1. DMC – Feb 13 2008 Die Casting Die Failure Cavitation Effect & Correction
Castings with breakout areas shown as risers
Die with breakout areas shown as pitting

2. Could this lead to a New Chapter in the study of High Pressure Die failure?

3. Correlation to Die Casting Dies? Steel Failure – Hydraulic Machinery
Construction Equipment – Excavators, Crawler Tractors, Loaders
High Impact Machines – Hammers, Crushers, Etc.

4. Correlation to Die Casting Dies? Steel Failure – Hydraulic Machinery
Steel Failure – Fast Fill Nitrogen Charge Areas Piston Cylinders
Cause and Correction Contamination of steel - Unsuccessful Design changes- Unsuccessful Failure of other related components

5. Joint Research Program with Caterpillar
High Speed Photography
Special pressure transducers

6. Failure Mode - Cavitation
Previously mistaken for: Bad steel Erosion Heat Treatment
None of the Above
Does this look familiar?

7. What is Cavitation – Really?
Fatigue by Fluid entrained gases
Tiny bubbles imploding on surface of the member on which or over which the fluid is flowing
Resulting in high cycle fatigue failure
Image source:
Dr. Joe Evans Ph.D

8. Breaking down the Bubble A tiny Jack Hammer
Stages 1-3 spherical
Stage 4 small depression
Depression more toroidal in its 3D shape.
Upon implosion, the re-entrant micro jet would form at the bottom of the bubble with its energy directed towards the solid surface.
Vapor bubble in various stages of collapse.
Solid lines predicted by model. Dotted lines obtained through experiment.
Image source:
Dr. Joe Evans Ph.D

9. Bubble Stage Collapse BELOW a Solid Boundary
1-18 shows a bubble collapsing
At stage 7, small dot at bottom of bubble
Grows in size in following stages then appears to penetrate the upper boundary in Stage 14.
Stage 18 is just prior to total collapse and shock wave generation.
Image source:
Dr. Joe Evans Ph.D

10. Cavitation Effect Cavitation pattern during flow
Bubbles formed at left result in damage at right
Source:
Dr. Joe Evans Ph.D

11. Where does Cavitation Show Up?
Gear Pump: suction side of pump negative pressures at entry positive pressures at first gear tooth
How to accelerate? Increase air entrainment cavitation failure was accelerated cavitation failure more pronounced
Photo at right shows damage at low pressure side of leading edge of impeller

12. Collapsing Bubble Damage
Propellers, Pumps, Cylinders,
High Pressure Die Casting

13. How do little bubbles do so much damage?
Each operational cycle: millions of low pressure cycles cycles go from void to positive pressures thousands – translates to billions
Billions of cycles cause extremely high cycle fatigue initially microscopic particles removed as more removed – visible to naked eye

14. How about Die Casting Dies?
Fact - Trapped gases in molten metal: collapse - billions of void to positive pressures cause loss of fatigue strength of metal initially microscopic
Jack hammer effect small microscopic particles grow in size visible chucks of metal from die previously attributed to thermal fatigue

15. Die Cast Trapped Gas – Phase 1
Die Steel Ejector Insert
Surface experiences void to positive
pressure cycles of trapped gas bubbles
Metal Flow
Die Steel Cover Insert
Bubbles implode on
surface as metal flows
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.
More Info on our web

16. Die Cast Trapped Gas – Phase 2
Die surface begins to fatigue
Effect of billions of low pressure
cycles during the implosion of
millions of bubbles on the metal
Metal Flow with
trapped gas
Die particles begin to be removed
At first, as metal weakens, only
microscopic particles are removed
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.
More Info on our web

17. Visible Break Out & Heat Checking
Die break out and/or heat check starts
Then removed particles increase
in size as surface fatigues
Metal Flow with
trapped gas
More die particles removed
Combined breakout and
heat checking evident
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.
More Info on our web

18. Over past 25 Years 100,000+ die casting dies
In the USA, Canada
& Mexico

19. Historical Evidence
100,000+ Dies in 25 years No Die Caster, Tool Shop –sees more
Castings tell the bubble story breakout prevalent at gate area of casting breakout prevalent at flow direction change
Everyday we see damage caused by cavitation damage attributed to bad steel, heat treat, erosion

20. Mistaken Identity
Asked to repair heat checks in die majority of time these are breakout conditions NOT HEAT CHECKING
Usually close to gate area can feel with eyes closed the pitting also evident in flow change areas

21. How to Counter Die Cast Die Cavitation Effect?
Remove all trapped gases - Impossible
Get rid of bubbles – Break them up
Increase fatigue resistance of steel
Place surface in compression
Increase surface hardness

22. How does help reduce cavitation effect?
Breaks up trapped gas bubbles
High compression to counter fatigue
Micro-texture improves flow

23. Compressive Texturing Effect
Compressive Textured Surface
As metal flows, compressive texturing
dissipates bubbles at die's surface
Metal Flow with
trapped gas
Removes damaging gas bubbles
Breakout problem addressed plus
die fatigue strength increased
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.

24. Residual Stress Curves
High Compressive Values help counter metal fatigue failure
X-Ray
Diffraction
Curves
T-41H
High Surface Compression
Shallow Knee
Maximized Depth
These curves are actual X-ray diffraction measurement plots of individual H-13 coupons that had the above five “T” processes applied. T-21 has the shallowest depth, while T-41H has the highest. Our NEW T-41H process significantly develops more compressive stress along with a higher texture than possible with the prior high compression T-71 Metallife process.

25. anti-soldering permanent flow effect
TOOLING CIRCLE OF LIFE
TOOLING CYCLE OF LIFE
“resistance to thermal fatigue cracking & breakout from cavitation effect
anti-soldering permanent flow effect
For more detailed information on our process, we encourage you to visit our web site:
Over 104 pages of information, photos, curves, FAQ’s, testimonies of our customers, and past issues of our newsletter are posted and kept current.
Badger Metal Tech, Inc. FAX Toll Free

26. Why apparent less porosity?
Additional Benefits
Reduced cavitation breakout and pitting
Eliminate lamination porosity
Better heat dissipation
Increased lubricity and improved metal flow
Compressive stress after weld repair
Better paint adherence – especially powder
All of the above benefits are directly related to the texturing of the tools surface.
Why apparent less porosity?

27. Lamination of Casting Skin
Casting Surface Lamination with trapped gas
Gas bubbles trapped
between casting layers
Solidified casting exhibits
porosity with gas
trapped laminations
Die Steel Cover Insert
Die Steel Ejector Insert
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.

28. Gas bubbles in molten metal dissipated which eliminates casting layers
Problem Solved
Casting Surface
Gas bubbles in molten
metal dissipated which
eliminates casting layers
Lamination and porosity
problem addressed
Die Steel Cover Insert
Die Steel Ejector Insert
Actual sub-surface depth is dependent on the hardness of the tool and final “T” finish that is applied to the die.

29. To make effect permanent
Where a need exists for an anti-soldering, anti-galling or washout
Return to first slide
Continue

30. Doesn’t this warrant further study by the DMC?