JPH0587327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for suppressing a decrease in plate thickness (edge drop) near the width edges of a plate that occurs during rolling of a plate.

(Prior Art) In recent years, in response to users' strict demands for plate thickness accuracy and improvement in yield, technology for obtaining a more uniform plate thickness distribution in the width direction of a plate during thin plate rolling has become important.

In a normal rolling mill, as shown in FIG. 6, when a material is bitten into a rolling roll 1, a region 1' in contact with a rolling plate 2 undergoes a flattening deformation D due to a reaction force from the rolling plate 2. In other words, this reaction force is
Since the force acts in the axial direction (X direction in FIG. 7), it acts as a compressive force in the radial direction of the roll 1 at the center of the rolled plate 2, but at the edges of the rolled plate, the force acts on the plate itself. is the width direction (Y direction in Figure 7)
The reaction force in the X-axis direction becomes smaller. As a result, the compressive force in the radial direction on the rolling roll 1 is reduced at the edge of the rolling plate 2,
The amount of flattening deformation of the rolling roll 1 is also reduced. Therefore, a phenomenon (edge drop) occurs in which the thickness of the edge portion is significantly reduced compared to the center portion. Due to this phenomenon, the current practice is to cut off the end region of the plate whose thickness is outside the tolerance compared to the thickness at the center of the plate width before shipping, resulting in a significant drop in yield.

For this reason, conventional methods for suppressing this edge drop include reducing the diameter of the roll in order to reduce flattening of the roll due to rolling reaction force, and reducing the flattening of the roll by varying the amount of flattening in the strip width direction as described above. A method of reducing the diameter of the roll surface at the portion where the rolled plate edge touches in advance in a tapered shape toward the end of the roll.
The cooling capacity for the rolls located outside the edge of the rolling plate is defined as _A1 , the cooling capacity for the roll at the edge of the rolling plate is defined as _A2 , and the cooling capacity slightly in the center of the edge of the rolling plate is defined as _A3 . Time, A ₁ > A ₃
> A ₂ , and a method has been considered in which the expansion pattern of the roll of the plate edge portion is tapered by performing cooling control to obtain the same effect as described above.

(Problems to be Solved by the Invention) However, with the above method, there is a limit to reducing the diameter of the rolling roll due to problems with torque transmission, speed limitations, and shape deterioration; If the rolls are made movable in the axial direction, it is possible to cope with changes in sheet width, but since the optimal taper amount of the sheet edge is related to the sheet thickness, changing the rolls in response to changes in sheet thickness will reduce production. Moreover, in order to adopt this method, it is necessary to make the rolling roll movable in the axial direction, which has the disadvantage that the equipment and industrial costs for this are high.

On the other hand, with the above method, the equipment cost is low, but with only cooling control, the roll at the edge part does not have a steep taper shape, but due to heat conduction in the roll axis direction inside the roll, it becomes a gradual shape. There is a drawback that the shape of the plate after rolling becomes poor.

In other words, in order to reduce shape deterioration and edge drop, the roll expansion difference ΔRc between the center of the roll axis and a position slightly inside the sheet width from the edge of the sheet should be reduced, as shown in Figure 8. It is desirable to prevent deterioration of the shape of the sheet by increasing the difference in roll expansion ΔRe between the sheet width end and a position slightly inside the sheet width from the sheet width end to increase the edge drop suppression effect. This ideal roll profile shape becomes the pattern indicated by the broken line A in FIG. Here, ΔRc
In order to reduce the cooling capacity of area B in Figure 8,
It is possible to make A ₂ even smaller, but
In order to further reduce A ₂ , it is necessary to further reduce the flow rate, which poses a problem of interfering with lubricity.

Furthermore, when the width of the rolled material increases, that is, when the width end of the rolled material is at the position shown in Figure 8, and the width end of the next rolled material is at the position shown in Figure 8, ΔRc becomes very If it becomes larger, it may deteriorate in shape and cause the plate to break. In other words, cooling control alone has the disadvantage that it cannot directly respond to changes in board width because the response is slow.

The present invention eliminates the drawbacks of the above-mentioned conventional techniques regarding edge drop suppression of rolled plates, and precisely controls the thermal expansion of rolling rolls by cooling and heating. The object of the present invention is to provide a method that enables excellent edge drop suppression.

(Means for Solving the Problems) In order to achieve the above object, the edge drop control method according to the present invention first moves the rolling rolls at arbitrary positions in the axial direction in order to deal with rolled materials of various widths. Assuming that the rolling mill is equipped with a device that can heat and cool at certain points and a device that can independently adjust the heating and cooling capacities at any point, When the cooling capacity is A ₁ , the cooling capacity of the rolling plate edge is A ₂ , the heating capacity is B ₂ , the cooling capacity for the rolling roll in the center from the rolling plate edge is A ₃ , and the heating capacity is B ₃ ,
By controlling cooling and heating so that A ₁ > A ₃ > A ₂ and B ₂ > B ₃ , the roll thermal expansion distribution in the vicinity of the plate edge is formed into a steep taper shape, thereby eliminating edge drops. This is what we are trying to suppress.

The present invention will be explained in detail below based on examples.

As mentioned above, the ideal roll profile shape for suppressing edge drop of a rolled plate is the pattern shown by the broken line A in FIG. , as follows.

In the present invention, in order to get as close as possible to the optimal roll thermal expansion distribution (pattern A in Figure 8), in the region B, strong cooling is performed using a low-temperature cooling medium to change the roll thermal expansion distribution near the width edge of the sheet. Make the slope steeper.
In addition, in region C, the cooling capacity _A2 of the coolant is reduced by restricting the flow rate so that ΔRc is as small as possible, and the roll is heated electrically or by injecting a fluid higher than the roll surface temperature. . As a result, the roll thermal expansion distribution approaches the optimum pattern shown in FIG. 8, the shape is good, and the edge drop reduction effect can be increased.

Furthermore, in the present invention, as a specific embodiment, when the width of the rolled plate of the current pass is larger than that of the rolled plate of the previous pass, the heating of the edge of the rolled plate of the current pass is increased in the early stage of rolling, and as the rolling progresses, the width of the rolled plate of the current pass is increased. By lowering the heating intensity, deterioration of the shape can be prevented and edge drops can be suppressed. That is, when the width of the plate is greatly changed, ΔRc becomes particularly large and the shape deteriorates significantly when the width end of the plate shown in FIG. 8 is changed to .
For this purpose, the heating in the C′ region is made even more powerful,
Get closer to the optimal distribution for the width of the plate as quickly as possible.
However, if the heating in the C′ region is kept strong, it will become too heated and the roll thermal expansion distribution will become a pattern like B, causing problems.
The heating intensity is gradually weakened as the rolling progresses.

In addition, in the present invention, in order to quickly approach the optimal roll thermal expansion distribution when changing rolls, A ₂ and A ₃ are initially made small and B ₂ and B ₃ are made large.
Edge drops can also be suppressed by increasing A ₂ and A ₃ and decreasing B ₂ and B ₃ as the rolling progresses. In other words, in order to increase the expansion amount of the rolls as quickly as possible when changing the rolls and to bring the pattern closer to the optimal pattern, the cooling capacity in the area D is increased.
A ₃ , reduce the absolute amount of cooling capacity A ₂ in area C while maintaining A ₃ > A ₂ , and reduce the heating capacity B ₂ , D in area C.
The absolute amount of heating capacity B ₃ of the region is increased while maintaining B ₂ >B ₃ .

In addition, in order to deal with changes in the width of the rolled plate, the cooling and heating devices are multi-divided in the roll axis direction or are movable in the axial direction.

(Example) Next, a typical example of the present invention will be described using FIG.

In the figure, the rolling plate 2 is progressing in the direction of the arrow, and a large number of cooling injection nozzles 3 are provided on the inlet side of the rolling roll 1 to cool the entire roll, and the rolling plate 2 is divided in the axial direction of the roll. The flow rate can be controlled in units (in this embodiment, each unit is divided into 40 mm pitches). Furthermore, a nozzle 4 for injecting a low-temperature coolant is provided on the exit side of the rolled sheet in order to powerfully cool the roll portion outside the edge of the rolled sheet, and an induction heating device 5 is provided to heat the roll at the edge of the rolled sheet. It is set up. The cooling nozzle 4 on the outlet side of the rolled plate and the heating device 5 are movable in the roll axis direction so as to be able to cope with changes in the width of the rolled plate.

This embodiment configured as described above will be explained with reference to FIG. 5. The vertical axis of the figure is the radius of the difference in roll expansion ΔRc (○, △ in the figure) between the center of the roll axis and the position 40 mm from the edge of the plate width, and the radius of the difference in roll expansion between the position 40 mm from the edge of the plate width and the edge of the plate width. minute ΔRe (●, ▲ in the figure),
The horizontal axis is rolling time. The rolling conditions are: entry side plate thickness 0.72mm, exit side plate thickness 0.53mm, entry side tension 16Kg/
mm ² , exit tension 16Kg/mm ² , plate width 960mm, roll diameter 600
mm, rolling material deformation resistance 75Kg/mm ² , rolling speed 1110m/
It is min.

Regarding cooling and heating of the roll, on the entry side, the flow rate of four nozzles (8 in Figure 1) up to 80 mm from the edge of the sheet width is reduced by 70% compared to other nozzles. The heat transfer coefficient at this time is 2500 kcal/m ² h℃ for the above nozzle,
For other nozzles it is 5000 kcal/m ² h°C.
In addition, the inlet coolant temperature is 50°C. The heat transfer coefficient of the cooling nozzle 4 outside the plate width on the outlet side is 5000kcal/
m ² h°C, the temperature is 30°C. For heating on the exit side, a heat input of 150,000 kcal/m ² h was applied at a position 80 mm from the edge of the sheet width at the initial stage when the rolls were rearranged and the sheet width was significantly changed, and at a later stage, a heat input of 100,000 kcal/m ² h was applied.

ΔRe is an index of edge drop reduction,
ΔRc represents a shape index. In other words, the larger ΔRe and the smaller ΔRc, the steeper the roll thermal expansion distribution near the plate edge (pattern A in Figure 8).
It is possible to obtain a plate with a large edge drop reduction effect and a good shape.

Now, in Fig. 5, under control only by cooling without using heating means, ΔRe=
31μm, ΔRc=25μm, and the plate width is from 960mm.
After changing to 1040mm, ΔRe = 34μm in 300 seconds,
ΔRc = 37 μm (800 seconds on the horizontal axis in Figure 5).
On the other hand, when heating and cooling control are performed simultaneously, ΔRe = 38 μm and ΔRc = 7 μm at around 500 seconds of rolling time, and ΔRe = 40 μm and ΔRc = 19 μm at 300 seconds after expanding the sheet width. From these results, it can be seen that by performing both heating and cooling control, edge drop can be improved and a plate with less deterioration in shape can be obtained.

Furthermore, when changing the rolls, it can be seen from FIG. 5 that heating control causes a rapid rise in ΔRe, and the response is better than cooling control.

FIGS. 2 and 3 show other embodiments.
In this embodiment, a small amount of emulsion with high oil concentration for lubrication is injected from the header 9 toward the contact point between the rolling roll 1 and the rolling plate 2 or directly onto the rolling plate 2. It consists of a group of divided nozzles, and it is possible to control the temperature and flow rate of the coolant in each division. and,
The header 7 is used exclusively for roll cooling, and coolant with a very low oil concentration is injected from each nozzle. In this embodiment, coolant with a low temperature is injected from the nozzles 4 outside the plate edge, and coolant with a higher temperature than the roll surface is injected from the nozzle 6 in the plate edge. With this configuration, when expanding the board width or changing rolls,
This can be dealt with by controlling the flow rate and temperature of the nozzle group 3 or 6 within the width of the plate.

Another embodiment is shown in FIG. The coolant on the inlet side is the same as that shown in FIG. 1, but the heating device on the outlet side is provided with a nozzle 6 for injecting high temperature coolant. With this configuration as well, the same effects as in each of the above embodiments can be obtained.

(Effects of the Invention) As detailed above, according to the present invention, cooling,
Since the thermal expansion distribution of the rolling rolls can be made into an optimal pattern by heating control, the effect of suppressing edge drop is extremely large, and furthermore, it is economical because no expensive special equipment is required. Also,
Especially when changing the width of the rolled plate or changing the rolls, edge drops can be similarly suppressed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the arrangement of cooling and heating devices in one embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams showing the arrangement of cooling and heating devices in another embodiment, and FIG. 4 is an explanatory diagram showing the arrangement of cooling and heating devices in another embodiment. Furthermore, an explanatory diagram showing the arrangement of the cooling and heating devices in another embodiment, FIG. 5 is a diagram comparing the present invention and the conventional method regarding the effect on edge drop and shape, and FIG. 6 is a diagram showing the flattening deformation of the rolling roll. FIG. 7 is an explanatory diagram showing the edge drop, and FIG. 8 is an explanatory diagram showing the roll thermal expansion distribution of the rolling roll. DESCRIPTION OF SYMBOLS 1... Rolling roll, 1'... Contact area between rolled material and roll, 2... Rolling plate, 3... Inlet coolant injection header, 4... Nozzle for injecting low-temperature fluid, 5...
Induction heating device, 6... Nozzle that injects high temperature fluid, 7... Coolant header exclusively for roll cooling, 8
...Injection nozzle with a small flow rate, 9...Nozzle header exclusively for lubrication.

Claims (1)

[Scope of Claims] 1. A rolling mill equipped with a device that can heat and cool a roll at any location in its axial direction, and a device that can independently adjust heating and cooling capabilities at any location. , the cooling capacity for the rolling rolls located outside the rolling plate edge is A ₁ , the cooling capacity for the rolling roll at the rolling plate edge is A ₂ , the heating capacity is B ₂ , and the area is slightly closer to the center than the rolling plate edge. The cooling capacity for the rolling roll is A ₃ ,
A method for suppressing edge drop of a rolled plate, characterized by controlling the cooling and heating of the rolling rolls so that when the heating capacity is _B3 , _A1 > _A3 > _A2 and _B2 > _B3 . . 2. When the width of the rolled plate in the current pass is larger than that of the rolled plate in the previous pass, the heating capacity _B2 of the rolled plate edge is increased at the beginning of the current pass and reduced as the rolling progresses. A method for suppressing edge drop according to claim 1. 3. When changing the rolling rolls, initially the above A ₂ and A ₃
The edge drop according to claim 1, characterized in that the B ₂ and B ₃ are increased, and as the rolling progresses, A ₂ and A ₃ are increased and B ₂ and B ₃ are decreased. Suppression method.