DESCRIPTION
ANTIOXIDANT AGENT AND PROCESS FOR PRODUCING METALLIC
MATERIAL
Technical Field
[0001]
The present invention relates to an antioxidant
agent and a process for producing a metallic material.
More particularly, it relates to an antioxidant agent
applied to the surface of a metallic starting material to
be heated, and a process for producing a metallic
material.
Background Art
[0002]
JP2007-314780A (Patent Document 1) discloses an
antioxidant agent for hot extrusion working, and
WO2007/122972 (Patent Document 2) discloses an
antioxidant agent for hot plastic working. The
antioxidant agents disclosed in these Patent Documents
contain a plurality of glass frits having different
softening points, and are applied to the surface of a
starting material to be subjected to hot plastic working.
; A metallic starting material to which the antioxidant
agent has been applied is heated at a temperature of 800
to 1300 C in a heating furnace or the like. The
antioxidant agents disclosed in Patent Documents 1 and 2
prevent oxides (hereinafter, referred to as scale) from
being formed on the surface of the heated metallic
starting material.
Disclosure of the Invention
[0003]
The above-described antioxidant agent is in a liquid
form, and is applied to the surface of metallic starting
material at normal temperature. At this time, it is more
favorable if the antioxidant agent is less liable to drip
down from the surface of metallic starting material.
That is, the antioxidant agent is required to have an
anti-dripping property.
[0004]
Further, although the antioxidant agent applied to
the surface of metallic starting material at normal
temperature is in a liquid form, the antioxidant agent is
solidified when it is dehydrated by heating or drying.
It is more favorable if the solidified antioxidant agent
is less liable to be peeled off the surface of metallic
starting material. That is, the antioxidant agent is
also required to have an anti-peeling property.
[0005]
An objective of the present invention is to provide
an antioxidant agent excellent in anti-dripping property
and anti-peeling property.
!
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! 3
[0006]
The antioxidant agent in accordance with an
embodiment of the present invention is to be applied to
the surface of metallic starting material to be heated.
The antioxidant agent contains a plurality of glass frits
having different softening points, potter's clay, and
bentonite and/or sepiolite.
[0007]
The antioxidant agent in accordance with this
embodiment has an excellent anti-dripping property due to
the potter's clay. The antioxidant agent in accordance
with this embodiment further has an excellent antipeeling
property due to the bentonite and/or sepiolite.
[0008]
Preferably, the plurality of glass frits contain
high-temperature glass frits and medium-temperature glass
frits. The viscosity at 1200°C of the high-temperature
glass frits is 2 x 102 to 106 dPa-s. The viscosity at
700°C of the medium-temperature glass frits is 2 x 102 to
106 dPa-s.
[0009]
In this case, the antioxidant agent can prevent the
oxidation of the surface of metallic starting material in
a board temperature range.
[0010]
Preferably, the antioxidant agent contains not less
than 6 weight parts of potter's clay with respect to 100
;
weight parts of the high-temperature glass frits and not
less than 4 weight parts of bentonite and/or sepiolite
with respect to 100 weight parts of the high-temperature
glass frits.
[0011]
In this case, the adhesive property and anti-peeling
property of the antioxidant agent are further improved.
[0012]
Preferably, the antioxidant agent contains less than
9 weight parts of bentonite and/or sepiolite with respect
to 100 weight parts of the high-temperature glass frits.
[0013]
In this case, the antioxidant agent is liable to be
slurried.
[0014]
Preferably, the antioxidant agent further contains
an inorganic compound having a melting point of 400 to
600°C. Preferably, the inorganic compound is boric acid
and/or boron oxide.
[0015]
In this case, the antioxidant agent can further
prevent the oxidation of the heated metallic starting
material.
Brief Description of the Drawings
[0016]
!
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1
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Figure 1 is a diagram showing the relationship
between the viscosity and temperature of each of the
components contained in an antioxidant agent in
accordance with an embodiment of the present invention;
Figure 2 is a flowchart showing one example of a
process for producing a metallic material in accordance
with an embodiment of the present invention;
Figure 3 is a diagram showing the relationship
between the contents of bentonite and potter's clay in an
antioxidant agent and the anti-dripping property in
Example; and
Figure 4 is a diagram showing the relationship
between the contents of bentonite and potter's clay in an
antioxidant agent and the anti-peeling property in
Example.
Best Mode for Carrying Out the Invention
[0017]
Embodiments of the present invention will now be
described in detail with reference to the accompanying
drawings.
The present inventors conducted studies on the antidripping
property and anti-peeling property of the
antioxidant agent, and obtained the findings described
below.
[0018]
i 6
(1) The potter's clay improves the anti-dripping
property of the antioxidant agent. More specifically,
when the liquid-form antioxidant agent containing the
potter's clay is applied to the surface of metallic
starting material at normal temperature, the antioxidant
agent is liable to adhere to the surface of metallic
starting material, and is less liable to drip down.
[0019]
(2) The bentonite and/or sepiolite improve the antipeeling
property of the antioxidant agent. More
specifically, when the antioxidant agent containing the
bentonite and/or sepiolite is applied to the surface of
metallic starting material and is solidified by drying,
the solidified antioxidant agent is less liable to peel
off the surface of metallic starting material.
i [0020]
The antioxidant agent in accordance with this
embodiment is based on the above-described findings.
Hereunder, the details of the antioxidant agent are
explained.
[0021]
[Constitution of antioxidant agent]
The antioxidant agent in accordance with this
embodiment contains the plurality of glass frits having
! different softening points and a suspending agent. The
suspending agent contains potter's clay and bentonite
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and/or sepiolite. Hereunder, the glass frits and the
suspending agent are explained.
[0022]
[Glass frits]
The plurality of glass frits are produced by the
process described below. A plurality of well-known
inorganic components constituting glass are mixed with
each other. The mixed plurality of inorganic components
are melted to produce molten glass. The molten glass is
rapidly cooled in water or air and is solidified. The
solidified glass is ground as necessary. The glass frits
are produced by the steps described above.
[0023]
The glass frits are of a flake form or a powder form.
As described above, the glass frits contain the plurality
of well-known inorganic components. Therefore, the
melting point of glass frits is not identified definitely.
In the case where each of inorganic components in the
glass frits is heated singly, each inorganic component
liquefies at its melting point. However, in the case of
glass frits, as the temperature rises, the inorganic
components in the glass frits begin to liquefy at
temperatures different from each other. For this reason,
with the increase in temperature, the glass frits soften
gradually. Therefore, as compared with the case where
the inorganic components are used singly as an
antioxidant agent, the glass frits produced by melting
I
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the plurality of inorganic components are liable to
adhere stably to the surface of the heated metallic
starting material. The glass frits can be regulated so
as to have a viscosity suitable for coating the surface
of metallic starting material.
[0024]
The antioxidant agent contains the plurality of
glass frits having different softening points.
Preferably, the plurality of glass frits contain hightemperature
glass frits and medium-temperature glass
frits. The high-temperature glass frits have a softening
point higher than that of the medium-temperature glass
frits. Hereunder, the details of the high-temperature
glass frits and medium-temperature glass frits are
explained.
[0025]
[High-temperature glass frits]
The high-temperature glass frits have a high
softening point. The antioxidant agent has a proper
viscosity in a high-temperature range of not lower than
1000°C on account of the plurality of high-temperature
glass frits. The antioxidant agent can wettingly spread
on the surface of metallic starting material in a hightemperature
range of not lower than 1000°C, and can cover
the metal surface. At this time, the antioxidant agent
adheres to the surface of metallic starting material.
[0026]
9
In effect, due to the high-temperature glass frits,
the antioxidant agent prevents the surface of metallic
starting material from coming into contact with the
outside air in the high-temperature range. Therefore,
the antioxidant agent can prevent scale from being
produced on the surface of metallic starting material in
the high-temperature range.
[0027]
If the antioxidant agent does not contain the hightemperature
glass frits, in the high-temperature range,
the viscosity of the antioxidant agent becomes too low.
Therefore, the antioxidant agent becomes less liable to
adhere stably to the surface of metallic starting
material, and becomes liable to flow down from the
surface. If the antioxidant agent flows down, the
1 surface of metallic starting material is partially
exposed. The exposed surface portion comes into contact
with the outside air, and scale is produced.
[0028]
' The preferable viscosity at 1200°C of the hightemperature
glass frits is 2 x 102 to 106 dPa-s. If the
viscosity at 1200°C of the high-temperature glass frits
is too low, in the high-temperature range, the
; antioxidant agent is less liable to adhere to the surface
of metallic starting material, and is liable to flow down
from the surface of metallic starting material. On the
other hand, if the viscosity at 1200°C of the high-
10 I
temperature glass frits is too high, in the hightemperature
range, the antioxidant agent is liable to
peel off the surface of metallic starting material. If
the viscosity at 1200°C of the high-temperature glass
frits is 2 x 102 to 106 dPa-s, in a high-temperature range
of 1000 to 1400°C, the high-temperature glass frits
soften, and become liable to adhere to the surface of
metallic starting material. Therefore, in the hightemperature
range, the antioxidant agent is liable to
cover the surface of metallic starting material, and is
liable to adhere stably to the surface of metallic
starting material. The upper limit of the preferable
viscosity at 1200°C of the high-temperature glass frits
is 105 dPa-s, and the lower limit thereof is 103 dPa-s.
The viscosity in this description means so-called "static
viscosity".
[0029]
In the case where the high-temperature glass frits
are of a spherical powder form, the preferable particle
diameter is not larger than 25 |um. The particle diameter
herein is a volume mean particle diameter D50. The volume
mean particle diameter D50 is determined by the method
described below. By using a particle counter, the volume
particle size distribution of the high-temperature glass
frits is determined. By using the obtained volume
particle size distribution, the particle diameter at
which the cumulative volume becomes 50% from the small
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particle diameter side in a cumulative volume
distribution is defined as a volume mean particle
diameter D50. If the particle diameter is not larger than
25 |jm, at normal temperature, the high-temperature glass
frits are liable to disperse in a liquid.
[0030]
As described above, the high-temperature glass frits
contain the plurality of well-known inorganic components.
For example, the high-temperature glass frits contain 60
to 70 mass% of silicon dioxide (Si02) , 5 to 20 mass% of
aluminum oxide (AI2O3) , and 0 to 20 mass% of calcium
oxide (CaO). Calcium oxide is an optional compound, and
need not be contained. Further, the high-temperature
glass frits may contain one or more kinds of magnesium
oxide (MgO), zinc oxide (ZnO), and potassium oxide (K20).
The inorganic components constituting the hightemperature
glass frits are not limited to the abovedescribed
examples. In effect, the high-temperature
glass frits can be produced by the well-known inorganic
components constituting the glass.
[0031]
[Medium-temperature glass frits]
The medium-temperature glass frits have a softening
point lower than that of the high-temperature glass frits.
The antioxidant agent has a proper viscosity in a mediumtemperature
range of 600 to 1000°C on account of the
medium-temperature glass frits. Therefore, the l
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antioxidant agent wettingly spreads on the whole surface
of the metallic starting material not only in the hightemperature
range but also in the medium-temperature
range, and covers the surface. Further, in the mediumtemperature
range, the antioxidant agent adheres stably
to the surface of metallic starting material. Therefore,
in the medium-temperature range, the surface of metallic
starting material is prevented from coming into contact
with the outside air, and the production of scale is
prevented.
[0032]
If the antioxidant agent does not contain the
medium-temperature glass frits, the antioxidant agent in
the medium-temperature range is less liable to adhere to
the surface of metallic starting material. Therefore, in
the medium-temperature range, the antioxidant agent flows
down from the surface of metallic starting material, or
! peels off, and thereby the surface of metallic starting
material is partially exposed. The exposed portion comes
into contact with the outside air, and scale is liable to
be produced.
[0033]
The preferable viscosity at 700°C of the mediumtemperature
glass-frits is 2 x 102 to 106 dPa-s. If the
viscosity of the medium-temperature glass-frits is too
low, in the medium-temperature range, the antioxidant
agent is less liable to adhere to the surface of metallic
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1
starting material, and is liable to drip down from the
surface of metallic starting material. On the other hand,
if the viscosity of the medium-temperature glass-frits is
too high, the antioxidant agent does not soften
sufficiently in the medium-temperature range. Therefore,
the antioxidant agent becomes liable to peel off the
surface of metallic starting material. If the viscosity
at 700°C of the medium-temperature glass-frits is 2 x 102
to 106 dPa-s, in the medium-temperature range of 600 to
1000°C, the medium-temperature glass-frits soften, and
become liable to adhere to the surface of metallic
starting material. Therefore, in the medium-temperature
range, the antioxidant agent becomes liable to cover the
surface of metallic starting material. The upper limit
of the preferable viscosity at 700°C of the mediumtemperature
glass frits is 105 dPa-s, and the lower limit
thereof is 103 dPa-s.
| [0034]
In the case where the medium-temperature glass frits
are of a spherical powder form, the preferable particle
diameter of the medium-temperature glass frits is not
larger than 25 |nm. The definition of the particle
diameter of the medium-temperature glass frits is the
same as that of the above-described particle diameter of
the high-temperature glass frits. That is, the particle
diameter of the medium-temperature glass frits is the
volume mean particle diameter D50. If the particle
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diameter is not larger than 25 fim, the medium-temperature
glass frits disperse stably in a liquid. Therefore, when
the antioxidant agent is applied to the surface of
metallic starting material, the medium-temperature glass
frits are liable to disperse substantially uniformly to
the whole surface of the metallic starting material.
[0035]
For example, the medium-temperature glass frits
contain 40 to 60 mass% of Si02, 0 to 10 mass% of Al203, 20
to 40 mass% of B203, 0 to 10 mass% of ZnO, and 5 to 15
mass% of Na20. Further, the medium-temperature glass
frits may contain at least one kind of MgO, CaO, and K20.
The inorganic components constituting the mediumtemperature
glass frits are not limited to the abovedescribed
examples. The medium-temperature glass frits
can be produced by the well-known inorganic components
constituting the glass.
[0036]
In the antioxidant agent, the preferable content of
the medium-temperature glass frits is 4 to 20 weight
parts with respect to 100 weight parts of the hightemperature
glass frits.
[0037]
•
[Water]
The antioxidant agent further contains water. Water
is mixed with the high-temperature glass frits, the
i medium-temperature glass frits, and the low-temperature
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inorganic compound to produce slurry. If water is mixed, I
the antioxidant agent turns to slurry. Therefore, the
antioxidant agent is liable to be applied substantially
uniformly to the surface of metallic starting material
before being heated.
[0038]
In the antioxidant agent, the preferable content of
water is 100 to 150 weight parts with respect to 100
weight parts of the high-temperature glass frits. If the
water content is too low or too high, the antioxidant
agent is less liable to be applied. If the water content
is regulated, the viscosity of the antioxidant agent can
be regulated to such a degree that the antioxidant agent
can be applied to the surface of metallic starting
1 material substantially uniformly at normal temperature.
[0039]
[Suspending agent]
The suspending agent causes the high-temperature and
medium-temperature glass frits and the like to disperse
substantially uniformly in a solution (water). The
suspending agent contains potter's clay and bentonite
and/or sepiolite. Due to the potter's clay and bentonite
and/or sepiolite, the antioxidant agent in accordance
i with this embodiment is less liable to drip down when
being applied to the surface of metallic starting
material, and is less liable to peel off the surface of
metallic starting material when being dried and
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solidified. Hereunder, the potter's clay and the
bentonite and/or sepiolite are explained.
[0040]
[Potter's clay]
The potter's clay contains kaolinic clay and a
plurality of quartz particles. More specifically, the
potter's clay contains kaolinite, hallosite, and quartz.
[0041]
The potter's clay improves the anti-dripping
property of liquid-form antioxidant agent. The
antioxidant agent containing potter's clay is less liable
to drip down after being applied to the surface of
metallic starting material at normal temperature.
Therefore, the antioxidant agent is liable to cover the
whole surface of metallic starting material at normal
temperature.
In the antioxidant agent, the content of potter's
clay is preferably not lower than 6 weight parts with
respect to 100 weight parts of the high-temperature glass
frits. In this case, the anti-dripping property at
normal temperature of the antioxidant agent improves.
i The content of potter's clay is further preferably not
lower than 7 weight parts, and still further preferably
not lower than 10 weight parts. If the antioxidant agent
contains potter's clay excessively, the glass frits in
the antioxidant agent become less liable to disperse on
the surface of metallic starting material uniformly, and
17
the oxidation preventing function of the antioxidant
agent decreases. Therefore, the upper limit of the
preferable content of potter's clay is 30 weight parts.
[0042]
However, even if the content of potter's clay is
lower than 6 weight parts, the anti-dripping property at
normal temperature of the antioxidant agent can be
achieved to some extent.
[0043]
[Bentonite and/or sepiolite]
The bentonite is clay consisting mainly of
montmorillonite. The bentonite further may contain
silicic acid ore such as quartz and opal, silicate ore
such as feldspar and zeolite, carbonate ore such as
; dolomite and sulfate ore, sulfide ore such as pyrite, and
the like.
Sepiolite is a water-containing magnesium silicate,
and is denoted by a chemical formula of
Mg8Sii203o (OH)4 (OH2) 4-8H20, for example.
[0044]
Either of the bentonite and sepiolite improves the
anti-peeling property of the antioxidant agent.
Specifically, the liquid-form antioxidant agent is
applied to the surface of metallic starting material.
Then, by heating or drying, the moisture of the
antioxidant agent applied to the surface of metallic
starting material is evaporated, and the antioxidant
18
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agent is solidified. The bentonite and sepiolite
prevents the solidified antioxidant agent from peeling
off the surface of metallic starting material. The
antioxidant agent containing the bentonite and/or
sepiolite is less liable to peel off even when being
subjected to an external force. The antioxidant agent
may contain at least one kind of bentonite and sepiolite.
[0045]
In the antioxidant agent, the preferable content of
bentonite and/or sepiolite is not lower than 4 weight
parts with respect to 100 weight parts of the hightemperature
glass frits. In the case where the
antioxidant agent contains the bentonite and sepiolite,
the total content of bentonite and sepiolite is
preferably not lower than 4 weight parts. If the content
of bentonite and/or sepiolite is not lower than 4 weight
parts, the anti-peeling property of the antioxidant agent
further improves.
[0046]
Also, the preferable content of bentonite and/or
sepiolite is lower than 9 weight parts with respect to
100 weight parts of the high-temperature glass frits. In
the case where the antioxidant agent contains the
bentonite and sepiolite, the total content of bentonite
| and sepiolite is preferably lower than 9 weight parts.
If the content of bentonite and/or sepiolite exceeds 9
weight parts, the glass frits become less liable to
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disperse in the liquid-form antioxidant agent. That is,
the antioxidant agent becomes less liable to be slurried.
[0047]
However, even if the content of bentonite and/or
sepiolite exceeds the above-described range, the antipeeling
property of the antioxidant agent can be achieved
to some extent.
[0048]
[Other components of suspending agent]
The suspending agent may contain other clays other
than the above-described potter's clay, bentonite, and
sepiolite. The clay contains, for example, 50 to 60
I
mass% of Si02 and 10 to 40 mass% of A.l203, and further
contains one or more kinds selected from a group
c o n s i s t i n g of Fe203, CaO, MgO, Na20, and K20 as other
minute-amount components.
[0049]
One example of other clays other than the potter's
clay, bentonite, and sepiolite contains about 55 mass% of
Si02, about 30 mass% of A1203, Fe203, CaO, MgO, Na20, K20,
and the like. Another example of other clays contains
about 60 mass% of Si02 and about 15 mass% of Al203, and
contains Fe203, CaO, MgO, Na20, K20, and the like as other
minute-amount components.
[0050]
i [Other components of antioxidant agent]
20
The antioxidant agent in accordance with this
embodiment may further contain the components described
below.
[0051]
[Low-temperature inorganic compound]
The antioxidant agent in accordance with this
embodiment further contains an inorganic compound having
a melting point not higher than 600°C (hereinafter,
referred to as a low-temperature inorganic compound).
The low-temperature inorganic compound preferably has a
melting point of 400 to 600°C. On account of the lowtemperature
inorganic compound, the antioxidant agent
wettingly spreads on the whole surface of the metallic
starting material in the low-temperature range of not
higher than 600°C, and is liable to adhere to the surface
of metallic starting material. That is, in the lowtemperature
range, the low-temperature inorganic compound
prevents the surface of metallic starting material from
coming into contact with the outside air, and prevents
scale from being produced in the low-temperature range.
[0052]
The preferable low-temperature inorganic compound is
an inorganic salt and/or an oxide having a melting point
of 400 to 600°C. The oxide having a melting point not
i
higher than 600°C is, for example, boric acid (H3B03) or
boron oxide (B203) . If being heated, boric acid turns to
! boron oxide. The melting point of boron oxide is about
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450°C. The inorganic salt having a melting point not
higher than 600°C is, for example, phosphate, thallium
bromide (TIBr), or silver metaphosphate (Ag03P) . The
melting point of thallium bromide is about 480°C, and the
melting point of silver metaphosphate is about 480°C.
Further preferably, the low-temperature inorganic
compound is boric acid and/or boron oxide.
[0053]
[Relationship between viscosities of high-temperature and
medium-temperature glass frits and viscosity of lowtemperature
inorganic compound]
Figure 1 is a diagram showing the relationship
between the viscosities of high-temperature and mediumtemperature
glass frits and the viscosity of lowtemperature
inorganic compound. Figure 1 was obtained by
the process described below. High-temperature glass
frits HT1 and HT2, medium-temperature glass frits LTl and
LT2, and low-temperature inorganic compound LL given in
Table 1 were prepared.
[Table 1]
TABLE 1
Chemical composition (wtft)
SiO, AI2Q3 B;03 CaO MgO ZnO Na2Q K20
High-temperature glass frits HT1 66J 9JS ; 13J IJi 3 ; 6.4 i
Medium-temperature glass frits LT1 5tS 2J> 28,4 OJ : 6J) 8J 2 >
High-temperature glass frits HT2 65-70 5-10 1-3 10-15 0-3 = ; 5-10
Medium-temperature glass frits LT2 50-55 0-5 20-25 5-10 0-3 - 10-15 0-5
[Low-temperature inorganic compound LL l - l - I I P P l - H - l - l - - r
[0054] :
Referring to Table 1, the low-temperature inorganic :
compound LL was boron oxide. By heating the components
[ L
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t
«
(HT1, HT2, LT1, LT2, and LL), the viscosities at
respective temperatures were measured. For the
measurement of viscosity, the well-known platinum ball
pulling-up method was used. Specifically, a platinum
ball submerged in molten glass and molten inorganic
compound was pulled up. Based on the load applied to the
platinum ball at this time and the pulling-up speed, the
viscosities were determined.
[0055]
Referring to Figure 1, the symbol "•" in the figure
denotes the viscosity of the high-temperature glass frits
HT1. The symbol "O" denotes the viscosity of the hightemperature
glass frits HT2. The symbol "•" denotes the
viscosity of the medium-temperature glass frits LT1. The
symbol "•" denotes the viscosity of the mediumtemperature
glass frits LT2. The symbol "A" denotes the
viscosity of the low-temperature inorganic compound LL.
[0056]
Referring to Figure 1, the viscosity of the lowtemperature
inorganic compound LL was 2 x 102 to 106 dPa-s
in the temperature range of 400 to 800°C, and was not
lower than 103 dPa-s in the temperature range of not
!
higher than 600 C. The viscosities of the mediumtemperature
glass frits LT1 and LT2 were 2 x 102 to 106
dPa-s in the temperature range of 600 to 1200°C. That is,
at 700°C, the viscosities of the medium-temperature glass
I frits LT1 and LT2 were in the range of 2 x 102 to 106
; 23
#
dPa-s. The viscosities of the high-temperature glass
frits HT1 and HT2 were 2 x 102 to 106 dPa-s in the
temperature range of 1000 to 1550°C. That is, at 1200°C,
the viscosities of the high-temperature glass frits HT1
and HT2 were in the range of 2 x 102 to 106 dPa-s.
[0057]
As described above, with the increase in temperature,
the viscosity lowers in the order of low-temperature
inorganic compound, medium-temperature glass frits, and
high-temperature glass frits, and softening occurs. On
account of the high-temperature glass frits, mediumtemperature
glass frits, and low-temperature inorganic
compound, the antioxidant agent is capable of having a
viscosity of a degree such as to be able to adhere stably
to the surface of metallic starting material in a broad
temperature range (400 to 1550°C) .
[0058]
[Antislipping agent]
The heated metallic starting material is sometimes
hot-worked. In this case, the metallic starting material
is rolled by a rolling roll to produce a metal plate or a
metal bar. Also, the metallic starting material is
! piercing-rolled by the plug and skew rolls of a piercing
machine to produce a metal pipe. Therefore, the metallic
starting material is preferably liable to be caught by
the rolling rolls or the skew rolls. If the friction
coefficient of metallic starting material against a hot-
24
working roll such as the rolling roll and the skew roll
is high, the metallic starting material is liable to be
caught by the hot-working rolls.
[0059]
Therefore, the antioxidant agent may contain an
antislipping agent to increase the friction coefficient.
The antislipping agent is, for example, an oxide having a
high melting point. The antislipping agent is, for
example, alumina or silica. When the metallic starting
material to which the antioxidant agent has been applied
comes into contact with the rolls, the antislipping agent
such as alumina or silica comes into contact with the
rolls. At this time, since the friction coefficient of
metallic starting material against the roll becomes high,
the metallic starting material becomes liable to be
caught by the rolls.
[0060]
[Gluing agent]
The antioxidant agent may further contain a gluing
agent to improve the adhering force to the surface of
metallic starting material. The gluing agent is, for
example, an organic binder. The organic binder is, for
example, an acrylic resin.
[0061]
Further, the antioxidant agent may contain an alkali
metal salt or a group 2 metal salt insoluble in water.
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These components prevent the viscosity of the antioxidant
agent from changing with time.
[0062]
[Alkali metal salt]
As described above, the antioxidant agent containing
water is slurry (a fluid) at normal temperature. In the
case where the antioxidant agent contains less than 50
wt% of water, at normal temperature, the antioxidant
agent sometimes sets to gel with the elapse of time. The
gelation increases the viscosity of the antioxidant agent.
Also, gel lumps are sometimes produced.
| [0063]
It is more favorable if the secular change of
viscosity of the antioxidant agent is restrained. The
alkali metal salt peptizes the antioxidant agent having
set to gel. Therefore, the antioxidant agent fluidizes
again, and the increase in viscosity is prevented. The
alkali metal salt is, for example, potassium carbonate
(KC03) , sodium hexametaphosphate, or the like.
[0064]
[Insoluble group 2 metal salt]
In the case where the antioxidant agent contains not
less than 55 wt% of water, at normal temperature, the
viscosity of antioxidant agent sometimes decreases with
the elapse of time. Such a secular change of viscosity
is preferably restrained.
I [0065]
I 26 I
The insoluble group 2 metal salt prevents the
decrease in viscosity of the antioxidant agent. Herein,
the group 2 metal salt is a metal corresponding to a
group 2 element in the periodic table, such as beryllium,
magnesium, calcium, strontium, barium, or radium. Also,
"insoluble" means insoluble in water, and "insoluble in
water" means that the solubility in water of 25°C is not
higher than 1000 ppm. Preferably, the insoluble group 2
metal salt is magnesium carbonate and/or calcium
carbonate.
j [0066]
The insoluble group 2 metal salt prevents the
decrease in viscosity of the antioxidant agent having
been produced. The reason described below is presumed.
The insoluble group 2 metal salt dissolves gradually in a
solution (water). When the group 2 metal salt dissolves,
group 2 metal ions are formed. Since the group 2 metal
ions improve the suspension force, the secular change of
viscosity of the antioxidant agent is restrained.
[0067]
[Other components]
The antioxidant agent may contain other components
in addition to the above-described components. For
example, the antioxidant agent may contain an inorganic
electrolyte represented by sodium nitrite.
[0068]
r
27 I
" 1
[Preferable content of each component in antioxidant
agent]
The preferable content of each component contained
in the antioxidant agent in accordance with this
embodiment is as described below. In the case where the
content of the high-temperature glass frits is taken as
100 weight parts, the preferable content of lowtemperature
inorganic compound is 4 to 20 weight parts.
The preferable content of antislipping agent is 15 to 35
weight parts. The preferable content of gluing agent is
1.0 to 4.0 weight parts. The preferable contents of the
alkali metal salt and the insoluble group 2 metal salt
are 0.1 to 1.5 weight part, respectively.
[0069]
If the components in the antioxidant agent satisfy
the above-described preferable contents, the abovedescribed
effects of the antioxidant agent are achieved
especially effectively. However, even if the content of
each of the components exceeds the preferable range, the
effects of the antioxidant agent can be achieved to some
extent.
[0070]
i [Process for producing antioxidant agent]
The antioxidant agent in accordance with this
embodiment is obtained by mixing the above-described
components. First, the plurality of components to be
| contained in the antioxidant agent are prepared. Next,
I 28
;
by using a grinding device, the plurality of components
are ground and mixed to produce a mixed composition. The
grinding device is, for example, a ball mill, a rod mill,
a vibrating mill, a planetary mill, a tower mill, an
attritor, a sand mill, or the like. The grinding device
is equipped with a cylindrical grinding vessel. The
prepared plurality of components are put in the grinding
vessel. In the grinding vessel, balls or rods are
further put. By rotating or vibrating the grinding vessel,
I the high-temperature glass frits and the mediumtemperature
glass frits are ground, and particles each
having a particle diameter of, for example, not larger
than 25 pan are formed. At the time of grinding and
mixing, water is also contained.
[0071]
By the above-described producing process, the
antioxidant agent is produced.
[0072]
i [Process for producing metallic material]
Figure 2 is a flowchart showing one example of a
process for producing a metallic material using the
above-described antioxidant agent. Referring to Figure 2,
| first, the antioxidant agent in accordance with this
embodiment is prepared (Sll). The antioxidant agent is
produced by the above-described process.
j [0073]
j
I
i
• 29 I
Successively, the antioxidant agent is applied to
the surface of a metallic starting material before being
heated (S12). That is, the antioxidant agent is applied
to the surface of metallic starting material having
normal temperature. The type of the metallic starting
material is not subject to any special restriction. The
metallic starting material consists of, for example,
steel, titanium, titanium alloy, any other alloy, or the
like. The steel is, for example, a carbon steel, a
ferritic stainless steel, a martensitic stainless steel,
' an austenitic stainless steel, an alloy steel, or the
like. The shape of the metallic starting material is
ingot, slab, bloom, billet, plate material, bar material
represented by rod material and wire rod, pipe, or the
1 i ke.
[0074]
The process for applying the antioxidant agent is
not subject to any special restriction. A worker may
apply the antioxidant agent to the surface of metallic
starting material by using a brush. Also, the
antioxidant agent may be applied to the surface of
! metallic starting material by using a spray or the like.
A bath in which the antioxidant agent has been stored may
be prepared, and the metallic starting material may be
immersed in the antioxidant agent in the bath (so-called
I "dipping"). By any of these applying processes, the
| antioxidant agent is applied to the surface of metallic
I
i
i
! 30
starting material. The antioxidant agent contains the
potter's clay. Therefore, the antioxidant agent applied
to the surface of metallic starting material is less
liable to drip down from the surface of metallic starting
material at normal temperature. After the antioxidant
agent has been applied to the surface of metallic
starting material, the antioxidant agent may be dried.
[0075]
Successively, the metallic starting material to
which the antioxidant agent has been applied is heated
| (S13). At the drying time or at the early stage of
heating, the moisture of the antioxidant agent evaporates,
so that the antioxidant agent solidifies. Because of
containing bentonite and/or sepiolite, the antioxidant
agent is less liable to peel off the surface of metallic
starting material when solidifying.
[0076]
When the heating temperature rises, the mediumtemperature
glass frits, the high-temperature glass frits,
the low-temperature inorganic compound, and the like in
the antioxidant agent soften and cover the surface of
metallic starting material. As described above, in the
; board temperature range (400°C to 1400°C) , the
antioxidant agent adheres stably to the surface of
metallic starting material. Therefore, scale is less
liable to be produced on the surface of the heated
metallic starting material.
i 31
- -— ^^^^^^
[0077]
[In the case where metallic starting material is heattreated]
In the case where the metallic starting material is
heat-treated, the heat treatment temperature is sometimes
not higher than 1000°C. For example, the quenching
temperature of stainless steel is about 900 to 1000°C.
Also, the tempering temperature is about 500 to 650°C.
In the case where the metallic starting material is heattreated,
the metallic starting material is put in a heat
treating furnace, and the metallic starting material is
heated to the heat treatment temperature. At this time,
the in-furnace temperature is increased stepwise with the
elapse of time. The in-furnace temperature is controlled
by a control unit, and is raised stepwise according to a
predetermined heat pattern.
[0078]
In the case where the heat treatment temperature is
lower than 1000°C, the medium-temperature glass frits in
the antioxidant agent mainly soften and cover the surface
of metallic starting material. In the case where the
antioxidant agent contains the low-temperature inorganic
compound, the low-temperature inorganic compound and the
medium-temperature glass frits mainly soften and cover
the surface of metallic starting material. When the infurnace
temperature becomes a temperature close to 1000°C,
! >
| 32
I,
the high-temperature glass frits also begin to soften,
and begin to function effectively as an antioxidant agent.
[0079]
As described above, in the case where the metallic
starting material is heat-treated at a temperature not
higher than 1000°C, the medium-temperature glass frits
mainly cover the surface of metallic starting material,
and prevent the production of scale.
[0080]
[In the case where metallic starting material is hotworked]
In the case where the metallic starting material is
hot-worked to produce a metallic material such as steel
! material, steel bar, steel pipe, or the like, the
metallic starting material is heated to various
temperature ranges.
[0081]
For example, when a steel starting material (round
billet) is piercing-rolled by the Mannesmann pipe making
process to produce a steel pipe, the steel starting
material is heated to a temperature of 1100 to 1300°C in
a heating furnace or a soaking pit. On the other hand,
in the Ugine pipe making process in which the steel
starting material is extruded to produce a steel pipe,
the steel starting material is heated to a temperature of
800 to 1000°C in a heating furnace or a soaking pit. The
steel starting material heated in the heating furnace or
I i
!
! 33
the soaking pit is, in some cases, further heated to
1200°C in a short period of time by high-frequency
heating. Further, when a starting material consisting of
titanium or titanium alloy is hot-worked to produce a
titanium material having a predetermined shape (plate,
bar, or pipe), the heating temperature of a titanium or
titanium alloy starting material is higher than the
heating temperature of the steel starting material.
[0082]
Thus, the heating temperature differs according to
the type and producing process of metallic starting
material. However, the antioxidant agent in accordance
with this embodiment can respond to various heating
temperatures because of containing the medium-temperature
glass frits and high-temperature glass frits.
[0083]
When the metallic starting material in the heating
furnace or the soaking pit is heated at a temperature of
600 to 1000°C, the medium-temperature glass frits mainly
soften, and cover the surface of metallic starting
material. Then, when the metallic starting material is
heated at a temperature not lower than 1000°C, the hightemperature
glass frits mainly soften, and cover the
surface of metallic starting material.
[0084]
In effect, the antioxidant agent in accordance with
this embodiment adheres stably to the surface of metallic
;
; i
I
34 I
«
starting material in a broad temperature range, and
covers the surface of metallic starting material.
Therefore, in various producing steps having different
heating temperatures, by heating, scale can be prevented
from being formed on the surface of metallic starting
material.
[0085]
Returning to Figure 2, if a heat treatment step is
being performed (YES in S14), after heating, heat
treatment is finished through a predetermined heat
treatment step. On the other hand, if a hot working step
is being performed (NO in S14), the metallic starting
material is hot-worked (S15). By the hot working, the
metallic starting material is produced into a desired
metallic material (pipe material, plate material, bar
material, etc.).
[0086]
In the case where the antioxidant agent contains the
antislipping agent, the antioxidant agent prevents the
slippage of metallic starting material with respect to
the rolls of a rolling mill. For example, in the case
where the antioxidant agent contains alumina particles as
the antislipping agent, the alumina particles adhere to
the surface of the heated metallic starting material.
The metallic starting material to which the alumina
particles have adhered is conveyed to the rolling mill.
When the front end of metallic starting material comes .
\ 35
into contact with the rolls, the alumina particles on the
surface of metallic starting material come into contact
with the rolls. At this time, the alumina particles
increase the friction coefficient of the metallic
starting material against the rolls, so that the metallic
starting material becomes liable to be caught by the
I rolls.
Example
[0087]
A plurality of antioxidant agents having the
different contents of potter's clay and bentonite were
prepared. The suspensibility, anti-dripping property,
and durability after drying of each of the plurality of
prepared antioxidant agents were evaluated.
[0088]
[Testing method]
The antioxidant agents given in Table 2 were
prepared.
36 :
[Table 2]
TABLE 2
Content (unit weight part with respect to 100 weight parts of high-temperature glass
frits)
number H*1 I Medium- I ~ H I TPO^T S u S p e n S i M *y
temperature temperature Alumina Water Bentonite
glass frits glass frits
1 100 7.7 2 5 3 1 0 0 10 5 Absent
2 100 11 253 100 5 10 Present
3 100 7.7 25.3 100 6 6 Present
4 100 7.7 2 5 3 1 0 0 9 9 Absent
5 100 7.7 25.3 100 4 4 Present
6 100 7.7 25.3 100 11 11 Absent
7 100 7.7 25.3 100 11 1 Absent
: 8 100 7.7 25.3 100 1 11 Present
9 100 7.7 25.3 100 4 14 Present
10 100 7.7 25.3 100 14 4 Absent
11 100 7.7 25.3 100 15 0 Absent
12 100 7.7 25.3 100 4 0 Present
13 100 7.7 2 5 3 1 0 0 8 0 Present
14 100 7.7 2 5 3 1 0 0 8 4 Present
15 100 7.7 25.3 100 8 14 Present
16 100 7.7 2 5 3 1 0 0 6 4 Present
17 100 7.7 25.3 100 6 14 Present
[0089]
Referring to Table 2, all of the antioxidant agents
of test numbers 1 to 17 contained high-temperature glass
frits, medium-temperature glass frits, alumina, water,
and suspending agent (bentonite and potter's clay). All
of the high-temperature glass frits of test numbers 1 to
17 were the high-temperature glass frits HT1 in Table 1.
Also, all of the medium-temperature glass frits of test
numbers 1 to 17 were the medium-temperature glass frits
LT1 in Table 1. The viscosities at 1200°C of the hightemperature
glass frits HT1 were in the range of 2 x 102
to 106 dPa-s. The viscosities at 700°C of the medium-
!
!
37
temperature glass frits LTl were in the range of 2 x 102
to 106 dPa-s.
[0090]
The contents (weight part) of the components with
respect to 100 weight parts of the high-temperature glass
frits of test numbers 1 to 17 were as given in Table 1.
Specifically, in test numbers 1 to 17, the contents of
high-temperature glass frits, medium-temperature glass
frits, alumina used as the antislipping agent, and water
were equal to each other. That is, in test numbers 1 to
17, only the contents of the suspending agents (bentonite
and potter's clay) were different from each other.
[0091]
[Evaluation of suspensibility]
The antioxidant agents of test numbers 1 to 17 were
produced by the above-described method. After one hour
has been elapsed after production, it was observed
whether or not the antioxidant agent of each test number
has been slurried. Specifically, the presence of
precipitates in the antioxidant agent was observed.
[0092]
[Evaluation of anti-dripping property]
On the slurried antioxidant agent of the antioxidant
agents of test numbers 1 to 17, the evaluation of antidripping
property was carried out. Specifically, a tank
• in which the antioxidant agent of the slurried test ;
number had been put was prepared. A rectangular
38 I
stainless steel plate having a surface of 75 mm x 200 mm
was immersed in the slurried antioxidant agent in the
tank in a state of being erected. After immersing, the
stainless steel plate was pulled up while being erected.
Simultaneously with the pulling-up, a collecting pan was
arranged under the stainless steel plate, and the
! antioxidant agent dripping from the stainless steel plate
was collected in the collecting pan.
[0093]
After the antioxidant agent had stopped dripping,
the weight of the antioxidant agent adhering to the
surface of stainless steel plate was measured. Also, the
weight of the antioxidant agent gathered in the
collecting pan was also measured.
[0094]
The weight of the antioxidant agent adhering to the
surface of stainless steel plate was defined as an
"adhesion amount at steady time". Also the total sum of
the weight of the antioxidant agent adhering to the
surface of stainless steel plate and the weight of the
antioxidant agent gathered in the collecting pan was
defined as an "adhesion amount at early time".
[0095]
For each test number, the yield was calculated based
on the following Formula (1).
Yield = adhesion amount at steady time / adhesion
amount at early time (1) i
39
:
[0096]
In the above-described test, the antioxidant agent
adhering to the surface of stainless steel plate
contained water. As described above, when the
antioxidant agent is actually used on the metallic
| starting material, the water component of the antioxidant
agent is evaporated by drying or heating, and only the
solid component (component other than water of
antioxidant agent) remains on the surface of metallic
starting material. Therefore, of the adhesion amount at
early time and the adhesion amount at steady time, the
adhesion amount of solid component was calculated. By
utilizing the calculated yield, the yield of the
antioxidant agent of each test number in the case where
the adhesion amount of solid component in the adhesion
amount at steady time was made equal (0.10 g/mm2) was
determined by conversion.
[0097]
[Evaluation of anti-peeling property]
On the slurried antioxidant agent, an anti-peeling
property test was conducted. Specifically, ten columnar
test specimens consisting of a stainless steel (the
chemical composition corresponds to SUS304) were prepared.
Each of the test specimens had a diameter of 11 mm and a
length of 10 mm.
[0098]
I 40 I
The prepared test specimen was immersed in the
slurried antioxidant agent of the test number. Then,
after being pulled up, the test specimen was dried in the
atmosphere of 80°C. The surface of test specimen was
covered with the solidified antioxidant agent. At this
time, the adhesion amount of the solidified antioxidant
agent was regulated so as to be 0.25 g/mm2. The adhesion
amount (g/mm2) was defined by the following Formula (2).
Adhesion amount = (total weight of 10 test specimens
after antioxidant agent has been applied and dried -
total weight of 10 test specimens to which antioxidant
agent is not applied) / total surface area of 10 test
specimens (2)
[0099] ;
Next, by using test specimens (ten specimens) >
covered with the antioxidant agent, the rattler test was >
conducted by using a rattler tester specified in Japan
Powder Metallurgy Association JPMA Pll-1992. In this :
test, ten test specimens were put in a wire net basket of
the rattler tester, and were rotated 300 turns at 84 rpm.
After the rotation of 300 turns, the weight of ten test
specimens was measured. Hereinafter, this weight is
referred to as a "weight after test". After the weight after test had been measured, the adhesion amount
(jag/mm2) defined by Formula (3) was calculated.
Adhesion amount = (total weight of 10 test specimens
after finish of test - total weight of 10 test specimens !
: I
41 I
to which antioxidant agent is not applied) / total
surface area of 10 test specimens (3)
[0100]
It was evaluated that the larger the adhesion amount
calculated by Formula (3) is, the higher the anti-peeling
property is.
[0101]
[Test results]
[Suspensibility]
The evaluation results of suspensibility are given
in Table 2. "Present" in the "Suspensibility" column of
Table 2 indicates that the antioxidant agent of the
corresponding test number has been slurried. "Absent"
indicates that the antioxidant agent of the corresponding
test number has not been slurried.
[0102]
Referring to Table 2, the antioxidant agents of test
numbers 1, 4, 6, 7, 10 and 11 had not been slurried.
That is, in this example, when not lower than 9 weight
parts of bentonite was contained with respect to 100
weight parts of the high-temperature glass frits, the
antioxidant agent had not been slurried. On the other
hand, the suspensibility (slurrying) did not depend on
the content of potter's clay. However, it is presumed
that if the content of water in the antioxidant agent is
increased, even the antioxidant agents of test numbers 1,
4, 6, 7, 10 and 11 are slurried.
42 1
[0103]
[Anti-dripping property]
Figure 3 is a diagram showing the evaluation result
of anti-dripping property. The ordinates of the figure
represent the weight part of potter's clay with respect
to 100 weight parts of the high-temperature glass frits
in each antioxidant agent, and the abscissas thereof
represent the weight part of bentonite with respect to
100 weight parts of the high-temperature glass frits in
each antioxidant agent. In the figure, the size of a
circle mark indicates the magnitude of yield. The
numerical values in the circle mark and the numerical
values at the side of the circle mark denote test number
and yield (%) .
[0104]
Referring to Figure 3, as the weight part of
potter's clay in the antioxidant agent increased, the
yield was higher, so that the anti-dripping property was
higher. Specifically, the antioxidant agents of test
numbers 2, 3, 8, 9, 15 and 17 contained not less than 6
weight parts of potter's clay. Therefore, the yield was
high, exceeding 58.0%.
[0105]
On the other hand, the antioxidant agents of test
numbers 5, 12 to 14, and 16 contained less than 6 weight
parts of potter's clay. Therefore, the yield was lower
than 58.0%. :
I 43 •
[0106]
Also, referring to Figure 3, the content of
! bentonite did not exert so great influence on the antidripping
property. More specifically, bentonite did not
exert an influence on the anti-dripping property as
compared with potter's clay.
. [0107]
[Anti-peeling property]
Figure 4 is a diagram showing the evaluation result
of anti-peeling property. The ordinates of the figure
represent the weight part of potter's clay with respect
to 100 weight parts of the high-temperature glass frits
in each antioxidant agent, and the abscissas thereof ;
represent the weight part of bentonite with respect to ;
100 weight parts of the high-temperature glass frits in '>
l
each antioxidant agent. In the figure, the size of a ;
!
circle mark indicates the magnitude of adhesion amount. *
•
The numerical values in the circle mark and the numerical ;
values at the side of the circle mark denote test number *
and adhesion amount ((Lig/mm2) obtained by Formula (3) .
[0108]
Referring to Figure 4, as the weight part of
bentonite in the antioxidant agent increased, the I
adhesion amount was larger. Specifically, the
antioxidant agents of test numbers 2, 3, 5, 9, 11, and 13 ;
to 17 contained not less than 4 weight parts of bentonite. i
44 '
Therefore, the adhesion amount exceeded 15 fag/mm2, and
excellent anti-peeling property was achieved.
[0109]
On the other hand, the antioxidant agent of test
number 8 contained less than 4 weight parts of bentonite.
Therefore, the adhesion amount was smaller than 15 fxg/mm2.
However, even the antioxidant agent of test number 8
achieved some degree of anti-peeling property.
[0110]
The above is the explanation of an embodiment of the
present invention. The above-described embodiment is
merely an illustration for carrying out the present
invention. Therefore, the present invention is not
limited to the above-described embodiment, and the abovedescribed
embodiment can be carried out by being changed
as appropriate without departing from the spirit and I
scope of the present invention. ;
Industrial Applicability
[0111] ^
The antioxidant agent in accordance with the present
invention can be applied widely to a metallic starting •
material to be heated. In particular, it can be utilized
for a metallic starting material to be heat-treated or a
»
I;
metallic starting material to be hot-worked.
45 I

We claim;
1. An antioxidant agent used for the surface of a
metallic starting material, containing:
a plurality of glass frits having different
softening points;
potter's clay; and
at least one of bentonite and sepiolite.
2. The antioxidant agent according to claim 1, wherein
the plurality of glass frits contain hightemperature
glass frits having a viscosity of 2 x 10^ to
10^ dPa-s at 1200°C and medium-temperature glass frits
having a viscosity of 2 x 10^ to 10^ dPa-s at 700°C.
3. The antioxidant agent according to claim 2, wherein
the antioxidant agent contains at least 6 weight >
parts of the potter's clay with respect to 100 weight ;
parts of the high-temperature glass frits and at least 4
weight parts of at least one of "the bentonite and '.
sepiolite with respect to 100 weight parts of the hightemperature
glass frits. '",
'•-
4. The antioxidant agent according to claim 3, wherein •
the antioxidant agent contains less than 9 weight
parts of at least one of the bentonite and sepiolite with ;
respect to 100 weight parts of the high-temperature glass :
frits. ^
46 I
5. The antioxidant agent according to any one of claims
' 2 to 4,, wherein
the antioxidant agent contains 4 to 20 weight parts
of the medium-temperature glass frits with respect to 100
weight parts of the high-temperature glass frits.
6. The antioxidant agent according to any one of claims
1 to 5, wherein
the antioxidant agent further contains an inorganic
compound having a melting point of 400 to 600°C.
7. The antioxidant agent according to claim 6, wherein
the inorganic compound is at least one of boric acid
and boron oxide.
I
8. A process for producing a metallic material, |
i
comprising the steps of: '
applying the antioxidant agent set forth in any one ?
of claims 1 to 7 to the surface of a metallic starting
material; and
heating the metallic starting material to which the
antioxidant agent has been applied.