JPH09256066A - Production of steel sheet for heat treatment excellent in peeling resistance of scale - Google Patents
Production of steel sheet for heat treatment excellent in peeling resistance of scaleInfo
- Publication number
- JPH09256066A JPH09256066A JP9056096A JP9056096A JPH09256066A JP H09256066 A JPH09256066 A JP H09256066A JP 9056096 A JP9056096 A JP 9056096A JP 9056096 A JP9056096 A JP 9056096A JP H09256066 A JPH09256066 A JP H09256066A
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- Japan
- Prior art keywords
- heat treatment
- scale
- steel sheet
- temperature
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Winding, Rewinding, Material Storage Devices (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、酸洗鋼板を大気中又は
非還元性雰囲気で加熱したときに生成する酸化スケール
が焼入れ焼戻し等の熱処理中に下地鋼から剥離しない熱
処理用鋼板を製造する方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention produces a heat-treating steel sheet in which an oxide scale produced when the pickled steel sheet is heated in the air or in a non-reducing atmosphere does not separate from the base steel during heat treatment such as quenching and tempering. Regarding the method.
【０００２】[0002]
【従来の技術】丸鋸用基板，ギア，ワッシャー等に使用
される鋼板は、熱処理特性は勿論、高い寸法精度や良好
な表面肌が要求される。そのため、熱処理工程ではスケ
ールに起因する疵の発生を極力防止する必要がある。通
常の熱処理では、熱延時に生成した黒皮スケールが除去
された鋼板が使用され、非酸化性雰囲気中で処理されて
いる。しかし、熱処理コストを低減するため、大気雰囲
気中での加熱が多用されるようになってきた。大気雰囲
気中で鋼板を加熱すると、鋼板表面に酸化スケールが発
生する。酸化スケールは、後続する焼入れ時に下地鋼か
ら剥離し、プレステンパー等の次工程で押込み疵を発生
させる原因となる。押込み疵がある鋼板では、熱処理後
の鋼板表面の研削代が嵩み、作業コストを上昇させる。
スケール疵の程度が著しいものは、寸法精度の面から製
品として使用できず、不適合になる場合がある。しか
も、スケール剥離があると、飛散したスケールによって
作業環境も悪化する。2. Description of the Related Art Steel sheets used for circular saw substrates, gears, washers, etc. are required to have high dimensional accuracy and good surface texture as well as heat treatment characteristics. Therefore, in the heat treatment process, it is necessary to prevent the occurrence of flaws due to scale as much as possible. In the ordinary heat treatment, a steel sheet from which the black scale produced during hot rolling is removed is used and treated in a non-oxidizing atmosphere. However, in order to reduce the heat treatment cost, heating in the air atmosphere has come to be frequently used. When the steel sheet is heated in the air atmosphere, oxide scale is generated on the surface of the steel sheet. The oxide scale peels off from the base steel during subsequent quenching, and causes indentation flaws in the next step such as press tempering. In the case of a steel sheet with an indentation flaw, the grinding allowance on the surface of the steel sheet after heat treatment increases, which increases the work cost.
If the scale is markedly damaged, it cannot be used as a product because of its dimensional accuracy, and it may become non-conforming. Moreover, if the scale is peeled off, the work environment is deteriorated due to the scattered scale.
【０００３】このようなことから、酸化スケールの剥離
を防止するため、特開昭６３−１７９０５６号公報，特
開平２−３４７９３号公報，特開平２−３８５２２号公
報，特開平２−１８５９１５号公報，特開平５−１９５
０５５号公報等で酸化スケールの密着性を向上させる方
法が種々紹介されている。これらは、熱延過程で急冷に
より熱延黒皮スケールを薄くし、巻取り温度の低下や非
酸化性雰囲気中での冷却によってスケール組成を密着性
の良好なＦｅ3 Ｏ4 にしたものである。何れも熱延鋼板
状態でのスケール密着性を改善しているが、熱処理時に
生成するスケールの密着性については触れられていな
い。また、表面に凹凸をつけたワークロールによって熱
延鋼板のスケール密着性を向上させることが特公平２−
１８２３０２号公報に紹介されている。更に、特開平２
−１０４６２５号公報では、Ｓｉ含有量を高くすること
により、熱処理時の加熱によるＦｅ3 Ｏ4 からＦｅＯへ
の変態を抑制している。From the above, in order to prevent the peeling of the oxide scale, JP-A-63-179056, JP-A-2-34793, JP-A-2-38522, and JP-A-2-185915. , JP-A-5-195
Various methods for improving the adhesion of oxide scales have been introduced in Japanese Patent Publication No. 055. These are obtained by thinning the hot-rolled black leather scale by quenching in the hot-rolling process, and reducing the winding temperature or cooling in a non-oxidizing atmosphere to make the scale composition Fe 3 O 4 with good adhesion. . All of them improve the scale adhesion in the hot rolled steel sheet state, but do not mention the adhesion of the scale formed during the heat treatment. In addition, it is possible to improve the scale adhesion of the hot rolled steel sheet with a work roll having an uneven surface.
No. 182302. Further, Japanese Patent Application Laid-Open
In Japanese Patent Laid-Open No. 104625, the transformation of Fe 3 O 4 to FeO due to heating during heat treatment is suppressed by increasing the Si content.
【０００４】[0004]
【発明が解決しようとする課題】特開昭６３−１７９０
５６号公報，特開平２−３４７９３号公報，特開平２−
３８５２２号公報，特開平２−１８５９１５号公報，特
開平５−１９５０５５号公報等で紹介されている方法
は、熱延黒皮ままで使用される製品に対しては有効であ
る。このような製品としては、熱処理を施すことなく切
削又は打抜き加工により製品とされる建築用材料，自動
車用材料等がある。しかし、これらの方法は、熱処理用
鋼板には不向きである。熱処理用鋼板では、黒皮スケー
ルままでは熱処理時の加熱により表面脱炭が生じること
や、酸化スケールが厚くなることによって部分的な剥離
が生じることから、押込み疵を発生させるためである。
また、酸洗して使用する場合でも、熱延板自体のスケー
ル密着性がよいことから逆に酸洗効率が低下し、スケー
ル密着性のよいＦｅ3 Ｏ4 を除去するために熱処理時の
スケール密着性が確保されない。[Problems to be Solved by the Invention] Japanese Patent Application Laid-Open No. 63-1790
56, JP-A-2-34793, JP-A-2-34793.
The methods introduced in Japanese Patent No. 38522, Japanese Unexamined Patent Publication No. 2-185915, Japanese Unexamined Patent Publication No. 5-195055, etc. are effective for products used as hot-rolled black leather. As such products, there are building materials, automobile materials, etc. which are manufactured by cutting or punching without heat treatment. However, these methods are not suitable for heat treatment steel plates. This is because, in the case of the heat treatment steel sheet, surface decarburization occurs due to heating during the heat treatment when the black scale is left as it is, and partial peeling occurs due to the thickening of the oxide scale, which causes indentation flaws.
In addition, even when used after pickling, the scale adhesion of the hot-rolled sheet itself is poor, so the pickling efficiency is reduced, and the scale during heat treatment is removed to remove Fe 3 O 4 with good scale adhesion. Adhesion is not secured.
【０００５】特公平２−１８２３０２号公報の方法で
は、ワークロール表面に凹凸を付ける加工が必要とされ
るため、ロールの製造コストが高くなる。しかも、実際
の操業では種々の鋼種を熱延するため、ロールの摩耗を
考慮すると安定した製品を得ることが難しくなる。ま
た、鋼種を限定した場合でも、ロール交換に要する時間
がかかり、ロール原単位が上昇する。特開平２−１０４
６２５号公報のように、Ｓｉ含有量を高くした熱処理用
鋼板では、熱延鋼板の表面に黒皮が付着しているため、
中〜高炭素鋼の場合にはスケール中の酸素による表面脱
炭が生じ、焼入れ不足が発生し、必要な熱処理特性が得
られないことがある。また、熱処理温度が９５０℃以上
になると、Ｓｉによる変態抑制効果が希薄になり、生成
スケールがＦｅＯになって、スケールが剥離することも
ある。本発明は、このような問題を解消すべく案出され
たものであり、熱延条件の制御によってアンカー効果を
もつ適正な粒界酸化を促進させ、大気雰囲気或いは酸化
性雰囲気中における熱処理時に生成する酸化スケールの
密着性を向上させ、焼入れ焼戻しの熱処理工程で酸化ス
ケールが剥離することがない熱処理用鋼板を得ることを
目的とする。In the method disclosed in Japanese Patent Publication No. 2-182302, it is necessary to make the surface of the work roll uneven, so that the manufacturing cost of the roll becomes high. Moreover, in actual operation, various steel types are hot-rolled, so that it is difficult to obtain a stable product in consideration of roll wear. Further, even when the type of steel is limited, it takes time to replace the rolls, and the roll unit consumption increases. JP-A-2-104
In the steel sheet for heat treatment having a high Si content as disclosed in Japanese Patent No. 625, since black skin adheres to the surface of the hot rolled steel sheet,
In the case of medium to high carbon steel, surface decarburization due to oxygen in the scale may occur, quenching may be insufficient, and necessary heat treatment characteristics may not be obtained. Further, when the heat treatment temperature is 950 ° C. or higher, the transformation suppressing effect of Si becomes weak, the produced scale becomes FeO, and the scale may peel off. The present invention has been devised to solve such a problem, and promotes proper intergranular oxidation having an anchor effect by controlling hot rolling conditions, and is produced during heat treatment in an air atmosphere or an oxidizing atmosphere. It is an object of the present invention to obtain a steel sheet for heat treatment in which the adhesion of the oxide scale to be improved is improved and the oxide scale does not peel off in the heat treatment process of quenching and tempering.
【０００６】[0006]
【課題を解決するための手段】本発明の熱処理用鋼板製
造方法は、その目的を達成するため、Ｃ：０．３〜１．
２重量％，Ｓｉ：０．１〜１．８重量％及びＭｎ：０．
３〜２．０重量％，Ｃｒ：２重量％以下及びＮｉ：２重
量％以下を含む鋼帯を熱間圧延した後、次式を満足する
巻取り温度ＣT で巻き取ることを特徴とする。 ＣT ≧６６０−３８×（％Ｃｒ）1/2 −６２×（％Ｎ
ｉ） また、熱間圧延後の仕上げ圧延機出側温度を８５０〜７
５０℃とし、仕上げ圧延機出側温度から巻取り温度まで
の平均冷却速度を４０℃／秒以下とし、巻取り後のコイ
ルを冷却速度２５℃／時以下で３５０℃まで冷却するこ
とが好ましい。この熱処理用鋼板は、特に丸鋸用基板や
ギヤ，ワッシャー等の焼入れ焼戻し等の熱処理を大気雰
囲気中の加熱で行う場合に最適な熱処理用鋼板である。In order to achieve the object, the method for producing a steel sheet for heat treatment of the present invention has a C: 0.3-1.
2% by weight, Si: 0.1 to 1.8% by weight and Mn: 0.
A steel strip containing 3 to 2.0% by weight, Cr: 2% by weight or less and Ni: 2% by weight or less is hot-rolled and then wound at a winding temperature C T satisfying the following formula. . C T ≧ 660-38 × (% Cr) 1/2 −62 × (% N
i) In addition, the hot rolling mill exit side temperature after hot rolling is set to 850 to 7
It is preferable that the temperature is 50 ° C., the average cooling rate from the exit side temperature of the finish rolling mill to the winding temperature is 40 ° C./sec or less, and the coil after winding is cooled to 350 ° C. at a cooling rate of 25 ° C./hour or less. This heat treatment steel plate is an optimum heat treatment steel plate when heat treatment such as quenching and tempering of a circular saw substrate, gears, washers and the like is performed by heating in an air atmosphere.
【０００７】[0007]
【作用】本発明者等は、熱延鋼板の表面に形成される酸
化スケールの密着性に及ぼす要因を種々調査・研究し
た。その結果、粒界酸化よって地鉄界面に付与された凹
凸の深さや個数がスケール密着性に大きな影響を及ぼし
ていることを見い出し、特願平７−８７３９２号として
提案した。本発明は、このような粒界酸化を適正に行わ
せるべく熱延条件を制御したものである。粒界酸化に起
因する凹部によってスケール密着性が改善されること
は、凹部のスケールアンカー効果が奏せられると共に、
スケール剥離の伝播が凹部によって抑制されることが原
因であると推察される。これにより、大気雰囲気中での
加熱によって生成される酸化スケールは、焼入れ焼戻し
等の熱処理工程で地鉄から剥離することがなくなる。こ
のような観点から、本発明では、このような粒界酸化を
適正に行わせるべく、具体的には深さ：３〜２０μｍ及
び個数：１０００μｍ線分長さ当り１０〜２００個の粒
界酸化部を形成するため、鋼材の組成との関連で熱延条
件を制御したものである。The present inventors investigated and studied various factors affecting the adhesion of oxide scale formed on the surface of hot-rolled steel sheet. As a result, it was found that the depth and the number of irregularities imparted to the base metal interface due to the grain boundary oxidation had a great influence on the scale adhesion, and it was proposed as Japanese Patent Application No. 7-87392. The present invention controls the hot rolling conditions in order to properly perform such grain boundary oxidation. Improving the scale adhesion by the recesses caused by the grain boundary oxidation, the scale anchor effect of the recesses is achieved,
It is speculated that this is because the propagation of scale peeling is suppressed by the recesses. As a result, the oxide scale produced by heating in the air atmosphere does not peel off from the base metal during a heat treatment process such as quenching and tempering. From such a viewpoint, in the present invention, in order to properly perform such grain boundary oxidation, specifically, depth: 3 to 20 μm and number: 1000 μm, 10 to 200 grain boundary oxidations per line segment length. In order to form the portion, the hot rolling conditions are controlled in relation to the composition of the steel material.
【０００８】Ｃ：０．３〜１．２重量％ 熱処理製品の強度を確保するために、０．３重量％以
上，望ましくは０．４重量％以上のＣが必要である。し
かし、１．２重量％を超える多量のＣが含まれると、セ
メンタイトの析出を抑えるために熱処理時の加熱温度を
下げることが必要とされる。この場合には、熱処理加熱
時に酸化スケールの生成が抑えられ、本発明を用いる必
要が生じない。通常、焼入れ焼戻し等の熱処理に使用さ
れる材料としては中〜高炭素鋼板が一般的であり、その
Ｃ含有量は０．４〜１．０重量％の範囲にある。このよ
うな中〜高炭素鋼板に対しては、本発明が顕著な効果を
発揮する。 Ｓｉ：０．１〜１．８重量％ Ｍｎと共に粒界酸化層を得るのに適した合金元素である
が、１．８重量％を超えるＳｉ含有量では表面肌が劣化
する。他方、０．１重量％に満たないＳｉ含有量は、粒
界酸化層を形成させる作用が小さくなる。C: 0.3 to 1.2% by weight In order to secure the strength of the heat-treated product, 0.3% by weight or more, preferably 0.4% by weight or more of C is necessary. However, when a large amount of C exceeding 1.2% by weight is contained, it is necessary to lower the heating temperature during the heat treatment in order to suppress the precipitation of cementite. In this case, generation of oxide scale is suppressed during heat treatment and heating, and there is no need to use the present invention. Usually, a medium to high carbon steel plate is generally used as a material used for heat treatment such as quenching and tempering, and its C content is in the range of 0.4 to 1.0% by weight. The present invention exerts a remarkable effect on such a medium to high carbon steel sheet. Si: 0.1 to 1.8% by weight It is an alloy element suitable for obtaining a grain boundary oxide layer together with Mn, but if the Si content exceeds 1.8% by weight, the surface skin deteriorates. On the other hand, if the Si content is less than 0.1% by weight, the effect of forming the grain boundary oxide layer becomes small.
【０００９】Ｍｎ：０．３〜２．０重量％ Ｓｉと同様に粒界酸化層を得るのに適した合金元素であ
る。０．３重量％未満のＭｎ含有量では焼入れ不足が生
じ、２重量％を超えるＭｎ含有量では焼き割れが発生し
易くなる。 Ｃｒ：２重量％以下 粒界酸化を促進させて地鉄界面に凹凸を生成することに
より、スケール密着性を向上させる有効な合金元素であ
り、熱処理時のスケール剥離防止効果が顕著になる。Ｃ
ｒの添加効果は、１重量％を超えるとほぼ飽和する。ま
た、２重量％を超える過剰のＣｒを添加しても、経済的
でないばかりか、却って靭性の低下を招く。Mn: 0.3 to 2.0% by weight Like Si, it is an alloying element suitable for obtaining a grain boundary oxide layer. If the Mn content is less than 0.3% by weight, insufficient quenching occurs, and if the Mn content exceeds 2% by weight, quench cracking tends to occur. Cr: 2 wt% or less It is an effective alloying element that improves scale adhesion by promoting grain boundary oxidation and generating irregularities at the base metal interface, and the scale peeling prevention effect during heat treatment becomes remarkable. C
The effect of addition of r is almost saturated when it exceeds 1% by weight. Further, addition of an excessive amount of Cr in excess of 2% by weight is not economical but rather causes deterioration of toughness.
【００１０】Ｎｉ：２重量％以下 Ｎｉは、熱間圧延中の二次酸化によって地鉄界面に濃化
する傾向を示す。濃化部分は凸状に残り、地鉄界面がミ
クロ的に凹凸形状になる。その結果、スケールに対する
アンカー効果が増大する。そのため、Ｎｉ添加量に応じ
て巻取り温度を低くしても、有効な凹凸を地鉄界面に形
成することができる。しかし、２．０重量％を超えるＮ
ｉ含有量は、経済的に不利となるばかりでなく、靭性，
延性を低下させる原因ともなる。他の合金元素として
は、必要に応じてＭｏ，Ｖ等を含有することも可能であ
る。Ni: 2% by weight or less Ni tends to be concentrated at the base metal interface due to secondary oxidation during hot rolling. The thickened portion remains convex, and the base metal interface becomes microscopically uneven. As a result, the anchor effect on the scale is increased. Therefore, even if the coiling temperature is lowered according to the amount of Ni added, effective unevenness can be formed at the base metal interface. However, N exceeding 2.0% by weight
The i content is not only economically disadvantageous, but also toughness,
It also causes a decrease in ductility. Other alloy elements may include Mo, V, etc., if necessary.
【００１１】仕上げ圧延機出側温度：８５０〜７５０℃ 熱間圧延された鋼帯は、仕上げ温度に応じて結晶粒の成
長が大きく変わる。本発明においては、仕上げ温度を適
正に調整するため、仕上げ圧延機の出側温度を８５０〜
７５０℃の範囲に設定している。仕上げ圧延機出側温度
が８５０℃を超えると、熱延鋼帯の結晶粒径が大きくな
り、粒界酸化の起点となる凹部の個数が減少し、熱処理
時にスケールが剥離し易くなる。そこで、熱延鋼板で得
られるフェライトやパーライトの粒径を極微細にするた
め、仕上げ圧延機出側温度を８５０℃以下に規制した。
結晶粒を微細化する効果は、仕上げ圧延機出側温度が低
いほど大きくなる。しかし、７５０℃を下回る仕上げ圧
延機出側温度では変形抵抗が増大し、通板性が著しく悪
化し、板厚精度の不良や電力原単位の増大等を引き起こ
す。Outlet temperature of finishing rolling mill: 850 to 750 ° C. In the hot-rolled steel strip, the growth of crystal grains greatly changes depending on the finishing temperature. In the present invention, in order to properly adjust the finishing temperature, the exit side temperature of the finishing rolling mill is set to 850 to 850.
It is set in the range of 750 ° C. When the temperature on the exit side of the finish rolling mill exceeds 850 ° C., the grain size of the hot-rolled steel strip becomes large, the number of recesses serving as the origin of grain boundary oxidation decreases, and the scale easily peels off during heat treatment. Therefore, in order to make the grain sizes of ferrite and pearlite obtained from the hot-rolled steel sheet extremely small, the finish rolling mill outlet temperature is regulated to 850 ° C or lower.
The effect of refining the crystal grains becomes greater as the temperature on the exit side of the finish rolling mill becomes lower. However, at a finish rolling mill outlet temperature of less than 750 ° C., the deformation resistance increases, the sheet passing property deteriorates significantly, and the sheet thickness accuracy becomes poor and the power consumption rate increases.
【００１２】平均冷却速度：４０℃／秒以下 粒界酸化は、熱間圧延機を出た後の熱延鋼帯が冷却され
る速度によっても影響される。このときの冷却速度が４
０℃／秒以下の緩慢な速度であると、粒界酸化が促進さ
れ、酸化スケールの剥離がより効果的に防止される。 巻取り温度：ＣT ≧６６０−３８×（％Ｃｒ）1/2 −６
２×（％Ｎｉ） 巻取り温度ＣT は、本発明者等による多数の実験結果か
ら定められたものであり、前掲の式に基づきＣｒ，Ｎｉ
の含有量に応じて巻取り温度を設定することにより、粒
界酸化が促進され、粒界酸化を起因とした凹部を生成す
ることが可能となる。その結果、熱処理スケールの剥離
を防止するアンカー効果が十分に引出される。これに対
し、前掲の式を満足しない巻取り温度ＣT で製造する
と、必要とする粒界酸化に由来する地鉄界面の凹凸が得
られないため、熱処理時にスケールが剥離し易くなる。
なお、粒界酸化は、一般的に巻取り温度を高く設定する
ことにより促進されるが、過度に高い巻取り温度では熱
延後にコイルの変形が生じ易くなることから、上限を７
５０℃とすることが好ましい。Average cooling rate: 40 ° C./sec or less Grain boundary oxidation is also affected by the rate at which the hot rolled steel strip is cooled after it leaves the hot rolling mill. The cooling rate at this time is 4
At a slow rate of 0 ° C./second or less, the grain boundary oxidation is promoted and the exfoliation of the oxide scale is more effectively prevented. Winding temperature: C T ≧ 660-38 × (% Cr) 1/2 −6
The 2 × (% Ni) coiling temperature C T is determined from a number of experimental results by the present inventors, and based on the above equation, Cr, Ni
By setting the winding temperature in accordance with the content of the grain boundary oxidation, the grain boundary oxidation is promoted, and it becomes possible to form the recesses due to the grain boundary oxidation. As a result, the anchor effect that prevents peeling of the heat-treated scale is sufficiently obtained. On the other hand, if the winding temperature C T that does not satisfy the above-mentioned formula is used for production, the unevenness of the base iron interface due to the required grain boundary oxidation cannot be obtained, so that the scale easily peels off during the heat treatment.
Grain boundary oxidation is generally promoted by setting the coiling temperature high. However, if the coiling temperature is excessively high, the coil is likely to be deformed after hot rolling.
The temperature is preferably set to 50 ° C.
【００１３】巻取り後の冷却速度：２５℃／時以下 巻取り後のコイルを冷却速度２５℃／時以下で３５０℃
まで冷却すると、粒界酸化層が安定的に成長し、板幅方
向及び長さ方向に関して均一な粒界酸化層が形成され
る。その結果、熱処理時にスケールが更に剥離し難くな
る。冷却速度の制御は３５０℃まででよく、３５０℃以
下の温度領域では冷却速度を遅くしても粒界酸化に起因
した凹部が生成しない。このように、熱延仕上げ温度，
巻取りまでの冷却速度，巻取り温度，巻取り後の冷却速
度等を制御することにより、酸化スケールに対するアン
カー効果を発揮する好適な粒界酸化層が形成される。こ
の粒界酸化層は、先願・特願平７−８７３９２号で提案
したように深さ：３〜２０μｍ及び個数：１０００μｍ
線分長さ当り１０〜２００個を満足することが好まし
い。また、酸化スケールの厚みに対する粒界酸化部の深
さの比が１以上であるとき、スケールの耐剥離性が一層
向上する。巻き取られたコイルは、熱延鋼帯としてその
まま、或いは酸洗後に熱処理を施して使用される。ま
た、通常の高炭素鋼で実施されている軟質化焼鈍を施し
た後で熱処理を行った場合でも、スケールに対するアン
カー効果は低下せず、良好な耐剥離性が維持される。ま
た、冷間圧延によって板厚調整や表面粗さを調整した場
合でも、同様に良好な耐剥離性が維持される。Cooling rate after winding: 25 ° C./hour or less 350 ° C. at a cooling rate of 25 ° C./hour or less for the coil after winding
When cooled down, the grain boundary oxide layer grows stably, and a uniform grain boundary oxide layer is formed in the plate width direction and the length direction. As a result, it becomes more difficult for the scale to peel off during heat treatment. The cooling rate may be controlled up to 350 ° C., and in the temperature range of 350 ° C. or lower, the recesses due to grain boundary oxidation are not generated even if the cooling rate is slowed. Thus, the hot rolling finish temperature,
By controlling the cooling rate up to winding, the winding temperature, the cooling rate after winding, etc., a suitable grain boundary oxide layer exhibiting an anchor effect on the oxide scale is formed. The grain boundary oxide layer has a depth of 3 to 20 μm and a number of 1000 μm as proposed in the prior application / Japanese Patent Application No. 7-87392.
It is preferable to satisfy 10 to 200 pieces per line segment length. Further, when the ratio of the depth of the grain boundary oxidized portion to the thickness of the oxidized scale is 1 or more, the peeling resistance of the scale is further improved. The wound coil is used as a hot-rolled steel strip as it is or after being pickled and subjected to heat treatment. Further, even when the heat treatment is carried out after the softening annealing which is usually carried out on the high carbon steel, the anchor effect on the scale is not lowered and the good peeling resistance is maintained. Further, even when the plate thickness and the surface roughness are adjusted by cold rolling, similarly good peel resistance is maintained.
【００１４】[0014]
【実施例】表１に示した組成をもつ鋼種Ａ〜Ｄのスラブ
を熱間圧延し、板厚３．５ｍｍの熱延板を製造した。酸
洗後、いくつかの熱延板については更に冷延−焼鈍又は
焼鈍−冷延−焼鈍を施し、板厚２．４ｍｍの冷延板を製
造した。EXAMPLES Slabs of steel types A to D having the compositions shown in Table 1 were hot-rolled to produce hot-rolled sheets having a plate thickness of 3.5 mm. After pickling, some hot rolled sheets were further subjected to cold rolling-annealing or annealing-cold rolling-annealing to manufacture cold rolled sheets having a plate thickness of 2.4 mm.
【００１５】 [0015]
【００１６】各熱処理用鋼板から幅２５ｍｍ及び長さ２
００ｍｍの試験片を切り出し、大気雰囲気中で加熱温度
８８０℃，保持時間１０分で加熱した後、６０℃の油槽
に焼入れする熱処理を施した。熱処理後に酸化スケール
の剥離性を、テープ剥離試験による剥離面積で定量化し
た。そして、スケール剥離性に及ぼす仕上げ圧延機出側
温度，巻取りまでの平均冷却速度，巻取り温度及び巻取
り後のコイル冷却速度との関係を調査した。表２の調査
結果にみられるように、試験番号１２〜１４の比較例で
は、巻取り温度が何れもＸ値より低いため、スケールの
耐剥離性が劣っていた。これに対し、巻取り温度がＸ値
より高い試験番号１〜１１の本発明例では、スケールの
剥離が全く観察されなかった。これは、仕上げ温度，巻
取りまでの冷却速度及び巻取り後の冷却速度がスケール
の耐剥離性に対して好適な範囲に調整されていることが
原因である。From each steel plate for heat treatment, width 25 mm and length 2
A 00 mm test piece was cut out, heated in an air atmosphere at a heating temperature of 880 ° C. for a holding time of 10 minutes, and then heat-treated by quenching in an oil tank at 60 ° C. The peelability of the oxide scale after heat treatment was quantified by the peeling area by a tape peeling test. Then, the relationship between the scale releasing property temperature on the exit side of the finish rolling mill, the average cooling rate until winding, the winding temperature, and the coil cooling rate after winding was investigated. As can be seen from the investigation results in Table 2, in the comparative examples of test numbers 12 to 14, the winding temperature was lower than the X value, so that the scale had poor peeling resistance. On the other hand, in the inventive examples of Test Nos. 1 to 11 in which the winding temperature was higher than the X value, no scale peeling was observed. This is because the finishing temperature, the cooling rate up to winding, and the cooling rate after winding are adjusted within a range suitable for the peel resistance of the scale.
【００１７】 [0017]
【００１８】[0018]
【発明の効果】以上に説明したように、本発明において
は、スケールに対して有効なアンカー作用を呈する粒界
酸化が生じるように熱延条件を調整することにより、加
熱雰囲気に関係なく熱処理時にスケールが地鉄から剥離
することを抑制している。そのため、大気雰囲気或いは
非還元性雰囲気中で焼入れ焼戻し等の熱処理をしても、
スケール剥離を生じることなく焼入れ焼戻し等の熱処理
が可能となり、従来の問題であったスケール押込み疵の
発生や寸法精度の不良等が解消される。その結果、熱処
理品の表面品質が向上されると共に、製造コストの低減
や作業環境の悪化防止も図られる。As described above, in the present invention, by adjusting the hot rolling conditions so that the grain boundary oxidation exhibiting an effective anchoring action on the scale is generated, the heat treatment is performed regardless of the heating atmosphere. It prevents the scale from peeling from the base steel. Therefore, even if heat treatment such as quenching and tempering is performed in an air atmosphere or a non-reducing atmosphere,
Heat treatment such as quenching and tempering can be performed without causing scale peeling, and the problems such as scale indentation flaws and poor dimensional accuracy, which have been problems in the past, can be eliminated. As a result, the surface quality of the heat-treated product is improved, and the manufacturing cost is reduced and the working environment is prevented from being deteriorated.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/00 ３０１ Ｃ２２Ｃ 38/00 ３０１Ｚ 38/58 38/58 (72)発明者 山田 利郎 広島県呉市昭和町11番１号 日新製鋼株式 会社技術研究所内─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification number Office reference number FI Technical display location C22C 38/00 301 C22C 38/00 301Z 38/58 38/58 (72) Inventor Toshiro Yamada Hiroshima Prefecture 11-11 Showa-machi, Kure City Nisshin Steel Co., Ltd. Technical Research Institute
Claims (4)
１〜１．８重量％及びＭｎ：０．３〜２．０重量％，Ｃ
ｒ：２重量％以下及びＮｉ：２重量％以下を含む鋼帯を
熱間圧延した後、次式を満足する巻取り温度ＣT で巻き
取ることを特徴とするスケールの耐剥離性に優れた熱処
理用鋼板の製造方法。 ＣT ≧６６０−３８×（％Ｃｒ）1/2 −６２×（％Ｎ
ｉ）1. C: 0.3 to 1.2% by weight, Si: 0.
1 to 1.8 wt% and Mn: 0.3 to 2.0 wt%, C
A steel strip containing r: 2% by weight or less and Ni: 2% by weight or less was hot-rolled, and then wound at a winding temperature C T satisfying the following formula, which was excellent in peeling resistance of a scale. Manufacturing method of steel sheet for heat treatment. C T ≧ 660-38 × (% Cr) 1/2 −62 × (% N
i)
５０〜７５０℃とする請求項１記載のスケールの耐剥離
性に優れた熱処理用鋼板の製造方法。2. The temperature at the exit side of the finish rolling mill after hot rolling is set to 8
50-750 degreeC, The manufacturing method of the steel plate for heat treatments excellent in the peeling resistance of the scale of Claim 1.
巻取り温度までの平均冷却速度を４０℃／秒以下で冷却
する請求項１又は２記載のスケールの耐剥離性に優れた
熱処理用鋼板の製造方法。3. The heat treatment with excellent peeling resistance of the scale according to claim 1, wherein the average cooling rate from the exit side temperature of the finish rolling mill to the winding temperature after hot rolling is cooled at 40 ° C./sec or less. Method for manufacturing steel sheet.
以下で３５０℃まで冷却する請求項１〜３の何れかに記
載のスケールの耐剥離性に優れた熱処理用鋼板の製造方
法。4. The method for producing a steel sheet for heat treatment having excellent scale peeling resistance according to claim 1, wherein the coil after winding is cooled to 350 ° C. at a cooling rate of 25 ° C./hour or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09056096A JP3839090B2 (en) | 1996-03-19 | 1996-03-19 | Manufacturing method of steel plate for heat treatment with excellent scale peeling resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09056096A JP3839090B2 (en) | 1996-03-19 | 1996-03-19 | Manufacturing method of steel plate for heat treatment with excellent scale peeling resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09256066A true JPH09256066A (en) | 1997-09-30 |
| JP3839090B2 JP3839090B2 (en) | 2006-11-01 |
Family
ID=14001813
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP09056096A Expired - Fee Related JP3839090B2 (en) | 1996-03-19 | 1996-03-19 | Manufacturing method of steel plate for heat treatment with excellent scale peeling resistance |
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| Country | Link |
|---|---|
| JP (1) | JP3839090B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010089107A (en) * | 2008-10-06 | 2010-04-22 | Kobe Steel Ltd | Method of cooling coil after coiling hot rolled material |
| CN101850492A (en) * | 2010-04-23 | 2010-10-06 | 九星控股集团有限公司 | Preparation process of special solid conductive plate and bus board for electrolysis |
| JP2011202192A (en) * | 2010-03-24 | 2011-10-13 | Nisshin Steel Co Ltd | Method for producing steel sheet for heat treatment and steel member |
| WO2016152870A1 (en) * | 2015-03-23 | 2016-09-29 | 新日鐵住金株式会社 | Hot-rolled steel sheet and manufacturing method of same, and manufacturing method of cold-rolled steel sheet |
-
1996
- 1996-03-19 JP JP09056096A patent/JP3839090B2/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010089107A (en) * | 2008-10-06 | 2010-04-22 | Kobe Steel Ltd | Method of cooling coil after coiling hot rolled material |
| JP2011202192A (en) * | 2010-03-24 | 2011-10-13 | Nisshin Steel Co Ltd | Method for producing steel sheet for heat treatment and steel member |
| CN101850492A (en) * | 2010-04-23 | 2010-10-06 | 九星控股集团有限公司 | Preparation process of special solid conductive plate and bus board for electrolysis |
| WO2016152870A1 (en) * | 2015-03-23 | 2016-09-29 | 新日鐵住金株式会社 | Hot-rolled steel sheet and manufacturing method of same, and manufacturing method of cold-rolled steel sheet |
| JP6070907B1 (en) * | 2015-03-23 | 2017-02-01 | 新日鐵住金株式会社 | Hot-rolled steel sheet and method for producing the same, and method for producing cold-rolled steel sheet |
| CN107429343A (en) * | 2015-03-23 | 2017-12-01 | 新日铁住金株式会社 | The manufacture method of hot rolled steel plate, its manufacture method and cold-rolled steel sheet |
| US11066720B2 (en) | 2015-03-23 | 2021-07-20 | Nippon Steel Corporation | Hot-rolled steel sheet and manufacturing method thereof, and manufacturing method of cold-rolled steel sheet |
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| Publication number | Publication date |
|---|---|
| JP3839090B2 (en) | 2006-11-01 |
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