JPS6352091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a cooling and drying method for a continuous strip annealing apparatus.

[Conventional technology]

An in-line skin-pass rolling mill (hereinafter referred to as a pressure regulating machine) installed at the exit side of a continuous annealing furnace for steel strips (hereinafter referred to as a strip) is used to prevent the mechanical properties of the strip from deteriorating. The temperature must be kept below 40℃. Usually the temperature of the strip at the exit of the continuous annealing furnace is 100~
Since the temperature is around 150℃, this temperature must be lowered to below 40℃ in order to apply it to the pressure regulator. Therefore, after the strip leaves the annealing furnace, it is cooled by passing through a water tank, and after being drained by high-pressure air blowing or a ringer roll, it is either passed through a pressure regulator, or it is left in a wet state as it is after leaving the water tank. I left it on the pressure regulator. However, in either case, the drying of the strip is insufficient, so the use of continuous annealing equipment has been limited to the operation of wet tempered materials, which are rolled using pressure regulating oil in a pressure regulating machine.

However, recently there has been an increase in demand for dry tempered materials that do not use pressure regulating oil, and it has become necessary to subject dry tempered materials to continuous annealing. To counter this, the strip in front of the pressure regulator inlet must have a dry surface and the temperature must be below 40°C. In the case of batch annealing, there is sufficient time between the annealing process and the pressure regulating process, during which time the strip is cooled to room temperature and dry tempering is also possible. However, in the case of continuous annealing, there is a short time between annealing and pressure adjustment, and cooling and drying must be performed during this short time.

FIG. 6 shows an example in which a hot air drying device was installed on a trial basis after the water tank of conventional equipment, and drying was attempted. In the figure, 1 is a strip, 2 is a continuous annealing furnace, 3 is a water tank,
4 is a hot air drying device, 5 is an air heater, 6 is steam or furnace combustion gas, 7 is a blower, 8 is outside air, 9 is hot air, 10 is a pressure regulator, 11 is an oil applicator, and 12 is a tension reel. 100-150℃ from continuous annealing furnace 2
The strip 1 that comes out at a temperature of is cooled in a water tank 3 and then dried in a hot air dryer 4. The hot air drying device 4 transfers the outside air 8 sent by the blower 7 to the air heater 5.
heated by steam or furnace combustion exhaust gas 6.
It is configured to inject hot air 9 at 90 to 100°C onto the strip 1 to heat and dry it.

In addition, the technology disclosed in Japanese Patent Application Laid-open No. 162229/1983 improves the above technology in terms of energy saving.
The sensible heat of the refrigerant that has risen in temperature by cooling the strip is recovered to produce hot air at a temperature of 100 to 150°C, and this hot air is used to remove water adhering to the strip after washing with water.

Furthermore, although the technology differs from the claimed invention in terms of perspective and configuration,
JP-A-56-72128 discloses a technology for steam exhaust or reducing gas sealing to prevent temper color (oxidation) when cooling water to below 100℃.
There is a publication.

Methods other than water cooling and hot air for cooling and drying the strip 1 include the gas jet method shown in Fig. 7, the roll cooling method shown in Fig. 8, and the gas jet method and roll cooling method shown in Fig. 9. There are combination methods.

First, the gas jet type has a first jet cooler 15 that injects outside air 13 onto the strip 1 using a blower 14 to cool it, and a gas cooler 16 that cools the outside air 13 to form cold air 17 at 15°C, and this cold air 17 is sent to a blower 18. The second jet cooler 19 cools the strip 1 by injecting water into the strip 1, and the temperature of the strip 1 at the outlet of the first jet cooler 15 is set to 75°C, and that of the second jet cooler 19 to 40°C. be.

Next, in the roll cooling type, as shown in FIG. The purpose is to lower the temperature of the strip 1 in contact with the surface of the roll 21. The cold water 23 is supplied by pump 2.
4.

Furthermore, in the combined system of the gas jet system and roll cooling system shown in FIG. 9, the aforementioned jet cooler 15 and water-cooled roll type cooler 20 are arranged in series as shown in the figure, thereby cooling the strip 1. The temperature of the strip 1 is 90° C. at the outlet of the jet cooler 14 and 40° C. at the outlet of the water-cooled roll cooler 20.

[Problem that the invention seeks to solve]

As mentioned above, various devices have been considered for cooling and drying the strip at 100 to 150℃ after leaving the continuous annealing furnace in front of the pressure regulator, but each of them has the following problems. There is.

In the drying method using a hot air dryer, the temperature of the hot air 9 of the hot air dryer 4 was too high, so even if the length of the hot air dryer 4 was shortened, the temperature of the strip 1 remained at 50°C.
℃ or higher, the conditions for dry tempering could not be met, and use had to be discontinued. This is because when hot air is used, it is necessary to suppress the temperature rise of the strip 1 in a short dry zone, and there is no suitable method for highly accurate non-contact temperature measurement, making it difficult to control the amount of hot air.

Technology to reduce oxidation caused by water cooling from high temperatures is effective in shortening continuous annealing lines, but it is expensive because it requires equipment and gas such as steam exhaust and reducing gas supply. Therefore, it is impossible to completely eliminate oxidation.
In addition, separate consideration was required to cool the temperature of the strip sent to the pressure regulator to an optimum temperature.

In the next gas jet type, since the strip 1 coming out of the furnace is cooled with air, the number of passes is increased, and equipment such as a gas cooler 16 is also required, which increases the equipment cost. Moreover, on the surface of strip 1,
Condensation may also occur due to increased relative humidity of moisture in the air or by cooling the strip below ambient temperature.

The water-cooled roll system has strip 1 and water-cooled roll 2.
It is difficult to make uniform contact with the strip, which may result in uneven cooling of the strip. The drawback is that not only a large number of water-cooled rolls are used, but also an expensive refrigerator is required for the water cooler 22, which increases the equipment cost.

Also, a combination of jet and water-cooled roll type coolers is available, such as jet cooler 15 and water-cooled roll type cooler 2.
The disadvantage is that it requires a large amount of equipment cost.

The present invention has been made to solve the above-mentioned problems of the conventional apparatus, and it is an object of the present invention to provide an efficient strip cooling and drying apparatus with low equipment cost.

[Means for solving problems]

In order to achieve the above-mentioned purpose, a water dip tank is installed between the continuous annealing furnace and the pressure regulator, which is configured to adjust the amount of water supplied and control the temperature of the wastewater to a constant level, and a water dip tank is installed between the continuous annealing furnace and the pressure regulator. A strip cooling and drying device was provided, which consisted of a drainer for removing the strips and a strip dryer for drying the strips. The water supply temperature of the above-mentioned water dip tank is kept at about the outside air temperature, and the drain temperature is kept below 40℃.The strip dryer consists of an air heater and a hot air injection header, and the air heater The hot air injection header is configured to inject hot air heated to a temperature slightly higher than the air temperature onto the surface of the strip.

[Effect]

The strip at 100-150℃ leaving the continuous annealing furnace is
First, it is cooled in a water dip tank to a temperature below 40℃ but above the outside temperature. In other words, the water supply temperature in the tank is maintained at around the outside temperature (for example, 30℃ in summer,
(approximately 10℃ in winter), and by adjusting the amount of water supplied, the water temperature in the tank is controlled so as not to exceed 40℃. This is possible by controlling the temperature of the wastewater. The water on the surface of the strip is removed to about 1gr/m ² by a draining device installed after the tank, and then the strip is passed through a strip dryer. The air injected onto the strips by the strip dryer is heated to a temperature 15 to 15 degrees Celsius higher than the outside air temperature, and therefore its relative humidity is considerably lower than that of the outside air. This dry air is used to evaporate and dry the attached water remaining on the surface of the strip, and the length of the dryer varies depending on the temperature of the jetted air and its relative humidity.

As mentioned above, the gist of the present invention is to cool the strip leaving the continuous annealing furnace to about the temperature of the water supply in a water dip tank, remove the water adhering to the surface with a drainer, and then cool the strip by 5 to 15 degrees Celsius above the outside temperature. The idea is to evaporate and dry the remaining water by spraying hot air whose temperature has been raised and the relative humidity has been lowered onto the strip. When hot air is used to dry the strips, the temperature of the strips does not rise above 40°C compared to when hot air is used. Compared to that, it is cheaper and does not require heat countermeasures, so
This has the great advantage of lower equipment costs.

A specific example will be explained below. If outside air with a temperature of 30°C and relative humidity of 80% is heated to 45°C and blown on, the relative humidity at 45°C will decrease to 35.1%.
The absolute humidity _H2 at a temperature of 30℃ and a relative humidity of 80% is
0.022Kg−H ₂ O/Kg−dry air, and the saturated absolute humidity Hw of air at 45℃ is 0.062Kg−H ₂ O/Kg−dry
It is air. Also, the heat transfer coefficient due to the jet flow is 80Kcal/m ²
Assuming hr・℃, mass transfer coefficient _kH is approximately 310Kg/m ²
h, the above-mentioned injected air is 45℃, absolute humidity 0.022
The evaporation rate R in the case of Kg-H ₂ O/Kg-dry air is expressed by the following formula.

R=k _H × (Hw−H) =310×(0.062−0.022) =12.4Kg/m ²・h If the injection is performed at 30℃ and 80%, the saturated absolute humidity of air at 30℃ is 0.027Kg−H Since it is ₂ O/Kg-dry air, R = 1.55Kg/m ² ·hr, and by heating to 15°C, the evaporation rate increases eight times. This is inversely proportional to the length of the dry zone.

Figure 5 shows the results of calculating the required drying length when the strip dryer according to the present invention is applied to a continuous annealing facility for strips with a processing capacity of 100 t/h under the following calculation conditions. This is shown in a graph.

Calculation conditions Amount of attached water 1gr/m ² Values normally used for dryer design Line speed 180mpm Plate width 1300mm Jet heat transfer coefficient 80Kcal/m ^2h ℃ In the same graph, the solid line is the same when the injection temperature is 40℃, and the dashed line is the same. This is the value at 45℃. outside temperature 30
℃ and relative humidity of 80%, the required drying length is 9.5 m when the outside air is heated to 40 ℃, and 5 m when heated to 45 ℃.

The strip dryer is provided with a small-capacity air heater for hot air, and is configured so that the heating temperature of the air in the air heater can be changed as appropriate depending on the temperature of the outside air.

The temperature of the hot air injected onto the strip is slightly higher than the outside air temperature, so if the dryer path length is longer than the distance to complete drying, the temperature of the strip may rise, but the degree of temperature rise is extremely small.
When using hot air at 45°C, the temperature rise in the strip during a path length of 20 m is approximately 0.6°C. Furthermore, during drying, the strip is cooled by the latent heat of vaporization, so even if the path length is actually 40 m, the temperature increase in the strip during that period is less than 1°C. This level of temperature rise poses no problem for the pressure regulator.
Note that by controlling the water temperature in the waiter dip tank, low-temperature drying is also possible at an even lower temperature.

[Embodiments of the invention]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a front view. In the figure, 1 is a strip, 2 is a continuous annealing furnace, 30 is a water dip tank, 31 is a pump, 32 is a water supply, 33 is a drain, 34 is a ring roll, 35 is a strip dryer, 36 is an air injection header, 37 is an air heater, 38 is a blower,
39 is furnace combustion exhaust gas, 40 is hot air, 10 is a pressure regulator, and 12 is a tension reel.

As shown in the figure, the temperature from the continuous annealing furnace is 150℃.
Strip 1 of the water dip tank 30
Inside, the water is cooled by water supply 32 supplied by a pump 31, and the temperature drops to 40°C. In addition, in the water dip tank 30, the temperature of the waste water 33 is controlled to be always maintained at 40° C. or lower by adjusting the amount of water supply 32. Next, the strip 1 is subjected to a ring roll 34 to remove adhering water from the surface to about 1 gr/m ² , and is then passed through a strip dryer 35 . The strip dryer 35 uses an air heater 37 that uses furnace combustion exhaust gas 39 as a heat source to reduce the outside temperature.
This device dries the surface of the strip 1 by spraying hot air 40 heated from 30°C to 45°C onto the surface of the strip 1 using a hot air jetting header 36, and the strip 1 passes through this strip dryer 35. During this time, the water adhering to the surface evaporates and is removed while maintaining the temperature at 40°C. 3a, b and 4 a, b are a front view and a side view showing the hot air injection header 36. The header 36 has a hole 42 or a slit 43 formed in a steel pipe 41 as shown in the figure. It was formed by In the strip dryer 35, a large number of headers 36 are arranged on both sides of the strip 1.

Strip 1 exiting the strip dryer 35
Pressure regulator 1 with a temperature of 40℃ and a dry surface.
0 and then coiled on a tension reel 12.

In addition, in the above example, the linga roll 34 is installed in the drainer.
However, it is also possible to use an air knife with a high-pressure air jet.

Further, the furnace combustion exhaust gas 3 is used as a heat source for the air heater 37.
9 may be replaced by steam or other heat source.

〔Effect of the invention〕

In the present invention, a water dip tank, a water drainer, and a strip dryer are installed after the continuous annealing furnace, and the strip at 100 to 150°C exiting the annealing furnace is water-cooled, water is drained, and then the strip is lowered by about 10°C from outside air. Since drying is performed using a strip dryer that sprays heated air, (1) Dry tempered materials, which were conventionally batch annealed, can be produced using continuous annealing equipment.

(2) Compared to conventional hot air drying methods, hot air rise and uneven cooling can be eliminated.

(3) Equipment costs are significantly reduced.

You can achieve great effects such as:

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a front view thereof, and FIGS. 3 and 4 are front and side views of two types of hot air injection headers of a strip dryer, respectively. , FIG. 5 is a diagram showing the relationship between outside air conditions and drying length. Fig. 6 is a block diagram of a conventional hot air drying device, and Figs. 7, 8, and 9 are block diagrams of a conventional gas jet method, a water-cooled roll method, and a combination of a jet method and a water-cooled roll method, respectively. It is. In the figure, 1 is a strip, 2 is a continuous annealing furnace, 30 is a water dip tank, 32 is its water supply, 33
34 is a draining device, 35 is a strip dryer, 36 is a hot air injection header, 37 is an air heater, 40 is hot air, and 10 is a temper rolling mill.

Claims (1)

[Claims] 1. Disposed after the continuous strip annealing furnace, comprising a water dip tank, a draining device for removing water adhering to the surface of the strip, and a strip dryer for drying the strip. The strip dryer is configured to maintain the temperature of the water supplied to the water dip tank at about the outside temperature, and the temperature of the waste water at 40°C or less, and the strip dryer to maintain the water temperature at about the outside temperature. A cooling drying method for continuous annealing of a strip, characterized in that hot air heated by 5 to 15° C. is injected onto the surface of the strip.