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

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

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

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

Joint Research Program with Caterpillar High Speed Photography Special pressure transducers

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

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 www.pumped101.com www.caltech.edu

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 www.pumped101.com www.caltech.edu

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.pumped101.com www.caltech.edu

Cavitation Effect Cavitation pattern during flow Bubbles formed at left result in damage at right Source: Dr. Joe Evans Ph.D www.pumped101.com www.caltech.edu

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

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

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

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

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

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

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

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

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

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

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

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

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.

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.

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: www.badgermetal.com 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 262-252-3956 Toll Free 800-366-1973

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?

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.

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.

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

Doesn’t this warrant further study by the DMC?