WO1998041661A1

WO1998041661A1 - Steel band heat-treating apparatus by gas jet stream

Info

Publication number: WO1998041661A1
Application number: PCT/JP1998/001072
Authority: WO
Inventors: Hirohisa Kawamura; Norichika Nagira; Mutsuo Shiraga; Jyunichi Hayashi; Yoshihiro Serizawa; Masanori Shimada; Kouichi Waki; Hisamoto Wakabayashi; Keiji Oogushi
Original assignee: Nippon Steel Corporation
Priority date: 1997-03-14
Filing date: 1998-03-13
Publication date: 1998-09-24
Also published as: EP0911418A1; KR100293139B1; TW404982B; CN1083896C; EP0911418A4; DE69833424D1; KR20000011032A; EP0911418B1; CN1219206A; DE69833424T2; BR9804782A

Abstract

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

Description Heat treatment equipment by gas jet of steel strip

The present invention relates to a heat treatment apparatus for heating, cooling, or drying a steel strip by spraying a gas jet onto the steel strip. Conventional technology

Conventionally, there was a heat treatment facility that heats and cools the steel strip by spraying a gas jet onto the steel strip.However, since heat transfer is performed using gas as a heat medium, the heat transfer coefficient α is low, which is a requirement from metallurgy. However, satisfactory performance has not been obtained for high heating and cooling rates. For example, the present inventors have previously proposed a cooling device for a steel strip using a gas jet in Japanese Patent Publication No. 2-16375, but the assumed region of the heat transfer coefficient is α ≤ 40 Okcal / m ^2. Hr ° C. With this heat transfer coefficient, a cooling rate of 100 ° CZsec can be achieved when the thickness of the steel strip is 0.6 mm, but a cooling rate of substantially 60 ° C / sec can be obtained when the thickness of the steel strip is 1.0 mm. No. For this reason, when a higher heat transfer coefficient is required, a method such as a roll cooling method using solid contact with a water cooling port or a gas-water cooling method using a mixture of gas and water is used. However, in the case of roll cooling, uniform contact is difficult due to solid contact, and there is a problem that the temperature of the steel strip is uneven and the shape of the steel strip is deteriorated. On the other hand, in the case of steam-water cooling, there is a problem that the surface of the steel strip is oxidized by dissolved oxygen because of the use of water. Disclosure of the invention In a heat treatment facility that heats and cools a steel strip by spraying a gas jet, the heat transfer rate can be increased by increasing the flow rate of the gas blown to the steel strip. The experimental results showed that the heat transfer coefficient increased almost in proportion to the gas flow velocity. However, as the gas flow rate increased, the pressure loss of the nozzles and pipes increased rapidly, and it became clear that a very large blower power was required to obtain the required heat transfer coefficient. It is an object of the present invention to reduce the required power in equipment that maintains a high heating or cooling rate in a heat treatment apparatus using a gas jet of a steel strip.

The heat treatment apparatus using a gas jet of a steel strip according to the present invention has the following features (1) to (4) in order to achieve the object.

① In a heat treatment system that heats, cools, or dries a steel strip by spraying a gas jet onto the steel strip, an antibody is applied to the tip of the nozzle that discharges the gas jet, and the projected area is 3 to A heat treatment system using a gas jet of a steel strip, which is installed so as to have a concentration of 12%.

② In a heat treatment system that heats, cools, or dries a steel strip by spraying a gas jet onto the steel strip, a resistive plate is attached to the tip of the nozzle that discharges the gas jet, and the projected cross-sectional area of the steel plate is compared to the nozzle cross-sectional area A heat treatment system using a gas jet of steel strip, characterized in that it is installed so that the plate length in the nozzle axis direction within the nozzle is less than 50% of the nozzle diameter.

(3) In a heat treatment device that heats, cools, or dries a steel strip by blowing a gas jet onto the steel strip, the nozzle has a nozzle that discharges a gas jet, and a plurality of nozzles, and supplies gas to the nozzle. And a gas distribution header for distributing gas to a plurality of gas blowing headers, and an opening or gap as a gas exhaust port between the gas blowing headers. An opening having an area of 5 times or more and 17 times or less of the opening area of the nozzle is provided. Heat treatment equipment by gas jet of steel strip.

(4) The heat treatment apparatus according to (3), wherein the nozzle is a protruding nozzle discharged from the tip of the gas blowing header.

(4) The heat treatment apparatus using a gas jet of a steel strip as described in (3), wherein the projecting length of the nozzle is large and is not more than 5 times the inner diameter of the nozzle.

ガス The tip of the gas blowing header is characterized in that the cross section of the gas flow path is gradually reduced in the gas blowing direction, and the tip of the nozzle does not protrude from the tip of the gas blowing header. Heat treatment equipment using gas jet of steel strip described in (3).

において In a heat treatment system that heats, cools, or dries the steel strip by blowing a jet of gas onto the steel strip, the distance Z between the steel strip and the tip of the nozzle is set to 70 mm or less, and the header from the header that supplies gas to the nozzle Heat treatment of steel strip by gas jet, characterized by satisfying the relationship of WZ 4 ≤ h between nozzle protrusion height h mm and blowing gas volume per unit area (air volume density) W m ³ / min m ² apparatus.

熱処理 A heat treatment device that heats, cools, or dries the steel strip by spraying a gas jet onto the steel strip, and the direction of travel of the steel strip between the gas-spraying spaces where the nozzles that discharge the gas jet are arranged In the heat treatment equipment, which has a roll insertion space in which the presser rolls are arranged alternately at a certain interval along the strip to prevent fluttering of the steel strip, A heat treatment device using a gas jet of a steel strip, characterized in that a nozzle for discharging a gas jet is arranged in the roll inlet space on the opposite side of the roll so as to extend the gas spray space.

熱処理 A heat treatment device that heats, cools, or dries the steel strip by spraying a gas jet onto the steel strip, and the traveling direction of the steel strip between the gas spraying space where the nozzles that discharge the gas jet are arranged With a certain interval along When a steel strip is cooled in a heat treatment device that has a roll insertion space in which presser rolls are provided to prevent fluttering of the steel strip, a cooling roll that cools down the presser roll is used. When the steel strip is heated or dried, the heating roll is a heated roll of the presser roll.

熱処理 In a heat treatment system that cools a steel strip by circulating a non-oxidizing atmosphere gas and spraying a jet, at least a heat exchanger for gas cooling is installed at the downstream side of the gas compressor such as a blower. Heat treatment equipment using gas jet of steel strip. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing the air flow density, the heat transfer coefficient, and the test range in the present invention.

FIGS. 2 (a), (b), (c), and (d) are diagrams showing nozzles of the gas jet heat treatment apparatus of the present invention.

Figures 3 (a) and 3 (b) show the flow of the gas jet at the nozzle tip.

Figure 4 shows the heat transfer characteristics of the nozzle.

FIG. 5 is a diagram showing the relationship between the ratio of the projected area of the resistor to the nozzle cross section and the heat transfer coefficient just below the nozzle.

FIG. 6 is a diagram showing the plate length Z of the resistance plate and the nozzle diameter and the heat transfer immediately below the nozzle.

FIG. 7 is a diagram showing the positional relationship between the nozzle and the steel strip.

FIGS. 8 (a) and 8 (b) are diagrams showing a conventional nozzle.

FIG. 9 is a diagram showing an example of a heat treatment apparatus having an opening for releasing gas on the back surface of the present invention.

FIGS. 10 (a), (b) and (c) show the nozzle arrangement of the heat treatment apparatus of the present invention. FIG. 6 is a diagram illustrating an example of a location.

FIG. 11 is a diagram showing the relationship between the opening area S 1 and the nozzle opening area S 2 in the heat treatment apparatus using a gas jet.

FIG. 12 is a diagram showing the relationship between the ratio of the opening area of the nozzle and the opening area of the nozzle and the ratio of the heat transfer coefficient in the heat treatment apparatus using a gas jet.

FIGS. 13 (a) and 13 (b) are diagrams showing gas flows in a heat treatment apparatus using gas jets.

FIG. 14 is a diagram showing a portion where a rising flow is generated between cooling nozzles of a cooling device by a gas jet.

FIGS. 15A and 15B are diagrams showing examples of the structure around the nozzle of the heat treatment apparatus of the present invention.

Fig. 16 is a diagram showing the effect of the ratio of the projecting length h of the nozzle to the inner diameter D of the nozzle on the heat transfer coefficient in the heat treatment apparatus using a gas jet.

FIG. 17 is a diagram showing a relationship between a gas blowing header having no opening and a nozzle in a heat treatment apparatus using a gas jet.

FIG. 18 is a diagram showing the relationship between the air flow density and the heat transfer coefficient ratio when the nozzle protrusion height h is changed in the heat treatment apparatus using a gas jet. FIG. 19 is a diagram showing an arrangement of a press roll and a gas spraying device in a conventional heat treatment apparatus using a gas jet.

FIG. 20 is a diagram showing an arrangement of a press roll and a gas blowing device in a heat treatment apparatus using a gas jet according to the present invention.

FIG. 21 is a cross-sectional view showing a press roll advance / retreat mechanism and a heating / cooling mechanism in a heat treatment apparatus using a gas jet.

Fig. 22 (a) is a diagram showing the arrangement of a conventional heat exchanger in a heat treatment apparatus using a gas jet, and Fig. 22 (b) is a diagram showing the arrangement of the heat exchanger of the present invention in a heat treatment apparatus using a gas jet. is there. FIG. 23 is a diagram showing a relationship between a blower-to-power ratio and a gas blowing temperature when cooling a steel strip in a heat treatment apparatus using a gas jet. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail. In order to solve the problem, we tried various approaches. In the present invention, solutions are sought from the viewpoints of nozzle configuration, gas exhaust, effective gas spray length ratio, and spray gas temperature, and will be sequentially described.

First, regarding the form of the nozzle, various tests were conducted to optimize the nozzle diameter and nozzle pitch, and comparisons were made. As a result, it was confirmed that the nozzle diameter and the nozzle pitch defined in Japanese Patent Publication No. 2-16375 previously proposed by the present inventors were the most efficient even when the gas blowing velocity was increased. Fig. 1 shows the test range in the present invention and the test range in the Japanese Patent Publication No. 2-16375.If there is no problem with gas exhaust described later, the heat transfer coefficient is 400 kcal Zm ² Hr ° C or more. It can be seen that the relationship between the air flow density and the heat transfer coefficient is almost on an extended line even in the region.

In addition, as a means of improving the heat transfer coefficient of the gas discharged from the nozzle, the stagnation point formed when the discharged gas hits the object reduces the heat transfer rate. It is generally known to promote turbulence. For example, Japanese Unexamined Utility Model Publication No. 61-40155 discloses that a resistance plate 3 and a spiral wire 6 are installed in a nozzle 1 as a turbulence promoter, as shown in FIG.

However, in order to cross the resistance plates 3 as described in Japanese Utility Model Application Laid-Open No. 61-40155, a nozzle length for inserting two or three resistance plates is required, and many industrially It is difficult to manufacture a nozzle. In addition, the spiral wire 6 is not effective because it is diverged by centrifugal force because the gas is rotated.

As mentioned above, the turbulence intensity is weak at the center of the gas flow. Increasing the turbulence in the center of the spill effectively increases the heat transfer coefficient. According to the present invention, as a measure for promoting turbulence in the center of the gas flow, which is industrially easy to implement, as shown in Fig. 2, a resistor 2 or a resistance plate 3 is installed at the center of the tip of the nozzle 1. And In this way, a turbulent flow 5 in which a vortex street develops is formed behind the resistor 2 and the resistor plate 3 as shown in FIGS. 3 (a) and 3 (b), disturbing the central region of the gas flow 4. Is possible. The cross-sectional shape of the resistor 2 may be polygonal or the like in addition to circular.

Second, we examined a method for smoothly exhausting gas discharged from the nozzle. As described above, in order to increase the heat transfer coefficient, the speed of the gas blown to the steel strip may be increased. In other words, the amount of gas to be blown should be increased. However, if the exhaust gas becomes insufficient, the gas once sprayed will stay and interfere with the new sprayed gas, causing a phenomenon in which the heat transfer coefficient does not increase as much as expected. In Fig. 1, the solid line is an example of a case where the exhaust is good, and the dotted line is an example of a case where the exhaust is poor. It can be seen that the rise in heat transfer coefficient slows down above a certain air flow density in the case of poor exhaust. Therefore, in order to efficiently increase the heat transfer coefficient, smooth exhaust of the blown gas becomes an important issue. The present invention has found two solutions to this problem.

As a result of investigating the gas flow after colliding with the steel strip, the gas jet discharged from the nozzle collides, flows along the steel strip, collides with the jet discharged from the adjacent nozzle, and leaves the steel strip It was found to flow in the direction. This ascending flow between nozzles occurred in the shaded area in Fig. 14, and it was found that the ascending flow was rising at a flow rate of 20 to 40% of the gas jet discharged from nozzle 1.o

Therefore, in the present invention, the gas jet discharged from the nozzle collides with the gas jet discharged from the adjacent nozzle and has an area sufficient to form an upward flow. An opening for gas exhaust was installed or a gap was secured. Na us, as shown in FIG. 13 (a) showing the relationship between the opening area S ₂ of Roh nozzle in Figure 1 1 the opening area S, and the gas jet discharged from Roh nozzle 1 after colliding with the steel strip 7 Then, it flows over the steel strip 7 and collides with a gas jet from an adjacent nozzle and rises. As shown in Fig. 13 (a), this ascending flow, if not forcedly exhausted, flows to the end in the width direction of the steel strip and is not sufficiently exhausted. Into the gas jet from As a result, the temperature of the gas jet from the nozzle 1 increases during cooling, and decreases during heating, and the predetermined performance cannot be obtained. In addition, since gas stays between the steel strip 7 and the gas blowing header 8, the plate-like gas flow flowing over the steel strip 7 is slowed down, and the cooling capacity in the vicinity of the gas jet collision from the nozzle 1 is also reduced. I do.

In the apparatus of the present invention, an opening 10 is provided between the gas blowing headers 18 as shown in FIG. 13 (b), and the upward flow exits through the opening 10. Therefore, the gas jet discharged from the nozzle 1 reaches the surface of the steel strip 7 almost without being affected by the gas that has been turned upside down, and the steel strip 7 can be cooled or heated. In addition, since gas does not stay between the steel strip 7 and the gas blowing header 8, the gas flow along the steel strip 7 is smooth, and the phenomenon that the gas cooling or heating capacity is reduced can be reduced.

FIG. 15 shows an example of the structure around the nozzle of the heat treatment equipment of the present invention. The nozzle 1 shown in FIG. 1A is a protruding nozzle whose tip protrudes from the tip of the gas blowing header 8, and the gas jet discharged from the nozzle 1 when exhausting gas from the opening 10. Part of the gas is prevented from being exhausted directly without colliding with the steel strip. In addition, in the example shown in FIG. 3B, the tip of the nozzle 1 is flush with the tip of the gas-blasting head 8, but the shape of the tip of the gas-blasting header 8 is broken in the gas flow path. Area The exhaust gas inlet between the gas blowing headers 8 is tapered, and the narrowest part of this exhaust gas flow path is regarded as the opening in the case of (a) in the figure. Therefore, the same effect as that shown in FIG.

Next is the second smooth gas exhaust method. In the first exhaust method, gas was evacuated to the so-called rear side of the nozzle through the opening between the gas blowing headers.However, the gas blowing header was divided into several parts due to the space of the opening. However, although it is an ideal exhaust method, it has a disadvantage that the equipment cost is high. Therefore, as a second exhaust method, we decided to eliminate the opening on the back side and take an appropriate nozzle protrusion height. In other words, by securing the nozzle protrusion height h shown in Fig. 17, interference with the spray gas is eliminated, and a space is provided to allow the gas to escape in the direction parallel to the steel strip instead of the back of the nozzle. This prevents gas from stagnating. This method has already been proposed by the present inventors in Japanese Patent Publication No. 2-16375, in which the distance Z between the steel strip and the tip of the nozzle is set to 70 mm or less, and the nozzle Projection height h is defined as (100-Z) thigh or more. However, are those when said as an assumed area of the heat transfer coefficient was a ^{≤40 Okca l / m 2 H r} ° C, this was subjected to a test to a region higher heat transfer Itaruritsu However, it is not sufficient to define the nozzle protrusion height h as (100—Z) mm or more as the air flow increases, and the air flow density per unit area W m ³ / minm ² must be added to the evaluation. It turned out that it did not become an evaluation standard. In other words, it was found that defining the gas emission space according to the amount of gas to be blown was physically important.

Thus, an experiment was conducted in which the heated steel strip was cooled by changing the nozzle projection height h, and the relationship between the air flow density and the heat transfer coefficient ratio was determined. Here, the heat transfer coefficient ratio indicates the ratio of the heat transfer coefficient based on a certain heat transfer coefficient. This function Figure 18 shows the relationship. According to Fig. 18, when the nozzle protrusion height h is 200 mm, the heat transfer coefficient ratio increases almost in proportion to the increase in the air flow density, and the discharged gas is discharged without stagnation. I understand. When the nozzle protrusion height is low, the rise in the heat transfer coefficient ratio becomes slower from a certain air flow density, and it can be seen that the discharged gas stays and interferes with the gas newly discharged from the nozzle. Also, it can be seen that this tendency starts to occur in the region where the airflow density is lower as the nozzle protrusion height h is lower. From these relationships, the relationship between the air flow density W m ³ / minm ² and the required nozzle protrusion height h mm is obtained as follows.

W / 4 ≤ h

Needless to say, the airflow density W is calculated using the maximum airflow density that can be achieved by the equipment so that the function can be effectively performed in all equipment performance areas. In addition, the minimum height of the nozzle protruding height h can be obtained based on the above grounds.However, if it is longer than necessary, it is necessary because nozzle pressure loss increases and equipment manufacturing cost increases. It is desirable to select near the minimum height.

Third, the effective gas spray length ratio was examined. Usually, in the case of cooling, the cooling rate is defined as Δt ZT ° C / sec based on the temperature difference Δt ° C of cooling and the time Tsec required for the cooling. In the case of heating, the heating rate is similarly defined. Here, what is important in metallurgy is the cooling rate and heating rate, and we have devised equipment to increase these. In heat treatment equipment that blows gas jets, the spacing between the nozzle and the steel strip was reduced to increase the heating or cooling rate, and the decay of the gas velocity discharged from the nozzle was prevented as much as possible. For this reason, as shown in Fig. 19, press rolls 16 and 17 are brought into contact with the steel strip 7 at certain intervals in order to suppress the warpage and fluttering of the steel strip, and these are straightened. The interval was narrow. However, the press rolls 16 and 17 are provided with roll press devices 18 and 19 in order to be able to move forward and backward with respect to the steel strip for operational reasons. Gas could not be sprayed on this part, which was a wasteful area for heat treatment. In addition, the presence of these spaces partially reduced the heating and cooling rates, which was disadvantageous in metallurgy. The heating rate and cooling rate, which are important in metallurgy, generally mean the average heating rate or average cooling rate.In order to increase these values, it is necessary to increase the efficiency in the gas spraying space and the space for the presser roll as much as possible Is effective.

In Fig. 19, the ratio of the length of the gas that is actually blown out of the length L1 from the start to the end of the gas spraying is called the effective gas spraying length ratio, but in the conventional case, in the continuous annealing equipment for steel strip, The effective cooling length ratio was around 80%. Therefore, in the present invention, heating or cooling in the holding roll insertion space was studied. The press roll insertion space shown in FIG. 19 is roughly divided into a side into which the roll is inserted and a side without a hole facing the steel strip 7. On the side without a roll, a gas blowing space can be provided by arranging a gas blowing device extension 22 as shown in FIG. In addition, on the side where the roll is located, there are holding rolls 16, 17 and a roll holding device that moves the holding roll forward and backward, so it is difficult to install a gas spraying device. It is difficult to do so, so efficiency becomes poor. Therefore, in the present invention, it has been devised that the press roll itself is heated or cooled to perform the roll heating or the cooling of the roll. As a result, the average heating rate or cooling rate can be improved by minimizing the roll insertion space, which was previously an invalid area for heating or cooling, or by heating and cooling even in the roll insertion space. Has become possible. Finally, a fourth study was made on optimizing the spray gas temperature when cooling the steel strip. As a general trend, lowering the spray gas temperature also lowers the required power, but once the temperature falls below a certain temperature, the temperature of the refrigerant and the spray gas used in the heat exchanger to lower the spray gas temperature Although the pressure difference in the heat exchanger increases due to the smaller difference, the spray gas temperature does not decrease and the required power of the probe increases rather. After examining the spray gas temperature in detail, the optimum spray gas temperature

In other words, the point at which the power of the blower is minimum is approximately in the range of 60 ° C to 200 ° C. The required heat transfer coefficient, the inlet and outlet steel strip temperatures of the heat treatment equipment, It was found that it fluctuated according to the temperature of the refrigerant. In particular, this time, as a result of a detailed investigation of the region with a high heat transfer coefficient, it was found that the optimum point was shifted toward the lower spray gas temperature compared to the conventional region with a low heat transfer coefficient, and that the spray gas temperature was lower. It was found that the effect on blower power was large. (Fig. 23)

Therefore, a method for efficiently reducing the spray gas temperature was studied. In a heat treatment apparatus that cools a steel strip by circulating and blowing a non-oxidizing atmosphere gas, a heat exchanger using water as a refrigerant is generally used as a method of cooling the atmosphere gas. Conventionally, the heat exchanger was installed on the inlet side of the blower in consideration of the temperature protection of the blower. Here, in order to lower the spray gas temperature, it is sufficient to increase the capacity of the heat exchanger.However, if the temperature difference between the refrigerant temperature and the gas temperature decreases, the heat exchange efficiency deteriorates, and The blown gas temperature does not decrease even though the pressure loss when the gas passes increases, and as a result, as can be seen from Fig. 23, if the blown gas temperature is too low, the blower power can be increased. Become. Therefore, in the present invention, attention has been paid to the fact that the temperature rises when the blowing gas is pressurized by the blower, and a heat exchanger is provided on the outlet side of the blower. In other words, the heat exchanger If the temperature difference between the gas temperature and the refrigerant can be increased even if the temperature difference between the gas temperature and the refrigerant is small, the heat exchange efficiency can be improved by increasing the temperature on the outlet side rather than increasing the temperature. This has made it possible to achieve the same heat transfer coefficient (<<) and gas blowing temperature with a lower blower power than before. In particular, the effect is remarkable because the gas temperature rise in the process becomes larger as the pressure of the blower is increased in order to increase the gas blowing speed to the steel strip. Example

Hereinafter, examples will be sequentially described. First, the resistor attached to the nozzle will be described. As shown in Figs. 2 (a) and (b), the heat transfer characteristics of a gas jet from a single nozzle equipped with a resistor 2 and a resistor plate 3 were investigated by cooling a hot plate. Air was used as the cooling medium. The nozzle diameter was 10.5 mm, the air velocity discharged from the nozzle was 150 / s, and the distance between the tip of the nozzle and the object to be cooled was 50 mm.

The characteristics of a nozzle with this resistor mounted at the tip were investigated by cooling a hot plate. The results are shown in Fig. 4, where the heat transfer coefficient was improved just below the center of the nozzle.

Figure 5 shows the ratio of the projected area of the resistor to the nozzle cross-sectional area under the cooling conditions described above. It can be seen that if the projected area is 3% or more of the nozzle cross-sectional area, there is an effect of improving the heat transfer coefficient. Further, when the projected area is 12% or more, the pressure loss at the tip of the nozzle due to the installation of the resistor increases, and the power for the blower increases, which is economically disadvantageous. Therefore, the projected area of the resistor is set to 3 to 12% of the nozzle cross-sectional area.

Similarly, when the resistance plate with a thickness of less than 3% of the nozzle cross-sectional area was examined for the plate length in the nozzle axial direction inside the nozzle, as shown in Fig. 6, It was confirmed that if the plate length was 50% or more of the chisel diameter, the heat transfer coefficient was improved. Further, with respect to the thickness of the resistor plate, if the plate thickness is 3% or more, the pressure loss of the gas becomes large because the length in the nozzle axis direction is longer than that of the resistor. Therefore, it is advantageous to reduce the thickness of the resistance plate to less than 3% in order to reduce the required power.

Second, an example of a method for smoothly exhausting the gas discharged from the nozzle will be described. FIG. 9 is a cross-sectional view of the heat treatment apparatus of the present invention. The nozzle 1 is protruded so as to face the steel strip 7 running in the direction of the arrow, and a gas jet is blown from the nozzle 1 onto the steel strip 1 to perform heat treatment. At this time, when the blowing gas is heated, it becomes a heating device, and when it is cooled, it becomes a cooling device. Note that the inside of the heat treatment chamber 12 is often set to a non-oxidizing atmosphere in which hydrogen is mixed with nitrogen in order to prevent oxidation of the steel strip, but the same effect is obtained even when gas such as air is used. The arrows in Fig. 1 indicate the gas flow.

The gas continuously supplied from the blower 9 is sent to a divided gas blowing header 8 via a gas distribution header (not shown), from which it is branched and supplied to each nozzle 1. The gas jet discharged from the nozzle 1 and collided with the steel strip 7 takes heat from the steel strip 1, reverses and is exhausted from the opening 10. That is, the gas is exhausted from the steel strip 7 to the back side of the nozzle 1. The exhausted gas is sent again to the blower 9 via the suction gas header 11 and is reused after the pressure is increased.

In FIG. 9, equipment for heating or cooling the gas, not shown, is provided before or after the blower 9. Also, in FIG. 9, only the gas that has passed through the opening 10 via the suction gas header 11 is recirculated, and the gas is supplied from a part of the heat treatment chamber without the suction gas header 11. May be sucked. At this time, the gas discharged from the nozzle 1 collides with the steel strip 7 and can pass through the opening only by the reversing upward flow force. And Further, in FIG. 9, the cross-sectional shape of the gas blowing header 18 is rectangular, but the cross-sectional shape may be circular, elliptical, polygonal, or a combination thereof for reasons of manufacturing convenience and the like.

Fig. 10 shows the arrangement of nozzle 1 and gas spray header 18 as viewed from the steel strip side. As shown in Fig. 10 (a), the nozzles 1 can be arranged in a staggered manner, as shown in Fig. 10 (b), and can also be arranged in a staggered manner for every three to seven rows as shown in Fig. 10 (b). is there. In addition, installing one gas blowing header per row of nozzles increases the equipment cost.Therefore, as shown in Fig. 2 (c), gas blowing headers are provided for every two or more rows of nozzles. It is also possible to reduce the number of openings by combining the die. However, in this case, since exhaust may be incomplete, it may be necessary to adjust the protrusion height h of the nozzle according to the area of the opening.

Using the apparatus of the present invention shown in FIGS. 9 and 10, cooling was performed with a gas jet of steel strip 1 having a thickness of 1.0 mm using a mixed gas of nitrogen and hydrogen as a cooling medium. The projection length h of the cooling nozzle at this time was 20 mm. Figure 12 shows the ratio of the heat transfer coefficient when the ratio of the opening to the nozzle opening area is changed with a constant blower power, and Table 1 shows the nozzle diameter and nozzle pitch. In Fig. 12, the cooling capacity of the steel strip by gas jet is evaluated based on the average heat transfer coefficient in the steel strip width direction. The ratios of the opening area of the nozzle and the opening area of the nozzle of 0, 3.4 and 17.3 show the results of the comparative example. Here, an area ratio of 0 means that the opening is completely closed. The ratio of the opening area of the nozzle to the opening area of the nozzle is from 5.8 to 15.7, indicating the results of the example. It can be seen that the ratio of the opening area to the opening area of the nozzle is larger than that of the comparative example in the range of 5 to 17. That is, when the ratio of the opening to the nozzle opening area is 5 to 17, the cooling capacity of the steel strip by the gas jet is improved. 〔table 1 〕

It is preferable that the protruding length h of the nozzle 1 is not more than 5 times the inner diameter D of the nozzle 1. If the protruding length h of the nozzle 1 exceeds five times the inner diameter D of the nozzle 1, the heat transfer coefficient is significantly reduced as shown in FIG. This is considered to be because if the protruding length h of the nozzle is long, the gas flow velocity is attenuated by the time the ascending flow of gas reaches the opening 10 between the gas blowing headers 8, making it difficult to exhaust the gas.

Next, an embodiment in which the opening of the gas blowing header is eliminated and the gas is exhausted with the nozzle protrusion height h set to an appropriate height will be described. FIG. 17 shows an embodiment, in which the gas blowing header 8 has no opening between the nozzles 1 and has a common large box-shaped gas blowing header for each nozzle. The distance Z between the tip of the nozzle and the steel strip 7 is generally set to 70 mm or less as discharged from the nozzle as specified in Japanese Patent Publication No. 2-163675.

Next, the gas flow 14 will be described with reference to FIG. The gas discharged from the nozzle 1 collides with the steel strip 7 and then flows along the steel strip 1, but then collides with the gas discharged from the adjacent nozzle, and in the opposite direction to the gas protruding from the nozzle, i.e., steel. It flows from zone 1 to gas spray header 18. After that, this gas collides with the gas blowing header and blows the gas. The gas flows in the direction along the header, and is eventually discharged through the area between the gas blowing header 18 and the steel strip 7. At this time, if the gas flow density is low, the gas flow along the gas blowing header flows in the region of the nozzle protrusion height h, but if the gas flow density increases, the steel flow is insufficient in this region. The gas after the collision with the steel sheet is filled up to the area between zone 7 and the tip of nozzle 1. In this case, the gas that once collides with the steel sheet is engulfed again by the gas that has protruded from the nozzle. For example, when cooling a steel sheet, the discharge gas is cooled, but the high-temperature gas that has already collided with the steel sheet causes the temperature of the gas colliding with the steel sheet to rise, resulting in a decrease in cooling efficiency. I will. In addition, if the nozzle height h is equal to or more than a certain value, the gas spray header can be evacuated properly. However, the gas spray header may be appropriately divided and opened between them to further promote the exhaust. In particular, when the size of the gas blowing header is large, such as when the strip width of the steel strip is large or the length of the gas blowing header in the longitudinal direction is large, dividing the gas blowing header is effective. o

Third, an embodiment will be described regarding the improvement of the effective gas spray length ratio. Figure 19 shows a conventional steel strip heat treatment system using a gas jet. The steel strip 7 and the nozzle 1 are brought close to each other to increase the gas jet efficiency.However, in order to prevent the nozzle from contacting the steel strip with the nozzle due to fluttering and warping of the plate, the left holding roll 16 and right holding roll 17 are used. It is held down alternately. However, since no gas is blown into the left presser roll insertion space 23 and right presser outlet opening space 24 in these presser rolls, cooling or heating is performed in the section L1. Despite this, there were portions ineffective in heating and cooling, and as a result, high cooling or heating rates could not be obtained. That is, the effective gas spray length ratio was low. An embodiment of the present invention will be described with reference to FIG. In FIG. 20, a gas blowing device extension 22 is provided on the opposite side to the steel strip 7 of the holding roll, and the length L 2 from the start to the end of gas blowing is shortened. Figures 19 and 20 show the same length of gas spraying, but comparing L1 and L2 shows that the length of L2 is shorter and the effective gas spraying ratio is higher. Assuming that the moving speed of the steel strip 7 is V m / sec, the time required for heating or cooling is

(L1-L2) Z V seconds are short, and the heating rate or cooling rate can be increased accordingly. When the present invention was applied to the actual continuous annealing equipment for steel strip, the effective gas spray length ratio increased from 82% to 90%.

Further, as described above, by heating or cooling the press roll, the heating and cooling capacity is increased, and the heating rate or the cooling rate is further improved. However, equipment for heating or cooling by contacting the rolls as described above generally has a drawback in that it is difficult to uniformly contact the rolls and the steel strip, so that the temperature of the steel strip tends to be uneven. However, according to the experiment, the diameter of the holding roll is usually ø.

It is as small as 300 mm or less, and the pressure (hereinafter referred to as the surface pressure) against which the steel strip is pressed against the roll is large compared to the roll diameter of 0.1000 mm, which is generally used as a heating or cooling roll. There was no problem with uneven heating and cooling.

FIG. 21 is a cross-sectional view of the right pressing roll portion. Note that the left press roll has almost the same equipment configuration, so the right press roll will be described as a representative here. In this example, a case is shown in which the holding roll is a water-cooled roll. As shown in FIG. 21, the right pressing roll 17 is rotatably supported by bearings 26 slidably provided on both side walls of the heat treatment chamber wall 13 in the front-rear direction. Here, gas blowing headers, nozzles, etc. are placed in the gap on the left side of steel strip 7, but they are omitted for simplicity. You. One end of a right holding roll 17 having a jacket structure inside is connected to a holding roll rotating motor 27. On the other hand, the bearing 26 on the opposite side has a rotary joint structure, and a water supply pipe 28 and a drain pipe 29 are connected. Here, the bearing 26 is slidable, and can be moved forward and backward by the transmission shaft 31, the distributor 32, and the press roll advance / retreat motor.

With this configuration, the cooling water can be supplied to the right holding roll 17 through the water supply pipe 28, and the used water can be discharged through the drain pipe 29. In this explanation, it is shown as a general cooling case, but if a heated fluid is used, it can be used as a heating roll. In the case of cooling, it is also possible to use a fluid other than water. In the case of heating, instead of using a fluid, an electric heating roll can be used by supplying power to the roll. In addition, the amount of heating or cooling can be controlled by controlling the temperature, volume, or electrical current of the fluid used.

Finally, as a fourth example, an example will be given regarding the efficient reduction of the gas spraying temperature. Fig. 22 (a) shows a conventional example of a heat treatment apparatus for cooling a steel strip by circulating a non-oxidizing atmosphere gas and blowing a jet. In Fig. 22 (a), reference numeral 7 denotes a steel strip as an object to be cooled, which is cooled in a non-oxidizing gas (not shown) atmosphere inside the heat treatment chamber wall of Fig. 13. Reference numeral 9 denotes a blower for sucking the non-oxidizing gas in the heat treatment chamber and increasing the pressure, and sucks the atmosphere gas in the heat treatment chamber through the duct. A heat exchanger 35 for cooling the atmospheric gas is installed in the middle of the duct, and the cooled gas is pressurized by the blower 19. The pressurized atmosphere gas is again introduced into the heat treatment chamber by the duct 34, and is blown to the steel strip 7 through the gas spraying head 18 and the nozzle 1, whereby the steel strip is rapidly cooled. Here, it is the position of the heat exchanger. The atmosphere gas in the heat treatment room was cooled in a heat exchanger to protect it from heat, and then suctioned by a blower. In other words, a heat exchanger was located upstream of the blower. In the past, the assumed area of the heat transfer coefficient of steel strip cooling was low, so the discharge flow velocity at the nozzle tip was not so high, and a high pressure increase in the blower was not required. There was no practical problem. However, as the heat transfer coefficient in the cooling of the steel strip increases, the discharge flow velocity at the tip of the nozzle must be increased, and a high pressure increase is required in the blower. For this reason, the temperature rise after the pressure rise cannot be ignored, and the cooling efficiency is improved by installing the heat exchanger 35 after the blower 19, that is, on the downstream side as shown in FIG. 22 (b). That is, when the gas temperature drop of the atmospheric gas is fixed, the capacity of the heat exchanger can be made smaller in (b) than in Fig. 22 (a), and as a result, Since the pressure loss is reduced, the professional capacity of the heat treatment apparatus can also be reduced. In Fig. 22 (b), heat exchangers are installed before and after the blower, but if there is no problem with the heat resistance of the professional, it is possible to remove the upstream heat exchanger and install it only on the downstream side. good. Industrial applicability

The present invention provides a heat treatment apparatus that heats, cools, or dries a steel strip by spraying a gas jet onto the steel strip, and can improve a heat transfer coefficient by promoting turbulence at the center of the gas jet. In addition, the gas blown to the steel strip can be smoothly exhausted, and interference with new blown gas can be prevented, so that the heat transfer coefficient can be improved.

Further, in the present invention, in a heat treatment apparatus for heating, cooling, or drying a steel strip by spraying a gas jet onto the steel strip, the left and right rolls The length of the free running portion in the insertion space, that is, the portion that does not contribute to heating, cooling, or drying the steel strip can be reduced, so that the equipment length of the heat treatment apparatus can be shortened. In addition, this shortens the time required to heat, cool, or dry the steel strip, so that the heating rate, cooling rate, or drying rate of the steel strip can be improved, and a gas compression device such as a blower can be used. A heat exchanger for gas cooling on the outlet side of the gas makes it possible to lower the spray gas temperature efficiently, resulting in increased cooling efficiency and the power required for gas compressors such as blowers. Can be reduced.

Therefore, the heating rate or cooling rate required for metallurgical or other processes can be easily secured without providing an excessive blower duct. In addition, since the equipment length can be shortened, the equipment becomes more compact and the required propulsion power can be significantly reduced compared to the conventional equipment, and a great advantage can be obtained in terms of running cost. Furthermore, the conventional cooling method in the range of heat transfer coefficient α≥400 kcal / m ² Hr ° C, such as the problem of uneven temperature and shape deterioration of steel strip seen in roll cooling, Since there is no problem with surface oxidation, the quality of the steel strip can be improved, and the pickling equipment for removing the oxide film is not required, which simplifies the equipment configuration.

Claims

The scope of the claims

1. In a heat treatment system that heats, cools, or dries a steel strip by spraying a gas jet onto the steel strip, a resistor is attached to the tip of the nozzle that discharges the gas jet, and the projected area of the resistor is in relation to the nozzle cross-sectional area. A heat treatment system using a gas jet of a steel strip, which is installed so as to be 3 to 12%.

2. In a heat treatment system that heats, cools, or dries a steel strip by spraying a gas jet onto the steel strip, a resistive plate is attached to the tip of the nozzle that discharges the gas jet, so that the projected cross-sectional area is A heat treatment apparatus using a gas jet of steel strip, characterized in that it is installed so that the plate length in the nozzle axis direction within the nozzle is at least 50% of the nozzle diameter.

3. In a heat treatment apparatus that heats, cools, or dries a steel strip by blowing a jet of gas onto the steel strip, it has a nozzle that discharges a jet of gas, a plurality of nozzles, and a gas is injected into the nozzle. A gas blowing header to be supplied and a gas distribution header for distributing gas to a plurality of gas blowing headers are provided, and a gas exhaust port is provided between the gas blowing headers. A heat treatment using a gas jet of a steel strip, wherein an opening having an area of 5 to 17 times the opening area of the nozzle is provided. apparatus.

4. The heat treatment apparatus according to claim 3, wherein the nozzle is a protruding nozzle discharged from a tip end of the gas blowing header.

5. The heat treatment apparatus according to claim 3, wherein the projecting length force of the nozzle is not more than 5 times the inner diameter of the nozzle.

6. The shape of the tip of the gas blowing header is such that the cross section of the gas flow path is gradually reduced in the gas blowing direction, and the tip of the nozzle is directed to gas blowing. 4. The heat treatment apparatus according to claim 3, wherein the heat treatment apparatus does not protrude from the tip end of the steel strip.

7. In a heat treatment device that heats, cools, or dries the steel strip by blowing a jet of gas onto the steel strip, the distance Z between the steel strip and the tip of the nozzle is set to 70 or less, and gas is supplied to the nozzle. Roh nozzle projecting and height h mm, spraying gas amount per unit area from the header one between (air volume density) W m ³ / minm ^2, the steel strip and satisfies the relation of WZ 4 ≤ h Gas jet heat treatment equipment.

8. A heat treatment device that heats, cools, or dries the steel strip by spraying a gas jet onto the steel strip. The steel strip is located between the gas spraying space where the nozzle that discharges the gas jet is installed. In a heat treatment device that has a roll insertion space in which presser rolls are alternately arranged at certain intervals along the traveling direction of the steel strip to prevent fluttering of the steel strip, A heat treatment system using a gas jet of steel strip, characterized in that a nozzle that discharges a gas jet is installed in the opposite roll inlet space to extend the gas spray space.

9. A heat treatment device that heats, cools, or dries the steel strip by spraying a gas jet onto the steel strip. The steel strip is located between the gas spraying space where the nozzle that discharges the gas jet is installed. The steel strip is cooled in a heat treatment device that has a roll insertion space in which presser rolls are arranged alternately at a certain interval in the traveling direction of the steel strip to prevent fluttering of the steel strip. Is a heat treatment apparatus using a gas jet of a steel strip, characterized in that a press roll is a cooling roll that is cooled, and a steel roll is heated when a steel strip is heated or dried.

10. In a heat treatment system that circulates a non-oxidizing atmosphere gas through a steel strip and sprays it to cool it, a heat exchanger for gas cooling was installed at least downstream of the gas compressor such as a blower. Features of steel strip Heat treatment equipment by gas jet.