Optimisations for the cold forging of steel

1. Optimization of Raw Material
(Steel)
 The amount of manganese in the chemical
composition must be increased.
 Manufacturers should incorporate tempering in
their manufacturing processes to improve
ductility.
 Heat Treatment for reduction in residual stress.
 High Temperature Annealing is found effective
in presence of Hydrostatic Pressure, forging
limit of the annealed specimen gets improved in
cold forging.

2. Manganese content
 Increase in the Manganese Content, Increases
strength at high temperatures by eliminating
the formation of iron sulphides. Manganese
also improves hardenability, ductility and wear
resistance.

3. Use of Tempering
 It is a heat treatment technique applied to
ferrous alloys, such as steel or cast iron, to
achieve greater toughness by decreasing the
hardness of the alloy. The reduction in hardness
is usually accompanied by an increase in
ductility, thereby decreasing the brittleness of
the metal.

4. Heat Treatment to reduce
Residual Stress
 Thermal stress relieving involves heating a
component to a temperature at which the
material yield strength has fallen, allowing creep
to take effect.
 There are frequent occasions when the item
requiring thermal treatment is part of a larger
fabrication which is either too large, or
inconvenient, to heat as a whole for financial or
technical reasons. In such circumstances local
heat treatment is preferred. This is done using
ceramic elements surrounding the resistance
heating wire.

5. High Temperature Annealing
 High-temperature annealing is effective to
reduce the degree of the texture anisotropy of
the specimen, and the forging limit of the
annealed specimen gets improved in cold
forging. On the other hand, In cold forging of
the annealed specimen with applying counter
pressure of 100-200 MPa during forging, the
critical punch stroke for forging limit of the
specimen without crack was improved by 25% in
punch stroke.

6. Optimization in Die Design
 Use of Carbide Material.
 New materials and material characterization.
 Surface polishing.
 Coatings.
 FEM Simulation
 Selective surface treatment.
 Hard roller burnishing.
 Surface Heat Treatment by LASER

7. Use of Carbide Material
 Carbides such as tungsten carbide and titanium
carbide are often the material of choice for the
inserts in order to improve the finishing of the
part. These provide pre-stress to the tool stack
and improve the tools total life.

8. New Materials & Material
Characterization
 In terms of material properties, the following is
required:
- high compressive strength since compressive
loads are typical in cold forging.
- high hardness to get the wear resistance.
- sufficient toughness to withstand fatigue load
since fatigue represents the predominating failure
mechanism in cold forging.
- high homogeneity of material structure being
simultaneously free of any inclusions which is also
due to enhanced fatigue resistance (crack
initiation).

9. Surface Polishing
 Besides the application of lubrication-
technology for the reduction of the friction, a
correct surface polishing procedure and surface
roughness level are among the most
determining factors for a successful cold
forging process and for obtaining the required
surface quality of the pressed parts.

10. Coatings
 In order to improve wear resistance, the coating
has a long tradition in general but for cold
forging tools as well.
 Looking to the required tolerances of cold
forging tools, this is quite an important aspect
since any subsequent operation of tempering
would lead to not acceptable distortions.

11. FEM Simulation
 The Finite Element Methods (FEM) is widely used in metal
forming analysis due to its capabilities to model the
complicated geometries of tools and parts in forming
processes.
 It can provide detailed information for forming designers
such as forming force, defects predictions, flow pattern,
and stress concentration in the dies. The strain output,
for instance, can display strain concentration areas to
identify the possible early failures in the tools or to
predict formability problems. Therefore, part fabrication
design can modified to improve tool’s life or to enhance
the formability conditions, and the new designs can be
checked with repeated finite element simulations before
experimental tests.

12. Hard Roller Burnishing
 The primary objective of hard roller burnishing
is to improve fatigue resistance of the tool
surface. The process consists of a ceramic ball
that is rolled on the machined tool surface
under high pressure, flattening the topography
by local plastification. The ball is hydrostatically
supported to roll with low friction.

13. Surface Heat Treatment by
LASER
 Laser heat treatment is a flexible method to
modify tool surface properties selectively by
martensitic transformation yielding locally
improved wear resistance. The laser spot moves
along a predefined track to cover the tool area
that is to be hardened. Depending on speed and
power of the laser spot, the tool surface is
heated up locally at a high heating rate. During
the immediately following self-quenching
process, the heated regions transform from
austenite to martensite yielding the high
hardness.

14. Process Flow Diagram
Material
Receiving
Inspection
Simulation
Study
Die Design Tempering
Cold
Forging
Heat
Treatment
Annealing Hardening
Surface
Finishing
Finished
Product
Shipment of
the Product