JP2005118787A - Hot rolling method and hot rolling equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot-rolling method and hot-rolling equipment by which occurrence of a spark caused by by the contact of a rough bar with a conveying table roller is completely suppressed by properly arranging sleeves having electric insulation in a plurality of places in the longitudinal direction of roll shafts of the conveying table rollers which are arranged in the vicinity of an induction heating device, in the hot-rolling equipment having the induction heating device. <P>SOLUTION: In the hot-rolling method by which the rough bar is heated with the induction heating device after the rough bar is made by rolling a slab with a roughing mill, the conveying table rollers on which the sleeves having electric insulation are externally fit in a plurality of the places in the longitudinal direction of the roll shaft are used as the conveying table rollers which are arranged in the vicinity of the induction heating device and a difference (H) in level between the sleeve and the roll shaft and an interval (L) between adjacent sleeves are set so that the tip and rear end parts of the rough bar which is conveyed on the conveying table rollers are not brought into contact with the roll surface between the adjacent sleeves. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hot rolling method and hot rolling equipment using an induction heating device for heating a rough bar.

  In a hot rolling facility, usually one or a plurality of induction heating devices using an eddy current method are arranged between a rough rolling mill and a finish rolling mill to heat the edges of the rough bars rolled by the rough rolling mill, The overall heating in the direction is performed to make the temperature in the coarse bar width direction uniform.

  However, as shown in FIG. 6, an induction heating device is used between the conveying table roll disposed in the vicinity of the induction heating device for heating the edge of the coarse bar or the entire width direction and the coarse bar that is the object to be heated. The induced eddy current (heating current) circulates, and when the circuit is interrupted by the state of conveyance of the rough bar, a spark current flows at that moment, and spark soot may be generated on the surface of the coarse bar. is there.

  When such spark wrinkles occur on the rough bar surface, the spark wrinkles remain after the subsequent finish rolling, which causes a problem in surface quality.

  Recently, in order to improve rolling efficiency, the generation of sparks has increased by increasing the induction current and by further shortening the installation interval of the conveyance table rolls in order to improve the transportability of the rough bars. Countermeasures against sparks are becoming important.

In order to solve this problem, a method of electrically insulating a transport table roll disposed in the vicinity of the induction heating device is known. For example, in a hot rolling line, an induction heating coil opposed to each other from the top and bottom of a rolled steel sheet is disposed, and the metal cored bar is disposed directly below or before and behind the induction heating apparatus that heats both ends in the width direction of the rolled steel sheet. A roller for hot rolling line (hereinafter referred to as a conveyance table roll) fitted with a ceramic sleeve on the ceramic sleeve, and the ceramic sleeve is fitted on both sides of the metal core bar in the body length direction. There is known a transport table roll in which an outer fitting portion has a larger diameter than a central portion in the body length direction of the roller (see, for example, Patent Document 1).
JP 2002-178020 A

  However, the above prior art has the following problems.

  The ceramic sleeve fitted in the transport table roll shown in Patent Document 1 can prevent the occurrence of sparks in the steady portion of the coarse bar. However, at the front and rear end portions of the coarse bar, there is a problem in that the front end of the rough bar enters between adjacent sleeves and comes into contact with the non-electrically insulated roll surface of the transport table roll to generate sparks.

  Here, FIG. 3 is an explanatory view showing a state in which the front and rear end portions of the coarse bar 4 enter between adjacent sleeves 3 of the transport table roll 1 and come into contact with the roll surface of the transport table roll 1. FIG. 4B is a side view. In FIG. 3, as will be described later, L indicates the interval between adjacent sleeves, r indicates the radius of curvature of the leading edge of the rough bar tip rear end, and H indicates the step between the sleeve 3 and the roll shaft 2. . Here, between the adjacent transport table rolls, a protective plate 5 is arranged to prevent the rough bar tip rear end from entering between the transport table rolls.

  Accordingly, an object of the present invention is to appropriately arrange sleeves having electrical insulation in a hot rolling facility having an induction heating device at a plurality of locations in the longitudinal direction of the roll axis of a transport table roll arranged in the vicinity of the induction heating device. Thus, an object of the present invention is to provide a hot rolling method and a hot rolling facility capable of completely suppressing the occurrence of sparks caused by contact of a rough bar with a transport table roll.

  Therefore, the inventors of the present invention are characterized by the shape of the front and rear end portions of the coarse bar that the front and rear end portions of the coarse bar come into contact with the surface of the conveyance table roll between the sleeves arranged on the roll shaft of the conveyance table roll. Inspired by the idea that there is, there was an intensive investigation on the shape of the front and rear ends of the coarse bar.

  As shown in FIG. 8, the front and rear end portions of the coarse bar have an unsteady planar shape with a narrow width called a tongue shape or a fish tail shape, according to the width killing amount in the rough rolling process. The present inventors have conceived that such a shape of the rough bar tip rear end portion is expressed as a curvature radius r of the most advanced portion. Accordingly, the radius of curvature r of the leading edge of the rough bar tip rear end was measured to determine the minimum radius of curvature R of the leading edge of the coarse bar. The target material was carbon steel having a plate thickness of 1.8 to 4.5 mm, a plate width of 900 to 1500 mm, and a C amount of 0.2% or less as a steel type. Moreover, the width killing amount in rough rolling was set to 0 to 300 mm, and those having various planar shapes from a tongue shape to a fishtail shape were used.

  As a result, as shown in FIG. 7, it was found that the radius of curvature r of the most distal portion is distributed over 140 mm in both the tongue shape and the fishtail shape. That is, the minimum radius of curvature R of the leading edge of the rough bar tip rear end is 140 mm.

  In this way, if the portion having the unsteady flat shape at the front end of the coarse bar can be expressed as the minimum radius of curvature R of the most advanced portion, the roll between the adjacent sleeves of the transport table roll is provided on the front end of the coarse bar. Whether or not it touches the surface can be determined by geometric analysis.

  The present invention has been made based on such findings, and the features thereof are as follows.

  [1] In a hot rolling method in which a slab is roughly rolled with a roughing mill to form a rough bar, and then the rough bar is heated by an induction heating device, a roll as a transport table roll disposed in the vicinity of the induction heating device Using a transport table roll in which sleeves having electrical insulation properties are externally fitted at a plurality of locations in the longitudinal direction of the shaft, the front and rear ends of the coarse bars transported on the transport table roll come into contact with the roll surface between adjacent sleeves. In order to prevent this, a step (H) between the sleeve and the roll shaft and an interval (L) between adjacent sleeves are set.

  [2] The hot rolling according to the above [1], wherein the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves are set so as to satisfy the following expression (1) Method.

L <2√ (2RH−H ² ) (1)
Where L: spacing between adjacent sleeves (mm), R: minimum radius of curvature of the leading edge of the rough bar tip rear end set in advance (mm), H: step between the sleeve and the roll shaft (mm)
[3] When the maximum incident angle with respect to the tangential direction of the transport table roll when the front and rear end portions of the coarse bar are in contact with the transport table roll is θ, the sleeve and the roll shaft are set so as to satisfy the following expression (2). The hot rolling method according to the above [1], wherein the step (H) and the interval (L) between adjacent sleeves are set.

L <2√ [(2R / sinθ) H− (H / sinθ) ² ] (2)
Here, L: spacing between adjacent sleeves (mm), R: preset minimum radius of curvature (mm) of the leading edge of the rough bar tip rear end, θ: leading and trailing end of the coarse bar to the transport table roll Maximum incident angle with respect to the tangential direction of the transport table roll at the time of contact, H: step between the sleeve and the roll axis (mm)
[4] The hot rolling as described in [1] above, wherein the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves are set so as to satisfy the following expression (3): Method.

L <4√ (140H−H ² ) (3)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)
[5] Step (H) between the sleeve and the roll shaft so that the step (H) between the sleeve and the roll shaft satisfies 5 mm ≦ H ≦ 50 mm and the interval (L) between adjacent sleeves satisfies L ≧ 50 mm. And the interval (L) between adjacent sleeves is set. The hot rolling method according to any one of the above [1] to [4].

  [6] In a hot rolling facility equipped with an induction heating device that has a conveyance table on the exit side of the roughing mill and heats the coarse bar in the middle of the conveyance table, conveyance arranged in the vicinity of the induction heating device As a table roll, sleeves having electrical insulation are externally fitted at a plurality of locations in the roll axis longitudinal direction, and the front and rear end portions of the coarse bar conveyed on the conveyance table roll do not contact the roll surface between adjacent sleeves. Thus, a hot rolling facility comprising a conveying table roll in which a step (H) between a sleeve and a roll shaft and an interval (L) between adjacent sleeves are set.

  [7] The above-mentioned [6], comprising a transport table roll in which a step (H) between the sleeve and the roll shaft and an interval (L) between adjacent sleeves are set so as to satisfy the following expression (3). ] The hot-rolling equipment described in the above.

L <4√ (140H−H ² ) (3)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)

  According to the present invention, it is possible to completely suppress the occurrence of sparks by appropriately arranging sleeves having electrical insulation properties at a plurality of locations in the longitudinal direction of the roll axis of the transport table roll disposed in the vicinity of the induction heating device. it can.

  FIG. 2 shows an example of the shape of the conveying table roll 1 used in the hot rolling facility of the present invention and the electrically insulating sleeve 3 arranged on the roll shaft 2. In this example, the sleeve 3 having electrical insulation is externally fitted with an interval (L) between sleeves adjacent to three locations in the longitudinal direction of the roll axis. At this time, the level difference (H) between the sleeve 3 and the roll shaft 2 and the adjacent portion are appropriately adjusted so that the front and rear end portions of the coarse bar 4 conveyed on the conveying table roll do not contact the roll surface between the adjacent sleeves 3. The interval (L) of the sleeve to be set is set. If the sleeve diameter is D and the roll shaft diameter is d, the step H between the sleeve 3 and the roll shaft 2 is H = (D−d) / 2.

  Here, the state where the front and rear end portions of the coarse bar 4 shown in FIG. 3 are in contact with the roll surface of the transport table roll 1 between the adjacent sleeves 3 is modeled as shown in FIG. That is, in FIG. 4, a portion having an unsteady planar shape at the rear end portion of the rough bar tip is represented as an arc having a minimum curvature radius R at the most distal portion. When FIG. 4 is geometrically analyzed, the following equation (5) is obtained.

L = 2 × √ (2RH−H ² ) (5)
Therefore, in order to prevent the front and rear end portions of the coarse bar conveyed on the conveyance table roll from coming into contact with the roll surface between the adjacent sleeves, the step between the sleeve and the roll shaft ( H) and the spacing (L) between adjacent sleeves.

L <2√ (2RH−H ² ) (1)
Here, assuming that the minimum radius of curvature R of the leading edge of the rough bar tip rear end is 140 mm, the following equation (4) can be obtained by substituting R = 140 into the above equation (1). Here, the unit of the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves is mm.

L <2√ (280H−H ² ) (4)
Further, as shown in FIG. 3 (b), the front and rear end portions of the coarse bar 4 are considered to contact the roll surface of the transport table roll 1 obliquely with respect to the transport table roll 1. Therefore, as shown in FIG. 5, θ is the maximum incident angle with respect to the tangential direction of the transport table roll when the front and rear end portions of the coarse bar 4 come into contact with the transport table roll.

  5 is geometrically analyzed, and the following equation (2) is satisfied so that the front and rear end portions of the coarse bar 4 conveyed on the conveyance table roll do not contact the roll surface between the adjacent sleeves 3. Thus, the step (H) between the sleeve 3 and the roll shaft 2 and the interval (L) between adjacent sleeves are set.

L <2√ [(2R / sinθ) H− (H / sinθ) ² ] (2)
Usually, a member such as a protective plate for preventing the rear end of the coarse bar from entering between adjacent transport table rolls is disposed, so that the value of the incident angle does not increase so much, and the maximum incident angle θ Is considered to be about 30 °. Therefore, θ = 30 ° and R = 140 can be substituted into the above equation (2) to obtain the following equation (3). The equation (1) is obtained by setting θ = 90 ° in the above equation (2). Here, the unit of the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves is mm.

L <4√ (140H−H ² ) (3)
Next, FIG. 1 shows a sleeve in which the front and rear end portions of the coarse bar transported on the transport table roll are adjacent to each other in the transport table roll in which the sleeves having electrical insulation properties are externally fitted at a plurality of locations in the roll shaft longitudinal direction. It is a graph which shows an example of the relationship between the level | step difference (H) of a sleeve and a roll axis | shaft and the space | interval (L) of an adjacent sleeve which were set so that it might not contact the roll surface between. Here, the aforementioned minimum radius of curvature R of the most advanced portion of the rear end of the rough bar tip set in advance was 140 mm.

  As shown in FIG. 1, in the present invention, the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves are set so as to satisfy the following expression (4).

L <2√ (280H−H ² ) (4)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)
By satisfying the above equation (4), it is possible to completely suppress the occurrence of sparks caused by the rough bar coming into contact with the transport table roll.

  As shown in FIG. 1, in the present invention, the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves can be set so as to satisfy the following expression (3).

L <4√ (140H−H ² ) (3)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)
The above formula (3) assumes that the incident angle with respect to the tangential direction of the transport table roll when the front and rear ends of the coarse bar contact the transport table roll is within 30 °, and satisfies the above formula (3). By setting the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves as described above, no spark is generated when the incident angle is within 30 °.

  Further, as shown in FIG. 1, in the present invention, it is preferable that the step (H) between the sleeve and the roll shaft satisfies 5 mm ≦ H ≦ 50 mm, and the interval (L) between adjacent sleeves satisfies L ≧ 50 mm. . This is because when the step (H) between the sleeve and the roll shaft is less than 5 mm, the strength of the sleeve is insufficient, and when the step (H) between the sleeve and the roll shaft exceeds 50 mm, the cost for manufacturing the sleeve is high. It is. Moreover, it is because it will become expensive if the space | interval (L) of an adjacent sleeve is less than 50 mm.

  In general, alumina ceramics or silicon nitride is used as the material of the sleeve having electrical insulation.

  In the present invention, the slab is roughly rolled with a roughing mill to form a rough bar, and then hot rolling is performed by heating the rough bar with an induction heating device. At this time, as a transport table roll disposed in the vicinity of the induction heating device, a transport table roll in which sleeves having electrical insulation properties are externally fitted at a plurality of locations in the longitudinal direction of the roll axis is used and transported on the transport table roll. The step (H) between the sleeve and the roll shaft and the interval (L) between the adjacent sleeves are set as described above so that the leading and trailing ends of the rough bars do not contact the roll surface between the adjacent sleeves.

  Here, the conveyance table rolls arranged in the vicinity of the induction heating device are usually adjacent to at least the entry side and the exit side among the conveyance table rolls arranged on the entry side and the exit side of each induction heating device. It refers to one roll at a time. However, the conveyance table roll of the present invention can be used for either the entry side or the exit side, and a conveyance table roll provided with other electrical insulation means can be used for the other conveyance table roll.

  By performing hot rolling using such a transport table roll, the occurrence of sparks can be prevented.

  As a transport table roll arranged in the vicinity of the induction heating device, a transport table roll in which sleeves having electrical insulation properties are externally fitted at a plurality of locations in the longitudinal direction of the roll axis is used, and a rough bar is transported on the transport table roll. Was conducted for a long time, and the occurrence rate of sparks was examined by visual confirmation.

  The conveyance table roll around the induction heating device used as an example of the present invention has a roll shaft diameter of 325 mm and a material of carbon steel. Further, the ceramic sleeve externally fitted to the transport table roll has a step (H) of 15 mm, intervals between adjacent sleeves (L) of 125 mm and 160 mm, a sleeve width of 100 mm, the number of the sleeves is three, and the material is nitrided. Silicon.

  On the other hand, a ceramic sleeve externally fitted to a transport table roll used as a comparative example has a step (H) of 15 mm, an interval between adjacent sleeves (L) of 200 mm, a sleeve width of 100 mm, and a number of 3 The material is silicon nitride.

Table 1 shows the visually observed spark occurrence rate. When the interval (L) between adjacent sleeves of the example of the present invention is 125 mm, the spark occurrence rate is 0% and the interval (L) between adjacent sleeves is 160 mm. In this case, the spark occurrence rate was 1%, but when the interval (L) between adjacent sleeves in the comparative example was 200 mm, the spark occurrence rate was 5%. Here, when the interval (L) between adjacent sleeves is 125 mm, L <2√ (280H−H ² ), and when the interval (L) between adjacent sleeves is 160 mm, 2√ (280H−H). ² ) <L <4√ (140H−H ² ). That is, in these invention examples, when the sleeve interval (L) is 125 mm, the rough bar tip rear end does not come into contact with the roll surface of the transport table roll at all, and when 160 mm, the coarse bar tip rear end touches the transport table roll. It is considered that the incident angle of the bar slightly exceeded 30 °, and in this case, the rear end of the rough bar contacted the transport table roll. On the other hand, when the interval (L) between adjacent sleeves in the comparative example was 200 mm, it was a case of L> 4√ (140H−H ² ), and the frequency with which the rough bar tip rear end contacted the transport table roll was high. I understand.

The graph which shows an example of the relationship between the level | step difference (H) of the sleeve and roll axis | shaft of a conveyance table roll used for the hot rolling equipment of this invention, and the space | interval (L) of an adjacent sleeve. Explanatory drawing which shows an example of the shape of the conveyance table roll used for the hot rolling equipment of this invention, and the sleeve which has the electrical insulation arrange | positioned at the roll axis | shaft The front and rear ends of the coarse bar enter between adjacent sleeves of the transport table roll and are in contact with the roll surface of the transport table roll, where (a) is a plan view and (b) is a side view. Explanatory drawing which modeled the state which the front-and-rear end part of the rough bar shown in FIG. 3 contacts the roll surface of the conveyance table roll between adjacent sleeves Explanatory drawing which has the largest incident angle (theta) with respect to a conveyance table roll tangent direction, and the front-and-rear end part of a rough bar contacts a conveyance table roll Explanatory drawing of the transport table roll around the induction heating device Graph showing the distribution of the radius of curvature r of the leading edge of the rough bar tip rear end It is explanatory drawing which shows the planar shape of a rough bar tip rear end part, (a) is a fishtail shape, (b) is a tongue shape.

Explanation of symbols

1 Transport table roll 2 Roll shaft 3 Sleeve 4 Coarse bar 5 Guard plate

Claims (7)

  In the hot rolling method in which the rough bar is heated by an induction heating device after the slab is roughly rolled by a rough rolling machine, a roll table longitudinal direction is used as a transport table roll disposed in the vicinity of the induction heating device. Using a transport table roll in which sleeves having electrical insulation properties are externally fitted at a plurality of locations, so that the front and rear end portions of the coarse bar transported on the transport table roll do not contact the roll surface between adjacent sleeves. A hot rolling method characterized by setting a step (H) between a sleeve and a roll shaft and an interval (L) between adjacent sleeves. The hot rolling method according to claim 1, wherein the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves are set so as to satisfy the following expression (1).
L <2√ (2RH−H ² ) (1)
Where L: spacing between adjacent sleeves (mm), R: minimum radius of curvature of the leading edge of the rough bar tip rear end set in advance (mm), H: step between the sleeve and the roll shaft (mm) When the maximum incident angle with respect to the tangential direction of the transport table roll when the front and rear end portions of the coarse bar come into contact with the transport table roll is θ, a step (H between the sleeve and the roll shaft so as to satisfy the following expression (2) ) And the interval (L) between adjacent sleeves are set.
L <2√ [(2R / sinθ) H− (H / sinθ) ² ] (2)
Here, L: spacing between adjacent sleeves (mm), R: preset minimum radius of curvature (mm) of the leading edge of the rough bar tip rear end, θ: leading and trailing end of the coarse bar to the transport table roll Maximum incident angle with respect to the tangential direction of the transport table roll at the time of contact, H: step between the sleeve and the roll axis (mm) The hot rolling method according to claim 1, wherein the step (H) between the sleeve and the roll shaft and the interval (L) between adjacent sleeves are set so as to satisfy the following expression (3).
L <4√ (140H−H ² ) (3)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)   The step (H) between the sleeve and the roll shaft and adjacent so that the step (H) between the sleeve and the roll shaft satisfies 5 mm ≦ H ≦ 50 mm and the interval (L) between adjacent sleeves satisfies L ≧ 50 mm. The hot rolling method according to any one of claims 1 to 4, wherein an interval (L) between the sleeves is set.   In a hot rolling facility having an induction heating device having a conveyance table on the exit side of the rough rolling mill and heating the coarse bar in the middle of the conveyance table, as a conveyance table roll arranged in the vicinity of the induction heating device The sleeve having electrical insulation is externally fitted at a plurality of locations in the longitudinal direction of the roll axis so that the front and rear end portions of the coarse bar conveyed on the conveyance table roll do not contact the roll surface between the adjacent sleeves. A hot rolling facility comprising a conveying table roll in which a step (H) between a sleeve and a roll shaft and an interval (L) between adjacent sleeves are set. The transport table roll according to claim 6, further comprising a step (H) between the sleeve and the roll shaft and a distance (L) between adjacent sleeves so as to satisfy the following expression (3). Hot rolling equipment.
L <4√ (140H−H ² ) (3)
Where L: spacing between adjacent sleeves (mm), H: step between sleeve and roll axis (mm)

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