JPS6216257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the catenary amount of a strip when the strip is continuously heated in a catenary manner.

As shown in Fig. 1, a method for continuously heating the strip is to sequentially join the joint _S0 between the end of the leading strip _St1 and the tip of the trailing strip _St2 by welding, etc., and then heat the strip continuously in a heating furnace. There is a method of supplying it into a chamber and heating it.

If the amount of catenary in the heating furnace is too small, the tension applied to the strip will be excessive, which may cause abnormal elongation or breakage of the strip, and if it is too large, the strip may come into contact with the hearth and cause scratches on the surface. There is. Furthermore, if the inside of the furnace is made large to prevent contact with the hearth, fuel will be wasted to raise the temperature of the furnace. Furthermore, there is a difference in temperature between the area immediately adjacent to the heating burner and the area further away from the heating burner, making it difficult to make the temperature distribution within the furnace uniform. Therefore, variations in the amount of catenary cause variations in the temperature rise history of the strip, which poses a problem in terms of quality stabilization. For this reason, the size of the heating furnace must be as small as possible to allow for the amount of catenary that does not apply excessive tension to the strip. It must be controlled so that the sheet does not come into contact with the heating burner and always passes at a certain distance from the heating burner.

By the way, the conventional method of controlling the catenary amount at a constant level is to press a roll equipped with a load cell or the like against the strip, indirectly measure the tension of the strip, and use this value to control the torque of the bridle roll 3 or 4 in Fig. 1. Alternatively, the catenary amount of the strip S is directly detected by the catenary amount detector 2 attached to the heating furnace 1 shown in FIG. (in this case, the speed of the exit bridle 4 is fixed at a constant value) to control the catenary amount at a constant value.

However, if the cross-sectional area, that is, the plate thickness and plate width, differ between the leading strip St ₁ and the trailing strip St ₂ with the strip junction S ₀ as the border, as shown in Fig. 2 B and C, the catenary detection point If the catenary amount is controlled as described above using the catenary amount at P, the following problems will occur.

In other words, A in Fig. 2 shows the catenary formation situation when the leading strip St ₁ and the trailing strip St ₂ have the same cross-sectional area, B shows the catenary formation situation when the leading strip St ₁ has a large cross-sectional area, and C shows the catenary formation situation when the leading strip St ₁ has a large cross-sectional area. shows the catenary formation situation when the cross-sectional area is small. First, in case (b), if the catenary amount at the catenary amount detection point P is controlled to be constant, the amount of catenary in the preceding strip St ₁ will become excessive, causing the strip to come into contact with the bottom of the furnace or causing a temperature change, resulting in poor quality. It causes In case C, on the other hand, the tension in the preceding strip _St1 becomes excessive, causing the strip to break.

The present invention provides a method for controlling the amount of catenary that solves these problems.

The catenary quantity is given by the following formula.

y≒ρl ² /8u where ρ is the density of the strip, l is the distance between the strip support points, u is the unit tension applied to the strip,
y indicates the catenary amount. Here, if ρ and l are constant, y≈k1/u (k is a constant).Therefore, the catenary amount y is inversely proportional to the unit tension u. Here, since the unit tension changes depending on the cross-sectional area,
The difference in catenary amount between the leading strip and the trailing strip is Δy=t×S ₁ /S ₂ . Here, Δy is the difference in catenary amount between the leading strip St ₁ and the trailing strip St ₂ , S ₁ is the cross-sectional area of the leading strip, S ₂ is the cross-sectional area of the trailing strip, and t is the reference catenary at the catenary detection point. Indicate quantity. Note that the standard catenary amount is 1/2 of the total amount of the maximum catenary amount and minimum catenary amount allowed.

From the above, in order to maintain the catenary amount or tension value of the preceding strip St ₁ within an appropriate range, it is necessary to correct the reference catenary amount at the catenary detection point P. By correcting the reference catenary amount by 1/2 of the difference Δy in the catenary amount between the leading strip St ₁ and the trailing strip St ₂ , that is, Δy/2, each catenary amount can be made to be approximately equal to the reference catenary amount. I can't stand it. That is, in case (b) of FIG. 2, the catenary amount of the trailing strip St ₂ is made smaller than the reference catenary amount by Δy/2, and in case (c), it is made larger by Δy/2.

As described above, the standard catenary amount is corrected at the point where the strip joint _S0 enters the entrance side of the furnace, and is returned to the original standard catenary amount at the point where the strip joint S0 exits the furnace.
The position and cross-sectional area of the joint of the strip may be set manually, but it can be easily realized by tracking the position of the joint and automatically inputting it using a computer or the like.

FIG. 3 shows the relationship between the position of the correction junction S ₀ and the catenary reference amount correction value.

FIG. 4 is an example of a circuit for implementing the present invention. The data of the cross-sectional area S ₁ of the preceding material St ₁ is input in advance to the memory circuit 11, and the data of the cross-sectional area S ₂ of the succeeding material St ₂ is input in advance to the memory circuit 12. Comparison circuit 1
In 3, the cross-sectional areas of the preceding material and the succeeding material are compared using the data S ₁ and S ₂ , and the catenary correction amount Δ, which will be described later, is calculated.
It is determined whether y/2 (=t/2·S ₁ /S ₂ ) is added or subtracted from the reference catenary amount. 1
A divider 4 calculates S ₂ /S ₁ , and a divider 16 calculates t/S from the signal of the reference catenary setter 15.
This is to perform the calculation of 2. Multiplier 17 calculates the catenary correction amount Δ from the output signals of dividers 14 and 16.
The calculation is y/2=t/2·S ₁ /S ₂ .

On the other hand, when the weld reaches the inlet of the heating furnace from the tracking signal of the weld, the signal sets the flip-flop 18 and opens the gate circuit 19, and the multiplier output signal 17 is added to the reference catenary signal by the adder 20. Ru. Reference numeral 24 denotes a sign inversion circuit which is turned ON by the signal calculated by the comparison circuit 13, that is, when S ₁ >S ₂ , the catenary correction amount is subtracted from the reference catenary command value. Conversely, if S ₁ > S ₂ , the side is turned on and becomes positive. The revised reference catenary amount command value is sent to the rotation speed controller 21 for catenary control.
The rotational speed of the motor 23 that drives the entry side bridle 25 is changed based on the deviation signal from the signal from the catenary amount detector 22, thereby correcting the catenary amount.

When the welding part signal reaches the outlet side of the furnace, the flip-flop 18 is reset and the gate circuit 19 is closed, so that the output of the adder 20 is the reference catenary command value as it is. The output from the adder 20 is input to the catenary control rotation speed controller 21, and the motor 2 drives the entry side bridle 25 based on the deviation signal from the catenary amount detection signal 22.
The rotation speed of 3 is changed to control the reference catenary amount.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing how the strips are connected and passed through a heating furnace; Fig. 2 A, B, and C are schematic diagrams showing how the leading and trailing strips are formed as catenaries;
The figure is a chart showing the relationship between the correction joint position and the catenary reference amount correction value, and FIG. 4 is an example of a circuit for implementing the present invention. St ₁ ... Leading strip, St ₂ ... Trailing strip,
_S0 ...Joint part, 1...Heating furnace, 2...Catenary amount detector, 3, 4...Bridle roll, 11, 12...Memory circuit, 13...Comparator, 14, 16...Divider, 1
5... Reference catenary setter, 17... Multiplier, 18
...Flip-flop, 19...Gate circuit, 20...
Adder, 21... Rotation speed controller for catenary control,
22... Catenary amount detector, 23... Motor, 24
...Sign inversion circuit.

Claims (1)

[Claims] 1. When a strip passes through a heating furnace forming a plurality of catenaries, and the leading strip and the trailing strip have different cross-sectional areas, each catenary is A strip catenary control method characterized by controlling the amount of catenary.