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Thermodynamic properties of NiCeO, NiCeOMn, NiCeOCu and NiCeOFe melts
Journal of the Less-Common
THERMODYNAMIC
Ni-Ce-0-Cu
Metals, 153 (1989) 43 - 49
PROPERTIES OF Ni-G-0,
AND Ni-C&O-Fe
43
Ni-Ce-0-Mn,
MELTS
GUO WEI, WANG CHANGZHEN and YANG LIZE Metallurgical Physicochemistry Shenyang (China)
Division, Northeast University of Technology,
(Received November 16,1988)
Summary The equilibrium constant of G-0 in molten nickel and the related interaction coefficient were determined experimentally and the following results obtained (at T = 1823 K): K = 1.12 X lo-” e$ = 0.033. In these experiments inductively coupled plasma (ICP) was used to determine the extremely low contents of the rare earth (RE) elements in the metal phase at equilibrium. In order to avoid errors caused by any partial inclusion of RE content of nonmetallic inclusions in the analytical results for the dissolved RE, the metal samples were electrolyzed in an organic electrolyte at low temperature and the dissolved rare earth contents determined by ICP. The oxygen activity in the melt was measured by solid electrolyte sensors made of CaZrOs(Y,Os) tube. The G-0 equilibrium constants in the systems Ni-Ce-0-Mn, Ni-Ce-0-Cu and Ni-G-O-Fe were determined and the interaction coefficients egen e$ and eg were determined to be -0.83, -0.92 and -0.20.
1. Introduction Rare earth additions to certain steels are reported to improve their workability as well as their chemical and physical properties [ 1 - 111. A series of previous investigations has shown that the rare earth elements had strong deoxidation and desulphurization effects, being able to change the size, shape, composition and distribution of sulphide inclusions. From these facts the same effects may be expected if rare earth is added to nickel and nickel alloys [ 12 - 141. The purpose of this investigation was to study the deoxidation of cerium in nickel melts and interaction coefficients of cerium with manganese, copper and iron in nickel melts. The Ni-Ce-0, Ni-Ce-0-Mn, Ni-Ce 0-Cu and Ni-G-O-Fe melts were studied at 1550 “C!. 0022-5088/89/$3.50
0 Elsevier Sequoia/Printed in The Netherlands
44
2. Experimental details
The nickel used in this experiment had a stated purity of 99.98 wt%. The impurities in the nickel metal are as follows: S 0.0005 wt%, P 0.002 wt%; Fe 0.0013 wt%; Al 0.00028 wt%; Si 0.00078%; C 0.002 wt%; 0 0.015 wt%. The purity of other materials are as follows: Fe 99.99%; Ce 99.99%; Cu 99.95%; Mn 99.95%. A thin sheet of CezOs was prepared on the internal surface of the CaO crucible by means of oxidizing metal cerium. In order to measure oxygen activity at high temperature and low oxygen pressure in nickel melts, we made solid electrolyte tubes of CaZr03(Y203). The reaction is expressed as the following cell: Mo(meta1 ceramic)
I [O]~i~CaZrO~(Y~O~~l~
CrzOs]Mo
In this temperature and pressure range, the electronic conductivity can be neglected. The oxygen activity in nickel melts was calculated from eqn. (1).
4EF ln Po,(Ni) = -
RT
+ In %(ref.j,
k
401 =
3.19 - (13683 - 10.08E)
(1) T in nickel melts, E is the voltage of the
where a[01 is the oxygen activity galvanic cell and T is the absolute temperature. The values of oxygen standard dissolved free energy in the nickel melts come from ref. 15. The standard free energy of formation of Cr*Os comes from ref. 16.
2.2. Apparatus A furnace with MoSi, heating elements was used to obtain the desired temperature. The temperature was regulated through an automatic controller and kept constant (3-l “C) for each experiment along a working zone of 6 cm. A PtRh~-PtRh~~ thermocouple was used to measure the tempe~t~e. Argon was purified using an oxygen pump, silica gel, P,05, molecular sieve and by magnesium chips at 520-540 “C. The e.m.f. was measured with a Keithley 610C solid state electrometer (1014 s2) and a high input impedance digital voltmeter. 2.3. Procedure In the dissolved equilibrium experiment, equilibrium was reached in about 2 h. The Ni-G-0-X system was operated as follows. 50 g pure nickel was put into CaO crucible (with a Cez03 liner); the furnace was then evacuated and filled with argon. At 1550 “C, a small piece of cerium wrapped in pure nickel was added into the molten nickel through the quartz tube and mixed with the molten nickel. A desired amount of “X” (which was Cu, Mn or Fe) was added into the molten nickel. After 2 h of deoxidation the product was removed and the oxygen activity in the molten nickel was measured with the solid electrolyte tube CaZr0,(Y,03). It took about
45
5-15 s to determine the oxygen activity. Then samples were taken with the quartz tube and quenched in water. The specimens were electrolyzed in an organic electrolyte which consisted of 1% LiCl, 5% (HOCH,CH2)3N and 94% CHsOH at low temperature (-20 “C). The dissolved cerium was determined by the inductively coupled plasma (ICP) method.
3. Results 3.1. Ni-Ce-0 system equilibrium The reaction of equilibrium G-0 in molten nickel is Cez03 = 2[Ce] + 3 [O]. The constant of equilibrium is expressed as follows: h = a&-a& = f&[%Ce12*a& If we assume that h’ = [%Ce12*a$ the constant
of equilibrium
becomes
k = k’f;, The relationship between lg 12’ and [%Ce] is represented as plots of lg{& [%Ce12> US. [%Ce] X lo2 in Fig. 1. When [%Ce] is very small, lg k’ becomes Ig k. The experimental results were treated by the linear regression method and the following results were obtained: lg k’ = -17.95
+ 17.2[%Ce]
and
lg k = -17.95.
The constant of equilibrium at 1550 “C is k = 1.12 X 10-l*. According to the standard free energy of formation of Ce,Os [3], the oxygen standard dissolved free energy in molten nickel and KCBx03, the cerium standard dissolved free energy in molten nickel at 1550 “C is calculated to be
IS
Fig. 1. Graph showing
the relationship
between
Ig h’ and %Ce.
46
Ce203(s) = 2Ce(l) + t 02(g) ;
02(g)
=
[OlNi
AG; = 424340 - 64.95T
AG; = -23270
Ce203(s) = 2[Ce]Ni + 3[O]Ni
+ 3.93T
AG: = 150700 (Cal)
(2) (3) (4)
From eqns. (2), (3) and (4), we obtain Ce(1) = [Ce],
AG”,, = -53460
(Cal)
In this experiment, elemental cerium was very dilute in molten nickel. According to Henry’s law, the coefficient of activity can be calculated [17] & = 1.0 x 10-4. ZiS AGo = RT ln(~~~‘~N~/lOO~~) Because the properties of nickel are similar to those of iron, the molten nickel which contained very dilute cerium could be considered a regular liquid. The interaction parameter and the activity coefficient can be exnressed by ei = -2 In y;, where t-g = -2 In & = 18.6 and eg = 0.036. 3.2. Ni-Ce-G-X system equilibrium For Ni-CeO-X, where X = Mn, Fe or Cu there was also the Ce-0 equilibrium to consider: Ce,Os = 2[Ce] + 3[0].
(5)
The constant of equ~ibrium is expressed as follows: h = a&*& = f&[%Ce]2*a& If we assume k’ = [%Ce]2*a& the constant of equilibrium becomes k = k’*f&
lgk=Igk’+21gfc,
Since lg fc, = lg fg: + lg fcoe+ lg f& = eEE[%Ce] + e&[%O] + $de[%X] eqn. (6) becomes lg k’ + 2e$$[%Ce] + 2e&[%O] = lg k - 2e&[%X] The eg was known, the e& was known from ref. 19 in which e$$ is-5.03, and the [%Ce] and [%O] are limiting values. ]2e$$[%Ce]( + 12e&[%O]I = 0.0044
41
In this experiment, neglected :
lg k’ was about
17.86,
so that egX[%Ce] and e& can be
lg 12’ = lg h - 2e& [ 5%,X]
(7)
in Figs. 2 - 4. The experiThe relationship of lg h’ and [WX] is represented mental results were treated by the linear regression method and are as follows: lg k’ = -17.96
+ 1.86[%Cu]
If f
0
0.J
0.2
0.1
0.J
ll4
[%Cul 2. Graph showing the relationship
between lg k’ and %Cu.
II-
lo:
.
.
--
I1-
aLs 0
I
0.1
a2
a3
a4
0.5
1%Hnl Fig. 3. Graph showing the relationship
between lg h’ and %Mn.
I
IS’ 0
I
0.2
Od
0.6
6.8
0.11
[%Fel Fig. 4. Graph showing the relationship
between lg k’ and %Fe.
48
lgk’=
-17.86
+ 1.65[%Mn]
lg k’ = -17.75
+ 0.40[%Fe]
When these equations are compared with ficients of Ce with Mn, Cu and Fe are . egt = -0.92,
eg
= -0.83,
eqn.
(7), the interaction
coef-
ez = -0.20.
4. Conclusions The activity of oxygen in molten nickel was measured with our own solid electrolyte tube of CaZrO,(Y,Os) used at high temperature and low oxygen pressure. The equilibrium constant for the reaction CezOS(s) = 2[Ce] + 3[0] at 1550 “C was determined to be k = 1.12 X 10-18. The standard dissolved free energy of cerium in molten nickel was calculated to coefficients of Th e interaction be AG& = -53460 (Cal) r& = 0.0001. Ce with Mn, Cu and Fe are ee = -0.83 e& = -0.32, e$$ = -0.92, ez = -0.42, e:E = -0.20 and e % = -0.077. Acknowledgment The project of China.
was supported
by the National
Natural Science Foundation
References 1 G. Kinne, A. F. Viohkarer and V. I. Yavojskij, Zzu. VUZ, Chernaya Metall., 5 (1963) 65. 2 W. A. Fisher and H. Bertram, Arch. Eisenhuettenwes., 44 (1973) 87,97. 3 D. Janke and W. A. Fischer, Arch. Eisenhuettenwes., 49 (1978) 425. 4 Wang Chenzhen, Wang Furhen, Du Yengmin and Zhang Xiaopin, Acta Metall. Sin., 16 (1980) 1,83. 5 G. Kinna, A. F. Vishkarev and V. I. Yavojskij, Zzv. VW?. Chernaya Metalb, 9 (1962) 92. 6 A. Vahed and D. A. R. Kay, Metall. Trans., 78 (1976) 375. 7 Han Qiyong, Liu Shiwei, Niu Honghing and Tan Zhiwei, Acta Metall. Sin., 18 (1982) 2. 8 J. Richerd, Mem. Sci. Rev. Metall., 59 (1962) 527,597. 9 F. C. Langenberg and J. Chipoman, Trans. AZME, 212 (1955) 290. 10 Han Qiyong, Dong Yu, Feng Xian, Xiang Chang Xian and Yang Shefu, Acta Metall. Sin., 20 (1984) A204. 11 Chen Dong, Hen Qingong, Xiang Changxian and Wang Tao, Acta Metall. Sin., 22 (1986) A156. 12 Wang Longme and Du Tieng, Trans. Iron Steel Inst. Beijing, 3 (1983) 30. 13 Wang Longme and Du Tieng, Acta Metall. Sin., 20 (1984) A287. 14 Wang Longme and Du Tieng, Acta Metall. Sin., 21 (1985) A249.
49
Arch. Eisenhuettenwes., 37 (1966) 43. Tetsu To Hagane 58 (1972) 1579. in G. Derge (ed.), Basic Open Hearth Steelmaking, New York,
15 W. A. Fischer and W. Ackermann, 16 K. Suzuki and K. Sambongi,
17 J. Chipman, 3rd edn., p. 640.
1964,
THERMODYNAMIC
Ni-Ce-0-Cu
Metals, 153 (1989) 43 - 49
PROPERTIES OF Ni-G-0,
AND Ni-C&O-Fe
43
Ni-Ce-0-Mn,
MELTS
GUO WEI, WANG CHANGZHEN and YANG LIZE Metallurgical Physicochemistry Shenyang (China)
Division, Northeast University of Technology,
(Received November 16,1988)
Summary The equilibrium constant of G-0 in molten nickel and the related interaction coefficient were determined experimentally and the following results obtained (at T = 1823 K): K = 1.12 X lo-” e$ = 0.033. In these experiments inductively coupled plasma (ICP) was used to determine the extremely low contents of the rare earth (RE) elements in the metal phase at equilibrium. In order to avoid errors caused by any partial inclusion of RE content of nonmetallic inclusions in the analytical results for the dissolved RE, the metal samples were electrolyzed in an organic electrolyte at low temperature and the dissolved rare earth contents determined by ICP. The oxygen activity in the melt was measured by solid electrolyte sensors made of CaZrOs(Y,Os) tube. The G-0 equilibrium constants in the systems Ni-Ce-0-Mn, Ni-Ce-0-Cu and Ni-G-O-Fe were determined and the interaction coefficients egen e$ and eg were determined to be -0.83, -0.92 and -0.20.
1. Introduction Rare earth additions to certain steels are reported to improve their workability as well as their chemical and physical properties [ 1 - 111. A series of previous investigations has shown that the rare earth elements had strong deoxidation and desulphurization effects, being able to change the size, shape, composition and distribution of sulphide inclusions. From these facts the same effects may be expected if rare earth is added to nickel and nickel alloys [ 12 - 141. The purpose of this investigation was to study the deoxidation of cerium in nickel melts and interaction coefficients of cerium with manganese, copper and iron in nickel melts. The Ni-Ce-0, Ni-Ce-0-Mn, Ni-Ce 0-Cu and Ni-G-O-Fe melts were studied at 1550 “C!. 0022-5088/89/$3.50
0 Elsevier Sequoia/Printed in The Netherlands
44
2. Experimental details
The nickel used in this experiment had a stated purity of 99.98 wt%. The impurities in the nickel metal are as follows: S 0.0005 wt%, P 0.002 wt%; Fe 0.0013 wt%; Al 0.00028 wt%; Si 0.00078%; C 0.002 wt%; 0 0.015 wt%. The purity of other materials are as follows: Fe 99.99%; Ce 99.99%; Cu 99.95%; Mn 99.95%. A thin sheet of CezOs was prepared on the internal surface of the CaO crucible by means of oxidizing metal cerium. In order to measure oxygen activity at high temperature and low oxygen pressure in nickel melts, we made solid electrolyte tubes of CaZr03(Y203). The reaction is expressed as the following cell: Mo(meta1 ceramic)
I [O]~i~CaZrO~(Y~O~~l~
CrzOs]Mo
In this temperature and pressure range, the electronic conductivity can be neglected. The oxygen activity in nickel melts was calculated from eqn. (1).
4EF ln Po,(Ni) = -
RT
+ In %(ref.j,
k
401 =
3.19 - (13683 - 10.08E)
(1) T in nickel melts, E is the voltage of the
where a[01 is the oxygen activity galvanic cell and T is the absolute temperature. The values of oxygen standard dissolved free energy in the nickel melts come from ref. 15. The standard free energy of formation of Cr*Os comes from ref. 16.
2.2. Apparatus A furnace with MoSi, heating elements was used to obtain the desired temperature. The temperature was regulated through an automatic controller and kept constant (3-l “C) for each experiment along a working zone of 6 cm. A PtRh~-PtRh~~ thermocouple was used to measure the tempe~t~e. Argon was purified using an oxygen pump, silica gel, P,05, molecular sieve and by magnesium chips at 520-540 “C. The e.m.f. was measured with a Keithley 610C solid state electrometer (1014 s2) and a high input impedance digital voltmeter. 2.3. Procedure In the dissolved equilibrium experiment, equilibrium was reached in about 2 h. The Ni-G-0-X system was operated as follows. 50 g pure nickel was put into CaO crucible (with a Cez03 liner); the furnace was then evacuated and filled with argon. At 1550 “C, a small piece of cerium wrapped in pure nickel was added into the molten nickel through the quartz tube and mixed with the molten nickel. A desired amount of “X” (which was Cu, Mn or Fe) was added into the molten nickel. After 2 h of deoxidation the product was removed and the oxygen activity in the molten nickel was measured with the solid electrolyte tube CaZr0,(Y,03). It took about
45
5-15 s to determine the oxygen activity. Then samples were taken with the quartz tube and quenched in water. The specimens were electrolyzed in an organic electrolyte which consisted of 1% LiCl, 5% (HOCH,CH2)3N and 94% CHsOH at low temperature (-20 “C). The dissolved cerium was determined by the inductively coupled plasma (ICP) method.
3. Results 3.1. Ni-Ce-0 system equilibrium The reaction of equilibrium G-0 in molten nickel is Cez03 = 2[Ce] + 3 [O]. The constant of equilibrium is expressed as follows: h = a&-a& = f&[%Ce12*a& If we assume that h’ = [%Ce12*a$ the constant
of equilibrium
becomes
k = k’f;, The relationship between lg 12’ and [%Ce] is represented as plots of lg{& [%Ce12> US. [%Ce] X lo2 in Fig. 1. When [%Ce] is very small, lg k’ becomes Ig k. The experimental results were treated by the linear regression method and the following results were obtained: lg k’ = -17.95
+ 17.2[%Ce]
and
lg k = -17.95.
The constant of equilibrium at 1550 “C is k = 1.12 X 10-l*. According to the standard free energy of formation of Ce,Os [3], the oxygen standard dissolved free energy in molten nickel and KCBx03, the cerium standard dissolved free energy in molten nickel at 1550 “C is calculated to be
IS
Fig. 1. Graph showing
the relationship
between
Ig h’ and %Ce.
46
Ce203(s) = 2Ce(l) + t 02(g) ;
02(g)
=
[OlNi
AG; = 424340 - 64.95T
AG; = -23270
Ce203(s) = 2[Ce]Ni + 3[O]Ni
+ 3.93T
AG: = 150700 (Cal)
(2) (3) (4)
From eqns. (2), (3) and (4), we obtain Ce(1) = [Ce],
AG”,, = -53460
(Cal)
In this experiment, elemental cerium was very dilute in molten nickel. According to Henry’s law, the coefficient of activity can be calculated [17] & = 1.0 x 10-4. ZiS AGo = RT ln(~~~‘~N~/lOO~~) Because the properties of nickel are similar to those of iron, the molten nickel which contained very dilute cerium could be considered a regular liquid. The interaction parameter and the activity coefficient can be exnressed by ei = -2 In y;, where t-g = -2 In & = 18.6 and eg = 0.036. 3.2. Ni-Ce-G-X system equilibrium For Ni-CeO-X, where X = Mn, Fe or Cu there was also the Ce-0 equilibrium to consider: Ce,Os = 2[Ce] + 3[0].
(5)
The constant of equ~ibrium is expressed as follows: h = a&*& = f&[%Ce]2*a& If we assume k’ = [%Ce]2*a& the constant of equilibrium becomes k = k’*f&
lgk=Igk’+21gfc,
Since lg fc, = lg fg: + lg fcoe+ lg f& = eEE[%Ce] + e&[%O] + $de[%X] eqn. (6) becomes lg k’ + 2e$$[%Ce] + 2e&[%O] = lg k - 2e&[%X] The eg was known, the e& was known from ref. 19 in which e$$ is-5.03, and the [%Ce] and [%O] are limiting values. ]2e$$[%Ce]( + 12e&[%O]I = 0.0044
41
In this experiment, neglected :
lg k’ was about
17.86,
so that egX[%Ce] and e& can be
lg 12’ = lg h - 2e& [ 5%,X]
(7)
in Figs. 2 - 4. The experiThe relationship of lg h’ and [WX] is represented mental results were treated by the linear regression method and are as follows: lg k’ = -17.96
+ 1.86[%Cu]
If f
0
0.J
0.2
0.1
0.J
ll4
[%Cul 2. Graph showing the relationship
between lg k’ and %Cu.
II-
lo:
.
.
--
I1-
aLs 0
I
0.1
a2
a3
a4
0.5
1%Hnl Fig. 3. Graph showing the relationship
between lg h’ and %Mn.
I
IS’ 0
I
0.2
Od
0.6
6.8
0.11
[%Fel Fig. 4. Graph showing the relationship
between lg k’ and %Fe.
48
lgk’=
-17.86
+ 1.65[%Mn]
lg k’ = -17.75
+ 0.40[%Fe]
When these equations are compared with ficients of Ce with Mn, Cu and Fe are . egt = -0.92,
eg
= -0.83,
eqn.
(7), the interaction
coef-
ez = -0.20.
4. Conclusions The activity of oxygen in molten nickel was measured with our own solid electrolyte tube of CaZrO,(Y,Os) used at high temperature and low oxygen pressure. The equilibrium constant for the reaction CezOS(s) = 2[Ce] + 3[0] at 1550 “C was determined to be k = 1.12 X 10-18. The standard dissolved free energy of cerium in molten nickel was calculated to coefficients of Th e interaction be AG& = -53460 (Cal) r& = 0.0001. Ce with Mn, Cu and Fe are ee = -0.83 e& = -0.32, e$$ = -0.92, ez = -0.42, e:E = -0.20 and e % = -0.077. Acknowledgment The project of China.
was supported
by the National
Natural Science Foundation
References 1 G. Kinne, A. F. Viohkarer and V. I. Yavojskij, Zzu. VUZ, Chernaya Metall., 5 (1963) 65. 2 W. A. Fisher and H. Bertram, Arch. Eisenhuettenwes., 44 (1973) 87,97. 3 D. Janke and W. A. Fischer, Arch. Eisenhuettenwes., 49 (1978) 425. 4 Wang Chenzhen, Wang Furhen, Du Yengmin and Zhang Xiaopin, Acta Metall. Sin., 16 (1980) 1,83. 5 G. Kinna, A. F. Vishkarev and V. I. Yavojskij, Zzv. VW?. Chernaya Metalb, 9 (1962) 92. 6 A. Vahed and D. A. R. Kay, Metall. Trans., 78 (1976) 375. 7 Han Qiyong, Liu Shiwei, Niu Honghing and Tan Zhiwei, Acta Metall. Sin., 18 (1982) 2. 8 J. Richerd, Mem. Sci. Rev. Metall., 59 (1962) 527,597. 9 F. C. Langenberg and J. Chipoman, Trans. AZME, 212 (1955) 290. 10 Han Qiyong, Dong Yu, Feng Xian, Xiang Chang Xian and Yang Shefu, Acta Metall. Sin., 20 (1984) A204. 11 Chen Dong, Hen Qingong, Xiang Changxian and Wang Tao, Acta Metall. Sin., 22 (1986) A156. 12 Wang Longme and Du Tieng, Trans. Iron Steel Inst. Beijing, 3 (1983) 30. 13 Wang Longme and Du Tieng, Acta Metall. Sin., 20 (1984) A287. 14 Wang Longme and Du Tieng, Acta Metall. Sin., 21 (1985) A249.
49
Arch. Eisenhuettenwes., 37 (1966) 43. Tetsu To Hagane 58 (1972) 1579. in G. Derge (ed.), Basic Open Hearth Steelmaking, New York,
15 W. A. Fischer and W. Ackermann, 16 K. Suzuki and K. Sambongi,
17 J. Chipman, 3rd edn., p. 640.
1964,