JPH0364729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a strip cooling roll for cooling a strip (steel strip) running in a continuous annealing furnace, continuous hot-dip galvanizing line, etc.

[Prior Art] As a method of cooling a strip in a continuous annealing furnace or the like, there is a cooling method using a roll whose inside is water-cooled. In this method, in order to improve cooling efficiency, the cooling medium is often flowed spirally inside a thin-walled outer cylinder (shell) 1 at a relatively high flow rate, as shown in Fig. 2, for example. . The case where cooling water is used as the cooling medium will be described above.

Since it is impossible to create a cooling water passage as shown in Figure 2 by making holes in a solid roll, in reality, the roll body is composed of an outer cylinder and a central member, and the outer cylinder and A method is adopted in which a cooling medium passage is formed between the central member and the central member.

Conventionally, no particular consideration was given to the connection between the outer cylinder and the central member, and the outer cylinder and the central member were only firmly connected at both ends of the roll body (to prevent cooling water from leaking outside). Consideration has been given to sealing the Therefore, even if the outer cylinder and the central member are apparently in contact at room temperature at the cooling medium passage partition (corresponding to the space between the passages), the temperature of the outer cylinder will rise due to the inflow of heat from the strip. When the outer cylinder thermally expands, the two will separate. Even if a gap is created between adjacent cooling water passages and the passages communicate, the effect on the flow of the cooling water is very small because the gap is small, and there is almost no problem. However, as explained below,
Thermal crown problems arise due to thermal expansion.

In the following, the size and shape of the thermal crown that occurs in conventional rolls will first be explained.

Thermal Crown Size and Shape Created by Conventional Rolls Cooling of the strip by internal cooling rolls consists of three factors:

Heat transfer from strip to roll surface Heat conduction inside the roll shell Heat transfer from the inner surface of the roll shell to the cooling water Here, the following formula (1) holds true.

β/360α _s (T _s − T ₁ ) = λ/δ (T ₁ − T ₂ ) = α _w (T ₂ − T _w ) …(1) where, β: Wrapping angle of the strip around the roll [degrees ] α _S : Heat transfer coefficient from strip to roll [kcal/m ² h°C] λ : Heat transfer coefficient of roll/shell [kcal/mh°C] δ : Wall thickness of conventional roll/shell [m] α _W : Heat transfer coefficient from roll shell to cooling water [kcal/m ² h°C] T _S : Average temperature of strip in contact with roll [°C] T ₁ : Roll surface temperature (average of entire circumference) [°C] ] T ₂ : Roll/shell inner temperature (average of entire circumference)
[°C] T _W : Average temperature of cooling water inside the roll [°C] Equation (1) is a normal one-dimensional steady heat conduction equation. Since the shell thickness is considerably smaller than the roll radius and plate width, the heat flow is close to one-dimensional and can be well approximated by equation (1). In equation (1), the fact that the strip is not wrapped around the entire circumference is approximately corrected by a coefficient of β/360.
However, if the roll rotation speed is high and each point on the roll surface is heated and unheated many times in a short period of time, the temperature inside the shell becomes nearly uniform in the circumferential direction. The degree of approximation by this coefficient also becomes good. Note that the heat transfer between the strip and the atmospheric gas when there is no contact is very small.
It is ignored in equation (1).

When quantities other than T ₁ and T ₂ are known, T ₁ and T ₂ can be obtained by solving equation (1) as a simultaneous equation. Therefore, β, α _s , λ in equation (1),
By substituting practical values for δ, α _w , T _s , and T _w in the case of a continuous strip annealing furnace, T ₁ and T ₂ are determined.
However, β is 180°. α _s is based on past performance
Since it is known that it is about 2000kcal/m ² h℃, it is set as 2000kcal/m ² h℃. λ is approximately 40kcal/ ^m2h ℃ if the shell is steel, and approximately 300kcal/m2 if the shell is copper.
m ² h°C, and we will consider both cases. δ is 10mm=0.01m. α _w is the flow velocity 3
m/sec, and when calculated using the tube turbulent heat transfer equation (2) below, it is approximately 10,000 kcal/m ² h°C, so this value is used. T _S is 550℃ and T _w is 50℃.

Here, T _s was 550°C as the temperature of the steel plate.

In the case of normal continuous annealing, the primary cooling after the soaking treatment is often performed using rolls from 700°C to about 400°C. This is because we considered an intermediate temperature. T _w was set as 50°C as the temperature of the cooling water, but it is considered as an intermediate value between the water injection temperature of the roll and the drainage temperature.

N _u =0.023R _e ^0.8 P _r ^1/3 …(2) N _u : Nusselt number P _r : Brunttle number R _e : Reynolds number Substituting the above values to find T ₁ and T ₂ ,
If the shell is steel, T ₁ = 180°C, T ₂ = 87°C; if the shell is copper, T ₁ = 109°C, T ₂ = 94
℃. Assuming that the average maximum temperature during roll cooling of the strip is T _s = 800°C, T _w = 50°C, for steel T ₁ = 244°C, T ₂ = 106°C, for copper, T ₁ =
138℃, T ₂ = 116℃.

The reason why T _s =800°C was used here is to evaluate the crown amount and temperature when roll cooling is performed from a high temperature state, since the tendency for high temperature annealing is increasing with the progress of continuous annealing technology.

Next, the roll radius is set to 500 mm, and the amount of thermal crown per radius is determined.

The coefficient of linear expansion of steel is 11×10 ^-6 (℃ ^-1 ), and the coefficient of linear expansion of copper is 17×10 ^-6 (℃ ^-1 ), so using these values, the average temperature of the shell ((T ₁ + T ₂ )/2) and the cooling water temperature, calculate the amount of thermal crown per radius. the result,
When T _s = 550℃, it is 0.46mm for steel and 0.46mm for copper.
0.44mm, and if T _s = 800℃, it is 0.69mm for steel.
becomes.

However, according to this simple calculation, the shape of the thermal crown is unknown, and there is no guarantee that the size is accurate. Therefore, we decided to use the finite element method to accurately determine the shape and size of the thermal crown.

The conditions for thermal expansion calculation using the finite element method are as follows.

Roll barrel = 1600mm Sheet width = 600mm and 1200mm Temperature distribution in the thickness direction within the shell at a position inside the sheet width = Changes linearly from T ₁ to T ₂ Within the shell at a position outside the sheet edge Temperature distribution in the thickness direction = 50°C (=average cooling water temperature) uniform from the outer surface to the inner surface As shown above, calculations were performed for the case where the shell is steel, given the condition that the temperature distribution changes suddenly at the edge of the plate. . The calculation results are shown in FIG. Curves A and B have board widths of 600mm and 1200mm, respectively.
The case is shown below. The broken line C is a value obtained by simple calculation. Despite the sudden change in temperature distribution at the edge of the plate, the thermal crown formed a smooth shape bordering the edge of the plate. The following is clear from FIG.

The size of the thermal crown almost matches the value (C) calculated by the simple calculation method. Therefore, if only the size of the thermal crown is to be determined, a simple calculation method is sufficient.

The shape of the thermal crown differs depending on the plate width (A, B). If the plate width is wide, (B) there will be a flat area near the center, but if the plate width is narrow (A), there will be no flat area. Additionally, the position of the slope of the convex crown moves according to the board width.

[Problem to be solved by the invention]

As mentioned above, thermal crowns occur in conventional methods, which cannot be canceled in all cases by a concave initial crown. In other words, the initial crown can only cancel thermal crowns of one size and shape, but the size of the thermal crown depends on the temperature of the strip and the wrapping angle (the method of changing the degree of cooling is to change the wrapping angle). Since the shape changes greatly depending on the sheet width as shown in FIG. 4, it is not possible to make the roll almost flat under various conditions.

For example, when a convex crown is formed on the roll, as shown in FIG. ), the cooling of that part will be considerably delayed. Since the metal strip has a large Young's modulus, such poor adhesion is very likely to occur even when the crown size is quite small. For this reason, uniform cooling in the board width direction becomes impossible. The material becomes non-uniform in the width direction, and the thinner the plate is, the more likely shape defects will occur.

Strip tension is also controlled to suppress this shape defect, but it is important to eliminate the essential cause of roll thermal crown.

In order to investigate the occurrence of shape defects, the following experiment was conducted. A conventional water-cooled roll (made of steel) with the same dimensions as in the calculation example above was additionally installed in the primary cooling zone (conventionally gas jet cooling) of the continuous annealing furnace, and cooling experiments were conducted for various plate thicknesses. Note that the roll is a flat roll without a crown. As a result of the experiment, as the plate thickness became smaller, the defective shape became larger, and in particular, when the plate thickness was 0.4 mm or less, the product could not be used at all, and a severe defective shape occurred that could not be corrected with a tension leveler. Furthermore, when a defective shape occurred, the strip meandered so much that it began to come into contact with the furnace wall, making it impossible to continue the experiment. As described above, when the material becomes thin, it becomes impossible to operate using the conventional method.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a strip cooling roll that hardly causes thermal crowns, in order to prevent shape defects due to cooling even in thin strips and to make the material uniform in the width direction after cooling. It is in.

[Means to solve the problem]

The gist of the present invention is as follows.

In a strip cooling roll where the roll body is formed by a central member of an outer cylinder and an inner cylinder, and a cooling medium passage between them, even if the temperature of the outer cylinder rises due to heat from the strip, the outer cylinder remains connected to the outer cylinder over the entire length of the roll. The inner cylinder is shrink-fitted with a shrink-fitting allowance that maintains the shrink-fitted state, and the center member of the inner cylinder satisfies the following formula, and the thickness from the outer surface of the outer cylinder to the passage is A strip cooling roll characterized in that the thickness t is 6 to 10 mm, and the cooling medium passage is formed on the inner surface of the outer cylinder.

δ ₂・E ₂ ≧ δ ₁・E ₁ However, in the above formula, δ ₂ is the wall thickness of the inner cylinder, E ₂ is the Young's modulus of the material of the inner cylinder, δ ₁ is the wall thickness of the outer cylinder between the passages, E ₁ is the Young's modulus of the material of the outer cylinder.

[Effect]

Next, the operation of the strip cooling roll shown in FIG. 1 based on the present invention will be explained. This is an example of a spiral waterway.

First, the central member 2 of the inner cylinder is made into a cylinder whose wall thickness is considerably larger than that of the outer cylinder 1 (the dimensions will be described later). The central member and the outer cylinder are shrink-fitted at all contact points between the outer cylinder and the inner cylinder as shown in FIG. 3A. At this time, the temperature of the outer cylinder rises due to the heat from the strip, and even if the outer cylinder expands thermally, the joints are shrink-fitted so that they will not separate. Also, the wall thickness t from the outer surface of the outer cylinder to the passage is 6 to 10
mm, and a spiral passage must be formed in the outer cylinder.

In addition, the wall thickness of the outer cylinder between the passages δ ₁ (Fig. 3A) and the wall thickness t from the outer surface of the outer cylinder to the passage
(Fig. 3A) is distinguished from the following because, as will be explained later, the value of t is important in terms of the efficiency of heat removal from the strip and the strength of the sleeve, and the wall thickness δ ₂ of the inner cylinder to be shrink-fitted. This is because the value of δ ₁ is important when evaluating .

With the roll described above, thermal crown hardly occurs even if only the center of the roll is heated due to the strip being narrower than the roll barrel. The reason for this will be explained below.

In the outer cylinder, the temperature near the center of the roll is higher than that near the end of the roll.
It is called the central member. ) has a uniform temperature distribution that is almost the same as the temperature of the cooling water. This is because most of the heat from the strip flows into the cooling water and only a small amount is transmitted to the central member, and the central member is also in contact with the cooling water with a large heat transfer coefficient similar to the outer cylinder. Because of the uniform temperature distribution, the central member itself does not attempt to form a thermal crown, but only the outer cylinder does.

However, the outer cylinder is shrink-fitted. In other words, it corresponds to being stretched in advance under tensile stress in the circumferential direction. Therefore, even if the temperature of the outer cylinder increases compared to the inner cylinder and the outer cylinder expands in the circumferential direction, if the amount of expansion is smaller than the initial strain caused by shrink fitting, the outer cylinder will still maintain a tensile state in the circumferential direction. Therefore, the outer sleeve does not lift up relative to the inner cylinder. Although it is a contact, it is the part of the outer sleeve that is in contact with the strip that causes the temperature of the outer sleeve to rise due to the heat from the strip.
There must be enough shrink-fitting allowance to maintain the shrink-fitted state even if the temperature of that part increases during use. In addition, since the outer sleeve thickness is very small compared to the radial direction, the crown caused by the thickness change due to thermal expansion of the outer sleeve is 2% (thickness/radius) compared to the crown due to circumferential expansion, which is extremely small. small. As long as the shrink fitting allowance is secured as described above, there is almost no heat crown formation.
Therefore, almost no thermal crown is formed (the quantitative results will be discussed later).

Hereinafter, each item necessary for configuring the roll of the present invention will be explained.

(1) How to join the outer cylinder and inner cylinder The joining methods include brazing, adhesive bonding, welding, and bolting, which maintain the jointed state even if a force that tries to separate the joint is applied. There are two possible methods: one by shrink fitting and the other by shrink fitting. The latter method of shrink fitting is easier to implement. Therefore, in the present invention, a method using shrink fitting is adopted. When shrink-fitting is performed, it is necessary to perform the shrink-fitting with the following shrink-fitting allowance.

In water-cooled rolls assembled by shrink-fitting, as the temperature of the outer cylinder rises due to heat from the strip, the shrink-fitting pressure becomes weaker, and the temperature of the outer cylinder ((T ₁
+T ₂ )/2) exceeds a certain value T ₀ and the joint separates. Therefore, a thermal crown begins to form when the temperature reaches T ₀ or higher. In order to prevent this situation, use the above-mentioned formula to find the maximum temperature rise of the outer cylinder under the water-cooled roll usage conditions, and then set a shrink-fit allowance that will maintain the shrink-fit condition even at that temperature. It is necessary to use

This shrink-fitting state must be maintained over the entire length of the roll even when the temperature of the outer cylinder increases. The reason for this is, for example, if the shrink fit is sufficient at both ends of the roll but insufficient at the center, the temperature of the outer cylinder will rise, and at a certain temperature the shrink fit is maintained at both ends of the roll, but at the center of the roll. This is because the shrink fit will come off at some points and a heat crown will occur.

Furthermore, a method to provide a shrink-fitting margin that will prevent the shrink-fit from coming off even if the temperature of the outer cylinder rises due to heat from the strip during use will be described below.

The shrink-fitting allowance is the difference between the outer diameter of the inner cylinder at room temperature before shrink-fitting and the inner diameter of the outer cylinder at room temperature before shrink-fitting to the roll.The shrink-fitting allowance per radius is Δγ. Calculate using the formula below.

Δγ=ΔT・α・γ Here, α: Coefficient of linear expansion of the outer cylinder γ: Roll radius ΔT: Thickness t from the surface of the outer cylinder to the passageway
Since the difference ΔT between the average temperature within and the average water temperature varies depending on the temperature of the threaded material,
Decide according to the maximum temperature to be used.

For example, if the plate material is heated to 800°C, ΔT = 100°, and if the outer cylinder is made of steel, Δγ is
It becomes 0.55mm.

Since it is not normally cooled from 800℃, Δγ
=0.55mm or more is sufficient. Even when a steel outer cylinder is used, if the strength of the outer cylinder is increased, a larger shrink-fitting allowance can be obtained, making it possible to cool the strip at a higher temperature. The above formula holds true not only for steel but also for various materials.

Next, a method for shrink-fitting the outer cylinder and the inner cylinder over the entire length of the roll will be described below.

The inner cylinder and outer cylinder of the roll are manufactured separately, but the outer cylinder is manufactured first. The inner and outer diameters of the outer cylinder are machined, but the accuracy of the inner surface is usually within 20 μm.
After the outer cylinder is finished, the outer diameter of the inner cylinder is machined to an accuracy of within 10 μm using the inner diameter of the inner cylinder plus the shrink-fitting allowance. By shrink-fitting the inner and outer cylinders into a pair, uniform shrink-fitting can be achieved over the entire length.

Shrink fitting usually involves heating only the outer cylinder to 200 to 300°C and fitting it into the inner cylinder, but in some cases, the inner cylinder may be cooled (cold fitting) or both may be combined.

Then, at the stage when it was assembled into a roll,
Finish the surface of the final roll.

(2) Inner cylinder (center member) and its wall thickness The roll of the present invention is a roll for cooling a high-temperature steel strip, and the steel strip is wound around the roll and heat is removed by a water-cooled roll. Therefore, since a large load is not applied to the water-cooled roll, it is not necessary to use a solid roll, and since the roll of the present invention is hollow, the roll body is used as an inner cylinder.

If it is made solid, it has the disadvantage of being difficult to use because it has a large weight and therefore requires a large amount of power to rotate, and because of its large inertia, it is difficult to minimize tension fluctuations during starting, stopping, acceleration and deceleration. .

However, if the wall thickness of the inner cylinder is too thin and its rigidity is insufficient, the inner cylinder will be deformed by the shrink-fitting pressure of the outer cylinder during shrink fitting, and this deformation will promote the occurrence of thermal crown during use. Become. In order to prevent this, it is necessary to satisfy δ ₂ ·E ₂ ≧ δ ₁ ·E ₁ .

Here, δ ₂ is the wall thickness of the inner cylinder, E ₂ is the Young's modulus of the inner cylinder, δ ₁ is the wall thickness of the outer cylinder between the passages, E ₁ is the Young's modulus of the outer cylinder, and δ ₁ and δ ₂ are as described above. See Figure 3A (3) Wall thickness of the outer cylinder The thicker the wall thickness t from the outer surface of the outer cylinder to the passage, the higher the temperature of the outer cylinder near the outer surface, so the heat removal effect from the strip becomes smaller. As a result, the intended purpose cannot be achieved. By making the wall thickness less than 10mm, heat can be removed efficiently.

In addition, the elongation of the outer cylinder in the circumferential direction due to the rise in temperature of the outer cylinder is offset by the elongation due to shrink fitting and does not result in a thermal crown, but the effect in the thickness direction of the outer cylinder cannot be avoided, and if the wall thickness is large The thinner the wall thickness of the outer cylinder is, the greater the expansion in the wall thickness direction becomes.

Thus, from the viewpoint of heat removal efficiency and degree of expansion in the wall thickness direction, the upper limit was set at 10 mm.

On the other hand, the lower limit is set to 6 mm because if it is less than 6 mm, sufficient rigidity of the outer cylinder cannot be ensured.

(4) Forming the cooling medium passage in the outer cylinder The reason why the cooling medium passage is provided on the outer cylinder side is that this increases the area of contact between the outer cylinder and the cooling medium, making it more effective to increase the temperature of the outer cylinder. This is because it can be prevented.

As shown in FIG. 3B, there is also a method of creating a cooling medium path on the inner cylinder side and shrink-fitting the outer cylinder into the roll as shown in FIG. 3B. In this case, compared to the case where a flow path is formed in the outer cylinder, the surface a, which is the contact area between the inner and outer cylinders, becomes a thermal resistance. Since heat flow is obstructed near the partition, the temperature of the outer cylinder increases and cooling efficiency decreases. Furthermore, since the average temperature of the outer cylinder also rises, the shrink-fitting allowance increases, which also poses a problem in terms of the material strength of the inner and outer cylinders. That is why the outer cylinder is machined with a passage.

〔Example〕

A steel cooling roll with an outer diameter of 1000 mm and a length of 2000 mm was created.

Here, as shown in Fig. 6, l ₁ = 22 mm, l ₂ =
8 mm, l ₃ = 12 mm, t = 6 mm, the wall thickness (δ ₁ ) of the outer cylinder between the passages was 18 mm, the inner cylinder thickness was 80 mm, and the cooling passage was an 8-thread spiral.

The shrink fit allowance was set at 0.55 mm per radius.

Temperature analysis and deformation analysis (thermal expansion analysis) were performed on the rolls created as described above using the finite element method, and the runnability of the shrink-fitted rolls was examined. The temperature of the cooling water is 50 degrees, and the heat transfer coefficient α _w of the tube with the roll shell cooling water is 9000 kcal/m ² h°C. Consider the case where a strip at 800°C is wound around a roll at an angle of 180°C, and the heat transfer coefficient from the strip to the roll α _s =1500 kcal/m ² h°C.

It is assumed that the contact surfaces between the outer cylinder 1 and the inner cylinder 2' are in perfect contact with each other and the thermal resistance is zero.

As a result of temperature analysis, the temperature distribution of the inner cylinder 2' is around 54℃ near the partition, and 51~51℃ in other parts (most parts).
The temperature was 52℃, almost the same as the cooling water. This is because the size of the partition of the cooling water passage is appropriate, so that most of the heat from the strip flows toward the cooling water before being transmitted to the inner cylinder 2'.

In this analysis example, the radial displacement of the roll surface, that is, the amount of thermal crown per radius, is
It became 0.046mm. On the other hand, using the same temperature distribution,
When thermal expansion analysis was performed assuming that the inner cylinder 2' and the outer cylinder 1 were not joined (that is, the conventional method), the thermal crown amount was 0.38 mm. Therefore, in this example, the thermal crown could be reduced by 12% compared to the conventional method by shrink fitting.

Also, since the calculated thermal crown without shrink fitting is 0.38 mm, it was found that the shrink fitting allowance of 0.55 mm for this roll is sufficient and appropriate.

Next, a strip cooling experiment similar to that described above was conducted using the roll of the present invention.

Four test rolls were installed in the primary cooling zone of the continuous annealing line, brought into contact with the steel plate whose temperature was 800 to 600℃, and cooled to approximately 400℃ as a whole (roll 1
The standard cooling water flow rate was 20T/h, and the line speed was 200m/min with a plate thickness of 0.7mm. ). Plate width
900 to 1600 mm and a plate thickness of 0.4 to 1.6 mm, but the temperature nonuniformity in the width direction was 15 mm.
It was cooled within ℃.

We also examined the effect of thermal crown by varying the tension, and found that with conventional rolls, squeezing was a problem with 0.4 mm thick material, but with the roll of the present invention, squeezing due to the convex crown was a problem even when the tension was increased. This did not occur, and it was clear from this point that the crown was sufficiently suppressed. When tension is included, it is also effective in preventing meandering of the board, which can be said to be an additional effect of this roll.

As a test, a 1400w strip of 0.15-0.25mm thick material was applied at an input side plate temperature of 550℃, 150m/min, and a tension of 3.
Cooling was performed while passing the plate at a rate of Kg/ ^mm2 .

As a result of the above experiment, almost no shape defects occurred even in a thin plate with a thickness of 0.15 mm, and uniform cooling could be performed in the width direction. In other words, the roll of the present invention enables roll cooling of thin materials, which was previously impossible.

In addition to the spiral passage, the present invention is also applicable to other methods of flowing cooling water, such as a method of flowing cooling water in the axial direction. In either case, care must be taken not to make the interval between the joint between the outer cylinder and the inner cylinder (that is, the interval between the cooling water passages) too large. The reason is that if the gap is too large, even if the rolls are flat at room temperature, when the temperature of the outer cylinder rises, the area between the joints will thermally expand to some extent, causing a local thermal crown. This is because fine irregularities are formed on the roll surface as shown in FIG. 7 (in the case of the dimensions shown in FIG. 6, such irregularities hardly occur).

Furthermore, if the temperature of the cooling water increases significantly, there will be a difference in the temperature of the inner cylinder between the side near the inlet of the cooling water and the side near the outlet, and the roll will not be sufficiently flat. There are two methods to deal with this problem:

By increasing the flow rate of cooling water, the amount of temperature rise of the cooling water is reduced.

As shown in Figure 1, there are two or more cooling water passages so that the cold water near the inlet and the cool water near the outlet and the high temperature cooling water near the outlet flow side by side, so that the average temperature of both flows. Make it the same in every part of the roll. For example, in a spiral passage, the cooling water passages are made like a double thread screw, and water flows in opposite directions in each passage.

In the above explanation, the term "cooling water"
It is not limited to only water, but also includes all other cooling media such as liquids or gases that have a cooling function.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, almost no thermal crown occurs on the roll, so the cooling of the strip becomes uniform in the width direction, the material quality after cooling becomes uniform in the width direction, and even thin materials Also, no shape defects occur.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the roll of the present invention. FIG. 2 is a longitudinal sectional view of a conventional strip cooling roll. FIGS. 3A and 3B are vertical cross-sectional views of the joint between the outer cylinder and the central member. Figure 4 is a graph showing the thermal crown of the roll. FIG. 5 is a plan view showing the state of contact between the strip and the roll, and FIG. 6 is a partial vertical sectional view of the roll showing an embodiment of the present invention. FIG. 7 is a partial longitudinal sectional view of the roll when a local thermal crown occurs. 1: Outer cylinder, 2: Center member (inner cylinder), 3: Partition member, 4: Strip, 5: Roll, 6: Cooling medium passage.

Claims (1)

[Scope of Claims] 1. In a strip cooling roll in which the roll body is formed by a central member of an outer cylinder and an inner cylinder and a cooling medium passage between them, even if the temperature of the outer cylinder rises due to heat from the strip, , the outer cylinder and the inner cylinder are shrink-fitted with a shrink-fitting allowance that maintains the shrink-fitting state over the entire length of the roll, and the central member of the inner cylinder satisfies the following formula; A strip cooling roll characterized in that the wall thickness t from the outer surface to the cooling medium passage is 6 to 10 mm, and the cooling medium passage is formed in an outer cylinder. δ ₂・E ₂ ≧ δ ₁・E ₁ However, in the above formula, δ ₂ is the wall thickness of the inner cylinder, E ₂ is the Young's modulus of the material of the inner cylinder, δ ₁ is the wall thickness of the outer cylinder between the passages, E ₁ is the Young's modulus of the material of the outer cylinder.