Page 248 - Mechanical Engineer's Data Handbook

236 MECHANICAL ENGINEER'S DATA HANDBOOK

6.9 Powdered metals

Powdered metal technology is used widely to produce They can be subject to secondary treatment such as
components which are homogeneous, have controlled forging, repressing, resintering, and heat treatment.
density, are inclusion free and of uniform strength.

POWDERED-METAL COMPONENTS
6.9. I Process
(1) Production of metal powder, mixing for alloys and
additives if required.
(2) Compacting in a shaped die with pressure of
40&800 N mm- to give required density.
(3) Sintering at high temperatures to bond particles,
e.g. 1100 "C for iron and 1600 "C for tungsten.
(4) Sizing and finishing.
Preform Gear
6.9.2 Metals used for gear

Iron and copper The most used metals.
High-melting-point metals For example, platinum
and tungsten.
Aluminium Special atmosphere and lubricant re-
quired because of the formation of the oxide.
Tin bronze Used for 'self-lubricating' bearings.
Stainless steel Used for filters. Level

6.9.3 Advantages

(1) For use in alloys where metals are insoluble.
(2) For high-melting-point metals, e.g. tungsten.
(3) Virtually no waste.
(4) Little or no finishing required.
(5) Controlled density and strength.
(6) Relatively inexpensive production method. Rotor Thrust plate

6.10 Low-melting-point alloys

Composition (%)
Melting point
Name Sn Pb Bi Cd ("C)
37.5 50.0 12.5 0 178
50.0 40.0 10.0 0 162
25.0 50.0 25.0 0 149