1

Study on Travelling Magnetic Field Casting of Sheet

School of Materials Science and EngineeringHarbin Institute of Technology, Harbin 150001, P.R. China

Guo Jingjie, Su Yanqing, Bi Weisheng, Zhang Tiejun, Huang Junyong, Jia Jun, Fu Hengzhi

2

OUTLINE

1.OBJECTIVE2.EXPERIMENTAL EQUIPMENT3.MAGNETIC FIELD INTENSITY 4.MOULD-FILLING EXPERIMENT 5.MAIN DEFECTS 6.CONCLUSIONS

HIT

3

1.OBJECTIVE

Main problems casting thin wall cast -ings: Very high cooling rate results in lowmould-filling abilityObjective of this paper :Improve filling mould ability

HIT

4

2.EXPERIMENTAL EQUIPMENT

HIT

5

Fig. 1 Illustration of a TMFC equipment and the photo of the inductor

1-kickstand 2-iron core 3-fastener 4-pouring basin5-windings 6-magnetic yoke7-molten metal 8-cope 9-drag 10-transformer

HIT

6

3.MAGNETIC FIELD INTENSITY

HIT

7

y

x

zABCDEF

Fig.2 X-Y-Z coordinated system on the inductor and the positions of points A to F.

HIT

8

Fig.3 Distribution of magnetic field intensity (z=5mm, ampere-turns is 1272At)

HIT

9

0 5 10 15 20 25 30 35 40

2

4

6

8

10

12

B (

mT

)

Height (mm)

experimental resultB

z(F) B

z(A)

regressed result

Fig.4 Changes of magnetic field intensity with height (ampere-turns is 1272At) and with ampere-turns (z=5mm) in z direction of point A and F

500 1000 1500 2000 25000

5

10

15

20

25

30

B (

mT

)

current times turns (At)

experimental resultB

z(A)B

z(F)

regressed reesult

IzB Az )1542.17/exp(01088.0)( IzB Fz )1159.114/exp(00238.0)(

HIT

10

0 400 800 1200 16000

5

10

15

20

withnonferromagnetic up-mould

with ferromagnetic up-mould

Bz (

mT

)

current times turns (At)

Fig.5 The influence of cope materials on magnetic field intensity of point A

HIT

11

2

4

6

8

10

12

14

A B C D E F

By

(mT

)

Point

Z=0.5 Z=1.0 Z=1.5 Z=2.0 Z=2.5 Z=3.0 Z=3.5

2

4

6

8

10

12

14

A B C D E F

Bz

(mT

)

Point

z=0.5 z=1.0 z=1.5 z=2.0 z=2.5 z=3.0 z=3.5

Fig.6 Distribution of By and Bz at y-z plane

HIT

12

5

10

15

20

25

30

35

Bz<B

y

Bz>B

y

A B C D E F

z (m

m)

Fig.7 Isoline for By and Bz over the inductor

HIT

13

Fig.8 Simulation result of travelling magnetic field(2Poles) HIT

14

Fig.8 Simulation result of travelling magnetic field (1Pole)HIT

15

Fig.8 Simulation result of travelling magnetic field (coil turns decrease)HIT

16

Fig.8 Simulation result of travelling magnetic field (2inductors)HIT

17

4. MOULD-FILLING EXPERIMENT

HIT

18

Fig.9 Experimental method to measure the equivalent pressure head

HIT

19

Fig.10 The equivalent pressure head change with magnetic field intensity

600 800 1000 1200 1400 1600 1800

5101520253035

40455055

Pre

ssur

e he

ad /

mm

Ampere-turns / At

with ferromagnetic cope

with ferromagnetic cope

HIT

20

1-computer, 2-camera, 3-gallium melt, 4-plunger, 5-induction coil, 6-mould cavity, 7-linear inductor

Fig.11 Schematic of physical simulation experimental apparatus

Note: The size of mould cavity is: 500mm, 100mm and 1mm in length, width and height

HIT

21

Fig.12 Filling processing of Ga melt in the mould and the final state under different conditions

a) Bz=0mT, b) Bz=12.5mT, c) Bz=27.5mT, d) Bz=42.5mT

a)

b)

c)

d)

HIT

22

Fig.13 Al-12Si alloy plate samples cast by TMFC

(a)660 (b)700 (c)740 ℃ ℃ ℃(0At)

(a) 740 (b) 700 (c) 660℃ ℃ ℃(1860At)

Note: Cavity size of the ferromagnetic cope:570x140x3mm

HIT

23

Fig.14 Effect of magnetic field intensityon the filling area and time

HIT

24

Fig.15 Effect of travelling magnetic field on the filling area proportion of Al-12Si alloy at different pouring temperatures

HIT

25

5.MAIN DEFECTS

HIT

26

1cm

Fig.16 Main defects of Al plate cast by TMFC

a) Cold shut and b) Misrun are related to the flow characteristic of molten metal c) Pit surface is related to the magnetic field intensity of y direction

a) b)

c)

HIT

27

6.CONCLUSIONS

HIT

28

Summary

The magnetic field intensity decreases quickly with increasing the distance from the surface of the inductor. The component By and Bz get the maximum values a

t the slot and tooth respectively. Over the inductor, more space is By>Bz.

Travelling magnetic field can enhance the mould-filling velocity remarkably. For Al alloy melt of 660oC, the mold cavity with 570mm in length, 140mm in width and 3mm in thickness can be filled fully under the condition of 43.9mT. While under gravity, the melt can flow only 50mm in length.

Travelling magnetic field also cause negative effect on the castings., the velocity of the melt front increases quickly because of electromagnetic force during filling processing and this results in the decrease of the cross section area of the forward filling melt. This is the reason of the misrun or cold shut formation.

Another problem is pit surface on the bottom surface of the plate casings. Its formation reason is existed y direction electromanetic field.

HIT

29

Thanks for your

attention!