APPLICATION OF MÖSSBAUER SPECTROSCOPY TO DEOXIDATION FROM LIQUID IRON BY ALUMINIUM

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APPLICATION OF MÖSSBAUER SPECTROSCOPY TO DEOXIDATION FROM LIQUID IRON BY

ALUMINIUM

S. Watanabe, A. Ohkawa, Y. Kaneko, Y. Shiraishi

To cite this version:

S. Watanabe, A. Ohkawa, Y. Kaneko, Y. Shiraishi. APPLICATION OF MÖSSBAUER SPEC-

TROSCOPY TO DEOXIDATION FROM LIQUID IRON BY ALUMINIUM. Journal de Physique

Colloques, 1979, 40 (C2), pp.C2-632-C2-633. �10.1051/jphyscol:19792220�. �jpa-00218601�

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JOURNAL DE PHYSIQUE Colloque C2, supplkment au

n "

3, Tome

40,

mars 1979, page C2-632

A?PLICATIilN

OF

MOSSBAUER SPECTF!OSC3?Y TO DEOXIDATION FROM LIQUID IRON BY ALUMINIUM

S. Watanabe, A. ~hkawa*, Y. Kaneko and Y. Shiraishi

Steelmaking Research Division i n Research I n s t i t u t e of Mineral Dressing and Metallurgy, Tohoku Uniuersity, Katahira, Sendai, Japan

RGsum6.- Cette 6tude a pour but d'gtudier la d6soxygLnation du fer liquide par l'aluminium. L'hercynite FeAl 0 et les formes y, K, 8 et

or

de A1203 sont les formes d'oxydes produits pendant l'op6ra-

tion. ~ e s ~ r z s u l t a t s expQrimentaux indiquent que le fer est sous forme de Fez+ dans l'hercynite et I-AL203 et dans l'btat Fe3+ pour K, 8 et a-A120,. On peut penser que les oxydes sont produits dans l'ordre suivant : d'abord l'hercynite, puis les formes y , K, 8 et

a

de A1203 successivement, par rEaction de l'hercynite avec A1 dans le fer liquide.

Abstract.- This study was carried out to investigate the deoxidation mechanism from liquid iron by aluminium. Hercynite (FeAl,O,),

y-,

K-, 8- and or-A1203 were the oxides produced during deoxidation.

From the ex erimental results, it was thought that iron species in hercynite and y-A1203 were in the state of Feb, and those in r-, 8- and a-AlZ0, were in the state of pel'. It was thought about the formation of the oxides as follows. Hercynite produced at first, and y-, K-, 8- and a-A1203 in that order produced by reaction of hercynite with aluminium in liquid iron, because electrons of iron species leaned around aluminium species in Fe-A1 alloy.

I. Introduction.- It is known that the oxides produced in molten iron with addition of small amount of aluminium (0.04-0.lwtZ) during solidifying are hercynite, y-, K-,

8-

and a-A1203. As the mechanism of their formation was not clarified, this studywas carried out to know the state of electron aroundiron species in the aluminous oxide by means of M6ssbauer spectroscopy and to investigate the mechanism of formation of aluminous oxides.

2. Experimental.-

2.1. 4~paratus.- The absorption of the 14.4 keVgamma ray of 5 7 ~ o diffused into chromium plate was measured at room temperature. A proportional counter was used to detect the 14.4 keV gamma ray. The sample was vi- brated sinusoidally at 3 Hz. The width

r

^{was about}

0.8 mm/s from the measurement of natural iron and 5 7 ~ o (Cr) at room temperature.

2.2. @mpie.- Electrolytic iron with addition of small amount of aluminium (0.04-0.IwtZ) was melted in the levitation furnace of purified Ar-gas atmos- phere and kept at 2200"-2300~~ for about 40 s. After that, the molten iron was quenched by a chill mould quenching method. The produced oxide during solidifying was extracted from the sample by iodine-alco- hol method and identified by X-ray diffraction. The extracted oxides were used as the sample for MESS- bauer effect measurement. The oxides were pasted in silicon grease and wrapped in aluminium foil.

3. Experimental results and discussion.- Figure I

shows the spectrum of ~gssbauer spectroscopy for the mixture of hercynite and G s t i t e (FeO).

Fig. 1 : Y6ssbauer spectrum of the mixture of hercynite and wcstite. Doublet : Gstite, singlet : hercynite.

It is thought that this spectrum consists of the spectra of hercynite and wiistite / 1,2/, and iron species in hercynite and wiistite are in the stateof Fe2+. Figure 2 shows the spectrum of Mzssbauer spectroscopy for the mixture of Y- and K - A L ~ O ~ .

a Atomic Nuclear Fuel Research Division

Fig. 2 : Mzssbauer spectrum of the mixture of Y- and K - A ~ ~ O ~ .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19792220

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Though t h e s p e c t r u m shown i n f i g u r e 2 i s complicated, i t seems t h a t t h e r e i s t h e Zeeman s p l i t t i n g p a t t e r n i n t h e spectrum.

F i g u r e 3 shows t h e mechanism o f f o r m a t i o n of aluminous o x i d e s . Isomer s h i f t of Fe-A1 a l l o y i s + 0.165

-+

0.425 mm/s from t h e s t a n d a r d a b s o r b e r of a-Fe a t room t e m p e r a t u r e 13-71. T h i s means t h a t aluminium s p e c i e s works a s t h e a c c e p t o r of e l e c t r o n i n t h e c a s e o f Fe-A1 a l l o y , i n o t h e r words, e l e c t r o n of i r o n s p e c i e s l e a n s around aluminium s p e c i e s .

F i g . 3 : Mechanism of f o r m a t i o n of aluminous o x i d e . ( 1 ) E l e c t r o n of i r o n s p e c i e s l e a n s around aluminium

s p e c i e s .

( 2 ) N u c l e a t i o n of o x i d e . ( 3 ) Formation o f h e r c y n i t e .

( 4 ) R e a c t i o n of h e r c y n i t e w i t h aluminium.

It i s t h o u g h t t h a t t h i s l e a n means t o combine i r o n s p e c i e s w i t h aluminium s p e c i e s s t r o n g l y . On t h e o t h e r hand, t h i s l e a n d e c r e a s e s t h e i n t e r a c t i o n between i n n e r e l e c t r o n and n u c l e u s of aluminium. B u t , i f l e a - v i n g t h e e l e c t r o n , which l e a n s around aluminium

s p e c i e s , around a n o t h e r s p e c i e s , i r o n b i n d s more s t r o n g l y w i t h aluminium.In s u c h a s t a t e , i f t h e r e i s oxygen a t t h e n e i g h b o u r s i t e of i r o n and aluminium, t h e e l e c t r o n , which l e a n s around aluminium, l e a v e s around oxygen s p e c i e s . I n t h i s s t a t e , n u c l e u s of o x i d e c o n s i s t i n g of i r o n , aluminium and oxygen forms i n l i q u i d i r o n . A f t e r t h a t , t h e n u c l e u s of o x i d e grows a s r e a c t i n g w i t h i r o n , aluminium and oxygen, and t h e o x i d e grows u n t i l i t ' s c h e m i c a l c o m p o s i t i o n becomes t o t h a t of h e r c y n i t e . I f oxygen s p e c i e s i s n o t around h e r c y n i t e , h e r c y n i t e c a n n o t grow. I n such a s t a t e , i f aluminium s p e c i e s d i f f u s e more around h e r c y n i t e , i n c o n t r a s t w i t h t h e f o r m a t i o n of hercy- n i t e , t h e r e a c t i o n of h e r c y n i t e w i t h a l u m i n i u m o c - c u r s , maybe. b e c a u s e e l e c t r o n o f i r o n s p e c i e s l e a n s around aluminium s p e c i e s . By t h i s r e a c t i o n , i r o n s p e c i e s i n h e r c y n i t e go o u t t o l i q u i d i r o n . A s , a t t h e b e g i n n i n g s t e p of t h e r e a c t i o n , t h e r e i s i r o n of f a i r amount i n t h e o x i d e , s p i n e l s t r u c t u r e of h e r c y n i t e does n o t b r e a k e n t i r e l y . So t h e o x i d e becomes t o y-A1203 o f s p i n e l t y p e s t r u c t u r e . It i s t h o u g h t t h a t i r o n s p e c i e s i n y-A120, i s i n t h e s t a t e of ~ e ~ + . The r e a c t i o n advances moreover, and amount of i r o n i n t h e o x i d e becomes s m a l l u n t i l t h e chemi- c a l c o m p o s i t i o n of t h e o x i d e becomes n e a r t o t h a t of A1203. ^SOK-, 8- and a-Al,03 o c c u r i n t h a t o r d e r . As i t seems t h a t i r o n s p e c i e s i n K-Al,O, i s i n t h e s t a t e of F e 3 + from t h e s p e c t r u m shown i n f i g u r e 2 , i t i s t h o u g h t t h a t i r o n s p e c i e s i n 8- and a-Al,03 a r e i n t h e s t a t e of F e 3 + .

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