JP2000233266A - Production of steel plate having good surface characteristic - Google Patents
Production of steel plate having good surface characteristicInfo
- Publication number
- JP2000233266A JP2000233266A JP11036290A JP3629099A JP2000233266A JP 2000233266 A JP2000233266 A JP 2000233266A JP 11036290 A JP11036290 A JP 11036290A JP 3629099 A JP3629099 A JP 3629099A JP 2000233266 A JP2000233266 A JP 2000233266A
- Authority
- JP
- Japan
- Prior art keywords
- slab
- cooling
- heating furnace
- charging
- cracks
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Continuous Casting (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、熱片装入による鋼
板の製造において、省エネルギー性に優れ、かつ表面割
れの発生のない表面性状の良好な鋼板の製造方法に関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel sheet which is excellent in energy saving and has good surface properties without occurrence of surface cracks in the production of a steel sheet by charging a hot strip.
【０００２】[0002]
【従来の技術】鋼板の製造にあたり、連続鋳造後のスラ
ブ温度を極力下げずに加熱炉に装入する熱片装入圧延(H
CR：Hot Charge Rolling)は、生産効率の向上効果の
みならず、スラブの持つ熱エネルギーの有効利用による
加熱炉原単位向上など、省エネルギーの観点からも望ま
しい技術である。さらに連続鋳造後、加熱炉装入を経ず
にそのまま熱間圧延を行う直送圧延(HDR：Hot Direct
Rolling)の開発も進められている。2. Description of the Related Art In the production of steel sheets, hot strip charging (H), which is charged into a heating furnace without lowering the slab temperature after continuous casting as much as possible.
CR (Hot Charge Rolling) is a technology that is desirable not only from the viewpoint of improving production efficiency, but also from the viewpoint of energy saving, such as improving the furnace unit consumption by effectively utilizing the heat energy of the slab. Furthermore, after continuous casting, hot-rolling (HDR: Hot Direct), in which hot rolling is performed without charging the heating furnace
Rolling) is also under development.
【０００３】一方、連続鋳造によるスラブの製造、及び
その後の熱間圧延工程において、表面割れなどの表面欠
陥を生じる場合がある。特に、熱片装入圧延技術（以下
ＨＣＲと略す）、あるいは直送圧延技術（以下ＨＤＲと
略す）を用いると、表面欠陥が発生し易いことが報告さ
れており、鋼種によってはＨＣＲ、ＨＤＲを行った場合
に表面欠陥の抑止が困難な場合がある。On the other hand, in the production of a slab by continuous casting and the subsequent hot rolling step, surface defects such as surface cracks may occur. In particular, it has been reported that surface defects are likely to occur when using a hot strip charging / rolling technology (hereinafter abbreviated as HCR) or a direct-feed rolling technology (hereinafter abbreviated as HDR). In some cases, it is difficult to suppress surface defects.
【０００４】表面欠陥には、大きく分けて鋳造性の割れ
と圧延性の割れがある。前者は、連続鋳造においてスラ
ブの段階で割れを生じる場合であり、含Ｎｂ，Ｖ鋼等の
横割れ、コーナー割れが代表的である。これは、ロール
間バルジングや曲げ矯正における低歪速度の変形によっ
て生じる割れであり、二次冷却帯域における冷却水量の
適正化、矯正点温度の管理等の対策が行われている。[0004] Surface defects are roughly divided into castability cracks and rollability cracks. The former is a case where cracks occur at the stage of slab in continuous casting, and are typically horizontal cracks and corner cracks of Nb-containing and V steel-containing steels. This is a crack caused by deformation at a low strain rate in roll bulging or bending straightening, and measures such as optimization of the amount of cooling water in the secondary cooling zone and management of the straightening point temperature have been taken.
【０００５】一方、後者は圧延により割れが生じる場合
であり、高歪速度による加工時に何らかの起点から割れ
が進展し、大きな深い割れに至るものである。特に、Ｈ
ＣＲを行った場合に生じる割れは、圧延初期に発生し、
圧延後の鋼板表面に大きな割れとして残る場合が多く、
製品歩留の著しい低下を招いている。[0005] On the other hand, the latter is a case where cracks are generated by rolling, and during processing at a high strain rate, cracks develop from some starting point, leading to large deep cracks. In particular, H
Cracks that occur when CR is performed occur at the beginning of rolling,
In many cases, large cracks remain on the steel sheet surface after rolling,
This leads to a significant decrease in product yield.
【０００６】ＨＣＲを行った場合の圧延割れの進展を抑
制するためには、熱片装入材において特徴的な表層近傍
の粗大なオーステナイト粒を微細化することが効果的で
あり、それが表層の冷却に伴う変態と、その後の再加熱
による逆変態によって達成されることが知られている。
例えば、特開平５−３２９５０５号公報には、スラブの
表層部を３５０℃〜５００℃の温度に１分以上冷却、保
持を行って、表層部を変態させた後、再加熱して圧延を
行うことによる低合金鋼の表面割れ防止方法が開示され
ている。特に、Ｃｒ，Ｎｉ，Ｍｏの１種以上が含有され
ている低合金鋼の場合には、５００℃〜６８０℃の温度
域に表層を冷却しても短時間で変態が終了しないため、
３５０℃〜５００℃の温度に冷却する方法が有効である
旨、記載されている。In order to suppress the development of rolling cracks when HCR is performed, it is effective to refine coarse austenite grains near the surface layer, which is characteristic of the hot strip charging material. It is known that the transformation is achieved by the transformation accompanied by cooling and subsequent reverse transformation by reheating.
For example, Japanese Patent Application Laid-Open No. 5-329505 discloses that the surface layer of a slab is cooled and held at a temperature of 350 ° C. to 500 ° C. for 1 minute or more to transform the surface layer, and then rolled by reheating. Thus, a method for preventing surface cracking of low alloy steel is disclosed. In particular, in the case of a low alloy steel containing at least one of Cr, Ni, and Mo, the transformation is not completed in a short time even if the surface layer is cooled to a temperature range of 500 ° C to 680 ° C.
It is described that a method of cooling to a temperature of 350 ° C to 500 ° C is effective.
【０００７】[0007]
【発明が解決しようとする課題】従来知見のとおり、Ｈ
ＣＲを行う場合、表層近傍を冷却により変態させ、その
後の再加熱による逆変態と併せてオーステナイト粒を微
細化することは、表面割れ発生の抑制に効果的である。
しかし、スラブの過大な冷却はスラブ自体の温度低下を
招き、熱片装入による省エネルギー効果を損なう。この
ため、スラブの温度低下を最小限に抑え、スラブ表層の
みが変態するように、冷却方法を最適化する必要があ
る。SUMMARY OF THE INVENTION As previously known, H
When performing CR, transforming the vicinity of the surface layer by cooling and refining the austenite grains together with the reverse transformation by subsequent reheating are effective in suppressing the occurrence of surface cracks.
However, excessive cooling of the slab causes a decrease in the temperature of the slab itself, and impairs the energy saving effect of charging the hot strip. For this reason, it is necessary to optimize the cooling method so that the temperature drop of the slab is minimized and only the surface layer of the slab is transformed.
【０００８】スラブ冷却方法について、前記特開平５−
３２９５０５号公報（以下従来技術）では、スラブの表
面温度測定により冷却条件を制御している。すなわち、
水スプレーによる強制冷却で、スラブ表面温度が500℃
になった時から、冷却を停止して復熱により表面が再び
500℃に達するまでの時間を１分以上、好ましくは１０
分以下と規定している。The slab cooling method is disclosed in
In Japanese Patent No. 329505 (hereinafter referred to as "prior art"), cooling conditions are controlled by measuring the surface temperature of a slab. That is,
Slab surface temperature 500 ℃ by forced cooling with water spray
When it becomes cold, the cooling is stopped and the surface is re-
The time to reach 500 ° C. is 1 minute or more, preferably 10 minutes.
Minutes or less.
【０００９】この従来技術の方法では、冷却停止につい
ての規定がなく、冷却した結果としての復熱までの時間
を規定しているため、一定条件での冷却が困難であると
ともに、スラブ自体の温度低下を最小限に抑え得る方法
とは言い難い。また、スラブの表面温度測定は、一般的
に放射温度形による表面の一部分の測定であるため、冷
却が不均一な場合には、場所によって表面温度にバラツ
キが生じ、変態が完了した部分と完了していない部分が
存在してしまう。In this prior art method, since there is no provision for stopping cooling and the time until reheating as a result of cooling is prescribed, it is difficult to cool under constant conditions and the temperature of the slab itself is reduced. It is hard to say that it is possible to minimize the decrease. In addition, since the surface temperature measurement of a slab is generally a measurement of a part of the surface using a radiation temperature type, if the cooling is not uniform, the surface temperature will vary depending on the location, and the part where the transformation is completed and the part where the transformation is completed There are parts that have not been done.
【００１０】また、スラブを冷却することによって表層
近傍を変態させ、さらに復熱あるいは再加熱によって逆
変態させるという熱サイクルを複数回繰り返すと、スラ
ブ表層近傍の変態部直下にフィルム状フェライトなどが
生成するため、スラブ表層には割れは無いが、その後の
圧延で表層下に割れを生じ、表面に割れが開口する、い
わゆる表層下割れが発生することも知られている。[0010] When the slab is cooled, the vicinity of the surface layer is transformed, and the heat cycle of reverse transformation by reheating or reheating is repeated a plurality of times. As a result, film-like ferrite or the like is formed immediately below the transformed part near the slab surface layer. Therefore, it is also known that there is no crack in the surface layer of the slab, but cracks occur below the surface layer in the subsequent rolling, so that cracks are opened on the surface, so-called cracks under the surface layer.
【００１１】本発明は、上記課題を解決するためになさ
れたもので、ＨＣＲによる鋼板の製造において、スラブ
冷却時の水量密度と冷却時間を制御することにより、冷
却条件を一定とし、かつ冷却を均一としてスラブ自体の
温度低下を抑え、このことのより、加熱炉原単位向上に
よる省エネルギー効果に優れ、かつ表面割れの発生の無
い表面性状の良好な鋼板を製造することを目的とする。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In the production of a steel plate by HCR, the cooling condition is kept constant by controlling the water density and cooling time during slab cooling. An object of the present invention is to manufacture a steel sheet having excellent surface properties without causing surface cracks and having excellent energy saving effect by improving the heating furnace basic unit, by suppressing the temperature drop of the slab itself as uniform.
【００１２】[0012]
【課題を解決するための手段】本発明の特徴とするとこ
ろは、スラブ表層の冷却による表面割れ抑制方法を冷却
条件の観点から規定した点であり、以下に示すとおりで
ある。The feature of the present invention is that a method for suppressing surface cracks by cooling the surface layer of a slab is specified from the viewpoint of cooling conditions, and is as follows.
【００１３】すなわち、連続鋳造における二次冷却帯曲
げ矯正終了点以降、スラブに対して1000リットル／m2mi
n.以上の水量密度の水冷を、１５秒以上６０秒以下行
い、復熱させる熱サイクルを１回行ってから、加熱炉に
装入して圧延することを特徴とする、表面性状の良好な
鋼板の製造方法である。That is, 1000 liters / m 2 mi with respect to the slab after the end point of secondary cooling zone bending straightening in continuous casting.
n. water cooling at a water density of not less than 15 seconds to 60 seconds, and a heat cycle for recuperation is performed once, and then the material is charged into a heating furnace and rolled. This is a method for manufacturing a steel sheet.
【００１４】[0014]
【発明の実施の形態】以下、本発明に係わる鋼板の製造
方法を詳細に説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a steel sheet according to the present invention will be described in detail.
【００１５】ＨＣＲによる鋼板、特に板厚6mm以上の厚
鋼板の製造では、連続鋳造にてスラブを製造した後、極
力スラブ温度を下げないように、短時間で加熱炉に装入
して熱間圧延を行う。本発明では、連続鋳造後、前記表
面割れを防止するため、連続鋳造における二次冷却帯曲
げ矯正終了点以降、厚板加熱炉装入までの間に、スラブ
冷却を行う。In the production of steel sheets by the HCR, especially steel sheets having a thickness of 6 mm or more, after the slab is manufactured by continuous casting, it is charged into a heating furnace in a short time so that the slab temperature is not reduced as much as possible. Perform rolling. In the present invention, after continuous casting, in order to prevent the surface cracks, slab cooling is performed after the secondary cooling zone bending straightening end point in continuous casting and before charging the thick plate heating furnace.
【００１６】本発明におけるスラブ冷却は、ノズルジェ
ットなどの水流方式を用いて行う。水冷の際の水量密度
は、本発明の重要な因子である。すなわち、水量密度が
1000リットル／m2min.より少ないと、鋼板表面に形成さ
れる蒸気膜等の影響により冷却能が複雑に変動し、冷却
が不均一になり易い。その結果、割れの生じる領域と生
じない領域が分布して存在するような鋼板になる場合が
ある。The slab cooling in the present invention is performed by using a water flow system such as a nozzle jet. Water mass density during water cooling is an important factor of the present invention. That is, the water density
If it is less than 1000 liters / m 2 min., The cooling capacity fluctuates complicatedly due to the influence of a vapor film or the like formed on the surface of the steel sheet, and the cooling tends to be uneven. As a result, there may be a case where the steel sheet has a region where cracks occur and a region where cracks do not occur.
【００１７】水量密度を1000リットル／m2min.以上とす
ると、冷却はスラブ中の熱伝導律速となるため、冷却能
は水量密度にあまり依存しなくなる。したがって、操業
中に若干の水量密度のバラツキが生じたとしても、再加
熱後のスラブ表層近傍に存在する微細オーステナイト組
織層の厚さは均一となる。よって、水量密度は1000リッ
トル／m2min.以上とする。When the water density is 1000 liters / m 2 min. Or more, cooling is limited by heat conduction in the slab, so that the cooling capacity does not depend much on the water density. Therefore, even if a slight variation in the water density occurs during the operation, the thickness of the fine austenite structure layer existing near the slab surface layer after reheating becomes uniform. Therefore, the water density is set to 1000 liter / m 2 min. Or more.
【００１８】また、この冷却は、連続鋳造における二次
冷却帯曲げ矯正終了点以降に行わなければならない。二
次冷却帯曲げ矯正終了点より前では、矯正による曲げ応
力によって鋳造割れを起こし易いためである。This cooling must be performed after the end point of secondary cooling zone bending correction in continuous casting. This is because casting cracks are likely to occur before the secondary cooling zone bending correction end point due to bending stress caused by the correction.
【００１９】上記冷却を１５秒以上行わないと、圧延割
れの発生を抑えるのに十分な厚さのスラブ表層近傍の微
細オーステナイト組織層を得ることができない。また、
６０秒以上行うと、スラブの平均温度の低下が大きく、
熱片装入による加熱炉原単位向上効果を損なう。したが
って、冷却時間は１５秒以上、６０秒以下とする。If the cooling is not performed for 15 seconds or more, a fine austenite structure layer near the surface of the slab having a thickness sufficient to suppress the occurrence of rolling cracks cannot be obtained. Also,
If performed for 60 seconds or more, the average temperature of the slab will drop significantly,
Impairs the effect of improving the unit consumption of the heating furnace by charging the heating piece. Therefore, the cooling time is 15 seconds or more and 60 seconds or less.
【００２０】冷却、復熱の熱サイクルは１回のみとす
る。複数回繰り返すと、スラブ表層近傍の変態部直下に
フィルム状フェライトなどが生成するため、表層下割れ
が発生する。また、スラブ自体の温度低下を招き、省エ
ネルギー効果を損ねてしまう。本発明では、１回の熱サ
イクルで、表面割れ抑制に必要な微細オーステナイト組
織層を均一に生成可能である。The heat cycle of cooling and recuperation is performed only once. If the process is repeated a plurality of times, a film-like ferrite or the like is generated immediately below the transformed portion in the vicinity of the slab surface layer, so that cracks under the surface layer occur. In addition, the temperature of the slab itself is lowered, and the energy saving effect is impaired. According to the present invention, a fine austenite structure layer required for suppressing surface cracks can be uniformly generated by one heat cycle.
【００２１】なお、熱片装入による加熱炉原単位向上効
果をより大きく得るためには、冷却終了後なるべく短時
間で加熱炉に装入することが好ましい。但し、工程上の
都合などで加熱炉への装入が遅れた場合でも、圧延割れ
抑止効果が失われることはない。In order to further increase the heating furnace unit consumption effect by charging the heating piece, it is preferable to charge the heating furnace in as short a time as possible after the completion of cooling. However, even if the charging into the heating furnace is delayed due to reasons in the process or the like, the effect of suppressing rolling cracks is not lost.
【００２２】本発明による熱片装入後の圧延割れ抑止効
果は、微量元素としてＮｂ，Ｖ，Ｔｉ，Ｍｏ，Ｃｕ，Ｎ
ｉなどを含む低合金鋼において、特に顕著に認められ
る。The effect of suppressing rolling cracks after charging the hot strip according to the present invention is as follows: Nb, V, Ti, Mo, Cu, N
This is particularly noticeable in low alloy steels containing i and the like.
【００２３】一般にＨＣＲにより厚鋼板を製造する場
合、加熱炉装入時のスラブ温度は、７００℃以下まで低
下していることが多い。その場合、Ｎｂ，Ｖ等の前記微
量添加元素を含まない鋼は、表層近傍において、オース
テナイトからフェライト＋パーライトなどに変態が完了
しているケースが多く、特段の考慮を払わなくても圧延
後に表面割れは生じにくい。一方、前記微量元素を含む
鋼では、変態の進行が遅く、再加熱後のスラブ表層は、
再び元の粗大な柱状オーステナイト組織となる結果、何
らかの割れの起点が存在すると、圧延時に大きな割れを
生じてしまう。In general, when a thick steel plate is manufactured by HCR, the slab temperature at the time of charging the heating furnace is often lowered to 700 ° C. or less. In this case, in many cases, the steel not containing the trace addition elements such as Nb and V has already undergone transformation from austenite to ferrite + pearlite in the vicinity of the surface layer, and the surface after rolling without special consideration. Cracks are less likely to occur. On the other hand, in steel containing the trace elements, the progress of transformation is slow, and the slab surface layer after reheating is
As a result of returning to the original coarse columnar austenite structure again, if there is any crack initiation point, a large crack occurs during rolling.
【００２４】もちろん、微量元素の添加の有無に関わら
ず、本発明法を用いることにより、圧延割れの発生の無
い良好な表面性状を有する厚鋼板を得ることができる
が、特に前記微量元素を含む鋼においては、圧延割れ抑
止効果が顕著に現れる。Of course, regardless of the presence or absence of a trace element, the method of the present invention can be used to obtain a thick steel plate having good surface properties without rolling cracks. In steel, the effect of suppressing rolling cracks appears remarkably.
【００２５】[0025]
【実施例】以下、実施例にて本発明を詳細に説明する。The present invention will be described below in detail with reference to examples.
【００２６】[実施例１]表１に示す組成のスラブ（250m
m厚）を連続鋳造機により製造した。図１に示す連続鋳
造曲げ矯正終了点後の水平帯（Ａ）、連続鋳造機出側ス
ラブカッター前方（Ｂ）、厚板加熱炉前（Ｃ）に水量密
度を調整できる水冷ノズルを仮設し、それぞれの位置で
スラブを冷却した。水量密度は、300〜2000リットル／m
2min.の範囲で変化させた。冷却時間は50秒で一定とし
た。Example 1 A slab having the composition shown in Table 1 (250 m
m thickness) was produced by a continuous casting machine. A water cooling nozzle capable of adjusting the water density is temporarily installed in the horizontal band (A) after the end point of continuous casting bending straightening shown in FIG. 1, in front of the slab cutter on the exit side of the continuous casting machine (B), and in front of the thick plate heating furnace (C). The slab was cooled at each location. Water volume density is 300-2000 liter / m
It was changed within the range of 2 min. The cooling time was fixed at 50 seconds.
【００２７】冷却完了後、加熱炉に装入した。連続鋳造
開始から加熱炉装入までに要した時間は、160〜180分の
範囲であった。厚板圧延における加熱温度は1150℃、在
炉時間は約2時間である。同一冷却条件のスラブを各々2
枚ずつ準備し、1枚は加熱炉から抽出後130mm厚まで圧延
し、割れの有無を確認した。もう１枚は、加熱炉から抽
出後そのまま加速冷却し、スラブ断面の組織観察に供し
て、表層近傍の微細オーステナイト組織層の厚さを測定
した。After the cooling was completed, it was charged into a heating furnace. The time required from the start of continuous casting to charging of the heating furnace was in the range of 160 to 180 minutes. The heating temperature in plate rolling is 1150 ° C and the furnace time is about 2 hours. 2 slabs with the same cooling conditions
Each sheet was prepared, and one sheet was extracted from a heating furnace and then rolled to a thickness of 130 mm to check for cracks. The other was accelerated and cooled as it was after being extracted from the heating furnace, and subjected to microstructural observation of the cross section of the slab to measure the thickness of the fine austenitic microstructure layer near the surface layer.
【００２８】表２に結果をまとめて示す。冷却を行わな
かったＮｏ.１〜3、水量密度300、500リットル／m2min.
で水冷を行ったＮｏ.4〜13では、圧延後の鋼板表面に多
くの割れが観察された。これに対して、水量密度1000リ
ットル／m2min.以上で冷却したＮｏ.14〜28には、圧延
後の鋼板表面に割れは全く認められなかった。Table 2 summarizes the results. Nos. 1 to 3 without cooling, water volume density 300, 500 l / m 2 min.
In Nos. 4 to 13 which were water-cooled, many cracks were observed on the surface of the steel sheet after rolling. On the other hand, in Nos. 14 to 28 cooled at a water density of 1000 liters / m 2 min. Or more, no cracks were observed on the steel sheet surface after rolling.
【００２９】スラブ断面の組織観察の結果、冷却を行わ
なかったＮｏ.1〜3、水量密度300リットル／m2min.で水
冷を行ったＮｏ.4〜8では、微細オーステナイト組織層
は認められなかった。また、水量密度500リットル／m2m
in.で冷却したＮｏ.9〜13では、場所によって3mm程度の
微細オーステナイト組織層が観察された。これに対し
て、水量密度が1000リットル／m2min.以上のＮｏ.14〜2
8では、いずれも15〜20mm程度の非常に均一な厚さの微
細オーステナイト組織層が観察された。As a result of observation of the microstructure of the cross section of the slab, a fine austenite structure layer was observed in Nos. 1 to 3 where cooling was not performed and Nos. 4 to 8 where water cooling was performed at a water density of 300 L / m 2 min. Did not. In addition, water volume density 500 liter / m 2 m
In Nos. 9 to 13 cooled at in., a fine austenitic structure layer of about 3 mm was observed depending on the location. On the other hand, Nos. 14 to 2 with water density of 1000 l / m 2 min.
In No. 8, a fine austenitic structure layer having a very uniform thickness of about 15 to 20 mm was observed in each case.
【００３０】水量密度1000リットル／m2min.以上では、
加熱炉装入温度、表層の微細オーステナイト組織層厚さ
は水量密度に依存しなかった。これは、冷却がスラブ中
の熱伝導律速になった結果であり、本発明は操業条件の
バラツキによる品質への影響が小さく、製造安定性に優
れていることを裏付けている。At a water density of 1000 liters / m 2 min. Or more,
The charging temperature of the heating furnace and the thickness of the fine austenitic structure layer on the surface layer did not depend on the water density. This is a result of the fact that the cooling becomes the rate of heat conduction in the slab, and the present invention has a small effect on the quality due to the variation in operating conditions, and supports the fact that the manufacturing stability is excellent.
【００３１】また、連続鋳造曲げ矯正終了点後の水平帯
（Ａ）、連続鋳造機出側スラブカッター前方（Ｂ）、厚
板加熱炉前（Ｃ）のいずれの位置で冷却しても同じ結果
が得られた。The same result is obtained by cooling at any of the horizontal band (A) after the end point of continuous casting bending straightening, the front side of the slab cutter on the exit side of the continuous casting machine (B), and the front side of the thick plate heating furnace (C). was gotten.
【００３２】なお、加熱炉装入時のスラブ温度が600℃
以上であれば、スラブは在炉2時間で十分に所定の加熱
温度に昇温保持される。圧延能率を考慮すれば、加熱炉
の在炉時間は最短でも２時間は必要なため、スラブ温度
が600℃以上であれば、熱片装入による加熱炉原単位向
上効果が得られる。本実施例では、加熱炉装入時のスラ
ブ温度は、いずれも600℃以上であり、本発明により省
エネルギー性に優れ、表面割れの発生の無い鋼板の製造
が可能となった。The slab temperature at the time of charging the heating furnace was 600 ° C.
If this is the case, the slab is sufficiently heated to a predetermined heating temperature for 2 hours in the furnace. In consideration of the rolling efficiency, the heating furnace must be kept in the furnace for at least two hours, so that if the slab temperature is 600 ° C. or higher, the effect of improving the heating furnace basic unit by charging the heating piece can be obtained. In the present example, the slab temperature at the time of charging the heating furnace was 600 ° C. or more, and the present invention made it possible to produce a steel sheet which was excellent in energy saving and free from surface cracks.
【００３３】[実施例２]表１の鋼種Ａ２を用い、厚板加
熱炉前に仮設した水量密度を調節できる水冷装置によ
り、熱片スラブの冷却を行った。水量密度は、500，120
0，1600リットル／m2min.、冷却時間は10〜90秒の範囲
で変化させた。スラブ厚は250mmであり、連続鋳造開始
から加熱炉装入に要した時間は160〜180分であった。厚
板圧延における加熱温度は1150℃、在炉時間は約2時間
である。実施例１と同様に、同一冷却条件のスラブを各
々2枚ずつ準備し、1枚は加熱炉から抽出後130mm厚まで
圧延し、割れの有無を確認した。もう１枚は、加熱炉か
ら抽出後そのまま加速冷却し、スラブ断面の組織観察に
供して、表層近傍の微細オーステナイト組織層の厚さを
測定した。[Example 2] Using a steel type A2 shown in Table 1, a hot slab was cooled by a water cooling device temporarily provided in front of a thick plate heating furnace and capable of adjusting the water density. Water volume density is 500,120
0,1600 l / m 2 min., The cooling time was changed in the range of 10 to 90 seconds. The slab thickness was 250 mm, and the time required for charging the heating furnace from the start of continuous casting was 160 to 180 minutes. The heating temperature in plate rolling is 1150 ° C and the furnace time is about 2 hours. As in Example 1, two slabs each having the same cooling conditions were prepared, and one slab was extracted from the heating furnace and rolled to a thickness of 130 mm to check for cracks. The other was accelerated and cooled as it was after being extracted from the heating furnace, and subjected to microstructural observation of the cross section of the slab to measure the thickness of the fine austenitic microstructure layer near the surface layer.
【００３４】表３に結果をまとめて示す。水量密度を50
0リットル／m2min.とした場合、Ｎｏ.55のように冷却時
間を90秒まで長くしても、圧延後の鋼板表面に割れが認
められた。スラブ表層近傍の組織観察の結果、50秒以上
冷却したＮｏ.53〜55では、微細オーステナイト組織層
が認められたが、組織が不均一であり、場所によって微
細オーステナイト組織層が認められない部分があった。Table 3 summarizes the results. 50 water density
In the case of 0 liter / m 2 min., Cracks were observed on the steel sheet surface after rolling even if the cooling time was extended to 90 seconds as in No. 55. As a result of observation of the structure near the surface of the slab, in Nos. 53 to 55 cooled for 50 seconds or more, a fine austenite structure layer was observed, but the structure was non-uniform, and there were portions where the fine austenite structure layer was not recognized depending on the location. there were.
【００３５】水量密度を1200、1600リットル／m2min.と
した場合、冷却時間が10秒のＮｏ.56、62は、いずれも
圧延後の鋼板表面に割れが認められた。一方、冷却時間
が30、50、70、90秒間のＮｏ.57〜60およびＮｏ.63〜66
には、割れは全く認められなかった。但し、60秒以上の
冷却を行ったＮｏ.59、60、65、66は、加熱炉装入時の
スラブ温度が600℃より低く、熱片装入による省エネル
ギー効果が十分得られなかった。スラブ表層の組織観察
の結果、10秒冷却したものには、約3mmの微細オーステ
ナイト組織層が認められ、30〜90秒冷却したものには10
mm以上の非常に均一な厚さの微細オーステナイト組織層
が観察された。When the water density was 1200 and 1600 liters / m 2 min., Cracks were observed on the steel sheet surface after rolling in Nos. 56 and 62, each of which had a cooling time of 10 seconds. On the other hand, Nos. 57 to 60 and Nos. 63 to 66 with cooling times of 30, 50, 70, and 90 seconds.
Did not show any cracks. However, in Nos. 59, 60, 65, and 66, which were cooled for 60 seconds or more, the slab temperature at the time of charging the heating furnace was lower than 600 ° C., and the energy saving effect by charging the heating piece was not sufficiently obtained. As a result of microstructure observation of the slab surface layer, a fine austenitic structure layer of about 3 mm was observed in the one cooled for 10 seconds, and
A fine austenitic structure layer with a very uniform thickness of not less than mm was observed.
【００３６】Ｎｏ.61では、水量密度を1200リットル／m
2min.として、10秒間の水冷を行い、その後30秒以上保
持して一旦復熱させてから、再び10秒間の水冷を行い、
表面割れに及ぼす繰り返し熱サイクルの影響を調査し
た。その結果、圧延後の鋼板表面に割れが発生した。組
織観察の結果、スラブ表層下に割れが認められ、繰り返
し熱サイクルにより表層化割れが発生することが確認さ
れた。In No. 61, the water density was 1200 liter / m
As 2 min., Perform water cooling for 10 seconds, then hold for 30 seconds or more and once re-heat, perform water cooling again for 10 seconds,
The effect of repeated thermal cycling on surface cracking was investigated. As a result, cracks occurred on the surface of the steel sheet after rolling. As a result of the microstructure observation, cracks were observed under the surface of the slab, and it was confirmed that surface cracks were generated by repeated thermal cycling.
【００３７】以上の実施例および比較例から明らかなよ
うに、スラブに対して、1000リットル／m2min.以上の水
量密度の水冷を15秒以上、60秒以下行い、復熱させる熱
サイクルを1回行ってから、加熱炉に装入して圧延する
ことにより、表面に割れの無い鋼板を製造することが可
能であり、加えて熱片装入による加熱炉原単位向上効果
を十分得ることが可能である。また、スラブの冷却条件
を規定することにより、操業条件によるバラツキがな
く、安定して表面性状の良好な鋼板を製造可能である。As is clear from the above Examples and Comparative Examples, the slab is subjected to water cooling at a water density of 1000 liters / m 2 min. It is possible to produce a steel plate with no cracks on the surface by charging it into a heating furnace and rolling it after performing it once. Is possible. Further, by defining the cooling conditions of the slab, it is possible to stably produce a steel sheet having good surface properties without variation due to operating conditions.
【００３８】[0038]
【表１】 [Table 1]
【００３９】[0039]
【表２】 [Table 2]
【００４０】[0040]
【表３】 [Table 3]
【００４１】[0041]
【発明の効果】本発明により、ＨＣＲにより鋼板を製造
する場合に、熱片装入による加熱炉原単位向上効果に優
れ、表面割れの発生のない表面性状の良好な鋼板を安定
的に製造する方法が確立された。これにより、鋼板の品
質、歩留が大幅に向上するばかりでなく、加熱炉原単位
向上による省エネルギー効果、さらには加熱炉在炉時間
短縮による生産性の向上を図ることができる。According to the present invention, when a steel plate is manufactured by HCR, a steel plate having an excellent effect of improving the unit consumption of a heating furnace by charging a heating piece and having good surface properties without generating surface cracks is stably manufactured. The method has been established. As a result, not only the quality and yield of the steel sheet can be significantly improved, but also the energy saving effect by improving the heating furnace basic unit and the productivity by shortening the heating furnace time can be achieved.
【図１】実施例において、水冷設備を仮設した位置を示
す模式図。FIG. 1 is a schematic diagram showing a position where a water cooling facility is temporarily provided in an embodiment.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 藤林 晃夫 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 上岡 悟史 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 鈴木 幹雄 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 淡路谷 浩 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 Ｆターム(参考） 4E004 KA14 KA20 MC02 MC22 MC24 MD05 NB01 NC01 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Fujibayashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside Nihon Kokan Co., Ltd. (72) Inventor Satoshi Ueoka 1-1-2, Marunouchi, Chiyoda-ku, Tokyo, Japan Inside the Honko Tube Co., Ltd. (72) Inventor Mikio Suzuki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Japan Inside the Honko Tube Co., Ltd. (72) Inventor Hiroshi Awajiya 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan F Tube (in reference) 4E004 KA14 KA20 MC02 MC22 MC24 MD05 NB01 NC01
Claims (1)
点以降、スラブに対して1000リットル／m2min.以上の水
量密度の水冷を、１５秒以上６０秒以下行い、復熱させ
る熱サイクルを１回行ってから、加熱炉に装入して圧延
することを特徴とする、表面性状の良好な鋼板の製造方
法。1. A thermal cycle in which a slab is subjected to water cooling at a water density of 1000 liters / m 2 min. Or more for 15 seconds to 60 seconds after the secondary cooling zone bending straightening end point in continuous casting to recover heat. A method of producing a steel sheet having good surface properties, wherein the method is carried out once, and then charged into a heating furnace and rolled.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11036290A JP2000233266A (en) | 1999-02-15 | 1999-02-15 | Production of steel plate having good surface characteristic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11036290A JP2000233266A (en) | 1999-02-15 | 1999-02-15 | Production of steel plate having good surface characteristic |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000233266A true JP2000233266A (en) | 2000-08-29 |
Family
ID=12465679
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11036290A Pending JP2000233266A (en) | 1999-02-15 | 1999-02-15 | Production of steel plate having good surface characteristic |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000233266A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009522110A (en) * | 2006-01-11 | 2009-06-11 | エス・エム・エス・デマーク・アクチエンゲゼルシャフト | Method and apparatus for continuous casting |
| JP2010005634A (en) * | 2008-06-24 | 2010-01-14 | Kobe Steel Ltd | Method for producing cast metal |
| CN108213367A (en) * | 2016-12-15 | 2018-06-29 | 株式会社Posco | The uniform austenitic stainless steel continuous cast method of water distribution of secondary cooling platform |
| CN109317631A (en) * | 2018-10-30 | 2019-02-12 | 武汉钢铁有限公司 | Improve the production method of continuous casting square billet structural homogenity |
| CN109865811A (en) * | 2019-04-04 | 2019-06-11 | 山东钢铁股份有限公司 | A kind of three times cooling device of conticaster and its continuous casting billet |
| CN114096362A (en) * | 2019-07-11 | 2022-02-25 | 杰富意钢铁株式会社 | Secondary cooling method and apparatus for continuously cast slab |
| CN109865811B (en) * | 2019-04-04 | 2024-06-11 | 山东钢铁股份有限公司 | Continuous casting machine and tertiary cooling device of continuous casting blank thereof |
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1999
- 1999-02-15 JP JP11036290A patent/JP2000233266A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009522110A (en) * | 2006-01-11 | 2009-06-11 | エス・エム・エス・デマーク・アクチエンゲゼルシャフト | Method and apparatus for continuous casting |
| JP2010005634A (en) * | 2008-06-24 | 2010-01-14 | Kobe Steel Ltd | Method for producing cast metal |
| CN108213367A (en) * | 2016-12-15 | 2018-06-29 | 株式会社Posco | The uniform austenitic stainless steel continuous cast method of water distribution of secondary cooling platform |
| CN109317631A (en) * | 2018-10-30 | 2019-02-12 | 武汉钢铁有限公司 | Improve the production method of continuous casting square billet structural homogenity |
| CN109317631B (en) * | 2018-10-30 | 2020-08-07 | 武汉钢铁有限公司 | Production method for improving texture uniformity of continuous casting square billet |
| CN109865811A (en) * | 2019-04-04 | 2019-06-11 | 山东钢铁股份有限公司 | A kind of three times cooling device of conticaster and its continuous casting billet |
| CN109865811B (en) * | 2019-04-04 | 2024-06-11 | 山东钢铁股份有限公司 | Continuous casting machine and tertiary cooling device of continuous casting blank thereof |
| CN114096362A (en) * | 2019-07-11 | 2022-02-25 | 杰富意钢铁株式会社 | Secondary cooling method and apparatus for continuously cast slab |
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