1. Factors That Affect Die Casting Die Life
Yulong Zhu
Ryobi Die Casting Inc. (USA)
David Schwam, Xuejun Zhu, John Wallace
Case Western Reserve University

2. Materials Related Design Related Process Related Sharp Features
Surface Finish
Internal Cooling Lines Location
Steel Composition
Steel Processing
Heat Treatment
Process Related
Die Preheating
Temperature Cycle
Lubricant Spray

3. Background
Many variables, including these listed on the previous
slide, act simultaneously to affect die life. In a production
environment it is difficult to separate these variables
and to determine their relative weight.
Objective
Quantify the effect of die lubricant application on die
temperature and die life: timing, duration and pressure
using the immersion test.

4. Specimen and equipment

5. Specimen for temperature measurement

6. Chemical Composition of H13 Steel
Mn, %
Cr, %
V, %
Mo, %
S, %
P %
H13
0.40
1.0
0.35
5.25
1.5
0.001
0.020

7. Typical temperature recording without any spray
(36s cycle time, no spray)

8. Typical temperature recording with 3 seconds spray
(36s cycle time, 60 psi)
Spray

9. Typical temperature recording with 8 seconds spray
(36s cycle time, 45 psi)
Spray

10. Typical temperature recording with 13 seconds spray
(36s cycle time, 45 psi)

11. Typical Temperature Cycle with 30 Seconds Cycle Time
Note: min. temperature 370oF
30s cycle time: 3s traveling down, 7s immersing, 2s traveling up, 14s dwelling, 3s spraying and 1s air blowing

12. Typical Temperature Cycle with 36 Seconds Cycle Time
Note: min. temperature 300oF
36s cycle time: 3s traveling down, 7s immersing, 2s traveling upper, 14s dwelling,
3s spraying, 1s air blowing and another 6 dwelling

13. Effect of Spraying Time on Cracking Behavior
Longer spraying times depress the lows in cycle temperature,
while increasing the ΔT (=Tmax-Tmin), causing more cracking.

14. Effect of Spraying Pressure on Cracking Behavior
Higher spraying pressures can overcome the vapor blanket at
higher temperatures, increasing the cooling and the temperature
extremes. More cracking can be expected.

15. Effect of Cycle Time on Cracking Behavior
Longer cycle time leads to more cracking if the temperature drops more.

16. Chemical Composition on Cracking Behavior Die Steels
wt.% Si
wt. % Mn Cr V Mo S P
Heat Checking
Resistance
Gross Cracking Resistance
P. G. H13
0.40
1.00
0.35
5.25
1.50
0.001
0.025
  

H11
0.38
5.20
1.20
<0.005
<0.02 

Dievar
0.20
0.50
5.00
0.60
2.30
0.002
0.02

KDA-1
0.21
0.42
0.51
1.85
0.01
TQ1
0.43
1.90
QRO90
0.37
0.30
0.63
2.46
0.84
2.22
0.015 
RPU
2.80
Die steels with slightly lower vanadium, silicon and carbon but higher molybdenum content seem to provide longer die life in many applications.

17. Effect of Chemical Composition on Basic Properties
Die Steels
Washout
Indentation
Temper Resistance
Hot Yield Strength
Ductility
Toughness
Hardenability
P. G. H13

 

H11 
Dievar
KDA-1
TQ1
QRO90
RPU
All modern die steels, when properly processed, will offer satisfactory performance in “routine” applications. Some will outperform others in demanding applications. The steel with the best combination of properties for the specific application will provide best die life.

18. Effect of Quench Cooling Rate on Microstructure
Fast cooling rates(1,2) produce martensitic structures while avoiding
grain boundary carbides and pearlite.

19. Effect of Quench Cooling Rate on Microstructure
and Fracture Toughness

20. Effect of Quench Cooling Rate on Cracking Behavior
Faster cooling rates during quenching provide better thermal fatigue resistance.

21. Effect of Hardness on Cracking Behavior
Higher hardness usually provides better thermal fatigue resistance.

22. CONCLUSIONS Excessive spray will significantly reduce the die life.
Longer cycle time led to more cracking if the temperature dropped more.
Chemical composition of the steel can affect die life. Die steels with slightly lower vanadium, silicon and carbon but higher molybdenum content seem to provide longer die life in many applications.
Proper heat treatment including optimized austenitizing temperature and time, fast quench cooling rate and higher hardness usually provide better thermal fatigue resistance.
Whenever practical, thermal control by internal cooling is preferable to aggressive external spraying from a die life standpoint.

23. ACKNOWLEDGEMENTS
This research work is supported by DOE funds provided through by ATI SMARRT program. NADCA and the members of Die Materials Committee approved this work and provided background. This work was performed at the Department of Materials Science and Engineering, Case Western Reserve University. The contribution of DOE, ATI, NADCA, and Case Western Reserve University are hereby acknowledged.
This publication was prepared with the support of the U.S. Department of Energy (DOE), Award No. DE-FC36-04GO14230.