MODELING OF INDUCTION HARDENING PROCESS PART 1: INDUCTION HEATING Dr. Jiankun Yuan Prof. Yiming (Kevin) Rong Acknowledgement:

Présentation au sujet: "MODELING OF INDUCTION HARDENING PROCESS PART 1: INDUCTION HEATING Dr. Jiankun Yuan Prof. Yiming (Kevin) Rong Acknowledgement:"— Transcription de la présentation:

1 MODELING OF INDUCTION HARDENING PROCESS PART 1: INDUCTION HEATING Dr. Jiankun Yuan Prof. Yiming (Kevin) Rong http://me.wpi.edu/~camlab Acknowledgement: This project is partially supported by Delphi and CHTE at WPI. Dr. Q. Lu was involved in the early work of the project.

2 Induction: Why Induction Heat Treatment? Greatly shortened heat treatment cycle Highly selective Highly energy efficiency Less-pollution process Advantages Practical Problems Lack of systematic heating time and temperature distribution control inside WP. Nonlinear effect of material properties. Lack phase transformation data inside WP for hardness and residual stress determination. Evaluate combination effect of AC power density, frequency and gap on final hardness pattern. Trial and error, cost and design period. Numerical modeling may provide better prediction Research content: FEM based electromagnetic/thermal analysis + quenching analysis + hardening analysis Research objective : (1) Provide T field, time history inside WP (2) Determine formed content of martensite, pearlite and bainite. (3) Determine hardness distribution in WP. (4) Guidance for induction system design.

3 Martensite content determines the hardness Introduction: Induction Hardening Process Induction heating: metal parts heated to austenite Phase Fast quenching process transforms austenite to martensite phase Martensitic structure is the most hardest microstructure workpieceInductor/coil Heating process Electromagnetic field Induction coil High freq. AC power Joule heat by eddy current

4 Principle: Electromagnetic and Thermal Analysis Calculation of magnetic vector potential (A) Calculation of magnetic flux density (B) Calculation of magnetic field intensity (H) Calculation of electric field intensity (E) Calculation of electric field density (D) Calculation of current density (J) Calculation of Inducting heat (Q induction ) B =   A H = B /  D =   E Q induction = E  J = J 2 /  Output: Heat generation Q induction in WP (Gauss’ Law for magnetic field) (Ampere’s Circuital Law) (Faraday’s Law) Input AC power to coil Electromagnetic Analysis Coil WP QCQC QEtQEt QNQN QWQW QSQS QBQB QEQE QNQN Q R + Q CV QSQS (Outside) (a) WP geometry (b) FEA model (c) Interior element (d) Surface element Thermal Analysis with finite element model Induced Joule heat Heat radiation Heat convection Heat conduction

5 Case Study: Complex Surface Hardening concave convex Geometry Model Automotive parts from Delphi Inc., Sandusky,Ohio Material: Carbon Steel, AISI 1070 Real spindle to be hardened FEA model and B.C. Mesh generated by ANSYS Concave and convex on surface of workpiece make the heating process not easy to control. ANSYS system is employed for the analysis. Mesh should be much finer at locations of convex and concave in both coil and workpiece.

6 Case Study: Material Properties -- AISI 1070 Emissivity conductivity WP relative permeability Electrical Resistivity Specific heat Convection coefficient (a) Electromagnetic Properties (b) Thermal Properties

7 Case Study: Magnetic Field Intensity Distribution

8 Effect of current density distribution Constant current distribution in coil can not result in good heating pattern, especially at concaves of workpiece Better hardened pattern resulted from modification of Finer coil mesh and enhanced coil current density at area neighboring to surface concaves of workpiece. Enhanced coil current density suggests utilization of magnetic controller at those area in coil design process. Physically this can be fulfilled by magnetic controller. (a1) Constant current distribution in coil (a2) heated pattern (b1) Adjusted current distribution in coil (b2) heated pattern

9 Case Study:Temperature Variation with Time in Induction Heating Process Total heating time t h = 7.05s t=0.5s f=9600Hz s=1.27mm J=1.256e6 A/m 2 t=2s t=4s

10 Case Study: Heating Curves Summary A finite element method based modeling system is developed to analyze the coupled electromagnetic/thermal process in induction heating and implemented in ANSYS package, with following capabilities. Provide electrical and magnetic field strength distribution. Provide instantaneous temperature field data in workpiece. Provide Temperature history at any location in heating process. Provide guidance for inductor/coil design based on adjustment of current density distribution and desired heating patterns.