Transcript Powder Metal Processing

Powder Metal
Processing
Manufacturing
Processes
Outline
Introduction
Powder Manufacturing
Powder Metallurgy Process
Sintering
Other Powder Metal Processes
Powder Metal Products
Powder Metallurgy Design
Powder Metallurgy
Powder Metallurgy
Metal
Powder
Metal Product
Examples of Powder
Metal Products
Gears
Cams
Cranks
Bearings
Roller bearing cages
Housings
Light bulb filaments
Sprinkler mechanisms
Powder Metal Materials
Elemental
A pure metal, most commonly
iron, aluminum or copper
Prealloyed
An alloy of the required
composition, most commonly
copper alloys, stainless steel or
high-speed steel
Powder Manufacturing
Conversion of molten metal to
powder
Atomization
Powder Manufacturing
Other methods of producing
powder:
- Chemical reduction of
particulate compounds
- Electrolytic deposition
- Pulverization or grinding of
brittle materials
- Thermal decomposition
- Precipitation from solutions
- Condensation of metal vapors
Particle Shape
Particle Size
The process of separating particles
by size is called classification
Particle Size
Micrograph of screened powder particles, showing
that particles may be longer than the mesh is wide
Particle Size
Mixing particles of different sizes allows decreased
porosity and a higher packing ratio
void
smaller, more numerous voids
voids filled by smaller particles,
small voids remain
Powder Metallurgy
Process
Blending and Mixing
Blending
Combining powders of the same material
but possibly different particle sizes
Mixing
Combining powders of different materials
Compaction
High pressure is applied to squeeze
the powder into the desired shape
Example of a Powder
Press
Sintering
Heats the powder below the melting
point to allow solid-state diffusion
and bond the particles together
Sintering
Diagram of particles in sintering, showing the
possible movements of atoms
Sintering
Sintering
Sintering Production
Lines
Examples of Sintering
Production Lines
Sintering
Strength of sintered structures as related to density,
showing that the strength is higher when the density
is higher (less residual porosity)
Other Powder Metal
Processes
Cold Isostatic Pressing
Hot Isostatic Pressing
Injection Molding
Powder Rolling
Powder Extrusion
Plasma Spraying
Isostatic Pressing
Uses pressurized fluid to compress the
powder equally in all directions
Cold Isostatic Pressing
Compaction performed at room
temperature
Hot Isostatic Pressing
Performed at high temperatures and
pressures
Example of an Isostatic
Press
Injection Molding
The powder is mixed with a binder
and molded, and the binder is
removed before sintering
Powder Rolling
Powder is compressed in a rolling mill
to form a strip
Powder Extrusion
The powder can be extruded within a
container or after being formed into
billets
Plasma Spraying
Uses a plasma arc to propel molten
droplets at a surface at a high
velocity, forming a high-density
structure
Plasma Spraying
Powder Metal Products
1. Porous or permeable
products
2. Products of complex shapes
3. Products made of materials
that are difficult to machine or
have high melting points
4. Products which require the
combined properties of
multiple materials
5. Products in which powder
metallurgy produces superior
properties
Powder Metallurgy
Design
1. The shape must permit removal
from the die
2. The shape should not have thin
walls or sharp corners
3. The shape should permit the
construction of strong tooling
4. The shape of the part should be
within the thickness range for
which the powder can be properly
compacted
5. The part should have as few
changes in section thickness as
possible
Powder Metallurgy
Design
6. Parts can be designed to take
advantage of the capabilities of
the powder metallurgy process
7. The design should be consistent
with available equipment
8. Consideration should be given for
product tolerances
9. Design should consider the
dimensional changes that occur
after pressing, such as shrinkage
during sintering
Powder Metallurgy
Design
Powder Metallurgy
Design
Powder Metallurgy
Advantages
1. Elimination/reduction of
machining
2. High production rates
3. Complex shapes can be
produced
4. Wide composition variations
are possible
5. Wide property variations are
possible
6. Scrap is eliminated or
reduced
Powder Metallurgy
Disadvantages
1. Inferior strength properties
2. Relatively high die cost
3. High material cost
Summary
Powder metallurgy can create
parts that would otherwise be
difficult to form, including those
with complex shapes or
porosity
Sintering bonds particles
together by allowing atoms to
move, forming necks and grain
boundaries between the
particles