JPH11140582A - High toughness thick steel plate excellent in toughness in weld heat-affected zone, and its production - Google Patents
High toughness thick steel plate excellent in toughness in weld heat-affected zone, and its productionInfo
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- JPH11140582A JPH11140582A JP30853997A JP30853997A JPH11140582A JP H11140582 A JPH11140582 A JP H11140582A JP 30853997 A JP30853997 A JP 30853997A JP 30853997 A JP30853997 A JP 30853997A JP H11140582 A JPH11140582 A JP H11140582A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、建築、海洋構造
物、鋼管、船舶、貯槽、土木建設機械などの用途に適用
できる厚鋼板およびその製造方法に関し、さらに厚鋼板
に限らず熱延鋼帯、形鋼、棒鋼等の非調質圧延鋼材の製
造方法にも適用できる。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick steel plate applicable to applications such as buildings, marine structures, steel pipes, ships, storage tanks, and civil engineering construction machines, and a method of manufacturing the same. The present invention can also be applied to a method for producing a non-heat treated rolled steel material such as a steel bar, a shape steel bar and a steel bar.
【０００２】[0002]
【従来の技術】強度、靱性をともに向上させた鋼材の製
造方法として、Ti、Nb、Ｖ等を含む鋼素材を用いＴＭＣ
Ｐ（TheromoMechanical Control Process ）により微細
な組織を得る技術が従来から知られている。しかし、こ
のＴＭＣＰ技術では、低温のオーステナイト未再結晶温
度域で高圧下を施す必要があり、圧延機に多大の負荷が
かかり、また、厚肉材の場合には十分な圧下量が確保で
きないなどの問題があった。また、温度調節のための待
ち時間が増大して、圧延能率が低下し、さらに、加速冷
却を施す場合には、低温まで冷却する必要があり、鋼板
に歪、応力が残留するなどの問題があった。2. Description of the Related Art As a method of producing a steel material having improved strength and toughness, TMC using a steel material containing Ti, Nb, V, etc.
A technique for obtaining a fine structure by P (Thermo Mechanical Control Process) has been conventionally known. However, in this TMCP technique, it is necessary to apply a high pressure in a low-temperature austenite non-recrystallization temperature range, which imposes a large load on a rolling mill, and in the case of a thick material, a sufficient amount of reduction cannot be secured. There was a problem. In addition, the waiting time for temperature adjustment increases, the rolling efficiency decreases, and when accelerated cooling is performed, it is necessary to cool to a low temperature, and there are problems such as distortion and stress remaining in the steel sheet. there were.
【０００３】一方、溶接熱影響部の靱性を向上させるた
めに、例えば、特開平2-125812号公報には、粒径0.05〜
10μm のTiを主成分とする酸化物を５×103 〜１×106
個／mm3 鋼中に分散させた溶接熱影響部靱性に優れた鋼
材の製造方法が開示されている。また、特開平4-48048
号公報には、母地中に0.001 〜0.100wt ％の割合で、粒
径0.5 μm 以下の（Ti，Nb）（Ｏ，Ｎ）複合結晶相を有
した酸化物系介在物を分散させ、溶接熱影響部の靱性を
向上させた溶接熱影響部靱性に優れた鋼材の製造方法が
提案されている。On the other hand, in order to improve the toughness of the heat affected zone, for example, Japanese Patent Application Laid-Open No. H2-125812 discloses that
Oxide mainly composed of 10 μm Ti is 5 × 10 3 to 1 × 10 6
A method for producing a steel material having excellent toughness in a weld heat-affected zone dispersed in steel / mm 3 steel is disclosed. Also, JP-A-4-48048
In the publication, oxide-based inclusions having a (Ti, Nb) (O, N) composite crystal phase with a particle size of 0.5 μm or less are dispersed in a matrix at a ratio of 0.001 to 0.100 wt%, and welding is performed. There has been proposed a method of manufacturing a steel material having improved toughness in a heat-affected zone, which has improved toughness in a heat-affected zone.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、酸化物
系介在物を鋼中に均一に分散させしかも所定の量に制御
するのには多くの困難を伴うなどの問題があった。この
発明は、上記した問題を解決し、母材強度・靱性に優れ
かつ溶接熱影響部靱性に優れた高靱性厚鋼板およびその
製造方法を提供することを目的とする。However, there have been problems in that it is difficult to uniformly disperse the oxide-based inclusions in the steel and control it to a predetermined amount. An object of the present invention is to solve the above-mentioned problems, and to provide a high-toughness thick steel sheet excellent in base metal strength and toughness and excellent in the heat-affected zone of the weld zone, and a method of manufacturing the same.
【０００５】[0005]
【課題を解決するための手段】本発明者らは、上記した
課題を解決するために、鋭意検討した結果、次のような
知見を得た。 Ti、Ｖ、Ｎ量を制御することにより、TiN 、VN、ある
いはTiN とVNの複合介在物を核としてフェライトが析出
し、微細なフェライト−パーライト組織となり靱性が向
上する。Means for Solving the Problems The present inventors have made intensive studies in order to solve the above-mentioned problems, and have obtained the following findings. By controlling the amounts of Ti, V, and N, ferrite is precipitated with TiN, VN, or a composite inclusion of TiN and VN as a nucleus, resulting in a fine ferrite-pearlite structure and improved toughness.
【０００６】TiN が円相当径で0.03μm 以上の大きさ
になるとフェライト生成核として作用する。 円相当径で0.05μm 以上の大きさのTiN は、加熱時の
オーステナイト粒の微細化に有効である。 TiN を、、に示される大きさに制御すると、フェ
ライト結晶粒が飛躍的に微細化し、靱性が顕著に向上す
る。When TiN has a diameter equivalent to a circle of 0.03 μm or more, it acts as a ferrite nucleus. TiN having a circle equivalent diameter of 0.05 μm or more is effective for refining austenite grains during heating. When TiN is controlled to the size indicated by, ferrite crystal grains are remarkably miniaturized and toughness is remarkably improved.
【０００７】この発明は上記した知見に基づき構成され
たものである。すなわち、この発明は、重量％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：0.005 〜0.30％、Ｎ：0.0050〜0.0200％を
含み、好ましくはTi／Ｎ：4.0〜12.0とし、さらに次
（１）式 Ｃeq（％）＝Ｃ＋Si/24 ＋Mn/6＋Ni/40 ＋Cr/5＋Mo/4＋Ｖ/14 ……（１） で定義されるＣeqが0.36〜0.45％で、残部Feおよび不可
避的不純物からなる組成で、かつ円相当径が0.05μm 以
下のTiN が１×103 個／mm2 以上、円相当径が0.03〜0.
2 μm のTiN を１×103 個／mm2 以上１×105 個／mm2
未満含有することを特徴とする溶接熱影響部靱性に優れ
た高靱性厚鋼板である。The present invention has been made based on the above findings. That is, the present invention provides, in weight percent, C:
0.01-0.18%, Si: 0.02-0.60%, Mn: 0.60-2.00%,
P: 0.030% or less, S: 0.015% or less, Al: 0.005-0.
100%, Ti: 0.005 to 0.30%, N: 0.0050 to 0.0200%, preferably Ti / N: 4.0 to 12.0, and the following equation (1): Ceq (%) = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 1 × 10 3 TiN having a Ceq defined by (1) of 0.36 to 0.45%, a composition comprising the balance of Fe and unavoidable impurities, and having a circle equivalent diameter of 0.05 μm or less. / Mm 2 or more, circle equivalent diameter 0.03 ~ 0.
2 μm TiN 1 × 10 3 / mm 2 or more 1 × 10 5 / mm 2
It is a high toughness steel plate excellent in toughness of a weld heat affected zone characterized by containing less than.
【０００８】また、この発明では、前記組成に加えて、
さらに重量％で、Cu：0.02〜1.50％、Ni：0.02〜0.60
％、Cr：0.05〜0.50％、Mo：0.02〜0.50％、Nb：0.003
〜0.030 ％の合金元素群から選ばれた１種または２種以
上を含有してもよく、また、前記組成に加えて、さらに
Ｖ：0.03〜0.15％を含有してもよく、また、前記組成に
加えて、さらにＢ：0.0002〜0.0020％、REM ：0.0010〜
0.0200％、Ca：0.0010〜0.0100％の合金元素群から選ば
れた１種または２種以上を含有してもよく、また、上記
した合金元素および各合金元素群から選ばれた１種また
は２種以上を複合して含有してもよい。In the present invention, in addition to the above-mentioned composition,
Further, by weight%, Cu: 0.02 to 1.50%, Ni: 0.02 to 0.60
%, Cr: 0.05 to 0.50%, Mo: 0.02 to 0.50%, Nb: 0.003
One or more elements selected from the group consisting of alloy elements of up to 0.030% may be contained. In addition to the above composition, V may further contain 0.03 to 0.15%. In addition, B: 0.0002-0.0020%, REM: 0.0010-
One or two or more selected from the alloying element group of 0.0200% and Ca: 0.0010 to 0.0100% may be contained, and one or two or more selected from the above alloying elements and each alloying element group. The above may be combined and contained.
【０００９】また、第２のこの発明は、重量％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：0.005 〜0.30％、Ｎ：0.0050〜0.0200％を
含み、好ましくはTi／Ｎ：4.0 〜12.0とし、さらに前記
（１）式で定義されるＣeqが0.36〜0.45％で、残部Feお
よび不可避的不純物からなる組成の鋼素材を、1050℃以
上の温度で加熱したのち、0.5 ℃／ｓ以下の冷却速度で
冷却し、ついで、1050℃以上の温度範囲に再加熱して、
Ａr3変態点以上の温度範囲で１パス当たりの圧下率で５
％以上の圧下を累積圧下率で20％以上施したのち、ある
いはさらにＡr3変態点〜Ａr1変態点の温度範囲で圧下率
５％以上の圧下を施したのち、室温まで冷却することを
特徴とする溶接熱影響部靱性に優れた高靱性厚鋼板の製
造方法である。[0009] In the second invention, C:
0.01-0.18%, Si: 0.02-0.60%, Mn: 0.60-2.00%,
P: 0.030% or less, S: 0.015% or less, Al: 0.005-0.
100%, Ti: 0.005 to 0.30%, N: 0.0050 to 0.0200%, preferably Ti / N: 4.0 to 12.0, and Ceq defined by the above formula (1) is 0.36 to 0.45%, and the balance Fe And a steel material having a composition consisting of unavoidable impurities is heated at a temperature of 1050 ° C or more, then cooled at a cooling rate of 0.5 ° C / s or less, and then reheated to a temperature range of 1050 ° C or more,
5% reduction per pass in temperature range above Ar 3 transformation point
It is characterized by cooling down to room temperature after applying a reduction of at least 5% in a temperature range from the Ar 3 transformation point to the Ar 1 transformation point after applying a reduction of at least 20% with a cumulative reduction ratio of at least 20%. This is a method for producing a high-toughness thick steel sheet having excellent toughness in the weld heat-affected zone.
【００１０】また、第２のこの発明では、前記組成に加
えて、さらに重量％で、Cu：0.02〜1.50％、Ni：0.02〜
0.60％、Cr：0.05〜0.50％、Mo：0.02〜0.50％、Nb：0.
003〜0.030 ％から選ばれた１種または２種以上を含有
してもよく、また、前記組成に加えて、さらに重量％
で、Ｖ：0.03〜0.15％を含有してもよく、また、前記組
成に加えて、さらに重量％で、Ｂ：0.0002〜0.0020％、
REM ：0.0010〜0.0200％、Ca：0.0010〜0.0100％から選
ばれた１種または２種以上を含有してもよく、また、上
記した合金元素および各合金元素群から選ばれた１種ま
たは２種以上を複合して含有してもよい。In the second aspect of the present invention, in addition to the above composition, Cu: 0.02 to 1.50% and Ni: 0.02 to
0.60%, Cr: 0.05 to 0.50%, Mo: 0.02 to 0.50%, Nb: 0.
One or two or more selected from 003 to 0.030% may be contained.
V: 0.03 to 0.15% may be contained, and in addition to the above composition, B: 0.0002 to 0.0020%,
REM: 0.0010 to 0.0200%, Ca: 0.0010 to 0.0100%, may contain one or more kinds, and one or two kinds selected from the above-mentioned alloy elements and each alloy element group. The above may be combined and contained.
【００１１】また、第３のこの発明は、重量％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：0.005 〜0.30％、Ｎ：0.0050〜0.0200％を
含み、好ましくはTi／Ｎ：4.0 〜12.0とし、さらに前記
（１）式で定義されるＣeqが0.36〜0.45％で、残部Feお
よび不可避的不純物からなる組成の鋼素材を、1050℃以
上の温度で加熱したのち、0.5 ℃／ｓ以下の冷却速度で
冷却することを特徴とする高靱性厚鋼板用圧延素材の製
造方法であり、前記組成に加えて、さらに重量％で、C
u：0.02〜1.50％、Ni：0.02〜0.60％、Cr：0.05〜0.50
％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％から選ば
れた１種または２種以上を含有してもよく、また、前記
組成に加えて、さらに重量％で、Ｖ：0.03〜0.15％を含
有してもよく、また、前記組成に加えて、さらに重量％
で、Ｂ：0.0002〜0.0020％、REM ：0.0010〜0.0200％、
Ca：0.0010〜0.0100％から選ばれた１種または２種以上
を含有してもよく、上記した合金元素および各合金元素
群から選ばれた１種または２種以上を複合して含有して
もよい。[0011] Further, the present invention according to a third aspect of the present invention, C:
0.01-0.18%, Si: 0.02-0.60%, Mn: 0.60-2.00%,
P: 0.030% or less, S: 0.015% or less, Al: 0.005-0.
100%, Ti: 0.005 to 0.30%, N: 0.0050 to 0.0200%, preferably Ti / N: 4.0 to 12.0, and Ceq defined by the above formula (1) is 0.36 to 0.45%, and the balance Fe A method for producing a rolled material for a high toughness steel plate, comprising: heating a steel material having a composition comprising unavoidable impurities at a temperature of 1050 ° C. or more, and then cooling the steel material at a cooling rate of 0.5 ° C./s or less. , In addition to the above composition, further in weight%, C
u: 0.02 to 1.50%, Ni: 0.02 to 0.60%, Cr: 0.05 to 0.50
%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030%, and may contain one or more kinds. In addition to the above composition, V: 0.03 to 0.15% by weight. %, And in addition to the composition,
And B: 0.0002-0.0020%, REM: 0.0010-0.0200%,
Ca: one or two or more selected from 0.0010 to 0.0100% may be contained, and one or two or more selected from the above alloy elements and each alloy element group may be contained in combination. Good.
【００１２】[0012]
【発明の実施の形態】まず、この発明における、化学組
成の限定理由を説明する。 Ｃ：0.01〜0.18％ Ｃは、強度を増加する元素であり、強度確保のために0.
01％以上の含有を必要とする。一方、0.18％を超えて含
有すると母材靱性および溶接性が劣化する。このため、
Ｃは0.01〜0.18％とした。なお、実用上の好適範囲は、
0.08〜0.16％の範囲である。First, the reasons for limiting the chemical composition in the present invention will be described. C: 0.01 to 0.18% C is an element that increases the strength, and is 0.2% for securing the strength.
Requires a content of 01% or more. On the other hand, if the content exceeds 0.18%, base metal toughness and weldability deteriorate. For this reason,
C was set to 0.01 to 0.18%. In addition, the preferred range for practical use is
It is in the range of 0.08 to 0.16%.
【００１３】Si：0.02〜0.60％ Siは、強度増加に有効な元素であるが、0.02％未満では
その効果が認められない。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。このため、Siは0.02
〜0.60％の範囲に限定した。 Mn：0.60〜2.00％ Mnは、強度増加に有効な元素であり、強度確保の観点か
ら0.60％以上含有することが必要である。一方、Mn含有
量が2.00％を超えると、圧延後空冷した場合に組織がフ
ェライト＋ベイナイトとなり、母材靱性が低下する。こ
のため、Mn含有量は、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。Si: 0.02 to 0.60% Si is an element effective for increasing the strength, but if less than 0.02%, the effect is not recognized. On the other hand, if it exceeds 0.60%, the toughness of the heat affected zone is significantly deteriorated. Therefore, Si is 0.02
Limited to the range of ~ 0.60%. Mn: 0.60 to 2.00% Mn is an element effective for increasing the strength, and it is necessary to contain 0.60% or more from the viewpoint of securing the strength. On the other hand, if the Mn content exceeds 2.00%, the structure becomes ferrite + bainite when air-cooled after rolling, and the base material toughness decreases. For this reason, the Mn content is limited to the range of 0.60 to 2.00%.
In addition, it is preferably in the range of 1.00 to 1.70%.
【００１４】Ｐ：0.030 ％以下 Ｐは靱性を劣化させる元素であり、できるだけ低減する
のが好ましいが、0.030 ％までは許容できるため、0.03
0 ％を上限とした。 Ｓ：0.015 ％以下 Ｓは、鋼中では主にMnS として存在し、VNと同様に圧延
後の組織を微細化する作用があるが、0.015 ％を超える
と鋼板の板厚方向の靱性・延性を劣化させるため、Ｓは
0.015 ％以下とした。なお、組織微細化の観点からはＳ
は0.004 〜0.010 ％の範囲とするのが好ましい。P: not more than 0.030% P is an element that deteriorates toughness, and it is preferable to reduce it as much as possible.
The upper limit was 0%. S: 0.015% or less S exists mainly as MnS in steel and has an effect of refining the structure after rolling like VN. However, if it exceeds 0.015%, the toughness and ductility of the steel sheet in the thickness direction are reduced. To degrade, S
0.015% or less. In addition, from the viewpoint of microstructural refinement, S
Is preferably in the range of 0.004 to 0.010%.
【００１５】Al：0.005 〜0.100 ％ Alは、脱酸のために0.005 ％以上の添加が必要である
が、0.100 ％を超えて添加しても脱酸効果は飽和する。
このため、Alは0.005 〜0.100 ％の範囲とした。 Ti：0.005 〜0.30％ Tiは、主としてTiN として存在し、結晶粒の微細化に有
効な元素である。TiNは、鋼素材加熱時のオーステナイ
ト粒の粒成長を抑制し、さらにオーステナイト粒中に析
出し、その後析出するVNの析出を促進する作用を有して
いる。この効果を得るためにはTiは0.005 ％以上添加す
る必要があるが、0.30％を超えると鋼の清浄性、靱性を
低下させる。このため、Tiは0.005 〜0.30％の範囲とし
た。なお、好ましくは0.010 〜0.10％である。Al: 0.005 to 0.100% Al needs to be added in an amount of 0.005% or more for deoxidation. However, even if added in excess of 0.100%, the deoxidizing effect is saturated.
Therefore, the content of Al is set in the range of 0.005 to 0.100%. Ti: 0.005 to 0.30% Ti is present mainly as TiN and is an element effective for refining crystal grains. TiN has an effect of suppressing grain growth of austenite grains during heating of a steel material, further promoting precipitation of VN that precipitates in the austenite grains and then precipitates. To obtain this effect, Ti must be added in an amount of 0.005% or more, but if it exceeds 0.30%, the cleanliness and toughness of the steel deteriorate. Therefore, Ti is set in the range of 0.005 to 0.30%. The content is preferably 0.010 to 0.10%.
【００１６】Ｎ：0.0050〜0.0200％ Ｎは、Ti、Ｖと結合してTiN 、VNを形成し、結晶粒の微
細化に有効に寄与する。これら窒化物は、加熱時のオー
ステナイト粒の粒成長を抑制し、さらにフェライト析出
核として作用する。VNは、フェライト変態後にフェライ
ト粒内に析出し、強度を増加させるため、圧延後の冷却
に際して強水冷を行わずに母材強度を高めることがで
き、鋼板板厚方向の特性の均一性、残留応力の低減、残
留歪の低減に有効となる。これらの効果を得るために
は、Ｎ含有量は0.0050％以上とする必要があるが、0.02
00％を超えると母材靱性、溶接性が劣化する。このた
め、Ｎ含有量は0.0050〜0.0200％の範囲に限定した。N: 0.0050 to 0.0200% N combines with Ti and V to form TiN and VN, and effectively contributes to the refinement of crystal grains. These nitrides suppress grain growth of austenite grains during heating and further act as ferrite precipitation nuclei. VN precipitates in ferrite grains after ferrite transformation and increases the strength, so the base metal strength can be increased without performing strong water cooling during cooling after rolling, and the uniformity of properties in the thickness direction of the steel sheet, residual This is effective for reducing stress and residual strain. In order to obtain these effects, the N content needs to be 0.0050% or more.
If it exceeds 00%, the base material toughness and weldability deteriorate. For this reason, the N content is limited to the range of 0.0050 to 0.0200%.
【００１７】Ti／Ｎ：4.0 〜12.0 Ti／Ｎが、4.0 未満ではフリーＮが存在し、溶接性を低
下させるとともに歪時効を助長させる。一方、Ti／Ｎが
12.0を超えるとTiC 、あるいはVCが形成され、母材靱性
を低下させる。このため、Ti／Ｎは4.0 〜12.0の範囲と
するのが好ましい。なお、より好ましくは5.0 〜10.0の
範囲である。Ti / N: 4.0 to 12.0 When Ti / N is less than 4.0, free N exists to lower weldability and promote strain aging. On the other hand, Ti / N
If it exceeds 12.0, TiC or VC is formed, and the toughness of the base material is reduced. For this reason, Ti / N is preferably set in the range of 4.0 to 12.0. It is more preferably in the range of 5.0 to 10.0.
【００１８】Ｖ：0.03〜0.15％ Ｖは、圧延冷却中にオーステナイト粒内にVNとして析出
し、このVNを核としてフェライトが析出することから、
結晶粒微細化に有効に寄与し、母材靱性を向上させる効
果を有する。また、Ｖは、フェライト変態後にもフェラ
イト中にVNが析出し、母材強度を増加させるため、圧延
後の冷却に際して強水冷を行わずに母材強度を高めるこ
とができ、鋼板板厚方向の特性の均一性、残留応力の低
減、残留歪の低減に有効となる。これらの効果を得るた
めには、Ｖ含有量は0.03％以上とする必要があるが、0.
15％を超えると母材靱性、溶接性が劣化する。このた
め、Ｖ含有量は0.03〜0.15％の範囲に限定した。なお、
母材靱性の観点から好ましくは0.05〜0.10％の範囲であ
る。V: 0.03 to 0.15% V precipitates as VN in austenite grains during rolling and cooling, and ferrite precipitates using this VN as a nucleus.
It effectively contributes to crystal grain refinement and has the effect of improving base material toughness. V also precipitates VN in ferrite even after ferrite transformation and increases the strength of the base material, so that the strength of the base material can be increased without performing strong water cooling during cooling after rolling, and the steel sheet thickness direction can be increased. This is effective for uniformity of characteristics, reduction of residual stress, and reduction of residual strain. To obtain these effects, the V content needs to be 0.03% or more.
If it exceeds 15%, the base material toughness and weldability deteriorate. For this reason, the V content was limited to the range of 0.03 to 0.15%. In addition,
From the viewpoint of base metal toughness, it is preferably in the range of 0.05 to 0.10%.
【００１９】Cu：0.02〜1.50％、Ni：0.02〜0.60％、C
r：0.05〜0.50％、Mo：0.02〜0.50％、Nb：0.003 〜0.0
30 ％から選ばれた１種または２種以上 Cu、Ni、Cr、Mo、Nbはいずれも焼入れ性向上に有効な元
素であり、Ａr3変態点を介してTiN 、VNの細粒化効果を
最適化するとともに、VNの析出強化にも有効に作用す
る。すなわち、Ａr3変態点を低下させることにより、フ
ェライト粒がより微細になり、VNの析出強化効果が大き
くなる。しかし、Ａr3変態点が低下しすぎると、組織が
ベイナイト主体の組織となり、強度は増加するが母材靱
性が低下する。Cu: 0.02 to 1.50%, Ni: 0.02 to 0.60%, C
r: 0.05 to 0.50%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.0
One or more selected from 30% Cu, Ni, Cr, Mo, and Nb are all effective elements for improving hardenability, and have the effect of reducing the grain size of TiN and VN through the Ar 3 transformation point. In addition to optimizing, it also works effectively for strengthening the precipitation of VN. That is, by lowering the Ar 3 transformation point, the ferrite grains become finer, and the effect of strengthening the precipitation of VN increases. However, when the Ar 3 transformation point is too low, the structure becomes a bainite-based structure, and although the strength increases, the base material toughness decreases.
【００２０】このような効果を得るためには、Cu、Ni、
Cr、Mo、Nbはそれぞれ0.02％、0.02％、0.05％、0.02
％、0.003 ％以上の添加が必要である。一方、Cuは1.50
％を超えると熱間加工性の低下が著しくなるため、1.50
％を上限とした。Niは、焼入れ性向上に加えて、Cuの熱
間加工性の低下を補償するため添加するが、そのために
はCu含有量と当量程度のNiを添加するのが望ましい。し
かし、0.60％を超えての添加は、経済的に高価となるた
め、Ni含有量の上限を0.60％とした。また、Cr、Mo、Nb
の多量添加は溶接性、靱性を劣化させるため、それぞれ
0.50％、0.50％、0.030 ％を上限とした。In order to obtain such an effect, Cu, Ni,
Cr, Mo and Nb are 0.02%, 0.02%, 0.05% and 0.02 respectively.
%, 0.003% or more is required. On the other hand, Cu is 1.50
%, The hot workability is significantly reduced.
% As the upper limit. Ni is added for improving the hardenability and for compensating for the decrease in the hot workability of Cu. For this purpose, it is desirable to add Ni in an amount equivalent to the Cu content. However, the addition exceeding 0.60% is economically expensive, so the upper limit of the Ni content is set to 0.60%. Also, Cr, Mo, Nb
Addition of large amounts degrades weldability and toughness.
The upper limits are 0.50%, 0.50% and 0.030%.
【００２１】Ｂ：0.0002〜0.0020％、REM ：0.0010〜0.
0200％、Ca：0.0010〜0.0200％から選ばれた１種または
２種以上 Ｂ、REM 、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。Ｂは結晶粒界に偏析し
て粗大な粒界フェライトの生成を抑制し、圧延後のフェ
ライト結晶粒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
超える添加は母材靱性を低下させる。このため、Ｂは0.
0002〜0.0020％の範囲に限定した。B: 0.0002-0.0020%, REM: 0.0010-0.
0, 200%, Ca: one or more selected from 0.0010 to 0.0200% B, REM, and Ca are all elements that effectively contribute to the refinement of ferrite grains after rolling. B has the effect of segregating at the crystal grain boundaries to suppress the formation of coarse grain boundary ferrite and to refine the ferrite crystal grains after rolling. This effect is observed with the addition of 0.0002% or more, but the addition of more than 0.0020% decreases the base material toughness. Therefore, B is 0.
Limited to the range of 0002 to 0.0020%.
【００２２】REM 、Caは高温で安定な酸化物を形成し母
地中に微細分散し、加熱時のオーステナイト粒の粒成長
を抑制するとともに、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（ HAZ部）靱性を向上させ
る。これらの効果はREM 、Caとも0.0010％以上の添加で
認められるが、REM 、Caともに、0.0200％を超えると、
鋼の清浄性、母材靱性を低下させる。このため、REM 、
Caともに、0.0010〜0.0200％の範囲とした。REM and Ca form stable oxides at high temperatures and are finely dispersed in the matrix, suppress the growth of austenite grains during heating, and refine the ferrite grains after rolling. Furthermore, the toughness of the heat affected zone (HAZ) is improved. These effects are recognized when both REM and Ca are added at 0.0010% or more, but when both REM and Ca exceed 0.0200%,
Decreases steel cleanliness and base metal toughness. For this reason, REM,
Both Ca were set in the range of 0.0010 to 0.0200%.
【００２３】なお、上記した合金元素および各合金元素
群から選ばれた１種または２種以上を複合して含有して
もよいことはいうまでもない。 Ｃeq：0.36〜0.45％ Ｃeqは（１）式で定義される。 Ｃeq（％）＝Ｃ＋Si/24 ＋Mn/6＋Ni/40 ＋Cr/5＋Mo/4＋Ｖ/14 ……（１） Ｃeqが0.36％未満では、母材およびHAZ 軟化部での強度
確保が困難となる。また、Ｃeqが0.45％を超えると溶接
割れ感受性が増大しHAZ 部靱性が低下する。このため、
Ｃeqを0.36〜0.45％の範囲に限定した。It goes without saying that one or two or more selected from the above-mentioned alloying elements and respective alloying element groups may be contained in combination. Ceq: 0.36 to 0.45% Ceq is defined by equation (1). Ceq (%) = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (1) If Ceq is less than 0.36%, it becomes difficult to secure strength in the base material and the HAZ softened portion. On the other hand, if Ceq exceeds 0.45%, the susceptibility to weld cracking increases and the toughness of the HAZ decreases. For this reason,
Ceq was limited to the range of 0.36-0.45%.
【００２４】本発明の厚鋼板は、円相当径が0.05μm 以
下 のTiN を１×103 個／mm以上、および円相当径が0.
03〜0.2 μm のTiN を１×103 個／mm2 〜１×105 個／
mm2含有する。TiN は、微細なほど、とくにその大きさ
が円相当径で0.05μm 以下の場合には、加熱保持時のオ
ーステナイト粒の微細化に有効である。さらに、オース
テナイト粒の微細化効果を十分に発揮させるためには、
0.05μm 以下の大きさのTiN が１×103 個／mm2 以上必
要である。このため、0.05μm 以下の大きさのTiN の個
数を１×103 個／mm2 以上に限定した。The thick steel sheet of the present invention contains 1 × 10 3 pieces / mm or more of TiN having an equivalent circle diameter of 0.05 μm or less, and a circle equivalent diameter of 0.1 μm or less.
1 × 10 3 pieces / mm 2 〜1 × 10 5 pieces of 03-0.2 μm TiN
mm 2 contains. The finer the TiN, particularly when the size is 0.05 μm or less in a circle equivalent diameter, is effective for refining austenite grains during heating and holding. Furthermore, in order to sufficiently exhibit the effect of refining austenite grains,
TiN having a size of 0.05 μm or less needs to be 1 × 10 3 pieces / mm 2 or more. For this reason, the number of TiN having a size of 0.05 μm or less is limited to 1 × 10 3 / mm 2 or more.
【００２５】また、TiN は、圧延後の冷却過程あるいは
溶接時の高温からの冷却過程でフェライトの生成核とな
りフェライト粒の微細化に寄与する。TiN がフェライト
の生成核となるためには、円相当径で0.03μm 以上の大
きさとなることが必要である。しかし、TiN が円相当径
で0.2 μm を超える大きさとなると、母材靱性およびHA
Z 部靱性に悪影響を及ぼす。このため、TiN の大きさは
円相当径で0.03〜0.2μm の範囲とした。また、上記し
た大きさのTiN の個数が１×103 個／mm2 未満では、フ
ェライト粒微細化の効果が不十分となり、TiN の個数が
１×105 個／mm 2 以上では母材靱性、HAZ 部靱性が劣化
する。このため、円相当径で0.03〜0.2μm のTiN の個
数は１×103 個／mm2 〜１×105 個／mm2 の範囲に限定
した。本発明では、円相当径で0.05μm 以下の大きさの
TiN の個数を１×103 個／mm2以上とし、合わせてさら
に、円相当径で0.03〜0.2 μm のTiN の個数は１×103
個／mm2 〜１×105 個／mm2 の範囲に限定することによ
り、飛躍的にフェライト粒の微細化が達成でき、母材お
よび溶接熱影響部の靱性を大幅に向上させることができ
る。Further, TiN is used in a cooling process after rolling or
During the cooling process from high temperature during welding,
This contributes to the refinement of ferrite grains. TiN is ferrite
In order to become a nucleus for the production of
It needs to be timely. However, TiN has an equivalent circle diameter
When the size exceeds 0.2 μm, the base metal toughness and HA
This has an adverse effect on the toughness of the Z part. Therefore, the size of TiN is
The equivalent circle diameter was in the range of 0.03 to 0.2 μm. Also,
Number of TiN of 1 × 10ThreePieces / mmTwoLess than
The effect of refining of ferrite grains becomes insufficient, and the number of TiN
1 × 10FivePieces / mm TwoAbove, the base metal toughness and HAZ toughness deteriorate
I do. For this reason, 0.03 to 0.2 μm TiN
Number is 1 × 10ThreePieces / mmTwo~ 1 × 10FivePieces / mmTwoLimited to
did. In the present invention, the circle equivalent diameter of 0.05μm or less
1 × 10 TiNThreePieces / mmTwoAbove
In addition, the number of TiN with a circle equivalent diameter of 0.03 to 0.2 μm is 1 × 10Three
Pieces / mmTwo~ 1 × 10FivePieces / mmTwoBy limiting to the range of
The ferrite grains can be dramatically reduced in size,
And the toughness of the heat affected zone can be greatly improved.
You.
【００２６】本発明の厚鋼板は上記した組成でかつ残部
Feおよび不可避的不純物からなる。不純物として、Ｏ：
0.010 ％以下が許容できる。つぎに、本発明の厚鋼板の
製造方法について説明する。上記した組成の鋼を転炉、
電気炉等公知の溶製方法で溶製し、連続鋳造法あるいは
造塊法で凝固させ、鋼素材とする。The steel plate according to the present invention has the above composition and the balance
Consists of Fe and inevitable impurities. As impurities, O:
0.010% or less is acceptable. Next, a method for manufacturing a thick steel plate according to the present invention will be described. Converter steel with the above composition steel,
It is smelted by a known smelting method such as an electric furnace and solidified by a continuous casting method or an ingot casting method to obtain a steel material.
【００２７】鋼素材は、まず、1050℃以上の温度に、好
ましくは1300〜1400℃の温度に加熱し、円相当径で0.05
μm 以下のTiN を１×103 個／mm2 以上の密度で、さら
に円相当径で0.03〜0.2 μm のTiN を１×103 個／mm2
〜１×105 個／mm2 の密度で析出させる。加熱温度が10
50℃未満では、TiN の成長が不十分で、上記した大き
さ、個数のTiN を得ることができない。なお、加熱温度
は、好ましくは1300℃以上である。一方、1400℃を超え
ると、鋼素材が溶解する危険がある。このため、鋼素材
の加熱温度は1050℃以上、好ましくは1300〜1400℃の温
度範囲とした。また、この温度域における保持時間は、
0.5hr 以上、好ましくは３〜10hrとするのが好ましい。
0.5hr 未満では、TiN の成長が不十分である。TiN を十
分成長させるためには、保持時間は0.5hr 以上、好まし
くは３hr以上である。一方、10hrを超えると鋼素材表層
の脱炭が著しくなる。このため、鋼素材の加熱保持時間
は0.5hr 以上、好ましくは３〜10hrとした。The steel material is first heated to a temperature of 1050 ° C. or more, preferably to a temperature of 1300 to 1400 ° C.
1 μm or less of TiN with a density of 1 × 10 3 / mm 2 or more and 0.03 to 0.2 μm of TiN with an equivalent circle diameter of 1 × 10 3 / mm 2
Precipitate at a density of １1 × 10 5 / mm 2 . Heating temperature is 10
If the temperature is lower than 50 ° C., the growth of TiN is insufficient, so that TiN having the above-mentioned size and number cannot be obtained. The heating temperature is preferably 1300 ° C. or higher. On the other hand, if it exceeds 1400 ° C, there is a risk that the steel material will melt. For this reason, the heating temperature of the steel material is set to 1050 ° C. or higher, preferably 1300 to 1400 ° C. The holding time in this temperature range is
It is preferably 0.5 hr or more, preferably 3 to 10 hr.
If the time is less than 0.5 hr, the growth of TiN is insufficient. In order to sufficiently grow TiN, the holding time is 0.5 hr or more, preferably 3 hr or more. On the other hand, if it exceeds 10 hours, decarburization of the surface layer of the steel material becomes remarkable. For this reason, the heating and holding time of the steel material is set to 0.5 hours or more, preferably 3 to 10 hours.
【００２８】鋼素材は上記した条件で加熱保持されたの
ち、0.5 ℃／ｓ以下の冷却速度で冷却し、室温まで徐冷
されるのが望ましい。冷却速度が0.5 ℃／ｓを超えると
TiNの成長が不十分となりその後の処理でフェライトの
微細化が図れない。上記したTiN の析出処理を経た鋼素
材は、ついで、1050℃以上、好ましくは1350℃以下の温
度範囲に再加熱される。It is desirable that the steel material is heated and held under the above conditions, then cooled at a cooling rate of 0.5 ° C./s or less, and gradually cooled to room temperature. When the cooling rate exceeds 0.5 ° C / s
The growth of TiN becomes insufficient, and the ferrite cannot be refined in the subsequent processing. The steel material that has undergone the above-described TiN precipitation treatment is then reheated to a temperature range of 1050 ° C. or more, preferably 1350 ° C. or less.
【００２９】加熱温度が1050℃未満では、鋼素材の高温
強度が高く、圧延荷重が高くなりすぎ、その後の圧延が
困難となる。また、1350℃を超えると加熱炉原単位が低
下するとともに、スケールロスの増加や、炉の改修頻度
の増加を招く。このようなことから、再加熱温度は1050
℃以上、好ましくは1350℃以下の温度範囲に限定した。If the heating temperature is lower than 1050 ° C., the high-temperature strength of the steel material is high, the rolling load becomes too high, and the subsequent rolling becomes difficult. On the other hand, if the temperature exceeds 1350 ° C., the unit consumption of the heating furnace decreases, and the scale loss increases and the frequency of furnace repairs increases. Therefore, the reheating temperature is 1050
It was limited to a temperature range of not lower than 1 ° C, preferably not higher than 1350 ° C.
【００３０】上記温度範囲に加熱された鋼素材は、Ａr3
変態点以上、好ましくは1100〜950℃の温度範囲で１パ
ス当たりの圧下率で５％以上の圧下を、累積圧下率で20
％以上施される。圧延温度範囲は、Ａr3変態点以上とす
る。なお、好ましくは1100〜950 ℃の温度範囲である。
圧延温度が1100℃を超えるとオーステナイト（γ）の再
結晶微細化の効果が少なく、また、950 ℃未満ではγの
再結晶が遅く、さらに集合組織の形成が著しくなり、音
響異方性、残留応力、残留歪が顕著となる。また、Ａr3
変態点未満では、フェライトが加工され、母材靱性の劣
化、材質の異方性が顕著となる。このため、加工は主と
してＡr3変態点以上とする。The steel material heated to the above temperature range is Ar 3
A reduction of 5% or more at a rolling reduction per pass in a temperature range of not less than the transformation point, preferably 1100 to 950 ° C., and a cumulative rolling reduction of 20%
% Or more. The rolling temperature range is equal to or higher than the Ar 3 transformation point. The temperature range is preferably 1100 to 950 ° C.
If the rolling temperature exceeds 1100 ° C, the effect of refining and refining austenite (γ) is small, and if it is lower than 950 ° C, the recrystallization of γ is slow, and furthermore the formation of texture becomes remarkable, acoustic anisotropy and residual Stress and residual strain become remarkable. Also, Ar 3
Below the transformation point, ferrite is processed, and the base material toughness deteriorates and the material anisotropy becomes remarkable. For this reason, processing is performed mainly at the Ar 3 transformation point or higher.
【００３１】上記したγの部分再結晶温度域で、１パス
当たりの圧下率で５％以上の圧下を繰り返し、累積圧下
率で20％以上とすることにより、γの再結晶微細化が達
成できる。γの再結晶微細化の観点からは、１パス当た
りの圧下率は大きいほどよい。しかし、１パス当たりの
圧下率で５％未満では、γの十分な微細化が達成できな
いため、１パス当たりの圧下率で５％以上に限定した。
また、累積圧下率が20％未満ではγの再結晶微細化が不
十分であるため、TiN 、VNによる組織微細化によっても
最終組織が粗くなり靱性の低下を招く。このようなこと
から、累積圧下率は20％以上に限定した。なお、累積圧
下率の上限はとくに限定しないが、圧延機の能力によっ
て決まる。In the above-mentioned partial recrystallization temperature range of γ, the reduction of 5% or more at a reduction rate per pass is repeated, and the cumulative reduction rate is set to 20% or more. . From the viewpoint of miniaturization of recrystallization of γ, the larger the rolling reduction per pass, the better. However, if the rolling reduction per pass is less than 5%, it is not possible to achieve sufficiently fine γ, so the rolling reduction per pass is limited to 5% or more.
If the cumulative rolling reduction is less than 20%, refining and refining of γ are insufficient, so that the final structure becomes coarse even by refining the structure with TiN and VN, resulting in a decrease in toughness. For these reasons, the cumulative draft was limited to 20% or more. The upper limit of the cumulative rolling reduction is not particularly limited, but is determined by the capacity of the rolling mill.
【００３２】本発明では、上記したオーステナイト粒の
微細化のための圧延後、さらに、Ａr3変態点〜Ａr1変態
点の温度範囲で圧下率５％以上の圧下を施してもよい。
Ａr3変態点〜Ａr1変態点の温度範囲で加工を施すことに
より、Ａr3変態点以下で生成したフェライトが加工さ
れ、より高強度を得ることが可能となる。そのため、オ
ーステナイトとフェライトの２相域で圧下率５％以上、
好ましくは20％以下の圧下を施す。圧下率が５％未満で
は、２相域圧下の効果が少なく、一方、20％を超える
と、フェライトが著しく加工され、音響異方性、残留応
力、残留歪が顕著となる。このため、Ａr3変態点〜Ａr1
変態点の温度範囲での圧下率は、５％以上好ましくは20
％以下とする。In the present invention, after the above-mentioned rolling for refining austenite grains, rolling may be further performed at a rolling reduction of 5% or more in the temperature range from the Ar 3 transformation point to the Ar 1 transformation point.
By performing the working in the temperature range from the Ar 3 transformation point to the Ar 1 transformation point, the ferrite generated below the Ar 3 transformation point is worked, and higher strength can be obtained. Therefore, a reduction ratio of 5% or more in the two-phase region of austenite and ferrite,
Preferably, a reduction of 20% or less is applied. When the rolling reduction is less than 5%, the effect of reducing the two-phase region is small. On the other hand, when it exceeds 20%, the ferrite is remarkably worked, and the acoustic anisotropy, residual stress, and residual strain become remarkable. Therefore, Ar 3 transformation point to Ar 1
The rolling reduction in the temperature range of the transformation point is 5% or more, preferably 20% or more.
% Or less.
【００３３】圧延後、室温まで冷却する。冷却は、とく
に限定する必要はなく放冷でよいが、緩冷却、または緩
冷却−高温冷停後室温まで５℃／ｓ以上の冷却速度で冷
却するのが好ましい。本発明で、緩冷却とは、空冷以上
３℃／ｓ未満の冷却速度を有する冷却をいう。また、緩
冷却−高温冷停とは、空冷以上３℃／ｓ未満の冷却速度
で冷却しＡr3点以下Ａr3点−100 ℃以上で冷却を停止
し、その後５℃／ｓ以上の冷却速度で室温まで急冷す
る。After rolling, it is cooled to room temperature. The cooling is not particularly limited and may be allowed to cool. However, it is preferable to cool slowly, or to cool to room temperature after slow cooling-high temperature cooling at a cooling rate of 5 ° C./s or more. In the present invention, slow cooling refers to cooling having a cooling rate of not less than air cooling and less than 3 ° C./s. Slow cooling-high temperature cold stop means cooling at a cooling rate of air cooling or more and less than 3 ° C / s, stopping cooling at Ar 3 points or less, and Ar 3 points of -100 ° C or more, and then cooling at a rate of 5 ° C / s or more. Rapidly cool to room temperature with.
【００３４】緩冷却の冷却速度が３℃／ｓ以上では冷却
中のVNの析出が抑制されるため、組織が粗大化するとと
もに、ベイナイト主体の組織となり靱性が低下する。ま
た、緩冷却の冷却停止温度がＡr3点を超えて高いと、組
織微細化が不十分となり、一方、Ａr3点−100 ℃より低
いと残留応力・残留歪が増大するため、冷却停止温度は
Ａr3点以下Ａr3点−100 ℃以上の範囲とするのが好まし
い。When the cooling rate of the slow cooling is 3 ° C./s or more, precipitation of VN during cooling is suppressed, so that the structure becomes coarse and the structure becomes mainly bainite, and the toughness is reduced. On the other hand, if the cooling stop temperature of the slow cooling is higher than the Ar 3 point, the microstructure becomes insufficient. On the other hand, if the cooling stop temperature is lower than the Ar 3 point of −100 ° C., the residual stress and residual strain increase. Is preferably in the range of not more than the Ar 3 point and not less than the Ar 3 point −100 ° C.
【００３５】さらに、緩冷却停止後、５℃／ｓ以上の冷
却速度で冷却するのが好ましく、これにより、フェライ
トの粒成長が抑制され、組織がさらに微細化し靱性が低
下する。なお、圧延終了温度がＡr3点未満、あるいは
（Ａr3点−100 ℃）未満の場合には、圧延後の冷却は、
室温まで放冷としてよいが、室温まで５℃／ｓ以上の冷
却速度で冷却するのが好ましい。Further, it is preferable to cool at a cooling rate of 5 ° C./s or more after the slow cooling is stopped, whereby the grain growth of ferrite is suppressed, the structure is further refined, and the toughness is reduced. When the rolling end temperature is lower than Ar 3 point or lower than (Ar 3 point-100 ° C), cooling after rolling is
Although it may be allowed to cool to room temperature, it is preferable to cool to room temperature at a cooling rate of 5 ° C./s or more.
【００３６】[0036]
【実施例】表１に示す化学組成を有する鋼を転炉で溶製
し、連続鋳造法で200 〜270mm 厚のスラブとした。これ
らスラブを表２に示す熱処理条件でTiN を析出させたの
ち、表２の示す圧延・冷却条件で板厚40〜60mmの厚鋼板
とした。これら厚鋼板について、板厚1/4 部から引張試
験片およびシャルピー衝撃試験片を採取し、引張特性、
衝撃特性を調査した。EXAMPLES Steel having the chemical composition shown in Table 1 was melted in a converter and slabs having a thickness of 200 to 270 mm were produced by continuous casting. After the TiN was precipitated from these slabs under the heat treatment conditions shown in Table 2, a thick steel plate having a thickness of 40 to 60 mm was obtained under the rolling and cooling conditions shown in Table 2. For these thick steel plates, tensile test specimens and Charpy impact test specimens were collected from a quarter of the plate thickness, and the tensile properties,
The impact characteristics were investigated.
【００３７】また、これら厚鋼板の板厚1/4 部から圧延
方向と直角方向に12t ×75×80mmの試験片を採取して、
高周波加熱装置により入熱100kJ/cmのサブマージアーク
溶接の粗粒域HAZ の受ける熱サイクル（最高加熱温度14
00℃）を付与したのち、シャルピー衝撃試験片を採取
し、０℃におけるシャルピー吸収エネルギー（Ｅ0 ）を
求めた。Further, a test piece of 12 t × 75 × 80 mm was taken from a quarter of the thickness of these thick steel plates in a direction perpendicular to the rolling direction,
The heat cycle (maximum heating temperature of 14 h
(00 ° C.), a Charpy impact test piece was sampled, and the Charpy absorbed energy (E 0 ) at 0 ° C. was determined.
【００３８】これらの結果を表２に示す。Table 2 shows the results.
【００３９】[0039]
【表１】 [Table 1]
【００４０】[0040]
【表２】 [Table 2]
【００４１】[0041]
【表３】 [Table 3]
【００４２】表２から、本発明例の厚鋼板は、引張強さ
（ＴＳ）が500MPa以上の高強度でかつＥ0 が300 Ｊ以
上、v Ｔrsが−40℃以下の高靱性を有している。一方、
本発明の範囲を外れる厚鋼板は、高強度を有しているが
靱性が低い。とくに、化学組成が本発明の範囲であって
も、TiN の大きさ、個数が本発明の範囲を外れる場合
（鋼板No.15 〜No. 18）には、母材およびHAZ 部靱性が
劣化している。As can be seen from Table 2, the steel sheet of the present invention has a high strength with a tensile strength (TS) of 500 MPa or more, a high toughness of E 0 of 300 J or more, and a vTrs of -40 ° C. or less. I have. on the other hand,
Thick steel plates outside the scope of the present invention have high strength but low toughness. In particular, even if the chemical composition is within the range of the present invention, if the size and number of TiN are out of the range of the present invention (steel sheets No. 15 to No. 18), the toughness of the base material and the HAZ portion deteriorates. ing.
【００４３】[0043]
【発明の効果】本発明によれば、高強度、高靱性で溶接
性に優れた厚鋼板が容易に製造でき、従来、製造が困難
であった建築構造物用柱梁材として適用が可能となり、
用途拡大という産業上有益な効果を奏する。According to the present invention, a thick steel plate having high strength, high toughness and excellent weldability can be easily manufactured, and can be applied as a column beam for a building structure, which was conventionally difficult to manufacture. ,
It has an industrially beneficial effect of expanding applications.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 大森 章夫 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 (72)発明者 川端 文丸 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 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Omori 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. 1-chome (without address) Inside Kawasaki Steel Corporation Mizushima Works
Claims (13)
％、 Ti：0.005 〜0.30％、 Ｎ：0.0050〜0.0200％ を含み、さらに下記（１）式で定義されるＣeqが0.36〜
0.45％で、残部Feおよび不可避的不純物からなる組成
で、かつ円相当径が0.05μm 以下のTiN が１×103個／m
m2 以上、円相当径が0.03〜0.2 μm のTiN を１×103
個／mm2 以上１×10 5 個／mm2 未満含有することを特徴
とする溶接熱影響部靱性に優れた高靱性厚鋼板。 記 Ｃeq（％）＝Ｃ＋Si/24 ＋Mn/6＋Ni/40 ＋Cr/5＋Mo/4＋Ｖ/14 ……（１）1. Weight%: 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: 0.005 to 0.30%, N: 0.0050 to 0.0200%, and Ceq defined by the following formula (1) is 0.36 to 0.36%.
0.45%, with the balance being Fe and unavoidable impurities
And 1 × 10 TiN with an equivalent circle diameter of 0.05 μm or lessThreePieces / m
mTwoAs described above, TiN with an equivalent circle diameter of 0.03 to 0.2 μmThree
Pieces / mmTwoMore than 1 × 10 FivePieces / mmTwoCharacterized by containing less than
High toughness thick steel plate with excellent toughness of weld heat affected zone. Note Ceq (%) = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (1)
u：0.02〜1.50％、Ni：0.02〜0.60％、Cr：0.05〜0.50
％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％から選ば
れた１種または２種以上を含有することを特徴とする請
求項１に記載の高靱性厚鋼板。2. In addition to the above composition, further in weight percent C
u: 0.02 to 1.50%, Ni: 0.02 to 0.60%, Cr: 0.05 to 0.50
%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030%, one or more selected from the group consisting of high toughness steel plate according to claim 1.
15％を含有することを特徴とする請求項１または２に記
載の高靱性厚鋼板。3. In addition to the above composition, V: 0.03 to 0.3.
The high-toughness steel plate according to claim 1 or 2, which contains 15%.
0.0020％、REM ：0.0010〜0.0200％、Ca：0.0010〜0.01
00％から選ばれた１種または２種以上を含有することを
特徴とする請求項１ないし３のいずれかに記載の高靱性
厚鋼板。4. In addition to the above composition, B: 0.0002 to
0.0020%, REM: 0.0010-0.0200%, Ca: 0.0010-0.01
The high toughness steel sheet according to any one of claims 1 to 3, comprising one or more kinds selected from 00%.
％、 Ti：0.005 〜0.30％、 Ｎ：0.0050〜0.0200％ を含み、さらに下記（１）式で定義されるＣeqが0.36〜
0.45％で、残部Feおよび不可避的不純物からなる組成の
鋼素材を、1050℃以上の温度で加熱したのち、0.5 ℃／
ｓ以下の冷却速度で冷却し、ついで、1050℃以上の温度
範囲に再加熱して、Ａr3変態点以上の温度範囲で１パス
当たりの圧下率で５％以上の圧下を累積圧下率で20％以
上施しのち、室温まで冷却することを特徴とする溶接熱
影響部靱性に優れた高靱性厚鋼板の製造方法。 記 Ｃeq（％）＝Ｃ＋Si/24 ＋Mn/6＋Ni/40 ＋Cr/5＋Mo/4＋Ｖ/14 ……（１）5. In% by weight, 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: 0.005 to 0.30%, N: 0.0050 to 0.0200%, and Ceq defined by the following formula (1) is 0.36 to 0.36%.
After heating a steel material having a composition of 0.45% and the balance of Fe and unavoidable impurities at a temperature of 1050 ° C or more, 0.5 ° C /
Cooling at a cooling rate of not more than 10 s, then reheating to a temperature range of 1050 ° C. or more, and a reduction of 5% or more per pass in a temperature range of Ar 3 transformation point or more and a cumulative reduction rate of 20% or more per pass. %, And then cooling to room temperature. Note Ceq (%) = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (1)
％、 Ti：0.005 〜0.30％、 Ｎ：0.0050〜0.0200％ を含み、さらに下記（１）式で定義されるＣeqが0.36〜
0.45％で、残部Feおよび不可避的不純物からなる組成の
鋼素材を、1050℃以上の温度で加熱したのち、0.5 ℃／
ｓ以下の冷却速度で冷却し、ついで、1050℃以上の温度
範囲に再加熱して、Ａr3変態点以上の温度範囲で１パス
当たりの圧下率で５％以上の圧下を累積圧下率で20％以
上施し、さらにＡr3変態点〜Ａr1変態点の温度範囲で圧
下率５％以上の圧下を施したのち、室温まで冷却するこ
とを特徴とする溶接熱影響部靱性に優れた高靱性厚鋼板
の製造方法。 記 Ｃeq（％）＝Ｃ＋Si/24 ＋Mn/6＋Ni/40 ＋Cr/5＋Mo/4＋Ｖ/14 ……（１）6. In% by weight, 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: 0.005 to 0.30%, N: 0.0050 to 0.0200%, and Ceq defined by the following formula (1) is 0.36 to 0.36%.
After heating a steel material having a composition of 0.45% and the balance of Fe and unavoidable impurities at a temperature of 1050 ° C or more, 0.5 ° C /
Cooling at a cooling rate of not more than 10 s, then reheating to a temperature range of 1050 ° C. or more, and a reduction of 5% or more per pass in a temperature range of Ar 3 transformation point or more and a cumulative reduction rate of 20% or more per pass. %, With a reduction of 5% or more in the temperature range from the Ar 3 transformation point to the Ar 1 transformation point, and then cooling to room temperature. Steel plate manufacturing method. Note Ceq (%) = C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 (1)
u：0.02〜1.50％、Ni：0.02〜0.60％、Cr：0.05〜0.50
％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％から選ば
れた１種または２種以上を含有することを特徴とする請
求項５または６に記載の高靱性厚鋼板の製造方法。7. In addition to the above composition, further in weight percent C
u: 0.02 to 1.50%, Ni: 0.02 to 0.60%, Cr: 0.05 to 0.50
%, Mo: 0.02 to 0.50%, Nb: 0.003 to 0.030%, one or more selected from the group consisting of:
Ｖ：0.03〜0.15％を含有することを特徴とする請求項５
ないし７のいずれかに記載の高靱性厚鋼板の製造方法。8. In addition to the composition, further in weight percent:
V: 0.03 to 0.15% is contained.
8. The method for producing a high toughness thick steel plate according to any one of the above items.
Ｂ：0.0002〜0.0020％、REM ：0.0010〜0.0200％、Ca：
0.0010〜0.0100％から選ばれた１種または２種以上を含
有することを特徴とする請求項５ないし８のいずれかに
記載の高靱性厚鋼板の製造方法。9. In addition to the composition, further in weight percent:
B: 0.0002-0.0020%, REM: 0.0010-0.0200%, Ca:
The method for producing a high toughness steel sheet according to any one of claims 5 to 8, comprising one or more kinds selected from 0.0010 to 0.0100%.
％、 Ti：0.005 〜0.30％、 Ｎ：0.0050〜0.0200％ を含み、さらに下記（１）式で定義されるＣeqが0.36〜
0.45％で、残部Feおよび不可避的不純物からなる組成の
鋼素材を、1050℃以上の温度で加熱したのち、0.5 ℃／
ｓ以下の冷却速度で冷却することを特徴とする高靱性厚
鋼板用圧延素材の製造方法。10. In% by weight, 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: 0.005 to 0.30%, N: 0.0050 to 0.0200%, and Ceq defined by the following formula (1) is 0.36 to 0.36%.
After heating a steel material having a composition of 0.45% and the balance of Fe and unavoidable impurities at a temperature of 1050 ° C or more, 0.5 ° C /
A method for producing a rolled material for a tough steel plate, characterized by cooling at a cooling rate of not more than s.
u：0.02〜1.50％、Ni：0.02〜0.60％、Cr：0.05〜0.50
％、Mo：0.02〜0.50％、Nb：0.003 〜0.030 ％から選ば
れた１種または２種以上を含有することを特徴とする請
求項10に記載の圧延素材の製造方法。11. In addition to the above composition, further by weight% C
u: 0.02 to 1.50%, Ni: 0.02 to 0.60%, Cr: 0.05 to 0.50
11. The method for producing a rolled material according to claim 10, wherein the method comprises one or more selected from the group consisting of: Mo: 0.02 to 0.50%, and Nb: 0.003 to 0.030%.
Ｖ：0.03〜0.15％を含有することを特徴とする請求項10
または11に記載の圧延素材の製造方法。12. In addition to the composition, further in weight percent:
V: 0.03 to 0.15% is contained.
Or a method for producing a rolled material according to item 11.
Ｂ：0.0002〜0.0020％、REM ：0.0010〜0.0200％、Ca：
0.0010〜0.0100％から選ばれた１種または２種以上を含
有することを特徴とする請求項10ないし12のいずれかに
記載の圧延素材の製造方法。13. In addition to the composition, further in weight percent:
B: 0.0002-0.0020%, REM: 0.0010-0.0200%, Ca:
The method for producing a rolled material according to any one of claims 10 to 12, comprising one or more selected from 0.0010 to 0.0100%.
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1997
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