JPS6026607B2 - How to remove scale - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scale removal method based on mechanical principles, and more particularly to a mechanical scale removal method for continuously removing scale from the surface of a steel plate.

There are two known methods (descaling methods) for removing the oxide film or scale generated on the surface of hot-rolled steel sheets or cold-rolled steel sheets: methods based on chemical principles and methods based on mechanical principles. There is.

Among these methods, the method based on chemical principles removes scale by immersing the steel plate in an organic acid bath such as picric acid, and this method is the most commonly used method. However, the equipment occupies a very large area and requires waste liquid treatment equipment. There are drawbacks such as.
On the other hand, methods based on mechanical principles include a method in which cracks are generated in the oxide film on the surface of the steel plate by bending the treated steel plate with a roll, a method in which cracks are generated in the oxide film on the steel plate in the process by rolling, and a method in which cracks are generated in the oxide film on the surface of the steel plate by rolling. There is a method of crushing and blowing away the oxide film on the surface of treated steel sheets by blasting.

Among these methods based on mechanical principles, the first method and the second method, that is, the method of bending the steel plate with rolls and the method of rolling, completely remove the oxide film, that is, the scale, on the surface of the steel plate to be processed. On the other hand, while the shotplast method removes scale almost completely, it also has the disadvantage that the shot can roughen the surface of the treated steel sheet, reducing the commercial value of the finished steel sheet. have. Therefore, in the past, chemical methods and mechanical methods have often been used in combination, but in this case, the equipment costs are extremely high and the equipment occupies a very large area.

An object of the present invention is to provide a scale removal method that can completely remove scale based on mechanical principles without roughening the surface of a steel plate to be treated.

In the present invention, an S-shaped sheet passing path is formed by a pair of work rolls rotated in opposite directions at different circumferential speeds, and a processed steel plate passing through this sheet passing path is threaded by the pair of work rolls. The system is configured so that the oxide film can be peeled off using the speed difference between the sheet passing speed and the work roll, and scale can be removed without roughening the surface of the steel sheet to be treated. Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 of the accompanying drawings shows an example of an apparatus for carrying out the method of the invention.

The work rolls designated by numerals 1 and 2 in FIG. 1 are arranged so that their axes are substantially parallel, and are rotated in opposite directions at different circumferential speeds.

Guide rolls 3 and 4 are arranged on both sides of the work rolls 1 and 2, respectively, and the winding angle of the treated steel plate 5 with respect to the circumferential surfaces of the work rolls 1 and 2 is determined by the guide rolls 3 and 4. The processing plate 5 has both work rolls 1,
A threading speed is applied to both the work rolls 1 and 2 so that the work rolls 1 and 2 move along a substantially S-shaped path along the circumferential surface of the work roll 2, and the paper is passed between the work rolls 1 and 2. When the steel plate 5 to be treated is passed between the work rolls 1 and 2, cracks occur in the oxide film on both sides, and the oxide film is removed by the frictional force caused by the difference in circumferential speed between the rolls 1 and 2. Peeled off. That is,
The basic principle of peeling off the oxide coatings 5A and 5B of the treated steel sheet 5 is that when the steel sheet 5 to be treated is passed between the work rolls 1 and 2, based on the difference in circumferential speed between the work rolls 1 and 2, Frictional force is generated between both work rolls 2 and the steel plate 5 to be treated, and the oxide films 5A and 5B are peeled off. FIG. 2 is a diagram illustrating a state in which the oxide film is removed from both surfaces of the steel sheet 5 to be treated when it is passed between the work rolls 1 and 2.

Work roll 1 and work roll 2 are rotating in opposite directions to each other at different circumferential speeds, and the processed steel plate 5 that passes between work rolls 1 and 2 has a passage midway between the circumferential speeds of both work rolls 1 and 2. Gives board speed. And, the post-treated steel plate 5 is
When the sheet is passed between the work rolls 2, it is first bent along the circumferential surface of the upper work roll, and a crack a is generated in the oxide film 5A on one of the outer surfaces due to tensile strain.
Next, when the steel plate 5 to be treated is caught between the work rolls 1 and 2 and rolled down, the other surface of the steel plate to be treated is suddenly compressed and deformed, and a crack b is generated in the oxide film 5B on that surface. . Note that the rolling reduction ratio of the steel plate 5 to be treated is preferably 0.1 to 5%. This is because if the shoring ratio is too small, cracks cannot be generated in the scale, and if it is too large, the work rolls 1 and 2 will be seriously worn out by the scale.
Moreover, this is because scratches are likely to occur on the steel plate 5 to be treated. In this way, the oxide films 5A and 5B, which have cracked and are in a state where they can be peeled off, are moved by the frictional force generated based on the difference between the road plate speed and the circumferential speed of both work rolls 1 and 2. It is peeled off from the surface of the steel plate 5.

Similar to the rolling reduction ratio, if the difference in circumference between these two work rolls 1 and 2 is too small, the scale removal effect will be low, and if it is too large, the rolls will be worn significantly and the steel plate 5 to be processed will be easily scratched. Therefore, it is desirable to set it to 0.5 to 20%. When setting the circumferential speed difference, the circumferential speed of the work roll on the high speed side is used as a reference, and the circumferential speed of the work roll on the low speed side is set to be 0.5 to 20% lower than this reference value. Set to . For example, if the lower work roll 2, which is one of the upper and lower work rolls 1 and 2, is on the high speed side and rotating at a circumferential speed V2, the circumferential speed V of the other upper work roll 1, which is on the low speed side, is (0.8~0.995)
It is sufficient to set it within the range of V2. Conversely, when the upper work roll 1 is on the high speed side, the peripheral speed V3 of the lower work roll 2 is set to (0.8 to 0.995 )V. In this way, the steel plate 5 from which almost all of the oxide films 5A and 5B have been removed between the work rolls 2 is further removed by tensile stress and compressive stress while moving along the circumferential surface of the lower work roll 2. The crushed oxide film is peeled off. The scale removal method of the embodiment described above is carried out at a speed corresponding to the normal rolling speed.

As an example, the case between a hot rolling mill and a cold rolling mill, where scale is most widely removed, is as follows. The normal line speed in mild steel pickling equipment located between the secondary hot rolling mill and cold rolling mill is 30
~400 kites/min.

The work roll length Dw may vary depending on the thickness and width of the steel plate 5 to be processed, but for example, the width of the plate may be set to 1219 ribs (
4 feet), Dw: 5 in a double rolling mill
00~80W Misaki, Dw=200~ in 4-layer rolling mill
45 enemies have been adopted. Therefore, when carrying out the scale removal method of the embodiment using work rolls having the above specifications, the circumferential speed of the reference high-speed work roll is set to a line speed of 30 to 400 m/min, which is the transfer speed of the steel plate 5 to be processed. The speed is controlled so that the peripheral speed of the low-speed side work roll is 0.5 to 20% slower than the high-speed side work roll, that is, a peripheral speed of 0.8 to 0.99 vowels of the line speed. to control the speed. Various embodiments of the apparatus for realizing the method of the present invention are conceivable. For example, the present invention may be applied to an apparatus having the roll arrangement shown in FIG. 3 instead of the roll arrangement shown in FIG. Able to implement methods.

The apparatus shown in FIG. 3 is equipped with work rolls 1 and 2 as well as backup rolls 6 and 7 for backing up these rolls, and this apparatus is more effective than the apparatus shown in FIG. Small diameter work rolls can be used, and
A higher reduction pressure can be generated on the work roll 2. In another embodiment shown in FIG. 4, the line connecting the axes of the pair of work rolls 1 and 2 is parallel to the conveyance direction of the steel plate 5 to be processed, and this type of device has a low device height. can do.

The device shown in FIG. 5 is the same as the device shown in FIG.
, 7 are added to apply a larger bending stress to the steel plate 5 to be processed and a higher rolling pressure.

In general, the apparatus shown in FIGS. 3 and 5 is suitable for descaling steel sheets with peeling and thick oxide coatings. Fig. 6 shows an embodiment in which the apparatus shown in Fig. 4 is arranged in tandem, and is suitable for processing steel plates in which the descaling effect is significantly increased by applying more than - times of reduction to the treated steel plate 5. It is a very good device.

According to the present invention, it is possible to realize a scale removal method using mechanical principles that can completely remove scale without roughening the surface of the steel plate to be treated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of an apparatus for implementing the method of the present invention, FIG. 2 is a diagram illustrating a state in which an oxide film is removed by the method of the present invention, and FIG. FIG. 4 is a diagram showing a third embodiment of the present invention; FIG. 5 is a diagram showing a fourth embodiment of the present invention; FIG. 6 is a diagram showing a fifth embodiment of the present invention. , is. Explanation of symbols, 1, 2... Work roll, 3, 4
...Guide roll, 6,7...Backup roll, 5
...Heat-treated steel plate, 5A, 5B... Oxide film, a
,b...Crack. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. By passing the steel plate to be treated between a pair of work rolls that are rotated in opposite directions at different circumferential speeds along an S-shaped path along the circumferential surface of the work rolls, the steel plate to be treated is A scale removal method characterized by removing surface scale.