1. In-plant Benchmarking of Die Steels St. Clair Die Casting Case Western Reserve University Bohler Uddeholm Dunn Steel NADCA DMC Meeting February 2005

2. METHOD Two dies, each with four cavities are currently participating in the benchmarking at St. Clair Die Casting. - Tank tread heat sink - Semi-trailer wheel hub Different die steels were used to fabricate the inserts. Castings from the production line are evaluated at Case for fins. The assumption is these fins represent the severity of thermal fatigue cracks in the inserts.

3. Tank tread heat-sink casting (four cavity die) # 21 QRO 90 # 22 Dievar # 20 QRO 90 # 23 Dievar

4. DIE CAST ALUMINUM HEAT SINKS FOR TANK TRACKS ABSORB HEAT FROM THE RUBBER, EXTEND TRACK LIFE, PREVENT STRIP-OFF FAILURE Material: A380 Size:4.5”x2.5”x1.15” Weight: 1.1 pounds

5. Evaluation of Heat Checking in Tank Tread Heat Sink Inserts Castings produced in 4 steel inserts were analyzed: Part # 20: QRO 90 die (44-46HRC) Part # 21: QRO 90 die (44-46HRC) Part # 22: Dievar die (49HRC) Part # 23: Dievar die (49HRC) Part # 30: “Soft Dievar”(42-43HRC) Part # 31: “Soft Dievar”(42-43 HRC)

6. Cracking Evaluation on Tank Tread Heat Sink

7. Cracking Evolution - Casting # 20 (QRO 90) #20 112,740#20 93,250 #20 58,360 #20 33,000 Welded Area

8. Cracking Evolution - Casting # 21 (QRO 90) #21 33,000#21 58,360 #21 93,250#21 112,740

9. Castings # 22 and # 23 (Dievar) After 112,740 shots #22 112,740#23 112,740

10. Cracking Evaluation on Die Cast Parts Two parameters were employed: Total Crack Length - sum of the crack lengths on a sampled area. Average Maximum Crack Depth - average of the profile depth, taken across the 3 cracks identified as the deepest on the sampled area.

11. Sampling Procedure

12. Sampled Area Appearance After 93,250 shots #22 (Dievar) 93,250 shots #23 (Dievar) 93,250 shots #20 (QRO 90) 93,250 shots #21 (QRO 90) 93,250 shots

13. Sampled Area Appearance After 112,740 shots 23 #20 (QRO 90) 112,740 shots#21 (QRO 90) 112,740 shots #22 (Dievar) 112,740 shots#23 (Dievar) 112,740 shots

14. Total Crack Length The length of the cracks on the sampled area were measured using an Image Analysis system.

15. Total Crack Length - Crack Marking The cracks are marked and automatically quantified The crack length is summed, resulting in a number equal to the Total Crack Length QRO90

16. Total Crack Length – Tank Tread Heat Sink Insert # 20 welded

17. Average Maximum Crack Depth The profile height across the cracks was determined by profilometry measurements.

18. Average Maximum Crack Depth The 3 deepest cracks were visually identified on the sampled area.

19. Average Maximum Crack Depth Measurements were taken across the selected cracks, and the depth of the cracks (height of the profile on the part) averaged. Casting Profilometer

20. Average Maximum Crack Depth - Crack Profile

21. Average Maximum Crack Depth

22. Evaluation of “Soft Dievar” for Rapid Tooling Applications Objective Compare performance of a “soft” 42-43 HRC Dievar insert made from pre-hardened material to a “hard” Dievar insert at 48-49HRC insert made by traditional methods. Method The two inserts are run side by side in a four cavity die. The hard 48-49HRC insert had 178,501 shots prior to being returned to service.

23. Performance Record for Tank Track Inserts Die AM703 22 23 30 31 Dievar 49HRC “Soft”Dievar 42-44HRC 6/03-5/04 22 23 20 21 Dievar 49HRC QRO 90 44-46HRC @178,501 Shots QRO-90 beyond repair (first repair at 33,000) 1/05 - 2/3/05(still running) @204,088 Shots@30,395 Shots Heat checking on back, cover side

24. Performance Record for Tank Track Inserts Die AM703 22 23 30 31 Dievar 49HRC “Soft”Dievar 42-44HRC @204,088 Shots @30,395 Shots Heat checking on back, cover side

25. Cracking Evaluation on Wheel Hub Cap Castings produced in 4 steel die casting dies were analyzed: Part # 21 : H13 insert (Dynablue coated) Part # 22D : Dievar insert (Uncoated) Part # 23M: Marlok insert (Uncoated) Part # 24 : H13 insert (Dynablue coated)

26. Cracking Evaluation on Wheel Hub

27. Cracking Evolution - Casting # 23M (Marlok) #23M (Marlok) 37,872 #23M (Marlok) 115,921 #23M (Marlok) 48,785 #23M (Marlok) 131,716

28. #24 (H13) 37,872 #24 (H13) 48,785 #24 (H13) 131,716#24 (H13) 115,921 Cracking Evolution - Casting # 24 (H13)

29. Casting # 22D (Dievar) #22D (Dievar) 37,872 #22D (Dievar) 131,716

30. Sampling Procedure Areas with the highest crack density were visually identified and the surface replicated. 0.5" #23M (Marlok) 131,716

31. Sampled Area Appearance - Replica #23M #24 48,785 shots #23M #24 131,716 shots #23M #24 115,921 shots

32. Total Crack Length – Hub Cap Castings

33. Average Maximum Crack Depth – Hub Cap Castings

35. Conclusions The results show that the Dievar with a hardness of 49 HRC is the best and has maximum life for the Tank tread heat sink. The QRO90 with a hardness of 44-46 HRC was second and the soft Dievar at 42-44 HRC was the worst. The Semi-trailer wheel hub also provided the best results with Dievar (44-46 HRC). This was followed by the H13 (44- 46 HRC) with considerably more cracks. Marlok (44-46 HRC) provided the worst results.

36. Acknowledgements This research work is supported by DOD funds provided through by ATI. The NADCA and the members of Die Materials Committee in that Association approved this work and provided background. The appreciation of this group of people is hereby acknowledged.