JPS61115653A - Continuous casting method of medium-carbon steel - Google Patents

Abstract

PURPOSE:To produce a deflectless ingot and to make possible the economization of energy and the improvement of yield by using powder for continuous casting which is controlled in the content of sulfur by the formula. CONSTITUTION:The powder for continuous casting controlled in the content of the sulfur within the range of the formula S(%)<=0.44/Vc-0.12, where S(%) is the content of sulfur in the powder for continuous casting and V is the draw ing speed (m/min) of the ingot in continuous casting, according to the drawing speed of the ingot, is used in the case of casting continuously the steel of the medium-carbon region where the content of carbon is in a 0.06-0.15% range.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は中炭素（、（Ｃ］　：　０．０６−０．１５％
）領域の鋼の連続鋳造において、無欠陥鋳片を得る方法
に関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention provides medium carbon (C): 0.06-0.15%
) relates to a method for obtaining defect-free slabs in the continuous casting of steel in the area.

〔従来技術１発明の解決しようとする問題点〕鋼の連続
鋳造においては、Ｃ，ＳｉＯ２゜ＡＱ、○、、Ｃａ○、
Ｎａ、Ｏ，Ｆ等を主成分とした連続鋳造用パウダー（以
下ＣＣパウダーと記す）を使用するのが一般的である。[Prior Art 1 Problems to be Solved by the Invention] In continuous casting of steel, C, SiO2゜AQ, ○, Ca○,
Continuous casting powder (hereinafter referred to as CC powder) containing Na, O, F, etc. as main components is generally used.

ＣＣパウダーの使用目的は、鋳型的溶鋼表面を被覆保温
することによる溶鋼面の凝固防止および酸化防止、溶鋼
中より浮上してくる非金属介在物の吸収による鋳片表面
介在物の防止、鋳型と鋳片の間に均一に流入潤滑にする
ことによるブレークアウトの防止および鋳片表面の割れ
疵発生防止である。特にブレークアウトおよび鋳片表面
の割れ疵は溶融後のＣＣパウダーの粘性を引抜速度に応
じて適正な範囲に設計することにより防止するのが一般
的である。The purposes of using CC powder are to prevent solidification and oxidation of the molten steel surface by coating and insulating the surface of the molten steel, to prevent inclusions on the surface of the slab by absorbing non-metallic inclusions floating from the molten steel, and to prevent inclusions on the surface of the slab by absorbing non-metallic inclusions that emerge from the molten steel. This is to prevent breakouts and cracks on the surface of the slab by uniformly inflowing lubrication between the slabs. In particular, breakouts and cracks on the surface of the slab are generally prevented by designing the viscosity of the CC powder after melting to an appropriate range depending on the drawing speed.

しかし凝固時に包晶反応を経る中炭素領域（ＣＣ：］　
　ニー０．０６〜０．１５％）の鋼の連続鋳造において
は、急激な体積収縮を伴い割れが発生しやすいため、Ｃ
Ｃパウダーの粘性を狭い範囲に規制し、より均一な溶融
スラグによる潤滑膜を形成させる必要がある。引抜速度
に応じた適正なＣＣパウダーの粘性については、日本鉄
鋼協会誌「鉄と鋼Ｊ　６９　　（１９８３）１２．Ｓ−
１０３６に記されている。ところが、適正領域にコント
ロールされた粘性範囲のＣＣパウダーを使用しても、鋳
片表面に割れが発生することがある。本発明は、従来法
では防止できなかった鋳片の割れを防止することを目的
としたものである。However, the medium carbon region (CC:) undergoes a peritectic reaction during solidification.
In continuous casting of steel with a carbon content of 0.06 to 0.15%, cracks are likely to occur due to rapid volumetric contraction.
It is necessary to control the viscosity of the C powder within a narrow range to form a more uniform lubricating film of molten slag. Regarding the appropriate viscosity of CC powder depending on the drawing speed, please refer to the Journal of the Iron and Steel Institute of Japan, "Tetsu to Hagane J 69 (1983) 12.S-
1036. However, even if CC powder with a viscosity controlled to an appropriate range is used, cracks may occur on the surface of the slab. The object of the present invention is to prevent cracking of cast slabs, which could not be prevented by conventional methods.

ｃ問題点の解決手段〕 本発明は炭素含有量が０．０６〜０．１５％の範囲にあ
る中炭素領域の鋼の連続鋳造において、鋳片引抜速度に
応じて次式 但しＳ（％）；連続鋳造用パウダー中の硫黄含有量（％
） Ｖ；連続鋳造の鋳片引抜速度（ｍ／ｍｉｎ）の範囲内に
硫黄の含有量を規制した連続鋳造用パウダーを使用する
ことにより無欠陥鋳片を得る連続鋳造法である。Solution to Problem c] The present invention is applicable to continuous casting of steel in the medium carbon range with a carbon content in the range of 0.06 to 0.15%, according to the following formula, S (%), depending on the slab drawing speed. ; Sulfur content in powder for continuous casting (%
) V: A continuous casting method that obtains defect-free slabs by using powder for continuous casting whose sulfur content is controlled within the range of the slab drawing speed (m/min) of continuous casting.

〔作用〕[Effect]

鋼中の硫黄（以下Ｓと記す）は、溶鋼の表面張力を下げ
るとともに鋼の脆性を増す働きがある。Sulfur (hereinafter referred to as S) in steel has the function of lowering the surface tension of molten steel and increasing the brittleness of steel.

このため連続鋳造鋳型内の溶鋼メニスカス半径は小さく
なり、かつ変形能が低下し鋳片表面に割れが発生しやす
くなる。さらに、オシレーションが深くなるため、オシ
レーション谷部で横割れが発生しやすくなる。また鋳造
速度が速くなるにつれ、初期に形成されるシェル厚は段
々薄くなるため、Ｓの影響はより大きくなる。Therefore, the radius of the molten steel meniscus in the continuous casting mold becomes smaller, and the deformability decreases, making it easier for cracks to occur on the surface of the slab. Furthermore, since the oscillation becomes deeper, transverse cracks are more likely to occur at the oscillation valley. Furthermore, as the casting speed increases, the initially formed shell thickness becomes progressively thinner, so the influence of S becomes larger.

したがって鋳片表面割れの発生しやすい中炭素領域の鋼
の連続鋳造においては鋼中のＳは低い方が好ましく、例
えばＳを０．０１％以下に押えるのが最近の脱硫技術の
進歩によって一般的である６本発明者は、実験によりＣ
Ｃパウダー中のＳが鋳片表層に移行することを確認し、
移行したＳは鋳片表層において溶鋼中のＳが増加したの
と同じ影響が、鋳片表面割れとなって現われることを確
認峯 した。また、ＣＣパウダー中のＳ含有許容量は鋳片引抜
速度と相関があることを見い出した。すなわち鋳片引抜
速度に応じて適正範囲の粘性を持ち、Ｓ含有量を変化さ
せたＣＣパウダーを用いて鋳造を行い、鋳片表面割れの
発生状況をｔＲ察した結果、中炭素領域の鋼の連続鋳造
においては、鋳片引抜速度に応じて次式 但しＳ（％）；ＣＣパウダー中のＳ含有量（％）ｖｃ；
連続鋳造の鋳片引抜速度（ｍ／ｍｉｎ）の範囲内にＣＣ
パウダー中のＳ含有量を下げることにより割れ発生のな
い良質の無欠陥鋳片の得られる事が明らかとなった。Therefore, in continuous casting of steel in the medium carbon range where slab surface cracks are likely to occur, it is preferable that the S content in the steel be low. For example, with recent advances in desulfurization technology, it is now common to suppress S to 0.01% or less. 6 The inventor has experimentally determined that C
It was confirmed that S in the C powder migrated to the surface layer of the slab,
It was confirmed that the transferred S had the same effect as an increase in S in molten steel on the surface layer of the slab, resulting in cracks on the slab surface. Furthermore, it has been found that the allowable S content in the CC powder is correlated with the slab drawing speed. In other words, as a result of casting using CC powder that has a viscosity within an appropriate range and varying the S content depending on the slab drawing speed, and observing the occurrence of slab surface cracks by tR, it was found that steel in the medium carbon range. In continuous casting, the following formula is used depending on the slab drawing speed, where S (%); S content (%) in CC powder vc;
CC within the range of continuous casting slab drawing speed (m/min)
It has become clear that by lowering the S content in the powder, it is possible to obtain defect-free cast slabs of good quality without cracking.

Ｓ含有量と鋳片表面割れの関係については、日本鉄鋼協
会誌「鉄と鋼Ｊ　５９．（１９７３）２゜５−９４に記
述がある。これは鋳片引抜速度がある速度以下に限定さ
れた場合には表面割れは発生しないが、鋳片引抜速度が
速くなった場合はさらにＣＣパウダー中のＳ含有量を低
く規制しなければならないことを示している。本法はこ
の考え方をさらに発展させ、ＣＣパウダー中のＳの値と
、鋳片表面割れの関係を定量的に把握したものである。The relationship between S content and slab surface cracking is described in the Iron and Steel Institute of Japan, ``Tetsu to Hagane J 59. (1973) 2゜5-94. However, when the slab drawing speed increases, it is necessary to control the S content in the CC powder even lower.This method further develops this idea. The relationship between the S value in CC powder and slab surface cracking was quantitatively understood.

〔実施例〕〔Example〕

第１表に実際操業に使用した各ＣＣパウダーの成分、物
性を示す。第２表に溶鋼の成分を示す。Table 1 shows the components and physical properties of each CC powder used in the actual operation. Table 2 shows the composition of molten steel.

第１図〜第５図に各ＣＣパウダーを鋳片引抜速度を変え
て鋳造した時の鋳片表面割れ疵の発生状況を示す。第１
図〜第５図から、鋳片表面割れが発生していない所の鋳
片引抜速度とＣＣパウダー中のＳの含有量の関係を示し
たのが第６図であり、鋳片表面割れは鋳片引抜速度に応
じてＣＣパウダー中のＳ含有量を規制することにより発
生しなくなることが明瞭である。第７図に本発明による
ＣＣパウダーの使用を開始する前と後の鋳片の割れ発生
状況を示すが、本発明によるＣＣパウダーを使用するこ
とにより鋳片割れ疵が大幅に改善された。FIGS. 1 to 5 show the occurrence of cracks on the slab surface when each CC powder was cast at different slab drawing speeds. 1st
From Figures 5 to 5, Figure 6 shows the relationship between the slab withdrawal speed and the S content in the CC powder where slab surface cracks have not occurred. It is clear that this problem can be prevented by regulating the S content in the CC powder according to the one-sided drawing speed. FIG. 7 shows the occurrence of cracks in slabs before and after the use of the CC powder according to the present invention. The occurrence of cracks in slabs was significantly improved by using the CC powder according to the present invention.

〔発明の効果〕〔Effect of the invention〕

このように本発明によれば、従来法のように鋳片表面割
れ部をホットスカーフその他の手段で取除く必要がない
ため、鋳片表面を無手入のまましかも高温の状態で圧延
工程の加熱炉に装入することが可能となり、大幅な省エ
ネルギーと歩留り向上が可能となる。１例として鋳片表
面を無手入で圧延工程に送れば歩留りは約１．２％向上
し、高温の状態で加熱炉に装入すれば、約７５，０００
ｋｃａｌ／　ＴＯＮ　−５ｔｅｅｌの省エネルギーにな
る。As described above, according to the present invention, there is no need to remove cracks on the slab surface using a hot scarf or other means as in the conventional method, so the rolling process can be carried out while the slab surface is left untouched and at high temperatures. It becomes possible to charge it into a heating furnace, making it possible to significantly save energy and improve yield. For example, if the slab surface is sent to the rolling process without any maintenance, the yield will increase by about 1.2%, and if it is charged into the heating furnace at a high temperature, the yield will increase by about 75,000 yen.
Energy saving of kcal/TON -5teel.

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

第１図はパウダーＡとＢを使用したときの縦割れ発生率
を示す。 第２図はパウダーＣとＤを使用したときの縦割れ発生率
を示す。 第３図はパウダーＥとＦを使用したときの縦割れ発生率
を示す６ 第４図はパウダーＧとＨを使用したときの縦割れ発生率
を示す。 第５図はパウダーエとＪを使用したときの縦割れ発生率
を示す。 第６図は第１図〜第５図から鋳片表面割れが発生してい
ない所の鋳片引抜速度とＣＣパウダー中のＳ含有量の関
係を示す。 第７図は本発明によるＣＣパウダーの使用を開始する前
と後の鋳片の割れ発生状況を示す。 特許出願人　　新日本製鐵株式会社 日鐵建材工業株式会社 代理人　　　弁理士　　　古島　　寧 第１図　　　第２図 第３図 鋳片引４反Ｕ〜、・ｎ） 第４図 第５図 鋳片３１易３乞斐（グん・〃）゛ 第６図 ７、□　　　　　　　　　　　　　　Ａ　、ｆ　　　　
　　　　　　　　　　２．０４与片引４友達度（ｍ／次
ｒ’ｎ） 第７図FIG. 1 shows the incidence of vertical cracking when powders A and B were used. FIG. 2 shows the incidence of vertical cracking when powders C and D were used. Figure 3 shows the incidence of vertical cracks when powders E and F are used6 Figure 4 shows the incidence of vertical cracks when powders G and H are used. FIG. 5 shows the incidence of vertical cracking when Powder E and J were used. FIG. 6 shows the relationship between the slab drawing speed and the S content in the CC powder at locations where slab surface cracks have not occurred from FIGS. 1 to 5. FIG. 7 shows the occurrence of cracks in slabs before and after the start of use of the CC powder according to the present invention. Patent Applicant: Nippon Steel Corporation Nippon Steel Kenzai Kogyo Co., Ltd. Representative Patent Attorney Yasushi Furushima Easy 3 begging (gun 〃) ゛Figure 6 7, □ A, f
2.04 Y/K 4 Friendship level (m/next r'n) Figure 7

Claims (1)

【特許請求の範囲】 炭素含有量が０．０６〜０．１５％の範囲にある中炭素
領域の鋼の連続鋳造において鋳片引抜速度に応じて次式 Ｓ（％）≦０．４４／Ｖｃ−０．１２ 但しＳ（％）；連続鋳造用パウダー中の硫黄含有量（％
） Ｖ；連続鋳造の鋳片引抜速度（ｍ／ｍｉｎ）の範囲内に
硫黄の含有量を規制した連続鋳造用パウダーを使用する
ことにより、無欠陥鋳片を得る連続鋳造法。[Claims] In continuous casting of steel in the medium carbon range with a carbon content in the range of 0.06 to 0.15%, the following formula S (%) ≦ 0.44/Vc is determined depending on the slab drawing speed. -0.12 However, S (%): Sulfur content (%) in continuous casting powder
) V: A continuous casting method in which defect-free slabs are obtained by using powder for continuous casting in which the sulfur content is controlled within the range of the continuous casting slab drawing speed (m/min).