Pretreatment apparatus

Abstract

To provide a pretreatment apparatus capable of adjusting a degree of oxidation of a steel strip.SOLUTION: A pretreatment apparatus 10 provided on a treatment upstream side of a reduction furnace 100 that removes an oxide film of a steel strip S includes: an induction heating apparatus 1 that heats the steel strip S by induction heating; an injection nozzle 2 that is provided on a treatment upstream or downstream side of the induction heating apparatus 1 and directly injects an atmospheric gas to the steel strip S; a circulation flow path 4 that circulates the atmospheric gas in a conveyance passage 3 through which the steel strip S is conveyed in the induction heating apparatus 1; an oxygen concentration measurement apparatus 5 that measures an oxygen concentration of the circulation flow path 4; and an oxygen-containing gas supply apparatus 6 that adjusts an amount of oxygen supplied to the circulation flow path 4 based on a measurement result of the oxygen concentration measurement apparatus 5. The injection nozzle 2 injects the atmosphere gas in the circulation flow path 4, to which the oxygen-containing gas is supplied by the oxygen-containing gas supply apparatus 6, to the steel strip S.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pretreatment device provided on the upstream side of a reduction furnace for removing an oxide film from a steel strip.

Background Art

[0002] Conventionally, in the annealing process of a steel strip, in order to prevent the formation of an oxide film on the surface of the steel strip or to remove the oxide film, heating and cooling treatments are performed on the steel strip in a reducing atmosphere in a reduction furnace. Prior to the heat treatment, as a pretreatment, Patent Document 1 discloses a configuration for improving the adhesion of plating after heat treatment in a reduction furnace by slightly oxidizing the surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration shown in Patent Document 1, only a weakly acidic gas is simply introduced into the pretreatment device, and it is difficult to adjust the components of the atmosphere in the device or to actively generate an oxide film. Further, since the introduced gas is naturally discharged from the inlet and outlet of the device, it is difficult to perform uniform pretreatment, and there is also a waste of discharging the introduced gas.

[0005] Therefore, as disclosed in Patent Document 2, there is a configuration in which an atmospheric gas is caused to flow along a steel strip and circulated within an induction heating type apparatus for reusing the gas, and as disclosed in Patent Documents 3 and 4, there is a configuration in which a dryer or a humidifier is provided in the circulation flow path of the atmospheric gas to adjust the dew point (moisture content) of the atmosphere inside the apparatus. However, in any case, it has been difficult for the circulated atmospheric gas to come into contact with the surface of the steel strip and to adjust the degree of oxidation of the steel strip.

[0006] Therefore, an object of the present invention is to provide a pretreatment apparatus capable of adjusting the degree of oxidation of a steel strip.

Means for Solving the Problems

[0007] The present invention is a pretreatment apparatus provided on the upstream side of the treatment of a reduction furnace for removing an oxide film of a steel strip, an induction heating device for heating the steel strip by induction heating, an injection nozzle provided on the upstream side or the downstream side of the treatment of the induction heating device for directly injecting an atmospheric gas onto the steel strip, in the induction heating device, a circulation flow path for circulating the atmospheric gas in the conveyance path through which the steel strip is conveyed, an oxygen concentration measuring device for measuring the oxygen concentration of the circulation flow path, an oxygen-containing gas supply device for adjusting the supply amount of the oxygen-containing gas supplied to the circulation flow path based on the measurement result of the oxygen concentration measuring device, and the injection nozzle is configured to inject the atmospheric gas in the circulation flow path supplied with the oxygen-containing gas by the oxygen-containing gas supply device onto the steel strip.

[0008] According to the above configuration, by adjusting the supply amount of the oxygen-containing gas to the circulation flow path based on the measurement result of the oxygen concentration of the circulation flow path, the oxygen concentration of the atmospheric gas injected from the injection nozzle can be adjusted. Furthermore, by directly injecting the atmospheric gas with the adjusted oxygen concentration from the injection nozzle onto the steel strip, the degree of oxidation of the surface of the steel strip can be adjusted. Also, by circulating the atmospheric gas in the conveyance path through which the steel strip is conveyed, the atmospheric gas for oxidizing the steel strip can be efficiently used.

Advantages of the Invention

[0009] According to the present invention, a pretreatment device capable of adjusting the degree of oxidation of a steel strip can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] FIG. 1 is a schematic configuration diagram of a pretreatment apparatus 10 according to an embodiment of the present invention. As shown in FIG. 1, the pretreatment apparatus 10 is provided upstream of a reduction furnace 100 that removes the oxide film of a steel strip S as a processing material, and includes an induction heating device 1 that heats the steel strip S by induction heating, an injection nozzle 2 provided downstream of the induction heating device 1 that directly injects gas onto the steel strip S, a circulation flow path 4 that circulates the atmosphere gas in a conveyance path 3 through which the steel strip S is conveyed in the induction heating device 1, an oxygen concentration measurement device 5 that measures the oxygen concentration of the circulation flow path 4, and an oxygen-containing gas supply device 6 that adjusts the supply amount of the oxygen-containing gas supplied to the circulation flow path 4 based on the measurement result of the oxygen concentration measurement device 5. The oxygen-containing gas only needs to contain oxygen in its components, and pure oxygen and air also fall under this category. In FIG. 1, the steel strip S is conveyed upward from the bottom in a vertical pretreatment apparatus 10. Although not shown, the conveyance is performed by winding the steel strip S into a coil shape downstream of the reduction furnace 100 or the like.

[0012] The induction heating device 1 includes a solenoid type induction heating device 11 and a transverse type induction heating device 12, and the solenoid type induction heating device 11 is provided upstream of the transverse type induction heating device 12.

[0013] A plurality of injection nozzles 2 are provided downstream of each of the solenoid type induction heating device 11 and the transverse type induction heating device 12. FIG. 2 is an enlarged schematic view of the injection nozzle 2 portion. As shown in FIG. 2, the injection nozzle 2 is provided as a pair so as to face the steel strip S perpendicularly. A pair of injection nozzles 21a, 21b on the side closer to the solenoid type induction heating device 11 are configured such that the gas injection direction forms an acute angle θ1 with respect to the steel strip S (with respect to the conveyance direction X of the steel strip S). And downstream of the injection nozzles 21a, 21b, a pair of injection nozzles 22a, 22b whose gas injection direction is perpendicular to the steel strip S (with respect to the conveyance direction X of the steel strip S) are arranged.

[0014] On the downstream side of the transverse induction heating device 12 as well, similar to the downstream side of the solenoid induction heating device 11, a pair of injection nozzles 2 are provided so as to face the steel strip S perpendicularly. The pair of injection nozzles 23a and 23b on the side closer to the transverse induction heating device 12 are configured such that the injection direction of the gas forms an acute angle θ1 with respect to the steel strip S (with respect to the conveyance direction X of the steel strip S). And on the downstream side of the injection nozzles 23a and 23b, a pair of injection nozzles 24a and 24b are arranged, where the injection direction of the gas is perpendicular to the steel strip S (with respect to the conveyance direction X of the steel strip S). Note that the structures of the injection nozzles 21a, 21b, 22a, 22b, 23a, 23b, 24a, and 24b are, for example, cylindrical pipes extending in the width direction of the steel strip S, and the injection ports A are small holes or slits (both not shown) connected in the extending direction of the pipe, and inject the atmosphere gas sent from the circulation flow path 4. For this reason, the injection nozzles 21a to 24b can adjust the injection amount in the width direction of the steel strip S by, as the state of the atmosphere gas, partitioning the inside of the pipe and providing a dedicated heater to make the temperature different in the width direction of the steel strip S, or by adjusting the position and size of the small holes or slits, etc. Also, by rotating the injection nozzles 21a to 24b as a whole, the injection direction may be freely set. In the present embodiment, a pair of injection nozzles whose injection direction is perpendicular to the steel strip S and a pair of injection nozzles that form an acute angle θ1 with respect to the steel strip S are provided. Further, another pair of injection nozzles may be provided, and the injection direction thereof may be perpendicular to the steel strip S or the acute angle θ1, or the injection direction may be a direction different from the above two directions with respect to the steel strip S. Also, although not shown, the injection nozzles may not be a pair and may be provided only on one side of the steel strip S.

[0015] An inlet seal device 71 is provided at the inlet 7 of the pretreatment device 10. The inlet seal device 71 suppresses the intrusion of outside air into the pretreatment device 10 from the inlet 7 and the release of the atmosphere gas inside the pretreatment device 10 to the outside by sandwiching and conveying the steel strip S.

[0016] In the induction heating apparatus 1, the circulation passage 4 is configured to circulate the atmosphere gas in the conveyance passage 3 through which the steel strip S is conveyed. In the present embodiment, since the induction heating apparatus 1 includes a solenoid type induction heating apparatus 11 and a transverse type induction heating apparatus 12, circulation passages 41 and 42 are provided for the respective induction heating apparatuses 11 and 12.

[0017] In the solenoid type induction heating apparatus 11, the circulation passage 41 is configured to circulate the atmosphere gas in the conveyance passage 31 through which the steel strip S is conveyed. The circulation passage 41 is provided with a circulation fan 411, a gas purification device 412, an oxygen concentration measurement device 51, an oxygen-containing gas supply device 61, a dew point measurement device 413, and a high dew point gas supply device 414. A dew point control device 410 for adjusting the dew point of the atmosphere gas is arranged in the circulation passage 41. The dew point control device 410 includes at least one of a deoxidation device 412a, a dehumidification device 412b, 412c included in the gas purification device 412, and the high dew point gas supply device 414. In the circulation passage 41, the atmosphere gas in the conveyance passage 31 is sucked by the circulation fan 411 from the upstream side of the process of the solenoid type induction heating apparatus 11, and the oxygen concentration and dew point of the atmosphere gas in the circulation passage 41 are adjusted by the gas purification device 412, the oxygen concentration measurement device 51, the oxygen-containing gas supply device 61, the dew point measurement device 413, and the high dew point gas supply device 414. Then, the adjusted atmosphere gas is supplied to the injection nozzles 21a, 21b, 22a, and 22b, and the atmosphere gas is directly injected from the injection nozzles 21a, 21b, 22a, and 22b toward the steel strip S. The atmosphere gas injected from the injection nozzles 21a, 21b, 22a, and 22b passes through the conveyance passage 31 while being used for the oxidation of the steel strip S (in the present embodiment, it flows in a direction opposite to the conveyance direction X of the steel strip S), is sucked by the circulation fan 411, and circulates through the circulation passage 41 again.

[0018] The gas purification device 412 includes an oxygen removal device 412a and dehumidifying towers 412b and 412c which are dehumidifying devices. The oxygen removal device 412a is configured to remove oxygen in the ambient gas in the transport passage 31 sucked by the circulation fan 411. Further, the dehumidifying towers 412b and 412c are arranged on the downstream side of the oxygen removal device 412a. The dehumidifying towers 412b and 412c contain a desiccant that adsorbs (dehumidifies) moisture from the gas from which oxygen has been removed by the oxygen removal device 412a. In actual use, one of the dehumidifying towers 412b and 412c is used for dehumidification, and during that time, the other performs a regeneration cycle (heating the desiccant to release the adsorbed moisture) to release the adsorbed moisture. By switching this operation at regular intervals, the dehumidifying capacity of the dehumidifying towers 412b and 412c is maintained.

[0019] Note that not all of the ambient gas in the transport passage 31 needs to pass through the gas purification device 412. Since the gas purification device 412 is used when the oxygen concentration or dew point of the ambient gas is high, when it is not necessary, part of the ambient gas may bypass the gas purification device 412. That is, a bypass passage 41a that bypasses the gas purification device 412 is provided in the circulation passage 41, and by opening the on-off valve 415 or adjusting the flow rate when necessary, the accuracy of adjusting the ambient gas circulating in the circulation passage 41 can be improved.

[0020] The oxygen concentration measuring device 51 is arranged on the downstream side of the oxygen-containing gas supply device 61 and is configured to measure the oxygen concentration of the gas flowing through the circulation passage 41. The oxygen-containing gas supply device 61 is a device that supplies an oxygen-containing gas (including pure oxygen or air) to the circulation passage 41. For example, when using pure oxygen, it includes an oxygen tank 61a and an oxygen supply valve 61b connected to the oxygen tank 61a. The oxygen-containing gas supply device 61 adjusts the opening degree of the oxygen supply valve 61b based on the measurement result of the oxygen concentration measuring device 51 to adjust the amount of oxygen supplied to the circulation passage 41.

[0021] In this embodiment, the dew point measuring device 413 is arranged on the downstream side of the oxygen concentration measuring device 51 and measures the dew point of the gas flowing through the circulation flow path 41. The high dew point gas supply device 414 is a device that supplies high dew point gas to the circulation flow path 41, and includes a humidifying device 414a and a high dew point gas supply valve 414b connected to the humidifying device 414a. In this embodiment, the high dew point gas supply device 414 is arranged on the upstream side of the oxygen-containing gas supply device 61, and based on the measurement result of the dew point measuring device 413, the humidifying device 414a is operated, and the opening degree of the high dew point gas supply valve 414b is adjusted to adjust the amount of high dew point gas supplied to the circulation flow path 41. Note that the dew point measuring device 413 may be arranged on the upstream side of the oxygen concentration measuring device 51, and the high dew point gas supply device 414 may be arranged on the downstream side of the oxygen-containing gas supply device 61.

[0022] The circulation passage 42 is configured to circulate the atmosphere gas in the conveyance passage 32 through which the steel strip S is conveyed in the transverse induction heating apparatus 12. The configuration of the circulation passage 42 is the same as that of the circulation passage 41. Specifically, the circulation passage 42 is provided with a circulation fan 421, a gas purification device 422, an oxygen concentration measurement device 52, an oxygen-containing gas supply device 62, a dew point measurement device 423, and a high dew point gas supply device 424. A dew point control device 420 for adjusting the dew point of the atmosphere gas is arranged in the circulation passage 42. The dew point control device 420 includes at least one of a deoxygenation device 422a and a dehumidification device 422b, 422c included in the gas purification device 422, and the high dew point gas supply device 424. In the circulation passage 42, the atmosphere gas in the conveyance passage 32 is sucked from the upstream side of the process of the transverse induction heating apparatus 12 by the circulation fan 421, and the oxygen concentration and dew point of the atmosphere gas in the circulation passage 42 are adjusted by the gas purification device 422, the oxygen concentration measurement device 52, the oxygen-containing gas supply device 62, the dew point measurement device 423, and the high dew point gas supply device 424. Then, the adjusted atmosphere gas is supplied to the injection nozzles 23a, 23b, 24a, and 24b, and the atmosphere gas is directly injected from the injection nozzles 23a, 23b, 24a, and 24b toward the steel strip S. The gas injected from the injection nozzles 23a, 23b, 24a, and 24b passes through the conveyance passage 32 while being used for the oxidation of the steel strip S (in this embodiment, it flows in a direction opposite to the conveyance direction X of the steel strip S), is sucked by the circulation fan 421, and circulates through the circulation passage 42 again.

[0023] The gas purification device 422 includes an oxygen removal device 422a and dehumidifying towers 422b and 422c which are dehumidifying devices. The configuration of the gas purification device 422 is the same as that of the gas purification device 412. The oxygen removal device 422a is configured to remove oxygen in the ambient gas in the transport passage 32 sucked by the circulation fan 421. Further, dehumidifying towers 422b and 422c are arranged on the downstream side of the oxygen removal device 422a. The dehumidifying towers 422b and 422c contain a desiccant that adsorbs (dehumidifies) moisture from the gas from which oxygen has been removed by the oxygen removal device 422a. In actual use, dehumidification is performed using one of the dehumidifying towers 422b and 422c, and during that time, the other performs a regeneration cycle (heating the desiccant to release the adsorbed moisture) to release the adsorbed moisture. By switching this operation at regular intervals, the dehumidifying capacity of the dehumidifying towers 422b and 422c is maintained.

[0024] Note that, similar to the circulation passage 41, the circulation passage 42 is also provided with a bypass passage 42a that bypasses the gas purification device 422. By opening the on-off valve 425 or adjusting the flow rate when necessary, the accuracy of adjusting the ambient gas circulating in the circulation passage 42 can be improved.

[0025] The oxygen concentration measuring device 52 is arranged on the downstream side of the oxygen-containing gas supply device 62 and is configured to measure the oxygen concentration of the gas flowing through the circulation passage 42. The oxygen-containing gas supply device 62 is a device that supplies an oxygen-containing gas (including pure oxygen or air) to the circulation passage 42. For example, when using pure oxygen, it includes an oxygen tank 62a and an oxygen supply valve 62b connected to the oxygen tank 62a. The configuration of the oxygen concentration measuring device 52 is the same as that of the oxygen concentration measuring device 51, and the configuration of the oxygen-containing gas supply device 62 is the same as that of the oxygen-containing gas supply device 61. The oxygen-containing gas supply device 62 adjusts the opening degree of the oxygen supply valve 62b based on the measurement result of the oxygen concentration measuring device 52 to adjust the amount of oxygen supplied to the circulation passage 42.

[0026] In this embodiment, the dew point measurement device 423 is arranged downstream of the oxygen concentration measurement device 52 and is configured to measure the dew point of the gas flowing through the circulation flow path 42. The high dew point gas supply device 424 is a device that supplies high dew point gas to the circulation flow path 42, and includes a humidifying device 424a and a high dew point gas supply valve 424b connected to the humidifying device 424a. The configuration of the dew point measurement device 423 is the same as that of the dew point measurement device 413, and the configuration of the high dew point gas supply device 424 is the same as that of the high dew point gas supply device 414. In this embodiment, the high dew point gas supply device 424 is arranged upstream of the oxygen-containing gas supply device 62, and based on the measurement result of the dew point measurement device 423, the humidifying device 424a is operated and the opening degree of the high dew point gas supply valve 424b is adjusted to adjust the amount of high dew point gas supplied to the circulation flow path 42. Note that the dew point measurement device 423 may be arranged upstream of the oxygen concentration measurement device 52, and the high dew point gas supply device 424 may be arranged downstream of the oxygen-containing gas supply device 62.

[0027] Also, the circulation fan 411 and the circulation fan 421 may be shared, and the gas purification device 412 and the gas purification device 422 may be shared. FIG. 3 is a schematic configuration diagram of the pretreatment device 10 in which the circulation fan 411 and the circulation fan 421 are shared and the gas purification device 412 and the gas purification device 422 are shared. As shown in FIG. 3, when the circulation fan 411 and the circulation fan 421 are shared and the gas purification device 412 and the gas purification device 422 are shared, the flow rates of the circulation flow path 41 and the circulation flow path 42 are individually adjusted by a plurality of flow rate adjustment valves 43. According to the above configuration, the cost and installation area of the expensive and large-sized circulation fan and gas purification device can be reduced.

[0028] (Treatment of the steel strip S by the pretreatment device 10) The steel strip S is carried into the pretreatment device 10 from the inlet 7. Since the steel strip S passes through the inlet seal device 71 and is conveyed into the pretreatment device 10, it suppresses the intrusion of outside air into the pretreatment device 10 from the inlet 7 and the release of the atmospheric gas in the pretreatment device 10 from the inlet 7 to the outside.

[0029] The steel strip S is first heat-treated in the solenoid-type induction heating device 11. The steel strip S is heat-treated in the atmosphere of the atmosphere gas in the transport passage 31 of the solenoid-type induction heating device 11. The atmosphere gas in the transport passage 31 is circulated by the circulation passage 41. The atmosphere gas in the transport passage 31 is sucked by the circulation fan 411 from the upstream side of the treatment of the solenoid-type induction heating device 11 and is deoxidized and dehumidified by the gas purification device 412. The gas deoxidized and dehumidified by the gas purification device 412 is supplied with oxygen-containing gas by the oxygen-containing gas supply device 61 and supplied with high dew point gas by the high dew point gas supply device 414, and is adjusted to have a desired oxygen concentration and dew point. The supply amount of the oxygen-containing gas by the oxygen-containing gas supply device 61 is controlled by the measurement result of the oxygen concentration measurement device 51 that measures the oxygen concentration of the gas flowing through the circulation passage 41. Also, the supply amount of the high dew point gas by the high dew point gas supply device 414 is controlled by the measurement result of the dew point measurement device 413 that measures the dew point of the gas flowing through the circulation passage 41. Thus, the gas with the adjusted oxygen concentration and dew point is directly injected toward the steel strip S from the injection nozzles 21a, 21b, 22a, and 22b. The injection nozzles 22a and 22b inject the atmosphere gas toward the steel strip S from a direction perpendicular to the steel strip S, and the injection nozzles 21a and 21b located upstream of the treatment of the injection nozzles 22a and 22b inject the atmosphere gas toward the steel strip S from a direction forming an acute angle with the steel strip S. The gas injected from the injection nozzles 21a, 21b, 22a, and 22b passes through the inside of the transport passage 31 while being used for the oxidation of the steel strip S, is sucked by the circulation fan 411, and circulates through the circulation passage 41 again.

[0030] The steel strip S heat-treated in the solenoid-type induction heating device 11 is then heat-treated in the transverse-type induction heating device 12. The steel strip S is heat-treated in the atmosphere of the atmosphere gas in the conveyance passage 32 of the transverse-type induction heating device 12. The atmosphere gas in the conveyance passage 32 is circulated by the circulation passage 42. The atmosphere gas in the conveyance passage 32 is sucked by the circulation fan 421 from the upstream side of the process of the transverse-type induction heating device 12 and is deoxidized and dehumidified by the gas purification device 422. The gas deoxidized and dehumidified by the gas purification device 422 is supplied with oxygen-containing gas by the oxygen-containing gas supply device 62 and supplied with high dew point gas by the high dew point gas supply device 424, and is adjusted to have a desired oxygen concentration and dew point. The supply amount of the oxygen-containing gas by the oxygen-containing gas supply device 62 is controlled by the measurement result of the oxygen concentration measurement device 52 that measures the oxygen concentration of the gas flowing through the circulation passage 42. Further, the supply amount of the high dew point gas by the high dew point gas supply device 424 is controlled by the measurement result of the dew point measurement device 423 that measures the dew point of the gas flowing through the circulation passage 42. In this way, the atmosphere gas with the oxygen concentration and dew point adjusted is directly injected from the injection nozzles 23a, 23b, 24a and 24b toward the steel strip S. The injection nozzles 24a and 24b inject the atmosphere gas toward the steel strip S from a direction perpendicular to the steel strip S, and the injection nozzles 23a and 23b located upstream of the process of the injection nozzles 24a and 24b inject the atmosphere gas toward the steel strip S from a direction forming an acute angle with the steel strip S. The gas injected from the injection nozzles 23a, 23b, 24a and 24b passes through the inside of the conveyance passage 32 while being used for the oxidation of the steel strip S, is sucked by the circulation fan 421, and circulates through the circulation passage 42 again.

[0031] The steel strip S heat-treated in the transverse-type induction heating device 12 is, for example, conveyed to the outlet 9 of the pretreatment device 10 after changing the conveyance direction to the horizontal direction by the roll 83, is located on the downstream side of the process of the pretreatment device 10, and is sent to the reduction furnace 100 that performs heat treatment in a reducing atmosphere. Also, here, an induction heating device advantageous for rapidly heating the steel strip S is used for heating, but other heating methods such as an electric heater or a radiant tube burner may be used.

[0032] In the above embodiment, the steel strip S is conveyed upward from below in the vertical pretreatment apparatus 10, but it may be conveyed downward from above, or the steel strip S may be conveyed in the horizontal direction in the horizontal pretreatment apparatus 10. Further, it may be conveyed obliquely in the inclined furnace body. Even in such a case, the conveyance is performed by winding the steel strip S in a coil shape downstream of the reduction furnace 100 or the like.

[0033] According to the pretreatment apparatus 10 having the above configuration, the following effects can be exhibited.

[0034] (1) Based on the measurement result of the oxygen concentration in the circulation passage 4 by the oxygen concentration measuring device 5, by adjusting the supply amount of the oxygen-containing gas to the circulation passage 4 by the oxygen-containing gas supply device 6, the oxygen concentration of the atmosphere gas injected from the injection nozzle 2 can be adjusted. Further, by directly injecting the atmosphere gas with the adjusted oxygen concentration from the injection nozzle 2 at a short distance to the steel strip S, the entire surface of the steel strip S can be surely oxidized compared to the case where the steel strip S is conveyed in an atmosphere with simply increased oxygen concentration, and the degree of oxidation of the surface of the steel strip S can be positively adjusted. In addition, by circulating the atmosphere gas in the conveyance passage 3 through which the steel strip S is conveyed, the atmosphere gas for oxidizing the steel strip S can be efficiently used.

[0035] (2) Since the injection nozzle 2 injects the atmosphere gas in at least two directions, namely, a direction perpendicular to the steel strip S and directions forming acute angles θ1 and θ2 with respect to the steel strip S, the effect of oxidizing the surface of the steel strip S can be improved, and at the same time, the gentle oxidation effect in the oblique injection can be mixed to promote oxidation. When the atmosphere gas is injected in a direction perpendicular to the steel strip S, the atmosphere gas hits the steel strip S without reducing the injection momentum at the shortest distance, so the oxidation effect can be improved. In addition, by injecting the atmosphere gas in a plurality of directions, the opportunity for the atmosphere gas to contact the steel strip S can be increased.

[0036] (3) The deoxygenation devices 412a and 422a are arranged in the circulation path 4, and the oxygen-containing gas supply devices 61 and 62 are arranged downstream thereof. When the oxygen concentration of the ambient gas in the circulation path 4 increases, the excess oxygen can be absorbed by the deoxygenation devices 412a and 422a to lower the oxygen concentration. When the oxygen concentration of the ambient gas in the circulation path 4 decreases, the insufficient oxygen can be added by the oxygen-containing gas supply devices 61 and 62 to raise the oxygen concentration. Therefore, the adjustment of the oxygen concentration of the ambient gas injected from the injection nozzle 2 can be performed more reliably.

[0037] (4) The high dew point gas supply devices 414 and 424 are arranged in the circulation path 4. When the dew point of the ambient gas in the circulation path 4 is low, the dew point of the ambient gas in the circulation path 4 can be raised by supplying a high dew point gas to the circulation path 4. The dehumidification devices 412b, 412c, 422b, and 422c are arranged in the circulation path 4. When the dew point of the ambient gas in the circulation path 4 is high, the moisture in the ambient gas in the circulation path 4 can be absorbed by the dehumidification devices 412b, 412c, 422b, and 422c to lower the dew point of the atmosphere in the circulation path 4. Therefore, the adjustment of the dew point of the ambient gas in the circulation path 4 can be performed more reliably.

[0038] (5) The induction heating device 1 includes a solenoid type induction heating device 11 and a transverse type induction heating device 12. The solenoid type induction heating device 11 is provided upstream of the transverse type induction heating device 12 in the process flow. Here, although the solenoid type induction heating device 11 has excellent temperature uniformity in the width direction of the steel strip S, when the thickness of the steel strip S is thin or at a temperature above the Curie point, the heating efficiency decreases. On the other hand, the transverse type induction heating device 12 is excellent in that the heating efficiency does not decrease even when the thickness of the steel strip becomes thin. By taking advantage of these characteristics, an appropriate induction heating device 1 can be selected according to the heat treatment temperature, the material and shape of the steel strip. Therefore, when the solenoid type induction heating device 11 and the transverse type induction heating device 12 are used in combination, in order to raise the temperature to a high temperature, it is preferable to first heat with the solenoid type induction heating device 11 to a temperature near the Curie point and then further raise the temperature with the transverse type induction heating device 12.

[0039] (6) Since the solenoid type induction heating device 11 is provided with a circulation channel 41 and the transverse type induction heating device 12 is provided with a circulation channel 42, an appropriate atmosphere for induction heating can be formed according to the type of the induction heating device.

[0040] (7) By using the induction heating device 1 as the heating device of the pretreatment device 10, the volumes of the conveying passages 31 and 32 of the steel strip S in the induction heating device 1 can be reduced, and the atmosphere in the conveying passages 31 and 32 can be adjusted more easily, accurately and quickly. That is, since the volume in the induction heating device 1 is small and the atmosphere in the conveying passages 31 and 32 where the atmosphere is difficult to circulate is forcibly circulated by the circulation channels 41 and 42, and the state affecting the formation of the oxide film on the surface of the steel strip S is controlled to inject the atmosphere gas onto the steel strip S, the state of the atmosphere can be controlled more accurately and quickly, and a stable oxide film can be formed. In this embodiment, the oxygen concentration and dew point of the atmosphere gas are adjusted in the circulation channels 41 and 42, but in addition, the state of the atmosphere gas affecting the surface oxidation of the steel strip S, such as the temperature of the atmosphere gas, etc. may be further adjusted by the circulation channels 41 and 42.

[0041] In the above-described embodiment, each injection nozzle 2 is a nozzle that injects the atmospheric gas in one direction. However, a pair of injection nozzles 2 may each inject the atmospheric gas in two directions. FIG. 4 is an enlarged schematic view of an injection nozzle portion where a pair of injection nozzles 25a and 25b each inject the atmospheric gas in two directions. As shown in FIG. 4, the injection nozzles 25a and 25b include inner peripheral side cylindrical portions 25a1 and 25b1 and outer peripheral side cylindrical portions 25a2 and 25b2. The inner peripheral side cylindrical portions 25a1 and 25b1 and the outer peripheral side cylindrical portions 25a2 and 25b2 are each configured to be rotatable about the center.

[0042] In the injection nozzle 25a, the inner peripheral side cylindrical portion 25a1 includes two openings 26a1 and 26a2, and the outer peripheral side cylindrical portion 25a2 includes two openings 27a1 and 27a2. By rotating the inner peripheral side cylindrical portion 25a1 and the outer peripheral side cylindrical portion 25a2 respectively and communicating the openings 26a1 and 26a2 of the inner peripheral side cylindrical portion 25a1 with the openings 27a1 and 27a2 of the outer peripheral side cylindrical portion 25a2 respectively, the atmospheric gas is injected in two directions. Note that the opening areas of the openings 26a1 and 26a2 of the inner peripheral side cylindrical portion 25a1 are larger than the opening areas of the openings 27a1 and 27a2 of the outer peripheral side cylindrical portion 25a2.

[0043] Similarly, in the injection nozzle 25b, the inner peripheral side cylindrical portion 25b1 includes two openings 26b1 and 26b2, and the outer peripheral side cylindrical portion 25b2 includes two openings 27b1 and 27b2. By rotating the inner peripheral side cylindrical portion 25b1 and the outer peripheral side cylindrical portion 25b2 respectively and communicating the openings 26b1 and 26b2 of the inner peripheral side cylindrical portion 25b1 with the openings 27b1 and 27b2 of the outer peripheral side cylindrical portion 25b2 respectively, the atmospheric gas is injected in two directions. Note that the opening areas of the openings 26b1 and 26b2 of the inner peripheral side cylindrical portion 25b1 are larger than the opening areas of the openings 27b1 and 27b2 of the outer peripheral side cylindrical portion 25b2.

[0044] Note that the rotation of the inner peripheral cylindrical portions 25a1 and 25b1 and the outer peripheral cylindrical portions 25a2 and 25b2 may be performed automatically or manually. Then, one of the two injection directions of the injection nozzles 25a and 25b is set to be perpendicular to the steel strip S, and the other direction is set to form an acute angle θ2 with respect to the steel strip S. The rotation of the inner peripheral cylindrical portions 25a1 and 25b1 and the outer peripheral cylindrical portions 25a2 and 25b2 may be configured to be fixed at a predetermined angle.

[0045] Further, in each of the pair of injection nozzles 25a and 25b that inject the atmospheric gas in two directions, the two injection directions may be configured to be changeable respectively. Note that the injection nozzles are preferably provided as a pair so as to face the steel strip S perpendicularly. Furthermore, it is preferable that the injection angles of the injection nozzles provided as a pair are symmetric with respect to the steel strip S. According to this configuration, since the injection directions of the injection nozzles 25a and 25b are configured to be changeable, oxygen can be directly injected to a desired position on the surface of the steel strip S.

[0046] Still another embodiment of the injection nozzle is shown in FIGS. 5 to 7. In FIGS. 5 to 7, only one side of the injection nozzle is shown as a representative.

[0047] FIG. 5 shows the initial state of the injection nozzle 28. The injection nozzle 28 includes a fixed outer peripheral cylindrical portion 101 and a rotatable inner peripheral cylindrical portion 111. In order to inject the atmospheric gas perpendicularly to the steel strip S, an opening 102 is provided in the outer peripheral cylindrical portion 101, and an opening 112 is provided in the inner peripheral cylindrical portion 111. The opening 112 of the inner pipe side cylindrical portion 111 is formed to be longer in the circumferential direction than the opening 102 of the outer peripheral cylindrical portion 101, as shown by X in FIGS. 5 to 7, so that the atmospheric gas can be injected even when the inner peripheral cylindrical portion 111 is rotated.

[0048] Further, since the atmosphere gas is jetted obliquely to the steel strip S, an opening 103 is further provided in the outer peripheral side cylindrical portion 101, and an opening 113 is further provided in the inner peripheral side cylindrical portion 111. The opening 103 of the outer peripheral side cylindrical portion 101 is formed to be longer in the circumferential direction than the opening 113 of the inner peripheral side cylindrical portion 111 as shown by Y in FIGS. 5 to 7 so that the atmosphere gas can be jetted even when the inner peripheral side cylindrical portion 111 is rotated.

[0049] Furthermore, in order to supply the atmosphere gas to the injection nozzle, an opening 104 is further provided in the outer peripheral side cylindrical portion 101, and an opening 114 is further provided in the inner peripheral side cylindrical portion 111. The opening 114 of the inner peripheral side cylindrical portion 111 is formed to be longer in the circumferential direction than the opening 104 of the outer peripheral side cylindrical portion 101 as shown by Z in FIGS. 5 to 7 so that the atmosphere gas can flow into the injection nozzle 28 even when the inner peripheral side cylindrical portion 111 is rotated.

[0050] FIG. 6 is a schematic view showing a state in which the inner peripheral side cylindrical portion 111 is rotated from FIG. 5, and FIG. 7 is a schematic view showing a state in which the inner peripheral side cylindrical portion 111 is rotated in the direction opposite to that in FIG. 6 from FIG. 5. By configuring as described above, as shown in FIGS. 6 and 7, it is possible to rotate the inner peripheral side cylindrical portion 111 and change the injection direction in the oblique direction of the injection nozzle 28 as θa, θb, θc in FIGS. 5 to 7. Therefore, since the injection direction of the injection nozzle is configured to be changeable, the atmosphere gas can be directly jetted to a desired position on the surface of the steel strip S.

[0051] In the above-described embodiment, the solenoid type induction heating device 11 and the transverse type induction heating device 12 are provided as the induction heating device 1, but only one of the induction heating devices may be provided, or three or more induction heating devices may be provided. However, when both the solenoid type induction heating device 11 and the transverse type induction heating device 12 are provided, for the reasons described above, it is preferable that the solenoid type induction heating device 11 is provided on the upstream side of the process of the transverse type induction heating device 12.

[0052] In the above-described embodiment, each of the induction heating devices 1 is provided with a circulation flow path (the solenoid type induction heating device 11 is provided with a circulation flow path 41, and the transverse type induction heating device 12 is provided with a circulation flow path 42). However, when the heating atmospheres of the induction heating devices 1 may be the same, the circulation flow paths may be shared. Further, although not shown, the temperature of the steel strip S may be monitored, and the atmosphere gas of the circulation flow path may be adjusted only for the necessary induction heating devices.

[0053] In the above-described embodiment, the injection nozzle 2 is provided on the downstream side of the process of the induction heating device 1, but it may be provided on the upstream side of the process of the induction heating device 1. In this case, the gas injected from the injection nozzle 2 will flow through the transport passage 3 from the upstream side of the process to the downstream side of the process. Further, when a plurality of induction heating devices 1 are provided, the injection nozzle 2 may be provided on the downstream side of the process of one induction heating device and on the upstream side of the process of the other induction heating device.

[0054] Summarizing the present invention and the embodiment, it is as follows.

[0055] (1) One embodiment of the present invention is a pretreatment device provided on the upstream side of the process of a reduction furnace for removing the oxide film of a steel strip, an induction heating device for heating the steel strip by induction heating, an injection nozzle provided on the upstream side or the downstream side of the process of the induction heating device for directly injecting gas onto the steel strip, in the induction heating device, a circulation flow path for circulating the atmosphere gas in the transport passage through which the steel strip is transported, an oxygen concentration measuring device for measuring the oxygen concentration of the circulation flow path, an oxygen-containing gas supply device for adjusting the supply amount of the oxygen-containing gas supplied to the circulation flow path based on the measurement result of the oxygen concentration measuring device, and the injection nozzle is configured to inject the atmosphere gas of the circulation flow path supplied with the oxygen-containing gas by the oxygen-containing gas supply device onto the steel strip.

[0056] According to the above configuration (1), by adjusting the supply amount of the oxygen-containing gas to the circulation channel based on the measurement result of the oxygen concentration in the circulation channel, the oxygen concentration of the gas ejected from the injection nozzle can be adjusted. Further, by directly ejecting the gas with the adjusted oxygen concentration from the injection nozzle onto the steel strip, the surface of the steel strip can be surely oxidized, and the degree of oxidation can be adjusted. Also, by circulating the atmosphere gas in the conveyance path through which the steel strip is conveyed, the atmosphere gas for oxidizing the steel strip can be efficiently used.

[0057] (2) In the above configuration (1), a dew point control device for adjusting the dew point of the atmosphere gas is arranged in the circulation channel.

[0058] According to the above configuration (2), the dew point of the atmosphere gas in the circulation channel can be controlled by the dew point control device, and the oxidation of the steel strip can be adjusted.

[0059] (3) In the above configuration (2), the dew point control device includes at least one of a deoxidizer, a dehumidifier, and a high dew point gas supply device.

[0060] According to the above configuration (3), the dew point of the atmosphere gas in the circulation channel can be controlled by the dew point control device including at least one of a deoxidizer, a dehumidifier, and a high dew point gas supply device.

[0061] (4) In the above configuration (2), the dew point control device includes a deoxidizer and a dehumidifier, and includes a bypass flow path that bypasses the deoxidizer and the dehumidifier.

[0062] According to the above configuration (4), by providing a bypass flow path that bypasses the deoxidizer and the dehumidifier, when it is not necessary to lower the dew point of the atmosphere gas in the circulation channel, the deoxidizer and the dehumidifier can be not used, and their service lives can be extended.

[0063] (5) In the above configuration (1), the injection nozzle is adapted to inject the atmosphere gas in at least two directions toward the steel strip.

[0064] According to the above configuration (5), since the injection nozzle injects the atmosphere gas in at least two directions toward the steel strip, the opportunity for the atmosphere gas to contact the steel strip can be increased.

[0065] (6) In the above configuration (5), at least one of the injection directions of the injection nozzle is a direction perpendicular to the steel strip.

[0066] According to the above configuration (6), when the atmosphere gas is injected in a direction perpendicular to the steel strip, the atmosphere gas hits the steel strip without reducing the injection momentum at the shortest distance, so that the oxidation effect can be improved.

[0067] (7) In the above configuration (1), the injection direction of the injection nozzle is configured to be changeable.

[0068] According to the above configuration (7), since the injection direction of the injection nozzle is configured to be changeable, the atmosphere gas can be directly injected to a desired position on the surface of the steel strip.

[0069] (8) In any one of the above configurations (1) to (7), the induction heating device includes a solenoid type induction heating device and a transversal type induction heating device, and the solenoid type induction heating device is provided on the upstream side of the transversal type induction heating device in terms of processing.

[0070] According to the above configuration (7), it is possible to heat to a high temperature while making the temperature in the width direction of the thin steel strip uniform.

[0071] It is also possible to make various deformations and changes without departing from the spirit and scope of the present invention described in the claims.

Industrial Applicability

[0072] In the present invention, a pretreatment device capable of adjusting the degree of oxidation of a steel strip can be provided, so it has great industrial utility value.

Explanation of reference numerals

[0073] 1 Induction heating device 11 Solenoid type induction heating device 12 Transverse type induction heating device 2 Injection nozzle 21a Injection nozzle 21b Injection nozzle 22a Injection nozzle 22b Injection nozzle 23a Injection nozzle 23b Injection nozzle 24a Injection nozzle 24b Injection nozzle 25a Injection nozzle 25a1 Inner peripheral side cylindrical part 25a2 Outer peripheral side cylindrical part 26a1 Opening 26a2 Opening 27a1 Opening 27a2 Opening 25b Injection nozzle 25b1 Inner peripheral side cylindrical part 25b2 Outer peripheral side cylindrical part 26b1 Opening 26b2 Opening 27b1 Opening 27b2 Opening 28 Injection nozzle 101 Outer peripheral side cylindrical part 111 Inner peripheral side cylindrical part 102 Opening 112 Opening 103 Opening 113 Opening 104 Opening 114 Opening 3 Conveying passage 31 Conveying passage 32 Conveying passage 4 Circulation flow path 41 Circulation flow path 41a Bypass flow path 410 Dew point control device 411 Circulation fan 412 Gas purification device 412a Deoxidizing device 412b Dehumidifying tower 412c Dehumidifying tower 413 Dew point measuring device 414 High dew point gas supply device 414a Humidifying device 414b High dew point gas supply valve 415 On-off valve 42 Circulation flow path 42a Bypass flow path 420 Dew point control device 421 Circulation fan 422 Gas purification device 422a Deoxidizer 422b Dehumidifying tower 422c Dehumidifying tower 423 Dew point measurement device 424 High dew point gas supply device 424a Humidifying device 424b High dew point gas supply valve 425 On-off valve 43 Flow rate adjustment valve 5 Oxygen concentration measurement device 51 Oxygen concentration measurement device 52 Oxygen concentration measurement device 6 Oxygen-containing gas supply device 61 Oxygen-containing gas supply device 62 Oxygen-containing gas supply device 61a Oxygen tank 61b Oxygen supply valve 62a Oxygen tank 62b Oxygen supply valve 7 Inlet 71 Inlet seal device 83 Roll 9 Outlet 10 Pretreatment device 100 Reduction furnace S Steel strip A Injection port

Claims

1. A pretreatment device provided on the upstream side of a reduction furnace for removing the oxide film of a steel strip, comprising: an induction heating device for heating the steel strip by induction heating; an injection nozzle provided on the upstream or downstream side of the induction heating device for directly injecting an atmospheric gas onto the steel strip; in the induction heating device, a circulation flow path for circulating the atmospheric gas in the conveyance path through which the steel strip is conveyed; an oxygen concentration measuring device for measuring the oxygen concentration in the circulation flow path; an oxygen-containing gas supply device for adjusting the supply amount of the oxygen-containing gas supplied to the circulation flow path based on the measurement result of the oxygen concentration measuring device; and the injection nozzle is configured to inject the atmospheric gas in the circulation flow path supplied with the oxygen-containing gas by the oxygen-containing gas supply device onto the steel strip.

2. The pretreatment device according to claim 1, wherein a dew point control device for adjusting the dew point of the atmospheric gas is arranged in the circulation flow path.

3. The pretreatment device according to claim 2, wherein the dew point control device comprises at least one of a deoxygenation device, a dehumidification device, and a high dew point gas supply device.

4. The dew point control device comprises a deoxygenation device and a dehumidification device, and the pretreatment device according to claim 2, further comprising a bypass flow path bypassing the deoxygenation device and the dehumidification device.

5. The pretreatment device according to claim 1, wherein the injection nozzle is configured to inject the atmospheric gas in at least two directions toward the steel strip.

6. The pretreatment device according to claim 5, wherein at least one of the injection directions of the injection nozzle is a direction perpendicular to the steel strip.

7. The pretreatment device according to claim 1, wherein the injection direction of the injection nozzle is configured to be changeable.

8. The induction heating device comprises a solenoid type induction heating device and a transverse type induction heating device, and the solenoid type induction heating device is provided on the upstream side of the transverse type induction heating device. The pretreatment device according to any one of claims 1 to 7.

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