JP5949167B2 - Manufacturing method of steel sheet excellent in laser cutting property and steel sheet excellent in laser cutting property - Google Patents
Manufacturing method of steel sheet excellent in laser cutting property and steel sheet excellent in laser cutting property Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims description 109
- 239000010959 steel Substances 0.000 title claims description 109
- 238000003698 laser cutting Methods 0.000 title claims description 62
- 238000004519 manufacturing process Methods 0.000 title claims description 21
- 238000005096 rolling process Methods 0.000 claims description 35
- 239000000203 mixture Substances 0.000 claims description 29
- 238000001816 cooling Methods 0.000 claims description 26
- 238000005098 hot rolling Methods 0.000 claims description 24
- 238000010583 slow cooling Methods 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 9
- 239000001301 oxygen Substances 0.000 claims description 9
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000004615 ingredient Substances 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 5
- 238000003303 reheating Methods 0.000 claims description 4
- 238000005520 cutting process Methods 0.000 description 66
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 28
- 238000000034 method Methods 0.000 description 17
- 239000000463 material Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 12
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 11
- 230000007423 decrease Effects 0.000 description 11
- 230000007547 defect Effects 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- 229910052759 nickel Inorganic materials 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 5
- 229910052761 rare earth metal Inorganic materials 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
- 239000010953 base metal Substances 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 230000031700 light absorption Effects 0.000 description 4
- 229920006395 saturated elastomer Polymers 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 3
- 229910052791 calcium Inorganic materials 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- 229910004283 SiO 4 Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
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- 238000002347 injection Methods 0.000 description 1
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- 238000005259 measurement Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
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- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000000879 optical micrograph Methods 0.000 description 1
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- 238000009628 steelmaking Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
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Description
本発明は、造船、土木、建築、橋梁、建産機械、海洋構造物、貯蔵タンク、圧力容器、等に供して好適なレーザー切断時に優れた切断品質が得られる板厚６ｍｍ以上のレーザー切断性に優れた鋼板の製造方法およびレーザー切断性に優れた鋼板に関する。 The present invention is applicable to shipbuilding, civil engineering, construction, bridges, construction machinery, offshore structures, storage tanks, pressure vessels, etc., and can be used for laser cutting with a thickness of 6 mm or more to obtain excellent cutting quality. The present invention relates to a method for producing a steel plate excellent in the quality and a steel plate excellent in laser cutting property.
造船、土木、建築、橋梁、建産機械、海洋構造物、貯蔵タンク、圧力容器などの鋼構造物に熱間圧延鋼板が用いられる際には、所望の形状に切断した後に組み立てるのが一般的である。鋼構造物の工作工程において切断作業の割合が高いため、作業の高能率化や低コスト化が常に要請され、近年では、意匠性などの観点から鋼構造物の形状が複雑化するとともに、切断以降の工程省略のため、切断面形状が複雑化し、切断面に対して高い精度が要求されるようになっている。 When hot rolled steel sheets are used in steel structures such as shipbuilding, civil engineering, architecture, bridges, construction machinery, offshore structures, storage tanks, pressure vessels, etc., it is common to assemble them after cutting them into the desired shape. It is. Since the rate of cutting work is high in the work process of steel structures, there is always a demand for higher work efficiency and lower costs. In recent years, the shape of steel structures has become more complex in terms of design and the like, and cutting Since the subsequent steps are omitted, the shape of the cut surface is complicated, and high accuracy is required for the cut surface.
従来から、厚鋼板の切断方法としてガス切断やプラズマ切断が広く用いられている。ガス切断は、設備が比較的簡単であり、非常に板厚が厚い鋼板まで切断可能であることから最も広く利用される。しかしながら、ガス炎の制御や監視など自動作業化が難しく、また切断速度が比較的遅いことから、作業性に劣る。プラズマ切断は、最大厚５０ｍｍ程度までは高速切断が可能であるが、トーチ寿命が数時間で、頻繁な交換作業のため作業性が低く、自動作業化は困難である。 Conventionally, gas cutting and plasma cutting have been widely used as cutting methods for thick steel plates. Gas cutting is most widely used because the equipment is relatively simple and it is possible to cut a steel plate having a very large thickness. However, automatic work such as control and monitoring of the gas flame is difficult, and the cutting speed is relatively slow, so the workability is poor. Plasma cutting is capable of high-speed cutting up to a maximum thickness of about 50 mm, but has a torch life of several hours, low workability due to frequent replacement work, and automatic work is difficult.
一方、レーザー切断は、薄鋼板の切断から普及し、近年では、レーザー発振器の高出力化、低価格化に伴い、板厚の厚い鋼板の切断にも適用範囲が拡大している。レーザー切断は、その装置寿命が長く、レーザーの出力管理が容易なため、切断作業の完全自動化に好適である。更に、切断による熱変形が小さいとともに、切断面の品質が良好である。このため、レーザー切断は作業性と切断品質の観点から理想的な厚鋼板の切断方法といえる。 On the other hand, laser cutting has been widely used since the cutting of thin steel plates, and in recent years, as the output of laser oscillators has increased and the price has been reduced, the range of application has also expanded to the cutting of thick steel plates. Laser cutting is suitable for complete automation of the cutting operation because of its long device life and easy laser output management. Furthermore, the thermal deformation due to cutting is small, and the quality of the cut surface is good. For this reason, laser cutting can be said to be an ideal method for cutting thick steel plates from the viewpoint of workability and cutting quality.
しかしながら、現状のレーザー出力では、板厚が２５ｍｍ前後から、切断の安定性が急激に低下するため、対象板厚は最大２５ｍｍ程度に限定されている。より板厚の厚い鋼板が切断できるようにレーザー切断機の更なる高出力化と共に、鋼板自体のレーザー切断性(切断不良が生じないこと）を向上させる検討がされている。 However, with the current laser output, since the stability of cutting sharply decreases from about 25 mm, the target plate thickness is limited to about 25 mm at the maximum. Studies are being made to improve the laser cutting performance of the steel sheet itself (to prevent cutting defects), along with further increasing the output of the laser cutting machine so that thicker steel sheets can be cut.
特許文献１には、質量％で、Ｃ：０．２０％以下−Ｓｉ：０．１〜１．０％−Ｍｎ：２．５％以下系にＣｕ、Ｎｉ、Ｔｉ、Ｚｒを添加した鋼素材を、低温加熱、低温圧延および加速冷却して、母材とスケール層の界面にＣｕ、Ｎｉ、Ｔｉ、Ｚｒの濃化層を生成させた鋼板とし、該濃化層がレーザー光のエネルギーを効率的に地鉄に吸収させてレーザー切断性を向上させる技術が報告されている。 In Patent Document 1, a steel material in which Cu, Ni, Ti, and Zr are added to a system in mass%, C: 0.20% or less, -Si: 0.1 to 1.0%, Mn: 2.5% or less. Is a steel plate in which a concentrated layer of Cu, Ni, Ti, Zr is formed at the interface between the base material and the scale layer by low temperature heating, low temperature rolling and accelerated cooling, and the concentrated layer efficiently uses the energy of the laser beam. In particular, a technique for improving the laser cutting property by absorbing it into the ground iron has been reported.
特許文献２では、Ｓｉを添加した鋼素材を、熱間圧延前に高圧デスケーリングした後、普通圧延、加速冷却および平坦度調整処理を組み合わせる製造方法により、スケール厚さを１０〜６０μｍに制御してレーザー切断性を向上させる技術が報告されている。 In Patent Document 2, a steel material added with Si is subjected to high-pressure descaling before hot rolling, and then the scale thickness is controlled to 10 to 60 μm by a manufacturing method that combines ordinary rolling, accelerated cooling, and flatness adjustment processing. Technologies that improve laser cutting performance have been reported.
特許文献３では、鋼板表面の光沢性、レーザー切断時の溶鋼の粘性を調整した重量％で０．０３〜０．０６％Ｃ−０．０５〜０．３％Ｓｉ−０．５〜１．５％Ｍｎ系にＣｕ、Ｎｉ、Ｃｒなどを添加した成分組成の鋼素材とし、特定温度に加熱後、制御圧延中に高圧のデスケーリングを複数回実施して鋼板表面に剥離したスケールやゴミを残さず、且つ、必要以上にスケールを厚くしないようにしてレーザー切断性を向上させる技術が報告されている。 In Patent Document 3, 0.03 to 0.06% C-0.05 to 0.3% Si-0.5 to 1. wt% adjusted for glossiness of the steel sheet surface and viscosity of the molten steel during laser cutting. 5% Mn-based steel material with Cu, Ni, Cr, etc. added to the composition, heated to a specific temperature, then subjected to high-pressure descaling multiple times during controlled rolling to remove scales and debris from the steel sheet surface There has been reported a technique for improving the laser cutting property by leaving no scale and making the scale unnecessarily thick.
しかしながら、特許文献１に記載された技術では、高価な合金元素の添加が必要で高コストになり、さらに、低温加熱−低温圧延により、鋼板内部にボイドなどの欠陥が残存したり、歪が生じたりすることが問題となる。 However, in the technique described in Patent Document 1, it is necessary to add an expensive alloy element, resulting in high cost. Further, due to low temperature heating-low temperature rolling, defects such as voids remain in the steel sheet or distortion occurs. Is a problem.
特許文献２に記載された技術では、加速冷却と平坦度調整処理により、鋼板内に歪が導入され、切断時の変形が問題となるだけでなく、鋼板の板内位置によるスケール形態（スケール厚さ、スケール組成）のばらつきが顕著でスケール厚のばらつきも大きく、安定して優れたレーザー切断性を確保することは困難である。 In the technique described in Patent Document 2, strain is introduced into the steel sheet by accelerated cooling and flatness adjustment processing, and deformation at the time of cutting becomes a problem. In addition, the variation in the scale composition) is remarkable and the variation in the scale thickness is also large, and it is difficult to ensure a stable and excellent laser cutting property.
特許文献３に記載された技術では、高価な合金元素の添加が必要であり高コストとなるだけでなく、圧延仕上げ温度が低温であるため、圧延パス間およびデスケーリングパス間の時間が長くなり、鋼板内位置によるスケール形態（スケール厚さ、スケール組成）のばらつきが顕著で、安定して優れたレーザー切断性を確保することは困難である。 In the technique described in Patent Document 3, not only is expensive alloy element required to be added and the cost becomes high, but also the rolling finishing temperature is low, so the time between rolling passes and between descaling passes becomes long. The variation of the scale form (scale thickness, scale composition) depending on the position in the steel plate is remarkable, and it is difficult to ensure stable and excellent laser cutting properties.
本発明は、これらの事実に鑑みてなされたもので、レーザー切断性に優れた鋼板の製造方法およびレーザー切断性に優れた鋼板を提供することを目的とする。 This invention is made | formed in view of these facts, and it aims at providing the manufacturing method of the steel plate excellent in laser cutting property, and the steel plate excellent in laser cutting property.
本発明者らは、上記課題を解決するため、鋼板の成分組成、製造方法、スケール形態（スケール厚さ、スケール組成）、およびレーザー切断部の溶融鋼の粘性を決定する各種要因に関して鋭意研究を行い、以下の知見を得た。本発明において、レーザー切断性に優れるとは、レーザー切断に適することを指し、具体的には切断の高速化および切断中の停止が無く安定した切断が可能であり、切断中での鋼板の変形が少なく作業性に優れ、切断後の鋼板断面にはノッチがなく、鋼板裏面にはドロス付着もない切断品質に優れていることを指す。
１．レーザー切断後の鋼板断面のノッチや、鋼板裏面のドロス付着を抑制するためには、表面スケールの密着性を高めることが重要である。このためには、スケール層の厚み上限の管理が必要となる。
２．切断安定性（レーザー切断が途中で停止しないこと）を向上させるためには、まず、スケール組成を管理することにより、レーザー光の吸収効率を高めることが重要である。さらに、スケール組成を管理した上で、スケール層の厚み下限を管理することも重要である。レーザー光により、鋼板が溶融したとき、溶融鋼の粘性に対してスケール量が大きく寄与し、必要量の表面スケールを確保することにより、溶融鋼の粘性を低下させ、効率よく切断するためである。
３．上記の表面性状を達成するためには、鋼板組成を管理するとともに、製造条件を厳格に管理することが不可欠である。まず、熱間圧延条件と熱間圧延中のデスケーリング条件を厳格に管理して、スラブ加熱〜熱間圧延前、および熱間圧延途中に生成、成長するスケールを制御することが重要である。
４．さらに、圧延完了直後から空冷し、さらに、途中から温度、冷却速度を厳格に管理して徐冷することも重要である。これにより、レーザー切断に適したスケール形態を安定して満足できるだけでなく、冷却終了後の鋼板中の残留応力を極力低減し、レーザー切断中の鋼板の変形を抑制することにより、レーザー光の焦点のずれを最小限にして、優れた切断性を安定して確保することができる。
In order to solve the above-mentioned problems, the present inventors have conducted intensive research on various factors that determine the composition of steel sheet, the manufacturing method, the scale form (scale thickness, scale composition), and the viscosity of the molten steel at the laser cutting part. The following findings were obtained. In the present invention, excellent laser cutting ability means that it is suitable for laser cutting, specifically, high speed cutting and stable cutting without stopping during cutting, deformation of the steel plate during cutting This means that it has excellent workability, has no notch in the cross section of the steel plate after cutting, and has excellent cutting quality with no dross adhesion on the back surface of the steel plate.
1. In order to suppress notches in the cross section of the steel plate after laser cutting and adhesion of dross on the back surface of the steel plate, it is important to improve the adhesion of the surface scale. For this purpose, it is necessary to manage the upper limit of the thickness of the scale layer.
2. In order to improve the cutting stability (that laser cutting does not stop halfway), it is important to first improve the absorption efficiency of laser light by managing the scale composition. Furthermore, it is also important to manage the lower limit of the thickness of the scale layer after managing the scale composition. This is because when the steel sheet is melted by laser light, the scale amount greatly contributes to the viscosity of the molten steel, and by ensuring the necessary amount of surface scale, the viscosity of the molten steel is reduced and the steel is efficiently cut. .
3. In order to achieve the above surface properties, it is indispensable to manage the steel sheet composition and strictly manage the production conditions. First, it is important to strictly control the hot rolling conditions and the descaling conditions during hot rolling to control the scales that are generated and grown before slab heating to hot rolling and during hot rolling.
4). Furthermore, it is also important to air-cool immediately after completion of rolling, and to gradually cool by controlling the temperature and cooling rate strictly in the middle. As a result, not only can the scale form suitable for laser cutting be stably satisfied, the residual stress in the steel sheet after cooling is reduced as much as possible, and the deformation of the steel sheet during laser cutting is suppressed, thereby reducing the focus of the laser beam. Therefore, it is possible to stably ensure excellent cutting performance.
本発明は、得られた知見に、さらに検討を加えてなされたもので、すなわち、本発明は、
１．成分組成が、質量％で、
Ｃ：０．０３〜０．２０％、
Ｓｉ：０．０１〜０．６０％、
Ｍｎ：０．１〜２．０％、
Ｐ：０．０５％以下、
Ｓ：０．０１％以下、
を含有し、残部がＦｅおよび不可避的不純物からなる鋳片または鋼片を、１０００〜１２００℃に再加熱後、鋳片または鋼片の表裏面に水を噴射してデスケーリングを行い、その後、熱間圧延を開始し、１０００℃〜圧延終了温度間の圧延パスの直前において、鋼板表裏面に水を噴射してデスケーリングを行うことを３回以上実施して、８００〜９５０℃で熱間圧延を終了した後、大気中で空冷し、５５０〜１５０℃から室温までの間に、合計１００℃以上の温度範囲を０．０５℃／ｓ未満で徐冷することを特徴とするレーザー切断性に優れた鋼板の製造方法。
２．成分組成が、更に、質量％で、
Ｃｕ：１．０％以下、
Ｎｉ：２．０％以下、
Ｃｒ：２．０％以下、
Ｍｏ：１．０％以下、
Ｎｂ：０．１％以下、
Ｖ：０．１％以下、
Ｔｉ：０．０３％以下、
Ｂ：０．００５％以下、
の１種または２種以上を含有することを特徴とする１に記載のレーザー切断性に優れた鋼板の製造方法。
３．成分組成が、更に、質量％で、
ＲＥＭ：０．０２％以下、
Ｃａ：０．００５％以下、
Ｍｇ：０．００５％以下、
を含有することを特徴とする１または２に記載のレーザー切断性に優れた鋼板の製造方法。
４．前記０．０５℃／ｓ未満での徐冷を段積み徐冷とすることを特徴とする１乃至３のいずれか一つに記載のレーザー切断性に優れた鋼板の製造方法。
５．前記８００〜９５０℃で終了する熱間圧延を実施して、大気中で空冷した後、酸素濃度が２０％未満のガス雰囲気に管理した炉で、６００〜１５０℃から５０℃以下まで０．０５℃／ｓ未満で徐冷することを特徴とする１乃至３のいずれか一つに記載のレーザー切断性に優れた鋼板およびその製造方法。
６．１乃至３の何れか一つに記載の成分組成を有し、鋼板表面スケールの平均厚さが１０〜４０μmで、かつ表面スケール中のＦｅ３Ｏ４およびＦｅＯが体積分率で合計８０％以上となることを特徴とするレーザー切断性に優れた鋼板。
The present invention has been made by further studying the obtained knowledge, that is, the present invention
1. Ingredient composition is mass%,
C: 0.03 to 0.20%
Si: 0.01-0.60%,
Mn: 0.1 to 2.0%,
P: 0.05% or less,
S: 0.01% or less,
A slab or steel slab comprising Fe and the inevitable impurities, and after reheating to 1000 to 1200 ° C., water is sprayed on the front and back surfaces of the slab or steel slab, and then descaling is performed. Hot rolling is started, and immediately before the rolling pass between 1000 ° C. and the rolling finish temperature, water is sprayed on the front and back surfaces of the steel sheet to perform descaling three times or more, and hot at 800 to 950 ° C. After finishing the rolling, it is air-cooled in the atmosphere, and the laser cutting property is characterized by gradually cooling the temperature range of 100 ° C. or more to less than 0.05 ° C./s between 550 and 150 ° C. to room temperature. Steel sheet manufacturing method with excellent performance.
2. Ingredient composition is further mass%,
Cu: 1.0% or less,
Ni: 2.0% or less,
Cr: 2.0% or less,
Mo: 1.0% or less,
Nb: 0.1% or less,
V: 0.1% or less,
Ti: 0.03% or less,
B: 0.005% or less,
The manufacturing method of the steel plate excellent in laser-cutting property of 1 characterized by including 1 type, or 2 or more types of these.
3. Ingredient composition is further mass%,
REM: 0.02% or less,
Ca: 0.005% or less,
Mg: 0.005% or less,
The manufacturing method of the steel plate excellent in the laser cutting property of 1 or 2 characterized by containing.
4). 4. The method for producing a steel sheet excellent in laser cutting property according to any one of 1 to 3, wherein the slow cooling at less than 0.05 ° C./s is stacked slow cooling.
5. After performing the hot rolling that ends at 800 to 950 ° C. and air-cooling in the air, the furnace is controlled to a gas atmosphere with an oxygen concentration of less than 20%, and the temperature is controlled from 600 to 150 ° C. to 50 ° C. or less by 0.05. The steel sheet excellent in laser cutting property according to any one of 1 to 3, wherein the steel sheet is slowly cooled at less than ° C./s, and a method for producing the same.
6.1 The composition of any one of 3 to 3, the average thickness of the steel sheet surface scale is 10 to 40 μm, and the total volume fraction of Fe 3 O 4 and FeO in the surface scale is 80 % Steel plate with excellent laser cutting properties.
本発明によれば、レーザー切断において、優れた作業性と切断品質とを有する鋼板が得られ、鋼構造物作製時の製造効率や安全性の向上に大きく寄与し、産業上格段の効果を奏する。 According to the present invention, in laser cutting, a steel plate having excellent workability and cutting quality is obtained, which greatly contributes to improvement in manufacturing efficiency and safety at the time of manufacturing a steel structure, and has a remarkable industrial effect. .
本発明では鋼板の成分組成と製造条件を規定する。
成分組成：説明において％はｍａｓｓ％とする。
Ｃ：０．０３〜０．２０％
Ｃは、鋼の強度を増加させ、構造用鋼材として必要な強度を確保するために必要な元素で、その効果を得るため０．０３％以上の含有を必要とする。一方、０．２０％を超える含有は、靭性を劣化させるとともに、溶接性が低下する。このため、０．０３〜０．２０％の範囲に限定する。好ましくは、０．０４〜０．１８％である。
In this invention, the component composition and manufacturing conditions of a steel plate are prescribed | regulated.
Component composition: In the description, “%” is “mass%”.
C: 0.03-0.20%
C is an element necessary for increasing the strength of steel and ensuring the necessary strength as a structural steel material. To obtain the effect, C is required to be contained in an amount of 0.03% or more. On the other hand, the content exceeding 0.20% deteriorates toughness and lowers weldability. For this reason, it limits to 0.03 to 0.20% of range. Preferably, it is 0.04 to 0.18%.
Ｓｉ：０．０１〜０．６０％
Ｓｉは、脱酸材として作用し、製鋼上、少なくとも０．０１％が必要である。また、熱間圧延時には、スケール層と地鉄の界面に濃化して、ファイアライト（Ｆｅ２ＳｉＯ４）主体のサブスケール層を生成し、圧延後の冷却過程におけるスケール層の成長速度を低下させる効果を有する。０．０１％未満の含有では、スケール層が厚くなりすぎるため、スケール層と地鉄との密着性が低下して、レーザー切断中にスケール層の剥離が生じ、ノッチやバーニングなどのレーザー切断欠陥が生じる。
Si: 0.01-0.60%
Si acts as a deoxidizing material, and at least 0.01% is necessary for steelmaking. Further, during hot rolling, it concentrates at the interface between the scale layer and the base iron to generate a subscale layer mainly composed of firelite (Fe 2 SiO 4 ), and reduces the growth rate of the scale layer in the cooling process after rolling. Has an effect. If the content is less than 0.01%, the scale layer becomes too thick, so the adhesion between the scale layer and the ground iron is reduced, and the scale layer peels off during laser cutting, resulting in laser cutting defects such as notches and burning. Occurs.
また、スケール組成中のＦｅ２Ｏ３量が増加し、レーザー光の吸収効率が悪くなるため、切断が途中で停止するなど、切断安定性が低下する。このため、少なくとも０．０１％必要である。 Moreover, since the amount of Fe 2 O 3 in the scale composition increases and the laser light absorption efficiency deteriorates, the cutting stability is lowered, for example, the cutting stops halfway. For this reason, at least 0.01% is necessary.
一方、０．６０％を超えて含有すると、母材の靭性、溶接部の低温割れ性が顕著に劣化するため、０．０１〜０．６０％の範囲に限定する。好ましくは、０．０２〜０．５５％である。 On the other hand, if the content exceeds 0.60%, the toughness of the base material and the low temperature cracking property of the welded portion are remarkably deteriorated, so the content is limited to the range of 0.01 to 0.60%. Preferably, it is 0.02 to 0.55%.
Ｍｎ：０．１〜２．０％
Ｍｎは、鋼の焼入れ性を増加させる効果を有し、母材の強度を確保するために０．１％以上は必要である。一方、２．０％を超えて含有すると、母材の靭性、延性および溶接性が著しく劣化する。このため、０．１〜２．０％の範囲に限定する。好ましくは、０．２〜１．７％である。
Mn: 0.1 to 2.0%
Mn has the effect of increasing the hardenability of the steel, and 0.1% or more is necessary to ensure the strength of the base material. On the other hand, when the content exceeds 2.0%, the toughness, ductility and weldability of the base material are remarkably deteriorated. For this reason, it limits to 0.1 to 2.0% of range. Preferably, it is 0.2 to 1.7%.
Ｐ：０．０５％以下
Ｐは、不可避的不純物元素として含有され、０．０５％を超えて含有すると、鋼の強度を増加させ著しく靭性を劣化させる。このため、０．０５％以下に限定する。なお、過度のＰ低減は精錬コストを高騰させ経済的に不利となるため、０．００５％以上とすることが好ましい。より好ましくは、０．００７〜０．０２５％である。
P: 0.05% or less P is contained as an unavoidable impurity element. When P is contained in excess of 0.05%, the strength of steel is increased and the toughness is remarkably deteriorated. For this reason, it limits to 0.05% or less. In addition, since excessive P reduction raises refining cost and becomes economically disadvantageous, it is preferable to set it as 0.005% or more. More preferably, it is 0.007 to 0.025%.
Ｓ：０．０１％以下
Ｓは母材の低温靭性や延性を劣化させる不可避的不純物であるため、０．０１％を上限とする。以上が基本成分系で、残部Ｆｅ及び不可避的不純物である。
S: 0.01% or less Since S is an unavoidable impurity that deteriorates the low temperature toughness and ductility of the base material, the upper limit is 0.01%. The above is the basic component system, and the balance is Fe and inevitable impurities.
本発明では、更に所望する特性を向上させるため、上記基本成分系に加えて、Ｃｕ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｖ、Ｔｉ、Ｂ、ＲＥＭ、Ｃａ、Ｍｇの１種または２種以上を含有することができる。 In the present invention, in order to further improve desired characteristics, in addition to the above basic component system, one or more of Cu, Ni, Cr, Mo, Nb, V, Ti, B, REM, Ca, and Mg are added. Can be contained.
Ｃｕ：１．０％以下、Ｎｉ：２．０％以下、Ｃｒ：２．０％以下、Ｍｏ：１．０％以下、Ｎｂ：０．１％以下、Ｖ：０．１％以下、Ｔｉ：０．０３％以下、Ｂ：０．００５％以下の１種または２種以上
Ｃｕ、Ｎｉ、Ｃｒ、Ｍｏ、Ｎｂ、Ｖ、Ｔｉ、Ｂは、いずれも鋼の強度向上に寄与する元素であり、所望する強度に応じて適宜含有できる。
Cu: 1.0% or less, Ni: 2.0% or less, Cr: 2.0% or less, Mo: 1.0% or less, Nb: 0.1% or less, V: 0.1% or less, Ti: One or more of 0.03% or less, B: 0.005% or less Cu, Ni, Cr, Mo, Nb, V, Ti, B are all elements that contribute to improving the strength of steel, It can contain suitably according to the intensity | strength to desire.
Ｃｕを添加する場合は、０．０５％以上とすることが好ましいが、１．０％を超えると熱間脆性を生じて鋼板の表面性状を劣化させるため、１．０％以下とする。 When adding Cu, it is preferable to set it as 0.05% or more, However, If it exceeds 1.0%, since hot brittleness will be produced and the surface property of a steel plate will be deteriorated, it shall be 1.0% or less.
Ｎｉを添加する場合は、０．０５％以上とすることが好ましいが、２．０％を超えると効果が飽和し、経済的に不利になるため、２．０％以下とする。 When adding Ni, it is preferable to set it as 0.05% or more, but when it exceeds 2.0%, since an effect will be saturated and it will become economically disadvantageous, it shall be 2.0% or less.
Ｃｒを添加する場合は、０．０５％以上とすることが好ましいが、２．０％を超えて含有すると、母材靭性、延性および溶接性が著しく劣化するため、２．０％以下とする。 When adding Cr, it is preferable to make it 0.05% or more, but if it contains more than 2.0%, the base metal toughness, ductility and weldability are remarkably deteriorated, so it is made 2.0% or less. .
Ｍｏを添加する場合は、０．０５％以上とすることが好ましいが、１．０％を超えると、母材靭性、延性および耐溶接割れ性に悪影響を及ぼすため、１．０％以下とする。 When Mo is added, the content is preferably 0.05% or more. However, if it exceeds 1.0%, the base material toughness, ductility and weld crack resistance are adversely affected. .
Ｎｂを添加する場合は、０．００５％以上とすることが好ましいが、０．１％を超えると、母材靭性および延性を劣化させるため、０．１％以下とする。 When Nb is added, the content is preferably 0.005% or more. However, if it exceeds 0.1%, the base metal toughness and ductility are deteriorated, so the content is made 0.1% or less.
Ｖを添加する場合は、０．０１％以上とすることが好ましいが、０．１％を超えると、母材靭性および延性を劣化させるため、０．１％以下とする。 When V is added, the content is preferably 0.01% or more. However, if it exceeds 0.1%, the base metal toughness and ductility are deteriorated, so the content is made 0.1% or less.
Ｔｉは、Ｎとの親和力が強く凝固時にＴｉＮとして析出し、溶接熱影響部でのオーステナイト粒の粗大化を抑制して高靭化に寄与する添加元素である。一方、０．０３％を超えて添加するとＴｉＮ粒子が粗大化して、母材および溶接部靭性を劣化させるため、Ｔｉを添加する場合は、０．０３％以下とする。 Ti is an additive element that has a strong affinity for N and precipitates as TiN during solidification, and contributes to high toughness by suppressing the coarsening of austenite grains in the weld heat affected zone. On the other hand, if added over 0.03%, TiN particles become coarse and deteriorate the base metal and weld zone toughness. Therefore, when adding Ti, the content is made 0.03% or less.
Ｂは、焼入れ性の向上を介して、鋼の強度を増加させる作用を有する。一方、０．００５％を超える含有は焼入れ性を著しく増加させ、母材の靭性、延性の劣化をもたらすため、Ｂを添加する場合は、０．００５％以下とする。 B has the effect of increasing the strength of the steel through improving hardenability. On the other hand, if the content exceeds 0.005%, the hardenability is remarkably increased and the toughness and ductility of the base material are deteriorated. Therefore, when B is added, the content is made 0.005% or less.
ＲＥＭ：０．０２％以下、Ｃａ：０．００５％以下およびＭｇ：０．００５％以下の１種または２種以上
ＲＥＭ、ＣａおよびＭｇは、いずれも靭性向上に寄与し、所望する特性に応じて選択して添加する。ＲＥＭを添加する場合は、０．００２％以上とすることが好ましいが、０．０２％を超えても効果が飽和するため、０．０２％を上限とする。
One or more of REM: 0.02% or less, Ca: 0.005% or less and Mg: 0.005% or less REM, Ca and Mg all contribute to toughness improvement, depending on the desired properties Select and add. When adding REM, it is preferable to set it as 0.002% or more, but since an effect will be saturated even if it exceeds 0.02%, 0.02% is made an upper limit.
Ｃａを添加する場合は、０．０００５％以上とすることが好ましいが、０．００５％を超えても効果が飽和するため、０．００５％を上限とする。 When adding Ca, it is preferable to make it 0.0005% or more, but since the effect is saturated even if it exceeds 0.005%, the upper limit is made 0.005%.
Ｍｇを添加する場合は、０．００１％以上とすることが好ましいが、０．００５％を超えても効果が飽和するため、０．００５％を上限とする。 When adding Mg, it is preferable to set it as 0.001% or more, but since an effect will be saturated even if it exceeds 0.005%, 0.005% is made an upper limit.
製造条件：説明において、温度に関する「℃」表示は、スラブ厚または板厚（t）の１／２における温度とする。 Manufacturing conditions: In the description, the “° C.” display relating to the temperature is a temperature at ½ of the slab thickness or the plate thickness (t).
スラブ加熱温度：１０００℃〜１２００℃
上述した組成の鋳片または鋼片のスラブを転炉、電気炉、真空溶解炉等、公知の方法による溶鋼から作成し、１０００℃〜１２００℃に再加熱する。再加熱温度が１０００℃未満では、熱間圧延での変形抵抗が高く、１パス当たりの圧下量が大きく取れなくなることから、圧延パス数が増加し、圧延能率の低下を招くとともに、鋼素材（スラブ）中の鋳造欠陥を圧着することができない場合が生じる。
Slab heating temperature: 1000 ° C to 1200 ° C
A slab of cast slab or steel slab having the above composition is prepared from molten steel by a known method such as a converter, electric furnace, vacuum melting furnace, etc., and reheated to 1000 ° C to 1200 ° C. If the reheating temperature is less than 1000 ° C., the deformation resistance in hot rolling is high, and the reduction amount per pass cannot be made large. Therefore, the number of rolling passes increases, and the rolling efficiency decreases, and the steel material ( In some cases, the casting defect in the slab cannot be crimped.
一方、再加熱温度が１２００℃を超えると、加熱時のスケールによって表面疵が生じやすく、圧延後の手入れ負荷が増大する。さらに、スラブ加熱中にサブスケール層が過度に成長するため、スケールの成長速度が低下し、所望のスケール厚さを得られなくなり、レーザー切断中に溶けた溶融鋼の粘性が上昇し、切断が途中で停止しやすくなり、切断安定性が低下する。このため、１０００〜１２００℃の範囲とする。 On the other hand, if the reheating temperature exceeds 1200 ° C., surface flaws are likely to occur due to the scale during heating, and the maintenance load after rolling increases. Furthermore, because the subscale layer grows excessively during slab heating, the scale growth rate decreases, the desired scale thickness cannot be obtained, the viscosity of the molten steel melted during laser cutting increases, and cutting occurs. It becomes easy to stop on the way, and cutting stability falls. For this reason, it is set as the range of 1000-1200 degreeC.
熱間圧延開始前のデスケーリング
スラブ加熱後は、熱間圧延開始前に鋼板表裏面に水を噴射してデスケーリングを実施する。熱間圧延前にデスケーリングを実施しないと、スラブ加熱時に生成したスケールが圧延で鋼板に押し込まれ、地鉄の凹凸が促進される。さらに、サブスケール層が過度に厚く、スケールの成長速度が低下し、所望のスケール厚さを得られなくなり、ひいては、レーザー切断中に溶けた溶融鋼の粘性が上昇し、切断が途中で停止するなど、切断安定性が低下する。
Descaling before starting hot rolling After slab heating, water is sprayed on the front and back surfaces of the steel sheet before starting hot rolling to perform descaling. If descaling is not performed before hot rolling, the scale generated during slab heating is pushed into the steel sheet by rolling, and the unevenness of the base iron is promoted. Furthermore, the subscale layer is excessively thick, the growth rate of the scale is reduced, the desired scale thickness cannot be obtained, and as a result, the viscosity of the molten steel melted during laser cutting increases, and the cutting stops midway. As a result, cutting stability decreases.
熱間圧延の圧延終了温度：８００〜９５０℃
熱間圧延の終了温度が９５０℃を超えるとスケールにブリスターが発生するだけでなく、圧延終了後の冷却過程でスケールが過度に成長するために後述する所望のスケール厚さを得られず、スケール層と地鉄との密着性が低下して、レーザー切断中にスケール層の剥離が生じ、ノッチやバーニングなどのレーザー切断欠陥が生じる。
Rolling end temperature of hot rolling: 800-950 ° C
When the end temperature of hot rolling exceeds 950 ° C., not only blisters are generated in the scale, but also the scale grows excessively in the cooling process after the end of rolling, so that the desired scale thickness described later cannot be obtained. The adhesion between the layer and the ground iron is lowered, peeling of the scale layer occurs during laser cutting, and laser cutting defects such as notches and burning occur.
また、スケール組成中のＦｅ２Ｏ３量が増加し、レーザー光の吸収効率が悪くなるため、切断が途中で停止するなど、切断安定性が低下する。 Moreover, since the amount of Fe 2 O 3 in the scale composition increases and the laser light absorption efficiency deteriorates, the cutting stability is lowered, for example, the cutting stops halfway.
一方、熱間圧延の終了温度が８００℃より低いと、圧延終了後の冷却過程でスケールの成長が小さく、後述する所望のスケール厚さが得らず、レーザー切断中に溶けた溶融鋼の粘性が上昇したり、鋼板中の残留応力が大きくなって、レーザー切断中に鋼板が変形し、レーザー光の焦点が目標位置からずれるなどして切断が途中で停止し、切断安定性が低下する。 On the other hand, if the end temperature of the hot rolling is lower than 800 ° C., the scale growth is small in the cooling process after the end of rolling, the desired scale thickness described later cannot be obtained, and the viscosity of the molten steel melted during laser cutting is lost. Or the residual stress in the steel plate increases, the steel plate is deformed during laser cutting, and the cutting is stopped midway due to the focus of the laser beam deviating from the target position.
また、熱間圧延の終了温度が８００℃より低い場合、鋼板の変形抵抗が高くなりすぎて、圧延荷重が増大し、圧延機への負担が大きくなる。また、圧延温度を低下させるためには、圧延途中で待機する必要があり、生産性を大きく阻害する。 Further, when the end temperature of hot rolling is lower than 800 ° C., the deformation resistance of the steel sheet becomes too high, the rolling load increases, and the burden on the rolling mill increases. Moreover, in order to reduce rolling temperature, it is necessary to wait in the middle of rolling, and productivity is inhibited greatly.
熱間圧延中のデスケーリング
本発明では、１０００℃〜圧延終了温度間における圧延パスの直前において、鋼板表裏面に水を噴射してデスケーリングすることを３回以上行う。熱間圧延における複数の圧延パスのうち、直前においてデスケーリングを施す圧延パスは特に規定しない。
Descaling during hot rolling In the present invention, immediately before the rolling pass between 1000 ° C. and the rolling end temperature, water is sprayed on the front and back surfaces of the steel sheet to perform descaling three or more times. Of the plurality of rolling passes in hot rolling, the rolling pass that is descaled immediately before is not particularly defined.
表面が後述する所望のスケール形態を安定して達成するためには、熱間圧延中のデスケーリングの実施回数を管理することが重要である。デスケーリングの回数が３回より少ないと、圧延中に生成、成長するスケールの剥離が不十分となりレーザー切断中にスケール層の剥離が生じ、ノッチやバーニングなどのレーザー切断欠陥が生じる。また、スケール組成中のＦｅ２Ｏ３量が増加し、レーザー光の吸収効率が悪くなるため、切断が途中で停止するなど、切断安定性が低下する。なお、デスケーリングの能力としては、噴射圧力が１０ＭＰａ以上あれば、本発明の効果を発揮することができる。 In order for the surface to stably achieve a desired scale form described later, it is important to manage the number of times descaling is performed during hot rolling. When the number of descaling is less than 3, peeling of the scale that is generated and grows during rolling becomes insufficient, and peeling of the scale layer occurs during laser cutting, resulting in laser cutting defects such as notches and burning. Moreover, since the amount of Fe 2 O 3 in the scale composition increases and the laser light absorption efficiency deteriorates, the cutting stability is lowered, for example, the cutting stops halfway. In addition, if the injection pressure is 10 MPa or more as the descaling capability, the effect of the present invention can be exhibited.
熱間圧延後の冷却
圧延終了直後の冷却方法は大気中で空冷とする。圧延終了後、水冷、油冷などの方法により、加速冷却を行うと、冷却後の鋼板中の残留応力が大きくなり、レーザー切断中に鋼板が変形し、レーザー光の焦点がずれるため、切断が途中で停止するなど切断安定性が低下する。
Cooling after hot rolling The cooling method immediately after the end of rolling is air cooling in the atmosphere. When accelerated cooling is performed by methods such as water cooling and oil cooling after the end of rolling, the residual stress in the steel sheet after cooling increases, the steel sheet deforms during laser cutting, and the focus of the laser beam shifts, so cutting is not possible. Cutting stability decreases, such as stopping in the middle.
さらに、本発明では、５５０〜１５０℃から室温までの間に、合計１００℃以上となる温度範囲を０．０５℃／ｓ未満で徐冷することが重要である。これにより、スケール組成がＦｅ３Ｏ４とＦｅＯ主体となり、レーザー吸収能が高く、また、後述する所望のスケール厚さとなり、レーザー切断中の鋼板の溶融鋼の粘性が低く、切断の安定性が向上し、ノッチなど切断不良も抑制され、優れたレーザー切断性を得ることができ、さらには、冷却後の鋼板中の残留応力を効果的に低減し、切断中の鋼板の変形を抑制し、レーザー切断の切断安定性が極めて向上する。 Furthermore, in the present invention, it is important that the temperature range in which the total is 100 ° C. or more is gradually cooled at less than 0.05 ° C./s from 550 to 150 ° C. to room temperature. As a result, the scale composition is mainly composed of Fe 3 O 4 and FeO, the laser absorption ability is high, the desired scale thickness is described later, the viscosity of the molten steel of the steel sheet during laser cutting is low, and the stability of cutting is low Improved, cutting defects such as notches can be suppressed, excellent laser cutting performance can be obtained, and further, residual stress in the steel sheet after cooling is effectively reduced, and deformation of the steel sheet during cutting is suppressed, Cutting stability of laser cutting is greatly improved.
徐冷の開始温度が５５０℃を超えると、室温に冷えるまでの冷却時間が極端に長くなるとともに、スケール中のＦｅ２Ｏ３が増加し、レーザー光の吸収効率が低下し、切断が途中で停止するなど、切断安定性が低下する。一方、徐冷の開始温度が１５０℃未満になると、冷却後の鋼板中の残留応力が大きくなり、レーザー切断中に鋼板が変形し、レーザー光の焦点がずれるため、切断が途中で停止するなど切断安定性が低下する。 When the start temperature of gradual cooling exceeds 550 ° C., the cooling time until cooling to room temperature becomes extremely long, Fe 2 O 3 in the scale increases, the laser light absorption efficiency decreases, and cutting is in progress. Cutting stability decreases, such as stopping. On the other hand, if the start temperature of slow cooling is less than 150 ° C., the residual stress in the steel sheet after cooling becomes large, the steel sheet is deformed during laser cutting, and the focus of the laser beam is shifted, so that cutting stops halfway. Cutting stability is reduced.
徐冷する温度範囲が合計１００℃未満であったり、徐冷の冷却速度が０．０５℃／ｓを超えると、上記のような効果は得られず、切断が途中で停止するなど切断安定性が低下する。徐冷は５５０〜１５０℃から室温までの間で、徐冷される温度範囲が分割されていても合計で１００℃以上あれば良い。
徐冷の方法としては段積み徐冷が好ましい。段積みにより、徐冷中に鋼板表面に供給される酸素量が減少することにより、冷却後のスケール形態は、より安定してＦｅ３Ｏ４とＦｅＯ主体とすることができ、レーザー光の吸収効率が上がり、レーザー切断性が安定する。
If the temperature range for slow cooling is less than 100 ° C. in total, or if the cooling rate for slow cooling exceeds 0.05 ° C./s, the above effects cannot be obtained, and cutting stability such as cutting stops in the middle. Decreases. The slow cooling is from 550 to 150 ° C. to room temperature, and even if the temperature range to be slowly cooled is divided, it is sufficient if the total temperature is 100 ° C. or higher.
As the slow cooling method, stacked slow cooling is preferable. By reducing the amount of oxygen supplied to the steel sheet surface during slow cooling, the scale form after cooling can be more stably composed mainly of Fe 3 O 4 and FeO, and the absorption efficiency of laser light can be improved. The laser cutting ability is stabilized.
また、徐冷を、段積みに代えて酸素濃度が２０％未満のガス雰囲気に管理した炉で、冷却することでも良い。酸素濃度が２０％以上になると、鋼板表面に供給される酸素量が増加し、スケール中のＦｅ２Ｏ３が増加し、レーザー光の吸収効率が低下して、切断が停止するなど切断安定性が低下する。なお、雰囲気中の酸素以外のガスは、窒素、アルゴンなど不活性なガスであれば良く特に限定しない。当該炉内において、段積みが可能であればより好ましい。 Further, the slow cooling may be performed in a furnace controlled in a gas atmosphere having an oxygen concentration of less than 20% instead of stacking. When the oxygen concentration is 20% or more, the amount of oxygen supplied to the steel sheet surface increases, Fe 2 O 3 in the scale increases, the laser beam absorption efficiency decreases, and cutting stability stops such as cutting stops. Decreases. The gas other than oxygen in the atmosphere is not particularly limited as long as it is an inert gas such as nitrogen or argon. It is more preferable if stacking is possible in the furnace.
上述した成分組成と製造条件により製造される鋼板のスケール形態は、鋼板表面のスケール層の平均厚さが１０〜４０μｍで、スケール組成はスケール層中にＦｅ３Ｏ４およびＦｅＯが体積分率で合計８０％以上含まれるものとなる。 The scale form of the steel sheet produced by the above-described component composition and production conditions is that the average thickness of the scale layer on the steel sheet surface is 10 to 40 μm, and the scale composition is the volume fraction of Fe 3 O 4 and FeO in the scale layer. A total of 80% or more is included.
スケール層の平均厚さが４０μｍよりも厚い場合、スケール密着性が低下するために、レーザー切断中にスケール層の剥離が生じ、ノッチやバーニングなどのレーザー切断欠陥が生じ、１０μm未満では、レーザー切断中に溶融鋼の粘性が上昇し、切断が途中で停止するなど安定性が低下するが、本発明によれば鋼板表面のスケール層の平均厚さは１０〜４０μｍとなる。スケールの平均厚さの求め方は実施例において後述する。 When the average thickness of the scale layer is larger than 40 μm, the scale adhesion deteriorates, so that the scale layer is peeled off during laser cutting, and laser cutting defects such as notches and burning occur. The viscosity of the molten steel rises and the stability is lowered, for example, the cutting stops halfway, but according to the present invention, the average thickness of the scale layer on the steel sheet surface is 10 to 40 μm. A method for obtaining the average thickness of the scale will be described later in Examples.
また、スケール層は、スケール層中にウスタイト（ＦｅＯ）およびマグネタイト（Ｆｅ３Ｏ４）を体積分率で合計で８０％以上有するレーザーの吸収能が高い、黒っぽい色調である。熱間圧延後の鋼板表面に生成するスケールは、主にウスタイト（ＦｅＯ）、マグネタイト（Ｆｅ３Ｏ４）、およびヘマタイト（Ｆｅ２Ｏ３）より形成される。スケール層の組成がウスタイト（ＦｅＯ）およびマグネタイト（Ｆｅ３Ｏ４）主体となるとスケールの色が黒色になり、レーザー吸収能が向上し、レーザー切断性が向上する。 In addition, the scale layer has a dark black color with a high absorption capability of a laser having a total volume fraction of 80% or more of wustite (FeO) and magnetite (Fe 3 O 4 ) in the scale layer. The scale generated on the surface of the steel sheet after hot rolling is mainly formed from wustite (FeO), magnetite (Fe 3 O 4 ), and hematite (Fe 2 O 3 ). When the composition of the scale layer is mainly wustite (FeO) and magnetite (Fe 3 O 4 ), the color of the scale becomes black, the laser absorption ability is improved, and the laser cutting property is improved.
ヘマタイトが多くなるほどスケールの色が赤色に近くなり、レーザー吸収能が低下するが、本発明によれば、２０％未満であるのでその影響は無視できる。 As hematite increases, the color of the scale becomes closer to red and the laser absorption ability decreases. However, according to the present invention, the effect is negligible because it is less than 20%.
転炉−取鍋精錬−連続鋳造法で、表１に示す種々の成分組成に調製した鋼スラブを、表２に示す種々の熱間圧延条件により板厚２５ｍｍの鋼板とした。 Steel slabs prepared with various component compositions shown in Table 1 by the converter-ladder refining-continuous casting method were made into steel plates with a thickness of 25 mm under various hot rolling conditions shown in Table 2.
得られた厚鋼板より引張方向が圧延方向に直交するように、ＪＩＳ ５号引張試験片を採取し、ＪＩＳ Ｚ ２２４１の規定に準拠して引張試験を実施し、母材の引張特性（降伏強さ(ＹＳ)、引張強さ(ＴＳ)、降伏比(ＹＲ)、伸び(Ｅｌ)）を求めた。 A JIS No. 5 tensile test piece was taken from the resulting thick steel plate so that the tensile direction was perpendicular to the rolling direction, and a tensile test was performed in accordance with the provisions of JIS Z 2241. (YS), tensile strength (TS), yield ratio (YR), elongation (El)).
また、得られた厚鋼板の板厚(t)のＩ／４位置から、試験片の長手方向が圧延方向に直交するように、ＪＩＳ Ｚ ２２４２の規定に準拠してＶノッチ試験片を採取し、試験温度：０℃でシャルピー衝撃試験を実施し、吸収エネルギーｖＥ０（Ｊ）を求めた。試験片は各３本とし、得られた吸収エネルギーの平均値をその厚鋼板の値として母材靭性を評価した。 In addition, from the I / 4 position of the thickness (t) of the obtained thick steel plate, a V-notch test piece was sampled in accordance with JIS Z 2242 so that the longitudinal direction of the test piece was perpendicular to the rolling direction. The Charpy impact test was performed at a test temperature of 0 ° C., and the absorbed energy vE0 (J) was obtained. Three test pieces were used, and the base material toughness was evaluated using the average value of the obtained absorbed energy as the value of the thick steel plate.
各鋼板長手方向の先端部から５００ｍｍ、中心、および尾端部から５００ｍｍの位置から、それぞれ板幅方向１／４幅および１／２幅の圧延方向から、板厚（ｔ）×２０ｍｍ（Ｌ）のサンプルを合計６個採取し、樹脂に埋め込んだ後、板厚（ｔ）×２０ｍｍ（Ｌ）の面を研磨した。各サンプルについて、地鉄およびスケール層を含む領域の倍率５００倍の光学顕微鏡写真を５枚撮影し、各写真の任意の１０ヶ所で画像解析装置を用いてスケール層の厚さを測定し、サンプル６個すべての測定値の平均をスケールの平均厚さとした。 From the position of 500 mm from the front end of each steel plate in the longitudinal direction and 500 mm from the center and from the tail end, from the rolling direction of 1/4 width and 1/2 width, respectively, the plate thickness (t) × 20 mm (L) A total of six samples were collected and embedded in a resin, and then the plate thickness (t) × 20 mm (L) surface was polished. For each sample, five optical micrographs of 500 times magnification of the region including the ground iron and the scale layer were taken, and the thickness of the scale layer was measured using an image analyzer at any 10 locations in each photo. The average of all 6 measurements was taken as the average thickness of the scale.
また、スケール組成の同定は、Ｘ線解析法による結果をもとに、スケール標準サンプルを用いた検量線法により求めた．
レーザー切断性は、６ｋＷの炭酸ガスレーザーを用いた。まず、切断限界速度の評価は、平均出力４ｋＷ、酸素圧力０．３ｋｇｆ／ｃｍ２、切断長５００ｍｍとして、レーザー切断速度を７５０ｍｍ／ｍｉｎ．から５０ｍｍ／ｍｉｎ．づつ、変化させて、切断長さ全長に渡って貫通し、切断中に停止しない切断速度を限界速度とした。また、切断品質の評価は、平均出力４ｋＷ、酸素圧力０．３ｋｇｆ／ｃｍ２、切断長５００ｍｍとして、レーザー切断速度を７５０ｍｍ／ｍｉｎ．で切断後、鋼板切断面におけるノッチの有無、および鋼板裏面でのドロスの付着有無を評価した。
In addition, the identification of the scale composition was obtained by the calibration curve method using the scale standard sample based on the result of the X-ray analysis method.
For the laser cutting property, a 6 kW carbon dioxide laser was used. First, the evaluation of the cutting limit speed was carried out with an average output of 4 kW, an oxygen pressure of 0.3 kgf / cm 2 , a cutting length of 500 mm, and a laser cutting speed of 750 mm / min. To 50 mm / min. The cutting speed was changed, and the cutting speed that penetrated the entire length of the cutting and did not stop during cutting was defined as the critical speed. In addition, the evaluation of the cutting quality was made with an average output of 4 kW, an oxygen pressure of 0.3 kgf / cm 2 , a cutting length of 500 mm, and a laser cutting speed of 750 mm / min. After cutting, the presence or absence of a notch on the cut surface of the steel plate and the presence or absence of dross on the back surface of the steel plate were evaluated.
本発明では、切断限界速度が８５０ｍｍ／ｍｉｎ．以上で、かつ７５０ｍｍ／ｍｉｎ．で切断時に、ノッチおよびドロスの発生のないものを、レーザー切断性に優れるとした。 In the present invention, the cutting limit speed is 850 mm / min. Above, and 750 mm / min. In the case of cutting, those having no notch and dross are considered to be excellent in laser cutting property.
得られた結果を表３に示す。発明例（鋼板記号Ａ、Ｂ、Ｌ〜Ｒ）は、スケールの平均厚さが１０〜４０μmで、かつスケール組成中のＦｅ３Ｏ４およびＦｅＯの体積分率の合計が８０％以上であり、レーザー切断性に優れる。一方、本発明の範囲を外れる比較例（鋼板記号Ｃ〜Ｋ、Ｓ、Ｔ）は、レーザー切断性に劣る。 The obtained results are shown in Table 3. Inventive examples (steel plate symbols A, B, L to R) have an average scale thickness of 10 to 40 μm, and the total volume fraction of Fe 3 O 4 and FeO in the scale composition is 80% or more, Excellent laser cutting ability. On the other hand, comparative examples (steel plate symbols C to K, S, T) outside the scope of the present invention are inferior in laser cutting properties.
Claims (6)
Ｃ：０．０３〜０．２０％、
Ｓｉ：０．０１〜０．６０％、
Ｍｎ：０．１〜２．０％、
Ｐ：０．０５％以下、
Ｓ：０．０１％以下、
を含有し、残部がＦｅおよび不可避的不純物からなる鋳片または鋼片を、１０００〜１２００℃に再加熱後、鋳片または鋼片の表裏面に水を噴射してデスケーリングを行い、その後、熱間圧延を開始し、１０００℃〜圧延終了温度間の圧延パスの直前において、鋼板表裏面に水を噴射してデスケーリングを行うことを３回以上実施して、８００〜９５０℃で熱間圧延を終了した後、大気中で空冷し、５５０〜１５０℃から室温までの間に、合計１００℃以上の温度範囲を０．０５℃／ｓ未満で徐冷することを特徴とするレーザー切断性に優れた鋼板の製造方法。 Ingredient composition is mass%,
C: 0.03 to 0.20%
Si: 0.01-0.60%,
Mn: 0.1 to 2.0%,
P: 0.05% or less,
S: 0.01% or less,
A slab or steel slab comprising Fe and the inevitable impurities, and after reheating to 1000 to 1200 ° C., water is sprayed on the front and back surfaces of the slab or steel slab, and then descaling is performed. Hot rolling is started, and immediately before the rolling pass between 1000 ° C. and the rolling finish temperature, water is sprayed on the front and back surfaces of the steel sheet to perform descaling three times or more, and hot at 800 to 950 ° C. After finishing the rolling, it is air-cooled in the atmosphere, and the laser cutting property is characterized by gradually cooling the temperature range of 100 ° C. or more to less than 0.05 ° C./s between 550 and 150 ° C. to room temperature. Steel sheet manufacturing method with excellent performance.
Ｃｕ：１．０％以下、
Ｎｉ：２．０％以下、
Ｃｒ：２．０％以下、
Ｍｏ：１．０％以下、
Ｎｂ：０．１％以下、
Ｖ：０．１％以下、
Ｔｉ：０．０３％以下、
Ｂ：０．００５％以下、
の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に記載のレーザー切断性に優れた鋼板の製造方法。 Ingredient composition is further mass%,
Cu: 1.0% or less,
Ni: 2.0% or less,
Cr: 2.0% or less,
Mo: 1.0% or less,
Nb: 0.1% or less,
V: 0.1% or less,
Ti: 0.03% or less,
B: 0.005% or less,
1 or 2 types or more of these are contained, The manufacturing method of the steel plate excellent in the laser cutting property of Claim 1 characterized by the above-mentioned.
ＲＥＭ：０．０２％以下、
Ｃａ：０．００５％以下、
Ｍｇ：０．００５％以下、
を含有することを特徴とする請求項１または２に記載のレーザー切断性に優れた鋼板の製造方法。 Ingredient composition is further mass%,
REM: 0.02% or less,
Ca: 0.005% or less,
Mg: 0.005% or less,
The manufacturing method of the steel plate excellent in the laser cutting property of Claim 1 or 2 characterized by the above-mentioned.
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| JPS6077922A (en) * | 1983-10-05 | 1985-05-02 | Nippon Steel Corp | Production of hot-rolled steel plate having high adhesion to scale |
| JP3218166B2 (en) * | 1995-06-30 | 2001-10-15 | 新日本製鐵株式会社 | Thick steel plate excellent in laser cutability and method for producing the same |
| JPH11277105A (en) * | 1998-03-27 | 1999-10-12 | Nippon Steel Corp | Manufacture of thick steel plate excellent in resistance to scale peeling |
| JP4702254B2 (en) * | 2006-10-13 | 2011-06-15 | 住友金属工業株式会社 | Thick steel plate for laser cutting and its manufacturing method |
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2012
- 2012-05-31 JP JP2012123838A patent/JP5949167B2/en active Active
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