JP4460463B2 - Mold powder for continuous casting of steel - Google Patents
Mold powder for continuous casting of steel Download PDFInfo
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- JP4460463B2 JP4460463B2 JP2005003483A JP2005003483A JP4460463B2 JP 4460463 B2 JP4460463 B2 JP 4460463B2 JP 2005003483 A JP2005003483 A JP 2005003483A JP 2005003483 A JP2005003483 A JP 2005003483A JP 4460463 B2 JP4460463 B2 JP 4460463B2
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Description
本発明は、鋼の連続鋳造用鋳型内に添加される鋼の連続鋳造用モールドパウダーに関するものである。 The present invention relates to a mold powder for continuous casting of steel added to a mold for continuous casting of steel.
連続鋳造用モールドパウダーは溶鋼表面で溶融して溶鋼面を被覆し、空気による溶鋼酸化を防止するとともに溶鋼を保温し、また鋳型と鋳片との間の潤滑剤としての機能も発揮するものである。このような目的を達成するためには、パウダーが適度の粘性や表面張力を有し、溶鋼内部への巻き込みが生じないようにすることが望まれる。 Mold powder for continuous casting melts on the surface of the molten steel to cover the molten steel surface, prevents the molten steel from being oxidized by air, keeps the molten steel warm, and also functions as a lubricant between the mold and the slab. is there. In order to achieve such an object, it is desired that the powder has an appropriate viscosity and surface tension so that the powder is not caught inside the molten steel.
連続鋳造用モールドパウダーに関する提案は従来から数多くなされている。例えば特許文献１には、加熱された際の結晶化温度を最適化することにより熱抵抗性を増大させ、鋳型内を緩冷却化して鋳片の表面性状を改善するモールドパウダーが開示されている。また特許文献２には、塩基度を高めるとともに1300℃におけるパウダー粘度を1.5ポアズ以下として、鋳片の表面性状を改善するモールドパウダーが開示されている。
Many proposals for continuous casting mold powder have been made. For example, Patent Document 1 discloses a mold powder that improves the surface property of a slab by increasing the thermal resistance by optimizing the crystallization temperature when heated and by slowly cooling the inside of the mold. .
さらに特許文献３には、モールドパウダーの凝固温度及び1300℃におけるパウダー粘度を鋳造速度との関連において規定し、ブレークアウトを防止したモールドパウダーが開示されている。また特許文献４には、塩基度を規定して鋳片の縦割れを防止したモールドパウダーが開示されている。
Further, Patent Document 3 discloses a mold powder in which the solidification temperature of the mold powder and the powder viscosity at 1300 ° C. are defined in relation to the casting speed to prevent breakout.
上記のように連続鋳造用モールドパウダーについては様々な角度からの検討がなされているが、モールドパウダーの溶鋼内部への巻き込みを完全に防止することは容易ではない。特にこの問題は浸漬ノズルから溶鋼中に吹き込まれるアルゴンガスが鋳型内の溶鋼メニスカスとモールドパウダー界面で破泡する際に生じやすく、自動車用鋼板のような高品質が要求される鋼板の場合には、モールドパウダーの溶鋼内部への巻き込みは大きな問題となっている。
従って本発明が解決しようとする課題は、溶鋼内部への巻き込みを防止することができ、自動車用鋼板のような高品質が要求される鋼板を製造する場合に用いるのに適した新規な連続鋳造用モールドパウダーを提供することである。 Therefore, the problem to be solved by the present invention is that a novel continuous casting suitable for use in manufacturing a steel plate that can prevent high-quality steel plates such as steel plates for automobiles can be prevented. It is to provide mold powder for use.
本発明者はモールドパウダーの溶鋼内部への巻き込みについて検討を重ねた結果、モールドパウダー溶融物の溶鋼中アルミニウムとの反応性が、巻き込みと関連することを見出した。すなわちパウダー溶融物中には溶鋼中のアルミニウムの酸化源となるSiO2、Na2O、Li2Oなどが含有されているが、これらの含有率とモールドパウダーの溶鋼内部への巻き込みとの間に関連性があることを初めて見出した。なお前記した特許文献を含み従来文献には、このような知見は示されていない。 As a result of repeated studies on the entrainment of mold powder into molten steel, the present inventor has found that the reactivity of the mold powder melt with aluminum in the molten steel is related to entrainment. In other words, the powder melt contains SiO 2 , Na 2 O, Li 2 O, etc., which are the oxidation sources of aluminum in the molten steel. Between these contents and the inclusion of the mold powder into the molten steel. For the first time found to be relevant. In addition, such knowledge is not shown by the conventional literature including the patent document mentioned above.
本発明は上記の知見に基づいてなされたものであって、4.3〜21.3質量％のAl 2 O 3 と、CaO/SiO 2 が1.22〜2.0となるSiO 2 及びCaOと、3.6〜15質量％のＦと、0.5〜10質量％のZrO 2 と、0.5〜10質量％のSrOとを必須的に含有し、1300℃におけるパウダー粘度が12ポアズ以下で、かつ質量％SiO2+(質量％Na2O+質量％Li2O)/2≦(0.32η０．１６-0.0756）/0.0087の式を満足することを特徴とするものである。 The present invention has been made on the basis of the above knowledge, and 4.3 to 21.3 mass% Al 2 O 3 , SiO 2 and CaO with CaO / SiO 2 of 1.22 to 2.0, 3.6 to 15 mass% F, 0.5 to 10% by mass of ZrO 2 and 0.5 to 10% by mass of SrO are essential, the powder viscosity at 1300 ° C. is 12 poise or less, and mass% SiO 2 + (mass% Na 2 and it is characterized in satisfying the O + wt% Li 2 O) / 2 ≦ (0.32η 0.16 -0.0756) /0.0087 formula.
本発明の連続鋳造用モールドパウダーは、溶鋼中に0.05％程度含有されているアルミニウムの酸化源となるSiO2、Na2O、Li2Oを従来よりも減少させ、溶鋼との反応性を抑制した。この結果、アルゴンガスの溶湯面での破泡時における溶鋼中へのパウダーの巻き込みが顕著に低減し、圧延後のコイル表面疵個数をコイル当り1個以下にまで減少させることが可能となった。なお、ZrO2、SrO、FはSiO2、Na2O、Li2Oをミニマムとした場合に、パウダーの融点と粘度を調整するために適した成分であり、後記する実施例に示すように適量を含有させることが好ましい。 The mold powder for continuous casting according to the present invention reduces SiO 2 , Na 2 O and Li 2 O, which are the oxidation sources of aluminum contained in molten steel by about 0.05%, and suppresses reactivity with molten steel. did. As a result, the entrainment of powder into the molten steel at the time of bubble breakage on the molten metal surface of argon gas is significantly reduced, and the number of coil surface defects after rolling can be reduced to 1 or less per coil. . ZrO 2 , SrO, and F are components suitable for adjusting the melting point and viscosity of the powder when SiO 2 , Na 2 O, and Li 2 O are minimum, as shown in the examples described later. It is preferable to contain an appropriate amount.
前記したように本発明の連続鋳造用モールドパウダーは、質量％SiO2+(質量％Na2O+質量％Li2O)/2≦(0.32η０．１６-0.0756)/0.0087の式(A)を満足するように、パウダー組成とパウダー粘度を決定したものである。ここでηは1300℃におけるパウダー粘度あって、12ポアズ以下の領域に限定される。上記の式(A)は図１のグラフ中に示される曲線を表しており、1300℃におけるパウダーの粘度がこの曲線よりも下側の領域にあれば、パウダーの巻き込みは生じないことが確認された。なお、質量％SiO2+(質量％Na2O+質量％Li2O)/2はアルミニウムの酸化源となる成分量を表す指数である。 As described above, the mold powder for continuous casting of the present invention has the formula (A) of mass% SiO 2 + (mass% Na 2 O + mass% Li 2 O) / 2 ≦ (0.32η 0.16 -0.0756) /0.0087. The powder composition and the powder viscosity are determined so as to satisfy the above. Here, η is a powder viscosity at 1300 ° C. and is limited to a region of 12 poise or less. The above formula (A) represents the curve shown in the graph of FIG. 1. If the viscosity of the powder at 1300 ° C is in the region below this curve, it is confirmed that the entrainment of the powder does not occur. It was. Note that mass% SiO 2 + (mass% Na 2 O + mass% Li 2 O) / 2 is an index representing the amount of a component that becomes an oxidation source of aluminum.
本発明において1300℃におけるパウダー粘度を12ポアズ以下に限定したのは、この範囲を越えるとパウダー流入厚が減少し、ブレークアウトが発生し易くなるためである。また本発明では、CaO/SiO 2 を1.22〜2.0とした。CaO/SiO 2 が1.22未満になるとSiO2の量が増加し、これが溶鋼中のアルミニウムと反応して界面張力が低下するため、パウダー巻き込み防止効果が低下する。逆にCaO/SiO2が2.0を越えると凝固温度が高くなり、潤滑性が損なわれるためにブレークアウトが発生しやすくなる。 The reason why the viscosity of the powder at 1300 ° C. is limited to 12 poise or less in the present invention is that, if this range is exceeded, the powder inflow thickness decreases and breakout is likely to occur. In the present invention, CaO / SiO 2 is set to 1.22 to 2.0. When CaO / SiO 2 is less than 1.22, the amount of SiO 2 increases, and this reacts with aluminum in the molten steel to lower the interfacial tension, thus reducing the effect of preventing powder entrainment. On the other hand, if CaO / SiO 2 exceeds 2.0, the solidification temperature becomes high and the lubricity is impaired, so that breakout is likely to occur.
また本発明では、パウダー中に0.5〜10質量％のZrO 2 と、0.5〜10質量％のSrOを含有させる。ZrO2は粘度を確保するために添加される成分であり、0.5質量％未満ではその効果が不十分である。逆に10質量％を越えると、粘度が上昇して潤滑性が損なわれるためにブレークアウトが発生しやすくなる。SrOは凝固温度を調整するために添加される成分であり、0.5質量％未満ではその効果が不十分である。逆に10質量％を越えるとコストが高くなり、経済性が損なわれる。 In the present invention, the ZrO 2 0.5 to 10% by weight in the powder, is contained 0.5 to 10 mass% of SrO. ZrO 2 is a component added to ensure viscosity, and its effect is insufficient when it is less than 0.5% by mass. On the contrary, if it exceeds 10% by mass, the viscosity increases and the lubricity is impaired, so that breakout is likely to occur. SrO is a component added to adjust the solidification temperature, and its effect is insufficient when it is less than 0.5% by mass. On the other hand, if it exceeds 10% by mass, the cost increases and the economic efficiency is impaired.
また本発明では、パウダー中に3.6〜15質量％のFを含有させる。Fは凝固温度や粘性を低下させるために添加される成分で、3.6質量％未満ではその効果がなく、15質量％を越えると浸漬ノズル耐火物の溶損が大きくなるため、3.6〜15質量％が適切である。 Moreover, in this invention, 3.6-15 mass% F is contained in powder. F is a component added to lower the coagulation temperature and viscosity. If it is less than 3.6 % by mass, it will not be effective, and if it exceeds 15% by mass, the refractory of the immersion nozzle refractory will increase, so 3.6 to 15% by mass Is appropriate.
上記した本発明の連続鋳造用モールドパウダーは、従来品と同様に鋼の連続鋳造用鋳型内に添加して用いられるものであるが、質量％SiO2+(質量％Na2O+質量％Li2O)/2で示されるアルミニウムの酸化源となる成分量を抑制したので溶鋼との反応性が低下する。このためアルゴンガスの破泡時におけるモールドパウダーの巻き込みがなくなり、以下の実施例に示すように、圧延後のコイル表面疵個数をコイル当り1個以下にまで減少させることが可能となった。 The above-described mold powder for continuous casting according to the present invention is used by being added to a continuous casting mold for steel in the same manner as in the conventional product, but is mass% SiO 2 + (mass% Na 2 O + mass% Li 2. Reactivity with molten steel decreases because the amount of the aluminum oxidation source represented by O) / 2 is suppressed. For this reason, the mold powder is not caught when the argon gas bubbles are broken, and the number of coil surface defects after rolling can be reduced to 1 or less per coil as shown in the following examples.
溶鋼２７０トンの極低炭素鋼を転炉−ＲＨで溶製した。タンディッシュ内溶鋼温度は1560〜1580℃であり、垂直型連続鋳造機を使用して250mm厚×1600mm幅の鋳片を製造した。鋳造速度Ｖｃは1.3〜2.0m/minで、表１に示した組成のモールドパウダーを用いた。得られた鋳片を通常の方法で圧延、酸洗、冷延、焼鈍して自動車用鋼板とした。 Molten steel 270 tons of ultra-low carbon steel was melted in a converter-RH. The molten steel temperature in the tundish was 1560-1580 ° C., and a slab of 250 mm thickness × 1600 mm width was produced using a vertical continuous casting machine. The casting speed Vc was 1.3 to 2.0 m / min, and the mold powder having the composition shown in Table 1 was used. The obtained slab was rolled, pickled, cold-rolled, and annealed by a usual method to obtain a steel plate for automobiles.
表１には1300℃における粘度と、式(A)の左辺と右辺の値及びコイル表面品位を示した。表面品位の判定はコイル表面疵個数がコイル当り１個以下のものを○、それ以上を×とした。また操業安定性はブレークアウト警報の有無により示し、警報なしを○、警報ありを×とした。 Table 1 shows the viscosity at 1300 ° C., the values on the left and right sides of the formula (A), and the coil surface quality. For the determination of the surface quality, ○ was given when the number of coil surface ridges was 1 or less per coil, and X was given above. Operational stability is indicated by the presence or absence of a breakout warning, with ○ indicating no alarm and × indicating alarm.
表１から明らかなように、実施例の連続鋳造用モールドパウダーは全て表面品位判定及び操業安定性が○である。なお各実施例のデータは図１中にも表示した。これに対して比較例B1〜B29は何れも式(A)を満たさず、表面品位判定が×である。またB29とB30は1300℃におけるパウダー粘度が１２ポアズを越えたもので、操業安定性も×となっている。 As is apparent from Table 1, all of the continuous casting mold powders of the examples have a surface quality determination and operational stability of ◯. The data for each example is also displayed in FIG. On the other hand, Comparative Examples B1 to B29 do not satisfy the formula (A), and the surface quality determination is x. B29 and B30 have a powder viscosity of more than 12 poise at 1300 ° C, and the operation stability is x.
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| CN102019382B (en) * | 2009-09-23 | 2013-05-29 | 宝山钢铁股份有限公司 | Low-sodium high-viscosity tin plate mold flux |
| JP6354411B2 (en) * | 2014-07-15 | 2018-07-11 | 新日鐵住金株式会社 | Mold flux for continuous casting |
| CN108580822B (en) * | 2018-07-09 | 2020-01-24 | 西峡龙成冶金材料有限公司 | Continuous casting crystallizer casting powder of high-viscosity special-shaped blank medium carbon steel or low alloy steel |
| JP7070185B2 (en) * | 2018-07-13 | 2022-05-18 | 日本製鉄株式会社 | Mold powder and continuous casting method using it |
| JP6718539B1 (en) * | 2019-04-18 | 2020-07-08 | 品川リフラクトリーズ株式会社 | Mold powder |
| JP6871525B2 (en) * | 2020-06-12 | 2021-05-12 | 品川リフラクトリーズ株式会社 | Mold powder |
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