Basics-of-Cold-Forming.pdf

1 | ©2016 QuEST Global Services Pte Ltd. Confidential
QuEST Global Confidential | TEG-TEM-013 | 11-Feb-16 | Revision: 02 | Template
©2016 QuEST Global Services Pte Ltd. The information in this document is the property of QuEST Global Services Pte Ltd. and may not be copied or communicated
to a third party or used for any purpose other than that for which it is supplied without the written consent of QuEST Global Services Pte Ltd.
QuEST Global
Basics of Cold Forming
30th
Dec 2016/ Virupaksha A M

QuEST TRAINING MATERIAL
Training Title#1 :
Author(s)#02
: Virupakshi AM Email#03
:virupakshi.am@quest-global.com Date #04
: 30/12/2016
Summary#05
:
Cold forming is a manufacturing process by which metal is shaped without removing material. A simple blank is placed within a die and a punch is
pressed into the blank at ambient temperature. The blank then takes on the form of the punch and the die. Put more simply, cold-forming is making a shape
from material at room temperature, just like Plasticine when it is pushed into a mould. With appropriate force, metals such as copper, aluminium, brass and now
even stainless steel can be formed into the required shape.
In cold forming, the metal is stretched beyond its yield strength, so that it takes on and retains the exact shape of the mould, but without
adversely affecting its tensile strength. Unlike conventional machining, where the material removal processes cut across the grain structure of each part, cold
forming allows the grain structure of the material to follow the contours of the die or mould. As a result, the strength of the part is maximised along its length,
while internal surfaces take on a highly polished finish.
Cold forming is a fast, economical way to produce robust, complex components in a wide range of materials. The process is capable of delivering
precision engineered parts with up to 80% less scrap than machine processes. Coupled with faster lead times, better surface finish and improved mechanical
characteristics, cold forming offers an opportunity for manufacturers across the industry to take advantage of enhanced component quality while also reducing
costs.
Basics of Cold Forming – Training Material
Revision Description Date
01 New Release 30th
Dec 2016

Topics:
• Introduction
• Terminology
• Processes
• Benefits
• Material Characteristics
• Applications
• Steps to Manufacture
• Coatings and Lubricants
Training Details

Introduction to Cold Forming
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 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

 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

• 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.

Material Description
Tensile
(ksi)
Yield
Formabili
ty
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
Copper
High corrosion resistance.
Expensive. Ex: 110
Electrolytic Tough Pitch
35 – 40 10 – 35 Excellent 6.5
Nickel Alloys
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
Materials - Characteristics

Typical max
Tensile as
annealed
Typical max
Tensile w/
50% cold
work
Formability
Cost Index
Steel = 1
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

Typical max
Tensile as
annealed
Typical max
Tensile w/
5% cold work
Formability
Cost Index
Steel = 1
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
Pyromet® 718
Hi Temperature
Alloy
120 135 Poor 12.0

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

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

 Equipment
 Which machine
 Which tools
 Skill of personnel
 Material
 Formability
 Incoming condition
 Part
 Accuracy
 Tolerances
 Additional treatments

Production of Headed Parts
Cold Heading Hot 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)
Warm
Heading

Cold Heading Warm Heading Hot Heading
Carbon Steel
>0.3% carbon, >3.0%
alloy
Room temp
550 - 850oC
1020 - 1560oF
>950oC
>1740oF
Austenitic Steels Room temp
400 - 450oC
750 - 840oF
Blue Brittleness Problem
550 - 850oC
1020 - 1560oF
Aluminum alloys
Room temp
420 - 480oC
790 - 900oF
Not applicable
Brass alloys Room temp
350 - 620oC
660 - 1150oF
Not applicable

Forming Type Cold Warm Hot
Temperature Room 550 - 950oC 950 - 1250oC
1020 - 1740oF 1740 - 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
General Aspects of Heading Methods

Tooling Loads in Heading Operations
0%
20%
40%
60%
80%
100%
120%
Cold Warm Hot
R
e
la
t
iv
e
L
o
a
d

38 | ©2016 QuEST Global Services Pte. Ltd. Confidential
Raw
Material
Heat
Treatment
Surface
Treatment
Cold
Forming
Formed
Part
Metal
Removal
Heat
Treatment
Metal
Removal
Finished
Part
Process Chain of Cold Forming

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

Heat Treatment of Raw Material
 Benefits
 Improves ability of deformation
 Reduces hardness
 Improves metal structure towards better forming
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

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

Surface Treatment
 Pre-coating
 Carbon
 Zinc phosphate
 Stainless
 Potassium sulfate
 Lime
 Drying
 Approx. 250of/ 120oc
 Metallic Coating
 Copper plating
 Non-metallic coatings
 Molybdenum disulfide – mos2
 Soaps
 Sodium stearates
 Calcium stearates

Cold Forming
 Single stage presses
 Multi stage presses
 up to 5 or 6 stages, as many as 8
 Secondary forming operations
 threading
 rolled
 machined

Heat treatment after Cold Forming
 Annealing
 Relieve stress
 Re-crystallize
 Normalize
 Hardening
 Increase the hardness after forming

Metal Removing
 Hard Surfaces
 Turning
 Grinding
 Honing
 Lapping
 Soft Surfaces
 Turning
 Drilling
 Milling

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
 Pre-coat
 Lime
 Copper plating
 Zinc phosphate
 Molybdenum disulfide
 Oxalate

Lubricants
Types
 Soaps
 Calcium stearate
 Sodium stearate
 Drawing oils
 Metal-removing coolants
 Oil
 Emulsion
 Synthetics

Process Lubricant
Hot Rolling Water
Drawing
Pre-coat: Phosphate, lime, oxalate
Lubricants: Soaps, Oils
Cold Forming Oils
Thread rolling
Metal removal coolant:
Emulsion, Solution, Oil
Cutting/slotting
Metal removal coolant:
Emulsion, Solution

Additional references
• 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)

©2016 QuEST Global Services Pte Ltd. The information in this document is the property of QuEST Global Services Pte Ltd. and may not be copied or communicated
to a third party or used for any purpose other than that for which it is supplied without the written consent of QuEST Global Services Pte Ltd.
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