U.S. patent application number 16/345522 was filed with the patent office on 2019-10-10 for molten steel treatment device and molten steel treatment method using same.
This patent application is currently assigned to POSCO. The applicant listed for this patent is POSCO. Invention is credited to Wook KIM.
Application Number | 20190309380 16/345522 |
Document ID | / |
Family ID | 61071124 |
Filed Date | 2019-10-10 |
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United States Patent
Application |
20190309380 |
Kind Code |
A1 |
KIM; Wook |
October 10, 2019 |
MOLTEN STEEL TREATMENT DEVICE AND MOLTEN STEEL TREATMENT METHOD
USING SAME
Abstract
Provided is a molten steel treatment device and a molten steel
treatment method using same. The molten steel treatment method may
include: preparing slag on molten steel; contacting a first
electrode to at least a portion of the slag and a second electrode
to at least a portion of the molten steel; and polarizing the slag
by applying a voltage to the first electrode and the second
electrode, to easily remove inclusions and impurity elements in the
molten steel by controlling basicity and oxidation degree of the
slag without using separate additives.
Inventors: |
KIM; Wook; (Pohang-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POSCO |
Pohang-si |
|
KR |
|
|
Assignee: |
POSCO
Pohang-si
KR
|
Family ID: |
61071124 |
Appl. No.: |
16/345522 |
Filed: |
October 30, 2017 |
PCT Filed: |
October 30, 2017 |
PCT NO: |
PCT/KR2017/012101 |
371 Date: |
April 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21C 7/0075 20130101;
C21C 7/064 20130101; C21C 7/0087 20130101 |
International
Class: |
C21C 7/00 20060101
C21C007/00; C21C 7/064 20060101 C21C007/064 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 1, 2016 |
KR |
10-2016-0144377 |
Claims
1. A molten steel treatment device, which is used for ladle
refining, comprising: power supply module comprising a first
electrode, a second electrode, and an insulator provided between
the first electrode and the second electrode to electrically
separate the first electrode from the second electrode; and a power
unit connected to the power supply module, wherein the first
electrode has a plate shape having an area, the second electrode
vertically extends while passing through the first electrode, and
an insulator is provided between the first electrode and the second
electrode.
2. The molten steel treatment device of claim 1, wherein an
extension part, which has an area and is disposed in parallel to
the first electrode, is provided to a lower portion of the second
electrode an insulator is provided between the first electrode and
the second electrode.
3. The molten steel treatment device of claim 2, wherein the first
electrode comprises a material having a specific gravity less than
that of the slag provided on molten steel.
4. The molten steel treatment device of claim 3, wherein the first
electrode comprises graphite, and the second electrode comprises a
conductive refractory material containing Al.sub.2O.sub.3(MgO)--C
an insulator is provided between the first electrode and the second
electrode to space the first electrode from the second
electrode.
5. The molten steel treatment device of claim 1, wherein the power
supply module is installed on a ladle cover so that the first
electrode and a portion of the second electrode are inserted into a
ladle.
6. A molten steel treatment device, which is used for ladle
refining, comprising: a power supply module comprising a first
electrode, a second electrode, and an insulator provided between
the first electrode and the second electrode to electrically
separate the first electrode from the second electrode; and a power
unit connected to the power supply module, wherein each of the
first electrode and the second electrode has a plate shape having
an area, and the insulator has a length greater than a thickness of
slag provided on the molten steel.
7. The molten steel treatment device of claim 6, wherein the first
electrode comprises a material having a specific gravity less than
that of the slag provided on molten steel.
8. The molten steel treatment device of claim 7, wherein the second
electrode comprises a conductive refractory material containing
Al.sub.2O.sub.3(MgO)--C.
9. The molten steel treatment device of claim 6, wherein the power
supply module is installed on a ladle cover so that the first
electrode and a portion of the second electrode are inserted into a
ladle.
10. A molten steel treatment method comprising: preparing slag on
molten steel; contacting a first electrode to at least a portion of
the slag and a second electrode to at least a portion of the molten
steel; and polarizing the slag by applying a voltage to the first
electrode and the second electrode.
11. The molten steel treatment method of claim 10, wherein the
first electrode floats on the slag, and at least a portion of the
second electrode is dipped into the molten steel.
12. The molten steel treatment method of claim 11, wherein in the
polarizing of the slag, the first electrode is connected to a
positive electrode, and the second electrode is connected to a
negative electrode.
13. The molten steel treatment method of claim 12, wherein the
first electrode comprises graphite, and in the polarizing of the
slag, oxygen ions in the slag react with the first electrode and
are removed in a form of a CO gas.
14. The molten steel treatment method of claim 13, wherein Ca
elements in the slag are reduced by being introduced into the
molten steel.
15. The molten steel treatment method of claim 14, wherein the Ca
elements react with sulfur elements in the molten steel to produce
CaS.
16. The molten steel treatment method of claim 15, wherein the CaS
is collected to the slag.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a molten steel treatment
device and a molten steel treatment method using same, and more
particularly, to a molten steel treatment device capable of:
preventing reoxidation of molten steel by controlling an interface
reaction between molten steel and slag; and controlling elements of
the molten steel, and a molten steel treatment method using
same.
BACKGROUND ART
[0002] A ladle refining process warms molten steel by using slag,
prevents external impurities from being introduced into the molten
steel, and performs a refining reaction for removing impurities in
the molten steel through an interface reaction between the slag and
the molten steel. The above-described slag is made of a compound
oxide, and exists in the form of an ionic solution at an upper
portion of the molten steel in case of a ladle refining condition.
Main elements of the slag include a basic oxide such as CaO and
MgO, an acid oxide such as SiO.sub.2 and Al.sub.2O.sub.3, and a
neutral oxide such as FeO and MnO, and exist in ion states such as
Ca.sup.2+, Mg.sup.2+, SiO.sub.4.sup.-, AlO.sub.4.sup.-,
Fe.sup.2+/3+, Mn.sup.2+/3+, and O.sup.2- to maintain electrical
neutrality.
[0003] Inclusions and impurity elements in the molten steel may be
removed through an interface reaction between the slag and the
molten steel during the ladle refining, and, for this, the basicity
and oxidation degree of the slag may be controlled. Here, the
basicity represents a ratio of a basic oxide content with respect
to an acid oxide content, and high basicity is required for the
ladle refining. Also, the oxidation degree of the slag represents a
content of a neutral oxide such as FeO and MnO contained in the
slag. Also, as the oxidation degree of the slag increases, the slag
reacts with deoxidation elements in the molten steel to easily
produce inclusions, which is called as reoxidation by the slag.
[0004] As described above, a method for increasing the basicity of
the slag by inputting quicklime and decreasing the oxidation degree
of the slag by inputting slag deoxidizer having main elements of
aluminum and calcium carbonate to easily remove the inclusions and
impurity elements in the molten steel by using the slag in the
ladle refining. However, since production costs increases by using
additives such as quicklime and slag deoxidizer, and particularly,
in case of the slag deoxidizer, inclusions are generated due to the
inputted aluminum, an alternative technology is required.
[0005] Also, Ca elements are inputted in forms of metallic Ca,
Fe--Ca, and Ca--Si to prevent alumina inclusions in the molten
steel from having a low melting point and being glomerate and MnS
from being generated by sulfur (S) in the molten steel during
casting. However, Ca has a limitation of high volatility and
extremely low yield rate. Thus, although there is attempt for
supplying Ca by inputting pulverized quicklime (CaO), the
dissolution and dissociative reaction of quicklime are difficult,
and, since a yield rate is also low, the elements of molten steel
is hardly controlled.
PRIOR ART DOCUMENT
[0006] Japanese Laid-Open Patent No. 1994-128618A
DISCLOSURE OF THE INVENTION
Technical Problem
[0007] The present disclosure provides a molten steel treatment
device capable of: restricting reoxidation of molten steel by
generating an interface reaction between slag and molten steel; and
adjusting elements of the molten steel, and a molten steel
treatment method using same.
Technical Solution
[0008] In accordance with an exemplary embodiment, a molten steel
treatment device, which is used for ladle refining, includes: a
power supply module comprising a first electrode, a second
electrode, and an insulator provided between the first electrode
and the second electrode to electrically separate the first
electrode from the second electrode; and a power unit connected to
the power supply module. Here, the first electrode has a plate
shape having an area, the second electrode vertically extends while
passing through the first electrode, and an insulator is provided
between the first electrode and the second electrode.
[0009] An extension part, which has an area and is disposed in
parallel to the first electrode, may be provided to a lower portion
of the second electrode.
[0010] The first electrode may include a material having a specific
gravity less than that of the slag provided on molten steel.
[0011] The first electrode may include graphite.
[0012] The second electrode may include a conductive refractory
material containing Al.sub.2O.sub.3(MgO)--C.
[0013] The power supply module may be installed on a ladle cover so
that the first electrode and a portion of the second electrode are
inserted into a ladle.
[0014] In accordance with another exemplary embodiment, a molten
steel treatment device, which is used for ladle refining, includes:
a power supply module including a first electrode, a second
electrode, and an insulator provided between the first electrode
and the second electrode to electrically separate the first
electrode from the second electrode; and a power unit connected to
the power supply module. Here, each of the first electrode and the
second electrode has a plate shape having an area, and the
insulator has a length greater than a thickness of slag provided on
the molten steel. The first electrode may include a material having
a specific gravity less than that of the slag provided on molten
steel.
[0015] The first electrode may include graphite.
[0016] The second electrode may include a conductive refractory
material containing Al.sub.2O.sub.3(MgO)--C.
[0017] The power supply module may be installed on a ladle cover so
that the first electrode and a portion of the second electrode are
inserted into a ladle.
[0018] In accordance with another exemplary embodiment, a molten
steel treatment method includes: preparing slag on molten steel;
contacting a first electrode to at least a portion of the slag and
a second electrode to at least a portion of the molten steel; and
polarizing the slag by applying a voltage to the first electrode
and the second electrode.
[0019] The first electrode may float on the slag, and at least a
portion of the second electrode may be dipped into the molten
steel.
[0020] In the polarizing of the slag, the first electrode may be
connected to a positive electrode, and the second electrode may be
connected to a negative electrode.
[0021] The first electrode may include graphite, and in the
polarizing of the slag, oxygen ions in the slag may react with the
first electrode and be removed in a form of a CO gas.
[0022] Ca elements in the slag may be reduced by being introduced
into the molten steel.
[0023] The Ca elements may react with sulfur elements in the molten
steel to produce CaS.
[0024] The CaS may be collected to the slag.
Advantageous Effects
[0025] In accordance with the exemplary embodiment, the inclusions
and impurity elements in the molten steel may be easily removed by
controlling the basicity and the oxidation degree of the slag
without using separate additives. That is, as a current is supplied
to the slag and the molten steel to induce the polarization
phenomenon in the slag, the inclusions and impurity elements in the
molten steel may be collected to the slag through the ion-exchange
at the interface between the slag and the molten steel. Also, the
elements of the molten steel may be adjusted by introducing a
specific element of the slag into the molten steel even without
using separate additives.
[0026] Also, the cleanliness of the molten steel may be prevented
from being degraded due to the use of the additives, and the
production costs may be prevented from increasing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic view illustrating a molten steel
treatment device in accordance with an exemplary embodiment.
[0028] FIG. 2 is a view illustrating a modified example of a power
supply module.
[0029] FIGS. 3 and 4 are views illustrating a state in which the
power supply module is installed in a ladle.
[0030] FIG. 5 is a view illustrating a slag polarization phenomenon
generated in a process of treating molten steel in a molten steel
treatment method in accordance with an exemplary embodiment.
[0031] FIG. 6 is a schematic view illustrating an interface
reaction generated in the process of treating the molten steel in
the molten steel treatment method in accordance with an exemplary
embodiment.
[0032] FIG. 7 is a graph showing experimental results obtained by
controlling a concentration of sulfur in molten steel in the molten
steel treatment method in accordance with an exemplary
embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0033] Hereinafter, specific embodiments will be described in more
detail with reference to the accompanying drawings. The present
invention may, however, be embodied in different forms and should
not be construed as limited to the embodiments set forth herein.
Rather, these embodiments are provided so that this disclosure will
be thorough and complete, and will fully convey the scope of the
present invention to those skilled in the art. In the descriptions,
the same elements are denoted with the same reference numerals. In
the figures, the dimensions of layers and regions are exaggerated
for clarity of illustration. Like reference numerals refer to like
elements throughout.
[0034] FIG. 1 is a schematic view illustrating a molten steel
treatment device in accordance with an exemplary embodiment, FIG. 2
is a view illustrating a modified example of a power supply module,
and FIGS. 3 and 4 are views illustrating a state in which the power
supply module is installed in a ladle.
[0035] Referring to FIG. 1, the molten steel treatment device in
accordance with an exemplary embodiment may include: a power supply
module 100 including a first electrode 110 having an area for
covering at least a portion of a melting surface of molten steel
and a second electrode 120 electrically separated from the first
electrode 110 and vertically extending while passing through the
first electrode 110 so that at least a portion there of is dipped
into the molten steel; and a power unit 140 connected to the power
supply module 100. Here, the power supply module 100 may be
provided as one unit and include an insulator 130 disposed between
the first electrode 110 and the second electrode 120 to
electrically separate the first electrode 110 from the second
electrode 120.
[0036] The power supply module 100 may be installed to float on an
upper portion of the molten steel or installed to a structure such
as a ladle cover. In the former case, as illustrate in FIG. 3, the
power supply module 100 may be inserted to the upper portion of the
molten steel so that the first electrode 110 floats in an upper
portion of a slag and a portion of the second electrode 120 is
dipped into the molten steel. In the latter case, as illustrated in
FIG. 4, when the ladle 10, in which the molten steel is
accommodated, is covered by the ladle cover 12 by connecting the
power supply module 100 to the ladle cover 12, the first electrode
110 may be disposed on the upper portion of the slag, and a portion
of the second electrode 120 may be dipped into the molten
steel.
[0037] The first electrode 110 may extend in one direction to have
an area. For example, the first electrode 110 may have a circular
plate shape corresponding to the melting surface of the molten
steel. Alternatively, the first electrode 110 may have various
shapes. However, the first electrode 110 preferably has a shape
corresponding to the melting surface of the molten steel in order
to induce polarization over a wide area of the slag. Also, an
insertion hole 112 for installing the second electrode may be
defined in the first electrode 110. The insertion hole 112 may
vertically pass through the first electrode 110. For example, the
insertion hole 112 may be defined in a central portion of the first
electrode 110. This is for forming a balance of the first electrode
110 at the upper portion of the molten steel or the upper portion
of the slag to increase a contact surface with the slag when the
first electrode 110 is installed.
[0038] The first electrode 110 may be installed so that a bottom
surface thereof is contactable to a surface of the slag, to
provide, e.g., a current to the slag. Accordingly, the first
electrode 110 may be manufactured by using graphite, which has high
electrical conductivity, is low in melting loss, and is not reacted
with the slag. Here, when the power supply module 100 is inserted
to the ladle 10 without being connected to an additional structure,
since the first electrode 110 has to maintain a floating state at
the upper portion of the slag, the first electrode 110 is
preferably made of a material having a specific gravity less than
that of the slag.
[0039] The second electrode 120 may have a bar shape vertically
extending while passing through the first electrode 110. The second
electrode 120, which is for supplying a power to the molten steel,
may be made of a material, which has high electrical conductivity,
is low in melting loss, and is not reacted with molten steel. Here,
since the second electrode 120 is dipped into the molten steel,
which is greater in temperature than the slag, the second electrode
120 is preferably made of a refractory material having electrical
conductivity. For example, the second electrode 120 may be made of
a material of Al.sub.2O.sub.3(MgO)--C.
[0040] The insulator 130 may be disposed between the first
electrode 110 and the second electrode 120 to electrically separate
the first electrode 110 from the second electrode 120. Here, the
insulator 130 may have a hollow shape to accommodate the second
electrode 120 therein and have opened upper and lower portions to
expose the second electrode 120, thereby receiving a power and
supplying the power to the molten steel.
[0041] When the power supply module 100 is installed in the ladle,
the second electrode 120 may be disposed from the upper portion of
the slag to the molten steel while the first electrode 110 floats
at the upper portion of the slag. Accordingly, since the second
electrode 120 is necessarily electrically separated from the first
electrode 110 at least in an area in which the second electrode 120
passes through the slag, the insulator 130 preferably has a length
H greater than at least a thickness of the slag.
[0042] However, an exemplary embodiment is not limited to the
above-described structure of the power supply module 100. For
example, the power supply module 100 may have various structures
capable of supply a power to the slag and the molten steel. For
example, referring to (a) of FIG. 2, the second electrode 120 may
include an extension part 120a disposed in parallel to the first
electrode 110 at a lower portion of the second electrode 120 to
increase a contact area with the molten steel.
[0043] Alternatively, as illustrate in (b) of FIG. 2, the first
electrode 110 and the second electrode 120, each of which has an
area, may be vertically separated from each other. Here, the first
electrode 110 and the second electrode 120 may have the same area
as or an area similar to each other, and may be connected to each
other by the insulator 130. Here, the insulator 130 preferably has
a length, i.e., a spaced distance between the first electrode 110
and the second electrode 120, greater than the thickness of the
slag. Also, a plurality of through holes 122 may be defined in the
second electrode 120 to easily install the power supply module
100.
[0044] The power unit 140 may be electrically connected to the
power supply module 100, i.e., the first electrode 110 and the
second electrode 120, to provide a power such as a current or a
voltage. The power unit 140 may be installed in the ladle in which
the molten steel is accommodated or installed in a separate
treatment place.
[0045] Also, each of the first electrode 110 and the second
electrode 120 may be connected to the power unit 140 through a
line. The line may be made of carbon steel or stainless steel
covered by a heat dissipation sheath, and be stretchable so that
the power supply module 100 is vertically movable according to
variation of a molten steel amount in the ladle 10.
[0046] Hereinafter, a molten steel treatment method in accordance
with an exemplary embodiment will be described.
[0047] FIG. 5 is a view illustrating a slag polarization phenomenon
generated during treatment of molten steel as the molten steel
treatment method in accordance with an exemplary embodiment, and
FIG. 6 is a schematic view illustrating an interface reaction
generated during the treatment of the molten steel as the molten
steel treatment method in accordance with an exemplary
embodiment.
[0048] An exemplary embodiment may be applied after converter
refining before casting, e.g., during transferring molten steel
after secondary refining. The exemplary embodiment may control an
oxidation degree and basicity of the slag by applying a power to
the slag for inducing polarization. Accordingly, inclusions and
impurity elements in the molten steel may be picked-up and removed
into the slag through ion-exchange at an interface between the slag
and the molten steel, and elements of the molten steel may be
adjusted by introducing components, which are necessary for
adjustment of the elements of the molten steel, into the molten
steel from the slag.
[0049] When the molten steel, which is completed in converter
refining or secondary refining, is prepared, the power supply
module 100 is installed in the ladle in which molten steel M is
accommodated. Here, the first electrode 110 contacts a slag S
formed at an upper portion of the molten steel M, and a portion of
the second electrode 120, i.e., a lower portion thereof, is dipped
into the molten steel M.
[0050] When the power supply module 100 is installed, each of the
first electrode 110 and the second electrode 120 is connected to
the power unit 140 through a line. Here, when the power unit 140 is
installed in the ladle, a process of connecting the power supply
module 100 and the power unit 140 may be omitted.
[0051] Thereafter, a power is applied to the power supply module
100 through the power unit 140. Here, the power, e.g., voltage, may
be applied so that the first electrode 110 has a positive electrode
(+) and the second electrode 120 has a negative electrode (-). That
is, a surface of the slag, at which the first electrode 110 is
disposed, has a positive electrode, and the molten steel, into
which the second electrode 120 is dipped, has a negative electrode.
Also, a surface of the molten steel, which contacts the slag, may
be an interface between an electrode and an electrolyte.
[0052] Referring to FIGS. 5 and 6, when a voltage is applied from
the power unit 140 to each of the first electrode 110 and the
second electrode 120, ions, which are randomly distributed in the
slag, move to the first electrode 110 and the second electrode 120
according to polarities. Electric charges, which are charged by the
first electrode 110 and the second electrode 120, and ions, which
move to satisfy electrical neutrality, are collected at an
electrode interface, i.e., the interface between the slag and the
molten steel. Accordingly, as negative ions are collected at an
upper layer, at which the first electrode 110 is disposed, and
positive ions are collected at a lower layer, at which the second
electrode 120 is disposed, polarization is generated.
[0053] Here, MnO, CaO, and FeO, which are contained in the slag,
may be ionized into Mn.sup.2+/3+, Ca.sup.2+, and Fe.sup.2+/3+ ions
and free oxygen ions (O2.sup.-). The free oxygen ions (O2-) in the
slag may move to the first electrode 110 containing graphite to
generate an electrochemical reaction, thereby being removed in a
form of a CO gas. Also, electrons separated from the free oxygen
ions may be supplied to the molten steel through the power unit
140. Also, the Ca.sup.2+, Fe.sup.2+/3+, and Mn.sup.2+/3+ ions move
toward the molten steel, into which the second electrode 120 is
dipped, i.e., the interface between the slag and the molten steel.
The Ca.sup.2+, Fe.sup.2+/3+, and Mn.sup.2+/3+ ions, which move to
the interface between the slag and the molten steel, may be reduced
and dissolved by electrons, which are supplied to the molten steel,
and introduced into the molten steel in a form of Ca, Fe, and
Mn.
[0054] Through the above-described reaction, MnO and FeO, which
affect the oxidation degree of the slag, may be reduced to decrease
the oxidation degree of the slag. Also, Ca.sup.2+, which affects
the basicity of the slag, may be collected at the interface between
the slag and the molten steel, to selectively increase the basicity
at the lower layer of the slag, which contacts the molten steel.
Accordingly, inclusions such as Al.sub.2O.sub.3 in the molten steel
may be collected into the slag to reduce the inclusions in the
molten steel.
[0055] Also, Ca elements, which are introduced to the molten steel,
may react with sulfur elements in the molten steel to produce CaS.
That is, the Ca elements, which are introduced from the slag to the
molten steel, may serve as additives that are inputted to control
the sulfur elements in the molten steel. The CaS, which is
generated due to the introduction of the Ca elements, may be
collected to the slag, and a concentration of the sulfur elements
in the molten steel may decrease.
[0056] Hereinafter, an experimental example for verifying effects
acquired by inducing the polarization of the slag will be
described.
[0057] FIG. 7 is a graph showing an experimental result obtained by
controlling a concentration of sulfur in the molten steel in a
molten steel treatment method in accordance with an exemplary
embodiment.
[0058] Firstly, an experiment for verifying a reaction generated by
introducing the Ca element of the slag into the molten steel is
performed.
[0059] In the experiment, molten silver containing about 4 ppm of
Ca elements is used instead of the molten steel, and
CaO--SiO.sub.2--Al.sub.2O.sub.3--MgO slag is used.
[0060] In an experimental example 1, 50 g of molten silver (Ag) and
25 g of slag having basicity of 1 are inserted into a melting pot,
and maintained for five hours. Thereafter, a content of the Ca
element in the molten silver is measured.
[0061] In an experimental example 2, 50 g of molten silver (Ag) and
25 g of slag having basicity of 3.2 are inserted into a melting
pot, and a voltage of 5V is applied for five hours. Thereafter, the
content of the Ca element in the molten silver is measured.
[0062] In an experimental example 3, 50 g of molten silver (Ag) and
25 g of slag having basicity of 3.2 are inserted into a melting
pot, and a voltage of 10V is applied for five hours. Thereafter,
the content of the Ca element in the molten silver is measured.
[0063] Results measured in the experimental examples are shown in
table 1 below.
TABLE-US-00001 TABLE 1 Ag (g)/ Applied Slag (g) Basicity voltage
(V) Ca [ppm] Ca [g] Experimental 50/25 1.0 0 9 0.00045 example 1
Experimental 50/25 3.2 5 100 0.005 example 2 Experimental 50/25 3.2
10 200 0.010 example 3
[0064] When the table 1 is reviewed, in case of the experimental
example 1 without forming the polarization in the slag, it may be
seen that a slight amount of Ca elements in the slag is introduced
into the molten silver.
[0065] On the other hand, in case of the experimental examples 2
and 3 with forming the polarization in the slag by applying a
voltage thereto, it may be seen that a quite great amount of Ca
elements are introduced into the molten silver in consideration of
an initial amount of Ca elements contained in the molten silver.
Also, when a magnitude of a voltage applied to the slag is greater
under the same condition, it may be seen that an introduced amount
of Ca elements increases.
[0066] Secondly, an experiment for verifying an effect, in which Ca
elements, which are introduced into the molten steel through the
polarization of the slag, control sulfur elements in the molten
steel, is performed.
[0067] The molten steel containing about 80 ppm of sulfur elements
and the CaO--SiO.sub.2--Al.sub.2O.sub.3--MgO slag having basicity
of 3.2 are inserted into a melting pot, and a power supply module
is installed in the melting pot. Also, a power is maintained as it
is without being applied to the power supply module at the
beginning of the insertion, and then a voltage of 10V is applied
during 220 minutes from a time when 175 minutes elapses (395
minutes after the insertion). Also, the concentration of the sulfur
in the molten steel is measured for 500 minutes from the time when
the molten steel and the slag are inserted into the melting pot,
and the measured values are recorded in FIG. 7.
[0068] Referring to FIG. 7, the concentration of the sulfur in the
molten steel gently decreases before a voltage is applied to the
power supply module from the time when the molten steel and the
slag are inserted into the melting pot. However, when a voltage is
applied to the power supply module, the concentration of the sulfur
in the molten steel sharply decreases, and then increases again
when time when about 200 minutes elapses after the voltage is
applied. Also, when the voltage applied to the power supply module
is blocked, the concentration of the sulfur in the molten steel
sharply increases again.
[0069] At the beginning of the insertion, as the Ca elements in the
slag are introduced into the molten steel by an interface reaction
between the molten steel and the slag, the concentration of the
sulfur in the molten steel gently decreases. However, when the
voltage is applied to the power supply module, Ca ions are
collected to the interface between the slag and the molten steel
due to the polarization of the slag. Due to this, the introduction
amount of the Ca elements increases, and the concentration of the
sulfur in the molten steel remarkably decreases. Also, when the
voltage supplied to the power supply module is blocked, as the
ions, which have moved around an electrode, randomly move again,
re-sulfurization is generated, and the concentration of the sulfur
in the molten steel remarkably increases.
[0070] Through the above-described experiments, it may be seen that
inclusions and impurity materials in the molten steel may be
removed, and element adjustment may be performed without inputting
separate additives by controlling the oxidation degree and the
basicity of the slag such that the slag is polarized by applying a
voltage to the slag and the molten steel during the ladle
refining.
[0071] Although embodiments have been described with reference to a
number of illustrative embodiments thereof, the embodiments are not
limited to the foregoing embodiments, and thus, it should be
understood that numerous other modifications and embodiments can be
devised by those skilled in the art that will fall within the
spirit and scope of the principles of this disclosure. Hence, the
real protective scope of the present invention shall be determined
by the technical scope of the accompanying claims.
INDUSTRIAL APPLICABILITY
[0072] The molten steel treatment device and the molten steel
treatment method using same in accordance with an exemplary
embodiment may easily remove the inclusions and impurity elements
in the molten steel by controlling the basicity and oxidation
degree of the slag without using separate additives. Thus, the
degradation in the cleanliness of the molten steel due to usage of
the additives may be prevented, and the increase in production
costs due to purchase of the additives may be prevented.
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