JPS59202104A - Manufacture of thin steel sheet having unequal thickness - Google Patents

Abstract

PURPOSE:To manufacture a thin steel sheet having unequal thickness in the width direction easily and without changing rolls by arranging rolling mills whose work rolls or intermediate ones are provided with horizontally bending functions, as hot strip finishing mills. CONSTITUTION:A thin sheet having unequal thickness in its width direction is easily manufactured without providing large crowns to work rolls and by preventing the damages of rolls, etc., by arranging rolling mills having each a function of horizontally bending the work rolls 10 by segmental backup rolls 13 through intermediate rolls 12, as the whole or a part of finishing mills for hot strip rolling, and operating said horizontal bending devices and vertical ones. Further, it is preferable to reduce a rolling reaction at the time of bending by setting the ratio; body length/body diameter of the work roll for providing the horizontal bending, to >=4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a method for producing a thin steel plate of unequal thickness having a large thickness difference in the width direction.

(Prior Art) Conventionally, thin steel sheets manufactured by hot rolling or cold rolling have been required to have a small difference in thickness, but in recent years,
For example, for steel plates used in panel parts such as automobile roofs and bonnets, the thickness ratio between the center part and the edge part of the plate should be 1.1 or more in order to reduce the weight without reducing the tension and rigidity of these panel parts. Thin plates of unequal thickness have been manufactured.

When manufacturing steel plates with such thickness differences,
As shown in FIG. 1, a method has been proposed in which negative initial crowns 2, 2 are provided on the work rolls 1, 1 so as to provide the required plate thickness ratio (Japanese Patent Laid-Open No. 54-119363
(see publication).

However, for example, when rolling a hot-rolled steel plate of unequal thickness with a finished plate thickness of 2.8 mm, the plate crown (difference between the plate thickness at the center and the plate width end plate thickness - plate thickness difference) is required to be 300μ or more.
The work roll 1 of the hot strip finishing mill must be provided with a very large negative initial crown 2, which results in very high roll grinding costs.

Further, since the work roll 1 having such a large initial crown 2 cannot be used for rolling a steel plate having a small plate crown, the work roll must be replaced each time, which reduces productivity.

In view of these points, Japanese Patent Application Laid-open No. 148403/1983 proposes a method in which a 6-layer rolling mill, which has a greater plate crown control capacity than a normal 4-layer rolling mill, is arranged in a row of finishing mills to roll steel plates with a large plate crown. We are proposing a method to do so.

However, the six-layer rolling mill with the intermediate roll shift method proposed in this proposal has a large control ability in the direction of making the plate crown smaller (concave shape direction), but the control ability in the direction of making the plate crown larger (convex shape direction) is It is comparable to a normal quadruple rolling mill.

Therefore, in order to roll a large crown with a convex cross section required for panel parts such as automobile roofs and bonnets, it is necessary to give the work roll itself a large negative initial crown, which reduces production volume. When rolling ordinary steel plates, which account for the overwhelming majority of steel sheets, a large increase bending force (pending force in the direction of pushing the chocks of the work rolls outward) is always exerted.

In this way, when rolling with a large increase suspending force applied to a work roll with a large negative initial crown, the contact surface pressure between the work roll and intermediate roll becomes very large at the roll end. When rolling large quantities of steel plates under such conditions, the risk of roll damage increases.

(Objective of the Invention) The object of the present invention is to easily produce a thin steel plate with a large concave or convex crown without the need to provide a large initial crown to a work roll, and to easily produce a thin steel plate with a large concave or convex crown. It is an object of the present invention to provide a method for manufacturing a thin steel plate of unequal thickness, which makes it possible to manufacture a steel plate without roll damage.

(Structure of the Invention) For this reason, the present invention provides that at least one work roll or intermediate roll, preferably a roll having a body length/body diameter ratio of 4 or more, is installed horizontally in all or part of a finishing mill for hot strip rolling. A rolling mill with a bending function is installed, and a horizontal bending device and a vertical bending device of work rolls or intermediate rolls are operated to manufacture thin steel sheets having unequal thicknesses in the width direction.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Examples of rolling mills having a horizontal bending function in work rolls or intermediate rolls include the 4-layer rolling mill A shown in Figure 2 (a) and the 5-layer rolling mill BI C shown in Figures 2 (b) and (C). There is a six-layer rolling mill shown in Figure 2(d).

In these rolling mills A and D, the diameter of at least one work roll 10 or intermediate roll 11 is formed to be smaller than the body length, so as to reduce the rolling reaction force during rolling.

A rolling mill having such small-diameter rolls 10, 11 is provided with a mechanism for reinforcing horizontal deflection of the rolls, which would not be a problem with normal large-diameter rolls.

For example, in the MKW mill shown in FIG. 2(a), the horizontal deflection of the work roll 10 is supported by a horizontal reinforcing roll 13 via an intermediate roll 12.

In addition, in the Taylor mill, by adjusting the friction torque between the drive intermediate roll and the small diameter work roll,
Adjusts the horizontal deflection of small diameter work rolls.

Furthermore, in the FFC mill shown in FIG. 2(b), the pressing force in the plate width direction of the horizontally divided reinforcing roll 13 is actively controlled,
Controls the plate crown or flatness of the plate. In the case of FIG. 2(C), the intermediate roll 11 is made small in diameter to adjust the horizontal deflection of the intermediate roll 11.

If the rolling mills A and D having the horizontal bending function of the work roll 10 or the intermediate roll 11 described above are used, the restraint of roll bending due to rolling pressure is smaller than in the conventional vertical bending method, so the roll bending can be made relatively small. This means that a large horizontal deflection of the work roll 10 or the intermediate roll 11 can be obtained by the force.

This amount of horizontal deflection increases as the roll diameter decreases if the roll body length is constant. That is, as shown in FIG. 3, if the limit of the amount of elastic deformation of the roll surface caused by roll deflection is constant, the smaller the roll diameter, the larger the allowable amount of roll deflection. For example, the roll body length is 2000 mm and the elastic strain is 0.03fo.

With a work roll having a roll diameter of 400 mm (body length/body diameter ratio of 5), it is possible to obtain a horizontal deflection of about 500 μ without fear of roll damage.

In addition, in rolling mills A and D that use the horizontal bending method of rolls 10 and 11, the rolling reaction force is less constrained in the roll bending direction, so the strip width of the roll gap is reduced as shown in Figure 4(a). The direction distribution is increased at the center of the body of the roll 10, that is, the plate crown is increased, and the roll gap at the center of the body of the roll 10 is made smaller, that is, the plate is bent as shown in FIG. 4(b). Great control over bending in either direction to make the crown smaller.

Therefore, it is not necessary to give a large initial crown to the work roll 10, and the plate 16 has a small initial crown.
When rolling, the contact pressure between the rolls increases locally,
There is no risk of damaging the roll 10.

Table 1 shows that a 5-layer rolling mill with horizontal bending function of intermediate rolls 11 is installed in the 4th stand after the 6-stand finish rolling mill row to roll large crown steel plates with a width of 1250 mm and a thickness of 2.8 mm. The main rolling conditions are shown below. Note that the roll body lengths of the finishing rolling mills are all 2186wn, and the length of the rolls of the finishing rolling mills is 2186wn. The second stand is a normal quadruple rolling mill.

Table 1 ×1 Horizontal bending crab roll central part pressing force *2 Vertical bending crab roll crease bending is positive, defree suspending is negative.

FIG. 5 shows the steepness of the exit side of each stand of the hot strip finishing mill when a large crown steel plate was rolled under the rolling conditions shown in Table 1.

At the middle stand (near stand number 3), the ratio crown (ratio of plate crown/plate thickness) at the exit side of each stand has changed, so the steepness is slightly greater, but at the exit side of the final stand, it is flat. A rolled product was obtained, and the plate crown of the rolled product was 450μ, which was the target value.

(Effects of the Invention) As is clear from the above explanation, the present invention provides a rolling mill having a horizontal bending function on the work roll or intermediate roll, arranged in a Holatos IJ tube finishing rolling mill, and a horizontal and vertical bending device. A method for manufacturing thin steel sheets with unequal thickness in the width direction by manipulating the method, which enables the production of thin steel sheets with large thickness differences in the width direction without imparting a large initial crown to the work roll. It's now possible. Furthermore, it goes without saying that the above-described finishing rolling mill can also manufacture thin steel sheets with a small crown, without replacing the work rolls or intermediate rolls.

[Brief explanation of the drawing]

Fig. 1 is a conventional roll arrangement diagram for manufacturing a thin steel plate of unequal thickness, and Fig. 2(a) to Fig. 2+d) are side views of a rolling mill having a horizontal bending function of work rolls or intermediate rolls according to the present invention. Figure 3 is a graph of the relationship between roll diameter and roll deflection, Figures 4+a) and 4+b) are schematic plan views of horizontal bending of work rolls or intermediate rolls, and Figure 5 is a graph of the relationship between roll diameter and roll deflection. It is a graph showing the steepness of the rolled material at the outlet side of each stand when the rolling material is rolled. 10...Work roll, 11...Intermediate roll, 12.
...Intermediate roll, 13...Divided reinforcement roll, 16...
・Rolled plate, A, D...rolling machine. Patent Applicant: Kobe Steel, Ltd. Agent Masu Aoyama, Physician, and 2 others (Y44'41/-110)

Claims (2)

[Claims] (1) Horatos) A rolling mill having a horizontal bending function is installed in at least one work roll or intermediate roll in all or part of the finish rolling mill for IJ Tsubu rolling, and the horizontal bending function of the work roll or intermediate roll is A method for producing a thin steel plate of unequal thickness, which comprises producing a thin steel plate of unequal thickness in the width direction by operating a device and a vertical bending device. (2) The work roll or the intermediate roll has a body length/body diameter ratio of 4 or more (
1) The method for producing a thin steel plate of unequal thickness as described in item 1).