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PAGE 1
K. U. Kainer, Z. Zhen, Y. Huang, N. Hort
Magnesium Innovation Centre MagIC, GKSS Forschungszentrum Geesthacht GmbH
Magnesium Die Casting
International Summer School on High-Integrity Die Castings
28 Jul.-1 Aug., 2008, WPI, Worcester, USA
PAGE 2
Challenges for Magnesium R&D
Magnesium for consumer products Early application in 1940’s and 1960’s
(VW Beetle) Revival since 1990’s; main application
areas:– Automotive (see figure)– 3C industries
computer, communication,consumer electronics
Friedrich H., Schumann S., Proc. of the Second Israeli International Conference (2000): 9–18.
Sheets, outside
Sheets, inside
Extrusions
Thixo-/ foring parts for chassis
Complex thin-walled casting parts for body
Casting for high thermal and
mechanical load
Casting
Time
Cha
lleng
e
PAGE 3
Reduced emissions ~ Cleaner AirChart courtesy of CSM Worldwide
Global emissions standards are getting more stringent
Magnesium in Automotive Today
PAGE 4
Weight Savings: Materials
Steering ColumnMg: 0,9 kgSteel: 1,4 kg33 %
Wheel caseMg: 11,4 kgSteel: 15,6 kg28 %
TailgateMg: 3,2 kgAl: 5,5 kg42 %
Steering Column SupportMg: 1,4 kgSteel: 2,3 kg40 %
Seat frameMg: 1,8 kgSteel: 5 kg64 %
Inner DoorMg: 5,4 kgAl: 8,2 kg33 %
Engine V-4Mg: 16 kgAl: 22 kgFe/Steel: 60 kg22 - 73 %
Quelle: www.magnesium.com
PAGE 5
Potential Weight Savings
4 kg
4-6 kg 34-40 kg
3 kg 23-37 kg
18 kg 38-49 kg
25 kg 59-82 kg 132-184 kg87-130 kg
Component
Grand Total
Power Train
Currently used on e.g. VW / Audi vehicles
short term< 5 years
long term> 10 years
medium term> 5 years
After Volkswagen AG, K-EFWM/Dr. Schumann/Sinomag11.2002
Additional Potential Use of Mg
24-29 kg
14-20 kg12-16 kg
31-49 kg 46-69 kg
PAGE 6
Before WW II
After WW II
1924
1941
1939
1952
1946-19781995
1939
Use of Magnesium in the Past
PAGE 7
Magnesium Applications Today
Interior PartsSeat ComponentsInstrument PanelsKnee BolstersSteering Column Comp.Steering WheelsBrake & Clutch Pedal BracketsAirbag RetainersBracketsRadio FramesRadio and HVAC Covers
Drive train PartsManual Transmission Housings4 WD Transfer Case
Engine PartsCrankcaseCylinder head CoversIntake ManifoldsDrive BracketsElectrical ConnectorsEngine CradleOil pans
Interior PartsSunroof ComponentsMirror FramesHeadlight RetainersInner Door Frames
PAGE 8
Magnesium Applications Today: High Pressure Die Casting
PAGE 9
suspension,crank shaft
fan, gasketsT < 100 °C
ignition plug, catalyst gear box housing
T < 175 °C
engine blockT > 200 °C
source: Volkswagen AG
pistonT > 250 °C
filter boxesT = 150-200 °C
Temperatures for Power Train Use
PAGE 10
Applications in Power Train: High Pressure Die Casting
PAGE 11
Forecast High Pressure Die Casting
Source: Hydro Magnesium intern: Probability Forecast
*) China domestic demand on die casting is included as of 2004
Casting ,000 tons
PAGE 12
2005 2006 2007 2008 2009 20100
20
40
60
80
[me
tric
kto
ns
]
Year
Powertrain Structural Components
Source:D. Webb http//www.intlmag.org
Forecast: Applications HPDC-Parts
PAGE 13
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 14
• 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
• 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 Alloy Systems
PAGE 15
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 16
Patents/Modifications for Pressure Die Cast Magnesium Alloys
Year/Originator
Chemical Composition
Al Zn Mn SE Ca others
1994 Nissan/Ube 1.5-10 < 2 0.25-5.5
1996 MEL < 0.1 0-0.4 0-0.5 0.05 0-1
1996 Hyundai 5.3-10 0.7-6.0 0.4-5 Si
1996 ITM Inc. 2-6 0.1-0.8
1996 Noranda 4.94.7-4.9
0.26-0.300.27-0.29
1.74-1.94 Sr1.23-1.35 Sr
1997 Honda 4.5-10 4.5-6
0.2-1 0.2-1
1-3 1-3
0.1-3 1.2-2.2
1997 Mazda 2-6 0.5-4
1997 IMRA America 2-9 6-1 0.2-0.5 0.1-2.0
1997 Hyundai 5.3-10 0.7-6.0 0.15-10 0.5-5 Si
1999 VW/DSM 6-9 0.7-0.9 0.18-0.37 0.15-0.92 0.45-1.1 0.03-0.11 Sr
2000 Norsk Hydro 1.9-2.5 0.25 0.05-0.15 0.06-0.25 0.7-1.2 Si
Source: Pekgüleryüz, 2000, King, 1998, Norsk Hydro, 2003
PAGE 17
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 18
Castability of Mg-Al-Zn Alloys
Zn-content (wt.-%)
AZ-Base 1AZ-Base 2ZA-Base
alloy-groups
castabledifficult
Source: Foerster
PAGE 19
78 9
10
6
1
5 42
3
1: AZ91
2: AS21X
3: MRI153M
4: AJ62X
5: AE42
6: AJ52X
7: ACM522
8: AX52J
9: MRI230D
10: AM-HP2
Castability
Cre
ep
Res
ista
nce
180 °C
150 °C
Source: Aghion et al., Dunlop et.
Al.
Castability and Creep Resistance
PAGE 20
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 21
Illustration of die casting process
Source: www.ekkinc.com
PAGE 22
Cold Chamber Die Casting Process
plunger
chamber
partejector
fixed platen
ejector die
moving platen
moving die
PAGE 23
Hot Chamber Die Casting Process
hydraulic closing die
piston
chamber
melt
die
PAGE 24
HPDC Unit
Source: www.rauch-ft.com
PAGE 25
HPDC and Vacuum HPDC
PAGE 26
Cover 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 < SF6
0,05% 5 % 100%
Cover Gases
PAGE 27
Relationship Between Magnesium Die Casting Defects And Processing Parameters
Metal velocity
Metal Pressure
Die Temperature
Gating system
Die vent Die lubricant Metal Temperature
Ejection defect
Casting rate
Incomplete filing
● ● ● ● ● ● ●
Cold shuts ● ●Pores ● ● ● ●
Gas bubbles
Shrinks ● ●Blisters ● ● ●
Flow marks ● ● ● ● ●Surface Swirls
● ●
Hot cracks ● ● ● ●Cracks/
fractures● ● ●
Deformation ● ●
PAGE 28
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,
2007
PAGE 29
Microstructure
Secondary dendrite arm spacing and grain size as a function of
solidification rate in AZ91D
Source: Gjestland et al. Adv Eng Mater,
2007
PAGE 30
Creep Properties Of Mg-al-ca Alloy Produced By Die Cast, Squeeze Cast And Gravity Cast
Source: Zhu et al, Mater.Sci.Eng.A,2008
Die
cast
Sq
uee
ze ca
stD
ie
cast
PAGE 31
Numerical Simulation Methods
Thin-wall casting geometry modeled by using FEM and FDM methods
FEM FDM
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.
Source: Marty McLaughlin, www.ekkinc.com
PAGE 32
Mold Filling Simulation Of Hot-chamber Diecast AM60B
Source: Li and Zhou, Materials Technology, 2003
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
Filling time:
11ms
Cast temp.:
650oC
Software:
self-developed
3D FDM
program
PAGE 33
A Mold Filling Simulation Case
Source: Song and Xu, North Hengli Sci. and Tech Co.
Ltd.
PAGE 34
Solidification Simulation Of HPDC Magnesium Alloys
Source: Song and Xu, North Hengli Sci. and Tech Co.
Ltd.
PAGE 35
Flow Simulation Within Shot Sleeve
Source: www.ekkinc.com
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.
PAGE 36
Solidification Simulation Of Low Pressure Die Cast Magnesium Wheel
Source: NERC-LAF, Shanghai Jiaotong
Uni.
PAGE 37
Solidification Simulation Of Low Pressure Die Cast Wheel
Source: NERC-LAF, Shanghai Jiaotong
Uni.
PAGE 38
Solidification Simulation Of Low Pressure Die Cast Engine Block
Source: NERC-LAF, Shanghai Jiaotong
Uni.
PAGE 39
Microstrutural Simulation Of Die Cast AM50
Source: Fu et al, Mater.Sci.Forum, 2008
Microstructure of die cast AM50 simulated by using a 2D Cellular Automaton based
model coupling with macro heat transfer calculation
PAGE 40
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 41
Recycling Alloys
PAGE 42
Que
lle: I
MA
, ME
L, H
ydro
Mag
nesi
um
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
0
50
100
150
200
Secondary Magnesium
PAGE 43
New Secondary Alloy
Alloy Al Zn Mn Si Cu Fe Ni
AZ91D 8.75 0.67 0.2 0.054 0.008 0.0022 0.0006
AZC1231 11.7 3.04 0.48 0.39 0.47 0.0087 0.0032
Composition and microstructure of the new secondary alloy compared to AZ91D
AZC1231 (~100 µm)AZ91D (600-800 µm)
PAGE 44
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 cm2 80 cm2
Impedance (after 36h in 3.5%NaCl, pH7)
263 cm2 149 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 45
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 46
Casting Properties
Thelix
[°C]
angle [°]
filled length of the helix
[cm]
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
Helix casting experiments* (700°C melt temperature, release agent Demotex S)
Better casting properties compared to AZ91D, thus no limitations in the possible casting processes
gravity die casting HPDCNRC
* C. S
charf, P
. Živan
ovic, A
. Ditze, K
. Ho
rny, G
. Fran
ke, C. B
lawert, K
.U. K
ainer, E
. M
orales,
Giesserei 94, N
r. 11 (2007), S.20-33
PAGE 47
Research into the Industrial Use
Gravity die casting6 kg melt volume (Lab)
HPDC housing1000 kg melt volume (Industry)
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
CRsalt spray (mm/year)
1 1 2,5 5
AZC secondary alloy has similar properties (casting behaviour, strength and corrosion resistance) compared to AZ91D
Patent application: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.
25 mm
250 mm
PAGE 48Source: Institut fuer Fahrzeugkonzepte,
DLR
PAGE 49Source: Institut fuer Fahrzeugkonzepte,
DLR
PAGE 50
Source: Institut fuer Fahrzeugkonzepte,
DLR
PAGE 51Source: Institut fuer Fahrzeugkonzepte,
DLR
PAGE 52Source: Institut fuer Fahrzeugkonzepte,
DLR
PAGE 53
Thank you for your attention!