JP2005171298A - Thick steel plate having excellent cut-off property with laser beam and its production method - Google Patents

Thick steel plate having excellent cut-off property with laser beam and its production method Download PDF

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JP2005171298A
JP2005171298A JP2003410596A JP2003410596A JP2005171298A JP 2005171298 A JP2005171298 A JP 2005171298A JP 2003410596 A JP2003410596 A JP 2003410596A JP 2003410596 A JP2003410596 A JP 2003410596A JP 2005171298 A JP2005171298 A JP 2005171298A
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JP4608877B2 (en
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Kenji Oi
健次 大井
Akihide Nagao
彰英 長尾
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JFE Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a thick steel plate having an excellent cut-off property with laser beam and its production method by optimizing a scale thickness and composition on the surface of the steel plate and the structure of the interface between the base steel and the scale. <P>SOLUTION: The method for producing thick steel plates having the excellent cut-off property with the laser beam is provided with the processes of; applying hot-rolling after heating to ≥950°C the thick steel plate composed, by mass, of 0.01 to 0.20% C, ≤0.80% Si, 0.4 to 2.5% Mn, ≤0.03% P, ≤0.01% S, ≤0.15% Al and the balance Fe with inevitable impurities; cooling the whole steel plate to ≤600°C by air-cooling or accelerated-cooling, heating again the surface layer of the steel plate to a temperature range of 650 to 850°C with a heating rate of ≥3°C/s within 300 sec, and then leaving the heated plate to cool. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、造船、土木、建築、橋梁、建設機械、鋼管等の溶接構造物として好適な厚鋼板及びその製造方法に関し、特にレーザ切断を施される使途に好適な厚鋼板及びその製造方法に関する。   The present invention relates to a thick steel plate suitable as a welded structure for shipbuilding, civil engineering, architecture, bridges, construction machinery, steel pipes and the like, and a method for producing the same, and more particularly to a thick steel plate suitable for use for laser cutting and a method for producing the same. .

近年、厚鋼板が使用される分野において高能率の施工性が要求されており、ガス切断やプラズマ切断に比べて切断面の形状や自動化への対応という点から、レーザ装置出力の増大に伴ってレーザ切断の適用が盛んに進められている。しかしながら、厚鋼板のレーザ切断性においては、切断時の安定性や厚肉材への適用限界において十分であるとは言えないのが現状である。そこで、ハード面ではレーザ切断機の高出力化が進められている。一方で、鋼板表面の高機能化によって切断性を向上させる試みがなされてきた。   In recent years, high-efficiency workability has been demanded in the field where thick steel plates are used, and with the increase in laser device output from the point of correspondence to the shape of the cut surface and automation compared to gas cutting and plasma cutting. Application of laser cutting has been actively promoted. However, the laser cutting property of thick steel plates is not sufficient in terms of stability at the time of cutting and application limits to thick materials. Therefore, on the hardware side, the output of laser cutting machines is being increased. On the other hand, attempts have been made to improve cutability by increasing the functionality of the steel sheet surface.

例えば、特許文献１には、鋼板表層のスケールがスケール厚み１０μｍ以下でＦｅ３Ｏ４の組成比が７０％以上となるように、冷却時間と総圧延時間の比率を制御する方法が開示されている。この方法では、強固な薄スケールによってスケールの密着性を向上させると、塗装むらの防止や加工時の剥離等が防げるために効果的である。しかし、レーザ切断性においては、レーザの先行部で熱応力における部分的なスケールの割れや剥離がおきるため、切断安定性が十分でない問題がある。特に、厚肉材ではその傾向が顕著になる。 For example, Patent Document 1 discloses a method for controlling the ratio of the cooling time and the total rolling time so that the scale of the steel sheet surface layer has a scale thickness of 10 μm or less and the composition ratio of Fe 3 O 4 is 70% or more. Yes. In this method, when the adhesion of the scale is improved by a strong thin scale, it is effective in preventing uneven coating and peeling during processing. However, in laser cutting property, there is a problem that cutting stability is not sufficient because partial scale cracking or peeling occurs due to thermal stress in the leading part of the laser. In particular, the tendency becomes remarkable in the thick material.

特許文献２には、Ｓｉ、ＭｎおよびＣｕ、Ｃｒを適量添加することによって酸化発熱反応の制御と溶鋼の粘性制御を行い、さらには圧延および冷却条件にて表面の光沢を抑えることでレーザ切断性を良好にする方法が開示されている。しかし、この方法の場合、高価な合金成分の添加が必要であり、圧延条件の制約からも経済性が悪い問題がある。   In Patent Document 2, by adding appropriate amounts of Si, Mn, Cu, and Cr, the oxidation exothermic reaction is controlled and the viscosity of the molten steel is controlled, and further the laser cutting property is suppressed by suppressing surface gloss under rolling and cooling conditions. A method for improving the accuracy is disclosed. However, in this method, it is necessary to add an expensive alloy component, and there is a problem of poor economic efficiency due to restrictions on rolling conditions.

特許文献３には、地鉄とスケール界面層において合金富化層の厚みを１μｍ以上とし、界面の粗さの制御によって耐剥離性に優れたスケール層の形成を行う厚鋼板について開示されている。しかし、この場合、特許文献２と同様に経済性に劣る問題がある。   Patent Document 3 discloses a thick steel plate in which the thickness of the alloy-enriched layer is 1 μm or more in the base iron and scale interface layer, and a scale layer having excellent peeling resistance is formed by controlling the roughness of the interface. . However, in this case, there is a problem inferior in economic efficiency as in Patent Document 2.

特許文献４には、スケール層厚さ、スケール層と地鉄界面の剥離率、及びスケール層内の空孔面積を規定した厚鋼板について開示されている。しかし、この場合、レーザ切断時の熱応力によるスケールの剥離性が不十分であり、安定したレーザ切断性が得られない問題があった。
特開平５−１９５０５５号公報 特開平９−２０９６２号公報 特開平１１−３４３５４１号公報 特開２００２−３３２５４０号 Patent Document 4 discloses a thick steel plate that defines the thickness of the scale layer, the separation rate between the scale layer and the iron-iron interface, and the pore area in the scale layer. However, in this case, there is a problem in that the peelability of the scale due to thermal stress during laser cutting is insufficient, and stable laser cutting properties cannot be obtained.
Japanese Patent Laid-Open No. 5-195055 JP-A-9-20962 Japanese Patent Laid-Open No. 11-343541 JP 2002-332540 A

本発明は上記事情を考慮してなされたもので、鋼板表面のスケール厚み、組成及び地鉄−スケール界面の構造を最適化することにより、レーザ切断性に優れた厚鋼板とその製造方法を提供することを目的とする。   The present invention has been made in view of the above circumstances, and provides a steel plate excellent in laser cutting property and a method for producing the same by optimizing the scale thickness, composition and structure of the iron-scale interface on the steel plate surface. The purpose is to do.

（１）本発明に係るレーザ切断性に優れた厚鋼板の製造方法は、
Ｃ ：０．０１〜０．２０質量％、
Ｓｉ：０．８０質量％以下、
Ｍｎ：０．４〜２．５質量％、
Ｐ ：０．０３質量％以下、
Ｓ ：０．０１質量％以下、
Ａｌ：０．１５質量％以下
を含有し残部がＦｅおよび不可避不純物からなる厚鋼板を９５０℃以上に加熱した後、熱間圧延を施す工程と、空冷あるいは加速冷却によって鋼板全体を６００℃以下まで冷却した後、３００秒以内に３℃／ｓ以上の昇温速度で加熱して鋼板表層を６５０℃以上８５０℃以下の温度域に加熱した後、放冷する工程とを具備することを特徴とする。 (1) A method for producing a thick steel plate having excellent laser cutting properties according to the present invention is as follows:
C: 0.01-0.20 mass%,
Si: 0.80 mass% or less,
Mn: 0.4 to 2.5% by mass,
P: 0.03 mass% or less,
S: 0.01% by mass or less,
Al: 0.15 mass% or less
Within 300 seconds after heating the thick steel plate containing Fe and the remainder of Fe and inevitable impurities to 950 ° C. or higher and then hot-rolling and cooling the whole steel plate to 600 ° C. or lower by air cooling or accelerated cooling. And heating the steel sheet surface layer to a temperature range of 650 ° C. or more and 850 ° C. or less by heating at a temperature rising rate of 3 ° C./s or more, and then allowing to cool.

（２）また、本発明に係るレーザ切断性に優れた厚鋼板の製造方法は、上記（１）において、前記Ｃ，Ｓｉ，Ｍｎ，Ｐ，Ｓ，Ａｌの他、Ｔｉ：０．００５〜０．２０質量％を含有し、かつＳｉ：０．２０質量％以上、Ｓｉ＋Ａｌ＋Ｔｉ≧０．３質量％を満足する、残部がＦｅおよび不可避不純物からなる厚鋼板を処理することを特徴とする。   (2) Moreover, the manufacturing method of the steel plate excellent in the laser cutting property which concerns on this invention is Ti: 0.005-0 in addition to said C, Si, Mn, P, S, Al in said (1). It is characterized by processing a thick steel plate containing 20% by mass and satisfying Si: 0.20% by mass or more and Si + Al + Ti ≧ 0.3% by mass, the balance being Fe and inevitable impurities.

（３）更に、本発明に係るレーザ切断性に優れた厚鋼板の製造方法は、上記（１）記載の各元素の他、選択元素として、
Ｃｕ：０．０１〜２．０質量％、
Ｎｉ：０．０１〜４．０質量％、
Ｃｒ：０．０１〜２．０質量％、
Ｍｏ：０．０１〜２．０質量％、
Ｎｂ：０．００３〜０．１質量％、
Ｖ ：０．００３〜０．５質量％、
Ｂ ：０．０００５〜０．００４質量％、
Ｃａ：０．０００１〜０．００６質量％、
Ｍｇ：０．０００１〜０．００６質量％、
REM ：０．０００１〜０．０２質量％
の１種または２種以上をさらに含有することを特徴とする。 (3) Furthermore, the manufacturing method of the steel plate excellent in laser cutting property according to the present invention includes, in addition to each element described in (1) above, as a selective element.
Cu: 0.01-2.0 mass%,
Ni: 0.01-4.0 mass%,
Cr: 0.01 to 2.0% by mass,
Mo: 0.01 to 2.0 mass%,
Nb: 0.003 to 0.1% by mass,
V: 0.003-0.5 mass%,
B: 0.0005-0.004 mass%,
Ca: 0.0001 to 0.006 mass%,
Mg: 0.0001 to 0.006 mass%,
REM: 0.0001 to 0.02 mass%
1 type or 2 types or more are further contained.

（４）更に、本発明に係るレーザ切断性に優れた厚鋼板は、上記（２）もしくは（３）のいずれかの成分を有するとともに、鋼板表面に１０μｍ以上のスケール層を有し、さらにスケール界面から地鉄中に１μｍ以上の選択酸化層を有することを特徴とする。   (4) Furthermore, the thick steel plate excellent in laser cutting property according to the present invention has either the component (2) or (3), and has a scale layer of 10 μm or more on the steel plate surface, and further has a scale. It has a selective oxidation layer of 1 μm or more from the interface to the ground iron.

本発明によれば、鋼板表面のスケール厚み、組成及び地鉄−スケール界面の構造を最適化することにより、レーザ切断性に優れた厚鋼板とその製造方法を提供できる。   ADVANTAGE OF THE INVENTION According to this invention, the steel plate excellent in laser cutting property and its manufacturing method can be provided by optimizing the scale thickness of a steel plate surface, a composition, and the structure of a ground-iron-scale interface.

以下、本発明について更に詳しく説明する。
本発明は、レーザ切断性を良好にするために、表面スケール厚み、組成および地鉄−スケール界面を最適化するものである。これらの最適化は、これまで検討されてきた薄く強固なスケールを鋼板表面に形成する技術とは異なる。本発明者らは、厚くやわらかいスケールを密着性よく形成させることが最もレーザ切断性にとって効果的であることを見出した。即ち、厚肉材の切断性には鋼板表面のレーザ吸収性が最も重要であり、金属表面よりも酸化物の方がレーザ吸収性が高いことを勘案すると、厚いスケール層が効果的である。 Hereinafter, the present invention will be described in more detail.
The present invention optimizes the surface scale thickness, composition, and the iron-scale interface in order to improve the laser cutting property. These optimizations are different from the technique of forming a thin and strong scale on the steel sheet surface that has been studied so far. The present inventors have found that forming a thick and soft scale with good adhesion is most effective for laser cutting properties. That is, the laser absorptivity on the surface of the steel sheet is the most important for the cutting property of the thick material, and a thick scale layer is effective considering that the oxide has a higher laser absorptivity than the metal surface.

また、これまでの開示技術では、スケールの強度を高めるためにスケール組成をＦｅＯからＦｅ３Ｏ４やＦｅ２Ｏ３へ変態させていた。しかし、スケール強度をいくら強くしても熱応力に耐えうるほどの強度は得られないため、十分な効果が現れなかった。そこで、本発明者らは、むしろスケール強度を低下させて変形に強くするためにＦｅＯの比率を高めることを行い、厚いスケールでも熱応力での割れが画期的に抑制できることを明らかにした。 Further, in the disclosed technology so far, the scale composition is transformed from FeO to Fe 3 O 4 or Fe 2 O 3 in order to increase the strength of the scale. However, no matter how much the strength of the scale is increased, the strength sufficient to withstand the thermal stress cannot be obtained. Therefore, the present inventors have clarified that cracking due to thermal stress can be remarkably suppressed even with a thick scale by increasing the ratio of FeO in order to lower the scale strength and make it more resistant to deformation.

鋼板表層に上記のスケール層を形成させるためには、厚鋼板を９５０℃以上に加熱後、熱間圧延を施し、空冷あるいは加速冷却によって鋼板全体を６００℃以下まで冷却した後３００秒以内に３℃／ｓ以上の昇温速度で加熱して鋼板表層を６５０℃以上８５０℃以下の温度域に加熱後放冷することによって達成できる。   In order to form the scale layer on the steel sheet surface layer, the thick steel plate is heated to 950 ° C. or higher, then hot-rolled, and the whole steel plate is cooled to 600 ° C. or lower by air cooling or accelerated cooling, and then within 3 seconds. This can be achieved by heating at a temperature increase rate of at least ° C./s and heating the steel sheet surface layer to a temperature range of from 650 ° C. to 850 ° C. and then allowing to cool.

ここで、６００℃以下への冷却は、鋼板の強度を確保するためにオーステナイトからフェライトやベイナイト、マルテンサイトヘの変態をある程度完了させるために必要である。また、その後の鋼板表面の加熱では、ＦｅＯがＦｅ３Ｏ４やＦｅ２Ｏ３へ変態することを抑制させる狙いがある。そのため、冷却後の滞留時間や加熱速度が重要となることからそれぞれ制限が必要である。また地鉄−スケール界面では、再加熱の効果で酸化反応が地鉄側に広がり、スケールと地鉄の密着性を向上させることも新たに知見した。 Here, cooling to 600 ° C. or lower is necessary to complete the transformation from austenite to ferrite, bainite, and martensite to some extent in order to ensure the strength of the steel sheet. Moreover, in the subsequent heating of the steel plate surface, there is an aim to suppress the transformation of FeO to Fe 3 O 4 or Fe 2 O 3 . For this reason, the residence time after cooling and the heating rate are important, so each of them needs to be restricted. In addition, it was newly found out that the oxidation reaction spreads to the side of the ground iron due to the effect of reheating at the ground iron-scale interface, thereby improving the adhesion between the scale and the ground iron.

なお、滞留時間を上述したように３００秒以内にするのは、滞留時間が３００秒を越えると、ＦｅＯがＦｅ２Ｏ３やＦｅ３Ｏ４へ変態し、所定のＦｅＯ比率が得られないからである。ここで、スケール層中のＦｅＯの望ましい比率は、３０％以上である。また、昇温速度を３℃／ｓ以上とするのは、昇温速度が３℃／ｓ未満では表層加熱した熱量が母材側へ熱伝導により移動するので、母材強度を低下させる恐れがあるからである。更に、上記のように、６５０℃以上８５０℃以下の温度域に加熱するのは、地鉄−スケール界面の密着性およびスケール厚みには６５０℃以上が必要であり、８５０℃を超えると、上記と同様、母材強度に影響を与えるからである。 Note that the reason why the residence time is within 300 seconds as described above is that when the residence time exceeds 300 seconds, FeO is transformed into Fe 2 O 3 or Fe 3 O 4 and a predetermined FeO ratio cannot be obtained. It is. Here, a desirable ratio of FeO in the scale layer is 30% or more. Further, if the rate of temperature rise is 3 ° C./s or more, if the rate of temperature rise is less than 3 ° C./s, the amount of heat heated on the surface layer moves to the base material side due to heat conduction, so that the strength of the base material may be reduced. Because there is. Furthermore, as described above, heating to a temperature range of 650 ° C. or more and 850 ° C. or less requires 650 ° C. or more for the adhesion and scale thickness of the ground iron-scale interface, and if it exceeds 850 ° C., This is because it affects the strength of the base material.

上述したことが、基本的なレーザ切断性向上のための基本プロセスである。本発明者らは、この発明に加えて、より地鉄とスケールの密着性を向上させるための方法を鋼板成分と上記プロセスとの組合せによって新しく見出した。即ち、Ｓｉ量を０．２質量％以上（０．８０質量％以下）添加し、Ｓｉの持つ選択酸化能をフルに活用することでスケールと地鉄界面での密着性を格段に向上できることがわかった。また、同時に酸化力が強く選択酸化を促進可能であるＡｌ、Ｔｉ量についてもＳｉとのトータルで０．３０質量％以上添加することがより効果的であることを見出した。   What has been described above is the basic process for improving the basic laser cutting performance. In addition to the present invention, the present inventors have newly found a method for further improving the adhesion between the base iron and the scale by combining the steel plate component and the above process. That is, by adding 0.2% by mass or more (0.80% by mass or less) of the Si amount and fully utilizing the selective oxidation ability of Si, the adhesion between the scale and the iron interface can be remarkably improved. all right. At the same time, the inventors have found that it is more effective to add 0.30% by mass or more of Al and Ti, which have strong oxidizing power and can promote selective oxidation, in total with Si.

従来、Ｓｉの選択酸化性を抑制し、切断時のドロスの粘性が高まるのを懸念してＳｉ量の添加を抑えるのが一般的であった。これに対し、本発明では、Ｓｉ添加によって高温時にスケール−地鉄界面で選択酸化によるスケールのアンカー効果が見られ−密着性が格段に向上していることを発見し、さらには再加熱プロセスによるそのアンカー効果をより増強できることを見出した。   Conventionally, it has been common to suppress the selective oxidation of Si and to suppress the addition of the Si amount in consideration of the increase in dross viscosity at the time of cutting. On the other hand, in the present invention, by adding Si, a scale anchoring effect due to selective oxidation was observed at the scale-base metal interface at a high temperature-it was found that adhesion was remarkably improved, and further, due to the reheating process. It has been found that the anchor effect can be further enhanced.

上記（４）に記載されているように、本発明に係るレーザ切断性に優れた厚鋼板は、上記（２）もしくは（３）のいずれかの成分を有するとともに、鋼板表面に１０μｍ以上のスケール層を有し、さらにスケール界面から地鉄中に１μｍ以上の選択酸化層を有することを特徴とする。ここで、スケール層の厚さを１０μｍ以上としたのはレーザ吸収性が高まるからであり、選択酸化層を１μｍ以上としたのは密着強度が上がるからである。なお、スケール層の厚さ、選択酸化層の厚さともに鋼の成分と再加熱温度で決まる。   As described in the above (4), the thick steel plate excellent in laser cutting property according to the present invention has either the component (2) or (3) and has a scale of 10 μm or more on the surface of the steel plate. And a selective oxidation layer of 1 μm or more from the scale interface to the ground iron. Here, the reason why the thickness of the scale layer is 10 μm or more is that the laser absorbability is increased, and the reason why the selective oxidation layer is 1 μm or more is that the adhesion strength is increased. The thickness of the scale layer and the thickness of the selective oxidation layer are determined by the steel components and the reheating temperature.

また、本発明者らは、ＭｎやＡｌ、Ｔｉの同時添加がこれまで切断時の湯流れ性低下の原因と考えられるＳｉＯ２の構造に見られるネットワーク構造を分断すること、及び生成するスラグがＳｉ量増加により酸性化することでむしろ低粘性化するために切断性に良好な湯流れ性をもつことも同時に見出した。 In addition, the present inventors have divided the network structure seen in the structure of SiO 2 , which is considered to be the cause of the decrease in the flowability of molten metal at the time of cutting by simultaneous addition of Mn, Al, and Ti, and the generated slag is At the same time, it was also found that the acidity was increased by increasing the amount of Si, so that the viscosity was rather lowered, so that the meltability was good.

本発明は、上記の知見に基づいて完成されたものであり、要旨は［課題を解決するための手段］の欄で記載した（１）〜（４）の通りである。   The present invention has been completed based on the above findings, and the gist is as described in (1) to (4) described in the section [Means for Solving the Problems].

次に、各組成の限定理由について説明する。
Ｃ：０．０１〜０．２０質量％
Ｃは鋼板の強度を確保するため、少なくとも０、０１質量％は必要である。ここで、Ｃを０．２０質量％を越えて添加すると、著しく溶接性を低下させる。
Ｓｉ：０．８０質量％以下
Ｓｉは本発明にとって重要な元素である。Ｓｉを０．８０質量％を越えて添加すると、母材の靭性を阻害する。一方、Ｓｉを０．２０質量％以上添加すると、地鉄−スケール界面の選択酸化を促進し、さらに密着性のよいスケールの性状が得られる。よって、Ｓｉ量は０．８０質量％以下、好ましくは０．２０〜０．８０質量％である。 Next, the reason for limitation of each composition is demonstrated.
C: 0.01-0.20 mass%
C is required to be at least 0,01% by mass in order to ensure the strength of the steel sheet. Here, when C is added exceeding 0.20 mass%, the weldability is remarkably lowered.
Si: 0.80 mass% or less
Si is an important element for the present invention. If Si is added in excess of 0.80 mass%, the toughness of the base material is impaired. On the other hand, when 0.20 mass% or more of Si is added, selective oxidation at the base iron-scale interface is promoted, and scale properties with better adhesion can be obtained. Therefore, the amount of Si is 0.80 mass% or less, preferably 0.20 to 0.80 mass%.

Ｍｎ：０．４〜２．０質量％
Ｍｎは、Ｃと同様に鋼板の強度を確保するために必要である。しかし、Ｍｎを過剰に添加すると溶接性を損なう問題があるため、添加量を０．４〜２．０質量％の範囲に限定した。
Ｐ：０．０３質量％以下、Ｓ：０．０１質量％以下
Ｐ，Ｓは、夫々不純物として鋼中に不可避的に含有される元素であり、鋼の靭性を劣化させる。従って、できるだけ低減することが好ましい。特に、Ｐ，Ｓの添加量が所定量を越えると、溶接熱影響部の靭性が劣化する。 Mn: 0.4 to 2.0% by mass
Mn is necessary to ensure the strength of the steel sheet in the same manner as C. However, when Mn is added excessively, there is a problem that the weldability is impaired, so the addition amount is limited to the range of 0.4 to 2.0 mass%.
P: 0.03 mass% or less, S: 0.01 mass% or less
P and S are elements inevitably contained in the steel as impurities, and degrade the toughness of the steel. Therefore, it is preferable to reduce as much as possible. In particular, when the addition amount of P and S exceeds a predetermined amount, the toughness of the weld heat affected zone deteriorates.

Ａｌ：０．１５質量％以下
Ａｌは、Ｓｉ，Ｔｉとともに本発明における重要な構成元素である。従って、所要の添加範囲が必要であるが、０．１５質量％を越えて添加すると鋼板の靭性を著しく低下させる。
Ｔｉ：０．００５〜０．２０質量％
Ｔｉは選択元素である。また、Ｔｉは、上記Ａｌ、Ｓｉとともに本発明の重要な構成元素であり、母材の靭性確保や溶接熱影響部での靭性確保の観点から所定の範囲が良好である。しかし、Ｔｉは選択酸化性の点からは必須ではないものの、
Ｓｉ＋Ａｌ＋Ｔｉ≧０．３質量％
を満足することが優れたアンカー効果を持ったスケール生成に寄与する。 Al: 0.15 mass% or less
Al is an important constituent element in the present invention together with Si and Ti. Therefore, the required addition range is necessary, but if it exceeds 0.15 mass%, the toughness of the steel sheet is remarkably lowered.
Ti: 0.005-0.20 mass%
Ti is a selective element. Ti is an important constituent element of the present invention together with the above Al and Si, and the predetermined range is good from the viewpoint of ensuring the toughness of the base material and ensuring the toughness in the weld heat affected zone. However, although Ti is not essential from the point of selective oxidation,
Si + Al + Ti ≧ 0.3 mass%
Satisfying this value contributes to the generation of a scale having an excellent anchor effect.

Ｃｕ：０．０１〜２．０質量％
Ｃｕは、強度を増加させるための元素で０、０１質量％以上でその効果を発揮する。しかし、Ｃｕは、２．０質量％を越えて添加すると，熱間脆性により鋼板表面の性状を劣化する。
Ｎｉ：０．０１〜４．０質量％
Ｎｉは、母材の強度を増加させつつ靭性も向上させることが可能である。また、Ｎｉは、０．０１質量％以上で効果を発揮し、４．０質量％以上では効果が飽和し経済的に不利である。 Cu: 0.01-2.0 mass%
Cu is an element for increasing the strength, and exhibits its effect at 0,01 mass% or more. However, if Cu is added in excess of 2.0 mass%, the properties of the steel sheet surface deteriorate due to hot brittleness.
Ni: 0.01-4.0 mass%
Ni can improve toughness while increasing the strength of the base material. Further, Ni exhibits an effect at 0.01% by mass or more, and at 4.0% by mass or more, the effect is saturated and is economically disadvantageous.

Ｃｒ：０．０１〜２．０質量％、Ｍｏ：０．０１〜２．０質量％
Ｃｒ，Ｍｏは、いずれも強度を増加するのに有効である。また、Ｃｒ，Ｍｏは、いずれも、０．０１質量％以上でその効果を発揮し、２．０質量％を越えて添加すると著しく靭性を劣化させる。
Ｎｂ：０．００３〜０．１質量％、Ｖ：０．００３〜０．５質量％
Ｎｂ，Ｖは母材の強度と靭性を向上させる元素であり、いずれも０．００３質量％以上の添加で効果を発揮する。また、Ｎｂは０．１質量％を越えると、Ｖは０．５質量％を越えると、かえって靭性の低下を招くおそれがある。 Cr: 0.01-2.0 mass%, Mo: 0.01-2.0 mass%
Both Cr and Mo are effective for increasing the strength. Further, Cr and Mo both exhibit the effect at 0.01% by mass or more, and when added exceeding 2.0% by mass, the toughness is remarkably deteriorated.
Nb: 0.003-0.1 mass%, V: 0.003-0.5 mass%
Nb and V are elements that improve the strength and toughness of the base metal, and both exhibit an effect when added in an amount of 0.003% by mass or more. On the other hand, if Nb exceeds 0.1% by mass and V exceeds 0.5% by mass, the toughness may be lowered.

Ｂ：０．０００５〜０．００４質量％
Ｂは、焼入れ性の向上によって強度を増加させることができる。この効果は、０．０００５％質量以上で顕著になり、０．００４質量％を越えて添加しても効果は飽和する。
Ｃａ：０．０００１〜０．００６％、Ｍｇ：０．０００１〜０．００６％、ＲＥＭ：０．０００１〜０．０２％
Ｃａ，Ｍｇ，ＲＥＭは、夫々鋼中のＳを固定して鋼板の靭性を向上させる働きがあり、０．０００１質量％以上の添加で効果がある。しかし、Ｃａは０．００６質量％、Ｍｇは０．００６質量％、ＲＥＭは０．０２質量％を越えて添加すると、鋼中の介在物量が増加し靭性をかえって劣化させる。 B: 0.0005-0.004 mass%
B can increase the strength by improving the hardenability. This effect becomes significant when the content is 0.0005% by mass or more, and the effect is saturated even if the content exceeds 0.004% by mass.
Ca: 0.0001 to 0.006%, Mg: 0.0001 to 0.006%, REM: 0.0001 to 0.02%
Ca, Mg, and REM each function to fix S in steel and improve the toughness of the steel sheet, and are effective when added in an amount of 0.0001% by mass or more. However, if Ca is added in an amount of 0.006% by mass, Mg is added in an amount of 0.006% by mass, and REM is added in an amount exceeding 0.02% by mass, the amount of inclusions in the steel is increased and the toughness is changed to deteriorate.

（実施例）
以下、実施例について本発明を説明する。
図１は、本発明の製造方法を実施するための製造ラインの一例を示す概略図である。図１に示すように、圧延ライン１には、上流から下流側に向かって熱間圧延機３、加速冷却装置４、インライン型誘導加熱装置５、ホットレベラー６が順次配置されている。インライン型誘導加熱装置５あるいは他の熱処理装置を、圧延設備である熱間圧延機３及びそれに引き続く冷却設備である加速冷却装置４と同一ライン上に設置することによって、圧延、冷却終了後迅速に再加熱処理が行えるので、圧延して加速冷却した後の鋼板２を、直ちに６５０℃以上に加熱することができる。 (Example)
Hereinafter, the present invention will be described with reference to examples.
FIG. 1 is a schematic view showing an example of a production line for carrying out the production method of the present invention. As shown in FIG. 1, in the rolling line 1, a hot rolling mill 3, an acceleration cooling device 4, an inline induction heating device 5, and a hot leveler 6 are sequentially arranged from the upstream side to the downstream side. By installing the in-line type induction heating device 5 or other heat treatment device on the same line as the hot rolling mill 3 as a rolling facility and the accelerated cooling device 4 as a subsequent cooling facility, the rolling and cooling can be quickly performed. Since the reheating treatment can be performed, the steel plate 2 after being rolled and accelerated and cooled can be immediately heated to 650 ° C. or higher.

次に、上記製造ラインを用いて鋼板を製造する方法を具体的に説明する。
まず、下記表１に示す組成の溶鋼（鋼Ｎｏ．１〜２５）を転炉で溶製しＲＨ脱ガス処理を施した後、連続鋳造法で鋼素材（２１５ｍｍｔ厚スラブ）とした。次に、その鋼を１１５０℃に再加熱し、９５０℃以上の温度で再結晶域圧延を６０％行った。つづいて、９００℃以下の温度で４０％の未再結晶域圧延を仕上げ温度８５０℃で行い、空冷および水冷にて３００〜６００℃の温度域へ冷却した。ひきつづき、０ｓ〜４００ｓの保持を行い、所定の加熱温度まで０．５〜２０℃／ｓで昇温した。更に、その後放冷して板厚２０ｍｍｔの鋼板を作製した。 Next, a method for producing a steel plate using the production line will be specifically described.
First, molten steel (steel Nos. 1 to 25) having the composition shown in Table 1 below was melted in a converter and subjected to RH degassing treatment, and then a steel material (215 mm thick slab) was formed by a continuous casting method. Next, the steel was reheated to 1150 ° C., and recrystallization zone rolling was performed 60% at a temperature of 950 ° C. or higher. Subsequently, 40% non-recrystallized zone rolling was performed at a temperature of 900 ° C. or lower at a finishing temperature of 850 ° C., and cooled to a temperature range of 300 to 600 ° C. by air cooling and water cooling. Subsequently, 0 s to 400 s were held, and the temperature was raised to a predetermined heating temperature at 0.5 to 20 ° C./s. Further, it was then allowed to cool to produce a steel plate having a thickness of 20 mmt.

評価は、それぞれの組成の鋼板でのスケール厚み、スケール組成および地鉄−スケール界面での選択酸化深さの測定を行った。また、スケール性状を評価したものについて、３．５ｋＷのＣＯ２レーザ切断機を用いて切断試験を行った。この切断試験では、断面の形状及びドロス付着の有無によって切断性を評価した。下記表２は、本発明に係る鋼Ｎｏ．１，２，５，６，９〜１３，１６〜２１及び比較例に係る鋼Ｎｏ．３，４，７，８，１４，１５，２２〜２５における冷却方法、冷却停止温度、滞留時間、加熱速度、加熱温度、スケール厚み、ＦｅＯ比率、選択酸化層の厚み及び切断性を表示したものである。 The evaluation was performed by measuring the scale thickness, the scale composition, and the selective oxidation depth at the base metal-scale interface in the steel sheets having the respective compositions. Also, for those of the evaluation of the scale properties were cut tested using the CO 2 laser cutting machine 3.5 kW. In this cutting test, the cutting performance was evaluated based on the cross-sectional shape and the presence or absence of dross adhesion. Table 2 below shows the steel No. 1 according to the present invention. 1, 2, 5, 6, 9 to 13, 16 to 21 and steel Nos. According to comparative examples. The cooling method, cooling stop temperature, residence time, heating rate, heating temperature, scale thickness, FeO ratio, thickness of selective oxidation layer and cutting property in 3,4,7,8,14,15,22-25 are displayed. It is.

図２は、鋼板の断面を模式的に示すもので、符号Ｔ１は選択酸化層の厚み、符号Ｔ２はスケールの厚みを示す。

Figure 2005171298
FIG. 2 schematically shows a cross section of the steel sheet, where symbol T 1 indicates the thickness of the selective oxidation layer and symbol T 2 indicates the thickness of the scale.
Figure 2005171298

Figure 2005171298
Figure 2005171298

表２より、冷却後の滞留時間が３００秒以内、加熱速度が３℃／ｓ以上、加熱温度が６５０〜８５０℃の範囲である本発明鋼では、鋼板表面に１０μｍ以上の厚みでＦｅＯ比率が３０％以上のスケールが形成され、良好な切断性を有することが確認された。特に、Ｓｉ＋Ａｌ＋Ｔｉ≧０．３％を満足する鋼Ｎｏ．１，６，９，１０，１１，１６〜２１は、選択酸化層の厚みが１μｍ以上であり、ドロスの付着もなく特に切断性に優れることが明らかとなった。   From Table 2, in the steel according to the present invention in which the residence time after cooling is within 300 seconds, the heating rate is 3 ° C./s or more, and the heating temperature is in the range of 650 to 850 ° C., the FeO ratio is 10 μm or more on the steel plate surface. A scale of 30% or more was formed, and it was confirmed that the film has good cutting properties. In particular, steel No. 1 satisfying Si + Al + Ti ≧ 0.3%. In 1, 6, 9, 10, 11, 16 to 21, it has been clarified that the thickness of the selective oxidation layer is 1 μm or more, and there is no adhesion of dross and particularly excellent cutting properties.

これに対し、比較例に係る鋼Ｎｏ３，４，７，８，１４，１５，２１〜２５の場合、スケール厚み、ＦｅＯ比率および選択酸化層の厚みの少なくともいずれか１つにおいて十分ではない。即ち、切断性において切断が途中停止し、ドロス付着量が大であり、本発明と比べて良好な切断性が得られないことが明らかになった。   On the other hand, in the case of steel Nos. 3, 4, 7, 8, 14, 15, 21 to 25 according to the comparative example, at least one of scale thickness, FeO ratio, and selective oxide layer thickness is not sufficient. That is, it became clear that cutting was stopped halfway in terms of cutting property, and the amount of dross attached was large, so that good cutting property was not obtained as compared with the present invention.

なお、この発明は、上記実施形態そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形することも可能である。   In addition, this invention is not limited to the said embodiment as it is, It is also possible to change a component in the range which does not deviate from the summary in an implementation stage.

本発明の製造方法を実施するための製造ラインの一例を示す概略図。Schematic which shows an example of the manufacturing line for enforcing the manufacturing method of this invention. 鋼板の断面を模式的に示す図。The figure which shows the cross section of a steel plate typically.

符号の説明Explanation of symbols

１…圧延ライン、 ２…鋼板、 ３…熱間圧延機、
４…加速冷却装置、 ５…インライン型誘導加熱装置、 ６…ホットレベラー。 DESCRIPTION OF SYMBOLS 1 ... Rolling line, 2 ... Steel plate, 3 ... Hot rolling mill,
4 ... Accelerated cooling device, 5 ... In-line induction heating device, 6 ... Hot leveler.

Claims (4)

Ｃ ：０．０１〜０．２０質量％、
Ｓｉ：０．８０質量％以下、
Ｍｎ：０．４〜２．５質量％、
Ｐ ：０．０３質量％以下、
Ｓ ：０．０１質量％以下、
Ａｌ：０．１５質量％以下
を含有し残部がＦｅおよび不可避不純物からなる厚鋼板を９５０℃以上に加熱した後、熱間圧延を施す工程と、空冷あるいは加速冷却によって鋼板全体を６００℃以下まで冷却した後、３００秒以内に３℃／ｓ以上の昇温速度で加熱して鋼板表面層を６５０℃以上８５０℃以下の温度域に加熱した後、放冷する工程とを具備することを特徴とするレーザ切断性に優れた厚鋼板の製造方法。 C: 0.01-0.20 mass%,
Si: 0.80 mass% or less,
Mn: 0.4 to 2.5% by mass,
P: 0.03 mass% or less,
S: 0.01% by mass or less,
After heating a thick steel plate containing Al: 0.15% by mass or less, with the balance being Fe and inevitable impurities to 950 ° C. or higher, hot rolling, and the entire steel plate to 600 ° C. or less by air cooling or accelerated cooling And after cooling, heating the steel sheet surface layer to a temperature range of 650 ° C. or more and 850 ° C. or less by heating at a temperature rising rate of 3 ° C./s within 300 seconds, and then allowing to cool. The manufacturing method of the thick steel plate excellent in laser cutting property. 前記Ｃ，Ｓｉ，Ｍｎ，Ｐ，Ｓ，Ａｌの他、Ｔｉ：０．００５〜０．２０質量％を含有し、かつＳｉ：０．２０質量％以上、Ｓｉ＋Ａｌ＋Ｔｉ≧０．３質量％を満足する、残部がＦｅおよび不可避不純物からなる厚鋼板を処理することを特徴とする請求項１記載のレーザ切断性に優れた厚鋼板の製造方法。   In addition to C, Si, Mn, P, S, Al, Ti: 0.005 to 0.20% by mass, Si: 0.20% by mass or more, and Si + Al + Ti ≧ 0.3% by mass is satisfied. 2. The method for producing a thick steel plate having excellent laser cutting properties according to claim 1, wherein the thick steel plate is made of Fe and inevitable impurities. 請求項１記載の各元素の他、選択元素として、
Ｃｕ：０．０１〜２．０質量％、
Ｎｉ：０．０１〜４．０質量％、
Ｃｒ：０．０１〜２．０質量％、
Ｍｏ：０．０１〜２．０質量％、
Ｎｂ：０．００３〜０．１質量％、
Ｖ ：０．００３〜０．５質量％、
Ｂ ：０．０００５〜０．００４質量％、
Ｃａ：０．０００１〜０．００６質量％、
Ｍｇ：０．０００１〜０．００６質量％、
ＲＥＭ：０．０００１〜０．０２質量％
の１種または２種以上をさらに含有することを特徴とする請求項１に記載のレーザ切断性に優れた厚鋼板の製造方法。 In addition to each element of claim 1, as a selective element,
Cu: 0.01-2.0 mass%,
Ni: 0.01-4.0 mass%,
Cr: 0.01 to 2.0% by mass,
Mo: 0.01 to 2.0 mass%,
Nb: 0.003 to 0.1% by mass,
V: 0.003-0.5 mass%,
B: 0.0005-0.004 mass%,
Ca: 0.0001 to 0.006 mass%,
Mg: 0.0001 to 0.006 mass%,
REM: 0.0001 to 0.02 mass%
1 or 2 types or more of these are further contained, The manufacturing method of the steel plate excellent in the laser cutting property of Claim 1 characterized by the above-mentioned. 請求項２もしくは請求項３のいずれかの成分を有するとともに、鋼板表面に１０μｍ以上のスケール層を有し、さらにスケール界面から地鉄中に１μｍ以上の選択酸化層を有することを特徴とするレーザ切断性に優れた厚鋼板。   A laser comprising the component according to claim 2 or 3, having a scale layer of 10 μm or more on the surface of the steel plate, and further having a selective oxidation layer of 1 μm or more in the ground iron from the scale interface. Thick steel plate with excellent cutting properties.
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JP2013128962A (en) * 2011-12-22 2013-07-04 Jfe Steel Corp Method of manufacturing test piece
JP2017538583A (en) * 2014-10-16 2017-12-28 エス・エム・エス・グループ・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツング Apparatus and method for the production of rough plates
JP2020114938A (en) * 2019-01-18 2020-07-30 日本製鉄株式会社 Thick steel plate
CN111809110A (en) * 2020-06-17 2020-10-23 包头钢铁（集团）有限责任公司 Rare earth treated 700 MPa-grade automotive frame steel strip with thick specification and manufacturing method thereof
CN115976409A (en) * 2022-12-15 2023-04-18 攀钢集团攀枝花钢铁研究院有限公司 Low-cost hollow anchor rod welded pipe, hot-rolled steel strip and preparation method
JP7445116B2 (en) 2019-12-18 2024-03-07 日本製鉄株式会社 thick steel plate

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JP2008195983A (en) * 2007-02-09 2008-08-28 Kobe Steel Ltd Steel plate superior in sectility
WO2009101951A1 (en) * 2008-02-12 2009-08-20 Sumitomo Metal Industries, Ltd. Steel material for thermal cutting with oxygen
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JP2009203532A (en) * 2008-02-28 2009-09-10 Jfe Steel Corp Method for producing steel material excellent in scale adhesiveness
JP2013128962A (en) * 2011-12-22 2013-07-04 Jfe Steel Corp Method of manufacturing test piece
JP2017538583A (en) * 2014-10-16 2017-12-28 エス・エム・エス・グループ・ゲゼルシャフト・ミト・ベシュレンクテル・ハフツング Apparatus and method for the production of rough plates
JP2020114938A (en) * 2019-01-18 2020-07-30 日本製鉄株式会社 Thick steel plate
JP7277707B2 (en) 2019-01-18 2023-05-19 日本製鉄株式会社 thick steel plate
JP7445116B2 (en) 2019-12-18 2024-03-07 日本製鉄株式会社 thick steel plate
CN111809110A (en) * 2020-06-17 2020-10-23 包头钢铁（集团）有限责任公司 Rare earth treated 700 MPa-grade automotive frame steel strip with thick specification and manufacturing method thereof
CN115976409A (en) * 2022-12-15 2023-04-18 攀钢集团攀枝花钢铁研究院有限公司 Low-cost hollow anchor rod welded pipe, hot-rolled steel strip and preparation method

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