JP2002283024A - Method for producing steel material for structure excellent in toughness at heat affected part of welding - Google Patents
Method for producing steel material for structure excellent in toughness at heat affected part of weldingInfo
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、船舶、建築、海
洋構造物、鋼管および貯槽などの用途に供して好適な溶
接熱影響部の靱性に優れた構造用鋼材の製造方法に関す
るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a structural steel material excellent in toughness of a weld heat affected zone suitable for use in ships, buildings, marine structures, steel pipes and storage tanks.
【０００２】[0002]
【従来の技術】鋼板の溶接熱影響部は、加熱中および冷
却中にオーステナイト粒が粗大化し、冷却後の組織も粗
大化して靱性が劣化する。このため、例えば特開昭55−
26164 号公報に開示されているように、鋼中に微細なTi
Ｎを分散させることによってオーステナイト粒の成長を
抑制して靱性を向上させる方法が広く採用されている。2. Description of the Related Art In a weld heat affected zone of a steel sheet, austenite grains are coarsened during heating and cooling, and the structure after cooling is coarsened to deteriorate toughness. For this reason, for example,
As disclosed in U.S. Pat.
A method of suppressing the growth of austenite grains by dispersing N to improve toughness has been widely adopted.
【０００３】このように、TiＮを利用する場合、オース
テナイト粒の微細化に十分な量のTiＮを確保する必要が
あるが、それと同時に連続鋳造鋳片の表面割れ防止およ
び固溶Ｎによる熱影響部の靱性劣化防止などの観点か
ら、例えば大入熱溶接用の造船向Ｅ級鋼等においては、
Ti量は0.01〜0.02mass％、Ｎ量は0.003 〜0.005 mass％
程度とする成分設計がなされている。As described above, when TiN is used, it is necessary to secure a sufficient amount of TiN for refining austenite grains, but at the same time, it is necessary to prevent surface cracking of continuous cast slab and heat affected zone by solid solution N. From the viewpoint of preventing the toughness of steel from deteriorating, for example, in shipbuilding E class steel for large heat input welding,
Ti content is 0.01-0.02 mass%, N content is 0.003-0.005 mass%
The components are designed to be on the order of magnitude.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、Tiおよ
びＮの添加量を所定の範囲に制御した場合であっても、
鋳造時の冷却条件が変化した場合には、製造した鋼板の
溶接熱影響部における靱性値にばらつきが生じるという
問題があった。この発明の目的は、上記の問題を有利に
解決して、溶接熱影響部の靱性に優れた構造用鋼材を提
供することである。However, even when the addition amounts of Ti and N are controlled within a predetermined range,
When the cooling conditions during casting change, there is a problem that the toughness value in the weld heat affected zone of the manufactured steel sheet varies. An object of the present invention is to solve the above problems advantageously and to provide a structural steel material excellent in toughness of a weld heat affected zone.
【０００５】[0005]
【課題を解決するための手段】さて、発明者らは、上記
の問題を解決するために、TiＮの粒径分布と鋼組成およ
び鋳造時の冷却条件について広範囲にわたる検討を行っ
た結果、以下に述べる知見を得た。 ａ）加熱時におけるオーステナイト粒の粗大化を防止す
るには、高温でも溶解しない程度のTi，Ｎ量を確保した
上で、TiＮの初期平均粒径（円相当直径）を0.02〜0.04
μm の範囲とすることが有効である。 ｂ）母材中におけるTiＮの分布状態は、鋳片の冷却速度
をTi／Ｎ比に応じて適切に制御することによって、コン
トロールすることができる。 この発明は、上記の知見に立脚するものである。Means for Solving the Problems In order to solve the above problems, the present inventors have conducted extensive studies on the particle size distribution of TiN, the steel composition, and the cooling conditions during casting. Obtained the findings described. a) In order to prevent the austenite grains from becoming coarse during heating, ensure that the Ti and N contents are such that they do not dissolve even at high temperatures, and then set the initial average particle size (equivalent circle diameter) of TiN to 0.02 to 0.04.
It is effective to set it in the range of μm. b) The distribution of TiN in the base material can be controlled by appropriately controlling the cooling rate of the slab according to the Ti / N ratio. The present invention is based on the above findings.
【０００６】すなわち、この発明の要旨構成は次のとお
りである。 １．質量％で、Ｃ：0.01〜0.18％、Si：0.02〜0.60％、
Mn：0.60〜2.00％、Ｐ：0.030 ％以下、Ｓ：0.015 ％以
下、Al：0.005 〜0.100 ％、Ti：0.007 〜0.030 ％およ
びＮ：0.0040〜0.0100％を含有し、残部はFeおよび不可
避的不純物の組成になる鋳片の冷却に際し、鋳片全厚に
わたって平均した1500℃から1100℃までの冷却時間ｔ
15/11 （秒）とTi／Ｎ比について、次式(1) 22600／(t15/11)1.25≦Ti／Ｎ≦ 1818000／(t15/11)1.7 --- (1) の関係を満足させることを特徴とする溶接熱影響部の靱
性に優れた構造用鋼材の製造方法。That is, the gist of the present invention is as follows. 1. In mass%, C: 0.01 to 0.18%, Si: 0.02 to 0.60%,
Mn: 0.60 to 2.00%, P: 0.030% or less, S: 0.015% or less, Al: 0.005 to 0.100%, Ti: 0.007 to 0.030% and N: 0.0040 to 0.0100%, the balance being Fe and inevitable impurities The cooling time t from 1500 ° C. to 1100 ° C., averaged over the entire thickness of the slab,
For 15/11 (second) and Ti / N ratio, the relationship of the following formula (1) 22600 / (t 15/11 ) 1.25 ≦ Ti / N ≦ 1818000 / (t 15/11 ) 1.7 --- (1) A method for producing a structural steel material having excellent toughness in a weld heat affected zone, characterized by satisfying.
【０００７】２．上記１において、鋼材が、さらに質量
％でCu：0.02〜1.5 ％、Ni：0.02〜0.6 ％、Cr：0.05〜
0.50％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％およ
びＶ：0.03〜0.15％のうちから選んだ１種または２種以
上を含有する組成になることを特徴とする溶接熱影響部
の靱性に優れた構造用鋼材の製造方法。[0007] 2. In the above item 1, the steel material further contains, by mass%, Cu: 0.02 to 1.5%, Ni: 0.02 to 0.6%, Cr: 0.05 to
0.50%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030%, and V: 0.03 to 0.15%. A method for producing structural steel with excellent toughness.
【０００８】３．上記１または２において、鋼材が、さ
らに質量％でＢ：0.0002〜0.0020％、REM：0.001 〜0.0
20 ％およびCa：0.001 〜0.010 ％のうちから選んだ１
種または２種以上を含有する組成になることを特徴とす
る溶接熱影響部の靱性に優れた構造用鋼材の製造方法。[0008] 3. In the above 1 or 2, the steel material further contains B: 0.0002 to 0.0020% and REM: 0.001 to 0.0% by mass%.
1 selected from 20% and Ca: 0.001 to 0.010%
A method for producing a structural steel material having excellent toughness in a heat-affected zone of a weld, characterized in that the composition has a composition containing at least two or more species.
【０００９】[0009]
【発明の実施の形態】以下、この発明を具体的に説明す
る。まず、この発明において、素材の成分組成を上記の
範囲に限定した理由について説明する。なお、以下に示
す成分組成の％表示はいずれも「質量％」である。 Ｃ：0.01〜0.18％ Ｃは、強度の向上に有用な元素であり、母材強度を確保
するためには0.01％以上の含有を必要とするが、0.18％
を超えて含有すると靱性および溶接性が劣化するので、
Ｃ量は0.01〜0.18％の範囲に限定した。なお、実用上の
好適範囲は0.06〜0.14％である。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, in the present invention, the reason why the component composition of the material is limited to the above range will be described. The percentages of the component compositions shown below are all “% by mass”. C: 0.01 to 0.18% C is an element useful for improving the strength, and it is necessary to contain 0.01% or more to secure the base material strength.
If it is contained in excess, the toughness and weldability deteriorate.
The amount of C was limited to the range of 0.01 to 0.18%. A practically preferable range is 0.06 to 0.14%.
【００１０】Si：0.02〜0.60％ Siは、強度増加に有用な元素であるが、含有量が0.02％
未満ではその添加効果に乏しく、一方0.60％を超えると
溶接熱影響部の靱性が著しく劣化するので、Si量は0.02
〜0.60％の範囲に限定した。Si: 0.02 to 0.60% Si is an element useful for increasing the strength, but the content is 0.02%
If the amount is less than 0.60%, the toughness of the heat affected zone is significantly deteriorated.
Limited to the range of ~ 0.60%.
【００１１】Mn：0.60〜2.00％ Mnも、Siと同様、強度増加に有用な元素であるが、含有
量が0.60％未満ではその添加効果に乏しく、一方2.00％
を超えると母材の靱性が著しく劣化するので、Mn量は0.
60〜2.00％の範囲に限定した。なお、好ましくは1.00〜
1.70％の範囲である。Mn: 0.60 to 2.00% Mn is also an element useful for increasing the strength, like Si, but if its content is less than 0.60%, the effect of its addition is poor.
If the Mn content exceeds 0.1%, the toughness of the base material is significantly degraded.
Limited to the range of 60-2.00%. In addition, preferably 1.00-
It is in the range of 1.70%.
【００１２】Ｐ：0.030 ％以下 Ｐは、靱性を劣化させる元素であるため、極力低減する
ことが好ましいが、0.030 ％までは許容できる。P: 0.030% or less Since P is an element that deteriorates toughness, it is preferable to reduce P as much as possible, but up to 0.030% is acceptable.
【００１３】Ｓ：0.015 ％以下 Ｓは、鋼中で主にMnＳとして存在し、圧延組織および溶
接熱影響部の組織を微細化する作用がある。しかしなが
ら、含有量が 0.015％を超えると母材の靱性を劣化させ
るので、0.015 ％を上限とした。S: 0.015% or less S is present mainly as MnS in steel and has an effect of making the rolled structure and the structure of the weld heat affected zone finer. However, if the content exceeds 0.015%, the toughness of the base material is degraded, so the upper limit is 0.015%.
【００１４】Al：0.005 〜0.100 ％ Alは、脱酸のために少なくとも 0.005％の添加を必要と
するが、0.100 ％を超えると脱酸効果は飽和し、むしろ
コストの上昇を招くので、Alは 0.005〜0.100％の範囲
で含有させるものとした。Al: 0.005 to 0.100% Al needs at least 0.005% for deoxidation, but if it exceeds 0.100%, the deoxidizing effect saturates and rather increases the cost. The content was made in the range of 0.005 to 0.100%.
【００１５】Ti：0.007 〜0.030 ％ Tiは、主にTiＮとして存在し、結晶粒の微細化に不可欠
の元素である。TiＮは高温においても安定で、溶接熱影
響部のオーステナイト粒成長を抑制する作用を有してい
る。溶接時において、溶融線近傍でもこの効果を得るた
めには、1400℃以上の高温域でも十分なTiＮ量を確保す
る必要があり、そのためには少なくとも0.007 ％のTiを
必要とする。一方、Ti量が 0.030％を超えると鋼の清浄
性、靱性を低下させる。従って、Ti量は 0.007〜0.030
％の範囲に限定した。Ti: 0.007 to 0.030% Ti is mainly present as TiN and is an indispensable element for refining crystal grains. TiN is stable even at high temperatures, and has the effect of suppressing austenite grain growth in the heat affected zone. In order to obtain this effect even in the vicinity of the melting line at the time of welding, it is necessary to secure a sufficient amount of TiN even in a high temperature region of 1400 ° C. or more, and therefore, at least 0.007% of Ti is required. On the other hand, if the Ti content exceeds 0.030%, the cleanliness and toughness of the steel decrease. Therefore, the Ti content is 0.007 to 0.030
%.
【００１６】Ｎ：0.0040〜0.0100％ Ｎは、Tiと結合してTiＮを形成し、結晶粒の微細化に有
効に寄与する。上述したとおり、TiＮは溶接熱影響部の
オーステナイト粒成長を抑制する作用を有しており、溶
接時に溶接線近傍でもこの効果を得るためには、1400℃
以上の高温域でも十分なTiＮ量を確保する必要があり、
そのためには0.0040％以上のＮを必要ととする。一方、
Ti量が0.0100％を超えると溶接加熱時に固溶状態で存在
し、熱影響部の靱性を低下させる。従って、Ｎ量は0.00
40〜0.0100％の範囲に限定した。N: 0.0040 to 0.0100% N combines with Ti to form TiN, and effectively contributes to refinement of crystal grains. As described above, TiN has an effect of suppressing austenite grain growth in the heat-affected zone of the welding.
It is necessary to secure a sufficient amount of TiN even in the above high temperature range,
For that purpose, N of 0.0040% or more is required. on the other hand,
If the Ti content exceeds 0.0100%, it exists in a solid solution state at the time of welding heating, and reduces the toughness of the heat-affected zone. Therefore, the amount of N is 0.00
Limited to the range of 40-0.0100%.
【００１７】以上、必須成分について説明したが、この
発明ではこれら必須成分の他にも、以下の成分を適宜含
有させることができる。 Cu：0.02〜1.5 ％、Ni：0.02〜0.6 ％、Cr：0.05〜0.50
％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％および
Ｖ：0.03〜0.15％のうちから選んだ１種または２種以上 Cu，Ni，Cr，Mo，NbおよびＶはいずれも、焼入れ性を向
上させることによって母材強度を向上させる元素である
が、この効果を得るためにはそれぞれ、Cu≧0.02％、Ni
≧0.02％、Cr≧0.05％、Mo≧0.02％、Nb≧0.003 ％、Ｖ
≧0.03％の添加が必要である。一方、Cuは 1.5％を超え
ると熱間加工性の低下が著しくなるので1.5 ％を上限と
した。Niは、0.60％を超えると製造コストの上昇を招く
ので0.60％を上限とした。Nbは、0.030 ％を超えると熱
影響部の靱性を低下させるので、0.030 ％を上限とし
た。また、Cr，Mo，Ｖについては、多量添加は溶接性、
靱性を劣化させるので、それぞれ0.50％、0.50％、0.15
％を上限とした。The essential components have been described above. In the present invention, the following components can be appropriately contained in addition to these essential components. Cu: 0.02 to 1.5%, Ni: 0.02 to 0.6%, Cr: 0.05 to 0.50
%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030% and V: 0.03 to 0.15% One or more selected from Cu, Ni, Cr, Mo, Nb and V are all hardenability. Is an element that improves the strength of the base metal by improving the Cu. To obtain this effect, Cu ≧ 0.02% and Ni
≧ 0.02%, Cr ≧ 0.05%, Mo ≧ 0.02%, Nb ≧ 0.003%, V
Addition of ≧ 0.03% is required. On the other hand, when the content of Cu exceeds 1.5%, the hot workability significantly decreases, so the upper limit is set to 1.5%. If Ni exceeds 0.60%, the production cost will increase, so the upper limit is set to 0.60%. If Nb exceeds 0.030%, the toughness of the heat-affected zone decreases, so the upper limit was made 0.030%. For Cr, Mo, and V, large additions have weldability,
0.50%, 0.50%, 0.15%
% As the upper limit.
【００１８】Ｂ：0.0002〜0.0020％、 REM：0.001 〜0.
020 ％およびCa：0.001 〜0.010 ％のうちから選んだ１
種または２種以上 Ｂ，REM およびCaはいずれも、圧延後のフェライト粒の
微細化に有効に寄与する元素である。すなわち、Ｂは、
結晶粒界に偏析して粗大なフェライトの生成を抑制し、
圧延後のフェライト粒径を微細化する作用を有してい
る。この効果は、0.0002％以上の添加により認められる
が、0.0020％を超える添加は母材の靱性を低下させるの
で、0.0002〜0.0020％の範囲とした。REM およびCaはそ
れぞれ、高温で安定な微細酸化物を形成することによ
り、圧延後のフェライト粒を微細化する。さらに、溶接
熱影響部の靱性を向上させる効果もある。これらの効果
は REM, Caいずれも 0.001％以上の添加で認められる。
一方、REM , Caはいずれも、多量に添加すると鋼の清浄
性、母材靱性が低下するので、それぞれ 0.020％、 0.0
10％を上限とした。B: 0.0002-0.0020%, REM: 0.001-0.
020% and Ca: 0.001 to 0.010%
B, REM and Ca are all elements that effectively contribute to the refinement of ferrite grains after rolling. That is, B is
Segregation at the grain boundaries suppresses the formation of coarse ferrite,
It has the function of reducing the ferrite grain size after rolling. This effect is recognized when the addition is 0.0002% or more. However, the addition exceeding 0.0020% lowers the toughness of the base material. REM and Ca each refine a ferrite grain after rolling by forming a fine oxide that is stable at high temperatures. Further, there is an effect of improving the toughness of the heat affected zone. These effects are observed when both REM and Ca are added at 0.001% or more.
On the other hand, when both REM and Ca are added in large amounts, the cleanliness of the steel and the base metal toughness decrease, so that 0.020% and 0.020%, respectively, are added.
The upper limit was 10%.
【００１９】なお、この発明では、製造された鋼材に含
有されるTiＮの初期平均粒径（円相当直径）を0.02〜0.
04μm とすることが重要である。というのは、TiＮは微
細なほど高密度となるため加熱時のオーステナイト粒の
微細化に有効であるが、径が小さいほど高温での溶解速
度が速く、平均粒径が0.02μm 未満では大部分のTiＮが
溶接中に溶解してしまうために十分な効果が得られず、
一方平均粒径が0.04μm より大きい場合には、TiＮ密度
が低くなるため十分なオーステナイト粒の微細化効果が
得られないからである。In the present invention, the initial average particle diameter (equivalent circle diameter) of TiN contained in the manufactured steel material is 0.02 to 0.2.
It is important to make it 04 μm. This is because TiN is effective for refining austenite grains during heating because it becomes denser as it becomes finer, but the smaller the diameter, the faster the dissolution rate at high temperatures. Of TiN is melted during welding, so it is not possible to obtain a sufficient effect.
On the other hand, if the average particle size is larger than 0.04 μm, the TiN density becomes low, so that a sufficient austenite grain refining effect cannot be obtained.
【００２０】TiＮの平均粒径を0.02〜0.04μm とするた
めには、TiおよびＮの添加量に加えて、凝固時の冷却速
度を制御する必要がある。図１は、この発明の成分組成
範囲を満足する５種類の鋼を４種類の冷却パターンで凝
固させた後、熱間圧延した鋼板について、TiＮ平均粒径
に及ぼすTi／Ｎ比と冷却速度の影響について調査した結
果である。なお、TiＮの平均粒径は、鋼板表面を電解エ
ッチングしたのち、SEM 観察し、SEM 像を画像解析する
ことにより求めた。また、冷却速度の指標としては、Ti
Ｎの析出、成長が起こる1500℃から1100℃までの冷却時
間ｔ15/11 を用いた。In order to make the average particle size of TiN 0.02 to 0.04 μm, it is necessary to control the cooling rate during solidification in addition to the amounts of Ti and N added. FIG. 1 shows the effect of the Ti / N ratio and cooling rate on the TiN average grain size of a hot rolled steel sheet after solidifying five types of steels satisfying the component composition range of the present invention with four types of cooling patterns. It is the result of investigating the effect. The average particle size of TiN was determined by subjecting the steel sheet surface to electrolytic etching, observing the SEM, and analyzing the SEM image by image analysis. As an index of the cooling rate, Ti
A cooling time t 15/11 from 1500 ° C. to 1100 ° C. where N precipitation and growth occur was used.
【００２１】同図に示したとおり、TiＮの平均粒径は、
Ti／Ｎ比と冷却速度によって大きく変化することが分か
る。そして、t15/11が一定で、TiおよびＮ量がこの発明
の適正範囲を満足していれば、TiＮの平均粒径はTi／Ｎ
比によってほぼ一義的に定まり、従ってTi／Ｎ比が粒径
制御に最適な指標であることも明らかとなった。As shown in the figure, the average particle size of TiN is
It can be seen that the temperature greatly changes depending on the Ti / N ratio and the cooling rate. If t 15/11 is constant and the amounts of Ti and N satisfy the appropriate range of the present invention, the average particle size of TiN is Ti / N
It was also found that the Ti / N ratio was almost uniquely determined by the ratio, and thus the Ti / N ratio was the most suitable index for controlling the particle size.
【００２２】次に、図２に、平均粒径：0.02μm および
0.04μm を与える冷却速度およびTi／Ｎ比をプロットし
た結果を示す。同図の結果から、0.02μm のTiＮ平均粒
径を与えるTi／Ｎ比：（Ti／Ｎ)20 は次式(2) （Ti／Ｎ)20 ＝ 22600／(t15/11)1.25 --- (2) で、また0.04μm のTiＮ平均粒径を与えるTi／Ｎ比：
（Ti／Ｎ)40 は次式(3) （Ti／Ｎ)40 ＝ 1818000／(t15/11)1.7 --- (3) で、それぞれ表されることが分かった。よって、平均粒
径を0.02〜0.04μm の範囲に制御するためには、Ti／Ｎ
比および1500℃から1100℃までの冷却時間ｔ15/11 につ
いて、次式(1) の関係を満足する範囲に制御すれば良い
ことが分かる。 22600／(t15/11)1.25≦Ti／Ｎ≦ 1818000／(t15/11)1.7 --- (1) Next, FIG. 2 shows that the average particle size is 0.02 μm and
The result of plotting the cooling rate and the Ti / N ratio giving 0.04 μm is shown. From the results shown in the figure, the Ti / N ratio giving a TiN average particle size of 0.02 μm: (Ti / N) 20 is given by the following formula (2) (Ti / N) 20 = 22600 / (t 15/11 ) 1.25 − -Ti / N ratio in (2), which also gives a TiN average particle size of 0.04 μm:
It was found that (Ti / N) 40 is represented by the following equation (3) (Ti / N) 40 = 1818000 / (t 15/11 ) 1.7 --- (3) Therefore, in order to control the average particle size in the range of 0.02 to 0.04 μm, Ti / N
It can be seen that the ratio and the cooling time t 15/11 from 1500 ° C. to 1100 ° C. should be controlled within a range that satisfies the following equation (1). 22600 / (t 15/11 ) 1.25 ≦ Ti / N ≦ 1818000 / (t 15/11 ) 1.7 --- (1)
【００２３】なお、従来では、冷却速度が大きいほどTi
Ｎの平均粒径が微細化することが知られていたが、従来
の鋼板で、成分組成や冷却速度をそれぞれ個別に所定の
範囲に制御しても最適なTiＮ粒径が得られないことがあ
ったのは、組成と冷却速度を同時に制御していなかった
ことが原因であると考えられる。Conventionally, as the cooling rate increases, the Ti
It has been known that the average particle size of N becomes finer. However, in a conventional steel plate, even if the component composition and the cooling rate are individually controlled within predetermined ranges, an optimum TiN particle size may not be obtained. This is probably because the composition and the cooling rate were not controlled at the same time.
【００２４】以上述べてきたように、Ti／Ｎ比およびｔ
15/11 を併せて制御すれば、TiＮ平均粒径を0.02〜0.04
μm の範囲に制御することができ、その結果、加熱時に
おけるオーステナイト粒の粗大化を効果的に抑制して、
熱影響部の靱性を確保することができるのである。この
理由については、まだ明確に解明されたわけではない
が、次のとおりと考えられる。すなわち、冷却中のTiＮ
の成長はTiの拡散に律速されているためTi量が多いほど
サイズが大きくなると考えられるが、この発明の成分範
囲では、冷却速度とTi／Ｎ比を一定に制御すればほぼ同
一の平均粒径を与えることができる。これは、TiＮの成
長がTi量の増加により大きくなる一方、Ti量が一定のと
きＮ量の増加（Ti／Ｎ比の減少）と共にTiＮ密度が増加
して一個当たりのサイズが小さくなるためであると推定
される。従って、冷却速度の制御に加えて、Ti，Ｎの添
加量だけではなく、Ti／Ｎ比を制御することにより、よ
り広い成分範囲および冷却条件において所定のTiＮ粒径
を得ることができるものと考えられる。As described above, the Ti / N ratio and t
By controlling 15/11 together, the average particle size of TiN can be 0.02-0.04.
μm range, and as a result, the austenite grain coarsening during heating can be effectively suppressed,
The toughness of the heat-affected zone can be ensured. The reason for this has not been clarified yet, but it is considered as follows. That is, TiN during cooling
Since the growth of Ti is limited by the diffusion of Ti, it is considered that the size increases as the Ti amount increases. However, in the component range of the present invention, if the cooling rate and the Ti / N ratio are controlled to be constant, almost the same average grain size is obtained. The diameter can be given. This is because the growth of TiN increases with an increase in the amount of Ti, but when the amount of Ti is constant, an increase in the amount of N (a decrease in the Ti / N ratio) increases the density of TiN and decreases the size per piece. It is estimated that there is. Therefore, by controlling the Ti / N ratio as well as the amount of Ti and N added in addition to controlling the cooling rate, it is possible to obtain a predetermined TiN particle size in a wider component range and cooling conditions. Conceivable.
【００２５】次に，この発明の鋼材の製造方法について
説明する。上記の好適成分組成範囲を満足する鋼を、転
炉、電気等で溶製し、連続鋳造法あるいは造塊法により
凝固させる。この時、1500℃から1100℃までの冷却時間
ｔ15/11 を、Ti／Ｎ比に応じて調整し、前記(1) 式を満
足する条件で冷却する。また、操業上冷却時間を変化さ
せることが困難な場合には、Ti／Ｎ比を冷却条件に合わ
せて適正範囲として製造すればよい。さらに、鋳片は所
定の厚さに圧延されるが、圧延時に通常行われている12
00℃以下で数時間以内の加熱ではTiＮの分布状態はほと
んど変化しない。以上述べてきたように、Ti／Ｎ比と15
00℃から1100℃までの冷却時間ｔ15/11を適切に制御す
れば、TiＮ平均粒径を0.02〜0.04μm とすることがで
き、その結果、熱影響部の靱性に優れた鋼材を製造する
ことができる。Next, a method of manufacturing a steel material according to the present invention will be described. Steel that satisfies the above preferred component composition range is melted by a converter, electricity, or the like, and solidified by a continuous casting method or an ingot casting method. At this time, the cooling time t 15/11 from 1500 ° C. to 1100 ° C. is adjusted according to the Ti / N ratio, and the cooling is performed under the condition satisfying the expression (1). Further, when it is difficult to change the cooling time during operation, the Ti / N ratio may be manufactured in an appropriate range according to the cooling conditions. Further, the slab is rolled to a predetermined thickness.
Heating at a temperature of 00 ° C. or less for a few hours hardly changes the distribution of TiN. As described above, the Ti / N ratio and 15
By appropriately controlling the cooling time t 15/11 from 00 ° C. to 1100 ° C., the average particle size of TiN can be 0.02 to 0.04 μm, and as a result, a steel material having excellent heat-affected zone toughness can be produced. be able to.
【００２６】[0026]
【実施例】表１に示す成分組成になる鋼を、転炉で溶製
し、連続鋳造法により 200mmおよび 300mm厚のスラブと
した。各スラブについて、凝固時における1500℃から11
00℃までの冷却時間ｔ15/11 を鋳込み速度、水冷条件な
どを基に計算した結果、厚さ方向で平均すると、厚み：
200 mmのスラブは1900ｓ、厚み：300 mmのスラブは3400
ｓであった。それぞれの冷却条件において、0.02μm お
よび0.04μm のTiＮ平均粒径を与えるTi／Ｎ比((Ti／
Ｎ)20 および (Ti／Ｎ)40 ) を前記(2), (3)式より算出
した。また、これらのスラブを加熱圧延により50mmの板
厚に仕上げたのち、板厚1/4部からTiＮ分布測定用試料
を採取し、SEM によりTiＮの平均粒径を求めた。さら
に、板厚1/4 部から圧延方向と直角方向に12mm×75mm×
80mmの試験片を採取し、高周波加熱装置により入熱：40
0 kJ／cmのエレクトロガスアーク溶接の溶融線近傍の熱
影響部に相当する熱サイクル（最高加熱温度1400℃）を
付与したのち、シャルピー衝撃試験片を採取し、−40℃
におけるシャルピー吸収エネルギー（vE-40)を測定し
た。得られた結果を表２に示す。EXAMPLES Steel having the composition shown in Table 1 was melted in a converter, and slabs having a thickness of 200 mm and 300 mm were formed by continuous casting. For each slab, from 1500 ° C during solidification to 11
As a result of calculating the cooling time t 15/11 to 00 ° C. based on the casting speed, water cooling conditions, and the like, the average in the thickness direction is:
200mm slab is 1900s, thickness: 300mm slab is 3400s
s. Under each cooling condition, the Ti / N ratio ((Ti /
N) 20 and (Ti / N) 40 ) were calculated from the above equations (2) and (3). After finishing these slabs by hot rolling to a thickness of 50 mm, a sample for measuring TiN distribution was sampled from 1/4 part of the thickness, and the average particle size of TiN was determined by SEM. Furthermore, 12 mm x 75 mm x
A test piece of 80 mm is sampled, and heat input by a high frequency heating device: 40
After applying a heat cycle (maximum heating temperature of 1400 ° C) corresponding to the heat-affected zone near the melting line of electrogas arc welding at 0 kJ / cm, a Charpy impact test specimen was sampled, and then -40 ° C.
Was measured for Charpy absorbed energy (vE-40). Table 2 shows the obtained results.
【００２７】[0027]
【表１】 [Table 1]
【００２８】[0028]
【表２】 [Table 2]
【００２９】表２から明らかなように、この発明に従い
得られた鋼材は、母材のTiＮ平均粒径が0.02〜0.04μm
の範囲を満足し、溶接熱影響部において高靱性が得られ
ている。これに対し、この発明の要件を満足しないもの
は、熱影響部の靱性が低い。特に成分組成がこの発明の
適正範囲を満足していても、Ti／Ｎ比と冷却条件がこの
発明の条件を満たしていない場合（No.11 〜16）には、
TiＮが微細化あるいは粗大化しすぎて、良好な靱性は得
られなかった。As apparent from Table 2, the steel material obtained according to the present invention has a TiN average particle size of 0.02 to 0.04 μm
And high toughness is obtained in the heat affected zone. On the other hand, those not satisfying the requirements of the present invention have low toughness of the heat-affected zone. In particular, even if the component composition satisfies the proper range of the present invention, if the Ti / N ratio and cooling conditions do not satisfy the conditions of the present invention (Nos. 11 to 16),
TiN was too fine or coarse, and good toughness was not obtained.
【００３０】[0030]
【発明の効果】かくして、この発明によれば、大入熱溶
接熱影響部においても良好な靱性を有する鋼材を歩留り
よく製造することが可能となり、各種溶接構造物の安全
性を格段に向上させることができる。As described above, according to the present invention, it is possible to produce a steel material having good toughness even in the heat-affected zone with a large heat input welding at a good yield, and to greatly improve the safety of various welded structures. be able to.
【図１】 TiＮ平均粒径におよぼす鋳片の冷却条件とTi
／Ｎ比の影響を示す図である。Fig. 1 Cooling conditions of cast slab and Ti
It is a figure which shows the influence of / N ratio.
【図２】 TiＮ平均粒径に及ぼす鋳片の冷却条件および
Ti／Ｎ比の影響を示す図である。FIG. 2 shows the effect of slab cooling conditions on TiN average particle size and
It is a figure showing the influence of Ti / N ratio.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｃ２２Ｃ 38/58 Ｃ２２Ｃ 38/58 (72)発明者 星野 俊幸 岡山県倉敷市水島川崎通１丁目（番地な し） 川崎製鉄株式会社水島製鉄所内 Ｆターム(参考） 4E004 KA12 MC02 NC01 ──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification symbol FI theme coat ゛ (Reference) C22C 38/58 C22C 38/58 (72) Inventor Toshiyuki 1-chome, Mizushima Kawasaki-dori, Kurashiki City, Okayama Prefecture F) Term in Kawasaki Steel Corporation Mizushima Works (reference) 4E004 KA12 MC02 NC01
Claims (3)
鋳片の冷却に際し、鋳片全厚にわたって平均した1500℃
から1100℃までの冷却時間ｔ15/11 （秒）とTi／Ｎ比に
ついて、次式(1) 22600／(t15/11)1.25≦Ti／Ｎ≦ 1818000／(t15/11)1.7 --- (1) の関係を満足させることを特徴とする溶接熱影響部の靱
性に優れた構造用鋼材の製造方法。C .: 0.01 to 0.18%, Si: 0.02 to 0.60%, Mn: 0.60 to 2.00%, P: 0.030% or less, S: 0.015% or less, Al: 0.005 to 0.100%, Ti : 0.007 to 0.030% and N: 0.0040 to 0.0100%, with the balance being 1500 ° C averaged over the entire thickness of the slab when cooling the slab to become Fe and inevitable impurities.
The cooling time t 15/11 (sec) from the temperature to 1100 ° C. and the Ti / N ratio are as follows: (1) 22600 / (t 15/11 ) 1.25 ≦ Ti / N ≦ 1818000 / (t 15/11 ) 1.7 − -A method for producing a structural steel material having excellent toughness in a weld heat affected zone, which satisfies the relationship (1).
％で Cu：0.02〜1.5 ％、 Ni：0.02〜0.6 ％、 Cr：0.05〜0.50％、 Mo：0.02〜0.50％、 Nb：0.003 〜0.030 ％および Ｖ：0.03〜0.15％ のうちから選んだ１種または２種以上を含有する組成に
なることを特徴とする溶接熱影響部の靱性に優れた構造
用鋼材の製造方法。2. The steel material according to claim 1, wherein the steel material further contains, by mass%, Cu: 0.02 to 1.5%, Ni: 0.02 to 0.6%, Cr: 0.05 to 0.50%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030. % And V: 0.03 to 0.15%. A method for producing a structural steel material excellent in toughness of a heat affected zone by welding, characterized in that the composition contains one or more selected from 0.03 to 0.15%.
らに質量％で Ｂ：0.0002〜0.0020％、 REM：0.001 〜0.020 ％および Ca：0.001 〜0.010 ％ のうちから選んだ１種または２種以上を含有する組成に
なることを特徴とする溶接熱影響部の靱性に優れた構造
用鋼材の製造方法。3. The steel material according to claim 1, wherein the steel material is at least one selected from the group consisting of B: 0.0002 to 0.0020%, REM: 0.001 to 0.020%, and Ca: 0.001 to 0.010% by mass%. A method for producing a structural steel material having excellent toughness in a heat affected zone by welding, characterized by having a composition containing
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Cited By (6)
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|---|---|---|---|---|
| JP2009019244A (en) * | 2007-07-12 | 2009-01-29 | Kobe Steel Ltd | Thick steel plate for high heat input welding having excellent brittle fracture propagation stop characteristic |
| JP2009174059A (en) * | 2004-07-21 | 2009-08-06 | Nippon Steel Corp | Steel plate for welded structure excellent in low temperature toughness of heat affected zone of welded part |
| JP2013019014A (en) * | 2011-07-11 | 2013-01-31 | Jfe Steel Corp | Steel for weld structure superior in ctod property at large heat input weld heat affected zone, and production method thereof |
| KR20150015506A (en) * | 2012-06-19 | 2015-02-10 | 가부시키가이샤 고베 세이코쇼 | Steel material having excellent toughness in weld-heat-affected zone |
| EP1726675A3 (en) * | 2005-05-25 | 2016-09-21 | The Japan Steel Works, Ltd. | Base material for a clad steel and method for the production of clad steel from same |
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2001
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2009174059A (en) * | 2004-07-21 | 2009-08-06 | Nippon Steel Corp | Steel plate for welded structure excellent in low temperature toughness of heat affected zone of welded part |
| EP1726675A3 (en) * | 2005-05-25 | 2016-09-21 | The Japan Steel Works, Ltd. | Base material for a clad steel and method for the production of clad steel from same |
| JP2009019244A (en) * | 2007-07-12 | 2009-01-29 | Kobe Steel Ltd | Thick steel plate for high heat input welding having excellent brittle fracture propagation stop characteristic |
| JP2013019014A (en) * | 2011-07-11 | 2013-01-31 | Jfe Steel Corp | Steel for weld structure superior in ctod property at large heat input weld heat affected zone, and production method thereof |
| KR20150015506A (en) * | 2012-06-19 | 2015-02-10 | 가부시키가이샤 고베 세이코쇼 | Steel material having excellent toughness in weld-heat-affected zone |
| KR101697845B1 (en) | 2012-06-19 | 2017-01-18 | 가부시키가이샤 고베 세이코쇼 | Steel material having enhanced toughness in weld-heat-affected zone |
| CN111334713A (en) * | 2020-03-30 | 2020-06-26 | 包头钢铁（集团）有限责任公司 | Q390D steel plate and production method thereof |
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