1 Chapter IX: Bulk Forming (Forging) 1 Content: Forging • Introduction • Examples of Application • Overview to Basic Forging Processes • Open-Die Forging • Forging Machine Tools • Closed-Die Forging • Forging Temperature • Forging Defects • Forging Dies • Current Trends Chapter IX: Bulk Forming (Forging) 2 Description of Forging Advantages of Forging Process: • High material utilization • High production rates • High process stability • High recyclability of products Forging consists of a group of manufacturing processes which are mainly deformation processes. The two other types of processes are separating (parting) and joining processes. In order to reduce stresses and forces and to increase formability, forging is usually carried out after heating to a temperature range at which recovery and recrystallization occurs. Hence the workpieces after forging do not show a permanent work hardening. Advantages of Forged Products: • Improved grain structure • Higher fatigue strength & ductility • Better surface quality than in casting • Beneficial grain flow (fibers) 2 Chapter IX: Bulk Forming (Forging) 3 Material Fibers (Grain Flow) Casting ForgingMachining Forging Industry Association The beneficial grain flow in forged parts leads to a longer fatigue life & higher ductility than machined or casted parts. ASM Handbook Chapter IX: Bulk Forming (Forging) 4 Forging Production 2.368.000 35.000 1.360.000 9.600.000 0 3.000.000 6.000.000 9.000.000 12.000.000 Turkey (1989) Germany (1999) Europe (1998) World (1998) Closed Die Forged Parts in t Tekkaya/Hirschvogel 3 Chapter IX: Bulk Forming (Forging) 5 Examples of Application: Various Parts IDS Chapter IX: Bulk Forming (Forging) 6 Examples of Application: Front Axle of a Truck Daimler Benz AG 4 Chapter IX: Bulk Forming (Forging) 7 Examples of Application: Automobile Front Wheel Suspension BMW AG Chapter IX: Bulk Forming (Forging) 8 Examples of Application: Truck Gear Box Daimler Benz AG 5 Chapter IX: Bulk Forming (Forging) 9 Examples of Application: Vehicle Power Shaft Gelenkwellenbau Gmbh Chapter IX: Bulk Forming (Forging) 10 Examples of Application: Aircraft Landing Gear Structure Airbus Industrie 6 Chapter IX: Bulk Forming (Forging) 11 Basic Forging Processes Open-Die Forging Closed-Die Forging Hot Forging Warm Forging Cold Forging Precision Forging Near-Net-Shape-Forging Net-Shape Forging Isothermal Forging Chapter IX: Bulk Forming (Forging) 12 Hot versus Cold Forging Hot Forging • Production of discrete parts • Greater technical and economical importance • Low stresses, no/low work- hardening, homogenized grain structure • High formability • Medium to low accuracy • Scale formation • Forging temperatures: – Steel: > 1000 o C (up to 1150 o C) – Al-Alloys: 360 o C-520 o C – Cu-Alloys: 700 o C-800 o C Cold Forging • Production of discrete parts • Processes covered: extrusion forging, upsetting, coining • High stresses, strain hardening, high die loads • Limited formability • Near-net shape or net shape • High surface quality 7 Chapter IX: Bulk Forming (Forging) 13 Open-Die versus Closed-Die Forging Open-Die Forging • Aim: To achieve a convenient mass distribution or shape for the successive operations (machining or closed-die forging) • Simple tools, whose geometry do not depend on the product geometry Closed-Die Forging • Aim: Achieve best possible dimensional and shape accuracy of the product. • Tools whose geometry is product dependent Chapter IX: Bulk Forming (Forging) 14 Open Die Forging Cogging Video Upsetting Heading (with no given form) Spreading Radial Forging (with no given form) Kalpakjian Geiger Lange 8 Chapter IX: Bulk Forming (Forging) 15 Basic Processes of Open-Die Forging and Achievable Cross-Section Changes Open-Die Forging Processes Cross-Section Change Cogging, spreading A 0 /A 1    4-5 Upsetting, heading A 1 /A 0 < 4-5 • Cogging (material displacement) • Spreading (material displacement) • Upsetting, heading (material concentration) Chapter IX: Bulk Forming (Forging) 16 Complete Plastification During Cogging Lange 9 Chapter IX: Bulk Forming (Forging) 17 Closed Die Forging (1) Impression Die Forging Video Closed Die Forging (no flash) Coining Heading Video Kalpakjian Chapter IX: Bulk Forming (Forging) 18 Closed Die Forging (2) Roll-Forging Skew-Roll-Forging Upsetting in a Die Kalpakjian 10 Chapter IX: Bulk Forming (Forging) 19 Closed Die Forging (3) Radial Forging (Swaging) Kalpakjian Chapter IX: Bulk Forming (Forging) 20 Terminology for Impression Die Forging Kalpakjian [...]... Lange Chapter IX: Bulk Forming (Forging) 27 Forging Presses (1) Hydraulic Press Eccentric Press Chapter IX: Bulk Forming (Forging) Kalpakjian 28 14 Forging Presses (2) Knuckle Joint Press Kalpakjian Friction Screw Press Gravity Drop Hammer Chapter IX: Bulk Forming (Forging) 29 Example for Forging Sequences Kalpakjian Chapter IX: Bulk Forming (Forging) 30 15 Examples of Forged Parts Courtesy Kanca Chapter. .. constant: – Heat losses due to radiation and conduction – Heat gain by friction and forming work Chapter IX: Bulk Forming (Forging) 35 Forging Defects Kalpakjian Chapter IX: Bulk Forming (Forging) 36 18 Forging Dies: Failure Wear (abrasion) Thermal fatigue Mechanical fatigue Plastic deformation Kannappan Chapter IX: Bulk Forming (Forging) 37 Forging Dies: Design • Positioning the forging stages • Design... Chapter IX: Bulk Forming (Forging) 31 Closed-Die Forging without Flash: Example Chapter IX: Bulk Forming (Forging) 32 16 Forging Force in tons Closed-Die Forging without Flash: ForceDisplacement Diagram Upsetting Corner Filling Punch Stroke in mm Johne Chapter IX: Bulk Forming (Forging) 33 Closed-Die Forging without Flash: Material Flow Punch Die Workpiece plastic zone sticking zone unfilled corner Chapter. .. compensated by saving post-machining costs – Disadvantages: • Very tight temperature window • Advance tool technology necessary • Not all materials can be thixoforged Chapter IX: Bulk Forming (Forging) 39 Computer Aided Forging unkown owner Chapter IX: Bulk Forming (Forging) 40 20 ... b1 < b2 r upper die z b2 b1 workpiece s lower die Force F sz,flash ,max,1 sz sf 21 Mechanics of Closed-Die Forging sz sz,flash, max,2 stresses Chapter IX: Bulk Forming (Forging) plastic region r Work W rigid region AF1 Adc AF2 Stroke Lange Chapter IX: Bulk Forming (Forging) 22 11 Effect of Flash Dimesions 15 10 5 50 80 mm 1000 4500 800 W 600 4000 400 3500 szmax 45 40 35 3000 30 2500 200 Forging Work... dimensional accuracy – Design for ease of machining Chapter IX: Bulk Forming (Forging) 38 19 Current Trends • Thixo-Forging: – Combination of casting and forming – Thixotropic state: both liquid and solid states co-exist – Materials: basically aluminum and magnesium alloys – Advantages: • Low forging loads • Complicated shapes can be forged in one stage • Near-net forming (as compared to casting) • Large wall... f ⋅π ⋅  + + µ ⋅   (Tresca)  12 ⋅ s    4 24 ⋅ s Lange Chapter IX: Bulk Forming (Forging) 25 Typical Hot Flow Curves for Ck45 400 & ε = 40 s −1 Flow stress in MPa T = 800oC 8 s −1 1.6 s −1 40 s −1 300 200 T = 1000oC 8 s −1 1.6 s −1 100 T = 1200oC 0 0 0.2 40 s −1 0.4 0.6 0.8 Equivalent plastic strain 8 s −1 1.6 s −1 1 Chapter IX: Bulk Forming (Forging) 1.2 MSC/AutoForge 26 13 Forging Press Characteristics... 2500 200 Forging Work W in kNm 20 55 5000 Dm Forging Force F in kN 25 5500 1200 Axial Stress in Flash szmax in MPa Excess Material Dm in % 30 25 F 0 0 0 2 4 6 8 Die-Land Ratio b/s 10 Vieregge Chapter IX: Bulk Forming (Forging) 23 Stress and Force Computation in Impression Die Forging: Slab Method In the flash land the axial stress is given according to the slab method by Siebel as: b σ zmax = −σ f... Simple method to estimate the forging load: F max = AP ⋅ σ zmax where, the total projection area Ap is given by: AP = Adc + AF Adc: Projection area of die cavity, AF: Projection area of flash Chapter IX: Bulk Forming (Forging) 24 12 Stress and Force Computation in Impression Die Forging: Upper Bound Method Assumptions for die with steep and deep cavities: • rigid region The material within the die... Corner Filling Punch Stroke in mm Johne Chapter IX: Bulk Forming (Forging) 33 Closed-Die Forging without Flash: Material Flow Punch Die Workpiece plastic zone sticking zone unfilled corner Chapter IX: Bulk Forming (Forging) Lange 34 17 Forging Temperature • Lower Temperature: Significantly larger than the recyrstallization temperature • Upper Temperature: As large as possible, but if too large: • – . Hammer Kalpakjian Chapter IX: Bulk Forming (Forging) 30 Kalpakjian Example for Forging Sequences 16 Chapter IX: Bulk Forming (Forging) 31 Examples of Forged Parts Courtesy Kanca Chapter IX: Bulk Forming. t Tekkaya/Hirschvogel 3 Chapter IX: Bulk Forming (Forging) 5 Examples of Application: Various Parts IDS Chapter IX: Bulk Forming (Forging) 6 Examples of Application: Front Axle of a Truck Daimler Benz AG 4 Chapter. radiation and conduction – Heat gain by friction and forming work Chapter IX: Bulk Forming (Forging) 36 Forging Defects Kalpakjian 19 Chapter IX: Bulk Forming (Forging) 37 Forging Dies: Failure Kannappan Wear