JPS6195710A - Method for restraining edge drop of rolling sheet - Google Patents

Abstract

PURPOSE:To restrain effectively an edge drop of sheet by specifying the relations between the cooling capacities of rolling-roll surfaces at the outsides of edge parts and edge parts of a rolling sheet and at the position near the central thereof. CONSTITUTION:A cooling device 6 provided with many coolant-spraying nozzles 3c used for entirely cooling a roll 1, is installed at the inlet side of the roll 1. And contraction plates 5 for decreasing a cooling capacity at the edge parts of a rolling sheet, are installed between the roll 1 and the device 6. Nozzles 3a, 3a for spraying a low temperature coolant for the purpose of more intensely cooling roll 1 parts located at both outsides of the sides edges of rolling sheet, are provided to the outlet side of rolling sheet 2. And the cooling of the roll surface is controlled so that A1>A3>A2, where; A1: cooling capacity for the roll surfaces existing at the outsides of the side edges of rolling sheet, A2: cooling capacity for the roll surfaces of the side-edge parts of sheet, A3: cooling capacity for the roll surfaces not far from the central part of sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention reduces the thickness of the edge of a rolled sheet (
The present invention relates to a method for suppressing edge drop.

[Conventional technology]

In a normal rolling mill, when a material is bitten by the rolling roll 1, the composition 1' in contact with the rolling plate 2 is flattened due to the reaction force from the rolling plate 2, as shown in FIG. Since this reaction force acts in the axial direction of Low/L/1 (X direction in Figure 3), it acts as a force that compresses the roll l in the radial direction at the center of the rolled plate 2. However, since the plate itself is expanded in the width direction (Y direction in FIG. 3) at the edge of the rolled plate, the reaction force in the X-axis direction is reduced. As a result, the compressive force in the radial direction on the roll 1 at the edge of the rolling plate 2 is small, and the amount of flattening of the rolling roll 1 is also reduced. As a result, there arises a drawback (referred to as edge drop) in that the thickness of the edge portion is significantly reduced compared to the center portion. Methods to alleviate this drawback include: - Making the diameter of the rolling roll smaller to reduce the flattening deformation in the center of the rolled plate; and - Taking into consideration the fact that the amount of flattening of the roll roll varies in the width direction as described above. Countermeasures have been considered, such as reducing the diameter of the roll surface at the flute portion of the rolled plate edge in advance in a tapered shape toward the end of the roll. However, regarding ■, there are practical limits related to torque transmission limits and horizontal curling, etc., and regarding ■, it is impossible to respond to changes in the width of the rolled material. There is a problem in that roles must be prepared separately and changed each time. Therefore, as shown in Figure 4, the surface of the roll roll located outside the edge of the rolled plate is intensively cooled, and the rolled surface in this area is thermally deformed to a locally contracted shape to reduce edge drop. There are ways to do this. Note that 3 is a coolant injection nozzle, and 4 is a baffle plate, so that the sprayed cooling water can be locally cooled to the roll surface outside the rolled plate edge.

[Problem that the invention seeks to solve]

In the explanation of Figure 4, we are talking about the case where only both ends of the roll are cooled, but if we consider actual cold rolling, the temperature near the center of the roll will rise and seizure will occur. (The heat crown may also be excessive.) Medium elongation may become noticeable and rolling may become impossible. In order to avoid these, for example, on the input side of the rolled plate, a coolant is injected over the entire width of the rolled plate roll to cool it, and on the exit side of the rolled plate, both grooves on the roll surface are further strengthened by the above-mentioned means. Cooling could also be considered, but as shown by the broken edges in Figure 5 (graph), a steep taper-shaped thermal deformation would have occurred outward from the edge of the rolling plate, but the central part of the rolling roll As a result of the heat being conducted to the edges of the roll, the shape becomes slow and the edge drop suppression effect at the edge of the rolled plate is poor.
It's nothing remarkable.

Therefore, the present inventors conducted repeated research on a method of reducing edge drop by controlling the thermal deformation of the rolling roll more precisely, and as a result, they completed the present invention.

[Means for solving problems]

In order to reduce the edge drop at the edge of the rolling plate, the present invention has a cooling capacity A1 for the surface of the rolling roll located outside the edge of the rolling plate, and a cooling capacity for the surface of the rolling roll at the edge of the rolling plate.

The cooling capacity for the rolling roll surface at the center of the rolling plate is A.
, the gist lies in controlling the cooling capacity of the rolling roll surface so that A + > As > At.

[Effect]

In the present invention, coolant is injected over almost the entire width of the roll for cooling and lubrication, and special cooling nozzles are added outside the edges of the roll to achieve even stronger performance. In addition to cooling, the cooling capacity is lowered by setting the injection amount or injection area of the coolant near the edges of the rolled plate to be smaller than that toward the center.
Increase the heat input to the rolling roll near the edge of the rolling plate. These control the thermal expansion deformation of the roll in the axial direction, thereby making the roll surface have a large difference in thermal expansion at the edges of the rolling plate, forming a steeply tapered shape. This reduces edge drop at the edge of the rolled plate. In other words, the parts with the greatest cooling capacity for the rolling roll surface are listed in descending order: - The part located on the outside of the edge of the rolled plate; - The central part that contacts the rolled plate; - The area near the edge of the rolled plate that contacts the rolled plate. This controls the cooling of the roll surface.

〔Example〕

A typical embodiment of the present invention will be explained with reference to FIG. The rolling plate 2 moves in the direction of the arrow, and the inlet side of the rolling roll 1 is equipped with a cooling device 6 provided with a large number of coolant injection nozzles 3C for cooling the roll as a whole. A drawing plate 5 is provided between the rolling roll 1 and the cooling device 6 for the purpose of attenuating the cooling capacity at the edge of the rolling plate. On the exit side of the rolled plate, there is a nozzle 3a that injects a low-temperature coolant to more strongly cool the rolling rolls outside the edge of the rolled plate.
, 3a are provided.

In this way, by only slightly changing the cooling device, the cooling capacity distribution on the rolling roll surface can be configured as described in the [Operation] section. Figure 5 shows a heat crown comparison between the embodiment of the present invention configured as described above and a conventional example in which the entire rolling roll is cooled and only the ends of the roll are intensively cooled. (graph). In this graph, the horizontal axis shows the distance (mm) from the center of the rolled plate, and the vertical axis shows the heat crown (μm) of the radius. The width of each rolled plate was 1100 mm, the intense cooling part was set within 00n+n+ from the edge of the rolled plate, and the coolant temperature was set at 30°C. The temperature of the coolant for cooling the entire rolling roll was 55°C. According to these comparison results, the heat crown in the conventional example is 950 mm from the edge of the rolled plate to the edge of the plate.
The difference in the amount of expansion on the inside is about 15 μm (dashed line graph in Figure 5). the flow rate of the agent,
When the injection amount on the center side is reduced to about 1/10 by using the throttle plate 5, the difference in the expansion amount is about 25 μm, as shown by the solid curve in FIG. 5, and it is not as steep as in the conventional example. It turns out that there has been an increase. FIG. 6 (graph) shows the results of an experiment conducted using an actual rolling mill. The plate thickness at the input side of the rolled plate is 2.0
The difference between the plate thickness at a position 950 mm inside the rolled plate edge and the plate end thickness under the conditions of one-pass rolling where the plate thickness on the exit side is 1.5 mm + 1.5 mm is shown. Finally, when comparing a conventional example in which uniform cooling was applied to the entire rolling roll (dashed line graph) and an example using the device of the present invention (solid line graph), the amount of change was smaller in the example of the present invention. , it can be seen that edge drop was significantly improved.

FIG. 7 shows another embodiment of the invention. Each coolant injection nozzle 3 is configured to be able to slide in the lateral direction according to the width of the rolled plate, and if the flow rate of the coolant can be adjusted using the nozzle 3, it is possible to adjust the flow rate of the coolant at the edge of the rolled plate. It is possible to adjust the coolant flow rate and perform more effective cooling control.

Further, the nozzle 3a for strongly cooling the outside of the edge of the rolled plate may be provided on the exit side of the rolled plate as described above, or it may be provided using a separate piping from the other nozzles 3b and 3c as shown in FIG. It may be placed on the entry side of the rolled plate.

Next, according to the analysis method of three-dimensional deformation using elementary solution method,
The edge drop suppression effect of the present invention in 5-pass cold rolling was predicted using the moxibustion conditions shown in Table 1 below. However, only the flattening deformation due to contact with the rolled plate material is considered as the cause of roll deformation.

The setting of the cooling capacity according to the present invention is as shown in FIG.

FIG. 9 shows the results of predicting the effects of the present invention in 5-pass cold rolling using the above analysis method. The vertical axis shows the difference in plate thickness between the center position of the rolled plate and the 10 mm inner side of one plate edge, and the horizontal axis shows the number of passes. The white circles indicate the conventional method of cooling the entire surface of the roll, and the black circles indicate the cooling capacity setting according to the present invention. Incidentally, since the final fifth pass is for shaping, it is always necessary to perform cooling using the conventional method as indicated by the white circle. According to the results, the effect of suppressing edge drop is highest in the case where the process of the present invention was performed continuously in the third and fourth passes. However, 3
Even when the process of the present invention is performed at either the 1st bus or the 4th pass, the edge drop reduction effect is more significant than when the process is continuously performed under conventional conditions. It has been found that executing the process of the present invention one or two times before the final bus is effective in suppressing edge drops. Next, based on the above findings, an experiment was conducted under various conditions in which the inlet side plate thickness was 3.2 m++z and the outlet side plate thickness after 5 passes was 1.0 mm in cold rolling using a 5-pass tandem mill. The results are generally as shown in Figure 10. In the example processed using the conventional method (broken line curve in Figure 10), the effect of suppressing edge drop was small, and in the 3rd and 4th pass, the processing of the present invention was applied. In the example conducted (solid curve in FIG. 10), edge drop was significantly suppressed. After all, by using the method of the present invention even in multi-pass rolling, it is possible to effectively reduce the suppression of edge drop, and in particular, by applying the method of the present invention to the first or second pass before the final pass. It turned out to be effective.

〔Effect of the invention〕

When a steel plate is rolled using the method of the present invention by controlling the cooling capacity to the rolling roll surface as described above,
It is effective by utilizing the thermal deformation of the rolling roll without causing problems such as the seizure phenomenon caused by the extremely high temperature of the rolling roll surface, or excessive heat crown resulting in significant mid-elongation. It is now possible to suppress edge drops.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an embodiment of the present invention, Fig. 2 is an explanatory view showing flattening deformation of a rolling roll, Fig. 3 is an explanatory view showing edge drop, and Fig. 4 is a plan view showing a conventional example. , FIG. 5 is a graph showing a comparison of the heat crown of the conventional example and the example of the present invention, FIG. 6 is a graph comparing the effect on edge drop of the example of the present invention and the conventional example, and FIG. 7 is a graph showing the effect on edge drop of the example of the present invention and the conventional example. Figure 8 is an explanatory diagram showing the cooling capacity settings used in the example of the analysis method for 5-pass cold rolling, and Figure 9 is the effect on edge drop in the analysis method for 5-pass cold rolling. A graph showing the effect, FIG. 10 shows a graph comparing the influence on edge drop between the example of the present invention and the conventional example in 5-pass rolling. 1... Rolling roll f... Area where the rolling roll contacts the rolling plate 2... Rolling plate 3... Coolant injection nozzle 4.
...Baffle plate 5...Aperture plate 6...Cooling device Drawing 1 Board width 1100 m i Fig. 7 Tc: Coolant temperature ("C") hr: Cooling capacity (kca I/rn2h r"C) +
23 45 −→− Panu number

Claims (1)

[Claims] A method for reducing edge drop in rolling, where A_1 is the cooling capacity for the surface of the rolling roll that exists outside the edge of the rolling plate, A_2 is the cooling capacity for the surface of the rolling roll at the edge of the rolling plate, and A_2 is the cooling capacity for the rolling roll surface that is located outside the edge of the rolling plate. Department b
A method for suppressing edge drop of a rolled plate, characterized by controlling the cooling of the surface of the rolling roll so that A_1>A_3>A_2, where A_3 is the cooling capacity for the surface of the rolling roll.