JP2002239623A - Cooling apparatus for hot-rolled steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling apparatus for hot-rolled steel strips, by which the hot steel strip is stably passed through and also rapid cooling is attained. SOLUTION: A planar apron guide 10 is provided between a plurality of conveying rolls 7 at a prescribed interval from the conveyed steel strip P, a guide hole 11, through which the cooling water passes, is provided on this apron guide, and a cooling box 8 is provided at a prescribed interval from the apron guide, thereby jetting a columnar cooling water toward the center of the guide hole to cool the steel strip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot-rolled steel strip cooling apparatus for cooling a hot-rolled high-temperature steel strip.

[0002]

2. Description of the Related Art In general, a hot-rolled steel strip heats a slab to a predetermined temperature in a heating furnace, and the heated slab is rolled to a predetermined thickness by a rough rolling mill to form a coarse bar. Finish rolling is performed in a continuous hot finishing rolling mill including a stand to form a steel strip having a predetermined thickness. Then, the hot-rolled steel strip is manufactured by cooling it in a cooling stand on a run-out table and winding it up by a winder.

[0003] In an online cooling device that conveys such a rolled high-temperature steel strip on a line and continuously cools it before it is wound up by a winder, firstly, the sheet passing property of the steel strip is increased. Must be considered.

For example, in order to cool the upper surface of a steel strip, a laminar cooling nozzle having a tubular shape is provided directly above a transport roll for transporting the steel strip in a straight line across the width of the steel strip. Cooling water is being injected. Therefore, even if the steel strip is pushed from above by water pressure, it is not necessary to push the steel strip out of the steel strip pass line.

[0005] On the other hand, as a method of cooling the lower surface of the steel strip, a spray nozzle is generally provided between the transport rolls, and cooling water is sprayed from the spray nozzle. In such a cooling mode, the cooling for the upper and lower surfaces of the steel strip is not strictly vertically symmetric,
Cooling of the steel strip becomes intermittent, and rapid cooling (for example, a cooling rate of 200 ° C./s or more at a plate thickness of 3 mm) is almost impossible.

[0006]

In recent years, a hot-rolled steel strip having a fine crystal grain size has excellent workability and low C content.
eq is also required due to its high strength and the like, and rapid cooling (strong cooling) is required for that.

In particular, in a steel having a low carbon concentration such as an ultra-low carbon steel, the grain size of the austenite grains after rolling is rapidly increased by recrystallization, causing coarsening. Therefore, this type of steel requires rapid cooling such that the cooling rate exceeds 200 ° C./s from the Ar3 temperature or higher.

Further, since the tip of the steel strip is conveyed in a free state from the exit of the rolling mill to the winding machine, the steel strip easily vibrates up and down and undulates. Therefore, in order to stably pass the steel strip, the transport rolls are densely arranged, and a spray nozzle is installed between the transport rolls as a cooling device for the lower surface of the steel strip.

However, in such a cooling device,
Strictly speaking, it could not be said to be continuous cooling, and the cooling capacity itself was low.

For example, in Japanese Patent Application Laid-Open No. 62-259610, a cooling device is arranged between transport rolls. This cooling device has a flat injection surface, a plurality of rows of cooling water injection holes, and a nozzle provided at a different angle to the pass line and provided in close proximity to the steel strip.

However, in this cooling device, if the guide is brought sufficiently close to the steel strip in order to stabilize the passability of the hot-rolled steel strip, the injection hole of the nozzle comes close to the steel strip. The cooling water flows through a narrow gap between the steel strip and the cooling water jetting surface.

After all, the cooling water is discharged from the space between the conveying roll before and after the cooling device and the conveying roll and from both side ends of the steel strip in the width direction. However, the cooling water cannot flow out smoothly, so-called poor metabolism and inefficiency. The cooling water temperature rises and temperature unevenness is likely to occur in the width direction of the steel strip.

Further, contact between the steel strip and the guide is unavoidable, and clogging of the injection nozzle occurs, so that uniform cooling of the hot-rolled steel strip cannot be performed. That is, since the nozzle hole formed in the guide is as small as several millimeters, the nozzle hole is deformed by contact with the steel strip, and foreign matter is easily attached to the nozzle hole.

Further, since only the lower surface is cooled, the hot rolled steel strip, especially a thin steel strip, may be lifted, and the cooling capacity may be changed so that uniform cooling is not possible. is there.

Next, as another example, Japanese Patent Application Laid-Open No.
Japanese Patent Publication No. 18 discloses a cooling method in which a guide having a height not exceeding the pass line of the steel strip is provided, and stagnant water is formed such that a water surface surrounded by the guide and the front and rear rolls contacts the lower surface of the steel strip. Have been.

In this case, the momentum of the water jetted from the nozzle is absorbed by the staying water when passing through the staying water layer, so that the collision force is reduced and the cooling capacity is reduced.

In addition, since the cooling water which has become hot due to contact with the steel strip stays between the nozzle and the steel strip, the temperature of the staying water rises to lower the cooling capacity, and the cooling water is locally cooled. Is in a film boiling state, and uneven cooling occurs.

Therefore, if the volume of the retained water is increased so that the water temperature of the retained water zone does not rise, the distance between the hot-rolled steel strip and the guide is increased, and as a result, the running stability of the steel strip is hindered. Can be

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot-rolled steel strip capable of stably passing a hot-rolled steel strip and enabling rapid cooling. To provide a cooling device.

[0020]

According to the present invention, a flat apron guide is provided between a plurality of transport rolls at an interval of 10 to 30 mm from a steel strip to be transported, and the apron guide is provided with a cooling water passage. Guide holes are provided. Cooling means is provided with a gap of 5 mm or more from the apron guide, and columnar cooling water is jetted toward the center of the guide hole. Such cooling means are arranged above and below the hot-rolled steel strip to be conveyed, and are cooled vertically symmetrically with respect to the steel strip.

Therefore, the hot-rolled steel strip can be stably run from the tip and rapid cooling can be performed.
The cooling conditions of the upper surface and the lower surface of the hot-rolled steel strip during cooling are completely the same, and bending during cooling and generation of residual stress after cooling are reduced.

By installing the apron guide only at the center in the width direction of the hot-rolled steel strip to be conveyed, the metabolism of the cooling water is improved, and the occurrence of uneven cooling and insufficient cooling capacity due to stagnant water is eliminated. I do. As a result, a hot rolled steel strip homogeneous in the width direction, the longitudinal direction, and the thickness direction can be stably obtained.

Further, even before the leading end of the steel strip reaches the winder, cooling is performed under the same conditions as cooling under tension by the winder. Therefore, the product yield is high and the quality of the steel strip is improved.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

As a first embodiment, FIG. 1A schematically shows a hot-rolled steel strip manufacturing facility, and FIG. 1B shows a cooling device.

The rough bar 2 rolled by the rough rolling mill 1 is continuously guided to seven continuous finishing rolling mills 3, and is sequentially rolled to a predetermined thickness. The hot rolled steel strip carried out from the final finishing mill 3Z is guided to a run-out table 5 provided immediately after the rolling mill 3Z.

The run-out table 5 is provided with a cooling device (cooling means) 4 to be described later, and the hot hot-rolled steel strip P is rapidly cooled here, and is then transferred to a winder 6 at the rear. Guided and wound, it becomes a hot rolled coil.

The runout table 5 has a hot rolled steel strip P
And a transfer roll 7 having a diameter of 310 mm arranged at a pitch of 500 mm along the transfer direction of the transfer roller 7. A total of twelve sets of cooling boxes 8 are provided, one set between each transport roll 7, and constitute a part of the cooling device 4.

The narrower the interval between the transport rolls 7 is, the more stable the passing of the steel strip is. However, if the interval is too narrow, there is no space for providing a cooling means such as a cooling box, so that the cooling length is short and the cooling efficiency is deteriorated. Therefore, the distance between the transport rolls 7 is
It is desirable that the pitch is from the roll diameter +100 mm to about three times the roll diameter.

Each cooling box 8 has a length direction of 180 mm along the transport direction of the hot-rolled steel strip P and a width direction of 1860 mm orthogonal to the length direction. The distance between the end face of the cooling box 8 and the transported hot-rolled steel strip P is set to 80 mm.

A 16 mm-thick steel plate is fitted on the surface of the cooling box 8 facing the steel strip P. Holes of 4 mmφ are provided in the steel plate in a staggered manner at intervals of 40 mm each in the vertical and horizontal directions, so that cooling water is jetted out. Since the steel plate is thick and the holes are straight cut holes, when the cooling water is injected from these holes, the cooling water becomes a columnar laminar flow.

As shown in FIG. 2, the cooling box 8
An apron guide 10 is provided between the hot-rolled steel strip P to be conveyed. The end face of the apron guide 10 and the steel strip P are set to have an interval of 10 mm to 30 mm.

For example, if the distance between the apron guide 10 and the hot-rolled steel strip P is set to 30 mm or more, as shown in FIG. It folds and collides with the next transport roll 7 and jumps up. As the tip of the steel strip P advances, the vertical vibration of the steel strip is promoted, and the stable threading is impaired. In the worst case, as shown in FIG. 3 (B), the steel strip P may be bent almost in an accordion shape, and eventually run out.

When the distance between the apron guide 10 and the hot-rolled steel strip P is set to 10 mm or less, the steel strip P is always in contact with the apron guide 10, and the steel strip is scratched and the cooling water becomes difficult to drain. The cooling effect deteriorates extremely. For the above reasons, the distance between the apron guide 10 and the hot-rolled steel strip P is preferably set to 10 to 30 mm.

The surface of the apron guide 10 facing the hot-rolled steel strip P is made of a material softer than the steel strip, for example, a plate made of synthetic resin, so that even if the steel strip comes into contact with the apron guide, flaws do not occur in the steel strip. Select

FIGS. 4A to 4D show different forms of the apron guide 10. FIG. (A) is an apron guide 10A having the above-mentioned configuration, (B) is an apron guide 10B formed in a cage shape, (C) is an apron guide 10C formed in a lattice shape, and (D)
Is an apron guide 10D made of expanded metal, any of which can be adopted.

For example, the hot-rolled steel strip P is
When it comes into contact with 0, when the contact portion is narrow, it is the same as point contact, the surface pressure of the contact portion increases, and burn-in or a press mark is easily generated.

For this reason, the apron guide 10 is provided with a guide hole 11 having a minimum necessary diameter for smoothly passing the cooling water injected from the cooling device as shown in FIG.

The thickness of the apron guide 10 depends on the material, but is 5 mm or more in the case of steel. The thinner is better,
In particular, if the thickness is less than 5 mm, the conveyed hot rolled steel strip P collides and breaks or deforms, which hinders cooling.

It is conceivable to increase the thickness in order to provide rigidity. However, if it is too thick, the distance between the cooling box 8 and the steel strip P is increased, and the cooling capacity is reduced. As will be described later, the space between the cooling box 8 and the hot-rolled steel strip P has an upper limit of 100 mm from the relationship of the cooling capacity, and the range within this condition is the upper limit.

Therefore, the apron guide 10 has a plate thickness of 30.
mm synthetic resin plate as a base
An apron guide 10 having an overall thickness of 40 mm is formed by laminating steel plates having a thickness of 40 mm as a reinforcing plate. However, the present invention is not limited to this, and combinations of various steel plates and resin plates can be made within the above thickness range.

The guide holes 11 of the apron guide 10 are opened coaxially with the center axis of the cooling water injection holes provided in the cooling box 8 in a staggered manner. The diameter of the guide hole 11 is set to be at least three times the diameter of the cooling water injection hole.

The diameter of the guide hole 11 is 3 times the diameter of the cooling water injection hole.
If it is less than twice, as shown in FIG. 5 (A), the space between the steel strip P and the apron guide 10 is filled, and the backflow of the cooling water that has lost its place prevents the momentum of the cooling water injected from the injection holes by the reverse flow. Therefore, the cooling capacity is attenuated.

However, if the diameter is too large, the apron guide 10 will be full of holes, and if the steel strip P comes into contact, the contact area of the steel strip will be narrowed, the surface pressure will increase, and burn-in and push marks will not occur. This diameter has an upper limit on the order of the nozzle pitch because the diameter tends to occur. With a normal nozzle arrangement having a nozzle diameter of about 2 to 10 mm, this corresponds to about 10 times the cooling water injection hole diameter.

FIG. 5 shows a case where the diameter of the guide hole 11 is preferable.
It is shown in (B). This figure shows a case where the diameter of the guide hole 11 is four times the diameter of the cooling water injection hole. If the diameter of the guide hole 11 is three times or more the diameter of the cooling water injection hole, a part of the cooling water will The cooling water does not stay between the apron guide and the steel strip. Further, there is no momentum of the cooling water to the guide holes so as to hinder the injection of the cooling water.

For the above reasons, the diameter of the guide hole 11 provided in the apron guide 10 coaxially with the center axis of the cooling water injection hole of the cooling box 8 should be at least three times the diameter of the cooling water injection hole and about the nozzle pitch. Good. Further, it is more preferable to set the diameter to 3 to 10 times the cooling water injection hole diameter.

In the above embodiment, the distance between the apron guide 10 and the end face of the cooling box 8 is set to 3
It is set to 0 mm. This is for the following reason. 5m gap between apron guide 10 and cooling box 8 end face
m or less, there is no escape of the backflow, the cooling water stays between the steel strip P and the apron guide 10, the pressure in this part rises, so-called water drainage becomes worse, and the injection cooling water Momentum weakens.

In order to generate a certain amount of backflow and to improve the drainage of the cooling water, the gap between the apron guide 10 and the cooling box 8 needs to be 5 mm, preferably 10 m.
m or more. However, if they are too far apart, the distance between the cooling box 8 and the steel strip P will be so large that the cooling capacity will be weakened. The space between the cooling box 8 and the hot-rolled steel strip P has an upper limit of 100 mm or more due to the cooling capacity. The range within this condition is the upper limit of the gap between the cooling box 8 and the apron guide 10. Here, since it is set to 30 mm, no problem occurs.

An extreme example is shown in FIG. This is the case where the apron guide 10 and the cooling box 8 are integrated to eliminate the gap, but most of the injected cooling water A stays around the guide hole 11 and the steel strip P, and the pressure in this portion is reduced. Rises, so-called water drainage becomes worse, and the momentum of the injection cooling water is remarkably increased. Therefore, the collision speed with the steel strip P is further reduced, and the cooling capacity is reduced.

On the other hand, the cooling water that has cooled the steel strip P passes through the gap between the steel strip and the apron guide 10 and the space between the apron guide 10 and the transport roll 7 or the cooling box 8.
Spill from both sides of the

As described above, the distance between the end face of the cooling box 8 and the conveyed hot-rolled steel strip P is set to 80 mm for the following reason.

When the distance between the cooling box 8 and the steel strip P is further increased, the force of the injected cooling water is absorbed by the fluid (cooling water) existing between the steel strip P and the cooling box 8 and weakened. On the other hand, if the number of cooling water nozzles is not increased too much, the entire steel strip cannot be covered unless the number of cooling water nozzles is increased, resulting in an increase in the number of nozzles per area and an increase in the amount of cooling water. This is uneconomical.

Ideally, the steel strip P must pass through a position where the surface pressure received from the cooling water from the upper surface and the surface pressure received from the lower surface are balanced. The effect of centering works.

In various experiments, the surface pressure, which is the pressure at which the fluid (cooling water) acts on the steel strip P, is 0.01 to 0.2 kg / c.
With about m ² G, the result that the above-described centering effect can be expected was obtained.

At this time, in order to cool the steel strip P with the laminar cooling water, the interval between the cooling box 8 and the steel strip P cannot be more than a predetermined value. When the diameter of the cooling water injection hole forming the laminar flow is 2 to 5 mm, the interval between the cooling box 8 and the steel strip P is 30 to 100 mm.

If it is 100 mm or more, the cooling water flow is weakened, and strong cooling becomes impossible. Conversely, if it is too close to 30 mm or less, the entire surface of the steel strip cannot be covered unless the number of cooling water nozzles is increased, and it is necessary to take measures to increase the number of nozzles per area or increase the amount of cooling water. It becomes inefficient and uneconomical.

As described above, the distance between the end face of the cooling box 8 and the conveyed hot-rolled steel strip P is set to 80 as described above.
mm.

As shown in FIGS. 1B and 2 again,
The cooling box 8 is arranged as a device for cooling the lower surface of the steel strip P. However, in order to perform the same cooling on the upper surface of the steel strip P, an upper surface cooling box 12 serving as a cooling means is also arranged above the steel strip. You.

[0059] The steel strip P is supported for transporting and traveling.
A drive roll 14 is provided which rotates in the opposite direction at the same peripheral speed as the transport roll 7, that is, in the direction in which the steel strip P is sent from the finishing mill 3 to the winding machine 6.

An upper surface side apron guide 13 is provided between the upper surface cooling box 12 and the conveyed hot rolled steel strip P. The shape and structure of the apron guide 13, the cooling water injection conditions of the cooling box 12, and the relative positional relationship between the cooling box 12, the apron guide 13 and the steel strip P are all set to be the same as the conditions on the lower surface side.

[0061] Incidentally, quantity of cooling water jetted as laminar flow for cooling of the steel strip P is are adjusted to about 3500L / minm ² against one side 1 m ² of the steel strip. At this time, the temperature of the cooling water was 25 ° C.

In the cooling apparatus 4 configured as described above, the hot-rolled steel strip P having a thickness of 3.2 mm, a width of 1500 mm, and a temperature of 900 ° C. after being rolled is guided while being conveyed at a conveying speed of 600 pm. And then carried out.

At the outlet side of the cooling device 4, the temperature of the steel strip P decreases to 710 ° C., and the temperature difference between the width direction and the longitudinal direction is within a range of about 20 ° C. was gotten.

In addition, the tip of the steel strip P passed between the upper and lower cooling boxes 8 and 12 in a stable state, and the steel strip P was always cooled stably. In addition, no flaws or indentation marks were generated on the whole including the tip of the steel strip P.

Next, a second embodiment will be described. A cooling device as a cooling means uses a cooling nozzle in place of the cooling box in the first embodiment. This cooling nozzle is a circular tube laminar nozzle that injects columnar cooling water.

FIG. 7A shows details of the cooling device 4A. Although only the lower-side cooling device is illustrated, an upper-side cooling device having the same structure as that of the lower-side cooling device is arranged as in the first embodiment.

The headers 16 are arranged between the transport rolls 7 having the same diameter in the longitudinal direction and provided at the same pitch as in the first embodiment.
15mm circular laminar nozzle 15 with straight pipe length of 100mm
Are arranged in a zigzag pattern at intervals of 40 mm in the width direction and the longitudinal direction.

The distance between the end of the circular tube laminar nozzle 15 and the steel strip P is set to 80 mm, and the flow of the cooling water injected from the circular tube laminar nozzle 15 becomes a columnar laminar flow A to form a steel strip. Reach P.

An apron guide 10 having a thickness of 40 mm is provided between the end of the circular tube laminar nozzle 15 and the steel strip P. The distance between the apron guide 10 and the steel strip P is set to 10 mm. The surface of the apron guide 10 with respect to the steel strip P is made of a material softer than the steel strip, for example, a flat plate made of a synthetic resin, so that the steel strip P is not damaged by contact with the steel strip P.

The apron guide 10 is provided with a guide hole 11 having a minimum diameter necessary for the columnar cooling water A injected from the circular laminar nozzle 15 to pass. The thickness of the apron guide 10 depends on the material.
Above. The thinner the better, the more particularly, if the thickness is less than 5 mm, the hot rolled steel strip P to be transported collides or breaks or deforms, which hinders cooling.

It is conceivable that the apron guide 10 is increased in thickness in order to provide rigidity. However, if it is too thick, the distance between the laminar nozzle 15 of the pipe and the steel strip P is increased, so that the cooling capacity is weakened, The length of the straight pipe portion of the laminar nozzle 15 becomes long, which causes a problem in cooling capacity. As will be described later, the interval between the tip of the laminar nozzle 15 and the hot-rolled steel strip P has an upper limit of 80 mm from the relation of the cooling capacity.

Therefore, the apron guide 10 has a plate thickness of 30.
mm synthetic resin plate as a base
An apron guide 10 having an overall thickness of 40 mm is formed by laminating steel plates having a thickness of 40 mm as a reinforcing plate. However, the present invention is not limited to this, and combinations of various steel plates and resin plates can be made within the above thickness range.

The guide hole 11 of the apron guide 10 is designed to be coaxial with the center axis of the cooling water injection hole of the circular tube laminar nozzle 15, and the diameter of the guide hole 11 is four times the diameter of the cooling water injection hole, that is, 16 mm.

The diameter of the guide hole 11 is set to be 3 to 10 times the diameter of the injection hole of the circular laminar nozzle 15.
When the diameter is three times or less, the flow velocity decreases due to flow resistance while passing through the guide hole 11, and the speed of collision with the steel strip decreases. If the diameter is 10 times or more, steel strip P and apron guide 1
The backflow of the cooling water filled between 0 and 0 impedes the momentum of the injected cooling water, and the collision velocity against the steel strip is attenuated.

If the diameter is too large, the apron guide 10 will be full of holes, and the contact area when contacting the steel strip P will be narrow, and the surface pressure will increase. Then, burn-in, press-in marks and the like are easily generated.

The ratio of the diameter of the cooling water injection hole to the length of the straight pipe portion of the circular laminar nozzle 15 is set in the range of 5 to 20.

That is, the positions of the cooling water injection hole at the tip of the circular tube laminar nozzle 15 and the height of the entrance surface of the guide hole 11 on the lower surface of the apron guide 10 are arranged to coincide with each other.

When the above-described wake is generated in the guide hole 11 of the apron guide 10, the attenuation of the columnar cooling water flow can be reduced, and the collision of the cooling water with the steel strip P at the collision point can be achieved. Speed is increased and high cooling efficiency can be obtained.

On the other hand, as shown in FIG.
When the distance between the header 16 of the circular tube laminar nozzle 15 and the apron guide 10 is set to 5 mm or less, the accompanying flow is almost eliminated, and the cooling water flows backward from the steel strip side to the cooling box side in the guide hole 11 and passes through the guide hole. The columnar cooling water flow is significantly attenuated.

In order to form a sufficient entrainment flow, the header 16 of the laminar nozzle 15 and the apron guide 10
Is more than 5 mm, preferably 10 mm or more.

As shown in FIG. 8A, when the apron guide 10 and the header 16 of the circular laminar nozzle 15 are in close contact with each other, the water injected from the nozzle 15 causes the guide hole 11 and the steel strip P to be in contact with each other. Since the cooling water that flows backward from the periphery and suppresses the momentum of the injected cooling water, the collision speed of the columnar cooling water against the steel strip decreases, and the cooling capacity decreases.

As shown in FIG. 8 (B), if the distance between the apron guide 10 and the header 16 of the circular tube laminar nozzle 15 is made large, the length of the circular tube portion of the circular tube laminar 15 must be extremely long. Must. Therefore, the flow resistance increases and the supply pressure of the cooling water must be increased, which is not economical. In addition, the circular tube laminar nozzle 15
Since the distance between the tip and the steel strip P is large, the cooling capacity is weakened. The distance between the tip of the laminar nozzle 15 and the hot-rolled steel strip P has an upper limit of 100 mm due to the cooling capacity, and the range within this condition is the upper limit of the gap between the header 16 of the laminar nozzle 15 and the apron guide 10. Become.

Conversely, if the circular tube portion of the circular tube laminar 15 is too short, the cooling water flow does not become columnar, and the collision force against the steel strip is weakened. Therefore, the ratio between the diameter of the cooling water injection hole of the circular laminar nozzle and the length of the straight pipe portion is preferably 5 to 20.

If it is less than 5, the water flow spreads at the nozzle outlet due to a turbulent flow instead of a columnar cooling water flow, and the power of the cooling water weakens before reaching the steel strip. On the other hand, if it exceeds 20, the straight pipe portion becomes longer and the flow resistance increases, so that a high injection pressure is required to obtain a columnar cooling water flow.

On the other hand, the cooling water for cooling the steel strip P is
It flows through the gap between the apron guide 10 and the apron guide 10, along the gap between the apron guide 10 and the transport roll 7, on both sides of the cooling device 4, or along the side wall of the guide hole 11 of the apron guide 10.

The distance (80 mm) between the tip of the circular tube laminar nozzle 15 and the steel strip P was determined as follows.

That is, if the interval between the nozzle 15 and the steel strip P is extremely large, the power of the cooling water is absorbed by the fluid existing between the steel strip P and the nozzle 15 and is weakened. On the other hand, if the number of cooling water nozzles is too close, the entire steel strip cannot be covered unless the number of cooling water nozzles is increased, resulting in an increase in the number of nozzles per area and an increase in the amount of cooling water. This is uneconomical.

Ideally, the steel strip P passes through a position where the surface pressure received from the upper surface and the surface pressure received from the lower surface are balanced, and the effect of centering the vibration and the uneven running of the steel strip P is exerted.

If the pressure at which the fluid (cooling water) acts on the steel strip P is about 0.01 to 0.2 kg / cm ² G, the above-described centering effect can be expected. At this time, in order for the laminar cooling water to reach the steel strip P and cool the steel strip, the space between the cooling device and the steel strip cannot be more than necessary.

If the cooling water injection hole diameter of the circular tube laminar nozzle 15 is about 2 to 5 mm, the distance between the circular tube laminar nozzle tip and the steel strip is preferably 30 to 100 mm. 100m
If m or more, the momentum of the cooling water flow is weakened and strong cooling becomes impossible. Conversely, if it is too close to 30 mm or less, there is no place for the cooling water to flow and it is difficult to obtain a good water flow, rapid cooling is impossible, and the flow of the cooling water differs between the central part and the side ends of the steel strip, Cooling unevenness occurs.

That is, the interval between the end of the circular laminar nozzle 15 and the steel strip P is optimally set to 80 mm.

In this embodiment, the amount of cooling water is about 7300 L / mi per 1 m ² of one side of the steel strip P.
It was adjusted to ensure nm ^2. Cooling water temperature is 25
° C.

The cooling device 4A thus configured
The plate thickness after rolling is 5.7 mm and the plate width is 1200 mm
The steel strip P whose temperature after rolling is 870 ° C.
It was cooled while passing at 50 pm.

At this time, on the exit side of the cooling device 4A, the steel strip P
Was lowered to 725 ° C., and the temperature difference between the width direction and the longitudinal direction was in the range of about 20 ° C., and a steel strip having a substantially uniform temperature distribution was obtained.

The steel strip P is kept in a stable state in the cooling device 4.
A, and the cooling to the tip was stable.
There were no flaws or indentation marks including the tip of the steel strip P.

Next, a comparative example of the above-described first embodiment will be described with reference to FIGS. 9 (A) and 9 (B), showing an outline view and a sectional view of the cooling device 4Z.

A cooling water injection hole b is provided directly on the apron guide 10Z, and cooling water is injected from the injection hole b. Steel plate guides 18 are provided at both ends of the apron guide 10Z.

The cooling device 4Z comprises a cooling box 17 in which a total of twelve sets are arranged between the transport rolls 7 under the same conditions, and has a width of 1860 mm. The space between the cooling water jetting surface of the cooling box 17 and the steel strip P is located 10 mm below the pass line in order to stably pass the steel strip tip, and this cooling water jetting surface also serves as the apron guide 10Z. ing.

The cooling box 17 is provided with 4 mmφ holes in a staggered manner with a length of 40 mm and a width of 40 mm. Since the steel plate is thick and the holes are straight guide holes,
The injected cooling water becomes a columnar laminar flow.

The steel plate guide 18 is provided at the height of the pass line opposite to both sides of the steel strip P so that cooling water is stored between the transport rolls 7 to form a stagnant zone. Therefore, the cooling water that has cooled the steel strip P is supplied to the water level adjusting drain 4, the gap between the steel strip P and the steel plate guide 18, the steel plate guide 1.
It flows out from the gap between the transfer roll 8 and the transport roll 7 or from both sides of the cooling device.

Although not particularly shown, the lower surface cooling box 17
A cooling box having the same structure is provided facing the upper part of the steel strip, and cooling water is injected under the same injection condition to cool the upper surface of the steel strip. In addition, since the steel plate guide 18 for forming a stagnant zone is not provided for cooling the upper surface of the steel strip, it is not provided.

In this comparative example, the cooling condition for the hot-rolled steel strip P is about 3500 L / m ^{2 on} one side of one side of the steel strip.
It was adjusted to inject cooling water of minm ² . The temperature of the cooling water is 25 ° C., and these cooling conditions are the same as in the first embodiment.

A steel strip having a thickness of 3.2 mm, a width of 1500 mm, and a temperature of 900 ° C. was passed through the 4Z cooling device from the tip at a conveying speed of 600 pm and cooled. However, at the exit side of the cooling device 4Z, the temperature of the steel strip is 8
The temperature drops only to 60 to 720 ° C., and the temperature difference between the width direction and the longitudinal direction is about 120 ° C., which is extremely large. Then, streak-like temperature unevenness occurred in the width direction.

That is, since the apron guide 10Z is brought close to the steel strip P in order to give priority to the running property of the steel strip P, a circulating flow is generated between the apron guide 10Z and the cooling box 17, and this flow is injected and cooled. Significantly impedes water momentum.

This circulating flow impedes the cooling water that is about to collide with the steel strip P in order to cool it. Therefore,
Because the cooling water that has lost its destination stays in the narrow area many times, the temperature of the stagnant water rises and the collision point of the cooling water cools well, but the cooling water weakens in the lateral flow area due to the stagnant water, causing unevenness. Conceivable.

The amount of cooling water was about 7 for 1 m ^{2 on} one side of the steel strip.
Even if it increased to 300 L / minm ² , the streak-like temperature unevenness was not eliminated. Further, if the cooling box 17 is separated from the steel strip by 30 mm or more, the tip of the steel strip vibrates, and it becomes difficult to stably pass the tip of the strip. In the case of a thin steel strip of 2 mm or less, when the cooling box was separated from the steel strip of 30 mm or more, no sheet was passed.

Next, a cooling device according to a third embodiment will be described.

[0108] Rolling equipment and a cooling device as shown in FIGS. 1A and 1B are used. That is, the cooling device 4
Each of the upper and lower surfaces is provided with cooling boxes 8 and 12 provided with a total of 15 sets, one set between each transport roll 7 in the longitudinal direction.

In particular, the interval between the cooling box 8 and the steel strip P is set to 80 mm, and a steel plate having a thickness of 20 mm is fitted into the surface of the cooling box 8 with respect to the steel strip P. This steel plate has a hole with an inner diameter of 4 mmf in the width direction of 40 mm,
They are arranged in a staggered manner at intervals of 40 mm in the longitudinal direction.
Since the steel plate is thick and the hole is a straight cut, the injected cooling water becomes a columnar laminar flow.

FIG. 1 shows a space between the cooling box 8 and the steel strip P.
An apron guide 10S as shown in FIGS. 0 (A) and (B) is provided. The apron guide 10S has a thickness d of 40 mm, a width k of 200 mm, and a length m of the lower surface of the guide of 180 mm, which is the same as the longitudinal length of the cooling box 8.
The length n on the upper surface side is 330 mm, and is formed in a substantially trapezoidal cross section.

The distance between the apron guide 10S and the steel strip P is set to 10 mm, but may be in the range of 10 to 30 mm. The surface of the apron guide 10S which comes into contact with the steel strip P is preferably made of a material (for example, resin) which is softer than the steel strip so as not to cause flaws, and its form may be selected from those described above with reference to FIG.

The shape of the apron guide 10S is preferably rounded by reducing the corners on both sides in the width direction. Accordingly, the surface pressure when the steel strip P comes into contact with the end of the apron guide 10S can be suppressed, and the occurrence of scratches can be prevented.

The apron guide 10S is disposed so as to face the center of the steel strip P to be conveyed in the width direction, that is, the center L of the cooling box 8 in the width direction.

For example, when the apron guide 10S is installed over the entire surface in the width direction, the cooling box 8 and the apron guide 1
0S, between the apron guide 10S and the steel strip P, and from both ends of the steel strip.

However, since the apron guide 10S is provided on the entire surface in the width direction, the cooling water tends to stay particularly in the vicinity of the center of the steel strip in the width direction. And cooling becomes inefficient. Further, the collision speed of the cooling water injected from the cooling box 8 to the steel strip P is attenuated due to the effect of the stagnant water that has lost the escape place.

The impact pressure on the steel strip between the case of installing the apron guide 10S in the third embodiment and the case of installing the apron guide so as to face the entire width direction of the cooling box 8 is shown. Measured and compared in cold experiments.

As a result, when the conditions of the third embodiment were adopted, there was almost no pressure difference due to the presence or absence of the apron guide, and the collision pressure was substantially uniform over the entire width of the steel strip P in the width direction. .

On the other hand, when the apron guide was provided over the entire surface in the width direction, the collision pressure was substantially uniform in the width direction.
The collision pressure was reduced by about 0%. This is considered to be due to the effect of the stagnant water between the apron guide and the cooling device, and between the apron guide and the steel strip, as described above.

Therefore, it is preferable that the apron guide 10S be installed so as to face the central portion in the width direction of the conveyed steel strip.
Will be obtained.

Further, the width 200 m used in the above embodiment is used.
The apron guide having a length of m was divided into three parts in the width direction. The apron guide was placed at a position 100 mm from the end of the steel strip P in the width direction and at the center in the width direction, and the collision pressure against the steel strip was measured by a cold experiment.

As a result, the collision pressure at the position where the split apron guide was installed was reduced by about 15% as compared with the case where the split apron guide was installed only at the center. That is, when the divided apron guide is installed at the end in the width direction of the steel strip, the drainage of the cooling water at the end is worse than when installed only at the center. From the above, it is preferable that the apron guide 10S be installed only at the center of the conveyed steel strip in the width direction.

The width of the apron guide 10S to be used is set to 2
Not only 00mm, but also 400mm, 600mm, 80
With 0 mm, 1000 mm, and 1200 mm, the impact pressure on each steel strip P was determined by a cold experiment.

As a result, the width of the apron guide was set to 400 m.
When the impact pressure is 200 m
m, and the impact pressure at other portions in the width direction of the steel strip was also substantially uniform.

On the other hand, the width of the apron guide is 1200 mm
In the case of, the collision pressure at the apron guide installation position is
15% of the area without apron guide
To some extent.

As described above, when the width of the apron guide 10S is increased, the cooling water tends to stay near the center L in the width direction of the steel strip P. Further, it was found that the impact speed of the cooling water injected from the cooling box 8 on the steel strip was attenuated by the effect of the accumulated water, and the collision pressure was reduced.

Conceptually, it is desirable that the width dimension of the apron guide 10S installed in the width direction of the steel strip P is at least １ ／ or less of the width dimension of the transport roll that transports the steel strip. Note that the guide width of the tip of the steel strip P is 200 mm.
There was no particular difference between -1000 mm and all were good.

A gap of 30 mm is provided between the apron guide 10S and the cooling box 8. 5m above gap
When it is less than m, the entrainment flow is reduced, and a backflow from the steel strip P to the cooling box 8 side occurs in the guide hole 11 of the apron guide, and the columnar cooling water flow passing through the guide hole 11 is significantly attenuated.

If there is no gap between the apron guide 10S and the cooling box 8, the cooling water always accumulates in the guide hole 11, and the injected cooling water generates a pressure loss when passing through the guide hole, and causes The collision speed when colliding with the belt is attenuated.

In the cold experiment, when the gap between the cooling box 8 and the apron guide 10S has a gap and when there is no gap, the pressure at which the cooling water collides with the steel strip P is measured. In the case of, the collision pressure was attenuated to 以下 or less as compared with the case where there was a gap.

When there is no gap between the cooling box 8 and the steel strip P, the apron guide 10S is provided only at the center L in the width direction.
However, the collision pressure of the cooling water in the width direction becomes non-uniform, and as a result, temperature unevenness occurs in the width direction of the steel strip.

As described above, it was found that when installing the apron guide 10S of this embodiment, a gap of at least 10 mm was required between the cooling box 8 and the apron guide 10S.

[0132]

As is clear from the above description, according to the present invention, the following effects can be obtained.

(1) While maintaining a stable steel strip passing,
Uniform and strong cooling was possible in the longitudinal and width directions of the steel strip.

(2) The unevenness in temperature in the width direction and the longitudinal direction of the steel strip was reduced, the product quality was stabilized, the variation in the material was reduced, and the shape defect due to thermal strain was eliminated.

(3) Stable cooling was performed from the leading edge of the steel strip, and the yield was greatly improved.

(4) Passing trouble of the cooling device is reduced.
The operation rate of the equipment has increased. The occurrence rate of flaws in the steel strip was greatly reduced and no flaws were formed.

(5) The yield loss due to material slippage was reduced, and the generation rate of scraps was reduced.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of a rolling device and a schematic configuration of a cooling device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of passing a steel plate at the tip end of a plate passing between a cooling device and an apron guide according to the embodiment;

FIG. 3 is a view for explaining a failure state of conveyance of a steel strip.

FIG. 4 is a diagram showing various types of apron guides.

FIG. 5 is a diagram illustrating an arrangement configuration of a cooling device and an apron guide and a laminar flow shape with respect to a steel strip according to the embodiment.

FIG. 6 is a diagram for explaining the arrangement of a cooling device and an apron guide with respect to a steel strip for comparison, showing an example having a defect less than three times and an example of a suitable range.

FIG. 7 is a diagram showing a state of passing a steel plate at a tip end of a steel plate passing between a cooling device and an apron guide according to a second embodiment of the present invention.

FIG. 8 is a view for explaining the arrangement of a cooling device and an apron guide with respect to a steel strip for comparison.

FIG. 9 is a perspective view and a schematic cross-sectional view of a cooling device (also used as an apron guide) of a comparative example.

FIG. 10 is a plan view of a cooling device according to a third embodiment,
FIG.

[Explanation of symbols]

 3Z: Final finishing mill, P: Hot-rolled steel strip, 7: Conveying roll, 10: Apron guide (lower surface side), 11: Guide hole, 4: Cooling device (cooling means), 8: Cooling box (lower surface side) Reference numeral 12: cooling box (upper side), 13: apron guide (upper side), 15: circular tube laminar nozzle (cooling nozzle).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshimichi Hino, Inventor 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Atsushi Watanabe 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Sun Honko Tube Co., Ltd.

Claims (8)

[Claims] 1. A plurality of rotating transport rolls, which are arranged at predetermined intervals and transport a hot hot-rolled steel strip led from a final finishing mill, and are transported between and between these transport rolls. A planar apron guide arranged at a position close to the hot-rolled steel strip; a guide hole for cooling water passage provided in each apron guide; Cooling means for injecting columnar cooling water into the hot-rolled steel strip through the guide hole. 2. The cooling of a hot-rolled steel strip according to claim 1, wherein the transport roll and the apron guide are provided at respective symmetrical positions on both upper and lower surfaces via the transported hot-rolled steel strip. apparatus. 3. The heat transfer device according to claim 1, wherein the apron guide is disposed so as to face at least a substantially central portion in a width direction of the conveyed hot-rolled steel strip. Cooling system for rolled steel strip. 4. The hot-rolled steel according to claim 1, wherein a distance between the conveyed hot-rolled steel strip and the apron guide is set to 10 to 30 mm. Belt cooling system. 5. The cooling of a hot-rolled steel strip according to claim 1, wherein the apron guide comprises a flat plate, and the guide hole is provided through the apron guide. apparatus. 6. A cooling device for a hot-rolled steel strip according to claim 1, wherein a gap between an end face of said cooling means and said apron guide is set to 5 mm or more. . 7. The cooling means is a cooling nozzle, and a diameter of a guide hole of the apron guide is set to be three to ten times a diameter of a cooling water injection hole of the cooling nozzle. The hot-rolled steel strip cooling device according to claim 6. 8. The cooling device for a hot-rolled steel strip according to claim 7, wherein the cooling nozzle has a ratio of a cooling water injection hole diameter to a length of a straight pipe portion set to 5 to 20. .