JP6439762B2 - Steel continuous casting method - Google Patents
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- JP6439762B2 JP6439762B2 JP2016157190A JP2016157190A JP6439762B2 JP 6439762 B2 JP6439762 B2 JP 6439762B2 JP 2016157190 A JP2016157190 A JP 2016157190A JP 2016157190 A JP2016157190 A JP 2016157190A JP 6439762 B2 JP6439762 B2 JP 6439762B2
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- 238000009749 continuous casting Methods 0.000 title claims description 67
- 229910000831 Steel Inorganic materials 0.000 title claims description 28
- 239000010959 steel Substances 0.000 title claims description 28
- 238000000034 method Methods 0.000 title claims description 16
- 239000010949 copper Substances 0.000 claims description 210
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 144
- 229910052802 copper Inorganic materials 0.000 claims description 144
- 239000000126 substance Substances 0.000 claims description 78
- 239000000463 material Substances 0.000 claims description 56
- 229910052751 metal Inorganic materials 0.000 claims description 53
- 239000002184 metal Substances 0.000 claims description 53
- 238000007747 plating Methods 0.000 claims description 38
- 229910052755 nonmetal Inorganic materials 0.000 claims description 36
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 35
- 230000005499 meniscus Effects 0.000 claims description 31
- 230000004907 flux Effects 0.000 claims description 28
- 239000011248 coating agent Substances 0.000 claims description 26
- 238000000576 coating method Methods 0.000 claims description 26
- 239000000498 cooling water Substances 0.000 claims description 20
- 230000007423 decrease Effects 0.000 claims description 16
- 238000009826 distribution Methods 0.000 claims description 10
- 238000005266 casting Methods 0.000 description 36
- 239000010410 layer Substances 0.000 description 32
- 230000000694 effects Effects 0.000 description 25
- 230000035882 stress Effects 0.000 description 25
- 238000005336 cracking Methods 0.000 description 18
- 238000007711 solidification Methods 0.000 description 17
- 230000008023 solidification Effects 0.000 description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- 230000009466 transformation Effects 0.000 description 10
- 238000001816 cooling Methods 0.000 description 9
- 238000009434 installation Methods 0.000 description 9
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 8
- 229910052742 iron Inorganic materials 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 239000011651 chromium Substances 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 229910052804 chromium Inorganic materials 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- 230000000737 periodic effect Effects 0.000 description 4
- 238000010583 slow cooling Methods 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 230000008646 thermal stress Effects 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910017709 Ni Co Inorganic materials 0.000 description 3
- 229910003267 Ni-Co Inorganic materials 0.000 description 3
- 229910003262 Ni‐Co Inorganic materials 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
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- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
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- 229910018605 Ni—Zn Inorganic materials 0.000 description 1
- 206010037660 Pyrexia Diseases 0.000 description 1
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
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- 230000007547 defect Effects 0.000 description 1
- 230000006355 external stress Effects 0.000 description 1
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910000623 nickel–chromium alloy Inorganic materials 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 150000002843 nonmetals Chemical class 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
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- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
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- 229910052703 rhodium Inorganic materials 0.000 description 1
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- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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- 239000002436 steel type Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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- Continuous Casting (AREA)
Description
本発明は、鋳型内での凝固シェルの不均一冷却に起因する鋳片表面割れを抑制して溶鋼を連続鋳造することのできる連続鋳造用鋳型、及び、この鋳型を使用した鋼の連続鋳造方法に関する。 The present invention relates to a continuous casting mold capable of continuously casting molten steel while suppressing slab surface cracking due to non-uniform cooling of the solidified shell in the mold, and a continuous casting method of steel using this mold. About.
鋼の連続鋳造では、鋳型内に注入された溶鋼は水冷式鋳型によって冷却され、鋳型との接触面で溶鋼が凝固して凝固層（「凝固シェル」という）が生成される。この凝固シェルを外殻とし、内部を未凝固層とする鋳片は、鋳型下流側に設置された水スプレーや気水スプレーによって冷却されながら鋳型下方に連続的に引き抜かれる。鋳片は、水スプレーや気水スプレーによる冷却によって中心部まで凝固し、その後、ガス切断機などによって切断されて、所定長さの鋳片が製造されている。 In continuous casting of steel, molten steel poured into a mold is cooled by a water-cooled mold, and the molten steel is solidified at a contact surface with the mold to generate a solidified layer (referred to as “solidified shell”). The slab having the solidified shell as an outer shell and the inside as an unsolidified layer is continuously drawn below the mold while being cooled by a water spray or an air / water spray installed on the downstream side of the mold. The slab is solidified to the center by cooling with water spray or air-water spray, and then cut by a gas cutter or the like to produce a slab of a predetermined length.
鋳型内における冷却が不均一になると、凝固シェルの厚みが鋳片の鋳造方向及び鋳型幅方向で不均一となる。凝固シェルには、凝固シェルの収縮や変形に起因する応力が作用し、凝固初期においては、この応力が凝固シェルの薄肉部に集中し、この応力によって凝固シェルの表面に割れが発生する。この割れは、その後の熱応力や連続鋳造機のロールによる曲げ応力及び矯正応力などの外力により拡大し、大きな表面割れとなる。凝固シェル厚みの不均一度が大きい場合には、鋳型内での縦割れとなり、この縦割れから溶鋼が流出するブレークアウトが発生する場合もある。鋳片に存在する割れは、次工程の圧延工程で表面欠陥となることから、鋳造後の鋳片の段階において、鋳片の表面を手入れして表面割れを除去することが必要となる。 If the cooling in the mold becomes non-uniform, the thickness of the solidified shell becomes non-uniform in the casting direction of the slab and in the mold width direction. A stress caused by the shrinkage or deformation of the solidified shell acts on the solidified shell, and in the initial stage of solidification, this stress is concentrated on the thin portion of the solidified shell, and the stress causes cracks on the surface of the solidified shell. This crack expands due to subsequent external stresses such as thermal stress, bending stress due to the roll of a continuous casting machine, and straightening stress, resulting in a large surface crack. When the non-uniformity of the solidified shell thickness is large, a vertical crack is generated in the mold, and a breakout in which the molten steel flows out from the vertical crack may occur. Since the cracks present in the slab become surface defects in the subsequent rolling process, it is necessary to care for the surface of the slab and remove the surface cracks at the stage of the cast slab after casting.
鋳型内の不均一凝固は、特に、炭素含有量が０．０８〜０．１７質量％の鋼（中炭素鋼という）で発生しやすい。炭素含有量が０．０８〜０．１７質量％の鋼では、凝固時に包晶反応が起こり、鋳型内の不均一凝固は、この包晶反応によるδ鉄（フェライト）からγ鉄（オーステナイト）への変態時の体積収縮による変態応力に起因すると考えられている。つまり、この変態応力に起因する歪みによって凝固シェルが変形し、この変形によって凝固シェルが鋳型内壁面から離れる。鋳型内壁面から離れた部位は鋳型による冷却が低下し、この鋳型内壁面から離れた部位（この鋳型内壁面から離れた部位を「デプレッション」という）の凝固シェル厚みが薄くなり、凝固シェル厚みが薄くなることで、この部分に上記応力が集中し、表面割れが発生すると考えられている。 Inhomogeneous solidification in the mold is likely to occur particularly in steel (referred to as medium carbon steel) having a carbon content of 0.08 to 0.17% by mass. In a steel having a carbon content of 0.08 to 0.17% by mass, a peritectic reaction occurs during solidification, and the non-uniform solidification in the mold is caused by the peritectic reaction from δ iron (ferrite) to γ iron (austenite). It is thought to be caused by transformation stress due to volume shrinkage during transformation. That is, the solidified shell is deformed by the strain caused by the transformation stress, and the solidified shell is separated from the inner wall surface of the mold by this deformation. Cooling by the mold is reduced at the part away from the inner wall surface of the mold, and the solidified shell thickness of the part away from the inner wall surface of the mold (the part away from the inner wall surface of the mold is referred to as “depression”) is reduced. It is considered that the above stress concentrates on this portion and the surface crack occurs due to the thinning.
特に、鋳片引き抜き速度を増加した場合には、凝固シェルから鋳型冷却水への平均熱流束が増加する（凝固シェルが急速冷却される）のみならず、熱流束の分布が不規則で且つ不均一になることから、鋳片表面割れの発生が増加傾向となる。具体的には、鋳片厚みが２００ｍｍ以上のスラブ連続鋳造機においては、鋳片引き抜き速度が１．５ｍ／ｍｉｎ以上になると表面割れが発生しやすくなる。 In particular, when the slab drawing speed is increased, the average heat flux from the solidified shell to the mold cooling water increases (the solidified shell is rapidly cooled), and the heat flux distribution is irregular and irregular. Since it becomes uniform, the occurrence of slab surface cracks tends to increase. Specifically, in a slab continuous casting machine having a slab thickness of 200 mm or more, surface cracks are likely to occur when the slab drawing speed is 1.5 m / min or more.
そこで、従来、上記の包晶反応を伴う、表面割れが発生しやすい鋼種の表面割れ（特に縦割れ）を抑制するために、種々の手段が提案されている。 Therefore, conventionally, various means have been proposed in order to suppress surface cracks (particularly longitudinal cracks) of the steel types that are likely to cause surface cracks that accompany the peritectic reaction.
例えば、特許文献１には、結晶化しやすい組成のモールドパウダーを使用し、モールドパウダー層の熱抵抗を増大させて凝固シェルを緩冷却することが提案されている。これは、緩冷却によって凝固シェルに作用する応力を低下させて表面割れを抑制するという技術である。しかしながら、モールドパウダーによる緩冷却効果のみでは、不均一凝固を十分に改善するまでには至っておらず、特に凝固に伴う僅かな温度低下で変態が生じる中炭素鋼では、表面割れの発生を防止することはできないのが実情である。 For example, Patent Document 1 proposes using mold powder having a composition that is easily crystallized, and increasing the thermal resistance of the mold powder layer to slowly cool the solidified shell. This is a technique of suppressing surface cracking by reducing the stress acting on the solidified shell by slow cooling. However, only the slow cooling effect by the mold powder has not sufficiently improved the non-uniform solidification, especially in medium carbon steel where transformation occurs due to a slight temperature drop accompanying solidification, preventing the occurrence of surface cracks. The fact is that you can't.
特許文献２には、鋳型内壁面に縦溝と横溝とを設け、これら縦溝及び横溝の内部にモールドパウダーを流入させ、これにより、鋳型の冷却を緩冷却化すると同時に鋳型幅方向で均一化し、鋳片の縦割れを防止する技術が提案されている。しかしながら、鋳片との接触によって鋳型内壁面は摩耗し、鋳型内壁面に設けた溝が浅くなると、モールドパウダーの流れ込み量が少なくなって緩冷却効果が低減するという問題、つまり、緩冷却効果が持続しないという問題がある。また、鋳造開始時の空の鋳型空間内への溶鋼注入時に、注入した溶鋼が鋳型内壁面に設けた溝の内部に侵入して凝固し、鋳型銅板と凝固シェルとが固着して、凝固シェルの引き抜きができなくなり、拘束性ブレークアウトが発生する虞があるという問題もある。 In Patent Document 2, a vertical groove and a horizontal groove are provided on the inner wall surface of the mold, and mold powder is allowed to flow into the vertical groove and the horizontal groove, thereby slowing down the cooling of the mold and at the same time uniforming in the mold width direction. A technique for preventing vertical cracking of a slab has been proposed. However, when the inner wall surface of the mold is worn due to contact with the slab, and the groove provided on the inner wall surface of the mold becomes shallow, the amount of mold powder flowing in decreases and the slow cooling effect is reduced. There is a problem of not persisting. In addition, when molten steel is poured into an empty mold space at the start of casting, the injected molten steel penetrates into the groove provided on the inner wall surface of the mold and solidifies, and the mold copper plate and the solidified shell adhere to each other, thereby solidifying the shell. There is also a problem in that it becomes impossible to pull out the wire and a constraining breakout may occur.
特許文献３には、鋳型内壁面に格子状の溝を設けた鋳型、及び、前記格子状の溝に異種金属（Ｎｉ，Ｃｒ）またはセラミックス（ＢＮ、ＡｌＮ、ＺｒＯ２）を充填した鋳型が提案されている。この技術は、溝部と溝部以外の部分とで抜熱量に差を生じさせ、凝固に伴う変態や熱収縮による応力を低抜熱の領域に分散させることで、鋳片の縦割れを抑制するという技術である。しかしながら、溝が格子状であり、格子溝形状では、鋳型内壁面の溝部と鋳型銅板（銅または銅合金）との境界が直線であり、熱膨張差に起因して境界面に割れが発生し且つ伝播しやすく、鋳型寿命が低下するという問題がある。 Patent Document 3 proposes a mold in which a lattice-shaped groove is provided on the inner wall surface of the mold, and a mold in which the lattice-shaped groove is filled with a different metal (Ni, Cr) or ceramics (BN, AlN, ZrO 2 ). Has been. This technology creates a difference in the amount of heat removal between the groove and the portion other than the groove, and suppresses vertical cracking of the slab by dispersing the stress due to transformation and thermal shrinkage accompanying solidification in the low heat removal region. Technology. However, the grooves are in a lattice shape, and in the lattice groove shape, the boundary between the groove portion of the inner wall surface of the mold and the mold copper plate (copper or copper alloy) is a straight line, and the boundary surface is cracked due to the difference in thermal expansion. In addition, there is a problem that propagation is easy and the mold life is reduced.
特許文献４には、鋳型内壁面に鋳造方向と平行な縦溝を設けた鋳型、及び、前記縦溝に異種金属（Ｎｉ，Ｃｒ）またはセラミックス（ＢＮ、ＡｌＮ、ＺｒＯ２）を充填した鋳型を用い、鋳片引き抜き速度と鋳型振動周期とを所定の範囲に規定する連続鋳造方法が提案されている。特許文献４によれば、鋳片引き抜き速度に応じて鋳型振動周期を適正化することで、鋳片に形成されるオシレーションマークが横溝を付与したように働き、縦溝のみでも、特許文献３と同様の表面割れ低減効果が認められるとしている。しかしながら、特許文献３と同様に、鋳型内壁面の溝部と鋳型銅板（銅または銅合金）との境界が直線であり、熱膨張差に起因して境界面に割れが発生し且つ伝播しやすく、鋳型寿命が低下するという問題がある。 Patent Document 4 discloses a mold in which a vertical groove parallel to the casting direction is provided on the inner wall surface of the mold, and a mold in which the vertical groove is filled with a different metal (Ni, Cr) or ceramics (BN, AlN, ZrO 2 ). There has been proposed a continuous casting method that uses a slab drawing speed and a mold vibration cycle within a predetermined range. According to Patent Document 4, by optimizing the mold vibration period in accordance with the slab drawing speed, the oscillation mark formed on the slab works as if a lateral groove was provided. It is said that the same effect of reducing surface cracks is observed. However, as in Patent Document 3, the boundary between the groove on the inner wall surface of the mold and the mold copper plate (copper or copper alloy) is a straight line, and the boundary surface is easily cracked and propagated due to the difference in thermal expansion. There is a problem that the mold life is reduced.
本発明は、上記事情に鑑みてなされたもので、その目的とするところは、鋳造開始時での拘束性ブレークアウトの発生及び鋳型銅板表面の割れによる鋳型寿命低下を起こすことなく、凝固初期の凝固シェルの不均一冷却による表面割れ、及び、包晶反応を伴う中炭素鋼でのδ鉄からγ鉄への変態に起因する凝固シェル厚みの不均一による表面割れを長期間に亘って抑制できる連続鋳造用鋳型を提供することであり、また、この連続鋳造用鋳型を使用した鋼の連続鋳造方法を提供することである。 The present invention has been made in view of the above circumstances, and the object of the present invention is to generate a constraining breakout at the start of casting and to reduce the mold life due to cracks on the surface of the mold copper plate, and at the initial stage of solidification. Surface cracks due to non-uniform cooling of solidified shells and surface cracks due to non-uniform solidified shell thickness due to transformation from δ iron to γ iron in medium carbon steel with peritectic reaction can be suppressed over a long period of time. It is to provide a continuous casting mold, and to provide a continuous casting method of steel using the continuous casting mold.
上記課題を解決するための本発明の要旨は以下のとおりである。
［１］水冷式銅合金製鋳型の内壁面の少なくともメニスカスを含む領域の銅合金製鋳型銅板の内壁面の凹部に、鋳型銅板の熱伝導率とは異なる熱伝導率の金属または非金属が充填された複数の異種物質充填部を有する連続鋳造用鋳型であって、前記異種物質充填部の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリットとの間の熱抵抗が下記の（１）式の範囲であり、且つ、鋳型銅板の熱伝導率と銅合金製鋳型銅板の内壁面に充填される金属または非金属の熱伝導率との比が下記の（２）式または（３）式の範囲である異種物質充填部を有することを特徴とする、連続鋳造用鋳型。
１．０×１０−５＜Ｒ＜６．０×１０−４・・・（１）
０．２＜λＣｕ／λｍａ＜１．０・・・（２）
１．０＜λＣｕ／λｍａ＜２０．０・・・（３）
但し、（１）式において、Ｒは鋳型銅板表面と鋳型銅板のスリットとの間の熱抵抗（ｍ２×Ｋ／Ｗ）であり、また、（２）式及び（３）式において、λＣｕは鋳型銅板の熱伝導率
（Ｗ／（ｍ×Ｋ））、λｍａは銅合金製鋳型銅板の内壁面に充填される金属または非金属の熱伝導率（Ｗ／（ｍ×Ｋ））である。
［２］前記連続鋳造用鋳型は、前記複数の異種物質充填部が設けられた銅合金製鋳型銅板の内壁面の範囲において、前記複数の異種物質充填部によって形成された周期的に増減する熱抵抗分布または熱流束分布を有することを特徴とする、［１］に記載の連続鋳造用鋳型。
［３］前記内壁面の凹部は、円形凹溝または擬円形凹溝であることを特徴とする、［１］または［２］に記載の連続鋳造用鋳型。
［４］前記複数の異種物質充填部は、互いに独立してなることを特徴とする、［１］から［３］の何れか１つに記載の連続鋳造鋳型。
［５］前記鋳型銅板の内壁面には、鍍金層の熱伝導率が鋳型銅板の熱伝導率に対して下記の（４）式を満足し、且つ、鍍金層の厚みが鋳型銅板の厚みに対して下記の（５）式を満足する鍍金層が形成されており、該鍍金層で前記異種物質充填部は覆われていることを特徴とする、［１］から［４］の何れか１つに記載の連続鋳造用鋳型。
０．５＜λＣｕ／λｃｏａｔｉｎｇ＜１５．０・・・（４）
４．０＜ＴＣｕ／Ｔｃｏａｔｉｎｇ＜２５０．０・・・（５）
但し、（４）式において、λＣｕは鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、λｃｏａｔｉｎｇは鍍金層の熱伝導率（Ｗ／（ｍ×Ｋ））であり、また、（５）式において、ＴＣｕは鋳型銅板の厚みであって、具体的には鋳型銅板表面と鋳型銅板のスリットの底との間の距離（ｍ）、Ｔｃｏａｔｉｎｇは鍍金層の厚み（ｍ）である。
［６］［１］から［５］の何れか１つに記載の連続鋳造用鋳型を用い、鋳型銅板の熱伝導率、異種物質充填部の熱伝導率、及び鋳型銅板のスリットの総断面積に応じて、鋳型冷却水の流量が下記の（６）式または（７）式を満足するように、鋳型冷却水の流量を制御して溶鋼を連続鋳造することを特徴とする、鋼の連続鋳造方法。
３＜（Ｑ／Ｓ）×（λＣｕ／λｍａ）＜１５０（但し、λＣｕ＞λｍａ）・・・（６）
３＜（Ｑ／Ｓ）×（λｍａ／λＣｕ）＜１２０（但し、λＣｕ＜λｍａ）・・・（７）
但し、（６）式及び（７）式において、Ｑは鋳型冷却水の流量（ｍ３／ｓｅｃ）、Ｓは
鋳型銅板のスリットの総断面積（ｍ２）、λＣｕは鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、
λｍａは異種物質充填部の熱伝導率（Ｗ／（ｍ×Ｋ））である。
The gist of the present invention for solving the above problems is as follows.
[1] The recess of the inner wall surface of the copper alloy mold copper plate in the region including at least the meniscus of the inner wall surface of the water-cooled copper alloy mold is filled with a metal or non-metal having a thermal conductivity different from that of the mold copper plate. A continuous casting mold having a plurality of dissimilar substance filling portions, wherein a thermal resistance between a surface of the mold copper plate at a position where the dissimilar substance filling portion is installed and a slit of the mold copper plate which is a flow path of the mold cooling water is The range of the following formula (1), and the ratio of the thermal conductivity of the mold copper plate to the thermal conductivity of the metal or nonmetal filled in the inner wall surface of the copper alloy mold copper plate is the following formula (2) Or a casting mold for continuous casting, characterized by having a foreign substance filling portion within the range of the formula (3).
1.0 × 10 −5 <R <6.0 × 10 −4 (1)
0.2 <λ Cu / λ ma <1.0 (2)
1.0 <λ Cu / λ ma <20.0 (3)
However, in the formula (1), R is the thermal resistance (m 2 × K / W) between the surface of the mold copper plate and the slit of the mold copper plate, and in the formulas (2) and (3), λ Cu Is the thermal conductivity (W / (m × K)) of the mold copper plate, and λ ma is the thermal conductivity (W / (m × K)) of the metal or non-metal filled in the inner wall surface of the copper alloy mold copper plate. is there.
[2] The continuous casting mold has a periodically increasing / decreasing heat formed by the plurality of different material filling portions in the range of the inner wall surface of the copper alloy mold copper plate provided with the plurality of different material filling portions. The mold for continuous casting according to [1], which has a resistance distribution or a heat flux distribution.
[3] The continuous casting mold according to [1] or [2], wherein the concave portion of the inner wall surface is a circular concave groove or a pseudo-circular concave groove.
[4] The continuous casting mold according to any one of [1] to [3], wherein the plurality of different substance filling portions are independent of each other.
[5] On the inner wall surface of the mold copper plate, the thermal conductivity of the plating layer satisfies the following formula (4) with respect to the thermal conductivity of the mold copper plate, and the thickness of the plating layer is equal to the thickness of the mold copper plate. On the other hand, any one of [1] to [4] is characterized in that a plating layer satisfying the following formula (5) is formed, and the dissimilar substance filling portion is covered with the plating layer. Continuous casting mold described in 1.
0.5 <λ Cu / λ coating <15.0 (4)
4.0 <T Cu / T coating <250.0 (5)
However, in Formula (4), λ Cu is the thermal conductivity (W / (m × K)) of the mold copper plate, λ coating is the thermal conductivity of the plating layer (W / (m × K)), and In Equation (5), T Cu is the thickness of the mold copper plate, specifically, the distance (m) between the surface of the mold copper plate and the bottom of the slit of the mold copper plate, and T coating is the thickness of the plating layer (m). It is.
[6] Using the continuous casting mold according to any one of [1] to [5], the thermal conductivity of the mold copper plate, the thermal conductivity of the dissimilar material filling portion, and the total sectional area of the slits of the mold copper plate Accordingly, the continuous casting of the steel is characterized in that the molten steel is continuously cast by controlling the flow rate of the mold cooling water so that the flow rate of the mold cooling water satisfies the following formula (6) or (7): Casting method.
3 <(Q / S) × (λ Cu / λ ma ) <150 (provided that λ Cu > λ ma ) (6)
3 <(Q / S) × (λ ma / λ Cu ) <120 (provided that λ Cu <λ ma ) (7)
However, in the formulas (6) and (7), Q is the flow rate (m 3 / sec) of the mold cooling water, S is the total sectional area (m 2 ) of the slits of the mold copper plate, and λ Cu is the heat conduction of the mold copper plate. Rate (W / (m × K)),
λ ma is the thermal conductivity (W / (m × K)) of the dissimilar substance filling portion.
本発明によれば、異種物質充填部を形成する物質として、鋳型銅板の熱伝導率に対する比率が所定の範囲である金属または非金属を使用し、異種物質充填部の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリットとの間の熱抵抗が所定の値である複数個の異種物質充填部を、メニスカス位置を含んでメニスカス近傍の連続鋳造用鋳型の幅方向及び鋳造方向に設置するので、メニスカス近傍の鋳型幅方向及び鋳造方向における連続鋳造用鋳型の熱抵抗が増減し、これによって、メニスカス近傍、つまり、凝固初期での凝固シェルから連続鋳造用鋳型への熱流束が増減する。この熱流束の増減により、δ鉄からγ鉄への変態による応力や熱応力が低減し、これらの応力によって生じる凝固シェルの変形が小さくなり、凝固シェルの変形が小さくなることで、凝固シェルの変形に起因する不均一な熱流束分布が均一化され、且つ、発生する応力が分散されて個々の歪量が小さくなる。その結果、凝固シェル表面における割れの発生が抑制される。 According to the present invention, a metal or a non-metal having a ratio with respect to the thermal conductivity of the mold copper plate within a predetermined range is used as a substance forming the foreign substance filling portion, and the mold copper plate surface at the installation position of the foreign substance filling portion A plurality of dissimilar substance filling portions having a predetermined value of thermal resistance between the slits of the mold copper plate, which is the flow path of the mold cooling water, include the meniscus position and the width direction of the continuous casting mold in the vicinity of the meniscus and casting. Since the thermal resistance of the continuous casting mold in the mold width direction and casting direction near the meniscus increases or decreases, the heat flux from the solidified shell near the meniscus, that is, in the initial stage of solidification, to the continuous casting mold. Increases or decreases. By increasing or decreasing this heat flux, the stress and thermal stress due to transformation from δ iron to γ iron are reduced, the deformation of the solidified shell caused by these stresses is reduced, and the deformation of the solidified shell is reduced, so that The non-uniform heat flux distribution resulting from the deformation is made uniform, and the generated stress is dispersed to reduce the amount of individual strain. As a result, the occurrence of cracks on the surface of the solidified shell is suppressed.
以下、発明の実施の形態を通じて本発明を具体的に説明する。図１は、本実施形態に係る連続鋳造用鋳型の一部を構成する鋳型長辺銅板であって、内壁面側に異種物質充填部が形成された鋳型長辺銅板を内壁面側から見た概略側面図、図２は、図１に示す鋳型長辺銅板のＸ−Ｘ’断面図である。 Hereinafter, the present invention will be specifically described through embodiments of the invention. FIG. 1 is a mold long side copper plate constituting a part of a continuous casting mold according to the present embodiment, and a mold long side copper plate in which a different substance filling portion is formed on the inner wall surface side is viewed from the inner wall surface side. FIG. 2 is a schematic side view, and FIG. 2 is a cross-sectional view taken along the line XX ′ of the long-side copper plate shown in FIG.
図１に示す連続鋳造用鋳型は、スラブ鋳片を鋳造するための連続鋳造用鋳型の一例である。スラブ鋳片用の連続鋳造用鋳型は、一対の銅合金製の鋳型長辺銅板と一対の銅合金製の鋳型短辺銅板とを組み合わせて構成され、図１は、そのうちの鋳型長辺銅板１を示している。鋳型短辺銅板も鋳型長辺銅板１と同様に、その内壁面側に異種物質充填部３が形成されるとして、ここでは、鋳型短辺銅板についての説明は省略する。但し、スラブ鋳片においては、スラブ厚みに対してスラブ幅が極めて大きいという形状に起因して、鋳片長辺面側の凝固シェルで応力集中が起こりやすく、鋳片長辺面側で表面割れが発生しやすい。したがって、スラブ鋳片用の連続鋳造用鋳型の鋳型短辺銅板には、異種物質充填部を設置しなくてもよい。 The continuous casting mold shown in FIG. 1 is an example of a continuous casting mold for casting a slab slab. A continuous casting mold for a slab slab is configured by combining a pair of copper alloy long mold copper plates and a pair of copper alloy short mold copper plates, and FIG. Is shown. Similarly to the long-side copper plate 1, the short-side copper plate is formed with the different material filling portion 3 on the inner wall surface side, and the description of the short-side copper plate is omitted here. However, in slab slabs, stress concentration is likely to occur in the solidified shell on the long side of the slab due to the shape of the slab width being extremely large relative to the slab thickness, and surface cracks occur on the long side of the slab It's easy to do. Therefore, the dissimilar substance filling part does not have to be installed on the short side copper plate of the continuous casting mold for the slab slab.
図１に示すように、鋳型長辺銅板１における定常鋳造時のメニスカスの位置よりも長さＬ１（長さＬ１は、ゼロ以上の任意の値）離れた上方の位置から、メニスカスよりも長さＬ２だけ下方の位置までの鋳型長辺銅板１の内壁面には、直径をｄとし、鋳型長辺銅板１の熱伝導率とは異なる熱伝導率の金属または非金属が充填された、複数個の異種物質充填部３が、異種物質充填部同士の間隔をＰとして設置されている。ここで、「メニスカス」とは「鋳型内溶鋼湯面」であり、非鋳造中にはその位置は明確でないが、通常の鋼の連続鋳造操業では、メニスカス位置を鋳型銅板の上端から５０ｍｍないし２００ｍｍ程度下方の位置としている。したがって、メニスカス位置が鋳型長辺銅板１の上端から５０ｍｍ下方の位置であっても、また、上端から２００ｍｍ下方の位置であっても、長さＬ１及び長さＬ２が、以下に説明する条件を満足するように異種物質充填部３を配置すればよい。 As shown in FIG. 1, from the upper position away from the meniscus by a length L 1 (the length L 1 is an arbitrary value equal to or greater than zero) from the position of the meniscus at the time of steady casting in the long copper plate 1 of the mold. The inner wall surface of the mold long side copper plate 1 up to a position below the length L 2 was filled with a metal or a nonmetal having a diameter d and a thermal conductivity different from that of the mold long side copper plate 1. A plurality of different substance filling portions 3 are set with P being the interval between the different substance filling portions. Here, “meniscus” is “molten steel surface in mold” and its position is not clear during non-casting, but in the normal continuous casting operation of steel, the meniscus position is 50 mm to 200 mm from the upper end of the mold copper plate. The position is about below. Therefore, even if the meniscus position is 50 mm below the upper end of the long copper plate 1 and 200 mm below the upper end, the length L 1 and the length L 2 will be described below. What is necessary is just to arrange | position the dissimilar substance filling part 3 so that conditions may be satisfied.
即ち、凝固シェルの初期凝固への影響を勘案すれば、異種物質充填部３の設置位置は、定常鋳造時の鋳片引き抜き速度Ｖｃに応じて、下記の（８）式から算出される長さＬ０以上メニスカスよりも下方の位置までとすることが必要である。つまり、図１に示す、メニスカス位置からの長さＬ２は、長さＬ０以上とする必要がある。 That is, considering the influence of the solidified shell on the initial solidification, the disposition position of the different substance filling portion 3 is a length calculated from the following equation (8) according to the slab drawing speed V c during steady casting. it is necessary to up position below the L 0 or meniscus. That is shown in FIG. 1, the length L 2 from the meniscus position is required to be a length L 0 greater.
Ｌ０＝２×Ｖｃ×１０００／６０・・・（８）
但し、（８）式において、Ｌ０は長さ（ｍｍ）、Ｖｃは定常鋳造時の鋳片引き抜き速度（ｍ／ｍｉｎ）である。
L 0 = 2 × V c × 1000/60 (8)
However, in the equation (8), L 0 is the length (mm), and V c is the slab drawing speed (m / min) during steady casting.
長さＬ０は、凝固開始した後の鋳片が異種物質充填部３の設置された範囲を通過する時間に関係しており、鋳片の表面割れを抑制するためには、凝固開始後から少なくとも２秒間は、鋳片が異種物質充填部３の設置された範囲内に滞在することが必要であることを、本発明者らは確認している。鋳片が凝固開始後から少なくとも２秒間は異種物質充填部３の設置された範囲に存在するためには、長さＬ０は（８）式を満たすことが必要となる。 The length L 0 is related to the time during which the slab after the start of solidification passes through the range where the foreign substance filling portion 3 is installed. The inventors have confirmed that it is necessary for the slab to stay in the range where the foreign substance filling portion 3 is installed for at least 2 seconds. In order for the slab to be present in the range where the foreign substance filling portion 3 is installed for at least 2 seconds after the start of solidification, the length L 0 needs to satisfy the equation (8).
凝固開始した後の鋳片が異種物質充填部３の設置された範囲内に滞在する時間を２秒以上確保することで、異種物質充填部３による熱流束の周期的な変動の効果が十分に得られ、表面割れの発生しやすい高速鋳造時や中炭素鋼の鋳造時に、鋳片の表面割れ抑制効果が得られる。異種物質充填部３による熱流束の周期的な変動の効果を安定して得るには、鋳片が異種物質充填部３の設置された範囲を通過する時間を４秒以上確保することがより好ましい。 By securing the time for the slab after the start of solidification to stay in the range where the foreign material filling unit 3 is installed for 2 seconds or more, the effect of periodic fluctuation of the heat flux by the foreign material filling unit 3 is sufficiently obtained. Thus, the effect of suppressing the surface cracking of the slab can be obtained at the time of high-speed casting in which surface cracks are likely to occur or when casting medium carbon steel. In order to stably obtain the effect of the periodic fluctuation of the heat flux by the foreign material filling section 3, it is more preferable to secure a time for the slab to pass through the range where the foreign material filling section 3 is installed for 4 seconds or more. .
長さＬ２の具体的な長さは、厚みが２００ｍｍ以上のスラブ連続鋳造機における鋳片引き抜き速度Ｖｃは、３．０ｍ／ｍｉｎ程度が上限であるので、長さＬ２が１００ｍｍ以上、望ましくは２００ｍｍ以上となるように、メニスカス位置に応じて異種物質充填部３を設置すればよい。長さＬ２の上限を定めなくてよく、鋳型下端まで異種物質充填部３を設置してもよい。 Specific lengths of L 2 are slab drawing speed V c thickness of 200mm or more slab continuous casting machine, since the order of 3.0 m / min is at an upper limit, the length L 2 is 100mm or more, What is necessary is just to install the dissimilar substance filling part 3 according to a meniscus position so that it may become 200 mm or more desirably. May not set the upper limit of the length L 2, the different materials filling unit 3 may be installed to the mold bottom.
一方、異種物質充填部３の上端部の位置は、メニスカスと同一位置またはメニスカス位置よりも上方であればどこの位置であってもよく、従って、図１に示す長さＬ１は、ゼロ以上の任意の値であればよい。但し、メニスカスは、鋳造中に異種物質充填部３の設置領域に存在する必要があり、しかも、メニスカスは鋳造中に上下方向に変動するので、異種物質充填部３の上端部が常にメニスカスよりも上方位置となるように、異種物質充填部３の上端部を想定されるメニスカス位置よりも１０ｍｍ程度上方位置とすることが好ましく、異種物質充填部３の上端部を想定されるメニスカス位置よりも２０ｍｍ〜５０ｍｍ程度上方位置とすることがより好ましい。 On the other hand, the position of the upper end portion of the heterologous material filling unit 3 may be anywhere in the location if above a than meniscus and the same position or the meniscus position, therefore, the length L 1 shown in FIG. 1, or zero Any value can be used. However, the meniscus needs to exist in the installation region of the foreign material filling portion 3 during casting, and the meniscus fluctuates in the vertical direction during casting, so that the upper end portion of the foreign material filling portion 3 is always higher than the meniscus. It is preferable that the upper end portion of the different material filling portion 3 is positioned about 10 mm above the assumed meniscus position so that the upper position is 20 mm from the assumed meniscus position. More preferably, the upper position is about 50 mm.
この異種物質充填部３は、図２に示すように、鋳型長辺銅板１の内壁面側に加工された円形凹溝２の内部に、鋳型長辺銅板１を構成する銅合金の熱伝導率とは異なる熱伝導率の金属または非金属が充填されて形成されたものである。なお、異種物質充填部３が互いに独立するように円形凹溝２を加工することがより好ましい。 As shown in FIG. 2, the dissimilar substance filling portion 3 has a thermal conductivity of the copper alloy constituting the long copper plate 1 in the circular groove 2 processed on the inner wall surface side of the long copper plate 1. It is formed by being filled with a metal or non-metal having a different thermal conductivity. In addition, it is more preferable to process the circular groove 2 so that the different-material filling portions 3 are independent from each other.
円形凹溝２の内部に充填される金属または非金属の熱伝導率は、一般的には、鋳型長辺銅板１を構成する銅合金の熱伝導率よりも低いが、例えば、鋳型長辺銅板１を構成する銅合金として熱伝導率の低い銅合金を使用した場合には、充填される金属または非金属の熱伝導率の方が高くなることもある。充填する物質が金属の場合には、鍍金処理または溶射処理によって充填し、充填する物質が非金属の場合には、円形凹溝２の形状に合わせて加工した非金属を円形凹溝２に嵌め込むなどして充填する。ここで、図２における符号４は、鋳型冷却水の流路を構成する、鋳型長辺銅板１の背面側に設置されたスリット、符号４ａはスリットの底、符号５は、鋳型長辺銅板１の背面と密着するバックプレートであり、スリット４を通る鋳型冷却水によって、鋳型長辺銅板１は冷却される。 The thermal conductivity of metal or nonmetal filled in the circular concave groove 2 is generally lower than the thermal conductivity of the copper alloy constituting the mold long-side copper plate 1, but for example, the mold long-side copper plate When a copper alloy having a low thermal conductivity is used as the copper alloy constituting 1, the thermal conductivity of the filled metal or nonmetal may be higher. When the material to be filled is metal, it is filled by plating or thermal spraying. When the material to be filled is non-metal, a non-metal processed according to the shape of the circular groove 2 is fitted into the circular groove 2. Fill and fill. Here, reference numeral 4 in FIG. 2 is a slit installed on the back side of the mold long-side copper plate 1 constituting the flow path of the mold cooling water, reference numeral 4a is the bottom of the slit, and reference numeral 5 is the long-side copper plate 1 of the mold. The long side copper plate 1 is cooled by the mold cooling water passing through the slit 4.
本実施形態において、鋳型銅板として使用する銅合金としては、一般的に連続鋳造用鋳型銅板として使用される、クロム（Ｃｒ）やジルコニウム（Ｚｒ）などを微量添加した銅合金を用いればよい。近年では、鋳型内の凝固の均一化または溶鋼中介在物の凝固シェルへの捕捉を防止するために、鋳型内の溶鋼を攪拌する電磁攪拌装置が設置されていることが一般的であり、電磁コイルから溶鋼への磁場強度の減衰を抑制するために、導電率を低減した銅合金が用いられている。この場合、導電率の低下に応じて熱伝導率も低減し、純銅（熱伝導率；約４００Ｗ／（ｍ×Ｋ））の１／２前後の熱伝導率の銅合金製鋳型銅板も使用されることがある。尚、鋳型銅板として使用される銅合金は、一般的に、純銅よりも熱伝導率が低い。 In this embodiment, as a copper alloy used as a mold copper plate, a copper alloy to which chromium (Cr), zirconium (Zr), or the like, which is generally used as a mold copper plate for continuous casting, is added may be used. In recent years, an electromagnetic stirrer for stirring the molten steel in the mold is generally installed in order to make the solidification in the mold uniform or prevent the inclusions in the molten steel from being trapped in the solidified shell. In order to suppress the attenuation of the magnetic field strength from the coil to the molten steel, a copper alloy with reduced conductivity is used. In this case, the thermal conductivity is reduced according to the decrease in conductivity, and a copper alloy mold copper plate having a thermal conductivity of about 1/2 that of pure copper (thermal conductivity: about 400 W / (mxK)) is also used. Sometimes. In addition, the copper alloy used as a mold copper plate generally has a lower thermal conductivity than pure copper.
図３に、鋳型銅板よりも熱伝導率の低い物質が充填されて形成された異種物質充填部３を有する鋳型長辺銅板１の三箇所の位置における熱抵抗を、異種物質充填部３の位置に対応して概念的に示す。この場合、異種物質充填部３の設置位置では熱抵抗が相対的に高くなる。 FIG. 3 shows the thermal resistance at three positions of the long copper plate 1 having a different material filling portion 3 formed by filling a material having a lower thermal conductivity than that of the mold copper plate. Conceptually corresponding to In this case, the thermal resistance is relatively high at the installation position of the foreign substance filling unit 3.
複数の異種物質充填部３を、メニスカス位置を含んでメニスカス近傍の連続鋳造用鋳型の幅方向及び鋳造方向に設置して、図３に示すように、メニスカス近傍の鋳型幅方向及び鋳造方向における連続鋳造用鋳型の熱抵抗が周期的に増減する熱抵抗の分布を形成させることが好ましい。これによって、メニスカス近傍、つまり、凝固初期での凝固シェルから連続鋳造用鋳型への熱流束が周期的に増減する熱流束の分布が形成される。 A plurality of different substance filling portions 3 are installed in the width direction and casting direction of the continuous casting mold near the meniscus including the meniscus position, and as shown in FIG. 3, continuous in the mold width direction and casting direction near the meniscus. It is preferable to form a thermal resistance distribution in which the thermal resistance of the casting mold periodically increases and decreases. As a result, a heat flux distribution is formed in which the heat flux in the vicinity of the meniscus, that is, in the initial stage of solidification, from the solidified shell to the continuous casting mold is periodically increased or decreased.
尚、鋳型銅板よりも熱伝導率の高い物質を充填して異種物質充填部３を形成した場合には、図３とは異なり、異種物質充填部３の設置位置で熱抵抗が相対的に低くなるが、この場合も同様に、メニスカス近傍の鋳型幅方向及び鋳造方向における連続鋳造用鋳型の熱抵抗が周期的に増減する。 In addition, when the different material filling portion 3 is formed by filling a material having higher thermal conductivity than the mold copper plate, unlike FIG. 3, the thermal resistance is relatively low at the installation position of the different material filling portion 3. However, in this case as well, the thermal resistance of the continuous casting mold in the mold width direction and the casting direction in the vicinity of the meniscus periodically increases and decreases.
この熱流束の周期的な増減により、δ鉄からγ鉄への変態（以下「δ／γ変態」と記す）によって発生する応力や熱応力が低減し、これらの応力によって生じる凝固シェルの変形が小さくなる。凝固シェルの変形が小さくなることで、凝固シェルの変形に起因する不均一な熱流束分布が均一化され、且つ、発生する応力が分散されて個々の歪量が小さくなる。その結果、凝固シェル表面における表面割れの発生が抑制される。 Due to the periodic increase and decrease of the heat flux, stress and thermal stress generated by transformation from δ iron to γ iron (hereinafter referred to as “δ / γ transformation”) are reduced, and deformation of the solidified shell caused by these stresses is reduced. Get smaller. By reducing the deformation of the solidified shell, the non-uniform heat flux distribution resulting from the deformation of the solidified shell is made uniform, and the generated stress is dispersed to reduce the amount of individual strain. As a result, the occurrence of surface cracks on the surface of the solidified shell is suppressed.
但し、凝固シェル表面における表面割れの発生を安定して抑制するためには、異種物質充填部３を設置したことによる熱流束の増減が適正でなければならない。つまり、熱流束の増減の差が小さすぎれば、異種物質充填部３を設置した効果が得られず、逆に、熱流束の増減の差が大きすぎれば、これに起因して発生する応力が大きくなり、この応力で表面割れが発生する。異種物質充填部３を設置したことによる熱流束の増減の差は、異種物質充填部３の設置位置における熱抵抗及び異種物質充填部３に充填する金属または非金属の熱伝導率に依存する。 However, in order to stably suppress the occurrence of surface cracks on the surface of the solidified shell, it is necessary to appropriately increase or decrease the heat flux due to the dissimilar substance filling portion 3 being installed. That is, if the difference in the increase and decrease in the heat flux is too small, the effect of installing the dissimilar substance filling unit 3 cannot be obtained. Conversely, if the difference in the increase and decrease in the heat flux is too large, the stress generated due to this is increased. The surface becomes cracked by this stress. The difference in increase / decrease in the heat flux due to the dissimilar material filling unit 3 depends on the thermal resistance at the installation position of the dissimilar material filling unit 3 and the thermal conductivity of the metal or non-metal filled in the dissimilar material filling unit 3.
そこで、本発明者らは、異種物質充填部３の設置位置における鋳型銅板表面と鋳型銅板のスリット４との間の熱抵抗が、鋳片表面割れに及ぼす影響、及び、異種物質充填部３に充填する金属または非金属の熱伝導率が、鋳片表面割れに及ぼす影響を調査した。調査方法は、異種物質充填部３を形成する金属または非金属、及び、異種物質充填部３の直径ｄ、間隔Ｐまたは充填厚みＨを種々変更して、図１に示す連続鋳造用鋳型を製作し、この連続鋳造用鋳型を用いて中炭素鋼の連続鋳造を行い、鋳造後のスラブ鋳片の表面割れ発生状況を調査した。鋳片の表面割れの調査は、面積２１ｍ２以上の鋳片表面を染色浸透探傷検査によって検査し、検出された長さ１．０ｍｍ以上の縦割れの個数を測定し、この個数を鋳片の測定面積で除算したものを鋳片表面割れ個数密度と定義し、この鋳片表面割れ個数密度で評価した。 Therefore, the inventors of the present invention have the effect that the thermal resistance between the mold copper plate surface and the slit 4 of the mold copper plate at the installation position of the foreign material filling portion 3 has an effect on the slab surface crack, and the foreign material filling portion 3 The effect of the thermal conductivity of the metal or nonmetal to be filled on the slab surface crack was investigated. The investigation method is to produce the continuous casting mold shown in FIG. 1 by variously changing the metal d or non-metal forming the foreign material filling portion 3 and the diameter d, interval P or filling thickness H of the foreign material filling portion 3. Then, continuous casting of medium carbon steel was performed using this continuous casting mold, and the occurrence of surface cracks in the slab slab after the casting was investigated. The surface cracks of the slab are examined by inspecting the surface of a slab having an area of 21 m 2 or more by dye penetration inspection, measuring the number of detected vertical cracks having a length of 1.0 mm or more, and measuring this number of slabs. The product divided by the measurement area was defined as the slab surface crack number density, and this slab surface crack number density was evaluated.
図４に、異種物質充填部３の設置位置における鋳型銅板表面とスリット４との間の熱抵抗Ｒが鋳片表面割れに及ぼす影響を調査した結果を示す。 In FIG. 4, the result of investigating the influence which the thermal resistance R between the casting_mold | template copper plate surface and the slit 4 in the installation position of the dissimilar substance filling part 3 has on a slab surface crack is shown.
図４に示すように、熱抵抗Ｒが、１．０×１０−５ｍ２×Ｋ／Ｗよりも大きく、６．０×１０−４ｍ２×Ｋ／Ｗよりも小さい範囲のときに、鋳片表面割れ個数密度が安定して０．４０個以下になることがわかった。つまり、異種物質充填部３の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリット４との間の熱抵抗Ｒ（ｍ２×Ｋ／Ｗ）は、下記の（１）式の範囲を満足する必要があることがわかった。 As shown in FIG. 4, when the thermal resistance R is in a range larger than 1.0 × 10 −5 m 2 × K / W and smaller than 6.0 × 10 −4 m 2 × K / W, It was found that the number density of cracks on the slab surface was stably 0.40 or less. That is, the thermal resistance R (m 2 × K / W) between the surface of the mold copper plate at the installation position of the dissimilar substance filling unit 3 and the slit 4 of the mold copper plate which is the flow path of the mold cooling water is expressed by the following (1) It turns out that the range of the formula needs to be satisfied.
１．０×１０−５＜Ｒ＜６．０×１０−４・・・（１）
これは、熱抵抗Ｒが１．０×１０−５ｍ２×Ｋ／Ｗ以下の場合、鋳型内での抜熱量が大きくなり、鋳片に表面割れが発生しやすくなる。一方、熱抵抗Ｒが６．０×１０−４ｍ２×Ｋ／Ｗ以上の場合は、鋳型内での抜熱量が不足し、異種物質充填部３を設置した効果が軽減して鋳片表面割れが発生しやすくなるのみならず、鋳型銅板の表面温度が高くなりすぎ、凝固シェル厚みが不足し、これに起因するブレークアウトの発生が懸念される。
1.0 × 10 −5 <R <6.0 × 10 −4 (1)
This is because when the thermal resistance R is 1.0 × 10 −5 m 2 × K / W or less, the amount of heat removed in the mold is increased, and surface cracks are likely to occur in the slab. On the other hand, when the thermal resistance R is 6.0 × 10 −4 m 2 × K / W or more, the amount of heat removal in the mold is insufficient, and the effect of installing the dissimilar substance filling portion 3 is reduced, and the surface of the slab Not only is cracking likely to occur, but the surface temperature of the mold copper plate becomes too high, the thickness of the solidified shell is insufficient, and there is a concern about the occurrence of breakout due to this.
また、図５に、円形凹溝の内部に充填される金属または非金属の熱伝導率λｍａ（Ｗ／（ｍ×Ｋ））の指標として、鋳型銅板の熱伝導率λＣｕ（Ｗ／（ｍ×Ｋ））と充填される金属または非金属の熱伝導率λｍａ（Ｗ／（ｍ×Ｋ））との比（λＣｕ／λｍａ）を用い、この比（λＣｕ／λｍａ）が鋳片表面割れに及ぼす影響を調査した結果を示す。 FIG. 5 shows the thermal conductivity λ Cu (W / (W / () of the mold copper plate as an index of the thermal conductivity λ ma (W / ( mxK )) of the metal or nonmetal filled in the circular concave groove. m × K)) and the ratio (λ Cu / λ ma ) of the thermal conductivity λ ma (W / (m × K)) of the metal or non-metal to be filled, and this ratio (λ Cu / λ ma ) The result of investigating the influence which has on the slab surface crack is shown.
図５に示すように、比（λＣｕ／λｍａ）が下記の（２）式、または（３）式を満足する場合に、鋳片表面割れ個数密度が安定して０．４０個以下になることがわかった。 As shown in FIG. 5, when the ratio (λ Cu / λ ma ) satisfies the following formula (2) or (3), the slab surface crack number density is stably reduced to 0.40 or less. I found out that
０．２＜λＣｕ／λｍａ＜１．０・・・（２）
１．０＜λＣｕ／λｍａ＜２０．０・・・（３）
（２）式は、円形凹溝の内部に充填される金属または非金属の熱伝導率λｍａが鋳型銅板の熱伝導率λＣｕよりも大きい場合であり、（３）式は、熱伝導率λＣｕが熱伝導率λｍａよりも大きい場合である。
0.2 <λ Cu / λ ma <1.0 (2)
1.0 <λ Cu / λ ma <20.0 (3)
Formula (2) is a case where the thermal conductivity λ ma of the metal or nonmetal filled in the circular concave groove is larger than the thermal conductivity λ Cu of the mold copper plate, and the formula (3) is the thermal conductivity. This is a case where λ Cu is larger than the thermal conductivity λ ma .
比（λＣｕ／λｍａ）が０．２以下の場合、異種物質充填部３を設置した箇所における熱流束が大きくなり、凝固シェルの抜熱量が過多になりすぎ、鋳片に表面割れが発生するおそれがある。逆に、比（λＣｕ／λｍａ）が２０．０以上の場合は、凝固シェルの緩冷却化が促進されすぎる結果、異種物質充填部３を設置した効果が軽減して鋳片表面割れが発生しやすくなるのみならず、凝固シェルの厚み不足によるブレークアウトが懸念される。 When the ratio (λ Cu / λ ma ) is 0.2 or less, the heat flux at the place where the different-material filling part 3 is installed becomes large, the heat removal amount of the solidified shell becomes excessive, and surface cracks occur in the slab. There is a risk. On the other hand, when the ratio (λ Cu / λ ma ) is 20.0 or more, as a result of the slow cooling of the solidified shell being promoted too much, the effect of installing the dissimilar material filling portion 3 is reduced and the slab surface cracks are reduced. In addition to being easily generated, there is a concern about breakout due to insufficient thickness of the solidified shell.
以上説明したように、本実施形態に係る連続鋳造用鋳型においては、異種物質充填部３の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリット４との間の熱抵抗Ｒが上記の（１）式の範囲であり、且つ、鋳型銅板の熱伝導率λＣｕと円形凹溝の内部に充填される金属または非金属の熱伝導率λｍａがとの比（λＣｕ／λｍａ）が上記の（２）式または（３）式の範囲であることが必要である。 As described above, in the continuous casting mold according to the present embodiment, the thermal resistance between the surface of the mold copper plate at the position where the dissimilar substance filling portion 3 is installed and the slit 4 of the mold copper plate that is the flow path of the mold cooling water. The ratio of the thermal conductivity λ Cu of the mold copper plate to the thermal conductivity λ ma of the metal or non-metal filled in the circular concave groove (λ Cu / Λ ma ) needs to be in the range of the above formula (2) or (3).
本実施形態に係る連続鋳造用鋳型において、上記の（１）〜（３）式を満足する限り、円形凹溝に充填使用する金属（以下、「充填金属」とも記載する）及び円形凹溝に充填使用する非金属（以下、「充填非金属」とも記す）は、特にその種類を特定しなくてよい。但し、参考までに充填金属として使用可能な金属の例を挙げれば、ニッケル（Ｎｉ、熱伝導率；９０Ｗ／（ｍ×Ｋ））、クロム（Ｃｒ、熱伝導率；６７Ｗ／（ｍ×Ｋ））、コバルト（Ｃｏ、熱伝導率；７０Ｗ／（ｍ×Ｋ））、及び、これら金属を含有する合金などが好適である。これらの金属や合金は、銅合金よりも熱伝導率が低く、また、鍍金処理や溶射処理によって容易に円形凹溝に充填することができる。また、銅合金よりも熱伝導率が高い純銅を、円形凹溝に充填使用する金属として使用することもできる。純銅を充填した場合には、異種物質充填部３を設置した部位の方が鋳型銅板の部位よりも熱抵抗が小さくなる。 In the continuous casting mold according to the present embodiment, as long as the above formulas (1) to (3) are satisfied, the metal used for filling the circular groove (hereinafter also referred to as “filling metal”) and the circular groove are used. The type of nonmetal used for filling (hereinafter also referred to as “filling nonmetal”) need not be specified. However, for reference, examples of metals that can be used as filler metals include nickel (Ni, thermal conductivity: 90 W / (m × K)), chromium (Cr, thermal conductivity: 67 W / (m × K). ), Cobalt (Co, thermal conductivity; 70 W / (mxK)), alloys containing these metals, and the like are suitable. These metals and alloys have lower thermal conductivity than copper alloys, and can be easily filled into circular grooves by plating or thermal spraying. Further, pure copper having a higher thermal conductivity than that of a copper alloy can be used as a metal used for filling circular concave grooves. When pure copper is filled, the thermal resistance of the part where the foreign substance filling part 3 is installed is smaller than the part of the mold copper plate.
また、円形凹溝に充填使用する充填非金属としては、ＢＮ、ＡｌＮ、ＺｒＯ２などのセラミックスが好適である。これらは、低熱伝導率であるので、充填非金属として好適である。 Moreover, ceramics such as BN, AlN, and ZrO 2 are suitable as the filling nonmetal used for filling the circular concave grooves. Since these have low thermal conductivity, they are suitable as filled nonmetals.
図１及び図２では、異種物質充填部３の鋳型長辺銅板１の内壁面における形状が円形である例を示したが、当該形状は円形に限られない。例えば楕円形のような、所謂「角」を有していない、円形に近い形状であれば、どのような形状であってもよい。以下、円形に近いものを「擬似円形」と称する。異種物質充填部３の形状が擬似円形の場合には、異種物質充填部３を形成させるために、鋳型長辺銅板１の内壁面に加工される凹溝を「擬似円形凹溝」と称する。 1 and 2 show an example in which the shape of the inner wall surface of the long-side copper plate 1 of the mold of the foreign substance filling portion 3 is circular, but the shape is not limited to a circle. For example, any shape may be used as long as it does not have a so-called “corner” such as an ellipse and has a shape close to a circle. Hereinafter, a shape close to a circle is referred to as a “pseudo circle”. In the case where the shape of the foreign substance filling portion 3 is a pseudo circle, the groove processed on the inner wall surface of the long copper plate 1 in order to form the foreign substance filling portion 3 is referred to as a “pseudo circular groove”.
擬似円形とは、例えば楕円形や、角部を円や楕円とする長方形などの角部を有していない形状であり、更には、花びら模様のような形状であってもよい。擬似円形の大きさは、擬似円形の面積から求められる円相当径で評価する。この擬似円形の円相当径ｄは下記の（９）式で算出される。 The pseudo circle is, for example, an ellipse or a shape having no corners such as a rectangle whose corners are circles or ellipses, and may be a petal pattern. The size of the pseudo circle is evaluated by an equivalent circle diameter obtained from the area of the pseudo circle. The pseudo circular equivalent circle diameter d is calculated by the following equation (9).
円相当径ｄ＝（４×Ｓｍａ／π）１／２・・・（９）
但し、（９）式において、Ｓｍａは異種物質充填部３の面積（ｍｍ２）である。
Equivalent circle diameter d = (4 × S ma / π) 1/2 (9)
However, in the formula (9), S ma is the area (mm 2 ) of the foreign substance filling portion 3.
特許文献３及び特許文献４のように、縦溝或いは格子溝を施し、この溝に充填金属または充填非金属を配置した場合には、充填金属または充填非金属と鋳型銅板との境界面及び格子部の直交部において、充填金属または充填非金属と銅との熱歪差による応力が集中し、鋳型銅板表面に割れが発生するという問題が起こる。これに対して、本実施形態に係る連続鋳造用鋳型は、異種物質充填部３の形状を円形または擬似円形にしている。これにより、充填金属または充填非金属と銅との境界面は曲面状となるので、境界面で応力が集中しにくく、鋳型銅板表面に割れが発生しにくいという利点が発現する。 When a longitudinal groove or a lattice groove is provided as in Patent Document 3 and Patent Document 4 and a filling metal or a filling nonmetal is disposed in the groove, a boundary surface and a lattice between the filling metal or the filling nonmetal and the mold copper plate In the orthogonal part of the part, the stress due to the thermal strain difference between the filled metal or filled nonmetal and copper concentrates, causing a problem that cracks occur on the surface of the mold copper plate. On the other hand, in the continuous casting mold according to the present embodiment, the shape of the dissimilar substance filling portion 3 is circular or pseudo-circular. As a result, the boundary surface between the filled metal or filled nonmetal and copper has a curved surface, so that the stress is less likely to concentrate on the boundary surface and the advantage that cracks are less likely to occur on the surface of the mold copper plate.
異種物質充填部３の直径ｄ及び円相当径ｄは、２〜２０ｍｍであることが好ましい。異種物質充填部３の直径ｄ及び円相当径ｄを２ｍｍ以上とすることで、異種物質充填部３における熱流束の低下が十分となり、鋳片の表面割れ抑制効果を得ることができる。また、２ｍｍ以上とすることで、充填金属を鍍金処理や溶射処理によって円形凹溝２や擬似円形凹溝（図示せず）の内部に充填することが容易となる。一方、異種物質充填部３の直径及び円相当径を２０ｍｍ以下とすることで、異種物質充填部３における熱流束の低下が抑制され、つまり、異種物質充填部３での凝固遅れが抑制されて、その位置での凝固シェルへの応力集中が防止され、凝固シェルでの表面割れ発生を抑制できる。即ち、直径及び円相当径が２０ｍｍを超えると表面割れが増加する可能性があることから、異種物質充填部３の直径及び円相当径は２０ｍｍ以下にすることが好ましい。 It is preferable that the diameter d and the equivalent circle diameter d of the foreign substance filling portion 3 are 2 to 20 mm. By setting the diameter d and equivalent circle diameter d of the foreign material filling portion 3 to 2 mm or more, the heat flux in the foreign material filling portion 3 is sufficiently lowered, and the effect of suppressing the surface cracking of the slab can be obtained. Moreover, by setting it as 2 mm or more, it becomes easy to fill a filling metal into the inside of the circular ditch | groove 2 or a pseudo-circular ditch | groove (not shown) by a plating process or a thermal spraying process. On the other hand, by setting the diameter and equivalent circle diameter of the foreign material filling portion 3 to 20 mm or less, a decrease in heat flux in the foreign material filling portion 3 is suppressed, that is, a solidification delay in the foreign material filling portion 3 is suppressed. The concentration of stress on the solidified shell at that position is prevented, and the occurrence of surface cracks in the solidified shell can be suppressed. That is, if the diameter and the equivalent circle diameter exceed 20 mm, surface cracks may increase. Therefore, the diameter and equivalent circle diameter of the dissimilar substance filling portion 3 are preferably 20 mm or less.
異種物質充填部３の充填厚みＨは０．５ｍｍ以上とすることが好ましい。充填厚みＨを０．５ｍｍ以上とすることで、異種物質充填部３における熱流束の低下が十分となり、鋳片の表面割れ抑制効果を得ることができる。 The filling thickness H of the foreign substance filling portion 3 is preferably 0.5 mm or more. By setting the filling thickness H to 0.5 mm or more, the heat flux in the foreign substance filling portion 3 is sufficiently lowered, and the effect of suppressing the surface cracking of the slab can be obtained.
また、異種物質充填部３の充填厚みＨは、異種物質充填部３の直径ｄ以下及び円相当径ｄ以下にすることが好ましい。充填厚みＨを異種物質充填部３の直径ｄ及び円相当径ｄと同等、またはそれらよりも小さくするので、鍍金処理や溶射処理による円形凹溝及び擬似円形凹溝への充填金属の充填が容易となり、且つ、充填金属と鋳型銅板との間に隙間や割れが生じることもない。充填金属と鋳型銅板との間に隙間や割れが生じた場合には、充填金属の亀裂や剥離が生じ、鋳型寿命の低下、鋳片の割れ、更には拘束性ブレークアウトの原因となる。 Moreover, it is preferable that the filling thickness H of the foreign substance filling portion 3 is not more than the diameter d of the foreign substance filling portion 3 and the equivalent circle diameter d or less. Since the filling thickness H is equal to or smaller than the diameter d and equivalent circle diameter d of the different substance filling portion 3, filling of the filling metal into the circular concave groove and the pseudo circular concave groove by plating or spraying is easy. In addition, there are no gaps or cracks between the filling metal and the mold copper plate. When a gap or crack occurs between the filling metal and the mold copper plate, the filling metal cracks or peels off, causing a reduction in mold life, cracking of the cast piece, and further a restrictive breakout.
異種物質充填部同士の間隔Ｐは、異種物質充填部３の直径ｄ及び円相当径ｄの０．２５倍以上であることが好ましい。ここで、異種物質充填部同士の間隔Ｐとは、図１に示すように、隣り合う異種物質充填部３の端部間の最短距離である。異種物質充填部同士の間隔Ｐを「０．２５×ｄ」以上とすることで、間隔が十分に大きく、異種物質充填部３における熱流束と銅合金部（異種物質充填部３が形成されていない部位）の熱流束との差が大きくなり、鋳片の表面割れ抑制効果を得ることができる。異種物質充填部同士の間隔Ｐの上限値は特に定めなくてよいが、間隔Ｐが大きくなると、異種物質充填部３の面積率が低下するので「２．０×ｄ」以下にすることが好ましい。 The distance P between the different substance filling portions is preferably 0.25 times or more the diameter d and equivalent circle diameter d of the different substance filling portion 3. Here, the interval P between the different substance filling parts is the shortest distance between the end parts of the adjacent different substance filling parts 3 as shown in FIG. By setting the interval P between the different substance filling portions to be “0.25 × d” or more, the interval is sufficiently large, and the heat flux and the copper alloy portion (the different substance filling portion 3 is formed in the different substance filling portion 3). The difference from the heat flux of the non-part) becomes large, and the effect of suppressing the surface cracking of the slab can be obtained. The upper limit value of the interval P between the different substance filling portions may not be determined. However, since the area ratio of the different substance filling portion 3 is reduced when the interval P is increased, it is preferably set to “2.0 × d” or less. .
異種物質充填部３が配置された領域内の鋳型銅板内壁面の面積Ａ（ｍｍ２）に対する、全ての異種物質充填部３の面積の総和Ｂ（ｍｍ２）の比である面積率ε（ε＝（Ｂ／Ａ）×１００）は、１０％以上であることが好ましい。面積率εを１０％以上確保することで、熱流束の小さい異種物質充填部３の占める面積が確保され、異種物質充填部３と銅合金部とで熱流束差が得られ、鋳片の表面割れ抑制効果を安定して得ることができる。 Area ratio ε (ε) which is a ratio of the total area B (mm 2 ) of all the different material filling portions 3 to the area A (mm 2 ) of the inner wall surface of the mold copper plate in the region where the different material filling portions 3 are arranged. = (B / A) × 100) is preferably 10% or more. By securing an area ratio ε of 10% or more, the area occupied by the different material filling portion 3 having a small heat flux is ensured, and a heat flux difference is obtained between the different material filling portion 3 and the copper alloy portion. A crack suppressing effect can be obtained stably.
異種物質充填部３の配列は、図１に示すような千鳥配列が好ましいが、千鳥配列に限らず、異種物質充填部同士の上記間隔Ｐを満たす配列であれば、どのような配列でもよい。 The arrangement of the different substance filling portions 3 is preferably a zigzag arrangement as shown in FIG. 1, but is not limited to the zigzag arrangement and may be any arrangement as long as the arrangement satisfies the interval P between the different substance filling portions.
本実施形態に係る連続鋳造用鋳型においては、図６に示すように、異種物質充填部３を形成させた鋳型銅板の内壁面に、凝固シェルによる磨耗や熱履歴による鋳型表面の割れを抑制することを目的として、鍍金層６を設けることが好ましい。この鍍金層６は、一般的に用いられるニッケルまたはニッケルを含有する合金、例えば、ニッケル−コバルト合金（Ｎｉ−Ｃｏ合金）やニッケル−クロム合金（Ｎｉ−Ｃｒ合金）などを鍍金処理することで得られる。 In the continuous casting mold according to the present embodiment, as shown in FIG. 6, the inner wall surface of the mold copper plate on which the dissimilar substance filling portion 3 is formed suppresses the wear of the solidified shell and the crack of the mold surface due to the thermal history. For this purpose, the plating layer 6 is preferably provided. The plating layer 6 is obtained by plating a commonly used nickel or nickel-containing alloy such as a nickel-cobalt alloy (Ni-Co alloy) or a nickel-chromium alloy (Ni-Cr alloy). It is done.
図７に、鋳型銅板内壁面の全面に鍍金層６を形成する際に、鋳型銅板を構成する銅合金及び鍍金層６を構成する金属を種々変更し、鋳型銅板の熱伝導率λＣｕと鍍金層の熱伝導率λｃｏａｔｉｎｇとの比（λＣｕ／λｃｏａｔｉｎｇ）が鋳片表面割れに及ぼす影響を調査した結果を示す。図７に示すように、比（λＣｕ／λｃｏａｔｉｎｇ）が下記の（４）式の範囲の場合に、鋳片表面割れが減少することがわかった。 In FIG. 7, when the plating layer 6 is formed on the entire inner surface of the mold copper plate, the copper alloy constituting the mold copper plate and the metal constituting the plating layer 6 are variously changed, and the thermal conductivity λ Cu and the plating of the mold copper plate are changed. It shows the results of the ratio of the thermal conductivity lambda coating layer (λ Cu / λ coating) was investigated the effect on the cast slab surface cracks. As shown in FIG. 7, when the ratio (λ Cu / λ coating ) is in the range of the following formula (4), it was found that the slab surface cracks were reduced.
０．５＜λＣｕ／λｃｏａｔｉｎｇ＜１５．０・・・（４）
比（λＣｕ／λｃｏａｔｉｎｇ）が０．５以下の場合は、熱抵抗が小さいために、鋳片に表面割れが生じ、好ましくない。一方、比（λＣｕ／λｃｏａｔｉｎｇ）が１５．０以上になると、鍍金層の熱抵抗が高く、連続鋳造中に鍍金層の温度が高くなりすぎて、鍍金層の剥離などが懸念される。また、鍍金層の熱抵抗が高くなり、異種物質充填部３を設置した効果が減少し、鋳片表面に割れが生成する。
0.5 <λ Cu / λ coating <15.0 (4)
When the ratio (λ Cu / λ coating ) is 0.5 or less, the thermal resistance is small, and surface cracking occurs in the slab, which is not preferable. On the other hand, if the ratio (λ Cu / λ coating ) is 15.0 or more, the thermal resistance of the plating layer is high, the temperature of the plating layer becomes too high during continuous casting, and there is a concern about peeling of the plating layer. Moreover, the thermal resistance of the plating layer is increased, the effect of disposing the different substance filling portion 3 is reduced, and cracks are generated on the surface of the slab.
また、図８に、鋳型銅板厚みＴＣｕと鍍金層厚みＴｃｏａｔｉｎｇとの比（ＴＣｕ／Ｔｃｏａｔｉｎｇ）が鋳片表面割れに及ぼす影響を調査した結果を示す。ここで、鋳型銅板厚みＴＣｕとは、図６に示すように、鋳型銅板の表面からスリット４の底４ａまでの距離である。図８に示すように、比（ＴＣｕ／Ｔｃｏａｔｉｎｇ）が下記の（５）式の範囲の場合に、鋳片表面割れが減少することがわかった。 FIG. 8 shows the results of investigating the influence of the ratio (T Cu / T coating ) between the mold copper plate thickness T Cu and the plating layer thickness T coating on the slab surface crack. Here, the mold copper plate thickness T Cu is a distance from the surface of the mold copper plate to the bottom 4a of the slit 4 as shown in FIG. As shown in FIG. 8, it was found that when the ratio (T Cu / T coating ) is in the range of the following formula (5), the slab surface crack is reduced.
４．０＜ＴＣｕ／Ｔｃｏａｔｉｎｇ＜２５０．０・・・（５）
比（ＴＣｕ／Ｔｃｏａｔｉｎｇ）が４．０以下の場合、鍍金層が相対的に厚く、鍍金層の熱抵抗が高くなり、異種物質充填部３を設置した効果が減少し、鋳片表面に割れが生成する。また、鍍金層が相対的に厚くなることから、凝固シェルの抜熱量が不足し、凝固シェル厚みの不足によるブレークアウトが懸念されるので好ましくない。一方、比（ＴＣｕ／Ｔｃｏａｔｉｎｇ）が２５０以上の場合、鍍金層厚みが薄く、鍍金層の剥離などが懸念されるので好ましくない。また、鍍金層厚みが薄い場合、鋳型全体の熱抵抗が小さくなるために、鋳片に表面割れが発生しやすい。尚、鍍金層厚みＴｃｏａｔｉｎｇが上記（５）式の関係を満足する限り、鍍金層６は鋳型上端から下端まで同一の厚みであっても、上端から下端にかけて厚みが異なっていてもよい。
4.0 <T Cu / T coating <250.0 (5)
When the ratio (T Cu / T coating ) is 4.0 or less, the plating layer is relatively thick, the thermal resistance of the plating layer is increased, and the effect of installing the dissimilar substance filling portion 3 is reduced. Cracks are generated. Further, since the plating layer becomes relatively thick, the amount of heat removed from the solidified shell is insufficient, and there is a concern about breakout due to insufficient thickness of the solidified shell. On the other hand, when the ratio (T Cu / T coating ) is 250 or more, the thickness of the plating layer is thin, and peeling of the plating layer is a concern. Further, when the thickness of the plating layer is small, the thermal resistance of the entire mold becomes small, and thus surface cracks are likely to occur in the slab. As long as the plating layer thickness T coating satisfies the relationship of the above formula (5), the plating layer 6 may have the same thickness from the upper end to the lower end of the mold or may have a different thickness from the upper end to the lower end.
このように構成される連続鋳造用鋳型を用いて鋳片を連続鋳造するにあたり、特に、表面割れ感受性が高い、炭素含有量が０．０８〜０．１７質量％の中炭素鋼のスラブ鋳片（厚み；２００ｍｍ以上）を連続鋳造する際に使用することが好ましい。従来、中炭素鋼のスラブ鋳片を連続鋳造する場合は、鋳片の表面割れを抑制するために、鋳片引き抜き速度を低速化することが一般的であるが、本実施形態に係る連続鋳造用鋳型を適用することで鋳片表面割れが防止できるので、１．５ｍ／ｍｉｎ以上の鋳片引き抜き速度であっても、表面割れのない、または表面割れの著しく少ない鋳片を連続鋳造することが実現される。 In continuous casting of a slab using the continuous casting mold configured as described above, a slab slab of medium carbon steel having particularly high surface cracking sensitivity and a carbon content of 0.08 to 0.17% by mass. (Thickness: 200 mm or more) is preferably used for continuous casting. Conventionally, when continuously casting a slab slab of medium carbon steel, it is common to reduce the slab drawing speed in order to suppress surface cracking of the slab, but the continuous casting according to this embodiment Since casting surface cracks can be prevented by applying molds for casting, continuous casting of slabs with no surface cracking or very little surface cracking is possible even at a slab drawing speed of 1.5 m / min or more. Is realized.
但し、その際に、鋳型銅板の熱伝導率、円形凹溝または擬似円形凹溝の内部に充填される金属または非金属の熱伝導率、及び鋳型銅板のスリットの総断面積に応じて鋳型冷却水の流量が下記の（６）式または（７）式を満足するように、鋳型冷却水の流量を制御して溶鋼を連続鋳造する必要がある。 However, at that time, the mold cooling depends on the thermal conductivity of the mold copper plate, the thermal conductivity of the metal or non-metal filled in the circular concave groove or the pseudo circular concave groove, and the total sectional area of the slit of the mold copper plate. It is necessary to continuously cast the molten steel by controlling the flow rate of the mold cooling water so that the water flow rate satisfies the following formula (6) or (7).
３＜（Ｑ／Ｓ）×（λＣｕ／λｍａ）＜１５０（但し、λＣｕ＞λｍａ）・・・（６）
３＜（Ｑ／Ｓ）×（λｍａ／λＣｕ）＜１２０（但し、λＣｕ＜λｍａ）・・・（７）
（６）式及び（７）式において、Ｑは鋳型冷却水の流量（ｍ３／ｓｅｃ）、Ｓは鋳型銅板のスリットの総断面積（ｍ２）、λＣｕは鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、λｍａは円形凹溝または擬似円形凹溝の内部に充填される金属または非金属の熱伝導率（Ｗ／（ｍ×Ｋ））である。
3 <(Q / S) × (λ Cu / λ ma ) <150 (provided that λ Cu > λ ma ) (6)
3 <(Q / S) × (λ ma / λ Cu ) <120 (provided that λ Cu <λ ma ) (7)
In the formulas (6) and (7), Q is the flow rate of the mold cooling water (m 3 / sec), S is the total cross-sectional area (m 2 ) of the slit of the mold copper plate, and λ Cu is the thermal conductivity of the mold copper plate ( W / (m × K)), λ ma is the thermal conductivity (W / (m × K)) of the metal or non-metal filled in the circular or pseudo-circular groove.
図９に、鋳型銅板の熱伝導率λＣｕが充填金属または充填非金属の熱伝導率λｍａよりも大きい条件下で、鋳型冷却水の流量Ｑ、鋳型銅板のスリットの総断面積Ｓ、鋳型銅板の熱伝導率λＣｕ、充填金属または充填非金属の熱伝導率λｍａを種々変更し、「（Ｑ／Ｓ）×（λＣｕ／λｍａ）」の値が鋳片表面割れに及ぼす影響を調査した結果を示す。図９に示すように、熱伝導率λＣｕが熱伝導率λｍａよりも大きい条件下では、「（Ｑ／Ｓ）×（λＣｕ／λｍａ）」が上記（６）式の範囲の場合に、鋳片の表面割れが抑制されることが確認できた。 FIG. 9 shows the flow rate Q of the mold cooling water, the total cross-sectional area S of the slits of the mold copper plate, the mold, under the condition that the thermal conductivity λ Cu of the mold copper plate is larger than the thermal conductivity λ ma of the filled metal or non-filled metal. Effect of the value of “(Q / S) × (λ Cu / λ ma )” on the slab surface cracks by variously changing the thermal conductivity λ Cu of the copper plate and the thermal conductivity λ ma of the filled metal or non-filled metal The results of the investigation are shown. As shown in FIG. 9, under the condition where the thermal conductivity λ Cu is larger than the thermal conductivity λ ma , “(Q / S) × (λ Cu / λ ma )” is in the range of the above equation (6). In addition, it was confirmed that surface cracking of the slab was suppressed.
図１０は、鋳型銅板の熱伝導率λＣｕが充填金属または充填非金属の熱伝導率λｍａよりも小さい条件下で、「（Ｑ／Ｓ）×（λｍａ／λＣｕ）」の値が鋳片表面割れに及ぼす影響を調査した結果を示す図である。図１０に示すように、熱伝導率λＣｕが熱伝導率λｍａよりも小さい条件下では、「（Ｑ／Ｓ）×（λｍａ／λＣｕ）」が上記（７）式の範囲の場合に、鋳片の表面割れが抑制されることが確認できた。 FIG. 10 shows that the value of “(Q / S) × (λ ma / λ Cu )” is obtained under the condition that the thermal conductivity λ Cu of the mold copper plate is smaller than the thermal conductivity λ ma of the filled metal or the filled nonmetal. It is a figure which shows the result of having investigated the influence which acts on a slab surface crack. As shown in FIG. 10, under the condition that the thermal conductivity λ Cu is smaller than the thermal conductivity λ ma , “(Q / S) × (λ ma / λ Cu )” is in the range of the above formula (7). In addition, it was confirmed that surface cracking of the slab was suppressed.
「（Ｑ／Ｓ）×（λＣｕ／λｍａ）」または「（Ｑ／Ｓ）×（λｍａ／λＣｕ）」が３以下の場合は、鋳型内での冷却が弱くなりすぎ、異種物質充填部３を設置した効果が減少し、鋳片表面に割れが生成する。また、凝固シェルの抜熱量が不足し、凝固シェル厚みの不足によるブレークアウトが懸念される。一方、「（Ｑ／Ｓ）×（λＣｕ／λｍａ）」が１５０以上の場合、及び、「（Ｑ／Ｓ）×（λｍａ／λＣｕ）」が１２０以上の場合は、鋳型内での冷却が強くなりすぎ、異種物質充填部３の効果が希釈されて鋳片に表面割れが生成する。 When “(Q / S) × (λ Cu / λ ma )” or “(Q / S) × (λ ma / λ Cu )” is 3 or less, the cooling in the mold becomes too weak, and the foreign substance The effect of installing the filling portion 3 is reduced, and cracks are generated on the surface of the slab. Moreover, there is a concern about breakout due to insufficient heat removal from the solidified shell and insufficient solidified shell thickness. On the other hand, when “(Q / S) × (λ Cu / λ ma )” is 150 or more, and when “(Q / S) × (λ ma / λ Cu )” is 120 or more, The cooling of the material becomes too strong, and the effect of the foreign substance filling portion 3 is diluted, and surface cracks are generated in the slab.
以上説明したように、本実施形態に係る連続鋳造用鋳型は、異種物質充填部３を形成する物質として鋳型銅板の熱伝導率に対する比率が所定の範囲である金属または非金属を使用し、異種物質充填部３の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリットとの間の熱抵抗Ｒが所定の値である複数個の異種物質充填部３を、メニスカス位置を含んでメニスカス近傍の連続鋳造用鋳型の幅方向及び鋳造方向に設置するので、メニスカス近傍の鋳型幅方向及び鋳造方向における連続鋳造用鋳型の熱抵抗が周期的に増減し、これによって、メニスカス近傍、つまり、凝固初期での凝固シェルから連続鋳造用鋳型への熱流束が周期的に増減する。この熱流束の周期的な増減により、δ／γ変態による応力や熱応力が低減し、これらの応力によって生じる凝固シェルの変形が小さくなり、凝固シェルの変形が小さくなることで、凝固シェルの変形に起因する不均一な熱流束分布が均一化され、且つ、発生する応力が分散されて個々の歪量が小さくなる。その結果、凝固シェル表面における割れの発生が抑制される。 As described above, the continuous casting mold according to the present embodiment uses a metal or a nonmetal having a ratio with respect to the thermal conductivity of the mold copper plate within a predetermined range as a material for forming the dissimilar material filling portion 3. A plurality of dissimilar substance filling portions 3 having a predetermined value of the thermal resistance R between the surface of the mold copper plate at the position where the material filling portion 3 is installed and the slit of the mold copper plate which is the flow path of the mold cooling water are arranged at the meniscus position. Including in the width direction and casting direction of the continuous casting mold near the meniscus, the thermal resistance of the continuous casting mold in the mold width direction and casting direction near the meniscus periodically increases and decreases, thereby the vicinity of the meniscus, That is, the heat flux from the solidified shell to the continuous casting mold in the initial stage of solidification periodically increases and decreases. Due to the periodic increase / decrease of the heat flux, the stress and thermal stress due to the δ / γ transformation are reduced, the deformation of the solidified shell caused by these stresses is reduced, and the deformation of the solidified shell is reduced. The non-uniform heat flux distribution resulting from this is made uniform, and the generated stress is dispersed to reduce the amount of individual strain. As a result, the occurrence of cracks on the surface of the solidified shell is suppressed.
尚、図１では、同一形状の異種物質充填部３を鋳造方向または鋳型幅方向に設置した例を示したが、異種物質充填部３の形状は同一でなくてもよい。但し、いずれの異種物質充填部３の直径ｄまたは円相当径ｄは２〜２０ｍｍであることが好ましい。また、図２では、充填厚みＨが同一の異種物質充填部３を鋳造方向に設置した例を示したが、鋳造方向または鋳型幅方向において、充填厚みＨは同一でなくてよく、個々の異種物質充填部３で充填厚みＨが異なっていてもよい。但し、いずれの異種物質充填部３の充填厚みＨも０．５ｍｍ以上であることが好ましい。また更に、図１では、鋳造方向または鋳型幅方向に同一間隔で異種物質充填部３を設置した例を示したが、異種物質充填部３を設置する間隔は、同一でなくてもよい。但し、この場合も、異種物質充填部同士の間隔Ｐは異種物質充填部３の直径ｄ及び円相当径ｄの０．２５倍以上であることが好ましい。 In FIG. 1, an example is shown in which the same-shaped different substance filling portion 3 is installed in the casting direction or the mold width direction, but the different substance filling portion 3 may not have the same shape. However, it is preferable that the diameter d or the equivalent circle diameter d of any of the different substance filling portions 3 is 2 to 20 mm. Further, FIG. 2 shows an example in which the different substance filling portions 3 having the same filling thickness H are installed in the casting direction, but the filling thickness H may not be the same in the casting direction or the mold width direction. The filling thickness H may be different in the substance filling portion 3. However, the filling thickness H of any dissimilar substance filling portion 3 is also preferably 0.5 mm or more. Furthermore, although FIG. 1 shows an example in which the different substance filling portions 3 are installed at the same intervals in the casting direction or the mold width direction, the intervals at which the different substance filling portions 3 are installed may not be the same. However, also in this case, it is preferable that the distance P between the different material filling portions is 0.25 times or more the diameter d of the different material filling portion 3 and the equivalent circle diameter d.
また、上記説明はスラブ鋳片の連続鋳造に関して行ったが、本実施形態に係る連続鋳造用鋳型はスラブ鋳片の連続鋳造に限定されるものではなく、ブルーム鋳片やビレット鋳片の連続鋳造においても上記に沿って適用することができる。 Moreover, although the said description was performed regarding the continuous casting of slab slab, the casting mold for continuous casting according to the present embodiment is not limited to continuous casting of slab slab, but continuous casting of bloom slab or billet slab. Can be applied along the above.
中炭素鋼（化学成分、Ｃ：０．０８〜０．１７質量％、Ｓｉ：０．１０〜０．３０質量％、Ｍｎ：０．５０〜１．２０質量％、Ｐ：０．０１０〜０．０３０質量％、Ｓ：０．００５〜０．０１５質量％、Ａｌ：０．０２０〜０．０４０質量％）を、内壁面に種々の条件で異種物質充填部が設置された水冷式銅合金製鋳型または水冷式純銅製鋳型を用いて連続鋳造し、鋳造後のスラブ鋳片の表面割れを調査する試験を行った。用いた水冷式銅合金製鋳型または水冷式純銅製鋳型は、長辺長さが１．８ｍ、短辺長さが０．２２ｍの内面空間サイズを有する鋳型である。 Medium carbon steel (Chemical component, C: 0.08 to 0.17 mass%, Si: 0.10 to 0.30 mass%, Mn: 0.50 to 1.20 mass%, P: 0.010 to 0 0.030% by mass, S: 0.005 to 0.015% by mass, Al: 0.020 to 0.040% by mass), and a water-cooled copper alloy in which different-material-filled portions are installed on the inner wall surface under various conditions A continuous casting was performed using a mold or a water-cooled pure copper mold, and a test was conducted to investigate surface cracks in the slab slab after casting. The water-cooled copper alloy mold or the water-cooled pure copper mold used is a mold having an inner space size with a long side length of 1.8 m and a short side length of 0.22 m.
使用した水冷式銅合金製鋳型または水冷式純銅製鋳型の上端から下端までの長さは９５０ｍｍであり、定常鋳造時のメニスカス（鋳型内溶鋼湯面）の位置を、鋳型上端から１００ｍｍ下方位置に設定し、鋳型上端から６０ｍｍ下方の位置から、鋳型上端から４００ｍｍ下方の位置までの領域に異種物質充填部を配置した。 The length from the upper end to the lower end of the water-cooled copper alloy mold or water-cooled pure copper mold used is 950 mm, and the position of the meniscus (molten steel surface in the mold) during steady casting is positioned 100 mm below the upper end of the mold. The dissimilar substance filling portion was arranged in a region from a position 60 mm below the upper end of the mold to a position 400 mm below the upper end of the mold.
鋳型銅板としては、熱伝導率が７０〜３８０Ｗ／（ｍ×Ｋ）である純銅または銅合金を用い、異種物質充填部の充填金属または充填非金属としては、純ニッケル（熱伝導率；９０Ｗ／（ｍ×Ｋ））、コバルト（熱伝導率；６５Ｗ／（ｍ×Ｋ））、ロジウム（熱伝導率；１８０Ｗ／（ｍ×Ｋ））、バナジウム（熱伝導率；３０Ｗ／（ｍ×Ｋ））、パラジウム（熱伝導率；６０Ｗ／（ｍ×Ｋ））、タンタル（熱伝導率；５５Ｗ／（ｍ×Ｋ））、Ｎｉ−Ｃｏ（熱伝導率；６５Ｗ／（ｍ×Ｋ））、ジルコニウム（熱伝導率；１５Ｗ／（ｍ×Ｋ））、アンチモン（熱伝導率；２２Ｗ／（ｍ×Ｋ））、チタン（熱伝導率；２０Ｗ／（ｍ×Ｋ））、及び、銅合金（熱伝導率；１８０、３６０、３８０Ｗ／（ｍ×Ｋ））を使用した。 As the mold copper plate, pure copper or a copper alloy having a thermal conductivity of 70 to 380 W / (m × K) is used, and as the filling metal or the filling nonmetal of the dissimilar substance filling portion, pure nickel (thermal conductivity; (MxK)), cobalt (thermal conductivity: 65 W / (mxK)), rhodium (thermal conductivity: 180 W / (mxK)), vanadium (thermal conductivity: 30 W / (mxK)) ), Palladium (thermal conductivity: 60 W / (mxK)), tantalum (thermal conductivity: 55 W / (mxK)), Ni-Co (thermal conductivity: 65 W / (mxK)), zirconium (Thermal conductivity: 15 W / (mxK)), antimony (thermal conductivity: 22 W / (mxK)), titanium (thermal conductivity: 20 W / (mxK)), and copper alloy (thermal Conductivity; 180, 360, 380 W / (m × K)) was used.
異種物質充填部の設置後、鋳型銅板内壁面の全面に、Ｎｉ−Ｃｏ合金（熱伝導率；６５、６７Ｗ／（ｍ×Ｋ））、タングステン（熱伝導率；９０Ｗ／（ｍ×Ｋ））、チタン（熱伝導率；２０Ｗ／（ｍ×Ｋ））、Ｎｉ−Ｚｎ合金（熱伝導率；３０Ｗ／（ｍ×Ｋ））、タングステン（熱伝導率；２６０Ｗ／（ｍ×Ｋ））、Ｎｉ−Ｃｒ合金（熱伝導率；１０Ｗ／（ｍ×Ｋ））、金（熱伝導率；３００Ｗ／（ｍ×Ｋ））、Ａｇ−Ｃｕ（熱伝導率；３６０Ｗ／（ｍ×Ｋ））、ジルコニウム（熱伝導率；１６Ｗ／（ｍ×Ｋ））、ニオブ（熱伝導率；５０Ｗ／（ｍ×Ｋ））を鍍金し、鍍金層を施工した。 After installing the dissimilar material filling part, Ni—Co alloy (thermal conductivity: 65, 67 W / (m × K)), tungsten (thermal conductivity: 90 W / (m × K)) is formed on the entire inner wall surface of the mold copper plate. , Titanium (thermal conductivity: 20 W / (m × K)), Ni—Zn alloy (thermal conductivity: 30 W / (m × K)), tungsten (thermal conductivity: 260 W / (m × K)), Ni -Cr alloy (thermal conductivity: 10 W / (mxK)), gold (thermal conductivity: 300 W / (mxK)), Ag-Cu (thermal conductivity: 360 W / (mxK)), zirconium (Thermal conductivity: 16 W / (m × K)) and niobium (thermal conductivity: 50 W / (m × K)) were plated, and a plated layer was constructed.
連続鋳造終了後、鋳片表面の２１ｍ２以上の面積を染色浸透探傷検査によって検査し、１．０ｍｍ以上の長さの表面割れの個数を測定し、その総和を鋳片測定面積で除算して得られる鋳片表面割れ個数密度を用いて、表面割れの発生状況を評価した。 After completion of continuous casting, the surface area of 21 m 2 or more on the surface of the slab is inspected by dye penetration inspection, the number of surface cracks with a length of 1.0 mm or more is measured, and the sum is divided by the slab measurement area. The state of occurrence of surface cracks was evaluated using the obtained slab surface crack number density.
表１に、本発明例１〜１１、比較例１〜６及び従来例の連続鋳造鋳型における鋳型銅板の熱伝導率、充填金属または充填非金属の熱伝導率、鍍金層の熱伝導率及び厚み、鋳型冷却水の流量、スリットの総断面積などを示す。尚、比較例は、異種物質充填部を有する水冷式銅合金製鋳型であるものの、熱抵抗Ｒ及び比（λＣｕ／λｍａ）の範囲を満足しない条件で異種物質充填部を有する連続鋳造用鋳型で鋳造した試験、従来例は、異種物質充填部を有していない水冷式銅合金製鋳型を使用して鋳造した試験である。 Table 1 shows the thermal conductivity of the mold copper plate, the thermal conductivity of the filled metal or the filled nonmetal, the thermal conductivity and the thickness of the plated layer in the continuous casting molds of Invention Examples 1 to 11, Comparative Examples 1 to 6, and the conventional example. The flow rate of mold cooling water, the total cross-sectional area of the slit, etc. are shown. The comparative example is a water-cooled copper alloy mold having a foreign material filling portion, but for continuous casting having a foreign material filling portion under conditions that do not satisfy the ranges of the thermal resistance R and the ratio (λ Cu / λ ma ). The test cast with a mold, the conventional example, is a test cast using a water-cooled copper alloy mold that does not have a foreign substance filling portion.
また、図１１に、本発明例１〜１１、比較例１〜６及び従来例におけるスラブ鋳片の鋳片表面割れ個数密度を比較して示す。 Moreover, in FIG. 11, the slab surface crack number density of the slab slab in this invention examples 1-11, comparative examples 1-6, and a prior art example is compared and shown.
図１１からも明らかなように、本発明例１〜１１では、鋳片表面割れ個数密度はいずれも０．４個／ｍ２以下であり、鋳片の表面割れが抑制されることが確認できた。特に、比（λＣｕ／λｃｏａｔｉｎｇ）及び比（ＴＣｕ／Ｔｃｏａｔｉｎｇ）が好適な範囲であり、且つ、鋳型冷却水の流量が上記の（６）式または（７）式を満足する本発明例１〜４では、鋳片の表面割れが抑制されることが確認できた。 As is clear from FIG. 11, in Examples 1 to 11 of the present invention, the number density of slab surface cracks is 0.4 pieces / m 2 or less, and it can be confirmed that surface cracks of the slab are suppressed. It was. In particular, the present invention is such that the ratio (λ Cu / λ coating ) and the ratio (T Cu / T coating ) are in a suitable range, and the flow rate of the mold cooling water satisfies the above expression (6) or (7). In Examples 1 to 4, it was confirmed that surface cracking of the slab was suppressed.
これに対して、比較例１〜６は、従来例に比べると鋳片の表面割れは減少したが、本発明例１〜１１に比較すると鋳片表面割れが多発した。 On the other hand, in Comparative Examples 1 to 6, although the surface cracks of the slab were reduced as compared with the conventional examples, the slab surface cracks occurred frequently as compared with Examples 1 to 11 of the present invention.
１ 鋳型長辺銅板
２ 円形凹溝
３ 異種物質充填部
４ スリット
５ バックプレート
６ 鍍金層
DESCRIPTION OF SYMBOLS 1 Mold long side copper plate 2 Circular groove 3 Dissimilar substance filling part 4 Slit 5 Back plate 6 Sheet metal layer
Claims (5)
前記異種物質充填部の設置位置における鋳型銅板表面と鋳型冷却水の流路である鋳型銅板のスリットとの間の熱抵抗が下記の（１）式の範囲であり、且つ、鋳型銅板の熱伝導率と銅合金製鋳型銅板の内壁面に充填される金属または非金属の熱伝導率との比が下記の（２）式または（３）式の範囲である異種物質充填部を有する連続鋳造用鋳型を用い、鋳型銅板の熱伝導率、異種物質充填部の熱伝導率、及び鋳型銅板のスリットの総断面積に応じて、鋳型冷却水の流量が下記の（６）式または（７）式を満足するように、鋳型冷却水の流量を制御して溶鋼を連続鋳造することを特徴とする、鋼の連続鋳造方法。
１．０×１０−５＜Ｒ＜６．０×１０−４・・・（１）
０．２＜λＣｕ／λｍａ＜１．０・・・（２）
１．０＜λＣｕ／λｍａ＜２０．０・・・（３）
３＜（Ｑ／Ｓ）×（λ Ｃｕ ／λ ｍａ ）＜１５０（但し、λ Ｃｕ ＞λ ｍａ ）・・・（６）
３＜（Ｑ／Ｓ）×（λ ｍａ ／λ Ｃｕ ）＜１２０（但し、λ Ｃｕ ＜λ ｍａ ）・・・（７）
但し、（１）式において、Ｒは鋳型銅板表面と鋳型銅板のスリットとの間の熱抵抗（ｍ２×Ｋ／Ｗ）であり、また、（２）式及び（３）式において、λＣｕは鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、λｍａは銅合金製鋳型銅板の内壁面に充填される金属または非金属の熱伝導率（Ｗ／（ｍ×Ｋ））であり、
（６）式及び（７）式において、Ｑは鋳型冷却水の流量（ｍ ３ ／ｓｅｃ）、Ｓは鋳型銅板のスリットの総断面積（ｍ ２ ）、λ Ｃｕ は鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、λ ｍａ は異種物質充填部の熱伝導率（Ｗ／（ｍ×Ｋ））である。 Plural in which recesses on the inner wall surface of the copper alloy mold copper plate in the area including at least the meniscus of the inner wall surface of the water-cooled copper alloy mold are filled with a metal or non-metal having a thermal conductivity different from the thermal conductivity of the mold copper plate A mold for continuous casting having a different substance filling portion of
The thermal resistance between the surface of the mold copper plate at the position where the dissimilar substance filling portion is installed and the slit of the mold copper plate which is the flow path of the mold cooling water is in the range of the following formula (1), and the heat conduction of the mold copper plate For continuous casting having a different material filling portion in which the ratio of the thermal conductivity of metal or nonmetal filled in the inner wall surface of the copper alloy mold copper plate is within the range of the following formula (2) or (3) Depending on the thermal conductivity of the mold copper plate, the thermal conductivity of the dissimilar substance filling part, and the total cross-sectional area of the slit of the mold copper plate, the mold cooling water flow rate is the following formula (6) or (7) In order to satisfy the above, a continuous casting method of steel, wherein the molten steel is continuously cast by controlling the flow rate of the mold cooling water.
1.0 × 10 −5 <R <6.0 × 10 −4 (1)
0.2 <λ Cu / λ ma <1.0 (2)
1.0 <λ Cu / λ ma <20.0 (3)
3 <(Q / S) × (λ Cu / λ ma ) <150 (provided that λ Cu > λ ma ) (6)
3 <(Q / S) × (λ ma / λ Cu ) <120 (provided that λ Cu <λ ma ) (7)
However, in the formula (1), R is the thermal resistance (m 2 × K / W) between the surface of the mold copper plate and the slit of the mold copper plate, and in the formulas (2) and (3), λ Cu Is the thermal conductivity (W / (m × K)) of the mold copper plate, and λ ma is the thermal conductivity (W / (m × K)) of the metal or non-metal filled in the inner wall surface of the copper alloy mold copper plate. Oh it is,
In the formulas (6) and (7), Q is the flow rate of the mold cooling water (m 3 / sec), S is the total cross-sectional area (m 2 ) of the slit of the mold copper plate , and λ Cu is the thermal conductivity of the mold copper plate ( W / (m × K)), λ ma is the thermal conductivity (W / (m × K)) of the dissimilar substance-filled portion.
０．５＜λＣｕ／λｃｏａｔｉｎｇ＜１５．０・・・（４）
４．０＜ＴＣｕ／Ｔｃｏａｔｉｎｇ＜２５０．０・・・（５）
但し、（４）式において、λＣｕは鋳型銅板の熱伝導率（Ｗ／（ｍ×Ｋ））、λｃｏａｔｉｎｇは鍍金層の熱伝導率（Ｗ／（ｍ×Ｋ））であり、また、（５）式において、ＴＣｕは鋳型銅板の厚みであって、具体的には鋳型銅板表面と鋳型銅板のスリットの底との間の距離（ｍ）、Ｔｃｏａｔｉｎｇは鍍金層の厚み（ｍ）である。 On the inner wall surface of the mold copper plate, the thermal conductivity of the plating layer satisfies the following formula (4) with respect to the thermal conductivity of the mold copper plate, and the thickness of the plating layer is as follows with respect to the thickness of the mold copper plate: 5. The plating layer satisfying the formula (5) is formed, and the different substance filling portion is covered with the plating layer. 5. Steel continuous casting method.
0.5 <λ Cu / λ coating <15.0 (4)
4.0 <T Cu / T coating <250.0 (5)
However, in Formula (4), λ Cu is the thermal conductivity (W / (m × K)) of the mold copper plate, λ coating is the thermal conductivity of the plating layer (W / (m × K)), and In Equation (5), T Cu is the thickness of the mold copper plate, specifically, the distance (m) between the surface of the mold copper plate and the bottom of the slit of the mold copper plate, and T coating is the thickness of the plating layer (m). It is.
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