JP2007167867A - Mold flux for continuously casting steel - Google Patents
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本発明は、環境汚染の要因となるＦの含有量が少ない、鋼の連続鋳造用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 for continuous casting of steel with a low content of F which causes environmental pollution.
鋳型内に添加されたモールドフラックスは、鋳型内溶鋼上に厚さ数mm〜１０数mmの溶融層を形成する。この溶融したモールドフラックスは、鋳型と鋳片（凝固シェル）との間に流入してパウダーフィルムを形成する。このうち鋳型側に位置するパウダーフィルムは冷やされて凝固し、結晶を晶出もしくは析出する。こうして形成された結晶層は、輻射伝熱を遮蔽する等の作用により必要な緩冷却効果を発揮する。 The mold flux added into the mold forms a molten layer having a thickness of several mm to several tens mm on the molten steel in the mold. The melted mold flux flows between the mold and the slab (solidified shell) to form a powder film. Among these, the powder film located on the mold side is cooled and solidified to crystallize or precipitate crystals. The crystal layer thus formed exhibits a necessary slow cooling effect by an action such as shielding radiant heat transfer.
ところで、パウダーフィルム中の一般的な結晶組成としてはカスピダイン（３ＣａＯ・２ＳｉＯ2・ＣａＦ2）が知られている。Ｆを含有する一般的なモールドフラックスでは、このカスピダインが広い化学組成範囲で安定して晶出もしくは析出するので、Ｆを含有したモールドフラックスが広く活用されている。 By the way, caspidine (3CaO.2SiO 2 .CaF 2 ) is known as a general crystal composition in a powder film. In general mold flux containing F, since this caspidine is stably crystallized or precipitated in a wide chemical composition range, mold flux containing F is widely used.
しかしながら、環境負荷を軽減するという観点からは、Ｆ濃度を低下させることが望ましい。
そこで、Ｆの含有量が少ないモールドフラックスが、例えば特許文献１〜３で開示されている。
Therefore, for example, Patent Documents 1 to 3 disclose mold fluxes with a low F content.
しかしながら、Ｆ濃度を低下させると、カスピダインの析出もしくは晶出が抑制され、全く出なくなる場合もある。したがって、Ｆ濃度の低いモールドフラックスにおいて、パウダーフィルム中の結晶層を安定して形成するには、カスピダインに代わる、Ｆを含有しない結晶を探すことが必要不可欠になる。 However, when the F concentration is lowered, the precipitation or crystallization of caspidyne is suppressed and may not occur at all. Therefore, in order to stably form a crystal layer in a powder film in a mold flux having a low F concentration, it is indispensable to search for crystals that do not contain F instead of cuspidyne.
しかるに、前記特許文献１および２に開示されたモールドフラックスは、析出もしくは晶出する結晶を意識して作られていないので、結晶化が不安定になって必要な緩冷却作用が得られなくなる可能性がある。 However, since the mold fluxes disclosed in Patent Documents 1 and 2 are not conscious of the crystals that precipitate or crystallize, the crystallization becomes unstable and the necessary slow cooling action cannot be obtained. There is sex.
また、特許文献３は、不純物として含まれるＭｇＯを、主成分として積極的に含有させることで、ＣａＭｇＳｉ2Ｏ6を主結晶として析出させるものであるが、結晶化が弱くガラス質であるので、鋳型内の緩冷却作用が小さい。 Further, Patent Document 3 actively precipitates MgO contained as an impurity as a main component to precipitate CaMgSi 2 O 6 as a main crystal. However, since crystallization is weak and glassy, Slow cooling action in the mold is small.
本発明が解決しようとする問題点は、特許文献１および２で開示されたモールドフラックスは、析出もしくは晶出する結晶を意識して作られていないので、結晶化が不安定になって必要な緩冷却作用が得られなくなる可能性があり、また特許文献３で開示されたモールドフラックスは、結晶化が弱くガラス質で、鋳型内緩冷却作用が小さいという点である。 The problem to be solved by the present invention is that the mold fluxes disclosed in Patent Documents 1 and 2 are not made in consideration of crystals that precipitate or crystallize, so that crystallization becomes unstable and necessary. There is a possibility that the slow cooling action cannot be obtained, and the mold flux disclosed in Patent Document 3 is weak in crystallization, is glassy, and has a low slow cooling action in the mold.
カスピダインに代わるＦを含有しない結晶に望まれる特性は、以下の３点である。
(1) 融点が適当な範囲、すなわち１２５０℃〜１４５０℃であること。
(2) 化学的に安定な結晶であること。
(3) 安価な原料から成ること。
The following three characteristics are desired for a crystal containing no F instead of caspidine.
(1) The melting point is in an appropriate range, that is, 1250 ° C to 1450 ° C.
(2) It must be a chemically stable crystal.
(3) Consists of inexpensive raw materials.
前記の結晶に望まれる特性(1)〜(3)のうちの(2)(3)は当然であるが、(1)は以下の理由による。
すなわち、結晶の融点が鋳造温度より高いと、溶鋼の温度で溶かせない結晶が成長するおそれがあり、潤滑性に問題が生じたり、固いスラグベア（鋳型壁に沿って成長するパウダーの焼結体）が肥大化する問題が生じたりするからである。
Of the properties (1) to (3) desired for the crystal, (2) and (3) are natural, but (1) is due to the following reasons.
That is, if the melting point of the crystal is higher than the casting temperature, crystals that cannot be melted at the temperature of the molten steel may grow, causing problems with lubricity, or hard slag bear (sintered powder that grows along the mold wall) This is because there is a problem that bloated.
また、結晶の融点が鋳型内凝固シェルの表面温度（鋼の液相線温度から１１５０℃程度の間）に比べて低すぎると、鋳型・凝固シェル間のパウダーフィルム中に結晶が析出もしくは晶出し難くなって、必要な緩冷却作用が得られなくなるからである。 In addition, if the melting point of the crystal is too low compared to the surface temperature of the solidified shell in the mold (between the liquidus temperature of steel and about 1150 ° C), crystals are precipitated or crystallized in the powder film between the mold and the solidified shell. This is because it becomes difficult to obtain the necessary slow cooling action.
発明者らは、研究の結果、前記(1)〜(3)を満たすＦ濃度の低いモールドパウダーに適した結晶のひとつとして、従来に無いＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2を見出し、以下の本発明を成すに到った。 As a result of research, the inventors have found an unprecedented Na 2 O.2CaO.3SiO 2 as one of crystals suitable for a mold powder having a low F concentration satisfying the above (1) to (3). Invented the invention.
すなわち、本発明の鋼の連続鋳造用モールドフラックスは、
ＣａＯ、ＳｉＯ2およびＮａ2Ｏを主成分とし、
ＣａＯ含有率（質量％）をＳｉＯ2含有率（質量％）で除した比であるＣａＯ／ＳｉＯ2の値が０．５〜０．９、
Ｎａ2Ｏ含有率が１０〜３０質量％で、
Ｆを含有しないか、または含有する場合でもその含有率が２質量％以下であって、
溶融後の凝固時に析出もしくは晶出する主たる結晶がＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2であることを最も主要な特徴としている。
That is, the mold flux for continuous casting of steel of the present invention is:
CaO, SiO 2 and Na 2 O as main components,
The value of CaO / SiO 2 , which is a ratio obtained by dividing the CaO content (mass%) by the SiO 2 content (mass%), is 0.5 to 0.9,
Na 2 O content is 10-30% by mass,
Even if it does not contain F or contains it, its content is 2% by mass or less,
The main feature is that the main crystals that precipitate or crystallize during solidification after melting are Na 2 O.2CaO.3SiO 2 .
本発明の鋼の連続鋳造用モールドフラックスは、ＣａＯ、ＳｉＯ2、Ｎａ2Ｏを除く成分の総含有量が１０質量%以下であり、凝固温度が９５０〜１２００℃、１３００℃における粘度が２〜１５poiseであることが望ましい。 The mold flux for continuous casting of steel of the present invention has a total content of components excluding CaO, SiO 2 and Na 2 O of 10% by mass or less, and has a solidification temperature of 950 to 1200 ° C. and a viscosity at 1300 ° C. of 2 to 2. It is desirable to be 15 poise.
本発明によれば、汎用性に優れた凝固温度の、Ｆレスあるいは低Ｆのモールドフラックスが容易に得られ、かつパウダーフィルムが安定して十分に結晶化するので、鋳型内における緩冷却効果が発揮される。また、製造される際の単価も低廉ゆえ、実用に適している。 According to the present invention, an F-less or low-F mold flux having a solidification temperature excellent in versatility can be easily obtained, and the powder film is stably and sufficiently crystallized. Demonstrated. Moreover, since the unit price at the time of manufacture is low, it is suitable for practical use.
以下、本発明を実施するための形態と共に最良の形態について、詳細に説明する。
通常のモールドフラックスは、化学組成として、ＣａＯおよびＳｉＯ2を主成分とし、それにＡｌ2Ｏ3、ＭｇＯ、Ｎａ2Ｏ等のアルカリ金属酸化物や、フッ素（Ｆ）等を含有して適正な凝固温度に調整したものに、滓化速度調整剤としてカーボンが１〜５質量%程度添加されている。
Hereinafter, the best mode as well as the mode for carrying out the present invention will be described in detail.
Ordinary mold flux contains CaO and SiO 2 as the main components, and contains alkali metal oxides such as Al 2 O 3 , MgO and Na 2 O, fluorine (F), etc. About 1 to 5% by mass of carbon is added as a hatching rate adjusting agent to the temperature adjusted.
これに対し、本発明の鋼の連続鋳造用モールドフラックスは、前述の通り、Ｆ含有濃度の低いモールドフラックスにおいて、カスピダインに代わる結晶として、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2を見出し、その析出もしくは晶出が安定する化学組成あるいはその化学組成のスラグが有する物性値を開示したものである。 In contrast, continuous casting mold flux of the steel of the present invention, as described above, the lower mold flux of F content level, as crystals in place of Kasupidain, found Na 2 O · 2CaO · 3SiO 2 , its precipitation or crystal The chemical composition in which the output is stable or the physical property value of the slag having the chemical composition is disclosed.
すなわち、本発明の鋼の連続鋳造用モールドフラックスは、
ＣａＯ、ＳｉＯ2およびＮａ2Ｏを主成分とし、
ＣａＯ含有率（質量％）をＳｉＯ2含有率（質量％）で除した比であるＣａＯ／ＳｉＯ2の値が０．５〜０．９、
Ｎａ2Ｏ含有率が１０〜３０質量％で、
Ｆを含有しないか、または含有する場合でもその含有率が２質量％以下であって、
溶融後の凝固時に析出もしくは晶出する主たる結晶がＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2であることを最も主要な特徴としている。
That is, the mold flux for continuous casting of steel of the present invention is:
CaO, SiO 2 and Na 2 O as main components,
The value of CaO / SiO 2 , which is a ratio obtained by dividing the CaO content (mass%) by the SiO 2 content (mass%), is 0.5 to 0.9,
Na 2 O content is 10-30% by mass,
Even if it does not contain F or contains it, its content is 2% by mass or less,
The main feature is that the main crystals that precipitate or crystallize during solidification after melting are Na 2 O.2CaO.3SiO 2 .
ここで、純粋なＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2の結晶組成を考えた場合、Ｎａ2Ｏは約１７．５質量%、ＣａＯは約３１．６質量%、ＳｉＯ2は約５０．９質量%となり、塩基度すなわちＣａＯ／ＳｉＯ2は約０．６２となる。従って、その純組成に配合したモールドフラックスであれば、その結晶の融点約１２８０℃に近い凝固温度となり、凝固時にはＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2のみが結晶として析出もしくは晶出するはずである。 Here, when considering the crystal composition of pure Na 2 O.2CaO.3SiO 2 , Na 2 O is about 17.5% by mass, CaO is about 31.6% by mass, and SiO 2 is about 50.9% by mass. Thus, the basicity, that is, CaO / SiO 2 is about 0.62. Therefore, if the mold flux is blended in the pure composition, the solidification temperature is close to the melting point of about 1280 ° C., and only Na 2 O.2CaO.3SiO 2 should be precipitated or crystallized during solidification.
しかしながら、工業的に不純物の無い前記純組成のモールドフラックスを得ることは困難であり、少なからずＡｌ2Ｏ3やＭｇＯ、酸化鉄等の不純物が含有されるので、前記結晶の融点よりも低い凝固温度のモールドフラックスとなる。 However, it is difficult to obtain a mold flux of the pure composition that is industrially free of impurities, and since it contains impurities such as Al 2 O 3 , MgO, and iron oxide, solidification lower than the melting point of the crystal. Temperature mold flux.
勿論、これら不純成分あるいは少量のＦの含有によって、適用する鋼種に適した凝固温度や粘度に調整するのが一般的である。
また、Ｎａ2Ｏ、ＣａＯ、ＳｉＯ2の組成割合が上記純組成からある程度外れても、結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2が安定して析出もしくは晶出する範囲内であれば、本発明のモールドフラックスであることは言うまでもない。
Of course, it is general to adjust the solidification temperature and viscosity suitable for the steel type to be applied by containing these impure components or a small amount of F.
Further, even if the composition ratio of Na 2 O, CaO, and SiO 2 deviates from the pure composition to some extent, as long as the crystalline Na 2 O.2CaO.3SiO 2 is within the range where it is stably precipitated or crystallized, Needless to say, it is a mold flux.
本発明のモールドフラックスにおいて、Ｆを含まないか、Ｆの含有量が２質量%以下となるようにするのは、本発明の主旨であるＦ含有量を低減するためである。
本発明では、その上で、溶融後の凝固時に析出もしくは晶出する主たる結晶が、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2となるようにするのである。これが本発明の骨子である。
The reason why the mold flux of the present invention does not contain F or the F content is 2% by mass or less is to reduce the F content, which is the gist of the present invention.
In the present invention, the main crystal that precipitates or crystallizes during solidification after melting is Na 2 O.2CaO.3SiO 2 . This is the gist of the present invention.
本発明において、化学組成に関して、質量%で規定したＣａＯ／ＳｉＯ2を０．５〜０．９と、また、Ｎａ2Ｏを１０〜３０質量%としたのは、これらの範囲を外れると、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2が主たる結晶として析出もしくは晶出する組成範囲を外れ、本発明が成立しなくなるからである。発明者らの実験結果によれば、ＣａＯ／ＳｉＯ2のより好ましい範囲は０．５５〜０．８０、Ｎａ2Ｏ濃度のより好ましい範囲は、１３〜２７質量%である。 In the present invention, regarding the chemical composition, CaO / SiO 2 defined by mass% is 0.5 to 0.9, and Na 2 O is 10 to 30 mass%. This is because the composition range in which Na 2 O.2CaO.3SiO 2 precipitates or crystallizes as the main crystal is out of range, and the present invention is not realized. According to the experimental results of the inventors, a more preferable range of CaO / SiO 2 is 0.55 to 0.80, and a more preferable range of Na 2 O concentration is 13 to 27% by mass.
ここで、溶融後の凝固時に析出もしくは晶出する主たる結晶とは、１４００℃で溶融させた後、２℃／minの冷却速度で凝固させ、そのまま室温まで冷却したスラグをＸ線回折分析した際の、ピーク高さが最も大きい結晶と定義する。かかる定義から、ピーク高さの違いが測定誤差程度に似通った強度の複数の結晶が検出された場合には、主たる結晶は存在しないことになる。 Here, the main crystal that precipitates or crystallizes during solidification after melting is when X-ray diffraction analysis is performed on slag that has been melted at 1400 ° C., solidified at a cooling rate of 2 ° C./min, and then cooled to room temperature. Is defined as the crystal having the largest peak height. From this definition, when a plurality of crystals having different intensities whose peak heights are similar to the measurement error are detected, there is no main crystal.
前記本発明の鋼の連続鋳造用モールドフラックスでは、ＣａＯ、ＳｉＯ2、Ｎａ2Ｏを除く成分の総含有量が１０質量%以下であり、凝固温度が９５０〜１２００℃、１３００℃における粘度が２〜１５poiseであることが望ましい。 In the mold flux for continuous casting of steel of the present invention, the total content of components excluding CaO, SiO 2 and Na 2 O is 10% by mass or less, and the viscosity at a solidification temperature of 950 to 1200 ° C. and 1300 ° C. is 2 It is desirable to be ~ 15 poise.
ＣａＯ、ＳｉＯ2、Ｎａ2Ｏを除く成分の総含有量が１０質量%以下であることが望ましいのは、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2を安定して析出もしくは晶出させる観点からである。 The total content of components excluding CaO, SiO 2 and Na 2 O is preferably 10% by mass or less from the viewpoint of stably depositing or crystallizing Na 2 O.2CaO.3SiO 2 .
凝固温度が９５０〜１２００℃の場合が望ましいのは、凝固温度が９５０℃未満にまで低下すると、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の析出もしくは晶出が阻害されるからである。また、結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の融点が約１２８０℃と、１４００℃を超えるカスピダインに比べて低いので、１２００℃以上の凝固温度を工業的に得ることが難しいからである。 The reason why the solidification temperature is 950 to 1200 ° C. is desirable because the precipitation or crystallization of Na 2 O.2CaO.3SiO 2 is hindered when the solidification temperature is lowered to below 950 ° C. Moreover, since the melting point of crystalline Na 2 O.2CaO.3SiO 2 is about 1280 ° C., which is lower than caspodyne exceeding 1400 ° C., it is difficult to industrially obtain a solidification temperature of 1200 ° C. or higher.
１３００℃における粘度が２〜１５poiseの場合が望ましいのは、Ｆ濃度が低いので、１３００℃における粘度を２poise未満にまで下げることは難しいからである。また、１５poiseを超えるほど粘度が高まると、物質移動速度が低下し、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の析出もしくは晶出が阻害されるからである。 The reason why the viscosity at 1300 ° C. is 2 to 15 poise is desirable because it is difficult to lower the viscosity at 1300 ° C. to less than 2 poise because the F concentration is low. Further, if the viscosity increases to exceed 15 poise, the mass transfer rate decreases, and precipitation or crystallization of Na 2 O.2CaO.3SiO 2 is inhibited.
以下、本発明の効果を確認するために行った実施結果について説明する。
本発明の実施例および比較例を下記表１に示す。なお、表１中の結晶名ＮＣ2Ｓ3はＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2を、Titanite（タイタナイトもしくはチタナイト）はＣａＯ・ＳｉＯ2・ＴｉＯ2を、Akermanite（アケルマナイト）は２ＣａＯ・ＭｇＯ・２ＳｉＯ2を示す。
Hereinafter, the implementation results performed to confirm the effect of the present invention will be described.
Examples and comparative examples of the present invention are shown in Table 1 below. In Table 1, the crystal name NC 2 S 3 is Na 2 O · 2CaO · 3SiO 2 , Titanite (titanite or titanite) is CaO · SiO 2 · TiO 2 , and Akermanite is 2CaO · MgO · 2SiO 2. Indicates.
表１中のＡ〜Ｃは、本発明の実施例である。
なお、表１に示した実施例Ａ〜Ｃの凝固温度、粘度といった物性値は、Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2が安定して晶出もしくは析出する範囲内で、Ｎａ2Ｏ濃度や、ＣａＯ／ＳｉＯ2、あるいは他の不純成分濃度を変更して調整した結果得られた値である。
A to C in Table 1 are examples of the present invention.
Incidentally, the solidification temperature of Example A~C shown in Table 1, the physical properties such as viscosity, to the extent that Na 2 O · 2CaO · 3SiO 2 is stably crystallisation or precipitation, and concentration of Na 2 O, CaO This is a value obtained as a result of adjustment by changing the concentration of / SiO 2 or other impurity components.
実施例Ａは、本発明の請求項１および２を満たす、Ｆ含有量が０のＦレスモールドフラックスである。
実施例Ａは化学組成が結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の純組成に近く、ＦやＡｌ2Ｏ3、ＭｇＯといった不純成分が少ないので、主たる結晶としてＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2が安定して析出もしくは晶出し、安定な鋳型内緩冷却効果が得られた。
Example A is an F-less mold flux having an F content of 0 that satisfies claims 1 and 2 of the present invention.
In Example A, the chemical composition is close to the pure composition of crystalline Na 2 O.2CaO.3SiO 2 and there are few impure components such as F, Al 2 O 3 , and MgO, so Na 2 O.2CaO.3SiO 2 is stable as the main crystal. As a result, precipitation or crystallization occurred, and a stable slow cooling effect in the mold was obtained.
なお、実施例Ａの凝固温度１１３０℃は、普通鋼であれば亜包晶鋼（[Ｃ]=０．０８〜０．１７質量%）を除く極低炭素鋼から高炭素鋼（[Ｃ]=１０ppm〜０．４質量%）、ステンレス鋼であればＳＵＳ３０４や１３%Ｃｒ鋼などに幅広く適用することが可能である。 In addition, the solidification temperature of 1130 ° C. in Example A is a low carbon steel to a high carbon steel ([C]) excluding hypoperitectic steel ([C] = 0.08 to 0.17 mass%) in the case of ordinary steel. = 10 ppm to 0.4 mass%), stainless steel can be widely applied to SUS304, 13% Cr steel, and the like.
実施例Ｂは、本発明の請求項１および２を満たす、Ｆ含有量が２質量%の低Ｆモールドフラックスである。
実施例Ｂは化学組成が結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の純組成に若干のＮａ2ＯおよびＦを加え、不純成分としてＡｌ2Ｏ3およびＭｇＯが含有されているもので、実施例Ａに比べると結晶化が弱いものの主たる結晶としてＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2が安定して析出もしくは晶出し、安定な鋳型内緩冷却効果が得られた。
Example B is a low F mold flux satisfying Claims 1 and 2 of the present invention and having an F content of 2 mass%.
Example B has a chemical composition of crystalline Na 2 O.2CaO.3SiO 2 with a slight addition of Na 2 O and F and contains Al 2 O 3 and MgO as impure components. As compared with, Na 2 O.2CaO.3SiO 2 was stably precipitated or crystallized as the main crystal although crystallization was weak, and a stable slow cooling effect in the mold was obtained.
なお、実施例Ｂの凝固温度１０６０℃は、普通鋼であれば高炭素鋼（[Ｃ]=０．４〜１．１質量%）への適用に適しており、実施例Ａおよび実施例Ｂを使い分けることにより、実用鋼の大半に適用することができる。 The solidification temperature 1060 ° C. of Example B is suitable for application to high carbon steel ([C] = 0.4 to 1.1% by mass) if it is plain steel. Example A and Example B By using properly, it can be applied to most practical steels.
実施例Ｃは、本発明の請求項１のみを満たす、Ｆ含有量が０質量%のＦレスモールドフラックスである。
実施例Ｃは化学組成が結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の純組成に不純成分としてＢ2Ｏ3、ＴｉＯ2、Ａｌ2Ｏ3およびＭｇＯが計１０質量%を超えて含有されているので、実施例Ａと比較すると主たる結晶Ｎａ2Ｏ・２ＣａＯ・３ＳｉＯ2の析出もしくは晶出がやや不安定でパウダーフィルムはガラス質であったが、実用上は問題のない程度に安定な鋳型内緩冷却効果が得られた。
Example C is an F-less mold flux satisfying only claim 1 of the present invention and having an F content of 0% by mass.
In Example C, the chemical composition contains crystalline Na 2 O.2CaO.3SiO 2 in a pure composition, and B 2 O 3 , TiO 2 , Al 2 O 3 and MgO are contained in excess of 10% by mass as impure components. Compared with Example A, the precipitation or crystallization of the main crystals Na 2 O.2CaO.3SiO 2 was somewhat unstable and the powder film was glassy, but it was loose enough in the mold to be practically stable. A cooling effect was obtained.
なお、実施例Ｃの凝固温度９８０℃は、実施例Ｂと同様に、普通鋼ならば高炭素鋼（[Ｃ]=０．４〜１．１質量%）への適用に適している。 The solidification temperature of 980 ° C. in Example C is suitable for application to high carbon steel ([C] = 0.4 to 1.1% by mass) in the case of plain steel, as in Example B.
一方、表１のＤ〜Ｆは、本発明の比較例である。
比較例Ｄは、ＣａＯ／ＳｉＯ2が０．３５と低い、特許文献３で開示された従来型のＦレスモールドフラックスである。
On the other hand, D to F in Table 1 are comparative examples of the present invention.
Comparative Example D is a conventional F-less mold flux disclosed in Patent Document 3 in which CaO / SiO 2 is as low as 0.35.
比較例Ｄを凝固させたものはガラス質であり、Ｘ線回折試験による結晶ピークは弱く、バックグラウンドノイズレベルに近いものであったが、ＣａＭｇＳｉ2Ｏ6が同定された。前記のようにガラス質で結晶化が弱い点、ＣａＯ／ＳｉＯ2が０．３５と低い点において、本発明の範囲から外れる。 The solidified product of Comparative Example D was glassy and the crystal peak by the X-ray diffraction test was weak and close to the background noise level, but CaMgSi 2 O 6 was identified. As described above, it is out of the scope of the present invention in that it is glassy and weakly crystallized, and CaO / SiO 2 is as low as 0.35.
比較例Ｄは、パウダーフィルムがガラス質であるので、鋳型内の緩冷却作用は小さい。比較例Ｄがガラス質であるのは、ＳｉＯ2濃度が高く、シリカのネットワーク構造が発達しているためである。また、比較例ＤのようにＣａＯ／ＳｉＯ2が低いモールドフラックスは、低級酸化物であるＳｉＯ2濃度が高いので、溶鋼を汚染しやすいという欠点もある。 In Comparative Example D, since the powder film is glassy, the slow cooling action in the mold is small. Comparative Example D is glassy because the SiO 2 concentration is high and the silica network structure is developed. Further, a mold flux having a low CaO / SiO 2 as in Comparative Example D also has a drawback that the molten steel is easily contaminated because the SiO 2 concentration, which is a lower oxide, is high.
比較例Ｅは、Akermaniteの純組成であるＣａＯ／ＳｉＯ2 =０．９３、ＭｇＯ=１５質量%に近い、ＣａＯ／ＳｉＯ2 =０．８５、ＭｇＯ=１３質量%を基本成分とし、前記基本成分に、不純成分としてＰ2Ｏ5、Ｂ2Ｏ3、ＴｉＯ2、Ａｌ2Ｏ3、Ｎａ2Ｏ、Ｆを少量ずつ加えた、Akermaniteを主たる結晶とする低Ｆモールドフラックスである。 Comparative Example E is a pure composition of Akermanite with CaO / SiO 2 = 0.93, MgO = 15% by mass, CaO / SiO 2 = 0.85, MgO = 13% by mass as basic components, In addition, P 2 O 5 , B 2 O 3 , TiO 2 , Al 2 O 3 , Na 2 O, and F are added in small amounts as impure components, and this is a low F mold flux having Akermanite as the main crystal.
比較例Ｅは、Akermaniteの純組成に近いので、パウダーフィルムの結晶化が進行し、凝固温度が高く、鋳型内の緩冷却作用も強いので、普通鋼ならば亜包晶鋼の鋳造に適する。これは、亜包晶鋼が凝固直後のδ→γ変態によって大きく収縮することに起因する不均一凝固を生じやすく、凝固収縮を抑制するための緩冷却を必要とするからである。 Since Comparative Example E is close to the pure composition of Akermanite, crystallization of the powder film proceeds, the solidification temperature is high, and the slow cooling action in the mold is strong, so that ordinary steel is suitable for casting of subperitectic steel. This is because hypoperitectic steel tends to cause non-uniform solidification due to large shrinkage due to the δ → γ transformation immediately after solidification, and requires slow cooling to suppress solidification shrinkage.
比較例Ｅは、主たる結晶組成において、本発明の範囲を外れる。比較例ＥのようにAkermaniteが主たる結晶である低ＦあるいはＦレスのモールドフラックスの場合、Akermaniteの融点が１４５４℃とＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2の融点約１２８０℃に比べると高いので、モールドフラックスの凝固温度も高くなりがちである。本発明である実施例ＡあるいはＢの方が、１１００℃前後の汎用性に優れる凝固温度を容易に得ることができる。 Comparative Example E is outside the scope of the present invention in the main crystal composition. In the case of a low F or F-less mold flux in which Akermanite is the main crystal as in Comparative Example E, the melting point of Akermanite is 1454 ° C, which is higher than the melting point of Na 2 O · 2CaO · 3SiO 2 of about 1280 ° C. The solidification temperature of the flux tends to be high. In Example A or B according to the present invention, a solidification temperature excellent in versatility of around 1100 ° C. can be easily obtained.
比較例Ｆは、ＴｉＯ2濃度が高く、ＣａＯ・ＳｉＯ2・ＴｉＯ2を主たる結晶として析出もしくは晶出する点で本発明の範囲から外れる低Ｆモールドフラックスである。
比較例Ｆは、凝固温度が１１８５℃と比較的高いので、比較例Ｅと同様に、普通鋼であれば亜包晶鋼の鋳造に適している。ＴｉＯ2の原料はＣａＯやＳｉＯ2、Ｎａ2Ｏの原料に比べると高価であるので、比較例Ｆの単価は実施例Ａ〜Ｃ、及び比較例Ｄ，Ｅに比べると高くなりがちなことが難点である。
Comparative Example F is a low F mold flux that has a high TiO 2 concentration and is out of the scope of the present invention in that CaO · SiO 2 · TiO 2 is precipitated or crystallized as the main crystals.
Since Comparative Example F has a relatively high solidification temperature of 1185 ° C., like Comparative Example E, ordinary steel is suitable for casting of peritectic steel. Since the raw material of TiO 2 is more expensive than the raw materials of CaO, SiO 2 and Na 2 O, the unit price of Comparative Example F tends to be higher than Examples A to C and Comparative Examples D and E. It is a difficulty.
本発明は上記の例に限らず、各請求項に記載された技術的思想の範囲内で、適宜実施の形態を変更しても良いことは言うまでもない。 The present invention is not limited to the above example, and it goes without saying that the embodiment may be appropriately changed within the scope of the technical idea described in each claim.
Claims (2)
ＣａＯ含有率（質量％）をＳｉＯ2含有率（質量％）で除した比であるＣａＯ／ＳｉＯ2の値が０．５〜０．９、
Ｎａ2Ｏ含有率が１０〜３０質量％で、
Ｆを含有しないか、または含有する場合でもその含有率が２質量％以下であって、
溶融後の凝固時に析出もしくは晶出する主たる結晶がＮａ2Ｏ・２ＣａＯ・３ＳｉＯ2であることを特徴とする鋼の連続鋳造用モールドフラックス。 CaO, SiO 2 and Na 2 O as main components,
The value of CaO / SiO 2 , which is a ratio obtained by dividing the CaO content (mass%) by the SiO 2 content (mass%), is 0.5 to 0.9,
Na 2 O content is 10-30% by mass,
Even if it does not contain F or contains it, its content is 2% by mass or less,
A mold flux for continuous casting of steel, characterized in that the main crystals that precipitate or crystallize during solidification after melting are Na 2 O.2CaO.3SiO 2 .
凝固温度が９５０〜１２００℃、
１３００℃における粘度が２〜１５poiseであることを特徴とする請求項１に記載の鋼の連続鋳造用モールドフラックス。
The total content of components excluding CaO, SiO 2 and Na 2 O is 10% by mass or less,
Solidification temperature is 950-1200 ° C,
The mold flux for continuous casting of steel according to claim 1, wherein the viscosity at 1300 ° C is 2 to 15 poise.
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