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Study on Induction Hardening Proc

VIEWS: 57 PAGES: 10

									    MODELING OF INDUCTION
     HARDENING PROCESS
        PART 1: INDUCTION HEATING



                  Dr. Jiankun Yuan
             Prof. Yiming (Kevin) Rong




Acknowledgement: This project is partially supported
by Delphi and CHTE at WPI. Dr. Q. Lu was involved
in the early work of the project.

           http://me.wpi.edu/~camlab
                       Induction: Why Induction Heat Treatment?
                                             Advantages

      Greatly shortened               Highly            Highly energy          Less-pollution
      heat treatment cycle            selective         efficiency             process

                                       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.

                                     Research content: FEM based electromagnetic/thermal analysis
Numerical modeling                                       + quenching analysis + hardening analysis
may provide better
prediction                           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.
                        Introduction: Induction Hardening Process

• Induction heating:
metal parts heated to
austenite Phase




 •Fast quenching
 process transforms
 austenite to
 martensite phase
                                                             workpiece         Inductor/coil


                                              Heating
 •Martensite                                  process
 content determines
 the hardness
                                             Joule heat by
                                             eddy current
 •Martensitic
 structure is the
 most hardest                                Electromagnetic       Induction        High
 microstructure                              field                 coil             freq. AC
                                                                                    power
                        Principle: Electromagnetic and Thermal Analysis                                                          WP                         Coil

                 Electromagnetic Analysis                                          Thermal Analysis with
                                                                                    finite element model
             Input AC
           power to coil

                                            0  I         dl
        Calculation of
  magnetic vector potential (A)
                                       A
                                             4       C   r

        Calculation of                                     (Gauss’ Law for
                                      B =A
    magnetic flux density (B)                               magnetic field)

                                                                                 (a) WP geometry                                       (b) FEA model
       Calculation of                 H=B/
  magnetic field intensity (H)
                                                                                          QN                                             QN

          Calculation of                        B         (Faraday’s Law)
                                      E 
    electric field intensity (E)                t                            QW           QC          QEt                      QE
                                                                                                                                           QB
                                                                                                                                                      QR+ QCV
                                                                                                                                                     (Outside)
         Calculation of               D=E                                               QS
    electric field density (D)                                                                                                           QS
                                                                                (c) Interior element                              (d) Surface element
         Calculation of                        D           (Ampere’s
                                       H       J        Circuital Law)                            Heat conduction
       current density (J)                     t

                                                                                       T
         Calculation of               Qinduction = E  J = J2/                c        k   2T  Qinduction
    Inducting heat (Qinduction)                                                        t

                                                                                      T
Output:
Heat generation Qinduction in WP
                                                                               c
                                                                                      t
                                                                                                                                             
                                                                                          k   2T  Qinduction  A      F  T 4  Tair  A  h  T  Tair 
                                                                                                                                           4




                                                                               Induced Joule heat             Heat radiation          Heat convection
                         Case Study: Complex Surface Hardening

                                                         concave
        Material: Carbon
        Steel, AISI 1070
                                                         convex
        Automotive parts from
        Delphi Inc.,
        Sandusky,Ohio


•Concave and convex on
surface of workpiece make
the heating process not easy     Real spindle to be hardened          Geometry Model
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.




                                      FEA model and B.C.           Mesh generated by ANSYS
               Case Study: Material Properties -- AISI 1070

                        (a) Electromagnetic Properties



                                                              conductivity
WP relative                            Electrical
permeability                           Resistivity




                           (b) Thermal Properties


                             Emissivity
 Specific
  heat
                                                               Convection
                                                               coefficient
Case Study: Magnetic Field Intensity Distribution
                     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
                                       (a1) Constant current distribution in coil   (a2) heated pattern
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.
                                       (b1) Adjusted current distribution in coil   (b2) heated pattern
Case Study:Temperature Variation with Time in Induction Heating Process

                 t=0.5s                                    t=2s
                 Total heating time
                 th = 7.05s

                  f=9600Hz
                  s=1.27mm
                  J=1.256e6 A/m2




                   t=4s
                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.

								
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