが、
０．０２０重量％を超えると、かえって母材の清浄性お
よび靭性を劣化する。N is 0.002 in order to form TiN in the base material and obtain the effect of refining the ferrite crystal grains.
It is necessary to be 0% by weight or more, but if it exceeds 0.0070% by weight, the toughness of the base material and the HAZ part deteriorates.
It was limited to the range of 0020 to 0.0070% by weight. RE
M is stable even at high temperatures and is effective for refining ferrite crystal grains, like TiN. To exert this effect, it is necessary to add 0.0010% by weight or more,
If it exceeds 0.020% by weight, the cleanliness and toughness of the base material are rather deteriorated.
【００１８】Ｂは、圧延冷却中に母材中にＢＮとして析
出し、フェライト変態の核として結晶粒の細粒化に有効
に作用する。特に、ＲＥＭ，ＴｉＮとの共存でフェライ
ト粒を細かくするが、その効果は０．０００２重量％以
上で得られる。しかし、０．００３０重量％を超える
と、母材の靭性がかえって低下するので、０．０００２
〜０．００３０重量％の範囲に限定した。なお、Ｔｉの
存在下でＢＮを形成させるためには、Ｔｉ（ＴｉＮ）に
対し過剰のＮが必要である。Ｔｉ／Ｎの比は、ＴｉＮの
化学量論的組み合わせよりも、Ｎが若干過剰に存在する
組み合わせ、すなわち、Ｔｉ／Ｎの比で２〜４であるこ
とが望ましい。B precipitates as BN in the base material during rolling and cooling, and acts effectively as a nuclei for ferrite transformation to refine the crystal grains. In particular, the ferrite grains are made fine by coexistence with REM and TiN, and the effect is obtained at 0.0002% by weight or more. However, if it exceeds 0.0030% by weight, the toughness of the base material rather deteriorates.
To 0.0030% by weight. In addition, in order to form BN in the presence of Ti, excess N is required with respect to Ti (TiN). The Ti / N ratio is preferably a combination in which N is slightly present in excess of the stoichiometric combination of TiN, that is, a Ti / N ratio of 2 to 4.
【００１９】（１）式で規定するＣ当量が４０％を超え
ると、熱間圧延後の７００〜６００℃域を急冷した場合
にベイナイト主体の組織となる。その結果、フェライト
析出による細粒化が図れず、母材の靭性が低下するとと
もに、溶接ＨＡＺ部に島状マルテンサイトが生成しやす
くなって該靭性が劣化するので、０．４０％以下に限定
した。When the C equivalent defined by the equation (1) exceeds 40%, a bainite-based structure is formed when the 700-600 ° C. region after hot rolling is rapidly cooled. As a result, the grain size cannot be reduced due to the precipitation of ferrite, the toughness of the base material is reduced, and island martensite is easily generated in the welded HAZ portion, which deteriorates the toughness, so it is limited to 0.40% or less. did.
【００２０】次に、上記素材を圧延する条件の限定理由
を述べる。熱間圧延のための加熱温度は、通常の極厚で
ないＨ形鋼の圧延に適用する１２００〜１３５０℃であ
れば十分である。そして、１２００℃以上の加熱で、
０．００３重量％以上あるＮｂの固溶は十分達成される
が、１３５０℃を超えると母材中の結晶粒が粗大化して
靭性が劣化するので，加熱温度は１２００〜１３５０℃
の範囲とした。Next, the reasons for limiting the conditions for rolling the above material will be described. It suffices that the heating temperature for hot rolling is 1200 to 1350 ° C., which is applied to the rolling of ordinary H-section steel that is not extremely thick. And by heating above 1200 ° C,
A solid solution of 0.003% by weight or more of Nb is sufficiently achieved, but if it exceeds 1350 ° C, the crystal grains in the base material become coarse and the toughness deteriorates. Therefore, the heating temperature is 1200 to 1350 ° C.
Range.
【００２１】また、熱間圧延において、１２００℃以下
温度で累積圧下率を４０％以上とするのは、再結晶細粒
化によって粗大な結晶粒を微細化し、母材の高靭性を確
保するためである。さらに、仕上温度が１０５０℃を超
えると、微細な結晶粒が得られず、９５０℃未満に低下
すると、Ｎｂ炭化物が析出し固溶Ｎｂが減少するため
に、Ｎｂによる強化が減少する。そこで、本発明では、
仕上温度を１０５０〜９５０℃に限定した。Further, in hot rolling, the cumulative rolling reduction is set to 40% or more at a temperature of 1200 ° C. or less in order to make coarse crystal grains fine by recrystallization grain refinement and to secure high toughness of the base material. Is. Further, when the finishing temperature exceeds 1050 ° C, fine crystal grains cannot be obtained, and when the finishing temperature falls below 950 ° C, Nb carbide precipitates and solid solution Nb decreases, so that strengthening by Nb decreases. Therefore, in the present invention,
The finishing temperature was limited to 1050-950 ° C.
【００２２】圧延を終了した後、冷却速度を０．２℃／
ｓ以上として急冷するのは、７００℃以上の高温域での
Ｎｂ炭化物の析出を抑制でき、Ｎｂによる析出強化を高
めるためである。冷却速度が３．０℃／ｓ以上になる
と、ベーナイト主体の組織となり、母材靭性が低下する
とともに、フランジ板厚方向の強度、靭性のバラツキが
大きくなり残留応力も大きくなる。したがって、冷却速
度は０．２〜３．０℃／ｓに限定した。そして、冷却停
止温度が７００℃を超える高温では、Ｎｂ炭化物が粗大
析出するため、母材の強度が充分でなくなる。一方、冷
却停止温度が６００℃を下回ると、Ｎｂ炭化物が析出強
化を活用できず、母材の表面と内部とでα変態時の冷却
速度差が大きくなり、板厚方向の特性値に差が生じる。
そのため、冷却停止温度は７００〜６００℃範囲とし
た。なお、その後の冷却は、空冷とすることによって、
フェライトを含む微細組織が得られるとともに、Ｎｂの
析出強化も達成できる。After the rolling is completed, the cooling rate is 0.2 ° C. /
The reason for quenching as s or higher is to suppress precipitation of Nb carbide in a high temperature range of 700 ° C. or higher and to enhance precipitation strengthening by Nb. When the cooling rate is 3.0 ° C./s or more, the structure is mainly composed of bainite, the toughness of the base material is lowered, and the variations in strength and toughness in the flange plate thickness direction are increased, and the residual stress is also increased. Therefore, the cooling rate is limited to 0.2 to 3.0 ° C./s. When the cooling stop temperature is higher than 700 ° C., Nb carbides are coarsely precipitated, so that the strength of the base material becomes insufficient. On the other hand, when the cooling stop temperature is lower than 600 ° C., Nb carbide cannot utilize precipitation strengthening, and the difference in cooling rate at the time of α transformation between the surface and the inside of the base material becomes large, resulting in a difference in the characteristic value in the plate thickness direction. Occurs.
Therefore, the cooling stop temperature is set in the range of 700 to 600 ° C. In addition, the subsequent cooling is by air cooling,
A fine structure containing ferrite can be obtained, and Nb precipitation strengthening can also be achieved.
【００２３】[0023]
【実施例】表１及び表２に化学組成を示す鋼片を１２５
０〜１３５０℃に加熱後、表３及び表４に示す種々の圧
延条件および冷却条件でフランジ板厚８０〜９０ｍｍの
極厚Ｈ形鋼を製造した。その際、冷却方法は、フランジ
部の外面から図１に示すように断続的に水を吹きつけ
（水冷−空冷を繰り返す）ることによって、フランジ１
／４ｔ部の冷却速度を０．３〜０．６℃／ｓに調整し
た。そして、各極厚Ｈ形鋼のフランジ幅の１／４部位置
で表面下８ｍｍ部分および１／２ｔ（ｔは板厚）部分よ
り、日本工業規格に規定する４号引張試験片および４号
衝撃試験片を採取し、それぞれの試験片で機械的性質
（降伏強度（ＹＳ），引張強度（ＴＳ），降伏比（Ｙ
Ｒ）及び衝撃靭性値（ｖＥ0 ））を調査した。その調査
結果は、表３及び表４に同時に示してある。EXAMPLE 125 steel pieces having chemical compositions shown in Tables 1 and 2 were used.
After heating to 0 to 1350 ° C., extra thick H-section steel with a flange plate thickness of 80 to 90 mm was manufactured under various rolling conditions and cooling conditions shown in Tables 3 and 4. At that time, the cooling method is as follows: intermittently spraying water from the outer surface of the flange portion as shown in FIG. 1 (repeating water cooling-air cooling).
The cooling rate of the / 4t part was adjusted to 0.3 to 0.6 ° C / s. Then, at the position of 1/4 of the flange width of each extra-thick H-section steel, from the 8 mm portion below the surface and the 1/2 t (t is the plate thickness) portion, the No. 4 tensile test piece and No. 4 impact specified in Japanese Industrial Standards Samples were taken and the mechanical properties (yield strength (YS), tensile strength (TS), yield ratio (Y
R) and impact toughness value (vE 0 )) were investigated. The survey results are shown in Table 3 and Table 4 at the same time.
【００２４】[0024]
【表１】 [Table 1]
【００２５】[0025]
【表２】 [Table 2]
【００２６】[0026]
【表３】 [Table 3]
【００２７】[0027]
【表４】 [Table 4]
【００２８】なお、表１及び表２の英文字記号のＡ〜Ｆ
は、本発明に係る製造方法の実施例に対応する鋼片で、
Ｇ，Ｉは、比較例のための鋼片である。但し、表３及び
表４に示すＡ５，Ｂ２，Ｃ２は、圧延後の冷却が通常の
空冷であり、Ａ６およびＩ１は、累積圧下率小さく、本
発明条件から外れ比較例としてある。。表３及び表４に
示すように、すべての本発明例では、表層と中心との強
度、靭性の差が小さく、ＴＳで５３０ＭＰａ以上の高強
度と、ｖＥｏで９０Ｊ以上の高靭性とが得られている。
しかし、比較例のＧは、Ｃ量およびＣ当量が高いため、
衝撃靭性がｖＥ０で４６Ｊ以下と低く、また、比較例Ｈ
は、Ｍｎ量が低く、Ｎｂを含まないため、１／４ｔ部の
強度はＴＳで４７６ＭＰａと低い。さらに、比較例Ｉ
は、Ｎｂ量が多いため細粒が得られず、良好な母材靭性
確保できない。The alphabetic characters A to F in Tables 1 and 2 are used.
Is a steel slab corresponding to the embodiment of the manufacturing method according to the present invention,
G and I are steel pieces for comparative examples. However, A5, B2, and C2 shown in Tables 3 and 4 are air-cooled normally after rolling, and A6 and I1 are smaller than the cumulative rolling reduction, and are out of the conditions of the present invention and are comparative examples. . As shown in Tables 3 and 4, in all the examples of the present invention, the difference in strength and toughness between the surface layer and the center was small, and high strength of 530 MPa or more in TS and high toughness of 90 J or more in vEo were obtained. ing.
However, since G of Comparative Example has a high C content and C equivalent,
Impact toughness is as low as 46 J or less at vE0, and Comparative Example H
Has a low Mn content and does not contain Nb, so the strength of the 1/4 t portion is as low as 476 MPa in TS. Furthermore, Comparative Example I
Since the Nb content is large, fine grains cannot be obtained and good base material toughness cannot be secured.
【００２９】次に、溶接割れ感受性を評価するため、Ｊ
ＩＳ Ｚ ３１５８に規定する「斜めｙ形溶接割れ試
験」を行った。本発明例中で、Ｃ当量の高いＢ，Ｄ，Ｅ
について、フランジから（板厚×長さ２００×幅１５０
ｍｍ）の試験片を切り出し、高張力鋼用被覆アーク溶接
棒を用いて、１７０アンペア、２４ボルト、溶接速度１
５０ｍｍ／ｍｉｎの条件で試験した。その際の溶接予熱
温度は５０℃としたが、上記いずれの試験片も割れの発
生は皆無であった。しかし、比較例のＧから同じサイズ
で採取した試験片では、同一の溶接条件で割れが発生し
た。Next, in order to evaluate the weld crack susceptibility, J
The "oblique y-type weld cracking test" specified in IS Z 3158 was performed. In the examples of the present invention, B, D and E having high C equivalents
About the flange (plate thickness x length 200 x width 150
(mm) test piece is cut out, 170 ampere, 24 volts, welding speed 1 using the coated arc welding rod for high strength steel.
The test was conducted under the condition of 50 mm / min. The welding preheating temperature at that time was 50 ° C., but no cracks were generated in any of the above test pieces. However, the test piece taken in the same size from Comparative Example G had cracks under the same welding conditions.
【００３０】[0030]
【発明の効果】以上述べたように、本発明に係る製造方
法を採用すれば、建築、土木構造物用鋼材として強度、
靭性及び溶接性に優れた極厚Ｈ形鋼の製造が可能になっ
た。As described above, when the manufacturing method according to the present invention is adopted, strength as a steel material for construction and civil engineering structures,
It has become possible to manufacture extremely thick H-section steel with excellent toughness and weldability.
【図１】本発明の実施における冷却方法を説明する図で
ある。FIG. 1 is a diagram illustrating a cooling method according to an embodiment of the present invention.
１ ウエブ ２ フランジ ３ 水の吹きつけ方向 ４ 試料採取位置 1 Web 2 Flange 3 Water spraying direction 4 Sampling position
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/12 (72)発明者 天野 虔一 千葉市中央区川崎町１番地 川崎製鉄株式 会社技術研究所内 (72)発明者 橋本 隆文 倉敷市水島川崎通１丁目（番地なし） 川 崎製鉄株式会社水島製鉄所内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification number Internal reference number FI Technical location C22C 38/12 (72) Inventor Shinichi Amano 1 Kawasaki-cho, Chuo-ku, Chiba City Kawasaki Steel Co., Ltd. Inside the laboratory (72) Inventor Takafumi Hashimoto 1-chome, Kawashima-dori, Mizushima Kurashiki City (no address) Kawasaki Steel Works Mizushima Works
Claims (2)
０．２０重量％以下，Ｍｎ：１．００〜１．８０重量
％，Ａｌ：０．００５〜０．０５０重量％，Ｎｂ：０．
００３〜０．０１５重量％，Ｖ：０．０１０〜０．０８
０重量％，Ｎ：０．００２０〜０．００７０重量％を含
有し、且つ、下記式で規定するＣ当量が０．４０％以下
で残部Ｆｅ及び不可避的不純物からなる鋼片を、１２０
０〜１３５０℃に加熱し、１２００℃以下の温度で４０
％以上の累積圧下を与え、９５０〜１０５０℃の温度で
熱間圧延を終了した後、直ちにフランジの板厚１／４ｔ
部を外面から０．２〜３．０℃／ｓの冷却速度で７００
〜６００℃まで急冷し、その後空冷することを特徴とす
る強度、靭性及び溶接性に優れた極厚Ｈ形鋼の製造方
法。 Ｃ当量（％）＝Ｃ（％）＋Ｓｉ（％）／２４＋Ｍｎ
（％）／６＋Ｎｉ（％）／４０＋Ｃｕ（％）／５＋Ｍｏ
（％）／４＋Ｖ（％）／１４・・・・（１）式1. C: 0.05 to 0.15% by weight, Si:
0.20% by weight or less, Mn: 1.00 to 1.80% by weight, Al: 0.005 to 0.050% by weight, Nb: 0.
003 to 0.015% by weight, V: 0.010 to 0.08
A steel slab containing 0% by weight, N: 0.0020 to 0.0070% by weight, and having a C equivalent defined by the following formula of 0.40% or less and the balance Fe and unavoidable impurities is
Heat to 0 to 1350 ° C and 40 at a temperature of 1200 ° C or less.
% Of cumulative reduction, and after finishing the hot rolling at a temperature of 950 to 1050 ° C., immediately after the plate thickness of the flange 1/4 t
700 parts from the outer surface at a cooling rate of 0.2 to 3.0 ° C./s
A method for producing an extremely thick H-section steel having excellent strength, toughness, and weldability, which comprises rapidly cooling to ~ 600 ° C and then air cooling. C equivalent (%) = C (%) + Si (%) / 24 + Mn
(%) / 6 + Ni (%) / 40 + Cu (%) / 5 + Mo
(%) / 4 + V (%) / 14 ... (1) Formula
０．６０重量％，Ｎｉ：０．０５〜０．６０重量％，Ｃ
ｒ：０．０５〜０．５０重量％，Ｍｏ：０．０２〜０．
３０重量％，Ｃａ：０．００１０〜０．０１０重量％，
Ｔｉ：０．００５〜０．０２０重量％，ＲＥＭ：０．０
０１〜０．０２重量％，Ｂ：０．０００２〜０．００３
０重量％の１種または２種以上を含有することを特徴と
する請求項１記載の強度、靭性及び溶接性に優れた極厚
Ｈ形鋼の製造方法。2. The steel slab is Cu: 0.05-
0.60 wt%, Ni: 0.05-0.60 wt%, C
r: 0.05 to 0.50% by weight, Mo: 0.02 to 0.
30% by weight, Ca: 0.0010 to 0.010% by weight,
Ti: 0.005-0.020% by weight, REM: 0.0
01-0.02% by weight, B: 0.0002-0.003
The method for producing an extra-thick H-section steel excellent in strength, toughness and weldability according to claim 1, characterized in that it contains 0% by weight of one kind or two or more kinds.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP897595A JP3622246B2 (en) | 1995-01-24 | 1995-01-24 | Method for producing extremely thick H-section steel with excellent strength, toughness and weldability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP897595A JP3622246B2 (en) | 1995-01-24 | 1995-01-24 | Method for producing extremely thick H-section steel with excellent strength, toughness and weldability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08197105A true JPH08197105A (en) | 1996-08-06 |
| JP3622246B2 JP3622246B2 (en) | 2005-02-23 |
Family
ID=11707696
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP897595A Expired - Fee Related JP3622246B2 (en) | 1995-01-24 | 1995-01-24 | Method for producing extremely thick H-section steel with excellent strength, toughness and weldability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3622246B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011157573A (en) * | 2010-01-29 | 2011-08-18 | Nippon Steel Corp | High strength extra-thick wide flange shape having excellent toughness, and method for producing the same |
| KR101298699B1 (en) * | 2011-04-27 | 2013-08-21 | 현대제철 주식회사 | High strength steel and method for manufacturing the same |
| JP2017186594A (en) * | 2016-04-04 | 2017-10-12 | 新日鐵住金株式会社 | H-shaped steel for low temperature and manufacturing method therefor |
| CN108504924A (en) * | 2018-03-28 | 2018-09-07 | 马钢(集团)控股有限公司 | A kind of 460MPa grades of hot rolled H-shaped and its production methods of yield strength containing vanadium with good low-temperature toughness |
-
1995
- 1995-01-24 JP JP897595A patent/JP3622246B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011157573A (en) * | 2010-01-29 | 2011-08-18 | Nippon Steel Corp | High strength extra-thick wide flange shape having excellent toughness, and method for producing the same |
| KR101298699B1 (en) * | 2011-04-27 | 2013-08-21 | 현대제철 주식회사 | High strength steel and method for manufacturing the same |
| JP2017186594A (en) * | 2016-04-04 | 2017-10-12 | 新日鐵住金株式会社 | H-shaped steel for low temperature and manufacturing method therefor |
| CN108504924A (en) * | 2018-03-28 | 2018-09-07 | 马钢(集团)控股有限公司 | A kind of 460MPa grades of hot rolled H-shaped and its production methods of yield strength containing vanadium with good low-temperature toughness |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3622246B2 (en) | 2005-02-23 |
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