UNIT 6 A
Unit- 6
2 marks
question
1. What is meant
by powder metallurgy?
A. Powder
metallurgy is a forming and fabrication technique consisting of three major
processing stages. First, the primary material is physically powdered, divided
into many small individual particles. Next, the powder is injected into a mold
or passed through a die to produce a weakly cohesive structure (via cold
welding) very near the dimensions of the object ultimately to be manufactured.
Pressures of 10-50 tons per square inch are commonly used. Also, to attain the
same compression ratio across more complex pieces, it is often necessary to use
lower punches as well as an upper punch. Finally, the end part is formed by
applying pressure, high temperature, long setting times (during which
self-welding occurs), or any combination thereof.
Two main
techniques used to form and consolidate the powder are sintering and metal
injection molding. Recent developments have made it possible to use rapid
manufacturing techniques which use the metal powder for the products. Because
with this technique the powder is melted and not sintered, better mechanical
strength can be accomplished.
2. Write down
the advantages of powder
metallurgy process.
A.Some of
the Advantages of Powder Metallurgy are as follows;
1. Powder metallurgy produces near net shape
components. The technique required few or no secondary operations.
2. Parts of powder metallurgy can be produce
from high melting point refractory metals with less cost and difficulties.
3. The tolerance of components produced by
this technique have quite high tolerance, therefore no further machining is not
required.
4. This technique involves high Production
Rate along with low Unit Cost.
5. It can produce complicated forms with a
uniform microstructure.
6. Powder metallurgy has full capacity for
producing a variety of alloying systems and particulate composites.
7. This technique has flexibilities for
producing PM parts with specific physical and mechanical properties like
hardness, strength, density and porosity.
8. By using powder metallurgy, parts can be
produced with infiltration and impregnation of other materials to obtain
special characteristics which are needed for specific application.
9. Powder metallurgy can be used to produce
bi-metallic products, porous bearing and sintered carbide.
10. Powder metallurgy makes use of 100% raw
material as no material is wasted as scrap during process.
3. Which are the
powder metallurgy process
steps? Enlist only
names.
A. PM process
steps
• Powder production
• Blending
•
Compaction
• Sintering
•
Finishing / secondary Operations
4. Give various
applications of power metallurgy.
A.
Applications:
Motor Cycle
Parts
Vehicles
Engine Parts
Industrial Machines
Parts
For Electric Motors
5. Write down
the disadvantages of powder
metallurgy.
A.Disadvantages
of Powder Metallurgy:
1. The production of powder for metallurgy is
very high.
2. The products of metallurgy can have limited
shapes and features.
3. This technique causes potential workforce
health problems from atmospheric contamination of the workplace.
4. The tooling and equipments require for
powder metallurgy are very expensive, therefore becomes main issue with low production
volume.
5. It’s difficult to produce large and
complex shaped parts with powder metallurgy.
6. The parts produce by powder metallurgy have
low ductility and strength.
7. Finally divided powder like aluminium,
magnesium, titanium and zirconium are fire hazard and explosive in nature.
8. This technique is not useful for low
melting powder such as zinc, cadmium and tin as they show thermal difficulties
during sintering operations.
6. State characteristics of
metal powder to be used
in powder metallurgy
process.
A. There
are following:
shape,size,texture,particlesizedistribution,crystallinesize,chemicalcomposition,hardness,density,
flowability,compressibility,sinterability,sintereddensity
7. State the
methods by which powders
suitable for powder
metallurgy can be
produced.
A.
Methods of Powder
Production
• Atomization
• Reduction
•
Electrolytic deposition
• Carbonyl
process
• Comminution processes
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