- APPLICATIONS TO GEAR COMPONENTS -

FEM SIMULATION OF SURFACE HARDENING TECHNIQUES - APPLICATIONS TO GEAR COMPONENTS - R.DUCLOUX 1, S. ANDRIETTI 1, J. BARLIER 1 1 TRANSVALOR SA - FRANCE

OUTLINE INTRODUCTION SURFACE HARDENING TECHNIQUES CASE STUDY#1 : HEAT TREATMENT OF A BEVEL GEAR CASE STUDY#2 : INDUCTION HARDENING OF A SPUR GEAR CONCLUSION & PERSPECTIVES

INTRODUCTION Standard goals of forming process simulations - Understand material flow : underfilling, folds & laps - Determine optimum forming sequence : reduce design cycle - Predict material properties : grain flow, microstructure - Extend die life : stress analysis, wear, load, Productivity, Quality, Innovation & Savings

INTRODUCTION Recent challenges - Predict the in-use properties of the forgings - Simulate the entire manufacturing process including all pre & postforming operations (from initial heating to final heat treatment) Today s presentation - Illustrate a wide range of heat treatment simulations - Application to surface hardening on forged components

SURFACE HARDENING TECHNIQUES Goal of surface (or case) hardening - Increase wear resistance and surface hardness - Keep inner metal softer - Applicable to low carbon & alloy steel - Followed by heat treatment to get desired hardness - Typical parts are : pinion, camshaft, gear, Among the most common techniques - Carburizing - Nitriding, other diffusion processes - Induction hardening - Shot peening

SURFACE HARDENING TECHNIQUES

SURFACE HARDENING TECHNIQUES Source : http://www.yourdictionary.com/bevel-gear Source : http://science.howstuffworks.com/transport/engines-equipment/gear2.htm Source : http://science.howstuffworks.com/transport/engines-equipment/gear4.htm Application of surface hardening on gear components Very located and non-constant contact area Need to increase hardness on the surface Need to maintain ductility in the core of the component

OUTLINE INTRODUCTION SURFACE HARDENING TECHNIQUES CASE STUDY#1 : HEAT TREATMENT OF A BEVEL GEAR CARBURIZING -> QUENCHING -> TEMPERING CASE STUDY#2 : INDUCTION HARDENING OF A SPUR GEAR CONCLUSION & PERSPECTIVES

CASE STUDY#1 : AUTOMOTIVE BEVEL GEAR Complete forming sequence description Two warm forging stages Piercing-Flash trimming, Machining Heat treatment operations (carburizing-quenching-tempering)

CASE STUDY#1 : PROCESS DATA Automotive bevel gear Max outer diameter ~ 52 mm Weight ~ 180 g Low carbon steel for carburizing (e.g. 20MnCr5) Carburizing conditions Process : 2h40 at 850 C Initial carbon rate in the part : 0.20% Atmosphere enriched in carbon : 0.8% Quenching Oil bath : 20 C during 2min HTC : 5500 W/ C.m 2 Tempering To relieve internal stresses : 200 C during 40min

CASE STUDY#1 : CARBURIZING STAGE 0.80% carbon ~ High quenchability from 0.20% to 0.8% of C 0.20% carbon ~ Low quenchability Objectives of the carburizing stage Increase of carbon concentration on surface Increase quenchability for low carbon steel Isothermal diagram is shifted according to the carbon rate

CASE STUDY#1 : CARBURIZING RESULTS Carburizing Carbon concentration (%) after carburizing

CASE STUDY#1 : QUENCHING RESULTS Phase distribution after oil quenching (martensite-bainite-pearlite-ferrite) Residual stress distribution (1 st principal stress)

CASE STUDY#1 : PART DISTORTION Quenching Distortion observed on the component after quenching due to plastic deformation (magnification x10)

CASE STUDY#1 : TEMPERING RESULTS Tempering Von Mises stress (MPa) Effective stress relieving due to tempering - before (left) & after (right) -

OUTLINE INTRODUCTION SURFACE HARDENING TECHNIQUES CASE STUDY#1 : HEAT TREATMENT OF A BEVEL GEAR CASE STUDY#2 : INDUCTION HARDENING OF A SPUR GEAR LOCAL HEATING BY INDUCTION -> QUENCHING CONCLUSION & PERSPECTIVES

CASE STUDY#2 : STRAIGHT-CUT OR SPUR GEAR Typical in-use conditions with loading / unloading sequence Alternative compression vs. tension mode at the root of the teeth

CASE STUDY#2 : STRAIGHT-CUT OR SPUR GEAR Pressure distribution Red => compression Blue => tension How to increase the resistance to fatigue loading for contact fatigue : increase local hardness for bending fatigue : increase compressive residual stress Objective : delay cracks propagation Material characteristics Resisting torque = 1000 N.m Yield stress = 600 Mpa Ultimate stress = 800 Mpa Elongation at break = 5 %

CASE STUDY#2 : HEAT TREATEMENT SEQUENCE Heating (induction) Quenching (water jets) Tempering (induction)

INDUCTION HEATING : FEM SOLVERS Heating Electro magnetic solver Heating source Temperature FORGE Solver Air Inductor Workpiece Only workpiece

INDUCTION HEATING : GLOBAL MESHING TECHNIQUE Heating Generation of a unique global FEM mesh Inductor & Part : import from CAD Air : defined via box or cylindrical area around the inductor The global mesh gathers all entities (air+inductor+part)

CASE STUDY#2 : PROCESS DATA Spur gear Diameter : 100mm (outer) 84mm (inner) Thickness : 10mm Alloy steel : 34CrNiMo6 (DIN 1.6582 AISI 9480) Heating (induction) Induction heating Current intensity : 4000 A Current frequency : from 5KHz to 20 KHz Heating time : from 2 to 10 sec Quenching (water jets) Quenching HTC : 2600 W/ C.m 2 Media temperature : room temperature Time : 15min

CASE STUDY#2 : RESULTS Heating (induction) Heat power (W/m3) Magnetic field (A/m)

CASE STUDY#2 : RESULTS Heating (induction) Temperature (deg C) Austenite rate

CASE STUDY#2 : RESULTS Heating (induction) Low frequency Heating time is longer Preferential heating zone: tooth base High frequency Heating time is shorter Preferential heating zone: tooth tip I rms = 4000 A f = 5 khz Heating time = 10 sec Austenite distribution Dual frequency? Austenite distribution I rms = 4000 A f = 20 khz Heating time = 2 sec

CASE STUDY#2 : RESULTS Heating (induction) Quenching (water jets) Temperature (deg C) Martensite rate

CASE STUDY#2 : RESULTS Heating (induction) Quenching (water jets) 800 700 600 500 400 300 200 100 0 Hardness (HV) Depth 0 0,5 1 1,5 2 2,5 3 300 200 Residual stresses (Mpa) tension 100 Depth 0-100 -200 0 0,5 1 1,5 2 2,5 3 Depth Martensite distribution - Frequency = 20000 Hz -300-400 compression Final material properties by the quenching end

CONCLUSION & PERSPECTIVES Process simulation is the key-solution : - Simulate the complete manufacturing process. - Associate Heat treatment & Forming operations. - Predict the final in-use properties of component. State of the art surface hardening techniques can be simulated : - Carburizing + Quenching + Tempering. - Impact of carbon rate on IT diagram for martensitic transformation. - Induction hardening (heating + quenching). - Right compromise for process parameters.

CONCLUSION & PERSPECTIVES Extensive capabilities in FORGE NxT : - Forming process & heat treatment simulations - Heat treatment capabilities : austenitisation, hydrogen diffusion, carburizing, quenching, tempering, - Unique electro-magnetic solver for induction heating, hardening, heat treating, Keep increasing our competitive advantages with : - Enhanced phase transformation models - Complementary surface treatment : nitriding, carbonitriding - Precipitate prediction incl. coupling with strain & stress

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