JP2005298972A - Heat treating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treating device which is excellent in prevention of sparks generated between a thick steel plate under heating in a moving condition and a conveying roller, and performs the induction heating of the thick steel plate moving on a convey line. <P>SOLUTION: The heat treating device has a convey line and an induction heating device to perform the heat treatment of a thick steel plate provided on the convey line. A conveying roll on the outlet side of the induction heating device has higher electric resistance than the thick steel plate, for example, at least a surface layer is formed of stainless steel. When a plurality of induction heating devices are provided, they are arranged between the adjacent conveying rolls. A pressing roll to press the thick steel plate from an upper face is provided at least on the outlet side of the induction heating device on the upmost stream side. At least the pressing roll on the upmost stream side is arranged facing the conveying roll above the conveying roll on the outlet side of the induction heating device. In addition, a pressing roll to press the thick steel plate from the upper face is provided on the inlet side of the induction heating device. The electric resistance of the pressing roll is set to be higher than that of the thick steel plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat treatment apparatus that performs high-frequency induction heating of a thick steel plate that moves on a conveyance line using an induction heating coil, and relates to a device that is excellent in preventing sparks that are generated between a thick steel plate that is moving and heated and a conveyance roller.

  As a heating device for induction heating (moving heating) of a thick steel plate by an induction heating coil, there are a device for partially heating a side end portion of a hot rolled steel material and a device for heating the entire plate width of the steel plate.

In the production of thick steel plates, if a hot rolling mill, a cooling device, and a heat treatment device are arranged on the same line, the production capacity is remarkably increased. Therefore, a thick steel plate that uses a high-frequency induction heating device that can be arranged on the line as a heat treatment device. Manufacturing equipment has been developed and put into practical use.
Patent Document 1 relates to a heat treatment method and apparatus for a thick steel plate, which describes a production line in which a hot-rolled thick steel plate is accelerated and cooled by a cooling device provided on the exit side of the rolling mill and then heat-treated by an induction heating device. It has been shown that a solenoid type induction heating device or a transverse type induction heating device is used as the device.
In a heating device that performs high-frequency induction heating (moving heating), sparks are generated between the thick steel plate and the transport roller, and the side edge of the back surface of the thick steel plate may be damaged, resulting in spark marks on the surface of the transport roller. Therefore, various techniques have been proposed.

  Patent Document 2 relates to a technique for preventing a spark generated between a metal plate and a transport roll due to an induced electromotive current when a side end portion of a metal plate such as a hot-rolled steel plate is partially induction-heated. By bringing a side roll that is electrically grounded into contact with the end of the metal plate between the induction heating device and the conveyance roll, the spread of the induced electromotive current up to the conveyance roll is suppressed and sparking is prevented.

Patent Document 3 relates to an apparatus for high-frequency induction heating by surrounding a continuously cast hot-rolled steel material such as a thin slab with a solenoid induction heating coil, and a circulating current caused by an eccentric magnetic flux by being wound with a lead angle in a spiral shape Is described in terms of how the coil winding is wound to prevent sparks generated between the thin slab and the surface of the transport roll due to the circulating current.
JP 2003-13133 A JP-A-9-38712 Japanese Patent Laid-Open No. 11-233247

  As described in Patent Document 1, when a thick steel plate is heated by an induction heating device, part of the magnetic flux is also drawn with the thick steel plate as the heated thick steel plate is carried out of the induction heating device. Become.

  Leakage magnetic flux generates an induced current that flows in a closed circuit from the thick steel plate to the transport roll, and when an air gap is generated between the thick steel plate and the transport roll, sparks are generated by the induced current, and the end of the thick steel plate or the surface of the transport roll is generated. Spark marks are generated.

  FIGS. 6 and 7 are diagrams for explaining how a spark is generated between the thick steel plate and the transport roll due to the induction current of the thick steel plate. The induction heating device 3 is provided with a shield plate 31 for preventing leakage of magnetic flux. The leakage magnetic flux A is drawn out by carrying out the thick steel plate 5, and an induced current loop B is formed between the thick steel plate 5 and the transport roll 6.

  Since the thick steel plate 5 often has distortion due to induction heating, a gap d is generated at the contact point C between the thick steel plate 5 and the transport roll 6 and spark is generated (FIG. 7).

  When the plate thickness of the thick steel plate 5 is large, since the distortion of the steel plate due to induction heating is large, the grounded side roll described in Patent Document 2 is brought into contact with the end of the thick steel plate, and it is difficult to eliminate the induced current, The method described in Patent Document 3 cannot be applied to existing facilities.

  In addition, the method of surrounding the thick steel plate moving on the transfer line with an induction heating coil and high frequency induction heating described in Patent Document 1 is not heated uniformly like the atmosphere heating in a heat treatment furnace. It tends to cause distortion such as warpage of the steel plate.

  The distortion of the thick steel plate causes trouble in conveyance, and further makes it difficult to uniformly heat the thick steel plate in the case of induction heating, so it must be corrected on the exit side of the induction heating device.

  An object of the present invention is to provide a thick steel plate heat treatment apparatus that can prevent the occurrence of a spark due to an induced current formed on a transport roll from a thick steel plate due to leakage magnetic flux, and can also correct the shape of the thick steel plate.

  In order to correct warpage due to distortion of the thick steel plate on the exit side of the induction heating device, the following was found as a result of observing the thick steel plate on the conveyance line in detail.

  When a high-temperature thick steel plate is cooled and heat-treated, it is difficult to perform uniform cooling, so the thick steel plate after cooling usually has distortion in the width direction and the longitudinal direction. When the thick steel plate is heat-treated with the induction heating device, warpage occurs in the width direction or the longitudinal direction of the thick steel plate on the exit side of the induction heating device.

  In addition, these warpages increase when the amount of temperature rise heated by the induction heating device is 50 ° C. or more, and collide with the shield plate, or when using a plurality of induction heating devices, there are two thick steel plate tips. It collides with the induction heating device of the eye and damages it, and it becomes impossible to convey it satisfactorily and sparks are generated.

When a thick steel plate is pressed from the upper surface with a pressing roll on the exit side of the induction heating device, warpage can be suppressed, and it can be transported without any problem, and the occurrence of sparks can also be suppressed.
The present invention was made by further study based on the obtained knowledge, that is, the present invention is
1 A heat treatment apparatus for a thick steel plate, comprising a transport line for moving a thick steel plate, and an induction heating device for heat-treating the thick steel plate by high-frequency induction heating on the transport line, the transport roll on the outlet side of the induction heating device However, the steel plate has a higher electrical resistance than the thick steel plate.

2. The heat treatment apparatus for a thick steel plate according to 1, wherein at least a surface layer of the transport roll is made of stainless steel.

3 In the heat treatment apparatus for thick steel plates according to 1 or 2, the induction heating device is disposed between adjacent conveying rolls, and a pressing roll for pressing the thick steel plate from the upper surface is provided on the exit side of the induction heating device. The thick steel plate heat treatment apparatus is characterized in that the pressing roll is disposed above the conveyance roll on the exit side of the induction heating device so as to face the conveyance roll.
43. A thick steel plate heat treatment apparatus, comprising a pressing roll for pressing the thick steel plate from the upper surface on the entry side of the induction heating device in the thick steel plate heat treatment apparatus according to Item 3. 53. A heat treatment apparatus for thick steel sheets, wherein the electrical resistance of the pressing roll in the heat treatment apparatus for thick steel sheets according to 3 or 4 is higher than that of the thick steel sheets.

  61. In the heat treatment apparatus for thick steel sheets according to 1 or 2, a plurality of induction heating devices are arranged between adjacent conveying rolls, and at least on the outlet side of the induction heating device at the most upstream of the induction heating devices. A pressing roll for pressing the thick steel plate from the upper surface is provided, and at least the uppermost pressing roll among the pressing rolls faces the conveying roll above the conveying roll on the exit side of the induction heating device. A heat treatment apparatus for thick steel plates, wherein

  7. A heat treatment apparatus for thick steel sheets, wherein a pressing roll for pressing the thick steel sheets from the upper surface is provided on the inlet side of the induction heating apparatus in the heat treatment apparatus for thick steel sheets according to 6.

  8. A heat treatment apparatus for thick steel sheets, wherein the electrical resistance of the pressing roll in the heat treatment apparatus for thick steel sheets is higher than that of the thick steel sheet.

  According to the present invention, since the induced current generated in the thick steel plate due to the leakage magnetic flux at the time of induction heating can be suppressed from flowing to the transport roll and the pressing roll, a spark is generated even if a gap is generated between the thick steel plate and the transport roll. Can be suppressed.

  In addition, warpage due to distortion of the thick steel plate after induction heating is eliminated, and it is possible to suppress the formation of voids between the thick steel plate and the transport roll, and the target heat treatment can be performed without hindering the transport of the thick steel plate. It is very useful industrially because it can produce thick steel plates with high productivity.

  The present invention is applied to a heat treatment apparatus for a thick steel plate provided with a conveyance line for moving the thick steel plate and an induction heating device for heat treating the thick steel plate by high-frequency induction heating installed on the conveyance line.

FIG. 1 shows an example of equipment layout of a thick steel plate heat treatment apparatus to which the present invention is applied. The thick steel plate 5 hot-rolled by the rolling mill 1 is cooled to a predetermined cooling stop temperature by the cooling device 2 at a predetermined cooling rate. Then, it is heated to a predetermined temperature by the induction heating device 3 and the distortion caused by the heating is removed by the hot leveler 4.
FIG. 2 is a view for explaining the configuration around the induction heating apparatus according to an embodiment of the present invention. In the figure, 3 is an induction heating apparatus main body, 31 is a shield plate for preventing magnetic flux leakage, and 6 is a steel plate The conveyance roll with high resistance is shown.

The leakage magnetic flux A is drawn out by carrying out the thick steel plate 5 and tries to generate an induced current from the thick steel plate 5 to the transport roll 6 immediately above the transport roll 6. Since the resistance is higher than the resistance, the induced current loop B is formed only inside the thick steel plate 5.
As a result, even if a gap is generated between the thick steel plate 5 and the transport roll due to distortion generated in the thick steel plate 5 or vibration during transport, the generation of sparks is suppressed.

When the transport roll 6 has an electric resistance higher than that of the thick steel plate, at least the surface of the roll contacting the thick steel plate is made of a material having higher electric resistance than carbon steel, for example, stainless steel, or the surface is welded with stainless steel. That's fine.
As the stainless steel, austenitic stainless steel that is non-magnetic and has a small induced electromotive force is desirable. In particular, it is preferable to use SUS309 that is easy to cut and has excellent maintainability. When corrosion resistance is required, SUS303 and SUS304 are used. You may process the whole roll from the said raw material.
FIG. 3 shows a heat treatment apparatus according to another embodiment of the present invention, in which the thick steel plate 5 is rolled down with a predetermined rolling force, facing the delivery roll 6 on the exit side and the entry side of the induction heating apparatus 3, and induction heating is performed. The case where the pressing roll 7 which corrects the distortion | strain by is shown is shown.
The pressing roll 7 has a predetermined rolling force that presses the thick steel plate in order to prevent deformation of the thick steel plate within elastic deformation.
Since the pressing roll is in close contact with the thick steel plate to be pressed, it may have an electrical resistance equivalent to that of the thick steel plate. It is desirable.
It is desirable that the pressing roll 7 and the conveying roll 6 have the same electric resistance value in order to make the spark generation suppressing effect on the front and back surfaces of the steel plate the same.
FIG. 4 shows an example in which a part of the transport roll 6 and the pressing roll 7 in the roll length direction is a high electrical resistance portion 8 having high electrical resistance, and FIG. 5 shows that the surface layer portion 9 in the vertical section of the roll has high electrical resistance. An example is shown in which the center portion 10 is made of a material having an electrical resistance equivalent to that of carbon steel.
When a part of the roll length direction is made of a material having high electrical resistance, the portion of the material in the roll length direction is arranged on the inside of both ends in the width direction of the thick steel plate arranged on the roll. Deploy.
When arranged in this manner, the induced current flowing from one end in the width direction of the thick steel plate to the other end via the roll flows through the roll because there is a portion with high electrical resistance in the roll length direction. The occurrence of sparks is suppressed even when voids are generated at both ends of the roll and the thick steel plate.
In the present invention, it is only necessary to increase the electrical resistance of the first transport roll on the downstream side of the induction heating device, and it is not necessary to further increase the electrical resistance of the downstream transport roll. Even when a thick steel plate is carried into the induction heating device, leakage magnetic flux may be drawn out, so it is desirable to increase the electrical resistance of the transport roll closest to the inlet of the induction heating device.
When induction heating the clad steel plate, it is possible to prevent the occurrence of sparks by bringing a base material made of carbon steel into contact with a transport roll.
The present invention can be applied not only to a single induction heating apparatus but also to a heat treatment apparatus for a thick steel plate including a plurality of induction heating apparatuses.
FIG. 8 is a schematic diagram for explaining a case where the present invention is applied to a heat treatment apparatus for a thick steel plate provided with a plurality of induction heating apparatuses. As shown in FIGS. A pressing roll 7 for pressing the thick steel plate 5 from the upper surface is disposed above the conveying roll on the entry side and the exit side of the sheet so as to face the conveyance roll 6.

FIG. 10 shows the relationship between the arrangement of the pressing roll 7 and the warp height h. As shown in FIGS. 8A to 8G, the pressing roll 7 presses the thick steel plate 5 from the upper surface facing the conveying roll 6 above the conveying roll on the entry side or the exit side of the induction heating device 3. Arranged.
Using a thick steel plate with a plate thickness of 40 mm and a plate width of 2000 mm, the solenoid-type induction heating device provided between the conveying rolls is heated so that the surface temperature of the thick steel plate increases by 60 ° C. The warp height h of the steel plate tip was determined. The pressing roll 7 was pressed against the thick steel plate 5 with a pressing force of 80000N.
FIG. 9 shows the definition of the warp height h. The highest point of the warped thick steel plate is the height measured from the surface of the thick steel plate when warpage does not occur. 8 (C), (D), (D), (E), (F), and (G), the pressing roll 7 is placed above the conveying roll on the exit side of the induction heating device 3, and the conveying roll. When it is provided so as to face the warp, the warp height can be suppressed to 20 mm or less, and the thick steel plate can be prevented from colliding with the transport roll or the induction heating device.
On the other hand, in the case of (A) or (B) where the pressing roll 7 is not above the conveying roll on the exit side of the induction heating device 3, the warp height exceeds 40 mm, and the steel plate collides with the conveying roll or the induction heating device. The risk of doing is very high.

Even if the pressing roll 7 is arranged above the first conveying roll 6 from the induction heating device 3 as shown in FIGS. 8C and 8E, the pressing roll 7 can be removed from the induction heating devices 3 to 2 as shown in FIG. 9D. Even if it is arranged above the second transport roll 6, the same effect can be obtained.
If it is placed above the second or third transport roll, if the tip of the thick steel plate passes through the heating device and then hits the pressing roll or rides on the pressing roll, the tip of the thick steel plate is placed on the pressing roll. You may install a guide roll etc. so that it may guide.

When a plurality of induction heating devices 3 are provided and the distance between the induction heating devices is increased, they are pressed above the plurality of conveying rolls 6 between the induction heating devices 3 as shown in FIGS. 8 (F) and (G). A roll 7 can be provided.
As shown in FIG. 8F, the pressing roll 7 does not necessarily have to be disposed immediately above the conveying roll 6, and is disposed so that a pressing force is applied to the thick steel plate 4 by the pressing roll 7 and the conveying roll 6. It only has to be.
If the pressing roll 7 is provided also on the entrance side of the induction heating device 3 as shown in FIG. 8E, the thick steel plate 5 is warped upward in the width direction on the entrance side of the induction heating device as shown in FIG. It is more effective in such cases.

In the case where a plurality of induction heating devices 3 are provided, it is effective to suppress the warpage of the thick steel plate by providing the pressing roll 7 at least on the outlet side of the induction heating device 3 in the uppermost stream. This is because in the most upstream induction heating apparatus, the amount of temperature rise when heating the thick steel plate is large, 50 ° C. or more, and the thick steel plate 5 is likely to be warped.
When the induction heating device 3 other than the most upstream induction heating device 3 is also heated with a large temperature increase, a pressing roll is provided on the outlet side of the induction heating device 3.

Further, the pressing force by the pressing roll 7 is constant when the plate width of the thick steel plate is constant, but is appropriately changed according to the plate width.
When the plate width is about 1000 mm or more, warping occurs in the width direction and the longitudinal direction, so that a larger pressing force is required as the plate width is reduced. For example, a pressing force of 100,000 N or more is required when the plate width is 1500 mm or less. On the other hand, when the plate width is 3000 mm or more, a pressing force of about 20000 N is sufficient.

A similar result can be obtained even if a transverse type is used as the induction heating device.

 The effects of the present invention will be described with reference to examples. The surface on the transport roll side of the thick steel plate heated by the induction heating apparatus was observed off-line, and the occurrence of spark marks was observed. The steel plate was a welded structural steel with a plate thickness of 30 mm, a width of 1500 mm, and a length of 3000 mm, and the electric resistance was 0.097 μΩ · m.

  A build-up roll made of SUS303 having an electrical specific resistance of 0.72 μΩ · m was used as the transport roll. As a comparative example, the generation | occurrence | production state of the spark trace was observed using the conveyance roll which consists of carbon steel.

  The presence or absence of occurrence of a spark mark was observed for three thick steel plates with varying power input amounts. Table 1 shows the observation results. In the example of the present invention, no spark mark was observed, but in the comparative example, generation was observed.

Using the production line of FIG. 11 or FIG. 12, the presence or absence of collision between the thick steel plate and the transport roll or the induction heating device and the occurrence of spark marks on the surface of the thick steel plate on the transport roll side were observed.
After producing a thick steel plate having a thickness of 12-40 mm and a width of 1500-4000 mm by the rolling mill 1, the steel plate is rapidly cooled to about room temperature by the cooling device 2, and heated to 300 ° C. by the induction heating device 3 in the uppermost stream of the heat treatment device 11, Variously changing the pressing force of the pressing roll arranged above the conveying roll 6 on the exit side of the most upstream induction heating device 3, the collision between the thick steel plate and the conveying roll or the induction heating device, and the conveying roll side of the thick steel plate We observed the occurrence of spark marks on the surface.
The transport roll was a roll made of SUS303. In addition, although the case where the thick steel plate was passed through the heat processing apparatus 11 by 3 passes was observed using the production line of FIG. 12, in this case, the pressing roll was used at the 1st pass.

  The induction heating device 3 was a solenoid type having a frequency of 1500 Hz, a coil opening of 200 mm (height) × 5000 mm (width), a length of 2000 mm, and a maximum output of 1 MW.

  Table 2 shows the test conditions and the observation results together. No collision with the transport roll or induction heating device occurred, and no spark trace was observed.

  When the heat treatment was performed in the reverse pass using the production line in FIG. 12, the use of the pressing roll in the first pass could avoid collision and no occurrence of spark marks.

The same observation was performed for the case where a pressing roll was provided facing the delivery roll on the exit side of the induction heating apparatus. The thick steel plate was a general structural steel having a plate thickness of 25 mm, a width of 3000 mm, and a length of 20000 mm, which produces distortion when heated by an induction heating device.
The pressing roll and the conveying roll were made of SUS303, and the spark mark and the distortion were observed in the case of the presence or absence of the pressing roll. The power input was 5 MW. Table 3 shows the observation results. In the example of the present invention in which the pressing roll was provided, no spark mark was generated, and the amount of warpage was as good as 2 mm.

The equipment arrangement | positioning figure explaining the thick board production line to which this invention is applied. The figure which shows one Example of this invention. The figure which shows the other Example of this invention. The figure which shows an example of the conveyance roll used for this invention. The figure which shows the other example of the conveyance roll used for this invention. Conventional example. Conventional example (a diagram for explaining the cause of occurrence of sparks). Example of the present invention (when a plurality of induction heating devices are arranged). The figure which shows the definition of curvature height h. The figure which shows the relationship between arrangement | positioning of the pressing roll 7, and curvature height h. Production line (Example). Production line (multi-pass embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rolling machine 2 Cooling device 3 Induction heating device 31 Shield plate 4 Hot leveler 5 Thick steel plate (material to be heated)
6 Transport roll
7 Pressing roll 8 High electrical resistance part 9 Surface layer part 10 Center part
11 Heat treatment equipment h Warp height

Claims (8)

  A heat treatment apparatus for a thick steel plate having a conveyance line for moving the thick steel plate and an induction heating device for heat-treating the thick steel plate by high-frequency induction heating on the conveyance line, wherein a conveyance roll on the outlet side of the induction heating device includes: An apparatus for heat treatment of a thick steel plate, characterized in that the electrical resistance is higher than that of the thick steel plate. The heat treatment apparatus for a thick steel plate according to claim 1, wherein at least a surface layer of the transport roll is made of stainless steel.
The heat treatment apparatus for a thick steel plate according to claim 1 or 2, wherein an induction heating device is disposed between adjacent conveying rolls, and a pressing roll for pressing the thick steel plate from the upper surface is provided on the exit side of the induction heating device. And the pressing roll is disposed above the transport roll on the exit side of the induction heating device and is opposed to the transport roll. 4. A heat treatment apparatus for thick steel sheets, comprising a pressing roll for pressing the thick steel sheets from the upper surface on the inlet side of the induction heating apparatus in the heat treatment apparatus for thick steel sheets according to claim 3. 5. A heat treatment apparatus for thick steel sheets, wherein the electric resistance of the pressing roll in the heat treatment apparatus for thick steel sheets according to claim 3 or 4 is higher than that of the thick steel sheets. 3. The heat treatment apparatus for a thick steel plate according to claim 1, wherein a plurality of induction heating devices are arranged between adjacent conveyance rolls, and further, at least on the outlet side of the induction heating device at the most upstream of the induction heating devices. Is provided with a pressing roll for pressing the thick steel plate from the upper surface, and at least the uppermost pressing roll among the pressing rolls is opposed to the conveying roll above the conveying roll on the outlet side of the induction heating device. The heat processing apparatus of the thick steel plate characterized by the above-mentioned.
7. A heat treatment apparatus for thick steel plates, comprising a pressing roll for pressing the thick steel plates from the upper surface on the entry side of the induction heating device in the heat treatment apparatus for thick steel plates according to claim 6. A heat treatment apparatus for thick steel sheets, wherein the electrical resistance of the pressing roll in the heat treatment apparatus for thick steel sheets according to claim 6 is higher than that of the thick steel sheets.

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