Semi-Solid Injection Moulding - fsb.unizg.hr · –Semi-Solid Injection Moulding . Paul Sponsel ... Husky Injection Molding Ltd. (Canada) are the only two manufacturers • Machines

Paul Sponsel

Thixomolding– Semi-Solid Injection Moulding

www.mmpmg.com

Paul Sponsel

Thixo-what?– Thixotropic flow characterics

“Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick, or viscous, under static conditions will flow (become thin, less viscous) over time when shaken, agitated, sheared or otherwise stressed (time dependent viscosity). They then take a fixed time to return to a more viscous state.” – Wikipedia

2

Examples?

Paul Sponsel

Thixo-what?– Thixotropic flow characterics

“Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick, or viscous, under static conditions will flow (become thin, less viscous) over time when shaken, agitated, sheared or otherwise stressed (time dependent viscosity). They then take a fixed time to return to a more viscous state.” – Wikipedia

3www.wikipedia.org

Paul Sponsel 4

1 Technical basics

2 Chemical and physical basics

3 Manufacturers

4 Applications

5 Summary and outlook

Agenda

www.nmfgmbh.de

Paul Sponsel

Semi-solid metal casting (SSM) – Processes

Semi-solid metalcasting

SIMAThixocasting Rheocasting Thixomolding

5www.wikipedia.org

Paul Sponsel

Semi-solid metal casting (SSM) – Processes

Semi-solid metalcasting

SIMAThixocasting Rheocasting Thixomolding

6www.wikipedia.org

Paul Sponsel

Thixomolding– Machine set-up

7

Mold Product

Slurry

Non-return

valve

Heater bands

Cylinder

Screw

Rotary drive

Accumulator

Automatic vacuum

conveying system

Feeder

Nozzle

Magnesium

chips

Inert gas

(Argon)

www.nmfgmbh.de

High speed

Injection system

Paul Sponsel

Thixomolding– Conditions and Process

• Basic material Magnesium granules (size ~0.5 – 5 mm)

• 3-zone-screw with feeding, compression and homogenization

• Granulat is molten by heater bands and sheared by screw

• Cylinder, screw and heater have to beheated up to operating temperature (560°C – 630°C)

• Injection speed up to 6 m/sHigh injection speed is necessary

due to low thermal capacity and conductivity of magnesium

• Cold slugs fall in separate cavity

8

Close tool Drive up injection

tool

Inject + press

Convey + cool

CoolDrive back injection

tool

Open tool

Remove work piece

Apply abherent

Thixospritzgießen von Magnesiumlegierungen - Gefüge und mechanische Eigenschaften; Scharrer, Martin [2008]

Paul Sponsel 9

1 Technical basics


3 Manufacturers

4 Applications


Agenda

Paul Sponsel

Magnesium– Grid structure and alloys

• Hexagonal structure underatmospheric pressure

• Stacking order is ABAB

• Most common alloy is Aluminum

• Eutectic at 436°C and 33% Aluminum

Improves castability through low melting point

• Technical alloys contain around 10% Aluminum bymass

Up to 12.7% by mass of Aluminum are solvable

Hardening process through heat treatment possible

Oxid layer improves corrosion protection

10

0 10 20 30 40 50

200

250

300

350

400

450

500

550

600

650

700

Aluminum % by mass

Tem

pera

ture

in °

C


Paul Sponsel

Magnesium– Aluminum, zinc, manganese alloys

• Zinc forms low melting eutectic at 51.3% by massand 342°C

• Maximal solubility 6.2% Zinc by mass

Improves castability through low melting point

Improves strength through solid solution hardening

Improves elongation

• Technical alloys contain up to 1% Zinc by mass

• Manganese improves corrosion behaviourIron impurities enter during alloying

Manganese binds them in Fe-Mn-Al compounds

• Technical alloys contain up to 0.4% Manganese

11

0 10 20 30 40 50 60

0

10

20

30

40

50

60

MgZnMg2Zn3

Aluminum % by mass


Paul Sponsel

Thixomolding– MicrostructureTwo-stage process:

1. Heating in the cylinder:

During heating in the cylinder the α-crystals

and melt exist in thermodynamic equilibrium,

the so called solidus-liquidus interval.

2. During and after injection:

The melt cools down at high cooling rates

which leaves the typical fine-grained casting

structure.

12Thixospritzgießen von Magnesiumlegierungen - Gefüge und mechanische Eigenschaften; Scharrer, Martin [2008]

Paul Sponsel

Rheology– Shear time, shear rate and temperature

13

Three parameters influence the viscosity of materials with thixotropic flow characteristics:

Shear time

Viscosity decreases with higher shear

time

Dendric structure is transformed to

equiaxed crystals

Shear rate

Viscosity decreases with higher share

rate

Local solid-phase accumulation in

the middle of the workpieces

Temperature

Viscosity decreases with higher

temperature

Lower solid-phase share in

the melt


Paul Sponsel

Thixomolding vs. die casting– Microstructure

14Thixospritzgießen von Magnesiumlegierungen - Gefüge und mechanische Eigenschaften; Scharrer, Martin [2008]

Paul Sponsel

Magnesium alloys– Short codes

“Magnesium alloys are referred to by short codes (defined in ASTM B275) which denote approximate chemical compositions by weight. For example, AS41 has 4% aluminum and 1% silicon; AZ81 is 7.5% aluminium and 0.7% zinc. If aluminium is present, a manganese component is almost always also present at about 0.2% by weight which serves improve grain structure; if aluminum and manganese are absent, zirconium is usually present at about 0.8% for this same purpose.” – Wikipedia

15

7.5% aluminum

A Z 8 1

0.7% zinc

Paul Sponsel

Thixomolding vs. die casting– Mechanical properties

16

Test.- temp.

(°C)

Thixomolding (NMF) Die Casting Reference

Rm

(MPa)

Rp02

(MPa)E (%)

Rm

(MPa)Rp02 (MPa) E (%)

AZ91D RT 260 170 8 260 160 6

150 175 130 19 160 100 18

AM60B RT 253 150 11 247 123 12

150 157 114 24 - - -

AZ70 RT 259 150 11 - - -

150 165 120 25 - - -

AJ52 RT 245 151 10 212 134 6

150 172 128 20 163 110 12

AJ62 RT 257 151 11 239 142 8

150 170 125 15 163 108 19

AS31 RT 251 145 13 216 130 8

150 155 113 26 - - -

AS41 RT 265 152 13 240 130 10

150 160 118 29 150 90 -

Advances in Magnesium Thixomolding®; Lohmüller et. Al. [2007]

Paul Sponsel

Thixomolding vs. die casting– PorosityOverall porosity can be measured with the Archimedes-principle (weighing each part in airand isopropyl alcohol).

17

6

4

2

0

8

poro

sity

in %

6

4

2

0

8

poro

sity

in %

AJ62ρ = 1,80 g/cm²

Pressure die casting

Thixomodling

AZ91ρ = 1,81 g/cm²

Pressure die casting

Thixomodling


Paul Sponsel

Thixomolding vs. die casting– Energy consumption

A rough estimate for the needed energyfor heating up the alloy can be obtainedwith the following equation:

∆𝐸 = න

𝑅𝑇

𝑇𝑆

𝐶𝑃,𝑆𝑜𝑙𝑖𝑑𝑑𝑇 + ∆𝐻 + න

𝑇𝐿

𝑇𝑃

𝐶𝐿,𝑙𝑖𝑞𝑢𝑖𝑑𝑑𝑇

Depending on the solid phase contentThixomolding has a significant lowerenergy consumption compared to die casting.

18

-24% -17% -12% -4%

200

800

600

400

1000

0

580 590 600 650 680

AZ91

Thixomolding Die casting

Energ

y (

kJ/k

g)

Temperature (°C)


Paul Sponsel

Thixomolding vs. die casting– Cover gas consumption

19

N2/

0,2% SF6

N2 /

0,25%

HCF-134a

N2 /

1,5% SO2

Cost

(%)

80

20

40

60

0

100

Thixo-

molding

24 Nl/h

Die casting

400 Nl/h

CO

2-E

quiv

ale

nt (t

/a)

ArgonN2/

0,2% SF6

N2 /

0,25%

HCF-134a

N2 /

1,5% SO2

Argon

Thixo-

molding

24 Nl/h

Die casting

400 Nl/h

800

200

400

600

0

1000

Toxic

, C

orr

osiv

e

1177 k

g S

O2/a


Paul Sponsel 20

1 Technical basics


3 Manufacturers

4 Applications


Agenda

Paul Sponsel

Thixomolding manufacturers– Highly specialized machines

21

• Thixomolding machines are a relativlynew technology

• Only approximately 300 machines aresold worldwide

• Japan Steel Works Ltd. (Japan) and Husky Injection Molding Ltd. (Canada) are the only two manufacturers

• Machines are available with clampforces between 75t and 1600t

• In Europe there are only companies in Austria, Belgium, France and Germany who are dealing with thistechnology

300

250

200

150

100

50

0

Gesamt

Europa

Japan/Südostasien

Nordamerika

Num

ber

of

machin

es


Paul Sponsel 22

1 Technical basics


3 Manufacturers

4 Applications


Agenda

Paul Sponsel

Thixomolding– Applications in automobile industry

• Seat frames

• Steering wheels

• Road wheel

• Oil pumps

• Key lock housing

• Transmission parts

• Navigation system parts

23www.jsw.co.jp

Paul Sponsel

Thixomolding– Electronic equipment

• Cameras

• Notebooks

• Mobile phones

• Monitors

• Heat sinks

• LCD projectors

• Optical pickups

24Neue Entwicklungen beim Thixospritzgießen von Magnesiumlegierungen; Eibisch et. Al. [2005]

Paul Sponsel 25

1 Technical basics


3 Manufacturers

4 Applications


Agenda

Paul Sponsel

Thixomolding– Summary

26

Advantages Disadvantages

+ Low energy consumption

+ Only argon needed as inert gas (no global

warming potential and low price)

+ Low porosity of work pieces

+ High tensile strength (Rm)

+ High yield strength (Rp02)

+ High E-modulus

+ Narrow wall thicknesses achievable

+ Near net-shaped work pieces

+ High market growth potential (especially

automobile sector)

- Small temperature range to achieve solidus-

liquidus intervall

- New technology, not researched a lot yet

- Only a few manufacturers (support?)

Paul Sponsel

Thixomolding– New developments

Particle Reinforced Magnesium alloys (Power steering pump bracket)

• Intense mixing

• Short contact times

• Low processing temperatures

Hot Runner Systems• Pre heated molds

• Reduces shot weight up to 35%

Melt metallurgical production of Magnesium granules• Cost of Magnesium chips is crucial to Thixomolding

• Prototype equipment for melt metallurgical technique

27Advances in Magnesium Thixomolding®; Lohmüller et. Al. [2007]

Documents

Semi-Solid Injection Moulding - fsb.unizg.hr · –Semi-Solid Injection Moulding . Paul Sponsel ... Husky Injection Molding Ltd. (Canada) are the only two manufacturers • Machines