JPH10192910A - Manufacture of hot rolled plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture with a high yield the hard hot rolled plate free from a defect on its surface, caused by a recessed flaw on a work roll by performing finish rolling after heating the surface of a part having the lowest temperature of a slab after rough rolling to a specific temperature. SOLUTION: The slab of a steel heated to a prescribed temperature by a heating furnace 1, is made to a crude bar by rolling it to about 30mm in thickness by roughing mills 2. By an induction heating system crude bar heating device 3 installed on the inlet side of a finishing mill 4, after heating the surfaces of parts having the lowest temperatures of the front and the rear tip parts of the crude bar to 850 deg.C or over, when performing finish rolling to the crude bar by the finishing mills 4, the recessed flaws do not occur on the work rolls of the finishing mills 4. Therefore, it is not necessary to cut away the front and the rear tip parts of the crude bar as before over a wide range of 300 to 500mm. That is, the hard hot rolled plate can be manufactured without lowering the yield. The plate subjected to the finish rolling, is cooled by a run-out cooling device 5, and is coiled by a coiler 6.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は熱延鋼板の製造方
法、特に高炭素熱延鋼板などの硬質な熱延鋼板の製造方
法に関する。The present invention relates to a method for manufacturing a hot-rolled steel sheet, and more particularly to a method for manufacturing a hard hot-rolled steel sheet such as a high-carbon hot-rolled steel sheet.

【０００２】[0002]

【従来の技術】一般に、熱延鋼板は、前工程で製造され
たスラブを加熱炉で所定の温度に再加熱した後、あるい
は加熱炉を通さず直接に粗圧延して所定の厚さの鋼片
（粗バーと呼ばれる）とした後、複数のスタンドからな
る連続熱間圧延機で所定の温度（仕上温度と呼ばれる）
で所定の板厚に仕上圧延し、ランナウトテーブルで所定
の温度（巻取温度と呼ばれる）まで冷却してコイラーで
巻取って製造される。2. Description of the Related Art Generally, a hot-rolled steel sheet is prepared by reheating a slab manufactured in a previous process to a predetermined temperature in a heating furnace, or by directly rough rolling without passing through a heating furnace. After forming into pieces (referred to as coarse bars), a predetermined temperature (referred to as finishing temperature) is applied to a continuous hot rolling mill comprising a plurality of stands.
And rolled to a predetermined thickness, cooled to a predetermined temperature (called a winding temperature) on a run-out table, and wound by a coiler.

【０００３】最近では、粗圧延を省略するために、粗バ
ー相当の厚みに鋳造された薄スラブを直接仕上圧延する
直送圧延法も実用化されている。In recent years, in order to omit rough rolling, a direct-conveying rolling method for directly finish-rolling a thin slab cast to a thickness equivalent to a coarse bar has been put to practical use.

【０００４】こうした方法により高炭素熱延鋼板などの
硬質な熱延鋼板を製造しようとすると、著しく温度低下
する粗バーの先後端部や薄スラブの先端部が著しく硬化
するため、仕上圧延機のワークロールに凹状疵が発生す
る。そして、ワークロールに発生したこの疵は被圧延材
である鋼板にも転写されて表面欠陥を誘発し、製品の歩
留りを著しく低下させる。[0004] When a hard hot-rolled steel sheet such as a high-carbon hot-rolled steel sheet is to be manufactured by such a method, the front and rear ends of the rough bar and the front end of the thin slab where the temperature is significantly lowered are extremely hardened. A concave flaw is generated on the work roll. And this flaw generated in the work roll is also transferred to the steel plate as the material to be rolled, and induces a surface defect, which significantly lowers the yield of the product.

【０００５】そのため硬質な熱延鋼板を製造するとき
は、通常、粗圧延後の粗バーの先後端部を３００〜５０
０ｍｍの広範囲にわたってクロップシャーで切り落とし
てから仕上圧延が行われている。[0005] Therefore, when a hard hot-rolled steel sheet is manufactured, usually, the front and rear ends of the rough bar after rough rolling are 300 to 50 mm.
Finishing rolling is performed after cutting off with a crop shear over a wide range of 0 mm.

【０００６】[0006]

【発明が解決しようとする課題】しかしながら、粗バー
の先後端部を３００〜５００ｍｍの広範囲にわたって切
り落とすことは著しく歩留りを低下させる。However, cutting off the front and rear ends of the coarse bar over a wide range of 300 to 500 mm significantly reduces the yield.

【０００７】本発明はこのような課題を解決するために
なされたもので、ワークロールの凹状疵に起因する表面
欠陥のない硬質な熱延鋼板を高歩留りで製造する方法を
提供することを目的とする。The present invention has been made in order to solve such problems, and an object of the present invention is to provide a method of manufacturing a hard hot-rolled steel sheet having no surface defects due to concave defects of a work roll at a high yield. And

【０００８】[0008]

【課題を解決するための手段】上記課題は、粗圧延と仕
上圧延の工程を有してなる熱延鋼板の製造方法におい
て、粗圧延後の鋼片を、その最も低温な部分の表面温度
が８５０℃以上になるように加熱後、仕上圧延すること
を特徴とする熱延鋼板の製造方法により解決される。The object of the present invention is to provide a method for producing a hot-rolled steel sheet comprising steps of rough rolling and finish rolling. The problem is solved by a method for producing a hot-rolled steel sheet, which is characterized by performing a finish rolling after heating to 850 ° C. or higher.

【０００９】温度低下の著しい粗バーの先後端部や薄ス
ラブの先端部を広範囲に切り落とさないで仕上圧延機の
ワークロールの凹状疵の発生を防ぐには、温度低下によ
り硬化した部分を再加熱して軟化させてやればよい。In order to prevent the occurrence of concave flaws in the work roll of the finishing mill without cutting off the leading and trailing ends of the rough bar and the leading end of the thin slab which have a remarkable temperature drop, re-heat the hardened portion due to the temperature drop. And soften it.

【００１０】そこで、本発明者等は、粗バーの最も低温
な部分（通常は先後端部）の表面温度を何℃以上まで加
熱して仕上圧延すればワークロールの凹状疵が発生しな
くなるかを、現行の種々の硬質熱延鋼板を用いて検討し
た。Therefore, the present inventors have determined that if the surface temperature of the lowest temperature portion (usually the front and rear end portions) of the coarse bar is heated to what degree or higher and finish-rolled, the concave defect of the work roll does not occur. Was examined using various existing hard hot-rolled steel sheets.

【００１１】図１に、粗バーの先後端部の表面温度とワ
ークロールの凹状疵の発生率との関係を示す。FIG. 1 shows the relationship between the surface temperature of the front and rear ends of the coarse bar and the incidence of concave flaws on the work roll.

【００１２】図の凹状疵発生率は下記の式で定義され
る。 凹状疵の発生率＝ｓ／ｎ×１００（％） ここで、 ｎ：通常の条件では凹状疵の発生する種々の成分系の熱
延鋼板の数、 ｓ：粗バーの先後端部の表面温度を変えて仕上圧延した
ときに凹状疵の発生した熱延鋼板の数である。The percentage of occurrence of concave flaws in the figure is defined by the following equation. Rate of occurrence of concave flaws = s / n × 100 (%) where, n: number of hot rolled steel sheets of various component systems in which concave flaws occur under normal conditions, s: surface temperature of front and rear ends of coarse bar Is the number of hot-rolled steel sheets in which concave flaws are generated when finish rolling is performed while changing the value.

【００１３】図に示したように、粗バーの先後端部の表
面温度を８５０℃以上に加熱すれば、凹状疵発生率をほ
ぼ０にできることがわかる。したがって、粗バーの先後
端部を広範囲にわたって切り落とす必要がなくなり、歩
留りを向上できる。As shown in the figure, it can be seen that the rate of occurrence of concave flaws can be reduced to almost zero by heating the surface temperature of the front and rear ends of the coarse bar to 850 ° C. or higher. Therefore, it is not necessary to cut off the front and rear ends of the rough bar over a wide range, and the yield can be improved.

【００１４】鋼の薄スラブを直接仕上圧延する場合も、
同様にその最も低温な部分の表面温度を８５０℃以上ま
で加熱すれば、ワークロールの凹状疵発生を防止でき
る。[0014] When a thin slab of steel is directly finish-rolled,
Similarly, if the surface temperature of the lowest temperature portion is heated to 850 ° C. or more, the occurrence of concave flaws on the work roll can be prevented.

【００１５】[0015]

【発明の実施の形態】図２に、本発明の１実施の形態で
ある熱延鋼板の製造方法を模式的に示す。図で、１は加
熱炉、２は粗圧延機、３は誘導加熱方式の粗バー加熱装
置、４は仕上圧延機、５はランナウト冷却装置、６はコ
イラー、７は放射温度計、８はクロップシャーを表す。FIG. 2 schematically shows a method for producing a hot-rolled steel sheet according to an embodiment of the present invention. In the figure, 1 is a heating furnace, 2 is a rough rolling machine, 3 is a rough bar heating device of an induction heating system, 4 is a finishing rolling machine, 5 is a runout cooling device, 6 is a coiler, 7 is a radiation thermometer, and 8 is a crop. Represents a shah.

【００１６】加熱炉１で所定の温度に加熱したた鋼のス
ラブを、粗圧延機２により厚さ３０ｍｍ程度まで圧延し
粗バーとし、仕上圧延機４の入側に設けた誘導加熱方式
の粗バー加熱装置３により粗バーの先後端部の最も低温
な部分の表面温度を８５０℃以上に加熱して仕上圧延機
４で仕上圧延すれば、仕上圧延機４のワークロールに凹
状疵が発生しない。したがって、従来のように粗バーの
先後端部を３００〜５００ｍｍの広範囲にわたって切り
落とす必要はなく、すなわち歩留りを低下させることな
く、硬質な熱延鋼板を製造できる。A steel slab heated to a predetermined temperature in a heating furnace 1 is rolled by a rough rolling mill 2 to a thickness of about 30 mm to form a rough bar, and an induction heating rough slab provided on the entrance side of a finishing mill 4. When the surface temperature of the coldest part of the front and rear ends of the coarse bar is heated to 850 ° C. or more by the bar heating device 3 and finish-rolled by the finish rolling machine 4, no concave flaw is generated on the work roll of the finish rolling machine 4. . Therefore, unlike the conventional case, it is not necessary to cut off the front and rear ends of the rough bar over a wide range of 300 to 500 mm, that is, a hard hot-rolled steel sheet can be manufactured without lowering the yield.

【００１７】仕上圧延された鋼板は、ランナウト冷却装
置５により冷却され、コイラー６で巻取られて製品とな
る。The finish-rolled steel sheet is cooled by a run-out cooling device 5 and wound up by a coiler 6 to be a product.

【００１８】上記のように、粗バーや薄スラブの先後端
部を加熱するには、仕上圧延機入側に加熱装置を備えた
熱延鋼板の圧延設備を用いればよいが、生産性を落とさ
ないために、この加熱装置は誘導加熱方式や通電加熱方
式などの制御応答性に優れる加熱装置であることが望ま
しい。As described above, in order to heat the leading and trailing ends of the coarse bar and the thin slab, it is possible to use a hot-rolled steel plate rolling equipment provided with a heating device on the side of the finishing rolling mill, but this reduces productivity. For this reason, it is desirable that the heating device is a heating device having excellent control responsiveness such as an induction heating system or an electric heating system.

【００１９】加熱は、粗バーや薄スラブの長手方向全体
にわたって行ってもよいが、仕上圧延する前に８５０℃
以下に温度降下する部分のみに行う方がエネルギーコス
ト的には好ましい。また、加熱温度の上限は特に規定し
ないが、エネルギーコスト的には１１００℃以下の温度
範囲で加熱することが好ましい。The heating may be performed over the entire length of the rough bar or the thin slab, but before the finish rolling, the heating is performed at 850 ° C.
It is preferable in terms of energy cost to perform the process only on the portion where the temperature drops below. Although the upper limit of the heating temperature is not particularly specified, it is preferable to perform heating in a temperature range of 1100 ° C. or less in terms of energy cost.

【００２０】[0020]

【実施例】表１に示す成分系の厚さ２５０ｍｍ、幅９５
０ｍｍ、長さ６５００ｍｍのスラブを、図２に模式的に
示した熱延鋼板の製造方法により表２に示す条件で熱間
圧延し、厚さ２ｍｍの熱延鋼板を製造した。このとき、
仕上圧延機入側に設けた誘導加熱方式の粗バー加熱装置
によって、表２に示すように粗バーの先後端部の表面温
度を変えた。そして、ワークロールの凹状疵に起因した
表面欠陥の発生の有無を目視調査した。EXAMPLES The composition shown in Table 1 has a thickness of 250 mm and a width of 95.
A slab having a length of 0 mm and a length of 6500 mm was hot-rolled under the conditions shown in Table 2 by the method for producing a hot-rolled steel sheet schematically shown in FIG. 2 to produce a hot-rolled steel sheet having a thickness of 2 mm. At this time,
As shown in Table 2, the surface temperature of the front and rear ends of the coarse bar was changed by an induction heating type coarse bar heating device provided on the entrance side of the finishing mill. Then, the presence or absence of a surface defect caused by the concave flaw of the work roll was visually inspected.

【００２１】結果を表２に示す。本発明法にしたがい粗
バーの先後端部の表面温度を８５０℃以上に加熱すれ
ば、ワークロールの凹状疵に起因した表面欠陥は発生し
ない。The results are shown in Table 2. If the surface temperature of the front and rear ends of the coarse bar is heated to 850 ° C. or higher according to the method of the present invention, no surface defects due to the concave flaws of the work roll are generated.

【００２２】[0022]

【表１】 [Table 1]

【００２３】[0023]

【表２】 [Table 2]

【００２４】[0024]

【発明の効果】本発明は以上説明したように構成されて
いるので、ワークロールの凹状疵に起因する表面欠陥の
ない硬質な熱延鋼板を高歩留りで製造する方法を提供で
きる。As described above, the present invention can provide a method of manufacturing a hard hot-rolled steel sheet having no surface defects due to concave flaws of a work roll at a high yield.

【図面の簡単な説明】[Brief description of the drawings]

【図１】粗バーの先後端部の表面温度とワークロールの
凹状疵の発生率との関係を示す図である。FIG. 1 is a diagram showing the relationship between the surface temperature of the front and rear ends of a rough bar and the incidence of concave flaws on a work roll.

【図２】本発明の１実施の形態である熱延鋼板の製造方
法を模式的に示す図である。FIG. 2 is a view schematically showing a method for manufacturing a hot-rolled steel sheet according to an embodiment of the present invention.

【符号の説明】[Explanation of symbols]

１ 加熱炉 ２ 粗圧延機 ３ 誘導加熱方式の粗バー加熱装置 ４ 仕上圧延機 ５ ランナウト冷却装置 ６ コイラー ７ 放射温度計 ８ クロップシャー DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Rough rolling mill 3 Induction heating coarse bar heating device 4 Finish rolling mill 5 Run-out cooling device 6 Coiler 7 Radiation thermometer 8 Crop shear

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 粗圧延と仕上圧延の工程を有してなる熱
延鋼板の製造方法において、粗圧延後の鋼片を、その最
も低温な部分の表面温度が８５０℃以上になるように加
熱後、仕上圧延することを特徴とする熱延鋼板の製造方
法。1. A method for producing a hot-rolled steel sheet comprising a step of rough rolling and a step of finishing rolling, wherein a billet after rough rolling is heated so that the surface temperature of the lowest temperature portion is 850 ° C. or higher. Thereafter, finish rolling is performed. 【請求項２】 鋼の薄スラブを直接仕上圧延する工程を
有してなる熱延鋼板の製造方法において、薄スラブを、
その最も低温な部分の表面温度が８５０℃以上になるよ
うに加熱後、仕上圧延することを特徴とする熱延鋼板の
製造方法。2. A method for producing a hot-rolled steel sheet comprising a step of directly finish-rolling a thin slab of steel,
A method for producing a hot-rolled steel sheet, comprising heating the surface of the lowest temperature portion to 850 ° C. or higher and then finish rolling.