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  • 1. ERC NSMNear Net Shape Cold, Warm & Hot Forging A Short Course Developed at The Engineering Research CenterFor Net Shape Manufacturing (ERC/NSM) Presented By Dr. Taylan Altan, Professor & Director © Copyright Engineering Research Center for Net Shape Manufacturing. All Rights Reserved. http://www.ercnsm.org 1
  • 2. ERC References NSM• T. Altan. S.Oh, H. Gegel, Metal Forming: Fundamentals and Applications, American Society for Metals, Metal Park Ohio 1983.• K. Lange, Hand Book of Metal Forming, McGraw-Hill Book Company 1985.• A.J. Schey, Tribology in Metal Working, American Society for Metals, Metal park Ohio 1983.• Forging Industry Association (FIA), Forging Handbook – www.forging.org• ASM International, ASM Hand Book: Forming and Forging, Volume 14, 1988.• T. Altan, F.W. Boulger, J.R. Becker, N.Akgerman, & H.J. Henning, Forging Equipment, Materials, and Practices, Metals and Ceramic Information Center, Ohio 1973.• International Cold Forging Group – Various Documents 2
  • 3. Near Net Shape Cold, Warm ERC & Hot Forging NSM 1.1 & 1.2 Forging Processes 3
  • 4. Forging Processes ERC NSMCold Forging - Starts at room temperature (RT to 600-800 F)Warm Forging - Below or near recrystallization temperature (900 F - 1800 F for steel)**Tool designs for cold & warm forging are similar, but temperatures and lubricants are differentHot Forging - Above recrystallization temperature (1800 F - 2200 F for steel, 800 F for Al) 4
  • 5. Effects of Test Temperature and ERC Test Speed NSM Effects of test temperature and test speed (strain rate) on tensile strength and reduction of area of hot rolled type 1045 steel (Courtesy: Technical Report by Bethlehem Steel Corporation, Bethlehem, PA) 5
  • 6. Cold, Warm, & Hot Forging ERC - Advantages & Disadvantages - NSM Cold Warm Hot Advantages Advantages Advantages• Precision Process (Tight • Combines Advantages of • Can Forge Complex Tolerances) Cold & Hot Forging Shapes• Improved Part Strength • Better Formability • Good Formability• Better Surface Finish • Lower Forming Pressures • Low Forming Pressures• Material Conservation • Higher Deformation Ratio • Can Forge Parts of Higher • No Annealing Required Weight and Volume Disadvantages• High Forming Pressures Disadvantages Disadvantages• Several Pre-Forming Steps Needed • High Tooling Costs • Formation of Scale• Annealing Steps May Be • Tooling Must Withstand • Decreased Accuracy Required During Process Forming Pressures as well as (Larger Tolerances)• Low Formability High Temperatures 6
  • 7. Cold Forging ERC- Forming Sequence - NSM Rear View Mirror Holder (Cold Forged) 7
  • 8. Forging With Flash ERC NSMStandard terminology for various features of a typical forging die 8
  • 9. ERCHot Forging With Flash NSM 9
  • 10. ERC Hot Forged Connecting Rods NSM Finish forgingPreforms prepared before andin reducer rolls after trimming 10
  • 11. ERCHot Forging - Track Links NSM 11
  • 12. Examples Of Hot Forgings ERC NSM 12
  • 13. Forging Without Flash ERC (trapped die) NSMA billet with carefully controlled volume is deformed (hot orcold) by a punch to fill a die cavity without any loss ofmaterial 13
  • 14. Multiple-step Cold Forging ERC NSM(a) Sheared Billet (c) Forward extrusion (e) Upsetting of flange and coining of shoulder (a) (b) (c) (d) (e) (b) Forward rod and (d) Backward cup backward cup extrusion extrusion Schematic illustration of forming sequences in cold forging of a gear blank 14
  • 15. Cold Forged Components ERC NSMReference: Mitsubishi Heavy Industries 15
  • 16. Cold Forged Parts ERC NSM Courtesy: Raufoss 16
  • 17. Open Die Forging ERC NSM 17
  • 18. Orbital Forging ERC NSMVarious Stages in Orbital Forging Processes 18
  • 19. Radial (Or Rotary) Forging ERC NSM Radial Forging of a Shaft 19
  • 20. Upset Forging ERC NSMUpsetting With Flat-heading Tool 20
  • 21. ERC Economics of Cold Forging NSM Number of forged parts in:Part Weight Universal Special machines machines<20 g…………..………………..… 10,000 500,00020 to 500 g……………………….. 5,000 50,000500 g to 10 kg……………………. 1,000 20,00010 to 50 kg…………….………….. 1,000 10,000 Minimum number of parts in a production lot for economic production in cold forging of steel 21
  • 22. Forging Process as a System ERC NSM (2) (4) (4) (6) (1) (3) (2) (5) (7)(1) Billet Material (5) Equipment(2) Tooling (6) Product(3) Tool/Material Interface (7) Plant Environment(4) Deformation Zone/Workpiece 22
  • 23. Forging Process as a System ERC - Significant Variables - NSM• Billet Material – Flow Stress (instantaneous yield stress) as a Function of Strain, Strain Rate,Temperature, & Microstructure – Workability (forgeability) as a Function of Strain, Strain Rate,Temperature, & Microstructure – Surface Conditions – Thermal/Physical Properties – Initial Conditions (composition, temperature, history) – Effects of Changes in Microstructure & Composition• Tooling – Geometry of Tools – Surface Conditions – Material/Heat Treatment/Hardness – Temperature 23
  • 24. Forging Process as a System ERC - Significant Variables - NSM• Conditions at Tool/Material Interface – Lubricant Type and Temperature – Insulation & Cooling Characteristics of the Interface Layer – Lubricity & Frictional Shear Stress – Characteristics Related to Lubricant Application & Removal• Deformation Zone – Deformation Mechanics, Model Used for Analysis – Metal Flow, Velocities, Strain Rates, & Strains – Stresses (variation during deformation) – Temperatures (Heat Generation & Transfer) 24
  • 25. Forging Process as a System ERC - Significant Variables - NSM• Equipment – Speed/Production Rate – Force/Energy Capabilities – Rigidity & Accuracy• Product – Geometry – Dimensional Accuracy, Tolerances, Surface Finish – Microstructure, Mechanical & Metallurgical Properties• Plant & Environment – Manpower – Air, Noise, & Wastewater Pollution – Plant & Production Facilities and Control 25
  • 26. Process & Equipment ERC Variables in Forging NSM PROCESS VARIABLES MACHINE VARIABLES STRAIN RATE SLIDE VELOCITY, Vp MATERIAL DIE TEMPERATURE CONTACT TIME, tp FLOW STRESS TEMPERATURE, θ STIFFNESS, C FRICTION, CLEARANCES, LUBRICATION FLATNESS, & PARALLELISM PART GEOMETRY SURFACE TO VOLUME RATIO MACHINE LOAD, LM PART TOLERANCES MACHINE ENERGY, EM VARIATIONS IN STROKES/MIN, no STOCK WEIGHT (IDLE) & TEMPERATUREREQ’D LOAD, Lp ENERGY, EP STROKES/MIN, no (UNDER LOAD) 26