JP5631026B2 - Continuous cooling method and apparatus after tempering of long steel material - Google Patents

Continuous cooling method and apparatus after tempering of long steel material Download PDF

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JP5631026B2
JP5631026B2 JP2010055049A JP2010055049A JP5631026B2 JP 5631026 B2 JP5631026 B2 JP 5631026B2 JP 2010055049 A JP2010055049 A JP 2010055049A JP 2010055049 A JP2010055049 A JP 2010055049A JP 5631026 B2 JP5631026 B2 JP 5631026B2
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JP2011190472A (en
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一郎 高須
一郎 高須
堺　毅
毅 堺
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Sanyo Special Steel Co Ltd
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棒鋼あるいは鋼管などの長尺鋼材の熱処理における焼戻し後の連続的に冷却する冷却方法およびその冷却装置に関する。   The present invention relates to a cooling method and a cooling device for continuously cooling after tempering in heat treatment of a long steel material such as a steel bar or a steel pipe.

従来、長尺鋼材を熱処理における焼戻し後の焼戻し温度から連続冷却する際に、長尺鋼材を水冷などにより急冷すると、長尺鋼材の靱性が向上し、より高い品質が得られる。しかし、水冷により急冷すると長尺鋼材に曲がりが発生するので、水冷後にその曲がりを矯正する必要があり、このために製造コストが高くなるとともに、焼戻しのための連続水冷設備に高額な設備設置費用や保守費用を必要とした。   Conventionally, when continuously cooling a long steel material from the tempering temperature after tempering in the heat treatment, if the long steel material is rapidly cooled by water cooling or the like, the toughness of the long steel material is improved and higher quality is obtained. However, when the steel is cooled rapidly by water cooling, the long steel material bends, so it is necessary to correct the bend after water cooling, which increases the manufacturing cost and the expensive equipment installation cost for continuous water cooling equipment for tempering. And maintenance costs.

一方、鋼管などの棒状ワークを水平に支持して軸芯線を中心にして回転させながら、棒状ワークの外周面のみを支持して軸芯線の方向に移動させながら、棒状ワークの外周面をその周囲の高周波コイルによって加熱し、加熱した棒状ワークの周囲にリング状に配置の焼入れ噴射用ジャケットから焼入れ液を噴射して冷却する方法が提案されている（例えば、特許文献１参照。）。この方法で、棒状ワークに歪を生じることなく焼入れおよび冷却できるが、このための装置は極めて複雑である。さらに、棒鋼の矯正冷却能を有し、簡潔接触方式より、自在に冷却調節可能とした常温冷却床による制御冷却方法が、提案されている（例えば、特許文献２参照。）。しかし、この方法は、棒鋼の種々の冷却パターンは意図されているが、冷却による曲がりの矯正については意図されていない。   On the other hand, while supporting a rod-shaped workpiece such as a steel pipe horizontally and rotating around the shaft core wire, while supporting only the outer peripheral surface of the rod-shaped workpiece and moving it in the direction of the shaft core wire, There has been proposed a method of cooling by heating with a high frequency coil, and injecting a quenching liquid from a quenching injection jacket arranged in a ring shape around the heated rod-shaped workpiece (see, for example, Patent Document 1). Although this method can quench and cool the rod-shaped workpiece without causing distortion, the apparatus for this purpose is extremely complicated. Furthermore, a control cooling method using a room temperature cooling bed has been proposed (see, for example, Patent Document 2) which has a straightening cooling ability for steel bars and can be freely adjusted by a simple contact method. However, this method is intended for various cooling patterns of steel bars, but is not intended for correction of bending due to cooling.

特開平７−４８６２０号公報JP 7-48620 A 特開２００９−７１１号公報JP 2009-711 A

本発明が解決しようとする課題は、棒鋼あるいは鋼管などの長尺鋼材の熱処理における焼戻し後に焼戻し温度から連続的に冷却する際に、冷却による長尺鋼材の曲がりを防止して靱性などに優れた長尺鋼材を製造する方法およびその装置を提供することである。   The problem to be solved by the present invention is that, when continuously cooling from the tempering temperature after tempering in the heat treatment of a long steel material such as a steel bar or a steel pipe, the bending of the long steel material due to cooling is prevented and the toughness is excellent. It is providing the method and apparatus for manufacturing a long steel material.

本発明は、棒鋼あるいは鋼管などの長尺鋼材を熱処理における焼戻し後に焼戻し温度から連続冷却する方法において、棒鋼あるいは鋼管などの長尺鋼材の焼戻し後の冷却ゾーンに水冷ノズルを切れ目なく長尺鋼材の上下に配置すると共に、水冷ノズルから噴射される水流が長尺鋼材に当たる角度を２０°以上４５°以下とし、かつ、焼戻し温度から水冷を開始し、その水冷開始温度から２５０℃〜１００℃までの長尺鋼材の表面の冷却速度を４００℃／秒以上とすることにより、曲りがなく、靱性などの特性の良好な長尺鋼材を製造する方法およびその方法を実施するための装置である。 The present invention relates to a method of continuously cooling a long steel material such as a steel bar or steel pipe from the tempering temperature after tempering in the heat treatment, and a water-cooling nozzle is provided in the cooling zone after tempering the long steel material such as a steel bar or steel pipe without a break. The angle at which the water stream sprayed from the water cooling nozzle hits the long steel material is set to 20 ° to 45 °, and water cooling is started from the tempering temperature, and from the water cooling start temperature to 250 ° C. to 100 ° C. This is a method for producing a long steel material having good characteristics such as toughness without bending and a device for carrying out the method by setting the cooling rate of the surface of the long steel material to 400 ° C./second or more .

すなわち、上記の課題を解決するための本発明の手段は、第１の手段では、棒鋼あるいは鋼管からなる長尺鋼材の熱処理における焼戻し処理後の焼戻し温度からの冷却方法における手段である。この手段では、長尺鋼材の冷却ゾーンの上下に、切れ目なく配置した水冷ノズルから水流を２０°以上４５°以下の角度として長尺鋼材に向けて噴射する。この噴流した水流により焼戻し温度から水冷を開始し、その水冷開始温度から２５０℃〜１００℃までの鋼材表面の冷却速度を４００℃／秒以上として長尺鋼材を冷却することからなる棒鋼あるいは鋼管からなる長尺鋼材の焼戻し時の冷却方法である。 That is, the means of the present invention for solving the above-described problem is, in the first means, means in a cooling method from a tempering temperature after tempering in a heat treatment of a long steel material made of steel bars or steel pipes. In this means, a water flow is sprayed toward the long steel material at an angle of 20 ° or more and 45 ° or less from a water-cooled nozzle disposed above and below the cooling zone of the long steel material. From the steel bar or the steel pipe, which starts cooling the water from the tempering temperature by the jetted water flow and cools the long steel material by setting the cooling rate of the steel material surface from the water cooling start temperature to 250 ° C to 100 ° C to 400 ° C / second or more. This is a cooling method during tempering of a long steel material.

第２の手段は、棒鋼あるいは鋼管からなる長尺鋼材の焼戻し処理後の焼戻し温度からの冷却装置における手段である。この手段では、長尺鋼材の冷却ゾーンに切れ目なく上下に水冷ノズルを配置し、この長尺鋼材の冷却ゾーンの上下に配置した水冷ノズルの向きを、長尺鋼材に対して２０°以上４５°以下の角度としている。さらに、この冷却ノズルは、長尺鋼材に噴出する冷却水量を長尺鋼材の焼戻し温度、すなわち、水冷開始温度から２５０℃〜１００℃までの鋼材表面の冷却速度を４００℃／秒以上とし得る水量を備えたノズルからなる棒鋼あるいは鋼管からなる長尺鋼材の焼戻し処理後の冷却装置である。 A 2nd means is a means in the cooling device from the tempering temperature after the tempering process of the long steel materials which consist of steel bars or a steel pipe. In this means, water cooling nozzles are arranged above and below the cooling zone of the long steel material without any break, and the direction of the water cooling nozzles arranged above and below the cooling zone of the long steel material is 20 ° or more and 45 ° with respect to the long steel material. The following angles are used. Further, the cooling nozzle is configured such that the amount of cooling water ejected to the long steel material is the tempering temperature of the long steel material, that is, the cooling rate of the steel surface from the water cooling start temperature to 250 ° C. to 100 ° C. is 400 ° C./second or more. It is the cooling device after the tempering process of the long steel material which consists of a steel bar or a steel pipe which consists of a nozzle provided with.

本発明の上記の手段において、焼戻し後の焼戻し温度からの長尺鋼材の冷却を水冷とする効果について説明する。長尺鋼材を焼入焼戻し処理する際に、焼戻し温度から空冷により冷却すると、鋼材の脆化温度である２５０〜３００℃に保持される時間が水冷よりも長い時間生じる。このように脆化温度に保持されると、例えば、−２０℃や−４０℃の低温におけるシャルピー衝撃値が低下するか、あるいはシャルピー衝撃値の遷移温度が上がる。すなわち、空冷に代えて、水冷により急冷をすることにより、鋼材の脆化温度に保持される時間を少なくして回避することにより、例えば、−２０℃や−４０℃におけるシャルピー衝撃値が上がり、かつシャルピー衝撃値の遷移温度が下る効果が得られる。   In the above-described means of the present invention, the effect of cooling the long steel material from the tempering temperature after tempering by water cooling will be described. When a long steel material is quenched and tempered, if it is cooled by air cooling from the tempering temperature, the time during which the steel material is kept at the embrittlement temperature of 250 to 300 ° C. is longer than that of water cooling. When the embrittlement temperature is maintained in this way, for example, the Charpy impact value at a low temperature of −20 ° C. or −40 ° C. decreases or the transition temperature of the Charpy impact value increases. That is, instead of air cooling, by quenching by water cooling, avoiding by reducing the time that the steel material is kept at the embrittlement temperature, for example, the Charpy impact value at −20 ° C. or −40 ° C. is increased, And the effect that the transition temperature of Charpy impact value falls is acquired.

次いで、水冷ノズルから噴射される水流が長尺鋼材に当たる角度を２０°以上４５°以下とする効果について説明する。長尺鋼材に当たる水流の角度が４５°を超えると、水流が鋼材表面を走って流れず、フッ素樹脂加工の表面に水流が当たったときのように、水流が鋼材表面で跳ねたり、あるいは熱処理炉に逆流してしまう恐れがある。熱処理炉に水が入ると水蒸気爆発を起こす恐れが生じる。一方、所定以上の流速で水流が鋼材に４５°以下の角度で当たれば、水流が鋼材表面を均一に覆うことにより、鋼材表面に蒸気膜を生成する。そこで生成された蒸気膜によって鋼材表面における冷却の不均一が防止される結果、長尺鋼材の全周が均一に冷却される。また、水冷ノズルから噴射される水流が長尺鋼材に当たる角度を２０°以上とする理由について、角度を２０°より小さくすると、下からの水が鋼材に到達する距離が長くなり届かなくなる現象が生じる。この結果上下の水たる位置がずれて焼入れにむらが生じる。なお水圧を上げれば幾分改善するが高圧仕様にする必要がある。これらを考慮し下限を２０゜とした。   Next, the effect of setting the angle at which the water flow injected from the water-cooled nozzle hits the long steel material to 20 ° or more and 45 ° or less will be described. If the angle of the water flow hitting the long steel material exceeds 45 °, the water flow does not run on the steel surface, and the water flow jumps on the surface of the steel material as if the water flow hit the surface of the fluororesin processing, or the heat treatment furnace There is a risk of backflow. If water enters the heat treatment furnace, a steam explosion may occur. On the other hand, when the water flow hits the steel material at an angle of 45 ° or less at a flow rate of a predetermined value or more, the water flow uniformly covers the steel material surface, thereby generating a vapor film on the steel material surface. As a result, the generated steam film prevents uneven cooling on the surface of the steel material, so that the entire circumference of the long steel material is uniformly cooled. Moreover, about the reason which makes the angle which the water flow injected from a water-cooling nozzle hits a long steel material 20 degrees or more, when the angle is made smaller than 20 degrees, the phenomenon that the distance from which water from below reaches a steel material becomes long and does not reach occurs. . As a result, the positions of the upper and lower water drops are shifted to cause unevenness in quenching. If the water pressure is increased, it will improve somewhat, but it will be necessary to use a high pressure specification. Considering these, the lower limit was set to 20 °.

さらに、焼戻し温度、すなわち、水冷開始温度から２５０℃好ましくは１００℃までの表面の冷却速度が４００℃／秒以上とする水冷ノズルの使用並びに冷却速度とする効果について説明する。水冷ノズルから噴射される水流が弱いと、すなわち水冷開始温度から２５０℃までの表面の冷却速度が４００℃／秒未満であると、鋼材表面に蒸気膜が生成し、蒸気膜の消滅するタイミングにずれが生じて、鋼材の冷却に不均一が発生する。一方、従来から、焼戻し後に水冷することにより、衝撃値などの機械的特性が改善されることは知られていたが、量産レベルでの処理では、鋼材に曲りが発生するために、矯正工程の追加が必要となりコストがかかるために採用できなかった。しかし、水冷開始温度から２５０℃までの表面の冷却速度が４００℃／秒以上とする水冷ノズルの使用並びに冷却水量とすることで、鋼材に曲りを発生することなく冷却できる。理想的には、冷却開始温度から１００℃まで、表面の冷却速度が４００℃／秒以上となるように冷却を行うべきであるが、最低限２５０℃までの表面の冷却速度を４００℃／秒以上とすることが必要である。 Further, the tempering temperature, that is, the use of a water-cooled nozzle with a surface cooling rate of 400 ° C./second or more from the water cooling start temperature to 250 ° C., preferably 100 ° C., and the effect of the cooling rate will be described. When water stream ejected from the water-cooled nozzle is weak, the cooling rate of the surface from ie water cooling start temperature to 250 ° C. is less than 400 ° C. / sec, vapor film generated on the steel surface, and disappearance of vapor film Deviations occur in timing, resulting in non-uniform cooling of the steel material. On the other hand, it has been conventionally known that mechanical properties such as impact value can be improved by water cooling after tempering. It was not possible to employ it because it required additional cost. However, by using a water-cooling nozzle with a surface cooling rate of 400 ° C./sec or more from the water cooling start temperature to 250 ° C. and the amount of cooling water, the steel material can be cooled without causing bending. Ideally, cooling should be performed so that the cooling rate of the surface is 400 ° C./second or more from the cooling start temperature to 100 ° C., but the cooling rate of the surface up to a minimum of 250 ° C. is 400 ° C./second. This is necessary.

このように、焼戻し後に水冷することにより、冷却速度が上り、シャルピー衝撃値が向上し、例えば、従来、Ｎｉなどの希少金属を使用する必要があったが、ＪＩＳ規定のクロムモリブデン鋼であるＳＣＭなどのＮｉを含まない合金鋼が使えるようになる。また、焼戻し後に水冷しても曲がりが発生しないので、矯正工程の追加の必要がなくなる結果、コストが掛かることによる量産できない心配がなく、コストメリットはきわめて大きい。   Thus, by cooling with water after tempering, the cooling rate is increased and the Charpy impact value is improved. For example, conventionally, it has been necessary to use a rare metal such as Ni. Alloy steels that do not contain Ni, such as, can be used. In addition, since bending does not occur even when water-cooled after tempering, there is no need to add a correction process, so there is no fear of mass production due to cost, and the cost merit is extremely large.

焼戻し後の棒鋼を水冷ノズルで冷却する模式図である。It is a schematic diagram which cools the steel bar after tempering with a water cooling nozzle.

本発明を実施するための形態において、先ず、冷却装置について説明し、続いてその冷却装置を用いて冷却する冷却方法について実施例により説明する。   In the mode for carrying out the present invention, first, a cooling device will be described, and subsequently, a cooling method for cooling using the cooling device will be described with reference to examples.

棒鋼２ａあるいは鋼管２ｂからなる長尺鋼材２を焼戻し処理後の焼戻し温度から冷却するための冷却装置１は、長尺鋼材２を水冷により冷却する冷却ゾーン４を有し、この冷却ゾーン４において長尺鋼材２を水冷するための水冷ノズル６を、長尺鋼材２の上下に切れ目なく配置している。この長尺鋼材２の冷却ゾーン４には、上下に複数の水冷用のヘッダー５を配置し、これらのヘッダー５には、向きを長尺鋼材２に対して２０°以上４５°以下の水流の角度８となるようにした複数の水冷ノズル６が設けられている。すなわち、長尺鋼材２の赤熱部３の表面に対して、４００℃／秒以上の冷却速度で長尺鋼材２の焼戻し温度から２５０℃まで冷却することができるように、長尺鋼材２に対して２０°以上４５°以下の角度として向けた水冷ノズル６が形成されて冷却装置１とされている。   The cooling device 1 for cooling the long steel material 2 composed of the steel bar 2a or the steel pipe 2b from the tempering temperature after the tempering treatment has a cooling zone 4 for cooling the long steel material 2 by water cooling. Water-cooling nozzles 6 for water-cooling the long steel material 2 are arranged on the upper and lower sides of the long steel material 2 without any breaks. In the cooling zone 4 of the long steel material 2, a plurality of water-cooling headers 5 are arranged above and below, and the direction of the water flow is 20 ° or more and 45 ° or less with respect to the long steel material 2. A plurality of water-cooling nozzles 6 arranged to have an angle 8 are provided. That is, with respect to the long steel material 2, the surface of the red hot part 3 of the long steel material 2 can be cooled from the tempering temperature of the long steel material 2 to 250 ° C. at a cooling rate of 400 ° C./second or more. The water-cooling nozzle 6 oriented at an angle of 20 ° to 45 ° is formed as the cooling device 1.

本発明の冷却装置１による冷却方法の第１の実施例について説明する。先ず、ＳＣＭ４４０からなるφ２５ｍｍの径で７０００ｍｍの長さからなる棒鋼２ａの９本を、それぞれ棒鋼２ａの軸芯の周りに回転させながら一括して熱処理炉に装入して焼入れし、さらに６７０℃に加熱して焼戻した。次いで、図１に模式的に示すように、ヘッダー５に有する水冷ノズル６を棒鋼２ａの長さ１０００ｍｍの上下にわたって切れ目なく配置した冷却ゾーン４において、水冷ノズル６から噴射する水流の棒鋼２ａの赤熱部３に対する水流の角度７を上下からそれぞれ４５°として焼戻した棒鋼２ａの赤熱部３を進行方向９の方向に移動させながら水冷した。この場合、６７０℃の焼戻し温度から冷却を開始し、その冷却開始温度から２００℃までの棒鋼２ａの冷却ゾーン４の水流面８の部分の冷却速度が４００℃／秒となる水流で棒鋼２ａを冷却した。その結果、棒鋼２ａには曲がりが発生することなく、したがって矯正工程を追加する必要はなかった。得られた棒鋼２ａの中心部の２０℃におけるシャルピー衝撃値の吸収エネルギーは１８５Ｊ／ｃｍ2で、空冷の場合の２０℃におけるシャルピー衝撃値の吸収エネルギーの１６７Ｊ／ｃｍ2と比較して向上し、靱性に優れた棒鋼２ａが得られた。 A first embodiment of the cooling method by the cooling device 1 of the present invention will be described. First, nine steel bars 2a made of SCM440 having a diameter of φ25 mm and a length of 7000 mm are simultaneously charged into a heat treatment furnace while being rotated around the axis of the steel bar 2a, and further quenched at 670 ° C. And tempered. Next, as schematically shown in FIG. 1, in the cooling zone 4 in which the water-cooling nozzle 6 included in the header 5 is arranged without any breaks over the length of 1000 mm of the steel bar 2a, the red hot of the steel bar 2a of the water flow injected from the water-cooling nozzle 6 The red hot part 3 of the steel bar 2a tempered with the water flow angle 7 with respect to the part 3 set to 45 ° from above and below was cooled with water while being moved in the direction of travel 9. In this case, the cooling is started from the tempering temperature of 670 ° C., and the steel bar 2a is made to flow at a cooling rate of 400 ° C./second in the portion of the water flow surface 8 of the cooling zone 4 of the steel bar 2a from the cooling start temperature to 200 ° C. Cooled down. As a result, the steel bar 2a is not bent, and therefore there is no need to add a straightening process. Absorption energy Charpy impact value at 20 ° C. at the center of the resulting bars 2a in 185j / cm 2, increased compared to 167J / cm 2 of energy absorbed Charpy impact value at 20 ° C. in the case of air cooling, A steel bar 2a having excellent toughness was obtained.

次に、本発明の冷却装置１による冷却方法の第２の実施例について説明する。先ず、ＳＣＭ４４０からなるφ４５ｍｍの径で７０００ｍｍの長さからなる棒鋼２ａの５本を、それぞれ棒鋼２ａの軸芯の周りに回転させながら一括して熱処理炉に装入して焼入れし、さらに６２０℃に加熱して焼戻した。次いで、図１に模式的に示すように、ヘッダー５に有する水冷ノズル６を棒鋼２ａの長さ１０００ｍｍの上下にわたって切れ目なく配置した冷却ゾーン４において、水冷ノズル６から噴射する水流の棒鋼２ａの赤熱部３に対する水流の角度７を上下からそれぞれ４５°として焼戻した棒鋼２ａの赤熱部３を進行方向９の方向に移動させながら水冷した。この場合、６２０℃の焼戻し温度から冷却を開始し、その冷却開始温度から１００℃までの棒鋼２ａの冷却ゾーン４の水流面８の部分の冷却速度が４００℃／秒となる水流で棒鋼２ａを冷却した。その結果、棒鋼２ａには曲がりが発生することなく、したがって矯正工程を追加する必要はなかった。得られた棒鋼２ａの中心部の−４０℃におけるシャルピー衝撃値の吸収エネルギーは４１Ｊ／ｃｍ2で、空冷の場合の−４０℃におけるシャルピー衝撃値の吸収エネルギーの３３Ｊ／ｃｍ2と比較して向上し、靱性に優れた棒鋼２ａが得られた。 Next, a second embodiment of the cooling method by the cooling device 1 of the present invention will be described. First, five steel bars 2a made of SCM440 having a diameter of 45 mm and a length of 7000 mm are collectively charged into a heat treatment furnace while being rotated around the axis of the steel bar 2a, and further quenched at 620 ° C. And tempered. Next, as schematically shown in FIG. 1, in the cooling zone 4 in which the water-cooling nozzle 6 included in the header 5 is arranged without any breaks over the length of 1000 mm of the steel bar 2a, the red hot of the steel bar 2a of the water flow injected from the water-cooling nozzle 6 The red hot part 3 of the steel bar 2a tempered with the water flow angle 7 with respect to the part 3 set to 45 ° from above and below was cooled with water while being moved in the direction of travel 9. In this case, cooling is started from the tempering temperature of 620 ° C., and the steel bar 2a is made to flow at a cooling rate of 400 ° C./second in the portion of the water flow surface 8 of the cooling zone 4 of the steel bar 2a from the cooling start temperature to 100 ° C. Cooled down. As a result, the steel bar 2a is not bent, and therefore there is no need to add a straightening process. Absorption energy Charpy impact value at -40 ℃ in the center of the resulting steel bar 2a at 41J / cm 2, increased as compared to 33J / cm 2 of energy absorbed Charpy impact value at -40 ℃ in the case of air-cooled And the steel bar 2a excellent in toughness was obtained.

さらに、本発明の冷却装置１による冷却方法の第３の実施例について説明する。先ず、ＳＣＭ４３５からなるφ７５ｍｍの径で７０００ｍｍの長さからなる棒鋼２ａの３本を、それぞれ棒鋼２ａの軸芯の周りに回転させながら一括して熱処理炉に装入して焼入れし、さらに５８０℃に加熱して焼戻した。次いで、図１に模式的に示すように、ヘッダー５に有する水冷ノズル６を棒鋼２ａの長さ１０００ｍｍの上下にわたって切れ目なく配置した冷却ゾーン４において、水冷ノズル６から噴射する水流の棒鋼２ａの赤熱部３に対する水流の角度７を上下からそれぞれ４５°として焼戻した棒鋼２ａの赤熱部３を進行方向９の方向に移動させながら水冷した。この場合、５８０℃の焼戻し温度から冷却を開始し、その冷却開始温度から２５０℃までの棒鋼２ａの冷却ゾーン４の水流面８の部分の冷却速度が４００℃／秒となる水流で棒鋼２ａを冷却した。その結果、棒鋼２ａには曲がりが発生することなく、したがって矯正工程を追加する必要はなかった。得られた棒鋼２ａの中心部の−４０℃におけるシャルピー衝撃値の吸収エネルギーは３６Ｊ／ｃｍ2で、空冷の場合の−４０℃におけるシャルピー衝撃値の吸収エネルギーの２９Ｊ／ｃｍ2と比較して向上し、靱性に優れた棒鋼２ａが得られた。 Furthermore, the 3rd Example of the cooling method by the cooling device 1 of this invention is described. First, three steel rods 2a each having a diameter of 75 mm and a diameter of 7000 mm made of SCM435 are simultaneously charged into a heat treatment furnace while being rotated around the axis of the steel bar 2a, and further quenched at 580 ° C. And tempered. Next, as schematically shown in FIG. 1, in the cooling zone 4 in which the water-cooling nozzle 6 included in the header 5 is arranged without any breaks over the length of 1000 mm of the steel bar 2a, the red hot of the steel bar 2a of the water flow injected from the water-cooling nozzle 6 The red hot part 3 of the steel bar 2a tempered with the water flow angle 7 with respect to the part 3 set to 45 ° from above and below was cooled with water while being moved in the direction of travel 9. In this case, the cooling is started from the tempering temperature of 580 ° C., and the steel bar 2a is made to flow at a cooling rate of 400 ° C./second in the portion of the water flow surface 8 of the cooling zone 4 of the steel bar 2a from the cooling start temperature to 250 ° C. Cooled down. As a result, the steel bar 2a is not bent, and therefore there is no need to add a straightening process. Absorption energy Charpy impact value at -40 ℃ in the center of the resulting steel bar 2a at 36J / cm 2, increased as compared to 29J / cm 2 of energy absorbed Charpy impact value at -40 ℃ in the case of air-cooled And the steel bar 2a excellent in toughness was obtained.

さらに、本発明の冷却装置１による冷却方法の第４の実施例について説明する。先ず、ＳＣＭ４３５からなるφ７０ｍｍの径で７０００ｍｍの長さからなる棒鋼２ａの３本を、それぞれ棒鋼２ａの軸芯の周りに回転させながら一括して熱処理炉に装入して焼入れし、さらに５９０℃に加熱して焼戻した。次いで、図１に模式的に示すように、ヘッダー５に有する水冷ノズル６を棒鋼２ａの長さ１０００ｍｍの上下にわたって切れ目なく配置した冷却ゾーン４において、水冷ノズル６から噴射する水流の棒鋼２ａの赤熱部３に対する水流の角度７を上下からそれぞれ４０°として焼戻した棒鋼２ａの赤熱部３を進行方向９の方向に移動させながら水冷した。この場合、５９０℃の焼戻し温度から冷却を開始し、その冷却開始温度から１５０℃までの棒鋼２ａの冷却ゾーン４の水流面８の部分の冷却速度が４００℃／秒となる水流で棒鋼２ａを冷却した。その結果、棒鋼２ａには曲がりが発生することなく、したがって矯正工程を追加する必要はなかった。得られた棒鋼２ａの中心部の−４０℃におけるシャルピー衝撃値の吸収エネルギーは３８Ｊ／ｃｍ2で、空冷の場合の−４０℃におけるシャルピー衝撃値の吸収エネルギーの３０Ｊ／ｃｍ2と比較して向上し、靱性に優れた棒鋼２ａが得られた。 Furthermore, the 4th Example of the cooling method by the cooling device 1 of this invention is described. First, three steel bars 2a each having a diameter of 70 mm and a diameter of 7000 mm made of SCM435 are simultaneously charged into a heat treatment furnace while being rotated around the axis of the steel bar 2a, and further quenched at 590 ° C. And tempered. Next, as schematically shown in FIG. 1, in the cooling zone 4 in which the water-cooling nozzle 6 included in the header 5 is arranged without any breaks over the length of 1000 mm of the steel bar 2a, the red hot of the steel bar 2a of the water flow injected from the water-cooling nozzle 6 The red hot part 3 of the steel bar 2a tempered with the water flow angle 7 with respect to the part 3 set to 40 ° from the top and bottom was cooled with water while moving in the direction of travel 9. In this case, the cooling is started from the tempering temperature of 590 ° C., and the steel bar 2a is made to flow at a cooling rate of 400 ° C./second in the portion of the water flow surface 8 of the cooling zone 4 of the steel bar 2a from the cooling start temperature to 150 ° C. Cooled down. As a result, the steel bar 2a is not bent, and therefore there is no need to add a straightening process. The absorption energy of the Charpy impact value at −40 ° C. at the central portion of the obtained steel bar 2a is 38 J / cm 2 , which is improved as compared with 30 J / cm 2 of the Charpy impact value absorption at −40 ° C. in the case of air cooling. And the steel bar 2a excellent in toughness was obtained.

１ 冷却装置
２ 長尺鋼材
２ａ 棒鋼
２ｂ 鋼管
３ 赤熱部
４ 冷却ゾーン
５ ヘッダー
６ 水冷ノズル
７ 水流の角度
８ 水流面
９ 進行方向 DESCRIPTION OF SYMBOLS 1 Cooling device 2 Long steel material 2a Bar steel 2b Steel pipe 3 Red hot part 4 Cooling zone 5 Header 6 Water-cooling nozzle 7 Water flow angle 8 Water flow surface 9 Traveling direction

Claims (2)

棒鋼あるいは鋼管からなる長尺鋼材の熱処理の焼戻し処理後の冷却方法において、長尺鋼材の冷却ゾーンの上下に切れ目なく配置した水冷ノズルから噴射する水流を２０°以上４５°以下の角度として長尺鋼材に噴射し、焼戻し温度から水冷を開始し、その水冷開始温度から２５０℃〜１００℃までの鋼材表面の冷却速度を４００℃／秒以上として長尺鋼材を冷却することを特徴とする棒鋼あるいは鋼管からなる長尺鋼材の焼戻し処理後の冷却方法。 In the cooling method after tempering of the heat treatment of a long steel material made of steel bars or steel pipes, the water flow injected from a water-cooled nozzle arranged seamlessly above and below the cooling zone of the long steel material is set to an angle of 20 ° to 45 °. A steel bar which is injected into a steel material, starts water cooling from the tempering temperature , and cools the long steel material at a cooling rate of the steel surface from the water cooling start temperature to 250 ° C. to 100 ° C. at 400 ° C./second or more. A cooling method after tempering a long steel material made of a steel pipe. 棒鋼あるいは鋼管からなる長尺鋼材の焼戻し処理後の冷却装置において、長尺鋼材の冷却ゾーンに切れ目なく上下に水冷ノズルを配置し、長尺鋼材の冷却ゾーンの上下に配置した水冷ノズルの向きを長尺鋼材に対して２０°以上４５°以下の角度とし、かつ、この水冷ノズルは長尺鋼材に噴出する冷却水量を長尺鋼材の熱処理での焼戻し温度である水冷開始温度から２５０℃〜１００℃までの長尺鋼材の赤熱部の表面の冷却速度を４００℃／秒以上とし得る水量を備えていることを特徴とする棒鋼あるいは鋼管からなる長尺鋼材の焼戻し処理後の冷却装置。 In a cooling device after tempering a long steel material made of steel bars or steel pipes, water-cooling nozzles are placed vertically above and below the cooling zone for long steel materials, and the direction of the water-cooling nozzles located above and below the cooling zone for long steel materials The water cooling nozzle has an angle of 20 ° or more and 45 ° or less with respect to the long steel material, and the amount of cooling water ejected to the long steel material is 250 ° C. to 100 ° C. from the water cooling start temperature which is the tempering temperature in the heat treatment of the long steel material. ° C. cooling device after tempering elongated steel consisting of steel bars or steel pipe, characterized in that it comprises a volume of water may be a 400 ° C. / sec or more cooling rate of the surface of the red-hot portion of the elongated steel up.
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