1. UNIT IV- Metal Forming Process
(Forging and Rolling Operations
2. Metal Forming Process
• Shaping the metal to required shape and size
• By application of force
• Metal is plastically deformed into required
shape.
• Deformation takes place at the yield point.
• Wastage of material is negligible or small
3. Hot Working and Cold Working
• Mechanical Working of metals above the re
crystallization temperature and below melting
temperature. (Hot working)
• Mechanical Working of metals below
recyrstallization temperature which is approx
half of the melting temperature of metal.
(Cold working)
4. Advantage of metal working process over
manufacturing process
• Higher production
• High standard Quality
• High Strength
• Better wear and corrosion resistance
• Minimum wastage of metals
• High dimensional accuracy and surface finish
• Impart any strength to the work
• Many variety of products
• Grain elongation in direction of metal flow
5. Classification of metal working
process
• Based on working temperature
– Hot working
– Cold working
– Warm or semi hot working
6. Cold Working
• Characteristic:
– Ability to deform more is reduced.
– Work Hardening or strain hardening
– Work may fracture before it is formed
– Cold working is done in several stages
– Intermediate annealing.
7.
8. Advantages of Cold Working
• No oxidation or scaling due to working in
room temperature.
• Surface defects are removed
• Excellent surface finish
• High dimensional accuracy
• Suitable for mass production
• Thin sheets
• Strength of material increased
9. Disadvantages of cold working
• Large force required to deform, high strength
• Ductility / formability is less
• Cost of production is high, involves several
stages
• Producing Complex products is minimized.
• High force, tool pressure, high power.
• Induces lot of stress, stress relieving, costs.
• Cold working is limited to ductile material.
12. Advantage of Hot working
• Strength is low in high temp – low tonnage
equipment is enough.
• Large work pieces are deformed
• Single stage process – high ductility – high
temperature
• Inter stage annealing and stress relieving not
required.
• Grain size is controlled to minimum .
13. Disadvantage of Hot Working
• Oxidation and scaling – material loss
• Automation not possible – high temperature
• High energy costs to produce high heat.
• Surface decarbonization.
14. Forging Mechanism
• Forgingis a metalformingprocess in which themetalis
heated and a force is applied in such a way thata required
shape can be obtain.
• It is basically a hot working process in which thework piece is
heated up to plastic stage and theforce is applied by manually
or by press according to therequirement.
15. Types of hot working processes
• hot Forging
– hammer Forging
– Drop Forging
– Upset Forging
– Press Forging
– Roll Forging
• hot Rolling
• hot Extrusion
• Drawing
• Swaging
• hot Spinning
16. Die Materials and Lubrication in Forging Operation.
• Chromium hot work steels (H10, H11, H13, H14 and H19) are
the most commonly used for forging applications.
• In general, chromium die steels retain their hardness upto 425
°C, tungsten hot work steels (H21 to H26) retain much of their
hardness upto to 620°C.
• Importance of lubrication In a Hot Forging process and die
lubrication is the key for quality and productivity.
• A lubricant for forging dies is a chemical compound that has
a formulation that makes possible the forging process to be
carried out within the limits and parameters considered by the
forging industry.
25. Forging Force
• The force is compressive in naturewhichis basic requirement
of forging.
• Sometimeforging operation is done withoutapplication of
heatknown as coldforging.
• Now days, Forging is used in every manufacturingindustries.
26. Forging Die design
• Die designis more empirical and requires experience.
• Designof diedepends on the processing steps, natureof work
piece material,its flow stress, temperature of working,
frictional condition at interfaceetc.
• Volume of billet is to be accurately calculated so thatthere is
neitherunder fillingnor excess filling.
49. Rolling
• Rolling is a deformation process in which the
thickness of the work is reduced by
compressive forces exerted by two opposing
rolls.
• For steel, the desired temperature for rolling is
around 12000C (2200F).
• The heating operation is called soaking
• The furnaces in which it is carried out are
called soaking pits.
50. • A bloom has a square cross section 150mm *
150 mm (6 in * 6 in) or larger.
• A slab is rolled from an ingot or a bloom and
has a rectangular cross section of width
250mm (10 in) or more and thickness 40 mm
(1.5 in) or more.
• A billet is rolled from a bloom and is square
with dimensions 40mm(1.5 in) on a side or
larger.
64. Defects in Rolling
• The following are typical defects in flat rolling.
– Wavy Edges
• Wavy edges on sheets are the result of roll bending.
The strip is thinner along its edges than at its center
thus, the edges elongate more than the center.
– Zipper Crackers
– Edge cracks.
– Alligatoring
• Non uniform bulk deformation of the billet during
rolling or by the presence of defects in the original cast
material.
