JPS6238047B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a descaling line drive device including a scale breaker and bridle rolls before and after the scale breaker.

A cold rolling mill further rolls the steel strip rolled in a hot rolling mill into a thin plate of a predetermined thickness, but since there is scale attached to the surface of the steel rolled in a hot rolling mill, before rolling it in a cold rolling mill. By removing this, the workability of cold rolling is improved, and the appearance, paintability, and workability of the cold rolled sheet are ensured. FIG. 1 shows this scale removal equipment, where 10 is a scale breaker that mechanically removes scale, and 20 is an acid (hydrochloric acid) tank that chemically removes scale. Reference numeral 12 denotes a loop car, which receives the steel strip S from a device (not shown) that unwinds the steel strip wound into a coil in a hot rolling mill, adjusts the tension, and transfers the steel strip to the bridle roll 14 on the input side of the scale breaker. Send S. scale breaker 10
Then, the steel strip S is passed through a plurality of rolls while being bent as shown in the figure, and relatively large scales are peeled off and removed by the bending. Reference numeral 16 denotes a bridle roll on the exit side of the scale breaker, which transports the steel strip coarsely descaled by the scale breaker to an acid tank 20, where fine scale is removed. 22 is a bridle roll on the outlet side of the acid tank.

In this example, the bridle rolls 14 and 16 on the inlet and outlet sides of the scale breaker consist of two rolls and three rolls, respectively, and each roll is individually driven by a motor 32, 34, 24, 26, 2, as shown in FIG. 2a.
8. Loop car 12 also has motor 3
0, and the exit bridle roll 16 determines the transport speed of the steel strip S, and the loop car 1
2 and the entrance bridle roll 14 pull the steel strip S to apply tension to it. The exit bridle roll 16 overcomes this tension and drives the steel strip S to send it to the acid tank 20 at a predetermined speed, but the scale breaker 10 generates dust due to descaling, and water is sprinkled to avoid this scattering. Therefore, the friction coefficient of the steel strip S decreases, and slips are likely to occur on the exit bridle roll 16.

If one of the exit bridle rolls slips, the drive motors of the remaining two rolls will carry the full load and may become overloaded. Figure 2b shows the current changes in each motor when the center roll slips.When the center roll slips at time _t0 , the current in the drive motor 26 decreases rapidly, and the drive motor 26 instead drives the left and right rolls. Motor 24, 2
The current at No. 8 increases rapidly, and the overload relay is activated, causing the power to be cut off (tripped). The load on the exit bridle roll 16 includes the power required by the scale breaker 10 in addition to the above-mentioned steel strip tension. In Fig. 3, the horizontal axis represents the scale brake inlet tension, the vertical axis represents the required power of the exit bridle roll 16, and the required power is illustrated using the thickness and rolling reduction of the steel strip to be scaled as parameters. In the graph, as the rolling reduction (the amount of thrust of the roll of the scale breaker) and the plate thickness increase, the curve changes in the order of C1, C2, . . . and the required power increases. Slips and motor trips are more likely to occur when the power is increased.

To prevent tripping, increase the motor capacity,
Possible options include dulling the exit bridle roll and controlling the reduction of the scale breaker. However, although it is effective as a trip countermeasure,
Equipment costs are high, especially due to dulling (roughening)
There is a problem in that the surface of the steel strip is scratched by the rolled rolls. Otherwise, the response is slow and therefore not very effective as a trip countermeasure, and it is necessary to install an electric valve.

The present invention aims to provide quick control response and low equipment costs, and the tension of the incoming bridle roll is adjusted according to the load on the outgoing bridle roll to prevent the tripping of the outgoing bridle roll drive motor. This is what we are trying to prevent.

The present invention is equipped with a scale breaker and its inlet and outlet bridle rolls. In a descaling line drive device that is equipped with a control device that controls the tension of The present invention is characterized in that it includes a circuit that outputs a signal for reducing the current of the entry side bridle roll drive motor to the control device of the entry side bridle roll drive motor when a set value is exceeded. Explain.

FIG. 4 shows an embodiment of the present invention, in which the same parts as in FIGS. 1 and 2 are given the same reference numerals. 3
Reference numeral 6 denotes a current control circuit for the drive motor 30 of the loop car 12, which controls the motor current and thus the tension of the steel strip S to a value set by a potentiometer 38. Reference numeral 40 denotes a current control circuit for the drive motors 32 and 34 of the entry side bridle roll 14, which controls the motor current and thus the tension of the steel strip S to a value set by a potentiometer 42. Exit bridle roll 1
The currents of the six drive motors 24, 26, and 28 are taken out by a current detector 44, and the maximum current is taken into a control circuit 48 by a diode 46. The details of that part are shown in FIG. That is, the control circuit 48 receives the output of the isolation amplifier 50 that outputs the maximum value, and produces an output when the output exceeds the value set by the set value 52 (it includes a comparator 54. The input circuit and the feedback circuit are equipped with capacitors to perform PID control, and the feedback circuit is equipped with anti-parallel diodes to control the output to a predetermined value.

The output of the control circuit 48 is applied to a subtracter 56, and when the maximum current of the motors 24, 26, 28 exceeds the setting value of the setting device 52, the current setting value of the drive motor of the entry side bridle roll 14 by the potentiometer 42 is changed. reduce Therefore, when a slip occurs and an overcurrent flows through the drive motor of a roll that does not cause slipping, the tension of the entry bridle roll is immediately reduced, the overcurrent is prevented, and a motor trip is avoided.

The subtracter 56 is composed of an adder as shown in FIG. separated from
The current reference value set by the potentiometer 42 is output. When the comparator 54 produces an output (the output terminal becomes low level), the diode 58 turns on, and the input voltage of the adder 56 decreases, causing the output voltage to decrease. The degree is set by the potentiometer 60. Note that 62 in FIG. 7 indicates the motor 24,
The power supply for 26 and 28 consists of a thyristor and its gate control circuit.

Figure 5 shows the tension of the incoming bridle roll (2Br) 14 versus the outgoing bridle roll (3Br) 16.
This is a graph showing the required power using plate thickness and rolling reduction as parameters, and the curves C1, C2, C3, C4
This is the case when the plate thickness and/or reduction increase in this order. Reducing the tension on 2Br will reduce the required power on 3Br and avoid motor trips.

Note that 64 in FIG. 4 is a speed control circuit for the drive motors 24, 26, and 28 of the exit bridle rolls, which controls the speed of the steel strip S to a value set by the setting device 66. Reference numeral 68 is an adder, which inputs the output of the detector 70 that detects the suspended state (catenary) of the steel strip S in the acid tank 20 together with the output of the setter 66, and adjusts the suspended state of the steel strip S to a predetermined value. produces an output that modifies the speed of the exit bridle roll so that it is maintained. FIG. 6 shows a specific example of a circuit for taking out the motor current, which includes a resistor 72 that receives the motor current and produces a voltage drop proportional to it, a potentiometer that takes out part of the voltage drop, and a diode 76.

As explained above, in the present invention, when the bridle roll on the outlet side of the scale breaker slips and the motor current on the healthy side becomes excessive, motor trip is prevented by reducing the tension of the inlet bridle roll. Rapidly responsive control can be performed, and only a relatively simple control circuit needs to be added, so an increase in equipment costs can be avoided.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams and graphs showing characteristic examples of the descaling line, FIG. 4 is an explanatory diagram showing an example of the present invention, and FIG. 5 is a graph for explaining the characteristics.
6 and 7 are circuit diagrams showing details of a part of FIG. 4. In the drawing, 10 is a scale breaker, 14 is an inlet bridle roll, 32 and 34 are drive motors thereof, 40 is a control device thereof, 16 is an outlet bridle roll, 24, 26, and 28 are drive motors, 6
4 is a control device thereof, 46 and 50 are maximum value detection circuits, and 52 and 54 are circuits that output a current reduction signal.

Claims (1)

[Claims] 1. A scale breaker and its inlet and outlet bridle rolls, and the drive motor of the outlet bridle roll is connected to a control device for controlling the steel strip transfer speed to a predetermined value, and also drives the inlet bridle roll. The motor is a descaling line drive device that is equipped with a control device that controls the tension of the steel strip to a predetermined value, and includes a circuit that detects the maximum current of each drive motor of the exit bridle roll, and an output from this circuit. A drive device for a descaling line, comprising a circuit that outputs a signal to a control device for an input bridle roll drive motor to reduce the current of the input bridle roll drive motor when the maximum current value exceeds a set value.