JP2607012B2 - Method for determining reverse rolling schedule - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversing rolling mill having a function of crossing upper and lower rolls in pairs, to realize a high-efficiency rolling with a minimum number of passes and to optimize a rolling shape. The method of determining.

[0002]

2. Description of the Related Art As a method of determining a pass schedule in a conventional rolling mill, in order to control a change in a sheet crown for each pass for the purpose of flattening a rolling shape, a rolling load less than a maximum allowable capacity of the equipment is limited. There is a method of determining a rolling schedule under conditions (Japanese Patent Laid-Open No. 62-259605).

Further, in order to perform rolling at high efficiency, there is a method in which rolling is performed at full load in an upstream pass having a small influence on the shape, and a pass schedule is determined by suppressing the load only in a downstream pass in which the change of the sheet crown is sensitive to the shape. (Japanese Patent Publication No. 63-123).

On the other hand, when the number of passes is fixed from the number of stands as in the case of continuous hot rolling, the schedule of the roll crossing angle is determined so as to satisfy the shape after the thickness schedule of all passes is determined in advance. (The Iron and Steel Institute of Japan 120th Lecture Meeting CAMP-ISIJ
Vo13 (1990) -p1383 NKK).

[0005]

By the way, in order to flatten the shape of the rolled material in the conventional rolling method, it is necessary to suppress the change of the sheet crown for each pass within a certain range.
The rolling load, which is a controlling factor of the mechanical crown, is restricted, and rolling must be performed with a load much smaller than the allowable capacity of the equipment. As a result, the number of passes is large and the rolling efficiency is reduced. Even if rolling is performed at full load in the upstream pass where the shape influence is small and rolling is suppressed only in the downstream pass where the change of the sheet crown is sensitive to the shape in order to perform rolling at high efficiency, even if the pass schedule is determined by Light rolling for the number of times is not eliminated, and the rolling load change in the lower-pass which gives priority to the full load path and shape is large, and because the rolling load change is empirically smoothed, the intermediate pass is connected with the pass, A rolled material having a good shape was not always obtained.

On the other hand, in the case of a pair cross rolling mill in a hot strip mill, the number of passes is basically unchanged from the number of stands. Therefore, after a draft schedule is determined in advance, the roll crossover is performed so as to satisfy the shape. The method determines the angle schedule, and cannot be applied as a method for determining the pass schedule of the plate rolling in which the number of passes is variable.

Further, as the final pass is approached, it is necessary to gradually increase and control the cross angle in order to reduce the crown of the plate, and for this reason, a thin plate which requires kiss roll rolling at the final stage is required. For rolled materials, there is a problem that an excessive thrust force is generated due to a large cross angle, and there is a problem that an excessive facility for withstanding a thrust load resistance and an extra control operation such as kiss roll avoidance are required.

The present invention is based on the premise that when a plate material is rolled in a reverse rolling mill having a function of crossing upper and lower rolls in pairs, the crossing angle is minimized in the final pass, and the rolling equipment is essentially used throughout the entire pass. To achieve the highest efficiency rolling with the minimum number of passes.
It is another object of the present invention to obtain a pass schedule that optimizes the rolling shape.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for determining a pass schedule for rolling a sheet by a reversing mill having a function of crossing upper and lower rolls in pairs. The concept of separating the conventional "load-constrained path for shape adjustment" + "pass rolling at full load" or the concept of setting the number of passes in advance and adjusting the load distribution for shape adjustment is eliminated. , The shape of the rolled material, the crown and the load (reduction) schedule are simultaneously calculated and determined for each pass in accordance with the shape control ability for all passes.
By performing the stacking calculation with the optimum value for each pass, the pass schedule that satisfies the shape consistently for all passes and can be rolled at the maximum value of the rolling equipment capacity is determined. Since the number of passes is automatically adjusted according to the shape control ability, the ability to vary the number of passes in the reversing mill can be sufficiently exhibited.

Hereinafter, the contents of the method of the present invention will be described with reference to FIG. In the method of determining a pass schedule according to the present invention, first, a target final exit sheet thickness and a sheet crown amount are set (S21). Next, the finish temperature and finish direction of the final pass are simply assumed (S22, S2).
3) After that, the rolling schedule and the roll crossing angle schedule are simultaneously determined for each pass sequentially from the downstream pass to the upstream pass by the following calculations. That is, first, the temperature on the entry side (biting side) of the pass and the expected rolling speed are assumed (S25, S26).

Here, the upper and lower limit range of the allowable steepness of this pass and the target value (each λ
_max , λ _min , λ _aim ). This λ _aim is basically 0, and the λ _max and λ _min values are parameters representing the allowable range of the shape of each rolled material size, and are empirically determined according to the operating conditions.

Using this λ value, the allowable elongation-strain difference and the target elongation-strain difference are calculated from Δε = (π / 2) ² · λ ² (1), and C _in / h _in = C _out / h _out −Δε / ξ + α (2), giving the max, min, and aim of Δε, and calculating the allowable range and the target value of the entrance-side sheet crown ratio (S2)
7). Where C _in : entrance side crown, h _in : entrance side thickness, C _out : exit side crown, h _out : exit side thickness, Δε: difference in elongation strain, ξ: value representing shape sensitivity (shape change coefficient), α: Shape change correction coefficient.

Here, max, mi of (C _in / h _in )
The allowable range and the target value of the mechanical crown restricted by the shape in this pass are calculated from n and aim by the following formula (S28). MCK = [1 / (1−η)] × [C _out −η · h _out · (C _in / h _in )]
(3) MCK: mechanical crown from shape η: crown genetic coefficient.

On the other hand, the mechanical crown based on the rolling load and the allowable capacity of the equipment can be estimated and calculated by the following equation based on the rolling load P, the roll bending load F, the roll crossing angle, and the roll profile. MCh = c1 · P + c2 · F + E + c3 (4) where, MCh: mechanical crown from equipment load, P: rolling load, F: roll bending load, E: mechanical crown amount formed by roll cross angle, c1 : Mechanical crown influence coefficient by rolling load, c2: Mechanical crown influence coefficient by bending load, c3: Mechanical crown amount formed by roll profile If there is no roll bending control device, the second term in the above equation is omitted. If there is no roll cloth device, the mechanical crown MCh from the equipment load can be calculated by omitting the third term in the above equation.

In the equation (4), MCh becomes maximum when the maximum rolling load P _max and the minimum crossing angle 2θ _min , and conversely, when the minimum rolling load P _min and the maximum crossing angle 2θ _max , the MCh becomes minimum and the load from the equipment load is reduced. The mechanical crown allowable range can be determined (S29). Here, in determining the mechanical crown amount: E formed by the roll crossing angle, a constraint condition is added so that the cross angle is minimized in the final pass, so that the mechanical load can be reduced from the rolling load constraint range at that time. The restricted range of the crown can be determined.

A range that satisfies both the mechanical crown restriction range from the shape according to equation (3) and the mechanical crown allowable range from equipment load according to equation (4) is determined as the true mechanical crown allowable range in this path. . Further, the true mechanical crown aim value MC _aim is determined by correcting the MCK _{aim to} be within this range (S30).

Next, on the premise that the MC _aim is achieved, the optimum combination of the rolling reduction r, the roll crossing angle 2θ, and the bending load F are determined simultaneously. That is, if P = fp (r) E = fe (2θ), then from equation (4), MC _aim = c1 · fp (r) + c2 · F + fe (2θ)
+ C3, it can be expressed as r = fr (MC _aim , 2θ, F) (5), and under a constant condition of MC _aim , the _rolling reduction r is 2
The search can be determined based on θ and the bending load F.

In the equation (5), since high-efficiency rolling is generally aimed at in operation, 2 is set so that the rolling reduction r is maximized.
θ and bending load F are determined. It is also possible to reflect the other operating conditions by using an evaluation function or the like, and to determine an optimal combination by a linear programming method or the like.

After determining the rolling reduction r of this pass (S31), the thickness of the sheet on the entrance side is calculated, and the amount of temperature drop on the exit side of this pass including the temperature change in the roll bite is calculated (S32).
Recalculate the plate temperature at the time of biting. Then, using the temperature, a more accurate rolling load (S33) and rolling torque (S34) are calculated, and after checking the load (S35), the calculation of the temperature, load, and crown in the next upstream pass is repeatedly performed.

The above-described calculation for each pass is performed in a stacking manner from the downstream pass to the upstream pass, so that the pass schedule is determined in order, and finally the pass entry side thickness exceeds the expected thickness at the start of rolling. To end the calculation repeatedly.

If the scheduled thickness at the start of rolling cannot be changed during the preparation of the pass schedule, load distribution correction calculation is performed as necessary, the thickness schedule is corrected, the calculation is terminated, and all the passes are completed. Determine a schedule.

[0022]

According to the pass schedule determining method according to the present invention, the shape of the rolled material, the crown and the load (reduction) schedule are simultaneously calculated for each pass in accordance with the shape control ability that is assumed to minimize the cross angle at the final stage. The pass schedule that satisfies the shape consistently for all passes and can be rolled at the maximum value of the rolling equipment capacity can be determined by performing the stacking calculation with the optimum value. In addition, since the number of passes is automatically adjusted according to the above-described shape control ability, the ability to vary the number of passes in a reversible rolling mill can be sufficiently exhibited.

[0023]

Next, an embodiment of the present invention in which the pass schedule of the rolled material is determined according to the above-described procedure (FIG. 1) will be described. (Example 1) The pass schedule of the rolled material was calculated under the following preconditions. Final target thickness: 6.0 mm Final pass exit side sheet crown: 0.02 mm Sheet width: 3500 mm Finish pass final temperature: 750 ° C (finish in the rear direction) Descaling execution pass: First pass & 3 from the initial pass
Passes Maximum cross angle: 0.585 ° Final cross angle constraint: 0.000 ° The above precondition is that in actual online calculation by the process computer, it is transmitted from the upper business computer as rolling material information, Alternatively, it is provided as information patterned according to the operating conditions.

By the following calculations, the rolling schedule and the roll crossing angle schedule were determined simultaneously for each pass from the downstream pass to the upstream pass. Here, the calculation process of the last one pass (calculation start pass) is shown by a numerical example. [Assumption of Inlet-side (biting side) Temperature] The temperature drop amount is assumed to be 30 ° C, and the assumed inlet-side biting temperature is set to 780 ° C. [Assumption of Scheduled Rolling Speed] From the sheet width of the rolled material and the exit side sheet thickness, the standard mill speed is set to 100 rpm. [Upper and lower limit range and target value of allowable steepness] λ _max = 0.4%, λ
_min = −0.4% and λ _aim = 0. This is a parameter indicating the allowable range of the shape according to each rolled material size, and is determined by an experienced person using a table value according to the operation situation. [Calculation of allowable elongation-strain difference and target elongation-strain difference] According to equation (1), Δε = (π / 2) ² · λ ² Δε _max = 0.004% Δε _min = −0.004% Δε _aim = 0 side calculating an allowable range and the target value of the strip crown ratio] (2) according to _{C in / h in = C out} / h out -Δ
ε / ξ + α α = 0.15 ξ = 0.61 C _out / h _out = 0.33% (C _in / h _in ) max = 0.49% min = 0.48% aim = 0.48% [Shape Calculate the allowable range and target value of the mechanical crown constrained from the following equation] From the equation (3), MCK = 1 / (1-η) · [C _out −η · h _out · (C _in / h _in )] η = 0.702 (Genetic coefficient) MCK _max = 0.00 mm min = 0.00 mm aim = 0.00 mm [Mechanical crown allowable range from rolling load and equipment allowable capacity] P _max = 6500 ton P _min = 2200 ton θ _max = 0. 000 ° θ _min = 0.000 ° That is, the final pass has a constraint of the cross angle = 0 degree,
As F = 130ton from (4), MCh = c1 · P = + c2 · F + E + c3 MCh max 0.72mm MCh min = + 0.01mm , where roll bending load was a fixed value preset premise. [Determination of true mechanical crown allowable range target value MC _aim ] MC _max = 0.01 mm MC _min = 0.01 mm MC _aim = 0.01 mm [Search and determination of rolling reduction r, roll cross angle 2θ, bending load F] ( 5) In the equation r = fr (MC _aim , 2θ, F), searching for the maximum rolling reduction for high-efficiency rolling,
Under the condition of fixing F, the maximum value is obtained when θ = θ _max = 0.000 °, and r = 0.1328 (= rseek) is obtained. [Calculate the thickness of the inlet side plate] From h _in = h _out / (1-r), h _in = 6.84 mm [Estimate the amount of temperature drop at the path exit side] Temperature drop amount = 15 ° C. Sheet temperature at biting = 765 ° C [Calculation of rolling load and rolling torque] P = 3120ton torqe = 98tonm, all within the equipment capacity range. [Estimation calculation of the temperature drop at the entrance of the pass] Temperature drop = 21 ° C The plate temperature at the exit of the previous pass = 786 ° C.

Thus, the calculation of the temperature, load and crown for one pass is completed. By performing the above calculation for each pass in a stacking manner from the downstream pass to the upstream pass, the pass schedule is determined in sequence, and finally the pass entry side thickness is repeatedly calculated with the pass exceeding the planned thickness at the start of rolling. To end. In this example, the scheduled thickness at the start of rolling was set to 45 mm, and the pass schedule for all passes was calculated. The results are shown in Table 1 and FIG. 2 in comparison with the conventional method.

[0026]

[Table 1]

In both cases, the shape adjustment ability by the roll cross function is the same, but the cross schedule at the final stage is not minimized in the pass schedule according to the conventional method, and the rolling load on the upstream side is not affected by the equipment maximum capacity. However, the number of passes increases as a result, whereas in the present invention,
Since the schedule calculation is performed by searching the allowable maximum of the rolling load under the cross constraint condition, the shortest number of passes can be achieved while keeping the shape by minimizing the cross angle at the final stage.

(Example 2) The pass schedule of the rolled material was calculated under the following preconditions. Final target thickness: 20.0mm Final pass exit side sheet crown amount: 0.00mm Sheet width: 3500mm Finishing temperature of final pass: 850 ° C (finish in back direction) Descaling execution pass: First pass from initial pass Maximum cross angle: 0 .600 ° Final pass cross angle constraint: 0.200 ° Maximum rolling load: 6000 tons Planned thickness at the start of rolling: 93 mm The pass schedule for all passes in the second embodiment was calculated. Table 2 shows the results.

[0029]

[Table 2]

Example 3 A pass schedule of a rolled material was calculated under the following preconditions. Final target thickness: 45.0mm Final pass exit side sheet crown amount: -0.20mm Sheet width: 1500mm Finishing temperature of final pass: 850 ° C (finish in back direction) Descaling execution pass: First, third & fifth pass from initial pass Angle: 0.500 ° Final pass cross angle constraint: 0.000 ° Maximum rolling load: 4200ton Maximum torque: 420ton Planned thickness at the start of rolling: 157mm The pass schedule for all passes in the third embodiment was calculated. . Table 3 shows the results.

[0031]

[Table 3]

[0032]

According to the pass schedule determination method according to the present invention, the shape of the rolled material, the crown and the load (reduction) schedule are simultaneously calculated and determined for each pass in accordance with the shape control ability for all the passes, and the optimum for each pass is determined. By performing the stacking calculation using the values, it is possible to determine a pass schedule that satisfies the shape consistently for all passes and can perform rolling at the maximum value of the rolling equipment capacity. Further, the number of passes is automatically adjusted in accordance with the shape control ability under the constraint condition of the cross angle, so that the ability to vary the number of passes in the reversing mill can be sufficiently exhibited.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the contents of a method for determining a path schedule according to the present invention.

FIG. 2 shows a pass schedule obtained in the first embodiment of the present invention.
2 is a graph showing the results obtained with the conventional method.

[Explanation of symbols]

Claims (1)

(57) [Claims] 1. A reverse rolling mill having a control device that relatively intersects an upper roll set and a lower roll set in which a backup roll and a work roll at upper and lower portions are paired with each other in a plane parallel to a rolled material. In determining the pass schedule when rolling, the mechanical crown allowable range determined from the shape in each pass and the mechanical crown allowable range determined from the equipment capacity so that the crossing angle of the roll in the final pass is minimized. Calculate the area that satisfies both of them, determine the thickness schedule by sequentially stacking from the bottom so that the allowable maximum rolling load is reached, and simultaneously determine the rolling and crossing angle schedule of the shortest number of passes that satisfy the shape A method for determining a reverse rolling schedule.