DMC Feb 13 2008 Die Casting Die Failure

Could this lead to a New Chapter in the study of High Pressure Die

Correlation to Die Casting Dies? Steel Failure – Hydraulic Machinery v Construction Equipment – Excavators, Crawler Tractors, Loaders v High Impact Machines – Hammers, Crushers, Etc. Copyright © 2008 Badger Metal Tech, Inc

Correlation to Die Casting Dies? Steel Failure – Hydraulic Machinery v Steel Failure – Fast Fill Nitrogen Charge Areas Piston Cylinders v Cause and Correction Contamination of steel - Unsuccessful Design changes- Unsuccessful Failure of other related components Copyright © 2008 Badger Metal Tech, Inc

Joint Research Program with Caterpillar v High Speed Photography v Special pressure transducers Copyright

Failure Mode - Cavitation Ø Previously mistaken for: Bad steel Erosion Heat Treatment Ø

What is Cavitation – Really? Ø Fatigue by Fluid entrained gases Ø Tiny bubbles imploding on surface of the member on which or over which the fluid is flowing Ø Resulting in high cycle fatigue failure Copyright © 2008 Badger Metal Tech, Inc Image source: Dr. Joe Evans Ph. D www. pumped 101. com www. caltech. edu

Breaking down the Bubble A tiny Jack Hammer Stages 1 -3 spherical Stage 4 small depression Vapor bubble in various stages of collapse. Depression more toroidal in its 3 D shape. Solid lines predicted by model. Upon implosion, the re-entrant micro jet would form at the bottom of the bubble with its energy directed towards the solid surface. Dotted lines obtained through experiment. Image source: Dr. Joe Evans Ph. D www. pumped 101. com www. caltech. edu Copyright © 2008 Badger Metal Tech, Inc

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 www. pumped 101. com www. caltech. edu Copyright © 2008 Badger Metal Tech, Inc

Cavitation Effect Cavitation pattern during flow Bubbles formed at left result in damage at right Source: Dr. Joe Evans Ph. D www. pumped 101. com www. caltech. edu Copyright © 2008 Badger Metal Tech, Inc

Where does Cavitation Show Up? Ø Gear Pump: suction side of pump negative pressures at entry positive pressures at first gear tooth Ø 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 Copyright © 2008 Badger Metal Tech, Inc

Collapsing Bubble Damage Ø Propellers, Pumps, Cylinders, ØHigh Pressure Die Casting Copyright © 2008

How do little bubbles do so much damage? Ø Each operational cycle: millions of low pressure cycles go from void to positive pressures thousands – translates to billions Ø Billions of cycles cause extremely high cycle fatigue initially microscopic particles removed as more removed – visible to naked eye Copyright © 2008 Badger Metal Tech, Inc

How about Die Casting Dies? Ø Fact - Trapped gases in molten metal: collapse - billions of void to positive pressures cause loss of fatigue strength of metal initially microscopic Ø Jack hammer effect small microscopic particles grow in size visible chucks of metal from die previously attributed to thermal fatigue Copyright © 2008 Badger Metal Tech, Inc

Die Cast Trapped Gas – Phase 1 Die Steel Cover Insert Die Steel Ejector

Die Cast Trapped Gas – Phase 2 Die particles begin to be removed Die

Visible Break Out & Heat Checking More die particles removed Die break out and/or

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

Historical Evidence Ø 100, 000+ Dies in 25 years No Die Caster, Tool Shop –sees more Ø Castings tell the bubble story breakout prevalent at gate area of casting breakout prevalent at flow direction change Ø Everyday we see damage caused by cavitation damage attributed to bad steel, heat treat, erosion Copyright © 2008 Badger Metal Tech, Inc

Mistaken Identity Ø Asked to repair heat checks in die majority of time these are breakout conditions NOT HEAT CHECKING Ø Usually close to gate area can feel with eyes closed the pitting also evident in flow change areas Copyright © 2008 Badger Metal Tech, Inc

How to Counter Die Cast Die Cavitation Effect? Ø Remove all trapped gases - Impossible Ø Get rid of bubbles – Break them up Ø Increase fatigue resistance of steel Ø Place surface in compression Ø Increase surface hardness Copyright © 2008 Badger Metal Tech, Inc

How does help reduce cavitation effect? Ø Breaks up trapped gas bubbles Ø High

Compressive Texturing Effect Removes damaging gas bubbles Compressive Textured Surface Copyright © 2008 Badger

$Residual Stress Curves T-41 H High Surface Compression Shallow Knee Maximized Depth X-Ray Diffraction$

Residual Stress Curves T-41 H High Surface Compression Shallow Knee Maximized Depth X-Ray Diffraction Curves High Compressive Values help counter metal fatigue failure Copyright © 2008 Badger Metal Tech, Inc

TOOLING CIRCLE OF LIFE anti-soldering permanent flow effect TOOLING CYCLE OF LIFE “resistance to thermal fatigue cracking & breakout from cavitation effect Badger Metal Tech, Inc. FAX 262 -252 -3956 Toll Free 800 -366 -1973 Copyright © 2008 Badger Metal Tech, Inc

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 © Why apparent less porosity? Copyright © 2008 Badger Metal Tech, Inc