John F. Wallace

John F. Wallace, an emeritus professor in the Department of Materials Science and Engineering, died September 5 at age 88. Wallace joined the university in 1954 as an associate professor of metallurgy, and held numerous positions before being named LTV Steel Professor of Metallurgy, Emeritus, in 1990. During his time with the university, he received over a dozen awards, and he supervised 80 master's degree and 68 doctoral theses.

Factors That Affect Die Casting Die Life

Yulong ZhuRyobi Die Casting Inc. (USA)

David Schwam, Xuejun Zhu, John Wallace Case Western Reserve University

Materials Related

• Steel Composition• Steel Processing• Heat Treatment

Design Related

Process Related

• Sharp Features• Surface Finish• Internal Cooling Lines Location

• Die Preheating• Temperature Cycle• Lubricant Spray

Background

Many variables, including these listed on the previous slide, act simultaneously to affect die life. In a productionenvironment it is difficult to separate these variablesand 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.

Specimen and equipment

Specimen for temperature measurement

Chemical Composition of H13 Steel

Steel 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

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

40 50 60 70 80 90 100 110 120 130 140 150

Time(s)

Die

Temp

erat

ure

(F)

Surface0.08"

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

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

130 140 150 160 170 180 190 200 210 220 230 240

Time(s)

Tem

per

atu

re(F

)

Surface

0.08"

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

Spray

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

3350 3360 3370 3380 3390 3400 3410 3420 3430

Time(s)

Tem

per

atu

re (

F)

Surface

0.08"

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

Spray

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

4395 4405 4415 4425 4435 4445 4455 4465 4475 4485

Time(s)

Tem

per

atu

re (

F)

Surface0.08"

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

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

255 265 275 285 295 305 315 325 335

Time(s)

Tem

per

atu

re(F

)

Surface

0.08"

Typical Temperature Cycle with 30 Seconds Cycle Time

30s cycle time: 3s traveling down, 7s immersing, 2s traveling up, 14s dwelling, 3s spraying and 1s air blowing

Note: min. temperature 370oF

Typical Temperature Cycle with 36 Seconds Cycle Time

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

330 340 350 360 370 380 390 400 410 420Time(s)

Tem

per

atu

re(F

)

Surface

0.08"

36s cycle time: 3s traveling down, 7s immersing, 2s traveling upper, 14s dwelling, 3s spraying, 1s air blowing and another 6 dwelling

Note: min. temperature 300oF

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14

Spraying Time (s)

Tota

l Cra

ck A

rea

(x 1

06 µm

2 )

15000 Cycles

10000 Cycles

5000 Cycles

0

5

10

15

20

25

0 2 4 6 8 10 12 14

Spraying Time(s)A

vera

ge M

ax. C

rack

Len

gth

(x 1

00 µ

m )

15000 Cycles

10000 Cycles

5000 Cycles

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.

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Spraying Pressure (psi)

Tot

al C

rack

Are

a (x

10

6 µm2 )

15000 Cycles

10000 Cycles

5000 Cycles

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60 70

Spraying Pressure (psi)A

vera

ge M

ax. C

rack

Len

gth

(x 1

00 µ

m )

15000 Cycles

10000 Cycles

5000 Cycles

Effect of Spraying Pressure on Cracking Behavior

Higher spraying pressures can overcome the vapor blanket at higher temperatures, increasing the cooling and the temperatureextremes. More cracking can be expected.

0

50

100

150

200

250

5000 10000 15000

Cycle Time

Tota

l Cra

ck A

rea

(x 1

0 6 µm

2 )

36

30

0

2

4

6

8

10

12

14

16

18

20

5000 10000 15000

Cycle TimeA

vera

ge M

ax. C

rack

Len

gth

(x 1

00 µ

m )

36

30

Effect of Cycle Time on Cracking Behavior

Longer cycle time leads to more cracking if the temperature drops more.

Die Steels

Cwt.%

Siwt. %

Mn wt.%

Crwt.%

Vwt.%

Mowt.%

Swt.%

Pwt.%

Heat Checking

Resistance

Gross Cracking

Resistance

P. G. H13

0.40 1.00 0.35 5.25 1.00 1.50 0.001 0.025

H11 0.38 1.00 0.40 5.20 0.40 1.20 <0.005 <0.02

Dievar 0.35 0.20 0.50 5.00 0.60 2.30 0.002 0.02

KDA-1 0.38 0.21 0.42 5.20 0.51 1.85 0.002 0.01

TQ1 0.35 0.40 0.43 5.20 0.60 1.90 0.002 0.02

QRO90 0.37 0.30 0.63 2.46 0.84 2.22 0.001 0.015

RPU 0.38 0.40 0.40 5.20 0.60 2.80 0.002 0.02

Chemical Composition on Cracking Behavior Die Steels

Die steels with slightly lower vanadium, silicon and carbon but higher molybdenum content seem to provide longer die life in many applications.

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.

Effect of Quench Cooling Rate on Microstructure

Fast cooling rates(1,2) produce martensitic structures while avoidinggrain boundary carbides and pearlite.

Effect of Quench Cooling Rate on Microstructure and Fracture Toughness

0

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300 350 400

Quenching Rate (oF/Min.)

Tot

al C

rack

Are

a (x

10

6 µm2 )

15000 Cycles

10000 Cycles

5000 Cycles

Austenitized at 1875 oFHardness: 50 -52 HRC

0

1

2

3

4

5

6

7

0 50 100 150 200 250 300 350 400

Ave

rage

Max

. Cra

ck L

engt

h (x

100

µm

)

15000 Cycles

10000 Cycles

5000 Cycles

Quenching Rate (oF/Min.)

Austenitized at 1875 oFHardness: 50 -52 HRC

Effect of Quench Cooling Rate on Cracking Behavior

Faster cooling rates during quenching provide better thermal fatigue resistance.

0

20

40

60

80

100

120

140

160

180

200

35 40 45 50 55

Hardness (HRC)

Tota

l Cra

ck A

rea

(x 1

0 6 µm

2 )

15000 Cycles

10000 Cycles

5000 Cycles

0

2

4

6

8

10

12

14

16

18

20

35 40 45 50 55

Hardness (HRC)

Tota

l Cra

ck A

rea

(x 1

00 µ

m )

15000 Cycles

10000 Cycles

5000 Cycles

Effect of Hardness on Cracking Behavior

Higher hardness usually provides better thermal fatigue resistance.

CONCLUSIONS

1. Excessive spray will significantly reduce the die life.2. Longer cycle time led to more cracking if the temperature dropped

more.3. 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.

4. Proper heat treatment including optimized austenitizing temperature and time, fast quench cooling rate and higher hardness usually provide better thermal fatigue resistance.

5. Whenever practical, thermal control by internal cooling is preferable to aggressive external spraying from a die life standpoint.

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.