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IMPROVED DIE CASTING PROCESS TO PRESERVE THE LIFE OF THE DIE CASTING DIE John F. Wallace

IMPROVED DIE CASTING PROCESS TO PRESERVE THE LIFE OF THE DIE CASTING DIE John F. Wallace David Schwam Nitin Jain Yulong Zhu Case Western Reserve University Cleveland, OH 44106 February 23, 2005. Objectives.

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IMPROVED DIE CASTING PROCESS TO PRESERVE THE LIFE OF THE DIE CASTING DIE John F. Wallace

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  1. IMPROVED DIE CASTING PROCESS TO PRESERVE THE LIFE OF THE DIE CASTING DIE John F. Wallace David Schwam Nitin Jain Yulong Zhu Case Western Reserve University Cleveland, OH 44106 February 23, 2005

  2. Objectives 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 in die steels.

  3. 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 Chemical Composition of the Four Die Steels

  4. Steels Austenitizing Temperature (F) Tempering Temperature (F) High Hardness (HRC) Medium Hardness (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

  5. Thermal Fatigue Testing Equipment and Specimen

  6. Total Crack Area of QRO90/50 HRC, Dievar/51 HRC and H13/ 47 HRC

  7. Average Maximum Crack Length of QRO90 /50 HRC, Dievar 51 HRC & H13/47 HRC

  8. Total crack area of QRO90/41 HRC, H 13/45 HRC & Dievar/44HRC

  9. Average maximum crack length of QRO90 /41 HRC, H13 / 45 HRC and Dievar/44HRC

  10. Hardness distribution after 15000 cycles - Different Steels

  11. 1500mm DIEVAR QRO90 P.G.H13 Thermal fatigue cracks in three die steels after 15,000 thermal cycles Corner

  12. Corner crack of H13 Surface crack of Dievar (2 joined surface cracks) 130X 0.035” (15x) SampleCorner Thermal Fatigue Fracture Surface Impact Fracture Surface Appearance of typical corner crack and surface crack

  13. Corner cracks and surface cracks of H13 Corner

  14. Appearance of these four steels with the structure as quenched

  15. Microstructure of the four steels after tempering at 1200F for 10 hours

  16. Effect of tempering cycle on different steels

  17. 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

  18.  CONCLUSIONS • 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. • The QRO90 has good thermal fatigue resistance but is more sensitive to gross cracking. • 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. • The higher austenitising temperature used for QRO90 produced a smaller number of carbides compared to H13. • The tempering curves of these materials show a higher temper resistance of Hotvar, QRO90 and Dievar relative to H13.

  19. 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.

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