JP5148385B2 - Mold powder for continuous casting of steel and continuous casting method - Google Patents
Mold powder for continuous casting of steel and continuous casting method Download PDFInfo
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- JP5148385B2 JP5148385B2 JP2008167483A JP2008167483A JP5148385B2 JP 5148385 B2 JP5148385 B2 JP 5148385B2 JP 2008167483 A JP2008167483 A JP 2008167483A JP 2008167483 A JP2008167483 A JP 2008167483A JP 5148385 B2 JP5148385 B2 JP 5148385B2
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- 239000000843 powder Substances 0.000 title claims description 143
- 238000009749 continuous casting Methods 0.000 title claims description 71
- 229910000831 Steel Inorganic materials 0.000 title claims description 52
- 239000010959 steel Substances 0.000 title claims description 52
- 238000000034 method Methods 0.000 title claims description 9
- 239000013078 crystal Substances 0.000 claims description 71
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 25
- 229910052799 carbon Inorganic materials 0.000 claims description 21
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 18
- 238000005266 casting Methods 0.000 claims description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 15
- 238000001816 cooling Methods 0.000 claims description 15
- 238000002844 melting Methods 0.000 claims description 14
- 230000008018 melting Effects 0.000 claims description 14
- 229910001209 Low-carbon steel Inorganic materials 0.000 claims description 11
- 229910052731 fluorine Inorganic materials 0.000 claims description 7
- 238000002425 crystallisation Methods 0.000 claims description 6
- 230000008025 crystallization Effects 0.000 claims description 6
- 229910000954 Medium-carbon steel Inorganic materials 0.000 claims description 5
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 5
- 239000010436 fluorite Substances 0.000 claims description 5
- 229910052839 forsterite Inorganic materials 0.000 claims description 4
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 claims description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 33
- 239000000203 mixture Substances 0.000 description 17
- 239000002893 slag Substances 0.000 description 14
- 239000011734 sodium Substances 0.000 description 13
- 229910001720 Åkermanite Inorganic materials 0.000 description 11
- 229910018068 Li 2 O Inorganic materials 0.000 description 10
- 239000002994 raw material Substances 0.000 description 10
- 238000007711 solidification Methods 0.000 description 10
- 230000008023 solidification Effects 0.000 description 10
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 229910004261 CaF 2 Inorganic materials 0.000 description 7
- 239000008187 granular material Substances 0.000 description 6
- 239000000377 silicon dioxide Substances 0.000 description 6
- 239000006104 solid solution Substances 0.000 description 6
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 5
- 229910001719 melilite Inorganic materials 0.000 description 5
- 229910010413 TiO 2 Inorganic materials 0.000 description 4
- 235000012241 calcium silicate Nutrition 0.000 description 4
- 229910052918 calcium silicate Inorganic materials 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 230000037303 wrinkles Effects 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 3
- 239000011575 calcium Substances 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 235000010755 mineral Nutrition 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000005909 Kieselgur Substances 0.000 description 2
- FUJCRWPEOMXPAD-UHFFFAOYSA-N Li2O Inorganic materials [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 description 2
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000000378 calcium silicate Substances 0.000 description 2
- JHLNERQLKQQLRZ-UHFFFAOYSA-N calcium silicate Chemical compound [Ca+2].[Ca+2].[O-][Si]([O-])([O-])[O-] JHLNERQLKQQLRZ-UHFFFAOYSA-N 0.000 description 2
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 description 2
- 150000004673 fluoride salts Chemical class 0.000 description 2
- 150000002222 fluorine compounds Chemical class 0.000 description 2
- 229910001678 gehlenite Inorganic materials 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 230000012447 hatching Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- 238000005461 lubrication Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 239000010456 wollastonite Substances 0.000 description 2
- 229910052882 wollastonite Inorganic materials 0.000 description 2
- FCRMJSYZVAIBRC-UHFFFAOYSA-N 1,2,4,5-tetraoxane-3,6-dione Chemical compound O=C1OOC(=O)OO1 FCRMJSYZVAIBRC-UHFFFAOYSA-N 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- -1 Li 2 O Chemical class 0.000 description 1
- GEIAQOFPUVMAGM-UHFFFAOYSA-N ZrO Inorganic materials [Zr]=O GEIAQOFPUVMAGM-UHFFFAOYSA-N 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 229910001610 cryolite Inorganic materials 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 229910001721 mellite Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000011775 sodium fluoride Substances 0.000 description 1
- 235000013024 sodium fluoride Nutrition 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229910052861 titanite Inorganic materials 0.000 description 1
- 238000004017 vitrification Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
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- Continuous Casting (AREA)
Description
本発明は、鋼の連続鋳造において、モールド内に添加され使用される鋼の連続鋳造用モールドパウダー及び該モールドパウダーを使用する連続鋳造方法に関する。 The present invention relates to a mold powder for continuous casting of steel used in a mold in continuous casting of steel and a continuous casting method using the mold powder.
鋼の連続鋳造において、モールドパウダーはモールド内に投入され、溶鋼からの受熱により滓化してモールドと凝固シェル間に流入して消費される一連の過程において、（１）モールド内の溶鋼表面の酸化防止；（２）モールド内の溶鋼表面の保温；（３）鋼中より浮上する非鉄介在物の除去；（４）モールドと凝固シェルの潤滑；（５）凝固シェルとモールド間の抜熱制御等の役割を果たす。 In continuous casting of steel, mold powder is put into the mold, hatched by heat received from the molten steel, and flows between the mold and the solidified shell and consumed (1) oxidation of the molten steel surface in the mold Prevention; (2) heat retention of the molten steel surface in the mold; (3) removal of non-ferrous inclusions floating from the steel; (4) lubrication of the mold and the solidified shell; (5) heat removal control between the solidified shell and the mold. To play a role.
モールドパウダーは、一般的にＳｉＯ２、ＣａＯを母材とし、Ａｌ２Ｏ３、ＭｇＯ、Ｎａ２Ｏ、Ｌｉ２Ｏ、Ｆ、ＢａＯ、ＳｒＯ、ＭｎＯ、Ｂ２Ｏ３及びＣ等の成分によって構成されており、その組成は、例えばＳｉＯ２：２０〜４５質量％、ＣａＯ：２０〜４５質量％、Ａｌ２Ｏ３：０．５〜１０質量％、ＭｇＯ：０．１〜８質量％、Ｎａ２Ｏ：１〜２０質量％、Ｆ：２〜１０質量％、Ｃ：１０質量％以下を有するものである。モールドパウダーを構成する主原料としては、ポルトランドセメント、合成珪酸カルシウム、ウォラストナイト、高炉スラグ、リンスラグ、ダイカルシウムシリケート等が用いられる。また、塩基度（ＣａＯ／ＳｉＯ２質量比）や粉体特性を調整するために、珪石、珪藻土、ガラス粉のようなシリカ原料が使用される。更に、軟化点、粘度及び結晶化温度を調整する役割を果たすフラックス源として、蛍石、弗化ナトリウム、弗化リチウム、氷晶石、弗化マグネシウム等の弗化物、炭酸ナトリウム、炭酸リチウム、炭酸バリウム等の炭酸塩が添加されている。また、溶融速度を調整する目的で、カーボンブラック、コークス粉、黒鉛等の炭素質原料が添加されている。更に、必要に応じて、Ｌｉ２Ｏ、Ｂ２Ｏ３、ＢａＯ、ＳｒＯ、ＭｎＯ、ＴｉＯ２、ＺｒＯ２等の金属酸化物を添加することもできる。また、モールドパウダーの形状は、粉末並びに押出顆粒、中空顆粒及び撹拌造粒顆粒等がある。なお、モールドパウダーの物性値は、１３００℃の粘度が０．１〜６ｐｏｉｓｅ、凝固温度が９５０〜１２５０℃の範囲内に設定されている。 Mold powder is generally composed of SiO 2 , CaO as a base material and composed of components such as Al 2 O 3 , MgO, Na 2 O, Li 2 O, F, BaO, SrO, MnO, B 2 O 3 and C. The composition is, for example, SiO 2 : 20 to 45% by mass, CaO: 20 to 45% by mass, Al 2 O 3 : 0.5 to 10% by mass, MgO: 0.1 to 8% by mass, Na 2 O: 1 to 20% by mass, F: 2 to 10% by mass, and C: 10% by mass or less. Portland cement, synthetic calcium silicate, wollastonite, blast furnace slag, phosphorus slag, dicalcium silicate and the like are used as the main raw material constituting the mold powder. Further, in order to adjust the basicity (CaO / SiO 2 mass ratio) and powder characteristics, silica, diatomaceous earth, silica raw materials, such as glass powder is used. Furthermore, as a flux source that plays a role in adjusting the softening point, viscosity and crystallization temperature, fluorides such as fluorite, sodium fluoride, lithium fluoride, cryolite, magnesium fluoride, sodium carbonate, lithium carbonate, carbonic acid Carbonate such as barium is added. Further, carbonaceous raw materials such as carbon black, coke powder, and graphite are added for the purpose of adjusting the melting rate. Furthermore, metal oxides such as Li 2 O, B 2 O 3 , BaO, SrO, MnO, TiO 2 and ZrO 2 can be added as necessary. The shape of the mold powder includes powder, extruded granule, hollow granule, and stirred granulated granule. The physical properties of the mold powder are set such that the viscosity at 1300 ° C. is 0.1 to 6 poise and the solidification temperature is 950 to 1250 ° C.
更に、最近では、鋼の生産性を向上するため鋳造速度の高速化が指向されている。しかし、高速鋳造を指向すれば、凝固シェル厚みは薄くなり、ブレークアウトなどの操業トラブルが発生する。また、熱流速の増大により、鋳片の表面割れが発生し易くなり、割れ感受性の低い低炭素鋼や極低炭素鋼にも表面割れが発生し易くなる。一方、高速鋳造を指向すると、２次冷却帯で凝固シェルに付着したパウダーフィルムが影響してくるという新たな課題も生ずる。２次冷却域での滞在時間が短縮されることでパウダーフィルムの剥離が完了せず、付着した状態で連鋳機を通過し、未剥離のパウダーフィルムが２次冷却帯での凝固シェルの冷却能を低下させるだけでなく、未剥離のパウダーフィルムが圧延工程での欠陥に繋がることも判明している。 Furthermore, recently, in order to improve the productivity of steel, the casting speed has been increased. However, if high speed casting is aimed at, the thickness of the solidified shell will be reduced, causing operational troubles such as breakout. Further, due to the increase in the heat flow rate, surface cracks of the slab are likely to occur, and surface cracks are also likely to occur in low carbon steel and extremely low carbon steel having low crack sensitivity. On the other hand, when oriented to high-speed casting, there is a new problem that the powder film attached to the solidified shell in the secondary cooling zone is affected. The time spent in the secondary cooling zone is shortened so that the peeling of the powder film is not completed, and the powder film passes through the continuous casting machine in an attached state, and the unseparated powder film cools the solidified shell in the secondary cooling zone. In addition to reducing performance, it has also been found that unpeeled powder film leads to defects in the rolling process.
このような状況下で使用される鋼の連続鋳造用モールドパウダーとして、例えば、特許文献１には、ＣａＯ、ＳｉＯ２及びＭｇＯを主成分とする鋼の連続鋳造用モールドパウダーであって、溶融凝固時の主結晶がＣａＭｇＳｉ２Ｏ６であることを特徴とする連続鋳造用モールドパウダー（請求項１）；ＣａＯ、ＳｉＯ２及びＭｇＯを主成分とする鋼の連続鋳造用モールドパウダーであって、ＣａＯ／ＳｉＯ２重量比が０．３５〜０．５５に、また、（ＣａＯ＋ＭｇＯ）／ＳｉＯ２重量比が０．７５〜０．９５に調整されてなることを特徴とする連続鋳造用モールドパウダー（請求項２）；Ｆ含有量が２重量％未満であることを特徴とする、請求項１又は２に記載の連続鋳造用モールドパウダー（請求項３）が開示されている。 As a mold powder for continuous casting of steel used under such circumstances, for example, Patent Document 1 discloses a mold powder for continuous casting of steel mainly composed of CaO, SiO 2 and MgO, which is melt-solidified. A continuous casting mold powder characterized in that the main crystal at the time is CaMgSi 2 O 6 (Claim 1); a casting powder for continuous casting of steel mainly composed of CaO, SiO 2 and MgO, / the SiO 2 weight ratio is 0.35-0.55, also, (CaO + MgO) / SiO 2 weight ratio of mold powder for continuous casting characterized by comprising adjusted to 0.75 to 0.95 (billing Item 2): The mold powder for continuous casting according to claim 1 or 2, wherein the F content is less than 2% by weight (claim 3).
また、特許文献２には、溶融スラグの凝固時に、ゲーレナイト、アケルマナイト、あるいは両者の全率固溶体であるメリライトを、主な結晶組成として析出させることを特徴とする連続鋳造用パウダー（請求項１）；溶融スラグの化学組成としてＴｉＯ２を３〜１５質量％含有し、凝固時の結晶組成としてペロブスカイトを析出させることを特徴とする請求項１記載の連続鋳造用パウダー（請求項２）；溶融スラグの化学組成の内、総Ｃａ量をＣａＯ量に換算したＴ．ＣａＯ質量％とＳｉＯ２質量％の比、（％Ｔ．ＣａＯ）／（％ＳｉＯ２）の値が１．１〜１．６、フッ素（Ｆ）含有量が５質量％以下であり、凝固温度が１１００〜１２８０℃、１３００℃における粘度が０．３０〜１．８０Ｐａ・Ｓであることを特徴とする請求項１または２記載の連続鋳造用パウダー（請求項３）；アルカリ金属酸化物の合計が８質量％以下であることを特徴とする請求項１乃至３のいずれか記載の連続鋳造用パウダー（請求項４）；溶鋼中の［ｓｏｌ．Ａｌ］の含有量が０．００３〜０．１００質量％の鋼を連続鋳造する際に、請求項３または４記載の連続鋳造用パウダーを使用することを特徴とする連続鋳造用方法（請求項５）が開示されている。また、特許文献２の［００２６］段落の例Ｃ及びＧには、析出結晶としてアケルマナイトとカスピダインを有するモールドパウダーが開示されている。 Further, Patent Document 2 discloses continuous casting powder characterized by precipitating melilite, which is a solid solution of gelenite, akermanite, or both, at the time of solidification of molten slag as a main crystal composition (Claim 1). The powder for continuous casting according to claim 1, wherein the molten slag contains 3 to 15% by mass of TiO 2 as a chemical composition, and perovskite is precipitated as a crystal composition during solidification (claim 2); molten slag Among the chemical compositions, the total amount of Ca is converted to the amount of CaO. The ratio of CaO mass% to SiO 2 mass%, the value of (% T. CaO) / (% SiO 2 ) is 1.1 to 1.6, the fluorine (F) content is 5 mass% or less, and the solidification temperature 1 to 1280 ° C., viscosity at 1300 ° C. is 0.30 to 1.80 Pa · S, powder for continuous casting according to claim 1 or 2 (claim 3); total of alkali metal oxides The powder for continuous casting according to any one of Claims 1 to 3 (Claim 4); [sol. A continuous casting method comprising using the powder for continuous casting according to claim 3 or 4 when continuously casting steel having a content of Al] of 0.003 to 0.100 mass% (claim). 5) is disclosed. Further, Examples C and G in [0026] paragraph of Patent Document 2 disclose a mold powder having akermanite and caspidyne as precipitated crystals.
更に、特許文献３には、一旦溶融した後、凝固したパウダーフィルム中に析出する結晶の内、１種類の「主な結晶」の析出量が他種結晶の析出量の２倍以上であることを特徴とする連続鋳造用パウダー（請求項１）；一旦溶融した後、凝固したパウダーフィルム中に析出する結晶が３種類以下であることを特徴とする請求項１記載の連続鋳造用パウダー（請求項２）；一旦溶融した後、凝固したパウダーフィルム中に析出する結晶の内、少なくとも２種類の結晶組が全率固溶体を形成し実質的に１種類の「主な結晶」をなすことを特徴とする請求項１または２記載の連続鋳造用パウダー（請求項３）；「主な結晶」ではない結晶のうち、少なくとも１種類の結晶単体の融点が、「主な結晶」に比べて３００℃以上融点が高い高融点結晶であることを特徴とする請求項１乃至３のいずれか記載の連続鋳造用パウダー（請求項４）；高融点結晶がペロブスカイトであることを特徴とする請求項４記載の連続鋳造用パウダー（請求項５）；フッ素（Ｆ）含有量が４質量％以下であり、カスピダインは「主な結晶」ではないことを特徴とする請求項１乃至５のいずれか記載の連続鋳造用パウダー（請求項６）；「主な結晶」がアケルマナイト、ケーレナイト、ダイオプサイト、チタナイト、ＣａＯ・ＳｉＯ２組成のうちのいずれか１種であることを特徴とする請求項１乃至６のいずれか記載の連続鋳造用パウダー（請求項７）；凝固温度が１１００〜１２８０℃、１３００℃における粘度が１．８０Ｐａ・Ｓ以下であることを特徴とする請求項１乃至７のいずれか記載の連続鋳造用パウダー（請求項８）；水分含有量が０．５％未満であることを特徴とする請求項１乃至８のいずれか記載の連続鋳造用パウダー（請求項９）が開示されている。また、特許文献３の［００１７］段落の例Ｄ及びＨには、析出結晶としてアケルマナイトとカスピダインを有するモールドパウダーが開示されている。 Furthermore, in Patent Document 3, the amount of precipitation of one kind of “main crystals” out of crystals precipitated in a solidified powder film after being once melted is more than twice the amount of precipitation of other types of crystals. Powder for continuous casting characterized in that (Claim 1): The powder for continuous casting according to Claim 1 characterized in that there are no more than three types of crystals precipitated in the solidified powder film after melting once. Item 2): The feature is that at least two kinds of crystals formed in the solidified powder film after being melted once form a solid solution in the whole and form substantially one kind of “main crystals”. The powder for continuous casting according to claim 1 or 2 (claim 3); among the crystals that are not "main crystals", the melting point of at least one kind of crystals is 300 ° C compared to "main crystals". High melting point crystal with high melting point The powder for continuous casting according to any one of claims 1 to 3 (claim 4); the powder for continuous casting according to claim 4 wherein the high melting point crystal is perovskite (claim 5). The powder for continuous casting according to any one of claims 1 to 5, wherein the fluorine (F) content is 4% by mass or less, and caspidyne is not a "main crystal" (claim 6); The powder for continuous casting according to any one of claims 1 to 6, wherein "main crystals" are any one of akermanite, kalenite, diopsite, titanite, and CaO · SiO 2 composition. (7) The powder for continuous casting according to any one of (1) to (7), wherein the solidification temperature is 1100 to 1280 ° C. and the viscosity at 1300 ° C. is 1.80 Pa · S or less. 8.); continuous casting powder according to any one of claims 1 to 8 moisture content and less than 0.5% (claim 9) is disclosed. In addition, Examples D and H in paragraph [0017] of Patent Document 3 disclose a mold powder having akermanite and caspidyne as precipitated crystals.
また、特許文献４には、溶融した後に凝固する際に、その凝固組織中にアケルマナイトが主たる結晶として析出することを特徴とする鋼の連続鋳造用モールドパウダ（請求項１）；Ｔ．ＣａＯ含有率（質量％）とＳｉＯ２含有率（質量％）との比Ｔ．ＣａＯ／ＳｉＯ２が０．６〜１．４であることを特徴とする請求項１に記載の鋼の連続鋳造用モールドパウダ（請求項２）；ＣａＯ、ＳｉＯ２、ＭｇＯ、アルカリ金属酸化物およびＦを基本組成とする鋼の連続鋳造用モールドパウダであって、質量％で、Ｔ．ＣａＯおよびＳｉＯ２の合計含有率が５０〜９０％、ＭｇＯ含有率が９〜２５％、アルカリ金属酸化物の合計含有率が０．５〜１５％、Ｆ含有率が５％以下であり、さらにＣ、Ａｌ２Ｏ３、ＴｉＯ２、ＺｒＯ２、ＭｎＯおよびＢ２Ｏ３のうちの１種または２種以上を合計で０〜１０％含有し、鋳型内の溶鋼表面に添加され溶融した後に凝固する際に、その凝固したスラグフィルム中にアケルマナイトが主たる結晶として析出することを特徴とする鋼の連続鋳造用モールドパウダ（請求項３）が開示されている。 Patent Document 4 discloses a mold powder for continuous casting of steel, characterized in that, when solidified after melting, akermanite is precipitated as a main crystal in the solidified structure (Claim 1); Ratio of CaO content (mass%) and SiO 2 content (mass%) Continuous casting mold powder of the steel according to claim 1, CaO / SiO 2 is characterized in that it is a 0.6 to 1.4 (claim 2); CaO, SiO 2, MgO, alkali metal oxides and A mold powder for continuous casting of steel having a basic composition of F. The total content of CaO and SiO 2 is 50 to 90%, the MgO content is 9 to 25%, the total content of alkali metal oxides is 0.5 to 15%, the F content is 5% or less, C, Al 2 O 3 , TiO 2 , ZrO 2 , MnO and B 2 O 3 are contained in a total of 0 to 10%, added to the molten steel surface in the mold and solidified after melting. In this case, there is disclosed a mold powder for continuous casting of steel (claim 3) characterized in that akermanite precipitates as main crystals in the solidified slag film.
更に、特許文献５には、アケルマナイト（Akermanite：２ＣａＯ・ＭｇＯ・２ＳｉＯ２）、ゲーレナイト（Gehlenite：２ＣａＯ・Ａｌ２Ｏ３・ＳｉＯ２）、或いは、両者の全率固溶体であるメリライト（Melilite）を、溶融スラグ凝固時に主な結晶組成として析出し、ＣａＯ濃度とＳｉＯ２濃度との比（ＣａＯ／ＳｉＯ２）が１．０〜１．５、Ａｌ２Ｏ３とＭｇＯとの濃度合計が１５〜２７質量％、Ｎａ２ＯとＬｉ２ＯとＫ２Ｏとの濃度合計が１〜１３質量％、Ｆ濃度が１〜５質量％、ＦｅＯとＭｎＯとの濃度合計が３質量％以下、Ｓ濃度が０．５質量％以下、凝固温度が１１００℃〜１２６０℃、１３００℃における粘度が０．２〜１．３Ｐａ・ｓであることを特徴とする鋼の連続鋳造用モールドパウダー（請求項１）；更にＴｉＯ２を１〜８質量％含有することを特徴とする請求項１記載の鋼の連続鋳造用モールドパウダー（請求項２）；骨材として膨張性黒鉛を１〜５質量％添加したことを特徴とする請求項１又は２記載の鋼の連続鋳造用モールドパウダー（請求項３）が開示されている。 Furthermore, in Patent Document 5, Akermanite (2CaO · MgO · 2SiO 2 ), Gehlenite (2CaO · Al 2 O 3 · SiO 2 ), or Mellite (Melilite), which is a solid solution of both, It precipitates as the main crystal composition during solidification of the molten slag, the ratio of CaO concentration to SiO 2 concentration (CaO / SiO 2 ) is 1.0 to 1.5, and the total concentration of Al 2 O 3 and MgO is 15 to 27. % By mass, total concentration of Na 2 O, Li 2 O and K 2 O is 1 to 13% by mass, F concentration is 1 to 5% by mass, total concentration of FeO and MnO is 3% by mass or less, and S concentration is 0.5% by mass or less, solidification temperature is 1100 ° C. to 1260 ° C., and viscosity at 1300 ° C. is 0.2 to 1.3 Pa · s (Claim 1); In addition TiO Characterized in that the expandable graphite was added to 5 mass% as an aggregate; the claim 1 steel mold powder for continuous casting according (claim 2), characterized in that it contains 1-8 wt% A mold powder for continuous casting of steel according to claim 1 or claim 2 (claim 3) is disclosed.
また、特許文献６には、ＣａＯ％をＳｉＯ２％で除した比（ＣａＯ／ＳｉＯ２）が１．１〜１．５、Ｆの含有量が５％未満で、かつＦ−０．６１３×Ｎａ２Ｏ−１．２７×Ｌｉ２Ｏの式で表される、Ｆ、Ｎａ２ＯおよびＬｉ２Ｏの含有量が０〜１．８％、Ａｌ２Ｏ３の含有量が１０〜２５％で、かつＡｌ２Ｏ３とＭｇＯの合計の含有量が１５〜３０％、ＴｉＯ２の含有量が７％未満であって、一旦溶融した後に徐冷した場合に晶出もしくは析出する分子量が５００未満の主たる結晶が、ゲーレナイトまたはアケルマナイト、もしくはこれらの全率固溶体であるメリライトで、さらに２番目に晶出もしくは析出する結晶がカスピダインであり、凝固温度が１０５０℃〜１２２０℃であることを特徴とする鋼の連続鋳造用モールドパウダー（請求項１）；鋳型内の溶鋼表面で溶融したモールドパウダーが鋳型内壁と凝固シェルの間隙に流入する際に凝固したパウダーフィルム中に生成する主たる結晶が、ゲーレナイトまたはアケルマナイト、もしくはこれらの全率固溶体であるメリライトであり、さらに２番目の結晶がカスピダインであることを特徴とする請求項１に記載の連続鋳造用モールドパウダー（請求項２）が開示されている。即ち、特許文献６には、溶融、凝固後のスラグフィルムに、ＭｇＯ系結晶であるアケルマナイトと、Ｆ系結晶であるカスピダインが共存するモールドパウダーが開示されている。 In Patent Document 6, the ratio obtained by dividing the CaO% with SiO 2% (CaO / SiO 2 ) is 1.1 to 1.5, the content of F is less than 5%, and F-0.613 × The content of F, Na 2 O and Li 2 O represented by the formula of Na 2 O-1.27 × Li 2 O is 0 to 1.8%, and the content of Al 2 O 3 is 10 to 25%. And the total content of Al 2 O 3 and MgO is 15 to 30%, the content of TiO 2 is less than 7%, and the molecular weight of crystallization or precipitation when it is once melted and then slowly cooled is 500 The main crystal of less than is gelenite or akermanite, or melilite which is a solid solution of all of them, and the second crystallized or precipitated crystal is caspidyne, and the solidification temperature is 1050 ° C to 1220 ° C. Mold for continuous casting of steel (Claim 1); the main crystals produced in the powder film solidified when the mold powder melted on the surface of the molten steel in the mold flows into the gap between the inner wall of the mold and the solidified shell are gehlenite or akermanite, or all of them. The mold powder for continuous casting according to claim 1 (claim 2), characterized in that it is melilite which is a solid solution, and the second crystal is caspidyne. That is, Patent Document 6 discloses a mold powder in which an akermanite that is an MgO-based crystal and caspidyne that is an F-based crystal coexist in a molten and solidified slag film.
また、特許文献７には、ＣａＯ、ＳｉＯ２、Ｌｉ２Ｏおよびフッ素化合物を基本成分とするモールドパウダであって、さらに、Ｎａ２ＯおよびＫ２Ｏのうちの１種以上、ならびにＡｌ２Ｏ３を含有し、フッ素化合物を構成するＦの含有率が４〜２５質量％、Ｎａ２ＯおよびＫ２Ｏの合計の含有率が１．５質量％以下であり、かつ、これらＣａＯ、ＳｉＯ２、Ｌｉ２Ｏ、Ｆ、Ｎａ２Ｏ、Ｋ２ＯおよびＡｌ２Ｏ３の含有率で表される、下記（イ）式、（ロ）式および（ハ）式によって規定される指標ａが０．４７〜０．７、指標ｂが０〜０．４、および指標ｃが０〜０．６であることを特徴とする連続鋳造用モールドパウダ：
ａ＝（％ＣａＯ）ｈ／｛（％ＣａＯ）ｈ＋（％ＳｉＯ２）ｈ＋（％Ａｌ２Ｏ３）ｈ｝（イ）
ｂ＝（％Ａｌ２Ｏ３）ｈ／｛（％ＣａＯ）ｈ＋（％ＳｉＯ２）ｈ＋（％Ａｌ２Ｏ３）ｈ｝（ロ）
ｃ＝（％ＣａＦ２）ｈ／｛（％ＣａＯ）ｈ＋（％ＳｉＯ２）ｈ＋（％ＣａＦ２）ｈ｝（ハ）
ここで、（％ＣａＯ）ｈ＝｛ＷＣａＯ−（％ＣａＦ２）ｈ×０．７１８｝ （ニ）
（％ＣａＦ２）ｈ＝（ＷＦ−ＷＬｉ２Ｏ×１．２７−ＷＮａ２Ｏ×０．６１３
−ＷＫ２Ｏ×０．４０４）×２．０５ （ホ）
（％ＳｉＯ２）ｈ＝ＷＳｉＯ２および（％Ａｌ２Ｏ３）ｈ＝ＷＡｌ２Ｏ３であり、また、ＷＣａＯ、ＷＳｉＯ２、ＷＬｉ２Ｏ、ＷＮａ２ＯおよびＷＫ２Ｏはモールドパウダ中に分析されるＣａ、Ｓｉ、Ａｌ、Ｌｉ、Ｎａ、Ｋが全てそれらの酸化物であるとして換算した含有率（質量％）であり、ＷＦは、分析されるＦの含有率（質量％）である
が開示されている。また、特許文献７の［００２１］段落には、モールドパウダーがＣａＯを３０〜６０％、ＳｉＯ２を１０〜３０％、Ｌｉ２Ｏを１〜１５％、Ｆを４〜２５％含むことが記載されている。更に、特許文献７の［００２６］段落には、モールドパウダーがＡｌ２Ｏ３を１０％以下含むことが記載されている。また、特許文献７の［００３１］段落には、モールドパウダーが更にＭｇＯを１〜２０％含んでいてもよいことが記載されている。
Patent Document 7 discloses a mold powder containing CaO, SiO 2 , Li 2 O and a fluorine compound as basic components, and further includes at least one of Na 2 O and K 2 O, and Al 2 O. 3 and the fluorine content constituting the fluorine compound is 4 to 25% by mass, the total content of Na 2 O and K 2 O is 1.5% by mass or less, and these CaO and SiO 2 , Li 2 O, F, Na 2 O, K 2 O and Al 2 O 3 , and the index a defined by the following formulas (a), (b) and (c) is 0. .47 to 0.7, the index b is 0 to 0.4, and the index c is 0 to 0.6.
a = (% CaO) h / {(% CaO) h + (% SiO 2) h + (% Al 2 O 3) h} ( b)
b = (% Al 2 O 3 ) h / {(% CaO) h + (% SiO 2 ) h + (% Al 2 O 3 ) h } (b)
c = (% CaF 2) h / {(% CaO) h + (% SiO 2) h + (% CaF 2) h} ( c)
Here, (% CaO) h = { WCaO - (% CaF 2) h × 0.718} ( d)
(% CaF 2) h = ( W F -W Li2O × 1.27-W Na2O × 0.613
-W K2O × 0.404) × 2.05 (e)
(% SiO 2 ) h = W SiO2 and (% Al 2 O 3 ) h = W Al2O3 , and W CaO , W SiO2 , W Li2O , W Na2O and W K2O are Ca analyzed in the mold powder, Si, Al, Li, Na, and K are all expressed as their oxides (% by mass), and WF is the content of F to be analyzed (% by mass). . In addition, the [0021] Paragraph Patent Document 7, the mold powder is 30% to 60% of CaO, a SiO 2 10 to 30%, 1 to 15% of Li 2 O, wherein to contain F 4 to 25% Has been. Further, paragraph [0026] of Patent Document 7 describes that the mold powder contains 10% or less of Al 2 O 3 . Further, paragraph [0031] of Patent Document 7 describes that the mold powder may further contain 1 to 20% of MgO.
上記特許文献１ないし６に記載されたモールドパウダーは、融点し凝固した時に、ＭｇＯ系結晶であるアケルマナイト、Ａｌ２Ｏ３系結晶であるゲーレナイト或いは両者の全率固溶体であるメリライトを主な結晶組成として晶出するものである。しかしながら、高速鋳造においては、モールドパウダーの消費量が低下するために、これらのモールドパウダーでは、結晶が過度に発達し易く、低凝固温度のモールドパウダーであってもスラグフィルム中の結晶層が成長し、高速域での鋳造安定性が損なわれ、高速鋳造と安定的な鋳造の両立は困難となり、ブレークアウト等の操業トラブルに繋がる可能性がある。更に、特許文献７に記載されたモールドパウダーは、Ｌｉ２Ｏを必須の構成成分として含有し、カスピダイン（３ＣａＯ・２ＳｉＯ２・ＣａＦ２）のようなＦを含む結晶を晶出させるものであるが、Ｆを含む結晶を晶出させてもパウダーフィルムを鋳片から剥離させるために充分な歪エネルギーを発生させることができない。 The mold powders described in Patent Documents 1 to 6 have, as their melting point and solidification, main crystal compositions of akermanite, which is an MgO-based crystal, gelenite, which is an Al 2 O 3 -based crystal, or melilite, which is a total solid solution of both. It crystallizes as. However, in high-speed casting, the consumption of mold powder decreases, so in these mold powders, crystals tend to develop excessively, and the crystal layer in the slag film grows even with mold powder with a low solidification temperature. However, casting stability at high speeds is impaired, and it is difficult to achieve both high speed casting and stable casting, which may lead to operational troubles such as breakout. Furthermore, the mold powder described in Patent Document 7 contains Li 2 O as an essential constituent component, and crystallizes crystals containing F such as caspidine (3CaO · 2SiO 2 · CaF 2 ). Even if crystals containing F are crystallized, sufficient strain energy cannot be generated to peel the powder film from the slab.
従って、本発明の目的は、充分な凝固シェル厚みを確保するために結晶種を制御することによって抜熱速度を制御し、パウダーフィルムの剥離性を向上させて２次冷却帯での冷却能を向上させて高速鋳造をより安定化させることができ、かつ残留するパウダーフィルムがなく、下工程でのパウダーフィルムによる欠陥を低減することができる鋼の連続鋳造用モールドパウダー及び該モールドパウダーを使用する連続鋳造方法を提供することにある。 Therefore, the object of the present invention is to control the heat removal rate by controlling the crystal seeds in order to ensure a sufficient solidified shell thickness, improve the peelability of the powder film, and improve the cooling ability in the secondary cooling zone. The mold powder for continuous casting of steel, which can be improved to stabilize high-speed casting, and there is no residual powder film, and can reduce defects caused by the powder film in the lower process, and the mold powder are used It is to provide a continuous casting method.
即ち、本発明の鋼の連続鋳造用モールドパウダーは、ＣａＯ／ＳｉＯ２質量比が０．９〜１．２であり、ＭｇＯ含有量が１０〜２０質量％、Ｆ含有量が１０〜２０質量％である鋼の連続鋳造用モールドパウダーであって、鋼の連続鋳造用モールドパウダーを溶融・冷却後のパウダーフィルムにＭｇＯを含む結晶とＦを含む結晶の２相以上が生成することを特徴とする。 That is, the mold powder for continuous casting of steel of the present invention has a CaO / SiO 2 mass ratio of 0.9 to 1.2, an MgO content of 10 to 20% by mass, and an F content of 10 to 20% by mass. A mold powder for continuous casting of steel, wherein two or more phases of a crystal containing MgO and a crystal containing F are formed in a powder film after melting and cooling the mold powder for continuous casting of steel. .
更に、本発明の鋼の連続鋳造用モールドパウダーは、ＭｇＯを含む結晶が、モンチセライト、メルウィナイト及びフォルステライトからなる群から選択される１種または２種以上であり、Ｆを含む結晶が、カスピダインまたはフルオライトまたはそれら両者であることを特徴とする。 Furthermore, in the mold powder for continuous casting of steel according to the present invention, the MgO-containing crystal is one or more selected from the group consisting of monticerite, merwinite, and forsterite, and the F-containing crystal is caspidine. Or it is characterized by being a fluorite or both.
また、本発明の鋼の連続鋳造用モールドパウダーは、Ａｌ２Ｏ３の含有量がゼロまたは８質量％以下であることを特徴とする。 Moreover, the mold powder for continuous casting of steel of the present invention is characterized in that the content of Al 2 O 3 is zero or 8% by mass or less.
更に、本発明の鋼の連続鋳造用モールドパウダーは、Ｎａ２Ｏ含有量がゼロまたは５質量％以下であることを特徴とする。 Furthermore, the mold powder for continuous casting of steel of the present invention is characterized in that the Na 2 O content is zero or 5% by mass or less.
また、本発明の鋼の連続鋳造用モールドパウダーは、ＭｎＯ、ＢａＯ及びＢ２Ｏ３からなる群から選択される１種または２種以上の含有量がゼロまたは５質量％以下であることを特徴とする。 The mold powder for continuous casting of steel of the present invention is characterized in that the content of one or more selected from the group consisting of MnO, BaO and B 2 O 3 is zero or 5% by mass or less. And
更に、本発明の鋼の連続鋳造用モールドパウダーは、トータルカーボン（Ｔ．Ｃ）量が、ゼロまたは１０質量％以下であることを特徴とする。 Furthermore, the mold powder for continuous casting of steel of the present invention is characterized in that the total carbon (TC) amount is zero or 10% by mass or less.
また、本発明の鋼の連続鋳造用モールドパウダーは、１３００℃での粘度が４ｐｏｉｓｅ以下であることを特徴とする。 Moreover, the mold powder for continuous casting of steel of the present invention is characterized in that the viscosity at 1300 ° C. is 4 poise or less.
更に、本発明の鋼の連続鋳造用モールドパウダーは、結晶化温度が１１００℃以下であることを特徴とする。 Furthermore, the mold powder for continuous casting of steel of the present invention is characterized in that the crystallization temperature is 1100 ° C. or lower.
また、本発明の鋼の連続鋳造方法は、上記鋼の連続鋳造用モールドパウダーを用い、炭素含有量が１００ｐｐｍ未満の極低炭素鋼、炭素含有量が０．０１〜０．０８質量％の低炭素鋼または炭素含有量が０．１６〜０．２０質量％の中炭素鋼を１．４〜３．０ｍ／分の鋳造速度で鋳造することを特徴とする。 Moreover, the continuous casting method of the steel of the present invention uses the above-mentioned mold powder for continuous casting of steel, an extremely low carbon steel having a carbon content of less than 100 ppm, and a low carbon content of 0.01 to 0.08% by mass. Carbon steel or medium carbon steel having a carbon content of 0.16 to 0.20 mass% is cast at a casting speed of 1.4 to 3.0 m / min.
本発明によれば、安定した高速鋳造が可能な鋼の連続鋳造用モールドパウダー及び該モールドパウダーを使用した鋼の連続鋳造方法を提供することができる。 According to the present invention, it is possible to provide a mold powder for continuous casting of steel capable of stable high-speed casting and a method of continuous casting of steel using the mold powder.
本発明の鋼の連続鋳造用モールドパウダー（以下、モールドパウダーと記載する）は、ＣａＯ／ＳｉＯ２質量比（塩基度）が０．９〜１．２の範囲内にあり、好ましくは０．９〜１．１４、更に好ましくは０．９〜１．１の範囲内にある。ここで、塩基度が０．９未満若しくは１．２を超える場合には、パウダーフィルムと鋳片上に生成したスケールとの反応性が高まり、パウダーフィルムとスケールの混合物が形成され、パウダーフィルムの剥離性が悪化し、鋳片の冷却効率の低下やパウダーフィルムの残留による疵が発生するために好ましくない。 The mold powder for continuous casting of steel of the present invention (hereinafter referred to as mold powder) has a CaO / SiO 2 mass ratio (basicity) in the range of 0.9 to 1.2, preferably 0.9. ˜1.14, more preferably in the range of 0.9 to 1.1. Here, when the basicity is less than 0.9 or exceeds 1.2, the reactivity between the powder film and the scale formed on the slab increases, and a mixture of the powder film and the scale is formed, and the powder film is peeled off. This is not preferable because the properties deteriorate, and the cooling efficiency of the slab decreases and wrinkles due to the residual powder film occur.
本発明のモールドパウダーにおいて、ＭｇＯの含有量は、１０〜２０質量％、好ましくは１０〜１８質量％の範囲内である。また、本発明のモールドパウダーにおいて、Ｆの含有量は１０〜２０質量％、好ましくは１１〜２０質量％の範囲内である。 In the mold powder of the present invention, the content of MgO is 10 to 20% by mass, preferably 10 to 18% by mass. In the mold powder of the present invention, the F content is in the range of 10 to 20% by mass, preferably 11 to 20% by mass.
モールドパウダーの塩基度、ＭｇＯ含有量及びＦ含有量を上述の範囲内とすることにより、モールドパウダーを溶融し、冷却した後のパウダーフィルムにＭｇＯを含む結晶（以下、ＭｇＯ系結晶という）並びにＦを含む結晶（以下、Ｆ系結晶という）が生成する。この２種類の異なる結晶相がパウダーフィルム中に生成して体積変化を生じ、それによってパウダーフィルム中に歪としてエネルギーが残留し易くなり、冷却時、特に、２次冷却帯で水に接触した時に大きな歪エネルギーが発生してパウダーフィルムが鋳片から剥離する。 By making the basicity, MgO content, and F content of the mold powder within the above-mentioned ranges, the powder containing the MgO in the powder film after melting and cooling the mold powder (hereinafter referred to as MgO-based crystal) and F (Hereinafter referred to as “F-based crystal”). These two different crystal phases are formed in the powder film, causing a volume change, thereby making it easy for energy to remain as strain in the powder film, and when cooling, especially when it comes into contact with water in the secondary cooling zone Large strain energy is generated and the powder film is peeled off from the slab.
パウダーフィルム中にＭｇＯ系結晶とＦ系結晶を生成、共存させるためには、モールドパウダーのＭｇＯ含有量とＦ含有量を１０〜２０質量％の範囲内とする必要がある。ここで、ＭｇＯ含有量並びにＦ含有量が２０質量％を超えると、スラグベアーを生成するために好ましくない。また、ＭｇＯ含有量とＦ含有量が１０質量％未満であると、目的とする種類の結晶が生成しにくくなるために好ましくない。 In order to produce and coexist MgO-based crystals and F-based crystals in the powder film, the MgO content and F content of the mold powder need to be in the range of 10 to 20% by mass. Here, when the MgO content and the F content exceed 20% by mass, it is not preferable because slag bears are generated. Further, if the MgO content and the F content are less than 10% by mass, it is not preferable because it is difficult to produce the target type of crystals.
なお、前記ＭｇＯ系結晶としては、例えばモンチセライト［Monticellite：ＣａＭｇＳｉＯ４または（Ｃａ，Ｍｇ）Ｏ・ＭｇＯ・ＳｉＯ２］、メルウィナイト（Merwinite：３ＣａＯ・ＭｇＯ・２ＳｉＯ２）、フォルステライト（Forsterite：２ＭｇＯ・ＳｉＯ２）等を挙げることができる。また、Ｆ系結晶としては、例えばカスピダイン（Cuspidine：３ＣａＯ・２ＳｉＯ２・ＣａＦ２）、フルオライト（Fluorite：ＣａＦ２）等を挙げることができる。ここで、本発明のモールドパウダーにおいては、モールドパウダーを溶融し、冷却する際に形成されるパウダーフィルム中に、ＭｇＯ系結晶とＦ系結晶が共存していることが重要である。また、ＭｇＯ系結晶及びＦ系結晶以外の結晶が生成しても良いが、Ｘ線粉末回折などで同定される結晶相における主要鉱物相がＭｇＯ系結晶とＦ系結晶である。なお、ＭｇＯ系結晶とＦ系結晶の生成する温度は同一であっても、異なっていてもよい。 Examples of the MgO-based crystal include monticite [Monticellite: CaMgSiO 4 or (Ca, Mg) O · MgO · SiO 2 ], merwinite (Merwinite: 3CaO · MgO · 2SiO 2 ), forsterite (Forsterite: 2MgO · SiO 2 ). Examples of the F-based crystals include caspidine (Cuspidine: 3CaO · 2SiO 2 · CaF 2 ) and fluorite (Fluorite: CaF 2 ). Here, in the mold powder of the present invention, it is important that the MgO-based crystal and the F-based crystal coexist in the powder film formed when the mold powder is melted and cooled. Crystals other than MgO-based crystals and F-based crystals may be generated, but the main mineral phases in the crystal phase identified by X-ray powder diffraction are MgO-based crystals and F-based crystals. The temperatures at which the MgO-based crystal and the F-based crystal are generated may be the same or different.
また、本発明のモールドパウダーにおいて、Ａｌ２Ｏ３の含有量は、ゼロまたは８質量％以下、より好ましくは７質量％以下である。ここで、Ａｌ２Ｏ３の含有量が８質量％を超えると、モールドパウダーを溶融・冷却した後に生成される主要鉱物相がＭｇＯ系結晶及びＦ系結晶から他の鉱物相へ変化してパウダーフィルムの剥離性が低下するために好ましくない。 In the mold powder of the present invention, the content of Al 2 O 3 is zero or 8% by mass or less, more preferably 7% by mass or less. Here, if the content of Al 2 O 3 exceeds 8% by mass, the main mineral phase generated after melting and cooling the mold powder changes from MgO-based crystals and F-based crystals to other mineral phases, and the powder This is not preferable because the peelability of the film is lowered.
更に、本発明のモールドパウダーは、Ｎａ２Ｏを含有することができる。Ｎａ２Ｏの含有量は、ゼロまたは５質量％以下、好ましくは４質量％以下である。ここで、Ｎａ２Ｏの含有量が５質量％を超えると、モールドパウダーのガラス化が促進され、ＭｇＯ系結晶とＦ系結晶が生成する時にも歪エネルギーが発生しにくくなり、パウダーフィルムの剥離性が低下するために好ましくない。なお、本発明のモールドパウダーにおいては、パウダーフィルムの剥離性を充分に確保するために、Ｌｉ２Ｏを含まないことが肝要である。 Furthermore, the mold powder of the present invention can contain Na 2 O. The content of Na 2 O is zero or 5% by mass or less, preferably 4% by mass or less. Here, when the content of Na 2 O exceeds 5% by mass, vitrification of the mold powder is promoted, and strain energy is hardly generated even when MgO-based crystals and F-based crystals are formed, and the powder film is peeled off. This is not preferable because the properties are lowered. In the mold powder of the present invention, in order to ensure a sufficient peelability powder film, it is important to be free of Li 2 O.
更に、本発明のモールドパウダーは、ＭｎＯ、ＢａＯ、Ｂ２Ｏ３等の成分を含有していても良いが、これらの含有量は合計で５質量％以下、好ましくは４質量％以下である。これらの含有量が５質量％を超えると、パウダーフィルムの剥離性が低下するために好ましくない。 Furthermore, the mold powder of the present invention may contain components such as MnO, BaO, and B 2 O 3, but the total content thereof is 5% by mass or less, preferably 4% by mass or less. If the content exceeds 5% by mass, the peelability of the powder film is lowered, which is not preferable.
また、本発明のモールドパウダーのトータルカーボン（Ｔ．Ｃ）量は、ゼロまたは１０質量％以下、好ましくは８質量％以下の範囲内である。Ｔ．Ｃが１０質量％を超えると、滓化速度が著しく低下するために好ましくない。なお、カーボン成分は滓化速度調整材として作用する。 Further, the total carbon (TC) content of the mold powder of the present invention is zero or 10% by mass or less, preferably 8% by mass or less. T.A. When C exceeds 10% by mass, the hatching rate is remarkably lowered, which is not preferable. The carbon component acts as a hatching speed adjusting material.
更に、本発明のモールドパウダーにおいて、１３００℃での粘度は、４．０ｐｏｉｓｅ以下、好ましくは３．５ｐｏｉｓｅ以下であることが好ましい。１３００℃での粘度が４．０ｐｏｉｓｅを超えると、流入性の低下に加え、結晶の生成も増大して、流入性が低下して潤滑不足となり、拘束性ブレークアウトが発生する可能性が高くなるために好ましくない。 Furthermore, in the mold powder of the present invention, the viscosity at 1300 ° C. is 4.0 poise or less, preferably 3.5 poise or less. When the viscosity at 1300 ° C. exceeds 4.0 poise, in addition to the decrease in inflow properties, the generation of crystals also increases, the inflow properties decrease, the lubrication becomes insufficient, and the possibility of a constraining breakout increases. Therefore, it is not preferable.
また、本発明のモールドパウダーにおいて、結晶化温度は、１１００℃以下、好ましくは９００〜１０８５℃、より好ましくは９００〜１０５０℃の範囲内である。ここで、結晶化温度が９００℃未満では、鋳片が過度に強冷却され、割れが発生する可能性が高くなるために好ましくない。また、１１００℃を超えると、鋳片が緩冷却され、凝固シェル厚みが薄くなり、ブレークアウトが発生する可能性が高くなり、また、スラグベアーの生成や成長を促進するために好ましくない。 In the mold powder of the present invention, the crystallization temperature is 1100 ° C. or lower, preferably 900 to 1085 ° C., more preferably 900 to 1050 ° C. Here, if the crystallization temperature is less than 900 ° C., the slab is excessively strongly cooled, and the possibility of cracking increases, which is not preferable. On the other hand, when the temperature exceeds 1100 ° C., the slab is slowly cooled, the thickness of the solidified shell is reduced, the possibility of breakout is increased, and the generation and growth of slag bear are promoted.
本発明のモールドパウダーは、上記組成を有するものであれば、その原料配合は特に限定されるものではないが、例えばポルトランドセメント、合成珪酸カルシウム、ウォラストナイト、高炉スラグ、リンスラグ、ダイカルシウムシリケート等を主原料とし、珪石、珪藻土、ガラス粉等のシリカ原料、アルカリ金属またはアルカリ土類金属の酸化物、炭酸塩または弗化物等や、カーボンブラック、コークス粉、黒鉛等のカーボン原料を配合することができる。 The raw material composition of the mold powder of the present invention is not particularly limited as long as it has the above composition. For example, Portland cement, synthetic calcium silicate, wollastonite, blast furnace slag, phosphorus slag, dicalcium silicate, etc. The main raw material, silica raw materials such as silica, diatomaceous earth, glass powder, oxides of alkali metals or alkaline earth metals, carbonates or fluorides, and carbon raw materials such as carbon black, coke powder, and graphite Can do.
なお、カーボン原料を除く原料を配合して事前に溶解、水冷若しくは空冷して所定の粒度へ粉砕した後、必要に応じてカーボン原料を配合する、いわゆるプリメルトタイプのモールドパウダーとしても良い。 In addition, it is good also as what is called a premelt type mold powder which mix | blends the raw material except a carbon raw material, melt | dissolves in advance, water-cools or air-cools, grind | pulverizes to a predetermined particle size, and mix | blends a carbon raw material as needed.
また、本発明のモールドパウダーは、その形状を限定されるものではなく、例えば、粉末タイプや押出顆粒、中空スプレー顆粒、撹拌造粒顆粒等、目的に応じた形状にて使用することができる。 Moreover, the shape of the mold powder of the present invention is not limited, and for example, it can be used in a shape according to the purpose such as powder type, extruded granule, hollow spray granule, stirred granulated granule and the like.
本発明のモールドパウダーは、炭素含有量が１００ｐｐｍ未満の極低炭素鋼、炭素含有量が０．０１〜０．０８質量％の低炭素鋼及び炭素含有量が０．１６〜０．２０質量％の中炭素鋼の鋼種の連続鋳造に好ましく使用することができる。なお、炭素含有量が０．０８を超え０．１６質量％未満の割れ感受性の高い中炭素鋼に使用すると、表面割れが発生するために好ましくない。 The mold powder of the present invention is an extremely low carbon steel having a carbon content of less than 100 ppm, a low carbon steel having a carbon content of 0.01 to 0.08 mass%, and a carbon content of 0.16 to 0.20 mass%. It can be preferably used for continuous casting of steel types of medium carbon steel. In addition, when it uses for medium carbon steel with a carbon content exceeding 0.08 and less than 0.16 mass% with high crack sensitivity, since surface cracks generate | occur | produce, it is unpreferable.
本発明のモールドパウダーを使用する連続鋳造操作において、鋳造速度は１．４〜３．０ｍ／分、好ましくは１．６〜３．０ｍ／分、より好ましくは１．８〜３．０ｍ／分の範囲内である。鋳造速度が１．４ｍ／分未満であると、溶融スラグ層が５ｍｍ以下になり、安定した操業を確保することができないために好ましくない。なお、本発明のモールドパウダーをより好ましい状態で使用するためには、１．８〜３．０ｍ／分の範囲内の条件で使用することが好ましい。 In the continuous casting operation using the mold powder of the present invention, the casting speed is 1.4 to 3.0 m / min, preferably 1.6 to 3.0 m / min, more preferably 1.8 to 3.0 m / min. Is within the range. When the casting speed is less than 1.4 m / min, the molten slag layer is 5 mm or less, and it is not preferable because stable operation cannot be ensured. In addition, in order to use the mold powder of this invention in a more preferable state, it is preferable to use on the conditions within the range of 1.8-3.0 m / min.
以下に実施例を挙げて本発明のモールドパウダーを更に説明する。
実施例
表１に記載する化学組成を有するモールドパウダーについて、以下に記載する操作にて溶融、冷却後に生成される結晶について調査した結果を表１に記載する。
また、モールドパウダーをスラブ連鋳機にて使用した結果を表１に併記する。
The mold powder of the present invention will be further described below with reference to examples.
Examples Table 1 shows the results of investigations on crystals produced after melting and cooling in the operations described below for the mold powder having the chemical composition shown in Table 1.
Table 1 also shows the results of using mold powder in a slab continuous casting machine.
結晶調査は、１５０ｇのモールドパウダーを１３００℃で溶解、安定後、４℃／分の冷却速度で炉冷することにより、パウダーフィルムを得、得られたパウダーフィルムを粉砕してＸ線粉末回折することによって行われた。なお、生成結晶について、”＋”記号の数が多い程、結晶生成量が多いことを示す。
また、鋳造操作は、スラブ連鋳機にて、５〜５０ｈｅａｔ行ったものである。なお、鋼種の欄の「ＵＬＣ」は極低炭素鋼を、「ＬＣ」は低炭素鋼をそれぞれ示す。
また、使用結果において、操業性は使用中のベアーの生成状況、ＢＯ予知（熱電対）の安全性を示すもので、○は極めて安全、△はまずまず、×は不安定をそれぞれ表す。また、フィルム剥離性は、２次冷却帯位置にカメラを設置してフィルムの剥離状況を観察した結果であり、○は剥離良好、×は剥離悪いをそれぞれ表す。更に、鋳片品質は鋳片を観察して評価したものであり、○はノロカミ、割れなし、△はノロカミ、割れ少、×はノロカミ、割れ多いをそれぞれ表す。また、コイル品質はコイル中のモールドパウダー性欠陥による不良率を示すもので、○はリジェクト無し、×はリジェクト多数発生をそれぞれ示す。
In the crystal investigation, 150 g of mold powder is melted at 1300 ° C., stabilized, and then cooled in a furnace at a cooling rate of 4 ° C./min to obtain a powder film. The obtained powder film is crushed and X-ray powder diffracted Was done by. As for the generated crystals, the larger the number of “+” symbols, the larger the amount of crystals generated.
Moreover, casting operation is performed for 5-50 heat with a slab continuous casting machine. In the steel type column, “ULC” indicates ultra-low carbon steel, and “LC” indicates low-carbon steel.
In the results of use, operability indicates the generation status of bears in use and the safety of BO prediction (thermocouple), ◯ indicates extremely safe, Δ indicates reasonable, and × indicates instability. Further, the film peelability is a result of observing the peeling state of the film by installing a camera at the secondary cooling zone position, where ◯ represents good peeling and x represents bad peeling. Further, the quality of the slab was evaluated by observing the slab, where ◯ represents no wrinkles and no cracks, Δ represents no wrinkles and few cracks, and × represents no wrinkles and many cracks. The coil quality indicates a defect rate due to a mold powder defect in the coil, ◯ indicates no rejection, and X indicates the generation of many rejects.
本発明の鋼の連続鋳造用モールドパウダーは、炭素含有量が１００ｐｐｍ以下の極低炭素鋼、炭素含有量０．０１〜０．０８質量％の低炭素鋼または炭素含有量０．１６〜０．２０質量％の中炭素鋼を１．４〜３．０ｍ／分の鋳造速度で鋳造する際に好適に使用することができる。 The mold powder for continuous casting of steel of the present invention is an extremely low carbon steel having a carbon content of 100 ppm or less, a low carbon steel having a carbon content of 0.01 to 0.08 mass%, or a carbon content of 0.16 to 0.00. It can be suitably used when 20% by mass of medium carbon steel is cast at a casting speed of 1.4 to 3.0 m / min.
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