Magnesium research activities · Department of Mechanical Engineering Magnesium research activities Tsinghua-TOYO research center of Mg & Al alloys processing technology Tsinghua

Department of Mechanical Engineering

Magnesium research activities

Tsinghua-TOYO research center of Mg & Al alloys processing technology

Tsinghua University

XIONG Shoumei


Outline

Background

Research Progress

Ongoing Research Work


Magnesium alloys

Strength/weight ratioExcellent damping capacityNon-magnetic, EMF shieldingGood heat dissipationHigh castabilityExcellent machinabilityLonger tooling life


WORLD ANNUAL PRIMARY MAGNESIUMPRODUCTION, BY COUNTRY, 2001

48%

20%

8%11%

7%

4%

1%1%

China

Canada

Norway

Russia

Israel

France

Brazil

Kasakhstan

Serbia and Montenegro

China

Total: 425,800 tons

Data from U.S. Geological Survey Minerals Book, 2001


Primary Magnesium Production of China

7392

123

157

195216

268

354

0

50

100

150

200

250

300

350

400

1996 1997 1998 1999 2000 2001 2002 2003

Production,ktons

Data from Chinese Magnesium Association, 2003


U.S. Structural Applications of Magnesium Alloys, 2001

1%

89%

3%

7%

Die casting

Permanent moldcastingSand casting

Wroght products

Data from U.S. Geological Survey Minerals Book, 2001


Western World


Challenges for Magnesium Die Casting Process

Design expertise & process development

Corrosion protection of Mg components

High temperature properties


Tsinghua-TOYO R&D Center of Magnesium and Aluminum Alloys Processing Technology

Jointly Established with TOYO Machinery & Metal Co., LtdEquipped with a set of 650-ton automatic Mg. and Al. alloys die-casting machine, Mg. and Al. melting furnaces, die temperature controller, vacuum system, and data logging system for cavity pressure and die temperature measurement


Experimental Station of Tsinghua-Toyo R&D Center of Magnesium and Aluminum Alloys

Processing Technology


Research Contents

Process development of Magnesium Die Casting Process for Automobile ComponentsDie Casting Magnesium AlloysMelt protection technologySurface protection technology of Magneisum die casting components


Fisrt Magnesium Component for FAW (Cylinder head cover)

300 Hongqi cars were installed the magnesium cylinder head cover (AZ91D) for test running in Dec. 2002, and now the component is in normal production for all Hongqi Cars.


Casting structure & Die Design

Cooling channel

Heating channel

Casting


Experimental DesignLow Speed Injection(LSI) stage; High Speed Injection(HSI) stage;Start position of HSI stage;Casting pressure;Biscuit thickness;Pouring temperature; Shot sleeve temperature;Die temperature;54 schemes for AZ91D alloy and 12 schemes for A356 alloy


Schematic diagram of the parameters for the LSI stage

I 0.1m/sII 0.2m/s;III 0.4m/sIV 0-0.4m/sV 0-0.2-04m/s


Positions for Pressure Measurement and Test Samples

P2

P1

P4 P3

P1-Runner, P2,P3-Casting, P4-Overflow.


Evaluation of the Castings

External quality

X-ray examination

Mechanical Properties

Density

Microstructure


Influences of different processing Influences of different processing conditions on the quality and properties of conditions on the quality and properties of the castingsthe castings

Quality IndexProcess parameters

Surface quality

Tensile strength Density Gas

porosity

Gas holes & Shrinkage porosity

LSI velocity ↑ O O X X X

HSI velocity ↑ O O O X O

Position from LSI to HIS ↑ X X O X X

Casting Pressure ↑ O O O O O

Position of PI ↑ U O U O O

Accelerated LSI ↑ U U O O U

Time of PI ↑ X X X X X

Biscuit Thickness ↑ X O X U O

DST X X U X X

DPT X X U X X


Cavity Pressure Profiles

PF －Maximum filling pressurePTP －Maximum transferred pressure of the Intensification pressure to the castingtTP －Holding time of the transferred pressure

0.34 0.36 0.38 0.40 0.42 0.44

0

10

20

30

40

50

60

Pre

ssur

e, M

Pa

T im e, s

P FtTP

PTP

63MPa

38MPa

26.9MPa

Cavity pressure of position P3 under different casting pressure


Influences of cavity pressure variables on quality of castings

1520

2530

3540

4550

55

5060

7080

90100

1.780

1.782

1.784

1.786

1.788

1.790

1.792

1.794

1.796

1.798

1.800

P TP(MPa)tTP (s)

Den

sity

(g/c

m3 )

20 25 30 35 40 45 50 55150

200

250

300

350

P2

P1

拉伸强度

,MPa

最大型腔压力PTP,MPa0 10 20 30 40 50

45

50

55

60

65

70

75

表面缺

陷分

值Q

充填压力PF，MPa

Influence of mold filling presure on surface quality

Influence of cavity pressure and holding time on density of castings

Influence of cavity pressure on tensile strength

Experimental Design LSI

HSI & Solidification

Die casting process of a cold chamber die casting machine


Mold filling simulation


Thermal balance analysis


Thermal stress analysis of dies

Stress value1.59 D+061.43 D+06

1.27 D+06

1.11 D+06

9.54 D+05

7.96 D+05

6.38 D+05

4.80 D+053.22 D+05

1.64 D+056.17 D+03

(a) 开模前

Stress value8.84 D+05 7.98 D+05 7.08 D+05

6.20 D+05 5.32 D+05

4.44 D+05

3.55 D+05

2.87 D+05 1.79 D+05

9.14 D+04 3.34 D+03

(b) 开模后 Before die open After die open


Deformation of dies

After die open

Before die open Final deformation of the die


Numerical simulation of low speed injection stage and Optimization

Three phases of metal flow in die casting process

Simulation LSI stage-Constant velocity

Piston position, mm

Vel

ocity

, m/s

④

The metal flow and gas entrapment in the shot sleeve were simulated under different velocities, the results show that there exists a critical value for the LSI velocity

0.45m/s:0.1m/s:0.4s1.78s

0.55m/s:（CV）

0.2m/s:

0.89s0.32s

0.6m/s:0.3m/s:0.3s0.59s

0.8m/s:0.4m/s:0.22s0.45s

Gas entrapment in shot sleeve under constant LSI velocities

Constant LSI velocityOptimum injection scheme

Piston position, mm④

Optimum scheme

Simulation LSI stage-Accelerated scheme

④

0.4m/s2

0.94s0.376m/s

1.4m/s2

0.5s0.70m/s

0.6m/s2

0.77s0.46m/s

1.6m/s2

0.47s0.75m/s

0.8m/s2

0.67s0.53m/s

1.8m/s2

0.44s0.8m/s

2m/s2

0.42s0.84m/s

1m/s2

0.6s0.6m/s

1.2m/s20.54s0.65m/s

2.8m/s2

0.36s1.0m/s

Gas entrapment in shot sleeve under accelerated LSI velocities

Accelerated LSI velocityOptimum injection scheme

④

Optimum LSI scheme


Ongoing research work

Systematically study the influences of process parameters on the quality, microstructure, and mechanical properties of magnesium die castingsExperimental study on vacuum die casting, ultra low speed die casting of magnesium alloysDie casting magnesium alloys

Gas content for various processes

1.5Welding

Heat treatment 4

Gas contentcc/100g 0.1 1 10 100

40Conventional Die casting

High vacuum die casting 3.5

Ultra-low speed die casting

1.20.6

8Pressure

test

(Data from High Integrity Die Casting Processes by Edward J. Vinarcik, 2003)


Step shape die


Vacuum die casting process

2B;压室销

2A;压室销

真空

1B

1A

1C

3Ａ真空传感器

3Ｂ压力传感器

2D;浇口厚変更入子

2C;浇口厚変更入子 2E;浇口厚変更入子

Vacuum technology for mg die casting processInfluence of vacuum parameters on quality of mg die castingsMaterials castability and properties by vacuum die casting processHeat treatment properties of vacuum die cast parts


Local intensification pressure technology

Effects of local intensification pressure on the cast partsDesign consideration for local intensification pressure technology

3C压力传感器

3D压力传感器

顶出CYL

1D;流体封口

2F;波动吸収销

1F;入子接触面的空气防止沟

1F;入子接触面的防止空气ｱ吸入防止沟

2G；通过变更可动入子可以变更产品模厚3种

1E;活塞环


Mechanical properties


Summary

Progress in experimental studies and numerical simulation of Mg die casting processOngoing research work include: high vacuum die casting process , ultra low speed die casting process, die casting magnesium alloys and melt protection technology


XIONG Shoumei, Dr.DirectorTsinghua-TOYO R&D Center of Magnesium and Aluminum Alloys Processing TechnologyProfessorDepartment of Mechanical Engineering,Beijing 100084, ChinaTel: 86-10-62773793Fax: 86-10-62773637Email: [email protected]

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Magnesium research activities · Department of Mechanical Engineering Magnesium research activities Tsinghua-TOYO research center of Mg & Al alloys processing technology Tsinghua