- APPLICATIONS TO GEAR COMPONENTS -

Transcription

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

2 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

3 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

4 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

5 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

6 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

7 SURFACE HARDENING TECHNIQUES

8 SURFACE HARDENING TECHNIQUES Source : Source : Source : 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

9 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

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

11 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

12 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

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

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

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

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

17 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

18 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

19 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 %

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

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

22 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)

23 CASE STUDY#2 : PROCESS DATA Spur gear Diameter : 100mm (outer) 84mm (inner) Thickness : 10mm Alloy steel : 34CrNiMo6 (DIN 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

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

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

26 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

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

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

29 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

30 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.

31 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

32 THANK YOU FOR YOUR ATTENTION ADDRESS: 694, av du Dr. Maurice Donat Parc de Haute Technologie Mougins cedex France CONTACT: +33 (0) (0)