a low density lubricant system with significantly improved green strength and ejection forces dennis...
TRANSCRIPT
A low Density Lubricant System with Significantly Improved Green Strength
and Ejection forces
Dennis Hammond
Apex Advanced Technologies
Cleveland, OH
Green Strength Problems• Cracks from ejection
• Chipping
• Handling system damage
• Defects post sintering
• Powders that do not hold together during compaction
• Inverse relationship with green density
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Mechanism of Green Strength
• Powder variables-geometric, intrinsic and surface related
• Inter-particle locking
• Weakest link-lubricant ,oxides
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New Lubricant SystemEnhancer ST
• Modified polymer, surface treated with a lubricant
• Lubricant portion allows for slippage- metal particle to metal particle
• Polymer portion deforms with shear
• Polymer simulates metal particle interlock
• Energy needed to deform 120 F( 49C ) to180 F (82 C) ideal part temperature
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Stainless Steel • Stainless powder is inherently on the low
side of ideal for green strength
• Stainless re-mill difficult to press
• Stainless gas atomized powder not considered press able due to low green strength
• Low density applications are not readily pressable due to low green strength
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Non-Press able Stainless Applications
• 316L, 5.5g/cc, special particle size, 1330 PSI, 1% Enhancer ST, in production
• 316L 100% re-mill, non-pressable 1% Enhancer ST, in production
• 316L gas atomized powder D-50, 40Micron, 50 TSI, 859 PSI green strength, 6.68g/cc, 2% Enhancer ST
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Iron Parts
• Low density- low green strength, cracks, chips, handling defects etc
• Rising cost of sponge verses water atomized
• Re-mill low green strength
• Off grade powder –inherently low green strength
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Non traditional Metals
• Product acts as binder
• Titanium CP, Titanium 6-4, Titanium Carbide, Zinc, Tungsten /Iron
Conclusions
• Stainless Steel P/M parts made with this product can be made having significantly higher green strength with better ejection
• Non typical Stainless applications can be pressed into parts-low density, gas atomized,100% re-mill
• Low density water atomized iron parts can be made with green strength adequate for processing
Conclusion cont.
• Water atomized can be substituted for sponge in some applications and can have adequate green strength, with better ejection and lower compressibility than sponge
• Copper base metal powder can have excellent green strength and lower ejection
• Non traditional powders can be processed
Conclusion cont.
• Zinc Stearate can be eliminated by using this product with better compressibility, lower ejection, and higher green strength without environmental issues
• A.D is not as good with this product as Zinc Stearate, more comparable to Acrawax. Flow is typically as good or better than either product
Conclusions Cont.
• A.D. can be improved with the co-addition of Zinc Stearate or Lithium Stearate 75-90% Enhancer ST 25-10% Zinc or Lithium Stearate
• Some loss of green strength with these additions, proportional to use E.G 10% ZnSt, 6 % decrease in G.S