Nathaniel M. ANACLET0.1)Hae-GeonLEEand Peter C. HAYES. Department of Mining and Metallurgical. Engineering, The University of aueensiand, Brisbane, ...
ISIJ Internationai,
Sulphur Partition saturated lron
33
(1
993), No.
5,
pp.
549~555
between CaO-SiO-Ce20 Slags and Carbon2
Nathaniel M. ANACLET0.1)Hae-GeonLEEand Peter C. Department of Mining and Metallurgical
1) Forme~ly postgraduate
Vol.
3
HAYES
Engineering, The University of aueensiand, Brisbane, aueensland. 4072, Australia. MSU-llT, Tibanga, Iligan City, Philippines.
Nowat
student.
(Received on November10. l992.• accepted in
final
form on February 25. 1993)
Aslag-metal
equilibrium study was carried out to investigate the effect of rare earth oxides on the sulphur between CaO-SiO,slags and carbon-saturated iron at 1500'C. The sulphur partition wasincreased with increase in Ce.03 concentration in the slag. The oxygen potential of the system was found to be controlled by the Fe-FeOequilibrium. Sulphide capacities of CaO-Si02-Ce=0,slags measuredin the present study agreed well with the values predicted by the optical basicity method, It was tentatively concluded that Ce20, decreases the activity coefficient of SiO, in the CaO-SiO.-Ce.03 slag. partition
iron; KEYWORDS:
steel;
slag;
sulphur;
equilibrium;
sulphide
partition;
capacity;
CaO-SiO,-Ce.03 system
rare
oxides;
earth
.
each
diameter and 50mm a graphite rod of 40 This allowed to equilibrate 5 different samples simultaneously.
Introduction
1.
Recently there has been an increasing demandof very 10w sulphur and phosphorus steels. In practice de-
2.2.
is carried sulphurisation out either in hot metal or during steelmaking/refining operations. The activity coefficient of sulphur is larger in pig iron than in steel. It is therefore prudent to perform substantial desulphurisation at the molten pig iron stage, particularly for steel grades which require vely low sulphur level, but would not be suitably refined with high sulphide capacity
A
1
Experimental
2.1.
Materials
Master
mm
were prepared by mixing appropriate weights of powdered CaO, Si02 and Ce02' The batch mixing ratios are shownin Table l. CaOwas prepared by calcinating calciurn carbonate of analytical grade at 800'C for 6h. Si02 and Ce02 Were dried at 300'C for 2h. Master alloys were prepared by melting electrolytic iron, high purity FeS and spectrographic grade carbon in a graphite crucible using a vacuuminduction furnance. The graphite crucible for equilibrium study wasprepared by drilling 5holes of II .5 diameter and 40 depth
LaCr03 resistance furnace was used. The
was controlled using a Eurotherm 818 programmablecontroller and the temperature variation at the uniform hot zone was maintained within 2'C. A type B thermocouple (Pt-60/.Rh/Pt-300/0Rh) was used to measure the system temperature. Figure I shows the schematic diagram of the experimental apparatus employed In the present study. The following procedure was followed in conducting slag-metal equilibration: (a) Four grams ofthe master alloy containing I wto/o Sand 2.5 grams of pelletized slag were placed in each
graphite hole. (b) graphite
A
lid
of the crucible.
was placed
to cover all the holes
(c) Ar gas, purified by passing through the copper turnings furnace at 450'C and the drierite column, was flown in the furnace at the flow rate of 500 ml/min. (d) The crucible was raised to the position where the prevailing temperature was OOO'C, and held for
l .5 h.
slags
mm
Procedure vertical
power input
slags such as calcium aluminate-based slags due to inclusion problems, etc. The sulphide capacities of various CaOSi02 based slags have been studied by many investigators.14) However, study on the sulphide capacity of CaO-Si02 slags containing rare earth oxides lacks. In the present work a slag-metal equilibrium study was carried out to investigate the effect of rare earth oxides on the sulphide capacity of CaO-Si02 slags equilibrated with carbon saturated lron at 500'C. 2.
in
length.
(e)
I
was
The crucible was then brought
into the uniform
hot zone.
Table
l.
'/*CaO/'1,Si02
mm
549
Mixing compositions of
slags.
oloCe02
l ,06
O, 2, 6, lO
l,13
O, 2, 6,
1.22
O, 2, 6,
10 10
C 1993 ISIJ
ISIJ International,
Vol.
for 3.5h: the (D The samples were equilibrated time'will choice of the equilibrium be explained in the section. subsequent (g) Thecrucible wasquickly pulled downto the lower temperature zone (1 OOO'C)and then taken out of the
33 (1993), No,
5
defined as o/oCa0/0/0Si02, was kept at 1.22, Ce203 addition (9.570/0) was madeto determine the effect on time. It was found that sulphur the equilibrium in all cases. The concentrations did not vary after in therefore was chosen as 3.5 time for equilibration the present study.
3h
furnace.
The chemical analysis of sulphur for both metal and was performed using the combustion analysis technique (LECO). The analysis for cerium and other elements was carried out by ICP-AESmethod.
h
(h)
Effect of Slag Composition on Sulphur Distribution
3.2.
slag
The effect of Ce203on the sulphur partition ratio defined by Eq. (1), was investigated using different
(L*),
slag
basicities.
Results and Discussion
3.
L.=(o/oS)/[o/oS]
Attainment of Equilibrium of experiment were carried out to determine A the time required to attain the slag-metal equilibrium in terms of sulphur distribution betweenthe slag and metal. Figure 2showsthe change of sulphur concentration with time in the metal and slag. The basicity of the slag (V), 3.1.
where,
series
7
(o/oS)
: sulphur concentration : sulphur concentration
As seen in partition against
4
ratio
4
9 5 8
defined by Eq.
(AL*(o/o)),
=(L.-L~)/L~ x 100
2
Observation hole
3
Water cooling
4 s
Oring seal
ii
12
I
Metal Cruciblo
3.3.
LaCr03 Resistance Fce.
10
Crucible support
11
Furnace Tube
12
Cooling water
13
Inert
Fig,
l,
Sulphide Capacity
Using the equilibrium data obtained for the sulphur between metal and slag, the sulphide capacity of CaO-Si02-Ce203slags can be calculated. The sul-
partition
phide capacity
gas outlet
is
defined as
C*
= (wto/o S)( Po,/ Ps2)
l/2
.(3) . . . .
. , , . . . . . . . . . . .
sulphide capacity, pressure of oxygen, Ps2 : Partial pressure of S2' In the gas-slag-metal system, the following
where, Cs : P02 :
15 Thermocouple
+
for
is
(Graphite)
14 Alumina rod support 15
more effective
is
clearly seen that, with the sulphur partition ratio. addition of samemolar quantity, Ce203is moreeffective than CaO.
(mullite)
4
.................(2)
5
Ce203 to determine which one
Slag
13
plotted
ratio sulphur partition at given Ce203 concentration, L' : sulphur partition ratio without Ce203. Addition of 1.83 molo/o of Ce203in the CaO-Si02 Slag (V= .22) increases the sulphur partition ratio by 53 olo, In Fig. a comparison has been madebetween CaOand
Graphite Lid
6 7 8 9
is
where, Ls : gas inlet
It
10
(2),
Ce203concentration. AL.(o/o)
1 Inert
in slag (wto/o),
in metal (wto/o). ratio increases Fig. 3, the sulphur partition with increase in Ce203concentration. This effect is more clearly seen in Fig. where the percent increase of sulphur [o/oS]
2
3
..........(1) ........
Schematic diagram of experimental apparatus.
Partial
gas dis-
10
~::~
~ ~ ,
1
-Metal (no Ce203) -Metal (with Ce203) -Slag (no Ce.03) -Slag (with Ce203)
~ =a)
c
8 ~
.1
aL IS ,cn CO
%CaO/%Si02 = 1.22
T= 1500'C
Fig.
2.
Changeof sulphur content
.ool
o
C 1993 ISIJ
50
1oo
150
20o
25o
Time (min) 550
3oo
in the
metal and slag with time.
ISIJ International,
1
Vol.
33 (1993), No,
5
%CaOl%Si02
l .06
D:
1.13 .22
I :
I
A:
T= 1500'C
o o
1 A
Jo
l
~ J
CO ~~s)
I
I
CO
Je
~:~s)
~
ll
l_L
Joeo
~~s
J~
%CaOl%Si02 = 1.06
T= 1500'C I
:CaO
o : Ce203
o
O.OIO
0.005
Mole fraction Frg.
of Ce203 addition
Effect
3.
(L.)
of
0.01
of
on sulphur
CaO-Si02slags.
5
O
O.02O
partition
Fig.
ratio
5.
:
I
l
D
~
Jco
D
Jco ll
~::s)
J~
D l
activity
1500'C.
O
Mole fraction Fig.
4.
tribution
O of
is
.020
Ce203
Percent increase in sulphur partition of Ce203in CaO-Si02slags.
reaction
o
O.O15
ratio
+ Q(wto/o) = CO(g)
by addition
1/2 S2(g) + Q(wto/o) = I/2 02(g) + ~(wto/o) AG~=-17907+26.3T, J5,6)
(
where, K4:
"/o
S]/ao)( Po./ Ps,)
(4) (5)
l/2
(6)
: activity ao : activity By combining Eqs.
C*
The actlvity studied recently
I
and (6),
= L*aoK4/fs
(7)
of sulphur in carbon saturated iron was
by Simeonov et
al.7)
By
.
....
.
..
. .
..
, .
................(9)
Rein et al.,9) the Si concentration in the carbon saturated iron in equilibrium with 550/0Ca0-45010Si02 (V= .22) is 16.5 o/o at 500'C. Figure shows however that the Si concentration is merely .18 o/o after reaction for 3.5h with the same slag composition, Under the present experimental conditions, therefore, the Si-Si02 reaction has not attained to the equilibrium state. FeO content in the slag mayalso be employed as a measure of the oxygen potential in the metal. The relevant
constant of reaction (4), coefficient of sulphur in metal, of oxygen.
(3)
J8)
...
to
equilibrium
,fs
.(8) . .
Assuming that the reaction has reached equilibrium and the COpressure prevailing inside the crucible is 1atm, the activity of oxygen in the metal is found to be 5.5 x l0~5 at the I wto/o standard state. If the whole system is under true equilibrium, the equilibrium oxygen potential in the metal calculated from ~i-Si02 or Fe-FeO equilibrium should be the sameas that calculated from C-COequilibrium. Silicon content in the metal was measured with the slags (V= I .22) at different Ce203 concentrations. The results are given in Fig. 6. According
at equilibrium:
K4= fs[wt
have
~
In order to calculate
AG~=2761.4-82.88T, 0.01
melt with
iron
in graphite crucibles, they coefficient of sulphur to be 6.92
C(gr)
O.OO5
of
ratio
CCO
Jco
I
partition
0.05 the sulphide capacity using Eq. (7), the oxygen activity prevailing in the system must be known. The equilibrium oxygen potential in the carbon saturated iron would ultimately be determined equilibrium. However, the distribution by the of sulphur between slag and metal maywell be related to the oxygen potentials associated with the two phase partitions of such elements as Si and Fe across the slagmetal interface. In the present study the graphite crucible was kept covered with a graphite lid during the experiments. The carbon-oxygen reaction in the system is then represented by at
~4 X
on sulphur
copper and carbon saturated
found the
A
T= 1500'C
O O
of fiux addition
CaO-CaF2-Si02Slags
1.06 1.13 1.22
I :
Effect
CaO-Si02slag. liquid
JL
o
O.
Flux addition (mole fraction)
%CaOl%Si02 D :
0.05
Ce203
equilibrating
551
1
I
6
C 1993 ISIJ
ISIJ International,
33 (1993), No.
Vol,
1.5
5
.3.5
%CaO/%Si02 = l.22
T = 1500'C
1.O
Ou,
g
40 l :
(1)S
Fe-FeO
D : C-CO
0.5
451.O
I
1J2
.1
%CaOl%Si02 Fig.
7.
oxygen rium, one for
o O
Mole fraction Fig.
6.
Silicon
equilibrium
Ce203
concentrations in metal after 3.5
Ce203contents
ent
of
condition
is
hafter
differ-
represented by Eq. (10).
= (FeO)
....................(lO)
10gKl0=6320/T-2.734,lo) ao = aF.o/aF.Klo
""-
..............(11)
""-""(12)
The activity of oxygen in the metal for the equilibrium of the reaction (10) can then be determined by Eq. (12), provided that the activities of FeOin the slag and Fe in the metal are known. Slags of different baslcities were analysed for the total Fe content. Prior to chemical
be 5.5 x
of
coefficient
FeOin CaO-Si02FeO
by extrapolating the data from Elliottl2) and found to be 4.3 at 500'C. According to the data by Elllottl2) the FeOiso-activity curves in the parallel the to CaO-Si02 CaO-Si02-FeOsystem become O. l). Therefore it line at low FeOconcentrations (aF.o is can be assumedthat the activity coefficient of FeO independent of the ratio of o/oCa0/010Si02 at low FeO concentrations. As the effect of Ce203on the FeOactivity is not known, it is assumedthat the activity coefficient of FeOis not affected by Ce203 the slag. E1-Kaddah and Robertsonl3) measured the activity of iron in the carbon saturated melt at 550'C. The value of 0.67 was obtained for the activity of iron by extrapolating their values to 500'C using regular solution assumption. The oxygen activity was then calculated using Eq. (12) and found to be .41 x l0~4. It is seen that there is one order of magnitude difference in the oxygen activity between
was obtained
1
IO
compositions investigated, Optical Basicity Sosinsky and Sommervillel5) have shownthat there
3.4.
m
1
an excellent correlationship
is
between optical basicity and
A
sulphide capacity of CaO-basedslags. numberof correlation equations have been proposed in the literaturel5~19) and equations for CaO-based slags are listed in Table 2. Duffy and Ingraham20) reported that the optical basicity of an oxide (AMO.) is related to the
1
I
C 1993 ISIJ
is
7
5~
activity
CCOreaction at activity in the metal will
If the
equilibrium, the oxygen ~ 5 as calculated earlier. If the Fe-FeOreaction is at partial equilibrium, on the other hand, the value of l.41 x lO4 should be the appropriate figure for the oxygen activity prevailing in the system. Figure shows the sulphide capacities calculated using different oxygen activities: one for Fe-FeOequilibrium and one for C-CO equilibrium. Results of Abrahamet al.2) are also included in the figure for comparison. The sulphide capacities calculated with assumption of FeFeO equilibrium show results excellent the with of Abrahamet agreement an a/.. Fruehan,11) Venkatradi et a!.10) and Chan and Omoril4) have also found that FeOcontent in the slag is a measure of the oxygen potential in the metal. It is concluded therefore that the oxygenpotential in the metal is controlled by the Fe-FeOreaction represented by Eq. (lO). The sulphide capacities for different slag compositions are given in Fig. 8. It is shown that addition of Ce203 increases the sulphide capacity for all slag partial
iron present in the slag was removed by magnetic separation to ensure that all Fe in the slag is in the form of FeO. The total Fe was found to be O.OI 0.005 wto/o. Existence of Fe3+ jn the slag was not checked, but assumednegligible because of the reducing condition prevailing in the present system. Chan and Fruehan,1 1) and Elliottl2) have reported that FeOin the slags deviates from ideal behaviour. The CaObased slag
calculated using
FeFeOequilib-
for
C-COor Fe-FeOreactlon,
analysis metallic
Henrian
one for
C-COequilibrium and for Fe-FeO This discrepancy together with low Si concentration in the metal indicates that the system is not under complete equilibrium. In other words the whole system is still on the way to t.he equilibrium state. The experimental results however show that the sulphur partition ratio becomesconstant after 3h. According to Eq. (7) the sulphur partition ratio varies only with oxygen activity for given slag compositions and temperature. It is concluded therefore in the that the oxygen activity metal becomesconstant after 3h and is controlled by partial equilibrium of a subsystem: this being either the values equilibrium.
in slag.
Fe + O(wto/o)
activities:
equilibrium. CCO
o.o2
O.O1
ofCaOSi02slags
Sulphide capacities different
A : Abraham2) T= 1500'C 1.3 1.4
552
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ISIJ
Vol.
5
33 (1993), No.
.3.25
-3.0
4 -3.eo
1
2
3
OcJ'
.3.5
O'
o
%CaO/%Si02
l
LA
Oco .3.75
I
o ~' 8.65
D : I
O
o.02
O.O1
of
Moie fraction
Sulphide capacities l 500'C.
8.
Fig.
9.
A T= 1500'C
425 Fig.
1.06 1.13 1,22
: :
of
Ce203
O.75
0.7O Optical basicity
%CaOl%Si02
400
:
A : T = 1500'C
o)
o
1,06 1,13 1.22
o :
Relationhisp
(A)
between sulphide capacity and optical
basicity:
solid lines represent the correlation
listed
Table
in
equations
2.
-3.0
CaOSi02-Ce203slags
at
.32
~ 8 1:'
Table
Correlations betweensulphide capacity and optical
2.
basicity
.3.4
CaO-basedslags.
for
7e
Correlation (1) (2) (3)
(4)
equations
II
.2 (1 500'C) log C, 12.3A = (1 500'C) log C, 12.6A 12.3 = log C, (22 690 54 640A)/T = + 43.6A - 25.2 log C, 14,2A 894/T- 7,55
Sosinsky
Tsao et
:L
Oc" -3.6
al. 17)
et al.1
A
AL
c" ~2
Duffy et al.16) Sommerville el
-9
=
o
Investigators
I
.3.8
a/. 18)
3.
4
!' .o
Pauling's electronegativity
CaO
Si02
l .O
1.8
Pauling's electronegativity
of oxides.21)
Ce203
.3.8
.3.6
(13).
3.5.
..........(13)
where,
A:
optical
basicity
of
'
'
Eq.
(2) in
Table
2
is
applied for
ThermodynamicConsiderations of Rare Earth Oxides in Slag
Slags are basically oxide solutions and the optical basicity of a slag is calculated using mole fractions and optical basicities of individual oxides: '
.3 .O
of the present study therefore strongly support the usefulness of the optical basicity method for predicting the sulphide capacity of metallurgical slags.
........
A= XMO*AMO* + XMO.AMO. +
.32
.3.4
measUred
Comparison of measured and calculated values of sulphide capacity: calculated values,
l .7
of the cation by Eq.
AMO*=0.74/(x-0.26)
10.
FeO
l.l
(x)
Fig.
1.06 1,13 1,22
:
A : T= 1500'C
5)
log Cs,
Table
%CaOl%Si02 D :
The stable form of cerium oxide in the slag is Ce203. This can be proved by thermodynamic considerations. The following data have been reported:
"-"-"(14)
2~~+3Q=Ce203(s) AG'= -613079 J at
slag,
xM0=: equivalent cation fraction of MOi. Pauling's electronegativity of various oxides involved in the present study are listed in Table 3. The measured sulphide capacities are plotted in Fig. against the optical basicities obtained from Eq. (14) for the slags investigated. The correlation equations listed in Table are superimposed in the figure for comparison. It is seen that the experimental results agree well with the correlation Eq. (2) suggested by Sommerville et al.17) The agreement is better depicted in Fig. 10 in which the measuredsulphide capacities are directly comparedwith those calculated using Eq. (2) in the Table 2. The results
Ce+20
Ce02(s)
Fromthese two
9
AG'=-306357J at
reactions,
.(15)
1600 C23)
.(16)
one can get
2Ce02(s)=Ce203(s)+Q AG'= -365
2
1600'C22)
J at 1600'C .(17)
K=(ac.,o,/a~.o,)ao = 1.02 at 1600'C .........(18) Using the oxygen activity of I .41 x 10~4, one can find
the activity ratio of ac.,o,/a~*0= being 100. This large value proves that Ce203is the stable oxide. In the rare steels, earth treated the sulphide precipitates as
7
553
C 1993 ISIJ
ISIJ International,
Vol.
33 (1993), No.
1
l 0~3
%C~O/%Si02(base) : l.06
ce203
T= 1500'C
ce202S
~~~
l 0~
o o
~~>*~
c~)
D : CaO I : Ce203
~~s
~ O
~ ~
O"'
~,
ce2S3
Q
0~5 l0~5
l
ce3S4
ceS
1
are
1.
Xsx)dXosx)2
o a, c
shown in
in silicon
(
,1'
J:
oo5 ~B' co
[%Si]/[%Sil'
o co
12.
Mole fraction change in
[o/oSi]
capaclty: for example, 1.83molo/o of Ce203 increases the sulphide capacity by about 50 "/o for the slag of basiclty of .22. Rare earth elements are however heavy:
O.o2
O.OI
Fractional
of
Ce203
and ("/~Si02)
I
after
Themolecular weight of Ce203being 328 comparedwith 56 for CaO. I .83 molo/. of Ce203is therefore equivalent to 9.57wto/o. Figure 13 shows the respective effects of CaO and Ce203 on the sulphide capacity of the CaO-Si02slag with the initial basicity of I .06. It is seen is that CaO moreeffective than Ce203in terms of weight
3.5h
of reaction.
Re202S.24) The predominance phase Fe-Ce-OSsystem reported by Fruehan23) given in Fig. Il Present experimental conditions shown
oxysulphide,
diagram for
percent basis.
.
Although the diagram is for the temperature of 1627'C thls also supports Ce202Sbeing a desulphurisation product. in the figure fall
in the
Ce202Sstable
area.
4.
Conclusions
A slag-metal
equilibrium study was carried out to the effect of rare earth oxides on the sulphur distribution between CaO-Si02 slag and carbonsaturated iron at 500'C. The results and findings are summarisedas follows: (1) Addition of Ce203in CaO-Si02slags increased
It is not knownhowthe rare earth oxides interact with other oxides such as CaOand Si02 in the slag. In the previous section it was reported that Si concentration in the metal after 3.5h of reaction differs with different Ce203concentration. Decrease in the Si concentratlon in the metal with increase in Ce203in the slag maybe due to decrease in either Si02 activity or mass transfer coefficient in the slag, depending on the rate controlllng mechanism. It was observed, although quantitative measurementswere not made, that the slag becamemore fluid by Ce203 addition. This observation implies that addition of Ce203gives a positive infiuence to the mass transfer in the slag. On the other hand, if the silicon reaction of Si02, transfer is limited by the interfacial decrease in Si concentration by increasing Ce203in the slag may be due to decrease in the activity of Si02' Addition of Ce203will dilute the slag. This dilution effect
C 1993 ISIJ
Applications
As seen in Fig. 5, the addition of rare earth oxides to CaO-Si02 slags Is effective in increasing the sulphide
T= 1500'C OO
Practical
3.6.
LL
is
addition on sulphide capacity,
Fig. 12 together with the fractional change concentration with Ce203addition in the slag. It is seen that decrease in Si concentratlon in the metal far exceeds that of Si02' This would imply that Ce203 strongly interacts with Si02 so that the actlvity coefficient of Si02 Is negatively influenced by Ce203in CaO-Si02Ce203slags. Cerlum in the metal might affect the silicon activlty of the metal. The Ce content in the metal was however found to be lower than the detection limit 0.001 wto/.). Therefore the influence of Ce on the Si activity would be negligible. Further study will be useful clarification of this system. for the quantitative
is
Fe-CeO-Ssystem
627'C:23) present experimental conditions indicated by the hatched area.
Fig.
Effect offlux
13.
O
(wt.91:oS)
Predominancephase diagram for at
Flux addition (wi,%)
Fig.
1Ooo
10~1
-2 10~2
as Il.
5
O
l 0~i 0~3 1 Fig.
5
investigate
1
the sulphur partition (2)
than
ratio.
on desulphurisation concentration, but CaOwas terms of molar
Ce203 was more effective
CaO
in
more effective in terms of weight percent. (3) The sulphide capacities of CaO-Si02Ce203 measuredin the present study agreed well with the values predicted by the optical basicity method: the relevant correlation equation at 1500'C is, log (4)
554
It
is
tentatively
C.= 12.6A -
12.3
.
concluded that Ce203decreases
ISIJ International.
the activity
coefficient
of Si02 in
Vol.
33 (1993), No.
CaO-Si02-Ce203
71.
l 2)
slags.
13)
l)
F. D. Richardson and Fincham: J. Iron Stee/ Insl., 178 (1954), 4. K. Abrahamand F. D. Richardson: J. Iron Steel Inst., 196 (1960),
4) 5)
6) 7)
8)
l O) l 1)
Y, Omori: Balst Furnace Phenomena and Modelling, ISIJ, (1987),
15)
D.
St. Pierre: Metall Trans. B, lOB (1979), 375. Z. Huangand G. R. St. Pierre: Proc. 3rd Intl. Sym. Metall. Slags Fluxes, TMS-AIME,(1988), 90.
l 6)
D. R. Stull and H. Prophet: JANAF,2nd, (1971). G. Sigworth and J. Elliott: Met. Sci., 8 (1974), 306. S. R. Simeonov, I. N. Ivanchev and A. V. Hainajiev: ISIJ Int,, 31 (1991), No, 12, 1396. G. Ferguson and R. J. Pomfret: Proc. 3rd Intl. Sym, Metall. Slags
18)
TMS-AIME,(1988),
R. H. Rein and
l
Sosinsky and
J.
J.
I,
D. Sommerville: Metall.
Trans. B,
17B
.
M. Ingram and I. D. Sommerville: J. Chem.Soc., Fraday 74 (1978), No. 6, 1410. D. Sommerville and D. J. Sosinsky: Proc. 2nd Intl. Sym. Metall. Duffy,
Trans.,
l 7) 19) 20) 21)
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