JP2019019394A - Heat treatment method and heat treatment apparatus for steel sheet - Google Patents

Heat treatment method and heat treatment apparatus for steel sheet Download PDF

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JP2019019394A
JP2019019394A JP2017140960A JP2017140960A JP2019019394A JP 2019019394 A JP2019019394 A JP 2019019394A JP 2017140960 A JP2017140960 A JP 2017140960A JP 2017140960 A JP2017140960 A JP 2017140960A JP 2019019394 A JP2019019394 A JP 2019019394A
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steel plate
furnace
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郁彦 ▲高▼濱
郁彦 ▲高▼濱
Ikuhiko Takahama
弘樹 永吉
Hiroki Nagayoshi
弘樹 永吉
西村 隆
Takashi Nishimura
隆 西村
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JFE Steel Corp
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Abstract

To suppress variation in mechanical properties in the longitudinal direction of a thick steel plate without decreasing the productivity.SOLUTION: In the heat treatment method, a steel plate is subjected to a heat treatment while going through the heat treatment apparatus. At least one of the fuel supply amount and a combustion gas flow rate to a heating source in each zone is adjusted in the heat treatment furnace partitioned into a plurality of zones to control the ambient temperature for each zone. In each of the zones, the temperature is measured at a plurality of points apart from each other, and at least one of the fuel supply amount and the combustion gas flow rate to the heating source in each zone is adjusted based on the measured temperature at the plurality of points.SELECTED DRAWING: Figure 1

Description

本発明は、鋼板、中でも厚みが6〜200mm程度の厚鋼板の熱処理方法および熱処理装置に関する。   The present invention relates to a heat treatment method and a heat treatment apparatus for a steel plate, particularly a thick steel plate having a thickness of about 6 to 200 mm.

鋼板の熱処理として代表的なものに、焼入れ処理、焼ならし処理、焼鈍処理、および焼戻し処理などがある。これら鋼板の熱処理においては、鋼板の処理温度が最終製品の品質に直接的に影響を及ぼすので、鋼板の熱処理を行う熱処理炉の温度管理は、鋼板の製造工程において極めて重要となっている。   Typical heat treatments for steel sheets include quenching, normalizing, annealing, and tempering. In the heat treatment of these steel plates, since the processing temperature of the steel plate directly affects the quality of the final product, the temperature control of the heat treatment furnace for performing the heat treatment of the steel plate is extremely important in the manufacturing process of the steel plate.

従来、鋼板の熱処理を行う炉として代表的な連続式加熱炉は、その内部が複数のゾーンに区画されており、各ゾーンごとに温度が調整されている。具体的には、各ゾーンの加熱装置(例えば、バーナーまたはラジアントチューブなど)に供給される燃料および燃焼用空気の流量を制御して各ゾーンの温度を調整している。   2. Description of the Related Art Conventionally, a continuous heating furnace, which is a typical furnace for heat-treating steel sheets, is divided into a plurality of zones, and the temperature is adjusted for each zone. Specifically, the temperature of each zone is adjusted by controlling the flow rate of fuel and combustion air supplied to the heating device (for example, a burner or a radiant tube) of each zone.

この各ゾーンの温度調整について、例えば、特許文献1には、板材の注目位置の表面温度を、炉内の各ゾーンに設置された放射温度計で測定し、連続炉における板材の表面状態を監視する方法が記載されている。   Regarding the temperature adjustment of each zone, for example, in Patent Document 1, the surface temperature of the target position of the plate material is measured with a radiation thermometer installed in each zone in the furnace, and the surface state of the plate material in the continuous furnace is monitored. How to do is described.

特開平5-142170号公報Japanese Patent Laid-Open No. 5-142170

ところで、熱処理炉内における鋼板の搬送方法は、熱処理する鋼板の板厚によって異なる。比較的薄い鋼板であれば、熱処理に必要な時間も短くなるため、熱処理炉の入口から出口にかけて、特許文献1に記載の通り、停止することなく一方向に連続的に通板させる。   By the way, the conveyance method of the steel plate in a heat treatment furnace changes with plate | board thickness of the steel plate to heat-process. If the steel plate is relatively thin, the time required for the heat treatment is shortened. Therefore, as described in Patent Document 1, the plate is continuously passed in one direction from the entrance to the exit of the heat treatment furnace.

これに対し、厚みが6〜200mm程度の厚鋼板の場合、熱処理に必要な時間は薄板に比べて長くなる。そのため、厚鋼板では、搬送ロールにより熱処理炉の入口側から出口側に向かって所定時間搬送した後に、搬送方向を逆にして、入口側に向かって所定時間搬送し、その後、再び出口側に向かって搬送するといった、いわゆるオシレーション(滞留)を、熱処理条件に応じて所定回数行うことが一般的である。   On the other hand, in the case of a thick steel plate having a thickness of about 6 to 200 mm, the time required for the heat treatment is longer than that of the thin plate. Therefore, with thick steel plates, after transporting for a predetermined time from the inlet side to the outlet side of the heat treatment furnace with a transport roll, the transport direction is reversed, transported for a predetermined time toward the inlet side, and then again toward the outlet side. In general, so-called oscillation (stagnation) is performed a predetermined number of times according to heat treatment conditions.

しかしながら、上記のような熱処理炉内でのオシレーションを含む熱処理を行った場合に、熱処理後の厚鋼板の長手方向において、引張強度及び靭性等の機械的特性にばらつきを生じることが厚鋼板の熱処理に特有の問題となっていた。   However, when heat treatment including oscillation in the heat treatment furnace as described above is performed, mechanical properties such as tensile strength and toughness may vary in the longitudinal direction of the thick steel plate after heat treatment. This was a problem specific to heat treatment.

このような問題について、鋭意検討した結果、熱処理炉の各ゾーンの温度調整はゾーンごとに設置した炉温計での測定温度に基づいて行われるが、厚鋼板のオシレーションを行う位置と炉温計との相対位置関係によっては、厚鋼板全体が所望の均一な温度となるように炉内温度を制御できておらず、厚鋼板に高温部と低温部が発生する場合があることを新たに知見した。   As a result of intensive studies on such problems, the temperature of each zone of the heat treatment furnace is adjusted based on the temperature measured by the furnace thermometer installed in each zone. Depending on the relative positional relationship with the gauge, the temperature inside the furnace may not be controlled so that the entire thick steel plate is at the desired uniform temperature, and a new high temperature part and low temperature part may occur in the thick steel plate. I found out.

すなわち、図4に示されるように、炉温計4の直下に厚鋼板Pが存在する、中央および正面から向かって右側のゾーン2では、測定温度が(設定炉温より)低下するため、燃料および燃焼用空気を増加して、該ゾーン内温度を上昇させる。しかしながら、正面から向かって左側のゾーン2のように炉温計4の真下に厚鋼板Pが存在しないが、当該ゾーン2内に厚鋼板Pが部分的に存在する場合は、炉温計4の測定温度は特に低下しないため、該ゾーン内温度の上昇操作は行われないことになる。その結果、左側のゾーン2に進入している厚鋼板の部分の加熱が不足し、上記した厚鋼板P内の温度偏差を招来することになる。   That is, as shown in FIG. 4, in the zone 2 on the right side from the center and the front where the thick steel plate P exists immediately below the furnace thermometer 4, the measured temperature decreases (from the set furnace temperature). And the combustion air is increased to increase the temperature in the zone. However, the thick steel plate P does not exist directly below the furnace thermometer 4 as in the left zone 2 from the front, but when the thick steel plate P partially exists in the zone 2, Since the measurement temperature is not particularly lowered, the operation for raising the temperature in the zone is not performed. As a result, the portion of the thick steel plate entering the zone 2 on the left side is not sufficiently heated, causing a temperature deviation in the thick steel plate P described above.

このような厚鋼板内の温度偏差を低減する方法としては、オシレーションの距離を長くすることで、厚鋼板の炉内滞在時間を長くして均一加熱をはかるという手法が考えられる。しかしながら、このような距離の長いオシレーションを行うと、熱処理炉内における鋼板の占有率(カバーレシオ)が下がり、生産性の低下を招いてしまう。   As a method for reducing the temperature deviation in the thick steel plate, a method of increasing the residence time of the thick steel plate in the furnace by increasing the oscillation distance to achieve uniform heating can be considered. However, when such an oscillation with a long distance is performed, the occupation ratio (cover ratio) of the steel plate in the heat treatment furnace decreases, leading to a decrease in productivity.

本発明は上記の事情に鑑みてなされたものであり、生産性を低下させることなく、厚鋼板の長手方向における機械的特性のばらつきを低減することを目的とする。   This invention is made | formed in view of said situation, and it aims at reducing the dispersion | variation in the mechanical characteristic in the longitudinal direction of a thick steel plate, without reducing productivity.

発明者らは、熱処理炉の各ゾーンにおける炉温計および厚鋼板の相対位置に起因した、厚鋼板の温度偏差の問題を解消する方途について究明したところ、各ゾーンにおいて離間する複数点での温度測定を行い、測定されたこれらの測定温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節することで、オシレーション条件を変更することなく、厚鋼板の長手方向における機械的特性のばらつきを低減できることを新規に知見し、本発明の完成に至った。   The inventors have investigated a method for solving the problem of temperature deviation of the thick steel plate due to the relative position of the furnace thermometer and the thick steel plate in each zone of the heat treatment furnace. Based on these measured temperatures measured, by adjusting at least one of the fuel supply amount to the heating source and the combustion gas flow rate in each zone, without changing the oscillation conditions, The inventors have newly found that the variation in mechanical properties in the longitudinal direction of the thick steel plate can be reduced, and the present invention has been completed.

本発明は、上記の新規な知見に立脚するものであり、その要旨構成は、以下のとおりである。
1.熱処理炉を複数のゾーンに区画し、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節してゾーン毎に雰囲気温度を制御する、熱処理装置の内部に鋼板を通して該鋼板に熱処理を施すにあたり、
前記各ゾーンにおいて、離間する複数点での温度測定を行って該複数点での測定温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する鋼板の熱処理方法。
The present invention is based on the above-described novel findings, and the gist of the present invention is as follows.
1. A heat treatment furnace is divided into a plurality of zones, and the atmosphere temperature is controlled for each zone by adjusting at least one of the fuel supply amount to the heating source and the combustion gas flow rate in each zone. In performing heat treatment on the steel sheet,
In each zone, temperature measurement is performed at a plurality of points separated from each other, and at least one of the fuel supply amount to the heating source and the combustion gas flow rate in each zone is adjusted based on the measurement temperatures at the plurality of points. Heat treatment method for steel sheet.

2.前記複数点での測定温度を平均して得られた平均温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する上記1に記載の鋼板の熱処理方法。 2. The steel sheet according to 1 above, wherein at least one of a fuel supply amount to a heating source and a combustion gas flow rate in each zone is adjusted based on an average temperature obtained by averaging the measurement temperatures at the plurality of points. Heat treatment method.

3.前記複数点での測定温度を、各ゾーンを占める鋼板の長さに応じてまたは定数αにより加重平均して平均温度とし、該平均温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する上記1に記載の鋼板の熱処理方法。 3. The temperature measured at the plurality of points is averaged by weighted averaging according to the length of the steel plate occupying each zone or by a constant α, and based on the average temperature, the amount of fuel supplied to the heating source in each zone and The heat treatment method for a steel sheet according to the above 1, wherein at least one of the combustion gas flow rates is adjusted.

4.熱処理炉の内部を複数のゾーンに区画形成した熱処理装置であって、
前記複数のゾーンの各々は、加熱源を備え、かつ各ゾーン内の温度を測定する温度計を離間する複数の位置に有する熱処理装置。
4). A heat treatment apparatus in which the inside of a heat treatment furnace is partitioned into a plurality of zones,
Each of the plurality of zones is provided with a heating source and has a thermometer for measuring a temperature in each zone at a plurality of positions spaced apart from each other.

5.前記複数のゾーンの各々の鋼板の搬送方向の長さがLであるとき、
前記温度計のうちの1つが、各ゾーンの入側から前記搬送方向に0.28L〜0.38Lの位置に配置され、
前記温度計のうちの別の1つが、各ゾーンの入側から前記搬送方向に0.62L〜0.72Lの位置に配置される、上記4に記載の厚鋼板の熱処理装置。
5. When the length in the conveyance direction of each steel plate of the plurality of zones is L,
One of the thermometers is disposed at a position of 0.28L to 0.38L in the transport direction from the entrance side of each zone,
5. The heat treatment apparatus for thick steel plates according to 4, wherein another one of the thermometers is disposed at a position of 0.62L to 0.72L in the transport direction from the entrance side of each zone.

本発明によれば、生産性を低下させることなく、厚鋼板の長手方向における機械的特性のばらつきを低減することができる。   According to the present invention, variations in mechanical properties in the longitudinal direction of a thick steel plate can be reduced without reducing productivity.

本発明の一実施形態に係る熱処理炉の概略図である。It is the schematic of the heat processing furnace which concerns on one Embodiment of this invention. 熱処理炉の複数のゾーンのうちの1つのゾーンの概略図である。It is a schematic diagram of one zone among a plurality of zones of a heat treatment furnace. 厚鋼板長さと板内温度差の関係を示すグラフである。It is a graph which shows the relationship between a thick steel plate length and the temperature difference in a board. 従来の熱処理方法を示す概略図である。It is the schematic which shows the conventional heat processing method.

以下、本発明に係る鋼板の熱処理方法および熱処理装置の詳細を説明する。
本発明の一実施形態では、図1に示すように、熱処理炉1(熱処理装置)の内部が複数のゾーン2に区画されている。複数のゾーン2の各々には、加熱を行うバーナ3(加熱源)が設けられているとともに、ゾーン2内の温度を測定する複数、図示例で2つの炉温計4(温度計)が離間して配置されている。このような熱処理炉1内へと、搬送ロール5により、厚鋼板Pが熱処理炉入口6から搬入される。熱処理炉1内を通過する厚鋼板Pは、図に矢印で示されるような炉の入側と出側との間で往復動作を与えてオシレーションQをさせながら加熱処理を施される。かように熱処理が施された厚鋼板Pは、熱処理炉出口7から熱処理炉1外へと搬送される。
Hereinafter, the detail of the heat processing method and heat processing apparatus of the steel plate concerning this invention is demonstrated.
In one embodiment of the present invention, as shown in FIG. 1, the interior of the heat treatment furnace 1 (heat treatment apparatus) is partitioned into a plurality of zones 2. Each of the plurality of zones 2 is provided with a burner 3 (heating source) for heating, and a plurality of furnace thermometers 4 (thermometers) in the illustrated example are separated from each other for measuring the temperature in the zone 2. Are arranged. The thick steel plate P is carried into the heat treatment furnace 1 from the heat treatment furnace inlet 6 by the transport roll 5. The thick steel plate P passing through the heat treatment furnace 1 is subjected to heat treatment while causing oscillation Q by reciprocating between the entrance side and the exit side of the furnace as indicated by arrows in the figure. The thick steel plate P that has been subjected to the heat treatment is transported from the heat treatment furnace outlet 7 to the outside of the heat treatment furnace 1.

熱処理炉1では、バーナ3への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節してゾーン2ごとに雰囲気温度を制御する。燃焼用気体としては、空気以外に純酸素が挙げられる。熱処理炉1の搬送方向の長さは、一般的に50〜100mである。   In the heat treatment furnace 1, the ambient temperature is controlled for each zone 2 by adjusting at least one of the fuel supply amount to the burner 3 and the combustion gas flow rate. The combustion gas includes pure oxygen in addition to air. The length of the heat treatment furnace 1 in the conveyance direction is generally 50 to 100 m.

ゾーン2のそれぞれは、搬送方向の長さが3〜10mであることが好ましい。より好適には、3〜5mである。図1では、ゾーン2が3つのみ区画形成されているが、図1は熱処理炉1の模式図に過ぎず、ゾーン2は、5〜10つ区画形成されていることが好ましい。   Each of the zones 2 preferably has a length in the transport direction of 3 to 10 m. More preferably, it is 3-5 m. In FIG. 1, only three zones 2 are sectioned, but FIG. 1 is only a schematic view of the heat treatment furnace 1, and it is preferable that five to ten zones 2 are formed.

バーナ3は、ゾーン毎に雰囲気温度を制御するための加熱源である。本実施形態では、バーナ3は、各ゾーン2の天井に配置されており、天然ガスや副生ガスのような燃料を空気または酸素を用いて燃焼させることにより、ゾーン2内の雰囲気温度を上昇させる。バーナ3を各ゾーン2の天井に配置することに代えて、炉の側壁に厚鋼板の上部と下部の高さに配置することとしてもよい。
また、本実施形態では、加熱源としてバーナを採用しているが、これに代えて、ラジアントチューブ等を加熱源として用いることとしてもよい。
The burner 3 is a heating source for controlling the ambient temperature for each zone. In the present embodiment, the burner 3 is disposed on the ceiling of each zone 2, and the ambient temperature in the zone 2 is increased by burning fuel such as natural gas or by-product gas using air or oxygen. Let Instead of disposing the burner 3 on the ceiling of each zone 2, it is also possible to dispose the burner 3 on the side wall of the furnace at the heights of the upper and lower parts of the thick steel plate.
In the present embodiment, a burner is used as a heating source, but instead, a radiant tube or the like may be used as a heating source.

炉温計4のそれぞれは、各ゾーン2内で、厚鋼板Pの搬送方向に離間して配置されている。ゾーン2の搬送方向の長さがをLとすると、炉温計4の1つは、熱処理炉入口6側のゾーン2の端部から搬送方向に0.28L〜0.38Lの位置に配置され、もう1つの炉温計4は、熱処理炉入口6側のゾーン2の端部から搬送方向に0.62L〜0.72Lの位置に配置されることが好ましい。このように配置することで、2つの炉温計により、より広範囲に炉温を検知できる。
より好適には、炉温計4の1つは、熱処理炉入口6側のゾーン2の端部から搬送方向に0.33Lの位置に配置され、もう1つの炉温計4は、熱処理炉入口6側のゾーン2の端部から搬送方向に0.67Lの位置に配置される。
Each of the furnace thermometers 4 is arranged in each zone 2 so as to be separated in the conveying direction of the thick steel plate P. If the length of the transport direction of the zone 2 is L, one of the thermometers 4 is arranged at a position of 0.28L to 0.38L in the transport direction from the end of the zone 2 on the heat treatment furnace inlet 6 side. One furnace thermometer 4 is preferably disposed at a position of 0.62 L to 0.72 L in the transport direction from the end of the zone 2 on the heat treatment furnace inlet 6 side. By arranging in this way, the furnace temperature can be detected in a wider range by two furnace thermometers.
More preferably, one of the thermometers 4 is disposed at a position of 0.33 L in the conveying direction from the end of the zone 2 on the heat treatment furnace inlet 6 side, and the other furnace thermometer 4 is disposed at the heat treatment furnace inlet 6. It is arranged at a position of 0.67 L in the transport direction from the end of the zone 2 on the side.

炉温計4の鋼板側の先端とゾーン2内を搬送される厚鋼板Pの表面との距離は、好適には、150〜300mmである。300mmより長くなると、鋼板による炉温低下を検知できなくな
り、150mmより短くなると、炉温計が鋼板による炉温低下を検知できる範囲が狭くなる。
また、本実施形態では、各ゾーン2に2つの炉温計4を配置しているが、これに代えて、3つ以上の炉温計4を、厚鋼板Pの搬送方向に離間して配置することとしてもよい。
The distance between the steel plate side tip of the furnace thermometer 4 and the surface of the thick steel plate P conveyed in the zone 2 is preferably 150 to 300 mm. When it is longer than 300 mm, it is impossible to detect the furnace temperature drop due to the steel plate, and when it is shorter than 150 mm, the range in which the furnace thermometer can detect the furnace temperature drop due to the steel plate becomes narrow.
In this embodiment, two furnace thermometers 4 are arranged in each zone 2, but instead of this, three or more furnace thermometers 4 are arranged apart from each other in the conveying direction of the thick steel plate P. It is good to do.

搬送ロール5は、ロールを回転させることにより厚鋼板Pを搬送する。熱処理炉入口6側から熱処理炉出口7側にかけて、厚鋼板Pを所定時間搬送した後に、ロールの回転方向を逆にして、熱処理炉出口7側から熱処理炉入口6側へと所定時間搬送し、その後、再び熱処理炉入口6側から熱処理炉出口7側にかけて搬送する。このようなオシレーションを、熱処理条件に応じて所定回数行ったのち、熱処理炉出口7側から、熱処理を施した厚鋼板Pを搬出する。   The conveyance roll 5 conveys the thick steel plate P by rotating the roll. After transporting the thick steel plate P from the heat treatment furnace inlet 6 side to the heat treatment furnace outlet 7 side for a predetermined time, reverse the rotation direction of the roll, and transport it from the heat treatment furnace outlet 7 side to the heat treatment furnace inlet 6 side for a predetermined time, Then, it conveys again from the heat treatment furnace inlet 6 side to the heat treatment furnace outlet 7 side. After such an oscillation is performed a predetermined number of times according to the heat treatment conditions, the heat-treated thick steel plate P is carried out from the heat treatment furnace outlet 7 side.

このような熱処理装置による熱処理方法を以下に説明する。
熱処理炉1内の各ゾーン2では、炉温計4により測定された複数点での測定温度に基づいて、各ゾーン2内の雰囲気温度を制御することにより、厚鋼板Pの熱処理温度を制御する。各ゾーン2内の雰囲気温度の制御は、上述のように、バーナ3への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節することにより行う。
A heat treatment method using such a heat treatment apparatus will be described below.
In each zone 2 in the heat treatment furnace 1, the heat treatment temperature of the thick steel plate P is controlled by controlling the atmospheric temperature in each zone 2 based on the temperature measured at a plurality of points measured by the furnace thermometer 4. . Control of the atmospheric temperature in each zone 2 is performed by adjusting at least one of the fuel supply amount to the burner 3 and the combustion gas flow rate as described above.

また、上記各ゾーン2内の雰囲気温度の制御の指標となるのは、炉温計4により測定された複数点での測定温度である。
一実施形態では、1つのゾーン2内で測定された複数点での測定温度の平均値を、ゾーン2内の雰囲気温度の制御の指標とする。例えば、1つのゾーン2内に2つの炉温計4が設置されており、それぞれの測定温度が620℃および610℃であるとすると、これらの測定温度の平均値である615℃を、ゾーン2内の雰囲気温度の制御の指標とする。このようにすることで、鋼板と測定点の位置関係により、測定温度がばらついて、適正に雰囲気温度が制御されないことに起因する、鋼板の焼き過ぎや焼け不足の発生を抑止することができる。
In addition, the measurement temperature at a plurality of points measured by the furnace thermometer 4 is an index for controlling the ambient temperature in each of the zones 2.
In one embodiment, an average value of measured temperatures at a plurality of points measured in one zone 2 is used as an index for controlling the ambient temperature in the zone 2. For example, if two furnace thermometers 4 are installed in one zone 2 and the measured temperatures are 620 ° C. and 610 ° C., the average value of these measured temperatures is set to 615 ° C. It is used as an index for controlling the ambient temperature inside. By doing so, it is possible to suppress the occurrence of over-baking and under-baking of the steel plate due to the variation in the measurement temperature due to the positional relationship between the steel plate and the measurement point, and the atmospheric temperature being not properly controlled.

別の実施形態では、ゾーン2を前段と後段に分け、前段と後段の測定温度を、前段と後段の厚鋼板Pの搬送方向における占有長に応じて加重平均して得た温度を、雰囲気温度の制御の指標とする。
具体的には、図2に示されるように、各ゾーン2のうち、前段(熱処理炉入口6側)を第1のゾーン2Aとし、後段(熱処理炉出口7側)を第2のゾーン2Bとして、以下の式(1)により加重平均を行い、式(1)により求めた値をゾーン2内の雰囲気温度の制御の指標とする。このようにすることで、鋼板が存在する箇所の炉温に基づいて燃焼制御が適切に行われるため、目的とする温度に炉内の雰囲気温度を制御して、鋼板に対して所望の温度での熱処理が行え、鋼板の焼け不足や鋼板が存在しない箇所の過加熱を防止できる。

[A(℃)×X/(X+Y)]+[B(℃)×Y/(X+Y)] …(1)
ここで、
Aは第1のゾーン2Aの測定温度であり、
Bは第2のゾーン2Bの測定温度であり、
Xは第1のゾーン2Aを鋼板が占有する搬送方向の長さであり、
Yは第2のゾーン2Bを鋼板が占有する搬送方向の長さである。
In another embodiment, the zone 2 is divided into a front stage and a rear stage, and the temperature obtained by performing a weighted average of the measured temperatures of the front stage and the rear stage according to the occupation length in the transport direction of the front and rear steel plates P is the ambient temperature. It is used as an index of control.
Specifically, as shown in FIG. 2, among each zone 2, the first stage (heat treatment furnace inlet 6 side) is the first zone 2A, and the second stage (heat treatment furnace outlet 7 side) is the second zone 2B. The weighted average is performed by the following formula (1), and the value obtained by the formula (1) is used as an index for controlling the ambient temperature in the zone 2. By doing in this way, since combustion control is appropriately performed based on the furnace temperature of the place where the steel sheet exists, the atmosphere temperature in the furnace is controlled to the target temperature, and the steel sheet is at a desired temperature. Heat treatment can be performed, and overheating of a portion where there is no steel plate and where there is no steel plate can be prevented.
[A (° C.) × X / (X + Y)] + [B (° C.) × Y / (X + Y)] (1)
here,
A is the measured temperature of the first zone 2A,
B is the measured temperature of the second zone 2B,
X is the length in the transport direction in which the steel plate occupies the first zone 2A,
Y is the length in the transport direction in which the steel plate occupies the second zone 2B.

上記第1のゾーン2Aの測定温度Aは、第1のゾーン2Aに設置されているすべての炉温計4の平均測定温度であることとしてもよく、あるいは、第1のゾーン2Aに配置されている炉温計4のうち、厚鋼板Pが占有している部分を測定している炉温計4の温度のみを、測定温度Aとして採用することとしてもよい。あるいは、第1のゾーン2Aに設置されている炉温計4のうち、第2のゾーン2B側に最も近く配置されている炉温計4の温度を、測定温度Aとして採用することとしてもよく、あるいは、第2のゾーン2B側に最も遠く配置されている炉温計4の温度を、測定温度Aとして採用することとしてもよい。
上記第2のゾーン2Bの測定温度Bは、第2のゾーン2Bに設置されているすべての炉温計4の平均測定温度であることとしてもよく、あるいは、第2のゾーン2Bに配置されている炉温計4のうち、厚鋼板Pが占有している部分を測定している炉温計4の温度のみを、測定温度Bとして採用することとしてもよい。あるいは、第2のゾーン2Bに設置されている炉温計4のうち、第1のゾーン2A側に最も近く配置されている炉温計4の温度を、測定温度Bとして採用することとしてもよく、あるいは、第1のゾーン2A側に最も遠く配置されている炉温計4の温度を、測定温度Bとして採用することとしてもよい。
The measured temperature A of the first zone 2A may be an average measured temperature of all the furnace thermometers 4 installed in the first zone 2A, or is arranged in the first zone 2A. It is good also as employ | adopting as the measurement temperature A only the temperature of the furnace thermometer 4 which is measuring the part which the thick steel plate P occupies among the furnace thermometers 4 which are present. Or it is good also as employ | adopting as the measurement temperature A the temperature of the furnace thermometer 4 arrange | positioned nearest to the 2nd zone 2B side among the furnace thermometers 4 installed in the 1st zone 2A. Alternatively, the temperature of the furnace thermometer 4 arranged farthest on the second zone 2B side may be adopted as the measurement temperature A.
The measurement temperature B of the second zone 2B may be an average measurement temperature of all the furnace thermometers 4 installed in the second zone 2B, or is arranged in the second zone 2B. It is good also as employ | adopting only the temperature of the furnace thermometer 4 which is measuring the part which the thick steel plate P occupies among the furnace thermometers 4 currently used as the measurement temperature B. Or it is good also as employ | adopting as the measured temperature B the temperature of the furnace thermometer 4 arrange | positioned nearest to the 1st zone 2A side among the furnace thermometers 4 installed in the 2nd zone 2B. Alternatively, the temperature of the furnace thermometer 4 arranged farthest on the first zone 2A side may be adopted as the measurement temperature B.

上記実施形態では、ゾーン2を前段と後段に分け、前段と後段の測定温度を、前段と後段の厚鋼板Pの搬送方向における占有長に応じて加重平均することとしたが、このように占有長に応じて加重平均することに代えて、定数αを用いて加重平均することとしてもよい。具体的には、各ゾーン2のうち、前段を第1のゾーン2Aとし、後段を第2のゾーン2Bとして、以下の式(2)により加重平均を行い、式(2)により求めた値をゾーン2内の雰囲気温度の制御の指標とする。

[A(℃)×α]+[B(℃)×(1−α)] …(2)
ここで、
αは定数であり、
Aは第1のゾーン2Aの測定温度であり、
Bは第2のゾーン2Bの測定温度である。
In the above embodiment, the zone 2 is divided into the former stage and the latter stage, and the measured temperatures of the former stage and the latter stage are weighted and averaged according to the occupation length in the conveying direction of the former stage and the latter stage thick steel plates P. Instead of performing the weighted average according to the length, the weighted average may be performed using the constant α. Specifically, among each zone 2, the first stage is the first zone 2A and the second stage is the second zone 2B. The weighted average is performed by the following formula (2), and the value obtained by the formula (2) is calculated. It is used as an index for controlling the atmospheric temperature in the zone 2.
[A (° C.) × α] + [B (° C.) × (1−α)] (2)
here,
α is a constant,
A is the measured temperature of the first zone 2A,
B is the measured temperature of the second zone 2B.

定数αは、厚鋼板Pと炉温計4の位置関係に応じて定めることとし、0から1までの任意の数値とする。例えば、連続する3つのゾーン2を、熱処理炉入口6側からぞれぞれゾーン2−1、ゾーン2−2、ゾーン2−3とし、各ゾーンの前段(熱処理炉入口6側)および後段(熱処理炉出口7側)のそれぞれに少なくとも1つの炉温計4が配置され、これらの3つのゾーン2−1〜2−3にわたって厚鋼板Pをオシレーションした場合、厚鋼板Pのボトム端が入ったり出たりするゾーン2−1については、ゾーン2−1内の後段に配置されている炉温計4の方が、前段に配置されている炉温計4よりも、高い頻度で厚鋼板Pが近接するため、αは小さい方がよい(後段の炉温計4の測定温度を重視する。)。そのため、ゾーン2−1では、αは0超0.4以下とすることが好ましい。
厚鋼板Pのトップ端が入ったり出たりするゾーン2−3については、前段に配置されている炉温計4の方が、後段に配置されている炉温計4よりも、高い頻度で厚鋼板Pが近接するため、αは大きい方がよい(前段の炉温計4の測定温度を重視する。)。そのため、ゾーン2−3では、αは0.6以上1未満とすることが好ましい。
中央のゾーン2−2については、厚鋼板Pが近接する頻度としては、前段と後段でそれほど変化はない。そのため、αは0.5とすることが好ましい。
なお、厚鋼板Pがゾーン2−1の前段まで入らない場合、ゾーン2−1のαは0とすることが好ましい(後段の炉温計4の測定温度だけで制御する)。また、厚鋼板Pがゾーン2−3の後段まで入らない場合、ゾーン2−3のαは1とすることが好ましい(前段の炉温計4の測定温度だけで制御する)。
The constant α is determined according to the positional relationship between the thick steel plate P and the furnace thermometer 4 and is an arbitrary value from 0 to 1. For example, three consecutive zones 2 are designated as zone 2-1, zone 2-2, and zone 2-3 from the heat treatment furnace inlet 6 side, respectively, and the front stage (heat treatment furnace inlet 6 side) and rear stage ( At least one furnace thermometer 4 is disposed on each of the heat treatment furnace outlet 7 side, and when the thick steel plate P is oscillated across these three zones 2-1 to 2-3, the bottom end of the thick steel plate P enters. For the zone 2-1 that goes out, the furnace thermometer 4 arranged in the rear stage in the zone 2-1 has a higher frequency than that of the furnace thermometer 4 arranged in the former stage. Therefore, it is preferable that α is small (the temperature measured by the subsequent thermometer 4 is regarded as important). Therefore, in the zone 2-1, it is preferable that α is more than 0 and 0.4 or less.
Regarding the zone 2-3 in which the top end of the thick steel plate P enters and exits, the furnace thermometer 4 arranged in the former stage is thicker than the furnace thermometer 4 arranged in the latter stage. Since the steel plates P are close to each other, it is better that α is larger (the measurement temperature of the preceding furnace thermometer 4 is emphasized). Therefore, in zone 2-3, α is preferably 0.6 or more and less than 1.
Regarding the central zone 2-2, the frequency with which the thick steel plate P approaches is not significantly changed between the former stage and the latter stage. Therefore, α is preferably set to 0.5.
In addition, when the thick steel plate P does not enter to the front | former stage of the zone 2-1, it is preferable to set (alpha) of the zone 2-1 to 0 (it controls only by the measurement temperature of the latter-stage furnace thermometer 4). Further, when the thick steel plate P does not enter the subsequent stage of the zone 2-3, it is preferable to set the α in the zone 2-3 to 1 (controlled only by the measured temperature of the furnace thermometer 4 in the previous stage).

上記のような指標に基づいて、ゾーン2内における雰囲気温度の制御を行うことにより、オシレーションされる鋼板の長さに関わらず、厚鋼板Pの全体を、長手方向にわたって所望の均一な温度で熱処理することができる。   By controlling the atmospheric temperature in the zone 2 based on the above index, the entire thick steel plate P can be obtained at a desired uniform temperature in the longitudinal direction regardless of the length of the oscillated steel plate. It can be heat treated.

(実施例1)
以下の条件で、厚さ120mmおよび長さ5.4〜12.0mの種々の厚鋼板Pの熱処理を図1に示す構造に従う下記仕様の熱処理炉において実施した。その際、熱処理炉1におけるゾーン2ごとの雰囲気温度の制御を行った。

設定炉温:625℃
在炉時間:120分
ゾーン長:4.8m
ゾーン数:3
オシレーション速度:1.5m/min
従来例では、厚鋼板Pの位置に関わらず、単に炉温計4の測定温度をそのままゾーン2の雰囲気温度としたのに対し、本発明例では、各ゾーン2の炉温計4の測定温度の平均値を算出し、これに基づいてゾーン2の雰囲気温度を制御した。
Example 1
Under the following conditions, heat treatment of various steel plates P having a thickness of 120 mm and a length of 5.4 to 12.0 m was performed in a heat treatment furnace having the following specifications according to the structure shown in FIG. At that time, the atmospheric temperature of each zone 2 in the heat treatment furnace 1 was controlled.
Setting furnace temperature: 625 ℃
Furnace time: 120 minutes Zone length: 4.8m
Number of zones: 3
Oscillation speed: 1.5m / min
In the conventional example, regardless of the position of the thick steel plate P, the measured temperature of the furnace thermometer 4 is simply used as the ambient temperature of the zone 2 as it is. In the present invention example, the measured temperature of the furnace thermometer 4 in each zone 2 is used. Was calculated, and the ambient temperature of zone 2 was controlled based on this value.

上記のような従来例および本発明例によるゾーン2内の雰囲気温度の制御により熱処理された厚鋼板Pの板内温度差を、それぞれ測定した。板内温度は、厚鋼板Pの板厚1/2t(鋼板表面より60mm)部分を、長手方向に50mmピッチで測定し、板厚方向伝熱差分計算を用いて計算した。また、板内温度差は、測定した点の最高温度(鋼板端部100mmの部分は除く)と最低温度の差として算出した。   The in-plate temperature difference of the thick steel plate P heat-treated by controlling the atmospheric temperature in the zone 2 according to the conventional example and the example of the present invention was measured. The in-plate temperature was calculated by measuring the thickness 1 / 2t (60 mm from the surface of the steel plate) of the thick steel plate P at a pitch of 50 mm in the longitudinal direction and calculating the heat transfer difference in the thickness direction. Further, the temperature difference in the plate was calculated as the difference between the maximum temperature of the measured points (excluding the portion of the steel plate end 100 mm) and the minimum temperature.

図3にその結果を示す。厚鋼板Pの長さが7mまででは、従来例と本発明例とのゾーン2における雰囲気温度の制御方法の違いによる、板内温度偏差にほとんど違いはない。しかしながら、厚鋼板Pの長さが7mを超えると、従来例では、徐々に温度差が大きくなり、厚鋼板Pの長さが12mでは、板内の温度差が最大で60℃となる。これに対し、本発明例では、板内の温度差を最大でも40℃程度に抑えることができている。このように、本発明によれば、オシレーションの距離を変えることなく、板内温度差を低減させることができた。これによって、板の長さ方向の機械的特性のばらつきを抑えることができた。   The result is shown in FIG. When the length of the thick steel plate P is up to 7 m, there is almost no difference in the temperature deviation in the plate due to the difference in the atmospheric temperature control method in the zone 2 between the conventional example and the present invention example. However, when the length of the thick steel plate P exceeds 7 m, the temperature difference gradually increases in the conventional example, and when the length of the thick steel plate P is 12 m, the temperature difference within the plate becomes 60 ° C. at the maximum. On the other hand, in the example of the present invention, the temperature difference in the plate can be suppressed to about 40 ° C. at the maximum. Thus, according to the present invention, the in-plate temperature difference can be reduced without changing the oscillation distance. As a result, variations in the mechanical properties in the length direction of the plate could be suppressed.

1 熱処理炉(熱処理装置)
2 ゾーン
2A 第1のゾーン
2B 第2のゾーン
3 バーナ(加熱源)
4 炉温計(温度計)
5 搬送ロール
6 熱処理炉入口
7 熱処理炉出口
P 厚鋼板
1 Heat treatment furnace (heat treatment equipment)
2 Zone 2A 1st zone 2B 2nd zone 3 Burner (heating source)
4 Furnace thermometer (thermometer)
5 Transport roll 6 Heat treatment furnace inlet 7 Heat treatment furnace outlet P Thick steel plate

Claims (5)

熱処理炉を複数のゾーンに区画し、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節してゾーン毎に雰囲気温度を制御する、熱処理装置の内部に鋼板を通して該鋼板に熱処理を施すにあたり、
前記ゾーンにおいて、離間する複数点での温度測定を行って該複数点での測定温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する鋼板の熱処理方法。
A heat treatment furnace is divided into a plurality of zones, and the atmosphere temperature is controlled for each zone by adjusting at least one of the fuel supply amount to the heating source and the combustion gas flow rate in each zone. In performing heat treatment on the steel sheet,
A steel plate that measures temperature at a plurality of points separated from each other in the zone and adjusts at least one of a fuel supply amount to a heating source and a combustion gas flow rate in each zone based on the measured temperatures at the plurality of points. Heat treatment method.
前記複数点での測定温度を平均して得られた平均温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する請求項1に記載の鋼板の熱処理方法。   The steel plate according to claim 1, wherein at least one of a fuel supply amount to a heating source and a combustion gas flow rate in each zone is adjusted based on an average temperature obtained by averaging the measured temperatures at the plurality of points. Heat treatment method. 前記複数点での測定温度を、各ゾーンを占める鋼板の長さに応じてまたは定数αにより加重平均して平均温度とし、該平均温度に基づいて、各ゾーンにおける加熱源への燃料供給量および燃焼用気体流量のいずれか少なくとも一方を調節する請求項1に記載の鋼板の熱処理方法。   The temperature measured at the plurality of points is averaged by weighted averaging according to the length of the steel plate occupying each zone or by a constant α, and based on the average temperature, the amount of fuel supplied to the heating source in each zone and The heat treatment method for a steel sheet according to claim 1, wherein at least one of the combustion gas flow rates is adjusted. 熱処理炉の内部を複数のゾーンに区画形成した熱処理装置であって、
前記複数のゾーンの各々は、加熱源を備え、かつ各ゾーン内の温度を測定する温度計を離間する複数の位置に有する熱処理装置。
A heat treatment apparatus in which the inside of a heat treatment furnace is partitioned into a plurality of zones,
Each of the plurality of zones is provided with a heating source and has a thermometer for measuring a temperature in each zone at a plurality of positions spaced apart from each other.
前記複数のゾーンの各々の鋼板の搬送方向の長さがLであるとき、
前記温度計のうちの1つが、各ゾーンの入側から前記搬送方向に0.28L〜0.38Lの位置に配置され、
前記温度計のうちの別の1つが、各ゾーンの入側から前記搬送方向に0.62L〜0.72Lの位置に配置される、請求項4に記載の厚鋼板の熱処理装置。
When the length in the conveyance direction of each steel plate of the plurality of zones is L,
One of the thermometers is disposed at a position of 0.28L to 0.38L in the transport direction from the entrance side of each zone,
The another one of the said thermometers is a heat processing apparatus of the thick steel plate of Claim 4 arrange | positioned in the position of 0.62L-0.72L in the said conveyance direction from the entrance side of each zone.
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