JPS5844034B2 - How to prevent water cooling nozzle clogging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for preventing clogging of a water spray cooling nozzle, which is characterized by adding air to a water spray nozzle for cooling steel material during a steel material cooling process.

As is well known, in the process of cooling steel materials, clogging of water cooling nozzles often seriously affects the quality and shape of the steel material to be cooled.

When cooling steel materials in this manner, it is essential to prevent water spray cooling nozzles from clogging, especially in processes that require uniform cooling.

The causes of such water cooling nozzle clogging can be broadly classified as follows.

(1) Scale foreign matter due to water spraying or corrosion of piping is carried to the nozzle tip and becomes clogged.

(2) SS (suspended solids) etc. in the water sprinkling combine with the organic binder in the water mentioned on the left and adhere to the pipes, and are carried to the nozzle tip due to changes in the flow rate of the water in the pipes, and when the water sprinkling is stopped, heat from the object to be cooled is released. It is sintered and fills the nozzle.

The inventors of the present invention have actively worked on countermeasures against clogging of the water spray nozzle, and as a result of conducting intensive studies, they have naturally concluded that if the diameter of the water spray nozzle is increased, the water spray nozzle will not become clogged.

That is, the present inventors conducted a long-term running test for several months using water of the quality normally used for cooling hot steel materials as shown in Table 1, with various nozzle diameters.
As shown in FIG. 1, conventionally only 50% of the nozzles were clogged within a nozzle diameter of 1, but no clogging occurred when the nozzle diameter was 41 nm or more.

As described above, enlarging the nozzle diameter is effective as a countermeasure against nozzle clogging.

However, simply increasing the nozzle diameter causes a problem in that when the amount of water is the same as the conventional amount, the pressure in front of the nozzle decreases, making it difficult to maintain a water sprinkling pattern.

In other words, the water amount range in which the watering pattern can be maintained becomes narrower.

In a process aimed at uniform cooling, this causes serious defects in the quality and shape of the steel material to be cooled, similar to the aforementioned clogging of the water spray nozzle.

The present invention solves the problem that it is difficult to secure the water sprinkling pattern when the diameter of the water sprinkling nozzle is increased, and it is used in the water sprinkling nozzle for cooling steel materials in order to prevent nozzle clogging without affecting the original cooling effect. It is characterized by the addition of air.

The purpose of the air added in the present invention is not for mist cooling to atomize (spray) water, but simply to increase the volume (flow rate) of the ejected fluid in front of the nozzle in order to form a water spray pattern.

For this reason, air-water cooling inherently has (1) a wide water flow rate range for maintaining water sprinkling patterns, (2) a wide range of cooling performance, and (3) an increased apparent jet flow velocity of the water nozzle, making it difficult for nozzle clogging to occur.

In addition to these advantages, compared to mist cooling, (1) the amount of added air is only about 1/10, so air running costs are low;

(2) Air control is easy because the amount of air needs to be constant even when the amount of water changes.

There are advantages such as

That is, in order for mist cooling to perform its original function, it is necessary to create a uniform mist, and therefore it is necessary to change the amount of air in accordance with the change in the amount of water.

In contrast, in the present invention, the main purpose of the addition was originally to compensate for the decrease in water flow rate due to the enlargement of the nozzle diameter.
Since water is not changed into mist, it is not necessary to strictly change the amount of air to follow changes in the amount of water, and it is sufficient to add air at a substantially constant level even when the amount of water changes.

Although some of the water sprinkled becomes mist by implementing the present invention, there is almost no difference in the cooling ability for the object to be cooled, and the original cooling effect is not adversely affected in any way.

In carrying out the present invention, the conditions for the added air are as follows.

First, in order to ensure a water sprinkling pattern when the nozzle diameter is set to a diameter that does not cause nozzle clogging, for example, 4 m/m or more, an air amount of 1001/in or more is required per nozzle.
For the upper limit, air volume per nozzle is 2501/ram.
Even if the amount of air is increased further, mist will only progress, and the running cost of the air will increase, making it uneconomical.

Incidentally, the air/water weight ratio for complete mist is 0.1 or more.

In carrying out the present invention as described above, it is of course possible to form a pattern by adding a liquid such as water instead of adding a gas such as air, but of course in this case the cooling effect on the steel material to be cooled is It is undesirable because it causes change.

Next, an example of the device of the present invention will be shown.

The example shown in FIG. 2 is an example in which one nozzle cools the entire width of the steel material.

In the figure, 1 is a spray nozzle for cooling steel materials, which is a wide angle flat nozzle, 2 is a main spray pipe, and 3 is a branch pipe for adding air.

7 indicates spray water and 3' indicates added air.

Further, 4 shows a cross section of the steel material to be cooled. The cross-sectional shape of the flat nozzle 1 is shown in FIG.

a indicates the short axis, and b indicates the long axis. As mentioned above, the minor axis a of the nozzle 1 is selected to be a diameter that does not cause nozzle clogging in the water quality normally used, that is, 4 mm or more.

When attaching the branch pipe 3 to the main pipe 2, the angle (air blowing angle) θ may be any arbitrary angle.

However, if the branch pipe 3 is installed too far away from the tip (distance l from the tip of the nozzle 1), as shown in Fig. 4, at a water volume of 201/mm, there will be more than 500 peaks, and 1011/mm.
In mrn, a breathing phenomenon occurs at a depth of about 420 mm or more, so with a normal amount of water, about 500 mm or less is required, and to ensure perfection, 300 yn□ or less is preferable.

Furthermore, the amount of added air is 250 for the amount of water 51/2 or more.
1/mrrL or more.

In the above configuration, if no air is added in the amount of water required for cooling, the desired water sprinkling pattern cannot be secured as shown by the dotted line in FIG.

On the other hand, when air is added according to the present invention,
As shown by the solid line in FIG. 2, a desired water sprinkling pattern can be secured over the entire width of the steel material 4 to be cooled.

In addition, in the example of FIG. 2, an example was shown in which the entire width direction of the steel material is cooled with one flat nozzle, but it is also possible to use a plurality of nozzles with a slightly smaller jetting angle.
The invention is implemented for each.

The same applies when a plurality of round nozzles are used in the width direction of the steel material.

Next, the present invention will be explained in detail.

Example The present invention was carried out in the state shown in FIG.

The implementation conditions are as shown in Table 1.

The present invention was carried out for 100 days under the conditions described in -E, and no nozzle clogging occurred during that time.

Furthermore, no quality defects caused by cooling occurred during this period.

By the way, before implementing the present invention, a = 1 mm, b = 8
A mm flat nozzle was used, but at that time the nozzle was clogged once every 10 days.

As described above, the present invention solves the problem of pattern non-formation when the nozzle diameter is increased and prevents nozzle clogging by adding air only for pattern formation to a water spray nozzle for cooling steel materials.

Moreover, compared to normal complete mist cooling, the amount of added air is very small, making it economical, and air control is easy because the amount of air remains constant even when the amount of water changes.

Application Examples The idea of the present invention can be utilized in all steel cooling processes, especially in processes where uniform cooling is a problem.

A few examples are (1) Continuous casting secondary cooling zone (Example) (2) Continuous casting and blooming slab cooler (3) Continuous hot rolling cooling table, etc.

As described above, the present invention greatly contributes to preventing clogging of water spray nozzles for cooling steel materials.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between nozzle diameter and nozzle clogging rate, Fig. 2 is a diagram showing an example of the device of the present invention, Fig. 3 is a diagram showing the cross-sectional shape of the nozzle used in Fig. 2, and Fig. 4 is a diagram showing the relationship between the distance from the nozzle tip to the air blowing position and the breathing phenomenon. 1... Nozzle, 2... Main water pipe, 3... Branch pipe,
2... Sprinkling cooling water, 3... Air, 4... Steel material.

Claims (1)

[Claims] 1. A method for preventing clogging of a water spray cooling nozzle, which is characterized by enlarging the nozzle diameter of the water spray cooling nozzle, which causes nozzle clogging in normal use, and compensating for the decrease in the flow rate of water at that time by adding gas.