JPS6116522B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for continuously cold rolling a steel strip (hereinafter simply referred to as a strip). It is generally known that the total cost of strip rolling, which consists of hot rolling, pickling, and cold rolling, decreases as the thickness of the hot rolled steel sheet, which is the original sheet for cold rolling, increases. However, as the thickness of the hot-rolled steel sheet increases, (1) the bite angle in the roll bite increases, and as a result, the bite into the work rolls of the cold rolling mill row becomes worse, resulting in scratches on the rolls and strips. It is more likely to occur. (2) There is an increased possibility that the thin-walled portion of the strip will break due to the increased tension between the stands in the cold rolling mill row. (3) The rolling load per stand in the cold rolling mill row increases, and the flatness of the strip decreases. There are other problems. For this reason, the present inventors have proposed adding a cold rolling mill capable of high reduction rolling in one pass, and making the continuous cold rolling mill row and the high reduction cold rolling mill completely continuous for rolling. An attempt was made to perform rolling by installing the high-pressure cold rolling mill in front of the continuous pickling device. Usually, in a high-reduction rolling mill, the reduction rate is large, so the rolling load increases, resulting in a large increase in the power consumption of the rolling mill and a decrease in strip flatness due to deflection of the work rolls. Therefore, in order to reduce power consumption and rolling load, it is necessary to reduce the diameter of the work roll, but when conventionally performing high rolling by reducing the diameter of the work roll, the neutral point position during rolling changes. As a result, rolling becomes unstable, causing a so-called chattering phenomenon, and furthermore, rolling becomes impossible, which poses a major problem not only in terms of rolling efficiency but also in terms of quality and cost. One way to eliminate this chattering phenomenon during high-pressure rolling has been considered to be to increase the friction coefficient between the strip and the rolls, but an increase in the friction coefficient increases the rolling load, which in turn leads to power consumption. The disadvantage was that it increased. The present invention solves the above-mentioned problems in conventional strip rolling under high pressure, and aims to provide a strip rolling method that can improve rolling workability, product quality, and reduce costs. be. Hereinafter, the present invention will be explained in detail based on preferred embodiments with reference to the drawings. The present invention reduces the diameter of the work rolls of a cold rolling mill capable of high reduction rolling, which is installed in front of a pickling device or in front of a row of continuous cold rolling mills, to an appropriate range in order to reduce the rolling load. , and in order to prevent chattering during rolling, the tension of the strip on the exit side of the rolling mill is set within an appropriate range. FIG. 1 is a diagram showing an example of the configuration of equipment for implementing the method of the present invention. In FIG. 1, the leading end of a hot-rolled steel sheet 11 rewound by an unwinding machine 1 is welded to the rear end of a preceding hot-rolled steel sheet 12 in a welding machine 2.
The thickness of the hot rolled steel plate 11 is larger than the conventional thickness of 2 to 6 m/m, and can be approximately 6 to 10 m/m. The hot rolled steel sheet 12 is then sent to a high reduction rolling mill 4 via a strip storage device 3, where it is cold rolled at a rolling reduction of 50 to 90%. The high-reduction rolling mill 4 is a rolling mill capable of achieving a rolling reduction of 90% in one pass, and for example, a high-reduction single-row multi-stage cold rolling mill such as a 6-high rolling mill is used. Note that the strip storage device 3 is made of a generally widely used looper.
The hot-rolled steel plates 12 connected by the welding machine 2 are continuously supplied. Therefore, by providing the welding machine 2 and the strip storage device 3, it is possible to make the pickling device 7 and the cold rolling mill row 9 following the high-reduction rolling mill 4 completely continuous. Following the above-mentioned high-reduction rolling, the intermediate-rolled strip 13 is pickled in a pickling device 7, and then continuously rolled to the required dimensions in a cold rolling mill row 9 at a total rolling reduction of 60 to 80%. Ru. A strip storage device 6 provided between the high-reduction rolling mill 4 and the pickling device 7 is provided to continuously supply strip to the pickling device 7 even when the high-reduction rolling mill 4 is stopped. In addition, a strip storage device 8 provided between the pickling device 7 and the cold rolling mill row 9 prevents the strip from stopping in the pickling device even if the strip stops in the cold rolling mill row 9. It's there to prevent. In the present invention, in order to particularly reduce the power consumption during high-reduction rolling, the diameter of the work roll of the high-reduction rolling mill 4 is reduced to an appropriate range, and a tension adjustment device 5 is provided on the exit side of the high-reduction rolling mill 4. There is. The tension adjustment device 5
These are provided to prevent chattering during rolling in the high-pressure rolling mill 4, and use known devices such as pinch rolls and bridle rolls. Next, details of the method of the present invention will be explained based on FIGS. 2 and 3. FIG. 2 is a graph showing the relationship between the reduction rate in one pass in cold rolling, the diameter of the work roll, and the rolling load per unit width of the strip.
The present inventors have found that from the viewpoint of the shape of the strip after rolling, the bearing strength of the auxiliary roll, etc., it is desirable that the rolling load per unit width of the strip is 1.5 ton/mm or less. Therefore, according to Fig. 2, when performing high reduction rolling with a reduction rate of 90% in one pass, the rolling force per unit width of the strip is 1.5 tons/
In order to make it less than mm, the diameter of the work roll is 350 mm.
Must be less than mm. On the other hand, in order to prevent the occurrence of chattering, it is generally known to increase the tension of the strip at the exit side of the rolling mill, the so-called front tension. However, simply increasing the tension value causes problems such as a significant increase in equipment costs for the tension adjustment device, tension in the strip, and increased horizontal deflection of the work roll. As a result of various experiments, the present inventors have discovered that there is a relationship between rolling conditions and the occurrence of chattering as shown in FIG. 3. The group of curves in the figure is the rolling reduction rate of 20, 30, ...90 in one pass.
The unit tension at the exit side of the rolling mill required to prevent the occurrence of chattering in each case is shown in relation to the diameter of the work roll. It can be seen from FIG. 3 that when the rolling reduction ratio is increased or when the work roll diameter is decreased, the unit tension at the exit side of the rolling mill 4 must be increased in order to prevent chattering. It can be seen from the figure that when the upper limit of the work roll diameter is 350 mm, the unit tension of the strip at the exit side of the rolling mill must be 12 Kg/mm ² or more, for example, if the rolling reduction is 50% or more. In addition, the present inventors have found that when the unit tension of the strip at the exit side of the rolling mill exceeds 30 Kg/mm ² , plate breakage due to strip tension frequently occurs. Therefore, as shown in Figure 3, in order to prevent the occurrence of chattering even when the unit tension of the strip at the exit of the rolling mill is 30 kg/ ^mm2 or less and the rolling reduction is 90% in one pass, it is necessary to adjust the diameter of the work roll. is 100
mm or more is required. When the group of curves in Figure 3 is expressed mathematically, the approximate value is σmin = (-0.025D + 0.25R + 8.75) (where σmin: lower limit value of the unit tension at the exit side of the rolling mill (Kg/mm ² ), D: work roll Diameter (m/m) R:
Reduction rate (%)). As described above, when rolling a strip by increasing the reduction rate in one pass with a high-reduction rolling mill, the tension of the strip at the exit side of the rolling mill is set within an appropriate range, and the diameter of the work roll is selected within an appropriate range. This makes it possible to perform high reduction rolling without causing chattering or increasing power consumption during high reduction rolling. Table 1 shows an example of specific working conditions of the present invention. The method of the present invention and the comparative method have the same conditions other than the exit tension of the high-pressure rolling mill, but in the method of the invention, chattering is eliminated by setting the exit tension within an appropriate range. I understand that.

[Table] Figures 4 to 6 show various examples of equipment configurations for carrying out the method of the present invention. The same reference numerals as in FIG. 1 indicate the same devices. The equipment configuration shown in FIG. 4 is such that a hot-rolled steel sheet rewound and sent from an unwinding machine 1 is rolled in a high pressure rolling mill 4, pickled in a pickling device 7, and then once passed through a winding machine 14.
The strip is wound up by the unwinder 15, and then the strip 13 is
The structure is such that the material is rewound and then rolled to a required size in a cold rolling mill row 9. The equipment configuration shown in FIG. 5 pickles a hot-rolled steel plate in a pickling device 7 and then rolls it in a high-pressure rolling mill 4.
Subsequently, it is configured to be rolled to the required dimensions in a cold rolling mill row 9. In addition, in the equipment configuration shown in FIG. 6, after pickling the hot-rolled steel plate in the pickling device 7, the hot-rolled steel plate 12 is once wound up in the winder 14, and then the hot-rolled steel plate 12 is unwound in the unwinding machine 15. The material is then passed through a welding machine 17 and a storage device 16, then rolled in a high reduction rolling mill 4, and then further rolled into a required dimension in a cold rolling mill row 9.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the equipment configuration for carrying out the present invention, Fig. 2 is a graph showing the mutual relationship between rolling reduction, work roll diameter, and rolling load, and Fig. 3 is a strip diagram showing the limit of chattering. Graphs showing the mutual relationship between forward tension, work roll diameter, and rolling reduction ratio, and FIGS. 4, 5, and 6 are schematic diagrams showing other examples of equipment configurations for carrying out the present invention. 1,15... Rewinding machine, 2,17... Welding machine,
3, 6, 8, 16... strip storage device, 4...
...High reduction rolling mill, 5... Tension adjustment device, 7... Pickling device, 9... Cold rolling mill row, 10, 14... Winding machine, 11, 12... Hot rolled steel plate, 13... Intermediate rolling strip.

Claims (1)

[Scope of Claims] 1. A hot-rolled steel plate rewound from an unwinding machine is rolled in a high-reduction single-row multistage cold rolling mill capable of rolling up to a maximum reduction rate of 90% in one pass, and then subjected to descaling treatment. Alternatively, in the manufacturing process of steel strip, the steel strip is rolled in a high-reduction single-row multi-stage cold rolling mill capable of rolling to a maximum reduction of 90% in one pass after descaling treatment, and then further rolled in a continuous cold rolling mill. When the rolling reduction rate of the high-reduction single-row multi-stage cold rolling mill is in the range of 50 to 90%, the work roll diameter of the high-reduction single-row multi-stage cold rolling mill is set to 100 to 350 mm, and the steel plate on the exit side of the rolling mill is The unit tension is the following formula: σmin = (-0.025D + 0.25R + 8.75) {However, σmin: Lower limit of unit tension (Kg/mm ² ),
R: rolling reduction ratio (%) in the high-reduction cold rolling mill, D: diameter of the work roll of the high-reduction rolling mill (mm)} Rolling should be carried out so that the rolling ratio is greater than or equal to the value calculated by: 30 kg/mm ² or less A method for cold rolling steel strips characterized by: