Technical Field
[0001] The present invention relates to a method and a device for manufacturing steam-treated
products such as black coated steel sheets.
Background Art
[0002] The need for black steel sheets and the like is increasing with design awareness
in a number of fields, including roofing and exterior materials for buildings, home
appliances and automobiles. For example, patent document 1 describes a method for
manufacturing black coated steel sheets.
[0003] The method for manufacturing black coated steel sheets in patent document 1 involves
a step that brings coated steel sheets into contact with steam in a closed container
and thus blackens the coating layer surface, and a step that introduces gas such as
outside air into the closed container and thus cools the blackened coated steel sheets.
[0004] In this specification, the treatment in which a treatment object such as coated steel
sheets has contact with steam in a closed container to blacken the coating layer may
be referred to as "steam treatment."
Citation List
Patent Literature
[0005] Patent document 1 Japanese Patent No.
6072952
Summary of Invention
Technical Problem
[0006] The cooling step for coated steel sheets in patent document 1 is not sufficiently
quick, leading to the lengthy manufacturing of black coated steel sheets.
[0007] Therefore, the present invention provides a method and a device for manufacturing
steam-treated products, allowing quick cooling of steam-treated objects and thus reducing
the manufacturing time of steam-treated products such as black coated steel sheets.
Solution to Problem
[0008]
- (1) The present invention provides a method for manufacturing steam-treated products,
which involves a steam treatment step that introduces steam into a closed container
containing a treatment object and brings the treatment object into contact with the
steam, and a treated object cooling step that cools the object treated with steam
in the steam treatment step, wherein said treated object cooling step introduces coolant
gas into said closed container, brings said treated object into contact with the coolant
gas, and discharges the introduced coolant gas from said closed container.
In construction (1), the treated object cooling step introduces coolant gas into the
closed container, and this coolant gas comes into contact with the treated object
that has an increased temperature as a result of steam treatment. Then the coolant
gas has an increased temperature through heat exchange during the contact, and this
coolant gas is discharged from the closed container. Thus, the coolant gas that has
removed heat from the treated object is discharged from the closed container, allowing
quick (short-time) cooling of the steam-treated object and thus reducing the manufacturing
time of steam-treated products such as black coated steel sheets.
- (2) The present invention provides the method for manufacturing steam-treated products
according to (1), wherein said treated object cooling step includes a coolant gas
introduction step that introduces coolant gas into said closed container and temporarily
keeps the introduced coolant gas confined in said closed container, and a coolant
gas discharge step that discharges said coolant gas from said closed container using
a gas discharge pump or gas discharge pumps after the coolant gas introduction step
so that the gas pressure in said closed container goes below the outside air pressure
level.
In construction (2), the treated object cooling step includes a coolant gas introduction
step and a coolant gas discharge step. In the coolant gas introduction step, the coolant
gas removes sufficient heat from the treated object. In the coolant gas discharge
step, the coolant gas with an increased temperature due to the heat removal from the
treated object is intensively discharged to the outside using a gas discharge pump
or gas discharge pumps. Thus, the steam-treated object can be cooled more quickly,
which further reduces the manufacturing time of steam-treated products such as black
coated steel sheets.
- (3) The present invention provides the method for manufacturing steam-treated products
according to (2), wherein said treated object cooling step alternately repeats said
coolant gas introduction step and said coolant gas discharge step.
In construction (3), the steam-treated object can be cooled more quickly than in construction
(2), which further reduces the manufacturing time of steam-treated products such as
black coated steel sheets.
- (4) The present invention provides the method for manufacturing steam-treated products
according to (1), wherein said treated object cooling step introduces coolant gas
into said closed container and brings said treated object into contact with the coolant
gas, simultaneously discharging the introduced coolant gas from said closed container.
In construction (4), coolant gas is introduced into the closed container and simultaneously
the introduced coolant gas is discharged from the closed container. Therefore, the
coolant gas with an increased temperature due to the heat removal from the treated
object can be smoothly replaced by the coolant gas with a relatively low temperature
that is ready for heat removal. Thus, the steam-treated object can be cooled more
quickly, which further reduces the manufacturing time of steam-treated products such
as black coated steel sheets.
- (5) The present invention provides the method for manufacturing steam-treated products
according to (1) or (4), wherein said treated object cooling step uses a fan installed
in said closed container that stirs and circulates the coolant gas in said closed
container.
In construction (5), the stirring and circulation of coolant gas in the closed container
allow uniform contact of coolant gas with the treated object and consequently quicker
uniform cooling of the treated object.
- (6) The present invention provides a device for manufacturing steam-treated products,
which comprises a closed container that can contain a treatment object, a steam introduction
means that introduces steam into said closed container and brings said treatment object
placed in said closed container into contact with the steam, a coolant gas introduction
means that introduces coolant gas into said closed container containing said steam-treated
object, and a coolant gas discharge means that discharges the introduced coolant gas
from said closed container.
In construction (6), as in construction (1), the steam-treated object can be cooled
quickly (in a short time), which reduces the manufacturing time of steam-treated products
such as black coated steel sheets.
Advantageous Effects of Invention
[0009] The present invention enables quick cooling of steam-treated objects, which reduces
the manufacturing time of steam-treated products such as black coated steel sheets.
Brief Description of Drawings
[0010]
Figure 1 is a flow chart of the method for manufacturing black coated steel sheets
in a first embodiment of the present invention.
Figure 2 is a schematic diagram of the device for manufacturing black coated steel
sheets in the first embodiment of the present invention.
Figure 3 is a flow chart showing the cooling step for coated steel sheets in the first
embodiment.
Figure 4 is a timing chart showing the relationship among (a) change in the internal
pressure of the closed container, (b) opening/closing timing for the gas introduction
valve, (c) opening/closing timing for the gas discharge valves, (d) on/off timing
for the gas discharge pumps and (e) opening/closing timing for the outside air admittance
valve in the cooling step for coated steel sheets in the first embodiment.
Figure 5 is a schematic diagram of the device for manufacturing black coated steel
sheets in a second embodiment of the present invention.
Figure 6 is a schematic diagram of a device for manufacturing black coated steel sheets
as a modified example of the second embodiment of the present invention.
Figure 7 is a timing chart showing the relationship among (A) change in the internal
pressure of the closed container, (B) opening/closing timing for the gas introduction
valve, (C) opening/closing timing for the gas discharge valve, (D) on/off timing for
the forced draft blower, (E) on/off timing for the induced draft blower and (F) on/off
timing for the circulation fan in the modified example of the second embodiment.
Description of Embodiments
[0011] Below is a description of the method and the device for manufacturing steam-treated
products according to the present invention. In the description, the steam-treated
products to be manufactured are black coated steel sheets.
[0012] In this specification, aluminum-magnesium-zinc (Zn-Al-Mg) alloy coated steel sheets
may be referred to as "coated steel sheets," and the Zn-Al-Mg alloy coating layer
as "the coating layer." "Atmospheric gas" means the gas that is present in the closed
container. More specifically, atmospheric gas is a general term indicating outside
air, steam, nitrogen gas and so forth. "kPa" is used to indicate absolute pressure.
First embodiment
[0013] In essence, the method for manufacturing steam-treated products in the first embodiment,
as shown in Figure 1, involves a step (S130) that blackens coated steel sheets with
steam treatment, and a step (S150) that cools the blackened coated steel sheets, and
the cooling step (S150) is the greatest feature. Below is a description of the device
for manufacturing black coated steel sheets, designed to perform the cooling step
(S150). This description is followed by a detailed description of the cooling step
(S150) itself.
Device for manufacturing black coated steel sheets
Construction of the device
[0014] The device for manufacturing black coated steel sheets in this embodiment (hereafter
sometimes referred to as "the black coated steel sheet manufacturing device") shown
in Figure 2, which is a schematic cross-sectional view of an example of the device,
comprises a closed container (10) that has a placement part (12) for placing coated
steel sheets (1) in a removable manner, a steam introduction regulation mechanism
(40) that introduces steam into the closed container (10), a gas introduction part
(50) that introduces gas (low-steam gas), whose dew point is lower than the temperature
of the coated steel sheets (1), into the closed container (10), and a gas discharge
regulation mechanism (30) that discharges atmospheric gas from the closed container
(10). The steam introduction regulation mechanism (40) is included in the steam introduction
means according to the present invention, the gas introduction part (50) in the coolant
gas introduction means, and the gas discharge regulation mechanism (30) in the coolant
gas discharge means.
[0015] In addition, the black coated steel sheet manufacturing device has an outside air
admittance valve (not illustrated) for returning the internal pressure of the closed
container (10) to the outside air pressure level, and a stirring unit (70) such as
a circulation fan (71) that stirs and circulates the atmospheric gas in the closed
container (10).
[0016] Furthermore, the black coated steel sheet manufacturing device may have a temperature
measurement unit (60) that measures the temperature of the coated steel sheets (1),
a pressure measurement unit (61) that measures the internal pressure of the closed
container (10), a gas temperature measurement unit (62) that measures the temperature
of the atmospheric gas, as well as a ceiling temperature regulation mechanism (21),
a vertical wall temperature regulation mechanism (20) and a heating device (24) such
as a sheath heater that heat (or cool) the inside of the closed container (10). Besides
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, the black coated
steel sheet manufacturing device may have a control unit (not illustrated) that controls
the opening and closing of valves in manufacturing black coated steel sheets (1).
If the black coated steel sheet manufacturing device has a drain pipe (35) and a drain
valve (36), the control unit (90) can control the drain valve (36) to drain water
from the device.
[0017] Below is a detailed description of an example of the black coated steel sheet manufacturing
device with reference to Figure 2.
[0018] The closed container (10) has a bottom frame (8) and an upper cover (9). The bottom
frame (8) has a placement part (12) for placing coated steel sheets (1). The upper
cover (9) has a ceiling (13) in the form of a dome and a vertical wall (14) in the
form of a cylinder. The upper cover (9) is bottomless. Two separate temperature regulation
mechanisms are installed on the exterior wall of the closed container (10): a ceiling
temperature regulation mechanism (21) and a vertical wall temperature regulation mechanism
(20). These temperature regulation mechanisms (21, 20) can heat and cool the inside
of the closed container (10) with flowing fluid. The container (10) can be in a closed
state to substantially block the inflow of gas from outside or in an open state to
receive coated steel sheets (1) from outside. The closed container (10) has strength
sufficient to withstand the pressure increase and decrease inside the closed container
(10) caused by introducing steam and discharging atmospheric gas as well as heating
and cooling.
[0019] 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 closed container (10), and a drain pipe (35). An intermediate
part of the gas discharge pipe (31) is connected with a gas introduction pipe (51).
These pipes (41, 31, 35, 51) have valves. When the valves are closed, the container
(10) is in a closed state.
[0020] The coated steel sheets (1) are placed in the placement part (12) installed on the
bottom frame (8). The coated steel sheets (1) can also be stacked with spacers (2)
between them. As shown in Figure 2, the placement part (12) has inlets (12A) for the
atmospheric gas flowing from the upper side to the lower side of the coated steel
sheets (1) to be sucked into the circulation fan (71), and outlets (12B) for the atmospheric
gas sucked into the circulation fan (71) to be blown out into the internal space of
the closed container (10). Because of this construction, the gas in the closed container
(10) passes through the gaps between the coated steel sheets (1) and thus circulates,
allowing more uniform contact of the atmospheric gas with the coated steel sheets
(1).
[0021] The gas discharge regulation mechanism (30) has a gas discharge pipe (31), gas discharge
valves (32) and gas discharge pumps (37). For example, the gas discharge pumps (37)
can be vacuum pumps. The gas discharge valves (32) are a group of gas discharge valves
(322, 324, 326) described below. The gas discharge pumps (37) are a group of gas discharge
pumps (372, 374, 376) described below. The gas discharge pipe (31) passes through
the bottom frame (8) to connect the inside of the closed container (10) to the outside
thereof. For example, the atmospheric gas in the closed container (10) is discharged
to the outside through the gas discharge pipe (31) with the suction power of the gas
discharge pumps (37).
[0022] In this embodiment shown in Figure 2, the gas discharge pipe (31) is composed of
one trunk pipe on the upstream side and three branch pipes (332, 334, 336) with different
nominal diameters on the downstream side (A is the branching point) along the gas
discharge direction. The branch pipes (332, 334, 336) are provided with gas discharge
valves (322, 324, 326) and gas discharge pumps (372, 374, 376). The gas discharge
pumps (372, 374, 376) are positioned downstream of the gas discharge valves (322,
324, 326) along the gas discharge direction.
[0023] For example, the valves (32) of three pipes (332, 334, 336) with nominal diameters
of 20A, 25A and 80A can be opened and closed by a control unit for accurate and precise
gas discharge regulation based on the required amount of steam in the closed container
(10). This is not the only possible embodiment, and the number and nominal diameters
of the branch pipes (332, 334, 336) can be altered for specific needs. In the second
and fourth steps described below, the gas discharge regulation mechanism (30) can
discharge atmospheric gas using the gas discharge pumps (372, 374, 376) so as to bring
the gas pressure in the closed container (10) to 70 kPa or less.
[0024] The drain pipe (35) passes through the bottom frame (8) to connect the inside of
the closed container (10) to the outside thereof. The fluid (dew, etc.) in the closed
container (10) is drained to the outside through the drain pipe (35).
[0025] The steam introduction regulation mechanism (40) has a steam supply pipe (41) and
steam supply valves (42), which serve to adjust the amount of steam to be supplied
to the closed container (10). The steam supply valves (42) are a group of steam supply
valves (422, 424, 426) described below. When the steam introduction regulation mechanism
(40) does not supply steam to the closed container (10), the steam supply valves (42)
are closed to block the supply of steam to the closed container (10) through the steam
supply pipe (41).
[0026] In the black coated steel sheet manufacturing device in this embodiment shown in
Figure 2, the steam supply pipe (41) is composed of one trunk pipe on the downstream
side and three branch pipes (432, 434, 436) with different nominal diameters on the
upstream side along the steam supply direction to adjust the amount of steam to be
supplied to the closed container (10) during steam treatment. The branch pipes (432,
434, 436) are provided with steam supply valves (422, 424, 426).
[0027] For example, the valves (42) of the three pipes (432, 434, 436) with nominal diameters
of 20A, 25A and 80A can be opened and closed by control for accurate and precise steam
introduction regulation based on the required amount of steam in the closed container
(10). This is not the only possible embodiment, and the number and nominal diameters
of the branch pipes (432, 434, 436) can be altered for specific needs.
[0028] The gas introduction part (50) has a gas introduction pipe (51) provided with a gas
introduction valve (52). In this embodiment, the downstream end B of the gas introduction
pipe (51) along the gas introduction direction is connected to the upstream part (the
trunk pipe upstream of the branching point A) of the gas discharge pipe (31) along
the gas discharge direction. Thus, the gas introduction pipe (51) leads through the
gas discharge pipe (31) to the inside of the closed container (10). In addition, the
upstream end of the gas introduction pipe (51) leads from a gas supply source (not
illustrated). For example, the gas introduction part (50) can be used to introduce
low-steam gas into the closed container (10) in the first and fifth steps (S10, S150)
described below.
[0029] The temperature measurement unit (60) consists of temperature sensors set in contact
with different areas on the surface of the coated steel sheets (1) to measure the
temperature of the coated steel sheets (1) using, for example, thermocouples. If the
coated steel sheets (1) are in coil form, thermocouples can be inserted between the
coiled sheets.
[0030] The pressure measurement unit (61) is a pressure gauge for measuring the internal
pressure of the closed container (10). This pressure gauge can measure pressure throughout
all steps from the first step (S110) to the fifth step (S150) described below.
[0031] The gas temperature measurement unit (62) is a temperature sensor that measures the
temperature of atmospheric gas in the closed container (10). For example, a thermocouple
can be used as the temperature sensor. It is also possible to place some temperature
sensors at some points in the closed container (10) so that the temperature sensors
are appropriately switched among themselves.
[0032] The stirring unit (70) has a circulation fan (71) positioned on the bottom frame
(8), and a drive motor (72) that rotates the circulation fan (71). When the drive
motor (72) rotates the circulation fan (71), the atmospheric gas passing through the
inner diameter part of the coated steel sheets (1), as shown by the arrows in Figure
2, flows into the inside of the placement part (12) through inlets (12A) in the upper
part of the placement part (12) and flows out from the inside of the placement part
(12) through outlets (12B) in the lateral portion of the placement part (12). Then
the atmospheric gas passes through the gap between the coils (1) and the interior
wall of the closed container (10), flows into the gaps between the coated steel sheets
(1) from the upper side of the coated steel sheets (1) and again flows into the inside
of the placement part (12) from the lower side of the coated steel sheets (1) through
the inlets (12A) in the upper portion of the placement part (12) to be sucked into
the circulation fan (71) for further circulation in the closed container (10). Thus,
the atmospheric gas in the closed container (10) during steam treatment is stirred
and supplied to the whole of the coated steel sheets (1). The stirring unit (70) can
be used during steam treatment (the third step (S130) described below) as well as
in the heating step (the first step (S110) described below) and the cooling step (the
fifth step (S150) described below) for the coated steel sheets (1).
Method for manufacturing black coated steel sheets
[0033] Below is a description of the method for manufacturing black coated steel sheets,
which brings Zn-Al-Mg alloy coated steel sheets (1) into contact with steam in a closed
container (10) using the black coated steel sheet manufacturing device described above
to manufacture black coated steel sheets.
[0034] The method for manufacturing black coated steel sheets in this embodiment shown in
a flow chart in Figure 1 involves five steps: first step (S110) - heating Zn-Al-Mg
alloy coated steel sheets (1) placed (loaded) in a closed container (10) (see Figure
2); second step (S120) - discharging atmospheric gas from the closed container (10)
and thus bringing the gas pressure in the closed container (10) to 70 kPa or less;
third step (S130) - introducing steam into the closed container (10) and treating
the coated steel sheets (1) with the steam; fourth step (S140) - returning the internal
pressure of the closed container (10) to the outside air pressure level and then bringing
the gas pressure in the closed container (10) to 70 kPa or less again; fifth step
(S150) - cooling the coated steel sheets (1) in the closed container (10). Note that
in the description below, a control unit outside the figure sending control signals
controls the operation of a heating device (24), temperature regulation mechanisms
(20, 21), a stirring device (70), valves (32, 42, 52) and gas discharge pumps (37),
among other things.
[0035] Below is a detailed description of the respective steps.
First step
[0036] The first step (S110) heats the coated steel sheets (1) placed in the closed container
(10).
[0037] The coated steel sheets (1) have a substrate steel sheet and a Zn-Al-Mg alloy coating
layer formed on the surface of the substrate steel sheet.
[0038] There are no special restrictions on the type of substrate steel sheet. For example,
the substrate steel sheet may be low carbon steel, medium carbon steel, high carbon
steel or alloy steel. If good press formability is required, deep drawing steel sheets,
for example steel sheets of low carbon steel with Ti or Nb added, are preferable as
substrate steel sheets. High-strength steel sheets containing P, Si, Mn or the like
are also possible.
[0039] The Zn-Al-Mg alloy coating layer should have a composition that causes blackening
when the coating layer is in contact with steam. For example, Zn-Al-Mg alloy coating
layers containing 0.1 to 60 wt% of Al and 0.01 to 10 wt% of Mg, when in contact with
steam, suitably blacken.
[0040] There are no special restrictions on the form of the coated steel sheets (1) if the
coating layer in the area to be blackened can have contact with steam. For example,
the coated steel sheets (1) can have a flat coating layer (e.g., plate form) or a
curved coating layer (e.g., coil form).
[0041] In the first step (S110), the coated steel sheets (1) are heated in the presence
of gas (low-steam gas) whose dew point at all times is lower than the temperature
of the coated steel sheets (1). Thus, the atmospheric gas that is present in the closed
container (10) is low-steam gas. The low-steam gas can be outside air to facilitate
the heating of the coated steel sheets (1), but it can also be inert gas such as nitrogen,
if the coated steel sheets (1) can be blackened, or atmosphere whose dew point is
lower than that of outside air. The low-steam gas can be introduced into the closed
container (10) through a gas introduction part (50) connected to the closed container
(10).
[0042] In the first step (S110), the coated steel sheets (1) are heated until the surface
temperature of the coating layer reaches the temperature at which the coating layer
is blackened in contact with steam (hereafter sometimes referred to as "blackening
temperature"). For example, the surface temperature of the coated steel sheets (1)
placed in the closed container (10) can be measured with a temperature measurement
unit (60) when the coated steel sheets are heated to the blackening temperature and
above.
[0043] The blackening temperature can be optionally adjusted depending on 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.
[0044] There are no special restrictions on the heating method for coated steel sheets (1)
if the surface of the coating layer can reach the blackening temperature. For example,
the coated steel sheets (1) can be heated in such a manner that a heating device (24),
such as a sheath heater, installed in the closed container (10) heats the atmospheric
gas in the closed container (10) and consequently the coated steel sheets (1).
[0045] The stirring device (70), such as a circulation fan (71), installed in the closed
container (10) can stir the atmospheric gas being heated in the closed container (10).
This allows quick, effective and uniform heating of the coated steel sheets (1).
Second step
[0046] The second step (S120) discharges atmospheric gas from the closed container (10)
through the gas discharge pipe (31) and thus brings the gas pressure in the closed
container (10) to 70 kPa or less. For example, gas discharge pumps (37) (not illustrated)
installed outside the closed container (10) can serve to discharge atmospheric gas
from the closed container (10), bringing the gas pressure in the closed container
(10) to the aforementioned range. The discharge of atmospheric gas in the second step
(S120) can be performed once or more than once. In the latter case, the discharge
of atmospheric gas and the introduction of low-steam gas through the gas introduction
pipe (51) can be repeated to further reduce the amount of the gas components other
than steam remaining in the closed container (10).
[0047] The second step (S120) discharges atmospheric gas from the closed container (10)
and thus reduces the gas pressure in the closed container (10) so that the gaps between
the coated steel sheets (1) can receive a sufficient supply of the steam introduced
in the third step (S130) described below. This allows more uniform steam treatment
of the whole coating layer and most probably uniform blackening thereof. For this
reason, the second step (S120) reduces the gas pressure in the closed container (10)
preferably to 70 kPa or less, more preferably to 50 kPa or less.
Third step
[0048] The third step (S130) introduces steam into the closed container (10) and blackens
the coating layer of the coated steel sheets (1). Thus, the third step (S130) performs
steam treatment for the coated steel sheets (1). The third step (S130) is included
in the steam treatment step according to the present invention.
[0049] In the third step (S130), the atmospheric temperature in the closed container (10)
during steam treatment is preferably 105°C or more. Atmospheric temperature in this
range allows quicker blackening. "Atmospheric temperature" in this specification means
the temperature of atmospheric gas in the closed container (10). The atmospheric temperature
can be measured with a gas temperature measurement unit (62) installed in the closed
container (10).
[0050] In the third step (S130), the atmospheric gas in the closed container (10) can be
stirred by the stirring unit (70) during the blackening after or while introducing
steam into the closed container (10) to prevent non-uniform blackening of the coated
steel sheets (1).
[0051] The time of steam treatment can be optionally adjusted depending on 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 time of steam treatment is preferably
24 or so hours.
Fourth step
[0052] The fourth step (S140) returns the internal pressure of the closed container (10)
to the outside air pressure level and then discharges atmospheric gas from the closed
container (10) to bring the gas pressure in the closed container (10) to 70 kPa or
less. For example, the internal pressure of the closed container (10) can be returned
to the outside air pressure level by opening the outside air admittance valve (not
illustrated) provided to the closed container (10). The gas pressure in the closed
container (10) can be brought to 70 kPa or less by using the gas discharge pumps (37)
installed outside the closed container (10) to discharge atmospheric gas from the
closed container (10) through the gas discharge pipe (31).
Fifth step
[0053] The fifth step (S150) cools the coated steel sheets (1) by introducing gas (low-steam
gas), whose dew point is lower than the temperature of the coated steel sheets (1)
at all times, into the closed container (10) through the gas introduction pipe (51),
bringing the coated steel sheets (1) with the low-steam gas and discharging the introduced
low-steam gas from the closed container (10). The fifth step (S150) is included in
the treated object cooling step according to the present invention. Low-steam gas
is included in the coolant gas according to the present invention. The gas to be introduced
in the fifth step (S150) is preferably unheated, but if necessary, the gas can be
heated to the extent that its temperature does not reach the temperature of the atmosphere
in the closed container (10).
[0054] For example, the low-steam gas to be introduced in the fifth step (S150) can be outside
air, nitrogen gas or inert gas. In consideration of workability, the preference is
to introduce outside air.
[0055] The fifth step (S150) includes a low-steam gas introduction step that introduces
low-steam gas into the closed container (10) and keeps the introduced low-steam gas
confined in the closed container (10), and an atmospheric gas discharge step that
discharges atmospheric gas (containing the introduced low-steam gas) to the outside
using the gas discharge pumps (37) after the low-steam gas introduction step so that
the gas pressure in the closed container (10) goes below the outside air pressure
level. The low-steam gas introduction step is included in the coolant gas introduction
step according to the present invention. The atmospheric gas discharge step is included
in the coolant gas discharge step according to the present invention. The low-steam
gas introduction step and the atmospheric gas discharge step are preferably repeated
alternately to speed up the cooling.
[0056] Figure 3 is a flow chart showing the details of the fifth step (S150) in Figure 1.
The example in Figure 3 performs the low-steam gas introduction step and the atmospheric
gas discharge step twice alternately: low-steam gas introduction step (S210) → atmospheric
gas discharge step (S220) → low-steam gas introduction step (S230) → atmospheric gas
discharge step (S240). After the last atmospheric gas discharge step (S240), the inside
of the closed container (10) is exposed to the outside air by opening the outside
air admittance valve outside the figure (S250). There are no special restrictions
on the number of the low-steam gas introduction steps and the atmospheric gas discharge
steps. These steps can be performed once, twice or more.
[0057] Figure 4 is a timing chart showing the relationship among (a) change in the internal
pressure of the closed container (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). The following
is a detailed description of the final stage of the fourth step (S140) and the fifth
step (S150).
Final stage of the fourth step
[0058] In the example in Figure 4, the fourth step (S140), when reducing the gas pressure
in the closed container (10) to 70 kPa or less (see pressure P0, state a0 in (a)),
closes the gas introduction valve (52) (see state b0 in (b)), turns on the gas discharge
pump(s) (37) (see state d0 in (d)) and opens the gas discharge valve(s) (32) (see
state c0 in (c)). The outside air admittance valve is closed (see state e0 in (e)).
Gas is discharged through at least one of the three pipes (332, 334, 336). It is not
absolutely necessary to turn on all gas discharge pumps (37) and open all gas discharge
valves (32).
Low-steam gas introduction step
[0059] Next, the low-steam gas introduction step (S210) included in the fifth step (S150)
starts. The example in Figure 4 closes all gas discharge valves (32) (see state c1
in (c)), turns off all gas discharge pumps (37) (see state d1 in (d)), and opens the
gas introduction valve (52) (see state b1 in (b)). Through these actions, the low-steam
gas introduction step introduces low-steam gas into the closed container (10) and
temporarily keeps the introduced low-steam gas confined in the closed container (10),
raising the gas pressure in the closed container (10) to the outside air pressure
level P2 (see state a1 in (a)). By introducing low-steam gas into the closed container
(10) and temporarily keeping the introduced low-steam gas confined in the closed container
(10), the coated steel sheets (1) are given sufficient contact with low-steam gas,
during which the heat of the coated steel sheets (1) is sufficiently removed by the
low-steam gas through heat exchange.
Atmospheric gas discharge step
[0060] Next, the atmospheric gas discharge step (S220) starts. This step closes the gas
introduction valve (52) (see state b2 in (b)), turns on the gas discharge pump(s)
(37) (see state d2 in (d)), and opens the gas discharge valve(s) (32) (see state c2
in (c)). These states are maintained until the gas pressure in the closed container
(10) decreases to pressure P1, half of pressure P2 or less (see state a2 in (a)).
This means that half or more of the gas (atmospheric gas containing low-steam gas)
in the closed container (10) is discharged. The example in (a) in Figure 4 reduces
the gas pressure in the closed container (10) to less than half of pressure P2. The
atmospheric gas is discharged with low-steam gas from the closed container (10). Gas
is discharged through at least one of the three pipes (332, 334, 336). It is not absolutely
necessary to turn on all gas discharge pumps (37) and open all gas discharge valves
(32). The same is true in the atmospheric gas discharge step (S240) to be performed
later.
Low-steam gas introduction step
[0061] Next, the low-steam gas introduction step (S230) starts. This step closes all gas
discharge valves (32) (see state c3 in (c)), turns off all gas discharge pumps (37)
(see state d3 in (d)), and opens the gas introduction valve (52) (see state b3 in
(b)). Through these actions, the low-steam gas introduction step (S230) introduces
low-steam gas into the closed container (10) and temporarily keeps the introduced
low-steam gas confined in the closed container (10), raising the gas pressure in the
closed container (10) to pressure P2 (see state a3 in (a)). Thus, the heat of the
coated steel sheets (1) is sufficiently removed by the low-steam gas. In this step,
the gas discharge pump(s) (37) may remain on (instead of turning it (them) off) if
the gas discharge valves (32) are closed to block the gas discharge.
Atmospheric gas discharge step
[0062] Next, the atmospheric gas discharge step (S240) starts. This step closes the gas
introduction valve (52) (see state b4 in (b)), turns on the gas discharge pump(s)
(37) (see state d4 in (d)), and opens the gas discharge valve(s) (32) (see state c4
in (c)). These states are maintained until the gas pressure in the closed container
(10) decreases to pressure P1, half of pressure P2 or less (see state a4 in (a)).
The example in (a) in Figure 4 reduces the gas pressure in the closed container (10)
to less than half of pressure P2. The atmospheric gas is discharged with low-steam
gas from the closed container (10).
Outside air admittance step
[0063] Next, the outside air admittance step (S250) starts. This step closes all gas discharge
valves (32) (see state c5 in (c)), turns off all gas discharge pumps (37) (see state
d5 in (d)), and opens the outside air admittance valve outside the figure (see state
e1 in (e)). Through these actions, the inside of the closed container (10) is exposed
to the outside air (see state a5 in (a)).
Effects of the first embodiment
[0064] In the first embodiment, the fifth step (S150) introduces low-steam gas into the
closed container (10) and brings the coated steel sheets (1) into contact with the
low-steam gas, during which the heat of the coated steel sheets (1) is removed by
the low-steam gas through heat exchange. Then the low-steam gas with an increased
temperature due to the heat removal from the coated steel sheets (1) is discharged
from the closed container (10). Thus, the low-steam gas that has removed heat from
the coated steel sheets (1) is discharged from the closed container (10), allowing
quick (short-time) cooling of the steam-treated coated steel sheets (1) and thus reducing
the manufacturing time of black coated steel sheets.
[0065] The low-steam gas introduced into the closed container (10) is temporarily kept confined
in the closed container (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 temperature
due to the heat removal from the coated steel sheets (1) is intensively discharged
to the outside using a gas discharge pump or gas discharge pumps (37). This effectively
speeds up the cooling of the steam-treated coated steel sheets (1) and greatly reduces
the manufacturing time of black coated steel sheets.
[0066] In this embodiment shown in Figures 3 and 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 of the coated steel
sheets (1).
[0067] In this embodiment, the fifth step (S150) can use the stirring device (70) such as
a circulation fan (71) installed in the closed container (10) to stir the atmospheric
gas (containing low-steam gas), which further improves the quick, effective and uniform
cooling of the coated steel sheets (1).
Second embodiment
[0068] In the first embodiment, the gas introduction pipe (51) is connected to the gas discharge
pipe (31). Figure 5 shows an alternative placement of the gas introduction pipe (51),
which passes through the bottom frame (8) to connect the inside of the closed container
(10) to the outside thereof. In this case, the gas introduction pipe (51) and the
gas discharge pipe (31) are independent of each other. Therefore, the fifth step (S150)
can be performed, for example, in the following manner.
[0069] Specifically, the gas introduction valve (52) and the gas discharge valve(s) (32)
are opened at the same time. Thus, the fifth step (S150) introduces low-steam gas
into the closed container (10) through the gas introduction pipe (51) and brings the
coated steel sheets (1) into contact with the low-steam gas, simultaneously discharging
the introduced low-steam gas from the closed container (10) through the gas discharge
pipe (31).
Effects of the second embodiment
[0070] In the second embodiment, the introduction and discharge of low-steam gas are performed
simultaneously. Therefore, in the closed container (10), the low-steam gas with an
increased temperature due to the heat removal from the coated steel sheets (1) is
smoothly replaced by the low-steam gas with a relatively low temperature that is ready
for heat removal. Thus, the steam-treated coated steel sheets (1) can be cooled more
quickly, which reduces the manufacturing time of black coated steel sheets.
[0071] As shown in Figure 5, the branch pipes (332, 334, 336) may join together on the downstream
side of the gas discharge valves (322, 324, 326). In the example shown in Figure 5,
the branch pipes (332, 334, 336) of the gas discharge pipe (31) are united at joining
point C into a single pipe (337). This single pipe (337) is provided with one gas
discharge pump (377). Thus, one pump (377) may serve for the three pipes (332, 334,
336) (a three-pipe system). The dotted arrow in Figure 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, and one gas discharge valve (326) is open. The discharge
rate through the gas discharge pipe (31) can be adjusted by opening any of the gas
discharge valves (322, 324, 326).
[0072] The first and second embodiments use a gas discharge pipe (31) with branching (A
is the branching point), but a gas discharge pipe without branching is also possible.
In this case, one gas discharge pump and one gas discharge valve will do for the gas
discharge pipe (31).
Modified example of the second embodiment
[0073] This modified example shares a common feature with the second embodiment described
above: low-steam gas is introduced into the closed container (10) at the same time
as the introduced low-steam is discharged from the closed container (10). However,
this modified example is different from the second embodiment in the structure for
introducing low-steam gas and the structure for discharging atmospheric gas. Below
is a description of the modified example of the second embodiment with reference to
Figures 6 and 7.
[0074] The modified example of the second embodiment has a gas introduction part (90) (see
Figure 6) instead of the gas introduction part (50) in the second embodiment, and
a gas discharge regulation mechanism (80). Note that the modified example of the second
embodiment has mechanisms corresponding to the steam introduction regulation mechanism
(40) and the gas discharge regulation mechanism (30) in the second embodiment, but
these mechanisms are not illustrated in Figure 6 for the purpose of convenience.
[0075] The gas introduction part (90) has a gas introduction pipe (91) that is provided
with a gas introduction valve (92) and a forced draft blower (93). The gas introduction
pipe (91) passes through the bottom frame (8) to connect the inside of the closed
container (10) with the outside thereof. The upstream end of the gas introduction
pipe (91) along the flow direction of the introduced low-steam gas leads from a gas
supply source (not illustrated). For example, the gas introduction part (90) can be
used to introduce low-steam gas into the closed container (10) in the first step (S110)
described above and the fifth step (S300) described below.
[0076] For example, the low-steam gas to be introduced in the fifth step can be outside
air, nitrogen gas or inert gas. In consideration of workability, the preference is
to introduce outside air.
[0077] 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)
passes through the bottom frame (8) to connect the inside of the closed container
(10) to the outside thereof. For example, the atmospheric gas in the closed container
(10) is discharged to the outside through the gas discharge pipe (81) with the suction
power of the induced draft blower (83). For example, the gas discharge regulation
mechanism (80) can be used to discharge atmospheric gas from the closed container
(10) in the fifth step (S300) described below.
[0078] The following describes the fifth step in the modified example of the second embodiment.
The fifth step introduces gas (low-steam gas), whose dew point is lower than the temperature
of the coated steel sheets (1) at all times, into the closed container (10) through
the gas introduction pipe (91), brings the coated steel sheets (1) into contact with
the low-steam gas, and discharges the introduced low-steam gas from the closed container
(10), thus cooling the coated steel sheets (1).
[0079] The fifth step introduces low-steam gas into the closed container (10) and brings
the coated steel sheets (1) into contact with the low-steam gas, simultaneously discharging
the introduced gas from the closed container (10).
[0080] Specifically, the fifth step includes a low-steam gas introduction step that introduces
low-steam gas into the closed container (10) until the gas pressure in the closed
container (10) reaches the outside air pressure level, a low-steam introduction/atmospheric
gas discharge step that, after the low-steam gas introduction step, continues to introduce
low-steam gas into the closed container (10) and bring the coated steel sheets (1)
into contact with the low-steam gas, simultaneously discharging atmospheric gas (containing
the introduced low-steam gas) from the closed container (10) so as to maintain the
gas pressure in the closed container (10) at the outside air pressure level, and a
finish step that finishes the fifth step, maintaining the gas pressure in the closed
container (10) at the outside air pressure level.
[0081] Figure 7 is a timing chart showing the relationship among (A) change in the internal
pressure of the closed container (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) described
before to the fifth step (S300). The following is a detailed description of the final
stage of the fourth step and the fifth step.
Final stage of the fourth step
[0082] In the example in Figure 7, the fourth step (S140), when reducing the gas pressure
in the closed container (10) to 70 kPa or less (see pressure P0, state A0 in (A)),
closes the gas introduction valve (92) (see state B0 in (B)) and opens the gas discharge
valve (82) (see state C0 in (C)). The forced draft blower (93), the induced draft
blower (83) and the circulation fan (71) are off (see state D0 in (D), state E0 in
(E) and state F0 in (F)) because these are not used. The outside air admittance valve
(not illustrated) is closed.
Fifth step
Low-steam gas introduction step
[0083] Next, the low-steam gas introduction step (S310) included in the fifth step (S300)
starts. The example in Figure 7 closes the gas discharge valve (82) (see state C1
in (C)) and opens the gas introduction valve (92) (see state B1 in (B)). At the same
time, the circulation fan (71) can be turned on (see state F1 in (F)). The forced
draft blower (93) can be turned on (see state D1 in (D)) or remain off (see state
D3 in (D)). Through these actions, the low-steam gas introduction step introduces
low-steam gas into the closed container (10) and temporarily keeps the introduced
low-steam gas confined in the closed container (10), raising the gas pressure in the
closed container (10) to the outside air pressure level P2 (see state A1 in (A)).
The low-steam gas, introduced into the closed container (10) and temporarily kept
confined therein, comes into sufficient contact with the coated steel sheets (1) and
removes sufficient heat from the coated steel sheets (1) through heat exchange. When
the gas pressure in the closed container (10) has reached outside air pressure level
P2, the outside air admittance valve (not illustrated) is opened.
Low-steam gas introduction/atmospheric gas discharge step
[0084] Next, the low-steam gas introduction/atmospheric gas discharge step (S320) starts.
This step opens the gas discharge valve (82) (see state C2 in (C)) and turns on the
induced draft blower (83) (see state E1 in (E)). If the forced draft blower (93) was
off in the low-steam introduction step described above, the low-steam gas introduction/atmospheric
gas discharge step (S320) turns on the forced draft blower (93). Through these actions,
the low-steam gas introduction/atmospheric gas discharge step maintains the gas pressure
in the closed container (10) at the outside air pressure level (see state A1 in (A)).
Thus, the introduction of low-steam gas into the closed container (10) and the discharge
of atmospheric gas (containing low-steam gas) from the closed container (10) are performed
simultaneously, maintaining the gas pressure in the closed container (10) at the outside
air pressure level.
Finish step
[0085] Next, the finish step (S330) starts. This step closes the gas introduction valve
(92) and the gas discharge valve (82) (see state B2 in (B) and state C3 in (C)), and
turns off the forced draft blower (93), the induced draft blower (83) and the circulation
fan (71) (see state D2 in (D), state E2 in (E) and state F2 in (F)). With the inside
of the closed container (10) exposed to the outside air, the fifth step ends (see
state A1 in (A)).
Effects of the modified example of the second embodiment
[0086] The modified example of the second embodiment introduces low-steam gas into the closed
container (10) with the help of the forced draft blower (93) and simultaneously discharges
atmospheric gas from the closed container (10) with the help of the induced draft
blower (83). This increases the amount of low-steam gas flowing into and out of the
closed container (10), intensifying the heat removal and quickening the cooling of
the coated steel sheets (1). The stirring of atmospheric gas (containing low-steam
gas) by the circulation fan (71) further improves the quick, effective and uniform
cooling of the coated steel sheets (1).
[0087] For effective cooling, the preference is to install both a forced draft blower (93)
and an induced draft blower (83). However, it is possible to omit one of the blowers.
[0088] In the embodiments described above, the present invention is applied to the manufacturing
of black coated steel sheets, but it can be applied to the manufacturing of steam-treated
products other than black coated steel sheets.
Industrial Applicability
[0089] The present invention can reduce the manufacturing time of steam-treated products
such as black coated steel sheets, leading to increased popularity of steam-treated
products such as black coated steel sheets.
Reference Signs List
[0090]
- 1
- Coated steel sheets
- 10
- Closed container
- 30, 80
- Gas discharge regulation mechanism (coolant gas discharge means)
- 37
- Gas discharge pumps
- 40
- Steam introduction regulation mechanism (steam introduction means)
- 50, 90
- Gas introduction part (coolant gas introduction means)
- 70
- Stirring unit
- 71
- Circulation fan
- 83
- Induced draft blower
- 93
- Forced draft blower