JP2633757B2 - Structural steel plate for welding with excellent brittle fracture arrestability and method of manufacturing the same - Google Patents
Structural steel plate for welding with excellent brittle fracture arrestability and method of manufacturing the sameInfo
- Publication number
- JP2633757B2 JP2633757B2 JP3315650A JP31565091A JP2633757B2 JP 2633757 B2 JP2633757 B2 JP 2633757B2 JP 3315650 A JP3315650 A JP 3315650A JP 31565091 A JP31565091 A JP 31565091A JP 2633757 B2 JP2633757 B2 JP 2633757B2
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- steel sheet
- rolling
- surface layer
- welding
- temperature
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、脆性破壊伝播停止特性
の優れた溶接用構造用鋼板とその製造方法に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structural steel sheet for welding having excellent brittle fracture arrestability and a method for producing the same.
【０００２】[0002]
【従来の技術】脆性破壊伝播停止（アレスト）性能を向
上させる手段として、未再結晶域で十分に圧下する製造
方法、あるいは、積極的に脆性破壊を生じ易い第二相粒
子を分散させて脆性亀裂先端にマイクロクラックを多数
発生せしめ亀裂先端の応力状態を緩和させ、且つマイク
ロクラックと主亀裂間の合体時に生じる延性破壊により
亀裂停止を容易にさせる方法が提案されている。2. Description of the Related Art As a means for improving the arrest performance of brittle fracture propagation, a production method of sufficiently reducing pressure in an unrecrystallized region, or a method of dispersing brittle fracture which is apt to cause brittle fracture is dispersed. A method has been proposed in which a large number of microcracks are generated at the tip of a crack to alleviate the stress state at the tip of the crack, and the crack is easily stopped by ductile fracture occurring when the microcrack and the main crack are united.
【０００３】しかし、それらの提案は、板厚中心部の組
織を改質し、脆性亀裂伝播停止性能を向上させるもので
あり、板厚表層部の組織で主として決定される落重試験
におけるＮＤＴ特性を必ずしも向上させるものではな
い。一方、亀裂伝播の形態により、板厚中心部の特性や
表層部の特性が必要であり、同時に両者を満足すること
が望まれている。However, these proposals modify the structure at the center of the sheet thickness and improve the brittle crack propagation stopping performance. The NDT characteristics in a drop load test mainly determined by the structure of the surface layer of the sheet thickness are proposed. Is not necessarily improved. On the other hand, depending on the mode of crack propagation, the properties of the center of the sheet thickness and the properties of the surface layer are required, and it is desired to satisfy both at the same time.
【０００４】[0004]
【発明が解決しようとする課題】本発明は、製造コスト
を大きく上昇させる高価なＮｉ元素等を添加することな
く、Ｋｃａ特性とＮＤＴ特性を両立させる鋼板及びその
製造方法を提供することを課題とする。SUMMARY OF THE INVENTION It is an object of the present invention to provide a steel sheet having both Kca characteristics and NDT characteristics without adding an expensive Ni element or the like which greatly increases the manufacturing cost, and a method for manufacturing the same. I do.
【０００５】[0005]
【課題を解決するための手段】本発明の要旨は、表層か
ら少なくとも０．１mm以上の範囲にわたり、平均円相当
径で３μｍ以下のフェライト粒からなり、且つそのフェ
ライト粒の同一結晶方位を有する集合組織のコロニーの
平均アスペクト比（長径／短径の比）が４以上の組織に
より構成されることを特徴とする脆性破壊伝播停止特性
の優れた溶接用構造用鋼板である。SUMMARY OF THE INVENTION The gist of the present invention is to provide a ferrite grain having an average equivalent circle diameter of 3 μm or less over a range of at least 0.1 mm from the surface layer and having the same crystal orientation. Tissue colony
It is a structural steel sheet for welding excellent in brittle fracture propagation arrestability , characterized by having an average aspect ratio (ratio of major axis / minor axis) of 4 or more.
【０００６】更に本発明は、鋼片もしくは鋼板を、最終
製品板厚をｔ、圧延中途中急冷時の板厚をｔ0 とした
時、表層から少なくとも板厚方向に０．１×ｔ0 ／ｔ
（mm）以上の領域を急冷して、その後、当該表層部がＡ
ｃ3 以下の温度から圧延を開始もしくは再開し、前記表
層部が内部の顕熱で昇温中に圧延を行い、仕上圧延終了
温度を（Ａｃ3 −１５０）℃からＡｃ 3 ℃の範囲とし
て、表層部から少なくとも０．１mm以上の範囲にわたっ
て平均円相当径で３μｍ以下のフェライト粒径からな
り、且つそのフェライト粒径の同一結晶方位を有する集
合組織のコロニーの平均アスペクト比（長径／短径の
比）が４以上の組織をうることを特徴とする脆性破壊伝
播停止特性の優れた溶接用構造用鋼板の製造方法であ
る。Further, according to the present invention, when the thickness of a slab or a steel plate is defined as t, the thickness of the final product is defined as t, and the thickness during quenching during rolling is defined as t 0 , at least 0.1 × t 0 / t
(Mm) or more, quenching the area
Rolling is started or restarted from a temperature of c 3 or less, and the surface layer is rolled while the internal sensible heat raises the temperature, and the finish rolling end temperature is set to a range from (Ac 3 −150) ° C. to Ac 3 ° C. The average aspect ratio (major axis / minor axis diameter) of a colony of a texture having a ferrite grain size of 3 μm or less in average circle equivalent diameter over a range of at least 0.1 mm from the surface layer portion and having the same crystal orientation of the ferrite grain size. The present invention is a method for producing a structural steel sheet for welding having excellent brittle fracture arrestability, characterized by obtaining a structure having a ratio of 4 or more.
【０００７】更に本発明は上記製造方法において、仕上
圧延終了後冷却速度が５℃／sec 以上で加速冷却し、必
要に応じて５５０℃以下で焼戻し熱処理を適用するもの
である。本発明において、対象とする構造用鋼は、例え
ば特公昭５８−１４８４９号公報に記載され、次記する
ように、通常の構造用鋼が所要の材質を得るために、従
来から当業分野での活用で確認されている作用・効果の
関係を基に定めている添加元素の種類と量を同様に使用
して同等の作用と効果が得られる。従ってこれ等の元素
を含む鋼を本発明は対象鋼とするものである。Further, in the present invention, in the above-mentioned manufacturing method, after the finish rolling, accelerated cooling is performed at a cooling rate of 5 ° C./sec or more, and a tempering heat treatment is applied at 550 ° C. or less as necessary. In the present invention, the structural steel of interest is described in, for example, Japanese Patent Publication No. 58-14849, and as described below, in order to obtain a required material from ordinary structural steel, it has been conventionally used in the art. The same operation and effect can be obtained by using the type and amount of the additional element determined based on the relation of the operation and effect confirmed by the use of the same. Accordingly, the present invention includes steels containing these elements as target steels.
【０００８】これ等の各成分元素とその添加理由は以下
の通りである。Ｃは鋼の強度を向上する有効な成分とし
て０．０２％以上含有するものであるが、０．２０％を
超える過剰な含有量では、２相域圧延時の変形抵抗を増
して圧延を困難にするばかりか、溶接部に島状マルテン
サイトを析出し、鋼の靭性を著しく劣化させるので、
０．０２％〜０．２０％に規制する。[0008] These constituent elements and the reasons for their addition are as follows. C contains 0.02% or more as an effective component for improving the strength of steel, but an excessive content exceeding 0.20% increases the deformation resistance during two-phase rolling, making it difficult to roll. As well as precipitation of island-like martensite in the weld, significantly deteriorating the toughness of the steel,
Restrict to 0.02% to 0.20%.
【０００９】Ｓｉは溶鋼の脱酸元素として必要であり、
且つ強度増加元素として有用であるが、１．０％を超え
ると鋼の加工性が低下し、溶接部の靭性が劣化し、０．
０１％未満では脱酸効果が不十分なため、０．０１〜
１．０％に規制する。Si is necessary as a deoxidizing element of molten steel,
Further, it is useful as a strength increasing element, but if it exceeds 1.0%, the workability of the steel deteriorates, the toughness of the welded part deteriorates, and
If it is less than 01%, the deoxidizing effect is insufficient, so
Regulate to 1.0%.
【００１０】Ｍｎは鋼材の強度を向上する成分として
０．３％以上の含有量が必要であるが、Ｍｎは変態温度
を下げるので、過剰の含有量は２相域圧延温度を下げ過
ぎ変形抵抗が上昇するので２．０％を上限とする。Mn must have a content of 0.3% or more as a component for improving the strength of the steel material. However, since Mn lowers the transformation temperature, an excessive content lowers the rolling temperature in the two-phase region so that the deformation resistance becomes too low. Rises to 2.0%.
【００１１】Ａｌ及びＮはＡｌ窒化物による鋼の微細化
の他、圧延過程での固溶、析出による鋼の結晶方位の整
合及び再結晶のために添加するが、添加量が少ない時は
効果がなく、過剰の添加は鋼の靭性を劣化させるので、
Ａｌは０．００１〜０．２０％に、Ｎは０．０２０％以
下とする。Al and N are added for the purpose of refining steel by solid solution and precipitation in the rolling process, in addition to refining steel by Al nitride, but it is effective when the addition amounts are small. And excessive addition degrades the toughness of the steel,
Al is set to 0.001 to 0.20%, and N is set to 0.020% or less.
【００１２】以上が本発明が対象とする鋼の基本成分で
あるが、母材強度の上昇或いは、継手靭性の向上の目的
のため、要求される性質に応じて、合金元素を添加する
場合は、変態温度を下げ過ぎると２相域での変形抵抗が
増し、圧延が困難になるので、添加する合金としてはＮ
ｉ，Ｃｒ，Ｍｏ，Ｃｕ，Ｗ，Ｐ，Ｃｏ，Ｖ，Ｎｂ，Ｔ
ｉ，Ｚｒ，Ｔａ，Ｈｆ，希土類元素，Ｙ，Ｃａ，Ｍｇ，
Ｔｅ，Ｓｅ，Ｂの１種類以上が使用できるが、その添加
量は合計で４．５％以下に規制する。The above are the basic components of the steel targeted by the present invention. For the purpose of increasing the strength of the base material or improving the toughness of the joint, when the alloy element is added according to the required properties, If the transformation temperature is too low, the deformation resistance in the two-phase region increases, and rolling becomes difficult.
i, Cr, Mo, Cu, W, P, Co, V, Nb, T
i, Zr, Ta, Hf, rare earth element, Y, Ca, Mg,
One or more of Te, Se, and B can be used, but the total amount thereof is regulated to 4.5% or less.
【００１３】本発明者らは前記従来技術が有する課題を
解決するために、一般的な構造用鋼を用いて種々の実験
・検討を繰り返した。その過程で、Ｋｃａ特性が優れて
いるにもかかわらずＮＤＴ特性が悪いのは、鋼板表層の
極限られた領域の組織に起因することを突き止め、鋼板
表面の組織を改質するだけでＮＤＴ特性とＫｃａ特性を
容易に両立しうる可能性を見いだした。The present inventors have repeated various experiments and studies using general structural steel in order to solve the problems of the above-mentioned prior art. In the process, it was found that the reason why the NDT characteristics were poor despite the excellent Kca characteristics was caused by the structure of the extremely limited region of the steel sheet surface layer. It has been discovered that Kca characteristics can be easily compatible.
【００１４】本発明者らは更に表層組織がＮＤＴ特性に
及ぼす影響の定量化、極表層組織の改質方法を検討する
ため、Ｃ：０．０２〜０．１５％、Ｓｉ：０．１５〜
０．２５％、Ｍｎ：０．８〜１．６％、Ａｌ：０．０１
〜０．０５％を有する一般的な構造用鋼を用いて、種々
の実験を行った。The present inventors further quantified the influence of the surface layer structure on the NDT characteristics and studied a method of modifying the very surface layer structure, in which C: 0.02 to 0.15%, Si: 0.15%
0.25%, Mn: 0.8 to 1.6%, Al: 0.01
Various experiments were performed using a general structural steel having ~ 0.05%.
【００１５】Ｋｃａ特性を向上させるために、未再結晶
域圧延を６０％以上実施した鋼板のＫｃａ特性とＮＤＴ
特性を調査したところ、Ｋｃａ値が６００kgｆ／mm1.5
以上の性能を示す温度でも落重試験では破断の結果を示
し、ＮＤＴ温度はそれよりも高温側となった。In order to improve the Kca characteristic, the Kca characteristic and NDT of a steel sheet which has been subjected to rolling in the non-recrystallization zone by 60% or more.
When the characteristics were investigated, the Kca value was 600 kgf / mm 1.5
Even at the temperature showing the above performance, the dropping test showed a fracture result, and the NDT temperature was higher than that.
【００１６】この実験結果を詳細に調べた結果、未再結
晶温度域圧延中に鋼板表面の温度はＡｒ3 点以下とな
り、一部変態したフェライトが圧延により歪を受けて加
工フェライトとなり、且つ一部の加工フェライトは圧延
によって得られた歪エネルギーを駆動力として異常粒成
長を起し、加工フェライト＋異常粗粒フェライトのきわ
めて靭性の劣化した組織が表層部に生成したためである
ことを知見した。As a result of examining the experimental results in detail, during the rolling in the non-recrystallization temperature range, the temperature of the steel sheet surface becomes lower than the Ar 3 point. It was found that the processed ferrite in the portion caused abnormal grain growth by using the strain energy obtained by rolling as a driving force, and a very deteriorated toughness structure of the processed ferrite and the abnormal coarse ferrite was formed in the surface layer.
【００１７】そこで、この靭性劣化相を表面研削し、こ
の靭性劣化相がＮＤＴ特性劣化に及ぼす影響を定量化し
た。その結果を図１に示す。靭性劣化相が０．１mmでも
存在するとＮＤＴ特性は劣化することが明らかとなり、
ＮＤＴ特性を向上させるためには表層の０．１mmレベル
の極限られた組織の改質がきわめて重要であることを知
見した。Therefore, the surface of the deteriorated toughness phase was ground, and the effect of the deteriorated toughness phase on the NDT characteristic deterioration was quantified. The result is shown in FIG. It becomes clear that the NDT characteristic is deteriorated when the toughness deteriorated phase exists even at 0.1 mm.
It has been found that in order to improve the NDT characteristics, it is extremely important to modify a very limited structure of the surface layer at a level of 0.1 mm.
【００１８】ところが、Ｋｃａ特性を向上させるために
は、低温域での圧延が重要であり、その結果として鋼板
表面の温度がより低温化してかような靭性劣化相が形成
してしまうのである。そこで、圧延中に鋼板表面を水冷
し、Ａｒ1 点以下とすることで一旦フェライト変態させ
てしまい、冷却によっても殆ど温度の低下しない板厚中
心部の顕熱を利用して、表層部のフェライト組織を昇温
させながら更に圧延を行い、表層部のみ３μｍ以下の超
細粒組織として、その表層改質組織の厚みを表面研削し
ながら変化させ、ＮＤＴ特性とその厚みの関係を定量化
した。However, in order to improve the Kca characteristics, it is important to perform rolling in a low temperature range, and as a result, a toughness-deteriorated phase is formed as if the surface temperature of the steel sheet was further lowered. Therefore, during rolling, the surface of the steel sheet is water-cooled, and the ferrite transformation is performed once by setting the Ar temperature to 1 point or less. The structure was further rolled while raising the temperature, and the thickness of the surface-modified structure was changed while the surface was ground as an ultrafine grain structure of 3 μm or less only in the surface layer, and the relationship between the NDT characteristics and the thickness was quantified.
【００１９】その結果を図２に示す。表層改質組織が
０．１mm以上あればＮＤＴ特性は１０℃以上向上し、且
つ２mm以上あってもその結果は殆ど変わらないことが明
らかとなった。FIG. 2 shows the results. It became clear that the NDT characteristics were improved by 10 ° C. or more if the surface layer modified structure was 0.1 mm or more, and the results were hardly changed even if the surface modified structure was 2 mm or more.
【００２０】この表層改質組織は、粒径が３μｍ以下と
細粒な上、集合組織が発達しているので容易にセパレー
ションを生じるために塑性域の小さな低温域でも脆性破
壊しない組織である。この集合組織の存在を規定するも
のとして、結晶方位によって酸化皮膜の厚みの変化を利
用したテンパーカラー法を適用して同一結晶方位を有す
るコロニーを現出させ、その平均アスペクト比（長径／
短径の比）と板厚方向の限界破壊応力を評価し、平均ア
スペクト比が４以上であればセパレーション発生させる
のに必要な板厚方向の限界破壊応力の低下を実現しうる
ことを見いだした。この時、板厚内部は未再結晶域圧延
温度で圧延されるので十分なＫｃａ特性が確保できた。The surface-modified structure is a structure that is fine, having a grain size of 3 μm or less, and has a developed texture, so that separation is easily generated, so that it is not brittle fracture even in a low-temperature region having a small plastic region. To define the existence of this texture, colonies having the same crystal orientation are revealed by applying a temper color method utilizing a change in the thickness of the oxide film depending on the crystal orientation, and the average aspect ratio (major axis / major axis /
The ratio of the minor axis) and the critical fracture stress in the thickness direction are evaluated. If the average aspect ratio is 4 or more, the critical fracture stress in the thickness direction required to cause separation is reduced. I found something wrong. At this time, since the inside of the sheet thickness was rolled at the unrecrystallized region rolling temperature, sufficient Kca characteristics could be secured.
【００２１】このことから、ＮＤＴ特性とＫｃａ特性を
両立させる鋼板としては、表層から少なくとも０．１mm
以上、２mmまでを平均円相当径が３μｍ以下のフェライ
ト粒からなり、且つそのフェライト粒の同一結晶方位を
有する集合組織のコロニーの平均アスペクト比（長径／
短径の比）が４以上の組織を達成すればよいことを見い
だした。Therefore, a steel sheet satisfying both the NDT characteristic and the Kca characteristic should be at least 0.1 mm from the surface layer.
Up to 2 mm, the average aspect ratio of the colonies of the textured colonies composed of ferrite grains having an average equivalent circle diameter of 3 μm or less and having the same crystal orientation of the ferrite grains (long diameter /
It has been found that it is only necessary to achieve a tissue having a ratio of minor axis of 4 or more.
【００２２】[0022]
【実施例】実施例の供試鋼の成分を表１に、製造条件及
び得られた材質を表２に比較例と共に示す。EXAMPLES The components of the test steels of the examples are shown in Table 1, and the production conditions and the obtained materials are shown in Table 2 together with comparative examples.
【００２３】[0023]
【表１】 [Table 1]
【表２】 [Table 2]
【表３】 本発明例の試験番号１〜１２及び比較例の試験番号２
１，２２，２４は、粗圧延後に冷却を適用し、鋼板表層
部をＡｒ1 点以下にしてフェライト変態させたものであ
るが、比較例の試験番号２１，２２は、冷却速度が遅か
ったため、鋼板全体の温度が低下し、冷却後の圧延が昇
温加工とはならなかった。また、比較例の試験番号２４
は、冷却後経過時間が長すぎて冷却後の圧延の所要条件
を満たすことができなかった。その為、比較例である試
験番号２１，２２，２４の表層部の組織は細粒化しなか
った。[Table 3] Test Nos. 1 to 12 of the present invention and Test No. 2 of the comparative example
Nos. 1, 22, and 24 were obtained by applying cooling after rough rolling, and performing ferrite transformation by setting the surface layer portion of the steel sheet to one point or less of Ar. Test numbers 21 and 22 of Comparative Examples had slow cooling rates. The temperature of the entire steel sheet decreased, and the rolling after cooling did not become a temperature raising process. In addition, test number 24 of the comparative example
However, the elapsed time after cooling was too long to meet the required conditions for rolling after cooling. Therefore, the structure of the surface layer portion of Test Nos. 21, 22, and 24, which are comparative examples, did not become fine.
【００２４】これらの比較例の材質は、板厚全体が二相
域圧延となってしまい、母材靭性であるｖＴｒｓも劣化
し、ＮＤＴ特性、アレスト特性ともに劣化した。また、
比較例の試験番号１３〜２０，２３は、いずれも粗圧延
後の冷却は実施しておらず、仕上げ圧延温度が板厚平均
でＡｒ3 点直上を狙っていたため、表面の温度はＡｒ3
点以下となり、ここでの圧延によりフェライトの異常粒
成長が生じ、その結果表層部のフェライト粒が粗大化し
た。In the materials of these comparative examples, the entire plate thickness was subjected to two-phase rolling, and the vTrs, which is the base material toughness, also deteriorated, and both the NDT characteristics and the arrest characteristics deteriorated. Also,
Test No. Comparative Example 13～20,23 are both not cooling after the rough rolling is conducted, since the finish rolling temperature was aimed directly above Ar 3 point in the thickness average, the temperature of the surface is Ar 3
Point, and rolling at this point caused abnormal ferrite grain growth, resulting in coarse ferrite grains in the surface layer.
【００２５】従って、これらの比較例である試験番号１
３〜２０，２３は仕上げ圧延により板厚中央部の組織は
細粒化してアレスト性能としてＫｃａ＝６００kgｆ／mm
1.5 を示す温度は−５０℃と良好なものの、ＮＤＴ特性
は−６０℃に達していない。これに対し、本発明例の試
験番号１〜１２の材質は、表２に示す通り、所要の製造
条件を満足し、目標の強度・靭性を満足すると共に、本
発明の狙いであるＮＤＴ温度が−６０℃以上を示し、ア
レスト性能であるＫｃａ＝６００kgｆ／mm1. 5 を示す温
度も十分な特性であった。Accordingly, Test No. 1 of these comparative examples was used.
In Nos. 3 to 20, 23, the structure in the central part of the sheet thickness was refined by finish rolling, and Kca = 600 kgf / mm as arrest performance.
Although the temperature indicating 1.5 is as good as −50 ° C., the NDT characteristic does not reach −60 ° C. On the other hand, as shown in Table 2, the materials of Test Examples 1 to 12 of the present invention satisfy the required manufacturing conditions, satisfy the target strength and toughness, and have the NDT temperature which is the target of the present invention. It indicates -60 ° C. or higher, a temperature showing a Kca = 600kgf / mm 1. 5 is arrest performance were satisfactory characteristics.
【００２６】[0026]
【発明の効果】本発明は上記した手段を用いて上記した
作用を利用したので、粗圧延後、表層部のみ冷却してＡ
ｒ1 点以下とした後板厚内部の顕熱により復熱しながら
圧延を実施すれば、ＮＤＴ特性を劣化させる表層部の脆
化組織を生成させることなく、板厚中心部に十分な未再
結晶域圧延を実施したため、アレスト性能であるＮＤＴ
特性とＫｃａ特性を両立することを可能とするもので、
その工業的効果が大きい。According to the present invention, since the above-mentioned action is utilized by using the above-mentioned means, after rough rolling, only the surface layer portion is cooled and A
If rolling is performed while recuperating by the sensible heat inside the rear plate thickness below r 1 point, sufficient unrecrystallized in the center of the plate thickness without generating a brittle structure in the surface layer that degrades the NDT characteristics. NDT, which has arrest performance,
It is possible to achieve both characteristics and Kca characteristics,
Its industrial effect is great.
【図１】（ａ）は加工フェライト及び粗粒フェライトを
含有する組織の存在する靭性劣化相の表層からの厚み
と、当該靭性劣化相によるＮＤＴ温度の劣化代の図表で
ある。（ｂ）は靭性劣化相の模式図である。FIG. 1 (a) is a chart of a thickness from a surface layer of a toughness deteriorated phase in which a structure containing a processed ferrite and a coarse ferrite is present, and a deterioration amount of an NDT temperature due to the toughness deteriorated phase. (B) is a schematic diagram of a toughness deterioration phase.
【図２】フェライト粒が３μｍ以下で集合組織コロニー
のアスペクト比が４以上の組織からなる表層改質相の厚
みと、ＮＤＴ特性の向上代の図表である。FIG. 2 is a chart showing the thickness of a surface-modified phase composed of a structure in which ferrite grains are 3 μm or less and the aspect ratio of a textured colony is 4 or more, and the amount of improvement in NDT characteristics.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 吉川 宏 大分県大分市大字西ノ洲１番地 新日本 製鐵株式会社 大分製鐵所内 (56)参考文献 特開 平５−148541（ＪＰ，Ａ) 特開 平５−9651（ＪＰ，Ａ) 特開 平３−64413（ＪＰ，Ａ) 特開 昭63−243220（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Yoshikawa 1 Nishinosu, Oita, Oita City, Oita Prefecture Nippon Steel Corporation Oita Works (56) References JP-A-5-148541 (JP, A) JP JP-A-5-9651 (JP, A) JP-A-3-64413 (JP, A) JP-A-63-243220 (JP, A)
Claims (4)
にわたり平均円相当径で３μｍ以下のフェライト粒から
なり、且つそのフェライト粒の同一結晶方位を有する集
合組織のコロニーの平均アスペクト比（長径／短径の
比）が４以上の組織により構成されることを特徴とする
脆性破壊伝播停止特性の優れた溶接用構造用鋼板。1. An average aspect ratio (major axis / short axis) of a textured colony composed of ferrite grains having an average equivalent circle diameter of 3 μm or less over a range of at least 0.1 mm from the surface layer and having the same crystal orientation of the ferrite grains. A steel sheet for welding structural use having excellent brittle fracture arrestability, characterized in that the steel sheet has a structure having a diameter ratio of 4 or more.
ｔ、圧延中途中急冷時の板厚をｔ0 とした時、表層から
少なくとも板厚方向に０．１×ｔ0 ／ｔ（mm）以上の領
域を急冷して、その後、当該表層部がＡｃ3 以下の温度
から圧延を開始もしくは再開し、前記表層部が内部の顕
熱で昇温中に圧延を行い、仕上圧延終了温度を（Ａｃ3
−１５０）℃からＡｃ 3 ℃の範囲として、表層部から少
なくとも０．１mm以上の範囲にわたって平均円相当径で
３μｍ以下のフェライト粒径からなり、且つそのフェラ
イト粒径の同一結晶方位を有する集合組織のコロニーの
平均アスペクト比（長径／短径の比）が４以上の組織を
うることを特徴とする脆性破壊伝播停止特性の優れた溶
接用構造用鋼板の製造方法。2. When a slab or a steel sheet is defined as t, the thickness of the final product is t, and the thickness during rapid cooling during rolling is t 0 , at least 0.1 × t 0 / t (mm) in the thickness direction from the surface layer. ) Rapidly quenching the above region, thereafter, the surface portion starts or restarts rolling from a temperature of Ac 3 or less, performs rolling while the surface portion is heated by internal sensible heat, and finish rolling finish temperature (Ac 3
-150) as a range of Ac 3 ° C. from ° C., consists of the following ferrite grain size 3μm in average circle equivalent diameter over at least 0.1mm or more in the range of from the surface layer portion, and the texture having the same crystal orientation of the ferrite grain size Colony of
A method for producing a structural steel sheet for welding excellent in brittle fracture arrestability, characterized in that a structure having an average aspect ratio (ratio of major axis / minor axis) of 4 or more is obtained.
上で加速冷却することを特徴とする請求項２記載の脆性
破壊伝播停止特性の優れた溶接用構造用鋼板の製造方
法。3. The method for producing a steel sheet for welding according to claim 2, wherein the cooling rate is 5 ° C./sec or more after the completion of the finish rolling.
上で加速冷却し、更に焼戻し熱処理をすることを特徴と
する請求項２記載の脆性破壊伝播停止特性の優れた溶接
用構造用鋼板の製造方法。4. The steel sheet for welding according to claim 2, wherein the steel sheet is subjected to accelerated cooling at a cooling rate of 5 ° C./sec or more after finish rolling, and further to a tempering heat treatment. Manufacturing method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3315650A JP2633757B2 (en) | 1991-11-29 | 1991-11-29 | Structural steel plate for welding with excellent brittle fracture arrestability and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3315650A JP2633757B2 (en) | 1991-11-29 | 1991-11-29 | Structural steel plate for welding with excellent brittle fracture arrestability and method of manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05148542A JPH05148542A (en) | 1993-06-15 |
| JP2633757B2 true JP2633757B2 (en) | 1997-07-23 |
Family
ID=18067925
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3315650A Expired - Fee Related JP2633757B2 (en) | 1991-11-29 | 1991-11-29 | Structural steel plate for welding with excellent brittle fracture arrestability and method of manufacturing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2633757B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4058097B2 (en) | 2006-04-13 | 2008-03-05 | 新日本製鐵株式会社 | High strength steel plate with excellent arrestability |
| JP5713135B1 (en) | 2013-11-19 | 2015-05-07 | 新日鐵住金株式会社 | steel sheet |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63243220A (en) * | 1987-03-31 | 1988-10-11 | Nippon Steel Corp | Production of thick steel plate having excellent toughness to center layer thereof |
| JPH0364413A (en) * | 1989-07-31 | 1991-03-19 | Kobe Steel Ltd | Production of high tensile steel excellent in brittle fracture propagation arresting property |
| JPH059651A (en) * | 1991-07-05 | 1993-01-19 | Kobe Steel Ltd | Steel plate having excellent property of stopping propagation of brittle fracture and its production |
-
1991
- 1991-11-29 JP JP3315650A patent/JP2633757B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05148542A (en) | 1993-06-15 |
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