23

THE SCIENCE AND ENGINEERING REVIEW OF DOSHISHA UNIVERSITY, VOL. 51, NO. 2 July 2010

Study on a New Semi-Solid Injection Molding Method

for Heat-Resistant Magnesium Alloys

Trial Production and Process Verification of Machine Tatsuya TANAKA*, Yutaka IMAIDA*, Kenji SHINOZAKI**, Makoto YOSHIDA***, Toshio FUJII****

(Received May 7, 2010)

Based on the experiment result of semi-solid injection molding machine which has the mold clamp force of 20 tonf

reported previously, the trial model with the mold clamp force of 200 tonf was designed and then was manufactured. By

using this trial model, accuracy of the control method of semi-solid temperature zone was verified, and it was checked that

a solid phase rate could fabricate at least 30%. As the result of the trial test by same molding conditions, it was clarified

that mobility differed by the molten state and the semi-solid one. And it was checked that there were many merits by

comparing this new semi-solid injection molding process with the conventional die casting. In order to verify this new

process, trial production molding of the clutch piston which was a main part of a car was carried out. At this time, in order

to obtain the clutch piston without defect, an experimental design was used. Durability was evaluated using an equipment

which allowed repeated load on a clutch piston without defect. As a result, trial production parts were inferior to the

conventional parts made from aluminum alloy. In order to conquer this problem, it turned out that the part shape which

was suitable for the Magnesium alloy of low rigidity compared with the aluminum alloy should be designed.

semi-solid processing, injection molding, magnesium, heat-resistance, solidification crack

* Department of Mechanical and Systems Engineering, Doshisha University, Kyoto

Tel: +81-774-65-6465, FAX: +81-774-65-6465, E-mail:tatanaka@mail.doshisha.ac.jp ** Department of Mechanical System Engineering, Graduate School of Engineering, Hiroshima University, Hiroshima *** Department of Material Science and Engineering, Waseda University, Tokyo **** Western Hiroshima Prefecture Industrial Institute, Kure, Hiroshima

CO2

CO2 18.5

A

Mg

24

1970

MIT Flemings1)

2,3)

Mg4)

4)

873K

200ton Mg5)

Mg

Ca AZ91D

AM60

Mg 5)

Fig.1 20ton4)

Mg 1 Pa s

30 40wt%

100 1000Pa s

4)

200ton

Fig.2

Fig.1. Schematic illustration of lab molding machine.

Screw mixing part

Shut-offvalve

Plunger injection part

Nozzle

Screw mixing part

Shut-offvalve

Plunger injection part

Nozzle

Fig.2. Schematic illustration of the trial injection

molding machine at clamp force 200ton.

90

25

Mg

Table 1

Mg

4m/s

40G 70MPa

Fig.3

(a)Mg

(b)

Mg (c)

(d)

Fig.4

Mg

200ton

Mg AM Ca %

(a)Metering (Valve shut)

(b)Filling (Valve shut)

(d)Product extraction

(c)Injection (Valve off)

(a)Metering (Valve shut)

(b)Filling (Valve shut)

(d)Product extraction

(c)Injection (Valve off)

Fig.3. The principle of operation of semi-solid injection molding machine.

Fig.4. The arrangement plan of a mechanical apparatus.

Table 1. The main specification of the trial injection molding machine at clamp force 200ton.

Item Main specification Injection speed Maximum 4 m/s

Acceleration at injection Minimum 40G Hold pressure at injection Maximum 70MPa

Capacity at injection 430cm3 Semi-solid ratio Maximum 30±5 % Vacuum in mold less than 5kPa

Cycle time less than 60sec Measurement accuracy less than ±1%

Clamp force 2000kN

91

26

AMC403 Mg-4mass% Al-3mass% Ca

882K 833K 6)

Fig.5

SB

PB

180

1 2

Fig.5. The positions where temperature were measured with the thermo couples.

Fig.6

3 SB-1

903K 913K

1

Table 2

SB

Fig.7

SB SN

15

15 SN

SN 1 SB2 1SN 2 SB2 2SB1 1 SB4 1SB1 2 SB4 2

Fig.6. Change of the barrel temperature time over.

913

908

893

898

893

888

8830 30 60 90 120

Tem

pera

ture

T (K

)

Time t (min)

Shot8 10

Shot11 15

Shot17 21

Shot22 27

SN 1 SB4 1SN 2 SB4 2SB1 1 SB3 2SB1 2 SB5 1SB2 1 SB5 2SB2 2 slurry

Tem

pera

ture

T (

K)

Fig.7. Change of the barrel temperature time over.

Table 2. Temperature condition at barrel. Unit K

Shot No. Slurry SN SB1 SB2 SB3 SB4 SB5 SB68 895 903 903 903 903 903 903 903

11 903 893 866 864 865 865 87317 891 87522 882 871 862 860 861 861 869

92

27

Fig.8 4.5m/s

4m/s

57G 40G

12ms

77MPa 70MPa

1s

Inje

ctio

n St

roke

(

0.1m

m)

Inje

ctio

n Fo

rce

F (

100N

)

Time t (ms)

Inje

ctio

n Sp

eed

V (

mm

/s)

Injection StrokeInjection ForceInjection Speed

Injection Speed :4.5 m/sAcceleration 57 G

Hold Time for Max. Pressure 1 s

Hold Pressure 77MPaTime until Max. Pressure 12ms

Fig.8. Injection wave to evaluate the trial machine.

Mg

Fig.9

Mg

7-8) Fig.10 11

Fig.11

873K

5min 873 875K

10%

896K

5

903K

Fig.9. The viscous model used for the numerical analysis.

Fig.10. The velocity distribution in the screw mixing section by a numerical analysis.

1

Enlarged view

Enlarged view

0

50(mm/s)

0

250

2

0

1 0

40 3

81 2

293 4

1

exp273.15

3.099 10 , 0.7552

3.641 10 , 58330

CC

CCT

C CC C

20

15

10

5

0773 823 873 923 973

Temperature T

Visc

osity

Pas

2

0

1 0

40 3

81

229

3

4

1

exp273.15

3.099 100.7552

3.641 1058330

CC

CCT

CCCC

K

93

28

1 min.

2 min.

3 min.

4 min.

5 min.

903903

873 903

903(a) The boundary condition of temperature.(Unit K)

(b) Change of the temperature distribution in every minute 873 K

903 K

Fig.11. Change of the temperature distribution over time

by a numerical analysis.

30wt%

Fig.12 SB1

PB7 Mg

PB7

903K

PB1

PB7 893K

Mg

Mg

882K

Mg

SB1 SB5

Fig.12. The mapping of the rate of solid phase by semi-solid temperature conditions.

30%

5mm

Fig.13

Semi SolidSlurry Metal

MoltenMetal Fig.13. The difference of flow status between semi-solid

and molten metal.

PB7 of Temperature T (K)

SB1

of T

empe

ratu

re T

(K)

853 863 913903893883873

863

873

883

893

903

913

853

883K 885K >893K

>893K

>893K

882K

882K

878K

875K 870K

>893K

94

29

/

Fig.14

A

Fig.14. A clutch piston sample. Numbers indicate

sites for the measurement of the rate of solid phase.

Fig.14

5wt% 30wt%

Fig.15 Table 3

Temperature 875KTemperature 865K

200 mPo

sition

Position

Fig.15. The metallographic structure photographs

in the positions of both and for 865K and 875K.

Table 3. The rate of solid phase in each position for 865K and 875K.

Temperature(K)

(%) (%) (%) (%)Calculatedvalue (%)

865 28.8 24.5 30.6 25.3 30875 7.9 6.9 10.1 5.1 10

Fig.16

(a)

(b)

12

95

30

(a) With void (b) Without void Fig.16. Existence of defect on the surface of the cast by

the color checks method.

7)

Table 4

L18

Table 4. The forming experimental condition by semi-solid injection molding machine.

Control factor Level

Condition setup of semi-solid injection molding mHold time

of injection pressureachine.

A Pressure-up speed (Valve open angle %)

High (20%)

Low (13%)

-

B Preset temperature of screw barrel (K)

913 875 865

C Injection speed (m/s) 1 2 4D Injection pressure (MPa) 20 40 70E Hold time of injection

pressure (msec.)200 600 1000

Condition setup of mold.

F Degree of vacuum (kPa) Atmosphere

50 5

G Temperature (K) 423 473 523H Chill time (s) 1 3 10

Fig.17 S/N

875K

10

Fig.16 (b)

S/N

Rat

io

6

5

4

3

2

High Low 913 875 865 1 2 4 20 40 70

B C DA

G H

S/N

Rat

io

6

5

4

3

2

200 600 1000 AT 50 5 423 473 523 1 3 10

E F

Fig.17. Influence on the optimum molding conditions by

evaluation of the number of cast defects.

Fig.18

Mg

A 2

Table 5

A A -1 395,400

847,800

Mg 334,200

104,400

Mg A

96

31

2

A

Mg 1.4 Mg

1.4

Fig.19

Fig.18. Test stand for the durability evaluation of a clutch piston.

Table 5. The evaluation result of the durability test.

Materials

SampleNo.

The number of times of breakage

The parts of breakage

Mg

Mg-1 334,200 Near a spring seat side

Mg-2 282,000 Near a spring seat side

Mg-3 161,000 The corner part of a spring seat side

Mg-4 232,200 The corner part of a spring seat side

Mg-5 104,400 The groove processing portion over all the circumferences

AlA -1 395,400 Near a spring seat side

A -2 847,800 The test close without damaging

A -3 847,800 The test close without damaging

Fig.19. The photograph of breakage near spring seat

side.

(1) Mg 200ton

(2) Ca AMC403 Mg

(3)

(4)

(5)

A

(6) Mg

Mg

http://www.kobelcokaken.co.jp/zigyou/kadaikaiketsu/it/2003/2003_all.pdf

(Cross section)

2 PT 1/8

Spring

107

97