JP4876782B2 - Steel sheet hot rolling equipment and hot rolling method - Google Patents

Description

  The present invention relates to a steel sheet hot rolling facility and a hot rolling method.

  In recent years, in the hot rolling of steel sheets, the production of steel sheets with excellent strength and toughness has been demanded. As an example, the thickness of a superior material can be increased by subjecting the rolled material to controlled rolling (CR). Steel plate is built in. That is, a slab heated to 1000 ° C. or higher is once rolled to a predetermined thickness, and then rolled to a finished thickness in a state where the temperature of the rolled material is in a non-recrystallization temperature range or a temperature range close to that temperature range. Is. For example, after heating a slab having a thickness of 200 to 300 mm to about 1100 to 1200 ° C., the slab was rolled to about 1.5 to 2 times the finished plate thickness, and then the temperature became 850 ° C. or less which is an unrecrystallized region. Control rolling is started at the time, and rolling is performed to a finished sheet thickness (for example, 15 mm).

  At that time, if the temperature at which controlled rolling is performed (controlled rolling start temperature) is low and the sheet thickness at which controlled rolling is performed (controlled rolling start plate thickness) is thick, a considerable amount of time is required until the rolled material reaches the controlled rolling start temperature. Since time is required, the rolled material is allowed to stand in a cool state until the controlled rolling start temperature is reached on the conveyance line in the vicinity of the rolling mill (reversible rolling mill). As a result, there is a problem that idle time is generated in the rolling mill due to the cooling and the rolling efficiency is lowered.

  In order to eliminate the occurrence of idle time in the rolling mill due to such cooling waiting and the reduction in rolling efficiency, for example, in Patent Document 1, a shower-type cooling device is installed in front of and behind the reversible rolling mill. In each rolling pass, there is shown a controlled rolling method in which a rolled material is rolled with a reversible rolling mill while being cooled with a cooling device.

Further, in Patent Document 2, a temperature adjustment cooling facility for cooling the rolled material to a predetermined controlled rolling start temperature is installed, and the rolled material rolled to a predetermined plate thickness by a reversible rolling mill is set to a predetermined temperature adjustment cooling facility. A technique is described in which, after cooling to a controlled rolling start temperature (temperature-controlled cooling), rolling is performed again to the finished sheet thickness with a reversible rolling mill. This temperature-controlled cooling facility is installed at a position about 20 m away from the reversible rolling mill in order to avoid interference with the following material.
JP-A-55-106615 JP 2005-000979 A

  However, in the technique described in Patent Document 1, the steel sheet is cooled by a shower-type cooling device, but drainage of the cooling water is not taken into consideration, so a large flow rate is obtained to obtain a predetermined temperature drop amount. If the cooling water is supplied to the upper surface of the steel plate, the cooling water staying on the upper surface of the steel plate will move freely on the upper surface of the steel plate, the cooling area of the steel plate will fluctuate and the cooling will become uneven. There is a problem of adversely affecting the shape.

  In addition, although there is a method of using a draining roll for draining the cooling water staying on the upper surface of the steel plate, there is a concern that a transport trouble such as a collision of the transported steel plate with the draining roll may occur. Also, there is a method of draining with air, but it is not effective for cooling water with a large flow rate.

  Further, in the technique described in Patent Document 2, since temperature-controlled cooling is performed to a predetermined controlled rolling start temperature with a temperature-controlled cooling facility installed at a position about 20 m away from the rolling mill, the conveying time of the steel plate is also increased. In addition, there is a problem that it takes time for cooling and the reduction in rolling efficiency cannot be solved sufficiently.

  The present invention has been made in view of the circumstances as described above, and when performing controlled rolling of a steel sheet, the steel sheet is uniformly cooled to obtain a good product quality, and a reduction in rolling efficiency due to waiting for cooling or the like. It is an object of the present invention to provide a hot rolling facility and a hot rolling method for a steel sheet that can be prevented.

  In order to solve the above problems, the present invention has the following features.

[1] Upper and lower surfaces of the steel sheet while passing the unrolled and / or rolled steel sheet at a position close to the reversible rolling machine on the entry side and / or exit side of the reversible rolling machine for hot rolling the steel sheet Cooling equipment for supplying cooling water having a water density of 4 m ³ / m ² min or more, respectively,
The cooling equipment on the upper surface has a nozzle that supplies rod-shaped cooling water obliquely from above the steel sheet toward the steel sheet, and the nozzles are respectively arranged in the conveying direction so that the cooling water faces each other in the conveying direction of the steel sheet on the steel sheet. A hot rolling facility for steel sheets, wherein a plurality of rows are arranged.

[ 2 ] The cooling area of the cooling facility is a position close to the reversible rolling mill excluding the side guide portion disposed on the entry side and / or the exit side from the reversible rolling mill. The steel sheet hot rolling facility according to [1] .

[ 3 ] The cooling area of the cooling facility is upstream of the side guide disposed on the entry side of the reversible rolling mill and / or downstream of the side guide disposed on the exit side of the reversible rolling mill. The hot rolling facility for a steel sheet according to [1] or [2] , wherein the hot rolling facility is a position close to a reversible rolling mill.

[ 4 ] A cooling facility is arranged at a position close to the reversible rolling mill on the entry side and / or the exit side of the reversible rolling mill for hot rolling the steel sheet, and before and / or after rolling from the cooling facility. While supplying the cooling water with a water volume density of 4 m ³ / m ² min or more to the upper and lower surfaces of the steel sheet while passing the steel sheet,
At that time, the upper surface of the steel plate is formed into a bar shape obliquely from above the steel plate toward the steel plate by nozzles arranged in a plurality of rows in the transfer direction so that the cooling water faces each other in the steel plate transfer direction on the steel plate. A method for hot rolling a steel sheet, comprising supplying cooling water.

[ 5 ] The cooling area of the cooling facility is a position close to the reversible rolling mill excluding the side guide portions arranged on the entry side and / or the exit side from the reversible rolling mill. The method for hot rolling a steel sheet according to [4] .

[ 6 ] The cooling area of the cooling facility is upstream of a side guide disposed on the entry side of the reversible rolling mill and / or downstream of a side guide disposed on the exit side of the reversible rolling mill. The hot rolling method for a steel sheet according to claim [4] or [5] , wherein the hot rolling method is a position close to a reversible rolling mill.

In the present invention, since a passing type cooling facility having a large water density of 4 m ³ / m ² min or more is disposed at a position close to the reversible rolling mill, the efficiency is improved by cooling the steel sheet while rolling it. Therefore, a predetermined controlled rolling start temperature can be obtained, and a reduction in rolling efficiency due to waiting for cooling or the like is avoided. The nozzles are arranged on the steel plate so that the cooling water faces each other in the transport direction, and the cooling water having a large water amount density of 4 m ³ / m ² min or more is supplied. The above stagnant cooling water is blocked and drained appropriately, and a stable cooling region is obtained.

  As a result, when performing the controlled rolling of the steel sheet, the steel sheet is uniformly cooled to obtain a good product quality, and it is possible to prevent a reduction in rolling efficiency due to waiting for cooling or the like.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a layout diagram of a steel sheet hot rolling facility according to an embodiment of the present invention. As shown in FIG. 1, in this embodiment, the heating furnace 11, the reversible rolling mill 12, and the reciprocating rolling mill 12 are cooled to positions adjacent to the entry side (upstream side) and the exit side (downstream side). Facility 20 is arranged. The cooling facility 20 is a passage-type cooling facility, and an upper header unit 21 for supplying cooling water toward the upper surface of the steel plate 10 and a lower header for supplying cooling water toward the lower surface of the steel plate 10. A header 31 is provided. In FIG. 1, reference numeral 13 denotes a table roller.

  2 and 3 are detailed views of the cooling facility 20. In FIG. 2, the cooling facility 20 is disposed between the reversible rolling mill 12 and the side guide 14. In FIG. 3, the cooling facility 20 is reversible on the upstream side (heating furnace side) of the side guide 14. It is arranged at a position close to the rolling mill 12. In any case, as described above, the cooling facility 20 includes the upper header unit 21 and the lower header 31.

  The upper header unit 21 is composed of a pair of upper headers 21a and 21b. Here, the upper header closer to the reversible rolling mill 12 is referred to as a first upper header 21a, and the side farther from the reversible rolling mill 12. The upper header is referred to as a second upper header 21b.

  And circular tube nozzle 22a, 22b (here 6 rows in the conveyance direction of the steel plate 10) which arranged in the width direction of the steel plate in each of the 1st upper header 21a and the 2nd upper header 21b, and was provided in multiple rows in the conveyance direction Are attached to the circular pipe nozzle (first upper nozzle) 22a of the first upper header 21a and the circular pipe nozzle (second upper nozzle) 22b of the second upper header 21b. Are arranged so as to face each other in the conveying direction of the steel plate 10. That is, the first upper nozzle 22a injects the rod-shaped cooling water 23a from the reversible rolling mill 12 side at a tilt angle (injection angle) of θ1, and the second upper nozzle 22b has a θ2 toward the reversible rolling mill 12 side. The rod-shaped cooling water 23b is jetted at a depression angle (jetting angle).

  Incidentally, the rod-shaped cooling water of the present invention refers to cooling water that is injected from a circular (including elliptical or polygonal) nozzle outlet. In addition, the rod-shaped cooling water of the present invention is not a spray-like jet, but a film-like laminar flow, the cross section of the water flow from the nozzle outlet to the steel plate is maintained in a substantially circular shape, and is continuous and straight. Cooling water with a water flow.

  Therefore, a region sandwiched between positions where rod-shaped cooling water from the circular tube nozzles in the row farthest from the upper header (outermost row) collides with the steel plate 10 is a cooling region.

  At this time, if the injection line of the rod-shaped cooling water 23a from the first upper nozzle 22a and the injection line of the rod-shaped cooling water 23b from the second upper nozzle 22b do not intersect, as shown in FIGS. A water film of the staying cooling water 24 is stably formed. Thereby, the rod-shaped cooling water from the circular tube nozzles in the row closest to the upper header of each other (innermost row) is jetted toward the water film of the staying cooling water 24, and This is preferable because the rod-shaped cooling water is not broken. And if it says that the space | interval of the position where the rod-shaped cooling water from the circular tube nozzle of the innermost line collides with the steel plate 10 is called a stay area length, it will stay if a stay area length shall be 1.5 m or less. Since the cooling water 24 cools the steel plate 10 at a relatively low rate, it is possible to prevent the cooling method from changing greatly when the leading edge or the rearmost end of the steel plate 10 passes in an unsteady state.

  FIGS. 4A and 4B show examples of arrangement of the circular tube nozzles 22a and 22b attached to the upper headers 21a and 21b. As described above, the circular tube nozzles 22 a and 22 b are arranged in six rows in the conveying direction of the steel plate 10. The reason why a plurality of rows are arranged in the conveying direction is that a single row of nozzles weakens the force to dam the stagnant cooling water between the cooling water colliding with the steel plate and the cooling water. Therefore, it is preferable to arrange three or more rows in the transport direction. More preferably, five or more rows are arranged. Moreover, it is attached so that cooling water can be supplied to the full width of the passing steel plate 10 in the plate width direction.

  On the other hand, with respect to the lower header 31, here, two lower headers 31 are arranged, and circular nozzles 32 are attached to each of the lower headers 31. The cooling water is supplied to the entire width of the steel plate 10 to be performed.

The cooling facility 20 supplies cooling water from the upper headers 21 a and 21 b so that the water density on the steel plate surface is 4 m ³ / m ² min or more toward the upper surface of the steel plate 10, and toward the lower surface of the steel plate 10. The cooling water is supplied from the lower header 31 so that the water density on the steel plate surface is 4 m ³ / m ² min or more.

Here, the reason why the water density is set to 4 m ³ / m ² min or more will be described. The staying cooling water 24 shown in FIGS. 2 and 3 is formed by damming with the rod-like cooling waters 23a and 23b to be supplied. At this time, if the water density is small, damming itself cannot be performed, and if the water density becomes larger than a certain amount, the amount of the staying cooling water 24 that can be dammed increases, and the cooling water discharged from the end of the plate width The amount of the cooling water supplied is balanced and the retained cooling water 24 is kept constant. In the case of a thick steel plate, the general plate width is ^{2 to 5} m, and if it is cooled with a water density of 4 m ³ / m ² min or more, the retained cooling water can be kept constant at these plate widths, A desired amount of temperature drop can be obtained while passing the steel plate 10.

The larger the water density is 4 m ³ / m ² min or more, the more control rolled material that eliminates the waiting for cooling. For example, if the water density is small, the waiting for cooling can be solved only with a rolled material having a thin plate thickness. However, if the water density is increased, the waiting for cooling can be eliminated even for a rolled material having a certain thickness. However, the effect of shortening the cooling waiting time for increasing the amount of water gradually decreases as the water density increases, so the water density takes into account the effect of shortening the cooling waiting time and the equipment cost, It is preferable to determine. A more preferable water density is 4 to 10 m ³ / m ² min.

  Further, in order to make the cooling equipment 20 compact and to cool the steel plate at a position close to the reversible rolling mill 12, the residence zone length is 1.5 m or less, the cooling zone is 3 m or less, The cooling equipment 20 is disposed so as to be in a position close to the reversible rolling mill 12 excluding the length of the side guide portion disposed on the entry side and / or the exit side of the reversible rolling mill 12. Generally, this position is within a range of 20 m from the work roll center 12a of the reversible rolling mill 12. If the cooling region is provided at a position excluding the side guide portion so as not to cover the side guide, the cooling water staying on the upper surface of the steel plate 10 is smoothly discharged from the end of the width of the steel plate 10 without being obstructed by the side guide 14.

  At that time, as shown in FIG. 2, the cooling facility 20 is arranged so that the cooling region is located between the work roll center 12a of the reversible rolling mill 12 and the side guide (about 2 to 4 m from the work roll center 12). This is preferable because the rolling efficiency can be improved efficiently.

  On the other hand, as shown in FIG. 3, the cooling area of the cooling facility 20 is provided at a position close to the reversible rolling mill 12 on the upstream side of the side guide 14 disposed on the entry side of the reversible rolling mill 12, or Providing at a position close to the reversible rolling mill 12 on the downstream side of the side guide 14 arranged on the exit side of the reversible rolling mill 13 may ensure a long cooling region by enlarging the equipment.

  Furthermore, it goes without saying that cooling regions may be provided both between the work roll center 12a of the reversible rolling mill 12 and the side guide 14 and on the upstream side of the side guide 14 shown in FIG.

And in this cooling equipment 20, since the rod-shaped cooling water 23a injected from the 1st upper nozzle 22a and the rod-shaped cooling water 23b injected from the 2nd upper nozzle 22b are made to oppose each other in the conveyance direction of the steel plate 10. The injected rod-like cooling water 23a, 23b itself blocks the stagnant cooling water 24 on the upper surface of the steel plate 10 from moving in the conveying direction of the steel plate 10. As a result, even if the cooling water is supplied with a large water density of 4 m ³ / m ² min or more, a stable cooling region can be obtained and uniform cooling can be performed.

  Note that the cooling water sprayed from the upper nozzles 22a and 22b is, for example, a rod-shaped cooling water instead of a film-shaped cooling water using a slit nozzle. This is because the power to dam is large.

  At that time, the injection angle θ1 of the first upper nozzle 22a and the injection angle θ2 of the second upper nozzle 22b are preferably set to 30 ° to 60 °. If the injection angles θ1 and θ2 are smaller than 30 °, the vertical velocity components of the rod-shaped cooling waters 23a and 23b are reduced, the collision with the steel plate 10 is weakened, and the cooling capacity is reduced. This is because if θ2 is larger than 60 °, the speed component in the conveying direction of the rod-shaped cooling waters 23a and 23b becomes small, and the force to dam the staying cooling water 24 becomes weak. The injection angle θ1 and the injection angle θ2 are not necessarily equal. Further preferable injection angles θ1 and θ2 are 40 ° to 50 °.

  Further, in order to obtain the desired cooling capacity and draining capacity, the upper nozzles 22a and 22b are arranged in five or more rows in the steel plate conveying direction, and the jet speed of the rod-shaped cooling waters 23a and 23b from the upper nozzles 22a and 22b is 8 m. / S or more is preferable. The upper limit of the number of nozzle rows may be appropriately determined depending on the size of the steel sheet to be cooled, the conveyance speed, the target temperature drop amount, and the like. In addition, when the injection speed exceeds 30 m / s, the pressure loss increases, causing the problem of increased wear on the inner surface of the nozzle, and the equipment cost also increases.

  Further, in order to prevent the upper nozzles 22a and 22b from being damaged by warpage of the steel plate 10, the positions of the tips of the upper nozzles 22a and 22b are preferably separated from the pass line. Therefore, the distance between the tip of the upper nozzles 22a and 22b and the pass line is preferably 500 mm to 1800 mm.

  And when performing control rolling using the hot rolling equipment of the steel plate comprised as mentioned above, it is predetermined in predetermined control rolling start board thickness (for example, 1.5-2 times of finishing board thickness). A reversible rolling mill while cooling the steel plate passing through the cooling region of the cooling equipment 20 before and / or during rolling and / or after rolling so that the controlled rolling start temperature (for example, 850 ° C. or less) is reached. Roll at 12. When the predetermined control rolling start plate thickness reaches the predetermined control rolling start temperature, after that, the cooling facility 20 is not cooled, and the sheet is rolled to a finished plate thickness (for example, 15 mm).

  In addition, it is not necessary to perform cooling by the cooling equipment 20 on the entry side and the exit side in all rolling passes until the control rolling start temperature is reached, so that the predetermined control rolling start temperature is reached with a predetermined control rolling start plate thickness. What is necessary is just to turn ON / OFF the cooling equipment 20 suitably.

  Moreover, although the cooling equipment 20 is arrange | positioned here in the entrance side and exit side of the reversible rolling mill 12, you may arrange | position the cooling equipment 20 in any one.

Thus, in this embodiment, since the passing-type cooling equipment 20 having a large water density of 4 m ³ / m ² min or more is arranged at a position close to the reversible rolling mill 12, the steel plate 10 is By cooling while rolling, a predetermined control temperature can be obtained efficiently, and a reduction in rolling efficiency due to waiting for cooling or the like is avoided. And since the circular pipe nozzles 22a and 22b are arranged so that the cooling water is opposed to each other in the transport direction on the steel plate 10, the cooling water having a large water amount density of 4 m ³ / m ² min or more is supplied, so that it is injected. The rod-shaped cooling waters 23a and 23b themselves dam the staying cooling water 24 on the steel plate 10 and appropriately drain the water, so that a stable cooling region is obtained.

  As a result, when performing the controlled rolling of the steel sheet, the steel sheet is uniformly cooled to obtain a good product quality, and it is possible to prevent a reduction in rolling efficiency due to waiting for cooling or the like.

In the above-described embodiment, rod-shaped cooling water having a water content density of 4 m ³ / m ² min or more is supplied to the lower surface of the steel plate, but the present invention is not limited thereto. If the cooling water can supply cooling water with a water density of 4 m ³ / m ² min or more on the steel plate surface, any film cooling water from other slit nozzles, spray cooling water from the spray nozzles, etc. The cooling water in such a form may be used.

  Examples of the present invention are described below.

  Here, the rolling time of the example of the present invention was compared with that of the conventional example when producing a thick steel plate having a plate thickness of 18.5 mm, a plate width of 2560 mm, and a plate length of 35 m by performing controlled rolling.

  The present invention example uses the hot rolling facility according to the above-described embodiment to cool the steel plate so that the predetermined control rolling start temperature (820 ° C.) is obtained at the predetermined control rolling start plate thickness (34 mm). It is a case where it rolls, cooling by cooling, and after that, cooling by the cooling equipment 20 is stopped and rolled to a finished plate thickness of 18.5 mm.

  In the conventional example, as in the technique described in Patent Document 2, after rolling to a predetermined control rolling start plate thickness (34 mm), the rolling is temporarily stopped and a predetermined control rolling start temperature (820 ° C.) is set by a temperature control cooling facility. This is a case where the temperature adjustment cooling is performed until rolling to a finished plate thickness of 18.5 mm.

  The result is shown in FIG. In the figure, ◯ and ● indicate the respective rolling passes. As described above, the time from extraction of the heating furnace to the end of rolling was 205 seconds in the conventional example, but was shortened by 165 seconds and 40 seconds in the example of the present invention. And the product quality of the example of the present invention was not inferior to the conventional example.

  Thereby, the effectiveness of the present invention could be confirmed.

It is a layout view of hot rolling equipment for steel sheets in one embodiment of the present invention. It is detail drawing of the cooling equipment in one Embodiment of this invention. It is detail drawing of the cooling equipment in one Embodiment of this invention. It is the figure which showed the nozzle arrangement example of the upper header in one Embodiment of this invention. It is a comparison figure of the rolling time in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Steel plate 11 Heating furnace 12 Reversible rolling mill 12a Work roll center 13 Table roller 14 Side guide 20 Cooling equipment 21 Upper header unit 21a First upper header 21b Second upper header 22a First upper nozzle 22b Second upper nozzle 23a Rod cooling Water 23b Bar-shaped cooling water 24 Stagnating cooling water 31 Lower header 32 Lower nozzle 33 Bar-shaped cooling water

Claims (6)

4 m on each of the upper and lower surfaces of the steel sheet while passing the unrolled and / or rolled steel sheet at a position close to the reversible rolling machine on the entry side and / or exit side of the reversible rolling machine for hot rolling the steel sheet. A cooling facility for supplying cooling water with a water density of ³ / m ² min or more is arranged,
The cooling equipment on the upper surface has a nozzle that supplies rod-shaped cooling water obliquely from above the steel sheet toward the steel sheet, and the nozzles are respectively arranged in the conveying direction so that the cooling water faces each other in the conveying direction of the steel sheet on the steel sheet. A hot rolling facility for steel sheets, wherein a plurality of rows are arranged. The cooling area of the cooling equipment, to claim 1, characterized in that the position close to the reversible rolling mill except for the side guide part disposed on the inlet side and / or delivery side of the reversible rolling mill Hot-rolling equipment for steel sheets as described. The cooling area of the cooling facility is reversible rolling on the upstream side of the side guide disposed on the entry side of the reversible rolling mill and / or on the downstream side of the side guide disposed on the exit side of the reversible rolling mill. The hot rolling facility for a steel sheet according to claim 1 or 2 , wherein the hot rolling facility is a position close to the machine. A cooling facility is arranged at a position close to the reversible rolling mill on the entry side and / or exit side of the reversible rolling mill for hot rolling the steel plate, and passes through the steel plate before rolling and / or after rolling from the cooling facility. While supplying cooling water having a water volume density of 4 m ³ / m ² min or more to the upper and lower surfaces of the steel sheet,
At that time, the upper surface of the steel plate is formed into a bar shape obliquely from above the steel plate toward the steel plate by nozzles arranged in a plurality of rows in the transfer direction so that the cooling water faces each other in the steel plate transfer direction on the steel plate. A method for hot rolling a steel sheet, comprising supplying cooling water. The cooling area of the cooling equipment, to claim 4, characterized in that the position close to the reversible rolling mill except for the side guide part disposed on the inlet side and / or delivery side of the reversible rolling mill The hot rolling method of the described steel plate. The cooling area of the cooling facility is reversible rolling on the upstream side of the side guide disposed on the entry side of the reversible rolling mill and / or on the downstream side of the side guide disposed on the exit side of the reversible rolling mill. The method for hot rolling a steel sheet according to claim 4 or 5 , wherein the hot rolling method is a position close to the machine.

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