JP3793503B2 - Steel plate heating method - Google Patents

Description

【００５４】
図１１に４種類の鋼板をバーヒータで加熱昇温（バーヒータの鉄心間距離＝２１０ｍｍ）させたそれぞれの仕上圧延機前でのバーヒータによる昇温量（ＢＨ昇温量）と仕上圧延機出側の板幅方向の温度分布の比較（バーヒータの加熱の有無の比較）結果を示す。図１１に示すように、粗圧延された各鋼板はアルファベットＭ型の温度偏差を有する点線で示す温度分布であったが、３台のバーヒータによる細い実線で示す温度分布の合計昇温量により昇温された。その結果、太い実線で示すように鋼板幅方向温度分布はほぼ均一化された。
【００５５】
このように幅方向温度分布を有する鋼板を仕上圧延することにより、鋼板幅方向に材質特性が均一化された熱延鋼板が得られる。
【００５６】
【発明の効果】
本発明によれば、鋼板幅方向の任意の領域を加熱昇温することができるので、熱間圧延において、鋼板（粗バー）幅方向の温度分布の均一化することができ、その結果熱延鋼板幅方向の材質特性の均一化を達成することができる。また、鋼板（粗バー）幅方向の温度分布を意図的に異ならしめることもでき、熱間圧延によって幅方向材質特性の異なるテーラード鋼板を得ることができる。
【図面の簡単な説明】
【図１】熱間圧延工程を示す模式図である。
【図２】連続熱間圧延工程を示す模式図である。
【図３】粗圧延した粗バー及び仕上圧延した鋼板の幅方向温度分布を示す図である。
【図４】（ａ）は、エッジヒーターによる昇温を行った鋼板幅方向温度分布を示す図で、（ｂ）はソレノイド型誘導加熱装置によって昇温された鋼板幅方向温度分布を示す図である。
【図５】（ａ）は６００ＭＰａ級高張力鋼板の熱間仕上温度（℃）と穴広げ率（％）との関係を示す図で、（ｂ）は６００ＭＰａ級高張力鋼板の熱間仕上温度（℃）と伸びＥＬ（％）との関係を示す図である。
【図６】トランスバース型バーヒータの概要を示す図である。
【図７】複数台のバーヒータを鋼板幅方向にシフトして、鋼板を加熱する際の幅方向昇温量を示す模式図である。
【図８】バーヒータによる幅方向昇温分布及び鋼板の幅方向温度偏差改善を示す図である。
【図９】実施例におけるバーヒータの幅方向シフトを説明するための図である。
【図１０】実施例におけるバーヒータによる昇温量及び昇温量差の規定を説明するための図である。
【図１１】実施例における鋼板幅方向温度偏差改善を示す図である。
【図１２】実施例における（ａ）〜（ｅ）の加熱試験に対応する幅方向シフトの状態を示す図である。
【符号の説明】
１ 加熱炉
２ スラブ
３ 粗圧延機
４ 粗バー
５ クロップシャー
６ エッジヒーター
７ 連続仕上圧延機
８ 冷却スタンド
９ コイラー
１０ コイルボックス
１１ 接合シャー
１２ 溶接装置
１３ 放冷大
１４ 低温部
１５ エッジヒーターによる昇温量
１６ ソレノイド型誘導加熱装置による昇温量
１７ トランスバース型誘導加熱装置
１８ 鉄心
１９ コイル
２０ 鋼板
２１ 鋼板（粗バー）
２２ バーヒータ
２３ 昇温量分布[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for heating a steel sheet, and more particularly to a method for heating a steel sheet that controls the temperature distribution in the width direction of the steel sheet.
[0002]
[Prior art]
As shown in FIG. 1, hot rolling of a steel plate is performed by inserting a low-temperature slab 2 into a heating furnace 1, reheating it to a predetermined temperature, and then reheating the reheated slab 2 with a rough rolling mill 3. In order to recover the temperature drop at both edges of the coarse bar 4 in the width direction by cutting the leading end of the coarse bar using a crop shear 5 This is performed by heating the section and finishing and rolling it into a predetermined hot-rolled steel sheet with a continuous finish rolling mill 7 composed of a plurality of stands, then cooling with a cooling stand 8 on a run-out table and winding it with a coiler 9. Yes.
[0003]
In addition, when endless rolling is performed in which rough bars are joined to each other before finish rolling, as shown in FIG. 2, a low-temperature slab 2 is inserted into a heating furnace 1 to obtain a predetermined The slab 2 is reheated to a temperature, rolled to a predetermined thickness by a roughing mill 3 to form a rough bar 4, wound by a coil box 10, and the tip of the rough bar unwound from the coil box In order to recover the temperature drop at both edge portions in the width direction of the coarse bar 4 by cutting with the joining shear 11 and joining the trailing end of the preceding coarse bar and the leading end of the following coarse bar with the welding device 12. The two edge portions are heated and rolled into a predetermined hot-rolled steel plate by a continuous finish rolling mill 7 composed of a plurality of stands, cooled at a cooling stand 8 on a run-out table, and wound by a coiler 9. Has been done.
[0004]
In such a hot-rolling or endless rolling process of a hot-rolled steel sheet, since the low-temperature slab is reheated in a heating furnace, the occurrence of uneven heat is inevitable, and the heat release from the heating furnace and the rolled material are rolled. Due to the fact that the plate thickness becomes smaller with respect to the plate width, temperature drop occurs at both edge portions of the coarse bar during rough rolling. These temperature drops cause non-uniform temperature distribution in the width direction of the coarse bars, and cause non-uniform finishing temperatures.
[0005]
If the temperature distribution in the width direction of the rough bar becomes non-uniform, ear waves and medium elongation occur in the hot-rolled steel plate during finish rolling, and the material properties such as the mechanical properties in the width direction of the hot-rolled steel plate are non-uniform. The problem of becoming.
[0006]
In order to prevent such problems due to uneven temperature distribution in the width direction of the rough bar, a heating device and an edge heater are provided between the rough rolling mill and the finish rolling mill, and rough rolling is performed by the rough rolling mill. It is known to heat the roughed bar. Conventionally, a solenoid-type induction heating device for heating the rough bar over the entire width direction and an edge heater for heating both edges of the rough bar are provided between the rough rolling mill and the finish rolling mill. It has been proposed to heat a rough bar on the entrance side of a finishing mill so as to have a uniform temperature in the width direction by a solenoid induction heating device and an edge heater (for example, Patent Document 1).
[0007]
The feature of the solenoid type induction heating device used here is that the coil is wound around the plate and a magnetic field is generated in parallel with the plate. The entire surface of the plate is heated centrally, and the temperature is averaged by heat transfer. Therefore, the temperature is increased by a uniform temperature over the entire width in a state where the temperature distribution in the plate width direction is substantially constant.
[0008]
That is, the coarse bar is uniformly heated in the width direction so that the rolling load is reduced by a solenoid type induction heating device, and both edge portions (edge portions) having a large temperature drop are heated by an edge heater so that the temperature in the width direction is uniform. It is intended to be a distribution.
[0009]
However, as a result of studying the material properties in the width direction of the hot-rolled steel sheet, the present inventor has heated the edge portion of the coarse bar on the finishing rolling mill entrance side with an edge heater to increase the temperature distribution in the width direction. It has been found that the material properties in the width direction of the steel sheet obtained by finish rolling are not uniform even when uniformized. That is, in the heating method in which the rough bar is uniformly heated in the width direction between the rough rolling mill and the finish rolling mill, and both the edge portions having a large temperature drop are heated by the edge heater, it is obtained by finish rolling. It was difficult to make uniform the material properties in the width direction of the hot-rolled steel sheet. The cause was investigated through various experiments, and it was found that there was a cause during slab heating in a heating furnace. That is, since the heating furnace heats the slab in a high temperature atmosphere, the temperature at the center of the slab is inevitably low, and this temperature distribution is maintained even if the plate thickness is reduced by rolling. It exhibits an M-shaped widthwise temperature distribution of the alphabet that is lower in the center than the average temperature and higher toward the edge.
[0010]
Therefore, it is impossible to equalize the material characteristics in the width direction of the plate by making the temperature distribution in the width direction uniform by the heating method using an edge heater or the heating method using a bar heater that raises the temperature in the width direction at a constant value.
[0011]
Further, tailored blank materials having different strengths in the plate width direction are manufactured as press materials (blank materials) for body parts such as automobiles. When this tailored blank material is press-molded into a vehicle body part, the mechanical properties of a predetermined part of the vehicle body part can be made different.
[0012]
Conventionally, a method of welding a plurality of steel strips to make a tailored blank is common, but when the hot-rolled steel strip is water-cooled with a run-out table (ROT) in recent years, the cooling rate in the steel strip width direction is changed. Various methods have been proposed for producing tailored blank materials without making welding by making the mechanical properties in the width direction of the steel strip different from each other (for example, Patent Documents 2 and 3).
[0013]
However, rather than changing the cooling rate in the width direction of the steel strip, by making the temperature difference in the width direction of the steel strip different before finish rolling to make a tailored blank material, mechanical properties, especially hole expansion rate and elongation characteristics It was found that a tailored blank material excellent in the production can be produced. In fact, this method requires a heating method and apparatus for a steel strip for effectively making the temperature difference in the steel strip width direction different.
[0014]
[Patent Document 1]
JP-A-3-314216 [Patent Document 2]
JP-A-11-192501 [Patent Document 3]
Japanese Patent Laid-Open No. 2000-11541
[Problems to be solved by the invention]
In view of the above, the present invention provides a method for heating a steel plate that can heat an arbitrary region in the width direction of the steel plate (steel strip) and can control the temperature distribution in the width direction of the steel plate. It is an object to do.
[0016]
[Means for Solving the Problems]
In order to obtain a hot-rolled steel sheet having no variation in material properties in the width direction, the inventor needs to make the temperature distribution in the width direction of the rough bar on the finishing rolling mill entrance side uniform. Heating and heating the low temperature part of the coarse bar due to the low temperature at the center of the slab during heating, and making the temperature difference in the width direction of the steel plate (coarse bar) different before finish rolling to obtain a tailored blank material Therefore, it is required to heat up an arbitrary region in the coarse bar width direction. For this reason, bar heaters composed of a plurality of transverse induction heating devices are arranged in the longitudinal direction of the steel plate (coarse bar), and there is a portion where each bar heater overlaps in the longitudinal direction of the steel plate (the total heating amount is large). If it is shifted in the width direction of the steel plate and each bar heater is heated and operated, any region in the width direction of the steel plate can be heated and heated with a temperature difference. Was completed.
[0017]
The gist of the present invention is as follows.
[0018]
(1) Bar heaters composed of a plurality of transverse type induction heating devices are arranged at different positions in the longitudinal direction of the steel sheet, and each overlapping position in the steel sheet width direction is controlled by operating the respective positions in the steel sheet width direction. A method for heating a steel plate, characterized in that a bar heater is heated to control temperature distribution in the width direction of the steel plate.
[0020]
(2) In the central portion intensive heating of the steel plate width direction, above, wherein the performing the heating operation by moving the bar heater comprising a plurality of transverse-type induction heating device in the steel sheet width direction center (1) steel sheet according Heating method.
[0021]
( 3 ) In the whole heating in the width direction of the steel sheet, the heating operation is performed by moving a bar heater including a plurality of transverse type induction heating devices at regular intervals in the entire width direction. (2) The heating method of the steel plate as described.
[0022]
( 4 ) Heating by a bar heater comprising a plurality of transverse type induction heating devices installed upstream from the finishing final stand of the hot rolling line, as described in any one of (1) to (3) above Method of heating steel sheet.
[0023]
( 5 ) The steel sheet width direction temperature distribution is measured by a width direction thermometer disposed upstream of the bar heater, and the shift amount of each bar heater is determined based on the measured temperature distribution (1) The heating method of the steel plate in any one of (4)-(4) .
[0024]
( 6 ) The method for heating a steel plate according to any one of the above (1) to (5) , wherein shifting is possible by in-coil.
[0025]
( 7 ) The method for heating a steel plate according to any one of (1) to (6) , wherein the heating amount of each bar heater is varied independently by in-coil.
[0026]
( 8 ) The method for heating a steel sheet according to any one of (1) to (7) , wherein the distance between the iron cores of each bar heater is varied independently by an in-coil.
[0027]
( 9 ) The method for heating a steel plate according to any one of the above (1) to (8), wherein an edge of the plate width direction is heated with an edge heater.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0029]
FIG. 3 is a diagram showing a temperature distribution in the width direction of a coarse bar obtained by roughly rolling a slab heated in a heating furnace.
[0030]
Since the heating furnace heats the slab in a high-temperature atmosphere, it is inevitable that the heated slab has a high temperature around it and a low temperature portion in the center. For this reason, as shown in FIG. 3 (a), the coarse bar obtained by roughly rolling the heated slab is lowered in temperature because the edge portion of the coarse bar 4 has a large cooling capacity 13, and the central portion is a low temperature portion of the slab. As shown in FIG. 3 (b), for example, the temperature at the center of the plate width is 1033 ° C., the maximum temperature from the center to the edge is 1056 ° C., and the edge is 1002 ° C. It becomes the temperature distribution in the width direction exhibiting the M type. When such a rough bar having a temperature distribution in the width direction is finish-rolled, as shown in FIG. 3C, the temperature at the center of the plate width is 852 ° C., the maximum temperature from the center toward the edge is 865 ° C., the edge Is a finish-rolled steel sheet exhibiting an alphabetical M shape with 800 ° C., so that the material properties such as the mechanical properties in the width direction of the hot-rolled steel sheet obtained after cooling are not uniform.
[0031]
In the conventional hot rolling method, as shown in FIG. 4 (a), only the edge portion of the coarse bar is allowed to cool and the temperature is lowered, so that it is considered that the temperature distribution in the width direction becomes uniform when heated by an edge heater. However, even if the edge portion is heated by a temperature increase of 15 (1056 ° C.) indicated by oblique lines at the edge portion, the central low temperature portion (1033 ° C.) cannot be raised. Also in the method of heating and heating the entire coarse bar width direction using the solenoid type induction heating device, as shown in FIG. 4B, the entire temperature is increased by the amount of temperature increase 16 by the solenoid type induction heating device indicated by hatching. Thus, the temperature distribution in the width direction of the M type is maintained. Accordingly, uniform temperature distribution in the width direction cannot be achieved by heating with an edge heater or solenoid induction heating device.
[0032]
In addition, when manufacturing tailored steel sheets with different mechanical properties in the width direction of the steel strip, in particular, the properties of hole expansion and elongation, by hot rolling, the temperature difference in the width direction of the steel plate is different before finish rolling. It has been found that when the finish rolling is performed, the hole expansion property of the steel sheet is effectively improved by the hot finishing temperature.
[0033]
For example, C: 0.09 to 0.11%, Si: 1.30 to 1.50%, Mn: 1.25 to 1.45%, P: 0.010% or less, S: 0.002% or less When applying 590MPa class high-strength steel strips consisting of the above components to automotive parts such as cross members, parts are removed in the width direction of the steel strip, and from the part shape, stretch flange processing is performed near the center of the coil width. In the quarter width to width edge portion of the band, the main processing is overhanging.
[0034]
In such processing, it is necessary for the stretch flanged portion to have a steel strip hole expansion ratio of 70% or more, preferably 80% or more. 34% or more is necessary.
[0035]
The conditions for obtaining the above mechanical properties will be examined.
[0036]
FIG. 5 (a) is a diagram showing the relationship between the hot finishing temperature (° C.) of the 590 MPa class high strength steel strip and the hole expansion rate (%), and FIG. 5 (b) is the heat of the 590 MPa class high strength steel strip. It is a figure which shows the relationship between interfinishing temperature (degreeC) and elongation EL (%). As shown in FIG. 5 (a), the hole expansion ratio of the steel strip is improved in response to the increase in hot finishing temperature, but as shown in FIG. 5 (b), it corresponds to the increase in hot finishing temperature. As a result, the elongation of the steel strip decreases. That is, the hole expansion characteristic and the elongation characteristic tend to conflict with each other with respect to the hot finishing temperature.
[0037]
Therefore, in order to obtain a hole expansion ratio of 70% or more from FIG. 5A, the hot finish temperature is required to be 878 ° C. or more indicated by an arrow, and from FIG. 5B, the elongation ratio is 31% or more. Therefore, it is required that the temperature is 860 ° C. or lower indicated by an arrow, and it is understood that the temperature range required for both is different. However, in order to obtain a steel strip having both characteristics, it can be obtained by controlling the hot finishing temperature to a very narrow range of 860 to 880 ° C. (range shown by hatching), but it is difficult to keep the temperature condition. There is a problem that a certain condition is deviated, and even if the temperature condition is correct, the yield is lowered due to the deviating material target due to the variation of the material.
[0038]
In the present invention, the hot finishing temperature in the width direction of the steel strip is made different so that the hot finishing temperature is 870 ° C. or more near the center of the steel strip width, and the quarter-width to width edge portion of the steel strip is hot finishing temperature 860 ° C. or less By setting the steel strip width center part to a hot finishing temperature condition of heating at 20 ° C. or more so that the center of the steel strip width has a hole expansion ratio of 70% or more, It was found that tailored steel strips having an elongation of 31% or more in the width edge portion can be easily manufactured with different mechanical properties in the width direction.
[0039]
However, it is necessary to control the width direction temperature distribution of the steel sheet, which is necessary for the manufacture of steel plates with uniform material properties in the width direction and tailored steel plates with different material properties in the width direction. A heating apparatus that can make the distribution uniform or can effectively vary the temperature in the width direction has not been proposed so far.
[0040]
The present inventor has intensively studied a method and apparatus for heating a steel sheet capable of arbitrarily controlling the temperature distribution in the width direction of the steel sheet, and arranged a plurality of bar heaters composed of a transverse type induction heating apparatus in the longitudinal direction (rolling line) of the steel sheet. Then, it has been found that the temperature distribution in the width direction can be arbitrarily controlled by shifting each bar heater in the width direction, controlling the overlapping portion amount of the bar heater in the longitudinal direction of the steel sheet, and heating each bar heater.
[0041]
As shown in FIG. 6, the transverse induction heating device 17 is configured by winding a coil 19 around an iron core 18 unlike a solenoid induction heating device, and the width direction specific portion of the steel plate 20 according to the iron core width. It has the characteristic that can be heated uniformly.
[0042]
And since it can arrange | position and use in the up-and-down position of a steel plate, it has the characteristic that a shift to a steel plate width direction can be performed easily and a wrinkle is not given to the steel plate surface.
[0043]
Fig.7 (a) is a figure which shows the arrangement | positioning of the steel plate width direction of 1 bar heater, and its heating amount, FIG.7 (c)-(e) arrange | positions 3 bar heaters in a steel plate longitudinal direction, It is a figure which shows the temperature rising amount of the steel plate width direction at the time of shifting a bar heater a predetermined amount to the width direction.
[0044]
As shown in FIG. 7A, when one bar heater (transverse induction heating device) 22 is arranged at the center of the steel plate 21 and the bar heater is heated, the temperature rise distribution 23 in the steel plate width direction is the bar heater. Corresponding to the width of the iron core (width of iron core), it becomes a mountain-shaped temperature rise distribution. Three bar heaters having such temperature rising characteristics are arranged in the longitudinal direction of the steel plate, and each bar heater is shifted by a predetermined amount in the width direction of the steel plate (the center in the width direction is used as a reference for the shift amount. For example, FIG. 7B shows an example in which the shift amount is zero and all three bar heaters overlap with each other. As shown in FIG. 7 (c), the upstream and downstream bar heaters are shifted in the opposite direction without shifting the central bar heater. In the example where the overlapping portions of the bar heaters are slightly reduced, the temperature rise amounts of the three bar heaters are added in a state shifted according to the shift amount, and as shown in the lower figure, in the steel plate width direction A wide mountain-shaped temperature rise distribution, and FIG. d) is an example in which the shift amount of the two bar heaters on the upstream side and the downstream side is made larger than that in FIG. 7C and the overlapping portion of the bar heaters is further reduced. The temperature distribution is a mountain-shaped temperature increase distribution that is wider than that in FIG. FIG. 7E shows an example in which the entire width is heated by moving the bar heater at regular intervals in the entire width direction so that the overlapping portions of the bar heaters are eliminated. Compared to FIG. Furthermore, it becomes a broad mountain-shaped temperature rise distribution.
[0045]
The bar heater to be shifted is not limited to the downstream side, and the same temperature rise distribution can be achieved by shifting any bar heater. In the above example, an example of three bar heaters is shown. However, if the number of bar heaters is further increased, the total temperature rise amount can be increased and the temperature rise amount distribution in the steel plate width direction can be accurately controlled. It becomes possible. That is, a plurality of (two or more) bar heaters can be shifted in the steel plate width direction, and the distribution of the steel plate temperature increase in the width direction can be varied by shifting. The temperature distribution in the width direction can be controlled. The bar heater can be shifted by an in-coil, and the bar heater can be used in combination with bar heaters having the same width and / or different widths. Furthermore, the plurality of bar heaters can be further improved in temperature controllability by varying the heating amount of each bar heater and the distance between the iron cores independently by in-coil.
[0046]
For example, when the temperature of the steel plate (coarse bar) center is low, an example in which the temperature deviation in the width direction is improved using three bar heaters having the same width will be described.
[0047]
As shown in FIG. 8 (a), the temperature distribution in the width direction of the 1500 mm wide rough bar was an M-shaped alphabet with a 40 ° C. lower central part (indicated by a dotted line). Therefore, in order to make the temperature distribution in the width direction uniform by increasing the temperature of the central portion of the steel plate to 40 ° C. by using an inverted M shape, the temperature was increased using three bar heaters (the shaded area is the temperature increase). The total amount of temperature increase (indicated by the solid line) of the three bar heaters needs to be a gentle mountain-shaped temperature increase distribution (reverse M type) at the central portion 40 ° C. higher. In order to obtain this temperature increase distribution, as shown in FIG. 8B, the three bar heaters have the same distance between the iron cores and the same temperature increase, and three bar heaters (No. 1 having a width of 600 mm). To 3), the two bar heaters (No. 1 and No. 3) were shifted by ± 150 mm with respect to the center in the width direction (plate width direction distance was 750 mm position), and the heating operation was performed. That is, the distance in the plate width direction is 600 mm to 900 mm (± 150 mm with respect to the center in the plate width direction). The presence of a portion of three core of all bar heater 1-3 overlap, (with reference to the center of the plate width direction, -300mm~ + 150mm) sheet width direction distance 450Mm～ 900 mm position No. The iron cores of the two bar heaters 1 and 2 have a plate width direction distance of 600 mm to 1050 mm ( −150 mm to +300 mm based on the center in the plate width direction). There were portions where the iron cores of the two bar heaters 2 and 3 overlap each other. As a result, the temperature increase amount distribution of each bar heater (No. 1 to No. 3) becomes a gentle mountain shape that is shifted, and the total temperature increase amount of the three units is a mountain-shaped temperature increase amount distribution that is 40 ° C. higher in the center. became.
[0048]
The method of determining the temperature rise of the steel sheet is that the heating profile in the width direction of the bar heater is stored in the computer for each width of the steel plate (rough bar), each shift amount of the bar heater, and each temperature rise amount of the bar heater. Grasping the temperature distribution in the width direction of the steel sheet with the width direction thermometer placed in, and selecting the nearest shift amount, temperature increase amount with a computer so as to heat the difference in the profile of the desired width direction temperature distribution, This command can be issued by instructing the electric sequencer to set the bar heater shift amount (bar heater overlapping portion amount) and the heating amount. This makes it possible to raise the temperature of an arbitrary region in the width direction of the steel plate by a predetermined amount.
[0049]
In addition, as a means for shifting the bar heater, for example, the bar heater can be shifted in the steel plate width direction by installing the bar heater on a cart that can travel on rails so that the bar heater can be moved up and down, and shifting the cart with a driving device. The upper and lower bar heaters can be raised and lowered to adjust the gap between the bar heaters.
[0050]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
[0051]
In hot rolling, four types of roughly rolled steel plates of 900 mm width, 1200 mm width, 1500 mm width and 1800 mm width using three 600 mm wide transverse bar heaters (BH1, BH2, BH3) Tests (a) to (e) were performed in which the (rough bar) was heated by shifting the bar heater in the width direction in front of the finish rolling mill and the steel plate width direction temperature distribution was made uniform. In addition, the distance (gap) between the iron cores of the upper and lower bar heaters was changed in three levels of (1) 210 mm, (2) 160 mm, and (3) 130 mm depending on the respective plate widths. And the temperature rising amount and temperature rising amount difference in each level were determined. Furthermore, in the case of 900 mm width, the test (e) in the case where heating with an edge heater was further added was also performed.
[0052]
Table 1 shows the test conditions and the temperature rise. As shown in Table 1, as the distance between the iron cores of the upper and lower bar heaters (gap) is narrower, the temperature rise and the temperature rise difference are larger, and as the bar heater overlap is larger, the temperature rise and the temperature rise difference are larger. It was. As shown in FIG. 9, each of the three bar heaters (BH1 to 3) was shifted to the WS (Work Side) side or the DS (Drive Side) side. (A)-(e) of FIG. 12 has shown the state of the width direction shift of the bar heater corresponding to each heating test ae. As shown in FIG. 10A, the “temperature increase amount” by the bar heater in Table 1 is the difference between the minimum temperatures in the plate width direction before and after the temperature increase. Similarly, as shown in FIG. 10B, the “temperature increase difference” in Table 1 is the difference in the temperature increase at a position 150 mm from the steel sheet edge with respect to the temperature increase at the center in the steel sheet width direction. It was.
[0053]
[Table 1]

[0054]
In FIG. 11, four types of steel plates are heated with a bar heater (bar heater core distance = 210 mm), and the heating amount by the bar heater (BH heating amount) in front of each finishing mill and the finish rolling mill outlet side A comparison of temperature distribution in the plate width direction (comparison of presence / absence of heating of the bar heater) is shown. As shown in FIG. 11, each of the roughly rolled steel plates had a temperature distribution indicated by a dotted line having a temperature deviation of the alphabet M type, but the temperature increased by the total temperature increase of the temperature distribution indicated by thin solid lines by three bar heaters. Warmed. As a result, as shown by the thick solid line, the temperature distribution in the width direction of the steel sheet was made substantially uniform.
[0055]
In this way, by hot rolling a steel sheet having a temperature distribution in the width direction, a hot rolled steel sheet having uniform material properties in the steel sheet width direction can be obtained.
[0056]
【The invention's effect】
According to the present invention, since an arbitrary region in the steel plate width direction can be heated and heated, the temperature distribution in the steel plate (coarse bar) width direction can be made uniform in hot rolling, and as a result, hot rolling. Uniformity of material properties in the width direction of the steel sheet can be achieved. Further, the temperature distribution in the width direction of the steel plate (coarse bar) can be intentionally varied, and a tailored steel plate having different width direction material properties can be obtained by hot rolling.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a hot rolling process.
FIG. 2 is a schematic diagram showing a continuous hot rolling process.
FIG. 3 is a diagram showing the temperature distribution in the width direction of a roughly rolled rough bar and a finish rolled steel plate.
4A is a diagram showing a steel plate width direction temperature distribution heated by an edge heater, and FIG. 4B is a diagram showing a steel plate width direction temperature distribution heated by a solenoid induction heating device. is there.
FIG. 5A is a diagram showing the relationship between the hot finishing temperature (° C.) of a 600 MPa class high strength steel sheet and the hole expansion rate (%), and (b) is the hot finishing temperature of a 600 MPa class high strength steel sheet. It is a figure which shows the relationship between (degreeC) and elongation EL (%).
FIG. 6 is a diagram showing an outline of a transverse bar heater.
FIG. 7 is a schematic diagram showing the amount of temperature increase in the width direction when a plurality of bar heaters are shifted in the steel plate width direction to heat the steel plate.
FIG. 8 is a diagram showing a width direction temperature rise distribution by a bar heater and an improvement in the width direction temperature deviation of a steel plate.
FIG. 9 is a diagram for explaining a shift in the width direction of the bar heater in the embodiment.
FIG. 10 is a diagram for explaining the regulation of the temperature rise by the bar heater and the temperature rise difference in the embodiment.
FIG. 11 is a diagram showing improvement in temperature deviation in the width direction of the steel plate in the example.
FIG. 12 is a diagram showing a state of a width direction shift corresponding to the heating test of (a) to (e) in an example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Slab 3 Coarse rolling mill 4 Coarse bar 5 Crop shear 6 Edge heater 7 Continuous finish rolling mill 8 Cooling stand 9 Coiler 10 Coil box 11 Joining shear 12 Welding device 13 Cooling large 14 Low temperature part 15 Temperature rise by edge heater Amount 16 Temperature rise by solenoid type induction heating device 17 Transverse type induction heating device 18 Iron core 19 Coil 20 Steel plate 21 Steel plate (rough bar)
22 Bar heater 23 Temperature rise distribution

Claims (9)

Bar heaters consisting of multiple transverse type induction heating devices are arranged at different positions in the longitudinal direction of the steel sheet, and each bar heater is heated by controlling the overlapping parts in the width direction of the steel sheet by operating the positions in the width direction of the steel sheet. A method for heating a steel sheet, characterized by operating and controlling the temperature distribution in the width direction of the steel sheet. 2. The method for heating a steel plate according to claim 1, wherein in the central heating in the width direction of the steel plate, a heating operation is performed by moving a bar heater comprising a plurality of transverse type induction heating devices to the center in the width direction of the steel plate. The steel plate according to claim 1 or 2, wherein in the overall heating in the width direction of the steel plate, a heating operation is performed by moving a bar heater composed of a plurality of transverse type induction heating devices at regular intervals in the entire width direction. Heating method. The method for heating a steel sheet according to any one of claims 1 to 3 , wherein the heating is performed by a bar heater comprising a plurality of transverse type induction heating devices installed upstream of the finishing final stand of the hot rolling line. The steel sheet width direction temperature distribution is measured by a width direction thermometer arranged upstream of the bar heater, and the shift amount of each bar heater is determined based on the measured temperature distribution . The heating method of the steel plate in any one. The method for heating a steel sheet according to any one of claims 1 to 5 , wherein shifting is possible by in-coil. The heating method for a steel sheet according to any one of claims 1 to 6 , wherein the heating amount of each bar heater is varied independently by in-coil. The method for heating a steel sheet according to any one of claims 1 to 7 , wherein the distance between the iron cores of each bar heater is varied independently by in-coil. The method for heating a steel plate according to any one of claims 1 to 8 , wherein the edge portion in the plate width direction is heated with an edge heater.

Images