JP2006231399A - Mold powder for continuous casting of medium carbon steel, and continuous casting method - Google Patents
Mold powder for continuous casting of medium carbon steel, and continuous casting method Download PDFInfo
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本発明は、中炭素鋼を連続鋳造法で製造する際に用いるモールドパウダー、およびこうしたモールドパウダーを用いて表面欠陥の発生を防止しつつ中炭素鋼鋳片を効果的に製造するための連続鋳造法に関するものである。 The present invention relates to a mold powder used when producing a medium carbon steel by a continuous casting method, and a continuous casting for effectively producing a medium carbon steel slab while preventing the occurrence of surface defects using such a mold powder. It is about the law.
鉄鋼業における生産性向上および高品質化が推進されるなかで、連続鋳造においては、高速鋳造時の鋳片の表面品質の改善が大きな課題となっている。特に、Ｃ含有量が０．０８〜０．１６％であるいわゆる中炭素鋼では、連続鋳造法で鋳造する際に表面割れが生じ易く、これまでにもこのような割れの発生機構について様々な研究がなされている。 In the continuous casting, improvement of the surface quality of the slab during high-speed casting has become a major issue as productivity improvement and quality improvement are promoted in the steel industry. In particular, in the so-called medium carbon steel having a C content of 0.08 to 0.16%, surface cracks are likely to occur when cast by a continuous casting method, and various mechanisms for the occurrence of such cracks have been proposed. Research has been done.
上記のような中炭素鋼は「亜包晶鋼」と呼ばれ、凝固温度直下でδ→γ変態に起因する大きな体積収縮を起こすことになる。そしてこの体積収縮によって、メニスカス直下の凝固シェルに凹凸ができ、鋳型による鋳片の冷却が不均一になり易い。鋳片の冷却が不均一になると、収縮応力が局所に集中して縦割れとなるものと考えられる。こうした割れを防止するためには、鋳型による鋳片の冷却を均一にすること、および鋳片を緩冷却することが有効であるとされている。 The above medium carbon steel is called “subperitectic steel” and causes a large volume shrinkage due to the δ → γ transformation just below the solidification temperature. Due to this volume shrinkage, the solidified shell just below the meniscus becomes uneven, and the slab cooling by the mold tends to be uneven. When cooling of the slab becomes non-uniform, it is considered that shrinkage stress concentrates locally and causes vertical cracks. In order to prevent such cracking, it is effective to make the slab cooled uniformly by the mold and to slowly cool the slab.
ところで、鋼の連続鋳造に際しては、鋳型内の溶鋼表面にモールドパウダーを散布して溶鋼表面の酸化を防止すると共に、溶融したモールドパウダー（以下、スラグと呼ぶ）が鋳型と鋳片の間に流れ込んで潤滑作用を発揮するようにして操業される。そして、鋳型による鋳片の均一冷却や緩冷却を達成させるためには、鋳型と鋳片の間に介在して冷却状態に大きな影響を与えるスラグを、常に安定して均一に流入させることと、スラグ自体の熱伝達特性を低下させて鋳片を緩冷却することが有効であるとされている。 By the way, during continuous casting of steel, mold powder is sprayed on the molten steel surface in the mold to prevent oxidation of the molten steel surface, and molten mold powder (hereinafter referred to as slag) flows between the mold and the slab. It is operated so as to exert a lubricating action. And in order to achieve uniform cooling and gradual cooling of the slab by the mold, the slag, which is interposed between the mold and the slab and has a large effect on the cooling state, always flows stably and uniformly, It is said that it is effective to slowly cool the slab by reducing the heat transfer characteristics of the slag itself.
モールドパウダーに関する技術として、例えば特許文献１には、Ｃ含有量が０．１８〜０．３０％である過包晶中炭素鋼の溶鋼を連続鋳造する際に用いるモールドパウダーとして、塩基度（ＣａＯ／ＳｉＯ2比）が０．８〜１．１、凝固温度：１０５０〜１２２０℃、１３００℃における粘度が０．０７〜１Ｐａ・ｓ、嵩比重：０．５〜０．９およびＣ含有量が２〜２０％であるものが提案されている。この技術では、上記のような低粘度のモールドパウダーを用いることによって、凝固シェルと鋳型との間への溶融パウダーの流入不足に起因する凝固シェルの焼き付き（即ち、拘束性ブレークアウト）の発生を防止するものである。 As a technique related to mold powder, for example, Patent Document 1 discloses basicity (CaO as a mold powder used when continuously casting molten steel of carbon steel with an overperitectic medium having a C content of 0.18 to 0.30%. / SiO 2 ratio) is 0.8 to 1.1, the solidification temperature is 1050 to 1220 ° C., the viscosity at 1300 ° C. is 0.07 to 1 Pa · s, the bulk specific gravity is 0.5 to 0.9, and the C content is What is 2-20% is proposed. In this technique, by using the low-viscosity mold powder as described above, solidified shell seizure (that is, constraining breakout) due to insufficient flow of molten powder between the solidified shell and the mold is prevented. It is to prevent.
上記のような過包晶中炭素鋼では、亜包晶鋼のような大きな収縮が凝固温度直下では発生しないので、鋳型−凝固シェル間の潤滑性だけを考慮したモールドパウダーの適用は極めて効果的である。またこうした状況は、Ｃ含有量が０．０８％未満の低炭素鋼においても同様である。しかしながら、Ｃ含有量が０．０８〜０．１６％程度の亜包晶鋼では、潤滑作用だけでなく、大きな収縮に起因する縦割れ（即ち、表面疵）を防止するためのパウダーを使用する必要がある。 In the peritectic medium carbon steel as described above, the large shrinkage unlike the subperitectic steel does not occur immediately below the solidification temperature, so it is very effective to apply the mold powder considering only the lubricity between the mold and the solidified shell. It is. This situation is the same for low carbon steel having a C content of less than 0.08%. However, in the subperitectic steel having a C content of about 0.08 to 0.16%, powder is used to prevent not only lubrication but also vertical cracks (ie, surface defects) due to large shrinkage. There is a need.
Ｃ含有量が０．０８〜０．１６％程度の亜包晶鋼を連続鋳造する際に用いるモールドパウダーとしては、低粘度のものを適用すると却って表面疵が増大する傾向を示すことから、基本的な思想として高粘度とすることによってメニスカス直下の均一冷却を図り、鋳片の表面疵の発生を防止するようにしている（例えば、特許文献２〜４）。また、これらの技術では、モールドパウダーの凝固温度や塩基度を指標として、緩冷却化モールドパウダーの設計がされている。 As the mold powder used when continuously casting hypoperitectic steel having a C content of about 0.08 to 0.16%, the surface flaws tend to increase when a low-viscosity one is applied. As a basic idea, high viscosity is used to achieve uniform cooling directly under the meniscus and prevent the occurrence of surface flaws on the slab (for example, Patent Documents 2 to 4). Further, in these techniques, the slowly cooled mold powder is designed using the solidification temperature and basicity of the mold powder as an index.
一方、鋳片表面の割れ欠陥を低減するには、鋳型内メニスカス直下の熱流束を下げることが有効であることが知られている。これは、凝固シェル厚みの変形を低減させ、凝固収縮による応力を緩和することができ、割れの発生を抑制できるためと考えられている。溶鋼−鋳型冷却水間の伝熱（熱流束：Ｑ）を一次元定常伝熱モデルで考慮すると、下記（２）式および（３）式で表現できることが知られている（非特許文献１）。
Ｑ＝（ＴM−ＴW）／ＲT …（２）
ＲT＝Ｒ1＋Ｒ2＋Ｒ3＋Ｒ4＋Ｒ5＋Ｒ6 …（３）
但し、ＴM：溶鋼温度、ＴW：鋳型冷却水温度、ＲT：溶鋼と冷却水間の総括熱抵抗
Ｒ1：溶鋼と凝固殻の界面の境膜熱抵抗、Ｒ2：凝固殻の熱抵抗、Ｒ3：モールドパウ
ダーによる膜の熱抵抗、Ｒ4：モールドパウダーによる膜と鋳型間の界面熱抵抗、Ｒ
5：鋳型銅板の熱抵抗、Ｒ6：冷却水と鋳型銅板間の境膜熱抵抗、を夫々示す。
On the other hand, it is known that it is effective to reduce the heat flux directly under the meniscus in the mold in order to reduce crack defects on the surface of the slab. This is considered to be because the deformation of the solidified shell thickness can be reduced, the stress due to the solidification shrinkage can be reduced, and the occurrence of cracks can be suppressed. It is known that the heat transfer between the molten steel and the mold cooling water (heat flux: Q) can be expressed by the following formulas (2) and (3) in consideration of the one-dimensional steady heat transfer model (Non-patent Document 1). .
Q = (T M −T W ) / R T (2)
R T = R 1 + R 2 + R 3 + R 4 + R 5 + R 6 (3)
T M : Molten steel temperature, T W : Mold cooling water temperature, R T : Overall thermal resistance between molten steel and cooling water R 1 : Film heat resistance at the interface between molten steel and solidified shell, R 2 : Heat of solidified shell Resistance, R 3 : Thermal resistance of the film by the mold powder, R 4 : Thermal resistance of the interface between the film by the mold powder and the mold, R
5 : Thermal resistance of the mold copper plate, R 6 : Film heat resistance between the cooling water and the mold copper plate, respectively.
尚、上記Ｒ2は凝固殻の厚さをｄshell、凝固殻の熱伝導度をλshellとしたときに（ｄshell／λshell）と、上記Ｒ3はモールドパウダーの厚さをｄpowder、モールドパウダーの熱伝導度をλpowderとしたときに（ｄpowder／λpowder）と、上記Ｒ5は鋳型銅板の厚さをｄCu、鋳型銅板の熱伝導度をλCuとしたときに（ｄCu／λCu）と、夫々表されるものである。またＲ4（モールドパウダーによる膜と鋳型間の界面熱抵抗）は、モールドパウダーによる膜と鋳型間の界面熱伝導率をｈ1としたときに（１／ｈ1）と、Ｒ6（冷却水と鋳型銅板間の境膜熱抵抗）は、冷却水と鋳型銅板間の界面熱伝導率をｈ2としたときに（１／ｈ2）と、夫々表されるものである。 When R 2 is the thickness of the solidified shell d shell and the thermal conductivity of the solidified shell is λ shell (d shell / λ shell ), R 3 is the thickness of the mold powder d powder , When the thermal conductivity of the mold powder is λ powder (d powder / λ powder ), the above R 5 is when the thickness of the mold copper plate is d Cu and the thermal conductivity of the mold copper plate is λ Cu (d Cu / λ Cu ), respectively. Further, R 4 (interfacial thermal resistance between the film and mold by the mold powder) is (1 / h 1 ) when the interfacial thermal conductivity between the film by the mold powder and the mold is h 1, and R 6 (cooling water). The film thermal resistance between the mold copper plate and the mold copper plate is expressed as (1 / h 2 ), where h 2 is the interface thermal conductivity between the cooling water and the mold copper plate.
上記（２）式、（３）式の関係の下において、メニスカス直下においては、モールドパウダーに関与する伝導抵抗（上記Ｒ3，Ｒ4）がＲTを決定する大部分を占めていることから、実操業での鋳片表面割れ欠陥を改善するために、各種モールドパウダーの開発が進められており、その手段として結晶化しやすいモールドパウダーが有用であるとされている（例えば、特許文献５）。
Ｃ含有量が０．０８〜０．１６％程度の亜包晶鋼を連続鋳造によって製造する際に用いるモールドパウダーとしては、基本的に高粘度とすることによってメニスカス直下の均一冷却を図ると共に、凝固温度や塩基度を指標として、緩冷却化モールドパウダーの設計がされている。しかしながら、連続鋳造機によるメニスカス直下の熱流束測定結果とこれらとの関係を調査したところ、モールドパウダーの凝固温度や塩基度によって定性的に緩冷却度合いを評価することはできるが、定量的な評価は困難であるという欠点がある。 As a mold powder used when producing a subperitectic steel having a C content of about 0.08 to 0.16% by continuous casting, it is basically intended to achieve uniform cooling directly under the meniscus by having a high viscosity, Slowly cooled mold powders are designed using the solidification temperature and basicity as indices. However, when we investigated the relationship between the heat flux measurement results directly below the meniscus using a continuous casting machine and the relationship between them, we can qualitatively evaluate the degree of slow cooling based on the solidification temperature and basicity of the mold powder. Has the disadvantage of being difficult.
本発明は上記の様な事情に着目してなされたものであって、その目的は、Ｃ含有量が０．０８〜０．１６％程度の亜包晶鋼を連続鋳造法によって製造しても、不均一冷却に起因する表面疵が発生しない鋳片を製造することのできる中炭素鋼連続鋳造用モールドパウダー、およびこうしたモールドパウダーを用いて上記のような表面性状に優れた鋳片を製造するための連続鋳造法を提供することにある。 The present invention has been made paying attention to the above-mentioned circumstances, and the object thereof is to manufacture a subperitectic steel having a C content of about 0.08 to 0.16% by a continuous casting method. A mold powder for continuous casting of medium carbon steel capable of producing a slab free from surface flaws due to non-uniform cooling, and a slab excellent in surface properties as described above using such mold powder It is to provide a continuous casting method.
上記目的を達成することのできた本発明のモールドパウダーとは、Ｃ含有量が０．０８〜０．１６％（質量％の意味、以下同じ）である中炭素鋼を連続鋳造法で鋳造する際に用いるモールドパウダーであって、下記（１）式の関係を満足する点に要旨を有するものである。
4.69-3.47×10-3・Ts＋0.786・logη-3.90×10-2・(T.CaO/SiO2)≦０．３０…（１）
但し、Ts：モールドパウダーの凝固温度（℃）
η：モールドパウダーの粘度（poise at 1300℃）
T.CaO/SiO2：塩基度（ＣａＦ2は、ＣａＯに換算）
を夫々示す。
The mold powder of the present invention that has achieved the above-mentioned object is when a medium carbon steel having a C content of 0.08 to 0.16% (meaning mass%, hereinafter the same) is cast by a continuous casting method. It is a mold powder used in the above, and has a gist in that the relationship of the following formula (1) is satisfied.
4.69-3.47 × 10 -3・ Ts + 0.786 ・ logη-3.90 × 10 -2・ (T.CaO / SiO 2 ) ≦ 0.30… (1)
Ts: Mold powder solidification temperature (℃)
η: Mold powder viscosity (poise at 1300 ° C)
T.CaO / SiO2: Basicity (CaF 2 is converted to CaO)
Respectively.
また、上記のようなモールドパウダーを用い、Ｃ含有量が０．０８〜０．１６％である中炭素鋼を連続鋳造法で製造することによって、表面疵のない中炭素鋼鋳片を得ることができる。 Moreover, by using a mold powder as described above and producing a medium carbon steel having a C content of 0.08 to 0.16% by a continuous casting method, a medium carbon steel slab having no surface defects is obtained. Can do.
本発明においては、モールドパウダーの凝固温度、粘度および塩基度を所定の関係式を満足するように管理することによって、上記目的を達成することのできるモールドパウダーが実現できたものであり、こうしたモールドパウダーを用いて中炭素鋼溶鋼を連続鋳造することによって、鋳造時の割れの発生を防止して表面性状の優れた中炭素鋼鋳片を製造することができる。 In the present invention, by controlling the solidification temperature, viscosity, and basicity of the mold powder so as to satisfy a predetermined relational expression, a mold powder that can achieve the above-described object has been realized. By continuously casting the medium carbon steel molten steel using the powder, it is possible to produce a medium carbon steel slab having excellent surface properties by preventing cracking during casting.
本発明者らは、種々のモールドパウダーを用いて中炭素鋼を連続鋳造したときのメニスカス直下における熱流束を実際に測定し、モールドパウダーの物性値（凝固温度、粘度および塩基度）と熱流束の関係、およびこれらの結果が鋳片表面疵に与える影響について調査した。その結果、鋳片表面疵の発生を防止するためには、モールドパウダーの凝固温度、粘度および塩基度を考慮した所定の関係式［前記（１）］式の関係を満足させつつ熱流束を制御する必要があることを見出した。尚、上記（１）式は実際の測定結果に基づき、線形回帰することによって求められた関係式である。 The present inventors actually measured the heat flux just below the meniscus when continuously casting medium carbon steel using various mold powders, and measured the physical properties (solidification temperature, viscosity and basicity) of the mold powder and the heat flux. And the effect of these results on the slab surface defect. As a result, in order to prevent occurrence of slab surface flaws, the heat flux is controlled while satisfying the relation of the predetermined relational expression [the above (1)] in consideration of the solidification temperature, viscosity and basicity of the mold powder. Found that there is a need to do. The above equation (1) is a relational expression obtained by linear regression based on actual measurement results.
本発明で規定する（１）式は、上記のように、モールドパウダーの凝固温度、粘度および塩基度をパラメータとするものである。このうちモールドパウダーの凝固温度については、溶融パウダーが凝固し始めると粘度が急激に上昇することが知られており［例えば、K.C.Mill等「Ironmaking and Steelmaking」,2000,vol.27,238］、本発明では溶融パウダーの温度をゆっくり低下させたときに観察される急激な粘度上昇温度を凝固温度とし定義する。この凝固温度（或いは結晶化温度）は、モールドパウダーによる膜（溶融スラグおよび固体部分を含む）中に結晶を析出させることにより膜の熱伝導度を低下させる、或いはモールドパウダーの膜と鋳型の界面熱抵抗を大きくする要因となるものであり、凝固温度を高めることによって、モールドパウダーに起因する領域におけるより低い熱伝導度、大きな熱抵抗が得られる傾向を示すものとなる。本発明では、こうした要件を（１）式中の要件の一つとしたものである。 Formula (1) prescribed | regulated by this invention uses the coagulation | solidification temperature, viscosity, and basicity of mold powder as a parameter as mentioned above. Among these, regarding the solidification temperature of the mold powder, it is known that the viscosity rapidly increases when the molten powder begins to solidify (for example, KCMill et al. “Ironmaking and Steelmaking”, 2000, vol. 27, 238), the present invention. Then, the rapid viscosity increase temperature observed when the temperature of the molten powder is slowly lowered is defined as the solidification temperature. This solidification temperature (or crystallization temperature) decreases the thermal conductivity of the film by precipitating crystals in the mold powder film (including molten slag and solid part), or the interface between the mold powder film and the mold. This is a factor that increases the thermal resistance. By increasing the solidification temperature, a lower thermal conductivity in the region caused by the mold powder and a higher thermal resistance tend to be obtained. In the present invention, such a requirement is one of the requirements in the equation (1).
一方、高温溶体の粘度測定法については、一般に『回転円筒式粘度測定法』、『球体引き上げ式粘度測定法』および『振動式粘度測定法』の３種類が知られているが、本発明のモールドパウダーでは振動式粘度測定法によって求められた粘度測定値（１３００℃における粘度）を採用する。尚、「モールドパウダーの粘度」とは、モールドパウダーが溶融した状態（スラグ）での粘度を意味する。但し、振動式測定法によって測定された粘度と、他の測定法によって測定された粘度値とは相関があるので、同一パウダーでの各粘度測定値を比較することによって、下記（４）式で規定する補正係数αを求めることによって容易に換算できる。尚、粘度は縦割れ発生段階、即ち鋳型上部でのパウダーの挙動が重要になるので、１３００℃における粘度と規定した。
η＝α×η’ …（４）
但し、η：振動式粘度測定法によって測定されるパウダーの粘度（poise at 1300℃）
η’：回転式若しくは球体引き上げ式粘度測定法によって測定されるパウダーの
粘度（poise at 1300℃）
On the other hand, there are generally known three types of viscosity measurement methods for high-temperature solutions: a “rotary cylinder type viscosity measurement method”, a “sphere pull-up type viscosity measurement method”, and a “vibration type viscosity measurement method”. For the mold powder, a viscosity measurement value (viscosity at 1300 ° C.) obtained by the vibration type viscosity measurement method is adopted. In addition, "viscosity of mold powder" means the viscosity in the state (slag) where mold powder melted. However, since there is a correlation between the viscosity measured by the vibration measurement method and the viscosity value measured by another measurement method, by comparing each viscosity measurement value with the same powder, the following equation (4) It can be easily converted by obtaining the prescribed correction coefficient α. The viscosity was defined as the viscosity at 1300 ° C. because the behavior of powder at the stage of occurrence of vertical cracks, that is, the upper part of the mold becomes important.
η = α × η ′ (4)
However, η: Viscosity of powder measured by vibration type viscosity measurement method (poise at 1300 ℃)
η ′: of powder measured by rotational or spherical pull-up viscosity measurement
Viscosity (poise at 1300 ℃)
モールドパウダーの塩基度は、凝固温度に影響を与えるものであり、より高い凝固温度を達成するためには、塩基度を高めにすれば良いことは知られている。しかしながら、従来提案されているモールドパウダーでは塩基度は依然として低く設定されており、結晶化温度が低くなってガラス化し易い傾向を示すものとなる。ガラス化しやすいモールドパウダーを使用すると、メニスカス直下での熱流束が高くなってしまい、抜熱のムラが非常に大きくなる傾向を示すものとなり、鋳片表面のストリークや縦割れが発生する原因ともなる。こうしたことから、本発明で用いるモールドパウダーの塩基度は比較的高い（ＣａＯ／ＳｉＯ2：１．５〜２．０）ものを使用することを想定したものであるが、他の要件との関係から、（１）式の要件として規定した。尚、この塩基度を設定するに当っては、モールドパウダーがＣａＦを含むものである場合には、これも塩基度の値に影響を及ぼすので、ＣａＯに換算して塩基度を測定する必要がある。 The basicity of the mold powder affects the solidification temperature, and it is known that the basicity may be increased in order to achieve a higher solidification temperature. However, in the conventionally proposed mold powder, the basicity is still set low, and the crystallization temperature tends to be low and the glass powder tends to be vitrified. If mold powder that is easy to vitrify is used, the heat flux directly under the meniscus increases, and the unevenness of heat removal tends to become very large, which may cause streaks and vertical cracks on the slab surface. . For these reasons, it is assumed that the mold powder used in the present invention has a relatively high basicity (CaO / SiO 2 : 1.5 to 2.0), but the relationship with other requirements From the above, it was defined as a requirement of equation (1). In setting the basicity, if the mold powder contains CaF, this also affects the basicity value, so it is necessary to measure the basicity in terms of CaO.
以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
下記表１に示す化学成分組成の各種モールドパウダーを用い、Ｃ含有量が０．０８〜０．１６％の中炭素鋼を連続鋳造し、厚さ：６０ｍｍ、幅：３００ｍｍの鋳片を製造した。このとき、鋳造速度は１．５ｍ／ｍｉｎとした。尚、下記表１には、用いたモールドパウダーにおける塩基度（ＣａＯ／ＳｉＯ2）、１３００℃における粘度、凝固温度、前記（２）式、（３）式によって求められる熱流束、および前記（１）式の左辺の値［4.69-3.47×10-3・Ts＋0.786・logη-3.90×10-2・(T.CaO/SiO2)］を同時に示した。また、表中「Ｆ−」は、モールドパウダー中のフッ素量、「Ｔ．Ｃ」は、モールドパウダー中の全炭素量を夫々示す。 Using various mold powders having the chemical composition shown in Table 1 below, medium carbon steel having a C content of 0.08 to 0.16% was continuously cast to produce a slab having a thickness of 60 mm and a width of 300 mm. . At this time, the casting speed was 1.5 m / min. In Table 1 below, the basicity (CaO / SiO 2 ) of the mold powder used, the viscosity at 1300 ° C., the solidification temperature, the heat flux determined by the above formulas (2) and (3), and the above (1 ) The value on the left side of the equation [4.69-3.47 × 10 −3 · Ts + 0.786 · log η-3.90 × 10 −2 (T.CaO / SiO 2 )] is also shown. In the table, “F-” represents the amount of fluorine in the mold powder, and “TC” represents the total amount of carbon in the mold powder.
得られた鋳片について、表面スケール除去後に磁粉深傷検査を実施し、割れ深さが０．５ｍｍ以上の疵が発生しているか否かによって鋳片表面品質について判定した（疵なし：「○」、疵あり：「×」）。その結果を、下記表１に併記する。 The obtained slab was subjected to a magnetic particle depth inspection after removing the surface scale, and the slab surface quality was determined by whether or not defects having a crack depth of 0.5 mm or more were generated (no defects: “O ”, Wrinkles:“ × ”). The results are also shown in Table 1 below.
これらの結果に基づき、モールドパウダーの凝固温度とメニスカス直下の熱流束の関係、およびモールドパウダー塩基度とメニスカス直下の熱流束の関係が、鋳片表面疵の発生に与える影響について調査した。 Based on these results, the relationship between the solidification temperature of the mold powder and the heat flux just below the meniscus, and the influence of the relationship between the mold powder basicity and the heat flux just below the meniscus on the occurrence of slab surface defects were investigated.
図１は、モールドパウダー凝固温度とメニスカス直下の熱流束の関係が鋳片表面疵の発生に与える影響を示したグラフであり、図２は、モールドパウダー塩基度とメニスカス直下の熱流束の関係が鋳片表面疵の発生に与える影響を示したグラフである。これらの結果から明らかなように、モールドパウダーの凝固温度や塩基度によって定性的に緩冷却度合いを評価することはできるが、定量的な評価は困難であることが分かる。 Fig. 1 is a graph showing the effect of the relationship between the mold powder solidification temperature and the heat flux just below the meniscus on the occurrence of slab surface defects. Fig. 2 shows the relationship between the mold powder basicity and the heat flux just below the meniscus. It is the graph which showed the influence which it has on generation | occurrence | production of slab surface flaw. As is apparent from these results, the degree of slow cooling can be qualitatively evaluated by the solidification temperature and basicity of the mold powder, but quantitative evaluation is difficult.
一方、図３は、表１の結果に基づき、（１）式の左辺の値とメニスカス直下熱流束との関係が鋳片表面品質に与える影響を示したグラフであるが、モールドパウダーの凝固温度、粘度および塩基度をパラメータとして規定される（１）式の値を適切に制御することによって、表面疵のない高品質の中炭素鋼鋳片が製造できることが分かる。 On the other hand, FIG. 3 is a graph showing the influence of the relationship between the value on the left side of the equation (1) and the heat flux directly below the meniscus on the surface quality of the slab based on the results of Table 1. The solidification temperature of the mold powder It can be seen that a high quality medium carbon steel slab having no surface defects can be produced by appropriately controlling the value of the formula (1) defined with the viscosity and basicity as parameters.
Claims (2)
4.69-3.47×10-3・Ts＋0.786・logη-3.90×10-2・(T.CaO/SiO2)≦０．３０…（１）
但し、Ts：モールドパウダーの凝固温度（℃）
η：モールドパウダーの粘度（poise at 1300℃）
T.CaO/SiO2：塩基度（ＣａＦ2は、ＣａＯに換算）
を夫々示す。 A mold powder used for casting a medium carbon steel having a C content of 0.08 to 0.16% (meaning mass%, hereinafter the same) by a continuous casting method, which has the relationship of the following formula (1): A mold powder for continuous casting of medium carbon steel characterized by satisfaction.
4.69-3.47 × 10 -3・ Ts + 0.786 ・ logη-3.90 × 10 -2・ (T.CaO / SiO 2 ) ≦ 0.30… (1)
Ts: Mold powder solidification temperature (℃)
η: Mold powder viscosity (poise at 1300 ° C)
T.CaO / SiO2: Basicity (CaF 2 is converted to CaO)
Respectively.
A continuous casting method for producing a medium carbon steel having a C content of 0.08 to 0.16% by a continuous casting method using the mold powder according to claim 1.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011147979A (en) * | 2010-01-22 | 2011-08-04 | Sumitomo Metal Ind Ltd | Mold flux for continuous casting of steel |
| JP2012187611A (en) * | 2011-03-11 | 2012-10-04 | Sumitomo Metal Ind Ltd | Continuous casting method of steel |
| JP2013078797A (en) * | 2011-09-21 | 2013-05-02 | Jfe Steel Corp | Method for continuously casting medium carbon steel |
| CN112355261A (en) * | 2020-10-26 | 2021-02-12 | 中天钢铁集团有限公司 | Crystallizer casting powder suitable for producing peritectic steel through efficient continuous casting |
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| JPH08197214A (en) * | 1995-01-18 | 1996-08-06 | Nippon Steel Corp | Powder for continuously casting steel |
| JP2002301551A (en) * | 2001-04-02 | 2002-10-15 | Sumitomo Metal Ind Ltd | Mold powder and continuously casting method |
| JP2004098092A (en) * | 2002-09-06 | 2004-04-02 | Sumitomo Metal Ind Ltd | Method for continuously casting molten hyper-peritectic medium carbon steel |
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| JPH08197214A (en) * | 1995-01-18 | 1996-08-06 | Nippon Steel Corp | Powder for continuously casting steel |
| JP2002301551A (en) * | 2001-04-02 | 2002-10-15 | Sumitomo Metal Ind Ltd | Mold powder and continuously casting method |
| JP2004098092A (en) * | 2002-09-06 | 2004-04-02 | Sumitomo Metal Ind Ltd | Method for continuously casting molten hyper-peritectic medium carbon steel |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011147979A (en) * | 2010-01-22 | 2011-08-04 | Sumitomo Metal Ind Ltd | Mold flux for continuous casting of steel |
| JP2012187611A (en) * | 2011-03-11 | 2012-10-04 | Sumitomo Metal Ind Ltd | Continuous casting method of steel |
| JP2013078797A (en) * | 2011-09-21 | 2013-05-02 | Jfe Steel Corp | Method for continuously casting medium carbon steel |
| CN112355261A (en) * | 2020-10-26 | 2021-02-12 | 中天钢铁集团有限公司 | Crystallizer casting powder suitable for producing peritectic steel through efficient continuous casting |
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