JPS633685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for grinding a mill roll so that the shape of the mill roll can be modified during rolling.

As rolling progresses, the rolls are worn out and lose their original shape. For example, in a quadruple rolling mill with a back-up roll, which is the most common plate rolling mill, the upper and lower work rolls 1, 1 are usually provided with appropriate crowns as shown in Fig. 1, and the back-up rolls 2, 2 are Ordinary parallel rolls are used, but in this case the wear of the rolls as the rolling progresses develops into the state shown by hatching in the figure. As the wear progresses, the plate thickness accuracy decreases, so it becomes necessary to change the rolls when a certain tolerance is exceeded. Needless to say, it is preferable in terms of rolling operation that the frequency of changing the rolls is low. Conventionally, in order to extend the period until the roll change as described above as much as possible, the following roll schedule has been adopted. That is, the work roll is initially provided with a large crown necessary for the wide width, and the roll is first rolled with a wide width, and as the roll wears out, the rolling target is gradually changed to a narrow width. However, even with such operations, the period until the roll change is limited to
The rolling capacity is limited to 5000 tons,
This still leaves me unsatisfied. Moreover, having to switch the object of rolling from a wide material to a narrow material is a major constraint on the rolling operation and is extremely inconvenient.

Furthermore, when the back-up roll 2 and the work roll 1 are compared with respect to the wear of the rolls in the rolling mill shown in FIG. 1, the wear of the latter is much more significant. As mentioned above, the period until roll change is at most 5,000 tons with work rolls, whereas it is possible to change the rolls between 100,000 and 150,000 tons with back-up rolls. In other words,
The work rolls must be replaced many times before the backup rolls are replaced. The appropriate crown amount for the work roll changes depending on the wear condition of the back-up roll, so when changing the work roll, consider the wear condition of the back-up roll at that time and adjust accordingly. It is necessary to prepare a roll with a suitable crown (the more worn the back-up roll is, the larger the crown is required), which makes the work of changing the work roll complicated and troublesome.

Furthermore, the used rolls removed from the rolling mill during roll change are recycled by being polished off-line with a grinder, but this grinding also takes time and effort.

As described above, there are many unresolved problems surrounding the wear and tear of the rolls, but if the roll surface shape of the rolls could be kept constant regardless of the wear caused by rolling, It is clear that the above problems can be solved all at once.

The present invention aims to provide a method for grinding a mill roll that makes it possible to correct deterioration of the roll shape due to wear of the roll during rolling while rolling.

That is, the present invention is a rolling process characterized by water-grinding a part of the surface of the roll by spraying high-pressure water of 50 to 500 kg/cm ² toward the part to be ground while rotating the roll. The gist is the method of grinding rolls. The grinding speed of this water grinding depends on the pressure and jetting amount of high-pressure water. The pressure of high-pressure water for water grinding can be determined as appropriate, taking into account the material of the roll and the required grinding speed.
As a result of experiments, it was confirmed that 50 to 500 Kg/cm ² is a practically effective range. In other words, Figure 6 shows the relationship between high water pressure and grinding speed in water grinding, and Figure 7 shows the relationship between high water pressure and grinding speed in water grinding.
The figure also shows experimental data showing the relationship between high water pressure and the surface condition of the abrasive. In other words, high-pressure water is sprayed onto the sample (surface hardness Hs: 38, 75) from a position 30 mm away from a nozzle (nozzle hole diameter 1.2 mm), and grinding is performed to a depth of 0.5 mm by continuous spraying at a certain point. The time required for grinding (grinding time) and the maximum amount of unevenness on the grinding surface (maximum height difference (H) of surface unevenness shown in Figure 8) were investigated and plotted in relation to the pressure of the high-pressure water used. .

The following can be seen from the figure. In the case of water grinding, the grinding speed increases as the pressure of the high-pressure water used increases, but when the pressure exceeds 500 kg/ ^cm2 , there is almost no improvement in the grinding speed due to the increase in pressure. The surface texture tends to deteriorate as the pressure increases, and when the pressure exceeds 500 kg/cm ² , there are cases where the surface texture required for a roll surface cannot be obtained. That is, for roll grinding, the appropriate pressure of high-pressure water is 500 kg/cm ² or less. Furthermore, if the lower limit is less than 50 kg/cm ² , the grinding speed is too low and it is difficult to put it into practical use for roll grinding.

By using the method of the present invention, it is therefore possible to maintain the roll shape at approximately the initially set proper shape for as long as necessary, despite the progress of wear during rolling. That is, during rolling, water grinding is applied to parts of the roll surface where wear progresses slowly, that is, parts 3 that are not hatched in FIG. It is to give.

Hereinafter, a specific example of a method for modifying the shape of a rolling roll using the method of the present invention will be described.

First, a side view and a front view of an example of a four-high rolling mill suitable for carrying out water grinding for modifying the shape of rolling rolls are schematically shown in FIGS. 2A and 2B. High-pressure water for grinding is sent from a supply source 5 to main piping 6, from which it flows into each of the header pipes 7 provided along the roll axis corresponding to the four rolls, and from there flows into each of the header pipes 7 provided along the roll axis corresponding to the four rolls. from the nozzles 8 toward the corresponding rolls. The nozzles 8 are provided for each roll surface for which they are in charge, so as to cover the portions that require grinding to correct the roll shape. The example shown in the figure is as above, but the high-pressure water piping system is not necessarily one.
Needless to say, there is no need to provide it in the system. In addition, hot rolling mills are usually equipped with piping for descaling water, but in such cases, the piping for grinding water is configured with piping for descaling water or using the same piping to reduce pressure. It is also possible to provide a shared water supply source, and it is clear that such a structure is advantageous in terms of equipment costs.

The modification of the shape of a roll by water grinding according to the present invention is carried out using the above-mentioned apparatus, for example, as follows. During rolling, high pressure water (50
-500 Kg/cm ² ) is carried out continuously or intermittently, the shape of the rolling roll is measured constantly or at any time, and the injection of high-pressure water from the nozzle 8 is controlled based on the measurement results. In other words, the amount of grinding necessary to make the current roll shape appropriate is determined from the measurement results of the roll shape, and based on this value, the amount of ejection from the nozzle in charge of grinding each part of the roll is adjusted depending on the roll shape. Adjust in the direction that corrects it to its original proper shape. The ejection amount for each nozzle may be adjusted by using a nozzle whose nozzle hole size can be changed, or by providing a flow rate control valve for each nozzle.

In addition, when configuring the grinding water piping using descaling water piping, if the water injection for grinding is performed intermittently at the same timing as the descaling water injection, it will be possible to modify the equipment when implementing the present invention. can be minimized, which is advantageous in terms of equipment costs.

Next, effects of implementing the present invention will be explained.

In a quadruple rolling mill, a pair of left and right header pipes 7, 7 were provided on a lower back roll having a body length of 4600 mm, corresponding to the circumferential surface near both ends of the roll, as shown in FIG. This header pipe is provided with five nozzles 8 per side facing the roll circumferential surface at a pitch of 150 mm, and each nozzle group on the left and right covers a range l on the circumferential surface near the roll end on the corresponding side. I did it like that. In both the left and right nozzle groups, the areas in charge of grinding of nozzles 8 ₁ ... 8 ₅ are as indicated by symbols l ₁ ... l ₅ in the same figure, respectively.

Rolling was carried out in the above rolling mill, during which high pressure water of 150 Kg/cm ² was continuously injected from the nozzle at a flow rate of 848/min per one header pipe. The jetting amount for each nozzle is 166/min, 189/min for both left and right nozzle groups, starting from the roll end side.
/min, 189/min, 166/min, and 138/min were fixed. Rolling was continued without changing the lower back up roll, and the shape of the roll was successively measured during this period of continued use. The results are shown in Figure 4.

As is clear from the figure, the lower back-up roll was used for a rolling amount of 133,000 tons, which is approximately twice the period of continuous use, without changing the rolls, but the roll shape was always approximately parallel during use. In the end, the parallel state was almost maintained. The condition of the surface skin of the lower back-up roll after use is as shown in Figure 5 (actual measurement data for part of the same roll) over its entire length, and the properties are sufficient to be used as a roll. It was hot.

Incidentally, if the water grinding according to the present invention is not carried out, the above-mentioned lower back up roll will have a rolling amount of
After continuous use of 45,000 tons, the shape as shown by the broken line P in the figure has already been reached, and a wear difference exceeding 0.4 mm has appeared.

As is clear from the above explanation, since the grinding method of the present invention enables grinding of the roll during rolling, by using this method, the shape of the roll during rolling can be maintained at a predetermined level despite the progress of wear due to rolling. This not only extends the usable period of the rolling rolls and greatly reduces the frequency of roll replacement, but also reduces the work roll shape in the case of rolling mills with back-up rolls. This eliminates the trouble of having to prepare a work roll with a shape that corresponds to the wear condition of the back-up roll each time the roll is changed, and also eliminates the restriction of sequentially switching the rolling object from wide material to narrow material. Many benefits can be expected, such as eliminating the need to adopt a roll schedule and allowing the freedom to select rolling targets.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the shape of rolling rolls in a quadruple rolling mill and the progress of wear due to rolling of each roll. Fig. 3 is a schematic side view and front view of an example of a quadruple rolling mill suitable for rolling mills; Diagrams showing the change in the shape of the lower back-up roll when rolling is continued while modifying the shape using the nozzle shown in Figure 3, and the shape of the same roll after continued use without water grinding. , Fig. 5 shows the actual measurement results of the surface texture of the lower back-up roll after rolling while water grinding, Fig. 6 shows the experimental results showing the relationship between high water pressure and grinding speed in water grinding, and Fig. 7 8 shows the experimental results showing the relationship between high water pressure and the condition of the surface of the abrasive material, and FIG. 8 shows the maximum amount of unevenness on the ground surface. In the figure, 1: work roll, 2: backup roll, 3: slow wear area, 4: fast wear area, 5: water supply source, 6: main piping, 7: header pipe, 8: nozzle.

Claims (1)

[Claims] 1. A method for grinding a rolling roll, which comprises spraying high-pressure water of 50 to 500 kg/cm ² onto a portion of the roll surface to be ground while rotating the rolling roll in a rolling line.