Presentation on theme: "Introduction to Cold Forming March 6, 2007 Independence, Ohio Presented by Carpenter Technology Corporation Copyright 2007 CRS Holdings, Inc."— Presentation transcript:
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.
March 23, 1794 Josiah Pierson – “Cold Header” Rivet Machine November 16, 1796 Isaac Garretson – U.S. Patent for nail cutting & heading machine History and Development of Cold Forming
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 Cold Forming Terminology
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 ExtrusionTrap Extrusion 30% area reduction75% area reduction
Examples using trap extrusion and open extrusion.
7 Station Cold Forming Process
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. Benefits of Cold Forming
MaterialDescription Tensile (ksi) YieldFormability Cost Index Steel = 1 Aluminum Alloys Tensile strength of mild steel with 1/3 the weight. Ex: Excellent5.0 Brass Alloy of Cu & Zn. Tough, rustproof. Relatively inexpensive. Ex: 274 Yellow Brass 60 min40 minExcellent6.0 Copper High corrosion resistance. Expensive. Ex: 110 Electrolytic Tough Pitch 35 – 4010 – 35Excellent6.5 Nickel Alloys Approximately 2/3 Nickel, 1/3 Cu with small amounts Fe. High strength, resistance to heat and corrosion. Ex: NiCu min60 minExcellent18.0 Materials - Characteristics
MaterialDescription Typical max Tensile as annealed Typical max Tensile w/ 50% cold work Formability Cost Index Steel = Low carbon5562Excellent1 1018Low carbon6598 Good to Excellent Medium carbon Good to Excellent Medium carbon 85157Fair to Good Medium carbon low alloy 83166Fair to Good1.5 Materials - Characteristics
MaterialDescription Typical max Tensile as annealed Typical max Tensile w/ 5% cold work Formability Cost Index Steel = Martensitic Stainless Steel 7890Fair Ferritic Stainless Steel 7586Fair HQ Austenitic Stainless Steel 7583Fair Austenitic Stainless Steel 8393Fair4.5 A-286 Austenitic Stainless Steel 95 Fair to Poor6.5 Pyromet® 718 Hi Temperature Alloy Poor12.0 Materials - Characteristics Pyromet is a reg. tm. of CRS Holdings, Inc.
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 Applications for Cold Formed Parts
Decision Process for Cold Forming
Equipment Material Part which machine which tools skill of personnel formability incoming condition accuracy tolerances additional treatments Decision Process for Cold Forming
Production of Headed Parts Cold HeadingHot Heading Room TemperatureForming of heatedForging temperatures No heatslugs at temperaturesfrom 950 – 1250 °C from: 550 – 950 °C(1740 – 2300 °F) (1020 – 1740 °F) Warm Heading Decision Process for Cold Forming
Cold Heading Warm Heading Hot Heading Carbon Steel >0.3% carbon, >3.0% alloy Room temp o C o F >950 o C >1740 o F Austenitic Steels Room temp o C o F Blue Brittleness Problem o C o F Aluminum alloys Room temp o C o F Not applicable Brass alloysRoom temp o C o F Not applicable Decision Process for Cold Forming
Forming TypeColdWarmHot TemperatureRoom o C o C o F o F accuracyhighgoodlow formabilityrestrictedgood materialrestrictedlarge variety energy costslowmoderatehigh surface qualityhighgoodlow tolerancesclosecloserlow grain structuregood variable heat treatmentsfew definite machiningleastlessnecessary General Aspects of Heading Methods Decision Process for Cold Forming
Steps to Manufacture: From raw material to finished parts
Process Chain of Cold Forming
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 170 o -190 o F/ 77 o -88 o C 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. 250 o F/ 120 o C Metallic Coating copper plating Steps to Manufacture
ProcessLubricant Hot RollingWater Drawing Pre-coat: phosphate, lime, oxalate Lubricants: Soaps, Oils Cold FormingOils Thread rolling Metal removal coolant: Emulsion, Solution, Oil Cutting/slotting Metal removal coolant: Emulsion, Solution Coatings and Lubricants
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)
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