JPH10291011A - Cooling method for hot rolling roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep left/right symmetry in the profile in the width direction due to thermal expansion of upper/lower work rolls and to prevent a steel plate from meandering when largely shifting upper/lower work rolls by setting a ratio of a cooling water quantity for an upper work roll to a cooling water quantity for a lower work roll to a specified range. SOLUTION: A cooling water injection hole 1a of a cooling header 1 has the same diameter as an injection hole 2a of a cooling header 2, a number of the injection holes 1a of the cooling header 1 is made more as compared to the cooling header 2. By this method, a cooling water quantity to inject to an upper work roll 3 is made 1.2-2.5 times that to a lower roll. The injection holes 1a on the lowest stage and the injection holes 2a on the upmost stage are formed up to a width direction edge part, a number of the injection holes 1a is decreased upward, a number of the injection holes 2a is decreased downward, by decreasing a number of the injection holes 1a, 2a at both ends. By arranging in this way, thermal expansion at a center part in the steel plate width direction is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling work rolls above and below a hot rolling mill having a work roll shift mechanism.

[0002]

2. Description of the Related Art In FIG. 4, the amount of gap in the roll axis direction between upper and lower work rolls 3 and 4 of a hot rolling mill is shown due to uneven wear of the rolls and a difference in thermal expansion between the upper and lower work rolls 3 and 4. As a result, problems such as a poor sectional shape of the steel sheet 7 and meandering of the steel sheet 7 during rolling occur.

Therefore, a hot rolling mill having a work roll shift mechanism for moving the upper and lower work rolls in the width direction of the steel sheet has been adopted. In a hot rolling mill having this work roll shift mechanism, the position of the upper and lower work rolls is shifted in units of coils or lots, so that wear of the upper and lower work rolls and dispersion of thermal expansion are attempted.

[0004]

However, even in a hot rolling mill having a work roll shift mechanism, the upper and lower work rolls are cooled by the same amount of cooling water as in a conventional rolling mill. In the upper work roll, as shown in FIG. 6, the cooling effect in the vicinity of the roll bite is lower than that of the lower work roll 4 due to the cooling water staying between the upper work roll 3 and the draining wiper 5. The thermal expansion of the work roll 3 is larger than that of the lower work roll 4. Due to the difference in the absolute amount of thermal expansion between the upper and lower work rolls 3 and 4, as shown in FIG. 5, the lateral symmetry of the roll gap in the width direction is lost at each shift, and the steel plate 7 meanders. Therefore, in a hot rolling mill having a work roll shift mechanism, an upper limit is usually set for the amount of shift per operation, and as a result, wear and wear of the upper and lower work rolls and thermal expansion which are the original effects of the work roll shift mechanism are obtained. It was not possible to maximize the effect of dispersal of the particles.

[0005] In order to eliminate unevenness in the thickness in the width direction which occurs when a high-speed roll having a larger thermal expansion amount than that of a conventional hot-rolling roll material is used, Japanese Patent Laid-Open No. 7-32 is disclosed.
In Japanese Patent No. 3316, the cooling water amount of the lower work roll is controlled in the width direction to generate a heat crown in which the unevenness is reversed with respect to the profile of the upper work roll in the lower work roll. A method has been proposed in which a lower work roll is formed with a concave heat crown with respect to an upper work roll having a heat crown formed thereon, thereby uniformly maintaining a roll gap in the width direction between the upper and lower work rolls. However, since this method basically uses a heat crown formed by thermal expansion, it is difficult to maintain the left-right symmetry in the width direction of the upper and lower rolls when a work roll shift mechanism is applied. Yes, it is still necessary to set an upper limit.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can reduce the difference in thermal expansion, thereby increasing the allowable upper limit of the work roll shift mechanism. It is another object of the present invention to provide a method for cooling a hot rolling roll in which a steel sheet does not meander.

[0007]

In order to achieve the above-mentioned object, a method for cooling a hot rolling roll according to the present invention is characterized in that the amount of cooling water to the upper work roll is set to 1.2 to less than the amount of cooling water to the lower work roll. It was 2.5 times. By doing so, the upper and lower thermal expansion differences are reduced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In a hot rolling roll, the cooling effect of an upper work roll and a lower work roll is compared.
In the upper work roll, the cooling water stays on the drain wiper as described above, so the cooling effect is lower than that of the lower work roll, and the thermal expansion of the upper work roll is larger than that of the lower work roll. The inventor made the following in order to reduce the difference in thermal expansion between the upper and lower work rolls.

That is, the present invention is a method for cooling a work roll in a hot rolling mill having a work roll shift mechanism, wherein the amount of cooling water to the upper work roll is 1.2 to less than the amount of cooling water to the lower work roll. It was 2.5 times.

[0010] In the method of the present invention, the amount of cooling water to the upper work roll is reduced by 1.2 to 2 times as compared with that to the lower work roll.
The reason for increasing the ratio by 2.5 is as follows. That is, 1.2
If it is less than twice, the upper work roll is not cooled so much, the thermal expansion of the upper work roll becomes larger than that of the lower work roll, and the thermal expansion difference with the lower work roll becomes large. This is because the lateral symmetry of the roll in the width direction is broken, and the steel sheet meanders during shifting by the work roll shift mechanism.

On the other hand, if the amount of cooling water to the upper work roll exceeds 2.5 times that to the lower work roll, then the upper work roll is supercooled and the thermal expansion with the lower work roll occurs. This is because the difference increases, and as a result, the steel sheet meanders as described above.

On the other hand, if the amount of cooling water for the upper work roll is set to be 1.2 to 2.5 times the amount of cooling water for the lower work roll, the difference in thermal expansion between the upper and lower work rolls is reduced. When the work roll shift mechanism is actuated, the deviation of the gap amount in the width direction between the upper and lower work rolls is reduced, the left-right symmetry in the width direction of the upper and lower work rolls is maintained, Do not meander.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIGS. 1A and 1B are views showing a periphery of upper and lower work rolls, and FIG. 1B is a view showing a cooling header in a hot rolling mill to which the hot rolling roll cooling method of the present invention is applied. FIG. 2 is a diagram illustrating a relationship between a cooling water amount ratio and a camber amount at the time of work roll shift when the hot rolling roll cooling method of the present invention is performed. FIG. 3 is a diagram showing the camber amount in FIG.

In FIG. 1, reference numeral 1 denotes a cooling header for cooling the upper work roll 3 of the hot rolling mill from the downstream side in the steel sheet transport direction. It is a cooling header. Among them, the cooling header 1 is arranged, for example, so as to inject cooling water to the upper work roll 3 from obliquely above, while the cooling header 2
Are arranged, for example, to inject cooling water to the lower work roll 4 from obliquely below.

The cooling water injection holes 1 a of the cooling header 1 have the same diameter as the injection holes 2 a of the cooling header 2, and the number of the injection holes 1 a of the cooling header 1 is larger than that of the cooling header 2. By doing so, the amount of cooling water injected to the upper work roll 3 is made larger than that to the lower work roll 4.

In this embodiment, as shown in FIG. 1, the arrangement of the injection holes 1a and 2a of the cooling headers 1 and 2 is such that the lowermost stage of the injection holes 1a and the uppermost stage of the injection holes 2a are formed up to the edge in the width direction. The number of the injection holes 1a, 2a at both ends is reduced toward the upper side of the injection hole 1a and downward toward the injection hole 2a. By arranging in this manner, the amount of thermal expansion at the center in the width direction of the steel sheet can be suppressed.

Reference numerals 5 and 6 denote roll wipers provided in contact with the peripheral surfaces of the upper and lower work rolls 3 and 4 in the axial direction thereof.
This is to prevent scattering on the steel plate.

In the method of the present invention, the amount of cooling water to the upper work roll 3 is set to 1.2 to 2.5 times the amount of cooling water to the lower work roll 4 in the above configuration.

Incidentally, in order to confirm the effects of the present invention,
The coefficient of linear expansion manufactured by centrifugal casting is 1.2 × 10 ^-5 1
/ ° C, covered with an outer layer (thickness: 50 mm) made of Ni gray cast iron having a coefficient of linear expansion of 1.1 × 10 ^-5 1 / ° C. around the core material made of ductile cast iron. The upper and lower work rolls 3 and 4 having a length of 2500 mm are assembled into a final finishing stand having a work roll shift mechanism, and a low-carbon hot-rolled steel strip having a thickness of 3.2 mm and a width of 980 mm (C: 0.04 wt%). Is rolled to a finishing temperature of 880 ° C., the water pressure is 10 kgf / cm ² and the amount of water is 350 to 1050 m.
^It was supplied to the cooling headers 1 and 2 in the range of ³ / hr, and the camber amount at the tip of the steel plate due to the work roll shift was examined.
Note that the camber amount is a distance of a gap at a central portion in the outer peripheral axis direction of the steel plate 7 as shown in FIG.

As a result, as shown in FIG. 2, when the shift amount of the work roll is 100 mm, the ratio of the amount of cooling water to the upper work roll and the amount of cooling water to the lower work roll is about 1.1. When it was smaller, the effective camber amount was out of the range indicated by oblique lines, and when it was larger than about 2.9, the effective camber amount was out of the range, and the steel sheet meandered.

On the other hand, as shown in FIG. 2, when the work roll shift amount is 400 mm, the ratio of the amount of cooling water to the upper work roll and the amount of cooling water to the lower work roll is smaller than about 1.2. Is out of the range of the effective camber amount shown by oblique lines, and when it is larger than about 2.5, it is also out of the range of the effective camber amount shown by oblique lines, and the steel sheet meanders.

In the above results, when the effective camber amount is out of the lower range, the cooling water stays between the upper work roll 3 and the roll wiper 5 to reduce the cooling effect. This is because if the range is out of the upper range, the upper work roll 3 is supercooled, so that the lateral symmetry of the profile in the width direction cannot be maintained.

When the ratio of the amount of cooling water from the upper and lower cooling headers 1 and 2 is set to 1.2 to 2.5 by the method of the present invention, the upper and lower work rolls 3 and 4 are cooled in a well-balanced manner.
Symmetry in the width direction of the profile was obtained, and even when the work roll shift amount was set to 400 mm, the camber amount at the tip end of the steel sheet could be kept in a range where it could be stably conveyed.

In the method of the present invention, the injection holes 1a and 2a are used in the above embodiment when the cooling water is injected at the same pressure.
The diameter of a is the same, and the number of the injection holes 1a and 2a is changed. However, for example, if the cooling water injection pressure is the same as in the above embodiment, In this case, the cooling efficiency may be adjusted in consideration of the positions of the injection holes 1a and 2a, and the upper and lower workpieces may be adjusted. It may be carried out by adjusting the injection pressure of the cooling water in each of the rolls 3 and 4.

[0025]

As described above, according to the hot rolling roll cooling method of the present invention, the amount of cooling water injected to the upper work roll is 1.2 to 2.5 times that of the lower work roll. By doing so, even when the upper and lower work rolls are largely shifted, the lateral symmetry of the profile in the width direction due to thermal expansion of the upper and lower work rolls is maintained, and therefore, the steel sheet does not meander.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a diagram showing a positional relationship between upper and lower work rolls and a cooling header in a hot rolling mill to which the method for cooling a hot rolling roll of the present invention is applied, and FIG. 1B is a diagram showing a cooling header. is there.

FIG. 2 is a diagram showing the relationship between the ratio of the amount of cooling water between upper and lower work rolls and the amount of camber when the method for cooling a hot rolling roll of the present invention is applied to a hot rolling mill having a work roll shift mechanism. It is.

FIG. 3 is a diagram for explaining a camber amount.

FIG. 4 is a cross-sectional view from the steel sheet conveying direction showing a relationship between upper and lower work rolls and a steel sheet in a state where a work roll is not shifted in a conventional method.

FIG. 5 is a cross-sectional view from the steel sheet conveying direction showing a relation between upper and lower work rolls and a steel sheet in a state where a work roll is shifted in a conventional method.

FIG. 6 is a diagram showing that cooling water stays near the upper work roll.

[Explanation of symbols]

 Reference Signs List 1 cooling header (for upper work roll) 1a injection hole (for upper work roll) 2 cooling header (for lower work roll) 2a injection hole (for upper work roll) 3 upper work roll 4 lower work roll 5 (for upper work roll) ) Wiper 6 (lower work roll) wiper

Claims (1)

[Claims] 1. A method of cooling a work roll in a hot rolling mill having a work roll shift mechanism, wherein the amount of cooling water to the upper work roll is 1.2 to 2.5 times the amount of cooling water to the lower work roll. A method for cooling a hot rolling roll.