JP4209737B2 - Cooling method for continuous casting bloom - Google Patents

Cooling method for continuous casting bloom Download PDF

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JP4209737B2
JP4209737B2 JP2003278915A JP2003278915A JP4209737B2 JP 4209737 B2 JP4209737 B2 JP 4209737B2 JP 2003278915 A JP2003278915 A JP 2003278915A JP 2003278915 A JP2003278915 A JP 2003278915A JP 4209737 B2 JP4209737 B2 JP 4209737B2
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bloom
cooling
water
continuous casting
cooler
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潔 川上
晴之 下口
康英 大塲
真一 北出
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Sanyo Special Steel Co Ltd
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Description

連続鋳造により鋳造されたブルームの表面疵欠陥を低減する方法   Method for reducing surface flaw defects in blooms cast by continuous casting

連続鋳造により鋳造されたブルームをブルームクーラー設備によって冷却する方法及び条件はすでに出願人により出願されて開示されている（特許文献１、特許文献２参照）。しかし、ブルームクーラー設備によってブルームを冷却する際は、図１に示す如くブルーム下面側が搬送ロールによって冷却水の噴流が遮られ冷却水が届いていない箇所が発生する。そのため冷却水が届いていない箇所は、周りが冷却されることにより徐々に冷却されていくが、上記の特許文献２で規定されている冷却スピード１０〜３００℃／ｓより遅いスピードで冷却されるため、ブルームクーラー注水の目的であるフェライト・パーライト結晶粒径の微細化が行われておらず、フェライト粒界を起点として圧延時に疵が発生する。   A method and conditions for cooling a bloom cast by continuous casting with a bloom cooler facility have already been filed and disclosed by the applicant (see Patent Document 1 and Patent Document 2). However, when the bloom is cooled by the bloom cooler facility, as shown in FIG. 1, a part where the cooling water jet is blocked by the conveying roll on the lower surface side of the bloom is not generated. Therefore, the part where the cooling water does not reach is gradually cooled by cooling the surroundings, but is cooled at a speed slower than the cooling speed of 10 to 300 ° C./s defined in Patent Document 2 above. For this reason, the ferrite / pearlite crystal grain size, which is the purpose of water injection of the bloom cooler, has not been reduced, and wrinkles are generated during rolling starting from the ferrite grain boundary.

特開平１０−１７１９号公報Japanese Patent Laid-Open No. 10-1719 特開平０９−２０６８９９号公報JP 09-206899 A

連続鋳造装置において連続鋳造され引き抜かれた連続鋳造片をブルームに切断後、連続鋳造装置からブルームクーラー設備に装入し、ブルームの表面温度をＡｒ3変態点以下に冷却して表面疵の発生を防止する。しかし、ブルームクーラー内で冷却する場合、ブルーム下面側は、搬送用ロールにより冷却水の噴流が遮られ十分な冷却が行われない。このためブルーム下面は十分な表面疵の発生防止の効果が得られていない。 After the continuous cast piece that has been continuously cast and pulled out in the continuous casting machine is cut into bloom, it is inserted into the bloom cooler equipment from the continuous casting machine, and the surface temperature of the bloom is cooled below the Ar 3 transformation point to generate surface defects. To prevent. However, when cooling in the bloom cooler, the lower surface side of the bloom is not cooled sufficiently because the jet of cooling water is blocked by the transfer roll. For this reason, the bloom lower surface is not sufficiently effective in preventing the occurrence of surface flaws.

そこで、本発明はブルームクーラーのブルーム下面側で、冷却水が搬送ロールにより遮られることにより噴流が届いていない箇所を解消することで、ブルーム下面側においても出願人が開示の特許文献２で規定しているＡｒ3変態点より５０℃高い温度から、冷却スピード１０〜３００℃／ｓで冷却することができる方法を提供することである。 Therefore, the present invention eliminates the location where the jet flow does not reach due to the cooling water being blocked by the conveying roll on the lower surface side of the bloom cooler, and the patent document 2 disclosed by the applicant also discloses the lower surface side of the bloom cooler. It is to provide a method capable of cooling at a cooling speed of 10 to 300 ° C./s from a temperature 50 ° C. higher than the Ar 3 transformation point.

上記の課題を解決するための本発明の手段は、請求項１の発明では、連続鋳造により鋳造されたブルームを所定の長さに切断した後、連続鋳造機外に設置されたブルームクーラーを用いてブルームをＡｒ3変態点〜Ａｒ 3 変態点＋５０℃の温度領域からＭｆ変態点以下まで冷却する際、ブルームクーラー内のブルームの移動速度を３〜１０ｍ／ｍｉｎにし、ブルーム上面の水量密度を５×１０ -4 〜４×１０ -3 ／ｓｍ 2 、側面の水量密度を上面の水量密度の１．５倍以上、下面の水量密度を上面の水量密度の２．０倍以上にすることにより、ブルーム下面からの冷却水の噴流がブルームを保持搬送する搬送ロールに遮られることなくブルーム下面を均一にかつ所定の冷却スピード１０〜３００℃／ｓを確保して冷却することを特徴とする連続鋳造ブルームの冷却方法である。 The means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, a bloom cooler installed outside the continuous casting machine is used after the bloom cast by continuous casting is cut to a predetermined length. upon cooling the bloom from the temperature region of Ar 3 transformation point to Ar 3 transformation point + 50 ℃ to below Mf transformation point Te, the speed of movement of the bloom in bloom cooler to 3 to 10 m / min, the water density of the bloom top 5 × 10 −4 to 4 × 10 −3 / sm 2 , by setting the water density on the side to 1.5 times or more of the water density on the upper surface and the water density on the lower surface to 2.0 or more times the water density on the upper surface. The continuous flow is characterized in that the jet of cooling water from the lower surface of the bloom is cooled by securing the predetermined cooling speed of 10 to 300 ° C./s without being interrupted by the transport roll for holding and transporting the bloom. casting Bloom cooling method.

すなわち、ブルームクーラーで冷却中にブルームを移動させることにより、搬送ロールによる冷却水の噴流が遮られている箇所をスプレー直上まで移動させながら注水による冷却を行う。この時、ブルームを移動させる速度は３〜１０ｍ／ｍｉｎである。注水時間に対し注水ゾーンが短くブルームクーラーからブルームが出てしまう場合には、ブルームクーラーでブルームを往復させて注水を継続するものである。 That is, by moving the bloom during cooling by the bloom cooler, cooling is performed by pouring water while moving the portion where the jet of cooling water by the transport roll is blocked to just above the spray. At this time, the speed at which the bloom is moved is 3 to 10 m / min . When the water injection zone is short with respect to the water injection time and the bloom comes out of the bloom cooler, the bloom is reciprocated by the bloom cooler to continue the water injection.

すなわち、
ブルームクーラー内での冷却中の移動スピードを従来の方法の移動スピード０．４ｍ／ｍｉｎを３〜１０ｍ／ｍｉｎの範囲、例えば５ｍ／ｍｉｎに上昇することにより、ブルーム下面全面の均一冷却化を図るものである。このようにすることで本発明は搬送ロールは凹型ロールの場合でも適用可能である。 That is,
By increasing the moving speed during cooling in the bloom cooler from the moving speed of 0.4 m / min in the conventional method to a range of 3 to 10 m / min, for example, 5 m / min, uniform cooling of the entire lower surface of the bloom is achieved. Is. By doing in this way, this invention is applicable even when a conveyance roll is a concave roll.

ブルーム下面の表面組織はブルーム全長においてベイナイト変態しており、中間製品であるφ１６７ｍｍ径の鋼片の表面欠陥が約５０％低減し、品質向上を図ることができた。すなわち、表面疵が低減することで疵取り手入れが減少し、生産性向上及びコストダウンが図れる。   The surface structure of the lower surface of the bloom was bainite transformed over the entire length of the bloom, and the surface defects of the 167 mm diameter steel slab, which is an intermediate product, were reduced by about 50%, and the quality could be improved. In other words, the reduction of surface wrinkles reduces the wrinkle care, thereby improving productivity and reducing costs.

ブルームクーラー１内で冷却水パイプ４を通じて冷却水ノズル５から噴流領域への冷却水６の注水時にブルーム２を搬送ロール３により移動速度５ｍ／ｍｉｎで、ブルームクーラー１の入口とブルームクーラー１の出口間を約３分間往復移動させる。注水量については、ブルーム２の上面の水量密度を５×１０-4〜４×１０-3／ｓｍ2、側面の水量密度を上面の水量密度の１．５倍以上とし、下面の水量密度を上面の水量密度の２倍以上にして注水して冷却を行うものである。 When the cooling water 6 is injected from the cooling water nozzle 5 into the jet region through the cooling water pipe 4 in the bloom cooler 1, the bloom 2 is moved by the transfer roll 3 at a moving speed of 5 m / min, and the inlet of the bloom cooler 1 and the outlet of the bloom cooler 1 Move back and forth for about 3 minutes. About the amount of water injection, the water volume density on the upper surface of the bloom 2 is 5 × 10 −4 to 4 × 10 −3 / sm 2 , the water volume density on the side surface is 1.5 times the water volume density on the upper surface, and the water volume density on the lower surface is Cooling is performed by injecting water with a water density of at least twice the upper surface.

ブルームクーラー１は所定の温度範囲（Ａｒ3変態点〜Ａｒ3変態点＋５０℃）から冷却を開始し、冷却速度１０〜３００℃／ｓでＭｆ変態点以下まで冷却することで表面疵低減の効果が得られる。本発明はブルームクーラー１内でのブルーム２の移動速度を上げることにより搬送ロール３上のブルーム下面部分がＡｒ3変態点以下になるまでにスプレー直上にブルームを移動させることで、表面疵の改善効果を得る方法である。 Bloom cooler 1 starts cooling from a predetermined temperature range (Ar 3 transformation point to Ar 3 transformation point + 50 ° C.), and cools to below the Mf transformation point at a cooling rate of 10 to 300 ° C./s to reduce surface defects. Is obtained. The present invention improves surface wrinkles by increasing the moving speed of the bloom 2 in the bloom cooler 1 and moving the bloom immediately above the spray until the lower surface of the bloom on the transport roll 3 falls below the Ar 3 transformation point. It is a method of obtaining an effect.

連続鋳造機によって鋳造された３８０×４９０ｍｍ×長さ４０００ｍｍのＣ：０．２０質量％含有の機械構造用鋼（ＳＣｒ４２０）からなるブルーム２において、ブルームクーラー１内を移動速度５ｍ／ｍｉｎで往復移動させながら冷却水パイプ４を通じて冷却水ノズル５から注水して冷却した結果、その後の圧延による中間製品であるφ１６７ｍｍ鋼片の軸通磁気探傷機で０．２ｍｍ以上の有害な表面疵の個数を検出したところ、その個数比率が約５０％低減した。また、図２の（ａ）に示す如くブルーム下面を切り出してその表面組織を顕微鏡で観察したところ、この部位はベイナイト組織７であり、ブルーム下面の全長にわたりベイナイト変態していることも確認された。これに対し、従来のブルームクーラー１内を移動速度０．４ｍ／ｍｉｎで搬送されるものは、図２の（ｂ）に示す如く搬送ロール３の影となる部分はフェライト相とパーライト相の混合組織８となり、この結果、表面欠陥は本発明の方法の約２倍であった。   In Bloom 2 made of machine structural steel (SCr420) containing 380 x 490 mm x 4000 mm long C: 0.20 mass% cast by a continuous casting machine, reciprocatingly moves in the bloom cooler 1 at a moving speed of 5 m / min. As a result, water was injected from the cooling water nozzle 5 through the cooling water pipe 4 and cooled. As a result, the number of harmful surface defects of 0.2 mm or more was detected by an axial magnetic flaw detector with a φ167 mm steel piece that was an intermediate product by subsequent rolling. As a result, the number ratio was reduced by about 50%. Further, as shown in FIG. 2 (a), the lower surface of the bloom was cut out and the surface structure was observed with a microscope. As a result, this portion was a bainite structure 7, and it was confirmed that the bainite transformation was performed over the entire length of the lower surface of the bloom. . On the other hand, as shown in FIG. 2 (b), the shaded part of the transport roll 3 is a mixture of ferrite phase and pearlite phase as shown in FIG. As a result, the surface defect was about twice that of the method of the present invention.

ブルームクーラーにおけるブルーム注水時の状態を示す図である。It is a figure which shows the state at the time of bloom water injection in a bloom cooler. 搬送ロール直上のブルームのミクロ組織を模式的に示す図で（ａ）は本発明の適用材、（ｂ）は従来材である。It is a figure which shows typically the microstructure of the bloom just above a conveyance roll, (a) is the application material of this invention, (b) is a conventional material.

符号の説明Explanation of symbols

１ ブルームクーラー
２ ブルーム
３ 搬送ロール
４ 冷却水パイプ
５ 冷却水ノズル
６ 冷却水
７ ベイナイト組織
８ フェライト相とパーライト相の混合組織 DESCRIPTION OF SYMBOLS 1 Bloom cooler 2 Bloom 3 Conveyance roll 4 Cooling water pipe 5 Cooling water nozzle 6 Cooling water 7 Bainite structure 8 Mixed structure of ferrite phase and pearlite phase

Claims (1)

連続鋳造により鋳造されたブルームを所定の長さに切断した後、連続鋳造機外に設置されたブルームクーラーを用いてブルームをＡｒ3変態点〜Ａｒ 3 変態点＋５０℃の温度領域からＭｆ変態点以下まで冷却する際、ブルームクーラー内のブルームの移動速度を３〜１０ｍ／ｍｉｎにし、ブルーム上面の水量密度を５×１０ -4 〜４×１０ -3 ／ｓｍ 2 、側面の水量密度を上面の水量密度の１．５倍以上、下面の水量密度を上面の水量密度の２．０倍以上にすることにより、ブルーム下面からの冷却水の噴流がブルームを保持搬送する搬送ロールに遮られることなく、ブルーム下面を均一にかつ所定の冷却スピード１０〜３００℃／ｓを確保して冷却することを特徴とする連続鋳造ブルームの冷却方法。 After cutting the bloom, which is cast by continuous casting into a predetermined length, Mf transformation bloom with Bloom cooler installed outside the apparatus the continuous casting from the temperature range of Ar 3 transformation point to Ar 3 transformation point + 50 ℃ When cooling to below , the bloom moving speed in the bloom cooler is 3 to 10 m / min, the water density on the bloom top surface is 5 × 10 −4 to 4 × 10 −3 / sm 2 , and the water density on the side surface is the top surface. By making the water volume density of 1.5 times or more and the water volume density of the lower surface 2.0 times or more of the water volume density of the upper surface, the jet of cooling water from the lower surface of the bloom is blocked by the transport roll that holds and transports the bloom. The cooling method of the continuous casting bloom characterized by cooling a bloom lower surface uniformly and ensuring predetermined cooling speed 10-300 degrees C / s .
JP2003278915A 2003-07-24 2003-07-24 Cooling method for continuous casting bloom Expired - Lifetime JP4209737B2 (en)

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JP5402790B2 (en) * 2010-04-01 2014-01-29 新日鐵住金株式会社 Method for cooling continuous cast bloom slab and method for manufacturing the slab
JP6053628B2 (en) * 2013-07-19 2016-12-27 株式会社神戸製鋼所 Slab cooling method
WO2016114208A1 (en) 2015-01-15 2016-07-21 新日鐵住金株式会社 Continuous casting method for slab

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