JP2008043987A - Mold powder used for continuous casting of molten metal - Google Patents
Mold powder used for continuous casting of molten metal Download PDFInfo
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本発明は、鋼等の溶融金属の連続鋳造に用いるモールドパウダーに関するもので、環境汚染が小さいことと鋳型内湯面の保温性が高いことを両立するモールドパウダーに関するものである。 TECHNICAL FIELD The present invention relates to a mold powder used for continuous casting of molten metal such as steel, and relates to a mold powder that achieves both low environmental contamination and high heat retaining properties of the mold surface.
鋼等の溶融金属の連続鋳造用モールドパウダーは、粉末もしくは顆粒状であり、この生パウダーが鋳型内に添加されると、湯面上で溶融して厚さ数mm〜十数mmの溶融層を形成する。溶融したモールドパウダーは、鋳型と鋳片(凝固シェル)との間に流入し、パウダーフィルムを形成する。このうち、鋳型側の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しつつ、鋳造の進行に伴って鋳型下方へ移動し、やがて下端から排出される。 Mold powder for continuous casting of molten metal such as steel is in the form of powder or granules. When this raw powder is added to the mold, it melts on the molten metal surface and has a thickness of several to tens of millimeters. Form. The molten mold powder flows between the mold and the slab (solidified shell) to form a powder film. Among these, the powder film on the mold side is cooled and solidified, crystallizes or precipitates, moves to the lower part of the mold as the casting progresses, and is eventually discharged from the lower end.
これら各過程において、モールドパウダーは様々な役割を果たす。その中で、生パウダー層が担う重要な役割に、湯面の保温がある。
モールドパウダーは、その粒形状が、粉末であるものと顆粒であるものに大別される。一般に、特許文献1で開示されたような、粉末品は、嵩比重を小さくできるので保温性の点で有利である反面、表面の粉末層が粉塵となって飛散しやすく環境汚染を引き起こしやすい。他方、顆粒品は、嵩比重を小さくすることが困難で保温性に劣る反面、粉塵の飛散は少なく環境汚染が小さい点で優れている。
Mold powder is roughly classified into powder and granule. In general, a powder product as disclosed in Patent Document 1 is advantageous in terms of heat retention because the bulk specific gravity can be reduced. On the other hand, the powder layer on the surface is likely to be scattered as dust and easily cause environmental pollution. On the other hand, the granule product is excellent in that it is difficult to reduce the bulk specific gravity and is inferior in heat retaining property, but on the other hand, dust scattering is small and environmental pollution is small.
つまり、従来のモールドパウダーでは、環境汚染が小さいことと鋳型内湯面の保温性に優れていることの2点を両立することが困難であった。従って、近年、作業環境の改善が重要視される中で、顆粒品を適用する場合が増えつつある。しかしながら、顆粒品を適用した場合は、その保温性の悪さに起因する操業や品質上の問題を誘発することが多いので、粉塵が少なくかつ保温性に優れたモールドパウダーが求められていた。 That is, in the conventional mold powder, it has been difficult to achieve both the environmental pollution and the excellent heat retaining property of the mold surface. Therefore, in recent years, the importance of improving the working environment is increasing, and the cases of applying granule products are increasing. However, when a granule is applied, operation and quality problems due to the poor heat retention are often induced, and therefore, a mold powder with less dust and excellent heat retention has been demanded.
本発明が解決しようとする問題点は、粉塵の飛散が少なく環境汚染が小さいように顆粒のモールドパウダーを使用した場合には、保温性の悪さに起因する操業や品質上の問題を誘発することが多いという点である。 The problem to be solved by the present invention is that when granulated mold powder is used so that dust scattering is small and environmental pollution is small, operation and quality problems due to poor heat retention are induced. There are many points.
本発明は、前記の問題を解消し、環境汚染を小さくし、かつ鋳型内湯面の保温性に優れるような顆粒のモールドパウダーについて調査・研究した結果、成されたものである。 The present invention has been made as a result of investigation and research on a granular mold powder that solves the above-described problems, reduces environmental pollution, and is excellent in the heat retaining property of the mold surface.
すなわち、本発明の溶融金属の連続鋳造に用いるモールドパウダーは、
膨張性黒鉛を配合した顆粒状のモールドパウダーであって、
加熱時に顆粒状のモールドパウダーが熱崩壊し、
熱崩壊後に膨張性黒鉛を含む炭素を完全燃焼させた後の嵩比重が、炭素原料を除く原料粉末の混合体の嵩比重よりも小さく、かつ0.65g/cc以下であることを最も主要な特徴としている。
That is, the mold powder used for continuous casting of the molten metal of the present invention is
A granular mold powder containing expansive graphite,
The granular mold powder collapses when heated,
Most importantly, the bulk specific gravity after the carbon containing expansive graphite is completely burned after the thermal collapse is smaller than the bulk specific gravity of the mixture of the raw material powders excluding the carbon raw material and not more than 0.65 g / cc. It is a feature.
本発明によれば、鋼等の溶融金属の連続鋳造において、環境汚染が小さいことと、鋳型内湯面の保温性が高いこと、を両立することができる。 ADVANTAGE OF THE INVENTION According to this invention, in continuous casting of molten metals, such as steel, it can satisfy | fill both that environmental pollution is small and the heat retaining property of the hot_water | molten_metal surface in a casting_mold | template is high.
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。
発明者は、顆粒状のモールドパウダーに膨張性黒鉛を加えて、鋳型内で加熱された際に粉末状に熱崩壊させる、いわゆる熱崩壊型の顆粒モールドパウダーにおいて、バインダを多く配合して顆粒の粉化を抑制した上で、膨張性黒鉛の配合量を増加すれば、熱崩壊後に非常に軽い発泡粒状の粉末が得られることを見出した。
Hereinafter, the best mode as well as the mode for carrying out the present invention will be described in detail.
The inventor adds expansive graphite to a granular mold powder and thermally collapses it into a powder when heated in a mold. It was found that if the blending amount of expandable graphite is increased after suppressing pulverization, a very light foamed granular powder can be obtained after thermal collapse.
この発泡粒状の粉末の嵩比重は、膨張性黒鉛を含む炭素を燃焼させた後も、炭素原料を除く原料粉末を混合したものの嵩比重よりも小さかった。このことは、すなわち、膨張性黒鉛が熱膨張する際に、発泡状の作用が生じて、気孔率の高い粉状の焼結体を形成したことを表している。発明者は、顕微鏡を用いた観察等によって、熱崩壊後に生じる発泡粒状の粉末が、上記のような粉状焼結体であることを確認した。 The bulk specific gravity of the foamed granular powder was smaller than the bulk specific gravity of the mixture of the raw material powder excluding the carbon raw material even after burning the carbon containing the expandable graphite. This means that, when the expandable graphite is thermally expanded, a foaming action is generated, and a powdery sintered body having a high porosity is formed. The inventor confirmed by observation with a microscope or the like that the foamed granular powder generated after the thermal collapse was a powdery sintered body as described above.
すなわち、本願の請求項1に係る発明は、
膨張性黒鉛を配合した顆粒状のモールドパウダーであって、
加熱時に顆粒状のモールドパウダーが熱崩壊し、
熱崩壊後に膨張性黒鉛を含む炭素を完全燃焼させた後の嵩比重が、炭素原料を除く原料粉末の混合体の嵩比重よりも小さく、かつ0.65g/cc以下であることを特徴とするものである。
That is, the invention according to claim 1 of the present application is
A granular mold powder containing expansive graphite,
The granular mold powder collapses when heated,
The bulk specific gravity after completely burning carbon containing expansive graphite after thermal collapse is smaller than the bulk specific gravity of the raw material powder mixture excluding the carbon raw material, and is 0.65 g / cc or less. Is.
この本願の請求項1に係る発明では、本願発明の基本事項である膨張性黒鉛を配合することと、熱崩壊後に炭素を完全燃焼させた後の嵩比重を規定している。 In the invention according to claim 1 of the present application, blending of expansive graphite, which is a basic matter of the present invention, and bulk specific gravity after completely burning carbon after thermal collapse are specified.
ここで、膨張性黒鉛とは、黒鉛の積層構造間に硫酸等の酸を含浸させた黒鉛であり、加熱によって酸が揮発する際に積層構造間隙が広がり、数十倍〜数百倍膨張する特性を有するものである。 Here, expansive graphite is graphite in which an acid such as sulfuric acid is impregnated between the laminated structures of graphite, and when the acid is volatilized by heating, the gap between the laminated structures widens and expands several tens to several hundreds times. It has characteristics.
また、熱崩壊後に膨張性黒鉛を含む炭素を完全燃焼させた後の嵩比重とは、800℃の大気雰囲気炉内で、モールドパウダーを45分間加熱して、顆粒を熱崩壊させるとともに、熱崩壊後の膨張性黒鉛および他の炭素を完全燃焼させた後に室温まで冷却し、外径が50mmの円筒容器内に100ccの試料を振動を加えることなく充填した際の重量から求められる比重である。 The bulk specific gravity after carbon containing expansive graphite is completely burned after thermal collapse means that the mold powder is heated for 45 minutes in an air atmosphere furnace at 800 ° C. The specific gravity obtained from the weight when the later expansive graphite and other carbon were completely burned, cooled to room temperature, and a 100 cc sample was filled in a cylindrical container having an outer diameter of 50 mm without vibration.
一般の粉末状モールドパウダーの嵩比重は、0.6〜1.0g/cc程度であることから、請求項1で規定した嵩比重0.65g/cc以下とは、粉末品の中でも特に軽く保温性が良いモールドパウダーに相当する。本発明では、熱崩壊後の嵩比重は、0.60g/cc以下であるとさらに好ましい。本発明の0.65g/cc以下、もしくは0.60g/cc以下という嵩比重は、炭素を除いた原料粉末の混合体よりも小さい(軽い)値であることが大きな特徴である。 Since the bulk specific gravity of general powdered mold powder is about 0.6 to 1.0 g / cc, the bulk specific gravity of 0.65 g / cc or less as defined in claim 1 is particularly lightly maintained among powder products. Corresponds to good mold powder. In the present invention, the bulk specific gravity after thermal collapse is more preferably 0.60 g / cc or less. The bulk specific gravity of 0.65 g / cc or less or 0.60 g / cc or less of the present invention is a large feature that it is a smaller (lighter) value than a mixture of raw material powders excluding carbon.
以上の本発明の請求項1に規定する要件を満たすモールドパウダーは、鋳型内に搬送されるまでは顆粒形状を保つので粉塵の発生が少なくなる。また、鋳型内では非常に軽く保温性の良い粉末となるので、保温性に優れる。すなわち、本発明では、環境汚染の小ささと、優れた保温性という二つの要求を、高次元で満たすことができるのである。 The mold powder that satisfies the above-mentioned requirements defined in claim 1 of the present invention maintains the granular shape until it is conveyed into the mold, so that the generation of dust is reduced. In addition, since the powder is very light and has good heat retention in the mold, it has excellent heat retention. That is, in the present invention, the two requirements of small environmental pollution and excellent heat retention can be satisfied at a high level.
また、本願の請求項2に係る発明は、
本願の請求項1に係る発明において、
顆粒成形用のバインダの含有量が1.5〜5.0質量%で、
前記膨張性黒鉛の含有量が1.5〜4.0質量%としたことを特徴とするものである。
The invention according to claim 2 of the present application is
In the invention according to claim 1 of the present application,
The content of the binder for granulation is 1.5 to 5.0% by mass,
The content of the expandable graphite is 1.5 to 4.0% by mass.
発明者の研究によれば、顆粒成形用のバインダが1.5質量%未満の場合には、鋳型内に供給される際に壊れて粉化する顆粒が増えることが分かった。発明者は、顆粒が粉化してしまうと、熱崩壊後に軽い粉末とならないことを知見し、本願の請求項1に係る発明の効果をより発揮させるための条件として、バインダの含有量は1.5質量%以上が必要であることを見出した。 According to the inventor's research, it was found that when the binder for granulation is less than 1.5% by mass, more granules are broken and pulverized when fed into the mold. The inventor has found that when the granule is pulverized, it does not become a light powder after thermal collapse, and as a condition for further exerting the effect of the invention according to claim 1 of the present application, the binder content is 1. It was found that 5% by mass or more is necessary.
一方、バインダの含有量が5.0質量%を超えると、顆粒成形前のスラリーの粘度が高くなりすぎて成形性が悪化するので好ましくない。発明者の実験によれば、鋳型内における粉化率を粒径0.21mm未満の粒子の重量割合と定義した場合、粉化率を25%以下、より好ましくは20%以下に抑制できれば、熱崩壊後に小さな嵩比重の粉末が得られた。 On the other hand, if the binder content exceeds 5.0% by mass, the viscosity of the slurry before granulation becomes too high, and the moldability deteriorates, which is not preferable. According to the inventor's experiment, when the powdering rate in the mold is defined as the weight ratio of particles having a particle size of less than 0.21 mm, if the powdering rate can be suppressed to 25% or less, more preferably 20% or less, A small bulk specific gravity powder was obtained after disintegration.
また、熱膨張作用によって軽い粉末を得るには、膨張性黒鉛を1.5質量%以上含有させることが必要である。一方、膨張性黒鉛の含有量が4.0質量%を超えると、モールドパウダーの滓化・溶融が遅くなる問題が生じるし、高コストとなるので好ましくない。 Further, in order to obtain a light powder by the thermal expansion action, it is necessary to contain 1.5% by mass or more of expandable graphite. On the other hand, if the content of expandable graphite exceeds 4.0% by mass, there is a problem that the mold powder is slowly hatched and melted, resulting in high costs.
また、本願の請求項3に係る発明は、
本願の請求項1又は2に係る発明において、
アルカリ金属酸化物であるNa2O、K2OおよびLi2Oの合計含有量を7質量%以下、
炭酸塩の合計含有量を10質量%未満としたことを特徴とするものである。
The invention according to claim 3 of the present application is
In the invention according to claim 1 or 2 of the present application,
The total content of Na 2 O, K 2 O and Li 2 O, which are alkali metal oxides, is 7% by mass or less,
The total content of carbonate is less than 10% by mass.
発明者は、環境汚染の防止と保温性の確保を両立して実現するのに有効な鋳型内でのモールドパウダー未溶融層の形態は、上部が顆粒層、下部が粉末層という層状の形態が安定して保たれることであることに思い至った。そして、アルカリ金属酸化物であるNa2O、K2OおよびLi2Oの合計含有量が7質量%より多くなると粉末層の焼結が進みやすく安定した粉末層の形成が阻害されること、および炭酸塩が10質量%以上になると、下部の粉末層が上部に吹き上がって安定した2層状態が保たれなくなることを見出し、上記の請求項3に係る発明を成立させた。 The inventor believes that the mold powder unmelted layer in the mold is effective in achieving both prevention of environmental pollution and ensuring heat retention in the form of a layered form in which the upper part is a granular layer and the lower part is a powder layer. I realized that it was to be kept stable. Then, the formation of alkali metal oxides in which Na 2 O, K 2 O and Li 2 total content of O is more than 7% by mass, the powder layer powder layer sintering proceeds easily stable in is inhibited, When the amount of carbonate is 10% by mass or more, the lower powder layer is blown upward and a stable two-layer state cannot be maintained, and the invention according to claim 3 has been established.
アルカリ金属酸化物であるNa2O、K2OおよびLi2Oの合計含有量は、3質量%以下であるとさらに好ましい。前記アルカリ金属酸化物は含有しなくても良いが、含有を意図しない場合にも、通常は不純分として0.5〜2質量%程度は含有される。 The total content of Na 2 O, K 2 O and Li 2 O is an alkali metal oxide, further preferably 3 wt% or less. The alkali metal oxide does not need to be contained, but even when it is not intended to be contained, usually about 0.5 to 2% by mass is contained as an impurity.
また、炭酸塩は配合しなくても良いが、撹拌作用による焼結防止効果が期待できるので、2質量%以上含有するのが好ましい。より好ましい上限値は7質量%である。なお、炭酸塩としては、炭酸ナトリウム、炭酸マグネシウム、炭酸カルシウム、炭酸ストロンチウム、等が用いられる。 Carbonate may not be blended, but it is preferable to contain 2% by mass or more because an anti-sintering effect due to a stirring action can be expected. A more preferred upper limit is 7% by mass. In addition, as carbonate, sodium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, etc. are used.
また、本願の請求項4に係る発明は、
本願の請求項1〜3の何れかに係る発明において、
カーボンブラックの含有量が0.8質量%以下、または含有していないことを特徴とするものである。
The invention according to claim 4 of the present application is
In the invention according to any one of claims 1 to 3 of the present application,
The carbon black content is 0.8% by mass or less, or is not contained.
カーボンブラックは、滓化・溶融を抑制する作用が安定して強いので、モールドパウダーには、通常1〜3質量%程度が添加される。このカーボンブラックは、微粉末ゆえに環境汚染作用が強い。 Since carbon black has a stable and strong action of suppressing hatching and melting, about 1 to 3% by mass is usually added to the mold powder. Since this carbon black is a fine powder, it has a strong environmental pollution effect.
しかしながら、本発明のモールドパウダーは、熱発泡によって生じる非常に軽い粉末層が高い断熱作用を有することから、カーボンブラック量が少なくても、滓化・溶融が適度に抑制される。さらに、本発明のモールドパウダーは、アルカリ金属酸化物が少ないので、溶融速度を下げて少ないカーボンブラック量での滓化・溶融制御が可能となる。 However, in the mold powder of the present invention, since the very light powder layer generated by thermal foaming has a high heat insulating action, hatching and melting are moderately suppressed even if the amount of carbon black is small. Furthermore, since the mold powder of the present invention has a small amount of alkali metal oxide, it is possible to control the hatching and melting with a small amount of carbon black by reducing the melting rate.
従って、本発明では、カーボンブラックの含有量が0.8質量%以下、もしくはカーボンブラックを含有しない環境に優しいモールドパウダーができる。カーボンブラック含有量上限値のより好ましい値は0.5質量%である。 Therefore, in the present invention, an environmentally friendly mold powder having a carbon black content of 0.8% by mass or less or containing no carbon black can be obtained. A more preferable value of the carbon black content upper limit is 0.5% by mass.
なお、本発明に似た従来の発明に、特許第3128496号公報に記載のモールドパウダーがある。特許第3128496号の請求項6は、膨張黒鉛を配合した顆粒状モールドパウダーである点で、本発明に類似している。 Incidentally, there is a mold powder described in Japanese Patent No. 3128496 as a conventional invention similar to the present invention. Claim 6 of Japanese Patent No. 3128496 is similar to the present invention in that it is a granular mold powder containing expanded graphite.
しかしながら、特許第3128496号には、保温性にとって重要な嵩比重や、顆粒の熱崩壊後嵩比重にとって重要なバインダ含有量についての記述が無く、環境汚染と保温性という観点での改善作用が明らかではない。 However, in Japanese Patent No. 3128496, there is no description about the bulk specific gravity important for heat retention and the binder content important for bulk specific gravity after thermal collapse of granules, and the improvement effect in terms of environmental pollution and heat retention is obvious. is not.
さらに特許第3128496号の実施例は全て、アルカリ金属酸化物の含有量が多いので、鋳型内において顆粒層下方の粉末層が焼結しやすく、保温性に劣るとともに、カーボンブラック低減時の溶融・滓化制御に難があると推定される。 Further, all examples of Japanese Patent No. 3128496 have a high content of alkali metal oxide, so that the powder layer below the granule layer in the mold is easy to sinter, inferior in heat retaining properties, and melt / reduced when carbon black is reduced. It is estimated that there is difficulty in hatch control.
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。
一般にモールドパウダーの化学組成は、CaOおよびSiO2を主成分とし、CaOとSiO2とを合わせて60〜80質量%程度含有し、CaOとSiO2との比率CaO/SiO2(塩基度)が0.6〜1.8程度の範囲にある。
Hereinafter, description will be given of the results of experiments performed to confirm the effects of the present invention.
Generally the chemical composition of the mold powder is composed mainly of CaO and SiO 2, together with CaO and SiO 2 contained about 60 to 80 wt%, the ratio CaO / SiO 2 (basicity) of CaO and SiO 2 is It is in the range of about 0.6 to 1.8.
そして、他に凝固温度や粘度あるいは結晶化等の調整剤として、Al2O3、MgO、TiO2、ZrO2、Na2O、Li2O、B2O3、F等を含有し、これら基材に、さらに滓化(溶融)速度調整を目的にカーボン等の骨材が数質量%添加されている。 In addition, Al 2 O 3 , MgO, TiO 2 , ZrO 2 , Na 2 O, Li 2 O, B 2 O 3 , F, etc. are contained as regulators such as solidification temperature, viscosity or crystallization. Several mass% of aggregate such as carbon is added to the base material for the purpose of adjusting the hatching (melting) rate.
顆粒品の場合には、これらを水で練ったスラリーにバインダ(糊)を加えて顆粒状に成形される。バインダとしては、CMC(カルボキシル・メチル・セルロース)が広く用いられている。 In the case of a granule product, a binder (glue) is added to a slurry obtained by kneading these with water to form a granule. As the binder, CMC (carboxyl methyl cellulose) is widely used.
上記に示した一般的な組成のモールドパウダーにおける、本発明の具体的な実施例および比較例を下記表1に示す。 Specific examples of the present invention and comparative examples in the mold powder having the general composition shown above are shown in Table 1 below.
表1のAおよびBは、本願の請求項1〜4を全て満たす実施例である。
これらは、常温における粒形状が顆粒(俵形状の押出成型顆粒)であり、かつ十分な量のバインダを含有しているので顆粒の粒子が強固で壊れ難い。したがって、鋳型内に散布されるまでの段階では粉塵をほとんど出すことがない。さらにアルカリ金属酸化物含有量が少なく、かつ炭酸塩の含有量が少ないので、鋳型内で上部の顆粒層と下部の粉末層とが安定して形成され鋳型内においても粉塵発生が少ない。また、微細粒のカーボンブラックを含有していないので、発生した粉塵の浮遊時間が短い。これらの特性により、実施例Aおよび実施例Bは、環境汚染が非常に少ないモールドパウダーである。
A and B in Table 1 are examples that satisfy all claims 1 to 4 of the present application.
In these, the particle shape at room temperature is a granule (an extrusion-molded granule), and since it contains a sufficient amount of binder, the particle of the granule is strong and hardly broken. Therefore, almost no dust is produced until it is sprayed into the mold. Furthermore, since the alkali metal oxide content is low and the carbonate content is low, the upper granule layer and the lower powder layer are stably formed in the mold, and the generation of dust is also small in the mold. Moreover, since fine carbon black is not contained, the floating time of the generated dust is short. Due to these properties, Example A and Example B are mold powders with very little environmental contamination.
同時に実施例Aおよび実施例Bは、熱崩壊後の嵩比重(ラボ測定値)が0.65以下と、鋳型内の溶鋼湯面近傍では非常に軽い粉末粒子となるので、湯面の保温性に優れている。このように軽い粉末粒子となるのは、十分な量の膨張性黒鉛を含有していることによる。 At the same time, in Examples A and B, the bulk specific gravity (lab measurement value) after thermal collapse is 0.65 or less, and very light powder particles are formed near the molten steel surface in the mold. Is excellent. Such light powder particles are due to containing a sufficient amount of expandable graphite.
また、実施例Aおよび実施例Bは、バインダが十分に含有されているので実際の鋳型内においても熱崩壊前に顆粒形状が保たれる割合が多い。したがって、実際の鋳型内においても上記ラボ測定値と同等の熱崩壊後の嵩比重が得られる。 In Examples A and B, since the binder is sufficiently contained, the ratio of the granular shape is maintained before the thermal collapse in the actual mold. Therefore, the bulk specific gravity after thermal collapse equivalent to the above laboratory measurement value can be obtained even in an actual mold.
さらに、実施例Aおよび実施例Bは、アルカリ金属酸化物含有量と炭酸塩含有量が少ないので、鋳型内で上部の顆粒層と下部の粉末層とが安定して形成され、保温性に優れる。
なお、実施例Bは、バインダ含有量が請求項2で規定する上限に近い4質量%と多かったので、顆粒成形前のスラリーの流動性がやや悪く、顆粒の成形性にやや難があった。
Further, Example A and Example B are low in alkali metal oxide content and carbonate content, so that the upper granular layer and the lower powder layer are stably formed in the mold, and are excellent in heat retention. .
In Example B, the binder content was as high as 4% by mass close to the upper limit defined in claim 2, so the fluidity of the slurry before granulation was slightly poor and the moldability of the granules was somewhat difficult. .
表1のCは、本願の請求項1および4を満たす実施例である。
実施例Cは、常温における粒形状が顆粒であるので、鋳型内に散布されるまでの段階での粉塵発生量が少ない。ただしバインダの含有量が1質量%と、1.5質量%を下回ってやや少ないので、顆粒の粒子が鋳型内散布までに粉化してしまう割合が、実施例Aや実施例Bに比べるとやや多かった。
C in Table 1 is an example satisfying claims 1 and 4 of the present application.
In Example C, since the particle shape at room temperature is a granule, the amount of dust generated at the stage until it is sprayed into the mold is small. However, since the content of the binder is 1% by mass and slightly less than 1.5% by mass, the proportion of the granule particles that are pulverized before being sprayed in the mold is slightly higher than in Examples A and B. There were many.
実施例Cは、炭酸塩含有量が上限値である10質量%を超え、13質量%と多いので、鋳型内での粉塵発生がやや目立った。また実施例Cは、微細粒のカーボンブラックを含有していないので、発生した粉塵の浮遊時間が短い。これら特性により、実施例Cは、実施例Aや実施例Bに比べると劣るものの、環境汚染が少ないモールドパウダーであることが分かる。 In Example C, the carbonate content exceeded the upper limit of 10 mass% and was as large as 13 mass%, so that dust generation in the mold was slightly noticeable. Moreover, since Example C does not contain fine-grained carbon black, the floating time of the generated dust is short. From these characteristics, it can be seen that Example C is a mold powder with less environmental pollution, although it is inferior to Examples A and B.
同時に実施例Cは、熱崩壊後の嵩比重(ラボ測定値)が0.65以下と、鋳型内の溶鋼湯面近傍では非常に軽い粉末粒子となるので、湯面の保温性に優れている。このように軽い粉末粒子となるのは、十分な量の膨張性黒鉛を含有していることによる。 At the same time, in Example C, the bulk specific gravity (lab measurement value) after thermal collapse is 0.65 or less, and very light powder particles are formed in the vicinity of the molten steel surface in the mold. . Such light powder particles are due to containing a sufficient amount of expandable graphite.
しかしながら、実施例Cは、バインダ含有量が1質量%と、下限値の1.5質量%を下回ってやや少ないので、顆粒の粒子が鋳型内散布までに粉化してしまう割合が、実施例Aや実施例Bに比べるとやや多かった。顆粒の粒子が粉化した場合には熱崩壊後の嵩比重がラボ測定値ほどは小さくならないので、実施例Cが実機に適用された場合の保温性は、実施例Aや実施例Bに比べるとやや劣った。 However, in Example C, the binder content is 1% by mass, which is slightly less than the lower limit of 1.5% by mass. Compared to Example B, the number was slightly higher. When granule particles are pulverized, the bulk specific gravity after thermal collapse is not as small as in laboratory measurements, so the heat retention when Example C is applied to an actual machine is compared to Example A or Example B. Somewhat inferior.
表1のDは、本願の請求項を満たさない比較例である。
比較例Dは、膨張性黒鉛を含有しない従来型の顆粒(俵形状の押出成型顆粒)のモールドパウダーであり、環境汚染は小さいものの、嵩比重が大きいので保温性に劣る。
D in Table 1 is a comparative example that does not satisfy the claims of the present application.
Comparative Example D is a mold powder of a conventional granule that does not contain expansive graphite (an extrudate-shaped extruded granule). Although the environmental contamination is small, the bulk specific gravity is large, so that the heat retaining property is inferior.
表1のEも、本願の請求項を満たさない比較例である。
比較例Eは、従来型の粉末のモールドパウダーであり、嵩比重が比較的小さいので保温性には優れるものの、環境汚染が大きいのが難点である。また比較例Eの嵩比重は、粉末のモールドパウダーとしては小さい部類に属するが、本発明の実施例A〜実施例Cの嵩比重ほどは小さくない。このことは、本発明に言う熱崩壊が、単に顆粒状に成形されたものが崩壊する現象を指すのではなく、発泡状の粒形態変化を伴いながら崩壊することによって元の粉末原料混合品よりも嵩比重の小さい発泡粒状の粉末に崩壊する現象を指すことを裏付ける。この発泡状の粒形態変化は、膨張性黒鉛が膨張する際に放出されるガスが引き起こしていると推定される。
E in Table 1 is also a comparative example that does not satisfy the claims of the present application.
Comparative Example E is a mold powder of a conventional type, and its bulk specific gravity is relatively small, so it is excellent in heat retention, but it is difficult to cause environmental pollution. Moreover, although the bulk specific gravity of the comparative example E belongs to a small class as a powder mold powder, it is not as small as the bulk specific gravity of Example A-Example C of this invention. This does not mean that the heat collapse referred to in the present invention is simply a phenomenon in which a granular product is collapsed, but rather than the original powder raw material mixture by collapsing while changing the foamed particle shape. This also confirms the phenomenon of collapse into a foamed granular powder having a small bulk specific gravity. This foam-like particle shape change is presumed to be caused by a gas released when the expandable graphite expands.
次に、表1の実施例Aおよび比較例Eを、具体的に連続鋳造に適用した事例を挙げて説明する。
実施例Aおよび比較例Eは、下記表2に示した化学組成(溶融後のスラグ組成であり、炭素は含まない)に配合され、連続鋳造に供された。鋳造条件は、鋳型サイズは300×400mm、鋳造速度は0.5m/minとし、炭素濃度が0.10質量%のAl−Siキルド普通鋼を鋳造した。
Next, Example A and Comparative Example E in Table 1 will be described with specific examples applied to continuous casting.
Example A and Comparative Example E were blended in the chemical composition (melted slag composition, not including carbon) shown in Table 2 below, and subjected to continuous casting. The casting conditions were as follows: mold size was 300 × 400 mm, casting speed was 0.5 m / min, and Al—Si killed plain steel with a carbon concentration of 0.10% by mass was cast.
同じ取鍋からの溶鋼を異なるストランドに分岐して鋳造し、両モールドパウダーをそれぞれ異なるストランドに供給して、鋳片品質への影響を調べた。
鋳片品質の評価は、長手方向に400mmの鋳片サンプルを採取し、その表面を塩酸を用いて酸洗し、表面に観察される直径1mm以上のピンホール数をカウントする方法によった。
The molten steel from the same ladle was branched into different strands and cast, and both mold powders were supplied to different strands to examine the influence on the slab quality.
The slab quality was evaluated by a method in which a slab sample having a length of 400 mm was taken in the longitudinal direction, the surface was pickled with hydrochloric acid, and the number of pinholes having a diameter of 1 mm or more observed on the surface was counted.
その結果、実施例Aを用いて鋳造した鋳片表面のピンホール数は、比較例Eを用いた場合のピンホール数を100とした場合に、28にまで低減した。これは、本発明によるモールドパウダーの保温性向上効果の現れと考えられる。さらに、実施例Aは、比較例Eに比べて、鋳造中に発生する粉塵が少なく、環境汚染が小さいことが確認された。 As a result, the number of pinholes on the slab surface cast using Example A was reduced to 28 when the number of pinholes using Comparative Example E was set to 100. This is considered to be the manifestation of the heat retention improvement effect of the mold powder according to the present invention. Furthermore, it was confirmed that Example A had less dust generated during casting and less environmental pollution than Comparative Example E.
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.
本発明は、実施例に示したような鋼の連続鋳造のみならず純Ni等の連続鋳造にも適用できる。
The present invention can be applied not only to continuous casting of steel as shown in the examples but also to continuous casting of pure Ni or the like.
Claims (4)
加熱時に顆粒状のモールドパウダーが熱崩壊し、
熱崩壊後に膨張性黒鉛を含む炭素を完全燃焼させた後の嵩比重が、炭素原料を除く原料粉末の混合体の嵩比重よりも小さく、かつ0.65g/cc以下であることを特徴とする溶融金属の連続鋳造に用いるモールドパウダー。 A granular mold powder containing expansive graphite,
The granular mold powder collapses when heated,
The bulk specific gravity after completely burning carbon containing expansive graphite after thermal collapse is smaller than the bulk specific gravity of the raw material powder mixture excluding the carbon raw material, and is 0.65 g / cc or less. Mold powder used for continuous casting of molten metal.
前記膨張性黒鉛の含有量が1.5〜4.0質量%であることを特徴とする請求項1に記載の溶融金属の連続鋳造に用いるモールドパウダー。 The content of the binder for granulation is 1.5 to 5.0% by mass,
The mold powder used for continuous casting of molten metal according to claim 1, wherein the content of the expandable graphite is 1.5 to 4.0% by mass.
炭酸塩の合計含有量が10質量%未満であることを特徴とする請求項1又は2に記載の溶融金属の連続鋳造に用いるモールドパウダー。 The total content of Na 2 O, K 2 O and Li 2 O, which are alkali metal oxides, is 7% by mass or less,
The mold powder used for continuous casting of molten metal according to claim 1 or 2, wherein the total content of carbonate is less than 10% by mass.
The mold powder used for continuous casting of molten metal according to any one of claims 1 to 3, wherein the content of carbon black is 0.8 mass% or less or is not contained.
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JPH1110297A (en) * | 1997-06-27 | 1999-01-19 | Sumitomo Metal Ind Ltd | Mold powder for continuous casting |
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