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.