Transcript Forging&forging process - Centroid works's Weblog

Forging&forging process
Forging is manufacturing
process where metal is
pressed, pounded or
squeezed under great
pressure into high strength
parts known as forgings.
The forging process
• Heated metal to be shaped is placed on a mold. Pressure is
applied to the metal with the help of a press or hammer and due
to this impact the malleable metal conforms to the
die cavity shape.
• Extreme pressure is produced when the die halves are closed.
The seam of the die as well as punch acts as a relief valve. Once
the metal object is shaped, flashing is removed
• Use of a proper lubricant during the process helps to prevent
sticking of the workpiece with the die. It also acts as a thermal
insulator and helps the wear and tear on the die
Advantages of Forging

The forgings are consistent in shape and do not
have any voids, porosity, inclusions, or defects.
• This is especially helpful in later finishing and coating
operations as surface preparation is minimized.

Parts that are produced by this method have high
strength to weight ratio and therefore used in the design
of the aircraft frames.

It offers low cost for moderate to long runs.
Different types of Forging processes
• Open Die Forgings or Hand forgings
In this process the forgings are made with
the help of repeated blows in an open die. Here the
operator manipulates the work piece in the die during
the ‘blow’ process, similar to the traditional
manufacturing process used by a blacksmith.
 Impression Die Forgings or Precision Forgings
These forgings are the refined form of blocker
forgings. The finished metal part much more identical
to the die impression.
• Upset Forgings
These forgings increase the cross-section by
reducing the length of the metal. The process is used
to make heads on valves, bolts and fasteners, and
other similar parts.
Specifications
The process is used on metals with good ductility such as copper,
aluminum, nickel, steel, and magnesium. Minimizing size, material
volume, and complexity of the design can reduce cost.
Example parts
Connecting rods, crankshafts, wrenches, hooks etc.
Forging Design Guidelines
• Avoid undercuts.
• Recommended external draft: 6 degrees (96).
• Recommended internal draft: 8-10 degrees (98-100).
• Provide generous fillet and corner radii to aid material flow.
• Provide support webs and ribs.
Once we receives a blueprint, we proceed to make the master
die. A plaster cast is made from the master die for approval.
After the plaster cast has been approved, the forging dies are
made, using the master die as a pattern
•Bar stock is ordered for the manufacture of the forgings. The
completed forging dies are then mounted in a hammer of sufficient
size to form the forgings.
•The bar stock is cut into lengths appropriate to the dimensions of
the finished forging.The lengths of material are heated in a forging
furnace
Each length is pulled from the forging furnace by the hammerman
using tongs, and placed in the blocker area of the forging die. The
hammer is activated for several blows
•Then, the rough formed forging is moved to the finisher area of
the forging die. The hammer is activated once again for several
blows.
• At this point, the forging is fully formed, but, still has a flash
attached to it. The flash is the excess material around the
formed forging.
• The forged piece is removed from the forging dies by a
trimmerman and is placed in a trim press. A few blows are
necessary to remove the flash from the forging
• The completed forging is then placed in a cooling bin. The
cooling bin may contain liquid, to comply with the specifications
provided on the blueprint supplied.
• Once cooled, the forgings are placed in a wheelabrator with
fine steel shot to clean off scale and discoloration formed in
the forging process
A Forged metal can result in the following
• Increase length, decrease cross-section, called drawing out the
metal.
• Decrease length, increase cross-section, called upsetting the
metal
• Change length, change cross-section, by squeezing in closed
impression dies. This results in favorable grain flow for strong parts
Cold Forging is a cold working process where the material is
squeezed into a die and the finished parts assume the shape of
the die. This process is also known as Cold Heading.
Bar stock or wire stock is fed into a die and is squeezed into the
closed die. The resultant part is a nail, a bolt or a screw with the
head.
A subsequent cold heading operation forms other features on the
head such as knurls or slots for screw drivers etc. the shaping
rod stock by forming the head as in rivets, bolts, nails and other
fasteners.
This process can be highly automated and parts can be made
economically.
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