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A NEW SCALE OF BASICITY IN OXIDE SLAGS
MORI, kazumi
茨城大学工学部紀要(2): 45-56
1960-02
http://hdl.handle.net/10109/4754
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お問合せ先
茨城大学学術企画部学術情報課（図書館） 情報支援係
http://www.lib.ibaraki.ac.jp/toiawase/toiawase.html
A NEW SCALE OF BASICITY IN OXIDE SLAGS＊
by Kazumi Mori N“’
The basicity of an oxicle slag． has an important bearing on the iron and
steel making processes． ln most cases some ratio of the arnounts of basic oxides
to those of acidic oxides is used as a measure of basicity， but it is oRly an
empirical measure aRd cannot afford a real measure of a chemical property．
Moreover in the expression of slag basicity little attention has been paid to the
behaviour of the amphoteric oxides such as AI20，｛ and TiOt，． ln the present report
a new scaie of basicity is described， tog． ether with the method of determina一一
tion of basicity and the results of the study on some slag systems containing
amphoteric oxides．
A New Scale of Basi6ity
It is well established that the scale of basicity or acidity of pure oxides is
given by the strength of the metal−oxygen boRd． However， this idea of basicity
has not been taken into consideration in the conventional expression of basicity
in multicomponent systems． lt is the chief object of ￡his paper to give a new
scale of basicity which is able to deal with pure oxides as well as multicomponent
oxide systems on the same grounds．
Because oxide slags contain large amounts of oxygen ions， it seems to be
most reasonable to express slag basicity by oxygen ion activity． However， in
general its practical measurement is very difficult． Accordingly the well−known
fact that the ferrous and ferric concentrations in a slag change regularly with
the basicity， which relates indirectly to oxygen ion activity， has beeR selected to
measure the basicity of slag． s， as was suggested by Larson and Chipman．（i）
According to Larson and Chipman the value of r ：FeL’Y（FeL’＋ 一十・ Fe3＋） is
increased by additions of basic oxides and decreased by acidic oxides under ￡he
constant oxygen pressure．
Since oxygen ions are common to all the components， it is adequate to use
ioRic fraction of cations in the expressions of the concentration of the slag，
whose basicity is to be determined． Then the concentratioR of the slag （C） is
represented by the expression
＊ This paper is a summary of the lectures delivered at the 53rd and 55th Grand Lecture
Meeting． s of the lron and Steel lnstitute of Japan， held respectiveiy in April 1957 and in
April 1958・
＊＊ Assista．nt Professor， Department of Metallurgy， Faculty of EngineeriRg， lbaraki University．
46
Journal of The Faculty of Engineering lbaraki University．
（Vol． 2．）
c一ΣF澱巌 （1）
ΣFeこFe2＋十Fe3÷
＝M ＝一 CaL’＋＋Si‘“＋A13’＋＋Ti‘＋＋…
Since in general the value of r changes with C， it is not adequate to choose
r at some concentration as the scale of basicity． Therefore， the gradient of an
’r−c curve at the infinitely dilute concentration， o．r （一ddikE’r）c−o，was chosen as the
・cal・・fb・・i・i・y． lf・ch・ng・・1i−lyw三・h q（一龍うC一。m・y b・pu・．in・h・
following form
（dr”’acde）C一。一㌢ （2）
which is indepeBdent of C． Here ro represents r o￡ the pure iron oxide．
In the present case， based on the assumption of linear relatinship between r
and C， the scale of basicity is given by the equation
B一．．エざ1｝×1・ （3）
in which the factor IO serves to make the value of B manageable．
Experimental Method
The studied systerns are as follows：
cao， sio，，， Tio，，
CaO−SiO，，， CaO一”lfiOL，， SiOL，一TiOy， CaO一一AIL，03， SiO2−AIL，03
CaO・一SiO2−TiOb CaO−SiOL，一AIL，O；i
Samples used in the experimeRt are iron oxide with additions of the slag，
whose basicity is to be determined．
The experirnental furnace was of a resistance−type， whose heating elements
were six carborandum rods． A small platinum crucib！e with a 1．5 g slag samp1e
was suspended oR a platinum wire inside a refractory alumina tube． The slag
was equilibrated under an atmosphere of COti／CO ＝13．3 at a temperature of
1480Q C． When the slag had reached equilibrium， the crucible was quenched by
being lowered rapidly． Samples were analyzed for FeL’“ and FeB＋， and their
basicity was calculated by Eq． （3）．
Experimental Results
Some of the experimental results are shown in Figs． 1−v5； among them Figs．
lt・kv3 are the basicity of three binary systems， and Figs． 4 and 5 are the basicity
of ternary systems with constant titania or alumina contents． ln the slags contai−
ning alumina， the melting point rises sharply with increase of alumina contents
and it was impossible in this investigation to know the basicity for the conceRt一
Mori ： A New Scale of Basicity in Oxide Slags
8 6 午 ￡ 0 2 4・ 6 8
q亀
ration range above 25 mol％A1203．
The values of Bfor CaO， SiO2
and TiO2 arc such as would be
expected from the metal−oxygen
bond strength（1＝；2z／a2）． In the
systems CaO−SiO2 and C哉0−TiO2，
approximately ．B changes 1inearly
with mo1％， but in tne system
SiO2−TiO2 a maximum appears．
In the temary systcms（Figs．
4and 5）at the constant TiO20r
A1203 contcnt B increascs smoothly
一8
SiO2
Fig． 1．
a7
ワ
CaO
25 SO 7S
C疏 0（motシ9
of the temary systems are shown
き
Basicity of the CaO−SiO2 system．
（below 45 ．0／o TiO￡，） in Fig．6 and
in Figs．6and 7・
？”！り
Isobasicity lines of B ＝ 一一一2．2
with CaO／SiO2． Isobasicity lines
B＝．一一〇．2 in Fig．7 coincides with
zf−
lines of constant CaOISiOL，， which
shews that at the constant CaO／
SiOL， the basicity does． not change
2
c） 0
with additions of TiOt， or Alt，O：，． At
lower ratios of CaO／SiOL， B is
increased and at higher ratios dec−
−2
一一4
reased by additions of TiOL｝ or
−6
AlyO：i． This is a very interesting
fact， because it shows the so−called
amphoteric behaviour， that an
−2
da o 2S SO 7S Ti O．
Ti 02 （mot o／o）
Fig． 2． Basicity of the CaO一一TiO，． system．
amphoteric oxide added to an
o，
acidic slag behaves as a base aRd it
一2
behaves as an acid when added
an
to a basic slag．
一阜
一一 6
−8
SiO． 2S’ S’0 7S’
一 Tt O，（．，to／．〉
一17， o， 一Fig・ 3．
Basicity of the SiO2−TiOL， system．．
48
@6
︽、6 4・ ￡ 0 ？︷ 4’ 6
・一
（Vol． ．2）
8
天佐2甑。ε％
Aし0312．5m・［％
6
4
2
c）o O
一2
一4
α酪‘亀 ／ 釦
}
一・
375 ’片
俵。（m・ど％＞
α礁儀 ／
80
・一一 8
Journal of The Faculty of Engineering lbaraki University．
U
伯 切
・一 8
0
Fig． 4． Basicity of the CaO一一SiO2−TiO2 system．
43．7S 87．S
azO （mot o／．＞
（TiO2 25 mol ％）
Basicity of the CaO−SiO，，一AIL）03 system・
Fig． 5・
（A），O， 12． 5 mol ％）
5tO之
陶シ＼
＼
0
②
ご、黙
繊
N
β 、
翠蝕・
81
、、
拳
、
箔＼，
、
噸
3
．、
、
、 齢 、
壱
戴
ぎ“
，／ノ盃
、Φ
、
の。
D
／
、
3
、
、
、
、
ノ
x
ca o
畠へ、
＼
j
蟻・、
＼
％“
︾
x
20 40 60 gO
’温
孔02
一一一一一一｝” Tl， O， （ o／，）
ebserved
一一一t一 calculated by ￡he empirical equation （4）
Fig． 6． lsobasicity ｝iRes iR the CaO−SiO，）一一［1’iOL｝ system．
For the ternary
as follows：
systems empirical equations of basicity have been obtained
49
iMori ： A New Scale of Basicity in Oxide S；ags
・‘
5
＼，
、
肴
「
C
＼
一 、、
5∬ 藁寺
ぎ こ
0 ミ
︸
、ギα
ぐ Z
3、
、
、
も
、
＼
︷
﹄篤
E一
蓉
、
3
2、
、
− 、
・N、
A、
、 0
・、
一、
@ぎ“
Aσ
@ @ 蝕
惑
ψ宅シ
／
一
4
ド◎
、
『
、
、
、
、
タ
、
＼
＼
、
、
、
、
q，
，
、
、
ヘ へ
fao
@2。 “。 6。 8。 A（、・3
−At。03（o／e）
observed
一一鵬尊 cεしlculate（i by the empirica】equation （6）
Fig．7． 王sobasicity lines in the CaO−SiO2−A120，s system．
CaO一一SiOLrrl”iOL， System （CaO／SiO20 ＝：一； 1／3t一・一4， TiOL， ＝ O”．・359060）
8一孤1諾薦161∵．＋ fT ＝ gi） ｛（CaO／SiO，，）｝ ・ hT｛（TiO2）｝
＝1一一 ’o’：b”o”’s’”’；’rr’””（”c’””！a””’u7s’i’o’／／，”〉””’” ＋ 2・350｝・｛一〇・0066（Tio，） ＋o．sgs） （s）
CaO−SiOL，・一AIL，O：i System （CaO／SiOL， ＝r：．：一 1／3”．v4， AIL，O：i ＝e．h−35；O」e60）
17．95
十 7．27
B ＝一
瞼（Siα驚叙1；。b”
fA ＝一T g，x ｛（CaO／SiO，，）｝ ・ hA｛（AIL，（ 3）｝
＝ ”一““（’oLosg＋（c！ao’7sio6’）’ ＋ O・955｝・1一一〇・OiO3（Ai20，，） ＋ o．sio／ （7）
where concentrations are expressed in weight 9（o（．
In Eqs． （4） and （6） the weight 9／o of TiOL， o｝’ AIL，03 are put in the denomi一
’nator of the fraction relating to coRcentration， being multiplied by the factor ftr
or fA． The factor is expressed by the product of a function of CaO／SiOL， and
that of （TiO2，） or （AIL，03） as written by Eqs． （5） and （7）．
50 Journal of The Faculty of Engineering lbaraki University． （Vol． 2．）
Although titanium−dioxide itself is rather classified as an acidic oxide like
silica， in the ternary system CaO−SiOジTiO2（TiO2＜35％）it is regarded as an
amphoteric oxide．
Diseussions
The newly defiRed basicity is characteristic in tow ways． ln the first place，
basicity of a pure oxide and that of any multicomponent oxide slag can be
expressed on the same scale． Secortdly， in principle values of ．the new basicity
can be obtained only by measurements， which is very different from the conven−
tional expression．
In aqueous chemistry a solution is classified as acidic， basic and neutral
according to the value of pH as compared with 7． Similarly， in oxide slag
systems the classification can be made as follows：
ll一部ll （8）
Hitherto we have had much information as to what is implied by an acid
or a base， but little is known of an amphoterite． Now it is possible to obtaiR
some iRsight into the nature of the arnphoteric oxides．
“．碍
％
Fig． 8 illustrates the relation
@丁‘0ユ 20
between the factor fu／ and CaO／
tF一一imbi SiOL， at TiOL， 20％o for CaO一一SiO，，一一一
TiOL， system． lt was obtained from
Eq．（5）． According to the curve in
．t−O・S
狽?ｗｗ Fig．8， the value of ￡r is found to
be zero at GaO／SiOL，＝一〇．42， and it
omu一 is positive in the range where
GaO／SiOL）＞O．42， on the other hand
it being negative in the range
−o．sL一一一一一一一一一！．一一一一一4一一一一一i一一一一一一一一L一一一．一． L where CaO／SiO，，〈O．42．
o i
2 3 4 5置
CaO／ScOx Thus it has become evident
Fig． 8． Change of the values of the factor
fT witWh cao／sio，． that amphoteric behaviour of Tio，
can be expressed quantitatively by
fT・
The same argument caa be applied to the CaO−SiOL，一一AIL，O：一｛ system， in which
the zero point of fA lies at CaO／SiOL，＝7−O．96， which is more basic than in the
GaO−SiOL，一TiOL， system．
Now the behaviour of the amphoteric oxide which has been described has・
51
Mori ： A New Scale of Basicity in Oxide Slags
a quite similar aspect to aqueous solutions． ln slags， as mentioned before， at a
・certain CaOISiO2 f・fi or fA is zero and there is no change of basicity by the
additioRs of the amphoteric oxide such as TiOf， or AIL，O”． Similarly in aqueous
・solutions at a certain concentration of the hydrogen ioR， which is termed the
’isoelectric point， additions of an amphoterite brings on no changes of the
concentration of the hydrogen ion． This definition of the isoelectric point in
aqueous solutions can be applied to slag systems．
The basicity Bi corresponding to the isoelectric poi．nt is illustrated in Table 1．
Table 1． Basicity corresponciing to the isoelectric point．
・b・e・v・d．紬糠描監，
Slag systems
1−wu’Cunatr7−tTOtii−i17i”一crsOJ，uzr，．・’IPiwwFi ｝IB，
cao／sio，
・竺％
CaO−SiO，）一TiO2 System
O 45
一2．2
CaO−SiO2−AlfiO3 System
1
一一 O． 2
’ir”’” I
I O．42 1
O． 96
一2．3
一〇 15
In aqueous solutions， in general， an amphoterite has not the neutral beha−
viour） and the isoeiectric point does not correspond to the neutral point． This
’is quite similar to the amphoteric behaviour of TiOL，， whose isoelectric point has
its location in the conslderable acidic range． On the other hand， in the case of
A120：i the isoelectric point nearly corresponds to the neutral point．
The location of the isoelectric point may depend upon the acid−base strength
！
of the arnphoteric oxide． ln Fig．9
the isoelectric point （Bi） is plotted
璽
’8in−m一一一一：；i against the strength of the metal−
、c∼†
oxygen bond which is a measure of
、
、
、
the acid−base strength of the pure
、
4an oxide． Fig．9 indicates a general
、
、
、
trend that the basicity of the isoe−
、
、＼A｛3÷
t）6−i l 1 ”xAi3t l l l lectric point decreases with increase
o
of the acid−base strength．
、
、 、
茨騨
、
’酔
婦
／希‘
A Generalized Formula of
、
q
、
、
the Newly Defined Basicity
、
、
、 、
5乙什
、
ﾊ．
a皿dits APP夏icaもion to Seve−
ral iron and Steel Making
一8
／ 2 3
Reactions
2Z／aL
Fig． 9． Relation between the basicity corres−
In order to extend the newly
ponding to the isoelctric point and the
defiRed basicity to any generalized
strength of the metal−oxy｛ en bond．
slag system， it is necessary to
52
Journal of The Faculty of Engineering， lbaraki Uuiversity．
（Vol． 2．）
undertake the same investigatioRs as before ior many complex multicomponent
slags． However， it has been expected that this procedure may possibly be very
complicated， and that the results is not necessarily fruitful．
Therefore， it is necessary from the practical point of viexAi to prepare an
approximate formula of basicity which car｝ be used generally to any corr｝plex
slag system．
As is suggested from jFig．1，2 and 7， it is like｝y that the newly defined
basicity is approximately line，ar agains￡ the mol sraction．
Accordingly， we can give the approximation
BL ：T一 X． ai Nj
三
＝ai Ni十aL， NL，十・…一・ （9）
Nip N2，・…t・ ： mol ／fraction of the constituents
ai， aL，，・・・… ： constants each characteristic of the coRstituent
as the simple generalized expression of the newly defined basicity．
The values of the constants ai are shown in ’1］able 2． ai for CaO， SiOL， and
TiO2 is the basicity of the respective pure oxide， al fbr A1203 the basicity（：Bの
corresponding to the isoelectric point， ai for MgO and MnO being taken from
the interpolation of the curve in Fig．9， and ai for FeO is chosen so as to
establish the best relationship between a certain chemical property of the slag
aRd its basicity， as will be stated later．
Now let us illustrate several app｝ications of Eq． （9）．
Tabie 2． Values of the Constants ai．
Oxides
ai
＝ （1） Solubility of magnesia in the
CaO一一SiO，，一一tFeO一一MgO slag
CaO
6． 05
SiOL，
−6 31
TiO2
Al，O，
MgO
MnO
FeO
Bishop et al．（L’） determiBed the solubi−
一一 4． 97
lity of matt’nesia in slags of the system
一一 O． 2
CaO一一SiOL，一一FeO−MgO， using the data of
4． 0
Fetters and Chipman（：”）． lt is to be noted
4． 8
that the solubility of magnesia decreases
3． 5
’ as the lron oxide content increases， and at
a constant iron oxide concentration， the
solubility decreases as the ratio CaO／SiO
2 mcreases．
． lf xve give tentatively 3．5 for the
Let us take BL ＝ 2 aiNi as slag basicity
iri Table 2， and plot the solubility against
constant ai of iron oxide， as is shown
BL， then Fig．10 can be obtained．
It is indicated that the solubility liBes repre−
iron oxide lie along the same curve
senting slags having different contents of
except for the high iron oxide contents．
53
Mori ： A New Scale of Basicity in Oxide Slags
（2） Sulphur capacity of blast
’600。‘’
60
furnace slags
se
Richardson（ti） drer4i attention
4e
to the fact that the x4；eight percent
t・F． 3・O
1
｝、
罵
ratio （CaO 十 MgO）／（SiOL， 十 A1203）
椀のオ綴％
S 20
寒
does not always determine the
45 53
sulphur partition． ratio for blast
6夕
furnace slags， and described that
io
n
what is proportienal to the sulphur
タ
partition ratio is the sulphur capa−
ーノ 0 ’ z 3 9・
city Cs． Richardson and his
co−worker measured the sulphur
capacity for several slags． Their
Fig． IO． Relation between the solubi］．ity of
results are cited and shown in
magnesia in the CaO−SiO2−FeO−MgO
Tab墨e 3．
slag and the basicity BL．
Table 3． Sulphur Capacity of the
CaO−SiO2−A1203−iMgO Slags．
s
（Richardson （4））
Slag composition （％）
Sulphur
capaclty
sio
CaO i， A12031 MgO
を
29・7｛kl・61
25
20
劃
14． 8
19． 0
ir gI
8．4×IO−4
・］
2．51 3．9×IO−4
15
12 1 8．4×10−4
20
12 1 1．1×10一：i
14s l 25
io 1 i．4×io−3
l ，6
9
1TT 1
30
0
ノ
30
42． 2 i
めミxご
31． 8
Cs
1
5 i 514×10一：一i
I
。． s
o
1 2 3
﹁﹂婁︸ ︸︸
0
4
B．
Fig． I l． Relation between the sulphur
capacity of blast furnace slags and
tlae basicity Bb
Fig． 11 shows the relatioR between the logarithm of the sulphur capacity
and slag basicity BL． lt is interesting that approximately the relationship can
be expressed by a straight line．
（3） Equi1三brium sulphur partition ratio between liquid iron and open hearth
￡ype sユags
Journal of The Faculty of Engineer1ng lbaraki University．
S4
（Vol． 2．）
The data of：Fetters and Chipman．（a．）were uscd to f圭nd the correlation of sulphur
20 partition ratio with the slag bas呈。圭ty
Bi．． F圭9．12 shows tha宅 there is a
・ good correlation betweer1（S）／［S］
○
’ρ and BL．
o
O
（4） Reduction of Ti and Si
♂
from slags of the system CaO一
o
O oo
ロ
08Qσ
ぎ
S三Q．、一Tio2
ミ Recen・ly・h・au・h・・（5）studi・d
o
G thc reduction of Ti and Si from
8
’
》
the slags・f the system CaO−SiOゾ
o
o
○
8
TiO2 to mo王ten P王9 1ron−m a
graphite cruciblc at l550。 C． The
。も竃
’ duration of each study was 75 min
o
during which Inetal and s互ag sam一・
o
Ples were taken at IO or l5 min
O． S intervals． From the analyses K，i， si
／ ㌔。3 卒 一［Ti］（Si）／（Ti）［S三］we・e d・…一
Fig．12． R・韮・t三・・b・tween・・IPh・・p・・titi・・ mined・
ratio and slag basic三ty BI、 in the tem− It was fourld that a certain
pe「atu「e∫ange 1555Q tQ 1650．C・ ・im。 h。d d。p、ed b・fo・e・h・qua・i−
equilibrium sta七e was attained， when I9，fi， si reac hed a constant value。 This
cons毛ant KTi， si is termed the index number of the quasi．equilibri疑m state．
Changcs in the index number with slag com、positions arc shown in Fig l3．
3，D
読0∼（％）
ノ菖“
2．0
X1 2・5
1 1
：
3‘
×
ぢ．芝
如
1
i
1
犀
×
﹁
；
el s
0，6 0．8 LO L2 L4
cao／sio2
Fig・ 13． Relation between the index number of the quasi一’
equilibrium state and CaO，iSiO2．
Mori ： A ±New Scale of Basicity in Oxide Slags
55
It is to be noted that at constant titania contents Kfyi， g． i ilncreases with CaO／
SiO2 ar｝d at constant CaO／SiOL， i￡ decreases as TiOy increases．
Then， Eq． （4） or （Ca（ ）／｛（SiO，，） 一1・ frr（［1］iO，，）｝ was taken as the basicity of
the sla，cr．， aRd KT」， si was plotted ag’ainst the basicity． Fig．14 is the result， which
shows that the points representing slags of different titaRia coRtents all lie along
the saixte line． The similar result may be obtained as showR iR Fig． 15， if BL is
used as the slag basicity．
3，e
3．0
2．S
辱i聰
2．0
x
ら1．0
￥
墜ゼ
9覧
切
η0之（％｝
as
潤I5’
w25
｢35
ﾁzO21％）
O． 5
◎ 15需
25’
醇 ％ ク8 ／．・o t．z
｢35
（CaO）／｛（sLO，｝．，fT（TtO，）｝
Fig． 14． Relation between the index number
of the quasi−equilibrium state and（CaO）
1｛（，SiO，） 十 fu（TiO，，）｝．
一3 一一．Z ・一一／ D i
8し
Fig． 15． Relation between the index number
of the quasi−equilibrium state and slag
basicity BL．
Su m mary
Thls paper g，，ives a new scale of basicity in oxide slags， and presents the
r匙
results of the measurements of basicity for the slags containing amphoteric
oxides． Based on the resul￡s of this study， the concepts of amphoteric behaviour
of slag constituents was developed．
In addition， a simple formula of siag basicity generally applicable to any
multicomponent slatt was given， and were illustrated several examples of its
application． lt well be interesting to review practical data in the light of the
new basicity．
References
（1）
H． Larson ＆ J． Chipman：J． Metals， 5 （1953） 1089
（2）
H・ L． Bishop， H． N． Lander， N．」， Grant ＆ 」． Chipman：J． Metals， 8 （1956） 862
（3）
K． L． Fetters 8i J． Chipman： Trans． AIME， 145 （1941） 95
56 Journal of The Faculty of Engineering lbaraki University．
（Vol． 2．）
（4） DISCUSSION， J． lron Steel lnst． 188 （！958） 360
（5） Kazumi Mori：A lecture delivered at the 57th Grand Lecture
and Steel lnstitute of Japan， April 1959
Meeting of the lron
’