JPH11277126A - Method for controlling temperature of work to be hot rolled - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the rolling efficiency by estimating or detecting the temperature of a work to be rolled at the position on the upstream side of a finish rolling mill, and changing the carrying speed of the work to the finish rolling mill and the rolling speed at a rough rolling mill based on the temperature to regulate the temperature of the work without any oscillation. SOLUTION: The temperature of a work to be rolled by final stand R3 of a rough rolling mill is measured by an R3 inlet side temperature detector, and compared with the set target value. When the measured value is lower than the target value, the rolling is still continued to feed the work into finish rolling mills F1-F7. When the measured value exceeds the upper limit of the target value, the rough rolling and table carrying time is newly operated, and the work is rolled based thereon. Alternatively, in place of this method, the upstream side stand R2 inlet side temperature is measured, and the measured value exceeds the upper limit of the set target temperature, the rolling speed is increased at the upstream side stand R2, and the rolling speed at the final stand R3 is decreased to drop the temperature of the work without changing the rough rolling and carrying time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of a material to be rolled in hot rolling, and more particularly to a method for controlling the temperature of a slab at the start of finish rolling. The present invention relates to a method for controlling the temperature of a material to be rolled.

[0002]

2. Description of the Related Art Generally, in hot rolling, a temperature range at the end of finish rolling (referred to as a finishing temperature) is specified by a steel type in order to guarantee mechanical properties of a product. Therefore, the temperature at the start of the finish rolling must be within a predetermined range in consideration of the temperature change during the finish rolling and the temperature control range to the finished temperature. In particular, since the slab on the lower limit side of the allowable range cannot be reheated on the entrance side of the finishing mill, the slab is heated so that the temperature of the slab after the rough rolling is close to the upper limit of the allowable range. It is common. Then, when the temperature is too high and deviates from the upper limit, a method is adopted in which the steel sheet is temporarily stopped on a transfer table in front of the finishing mill to lower the temperature. At this time, if the slab is completely stopped on the table, the temperature of the contact portion between the table roller and the slab is locally lowered. Therefore, the slab is reciprocated back and forth (referred to as oscillation), and the standby state is established. It is common to do.

[0003] Specifically, as shown in FIG.
The steel slab 10 rolled in Step 2 was oscillated on the table roller 24 in front of the finish rolling mill 26 as shown by the arrow A so that the temperature at the start of finish rolling falls within a predetermined range. FIG. 9 shows the relationship between the amount of temperature drop of the steel slab and the time. In the method of oscillating, the time of the start of the finish rolling is delayed based on the relationship as shown in FIG.

[0004]

However, in order to convey the slab to the front of the finish rolling mill, the tail end of the slab that has been subjected to the finish rolling before that is removed from the table in front of the finish rolling mill. There must be. Therefore, when the billet is oscillated on the transfer table for controlling the temperature, the finish rolling is interrupted and the rolling efficiency is remarkably reduced.
In addition, depending on the hot rolling equipment, there may be a billet winding facility that once winds a billet into a coil in front of a finishing mill, but in the state of the billet coil, there is almost no temperature change,
Since it is not possible to oscillate the unwound billet coil, temperature control was virtually impossible.

The present invention has been made to solve the above-mentioned conventional problems, and has as its object to improve the rolling efficiency by controlling the temperature of the material to be rolled without oscillating the material to be rolled. I do.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for controlling the temperature of a material to be rolled in hot rolling for controlling the temperature of the material to be rolled at the start of finish rolling. The problem was solved by predicting or detecting the temperature of the rolled material, and changing the transport speed of the material to be rolled to the finishing mill or the rolling speed in the rough rolling mill based on the predicted or detected temperature. Things.

When the predicted or detected temperature exceeds the upper limit of the finish rolling start temperature, the conveying speed and the rough rolling speed of the material to be rolled to the finish rolling mill are reduced.

[0008] Further, the prediction or detection is performed at the entrance of the upstream stand among the plurality of rough rolling mills, and when the predicted or detected temperature exceeds the upper limit, the rolling at the upstream stand of the rough rolling mill is performed. The speed is increased, and the rolling speed at the downstream stand is reduced, so that the temperature drop during the rough rolling is increased without changing the total time required for the rough rolling and the transport.

[0009]

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

FIG. 1 shows a change in the conveying speed of the table roller according to the first embodiment of the present invention. In the drawing, a dashed line B is a basic speed pattern. Conventionally, according to the basic speed pattern B, rough rolling is performed and the material is conveyed on a table. On the other hand, in the first embodiment of the present invention, before starting the final pass of rough rolling, the temperature of the billet at the end of rough rolling is predicted, and when the temperature exceeds the upper limit of the temperature range at the start of finish rolling, Changes the rolling and conveying speed as shown by the solid line C.

Although the billet temperature decreases with time, the temperature drop rate during rolling differs from the temperature drop rate during transport. Furthermore, the rate of temperature decrease during rolling increases as the rolling rate decreases, because the contact time with the rolls increases.
This embodiment utilizes this, when the billet temperature is higher than the reference on the rough rolling mill entry side, slows the rough rolling speed, that is, lengthens the rough rolling time, and reduces the temperature drop during rolling. The slab temperature is reduced to a target finish rolling mill entry side temperature by increasing the amount without performing the oscillation or shortening the oscillation time as much as possible.

For example, in the hot rolling equipment shown in FIG.
FIG. 2 shows a state of temperature change with time from the entrance of the final stand R3 of the rough rolling mill to the entrance of the first stand F1 of the finishing mill.
Shown in In the figure, the dashed line indicates the reference speed pattern,
The broken line indicates the actual value T of the entrance temperature of the final stand R3 of the rough rolling mill.
conventional speed pattern when re ′ is larger than the target value Tre,
The dashed line is the velocity pattern according to the invention for the same case.

As shown in FIG. 2, the final stand R of the roughing mill
3. When the actual value Tre 'of the inlet temperature is larger than the target value Tre, conventionally, the rough rolling time t _R + the table transfer time t _T.
While the + oscillation time t _os is the time required from the entrance of the final stand of the rough rolling mill to the entrance of the first stand of the finishing mill, in the present embodiment, the rough rolling time t _R ′, the table transport time The rolling speed and the conveying speed are changed so as to be t _T '.

Specifically, as shown in FIG. 3, the actual temperature Tre 'is measured in step 100, for example, at the entrance of the final stand R3 of the rough rolling mill shown in FIG.
At 10, comparison is made with the target temperature Tre. If actual value is less than the target value, the process proceeds to step 120, similar to the conventional rough rolling time t _R and table carrying time t _T, as it is rough rolling, transports. On the other hand, the actual value Tre 'is the target value T
If higher than re proceeds to step 130, the new rough rolling time calculates the t _R 'and table carrying time t _T', in step 140, the calculated rough rolling time t _R 'and table transport time t _T ′ To perform rough rolling and transport.

The new rough rolling in step 130
Time t_R'And table transfer time t _T′ Is calculated by the following equation
Performed by

[0016] _{at R '+ bt T' =} Tre'-Tfe ... (1) t R + t T ≦ t R '+ t T'<t R + t T + t os ... (2) t R min ≦ t R '≦ t R _{max ... (3) t T min} ≦ t T '≦ t T max ... (4) where, a: the temperature drop rate during the rough rolling (see FIG. 2) b: temperature in the table conveyance rate of descent Tfe: finish rolling Start target temperature t _os : Conventional oscillation time t _R min: Lower limit of coarse rolling time t _R max: Upper limit of coarse rolling time t _T min: Lower limit of table transfer time t _T max: Upper limit of table transfer time

A and b are constants determined by the material and dimensions of the material to be rolled, cooling conditions of rolls or table rollers, etc. t _R and t _T are the initial set rolling speed, the initial set conveying speed, and the length of the material to be rolled. constant determined by, t _os is 'constant determined by, Tre' R3 entry side actual temperature Tre is measured value, Tf
Since e is a target value, and Mitsuru above (1) to (4) simultaneously, and, t _R and t _T smallest t _R sum of, by obtaining the t _T, can shortest oscillation time .

For example, when the distance between the final stand R3 of the rough rolling mill and the first stand F1 of the finishing mill as shown in FIG.
00m, billet 1 on the exit side of the final stand R3 of the roughing mill
0 is 80 m, and the rolling speed in the rough rolling and the conveying speed on the table roller are both 10 m / sec (6
00 mpm), the rough rolling time t _R is 8
Second, the table transfer time t _T is 2 seconds. Now, assuming that the finish rolling start target temperature (FET) Tfe is 1000 ° C., the target temperature Tre at the side of the final stand R3 of the rough rolling mill is 1040 °, which drops by 38 ° C. during rough rolling and drops by 2 ° C. during table transfer. The temperature drop rate a during the rough rolling is 4.75 ° C.
/ Sec, and the temperature drop rate b during the table transfer is 1.0 ° C./sec.

For the reference speed pattern as described above,
Actual rough rolling mill final stand entrance side temperature Tre 'is 1045
In the case of ° C., conventionally, as shown by the following equation, oscillation was performed with t _os = 5 seconds.

T _os = (Tre′−Tre) / b = 5/1 = 5 seconds (5)

It is clear from FIG. 5 that the sum of the rough rolling time t _R ′ and the table transfer time t _T ′ satisfies the above equations (1) to (4) at the same time, and that the sum of the table rolling time t _T ′ is minimum. The transfer time t _T ′ = 1 second and the rough rolling time t _R ′ = 9.26 seconds. Therefore, the sum of the two is 10.26 seconds,
Conventional _{(t R + t T + t} os = 8 + 2 + 5 =) compared to 15 seconds, is shortened (15-10.26 =) 4.74 seconds.

At this time, the rough rolling mill 22 performs the rough rolling time t.
_{To make R} ′ = 9.26 seconds, (80 / 9.26) =
The material to be rolled is rolled at 8.64 m / sec = 518.4 mpm, and after the rough rolling is completed, the material to be rolled is conveyed to the entry side of the finishing mill 26 with a table conveyance time t _T = 1 second.

In the above-described embodiment, the calculation is made to minimize the sum of the rough rolling time t _R and the table transfer time t _T. For example, the table transfer time t _T ′ is set to 2 seconds which is the same as the reference speed pattern. Can be set so that the table is transported without difficulty. In this case,
By a similar calculation, the rough rolling time t _R ′ = 9.05 seconds, and the sum of the rough rolling time t _R ′ and the table transfer time t _T ′ is (9.
05 + 2 =) 11.05 seconds, which is also 3.95 seconds shorter than the time until the end of the conventional oscillation.

In this embodiment, since only the rolling speed by the final stand R3 of the rough rolling mill is reduced,
The configuration is simple.

Next, a second embodiment of the present invention will be described in detail.

The rough rolling mill 22 generally comprises a plurality of stands, but the temperature drop rate during rolling and transport is slower toward the upstream side because the steel sheet is thicker. Therefore, by shortening the rolling time and the transport time in the upstream rough stand rolling and increasing the rolling time and the transport time in the downstream rough stand rolling, the time required for the rough rolling and the transport (upstream rough rolling time + rough rolling time) The temperature drop amount can be increased without changing (inter-stand transfer time + downstream rough rolling time + downstream rough stand exit side transfer time). This embodiment focuses on this point.
As shown in FIG. 4, after three-pass rolling at the first stand R1 of the rough rolling mill, the conveyed material is transferred to the second stand R2 of the rough rolling mill, and three-pass rolling is performed at the second stand R2 of the rough rolling mill. Conveyed to the final stand R3,
In the case where the steel sheet is conveyed to the first stand F1 of the finishing rolling mill after one-pass rolling in Step 3, the temperature drop pattern of the billet after measuring the temperature on the third pass entry side of the second stand R2 of the rough rolling mill is shown in FIG. As shown in FIG.

In FIG. 6, the dashed line indicates that the R2-3 entry actual temperature Tr2e 'is equal to the target temperature Tr2e, and the broken line indicates that the R2-3 entry temperature Tr2e' is equal to the target temperature T2e '.
3 shows a conventional speed pattern when the speed is higher than r2e. In the conventional case, when the rolling at the R3 stand is completed and the slab is conveyed to the finishing entrance side, the billet temperature is high, and oscillation is performed to lower the temperature to the finishing entrance side target temperature Tfe. On the other hand, in the present invention, as indicated by the dashed line, the R2-3 rolling time is set to t _R2 ′ shorter than the reference rolling time t _R2 (determined from the reference rolling speed of the rolling mill and the length of the billet), and the R3 rolling time is set. _{Is set} to t _R3 ′ longer than the reference rolling time t _R3 .

Here, t _R2 ′ and t _R3 ′ are obtained as follows. First, the temperature drop rates a to
d changes depending on the cooling condition of the roll and the thickness of the steel slab to be rolled, but is determined empirically. Where a is R2-
3 The temperature drop rate during rolling, b is the temperature drop rate during R2 exit side transport, c is the temperature drop rate during R3 rolling, and d is the temperature drop rate during R3 exit side transport.

Then, in order to achieve the temperature drop of Tr2'-Tfe in the rolling / transporting time of t _R2 ', t _R3 ', t _T2 , t _T3 , the following equation must be satisfied.

A × t _R2 ′ + c × t _R3 ′ = Tr ₂ ′ −Tfe−b × t _T2 −d × t _T3 (6) where t _T2 is the transport time on the R2 exit side, and t _T3 is the R3 output time. Is the transfer time on the side.

Further, in order to satisfy the condition that the reference rolling time is t _R2 + t _R3 or more and shorter than the case where there is an oscillation, the following equation must be satisfied.

[0032] _{t R2 + t R3 ≦ t R2} '+ t R3'<t R2 + t R2 + t os ... (7) where, t _os is, oscillation time prediction of when R2-3 entry side temperature was Tr2e ' Value.

Further, the R2-3 rolling time t _R2 ′ is not less than the lower limit t _R2 min and not more than the maximum value t _R2 max determined by the equipment specifications (the maximum value and the minimum value of the rolling speed) and the slab length. Therefore, it is necessary to satisfy the following relationship.

T _R2 min ≦ t _R2 ′ ≦ t _R2 max (8)

Similarly, since the R3 rolling time t _R3 'needs to be not less than its minimum value t _R3 min and not more than its maximum value t _R3 max, it is necessary to satisfy the following equation.

T _R3 min ≦ t _R3 ′ ≦ t _R3 max (9)

Therefore, from the ones satisfying the above equations (6) to (9), the one that minimizes t _R2 ′ + t _R3 ′ may be obtained.

R2-3 exit bar length 56m, R3 exit bar length 80m, R2-3 distance 70m, R3-F1 distance 1
00m, minimum rolling speed of R2 and R3 300 mpm,
The maximum value is 700 mpm, the reference rolling speed R2-3 = 9 m /
Second (540 mpm), R3 = 10 m / sec (600 mpm)
m), R2 output side reference transport speed 7 m / sec (420 mp
m), R3 output side reference transport speed 10 m / s (600 mp
m), the target temperature Tr2 at the entrance of the R2-3 pass, Tr2 = 1055 ° C
When the FET target temperature Tfe = 1000 ° C., R2-3 rolling time t _R2 = 6.22 seconds, R3 rolling time t _R3 = 8 seconds, R2
Outgoing side transport time t _T2 = 2 seconds, R3 outgoing side transport time t _T3 = 2
Seconds, the total rolling / transporting time is 18.22 seconds, and the temperature drop rate is as follows: a = 2.17 ° C./second during R2-3 rolling;
2 During the delivery side b = 0.75 ° C./sec, during R3 rolling c = 4.
75 ° C./sec, and d = 1 ° C./sec during conveyance on the R3 exit side. Therefore, when the R2-3 inlet temperature is higher than the target value, R3
The rolling time is lengthened, and the R2-3 rolling time is shortened accordingly. The transport speed is constant for both the R2 exit side and the R3 exit side,
When R2-3 entry side temperature T _r2 'was 1065 ° C., conventionally, using _{t os (= 10/1 =} ) that was 10 seconds, the supra (6) to (9) T _R2 '=
When 4.8 seconds and t _R3 ′ = 10.755 seconds, t _R2 ′ + t
_It can be seen that _R3 'is the smallest, and the total rolling / transfer time at this time is (4.8 + 10.755 + 2 + 2 =) 1
In 9.555 seconds, the conventional (18.22 + 10 =) 28.2
8.67 seconds were reduced from 2 seconds.

In each of the above-described embodiments, the case where the finishing rolling mill 26 follows the rough rolling mill 22 is exemplified. However, equipment such as a billet winding facility is provided before the finishing rolling mill 26. In the case of the arrangement, the same effect can be obtained when the rolling speed of the rough rolling mill and the transport speed from the rough rolling mill to the winding of the billet are changed. In this case, in the billet winding facility, temperature control was practically impossible because oscillation was not conventionally possible. However, the present invention enables temperature control.

[0040]

According to the present invention, the temperature at the start of the finish rolling can be controlled by controlling the rough rolling speed and the conveying speed. Therefore, it is not necessary to oscillate the slab at the table in front of the finishing mill as in the related art, or the oscillation time can be shortened,
The rolling efficiency can be significantly improved. Further, even when temperature control by oscillation cannot be performed, such as when a billet winding facility is provided on the entrance side of the finishing mill, the temperature can be controlled.

FIG. 7 shows the effect of the present invention. E in FIG. 7 is the temperature range at the start of the finish rolling. The thin line F is the case of the billet arriving before the finish rolling mill by the conventional method, and the temperature range E
Oscillation was carried out at the table in front of the finishing mill until it could fit in. On the other hand, in the case of the present invention shown by the thick line G, the target temperature range E could be achieved. Therefore, the finish rolling can be started without oscillation in front of the finish rolling mill, so that the efficiency of the rolling can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a speed change state in a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a change state of a billet temperature in the same manner.

FIG. 3 is a flowchart showing a procedure for determining a rough rolling time and a table transport time.

FIG. 4 is a process chart showing an example of arrangement of a rough rolling mill to a finishing rolling mill.

FIG. 5 is a diagram for explaining a method of determining a rough rolling time and a table transport time.

FIG. 6 is a diagram showing an example of a change state of a billet temperature according to a second embodiment of the present invention.

FIG. 7 is a diagram for explaining the effect of the present invention.

FIG. 8 is a diagram for explaining a conventional problem.

FIG. 9 is a diagram showing the principle of conventional temperature control.

[Explanation of symbols]

10 ... billet 22 ... roughing mill 24 ... table rollers 26 ... finishing mill t _R ... rough rolling time t _T ... table carrying time t _os ... oscillation time

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B21B 37/78 B21B 37/00 133 45/02 320 134

Claims (3)

[Claims] 1. A method for controlling the temperature of a material to be rolled in hot rolling for controlling the temperature of the material to be rolled at the start of finish rolling, wherein the temperature of the material to be rolled is predicted or detected at a position upstream of the finishing mill. And a method for controlling a temperature of a material to be rolled in hot rolling, wherein a conveying speed of the material to be rolled to a finishing mill or a rolling speed in a rough rolling mill is changed based on the predicted or detected temperature. 2. The method for controlling the temperature of a material to be rolled in hot rolling according to claim 1, wherein the predicted or detected temperature exceeds a predetermined upper limit of a target temperature, and the rolled material to a finish rolling mill is provided. A method for controlling the temperature of a material to be rolled in hot rolling, wherein the conveying speed and the rough rolling speed of the material are reduced. 3. The method for controlling the temperature of a material to be rolled in hot rolling according to claim 2, wherein the prediction or detection is performed on the entrance side of an upstream stand among a plurality of rough rolling mills, and the prediction or detection is performed. When the temperature exceeds the upper limit, the rolling speed in the upstream stand of the rough rolling mill is increased, and the rolling speed in the downstream stand is reduced, without changing the total time required for the rough rolling and the transport, and the rough rolling is performed. A method for controlling the temperature of a material to be rolled in hot rolling, characterized by increasing the amount of temperature drop during heating.