Mg Die Casting

Magnesium Die Casting International Summer School on High-Integrity Die Castings 28 Jul.-1 Aug., 2008, WPI, Worcester, USA

K. U. Kainer, Z. Zhen, Y. Huang, N. Hort Magnesium Innovation Centre MagIC, GKSS Forschungszentrum Geesthacht GmbH PAGE 1

Challenges for Magnesium R&D

– Automotive (see figure) – 3C industries computer, communication, consumer electronics

Sheets, inside

Challenge

 Magnesium for consumer products  Early application in 1940’s and 1960’s (VW Beetle)  Revival since 1990’s; main application areas:

Sheets, outside

Extrusions Thixo-/ foring parts for chassis Complex thin-walled casting parts for body Casting for high thermal and mechanical load Casting

Time Friedrich H., Schumann S., Proc. of the Second Israeli International Conference (2000): 9–18. PAGE 2

Magnesium in Automotive Today Global emissions standards are getting more stringent

Chart courtesy of CSM Worldwide PAGE 3

Reduced emissions ~ Cleaner Air

Weight Savings: Materials

Engine V-4 Mg: 16 kg Al: 22 kg Fe/Steel: 60 kg 22 - 73 %

Wheel case Mg: 11,4 kg Steel: 15,6 kg 28 %

PAGE 4

Steering Column Support Mg: 1,4 kg Steel: 2,3 kg 40 %

Tailgate Mg: 3,2 kg Al: 5,5 kg 42 % Seat frame Mg: 1,8 kg Steel: 5 kg 64 %

Steering Column Mg: 0,9 kg Steel: 1,4 kg 33 %

Inner Door Mg: 5,4 kg Al: 8,2 kg 33 % Quelle: www.magnesium.com

Potential Weight Savings Component

Power Train

Additional Potential Use of Mg

Currently used on e.g. VW / Audi vehicles

short term < 5 years

medium term > 5 years

18 kg

24-29 kg

38-49 kg

4 kg

3 kg

Grand Total

25 kg

After Volkswagen AG, K-EFWM/Dr. Schumann/Sinomag11.2002 PAGE 5

12-16 kg

23-37 kg

59-82 kg

long term > 10 years

14-20 kg

31-49 kg

46-69 kg

4-6 kg

34-40 kg

87-130 kg

132-184 kg

Use of Magnesium in the Past

1939

Before WW II

1924

1941 1939

After WW II

1952 1995 PAGE 6

1946-1978

Magnesium Applications Today Interior Parts Sunroof Components Mirror Frames Headlight Retainers Inner Door Frames

Interior Parts Seat Components Instrument Panels Knee Bolsters Steering Column Comp. Steering Wheels Brake & Clutch Pedal Brackets Airbag Retainers Brackets Radio Frames Radio and HVAC Covers

Drive train Parts Manual Transmission Housings 4 WD Transfer Case

Engine Parts Crankcase Cylinder head Covers Intake Manifolds Drive Brackets Electrical Connectors Engine Cradle Oil pans PAGE 7

Magnesium Applications Today: High Pressure Die Casting

PAGE 8

Temperatures for Power Train Use

suspension, crank shaft

engine block T > 200 °C

piston T > 250 °C

fan, gaskets T < 100 °C filter boxes T = 150-200 °C source: Volkswagen AG PAGE 9

ignition plug, catalyst

gear box housing T < 175 °C

Applications in Power Train: High Pressure Die Casting

PAGE 10

Forecast High Pressure Die Casting

Casting ,000 tons

Source: Hydro Magnesium intern: Probability Forecast *) China domestic demand on die casting is included as of 2004 PAGE 11

Forecast: Applications HPDC-Parts 80

Powertrain Structural Components

[metric ktons]

60

40

20

0 2005

2006

2007

2008

Year Source:D. Webb http//www.intlmag.org PAGE 12

2009

2010

Use of Magnesium Alloys

• Casting - Die casting (AZ, AS, AE, AM) - Gravity casting (AZ, K, ZK, ZE, EZ, QE, WE) - Squeeze casting (AZ, AS, AE, AM, K, ZK, ZE, EZ, QE) - Semi-solid (AZ, AS, AE, AM) • Extrusion (AZ31, AZ61, AZ80, WE54, WE43) • Rolling (AZ31, HK31, HM21, ZK60) • Forging (AZ31, AZ60, AZ80, ZK) • Corrosion protection • Welding

PAGE 13

Magnesium Alloy Systems

• AZ (Mg-Al-Zn) • good room temperature properties • small properties at elevated temperatures • low ductility

• AM (Mg-Al-Mn) • better ductility • moderate room temperature properties • constricted castability

• AS (Mg-Al-Si) • better strength • improved creep resistance • constricted castability PAGE 14

• AE (Mg-Al-SE) • AJ (Mg-Al-Sr) • MRI (Mg-Al-Mn-Ca-RE) • good properties at elevated temperatures • good creep resistance • constricted castability

Magnesium Casting Alloys

• Die casting - AZ, AS, AE, AM • Gravity casting - AZ, K, ZK, ZE, EZ, QE, WE • Squeeze casting - AZ, AS, AE, AM, K, ZK, ZE, EZ, QE • Semi-solid - AZ, AS, AE, AM

PAGE 15

Patents/Modifications for Pressure Die Cast Magnesium Alloys Year/ Originator

Chemical Composition Al

Zn

Mn

SE

Ca

<2

0.25-5.5

0.05

0-1

1994 Nissan/Ube

1.5-10

1996 MEL

< 0.1

0-0.4

1996 Hyundai

5.3-10

0.7-6.0

1996 ITM Inc.

2-6

1996 Noranda

4.9 4.7-4.9

0.26-0.30 0.27-0.29

1997 Honda

4.5-10 4.5-6

0.2-1 0.2-1

1997 Mazda

2-6

1997 IMRA America

2-9

6-1

1997 Hyundai

5.3-10

0.7-6.0

1999 VW/DSM

6-9

0.7-0.9

0.18-0.37

0.15-0.92

1.9-2.5

0.25

0.05-0.15

0.06-0.25

2000 Norsk Hydro

0.4-5 Si 0.1-0.8 1.74-1.94 Sr 1.23-1.35 Sr 1-3 1-3

0.1-3 1.2-2.2 0.5-4

Source: Pekgüleryüz, 2000, King, 1998, Norsk Hydro, 2003 PAGE 16

0-0.5

others

0.2-0.5

0.1-2.0 0.15-10

0.5-5 Si

0.45-1.1

0.03-0.11 Sr 0.7-1.2 Si

VW Objectives For HPDC High Temperature Magnesium Alloys • Room temperature characteristics at least as good as AZ91. • Elevated strength better than AZ91 beyond 120ºC. • Minimum creep rate better than AE42. • Castability similar to AZ91. • Corrosion resistance similar to HP AZ91. • Cost ≤ 1.2 x AZ91

PAGE 17

Castability of Mg-Al-Zn Alloys

alloygroups AZ-Base 1 AZ-Base 2 ZA-Base

castable difficult

Zn-content (wt.-%) Source: Foerster PAGE 18

Castability and Creep Resistance 180 °C 8

1: AZ91 10

2: AS21X

9

3: MRI153M

Creep Resistance

7

4: AJ62X 5: AE42

6 5 4 2 150 °C

3

6: AJ52X 7: ACM522 8: AX52J

1

9: MRI230D 10: AM-HP2

Source: Aghion et al., Dunlop et. PAGE 19

Al.

Castabilit y

Die Casting of Magnesium Alloys

• • • • • •

Filling time 30 % shorter compared to Al Life time of tools higher Ingate speed appr. 90-100m s-1 Ingate thickness > 0.8 mm Temperature of the die: 220-240 ºC Die casting alloys - Hot chamber: AZ, AM - Cold chamber: AZ, AM, AE, AS

• Not all Mg-alloys can be used for die casting!!

PAGE 20

Illustration of die casting process

Source: www.ekkinc.com PAGE 21

Cold Chamber Die Casting Process

moving platen fixed platen ejector

moving die part

ejector die plunger chamber PAGE 22

Hot Chamber Die Casting Process

hydraulic closing die

die piston melt

chamber

PAGE 23

HPDC Unit

Source: www.rauch-ft.com PAGE 24

HPDC and Vacuum HPDC

PAGE 25

Cover Cover Gases Gases

Unsolved status in the EU: Fluor containing gases are likely to be abandonned. Cover gas components: SF6, SO2, R134a (HFC134a) New protective gases: Novec 612, Fluorokethone, Hydro-Fluorether Global warming potential (GWP): FK < HFC134a < 0,05% 5%

PAGE 26

SF6 100%

Relationship Between Magnesium Die Casting Defects And Processing Parameters

Incomplete filing

Metal velocity

Metal Pressure

Die Temperature

Gating system

Die vent

Die lubricant

Metal Temperature

●

●

●

●

●

●

●

●

Cold shuts Pores

●

●

Ejection defect

Casting rate

● ●

●

Gas bubbles

●

Shrinks

●

Blisters Flow marks

●

●

●

Hot cracks Cracks/fractu res Deformation

PAGE 27

●

●

●

●

●

Surface Swirls

●

● ●

●

● ●

● ●

●

●

●

Quality Control

Alleviation of pre-solidification in the shot sleeve: • Reduce the heat transfer from the melt to the sleeve wall by insulating the inner sleeve wall. • Reduce the heat conductivity in the sleeve wall. • Reduce the heat transfer by maintaining a higher temperature in the sleeve wall.

Source: Gjestland et al. Adv Eng Mater, PAGE 28 2007

Microstructure

Secondary dendrite arm spacing and grain size as a function of solidification rate in AZ91D

Source: Gjestland et al. Adv Eng Mater, PAGE 29 2007

Creep Properties Of Mg-al-ca Alloy Produced By Die Cast, Squeeze Cast And Gravity Cast Die cast Squeeze cast Die cast

Source: Zhu et al, Mater.Sci.Eng.A,2008 PAGE 30

Numerical Simulation Methods

Finite Difference Method (FDM) and Finite Element Method (FEM) FDM is easy on programming and gives result with reasonable accuracy, while FEM shows advantages on simulating complex and thin-wall castings, due to its better geometry replication.

FEM

FDM

Thin-wall casting geometry modeled by using FEM and FDM methods Source: Marty McLaughlin, www.ekkinc.com PAGE 31

Mold Filling Simulation Of Hot-chamber Diecast AM60B

Filling time: 11ms Cast temp.: 650oC Software: self-developed 3D FDM program

Mold filling simulation results of diecast AM60B alloy, showing that the melt enters a cylindrical bar in the way of a jet and is “bounced” backward along the wall when striking the filled part

Source: Li and Zhou, Materials Technology, 2003 PAGE 32

A Mold Filling Simulation Case

Source: Song and Xu, North Hengli Sci. and Tech Co. PAGE 33 Ltd.

Solidification Simulation Of HPDC Magnesium Alloys

Source: Song and Xu, North Hengli Sci. and Tech Co. Ltd.PAGE 34

Flow Simulation Within Shot Sleeve

Magnesium die casting part is usually very thin and the heat capacity (combining the specific heat and latent heat of fusion) of magnesium is small compared with that of aluminum. Therefore, magnesium die castings solidify during the die filling more remarkably than aluminium die castings. It also indicates that the accuracy of mold filling simulation for magnesium die castings is more significant than that of aluminium alloys. To further improve the accuracy of flow simulation, recently, melt motion within shot sleeve had been integrated into the mold filling simulation for magnesium alloys.

Source: www.ekkinc.com PAGE 35

Solidification Simulation Of Low Pressure Die Cast Magnesium Wheel

Source: NERC-LAF, Shanghai Jiaotong Uni.PAGE 36

Solidification Simulation Of Low Pressure Die Cast Wheel

Source: NERC-LAF, Shanghai Jiaotong PAGE 37 Uni.

Solidification Simulation Of Low Pressure Die Cast Engine Block

Source: NERC-LAF, Shanghai Jiaotong PAGE 38 Uni.

Microstrutural Simulation Of Die Cast AM50

Microstructure of die cast AM50 simulated by using a 2D Cellular Automaton based model coupling with macro heat transfer calculation Source: Fu et al, Mater.Sci.Forum, 2008 PAGE 39

Magnesium Recycling

• Driving force is saving energy: - 35 kWh/kg for prime-production - 3 kWh/kg for remelting magnesium-scrap • Prime scrap: casting alloys, crap of production • Old scrap: alloys, partly polluted • Alloy mix - Definition of recycling alloys - Base alloy system - Influence of alloying elements, impurities on property profile

PAGE 40

Recycling Alloys

PAGE 41

2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992

PAGE 42

1991 0

Quelle: IMA, MEL, Hydro Magnesium

Secondary Magnesium

200

150

100

50

New Secondary Alloy

Composition and microstructure of the new secondary alloy compared to AZ91D

Alloy Al Zn AZ91D 8.75 0.67 AZC1231 11.7 3.04

AZ91D (600-800 µm)

PAGE 43

Mn 0.2 0.48

Si 0.054 0.39

Cu 0.008 0.47

Fe Ni 0.0022 0.0006 0.0087 0.0032

AZC1231 (~100 µm)

Corrosion Properties Corrosion properties of AZ91D and AZC1231 determined in various corrosion tests (gravity die casting except * HPDC housing)

Corrosion test condition

AZ91D

AZC1231

Pot.dyn. polarisation (after 1h in 5%NaCl, pH11)

0.43 ± 0.04 mm/year

1.81 ± 0.59 mm/year

Lin. polarisation resistance (after 24h in 5%NaCl, pH11)

247 Ω cm2

80 Ω cm2

Impedance (after 36h in 3.5%NaCl, pH7)

263 Ω cm2

149 Ω cm2

Saltspray (after 48h in 5%NaCl, pH7)

1.07 ± 0.23 mm/year

0.99 ± 0.58 mm/year

Immersion* (average after 400 h in 3.5%NaCl, pH6)

1.49 mm/year

1.42 ± 0.26 mm/year

PAGE 44

Mechanical Properties Comparison of the mechanical properties of the new alloy AZC1231 and AZ91D Property

AZ91

AZC1231

Hardness (HV5)**

83,2 ± 3,3

104,9 ± 2,8

Friction coefficient**

0.27

0.23

Wear volume** (mm3/N/m)

11.5 * 10-4

6.7 * 10-4

Rm* (MPa)

263 ± 14

246 ± 17

Rp* (MPa)

198 ± 15

187 ± 27

A5* (%)

2.1 ± 0.5

0.7 ± 0.5

Creep rate ** (s-1 )

4,38 * 10-8

1,74 * 10-8

SCC threshold stress*** (MPa)

90

130

* HPDC housing, ** HPDC test specimen, *** gravity die cast PAGE 45

Casting Properties Helix casting experiments* (700°C melt temperature, release agent Demotex S)

completely filled length of the helix [cm]

AZ91D

159.0 ± 5.7

256.8 ± 36.1

48.6 ± 7.4

23.0 ± 1.8

AZC1231

158.8 ± 2.5

408.8 ± 28.4

66.1 ± 5.6

39.5 ± 6.0

Better casting properties compared to AZ91D, thus no limitations in the possible casting processes gravity die casting

PAGE 46

NRC

HPDC

* C. Scharf, P. Živanovic, A. Ditze, K. Horny, G. Franke, C. Blawert, K.U. Kainer, E. Morales,

angle [°] filled length of the helix [cm]

Giesserei 94, Nr. 11 (2007), S.20-33

Thelix [°C]

Research into the Industrial Use ingot (AZ91D)

ingot (AZC)

housing (AZ91D)

housing (AZC)

Rm (MPa)

198

189

258

250

Rp0,2 (MPa)

81

152

187

187

A5 (%)

5,6

0,5

2,8

1,4

1

1

2,5

5

Gravity die casting 6 kg melt volume (Lab)

25 mm

HPDC housing 1000 kg melt volume (Industry)

CRsaltspray (mm/year)

AZC secondary alloy has similar properties (casting behaviour, strength and corrosion resistance) compared to AZ91D Patent application:

250 mm

Ditze, A. Scharf, C., Blawert, C., Kainer, K. U., Morales, G.E.D.: Magnesiumsekundärlegierung. DE 10 2005 033835 A1, 2005. Ditze, A. Scharf, C., Blawert, C., Kainer, K. U., Morales, G. E. D.: Magnesium Alloy. WO 2007/009435 A1, 2006.

PAGE 47

Source: Institut fuer Fahrzeugkonzepte, PAGE 48

DLR

Source: Institut fuer Fahrzeugkonzepte, PAGE 49

DLR

Source: Institut fuer Fahrzeugkonzepte, PAGE 50

DLR

Source: Institut fuer Fahrzeugkonzepte, PAGE 51

DLR

Source: Institut fuer Fahrzeugkonzepte, PAGE 52

DLR

Thank you for your attention! PAGE 53