JPH10323706A - Roll crown control method - Google Patents

Abstract

(57) [Problem] To provide not only a thermal crown can be reduced, but also a roll crown required at an early stage of rolling can be obtained, and downsizing and cost reduction of equipment can be achieved. SOLUTION: A plurality of cooling water / steam headers 6 are arranged along a body length direction of a rolling roll 1, and a cooling water injection nozzle 7 is provided for an inner portion having a plate width of +150 mm according to a plate width during rolling. Supply of cooling water from the cooling water injection nozzle 7 to the outer portion with a plate width of +150 mm, and supply of steam 2 from the steam injection nozzle 8 to control the thermal crown. I do. At this time, the steam injection nozzle 8 was a round pipe having an inner diameter D of 20 mm, and the distance L between the nozzle tip and the roll surface was 150 mm.
The relationship of L ≦ 8 × D was satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a roll crown of a rolling roll, particularly in hot rolling.

[0002]

2. Description of the Related Art In hot rolling, for example, a roll is bent by a reaction force from a rolled material being rolled, and this bending becomes thicker at the center in the width direction of the rolled material and thinner at the ends. This causes the crown to occur.

[0003] Since a flat rolled material is required, a rolling mill is designed to allow the roll to be bent in advance so as to reduce the difference in thickness in the width direction of the rolled material. In many cases, the roll crown is formed by grinding such that the diameter of the center part of the body a in the body length direction becomes large.

[0004] As described above, the roll crown is applied to the rolling roll a so that the rolled material after rolling is flat and the thickness difference in the width direction of the roll is small. As shown in (1), thermal expansion occurs due to the temperature rise on the roll surface and inside due to contact with the rolled material (particularly remarkable in hot rolling), and the roll crown during rolling (thermal crown) It is different from a crown and adversely affects the planar shape of the product.

Incidentally, since the thermal crown is formed by the roll temperature difference in the roll length direction of the rolling roll, heating the roll portion where the rolled material is not in contact is a very effective method for reducing the thermal crown. As a prior art employing such a method, for example, Japanese Patent Laid-Open No. 58-1
Japanese Patent No. 35709 discloses a method of controlling the thermal expansion of a roll caused by heat input from a rolled material by changing the amount of roll cooling water injected to the surface of a rolling roll in hot rolling in the body length direction. As disclosed in JP-A-60-108109, a method has been proposed in which hot water is sprayed onto the surface of a rolling roll to heat the roll.

[0006]

However, as disclosed in Japanese Patent Application Laid-Open No. 58-135709, the amount of roll cooling water sprayed on the surface of the roll in hot rolling is changed in the body length direction to change the rolled material from the rolled material. In the method of controlling the thermal expansion of the roll due to heat input, in the state where the rolled material is not bitten by the roll, there is no heat input from the rolled material to the roll, so that a roll crown cannot be formed. As a result, there is an inconvenience that a necessary roll crown cannot be obtained at the beginning of rolling.

Also, as disclosed in Japanese Patent Application Laid-Open No. 60-108109, in a method of heating a roll by injecting hot water onto the surface of the rolling roll, when cooling water and hot water coexist, the roll is heated to a predetermined temperature. Heating requires a large amount of warm water.

More specifically, the heat transfer coefficient by spraying is generally represented by the following equation (1) (see “Forced Cooling of Steel”, page 98, issued by The Iron and Steel Institute of Japan). logα = 2.354 + 0.646 logW (surface temperature 50 ° C.) (1) α: heat transfer coefficient (kcal / m ² hr ° C) W: water density (l / m ² min) Here, FIG. Rolling roll d (roll diameter φ
700 mm, body length 2000 mm).
When cooling water e of 300 t / hr · m (width) is supplied and cooled in the range of 5 °, the water density becomes W ≒ 18200,
The heat transfer coefficient at this time is α ≒ 128000. In the hot rolling, a large amount of the cooling water e as described above is used in order to prevent the temperature of the roll d during rolling from increasing, and when the temperature of the cooling water e is 30 ° C., the temperature of the roll d is 60 °. C
In this case, about 90 ° C. hot water, which is almost the same amount as the cooling water e, is required, resulting in an inconvenience of increasing the size of the equipment.

In this case, the cooling water amount is set to 300 t / hr · m
Is 1/10 (30 t / hr · m), the heat transfer coefficient is α = 29000. In order to set the temperature of the cooling water e to 30 ° C. and the temperature of the roll d to 60 ° C., 30 t / h
A large amount of 90 ° C. hot water of rm is required.

[0010] Further, using 10 kgf / cm ² saturated steam, 30 ° C. water to 90 ° C. hot water is converted into 30 t / hr ·
In order to make m, the following quantities are required. 1000x × h1 + 1000y × 30 = 1000 (x + y) × 90, x + y = 30 (2) x: steam amount (t / hr), y: water amount (t / hr), h
Enthalpy of steam with 1:10 kgf / cm ² saturation (=
By solving the above equation, the amount of steam becomes x ≒ 4.1 t / hr, and a large amount of steam is required. The heat transfer amount at this time is as follows: Heat transfer amount = α × (90−60) × (π × 0.7 / 8 × 1/10) ≒ 24000 kcal / hr · m.

The present invention has been made in order to solve such inconveniences. In addition to being able to reduce the thermal crown, it is possible to obtain a roll crown required at the beginning of rolling and to reduce the size of the equipment. It is an object of the present invention to provide a roll crown control method capable of achieving cost reduction and cost reduction.

[0012]

In order to achieve the above object, a method for controlling a roll crown according to a first aspect of the present invention is to provide a method for controlling a roll crown by supplying steam to a surface of a roll along a length direction of the roll. Cooling water is supplied to the surface of the rolling roll from a plurality of cooling water headers arranged at predetermined intervals in the longitudinal direction, and further, cooling positioned outside the width of the rolled material in the plurality of cooling water headers The amount of cooling water supplied from the water header is changed and controlled in accordance with the width of the rolled material.

According to a second aspect of the present invention, there is provided a roll crown control method according to the first aspect, wherein the steam is continuously supplied along a body length direction of the rolling roll. According to a third aspect of the present invention, there is provided the roll crown control method according to the first or second aspect, wherein the means for supplying the steam to the roll surface is a steam injection nozzle, and a distance between the tip of the injection nozzle and the surface of the rolling roll. Where L is an inner diameter when the nozzle opening shape is circular, and D when a shorter side length is D when the nozzle opening shape is rectangular, and a relationship of L ≦ 8 × D is satisfied.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory schematic diagram for explaining a roll crown control method according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining vapor condensation, and FIG. 3 is a roll surface temperature and average heat. FIG. 4 is a graph showing the relationship between the roll surface temperature and the amount of steam, FIG. 5 is a graph showing the relationship between the heat transfer coefficient, the L / D value, and D, and FIG. Is an explanatory view for explaining a potential core, FIG. 7 is a side view showing a state in which a plurality of steam / cooling water headers are arranged along the body length direction of the rolling roll, and steam and cooling water in the body length direction of the rolling roll. FIG. 9 is a graph showing changes in the thermal crown before and after performing the roll crown control of the present invention.

As shown in FIG. 1, the roll crown is controlled by a method in which steam 2 is fed from a steam header (not shown) at the exit side of a roll 1 (roll diameter φ700 mm, body length 2000 mm). At the same time as spraying continuously on the surface of the roll 1 from a plurality of cooling water headers (not shown) arranged at substantially equal intervals in the length of the roll 1 on the surface of the roll 1. The cooling water 3 is sprayed at an angle of 45 ° in a range of 30 t / hr · m (width), and is further sprayed from a cooling water header located outside the width of the rolled material 4 among a plurality of cooling water headers. The amount of the cooling water 3 is changed and controlled in accordance with the width of the rolled material 4 to change the roll crown of the rolling roll 1 in the roll body length direction.

When the roll surface temperature is lower than the saturation temperature of the steam 2, the roll surface is heated. When the roll surface temperature is higher than the saturation temperature, the roll 2 is hardly heated or cooled.
Is continuously sprayed on the surface of the rolling roll 1 along the body length direction, thereby heating the roll surface inside and outside the plate width.

The heating by the steam 2 uses the latent heat of the steam 2 to effectively heat the roll surface with a small amount of steam. FIG. 2 shows a schematic diagram when the vapor 2 is condensed. When the vapor 2 is cooled by the roll 1 and condensed, a liquid film 5 of the condensed liquid is generated on the roll surface, and the liquid film 5 becomes a resistance heat. The heat transfer coefficient α is determined in this manner, and the thinner the liquid film 5, the higher the heat transfer coefficient α. The experimental results at this time are shown in FIGS.

As is clear from FIG. 3, a large heat transfer coefficient α ≒ 25000 can be obtained at a roll surface temperature of 60 ° C. 10kgf / c with the temperature of cooling water at 30 ° C
Assuming that the roll is heated to 60 ° C. using m ² saturated steam, the heat transfer amount is α × (90−60) × (0.1 ) ≒ 75000 kcal / hr · m. Compared with the conventional method in which hot water obtained by steam heating is sprayed on the roll surface to heat the rolling roll,
It can be seen that about three times as much heat transfer is possible with about one third of the steam flow, and thus about ten times as much heating capacity.

Next, the experimental results of the heating ability when the roll surface is heated with a nozzle using a nozzle are shown by the heat transfer coefficient and L /
The relationship between the D value and D is shown in FIG. Here, L is the distance between the tip of the steam injection nozzle and the roll surface, D is the inside diameter when the nozzle opening shape is circular, and the short side length when the nozzle opening shape is rectangular.

As is apparent from FIG. 5, it is possible to have a higher heating capacity in a range satisfying the relationship of L / D ≦ 8, that is, L ≦ 8 × D (hereinafter referred to as the formula (3)). I understand.
This is because, as shown in FIG. 6, as the nozzle tip moves away from the roll surface, the steam jet from the nozzle entrains the surrounding air and the steam concentration decreases, whereas the distance L between the nozzle tip and the roll surface becomes 8 ×. Below D, there is a region within the steam jet that does not lose the discharge speed, and this region is usually called a potential core.

In this manner, heating the roll surface directly with steam 2 heats the roll with much higher efficiency than heating the rolling roll by spraying hot water obtained by steam heating onto the roll surface. can do. In this case, it is necessary that the steam 2 is directly condensed on the roll surface as shown in FIG. 2, but in this embodiment, since the steam 2 is directly blown on the roll 1, the water film is removed by the cooling water. The effect works, and the above-mentioned highly efficient roll heating can be guaranteed.

The steam 2 has a large heating capacity because it condenses below its saturation temperature, but has a large heating capacity when it exceeds the saturation temperature, so that it has little heating capacity and does not heat the roll 1 further. Therefore, it is not necessary to change the spray amount of the steam 2 in the body length direction of the roll according to the sheet width of the rolled material 4.

On the other hand, with respect to the roll cooling water 3, the amount of the cooling water 3 jetted toward the roll surface from each of the cooling water heads arranged along the body length direction of the rolling roll 1 is determined by the plate of the rolled material 4. Change control is performed in the roll body length direction according to the width.

That is, the cooling water 3 is sprayed on the surface of the rolling roll 1 corresponding to the inner portion of the width of the plate being rolled to cool the roll 1 along the body length direction. When the rolling roll 1 corresponding to the outer portion of the plate width is strongly cooled, the high-efficiency roll heating effect by the steam 2 described above is reduced, so that the cooling water 3
Is stopped or the injection amount is controlled to be small so that the heating of the roll 1 by the steam 2 is not hindered.

Further, as described above, when the liquid film on the roll surface is thick, the roll heating effect due to the steam is reduced. Therefore, a drainer (wiper) is provided along the roll body length direction, and the steam is removed by the drainer. The injection position and the roll cooling water injection position may be separated to remove the cooling water on the roll surface at the steam injection position.

As is apparent from the above description, in this embodiment, by directly heating the surface of the rolling roll 1 with the steam 2, it is possible to perform high-efficiency roll heating with a small amount of steam, and With respect to the rolling roll 1 corresponding to the outer width portion, the injection of the cooling water 3 is stopped or the injection is controlled according to the sheet width of the rolled material 4 so that the injection amount is reduced so that the heating of the roll 1 by the steam 2 is not hindered. Therefore, high-efficiency roll heating with a small amount of steam can be satisfactorily maintained irrespective of the width of the plate, and only by controlling the injection amount of the cooling water 3 in the roll body length direction. As a result, the size and cost of the equipment can be reduced at the same time.

Further, since the roll portion not in contact with the rolled material 4 is also heated by the steam 2, the difference in roll temperature in the roll length direction of the roll 1 is reduced, and the thermal crown can be greatly reduced. .

Furthermore, since the roll 2 is directly heated by the steam 2, the roll crown can be formed even when the rolled material 4 is not bitten by the roll 1, and as a result, The necessary roll crown can be obtained even at the beginning of rolling.

Further, since the roll crown is controlled using the steam 2 and the cooling water 3, the roll crown can be suitably used in a bad environment (high temperature and high humidity) such as hot rolling.
In particular, when the rolling time is long, such as endless rolling, it can be effective.

In the above embodiment, the rolling roll 1
The amount of cooling water 3 injected toward the roll surface from each of the cooling water heads arranged along the body length direction of the roll is controlled to be changed in the roll body length direction. In the case where the steam is continuously blown along the roll, the steam 2 is applied to the roll surface from each steam head disposed along the body length direction of the rolling roll 1 in the same manner as the cooling water 3. The amount of the steam 2 blown toward the roll body may be changed and controlled in the roll body length direction.

That is, since the rolled material 4 is always rolled and heated in the vicinity of the central portion of the rolling roll 1 in the body length direction, it is not necessary to spray the steam 2, and when the plate width of the rolled material 4 is narrow, the roll body length is reduced. This is because it is not necessary to blow steam 2 to both outer ends in the direction. Thereby, steam saving can be achieved.

[0032]

Referring to FIGS. 7 and 8, a plurality of cooling water / steam headers 6 are arranged along the body length direction of a rolling roll 1;
Depending on the width of the plate during rolling, the cooling water injection nozzle 7 supplies 300 t /
hr.m (width), the supply of the cooling water from the cooling water injection nozzle 7 is stopped and the steam 2 of 2 t / hr.m is supplied from the steam injection nozzle 8 to the outer portion having a plate width of +150 mm. To control the thermal crown. At this time, the steam injection nozzle 8 was a round pipe having an inner diameter D of 20 mm, and the distance L between the nozzle tip and the roll surface was 150 mm.
The above expression (3) was satisfied.

Then, the rolled material 4 having a width of 1000 mm
The rolling roll 1 after the main rolling was extracted, and its temperature distribution was measured. FIG. 9 shows the measurement result and the measurement result before control.
As is clear from the figure, the temperature difference has been largely eliminated compared to before the control, and it can be seen that the thermal crown has been greatly reduced accordingly.

[0034]

As is apparent from the above description, according to the present invention, by directly heating the rolling rolls with steam, high-efficiency roll heating can be performed with a small amount of steam, and at the same time, the outer width of the sheet is reduced. For the rolls corresponding to the part, it is possible to stop the supply of the cooling water or control according to the sheet width of the rolled material so that the supply amount is reduced so as not to hinder the heating of the roll by steam, Regardless of the width of the plate, high-efficiency roll heating with a small amount of steam can be maintained satisfactorily, and only the cooling water supply in the roll body length direction needs to be controlled. And cost reduction can be achieved at the same time.

Further, since the roll portion which is not in contact with the rolled material is also heated by the steam, the roll temperature difference in the roll length direction of the roll is reduced and the thermal crown can be greatly reduced. can get.

Further, since the rolling roll is directly heated by the steam, the roll crown can be formed even when the rolled material is not bitten by the rolling roll. As a result, even at the beginning of rolling, the roll crown can be formed. The effect that a required roll crown can be obtained is obtained.

Further, since the roll crown is controlled using steam and cooling water, an effect is obtained that the roll crown can be suitably used in a bad environment (high temperature and high humidity) such as hot rolling. .

According to the invention of claim 3, claim 1 or 2
In addition to the invention described above, the effect that the roll can be heated with higher efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory schematic diagram for explaining a roll crown control method which is an example of an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining vapor condensation.

FIG. 3 is a graph showing a relationship between a roll surface temperature and an average heat transfer function.

FIG. 4 is a graph showing a relationship between a roll surface temperature and a steam amount.

FIG. 5 is a graph showing a relationship between a heat transfer coefficient, an L / D value, and D.

FIG. 6 is an explanatory diagram for explaining a potential core.

FIG. 7 is a side view showing a state in which a plurality of steam / cooling water headers are arranged along the body length direction of the rolling roll.

FIG. 8 is an explanatory diagram for describing the injection positions of steam and cooling water in the body length direction of the rolling roll.

FIG. 9 is a graph showing changes in thermal crown before and after performing roll crown control according to the present invention.

FIG. 10 is an explanatory diagram for describing a roll having a roll crown formed by grinding.

FIG. 11 is an explanatory diagram for explaining a thermal crown.

FIG. 12 is an explanatory diagram for explaining a conventional roll crown control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Roll roll 2 ... Steam 3 ... Cooling water 8 ... Steam injection nozzle

Claims (3)

[Claims] At the same time, steam is supplied to the surface of the rolling roll along the body length direction, and at the same time, a plurality of cooling water headers arranged at predetermined intervals in the body length direction of the rolling roll cool the surface of the rolling roll. Water is supplied, and the amount of cooling water supplied from the cooling water header positioned outside the plate width of the rolled material among the plurality of cooling water headers is changed and controlled according to the plate width of the rolled material. A roll crown control method, characterized in that: 2. The roll crown control method according to claim 1, wherein the steam is continuously supplied along a body length direction of the rolling roll. 3. A means for supplying the steam to the roll surface is a steam injection nozzle, wherein a distance between the tip of the injection nozzle and the surface of the rolling roll is L, and an inner diameter when the nozzle opening shape is circular, 3. The roll crown control method according to claim 1, wherein, when the nozzle opening shape is rectangular, the relationship of L ≦ 8 × D is satisfied when the short side length is D.