JPS59129717A - Direct hardening device for steel plate - Google Patents

Abstract

PURPOSE:To provide a titled device which improves extremely stably and highly material quality when water cooling is performed right after hot rolling by disposing devices for detecting rate of transformation from the austenite state to ferrite of a steel plate under hardening to a hot rolling device and a water cooling device CONSTITUTION:The device of this invention is constituted of a heating furnace 1, hot rolling mills 2, 3, a hot leveler 4 and a cooling device 5. Transformation rate meters 6 are disposed just before the device 5 and if necessary in the device 5. The rate of transformation from the austenite state to ferrite of a steel plate subjected to heating and rolling is first detected from the rate of a change in the magnetic flux density of the meter 6 in front of the device 5 upon passage of the steel plate through the leveler 4. The rate of said transformation is measured and is reflected to the rolling temp. of the succeeding rolling mill so that the rate of transformation at the point of time of cooling attains a required best value.

Description

【発明の詳細な説明】 本発明は熱間圧延した鋼板を水冷して材質を安定して向
上させるために、熱間圧延装置と水冷装置又は水冷装置
中に、焼入れ中の鋼板のオーステナイト状態からフェラ
イトへの変態量を検出する装置を配置した鋼板の連続直
接焼入装置に係る。DETAILED DESCRIPTION OF THE INVENTION In order to stably improve the material quality by water-cooling a hot-rolled steel plate, the present invention uses a hot-rolling device, a water-cooling device, or a water-cooling device to change the austenitic state of the steel plate during quenching. This invention relates to a continuous direct quenching apparatus for steel sheets equipped with a device for detecting the amount of transformation into ferrite.

一般に鋼の強靭性等材質を改善する目的で鋼板の熱間圧
延直後、該鋼板が高温にある状態から、これを所定の冷
却速度で冷却して焼入れを行なうことはよく知られてい
る。It is generally well known that immediately after hot rolling a steel plate, the steel plate is cooled at a predetermined cooling rate and quenched for the purpose of improving the material properties such as toughness of steel.

水冷によシ材質改善を行なうには鋼板全体を均一に、即
ち鋼板の全箇所を極力同一の温度から同一の温度まで、
同じ冷却速度で冷却することが必須でアシ、温度狙いの
範囲も材質要求の高級化に伴ない狭少化の傾向にある。In order to improve the material quality by water cooling, the entire steel plate should be uniformly heated, that is, all parts of the steel plate should be heated to the same temperature as much as possible.
Cooling at the same cooling rate is essential, and the target temperature range is also becoming narrower as material requirements become more sophisticated.

冷却方法としては浸漬法、ラミナーフロー、スプレ一方
式などが知られ、鋼板の板肉および板間の材質を安定さ
せるため、板中方向に水量勾配をつけるなど種々の対策
がとられているところであるがなお、安定した材質が必
ずしも得られないのも実情である。The immersion method, laminar flow, spray method, etc. are known as cooling methods, and various measures are taken to stabilize the thickness of the steel plate and the material between the plates, such as creating a water flow gradient in the direction of the plate. However, the reality is that stable materials cannot always be obtained.

従来から行なわれている材質改善のための他の方法とし
て圧延加工後の鋼板を再加熱して焼入れをすることが知
られているが、この方法の場合、加熱から焼入れまでの
距離が短くほとんど温度降下せずに、完全オーステナイ
トからの焼入れであるので鋼板の温度を監視することと
前記均一冷却条件を確保することで通常の場合は安定し
た材質の鋼板が得られやすい。Another conventional method for improving material quality is to reheat and quench the steel plate after rolling, but in this method, the distance from heating to quenching is short and most Since quenching is performed from complete austenite without temperature drop, by monitoring the temperature of the steel plate and ensuring the uniform cooling conditions mentioned above, it is easy to obtain a steel plate of stable material in normal cases.

しかし前述したような熱間圧延後直ちに焼入れされる方
法の場合には、圧延機でのロールとの接触、圧延時の冷
却水による冷却、レペラーでの冷却、さらに圧延から冷
却までの時間による放冷など冷却要因が多く、焼入れ時
の温度が予測しにくいことが材質安定化の阻害要因の一
つの原因となっている。However, in the case of the above-mentioned method in which quenching is performed immediately after hot rolling, the contact with the rolls in the rolling mill, the cooling with cooling water during rolling, the cooling in the repeller, and the time between rolling and cooling are There are many cooling factors such as cold, and the difficulty in predicting the temperature during quenching is one of the factors that hinders material stabilization.

本発明者等はこれらの対策の一つとして焼入れ直前に温
度計を設置し、それによって材質を管理することを試み
たがこれによシ・々ラツキは減るものの十分でないこと
が判明した。As one of these countermeasures, the present inventors installed a thermometer immediately before quenching and attempted to control the material quality using this method, but it was found that although this reduced the unevenness, it was not sufficient.

その原因を検討した結果、材質を決めているのは温度と
いうよシは、オーステナイトからフェライトへの変態状
況であシ、且つその変態挙動が温度はかシでなく圧延状
況によっても変化す゛ることを見出し、変態挙動を制御
することが材質コントロールに大きく影響することを確
認した。As a result of examining the causes, we found that it is not temperature that determines the material quality, but the transformation from austenite to ferrite, and that the transformation behavior changes not only with temperature but also with the rolling conditions. It was confirmed that controlling the transformation behavior has a large effect on material quality control.

即ち鋼の変態点、変態速度は、鋼の成分、或いは前履歴
（例えば圧延の場合には、圧下により導入される歪量が
増力口すると変態が誘起され変態点が上昇する）、冷却
速度（例えば板厚、ロールとの接触、外気温、デスケ水
等で変化する）等によシ変るので温度によυこれらの管
理を行なう場合は、各種の状況を設定して、その状況下
ごとの変態点および変態量を予じめ測定しておかねばな
らず、これら方式の実際上の適用は困難であるｂ第１図
は通常制御圧延に用いられる変態点予測式（開銀の式）
と実測変態点との相関を示□すが例えばｔ＝４２（％）
　Ｋ３２Ｅ鋼では変態点の予測値と実測値の差が圧下量
によシ変ることを示している。In other words, the transformation point and transformation rate of steel are determined by the composition of the steel, the previous history (for example, in the case of rolling, when the amount of strain introduced by rolling is increased, transformation is induced and the transformation point rises), cooling rate ( For example, it varies depending on the board thickness, contact with rolls, outside temperature, water, etc.), so if you want to manage these depending on temperature, you can set various situations and adjust them according to each situation. The transformation point and amount of transformation must be measured in advance, making it difficult to practically apply these methods.b Figure 1 shows the transformation point prediction formula (open silver formula) normally used in controlled rolling.
For example, t = 42 (%).
This shows that for K32E steel, the difference between the predicted value and the actual value of the transformation point changes depending on the amount of reduction.

又従来から例えばホットストリップでストリップの変態
点を検出して材質をコントロールする例は発表されてい
るが、変態点のみでは変態挙動は十分でなく、場合によ
っては変態が一部始まってから焼入れでも材質上優れた
ものが得られる場合もある。In addition, examples have been published in which the material quality is controlled by detecting the transformation point of a strip using a hot strip, but the transformation behavior is not sufficient to be determined by the transformation point alone, and in some cases, even if quenching is performed after some transformation has begun. In some cases, materials with superior quality can be obtained.

第２図は本発明者等で確認したＳ　ｉ−Ｍｎ−Ｖ−Ｔ　
ｌ　−Ｂ系ＷＴ６．０　（ｔ　＝２５　）の変態量と材
質の関係を示しておシ、この成分の場合には変態開始直
後（フェライトが数多程度出現）焼入れると強度、靭性
ともに最高値となシ、焼入れにあたっては変態量を測定
することが極めて重要なことが判る。Figure 2 shows the S i-Mn-V-T confirmed by the inventors.
This shows the relationship between the amount of transformation and material quality for l-B series WT6.0 (t = 25). In the case of this component, both strength and toughness are the highest when quenched immediately after the start of transformation (a large number of ferrites appear). It can be seen that it is extremely important to measure the amount of transformation during quenching.

本発明は、かかる観点から熱間圧延機と焼入れ装置との
間に変態量測定装置を介在させることによシ材質の安定
化を図らんとするものである。From this point of view, the present invention attempts to stabilize the quality of the steel material by interposing a transformation measuring device between the hot rolling mill and the quenching device.

本発明に一見類似した技術として、熱間加工中の鋼材の
変態量を測定し、加工温度や加工速度を一調整すること
によシ、熱間加工中の鋼材変態量を制御する方法を同一
出願人において提案している（特公昭５３〜２５３０９
号公報）。As a technology seemingly similar to the present invention, the method of controlling the transformation amount of steel material during hot working is the same, by measuring the amount of transformation of steel material during hot working and adjusting the processing temperature and processing speed. The applicant has proposed (Japanese Patent Publication No. 53-25309)
Publication No.).

しかし、この先行発明の目的は、所謂目標とする最適変
態量領域のもとて熱間加工を行なうことにより熱間加工
中の変態挙動を管理するものでち夛、塑性別工面での鋼
の強化という点で、それ自体極めて重要な技術であるが
、圧延後、特に圧延直後の直接焼入れ開始時点の変態量
を管理して熱処理面での材質の安定化を意図するものと
は本質的に相違する。However, the purpose of this prior invention is to control the transformation behavior during hot working by performing hot working in the so-called target optimum transformation amount range, and to control the transformation behavior of steel on the plastic working surface. In terms of strengthening, it is an extremely important technology in itself, but it is essentially aimed at stabilizing the material during heat treatment by controlling the amount of transformation after rolling, especially at the start of direct quenching immediately after rolling. differ.

以下本発明を図面に示す実施例に基づいて具体的に説明
する。The present invention will be specifically described below based on embodiments shown in the drawings.

第３図は本発明装置の全体図を示しておシ、′１は加熱
炉、２．３は熱間圧延機、４はホットレペラー、５は冷
却装置であシ、冷却装置５の直前又は必要に応じて冷却
装置５内に変態量計６を配置する。Figure 3 shows an overall view of the apparatus of the present invention, where 1 is a heating furnace, 2.3 is a hot rolling mill, 4 is a hot repeller, and 5 is a cooling device, immediately before or necessary for the cooling device 5. A transformation amount meter 6 is placed in the cooling device 5 according to the requirements.

変態量計６は、磁気的方法とＸ線による方法などが知ら
れておシ第４図に前者の例を示している。The transformation amount meter 6 is known to use a magnetic method or an X-ray method, and FIG. 4 shows an example of the former method.

即ち７は磁界発生装置であシ８は磁束密度計、９は計器
、１０は鋼板であシ変態すると強磁性になることを利用
して磁束密度の変化によシ変態量を測定するものである
。In other words, 7 is a magnetic field generator, 8 is a magnetic flux density meter, 9 is a meter, and 10 is a steel plate that measures the amount of transformation by changing the magnetic flux density by utilizing the fact that it becomes ferromagnetic when it undergoes transformation. be.

第５図に第４図の装置によって得られるフェライト量と
漏洩磁束の関係を示しておシ、磁束密度を測定すること
によシ変態量を把握することができる。FIG. 5 shows the relationship between the amount of ferrite obtained by the apparatus shown in FIG. 4 and the leakage magnetic flux, and the amount of transformation can be determined by measuring the magnetic flux density.

図において、加熱、圧延を終えた鋼板がホットレベラー
４を通過後、まず、冷却装置５（水冷ゾーン）前面の変
態量計６の磁束密度の変化量によシ、変態量を検知する
。この時に、適正な材質が得られる変態量を温度で推定
することは、前履歴の影響によシ、バラツキを多くする
が、本装置の場合それらの結果としての変態量を直接に
検知するものである。又、冷却装置５（水冷ゾーン内）
の変態量針６については、ゾーン内釜位置の変態量を検
知し、水冷ゾーン内で部分的に冷却水量を変化させる。In the figure, after the heated and rolled steel plate passes through the hot leveler 4, the amount of transformation is first detected based on the amount of change in magnetic flux density of the transformation amount meter 6 in front of the cooling device 5 (water cooling zone). At this time, estimating the amount of transformation that will yield the appropriate material based on temperature will be affected by the previous history and will result in a large amount of variation, but with this device, the resulting amount of transformation can be directly detected. It is. Also, the cooling device 5 (inside the water cooling zone)
The transformation amount needle 6 detects the transformation amount at the pot position within the zone and partially changes the cooling water amount within the water cooling zone.

この時、変態量検知と“、水量変化までの時間的な差は
、変態量の差分により、保証する。At this time, the time difference between the detection of the amount of transformation and the change in the amount of water is guaranteed by the difference in the amount of transformation.

以上の操作によシ５適正な最終組織を確保し、目的とす
る材質を得る。Through the above operations, an appropriate final structure is secured and the desired material is obtained.

変態量針で測定された測定値は、次のように多様な制御
方法に用いられる。The measured value measured by the transformation amount needle is used in various control methods as follows.

（１）変態量を計測し、冷却時点での変態量が所要の最
適値となるように、次の圧延機の圧延温度に反映させる
。(1) The amount of transformation is measured and reflected in the rolling temperature of the next rolling mill so that the amount of transformation at the time of cooling becomes the required optimum value.

（２）変態量から冷却装置での冷却条件を調整する。即
ち高張力鋼では、変態量が多いほど、水冷を多くする必
要がある。(2) Adjust the cooling conditions in the cooling device based on the amount of transformation. That is, in high-strength steel, the greater the amount of transformation, the more water cooling is required.

（３）変態量から冷却装置に入る待ち時間を管理する。(3) Manage the waiting time for entering the cooling device based on the amount of transformation.

即ち材質によっては、一部変態してから水冷を始めるこ
とが好ましく、一定の変態量になるまで保定する。That is, depending on the material, it is preferable to start water cooling after a portion of the material has been transformed, and the water cooling is maintained until a certain amount of transformation is reached.

（４）　　その他圧延中の冷却条件（デスケーリング、
ロール冷却など）圧延直後の強制空冷などの冷却或いは
加熱などを付加して変態量を制御する。(4) Other cooling conditions during rolling (descaling,
Roll cooling, etc.) The amount of transformation is controlled by adding cooling such as forced air cooling or heating immediately after rolling.

これらのうち（３）に基づく試験の結果得られたのが第
２図である。Among these, FIG. 2 shows the results obtained from the test based on (3).

従来は完全オーステナイトから焼入れた方が強靭化する
とされていたが本発明装置によシ適度に変態した状態で
焼入れすることが好ましいことが判明した。Conventionally, it was thought that quenching from complete austenite would make it tougher, but with the apparatus of the present invention, it has been found that it is preferable to quench in a moderately transformed state.

以上のように本発明によれば熱間圧延直後水冷を行なう
場合に極めて安定し、且つ高度な材質改善を図れるとい
う効果が奏されうる。As described above, according to the present invention, when water cooling is performed immediately after hot rolling, it is extremely stable and the material quality can be improved to a high degree.

なお本発明による変態量針を用いて冷却管理を行なう技
術は、熱間圧延後、再加熱して冷却する際、例えば２相
域焼入れなどにも活用でき、又鋼板にとどまらず同様の
工程をもつ鋼管製造工程にも活用の可能性をもっている
。The technology of controlling cooling using the transformation amount needle according to the present invention can be used for, for example, two-phase region quenching when reheating and cooling after hot rolling, and can be used not only for steel sheets but also for similar processes. It also has the potential to be used in the steel pipe manufacturing process.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は通常の制御圧延で用いられる変態点予測値と実
測値との関係を示す図、第２図は本発明の試験によって
求めた鋼板の冷却開始時の変態量と材質との関係を示す
図、第３図は本発明装置の全体図、第４図は変態量針の
概略図、第５図は変態量針による磁束密度と変態量の関
係を示す図である。 第１図 ＷＡＩＬの式１；よるＡｔＪ１＋箕備（で）第２図 フェライト麦悠１（％） Ｌ−１−（（ｙＯｔｌｓｓＩFigure 1 is a diagram showing the relationship between the predicted value of transformation point used in normal controlled rolling and the actual value, and Figure 2 is a diagram showing the relationship between the amount of transformation at the start of cooling of the steel plate and the material quality determined by the test of the present invention. 3 is an overall view of the apparatus of the present invention, FIG. 4 is a schematic diagram of the transformation amount needle, and FIG. 5 is a diagram showing the relationship between the magnetic flux density and the transformation amount by the transformation amount needle. Fig. 1 WAIL formula 1; According to AtJ1 + Minobi (de) Fig. 2 Ferrite Mugiyu 1 (%) L-1-((yOtlssI

Claims (1)

【特許請求の範囲】[Claims] 熱間圧延後の鋼板を直接焼入れする装置において、直接
焼入れを行なう直前または焼入れ中の位置に鋼板のオー
ステナイト状態からフェライトに変態する変態量を検出
する装置を配置したことを特徴とする鋼板の直接焼入装
置。A device for directly quenching a steel plate after hot rolling, characterized in that a device for detecting the amount of transformation of the steel plate from an austenite state to a ferrite state is disposed at a position immediately before direct quenching or during quenching. Quenching equipment.