JP5773891B2 - Bottom pouring method - Google Patents

Bottom pouring method Download PDF

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JP5773891B2
JP5773891B2 JP2012002189A JP2012002189A JP5773891B2 JP 5773891 B2 JP5773891 B2 JP 5773891B2 JP 2012002189 A JP2012002189 A JP 2012002189A JP 2012002189 A JP2012002189 A JP 2012002189A JP 5773891 B2 JP5773891 B2 JP 5773891B2
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molten steel
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heat insulating
ingot
insulating material
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JP2013141678A (en
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渡辺　大輔
大輔 渡辺
哲史 出浦
哲史 出浦
浩司 岩永
浩司 岩永
晴記 飛松
晴記 飛松
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Kobe Steel Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は、溶鋼を注入管を介して鋳型に装入することにより鋳塊を製造する下注ぎ造塊方法に関する。   The present invention relates to an ingot casting method for producing an ingot by inserting molten steel into a mold through an injection tube.

溶鋼を注入管を介して鋳型に装入することにより鋳塊を製造する方法として、鋳型の下方から鋳型内に溶鋼を注入することにより鋳塊を製造する下注ぎ造塊方法がある。特許文献１は、このような下注ぎ造塊方法を開示するものである。
特許文献１では、下注ぎ法または上注ぎ法によってキルド鋼を製造するにあたって、鋳込前溶鋼の温度をＴＬ（液相開始温度）＋２０℃以上にするとともに、その溶鋼の注入中ないしはその直後に、溶鋼トン当りの総発熱量が１８００Ｋｃａｌ以上になる量の早期燃焼型高カロリー保温剤、ただし発熱して最高温度に達するピーク時間が３分以内のものをもって、鋳型内湯面上を被覆し、鋼塊底部の沈澱晶帯における介在物集積を、軽減抑制している。 As a method for producing an ingot by inserting molten steel into a mold via an injection tube, there is a bottom pouring ingot method for producing an ingot by injecting molten steel into the mold from below the mold. Patent Document 1 discloses such a down-pour ingot-making method.
In Patent Document 1, when producing killed steel by the down-pour method or the top-pour method, the temperature of the molten steel before casting is set to TL (liquid phase start temperature) + 20 ° C. or more and during or immediately after the injection of the molten steel. An early-burning high-calorie heat-retaining agent with a total calorific value per ton of molten steel of 1800 Kcal or more, but with a peak time of less than 3 minutes to generate heat and reach the maximum temperature, coats the hot water surface in the mold, Inclusion accumulation in the precipitation zone at the bottom of the lump is reduced.

また、特許文献１に示すような下注ぎ造塊法ではないが介在物の群生化を防止するものとして特許文献２に開示されたものがある。
特許文献２では、アルミニウム、チタン、ジルコニウム等を単独又は複合して含有する溶鋼を０．５〜３０ｔｏｎ／分の注入速度で鋳造するに際して金属カルシウム若しくはカルシウムを含む合金粒を０．５〜２．０ｋｇ／分の供給速度で注入溶鋼流に添加している。 Moreover, although it is not the bottom pouring method as shown in patent document 1, there exists what was disclosed by patent document 2 as what prevents the clustering of inclusions.
In Patent Document 2, when casting molten steel containing aluminum, titanium, zirconium or the like alone or in combination at an injection rate of 0.5 to 30 ton / min, metallic calcium or alloy grains containing calcium are added in an amount of 0.5 to 2. It is added to the molten molten steel stream at a feed rate of 0 kg / min.

特開昭４７−０２６３３４号公報JP 47-026334 A 特開昭４９−０３５２３２号公報JP 49-035322 A

特許文献１及び特許文献２には、鋳塊中の介在物の集積を低減する技術が開示されている。しかし、これら文献に開示の技術を下注ぎ造塊方法による鋳塊の製造に用いたとしても、介在物の集積を十分に低減することは困難であり、その結果、サイズの大きな介在物である粗大介在物の発生を十分に抑制することが困難となっているのが実情である。
本発明は、上述の問題に鑑みてなされたもので、鋳塊中の粗大介在物の発生を抑制し、清浄度の優れた鋳塊を製造することができる下注ぎ造塊方法を提供することを目的とする。 Patent Documents 1 and 2 disclose a technique for reducing accumulation of inclusions in an ingot. However, even if the techniques disclosed in these documents are used for the production of ingots by the down-pour ingot casting method, it is difficult to sufficiently reduce the accumulation of inclusions, and as a result, the inclusions are large in size. In fact, it is difficult to sufficiently suppress the generation of coarse inclusions.
This invention is made | formed in view of the above-mentioned problem, and suppresses generation | occurrence | production of the coarse inclusion in an ingot, and provides the bottom pouring ingot method which can manufacture the ingot which was excellent in the cleanliness. With the goal.

本発明は、上記目的を達成するために、次の手段を講じた。
即ち、本発明における課題解決のための技術的手段は、溶鋼を注入管を介して下方から鋳型に装入することにより鋳塊を製造する下注ぎ造塊方法を行うに際し、前記鋳型内の溶鋼に浴面を被覆するための被覆材を、その厚みである被覆材厚が３ｍｍ以上２０ｍｍ以下となるように添加した後、金属Ｃａ及び／又はＣａ合金を、保温材を添加する前又は同時に添加することとし、前記浴面の表面積に対する前記金属Ｃａ及び／又はＣａ合金のＣａ成分の添加量が０．３５ｋｇ／ｍ２以上１０ｋｇ／ｍ２以下の範囲内の値となるように前記金属Ｃａ及び／又はＣａ合金を添加すると共に、保温材の成分含有量と添加した前記金属Ｃａ及び／又はＣａ合金のＣａ成分含有量との関係を示す含有割合である［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）の値を０．０８以上０．２５以下の範囲内となるようにするとともに、前記含有割合を前記被覆材厚で除して得られる値が０．００８以上となるようにしている点にある。 In order to achieve the above object, the present invention has taken the following measures.
That is, the technical means for solving the problem in the present invention is that the molten steel in the mold is produced by performing the pouring and ingot making method for producing the ingot by inserting the molten steel into the mold from below through the injection pipe. After the coating material for coating the bath surface is added so that the coating material thickness is 3 mm or more and 20 mm or less, the metal Ca and / or Ca alloy is added before or simultaneously with the addition of the heat insulating material. and that, the metallic Ca and to a value within a range the amount added is 0.35 kg / m 2 or more 10 kg / m 2 or less of Ca component of the metallic Ca and / or Ca alloy to the surface area of the bath surface [% Ca] / ([% Al] which is a content ratio indicating the relationship between the component content of the heat insulating material and the added Ca component of the metal Ca and / or Ca alloy while adding the Ca alloy +3 [% Fe 2 O 3 ] + [% FeO] +2 [% SiO 2 ] +2 [% MnO 2 ] + [% S]) within the range of 0.08 or more and 0.25 or less, and the content ratio Is obtained by dividing the above by the thickness of the covering material so that the value obtained is 0.008 or more.

本発明の他の技術的手段は、溶鋼を注入管を介して下方から鋳型に装入することにより鋳塊を製造する下注ぎ造塊方法を行うに際し、前記鋳型内の溶鋼に浴面を被覆するための被覆材を、その厚みである被覆材厚が３ｍｍ以上２０ｍｍ以下となるように添加した後、金属Ｃａ及び／又はＣａ合金を含有する保温材を添加することとし、前記浴面の表面積に対する前記金属Ｃａ及び／又はＣａ合金のＣａ成分の添加量が０．３５ｋｇ／ｍ２以上１０ｋｇ／ｍ２以下を満たすように前記保温材を添加すると共に、保温材の成分含有量と添加した前記金属Ｃａ及び／又はＣａ合金のＣａ成分含有量との関係を示す含有割合である［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）の値を０．０８以上０．２５以下の範囲内となるようにするとともに、前記被覆材厚を前記含有割合で除して得られる値が０．００８以上となるようにしている点にある。なお、[％Ｘ]は、保温材中Ｘ含有量（モル％）である。 The other technical means of the present invention is to cover the molten steel in the mold with a bath surface when performing the pouring and ingot forming method for producing the ingot by inserting the molten steel into the mold from below through the injection pipe. After adding a covering material for the thickness of the covering material to be 3 mm or more and 20 mm or less, a heat insulating material containing metal Ca and / or a Ca alloy is added, and the surface area of the bath surface wherein the addition amount of Ca component of the metallic Ca and / or Ca alloy with the addition of the thermal insulation material so as to satisfy the 0.35 kg / m 2 or more 10 kg / m 2 or less, it was added and ingredient content of heat insulating material for a content showing the relationship between the Ca content of the component metals Ca and / or Ca alloy [% Ca] / ([% Al] +3 [% Fe 2 O 3] + [% FeO] +2 [% SiO 2] +2 [% MnO 2 ] + [% S ]) Within the range of 0.08 or more and 0.25 or less, and the value obtained by dividing the coating material thickness by the content ratio is 0.008 or more. It is in. [% X] is the X content (mol%) in the heat insulating material.

本発明によれば、鋳塊中の粗大介在物の発生を抑制し、清浄度の優れた鋳塊を製造することができる。   According to the present invention, it is possible to suppress the generation of coarse inclusions in an ingot and to manufacture an ingot having excellent cleanliness.

下注ぎ造塊を行う下注ぎ造塊装置の概略図である。It is the schematic of the bottom pouring lump apparatus which performs bottom pouring lump. 下注ぎ造塊の流れを示す図であって、（ａ）造塊の初期段階であり、（ｂ）造塊の中期段階であり、（ｃ）終期段階でＣａを添加した時であり、（ｄ）終期段階で保温材を添加した時を示している。It is a figure which shows the flow of a bottom pouring ingot, Comprising: (a) It is the initial stage of ingot, (b) It is the middle stage of ingot, (c) It is the time of adding Ca in the final stage, d) The time when the heat insulating material is added in the final stage is shown. 実施例における［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）の値と介在物最大径との関係図である。Up [% Ca] / ([% Al] +3 [% Fe 2 O 3] + [% FeO] +2 [% SiO 2] +2 [% MnO 2] + [% S]) values of inclusions in Examples It is a relationship figure with a diameter. 実施例におけるＣａの添加量の値と介在物最大径との関係図である。It is a related figure of the value of the addition amount of Ca in an Example, and the maximum diameter of an inclusion. 被覆材の厚み、及び被覆材厚とＣａ含有割合との比を調整した場合の実施例及び比較例の結果を表わす分布図である。It is a distribution map showing the result of the Example and comparative example at the time of adjusting the ratio of the thickness of a coating | covering material, and coating | coated material thickness and Ca content rate.

以下、図を参照しながら、本発明の実施形態による下注ぎ造塊方法について説明する。
まず図１を参照して、本実施形態の下注ぎ造塊方法が適用される下注ぎ造塊装置１について説明する。図１は、下注ぎ造塊を行う下注ぎ造塊装置１の概略構成を示している。
下注ぎ造塊装置１は、下注ぎ造塊法により溶鋼２を鋳造するものであって、取鍋３内の溶鋼２を注入する注入管４と、この注入管４に注入された溶鋼２が装入される鋳型５と、注入管４と鋳型５とを連通する定盤６とを備えている。 Hereinafter, the bottom pouring and ingot-making method according to the embodiment of the present invention will be described with reference to the drawings.
First, with reference to FIG. 1, the bottom pouring and ingot-making apparatus 1 to which the bottom pouring and ingot making method of this embodiment is applied will be described. FIG. 1 shows a schematic configuration of a bottom pouring and ingot forming apparatus 1 that performs bottom pouring and ingot making.
The bottom pouring and ingot-making apparatus 1 casts molten steel 2 by the bottom pouring and ingot casting method. An injection pipe 4 for injecting molten steel 2 in a ladle 3 and a molten steel 2 injected into the injection pipe 4 are provided. A casting mold 5 to be charged, and a surface plate 6 for communicating the injection tube 4 and the casting mold 5 are provided.

注入管４及び定盤６には溶鋼２が通る湯道７が形成されていて、注入管４は、定盤６から上方に向かって立つように設けられている。鋳型５は、下方に下注入口９が形成されており定盤６上に設置されている。鋳型５は、溶鋼２が定盤６の湯道７から下注入口９を経て下方から装入される構造となっている。鋳型５の上部には、押湯枠８が装着されている。   A runner 7 through which the molten steel 2 passes is formed in the injection tube 4 and the surface plate 6, and the injection tube 4 is provided so as to stand upward from the surface plate 6. The casting mold 5 has a lower inlet 9 formed below and is placed on the surface plate 6. The mold 5 has a structure in which the molten steel 2 is inserted from the runner 7 of the surface plate 6 through the lower inlet 9 from below. A feeder frame 8 is attached to the upper part of the mold 5.

このような下注ぎ造塊装置１にて下注ぎ造塊を行うにあたっては、まず、取鍋３を注入管４上に配置して、取鍋３内の溶鋼２を注入管４に注入する。溶鋼２は、注入管４及び定盤６に形成された湯道７を通り、下注入口９を経て鋳型５へ下方から到達し、鋳型５内で冷却されてインゴット等の鋳塊となる。この下注ぎ造塊方法においては、例えば船舶用部品や発電機用部品などに用いられる大型鍛造品等の素材となる鋳塊を製造することができる。   In performing the bottom pouring and ingot using such a bottom pouring and ingot apparatus 1, first, the ladle 3 is placed on the pouring tube 4, and the molten steel 2 in the ladle 3 is poured into the pouring tube 4. The molten steel 2 passes through the runner 7 formed in the injection pipe 4 and the surface plate 6, reaches the mold 5 from below through the lower injection port 9, is cooled in the mold 5, and becomes an ingot such as an ingot. In this bottom pouring and ingot forming method, for example, an ingot that becomes a raw material such as a large forged product used for a marine component or a generator component can be manufactured.

本実施形態の下注ぎ造塊方法について詳しく説明する。
下注ぎ造塊方法において、鋳型５に装入された溶鋼２の浴面が大気と接触すると、溶鋼２は大気との接触面から酸化して清浄度を低下させる。そこで本実施形態では、溶鋼２の酸化を防止するために、溶鋼２の鋳型５内への注入が始まった段階で、溶鋼２の浴面を被覆するための被覆材１０（Ｃ−ＳｉＯ２−ＣａＯ−Ａｌ２Ｏ３系の被覆材）を鋳型５の上方から添加する。 The bottom pouring method of the present embodiment will be described in detail.
In the bottom pouring and ingot forming method, when the bath surface of the molten steel 2 charged in the mold 5 comes into contact with the atmosphere, the molten steel 2 is oxidized from the contact surface with the atmosphere to reduce the cleanliness. Therefore, in this embodiment, in order to prevent the molten steel 2 from being oxidized, the coating material 10 (C—SiO 2 − for covering the bath surface of the molten steel 2 at the stage where the injection of the molten steel 2 into the mold 5 has started. CaO—Al 2 O 3 -based coating material) is added from above the mold 5.

図２（ａ）に示すように、具体的には、溶鋼２が鋳型５内に注入される前に、被覆材１０が装入された袋を鋳型５内の下注入口９の近傍に配置する。こうすれば、溶鋼２の鋳型５内への注入が始まった直後に溶鋼２の熱によって袋が溶けるので、溶鋼２の鋳型５内への注入が始まった早い段階から溶鋼２の浴面が被覆材１０で覆われる。
次に、図２（ｂ）に示すように、鋳型５内への溶鋼２の装入が続くと、溶鋼２の浴面は徐々に上昇してゆき、浴面上の被覆材１０は、浴面が上昇する溶鋼２と鋳型５の内面との間に流入しながら消費されていく。この過程では、消費量に応じて鋳型５の上方から被覆材１０を追加添加することで、溶鋼２の浴面が大気に露出しないようにし、溶鋼２の大気との接触を防止している。被覆材１０の追加は、鋳型５内への溶鋼２の装入が開始されてから溶鋼２の浴面が押湯枠８に到達するまで実施した。なお、被覆材１０の添加方法は、上述した方法に限らない。被覆材１０の入った袋を溶鋼２の注入開始前に鋳型５内に置かなくとも、溶鋼２の鋳型５内への注入が始まった直後から、被覆材１０を鋳型５の上方から溶鋼２の浴面に直接添加してもよいし、その他の方法により添加してもよい。 Specifically, as shown in FIG. 2A, before the molten steel 2 is injected into the mold 5, the bag in which the covering material 10 is charged is disposed in the vicinity of the lower inlet 9 in the mold 5. To do. In this way, the bag is melted by the heat of the molten steel 2 immediately after the injection of the molten steel 2 into the mold 5 starts, so that the bath surface of the molten steel 2 is covered from the early stage when the injection of the molten steel 2 into the mold 5 starts. Covered with material 10.
Next, as shown in FIG. 2 (b), when the molten steel 2 is continuously charged into the mold 5, the bath surface of the molten steel 2 gradually rises, and the covering material 10 on the bath surface It is consumed while flowing between the molten steel 2 whose surface rises and the inner surface of the mold 5. In this process, the coating material 10 is additionally added from above the mold 5 in accordance with the consumption amount so that the bath surface of the molten steel 2 is not exposed to the atmosphere, and the molten steel 2 is prevented from coming into contact with the atmosphere. Addition of the covering material 10 was performed until the bath surface of the molten steel 2 reached the feeder frame 8 after the start of charging the molten steel 2 into the mold 5. In addition, the addition method of the coating | covering material 10 is not restricted to the method mentioned above. Even if the bag containing the covering material 10 is not placed in the mold 5 before the injection of the molten steel 2 is started, the covering material 10 is placed on the molten steel 2 from above the mold 5 immediately after the injection of the molten steel 2 into the mold 5 starts. It may be added directly to the bath surface or may be added by other methods.

通常、下注ぎ造塊方法では、溶鋼２の浴面が鋳型５の上部付近に到達したときに、溶鋼２の温度を保つための保温材１１を添加する。ここで、保温材１１として酸化鉄（ＦｅｔＯ）、ＭｎＯ２、ＳｉＯ２、及びＡｌを含む粉粒体などを添加するが、溶鋼２に保温材１１を添加することで大きな粒径の高アルミナ系介在物（粗大介在物）が生成し、溶鋼２の清浄度が低下することがある。この保温材１１は、パウダー形状の粉粒体であっても、ボード等の成形形状であってもよい。 Usually, in the bottom pouring and ingot-making method, when the bath surface of the molten steel 2 reaches near the upper part of the mold 5, a heat insulating material 11 for maintaining the temperature of the molten steel 2 is added. Here, the iron oxide as a heat insulating material 11 (Fe t O), MnO 2, SiO 2, and although the addition of such particulate material containing Al, a large particle diameter of the high by the addition of heat insulating material 11 in the molten steel 2 Alumina inclusions (coarse inclusions) may be generated, and the cleanliness of the molten steel 2 may be reduced. The heat insulating material 11 may be a powder-shaped powder or a molded shape such as a board.

そこで、本発明では、保温材１１を添加する前、又は保温材１１の添加と同時にカルシウム（Ｃａ）１２を溶鋼２に添加する。この添加されたＣａ１２によって、保温材１１の添加時に生成する高アルミナ系介在物を、下記式（１）〜（３）に従ってＣａＯ−Ａｌ２Ｏ３系介在物へと改質する。このＣａＯ−Ａｌ２Ｏ３系介在物は凝集しにくく、その大きさは高アルミナ系介在物に比べて小さいので、溶鋼２の清浄度を向上させることができる。 Therefore, in the present invention, calcium (Ca) 12 is added to the molten steel 2 before the heat insulating material 11 is added or simultaneously with the addition of the heat insulating material 11. With this added Ca12, the high alumina inclusions generated when the heat insulating material 11 is added are modified into CaO—Al 2 O 3 inclusions according to the following formulas (1) to (3). The CaO—Al 2 O 3 inclusions are less likely to agglomerate and the size thereof is smaller than that of the high alumina inclusions, so that the cleanliness of the molten steel 2 can be improved.

２Ａｌ＋３ＦｅtＯ＝Ａｌ２Ｏ３＋３tＦｅ ・・・（１）
２Ａｌ＋３／２ＭｎＯ２＝Ａｌ２Ｏ３＋３／２Ｍｎ ・・・（２）
２Ａｌ＋３／２ＳｉＯ２＝Ａｌ２Ｏ３＋３／２Ｓｉ ・・・（３）
以下、Ｃａ１２の添加方法や添加量について詳しく説明する。
本実施形態では、図２（ｃ）に示すように、鋳型５内への溶鋼２の注入が開始されてから溶鋼２が押湯枠８に達して鋳造が終了するまでの間に、Ｃａ１２を添加する。Ｃａ１２の添加後に、図２（ｄ）に示すように保温材１１を添加する。 2Al + 3Fe t O = Al 2 O 3 + 3tFe ··· (1)
2Al + 3 / 2MnO 2 = Al 2 O 3 + 3 / 2Mn (2)
2Al + 3 / 2SiO 2 = Al 2 O 3 + 3 / 2Si (3)
Hereinafter, the addition method and addition amount of Ca12 will be described in detail.
In the present embodiment, as shown in FIG. 2 (c), Ca12 is inserted between the start of the injection of the molten steel 2 into the mold 5 and the time when the molten steel 2 reaches the feeder frame 8 and the casting is finished. Added. After the addition of Ca12, the heat insulating material 11 is added as shown in FIG.

具体的には、鋳造の終了が近くなった段階で、溶鋼２の浴面を覆った被覆材１０の上方からＣａ１２を添加して、Ｃａ１２の添加後に保温材１１を添加する。
添加されるＣａ１２は、純金属Ｃａ（金属Ｃａ）であってもＣａ合金であってもよい。Ｃａ合金としては、Ｃａ−Ｓｉ合金、Ｃａ−Ｎｉ合金などがあるが、鋼成分の規格に応じて任意に選択することができる。また、保温材１１は、Ｃａ１２の添加に続いて連続的に添加され、且つ、Ｃａ１２の添加から１分以内に添加されるのが好ましく、長くても１０分以内とする方がよい。Ｃａ１２の添加から保温材１１の添加までの時間は、鋳造の作業手順や鋳造設備の制約などに応じて１分より長くなってもかまわないが、この時間があまり長くなってしまうと、Ｃａ１２が上述の改質剤としては十分に働かなくなることに注意しなくてはならない。 Specifically, at the stage when the end of casting is near, Ca12 is added from above the covering material 10 covering the bath surface of the molten steel 2, and the heat insulating material 11 is added after the addition of Ca12.
The added Ca12 may be pure metal Ca (metal Ca) or a Ca alloy. Examples of the Ca alloy include a Ca—Si alloy and a Ca—Ni alloy, which can be arbitrarily selected according to the standard of steel components. Moreover, it is preferable that the heat insulating material 11 is continuously added following the addition of Ca12, and is added within 1 minute from the addition of Ca12, and it is better to be within 10 minutes at the longest. The time from the addition of Ca12 to the addition of the heat insulating material 11 may be longer than 1 minute depending on the casting work procedure and the restrictions on the casting equipment, but when this time becomes too long, It must be noted that the above modifiers do not work well.

なお、鋳造の終了が近くなった段階でＣａ１２を添加すると述べたが、鋳造の終了が近くなった段階とは、鋳造終了の１０分前くらいが目安となる。もちろんこの目安は、鋳造終了の１０分前に限らず、鋳造工程の操業条件や上述の式（１）〜（３）の反応速度に応じて任意に変更することができる。
上述のように、大きな粒径の高アルミナ系介在物（粗大介在物）の生成を抑制することを目的として、保温材１１を添加する前、又は保温材１１の添加と同時にＣａ１２を溶鋼２に添加する。このとき、本実施形態では、Ｃａ１２の添加量について２つの条件を課している。以下、それぞれの条件について説明する。 Although it has been described that Ca12 is added at the stage where the end of casting is near, the stage where the end of casting is near is about 10 minutes before the end of casting. Of course, this guideline is not limited to 10 minutes before the end of casting, but can be arbitrarily changed according to the operating conditions of the casting process and the reaction rates of the above-described formulas (1) to (3).
As described above, Ca12 is added to the molten steel 2 before the heat insulating material 11 is added or simultaneously with the addition of the heat insulating material 11 for the purpose of suppressing the formation of high alumina inclusions (coarse inclusions) having a large particle size. Added. At this time, in this embodiment, two conditions are imposed on the amount of Ca12 added. Hereinafter, each condition will be described.

まず１つめの条件として、Ｃａ１２を添加するに際し、溶鋼２の浴面の表面積（ｍ２）に対するＣａ１２中のＣａ成分（純Ｃａ）の添加量（ｋｇ）である１ｍ２当たりの添加量が、０．３５ｋｇ／ｍ２以上１０ｋｇ／ｍ２以下（０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２）の範囲を満たすこととしている（第１条件）。言い換えれば、添加される金属Ｃａ及び
Ｃａ合金中のＣａ成分相当量を押湯枠８から内側の浴面の表面積で割って得られた値を、Ｃａ成分の添加量として規定する。その上で、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲内となるようにＣａ１２の添加量を決定し添加する。 First, as the first condition, when adding Ca12, the addition amount per 1 m 2 that is the addition amount (kg) of the Ca component (pure Ca) in Ca12 to the surface area (m 2 ) of the bath surface of the molten steel 2, 0.35 kg / m 2 or more 10 kg / m 2 or less is set to satisfy the range of (0.35kg / m 2 ~10kg / m 2) ( first condition). In other words, a value obtained by dividing the Ca component equivalent amount in the added metal Ca and Ca alloy by the surface area of the inner bath surface from the feeder frame 8 is defined as the Ca component addition amount. Then, the addition amount of Ca12 is determined and added so that the addition amount of Ca component is in the range of 0.35 kg / m 2 to 10 kg / m 2 .

Ｃａ成分の添加量が０．３５ｋｇ／ｍ２未満であると、高アルミナ系介在物を十分にＣａＯ−Ａｌ２Ｏ３系介在物へと改質するにはＣａ成分は不足する。一方で、Ｃａ成分の添加量が１０ｋｇ／ｍ２よりも多いと、大きな粒径のＣａＯ系の介在物が発生してしまうことにより溶鋼２の清浄度が低下してしまうおそれがある。
ところで、保温材１１は、Ａｌ、Ｓｉ、ＦｅｔＯ、ＭｎＯ、ＳｉＯ２、ＭｎＯ２、Ｃ、Ｓの各成分を含有している。例えば、保温材１１の組成は、ＦｅＯ：１０〜２０質量％、Ｆｅ２Ｏ３：１０〜２０質量％、Ａｌ：２０〜２５質量％、Ａｌ２Ｏ３：２５〜４０質量％、ＳｉＯ２：５〜１０質量％程度である。 When the added amount of the Ca component is less than 0.35 kg / m 2 , the Ca component is insufficient to sufficiently reform the high alumina-based inclusions into CaO—Al 2 O 3 -based inclusions. On the other hand, when there is more addition amount of Ca component than 10 kg / m < 2 >, there exists a possibility that the cleanliness of the molten steel 2 may fall by generating the CaO type inclusion of a big particle size.
Meanwhile, heat insulating material 11, Al, Si, Fe t O , MnO, SiO 2, MnO 2, C, contains the components of the S. For example, the composition of the heat insulating material 11 is FeO: 10 to 20% by mass, Fe 2 O 3 : 10 to 20% by mass, Al: 20 to 25% by mass, Al 2 O 3 : 25 to 40% by mass, SiO 2 : It is about 5-10 mass%.

そこで２つめの条件に関して、本実施形態では、保温材１１中の各成分の含有量（成分含有量）とＣａ１２中のＣａ成分の含有量（Ｃａ成分含有量）との関係を、保温材の成分含有量に対するＣａ成分含有量の割合（含有割合）Ｘとして規定する。保温材１１によってＣａ１２のＣａ成分が消費されるため、保温材１１の成分にあわせて保温材１１中のＣａ成分の含有割合Ｘを規定する必要がある。Ｃａ成分の含有割合Ｘを規定するために、保温材１１の各成分の含有量とＣａ成分の含有量との関係を下記の式（４）で表現し、式（４）で得られる値である含有割合Ｘが０．０８以上０．２５以下（０．０８〜０．２５）の範囲を満たすことを、２つめの条件としている（第２条件）。   Therefore, regarding the second condition, in the present embodiment, the relationship between the content of each component in the heat insulating material 11 (component content) and the content of the Ca component in Ca 12 (Ca component content) is as follows. It is defined as the ratio (content ratio) X of the Ca component content to the component content. Since the Ca component of Ca12 is consumed by the heat insulating material 11, it is necessary to define the content ratio X of the Ca component in the heat insulating material 11 in accordance with the components of the heat insulating material 11. In order to regulate the content ratio X of the Ca component, the relationship between the content of each component of the heat insulating material 11 and the content of the Ca component is expressed by the following formula (4), and the value obtained by the formula (4): The second condition is that a certain content ratio X satisfies a range of 0.08 to 0.25 (0.08 to 0.25) (second condition).

Ｘ＝［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］） ・・・（４）
ただし、式（４）で示される「％」は、「モル％」を意味している。
ここで、保温材１１中には、硫黄Ｓが含有されているが、Ｓの含有量は２００ｐｐｍ程度（不可避不純物程度の量）であり、実質的に零（≒０）と考えてもよい。言い換えれば、Ｓの含有量は他の成分に比べて微量であるため、式（４）にＳの含有量を代入したとしても、式（４）の値Ｘが大きく変化することはなく、実質的に影響が出ない。 X = [% Ca] / ( [% Al] +3 [% Fe 2 O 3] + [% FeO] +2 [% SiO 2] +2 [% MnO 2] + [% S]) ··· (4)
However, “%” represented by the formula (4) means “mol%”.
Here, although the heat insulating material 11 contains sulfur S, the content of S is about 200 ppm (amount of inevitable impurities) and may be considered to be substantially zero (≈0). In other words, since the S content is very small compared to other components, even if the S content is substituted into the formula (4), the value X of the formula (4) does not change greatly, There will be no impact.

式（４）の値が０．０８未満であると、保温材１１によって生成する高アルミナ系介在物量に対するＣａ成分の量が少なすぎるために、添加したＣａ１２によっては、十分に高アルミナ系介在物をＣａＯ−Ａｌ２Ｏ３系介在物へと改質することができない。一方、式（４）の値が０．２５よりも大きいと、保温材１１に対するＣａ成分の量が多すぎるために大きな粒径のＣａＯ系の介在物が発生してしまい、溶鋼２の清浄度が低下してしまうおそれがある。この事実に基づけば、式（４）で得られる含有割合Ｘは、溶鋼２の高アルミナ系介在物を改質して高い清浄度を実現するために有効に働くカルシウムの量（有効カルシウム量）を規定するための値であり、この有効カルシウム量を表現しているといえる。 If the value of the formula (4) is less than 0.08, the amount of Ca component relative to the amount of high alumina inclusions produced by the heat insulating material 11 is too small. Cannot be modified into CaO—Al 2 O 3 inclusions. On the other hand, if the value of the formula (4) is larger than 0.25, the amount of Ca component with respect to the heat insulating material 11 is too large, so that a CaO-based inclusion with a large particle size is generated, and the cleanliness of the molten steel 2 May decrease. Based on this fact, the content ratio X obtained by the formula (4) is the amount of calcium that works effectively to improve the high alumina inclusions of the molten steel 2 to achieve high cleanliness (effective calcium amount). It can be said that this effective calcium amount is expressed.

したがって本実施形態では、１つめの条件である、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲にあることと、２つめの条件である、式（４）に示す含有割合Ｘが０．０８〜０．２５の範囲の値となることとを同時に満たすようにＣａ１２を添加する。
なお、保温材１１とＣａ１２とを別々に添加する場合には、保温材１１が微量の金属Ｃａ及びＣａ合金を含有していてもよい。保温材１１が微量の金属Ｃａ及びＣａ合金を含有している場合であっても、式（４）に示す保温材１１中の各成分の含有量とＣａ成分の添加量との関係（含有割合Ｘ）が、０．０８〜０．２５の範囲に含まれる値であればよい。 Therefore, in the present embodiment, the first condition, that is, the addition amount of the Ca component is in the range of 0.35 kg / m 2 to 10 kg / m 2 , and the second condition is shown in the formula (4). Ca12 is added so that it may satisfy | fill simultaneously that the content rate X becomes the value of the range of 0.08-0.25.
In addition, when adding the heat insulating material 11 and Ca12 separately, the heat insulating material 11 may contain a trace amount metal Ca and Ca alloy. Even when the heat insulating material 11 contains a trace amount of metal Ca and Ca alloy, the relationship between the content of each component in the heat insulating material 11 shown in Formula (4) and the added amount of the Ca component (content ratio) X) should just be a value included in the range of 0.08-0.25.

上述の説明では、鋳造の開始から溶鋼２が押湯枠８に達して鋳造が終了するまでの間に、Ｃａ１２と保温材１１とを別々に添加していたが、これに代えて、保温材１１とＣａ１２とを混ぜ合わせて、保温材１１とＣａ１２とを同時に添加するようにしてもよい。例えば、保温材１１を添加する前にＣａ１２を保温材１１に混合して、Ｃａ成分を含有する保温材１１を用意しておき、その保温材１１を溶鋼２に添加するようにしてもよい。   In the above description, Ca12 and the heat insulating material 11 are added separately from the start of casting until the molten steel 2 reaches the feeder frame 8 and the casting is finished, but instead of this, the heat insulating material is replaced. 11 and Ca12 may be mixed and the heat insulating material 11 and Ca12 may be added simultaneously. For example, Ca12 may be mixed with the heat insulating material 11 before the heat insulating material 11 is added to prepare the heat insulating material 11 containing the Ca component, and the heat insulating material 11 may be added to the molten steel 2.

Ｃａ１２が混合された保温材１１を添加する場合も、式（４）に示す含有割合Ｘが０．０８〜０．２５の範囲に含まれる値であればよい。また、上述したように、Ｃａ１２が混
合された保温材１１を、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２を満たすように添加する必要がある。 Also when adding the heat insulating material 11 with which Ca12 was mixed, the content ratio X shown in Formula (4) should just be a value included in the range of 0.08-0.25. As described above, the heat insulating material 11 Ca12 is mixed, the addition amount of Ca component needs to be added so as to satisfy the 0.35kg / m 2 ~10kg / m 2 .

表１は、本発明の下注ぎ造塊方法によって鋳塊を製造した実施例と、本発明の下注ぎ造塊方法とは異なる方法によって鋳塊を製造した比較例とを示したものである。   Table 1 shows an example in which an ingot was produced by the under-pour ingot casting method of the present invention, and a comparative example in which the ingot was produced by a method different from the under-ingot ingot ingot method of the present invention.

Figure 0005773891
Figure 0005773891

実施例及び比較例において、下注ぎ造塊方法を行う前の一次精錬は、当業者常法により電気炉にてスクラップを溶解した後に精錬を行い、２０〜１００トンの溶鋼２を取鍋３に出鋼した。また、一次精錬後の溶鋼２に対してＬＦ装置及び蓋脱ガス装置（ＶＤ）による二次精錬を行い、溶鋼２の成分調整及び温度調整をした。一次精錬及び二次精錬が終了した溶鋼２に対して、下注ぎ造塊方法によって鋳塊（インゴット）を製造した。   In the examples and comparative examples, the primary refining before the bottom pouring and ingot casting method is performed by melting the scraps in an electric furnace according to the ordinary method of those skilled in the art, and the molten steel 2 of 20 to 100 tons is taken into the ladle 3 Steel was produced. Moreover, the secondary refining by the LF apparatus and a cover degassing apparatus (VD) was performed with respect to the molten steel 2 after the primary refining, and the component adjustment and temperature adjustment of the molten steel 2 were performed. With respect to the molten steel 2 in which the primary refining and the secondary refining were finished, an ingot was manufactured by the down-pour ingot casting method.

本実施形態では、鋳型５による鋳造後に、凝固したインゴットを当業者常法によって約１３００℃まで加熱して、熱間鍛造により１５０〜７００ｍｍの断面直径を有する鍛造材に成形した。
上述の一次精錬は、電気炉による精錬でなくてもよく転炉などの他の装置で行ってもよい。また、二次精錬も、必ずしもＬＦ装置や蓋脱ガス装置で行う必要はなく、還流脱ガス装置（ＲＨ）やＣＡＳ装置などの他の装置で行ってもよい。さらに、一次精錬や二次精錬における溶鋼２の成分、処理温度及び溶鋼量などは、本発明の本質に関わる部分ではなく上述した数値に限定されるものではない。なお、下注ぎ造塊方法における鋳型５のサイズは、２０トン〜９０トンのインゴットを製造できるものとしているが、インゴットのサイズ及び形状も、本実施形態で開示したものに限定されるものではない。 In this embodiment, after casting with the mold 5, the solidified ingot was heated to about 1300 ° C. by a conventional method of those skilled in the art, and formed into a forged material having a cross-sectional diameter of 150 to 700 mm by hot forging.
The primary refining described above may not be performed by an electric furnace, but may be performed by another apparatus such as a converter. The secondary refining is not necessarily performed by the LF apparatus or the lid degassing apparatus, and may be performed by other apparatuses such as a reflux degassing apparatus (RH) or a CAS apparatus. Furthermore, the components of the molten steel 2 in the primary refining and the secondary refining, the processing temperature, the amount of molten steel, and the like are not parts related to the essence of the present invention and are not limited to the above-described numerical values. In addition, although the size of the casting_mold | template 5 in the bottom pouring ingot-making method shall be able to manufacture an ingot of 20 tons-90 tons, the size and shape of an ingot are not limited to what was disclosed by this embodiment. .

また、実施例及び比較例では、誘導溶解炉を鋳型５に模した小型実験も一部実施した。小型実験では、溶鋼量３〜３０ｋｇの溶鋼２を誘導溶解炉で溶解して成分を調整した後、鋳型５の場合と同様に、速やかに被覆材１０を添加した。その後、溶鋼２の浴面の表面積に対するＣａ成分の添加量が０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲を満たすように、パウダー状のＣａ１２とＣａ成分を含まない保温材１１を同時に添加、またはＣａ１２を含有する保温材１１を添加した。なお、Ｃａ成分を含有する保温材１１又はＣａ１２を
添加するにあたっては、式（４）として示した“Ｘ＝［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）”が、０．０８〜０．２５を満たすように保温材１１及びＣａ１２を添加した。そして、保温材１１を添加した後は、誘導溶解炉の電力を停止して炉内で溶鋼２を凝固させた。 Further, in the examples and comparative examples, some small-scale experiments simulating an induction melting furnace as the mold 5 were also performed. In a small experiment, after the molten steel 2 having a molten steel amount of 3 to 30 kg was melted in an induction melting furnace to adjust the components, the covering material 10 was quickly added as in the case of the mold 5. Thereafter, the powdered Ca12 and the heat insulating material 11 not containing the Ca component are simultaneously added so that the addition amount of the Ca component with respect to the surface area of the bath surface of the molten steel 2 satisfies the range of 0.35 kg / m 2 to 10 kg / m 2. Or the heat insulating material 11 containing Ca12 was added. In addition, when adding the heat insulating material 11 or Ca12 containing the Ca component, “X = [% Ca] / ([% Al] +3 [% Fe 2 O 3 ] + [% FeO] shown as the formula (4)” ] +2 [% SiO 2] +2 [% MnO 2] + [% S]) " was added heat insulating material 11 and Ca12 to satisfy 0.08 to 0.25. And after adding the heat insulating material 11, the electric power of the induction melting furnace was stopped and the molten steel 2 was solidified in the furnace.

鍛造後の鋼塊や誘導溶解炉（小型実験）にて凝固させた鋼塊から試料として小片を取り出して研磨した後、電子顕微鏡（ＳＥＭ）による介在物の観察を行った。実施例及び比較例では、１５×１５ｍｍ四方の視野内で検出された最大介在物の大きさを表中の介在物サイズとした。
表１に示すように、このように試料を作成して観察した結果、実施例１〜１１では、最大介在物のサイズを２００μｍ以下とすることができた。実施例１〜１１は、上述の本実施形態による下注ぎ造塊方法に従って、鋳型５内の溶鋼２に浴面を被覆するための被覆材１０を添加した後、Ｃａ１２を含有する保温材１１を添加するか、又は保温材１１とＣａ１２とを別々に添加するかのいずれかを行った。このとき、上述したように、浴面の表面積に対するＣａ成分の添加量は０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲を満たすようにし、さらに、式（４）の値Ｘが０．０８〜０．２５の範囲を満たすようにした。 A small piece was taken out as a sample from a steel ingot after forging or a steel ingot solidified in an induction melting furnace (small experiment) and polished, and the inclusions were observed with an electron microscope (SEM). In the examples and comparative examples, the size of the maximum inclusion detected in a 15 × 15 mm square field of view was defined as the inclusion size in the table.
As shown in Table 1, as a result of preparing and observing the sample in this way, in Examples 1 to 11, the size of the maximum inclusion was able to be 200 μm or less. In Examples 1 to 11, after the coating material 10 for coating the bath surface on the molten steel 2 in the mold 5 is added according to the above-described ingot casting method according to the present embodiment, the heat insulating material 11 containing Ca12 is added. Either the thermal insulation material 11 or Ca12 was added separately. At this time, as described above, the addition amount of the Ca component with respect to the surface area of the bath surface satisfies the range of 0.35 kg / m 2 to 10 kg / m 2 , and the value X of the formula (4) is 0.08. The range of ˜0.25 was satisfied.

図３は、実施例１〜１１に関して、上述した式（４）の値と表１に示した介在物最大径との関係をまとめたものである。図３に示すように、Ｃａ成分の添加量を０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲の値となるように調整すると、式（４）の値Ｘが０．０８〜０．２５の範囲にあるときは、介在物最大径は２００μｍ未満である。しかし、式（４）の値Ｘが０．０８未満であれば、介在物最大径は２００μｍを大きく超えて５００μｍ以上となり、式（４）の値Ｘが０．２５より大きいときも、介在物最大径は２００μｍを大きく超えて４００μｍ以上となることがわかる。即ち、図３のグラフから見ても、式（４）の値が０．０８や０．２５となったときが、介在物最大径を小さくするための境界となる。 FIG. 3 summarizes the relationship between the value of the above-described formula (4) and the maximum inclusion inclusion diameter shown in Table 1 for Examples 1 to 11. As shown in FIG. 3, when the addition amount of the Ca component is adjusted so as to be in the range of 0.35 kg / m 2 to 10 kg / m 2 , the value X of the formula (4) is 0.08 to 0.25. In the range, the maximum inclusion diameter is less than 200 μm. However, if the value X of the formula (4) is less than 0.08, the maximum diameter of inclusions is more than 200 μm and becomes 500 μm or more. Even when the value X of the formula (4) is more than 0.25, the inclusions It can be seen that the maximum diameter greatly exceeds 200 μm and becomes 400 μm or more. That is, also from the graph of FIG. 3, when the value of Formula (4) becomes 0.08 or 0.25, it becomes a boundary for reducing the maximum diameter of inclusions.

図４は、実施例１〜１１に関して、Ｃａ成分の添加量と介在物最大径との関係をまとめたものである。図４に示すように、式（４）の値を０．０８〜０．２５の範囲の値となるように調整すると、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２〜１０ｋｇ／ｍ２の範囲にあるときは、介在物最大径は２００μｍ未満である。しかし、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２未満であれば、介在物最大径は２００μｍを大きく超えて３５０μｍ以上となり、Ｃａ成分の添加量が１０ｋｇ／ｍ２より大きいときも、介在物最大径は２００μｍを大きく超えて４００μｍ以上となることがわかる。即ち、図４のグラフから見ても、Ｃａ成分の添加量が０．３５ｋｇ／ｍ２や１０ｋｇ／ｍ２となったときが、介在物最大径を小さくするための境界となる。 FIG. 4 summarizes the relationship between the amount of Ca component added and the maximum inclusion diameter for Examples 1 to 11. As shown in FIG. 4, when the value of Equation (4) is adjusted to a value in the range of 0.08 to 0.25, the amount of Ca component added is 0.35 kg / m 2 to 10 kg / m 2 . When in the range, the maximum inclusion diameter is less than 200 μm. However, if the addition amount of the Ca component is less than 0.35 kg / m 2 , the maximum diameter of inclusions is more than 200 μm and becomes 350 μm or more, and even when the addition amount of the Ca component is more than 10 kg / m 2 It can be seen that the maximum diameter greatly exceeds 200 μm and becomes 400 μm or more. In other words, even when viewed from the graph in FIG. 4, when the added amount of the Ca constituent became 0.35 kg / m 2 and 10 kg / m 2 becomes the boundary for reducing inclusions maximum diameter.

一方で、被覆材１０を添加した比較例１２〜２７では、Ｃａ成分の添加量に関する第１条件、及び、式（４）に関する第２条件のいずれかが満たされておらず、介在物最大径は２００μｍよりも大きくなった。つまり、第１条件が満たされているが第２条件が満たされていない、又は、第２条件が満たされているが第１条件が満たされていない比較例１２〜２７では、介在物最大径は２００μｍよりも大きくなった。   On the other hand, in Comparative Examples 12 to 27 to which the coating material 10 is added, either the first condition regarding the addition amount of the Ca component or the second condition regarding the formula (4) is not satisfied, and the maximum diameter of inclusions Became larger than 200 μm. That is, in the comparative examples 12 to 27 in which the first condition is satisfied but the second condition is not satisfied, or the second condition is satisfied but the first condition is not satisfied, the inclusion maximum diameter Became larger than 200 μm.

さらに、比較例２８〜３２は、被覆材１０を添加しなかったり、途中で被覆材１０が消費されても被覆材１０を追加添加しなかったりした場合（表中、被覆材の添加「ナシ」）であり、これらの場合でも、介在物最大径は２００μｍよりも大きくなった。
以上、本実施形態の下注ぎ造塊方法によれば、鋳型５内の溶鋼２に浴面を被覆するための被覆材１０を添加した後、上述の第１条件及び第２条件を満たすように、Ｃａ１２を含有する保温材１１を添加するか、保温材１１を添加する前又は同時にＣａ１２を添加する。これによって、溶鋼２での粗大介在物の発生を抑制するとともに鋳塊中の介在物最大径を２００μｍ以下にすることができ、清浄度の優れた鋳塊を製造することができる。 Further, in Comparative Examples 28 to 32, when the covering material 10 is not added, or when the covering material 10 is consumed in the middle, the additional covering material 10 is not added (in the table, the addition of the covering material “pear”). In these cases, the maximum inclusion diameter was larger than 200 μm.
As described above, according to the bottom pouring ingot method of the present embodiment, after adding the coating material 10 for coating the bath surface to the molten steel 2 in the mold 5, the first condition and the second condition described above are satisfied. The heat insulating material 11 containing Ca12 is added, or Ca12 is added before or simultaneously with the addition of the heat insulating material 11. Thereby, generation | occurrence | production of the coarse inclusion in the molten steel 2 can be suppressed, and the maximum diameter of the inclusion in an ingot can be made 200 micrometers or less, and the ingot excellent in the cleanliness can be manufactured.

ここまで説明した本実施形態による下注ぎ造塊方法において、介在物最大径をさらに小さくする方法について、以下に説明する。上述の下注ぎ造塊方法では、第１条件及び第２条件を満たすことで介在物最大径を２００μｍ以下に抑制できると説明したが、第１条件及び第２条件を満たすことに加えて、被覆材１０の厚み（被覆材厚ｄ）を調整し、その上
で被覆材厚ｄと上述の含有割合Ｘとの比（Ｘ／ｄ値）を調整すると、介在物最大径を２００μｍ未満に抑制することができて、介在物の平均粒径も小さくすることができる。 A method for further reducing the maximum inclusion diameter in the bottom pouring method according to the present embodiment described so far will be described below. In the above-described ingot casting method, it has been explained that the maximum inclusion diameter can be suppressed to 200 μm or less by satisfying the first condition and the second condition, but in addition to satisfying the first condition and the second condition, When the thickness of the material 10 (coating material thickness d) is adjusted, and the ratio (X / d value) between the coating material thickness d and the above-described content ratio X is adjusted, the maximum inclusion diameter is suppressed to less than 200 μm. And the average particle size of the inclusions can be reduced.

具体的には、被覆材１０の厚みである被覆材厚ｄを２０ｍｍ以下となるように調整し、その上でＸ／ｄ値が０．００８以上となるように式（４）の含有割合Ｘを調整する。既に述べたように、含有割合Ｘは、式（４）に従って保温材１１及びＣａ１２の添加量（モル％）によって決まる。以下の表２に示す実施例１〜１８のように、第１条件及び第２条件を満たすことに加えて、被覆材厚ｄを２０ｍｍ以下となるように調整し、Ｘ／ｄ値が０．００８以上となるように調整することで、介在物最大径を１５０μｍ以下に抑制することができる。好ましくは、被覆材厚ｄを１５ｍｍ以下とする。   Specifically, the coating material thickness d, which is the thickness of the coating material 10, is adjusted to be 20 mm or less, and the X / d value is 0.008 or more, and then the content ratio X of the formula (4) Adjust. As already described, the content ratio X is determined by the amount (mol%) of the heat insulating material 11 and Ca12 according to the formula (4). As in Examples 1 to 18 shown in Table 2 below, in addition to satisfying the first condition and the second condition, the coating material thickness d is adjusted to be 20 mm or less, and the X / d value is 0. By adjusting to become 008 or more, the maximum inclusion diameter can be suppressed to 150 μm or less. Preferably, the coating material thickness d is 15 mm or less.

Figure 0005773891
Figure 0005773891

すでに述べたように、Ｃａ１２として金属ＣａやＣａ合金を添加する目的は、保温材１１の添加時に生成する高アルミナ系介在物を、凝集しにくいＣａＯ−Ａｌ２Ｏ３系介在物へと改質することである。しかし、Ｃａ１２のＣａ成分は、改質に寄与する前に保温材１１の成分であるＦｅ２Ｏ３やＳｉＯ２などによって酸化されてＣａＯへと変化してしまう。そこで、本願発明の発明者らは、Ｃａ１２の表面側のＣａ成分がＣａＯに変化しても、当該Ｃａ１２の中心部分のＣａ成分が保温材１１内で残り、介在物改質効果が得られるように被覆材厚ｄやＸ／ｄ値を調整する試みを行った。その結果、表２の実施例１〜１８に示すような優良な結果を得ることができた。 As already described, the purpose of adding metal Ca or Ca alloy as Ca12 is to modify the high alumina inclusions that are formed when the heat insulating material 11 is added into CaO—Al 2 O 3 inclusions that are less likely to aggregate. It is to be. However, the Ca component of Ca12 is oxidized by Fe 2 O 3 , SiO 2, or the like, which is a component of the heat insulating material 11, before it contributes to the modification and changes to CaO. Therefore, the inventors of the present invention seem to obtain inclusion modification effect even if the Ca component on the surface side of Ca12 is changed to CaO, the Ca component in the central part of the Ca12 remains in the heat insulating material 11. An attempt was made to adjust the coating material thickness d and the X / d value. As a result, excellent results as shown in Examples 1 to 18 in Table 2 could be obtained.

表２の比較例についても触れておく。表２における比較例１９〜比較例２６（ただし、比較例２１を除く）では、被覆材厚ｄが２０ｍｍ以下となるように、且つ、Ｘ／ｄ値が０．００８以上となるように調整したにもかかわらず、Ｃａ成分の添加量に関する第１条件、及び、式（４）に関する第２条件のいずれか又は両方を満たさなかった。従って、介在物最大径は、１５０μｍを遥かに超える大きな値となった。比較例２１，２７では、第１条件及び第２条件のいずれかを満たさなかっただけでなく、被覆材厚ｄも２０ｍｍ以下ではなかった、又はＸ／ｄ値も０．００８以上ではなかったため、介在物最大径は１５０μｍを遥かに超える大きな値となった。   The comparative example of Table 2 is also mentioned. In Comparative Example 19 to Comparative Example 26 (excluding Comparative Example 21) in Table 2, the coating material thickness d was adjusted to 20 mm or less and the X / d value was adjusted to 0.008 or more. Nevertheless, either or both of the first condition regarding the addition amount of the Ca component and the second condition regarding the formula (4) were not satisfied. Accordingly, the maximum inclusion diameter was a large value far exceeding 150 μm. In Comparative Examples 21 and 27, not only the first condition and the second condition were not satisfied, but the coating material thickness d was not 20 mm or less, or the X / d value was not 0.008 or more. The maximum inclusion diameter was a large value far exceeding 150 μm.

比較例２８〜３６は、被覆材厚ｄが２０ｍｍ以下となっていない状態、又は、Ｘ／ｄ値
が０．００８以上となっていない状態であった。しかし、すでに述べたように第１条件及び第２条件をともに満たしたので、介在物最大径は１５０μｍよりも大きいものの２００μｍ以下に抑制できた。
図５のグラフは、これら実施例１〜１８と比較例１９〜３６の結果を表わす分布図である。黒のひし形が実施例１〜１８の結果を示し、白抜きの正方形が比較例１９〜３６の結果を示している。図５に示すように、介在物最大径（又は介在物最大長径）が１５０μｍ以下となるのは、被覆材厚ｄを２０ｍｍ以下となるように調整し、その上でＸ／ｄ値が０．００８以上となるように式（４）の含有割合Ｘを調整した実施例１〜１８においてであることが一目でわかる。 In Comparative Examples 28 to 36, the coating material thickness d was not 20 mm or less, or the X / d value was not 0.008 or more. However, since both the first condition and the second condition were satisfied as described above, the maximum inclusion inclusion diameter was larger than 150 μm but could be suppressed to 200 μm or less.
The graph of FIG. 5 is a distribution diagram showing the results of Examples 1 to 18 and Comparative Examples 19 to 36. Black diamonds show the results of Examples 1 to 18, and white squares show the results of Comparative Examples 19 to 36. As shown in FIG. 5, the maximum inclusion diameter (or maximum inclusion longest diameter) is 150 μm or less, so that the coating material thickness d is adjusted to 20 mm or less, and the X / d value is 0. It can be seen at a glance that it is in Examples 1 to 18 in which the content ratio X of the formula (4) is adjusted to be 008 or more.

このように、本実施形態の下注ぎ造塊方法によれば、鋳型５内の溶鋼２に浴面を被覆するための被覆材１０を被覆材厚ｄが２０ｍｍ以下となるように添加した後、上述の第１条件及び第２条件を満たすように、なお且つ、被覆材厚ｄと含有割合Ｘとの比（Ｘ／ｄ値）が０．００８以上となるように、Ｃａ１２を含有する保温材１１を添加するか、保温材１１を添加する前又は同時にＣａ１２を添加する。このように被覆材厚ｄとＸ／ｄ値とを調整することによって、溶鋼２での粗大介在物の発生を抑制するとともに鋳塊中の介在物最大径を１５０μｍ以下にすることができ、さらに清浄度の優れた鋳塊を製造することができる。   Thus, according to the bottom pouring ingot method of the present embodiment, after adding the coating material 10 for coating the molten steel 2 in the mold 5 to the bath surface so that the coating material thickness d is 20 mm or less, A heat insulating material containing Ca12 so as to satisfy the first condition and the second condition described above, and so that the ratio (X / d value) between the coating material thickness d and the content ratio X is 0.008 or more. 11 or Ca12 is added before or simultaneously with the addition of the heat insulating material 11. By adjusting the coating material thickness d and the X / d value in this way, it is possible to suppress the generation of coarse inclusions in the molten steel 2 and to reduce the maximum inclusion inclusion diameter in the ingot to 150 μm or less. An ingot with excellent cleanliness can be produced.

本実施形態において、被覆材厚ｄの値を２０ｍｍ以下にすると説明したが、その被覆材厚ｄの下限を特に設けてはいない。いうまでもなく、被覆材厚ｄの値を０ｍｍとして浴面を大気に晒すことはないが、上述の下注ぎ造塊方法を実施するには、実際の操業上の諸条件や、被覆材１０上に添加されたＣａ１２が溶鋼２に辿り着くまでの時間や、保温材１１とＣａ１２の化学反応速度などを考慮して被覆材厚ｄの値の下限が決定される。本願の発明者らは、本実施形態による下注ぎ造塊方法では、被覆材厚ｄの値は３ｍｍ程度を下限とするのが好ましいとの知見を得ている。   In the present embodiment, it has been described that the value of the coating material thickness d is 20 mm or less, but the lower limit of the coating material thickness d is not particularly provided. Needless to say, the value of the coating material thickness d is set to 0 mm, and the bath surface is not exposed to the atmosphere. The lower limit of the value of the coating material thickness d is determined in consideration of the time until the Ca 12 added above reaches the molten steel 2, the chemical reaction rate between the heat insulating material 11 and Ca 12, and the like. The inventors of the present application have obtained knowledge that it is preferable that the value of the coating material thickness d is about 3 mm as the lower limit in the bottom pouring ingot method according to the present embodiment.

なお、今回開示された実施の形態はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味及び範囲内でのすべての変更が含まれることが意図される。上記の実施形態では、保温材１１の添加は、鋳込み途中で行っているが、鋳込み終了時（浴面の上昇が停止したタイミング）でもあっても構わない。   The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In the above embodiment, the heat insulating material 11 is added during casting, but it may be at the end of casting (timing when the rise of the bath surface is stopped).

１ 下注ぎ造塊装置
２ 溶鋼
３ 取鍋
４ 注入管
５ 鋳型
６ 定盤
７ 湯道
８ 押湯枠
９ 下注入口
１０ 被覆材
１１ 保温材 DESCRIPTION OF SYMBOLS 1 Bottom pouring and ingot making apparatus 2 Molten steel 3 Ladle 4 Injection pipe 5 Mold 6 Surface plate 7 Runway 8 Feeding frame 9 Lower inlet 10 Covering material 11 Heat insulating material

Claims (2)

溶鋼を注入管を介して下方から鋳型に装入することにより鋳塊を製造する下注ぎ造塊方法を行うに際し、
前記鋳型内の溶鋼に浴面を被覆するための被覆材を、その厚みである被覆材厚が３ｍｍ以上２０ｍｍ以下となるように添加した後、金属Ｃａ及び／又はＣａ合金を、保温材を添加する前又は同時に添加することとし、
前記浴面の表面積に対する前記金属Ｃａ及び／又はＣａ合金のＣａ成分の添加量が０．３５ｋｇ／ｍ２以上１０ｋｇ／ｍ２以下の範囲内の値となるように前記金属Ｃａ及び／又はＣａ合金を添加すると共に、保温材の成分含有量と添加した前記金属Ｃａ及び／又はＣａ合金のＣａ成分含有量との関係を示す含有割合である［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）の値を０．０８以上０．２５以下の範囲内となるようにするとともに、前記含有割合を前記被覆材厚で除して得られる値が０．００８以上となるようにしていることを特徴とする下注ぎ造塊方法。
ただし、[％Ｘ]：保温材中Ｘ含有量（モル％）とする。 In carrying out the bottom pouring and ingot-making method for producing an ingot by inserting molten steel into the mold from below through an injection tube,
After adding the coating material for coating the bath surface to the molten steel in the mold so that the coating material thickness is 3 mm or more and 20 mm or less, the metal Ca and / or Ca alloy is added with a heat insulating material. To be added before or simultaneously,
The metallic Ca and / or Ca alloy as the added amount of the Ca constituent of the metallic Ca and / or Ca alloy to the surface area of the bath surface is a value within the range of 0.35 kg / m 2 or more 10 kg / m 2 or less [% Ca] / ([% Al] +3 [% Fe] which is a content ratio indicating the relationship between the component content of the heat insulating material and the Ca component content of the added metal Ca and / or Ca alloy. 2 O 3 ] + [% FeO] +2 [% SiO 2 ] +2 [% MnO 2 ] + [% S]) is within the range of 0.08 or more and 0.25 or less, A value obtained by dividing the ratio by the thickness of the covering material is set to 0.008 or more.
However, [% X]: X content in the heat insulating material (mol%). 溶鋼を注入管を介して下方から鋳型に装入することにより鋳塊を製造する下注ぎ造塊方法を行うに際し、
前記鋳型内の溶鋼に浴面を被覆するための被覆材を、その厚みである被覆材厚が３ｍｍ以上２０ｍｍ以下となるように添加した後、金属Ｃａ及び／又はＣａ合金を含有する保温材を添加することとし、
前記浴面の表面積に対する前記金属Ｃａ及び／又はＣａ合金のＣａ成分の添加量が０．３５ｋｇ／ｍ２以上１０ｋｇ／ｍ２以下を満たすように前記保温材を添加すると共に、保温材の成分含有量と添加した前記金属Ｃａ及び／又はＣａ合金のＣａ成分含有量との関係を示す含有割合である［％Ｃａ］／（［％Ａｌ］＋３［％Ｆｅ２Ｏ３］＋［％ＦｅＯ］＋２［％ＳｉＯ２］＋２［％ＭｎＯ２］＋［％Ｓ］）の値を０．０８以上０．２５以下の範囲内となるようにするとともに、前記被覆材厚を前記含有割合で除して得られる値が０．００８以上となるようにしていることを特徴とする下注ぎ造塊方法。
ただし、[％Ｘ]：保温材中Ｘ含有量（モル％）とする。 In carrying out the bottom pouring and ingot-making method for producing an ingot by inserting molten steel into the mold from below through an injection tube,
After adding a coating material for coating the molten steel in the mold to the bath surface so that the coating material thickness is 3 mm or more and 20 mm or less, a heat insulating material containing metal Ca and / or Ca alloy is added. To add,
With the addition of Ca component of the metallic Ca and / or Ca alloy to the surface area of the bath surface is added to the thermal insulation material so as to satisfy the 0.35 kg / m 2 or more 10 kg / m 2 or less, component-containing heat insulating material [% Ca] / ([% Al] +3 [% Fe 2 O 3 ] + [% FeO] +2 which is a content ratio indicating the relationship between the amount and the Ca component content of the added metal Ca and / or Ca alloy) The value of [% SiO 2 ] +2 [% MnO 2 ] + [% S]) is within the range of 0.08 or more and 0.25 or less, and the coating material thickness is divided by the content ratio. The bottom pouring method is characterized in that the obtained value is 0.008 or more.
However, [% X]: X content in the heat insulating material (mol%).
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