JPS5941805B2 - Crown control hot rolling method for hot strips - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crown-controlled hot rolling method for hot strip, and in particular, during hot finish rolling, the reduction distribution is changed to correspond to changes in the thermal crown of the roll, so that a constant and appropriate strip is always produced. This paper proposes a method for controlling the crown and also realizing shape control at the same time.

The crown of the rolled material within one rolling cycle in hot finish rolling (rolling cycle from one work roll change to the next change: number of rolling coils 50 to 150 coils) is shown in Figure 1. As shown in the example, immediately after the start of rolling, 11
This is about 0 μm, and as rolling progresses, it gradually decreases due to the increase in the thermal crown of the work roll, and by the final coil of the rolling cycle, it decreases to about 20 μm, and it changes by about 90 μm within the rolling cycle.

A large crown of a hot-rolled sheet material means that the accuracy of the sheet thickness in the width direction is poor, and there is also the disadvantage of increasing the cutting allowance for the ears.

In addition, even after subsequent cold rolling, an amount approximately proportional to the amount of plate thickness reduction will always remain as a crown, which will cause poor shape and shape defects, which will deteriorate the plate thickness accuracy in the width direction of the cold rolled plate. It can also be the cause of

For this reason, there is a need for a control technique that always maintains the crown of the hot-rolled material at a constant, appropriate value.

Currently, the method of controlling the crown of the rolled material during hot rolling is to use a roll heater (mainly a work roll heater) to heat the roll in advance to form a thermal crown before changing the roll. There is no effective method other than minimizing the change in .

Note that the roll bender has almost no crown modification effect under the current equipment capacity, and the current 5 to 1 crown modification effect is low.
Although it is necessary to strengthen the capacity by about 0 times, it is actually impossible because the strength of the roll neck and the load-bearing capacity of the bearings become problems.

This invention controls plate crown in hot finish rolling by changing the reduction distribution of each stand in the three subsequent stands, and especially in the three subsequent stands excluding the final stand, as the rolling progresses. It is possible to control the shape at the same time by making the entrance side plate crown ratio and the exit side plate crown ratio almost equal,
Through the above-mentioned set-up and learning control of its results, an appropriate sheet crown (Cst' rolled product sheet crown (μm)) can be obtained here.

A detailed explanation will be given below using a 7-stand hot finishing rolling mill as an example.

First, set up as follows.

(1) Prediction of thermal crown and wear amount of work rolls The formula for predicting wear of work rolls is shown in Figure 2. For stands using nickel grain rolls, (1)
Here, Cwe: Work roll wear amount (μm) P2 Calculated rolling weight (tons) r
W: Width of rolled sheet - I,: Rolling coil length - a, b: Constants determined by stand, rolling temperature and steel type In addition, in stands using T-damite rolls,
There is almost no wear due to the formation of black skin.

As is clear from the rolling results shown in Figure 3, if there is no downtime, the thermal crown of the work roll is
2) It can be approximated by formula.

CTh2c (1-exp (-dX pX n )
l<2) where, CTh: Thermal crown of work roll (μm) p: Rolling pitch (min/coil), n: Number of rolling coils c, d: Constant determined by stand, rolling temperature, steel type, and cooling conditions (2 ) Predictive force method for rolling reduction distribution mode As shown in Figure 4, there is a very good correlation between the total rolling reduction ratio of the latter three stands excluding the final stand and the crown of the product plate, and as shown in Figure 5, the There is also a good correlation between temperature (hereinafter referred to as FDT) and plate crown.

FDT can be controlled by the scale breaker or the amount of cooling water in the strip coolant, as shown in FIG.

Using this relationship, the plate crown is shaped as shown in equation (3).

Total rolling reduction rate (total) of the latter three stands θFDT: FDT (%), θBa5e' standard FDT
(Throughput 850°C) e: Value determined by steel type and number of rolling coils fig" Constant determined by steel type and dimensions In equation (3), the second term on the right side of the rolling reduction ratio is a rough adjustment, and the third term is FDT. It is most effective to use this term in predictions as a fine adjustment.

If wear, thermal crown, and initial crown are taken into account, it can be expressed as equation (4).

Here, CIn: initial roll crown, 1: constant determined by stand From here, if the target plate crown is C3et2Cst, the total rolling reduction rate of the three subsequent stands is determined as shown in equation (5).

Once the total rolling reduction ratio of the three subsequent stands is determined as described above, by creating a table in advance of the relationship between this and the rolling reduction distribution mode of all stands, it is possible to select an appropriate rolling reduction distribution mode from the table. do.

At this time, the F6 stand can be advantageously controlled simultaneously with the plate crown shape by distributing the reduction so that the plate crown ratios on the entry side and the exit side of the F7 stand are equal.

The determining force for the rolling reduction ratio at which the entrance side plate crown ratio and the exit side plate crown ratio are almost equal is that the rolling reduction rate at the final stand is determined by the exit side plate thickness ht, that is, the product thickness, that is, the set value. It is sufficient to determine the entrance side plate thickness H.

In general, the stand outlet side plate crown Ch is the thickness of the plate to be rolled, the plate width, the diameter of the stand entrance side crown roll, the body length,
It is determined by the crown (consisting of a thermal crown, a worn crown, and an initial crown), rolling load, and roll pending force, and is expressed by equation (6).

The specific content of this equation may be a completely theoretical equation, an approximation thereof, or an experimental equation.

Ch2F(P, W, D, B, CH2CTh, Cwe.

Here, DH: stand entrance plate crown, D: roll diameter, B: roll body length, J: roll pending force, and F means a function.

The rolling load P may be a normal rolling load formula such as the Sims (51m5) formula, which is generally expressed as formula (7).

P=G (H, h, W, R, kf)...
-(7) Here, R: roll radius, kf: deformation resistance, and G means a function.

First, based on the rolling schedule planned at the beginning (7)
Calculate the rolling load P using the equation (6), and from this calculate the crown Ch of the stand exit plate based on equation (6).

If the Ch obtained here does not satisfy the condition of constant crown ratio shown in equation (8), the entrance plate thickness H is set again, a new rolling load P is obtained, and the Ch at this time is obtained.

This process is repeated until equation (8) is almost satisfied.

Crown ratio constant condition is required.

Further, the deviation from the crown of the lower plate under the constant crown ratio condition is determined from the Ch determined from the initially planned rolling schedule, and the thickness of the entrance side plate is changed to correspond to the deviation.

That is, from the formula (2), the entry side plate thickness H' = H + ΔH that satisfies the input side plate crown modification and exit side plate crown ratio is determined.

Note that Δch is not a very large value because ΔH is a change of several hundred μm.In addition, if the shape cannot be controlled only under the condition that the plate crown ratio is constant only for the final stand, it is also necessary to change the value for the stand before the final stand. You can do the same thing.

Even in this case, the product crown will have an appropriate value if the total rolling reduction ratio of the three subsequent stands is a predetermined value.

FIG. 7 shows an embodiment of crown control according to the method of the present invention.

1 is the main computer, 2 is the rolled material, 3 is the work roll,
4 is a reduction device, 5 is a roll drive morph, 6 is a strip coolant, 7 is a scale breaker valve, 8 is a scale breaker, 19 is a finishing inlet thermometer, 10 is a finishing outlet thermometer, 11 is a profile meter, 12 is a comparison calculator.

First, the main computer 1 starts with the target plate crown (
The rolling distribution mode of all the stands is determined based on the plowing stand (Cset), and the rolling device for each stand is output to the rolling device 4, the number of rotations of the roll is output to the roll drive morph 5, and setup is performed.

Next, when rolling is started, the profile after rolling is measured by the profile meter 11, and the comparator 12 calculates the plate crown and calculates the difference (ΔCst −= Cs) between the actual crown (Cst) and the target crown (C5et).
t = Cst C5et ), and further determine whether coarse adjustment (ΔCst > 10 μm) is necessary or fine adjustment (ΔCst
<10 μm).

In the case of rough adjustment, the main computer 1 determines loaf wear.

The thermal crown is calculated, the total rolling reduction rate of the three subsequent stands is calculated, and the rolling reduction distribution of all stands is recalculated using the method described above, and the result is output to the rolling down device 4 and the roll 1 drive moke 5.

For fine adjustment, use the finishing inlet thermometer 9 and the finishing outlet thermometer 1.
The main computer 1 determines the optimum FDT based on the measurement result of the temperature of the rolled material by 0, and calculates and corrects the amount of cooling water for the strip coolant 6 and the scale breaker 8.

This control may be performed within one coil, but if coarse adjustment is required, it is better to control between coils.
Good in terms of plate thickness control.

The results of implementing this invention are shown below.

FIG. 8 shows the change in the plate crown within one rolling cycle according to the method of the present invention.

In the conventional method, there was a change in the plate crown of about 90 μm during one rolling cycle, but with the method of this invention, the change was 30 μm.
Due to the change in m, it has decreased by about one third, and the plate crown has also decreased to 60.
The value is from μm to 30 μm, which is an appropriate value.

Figure 9 shows the case where the reduction distribution is considered (taking into account shape correction) so that the plate crown ratio on the entry side and the plate crown ratio on the exit side are almost equal in the final stand, and the reduction distribution of all stands in the method of this invention. This is the result of examining the product shape on the exit side of the final stand, on the input side of the coiler, and after complete cooling.

It can be seen that the shape is significantly improved when the final stand is set to [the plate crown ratio on the entry side] and [the plate crown ratio on the exit side].

The shape was roughened with steepness%. With this invention, the sheet crown after hot rolling can be reduced to 60 μm to 30 μm within one rolling cycle.
It has become possible to control it within the μm range.

By appropriately selecting the initial crown of the work roll, it is possible to produce a hot rolled material with a plate crown as close to 0 μm as possible.

In addition, shape and dimensional accuracy have been improved, and product quality has been improved by reducing edge cutting allowance.

In this way, the number of rolling coils in one rolling cycle was increased, the rolling efficiency was significantly improved, and the unit consumption of the rolls was also improved.

Note that the crown and shape of the plate after cold rolling are greatly influenced by the crown of the hot rolled plate, so implementing this invention will greatly improve the crown and shape of the plate even during cold rolling, improving product quality,
Improves yield and rolling efficiency.

[Brief explanation of drawings]

Fig. 1 is a graph showing the change in plate crown within one rolling cycle by the conventional hot finish rolling force method; Fig. 2 i;
l: A graph showing the relationship between the rolling load (Σ-XL) and roll wear amount in a work roll (Keckelgren roll), FIG. 3 is a graph showing changes in the thermal crown of the work roll depending on the number of rolling coils, Figure 4 is a graph showing the relationship between the total rolling reduction rate of the three rear stands and the product plate crown, Figure 5 is a graph showing the relationship between FDT and the product plate crown, and Figure 6 is a graph showing the relationship between FDT and scale breaker and product plate crown. A graph showing the relationship with the amount of cooling water such as strip coolant,
FIG. 1 is a block diagram showing an embodiment of hot strip crown control according to the present invention, FIG. 8 is a graph showing changes in plate crown in one rolling wheel according to the method of the present invention, and FIG. In particular, in this invention, it is a graph showing a comparison of the product shape when shape correction is taken into consideration at the final stand and when it is not taken into account.

Claims (1)

[Scope of Claims] 1. During hot finish rolling, a target plate crown is given, and the wear amount and thermal crown of the roll are predicted and calculated, and based on these, the total rolling reduction rate of the three subsequent stands and the corresponding stand are calculated. Based on this, the rolling position and roll rotation speed of each stand are set up.Then, the actual sheet crown is measured using a profile maker installed on the exit side of the rolling mill group, and the target sheet crown is determined. The comparison calculation machine determines whether coarse adjustment or fine adjustment is necessary by performing a comparison calculation with The rolling reduction distribution of each stand is redetermined based on the recalculation of the total rolling reduction rate of the three subsequent stands that can correct the difference between the target sheet crown and the actual sheet crown, and from this the rolling position and roll rotation of each stand are determined. To correct the number and make fine adjustments, calculate the amount of change in the finish outlet temperature that is commensurate with the amount of plate crown correction based on the relationship between the finish outlet temperature and the plate crown, and from this calculate the amount of cooling water for the strip coolant and scale breaker. A method for crown control hot rolling of Horatos 1 helices, characterized in that these setup and feedback controls are performed within the coil or between the coils. 2. During hot finish rolling, give a target plate crown, predict and calculate roll wear amount and thermal crown,
Based on these, first determine the total rolling reduction ratio of the latter three stands excluding the final stand and the corresponding rolling reduction distribution of each stand, set up the rolling position and roll rotation speed of each stand based on this, and then set up the rolling mill. The actual plate crown is measured by a profilometer installed on the exit side of the group, and a comparison calculation is made with the target plate crown to determine whether coarse adjustment or fine adjustment is necessary. According to the results of the judgment, rough adjustment is made by adding up the amount of roll wear and thermal crown at the time of rolling, and recalculating the total reduction rate of the three subsequent stands that can correct the difference from the actual plate crown. Redetermine the reduction distribution of the plate, and from now on, correct the reduction position and roll rotation speed of each stand. Also, make fine adjustments to the finish exit side that is commensurate with the amount of correction of the plate crown, based on the relationship between the finish exit side temperature and the plate crown. Calculate the amount of temperature change, calculate and correct the amount of cooling water for the strip coolant and scale breaker, perform set-up and feedback control within the coil or between the coils, and at the final stand. , a crown-controlled hot rolling method for hot strip, which is characterized in that the entrance plate crown ratio and the exit plate crown ratio are made almost equal, and the plate crown and shape are simultaneously controlled.