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Near Full Density Low Alloy Steel and Ductile Cast Iron by a New P/M Process. Dennis Hammond Apex Advanced Technologies. Process Overview. Highly compressible, standard water atomized powder, pre-alloyed and straight iron Special additive/lubricant master batch

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near full density low alloy steel and ductile cast iron by a new p m process

Near Full DensityLow Alloy Steel and Ductile Cast Iron by a New P/M Process

Dennis Hammond

Apex Advanced Technologies

process overview
Process Overview
  • Highly compressible, standard water atomized powder, pre-alloyed and straight iron
  • Special additive/lubricant master batch
  • Conventional blending, standard tooling and conventional pressing
  • Part pressing controlled to mass
  • Compaction range 45-55 TSI
  • Modified de-binding, controlledtemperature, time, and atmosphere
process overview cont
Process Overview Cont.
  • Modified sintering rate and temperatures up to 2500F for low alloy and 2200F for cast
  • Sintering atmosphere can be low % hydrogen or vacuum
  • Heat treating similar to conventional wrought and cast products
  • Lower alloying additions to achieve properties verses conventional P/M
  • Sintered densities >96%; up to 99+
process overview cont4
Process Overview Cont.
  • Properties comparable/superior to wrought and cast products
  • MPIF standards for P/M structural parts will not predict properties, technology is more like a wrought/PM hybrid
  • Not all conventional P/M alloy systems are feasible with this technology.
  • Not all iron powders are suitable
key features additive lubricant master batch
Key FeaturesAdditive/Lubricant Master Batch
  • Calculations for feasibility of full density, desired lubrication, and needed additives
  • Target volume 98.5-99.5% of theoretical at target green density
  • Need for a green compact free of density gradients
  • Need for excellent lubrication, Apex Superlube®
  • Need for mobile lubricant to achieve best fit of metal particles during compaction and spread of additives
key features additive lubricant master batch6
Key FeaturesAdditive/Lubricant Master Batch
  • Need for excellent distribution of additives in powder mix and compact
  • Need for excellent dispersion of additives
  • Need for no segregation of additives, particles charged during making the master batch
  • Master batch includes all additives including proprietary additives, pre-mixed and screened, ready to mix with iron powder
key features additive lubricant master batch7
Key FeaturesAdditive/Lubricant Master Batch
  • Easy blending of additive master batch and metal
  • A.D. and flow of final mix may be not the same as a conventional mix
  • Static dissipative tubing should be use between the hopper and press, with grounding
scope mo ni c low alloy steels
Scope Mo, Ni, C Low Alloy Steels
  • Molybdenum range from 0.3% to 1.5%
  • Nickel range from 2% to 6.6%
  • Graphite .65% to .9%
properties observations
Properties Observations
  • Low alloy content gives properties comparable to higher alloy content
  • It is possible to save on high cost alloy components Mo, Ni
  • Process gives properties far superior to comparable P/M conventional formulations
  • Process give properties superior to wrought and forged due to higher alloy content
properties observations15
Properties Observations
  • Heat treatment variation opens doors to modify properties to fit applications
  • A variety of surface treatments can now be used with this process due to the lack of porosity
  • Costly operations such as resin infiltration can now be eliminated
scope cr mo mn ni c
Scope Cr,Mo,Mn,Ni,C
  • Chromium .75%
  • Manganese up to .75%
  • Nickel up to 1%
  • Graphite .65% to .9%
ductile cast iron
Ductile Cast Iron
  • Base formula studied .7% silicon, 2% Graphite
  • Alloying components added with lubricant/additives as a master batch
  • Formula pressed green 6.95 to 7.00g/cc
  • Sintering 2180 F 25%hydrogen/75% nitrogen mixture, 7.67 g/cc as sintered, gray cast iron
  • Heat treated, similar to conventional cast 7.44g/cc after heat treatment (ductile cast)
ductile cast iron heat treated gray cast iron
Ductile Cast IronHeat Treated Gray Cast Iron
  • Easily machined
  • Low porosity, near full density
  • For machine applications with fair degree of toughness with high yield strength
  • Nodular cast iron possible
  • Many micro structures variations based on different heat treatments, ferritic, pearlitic, or martensitic
dimensional control variables
Dimensional Control Variables
  • Green density gradients - highly effective mobile lubricant, volume at G.D.
  • Elephant foot- caused by friction forces on support medium- reduced friction medium
  • Temperature –tendency to slump with temperature and time- controlled time and temperature
  • Liquid phase components- uniformity of component and temperature
dimensional stability examples
Dimensional Stability Examples
  • High Nickel 4%,Mo,C
  • Part design, bushing 1.5 In. O.D.,1in I.D. height ~1inch
  • Ave. Density green 7.28g/cc
  • Ave. Density Sintered 7.79g/cc
  • Max. roundness top .002,mid .001,btm .002 inches
  • Max taper .003 inches
dimensional stability examples27
Dimensional Stability Examples
  • Nickel 2%,Mo,C
  • Part design, bushing 1.5 In. O.D.,1in I.D. height ~1inch
  • Ave. Density green 7.24g/cc
  • Ave Density Sintered 7.75g/cc
  • Max. roundness top .001,mid .001,btm .002 inches
  • Max. taper .002 inches
dimensional stability examples28
Dimensional Stability Examples
  • .75%Chromium, .25%Mo, .85%C
  • Part design, modified bushing 2.295 O.D., 1.186 I.D. .780 height
  • Ave. Density green 7.16g/cc
  • Ave. Density Sintered 7.65g/cc
  • Max. roundness top .002, mid.003, btm .002
  • Max taper .003
conclusions
Conclusions
  • New net shape processes may open significantly new applications for P/M
  • High levels of alloy content are not needed to get excellent physical properties
  • Properties allow for favorable comparison to cast, wrought and forged applications
  • Heat treatments can significantly modify properties
conclusions30
Conclusions
  • A variety of wrought surface treatments will be able to be used with this technology
  • Modifications to de- binding and sintering will slow introduction to the market
  • Combining heat treating with the sintering process will lead to higher flexibility, customizing properties and cost saving
  • Forward thinkers will be needed