Viscosity Measurements of Molten Slag*

- Properties of Slag at Elevated Tetnperature (Part 1)-

By Makoto K ATO** and SIlSlltnll MINO WA**

Synopsis

Viscosiry and densiry of liquid slag were measured with J;latinum-ball­

and-balance viscometer. T he systems studied were a temalY system of

CaO-S iO,- AI 20 3 and a quaterntlly system of CaO-SiOc AI 20 3 con­

taining other oxides, fluorides, and chlorides. The relatioll between the

viscosiry and densiry was disc1lssed.

1. Introduction

In order to understand the structure of liq uid slag, the viscosity measurement of slag is one of the impor­tant measurements, a nd a lso the viscosity data are necessary for the improvement of opera tion of iron­a nd steel-m a king. Many investigations on the viscos­ity of slags were reported ,1l - 25) but there is a few studies on the relationship of the viscosity with the o ther pro­perties (density, surface tension, clec tri ca l conductivity, etc. ) in the sam e composition slags . In this study, the viscosity of slag composed from CaO- SiOz- Alz03 ter­nary sys tem was measured and the effect of a dditions on the properties of this sys tem was examincd . The viscosity of liq uid slags was measured by the balance­pla tinum sph ere viscometer and the density was ca l­culated from the buoyancy of the sphere in the melts.

I f the detecting parts of apparatus are made of g ra ph ite, the properties of slags may be changed by suspension of Aaky carbon in slags or by the chemical reaction between slags and carbon. 9 ) - Il) Therefore, the detecting parts made of platinum were used in this work and the properties were m easured under the carbon fr ee condition.

II. Experimental

1. Apparatus and M ethods

The bala nce- platinum sph ere viscometer shown III

Fig. I was U3ed in a ir. The viscosity coefficient (7J) is g iven by the expression ( I ) .

7J = KW(T 1 - T z) .. . ... .. . . ... . ....... (1)

where, K: appa ra tus constant W: weight necessary to rise the sphere through the

liquid T , : time necessary to rise the sphere by 10 mm in the

liquid by weight W T 2 : time necessary to ri se the sphere by 10 mm in a ir

by weight W.

K is d etermined experimenta lly with the rela tion ( I) by the measurements of time, using the viscosity

CD @ @

@

® @ (J)

@

®

-- -----(j) ®

_--...1

,/ .1.// ///,//,,,./, .,,1,. ,

Scale @) Beam ho lder Rider bar ® Beam res t @ Rest handle Scale for weight (W) @ P t wire (0.2 mm¢) @) H eat shield

Pt sphere (8 mmsb)

®

,-

Pt crucible (45 mm i.d. ,

55 mm h) Alumina crucible

Pt-Pt.Rh (1300 )

thermocouple E lema furnace Pt wire for grounding of Pt crucible

Fig. I. Apparatus for viscos ity measurement

standard solut ion OS 200, JS I 000 which are author­ized by the N RLM) and caster o il a t room temper­atures, and fused borax a t elevated temperature, a ll with known viscosity. Temperature is measured with Pt-Pt.Rh (13%) thermocouple which is immersed in slag without a protecting tube and is controlled within 3°C by changing the tap of tra nsformer. Time was measured repeatedly at the same balance weight and the mean value of the times is adopted to T. The 7J is determined from th e mean value wh ich was obtained under various weights a t the constant tem­p era ture.

Density of molten slag is also measured with the same a pparatus. Based on the Archimedian principle, the d ensity (p) is given by the expression (2) with measure­ments of buoyancy of the platinum sphere.

* Presented at the 70th and 7 1st ISf] M eetings, October, 1965 in Kita-Kyushu a nd April, 1966 in Tokyo, resp ec tively. M anuscript received ]une 6, 1968.

** The Government Industria l R esearch Institute (Nagoya), Hirate-cho, Kita-ku, Nagoya 462.

Research Article ( 31 )

[ 32 ) Transactions ISIJ, Vol. 9, 1969

p = W'JV .... . . .. .. ............ (2)

where, 11j!': buoyancy of platinum sphere, (g) V : volume of sphere corrected by the thermal vo lume

expansion coefficient, (cm 3).

2. Slag

Number 14 in Fig. 3 is the mother slag and the various slags were remelted after mixing additive reagent in a platinum crucible. The viscosity of slags was measured, successively.

3. Preliminary Afeasllrements

With the balance- sphere viscometer, the accurate measurements could be done at the viscosity range of 101.5 to 105 poises, but be low several poises the ob­tained results are less accurate. Therefore, to de­termine the d egree of experimenta l errors, the slags below several poises were synthesized from the chemi­call y pure reagents and the v iscosity was measured. The temperature dependence of the viscosity is shown in Fig. 2. Though the extent of errors of r; m easured at the constant temperature is l"ather large below about five poises, the reproducibility is of degree of about 15% . The r; of CaO- Si02- AI20 3 system is well in agreement with the data after Machin and Yee.12)

Therefore, the experimental errors with the balance­sphere viscometer seem sm a ll even to measure th e viscosity of slag with less than several poises, when the r; is determined from the average of several measure­ments.

I (O C )

1500 1400 1300 1200 300

I 100 / .

/ 70 7 50 .- ?-'"

~~ ~

~ 30 'i'''-' ", . -

'" ?-'" ()

0 c. 'i'''''' ~

6.0 6.5 7.0

10' · liT O F K )

o By M achin and Yee12)

Fig. 2. Influence of Na20 and Na2SiF. addition on the viscosity of CaO(41 )-Si0 2(48)- AI 20 3 (11) slag

III. R esults and Discussion

1. CaO- Si02- AI20 a Ternary System

Figure 3 shows the temperature dependence of r; of slag. The content of one component was changed a t the constant ratio of the other two components. The gradient of lines of the relation between log r; and l i T is remarkably changed by the tempera ture range. At

Research Article

6.0

104·1/T (1/ oK )

6.5

No. Constant ratio Changed component

9

10

11

12

13

NA1 ,O, = 0.141

0.205

0.238

N S iO , = 0.514

0.417

14 N Cao = 0.473, NSiO , = 0.443, NAI ,O, = 0.084

15

16

17

18

~ 6.0

N SiO , = 0.585

NCaO = 0.521

0.384

0.348 - - - - ._--------- --~-----

Fig. 3. T emperature dependence of the viscosity of molten CaO- Si02- AI 20 3 system

elevated temperature, alumina or silica increased the viscosity, but lime lowered the viscosity. Therefore, alumini urn or silicon ion is considered to act as a network former, contrary to calcium ion which acts as a network modifier. The tempera ture dependence of the viscos­ity is also expressed by the Arrhenius' type equation (3 ) , named Andrade's equation.

r; = A ~ . exp (E~/RT) ... .. ............. (3)

where, A ~ : frequency factor E~ : activation energy for viscous flow R: gas constant

T: absolute temperature.

Therefore, E~ and A~ are determined by inserting measured data to Eq. (3) . The obtained values are shown in Fig. 4. The effect of Si02 contents on E~ and A~ is similar to the effect of AI20 a, but con­trary to the effect of CaO. That is, E~ value increases with Al20 a or Si0 2 contents, and the slag is more viscous, possibly due to network formation. Lime reduces the E~ and decreases the viscosity by cutting

0 E

-----oJ U

-'"

'" k1

100

70

SO

30

10

7

S

,-------,,: \'-,---1 - - ------,1000

--,---L-L ----1 700 \ ~t-- SOO

\ ~\! - - 300

\ I \\ 1 \ H -- 1- .-- 100

~-~--~-tr_-----~ 70

- \ - I -'fj'--------I SO

r--\--1-~\-------I 30 ~ I I 1\ \ ;

1----1- - I] \ -------1 10 0

I. \ *- -----1 7 -l Y0-1-- --IS

-- \ • > AI20 3 change o J (N CaO / Ns ;o, =e 1.07)

J &} Si02 change I---- \_ _ _" (Ncao NAI ,O,=e S.6S ) _

. } CaO change . \ - - 0 (Ns ;o,/NA I , O,~ S . 2 7)

__ \0 _ ®} CaO change • (Ns ;o,/NAI,O,=e 6.0 )

3

0.7

O. S

31-----~::::;I;=:::;:::=:::L:=:::i:==::i~ 0.3 o 50 100

Changed com ponent in s lag (mol%)

F ig . 4. Dependence or component change on E . and A.

the network. In the lower tempera ture region, the TJ

increases as shown by broken lines in Fig. 3 possibly due to freezing of slag. T he effect of the components on th e viscosity is sim ilar to that in higher tem pera tu re region : though Al20 3 or Si0 2 makes slag more viscous, CaO makes slag fluid a ccompanied wi th lowering of freezing point or liquidus tempera tu re which is closely rela ted to viscosity. Na mely, it should be considered tha t th e viscosity is a ffected by th e liq uidus tempera­ture of slags. The bending point of Arrhenius plot of r; will be discussed in the next repor t, rela ted with the electrica l cond uctivity.

Fig ure 5 shows the compa rison of this work's data with Sai to and K awa i's16) or Kozakevitch's.15) For this system, many other works are reported. 2),12)-16) The da ta are well in agreement with each other in the composition range of a bou t Si02/CaO < 1, but they are differen t in the range of the ratio over a bou t 1, respec­tively. T hese differences would be caused from the difference of impurity con tents of slag (especia ll y net­work m odifier), because th e modifier is genera lly more effective in th e acid slags.

2. [CaO (43)-Si0 2(43)-AI20 3( 14)] - Monoxide (' FeO ', MnO, or M gO ) QJtaterna~y Sy stem

Figure 6 shows the temperature dependence of r; of the qua ternary melts with' FeO ' , MnO, or M gO.

CaO

Fig. 5.

., <fJ

0 0.

i':-

Transactions ISIJ, Vol. 9, 1969 ( 33 J

S i0 2

AI 20 3(%) ( Uude rlin ed nu mber ) : p r esent wor k

Kozake vitch

S ait o and Kaw a i

V iscosity coefficient o f CaO- Si02- AI20 3 sys tem a t I 500°C

t (OC )

1500 1400 1300 30 '-~r----~~---~--'

10

7

S

3

","'- -,:0-

1 S.5 6.0 6.S

10' · lI T OF K) ---- T anabe et al.

(CaO (39.8)- S i0 2( 3S.7) - Alz0 3( IS)-MnO (10) J --+-- Machin and Hanna

[CaO (40 )-S i02( 40 )-AI20 3( I S)-MgO (S) J

No.

31

32

33

Addition

FeO

34 MgO

35

36

37 MnO

38

39

(mol% )

2.90

5. 10

1.40

5 .00

8.67

2. 50

2.9 1

5. 11

1. 45

I E . (kcaljmol) 1 A. (poise)

76 .4 6.8 x 10- 10

86 . 3 3 .0 x 10- 11

76. 1 1.2 X 10- 9

-- --

60. 1 1. 2 X 10- 7

68.8 1. 6 X 10- 8

57 .5 2.8 x 10- 7

63 .6 3 . 7 X 10- 8

70.0 4 .3 X 10- 9

63.0 5.4 X 10- 8

Fig. 6. Infl uence of monoxide add ition on the viscosity of CaO (43 )- Si02(43)- AI20 3( 14) slag

Viscosity of the melts is reduced by the above oxide addition a nd this effect is ra nked as FeO > M nO > M gO at the equimolar addition. Since the measured values

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[34 J Transactions lSIJ, Vol. 9, 1969

satisfy Eq. (3), E~ and A~ are calculated from the data. The calculated values are shown in Fig. 6. E~ increases with each oxide addition and the influ­ence on E~ is ranked as FeO> MnO> MgO at the equimolar addition. A~ is reduced by the oxide addition and' FeO ' is the most effective among those oxides.

Rontgen et at.17) measured the viscosity of CaO­Si0 2- AI 20 3-FeO system, but the composition differs from the composition of slags in this work. Therefore, the comparison of both results is impossible. But they reported that the addition ofFeO reduces the viscosity of slag, as same as in the present a uthor's measurement. On the quaternary system containing MnO, the meas­urement is done by Tanabe et at. IS) Their results are shown in Fig. 6, and differ from the present a uthor's in spite of nearly same slag composition . The difference of the materials of the detecting part of viscosity is con­sidered as a cause of disagreement, as they adopted the graphite material to that part. Only the Machin et at.'s

data23) are shown in Fig. 6. However, there are many others' 19) - 23) on the quaternary system containing MgO. The effect of MgO addition is well in agree­ment with each other, giving the nearly same value of E~.

3. [CaO (43)-Si02 ( 43)-AI20 3 (l4) ]- Comptex Oxide (V 20 5, Cr20 3, P205, or Ti02) Quaternary System

Figure 7 shows the temperature dependence of 7J

of slag containing V 205' Cr20 3, P 20S, or Ti0 2•

The results satisfy Eq. (3), except the slag con­taining Cr20 3 at lower temperature region. In slag containing Cr20 3, it seems that the crystallization is partly taking place and thus the composition of slag in low temperature region is changed remarkably from initial one in high temperatures. Such phenomena were reported by Saito et at.24) as same as in this work. From Fig. 7, it is known that the viscosity is reduced obviously by V 20 S or Ti02 addition but not by P20 S' The high viscosity is obtained by the Cr20 3 addition.

Figure 8 shows the relation between oxide addition and E~ or A ~ which was calculated from the data at elevated temperature region. E~ increases with the oxide addition , but A~ is reduced. In the case of Cr20 3 addition, the abnormal changes of E~ and A~ values were recognized at Cr20 3= 1.5 mol % and it is expected that the effect of Cr20 3 addition on the viscos­ity is not as simple as those of V 20 S, Ti02, or P20 S

addition. There is no report on the viscosity of quaternary

system containing V 20 S' P20 5, or Cr20 3. But it is reported that the Cr20 3 addition increased the viscos­ity of melts with CaO- Si02- Cr20 3 ternary system.24 )

On the quaternary system containing Ti02, viscosity measurements are done in the high Ti02 content region by Ono et at.25) Though their data are not compared with the present data numerically, the effect of Ti02

reported is similar to the present results.

4. [CaO (43) - Si02 (43) - AI20 3 ( 14)]- Fluoride (NaF, CaF 2, MgF 2' or AIF 3) Quaternary System

As the fluorine loss is expected in the melts con-

Research Article

t ( Oe )

1400

'"

1300

1------';;-1----- ---- -I

No.

19

20

21

22

23

24

25

26

27

28

29

30

z

6.0

10 4· l/T (l /"K )

Addition

V 20.

Cr20 3

P,O,

Ti02

6.5

(mol % )

1. 16

2 .06

3 .63

1.38

2 .45

0.68

0.74

1.47

2.60

2.58

4.55

7.90

Fig. 7. Influence of oxide addition on the viscosity of CaO(43)- Si02(43)- AI,03(14) slag

taining fluorides, the fluorine in slag after measurements was analysed quantitatively by the method of NaOH titration after ion-exchange treatment.26) The results are shown in Table I. Considering the accuracy of analysis and impurity contents of raw material, the fluorine loss of slag containing NaF, CaF2, or MgF2 is not so much, but the loss from slag containing AIF3 is not negligible.

Figure 9 shows the temperature dependence of viscosity of slag containing fluorides. The viscosity of slag is reduced by each addition of fluoride. The effect on the viscosity is ranked as CaF2 >MgF2>AIF3>NaF at the equimolar addition. This effect of fluoride is considered generally27),2S) that the size of the network is decreased by breaking action of fluorine. From this consideration, AIF3 should be ranked as the first, dif­ferent from the rank obtained in this experiment.

100

70 / , :"--' ...,..-

0 50

~ '" u

30 -'"

".

~ Cr203

• V20S

10 P2 0 S

• Ti02

~-

~~ 1'\ \. \ \ 1\ \ \ \ \ ~. \ \ "-

1\ \

\ . 1\

o 2 4 6 8 Oxide addition (mo l%)

1000

700

500

300

100

70

50

30

10

7

5

1 10

Q)

'" 0 0-

'" ~ 00

<=> -

F ig. 8. Dependence of oxide addi tion on E~ and A ~

Table I. F luorine contents of slags

No. At arrangement After measurement

40 10.0% as Caf, 8.28% as CaF,

41 20.0 17.3

42 40.0 33.6

43 10.0% as NaF 13.4% as NaF

45 40.0 38.4 ----

49 10.0% as MgF, 10.3 % as MgF,

51 40.0 36.6

46 10.0% as AIFs 5.1 3% as Alfs

48 40.0 18.5

This difference is perhaps caused by the fluorine loss and by the fact that some portion of a luminium ion, of AlF 3' acts as network former as in the melts con­taining A120 3.

Figure 10 shows the relation between fluoride con­tents a nd E~ or A~ . E~ is reduced with the increase of each fluoride content, further the log E~ is reduced linearly w ith number of moles of fluoride. A ~ in­creased with the increase of fluoride contents.

Tran saction s ISIJ, Vol. 9 , 1969 [ 35 J

30~-----+-----------+----------~

10

7 5

Q) ~O.S~ __ '" 3 0 0-

i':-

-,---0.7

0.5

0.3

0.1 6.0 6.5 7.0

104 . 1/T (1/o K )

No. Addition (mol% )

40 CaF, 6.66

41 14.2

42 28.5

43 NaF 18 .6

44 29.4

45 47 .8

46 AIF g 3 .82

47 7 . 36

48 14.3

49 MgF, 10.2

50 19.3

51 36.4

Fig. 9. I nfluence of fluoride addition on the viscos ity of

CaO(43)- SiO,(43)- AI,03(14) slag

Bills2S) and Kozakevitch29 ) have measured the viscos­ity of the quaternary system containing CaF 2 or MgF 2.

By Kozakevitch, MgF 2 is more effective than CaF 2 for reducing viscosity, contrarily to the present results. The viscosity dealt by Bills is higher than th e present results, perhaps caused from the difference of impurity contents. But his results on the reducing power are a lmost same as this work.

5. [CaO ( 43)- Si02 ( 43)- AI20 3 ( 14) ]- Chloride(NaCl, CaCI2, or MgCI2) Quaternary System

Because the loss of chlorine is anticipated in this system as fluoride-con taining slag, the chlorine contents of slag after measurement were analysed quantitatively by the Vol hard 's m ethod.30 ) The results are shown in Table 2. The chlorine loss is large, i.e., about the half of chlorine is lost in the melt containing CaC12 and a bout 70% is lost in the melt containing NaC!.

Research Article

[ 36) Transactions ISIJ, Vol. 9 , 196 9

10 7 5

3

"0 CaF, 1*. ~

E "" '-- MgF, -;; 100 -t- I CD

AIF3 c u

-" 70 -~ k1 50 ~r-

30 -I -·I·ct 10

0 10 20 30 60 F luoride contents (mol %)

Fig. 10. Dependence of fluorid e addition on E . and A.

No.

53

52

54

55

<I.l

'" c .:

l=::-

50

30

10

7

5

3

I

0.7

0.5

0.3

Table 2. Chlorine contents of slags

At arrangement After measurement

10.0% as CaCl, 4.34% as CaCI2 20.0 6.45

40.0 24.8

10.0% as NaCI 1.36% as NaCI

1500

I---

I ( oC )

1400 1300

-j-

"" ,,'" I:.. 'O·?~O· -2;-0> /~';/ ''':; • ,,'l-

)./.,~ / ",0

:=- /A/Y / ,,'/.LV f/ ~o/~ /

/ / /

I

I

':1'-~~

0.1 5.5

i 6.0 6.5

1O'·I/T (l /O K )

No. Addition (mol% ) E . (kcal/mol) A. (poise)

52 CaCl, 4.28 55.2 2.8 x 10- 7

53 2 .61 40.1 4.0 X 10- 5

54 18 . 7 87 . 7 20 x 10- 12

55 NaCI 0.83 61.0 8.7 x l 0- 8

56 1.80 98 .9 4.0 x 10- 14

57 MgCI2 3.50 80.6 1.7 x I0- lo

Fig. II. Influence of chloride addition on the viscosity of CaO(43)- SiO,(43)- AI,03(14) slag

Research Article

Figure 11 shows the temperature dependence of viscosity of the slag containing NaCl, CaC12, or MgCI2•

NaCI is m ore effective in reducing slag viscosity and CaCl 2 should have nearly equal effect on MgCI 2 • E~ and A~ which were calculated using Eq. (3) are also shown in Fig. 11. The mechanism of reducing viscosity is supposed to differ between fluoride addition and chlo­ride addition. In the case of the carbon-containing slag, it is known that the viscosity is reduced obviously and E~ increases with the carbon contents.3l ) The effect of chlorides on slag viscosity is similar to the effect of carbon. However, the simi larity of the structure of liquid slags containing chloride or carbon has not been examined.

There is no report on the viscosity of quaternary system containing CaC12 or MgCI2 • The investiga­tion on a system containing NaCI was reported by Nakaya et al. 32 ) However, they measured the viscosity with graphite detecting apparatus.

6. Summary of Influence of the Addition on the Viscosiry of Quaternary M elts

7J at 1 400°C or E~ is shown in Fig. ]2 or Fig. 13 with the contents of additions, to compare the inAuence of the additions . From Fig. 12, NaC] , CaF2, V 20 5, or MgF2

are named as the materia l more effective to reduce the viscosity of melts, contrarily to Cr20 3 which increases the viscosity remarkably. P205 is not effective to reduce the viscosity. Fig. 13 shows that E~ d ecreases with the increase of fluoride contents, contrary to oxides or chlorides which increase the E~ . Such influence of oxides and chlorides which decrease the viscosity but

--; '" 0 0.

s-:> C> C> ;::; ~

'" ~

::r-: -~ • FeO • MgO • MnO • V20 S o Cq03 o P20S

10 o Ti02 ® NaF

7 ® CaF2

5 ~ MgF2 ~ AlF3 • CaCl 2 1_ • NaCI

3

I

I

1 - _L 0.7

0.5

0.3 -

Addition (mol %)

Fig. 12. Effect of additions on the viscosity o f CaO(43)-SiO,(43)- AI,03( 14) slag

300 I ~T

FeO MgO

• MnO D V20 S ° Cr20 3 • P20S D Ti02

.. NaF " CaF2 8 MgF2 • AIF3 8 CaCI 2

aC I

' 00:----'--:-', OO---'-----2""0-L---"30.,------"-----4...L0- .l....---,J50

Additi on (mol %)

Fig . 13. Dependence of additions on the activation energies for viscolls fl ow

increase the E~ obviously, should be considered with the structure of molten slags.

7. D ensity if Molten [CaO (43)-Si02(43)-AI203(14)]­Addition Q,uaternary System

Though the errors of density measurements arc not sma ll due to delay of the response of balance for highly viscous liquid , th e shift of zero point of ba la nce, the influence of surface ten sion, an d the too small volume of platinum sphere (about 0.286 cm 3 a t I 500°C), the results a re shown in Fig. 14. Th e density of molten quaternary system is in the range of 2. 5 to 3.0 gjem3 • The slag conta ining ' FeO ' or MnO shows th e unusua l temperature dependence of density. And the density is reduced with th e NaF or AIF 3 addition.

IV. Conclusions

Th e viscosity of molten slag was measured with the balance-platinum sphere viscom eter. The results are as fo llows.

(1) The viscosity coeffi cient of CaO- Si0 2- Al z0 3 melts was measured. Viscosity a nd the activa tion energy ofternary melts increased with the increasing of Alz0 3 or Si02 contents, while CaO lowered these va lues. Then a luminium a nd silicon ions should be supposed to act as network formers, and calcium ion as network m odifier. These results are valid in th e melts with the sam e freezing point.

(2) Th e influence of oxides, fluorides, or chlorides addition on the viscosity of CaO (43)-Si02 (43)­Alz0 3(14) melts was observed.

The addition of' FeO ', MnO, or MgO which is popular in steel-making slags, lowered the viscosity of melts, but increased the activation energy. The addition ofV20 5, Ti02, or P20 5 reduced the viscosity of melts but increased the activa tion energy. The viscosity of melts increased obviously by Cr20 3 addi tion and the tendency of the effect on the E~ was reversed a t about 1.5 m ol% Cr20 3. The structure of molten slags conta ining Cr20 3 is supposed to be rather

Transactions lSI], Vol. 9 , 1969 ( 37 )

3.2,-----,--- -----,-------, No.38

3.0 No.~,," _--. _____ -+-_---"'-"_037_ C 1N.~ ~'~8 - r\ o 51 "'0 '"'° 41 , -.- No;J2 ~ ...... ~ _ :.. • . ~ . ... No.J6 ---r" , 0.27 ~'IIt26 No.33

E 2.8 No. U No.SO ", .c:. ..,. _ No.:~5 ~ No.42 No .• ' No.46 '" ~ :..2 • • No.3~.J9 No.23

bJ) ... - - - ~o.40 N~: 134 ~~ NO.48 . No.U

Q. 2 . 6 t-----""~~_f-=:==-~~--+----------j

2.4 1-----..

T" 2.2 1200 1300 1400 1500

t ( OC )

No. Addition (mol% ) No. Addition (mol % )

22 Cr20 a 1. 38 37 MnO 2,9 1 23 2,45 38 5. II 24 0 .68 39 1. 45

---25 P20 S 0.74 40 CaF2 6,66 26 1.47 41 14, 2 27 2,60 42 28.5 - ~I 28 Ti02 2.58 43 NaF 18.6 29 4 ,55 44 29 .4 30 7.90 45 47.8

31 FeO 2,90 46 1- AIFa 3,82 32 5, 10 47 7.36 33 1.40 48

I 14.3

34 MgO 5. 00 49

I MgF, 10.2

35 8,67 50 19.3 36 2.50 51 I 36,4

---- -----

Fig, 14. Temperature dependence of the density o f molten slags

complex. By the addi tion of NaF, CaF2, MgF2' or AIF3, th e

viscosity of melts and the activation energy were reduced obviously. The effect of the fluidi ty increase was ranked as CaF2> M gF2> AIF3> NaF. Such po­sition of AIF 3 is supposed to be caused by the loss of fluorine a nd a luminium ion added as AIF 3 which acts as network former.

The addition ofNaCI , CaCI2, or M gCI2 reduced the viscosity of melts. NaCI was more effective a nd the others were nearl y equa l in its effects. The loss of chlorine at this experiment was the greatest in the melt conta mmg aCl, from which about 70 % of the chlo­rine was lost. The activa tion energy increased by the addition of chlorides.

It should be noticed to consider the structure of molten slags, that there are additions~as chlorides and som e of oxides~to reduce the viscosity but rise the activa tion energy.

(3) The tempera ture dependence of viscosity co­efficient of molten slags is expressed by the Andrade's equa tion.

(4) The density of molten [CaO (43)- Si02(43)­AI20 3(14)]- addition system is in the range of 2.5 to

Research Article

[ 38 ) Transactions ISIJ, Vol. 9, 1969

3.0 gjcm3. Temperature dependence of density was irregular on the melts containing' FeO ' or MnO.

REFERENCES

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