JPH0253122B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method of rolling metal strip. A method is known in which three or more work rolls are arranged in a row to form two or more rolling passes, and the material is passed through these rolling passes continuously to roll a strip (one-stand multi-pass rolling method). It is being During rolling, the strip is wrapped approximately half a circumference around the work roll. In this rolling method, one rolling stand can perform rolling for a plurality of rolling stands, so there is an advantage that the entire rolling equipment can be downsized and the equipment cost can be reduced. When rolling a strip using a plurality of rolling stands arranged in tandem, the strip may break due to tension. Therefore, it is necessary to suppress the tension applied to the strip to a low value (for example, 20 kg/mm ² or less). On the other hand, if the tension is too low, the strip will sag when wrapped around the work roll. When the slack of the strip increases, the strip moves (walks) in the width direction. As the sagging progresses further, the strip overlaps in wrinkles and passes through the roll gap, resulting in so-called squeezing, and eventually the strip breaks and becomes unrollable. Furthermore, as the rolling reduction rate increases, sagging of the strip becomes more likely to occur. This invention was made to solve the above-mentioned problems in the one-stand multi-pass rolling method, and it is possible to prevent the strip from sagging when wound around the work roll and to stably roll the strip under high pressure. The object of the present invention is to provide a strip rolling method that is possible. In the strip rolling method of the present invention, the strip is rolled in one-stand multi-pass rolling using work rolls whose surface roughness becomes progressively rougher as the roll position moves closer to the exit side of the rolling machine. As described above, if the work roll closer to the exit side (downstream side) of the rolling mill has a rougher surface, the friction force between the strip and the roll will be greater as the strip wraps around the work roll closer to the downstream side. As a result, the strip is placed under tension by the downstream work roll. Therefore, even if the tension applied to the strip is quite low, the winding of the strip around the work roll will not slacken. In the present invention, as described above, since the winding of the strip is difficult to sag, the strip can be stably rolled even under a high rolling reduction ratio. This invention will be explained in detail below. FIG. 1 schematically shows the roll arrangement of a one-stand n-pass rolling mill. Work roll 1,
_{2 .} Backup rolls 11 and 12 are arranged above and below the work roll row. The strip S is rolled in each rolling pass _P1 ...Pn while being wound around the work rolls 2...n approximately semicircularly. In the above roll configuration, if the surface roughness (root mean square roughness) of the roll surface of work roll 1...n+1 is R ₁ and R ₂ ...Rn ₊₁ , respectively, then Rn ₊₁ >Rn>...>R The roll surface is processed so that it is ₁ . The difference in surface roughness between adjacent work rolls is 0.01μ
It is desirable that it is more than m. If the difference in surface roughness between the two work rolls is too small, there is a risk that the strip will sag. On the other hand, if the difference in surface roughness is too large, the surface roughness of work rolls n and n+1 on the exit side of the rolling mill will become extremely rough, which will impair the surface quality of the product strip. The upper limit of the difference in surface roughness is determined by the required surface quality of the strip. FIG. 2 is a diagram showing an example of the relationship between the surface roughness of the work roll, the rolling reduction, and the slack of the strip. The rolls of the test rolling mill were arranged to form three rolling passes, and the surface roughness of each work roll is shown in Table 1.

【table】 Further, rolling conditions are shown in Table 2.

[Table] As is clear from Fig. 2, in the case of Control Examples (A) and (B), the strip sagged relative to the work roll when the rolling reduction rate was 60% or less. On the other hand, in the case of the present invention, the sagging of the strip occurs after the rolling reduction exceeds 70%.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the arrangement of rolls in one-stand multi-pass rolling, and FIG. 2 is a diagram showing the relationship between roll surface roughness, rolling reduction, and occurrence of strip sag. 1, 2 to n-1, n, 21 to 24... Work roll, 11, 12... Back up roll.

Claims (1)

[Claims] 1. A method in which multiple work rolls are arranged, a metal strip is wound around the work rolls and passed continuously, and the metal strip is rolled between a pair of adjacent work rolls, wherein the work roll position is A feature of the rolling method is that the surface roughness of the work roll is gradually increased as it approaches the exit side, and the friction force at the part where the metal strip is wound on the work roll increases as it approaches the later passes. Strip rolling method.