Residual Stress Build Up Baseline NADCA Test

1. Residual Stress Build UpBaseline NADCA Test • Determine how quickly stress builds? • What happens when tensile drops? • What other factors contribute? • How virgin base H-13 is affected? Die Materials Committee March 5, 2003

2. Baseline Testing • Pre - Dip tank testing • virgin specimen • no surface treatments • polished corners and side • Proto X-ray • include corners • Case Western specified measurement points • baselines H-13 Dip Tank Specimen 2” each side 7” All corners square +.003” to -.003” All corners have .010” radius

3. Cycles till measured0,10,100,500,1000,5000,10000,15000 • Dip tank testing – no v or p • Immersion aluminum • 12 seconds immersion • 24 seconds air cool • Water based lube 50:1 • Repetitive cycles • X-ray diffraction measure • micro hardness before and after readings - softening • measure corner cracking • photograph x-ray MEASURED surface area H-13 Dip Tank Specimen 2” each side 7” Photography not performed on this 1st specimen All corners square +.003” to -.003” All corners have .010” radius

4. Proto X-Ray Reading Criteria • location measurements • Corners 1,2,3,4,5,6,7,8 • Middle – 1,3,5,7 • 3 points each corner (avg) • 3 points each middle (avg) • 45o at point #2 (middle) – only for zero cycles • Measurements in ksi -1ksi = 6.895Mpa Error range ∓ 5 with average ∓ 2 (zero-1000) Error range ∓ 8 with average ∓ 5 (5000 cycles) Error range ∓ 8 with average ∓ 4 (10,000 cycles) Error range ∓ 2 with average ∓ 1 (15,000 cycle)

5. 2” each side Phase II – Baseline Testing Side 5 Side 7 Side 3 • Measured corners • 6ea per side x 4 = 24 points • Measured middle side 1,3,5,7 • Axial 3ea per side x 4 = 12 • Trans 3ea per side x 4 = 12 Total of 48 x-ray diffraction measurements from 36 locations Side 1 3.5” H-13 Dip Tank Specimen 1” .5” 3.5” 1.0” All corners square +.003” to -.003” All corners have .010” radius

6. What the following data proves • Tensile relieved by cracking • Tensile rebuilds to higher levels • Subsequent cracking develops • Each time tensile drops to lower level.

7. No Dip Cycles - Baseline All but 4 measurements indicate polished compression

8. 10 Cycles All compressive stress converts to tensile

9. 100 Cycles Tensile stress values reduced by cracking

10. 500 Cycles Tensile stress again on the rise

11. 1000 Cycles Tensile stress approaching values seen at 10 cycles

12. 5000 Cycles Tensile stress continuing increase

13. 10000 Cycles Tensile stresses at highest levels

14. 15000 Cycles Tensile stress drops off again – by larger amountwhen visible cracking develops

15. What was confirmed? • Cycling of tensile stresses and micro cracking occurs on first 10 shot of unprotected steel. • Virgin steel with no surface treatment and only polished compression, changes rapidly to tensile • stresses increases between 100 & 10000 cycles • Visible tensile stress reading at 15000 occurs • Beneficial prior to use to induce high levels of subsurface compressive stress values when die is NEW to prevent initial cracking.