improved die casting process to preserve the life of the die casting die john f. wallace david...
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IMPROVED DIE CASTING PROCESS TO PRESERVE THE LIFE OF THE DIE CASTING DIE
John F. WallaceDavid Schwam
Nitin JainYulong Zhu
Case Western Reserve UniversityCleveland, OH 44106
February 23, 2005
This investigation compares the composition, thermal fatigue behavior toughness and the microstructure after austenitizing and tempering ability of four steels of P.G H13, QRO90, Dievar and Hotvar.
It is is presented to show some of the recent improvements indie steels.
Objectives
Chemical Composition of the Four Die Steels
Steels C, % Si, % Mn, % Cr, % V, % Mo, % S, % P %
H13 0.40 1.0 0.35 5.25 1.0 1.5 0.001 0.020
QRO90 0.36 0.27 0.82 2.50 0.86 2.21 0.001 0.005
Dievar 0.35 0.16 0.50 5.06 0.54 2.39 0.0004 0.010
Hotvar 0.55 1.0 0.75 2.6 0.85 2.25 0.001 0.016
Steels Austenitizing Temperature
(F)
Tempering Temperature
(F)
High Hardness
(HRC)
MediumHardness
(HRC)
Low Hardness
(HRC)
H13 1870 1050 – 1150 47.5 45 42
QRO90 1920 1100 – 1235 50 Not Tested 41
Dievar 1870 1050 – 1115 50 46.5 43
Hotvar 1920 1020 - 1150 56.5 46 Not Tested
Hardness Level of the Thermal Fatigue Specimens
Thermal Fatigue Testing Equipment and Specimen
0
20
40
60
80
100
120
140
160
180
200
0 2500 5000 7500 10000 12500 15000
Thermal Cycles
To
tal C
rac
k A
rea
(x
10
6 mm
2 )
QRO90/ 50 HRC
Dievar/ 51 HRC
H13/ 47 HRC
2"X2"X7", WC7
Dievar / 51HRC
QRO90/ 50 HRC
H13/ 47 HRC
Total Crack Area of QRO90/50 HRC, Dievar/51 HRC and H13/ 47 HRC
0
2
4
6
8
10
12
14
16
18
20
0 2500 5000 7500 10000 12500 15000
Thermal Cycles
Av
era
ge
Ma
x C
rac
k L
en
gth
(x
10
0 m
m)
QRO90 / 50 HRC
Dievar 51 HRC
H13/ 47 HRC
2"X2"X7", WC7
QRO90 /50 HRC
DIEVAR 51 HRC
H 13/ 47 HRC
Average Maximum Crack Length of QRO90 /50 HRC, Dievar 51 HRC & H13/47 HRC
Total crack area of QRO90/41 HRC, H 13/45 HRC & Dievar/44HRC
0
20
40
60
80
100
120
140
160
180
200
0 2500 5000 7500 10000 12500 15000
Thermal Cycles
To
tal C
rac
k A
rea
(x
10
6 mm
2 )
QRO90/ 41 HRC
H13/ 45 HRC
Dievar/ 44 HRC
2"X2"X7", WC7
QRO90 / 41 HRC
H13/ 45 HRC
Dievar/ 44 HRC
Average maximum crack length of QRO90 /41 HRC, H13 / 45 HRCand Dievar/44HRC
0
2
4
6
8
10
12
14
16
18
20
0 2500 5000 7500 10000 12500 15000
Thermal Cycles
Av
era
ge
Ma
x C
rac
k L
en
gth
(x
10
0 mm
)
QRO90 (HRC 41)
H13/10 bar/45 HRC
Dievar/ 44 HRC
2"X2"X7", WC7
QRO90 (41 HRC)
H 13 (45 HRC)
Dievar (44 HRC)
Hardness distribution after 15000 cycles - Different Steels
P.G.H13QRO90DIEVAR
1500mm
Thermal fatigue cracks in three die steels after 15,000 thermal cycles
Corner
Thermal Fatigue Fracture Surface
Impact Fracture Surface
Sample Corner
Surface crack of Dievar (2 joined surface cracks)
Corner crack of H13
130X0.035” (15x)
Appearance of typical corner crack and surface crack
Corner
Corner cracks and surface cracks of H13
Appearance of these four steels with the structure as quenched
Microstructure of the four steels after tempering at 1200F for 10 hours
Effect of Tempering Time on Tempering Resistance(at 1200 F)
25
30
35
40
45
50
55
60
0 2 4 6 8 10 12Time (Hour)
Har
dn
ess
(HR
C)
H13
QRO90
Dievar
Hotvar
Effect of tempering cycle on different steels
Steel
High Hardness Medium Hardness Low Hardness
Hardness (HRC)
Impact (ft-lbs)
Hardness (HRC)
Impact (ft-lbs)
Hardness (HRC)
Impact (ft-lbs)
H13 47 12 45 13.5 41 21
QRO90 49.5 9 X X 39.5 21
Dievar 48.5 11 46.5 15.5 42 19
Hotvar 55 12 47.5 9.5 X X
Impact Results and Hardness of Impact Tests at Room Temperature
CONCLUSIONS
1. Results of the work show that thermal fatigue resistance of Dievar is somewhat better than H13. The improved thermal fatigue resistance makes this steel preferable for demanding die casting applications.
2. The QRO90 has good thermal fatigue resistance but is more sensitive to gross cracking.
3. The Hotvar material has low resistance to gross cracking therefore is not suitable for use in demanding aluminum die casting dies exposed to severe thermal gradients or thermal shock.
4. The higher austenitising temperature used for QRO90 produced a smaller number of carbides compared to H13.
5. The tempering curves of these materials show a higher temper resistance of Hotvar, QRO90 and Dievar relative to H13.
Acknowledgements
This research work is supported by DOE funds provided through by ATI. NADCA and the members of Die Materials Committee approved this work and provided background. The contribution` of this group of people is hereby acknowledged.