KR20000011032A - Steel band heat-treating apparatus by gas jet stream - Google Patents

Abstract

PURPOSE: A steel band heat-treating method is provided to reduce the amount of driving force being required from a steel band heat-treating device by a gas jet stream while maintaining a heating and cooling rates. CONSTITUTION: A heat-treating apparatus for heating, cooling or drying a steel band by blowing a jet streams of a gas to the steel band, including a resistance body provided at the distal end of a nozzle for jetting a gas jet stream in such a manner that the projection area of the resistance body is not more than 3 to 12 % of the sectional area of the nozzle, or a resistance plate provided at the distal end of a nozzle for jetting a gas jet stream in such a manner that the projection sectional area of the resistance plate is less than 3 % of the sectional area of the nozzle and the plate length in a nozzle axial direction inside the nozzle is at least 50 % of the nozzle diameter.

Description

Steel Band Heat Treatment Apparatus by Gas Jet Flow

A heat treatment apparatus for heating or cooling a steel band by blowing a gas jet stream onto the steel band has also been conventionally provided. However, in the conventional heat treatment apparatus, since gas is used as a thermal medium for performing heat transfer, the heat transfer rate α is low. Therefore, a sufficiently high performance cannot necessarily be provided by the conventional heat treatment apparatus, and the requirement of high heating or cooling rate which must be achieved from the metallurgy point of view cannot be satisfied. For example, the present inventors provided a cooling apparatus for cooling a steel band by blowing a gas jet stream on a steel band, disclosed in Japanese Patent Publication No. 2-16375. In the above cooling apparatus for cooling the steel band, the heat transfer rate was assumed to be in the range of α ≦ 400 kcal / m 2 Hr ° C. When the heat transfer rate is in the above range, it is possible to obtain a cooling rate of 100 ° C./sec when the thickness of the steel band is 0.6 mm. However, when the thickness of the steel band is 1.0 mm, only a cooling rate of 60 ° C./sec can actually be obtained. For the above reasons, when it is necessary to achieve higher heat transfer rates, a roll cooling method in which the water-cooled rolls are made in solid contact with the steel bands, or alternatively the gas and water mix with each other and the steel bands A gas-water cooling method is used which is cooled. However, the roll cooling method is disadvantageous because the roll comes into solid contact with the steel band. Thereby, it is difficult to make the water-cooling roll contact the steel band uniformly. As a result, the steel band cannot be cooled uniformly, resulting in deterioration of the steel band profile. On the other hand, the gas-water cooling method is disadvantageous in that the surface of the steel band is oxidized by dissolved oxygen contained in water since water is used for cooling. Thus, when the gas-water cooling method is used, it is necessary to perform acid cleaning again on the steel band after the end of the heat treatment.

Summary of the Invention

In order to increase the heat transfer rate in the heat treatment apparatus for heating or cooling the steel band by blowing a gas jet stream onto the steel band, it is preferable to increase the flow rate of the gas called onto the steel band. According to experiments conducted by the inventors, it was found that the heat transfer rate can be increased in proportion to the increase in the flow rate of the gas blowing on the steel band. However, as the flow rate of gas increases, the pressure loss in the piping increases dramatically, so it is necessary to provide a very large blower in order to obtain the desired heat transfer rate.

An object of the present invention is to reduce the amount of power required in a steel band heat treatment apparatus by gas jet flow while maintaining a high heating rate or cooling rate.

In order to achieve the above object, the steel band heat treatment apparatus according to the gas jet stream according to the present invention is characterized as described in the following items (1) to (10).

(1) A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band to heat, cool, or dry the steel band, comprising a resistor attached to the tip of the nozzle from which the gas jet stream is ejected; A steel band heat treatment apparatus according to a gas jet stream, wherein the projected area of the resistor is determined to be 3% to 12% with respect to the nozzle cross-sectional area.

(2) a heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band to heat, cool, or dry the steel band, comprising a resistance plate attached to the tip of the nozzle from which the gas jet stream is ejected; And the projection area of the resistance plate is determined to be smaller than 3% with respect to the nozzle cross-sectional area, and the length of the resistance plate in the nozzle axial direction is determined not to be smaller than 50% of the nozzle diameter.

(3) a heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried, comprising: a plurality of nozzles; A plurality of gas ejection headers for supplying gas to the nozzles, to which the plurality of nozzles are mounted; A gas distribution header for supplying gas to the plurality of gas ejection headers, wherein an opening or gap, which is a gas discharge port, is provided between the gas ejection headers, the area of the opening being less than 5 times the nozzle opening area Steel band heat treatment apparatus by gas jet stream not greater than 17 times without.

(4) The steel band heat treatment apparatus according to item (3), wherein the nozzle is a protruding nozzle that protrudes from the tip of the gas ejection header.

(5) The steel band heat treatment apparatus according to item (3), wherein the protruding length of the nozzle is no longer than five times the nozzle inner diameter.

(6) In the item (3), the side profile of the gas ejection header tip is gradually tapered so that the cross-sectional area of the gas passage gradually decreases in the gas ejection direction, and the nozzle tip is a gas ejection that does not protrude from the front end face of the gas ejection header. Steel band heat treatment apparatus by the same type.

(7) A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried, wherein the distance Z from the steel band to the tip of the nozzle is determined not to be greater than 70 mm, The inequality of W / 4 ≤ h is satisfied when the nozzle protrusion elongation from the header for supplying the gas to the nozzle is h mm and the amount of gas (gas amount density) ejected onto the unit area is W m 3 / min · m 2. The steel band heat treatment apparatus by the gas jet stream made into it.

(8) A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried, wherein the supporting rolls are alternately arranged along the advancing direction of the steel band at regular intervals. Roll insertion spaces are provided in the gas ejection space in which nozzles for ejecting the gas ejection stream are provided to prevent rocking of the steel band; In order to extend the gas ejection space, the nozzles for ejecting the gas ejection stream are installed in a roll insertion space opposite the portion in which the roll is inserted with respect to the steel band.

(9) A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried, wherein the supporting rolls are alternately arranged along the advancing direction of the steel band at regular intervals. Roll insertion spaces are provided in the gas ejection space in which nozzles for ejecting the gas ejection stream are provided to prevent rocking of the steel band; In the case of cooling the steel band, the support rolls are cooled; When the steel band is heated or dried, the supporting bands are heated, wherein the steel band heat treatment apparatus according to the gas jet stream.

(10) A steel band heat treatment apparatus using a gas jet stream in which a non-oxidizing atmosphere gas is circulated and ejected on a steel band to cool the steel band, wherein a heat exchanger for the cooling gas is installed at least downstream of a gas compressor such as a blower. Steel band heat treatment apparatus by a gas jet stream, characterized in that the.

The present invention relates to a heat treatment apparatus for heating, cooling or drying a steel band by blowing a gas jet stream onto the steel band.

1 is a graph showing the relationship between density of quantity of gas and heat transfer rate and showing the range of tests conducted in the present invention.

2A, 2B, 2C and 2D show nozzles in a steel band heat treatment apparatus by gas jet flow according to the present invention, respectively.

3A and 3B show the state of gas jet flow at the nozzle tip, respectively.

4 is a graph showing the heat transfer characteristics of the nozzle.

5 is a graph showing the relationship between the ratio of the projected area of the resistor to the cross-sectional area of the nozzle and the heat transfer rate at the position directly below the nozzle;

6 is a graph showing the relationship between the ratio of the resistance plate length to the nozzle diameter and the heat transfer rate directly under the nozzle.

7 shows a positional relationship between a nozzle and a steel band.

8A and 8B show a conventional nozzle, respectively.

9 shows an example of the inventive heat treatment apparatus provided with openings for discharging gas backwards.

10A, 10B and 10C show an example of nozzle arrangement of the heat treatment apparatus of the present invention, respectively.

FIG. 11 is a view showing a relationship between an opening area S ₁ and a nozzle opening area S ₂ in a steel band heat treatment apparatus by gas jet flow. FIG.

Fig. 12 is a graph showing the relationship between the ratio of the opening area to the nozzle opening area and the heat transfer ratio in the steel band heat treatment apparatus by gas jet flow;

13A and 13B show a gas flow in a steel band heat treatment apparatus by gas jet flow, respectively.

FIG. 14 is a view showing a portion where a rising gas flow is generated between cooling nozzles in a steel band heat treatment apparatus by gas jet flow; FIG.

15A and 15B are views showing the structure around the nozzle in the steel band heat treatment apparatus according to the gas jet stream according to the present invention, respectively.

Fig. 16 is a graph showing the influence given to the heat transfer rate by the ratio of the nozzle protrusion length h to the nozzle inner diameter D in the steel band heat treatment apparatus by the gas jet stream.

FIG. 17 shows a relationship between a gas ejection header having no opening and a nozzle in a steel band heat treatment apparatus by gas ejection flow; FIG.

Fig. 18 is a graph showing the relationship between the gas amount density and the heat transfer ratio when the nozzle protrusion length h is changed in the steel band heat treatment apparatus by the gas jet stream.

19 is a view showing the arrangement of the support roll and the gas ejection apparatus in the steel band heat treatment apparatus by the conventional gas ejection flow;

20 is a view showing the arrangement of the support roll and the gas ejection device in the steel band heat treatment apparatus by the gas jet flow according to the present invention.

21 is a cross sectional view of a heating and cooling mechanism and a forward and reverse mechanism of a support roll in a steel band heat treatment apparatus by gas jet flow;

Figure 22a is a view showing the arrangement of a conventional heat exchanger in a steel band heat treatment apparatus by gas jet flow.

Figure 22b is a view showing the arrangement of the heat exchanger in the steel band heat treatment apparatus by the gas jet stream according to the present invention.

Fig. 23 is a graph showing the relationship between the ratio of blower power and the gas blowing temperature when the steel band is cooled in the steel band heat treatment apparatus by gas jet flow;

[Description of Reference Number]

1 ... nozzle

2 ... resistor

3 ... resistance plate

4 ... gas jet

5 ... turbulence

6 ... spiral line

7 ... River Band

8 ... gas blowing header

9 ... blower

10 .. Opening

11 .. Gas Suction Header

12 .. Heat treatment chamber

13 .. Heat treatment chamber wall

14 .. Gas Flow

15 .. Upper conveying roll

16 .. Left Support Roll

17 .. Right foot roll

18 .. Left roll support

19 .. Right roll support device

20 .. Lower conveying roll

21 .. Gas blowing device

22 .. Extension of gas blowing device

23 .. Left support roll insertion space

24 .. Right foot roll insertion space

25 .. gas blowing space

26 .. Bearing

27 .. Support Roll Drive Motor

28 .. water supply pipe

29 .. Drainage pipe

30 .. Bellows

31 .. Electric Shaft

32 .. Distributor

33 .. Support roll reverse motor

34 .. Duct

35 .. Heat Exchanger

Most Preferred Embodiment

The invention is explained in detail as follows. In this regard, the present inventors have explored various fields to solve the problems. In the present invention, problems have been solved in terms of nozzle type, gas discharge, ratio of effective gas ejection length and ejection gas temperature, which will be described below in succession.

First, with regard to the nozzle type, various experiments were conducted to optimize the nozzle diameter and nozzle pitch and the results were compared with each other. As a result of the experiments, it was confirmed that the nozzle diameter and nozzle pitch defined by Japanese Patent Publication No. 2-16375 proposed by the present inventors are most effective even when the flow velocity of gas is increased. Fig. 1 shows the range of the test performed in the present invention and the range of the test performed in Japanese Patent Publication No. 2-16375. As can be seen in FIG. 1, the relationship between the density of a quantity of gas and the heat transfer rate is shown on the graph, even if the heat transfer rate is not lower than 400 kcal / m 2 Hr ° C. unless problems are caused in the discharge of the gas. It is on an extension line.

The stagnation point caused when a gas jet collides with an object causes poor heat transfer rates. Therefore, it is well known that it is effective to promote turbulence at this stagnation point as a means for improving the heat transfer rate of the gas ejected from the nozzle. For example, as shown in Figs. 8A and 8B, Japanese Utility Model Publication No. 61-40155 discloses a structure in which a resistance plate 3 or a spiral line 6 is installed in a nozzle to promote turbulence.

However, in order to install the cross resistance plate 3 as described in Japanese Utility Model Publication No. 61-40155, the nozzle length must be long so that two or three resistance plates can be installed inside the nozzle. Therefore, it is difficult to industrially manufacture a plurality of nozzles having such a structure. When the spiral line 6 is integrated inside the nozzle as described above, the gas is disturbed and released by centrifugal force. As such, this structure is not effective.

As previously described, the turbulence intensity is low at the center of the gas flow. Therefore, in order to effectively increase the heat transfer rate, it is necessary to increase the turbulence intensity at the gas flow center. According to the present invention, as a means for facilitating turbulence at the center of the gas flow and easily usable practically from an industrial point of view, the inventors of the present invention have a resistor (at the center of the tip of the nozzle 1) as shown in FIG. 2) or a structure in which the resistance plate 3 is provided. Due to the above structure of the nozzle 1, as shown in FIGS. 3A and 3B, a turbulent flow 5 in which a vortex row is developed is formed behind the resistor 2 or the resistor plate 3. This makes it possible to create turbulence in the central region of the gas stream 4. In this regard, the cross section of the resistor 2 is not limited to a circle, but may be made in polygonal or other form.

Secondly, the inventors have explored a method for releasing exhaust gas from a nozzle. As previously described, in order to increase the heat transfer rate, the flow rate of the gas blowing on the steel band can be increased. In other words, a quantity of gas blown on the steel band can be increased. However, when the gas is not discharged sufficiently, the gas blown once on the steel band remains on the surface of the steel band and interferes with the new gas blown on the steel band. As a result, the heat transfer rate does not increase significantly. In the graph of FIG. 1, the solid line shows an example in which gas discharge is performed in a good state, and the dotted line shows an example in which gas discharge is not performed in a good state. When the gas is not released in a good state, the heat transfer rate is deteriorated in a range where the gas amount density is higher than a predetermined value. For the above reasons, in order to effectively increase the heat transfer rate, it is very important to smoothly discharge the gas blown onto the steel band. In order to solve the above problems, the present inventors found the following two solutions.

As a result of the exploration of the gas flow after the gas has collided with the steel band, the gas jets from the nozzles collide with the steel bands, flow along the surface of the steel bands, and then with the gas jets from adjacent nozzles, and then Was found to flow in a direction that could be separated from the steel band. This upward flow of gas between the nozzles was produced at the hatched portion in FIG. 14. The flow rate of the upward flow of this gas was 20% to 40% of the flow rate of the gas jet stream coming out of the nozzle.

Therefore, according to the present invention, there is provided an opening or a gap from which gas is discharged, the area of which is sufficient to form an upward flow of the exhaust gas after the gas jet stream from the nozzle collides with the gas jet stream from an adjacent nozzle. Big. In this regard, FIG. 11 shows the relationship between the opening area S ₁ and the nozzle opening area S ₂ .

As shown in FIG. 13A, the gas jet stream from the nozzle 1 collides with the steel band 7, then flows on the steel band 7 and then collides with the gas jet stream from an adjacent nozzle. To rise upwards. As shown in Fig. 13A, when no forced ventilation is performed, this upward flow flows to the widthwise end of the steel band. As a result, this upward flow is not sufficiently discharged. Therefore, it returns from the surface of the gas jet header 8 and mixes with the gas jet stream coming out of the nozzle 1. As a result, the temperature of the gas jet stream from the nozzle 1 rises when the steel band is to be cooled, and the temperature of the gas jet stream from the nozzle 1 decreases when the steel band is to be heated. Therefore, it is impossible to obtain a predetermined heating or cooling capacity. Since the gas remains between the steel band 7 and the gas blowing header 8, the flow rate of the sheet-shaped gas flow on the steel band 7 is lowered. Therefore, the cooling capacity deteriorates around the collision site of the gas jet stream emitted from the nozzle 1.

In the arrangement according to the invention, an opening 10 is provided between the gas ejection headers 8 as shown in FIG. 13B. The upward flow flows into the opening 10. As a result, the gas jet flow from the nozzle 1 reaches the surface of the steel band hardly affected by the upward flow of the returned gas. Thus, the steel band can be cooled or heated effectively. Since no gas remains between the steel band 7 and the gas blowing header 8, the gas can flow smoothly along the steel band 7. Thus, deterioration of the cooling or heating capacity of the gas can be alleviated.

An example of the structure around the nozzle of the heat treatment apparatus according to the present invention is shown in FIG. 15. As shown in FIG. 15A, the nozzle 1 is a protruding nozzle whose tip protrudes more than the tip of the gas ejection header 8. Thus, when the gas is discharged from the opening 10, a part of the gas jet stream from the nozzle 1 is prevented from being discharged directly without colliding with the steel band. In the example shown in FIG. 15B, although the tip of the nozzle 1 is at the same level as the tip surface of the gas jet header 8, the profile of the tip of the gas jet header 8 is gradually narrowing ( is tapering). In other words, the cross-sectional area of the gas passage is gradually reduced in the gas ejection direction. As a result, the exhaust gas inlet portion between the gas ejection headers 8 is gradually narrowing. Thus, the smallest area in the exhaust gas passage can be assumed to be an opening in the case shown in FIG. 15A. As a result, it is possible to provide the same effect as in the structure shown in Fig. 15A.

Next, a second gas discharging method by which the gas can be smoothly discharged is described below.

According to the first gas discharge method, the gas is discharged behind the nozzles through the opening between the gas ejection headers. However, the first gas discharge method is disadvantageous in that the gas ejection header is divided into a plurality of parts at the opening intervals. For the above reasons, although the first gas release method is ideal, the equipment cost is increased. Therefore, according to the second gas evacuation method, there is no opening communicating with the rear of the nozzle, and the nozzle protrudes to an appropriate protruding height. That is, if the nozzle protrusion extension h shown in Fig. 17 is assured, there is no interference with the ejecting gas since the space in which the gas is discharged is formed behind the nozzle and in a direction parallel to the steel band, and no gas remains. Do not. The method has already been proposed by the inventors in Japanese Patent Publication No. 2-16375. According to Japanese Patent Publication No. 2-16375, the distance Z from the steel band to the tip of the nozzle is defined to be not greater than 70 mm, and the nozzle protrusion length h is not less than (100-Z) mm. Is limited. However, as previously described, these values are determined under the assumption that the heat transfer rate is α ≦ 400 kcal / m 2 Hr ° C. This time, experiments were conducted on a range where the heat transfer rate was higher than the above mentioned value, and the following was found. With the increase in the amount of gas, the limitation that the nozzle protrusion length h should not be smaller than (100-Z) mm is not sufficient. Unless a term of density Wm 3 / min · m 2 of gas amount per unit area is added to the evaluation, it is impossible to make appropriate evaluation criteria. In other words, the inventors have found that it is important from the physical point of view to limit the gas discharge space according to the amount of gas to be blown.

Therefore, the inventors conducted an experiment in which the heated steel band was cooled by varying the nozzle protrusion elongation h, and thus a relationship between the gas amount density and the heat transfer ratio was found. Here, the heat transfer rate ratio is defined as the ratio of heat transfer rates when a certain heat transfer rate is determined to be a reference value. This relationship is shown in FIG. According to Fig. 18, when the nozzle protrusion extension is 200 mm, the heat transfer rate ratio increases substantially in proportion to the increase in gas amount density. When the nozzle protrusion elongation h is small, the increase in the heat transfer rate ratio is suppressed from a certain gas amount density, and the ejected gas remains and interferes with the newly ejected gas. This tendency occurs in a range where the gas quantity density is low when the nozzle protrusion extension h is small. From the above relationship, the following equation can be obtained.

W / 4 ≤ h,

Here, the gas amount density is W m 3 / min · m 2, and the required nozzle protrusion extension is h mm.

In this regard, for gas quantity density W, of course, calculations are made for the maximum gas quantity density, in order to ensure that the function appears effectively in all ranges of the device performance. For nozzle protrusion elongation h, it is possible to find the minimum elongation according to the above principle. However, if the elongation h becomes unnecessarily long, the pressure loss at the nozzle is increased and the production cost of the device is increased. Therefore, it is desirable to select the minimum elongation required.

Third, the inventors explored the ratio of effective gas blow lengths. Usually, in the case of cooling, the cooling rate is defined as Δt / T ° C / sec, where the cooling temperature difference is Δt ° C and the period required for cooling is T sec. In the case of heating, the heating rate is defined in the same way as for the cooling rate. From a metallurgical point of view, cooling and heating rates are important. In order to increase the cooling and heating rate, the inventors devised the device. In the steel band heat treatment apparatus by the gas jet stream, in order to increase the heating rate or cooling rate, the distance between the nozzle and the steel band is reduced so that the reduction in the flow rate of the gas ejected from the nozzle can be prevented as much as possible. Accordingly, in order to suppress warp or flutter of the steel band, the supporting rolls 16 and 17 are made to contact the steel band 7 at a slight interval, as shown in FIG. The warping or the fluctuation of the band is corrected and the gap between the nozzle 1 and the steel band 7 is reduced.

However, for reasons of work performance, these support rolls 16, 17 are provided with roll support devices 18, 19 so that these support rolls 16, 17 can be advanced and retracted during the operation. Accordingly, it is necessary to provide the supporting roll insertion spaces in the apparatus, and it is impossible to blow gas into these spaces. That is, the supporting roll insertion spaces become useless areas in terms of heat treatment. Due to the presence of these spaces, the heating rate and cooling rate are partially lowered, which is disadvantageous from a metallurgical point of view. In metallurgy, it is important to increase the average heating rate or average cooling rate. In order to increase these values, it is effective to increase the efficiency of the gas blowing space, and it is effective to reduce the supporting roll insertion space as much as possible.

In Fig. 19, the effective gas ejection length ratio is defined as the ratio of the length of gas actually ejected to the length L1 from the start to the end of the ejection gas. In the case of a conventional continuous annealing apparatus for continuously annealing steel bands, the effective cooling length ratio was about 80%. In order to improve the above situation, the inventors have explored how heating or cooling is performed even in the supporting roll insertion space. The support roll insertion space shown in FIG. 19 is separated on both sides. One is the side into which the roll is inserted, and the other is the side facing the steel band without the roll being installed. As shown in FIG. 20, when the extension part 22 of a gas blowing device is provided in the side where a roll is not provided, it is possible to change this part to a gas blowing space. On the side where the roll is installed, a roll supporting device for advancing and reversing the supporting rolls 16 and 17 is provided. Therefore, it is difficult to provide a gas blowing device on this side. Even if a gas ejection device is provided on this side, it is difficult for the gas ejection device to approach the steel band. Thus, the efficiency is low. Accordingly, the inventors have devised an apparatus in which the supporting roll itself is heated or cooled to perform roll heating or roll cooling. By virtue of the foregoing, the support roll inserting region, which has been a useless area with respect to conventional heating or cooling, can be made very small, and heating or cooling can be performed even in such a support roll inserting region. By the above, it becomes possible to improve an average heating or cooling rate.

Fourthly, the inventors have explored the optimization of blowing gas temperature in the case of cooling the steel band. In general, as the blowoff gas temperature decreases, the power required for the blower tends to decrease. However, when the blowing gas temperature is reduced to a value lower than a predetermined value, in order to reduce the blowing gas temperature, the temperature difference between the coolant and the blowing gas used in the thermally effective ventilator is reduced. Therefore, even if the pressure loss in the heat exchanger increases, the temperature of the blowing gas does not decrease much. As a result, the power required for the blower is conversely increased. The inventors have investigated in detail the blowing gas temperature. As a result, the following was found. The optimum blowing gas temperature, ie the power required for the blower, was minimized in the range of approximately 60 ° C to 200 ° C. The inventors also note that this varies with the heat transfer rate, with the steel band temperature at the inlet side of the heat treatment apparatus, with the steel band temperature at the delivery side of the heat treatment apparatus, and with the temperature of the coolant used in the heat exchanger. Found. The present inventors also investigated in detail the range with high heat transfer rate. As a result of the investigation, the following was found. As shown in Fig. 23, in the range with a high heat transfer rate, the optimum point is shifted to the lower side of the ejection gas temperature as compared with the conventional range with the low rate of heat transfer, and the ejection gas temperature greatly influences the power required for the blower.

Accordingly, the inventors have studied how the blown gas temperature can be effectively reduced. In a heat treatment apparatus in which a non-oxidizing gas is circulated on a steel band and cooled, the heat band is cooled, and a heat exchanger in which water is used as a coolant is generally used as a cooling method for cooling the gas. In view of protecting the blower from heat, a heat exchanger has conventionally been installed at the inlet side of the blower. In this case, in order to lower the blowing gas temperature, the capacity of the heat exchanger can be increased. However, when the temperature difference between the coolant and the gas is reduced, the heat exchange efficiency becomes worse and the pressure loss increases when the gas flows through the heat exchanger. However, regardless of the increase in the pressure loss, the blowing gas temperature is not reduced. As a result, as shown in FIG. 23, when the blowing gas temperature becomes too low, the power required for the blower, on the contrary, increases. Therefore, the inventors aimed at increasing the temperature of the blowing gas in the case of increasing the pressure of the blowing gas by the blower. Accordingly, the inventors devised an arrangement in which the heat exchanger is installed on the carrying side of the blower. In other words, instead of further installing a heat exchanger on the inlet side of the blower, a heat exchanger is further installed on the carrying side of the blower. By the foregoing, the temperature difference between the gas and the coolant can be increased, and thus the heat exchange efficiency can be improved. By this arrangement, even in the case of the same heat transfer rate α, the same blowing gas temperature can be obtained by the blower power lower than the power in the conventional arrangement. In particular, when the increase in the pressure of the blower is increased so that the gas blowing speed to the steel band can be increased, the effect can be remarkable because the gas temperature at the blower is greatly increased.

[Examples]

Examples continue to be described as follows. First, the resistance plate attached to the nozzle is described below.

The heat transfer characteristics of the single nozzles shown in FIGS. 2A and 2B were investigated, with the resistor 2 attached to the single nozzle shown in FIG. 2A and the resistor plate 3 attached to the single nozzle shown in FIG. 2B. . Here air was used as the gas for cooling. The nozzle diameter was set at 10.5 mm, the speed of air blown out of the nozzle was set at 150 m / s, and the distance from the tip of the nozzle to the object to be cooled was set at 50 mm.

The characteristics of the nozzle with the resistor attached to the tip were investigated as the hot plate was cooled using this nozzle. The results of the investigation are shown in FIG. As shown in FIG. 4, the heat transfer rate was increased at the position just below the nozzle center.

As for the resistor, the ratio of the projected area of the resistor to the cross-sectional area of the nozzle under the above cooling conditions is shown in FIG. As can be seen in FIG. 5, the effect of improving the heat transfer rate can be provided when the ratio of the projected area of the resistor to the cross-sectional area of the nozzle is not lower than 3%. When the ratio of the projected area of the resistor to the cross section of the nozzle is not lower than 12%, the pressure loss at the tip of the nozzle caused by installing the resistor is increased. Thus, the amount of power required for the blower is increased. Therefore, an arrangement in which the ratio of the projected area of the resistor to the cross-sectional area of the nozzle is not lower than 12% is not economical. For the above reasons, the ratio of the projected area of the resistor to the cross-sectional area of the nozzle was determined to be 3% to 12%.

In the same way, for a resistive plate of thickness less than 3% of the nozzle cross-sectional area, the length of the plate in the nozzle axial direction was studied. As a result of the study, it was confirmed that the heat transfer rate was improved when the length of the plate was not less than 50% with respect to the nozzle diameter. Regarding the thickness of the resistance plate, when the thickness is not less than 3%, the pressure loss of the blowing gas is increased due to the resistance plate length in the nozzle axial direction compared to the above-described resistor. Therefore, in order to reduce the amount of power for the blower, it is advantageous that the thickness of the resistance plate is less than 3%.

Secondly, an example of a gas discharge method for allowing gas to be smoothly discharged from a nozzle is described as follows. 9 is a longitudinal cross-sectional view of the heat treatment apparatus of the present invention. It is provided with nozzles 1 protruding against the steel band 7 moving in the direction of the arrow. The gas jet flows from the nozzles 1 onto the steel band 7 so that the steel band 7 can be heat treated. Here, when the blowing gas is heated, this heat treatment device is used as a heating device, and when the blowing gas is cooled, this heat treatment device is used as a cooling device. In many cases, the heat treatment chamber 12 is filled with a non-oxidizing atmosphere in which hydrogen is mixed with nitrogen to prevent oxidation of the steel bands. However, even when a gas such as air is used, the same effect can be provided. Arrows shown in FIG. 1 indicate the flow of gas.

Gas is provided continuously from the blower 9. The gas is then sent to the gas ejection headers 8 divided via a gas distribution header (not shown). The gas jet stream blown from each nozzle 1 and colliding with the steel band 7 takes heat from the steel band 7. Then, the gas jet flow changes direction and is discharged from the opening portion 10. That is, the gas is discharged behind the nozzle 1 with respect to the steel band 7. After the gas is discharged, the gas is sent back to the blower 9 via a suction gas header 11. The pressure of the gas is raised by the blower 9 and then recycled.

Although not shown in FIG. 9, an apparatus for heating or cooling the gas is installed before or after the blower 9. In the arrangement shown in FIG. 9, only the gas which has passed through the opening 10 via the gas suction header 11 is circulated again. However, it is possible to suck gas from any part of the heat treatment chamber without providing the gas suction header 11. Here, the gas jet flow blown out from each nozzle 1 collides with the steel band 7, and passes through the opening part with the upward flow force formed by the gas jet flow which has changed in the next direction. In FIG. 9, the cross section of the gas ejection header 8 is rectangular. However, for manufacturing gas ejection header 8, the cross section of the gas ejection header 8 may be circular, elliptical or polygonal; alternatively, the cross section of the gas ejection header 8 may be of a combined shape. Can be.

10 is a view of the arrangement of the nozzles 1 and the gas blowing headers 8 seen from the steel band side. As shown in FIG. 10A, the nozzles 1 may be arranged in a zigzag fashion. Also, as shown in Fig. 10B, sets of nozzles 1 each consisting of three to seven rows of nozzles 1 may be arranged in a zigzag fashion. When one gas blowing header is installed for each row of nozzles, the installation cost is increased. Therefore, as shown in Fig. 10C, it is possible to reduce the number of openings when one gas ejection header is installed for a plurality of nozzle rows. In this case, however, there is a possibility that the discharge of the gas cannot be carried out completely. Therefore, it is necessary to adjust the length of the nozzle protrusion extension h in accordance with the area of the opening.

Using the heat treatment apparatus of the present invention shown in Figs. 9 and 10, the steel band 1 having a thickness of 1.0 mm was cooled by blowing a gas jet stream in which a mixed gas of nitrogen and hydrogen was used as a coolant. Here, the cooling nozzle protrusion length h was set to 20 mm. In Fig. 12, the heat transfer rate ratio when the ratio of the opening area to the nozzle opening area is changed under the conditions of a constant blower power is shown. In Table 1, nozzle diameter, nozzle pitch, and the like are shown. In the graph shown in FIG. 12, the cooling capacity for cooling the steel band was evaluated by the heat transfer rate in the steel band width direction. The results of the comparative example are shown at points where the ratio of opening area to nozzle opening area is 0, 3.4 and 17.3. Here, when the area ratio is zero, all the openings are sealed. The results of the example are shown in the range from the point of the opening area to the nozzle opening area of 5.8 to the point of 15.7. In the range from the ratio of 5 to the point of ratio 17, the heat transfer ratio of the example is higher than the heat transfer ratio of the comparative example. That is, when the ratio of the opening area to the nozzle opening area is 5 to 17, the cooling capacity for cooling the steel band by blowing the gas jet stream is improved.

number Distance Z from nozzle to steel band Nozzle Diameter (Inner Diameter) D (mm) Distance from nozzle to nozzle (mm) Ratio of opening area to nozzle opening area Comparative example One 50 9.4 50 0 2 50 9.4 25 3.6 Example of invention 3 50 10.5 25 5.8 4 50 9.4 25 7.2 5 50 12.7 50 7.9 6 50 10.5 50 11.6 7 50 9.4 50 14.4 8 50 7.8 25 15.7 Comparative example 9 50 10.5 50 17.3

It is preferable that the protruding length h of the nozzle 1 is not larger than five times the inner diameter D of the nozzle 1. This is because when the protrusion length h of the nozzle 1 exceeds five times the nozzle inner diameter D, as shown in Fig. 16, the heat transfer ratio is significantly reduced. The reason why the heat transfer ratio is significantly reduced is that when the nozzle protrusion length h is large, the flow rate of the gas decreases until the rising flow of the gas reaches the opening 10 between the gas ejection headers 8, and accordingly It is considered that the gas is difficult to be discharged.

Next, an example is shown in which the gas is discharged by setting the nozzle protrusion length h to an appropriate value without the opening of the gas ejection header. This example is shown in FIG. In this structure, no opening is provided between the nozzles 1, and the gas blowing header 8 is formed of a box-type gas blowing header in which several nozzles are arranged. In this regard, with respect to the distance Z between the tip of the nozzle and the steel band 7, as disclosed in Japanese Patent Publication No. 2-16375, the distance Z is usually set to a value not larger than 70 mm.

Next, with reference to FIG. 17, the flow of gas 14 is described below. After the gas jet stream blows off from the nozzle 1, it collides with the steel band 7. The gas jet then flows along the steel band 7. The gas jet stream subsequently collides with the gas jet stream ejected from adjacent nozzles. Thus, the gas jet flows in the direction opposite to the gas jet flow direction from the nozzle, that is, from the steel band toward the gas jet header 8. This gas jet stream then collides with the gas jet header and flows along the gas jet header. Subsequently, this gas jet stream is discharged to the outside through the region lying between the gas jet header 8 and the steel band 7. At this time, when the gas density is low, the gas flow flowing along the gas ejection header flows in the region of the nozzle protrusion extension h. However, when the gas density becomes high, this region is not large enough, and the gas flow which has already collided with the steel band flows to the region between the steel band 7 and the tip of the nozzle 1. In the above state, the gas stream collided with the steel band is mixed with the gas jet stream ejected from the nozzle. For example, when the steel band is cooled, the gas jet stream ejected from the nozzle is cooled, but if a hot gas stream already collided with the steel band is mixed with the gas jet stream ejected from the nozzle, the gas jet collides with the steel band. The temperature of the stream rises and the cooling efficiency decreases. In this regard, for the gas ejection header, when it is determined that the elongation h of the nozzle is not lower than a predetermined value, the gas can be smoothly discharged. However, the gas ejection header may be properly divided so that spaces may be formed between the divided gas ejection headers and gas may be discharged through the spaces. In particular, when the width of the steel band is large or the length of the gas blowing header is long in the longitudinal direction, that is, when the size of the gas blowing header is large, it is effective to divide the gas blowing header.

Thirdly, the ratio of the effective gas ejection length is improved. 19 is a view showing a steel band heat treatment apparatus using a conventional gas jet stream. The steel band 7 and the nozzle 1 are made adjacent to each other in this facility so that the efficiency of the gas jet stream can be improved. In order to prevent the nozzle from coming into contact with the steel band when the steel band swings or flexes, the steel band is alternately pressed by the left support roll 16 and the right support roll 17. However, no gas is blown into the left supporting roll inserting space 23 and the right supporting roll inserting space 24. Thus, although cooling or heating is performed in the range of L1, useless portions where cooling or heating is not performed are included in the range of L1. As a result, it is impossible to obtain high cooling or heating rates. In other words, the conventional heat treatment apparatus is in a state where the ratio of the effective gas ejection lengths is small.

Referring to Fig. 20, one example of the present invention is described below. In the arrangement shown in FIG. 20, an extension 22 of the gas blowing device is provided opposite the support roll with respect to the steel band 7. With this arrangement, the length L2 from the start position to the end position of the gas ejection is shortened. The actual gas blowing length shown in FIG. 19 is the same as the actual gas blowing length shown in FIG. 20. However, when length L1 is compared with length L2, length L2 is shorter than length L1. That is, the ratio of the effective gas ejection length was improved. In this case, the period required for heating or cooling was reduced by (L1-L2) / V seconds. Here, the moving speed of the steel band 7 is V m / sec. As for the heating or cooling rate, it is possible to improve the heating or cooling rate accordingly. In this regard, when the present invention is applied to an actual continuous annealing apparatus for continuously annealing steel bands, the ratio of the effective gas ejection length is increased from 82% to 90%.

As described above, when the backing roll is heated or cooled, the heating or cooling capacity can be improved, and as a result, the heating or cooling rate can be higher. However, as described above, the heat treatment apparatus in which the backing rolls are in direct contact with the steel band to perform heating or cooling is generally difficult to bring the rolls into uniform contact with the steel band, so that the temperature of the steel band is uniform. It is disadvantageous to do so. However, according to an experiment conducted by the inventors, the diameter of the supporting rolls is usually not larger than 300 mm ψ. That is, the diameter of the backing rolls is generally small. Thus, when defining the surface pressure as the pressure at which the steel band is pressed against the roll, the surface pressure of the backing roll is higher than that of commonly used heating or cooling rolls with a diameter of 1000 mmψ. Therefore, it turned out that problems with non-uniform temperature in the case of heating or cooling were not caused.

21 is a cross sectional view showing a right base roll portion; In this regard, the structure of the left bearing roll portion is substantially the same as that of the right bearing roll portion. Therefore, only the right base roll is described here. In this example, the backing roll is a water cooled roll. As shown in FIG. 21, the right support roll 17 is rotatably supported by bearings 26 which are installed between both side walls of the heat treatment chamber wall 13 and can slide longitudinally at the side walls. Here, the gas blowing headers and the nozzles are installed with a gap on the left side of the steel band 7 but are omitted in the drawing for simplicity. One end of the right support roll 17 formed inside of the jacket structure is connected to a motor 27 for rotating the support roll. On the other hand, the bearing 26 installed on the opposite side has a rotary joint structure, and the water supply pipe 28 and the drain pipe 29 are connected to the rotary joint. Here, the bearing 26 is installed so that it can slide. Therefore, the bearing 26 can be advanced or reversed by a motor for moving the support roll via the transmission shaft 31 and the distributor 32.

With this structure, the cooling water can be supplied to the right support roll 17 through the water supply pipe 28, and the used water is discharged to the outside through the drain pipe 29. In this description, the backing roll is used as the cooling roll, but when the heated fluid is used, it is also possible to use the backing roll as the heating roll. Even in the case of cooling, it is possible to use a fluid other than water. In addition, in the case of heating, electric power may be supplied to the roll instead of using the fluid, so that the roll may be used as an electrically heated roll. It is possible to adjust the heating or cooling capacity by adjusting the temperature or amount of fluid supplied or by controlling the current supplied to the roll.

Fourthly, the gas blowing temperature is effectively reduced. FIG. 22A shows an example of a conventional heat treatment apparatus in which a non-oxidizing gas jet is blown onto a steel band so that the non-oxidizing gas can be circulated and the steel band can be cooled. In Fig. 22A, reference numeral 7 is a steel band which is an object to be cooled. The steel band 7 is cooled in a non-oxidizing gas (not shown) inside the heat treatment chamber wall 13. Reference numeral 9 is a blower for sucking and blowing non-oxidizing gas in the heat treatment chamber. This blower 9 sucks gas from the heat treatment chamber through the duct 34. In the middle of this duct 34, a heat exchanger 35 for cooling gas is provided, and the gas so cooled is boosted by the blower 9. The gas so propagated is introduced back into the heat treatment chamber via the duct 34 and blown onto the steel band 7 via the gas ejection header 8 and the nozzle 1. Thus, the steel band 7 can be cooled quickly. As for the position of the heat exchanger 35, according to the conventional arrangement, in order to protect the blower 9 from heat, the gas in the heat treatment chamber is sucked by the blower after being cooled by the heat exchanger. That is, the heat exchanger is installed upstream of the blower. In the conventional heat treatment apparatus, the estimated region of the heat transfer rate for cooling the steel band is low. Therefore, the flow rate at the nozzle end is not high. Thus, the blower does not require high boosting pressure, and the gas temperature increase in the blower is small. For the above reasons, no problem arises in practical use. However, when the heat transfer rate increases in cooling of the steel band, it is necessary to increase the flow rate at the nozzle end, and the blower requires a high propulsion pressure. For the above reasons, the temperature increase caused in the propulsion process cannot be ignored. As a result, the cooling efficiency can be improved when the heat exchanger 35 is also installed after the blower 9 as shown in FIG. 22B. That is, the cooling efficiency can be improved when the heat exchanger 35 is also installed downstream of the blower 9. In other words, when the amount of temperature reduction of atmospheric gas is set constant, the capacity of the heat exchanger in the arrangement shown in FIG. 22B can be made smaller than the capacity of the heat exchanger in the arrangement shown in FIG. 22A. As a result, the pressure loss in the heat exchanger is reduced, and the capacity of the blower can be made smaller. In this regard, in the arrangement shown in Fig. 22B, heat exchangers are installed before and after the blower. However, if no problem is caused in the blower from the standpoint of thermal resistance, the heat exchanger installed upstream can be removed, and the heat exchanger can be installed only downstream.

According to the present invention, in the steel band heat treatment apparatus using gas jet flow, it is possible to improve the heat transfer rate by promoting turbulence in the center of the gas jet flow, and also to smoothly discharge the gas blown onto the steel band. In addition, it is possible to prevent interference between the gas discharged and the gas newly blown onto the steel band. Thereby, the heat transfer rate can be improved.

According to the present invention, in the steel band heat treatment apparatus by the gas jet flow, the length of the useless portion in the left and right roll insertion space can be reduced. That is, the length of the portion that does not contribute to heating, cooling or drying of the steel band can be reduced. Therefore, the overall length of the heat treatment apparatus can be reduced. Thereby, it is possible to shorten the period for heating, cooling or drying the steel band, so that the heating rate, cooling rate or drying rate for heating, cooling or drying the steel band can be improved. In addition, a heat exchanger for cooling gas is installed on the conveying side of the gas compressor, such as a blower. Thereby, it becomes possible to effectively reduce the temperature of the blowing gas. As a result, the cooling efficiency can be improved, and the power required for the gas compressor such as the blower can be reduced.

As a result, it is possible to ensure the heating or cooling rate required from a metallurgical standpoint without providing an excessively large blower or duct. It is also possible to reduce the length of the device. Therefore, the device can be made compact and the blower power can be made very small compared to the blower power in a conventional installation. Therefore, from the viewpoint of reducing the operating cost, it is possible to provide a great advantage. In addition, according to the cooling system according to the present invention, cooling is performed without causing the temperature of the steel band to cause non-uniform problems, and also caused by roll cooling of the conventional cooling system at a heat transfer rate α ≥ 400 kcal / m 2 Hr ° C. The cooling is carried out without causing oxidation of the steel band surface and deterioration of the profile of the steel band resulting from the cooling process using gas and water. Therefore, it is possible to improve the quality of the steel band, and it is unnecessary to provide an pickling device for removing the oxide film. Therefore, the device can be simplified.

Claims (10)

A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band to heat, cool, or dry the steel band, the heat treatment apparatus including a resistor attached to a tip of a nozzle from which the gas jet stream is ejected, and projecting the resistor. Steel band heat treatment apparatus by gas jet flow is determined so that the area is 3% to 12% with respect to the nozzle cross-sectional area. A heat treatment apparatus for performing a steel band heat treatment while ejecting a gas jet stream onto a steel band to heat, cool, or dry the steel band, the resistance plate including a resistance plate attached to the tip of the nozzle from which the gas jet stream is ejected. And the projection area of the steel band heat treatment apparatus by gas jet flow is determined to be smaller than 3% with respect to the nozzle cross-sectional area, and the length of the resistance plate in the nozzle axial direction is not smaller than 50% of the nozzle diameter. A heat treatment apparatus for performing a steel band heat treatment while blowing a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried. A plurality of nozzles; A plurality of gas ejection headers for supplying gas to the nozzles, to which the plurality of nozzles are mounted; A gas distribution header for supplying gas to the plurality of gas ejection headers, An opening or a gap, which is a gas discharge port, is provided between the gas ejection headers, and the area of the opening is not less than 5 times the nozzle opening area and not more than 17 times the steel band heat treatment apparatus. 4. The steel band heat treatment apparatus according to claim 3, wherein the nozzle is a protruding nozzle that protrudes from the tip of the gas jet header. 4. The steel band heat treatment apparatus according to claim 3, wherein the protruding length of the nozzle is no longer than five times the nozzle inner diameter. 4. The gas profile according to claim 3, wherein the side profile of the gas ejection header tip is tapered so that the cross-sectional area of the gas passage is gradually reduced in the gas ejection direction, and the nozzle tip is formed by the gas jet flow which does not protrude from the front end face of the gas ejection header. Band heat treatment device. A heat treatment apparatus for performing a steel band heat treatment while blowing a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried. The distance Z from the steel band to the tip of the nozzle is determined not to be greater than 70 mm, The inequality of W / 4 ≤ h is satisfied when the nozzle protrusion elongation from the header for supplying the gas to the nozzle is h mm and the amount of gas (gas amount density) ejected onto the unit area is W m 3 / min · m 2. The steel band heat treatment apparatus by the gas jet stream made into it. A heat treatment apparatus for performing a steel band heat treatment while blowing a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried. A roll insertion space in which the supporting rolls are alternately arranged along the advancing direction of the steel band at regular intervals is provided in the gas ejection space in which nozzles for ejecting the gas jet stream are installed to prevent rocking of the steel band; In order to extend the gas ejection space, the nozzles for ejecting the gas ejection stream are installed in a roll insertion space opposite the portion in which the roll is inserted with respect to the steel band. A heat treatment apparatus for performing a steel band heat treatment while blowing a gas jet stream onto a steel band so that the steel band is heated, cooled, or dried. A roll insertion space in which the supporting rolls are alternately arranged along the advancing direction of the steel band at regular intervals is provided in the gas ejection space in which nozzles for ejecting the gas jet stream are installed to prevent rocking of the steel band; In the case of cooling the steel band, the support rolls are cooled; When the steel band is heated or dried, the supporting bands are heated, wherein the steel band heat treatment apparatus according to the gas jet stream. In the steel band heat treatment apparatus by a gas jet stream for circulating a non-oxidizing atmosphere gas and blowing on the steel band to cool the steel band, And a heat exchanger for cooling gas is installed at least downstream of a gas compressor such as a blower.