mame of Document] DESCRIPTION
[Title of the Invention] ALLOYED POSITION DETERMINING METHOD, ALLOYED
POSITION DETERMINING APPARATUS, AND RECORDNG MEDIUM
[Technical Field]
5 [OOOl]
The present invention relates to an alloyed position determining method, an
alloyed position determining apparatus, and a recording medium.
[Background Art]
[0002]
10 In a hot dip galvanizing line, which is a line for plating a steel sheet with zinc, the
steel sheet is conveyed through a molten zinc bath and then heated, so that an alloying
layer of zinc and iron is formed on an outer layer of the steel sheet. At this time, it is
important in terms of quality management to perform operation so that zinc plating can be
alloyed in a predetermined state. That is, both an unalloyed layer in which alloying is
15 insufficient and an overalloyed layer in which alloying is performed too much degrade
quality.
[0003]
Accordingly, for example, the following Patent Document 1 discloses a method to
measure radiant energy by use of radiation thermometers at a plurality of points in the
20 height direction of an alloying furnace, to specify an alloyed position by use of the
obtained results of measurement of radiant energy, and to control a furnace temperature in
the alloying furnace for performing alloying.
[0004]
Further, the following Patent Document 2 discloses a method to install three or
25 more radiation thermometers in an alloying furnace, and to determine an alloyed position
by focusing on differences between adjacent indicated temperatures.
[0005]
Furthermore, the following Patent Document 3 discloses a method to measure
steel sheet radiant temperatures at a plurality of positions in a sheet temperature holding
zone in an alloying furnace, and to determine an alloyed position based on emissivity
5 calculated by use of the measurement results.
[Prior Art Document(s)]
[Patent Document(s)]
[0006]
[Patent Document 11 PS57- 185966A
10 [Patent Document 21 JPH4-2 1 8654A
[Patent Document 31 JPH7-150328A
[Summary of the Invention]
[Problems to Be Solved by the Invention]
[0007]
15 Techniques disclosed in the above Patent Documents 1 to 3, however, have been
made for processes in which flame is lit inside an alloying furnace and a steel sheet is
heated to be alloyed. In such hrnaces including a high-temperature heat source, stray
radiation noise might be a problem and it might be difficult to measure the emissivity
precisely. Here, stray radiation noise refers to the phenomenon that, when a heat source
20 exists around a target to be measured, emission from the heat source is mixed into a value
measured by a radiation thermometer as disturbance. Mixing of such stray radiation noise
can cause a problem that true heat emission from the target to be measured becomes
obscure.
[0008]
2 5 Further, in alloying processes in which induction heating is used in a previous
section of alloying, which have been becoming more common in recent years, unlike in
conventional processes, burning is not performed in a heat holding zone, and a steel sheet
is alloyed by being gradually cooled in the heat holding zone. The present inventors have
studied such alloying processes and have revealed that the temperature of the steel sheet is
decreased in the heat holding zone unlike in conventional processes, as described below.
5 [0009]
The techniques disclosed in the above Patent Documents 1 to 3 are each used
under a situation in which the heat source exists inside the alloying furnace and the
temperature of the steel sheet is maintained almost constantly, so that a decrease in steel
sheet temperature is not considered. Therefore, when such a method is applied to the
10 processes that have been becoming more common in recent years, there arises a problem of
failure to determine the alloyed position precisely.
[OO lo]
Thus, the present invention has been made in view of the above problem, and
aims to provide an alloyed position determining method, an alloyed position determining
15 apparatus, and a recording medium each of which enables more precise determination of
the alloyed position even in the processes in which induction heating is used in a previous
section of alloying, which have been becoming more common in recent years, and the steel
sheet is alloyed by being gradually cooled in the heat holding zone.
[Means for Solving the Problems]
20 [OOll]
In order to solve the above-described problems, according to an aspect of the
present invention, there is provided an alloyed position determining method including a
radiance information acquiring step, a steel sheet temperature estimating step, an
emissivity calculating step, and an alloyed position determining step. The radiance
25 information acquiring step is for acquiring information regarding a result of measurement
of radiance from each of a plurality of radiation thermometers installed in a vicinity of a
heat holding zone in a hot dip galvanizing line of a steel sheet and along a conveying
direction of the steel sheet in the heat holding zone, the radiation thermometers measuring
radiance of the steel sheet conveyed. The steel sheet temperature estimating step is for
estimating steel sheet temperatures at installation positions of the radiation thermometers
5 by use of information regarding a temperature decreasing pattern of the steel sheet,
accompanied by a position change in the conveying direction in the heat holding zone, and
information regarding the installation positions of the radiation thermometers. The
emissivity calculating step is for calculating emissivity at the installation positions of the
radiation thermometers by use of the estimated steel sheet temperatures estimated at the
10 installation positions of the radiation thermometers and the information regarding the result
of measurement of radiance. The alloyed position determining step is for determining an
alloyed position based on the calculated emissivity.
[OO 121
In the steel sheet temperature estimating step, an amount of temperature decrease
15 in the steel sheet is preferably calculated based on the information regarding the
temperature decreasing pattern of the steel sheet and the information regarding the
installation positions of the radiation thermometers, and the estimated steel sheet
temperatures are preferably calculated by subtracting the calculated amount of temperature
decrease from a temperature of the steel sheet on an entry section of the heat holding zone.
20 [0013]
In the steel sheet temperature estimating step, the temperature decreasing pattern
may be calculated based on a measured temperature of the steel sheet before the steel sheet
enters the heat holding zone, measured with a spectral radiation thermometer, and a
measured temperature of the steel sheet in the heat holding zone, measured with a
25 multicolor radiation thermometer, and the steel sheet temperature may be estimated by use
of the calculated temperature decreasing pattern and the information regarding the
installation positions of the radiation thermometers.
[00 141
In the alloyed position determining step, when emissivity which is calculated in
the emissivity calculating step and which corresponds to a position of an (n-l)(nl2)-th
5 radiation thermometer from the entry section of the heat holding zone is lower than a
predetermined threshold value and emissivity which corresponds to a position of an n-th
radiation thermometer is higher than or equal to the predetermined threshold value, it may
be determined that a position where alloying has occurred is a section between an
installation position of an (n-1)-th radiation thermometer and an installation position of the
10 n-th radiation thermometer in the heat holding zone.
[00 151
Further, in order to solve the above-described problems, according to another
aspect of the present invention, there is provided an alloyed position determining apparatus
including a radiance information acquiring unit, a steel sheet temperature estimating unit,
15 an emissivity calculating unit, and an alloyed position determining unit. The radiance
information acquiring unit is configured to acquire information regarding a result of
measurement of radiance from each of a plurality of radiation thermometers installed in a
vicinity of a heat holding zone in a hot dip galvanizing line of a steel sheet and along a
conveying direction of the steel sheet in the heat holding zone, the radiation thermometers
20 measuring radiance of the steel sheet conveyed. The steel sheet temperature estimating
unit is configured to estimate steel sheet temperatures at installation positions of the
radiation thermometers by use of information regarding a temperature decreasing pattern
of the steel sheet, accompanied by a position change in the conveying direction in the heat
holding zone, and information regarding the installation positions of the radiation
25 thermometers. The emissivity calculating unit is configured to calculate emissivity at the
installation positions of the radiation thermometers by use of the estimated steel sheet
temperatures estimated at the installation positions of the radiation thermometers,
estimated by the steel sheet temperature estimating unit, and the information regarding the
result of measurement of radiance. The alloyed position determining unit is configured to
determine an alloyed position based on the emissivity calculated by the emissivity
5 calculating unit.
[00 1 61
The steel sheet temperature estimating unit preferably calculates an amount of
temperature decrease in the steel sheet based on the information regarding the temperature
decreasing pattern of the steel sheet and the information regarding the installation positions
10 of the radiation thermometers, and preferably calculates the estimated steel sheet
temperatures by subtracting the calculated amount of temperature decrease from a
temperature of the steel sheet on an entry section of the heat holding zone.
[00 1 71
The steel sheet temperature estimating unit may calculate the temperature
15 decreasing pattern based on a measured temperature of the steel sheet before the steel sheet
enters the heat holding zone, measured with a spectral radiation thermometer, and a
measured temperature of the steel sheet in the heat holding zone, measured with a
multicolor radiation thermometer, and may estimate the steel sheet temperature by use of
the calculated temperature decreasing pattern and the information regarding the installation
20 positions of the radiation thermometers.
[00 181
The alloyed position determining unit may determine, when emissivity which is
calculated by the emissivity calculating unit and which corresponds to a position of an
(n-l)(n?2)-th radiation thermometer from the entry section of the heat holding zone is
25 lower than a predetermined threshold value and emissivity which corresponds to a position
of an n-th radiation thermometer is higher than or equal to the predetermined threshold
value, that a position where alloying has occurred is a section between an installation
position of an (n-1)-th radiation thermometer and an installation position of the n-th
radiation thermometer in the heat holding zone.
[00 191
5 Furthermore, in order to solve the above-described problems, according to another
aspect of the present invention, there is provided a program for causing a computer to
execute a radiance information acquiring function, a steel sheet temperature estimating
function, an emissivity calculating function, and an alloyed position determining function.
The radiance information acquiring function is to acquire information regarding a result of
10 measurement of radiance from each of a plurality of radiation thermometers installed in a
vicinity of a heat holding zone in a hot dip galvanizing line of a steel sheet and along a
conveying direction of the steel sheet in the heat holding zone, the radiation thermometers
measuring radiance of the steel sheet conveyed. The steel sheet temperature estimating
function is to estimate steel sheet temperatures at installation positions of the radiation
15 thermometers by use of information regarding a temperature decreasing pattern of the steel
sheet, accompanied by a position change in the conveying direction in the heat holding
zone, and information regarding the installation positions of the radiation thermometers.
The emissivity calculating function is to calculate emissivity at the installation positions of
the radiation thermometers by use of the estimated steel sheet temperatures estimated at the
20 installation positions of the radiation thermometers, estimated by the steel sheet
temperature estimating function, and the information regarding the result of measurement
of radiance. The alloyed position determining function is to determine an alloyed
position based on the emissivity calculated by the emissivity calculating function.
[0020]
2 5 Furthermore, in order to solve the above-described problems, according to another
aspect of the present invention, there is provided a recording medium having a program
recorded thereon for causing a computer to. execute a radiance information acquiring
function, a steel sheet temperature estimating function, an emissivity calculating function,
and an alloyed position determining function. The radiance information acquiring
function is to acquire information regarding a result of measurement of radiance from each
5 of a plurality of radiation thermometers installed in a vicinity of a heat holding zone in a
hot dip galvanizing line of a steel sheet and along a conveying direction of the steel sheet
in the heat holding zone, the radiation thermometers measuring radiance of the steel sheet
conveyed. The steel sheet temperature estimating function is to estimate steel sheet
temperatures at installation positions of the radiation thermometers by use of information
10 regarding a temperature decreasing pattern of the steel sheet, accompanied by a position
change in the conveying direction in the heat holding zone, and information regarding the
installation positions of the radiation thermometers. The emissivity calculating function
is to calculate emissivity at the installation positions of the radiation thermometers by use
of the estimated steel sheet temperatures estimated at the installation positions of the
15 radiation thermometers, estimated by the steel sheet temperature estimating function, and
the information regarding the result of measurement of radiance. The alloyed position
determining function is to determine an alloyed position based on the emissivity calculated
by the emissivity calculating function.
[Effects of the Invention]
20 [0021]
As described above, according to the present invention, calculation of the
emissivity considering the decrease in steel sheet temperature in the heat holding zone
enables precise estimation of the steel sheet temperature and more precise determination of
an alloyed position.
25 [Brief Description of the Drawings]
[0022]
[FIG I] FIG 1 is an explanatory view schematically showing a hot dip
galvanizing line according to a first embodiment of the present invention.
[FIG 21 FIG 2 is a graph showing an example of change in steel sheet
temperature in a hot dip galvanizing line.
5 [FIG. 31 FIG 3 is a graph showing an example of change in spectral emissivity
accompanied by progress of alloying.
[FIG 41 FIG 4 is a block diagram showing a configuration of an alloyed position
determining apparatus according to the embodiment.
[FIG. 51 FIG 5 is an explanatory view showing an example of installation
10 positions of radiation thermometers.
[FIG 61 FIG. 6 is an explanatory view showing an estimating method of a steel
sheet temperature.
[FIG 71 FIG. 7 is an explanatory view for explaining stray radiation noise.
[FIG 81 FIG. 8 is a graph showing an example of temperature change in steel
15 sheet temperature and inner wall temperature.
[FIG 9A] FIG 9A is a graph showing a relation between true emissivity and
pseudo emissivity.
[FIG 9B] FIG 9B is a graph showing a relation between true emissivity and
pseudo emissivity.
20 [FIG 101 FIG 10 is a graph showing a relation between spectral emissivity and
true emissivity when a steel sheet temperature is assumed to be constant.
[FIG 1 I] FIG 11 is a graph showing a relation between a temperature difference
between steel sheet temperature and inner wall temperature and pseudo emissivity.
[FIG 121 FIG. 12 is a flow chart showing a flow of an alloyed position
25 determining method according to the embodiment.
[FIG. 131 FIG. 13 is a block diagram showing a hardware configuration of an
alloyed position determining apparatus according to an embodiment of the present
invention.
[FIG. 141 FIG 14 is an explanatory view for explaining a method for calculating a
temperature decreasing pattern.
5 [FIG 151 FIG 15 is an explanatory view for explaining thermometers installed in
a hot dip galvanizing line in Example 1 of the present invention.
[FIG 161 FIG 16 is a graph showing measured values of steel sheet temperatures
with a spectral radiation thermometer and a two-color thermometer and estimated steel
sheet temperatures at installation positions of radiation thermometers.
10 [FIG 171 FIG. 17 is a graph showing measured values (temperature converted
values when emissivity is 1) with radiation thermometers.
[FIG. 181 FIG. 18 is a graph showing emissivity calculated from steel sheet
temperatures and radiance.
[Mode for Carrying out the Invention]
15 [0023]
Hereinafter, referring to the appended drawings, preferred embodiments of the
present invention will be described in detail. It should be noted that, in this specification
and the appended drawings, structural elements that have substantially the same function
and structure are denoted with the same reference numerals, and repeated explanation
20 thereof is omitted.
[0024]
(First embodiment)

First, a summary of a hot dip galvanizing line according to a first embodiment of
25 the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is an
explanatory view schematically showing the hot dip galvanizing line according to this
embodiment. FIG 2 is a graph showing an example of change in steel sheet temperature
in the hot dip galvanizing line.
[0025]
First, a hot dip galvanizing line 1 according to this embodiment will be described
5 with reference to FIG 1.
[0026]
As shown in FIG. 1, a steel sheet S conveyed from an annealing furnace is
immersed in a zinc bath 10 containing molten zinc and a variety of additives. The
direction of the steel sheet S is changed by a sink roll (a roll that exists in a molten zinc
10 bath and changes the conveying direction of the steel sheet) 11 installed in the zinc bath 10,
and the steel sheet 10 is conveyed in a substantially vertical direction.
[0027]
The steel sheet S that has exited the zinc bath 10 has hot dip galvanized layers
formed on surfaces thereof. The steel sheet S having the galvannealed layers formed on
15 surfaces thereof is conveyed to an alloying furnace 20 such as an induction heater, and is
heated to a predetermined steel sheet temperature. The steel sheet S that has exited the
alloying furnace 20 (the steel plate S having the galvannealed layers formed on surfaces
thereof) is then conveyed to a heat holding zone 30.
[0028]
20 The steel sheet S having the galvannealed layers formed on surfaces thereof
undergoes alloying of the galvannealed layers at a certain position in the heat holding zone
30. The steel sheet S that has exited the heat holding zone 30 is cooled in a cooling zone
40 and is cooled to almost room temperature.
[0029]
25 Here, in the hot dip galvanizing line 1 according to this embodiment, in order to
determine the alloyed position of the steel sheet S having the galvannealed layers formed
thereon, radiation thermometers 50 are installed at a plurality of positions in the heat
holding zone 30 including an entry section of the heat holding zone 30.
[0030]
Further, the hot dip galvanizing line 1 according to this embodiment includes an
5 alloyed position determining apparatus 100 that determines the alloyed position by use of
the measurement results obtained by the radiation thermometers 50.
[003 11
Here, the state of temperature change in the hot dip galvanizing line 1 according
to this embodiment will be described with reference to FIG 2. Here, in the graph shown
10 in FIG. 2, the vertical axis represents steel sheet temperature and the horizontal axis
represents elapsed time after bathing in the zinc bath 10. FIG. 2 shows an example of
change in temperature of the steel sheet S being conveyed at a certain sheet-conveying
speed.
[0032]
15 As shown in FIG. 2, the zinc bath 10 is controlled at a substantially constant
temperature (approximately 450 OC in FIG. 2), and in the zinc bath 10, the temperature of
the steel sheet S becomes substantially equal to the temperature of the zinc bath 10.
Although the temperature of the steel sheet S that has exited the zinc bath 10 is decreased
before the steel sheet S enters the alloying furnace 10, when the steel sheet S is conveyed
20 into the alloying furnace 20 using an induction heater or the like, the steel sheet
temperature rises. Accordingly, as shown in FIG. 2, at a time when the steel sheet S exits
the alloying furnace 20 and enters the heat holding zone 30, the steel sheet temperature is
increased to approximately 520 O C .
[0033]
25 Here, the present inventors' studies have revealed that, in a hot dip galvanizing
process that has been becoming more common in recent years, the steel sheet temperature
is not constant in the heat holding zone 30, and as shown in FIG 2, the steel sheet
temperature is gradually decreased. The steel sheet having the galvannealed layers
formed on surfaces thereof undergoes alloying at a certain position in the heat holding zone
30 while the temperature is gradually decreased in the heat holding zone 30. The plated
5 steel sheet that has undergone alloying exits the heat holding zone 30 and is then conveyed
into the cooling zone 40 so as to be further cooled to almost room temperature.
[0034]

Next, change in spectral emissivity (hereinafter also simply referred to as
10 "emissivity") accompanied by progress of alloying will be described with reference to FIG
3. FIG 3 is a graph showing an example of the change in spectral emissivity
accompanied by the progress of alloying.
[0035]
It is known that the emissivity (or reflectance) is suddenly changed when zinc on
15 the plated surface is alloyed with a base metal. The steel sheet surface immediately after
plating is like a mirror surface and has low emissivity. However, in a process where
alloying causes iron to diffuse into a zinc layer, surface roughness of the steel sheet is
suddenly increased, and accordingly, the emissivity is increased. For example, it is
known that, although the emissivity immediately after plating is approximately 0.2,
20 alloying increases the emissivity to 0.6 to 0.8 depending on the kind of steel.
[0036]
The present inventors have confirmed such change in emissivity accompanied by
the progress of alloying by conducting tests at laboratories. In these tests, a sample made
of a steel material was irradiated with a laser and laser intensity reflected by the steel
25 material sample was measured very precisely by use of an integrating sphere. That is,
these tests were conducted to measure the reflectance very precisely with cold work.
After that, the emissivity was calculated based on the optical law that "emissivity =
1-reflectance". Here, a semiconductor laser with a wavelength of 680 nrn was used as a
laser source. This laser wavelength corresponds to the wavelength at which emissivity is
observed.
5 [0037]
In the tests, two steel types of samples were prepared and a plurality of samples
were fabricated by changing states of alloying progress depending on heat time for each
steel type. The obtained measurement results are shown in FIG 3. White squares and
black rhombuses in FIG 3 correspond to the respective samples. As shown in FIG 3, it
10 was confirmed that the emissivity of a sample immediately after plating was approximately
0.17 but that after completion of alloying was approximately 0.6. The initial emissivity
of 0.17 is assumed to be a value peculiar to zinc and to be constant at all times. Therefore,
as is clear from FIG. 3, it is possible to determine that alloying of the galvannealed layer is
completed when the measured emissivity exceeds a predetermined threshold value. Note
15 that the phenomenon that alloying increases the emissivity is caused by increase in surface
roughness at a time of alloying. Accordingly, it is considered that similar change in
emissivity can occur in a wavelength region from the visible light region to the near
infrared light region also when the wavelength is not 680 nm, which is the value at these
tests.
20 [0038]

Subsequently, a configuration of the alloyed position determining apparatus 100
according to this embodiment will be shown in detail with reference to FIG 4. FIG. 4 is a
block diagram showing the configuration of the alloyed position determining apparatus
25 according to this embodiment.
[0039]
The alloyed position determining apparatus 100 according to this embodiment
mainly includes, as illustrated in FIG. 4, a radiance information acquiring unit 101, a steel
sheet temperature estimating unit 103, an emissivity calculating unit 105, an alloyed
position determining unit 107, a display controlling unit 109, and a storage unit 11 1.
5 [0040]
The radiance information acquiring unit 101 is achieved with, for example, a CPU
(Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory),
a communication device, or the like. The radiance information acquiring unit 101 is
installed in the vicinity of the heat holding zone 30 in the hot dip galvanizing line 1 and
10 acquires information regarding the results of measurement of radiance (hereinafter referred
to as "radiance information") from each of the plurality of radiation thermometers 50 that
measure the radiance of the steel sheet S being conveyed.
[004 11
Here, in the hot dip galvanizing line 1 according to this embodiment, as shown in
15 FIG. 5, the plurality of radiation thermometers 50 are installed along the heat holding zone
30. FIG 5 is an explanatory view showing an example of installation positions of the
radiation thermometers. In the following description, it is assumed that n radiation
thermometers 50 including a radiation thermometer 1 to a radiation thermometer n are
installed in the vicinity of the heat holding zone 30 in addition to a radiation thermometer 0
20 on the entry section of the heat holding zone 30, as shown in FIG. 5. Note that the
radiation thermometers from the radiation thermometer 1 to the radiation thermometer n
are each used as a "radiance measuring apparatus". Therefore, the radiation thermometers
are set so as to directly output the observed radiance value without performing processing
to convert the observed radiance value to a pseudo temperature (black body temperature),
25 which is normally performed inside a radiation thermometer, or temperature information
output once as the pseudo temperature is made to be substituted for the Planck's law of
black-body radiation to perform processing to convert the temperature information into
radiance information.
[0042]
Note that the vicinity of the heat holding zone 30 refers to an area including the
5 following in the hot dip galvanizing line: the heat holding zone 30; an area between the
alloying furnace 20 and the heat holding zone 30; and an area between the heat holding
zone 30 and the cooling zone 40 (hereinafter these areas are also collectively referred to as
"radiance measuring area").
[0043]
10 In the following description, the z-axis is defined along the conveying direction of
the steel sheet S and the installation position of the radiation thermometer 0 provided on
the entry section of the heat holding zone 30 is set as z = 0. Further, the steel sheet
temperature immediately before the steel sheet is conveyed into the heat holding zone 30,
measured with the radiation thermometer 0, is represented by TO, and the steel sheet
15 temperature in the heat holding zone 30 is represented by T(z). As described above, since
it is clear that the steel sheet temperature is gradually decreased in the heat holding zone 30,
the steel sheet temperature T(z) in the heat holding zone 30 is a function of a variable z
representing the steel sheet position.
[0044]
20 Further, windows 31 are provided at a plurality of positions in the heat holding
zone 30 such that the respective radiation thermometers 50 measure heat emission (i.e.,
radiance) from the steel sheet S through the windows 31 corresponding to the installation
positions of the radiation thermometers 50. Here, as shown in FIG. 5, the radiance
measured with the n-th radiation thermometer from the entry section of the heat holding
25 zone 30 is represented by L,.
[0045]
The radiance information acquiring unit 101 according to this embodiment
acquires information (radiance information) regarding the radiance L, measured with each
radiation thermometer from each radiation thermometer 50 installed as shown in FIG 5,
and outputs the acquired information to the steel sheet temperature estimating unit 103 and
5 the emissivity calculating unit 105, which will be described later.
[0046]
Further, the radiance information acquiring unit 101 may associate the radiance
information acquired from each radiation thermometer 50 with time information or the like
regarding date and time when the radiance information is acquired, and may store the
10 associated information as history information in the storage unit 111, which will be
described later.
[0047]
The steel sheet temperature estimating unit 103 is achieved with, for example, a
CPU, ROM, RAM, or the like. The steel sheet temperature estimating unit 103 estimates
15 steel sheet temperatures at predetermined positions in the heat holding zone 30 by use of
information regarding a temperature decreasing pattern of the steel sheet accompanied by
position change in the conveying direction of the steel sheet in the heat holding zone 30
and information regarding installation positions of the radiation thermometers 50. Here,
the information regarding the temperature decreasing pattern of the steel sheet (hereinafter
20 also simply referred to as "steel sheet temperature decreasing pattern") is specified in
advance for each manufacturing condition, i.e., the condition of the steel type, the
thickness, or the conveying speed of the steel sheet, by use of operation achievement data
in the past, and is stored in the storage unit 11 1. Alternatively, the steel sheet temperature
decreasing pattern can be calculated from the results of heat transfer model simulation
25 regarding extracted heat from the steel sheet due to an atmosphere in the furnace and an
inner wall, or the like. In this case, the heat transfer model simulation is calculated in a
form of a decrease in temperature with respect to elapsed time of conveying the steel sheet
in the heat holding zone 30. Accordingly, in such a case, by combination with
information of the conveying speed, the steel sheet temperature decreasing pattern
accompanied by the position change in the conveying direction of the steel sheet is
5 calculated. Such a steel sheet temperature decreasing pattern is, for example, stored in
the storage unit 11 1. The steel sheet temperature decreasing pattern may be stored in the
storage unit 11 1 in a form of a database for each type of the steel sheet, or may be stored in
the storage unit 1 I1 in a form of a lookup table for each type of the steel sheet.
[0048]
10 An example of estimating processing of the steel sheet temperature, performed in
the steel sheet temperature estimating unit 103, will be specifically described with
reference to FIG. 6. FIG. 6 is an explanatory view showing an estimating method of the
steel sheet temperature. In the example shown in FIG. 6, as the steel sheet temperature
decreasing pattern, the inclination of a straight line representing the degree of decrease in
15 the steel sheet temperature in the heat holding zone 30 is used. Further, this straight line
is represented by a straight line in a coordinate system having a horizontal axis
representing the distance from the entry section of the heat holding zone (2-coordinate) and
a vertical axis representing the steel sheet temperature ("C). That is, in the example
shown in FIG 6, the distance from the entry section of the heat holding zone corresponds
20 to the installation position of the radiation thermometer.
[0049]
The steel sheet temperature estimating unit 103 calculates the amount of a
decrease in steel sheet temperature based on the steel sheet temperature decreasing pattern
stored in the storage unit 11 1 and the installation positions (2-coordinates) of the radiation
25 thermometers. For example, when the steel sheet temperature decreasing pattern is
shown as the inclination representing the degree of decrease in the steel sheet temperature
as shown in FIG 6, the steel sheet temperature estimating unit 103 first calculates the
amount of temperature decrease represented by AT in FIG 6 by use of the distance from
the entry section of the heat holding zone. Next, the steel sheet temperature estimating
unit 103 subtracts the amount of temperature decrease AT calculated from the steel sheet
5 temperature To immediately before the steel sheet is conveyed into the heat holding zone
30, the steel sheet temperature To being calculated by use of radiance Lo of the radiation
thermometer 0 in FIG. 5. Accordingly, the steel sheet temperature estimating unit 103 can
calculate the estimated steel sheet temperature T(z) at the position z in the heat holding
zone. That is, the estimated steel sheet temperature is the amount represented by T(z) =
10 TO-AT. Note that the temperature TO is obtained by converting the observed radiance LO
into temperature on the assumption that the emissivity is 0.2 (more precisely, the
emissivity may be 0.17) because alloying is not started at this position.
[0050]
By the above-described method, the steel sheet temperature estimating unit 103
15 calculates the estimated steel sheet temperature at each installation position of the radiation
thermometer corresponding to the radiance information notified by the radiance
information acquiring unit 101. That is, as shown in FIG 5, when the n radiation
thermometers 50 are installed, the steel sheet temperature estimating unit 103 calculates
each of the following estimated steel sheet temperatures: an estimated steel sheet
20 temperature T(z1) corresponding to an installation position zl of the radiation thermometer
1 to an estimated steel sheet temperature T(zn) corresponding to an installation position z,
of the radiation thermometer n.
[005 11
The steel sheet temperature estimating unit 103 outputs each estimated steel sheet
25 temperature T(zn), calculated in the above manner, to the emissivity calculating unit 105.
Further, the steel sheet temperature estimating unit 103 may associate the calculated
estimated steel sheet temperature with time information or the like regarding the date and
time when the estimated steel sheet temperature is calculated, and may record the
associated information as history information in the storage unit 111, which will be
described later.
5 [0052]
The emissivity calculating unit 105 is achieved with, for example, a CPU, ROM,
RAM, or the like. The emissivity calculating unit 105 calculates emissivity E, by use of
the estimated steel sheet temperature T(z) at a predetermined position in the heat holding
zone, the estimated steel sheet temperature T(z) being estimated by the steel sheet
10 temperature estimating unit 103, and the radiance information L, at a position
corresponding to the estimated steel sheet temperature T(z) acquired by the radiance
information acquiring unit 101 (i.e., the radiance L, at a position z).
[0053]
Specifically, the emissivity calculating unit 105 calculates the emissivity E, from
15 the following expression 101 by use of the radiance information L, and the calculated
estimated steel sheet temperature T(z).
[0054]
[Math 11
E: =- *' = A x [ exp {L:Gd - - I] (Expression 101)
L,(T) c,x5
20 [0055]
Here, in the above expression 10 1, Lb(T) represents radiance of the black body at
a temperature T[K], a constant cl is a value represented by use of the speed c of light in
vacuum and a Planck's constant h, and a constant c2 is a value represented by use of the
speed c of light in vacuum, the Planck's constant h, and a Boltzmann's constant k. Details
25 of these values are shown in the following expressions 102 and 103. Further, h is a
wavelength observed by the radiation thermometer 50 and is set in the infrared region
(more specifically, near infrared region, such as 1.5 pm).
[0056]
[Math 21
c, = 2c2h= 1.1910x10-'6 [W.m2] (Expression 102)
5
ch
c, = - = 0.014388 [m.K ] (Expression 103)
k
In the following description, prior to detailed explanation of emissivity calculating
processing performed by the emissivity calculating unit 105, first, some problems
influencing the calculation of the emissivity will be described.
10 [0058]
In processes that have been becoming more common in recent years, unlike in
conventional processes, there are no conspicuous heat source such as burner flame in the
heat holding zone where alloying proceeds. However, even under such circumstances,
the inner wall of the heat holding zone 30 having heat can serve as a source of stray
15 radiation noise. Therefore, first, the following description will briefly explain how the
calculation of the emissivity is influenced by stray radiation noise from the inner wall of
the heat holding zone.
[0059]
FIG 7 is an explanatory view for explaining stray radiation noise, and
20 schematically shows the state in the heat holding zone 30. In the heat holding zone 30,
the steel sheet S is conveyed, which has the steel sheet temperature T ["C] and the
emissivity E. Further, an inner wall 33 of the heat holding zone 30 is heated by heat
emission or the like from the steel sheet S conveyed at higher temperatures, and the inner
wall temperature is assumed to reach Tw ["C]. The radiation thermometer 50 installed in
25 the vicinity of the heat holding zone 30 measures heat emission from the steel sheet S, i.e.,
spontaneous light emission 35. Further, since the inner wall 33 of the heat holding zone
also has heat, the inner wall 33 of the heat holding zone also emits heat emission. The
heat emission is reflected by the steel sheet S and the radiation thermometer 50 observes
the reflected heat emission as stray radiation 37 at the same time. In this manner, the
radiance L, observed by the radiation thermometer 50 is the sum of the radiance due to
5 spontaneous light emission from the steel sheet and the radiance due to heat emission from
the inner wall, as shown in the following expression 104. The radiance due to heat
emission from the inner wall is called stray radiation noise, and serves as an error factor.
[Math 31
10 L: = E L,(T)+ (1 - E ) . L,(T,) (Expression 104)
Here, in the expression 104, E represents the true emissivity of the steel sheet and
the right side first term represents the radiance due to spontaneous light emission from the
steel sheet. Further, the right side second term represents the radiance (stray radiation
15 noise) mixed by reflection by the steel sheet, of heat emission from the inner wall of the
heat holding zone.
[0062]
Here, as is clear from the above expression 104, stray radiation noise is relatively
increased when the temperature difference between the target steel sheet and the inner wall
20 is small or when the true emissivity E is a small value. Accordingly, the observed
radiance L, deviates from the true heat emission from the steel sheet.
[0063]
Further, also when the estimated steel sheet temperature deviates from the true
value, the calculated emissivity becomes imprecise. The present inventors have
25 investigated whether alloying can be determined based on the emissivity in a state where
such disturbance exists. FIG 8 is a graph showing a relation between the steel sheet
temperature and the inner wall temperature at a time when the steel sheet passes through
the heat holding zone in the hot dip galvanizing line 1 according to this embodiment.
Note that in FIG 8, the horizontal axis represents elapsed time after the steel sheet exits
from the zinc bath 10, instead of the z-axis coordinate.
[0064]
5 As is clear from FIG. 8, it is found that the steel sheet S conveyed into the heat
holding zone 30 at approximately 520 "C is gradually cooled in the heat holding zone 30.
It is also found that the inner wall temperature is gradually increased and near an delivery
section of the heat holding zone, the temperature is increased to a temperature that is lower
than the steel sheet temperature by approximately 100 "C.
10 [0065]
The present inventors have assumed that four radiation thermometers are installed
at positions where the elapsed time is 12 seconds, 21 seconds, 31 seconds, and 40 seconds
(where the steel sheet temperature is 520 "C, 500 "C, 480 "C, and 460 "C), respectively,
under a condition of temperature change shown in FIG. 8 (i.e., temperature change in a
15 production line). On that assumption, the present inventors have calculated pseudo
emissivity from the expression 101 by use of the radiance L, calculated from the
expression 104 and the estimated steel sheet temperature T(z) shown in FIG 8.
. [0066]
FIGS. 9A and 9B each show the results of calculation of influence of stray
20 radiation noise due to high and low of the inner wall temperature on the assumption that
alloying occurs at the center of the heat holding zone. FIGS. 9A and 9B are each a graph
showing a relation between the true emissivity and the pseudo emissivity. Here, the
values shown in FIG 8 are each used as the steel sheet temperature.
[0067]
25 FIG 9A shows the calculation results when the steel sheet temperature is equal to
the inner wall temperature (that is, T = T, is satisfied) on the assumption of an alloying
furnace employing a gas burner heating method of the conventional art before heating with
an induction heater is introduced. The condition that the steel sheet temperature is equal
to the inner wall temperature corresponds to setting that temperature change in inner wall
temperature is the same as temperature change in steel sheet temperature in the
5 temperature change shown in FIG 8.
[0068]
As is clear from the expression 104, as the true emissivity of the steel sheet is low,
stray radiation noise contributes more greatly. Therefore, even when the true emissivity
is changed in a manner shown in FIG 9A, the pseudo emissivity is 1. In other words,
10 since the condition that T = Tw is satisfied, the term relating to the emissivity E in the
expression 104 is cancelled, and the obtained radiance L, becomes equal to the radiance
Lb(T) emitted from the black body at the temperature T. Therefore, the pseudo emissivity
E, calculated from the expression 10 1 is constantly 1.
[0069]
15 In contrast, the example shown in FIG. 9B shows the results when the pseudo
emissivity is simulated in accordance with the temperature changing pattern shown in FIG
8. As is clear from FIG 9B, the true emissivity of the steel sheet substantially
corresponds to the pseudo emissivity. Further, it is found that the pseudo emissivity is
slightly higher than the true emissivity at an observing position when the elapsed time is 40
20 seconds. This is an influence of stray radiation noise. Therefore, it is found that, in
processes that have been becoming more common in recent years, the steel sheet
temperature in the heat holding zone 30 is higher than the inner wall temperature of the
heat holding zone, and that, as is clear from the temperature changing pattern shown in FIG
8, the influence of stray radiation noise is slight and the change in the emissivity due to
25 alloying can be sufficiently detected.
[0070]
The influence of stray radiation noise when the emissivity is calculated has been
explained above.
Subsequently, the influence of estimation accuracy of the steel sheet temperature
when the emissivity is calculated will be briefly explained.
5 [0071]
In order that the emissivity calculation unit 105 calculates the emissivity, it is
necessary to substitute the estimated steel sheet temperature T for the expression 101.
Therefore, in order to discuss the influence of the estimation accuracy of the estimated
steel sheet temperature on the calculated emissivity, the preset inventors have calculated
10 the pseudo emissivity when the estimated value of the steel sheet temperature deviates
from the true value. Here, when the pseudo emissivity is calculated, the inner wall
temperature in the heat holding zone is set as the inner wall temperature with the
temperature change shown in FIG 8.
[0072]
15 The obtained results are shown in FIG 10. FIG 10 is a graph showing a relation
between the spectral emissivity and the true emissivity when the steel sheet temperature is
assumed to be constant, even when the true steel sheet temperature is the values shown in
FIG. 8. The calculation results shown in FIG 10 are obtained under the condition that the
steel sheet temperature is not decreased in the heat holding zone and is constant (that is,
20 under the condition assuming the alloying furnace employing the gas burner heating
method of the conventional art). According to the calculation results, the calculated
emissivity is estimated higher than the true value in a range where the elapsed time is short, ;
/
and the calculated emissivity is estimated lower than the true value in a range where the
elapsed time is long.
25 [0073]
As is clear from the results shown in FIG. 10, under the condition where the steel
sheet temperature is constant in the heat holding zone 30 (that is, under the condition
where the steel sheet temperature decrease is not considered), it is unclear whether the
change of the pseudo emissivity is truly caused by the emissivity or the temperature change,
and it is difficult to determine an alloyed position by setting a predetermined threshold
5 value in the emissivity.
[0074]
Accordingly, in view of the above-described knowledge, the emissivity
calculation unit 105 according to this embodiment calculates the emissivity E, based on the
expression 101 by use of the estimated steel sheet temperature T(z) at a predetermined
10 position in the heat holding zone, the estimated steel sheet temperature T(z) being
estimated by the steel sheet temperature estimating unit 103, and the radiance information
L, at a position corresponding to the estimated steel sheet temperature T(z) acquired by the
radiance information acquiring unit 10 1 (i.e., the radiance L, at the position 2).
[0075]
15 For emissivity calculating processing, the emissivity calculating unit 105 performs
processing considering the steel sheet temperature decrease in the heat holding zone 30 by
use of the estimated steel sheet temperature obtained by the steel sheet temperature
estimating unit 103. Therefore, as described above, the error in calculation of emissivity
due to the estimation accuracy of the estimated steel sheet temperature can be suppressed.
20 Further, since the inner wall temperature of the heat holding zone is lower than the steel
sheet temperature, the influence of stray radiation noise contained in the calculated
emissivity is small.
[0076]
The emissivity calculating unit 105 according to this embodiment calculates the
25 emissivity E, at the respective installation positions of the radiation thermometers 50, and
outputs the calculated emissivity E, to the alloyed position determining unit 107, which will
be described later. Further, the emissivity calculating unit 105 may associate the
calculated emissivity with time information or the like regarding the date and time when
the emissivity is calculated, and may record the associated information as history
information in the storage unit 11 1, which will be described later.
5 [0077]
Note that the difference between the steel sheet temperature and the inner wall
temperature shown in FIG. 8 (at least approximately 100 "C) is only an example, and the
temperature difference between the steel sheet temperature and the inner wall temperature
is not limited to such a temperature difference and the inner wall temperature may be other
10 temperature as long as the temperature does not serve as disturbance when the emissivity is
calculated.
[0078]
FIG 11 shows the results of calculation regarding how the pseudo emissivity is
changed when the temperature difference between the steel sheet and the inner wall is
15 changed on the assumption that the steel sheet temperature is 460 "C. At this time, a solid
line represents the change in the emissivity before alloying and is the results when the true
emissivity is assumed to be 0.2. Further, a dotted line represents the change in the
emissivity after alloying and is the results when the true emissivity is assumed to be 0.6.
[0079]
20 When focusing on the emissivity represented by the solid line in FIG 11, as is
clear from the graph, it is found that the influence of stray radiation noise is negligible as
long as the temperature difference between the steel sheet and the inner wall is 200 "C or
more. Further, when the threshold value for determining, by the alloyed position
determining unit 107, which will be described later, whether or not alloying occurs is set to
25 the emissivity of 0.4, when the temperature difference between the steel sheet and the inner
wall is 70 "C or less, the pseudo emissivity before alloying is observed as if it is the
emissivity after alloying. Therefore, the temperature difference is an acceptable limit
value of the inner wall temperature. In a similar manner, when focusing on the graph
represented by the dotted line, it is found that the emissivity (precisely 0.6) after alloying is
apparently increased by decrease in the temperature difference.
5 [0080]
The alloyed position determining unit 107 is achieved with, for example, a CPU,
ROM, RAM, or the like. The alloyed position determining unit 107 determines the
position where the galvannealed layer is alloyed in the heat holding zone based on the
emissivity E, calculated by the emissivity calculating unit 105. In order to determine
10 whether or not alloying occurs, a predetermined threshold value is used. As shown in FIG.
3, the emissivity of the steel sheet before alloying is a low value while the emissivity of the
steel sheet is changed to a large value by alloying. Accordingly, the alloyed position
determining unit 107 can determine whether or not alloying occurs by use of a
predetermined threshold value in accordance with the type of the steel sheet and
15 galvannealed layer, or the like. That is, when the calculated emissivity is lower than the
predetermined threshold value, the alloyed position determining unit 107 determines that
alloying has not occurred yet, and when the calculated emissivity is higher than or equal to
the predetermined threshold value, the alloyed position determining unit 107 determines
that the alloying has occurred. Such a threshold value can be set as appropriate in
20 accordance with the type of the steel sheet or galvannealed layer, or the like, and for
example, the threshold value can be set to approximately 0.3 or 0.4.
[008 11
More specifically, the alloyed position determining unit 107 determines whether
or not all the emissivity cZ notified by the emissivity calculating unit 107 is higher than or
25 equal to the predetermined threshold value. For example, when the emissivity E,
corresponding to a position of the (n-l)(n?2)-th radiation thermometer from the entry
section of the heat holding zone is lower than the predetermined threshold value and the
emissivity E= corresponding to a position of the n-th radiation thermometer is higher than or
equal to the predetermined threshold value, the alloyed position determining unit 107
determines that the position where alloying has occurred is a section in the heat holding
5 zone between an installation position of the (n-1)-th radiation thermometer and an
installation position of the n-th radiation thermometer.
[0082]
For example, as shown in FIG. 5, when the n radiation thermometers are installed,
the emissivity corresponding to a position of the radiation thermometer 2 is lower than
10 the predetermined threshold value, and the emissivity ~~3 corresponding to a position of the
radiation thermometer 3 is higher than or equal to the predetermined threshold value for
the first time, the alloyed position determining unit 107 determines that the alloyed
position is a section between an installation position of the radiation thermometer 2 and an
installation position of the radiation thermometer 3 (i.e., a section between z2 and z3 in FIG
15 5).
[0083]
Note that the alloyed position determining unit 107 has information regarding
where each radiation thermometer is installed (i.e., information regarding an installation
order and installation positions of the plurality of radiation thermometers).
20 [0084]
The alloyed position determining unit 107 determines the position where alloying
has occurred, and then outputs the obtained results to the display controlling unit 109,
which will be described later. Further, the alloyed position determining unit 107 may
associate the determination results regarding the alloyed position with time information or
25 the like regarding the date and time when the determination is performed, and may record
the associated information as history information in the storage unit 111, which will be
described later.
lo0851
The display controlling unit 109 is achieved with, for example, a CPU, ROM,
RAM, or the like. The display controlling unit 109 controls display when the information
5 regarding the alloyed position transmitted from the alloyed position determining unit 107 is
displayed on a display unit of a display or the like included in the alloyed position
determining apparatus 100. Further, the display controlling unit 109 can allow the display
unit to display a variety of pieces of information such as the calculated estimated steel
sheet temperature, the calculated emissivity value, and a graph showing change of these
10 values, in addition to the information regarding the alloyed position. The display
controlling unit 109 allows the display unit to display the results regarding the alloyed
position, and thereby a user of the alloyed position determining apparatus 100 can acquire
the information regarding the alloyed position of the steel sheet S that is being conveyed.
[0086]
15 The storage unit 111 is an example of a storage device included in the alloyed
position determining apparatus 100. The storage unit 111 stores information regarding
the temperature decreasing pattern of the steel sheet that is used when the steel sheet
temperature estimating unit 103 estimates the estimated steel sheet temperature. The
storage unit 11 1 may store information regarding the installation order and the installation
20 positions of the plurality of radiation thermometers. Further, the storage unit 11 1 stores,
as appropriate, a variety of parameters, development processes of processing, and the like,
which need to be stored when the alloyed position determining apparatus 100 according to
this embodiment performs certain processing, or a variety of databases or the like. For
the storage unit 111, reading and writing can be freely performed by the radiance
25 information acquiring unit 101, the steel sheet temperature estimating unit 103, the
emissivity calculating unit 105, the alloyed position determining unit 107, the display
controlling unit 109, and the like.
[0087]
An example of functions of the alloyed position determining apparatus 100
according to this embodiment is described above. Each of the structural elements
5 described above may be configured using a general-purpose material or circuit, or may be
configured from hardware dedicated to the function of each structural element. Further,
the functions of each structural element may be all performed by a CPU or the like.
Accordingly, the configuration to be used can be changed as appropriate according to the
technical level at the time of carrying out this embodiment.
10 [OOSS]
Note that a computer program for realizing each function of the above-described
alloyed position determining apparatus according to this embodiment can be produced and
incorporated in a personal computer or the like. Further, it is possible to provide a
computer-readable recording medium storing such a computer program therein,
15 Examples of the recording medium include a magnetic disk, an optical disk, a
magneto-optical disk, flash memory, and the like. Further, the above-described computer
program may be distributed via a network, for example, without using the recording
medium.
[0089]
20
Next, with reference to FIG. 12, a flow of an alloyed position determining method
according to this embodiment will be described. FIG. 12 is a flow chart showing the flow
of the alloyed position determining method according to this embodiment.
[0090]
2 5 In the alloyed position determining method according to this embodiment, first,
the radiance information acquiring unit 101 acquires information regarding the radiance
(radiance information) measured by the plurality of radiation thermometers 50, from the
radiation thermometers installed in the vicinity of the hot dip galvanizing line 1 (step S101).
The radiance information acquiring unit 101 outputs the acquired radiance information to
the steel sheet temperature estimating unit 103 and the emissivity calculating unit 105.
5 [0091]
Next, the steel sheet temperature estimating unit 103 estimates the steel sheet
temperature T(z) at a predetermined position in the heat holding zone 30 by use of the tee1
sheet temperature decreasing pattern stored in advance in the storage unit 11 1 or the like
and information regarding the installation position of the radiation thermometers 50 or
10 information that can be converted into the installation positions (step S103). This
estimating processing of the steel sheet temperature is, as described above, temperature
estimating processing considering the steel sheet temperature decrease in the heat holding
zone. When the estimated steel sheet temperature T(z) is calculated from each pieces of
radiance information measured by the radiation thermometers 50 provided at the respective
15 positions in the heat holding zone 30, the steel sheet temperature estimating unit 103
outputs the calculated plurality of estimated steel sheet temperatures to the emissivity
calculating unit 105.
[0092]
Subsequently, the emissivity calculating unit 105 calculates the emissivity at a
20 predetermined position in the heat holding zone 30 by use of the radiance information
transmitted from the radiance information acquiring unit 101 and the estimated steel sheet
temperature notified from the steel sheet temperature estimating unit 103 (step S 105).
When the calculation of the emissivity ends, information regarding the calculated
emissivity is output to the alloyed position determining unit 107.
25 [0093]
Next, the alloyed position determining unit 107 determines a position where the
galvannealed layer is alloyed in the heat holding zone by use of the predetermined
threshold value and the information regarding the emissivity transmitted from the
't
emissivity calculating unit 105. By performing processing according to such a flow, in
the alloyed position determining method according to this embodiment, it is possible to
5 precisely determine the position where the galvannealed layer is alloyed.
[0094]
(Regarding hardware configuration)
Next, a hardware configuration of the alloyed position determining apparatus 100
according to an embodiment of the present invention will be described in detail with
10 reference to FIG 13. FIG. 13 is a block diagram for explaining the hardware
configuration of the alloyed position determining apparatus 100 according to the
embodiment of the present invention.
[0095]
The alloyed position determining apparatus 100 mainly includes a CPU 901,
15 ROM 903, and RAM 905. Furthermore, the alloyed position determining apparatus 100
also includes a bus 907, an input device 909, an output device 91 1, a storage device 913, a
drive 9 1 5, a connection port 9 17, and a communication device 9 19.
[0096]
The CPU 901 serves as an arithmetic processing apparatus and a control device,
20 and controls the overall operation or a part of the operation of the alloyed position
determining apparatus 100 according to various programs recorded in the ROM 903, the
RAM 905, the storage device 9 13, or a removable recording medium 92 1. The ROM 903
stores programs, operation parameters, and the like used by the CPU 901. The RAM 905
primarily stores programs used by the CPU 901 and parameters and the like varying as
25 appropriate during the execution of the programs. These are connected to each other via
the bus 907 configured from an internal bus such as a CPU bus or the like.
[0097]
The bus 907 is connected to an external bus such as a PC1 (Peripheral Component
Interconnectnnterface) bus via a bridge.
[0098]
5 The input device 909 is an operation means operated by a user, such as a mouse, a
keyboard, a touch panel, buttons, a switch, and a lever. Also, the input device 909 may be
a remote control means (a so-called remote control) using, for example, infrared light or
other radio waves, or may be an externally connected device 923 such as a PDA
conforming to the operation of the alloyed position determining apparatus 100.
10 Furthermore, the input device 909 generates an input signal based on, for example,
information which is input by a user with the above operation means, and is configured
from an input control circuit for outputting the input signal to the CPU 901. The user of
the alloyed position determining apparatus 100 can input various data to the alloyed
position determining apparatus 100 and can instruct processing by operating this input
15 device 909.
[0099]
The output device 911 is configured from a device capable of visually or audibly
notifying acquired information to a user. Examples of such a device include display
devices such as a CRT display device, a liquid crystal display device, a plasma display
20 device, an EL display device, and a lamp, audio output devices such as a speaker and a
headphone, a printer, a mobile phone, a facsimile machine, and the like. For example, the
output device 91 1 outputs the results obtained by various processes performed by the
alloyed position determining apparatus 100. More specifically, the display device
displays the results obtained by various processes performed by the alloyed position
25 determining apparatus 100 in the form of texts or images. On the other hand, the audio
output device converts an audio signal such as reproduced audio data and sound data into
an analog signal, and outputs the analog signal.
[O 1001
The storage device 913 is a device for storing data configured as an example of a
storage unit of the alloyed position determining apparatus 100. The storage device 913 is
5 configured from, for example, a magnetic storage device such as an HDD (Hard Disk
Drive), a semiconductor storage device, an optical storage device, or a magneto-optical
storage device. This storage device 913 stores programs to be executed by the CPU 901,
various data, and various data obtained from the outside.
[OlOl]
10 The drive 915 is a readerlwriter for a recording medium, and is embedded in the
alloyed position determining apparatus 100 or attached externally thereto. The drive 915
reads information recorded in the attached removable recording medium 921 such as a
magnetic disk, an optical disk, a magneto-optical disk, or semiconductor memory, and
outputs the read information to the R4M 905. Furthermore, the drive 915 can write
15 record in the attached removable recording medium 92 1 such as a magnetic disk, an optical
disk, a magneto-optical disk, or semiconductor memory. The removable recording
medium 921 is, for example, a CD medium, a DVD medium, or a Blu-ray medium. The
removable recording medium 921 may be a CompactFlash (CF; registered trademark),
flash memory, an SD memory card (Secure Digital memory card), or the like.
20 Alternatively, the removable recording medium 921 may be, for example, an IC card
(Integrated Circuit card) equipped with a non-contact IC chip or an electronic appliance.
[o 102 3
The connection port 917 is a port for allowing devices to directly connect to the
alloyed position determining apparatus 100. Examples of the connection port 91 7 include
25 a USB (Universal Serial Bus) port, an IEEE1394 port, an SCSI (Small Computer System
Interface) port, an RS-232C port, and the like. By the externally connected device 923
connecting to this connection port 917, the alloyed position determining apparatus 100
directly obtains various data from the externally connected device 923 and provides
various data to the externally connected device 923.
[0 1031
5 The communication device 919 is a communication interface configured from, for
example, a communication device for connecting to a communication network 925. The
communication device 91 9 is, for example, a wired or wireless LAN (Local Area Network),
Bluetooth (registered trademark), a communication card for WUSB (Wireless USB), or the
like. Alternatively, the communication device 919 may be a router for optical
10 communication, a router for ADSL (Asymmetric Digital Subscriber Line), a modem for
various communications, or the like. This communication device 919 can transmit and
receive signals and the like in accordance with a predetermined protocol such as TCP/IP on
the Internet and with other communication devices, for example. The communication
network 925 connected to the communication device 91 9 is configured from a network and
15 the like, which is connected via wire or wirelessly, and may be, for example, the Internet, a
home LAN, infrared communication, radio wave communication, satellite communication,
or the like.
[0 1041
Heretofore, an example of the hardware configuration capable of realizing the
20 functions of the alloyed position determining apparatus 100 according to the embodiment
of the present disclosure has been shown. Each of the structural elements described
above may be configured using a general-purpose material, or may be configured from
hardware dedicated to the function of each structural element. Accordingly, the hardware
configuration to be used can be changed as appropriate according to the technical level at
25 the time of carrying out this embodiment.
[Example]
[0 10.51
Hereinafter, the results when radiation thermometers were installed in a radiance
measuring area in an actual hot dip galvanizing line and the alloyed position determining
method according to an embodiment of the present invention is applied will be described
5 specifically. Note that a specific example shown below is an example of the alloyed
position determining method according to the embodiment of the present invention, and
the alloyed position determining method according to the present invention is not limited
to the following example.
[0 1 061
10 In the Example shown below, in addition to the radiation thermometers each used
as a radiance measuring means to determine an alloyed position, in order to calculate a
temperature decreasing pattern of a steel sheet, a spectral radiation thermometer A1 and a
multicolor radiation thermometer AZ were installed in the vicinity of the hot dip
galvanizing line (i.e., in the radiance measuring area) as shown in FIG. 14.
15 The spectral radiation thermometer refers to a radiation thermometer where the
radiance is measured in one wavelength region, and is used when the emissivity of a target
is not changed during measurement. Further, the multicolor radiation thermometer refers
to a radiation thermometer where the radiance is measured in a plurality of wavelength
regions, and can measure surface temperature even when the emissivity is changed.
20 [0107]
Since zinc exists alone on surfaces of the steel sheet conveyed in the hot dip
galvanizing line immediately after the alloying &mace 20, it is possible to measure the
steel sheet temperature with the radiation thermometer (spectral radiation thermometer)
with the emissivity E of about 0.17. Further, since the emissivity varies in accordance
25 with the progress of alloying in an upper part of the heat holding zone 30, it is possible to
measure the steel sheet temperature with a multicolor radiation thermometer (e.g.,
two-color thermometer).
[0 1 081
Here, as shown in FIG 14, the steel sheet temperature is measured by installing
the spectral radiation thermometer A1 immediately after the alloying furnace 20 (at a
5 position ZA) and installing the multicolor radiation thermometer A2 in the upper part of the
heat holding zone 30 (at a position zB). When the steel sheet temperature measured with
the spectral radiation thermometer A1 is referred to as TA and the steel sheet temperature
measured with the multicolor radiation thermometer A2 is referred to as TB, the steel sheet
temperature in the heat holding zone 30 can be represented by the following expression
10 151 by linear interpolation in accordance with the height of the installed radiation
thermometer.
[0 1091
[Math 41
TB T(z) = TA + ---- TA- (2-ZA) (Expression 15 1)
ZB - ZA
15 [OllO]
Here, as described above, the higher the position is in the heat holding zone 30,
the lower the steel sheet temperature becomes; therefore, (TB-TA) < 0 is satisfied in the
expression 151. Accordingly, it is found that the expression represented by the
expression 15 1 can be used as the temperature decreasing pattern used for estimating the
20 degree to which the steel sheet temperature is decreased at a position z in the heat holding
zone, the steel sheet temperature being TA on the entry section of the heat holding zone 30.
[Olll]

States of installation of each thermometer used for measurement in the following
25 Example will be described in detail with reference to FIG 15.
As shown in FIG 15, in the hot dip galvanizing line for experiment, the spectral
radiation thermometer Al was installed on an delivery section (z = 0) of the alloying
furnace, and the two-color thermometer A2 was installed in the upper part (z = 34 m) in the
heat holding zone. Further, two radiation thermometers were installed at positions where
z = 21 m and z = 29 m, respectively.
5 [0112]
In the following description, the temperature decreasing pattern of the steel sheet
was calculated by use of measured temperatures obtained from the spectral radiation
thermometer A1 and the two-color thermometer Az, and the temperature decreasing pattern
was used to estimate the steel sheet temperature in the heat holding zone.
10 [0113]
Further, for the radiation thermometers installed at z = 21 m and z = 29 m, the
emissivity E was set to 1, and these radiation thermometers were used to measure the steel
sheet conveyed in the heat holding zone. That is, in this Example, these two radiation
thermometers were set to output pseudo temperatures (black body temperatures at E = 1) by
15 converting observed values of radiance into the pseudo temperatures. The output values
correspond to the value of L, shown in the expression 104.
[0114]
Accordingly, the radiance information acquiring unit 101 executes processing for
converting the pseudo temperature information output from the radiation thermometers
20 into radiance information by use of the following expression 152.
[0115]
[Math 51
(Expression 152)
[0116]
2 5 Here, in the expression 152, L, is the radiance at z = 21 m or z = 29 m, and T'(z) is
temperature information output from the radiation thermometer installed at z = 21 m or z =
29 m. Further, in the expression 152, cl and c2 are constants shown in the expression 102
and the expression 103, respectively, and h is a measured wavelength the value of which is
1.55 pm.
[0117]
5 The steel sheet serving as a measurement target was mild steel with a sheet
thickness of 1.4 mm and a sheet width of 1350 mm. This steel sheet was conveyed at a
line steed of 90 mpm through the hot dip galvanizing line where the above-described
thermometers were installed.
[0118]
10 FIG 16 shows steel sheet temperatures measured with the two thermometers (the
spectral radiation thermometer A1 and the two-color thermometer A*) together with
estimated steel sheet temperatures at positions of 21 m and 29 m, which were calculated
based on the obtained steel sheet temperatures.
[0119]
15 As shown in FIG 16, the steel sheet temperature on the delivery section of the
alloying furnace was 567 "C and the steel sheet temperature at the position of 34 m in the
heat holding zone was 527 "C. Further, the steel sheet temperatures at the position of 21
m and at the position of 29 m were calculated to be 542 "C and 533 "C, respectively, based
on the expression 15 1 by use of the above measurement results.
20 [0120]
Further, the measured values (these values correspond to the value Lz in the
expression 104) measured by the radiation thermometers at the positions of 21 m and 29 m
in the heat holding zone are shown in FIG 17. In this Example, the emissivity E of each
of the radiation thermometers installed at the above positions was set to 1, and the
25 measured values were pseudo temperatures at E =l.
[O 12 11
Radiance information was calculated from the expression 152 by use of the
measured values by the radiation thermometers shown in FIG 17, and emissivity was
calculated based on the expression 101 by use of the calculated radiance information L,
and the estimated steel sheet temperature T(z) shown in FIG 16. The thus obtained
5 values of emissivity are shown in FIG. 18.
[O 1221
Referring to FIG 18, the emissivity is 0.28 to 0.38 at the position of 21 m, which
shows that the steel sheet has an unalloyed layer on the assumption that the alloying
threshold value is 0.4. On the other hand, the emissivity is 0.6 and is almost constant at
10 the position of 28 m, and it is found that the alloying is completed at this position. From
these results, the alloyed position can be determined to be between 21 m and 28 m.
[0123]
As described above, according to the alloyed position determining method and
alloyed position determining apparatus each according to an embodiment of the present
15 invention, the steel sheet temperature is estimated considering a decrease in steel sheet
temperature in a heat holding zone and the steel sheet temperature obtained by the
estimation is used to calculate emissivity; therefore, the emissivity can be calculated more
precisely. Accordingly, even in processes using an alloying hrnace such as an induction
heater, which have been becoming more common in recent years, an alloyed position can
20 be determined more precisely. As a result, by use of information regarding the alloyed
position, it is possible to control the applied amount of induction heating and
sheet-conveying speed in the alloying furnace such as an induction, and to perform
operation so that alloying can be stable, and it is possible to prevent generation of defective
quality called an unalloyed layer or an overalloyed layer.
25 [0124]
Heretofore, preferred embodiments of the present invention have been described
in detail with reference to the appended drawings, but the present invention is not limited
thereto. It should be understood by those skilled in the art that various changes and
alterations may be made without departing from the spirit and scope of the appended
claims.
5 [Reference Signs List]
[0125]
1 hot dip galvanizing line
10 zinc bath
20 alloying furnace
30 heat holding zone
40 cooling zone
50 radiation thermometer
100 alloyed position determining apparatus
101 radiation information acquiring unit
103 steel sheet temperature estimating unit
105 emissivity calculating unit
107 alloyed position determining unit
109 display controlling unit
11 1 storage unit

[Name of Document] CLAIMS
[Claim 11
An alloyed position determining method comprising:
a radiance information acquiring step for acquiring information regarding a result
5 of measurement of radiance from each of a plurality of radiation thermometers installed in
a vicinity of a heat holding zone in a hot dip galvanizing line of a steel sheet and along a
conveying direction of the steel sheet in the heat holding zone, the radiation thermometers
measuring radiance of the steel sheet conveyed;
a steel sheet temperature estimating step for estimating steel sheet temperatures at
10 installation positions of the radiation thermometers by use of information regarding a
temperature decreasing pattern of the steel sheet, accompanied by a position change in the
conveying direction in the heat holding zone, and information regarding the installation
positions of the radiation thermometers;
an emissivity calculating step for calculating emissivity at the installation
15 positions of the radiation thermometers by use of the estimated steel sheet temperatures
estimated at the installation positions of the radiation thermometers and the information
regarding the result of measurement of radiance; and
an alloyed position determining step for determining an alloyed position based on
the calculated emissivity.
20 [Claim 21
The alloyed position determining method according to claim 1, wherein, in the
steel sheet temperature estimating step, an amount of temperature decrease in the steel
sheet is calculated based on the information regarding the temperature decreasing pattern
of the steel sheet and the information regarding the installation positions of the radiation
25 thermometers, and the estimated steel sheet temperatures are calculated by subtracting the
calculated amount of temperature decrease from a temperature of the steel sheet on an
[Claim 31
The alloyed position determining method according to claim 1, wherein, in the
steel sheet temperature estimating step, the temperature decreasing pattern is calculated
5 based on a measured temperature of the steel sheet before the steel sheet enters the heat
holding zone, measured with a spectral radiation thermometer, and a measured temperature
of the steel sheet in the heat holding zone, measured with a multicolor radiation
thermometer, and the steel sheet temperature is estimated by use of the calculated
temperature decreasing pattern and the information regarding the installation positions of
10 the radiation thermometers.
[Claim 41
The alloyed position determining method according to any one of claims 1 to 3,
wherein, in the alloyed position determining step, when emissivity which is calculated in
the emissivity calculating step and which corresponds to a position of an (n-l)(n>2)-th
15 radiation thermometer from the entry section of the heat holding zone is lower than a
predetermined threshold value and emissivity which corresponds to a position of an n-th
radiation thermometer is higher than or equal to the predetermined threshold value, it is
determined that a position where alloying has occurred is a section between an installation
position of an (n-1)-th radiation thermometer and an installation position of the n-th
20 radiation thermometer in the heat holding zone.
[Claim 51
An alloyed position determining apparatus comprising:
a radiance information acquiring unit configured to acquire information regarding
a result of measurement of radiance from each of a plurality of radiation thermometers
25 installed in a vicinity of a heat holding zone in a hot dip galvanizing line of a steel sheet
and along a conveying direction of the steel sheet in the heat holding zone, the radiation
thermometers measuring radiance of the steel sheet conveyed;
a steel sheet temperature estimating unit configured to estimate steel sheet
temperatures at installation positions of the radiation thermometers by use of information
regarding a temperature decreasing pattern of the steel sheet, accompanied by a position
5 change in the conveying direction in the heat holding zone, and information regarding the
installation positions of the radiation thermometers;
an emissivity calculating unit configured to calculate emissivity at the installation
positions of the radiation thermometers by use of the estimated steel sheet temperatures
estimated at the installation positions of the radiation thermometers, estimated by the steel
10 sheet temperature estimating unit, and the information regarding the result of measurement
of radiance; and
an alloyed position determining unit configured to determine an alloyed position
based on the emissivity calculated by the emissivity calculating unit.
[Claim 61
15 The alloyed position determining apparatus according to claim 5, wherein the
steel sheet temperature estimating unit calculates an amount of temperature decrease in the
steel sheet based on the information regarding the temperature decreasing pattern of the
steel sheet and the information regarding the installation positions of the radiation
thermometers, and calculates the estimated steel sheet temperatures by subtracting the
20 calculated amount of temperature decrease from a temperature of the steel sheet on an
entry section of the heat holding zone.
[Claim 71
The alloyed position determining apparatus according to claim 5, wherein the
steel sheet temperature estimating unit calculates the temperature decreasing pattern based
25 on a measured temperature of the steel sheet before the steel sheet enters the heat holding
zone, measured with a spectral radiation thermometer, and a measured temperature of the
steel sheet in the heat holding zone, measured with a multicolor radiation thermometer, and
estimates the steel sheet temperature by use of the calculated temperature decreasing
pattern and the information regarding the installation positions of the radiation
thermometers.
5 [Claim 81
The alloyed position determining apparatus according to any one of claims 5 to 7,
wherein the alloyed position determining unit determines, when emissivity which is
calculated by the emissivity calculating unit and which corresponds to a position of an
(n-l)(n>2)-th radiation thermometer from the entry section of the heat holding zone is
10 lower than a predetermined threshold value and emissivity which corresponds to a position
of an n-th radiation thermometer is higher than or equal to the predetermined threshold
value, that a position where alloying has occurred is a section between an installation
position of an (n-1)-th radiation thermometer and an installation position of the n-th
radiation thermometer in the heat holding zone.
15 [Claim 91
A recording medium having a program recorded thereon for causing a computer to
execute:
a radiance information acquiring function to acquire information regarding a
result of measurement of radiance from each of a plurality of radiation thermometers
20 installed in a vicinity of a heat holding zone in a hot dip galvanizing line of a steel sheet
and along a conveying direction of the steel sheet in the heat holding zone, the radiation
thermometers measuring radiance of the steel sheet conveyed;
a steel sheet temperature estimating function to estimate steel sheet temperatures
at installation positions of the radiation thermometers by use of information regarding a
25 temperature decreasing pattern of the steel sheet, accompanied by a position change in the
conveying direction in the heat holding zone, and information regarding the installation
an emissivity calculating function to calculate emissivity at the installation
positions of the radiation thermometers by use of the estimated steel sheet temperatures
estimated at the installation positions of the radiation thermometers, estimated by the steel
5 sheet temperature estimating function, and the information regarding the result of
measurement of radiance; and
an alloyed position determining function to determine an alloyed position based
on the emissivity calculated by the emissivity calculating function.
Dated this 24.12.2013
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]