JP6188632B2 - Bottom pouring method - Google Patents
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- JP6188632B2 JP6188632B2 JP2014103345A JP2014103345A JP6188632B2 JP 6188632 B2 JP6188632 B2 JP 6188632B2 JP 2014103345 A JP2014103345 A JP 2014103345A JP 2014103345 A JP2014103345 A JP 2014103345A JP 6188632 B2 JP6188632 B2 JP 6188632B2
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Description
本発明は、溶鋼を鋳型に下注ぎ注入して鋼塊を製造する下注ぎ造塊方法に関するものである。 The present invention relates to a bottom pouring and ingot-making method for producing a steel ingot by pouring molten steel into a mold.
一般に鋳型内で溶鋼を凝固させ鋳片を製造する造塊法には、鋳型内への溶鋼の注入方式によって上注ぎ法と下注ぎ法とが知られている。これらの造塊法のうち、下注ぎ法は、良好な鋳塊肌が得られるという利点を有しており、品質が重視される高級鋼の製造などに適用される。
この下注ぎ造塊方法では、下注ぎされた鋳型内の溶鋼の温度を保つなどの目的のため、溶鋼の浴面に対して「溶鋼被覆剤」とよばれる保温材を添加することが行われている。この溶鋼被覆剤は、溶湯の表面を被覆し、溶湯の表面からの抜熱を可能な限り小さくして鋳塊の冷却速度（鋳込み速度）を制御する機能を有している。
In general, an ingot casting method for solidifying molten steel in a mold to produce a slab is known by an upper pouring method and a lower pouring method depending on the molten steel injection method into the mold. Of these ingot-making methods, the bottom pouring method has an advantage that a good ingot surface can be obtained, and is applied to the production of high-grade steel in which quality is important.
In this ingot casting method, a heat insulating material called “molten steel coating agent” is added to the bath surface of the molten steel for the purpose of maintaining the temperature of the molten steel in the poured mold. ing. The molten steel coating agent has a function of covering the surface of the molten metal and reducing the heat removal from the surface of the molten metal as much as possible to control the cooling rate (casting rate) of the ingot.
ところで、このような「溶鋼被覆剤」は、カルシウムなどの酸化物を主成分とし、溶鋼の表面に浮遊状態となっているため、通常であれば鋼塊に巻き込まれることはない。しかし、鋳型内での浴面が乱れるなどして浮遊した溶鋼被覆剤が溶鋼中に巻き込まれると、介在物欠陥となって製品の品質を低下させたり、製品の歩留まりを低下させたりする場合がある。特に、船舶のクランク軸などに用いられる鋳鍛鋼を鋳込む場合は、上述した非金属介在物は完全に取り除かれているのが好ましい。そのため、従来の造塊方法では、上記した非金属介在物の混入を防止するために、特許文献１や特許文献２に示すようなさまざまな手段が講じられている。 By the way, such a “molten steel coating agent” has an oxide such as calcium as a main component and is in a floating state on the surface of the molten steel. However, if the molten steel coating that floats due to disturbance of the bath surface in the mold is caught in the molten steel, it may result in inclusion defects that reduce product quality or product yield. is there. In particular, when casting forged steel used for a ship crankshaft or the like, it is preferable that the non-metallic inclusions described above are completely removed. Therefore, in the conventional agglomeration method, various means as shown in Patent Document 1 and Patent Document 2 are taken in order to prevent the above-mentioned inclusion of non-metallic inclusions.
例えば、特許文献１には、鋳型内に溶鋼を注入する下注造塊方法において、湯道煉瓦に溶鋼を通すことにより、溶鋼中の非金属介在物を湯道孔の孔壁に吸着させて除去し、鋼塊中への非金属介在物の混入を防止する方法が開示されている。この造塊方法は、取鍋に生じている非金属介在物が湯道を通って鋳型に混入することを防止するものであり、取鍋由来の非金属介在物の発生を防止できるようになっている。 For example, in Patent Document 1, in the ingot casting method of injecting molten steel into a mold, non-metallic inclusions in the molten steel are adsorbed on the hole wall of the runner hole by passing the molten steel through the runner brick. A method for removing and preventing inclusion of non-metallic inclusions in the steel ingot is disclosed. This ingot-making method prevents non-metallic inclusions generated in the ladle from entering the mold through the runner, and can prevent the occurrence of non-metallic inclusions derived from the ladle. ing.
また、特許文献２には、下注ぎ造塊時に、製造効率を下げることなく溶鋼表面の裸湯の発生を防止しつつも溶鋼被覆剤の使用量を低減する方法が開示されている。この造塊方法でも、溶鋼被覆剤の使用量が低減されるため、結果的に非金属介在物の発生が防止可能となる。 Further, Patent Document 2 discloses a method of reducing the amount of molten steel coating agent while preventing the generation of bare hot water on the surface of molten steel without lowering the production efficiency at the time of pouring ingot. Even with this ingot-making method, the amount of molten steel coating agent used is reduced, and as a result, generation of non-metallic inclusions can be prevented.
ところで、鋳型中の溶鋼が激しく乱れたりする場合、鋳造中の溶鋼の表面に浮遊する溶鋼被覆剤が溶湯の下降流に巻き込まれて溶湯内に入り込み凝固殻に捕捉されてしまうと、溶鋼中に混入した非金属介在物が原因となって介在物欠陥が発生してしまう可能性がある。
このような非金属介在物の混入に対し、上述した特許文献１及び特許文献２の造塊方法は、取鍋の非金属介在物の混入に起因する介在物欠陥の発生を防止したり、過剰な溶鋼被覆剤の撒布に起因する介在物欠陥の発生を防止したりする技術を開示するものであり、溶鋼への溶鋼被覆剤の巻き込みを原因とする非金属介在物の発生を抑制する技術を開示するものとはなっていない。
By the way, when the molten steel in the mold is violently disturbed, the molten steel coating that floats on the surface of the molten steel being cast is caught in the molten metal descending and enters the molten metal and is trapped in the solidified shell. Inclusion defects may occur due to mixed non-metallic inclusions.
With respect to such inclusion of non-metallic inclusions, the ingot forming methods of Patent Document 1 and Patent Document 2 described above prevent the occurrence of inclusion defects due to the inclusion of non-metallic inclusions in the ladle, or excessive The technology that prevents the occurrence of inclusion defects caused by the distribution of the molten steel coating material is disclosed, and the technology that suppresses the occurrence of non-metallic inclusions caused by the inclusion of the molten steel coating material in the molten steel. It is not intended to be disclosed.
本発明は、上述の問題に鑑みてなされたものであり、溶鋼への溶鋼被覆剤の巻き込みに起因する介在物欠陥の発生を防止して、鋼塊品質を向上させ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している。 The present invention has been made in view of the above-described problems, and prevents the occurrence of inclusion defects caused by the inclusion of the molten steel coating agent in the molten steel, thereby improving the quality of the steel ingot. It aims to provide a method.
上記課題を解決するため、本発明の下注ぎ造塊方法は以下の技術的手段を講じている。
即ち、本発明の下注ぎ造塊方法は、鋳型内に注入された溶鋼の表面に溶鋼被覆剤を２回以上に分けて又は連続的に投入しつつ鋼を下注ぎ造塊するに際しては、前記鋳型内における溶鋼の液深をh［mm］、前記鋳型の直径をd［mm］、前記鋳型内への溶鋼の吐出速度をV［m/s］とした場合であって、前記鋳型で鋳造される鋼塊の重量範囲が2.0〜200tonの範囲であり、前記鋳型内に溶鋼を送る湯道径の範囲がφ30〜120mmの範囲にあり、前記鋳型に最底部から略１０００ｍｍより下の位置では３〜４°のテーパを有すると共に最底部から略１０００ｍｍより上の位置では鋳塊径が変動しない鋳型を用いた場合に、前記鋳型内における溶鋼被覆剤の厚さs［mm］が式（１）を満たすように前記溶鋼被覆剤を投入することを特徴とする。
In order to solve the above-described problems, the method of undercoating and ingoting of the present invention employs the following technical means.
That is, in the down-pour ingot casting method of the present invention, when the steel is poured down and ingot while the molten steel coating agent is divided into two or more times on the surface of the molten steel injected into the mold or continuously, the liquid depth of the molten steel in the mold h [mm], the diameter of the mold d [mm], the discharge rate of molten steel into said mold in a case where the V [m / s], cast in the mold The weight range of the steel ingot is in the range of 2.0 to 200 tons, the range of the runner diameter that sends the molten steel into the mold is in the range of φ30 to 120 mm, and at a position below about 1000 mm from the bottom to the mold When using a mold having a taper of 3 to 4 ° and having an ingot diameter that does not vary at a position above about 1000 mm from the bottom , the thickness s [mm] of the molten steel coating in the mold is expressed by the formula (1 The molten steel coating agent is introduced so as to satisfy the above).
本発明の下注ぎ造塊方法によれば、溶鋼への溶鋼被覆剤の巻き込みに起因する介在物欠陥の発生を防止して、鋼塊品質の向上させることができる。 According to the ingot casting method of the present invention, it is possible to prevent the occurrence of inclusion defects due to the inclusion of the molten steel coating agent in the molten steel, and to improve the quality of the steel ingot.
以下、図を参照しながら、本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及び図２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。なお、図１は、下注ぎ造塊を行う下注ぎ造塊装置１の概略構成を示したものであり、図２は、下注ぎ造塊装置１の鋳型２を示した図である。
図１に示すように、下注ぎ造塊装置１は、取鍋３内の溶鋼が注入される注入管４と、この注入管４を介して取鍋３の溶鋼が装入される鋳型２と、鋳型２が上面に載置される定盤５とを備えている。
Hereinafter, the bottom pouring method according to the present embodiment will be described with reference to the drawings.
First, with reference to FIG.1 and FIG.2, the bottom pouring lump apparatus 1 to which the bottom pouring lump method of this embodiment is applied is demonstrated. FIG. 1 shows a schematic configuration of a bottom pouring and aggregating apparatus 1 that performs bottom pouring and agglomeration, and FIG. 2 shows a mold 2 of the bottom pouring and agglomeration apparatus 1.
As shown in FIG. 1, the bottom pouring and ingot-making apparatus 1 includes an injection pipe 4 into which molten steel in a ladle 3 is poured, and a mold 2 into which molten steel in the ladle 3 is charged via the injection pipe 4. And a surface plate 5 on which the mold 2 is placed on the upper surface.
具体的には、注入管４は、定盤５の中央側から上方に向かって立つように設けられた塔状の部材であり、内部には溶鋼が通る湯道６が上下方向に沿って形成されている。この注入管４の湯道６は、耐火煉瓦を内張りして円形の断面となるように形成されており、この湯道６を通じて取鍋３の溶鋼を取り込むことができるようになっている。
定盤５は、注入管４及び鋳型２の下側に形成された平板状の部材であり、注入管４及び鋳型２を下方から支持可能となっている。定盤５の内部には、溶鋼が通る湯道６が、注入管４の下側と、鋳型２の下側との２点間を結ぶように形成されていて、注入管４に注入された溶鋼を鋳型２内に送ることができるようになっている。鋳型２は、溶鋼を鋳込むことができるように鋳鉄で形成された容器である。鋳型２の上側は上方に向かって開口しており、また鋳型２の下側には定盤５の湯道６から溶鋼を注入可能な下注入口７（溶鋼吐出口）が形成されている。
Specifically, the injection pipe 4 is a tower-like member provided so as to stand upward from the center side of the surface plate 5, and a runner 6 through which molten steel passes is formed along the vertical direction. Has been. The runner 6 of the injection pipe 4 is formed so as to have a circular cross section by lining a refractory brick, and the molten steel of the ladle 3 can be taken in through the runner 6.
The surface plate 5 is a flat member formed below the injection tube 4 and the mold 2 and can support the injection tube 4 and the mold 2 from below. Inside the surface plate 5, a runner 6 through which molten steel passes is formed so as to connect between the lower side of the injection pipe 4 and the lower side of the mold 2, and was injected into the injection pipe 4. Molten steel can be fed into the mold 2. The mold 2 is a container formed of cast iron so that molten steel can be cast. The upper side of the mold 2 is opened upward, and a lower injection port 7 (molten steel discharge port) through which molten steel can be injected from the runner 6 of the surface plate 5 is formed on the lower side of the mold 2.
上述した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の上方にクレーンで配置し、取鍋３の底部に形成されたチェンジノズル９を注入管４の上端部に開口する湯道６に接続する。その後、取鍋の底部のスライドバルブ１０を開状態とすることで、チェンジノズル９を介して、取鍋３内の溶鋼を注入管４の湯道６に
導き入れ、定盤５の湯道６を経由して鋳型２に送る。このようにして鋳型２に達した溶鋼は、鋳型２の下注入口７から鋳型２内に入り込み、鋳型２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 ingot with the above-described bottom pouring ingot device 1, first, the ladle 3 is arranged with a crane above the injection pipe 4, and the change nozzle 9 formed at the bottom of the ladle 3. Is connected to a runner 6 opening at the upper end of the injection tube 4. Thereafter, by opening the slide valve 10 at the bottom of the ladle, the molten steel in the ladle 3 is introduced into the runner 6 of the injection pipe 4 through the change nozzle 9, and the runner 6 of the surface plate 5. To the mold 2 via. The molten steel that has reached the mold 2 in this way enters the mold 2 from the lower inlet 7 of the mold 2 and is cooled in the mold 2 to become 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 marine parts and the like can be manufactured.
ところで、上述した下注ぎ造塊方法において、鋳型２に装入された溶鋼の浴面が大気に接触すると、溶鋼は大気との接触面から酸化して清浄度が低下してしまう。そこで本実施形態では、溶鋼の酸化を防止するために、溶鋼の鋳型２内への注入が始まった段階で、溶鋼の浴面を被覆する溶鋼被覆剤が添加される。この溶鋼被覆剤は、溶融スラグ成分となる酸化物（例えばSiO2-CaO-Al2O3）や保温性確保のための骨材である炭素などを含むものであり、溶鋼浴面上を浮遊しつつ溶鋼の表面を被覆することが可能となっている。 By the way, in the above-described ingot casting method, when the bath surface of the molten steel charged in the mold 2 comes into contact with the atmosphere, the molten steel is oxidized from the contact surface with the atmosphere and the cleanliness is lowered. Therefore, in the present embodiment, in order to prevent the molten steel from being oxidized, a molten steel coating agent that coats the bath surface of the molten steel is added when the injection of the molten steel into the mold 2 is started. This molten steel coating contains oxide (such as SiO 2 -CaO-Al 2 O 3 ) that is a molten slag component and carbon that is an aggregate for ensuring heat retention, and floats on the surface of the molten steel bath. However, it is possible to coat the surface of the molten steel.
溶鋼被覆剤は、溶鋼が凝固する際に浮遊したままであるため、通常であれば浮遊した溶鋼被覆剤が鋳塊に入り込むことはない。しかし、鋳型２内で溶鋼が激しく動くと、浮遊した溶鋼被覆剤が溶鋼の内部に入り込み、そのまま凝固が行われると、凝固殻に捕捉されて溶鋼中に混入した非金属介在物が介在物欠陥となってしまう可能性がある。
そこで、本実施形態の下注ぎ造塊方法では、このような溶鋼中への溶鋼被覆剤の巻き込みを抑制することで、介在物欠陥の発生を防止するようにしている。
Since the molten steel coating remains floating when the molten steel solidifies, the floating molten steel coating does not normally enter the ingot. However, when the molten steel moves vigorously in the mold 2, the floating molten steel coating material enters the molten steel, and when solidification is performed as it is, non-metallic inclusions trapped in the solidified shell and mixed in the molten steel become inclusion defects. There is a possibility of becoming.
Therefore, in the bottom pouring ingot method of this embodiment, the occurrence of inclusion defects is prevented by suppressing the entrainment of the molten steel coating agent in the molten steel.
具体的には、本実施形態の下注ぎ造塊方法では、鋳型２内に注入された溶鋼の表面に溶鋼被覆剤を１回で投入するのではなく、２回以上に分けて投入するか、連続的に投入するようにしている。そして、個々の溶鋼被覆剤の投入に際しては、鋳型２内における溶鋼の液深をh［mm］、鋳型２の直径をd［mm］、鋳型２内への溶鋼の吐出速度をV［m/s］とした場合に、鋳型２内における溶鋼被覆剤の厚さs［mm］が式（１）を満たすように溶鋼被覆剤を投入するようにしている。 Specifically, in the bottom pouring ingot method of the present embodiment, the molten steel coating agent is not charged once on the surface of the molten steel injected into the mold 2, but is divided into two or more times, It is designed to be continuously input. When each molten steel coating is introduced, the molten steel liquid depth in the mold 2 is h [mm], the mold 2 diameter is d [mm], and the molten steel discharge speed into the mold 2 is V [m / s], the molten steel coating agent is introduced so that the thickness s [mm] of the molten steel coating agent in the mold 2 satisfies the formula (1).
なお、式中の吐出速度Vは、鋳込み時に下注入口７から注入される溶鋼の吐出速度である。この吐出速度Vの単位は［m/s］であり、単位時間あたりの鋳込み溶鋼流量［m3/s］を、ノズル断面積［m2］で除して算出される。
また、式中の液深h［mm］は、鋳込み時における鋳型２内の溶鋼深さであり、図２に示すように鋳型２底部の凹部（シュー部分）上端から湯面までの距離を基にして求められる。さらに、式中の直径d［mm］は最底部の鋳塊径であり、厚さs［mm］は溶鋼被覆剤の厚さである。
In addition, the discharge speed V in a type | formula is a discharge speed of the molten steel inject | poured from the lower inlet 7 at the time of casting. The unit of the discharge velocity V is [m / s], and is calculated by dividing the flow rate of cast molten steel [m 3 / s] per unit time by the nozzle cross-sectional area [m 2 ].
In addition, the liquid depth h [mm] in the formula is the depth of molten steel in the mold 2 at the time of casting, and is based on the distance from the upper end of the recess (shoe part) at the bottom of the mold 2 to the molten metal surface as shown in FIG. Is required. Further, the diameter d [mm] in the formula is the ingot diameter at the bottom, and the thickness s [mm] is the thickness of the molten steel coating agent.
次に、上述した式が導かれる理由について説明する。
上述した溶鋼被覆剤の厚さs［mm］の上限値と下限値、言い換えれば溶鋼被覆剤の最大投入量及び最小投入量は、「溶鋼の巻き込みを防止する」と「スラグとして消費されるのに十分な量を確保する」という２つの観点からそれぞれ決定される。
まず、前者の「溶鋼の巻き込みを防止する」という観点から、溶鋼被覆剤の厚さの上限値が以下のように決定される。
Next, the reason why the above formula is derived will be described.
The upper limit value and the lower limit value of the thickness s [mm] of the molten steel coating described above, in other words, the maximum input amount and the minimum input amount of the molten steel coating agent are “to prevent entrainment of molten steel” and “slag is consumed. Are determined from the two viewpoints of “ensuring a sufficient amount of
First, from the viewpoint of “preventing entrainment of molten steel”, the upper limit value of the thickness of the molten steel coating agent is determined as follows.
つまり、図２に示すように、溶鋼被覆剤が溶鋼へ巻き込まれる現象は、鋳型２内の溶鋼に強い下降流の垂直成分が発生した場合に、発生した下降流の垂直成分に溶鋼被覆剤が巻き込まれることで生じる。例えば、下注入口７から鋳型２内に注入された溶鋼は鋳型２内を下方から上方に向かって移動し、やがて浴面付近に到達する。このとき、溶鋼の吐出圧が大きい場合には、図２にＡで示すように溶鋼被覆剤の浴面の中央付近が上方に向かって盛り上がるように沸き上がる。この沸き上がっている部分はその上方からの外観から一般に「目玉」と呼ばれる。「目玉」の中央では、上方に向かって勢いをつけて吹き上がった溶鋼が、「目玉」の上端付近に達すると勢いを失って「目玉」の外側に向かって流れ落ち
、ちょうど噴水のような溶鋼の流れが生じている。また、「目玉」の周囲では、外側に向かって流れ落ちる溶鋼に押されて溶鋼被覆剤が浴面の外周縁部に追いやられ、溶鋼被覆剤で覆われていない裸湯ゾーンが盛り上がるように形成される。
That is, as shown in FIG. 2, when the molten steel coating material is entrained in the molten steel, when the vertical component of the strong downward flow is generated in the molten steel in the mold 2, the molten steel coating agent is added to the vertical component of the generated downward flow. It is caused by being involved. For example, the molten steel injected into the mold 2 from the lower injection port 7 moves from below to above in the mold 2 and eventually reaches the vicinity of the bath surface. At this time, when the discharge pressure of the molten steel is large, as shown by A in FIG. 2, the vicinity of the center of the bath surface of the molten steel coating is boiled so as to rise upward. This heated portion is generally called “eyeball” because of its appearance from above. In the center of the “eyeball”, the molten steel blown up with momentum loses momentum when it reaches near the upper end of the “eyeball” and flows down toward the outside of the “eyeball”, just like a fountain. The flow of is occurring. Also, around the "eyeball", the molten steel coating is pushed to the outer peripheral edge of the bath surface by the molten steel flowing down toward the outside, and the bare hot water zone not covered with the molten steel coating is formed to rise. The
つまり、「目玉」の近傍では、外側に向かって流れ落ちる溶鋼により、鋳型２内を上方から下方に向かって下降する溶鋼の下降流が形成される。この下降流のすぐ近くには外周縁部に追いやられた溶鋼被覆剤が存在しているため、下降流の垂直成分に溶鋼被覆剤が巻き込まれる可能性がある。ただ、下降流の垂直成分の流速が小さい場合には、溶鋼被覆剤の浮上速度（浮上力）の方が勝っているため、巻き込まれが発生しても溶鋼被覆剤がすぐに浮上し、介在物欠陥になることはない。しかし、下降流の垂直成分が大きくなって、溶鋼被覆剤の浮上速度を超えた場合に、溶鋼被覆剤が浮上できなくなって巻き込まれた溶鋼被覆剤が凝固殻に捕捉された場合、介在物欠陥になってしまう。それゆえ、溶鋼被覆剤の巻込みを低減するためには、「目玉」で生じる下降流の垂直成分を弱くして溶鋼被覆剤が鋳塊内部にまで入り込まないようにする必要がある。 That is, in the vicinity of the “eyeball”, the molten steel flowing down toward the outside forms a descending flow of molten steel that descends from the upper side to the lower side in the mold 2. Since the molten steel coating repelled by the outer peripheral edge exists in the immediate vicinity of the downward flow, the molten steel coating may be caught in the vertical component of the downward flow. However, when the flow velocity of the vertical component of the downward flow is small, the floating speed (levitation force) of the molten steel coating is superior, so even if entanglement occurs, the molten steel coating immediately rises and intervenes. There will be no physical defects. However, if the vertical component of the downflow increases and the rising speed of the molten steel coating is exceeded, the molten steel coating cannot be lifted and the entrained molten steel coating is trapped in the solidified shell. Become. Therefore, in order to reduce the entrainment of the molten steel coating material, it is necessary to weaken the vertical component of the downward flow generated at the “eyeball” so that the molten steel coating material does not enter the ingot.
このような下降流の垂直成分の強弱には、「溶鋼被覆材の厚み」が大きく影響する。
具体的には、「溶鋼被覆材の厚み」を変化させると、浴面に形成される「目玉」の形状が変化し、下降流の垂直成分の強弱が大きく変化する。例えば、溶鋼被覆剤が薄い場合、「目玉」の周囲の溶鋼被覆剤が外周側に向かって押しやられ、反転流が水平方向に広がるので、「目玉」の形状は低く広がったものとなる。そして、このときできる反転流は水平方向に沿ったものとなるので、垂直方向に沿って下降する下降流としてはそれほど強いものとはならず、溶鋼被覆剤の巻き込みも起きにくくなる。ところが、溶鋼被覆剤が厚い場合、溶鋼被覆剤が反転流に乗って外周側に向かって動きにくくなるので、「目玉」の形状は水平方向に狭幅で高く盛り上がったものとなり、垂直方向に沿って強い反転流が生じ、垂直方向に沿った下降流が優勢となって溶鋼被覆剤の巻き込みが起きやすくなる。
The strength of the vertical component of the downward flow is greatly influenced by the “thickness of the molten steel coating material”.
Specifically, when the “thickness of the molten steel coating material” is changed, the shape of the “eyeball” formed on the bath surface changes, and the strength of the vertical component of the downward flow changes greatly. For example, when the molten steel coating is thin, the molten steel coating around the “eyeball” is pushed toward the outer peripheral side, and the reverse flow spreads in the horizontal direction, so that the shape of the “eyeball” spreads low. And since the reversal flow which can be done at this time is along the horizontal direction, it is not so strong as the downward flow descending along the vertical direction, and the entrainment of the molten steel coating agent is difficult to occur. However, when the molten steel coating is thick, the molten steel coating rides in a reverse flow and is difficult to move toward the outer periphery, so the shape of the “eyeball” is a narrow and high swell in the horizontal direction, along the vertical direction. A strong reversal flow is generated, and the downward flow along the vertical direction becomes dominant and the entrainment of the molten steel coating is likely to occur.
また、「溶鋼の吐出速度」も、垂直方向に沿った下降流の強さに影響する。例えば、下注入口７から鋳型２内に注入された溶鋼の吐出圧、言い換えれば鋳型２内への溶鋼の吐出速度が大きい場合には、溶鋼被覆剤が厚い場合と同様に「目玉」は高く盛り上がったものとなり、反転流は垂直方向に沿って強くなり、垂直方向に沿った下降流が優勢となって巻き込みが起きやすくなる。また、吐出圧が大きいと、鋳型２内の溶鋼が乱流になり易く、溶鋼被覆剤が溶鋼中に巻き込まれ、凝固殻に捕捉されて欠陥不良となりうる可能性が高くなる。そのため、鋳型２内への溶鋼の吐出速度が大きい場合にも、下降流が優勢となって巻き込み現象が顕著になる。また、逆に鋳型２内への溶鋼の吐出速度が小さい場合には、下降流が弱くなって巻き込み現象が起こりにくくなる。 Further, the “discharging speed of molten steel” also affects the strength of the downward flow along the vertical direction. For example, when the discharge pressure of the molten steel injected into the mold 2 from the lower inlet 7, in other words, when the discharge speed of the molten steel into the mold 2 is large, the “eyeball” is high as in the case where the molten steel coating is thick. The reversal flow becomes stronger along the vertical direction, and the downward flow along the vertical direction becomes dominant, and the entrainment tends to occur. Further, if the discharge pressure is large, the molten steel in the mold 2 tends to be turbulent, and the possibility that the molten steel coating agent is caught in the molten steel and is trapped by the solidified shell and becomes defective becomes high. Therefore, even when the discharge speed of the molten steel into the mold 2 is high, the downward flow becomes dominant and the entrainment phenomenon becomes remarkable. Conversely, when the discharge rate of the molten steel into the mold 2 is low, the downward flow becomes weak and the entrainment phenomenon is less likely to occur.
以上のことから、上述した巻き込み現象の発生を抑制するためには、溶鋼被覆剤の厚さを所定の上限値を超えないものとするのがよいと判断され、この上限値は下注入口７からの溶鋼の吐出速度V［m/s］の関数として式（１）のように規定できることがわかる。
一方、溶鋼被覆剤の巻込みを低減するためには、鋳型２での溶鋼の深さについても考えておく必要がある。というのも、上述した下降流の大きさは、鋳型２での溶鋼の深さにも影響を受けるからである。例えば、鋳型２内での溶鋼の深さが深い場合、下注入口７の近傍では吐出する溶鋼に勢いがあっても、溶鋼の浴面に達して反転する際には溶鋼に勢いが無くなり、結果として溶鋼の反転流は緩やかとなって、溶鋼被覆剤の巻き込まれは起きにくくなる。逆に、鋳型２内での溶鋼の深さが浅い場合は、溶鋼の浴面に達しても溶鋼の勢いは十分に大きいので、反転流が大きくなって溶鋼被覆剤の巻込みが起きやすくなる。そのため、溶鋼被覆剤の厚さの上限値は、鋳型２内での溶鋼の深さh［mm］の関数としても式（１）のように規定される。
From the above, in order to suppress the occurrence of the entrainment phenomenon described above, it is determined that the thickness of the molten steel coating material should not exceed a predetermined upper limit value. It can be seen that it can be defined as a function of the discharge rate V [m / s] of molten steel from Eq. (1).
On the other hand, in order to reduce the entrainment of the molten steel coating agent, it is necessary to consider the depth of the molten steel in the mold 2. This is because the size of the downflow described above is also affected by the depth of the molten steel in the mold 2. For example, when the depth of the molten steel in the mold 2 is deep, even if the molten steel discharged in the vicinity of the lower inlet 7 has a momentum, the molten steel loses momentum when it reaches the bath surface of the molten steel and reverses. As a result, the reversal flow of the molten steel becomes gentle and the molten steel coating agent is less likely to be involved. On the contrary, when the depth of the molten steel in the mold 2 is shallow, even if the molten steel reaches the bath surface, the momentum of the molten steel is sufficiently large, so that the reverse flow becomes large and the molten steel coating agent is likely to be involved. . Therefore, the upper limit value of the thickness of the molten steel coating agent is also defined as a function of the depth h [mm] of the molten steel in the mold 2 as shown in Expression (1).
以上のことから、鋳型２内における溶鋼被覆剤の厚さs［mm］の上限値は、吐出速度V［m/s］及び鋳型２内での溶鋼の深さh［mm］を用いて上述した式（１）のように示されるのである。
次に、後者の「スラグとして消費されるのに十分な量を確保する」という観点から、溶鋼被覆剤の厚さの下限値が以下のように決定される。
From the above, the upper limit value of the thickness s [mm] of the molten steel coating material in the mold 2 is described above using the discharge speed V [m / s] and the depth h [mm] of the molten steel in the mold 2. It is shown as the following formula (1).
Next, from the viewpoint of securing the sufficient amount to be consumed as slag, the lower limit value of the thickness of the molten steel coating material is determined as follows.
つまり、溶鋼被覆剤は、溶鋼の表面を覆うことで、溶鋼の温度低下や溶鋼の再酸化を防
止したり、溶鋼の大気中からの水素ピックアップを防止したりするという機能を有している。しかし、この溶鋼被覆剤には、上記した機能に加え、鋳型２と鋼塊との間の焼付きを防止するという機能も有している。つまり、溶鋼の熱で溶融した溶鋼被覆剤が、スラグ状態で鋳型２と鋼塊との間に侵入し、緩衝材として機能することで鋼塊の鋳型２への焼付きを防止する。
In other words, the molten steel coating agent has a function of preventing the temperature of molten steel from being lowered and re-oxidation of molten steel by covering the surface of the molten steel, or preventing hydrogen pick-up from the atmosphere of molten steel. However, this molten steel coating has a function of preventing seizure between the mold 2 and the steel ingot in addition to the above-described function. That is, the molten steel coating material melted by the heat of the molten steel penetrates between the mold 2 and the steel ingot in the slag state, and functions as a buffer material to prevent the steel ingot from being seized onto the mold 2.
つまり、上述した浴面を覆う溶鋼被覆剤は、鋳型２に対する鋳塊の焼き付きを防止する部材ともなっており、浴面を覆っていた溶鋼被覆剤の一部が鋳塊の側面に回り込んで、鋳型２の表面と溶鋼との界面に供給されることで鋳型２への溶鋼の焼き付きを防止する構成となっている。そのため、溶鋼被覆剤が鋳型２と鋼塊の間に侵入して消費されていくと、浴面を覆う溶鋼被覆剤量が少なくなり、溶鋼の温度低下、溶鋼の再酸化、溶鋼の水素ピックアップなどの問題が発生する。 That is, the molten steel coating covering the bath surface described above is also a member that prevents the ingot from sticking to the mold 2, and a part of the molten steel coating covering the bath surface goes around the side of the ingot, Supplying to the interface between the surface of the mold 2 and the molten steel prevents the molten steel from sticking to the mold 2. Therefore, when the molten steel coating enters and is consumed between the mold 2 and the steel ingot, the amount of the molten steel coating covering the bath surface decreases, the temperature of the molten steel decreases, the reoxidation of the molten steel, the hydrogen pickup of the molten steel, etc. Problems occur.
そこで、本発明では、鋳型２内の溶鋼の浴面を覆う溶鋼被覆剤が、すべて鋳塊の側面に覆うに十分な厚さとなっているかどうかという観点から、鋳塊の側面の表面積を計算し、計算した表面積を覆うことができる量から溶鋼被覆剤の厚さs［mm］の下限値を上述した式（１）のように定めている。
具体的には、実際に「溶鋼の深さh［mm］」と「溶鋼被覆剤の厚さs［mm］」とをそれぞれ変化させて下注ぎ造塊した際に、非金属介在物が発生するかどうかを、溶鋼の吐出速度Vが0.71［m/s］、0.40［m/s］、1.02［m/s］、1.33［m/s］のそれぞれについて調査した。そして、得られた調査の結果（図３〜図６に示す結果）から、非金属介在物が発生する領域と発生しない領域とを分ける閾値を決定し、決定された閾値を関数式として示すことで式（１）が導かれる。
Therefore, in the present invention, the surface area of the side surface of the ingot is calculated from the viewpoint of whether or not the molten steel coating covering the molten steel bath surface in the mold 2 is sufficiently thick to cover the side surface of the ingot. The lower limit value of the thickness s [mm] of the molten steel coating agent is determined from the amount that can cover the calculated surface area as in the above-described equation (1).
Specifically, non-metallic inclusions are generated when the molten steel depth h [mm] and the molten steel coating material thickness s [mm] are changed and poured into pieces. Whether the discharge rate V of molten steel was 0.71 [m / s], 0.40 [m / s], 1.02 [m / s], and 1.33 [m / s] was investigated. Then, from the results of the obtained investigation (results shown in FIG. 3 to FIG. 6), a threshold value that divides a region where non-metallic inclusions are generated and a region where non-metallic inclusions are generated is determined, and the determined threshold value is shown as a function expression The following formula (1) is derived.
なお、上述した下注ぎ造塊に用いた溶鋼は、一次精錬、二次精錬されたものである。この一次精錬は、電気炉（交流式アーク炉）を用いてスクラップを溶解し、溶解された溶鋼を取鍋へ傾注しつつ出鋼している。また、二次精錬は、LF（Ladle Furnace）法を用いて、成分調整、介在物除去を行った後、取鍋を蓋で覆い、取鍋内を真空状態とした上でArガスプラグ（底吹き用プラグ）からArガスを吹込み、真空脱ガス処理を行っている。さらに、下注ぎ造塊は、取鍋から湯道６を通じて、鋳型２内に溶鋼を鋳込み、溶鋼が鋳型２の凹部（シュー部分）の上部に達した際、鋳型２内に吊るしてある溶鋼被覆剤が入った袋と接触し、袋が燃えることで、溶鋼被覆剤を溶鋼表面に散布して行っている。 In addition, the molten steel used for the above-mentioned bottom pouring ingot is primary refining and secondary refining. In this primary refining, scrap is melted using an electric furnace (AC arc furnace), and the melted molten steel is poured into a ladle and discharged. In secondary refining, the LF (Ladle Furnace) method is used to adjust the components and remove inclusions, then cover the ladle with a lid and evacuate the ladle to the Ar gas plug (bottom Ar gas is blown from a blowing plug) to perform vacuum degassing. Further, the bottom pouring ingot is cast into the mold 2 from the ladle through the runner 6 and when the molten steel reaches the upper part of the recess (shoe part) of the mold 2, the molten steel coating is suspended in the mold 2. The molten steel coating agent is sprayed onto the molten steel surface by contacting the bag containing the agent and burning the bag.
また、上述した下注ぎ造塊においては、鋳込み中、溶鋼被覆剤は鋳型２又は鋼塊間に侵入してスラグスキンとなり消費されていく。しかし、溶鋼表面に裸湯が見えた場合は、溶鋼被覆剤を適宜追装している。
このようにして所定位置まで鋳込みが終了した後、鋳塊が完全凝固するまで静置する。そして、完全凝固後、脱型し、鍛造工程に移行する。このようにして鍛造工程に送られた鋼塊に対して、介在物の発生を検査した。
Further, in the above-described ingot casting, the molten steel coating agent enters between the mold 2 or the steel ingot and is consumed as slag skin during casting. However, when naked water is visible on the surface of the molten steel, a molten steel coating agent is appropriately added.
In this way, after the casting is finished to a predetermined position, it is left until the ingot is completely solidified. And after complete solidification, it demolds and shifts to a forging process. Thus, the occurrence of inclusions was inspected for the steel ingot sent to the forging process.
具体的には、この介在物の検査は、鋳塊を鍛造成形し、製品形状とした後、超音波探傷試験により、製品形状の介在物検査を実施したものである。「○」が介在物なかった結果を示し、１つでも介在物が発生した場合は「×」の評価とした。なお、この介在物の検査は、型内材１mmの粒が浮上するときの浮上速度を理論的に計算して、それと下降流の垂直成分との比較を行っても、求めることができる。 Specifically, this inclusion inspection is performed by forging an ingot to obtain a product shape, and then performing an inspection of the product shape inclusion by an ultrasonic flaw detection test. “◯” indicates the result of no inclusion, and “×” is evaluated when even one inclusion is generated. This inclusion inspection can also be obtained by theoretically calculating the ascending speed when 1 mm of the inner material of the mold rises and comparing it with the vertical component of the downward flow.
介在物の検査結果を表１及び図３〜図６に示す。なお、表１における「巻込み発生有無」は、上述した介在物検査の判定結果を示している。また、表１における「溶鋼被覆剤量
十分／不十分」については、溶鋼の表面に溶鋼被覆剤が少しでもある場合（溶鋼被覆剤の厚さが０mmを超える場合）に溶鋼被覆剤量が十分であると考えて「○」の評価とし、溶鋼の表面に溶鋼被覆剤が全くない場合（溶鋼被覆剤の厚さが０mmの場合）に溶鋼被覆剤量が不十分であると考えて「×」の評価とした。さらに、図３〜図６における「溶鋼液深」は、溶鋼の深さh［mm］を示すものである。
The inspection results of the inclusions are shown in Table 1 and FIGS. In Table 1, “Presence / absence of entrainment” indicates the determination result of the inclusion inspection described above. In Table 1, “Amount of molten steel coating is sufficient / insufficient” indicates that the amount of molten steel coating is sufficient when there is even a small amount of molten steel coating on the surface of the molten steel (when the thickness of the molten steel coating exceeds 0 mm). If the surface of the molten steel has no molten steel coating (when the thickness of the molten steel coating is 0 mm), the amount of the molten steel coating is considered to be insufficient. Was evaluated. Furthermore, the “molten steel liquid depth” in FIGS. 3 to 6 indicates the depth h [mm] of the molten steel.
図３に示す吐出速度Vが0.71［m/s］の結果（表１に示す実験No.1〜実験No.15）では、上述した式（１）の関係を満足する網掛け部分に溶鋼被覆剤の厚さs［mm］が含まれるように鋳造を行ったもの（実験No.2〜実験No.5、実験No.7〜実験No.13）についてはいずれも○の結果となっている。ところが、式（１）の関係を満足しない場合（実験No.1、実験
No.6、実験No.14、実験No.15の場合）、つまり網掛け部分以外の部分に溶鋼被覆剤の厚さs［mm］が入るような鋳造を行うと、×の評価となり、介在物欠陥が発生している。このことから、吐出速度Vを0.71［m/s］として式（１）の関係を満足する場合に、介在物欠陥の発生を抑制できていることが分かる。
In the result of the discharge speed V shown in FIG. 3 of 0.71 [m / s] (Experiment No. 1 to Experiment No. 15 shown in Table 1), the molten steel coating is applied to the shaded portion that satisfies the relationship of the above-described formula (1). In the case of casting (experiment No.2 to experiment No.5, experiment No.7 to experiment No.13) in which the thickness s [mm] of the agent is included, the result is ○. . However, when the relationship of formula (1) is not satisfied (Experiment No.1, Experiment
In case of No.6, Experiment No.14, Experiment No.15), that is, casting with the thickness s [mm] of the molten steel coating in the part other than the shaded part, it was evaluated as x, and the intervening A physical defect has occurred. From this, it can be seen that when the discharge speed V is 0.71 [m / s] and the relationship of formula (1) is satisfied, the occurrence of inclusion defects can be suppressed.
一方、図４に示す吐出速度Vが0.40［m/s］の結果（表１に示す実験No.46〜実験No.56）、図５に示す吐出速度Vが1.02［m/s］の結果（表１に示す実験No.16〜実験No.30）、図６に示す吐出速度Vが1.33［m/s］の結果（表１に示す実験No.31〜実験No.45）では、吐出速度Vの変化によりB(V)が変化しており、吐出速度Vが大きくなるほど上限値を示す線の傾きが小さくなっていることが分かる。このような上限値の変化に対応して、介在物欠陥の発生状況も変化しており、式（１）の関係を示す網掛け部分に○の評価が集まり、吐出速度Vが変化しても介在物欠陥の発生状況は式（１）に対応していることがわかる。このことから、吐出速度Vが0.40［m/s］〜1.33［m/s］の範囲にある場合には、鋳型２への鋳塊の焼き付きを防止しつつ、介在物欠陥の発生を確実に防止することが可能となると判断される。 On the other hand, the result of the discharge speed V shown in FIG. 4 is 0.40 [m / s] (Experiment No. 46 to Experiment No. 56 shown in Table 1), and the result of the discharge speed V shown in FIG. 5 is 1.02 [m / s]. (Experiment No. 16 to Experiment No. 30 shown in Table 1), in the result (Experiment No. 31 to Experiment No. 45 shown in Table 1) where the discharge speed V shown in FIG. 6 is 1.33 [m / s] It can be seen that B (V) changes due to the change in the speed V, and the slope of the line indicating the upper limit value decreases as the discharge speed V increases. Corresponding to such a change in the upper limit value, the occurrence state of the inclusion defect is also changed. Even if the evaluation of “◯” is gathered in the shaded portion indicating the relationship of Expression (1) and the discharge speed V is changed. It can be seen that the occurrence state of the inclusion defect corresponds to the equation (1). From this, when the discharge speed V is in the range of 0.40 [m / s] to 1.33 [m / s], the occurrence of inclusion defects is reliably prevented while preventing the ingot from sticking to the mold 2. It is determined that it can be prevented.
なお、図３の「溶鋼液深」が浅い領域を見れば分かるように、鋳込開始直後は溶鋼被覆剤の巻き込みを抑制できる網掛け部分が非常に狭いため、溶鋼への溶鋼被覆剤の巻き込みを防止することが困難となる。
理想的には網掛け部分に溶鋼被覆剤の厚みが位置するように溶鋼被覆剤を投入するのが望ましいが、溶鋼再酸化、水素ピックアップ、溶鋼温度低下の観点から、このような溶鋼被覆剤の投入は困難な場合がある。それゆえ、巻き込み抑制が困難な鋳込初期、例えば「溶鋼液深」が200mm以下の場合には、作業者の判断に委ねて溶鋼被覆剤を投入し、「溶鋼液深」が200mm超えてから、本発明範囲の操業条件で操業を行うのが好ましい。
As can be seen from the region where the “molten liquid depth” in FIG. 3 is shallow, the shaded portion that can suppress the entrainment of the molten steel coating is very narrow immediately after the start of casting. It becomes difficult to prevent.
Ideally, it is desirable to introduce the molten steel coating so that the thickness of the molten steel coating is located in the shaded area, but from the viewpoint of molten steel reoxidation, hydrogen pickup, and lowering of molten steel temperature, Input may be difficult. Therefore, at the beginning of casting when it is difficult to suppress entrainment, for example, when the `` molten steel liquid depth '' is 200 mm or less, the molten steel coating agent is introduced at the discretion of the operator, after the `` molten steel liquid depth '' exceeds 200 mm. It is preferable to operate under the operating conditions within the scope of the present invention.
また、溶鋼被覆剤の投入は、２回以上に分けて投入するか、連続的に投入するようにするのが好ましい。例えば、図３上に「Ｂ」で示される溶鋼液深h=800［mm］、溶鋼被覆剤の厚さs=60［mm］の造塊条件で造塊する場合を考える。このような造塊を行う際に、図中に「点線」で示すように鋳型２内の溶鋼の深さが浅いのに溶鋼被覆剤を１回で全量投入すると、溶鋼被覆剤の厚さsが上限を上回ることになり、本発明範囲の操業条件で操業を行うことができなくなる。 The molten steel coating agent is preferably introduced in two or more times or continuously. For example, let us consider a case where ingot forming is performed under the ingot forming conditions of a molten steel liquid depth h = 800 [mm] and a molten steel coating material thickness s = 60 [mm] indicated by “B” in FIG. When such agglomeration is carried out, as shown by the “dotted line” in the figure, the molten steel coating agent is introduced into the mold 2 in a single depth, but the molten steel coating material thickness s Exceeds the upper limit, and it becomes impossible to operate under the operating conditions within the scope of the present invention.
といって、鋳型２内の溶鋼の深さが深くなってから溶鋼被覆剤を１回で全量投入することは、溶鋼被覆剤の厚さsが下限を下回った条件で大部分を造塊することに他ならないので、いずれにせよ本発明範囲の操業条件で操業を行うことは困難になる。
そのため、図中に「実線」で示すように、トータルの厚さでs=60［mm］となる溶鋼被覆剤のうち、全量の２／３となるs=40［mm］の溶鋼被覆剤を、例えば溶鋼液深がh=400［mm］となったときに加え、残りの１／３となるs=20［mm］の溶鋼被覆剤を、溶鋼液深がh=800［mm］となったときに加えるようにする。このように溶鋼被覆剤を複数回に分けて添加すれば、式（１）の関係を満足しつつ造塊を行うことが可能となる。
However, when the molten steel coating agent is introduced in a single amount after the depth of the molten steel in the mold 2 has increased, most of the molten steel is ingoted under the condition that the thickness s of the molten steel coating agent is below the lower limit. In any case, it is difficult to operate under any operating condition within the scope of the present invention.
Therefore, as shown by the “solid line” in the figure, out of the molten steel coating with a total thickness of s = 60 [mm], the molten steel coating with s = 40 [mm], which is 2/3 of the total amount, is used. For example, when the molten steel liquid depth becomes h = 400 [mm], the remaining molten steel coating agent of s = 20 [mm], which becomes 1/3, becomes the molten steel liquid depth h = 800 [mm]. Add it when If the molten steel coating agent is added in a plurality of times as described above, ingot forming can be performed while satisfying the relationship of the formula (1).
なお、溶鋼被覆剤の投入回数を多くすればするほど、式（１）の関係を満足する造塊条件で操業することが可能となる。そのため、式（１）の関係を満足するように溶鋼被覆剤を小量ずつ途切れなく連続的に投入するのがより好ましい。しかし、溶鋼被覆剤を投入回数を多くし過ぎると装置構成が複雑となったり製造コストが高騰したりする可能性もあるので、そのような場合には溶鋼被覆剤を２回か３回に分けて投入することもできる。 In addition, it becomes possible to operate on the ingot-making condition which satisfies the relationship of Formula (1), so that the injection | throwing-in frequency of molten steel coating agent is increased. Therefore, it is more preferable that the molten steel coating agent is continuously added in small amounts without interruption so as to satisfy the relationship of the formula (1). However, if the number of injections of molten steel coating is increased too much, the equipment configuration may become complicated and the manufacturing cost may increase. In such cases, the molten steel coating is divided into two or three times. It can also be input.
また、図３中に「１点鎖線（Ｃ）」として示すように、先に投入した溶鋼被覆剤が消費され、表面被覆剤の厚さsが薄くなっている場合には、式（１）の関係を満足するような溶鋼被覆剤に、消費された分だけ溶鋼被覆剤を多めに加えるのが好ましい。
また、式中に用いられる溶鋼の吐出速度は、製造効率を考慮した鋳込速度に基づいて決定されるものでもあるので、巻き込み現象の発生を抑制したいからといって鋳込速度を大幅に低減することは、製造効率の点から困難になる場合がある。それゆえ、製造効率の点から溶鋼の吐出速度を式に示す下限値まで下げられない場合もある。
Further, as shown as “one-dot chain line (C)” in FIG. 3, when the molten steel coating material previously charged is consumed and the thickness s of the surface coating material is reduced, the formula (1) It is preferable to add as much molten steel coating as the consumed amount to the molten steel coating that satisfies the above relationship.
In addition, the discharge speed of the molten steel used in the formula is also determined based on the casting speed considering production efficiency, so the casting speed is greatly reduced just because we want to suppress the occurrence of the entrainment phenomenon. This may be difficult in terms of manufacturing efficiency. Therefore, in some cases, the discharge rate of molten steel cannot be lowered to the lower limit shown in the equation from the viewpoint of production efficiency.
さらに、実際の下降流の大きさは、下注入口７の大きさに応じても変化する。つまり、式（１）における溶鋼の吐出速度は、鋳込流量と湯道６の径から算出される値である。そ
のため、鋳込流量が同じでも、湯道６径が変動すれば、溶鋼の吐出速度も変更してしまう。
係る点を鑑みた上で、本願発明の式（１）は、鋼塊の重量範囲が2.0〜200tonの範囲にある場合や、湯道６径の範囲がφ30〜120mmの範囲にある場合に成立するものとなっている。なお、式（１）の関係は、溶鋼被覆剤の種類には依らないものとなっている。
Furthermore, the actual size of the downward flow varies depending on the size of the lower inlet 7. That is, the discharge speed of the molten steel in the formula (1) is a value calculated from the casting flow rate and the diameter of the runner 6. Therefore, even if the casting flow rate is the same, if the diameter of the runner 6 fluctuates, the discharge rate of the molten steel will also change.
In view of this point, the formula (1) of the present invention is established when the weight range of the steel ingot is in the range of 2.0 to 200 tons or when the range of the runner 6 diameter is in the range of φ30 to 120 mm. It is supposed to be. In addition, the relationship of Formula (1) is not dependent on the kind of molten steel coating material.
さらに、上述した式（１）に用いる鋳型２の直径をd［mm］には、鋳型２の最も下側の底部の径を用いている。これは、本来の鋳型２には脱型の容易さを考慮し、3〜4°のテーパーが付いているが、本発明が着目している最底部から１０００ｍｍ程度の位置では鋳塊径が大きく変動しないことが多い。そのため、式（１）では、鋳型２の最底部の径を用いている。 Further, the diameter of the bottom of the lowermost side of the mold 2 is used as the diameter d [mm] of the mold 2 used in the above formula (1). This is because the original mold 2 has a taper of 3 to 4 ° in consideration of ease of demolding, but the ingot diameter is large at a position of about 1000 mm from the bottom of the present invention. Often does not fluctuate. Therefore, in the formula (1), the diameter of the bottom of the mold 2 is used.
なお、実機における溶鋼被覆剤厚さは、鋳込み状況によりばらつきが発生するが、本発明では、投入する溶鋼被覆剤量、溶鋼被覆剤密度、鋳型２径から決定される平均の厚さとしている。
以上、今回開示された実施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。特に、今回開示された実施形態において、明示的に開示されていない事項、例えば、運転条件や操業条件、各種パラメータ、構成物の寸法、重量、体積などは、当業者が通常実施する範囲を逸脱するものではなく、通常の当業者であれば、容易に想定することが可能な値を採用している。
Although the thickness of the molten steel coating material in the actual machine varies depending on the casting condition, in the present invention, the average thickness is determined from the amount of molten steel coating agent to be introduced, the molten steel coating material density, and the mold 2 diameter.
As mentioned above, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.
１ 下注ぎ造塊装置
２ 鋳型
３ 取鍋
４ 注入管
５ 定盤
６ 湯道
７ 下注入口（溶鋼吐出口）
９ チェンジノズル
１０ スライドバルブ
DESCRIPTION OF SYMBOLS 1 Bottom pouring lump device 2 Mold 3 Ladle 4 Injection pipe 5 Surface plate 6 Runway 7 Lower injection port (molten steel discharge port)
9 Change nozzle 10 Slide valve
Claims (1)
前記鋳型内における溶鋼の液深をh［mm］、前記鋳型の直径をd［mm］、前記鋳型内への溶鋼の吐出速度をV［m/s］とした場合であって、前記鋳型で鋳造される鋼塊の重量範囲が2.0〜200tonの範囲であり、前記鋳型内に溶鋼を送る湯道径の範囲がφ30〜120mmの範囲にあり、前記鋳型に最底部から略１０００ｍｍより下の位置では３〜４°のテーパを有すると共に最底部から略１０００ｍｍより上の位置では鋳塊径が変動しない鋳型を用いた場合に、前記鋳型内における溶鋼被覆剤の厚さs［mm］が式（１）を満たすように前記溶鋼被覆剤を投入することを特徴とする下注ぎ造塊方法。
When the liquid depth of the molten steel in the mold is h [mm], the diameter of the mold is d [mm], and the discharge speed of the molten steel into the mold is V [m / s] , The weight range of the steel ingot to be cast is in the range of 2.0 to 200 tons, the range of the runner diameter for sending the molten steel into the mold is in the range of φ30 to 120 mm, and the position below the bottom of about 1000 mm from the bottom of the mold Then, when a mold having a taper of 3 to 4 ° and having a diameter of ingot at a position above about 1000 mm from the bottom is used , the thickness s [mm] of the molten steel coating in the mold is expressed by the formula ( 1) A pouring ingot-making method, wherein the molten steel coating agent is added so as to satisfy the above-mentioned condition.
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| JPH0711056B2 (en) * | 1985-05-30 | 1995-02-08 | 大同特殊鋼株式会社 | Die steel manufacturing method |
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