JPS583443B2 - Steel bar production equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel bar production device that produces steel bars such as wire rods, bars, and small strips by rolling slabs obtained from a continuous casting machine using a subsequent rolling mill group without cutting them. Regarding.

Conventionally, in order to make wire rod and steel bar products, molten steel is first poured into individual molds, slabs such as billets are made using ingot making equipment or continuous casting machines (hereinafter simply referred to as continuous casting machines), and then the billets are rolled using rolling equipment. They were trying to obtain wire rods and steel bars.

In this case, a billet produced by a continuous casting machine was cut into a certain size, and after being cooled from a temperature of 700° C. to 800° C. to room temperature, quality inspection and surface care were performed.

Thereafter, the billet cooled to room temperature is sent to a heating furnace and heated again to the temperature required for rolling, for example, 1100° C. to 1200° C., and then the heated billet is rolled using rolling equipment to obtain wire rods and steel bars.

Conventionally, in order to inspect the quality of billets, the billets produced in a continuous caster were cooled to room temperature, and then the quality-inspected billets were heated again, which reduced the amount of energy consumed to heat the billets. In addition, there was a lot of scaling caused by surface oxidation due to cooling and heating.

Furthermore, when cutting the billet into a certain length, the leading and trailing ends of the billet were cropped, and the yield was very poor due to short lengths.

Therefore, there has been a drawback that the productivity of wire rods and steel bars is low and the cost thereof is high.

Therefore, it is desired to develop a steel bar manufacturing apparatus that can feed billets obtained from a continuous caster to rolling equipment without cutting them.

However, two problems arise when developing such a steel bar manufacturing apparatus.

In other words, the first problem is that hot material quality inspection technology has not been established, so the billet must be cooled to room temperature, but in recent years hot material quality inspection technology has gradually been established. This is not a problem as it is becoming more and more common.

The second problem is that since the continuous caster is configured to be able to be transported in the following manner, the drawing speed of the continuous caster fluctuates as shown in FIG.

Figure 2 shows a conventional continuous casting machine, with tundish 1
A slab 4 is obtained by pouring the molten steel (hot water) 2 contained in the mold into a mold 3, and this slab 4 is drawn out by a drawing roll 5.

On the other hand, the molten steel level height in the mold 3 is detected by a molten metal level height detector 6, and this detection signal, that is, a molten metal level height signal, is converted into a speed correction amount by a conversion circuit 7 and sent to one of the adder circuits 8. is applied to the input terminal of

A speed setting signal from a speed setting device 9 is applied to the other input terminal of the adder circuit 8.

Therefore, the output of the adding circuit 8, that is, the sum of the speed correction amount and the speed setting signal according to the height of the hot water level, is added to the thyristor power supply device 10, which is the power source of the drive motor 11 that drives the drawing roll 5.

As a result, the speed of the electric motor 11 that drives the drawing roll 5 is corrected so that the height of the molten steel level in the mold 3 is constant.
The speed of the electric motor varies, which causes the speed of the drawing roll 5 to vary as shown in FIG.

When the speed of the drawing roll 5 is controlled in accordance with the height of the hot water level, so-called drawing speed correction control, the drawing speed varies.

To prevent this, it is possible to control the amount of molten steel injected for machines with a large cross-sectional area of slabs, such as continuous slab casters, but it is possible to Since it is difficult to control the injection amount itself due to the performance of the nozzle and control valve, the drawing roll speed is ultimately controlled according to the above-mentioned hot water level height.

For these reasons, when continuously rolling slabs in a continuous casting machine without cutting them, the drawing rolls of the continuous casting machine must be operated in synchronization with the rolling machine.

Further, since the drawing roll has speed fluctuations, the capacity of the rolling mill requires acceleration and deceleration power corresponding to the fluctuations, and the capacity of the drive motor must be increased accordingly.

Further, rolling with speed fluctuations does not result in optimal formation of intermediate loops, especially at high line speed positions near the finishing mill.

Furthermore, if the speed of the final rolling mill changes, the accuracy of the cutting length of the material will be adversely affected.

This invention was made in view of these circumstances, and by configuring the rolling mill so that speed fluctuations are as small as possible, it is possible to reduce the speed fluctuations of the rolling mill without increasing the electric motor capacity for acceleration and deceleration due to speed fluctuations. The purpose of the present invention is to provide a steel bar production device that can optimally perform loop control near a finishing mill.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 3 shows a schematic configuration of the apparatus of the present invention. In this figure, only one strand is shown to simplify the explanation, but in reality it is a continuous rolling line for multiple strands.

A is the continuous casting machine configured as described above, B is the drawing pinch roll of the continuous casting machine A, and C is the temperature required for rolling the slab, e.g.
Reheating furnace that reheats from 100℃ to 1200℃, D is the first
Since the cross-sectional area of the material on the upstream side of the rolling mill group (rough rolling mill group) is large, a loop cannot be formed on the upstream side.

Further, F is the second rolling mill group (intermediate rolling mill group), and since the cross-sectional area of the material on the upstream side is small, the lube E can be formed.

H is a third rolling mill group (finishing rolling mill group), and a lube G can be formed on the upstream side thereof in the same way as in the second rolling mill group.

J is a cutting machine that cuts the material into predetermined dimensions.

FIG. 4 is a block diagram showing an embodiment of the present invention,
In reality, an amplifier, single mode, and successive mode are provided in addition to this, but they are omitted here.

In the figure, 6 is a molten steel level height detector in the mold, 7 is a conversion circuit,
8 is an adder circuit, and 9 is a drawing speed setter, both of which operate in the same manner as described above.

13e and 13g are computing units that add a correction signal to the speed signal from the drawing speed setting device 9, and 14e and 14g are loop length detectors, which are, for example, loop height detectors and convert the loop height into length. It consists of an arithmetic circuit.

Limiter circuits 15e and 15g do not respond to small fluctuations in the loop amount, but perform loop control only when the loop amount exceeds the set range, that is, the set range of the loop length setters 16e and 16g. .

Reference numerals 17e and 17g are speed correction circuits that apply speed correction to the rolling mill groups F and H after the intermediate rolling mill so that the loop amount falls within the set range.

In such a configuration, the adding circuit 8 of the continuous casting machine A
Since the output signal of is applied to the rough rolling mill group D, the speed of the rough rolling mill group D is synchronized with the speed of the drawing roll B of the continuous casting machine A.

Further, unlike the drawing speed applied to the rough rolling mill group D, a variable signal is not applied to the intermediate rolling mill group F and the finishing rolling mill group H, but a setting signal from the drawing speed setting device 9, that is, a constant signal is applied.

The speed of the rough rolling mill group D fluctuates due to fluctuations in the molten steel level in the mold 3.

Therefore, a speed difference occurs between the roughing mill group D and the intermediate rolling mill group F, and this variation occurs in the lube E between the roughing and intermediate rolling mill groups D and F.

The loop amount of the loop E is detected by the loop length detector 14e, and when this detected value exceeds the setting range of the loop length setter 16e, an output signal is generated from the speed correction circuit 17e and is added to the calculator 13e. .

The loop length is controlled to be within the set range as shown in Figure B.

Therefore, high-frequency speed fluctuations do not occur in the intermediate rolling mill group F and the finishing rolling mill group H.

Therefore, there is no need to increase the motor capacity due to unnecessary acceleration/deceleration power caused by fluctuations in the molten steel level.

Further, the loop shape formed near the finishing mill group H does not become obtrusive.

Furthermore, since the finish rolling mill group H does not cause high-frequency speed fluctuations, the cutting accuracy of the material does not deteriorate, and optimal continuous rolling is possible.

FIG. 5 shows another embodiment of the present invention, which is used in the case where the variation cannot be sufficiently absorbed in the lube E between the roughing and intermediate rolling mill groups D and F due to the machine configuration in the above-mentioned embodiment. It is effective for

The difference from FIG. 4 is that the setting signal of the drawing speed setting device 9 is directly input to the loop control circuit of the finishing rolling mill group H without going through the intermediate rolling mill group F, and the calculation of the loop control circuit of the intermediate rolling mill group F is performed. An adder circuit 8' is newly added to the input side of the circuit 13e.

With this configuration, speed fluctuations of the final finishing mill will not occur.

In other words, the variation in the output signal of the adder circuit 8' is transferred to the converter circuit 7.
The gain of the correction signal is lowered to make it smaller than the output of the adding circuit 8, and it is applied to the finishing rolling mill H, so that the lube G immediately before it can also absorb the speed fluctuation.

According to the invention described above, since the speed fluctuation of the continuous casting machine is made as small as possible,
Loop control near the finishing mill can be optimally performed without increasing the capacity of the electric rolling machine to perform acceleration/deceleration in response to speed fluctuations, making continuous rolling possible.

If continuous rolling becomes possible, a slab cast in a continuous casting machine at a temperature of, for example, 7,000°C to 800°C will be cooled to room temperature, and then rolled in a heating furnace at a temperature of, for example, 1,000°C to 12°C.
Loss of energy in heating to 00° C., scaling due to surface oxidation due to cooling and reheating, and yield when cutting the material to a certain length are improved.

Therefore, the productivity of products such as wire rods and steel bars is improved, and the cost thereof is also reduced.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing the relationship between drawing speed and time in a continuous casting machine, Fig. 2 is a block diagram showing the schematic configuration of the continuous casting machine,
FIG. 3 is a diagram showing a schematic configuration of the present invention, and FIG. 4 is a block diagram showing an embodiment of the steel bar manufacturing apparatus according to the present invention.
FIG. 5 is a block diagram showing another embodiment of the steel bar manufacturing apparatus according to the present invention. 4... Slab, 5... Drawing roll, 6... Molten steel level height detector, 7... Conversion circuit, 8, 8'... Addition circuit, 9... Speed setting device , 13e, 13g... Calculator for adding speed correction, 14e, 14g... Loop length detector, 15e, 15g... Limiter circuit,
16e, 16g...Loop length setting device, 17e, 17g
...Speed correction circuit.

Claims (1)

[Claims] 1. A drawing roll that controls the drawing speed of the slab so that the level of molten steel in the mold is constant, and at least a first rolling process that continuously rolls the slab drawn from the drawing roll without cutting it. a circuit for providing a speed standard synchronized with the slab drawing speed of the drawing roll to the first rolling mill group; and a circuit for providing the speed reference to the second rolling mill group and thereafter As a speed reference, a setting signal of a speed setter that provides a speed reference of the drawing roll is given, and the amount of loop formed in the material between the first rolling mill group and the second rolling mill group is set to a certain value. and a speed correction circuit that applies speed correction to the second and subsequent rolling mills according to the amount exceeded.