JPH0584515A - Method for preventing coil tightening flaw of strip in temper rolling - Google Patents

Abstract

PURPOSE:To prevent the coiling slip of a coil and to prevent the generation of recoiling flaw by applying the prescribed pressure to this coil with a roll in the time of recoiling. CONSTITUTION:In the time when a coil 1 is recoiled from a mandrel 13 of a pay-off reel supplying the coil to the temper rolling mill, the recoiling flaw can be surely prevented and the product yield of cold rolled steel sheet product can be improved by the simple means pressurizing the strip S from the outer circumference with a roll 2 and applying the load W.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing the occurrence of surface flaws on a coil unwound from a payoff reel when temper-rolling an annealed cold rolled steel sheet.

[0002]

2. Description of the Related Art In the process of manufacturing cold-rolled steel sheets (cold strips), the elongation of 0.3-
It is lightly temper-rolled by about 3.0%. In this temper rolling process, the strip wound in the previous process is installed on the pay-off reel, and is unwound (rewound) from here.
It is then supplied to the temper rolling mill.

When the above-mentioned pay-off reel is unwound, a flaw called winding tight flaw occurs on the surface of the strip. This is because the coil winding slips loosely when it is unwound, so-called winding deviation occurs, and the strip surfaces rub against each other. This phenomenon tends to occur particularly in the case of a large-diameter coil, which causes a decrease in product yield.

As a method for preventing winding tightening flaws that occur in the temper rolling step, the coil winding tension is increased in the pre-annealing step, the coil is appropriately seized during annealing, and the seizure force is used. There is a method to prevent slip. Further, there has been taken a means of increasing the expanding pressure of the mandrel of the pay-off reel and increasing the surface pressure between the strips to increase the frictional force to prevent winding deviation.

However, if the tension is increased in the coiling process in the pre-annealing step, the coil may seize more than necessary, which may cause a decrease in the yield of the product. Further, when the mandrel expansion pressure of the pay-off reel is increased to increase the surface pressure to prevent winding tightening flaws, a reel mark is generated, which also causes a decrease in yield. That is, there are drawbacks in the techniques for preventing winding-tightening flaws that depend on the adjustment of the winding tension and the expanding pressure of the mandrel, and their effects are limited.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of preventing the occurrence of winding tightening flaws in the temper rolling process of a cold rolled steel sheet relatively easily. It is to provide a method without such drawbacks.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a strip winding tightening flaw characterized in that, when a coil is unwound from a pay-off reel for supplying the coil to a temper rolling mill, the strip is pressed from the outer periphery by a roll. Prevention method "is the gist.

FIG. 1 is a schematic side view of a coil unwinding portion for explaining the concept of the method of the present invention.

As shown in the figure, in the method of the present invention, when the coil 1 is unwound from the mandrel 13 of the payoff reel, the strip S is pressed from the outer periphery by the roll 2 and the load W is applied.
It is characterized by adding.

[0010]

[Operation] The force applied to the coil during unwinding is the unwinding tension,
Centrifugal force and own weight. From these, the shear force F between the strips and the surface pressure N can be calculated in the coil radial direction. If the friction coefficient between the strip surfaces at this time is μ, then μ = F / N, but when this μ exceeds the static friction coefficient μ ′ (constant), winding deviation occurs.

Even when μ has a negative value, N is negative, that is, the surface pressure is 0, so that winding deviation occurs.

Coefficient of static friction between ordinary cold-rolled steel sheets (μ ')
Was found to be approximately 0.2. When the above μ exceeds this μ ′ (≈0.2), slip occurs and winding tightness flaws appear. Therefore, in the method of the present invention, as shown in FIG. 1, the load W is applied to reduce the value of μ, and unwinding is performed in a state where μ ≦ μ ′ is always satisfied.

When a load W is applied by a roll as shown in FIG. 1, μ = F / (N + W). So this W
The calculation for obtaining the appropriate value of The calculation conditions are shown in Table 1 and the calculation results are shown in FIG.

[0014]

[Table 1]

The horizontal axis of FIG. 2 is the radial position (mm) from the center of the coil, and the vertical axis is the calculated value of the friction coefficient μ.

FIG. 2A shows the case where no pressure is applied by the roll, that is, W = 0. (B) is 15 kgf per unit length (1 mm width) by pressurization, and (c) is 25
When a load of kgf is applied, respectively (a)
Both (b) and (c) show the state 16 seconds after unwinding, that is, immediately after the steady rolling speed is reached. As for (a), the coefficient of friction μ exceeds 0.2 or is negative in the range of the coil radial position of 550 to 850 mm (coil winding height is 300 to 600 mm). It turns out that occurs. In the case of (b), this range is reduced to 620 to 800 mm by pressurization, and in the case of (c), μ is 0.2 or less over the entire area.

Under this calculation condition, the pressing force per unit width is 25
It can be seen that when a load W of kgf / mm is applied, the friction coefficient μ is always smaller than 0.2, and winding tightness disappears. If this load is concentrated and applied to a width of 100 mm, 25 kgf / mm
× 100mm = 2.5ton.

Next, an example of an apparatus for carrying out the method of the present invention will be described with reference to FIGS.

FIG. 3 is a side view of the payoff device, and FIG.
FIG. 7 is a horizontal sectional view taken along the line AA ′ of FIG.

As shown, the pressure roll 2 includes a bearing 3,
It is rotatably supported by 3 ', and the bearings 3, 3'are fixed to the pressure support plate 4. Guide receivers 8 and 8'are provided at the corners of the pressure support plate 4, and the guides 5 and 5'are provided.
It can be moved up and down by sliding with. Guide 5, 5 '
Is fixed to the columns 10 and 10 'by fixing plates 9 and 9'.
10 and 10 'are fixed to the floor through bottom plates 11 and 11'. The upper portions of the columns 10 and 10 'are connected by an upper structure 12, and a hydraulic cylinder 7 is attached to the upper structure 12.

A tip end portion which moves up and down by the hydraulic pressure of the hydraulic cylinder 7 is fixed to the pressure support plate 4 by a bolt 6. The pressure roll 2 is in contact with the upper surface of the coil 1, and the coil 1 is rotatably supported by the tension reel mandrel 13.

When a predetermined hydraulic pressure is applied to the cylinder 7 by a hydraulic pressure generator (not shown), a downward force is applied to the pressure support plate 4 fixed to the cylinder 7. The force is transmitted to the pressure roll 2 through the bearings 3 and 3'and presses the upper surface of the coil 1. When the coil diameter is reduced by unwinding the strip, the pressure support plate 4 descends while being kept horizontal by the sliding of the guides 5 and 5'and the guide receivers 8 and 8 '. The pressing pressure during is kept constant.

Although hydraulic pressure was used as the pressure source here,
Other methods are also conceivable, for example reduction using pneumatic cylinders or electric screws. However, considering that the total load is several tons, pneumatic pressure is too small and electric screw is too large, so hydraulic pressure is still desirable.

The stroke of the pressurizing cylinder does not need to be so long, and about 300 mm is sufficient. This is because winding tightening becomes less likely to occur rapidly as the coil diameter decreases. For example, according to the calculation under the conditions in Table 1 above,
When the outer radius of the coil is reduced to 1 m, no tightening occurs even without pressure. This is because the centrifugal force due to the rotation is small.

The material of the pressure roll is not particularly limited,
It is desirable to use a roll made of a soft elastic material such as rubber because a hard material may damage the coil.

Although the apparatus shown in FIGS. 3 and 4 has one pressure roll, as shown in FIG.
Books (2 and 2 ') may be provided. In this case, the load of one roll is halved, and there is an advantage that the risk of pressing flaws caused by the roll is reduced.

The method of the present invention can be used in combination with the method utilizing the expanding pressure of the mandrel diameter. Even in that case, since the expansion pressure can be reduced, there is no possibility that a reel mark will occur.

[0028]

Example 1 The apparatus shown in FIG. 3 was operated under the conditions shown in Table 2.

In the example of the present invention, the pressure roll has a diameter of 100 m.
Using a rubber roll with m and body length of 100 mm,
The pressure was kept constant at 2.5 tons and pressure was applied until the coil diameter decreased from the initial diameter to 1 m. No pressure was applied in the comparative example.

After the above operation, winding tightness flaws were detected by unwinding on the inspection line.

The results are also shown in Table 2. As shown in the table, according to the method of the present invention, the tightening of the winding is eliminated and the flaws on the coil surface can be completely prevented.

[0032]

[Table 2]

[0033]

According to the method of the present invention, the unwinding flaw can be surely prevented by a relatively simple means of applying a predetermined pressure to the strip by the roll when the coil is unwound.
This method largely contributes to the improvement of product yield when manufacturing cold-rolled steel sheet.

[Brief description of drawings]

FIG. 1 is a schematic side view of a coil unwinding portion for explaining the concept of the method of the present invention.

FIG. 2 is a diagram showing a calculation result for estimating the occurrence state of coil tightening.

FIG. 3 is a side view showing an example of a payoff device used for carrying out the method of the present invention.

FIG. 4 is a horizontal sectional view taken along the line AA ′ of FIG.

FIG. 5 is a side view showing another example of the payoff device used for carrying out the method of the present invention.

[Explanation of symbols]

S: strip, 1: coil, 2 and 2 ': pressure roll, 3 and 3': bearing, 4: pressure support plate, 5 and 5 ':
Guides, 6: Bolts, 7: Hydraulic cylinders, 8 and 8 ': Guide receivers, 9 and 9': Fixing plates, 10 and 10 ': Posts, 11 and 11': Bottom plates, 12: Superstructure, 13: Mandrel

Claims (1)

[Claims] 1. A method for preventing wound tightening defects of a strip, characterized in that when the coil is unwound from a pay-off reel for supplying the coil to a temper rolling mill, the strip is pressed from the outer periphery by a roll.