Introduction to Cold
Forming
March 6, 2007
Independence, Ohio
Presented by
Carpenter Technology Corporation
Copyright 2007 CRS Holdings, Inc.
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Introduction
Terminology
Processes
Benefits
Material Characteristics
Applications
Steps to Manufacture
Coatings and Lubricants
The information and data presented herein are typical or average values and are not a guarantee of maximum or
minimum values. Applications specifically suggested for material described herein are made solely for the
purpose of illustration to enable the reader to make his/her own evaluation and are not intended as warranties,
either express or implied, of fitness for these or other purposes.
History and Development of
Cold Forming

March 23, 1794


Josiah Pierson – “Cold Header” Rivet
Machine
November 16, 1796

Isaac Garretson – U.S. Patent for nail
cutting & heading machine
Cold Forming Terminology
Cold Forming terms:

Cold Heading:

cold forming process in which the force of
the punch must exceed the material’s
elastic limit to cause plastic flow

elastic limit = yield strength

forging operation without the heat
Cold Forming Terminology
Cold Forming terms:

Cold Extrusion



decreasing the diameter of the blank by
pushing it through a smaller hole
reduces size without yield loss
Cold Forming:

generic term describing the combination of
cold heading with cold extrusion
Applications:

Cold forming machines - by the number
of dies and blows

for example:

1 Die/2 blow

2 Die/3 blow

2 Die/4 blow
•
•
The wire is fed in
through the cut-off
die to a wire stop.
The cut-off knife
shears the blank.
•
The cut-off knife
transfers the blank
to the heading die.
•
•
•
Now the blank is
ready to receive the
first punch
operation.
Proper cut-off of
blank is critical.
Blank mass equals
mass of finished
part.
•
Upsetting of a
fastener head is
accomplished by
using one of these
4 methods.
Typical 1-Die/2punch method is
common in
producing headed
fasteners.
• The first blow
combines coning
with shank
extrusion.
• Coning is a partial
head upset.
• The second blow
finishes the head
shape.
•
• Knockout pin acts as
a blank support,
during heading
operation.
• Then ejects finished
part.
• Rule of thumb:
• Unsupported pin not
to exceed 8D
• Supported pin is
recommended over
8D
Open Extrusion
30% area reduction
Trap Extrusion
75% area reduction
•
Examples using trap
extrusion and open
extrusion.
7 Station Cold Forming Process
7 Station Cold Forming Process
7 Station Cold Forming Process
7 Station Cold Forming Process
7 Station Cold Forming Process
7 Station Cold Forming Process
7 Station Cold Forming Process
Benefits of Cold Forming
Advantages of Cold Forming
Design Versatility
 High strength parts from non-heattreatable alloys
 Most cost effective way vs. milling,
machining, hobbing and chemical etching
 High production rates
Metallurgical Effects
 Grain flow
 Improves strength, hardness, toughness &
fatigue resistance
Material Savings
Benefits of Cold Forming
•
Heading improves
the finished part’s
grain structure by
making it conform to
the flow of the
design.
•
The machined
diagram shows how
the grain structure is
weakened by cutting
operations.
Materials - Characteristics
Material
Description
Tensile
(ksi)
Yield
Formability
Cost Index
Steel = 1
Aluminum
Alloys
Tensile strength
of mild steel with
1/3 the weight.
Ex: 2024
55
50
Excellent
5.0
Brass
Alloy of Cu & Zn.
Tough, rustproof.
Relatively
inexpensive. Ex:
274 Yellow Brass
60 min
40 min
Excellent
6.0
High corrosion
resistance.
Expensive. Ex:
110 Electrolytic
Tough Pitch
35 – 40
10 – 35
Excellent
6.5
Approximately
2/3 Nickel, 1/3 Cu
with small
amounts Fe. High
strength,
resistance to heat
and corrosion.
Ex: NiCu400
80 min
60 min
Excellent
18.0
Copper
Nickel
Alloys
Materials - Characteristics
Material
Typical max
Description Tensile as
annealed
Typical max
Cost Index
Tensile w/
Formability
50% cold
Steel = 1
work
1010
Low carbon
55
62
Excellent
1
1018
Low carbon
65
98
Good to
Excellent
1
1022
Medium
carbon
70
108
Good to
Excellent
1
1038
Medium
carbon
85
157
Fair to Good
1
4037
Medium
carbon low
alloy
83
166
Fair to Good
1.5
Materials - Characteristics
Material
Typical max Typical max
Cost Index
Tensile w/ Formability
Description Tensile as
Steel = 1
annealed
5% cold work
410
Martensitic
Stainless Steel
78
90
Fair
4.0
430
Ferritic
Stainless Steel
75
86
Fair
4.0
302HQ
Austenitic
Stainless Steel
75
83
Fair
4.5
305
Austenitic
Stainless Steel
83
93
Fair
4.5
A-286
Austenitic
Stainless Steel
95
95
Fair to Poor
6.5
120
135
Poor
12.0
Pyromet® Hi
Temperature
718
Alloy
Pyromet is a reg. tm. of CRS Holdings, Inc.
Applications for Cold
Formed Parts
Applications for Cold Formed Parts
Automotive
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brake parts
ball joints & steering parts
starter pinions
oxygen sensors
constant velocity joints
manifold bolts
engine valves
Appliance Industry

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gears
fasteners for assembly
Applications for Cold Formed Parts
Construction, Off-road
equipment


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bolts, nuts
screws – tapping, window,
roofing, deck
transmission gears
similar parts for automotive
Aerospace
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
rivets, fuselage
engine bolts
fasteners - landing gear,
interior
Decision Process for Cold Forming
Production of
Formed Parts
Equipment
Material
Cold, Warm or Hot
Forming
Part
Decision Process for Cold Forming


Equipment
Material
which machine
 which tools
 skill of personnel



accuracy
 tolerances
 additional
treatments


Part
formability
incoming condition
Decision Process for Cold Forming
Production of Headed Parts
Cold Heading
Room Temperature
No heat
Warm
Heading
Forming of heated
slugs at temperatures
from: 550 – 950 °C
(1020 – 1740 °F)
Hot Heading
Forging temperatures
from 950 – 1250 °C
(1740 – 2300 °F)
Decision Process for Cold Forming
Carbon Steel
>0.3%
carbon,
>3.0% alloy
Austenitic
Steels
Aluminum
alloys
Brass alloys
Cold Heading
Warm
Heading
Hot Heading
Room temp
550 - 850oC
1020 - 1560oF
>950oC
>1740oF
Blue Brittleness
Problem
Room temp
400 - 450oC
750 - 840oF
Room temp
420 - 480oC
790 - 900oF
Not applicable
Room temp
350 - 620oC
660 - 1150oF
Not applicable
550 - 850oC
1020 - 1560oF
Decision Process for Cold Forming
General Aspects of Heading Methods
Forming Type
Cold
Temperature
Room
accuracy
formability
material
energy costs
surface quality
tolerances
grain structure
heat treatments
machining
Warm
Hot
550 - 950oC 950 - 1250oC
1020 1740 1740oF
2300oF
high
good
low
restricted
good
good
restricted large variety large variety
low
moderate
high
high
good
low
close
closer
low
good
good
variable
few
few
definite
least
less
necessary
Decision Process for Cold Forming
Tooling Loads in Heading Operations
120%
Relative Load
100%
80%
60%
40%
20%
0%
Cold
Warm
Hot
Steps to Manufacture:
From raw material to
finished parts
Process Chain of Cold Forming
Raw
Material
Heat
Treatment
Surface
Treatment
Cold
Forming
Metal
Removal
Heat
Treatment
Metal
Removal
Finished
part
Formed
Part
Steps to Manufacture
Raw Material
Wire/Rod
 hot rolled
 shaved - ‘seam’ free
 cf/anl
 material in the ‘softest’ condition
 optimum for cold forming
 anl/cf
 uniform volume
 uniform diameter
 specific incoming mechanical properties desired
Steps to Manufacture
Heat Treatment of Raw Material
Benefits
 Improves ability of deformation
 Reduces hardness
 Improves metal structure towards better
forming
Steps to Manufacture
Heat Treatment of Raw Material
Types of heat treatment
 Tempering to form spherical cementite
 Annealing
 to remove strain hardening
 to set the desired mechanical properties
 to normalize the microstructure
Steps to Manufacture
Surface Treatment
Alkaline cleaning
 warm 170o-190oF/ 77o-88oC
Cold rinsing
 removes alkaline cleaner
Acid pickling
 sulphuric
 hydrochloric
 nitric/hydrofluoric
Cold/warm/hot rinsing
 removes acids
Steps to Manufacture
Surface Treatment
Pre-coating
 carbon
 zinc phosphate
 stainless
 potassium sulfate
 lime
Drying
 approx. 250oF/ 120oC
Metallic Coating
 copper plating
Steps to Manufacture
Surface Treatment
Non-metallic coatings
 molybdenum disulfide – MoS2
 Soaps
 sodium stearates
 calcium stearates
Steps to Manufacture
Cold Forming
Single stage presses
Multi stage presses
 up to 5 or 6 stages, as many as 8
Secondary forming operations
 threading
 rolled
 machined
Steps to Manufacture
Heat treatment after Cold Forming
Annealing
 relieve stress
 re-crystallize
 normalize
Hardening
 increase the hardness after forming
Steps to Manufacture
Metal Removing
Hard Surfaces




turning
grinding
honing
lapping
Soft Surfaces
 turning
 drilling
 milling
Steps to Manufacture
Surface Treatment
Cleaning of parts
 de-phosphate
 washing
 acid to remove copper coating
Corrosion protection
 passivation – stainless steel
Plating
 zinc
 chromate - Cr+6 (hexavalent chrome) can
be a problem
Coatings and Lubricants
Coatings
Uses
 prevent metal to metal contact with tooling, galling
 act as a carrier for machine lubricants
Types


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
precoat
lime
copper plating
zinc phosphate
molybdenum disulfide
oxalate
Coatings and Lubricants
Lubricants
Types
 soaps
 calcium stearate
 sodium stearate
 drawing oils
 Metal-removing coolants
 oil
 emulsion
 synthetics
Coatings and Lubricants
Process
Lubricant
Hot Rolling
Water
Drawing
Pre-coat:
phosphate, lime, oxalate
Lubricants:
Soaps, Oils
Cold Forming
Oils
Thread rolling
Cutting/slotting
Metal removal coolant:
Emulsion, Solution, Oil
Metal removal coolant:
Emulsion, Solution
Sources:

“Heading Hints: A Guide to Cold Forming Specialty Alloys” Carpenter Technology Corporation (2001)

“Steel Wire Handbook Vol. 3” – The Wire Association, Inc.(1972)

“Tool Design and Part Shape Development for Multi-die Cold
Forming” - National Machinery Co.(1976)

“Cold Forming 101” - Fastener Technology International (June
2005)
Thank you for your interest in cold forming of wire.
More information about Carpenter is available on this
website including technical datasheets and articles,
Products and Markets. Visit Product Literature to
request a free copy of “Heading Hints: A Guide to Cold
Forming Specialty Alloys.”
To contact Carpenter, call 1-800-654-6543 in the U.S.
or refer to the Contact Us page for the location nearest
you.