JP2008255414A

JP2008255414A - Method for cooling steel sheet and steel sheet continuous heat-treatment facility

Info

Publication number: JP2008255414A
Application number: JP2007098839A
Authority: JP
Inventors: Shintaro Harada; 新太郎原田
Original assignee: Nippon Steel Engineering Co Ltd
Current assignee: Nippon Steel Engineering Co Ltd
Priority date: 2007-04-04
Filing date: 2007-04-04
Publication date: 2008-10-23
Anticipated expiration: 2027-04-04
Also published as: JP5226965B2

Abstract

<P>PROBLEM TO BE SOLVED: To raise a steel sheet passing-through speed and to improve production efficiency by using a part of the front step of a cooling device disposed in a rapid-cooling zone for slow-cooling, in cooling the steel sheet, when the passing-through speed of the steel sheet is limited due to the cooling capacity limit in the slow-cooling zone, that is, when the slow-cooling can not be performed to the outlet side temperature set in the slow-cooling zone and the inlet side temperature to the rapid-cooling zone becomes high, in the cooling zone composed of the slow-cooling zone and successively, the rapid-cooling zone. <P>SOLUTION: In the steel sheet cooling method, with which the heated steel sheet is slowly cooled in the slow-cooling zone and successively, rapidly cooled in the rapid-cooling zone in the steel sheet continuous heat-treatment facility having the cooling zone constituted of a cooling device having a plurality of steps of the slow-cooling zones and the rapid-cooling zones, respectively, when the steel sheet can not be cooled to the target slow-cooling zone outlet side sheet temperature in only the slow-cooling zone, a part of the cooling device at the front step of the rapid-cooling zone is used for slow-cooling and the sheet temperature is controlled while making the outlet side the imaginary slow-cooling zone outlet side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、鋼板連続熱処理設備において鋼板を徐冷し、次いで急冷する鋼板冷却方法及びこの方法を実施するための鋼板連続熱処理設備に関する。 The present invention relates to a steel plate cooling method in which a steel plate is gradually cooled and then rapidly cooled in a steel plate continuous heat treatment facility, and a steel plate continuous heat treatment facility for carrying out this method.

走行する鋼板を加熱、冷却して連続的に焼鈍するのに鋼板連続熱処理設備が利用されている（特許文献１）。 Steel plate continuous heat treatment equipment is used to heat and cool a traveling steel plate and continuously anneal it (Patent Document 1).

図４（ａ）は鋼板連続熱処理設備の概略図、（ｂ）は溶融亜鉛メッキ設備の鋼板連続熱処理設備の概略図である。 FIG. 4A is a schematic view of a steel plate continuous heat treatment facility, and FIG. 4B is a schematic view of a steel plate continuous heat treatment facility of a hot dip galvanizing facility.

図４（ａ）において、デフレクターロール１から鋼板２は炉内に導入され、炉内の上部及び下部の搬送ロール３により、加熱帯４、均熱帯５、徐冷帯６、急冷帯７、過時効帯８、２次冷却帯９、３次冷却帯１０を順次搬送されてクエンチ装置１１を経て次工程へ搬送される。 In FIG. 4 (a), the steel plate 2 is introduced from the deflector roll 1 into the furnace, and heated zone 4, soaking zone 5, slow cooling zone 6, quench zone 7, The aging zone 8, the secondary cooling zone 9, and the tertiary cooling zone 10 are sequentially conveyed, and are conveyed to the next process via the quench device 11.

また、図４（ｂ）に示す溶融亜鉛メッキ設備は、炉内に導入された鋼板２は、加熱帯４、均熱帯５、徐冷帯６、急冷帯１２、調整帯１３，１４へ順次搬送され、スナウト１５を経てメッキポット１６で溶融亜鉛メッキされる。 4B, the steel sheet 2 introduced into the furnace is sequentially conveyed to the heating zone 4, the soaking zone 5, the slow cooling zone 6, the quenching zone 12, and the adjustment zones 13 and 14. Then, it is hot dip galvanized in the plating pot 16 through the snout 15.

図５は徐冷帯及び急冷帯の一例を示す概略図である。 FIG. 5 is a schematic view showing an example of a slow cooling zone and a rapid cooling zone.

図５において、徐冷帯６、急冷帯１２においては、走行する鋼板２を挟んで冷却用気体を鋼板２に吹き付ける複数の冷却用ウインドボックス１７が間隔をおいて配置され、各冷却用ウインドボックス１７には冷却ブロワ１８により冷却用気体が供給される。徐冷帯６、急冷帯１２では、鋼板の出側温度が所定の温度となるように冷却ブロワ１８により冷却用ウインドボックス１７から冷却用気体を鋼板２の両側に吹き付けて冷却を制御している。 In FIG. 5, in the slow cooling zone 6 and the quenching zone 12, a plurality of cooling wind boxes 17 for blowing cooling gas to the steel plate 2 with the traveling steel plate 2 interposed therebetween are arranged at intervals, and each cooling wind box is arranged. 17 is supplied with a cooling gas by a cooling blower 18. In the slow cooling zone 6 and the rapid cooling zone 12, the cooling blower 18 blows a cooling gas from the cooling wind box 17 to both sides of the steel plate 2 so that the outlet temperature of the steel plate becomes a predetermined temperature. .

徐冷帯６の入側板温は板温検出器２１、徐冷帯６の出側板温は板温検出器１９、急冷帯の出側板温は板温検出器２０により測定され、プロセスコンピューターにおいて、鋼種毎の温度パターンと鋼板サイズから、各炉帯での処理可能な通板速度が演算され、その中で最も小さな通板速度を、その鋼種、サイズの最大通板速度として、通板速度を制限している。 The inlet side plate temperature of the slow cooling zone 6 is measured by the plate temperature detector 21, the outlet side plate temperature of the slow cooling zone 6 is measured by the plate temperature detector 19, and the outlet side plate temperature of the rapid cooling zone is measured by the plate temperature detector 20. From the temperature pattern for each steel type and the steel plate size, the plate passing speed that can be processed in each furnace zone is calculated, and the lowest plate passing speed is calculated as the maximum plate passing speed for that steel type and size. Restricted.

鋼板２は、徐冷帯６により加熱・均熱帯の焼鈍温度から徐冷した後に、急冷帯１２で急冷することにより、所定の機械的特性が得られるようにしている。 The steel sheet 2 is gradually cooled from a heating / soaking annealing temperature by the annealing zone 6 and then rapidly cooled by the quenching zone 12 so that predetermined mechanical characteristics can be obtained.

冷却帯の冷却方法として、特許文献２には、鋼板連続焼鈍設備の均熱後の１次冷却帯で、鋼板の表面にノズルから気体を吹き付けて冷却するガスジェット冷却装置を通板方向に設けた複数段冷却ユニットの冷却能力を独立して制御可能にして前段側の冷却ユニットを徐冷可能に、後段側の冷却ユニットを急冷可能にして冷却することが開示されている（特許文献２参照）。
特開２００５−２２６１５７号公報特開２００６−１２４８１７号公報 As a cooling method of the cooling zone, Patent Document 2 discloses a primary cooling zone after soaking of the steel plate continuous annealing equipment, and a gas jet cooling device that cools the surface of the steel plate by blowing a gas from a nozzle is provided in the plate direction. In addition, it is disclosed that the cooling capacity of the multi-stage cooling unit can be controlled independently so that the cooling unit on the front stage side can be gradually cooled, and the cooling unit on the rear stage side can be cooled rapidly (see Patent Document 2). ).
JP 2005-226157 A JP 2006-124817 A

特許文献２の均熱後の１次冷却帯で緩冷急冷する方法では、緩冷帯と急冷帯の境界が固定であり、緩冷帯の冷却能力不足を急冷帯で補う手法については提示されておらず、緩冷帯の能力がネックとなる場合には、緩冷帯最大通板速度以上に通板速度を上げることができない。 In the method of slow cooling and quenching in the primary cooling zone after soaking in Patent Document 2, the boundary between the slow cooling zone and the quenching zone is fixed, and a method for compensating for the lack of cooling capacity in the slow cooling zone is presented. However, if the ability of the slow cooling zone becomes a bottleneck, the feeding speed cannot be increased beyond the maximum feeding speed of the slow cooling zone.

そこで、本発明は、徐冷帯及びこれに続く急冷帯からなる冷却帯において、徐冷帯の冷却能力限界が通板速度を制限する場合、即ち徐冷帯において設定した出側温度に徐冷ができずに急冷帯への入側温度が高くなる場合の鋼板の冷却において、急冷帯に配設された前段の冷却装置の一部を徐冷用として使用することにより、通板速度を上げることを可能にし、生産効率を向上させることができる鋼板冷却方法及び鋼板連続焼鈍設備を提供するものである。 Therefore, in the present invention, in the cooling zone composed of the slow cooling zone and the subsequent rapid cooling zone, when the cooling capacity limit of the slow cooling zone limits the plate passing speed, that is, the slow cooling to the outlet temperature set in the slow cooling zone. In cooling the steel sheet when the temperature on the entrance side to the quenching zone becomes high without being able to perform the cooling, the sheet passing speed is increased by using a part of the preceding cooling device disposed in the quenching zone for slow cooling. It is possible to provide a steel plate cooling method and a steel plate continuous annealing facility that can improve production efficiency.

本発明の鋼板冷却方法は、徐冷帯と急冷帯が各々複数段の冷却装置で構成される冷却帯を配する鋼板連続熱処理設備にて、加熱された鋼板を徐冷帯で徐冷し次いで急冷帯で急冷する鋼板冷却方法であって、徐冷帯だけでは目標の徐冷帯出側板温に冷却できない場合に、急冷帯の前段の冷却装置の一部を徐冷用として使用し、その出側を仮想の徐冷帯出側として板温を制御することを特徴とする。 The steel sheet cooling method of the present invention is a steel sheet continuous heat treatment facility in which a slow cooling zone and a rapid cooling zone each include a cooling zone composed of a plurality of stages of cooling devices. A steel plate cooling method that rapidly cools in the quench zone, and if the cooling zone alone cannot cool to the target plate temperature on the outlet side of the slow zone, a part of the cooling device in the preceding stage of the quench zone is used for slow cooling. The plate temperature is controlled by using the side as a virtual annealing zone exit side.

冷却帯の最大通板速度を次の手順１〜３で求めて通板速度を制御する。 The maximum plate passing speed of the cooling zone is obtained in the following procedures 1 to 3 to control the plate passing speed.

手順１：
次の１式から徐冷帯及び急冷帯の冷却装置の冷却負荷ＴＤ_Ａを求め、次の２式から装置容量による冷却負荷ＴＤ_Ａ＝通板条件による冷却負荷ＴＤ_Ｓとして各冷却装置の通板速度Ｌｓを求める。 Step 1:
The cooling load TD _A of the cooling device in the slow cooling zone and the rapid cooling zone is obtained from the following formula 1, and the cooling load TD _A by the device capacity is calculated from the following two formulas as the cooling load TD _S by the passing plate condition. The speed Ls is obtained.

装置容量による冷却可能負荷ＴＤ_Ａ
ＴＤ_Ａ＝２・Ｌｆ・α_ｍａｘ／（ｍ・Ｃ）・・・・１式
通板条件による冷却負荷ＴＤ_Ｓ
ＴＤ_Ｓ＝ｈ・Ｌｓ・ｌｎ｛（Ｔ_Ｓ１−Ｔ_ｇ）／（Ｔ_Ｓ２−Ｔ_ｇ）｝・・・・２式
ただし、
ｈ：板厚（ｍ）
Ｌｓ：通板速度（ｍ／ｓｅｃ）
Ｔ_Ｓ１：入側板温（℃）
Ｔ_ｇ：冷却ガス温度（℃）
Ｔ_Ｓ２：出側板温（℃）
Ｌｆ：有効炉長（ｍ）
α_ｍａｘ：熱伝達係数（ｋｃａｌ／ｍ^２・ｓｅｃ・℃）
Ｃ：鋼板比熱（ｋｃａｌ／ｋｇ・℃）
ｍ：鋼板密度（ｋｇ／ｍ^３） Coolable load TD _A due to equipment capacity
TD _A = 2 · Lf · α _max / (m · C)... Formula 1 Cooling load TD _S depending on plate passing conditions
TD _S = h · Ls · ln {(T _S1 −T _g ) / (T _S2 −T _g )}...
h: Plate thickness (m)
Ls: Plate speed (m / sec)
T _S1 : Entrance side plate temperature (° C)
T _g : Cooling gas temperature (° C)
T _S2 : Delivery side plate temperature (° C)
Lf: Effective furnace length (m)
α _max : Heat transfer coefficient (kcal / m ² · sec · ° C)
C: Specific heat of steel plate (kcal / kg · ° C)
m: Steel sheet density (kg / m ³ )

手順２：
手順１で求めた徐冷帯の最大通板速度が急冷帯のどの段数で通板可能であるか求めて急冷帯で急冷に使用できる冷却装置の段数を求め、この段数を急冷帯の冷却装置の全段数から差し引いて徐冷用として切り替えることができる段数を求める。 Step 2:
Determine the number of steps in the quenching zone where the maximum plate speed of the slow cooling zone obtained in step 1 can be passed, determine the number of cooling units that can be used for quenching in the quenching zone, and use this number of cooling units in the quenching zone The number of stages that can be switched for slow cooling is obtained by subtracting from the total number of stages.

手順３：
前記手順２で求めた切り替えることができる段数のすべてのケースの段数について、手順１にしたがっておのおの通板速度を求め、求めた切り替え後の徐冷帯及び急冷帯での最大通板速度のうち、最小の最大通板速度を求め、これを徐冷帯と急冷帯をまとめた冷却帯の最大通板速度とする。この際に徐冷用に切り替える急冷帯の熱伝達係数は徐冷帯相当に修正するとともに、すべてのケースの切り替え段数の中で、冷却帯の最大通板速度の最大値とその切り替え段数を求める。 Step 3:
For the number of stages in all cases that can be switched determined in the procedure 2, the plate passing speed is determined according to the procedure 1, and among the maximum plate passing speeds in the slow cooling zone and the quenching zone obtained after switching, The minimum maximum plate passing speed is obtained, and this is defined as the maximum plate passing speed of the cooling zone that combines the slow cooling zone and the quench zone. At this time, the heat transfer coefficient of the quenching zone to be switched to slow cooling is corrected to the equivalent of the slow cooling zone, and the maximum value of the maximum feeding speed of the cooling zone and the number of switching steps are obtained among the switching steps of all cases. .

また、前記仮想の徐冷帯出側の板温Ｔ（ｔ）を次の３式及び４式から演算して板温を制御する。
Ｔ（ｔ）＝｛Ｋ・α・（Ｔ_ｇ−Ｔ_ｏ／２）・ｔ＋ｈ・Ｃ・Ｔ_ｏ｝／（Ｋ・α・ｔ／２＋ｈ・Ｃ）・・・３式
α∝lｎ｛（Ｔ_ｏ−Ｔ_ｇ）／（Ｔ_ｓ−Ｔ_ｇ）｝・・・４式
ただし、
Ｔ（ｔ）：板温（℃）
Ｋ：２／（７．８５ｇ／ｃｍ^３×３６００ｓｅｃ／ｈｒ）＝７．１×１０^−５
α：熱伝達係数（ｋｃａｌ／ｍ^２・ｈｒ・℃）
Ｔ_ｇ：冷却ガス温度（℃）
Ｔ_ｏ：入側板温（℃）＝設備徐冷帯出側の実績板温
ｔ：時間（ｓｅｃ）
ｈ：板厚（ｍｍ）
Ｃ：鋼板比熱（ｋｃａｌ／ｋｇ・℃）
Ｔ_ｓ：出側板温 Further, the plate temperature T (t) on the virtual slow cooling zone outlet side is calculated from the following equations 3 and 4 to control the plate temperature.
T (t) = {K · α · (T _g −T _o / 2) · t + h · C · T _o } / (K · α · t / 2 + h · C) (3 formulas)
α∝ln {(T _o −T _g ) / (T _s −T _g )} (4 formulas)
T (t): Plate temperature (° C)
K: 2 / (7.85 g / cm ³ × 3600 sec / hr) = 7.1 × 10 ⁻⁵
α: Heat transfer coefficient (kcal / m ² · hr · ° C)
T _g : Cooling gas temperature (° C)
T _o : inlet side plate temperature (° C) = actual plate temperature on the equipment slow cooling side t: time (sec)
h: Plate thickness (mm)
C: Specific heat of steel plate (kcal / kg · ° C)
T _s : Outlet plate temperature

また、本発明の鋼板連続熱処理設備は、加熱された鋼板を徐冷する徐冷帯と次いで急冷する急冷帯が各々複数段の冷却装置で構成される冷却帯を配する鋼板連続熱処理設備において、徐冷帯だけでは目標の徐冷帯出側板温に冷却できない場合に、急冷帯の前段の冷却装置の一部を仮想の徐冷帯として、板温を制御する制御装置を備えたことを特徴とする。 Moreover, the steel plate continuous heat treatment facility of the present invention is a steel plate continuous heat treatment facility in which a slow cooling zone for slowly cooling a heated steel plate and a quenching zone for rapid cooling are arranged in a cooling zone composed of multiple stages of cooling devices. It is characterized by having a control device that controls the plate temperature by using a part of the cooling device in the previous stage of the quenching zone as a virtual annealing zone when it cannot be cooled to the target cooling zone outlet side temperature only by the slow cooling zone. To do.

制御装置は、前記手順１〜３にしたがって冷却帯の最大通板速度を演算して通板速度を制御する制御装置、前記仮想の徐冷帯出側の板温Ｔ（ｔ）を３式及び４式から演算して板温を制御する制御装置である。 The control device calculates the maximum plate passing speed of the cooling zone according to the procedures 1 to 3 and controls the plate passing speed, and sets the virtual plate temperature T (t) on the outlet side of the slow cooling zone to three types and 4 It is a control device that controls the plate temperature by calculating from the equation.

通常は、徐冷帯出側と急冷帯出側でおのおの板温を管理している。熱処理炉の通板速度は、徐冷帯冷却容量により最大通板速度が決まる場合もあれば、急冷帯冷却容量により最大通板速度が決まる場合もあれば、他の加熱帯などの容量により最大通板速度が決まる場合もある。加熱帯、均熱帯、徐冷帯及び急冷帯の最大速度のうち、徐冷帯が最低速度である場合に、この徐冷帯の最低速度が熱処理炉最大速度となる。 Usually, each plate temperature is managed on the slow cooling zone exit side and the quenching zone exit side. In the heat treatment furnace, the maximum plate passing speed may be determined by the slow cooling zone cooling capacity, the maximum cooling plate cooling capacity may be determined by the quench zone cooling capacity, or the maximum by the capacity of other heating zones. In some cases, the plate speed is determined. Of the maximum speeds of the heating zone, the soaking zone, the slow cooling zone, and the rapid cooling zone, when the slow cooling zone is the lowest speed, the lowest speed of the slow cooling zone becomes the maximum heat treatment furnace speed.

本発明では、徐冷帯及びこれに続く急冷帯からなる冷却帯において、徐冷帯の冷却能力限界が通板速度を制限する場合、即ち徐冷帯において設定した出側温度に徐冷ができずに急冷帯への入側温度が高くなる場合の鋼板の冷却において、急冷帯に配設された前段の冷却装置の一部を徐冷用として使用することにより、通板速度を上げることを可能にし、生産効率を向上させることができる。 In the present invention, in the cooling zone composed of the slow cooling zone and the subsequent rapid cooling zone, when the cooling capacity limit of the slow cooling zone limits the plate passing speed, that is, the outlet side temperature set in the slow cooling zone can be gradually cooled. In the cooling of steel sheets when the temperature on the entrance side to the quenching zone is high, it is possible to increase the sheet feeding speed by using a part of the previous stage cooling device arranged in the quenching zone for slow cooling. And improve production efficiency.

徐冷帯の冷却能力限界により通板速度が制限され、急冷帯の冷却能力に余裕がある場合に、急冷帯前段の冷却装置の一部を徐冷用として使用し、通板速度を最大にできる急冷帯の徐冷使用切換段数を演算し、その出側を仮想の徐冷帯出側として板温制御できるので、この場合の通板速度を従来よりも大きくできるので、熱処理設備を効率的に操業することができる。 If the cooling speed limit of the slow cooling zone limits the plate feeding speed and there is a margin in the cooling capacity of the quenching zone, use a part of the cooling device in the previous stage of the quenching zone for slow cooling to maximize the plate passing speed. Since the plate temperature can be controlled by calculating the number of switching stages of the slow cooling use that can be performed and setting the exit side as the hypothetical slow cooling zone exit side, the plate passing speed in this case can be made larger than before, so heat treatment equipment can be efficiently Can operate.

本発明を実施例により説明する。 The present invention is illustrated by examples.

本発明では、徐冷帯に次いで急冷帯の前段で徐冷を行うために、冷却帯の最大通板速度と切り替え段数を次の手順で演算する。 In the present invention, in order to perform slow cooling in the preceding stage of the rapid cooling zone after the slow cooling zone, the maximum plate passing speed and the number of switching stages in the cooling zone are calculated according to the following procedure.

図１は徐冷帯及び急冷帯の冷却装置（ウインドボックス）の配置を示す模式図である。 FIG. 1 is a schematic diagram showing the arrangement of cooling devices (wind boxes) in a slow cooling zone and a rapid cooling zone.

（１）通板条件として、通板サイズ、徐冷帯入側目標板温、徐冷帯出側目標板温（急冷帯入側板温と同じ）、急冷帯出側目標板温を読み取る。 (1) As the plate passing condition, the plate passing size, the slow cooling zone entry side target plate temperature, the slow cooling zone exit side target plate temperature (same as the quenching zone entry side plate temperature), and the rapid cooling zone exit side target plate temperature are read.

本実施例では、板厚ｈ：１ｍｍ、Ｔ_Ｓ１：徐冷帯入側板温Ｔ_Ｓ１：８００℃、徐冷帯出側板温（急冷帯入側板温と同じ）Ｔ_Ｓ２：７００℃、急冷帯出側板温：４００℃、冷却ガス温度Ｔ_ｇ：５０℃、鋼板比熱Ｃ：０．１３４ｋｃａｌ／ｋｇ・℃、鋼板密度：７８５０ｋｇ／ｍ^３である。 In this example, the plate thickness h: 1 mm, T _S1 : annealing zone plate temperature T _S1 : 800 ° C, annealing zone exit side plate temperature (same as quenching zone entry side plate temperature) T _S2 : 700 ° C, quenching zone exit side plate temperature : 400 ° C., cooling gas temperature T _g : 50 ° C., steel plate specific heat C: 0.134 kcal / kg · ° C., steel plate density: 7850 kg / m ³ .

（２）急冷帯前段の徐冷用の切り替え段数と冷却帯の通板可能速度の演算を次の冷却負荷ＴＤについての前記１式及び２式により求める。
装置容量による冷却可能負荷ＴＤ_Ａ
ＴＤ_Ａ＝２・Ｌｆ・α_ｍａｘ／（ｍ・Ｃ）・・・・１式
通板条件による冷却負荷ＴＤ_Ｓ
ＴＤ_Ｓ＝ｈ・Ｌｓ・ｌｎ｛（Ｔ_Ｓ１−Ｔ_ｇ）／（Ｔ_Ｓ２−Ｔ_ｇ）｝・・・・２式
前記１式から徐冷帯の各ウインドボックス（ＳＣＦ１〜６）、急冷帯の各ウインドボックス（ＲＣＦ１〜６）のＴＤ_Ａを求め、ＴＤ_Ａ＝ＴＤ_Ｓとして前記２式のＬＳから、各ウインドボックス（ＳＣＦ１〜６、ＲＣＦ１〜６）での通板速度（Ｖｓｃｆ１〜６、Ｖｒｃｆ１〜６）を求める。ここで、例えばＶｓｃｆ３とは徐冷帯の冷却装置の１〜３段を使用して、所定の板厚、温度サイクルを達成しうる最大速度であり、Ｖｒｃｆ４とは急冷帯の冷却装置の後ろから４段を使用して、所定の板厚、温度サイクルを達成しうる最大速度である。 (2) The calculation of the number of switching stages for slow cooling in the preceding stage of the quenching zone and the plate passing speed of the cooling zone is obtained by the above formulas 1 and 2 for the next cooling load TD.
Coolable load TD _A due to equipment capacity
TD _A = 2 · Lf · α _max / (m · C)... Formula 1 Cooling load TD _S depending on sheet passing conditions
TD _S = h · Ls · ln {(T _S1 −T _g ) / (T _S2 −T _g )}... 2 type Each wind box (SCF 1 to 6) of the slow cooling zone from the above 1 type, quench zone TD _A of each of the wind boxes (RCF 1 to 6) is obtained, and TD _A = TD _S , and from the LS of the above two formulas, the plate feed speed (Vscf 1 to 6, SCF 1 to 6, RCF 1 to 6) Vrcf1 to 6) are obtained. Here, for example, Vscf3 is the maximum speed at which a predetermined plate thickness and temperature cycle can be achieved by using 1 to 3 stages of a cooling device in the slow cooling zone, and Vrcf4 is from behind the cooling device in the quenching zone. The maximum speed at which a predetermined plate thickness and temperature cycle can be achieved using four stages.

表１に演算により求めた通板速度を示す。

Table 1 shows the plate passing speed obtained by calculation.

（３）表１から、現徐冷帯の最大通板速度から急冷帯で急冷に必要な段数ｎを演算する。表１において、徐冷帯での最大速度は２６６ｍｐｍであり、
２４６ｍｐｍ（Ｖｒｃｆ３）＜２６６ｍｐｍ≦３２８ｍｐｍ（Ｖｒｃｆ４）
から急冷帯でウインドボックスＲＣＦ４（４段目）まで、即ち後段４つのウインドボックスは必ず急冷に使用しなければならないことが求まる（ｎ＝４）。 (3) From Table 1, the number of stages n required for quenching in the quenching zone is calculated from the maximum plate speed in the current slow cooling zone. In Table 1, the maximum speed in the slow cooling zone is 266 mpm,
246 mpm (Vrcf3) <266 mpm ≦ 328 mpm (Vrcf4)
To the wind box RCF4 (fourth stage) in the quenching zone, that is, the subsequent four wind boxes must be used for quenching (n = 4).

（４）徐冷用に切り替えることができる最大段数の演算
切り替え可能段数Ｉは、急冷帯の全段数Ｎから急冷に必要な段数ｎを差し引いたもの（Ｉ＝Ｎ−ｎ）であるから、切り替え可能段数Ｉ＝６−４＝２となり、急冷帯の前段の２段まで、すなわち１段あるいは２段を徐冷用として切り替え可能と求まる。 (4) Calculation of the maximum number of stages that can be switched to slow cooling The switchable stage number I is obtained by subtracting the number of stages n required for rapid cooling from the total number N of quenching zones (I = N−n). The number of possible stages I = 6−4 = 2, and up to two stages before the quenching zone, that is, one or two stages can be switched for slow cooling.

（５）徐冷用に切り替える段数毎（本実施例では、１段あるいは２段）に徐冷帯の最大通板速度、急冷帯の最大通板速度について求め、冷却帯の最大通板速度を求める。この際、徐冷用に使用する急冷帯の熱伝達係数は徐冷帯と同等に修正しておく。 (5) Obtain the maximum plate passing speed of the slow cooling zone and the maximum plate passing speed of the quench zone for each number of stages to be switched to slow cooling (in this embodiment, one or two stages), and calculate the maximum plate passing speed of the cooling zone. Ask. At this time, the heat transfer coefficient of the quenching zone used for slow cooling is corrected in the same manner as that of the slow cooling zone.

表２に２段切り替えの場合の演算結果を示す。

Table 2 shows the calculation results in the case of two-stage switching.

表３に１段切り替えの場合の演算結果を示す。

Table 3 shows the calculation results in the case of one-stage switching.

求めた切り替え後の徐冷帯及び急冷帯での最大通板速度のうち、最小の通板速度が冷却帯での最大制限速度となる。 Of the maximum plate passing speeds in the slow cooling zone and the rapid cooling zone after switching, the minimum plate passing speed is the maximum speed limit in the cooling zone.

２段切り替えの場合、表２から、切り替え後の徐冷帯に相当するＲＣＦ２の最大速度４４３ｍｐｍより急冷帯のＲＣＦ３の最大速度３２８ｍｐｍが小さいので、徐冷帯の最大速度３２８ｍｐｍが徐冷帯及び急冷帯をまとめた冷却帯での最大通板速度となる。 In the case of two-stage switching, from Table 2, since the maximum speed 328 mpm of the RCF 3 in the quenching zone is smaller than the maximum speed 443 mpm of the RCF 2 corresponding to the slow cooling zone after the switching, the maximum speed 328 mpm in the slow cooling zone is It becomes the maximum plate passing speed in the cooling zone that combines the belts.

１段切り替えの場合、表３から、切り替え後の徐冷帯に相当するＲＣＦ１の最大速度３５４ｍｐｍの方が急冷帯のＲＣＦ２の最大速度４１０ｍｐｍより小さいので、徐冷帯の最大速度３５４ｍｐｍが徐冷帯及び急冷帯をまとめた冷却帯での最大通板速度となる。 In the case of one-stage switching, from Table 3, the maximum speed 354 mpm of RCF 1 corresponding to the slow cooling zone after switching is smaller than the maximum speed 410 mpm of RCF 2 in the quenching zone, so the maximum speed 354 mpm of the slow cooling zone is the slow cooling zone. And the maximum plate passing speed in the cooling zone that combines the quenching zone.

１段切り替えの場合と２段切り替えの場合を比較すると、本ケースの場合、１段切り替えの方が通板速度が大きくなり、最大通板速度３５４ｍｐｍが求まる。 Comparing the case of one-stage switching and the case of two-stage switching, in this case, the one-stage switching increases the plate passing speed, and the maximum plate passing speed 354 mpm is obtained.

（６）加熱帯、均熱帯、前記５で求めた１段切り替えの場合切り替え後の徐冷帯及び急冷帯の最大速度を比較して、最も低い値の最大速度を求める。この最も低い値の最大速度が熱処理炉での最大制限速度となる。１段切り替えの場合の冷却帯の最大速度３５４ｍｐｍが、加熱帯の最大速度３７０ｍｐｍ、均熱帯の最大速度４２０ｍｐｍに比べて最も低い値であることから、３５４ｍｐｍが熱処理炉の最大制限速度となる。 (6) In the case of the heating zone, the soaking zone, and the one-stage switching obtained in 5 above, the maximum speeds of the slow cooling zone and the quenching zone after the switching are compared, and the lowest maximum speed is obtained. This lowest maximum speed is the maximum speed limit in the heat treatment furnace. The maximum speed 354 mpm of the cooling zone in the case of one-stage switching is the lowest value compared to the maximum speed 370 mpm of the heating zone and the maximum speed 420 mpm of the soaking zone, so 354 mpm is the maximum speed limit of the heat treatment furnace.

以上の結果から、図２の温度履歴に示すように、急冷帯の前段の１段のウインドボックス（ＲＣＦ１）を徐冷用に切り替え、こののウインドボックス（ＲＣＦ１）の出側が仮想の徐冷帯出側となる。 From the above results, as shown in the temperature history of FIG. 2, the first-stage windbox (RCF1) in the preceding stage of the rapid cooling zone is switched to slow cooling, and the exit side of this windbox (RCF1) is the virtual slow cooling zone exit. Become the side.

また、本願発明では、仮想の徐冷帯出側の板温Ｔ（ｔ）を前記の３式及び４式から演算して板温を制御する。 Moreover, in this invention, the plate | board temperature T (t) of the virtual slow cooling zone exit side is calculated from said 3 type | formula and 4 type | formula, and plate | board temperature is controlled.

Ｔ（ｔ）＝｛Ｋ・α・（Ｔ_ｇ−Ｔ_ｏ／２）・ｔ＋ｈ・Ｃ・Ｔ_ｏ｝／（Ｋ・α・ｔ／２＋ｈ・Ｃ）・・・３式
α∝lｎ｛（Ｔ_ｏ−Ｔ_ｇ）／（Ｔ_ｓ−Ｔ_ｇ）｝・・・４式
徐冷用に切り替えた急冷帯のブロワの回転数は、徐冷帯のブロワと一括制御するようにする。急冷帯の冷却装置と徐冷帯の冷却装置では、冷却能力が異なるので、急冷帯の前段を徐冷用に使用する際には、急冷帯の冷却装置の回転数を小さくして徐冷帯の熱伝達係数と同等になるように制御する必要がある。急冷帯の前段を徐冷用に使用する際の制御レンジは、徐冷帯の熱伝達係数と冷却装置の回転数との関係と、徐冷帯の熱熱伝達係数と冷却装置の回転数との関係から求めることができる。 T (t) = {K · α · (T _g −T _o / 2) · t + h · C · T _o } / (K · α · t / 2 + h · C) (3 formulas)
α∝ln {(T _o −T _g ) / (T _s −T _g )} (4 formulas) The rotational speed of the blower in the quenching zone switched to slow cooling is controlled collectively with the blower in the slow cooling zone To. Since the cooling capacity of the quenching zone cooling device and that of the slow cooling zone are different, when using the preceding stage of the quenching zone for slow cooling, the number of rotations of the quenching zone cooling device is reduced and the slow cooling zone It is necessary to control so as to be equal to the heat transfer coefficient. The control range when using the first stage of the quenching zone for slow cooling is the relationship between the heat transfer coefficient of the slow cooling zone and the rotational speed of the cooling device, the thermal heat transfer coefficient of the slow cooling zone, and the rotational speed of the cooling device. It can be obtained from the relationship.

図３は熱伝達係数と徐冷帯および冷却装置の回転数の関係を示すグラフである。 FIG. 3 is a graph showing the relationship between the heat transfer coefficient, the slow cooling zone, and the rotational speed of the cooling device.

例えば、図３において、徐冷帯（ＳＣＦ）のブロワの回転数が１００％の場合の熱伝達係数（α）は１００であり、これに相当する急冷帯（ＲＣＦ）のブロワの回転数は２０％である。徐冷帯のブロワに対する回転数指令値０−１００％に対応して、徐冷用に切り替えた急冷帯のブロワの回転数は０−２０％で制御されるように制御レンジを設定しておく。 For example, in FIG. 3, the heat transfer coefficient (α) is 100 when the rotational speed of the slow cooling zone (SCF) blower is 100%, and the rotational speed of the blower in the rapid cooling zone (RCF) corresponding to this is 20 %. Corresponding to the rotational speed command value 0-100% for the slow cooling blower, the control range is set so that the rotational speed of the rapid cooling blower switched to slow cooling is controlled at 0-20%. .

徐冷帯及び急冷帯の冷却装置（ウインドボックス）の配置を示す模式図である。It is a schematic diagram which shows arrangement | positioning of the cooling device (wind box) of a slow cooling zone and a rapid cooling zone. 演算された温度履歴を示す図である。It is a figure which shows the calculated temperature history. 熱熱伝達係数と徐冷帯および冷却装置の回転数の関係を示すグラフである。It is a graph which shows the relationship between a heat-heat transfer coefficient, a slow cooling zone, and the rotation speed of a cooling device. （ａ）は鋼板連続熱処理設備の概略図、（ｂ）は溶融亜鉛メッキ設備の鋼板連続熱処理設備の概略図である。(A) is the schematic of a steel plate continuous heat treatment equipment, (b) is the schematic of the steel plate continuous heat treatment equipment of a hot dip galvanization equipment. 徐冷帯及び急冷帯の概略図である。It is the schematic of a slow cooling zone and a rapid cooling zone.

符号の説明Explanation of symbols

１：デフレクターロール
２：鋼板
３：搬送ロール
４：加熱帯
５：均熱帯
６：徐冷帯
７：１次冷却帯
８：過時効帯
９：２次冷却帯
１０：３次冷却帯
１１：クエンチ装置
１２：急冷帯
１３，１４：冷却調整帯
１５：スナウト
１６：メッキポット
１７：冷却用ウインドボックス
１８：冷却ブロワ
１９，２０：温度検出器 1: Deflector roll 2: Steel plate 3: Transport roll 4: Heating zone 5: Soaking zone 6: Slow cooling zone 7: Primary cooling zone 8: Overaging zone 9: Secondary cooling zone 10: Third cooling zone 11: Quench Device 12: Rapid cooling zone 13, 14: Cooling adjustment zone 15: Snout 16: Plating pot 17: Winding box 18 for cooling 18: Cooling blower 19, 20: Temperature detector

Claims

徐冷帯と急冷帯が各々複数段の冷却装置で構成される冷却帯を配する鋼板連続熱処理設備にて、加熱された鋼板を徐冷帯で徐冷し次いで急冷帯で急冷する鋼板冷却方法であって、徐冷帯だけでは目標の徐冷帯出側板温に冷却できない場合に、急冷帯の前段の冷却装置の一部を徐冷用として使用し、その出側を仮想の徐冷帯出側として板温を制御することを特徴とする鋼板冷却方法。 Steel sheet cooling method in which a steel sheet is continuously cooled in a slow cooling zone and then rapidly cooled in a rapid cooling zone in a steel sheet continuous heat treatment facility in which a slow cooling zone and a rapid cooling zone are each composed of a cooling device having a plurality of stages. If the cooling zone alone cannot cool to the target cooling zone outlet side plate temperature, a part of the cooling device in the previous stage of the quenching zone is used for annealing, and the outlet side is used as the virtual annealing zone outlet side. The steel sheet cooling method characterized by controlling plate temperature as.

冷却帯の最大通板速度と該最大通板速度の実現に必要な急冷帯を徐冷帯に切り替える切り替え段数を次の手順１〜３で求めて板温を制御することを特徴とする請求項１記載の鋼板冷却方法。
手順１：
次の１式から徐冷帯及び急冷帯の冷却装置の冷却負荷ＴＤ_Ａを求め、次の２式から装置容量による冷却負荷ＴＤ_Ａ＝通板条件による冷却負荷ＴＤ_Ｓとして各冷却帯の使用段数と達成しうる通板速度Ｌｓを求める。
装置容量による冷却可能負荷ＴＤ_Ａ
ＴＤ_Ａ＝２・Ｌｆ・α_ｍａｘ／（ｍ・Ｃ）・・・・１式
通板条件による冷却負荷ＴＤ_Ｓ
ＴＤ_Ｓ＝ｈ・Ｌｓ・ｌｎ｛（Ｔ_Ｓ１−Ｔ_ｇ）／（Ｔ_Ｓ２−Ｔ_ｇ）｝・・・・２式
ただし、
ｈ：板厚（ｍ）
Ｌｓ：通板速度（ｍ／ｓｅｃ）
Ｔ_Ｓ１：入側板温（℃）
Ｔ_ｇ：冷却ガス温度（℃）
Ｔ_Ｓ２：出側板温（℃）
Ｌｆ：有効炉長（ｍ）
α_ｍａｘ：熱伝達係数（ｋｃａｌ／ｍ^２・ｓｅｃ・℃）
Ｃ：鋼板比熱（ｋｃａｌ／ｋｇ・℃）
ｍ：鋼板密度（ｋｇ／ｍ^３）
手順２：
徐冷帯の最大通板速度が炉の最大通板速度である場合、手順１で求めた徐冷帯の最大通板速度が急冷帯のどの段数で通板可能であるか求めて急冷帯で急冷に使用できる冷却装置の段数を求め、この段数を急冷帯の冷却装置の全段数から差し引いて徐冷用として切り替えることができる段数を求める。
手順３：
前記手順２で求めた切り替えることができる段数のすべてのケースの段数について、手順１にしたがっておのおの通板速度を求め、求めた切り替え後の徐冷帯及び急冷帯での最大通板速度のうち、最小の最大通板速度を求め、これを徐冷帯と急冷帯をまとめた冷却帯の最大通板速度とする。この際に徐冷用に切り替える急冷帯の熱伝達係数は徐冷帯相当に修正するとともに、すべてのケースの切り替え段数の中で、冷却帯の最大通板速度の最大値とその切り替え段数を求める。 The plate temperature is controlled by obtaining the maximum plate passing speed of the cooling zone and the number of switching stages for switching from the quenching zone required for realizing the maximum plate passing rate to the slow cooling zone in the following steps 1 to 3. The steel plate cooling method according to 1.
Step 1:
The cooling load TD _A of the cooling device of the slow cooling zone and the rapid cooling zone is obtained from the following formula 1, and the cooling load TD _A by the device capacity is calculated from the following two formulas = the cooling load TD _S by the passage condition is the number of stages used in each cooling zone Then, a plate speed Ls that can be achieved is obtained.
Coolable load TD _A due to equipment capacity
TD _A = 2 · Lf · α _max / (m · C)... Formula 1 Cooling load TD _S depending on sheet passing conditions
TD _S = h · Ls · ln {(T _S1 −T _g ) / (T _S2 −T _g )}...
h: Plate thickness (m)
Ls: Plate speed (m / sec)
T _S1 : Entrance side plate temperature (° C)
T _g : Cooling gas temperature (° C)
T _S2 : Delivery side plate temperature (° C)
Lf: Effective furnace length (m)
α _max : Heat transfer coefficient (kcal / m ² · sec · ° C)
C: Specific heat of steel plate (kcal / kg · ° C)
m: Steel sheet density (kg / m ³ )
Step 2:
If the maximum plate feeding speed of the slow cooling zone is the maximum plate feeding speed of the furnace, the maximum plate feeding speed of the slow cooling zone obtained in step 1 is determined in which number of stages of the quenching zone can be passed. The number of stages of the cooling device that can be used for rapid cooling is obtained, and the number of stages that can be switched for slow cooling is obtained by subtracting the number of stages from the total number of stages of the cooling device in the quenching zone.
Step 3:
For the number of stages in all cases that can be switched determined in the procedure 2, the plate passing speed is determined according to the procedure 1, and among the maximum plate passing speeds in the slow cooling zone and the quenching zone obtained after switching, The minimum maximum plate passing speed is obtained, and this is defined as the maximum plate passing speed of the cooling zone that combines the slow cooling zone and the quench zone. At this time, the heat transfer coefficient of the quenching zone to be switched to slow cooling is corrected to the equivalent of the slow cooling zone, and the maximum value of the maximum feeding speed of the cooling zone and the number of switching steps are obtained among the switching steps of all cases. .

前記仮想の徐冷帯出側の板温Ｔ（ｔ）を、設備徐冷帯出側の板温計で測定する設備徐冷帯出側の実績板温をもとに、次の３式及び４式から演算して板温を制御することを特徴とする請求項１又は２記載の鋼板冷却方法。
Ｔ（ｔ）＝｛Ｋ・α・（Ｔ_ｇ−Ｔ_ｏ／２）・ｔ＋ｈ・Ｃ・Ｔ_ｏ｝／（Ｋ・α・ｔ／２＋ｈ・Ｃ）・・・３式
α∝lｎ｛（Ｔ_ｏ−Ｔ_ｇ）／（Ｔ_ｓ−Ｔ_ｇ）｝・・・４式
ただし、
Ｔ（ｔ）：板温（℃）
Ｋ：２／（７．８５ｇ／ｃｍ^３×３６００ｓｅｃ／ｈｒ）＝７．１×１０^−５
α：熱伝達係数（ｋｃａｌ／ｍ^２・ｈｒ・℃）
Ｔ_ｇ：冷却ガス温度（℃）
Ｔ_ｏ：入側板温（℃）＝設備徐冷帯出側の実績板温
ｔ：時間（ｓｅｃ）
ｈ：板厚（ｍｍ）
Ｃ：鋼板比熱（ｋｃａｌ／ｋｇ・℃）
Ｔ_ｓ：出側板温 From the following formulas 3 and 4, based on the actual plate temperature of the facility slow cooling zone, where the virtual temperature zone T (t) of the slow cooling zone exit side is measured with a thermometer on the facility slow cooling zone exit side. 3. The steel sheet cooling method according to claim 1, wherein the plate temperature is controlled by calculation.
T (t) = {K · α · (T _g −T _o / 2) · t + h · C · T _o } / (K · α · t / 2 + h · C) (3 formulas)
α∝ln {(T _o −T _g ) / (T _s −T _g )} (4 formulas)
T (t): Plate temperature (° C)
K: 2 / (7.85 g / cm ³ × 3600 sec / hr) = 7.1 × 10 ⁻⁵
α: Heat transfer coefficient (kcal / m ² · hr · ° C)
T _g : Cooling gas temperature (° C)
T _o : inlet side plate temperature (° C) = actual plate temperature on the equipment slow cooling side t: time (sec)
h: Plate thickness (mm)
C: Specific heat of steel plate (kcal / kg · ° C)
T _s : Outlet plate temperature

加熱された鋼板を徐冷する徐冷帯と次いで急冷する急冷帯が各々複数段の冷却装置で構成される冷却帯を配する鋼板連続熱処理設備において、
徐冷帯だけでは目標の徐冷帯出側板温に冷却できない場合に、急冷帯の前段の冷却装置の一部を仮想の徐冷帯として、板温を制御する制御装置を備えたことを特徴とする鋼板連続熱処理設備。 In the steel plate continuous heat treatment facility in which a slow cooling zone for gradually cooling the heated steel plate and a rapid cooling zone for rapid cooling are arranged in a cooling zone composed of multiple stages of cooling devices,
It is characterized by having a control device that controls the plate temperature by using a part of the cooling device in the previous stage of the quenching zone as a virtual annealing zone when it cannot be cooled to the target cooling zone outlet side temperature only by the slow cooling zone. Steel plate continuous heat treatment equipment.

制御装置が、請求項２記載の鋼板冷却方法の手順１〜３にしたがって冷却帯の最大通板速度を演算して通板速度を制御する制御装置であることを特徴とする請求項４記載の鋼板連続熱処理設備。 5. The control device according to claim 4, wherein the control device is a control device that controls the plate passing speed by calculating a maximum plate passing speed of the cooling zone according to steps 1 to 3 of the steel sheet cooling method according to claim 2. Steel plate continuous heat treatment equipment.

制御装置が、請求項３記載の鋼板冷却方法の前記仮想の徐冷帯出側の板温Ｔ（ｔ）を請求項３記載の鋼板冷却方法の３式及び４式から演算して板温を制御する制御装置であることを特徴とする請求項４又は５記載の鋼板連続熱処理設備。 The control device calculates the plate temperature T (t) on the virtual annealing zone outlet side of the steel sheet cooling method according to claim 3 from Formulas 3 and 4 of the steel plate cooling method according to Claim 3, and controls the plate temperature. The steel plate continuous heat treatment facility according to claim 4, wherein the steel plate continuous heat treatment facility is a control device.