taniguchi_et_al_2003
5 pág.

taniguchi_et_al_2003


DisciplinaLingotamento Contínuo de Aços30 materiais72 seguidores
Pré-visualização2 páginas
stirring, and hybrid stirring. In the case of the vertical stirring, Fig.8 (a), 
magnetic field moves downward. There can be seen vigorous fluctuation composed of not only short 
period (less than 1 second) but also long period (several seconds). The short period fluctuation seems 
to be turbulence of liquid flow, and, on the other hand, the long priod fluctuation may be formed by 
the interference between downward and upward flows generated in the liquid gallium. On the 
-5 0 5 10 15 20 25
-3
-2
-1
0
1
2
400Hz, 3.65A
 
 
H
ei
gh
t/m
m
Radius/mm
 Upward
 Downward
Fig.4. Free surface profiles for case-1.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
contrary, there can be seen very small fluctuation 
for the case of simple rotational stirring, Fig.8 (b). 
For the case of rotational stirring, as Spitzer et 
al.[5] pointed out, the rotational speed in the outer 
region is faster than that in the inner region, so that 
turbulent flow is hard to be generated. In such case, 
mixing of liquid metal will be insufficient even if 
a higher power is imposed. Finally, Fig.8 (c) 
indicates the case of hybrid stirring. In this case, 
the level of turbulence is comparable to the 
vertical stirring (Fig.8 (a)) and the long period 
fluctuation seen in the vertical stirring disappears 
completely. Such tendency was also seen in the 
observation of the free surface fluctuation. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Conclusions 
 The present study has been carried out to develop a new rotary stirrer without free surface 
depression that is an essential problem in conventional rotary stirrers if a strong stirring is needed. The 
following results are obtained. 
0 5 10 15 20 25
-10
-8
-6
-4
-2
0
2
4
6
 
 
H
ei
gh
t/m
m
Radius/mm
 Rotatry stirring
 Hybrid stirring
7 8 9 10 11 12
200
250
300
350
400
 
 
R
ot
at
io
n 
sp
ee
d 
/rp
m
Current(rotation) /A
 Rotary stirring
 Hybrid stirring
Fig.6. Free surface profiles for case-2. 
 50Hz, 7.5A for rotary stirring, 
1300Hz, 12A for vertical stirring. 
Fig.7. Rotational speed as a function of 
 imposed current for rotary and hybrid 
stirring.
Fig.8. Velocities of liquid gallium measured by Vives probe for (a) vertical stirring, (b) rotational 
stirring, and (c) hybrid stirring. 
0 5 10 15
-100
-50
0
50
(a) Velocity in z-direction
 Average:-25.7 cm/s
 Downward (1300Hz,12A)
 
 
Ax
ia
l v
el
oc
ity
/c
m
 s
-1
Time/s
0 5 10 15
-50
0
50
100
(b) Velocity in \u3b8-direction
 Average:29.1cm/s
 Rotation (50Hz,7.5A)
 
 
C
irc
um
fe
re
nt
ia
l v
el
oc
ity
 /c
m
 s
-1
Time/s
0 5 10 15
-100
-50
0
50
(c) Velcity in z-direction
 Average: -12.7 cm/s
 Hybrid: downward(1300Hz,12A)
 rotation(50Hz,7.5A)
 
 
Ax
ia
l v
el
oc
ity
 /c
m
 s
-1
Time/s
(1) A stirrer with helical coils of which the angle of inclination is 45 degrees is examined of its 
performance by using liquid gallium. Free surface profile measured by an electrical probe is not 
improved at all. It is thought that the flow resistance in the circumference direction is much 
smaller than that in the vertical direction, and as a result, the vertical flow which is expected to 
lower the raised surface in the outer region does not work well. 
(2) A hybrid stirrer composed of two coil systems generating vertical and rotational flow, is proposed 
and its performance is examined. The profile of the free surface of liquid gallium measured by an 
electrical probe is found to be almost flat if the downward flow is generated in the outer area of 
the liquid metal. 
(3) Rotational speed of liquid gallium measured by an impeller immersed in a liquid metal is slightly 
smaller in the case of hybrid stirring compared with the case of rotary stirring. 
(4) Liquid velocities are measured by Vives probe. For the case of vertical stirring without rotation, 
there can be seen a strong turbulence accompanied by long period fluctuations. This long period 
fluctuation also appears as the vigorous free surface oscillation. For the case of simple rotary 
stirring, the level of turbulence is quite small because of the suppressing effect of turbulence in a 
rotating flow filed. For the case of hybrid stirring, strong turbulence is observed but the long 
period fluctuation is not observed. This means that the hybrid stirring is able to generate intense 
turbulence without free surface deformation or oscillation. 
 
Acknowledgment 
 This study was partly supported by the Ministry of Education, Science, Sports and Culture, Grant- 
in-Aid for Scientific Research on Priority Areas (1998-2001). 
 
References 
[1] The Division of High-Temperature Processes, ISIJ, Innovative Propositions to Achieve High 
Efficiency in Refining and Solidification Processes, ISIJ, 2002. 
[2] T.Ozono, Research and Development of Advanced Technology on Recycling of Aluminum 
Materials, The Journal of Japan Institute of Light Metals, 50 (9) (2000) 468-474. 
[3] O.J.Ilegbusi, J.Szekely, Mathematical Representation of the Velocity, Temperature and Solid 
Fraction in an Electromagnetically Stirred Solidifying Melt, ISIJ International, 30 (5) (1990) 372-
380. 
[4] Y.Miki, H.Shibata, N.Bessho, Y.Kishimoto, K.Sorimachi and T.Hirota, Cleaning Molten Steel with the 
Centrifugal Flow Tundish, Tetsu-to-Hagane, 86 (4) (2000) 239-246. 
[5] K.H.Spitzer, M.Dubke and K.Schwerdtfeger, Rotational Electromagnetic Stirring in Continuous 
Casting of Round Strands, Metall. Trans.,B, 17B (March) (1986) 119-131. 
[6] C.Vives, Mew Electromagnetic Manufacturing Processes for Semisolid Alloys and Metal Matrix 
Composites Synthesis, Proc. of Int. Symp. on EPM, EPM\u201994, Nagoya, (1994), 223. 
[7] T.Ando, K.Ueno, S.Taniguchi and T.Takagi: Induction Pump for High-Temperature Molten 
Metals Using Rotating Twisted Magnetic Field, IEEE Transactions of Magnetics, 38 (4) (2002) 
1789-1796.