JP4881203B2 - Powder for continuous casting - Google Patents
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- JP4881203B2 JP4881203B2 JP2007082606A JP2007082606A JP4881203B2 JP 4881203 B2 JP4881203 B2 JP 4881203B2 JP 2007082606 A JP2007082606 A JP 2007082606A JP 2007082606 A JP2007082606 A JP 2007082606A JP 4881203 B2 JP4881203 B2 JP 4881203B2
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- 239000000843 powder Substances 0.000 title claims description 179
- 238000009749 continuous casting Methods 0.000 title claims description 36
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 68
- 238000007711 solidification Methods 0.000 claims description 31
- 230000008023 solidification Effects 0.000 claims description 31
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 18
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 description 23
- 239000010959 steel Substances 0.000 description 23
- 238000005266 casting Methods 0.000 description 15
- 229910001678 gehlenite Inorganic materials 0.000 description 15
- 229910052751 metal Inorganic materials 0.000 description 14
- 239000002184 metal Substances 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 11
- 239000013078 crystal Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 238000005461 lubrication Methods 0.000 description 8
- 230000007547 defect Effects 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 230000005499 meniscus Effects 0.000 description 6
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 238000007654 immersion Methods 0.000 description 4
- 229910010413 TiO 2 Inorganic materials 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 239000002893 slag Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- -1 B 2 O 3 Inorganic materials 0.000 description 1
- 229910004261 CaF 2 Inorganic materials 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910018068 Li 2 O Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
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- Continuous Casting (AREA)
Description
本発明は、溶融金属の連続鋳造において鋳型内に添加する連続鋳造用パウダーに関するものである。 The present invention relates to a powder for continuous casting added to a mold in continuous casting of molten metal.
溶融金属の連続鋳造においては、鋳型内に注入された溶融金属の表面に連続鋳造用パウダー(以下単に「パウダー」ともいう。)を添加する。鋳型内に添加された連続鋳造用パウダーは、高温の溶融金属に加熱されて溶融し、鋳型と凝固シェルの間に流入する。連続鋳造用パウダーは主として、鋳型内の溶融金属表面の保温及び酸化防止、溶融金属中を浮上した非金属介在物の吸収、鋳型とシェル間に流入するパウダーフィルムによる潤滑作用、このフィルムによる鋳型よりの抜熱の制御を行う機能を発揮する。また、溶融パウダーが溶融金属中に巻き込まれると品質不良の原因となるので、パウダー巻き込みの少ない連続鋳造を行うことが必要である。 In continuous casting of molten metal, powder for continuous casting (hereinafter also simply referred to as “powder”) is added to the surface of the molten metal injected into the mold. The powder for continuous casting added to the mold is heated and melted by the high-temperature molten metal and flows between the mold and the solidified shell. Continuous casting powder is mainly used for heat insulation and oxidation prevention on the surface of the molten metal in the mold, absorption of non-metallic inclusions floating in the molten metal, lubrication by the powder film flowing between the mold and the shell, Exhibits the function of controlling heat removal. In addition, if the molten powder is caught in the molten metal, it may cause a quality defect. Therefore, it is necessary to perform continuous casting with less powder entrainment.
鋳型と凝固シェル間の潤滑特性は最も重要視され、鋳造品種や連続鋳造条件に応じて溶融物性を調整した多くのパウダー品種がつくられてきた。パウダー溶融物性のうち、1300℃における粘度は潤滑性を制御する上で重要な指標であり、粘度の低いものほど鋳型と凝固シェル間への流入量が多く、高い潤滑効果が期待できる。一方、鋳型内に溶融金属を供給するために浸漬ノズルが用いられる。浸漬ノズルから吐出する溶融金属流により、鋳型内の溶融金属は攪拌されており、溶融金属のメニスカス部も攪拌の影響を受けている。連続鋳造用パウダーとして低粘度パウダーを使用すると、メニスカス部の溶融金属攪拌や浸漬ノズル近傍に生じる渦流によって溶融パウダーが溶融金属中に巻き込まれやすくなる性質があり、巻き込まれたパウダー起因の溶融スラグは鋳片内部に残存して介在物欠陥となる。そのため、鋳片内部欠陥に対して厳格な用途に使われることの多い極低炭素鋼用のパウダーについては、潤滑に支障のない範囲で高粘度化し、パウダー巻き込みを最低限に抑える試みがなされている。 The lubrication characteristics between the mold and the solidified shell are regarded as the most important, and many powder varieties with adjusted melt properties according to casting varieties and continuous casting conditions have been produced. Among the powder melt properties, the viscosity at 1300 ° C. is an important index for controlling the lubricity, and the lower the viscosity, the larger the amount of inflow between the mold and the solidified shell, and the higher the lubrication effect can be expected. On the other hand, an immersion nozzle is used to supply molten metal into the mold. The molten metal in the mold is stirred by the molten metal flow discharged from the immersion nozzle, and the meniscus portion of the molten metal is also affected by the stirring. When low-viscosity powder is used as the powder for continuous casting, there is a property that the molten powder is easily caught in the molten metal due to the stirring of the molten metal in the meniscus part and the vortex generated near the immersion nozzle. It remains inside the slab and becomes an inclusion defect. For this reason, powder for ultra-low carbon steel, which is often used for strict applications against internal defects in slabs, has been tried to increase the viscosity within a range that does not interfere with lubrication and minimize powder entrainment. Yes.
特許文献1においては、1300℃での粘度が10poise以上150poise以下であり、かつ凝固時の固相率と温度の関係を規定したパウダーが開示されている。これにより、パウダー流入不良によるトラブルを防止しつつ、介在物やパウダーの巻き込みに起因する加工時の欠陥を防止できる。また特許文献2においては、CaO/SiO2が0.3〜0.8の範囲にあり、1300℃における粘度が10poise超50poise以下とし、さらに凝固温度及び冷却後の結晶化率を規定したパウダーが開示されている。これにより、流入性を確保しつつパウダー巻き込みが少なく、かつ表面性状に優れた鋼材を製造することができる。 Patent Document 1 discloses a powder having a viscosity at 1300 ° C. of 10 poise to 150 poise and defining a relationship between a solid phase ratio and a temperature at the time of solidification. Thereby, the defect at the time of the process resulting from inclusion and the entrainment of powder can be prevented, preventing the trouble by powder inflow failure. In Patent Document 2, there is a powder in which CaO / SiO 2 is in the range of 0.3 to 0.8, the viscosity at 1300 ° C. is more than 10 poise and 50 poise or less, and the solidification temperature and the crystallization rate after cooling are defined. It is disclosed. As a result, it is possible to manufacture a steel material with less powder entrainment and excellent surface properties while ensuring inflow properties.
特許文献1、2に記載のパウダーは、1300℃での粘度を10poise以上の高粘度とするための手段として、パウダー中のSiO2含有量を高い含有量とし、CaO含有量を低い含有量とし、CaO/SiO2の値を低くしている。 The powders described in Patent Documents 1 and 2 have a high content of SiO 2 in the powder and a low content of CaO as a means for making the viscosity at 1300 ° C. a high viscosity of 10 poise or more. The value of CaO / SiO 2 is lowered.
炭素濃度が0.01質量%以下である極低炭素鋼は、脱酸等を目的としてAlやTiを含有している。鋳型内メニスカスにおいて、溶鋼と溶融パウダーが接しており、この界面において溶鋼中のAlやTiは溶融パウダー中のSiO2と反応し、以下の反応が生成する。
4[Al]+3(SiO2) → 2(Al2O3)+3[Si] (1)
[Ti]+(SiO2) → (TiO2)+[Si] (2)
ここで[ ]は溶鋼中の成分、( )は溶融スラグ中の成分を意味している。
The ultra-low carbon steel having a carbon concentration of 0.01% by mass or less contains Al and Ti for the purpose of deoxidation and the like. At the meniscus in the mold, the molten steel is in contact with the molten powder. At this interface, Al and Ti in the molten steel react with SiO 2 in the molten powder, and the following reaction is generated.
4 [Al] +3 (SiO 2 ) → 2 (Al 2 O 3 ) +3 [Si] (1)
[Ti] + (SiO 2 ) → (TiO 2 ) + [Si] (2)
Here, [] means a component in molten steel, and () means a component in molten slag.
上記(1)(2)式の反応によって溶融パウダー中のSiO2含有量が低下すると、結果として溶融パウダーの1300℃における粘度が低下する。そのため、パウダーが当初有していた高粘度という性質を失い、パウダー巻き込みを十分に防止することができなくなる。 When the SiO 2 content in the molten powder is reduced by the reaction of the above formulas (1) and (2), the viscosity of the molten powder at 1300 ° C. is reduced as a result. Therefore, the property of the high viscosity that the powder originally had is lost, and the entrainment of the powder cannot be sufficiently prevented.
溶鋼と溶融パウダーの界面における上記(1)(2)式の反応を防止するためには、溶融パウダー中のSiO2活量を下げることが有効である。そのため、パウダー中のSiO2含有量を低減する試みがなされている。例えば特許文献3においては、高粘度の高塩基度パウダーとして、1300℃における粘度が3〜8poise、塩基度(CaO/SiO2)が1.3以上3.0未満である連続鋳造用パウダーが提案されているが、粘度が8poise以下であって決して高粘度ということはできない。 In order to prevent the reaction of the above formulas (1) and (2) at the interface between the molten steel and the molten powder, it is effective to lower the SiO 2 activity in the molten powder. Therefore, attempts have been made to reduce the SiO 2 content in the powder. For example, Patent Document 3 proposes a powder for continuous casting having a viscosity at 1300 ° C. of 3 to 8 poise and a basicity (CaO / SiO 2 ) of 1.3 or more and less than 3.0 as a highly basic powder having a high viscosity. However, the viscosity is 8 poise or less, and it cannot be said that the viscosity is high.
特許文献4においては、高塩基度パウダーの粘度上昇にはAl2O3等の添加が有効であるが、高塩基度パウダーに単にAl2O3等を添加すると形成するパウダーフィルム中への結晶析出が不安定になるとしている。そして同文献では、アケルマナイト、ゲーレナイト等を溶融スラグ凝固時に主な結晶組成として析出し、CaO/SiO2が1.0〜1.5であり、Al2O3、MgO、Na2O、Li2O等の成分範囲及び凝固温度を規定し、1300℃における粘度が0.2〜1.3poiseであるパウダーが開示されている。同文献に記載のパウダーも、十分に高粘度であるということはできない。 In Patent Document 4, Al 2 O 3 or the like is effective for increasing the viscosity of the high basicity powder. However, when Al 2 O 3 or the like is simply added to the high basicity powder, crystals formed in the powder film are formed. It is said that the precipitation becomes unstable. And in this document, Akerumanaito, precipitated as main crystals composition when melted slag solidifying the Gehlenite like, CaO / SiO 2 is 1.0~1.5, Al 2 O 3, MgO , Na 2 O, Li 2 A powder having a component range such as O and a solidification temperature and a viscosity at 1300 ° C. of 0.2 to 1.3 poise is disclosed. The powder described in this document cannot be said to have a sufficiently high viscosity.
特許文献5では、パウダーのSiO2の活量を低下させることで、パウダーと溶鋼との反応が抑制されて、溶鋼とパウダーとの界面張力の低下を抑制し、あわせて粘度の低下も抑制し、溶鋼中へのパウダーの巻き込みを防止できるとしている。そして、パウダー中のCaO/SiO2を0.6〜1.2、SiO2含有量を10〜35%とし、パウダーのSiO2活量を低下させている。実施例によると、1300℃における粘度が8〜20poiseの例が示されている。 In Patent Document 5, by reducing the activity of SiO 2 in the powder, the reaction between the powder and the molten steel is suppressed, the decrease in the interfacial tension between the molten steel and the powder is suppressed, and the decrease in the viscosity is also suppressed. It is said that it is possible to prevent entrainment of powder in molten steel. Then, the CaO / SiO 2 in the powder 0.6-1.2, the SiO 2 content is 10 to 35% and reduce the SiO 2 activity of the powder. According to the Example, the example whose viscosity in 1300 degreeC is 8-20 poise is shown.
特許文献6に記載のものは、1300℃におけるパウダー粘度が12poise以下で、パウダー中のSiO2含有量及びNa2O等の含有量をパウダー粘度から定まる一定値よりも低い値とする発明である。これにより、パウダー溶融物と溶鋼中アルミニウムとの反応性が低減し、アルゴンガスの溶湯面での破泡時における溶鋼中へのパウダーの巻き込みが顕著に減少する。 The one described in Patent Document 6 is an invention in which the powder viscosity at 1300 ° C. is 12 poise or less, and the content of SiO 2 and the content of Na 2 O or the like in the powder is lower than a constant value determined from the powder viscosity. . Thereby, the reactivity of the powder melt and aluminum in the molten steel is reduced, and the entrainment of powder in the molten steel at the time of bubble breakage on the molten metal surface of argon gas is significantly reduced.
連続鋳造鋳型内に熱電対を埋め込み、鋳造中の鋳型温度の変動を監視することにより、拘束性ブレークアウト(以下「BO」という。)の発生を予知することが行われている。メニスカス部よりも下方の鋳型温度を監視し、この部位の鋳型温度が非定常に上昇したときには、拘束によるシェルの破断部がこの部位まで下降してきたと認識し、鋳造速度を急減速する。これによりシェルの破断部を修復し、拘束性BO発生を防止することができる。パウダーの種類によって拘束性BO予知信号の発生頻度が異なり、発生頻度が少ないパウダーほど鋳造が安定しており好ましい。また、鋳型内熱電対の温度の時間変動が多い場合には、パウダーの流入状況が不安定であると認識することができる。 It has been practiced to predict the occurrence of a constraining breakout (hereinafter referred to as “BO”) by embedding a thermocouple in a continuous casting mold and monitoring fluctuations in the mold temperature during casting. The mold temperature below the meniscus portion is monitored, and when the mold temperature at this portion rises unsteadily, it is recognized that the fracture portion of the shell due to restraint has fallen to this portion, and the casting speed is rapidly reduced. Thereby, the fracture | rupture part of a shell can be repaired and restraint BO generation | occurrence | production can be prevented. The frequency of occurrence of the restrictive BO prediction signal differs depending on the type of powder, and powder having a lower frequency of occurrence is more stable and preferable. In addition, when the time variation of the temperature of the thermocouple in the mold is large, it can be recognized that the inflow state of the powder is unstable.
特許文献3、4に記載のものは、高塩基度パウダーを用いることによってパウダー中SiO2成分と溶鋼中のAl等との反応を低減しているものの、1300℃における粘度が決して高粘度ということはできない。 Those described in Patent Documents 3 and 4, although reducing the reaction between Al and the like of the SiO 2 in the component and the molten steel in powder by using a high basicity powder, that never high viscosity viscosity at 1300 ° C. I can't.
特許文献5に記載のものは、パウダーのSiO2活量を低下させてパウダーと溶鋼との反応を抑制し、同時に1300℃における粘度が8〜20poiseと高粘度を実現している。また特許文献6に記載のものは、1300℃における粘度が12poise以下で溶鋼成分との反応性の低いパウダーが開示されている。しかし特許文献5、6に記載のもののうち高粘度のパウダーを連続鋳造に用いると、鋳型内に埋め込んだ熱電対で測定する鋳型温度の変動が増加することが分かった。 Those described in Patent Document 5, to lower the SiO 2 activity of the powder suppresses the reaction between the powder and the molten steel has a viscosity at 1300 ° C. simultaneously achieves high viscosity and 8~20Poise. Patent Document 6 discloses a powder having a viscosity at 1300 ° C. of 12 poise or less and low reactivity with molten steel components. However, it has been found that when high-viscosity powders described in Patent Documents 5 and 6 are used for continuous casting, fluctuations in the mold temperature measured by a thermocouple embedded in the mold increase.
本発明は、パウダーの粘度が十分に高くパウダー巻き込みを低減することができ、パウダーと溶鋼成分との反応を防止して鋳造中におけるパウダー粘度の低下を防止し、さらに鋳造時に鋳型に埋め込んだ熱電対の温度変動を少なくすることのできる連続鋳造用パウダーを提供することを目的とする。 The present invention has a sufficiently high powder viscosity that can reduce the entrainment of powder, prevent the reaction between the powder and molten steel components to prevent the powder viscosity from being lowered during casting, and the thermoelectric embedded in the mold during casting. An object of the present invention is to provide a powder for continuous casting which can reduce the temperature fluctuation of the pair.
即ち、本発明の要旨とするところは以下のとおりである。
(1)質量%で、SiO2:5.0〜35.0%、Al2O3:5.0〜35.0%、T.CaO:40.0%以下、Na2O:3.0〜15.0%、F:2.0〜10.0%を含有し、MgOを1.5%以下に規制し、その他成分含有量が20%以下であり、T.CaO/SiO2が0.15〜1.05であり、1300℃での粘度が10〜20poise、凝固温度が1260℃以下であることを特徴とする連続鋳造用パウダー。
That is, the gist of the present invention is as follows.
(1) By mass%, SiO 2 : 5.0 to 35.0%, Al 2 O 3 : 5.0 to 35.0%, T.I. CaO: 40.0% or less, Na 2 O: 3.0 to 15.0%, F: 2.0 to 10.0%, MgO is regulated to 1.5% or less, and other component contents Is 20% or less. A powder for continuous casting, wherein CaO / SiO 2 is 0.15 to 1.05, the viscosity at 1300 ° C. is 10 to 20 poise, and the solidification temperature is 1260 ° C. or less.
ただしT.CaOは、パウダー中のCaがすべてCaOであるとして算出したCaO含有量である。
(2)さらにZrO2を1.0〜10質量%含有することを特徴とする上記(1)に記載の連続鋳造用パウダー。
(3)さらにCを0.4〜5.0%含有することを特徴とする上記(1)又は(2)に記載の連続鋳造用パウダー。
(4)さらにSrOを5.0%以下に規制することを特徴とする上記(1)乃至(3)のいずれかに記載の連続鋳造用パウダー。
However, T.W. CaO is the CaO content calculated assuming that all Ca in the powder is CaO.
(2) further continuous casting powder according to (1), characterized in that it comprises 1.0 to 10 wt% including the ZrO 2.
(3) further continuous casting powder according to (1) or (2) and having containing 0.4 to 5.0% of C.
(4) The powder for continuous casting according to any one of (1) to (3), wherein SrO is further regulated to 5.0% or less.
本発明は、1300℃での粘度を6poise以上と高粘度にすることによってパウダー巻き込みを防止し、SiO2含有量を35.0%以下とすることによってパウダーと溶鋼との反応を防止して粘度の低下を防止し、MgO含有量を2.5%以下とすると同時に塩基度を1.05以下とすることによって鋳造時に鋳型に埋め込んだ熱電対の温度変動を少なくすることができ、極低炭素鋼鋳造時において安定してパウダー巻き込みを低減することができる。 The present invention prevents the entrainment of powder by increasing the viscosity at 1300 ° C. to 6 poise or higher, and prevents the reaction between the powder and molten steel by setting the SiO 2 content to 35.0% or less. By reducing the MgO content to 2.5% or less and at the same time the basicity to 1.05 or less, temperature fluctuations of the thermocouple embedded in the mold during casting can be reduced, and extremely low carbon Powder entrainment can be stably reduced during steel casting.
本発明の連続鋳造用パウダーは、1300℃での粘度を6〜30poiseとする。粘度が6poise未満では、極低炭素鋼の鋳造においてパウダーの巻き込みを十分に低減することができない。一方、粘度が30poiseを超えると、パウダーフィルムによる鋳型内潤滑機能を十分に得ることができなくなる。1300℃での粘度は8〜20poiseの範囲であるとより好ましい。粘度下限を10poiseとするとさらに好ましく、粘度下限を12poiseとするとより一層好ましい。 The powder for continuous casting of the present invention has a viscosity at 1300 ° C. of 6 to 30 poise. When the viscosity is less than 6 poise, the entrainment of powder cannot be sufficiently reduced in the casting of ultra-low carbon steel. On the other hand, if the viscosity exceeds 30 poise, the in-mold lubricating function by the powder film cannot be sufficiently obtained. The viscosity at 1300 ° C. is more preferably in the range of 8 to 20 poise. The lower limit of viscosity is more preferably 10 poise, and the lower limit of viscosity is more preferably 12 poise.
従来の高粘度連続鋳造用パウダーにおいては、粘度を高めるためにパウダー中のSiO2含有量を高め(40〜60%)、CaO/SiO2の値も低い値としていた。本発明においては、パウダーのSiO2活量を低下させて溶鋼中成分とパウダー中SiO2との反応を低減するために、パウダー中のSiO2含有量を低い値とする。パウダー中SiO2含有量を35質量%以下、好ましくは30質量%以下とする。 In the conventional high-viscosity continuous casting powder, the SiO 2 content in the powder is increased (40 to 60%) to increase the viscosity, and the CaO / SiO 2 value is also low. In the present invention, the content of SiO 2 in the powder is set to a low value in order to reduce the SiO 2 activity of the powder and reduce the reaction between the components in the molten steel and the SiO 2 in the powder. The SiO 2 content in the powder is 35% by mass or less, preferably 30% by mass or less.
SiO2含有量を減らしても高粘度を確保することが必要であり、またSiO2含有量を低減した分だけ他の成分を補う必要がある。 Even if the SiO 2 content is reduced, it is necessary to ensure a high viscosity, and it is necessary to supplement other components by the amount that the SiO 2 content is reduced.
パウダー中のAl2O3含有量を増大すると粘度を上昇させることができる。そこで本発明においては、パウダー粘度を低下させずにSiO2含有量を低減するため、第1にAl2O3含有量の増大を図る。Al2O3含有量が5.0質量%以上であればパウダー粘度を6poise以上に確保することができるので、下限を5.0質量%とする。好ましくは下限を15.0質量%とする。一方、Al2O3含有量が35.0質量%を超えると正常な溶融状態が得られないので、上限を35.0質量%とする。Al2O3含有量上限を25.0質量%とすると好ましい。上限を20.0質量%とするとより好ましい。好ましい範囲内でAl2O3含有量を高くするほど、粘度を高く保つとともに、SiO2含有量を低減する際に補う他の成分を少なくすることができるので好ましい。 Increasing the Al 2 O 3 content in the powder can increase the viscosity. Therefore, in the present invention, in order to reduce the SiO 2 content without reducing the powder viscosity, first, the Al 2 O 3 content is increased. If the Al 2 O 3 content is 5.0% by mass or more, the powder viscosity can be secured at 6 poise or more, so the lower limit is made 5.0% by mass. Preferably, the lower limit is 15.0% by mass. On the other hand, if the Al 2 O 3 content exceeds 35.0% by mass, a normal molten state cannot be obtained, so the upper limit is made 35.0% by mass. The upper limit of the Al 2 O 3 content is preferably 25.0% by mass. The upper limit is more preferably 20.0% by mass. The higher the Al 2 O 3 content within the preferred range, the higher the viscosity, and the other components that can be supplemented when reducing the SiO 2 content is preferred.
パウダー中のSiO2含有量を低減する際に増量する対象としてT.CaOが挙げられるが、T.CaO含有量を増やすと粘度が低減する。1300℃での粘度を6poise以上とするため、T.CaO含有量の上限は40.0質量%とする。T.CaO含有量の上限を35.0質量%とすれば、粘度をより一層上昇させることができるので好ましい。一方、T.CaO含有量が20質量未満となるとSiO2含有量を35質量%以下とすることが難しくなるので、T.CaO含有量の下限を20質量%とすると好ましい。T.CaOとは前述のとおり、パウダー中のCaがすべてCaOであるとして算出したCaO含有量である。 As an object to be increased when the content of SiO 2 in the powder is reduced, T.P. Examples include CaO. Increasing the CaO content decreases the viscosity. In order to set the viscosity at 1300 ° C. to 6 poise or more, T.C. The upper limit of the CaO content is 40.0% by mass. T.A. If the upper limit of the CaO content is 35.0% by mass, the viscosity can be further increased, which is preferable. On the other hand, T.W. When the CaO content is less than 20%, it is difficult to make the SiO 2 content 35% by mass or less. The lower limit of the CaO content is preferably 20% by mass. T.A. As described above, CaO is the CaO content calculated assuming that all Ca in the powder is CaO.
パウダーの溶融状態を好適に保つため、通常のパウダーにおいてNa2Oを含有させていることが多い。パウダー中のSiO2含有量を減らすためにNa2O含有量を増大することができるが、Na2O含有量が15.0質量%を超えると1300℃での粘度を6poise以上に保持することが困難となるので、Na2O含有量の上限は15.0質量%とする。好ましくはNa2O含有量上限を10.0質量%とする。一方、Na2O含有量が少なすぎると正常なパウダー溶融を得ることが難しくなるので、下限を3.0質量%とする。下限が5.0質量%であるとより好ましい。 In order to keep the molten state of the powder suitably, the normal powder often contains Na 2 O. To reduce the SiO 2 content in the powder, the Na 2 O content can be increased, but if the Na 2 O content exceeds 15.0% by mass, the viscosity at 1300 ° C. should be maintained at 6 poise or more. Therefore, the upper limit of the Na 2 O content is 15.0% by mass. Preferably, the upper limit of the Na 2 O content is 10.0% by mass. On the other hand, if the Na 2 O content is too small, it is difficult to obtain normal powder melting, so the lower limit is made 3.0% by mass. The lower limit is more preferably 5.0% by mass.
パウダーの溶融状態を好適に保つため、Fを通常のパウダーにおいて含有させている。パウダー中のSiO2含有量を減らすためにF含有量を増大することができるが、F含有量が10.0質量%を超えると1300℃での粘度を6poise以上に保持することが困難となるので、F含有量の上限は10.0質量%とする。好ましくはF含有量上限を8.0質量%とする。一方、F含有量が少なすぎると正常なパウダー溶融を得ることが難しくなるので、下限を2.0質量%とする。下限が4.0質量%であるとより好ましい。 In order to keep the molten state of the powder suitably, F is contained in normal powder. The F content can be increased to reduce the SiO 2 content in the powder. However, if the F content exceeds 10.0% by mass, it becomes difficult to maintain the viscosity at 1300 ° C. at 6 poise or more. Therefore, the upper limit of the F content is 10.0% by mass. Preferably, the upper limit of the F content is 8.0% by mass. On the other hand, if the F content is too small, it is difficult to obtain normal powder melting, so the lower limit is made 2.0 mass%. The lower limit is more preferably 4.0% by mass.
パウダー中のSiO2含有量を減らすために含有させるその他成分として、MgOは最も好まれて使用されている成分である。ところが、本発明において、パウダー中にMgOを3%程度含有させると、溶融パウダーが凝固する際にパウダーフィルム中に等軸晶が生成し、分析の結果この結晶はわずかにアケルマナイト(2CaO・MgO・2SiO2)を含むゲーレナイト(2CaO・Al2O3・SiO2)であることが判明した。そしてゲーレナイトが生成することと関連して、鋳型内に埋め込んだ熱電対で連続鋳造中の鋳型内温度を測定したとき、メニスカス部よりも下方の部位において、連続鋳造中の鋳型内温度の変動が大きくなることが観察された。パウダー成分が低SiO2であって、さらに高Al2O3である場合に、特に上記MgO含有によるゲーレナイトの生成が顕著である。 As another component to be included for reducing the SiO 2 content in the powder, MgO is the most preferred component used. However, in the present invention, when about 3% of MgO is contained in the powder, equiaxed crystals are formed in the powder film when the molten powder is solidified. As a result of analysis, the crystals are slightly acermanite (2CaO · MgO · it has been found 2SiO 2) is gehlenite (2CaO · Al 2 O 3 · SiO 2) containing. In connection with the formation of gehlenite, when the temperature in the mold during continuous casting is measured with a thermocouple embedded in the mold, the temperature in the mold during continuous casting varies at a position below the meniscus part. It was observed to grow. When the powder component is low SiO 2 and further high Al 2 O 3 , the generation of gehlenite due to the MgO content is particularly remarkable.
現在用いられている連続鋳造パウダーにおいてパウダーフィルム中に結晶が生成する場合、生成する結晶はそのほとんどがカスピダイン(3CaO・2SiO2・CaF2)である。カスピダインはパウダーフィルム中に柱状晶としてフィルムの鋳型側に沿って層状に生成する。これに対し、パウダーフィルム中にゲーレナイトが生成する場合には、フィルム内で局所的に核生成および成長するため、結晶粒界での輻射伝熱を散乱させ、結果として局所的に鋳型抜熱を乱していると推測される。従って、パウダーフィルムを介しての鋳型伝熱を安定化させるためには、パウダーフィルムへのゲーレナイトの生成を防止することが必要である。 When crystals are formed in a powder film in a continuous casting powder that is currently used, most of the crystals that are formed are caspodyne (3CaO · 2SiO 2 · CaF 2 ). Caspodyne is formed in a layer form along the mold side of the film as columnar crystals in the powder film. On the other hand, when gehlenite is generated in the powder film, it nucleates and grows locally in the film, so that the radiant heat transfer at the grain boundaries is scattered, resulting in local heat removal from the mold. Presumed to be disturbed. Therefore, in order to stabilize the mold heat transfer through the powder film, it is necessary to prevent the formation of gehlenite on the powder film.
本発明においては、パウダー含有成分としてのMgO含有量を2.5質量%以下に限定することにより、パウダーフィルム中へのゲーレナイトの生成を防止することを可能とした。MgO含有量は1.5質量%以下であるとより好ましい。本発明のように、パウダーの高粘度を保持しつつパウダー中のSiO2含有量を低減する場合、代わりに添加する成分としてMgOが最も好まれる成分である。特許文献5に記載のパウダーについても、1300℃での粘度が8poise以上でかつSiO2含有量を低く保持した実施例については、MgO含有量が2.5%を超えていることが明らかである。本発明は、MgO含有量の上限を2.5%と限定することにより、高粘度でかつSiO2含有量を低減するに際し、ゲーレナイトの生成を防止し、安定した伝熱特性を確保することを可能にした。 In the present invention, the content of MgO as a powder-containing component is limited to 2.5% by mass or less, thereby making it possible to prevent the formation of gehlenite in the powder film. The MgO content is more preferably 1.5% by mass or less. In the case of reducing the SiO 2 content in the powder while maintaining the high viscosity of the powder as in the present invention, MgO is the most preferred component to be added instead. Also for the powder described in Patent Document 5, it is clear that the MgO content exceeds 2.5% for the examples in which the viscosity at 1300 ° C. is 8 poise or more and the SiO 2 content is kept low. . In the present invention, by limiting the upper limit of MgO content to 2.5%, it is possible to prevent the formation of gehlenite and ensure stable heat transfer characteristics when reducing the SiO 2 content with high viscosity. Made possible.
本発明においては、パウダーフィルム中へのゲーレナイト生成を防止するためには、MgO含有量の上限を規定することに加え、T.CaO/SiO2を1.05以下に限定する。本発明のパウダー成分範囲内においてT.CaO/SiO2が増大すると、パウダー組成がゲーレナイト(2CaO・Al2O3・SiO2)に近づくのでパウダーフィルム中へのゲーレナイトが生成しやすくなるが、T.CaO/SiO2を1.05以下に限定することにより、パウダーフィルム中へのゲーレナイト生成を抑制することが可能となる。一方、T.CaO/SiO2が0.15未満となるとSiO2含有量を35%以下とすることが難しくなるので、T.CaO/SiO2の下限を0.15とする。T.CaO/SiO2の下限を0.55とするとより好ましい。 In the present invention, in order to prevent the formation of gehlenite in the powder film, in addition to defining the upper limit of the MgO content, T.I. CaO / SiO 2 is limited to 1.05 or less. Within the powder component range of the present invention, T.I. When CaO / SiO 2 increases, the powder composition approaches that of gehlenite (2CaO · Al 2 O 3 · SiO 2 ), so that gehlenite is easily generated in the powder film. By limiting CaO / SiO 2 to 1.05 or less, it becomes possible to suppress the generation of gehlenite in the powder film. On the other hand, T.W. When CaO / SiO 2 is less than 0.15, it is difficult to reduce the SiO 2 content to 35% or less. The lower limit of CaO / SiO 2 is 0.15. T.A. More preferably, the lower limit of CaO / SiO 2 is 0.55.
本発明の連続鋳造用パウダーは、1300℃での粘度を高粘度とすることにより、パウダー巻き込みの少ない連続鋳造を可能にする。一方、1300℃での粘度が高くなることに引きずられて凝固温度が高くなりすぎると、鋳型と凝固シェル間へ流入したパウダーフィルムの凝固が早すぎ、パウダーフィルムの流入潤滑特性が悪化することとなる。本発明においては、パウダーの凝固温度を1260℃以下とすることにより、パウダーの流入潤滑特性を良好に保持することができる。 The powder for continuous casting of the present invention enables continuous casting with less powder entrainment by setting the viscosity at 1300 ° C. to a high viscosity. On the other hand, if the solidification temperature becomes too high due to the increase in viscosity at 1300 ° C., the powder film that has flowed into the space between the mold and the solidified shell will solidify too early, and the inflow lubrication characteristics of the powder film will deteriorate. Become. In the present invention, when the solidification temperature of the powder is 1260 ° C. or less, the inflow lubrication characteristics of the powder can be maintained well.
従来の高粘度パウダーは、SiO2含有量を高くすることによって高粘度を実現しており、鋳造中に溶鋼成分とパウダー中SiO2が反応するため、反応の結果生じるパウダー成分変化によってパウダーの凝固温度が低下する現象が見られた。そのため、使用前パウダーの特性としての凝固温度が比較的に高い温度であっても、実際にはパウダー流入潤滑特性が良好に保たれる傾向があった。それに対して本発明のパウダーは、SiO2含有量を低く抑えた結果として鋳造中におけるパウダー成分変化が少なくなり、鋳造中における凝固温度の低下が抑制されることとなった。そのため、従来の高SiO2含有量パウダーに比較し、使用前パウダーの特性としての凝固温度をより低い温度とした方が好ましい結果が得られることがわかった。具体的には、パウダーの凝固温度を1160℃以下とすることにより、パウダーの好ましい流入潤滑特性を実現することができる。凝固温度を1120℃以下とするとより好ましい。 Conventional high-viscosity powder achieves high viscosity by increasing the SiO 2 content, and since the molten steel component reacts with SiO 2 in the powder during casting, the powder solidifies due to the change in the powder component resulting from the reaction. A phenomenon in which the temperature decreased was observed. Therefore, even if the solidification temperature as a characteristic of the powder before use is a relatively high temperature, the powder inflow lubrication characteristic tends to be kept good in practice. On the other hand, the powder of the present invention has a small change in the powder component during casting as a result of keeping the SiO 2 content low, and the solidification temperature during casting is suppressed from decreasing. Therefore, it has been found that a preferable result can be obtained when the solidification temperature as a characteristic of the powder before use is set to a lower temperature as compared with the conventional high SiO 2 content powder. Specifically, a preferable inflow lubrication characteristic of the powder can be realized by setting the solidification temperature of the powder to 1160 ° C. or less. More preferably, the solidification temperature is 1120 ° C. or lower.
パウダー中のZrO2含有量を増大すると粘度を上昇させることができる。そこで本発明においては、1300℃での粘度をより一層高い値として好ましい特性を得ようとする場合には、ZrO2を含有させると好ましい。一方、ZrO2を含有させると、パウダーの凝固温度を上昇させることとなるので、ZrO2含有量を10質量%以下とする。ZrO2を含有させて1300℃での粘度を上昇させつつ、同時にパウダーの凝固温度を1120℃以下に保持するためには、ZrO2含有量を3.0質量%以下に保つと良い。また、ZrO2含有量1.0質量%以上においてZrO2含有の効果を発揮することができる。 Increasing the ZrO 2 content in the powder can increase the viscosity. Therefore, in the present invention, it is preferable to contain ZrO 2 in order to obtain preferable characteristics by setting the viscosity at 1300 ° C. to a higher value. On the other hand, if ZrO 2 is contained, the solidification temperature of the powder is raised, so the ZrO 2 content is set to 10% by mass or less. In order to increase the viscosity at 1300 ° C. by containing ZrO 2 and at the same time maintain the solidification temperature of the powder at 1120 ° C. or less, the ZrO 2 content is preferably maintained at 3.0% by mass or less. Moreover, the effect of containing ZrO 2 can be exhibited when the ZrO 2 content is 1.0% by mass or more.
パウダーの凝固温度を下げる機能を有する成分として、MgOが知られている。しかし上述のとおり、本発明のパウダー中にMgOを含有させると、パウダー凝固時に有害なゲーレナイトが生成するので、MgOを含有させることによって凝固温度を下げることはできない。 MgO is known as a component having a function of lowering the solidification temperature of the powder. However, as described above, when MgO is contained in the powder of the present invention, harmful gelenite is generated at the time of powder solidification, so that the solidification temperature cannot be lowered by containing MgO.
パウダー中のNa2O含有量を増大させると、パウダーの凝固温度を下げることができる。通常のパウダー成分設計において、Na2O含有量は3〜4%とすることが多い。本発明においては、パウダーの凝固温度を低減することを目的として、許容範囲(上限15.0%、好ましくは上限10.0%)においてNa2O含有量を増やすことができる。 Increasing the Na 2 O content in the powder can lower the solidification temperature of the powder. In normal powder component design, the Na 2 O content is often 3-4%. In the present invention, the Na 2 O content can be increased within an allowable range (upper limit: 15.0%, preferably upper limit: 10.0%) for the purpose of reducing the solidification temperature of the powder.
パウダーの溶融速度調整剤として、パウダー中にCを含有させても良い。Cを含有させることにより、パウダーの溶融速度を抑えることができる。C含有量を0.4質量%以上とすればこの効果を発揮することができる。一方、極低炭素鋼の連続鋳造に用いるパウダーにおいては、パウダーから溶鋼への加炭が問題となるので、C含有量上限を5.0質量%とする。 As a powder melting rate adjusting agent, C may be contained in the powder. By containing C, the melting rate of the powder can be suppressed. This effect can be exhibited if the C content is 0.4 mass% or more. On the other hand, in the powder used for continuous casting of ultra-low carbon steel, carburization from powder to molten steel becomes a problem, so the upper limit of the C content is 5.0 mass%.
本発明においては、SiO2以外の成分含有量を所定範囲に抑えた上でSiO2含有量を減らすために、さらにその他の成分を含有させる必要が生じるときがある。また、原料からの不可避不純物としてその他の成分を含有する。その他の成分として、SrO、BaO、MnO、TiO2、B2O3、Li2O、K2Oなどを挙げることができる。本発明においては、これらのその他成分の合計含有量を極力少なくすることにより、目標とするパウダーの品質を保持することができる。その他成分の合計含有量は20質量%以下とすると好ましい。その他成分の合計含有量は15質量%以下とするとより好ましい。10質量%以下とするとさらに好ましい。 In the present invention, it may be necessary to further contain other components in order to reduce the SiO 2 content after suppressing the content of components other than SiO 2 within a predetermined range. Further, it contains other components as inevitable impurities from the raw materials. Examples of other components include SrO, BaO, MnO, TiO 2 , B 2 O 3 , Li 2 O, and K 2 O. In the present invention, the targeted powder quality can be maintained by reducing the total content of these other components as much as possible. The total content of other components is preferably 20% by mass or less. The total content of other components is more preferably 15% by mass or less. More preferably, it is 10 mass% or less.
その他成分のうち、SrOについては炭酸塩であるSrCO3を原料としてパウダーに添加されることがある。パウダー中に炭酸塩を含有すると、鋳型内で酸化物と二酸化炭素とに分解し、発生した二酸化炭素が未溶融パウダーを攪拌し、パウダー中のCの燃焼が促進されてパウダーの溶融特性が変化する可能性がある。SrO含有量を2.5質量%以下に制限することにより、このような現象の発生を抑えることができる。 Of the other components, SrO may be added to the powder using SrCO 3 as a raw material. When carbonate is contained in the powder, it decomposes into oxide and carbon dioxide in the mold, and the generated carbon dioxide stirs the unmelted powder, which promotes the combustion of C in the powder and changes the melting characteristics of the powder. there's a possibility that. By restricting the SrO content to 2.5% by mass or less, occurrence of such a phenomenon can be suppressed.
本発明の連続鋳造用パウダーは、SiO2含有量を35質量%以下、さらに好ましい30質量%以下としつつ、1300℃での粘度を6poise以上、好ましくは8poise以上、さらに好ましくは10poise以上、より好ましくは12poise以上とすることができる。同時にパウダーの凝固温度を1260℃以下、好ましくは1160℃以下、さらに好ましくは1120℃以下とすることができる。パウダーの1300℃での粘度をより高い粘度とするためには、まずSiO2含有量を目標とする上限値の近傍の値とする。CaO含有量は低い方が高い粘度を実現することができるが、SiO2含有量を減らすために含有する他の成分として欠かすことはできず、T.CaO含有量を30質量%前後とすると好ましい。SiO2含有量を減らしつつ粘度を高い値に保持するために、Al2O3含有量は好ましい範囲でできるだけ高い値とする。Na2O含有量は好ましい範囲内で含有量を減らすほど粘度を高くすることができる。高粘度化と凝固温度の低下を合わせて実現する場合には、Na2O含有量を下げすぎず、6%前後とすると好ましい。F含有量についても好ましい範囲内において含有量を低くするほど高粘度を実現することができる。さらにZrO2を含有し、含有量を好ましい範囲内で増大するほど粘度を高くすることができる。Zr含有量を3%以下に抑えることにより、粘度を高くしつつ凝固温度を1120℃以下に保持することが可能となる。 The continuous casting powder of the present invention has a SiO 2 content of 35% by mass or less, more preferably 30% by mass or less, and a viscosity at 1300 ° C. of 6 poise or more, preferably 8 poise or more, more preferably 10 poise or more, more preferably Can be 12 poise or more. At the same time, the solidification temperature of the powder can be 1260 ° C. or lower, preferably 1160 ° C. or lower, more preferably 1120 ° C. or lower. In order to make the viscosity at 1300 ° C. of the powder higher, first, the SiO 2 content is set to a value near the target upper limit. The lower the CaO content, the higher the viscosity can be realized. However, it is indispensable as another component contained in order to reduce the SiO 2 content. The CaO content is preferably about 30% by mass. In order to maintain the viscosity at a high value while reducing the SiO 2 content, the Al 2 O 3 content is set as high as possible within a preferable range. The Na 2 O content can be increased as the content decreases within a preferred range. In the case where the increase in viscosity and the decrease in the solidification temperature are realized together, it is preferable that the Na 2 O content is not reduced too much and is set to about 6%. As for the F content, the higher the viscosity is, the lower the content is within the preferable range. Furthermore, it contains ZrO 2, and the viscosity can be increased as the content is increased within a preferable range. By suppressing the Zr content to 3% or less, it is possible to maintain the solidification temperature at 1120 ° C. or less while increasing the viscosity.
即ち、本発明の成分範囲内において1300℃での粘度を6poise以上とすることができ、さらに上述の指針に従って各成分の含有量を調整することにより、1300℃での粘度をさらに高めることができる。SiO2含有量を30%程度とし、Al2O3含有量を20%前後、T.CaO含有量を30%弱、Na2O含有量を6%程度、F含有量を4%強、ZrO2含有量を3%程度とすることにより、低SiO2含有量にもかかわらず、1300℃での粘度を12poise程度の高い値とし、凝固温度を1100℃程度の良好な温度範囲とすることができる。SiO2含有量が低いので溶鋼と溶融パウダーとの反応を抑えることができ、パウダー溶融後のパウダーの特性変化を最小限に抑え、パウダー巻き込みの少ない鋳造を可能とする。さらに凝固温度が低いとともに、パウダーフィルム中へのゲーレナイト結晶の生成を防止するので、パウダーフィルムを通じての鋳片の抜熱挙動を安定化させることができる。 That is, the viscosity at 1300 ° C. can be 6 poise or more within the component range of the present invention, and the viscosity at 1300 ° C. can be further increased by adjusting the content of each component according to the above guidelines. . The SiO 2 content is about 30%, the Al 2 O 3 content is about 20%. By setting the CaO content to less than 30%, the Na 2 O content to about 6%, the F content to over 4%, and the ZrO 2 content to about 3%, the low SiO 2 content is 1300. The viscosity at ° C. can be set to a high value of about 12 poise, and the solidification temperature can be set to a favorable temperature range of about 1100 ° C. Since the SiO 2 content is low, the reaction between the molten steel and the molten powder can be suppressed, the characteristic change of the powder after powder melting is minimized, and casting with less powder entrainment is possible. Furthermore, since the solidification temperature is low and the formation of gehlenite crystals in the powder film is prevented, the heat removal behavior of the slab through the powder film can be stabilized.
本発明において、パウダーの粘度の測定方法として、回転円筒法を用いると好ましい。測定対象の連続鋳造用パウダーをルツボに装入し1400℃で完全に溶融させた後に縦型環状炉(エレマ炉)に入れ、E形粘度計のローターを溶融パウダー中に浸漬し、1300℃で30分間安定させた後、ローターを回転させ粘性抵抗によるトルクを測定し、粘度を求める。なおE形粘度計は事前に標準粘度計にて較正しておく。 In the present invention, the rotating cylinder method is preferably used as a method for measuring the viscosity of the powder. The continuous casting powder to be measured is charged into a crucible and completely melted at 1400 ° C., then placed in a vertical annular furnace (Elema furnace), and the rotor of the E-type viscometer is immersed in the molten powder at 1300 ° C. After stabilizing for 30 minutes, the rotor is rotated and the torque due to viscous resistance is measured to determine the viscosity. The E-type viscometer is calibrated with a standard viscometer in advance.
パウダーの凝固温度の測定方法としては、前述の粘度測定用縦型環状炉において、1300℃の粘度を測定後、炉の温度を徐々に下げながら粘度を連続測定する。このとき粘度は、温度降下に従って漸次大きくなっていく。この粘度が急激に大きくなる温度を凝固温度とする。 As a method for measuring the solidification temperature of the powder, in the above-described vertical annular furnace for measuring viscosity, after measuring the viscosity at 1300 ° C., the viscosity is continuously measured while gradually decreasing the temperature of the furnace. At this time, the viscosity gradually increases as the temperature drops. The temperature at which this viscosity rapidly increases is defined as the solidification temperature.
転炉にて溶製した溶鋼300tonを、RHにて所定の成分濃度に調整した極低炭素鋼の溶鋼を、タンディッシュ、浸漬ノズルを介して垂直曲げ型の連続鋳造機で、厚み240mm、幅1600mmの鋳片に鋳造した。溶鋼成分範囲を表1に示す。 300ton of molten steel melted in a converter, adjusted to a specified component concentration with RH, is an ultra-low carbon steel molten steel with a vertical bending type continuous casting machine through a tundish and immersion nozzle. Cast into a 1600 mm slab. The molten steel component range is shown in Table 1.
表2に示す成分・特性を有する連続鋳造用パウダーを準備し、連続鋳造において鋳型内に添加した。鋳造速度は1.8m/min程度とした。連続鋳造用パウダーの1300℃における粘度、凝固温度については、前述の方法を用いて測定を行った。 Powders for continuous casting having the components and characteristics shown in Table 2 were prepared and added into the mold in continuous casting. The casting speed was about 1.8 m / min. The viscosity at 1300 ° C. and the solidification temperature of the powder for continuous casting were measured using the methods described above.
鋳片へのパウダー巻き込み状況については、鋳片を冷延した後のコイル表面欠陥発生率を比較することにより評価し、比較例No.6の発生指数を1.0として標準化した。また鋳型伝熱特性については、鋳型内メニスカス部から40〜400mm下方に埋め込んだ熱電対による鋳型温度測定を行い、BO予知信号の発生頻度により評価した。 About the powder entrainment situation to a slab, it evaluated by comparing the coil surface defect incidence after cold-rolling a slab, and comparative example No. The generation index of 6 was standardized as 1.0. The mold heat transfer characteristics were evaluated by measuring the mold temperature using a thermocouple embedded 40 to 400 mm below the meniscus portion in the mold and generating the BO prediction signal.
表2の本発明例No.1は本発明の好ましいパウダー成分系の条件を全て満たしており、良好な結果を得ることができた。本発明例No.2は請求項1の範囲内であり、良好な結果を得ることができたが、SrO含有量が好適範囲から外れ、溶融スラグ肥大化が見られるとともに、凝固温度が好適範囲よりは高めであり、BO予知発生頻度の上昇が若干見られた。本発明例No.3は請求項1の範囲内であり、良好な結果を得ることができたが、凝固温度が好適範囲よりは高めであり、BO予知発生頻度の上昇が若干見られた。 Invention Example No. 2 in Table 2 No. 1 satisfied all the conditions of the preferred powder component system of the present invention, and good results could be obtained. Invention Example No. 2 is within the scope of claim 1 and good results could be obtained, but the SrO content deviated from the preferred range, the molten slag was enlarged, and the solidification temperature was higher than the preferred range. Some increase in the frequency of BO prediction occurred. Invention Example No. 3 was within the scope of claim 1 and good results could be obtained, but the coagulation temperature was higher than the preferred range, and a slight increase in the BO prediction occurrence frequency was observed.
比較例No.4はMgO含有量が本発明範囲を外れ、パウダーフィルム中にゲーレナイトが発生しており、BO予知発生頻度の上昇が顕著になった。比較例No.5はCaO/SiO2が本発明範囲を上限に外れ、パウダーフィルム中にゲーレナイトが発生しており、BO予知発生頻度増大が顕著になった。 Comparative Example No. In No. 4, the MgO content deviated from the scope of the present invention, gehlenite was generated in the powder film, and the increase in the BO prediction occurrence frequency became remarkable. Comparative Example No. In No. 5, CaO / SiO 2 deviated from the upper limit of the range of the present invention, and gehlenite was generated in the powder film, and the increase in the BO prediction occurrence frequency became remarkable.
比較例No.6はSiO2含有量が本発明範囲を上限に外れており、鋳造中にSiO2含有量が40.0%前後まで下がり、Al2O3、TiO2含有量が増大した。鋳型内から溶融パウダーを採取し、1300℃での粘度と凝固温度を測定したところ粘度は8poise、凝固温度は1100℃まで下がっていた。凝固温度の低下によって鋳造伝熱特性は良好であったが、パウダー巻き込みによる表面欠陥発生指数が1.0と不良であった。比較例No.7も同様であった。 Comparative Example No. In No. 6, the SiO 2 content deviated from the upper limit of the range of the present invention. During casting, the SiO 2 content dropped to around 40.0%, and the Al 2 O 3 and TiO 2 contents increased. The molten powder was sampled from the mold and the viscosity at 1300 ° C. and the solidification temperature were measured. The viscosity was 8 poise and the solidification temperature was reduced to 1100 ° C. Although the heat transfer characteristics of the casting were good due to the decrease in the solidification temperature, the surface defect occurrence index due to the entrainment of powder was poor at 1.0. Comparative Example No. 7 was the same.
比較例No.8は、もともと粘度が低くさらにSiO2濃度が上限外れであるため、表面欠陥発生指数が不良であった。 Comparative Example No. No. 8 had a low surface defect index because the viscosity was originally low and the SiO 2 concentration was outside the upper limit.
Claims (4)
ただしT.CaOは、パウダー中のCaがすべてCaOであるとして算出したCaO含有量である。 In terms of mass%, SiO 2 : 5.0 to 35.0%, Al 2 O 3 : 5.0 to 35.0%, T.I. CaO: 40.0% or less, Na 2 O: 3.0 to 15.0%, F: 2.0 to 10.0%, MgO is regulated to 1.5% or less, and other component contents Is 20% or less. A powder for continuous casting, wherein CaO / SiO 2 is 0.15 to 1.05, the viscosity at 1300 ° C. is 10 to 20 poise, and the solidification temperature is 1260 ° C. or less.
However, T.W. CaO is the CaO content calculated assuming that all Ca in the powder is CaO.
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