JP6562223B2 - Heating method and heating equipment for continuous casting slab - Google Patents

Description

  The present invention relates to a heating method and a heating equipment for a widthwise edge portion of a continuous casting slab (hot piece) cast by a continuous casting equipment, and in particular, reheating the continuous casting slab cast by the continuous casting equipment in a heating furnace. The present invention relates to a heating method and heating equipment for a continuous cast slab suitable for direct feed rolling (HDR).

  Direct feed rolling is a direct connection between continuous casting equipment and hot rolling equipment, and uses the sensible heat of continuous cast slabs (hereinafter also simply referred to as “slabs”) cast by continuous casting equipment to save energy and greatly It is a technology that enables shortening of the process.

  Since the speed of continuous casting is several meters per minute and it takes several minutes for one slab to finish casting, the temperature of the edge portion in the width direction of the slab (hereinafter also simply referred to as “edge portion”) decreases during this time. In some cases, direct temperature rolling without passing through a heating furnace may require some temperature compensation.

  In this regard, Patent Document 1 proposes providing a heating device that heats the end surface of the slab in the vicinity of the cutter of the continuous casting machine.

  Patent Document 2 proposes that an apparatus for heating the edge portion in the width direction of the slab with a burner is installed in the vicinity of the slab heating furnace for hot rolling.

  Non-Patent Document 1 discloses a method of induction heating a width direction edge portion of a slab.

  Non-Patent Document 2 discloses a method of heating a billet that is smaller than a slab while the billet is housed in an induction heating coil.

Japanese Patent Laid-Open No. 60-18201 JP-A-55-41902

Steelmaking Research No. 313 (1984) 6 Nippon Steel Corporation Hitachi review June 1967 issue 17

  However, in the heating apparatus of Patent Document 1, the conveying direction of the slab being heated is one direction, and the edge portion on the tip side of the slab that has been heated first starts to dissipate and the heating of the tail end ends. The temperature at the edge part on the tip side is greatly reduced. In the embodiment shown in FIG. 3 of Patent Document 1 where a heating device is installed in the vicinity of the cutter of the continuous casting machine, the slab once exceeds the Al-N resolution temperature while the slab is transported to the roughing mill. The temperature of the edge portion of the steel sheet has fallen again to about 1000 ° C. (see FIG. 2 of the same document). When rolling in that state, the center in the width direction is rolled at about 1200 ° C. from the viewpoint of strict quality control in recent years. There is a concern about the influence on the quality of the edge portion as compared with the portion.

  Moreover, in the heating apparatus of patent document 1, since the conveyance speed of the slab at the time of a heating is dependent on the speed of the continuous casting by a continuous casting machine, it cannot heat at the speed independent of the casting speed. Therefore, the heating time becomes as long as about 10 minutes (see FIG. 2 of the same document), and the temperature at the center portion in the width direction of the slab continues to decrease during about 10 minutes for heating the edge portion. When the temperature drop becomes large, there is a problem that the temperature is lower than the Al-N solid solution temperature or the temperature required for rough rolling, and there is a problem in terms of energy saving if large heat input is performed considering the temperature drop.

  In Patent Document 2, the edge portion heating device is arranged on the conveyance table for sending the slab to the roughing mill and the temperature compensation of the edge portion in the width direction of the slab is performed immediately before rolling, but the heating is performed by the burner. It takes about 10 minutes to heat a large heat capacity such as a slab, and it has the same problem that the temperature in the center in the width direction decreases while the edge is heated. Yes.

  In this way, the heating by the burner takes a long time, but the method by induction heating as described in Non-Patent Document 1 can heat at a conveyance speed of about 4 m / min, for example, a length of 10 m. If the slab has, the heating is completed in about 2.5 minutes, the heat dissipation loss can be remarkably reduced, and the heating process can be prevented from becoming the rate-limiting step of production.

  By the way, in order to hold and transfer the slab, a large number of holding and conveying rollers are installed, and an induction heating coil for heating the edge in the width direction of the slab must be installed between them. Arranged to be empty. In the case of slab heating, the holding / conveying roller is highly rigid and has a heat resistance function, so that the interval between the induction heating coils along the slab conveying direction is equal to or longer than the heating length of the coil. Become. For this reason, when the slab is stopped and heated, a heated portion and a non-heated portion are generated, resulting in uneven heating over the entire length. Therefore, it is necessary to heat the slab while moving it. Further, since the heating length of the induction heating coil is shorter than the moving distance of the slab, the slab must be moved at a low speed in order to give sufficient heat.

  However, when heating while moving the slab using an induction heating device, the induction section of the slab that has passed through the induction heating device and has been heated only by setting the section of the induction heating device to be approximately the same as the length of the slab. The edge portion is dissipated for a long time until the tail end side finishes heating, and uniform heating is not possible under the influence. That is, it has the same problem as Patent Document 1 in that the temperature of the edge portion on the front end side that has been heated first decreases while the slab is heated over its entire length. On the other hand, if temperature compensation is performed in consideration of heat dissipation on the tip side of the slab, a part that is heated to a higher temperature than necessary is generated, which is not economical, and the temperature at the time of rolling becomes uneven, and deformation resistance Becomes uneven and adversely affects the thickness accuracy.

  For this reason, in order to perform uniform heating, it is necessary to arrange the induction heating device in a range equal to or longer than the length of the slab, and in order to apply heat uniformly over the entire length, it is usually twice that of the slab. A large number of induction heating devices must be arranged in a range corresponding to the length, which is uneconomical.

  On the other hand, when heating a relatively short material to be heated such as a billet, as described in Non-Patent Document 2, the material to be heated is housed in a coil of an induction heating device, and the whole is all at once. It is possible to heat to However, it is not practical to simultaneously induction heat the entire length of a long slab. Further, there is a problem that a mechanism for holding the slab of 30 tons and moving the slab in some cases cannot be accommodated inside the coil.

  The present invention provides a heating method and heating equipment for a continuous casting slab that solves the above-described problems of the prior art, can uniformly heat the edge in the width direction over the entire length of the continuous casting slab, and is economical. The purpose is to do.

  In the present invention, when a continuous cast slab cast by a continuous casting facility is directly rolled by a hot rolling facility, the continuous casting slab is heated continuously at the edge in the width direction before hot rolling the continuous cast slab. A heating method for a slab, in which a plurality of induction heating devices are arranged in the conveying direction at intervals in the conveying path of the continuous casting slab from the exit side of the continuous casting facility to the entry side of the hot rolling facility. Equipment is provided, and the widthwise edge portion of the continuous casting slab is heated by a plurality of induction heating devices while reciprocating the continuous casting slab in the heating equipment.

  In the method for heating a continuous cast slab according to the present invention, it is preferable that the continuous cast slab is reciprocated by a transport roller capable of forward and reverse rotation disposed between a plurality of induction heating devices.

  Further, in the heating method of the continuous casting slab of the present invention, a plurality of induction heating devices are arranged at a predetermined pitch, and the continuous casting slab is moved by a distance corresponding to a natural number multiple of the pitch in each reciprocation. It is preferable to heat the edge portion in the width direction.

  Furthermore, in the heating method of the continuous casting slab of the present invention, the pitch of the induction heating device is Ld, the length of the continuous casting slab is Ls, the heating length of each induction heating device is Lc, When the installation number is N, it is preferable to determine the installation number N of induction heating devices so that the relationship Ld × (N−1) −Lc <Ls ≦ Ld × N−Lc is satisfied.

  Furthermore, in the method for heating a continuous cast slab according to the present invention, it is preferable to reduce or stop the output of the induction heating device when the moving direction of the continuous cast slab is reversed.

  Furthermore, in the method for heating a continuous cast slab according to the present invention, the slab transport speed from the continuous casting equipment to the heating equipment and the slab transport speed from the heating equipment to the hot rolling equipment are determined by the heating equipment. It is preferable to make it larger than the reciprocating speed inside.

  Further, the present invention provides a continuous casting for heating a widthwise edge portion of the continuous casting slab before rolling the continuous casting slab when the continuous casting slab cast by the continuous casting equipment is directly rolled by the hot rolling equipment. A plurality of induction heating devices which are heating equipment for a slab and are arranged in a conveying path of a continuous casting slab from the exit side of the continuous casting facility to the entry side of the hot rolling facility, and are spaced apart from each other in the conveying direction. And a moving means for reciprocating the continuously cast slab heated by the plurality of induction heating devices.

  In the heating apparatus for continuous cast slabs according to the present invention, it is preferable that the moving means has a transport roller that can be rotated in forward and reverse directions and disposed between a plurality of induction heating devices.

  Further, in the heating equipment for the continuous casting slab of the present invention, the heating section length from the induction heating device located at the uppermost stream in the conveying direction to the induction heating device located at the most downstream is equal to or longer than the length of the continuous casting slab. The length is preferably 1.5 times or less.

  Further, the continuous casting slab heating facility of the present invention preferably includes output adjusting means for reducing or stopping the output of the induction heating device when the moving direction of the continuous casting slab is reversed.

  Furthermore, in the continuous casting slab heating facility of the present invention, it is preferable that the plurality of continuous heating devices are arranged at equal intervals.

  Furthermore, in the heating apparatus for continuous cast slabs according to the present invention, it is preferable that the moving means has a pusher that reciprocates by directly pressing the tip and tail ends of the continuous cast slab.

  According to the present invention, since the edge portion is heated while reciprocating the slab in the heating facility in which the plurality of induction heating devices are arranged at intervals in the transport direction, the heating of the tail end portion of the slab is finished. It is possible to prevent the tip portion from being allowed to cool in the meantime, and to significantly reduce the number of necessary induction heating devices. Moreover, since it can heat in a short time compared with the case where it heats with a burner, the temperature fall of the width direction center part of the slab during heating an edge part can be suppressed.

FIG. 1 schematically shows a hot-rolled steel sheet manufacturing facility equipped with a continuous casting slab heating facility according to an embodiment of the present invention, wherein (a) is a side view and (b) is a plan view. FIG. 2 shows the heating equipment for the continuous cast slab of this embodiment, where (a) is a side view and (b) is a front view. FIGS. 3A to 3E are explanatory views showing the distribution in the longitudinal direction of the accumulated heat amount to the edge portion of the slab when the edge portion is heated while conveying the slab in each heating stage together with the induction heating device. It is. FIG. 4 is a side view showing a continuous casting slab heating facility according to another embodiment of the present invention. FIG. 5 is a side view showing a continuous casting slab heating facility according to still another embodiment of the present invention. It is explanatory drawing which showed the heating equipment of the continuous casting slab of a prior art with distribution of the accumulated heat amount of the edge part of a slab in the longitudinal direction. It is explanatory drawing which showed the heating equipment of the continuous casting slab of another prior art with distribution of the accumulated heat amount of the edge part of a slab with the longitudinal direction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a hot-rolled steel sheet manufacturing facility equipped with a continuous casting slab heating facility according to an embodiment of the present invention, (a) is a side view, (b) is a plan view, FIG. 2 shows the heating equipment for the continuous cast slab of this embodiment, where (a) is a side view and (b) is a front view.

  The hot-rolled steel sheet manufacturing facility 10 shown in FIG. 1 is hot without heating a continuous cast slab (hereinafter also simply referred to as “slab”) S cast in a continuous casting facility 12 in a heating furnace. This is a direct feed rolling (HDR) equipment that is directly sent to the rolling equipment 14, reduced in thickness to a predetermined thickness and wound in a coil shape.

  In the continuous casting facility 12, the molten steel poured into the mold 12b from the tundish 12a is cooled by the mold 12b to become a slab, and continuously from below the mold 12b along a plurality of rolls (not shown) provided below the mold 12b. Pulled out. The slab is cooled with cooling water while passing through the roll, and eventually solidification to the inside is completed. The slab that has been solidified is cut into a predetermined length by a cutter 12c such as a gas cutter to form a slab S.

  The slab S manufactured by the continuous casting facility 12 is transported to the hot rolling facility 14 by the transport roller 16. The slab sent to the hot rolling facility 14 is rolled to a predetermined thickness by the roughing mill 14a and the finishing mill 14b, and the rolled steel sheet is made into a predetermined material by the water cooling facility 18 and then wound in a coil shape. Taken into a hot rolled coil product.

  The quality of the slab S manufactured by the continuous casting facility 12 is improved when the temperature of the edge portion in the width direction (hereinafter also simply referred to as an “edge portion”) is lowered until the slab S is conveyed to the hot rolling facility 14. Is concerned about the impact of Therefore, in this hot-rolled steel sheet manufacturing facility 10, a heating facility 20 is provided in the transport path of the slab S from the exit side of the cutter 12c to the entrance side of the hot rolling facility 14 to compensate the temperature of the edge portion of the slab S. It is configured to do.

  Specifically, the heating equipment 20 of this embodiment heats both the left and right edge portions of the slab S, and is arranged at an equal pitch with an interval in the transport direction as shown in FIG. 2 (a). A plurality of induction heating devices 22 are provided. Each induction heating device 22 includes a pair of left and right core members 24a and 24b made of iron, ferrite, or the like, which are substantially C-shaped when viewed in the conveying direction, as shown in FIG. 24b and a coil conductor 26 wound around the outer periphery of the core 24b. The core members 24a and 24b are arranged opposite to each other so that the edge portion of the slab S is located in the opening, and a high-frequency current is applied to the coil conductor 26. A high frequency magnetic flux is generated inside the core members 24a and 24b by energization, and the edge portion of the slab S is heated by an eddy current generated by the magnetic flux. Further, the heating equipment 20 includes an output adjusting means 28 that adjusts the amount of current flowing through the coil conductor 26 in conjunction with the rotation control of the conveying roller 16 as a moving means. Specifically, the output adjusting means 28 includes the slab S. The amount of current flowing through the coil conductor 26 during the substantial stop period of the slab S obtained in advance by actual measurement or the like until the slab S starts to reversely run with the rotation stop or deceleration of the transport roller 16 as a trigger when the direction is changed. It is configured to reduce or stop the current supply. In this embodiment, the process computer performs this. The output adjusting means 28 gradually decreases the output of the induction heating device 22 in conjunction with the deceleration of the conveying roller 16 when the slab S changes its direction, and induction heating in conjunction with the increased speed after the conveying roller 16 is reversed. You may comprise so that the output of the apparatus 22 may be gradually returned to the original value.

  The induction heating device 22 is disposed between the adjacent conveyance rollers 16, and the pitch Ld of the induction heating device 22 is preferably the same as the pitch of the conveyance rollers 16. In addition, by making the pitch Ld of the induction heating device 22 satisfy Ld ≧ 2 × Lc with respect to the heating length Lc of the induction heating device 22, the conveyance roller 16 that supports the slab S can be sufficiently removed from the induction heating device 22. It can be separated and protected from thermal effects.

  The transport roller 16 is connected to a drive motor 32 via a free joint 30 and is configured to be able to rotate forward and reverse. Thereby, in the section where the plurality of induction heating devices 22 are arranged, the slab S is reciprocated in the forward direction from the continuous casting facility 12 toward the hot rolling facility 14 and in the reverse direction by the plurality of induction heating devices 22. The edge part of the slab S can be heated. Thus, the conveyance roller 16 constitutes a moving means for reciprocating the slab S during heating by the induction heating device 22.

  In the heating facility 20 of this embodiment, when the pitch of the induction heating device 22 is Ld, the length of the slab S is Ls, and the heating length of each induction heating device 22 is Lc, Ld × (N− 1) The installed number N of induction heating devices 22 is determined so that the relationship of −Lc <Ls ≦ Ld × N−Lc is established. Here, the length Ls of the slab S means the length of the maximum slab that can be handled by the hot-rolled steel sheet manufacturing facility 10. For example, when the length Ls of the slab S is 8000 mm, the pitch Ld of the induction heating device 22 is 1500 mm, and the heating length Lc of the induction heating device 22 is 500 mm, 5.66 ≦ N <6.66 from the above relationship. It is sufficient to provide six induction heating devices 22.

  Furthermore, in the heating equipment 20 of this embodiment, the length of the heating section from the induction heating device 22 located on the most upstream side in the conveying direction to the induction heating device 22 located on the most downstream side is equal to or longer than the length Ls of the slab S. Is preferably 1.5 times or less.

  With reference to FIG. 3, the heating method of the continuous casting slab of one Embodiment according to this invention using the heating equipment 20 of this embodiment is demonstrated. FIGS. 3A to 3E are explanatory views showing the distribution in the longitudinal direction of the accumulated heat amount of the edge portion of the slab when heating the edge portion while conveying the slab in each heating stage, together with the heating equipment 20. is there.

  In the heating method of the slab of this embodiment, a plurality of induction heating devices 22 are arranged at intervals in the conveying direction between the continuous casting equipment 12 and the hot rolling equipment 14, and the plurality of induction heating devices 22 are arranged. The edge portion of the slab S is heated by the plurality of induction heating devices 22 while reciprocating the slab S in the section of the heating equipment 20, and the reciprocation of the slab S is arranged between the plurality of induction heating devices 22. This is performed by the transport roller 16 that can be driven forward and reverse.

  The conveyance of the slab S from the continuous casting facility 12 to the heating facility 20 and the conveyance of the slab from the heating facility 20 to the hot rolling facility 14 are performed at a speed faster than the reciprocating movement of the slab S during heating by the heating facility 20. Preferably, according to this, the temperature drop of the slab during conveyance from the continuous casting equipment 12 to the heating equipment 20 and from the heating equipment 20 to the hot rolling equipment 14 can be suppressed.

  The reciprocating speed (low speed conveyance speed) V and the number of reciprocations m of the slab S during heating by the heating equipment 20 are the heating time required to heat the edge portion of the slab S to a predetermined temperature, which is obtained in advance by actual measurement or the like. It can be determined so as to satisfy m × 2 × Lc ÷ V = t in relation to t.

  First, FIG. 3A shows a state in which the slab S exiting the continuous casting facility 12 has entered the heating facility 20. In this state, since the slab S is not yet heated, the accumulated heat amount in the longitudinal direction of the slab S is Zero. The slab S is transported from the continuous casting facility 12 to the heating facility 20 at a relatively high speed (for example, 120 mpm), and a predetermined speed (for example, until the slab S enters the heating facility 20 and reaches a predetermined heating start position). It is preferable to decelerate to 5 mpm), and in this way, the temperature drop during the conveyance can be suppressed, and the slab S is accurately arranged at a predetermined heating start position in the heating equipment 20, and the subsequent steps It is possible to prevent uneven heating from occurring in the heating step. The reciprocating movement of the slab S during heating by the induction heating device 22 is preferably performed at a low speed (for example, 5 mpm), and according to this, heat input to the slab S by induction heating can be reliably performed.

  FIG. 3B shows a state in which the slab S is advanced in the forward direction (downstream) by about 1/3 of the pitch Ld of the induction heating device 22, and the portion heated by the induction heating device 22 is still heated. There is no part.

  In each reciprocating movement, the slab S is moved by a distance corresponding to a natural number multiple of the pitch Ld of the induction heating device 22 while simultaneously heating the edge portion by all the induction heating devices 22, and FIG. Is stored in the forward direction by one pitch (Ld × 1), and the accumulated heat amount at the time when the first progressive heating is completed is shown. The accumulated heat amount is almost equal over the entire length.

  Next, when switching the slab S from the forward feed to the reverse feed, the conveying roller 16 is decelerated and stopped, and reverse acceleration (for example, a peripheral speed of −60 mpm) is applied, while the slab S is substantially stopped due to inertia. It becomes. At this time, if the induction heating device 22 continues to operate, heat is applied only to the portion of the slab S that faces the induction heating device 22, and the amount of accumulated heat locally increases as shown by the dotted line in the figure. Although there is no problem from the viewpoint of temperature compensation at the edge portion, in order to perform uniform heating with a constant amount of accumulated heat, in this embodiment, the output adjusting means 28 when the slab S is in a substantially stopped state accompanying the change of direction. Thus, the output of the induction heating device 22 is lowered or stopped.

  FIG. 3D shows a state in which the reverse heating is completed by heating by the induction heating device 22 while conveying the slab S in the reverse direction by one pitch (Ld × 1). Thereafter, the transport direction of the slab S is switched to the forward direction. In this case as well, when the slab S is in a substantially stopped state accompanying the change of direction, the output of the induction heating device 22 is lowered or stopped by the output adjusting means 28. Thus, a uniform accumulated heat amount (heating amount) can be obtained.

  FIG. 3E shows a state in which the induction heating of the edge portion performed in the order of the forward feed, the reverse feed, and the forward feed is completed in the heating facility 20. At this time, since heating is completed almost simultaneously over the entire length of the slab S, the output of the induction heating device 22 is set to zero, and the slab S is withdrawn from the heating equipment 20 and conveyed to the hot rolling equipment 14 in the next step. At this time, the conveying speed of the slab 2 toward the hot rolling maintenance 14 is preferably larger than the reciprocating speed of the slab S being heated, and can be set to 120 mpm, for example.

  According to the slab heating facility 20 and the heating method of this embodiment, a plurality of induction heating devices 22 are arranged at intervals in the transport direction, and the slab S is disposed in the section of the heating facility 20 where the induction heating devices 22 are disposed. Since the edge portion is heated while reciprocating, the tip portion can be prevented from being cooled before the tail end portion of the slab S is heated, and a necessary induction heating device can be used. The number of installed 22 can be reduced, which is economical. In addition, by using the induction heating device 22, heating in a shorter time is possible as compared with the case of heating with a burner, and the temperature of the center portion in the width direction of the slab S decreases while the edge portion is heated. Can be suppressed.

  According to the slab heating equipment 20 and heating method of this embodiment, a plurality of induction heating devices 22 are arranged at a predetermined pitch Ld, and the slab S is a distance corresponding to a natural number multiple of the pitch Ld in each reciprocating movement. Since the edge portion is heated while being moved, all portions in the length direction of the edge portion of the slab S can be reliably heated.

  Furthermore, according to the slab heating equipment 20 and the heating method of this embodiment, when the pitch of the induction heating device 22 is Ld, the length of the slab S is Ls, and the heating length of each induction heating device 22 is Lc In addition, since the number N of installed induction heating devices 22 is determined so that the relationship of Ld × (N−1) −Lc <Ls ≦ Ld × N−Lc is established, the edge portion of the slab S can be reliably The number of installed induction heating devices 22 can be minimized while realizing proper heating.

  Furthermore, according to the slab heating equipment 20 and the heating method of this embodiment, the output of the induction heating device 22 is reduced or stopped when the moving direction of the slab S is reversed. The slab S can be prevented from being heated while the slab S is substantially stopped, and the edge portion of the slab S can be heated uniformly in the length direction.

  Furthermore, according to the heating equipment 20 and heating method of the slab of this embodiment, the transportation speed of the slab S from the continuous casting equipment 12 to the heating equipment 20 and the transportation speed of the slab from the heating equipment to the hot rolling equipment 14 are: Since it is configured to be larger than the reciprocating speed during heating of the slab S by the heating equipment 20, the temperature drop of the slab S during conveyance other than during the heating of the slab S is suppressed, and the slab S is hot-rolled while maintaining a high temperature. It becomes possible to roll with the equipment 14, and a high-quality steel plate can be manufactured.

  Furthermore, according to the heating equipment 20 and heating method of the slab of this embodiment, the heating section length from the induction heating device 22 located at the most upstream position to the induction heating device 22 located at the most downstream position in the conveying direction is set to the slab S. When the length is not less than Ls and not more than 1.5 times the length Ls, when the slab S is heated over its entire length, the amount of reciprocation of the slab S during heating can be reduced and heating can be performed in a shorter time. Become. In addition, when the heating section length exceeds 1.5 times the length Ls of the slab S, the induction heating equipment 22 more than necessary is installed, which is uneconomical.

  FIG. 4 shows a slab heating equipment 20 and a heating method of another embodiment according to the present invention. This embodiment is the length Ls of the slab S and the pitch Ld of the induction heating device 22 in the previous embodiment. In addition, by adding n induction heating devices 22 to the number N of induction heating devices 22 calculated from the heating length Lc, the reciprocating transfer speed of the slab S being heated can be increased while obtaining a predetermined heating amount. Specifically, n is such that Ld × (N−1 + n) −Lc <1.5 × Ls ≦ Ld × (N + n) −Lc with respect to the length Ls of the slab S. And N + n induction heating devices 22 are arranged in the conveying direction in total, the heating start position of the slab S is set to n before the most downstream induction heating device 22, and the distance to reciprocate the slab S is n × Ld According to this, induction heating equipment 22 as compared with the case of installing N units, it is possible to increase the reciprocating speed of the slab S during heating, it is possible to reduce the number of stop speed switching.

  FIG. 5 shows a slab heating facility 20 and a heating method according to still another embodiment of the present invention. The slab heating facility 20 according to this embodiment has a moving means for reciprocating the slab S in the heating facility 20. A pusher 34 is provided. A pair of pushers 34 are arranged so as to sandwich the heating equipment 20 back and forth, and are configured to be lifted and lowered via a lifting mechanism. When the slab S enters the heating equipment 20, the pushers 34 are retracted upward and then lowered. The slab S is directly pressed against the tip and tail ends of the slab S so that the slab S is repeatedly moved back and forth. After the heating is finished, the slab S is retracted upward to allow the slab S to be carried out. The pusher 34 can be driven by, for example, a hydraulic cylinder, but the drive type is not limited to this. Further, during the operation of the pusher 34, the slab S may be reciprocated by using the conveyance roller 16 connected to the drive motor 32 and capable of rotating in the forward and reverse directions. In this case, the pusher 34 and the transport roller 16 capable of rotating in the forward and reverse directions constitute a moving means of the present invention. By using such a pusher 34, the stop time of the slab S when switching the moving direction can be shortened, and the time required from the start to the end of heating can be shortened. Further, when the output adjusting means 28 is used, the time for reducing or stopping the output of the induction heating device 22 can be shortened.

  Next, examples of the present invention will be described.

  In the first embodiment, the edge portion in the width direction of the slab S is heated by the plurality of induction heating devices 22 while reciprocating the slab S using the heating equipment 20 shown in FIG.

  In Example 1, the slab S has a thickness of 250 mm, a width of 1500 mm, and a length of 8000 mm. Immediately before entering the heating facility 20, the surface temperature of the center portion in the width direction of the slab S is 1100 ° C. The surface temperature was 900 ° C. The surface temperature was measured with a radiation thermometer.

  The heating equipment 20 was composed of six induction heating devices 22 arranged at equal intervals in the transport direction. The pitch Ld of the induction heating device 22 is the same as the pitch of the transport roller 16 and is 1500 mm. The induction heating device 22 has an effective heating length of a length Lc in the transport direction, and is 500 mm in this embodiment. The induction heating device 22 of this embodiment is obtained by winding a coil conductor 26 around C-type iron cores 24a and 24b, a drive frequency is 300 Hz, and a pair of two coil conductors 26 that heats the edge in the width direction of the slab S. The output was 1 MW, and the total of the pair was 2 MW.

  N, which is the number of induction heating devices 22 installed, is 6, Ld × (N−1) −Lc = 7000 mm, which is smaller than the slab length Ls (8000 mm), and Ld × N−Lc = 8500 m, which is the slab length. Ls or more.

  In Example 1, the slab S is conveyed at a high speed of 120 mpm from the continuous casting facility 12 to the heating facility 20, and is decelerated to 5 mpm before the tip of the slab S reaches a predetermined heating start position in the heating facility 20, The heating start position was a position 500 mm (pitch Ld × 1/3) before the most downstream induction heating device 22.

  When the slab S reaches the heating start position, each coil conductor 26 of each induction heating device 22 is energized (maximum output 1 MW), and the slab S is reciprocated at a low speed by 1 pitch Ld of the induction heating device 22. The edge in the width direction was heated. In this example, heating was completed in 1.5 reciprocations consisting of 2 forward feeds (forward feed) and 1 reverse feed (reverse feed). The conveyance speed V (maximum value) during heating was 5 mpm. As a result, when m × 2 × Lc ÷ V = t, Lc = 500 mm and m = 1.5, and at an arbitrary position in the longitudinal direction of the slab S, the width direction edge portion is 500 mm × 3 times ÷ 5 mpm = 18 The heating time was seconds.

  In Example 1, the output of the induction heating device 22 was not reduced or stopped even when the moving direction of the slab S was reversed, and the edge of the slab S in the width direction was always heated with a constant output.

  After the heating of the edge portion of the slab S by the forward feed, the reverse feed and the forward feed is completed, the induction heating device 22 is stopped, the speed is increased to 120 mpm, and the slab S is sent to the hot rolling facility 14 in the next process. . The surface temperature of the edge portion in the width direction of the slab S upon completion of heating was 1100 ° C., and the temperature could be compensated by heating to the same temperature or higher as the surface temperature of the center portion in the width direction.

  And when it hot-rolled to plate | board thickness 3mm with subsequent hot rolling equipment 14 with respect to the slab S, and manufactured the hot rolling coil, since the temperature of the width direction edge part of the slab S was kept high, it was hot. No material abnormality occurred at the edge of the rolled coil. Further, the hot rolling coil manufactured by the heating equipment 20 and the heating method of Example 1 had a fluctuation range of the plate thickness of 51 μm, which was equivalent to an average fluctuation range of 50 μm in normal hot rolling.

  The second embodiment is different from the first embodiment only in that the output adjusting means 28 sets the output of the induction heating device 22 to zero when the moving direction in the heating equipment 20 is reversed, and the heating equipment 20 of the second embodiment and The hot rolled coil produced by the heating method had a thickness variation range of 30 μm or less, and a dimensional system superior to that of normal rolling was obtained.

  In the third embodiment, one induction heating device 22 is added to the heating facility 20 of the first embodiment, and the moving speed of the slab S during heating in the heating facility 20 is set to 10 mpm. Each moving distance in feeding was set to 1000 mm (twice Ld). When the slab S heated by the heating equipment 20 and the heating method of Example 3 was hot-rolled to a plate thickness of 3 mm by the subsequent hot-rolling equipment 14 to produce a hot-rolled coil, an edge portion of the slab S was obtained. Therefore, no material abnormality occurred at the edge of the hot rolled coil. Moreover, in the hot rolling coil manufactured from the slab S heated by the heating equipment 20 and the heating method of Example 3, the fluctuation range of the plate thickness is 48 μm, which is equivalent to the average fluctuation range of 50 μm in normal hot rolling. Met.

  The slab heating method of the prior art example 1 shown in FIG. 6 performs heating while moving the slab S using the six induction heating devices 22 as in the first embodiment, but the moving direction of the slab S is reversed. In this case, heating was performed during a single forward feed at a constant speed of 10 mpm. The slab S after the heating by the induction heating device 22 is hot-rolled to a plate thickness of 3 mm with the hot rolling equipment 14 to produce a hot-rolled coil, and before being sent to the hot rolling equipment 14. The surface temperature of the edge in the width direction on the tip side of the slab was lowered, and a material abnormality occurred in the edge in the width direction of the hot rolled coil.

  The slab heating method of Conventional Example 2 shown in FIG. 7 includes 11 induction heating devices 22 arranged at a pitch of 1500 mm in a range of about twice the length of the slab S, and sent in a forward direction at a speed of 60 mpm. When the tip of the slab reaches the point A, the induction slab 22 is energized to start heating while moving the slab in the forward direction at 10 mpm, and then the induction heating is performed when the tail end of the slab S reaches the point B. Stopped. As a result, all the portions of the entire length of the slab S are heated by the six induction heating devices 22 for 18 seconds, and the heating ends simultaneously. Therefore, the temperature drop of the edge portion on the tip side of the slab S as in the conventional example 1 is reduced. Although no problem occurred, a large number of induction heating devices 22 were required, resulting in high costs.

  By this invention, it became possible to provide the heating method and heating equipment of the continuous casting slab which can heat the edge part of the width direction uniformly over the full length of the continuous casting slab, and is economical.

DESCRIPTION OF SYMBOLS 10 Manufacturing equipment of hot-rolled steel sheet 12 Continuous casting equipment 14 Hot rolling equipment 16 Conveying roller 18 Water cooling equipment 20 Heating equipment 22 Induction heating device 24a, 24b Core material 26 Coil conductor 28 Output adjustment means 30 Free joint 32 Drive motor 34 Pusher

Claims (12)

A method for heating a continuous cast slab in which when a continuous cast slab cast by a continuous casting facility is directly fed and rolled by a hot rolling facility, the edge in the width direction of the continuous cast slab is heated before hot rolling the continuous cast slab Because
In the conveyance path of the continuous casting slab from the exit side of the continuous casting facility to the entry side of the hot rolling facility, a heating facility in which a plurality of induction heating devices are arranged at intervals in the conveyance direction is provided.
A method for heating a continuous cast slab, wherein the continuous casting slab is heated by reciprocating the continuous cast slab in the heating equipment, and the plurality of induction heating devices heat the widthwise edge of the continuous cast slab.   The continuous casting slab heating method according to claim 1, wherein the continuous casting slab is reciprocated by a transport roller that is capable of rotating forward and backward between the plurality of induction heating devices. The plurality of induction heating devices are arranged at a predetermined pitch,
The heating method of the continuous casting slab according to claim 1 or 2, wherein the widthwise edge portion is heated while moving a distance corresponding to a natural number multiple of the pitch in the reciprocating movement. When the pitch of the induction heating device is Ld, the length of the continuous casting slab is Ls, the heating length of each induction heating device is Lc, and the number of installed induction heating devices is N,
4. The number N of installed induction heating devices is determined so that the relationship of Ld × (N−1) −Lc <Ls ≦ Ld × N−Lc is satisfied. 5. The heating method of the continuous casting slab described in 1.   The method for heating a continuous cast slab according to any one of claims 1 to 4, wherein the output of the induction heating device is lowered or stopped when the moving direction of the continuous cast slab is reversed.   The continuous casting slab conveyance speed from the continuous casting equipment to the heating equipment and the continuous casting slab conveyance speed from the heating equipment to the hot rolling equipment should be larger than the reciprocating speed during heating of the continuous casting slab by the heating equipment. The heating method of the continuous casting slab as described in any one of Claim 1-5 characterized by these. When a continuous casting slab cast by a continuous casting facility is directly rolled by a hot rolling facility, the continuous casting slab heating facility heats the edge in the width direction of the continuous casting slab before hot rolling the continuous cast slab. Because
A plurality of induction heating devices arranged in the conveying path of the continuous casting slab from the outlet side of the continuous casting facility to the inlet side of the hot rolling facility, and spaced from each other in the conveying direction;
And a moving means for reciprocating the continuous casting slab heated by the plurality of induction heating devices.   8. The continuous casting slab heating facility according to claim 7, wherein the moving means includes a transport roller capable of rotating in the forward and reverse directions between the plurality of induction heating devices.   The heating section length from the induction heating device located at the most upstream in the conveying direction to the induction heating device located at the most downstream is not less than the length of the continuous casting slab and not more than 1.5 times the length. The continuous casting slab heating equipment according to claim 7 or 8.   The continuous casting slab heating equipment according to any one of claims 7 to 9, further comprising output adjusting means for lowering or stopping the output of the induction heating device when the moving direction of the continuous casting slab is reversed. .   The said continuous heating apparatus is arrange | positioned at equal intervals, The heating apparatus of the continuous casting slab as described in any one of Claim 7-10 characterized by the above-mentioned.   The heating device for a continuous casting slab according to any one of claims 7 to 11, wherein the moving means includes a pusher that directly presses the tip and tail ends of the continuous casting slab to reciprocate.

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