CA3058594A1

CA3058594A1 - Method and device for manufacturing steam-treated product

Info

Publication number: CA3058594A1
Application number: CA3058594A
Authority: CA
Inventors: Masaki Yamamoto; Yoshinobu Kurisu; Toshiaki Sato; Toyoharu Yasuda; Ichiro Takahashi; Hiroyuki Nakamizo; Tadashi Nakano; Hirokazu Tsuji; Takahide HAYASHIDA; Yoshitaka Yukura; Tsutomu Ohta; Shinichi Kajimoto; Takumi Uchiyama; Noboru Suzuki; Masahiko Tsuchiyama; Yuusuke Murai
Original assignee: Nippon Steel Nisshin Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 2017-03-31
Filing date: 2018-03-29
Publication date: 2018-10-04
Also published as: JP2019056171A; KR20190133159A; PH12019502242A1; KR102463338B1; RU2019130770A; JP6886936B2; MX2019011159A; EP3608437A4; EP3608437A1; AU2018246441B2; AU2018246441A1; BR112019020509A2; CN110325661A

Abstract

The purpose of the present invention is to reduce the time for manufacturing a steam-treated product such as a blued steel sheet by quickly cooling an object after steam treatment. A method for manufacturing the steam-treated product involves a steam treatment step for introducing steam into an airtight container 10 in which an object 1 to be treated is placed, thereby bringing into contact the steam and the object 1 to be treated, and a treated object cooling step for cooling the object 1 treated in the steam treatment step, and is characterized in that the treated object cooling step is a step in which cooling gas is introduced into the airtight container 10 thereby causing the cooling gas to come into contact with the object 1 treated, and the introduced cooling gas is vented from the airtight container 10.

Description

METHOD AND DEVICE FOR MANUFACTURING
STEAM-TREATED PRODUCT
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] The present invention relates to a method and a device for manufacturing a steam-treated product such as a black coated steel sheet.
DESCRIPTION OF THE BACKGROUND ART

[0002] Needs for steel sheets such as a steel sheet of black appearance have been growing, with a design awareness, in the field of roofing and exterior materials for buildings, home appliances, automobiles, and the like. A method is described, in e.g.
Patent Document 1, by which black plated steel sheets (coated steel sheets) have been manufactured.

[0003] The method for manufacturing the black plated steel sheets described in Patent Document 1 includes: a steam treatment step of bringing steam into contact with plated steel sheets in a sealed chamber so as to blacken a surface of a plating layer (coating layer) of the plated steel sheets; and a cooling step of introducing gas, such as outside air, into the sealed chamber so as to cool down the blackened plated steel sheets.

[0004] It is to be noted that, hereinafter, a contact treatment by which steam is brought into contact with objects to be treated, such as the coated steel sheets, in the sealed chamber so as to blacken the coating layer will be occasionally referred to as "steam treatment" for short.

[0005] (Prior Art Document) (Patent Document) Patent Document 1: Japanese Patent No. 6072952

[0006] (Problem to be solved) A rate, in the cooling step, of cooling down the coated steel sheets described in Patent Document 1 has not been sufficiently high, resulting in a lengthy manufacturing of black coated steel sheets.
SUMMARY OF THE INVENTION

[0007] In view of the above-described problems, there is provided the present invention whose objective is to provide a method and a device for manufacturing steam-treated products capable of cooling quickly down objects to be steam-treated, and as a result, capable of reducing a manufacturing time period of steam-treated products such as black coated steel sheets.

[0008] (Means for Solving Problems) [1] The present invention provides a method for manufacturing a steam-treated product comprising: a steam treatment step of introducing steam into a sealable chamber having an object to be treated arranged therein so as to bring the steam into contact with the object to be treated; and a cooling step of introducing coolant gas into the sealable chamber so as to allow the coolant gas introduced into the sealable chamber to have contact with the object to be treated having been treated with the steam in the steam treatment step, and discharging from the sealable chamber the coolant gas introduced into the sealable chamber.

[0009] According to the above-configured [1], in the cooling step, the coolant gas introduced into the sealable chamber could be brought into contact with the object to be treated having a temperature increased in level as a result of having been treated with the steam, and the coolant gas having a temperature increased in level alternatively by heat exchange through contact with the object to be treated could be discharged from the sealable chamber. In such a manner, by discharging from the sealable chamber the coolant gas accompanied with heat removed from the object to be treated, the object to be treated having been treated with the steam could be cooled quickly (in a short time) down, and a manufacturing time period of steam-treated products such as black coated steel sheets could be reduced.

[0010] [2] The method is provided for manufacturing the steam-treated product, in the above-configured [1], of which: the cooling step includes a coolant gas introduction step of introducing coolant gas into the sealable chamber so as to maintain temporarily in the sealable chamber, the coolant gas introduced into the sealable chamber, in a confinable manner, and a coolant gas discharge step of discharging the coolant gas from the sealable chamber through the use of a gas discharge pump after completion of the coolant gas introduction step so that a gas pressure in the sealable chamber is lower in value than an outside air pressure.

[0011] According to the above-configured [2], in the coolant gas introduction step, heat could be sufficiently removed by the coolant gas from the object to be treated, and thereafter, in the coolant gas discharge step, the coolant gas accompanied with heat having a temperature increased in level could be intensively discharged to an outside through the use of a gas discharge pump. As a result, the steam-treated object could be cooled more quickly down, thereby capable of further reducing a manufacturing time period of steam-treated products such as black coated steel sheets.

[0012] [3] The method is provided for manufacturing the steam-treated product in the above-configured [2], of which: in the cooling step, the coolant gas introduction step and the coolant gas discharge step are repeated alternately.

[0013] According to the above-configured [3], the steam-treated object could be cooled more quickly down in comparison with that in the above-configured [2], thereby capable of further reducing a manufacturing time period of steam-treated products such as black coated steel sheets.

[0014] [4] The method is provided for manufacturing the steam-treated product in the above-configured [1], of which: in the cooling step, the coolant gas is introduced into the sealable chamber and is brought into contact with the object to be treated, while concurrently, the coolant gas introduced into the sealable chamber is discharged from the sealable chamber.

[0015] According to the above-configured [4], the coolant gas is introduced concurrently with being discharged into/from the sealable chamber, and thereby, the coolant gas with an increased level of temperature due to heat removed from the object to be treated could be smoothly replaced by the coolant gas with a relatively low level of temperature for heat removal. As a result, the steam-treated object could be cooled more quickly down, thereby capable of further reducing the manufacturing time period of steam-treated products such as black coated steel sheets.

[0016] [5] The method for manufacturing steam-treated products, in any one of the above-configured [1] to [4], of which: in the cooling step, by a fan installed in the sealable chamber, the coolant gas is stirred and circulated in the sealable chamber.

[0017] According to the above-configured [5], as a result of stirring and circulating the coolant gas in the sealable chamber, the coolant gas is allowed to have uniform contact with the object to be treated, and thereby the object to be treated could be cooled more quickly and uniformly down.

[0018] [6] The present invention provides a device for manufacturing a steam-treated product comprising: a sealable chamber configured to allow an object to be treated to be arranged therein; a steam introduction unit configured to introduce steam into the sealable chamber so as to allow the steam introduced into the sealable chamber to have contact with the object to be treated arranged in the sealable chamber; a coolant gas introduction unit configured to introduce coolant gas into the sealable chamber having the object to be treated having been treated with the steam as a result of contact with the steam; and a coolant gas discharge unit configured to discharge from the sealable chamber the coolant gas introduced into the sealable chamber.

[0019] According to the above-configured [6], in similar to the above-configured [1], the steam-treated object could be cooled quickly (in a short time) down, thereby capable of reducing a manufacturing time period of steam-treated products such as black coated steel sheets.

[0020] (Advantageous Effects of the Invention) According to the present invention, steam-treated objects could be cooled quickly down, which results in the reduction of a manufacturing time period of steam-treated products such as black coated steel sheets.
BRIEF DESCRIPTIONS OF THE DRAWINGS

[0021] For more thorough understanding of the present invention and advantages thereof, the following descriptions should be read in conjunction with the accompanying drawings in which:
FIG. 1 depicts a flow chart of a method for manufacturing black coated steel sheets in a first embodiment according to the present invention.
FIG. 2 depicts a schematic view of a device for manufacturing black coated steel sheets in a first embodiment according to the present invention.
FIG. 3 depicts a flow chart of a cooling step for coated steel sheets in a first embodiment according to the present invention.
FIG. 4 depicts a timing chart showing a relation among: (a) change in internal pressure of a sealable chamber; (b) opening/closing of a gas introduction valve; (c) opening/closing of a gas discharge valve; (d) on/off of a gas discharge pump;
and (e) opening/closing of an outside air admittance valve in a cooling step for coated steel sheets in a first embodiment according to the present invention.
FIG. 5 depicts a schematic view of a device for manufacturing black coated steel sheets in a second embodiment according to the present invention.
FIG. 6 depicts a schematic view of a device for manufacturing black coated steel sheets as a modified example of a second embodiment according to the present invention.
FIG. 7 depicts a timing chart showing a relation among: (A) change in internal pressure of a sealable chamber; (B) opening/closing of a gas introduction valve; (C) opening/closing of a gas discharge valve; (D) on/off of a forced draft blower;
(E) on/off of an induced draft blower; and (F) on/off of a circulation fan as a modified example of a second embodiment according to the present invention.
DESCRIPTIONS OF EMBODIMENTS OF THE INVENTION

[0022] Hereinafter, descriptions will be provided for applying a manufacturing method of a steam-treated product, according to the present invention, to a manufacturing method of a black coated steel sheet, and a manufacturing device of a black coated steel sheet capable of implementing such a manufacturing method.

[0023] In this specification, it is to be noted that hot-dip zinc-aluminum-magnesium (Zn-Al-Mg) alloy coated steel sheets will be occasionally referred to as "coated steel sheets" for short. Further, a hot-dip Zn-Al-Mg alloy coating layer will be occasionally referred to as "coating layer" for short. Still further, "atmospheric gas"
means gases present in a sealable chamber, and more specifically, such atmospheric gas is a general term indicative collectively of outside air, steam, nitrogen gas, and so forth. Still further, "kPa" in this specification is indicative of a unit of absolute pressure.

[0024] [FIRST EMBODIMENTS]
The method for manufacturing steam-treated products in a first embodiment, as schematically shown in FIG. 1, includes: a step (S130) of blackening coated steel sheets with steam treatment; and a step (S150) of cooling down blackened coated steel sheets, of which the cooling step (S150) is characterized at the maximum. The device for manufacturing black coated steel sheets by performing the cooling step (S150) will be described below prior to detailed descriptions of the cooling step (S150).

[0025] [Device for Manufacturing Black Coated Steel Sheets]
(Structure of Device) The device for manufacturing black coated steel sheets (which will be, hereinafter, occasionally referred to as "black coated steel sheet manufacturing device") in an embodiment, as shown schematically in FIG. 2 of a cross-sectional view of an example, includes: a sealable chamber (10) having an arrangement portion (12) for arranging therein coated steel sheets (1) in a removable manner; a steam introduction regulation mechanism (40) configured to introduce steam into the sealable chamber (10), a gas introduction unit (50) configured to introduce gas whose dew point is lower than the level of temperature of the coated steel sheets (1) (low-steam gas), into the sealable chamber (10); and a gas discharge regulation mechanism (30) configured to discharge atmospheric gas from the sealable chamber (10). The steam introduction regulation mechanism (40) is included as an embodiment in "steam introduction unit" according to the present invention; the gas introduction unit (50) is included as an embodiment in "coolant gas introduction unit"; and the gas discharge regulation mechanism (30) is included as an embodiment in "coolant gas discharge unit."

[0026] Further, the black coated steel sheet manufacturing device includes an outside air admittance valve (not shown) in order to return the internal pressure of the sealable chamber (10) to an outside air pressure value, and a stirring unit (70) such as a circulation fan (71) for stirring and circulating atmospheric gas in the sealable chamber (10).

[0027] Still further, the black coated steel sheet manufacturing device may include: a temperature measurement unit (60) configured to measure the level of temperature of the coated steel sheets (1); a pressure measurement unit (61) configured to measure the internal pressure of the sealable chamber (10); a gas temperature measurement unit (62) configured to measure the level of temperature of atmospheric gas. Still further, the black coated steel sheet manufacturing device may include: a ceiling temperature regulation mechanism (21); a vertical wall temperature regulation mechanism (20); and a heating device (24) such as a sheath heater for heating (or cooling) an inside of the sealable chamber (10). Still further, the black coated steel sheet manufacturing device may include, in addition to a steam introduction regulation mechanism (40), a gas introduction part (50), a gas discharge regulation mechanism (30), a stirring unit (70), temperature regulation mechanisms (21, 20), a heating device (24) such as a sheath heater: a control unit (not shown) configured to control opening/closing of valves in manufacturing the black coated steel sheets (1). Still further, if the black coated steel sheet manufacturing device includes a drain pipe (35) and a drain valve (36), the control unit (90) may control the operation of the drain valve (36) so as to drain water from the device.

[0028] Hereinafter, detailed descriptions of an example of the black coated steel sheet manufacturing device will be provided with reference to FIG. 2.

[0029] The sealable chamber (10) has a bottom frame (8) and an upper cover (9). The bottom frame (8) has the arrangement portion (12) for arranging the coated steel sheets (1) inside the sealable chamber (10). The upper cover (9) has an upper-cover ceiling portion (13) formed in a dome-like shape for a ceiling surface and an upper-cover vertical wall (14) formed in a cylindrical shape for a side surface. The upper cover (9) is configured in such a shape that a bottom side is opened. Further, the separable chamber (10) has the temperature regulation mechanisms (21, 20) independently provided on an exterior wall surface thereof, the ceiling temperature regulation mechanism (21) and the vertical wall temperature regulation mechanism (20), capable of heating and cooling, through a fluid flow, an interior of the sealable chamber (10). Still further, the sealable chamber (10) is configured such that it is capable of being in a closed state to substantially prevent gas flowing thereinto from outside or in an open state to allow coated steel sheets (1) to be brought therein from outside. Such a sealable chamber (10) is of strength enough to withstand decrease in internal pressure caused by discharging atmospheric gas from the sealable chamber (10) in a closed state and increase in internal pressure caused by introducing steam into the sealable chamber (10) in a closed state as well as strength enough to withstand heating and cooling.

[0030] The bottom frame (8) is connected with: a steam supply pipe (41) for introducing steam from a steam supply source; a gas discharge pipe (31) for discharging atmospheric gas and steam from the sealable chamber (10); the drain pipe (35). The gas discharge pipe (31) is connected, at an intermediate pint thereof, with a gas introduction pipe (51).
By closing the valves provided on these pipes (41, 31, 35, 51), the interior of the sealable chamber (10) could be in a closed state.

[0031] The arrangement portion (12), which is installed on the bottom frame (8), is configured to allow the coated steel sheets (1) to be arranged thereon. The coated steel sheets (1) may be stacked with spacers (2) interposed between them. As shown in FIG. 2, the arrangement portion (12) has inlets (12A) to allow atmospheric gas flowing from an upper side to a lower side of the coated steel sheets (1) sucked into the circulation fan (71) to pass therethrough, and has outlets (12B) to allow the atmospheric gas thus sucked into and blown out from the circulation fan (71) to pass therethrough within the interior of the sealable chamber (10). Because of such a configuration, the gas in the sealable chamber (10) passes through the gaps between the coated steel sheets (1) for circulation, and as a result, the coated steel sheets (1) could allow the atmospheric gas to have more uniform contact therewith.

[0032] The gas discharge regulation mechanism (30) includes a gas discharge pipe (31), gas discharge valves (32), and gas discharge pumps (37). The gas discharge pumps (37) may be e.g. vacuum pumps. The "gas discharge valves (32)" are indicative collectively of gas discharge valves (322, 324, 326), which will be described later. The "gas discharge pumps (37)" are indicative collectively of gas discharge pumps (372, 374, 376), which will be described later. The gas discharge pipe (31) is a pipe formed on an outer side of the bottom frame (8) to pass through the bottom frame (8) between its outer and inner sides so that the inside and outside of the sealable chamber (10) could communicate with each other. Atmospheric gas, e.g., in the sealable chamber (10) is discharged to the outside through the gas discharge pipe (31) with the suction power of the gas discharge pumps (37).

[0033] In an embodiment as shown in FIG. 2, it is to be noted that, for adjusting the amount of steam in the sealable chamber (10) during the steam treatment, the gas discharge pipe (31) is composed of one trunk pipe in a predetermined section from an upstream side to a branching point (A) in a gas discharge direction, and is further composed of branching pipes (332, 334, 336) having their respective nominal diameters different from one another in a section downstream of the predetermined section in a gas discharge direction. The branching pipes (332, 334, 336) are provided with their respective gas discharge valves (322, 324, 326) and their respective gas discharge pumps (372, 374, 376). The gas discharge pumps (372, 374, 376) are positioned downstream of their respective gas discharge valves (322, 324, 326) in a gas discharge direction.

[0034] By setting the pipes (332, 334, 336) to have their respective nominal diameters of 20A, 25A, 80A, e.g., accurate and precise gas discharge regulation could be performed, through the opening and closing of the gas discharge valves (32) by a control unit, in response to the amount of steam required in the sealable chamber (10). As a matter of course, an embodiment should not be limited to the only possible one, and the number and nominal diameters of the branching pipes (332, 334, 336) may be altered for any specific needs. In second and fourth steps, which will be described later, the gas discharge regulation mechanism (30) is configured to discharge atmospheric gas through the use of the gas discharge pumps (372, 374, 376), thereby adjusting the gas pressure in the sealable chamber (10) to 70 kPa or lower.

[0035] The drain pipe (35) is a pipe formed on an outer side of the bottom frame (8) to pass through the bottom frame (8) between its outer and inner sides so that the inside and outside of the sealable chamber (10) could communicate with each other.
The fluid (dew, etc.) in the sealable chamber (10) could be drained to the outside through this drain pipe (35).

[0036] The steam introduction regulation mechanism (40) has the steam supply pipe (41) and steam supply valves (42), for adjusting the amount of steam to be supplied to the sealable chamber (10). It is to be noted that the "steam supply valves (42)"
are indicative collectively of steam supply valves (422, 424, 426), which will be described later.
When the steam introduction regulation mechanism (40) is in a mode of not supplying steam to the sealable chamber (10), the steam supply valves (42) are closed to prevent steam from being supplied to the sealable chamber (10) through the steam supply pipe (41).

[0037] In the black coated steel sheet manufacturing device in an embodiment as shown in FIG. 2, it is to be noted that, for adjusting the amount of steam in the sealable chamber (10) during the steam treatment, the steam supply pipe (41) is composed of one trunk pipe in a predetermined section from a connection point of the sealable chamber (10) to an upstream side in a steam supply direction, and is further composed of branching pipes (432, 434, 436) having their respective nominal diameters different from one another in a section upstream of the predetermined section in a steam supply direction. The branching pipes (432, 434, 436) are provided with their respective steam supply valves (422, 424, 426).

[0038] By setting the pipes (432, 434, 436) to have their respective nominal diameters of 20A, 25A, 80A, e.g., accurate and precise steam introduction regulation could be performed, through the opening and closing of the steam supply valves (42), in response to the amount of steam required in the sealable chamber (10). As a matter of course, an embodiment should not be limited to the only possible one, and the number and nominal diameters of the branching pipes (432, 434, 436) may be altered for any specific needs.

[0039] The gas introduction unit (50) has the gas introduction pipe (51) and a gas introduction valve (52) provided on the gas introduction pipe (51). In an embodiment, a downstream end point (B) of the gas introduction pipe (51) in a gas introduction direction is connected to an upstream portion of the branching point (A) (the one trunk pipe) of the gas discharge pipe (31) in a gas discharge direction. In other words, the gas introduction pipe (51) communicates via the gas discharge pipe (31) with an inside of the sealable chamber (10). Further, an upstream end of the gas introduction pipe (51) communicates with a gas supply source (not shown). The gas introduction unit (50) may be used for introducing "low-steam gas" into the sealable chamber (10) in first and fifth steps (S110, S150), which will be described later.

[0040] The temperature measurement unit (60) includes a plurality of temperature sensors set in contact with different areas on the surface of the coated steel sheets (1) configured to detect the level of temperatures of the coated steel sheets (1), e.g., serving as thermocouples. When the coated steel sheets (1) are in a coil form, the thermocouples may be inserted between the sheets in a coil form.

[0041] The pressure measurement unit (61) is configured to measure the internal pressure of the sealable chamber (10). This unit includes a pressure gauge configured to detect a gauge pressure throughout all the steps: first step (S110); second step (S120);
third step (S130); fourth step (S140); and fifth step (S150), which will be described later.

[0042] The gas temperature measurement unit (62) includes a temperature sensor configured to detect the level of temperature of atmospheric gas in the sealable chamber (10). A thermocouple, e.g., may be used for the temperature sensor. In place of one sensor placed at one point of an interior of the sealable chamber (10), a plurality of sensors placed at a plurality of points of the interior may be used, in an appropriately switchable manner, among them.

[0043] The stirring unit (70) includes the circulation fan (71) with respect to the bottom frame (8), and a drive motor (72) configured to rotate the circulation fan (71). When the drive motor (72) rotates the circulation fan (71), as shown by the arrows in FIG. 2, atmospheric gas is allowed to pass through an inner diameter potion of the coated steel sheets (1) in a coil form, flow into an inside of the arrangement portion (12) through inlets (12A) formed on an upper side, and flow out from an inside of the arrangement portion (12) through outlets (12B) formed on lateral sides. Subsequently, the atmospheric gas is allowed to pass through gaps between the coated steel sheets (1) in a coil form and an interior wall of the sealable chamber (10), flow into gaps between the coated steel sheets (1) from an upper side, again flow into an inside of the arrangement portion (12) from a lower side of the coated steel sheets (1) through inlets (12A) formed on an upper side so as to be sucked into the circulation fan (71) for further circulation in the sealable chamber (10). As a result, the atmospheric gas in the sealable chamber (10) during the steam treatment is stirred and supplied to an entire area of the coated steel sheets (1). As a matter of course, the use of the stirring unit (70) should not be limited to the only possible embodiment during the steam treatment (in third step (5130) which will be described later), and the stirring unit (70) may be used in a heating step (in first step (S110) which will be described later) and a cooling step (in fifth step (S150) which will be described later) for the coated steel sheets (1).

[0044] [Method for Manufacturing Black Coated Steel Sheets]
The method for manufacturing black coated steel sheets includes a method of bringing steam into contact with hot-dip Zn-Al-Mg alloy coated steel sheets (1) in the sealable chamber (10) through the use of the above-described black coated steel sheet manufacturing device.

[0045] The method for manufacturing black coated steel sheets in an embodiment as shown in the flow chart of FIG. 1 is performed in the following order of five steps:
first step (S110) of heating hot-dip Zn-Al-Mg alloy coated steel sheets (1) arranged (loaded) in a sealable chamber (10) (see FIG. 2);
second step (S120) of discharging atmospheric gas from the sealable chamber (10) so as to adjust a gas pressure in the sealable chamber (10) to 70 kPa or lower;
third step (5130) of introducing steam into the sealable chamber (10) so as to steam-treat the coated steel sheets (1);
fourth step (S140) of, after the third step (S130), returning an internal pressure of the sealable chamber (10) to an outside air pressure value, and thereafter, reducing a gas pressure in the sealable chamber (10) to 70 kPa or lower again;
and fifth step (S150) of cooling down the coated steel sheets (1) in the sealable chamber (10).
It is to be noted that, hereinafter, a control unit outside the figure is capable of outputting control signals to control the operation of a heating device (24), temperature regulation mechanisms (20, 21), a stirring device (70), each of valves (32, 42, 52), gas discharge pumps (37), and the like.

[0046] Hereinafter, a detailed explanation will be provided for each step.

[0047] (First Step) In the first step (S110), the coated steel sheets (1) arranged are heated in the sealable (10).

[0048] Each of the coated steel sheets (1) has a substrate steel sheet, and a hot-dip Zn-Al-Mg alloy coating layer formed on a surface of the substrate steel sheet.

[0049] The substrate steel sheet is not particularly restricted on its type, and e.g., low carbon steel, medium carbon steel, high carbon steel, or alloy steel may be adopted for such a substrate steel sheet. If a good press formability is required, it is preferable that a deep drawing steel sheet, such as Ti or Nb-containing low-carbon steel sheets, be adopted for the substrate steel sheet. Further, a high-strength steel sheet containing P, Si, Mn, or the like may also be adopted.

[0050] The hot-dip Zn-Al-Mg alloy coating layer is so configured at least in composition as to provoke blackening by bringing steam into contact with this coating layer.
The Zn-Al-Mg alloy coating layer, e.g., generated at a ratio of: 0.1 to 60 wt% of Al; 0.01 to 10 wt% of Mg; and the rest of Zn could be preferably blackened, by bringing steam into contact with this coating layer.

[0051] There are no particular restrictions on the form of the coated steel sheets (1) insofar as the coating layer of an area to be blackened could have contact with steam.
The coated steel sheets (1) could be coated with, e.g., a flat coating layer (such as plate form) or a curved coating layer (such as coil form).

[0052] Further, in the first step (5110), the coated steel sheets (1) are heated in the presence of gas whose dew point is lower than the level of temperature of the coated steel sheets (1) at all times (low-steam gas). In other words, the atmospheric gas present in the sealable chamber (10) is to be low-steam gas. For the low-steam gas, the outside air may be adopted from the viewpoint of the facility with which the coated steel sheets (1) could be heated. The outside air may be replaced, however, by the inert gas such as nitrogen, insofar as the coated steel sheets (1) could be blackened, or the outside air may be replaced by some atmosphere lower in dew point than the outside air. The low-steam gas could be introduced into the sealable chamber (10) through a gas introduction unit (50) connected to the sealable chamber (10).

[0053] In the first step (S110), the coated steel sheets (1) are heated until the surface temperature of the coating layer reaches a level at which the coating layer is blackened as a result of being in contact with steam (which will be, hereinafter, occasionally referred to as "blackening temperature"). The coated steel sheets (1) arranged in the sealable chamber (10) may be heated to above the blackening temperature while the level of surface temperature being measured, e.g., through a temperature sensor.

[0054] The blackening temperature may be arbitrarily adjusted depending upon the composition (e.g., amounts of Al and Mg in the coating layer) or thickness of the coating layer, the required lightness, and so forth.

[0055] There are no particular restrictions on the heating method for the coated steel sheets (1) insofar as the surface of the coating layer could be heated until a resultant temperature reaches the level of blackening temperature. The coated steel sheets (1) may be heated in such a manner that, e.g., a heating device (24) such as a sheath heater installed within an interior of the sealable chamber (10) is configured to heat the atmospheric gas within the interior of the sealable chamber (10) so as to, through convection of such a heated gas, heat the coated steel sheets (1).

[0056] It is to be noted that a stirring device (70) such as a circulation fan (71) may be installed inside the sealable chamber (10) for stirring the atmospheric gas heated in the sealable chamber (10), which results in quick, effective, and uniform heating of the coated steel sheets (1).

[0057] (Second Step) In the second step (S120), the atmospheric gas is discharged from the sealable chamber (10) through the gas discharge pipe (31) in order to reduce the gas pressure in the sealable chamber (10) to 70 kPa or lower. Gas discharge pumps (37), e.g., installed outside the sealable chamber (10) is configured to evacuate the sealable chamber (10) for reducing an internal pressure of the atmospheric gas therein to fall within the above-described range. The discharge of the atmospheric gas in the second step (S120) may be performed on a one-time basis or more than one-time basis. In the latter case, the discharge of the atmospheric gas through the gas discharge pipe (31) from the sealable chamber (10) and the introduction of the low-steam gas through the gas introduction pipe (51) into the sealable chamber (10) may be performed in a repeated manner in order to further reduce the amount of the gas components other than steam remaining in the sealable chamber (10).

[0058] In the second step (S120), the atmospheric gas is discharged from the sealable chamber (10) to reduce the gas pressure therein so that steam, to be introduced into the third step (S130) which will be described later, could be distributed sufficiently around an interval area between the coated steel sheets (1), thereby enabling the more uniform steam treatment over the whole coating layer to be blackened, and enabling the reduction of non-uniform blackening. From these points of view, in the second step (S120), the gas pressure in the sealable chamber (10) is preferably 70 kPa or lower, and more preferably 50 kPa or lower.

[0059] (Third Step) In the third step (S130), steam is introduced into the sealable chamber (10) so that the coating layer of the coated steel sheets (1) is blackened. In other words, in the third step (S130), the steam treatment is performed for the coated steel sheets (1). The third step (S130) is included as an embodiment in the "steam treatment step"
according to the present invention.

[0060] Further, in the third step (S130), an atmospheric temperature in the sealable chamber (10) during the steam treatment is preferably 105 C or higher. By adjusting the atmospheric temperature to be above 105 C, the blackening could be performed within a shorter period of time. In the present specification, the temperature of atmospheric gas in the sealable chamber (10) will be referred to as "atmospheric temperature."
The atmospheric temperature could be measured with a gas temperature measurement unit (62) installed in the sealable chamber (10).

[0061] Still further, in the third step (S130), the atmospheric gas in the sealable chamber (10) may be stirred by a stirring unit (70) during the blackening after having introduced or while introducing steam into the sealable chamber (10) to prevent non-uniform blackening of the coated steel sheets (1).

[0062] Still further, a steam treatment time may be arbitrarily adjusted depending upon the composition (e.g., amounts of Al and Mg in the coating layer) or thickness of the coating layer, the required lightness, and so forth. However, the steam treatment time is preferably 24 hours or so.

[0063] (Fourth Step) In the fourth step (S140), the internal pressure of the sealable chamber (10) is returned to an outside air pressure value, and thereafter, the atmospheric gas is discharged from the sealable chamber (10) so as to reduce the gas pressure therein to 70 kPa or lower. In order to return the internal pressure of the sealable chamber (10) to an outside air pressure value, e.g., an outside air admittance valve (not shown) provided to the sealable chamber (10) is opened. Further, in order to reduce the gas pressure in the sealable chamber (10) to 70 kPa or lower, the atmospheric gas is discharged from the sealable chamber (10), through the gas discharge pipe (31), by a gas discharge pump (37) installed outside the sealable chamber (10) configured to evacuate the sealable chamber (10).

[0064] (Fifth Step) In the fifth step (S150), the coated steel sheets (1) are cooled down in the presence of gas, whose dew point is lower than the level of temperature of the coated steel sheets (1) at all times (low-steam gas), by introducing such low-steam gas through the gas introduction pipe (51) into the sealable chamber (10) to bring the low-steam gas into contact with the coated steel sheets (1), and by discharging the low-steam gas from the sealable chamber (10). The fifth step (S150) is included as an embodiment in the "cooling step" of cooling down an object to be treated according to the present invention.
Further, the "low-steam gas" is included as an embodiment in the "coolant gas"
according to the present invention. It is preferred that the gas introduced in the fifth step (S150) be in an unheated state; however, if necessary, the gas may be heated to such an extent that its temperature is lower in level than the atmospheric temperature in the sealable chamber (10).

[0065] The low-steam gas introduced into the sealable chamber (10), in the fifth step (S150), may be, e.g., outside air, nitrogen gas, or inert gas. In view of workability, the sealable chamber (10) is preferably configured to admit the outside air therein.

[0066] The fifth step (S150) includes: a low-steam gas introduction step of introducing low-steam gas into the sealable chamber (10) and maintaining the low-steam gas to be confined in the sealable chamber (10); and an atmospheric-gas discharge step of, after the low-steam gas introduction step, discharging atmospheric gas (containing the introduced low-steam gas) to an outside from an inside of the sealable chamber (10), through the use of the gas discharge pumps (37), so that the gas pressure in the sealable chamber (10) is lower than an outside air pressure value. The "low-steam gas introduction step" is included as an embodiment in the "coolant gas introduction step" according to the present invention. The "atmospheric-gas discharge step" is included as an embodiment in the "coolant gas discharge step" according to the present invention. It is preferred that the "low-steam gas introduction step" and the "atmospheric-gas discharge step" be repeated alternately in order to speed up the cooling down.

[0067] FIG. 3 depicts a flow chart showing details as an example of fifth step (S150) shown in FIG. 1. In the example of FIG. 3, a low-steam gas introduction step and atmospheric-gas discharge step are performed twice alternately in the following order:
the low-steam gas introduction step (S210) is followed by the atmospheric-gas discharge step (S220); and thereafter, the low-steam gas introduction step (S230) is followed by the atmospheric-gas discharge step (S240). After the completion of the last atmospheric-gas discharge step (5240), an interior of the sealable chamber (10) is released to the outside air through the opening of the outside air admittance valve positioned outside the figure (S250). The number of repetition times of performing the low-steam gas introduction step followed by the atmospheric-gas discharge step should not be limited to the only possible embodiment. The repetition times of step may be three or higher, or each low-steam gas introduction step followed by atmospheric-gas discharge step may be performed once.

[0068] FIG. 4 depicts a timing chart showing a relation among: (a) change in internal pressure of the sealable chamber (10) (measured by the pressure measurement unit (61));
(b) opening/closing timing for the gas introduction valve (52); (c) opening/closing timing for the gas discharge valves (32); (d) on/off timing for the gas discharge pumps (37); and (e) opening/closing timing for the outside air admittance valve from the final stage of the fourth step (S140) to the fifth step (S150). Hereinafter, a detailed explanation will be provided for the final stage of the fourth step (S140) and the fifth step (5150).

[0069] (Final Stage of Fourth Step) In an example of the fourth step (S140) shown in FIG. 4, when the gas pressure in the sealable chamber (10) is reduced in value to 70 kPa or lower (see pressure PO, state a0 in (a)), the gas introduction valve (52) is closed (see state b0 in (b)); the gas discharge pumps (37) are energized (see state dO in (d)); and the gas discharge valves (32) are opened (see state c0 in (c)). It is to be noted that the outside air admittance valve is maintained in a closed state (see state e0 in (e)). Discharge of gas at least through one of the three pipes (332, 334, 336) is sufficient, and therefore, it is not absolutely necessary to energize all the gas discharge pumps (37) and open all the gas discharge valves (32).

[0070] (Low-Steam Gas Introduction Step) Subsequently, the low-steam gas introduction step (5210) in the fifth step (S150) is started. In an example shown in FIG. 4, all the gas discharge valves (32) are closed (see state cl in (c)); all the gas discharge pumps (37) are turned off (see state dl in (d)); and the gas introduction valve (52) is opened (see state bl in (b)). Through these operations, in the low-steam gas introduction step, low-steam gas is introduced into the sealable chamber (10) and the low-steam gas thus introduced is maintained temporarily to be confined in the sealable chamber (10), and the gas pressure in the sealable chamber (10) is increased in value to an outside air pressure P2 (see state al in (a)). By introducing low-steam gas into the sealable chamber (10) and temporarily maintaining the introduced low-steam gas to be confined in the sealable chamber (10), the coated steel sheets (1) and the low-steam gas have sufficient contact with each other, during which heat could be sufficiently removed by the low-steam gas, through heat exchange, from the coated steel sheets (1).

[0071] (Atmospheric-Gas Discharge Step) Subsequently, the atmospheric-gas discharge step (S220) is started. In this step, the gas introduction valve (52) is closed (see state b2 in (b)); the gas discharge pumps (37) are energized (see state d2 in (d)); and the gas discharge valves (32) are opened (see state c2 in (c)). These states are maintained until the gas pressure in the sealable chamber (10) is decreased in value to pressure Pt, that is, a half of pressure P2 or lower (see state a2 in (a)). In other words, a half or larger amount of the gas (atmospheric gas containing low-steam gas) in the sealable chamber (10) is discharged. In the example of (a) shown in FIG. 4, the gas pressure in the sealable chamber (10) is reduced in value to lower than a half of pressure P2. The atmospheric gas is discharged along with low-steam gas from the sealable chamber (10). Gas is discharged at least through one of the three pipes (332, 334, 336). It is not absolutely necessary to energize all the gas discharge pumps (37) and open all the gas discharge valves (32). A similar discussion applies in the atmospheric-gas discharge step (S240) to be performed later.

[0072] (Low-Steam Gas Introduction Step) Subsequently, the low-steam gas introduction step (S230) is started. In this step, all the gas discharge valves (32) are closed (see state c3 in (c)); all the gas discharge pumps (37) are closed (see state d3 in (d)); and the gas introduction valve (52) is opened (see state b3 in (b)). Through these operations, in the low-steam gas introduction step (5230), low-steam gas is introduced into the sealable chamber (10) and the low-steam gas thus introduced is maintained temporarily to be confined in the sealable chamber (10), and the gas pressure in the sealable chamber (10) is increased in value to pressure P2 (see state a3 in (a)). As a result, heat could be sufficiently removed by the low-steam gas from the , , coated steel sheets (1). In this step, the gas discharge pumps (37) may remain on (instead of being turned off) as long as the gas discharge valves (32) are closed to prevent the gas discharge.

[0073] (Atmospheric-Gas Discharge Step) Subsequently, the atmospheric-gas discharge step (S240) is started. In this step, the gas introduction valve (52) is closed (see state b4 in (b)); the gas discharge pumps (37) are energized (see state d4 in (d)); and the gas discharge valves (32) are opened (see state c4 in (c)). These states are maintained until the gas pressure in the sealable chamber (10) is decreased in value to pressure P1, that is, a half of pressure P2 or lower (see state a4 in (a)). In the example of (a) shown in FIG. 4, the gas pressure in the sealable chamber (10) is reduced in value to lower than a half of pressure P2. The atmospheric gas is discharged along with low-steam gas from the sealable chamber (10).

[0074] (Outside Air Admittance Step) Subsequently, the outside air admittance step (S250) is started. In this step, all the gas discharge valves (32) are closed (see state c5 in (c)); all the gas discharge pumps (37) are energized (see state d5 in (d)); and the outside air admittance valve positioned outside the figure (see state el in (e)). Through these operations, an interior of the sealable chamber (10) is released to the outside air (see state a5 in (a)).

[0075] [EFFECTS OF FIRST EMBODIMENTS]
According to the first embodiments, in the fifth step (S150), low-steam gas is introduced into the sealable chamber (10) and is brought into contact with the coated steel sheets (1), during which heat is removed by the low-steam gas, through heat exchange, from the coated steel sheets (1). Subsequently, the low-steam gas with an increased level of temperature due to heat removed from the coated steel sheets (1) is discharged from the sealable chamber (10). In such a manner, the low-steam gas accompanied with heat removed from the coated steel sheets (1) is discharged from the sealable chamber (10), and thereby, the steam-treated coated steel sheets (1) could be quickly (short-time) cooled down, and a manufacturing time of black coated steel sheets could be reduced.

[0076] Further, according to the first embodiments, the low-steam gas introduced into the sealable chamber (10) is temporarily maintained to be confined in the sealable chamber (10). This allows the low-steam gas to remove sufficient heat from the coated steel sheets (1). Then the low-steam gas with an increased level of temperature due to heat removed from the coated steel sheets (1) is intensively discharged to an outside through the use of gas discharge pumps (37). This effectively speeds up the cooling down of the steam-treated coated steel sheets (1) and greatly reduces a manufacturing time period of black coated steel sheets.

[0077] Still further, according to the first embodiments, as shown in FIGS. 3, 4, the introduction of low-steam gas with subsequent temporary confinement and the discharge of the introduced low-steam gas are performed alternately, which effectively speeds up the cooling down of the coated steel sheets (1).

[0078] In these embodiments, it is to be noted that, in the fifth step (S150), by causing the stirring device (70) such as a circulation fan (71) installed in the sealable chamber (10) to stir the atmospheric gas (containing low-steam gas), the quick, effective, and uniform cooling down of the coated steel sheets (1) could be further improved.

[0079] [SECOND EMBODIMENTS]
In the first embodiments, the gas introduction pipe (51) is connected to the gas discharge pipe (31). As shown in FIG. 5, an alternative arrangement may be made such that a gas introduction pipe (51) is formed to pass through a bottom frame (8) between its outer and inner sides so that an inside and outside of a sealable chamber (10) could communicate with each other; where such a gas introduction pipe (51) is independent of a gas discharge pipe (31). As a result, the fifth step (S150) could be performed, e.g., in the following manner.

[0080] More specifically, the gas introduction valve (52) and the gas discharge valves (32) are opened concurrently with each other. In the fifth step (5150), therefore, low-steam gas is introduced into the sealable chamber (10) through the gas introduction pipe (51), and is brought into contact with the coated steel sheets (1), and concurrently, the introduced low-steam gas is discharged from the sealable chamber (10) through the gas discharge pipe (31).

[0081] [EFFECTS OF SECOND EMBODIMENTS]
According to the second embodiments, the introduction of low-steam gas and the discharge of the low-steam gas thus introduced are performed concurrently with each other. In the sealable chamber (10), therefore, the low-steam gas with an increased level of temperature due to heat removed from the coated steel sheets (1) is smoothly replaced by the low-steam gas with a relatively low level of temperature for heat removal. As a result, the steam-treated coated steel sheets (1) could be cooled more quickly down, thereby capable of further reducing a manufacturing time period of black coated steel sheets.

[0082] Further, as shown in FIG. 5, the branching pipes (332, 334, 336) may join together downstream of the gas discharge valves (322, 324, 326) in a gas discharge direction. In the example shown in FIG. 5, the branching pipes (332, 334, 336) of the gas discharge pipe (31) are integrated at a joining point C into a single pipe (337). This single pipe (337) is provided with one gas discharge pump (377). In other words, one pump (377) may serve for the three pipes (332, 334, 336) (a three-pipe system). It is to be noted that the dotted arrow in FIG. 5 running in the gas discharge pipe (31) indicates the flow of atmospheric gas (discharge gas) when two gas discharge valves (322, 324) are closed while one gas discharge valve (326) is opened. A discharge rate through the gas discharge pipe (31) could be adjusted by opening any of the gas discharge valves (322, 324, 326).

[0083] It is to be noted that, in the first and second embodiments, a gas discharge pipe (31) with branching (at a branching point (A)) is used; however, a gas discharge pipe without branching may also be possible. In this case, one gas discharge pump and one gas discharge valve may apply for the gas discharge pipe (31).

[0084] [MODIFIED EXAMPLES OF SECOND EMBODIMENTS]
In modified examples, a common feature is shared with the second embodiments described above: low-steam gas is introduced into the sealable chamber (10) concurrently with the low-steam thus introduced being discharged from the sealable chamber (10).
These modified examples are different from the second embodiments in the structure for introducing low-steam gas thereinto and the structure for discharging atmospheric gas therefrom. Hereinafter, an explanation will be provided for the modified example of the second embodiments with reference to FIGS. 6, 7.

[0085] A modified example of the second embodiments has a gas introduction unit (90) (see FIG. 6) instead of the gas introduction unit (50) in the second embodiments, and a gas discharge regulation mechanism (80). It is to be noted that a modified example of the second embodiments has mechanisms corresponding to the steam introduction regulation mechanism (40) and the gas discharge regulation mechanism (30) in the second embodiments; however, these mechanisms are not shown in FIG. 6, for the purpose of convenience.

[0086] The gas introduction unit (90) has a gas introduction pipe (91) provided with a gas introduction valve (92) and a forced draft blower (93). The gas introduction pipe (91) is a pipe formed on an outer side of a bottom frame (8) to pass through the bottom frame (8) between its outer and inner sides so that the inside and outside of the sealable chamber (10) could communicate with each other. An upstream end of the gas introduction pipe (91) in a flow direction of the introduced low-steam gas communicates with a gas supply source (not shown). The gas introduction unit (90) may be used for introducing low-steam gas into the sealable chamber (10), e.g., in the first step (5110) described above and in a fifth step (S300) to be described later.

[0087] It is to be noted that the low-steam gas introduced, in the fifth step, may be, e.g., outside air, nitrogen gas, or inert gas. In view of workability, it is preferred that the outside air be introduced.

[0088] The gas discharge regulation mechanism (80) has a gas discharge pipe (81), a gas discharge valve (82), and an induced draft blower (83). The gas discharge pipe (81) is a pipe formed on an outer side of a bottom frame (8) to pass through the bottom frame (8) between its outer and inner sides so that the inside and outside of the sealable chamber (10) could communicate with each other. Atmospheric gas, e.g., in the sealable chamber (10) is discharged to the outside through the gas discharge pipe (81) with the suction power of the induced draft blower (83). The gas discharge regulation mechanism (80) may be used for discharging atmospheric gas from the sealable chamber (10), e.g., in a fifth step (S300) to be described below.

[0089] The fifth step in a modified example of the second embodiments will be described below. In the fifth step, gas having a dew point lower than the level of temperature of the coated steel sheets (1) (low-steam gas) at all times is introduced into the sealable chamber (10) through the gas introduction pipe (91) so as to be brought into contact with the coated steel sheets (1), and the introduced low-steam gas is discharged from the sealable chamber (10), and thereby, the coated steel sheets (1) are cooled down.

[0090] In the fifth step, low-steam gas is introduced into the sealable chamber (10), and is brought into contact with the coated steel sheets (1), and concurrently, the introduced . . .

gas is discharged from the sealable chamber (10).

[0091] More specifically, the fifth step includes: a low-steam gas introduction step of introducing low-steam gas into the sealable chamber (10) until a gas pressure therein reaches an outside air pressure value; a low-steam introduction and atmospheric-gas discharge step of, after the low-steam gas introduction step, subsequently introducing low-steam gas into the sealable chamber (10) so as to bring the low-steam gas into contact with the coated steel sheets (1) concurrently with discharging atmospheric gas (containing the introduced low-steam gas) from the sealable chamber (10) so as to maintain a gas pressure in the sealable chamber (10) at an outside air pressure value; and a completion step of completing the fifth step while maintaining a gas pressure in the sealable chamber (10) at an outside air pressure value.

[0092] FIG. 7 depicts a timing chart showing a relation among: (A) change in internal pressure of the sealable chamber (10) (measured by the pressure measurement unit (61));
(B) opening/closing timing for the gas introduction valve (92); (C) opening/closing timing for the gas discharge valve (82); (D) on/off timing for the forced draft blower (93); (E) on/off timing for the induced draft blower (83); and (F) on/off timing for the circulation fan (71) from the final stage of the fourth step (S140) to the fifth step (S300).
Hereinafter, a detailed explanation will be provided for the final stage of the fourth step (5140) and the fifth step (S150).

[0093] (Final Stage of Fourth Step) In an example of the fourth step (S140) shown in FIG. 7, when the gas pressure in the sealable chamber (10) is reduced in value to 70 kPa or lower (see pressure PO, state AO
in (A)), the gas introduction valve (92) is closed (see state BO in (B)); and the gas discharge valve (82) is opened (see state CO in (C)). The forced draft blower (93), the induced draft blower (83), and the circulation fan (71) are in off states, respectively (see state DO in (D), state E0 in (E), and state FO in (F)) because these are not used. The outside air admittance valve (not shown) is in a closed state.

[0094] (Fifth Step) (Low-Steam Gas Introduction Step) Subsequently, the low-steam gas introduction step (5310) in the fifth step (S300) is started. In an example shown in FIG. 7, the gas discharge valve (82) is closed (see state Cl in (C)); and the gas introduction valve (92) is opened (see state B1 in (B)).
Concurrently, the circulation fan (71) may be turned on (see state F1 in (F)).
The forced draft blower (93) may be turned on (see state D1 in (D)) or remain off (see state D3 in (D)).
Through these operations, in the low-steam gas introduction step, low-steam gas is introduced into the sealable chamber (10) and the low-steam gas thus introduced is maintained temporarily to be confined in the sealable chamber (10), and the gas pressure in the sealable chamber (10) is increased in value to an outside air pressure P2 (see state Al in (A)). By introducing low-steam gas into the sealable chamber (10) and temporarily maintaining the introduced low-steam gas to be confined in the sealable chamber (10), the coated steel sheets (1) and the low-steam gas have sufficient contact with each other, during which heat could be sufficiently removed by the low-steam gas, through heat exchange, from the coated steel sheets (1). When the gas pressure in the sealable chamber (10) reaches an outside air pressure value P2, the outside air admittance valve . .

(not shown) is opened.

[0095] (Low-Steam Gas Introduction And Atmospheric-Gas Discharge Step) Subsequently, the low-steam gas introduction and atmospheric-gas discharge step (S320) is started. In this step, the gas discharge valve (82) is opened (see state C2 in (C)) and the induced draft blower (83) is turned on (see state El in (E)). If the forced draft blower (93) remains off in the low-steam introduction step described above, in the low-steam gas introduction and atmospheric-gas discharge step (S320), the forced draft blower (93) is turned on. Through these operations, in the low-steam gas introduction and atmospheric-gas discharge step, the gas pressure in the sealable chamber (10) is maintained at an outside air pressure value (see state Al in (A)). In other words, by the introduction of low-steam gas into the sealable chamber (10) concurrently with the discharge of atmospheric gas (containing low-steam gas) from the sealable chamber (10), the gas pressure in the sealable chamber (10) is maintained at an outside air pressure value.

[0096] (Completion Step) Subsequently, the completion step (5330) is started. In this step, the gas introduction valve (92) and the gas discharge valve (82) are closed (see state B2 in (B) and state C3 in (C)), and the forced draft blower (93), the induced draft blower (83), and the circulation fan (71) are turned off (see state D2 in (D), state E2 in (E) and state F2 in (F)).
When an interior of the sealable chamber (10) is released to the outside air, the fifth step is completed (see state Al in (A)).

[0097] (EFFECTS OF MODIFIED EXAMPLES OF SECOND EMBODIMENTS) According to the above-modified example of the second embodiments, the introduction of the low-steam gas into the sealable chamber (10) with the aid of the forced draft blower (93) and the discharge of atmospheric gas from the sealable chamber (10) with the aid of the induced draft blower (83) are performed concurrently with each other. The amount of low-steam gas flowing into/out of the sealable chamber (10) could be increased, and the heat removal and quickness of the cooling down of the coated steel sheets (1) could be intensified. Further, as a result of the stirring of atmospheric gas (containing low-steam gas) through the use of the circulation fan (71), the quick, effective, and uniform cooling down of the coated steel sheets (1) could be improved.

[0098] For effective cooling down, it is preferred that both a forced draft blower (93) and an induced draft blower (83) be installed; however, one of the blowers may be omitted.

[0099] In each of the embodiments described above, the manufacturing of black coated steel sheets is escribed; however, each embodiment may be applied to the manufacturing of steam-treated products other than black coated steel sheets.

[0100] (Industrial Applicability) The present invention could reduce a manufacturing time period of steam-treated products such as black coated steel sheets, thereby to be expected to contribute to further increased popularity of the steam-treated products such as black coated steel sheets.

[0101] (Reference Numerals) 1 Coated steel sheets Sealable chamber 30, 80 Gas discharge regulation mechanism (coolant gas discharge unit) 37 Gas discharge pumps 40 Steam introduction regulation mechanism (steam introduction unit) 50, 90 Gas introduction unit (coolant gas introduction unit) 70 Stirring unit 71 Circulation fan 83 Induced draft blower 93 Forced draft blower

Claims

WHAT IS CLAIMED IS:

1. A method for manufacturing a steam-treated product comprising:
a steam treatment step of introducing steam into a sealable chamber having an object to be treated arranged therein so as to bring the steam into contact with the object to be treated; and a cooling step of introducing coolant gas into the sealable chamber so as to allow the coolant gas introduced into the sealable chamber to have contact with the object to be treated having been treated with the steam in the steam treatment step, and discharging from the sealable chamber the coolant gas introduced into the sealable chamber.

2. The method for manufacturing the steam-treated product according to claim 1, wherein the cooling step includes a coolant gas introduction step of introducing coolant gas into the sealable chamber so as to maintain temporarily in the sealable chamber, the coolant gas introduced into the sealable chamber, in a confinable manner, and a coolant gas discharge step of discharging the coolant gas from the sealable chamber through the use of a gas discharge pump after completion of the coolant gas introduction step so that a gas pressure in the sealable chamber is lower in value than an outside air pressure.

3. The method for manufacturing the steam-treated product according to claim 2, wherein, in the cooling step, the coolant gas introduction step and the coolant gas discharge step are repeated alternately.

4. The method for manufacturing the steam-treated product according to claim 1, wherein, in the cooling step, the coolant gas is introduced into the sealable chamber and is brought into contact with the object to be treated, while concurrently, the coolant gas introduced into the sealable chamber is discharged from the sealable chamber.

5. The method for manufacturing the steam-treated product according to any one of claims 1 to 4, wherein, in the cooling step, by a fan installed in the sealable chamber, the coolant gas is stirred and circulated in the sealable chamber.

6. A device for manufacturing a steam-treated product comprising:
a sealable chamber configured to allow an object to be treated to be arranged therein;
a steam introduction unit configured to introduce steam into the sealable chamber so as to allow the steam introduced into the sealable chamber to have contact with the object to be treated arranged in the sealable chamber;
a coolant gas introduction unit configured to introduce coolant gas into the sealable chamber having the object to be treated having been treated with the steam as a result of contact with the steam; and a coolant gas discharge unit configured to discharge from the sealable chamber the coolant gas introduced into the sealable chamber.