JP3697202B2 - Steel with excellent toughness of weld heat affected zone and method for producing the same - Google Patents
Steel with excellent toughness of weld heat affected zone and method for producing the same Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は小入熱溶接から中入熱溶接の熱影響部(HAZ)の靭性が優れた鋼とその製造方法に関するものである。
【0002】
【従来の技術】
低合金鋼のHAZ靭性は、(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)及びフェライトサイドプレート(FSP)などの硬化相の分散状態、(3)析出硬化状態、(4)粒界脆化の有無、(5)元素のミクロ偏析など種々の要因に支配される。
【0003】
これらの要因は靭性に大きな影響を与えることが知られており、HAZ靭性を改善するために多くの技術が実用化されている。
【0004】
特に優れている技術として、Ti酸化物でミクロ組織を微細化し、これに加え、Ti、O、Nのバランスを適正化してTiCの析出を抑制して析出効果を低減し、靭性を向上させることが知られている(特開平5−247531号公報)。
【0005】
しかしながら、溶接熱影響部の脆性亀裂発生特性(CTOD)は上述したM*等の硬化相の影響が極めて大きく、これまでの技術ではM*生成の抑制のために鋼成分の焼入性(DI、Ceq)を低く抑える必要があり、高強度化のための障害となっていた。
【0006】
【発明が解決しようとする課題】
本発明は小〜中入熱の多層溶接において破壊靭性(CTOD)の優れた高強度の鋼を安価に製造する技術を提供するものである。
【0007】
本発明により製造した鋼は多層溶接部のミクロ組織を微細化して、優れた靭性を示す。
【0008】
【課題を解決するための手段】
本発明の要旨は以下の通りである。
【0009】
(1) 質量%で、
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(2.0%を除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、AGB-1が0.39〜0.47の範囲で、残部が鉄及び不可避的不純物からなる実質的にAlを含有しないことを特徴とする溶接熱影響部の靭性が優れた鋼。
ここで、AGB-1=C+1/24Si+1/6Mn+2Nb
【0010】
(2) 質量%で、
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(2.0%を除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、
Ni:0.3%以下、
Cu:0.3%以下、
Mo:0.1%以下、
V:0.03%以下
の1種又は2種以上を更に含有し、かつ、AGB-2が0.39〜0.47の範囲で、残部が鉄及び不可避的不純物からなる実質的にAlを含有しないことを特徴とする溶接熱影響部の靭性が優れた鋼。
ここで、AGB-2=C+1/24Si+1/6Mn+1/40(Ni+Cu)+1/4Mo+2Nb+1/14V
【0011】
(3) 質量%で、
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%を除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、AGB-1が0.39〜0.47の範囲で、残部が鉄及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、その後1200℃以下の温度に再加熱後、加工熱処理することを特徴とする溶接熱影響部の靭性が優れた鋼の製造方法。
ここで、AGB-1=C+1/24Si+1/6Mn+2Nb
【0012】
(4) 質量%で、
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%は除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、
Ni:0.3%以下、
Cu:0.3%以下、
Mo:0.1%以下、
V:0.03%以下
の1種又は2種以上を更に含有し、かつ、AGB-2が0.39〜0.47の範囲で、残部が鉄及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、その後1200℃以下の温度に再加熱後、加工熱処理することを特徴とする溶接熱影響部の靭性が優れた鋼の製造方法。
ここで、AGB-2=C+1/24Si+1/6Mn+1/40(Ni+Cu)+1/4Mo+2Nb+1/14V
【0013】
【発明の実施の形態】
本発明者らの研究によれば、小〜中入熱(例えば50mmで1.5〜60kJ/mm)溶接HAZの脆性亀裂の発生特性(−10℃程度の温度におけるCTOD特性)は極めて局部的な領域の靭性が支配的であり、この部分のミクロ組織の制御が重要であることを明らかにした。
【0014】
本発明者らの検討では、CTOD特性に最も大きな影響を及ぼす局所的な領域は旧オーステナイト粒界近傍の粒界フェライト(GBF)やM*、FSPであることをつきとめた。
【0015】
このため、本発明者らは、溶接熱履歴を前提としたオーステナイトからの変態挙動を検討し、オーステナイトからフェライトの変態開始温度がミクロ組織の生成に大きく影響し、変態開始温度が高い場合にGBFやM*、FSPが生成し易いことをつきとめた。
【0016】
しかしながら、変態開始温度が低い場合でもBuが生成して、靭性が劣化することを見出した。
【0017】
また、変態開始温度は鋼成分や熱履歴により決まることが知られており、良好なミクロ組織を得るための鋼成分について検討し、以下のAGB式で0.39〜0.47の範囲に制御できることにより靭性を劣化させるGBF、M*、FSPの生成を抑えることができることを見出した。
AGB-1=C+1/24Si+1/6Mn+2Nb
AGB-2=C+1/24Si+1/6Mn+1/40(Ni+Cu)+1/4Mo+2Nb+1/14V
【0018】
鋼成分を適性化するためには、NbとMnが最も効果的であるが、その添加量も適正範囲が存在し、以下の通りである。
【0019】
Nbは、0.01%未満ではミクロ組織を適正化する効果が少なく、0.03%超では多層溶接でBuの生成やNbの析出効果が顕著となり靭性を劣化させるため、0.01〜0.03%が適正範囲である。
【0020】
Mnはミクロ組織を適正化する効果が大きく安価な元素であるため、添加量は多くしたいが、2.5%超では靭性に有害なBuを生成し易くするため2.5%を上限とした。
【0021】
また、少ないと効果が少ないので下限を2.0%(ただし、2.0%を除く)とした。
【0022】
これらを限定するだけでは良好な靭性は得られない。
【0023】
即ち、AGB式の適正範囲の限定は粒界近傍のミクロ組織の制御に効果を発揮するが、粒内では効果は期待できない。
【0024】
粒内のミクロ組織の制御は微細なTi酸化物及びTi窒化物が必要であり、このためTi、O、Nを以下の範囲に限定する必要がある。
【0025】
TiはTi酸化物やTi窒化物を生成して粒内のミクロ組織を微細化し、靭性を向上させるが、0.005%未満では効果が少なく、0.02%超ではTiの炭化物を生成し易くなり、靭性を劣化させるので0.005〜0.02%が適正範囲である。
【0026】
OはTiの酸化物生成に必要であるが、0.0035%超では粗大なTi酸化物を生成し、靭性を極端に劣化させるため上限を0.0035%とした。
【0027】
NはTi窒化物生成に必要であるが、0.003%未満では効果が少なく、0.006%超では鋼片製造時に表面疵が発生するため上限を0.006%とした。
【0028】
これら以外の鋼成分の限定理由を以下に述べる。
【0029】
Cは高強度を得るため0.03%以上必要であるが0.09%超では母材とHAZの靭性を害するため、0.09%を上限とする。
【0030】
Siは良好なHAZ靭性を得るため少ない方が好ましいが、発明鋼ではAlを添加していないため、脱酸上0.05%以上は必要である。しかしながら、0.2%超ではHAZ靭性を害するため、0.2%を上限とする。
【0031】
P、Sは母材靭性、HAZ靭性からともに少ない方が良いが、工業生産的な制約もあり、それぞれ0.008%、0.005%を上限とした。
【0032】
AlはTi酸化物を生成させるために少ない方が好ましいので、実質的にAlを含有しないようにする。しかし、工業生産的に制約があり、0.004%が許容できる上限である。したがって、実質的にAlを含有しないとは、0.004%以下(0%を含む)のAl含有量とすることである。
【0033】
更に、基本となる成分にNi、Cu、Mo、Vを添加する目的はHAZ靭性に及ぼす影響が少なく、母材の強度向上に効果があるためである。
【0034】
しかしながら、Ni:0.3%、Cu:0.3%、Mo:0.1%、V:0.03%を超えるとHAZ靭性を害するだけでなく、鋼材のコストにも影響するため、上限とした。
【0035】
鋼の成分を上記のように限定しても製造方法が適切でなければ目的とした効果は発揮できない。このため、製造条件についても限定が必要である。
【0036】
本発明鋼は工業的には連続鋳造法で製造することが必須である。
【0037】
その理由は、溶鋼の凝固冷却速度が速く、スラブ中に微細なTi酸化物とTi窒化物を多量に生成することが可能なためである。
【0038】
スラブの圧延に際し、その再加熱温度は1200℃以下とする必要がある。
【0039】
再加熱温度が1200℃を超えるとTi窒化物が粗大化してHAZ靭性改善効果が期待できないためである。
【0040】
次に、再加熱後の製造方法は加工熱処理が必須である。
【0041】
その理由は、優れたHAZ靭性が得られても、母材の靭性が劣っている鋼材としては不十分なためである。
【0042】
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)圧延後直接焼入れ−焼戻しなどが挙げられ、どの方法でも良いが、好ましい方法は、2)制御圧延−加速冷却法である。
【0043】
なお、この鋼を製造後、脱水素などの目的でAr3変態点以下の温度に再加熱しても、本発明の特徴を損なうものではない。
【0044】
【実施例】
転炉−連続鋳造−厚板工程の種々の鋼成分の厚鋼板を製造し、母材強度や溶接継手のCTOD試験を実施した。
【0045】
溶接は一般的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)が垂直になるようにK開先で溶接入熱は4.5〜5.0kJ/mmで実施した。
【0046】
CTOD試験はt(板厚)×2tのサイズでノッチは50%疲労亀裂でFL位置で実施した。
【0047】
表1、表2に実施例を示す。
【0048】
【表1】
【0049】
【表2】
【0050】
本発明で製造した鋼板(本発明鋼)は降伏強度(YS)が420N/mm2以上で、−10℃のCTOD値が0.63mm以上の良好な破壊靭性を示した。
【0051】
これに対し、比較鋼では、強度は発明鋼と同等であるが、CTOD値が劣り、厳しい環境下で使用される鋼板として適切でない。
【0052】
比較鋼16はMnやAGB値が低いため、粒界フェライト、島状マルテンサイトが生成し、CTOD値が低い値であった。
【0053】
比較鋼17はAGB値が高すぎ、Nbの添加量も多すぎるため、ミクロ組織にベイナイトが多く、硬さ値も高いためCTOD値が低い値であった。
【0054】
比較鋼18はC、Si、Mn、Nb等は発明鋼と同じであるが、AGB値が高すぎなため、ミクロ組織にベイナイトが多く、CTOD値が低い値であった。
【0056】
比較鋼19はAGBが高すぎ、窒素(N)が少ないため、ミクロ組織にベイナイトが多く観察され、低いCTOD値であった。
【0057】
【発明の効果】
本発明により製造した鋼は、溶接時に最も靭性が劣化する旧オーステナイト粒界とその近傍のミクロ組織を適正化して、優れた靭性を示す。
【0058】
これにより、海洋構造物、耐震性建築物等の厳しい環境で使用される高強度の鋼材の製造を可能とした。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel excellent in toughness of a heat-affected zone (HAZ) from small heat input welding to medium heat input welding, and a manufacturing method thereof.
[0002]
[Prior art]
The HAZ toughness of low alloy steel is (1) grain size, (2) high carbon martensite (M * ), upper bainite (Bu) and ferrite side plate (FSP) hardened phase dispersion state, (3 It is governed by various factors such as :) precipitation hardening state, (4) presence / absence of grain boundary embrittlement, and (5) elemental microsegregation.
[0003]
These factors are known to have a great influence on toughness, and many techniques have been put to practical use in order to improve HAZ toughness.
[0004]
As a particularly excellent technology, the microstructure is refined with Ti oxide, and in addition to this, the balance of Ti, O, and N is optimized to suppress the precipitation of TiC, thereby reducing the precipitation effect and improving the toughness. Is known (Japanese Patent Laid-Open No. 5-247531).
[0005]
However, brittle cracking characteristics of the weld heat affected zone (CTOD) the effect of hardening phase of M * such as described above is extremely large, hardenability of the steel components for this in the previous techniques M * generation suppression (D I , Ceq) must be kept low, which has been an obstacle for increasing the strength.
[0006]
[Problems to be solved by the invention]
The present invention provides a technique for inexpensively producing a high-strength steel excellent in fracture toughness (CTOD) in multilayer welding with small to medium heat input.
[0007]
The steel produced according to the present invention refines the microstructure of the multilayer weld and exhibits excellent toughness.
[0008]
[Means for Solving the Problems]
The gist of the present invention is as follows.
[0009]
(1) In mass%,
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
In the range of A GB-1 in the range of 0.39 to 0.47, the balance is excellent in toughness of the heat affected zone, characterized in that the balance is substantially free of Al consisting of iron and inevitable impurities. steel.
Here, A GB-1 = C + 1 / 24Si + 1 / 6Mn + 2Nb
[0010]
(2) By mass%
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
Containing
Ni: 0.3% or less,
Cu: 0.3% or less,
Mo: 0.1% or less,
V: One or more of 0.03% or less is further contained, A GB-2 is in the range of 0.39 to 0.47, and the balance is substantially made of iron and inevitable impurities. Steel with excellent toughness of weld heat-affected zone, characterized in that it does not contain.
Here, A GB-2 = C + 1 / 24Si + 1 / 6Mn + 1/40 (Ni + Cu) + 1 / 4Mo + 2Nb + 1 / 14V
[0011]
(3) In mass%,
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
A GB-1 is in the range of 0.39 to 0.47, and the balance is made of iron and unavoidable impurities and substantially free of Al. A method for producing steel with excellent toughness of a heat affected zone of welding, characterized by performing a heat treatment after reheating to a temperature.
Here, A GB-1 = C + 1 / 24Si + 1 / 6Mn + 2Nb
[0012]
(4) By mass%
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
Containing
Ni: 0.3% or less,
Cu: 0.3% or less,
Mo: 0.1% or less,
V: One or more of 0.03% or less is further contained, A GB-2 is in the range of 0.39 to 0.47, and the balance is substantially made of iron and inevitable impurities. A method for producing a steel having excellent toughness of a weld heat affected zone, characterized in that a steel containing no slab is made into a slab by a continuous casting method, and then reheated to a temperature of 1200 ° C. or lower and then subjected to a heat treatment.
Here, A GB-2 = C + 1 / 24Si + 1 / 6Mn + 1/40 (Ni + Cu) + 1 / 4Mo + 2Nb + 1 / 14V
[0013]
DETAILED DESCRIPTION OF THE INVENTION
According to the study by the present inventors, the brittle crack generation characteristic (CTOD characteristic at a temperature of about −10 ° C.) of small to medium heat input (for example, 1.5 to 60 kJ / mm at 50 mm) welding HAZ is extremely local. It was clarified that the toughness of this region is dominant and the microstructure control of this part is important.
[0014]
In the study by the present inventors, it has been found that the local region having the greatest influence on the CTOD characteristics is grain boundary ferrite (GBF), M * , and FSP in the vicinity of the prior austenite grain boundary.
[0015]
For this reason, the present inventors have examined the transformation behavior from austenite on the premise of welding heat history, and the transformation start temperature of ferrite from austenite has a great influence on the formation of microstructure, and when the transformation start temperature is high, the GBF I found out that M * and FSP are easy to generate.
[0016]
However, it has been found that even when the transformation start temperature is low, Bu is generated and the toughness deteriorates.
[0017]
Also, transformation start temperature is known to determined by the steel composition and heat history, consider the steel component to obtain a good microstructure in the range of 0.39 to 0.47 in the following A GB formula It has been found that the generation of GBF, M * , and FSP that degrade toughness can be suppressed by being controllable.
A GB-1 = C + 1 / 24Si + 1 / 6Mn + 2Nb
A GB-2 = C + 1 / 24Si + 1 / 6Mn + 1/40 (Ni + Cu) + 1 / 4Mo + 2Nb + 1 / 14V
[0018]
Nb and Mn are the most effective for optimizing the steel components, but the addition amount also has an appropriate range as follows.
[0019]
If Nb is less than 0.01%, the effect of optimizing the microstructure is small, and if it exceeds 0.03%, the formation of Bu and the precipitation effect of Nb become noticeable in multi-layer welding and the toughness is deteriorated. 0.03% is the appropriate range.
[0020]
Mn is an inexpensive element that has a great effect on optimizing the microstructure. Therefore, it is desirable to increase the amount of addition, but if it exceeds 2.5%, the upper limit is set to 2.5% in order to easily generate Bu harmful to toughness. .
[0021]
It was also less 2.0% lower limit the effect is small (excluding 2.0%).
[0022]
Only by limiting these, good toughness cannot be obtained.
[0023]
That is, the limitation of the appropriate range of the AGB type is effective in controlling the microstructure near the grain boundary, but the effect cannot be expected in the grains.
[0024]
In order to control the microstructure in the grains, fine Ti oxides and Ti nitrides are required, and therefore Ti, O, and N must be limited to the following ranges.
[0025]
Ti produces Ti oxide and Ti nitride to refine the microstructure inside the grains and improves toughness, but less than 0.005% is less effective, and more than 0.02% produces Ti carbide. It becomes easy and deteriorates toughness, so 0.005 to 0.02% is an appropriate range.
[0026]
O is necessary for the production of Ti oxide, but if it exceeds 0.0035%, coarse Ti oxide is produced and the toughness is extremely deteriorated, so the upper limit was made 0.0035%.
[0027]
N is necessary for Ti nitride formation, but if it is less than 0.003%, the effect is small, and if it exceeds 0.006%, surface flaws occur during the manufacture of steel slabs, so the upper limit was made 0.006%.
[0028]
The reasons for limiting the other steel components will be described below.
[0029]
C needs to be 0.03% or more in order to obtain high strength, but if it exceeds 0.09%, the toughness of the base material and HAZ is impaired, so 0.09% is made the upper limit.
[0030]
Si is preferable to be small in order to obtain good HAZ toughness, but 0.05% or more is necessary in terms of deoxidation because Al is not added in the invention steel. However, if over 0.2%, the HAZ toughness is impaired, so 0.2% is made the upper limit.
[0031]
P and S should be less in terms of base metal toughness and HAZ toughness, but there are also restrictions on industrial production, so 0.008% and 0.005% were made the upper limits, respectively.
[0032]
Al is preferably contained in a small amount to form a Ti oxide, so that Al is not substantially contained. However, there are restrictions on industrial production, and 0.004% is an allowable upper limit. Therefore, “substantially not containing Al” means that the Al content is 0.004% or less (including 0%).
[0033]
Furthermore, the purpose of adding Ni, Cu, Mo, V to the basic components is because it has little effect on the HAZ toughness and is effective in improving the strength of the base material.
[0034]
However, if Ni: 0.3%, Cu: 0.3%, Mo: 0.1%, V: over 0.03%, not only will the HAZ toughness be impaired, but also the cost of the steel material will be affected. It was.
[0035]
Even if the components of the steel are limited as described above, the intended effect cannot be exhibited unless the manufacturing method is appropriate. For this reason, it is necessary to limit the manufacturing conditions.
[0036]
The steel of the present invention is industrially required to be produced by a continuous casting method.
[0037]
The reason for this is that the solidification cooling rate of the molten steel is fast, and a large amount of fine Ti oxide and Ti nitride can be generated in the slab.
[0038]
In rolling the slab, the reheating temperature needs to be 1200 ° C. or less.
[0039]
This is because when the reheating temperature exceeds 1200 ° C., the Ti nitride becomes coarse and an effect of improving the HAZ toughness cannot be expected.
[0040]
Next, the heat treatment is essential for the manufacturing method after reheating.
[0041]
The reason is that even if excellent HAZ toughness is obtained, it is insufficient as a steel material having poor base material toughness.
[0042]
Examples of the heat treatment method include 1) controlled rolling, 2) controlled rolling-accelerated cooling, 3) direct quenching-tempering after rolling, and any method may be used, but 2) controlled rolling-accelerated cooling is preferable. Is the law.
[0043]
In addition, even if this steel is manufactured and reheated to a temperature not higher than the Ar 3 transformation point for the purpose of dehydrogenation, the characteristics of the present invention are not impaired.
[0044]
【Example】
Thick steel plates of various steel components in the converter-continuous casting-thick plate process were manufactured, and the base material strength and the CTOD test of the welded joint were performed.
[0045]
Welding is a submerged arc welding (SAW) method that is generally used as test welding. The welding heat input is 4.5 to 5.0 kJ / mm with a K groove so that the weld penetration line (FL) is vertical. It carried out in.
[0046]
The CTOD test was performed at the FL position with a size of t (plate thickness) × 2 t and a notch of 50% fatigue crack.
[0047]
Tables 1 and 2 show examples.
[0048]
[Table 1]
[0049]
[Table 2]
[0050]
The steel sheet produced in accordance with the present invention (present invention steel) exhibited a good fracture toughness with a yield strength (YS) of 420 N / mm 2 or more and a CTOD value of −10 ° C. of 0.63 mm or more.
[0051]
On the other hand, the comparative steel has the same strength as that of the invention steel, but the CTOD value is inferior, and it is not suitable as a steel sheet used in a severe environment.
[0052]
Comparative Steel 16 has a low Mn and A GB value, generated by the grain boundary ferrite, island martensite, CTOD value was low.
[0053]
Comparative Steel 17 too high A GB value, since the addition amount too much of Nb, bainite microstructure lot was value CTOD value is lower for higher hardness values.
[0054]
Comparative Steel 18 C, Si, Mn, although Nb and the like are the same as the invention steels, since such A GB value is too high, many bainite microstructure, CTOD value was low.
[0056]
In Comparative Steel 19 , A GB was too high and nitrogen (N) was small, so that a lot of bainite was observed in the microstructure, and the CTOD value was low.
[0057]
【The invention's effect】
The steel produced according to the present invention exhibits excellent toughness by optimizing the prior austenite grain boundaries where the toughness is most deteriorated during welding and the microstructure in the vicinity thereof.
[0058]
This made it possible to manufacture high-strength steel materials used in harsh environments such as offshore structures and earthquake-resistant buildings.
Claims (4)
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、AGB-1が0.39〜0.47の範囲で、残部が鉄及び不可避的不純物からなる実質的にAlを含有しないことを特徴とする溶接熱影響部の靭性が優れた鋼。
ここで、AGB-1=C+1/24Si+1/6Mn+2Nb% By mass
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
In the range of A GB-1 in the range of 0.39 to 0.47, the balance is excellent in toughness of the heat affected zone, characterized in that the balance is substantially free of Al consisting of iron and inevitable impurities. steel.
Here, A GB-1 = C + 1 / 24Si + 1 / 6Mn + 2Nb
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、
Ni:0.3%以下、
Cu:0.3%以下、
Mo:0.1%以下、
V:0.03%以下
の1種又は2種以上を更に含有し、かつ、AGB-2が0.39〜0.47の範囲で、残部が鉄及び不可避的不純物からなる実質的にAlを含有しないことを特徴とする溶接熱影響部の靭性が優れた鋼。
ここで、AGB-2=C+1/24Si+1/6Mn+1/40(Ni+Cu)+1/4Mo+2Nb+1/14V% By mass
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
Containing
Ni: 0.3% or less,
Cu: 0.3% or less,
Mo: 0.1% or less,
V: One or more of 0.03% or less is further contained, A GB-2 is in the range of 0.39 to 0.47, and the balance is substantially made of iron and inevitable impurities. Steel with excellent toughness of weld heat-affected zone, characterized in that it does not contain.
Here, A GB-2 = C + 1 / 24Si + 1 / 6Mn + 1/40 (Ni + Cu) + 1 / 4Mo + 2Nb + 1 / 14V
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、AGB-1が0.39〜0.47の範囲で、残部が鉄及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、その後1200℃以下の温度に再加熱後、加工熱処理することを特徴とする溶接熱影響部の靭性が優れた鋼の製造方法。
ここで、AGB-1=C+1/24Si+1/6Mn+2Nb% By mass
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
A GB-1 is in the range of 0.39 to 0.47, and the balance is made of iron and unavoidable impurities and substantially free of Al. A method for producing steel with excellent toughness of a heat affected zone of welding, characterized by performing a heat treatment after reheating to a temperature.
Here, A GB-1 = C + 1 / 24Si + 1 / 6Mn + 2Nb
C:0.03〜0.09%、
Si:0.05〜0.2%、
Mn:2.0〜2.5%(ただし、2.0%除く)、
P:0.008%以下、
S:0.005%以下、
Ti:0.005〜0.02%、
Nb:0.01〜0.03%、
O:0.0035%以下、
N:0.003〜0.006%
を含有し、
Ni:0.3%以下、
Cu:0.3%以下、
Mo:0.1%以下、
V:0.03%以下
の1種又は2種以上を更に含有し、かつ、AGB-2が0.39〜0.47の範囲で、残部が鉄及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、その後1200℃以下の温度に再加熱後、加工熱処理することを特徴とする溶接熱影響部の靭性が優れた鋼の製造方法。
ここで、AGB-2=C+1/24Si+1/6Mn+1/40(Ni+Cu)+1/4Mo+2Nb+1/14V% By mass
C: 0.03 to 0.09%,
Si: 0.05-0.2%
Mn: 2.0 to 2.5% (excluding 2.0%)
P: 0.008% or less,
S: 0.005% or less,
Ti: 0.005 to 0.02%,
Nb: 0.01-0.03%,
O: 0.0035% or less,
N: 0.003 to 0.006%
Containing
Ni: 0.3% or less,
Cu: 0.3% or less,
Mo: 0.1% or less,
V: One or more of 0.03% or less is further contained, A GB-2 is in the range of 0.39 to 0.47, and the balance is substantially made of iron and inevitable impurities. A method for producing a steel having excellent toughness of a weld heat affected zone, characterized in that a steel containing no slab is made into a slab by a continuous casting method, and then reheated to a temperature of 1200 ° C. or lower and then subjected to a heat treatment.
Here, A GB-2 = C + 1 / 24Si + 1 / 6Mn + 1/40 (Ni + Cu) + 1 / 4Mo + 2Nb + 1 / 14V
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