Note: Descriptions are shown in the official language in which they were submitted.
CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
METHOD FOR MANUFACTURING COMPOSITE DEOXIDIZER OF MOLTEN
STEEL AND THE COMPOSITE DEOXIDIZER B1' USING THE METHOD
THEREOF
The present invention relates to metallurgy and, in particular, the methods of
the
molten steel deoxidation and alloying with Aluminium and method for
manufacturing
composite deoxidizer of molten steel and the composite deoxidizer by using the
method
thereof.
One method is known, where the molten steel is treated with Fe-A1 alloy that
contain 40-50% AI. The Fe-A1 alloy's density has the value roughly 0.6 of the
molten
steel's density. That's why it's well mixed into the melt. It provides a good
level of its
assimilation into the melt with low level of waste. But the Fe-Al alloy is of
high price.
Besides it Fe-A1 alloy has a high melting point ( 1400-1500 ~C ). By the way
Aluminium
1:~ in the Fe-Al alloy has the form of inter-metallic compound Fe3A1 and FeAI.
Besides it
Fe-A1 alloy is slowly dissolved in the molten steel and during a long period
of time
Aluminium is distributed in the melt.
According to another known method, the molten steel is treated by pure
Aluminium.
Low melting point and low cost of the used Aluminium are the advantages of the
method. But pure Aluminium has a low density(value is about 0.33-0.37, if
compare to
the molten steel density). According to it aluminium is hardly mixed into the
melt with
the help of steel rod or steel weight. But in this case Aluminium losses are
substantially
high and non-stable. That is why the large drops of liquid Aluminium are
formed of
2:~ Aluminium pieces and ingots, and such drops are quickly come to the
surface and stunk
the slag.
The target of the present invention is to work out the method of molten steel
treating
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CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
by Aluminium where the listed disadvantages are eliminated and also the listed
advantages such as high density of Fe-Al, low-melting point and cheapness of
pure
Aluminium are kept.
Fig. 1 is a view shov~-ing the longitudinal section being cut after
manufacturing a composite deoxidizes.
Fig. 2a is a drawing illustrating a process in which composite deoxidizes is
dissolved, circulated in molten steel, according to the present invention.
Fig. 2b is a drawing illustrating Aluminium deoxidizes in molten steel
according to
a conventional art.
The method for manufacturing a composite deoxidizes includes several
processes;
pure aluminum having high-purity is dissolved in a furnace and thereafter a
metal
piece(metal reinforced component) having high melting point is inserted slowly
and
mixed in the molten steel.
1;p
Conventionally, an alloy is manufactured by adding the metal having low
melting point
to the molten metal having high melting point, whereas a composite deoxidizes
of the
present invention is developed by adding the metal(metal reinforced component)
having high melting point to the molten metal having low melting point. In the
present
invention, the materials added in the molten steel are one or more of REM(Rear
Earth
Metal), Fe, Ca, Si, Mg and Ti or the metal may be used in different
combination : as
pure one(AI), as double(Fe-Mn, Fe-Si, Fe-Al, Fe-Ti, Fe-Ce) and treble(Fe-Si-
Ca, Al-Si-
Ca and so on) and as more complex alloys. The composite deoxidizes made is
shown in
Fig. 1. The part of white color represents an Al-based and the part of black
color
2:p represents a metal piece including one or more of Fe, Ca, Si, Mg, Ti or
REM(Rear
Earth Metal).
According to the present invention there is provided a method of molten steel
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WO 01/51675 PCT/KR00/01017
treating with Aluminium. Wherein the Aluminium is placed in the melt together
with
the Iron-based Alloy, and wherein the Aluminium and Iron-based Alloy are put
into the
Melt in the form of Composite with initial density which value is not less
than 0.5, if
compare to the molten steel's density, and which contain Al, C, Si, Mn, Ti and
wherein
range of ingredients is as follows(% of mass):
A1 25-50
C 0.05-0.90
Si 0.05-1.50
Mn 0.15-I
.25
Fe the Rest,
by the way, the composite contains Aluminium as the matrix component and other
ingredients-in the from of Iron-based alloy and as the reinforced component
and by the
way aluminium Dissolution in the molten steel is realized by the continuous
increasing
of the composite relative density to the value of 1.00-1.05.
to
According to the present invention the process ensures the favorable
conditions for
the Aluminium dissolution in the molten steel. The treating of the molten
steel by the
composite, where the Aluminium is contained as an matrix component and the
initial
low-melting point are kept, provides its rapid dissolution in the melt. The
treating of the
molten steel by the composite, in which the lron-based alloy is as a
reinforcing
component, make its heavier as necessary. That is to say the increasing of
composite
density to the 0.4-0.70 if compare to the molten steel density. At such level
of density
the composite does not stick into the Slag and it is easily drawn into the
circulating melt
Flow and it is sunk into the molten steel.
2;~
During the molten steel treating by the AI-Fe alloy composite, firstly only
Aluminium is melted. The reinforcing component from Iron-based alloy is not
melted
until the full aluminium dissolution. That's why during the Aluminium
dissolution the
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composite density is continuously increased and at the moment of entire
Aluminium
dissolution it has the value 1.00-1.05 if compare to the molten steel's is
kept.
The reinforcing component from Iron-based alloy is melted after the Aluminium
dissolution. It's composition is similar to the molten steel's one. Because of
the
;p reinforced part of composite is easily mixed with the molten steel and
entirely
assimilated.
During the molten steel treating with Al-Fe-based alloy the composite pieces
are
disintegrated on the fragments because of the influence of convectional flows.
In its turn
these fragments are disintegrated on the smaller fragments.
Combination of the decreasing of the composite fragment's size and the
increasing
of the fragment's density provides more rapidly Aluminium dissolution into the
molten
steel and more even its distribution in the melt. It ensures the decrease of
the
Aluminium losses and stabilization of the steel deoxidation and alloying with
Aluminium.
If Aluminium part in the composite is in the limit 25-SO%, the most favorable
conditions for steel treatment are provided. If the aluminium part in the
composite is
lower, the cooling influence of the composite on the melt is become stronger
because of
the increasing of the reinforcing component part and necessity of the
increasing of the
composite expenses. The bigger part of the Aluminium in the composite the
lower its
density, worse its mixing into the melt and bigger Aluminium losses.
2~ Regulation of the C, Si, Mn, Mg, Ti, Fe content in the composite in the
listed limits
depends on the necessity of the reinforced component obtaining that is similar
by the
content to the treated steel content. By the way the molten steel treatment
with Al-Fe-
based alloy composite doesn't change its chemical composition.
CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
Fig. 2a is a drawing illustrating a process in which composite deoxidizer is
dissolved, circulated in molten steel, according to the present invention. As
shown in
Fig. 1, since the density of composite deoxidizer is above 0.4, it is higher
than the value
of density of 0.35 when adding pure Aluminium, that is, the composite
deoxidizer is
p fallen and then is risen when dissolving Aluminium, and the density of the
composite
deoxidizer is increased in proportion to the amount of the dissolved Aluminium
and it is
fallen. 'That is, Aluminium having low melting point is dissolved in the
molten steel, it
is risen by the convection flows. In the molten steel, since Aluminium is
dissolved
continuously, the density of the composite deoxidizer is increased and become
1.00-1.05, it is high. As a result, in the molten steel, the process of
dissolution of the
composite deoxidizer is represented roughly as a circle type and that is, the
dissolution
process is repeated up and down and the aluminium is uniformly dissolved and
deoxydized in the molten steel. In the convention art, as shown in Fig. 2b,
when putting
into Aluminium deoxidizer, since the density of it is low, it does not to be
put into
1:p deeply in the molten steel and it is to react chemically at the position
that is not deep at
the necessity from the surface of the molten steel and it is formed as slag
and rizen at
the surface of the molten steel. Accordingly, in the present invention, the
quality of steel
is superior to that of the conventional art, in particular, as the result of
laboratory, it is
manifested that the reacted deoxidizer do not affected the molten steel.
Example
Steel that content 0.25% C, 0.70% Mn, 0.25% Si, 0.02% S, 0.03% P is melted in
the electric-furnace and at the end it is deoxidized by Aluminium in the ladle
at the
moment of the output of the melt outside the furnace. The composite
deoxidizer, contain
2,~ the Aluminium is preliminarily obtained by the mixing of the carbon steel
with the
liquid aluminium. To compare steel is deoxidized by the listed method: the
loading of
the pure aluminium piece into the melt with steel weight. Quantity of the pure
aluminium and steel weight is appropriate to the expenses of the aluminium and
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CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
reinforced components.
Efficiency of the steel treatment methods is evaluated with the help of ratio
of the
aluminium losses.
Ratio of the aluminium expenses Kus;~,, is calculated by the formula:
K~"n,_ _ (Ahz" + Al,,)* 100/Al=o -__________ ( I )
Where A1~2,, : residual content of the aluminium in the steel, %;
Al;, : aluminium expenses on the linking of the dissolved oxygen in a
reaction.
?[Al] + 3[O] = Al=O;
Al"= ([O];~";,,~ - [O]~,wntual)*~2*27/~*16) _________-___ (2)
[O];~;,;;,, and [O]2,.zntual : the content of the dissolved oxygen in the
steel before and after
steel deoxidation by aluminium.
A1 ~- Aluminium expenses on the steel deoxidation; %.
Dissolved oxygen content is calculated as follows:
1:p 1g[%0] - e,;'[%O] = 1g a;, + ~;e~ R[%R], ____________ (3)
e,;' and a"'~ : parameters of the interaction of the oxygen with oxygen with
and the
component of the steel R.
a" : activity of the oxygen in the liquid steel, %.
The value of the 1g a,., was determined experimentally by the loading of the
electric-
chemical sensing element into the liquid steel. For measurement the sensor
from Zr0- +
17%Y,O; with electrode of the comparison M,, + M,., O, was used. In this case:
1g a" _ ?,685 - (10,087*E + 5,660)/T ------------ (4)
2;p Where E : measured value of the Electromotive force sensing element, mV;
T : temperature, K
Ratio of the aluminium losses is calculated by the formulae:
G
CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
~lo~seo 1 ~~ - ~usms
The ways of the steel treatment are shown in the table I and 2.
If the aluminium expenses for steel treatment are identical(0, 1 %), the Al-Fe
based alloy
composite expenses are higher 2-4 times than the pure aluminium's one because
of the
lower aluminium content in the composite.
Initial density of the Al-Fe based alloy composite is I .47-1.92 times higher
than
the pure aluminium's one. During the dissolution process its difference is
increased: at
the beginning of the dissolution its value is 1.52-2.04, at the end it can
reach the value
of 3.
By the way the ratio of aluminium expenses increases from 0.46 till 0.64-0.77,
it
means that it increased on 39-67%. Accordingly aluminium losses are decreased
from
54 till 23-36%.
l ;p
By this invention steel treatment by aluminium ensures its efficiency.
Increasing
by the way of improvement of the steel quality. The quality is improved by
deeper melt
deoxizing, more stable aluminium assimilation and decreasing of the aluminium
losses.
2;p
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CA 02391910 2002-05-15
WO 01/51675 PCT/KR00/01017
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