JP4876960B2 - Manufacturing equipment and manufacturing method for thick steel plate - Google Patents

Description

  The present invention relates to a thick steel plate manufacturing facility and a manufacturing method.

  In recent years, in the hot rolling of thick steel plates, the production of steel plates with excellent strength and toughness has been demanded. As an example, by applying controlled rolling (CR) to the rolled material, an excellent material can be obtained. Made of thick steel plate. 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 rolling line near 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 a waiting for cooling and a reduction in rolling efficiency, in Patent Document 1 and Patent Document 2, a steel sheet that needs to wait for cooling is provided outside the rolling line. The steel plate is moved to the standby position for cooling, and other steel plates are rolled while the cooling is being performed, and when the steel plate cooled at the standby position reaches a predetermined controlled rolling start temperature, the standby position is moved to the rolling line. There has been proposed a technique of returning and performing controlled rolling.

  However, in the techniques described in Patent Documents 1 and 2, a space for providing a standby position outside the rolling line and means for moving the steel plate between the rolling line and the standby position are required, which is a large facility. There is a problem of becoming.

  On the other hand, Patent Document 3 and the like describe a technique in which rolling is performed by water-cooling a steel sheet with a shower cooling facility or the like in a rolling line in order to shorten the cooling waiting time until performing controlled rolling. .

In addition, Patent Document 4 discloses that although not controlled rolling of a thick steel plate, as an on-line cooling technique in direct quenching of a thick steel plate, the amount of water by a slit jet nozzle in a state where the thick steel plate is restrained from above and below by a press roller The first cooling is performed with a density of 2 m ³ / m ² min or more, and then the second cooling with a water nozzle density of 0.7 m ³ / m ² min or more using a pipe nozzle for upper surface cooling and a spray nozzle for lower surface cooling. Techniques for performing are described.
JP-A-53-146208 JP 60-180604 A JP-A-55-106615 JP-A-61-153235

  As described in Patent Document 3, in the technique of rolling a steel sheet by water cooling in a rolling line, when the control rolling start temperature is low and the control rolling start plate thickness is thick, the rolling is interrupted before the control rolling. Water cooling must take place for a fairly long time before the starting temperature is reached. Therefore, in the case of the passing cooling type in which water cooling is performed while passing the steel plate, it is necessary to carry out reciprocating conveyance while allowing the entire steel plate to pass through the cooling facility so that a predetermined water cooling time is obtained, but compared to the length of the steel plate. When the length of the cooling equipment is short, the ratio of the time during which the steel sheet is air-cooled becomes large and is not cooled so quickly. Therefore, in the past, there were many cases of stay-cooling type in which water cooling was performed by stopping or oscillating the steel plate with a cooling facility long enough to fit the entire steel plate, but the water cooling at that time is a relatively low water density However, a sufficient cooling rate was not always obtained.

  Therefore, it is conceivable to increase the water density of the shower cooling described above, increase the cooling rate, shorten the water cooling time, and improve the productivity. When the density is increased, it is necessary to increase the amount of cooling water in large quantities, and there is a problem that equipment costs such as a water pump and piping are required. Of course, if the cooling equipment is shortened, it becomes impossible to cool the steel plate longer than the cooling equipment uniformly while stopping or oscillating.

  Moreover, although it is possible to use the technique of patent document 4 in order to shorten the cooling waiting time for performing control rolling, there exist many problems as follows.

  First, since a press roller is necessary, there is a problem that the equipment cost is high.

  Secondly, direct quenching is not a problem because it is performed away from the rolling mill, but when the technique described in Patent Document 4 is applied near the rolling mill, the risk of equipment damage is extremely high. There is a problem. When the tip of the thick steel plate warped by rolling hits the presser roller, there is a problem that if the rear portion is still rolling, the thick steel plate is conveyed while damaging the equipment. If it is what is called a floating material which is not under rolling, a protector etc. can protect an installation to some extent, However, During rolling, the whole protector will be damaged with the power of a rolling mill.

  Thirdly, the technique described in Patent Document 4 is based on the premise that the conveyance of the thick steel plate is in one direction, so that the cooling uniformity when the conveyance in the reverse direction is performed near the rolling mill is performed. It cannot be secured. When transported from the second cooling device to the first cooling device, there is a problem that the cooling water is not supplied to the tip portion in the first cooling device, resulting in insufficient cooling.

  The present invention has been made in view of the above circumstances, and in the case of manufacturing a thick steel plate by controlled rolling, the cooling waiting time of the rolled material can be shortened, and productivity can be dramatically improved. It aims at providing the manufacturing equipment and manufacturing method of a thick steel plate which can be performed.

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

[1] A steel plate manufacturing facility arranged in the order of a heating furnace, a reversible rolling mill, a first cooling facility, and a second cooling facility,
The first cooling facility is a facility for supplying cooling water having a flow rate density of 4 m ³ / m ² min or more to the upper and lower surfaces of the thick steel plate over a length of 0.5 to 5 m, and among them, the upper surface of the thick steel plate. The upper surface cooling device for supplying cooling water is a device that has a plurality of nozzles for supplying cooling water obliquely toward the upper surface of the thick steel plate and injects rod-shaped cooling water so as to face each other in the conveying direction. Yes,
The second cooling facility is a facility for supplying cooling water having a flow density of 0.05 to ¹ m ³ / m ² min over the length of 15 to 35 m to the upper and lower surfaces of the thick steel plate. Facility.

[2] The slab is heated, and the thick steel plate that has been rolled by one or more passes with a reversible rolling mill is passed through the first cooling facility and conveyed into the second cooling facility, and is thickened in the second cooling facility. Water cooling while stopping or oscillating the steel sheet, and then passing through the first cooling equipment and transporting to a reversible rolling mill to roll one pass or more,
Cooling water having a flow density of 4 m ³ / m ² min or more over a length of 0.5 to 5 m without stopping the steel plate at least once out of the two times passing through the first cooling facility. Supplying to the lower surface, and cooling the upper surface of the thick steel plate is performed by injecting rod-shaped cooling water so as to face diagonally toward the upper surface of the thick steel plate,
Cooling in the second cooling facility is performed by supplying cooling water having a flow density of 0.05 to ¹ m ³ / m ² min over the length of 15 to 35 m to the upper and lower surfaces of the steel sheet. Manufacturing method.

  [3] The cooling water can be supplied from the same cooling water pipe to the first cooling facility and the second cooling facility, and cooling in the first cooling facility and cooling in the second cooling facility are performed. The method for producing a thick steel plate according to [2], wherein the supply is switched.

  [4] The thick steel plate according to [2] or [3], wherein the subsequent thick steel plate is rolled at least once between a first pass and a final pass of the thick steel plate. Manufacturing method.

  By using this invention, when manufacturing a thick steel plate by controlled rolling, the cooling waiting time of a rolling material can be shortened and productivity can be improved dramatically.

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

  FIG. 1 is a diagram illustrating an example of a steel plate manufacturing facility according to an embodiment of the present invention and a conveyance / cooling pattern when a steel plate is manufactured using the manufacturing facility.

  The steel plate manufacturing facility in this embodiment includes a heating furnace 1, a reversible rolling mill 2, a first cooling facility 3, and a second cooling facility 4 in order from the upstream side.

  And after extracting from the heating furnace 1, the thick steel plate (henceforth only called a steel plate) 10 rolled to the predetermined plate thickness with the reversible rolling mill 2 is conveyed by the 1st cooling equipment 3, and passes this. Then, the water is cooled and then transported to the second cooling facility 4, and then stopped or oscillated while being water-cooled. Then, the transport is reversed and transported again to the first cooling facility 3 and passes therethrough. While cooling with water.

  Here, the first cooling facility 3 is a through-cooling type cooling facility as shown in FIG. 2, and the upper surface cooling device that supplies the cooling water to the upper surface of the steel plate 10 has a rod-shaped cooling water obliquely toward the upper surface of the steel plate. 2 is a cooling device in which two upper headers 21 each having six upper nozzles 22 for jetting 23 are arranged in the conveying direction so as to face each other in the conveying direction, and a lower surface for supplying cooling water to the lower surface of the steel plate 10 The cooling device is a cooling device in which two lower headers 31 each having three rows of lower nozzles 32 for injecting the rod-shaped cooling water 33 vertically toward the lower surface of the steel plate in the conveying direction are disposed with the table roller 13 interposed therebetween. Yes.

  In this way, the first cooling equipment 3 is configured so that the upper surface cooling device injects the rod-shaped cooling water 23 so as to face each other in the transport direction, so that the supplied cooling water itself is the staying cooling on the steel plate 10. The water 24 is dammed up and drained appropriately, and uniform and stable cooling can be performed.

  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.

  In addition, the 1st cooling equipment 3 should just be between the reversible rolling mill 2 and the 2nd cooling equipment 4, It is desirable to install in the immediate vicinity of the reversible rolling mill 2, or the 2nd cooling equipment 4 vicinity. Good. However, since the cooling water flows out from the first cooling equipment 3 to the outside in the sheet width direction, it is better not to be at the same position as the side guide of the reversible rolling mill 2, and when it is near the measurement sensor of the rolled material, Since it becomes impossible to measure the plate thickness, temperature, etc., it should be installed at a position somewhat away from the measurement sensor installation position.

  If the first cooling facility 3 is between the heating furnace 1 and the reversible rolling mill 2, the transport time to the second cooling facility 4 becomes long, so the effect of improving productivity becomes small. Further, even if the first cooling facility 3 is further downstream in the transport direction than the second cooling facility 4, the transport time is not good.

And since the 1st cooling equipment 3 is normally used together with the 2nd cooling equipment 4, in order to obtain a certain amount of temperature fall in a short cooling time, it is necessary to supply a lot of cooling water, The density must be 4 m ³ / m ² min or more. The length of the cooling zone where the cooling water hits the steel sheet must be 0.5-5 m. The longer the cooling zone, the more the cooling water is required, which increases the equipment cost, and the second cooling equipment 4 is far from the reversible rolling mill 2 and the transport time of the steel sheet is increased. This is because the effect of improving the properties is reduced. Here, the cooling zone is a distance from a point at which the cooling water is first supplied to a point at which the cooling water is supplied last as shown in FIG.

  On the other hand, the second cooling equipment 4 is a cooling equipment similar to the conventional one, is a stay-cooling type having a length that can accommodate the entire steel sheet, and is a shower cooling equipment with a relatively low water density.

That is, the second cooling facility 4 has the length of the cooling facility longer than the length of the steel plate in order to stop or oscillate cooling the entire steel plate therein, so that the length of the steel plate is about 15 to 35 m. Length is needed. However, since the whole steel plate should just be settled in an installation, it does not need to be an unnecessarily long installation. In a long cooling facility, if the flow density is increased, the cost of equipment such as pumps, water supply pipes, and drain pits increases. Therefore, a relatively low flow density, specifically 0.05 to ¹ m ³ / m ² , as in conventional equipment. Min is good, and more preferably 0.05 to 0.2 m ³ / m ² min. If it is less than 0.05 m ³ / m ² min, the cooling capacity is too small, and the cooling water (stagnation cooling water) after cooling becomes sparse on the steel sheet, and uneven cooling tends to occur. If it exceeds 1 m ³ / m ² min, the cost of equipment such as pumps and piping becomes abnormally high, and the water after cooling flows out of the cooling equipment, making it impossible to drain water and causing uneven cooling.

  FIG. 3 shows an example of a procedure for cooling the steel plate 10 using the first cooling equipment 3 and the second cooling equipment 4 as described above and a change over time in the amount of cooling water used at that time.

  That is, as shown in FIG. 3, water injection of the first cooling facility 3 is started earlier than the tip of the steel plate passes through the first cooling facility 3. Water injection stop after the tip of the steel plate has passed through the first cooling facility 3 may be anytime. After the entire steel sheet has entered the second cooling facility 4, the oscillation is started, and water injection of the second cooling facility 4 is started immediately. When a predetermined temperature drop is obtained, water injection is stopped and the oscillation is terminated. The conveyance is started immediately and the steel plate is sent to the first cooling facility 3, but the water injection of the first cooling facility 3 is started before the front end of the steel plate passes through the first cooling facility 3. Water injection stop after the tail end of the steel plate has passed through the first cooling facility 3 may be anytime.

  In addition, in the above, the piping system of the 1st cooling equipment 3 and the piping system of the 2nd cooling equipment 4 are integrated and made common, and the water injection to the 1st cooling equipment 3 and the water injection to the 2nd cooling equipment 4 are three way valves You may make it switch by. Thereby, compared with the case where a piping system is separately installed in the 1st cooling equipment 3 and the 2nd cooling equipment 4, equipment expenses, such as piping, can be made far cheaper. Further, the cooling water can be used efficiently, and the running cost can be suppressed.

  In this way, in this embodiment, the rolling material is cooled by appropriately combining the first cooling facility 3 with a high water content density and the second cooling facility 4 with a low water content density and the stay cooling type. Therefore, when a thick steel plate is manufactured by controlled rolling, the cooling waiting time of the rolled material can be shortened, and productivity can be dramatically improved.

  Here, as shown in FIG. 1, the case where the steel plates are rolled one by one has been described, but as shown in FIG. 4, rough rolling of the subsequent steel plates while the preceding steel plates are waiting for cooling. (Stage before controlled rolling) may be performed. This is preferable because the production efficiency can be improved.

  Therefore, the second cooling facility 4 is conventionally, but the distance from the reversible rolling mill 2 is preferably about 15 to 30 m. Thereby, as described above, while the preceding steel plate is waiting for cooling, the subsequent steel plate can be roughly rolled to improve the production efficiency. The succeeding steel plate is a stage before performing the controlled rolling, and the plate thickness is relatively thick, and the length is usually within 30 m. Therefore, a suitable distance from the reversible rolling mill 2 to the second cooling equipment 4 is as described above. It is determined as follows.

  In addition, here, as shown in FIG. 2, a cooling device that injects rod-shaped cooling water from a vertical nozzle is used as the lower surface cooling device of the first cooling equipment 3, but the present invention is not limited to this. Instead, the lower surface cooling device of the first cooling facility 3 may be a cooling device that injects film-like cooling water from the slit nozzle, or a cooling device that injects spray-like cooling water from the spray nozzle.

  Further, here, as shown in FIG. 1, the water cooling by the first cooling equipment 3 is performed twice during the reciprocating conveyance of the steel plate 10, but when the target temperature drop is small, the water cooling is performed only once. You may go. Accordingly, if the time for waiting for water cooling or air cooling in the second cooling facility 4 can be shortened, a sufficient effect is exhibited. Further, the steel plate 10 may be cooled by carrying it such that the first cooling facility 3 is reciprocated twice or more.

  And even if the second cooling equipment 4 is already installed, it is relatively easy to add the first cooling equipment 3 that does not take up much installation space. Since the water cooling in the first cooling facility 3 and the water cooling in the second cooling facility 4 do not overlap in time, it is possible to add a water pump and piping in common. Thereby, the effect of the present invention can be sufficiently obtained that the waiting time for cooling is shortened and the productivity of the control rolled material is improved.

  As an example of the present invention, a thick steel plate was manufactured based on one embodiment of the present invention shown in FIGS. In that case, the case where it cooled using the 1st cooling equipment 3 and the 2nd cooling equipment 4 is set as the example of this invention, and the case where it cools using only the 2nd cooling equipment 4 is a comparative example, and each 5 types of steel plates AE Was cooled.

  The control rolling start plate thickness is 40 mm for steel plate A, 30 mm for steel plates B and D, 20 mm for steel plates C and E, and the steel plate length during cooling is 20 m for steel plates A to D and 30 m for steel plate E. there were.

  In addition, the temperature at which rolling is interrupted due to waiting for cooling is all 950 ° C., steel plates A to C and E start controlled rolling at 800 ° C. (resume rolling), and steel plate D starts controlled rolling at 890 ° C. (Rolling resumed). The conveyance speed was 4 m / s, and the time required to reciprocate between the reversible rolling mill 2 and the second cooling equipment 4 was 20 s.

And as mentioned above, the 1st cooling equipment 3 is a through-cooling type cooling equipment as shown in FIG. 2, supplies the bar-shaped cooling water with a flow density of 4 m ³ / m ² min to the upper surface of the steel plate, Was supplied with rod-shaped cooling water having a flow density of 5.5 m ³ / m ² min. The length of the cooling zone, defined as the distance from the point where the cooling water was first supplied to the point where it was last supplied, was 1 m.

Further, as described above, the second cooling equipment is a stay cooling shower cooling equipment similar to the conventional technology, the cooling zone length is 25 m, and the flow density is 0.1 m ³ / m ² min on the upper surface of the steel plate. Cooling water was supplied, and cooling water with a flow density of 0.2 m ³ / m ² min was supplied to the lower surface of the steel plate.

  The results of cooling the steel plates A to E as described above are shown in FIG. In addition, in the steel plate E, since the whole steel plate does not fit in the 2nd cooling equipment 4, the 2nd cooling equipment 4 was not able to perform water cooling, and only waited by air cooling.

  First, FIGS. 5A to 5C are diagrams showing temperature histories from the rolling interruption of the steel plates B, D, and E to the resumption of rolling, respectively. It can be seen that the time from the interruption to the resumption of rolling is shortened.

  As shown in Table 1, in the comparative example, the steel plates A to D were air-cooled during conveyance for 20 s and water-cooled after entering the second cooling facility, but the time required for water-cooling (cooling waiting time) was The longer the sheet thickness, the longer the difference between the rolling interruption temperature and the rolling restart temperature (control rolling start temperature). In particular, in the steel plate A, the cooling waiting time was as long as 74 seconds, and the productivity was low. Furthermore, since the steel plate E was merely waiting for air cooling, the cooling waiting time was as long as 100 s, and the productivity was extremely low.

  On the other hand, in the example of the present invention, while the steel plates A to E are reciprocally conveyed to the second cooling facility 4, the cooling water having a large flow density is supplied while passing through the first cooling facility 3, and the two times. Since the cooling was performed, the water cooling time in the first cooling facility 3 was as short as 0.5 s in the round trip, but the temperature drop of the steel sheet was 30-40 ° C. Accordingly, for the steel plates A to D, the water cooling time in the second cooling facility 4 could be shortened. In particular, in the steel plate D, water cooling in the second cooling facility 4 was not performed, and the steel plate D could be conveyed in the reverse direction as soon as the tail end of the steel plate passed through the first cooling facility 3. Furthermore, even with the steel plate E that could not be cooled with water in the second cooling facility, after the tail end of the steel plate passed through the first cooling facility, it was allowed to air-cool for 40 s and then transported in the reverse direction.

  As a result, in the example of the present invention, the cooling waiting time was shortened by 12 s for the steel plates A to D and 40 s for the steel plate E as compared with the comparative example. Since the time required to manufacture one steel plate was about 240 s on average, productivity could be improved by 5 to 17%.

  Moreover, since the length of the cooling zone of the first cooling and cooling facility 3 is as short as 1 m, the amount of cooling water is almost the same as that of the second cooling facility, and the cooling water can be used efficiently and the running cost can be suppressed. It was.

It is a figure showing the conveyance and cooling pattern of the thick steel plate manufacturing equipment by it in one Embodiment of this invention. It is a figure showing 1st cooling equipment. In one Embodiment of this invention, it is a figure showing the example of the time-dependent change of the procedure which cools a steel plate, and the cooling water usage amount in that case. It is a figure showing the other example of the conveyance and cooling pattern of the thick steel plate in one Embodiment of this invention. It is a figure showing the temperature history from rolling interruption in the Example of this invention to rolling restart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Reversible rolling mill 3 1st cooling equipment 4 2nd cooling equipment 10 Steel plate (thick steel plate)
13 Table Roller 21 Upper Header 22 Upper Nozzle 23 Bar Cooling Water 24 Retention Cooling Water 31 Lower Header 32 Lower Nozzle 33 Bar Cooling Water

Claims (4)

A steel plate manufacturing facility arranged in the order of a heating furnace, a reversible rolling mill, a first cooling facility, and a second cooling facility,
The first cooling facility is a facility for supplying cooling water having a flow rate density of 4 m ³ / m ² min or more to the upper and lower surfaces of the thick steel plate over a length of 0.5 to 5 m, and among them, the upper surface of the thick steel plate. The upper surface cooling device for supplying cooling water is a device that has a plurality of nozzles for supplying cooling water obliquely toward the upper surface of the thick steel plate and injects rod-shaped cooling water so as to face each other in the conveying direction. Yes,
The second cooling facility is a facility for supplying cooling water having a flow density of 0.05 to ¹ m ³ / m ² min over the length of 15 to 35 m to the upper and lower surfaces of the thick steel plate. Facility. The slab is heated, and the thick steel plate that has been rolled for one or more passes by the reversible rolling mill is passed through the first cooling facility and transported into the second cooling facility, and the thick steel plate is stopped in the second cooling facility. Alternatively, it is a method for producing a thick steel plate that performs water cooling while oscillating, then passes through the first cooling facility and transports it to a reversible rolling mill to perform one or more passes of rolling.
Cooling water having a flow density of 4 m ³ / m ² min or more over a length of 0.5 to 5 m without stopping the steel plate at least once out of the two times passing through the first cooling facility. Supplying to the lower surface, and cooling the upper surface of the thick steel plate is performed by injecting rod-shaped cooling water so as to face diagonally toward the upper surface of the thick steel plate,
Cooling in the second cooling facility is performed by supplying cooling water having a flow density of 0.05 to ¹ m ³ / m ² min over the length of 15 to 35 m to the upper and lower surfaces of the steel sheet. Manufacturing method.   The cooling water can be supplied to the first cooling facility and the second cooling facility from the same cooling water pipe, and the cooling water supply is switched between the cooling in the first cooling facility and the cooling in the second cooling facility. The method for producing a thick steel plate according to claim 2, wherein the method is performed.   The method for producing a thick steel plate according to claim 2 or 3, wherein the subsequent thick steel plate is rolled at least once between a first pass and a final pass of rolling of the thick steel plate.

Images