JPS609559A - Surface cleaning method of continuous casting billet - Google Patents

Abstract

PURPOSE:To enable drawing of a billet having no surface defect at a high speed by covering the surface of the molten steel in the casting space of a continuous casting machine with a covering material contg. both of an agent to be oxidized and an oxidizing agent having high calorific value of reaction. CONSTITUTION:A continuous casting machine produces a thin billet 3 by pouring a molten steel 2 through an immersion nozzle 1 into a casting space 7 formed of a pair of oppositely disposed movable belts 4, 4' which form the wall surfaces on the long side of the billet 3 and move in synchronization with the billet 3 and a pair of stationary side plates (not shown in the figure) which form the wall surfaces on the short side of the billet 3 and have a convergent shape and drawing said billet 3 at >=4m/min casting speed. A covering material contg. both of an agent to be oxidized and an oxidizing agent and having >=150kcal reaction heat of both agents at 25 deg.C for each 1kg of the covering material is added to the molten steel 2 in the above-mentioned casting space 7 as the covering material for covering the surface of said steel, thereby cleaning the surface of the billet 3 and yielding the billet 3 having no surface defect.

Description

【発明の詳細な説明】 この発明は、連続鋳造鋳片の表面清浄化方法に関し、と
くに従来高速で鋳片を引抜く場合に懸念された鋳片の表
面性状の劣化を有利に回避して、清浄な表面を得ようと
するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning the surface of continuously cast slabs, and in particular, advantageously avoids deterioration of the surface properties of slabs, which was a concern when conventionally drawing slabs at high speed. The aim is to obtain a clean surface.

最近、第１図に示したような、鋳片短辺側が先すぼまり
状になる鋳造空間をそなえるいわゆる絞り込み式の連続
鋳造鋳片が開発され、溶鋼から直接厚み８０節程度の薄
肉鋳片の製造が可能になった。Recently, so-called continuous cast slabs of the drawing type, which have a casting space where the short sides of the slab taper into a tapered shape, as shown in Fig. 1, have been developed. became possible to manufacture.

第１図に示したところにおいて、番号１は浸漬ノズル、
２は溶鋼、８は凝固鋳片、モして４，４′はエンドレス
金属ベルトからなるを可とする可動帯状体であって、こ
れらの可動帯状体４，４′は鋳片長辺側の壁面を形成し
つつ鋳片３の移動と同期して移動するしくみとされる。In the place shown in FIG. 1, number 1 is an immersion nozzle;
Reference numeral 2 indicates molten steel, 8 indicates a solidified slab, and 4 and 4' are movable belt-like bodies that can be made of endless metal belts. It is designed to move in synchronization with the movement of the cast slab 3 while forming the same.

また５、５／は可動帯状体４の支持ロール、６１６’：
よ水冷パッドである。なお図示は省略したが、可動帯状
体４．４′の側縁近傍には、鋳片短辺側の壁面を形成す
る、垂直でかつ先細り形状になる一対の固定側板がはめ
込まれて°いて、これらと可動帯状体４，４′とで鋳造
空間７を形成する。かような構成になる連続鋳造装置に
おいて、浸漬ノズルｌを介して鋳造空間７に注入された
溶鋼は、長辺側については可動帯状帯４゜４′の背後の
水冷パッド６．６′によって凝固が促進されて肉厚を増
しつつシェルを形成し、一方短辺側についてはシェルの
形成を遅らせることにより、薄肉の鋳片が製造できるわ
けである。なお鋳造空間７において、鋼浴面は図示した
程度Ａ−Ａ’レベルに保持するが、絞り込み部に引続（
Ｂ−Ｂ’レベル以下の一定厚さ部で凝固を完了するよう
な条件で操業することが肝要である。Further, 5, 5/ is a support roll of the movable band-like body 4, 616':
It's a water cooling pad. Although not shown in the drawings, a pair of vertical and tapered fixed side plates are fitted near the side edges of the movable strip 4.4' and form a wall surface on the shorter side of the slab. A casting space 7 is formed by these and the movable strips 4, 4'. In the continuous casting apparatus configured as described above, the molten steel injected into the casting space 7 through the immersion nozzle l is solidified on the long side by the water cooling pad 6, 6' behind the movable band 4°4'. This promotes the formation of a shell while increasing the wall thickness, while delaying the formation of the shell on the short side, making it possible to produce a thin slab. In the casting space 7, the steel bath surface is maintained at the level A-A' as shown in the figure, but the surface of the steel bath is maintained at the level shown in the figure.
It is important to operate under conditions such that solidification is completed at a certain thickness below the B-B' level.

ところでこの種連続鋳造装置においても、従来同様、鋳
型的溶鋼表面の保温および酸化防止、さらには鋳型と鋳
片との間隙へ浸入することによる冷却効率の向上などの
ために、溶滓化性の粉粒状被覆剤を鋼浴表面に添加する
必要がある。By the way, in this type of continuous casting equipment, as in the past, in order to keep the molten steel surface warm and prevent oxidation, and to improve the cooling efficiency by penetrating into the gap between the mold and the slab, the slag-forming property has to be reduced. A granular coating must be added to the steel bath surface.

しかるにかような絞り込み式連続鋳造法においては、生
産性を確保するために、鋳片の引き抜き速度が４１７１
７．ｉ。以上の高速鋳造が望まれるところ、従来の被覆
剤は溶滓化速度が遅かったために、十分滓化していない
粉粒状のままあるいは焼結体の状態で可動帯状体と溶鋼
との間にとり込まれ、鋳片表面にのろかみなどの表面欠
陥が生じるところに問題を残していた。However, in such a drawing continuous casting method, in order to ensure productivity, the drawing speed of the slab is set at 4171.
7. i. Although high-speed casting is desired, conventional coating materials have a slow slag formation rate, so they are trapped between the movable strip and the molten steel in the form of powder particles that have not sufficiently slaged or in the form of sintered bodies. However, there remained a problem in that surface defects such as sluggishness occurred on the surface of the slab.

この発明は、上記の問題を有利に解決するもので、４１
ｎ／ｍ１０以上の高鋳造速度で引き抜いてものろかみな
どの表面欠陥を生じることのない鋳片表面の効果的な清
浄化を可能ならしめるものであり、そのためには、被覆
剤中に積極的に酸化剤ならびに被酸化剤を添加して、両
者の酸化発熱を利用することが、所期した目的の達成に
極めて有効であることの新規知見に由来する。This invention advantageously solves the above problems, and 41
This makes it possible to effectively clean the surface of a slab without causing surface defects such as sluggishness when drawn at a high casting speed of n/m10 or more. This is derived from the new finding that adding an oxidizing agent and an oxidizable agent to the oxidizing agent and utilizing the oxidation heat generated by both is extremely effective in achieving the intended purpose.

すなわちこの発明は、鋳片遠辺側の壁面を形成しつつ鋳
片の移動と同期して移動する、一対の対向配置になる可
動帯状体と、これら両回動帯状体にその側縁近傍で挾ま
れて鋳片短辺側の壁面を形成する、画直でかつ先細り形
状になる一対の固定側板とで鋳造空間を形成する連続鋳
造機を用いて、’　”ｍｉｎ以上の鋳造速度で薄鋳片を
連続鋳造する°に当り、鋳造空間内の溶鋼表面を覆う被
覆剤として、被酸化剤と酸化剤とを併せて含有し、かつ
両者の２５℃における反応発熱量が、被覆剤１ゆ当り１
５０　Ｋｃａ１以上のものを添加することをもって、上
記課題の解決手段とするものである。In other words, this invention includes a pair of movable band-like bodies disposed opposite each other, which move in synchronization with the movement of the slab while forming a wall surface on the far side of the cast slab, and a movable band-like body arranged opposite to each other, which forms a wall surface on the far side of the slab. Using a continuous casting machine that forms a casting space with a pair of straight and tapered stationary side plates that are sandwiched together to form the walls on the short sides of the slab, thin casting can be performed at a casting speed of ``min'' or higher. When continuously casting a piece, the coating material that covers the surface of the molten steel in the casting space contains both an oxidizing agent and an oxidizing agent, and the reaction heat value of both at 25 ° C. 1
The solution to the above problem is to add 50 Kca1 or more.

この発明において、被覆剤中に含有させる被酸化剤とし
てはＡＪやＭｙなどが、また酸化剤としてはＭｎＯ２や
Ｆｅ、０．などが有利に適合する。In this invention, the oxidizable agent to be contained in the coating material is AJ, My, etc., and the oxidizing agent is MnO2, Fe, O. etc. are advantageously suited.

以下この発明を由来するに至った実験結果に基き、この
発明を具体的に説明する。This invention will be specifically explained below based on the experimental results that led to this invention.

第２図に、表１に示した成分組成になる６種（銘柄Ａ−
Ｆ）の被覆剤をそれぞれ使用して、前掲第１図に示した
連続鋳造装置により、下記の条件下に低炭アルミΦルド
鋼薄鋳片を製造した場合の表面性状について訓べた結果
を示す。Figure 2 shows six types (brand A-
The following are the results obtained regarding the surface properties when low carbon aluminum Φ-hard steel thin slabs were produced using each of the coating materials in F) using the continuous casting apparatus shown in Figure 1 above under the following conditions. .

記 ０鋼種：低炭アルミキルド鋼（０：　０．０８〜０．０
４％、　Ｓｉ　：　Ｔｒ　、　Ｉｎ　：　０．４０〜０
．５０％。Steel type: Low carbon aluminum killed steel (0: 0.08~0.0
4%, Si: Tr, In: 0.40~0
．． 50%.

Ｐ　：　０．０１０〜０．０１５％、　Ｓ　：　０．０
１０〜０．０１５％、ＡＩＢｏｌ）　：　０．０２５〜
０．０４５％）Ｏ溶鋼過熱度＝　５０℃ ０鋳造速度：４ｍｌ。P: 0.010-0.015%, S: 0.0
10~0.015%, AI Bol): 0.025~
0.045%) O Molten steel superheat degree = 50°C 0 Casting speed: 4ml.

１ｎ Ｏ鋳片サイズ：幅２００ｍ＋ｍ＋厚み３０」なお表１中
に併記した発ｆＡ尿とは、温度２５℃において実測した
被覆剤１ｋｇ当りの発熱量であり、また鋳片の表面性状
は、鋳片長さ１ｍ当りの表面のろかみ個数で評価した。1n O slab size: Width 200m + m + thickness 30" Note that the heat generated in Table 1 is the calorific value per 1 kg of coating material measured at a temperature of 25°C, and the surface texture of the slab is determined by the length of the slab. The evaluation was based on the number of surface roughnesses per meter of surface.

第２図に示した結果から明らかなように、被覆剤中に被
酸化剤および発熱用の酸化剤を含有しない従来例（銘柄
Ａ）は、のろかみ個数５５個と表面性状は極めて悪く、
また被酸化剤および酸化剤を含有させたものの２５°Ｃ
における発熱凰がこの発明の下限を下回る比較例（銘柄
Ｂ）では、表面性状は従来例に比べ幾分改善されるもの
の、やはり十分とはいい難い。As is clear from the results shown in Fig. 2, the conventional example (brand A), which does not contain an oxidizable agent or a heat generating oxidizing agent in the coating material, had an extremely poor surface quality with 55 loose particles.
Also, at 25°C for those containing an oxidizable agent and an oxidizing agent.
In the comparative example (brand B), in which the exothermic temperature in is below the lower limit of this invention, the surface quality is somewhat improved compared to the conventional example, but it is still not sufficient.

これに対し、この発明に従う被覆剤（銘柄Ｃ〜Ｆ）を用
いた場合は、のろかみの発生は皆無か、あっても極く僅
かであり、清浄な表面の鋳片が得られた。On the other hand, when the coating materials according to the present invention (brands C to F) were used, there was no or very little sluggishness, and slabs with clean surfaces were obtained.

以上実験例では、アルミキルド鋼の薄鋳片の清浄化を行
う場合について説明したが、元来、薄鋼板用素材として
は、ＡＩなどの脱酸成分が不用でありしかも清浄なリム
層をそなえるリムド鋼の方がより好適とされ、従って連
続鋳造法によってリムド鋼の薄鋳片を製造することがで
きれば、安価な薄鋼板を得る上でとりわけ有利なわけで
ある。In the above experimental example, we explained the case of cleaning a thin cast slab of aluminum killed steel. Originally, as a material for thin steel sheets, rim material does not require deoxidizing components such as AI and has a clean rim layer. Steel is considered to be more suitable, and therefore, if thin slabs of rimmed steel can be produced by continuous casting, it is particularly advantageous in obtaining inexpensive thin steel sheets.

しかしながら鋳造空間が箱型をなす従来の連続°鋳造装
置では、以下に述べるとおり、リムド鋼の円滑な鋳造は
困難であったため、これまで連続鋳造法を利用したリム
ド鋼薄板の製造は事実上不可能とされていた。However, with conventional continuous casting equipment in which the casting space is box-shaped, it has been difficult to smoothly cast rimmed steel, as described below, so it has been virtually impossible to manufacture rimmed steel thin plates using the continuous casting method. It was considered possible.

すなわち、 （１１従来の連続＠膜装置では、気泡の離脱が十分でな
いため、リム層中にスキンホールと呼ばれる小気泡が残
留し、内部性状さらには表面性状を損い易い、 （２）　溶鋼の静圧が高くなる下部においては、ＣＯガ
スの発生力が弱＜、シたがってリミングアクションが弱
いので発生ガスは気泡となって残留するところ、時とし
てこの気泡が離脱して静圧の高い下部から鋳型内湯面近
傍まで浮上すると、いわゆる突沸現象が生じ、溶鋼が飛
散する場合がｌる、 などの理由による。That is, (11) In the conventional continuous @ membrane device, bubble removal is not sufficient, so small bubbles called skin holes remain in the rim layer, which tends to damage the internal and surface properties. In the lower part where the static pressure is high, the power to generate CO gas is weak, so the rimming action is weak, so the generated gas remains as bubbles, but sometimes these bubbles break away and move to the lower part where the static pressure is high. This is because when the molten steel rises to near the surface of the mold, a so-called bumping phenomenon occurs, and molten steel may scatter.

ところで前掲した絞り込み式連続鋳造装置は、すでに述
べたように鋳造空間が下向きに先すぼまり状、逆に言え
ば上向きに末広がり状であり、従つて気泡の浮上除去に
とっては有利と考えられる。By the way, in the above-mentioned narrowing type continuous casting apparatus, the casting space is tapered downward, or conversely, widened upward, as described above, and is therefore considered to be advantageous for floating and removing air bubbles.

そこで発明者らは、かような連続鋳造装置を用いれば、
リム層中への小気泡の残留に基因した表面性状の劣化を
伴）ことなしにリムド鋼の連続鋳造を実現できるのでは
ないかと考え、この連続鋳造装置によるリムド鋼薄鋳片
の製造を試みたところ、引抜き速度が４　ｍ／、エユ程
度の高速鋳造においても発生した気泡が効果的に除去さ
れて、残留気泡がほとんどない清浄なリム層をそなえる
リムド鋼薄鋳片が得られるという、望外の成果が得られ
たのである。Therefore, the inventors believe that if such a continuous casting device is used,
We thought that it would be possible to continuously cast rimmed steel without deteriorating the surface quality due to small bubbles remaining in the rim layer, and we attempted to manufacture thin slabs of rimmed steel using this continuous casting equipment. However, we found that even in high-speed casting with a drawing speed of 4 m/E, the bubbles generated were effectively removed, and a thin rimmed steel slab with a clean rim layer with almost no residual bubbles was obtained, which was an unexpected result. results were obtained.

しかしながら引抜き速度がさらに速くなると、幾分気泡
が残留してやはり表面性状を損うきらいがあった。そこ
で発明者らはこの点についてもさらに検討を重ねた結果
、絞り込み注湯部におけるリミングは溶鋼中に水紫な少
量添加することによって著しく改善され、発生気泡の離
脱除去は極めてスムーズに進行し、かくして引抜き速度
４　ｍ４゜以上の高速鋳造においてもリムド鋼薄鋳片の
表面清浄化が効果的に達成されることを究明したのであ
る。However, when the drawing speed was increased, some air bubbles remained, which tended to impair the surface quality. Therefore, the inventors conducted further studies on this point and found that rimming at the drawing and pouring section was significantly improved by adding a small amount of water purple to the molten steel, and the removal of generated bubbles proceeded extremely smoothly. Thus, it was found that surface cleaning of rimmed steel thin slabs can be effectively achieved even in high-speed casting at a drawing speed of 4 m4° or higher.

なお溶鋼中への水素の添加は、たとえばタンディツシュ
内の溶鋼中に炭化水素系ガスを吹込むことにより容易に
達成でき、またその添加量は、溶畑トン当り２〜１０　
ｐｐｍ程度が望ましい。The addition of hydrogen to molten steel can be easily achieved, for example, by blowing hydrocarbon gas into molten steel in a tundish, and the amount of hydrogen added is 2 to 10 per ton of molten steel.
Approximately ppm is desirable.

以下この発明の実施例について説明する。Examples of the present invention will be described below.

実施例　１ 注湯部の長辺側長さが６００　ｖａｔ　＊短辺側の鋼浴
面レベルでの厚み幅が２００１１１＋Ｋ　、一定厚さ部
での幅がＢＯ鰭で、がっ鋼浴面がら一定厚さ部までの距
ｐ１［（が５００　朋になる絞り込み式の連続＠造装置
を用いて、Ｇ　：　０．０５％、　Ｍｎ　：　０．８５
％を含むリムド鋼溶鋼を、４　ｍｌ、□。の引抜き速度
で鋳造し、リムド鋼の薄１片を製造した。使用した被覆
剤の成分組成および発熱量は次のとおりである。Example 1 The length of the long side of the pouring part is 600 vat *The thickness width at the steel bath surface level on the short side is 200111+K, the width at the constant thickness part is BO fin, and the width is constant from the steel bath surface. The distance to the thickness part p1 [( is 500 mm).
4 ml of molten steel containing %. A thin piece of rimmed steel was produced by casting at a drawing speed of . The composition and calorific value of the coating material used are as follows.

０被覆削成分組成（重量％） ０２５℃における被覆剤１ｋｌｉ＋当りの発熱量：２５
０Ｋｃａ／ 得られたリムド鋼薄鋳片の表面を観察したところ、のろ
かみの発生は皆無であり、美麗で清浄な表面性状を呈し
ていた。0 Coating cutting component composition (wt%) 0 Calorific value per 1kli+ of coating material at 25°C: 25
0 Kca/ When the surface of the obtained rimmed steel thin slab was observed, no sluggishness was observed, and the surface had a beautiful and clean surface quality.

実施例　２ 実施例１に述べたのと同じ連続鋳造装置を用いて、Ｏ：
　０．０５％、　Ｉｎ　：　０．８５％を含みかつタン
ディツシュ内でプロパンを０．８　Ｎｍ８／　トンの割
合で添加したリムド鋼溶鋼を、６ｒｎ／ｒ１１よｎの引
抜き速度で鋳造し、リムド鋼の薄鋳片を製造した。使用
した被覆剤の成分組成および発熱量は次のとおりである
。Example 2 Using the same continuous casting equipment as described in Example 1, O:
Molten rimmed steel containing 0.05% In and 0.85% In and propane added at a rate of 0.8 Nm8/ton in a tundish was cast at a drawing speed of 6rn/r11 to form a rimmed steel. A thin slab was manufactured. The composition and calorific value of the coating material used are as follows.

０被覆削成分組成（重量％） ＯＺ　５　”Ｃにおける被覆剤１ｋｇ当りの発熱量：２
５０ＫｃａＪ 得られたリム１゛鋼薄鋳片の表面には、のろかみ°は全
く観察されず清浄な表面であった。0 Coating cutting component composition (wt%) Calorific value per 1 kg of coating material at OZ 5 ”C: 2
50KcaJ The surface of the obtained rim 1 steel thin slab had a clean surface with no sluggishness observed at all.

なおこのリムド鋼鋳片を、常法に従って０．８図面厚の
薄鋼板に圧延加工してみたところ、その表面は美麗であ
って造塊法で製造したものと比べてみても、その表面性
状は同等かそれ以上であった。When this rimmed steel slab was rolled into a thin steel plate with a drawing thickness of 0.8 in accordance with the conventional method, the surface was beautiful and the surface quality was even better than that produced by the ingot method. was the same or better.

以上述べたようにこの発明によれば、引抜き速度が４ｍ
／ｍ□。以上の高速の連続鋳造においても、のろかみな
どの欠陥の発生な貼止して、鋳片表面の清浄化が達成で
き、またとりわけリムド鋼の連続鋳造においては、残留
気泡に基因したリム層の表面劣化も併せて効果的に阻止
して美麗な表面性状とすることができ、有利である。As described above, according to this invention, the drawing speed is 4 m
/m□. Even in the above-mentioned high-speed continuous casting, it is possible to clean the slab surface by pasting without causing defects such as sluggishness. It is also advantageous because it can effectively prevent surface deterioration and provide beautiful surface properties.

【図面の簡単な説明】[Brief explanation of drawings]

第１図はこの発明の実施に用いて好適な絞り込み式連続
鋳造装置の断面図、 第２図は被覆剤の２５°Ｃにおける発熱量とのろかみ１
固数との１３’Ｊ　ｆ系を示したグラフである。Fig. 1 is a sectional view of a drawing type continuous casting apparatus suitable for carrying out the present invention, and Fig. 2 shows the calorific value and slowness of the coating material at 25°C.
It is a graph showing a 13'J f system with a fixed number.

Claims (1)

【特許請求の範囲】 Ｌ　鋳片艮辺側の壁面を形成しつつ鋳片の移動と同期し
て移動する、一対の対向配置になる可動帯状体と、これ
ら両回動帯状体にその側縁近傍で挾まれて鋳片短辺側の
壁面を形成する、垂直でかつ先細り形状になる一対の固
定側板とで鋳造空間を形成する連続鋳造機を用いて、’
　”’ｍｉｎ以上の鋳造速度で薄鋳片を連続鋳造するに
当り、鋳造空間内の溶鋼表面を偉う被覆剤として、被酸
化剤と酸化剤とを併せてき有し、かつ両者の２５℃にお
ける反応発熱量が、被覆剤１ｋｇ当り１５０　Ｋｃａｊ
！以上のものを添加することを特徴とする連続鋳造鋳片
の表面清浄化方法。 ２　溶鋼が、リムド鋼である特許請求の範囲第１項記載
の方法。 ＆　溶鋼が、水素を含むリムド鋼である特許請求の範囲
第１項記載の方法。[Scope of Claims] L A pair of movable band-like bodies disposed opposite each other, which move in synchronization with the movement of the slab while forming a wall surface on the side of the slab, and a side edge of both rotating belt-like bodies. Using a continuous casting machine, a casting space is formed by a pair of vertical and tapered stationary side plates that are sandwiched in the vicinity to form a wall surface on the short side of the slab.
When continuously casting thin slabs at a casting speed of 10 min or higher, the molten steel surface in the casting space is coated with an oxidizing agent and an oxidizing agent, and both of them at 25°C. The reaction heat value is 150 Kcaj per 1 kg of coating material.
! A method for cleaning the surface of continuously cast slabs, characterized by adding the above substances. 2. The method according to claim 1, wherein the molten steel is rimmed steel. & The method according to claim 1, wherein the molten steel is rimmed steel containing hydrogen.