JPS6114890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a taper rolling control device for hot rolling.

In general, in hot rolling, the rolling time differs depending on the length of the rolled material, but the rolling time is about 30 seconds to 2 minutes between the leading end and trailing end of the finish-rolled material. The amount of temperature decrease due to heat dissipation differs between the two, resulting in a temperature difference at the front and rear ends of the rolled material.
This temperature difference is undesirable because it adversely affects the mechanical properties of the rolled material.

In order to eliminate this temperature difference, the applicant developed the so-called taper rolling method, and filed a patent application in 1975.
It was disclosed in No. 57409 (Japanese Unexamined Patent Publication No. 52-139652) as "Finishing temperature control method in hot rolling". In this method, the thickness of a semi-finished rolled material is gradually increased from the leading end to the trailing end by adjusting the rolling reduction amount of a rough rolling mill. It is called taper rolling because the thickness of the rolled material tapers in the longitudinal direction. According to this method, the heat dissipation at the rear end of the rolled material is somewhat reduced, so that the finish exit temperature at the front and rear ends of the rolled material can be made uniform during finish rolling.

In the finishing temperature control method described above, the tapered shape is selected so that the difference in thickness between the leading end and the trailing end of the rolled material is 3 mm or more.

The present invention further develops this method to provide a taper rolling control device that can meet various demands.

As shown in FIG. 1A, taper rolling is applied to the final stand of a roughing mill. In the case of tandem mills, it applies to the last stand. Taper shapes include tapers that gradually increase with a constant slope from the leading end to the rear end of the rolled material (hereinafter referred to as constant taper, see Figure 1B), and tapers that gradually increase with a variable slope (hereinafter referred to as variable taper). (See Figure 1C) and one in which the taper starts from a position where the taper advances backwards by a predetermined distance _l1 from the tip (hereinafter referred to as a stepped taper; see Figure 1D). . In the last stepped taper, the taper length l ₂ can be either a constant taper or a variable taper.

The taper rolling control device of the present invention is configured to measure the temperature distribution of the rolled material just before the final stand of the rough rolling mill bites, determine the taper shape from this measurement result, and control the rolling device of the final stand. Ru. In the case of a tandem mill, the rolling devices of the last two stands are controlled in the same way, and the rolling speed of the previous stand is corrected based on the taper shape.

Next, specific embodiments of the apparatus of the present invention will be described with reference to the drawings. FIG. 2 shows an embodiment in which the taper rolling control device 2 of the present invention is applied to the final stand 1 of a normal rough rolling mill. In order to measure the temperature distribution in the longitudinal direction of the rolled material immediately before it is bitten into the final stand 1, a thermometer 21 and a feed table speed detector 22 are installed on the entrance side of the stand 1. The outputs of the thermometer 21 and speed detector 22 are input to a temperature distribution calculator 23. Here, the temperature distribution of the rolled material is calculated. The temperature of the rolled material will be described in detail later, but as shown in FIGS. 5 to 7, there is some unevenness along the longitudinal direction of the rolled material. Therefore, by finding the average value of all measured values or the average value of only the PIC values, we can calculate the temperature distribution in the longitudinal direction of the rolled material.
In other words, the actually measured temperature pattern is determined. In this temperature pattern, the temperature decreases at a constant inclination angle θm from the rear end to the front end in the longitudinal direction of the rolled material. This inclination angle θm is hereinafter referred to as an actual measured temperature pattern. On the other hand, an ideal temperature pattern that does not require taper rolling is hereinafter referred to as a reference temperature pattern θf. The reference temperature pattern θf is determined in advance based on rolling results for each type of rolling condition.

The output of the temperature distribution calculator 23 is sent to a constant speed/variable speed control determiner 24 and a taper rolling start timing determiner 2.
5 respectively. The constant speed/variable speed control determiner 24 compares the actually measured temperature pattern θm of the rolled material with a reference temperature pattern θf determined in advance before the final stand of rough rolls, and determines when θm<θf (fifth
(Fig. 1B), it is determined that the rolling control is with the constant taper described above (Fig. 1B), and if θm changes midway (for example, θm<θf on the rear end side and θm≧θf on the leading end side).
f (Fig. 6)), it is determined that the aforementioned variable taper (Fig. 1 C) rolling control is performed, and θm≧θf
In the case (FIG. 7), taper rolling control is not performed. This determination result is sent to the rolling speed controller 26.

The taper rolling start timing determiner 25 determines to start taper rolling from the leading edge of the rolled material when θm<θf, as described above, and when θm changes midway (θm≧θf and θm<θf)
In this case, it was decided to use stepped taper rolling control (Fig. 1D). In the latter case, the timing to start taper rolling,
That is, the taper rolling start position from the leading edge of the rolled material is determined. Taper rolling start timing determiner 25
receives a detection signal from a material entrainment detector 11, which is comprised of a load cell or the like installed in the final stand 1, and sends the above-mentioned taper rolling timing determination signal to the reduction speed controller 26.

The rolling-down speed controller 26 receives signals from the constant-speed/variable-speed control determiner 24 and the taper rolling start timing determiner 25, respectively, and compares the signals with the coarse roll final stand rolling set value to determine the rolling speed control signal. A control signal is sent to the lowering device 12 installed on the stand 1. The set value is determined in advance through experiments.

The reduction device 12 may be either a conventional screw reduction device or a hydraulic reduction device. Reduction device 12
is subjected to normal plate thickness control (AGC) and
The normal rolling control is changed in response to a signal instructing the rolling raising timing and rolling raising speed from the aforementioned rolling speed controller 26. In this way, the rolled material is rolled into a predetermined tapered shape.

FIG. 3 shows an embodiment in which the taper rolling control device 2' of the present invention is applied to the last two stands 1' of a tandem mill. In FIG. 3, the same reference numbers as in FIG. 2 indicate the same components. In this embodiment as well, the same rolling down control signal is sent from the rolling down speed controller 26 to the rolling down device 12B of the front stage stand 1B and the rolling down device 12A of the rear stage stand 1A. However, in this case, the control signal is delayed by the delay circuit 27 by the time required for the rolling material to pass between the front and rear stands before reaching the rolling device 12A.

When such taper rolling is performed in a tandem mill, the rolling speed of the front stand 1B increases compared to the rolling speed of the rear stand 1A, and a loop occurs between the front and rear stands. Therefore, it is necessary to correct the rolling speed of stand B. The speed increase rate of the front stand 1B is the sum of the change in the advance rate of the front stand 1B and the change in the backward movement rate of the rear stand 1A.

Based on this idea, when the thickness at each position of the rolled material is defined as shown in FIG. 4, the speed increase rate ΔK of the front stand 1B is expressed by the following equation.

△K=hi _B (h'o _B -ho _B )/2ho _B・h'o
_B + 2(ho _B・h′o _A −h′o _B・ho _A )/(ho
_B +ho _A ) (h'o _B +h'o _A ) However, hi _B : Thickness of the rolled material on the entry side of the front stand 1Bho _B : Thickness of the rolled material on the exit side of the front stand 1Bho _A : Thickness of the rolled material on the exit side of the front stand 1B Thickness of the rolled material on the exit side h′o _B : Ho _B changed by rolling control h′o _A : Ho _A changed by rolling control This speed increase rate △K is used as the rolling speed correction signal
K) is input to the rolling speed controller 28, which controls the rotational speed of the rolling roll driving electric motor 13 of the front stand 1B.

<Example 1> A slab was tapered rolled in the final stand of a rough rolling mill to which the taper rolling control device shown in FIG. 2 was applied, and then subjected to normal rolling in a finishing mill to obtain a product. The results are shown in FIG.

Slab material: Low carbon steel with carbon content of 0.20% Slab dimensions: Thickness (mm) x Width (mm) x Length (mm) 300 x 1500 x 7 250 x 1000 x 7 Actual temperature pattern θm: 0℃/m ( Both the leading and trailing ends are approximately 1050°C) Reference temperature pattern θf: 20/75°C/m Taper rolling: Constant taper rolling A thickness difference of 3 mm was given in 15 seconds.

Rolling speed V: 5 m/sec Product: 2.3 mm x 1500 mm x coil 1.6 mm x 1000 mm x coil The mechanical properties of the product were almost uniform at both the front and rear ends.

In addition, the material is tapered rolled at the final stage of rough rolling,
After that, the rolled material was kept on standby on a day table (table before finish rolling), and the temperature distribution immediately before finish rolling after temperature adjustment was measured in a short time.
Also included in the figure. This temperature pattern approximates θf.

<Example 2> The results of rough rolling of the same material and dimensions as the above-mentioned slab are shown in FIG.

The temperature distribution of the rolled material before the final stand is 1050℃ from the tip to 25m and 1100℃ from then to the rear end.
It was warm at ℃. In the area up to 25m from the tip, the actual temperature pattern (θm)25=50/25(℃/
m), since the reference temperature pattern θm=20/75 (°C/m), θm>θf. Therefore, this portion is not tapered.

From the center 25m to the rear end (θm) 50
Since θf=0 and θf=20/75, θm<θf, and therefore taper rolling is performed. In this case, the stepped taper rolling starts at a passing position 5 to 6 seconds from the tip, and the taper is rolled at 3 in 15 seconds.
A reduction increase of mm was selected. In this case too, the mechanical properties of the product were homogeneous.

Incidentally, for comparison, an ideal model in the case where no taper rolling is performed is shown in FIG. In this case θ
Let m=θf.

As is clear from the above description, according to the present invention, taper rolling, which was conventionally performed manually, can be automated, and productivity can be improved and quality stabilized.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of taper rolling. FIG. 2 is a schematic configuration diagram of the taper rolling control device of the present invention. FIG. 3 is a schematic diagram of another embodiment of the apparatus of the present invention. Fourth
The figure is a schematic explanatory diagram for explaining correction of rolling speed in tandem rolling. FIG. 5 and FIG. 6 are schematic explanatory diagrams showing specific embodiments of the present invention. FIG. 7 is a drawing similar to FIG. 5, and is a schematic explanatory diagram showing an ideal model as a comparative example.

Claims (1)

[Scope of Claims] 1. A temperature distribution calculator that calculates the temperature distribution in the length direction of the rolled material in the final stand of the rough rolling mill from the feed rate of the rolled material before the final stand bites and the sequentially detected temperatures; a constant speed/variable speed control determiner that compares the output signal from the calculator with a set value to determine whether the taper is a constant taper or a variable taper; a taper rolling start time determiner that determines a start time and outputs the determination signal in response to a detection signal from a rolling material jamming detector installed at the final stand; the constant speed/variable speed control determiner; A taper rolling control device comprising a rolling speed controller that receives each output signal from a rolling start time determining device, compares it with a set value, and controls the rolling speed of a rolling device installed at the final stand. 2. In the final tandem stand of the rough rolling mill, a temperature distribution calculator that calculates the temperature distribution in the length direction of the rolled material from the feed rate of the rolled material before biting into the final pre-stage stand and sequentially detected temperatures, and the calculation a constant speed/variable speed control determiner that compares the output signal from the calculator with a set value to determine whether the taper is constant or variable; and a controller that compares the output signal from the calculator with the set value to determine when to start taper rolling. a taper rolling start timing determiner that determines the determination signal and outputs the determination signal in response to a detection signal from a rolling material jamming detector installed in the front stage stand; the constant speed/variable speed control determiner; A rolling speed controller receives each output signal from the start time determining device, compares it with a set value, and controls the rolling speed of each rolling device installed in the final front stage stand and rear stage stand, and receives the rolling speed correction signal and compares it with the set value. A taper rolling control device comprising a rolling speed controller that controls the rotational speed of an electric motor for driving a rolling roll in a final pre-stage stand.