JP4389057B2 - Mold flux for continuous casting of steel - Google Patents
Mold flux for continuous casting of steel Download PDFInfo
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Description
本発明は、鋼の連続鋳造においてモールド内の溶鋼上に添加して溶融させ、モールドと鋳片間で潤滑作用を行わせるモールドフラックスに関するものである。 The present invention relates to a mold flux which is added and melted on molten steel in a mold in continuous casting of steel to perform a lubricating action between the mold and the cast piece.
一般に鋼の連続鋳造では、モールド（鋳型）内の溶鋼保温、溶鋼の酸化防止、溶鋼から浮上する非金属介在物の吸収、モールドと鋳片間の潤滑、鋳片の抜熱コントロ−ル等の目的で、粉末、または、顆粒状モールドフラックスが使用されているが、連続鋳造用モールドフラックスは操業の安定化と鋳片品質の向上にとって重要な役割を担っている反面、鋼中に巻き込まれて介在物欠陥を生じやすい欠点を有している。 In general, in continuous casting of steel, molten steel insulation in the mold (mold), oxidation prevention of the molten steel, absorption of non-metallic inclusions floating from the molten steel, lubrication between the mold and the slab, heat removal control of the slab, etc. For the purpose, powder or granular mold flux is used, but mold flux for continuous casting plays an important role in stabilizing the operation and improving the quality of the slab, but it is caught in steel. It has a defect that tends to cause inclusion defects.
そのため、自動車用外板、深絞り用鋼板等の品質厳格材における溶鋼の清浄化ニーズの高まりと共に、モールドフラックスの溶鋼への巻き込みに起因する欠陥を防止する手段として、モールドフラックスの高粘度化が指向されてきた。しかし、単純に粘度を上げるだけでは潤滑性の低下によるブレークアウト等の操業トラブルや流入の不均一による割れ疵等の表面欠陥が増加しやすくなるなどの問題点が指摘されており、８Ｐｏｉｓｅ以上の高粘度モールドフラックスについては、高粘度化に伴う弊害防止対策が不十分なため、実操業への適用が困難な状況にある。 Therefore, as the means for preventing defects caused by entrainment of molten mold flux into molten steel, as well as increasing needs for cleaning molten steel in strict quality materials such as automotive outer plates and deep drawing steel plates, increasing the viscosity of mold flux Has been oriented. However, it has been pointed out that simply increasing the viscosity tends to increase operational troubles such as breakout due to reduced lubricity and surface defects such as cracks due to non-uniform inflow. The high-viscosity mold flux is in a situation where it is difficult to apply it to actual operations because there are insufficient measures to prevent harmful effects associated with increasing the viscosity.
その対策として、高粘度化と並行して凝固温度等の物性値に一定の制限を設ける提案が多数なされているが、モールドフラックスの物性値には鋼種と操業条件に応じた最適値が存在するため、物性値選択の自由度が減少することで、鋼種と操業条件に対する適用範囲が制約され、汎用的な対策にはなり得ない。また、特開２００２−１１３５６１号公報では、顆粒を構成する主要原料の平均粒子径より大きくした粗粉の有機質物質及び／または粗粉の炭素質物質を配合し、噴霧乾燥方式で顆粒状に造粒することにより、粗粉の有機質物質及び／または粗粉の炭素質物質を顆粒内部に集積せしめたことを特徴とする保温効果に優れる顆粒状モールドフラックスが開示されている。しかし、８Ｐｏｉｓｅ未満の粘度であれば良好な鋳片品質が得られるものの、８Ｐｏｉｓｅ以上の高粘度になると、原料配合やモールドフラックスの保有熱量の如何で、不均一流入に起因すると思われる割れ疵等の表面欠陥が発生する場合があり、高粘度モールドフラックスへの適用が困難である。その大きな理由として、高粘度では保温効果だけではなくモールドフラックスの原料配合や均質性にも配慮が必要なこと、および、高粘度化により消費原単位が低下するとモールドフラックスが溶鋼に与える単位時間当たりの熱量が相対的に減少するためより大きな熱量を付与する必要があること等が考えられる。なお、特開２０００−２８００５１号公報では、鋳型内電磁攪拌でメニスカス近傍の溶鋼流速を８ｃｍ／ｓｅｃ以上にすることにより、３Ｐｏｉｓｅ以上の高粘度モールドフラックスを安定して鋳造可能としているが、高粘度化の弊害を操業方法で改善したものであり、全ての連鋳機に適用出来る汎用的な対策にはなり難い。
本発明は、モールドフラックスの高粘度化による弊害（潤滑性の低下によるブレークアウト等の操業トラブルや、流入の不均一による割れ疵等の表面欠陥の発生）を防止するためになされたもので、８Ｐｏｉｓｅ以上の高粘度でも均質溶融性に優れ、また均一流入性に優れたモールドフラックスを提案することにより、物性値の選択や操業上の制約条件を解消すると共に、良好な品質と生産性の向上に寄与することを目的とする。 The present invention was made in order to prevent adverse effects caused by high viscosity of the mold flux (operation troubles such as breakout due to reduced lubricity and occurrence of surface defects such as cracks due to uneven inflow) By proposing a mold flux that is excellent in homogenous meltability and excellent inflow properties even at a high viscosity of 8 poise or higher, it eliminates physical property selection and operational constraints, and improves good quality and productivity. The purpose is to contribute.
本発明は前記した問題点を解決するためになされたものであって、その要旨するところは、下記の通りである。
（１）自動車用外板及び深絞り鋼板用の鋼の連続鋳造に使用するモールドフラックスにおいて、１３００℃における粘度が８Ｐｏｉｓｅ以上であり、１８００℃以上の融点を有する、アルミナ（Ａｌ２Ｏ３）、マグネシア（ＭｇＯ）、ライム（ＣａＯ）、ジルコン（ＺｒＳｉＯ４）、酸化ストロンチウム（ＳｒＯ）のうち、１種または２種以上からなる高融点原料の使用比率がスラグ状態での酸化物換算値で８質量％以下かつ４質量％以上であり、フッ素（Ｆ）を３．０〜４．２質量％含み、有機質物質および１質量％の炭素質物質を配合して２００ｃａｌ/ｇ以上の発熱量を付与し、かつ顆粒状にしたことを特徴とする鋼の連続鋳造用のモールドフラックス。
The present invention has been made to solve the above-described problems, and the gist thereof is as follows.
(1) Alumina (Al 2 O 3 ) having a viscosity at 1300 ° C. of 8 Poise or higher and a melting point of 1800 ° C. or higher in a mold flux used for continuous casting of steel for automobile outer plates and deep-drawn steel plates , Among magnesia (MgO), lime (CaO), zircon (ZrSiO 4 ), and strontium oxide (SrO), the mass ratio of one or more high melting point raw materials is 8 mass in terms of oxide in the slag state. % Or less and 4 mass% or more, containing 3.0 to 4.2 mass% of fluorine (F), blending an organic substance and 1 mass% of a carbonaceous substance to give a calorific value of 200 cal / g or more. A mold flux for continuous casting of steel, characterized by being granulated.
モールドフラックスの粘度を高粘度（１３００℃における粘度が８Ｐｏｉｓｅ以上）にすることで、モールドフラックスの溶鋼への巻き込みは防止される。そして、１８００℃以上の融点を有する高融点原料の使用比率を、スラグ状態での酸化物換算値で合計８質量％以下に制限することで、溶融スラグの均質溶融性が確保される。また、有機質物質および１質量％の炭素質物質を配合して発熱量が２００ｃａｌ/ｇ以上になるようにしかつ顆粒状にすることで、溶融スラグのモールドと凝固シェル間への均一流入性が確保される。これにより、モールドフラックスの高粘度化の長所を確保しつつ、高粘度化による弊害、すなわち、均質溶融性や均一流入性の低下に起因する操業トラブル、品質トラブルを回避して、操業の安定性と品質向上に寄与出来る新規な高粘度モールドフラックスを提供することが可能になった。 By making the viscosity of the mold flux high (viscosity at 1300 ° C. is 8 poise or more), the mold flux is prevented from being caught in the molten steel. And the homogeneous meltability of molten slag is ensured by restrict | limiting the use ratio of the high melting-point raw material which has melting | fusing point of 1800 degreeC or more to a total of 8 mass% or less by the oxide conversion value in a slag state. In addition, by blending organic substance and 1% by mass carbonaceous substance so that the calorific value is 200 cal / g or more and granulate, uniform flowability between molten slag mold and solidified shell is ensured. Is done. As a result, while ensuring the advantages of increasing the viscosity of the mold flux, the adverse effects of increasing the viscosity, i.e., avoiding operational troubles and quality troubles due to reduced homogenous meltability and uniform inflow properties, and stable operation It has become possible to provide a new high-viscosity mold flux that can contribute to quality improvement.
鋼の連続鋳造においては、モールド内に注入された溶鋼表面上にモールドフラックスが添加される。溶鋼面上に添加されたモールドフラックスは一旦溶融してスラグプール層を形成した後、順次モールドと凝固シェル間に流入して消費されるが、その際、良好な鋳片品質を維持するためには溶融スラグが均質な状態で均一に流入することが不可欠である。このことを考慮すると、単純に粘度を上げるだけでは良好な結果が得られない原因として、高粘度モールドフラックスではこれらの挙動特性、すなわち、均質な状態で均一に流入するという挙動特性が不十分であることが推測される。即ち、異種成分原料を混合して製造された一般的なモールドフラックスでは、溶融直後スラグには原料起因の不均一性（ミクロ的な成分偏析や局部的な溶融温度の相違）を残存しており、粘度が高くなるほどスラグプール内での流動や拡散による溶融スラグの均質化が困難になる。また、粘度が高くなるほど流入量が減少するため、流入部位であるメニスカス部の温度低下や温度変化の影響を受けやすくなることで流入が不均一になるものと考えられる。そのため、発明者らは、高粘度モールドフラックスの開発を進める中で、均質溶融性と均一流入性に着目して、これらの挙動特性を維持向上させる手段を種々検討した結果、以下の知見を得て本発明を完成させたものである。 In continuous casting of steel, mold flux is added on the surface of molten steel injected into the mold. The mold flux added on the molten steel surface is melted once to form a slag pool layer, and then flows between the mold and the solidified shell and is consumed in order to maintain good slab quality. It is essential that the molten slag flows uniformly in a homogeneous state. Considering this, as a reason that a good result cannot be obtained by simply increasing the viscosity, these behavior characteristics, that is, the behavior characteristics of flowing uniformly in a uniform state are insufficient with a high viscosity mold flux. Presumed to be. That is, in a general mold flux manufactured by mixing different component raw materials, non-uniformity (micro component segregation or local melting temperature difference) due to the raw material remains in the slag immediately after melting. The higher the viscosity, the more difficult it is to homogenize the molten slag by flow and diffusion in the slag pool. Further, since the inflow amount decreases as the viscosity increases, it is considered that the inflow becomes non-uniform by being easily affected by the temperature drop or temperature change of the meniscus portion that is the inflow site. Therefore, the inventors obtained the following knowledge as a result of various investigations for maintaining and improving these behavioral characteristics, while focusing on homogeneous meltability and uniform inflowability, while developing high-viscosity mold fluxes. This completes the present invention.
まず、均質溶融性については、溶融直後スラグの粘度が極めて不安定で、高粘度化により溶融スラグの粘度安定化時間が増加しやすく、それにつれて鋳片品質も悪化する事実が判明した。そこで、原料配合や製品粘度を変更した複数のサンプルによって、溶融スラグの粘度安定化時間と鋳片品質との対応関係を調査した結果、均質溶融性を確保する条件として、アルミナ（Ａｌ２Ｏ３）、マグネシア（ＭｇＯ）、ライム（ＣａＯ）、ジルコン（ＺｒＳｉＯ４）、酸化ストロンチウム（ＳｒＯ）等、１８００℃以上の融点を有する高融点原料の使用比率を、スラグ状態での酸化物換算値で合計８質量％以下に制限する必要があることを見出した。 First, regarding the homogenous meltability, it has been found that the viscosity of the slag immediately after melting is extremely unstable, the viscosity stabilization time of the molten slag tends to increase due to the increase in viscosity, and the quality of the slab deteriorates accordingly. Therefore, as a result of investigating the correspondence relationship between the viscosity stabilization time of the molten slag and the slab quality using a plurality of samples whose raw material composition and product viscosity were changed, alumina (Al 2 O 3) was used as a condition for ensuring homogeneous meltability. ), Magnesia (MgO), lime (CaO), zircon (ZrSiO 4 ), strontium oxide (SrO), etc., the total use ratio of high melting point materials having a melting point of 1800 ° C. or higher in terms of oxides in the slag state It has been found that it is necessary to limit the amount to 8 % by mass or less.
ここで、１８００℃以上の融点を有する高融点原料に限定した理由は、ベース原料以外の異種成分原料は全て均質溶融性を阻害する原因にはなるが、１８００℃以上の高融点原料だけが特別に大きな影響を持ち、その合計量で製品全体の均質溶融性をほぼ評価できるためである。また、高融点原料の使用比率を合計で８質量％以下に限定した理由は、高融点原料の使用比率と粘度安定化時間の関係の測定結果を示した図２の通り、８Ｐｏｉｓｅ以上の高粘度モールドフラックスでは、製品粘度に関わらず８％超で粘度安定化時間が急激に増加するためである。 Here, the reason for limiting to the high-melting-point raw material having a melting point of 1800 ° C. or higher is that all the different-component raw materials other than the base raw material cause a hindrance to homogeneous melting, but only the high-melting-point raw material of 1800 ° C. or higher is special. This is because the homogeneous meltability of the entire product can be almost evaluated by the total amount. The reason why the total use ratio of the high melting point raw material is limited to 8 % by mass or less is that, as shown in FIG. 2 showing the measurement result of the relationship between the use ratio of the high melting point raw material and the viscosity stabilization time, the high viscosity of 8 poise or more. This is because with mold flux, the viscosity stabilization time suddenly increases above 8 % regardless of the product viscosity.
次に、均一流入性については、高粘度モールドフラックスに熱量を付与して保温性を高めることにより鋳片品質の改善傾向が見られる事実が判明したため、発熱原料や製品形状を変更したサンプルで、鋳造試験を行ない鋳片品質の良否により均一流入性を評価した結果、均一流入性を確保する条件として、有機質物質および１質量％の炭素質物質を配合して２００ｃａｌ/ｇ以上の発熱量を付与し、かつ、顆粒状に造粒する必要があることを見出した。 Next, with regard to uniform inflowability, it was found that a tendency to improve the quality of the slab by adding heat to the high-viscosity mold flux to increase the heat retention, so in the sample that changed the exothermic raw material and product shape, As a result of performing a casting test and evaluating the uniform inflow by the quality of the slab, as a condition to ensure the uniform inflow, an organic substance and 1% by mass of a carbonaceous substance are blended to give a calorific value of 200 cal / g or more. And it has been found that it is necessary to granulate into granules.
発熱原料（燃焼物質）を有機質物質および１質量％の炭素質物質に限定した理由は、燃焼残滓が残存してスラグ成分の一部となるような金属粉等の燃焼物質は溶融スラグの粘度安定化時間が極端に増加して均質溶融性が阻害されるためである。
また、熱量を２００cal/g以上に限定した理由は、２００cal/g未満では熱量が不足してメニスカス部の保温による均一流入性が阻害されるためである。
更に、顆粒状に造粒する理由は、粉末製品では炭素質物質や有機質物質が早期に燃焼焼失して保温効果の持続性が得られないためである。ここで顆粒状とは、転動、押出し、攪拌、噴霧乾燥等のあらゆる方法で造粒した顆粒を意味する。特開２００２−１１３５６１公報では、顆粒表面に露出する燃焼物質の量を極端に少なくして骨材効果（溶融速度調整機能）を抑制する目的で、噴霧乾燥方式で造粒した顆粒に限定しているが、本発明では、熱源（発熱原料）である炭素質物質や有機質物質を顆粒の内部に閉じこめることで、燃焼の安定持続性を向上させることが主目的のため造粒方法の制限は無い。
また、炭素質物質や有機質物質の粒度や組み合わせを変更することで溶融速度調整も可能である。しかし、より望ましくは、発熱原料として、顆粒を構成する主要原料の平均粒子径より大きくした粗粉の有機質物質および１質量％の粗粉の炭素質物質を配合して、噴霧乾燥方式で顆粒状に造粒するのが理想的である。その理由は、噴霧乾燥方式の造粒方法では、顆粒品の造粒過程でスラリー液滴が高温雰囲気中で瞬間的に蒸発乾燥する際に水分と同時に微粒物質も表面に移動して粒内構成物質の再分布が生じる結果、顆粒を構成する主原料の平均粒子径よりも大きい平均粒子径を有する燃焼物質の大半を顆粒状モールドフラックスの内部に集積せしめることが可能となり、燃焼の安定持続性がより向上して好結果が得られるためである。
The reason why the exothermic raw materials (combustion substances) are limited to organic substances and 1% by mass carbonaceous substances is that the combustion substances such as metal powder that remains as a part of the slag component remain, and the viscosity of molten slag is stable. This is because the homogenization time is extremely increased and the homogeneous meltability is inhibited.
Moreover, the reason for limiting the amount of heat to 200 cal / g or more is that if it is less than 200 cal / g, the amount of heat is insufficient and the uniform inflow due to the heat retention of the meniscus portion is hindered.
Furthermore, the reason for granulating in a granular form is that in a powder product, carbonaceous substances and organic substances are burnt and burned out at an early stage, and the sustainability of the heat retaining effect cannot be obtained. Here, the granular form means granules granulated by any method such as rolling, extruding, stirring, spray drying and the like. In JP-A-2002-113561, it is limited to granules granulated by a spray drying method for the purpose of suppressing the aggregate effect (melting rate adjusting function) by extremely reducing the amount of combustion substances exposed on the surface of the granules. However, in the present invention, there is no limitation on the granulation method because the main purpose is to improve the stability and stability of combustion by confining the carbonaceous substance or organic substance, which is a heat source (heating material), inside the granules. .
Also, the melting rate can be adjusted by changing the particle size and combination of carbonaceous materials and organic materials. However, more preferably, as the heat-generating raw material, a coarse powdery organic material larger than the average particle diameter of the main raw material constituting the granule and 1% by weight of the coarse powdery carbonaceous material are blended and granulated by spray drying. Ideally granulate. The reason for this is that in the spray-drying granulation method, when the slurry droplets instantaneously evaporate and dry in a high-temperature atmosphere during the granulation process of the granule, the fine substance also moves to the surface at the same time as the moisture, and the intragranular structure As a result of the redistribution of the substance, it becomes possible to accumulate most of the combustion substance having an average particle size larger than the average particle size of the main raw material constituting the granule inside the granular mold flux, and stable combustion sustainability This is because better results can be obtained.
ベース原料以外の異種成分原料の種類と量、製品粘度、発熱原料の種類と量（発熱量）および製品形状を変更した複数のサンプルを製造して、粘度安定化時間の測定により均一溶融性を評価するとともに、モールドサイズ（２００〜２８０）×（８００〜１８００）ｍｍ、鋳造速度１．０〜１．８ｍ／ｍｉｎの代表的なスラブ連鋳機で、各種の鋳造条件毎に最低でも３キャスト（３〜６チャージ／キャスト）の比較鋳造試験を実施して、鋳片品質との対応関係を調査した。 Produces multiple samples with different types and amounts of raw materials other than base materials, product viscosity, types and amounts of exothermic materials (heat generation amount), and product shapes, and measures uniform viscosity by measuring viscosity stabilization time A typical slab continuous caster with a mold size (200-280) x (800-1800) mm and a casting speed of 1.0-1.8 m / min, and at least 3 casts for each casting condition A comparative casting test (3-6 charges / cast) was conducted to investigate the correspondence with the slab quality.
モールドフラックスの粘度安定化時間は、予め７００℃で６０分間脱炭処理して鉄ルツボに入れた測定試料を直接１３００℃に保持した縦型管状炉（エレマ炉）にセットし、試料が溶融したことを確認してからＥ型粘度計の回転ローターをスラグ中に浸漬し、試料温度が１３００℃に到達した時点から、回転ローターの粘性抵抗値を連続測定して粘性抵抗のＣＶ値（変動係数、すなわち、標準偏差／平均値×１００）が安定するまでの時間を測定した。（本実験では３分間隔で、その時刻を中心とした前後１０回の測定値から求めたＣＶ値が０．２％になるまでの時間とした）この時の測定例を図１に示す。図１で横軸は１３００℃到達後の経過時間（min.）、縦軸は粘性抵抗のＣＶ値（％）である。なお、この粘度安定化時間測定に使用したサンプルは後述の表１〜表３のＮｏ．３と８である。 The viscosity stabilization time of the mold flux was set in a vertical tubular furnace (Elema furnace) in which a measurement sample previously decarburized at 700 ° C. for 60 minutes and placed in an iron crucible was directly held at 1300 ° C., and the sample was melted After confirming this, the rotor of the E-type viscometer is immersed in the slag, and when the sample temperature reaches 1300 ° C., the viscosity resistance value of the rotor is continuously measured to determine the CV value (variation coefficient) of the viscosity resistance. That is, the time until the standard deviation / average value × 100) was stabilized was measured. (In this experiment, the time taken until the CV value obtained from 10 measurements before and after the time at the center is 0.2% at intervals of 3 minutes) FIG. 1 shows a measurement example at this time. In FIG. 1, the horizontal axis represents the elapsed time (min.) After reaching 1300 ° C., and the vertical axis represents the CV value (%) of the viscous resistance. In addition, the sample used for this viscosity stabilization time measurement is No. 1 in Tables 1 to 3 described later. 3 and 8.
上記の方法で各種のモールドフラックス（使用したモールドフラックスの詳細は省略する）について粘度安定化時間を測定したところ、粘度が８Ｐｏｉｓｅ未満のモールドフラックスでは１０分程度の比較的短時間で安定化して品種間での大きな相違は見られなかったが、８Ｐｏｉｓｅ以上の高粘度になると、初期溶融段階（すなわち溶融直後スラグの段階）で見掛け上は均質に溶融したように見えても品種によっては溶融スラグが均質化して粘度が安定するまでに長時間を要した。なお、繰り返し実験でも同様な結果が得られ再現性が確認出来た。このことについては、粘度安定化時間の初期の１０分程度は測定サンプル全体の温度が完全に均一化するまでのタイムラグも影響している可能性はあるが、その後の遅延は明らかに均質溶融性の低下が原因と考えられる。なお、粘度安定化時間の初期の１０分程度を実機鋳造でのスラグプール内の滞留時間に相当すると仮定すれば、粘度安定化時間のこれ以上の遅延は、不均質スラグの不均一流入を助長して鋳片品質に悪影響を及ぼす原因となる。 When the viscosity stabilization time was measured for various mold fluxes (details of the mold flux used were omitted) by the above method, the mold flux with a viscosity of less than 8 poise was stabilized in a relatively short time of about 10 minutes. However, when the viscosity becomes higher than 8 poise, it may appear that the molten material is homogeneously melted in the initial melting stage (that is, the slag stage immediately after melting). It took a long time to homogenize and stabilize the viscosity. Similar results were obtained in repeated experiments, and reproducibility was confirmed. Regarding this, the initial lag time of about 10 minutes may affect the time lag until the temperature of the entire measurement sample becomes completely uniform, but the subsequent delay is clearly homogeneous meltability. This is thought to be due to the decline in If it is assumed that the initial 10 minutes of viscosity stabilization time corresponds to the residence time in the slag pool in actual casting, further delay in viscosity stabilization time will promote non-uniform flow of heterogeneous slag. As a result, the slab quality is adversely affected.
上記の如き粘度安定化時間の差異が生じるのは、モールドフラックスの配合の相違に起因すると考えられることから、モールドフラックスの配合（ベース原料以外の異種成分原料の種類と量）と粘度安定化時間の関係を調査したところ、図２のような結果が得られた。すなわち、粘度が８Ｐｏｉｓｅ未満のモールドフラックスでは（図２の６Ｐｏｉｓｅ品で高融点原料の使用比率を変更した例のように）１０分程度の比較的短時間で安定化して、高融点原料の使用比率による大きな相違は見られないが、８Ｐｏｉｓｅ以上の高粘度のモールドフラックスでは、（図２の１０、２０、５０Ｐｏｉｓｅ品で高融点原料の使用比率を変更した例のように）高融点原料を８％超添加することで、粘度安定化時間が急激に増加するという結果が得られた。図２の結果から、８Ｐｏｉｓｅ以上の高粘度になると、初期溶融段階で見掛け上は均質に溶融
したように見えても配合如何（高融点原料の配合の如何）では溶融スラグが均質化して粘度が安定するまでに長時間を要する、という上述のことが確認された。
なお、図２の試験における高融点原料は、アルミナ（Ａｌ２Ｏ３）、マグネシア（ＭｇＯ）、ライム（ＣａＯ）、ジルコン（ＺｒＳｉＯ４）、酸化ストロンチウム（ＳｒＯ）等の、１８００℃以上の融点を有する高融点原料であるが、これらの高融点原料は単独で用いても複数種類を用いても合計で８％超であれば、粘度安定化時間が急激に増加するという効果は同じであった。高融点原料を合計量で一律に評価しても大きな支障が無いのは、これらの原料が、「モールドフラックスのベース成分である珪酸カルシウムよりも極端に高融点である」という溶融や均質化を阻害する原因を共有しているためと考えられる。
The difference in viscosity stabilization time as described above can be attributed to the difference in the blending of the mold flux. Therefore, the blending of the mold flux (type and amount of different component raw materials other than the base raw material) and the viscosity stabilization time. As a result of investigating the relationship, a result as shown in FIG. 2 was obtained. That is, when the mold flux has a viscosity of less than 8 poise (as in the example of changing the use ratio of the high melting point raw material in the 6 poise product in FIG. 2), it stabilizes in a relatively short time of about 10 minutes, and the use ratio of the high melting point raw material However, in the case of a mold flux having a high viscosity of 8 poise or more, the high melting point raw material is 8 % (as in the example of changing the use ratio of the high melting point raw material in 10, 20, and 50 poise products in FIG. 2). The result that the viscosity stabilization time increased rapidly by adding excessively was obtained. From the results shown in FIG. 2, when the viscosity becomes 8 poise or higher, the molten slag is homogenized and the viscosity becomes uniform depending on the blending (whether the blending of the high melting point raw material), even though it appears to have melted homogeneously in the initial melting stage. It has been confirmed that it takes a long time to stabilize.
2 has a melting point of 1800 ° C. or higher, such as alumina (Al 2 O 3 ), magnesia (MgO), lime (CaO), zircon (ZrSiO 4 ), strontium oxide (SrO). The high-melting-point raw material has the same effect that the viscosity stabilization time increases abruptly if the total high-melting-point raw material exceeds 8 % regardless of whether it is used alone or in combination. . Even if the high-melting-point raw materials are uniformly evaluated by the total amount, there is no big problem because these raw materials have the melting and homogenization of "extremely higher melting point than calcium silicate which is the base component of mold flux". This is thought to be due to sharing the cause of inhibition.
次に、原料配合と粘度以外に、発熱量（すなわち発熱原料の種類と量）および製品形状を変更したモールドフラックスを試作して鋳造試験を実施した結果の代表例を表１〜表３に示す。表１は、各モールドフラックスの配合と灼熱減量（１０００℃×１時間加熱時の減量分）、表２は、各モールドフラックスのスラグ状態での主要組成と高融点原料の比率、表３は、各モールドフラックスの特徴と鋳造結果であり、Ｎｏ．１〜６が本発明例、Ｎｏ．７〜１２が比較例である。なお、スラグ状態での主要組成は、灼熱減量を含む製品組成から灼熱減量を除いた百分率に換算したものである。又、発熱量は、使用原料の吸発熱に伴う熱量変化を単体または化合物の標準生成熱から算出して製品合計で表示したものである。 Tables 1 to 3 show typical examples of the results of performing a casting test by making a prototype of a mold flux in which the heat generation amount (that is, the type and amount of the heat generation raw material) and the product shape are changed in addition to the raw material composition and viscosity. . Table 1 shows the composition of each mold flux and loss on ignition (1000 ° C. × 1 hour heating loss), Table 2 shows the ratio of main composition and refractory raw material in the slag state of each mold flux, and Table 3 shows The characteristics and casting results of each mold flux 1 to 6 are examples of the present invention, No.1. 7 to 12 are comparative examples. The main composition in the slag state is converted to a percentage obtained by excluding the loss of ignition from the product composition including the loss of ignition. Further, the calorific value is a product total calculated by calculating the calorific value accompanying the endothermic heat of the used raw material from the standard heat of formation of the single substance or compound.
鋳造試験の結果、製品粘度が６Ｐｏｉｓｅの比較材７は巻き込み性の欠陥、高融点原料の配合比率が１６％と１２％の比較材８と９では割れ性の欠陥やブレークアウト警報、発熱量が１５２と６３ｃａｌ／ｇの比較材１０と１１ではピンホール系の欠陥、更に、粉末タイプの比較材１２でも割れ性の欠陥が発生したが、粘度８Ｐｏｉｓｅ以上、高融点原料の配合比率８質量％以下、発熱量２００ｃａｌ／ｇ以上にして、顆粒形状に造粒した本発明例１〜６では鋳片表面品質が大幅に改善した。
このことは、１８００℃以上の融点を有する高融点原料の使用比率を合計で８質量％以下に制限して粘度安定化時間の増加を防止することで均質溶融性を維持したこと、および、有機質物質および１質量％の炭素質物質を配合して２００ｃａｌ/ｇ以上の発熱量を付与しかつ顆粒状にしたことで燃焼保温効果の安定持続性が向上し均一流入性が改善したことによる結果と考えられる。
なお、上記の有機質物質としては、使用時の燃焼ガスが作業環境を害さない範囲で、燃焼熱量を有する木粉、木屑、木皮、大鋸屑、パルプ、紙、竹、植物の茎、種子や穀物及びその外皮、等の粉末の他、造粒用のバインダーとして使用されるデキストリン、ＣＭＣ（カルボキシメチルセルロース）、リグニン、αスターチ等が使用可能である。
また、炭素質物質としては、燃焼残滓や含有不純物がスラグ成分に悪影響を及ぼさない範囲で、固定炭素約７０質量％以上の天然または人造黒煙、コークス、石炭、木炭、その他の一般的な炭素質物質の粗粉が使用可能である。
As a result of the casting test, the comparative material 7 having a product viscosity of 6 poise has an entrainment defect, and the comparative materials 8 and 9 having a blending ratio of high melting point raw materials of 16% and 12% have a cracking defect, a breakout warning, and a heat generation amount. In
This is because the use ratio of the high-melting-point raw materials having a melting point of 1800 ° C. or higher is limited to 8 % by mass or less to prevent the viscosity stabilization time from increasing, and the homogeneous meltability is maintained. The result of improving the uniform inflow and improving the stable sustainability of the combustion heat retention effect by adding a calorific value of 200 cal / g or more by blending the substance and 1% by mass of carbonaceous substance and making it granular. Conceivable.
In addition, the above-mentioned organic substances include wood powder, wood chips, bark, large sawdust, pulp, paper, bamboo, plant stems, seeds and grains, and so on, as long as the combustion gas during use does not harm the work environment. In addition to the powder such as the outer skin, dextrin, CMC (carboxymethylcellulose), lignin, α starch and the like used as a binder for granulation can be used.
Carbonaceous materials include natural or artificial black smoke, coke, coal, charcoal, and other common carbons with a fixed carbon content of about 70% by mass or more as long as combustion residues and impurities do not adversely affect slag components. Coarse coarse powder can be used.
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