U.S. patent application number 15/535118 was filed with the patent office on 2017-11-30 for methods for manganese removal of cast iron.
This patent application is currently assigned to KINOSHITA MANUFACTORY CO.,LTD.. The applicant listed for this patent is KINOSHITA MANUFACTORY CO.,LTD.. Invention is credited to Kiyoshi KINOSHITA, Hirotoshi MURATA.
Application Number | 20170342515 15/535118 |
Document ID | / |
Family ID | 56107283 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170342515 |
Kind Code |
A1 |
KINOSHITA; Kiyoshi ; et
al. |
November 30, 2017 |
METHODS FOR MANGANESE REMOVAL OF CAST IRON
Abstract
The present invention does not require a demanganese agent such
as a sulfide or a combustible gas in the removal of manganese of
cast iron. The method for removing manganese of cast iron according
to the present invention is implemented by performing the removal
of a manganese component by allowing a furnace to be in an oxygen
atmosphere, and by blowing air into a molten cast iron in the
furnace, while a carbon component in the molten cast iron is being
maintained at an approximately constant amount. Alternatively, the
method for removing manganese of cast iron according to the present
invention is implemented by performing the removal of the manganese
component by allowing the furnace to be in an oxygen atmosphere and
by stirring the molten cast iron in the furnace, while the carbon
component in the molten cast iron is being maintained at an
approximately constant amount.
Inventors: |
KINOSHITA; Kiyoshi;
(Hiroshima, JP) ; MURATA; Hirotoshi; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KINOSHITA MANUFACTORY CO.,LTD. |
Hiroshima |
|
JP |
|
|
Assignee: |
KINOSHITA MANUFACTORY
CO.,LTD.
Hiroshima
JP
NANIWA ROKI CO.,LTD.
Osaka
JP
|
Family ID: |
56107283 |
Appl. No.: |
15/535118 |
Filed: |
November 30, 2015 |
PCT Filed: |
November 30, 2015 |
PCT NO: |
PCT/JP2015/083567 |
371 Date: |
June 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 1/00 20130101; C21C
1/04 20130101; C22C 37/10 20130101; B22D 1/002 20130101 |
International
Class: |
C21C 1/04 20060101
C21C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2014 |
JP |
2014-252462 |
Claims
1. A method for removing manganese of cast iron, wherein the
removal of a manganese component is performed by allowing a furnace
to be in an oxygen atmosphere by introducing oxygen gas into the
furnace, and by blowing air into a molten cast iron in the furnace,
while a carbon component in the molten cast iron is being
maintained at an approximately constant amount.
2. A method for removing manganese of cast iron, wherein the
removal of a manganese component is performed by allowing a furnace
to be in an oxygen atmosphere by introducing oxygen gas into the
furnace, and by stirring a molten cast iron in the furnace, while a
carbon component in the molten cast iron is being maintained at an
approximately constant amount.
3. The method for removing manganese of cast iron according to
claim 2, wherein the removal of the manganese component is
performed while the amount of oxygen fed into the furnace or/and
the stirring speed of the molten cast iron in the furnace are being
regulated.
4. The method for removing manganese of cast iron according to
claim 1, wherein the removal of manganese is performed while the
ratio between the removal rate of a silicon component and the
removal rate of the manganese component is being maintained at an
approximately constant value.
5. The method for removing manganese of cast iron according to
claim 1, wherein the removal of manganese is performed while the
decrease of a silicon component is being suppressed.
6. The method for removing manganese of cast iron according to
claim 1, wherein the removal of manganese is performed while the
temperature of the molten cast iron is being maintained at an
approximately constant temperature.
7. The method for removing manganese of cast iron according to
claim 1, wherein the temperature of the molten cast iron is
1400.degree. C. to 1200.degree. C.
8. A method for removing a metal component of cast iron, wherein
the removal of a manganese component as well as the removal of the
metal component such as chromium, titanium, aluminum, boron or zinc
is performed by allowing a furnace to be in an oxygen atmosphere by
introducing oxygen gas into the furnace, and by blowing air into a
molten cast iron in the furnace, or by allowing the furnace to be
in an oxygen atmosphere, and by stirring the molten cast iron in
the furnace, while a carbon component in the molten cast iron is
being maintained at an approximately constant amount.
9. The method for removing manganese of cast iron according to
claim 2, wherein the removal of manganese is performed while the
ratio between the removal rate of a silicon component and the
removal rate of the manganese component is being maintained at an
approximately constant value.
10. The method for removing manganese of cast iron according to
claim 2, wherein the removal of manganese is performed while the
decrease of a silicon component is being suppressed.
11. The method for removing manganese of cast iron according to
claim 2, wherein the removal of manganese is performed while the
temperature of the molten cast iron is being maintained at an
approximately constant temperature.
12. The method for removing manganese of cast iron according to
claim 2, wherein the temperature of the molten cast iron is
1400.degree. C. to 1200.degree. C.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for removing
manganese in a feedstock having a high manganese content to be used
for the production of cast iron members.
BACKGROUND ART
[0002] Cast iron castings have been used for vehicle components or
machine components, approximately half of the amount of cast iron
castings produced is for vehicles, and cast iron castings account
for approximately 10% of the gross vehicle weight. The feedstock
used for the production of cast iron castings utilizes steel scraps
of automobile steel plates; the recent request for weight reduction
has increased the manganese content in automobile steel plates;
manganese is a pearlitization accelerating element, and accordingly
causes a problem which is that the toughness is degraded and
internal defects tend to be caused.
[0003] For the problem of the increase of the manganese content in
the feedstock used for the production of cast iron members, the
following proposals have been made. For example, Patent Literature
1 proposes a demanganese treatment method of cast iron in which
manganese is removed from the molten metal by adding a
sulfur-containing demanganese treatment agent to the molten cast
iron containing manganese, to float manganese as manganese sulfide.
In the removal of the manganese component, the MnS produced in the
molten metal is floated, and removed into the slag on the surface
of the molten metal. In order to promote the flotation removal, it
is effective to stir the molten metal by, for example, blowing a
gas from the porous plug in the bottom of the ladle containing the
molten metal. In the case of the gas stirring, as the blowing-in
gas, compressed air or compressed nitrogen gas is low in price and
easy to use. In this regard, it is regarded as preferable to use an
inert gas such as Ar in order to suppress the increase of the
amount of oxygen or the amount of nitrogen in the molten metal.
[0004] Patent Literature 2 proposes a method for decreasing the
manganese content in the production of a cast iron, wherein the
method is a method for removing manganese in the molten cast iron
by adding and mixing only sodium nitrate as an additive in the
molten cast iron at a temperature of 1400 to 1500.degree. C. In the
method for removing manganese, when the temperature of the molten
cast iron is lower than 1300.degree. C., SiO.sub.2 is produced in
large amounts, and Si, a main component of the cast iron, is
unpreferably depleted significantly. In addition, in the molten
cast iron at 1300.degree. C. or higher, MnS is regarded to be
formed only in a region having an extremely high Mn or S content
(%). According to this invention, it is possible to achieve a Mn
removal rate of 70% or more even when the Mn content of the molten
cast iron is 1.5% by mass or more. The Mn removal rate is described
to be improved according to the amount of Na.sub.2SO.sub.4 added,
when the amount of Na.sub.2SO.sub.4 added is approximately 10% by
mass or less.
[0005] Patent Literature 3 proposes a method for producing a
spheroidal graphite cast iron, wherein in the melting by using a
rotary furnace by utilizing a heat source such as a natural gas, a
liquefied petroleum gas or kerosene and pure oxygen, as a charge
material raw metal, steel scraps and return scraps or only steel
scraps are used, and an original molten metal obtained by
performing a Mn-removal melting in an oxidative combustion period,
and a molten metal preliminarily melted in another furnace and
regulated in components are combined by a molten-metal combining
device to produce the spheroidal graphite cast iron. In Example of
the method for producing the spheroidal graphite cast iron, a
material raw metal having mixing proportions of 60% of steel scraps
and 40% of return scraps was charged from a material charge inlet
into a rotary furnace, and 1.62% of silica sand and 0.30% of
limestone were sparged as a forming agent on the material raw
metal. It has been reported that the melting was performed while
the volume ratio of pure oxygen and natural (CH.sub.4) gas was
being regulated in a range from 1.95 to 2.10.
[0006] Patent Literature 4 proposes a method for removing
impurities in a molten cast iron, wherein the method is a method
for removing impurities containing manganese (Mn) while the
depletion of carbon (C) and silicon (Si) contained in a molten cast
iron preliminary melted is being suppressed; under the condition
that the temperature of the molten cast iron is maintained at
1250.degree. C. or higher and lower than 1500.degree. C., while the
aforementioned molten metal and an acidic slag layer are being
allowed to contact with each other, an excessive oxygen flame
having a theoretical combustion ratio of fuel and oxygen (amount
(volume) of oxygen.times.5/amount (volume) of fuel) of 1 to 1.5 is
directly exposed to the surface of the molten cast iron to overheat
the surface of the molten cast iron. The temperature of the molten
cast iron at the time of feeding the molten cast iron is preferably
lower than 1500.degree. C., and more preferably 1250.degree. C. or
higher and lower than 1500.degree. C. In such a temperature range,
the Mn removal treatment after the feeding of the molten cast iron
is made easy while the depletion of C or Si is being suppressed.
The excessive oxygen flame is considered to be preferably a flame
of a burner obtained by combusting LPG gas or LNG gas while feeding
oxygen in an amount excessive than the amount of oxygen necessary
for combustion. The excessive oxygen flame removes impurities while
directly exposing the molten metal surface to the flame and
allowing the rest of the molten metal surface to contact with the
acidic slag, without increasing the temperature of the whole molten
metal; thus, it is considered that the depletion of C or Si can be
made small while the oxidation removal of Mn is proceeding.
CITATION LIST
Patent Literature
[0007] [Patent Literature 1] Japanese Patent Laid-Open No.
2003-105420 [0008] [Patent Literature 2] Japanese Patent No.
4210603 [0009] [Patent Literature 3] Japanese Patent Laid-Open No.
7-268432 [0010] [Patent Literature 4] Japanese Patent Laid-Open No.
2011-153359
SUMMARY OF INVENTION
Technical Problem
[0011] The method for removing manganese described in Patent
Literature 1 or 2 uses a sulfide as a demanganese agent, requires
the amount of the sulfide to be a few percent in terms of percent
by mass, and suffers from a problem which is that a large amount of
a sulfur-containing slag is produced. The method described in
Patent Literature 2 gives a small increase of sulfur in the molten
cast iron; however, the sulfur content is increased to 0.02 to
0.03%, and hence the method concerned suffers from a problem which
is that desulfurization is required when the cast iron is used for
spheroidal graphite cast iron members.
[0012] On the other hand, the method for removing manganese
described in Patent Literature 3 or 4 is a method in which the
manganese contained in the cast iron is oxidized and removed as
slag, and accordingly has an advantage that the amount of the
produced slag is small. In particular, the method described in
Patent Literature 4, in contrast to the method described in Patent
Literature 3, uses no slag forming flux, and accordingly the amount
of the produced slag can be made small. However, the method for
treating manganese described in Patent Literature 3 or 4 requires a
combustible gas, and suffers from a problem that the method
concerned is not preferable at a site of work in hot
environment.
[0013] As a method for removing manganese of cast iron, in a
society emphasizing environmental conservation, a method producing
a large amount of slag and a sulfur-containing slag is not
preferable. In addition, the method for removing manganese of cast
iron is preferably a method requiring no combustible gas from the
viewpoints of handleability and work efficiency. The treatment
temperature in the removal of manganese of cast iron is preferably
as low as possible from the viewpoint of energy saving.
[0014] In view of such conventional problems and requirements, an
object of the present invention is to provide a method for removing
manganese of cast iron, not requiring a demanganese agent such as a
sulfide or a combustible gas in the removal of manganese of cast
iron, being small in the amount of the produced slag, being high in
the manganese removal efficiency, and allowing the work to be
performed safely.
Solution to Problem
[0015] The method for removing manganese of cast iron according to
the present invention is implemented by performing the removal of a
manganese component by allowing a furnace to be in an oxygen
atmosphere, and by blowing air into a molten cast iron in the
furnace, while a carbon component in the molten cast iron is being
maintained at an approximately constant amount.
[0016] Alternatively, the method for removing manganese of cast
iron according to the present invention is implemented by
performing the removal of the manganese component by allowing the
furnace to be in an oxygen atmosphere, and by stirring the molten
cast iron in the furnace, while the carbon component in the molten
cast iron is being maintained at an approximately constant
amount.
[0017] In the foregoing invention, the removal of the manganese
component can be performed while the amount of oxygen fed into the
furnace or/and the stirring speed of the molten cast iron in the
furnace are being regulated, and the carbon component in the molten
cast iron is being maintained at an approximately constant
amount.
[0018] In the foregoing invention, the removal of the manganese
component can also be performed while the ratio between the removal
rate of the silicon component and the removal rate of the manganese
component is being maintained at an approximately constant value,
and the removal of the manganese component can be performed while
the decrease of the silicon component is being suppressed.
[0019] In the foregoing invention, the removal of the manganese
component can also be performed while the temperature of the molten
cast iron is being maintained at an approximately constant value,
and the temperature of the molten cast iron can be set at
1400.degree. C. to 1200.degree. C.
Advantageous Effects of Invention
[0020] The method for removing manganese of cast iron of the
present invention provides a method for removing manganese, not
requiring a demanganese agent such as a sulfide or a combustible
gas, and being small in the amount of the produced slag, and can
remove manganese in a high efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a diagram illustrating the furnace used in the
test A of the present invention.
[0022] FIG. 2 is a diagram illustrating the furnace used in the
test B of the present invention.
[0023] FIG. 3 is a graph showing the test results of Example 1 in
the test A.
[0024] FIG. 4 is a graph showing the Mn residual rates of the test
A.
[0025] FIG. 5 is a graph showing the C residual rates of the test
A.
[0026] FIG. 6 is a graph showing the Si residual rates of the test
A.
[0027] FIG. 7 is a graph showing the temperatures of the molten
cast irons of the test A.
[0028] FIG. 8 is a graph showing the Mn residual rates of the test
B.
[0029] FIG. 9 is a graph showing the C residual rates of the test
B.
[0030] FIG. 10 is a graph showing the Si residual rates of the test
B.
[0031] FIG. 11 is a graph showing the temperatures of the molten
cast irons of the test B.
[0032] FIG. 12 is a graph showing the relation between the stirring
speed and the Mn removal rate of the test B.
[0033] FIG. 13 is a graph showing the Si/Mn decrease ratios.
DESCRIPTION OF EMBODIMENTS
[0034] Hereinafter, the embodiments of the present invention are
described. The method for removing manganese according to the
present invention is a method for removing manganese of cast iron
by allowing a furnace to be in an oxygen atmosphere, and by blowing
air into the molten cast iron to remove the manganese component
contained in the molten cast iron, wherein the method concerned is
implemented by performing the removal of the manganese component
while the carbon component in the molten cast iron is being
maintained at an approximately constant amount. In other words, the
present method for removing manganese performs the manganese
removal treatment by blowing air into the molten cast iron in the
furnace allowed to be in an oxygen atmosphere, and accordingly
belongs to an oxygen treatment method. In addition, the manganese
removal treatment is implemented by performing the removal of the
manganese component while the carbon component is maintained at a
constant amount.
[0035] In the present invention, for the feeding of oxygen, it is
important to allow the furnace to be in an oxygen atmosphere.
Although oxygen can be fed by bubbling with air, it is preferable
to feed oxygen by providing a dedicated unit capable of feeding
oxygen onto the surface of the molten cast iron in the furnace. In
the present invention, the method for feeding oxygen and the amount
of oxygen fed affects the effect of the manganese removal
treatment. In the present invention, by regulating the amount of
oxygen fed, the removal rate of the manganese component in the
molten cast iron, the temperature of the molten metal or the like
can be regulated.
[0036] The blowing of air into the molten cast iron expands the
reaction interface between the oxygen in the air blown into the
molten cast iron by the fluidization/stirring of the molten cast
iron and the oxygen fed into the furnace, and thus promotes the
oxidation of manganese. Accordingly, an inert gas is not
preferable. A mixed gas of air and oxygen is not preferable because
such a mixed gas causes oxidation/combustion. The degree of the
blowing of air into the molten cast iron is not required to have an
amount or strength to scatter the molten metal or the slag. In
other words, the blowing of air into the molten cast iron is not
required to be an intense bubbling.
[0037] The temperature of the molten metal in performing the
manganese removal treatment is favorably 1400.degree. C. or lower
for the purpose of suppressing the consumption of carbon in the
molten cast iron, and can be regulated to be 1350.degree. C. to
1175.degree. C. The temperature of the molten cast iron is
preferably as low as possible from the viewpoint of energy saving;
however, in consideration of the energy saving inclusive of the
successive steps, the temperature of the molten cast iron is
preferably 1350.degree. C. to 1200.degree. C. Specifically, this is
because the molten cast iron having been subjected to the removal
of Mn is increased in temperature to 1400 to 1550.degree. C., and
then used for casting or the like.
[0038] The furnace for treating the molten cast iron in the present
invention may be a tool having no heating unit by itself such as a
ladle, or alternatively, may be a furnace being capable of allowing
the furnace to be in an oxygen atmosphere and having an air feeding
unit capable of blowing air into the molten cast iron. For example,
such a ladle as shown in FIG. 1 can be used. In FIG. 1, a furnace
10 has a furnace body 11, a furnace lid 12, an air feeding unit 15
capable of blowing air into a molten cast iron 20, and an oxygen
feeding unit 16 capable of allowing the furnace 10 to be in an
oxygen atmosphere. In addition, the furnace 10 also has an
operation opening 12a for performing the taking out of a sample,
and an exhaust outlet 12b for discharging the gas generated during
the treatment operation.
[0039] As described above, in the method for removing manganese of
cast iron according to the present invention, by blowing air into
the molten cast iron in an oxygen atmosphere to subject the molten
cast iron to fluidization/stirring, the area of the reaction
interface between the molten cast iron and oxygen is expanded to
promote the oxidation of Mn. Such a method of subjecting the molten
cast iron to fluidization/stirring may be a method of directly
stirring the molten cast iron. Specifically, the furnace is allowed
to be in an oxygen atmosphere, then the molten cast iron in the
furnace is stirred, and thus the removal of the manganese component
can be performed while the carbon component in the molten cast iron
is being maintained at an approximately constant amount. Such a
method of directly stirring the molten cast iron has an advantage
of being relatively simple to control.
[0040] The method of directly stirring the molten cast iron is
small in the temperature decrease of the molten cast iron, and
allows the manganese component to be removed at an approximately
constant temperature while the carbon component in the molten cast
iron is being maintained at an approximately constant amount. In
addition, the method of directly stirring the molten cast iron can
regulate the removal rate of the manganese component in the molten
cast iron by regulating the stirring speed or the stirring force in
the stirring of the molten cast iron. Moreover, by regulating the
stirring speed or the stirring force in the stirring of the molten
cast iron, the molten cast iron can be maintained at an
approximately constant temperature, or can be increased in
temperature.
[0041] As described above, the present invention can perform an
efficient removal of the manganese component in the molten cast
iron, by allowing the furnace to be in an oxygen atmosphere, and by
regulating the amount of oxygen fed or/and the stirring speed or
the stirring force in the stirring of the molten cast iron. The
furnace 10 shown in FIG. 2 can implement the foregoing method of
performing the removal of the manganese component in the molten
cast iron by allowing the furnace to be in an oxygen atmosphere and
by stirring the molten cast iron in the furnace. The furnace 10 has
the furnace body 11, the furnace lid 12, a stirring unit 17 for
stirring the molten cast iron 20, and the oxygen feeding unit 16
capable of allowing the furnace 10 to be in an oxygen atmosphere.
In addition, the furnace 10 has the operation opening 12a for
performing the taking out of a sample, and the exhaust outlet 12b
for discharging the gas generated during the treatment operation.
The furnace 10 of the present example mechanically stirs the molten
cast iron 20 by the stirring unit 17 having a driving source such
as a motor; however, there may be adopted a furnace having a
stirring unit capable of stirring the molten cast iron on the basis
of an electromagnetic method involving a high frequency wave or the
like.
EXAMPLE 1
[0042] By using the furnace shown in FIG. 1, a manganese removal
test (test A) of a cast iron was performed. During the present
test, the measurement of the components of the molten cast iron was
performed for the specimens sampled at appropriate times from the
furnace by using an emission spectrophotometer (PDA-7020,
manufactured by Shimadzu Corp.). The temperature measurement of the
molten cast iron was performed by using an immersion type
thermocouple. The amount of the molten cast iron poured was set to
be 500 kg or 300 kg (only in Example 2). The oxygen feeding unit
for feeding oxygen used a burner capable of feeding only oxygen or
a mixed gas of oxygen and propane gas (LPG), or a sonic nozzle
capable of feeding oxygen at a supersonic speed. When only oxygen
was fed with a burner, the oxygen flow rate was 5 Nm.sup.3/h. When
oxygen was fed with a sonic nozzle, oxygen flow rate was 3
Nm.sup.3/h. The inner diameter of the gas feed opening of the
burner was approximately 15 mm, and the inner diameter of the gas
feed opening of the sonic nozzle was approximately 2 mm.
[0043] The test conditions of the test A are shown in Table 1. In
Table 1, the treatment time means the elapsed time after the start
of the manganese removal test in which the molten cast iron melted
in a cast iron melting furnace was poured into a preheated furnace.
In Example 1, the blowing of air into the molten cast iron was
performed at a flow rate of 200 L/min, and the feeding of oxygen
was first performed with a burner for 15 minutes, and then
successively performed with a sonic nozzle to an elapsed time of 34
minutes. In Example 2, only the blowing of air (400 L/min) was
performed. In Example 3, the blowing of air (200 L/min) and the
feeding of oxygen were performed. In Comparative Example 1, a mixed
gas of oxygen and LPG was fed with a burner, and the blowing of air
was first performed at a flow rate of 200 L/min for 21 minutes and
then successively performed at an increased flow rate of 400 L/min
to an elapsed time of 41 minutes. In Comparative Example 2, the
blowing of air (200 L/min) and the feeding of oxygen were
performed. In addition, for 15 minutes from the start of the test,
10 to 20 kg of charcoal was intermittently input in the furnace.
When charcoal was input, active flame was observed from the sample
input opening. It is to be noted that in Comparative Example 1, the
mixed gas of oxygen and LPG was an excessive oxygen gas in relation
to the theoretical combustion gas. When a sonic nozzle is used,
oxygen can be fed at an ultrafast speed (equal to or faster than
sonic speed). When the blowing of air was performed at a flow rate
of 400 L/min, fierce bubbling occurred, but when the blowing of air
was performed at a flow rate of 200 L/min, such fierce bubbling did
not occur.
TABLE-US-00001 TABLE 1 COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE 2
EXAMPLE 3 EXAMPLE 1 EXAMPLE 2 TREATMENT AIR AIR AIR AIR AIR TIME
OXYGEN L/ OXYGEN L/ OXYGEN L/ OXYGEN LPG L/ OXYGEN L/ min
Nm.sup.3/h min Nm.sup.3/h min Nm.sup.3/h min Nm.sup.3/h Nm.sup.3/h
min Nm.sup.3/h min 0 5 200 0 400 5 200 18 3 200 0 200 3 .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. 10 .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. .dwnarw. 24 4 .dwnarw. .dwnarw. .dwnarw. 15 .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. 17 3 .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 21 .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. 26 .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw.
400 .dwnarw. .dwnarw. 34 .dwnarw. .dwnarw. .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 35 .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. .dwnarw. .dwnarw. 40 .dwnarw. .dwnarw.
.dwnarw. .dwnarw. .dwnarw. 41 .dwnarw. .dwnarw. .dwnarw.
[0044] The results of the test A of Example 1 are shown in Table 2.
In Table 2, the contents of the components are given in percent by
mass, the residual components other than the components shown in
Table 2 are iron and inevitable impurities. For the components
other than foregoing manganese (Mn), carbon (C) and silicon (Si),
according to Table 2, the content of titanium (Ti) was 0.017% at
the beginning, was reduced to 0.008% after a treatment time of 34
minutes, and thus was reduced nearly by half. The content of
aluminum (Al) was reduced by approximately 20% after a treatment
time of 34 minutes, and the contents of chromium (Cr), boron (B)
and zinc (Zn) are seen to be reduced to some extents.
TABLE-US-00002 TABLE 2 TEMPERATURE TREATMENT OF TIME MOLTEN min
METAL.degree. C. Mn % C % Si % Cr % Ti % Al % B % Zn % 0 1257 0.896
3.82 2.40 0.07 0.017 0.019 0.0008 0.003 5 1218 0.837 3.88 2.36 0.07
0.017 0.018 0.0008 0.004 10 1197 0.783 3.88 2.31 0.07 0.016 0.017
0.0012 0.004 15 1181 0.700 3.83 2.21 0.07 0.013 0.016 0.0006 0.003
20 1152 0.631 3.90 2.17 0.06 0.010 0.015 0.0005 0.003 29 1159 0.584
3.91 2.09 0.06 0.009 0.015 0.0004 0.002 34 1181 0.538 3.87 2.02
0.06 0.008 0.015 0.0007 0.002
[0045] The results of Example 1 are shown in FIG. 3. In FIG. 3, the
abscissa represents the treatment time, and the ordinate represents
the residual rate of Mn, Si or C, or the temperature of the molten
metal. The residual rate means the rate of the residual content in
relation to the initial content of Mn, C or Si. According to FIG.
3, the residual rate of C falls within a range from 1.00 to 1.02,
and thus the content of C is maintained at an approximately
constant value falling within a variation range of 2% of the
initial content thereof. In contrast, the Mn residual rate curve is
a steep downward curve, and the residual rate of Mn after a
treatment time of 34 minutes is 0.6 (60% of the initial content),
showing that the amount of Mn is rapidly decreased. On the other
hand, the Si residual rate curve declines slowly, and the residual
rate of Si after a treatment time of 34 minutes is 0.84 (84% of the
initial content). In other words, in the present Example, Mn is
removed at a speed faster by a factor of 2 or more as compared with
Si. The temperature of the molten metal is gradually decreased from
the initial temperature of 1257.degree. C. to 1152.degree. C., then
gradually increased after an elapsed treatment time of 20 minutes,
and reached 1181.degree. C. after an elapsed treatment time of 34
minutes. This is understood that the effect of the sonic nozzle was
manifested.
[0046] The graphs in FIGS. 4 to 7 show the relations of the Mn
residual rate, the C residual rate, the Si residual rate and the
temperature of the molten metal with the treatment time in the
present test A. In FIGS. 4 to 6, the abscissa represents the
treatment time, and the ordinate represents the residual rate of
Mn, C or Si. In FIG. 7, the abscissa represents the treatment time,
and the ordinate represents the temperature of the molten metal. In
the Mn residual rate curve or the Si residual rate curve, the
gradient or the removal rate means the ratio of the amount of a
component removed per unit treatment time to the initial content
((residual rate a-residual rate b)/(treatment time b-treatment time
a)).
[0047] <Blowing of Combustion Gas>
[0048] Comparative Example 1 (symbol: .quadrature.) is a case where
a manganese removal test was performed in an excessive oxygen
furnace, by blowing LPG combustion gas to the surface of the molten
cast iron. Comparative Example 1 is an example of the case where
the amount of oxygen and the amount of LPG gas were increased after
an elapsed treatment time of 10 minutes, and the blowing of air
into the molten cast iron was also increased from 200 L/min to 400
L/min after an elapsed treatment time of 26 minutes. According to
FIG. 4, the gradient of the Mn residual rate curve of Comparative
Example 1 is smaller than the gradients of the Mn residual rate
curves of Examples 1 to 3, and the Mn removal rate of Comparative
Example 1 is approximately 80% of the Mn removal rates of Examples
1 to 3. According to FIG. 5, the removal of C is approximately 4%
at an elapsed treatment time of 40 minutes even under the condition
of an increased amount of air, showing that the removal of C
(consumption of C) is suppressed. The gradient of the Si residual
rate curve shown in FIG. 6 is the smallest until an elapsed
treatment time of 20 minutes, and the removal of Si is also
suppressed.
[0049] The effects of the increase of the amount of oxygen and the
increase of the amount of LPG gas are not manifested in the Mn
residual rate curves (FIG. 4), and also little manifested in the C
residual rate curves (FIG. 5) and in the Si residual rate curves
(FIG. 6). However, the temperature of the molten metal is increased
after an elapsed treatment time of 10 minutes, well corresponding
to the increase of the amount of oxygen and the increase of the
amount of LPG gas. On the other hand, the effect of the increase of
the amount of air is manifested in the Mn residual rate curves, and
is clearly manifested in the C residual rate curves and the Si
residual rate curves.
[0050] <Furnace Atmosphere>
[0051] Comparative Example 2 (symbol: .largecircle.) is a case
where the feeding of oxygen to the molten cast iron and the blowing
of air into the molten cast iron were the same as in Example 1 or
3, but the manganese removal test was performed under the condition
that charcoal was input in the furnace to alter the environment in
the furnace from the case of Example 1 or 3. As shown in FIG. 4,
the gradient of the Mn residual rate curve is most gentle, and the
Mn removal rate of Comparative Example 2 is approximately 40% of
the Mn removal rate of Example 1 or 3. According to the C residual
rate curves shown in FIG. 5, the carburization effect due to
charcoal is observed, but the amount of the residual C falls within
a variation range of 4% of the initial content. According to the Si
residual rate curve shown in FIG. 6, the Si residual rate is
highest, and even after an elapsed treatment time of 30 minutes,
the residual rate is 0.93. In other words, it is understood that
the furnace offers an environment unlikely to allow oxidation to
occur, and offers an environment suppressing the oxidation of Si.
According to the temperature curves of the molten metals shown in
FIG. 7, the increase of the temperature of the molten metal due to
the combustion of charcoal is not observed, the temperature curve
of the molten metal of Comparative Example 2 overlaps with the
temperature curve of the molten metal of Example 3. It is to be
noted that the straight line of indicator a shown in FIG. 4 and the
straight line of indicator a shown in FIG. 6 are the straight lines
having the same gradient. In other words, the Mn removal rate of
Comparative Example 2 shown in FIG. 4 is almost the same as the Si
removal rates of Examples 1 to 3 shown in FIG. 6.
EXAMPLE 2
[0052] By using the furnace shown in FIG. 2, a manganese removal
test (test B) of a cast iron was performed. The test was performed
by variously changing the oxygen feeding conditions or the stirring
conditions .sub.of the molten cast iron as shown in Table 3. In
Examples 4 to 6, the blowing of air at 200 L/min as well as the
feeding of oxygen was performed. The blowing of air was performed
by the same method as in Example 1 or 3 of the test A. In Examples
7 to 9, oxygen was fed at 20 Nm.sup.3/h from the start to the end
of the test, and stirring speed of the stirring unit 17 was
variously changed. For example, in Example 7, the stirring speed of
the stirring unit 17 was 200 rpm from the start to the end of the
test; in Example 8, the test was started at 100 rpm and the
stirring speed was increased to 200 rpm after an elapsed treatment
time of 11 minutes. In the present test, the measurement of the
components of the molten cast iron or the measurement of the
temperature of the molten cast iron was performed by using the same
emission spectrophotometer as in the case of the test A or by using
the same immersion type thermocouple as in the case of the test A,
respectively. The amount of the molten cast iron poured into the
furnace was set to be 500 kg.
TABLE-US-00003 TABLE 3 TREATMENT TIME min 0 7 11 15 16 29 OXYGEN
EXAMPLE # FEEDING RATE Nm.sup.3/h REMARKS EXAMPLE 4 50 20 .rarw. 10
AIR: 200 L/min EXAMPLE 5 15 .rarw. 20 .rarw. 25 AIR: 200 L/min
EXAMPLE 6 25 15 .rarw. .rarw. .rarw. 25 AIR: 200 L/min EXAMPLE 7 20
STIRRING: 200 rpm EXAMPLE 8 20 STIRRING: 100 to 200 (11 min)rpm
EXAMPLE 9 20 STIRRING: 150 to 250(20 min)rpm
[0053] The results of the test B are shown in FIGS. 8 to 11. FIG. 8
shows the Mn residual rates, FIG. 9 shows the C residual rates, and
FIG. 10 shows the Si residual rates; in each of these figures, the
abscissa represents the treatment time, and the ordinate represents
the residual rate of Mn, C or Si. In FIG. 11, the abscissa
represents the treatment time, and the ordinate represents the
temperature of the molten metal. The Mn residual rates shown in
FIG. 8 include the results of the test B as well as the results of
the test A of Examples 1 and 3. The straight line of indicator a
and the straight line of indicator b in FIG. 8 have the same
gradients as the gradients of the straight line of indicator a and
the straight line of indicator b shown in FIG. 6 or FIG. 10. The
gradients of the straight line of indicator a, the straight line of
indicator b, and the straight line of indicator c are 1:3.2:6.1
with reference to the gradient of the straight line of indicator
a.
[0054] According to FIG. 8, the Mn residual rates decrease
approximately along the straight line of indicator b or the
straight line of indicator c from the start of the treatment to an
elapsed treatment time of 10 to 20 minutes. The Mn residual rates
of Example 1, Example 3, Example 5 and Example 8 decrease along the
straight line of indicator b. The Mn residual rates of Example 4,
Example 6, Example 7 and Example 9 decrease along the straight line
of indicator c. The Mn residual rate curves of Example 5 and
Example 8 flex downward at an elapsed treatment time of 11 minutes,
and have forms different from the forms of the other Mn residual
rate curves.
[0055] According to FIG. 9, the C residual rates fall approximately
within a range from 1.02 to 0.96, and are approximately constant
values. In other words, the removal of C (decarburization) is
suppressed. According to FIG. 10, the Si residual rate of each of
Examples decreases approximately along the straight line of
indicator b. The Si residual rate of Example 5 decreases at first
along the straight line of indicator a, decreases rapidly after an
elapsed treatment time of 16 minutes, and decreases after an
elapsed treatment time of 25 minutes along the straight line of
indicator b. In the case of Example 9, the removal of Si most
proceeds. FIG. 11 shows that the treatment proceeds at a molten
metal temperature of 1410 to 1270.degree. C., the temperature
curves of the molten metals are generally raised midway of the
treatment, and the temperatures of the molten metals are
increased.
[0056] <Feeding of Oxygen>
[0057] Examples 1, 3 and 4 to 6 shown in FIG. 8 are the same as
each other with respect to the blowing of air at 200 L/min, but are
different from each other with respect to the amount of oxygen fed
or the feeding manner of oxygen. From the observation of these Mn
residual rate curves, it can be seen that the amount of oxygen fed
can regulate the Mn removal rate. Specifically, according to the Mn
residual rate curve of Example 4, the gradient is the largest until
an elapsed treatment time of 7 minutes in which a large amount of
oxygen (50 Nm.sup.3/h) was fed, and 30% of the initial Mn content
is removed at an elapsed treatment time of 12 minutes. It is
understood that a sufficient feeding of oxygen at the beginning was
effective. In the case of Example 5, due to the increase of the
feeding of oxygen from the initial flow rate of 15 Nm.sup.3/h to
the flow rate of 20 Nm.sup.3/h after an elapsed treatment time of
11 minutes, the Mn residual rate curve flexes after an elapsed
treatment time of 11 minutes, and thus a promotion of the removal
of Mn is observed.
[0058] The amounts of residual C of Examples 1, 3 and 4 to 6 fall
within a range from 1.02 to 0.97 according to FIGS. 5 and 9, and
are approximately constant values. The C residual rate is little
affected by the amount of oxygen fed and the feeding manner of
oxygen. On the other hand, FIGS. 6 and 10 show that the Si residual
rate is affected by the amount of oxygen fed and the feeding manner
of oxygen. Generally, when the amount of oxygen fed is small, the
Si residual rate decreases along the straight line of indicator a,
and when the amount of oxygen fed is large, the Si residual rate
decreases along the straight line of indicator b. The effect of the
variation of the amount of oxygen fed is well manifested in the
case of Example 5. Specifically, the Si residual rate decreases
along the straight line of indicator a when the feeding flow rate
of oxygen is 15 Nm.sup.3/h, and rapidly decreases when the feeding
flow rate of oxygen is increased to 20 Nm.sup.3/h. In addition, the
Si residual rate decreases along the straight line of indicator b
after an elapsed treatment time of 25 minutes. On the other hand,
in Example 4 where a large amount of oxygen (50 Nm.sup.3/h) was fed
at the beginning, and the amount of oxygen fed was drastically
decreased at an elapsed treatment time of 7 minutes (20 Nm.sup.3/h)
and at an elapsed treatment time of 15 minutes (10 Nm.sup.3/h), the
effect of such a variation of the feeding flow rate of oxygen is
little manifested in the Si residual rate curves, the C residual
rate curves and the temperature curves of the molten metals (FIGS.
9 to 11).
[0059] From a comparison of FIG. 7 with FIG. 11, the temperature of
the molten metal of Example 1 or 3 decreases by approximately
100.degree. C. during the treatment. In contrast, the decreases of
the temperatures of the molten metals of Examples 4 to 6 are small,
and the decrease of the temperature in Example 4 is 55.degree. C.
at maximum. It is understood that when the amount of oxygen fed is
equal to or larger than a predetermined amount (for example, 15
Nm.sup.3/h), the decrease of the temperature of the molten metal
due to the blowing of air into the molten metal can be suppressed.
As can be seen from FIG. 11, the increase of the amount of oxygen
tends to increase the temperature of the molten metal. In other
words, by regulating the amount of oxygen fed, the regulation of
the temperature of the molten metal can be performed.
[0060] <Stirring of Molten Metal>
[0061] As shown in Table 3, Examples 7, 8 and 9 are the tests in
which the oxygen feeding was performed at 20 Nm.sup.3/h, and the
stirring conditions of the molten cast iron were varied. Example 7
is the case where the test was performed at a stirring speed of 200
rpm. According to Example 7, Mn can be removed efficiently (FIG.
8), the decarburization is low (FIG. 9), the decrease of the
temperature of the molten metal is as small as approximately
20.degree. C., and the Mn removal can be performed at an
approximately constant temperature of the molten metal (FIG. 11).
In the case of Example 8, due to the increase of the stirring speed
from the initial speed of 100 rpm to 200 rpm after an elapsed
treatment time of 11 minutes, the Mn residual rate decreases
initially along the straight line of indicator b, but rapidly
decreases and decreases along the straight line of indicator c
after an elapsed treatment time of 18 minutes. In other words, it
is shown that by regulating the stirring speed of the molten metal,
the degree of the Mn removal can be regulated. According to FIG. 8,
the Mn residual rates of Examples 7 to 9 decrease linearly up to an
elapsed treatment time of 10 minutes. The relation between the
gradient (Mn removal rate) of the Mn residual rate curve and the
stirring speed is shown in FIG. 12. According to FIG. 12, a certain
relation is observed between the Mn removal rate and the stirring
speed. Accordingly, the degree of the removal of Mn can be
regulated by regulating the stirring speed of the molten metal on
the basis of FIG. 12.
[0062] According to FIG. 11, in Example 8, the temperature of the
molten metal increases after an elapsed treatment time of 15
minutes, and this well corresponds to the increase of the stirring
speed from 100 rpm to 200 rpm after an elapsed treatment time of 11
minutes. Example 9 is an example where the treatment was started at
a stirring speed of 150 rpm and the stirring speed was increased to
250 rpm after an elapsed treatment time of 20 minutes, the
temperature of the molten metal increases after an elapsed
treatment time of 20 minutes, and the effect of the alteration of
the stirring speed is clearly manifested. In the case of Example 9,
as shown in FIGS. 8 to 10, the effect of the alteration of the
stirring speed is little manifested in the Mn residual rate, the C
residual rate and the Si residual rate.
[0063] <Removal of Mn and Removal of Si>
[0064] According to FIG. 8, the Mn residual rates decrease along
the straight line of indicator b and the straight line of indicator
c. According to FIGS. 6 and 10, the Si residual rates decrease
along the straight line of indicator b and the straight line of
indicator c. The ratio between the gradient of the straight line of
indicator b and the gradient of the straight line of indicator c is
32/61 and hence approximately 1/2. In other words, the decrease
rate ratio is approximately 1/2.
[0065] FIG. 13 is a graph showing the relation between the Si/Mn
decrease ratio ((1.00-Si residual rate a)/(1.00-Mn residual rate
a)) at an elapsed treatment time of a and the treatment time.
According to FIG. 13, the Si/Mn decrease ratio of Example 7 is
approximately 0.5 and approximately constant. In other words, the
decrease rate of Si is 1/2 of the decrease rate of Mn. According to
FIG. 13, the Si/Mn decrease ratio of Example 9 is approximately 0.8
and approximately constant, but the Si/Mn decrease rate of Example
4 vibrates within a range from 0.1 to 0.7. The Si/Mn decrease ratio
of Example 6 increases approximately linearly within a range from
0.62 to 0.9. The Si/Mn decrease ratio of Example 8 increases
approximately linearly within a range from 0.01 to 0.5, and the
removal (consumption) of Si is suppressed.
[0066] In the method for removing manganese of molten cast iron,
preferably the degree of the removal of Si can be predicted in
relation to the removal of Mn. From such a viewpoint, the method of
Example 7 or 9 is preferable.
[0067] <Cr, Ti, Al, B and Zn>
[0068] The present invention can remove the metal components such
as Cr, Ti, Al, B and Zn. Table 4 shows the results obtained in
Example 5, and Table 5 shows the results obtained in Example 7. In
each of these tables, the time means the treatment time, and the
temperature means the temperature of the molten metal. The contents
of the respective components are given in percent by mass. From a
comparison between Table 4 and Table 5, B can be efficiently
removed in both of the case of Example 5 and the case of Example 7.
However, the removal of Zn is difficult in the case of Example 5
based on the blowing of air, and the removal of Cr and Al is
difficult in the case of Example 7 based on the stirring of the
molten metal. According to Example 5, a treatment of approximately
30 minutes can remove 40 to 50% of Cr, Ti or Al. According to
Example 7, a treatment of 15 minutes can remove 50 to 60% of Ti or
Zn.
TABLE-US-00004 TABLE 4 TIME min TEMPERATURE .degree. C. Cr % Ti %
Al % B % Zn % 0 -- 0.05 0.019 0.027 0.0007 0.003 4 -- 0.05 0.019
0.023 0.0007 0.003 11 1343 0.05 0.018 0.023 0.0005 0.002 16 1328
0.04 0.017 0.021 0.0004 0.002 21 1350 0.04 0.014 0.019 0.0002 0.002
26 1360 0.04 0.011 0.017 0 0.002 31 1377 0.03 0.009 0.016 0
0.002
TABLE-US-00005 TABLE 5 TIME min TEMPERATURE .degree. C. Cr % Ti %
Al % B % Zn % 0 1336 0.05 0.008 0.015 0.0002 0.0019 5 1329 0.05
0.007 0.014 0.0001 0.0014 10 1326 0.05 0.005 0.014 0 0.0009 15 1315
0.05 0.004 0.014 0 0.0007
REFERENCE SIGNS LIST
[0069] 10 furnace [0070] 11 furnace body [0071] 12 furnace lid
[0072] 15 air feeding unit [0073] 16 oxygen feeding unit [0074] 20
molten cast iron
* * * * *