TWI268820B - Method for producing ultra low carbon steel slab - Google Patents
Method for producing ultra low carbon steel slab Download PDFInfo
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- TWI268820B TWI268820B TW093125776A TW93125776A TWI268820B TW I268820 B TWI268820 B TW I268820B TW 093125776 A TW093125776 A TW 093125776A TW 93125776 A TW93125776 A TW 93125776A TW I268820 B TWI268820 B TW I268820B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/14—Plants for continuous casting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D41/00—Casting melt-holding vessels, e.g. ladles, tundishes, cups or the like
- B22D41/50—Pouring-nozzles
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
Abstract
Description
1268820 融鋼表面，以防止使用於將熔融鋼自分配器（t u n d i s h )供給 至模具中之浸入噴嘴阻塞。當經捲入於熔融鋼中時，經如 此供給之氬氣可僅以氣泡形式殘留於熔融鋼中，或可與經 由前述之去氧化作用形成之反應產物（以下稱為「去氧化反 應產物」）結合，而形成殘留於熔融鋼中之氣泡。在前述之 兩種情況中皆會產生表面瑕疵。此外，當如此添加之模具 粉末殘留於熔融鋼中時，亦會產生與去氧化反應產物類似 的表面瑕疲。 在過去，在經由用於形成冷軋鋼板之連續鑄造製備得之 一般扁鋼胚的情況中進行熱軋，而不進行扁鋼胚之表面處 理。然而，在使用於形成汽車外板之扁鋼胚的情況中，例 如，經由嵌接將厚度大約1至4毫米之扁鋼胚的表面部分 移除，以將會導致於熱軋之後形成之鋼板之表面瑕疵之去 氧化反應產物、氣泡、模具助炫劑及其類似物的包含物移 除，及接著再進行熱軋及冷軋。 如前所述之扁鋼胚完成處理令使用作為原料之扁鋼胚 的產率減小，此外，其會不利地導致製程的延遲。因此， 在使用連續鑄造裝置製造扁鋼胚之步驟中，嘗試防止會導 致前述鋼板表面瑕疵之扁鋼胚表面瑕疵的產生。 前述嘗試之基本概念主要係基於以下的（1 )至（6 )項： (1 )提高扁鋼胚厚度，以致其之截面積增加，而減小鑄 造速度（米/分鐘），由於當經輥軋時，扁鋼胚寬度受限。 因此，不使生產力退化而使熔融鋼於模具中之滯留時間增 加，結果，使外來物質諸如去氧化反應產物、模具粉末、 6 312/發明說明書(補件)/93-11 /93125776 1268820 氣泡及其類似物自模具中之熔融鋼内部消除至表面的時間 增力σ 。 (2 )使用具有垂直部分之連續鑄造裝置進行鑄造，以使 去氧化反應產物、模具粉末、氣泡及其類似物可逐漸自模 具中之熔融鋼内部移至表面而分離。 (3 )藉由電磁力在彎月面附近產生在水平方向中移動的 流動，以致可防止浮於炫融鋼中之外來物質被固化外殼陷 入（洗滌效應）。 (4 )適當控制模具粉末之黏度，以減小模具粉末被捲入 熔融鋼中的可能性。 (5 )適當控制供連續鑄造用之模具的震盪（垂直振動）條 件，以降低於模具中形成之固化外殼之硬殼（n a i 1 )的產生 (部分固化外殼由於震盪而朝熔融鋼側傾斜的現象），因而 減小陷於此硬殼内之去氧化反應產物、模具粉末、氣泡及 其類似物的量。 (6 )經由對自浸入噴嘴供給至模具内之熔融鋼的流動進 行電磁攪拌或運用電磁制動，適當地控制熔融鋼之流動， 以致防止伴隨去氧化反應產物之熔融鋼的流動到達模具中 之深處。 舉例來說，日本未審查專利申請案公告第5 - 7 6 9 9 3號中 揭示一種當使用具2 0米或以上長度之垂直部分之連續鑄 造裝置在1 . 0米/分鐘或以上及4噸/分鐘或以上之鑄造 速度下進行包含低於0 . 1 0重量％碳之熔融鋼之鑄造，而形 成具多於200毫米厚度及多於900毫米寬度之扁鋼胚，同 312/發明說明書(補件)/93-11 /93125776 7 1268820 時將粉末黏度設為1 . 0泊（p 〇 i s e )以上，及將來自浸入 之惰性氣體流率設為1公升/分鐘或以上時，對存在 彎月面至1 . 5米深度之區域中之熔融鋼在水平方向中 至4 0公分/秒之流動速度下進行電磁攪拌的技術。此 主要係基於以上的段落（1 )、（ 2 )、（ 3 )、（ 4 )、及（6 ) 此外，曰本未審查專利申請案公告第7 - 1 5 5 9 0 2號1 示一種適當地控制模具震盪條件，以抑制包含物易陷 其中之硬殼部分之產生的技術，此硬殼部分係於扁鋼 面部分之起始固化階段形成。此技術主要係基於以上 落（5 ) 〇 然而，前述之技術仍有問題。 換言之，如日本未審查專利申請案公告第5-76993 所揭示，當扁鋼胚之截面積增加時，尤其係當其之厚 加時，在多於1 . 5米/分鐘之鑄造速度下，由包含物 類似物所造成之在扁鋼胚表面附近的瑕疵數並未減少 預期般之多。其原因為雖然經由於水平方向中施加電 而將在彎月面部分之炫融鋼之流動速度v m控制至一：ί 值，但當在與未增加截面積之情況中相同之鑄造速度 及相同之扁鋼胚寬度（W)下進行鑄造時，出料量隨扁鋼 度之增力σ而增力a ，且自浸入喷嘴之排出速度ν i增加 此，雖然熔融鋼之流動速度v m之平均值的變化小，但 變化量增加，以致模具助熔劑逐漸被捲入於熔融鋼中 言之，其顯示在扁鋼胚表面部分附近的清潔度並不僅 由在彎月面附近之熔融鋼的流動速度所決定。 312/發明說明書(補件)/93-11 /93125776 喷嘴 於自 在1 5 技術 卜揭 入於 胚表 的段 號中 度增 或其 地如 磁力 k佳 (Vc) 胚厚 5因 其之 。換 只是 8 1268820 此外，來自浸入喷嘴之熔融鋼之喷射流動的影響變得顯 著，且外殼之成長沿模具之短邊部分延遲。其原因為在扁 鋼胚連續鑄造裝置之情況中，當將熔融鋼排入至模具中 時，由於使用所謂的「雙嘴（t W 0 - S P 0 u t )喷嘴」於沿存在於 模具中之鑄造空間之寬度方向均勻供給熔融鋼，且此雙嘴 噴嘴之排出嘴的寬度d相較於模具内的短邊長度D (相當於 扁鋼胚之厚度）相當小，因而熔融鋼之流動速度於扁鋼胚厚 度方向中改變。因此，具高流動速度之熔融鋼不均勻地撞 擊沿短邊之一部分的固化外殼，以致此部分前述固化外殼 之成長延遲。此外，在扁鋼胚厚度方向中之熔融鋼之流動 速度的變化亦部分促成在前述彎月面附近之熔融鋼之流動 速度的變化。 接下來，在日本未審查專利申請案公告第7-155902號 所說明之技術中，為改良扁鋼胚表面品質，當經由調整模 具震盪條件，尤其係經由減小模具震盪振幅及經由提高模 具之震盪頻率，而將由鑄造速度、模具震盪振幅及模具之 震盪頻率所決定之負剝離時間（n e g a t i v e s t r i p t i m e ) T控 制於一特定範圍内時，發現其會發生以下的問題。 換言之，當經由在多於2.0米/分鐘之鑄造速度及多於 1 8 5循環/分鐘之模具之震盪頻率下形成超低碳鋼時，雖 然未相當經常地觀察到，但會發生熔融鋼表面液位突然大 大改變的異常現象。結果，模具助熔劑會被捲入於熔融鋼 中或會陷入於固化外殼中，因而產生鑄造鋼板之表面瑕 疵。因此，經常會在產物上產生當在多於2 . 0米/分鐘之 9 312/發明說明書(補件)/93-11/93125776 1268820 鎢造速度下進行鑄造時由模具助熔劑所造成的表面瑕蔽。 結果，會有無法穩定地製得具有優良表面品質之產物的問 題。 如由以上說明明顯可見，當在多於2 . 0米/分鐘之速度 下之高速鑄造中製造用於形成汽車外板及其類似物之超低 碳扁鋼胚時，無法不進行諸如嵌接之扁鋼胚調理而如同目 前進行高品質扁鋼胚的穩定製造。 因此，最好能提供一種製造超低碳扁鋼胚之連續鑄造方 法，其中即使係在多於2 . 0米/分鐘之高鑄造速度下亦能 穩定地製得不利用任何扁鋼胚調理諸如嵌接之具有優良表 面品質的扁鋼胚。 【發明内容】 本發明提供一種超低碳扁鋼胚之製造方法，其包括： 提供一連續鑄造裝置，此裝置包括設有具約1 5 0至約2 4 0 毫米之短邊長度D之鑄造空間的模具，及設有至少一具橫 向寬度d之排出嘴之浸入喷嘴，其中D / d之比係在自約1 . 5 至約3 . 0之範圍内； 經由浸入喷嘴將熔融鋼引入至模具中；及 利用連續鑄造裝置在多於約2 . 0米/分鐘之鑄造速度下 鑄造熔融鋼，而產生具約0 . 0 1質量百分比或以下之碳含量 的超低碳扁鋼胚。 扁鋼胚連續鑄造方法進一步包括在約1 8 5循環/分鐘或 以下之頻率下震盪模具較佳。熔融鋼表面液位突然大大改 變之異常現象的發生機率受到抑制。因此，由於當模具震 10 312/發明說明書(補件)/93-11/93125776 1268820 盪循環係約1 8 5循環/分鐘或以下時，在熔融鋼表面之震 盪與模具之震盪之間之諧振的發生率減小，因而可減小由 助熔劑所產生的瑕疵數。 鑄造速度係約2 . 4米/分鐘或以上較佳。當鑄造速度係 約2 . 4米/分鐘或以上時，硬殼深度成為約0 . 7毫米或以 下，即陷入外來物質之厚度成為不多於硬殼深度。因此， 將鑄造速度設為約2 . 4米/分鐘或以上較佳。 關於前述之浸入喷嘴，一般係使用圓柱形喷嘴（所謂的 「直噴嘴」）或雙嘴喷嘴（其中前端經封閉，及兩大致圓形 的排出嘴朝模具之兩短邊設置）。 當除了產品品質之外，尚將扁鋼胚厚度、浸入噴嘴耐用 性及期望流率列入考慮時，短邊長度D對浸入噴嘴之排出 嘴之橫向寬度d之比D / d係約2. 1至約2. 9較佳。 前述之超低碳扁鋼胚係用於形成汽車外板之冷軋鋼板 的原料較佳。 前述之扁鋼胚連續鑄造方法進一步包括使用電磁力對 模具之鑄造空間中之熔融鋼之流動施加制動較佳。可提及 以下的段落（A )至（C )作為使用電磁力施加制動的較佳方 法： (A )經由使用上方磁場施加裝置及下方磁場施加裝置在 與模具厚度相交之方向中對實質上整個模具施加靜磁場， 而進行使用電磁力施加制動。上方磁場施加裝置係設置於 包括模具中之熔融鋼表面液位之模具的上部，及下方磁場 施加裝置係設置於上方磁場施加裝置之下側。浸入喷嘴係 11 312/發明說明書(補件)/93-11/93125776 1268820 設置於上方及下方磁場施加裝置之間，且將浸入深度設為 約200至約350毫米。 (B )經由使用設置於包括模具中之熔融鋼表面液位之模 具之上部的磁場施加裝置在與模具厚度相交之方向中對整 個模具重疊施加靜磁場及A C磁場，而進行使用電磁力施加 制動。浸入喷嘴係設置於磁場施加裝置下方，且將浸入深 度設為約2 0 0至約3 5 0毫米。 (C )經由使用上方磁場施加裝置在與模具厚度相交之方 向中對整個模具重疊施加靜磁場及AC磁場，且除此之外， 經由使用下方磁場施加裝置在與模具厚度相交之方向中對 整個模具施加靜磁場，而進行使用電磁力施加制動。上方 磁場施加裝置係設置於包括模具中之熔融鋼表面液位之模 具的上部，及下方磁場施加裝置係設置於上方磁場施加裝 置之下側。浸入噴嘴係設置於上方及下方磁場施加裝置之 間，且將浸入深度設為約2 0 0至約3 5 0毫米。 【實施方式】 吾人發現具超低碳含量之扁鋼胚可經由除所需要之適 當控制模具之震盪頻率，或於熔融鋼流動上有效利用電磁 制動之外，再適當控制鑄造速度、連續鑄造模具之鑄造空 間的短邊長度D、及短邊長度D對浸入噴嘴之排出嘴之橫 向寬度d之比D/d而有利地製得。 根據本發明態樣之一類型的鋼係具約0 . 0 1質量百分比 或以下之碳含量之所謂的「超低碳鋼」。除C外之成分並無 特殊之限制。然而，可利用深引伸適當地加工而形成汽車 12 312/發明說明書(補件)/93 -11/93125 776 1268820 厚度）設為約1 5 0至約2 4 0毫米及將鑄造速度設為多於約 2 . 0米/分鐘之條件下進行鑄造時，在模具中發生各種現 象。接著將說明關於前述現象的新穎發現。以下將包含物、 氣泡及其類似物稱為「外來物質」。 (1 )陷入外來物質之區域的減小 當將鑄造速度V c設為多於約2 . 0米/分鐘，或以設為 約2 . 4米/分鐘或以上較佳時，可顯著地抑制在彎月面部 分之起始固化外殼（其係所謂的「硬殼」）之形成。吾人相 信其原因為由於在距熔融鋼表面液位非必需恒定深度處形 成之固化外殼之厚度因熔融鋼之靜壓力之影響而隨鑄造速 度V c之增加而減小，因而朝模具側施加之力變得較取決於 其厚度之固化外殼之熱收縮所造成之朝熔融鋼側傾斜之硬 殼的力大。此外，當扁鋼胚厚度減小時，以「扁鋼胚厚度 X溫度差X熱膨脹係數」所表示之在厚度方向中之外殼收 縮量的絕對值減小，外殼之朝熔融鋼側傾斜進一步受到抑 制，結果，抑制硬殼之傾斜的效果變得更為顯著。 圖1顯示鑄造速度對硬殼深度之影響。當鑄造速度係多 於約2. 0米/分鐘，及模具之鑄造空間之短邊長度（扁鋼胚 厚度）係約2 4 0毫米或以下時，硬殼深度變為1毫米或以 下。此外，當鑄造速度係約2 . 4米/分鐘或以上時，硬殼 深度變為約0 . 7毫米或以下。 (2 )外來物質之吸附的抑制 由於集中於固化外殼界面之溶質之離析所致之伴隨固 化，因而產生表面張力之梯度，及由於由此梯度所產生之 15 312/發明說明書(補件)/93-1〗/93125776 1268820 力，因而產生外來物質可能會被吸附或陷入於固化外殼之 界面上的現象。因此，已進行使S或T i之濃度減小的嘗試， 其作為增進吸附及陷入外來物質之力之溶質元素具有特別 顯著的影響。然而，在一些情況中，成分之操控當S減小 時會不利地導致成本增力π ，及當T i減小時會導致品質退 化。 根據本發明，經由提高鑄造速度Vc而抑制將外來物質 吸附及陷入於固化外殼界面上之力。換言之，當鑄造速度 V c高，諸如多於約2. 0米/分鐘時，由於在彎月面部分之 固化量減小，因而離析量亦減小。因此，作為吸引外來物 質之力之表面張力的梯度亦減小。結果，吸附及陷入於固 化外殼側之外來物質之量亦減小。 (3 )陷入外來物質之厚度的減小 圖2顯示在扁鋼胚之表面部分中在陷入外來物質之距扁 鋼胚表面之陷入深度h與陷入外來物質數目之間的關係。 此外，圖3顯示在陷入外來物質數目與經由轉變距扁鋼胚 表面之陷入深度h而得之距彎月面（熔融鋼之表面）之距離 L之間的關係。此轉變係根據以下方程式進行： h 二 k(L/Vc)1/2 在此方程式中，V c指示鑄造速度，及固化常數k係2 0毫 米•分鐘_ w 2。 如可由圖2及3所見，外來物質被外殼陷入於自熔融鋼 表面至2 0毫米深度之區域中。此外，陷入深度隨鑄造速度 之增加而減小，及在多於2.0米/分鐘之鑄造速度Vc下， 16 312/發明說明書(補件)/93-11 /93125776 1268820 距扁鋼胚表面之陷入深度h為1毫米或以下。 當陷入深度h為1毫米或以下時，雖然外來物質經 外殼，但在後續的程序中，形成產物通過熱軋步驟及 步驟，將外來物質與形成於鑄造鋼板表面上之氧化物 起刮除及移除。因此，可不進行扁鋼胚調理而製得無 的產物。此外，當鑄造速度係約2 . 4米/分鐘或以上 硬殼深度成為0. 7毫米或以下，換言之，陷入厚度h 為不多於硬殼深度。因此，將鑄造速度設為約2 . 4米 鐘或以上更佳。 (4 )陷入外來物質之機率的降低 外來物質可能會被固化外殼陷入之自熔融鋼表面至 毫米深度區域中之固化外殼之滯留時間係隨鑄造速度 加而減小。因此，即使當存在相同量之浮於熔融鋼中 來物質時，外來物質經固化外殼陷入的機率亦會減小 例來說，當V c為3 . 0米/分鐘時，陷入機率減低至1 為1 . 5米/分鐘時的一半。 (5 )防止熔融鋼表面液位突然變化之模具的較佳震盪步 當在多於約2. 0米/分鐘之鑄造速度V c下進行鑄ΰ 時，由於模具中之固化外殼之厚度進一步減小，因而 並非相當明顯，但會產生膨脹現象。膨脹現象係固化 受熔融鋼之靜壓力之影響被推向模具侧的現象。在此 現象中，當外殼之溫度高時，及當鋼之類型係超低碳 其具有較其他類型鋼小之外殼強度之類似物時，膨脹（ 向模具）速度變得較模具之震盪速度高。當使一般具有 312/發明說明書(補件)/93-11/93125776 陷入 冷軋 垢一 瑕疵 時， 亦成 /分 20 之增 之外 。舉 Γ Vc i率 雖然 外殼 膨脹 鋼或 被推 錐形 17 1268820 以補償由固彳匕收縮及/或熱收縮所造成之體積收縮之模具 垂直震盪時，固化外殼膨脹伴隨模具之下降的膨脹量 5 b。 相對地，伴隨模具之上升，模具利用大約相當於 δ b之推 動力 δ p推動經如此膨脹之外殼。當經簡單計算時，由此 體積變化所造成之熔融鋼表面液位之變化小，諸如低於約 1毫米。然而，當重複進行前述之現象時，熔融鋼表面液 位之震盪與模具之震盪會彼此諧振。結果，在極少的情況 中會發生熔融鋼表面液位突然大大改變的異常現象。由於 此異常現象係發生於模具之邊緣部分，因而很難使用供熔 融鋼表面用之一般的渦流型液位感測器偵測此現象。然 而，本發明人首次經由研究鑄造扁鋼胚之震盪標記隨時間 之扭曲而發現此現象。尤其，當鑄造速度多於約2 . 0米/ 分鐘及模具之震盪頻率高，諸如多於約1 8 5循環/分鐘 時，可能會觀察到前述的此異常現象。結果，模具助熔劑 會被捲入於熔融鋼中，且會陷入於固化外殼中，因而於鑄 造鋼板之表面部分中產生瑕疵。因此，在於多於約2 . 0米 /分鐘之錄造速度下錄造之情況中，由模具助炫劑所造成 之產物中之表面瑕疵的數目突然增加。結果，很難減小表 面瑕疲。 然而，由在模具之震盪頻率與助熔劑相關瑕疵對總瑕疵 之比（將此比使用作為顯示突然異常現象之發生率的指數） 之間的關係，發現當將模具之震盪頻率設為約1 8 5循環/ 分鐘或以下時，即使當鑄造速度V c多於約2 . 0米/分鐘 時，亦可有效防止如前所述的異常現象。 18 312/發明說明書(補件)/93-11 /93125776 1268820 此外，模具之震盪頻率的下限可鑑於陷入外來物質之面 積的降低而設為不使硬殼深度增力〇 ，及亦鑑於防止由模具 中之潤滑劑性質之減低（模具助炫劑之消耗量）所造成之限 制鑄漏（b r e a k 〇 u t)而設定。舉例來說，負剝離時間係約 0 . 0 2秒或以上，及負剝離長度係約0 . 1毫米或以上較佳。 負剝離時間係用於定義模具震盪條件之一特性值，且其指 示模具之下降速度高於鑄造扁鋼胚之下降速度的時間。負 剝離長度指示在負剝離時間内在模具與鑄造扁鋼胚之間的 最大距離，模具通過經引伸之鑄造扁鋼胚。當假設模具之 震盪波形具有正弦波形時，滿足7Γ S f / V c > 1，其中S指示 模具之震盪行程，f指示模具頻率，及V c指示鑄造速度。 舉例來說，當V c係2 . 0米/分鐘及S係9毫米時，模具頻 率f之下限為7 1 c p m (循環/分鐘），及當S為5毫米時， 下限為1 2 7 c p m。模具之震盪波形並不需限定為正弦波形。 此外，當考慮連續鑄造裝置之震盪條件之規格及其之可控 制性時，可適當地決定頻率之下限及波形。 (6 )防止短邊膨脹（模具之鑄造空間之短邊長度之上限的理 由） 雖然使用滿足模具之鱗造空間之短邊長度（扁鋼胚厚 度）D對浸入噴嘴之排出嘴之橫向寬度d之比D / d之浸入喷 嘴，但當短邊長度太大時，當在多於約2 . 0米/分鐘之鑄 造速度Vc下鑄造時，會發生問題。尤其會由短邊膨脹產生 與扁鋼胚形狀相關的瑕疵及/或鑄漏。相對地，當短邊長 度小時，及當鑄造速度Vc高時，可抑制由熔融鋼之靜壓力 19 312/發明說明書(補件)/93-11 /93125776 1268820 所造成之通過模具之扁鋼胚之短邊的膨脹，且鑄漏產生的 風險小。 然而，如圖4所示，當短邊長度（即扁鋼胚厚度）多於2 4 0 毫米時，雖然鑄造速度為2 . 4米/分鐘，但藉由由於扁鋼 胚厚度增加所致之來自浸入喷嘴之排出嘴之熔融鋼之喷射 流動速度的增力σ ，第二流動速度經由施加電磁制動而增 加。因此很難抑制沿短邊之外殼之成長的延遲。因此，在 模具之底部端的短邊膨脹變得明顯，且鑄漏產生的風險（1 〇 毫米或以上之膨脹量）增力π 。 此外，當短邊長度（即扁鋼胚厚度）多於2 4 0毫米時，基 於如前所述的相同理由，由於熔融鋼表面液位之波動經反 向流動及熔融鋼之喷射流動的第二流動（此等流動係來自 固化外殼之短邊）增進，因而易發生模具助炫劑的捲入及陷 入。此外，由於扁鋼胚厚度之增加，因而易發生炫融鋼停 滯於彎月面部分，尤其係於浸入喷嘴附近。結果，如圖5 所示，扁鋼胚表面瑕疵數及產品瑕疵數增加。 (7 )模具鑄造空間之短邊長度下限的理由 基於下述理由，模具鑄造空間之短邊長度（扁鋼胚厚度） 低於約1 5 0毫米並不佳。 當扁鋼胚之截面積過度減小時，鑑於熔融鋼表面液位之 可控制性，並無法得到以上的效果（1 )。其理由為當改變鑄 造量時，炫融鋼表面液位之波動相較於形成具大截面積之 扁鋼胚的情況增加。此外，由於因而形成熔融鋼波紋，因 而具1毫米或以上之深度之硬殼的產生率增力口 。此外，由 20 3 ] 2/發明說明書(補件)/93-1 ] /93125776 1268820 於熔融鋼表面液位之波動，易發生模具助熔劑的捲入及陷 入（見圖5 )。再者，一般浸入噴嘴之外徑係由考慮财用性 所決定之壁厚（約2 0毫米或以上）及為確保自5 . 4噸/分鐘 (1 5 0毫米厚，2，2 0 0毫米寬，及2 . 1米/分鐘或以上之V c ) 至1 4 . 5噸/分鐘（2 4 0毫米厚，2，2 0 0毫米寬，及3 . 5米/ 分鐘或以上之V c )之出料量所決定之内徑（約7 0至約1 3 0 毫米）的總和所決定。在此情況，當短邊長度（扁鋼胚厚度）D 過小時，在浸入喷嘴之外壁與固化外殼之長邊之間的距離 變得太小（低於2 0毫米），其間之流動變得不均勻，因而導 致縱向裂紋的產生。在一極端的情況中，固化外殼與噴嘴 接觸並與其黏合，而導致鑄漏產生。因此，將短邊長度（扁 鋼胚厚度）D設為不低於約1 5 0毫米（7 0毫米之内徑+ 4 0毫 米（2 0 X 2 )之總外壁厚度+ 4 0毫米（2 0 X 2 )之在浸入噴嘴之 外壁與固化外殼之長邊之間的距離）。 此外，模具鑄造空間之長邊長度（扁鋼胚寬度）並無特殊 之限制，其可等於普通冷軋鋼板（尤其係汽車用之冷軋鋼板 之寬度。大約9 0 0至2，2 0 0毫米之長度為較佳。 模具之垂直方向中的高度並無特殊之限制。然而，由於 必需形成具有特定厚度之固化外殼，以致即使當在多於約 2 . 0米/分鐘之鑄造速度下進行鑄造時，通過模具之鑄造 扁鋼胚亦不會膨脹，因而將高度設為大約8 0 0至1，0 0 0毫 米較佳。 (8 )模具鑄造空間之短邊長度D對浸入噴嘴之排出嘴之橫 向寬度d之比D / d的最佳化 21 312/發明說明書(補件)/93-11/93125776 1268820 雖然經減速，但由浸入噴嘴之排出嘴噴出之熔融鋼於其 之寬度延伸，直至其碰撞到短邊外殼為止。然而，碰撞到 短邊外殼之熔融鋼的減速程度及喷射流動速度之分佈係視 扁鋼胚寬度W、鑄造速度Vc、及D/d比而定。當浸入噴嘴 之排出嘴之寬度d相對於模具之鑄造空間之短邊長度（扁 鋼胚寬度）D太小（D/d太大）時，隨D、Vc及W之增加，具 高流動速度之熔融鋼碰撞短邊外殼之區域寬度對扁鋼胚厚 度（短邊寬度）之比減小。因此，固化外殼之成長變得不均 勻，且易受干擾。此外，當固化外殼之厚度極度減小時， 在一些情況中會發生鑄漏。另一方面，當浸入噴嘴之排出 嘴之寬度d相對於模具之鑄造空間之短邊長度（扁鋼胚寬 度）D太大（D / d太小）時，隨D、V c及W之增加，由於、丨 容融 鋼之喷射流動在其碰撞到其之短邊之前先碰撞到固化外殼 之長邊，因而固化外殼之長邊的成長受到干擾，故而導致 橫向裂紋及/或斜向裂紋的產生。此外，當固化外殼之厚 度極度減小時，在一些情況中亦會發生鑄漏。在前述之兩 種情況中，幾乎未觀察到扁鋼胚寬度的影響。 此外，在熔融鋼碰撞到固化外殼之短邊，上升，然後再 於長邊沿炫融鋼表面流動的情況中，當D / d比由於炫融鋼 在扁鋼胚厚度方向中之流動速度之變化而超出最佳範圍 時，在彎月面附近之流動速度的變化會因而部分地受影 響，且模具助炫劑之捲入量增加。 經定為可確保約5 . 4至約1 4. 5噸/分鐘之出料量之排 出嘴的最大寬度d鑑於其之耐用性係等於或小於浸入喷嘴 22 312/發明說明書(補件)/93-11/93125776 1268820 之内徑（7 0至1 3 0毫米）較佳。因此，D / d比係考慮模具鑄 造空間之最佳短邊長度（扁鋼胚厚度）D(150至240毫米）及 排出嘴之寬度d ( 7 0至1 3 0毫米）而決定。在進行3 0 0分鐘 或以上之長期鑄造的情況中，將總外壁厚度設為25毫米X 2 = 5 0毫米或以上較佳。此外，將在模具與喷嘴之間的距離 設為4 0毫米或以上，以確保更穩定的品質較佳。換言之， 除内徑外之所需厚度為50 + 40x 2 = 130毫米。另一方面，在 短期鑄造之情況中，可將總外壁厚度設為20毫米X 2 = 40 毫米，及可將在模具與噴嘴之間的距離設為大約20毫米。 換言之，除内徑外之厚度為40 + 20x 2 = 80亳米。 表1顯示D/d比對產品品質之影響的研究結果。D/d比 係在1 . 5至3 . 0之範圍内較佳。然而，當亦將最佳扁鋼胚 厚度、浸入噴嘴之耐用性及所需流率列入考慮時，此比係 在自約2 . 1至約2 . 9之範圍内更佳。 23 312/發明說明書(補件)/93-11 /93125776 1268820 比較例 比較例 實施例 實施例 實施例 實施例 實施例 實施例 比較例 鎢漏之產生 B0在短邊 K〇 κ〇 BO在長邊 璀馍π 壤磔g κ r—< oi CD ◦ CD CZ> 〇> CD CD 23.5 4痛Q 瀑智All b 傅 V0 v—^ LO CO CO CNJ o CD LO ◦ 〇 r—1 ^100 電磁制動 類型1 類型1 類型1 類型1 類型1 類型2 類型2 類型2 類型2 ^ 3 0.098 0.098 0.098 0.098 0. 098 0.098 0.098 0.098 0.098 模具之震 盪頻率 f (次/分鐘) § τ—4 § r-H § § r-H S 't-η g r-H g § S r-Ή 模具行程 S (總振幅) (mm) 卜 卜 卜 卜 卜 卜 卜 卜 卜 CO 寸 τ—Η CO CO 03 LO c<i CD ① τ—Η CD οό LO CO od CO r-Ή τ—H ¥ξ,^ η V W § ο LO § 另 r-H oo oo g r-H r-H § r-H 鑄造速度 Vc (m/min) od 呀 oi 寸 oi od oi 呀 csi 呀 CM· c<i 寸 oi 扁鋼胚寬度 W (mm) 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 扁鋼胚厚度 D (mm) Cvl CD cva CNl ◦ CNI <NI (NJ CD οα LO CO CNl LO CO C<I LO CO CNl LO CO oa 編號 r-H (N1 CO LO CO 卜 OO 05 igTwlxQ^^£§β s 1-- s 寸3 · Aw 9Az^ne6/I\.e6/(i)s_sle 1268820 (9 )藉由電磁力制動流動 當鑄造速度V c係約2. 4米/分鐘或以上，或出料量係 約7噸/分鐘或以上時，雖然D / d經最佳化，但仍輕微觀 察到產品瑕疵率的增力口。 在前述情況中，額外進行利用電磁力使流動制動較佳， 且藉由此流動之制動，可獲致更穩定的操作及品質的改良。 關於使用電磁力使流動制動之方法，如前所述使用揭示 於日本未審查專利申請案公告第2-284750及57-17356號 中之技術較佳。 圖7 A至7 C中概略顯示適用於本發明之各設有磁場施加 裝置之連續鑄造模具。 圖7A顯示設置於包括熔融鋼表面液位之模具之上部及 在其下方預定距離，以分兩階段施加靜磁場之磁場施加裝 置1。圖7 B顯示僅將磁場施加裝置2設置於包括熔融鋼表 面液位之模具之上部，以重疊施加靜磁場及AC磁場。圖 7 C顯示將磁場施加裝置2設置於包括熔融鋼表面液位之模 具之上部，以重疊施加靜磁場及A C磁場，及將磁場施加裝 置1設置於磁場施加裝置2下方之預定距離處，以施加靜 磁場。 在前述之各種磁場施加裝置中，當使用用於施加靜磁場 之磁場施加裝置時，將DC磁場之大小（磁通量密度）設為大 約1，0 0 0至大約7，0 0 0高斯（g a u s s )較佳。可將前述之值應 用於將兩裝置設置於上方及下方位置，及僅將一裝置設置 於下方位置之兩種情況。 25 312/發明說明書(補件)/93-11/93125776 1268820 A C磁場有兩種類型’即A C震盈磁場和A C行磁场 (travelling magnetic field) 5在本發明，同時使用兩者 較佳。 圖8顯示AC震盪磁場係將具有實際上彼此反相之AC電 流施加至彼此相鄰之線圈的磁場’或將具有同相之A C電流 施加至具有彼此相反盤繞方向之線圈，以使於相鄰線圈中 產生之磁場實際上反向之磁場。當將此A C震盪磁場重疊於 DC磁場上時，可於模具中之熔融鋼中引發局部流動。在此 圖中，元件符號3係指示DC線圈，元件符號4係指示AC 線圈，元件符號5係指示模具，及元件符號6係指示熔融 鋼（以斜線顯示之部分係緩慢流動區域）。 此外，A C行磁場係當將具經位移3 6 0 V N之相之A C電流 外加至相鄰非必需線圈之N物件時所得之磁場。一般而 言，如圖9所示，由於可得到高效率，因而使用N = 3 ( 1 2 0 ° 之相差）。亦如前所述，當將此A C行磁場重疊於D C磁場上 時，可於模具中之熔融鋼中引發局部流動。 當使用如前所述之用於施加AC磁場之磁場施加裝置 時’將A C磁場之磁通量密度設為大約1 0 0至大約1，0 ◦ 0 高斯較佳，及將震盪磁場之頻率設為大約1至大約1 0 Η z 較佳。 再者，當使用用於重疊施加靜磁場及A C磁場之磁場施 加裝置時，將D C磁場之大小設為大約1，0 0 0至大約7，0 0 0 高斯較佳，及將A C磁場之磁通量密度設為大約1 0 0至大約 1，0 0 0高斯較佳。 26 312/發明說明書(補件)/93-11/93125776 1268820 1毫米，使用剛砂紙# 1 0 0 0進行拋光，及使用氫氯酸及過氧 化氫之混合溶液進行I虫刻。 此外，冷軋鋼板之表面瑕疵率係由鑄造所造成之瑕疵 (諸如刮傷及裂縫）數相對於總瑕疵之以百分比計的比，此 瑕疵數係於每 1，0 0 0米之冷軋鋼板之前及後表面上測量。 當於鑄造中在各個別條件下發生即使至少一鑄漏時，將 鑄漏之產生定義為「是」。 此外，經描述為電磁制動之「類型1」係指示在模具之 底部端附近對整個模具進行之靜磁場施加（Ε Μ B R )，經描述 為電磁制動之「類型2」係指示在浸入喷嘴之排出嘴對整 個模具進行之靜磁場施加（E M L S)，及「類型1」及「類型2」 分別係基於揭示於曰本未審查專利申請案公告第 2 - 2 8 4 7 5 0 A 5 7 - 1 7 3 5 6號中之技術所進行。 負剝離時間tn係用於定義模具震盪條件之一特性值， 且其指示模具之下降速度高於鑄造鋼板之下降速度的時 間。如可由表3及圖6所見，當經由根據本發明之鑄造形 成扁鋼胚時，即使當鑄造速度高，諸如多於约2 . 0米/分 鐘時，經如此形成之扁鋼胚的表面瑕疵程度輕微，且實質 上無法偵測到自其形成之冷軋鋼板的表面瑕疵，或甚至當 存在瑕疵時，其之數目亦相當小。 如可由前述實施例所見，根據本發明，將操作條件最佳 化，以致可達成以下狀態較佳： (1 )由施加至於模具中之熔融鋼表面附近固化之外殼之 熔融鋼之靜壓力朝模具壁的相對推動力增加， 30 312/發明說明書(補件)/93-11/93125776 1268820 (2 )包含物、炫潰、助熔劑及氣泡經吸附於固化外表 界面上之現象受到抑制，及陷入外來物質之機率減小 (3 )外來物質陷入至固化外殼中之深度儘可能地減Λ 因此，即使當在高速度，諸如多於約2 . 0米/分鐘 行鑄造，同時維持高生產力及穩定操作時，可提供用 成汽車外板之供冷軋鋼板用的高品質扁鋼胚，而無需 胚表面處理。 實施例2 使用設有圖7Α至7C中所示之其中一磁場施加裝置 續鑄造裝置經由連續鑄造將熔融鋼（大約3 0 0噸）（其4 由於轉爐中熔融隨後再進行R Η處理而製得）形成為扁 胚，此熔融鋼具有包含0.0015質量百分比之C、0.02 百分比之Si、0.08質量百分比之Μη、0.015質量百分 Ρ、0 . 0 0 4質量百分比之S、0 . 0 4質量百分比之A 1、0 質量百分比之T i、其餘為F e及無可避免之不純物的 物。此實施例中之製造條件示於表2。關於浸入喷嘴 用具有矩形排出嘴之雙嘴浸入喷嘴，此矩形排出嘴各 1 5 °之向下排出角。 接著測量經如此形成之扁鋼胚的表面離析及非金屬 含物之量及於冷軋後由模具助熔劑所造成的表面瑕疫 結果示於表3。 表面離析係於進行扁鋼胚拋光及蝕刻之步驟後，經 覺檢查來自每1平方米之離析數而評估。此外，經由 在距其表面四分之一厚度之深度之部分之鑄造鋼板的 312/發明說明書(補件)/93-】1 /93125776 ί之 ，及 \ 〇 下進 於形 扁鋼 之連 卜、經 鋼 質量 比之 .04 組成 ，使 具有 包 。其 由視 自位 黏液 31 1268820 萃取而對非金屬包含物進行萃取。接著測量包含物之重 量。此外，經由視覺檢查查驗由冷軋所形成之線圈的表面 瑕疵，然後取樣，隨後再分析。測得由模具助熔劑所造成 的瑕蔽數。為降低表面離析、包含物之量及由模具助炫劑 所造成之瑕疵數對指數值以供比較，將在所有條件中所得 之最差的結果視為1 0之指數值。基於在其間滿足線性關係 的假設，將各結果以對最差結果之比表示。 如可由表3所見，根據本發明，當與對模具中之熔融鋼 之流動適當施加電磁制動一起適當控制鑄造速度、模具之 鑄造空間之短邊長度D、喷嘴浸入深度、短邊長度D對浸 入噴嘴之排出嘴之橫向寬度d之比D / d時，可降低表面離 析之數目、非金屬包含物之量及由模具粉末所造成之瑕疵 數。 當震盪磁場之強度太高時，助熔劑之捲入於熔融鋼表面 增力π ，導致表面品質之退化。此外，當頻率太高時，熔融 鋼表面液位無法跟隨磁場，且洗滌固化外殼之界面的效果 減小，因而導致氣泡及包含物瑕/疵之數目的增加。 32 312/發明說明書(補件)/93-11 /93125776 1268820 m ur( s ·0 ζΐι·{ 660 ·0 g卜0·0 Z15.0 6zr( §·(1268820 Melt steel surface to prevent clogging of the immersion nozzle used to supply molten steel from the distributor (t u n d i s h ) into the mold. When it is entangled in the molten steel, the argon gas thus supplied may remain in the molten steel only in the form of bubbles, or may be a reaction product formed by the above-described deoxidation (hereinafter referred to as "deoxidation reaction product"). ) combine to form bubbles remaining in the molten steel. Surface flaws are produced in both of the above cases. Further, when the mold powder thus added remains in the molten steel, surface fatigue similar to that of the deoxidation reaction product is also produced. In the past, hot rolling was carried out in the case of a normal flat steel preform prepared by continuous casting for forming a cold rolled steel sheet without surface treatment of a flat steel blank. However, in the case of a flat steel blank used for forming an outer panel of an automobile, for example, a surface portion of a flat steel blank having a thickness of about 1 to 4 mm is removed via inlaying, which will result in a steel sheet formed after hot rolling. The inclusions of the surface deoxidation reaction products, bubbles, mold aids and the like are removed, and then hot rolling and cold rolling are performed. The completion of the flat steel blank as described above reduces the yield of the flat steel embryo used as a raw material, and further, it disadvantageously causes a delay in the process. Therefore, in the step of producing a flat steel blank using a continuous casting apparatus, attempts have been made to prevent the occurrence of flaws in the surface of the flat steel which will cause the surface of the steel sheet to be flawed. The basic concepts of the above attempts are mainly based on the following items (1) to (6): (1) increasing the thickness of the flat steel, so that the cross-sectional area thereof is increased, and the casting speed is reduced (m/min) due to the roller When rolling, the width of the flat steel embryo is limited. Therefore, the residence time of the molten steel in the mold is increased without deteriorating the productivity, and as a result, foreign substances such as the deoxidation reaction product, the mold powder, the bubble (6) / invention specification (supplement) / 93-11 /93125776 1268820 Its analog is removed from the interior of the molten steel in the mold to the surface with a time increment σ. (2) Casting is carried out using a continuous casting apparatus having a vertical portion so that deoxidation reaction products, mold powders, bubbles, and the like can be gradually separated from the inside of the molten steel in the mold to the surface. (3) The flow in the horizontal direction is generated in the vicinity of the meniscus by the electromagnetic force, so that the substance floating in the molten steel can be prevented from being trapped by the solidified casing (washing effect). (4) The viscosity of the mold powder is appropriately controlled to reduce the possibility that the mold powder is drawn into the molten steel. (5) appropriately controlling the oscillating (vertical vibration) condition of the mold for continuous casting to reduce the generation of the hard shell (nai 1 ) of the solidified shell formed in the mold (the partially solidified shell is inclined toward the molten steel side due to the oscillation) Phenomenon, thereby reducing the amount of deoxidation reaction product, mold powder, bubbles and the like which are trapped in the hard shell. (6) appropriately controlling the flow of the molten steel by electromagnetic stirring or electromagnetic braking using the flow of the molten steel supplied from the immersion nozzle into the mold, so that the flow of the molten steel accompanying the deoxidation reaction product reaches the depth in the mold At the office. For example, a continuous casting device using a vertical portion having a length of 20 meters or more is used at 1.0 m/min or more and 4 Casting of molten steel containing less than 0.1% by weight of carbon is carried out at a casting speed of ton per minute or more to form a flat steel preform having a thickness of more than 200 mm and a width of more than 900 mm, as in the 312/invention specification (Supplement) /93-11 /93125776 7 1268820 When the viscosity of the powder is set to 1.0 poise (p 〇ise ) or more, and the flow rate of the inert gas from the immersion is set to 1 liter / minute or more, the presence of A technique of electromagnetic stirring of molten steel in a region from a meniscus to a depth of 1.5 m in a horizontal direction to a flow velocity of 40 cm/sec. This is mainly based on the above paragraphs (1), (2), (3), (4), and (6). In addition, the unexamined patent application publication No. 7 - 1 5 5 9 0 2 The technique of appropriately controlling the mold oscillating conditions to suppress the generation of the hard shell portion in which the inclusions are trapped is formed in the initial solidification stage of the flat steel surface portion. This technology is mainly based on the above (5). However, the aforementioned technology still has problems. In other words, as disclosed in Japanese Unexamined Patent Application Publication No. 5-76993, when the cross-sectional area of the flat steel embryo is increased, especially when it is thick, at a casting speed of more than 1.5 m/min, The number of turns near the surface of the flat steel embryo caused by the inclusion analogs did not decrease as much as expected. The reason for this is that although the flow velocity vm of the molten steel in the meniscus portion is controlled to a value of ί by applying electricity in the horizontal direction, the same casting speed and the same in the case of not increasing the cross-sectional area When casting at the width of the flat steel (W), the discharge amount increases with the increase in force σ of the flat steel, and the discharge velocity ν i from the immersion nozzle increases, although the flow velocity of the molten steel vm is averaged. The change in value is small, but the amount of change is increased, so that the mold flux is gradually drawn into the molten steel, which shows the cleanliness near the surface portion of the flat steel and not only by the flow of molten steel near the meniscus. Speed is determined. 312 / invention specification (supplement) / 93-11 /93125776 The nozzle is increased in the segment number of the embryonic table from the 1 5 technique or its magnetic field k (Vc) embryo thickness 5 is due to it. The change is only 8 1268820 In addition, the influence of the jet flow from the molten steel immersed in the nozzle becomes remarkable, and the growth of the outer casing is delayed along the short side portion of the mold. The reason is that in the case of a flat steel continuous casting device, when the molten steel is discharged into the mold, the so-called "double nozzle (t W 0 - SP 0 ut ) nozzle" is used along the existing mold. The molten steel is uniformly supplied in the width direction of the casting space, and the width d of the discharge nozzle of the double nozzle is relatively small compared to the short side length D (corresponding to the thickness of the flat steel blank) in the mold, so that the flow speed of the molten steel is The flat steel embryo changes in the thickness direction. Therefore, the molten steel having a high flow velocity unevenly hits the solidified casing along a portion of the short side, so that the growth of the aforementioned solidified casing is delayed. In addition, the change in the flow velocity of the molten steel in the thickness direction of the flat steel section also contributes in part to the change in the flow velocity of the molten steel in the vicinity of the aforementioned meniscus. Next, in the technique described in Japanese Unexamined Patent Application Publication No. No. No. No. No. 7-155902, in order to improve the surface quality of the flat steel, by adjusting the mold oscillation conditions, in particular, by reducing the oscillation amplitude of the mold and by increasing the mold When the frequency is oscillated, and the negative stripping time T determined by the casting speed, the mold oscillation amplitude, and the oscillation frequency of the mold is controlled within a specific range, the following problems are found. In other words, when ultra-low carbon steel is formed via a casting speed of more than 2.0 m/min and an oscillating frequency of more than 185 cycles/min, although not observed very often, molten steel surface may occur An abnormal phenomenon in which the liquid level suddenly changes greatly. As a result, the mold flux may be caught in the molten steel or may be trapped in the solidified casing, thereby producing a surface enthalpy of the cast steel sheet. Therefore, the surface caused by the mold flux at the time of casting at a tungsten production speed of more than 2.0 m/min 9 312 / invention specification (supplement) / 93-11/93125776 1268820 is often generated on the product. Covered. As a result, there is a problem that a product having an excellent surface quality cannot be stably produced. As is apparent from the above description, when an ultra-low carbon flat steel blank for forming an automobile outer panel and the like is manufactured in high speed casting at a speed of more than 2.0 m/min, such as inlaying cannot be performed. The flat steel embryo is conditioned as the current stable production of high quality flat steel. Therefore, it is preferable to provide a continuous casting method for producing an ultra-low carbon flat steel, in which even if it is at a casting speed of more than 2.0 m/min, it can be stably produced without using any flat steel embryo conditioning such as A flat steel embryo with excellent surface quality embedded. SUMMARY OF THE INVENTION The present invention provides a method of manufacturing an ultra-low carbon flat steel blank, comprising: providing a continuous casting apparatus comprising casting with a short side length D of from about 150 to about 240 mm a mold for the space, and a immersion nozzle provided with at least one discharge nozzle having a lateral width d, wherein the D / d ratio is in the range of from about 1.5 to about 3.0; the molten steel is introduced through the immersion nozzle And casting a molten steel at a casting speed of more than about 2.0 m/min using a continuous casting apparatus to produce an ultra-low carbon flat steel having a carbon content of about 0.1 mass% or less. The continuous casting method of the flat steel embryo further comprises oscillating the mold at a frequency of about 185 cycles/minute or less. The probability of occurrence of an abnormal phenomenon in which the liquid level on the molten steel surface suddenly changes greatly is suppressed. Therefore, the resonance between the oscillation of the surface of the molten steel and the oscillation of the mold is caused when the mold vibration 10 312 / invention specification (supplement) / 93-11/93125776 1268820 circulatory system is about 185 cycles / minute or less. The incidence is reduced, thereby reducing the number of turns produced by the flux. The casting speed is preferably about 2.4 m/min or more. When the casting speed is about 2.4 m/min or more, the hard shell depth becomes about 0.7 mm or less, that is, the thickness of the foreign matter is not more than the hard shell depth. Therefore, it is preferred to set the casting speed to about 2.4 m/min or more. Regarding the aforementioned immersion nozzle, a cylindrical nozzle (so-called "straight nozzle") or a double nozzle (where the front end is closed, and two substantially circular discharge nozzles are disposed toward the short sides of the mold) are generally used. When considering the thickness of the flat steel, the durability of the immersion nozzle and the desired flow rate in addition to the product quality, the ratio D / d of the short side length D to the lateral width d of the discharge nozzle of the immersion nozzle is about 2. 1至约2. 9优选. The aforementioned ultra-low carbon flat steel blank is preferably used as a raw material for forming a cold rolled steel sheet for an automobile outer panel. The foregoing continuous casting method for flat steel blanks further includes applying electromagnetic force to apply a brake to the flow of the molten steel in the casting space of the mold. The following paragraphs (A) to (C) can be mentioned as a preferred method of applying the brake using electromagnetic force: (A) substantially entirely in the direction intersecting the thickness of the mold by using the upper magnetic field applying means and the lower magnetic field applying means The mold applies a static magnetic field and applies braking using electromagnetic force. The upper magnetic field applying means is disposed on the upper portion of the mold including the molten steel surface level in the mold, and the lower magnetic field applying means is disposed on the lower side of the upper magnetic field applying means. The immersion nozzle system 11 312 / invention specification (supplement) / 93-11 / 93125776 1268820 is disposed between the upper and lower magnetic field applying means, and the immersion depth is set to about 200 to about 350 mm. (B) applying a static magnetic field and an AC magnetic field by applying a static magnetic field and an AC magnetic field to the entire mold in a direction intersecting the thickness of the mold by using a magnetic field applying device provided on an upper portion of the mold including the molten steel surface level in the mold . The immersion nozzle is disposed below the magnetic field application device and sets the immersion depth to be about 200 to about 350 mm. (C) applying a static magnetic field and an AC magnetic field to the entire mold overlap by using the upper magnetic field applying means in a direction intersecting the thickness of the mold, and otherwise, by using the lower magnetic field applying means in the direction intersecting the thickness of the mold The mold applies a static magnetic field and applies braking using electromagnetic force. The upper magnetic field applying means is disposed on the upper portion of the mold including the molten steel surface level in the mold, and the lower magnetic field applying means is disposed on the lower side of the upper magnetic field applying means. The immersion nozzle is disposed between the upper and lower magnetic field applying means and has an immersion depth of about 200 to about 350 mm. [Embodiment] We have found that flat steel embryos with ultra-low carbon content can properly control the casting speed and continuous casting mold by appropriately controlling the oscillation frequency of the mold or the electromagnetic braking on the molten steel flow. The short side length D of the casting space and the ratio D/d of the short side length D to the lateral width d of the discharge nozzle immersed in the nozzle are advantageously produced. A steel according to one of the aspects of the present invention has a so-called "ultra-low carbon steel" having a carbon content of about 0.1% by mass or less. There are no special restrictions on the ingredients other than C. However, the deep drawing can be suitably processed to form the automobile 12 312 / invention specification (supplement) / 93 -11 / 93125 776 1268820 thickness) set to about 150 to about 240 mm and the casting speed is set to When casting was carried out under conditions of about 2.0 m/min, various phenomena occurred in the mold. A novel discovery regarding the aforementioned phenomenon will be explained next. Hereinafter, inclusions, bubbles, and the like are referred to as "foreign substances." (1) Reduction of the area trapped in foreign matter When the casting speed Vc is set to be more than about 2.0 m/min, or preferably set to be about 2.4 m/min or more, it is remarkably suppressed The formation of a so-called "hard shell" is cured at the beginning of the meniscus portion. I believe that the reason is that the thickness of the solidified shell formed at a non-essentially constant depth from the surface of the molten steel is reduced by the increase of the casting speed V c due to the static pressure of the molten steel, and thus is applied toward the mold side. The force becomes greater than the hard shell which is inclined toward the molten steel side due to the heat shrinkage of the cured outer casing of its thickness. In addition, when the thickness of the flat steel is reduced, the absolute value of the shrinkage of the outer shell in the thickness direction, which is expressed by the "flat steel thickness X temperature difference X thermal expansion coefficient", is reduced, and the inclination of the outer shell toward the molten steel side is further suppressed. As a result, the effect of suppressing the inclination of the hard shell becomes more remarkable. Figure 1 shows the effect of casting speed on the hard shell depth. When the casting speed is more than about 2.0 m/min, and the short side length (flat steel slab thickness) of the casting space of the mold is about 240 mm or less, the hard shell depth becomes 1 mm or less. Further, when the casting speed is about 2.4 m/min or more, the hard shell depth becomes about 0.7 mm or less. (2) The inhibition of the adsorption of foreign substances is accompanied by the solidification caused by the segregation of the solute concentrated at the interface of the solidified shell, thereby causing a gradient of the surface tension, and the resulting gradient (15 312 / invention specification (supplement) / 93-1〗 /93125776 1268820 Force, thus causing the phenomenon that foreign matter may be adsorbed or trapped at the interface of the cured casing. Therefore, an attempt has been made to reduce the concentration of S or Ti, which has a particularly significant effect as a solute element for enhancing the adsorption and the force of foreign matter. However, in some cases, the manipulation of the composition may disadvantageously result in a cost increase π when S is decreased, and may result in quality degradation when Ti decreases. According to the present invention, the force for adsorbing and trapping foreign matter on the interface of the solidified casing is suppressed by increasing the casting speed Vc. In other words, when the casting speed Vc is high, such as more than about 2.0 m/min, the amount of solidification is also reduced because the amount of solidification in the meniscus portion is reduced. Therefore, the gradient of the surface tension as a force for attracting foreign matter is also reduced. As a result, the amount of the substance adsorbed and trapped outside the side of the solidified shell is also reduced. (3) Reduction in thickness of foreign matter trapped Fig. 2 shows the relationship between the depth h of the foreign matter in the surface portion of the flat steel embryo and the number of foreign matter trapped in the surface of the flat steel. Further, Fig. 3 shows the relationship between the number of foreign matter trapped and the distance L from the meniscus (surface of molten steel) obtained by the depth h of the transition from the surface of the flat steel embryo. This transformation is made according to the following equation: h 2 k(L/Vc) 1/2 In this equation, V c indicates the casting speed, and the solidification constant k is 20 mm • min _ w 2 . As can be seen from Figures 2 and 3, the foreign matter is trapped by the outer casing in the region from the surface of the molten steel to a depth of 20 mm. In addition, the depth of penetration decreases with increasing casting speed, and at a casting speed Vc of more than 2.0 m/min, 16 312 / invention specification (supplement) / 93-11 /93125776 1268820 is trapped from the surface of the flat steel embryo The depth h is 1 mm or less. When the depth h is 1 mm or less, although the foreign matter passes through the outer casing, in a subsequent procedure, the formed product is scraped off by the hot rolling step and the step of the foreign matter and the oxide formed on the surface of the cast steel sheet. Remove. Therefore, no product can be obtained without conditioning the flat steel. Further, when the casting speed is about 2.4 m/min or more, the hard shell depth becomes 0.7 mm or less, in other words, the trapped thickness h is not more than the hard shell depth. Therefore, it is more preferable to set the casting speed to about 2.4 m or more. (4) The probability of getting into foreign matter is reduced. The residence time of the solidified material that may be trapped by the solidified casing from the surface of the molten steel to the depth of the millimeter is reduced with the casting speed. Therefore, even when there is the same amount of material floating in the molten steel, the probability of the foreign matter sinking into the cured casing is reduced. For example, when V c is 3.0 m/min, the probability of sinking is reduced to 1. It is half of the 1.5 m/min. (5) The preferred oscillating step of the mold for preventing sudden changes in the surface level of the molten steel is further reduced by the thickness of the solidified shell in the mold when casting is carried out at a casting speed V c of more than about 2.0 m/min. Small, so it is not quite obvious, but it will cause swelling. The expansion phenomenon is a phenomenon in which the solidification pressure of the molten steel is pushed to the mold side. In this phenomenon, when the temperature of the outer casing is high, and when the type of steel is ultra-low carbon, which has an outer shell strength similar to that of other types of steel, the expansion (to the mold) speed becomes higher than the oscillating speed of the mold. . When the general 312/invention specification (supplement)/93-11/93125776 is immersed in cold rolling scale, it is also increased by 20 points. ΓVc i rate, although the shell expands the steel or is pushed to taper 17 1268820 to compensate for the vertical vibration of the mold caused by the shrinkage of the solid shrinkage and/or heat shrinkage, the expansion of the solidified shell is accompanied by the decrease of the mold. b. In contrast, with the rise of the mold, the mold pushes the thus expanded casing with a pushing force δ p corresponding to δ b . When calculated simply, the change in the surface level of the molten steel caused by this volume change is small, such as less than about 1 mm. However, when the foregoing phenomenon is repeated, the oscillation of the surface level of the molten steel and the oscillation of the mold resonate with each other. As a result, in a rare case, an abnormal phenomenon in which the liquid level of the molten steel surface suddenly changes greatly occurs. Since this anomaly occurs at the edge portion of the mold, it is difficult to detect this phenomenon using a general eddy current level sensor for the molten steel surface. However, the inventors discovered this phenomenon for the first time by studying the distortion of the oscillating mark of the cast flat steel embryo over time. In particular, this anomaly may be observed when the casting speed is more than about 2.0 m/min and the oscillation frequency of the mold is high, such as more than about 185 cycles/min. As a result, the mold flux is caught in the molten steel and is trapped in the solidified casing, thereby generating flaws in the surface portion of the cast steel sheet. Therefore, in the case of recording at a recording speed of more than about 2.0 m/min, the number of surface defects in the product caused by the mold aiding agent suddenly increases. As a result, it is difficult to reduce surface fatigue. However, it is found that when the oscillation frequency of the mold is related to the flux to the total enthalpy (this ratio is used as an index showing the incidence of sudden abnormal phenomena), it is found that when the oscillation frequency of the mold is set to about 1 At 8 cycles/min or less, even when the casting speed Vc is more than about 2.0 m/min, the abnormality as described above can be effectively prevented. 18 312/Inventive Manual (Repair)/93-11 /93125776 1268820 In addition, the lower limit of the oscillation frequency of the mold can be set so as not to increase the depth of the hard shell in view of the decrease in the area of the foreign matter, and also It is set by limiting the leakage of the lubricant in the mold (the amount of lubricant consumed by the mold). For example, the negative peeling time is about 0.02 seconds or more, and the negative peeling length is preferably about 0.1 mm or more. The negative stripping time is used to define one characteristic value of the mold oscillating condition, and it indicates the time at which the falling speed of the mold is higher than the falling speed of the cast flat steel. The negative peel length indicates the maximum distance between the mold and the cast flat steel in the negative stripping time, and the mold passes through the cast cast flat steel. When it is assumed that the oscillating waveform of the mold has a sinusoidal waveform, 7 Γ S f / V c > 1, where S indicates the oscillating stroke of the mold, f indicates the mold frequency, and V c indicates the casting speed. For example, when the V c is 2.0 m/min and the S system is 9 mm, the lower limit of the mold frequency f is 7 1 cpm (cycle/min), and when S is 5 mm, the lower limit is 1 2 7 cpm. . The oscillating waveform of the mold does not need to be limited to a sinusoidal waveform. Further, when considering the specifications of the oscillation conditions of the continuous casting apparatus and the controllability thereof, the lower limit of the frequency and the waveform can be appropriately determined. (6) Reason for preventing short-side expansion (the upper limit of the short side length of the casting space of the mold) Although the length of the short side (flat steel thickness) D satisfying the scale space of the mold is used, the lateral width d of the discharge nozzle of the immersion nozzle is used. The ratio D / d is immersed in the nozzle, but when the length of the short side is too large, a problem occurs when casting at a casting speed Vc of more than about 2.0 m/min. In particular, short-side expansion produces enthalpy and/or casting leakage associated with the shape of the flat steel. In contrast, when the length of the short side is small, and when the casting speed Vc is high, the flat steel embryo passing through the mold caused by the static pressure of the molten steel 19 312 / invention specification (supplement) / 93-11 /93125776 1268820 can be suppressed. The short side of the expansion, and the risk of casting leakage is small. However, as shown in Fig. 4, when the length of the short side (i.e., the thickness of the flat steel) is more than 240 mm, although the casting speed is 2.4 m/min, it is caused by the increase in the thickness of the flat steel. The boosting force σ of the jet flow velocity from the molten steel immersed in the discharge nozzle of the nozzle is increased by applying electromagnetic braking. Therefore, it is difficult to suppress the delay of growth of the outer casing along the short side. Therefore, the short side expansion at the bottom end of the mold becomes conspicuous, and the risk of casting leakage (expansion amount of 1 毫米 mm or more) is increased by π. In addition, when the length of the short side (ie, the thickness of the flat steel) is more than 240 mm, for the same reason as described above, due to the fluctuation of the surface level of the molten steel through the reverse flow and the jet flow of the molten steel The second flow (the flow is from the short side of the cured outer casing) is enhanced, so that the mold assisting agent is entangled and trapped. In addition, due to the increase in the thickness of the flat steel, it is prone to stagnation of the molten steel in the meniscus, especially near the immersion nozzle. As a result, as shown in Fig. 5, the number of turns on the flat steel and the number of product turns increased. (7) Reasons for the lower limit of the short side length of the mold casting space For the following reasons, the short side length (flat steel blank thickness) of the mold casting space is not preferable to be less than about 150 mm. When the cross-sectional area of the flat steel embryo is excessively reduced, the above effects cannot be obtained in view of the controllability of the molten steel surface level (1). The reason is that when the amount of casting is changed, the fluctuation of the surface level of the molten steel is increased as compared with the case of forming a flat steel with a large cross-sectional area. Further, since the molten steel corrugation is thus formed, the generation rate of the hard shell having a depth of 1 mm or more is increased. In addition, the fluctuation of the liquid level on the molten steel surface is prone to the entrapment and trapping of the mold flux by 20 3 ] 2 / invention specification (supplement) / 93-1 ] /93125776 1268820 (see Figure 5). Furthermore, the outer diameter of the general immersion nozzle is determined by consideration of the wall thickness (about 20 mm or more) determined by the financial property and is ensured since 5.4 tons/min (150 mm thick, 2,200). Mm wide, and V c ) of 2.1 m/min or more to 14. 5 t/min (240 mm thick, 2,200 mm wide, and 3.5 m/min or more V) c) The sum of the internal diameter (about 70 to about 130 mm) determined by the discharge amount is determined. In this case, when the short side length (flat steel thickness) D is too small, the distance between the outer wall of the immersion nozzle and the long side of the solidified outer casing becomes too small (less than 20 mm), and the flow therebetween becomes It is uneven, thus causing the generation of longitudinal cracks. In an extreme case, the cured outer casing contacts and adheres to the nozzle, causing a casting leak. Therefore, the length of the short side (the thickness of the flat steel) D is set to be not less than about 150 mm (the inner diameter of the inner diameter of 70 mm + the outer wall thickness of 40 mm (2 0 X 2 ) + 40 mm (2 0 X 2 ) the distance between the outer wall of the immersion nozzle and the long side of the cured casing). In addition, the length of the long side of the mold casting space (flat steel slab width) is not particularly limited, and it can be equal to the width of ordinary cold-rolled steel sheets (especially the width of cold-rolled steel sheets for automobiles. About 9000 to 2,200) The length of the millimeter is preferably. The height in the vertical direction of the mold is not particularly limited. However, since it is necessary to form a cured outer shell having a specific thickness, even when the casting speed is more than about 2.0 m/min. At the time of casting, the cast flat steel by the mold does not expand, so the height is preferably set to about 800 to 1,0 mm. (8) The short side length D of the mold casting space is discharged to the immersion nozzle. Optimization of the ratio D / d of the lateral width d of the mouth 21 312 / Invention specification (supplement) / 93-11/93125776 1268820 Although the steel is deflated, the molten steel ejected from the discharge nozzle of the immersion nozzle extends over its width Until it hits the short-side casing. However, the degree of deceleration of the molten steel colliding with the short-side casing and the distribution of the jet flow velocity are determined by the width W of the flat steel, the casting speed Vc, and the D/d ratio. Immersion nozzle When the degree d is shorter than the short side length of the casting space of the mold (flat steel embryo width) D is too small (D/d is too large), with the increase of D, Vc and W, the molten steel with high flow velocity collides with the short side shell The ratio of the width of the region to the thickness of the flat steel (short edge width) is reduced. Therefore, the growth of the cured casing becomes uneven and susceptible to interference. Further, when the thickness of the cured casing is extremely reduced, in some cases, Casting leakage occurs. On the other hand, when the width d of the discharge nozzle immersed in the nozzle is too large (D / d is too small) with respect to the short side length of the casting space of the mold (D / d is too small), along with D, V c And the increase of W, because the jet flow of the molten steel collides with the long side of the solidified shell before it hits the short side thereof, the growth of the long side of the solidified shell is disturbed, thereby causing lateral cracks and/or In addition, when the thickness of the cured casing is extremely reduced, casting leakage may occur in some cases. In the foregoing two cases, the influence of the width of the flat steel is hardly observed. Steel collides into the cured casing In the case where the short side, the rise, and then the long edge along the surface of the molten steel, when the D / d ratio exceeds the optimum range due to the change of the flow speed of the molten steel in the thickness direction of the flat steel, in the meniscus The change in the flow velocity near the surface is thus partially affected, and the amount of mold-assisted toner is increased. The discharge nozzle is determined to ensure a discharge amount of about 5.4 to about 14.5 tons/minute. The maximum width d is preferably equal to or less than the inner diameter (70 to 130 mm) of the immersion nozzle 22 312 / invention specification (supplement) / 93-11 / 93125776 1268820. Therefore, D / The d ratio is determined by considering the optimum short side length (flat steel thickness) D (150 to 240 mm) of the mold casting space and the width d (70 to 130 mm) of the discharge nozzle. In the case of performing long-term casting of 300 minutes or more, it is preferred to set the total outer wall thickness to 25 mm X 2 = 50 mm or more. Further, the distance between the mold and the nozzle is set to 40 mm or more to ensure a more stable quality. In other words, the required thickness other than the inner diameter is 50 + 40 x 2 = 130 mm. On the other hand, in the case of short-term casting, the total outer wall thickness can be set to 20 mm X 2 = 40 mm, and the distance between the mold and the nozzle can be set to be about 20 mm. In other words, the thickness except for the inner diameter is 40 + 20 x 2 = 80 mm. Table 1 shows the results of the study on the effect of D/d ratio on product quality. The D/d ratio is preferably in the range of from 1.5 to 3.0. However, when the optimum slab thickness, the durability of the immersion nozzle, and the required flow rate are also taken into consideration, the ratio is preferably in the range of from about 2.1 to about 2.9. 23 312/Invention Manual (Supplement)/93-11/93125776 1268820 Comparative Example Comparative Example Embodiment Example Embodiment Example Embodiment Example Comparative Example Tungsten leak generation B0 on the short side K〇κ〇BO on the long side璀馍π 磔 磔 g κ r— < oi CD ◦ CD CZ>〇> CD CD 23.5 4 Pain Q Waterfall wise All b 傅V0 v—^ LO CO CO CNJ o CD LO ◦ 〇r—1 ^100 Electromagnetic brake type 1 Type 1 Type 1 Type 1 Type 1 Type 2 Type 2 Type 2 Type 2 ^ 3 0.098 0.098 0.098 0.098 0. 098 0.098 0.098 0.098 0.098 Oscillation frequency f (times / minute) § τ -4 § rH § § rH S 't-η g rH g § S r-Ή Mold stroke S (total amplitude) (mm) 卜 卜 卜 卜 卜 CO CO CO CO CO CO CO CO CO LO LO LO <i CD 1 τ-Η CD οό LO CO od CO r-Ή τ—H ¥ξ,^ η VW § ο LO § another rH oo oo g rH rH § rH casting speed Vc (m/min) od 呀oi Inch oi od oi ah csi 呀 CM· c <i inch oi flat steel embryo width W (mm) 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 1100-1800 flat steel embryo thickness D (mm) Cvl CD Cva CNl ◦ CNI <NI (NJ CD οα LO CO CNl LO CO C <I LO CO CNl LO CO oa No. rH (N1 CO LO CO BU OO 05 igTwlxQ^^£§β s 1-- s inch 3 · Aw 9Az^ne6/I\.e6/(i)s_sle 1268820 (9 Braking flow by electromagnetic force When the casting speed V c is about 2.4 m/min or more, or the discharge amount is about 7 t/min or more, although D / d is optimized, it is slightly observed. In the case of the above, the use of electromagnetic force to make the flow brake better, and the braking by this flow, can achieve more stable operation and quality improvement. The method of braking is preferably as described above, and the technique disclosed in Japanese Unexamined Patent Application Publication No. Publication Nos. Nos. 2-284750 and No. 57-17356 is shown in Fig. 7A to 7C. The continuous casting mold of the magnetic field applying device. Fig. 7A shows the magnetic field applying device 1 which is disposed on the upper portion of the mold including the liquid level of the molten steel and a predetermined distance below it to apply a static magnetic field in two stages. Fig. 7B shows only the magnetic field The applying device 2 is disposed on the upper part of the mold including the molten steel surface level to A static magnetic field and an AC magnetic field are applied. Fig. 7C shows that the magnetic field applying device 2 is placed on the upper portion of the mold including the molten steel surface level to superimposely apply the static magnetic field and the AC magnetic field, and the magnetic field applying device 1 is placed on the magnetic field applying device 2. At a predetermined distance below, a static magnetic field is applied. In the above various magnetic field applying devices, when a magnetic field applying device for applying a static magnetic field is used, the magnitude (magnetic flux density) of the DC magnetic field is set to about 1,0 0 0 Preferably, the gauss are about 750. The foregoing values can be applied to the two devices in the upper and lower positions, and only one device is placed in the lower position. 25 312/Invention Manual (Supplement) / 93-11/93125776 1268820 There are two types of AC magnetic fields, namely, AC shock magnetic field and AC magnetic field. In the present invention, both are preferred. Figure 8 shows an AC oscillating magnetic field. Applying a magnetic field having an AC current that is actually opposite to each other to a coil adjacent to each other' or applying an AC current having the same phase to a coil having opposite winding directions to each other, so that The magnetic field generated in the adjacent coil is actually a reverse magnetic field. When this AC oscillating magnetic field is superimposed on the DC magnetic field, local flow can be induced in the molten steel in the mold. In this figure, the symbol 3 indicates the DC coil. The component symbol 4 indicates the AC coil, the component symbol 5 indicates the mold, and the component symbol 6 indicates the molten steel (the portion indicated by the oblique line is a slow flowing region). Further, the A C magnetic field is a magnetic field obtained when an A C current having a phase shifted by 3 60 V N is applied to an N object of an adjacent unnecessary coil. In general, as shown in Fig. 9, since high efficiency is obtained, N = 3 (phase difference of 1 2 0 °) is used. As also mentioned above, when this A C-line magnetic field is superposed on the DC magnetic field, local flow can be induced in the molten steel in the mold. When the magnetic field applying device for applying an AC magnetic field as described above is used, 'the magnetic flux density of the AC magnetic field is set to about 100 to about 1,0 ◦ 0 Gauss is preferable, and the frequency of the oscillating magnetic field is set to about 1 to about 10 Η z is preferred. Furthermore, when a magnetic field applying device for superimposing a static magnetic field and an AC magnetic field is used, the magnitude of the DC magnetic field is set to about 1,0 0 0 to about 7,0 0 0 Gauss is preferable, and the magnetic flux of the AC magnetic field is used. The density is set to be about 1 0 0 to about 1,0 0 0 Gauss is preferred. 26 312/Invention Manual (supplement)/93-11/93125776 1268820 1 mm, polishing was carried out using a sandpaper #1 0 0 0, and a mixed solution of hydrochloric acid and hydrogen peroxide was used for I insect engraving. In addition, the surface enthalpy of the cold-rolled steel sheet is the ratio of the number of defects (such as scratches and cracks) caused by casting to the percentage of the total enthalpy, which is the cold rolling per 10,000 meters. Measured on the front and back surfaces of the steel plate. When at least one casting leak occurs under various conditions in casting, the occurrence of casting leakage is defined as "yes". In addition, the "type 1" described as electromagnetic braking indicates the application of static magnetic field (Ε Μ BR) to the entire mold near the bottom end of the mold, and the "type 2" described as electromagnetic braking is indicated in the immersion nozzle. The static magnetic field application (EMLS) of the discharge nozzle to the entire mold, and "Type 1" and "Type 2" are based on the disclosure of Unexamined Patent Application Publication No. 2 - 2 8 4 7 5 0 A 5 7 - The technology was carried out in 1 7 3 5 6 . The negative peeling time tn is used to define one characteristic value of the mold oscillating condition, and it indicates the time at which the falling speed of the mold is higher than the falling speed of the cast steel sheet. As can be seen from Table 3 and Figure 6, when a flat steel blank is formed by casting according to the present invention, even when the casting speed is high, such as more than about 2.0 m/min, the surface of the thus formed flat steel blank The degree is slight, and it is substantially impossible to detect the surface flaw of the cold-rolled steel sheet formed therefrom, or even when flaws are present, the number is also relatively small. As can be seen from the foregoing embodiments, according to the present invention, the operating conditions are optimized such that the following conditions are preferably achieved: (1) the static pressure of the molten steel of the outer shell solidified near the surface of the molten steel applied to the mold toward the mold The relative driving force of the wall increases, 30 312 / invention manual (supplement) / 93-11/93125776 1268820 (2) inclusions, smashing, flux and bubbles are adsorbed on the cured surface interface is inhibited, and trapped The probability of foreign matter is reduced (3) the depth of foreign matter trapped into the cured casing is reduced as much as possible. Therefore, even when casting at high speeds, such as more than about 2.0 m/min, while maintaining high productivity and stability In operation, high-quality flat steel blanks for cold-rolled steel sheets used as outer panels of automobiles can be provided without the need for surface treatment of the embryo. Example 2 Using a magnetic field applying device continued to be cast as shown in Figs. 7A to 7C, molten steel (about 3,000 tons) was continuously cast by casting (the 4 was made by melting in a converter and then subjected to R Η treatment). Formed as a flat embryo, the molten steel has a content of 0.0015 mass% of C, 0.02% of Si, 0.08 mass% of Μ, 0.015 mass% Ρ, 0.04 mass% of S, 0.44 mass The percentage of A 1 , 0 mass percent of T i , the rest of F e and the inevitable impurities. The manufacturing conditions in this example are shown in Table 2. Regarding the immersion nozzle, a double nozzle immersion nozzle having a rectangular discharge nozzle having a downward discharge angle of 15 ° each. Next, the surface segregation and non-metallic content of the thus formed flat steel blank and the surface plague caused by the mold flux after cold rolling were measured and shown in Table 3. The surface segregation was evaluated after the steps of polishing and etching the flat steel, and the number of segregation per square meter was examined by inspection. In addition, through the casting of the steel plate at a depth of a quarter of the thickness from the surface of the 312 / invention specification (supplement) /93-] 1 /93125776 ί, and \ 〇下 into the shape of flat steel The quality of the steel is composed of .04, so that it has a package. It is extracted from the non-metallic inclusions by extraction from the self-level mucus 31 1268820. The weight of the inclusions is then measured. In addition, the surface flaw of the coil formed by cold rolling was examined by visual inspection, and then sampled and then analyzed. The number of defects caused by the mold flux was measured. In order to reduce the surface segregation, the amount of inclusions, and the number of turns caused by the mold aid to the index value for comparison, the worst result obtained in all conditions is regarded as the index value of 10. Based on the assumption that the linear relationship is satisfied, the results are expressed as the ratio of the worst results. As can be seen from Table 3, according to the present invention, the casting speed, the short side length D of the casting space of the mold, the nozzle immersion depth, and the short side length D are immersed appropriately when the electromagnetic brake is appropriately applied to the flow of the molten steel in the mold. When the ratio of the lateral width d of the discharge nozzle of the nozzle is D / d, the number of surface segregation, the amount of non-metallic inclusions, and the number of turns caused by the mold powder can be reduced. When the strength of the oscillating magnetic field is too high, the flux is entrained on the surface of the molten steel to increase the force π, resulting in degradation of the surface quality. In addition, when the frequency is too high, the molten steel surface level cannot follow the magnetic field, and the effect of washing the interface of the solidified shell is reduced, resulting in an increase in the number of bubbles and inclusions/疵. 32 312/Invention Manual (supplement)/93-11 /93125776 1268820 m ur( s ·0 ζΐι·{ 660 ·0 g Bu 0·0 Z15.0 6zr( §·(
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表2B 編號 浸入噴嘴之深度 (mm) AC磁場之類型 上方AC磁場 (南斯） 上方DC磁場 (南斯） 下方DC磁場 (南斯） 1 280 否 0 0 0 2 280 否 0 0 0 3 280 否 0 0 0 4 280 否 0 0 0 5 280 否 0 0 0 6 280 否 0 0 0 7 280 類型1 1000 1000 0 8 280 類型1 700 1000 0 9 280 類型1 500 1000 0 10 280 類型1 300 1000 0 11 280 類型1 300 1000 0 12 280 類型1 300 1000 0 13 280 類型1 300 1000 0 14 280 類型1 300 1000 0 15 280 類型1 300 1000 0 16 280 類型1 300 1000 0 17 280 類型1 0 1000 1500 18 280 類型1 0 1500 2000 19 280 類型1 0 2000 2500 20 280 類型1 0 2500 3000 21 280 類型1 0 0 0 22 280 類型1 200 1000 0 23 280 類型1 200 1000 0 24 280 類型1 200 1000 0 25 280 類型1 200 1000 0 26 280 類型1 200 1000 0 27 280 否 0 0 0 28 280 否 0 0 0 29 280 類型2 600 0 0 30 280 類型2 600 1000 0 31 280 類型2 600 1000 0 32 180 類型1 200 1000 0 33 200 類型1 200 1000 0 34 350 類型1 200 1000 0 35 370 類型1 200 1000 0 36 280 類型1 300 1000 1500 37 280 類型1 300 1000 1500 34 312/發明說明書(補件)/93-11/93125776 1268820 表3 編號 最大短邊 膨脹量 (_) 最大硬 殼深度 (mm) 最大扁鋼胚 表面瑕疲數 (/in2) 表面瑕疲率 (%) 鑄漏之產生 粉末瑕疵對 總瑕疵之比 (%) 註 1 0 3. 5 3. 10 否 49 比較例1 2 1 2.7 185 2.35 否 24 比較例2 3 1 2.6 120 1.23 否 20 比較例3 4 2 1. 5 90 0.30 否 36 比較例4 5 2 1. 1 55 0. 15 否 0 實施例1 6 1 0· 7 45 0.05 否 3 實施例2 7 1 3. 0 3. 10 否 33 比較例5 8 1 2. 9 1.54 否 20 比較例6 9 2 2. 2 0. 50 否 16 比較例7 10 4 0.8 0 否 0 實施例3 11 4 0· 9 0. 11 否 5 實施例4 12 3 1.3 2. 6 否 74 比較例8 13 3 1. 3 4. 1 否 85 比較例9 14 2 1. 0 50 0 否 0 實施例5 15 3 0· 6 30 0 否 0 實施例6 16 3 0. 5 20 0 否 0 實施例7 17 3 0.2 10 0 否 0 實施例8 18 5 0· 2 3 0 否 0 實施例9 19 5 0. 1 3 0 否 0 實施例10 20 6 0· 2 5 0 否 0 實施例11 21 1 1.4 70 否 比較例10 22 1 0. 1 15 0.02 否 0 實施例12 23 2 0. 2 11 0 否 0 實施例13 24 5 0. 3 13 0 否 0 實施例14 25 10 0.8 25 0.3 否 4 比較例11 26 15 1·1 60 0.4 否 60 比較例12 27 9 0· 7 0.03 是 15 實施例15 28 9 0. 6 0. 05 否 21 實施例16 29 0 2. 5 5.90 否 37 比較例13 30 1 0.8 0 否 0 實施例17 31 2 0.4 0 否 0 實施例18 32 2 0.4 0.05 否 33 實施例19 33 2 0.4 0 否 0 實施例20 34 2 0.4 0 否 0 實施例21 35 2 0.6 L5 否 67 比較例14 36 2 1. 0 20 0 否 0 實施例22 37 3 0· 5 12 0 否 0 實施例23 *空白攔：未測量 比較例：比較實施例 35 312/發明說明書(補件)/93-11 /93125776 1268820 【圖式簡單說明】 圖1係顯示根據本發明態樣之在鑄造速度與硬殼深度之 間之關係的圖； 圖2係顯示根據本發明態樣之在距扁鋼胚表面之陷入深 度h與陷入包含物之數目之間之關係的圖，此關係係在不 同的鑄造速度下得到； 圖3係顯示根據本發明態樣之在距彎月面之距離L與陷 入包含物之數目之間之關係的圖，此關係係在不同的鑄造 速度下得到； 圖4係顯示根據本發明態樣之扁鋼胚厚度及鑄造速度對 短邊膨脹量之影響的圖； 圖5係顯示根據本發明態樣之扁鋼胚厚度對產物之表面 瑕疵率之影響的圖； 圖6係顯示根據本發明態樣之鑄造速度對產物之表面瑕 疵率之影響的圖； 圖7 A至7 C係各顯示設有磁場施加裝置之連續鑄造模具 之示意圖，此模具係根據本發明之態樣適當地使用； 圖8係顯示根據本發明態樣之AC震盪磁場之應用實例 的示意圖；及 圖9係顯示根據本發明態樣之A C行磁場之應用實例的 示意圖。 【主要元件符號說明】 3 DC線圈 4 AC線圈 36 312/發明說明書(補件)/93-11 /93125776 1268820 5 模具 6 溶融鋼Table 2B Number of immersion nozzle depth (mm) AC magnetic field type above AC magnetic field (Nans) Upper DC magnetic field (Nans) Lower DC magnetic field (Nans) 1 280 No 0 0 0 2 280 No 0 0 0 3 280 No 0 0 0 4 280 No 0 0 0 5 280 No 0 0 0 6 280 No 0 0 0 7 280 Type 1 1000 1000 0 8 280 Type 1 700 1000 0 9 280 Type 1 500 1000 0 10 280 Type 1 300 1000 0 11 280 Type 1 300 1000 0 12 280 Type 1 300 1000 0 13 280 Type 1 300 1000 0 14 280 Type 1 300 1000 0 15 280 Type 1 300 1000 0 16 280 Type 1 300 1000 0 17 280 Type 1 0 1000 1500 18 280 Type 1 0 1500 2000 19 280 Type 1 0 2000 2500 20 280 Type 1 0 2500 3000 21 280 Type 1 0 0 0 22 280 Type 1 200 1000 0 23 280 Type 1 200 1000 0 24 280 Type 1 200 1000 0 25 280 Type 1 200 1000 0 26 280 Type 1 200 1000 0 27 280 No 0 0 0 28 280 No 0 0 0 29 280 Type 2 600 0 0 30 280 Type 2 600 1000 0 31 280 Type 2 600 1000 0 32 180 Type 1 200 1000 0 33 200 Type 1 200 1000 0 34 350 Type 1 200 1000 0 35 370 Type 1 200 1000 0 36 280 Type 1 300 1000 1500 37 280 Type 1 300 1000 1500 34 312/Invention Manual (supplement) /93-11/93125776 1268820 Table 3 Number Maximum Short Edge Expansion (_) Maximum Hard Shell Depth (mm) Maximum Flat Steel Embryo surface fatigue (/in2) Surface fatigue rate (%) Casting leakage produced powder 瑕疵 to total 瑕疵 ratio (%) Note 1 0 3. 5 3. 10 No 49 Comparative Example 1 2 1 2.7 185 2.35 No 24 Comparative Example 2 3 1 2.6 120 1.23 No 20 Comparative Example 3 4 2 1. 5 90 0.30 No 36 Comparative Example 4 5 2 1. 1 55 0. 15 No 0 Example 1 6 1 0· 7 45 0.05 No 3 Implementation Example 2 7 1 3. 0 3. 10 No 33 Comparative Example 5 8 1 2. 9 1.54 No 20 Comparative Example 6 9 2 2. 2 0. 50 No 16 Comparative Example 7 10 4 0.8 0 No 0 Example 3 11 4 0· 9 0. 11 No 5 Example 4 12 3 1.3 2. 6 No 74 Comparative Example 8 13 3 1. 3 4. 1 No 85 Comparative Example 9 14 2 1. 0 50 0 No 0 Example 5 15 3 0 · 6 30 0 No 0 Example 6 16 3 0. 5 20 0 No 0 Example 7 17 3 0.2 10 0 No 0 Example 8 18 5 0· 2 3 0 No 0 Example 9 19 5 0. 1 3 0 No 0 Embodiment 10 20 6 0· 2 5 0 No 0 Embodiment 11 21 1 1.4 70 No ratio Example 10 22 1 0. 1 15 0.02 No 0 Example 12 23 2 0. 2 11 0 No 0 Example 13 24 5 0. 3 13 0 No 0 Example 14 25 10 0.8 25 0.3 No 4 Comparative Example 11 26 15 1·1 60 0.4 No 60 Comparative Example 12 27 9 0· 7 0.03 Yes 15 Example 15 28 9 0. 6 0. 05 No 21 Example 16 29 0 2. 5 5.90 No 37 Comparative Example 13 30 1 0.8 0 No 0 Example 17 31 2 0.4 0 No 0 Example 18 32 2 0.4 0.05 No 33 Example 19 33 2 0.4 0 No 0 Example 20 34 2 0.4 0 No 0 Example 21 35 2 0.6 L5 No 67 Comparative Example 14 36 2 1. 0 20 0 No 0 Example 22 37 3 0· 5 12 0 No 0 Example 23 *Blank barrier: not measured Comparative example: Comparative Example 35 312 / Invention specification (supplement) / 93-11 /93125776 1268820 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing the relationship between the casting speed and the hard shell depth according to the aspect of the present invention; Fig. 2 is a view showing the depth of the surface of the flat steel embryo according to the aspect of the present invention. a graph of the relationship between h and the number of inclusions, which is obtained at different casting speeds; Figure 3 shows the distance in accordance with the present invention. The relationship between the distance L of the meniscus and the relationship between the number of inclusions, which is obtained at different casting speeds; Figure 4 shows the thickness of the flat steel and the casting speed to the short side according to the aspect of the present invention. Figure 5 is a graph showing the effect of the thickness of the flat steel blank on the surface enthalpy of the product according to the aspect of the present invention; and Figure 6 is a graph showing the surface enthalpy of the casting speed versus the product according to the aspect of the present invention. Figure 7A to 7C are schematic views each showing a continuous casting mold provided with a magnetic field applying device, which is suitably used according to the aspect of the present invention; Fig. 8 is a view showing an AC according to the aspect of the present invention. A schematic diagram of an application example of an oscillating magnetic field; and Fig. 9 is a schematic view showing an application example of an AC traveling magnetic field according to an aspect of the present invention. [Main component symbol description] 3 DC coil 4 AC coil 36 312/Invention manual (supplement)/93-11 /93125776 1268820 5 Mold 6 molten steel
312/發明說明書(補件)/93-11/93125776 37312/Invention Manual (supplement)/93-11/93125776 37
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| JP2003307108A JP4259232B2 (en) | 2003-08-29 | 2003-08-29 | Slab continuous casting method for ultra-low carbon steel |
| JP2003395818A JP4411945B2 (en) | 2003-11-26 | 2003-11-26 | Slab continuous casting method for ultra-low carbon steel |
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| US (2) | US20050045303A1 (en) |
| EP (1) | EP1510272B1 (en) |
| KR (1) | KR100654738B1 (en) |
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| TWI599417B (en) * | 2015-09-16 | 2017-09-21 | Jfe Steel Corp | Continuous Casting of Steel Emboss Casting |
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| US8146649B2 (en) * | 2006-04-25 | 2012-04-03 | Kobe Steel, Ltd. | Method of continuous casting of high-aluminum steel and mold powder |
| US8372327B2 (en) | 2007-09-13 | 2013-02-12 | The Boeing Company | Method for resin transfer molding composite parts |
| US8343402B1 (en) * | 2007-09-13 | 2013-01-01 | The Boeing Company | Consolidation of composite material |
| US8017059B2 (en) | 2007-09-13 | 2011-09-13 | The Boeing Company | Composite fabrication apparatus and method |
| US8865050B2 (en) | 2010-03-16 | 2014-10-21 | The Boeing Company | Method for curing a composite part layup |
| JP4569715B1 (en) * | 2009-11-10 | 2010-10-27 | Ｊｆｅスチール株式会社 | Steel continuous casting method |
| JP4807462B2 (en) * | 2009-11-10 | 2011-11-02 | Ｊｆｅスチール株式会社 | Steel continuous casting method |
| CN102791400B (en) * | 2010-03-10 | 2014-07-30 | 杰富意钢铁株式会社 | Method for continuously casting steel and process for producing steel sheet |
| CN102095624B (en) * | 2011-02-25 | 2012-01-25 | 首钢总公司 | Preparation of ultralow-carbon sheet metallographic phase sample and tissue display method |
| CN102252888B (en) * | 2011-06-30 | 2012-10-10 | 首钢总公司 | Preparation and tissue display method of ultralow carbon ultrathin cold heading steel wire metallographical sample |
| BR112014014324B1 (en) * | 2011-12-22 | 2018-07-03 | Abb Ab | ARRANGEMENT FOR A CONTINUOUS CASTING PROCESS AND METHOD FOR METAL FLOW CONTROL IN A VASE FOR A CONTINUOUS CASTING PROCESS |
| DE112013006741B4 (en) | 2013-02-27 | 2019-05-09 | Hyundai Steel Company | A method of controlling a surface quality of a very low carbon beam beam |
| KR101510265B1 (en) * | 2013-12-13 | 2015-04-08 | 주식회사 포스코 | Apparatus for treating molten metal |
| JP6336210B2 (en) * | 2014-11-20 | 2018-06-06 | アーベーベー シュヴァイツ アクツィエンゲゼルシャフト | Electromagnetic brake system and molten metal flow control method in metal manufacturing process |
| EP3415251A1 (en) * | 2017-06-16 | 2018-12-19 | ABB Schweiz AG | Electromagnetic brake system and method of controlling an electromagnetic brake system |
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| CA2011410C (en) * | 1990-03-02 | 1996-12-31 | Mikio Suzuki | Method for continuous casting of steel |
| KR0184240B1 (en) * | 1991-09-25 | 1999-04-01 | 도오자끼 시노부 | Process of continuously casting steel using electromagnetic field |
| JP2778455B2 (en) * | 1993-10-13 | 1998-07-23 | 日本鋼管株式会社 | Immersion nozzle for continuous casting |
| JP3316108B2 (en) | 1994-07-14 | 2002-08-19 | 川崎製鉄株式会社 | Steel continuous casting method |
| JPH08158007A (en) * | 1994-12-06 | 1996-06-18 | Kobe Steel Ltd | Production of cold rolled steel sheet excellent in surface characteristic and workability |
| SE503562C2 (en) * | 1995-02-22 | 1996-07-08 | Asea Brown Boveri | Methods and apparatus for string casting |
| JP3388933B2 (en) * | 1995-03-03 | 2003-03-24 | 新日本製鐵株式会社 | Continuous casting method of titanium-added ultra low carbon steel |
| DE19512209C1 (en) * | 1995-03-21 | 1996-07-18 | Mannesmann Ag | Appts. for delivering metal melt into continuous casting mould |
| JP3125664B2 (en) * | 1996-01-19 | 2001-01-22 | 日本鋼管株式会社 | Continuous casting method of ultra low carbon steel slab |
| EP0880417B1 (en) * | 1996-02-13 | 2000-05-03 | Abb Ab | A device for casting in a mould |
| DE19625932A1 (en) * | 1996-06-28 | 1998-01-08 | Schloemann Siemag Ag | Electromagnetic brake for a continuous casting mold |
| CN1205924A (en) * | 1997-03-17 | 1999-01-27 | Sms舒路曼-斯玛公司 | Continuous casting mould for casting flat-rolled steel and optimization shape of immersion running gate thereof |
| JPH10263767A (en) * | 1997-03-21 | 1998-10-06 | Kawasaki Steel Corp | Method for continuously casting extra-low carbon steel and mold powder for continuous casting |
| KR100376504B1 (en) * | 1998-08-04 | 2004-12-14 | 주식회사 포스코 | Continuous casting method and continuous casting apparatus used |
| JP3365362B2 (en) | 1999-08-10 | 2003-01-08 | 住友金属工業株式会社 | Continuous casting method |
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| JP3620384B2 (en) * | 1999-12-15 | 2005-02-16 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet with excellent surface properties and method for producing the same |
| JP2003170252A (en) * | 2001-12-04 | 2003-06-17 | Kawasaki Steel Corp | Method for casting slab at high speed |
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2004
- 2004-08-19 US US10/921,434 patent/US20050045303A1/en not_active Abandoned
- 2004-08-26 EP EP04020281A patent/EP1510272B1/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
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| TWI599417B (en) * | 2015-09-16 | 2017-09-21 | Jfe Steel Corp | Continuous Casting of Steel Emboss Casting |
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| DE602004026253D1 (en) | 2010-05-12 |
| TW200518858A (en) | 2005-06-16 |
| CN1299855C (en) | 2007-02-14 |
| EP1510272B1 (en) | 2010-03-31 |
| KR100654738B1 (en) | 2006-12-08 |
| EP1510272A1 (en) | 2005-03-02 |
| KR20050021961A (en) | 2005-03-07 |
| CN1597182A (en) | 2005-03-23 |
| US20060102316A1 (en) | 2006-05-18 |
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