JP6123153B2 - Rolling pass schedule creation method - Google Patents

Description

  The present invention relates to a rolling pass schedule creation method for creating a rolling pass schedule for performing cooling while rolling a steel plate using a water cooling facility provided immediately after a rolling mill in a thick plate rolling line.

  In the thick plate production line, in order to improve low temperature toughness, controlled rolling (hereinafter referred to as CR (Controlled Rolling)) in which cooling is performed during rolling is performed. In this case, in order to prevent efficiency reduction due to cooling, "tandem rolling" in which CR materials are alternately rolled using their cooling time, and CR materials are lifted with a lift device and cooled, In the meantime, “overtaking rolling” is performed in which the subsequent material is rolled. Furthermore, there is a method in which the cooling time is shortened by a method of cooling using a water cooling facility or the like while rolling the steel sheet (hereinafter referred to as actual pass water cooling) (for example, see Patent Document 1).

  In the conventional actual pass water cooling, a rolling schedule with a pass number priority type is created so as to minimize the number of cooling passes using the water cooling equipment.

JP 2007-203370 A

  However, according to the conventional pass number-priority rolling schedule, the number of cooling passes is reduced, but in order to satisfy the cooling conditions, the water cooling equipment passing speed (hereinafter referred to as the water cooling speed as appropriate) becomes slow, and the rolling efficiency is reduced. There is a case where it falls, and it is not necessarily a suitable pass schedule.

  This invention is made | formed in view of the above, Comprising: It aims at providing the rolling pass schedule preparation method which can implement efficiently the cooling using water cooling equipment.

  In order to solve the above-described problems and achieve the object, the rolling pass schedule creation method according to the present invention uses a water cooling facility provided immediately after the rolling mill in the thick plate rolling line to cool the steel plate while rolling it. In the rolling pass schedule creation method for creating a rolling pass schedule to be performed, after creating a schedule for controlled rolling and obtaining a temperature control thickness, a temperature control target temperature and a temperature control start temperature, the steel plate temperature after using the water cooling equipment So as to create a speed-priority rolling pass schedule that maximizes the passage speed of the water-cooled equipment by obtaining cooling conditions under the conditions of the temperature control thickness and the temperature control start temperature so that the temperature control target temperature becomes the temperature control target temperature. It is characterized by that.

  Further, the rolling pass schedule creation method according to the present invention is the above invention, wherein the steel sheet temperature after using the water cooling equipment is the temperature control target temperature so that the steel plate temperature becomes the temperature control target temperature. Finding the cooling conditions, creating a pass number priority rolling pass schedule that minimizes the number of passes using the water cooling equipment, and creating the speed priority rolling pass schedule and the pass number priority rolling pass schedule, And a short rolling pass schedule is selected.

  According to the present invention, since a speed-priority rolling pass schedule that maximizes the water-cooling equipment passage speed is created, a rolling pass schedule creation method that can efficiently perform cooling using the water-cooling equipment is provided. can do.

FIG. 1 is a schematic side view showing a part of a thick plate rolling line to which the present embodiment is applied. FIG. 2A is an explanatory diagram illustrating an example of a rolling schedule for explaining the creation procedure A. FIG. FIG. 2B is an explanatory diagram showing an example of a rolling schedule for explaining the creation procedure B. FIG. 2C is an explanatory diagram illustrating an example of a rolling schedule for explaining the creation procedure C. FIG. 2D is an explanatory diagram illustrating an example of a rolling schedule for explaining the creation procedure D. FIG. 2E is an explanatory diagram showing an example of a rolling schedule for explaining the creation procedure E. FIG. 3 is a flowchart for determining the water cooling condition.

  Hereinafter, an embodiment of a rolling pass schedule creation method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic side view showing a part of a thick plate rolling line to which the present embodiment is applied. A rolling mill 2 having a work roll pair 2a for performing a rolling process on a steel plate 1 extracted from a heating furnace (not shown) is provided, and the steel plate 1 is installed near the rear surface (downstream) of the rolling mill 2 while rolling. The water cooling equipment 3 which cools is provided. The upper cooling water nozzle header 3a of the water cooling facility 3 is configured to move up and down according to the plate thickness so that the distance from the steel plate 1 is always constant. Therefore, the temperature drop due to the water cooling equipment 3 depends on the cooling water flow rate, the water cooling speed, and the number of cooling paths.

  A rolling schedule creation procedure when rolling and cooling the steel plate 1 using such a thick plate rolling line will be described.

First, an outline of a rolling schedule creation procedure will be described.
A. A normal CR schedule is created, and the temperature adjustment thickness, temperature adjustment target temperature, and temperature adjustment start temperature are obtained.
B. Water cooling conditions are obtained so that the steel plate temperature after water cooling becomes the temperature control target temperature, and the number of cooling passes, the cooling water flow rate, the water cooling speed, and the steel plate temperature are provisionally determined. The plate thickness of each cooling path at this time is temporarily determined by multiplying the amount of reduction of the normal CR schedule by α (0 <α <1). This is because, in the case of a normal CR schedule, the temperature is lower in the case of a rolling schedule with water cooling than in the case where the temperature is high, so the reduction amount is reduced correspondingly.
C. Recalculate the cooling path reduction.
D. Recalculate the amount of rolling reduction from the finishing start pass to the water cooling start pass.
E. Final correction calculation of water cooling conditions.

  The details of the rolling schedule creation procedure will be described below.

  A. First, as shown in FIG. 2A, a normal CR schedule is created, and the temperature adjustment thickness, temperature adjustment target temperature, and temperature adjustment start temperature indicated at points A and D are obtained. “Temperature control” refers to waiting on the front and rear surfaces of the rolling mill near the final pass and rolling after reaching a predetermined temperature range.

  B. Assuming an actual pass, the number of cooling passes, the cooling water flow rate, the water cooling rate, and the steel plate temperature are provisionally determined according to the water cooling cooling condition determination flowchart shown in FIG. 3 so that the steel plate temperature after water cooling becomes the temperature control target temperature.

  Here, the water cooling cooling condition determination flowchart of FIG. 3 will be described. First, a cooling state in the case of two passes at a high flow rate and a maximum speed is calculated (step S101). If the result of this calculation is that it is too cold, the number of cooling passes is set to 2 (step S102). On the other hand, if the cooling is insufficient, the cooling state in the case of 4 passes at a high flow rate and the maximum speed is calculated (step S103). If the result of this calculation is that it is too cold, the number of cooling passes is set to 4 (step S104). On the other hand, if the cooling is insufficient, the cooling state in the case of 6 passes at a high flow rate and the maximum speed is calculated (step S105). If the result of this calculation is that it is too cold, the number of cooling passes is set to 6 (step S106). Thereafter, similarly, a process of increasing the number of passes by two is performed, and a cooling state in the case of N passes at a high flow rate and a maximum speed is calculated (step S107). If the result of this calculation is that it is too cold, the number of cooling passes is set to N (step S108). On the other hand, if the cooling is insufficient, the air cooling standby time is calculated in the case of a high flow rate and maximum speed (step S109). Through the processes in steps S101 to S109 described above, the number of cooling passes that satisfy the cooling condition that first causes the overcooling state from the smaller number of passes while satisfying the speed priority condition of the maximum speed is provisionally determined.

  Next, under the condition of the number of cooling paths set provisionally, first, the cooling state in the case of the low flow rate and the maximum speed is calculated (step S121). If the result of this calculation is insufficient cooling, the optimum speed is calculated under low flow conditions (step S122). On the other hand, if it is too cold, the number of cooling passes is decremented by -1 (step S123).

  Then, under the condition that the number of cooling passes is reduced by 1, the cooling state at the high flow rate and the maximum speed is calculated (step S124). If the result of this calculation is insufficient cooling, the optimum speed is calculated under high flow conditions (step S125). On the other hand, if it is too cold, the condition is changed to a low flow rate / maximum speed to calculate the cooling state (step S126). If the result of this calculation is insufficient cooling, the optimum speed is calculated under low flow conditions (step S127). If it is too cold, the number of cooling passes is decremented by -1 (step S128). Then, it is determined whether or not the number of cooling passes is 0 (step S129). If the result of determination is other than 0, the air cooling standby time is calculated in the case of high flow rate and maximum speed (step S130). On the other hand, if it is 0, it is determined as abnormal (step S131).

  Through the processing of these steps S121 to S131, the provisionally set correction of the number of cooling paths, the correction of the cooling water flow rate, and the water cooling speed are performed, and finally the number of cooling paths, the cooling water flow rate, and the water cooling speed are provisionally determined. The At this time, the temporarily determined water cooling speed is maximized to a speed that is at least larger than the minimum speed under the conditions that satisfy the cooling condition.

  FIG. 2B is a schematic diagram showing a rolling schedule when the number of cooling passes is provisionally determined to be 4 passes by the above processing. That is, a state is shown in which the number of cooling passes 2 is assigned between points A and B, and the number of cooling passes 2 is assigned between points C and D. Between the points B and C, two passes of rolling are shown.

  C. As shown in FIG. 2C, in the interval from point B to point C, the ascending schedule calculation and the descending schedule calculation are repeated until the point C temperature converges to obtain the amount of reduction in the cooling path. Thereby, the point B temperature changes to the point B ′, and the point C temperature changes to the point C ′. At this time, the amount of reduction is calculated by the upward schedule calculation so that the load is equal to the initial normal CR schedule (in the direction of C ′ → B ′ in FIG. 2C). The amount of reduction decreases by Δh1 and Δh2 in accordance with two rolling passes from point B ′ to point C ′.

  D. As shown in FIG. 2D, in the section from the finishing start thickness to the water cooling start thickness (point A), the rolling schedule calculation is repeated until the temperature of the water cooling start thickness converges, and the rolling schedule calculation is repeated. As a result, the point A temperature changes to the point A ′.

  E. As shown in FIG. 2E, the water cooling condition is subjected to final correction calculation by correcting the speed during cooling so as to satisfy the temperature conditions up to the points A ′ and B ′ and the points C ′ and D.

  As described above, in the example illustrated in FIGS. 2A to 2E, the example in the case where the number of cooling passes is four has been described. When the number of cooling passes is an odd number, two cooling passes are allocated from the thicker one so that the water-cooling equipment at the temperature-controlled thickness is forward rotation / one pass.

  Thus, according to the present embodiment, since the speed priority type rolling pass schedule for maximizing the water cooling speed is created, cooling using the water cooling equipment can be efficiently performed even if the number of passes increases. A rolling pass schedule can be created. For example, when the maximum speed / cooling pass number is 4, the number of passes increases but the processing is completed in a short time and the efficiency may be better than when the minimum speed / cooling pass number is 2.

  In the present embodiment, only the case where the speed priority type rolling pass schedule is created has been described. However, in parallel with the creation of the speed priority type rolling pass schedule, the number of passes using the water-cooling equipment is conventionally used. Create a pass number priority rolling pass schedule that minimizes the number of passes, and compare the created speed priority type rolling pass schedule with the number of pass priority rolling pass schedule (one that takes less time) ) May be selected.

1 Steel plate 2 Rolling machine 3 Water cooling equipment

Claims (1)

In a rolling pass schedule creation method for creating a rolling pass schedule for cooling while rolling a steel plate using a water cooling facility provided immediately after a rolling mill in a thick plate rolling line,
After creating the schedule for controlled rolling and obtaining the temperature control thickness, temperature control target temperature and temperature control start temperature,
The number of cooling passes of the cooling facility is minimized and the cooling water flow rate is maximized under the conditions of the temperature adjustment thickness and temperature adjustment start temperature so that the steel plate temperature after using the water cooling facility becomes the temperature adjustment target temperature. And a provisional decision to maximize the water cooling rate, and correct the increase in the number of cooling passes in preference to the decrease in the amount of cooling water, and then create a speed priority type rolling pass schedule for correcting the water cooling rate. A rolling pass schedule creation method characterized by the above.

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