Introduction to Cold

Forming

March 6, 2007
Independence, Ohio
Presented by
Carpenter Technology Corporation

Copyright 2007 CRS Holdings, Inc.

 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/2-
punch 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 Trap Extrusion

30% area reduction 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-heat-
treatable 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
Tensile Cost Index
Material Description Yield Formability
(ksi) Steel = 1
Tensile strength
Aluminum of mild steel with
55 50 Excellent 5.0
Alloys 1/3 the weight.
Ex: 2024

Alloy of Cu & Zn.

Tough, rustproof.
Brass Relatively 60 min 40 min Excellent 6.0
inexpensive. Ex:
274 Yellow Brass

High corrosion
resistance.
Copper Expensive. Ex: 35 – 40 10 – 35 Excellent 6.5
110 Electrolytic
Tough Pitch
Approximately
2/3 Nickel, 1/3 Cu
with small
Nickel amounts Fe. High
strength, 80 min 60 min Excellent 18.0
Alloys
resistance to heat
and corrosion.
Ex: NiCu400
 Materials - Characteristics
Typical max
Typical max Tensile w/ Cost Index
Material Description Tensile as Formability
annealed 50% cold Steel = 1
work

1010 Low carbon 55 62 Excellent 1

Good to
1018 Low carbon 65 98 1
Excellent

Medium Good to
1022 70 108 1
carbon Excellent

Medium
1038 85 157 Fair to Good 1
carbon

Medium
4037 carbon low 83 166 Fair to Good 1.5
alloy
 Materials - Characteristics
Typical max Typical max Cost Index
Material Description Tensile as Tensile w/ Formability
annealed 5% cold work Steel = 1

Martensitic
410 Stainless Steel
78 90 Fair 4.0

Ferritic
430 Stainless Steel
75 86 Fair 4.0

Austenitic
302HQ Stainless Steel
75 83 Fair 4.5

Austenitic
305 Stainless Steel
83 93 Fair 4.5

Austenitic
A-286 Stainless Steel
95 95 Fair to Poor 6.5

Pyromet® Hi
Temperature 120 135 Poor 12.0
718 Alloy

Pyromet is a reg. tm. of CRS Holdings, Inc.

Applications for Cold
Formed Parts
Applications for Cold Formed Parts

Automotive
 brake parts
 ball joints & steering parts
 starter pinions
 oxygen sensors
 constant velocity joints
 manifold bolts
 engine valves
Appliance Industry
 gears
 fasteners for assembly
Applications for Cold Formed Parts

Construction, Off-road
equipment
 bolts, nuts
 screws – tapping, window,
roofing, deck
 transmission gears
 similar parts for automotive
Aerospace
 rivets, fuselage
 engine bolts
 fasteners - landing gear,
interior
Decision Process for Cold Forming

Production of
Formed Parts

Part
Equipment Material

Cold, Warm or Hot

Forming
Decision Process for Cold Forming

 Equipment  which machine

 which tools
 skill of personnel

 formability
 Material  incoming condition

 accuracy
 tolerances
 Part
 additional
treatments
Decision Process for Cold Forming

Production of Headed Parts

Warm
Cold Heading Hot Heading
Heading

Room Temperature Forming of heated Forging temperatures

No heat slugs at temperatures from 950 – 1250 °C
from: 550 – 950 °C (1740 – 2300 °F)
(1020 – 1740 °F)
 Decision Process for Cold Forming
Warm
Cold Heading Hot Heading
Heading
Carbon Steel
>0.3% 550 - 850oC >950oC
Room temp
carbon, 1020 - 1560oF >1740oF
>3.0% alloy
Blue Brittleness
Austenitic 400 - 450oC Problem
Room temp 550 - 850oC
Steels 750 - 840oF
1020 - 1560oF
Aluminum
420 - 480oC
alloys Room temp Not applicable
790 - 900oF

350 - 620oC
Brass alloys Room temp Not applicable
660 - 1150oF
Decision Process for Cold Forming
General Aspects of Heading Methods
Forming Type Cold Warm Hot
Temperature Room 550 - 950oC 950 - 1250oC
1020 - 1740 -
1740oF 2300oF
accuracy high good low
formability restricted good good
material restricted large variety large variety
energy costs low moderate high
surface quality high good low
tolerances close closer low
grain structure good good variable
heat treatments few few definite
machining least less necessary
 Decision Process for Cold Forming
Tooling Loads in Heading Operations

120%

100%
Relative Load

80%

60%

40%

20%

0%
Cold Warm Hot
Steps to Manufacture:

From raw material to

finished parts
 Process Chain of Cold Forming

Raw Heat Surface Cold Formed

Material Treatment Treatment Forming Part

Metal Heat Metal Finished

Removal Treatment Removal 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
 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
Pre-coat:
phosphate, lime, oxalate
Drawing
Lubricants:
Soaps, Oils
Cold Forming Oils
Metal removal coolant:
Thread rolling
Emulsion, Solution, Oil
Metal removal coolant:
Cutting/slotting
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.