JPH0440081B2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) For 4Hi or 6Hi rolling mills aiming to match crown control with edge drop control and shape control, prevent local wear of work rolls and prevent edge build-up together with crown control. The development results regarding this are described below.

(Background Art) In recent years, the demand for improving the accuracy of plate thickness in the width direction of rolling mills has come to the fore as a means of improving yield.

(Prior art and its problems) Various crown control methods have been proposed to improve the accuracy of plate thickness in the width direction.

Among them, the edge drop can be improved by changing the geometry of the work roll, for example,
The trapezoidal roll rolling method shown in Publication No. 20081 is effective.

In this case, the work roll shift method disclosed in Japanese Patent Publication No. 53-151552 is an effective method for crown control since the crown control effect is weakened by changing the plate width.

In general, as the number of rolls rolled at the same width increases in hot finish rolling, the plateway portion 2 of the work roll 1 becomes smaller in both side portions than in the central portion 2a, as shown in FIG.
The wear becomes greater at point b, and then the rolled material 3 has a cross-sectional profile with abnormal protrusions p and p' (called edge build-up) at the width ends of the rolled material 3, as shown in FIG. It is clear that such edge build-up is the biggest impediment to controlling the crown and performing roll-chance-free rolling (that is, rolling that allows width return). The situation is no different with the crown control method.

(Objective of the Invention) Therefore, the object of the present invention is to enable crown control that eliminates the factors that inhibit edge build-up and, ultimately, roll chance-free rolling due to uneven wear in the plateway section 2 as described above. .

(Start of Idea) As shown in FIG. 3a, the inventors used a pair of so-called single-trapezoidal rolls in which one end of the roll cylinder 4 was tapered and ground 4' as a work roll 1', and the one end of the roll cylinder 4 was tapered and ground 4'. When crown control is performed by stacking the rolled materials 3 vertically in an alternating arrangement and positioning the width ends of the rolled materials 3 in the tapered grinding region 4', the shape limit of the plates between the stands is determined as shown in Figure b. effective
It was found that a range of E _L values exists. Here, assuming that the clearance E _H from the tapered grinding area 4' at the width end of the rolled material 3 is constant, the distance to the boundary of the grinding area 4' at the width end is expressed as E _L.

If this E _L value exceeds the effective E _L range by shifting the work roll to increase it, the plate shape limit on the exit side will be exceeded and rolling will become impossible, while if the opposite shift limit is exceeded, the crown control ability will be lost. be exposed.

Therefore, we conducted a study focusing on this effective E _L range, and by shifting the work roll 1' within the effective E _L range in order to reduce edge build-up, the hot rolling method of the present invention achieves both crown control and roll chance-free rolling. This method has been established.

(Structure of the Invention) This invention provides a hot finishing rolling mill in which the work rolls are movable in the axial direction, and a pair of work rolls each having one end of the roll body tapered and ground. When rolling is performed by placing the upper and lower work rolls in an alternating arrangement between the respective tapered grinding areas, the work rolls are shifted cyclically to the extent that both width ends of the material to be rolled do not come off the tapered grinding surface, and edge build is performed. This hot rolling method is characterized by preventing roll-up and controlling crown.

The present invention is useful when applied to hot rolling methods, particularly hot thin plate rolling.

Now, an example in which this invention is applied to a 4Hi rolling mill will be explained. Fig. 4 shows an example when the E _L value shown in Fig. 3 is increased to the maximum (a value that does not exceed the shape limit on the exit side), while Fig. 5 shows an example in which the E _L value shown in Fig. 3 is increased to the maximum (value that does not exceed the shape limit on the exit side). The limit shift position of the work roll 1' is illustrated, where the crown control capability is reduced to the remaining limit. Figure 5 shows the backup roll.

Even if the number of rolls rolled at the same width increases by cyclically shifting the work roll 1' within the effective E _L range from Fig. 4 to Fig. It becomes possible to disperse the local wear 2b' in the case of E _L in the width direction of the work roll 1' as shown by 2b'' in FIG.

(Example) JIS standard SPHC2.0mm x 1040mm width size E _L =
FIG. 8 shows an example of the change in the cross-sectional profile of the plate on the rolling exit side when the plate is continuously rolled using the single trapezoidal roll rolling method with a fixed width of 200 mm.

There is no abnormality until the 10th rolling, but 20
During the actual rolling process, the edge build-up p, p' became noticeable and reached a maximum of 20μ, making further rolling of the same width impossible.

FIG. 9 shows changes in the cross-sectional profile of a plate due to continuous rolling similar to the comparative example in which cyclic shifts were performed every 20 mm/2 in accordance with the present invention in the range of E _L 200 mm to 100 mm. Even after rolling 46 rolls of the same width, almost no edge build-up p, p' was observed.

(Effects of the Invention) This rolling method disperses and reduces local wear on the work roll plate during rolling of the same width, and therefore maintains sufficient crown control (edge drop improvement effect), making it possible to achieve roll change, which was previously difficult. This makes it possible to achieve both free rolling and crown control.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the roll wear situation, Fig. 2 is an explanatory diagram of the edge build up profile, Fig. 3a is a sectional view showing the rolling situation with a single trapezoidal roll,
Figure 3b is a graph showing the effective E _L range, Figure 4 is an explanatory diagram of the rolling situation at maximum E _L , and Figure 5 is a graph showing the effective E L range.
The figures are explanatory diagrams of rolling conditions at E _L minimum, Figures 6 and 7.
The figure is a comparison diagram of roll wear examples, FIG. 8 is a plate profile graph on the exit side of a rolling mill according to a conventional example, and FIG. 9 is a plate profile graph on the exit side of a rolling mill according to the present invention.

Claims (1)

[Scope of Claims] 1. In a hot finishing rolling mill in which the work rolls are movable in the axial direction, a pair of work rolls each having one end of the roll body tapered and ground are arranged alternately at one end. When rolling is performed by stacking the rolled material one above the other and positioning both width ends between the respective tapered grinding areas of the upper and lower work rolls according to the width of the material to be rolled, both width ends of the material to be rolled have a tapered grinding surface. A hot rolling method characterized by cyclically shifting work rolls within a range that prevents edge build-up and controlling crown.