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Copper Powders
for Sintered Components
Sintering is a method
for making objects from powder, by heating the material in a sintering
furnace below its melting point (solid state sintering) until its
particles adhere to each other. Sintering is traditionally used for
manufacturing ceramic objects, and has also found uses in such fields as
powder metallurgy.
Metal powders open up new possibilities for
creative and cost-effective design solutions.
Almost 80% of global Copper and steel powder production is converted into
sintered components. The manufacturing process involves the shaping of a
tailor-made powder formulation by pressure and heat (sintering).
Sintered components offer design freedom, almost 100% material
utilization and many other benefits. Over 40 million sintered components
are produced every day for use in numerous applications including
vehicles, power tools and white goods (Air conditioners, refrigerators,
stoves, etc.).
The automotive industry
is the main user of sintered components, which are common in transmission and
engine applications. It is in the automotive area that sintered components have
made the most spectacular advances. Many of the early parts for vehicles, such
as the bushings and bearings introduced in the 1960s were simple shapes.
Components of today can be made in highly complex designs and meet the
industry's demands for strength and tolerances.
A modern automobile contains on average 10 kg of sintered components, but there
are big variations depending on its origin. US automobiles tend to have far more
sintered components than those produced in Asia.
The use of sintered components is increasing outside the automotive sector, but
there is still a huge potential. Parts produced from powder serve special
functions
in power tools, white goods, appliances, air-conditioners, computers, lawn
movers, locks and pumps. These are just a few examples and the possibilities are
endless.
Features and Benefits
More and more designers are choosing sintered components rather than metal parts
traditionally manufactured by casting, forging, blanking or machining. Producing
parts from powder creates value for small to medium-size components with complex
shapes in large volumes.
With sintered components, less is more. Fewer process steps, less machining and
less wastage of material and energy in production add up to a solution with
lowest total cost.
Sintered components have been increasingly adopted in designs over the past few
decades. Their success is mainly due to the significant cost savings derived
from net or near-net shape processing compared to other metalworking methods.
Machining is generally the largest single cost in metal component production.
Sintered components can offer far more than cost savings. They can be made from
tailored materials serving specific purposes and with a design that would be
impractical or impossible for other manufacturing technologies.
Manufacturing
A Copper-based powder mix is the initial material for manufacturing of many sintered
components. Properties of the final component can be easily tailored by using
different alloying elements and other additives. The powder mix also contains a
solid lubricant, which is primarily added to reduce friction between the powder
mass and surfaces of the compaction tool.
The most common compaction method is axial pressing in a steel or carbide die,
usually under pressures of 400-800 MPa (58000-116000psi). It is possible to press parts with
complicated shapes in a single operation and with a high production rate, up to
25 parts per minute. The part receives its predetermined shape after compaction,
but not its final dimensions.
Sintering is a heat treatment from which the pressed parts gain strength. The
parts are heated in a controlled atmosphere to a temperature that is below the
melting point of the main metal. For Copper-based alloys this is usually at
750-900 °C, for about 5 to 7 minutes, depending on the application. The
main mechanisms of sintering are surface and volume diffusion.
The parts are transported on a belt through three furnace zones; dewaxing, where
the lubricant is burned off, sintering and cooling. During sintering, a minor
dimensional change takes place, which gives the component its final dimensions.
Properties of the component can be steered by changing the cooling rate.
Various optional post-sintering process steps are available for sintered
components. Hardening operations, for example, are carried out in the same way
as for conventional steel, so all treatments applicable to a given alloy are
also applicable for sintered material.
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