JPH07278653A - Production of steel excellent in cold toughness on welding heat affected zone - Google Patents
Production of steel excellent in cold toughness on welding heat affected zoneInfo
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- JPH07278653A JPH07278653A JP6075599A JP7559994A JPH07278653A JP H07278653 A JPH07278653 A JP H07278653A JP 6075599 A JP6075599 A JP 6075599A JP 7559994 A JP7559994 A JP 7559994A JP H07278653 A JPH07278653 A JP H07278653A
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は小入熱溶接から中入熱溶
接の熱影響部（ＨＡＺ）の低温靱性が優れた鋼の製造法
に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing steel having excellent low temperature toughness in the heat affected zone (HAZ) of small heat input welding to medium heat input welding.
【０００２】[0002]
【従来の技術】低合金鋼のＨＡＺ靱性は、数多くの技術
が開発実用化されている。特に優れている技術として、
Ｔｉ酸化物とＴｉＮを微細分散した鋼（特開昭６３−２
１０２３５号公報）が知られている。この鋼では、溶接
後の冷却過程でγ粒内のＴｉ酸化物よりフェライトを発
生させてミクロ組識を微細化して靱性を向上させてい
る。しかしながら、１４００℃以上の温度にさらされる
溶融線近傍のごく狭い領域では、溶接熱により酸化物は
溶解しないが、ＴｉＮが溶解し、その後の溶接熱でＴｉ
Ｃとして生成するため、靭性の劣化を生じる。この様
に、局部的な脆化領域が存在した場合、その悪影響はシ
ャルピー試験では少ないが、脆性亀裂の発生特性である
ＣＴＯＤ試験では大きな劣化が認められる。また、実構
造物に近い脆性亀裂の伝播停止特性を評価する大型試験
（溶接部の混成ＥＳＳＯ試験等）でも、脆性亀裂が局部
的な脆化領域を選択的に伝播するため大きな劣化が認め
られる。2. Description of the Related Art Regarding the HAZ toughness of low alloy steels, many techniques have been developed and put into practical use. As a particularly excellent technology,
Steel in which Ti oxide and TiN are finely dispersed (Japanese Patent Laid-Open No. 63-2
No. 10235) is known. In this steel, ferrite is generated from the Ti oxide in the γ grains in the cooling process after welding to refine the microstructure and improve the toughness. However, in a very narrow region near the melting line exposed to a temperature of 1400 ° C. or higher, the oxide does not melt due to welding heat, but TiN melts and Ti
Since it is generated as C, toughness is deteriorated. As described above, when a local embrittlement region exists, its adverse effect is small in the Charpy test, but a large deterioration is recognized in the CTOD test, which is a brittle crack initiation characteristic. Further, even in a large-scale test (e.g., mixed ESSO test of welds) that evaluates the propagation stop property of a brittle crack close to an actual structure, a large deterioration is recognized because the brittle crack selectively propagates in a localized embrittlement region. .
【０００３】従って、この鋼の多パス溶接部の脆性亀裂
発生特性（ＣＴＯＤ特性）や伝播停止特性には限界があ
り、ＣＴＯＤ特性や伝播停止特性は−３０℃程度が限界
とされていた。この様に現在のところ小〜中入熱溶接に
於いて、−４０℃以下で良好なＣＴＯＤ特性や伝播停止
特性が満足出来る鋼の製造技術は存在せず、新知見に基
づいた新しい鋼の開発が強く望まれていた。Therefore, the brittle crack initiation characteristic (CTOD characteristic) and the propagation stopping characteristic of the multipass welded portion of this steel are limited, and the CTOD characteristic and the propagation stopping characteristic are limited to about -30 ° C. As described above, at the present time, in the small to medium heat input welding, there is no steel manufacturing technology capable of satisfying favorable CTOD characteristics and propagation stopping characteristics at -40 ° C or lower, and development of new steel based on new knowledge. Was strongly desired.
【０００４】[0004]
【発明が解決しようとする課題】本発明は小〜中入溶接
においてＨＡＺ靭性（特にＣＴＯＤ特性、伝播停止特
性）の極めて優れた鋼を安価に製造する技術を提供する
ものである。本発明により製造した鋼は、溶接時に溶融
線近傍においてもＨＡＺ組織が微細化し、ＨＡＺの全域
で優れた低温靱性を示す。DISCLOSURE OF THE INVENTION The present invention provides a technique for inexpensively producing steel having excellent HAZ toughness (particularly CTOD characteristics and propagation stopping characteristics) in small to medium penetration welding. The steel produced according to the present invention has a fine HAZ structure even near the fusion line during welding, and exhibits excellent low temperature toughness throughout the HAZ.
【０００５】[0005]
【課題を解決するための手段】本発明の要旨は （１） 重量％で、Ｃ： ０．０４〜０．１２％、Ｓ
ｉ： ０．４％以下、Ｍｎ： ０．８〜２．０％、Ｐ：
０．０２０％以下、Ｓ： ０．００５％以下、Ａ
ｌ： ０．００４％以下、Ｎｉ： １．０〜４．０％、
Ｔｉ： ０．００５〜０．０１２％、Ｎ： ０．００
１５〜０．００６０％、Ｏ： ０．００１０〜０．０
０３０％を含有し、Ｄ1 *＝0.316Ｃ1/2(1＋0.7Ｓi)(0.35
＋4.1Ｍn)(1＋0.36Ｎi)(1＋0.37Ｃu)が０．８〜１．２
の範囲で、且つ−0.015％≦［Ｔi］−２［Ｏ］−3.4
［Ｎ］≦０％を満足し、残部が鉄および不可避的不純物
からなる実質的にＡｌを含有しない鋼を連続鋳造法によ
ってスラブとし、これを１１００℃以下の温度で再加熱
後、加工熱処理することを特徴とする溶接熱影響部の低
温靱性が優れた鋼の製造法。The gist of the present invention is (1) by weight, C: 0.04 to 0.12%, S
i: 0.4% or less, Mn: 0.8 to 2.0%, P:
0.020% or less, S: 0.005% or less, A
1: 0.004% or less, Ni: 1.0 to 4.0%,
Ti: 0.005 to 0.012%, N: 0.00
15-0.0060%, O: 0.0010-0.0
Containing 030%, D 1 * = 0.316C 1/2 (1 + 0.7Si) (0.35
+ 4.1Mn) (1 + 0.36Ni) (1 + 0.37Cu) is 0.8 to 1.2
In the range of -0.015% ≤ [Ti] -2 [O] -3.4
A steel which satisfies [N] ≦ 0% and the balance of which is iron and unavoidable impurities and which does not substantially contain Al is made into a slab by a continuous casting method, which is reheated at a temperature of 1100 ° C. or lower and then thermomechanically treated. A method for producing steel having excellent low temperature toughness in the heat-affected zone of welding.
【０００６】（２） 重量％で、Ｃ： ０．０４〜
０．１２％、Ｓｉ： ０．４％以下、Ｍｎ： ０．８〜
２．０％、Ｐ： ０．０２０％以下、Ｓ： ０．０
０５％以下、Ａｌ： ０．００４％以下、Ｎｉ： １．
０〜４．０％、Ｔｉ： ０．００５〜０．０１２％、
Ｎ： ０．００１５〜０．００６０％、Ｏ： ０．
００１０〜０．００３０％及び、Ｃｕ： ０．０５〜
０．５％、Ｎｂ： ０．００５〜０．０１５％の一種ま
たは二種を含有し、Ｄ1 *＝0.316Ｃ1/2(1＋0.7Ｓi)(0.35
＋4.1Ｍn)(1＋0.36Ｎi)(1＋0.37Ｃu)が０．８〜１．２
の範囲で、且つ−0.015％≦［Ｔi］−２［Ｏ］−3.4
［Ｎ］≦０％を満足し、残部が鉄および不可避的不純物
からなる実質的にＡｌを含有しない鋼を連続鋳造法によ
ってスラブとし、これを１１００℃以下の温度で再加熱
後、加工熱処理することを特徴とする溶接熱影響部の低
温靱性が優れた鋼の製造法にある。(2) C: 0.04% by weight.
0.12%, Si: 0.4% or less, Mn: 0.8-
2.0%, P: 0.020% or less, S: 0.0
05% or less, Al: 0.004% or less, Ni: 1.
0-4.0%, Ti: 0.005-0.012%,
N: 0.0015 to 0.0060%, O: 0.
0010-0.0030% and Cu: 0.05-
0.5%, Nb: 0.005 to 0.015% of one or two kinds, and D 1 * = 0.316C 1/2 (1 + 0.7Si) (0.35
+ 4.1Mn) (1 + 0.36Ni) (1 + 0.37Cu) is 0.8 to 1.2
In the range of -0.015% ≤ [Ti] -2 [O] -3.4
A steel which satisfies [N] ≦ 0% and the balance of which is iron and unavoidable impurities and which does not substantially contain Al is made into a slab by a continuous casting method, which is reheated at a temperature of 1100 ° C. or lower and then thermomechanically treated. This is a method for producing steel having excellent low temperature toughness in the heat-affected zone of welding.
【０００７】本発明者らの研究によれば、脆性亀裂の発
生特性（ＣＴＯＤ特性）や脆性亀裂の伝播停止特性が問
題となるような小〜中熱溶接部のＨＡＺ脆性は、（１）
結晶粒のサイズ、（２）高炭素マルテンサイト
（Ｍ*）、上部ベイナイト（Ｂｕ）などの硬化相の分散
状態、（３）析出硬化状態、（４）Ｎｉ添加によるマト
リックス（地）の靱化、（５）粒界脆化の有無、（６）
元素のミクロ偏析など種々の冶金的要因に支配される。According to the research conducted by the present inventors, the HAZ brittleness of small-to-medium heat welds, which causes problems of brittle crack initiation characteristics (CTOD characteristics) and brittle crack propagation stopping characteristics, is (1)
Size of crystal grains, (2) dispersion state of hardening phase such as high carbon martensite (M * ) and upper bainite (Bu), (3) precipitation hardening state, (4) toughening of matrix (ground) by addition of Ni , (5) Presence or absence of grain boundary embrittlement, (6)
It is governed by various metallurgical factors such as elemental microsegregation.
【０００８】このため、本発明者らは、鋼中に微細に
酸化物を分散させ、結晶粒の微細化、Ｍ*やＢｕなど
硬化相の生成抑制と分散化のため、最適な鋼成分（焼入
性の限定Ｄ1 *０．８〜１．２）や酸化物微細分散による
結晶粒の微細化、ＨＡＺ靱性を劣化させる析出硬化の
原因となるＴｉＣの生成を抑制するため、Ｔｉの適正量
を限定し、その後生成するＴｉＣを極力少なくするた
め、適正なＴｉ，Ｏ，Ｎ量のバランス（Ｔｉ：０．００
５〜０．０１２％、−０．０１５％≦［Ｔi］−２
［Ｏ］−３．４［Ｎ］≦０％）が重要であることを見い
だした。上記３項目とともに、マトリックスの靱化の
ため相当量のＮｉの添加、および、粒界脆化やミクロ
偏析の抑制のための不純物元素の低減。上記５項目につ
いて、適正な成分範囲や限定を実施することにより従来
にない良好なＣＴＯＤ特性と伝播停止特性を兼ね備えた
鋼の製造を可能にしたものである。Therefore, the present inventors have made it possible to disperse an oxide finely in the steel to refine the crystal grains, suppress the generation of hardened phases such as M * and Bu, and disperse the optimum steel components ( Hardness limit D 1 * 0.8 to 1.2), refinement of crystal grains due to oxide fine dispersion, and generation of TiC that causes precipitation hardening that deteriorates HAZ toughness are suppressed. In order to limit the amount of TiC and minimize the amount of TiC generated thereafter, an appropriate balance of Ti, O, and N (Ti: 0.00
5 to 0.012%, -0.015% ≤ [Ti] -2
It has been found that [O] -3.4 [N] ≦ 0%) is important. In addition to the above three items, addition of a considerable amount of Ni for toughening the matrix and reduction of impurity elements for suppressing grain boundary embrittlement and microsegregation. By making appropriate composition ranges and limits for the above-mentioned 5 items, it is possible to manufacture steel having both excellent CTOD characteristics and propagation stopping characteristics which have never been obtained.
【０００９】さらに、上記のＨＡＺ靱性要因のうち、本
発明鋼として重要なＴｉ，Ｏ，Ｎ量のバランスと相当量
のＮｉ（１．０〜４．０％）添加について詳細に説明す
る。すなわち、Ｔｉ量は０．００５％〜０．０１２％が
適正範囲で、Ｏ量は０．００１０〜０．００３０％が適
正範囲である。ＴｉやＯ量がこの範囲より多い場合は、
酸化物数が増加し、そのサイズも大きくなり、酸化物を
起点として脆性亀裂が発生し易くなる。また、この範囲
より少ない場合は、ミクロ組織微細化に有効な酸化物が
生成しないため、靱性は向上しない。Ｔｉ酸化物は溶鋼
の凝固中に優先して生成するが、酸素と結合しないＴｉ
はＮと結合し、ＴｉＮが生成する。ＴｉＮは溶接時の１
３５０℃以下の温度ではミクロ組織を微細化して靱性を
向上させるが、１４００℃を超える温度では溶解する。Further, among the above HAZ toughness factors, the balance of the amounts of Ti, O and N, which are important for the steel of the present invention, and the addition of a considerable amount of Ni (1.0 to 4.0%) will be described in detail. That is, the Ti amount is 0.005% to 0.012% in the proper range, and the O amount is 0.0010 to 0.0030% in the proper range. If the amount of Ti or O is larger than this range,
The number of oxides increases, the size also increases, and brittle cracks tend to occur starting from the oxide. On the other hand, if the amount is less than this range, an oxide effective for microstructural refinement is not formed, and the toughness is not improved. Ti oxide preferentially forms during solidification of molten steel, but does not combine with oxygen.
Combines with N to form TiN. TiN is 1 when welding
At a temperature of 350 ° C. or lower, the microstructure is refined to improve toughness, but at a temperature of higher than 1400 ° C., it melts.
【００１０】溶解したＴｉは冷却中に、ＴｉＮやＴｉＣ
を形成する。この場合Ｔｉ量が多く、Ｎ量が少ないとＴ
ｉＣが形成され靱性が著しく劣化する。従って、靱性を
劣化させないため、Ｎ量の規制とともにＴｉ，Ｏ，Ｎ量
のバランスを適正範囲に規制することが必要条件であ
り、Ｎ量は、０．００１５〜０．００６０％、Ｔｉ、
Ｏ、Ｎのバランスは、−０．０１５％≦［Ｔｉ］−２
［Ｏ］−３．４［Ｎ］≦０％が適合範囲である。During the cooling, the melted Ti becomes TiN or TiC.
To form. In this case, when the amount of Ti is large and the amount of N is small, T
iC is formed and the toughness is significantly deteriorated. Therefore, in order to prevent deterioration of toughness, it is necessary to regulate the balance of Ti, O, and N amounts within a proper range together with the N amount, and the N amount is 0.0015 to 0.0060%, Ti,
The balance of O and N is -0.015% ≤ [Ti] -2.
[O] -3.4 [N] ≦ 0% is the conforming range.
【００１１】また、ＨＡＺ靱性を改善するためのＮｉ添
加量について、従来は最小２．５％程度は必要とされて
いた。しかしながら、本発明鋼の場合、ミクロ組織を微
細化しているため、Ｎｉ添加量が１．０％以上でＨＡＺ
靱性改善効果が現われる。従って、本発明鋼では、Ｎｉ
量は最小１．０％が必須である。しかしながら、Ｎｉは
高価な合金であるため、４．０％を超えるとコスト増と
なり、特性は良好でも、経済性が失われるため、上限を
４．０％とした。In addition, the amount of Ni added for improving the HAZ toughness has conventionally been required to be at least about 2.5%. However, in the case of the steel of the present invention, since the microstructure is made finer, the HAZ is
The toughness improving effect appears. Therefore, in the steel of the present invention, Ni
A minimum amount of 1.0% is essential. However, since Ni is an expensive alloy, if it exceeds 4.0%, the cost increases, and although the characteristics are good, the economy is lost, so the upper limit was made 4.0%.
【００１２】本発明鋼の特徴であるＴｉ，Ｏ，Ｎ量バラ
ンスとＮｉ添加量の適正範囲について述べたが、たとえ
これらの要件が満たされていても、基本成分が適正でな
ければ、優れたＨＡＺ靱性は得られない。以下この点に
ついて説明する。Ｃの下限０．０４％は、母材及び溶接
部の強度の確保のため必要である。しかし、Ｃ量が多す
ぎると、母材の低温靱性や溶接性、ＨＡＺ靱性も劣化さ
せるので、上限を０．０１２％とした。Ｓｉは脱酸上、
鋼に含まれる元素であるが、多く添加すると溶接性、Ｈ
ＡＺ靱性が劣化するため、上限を０．４％に限定した。
ＨＡＺ靱性を改善する観点から０．１５％以下が望まし
い。Although the balance of Ti, O, N content and the proper range of Ni content, which are characteristics of the steel of the present invention, have been described, even if these requirements are satisfied, if the basic components are not proper, it is excellent. HAZ toughness cannot be obtained. This point will be described below. The lower limit of 0.04% of C is necessary to secure the strength of the base material and the welded portion. However, if the amount of C is too large, the low temperature toughness, weldability, and HAZ toughness of the base material deteriorate, so the upper limit was made 0.012%. Si is deoxidized,
It is an element contained in steel, but if added in large quantities, it has weldability and
Since the AZ toughness deteriorates, the upper limit was limited to 0.4%.
From the viewpoint of improving the HAZ toughness, 0.15% or less is desirable.
【００１３】Ｍｎは強度、靱性を確保するため不可欠な
元素であり、その下限は０．８％である。Ｍｎはγ粒界
に生成する粗大な初析フェライトを防止しＨＡＺ靱性改
善に効果があるがＭｎが多すぎると溶接性、ＨＡＺ靭性
を劣化させるので上限を２．０％とした。本発明鋼に於
いて不純物であるＰ、Ｓをそれぞれ０．０２０％、０．
００５％以下とした理由は母材、溶接部の低温靱性をよ
り一層向上させるためである。Ｐの低減はＨＡＺにおけ
る粒界破壊を減少させ、Ｓの低減は粒界フェライトの生
成を抑制する傾向がある。Ａｌは一般に脱酸上鋼に含ま
れる元素であるが、本発明鋼では好ましくない元素であ
り、その上限を０．００４％とした。これはＡｌが鋼中
に含まれているとＴｉより早くＯと結合しＴｉ酸化物が
生成しないためである。Mn is an essential element for ensuring strength and toughness, and its lower limit is 0.8%. Mn has the effect of preventing coarse proeutectoid ferrite generated at γ grain boundaries and improving the HAZ toughness, but if too much Mn deteriorates weldability and HAZ toughness, the upper limit was made 2.0%. In the steel of the present invention, the impurities P and S are 0.020% and 0.
The reason for setting it to 005% or less is to further improve the low temperature toughness of the base material and the welded portion. The reduction of P tends to reduce the grain boundary fracture in the HAZ, and the reduction of S tends to suppress the production of the grain boundary ferrite. Although Al is an element generally contained in deoxidized upper steel, it is an unfavorable element in the steel of the present invention, and its upper limit was set to 0.004%. This is because when Al is contained in the steel, it bonds with O earlier than Ti and Ti oxide is not formed.
【００１４】つぎにＣｕ、Ｎｂを添加する理由を説明す
る。ＣｕはＮｉとほぼ同様な効果をもち、０．０５％以
上で、耐食性、耐水素誘起割れ性などにも効果がある
が、０．５％を超えると熱間圧延時にＣｕクラックが発
生し、製造困難となる。このため、上限を０．５％とし
た。Ｎｂはγ粒界に生成するフェライトを抑制し、Ｔｉ
酸化物を核とする微細なフェライトの生成を促進する働
きがある。しかしながら、多すぎると逆に微細なフェラ
イトの生成を妨げるので０．００５〜０．０１５％を規
制範囲とした。Next, the reason for adding Cu and Nb will be explained. Cu has almost the same effect as Ni, and if it is 0.05% or more, it is also effective in corrosion resistance, hydrogen induced cracking resistance, etc., but if it exceeds 0.5%, Cu cracks occur during hot rolling, Manufacturing becomes difficult. Therefore, the upper limit is set to 0.5%. Nb suppresses the ferrite generated at the γ grain boundary, and Ti
It has a function of promoting the generation of fine ferrite whose core is an oxide. However, if too large, on the contrary, the formation of fine ferrite is hindered, so 0.005 to 0.015% was made the regulated range.
【００１５】鋼の成分を上記の様に限定しても、制造法
が適切でなければ溶接継手の良好な靱性は得られない。
このため、制造条件についても限定する必要がある。発
明鋼としての特性を得るためには、まず、工業的には連
続鋳造法で製造することが必須である。この理由は、連
続鋳造法では溶鋼の冷却速度が速く、スラブ中に微細な
Ｔｉ酸化物が多量に得られるためである。大型鋼塊で
は、凝固時の冷却速度が遅いため、微細なＴｉ酸化物を
得ることが出来ない。連続鋳造法の場合、スラブ厚の増
加により冷却速度が遅くなるため、微細なＴｉ酸化物の
生成が少なくなる。このため、適用するスラブ厚は３５
０ｍｍ以下が好ましい。スラブの再加熱温度は１１００
℃以下とする必要がある。これ以上の温度で再加熱する
とＴｉＮが粗大化するため、溶接の１３５０℃以下のＨ
ＡＺのミクロ組織微細化が不十分となる。Even if the components of the steel are limited as described above, good toughness of the welded joint cannot be obtained unless the manufacturing method is appropriate.
Therefore, it is necessary to limit the manufacturing conditions. In order to obtain the properties of the invention steel, it is essential industrially to manufacture it by a continuous casting method. The reason for this is that in the continuous casting method, the molten steel has a high cooling rate and a large amount of fine Ti oxide is obtained in the slab. In the case of a large steel ingot, fine Ti oxide cannot be obtained because the cooling rate during solidification is slow. In the case of the continuous casting method, since the cooling rate becomes slow due to the increase in the slab thickness, the production of fine Ti oxide is reduced. Therefore, the applicable slab thickness is 35
It is preferably 0 mm or less. Slab reheating temperature is 1100
It must be below ℃. If reheated at a temperature higher than this, TiN will become coarse, so that the H of 1350 ° C or lower for welding.
The microstructure refinement of AZ becomes insufficient.
【００１６】つぎに、スラブ再加熱後の圧延法は加工熱
処理法が必須である。この理由は例え優れたＨＡＺ靱性
が得られたとしても、母材の靱性が劣っていると鋼材と
して不十分なためである。加工熱処理の方法としては、
１）制御圧延、２）制御圧延−加速冷却、３）圧延後直
接焼入−焼戻などが挙げられるが、最も好ましい方法は
制御圧延と加速冷却の組み合わせである。なお、この鋼
を制御後、脱水素などの目的でＡc1変態点以下の温度に
再加熱しても、本発明鋼の特徴を損なうものではない。Next, as a rolling method after reheating the slab, a thermomechanical treatment method is essential. The reason for this is that, even if excellent HAZ toughness is obtained, if the toughness of the base material is inferior, it is insufficient as a steel material. As a method of processing heat treatment,
1) controlled rolling, 2) controlled rolling-accelerated cooling, 3) direct quenching after rolling-tempering, etc. are mentioned, but the most preferable method is a combination of controlled rolling and accelerated cooling. Even if the steel is controlled and then reheated to a temperature not higher than the A c1 transformation point for the purpose of dehydrogenation, the characteristics of the steel of the present invention are not impaired.
【００１７】転炉−連続鋳造−厚板工程で種々の鋼成分
の鋼板を製造し、実溶接継手を作成しシャルピー試験、
ＣＴＯＤ試験（脆性亀裂／発生特性）、ＮＲＬ落重試験
（脆性亀裂／伝播停止特性）を実施した。溶接は一般に
試験溶接として用いられている潜弧溶接（ＳＡＷ）法で
溶接溶け込み線（ＦＬ）が垂直になる様にＫ開先で実施
した。また、シャルピー試験片はＪＩＳ４号で、板厚の
１／４ｔよりＢｏｎｄノッチ（溶接金属とＨＡＺが５０
％）で実施し、ＣＴＯＤ試験片はｔ（板厚）×２ｔサイ
ズのＦＬ／ヒロウノッチで、ＮＲＬ落重試験片はＰ−３
タイプ（１６×５１×１２７ｍｍサイズ）で表面のビー
ドを削除しノッチをＦＬにいれて実施した。表１〜表３
に実施例を示す。Steel plates of various steel components are manufactured in a converter-continuous casting-thick plate process, actual welded joints are prepared, a Charpy test,
A CTOD test (brittle crack / generation property) and an NRL drop weight test (brittle crack / propagation stopping property) were performed. Welding was carried out with the K groove so that the weld penetration line (FL) was vertical by the latent arc welding (SAW) method generally used as test welding. Also, the Charpy test piece is JIS No. 4, and Bond notch (weld metal and HAZ is 50
%), The CTOD test piece is t (plate thickness) × 2t size FL / Hirow notch, and the NRL drop weight test piece is P-3.
A type (16 × 51 × 127 mm size) bead was removed from the surface and a notch was placed in the FL to carry out. Table 1-Table 3
An example is shown in FIG.
【００１８】[0018]
【表１】 [Table 1]
【００１９】[0019]
【表２】 [Table 2]
【００２０】[0020]
【表３】 [Table 3]
【００２１】本発明法で製造した鋼板（本発明鋼）はす
べて良好なＨＡＺ靱性（−８０℃のシャルピー値≧１３
８Ｊ、−５０℃のＣＴＯＤ値≧０．２６ｍｍ、ＮＤＴＴ
≦−１２５℃）を有するのに対し、本発明法によらない
比較鋼はＨＡＺ靱性が劣り、厳しい環境下で使用される
鋼板として適切でない。比較鋼において鋼１１はＡｌ量
が多いため、ミクロ組織が微細化せず、このためシャル
ピー、ＣＴＯＤ値およびＮＤＴＴともに悪い値であっ
た。また、鋼１２では、酸素量が多いため、シャルピ
ー、ＣＴＯＤ値およびＮＤＴＴともに悪い値であった。The steel sheets produced by the method of the present invention (inventive steels) all have good HAZ toughness (Charpy value at -80 ° C. ≧ 13.
8J, -50 ° C CTOD value ≧ 0.26 mm, NDTT
≦ −125 ° C.), the comparative steels not according to the method of the present invention have inferior HAZ toughness and are not suitable as steel sheets used in severe environments. In Comparative Steel, Steel 11 had a large amount of Al, so that the microstructure did not become fine, and therefore Charpy, CTOD value, and NDTT were all bad values. Further, in Steel 12, the Charpy, CTOD value and NDTT were all bad values because of the large amount of oxygen.
【００２２】鋼１３では、Ｔｉ、Ｎ、Ｏのバランスが悪
く、シャルピー、ＣＴＯＤ値およびＮＤＴＴともに悪い
値であった。鋼１４では、Ｄ1 *が低いためミクロ組織が
微細化せず、母材強度が低く、溶接部のシャルピー、Ｃ
ＴＯＤ値およびＮＤＴＴともに悪い値であった。さら
に、鋼１５では、Ｄ1 *が高すぎたため、シャルピー、Ｃ
ＴＯＤ値およびＮＤＴＴともに悪い値であった。本発明
鋼は厚板に適用することが最も好ましいが、ホットコイ
ル、形鋼などにも適用可能である。In Steel 13, the balance of Ti, N and O was poor, and Charpy, CTOD value and NDTT were all bad values. In Steel 14, since D 1 * is low, the microstructure does not become fine, the base metal strength is low, and the Charpy and C
Both the TOD value and the NDTT were bad values. Further, the steel 15, since D 1 * is too high, Charpy, C
Both the TOD value and the NDTT were bad values. The steel of the present invention is most preferably applied to thick plates, but is also applicable to hot coils, shaped steel and the like.
【００２３】[0023]
【発明の効果】本発明は小〜中入熱溶接において、ＨＡ
Ｚ靱性（特に脆性亀裂の発生、伝播特性）が極めて優れ
た鋼の製造技術を提供するものである。これにより、極
低温域（−５０℃以下）や低温タンク、ラインパイプ等
の厳しい環境で使用される鋼材の製造を可能とした。INDUSTRIAL APPLICABILITY The present invention is applicable to HA in small to medium heat input welding.
The present invention provides a manufacturing technique for steel having extremely excellent Z toughness (especially, occurrence of brittle cracks and propagation characteristics). This made it possible to manufacture steel products used in severe environments such as extremely low temperatures (-50 ° C or lower), low temperature tanks, and line pipes.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 磯田 征司 千葉県君津市君津１番地 新日本製鐵株式 会社君津製鐵所内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Isoda 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Stock of Kimitsu Works
Claims (2)
＝0.316Ｃ1/2(1＋0.7Ｓi)(0.35＋4.1Ｍn)(1＋0.36Ｎi)
(1＋0.37Ｃu)が０．８〜１．２の範囲で、且つ−0.015
％≦［Ｔi］−２［Ｏ］−3.4［Ｎ］≦０％を満足し、残
部が鉄および不可避的不純物からなる実質的にＡｌを含
有しない鋼を連続鋳造法によってスラブとし、これを１
１００℃以下の温度で再加熱後、加工熱処理することを
特徴とする溶接熱影響部の低温靱性が優れた鋼の製造
法。1. By weight%, C: 0.04 to 0.12%, Si: 0.4% or less, Mn: 0.8 to 2.0%, P: 0.020% or less, S: 0 0.005% or less, Al: 0.004% or less, Ni: 1.0 to 4.0%, Ti: 0.005 to 0.012%, N: 0.0015 to 0.0060%, O: 0.0. Containing 0010-0.0030%, D 1 *
= 0.316C 1/2 (1 + 0.7Si) (0.35 + 4.1Mn) (1 + 0.36Ni)
(1 + 0.37 Cu) is in the range of 0.8 to 1.2, and -0.015
% Of [Ti] −2 [O] −3.4 [N] ≦ 0%, and a balance of iron and unavoidable impurities, which is substantially free of Al, is used as a slab by continuous casting method.
A method for producing steel having excellent low-temperature toughness in a heat-affected zone of welding, which comprises reheating at a temperature of 100 ° C. or lower and then performing heat treatment.
５〜０．０１５％の一種または二種を含有し、Ｄ1 *＝0.
316Ｃ1/2(1＋0.7Ｓi)(0.35＋4.1Ｍn)(1＋0.36Ｎi)(1＋
0.37Ｃu)が０．８〜１．２の範囲で、且つ−0.015％≦
［Ｔi］−２［Ｏ］−3.4［Ｎ］≦０％を満足し、残部が
鉄および不可避的不純物からなる実質的にＡｌを含有し
ない鋼を連続鋳造法によってスラブとし、これを１１０
０℃以下の温度で再加熱後、加工熱処理することを特徴
とする溶接熱影響部の低温靱性が優れた鋼の製造法。2. By weight%, C: 0.04 to 0.12%, Si: 0.4% or less, Mn: 0.8 to 2.0%, P: 0.020% or less, S: 0 0.005% or less, Al: 0.004% or less, Ni: 1.0 to 4.0%, Ti: 0.005 to 0.012%, N: 0.0015 to 0.0060%, O: 0.0. 0010 to 0.0030%, Cu: 0.05 to 0.5%, Nb: 0.00
It contains 5 to 0.015% of one or two kinds, and D 1 * = 0.
316C 1/2 (1 + 0.7Si) (0.35 + 4.1Mn) (1 + 0.36Ni) (1+
0.37 Cu) in the range of 0.8 to 1.2, and -0.015% ≦
A steel which satisfies [Ti] -2 [O] -3.4 [N] ≤0% and which is substantially Al-free with the balance being iron and unavoidable impurities is made into a slab by a continuous casting method.
A method for producing steel having excellent low-temperature toughness in a heat-affected zone of welding, which comprises reheating at a temperature of 0 ° C. or lower and then performing heat treatment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6075599A JPH07278653A (en) | 1994-04-14 | 1994-04-14 | Production of steel excellent in cold toughness on welding heat affected zone |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6075599A JPH07278653A (en) | 1994-04-14 | 1994-04-14 | Production of steel excellent in cold toughness on welding heat affected zone |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH07278653A true JPH07278653A (en) | 1995-10-24 |
Family
ID=13580838
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6075599A Withdrawn JPH07278653A (en) | 1994-04-14 | 1994-04-14 | Production of steel excellent in cold toughness on welding heat affected zone |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07278653A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009072663A1 (en) * | 2007-12-07 | 2009-06-11 | Nippon Steel Corporation | Steel with weld heat-affected zone having excellent ctod properties and process for producing the steel |
| WO2010134353A1 (en) * | 2009-05-21 | 2010-11-25 | 新日本製鐵株式会社 | Steel material for welding and method for producing same |
| WO2010134323A1 (en) * | 2009-05-19 | 2010-11-25 | 新日本製鐵株式会社 | Steel material for welding and method for producing same |
| CN104131225A (en) * | 2014-07-30 | 2014-11-05 | 宝山钢铁股份有限公司 | Ultralow temperature nickel steel with low cost and manufacturing method thereof |
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-
1994
- 1994-04-14 JP JP6075599A patent/JPH07278653A/en not_active Withdrawn
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009072663A1 (en) * | 2007-12-07 | 2009-06-11 | Nippon Steel Corporation | Steel with weld heat-affected zone having excellent ctod properties and process for producing the steel |
| JP4547037B2 (en) * | 2007-12-07 | 2010-09-22 | 新日本製鐵株式会社 | Steel excellent in CTOD characteristics of weld heat affected zone and method for producing the same |
| JPWO2009072663A1 (en) * | 2007-12-07 | 2011-04-28 | 新日本製鐵株式会社 | Steel excellent in CTOD characteristics of weld heat affected zone and method for producing the same |
| US8361248B2 (en) | 2007-12-07 | 2013-01-29 | Nippon Steel Corporation | Steel superior in CTOD properties of weld heat-affected zone and method of production of same |
| WO2010134323A1 (en) * | 2009-05-19 | 2010-11-25 | 新日本製鐵株式会社 | Steel material for welding and method for producing same |
| US8668784B2 (en) | 2009-05-19 | 2014-03-11 | Nippon Steel & Sumitomo Metal Corporation | Steel for welded structure and producing method thereof |
| WO2010134353A1 (en) * | 2009-05-21 | 2010-11-25 | 新日本製鐵株式会社 | Steel material for welding and method for producing same |
| US8920713B2 (en) | 2009-05-21 | 2014-12-30 | Nippon Steel & Sumitomo Metal Corporation | Steel for welded structure and producing method thereof |
| US9403242B2 (en) | 2011-03-24 | 2016-08-02 | Nippon Steel & Sumitomo Metal Corporation | Steel for welding |
| CN104131225A (en) * | 2014-07-30 | 2014-11-05 | 宝山钢铁股份有限公司 | Ultralow temperature nickel steel with low cost and manufacturing method thereof |
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