Induction Surface Hardening

Induction hardening in general is a form of heat treatment in which a whole metallic body or its selected part is heated by induction, then kept for some short time in order to achieve requested temperature distribution and finally quenched. It is the energy saving technology of heat treatment especially used for axi-symmetric and flat steel elements. It is in fact the most popular application of induction heating in the industry. During my presentation after a short introduction dealing with idea of surface induction hardening and its features I will cover following topics:
Mathematical Modelling of Induction Hardening
Through and surface hardening
Specific mathematical models for induction surface hardening and software
Metallurgical aspects of Induction Surface Hardening process
Hardenability. Kinds of steel applied for induction hardening. Their material properties.
Iron-carbon equilibrium diagram and modified TTA and CTPc diagrams
Properties and microstructures of induction surface hardening
Kinds of induction surface hardening: scan hardening, single-shot hardening, continuous hardening, dual frequency hardening etc.
Inductors and flux concentrators
Selection of field current frequency, power and time of heating and cooling
Quenching systems
Depth of hardening. Methods of measurements.
Residual Stresses
Review of practical applications of induction surface hardening technology
Induction hardening of steel pipes by external and internal inductor
Continual induction hardening of conical mandrels
Surface induction hardening of angle bars
Induction hardening of gear wheels
Dual frequency method.

1. WEBINAR
07.05.2015
2:00-3:00 pm
1
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland

2. WEBINAR
07.05.2015
2:00-3:00 pm
2
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
CONTENTS
-Introduction
-Mathematical Modelling of InductionSurface
Hardening
-Metallurgical Aspectsand UnbalancedDiagrams
-Review of practical applications
Conicalmandrels
Internalsurfacesof steeltubes
Steel sections
Circularsaw
Gear wheels.
-Conclusions

3. WEBINAR
07.05.2015
2:00-3:00 pm
3
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SHORT INFORMATION ABOUT SILESIAN UNIVERSITY OF
TECHNOLOGY
The Silesian University of Technology
₋one of the biggest technical universities in Poland
⁻thirteen faculties with 50 areas/directions of education and
almost 190 specializations
⁻about 1900 scientific-didactic staff
⁻about 30,000 students at the University
History:
-the Silesian University of Technology was founded on 24th May
1945 with setting up of four faculties: Mechanical, Electrical,
Metallurgical and Civil Engineering
-the first inauguration of the academic year at the University in
Gliwice took place on 29th October 1945 and 2750 students began
their studies
so far 138,000 engineers have graduated from the University
which has also granted 3,500 PhD and 550 DSc degrees
The Rector’s
insygnia
A lectureatthe Facultyof
ElectricalEngineering in the 1950s

4. WEBINAR
07.05.2015
2:00-3:00 pm
4
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
RESEARCH ACTIVITIES
•surfaceinductionhardening,
•optimizationoftransversefluxinductionheaters
•inductionheatingforsemi-liquidstate,
•levitationandsemi-levitationmelting,
•newconstructionsofinductionfurnaces,
•magnetohydrodynamicdevicesfortransportation,stirringandpurification
ofliquidmetal.

5. WEBINAR
07.05.2015
2:00-3:00 pm
5
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
STAGES OF THE PROCESS
Surfaceinductionhardeningrepresentsthemost
interestingapplicationofinductionheatingmaking
possibletoachievethinsurfacelayerwithdifferent
mechanicalpropertiesincomparisontothoseofthecore
material.
Theprocessconsistsof:
-fastheatingthelayertobehardeneduptoatemperature
higherthantheuppercriticaltemperaturemaking
possibletoformaustenitestructure,
-holdingthebodyatthistemperatureforasufficienttime
inordertoobtainastructuralequilibriumintheregions,
-subsequentfastquenchinginordertocoolintensivelythe
structurestableathightemperatureoroneconvenient
transformation(martensiticstructure).
T (°C)
T
T
T
T
Ac
max
min
finish
i
t
hardness (HV)
 t
1
3
 t
1
Ac
3
1
2
3 4
1
2
3
4
T
h
2
 t

6. WEBINAR
07.05.2015
2:00-3:00 pm
6
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
FEATURES
-possibilitytolocalizethetreatmentwithinasurfacelayerofthe
bodyfacingtheinductor,
-thicknessofhardenedlayerdependsonfrequencyoffieldcurrent,
powerdensity,materialpropertiesofmaterialandtheheatingtime;
-bigvolumetricJoulelossesachievedbyusingofhighfrequencyfield
currentsandshortheatingtimes,makepossibletoobtainrequested
verythinhardenedlayer

7. WEBINAR
07.05.2015
2:00-3:00 pm
7
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DEFINITION OF OPTIMAL PARAMETERS
Therearenosimplegeneralrulesthatallowtodefineoptimalparametersof
theprocess:
-distributionoftheeddy-currentsinthetreatedbodyandoptimumvalues
oftheheatingtime,thetimeintervalbetweentheendoftheheatingand
thebeginningofthequenchingandthequenchingvelocity.
Besidesonthematerialproperties,theseelementsdependontheshapeof
thehardenedbody,thepresenceofholes,teethoredges,thethicknessof
thelayertobehardened,thedistancebetweentheinductorandworkpiece
surface,thepositionoftheinductor’sedgesetc.

8. WEBINAR
07.05.2015
2:00-3:00 pm
8
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
HARDENED PROFILE
Also the results obtained with the most modern models of numerical
simulation, require a successive experimental verification and adjustment of
the inductor, usage of flux concentrators in order to achieve the results
required.
Moreover, in many cases, the hardened profile is not the one desired by the
designer (hardening of gears, crankshaftsetc.) but the one that can be
obtained by the practice of induction heating.

9. WEBINAR
07.05.2015
2:00-3:00 pm
9
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
THE MAIN FACTORS
The main factors influencing on the results of the induction surface
hardening process:
steel grade
value and distribution of the temperature in the hardened region
the speed of quenching
the type and geometry of the inductor-sprayer system.
usage of inductor with flux concentrators

10. WEBINAR
07.05.2015
2:00-3:00 pm
10
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
CONTENT OF CARBON
Andthepercentofmartensite(thecurveat99%correspondsto
acompletehardeningwithatotaltransformationofausteniteinto
martensite);itshowsthatinpractice,onlyasmallimprovementofthe
hardnessmaybeachievedwhenthecarboncontentofthesteel
exceeds0.6%.Forthisreason,onlysteelswithacarboncontent
between0,4to0,6%arenormallyused.

11. WEBINAR
07.05.2015
2:00-3:00 pm
11
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DEPENDENCE OF HARDNESS
ON CARBON CONTENT

12. WEBINAR
07.05.2015
2:00-3:00 pm
12
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DIAGRAM IRON-CARBON-STEEL
1.Itcanbeobservedthatthe
carboncontentinfluencesonthe
uppercriticaltemperatureA
C3
abovewhichtheformationof
austenitetakesplace.
2.Alsothevalueoftheupper
criticaltemperatureA
C3depends
onrateofheating.
3.Forrapidinductionheatingthe
hardeningtemperaturemustbe
increasedabovetheAC3inorder
toguaranteeaminimumtime
intervalabovethetemperatureof
austeniteformation

13. WEBINAR
07.05.2015
2:00-3:00 pm
13
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INFLUENCE OF ADDITIONS CONTENT
Critical temperatures
increaseforsteelcontaining
alloyingelementspromoting
theformationofcarbides,
liketitanium,silicon,
molybdenum,vanadiumor
tungsten.
.

14. WEBINAR
07.05.2015
2:00-3:00 pm
14
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
TEMPERATURE DISTRIBUTION
Oncethehardeningdepthandthesteelgradearegiven,itisnecessary
toheatallpointsofthelayertobehardenedtoatemperatureabove
theA
C3(ortohighervaluesforrapidheating),whileatthesametime
keepingtolowertemperaturetheinternallayers.
Thiscanbeachievedwithrapidheatingathighormediumfrequency
fieldcurrent,whichcangiverisetoconsiderabletemperaturegradients
inthelayertobehardenedmuchhigherthantheonesachievableby
theflamehardening.

15. WEBINAR
07.05.2015
2:00-3:00 pm
15
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
NECESSITY OF EXPERIMENTS
Theexaminationofthecurvesconfirmsthealreadymentioned
difficultyofanexacttheoreticalestimationofthehardening
parametersandtheconsequentnecessityofthefinalexperimental
verification.
SIMULATIONVERIFIEDBYWELLPLANNEDEXPERIMENT

16. WEBINAR
07.05.2015
2:00-3:00 pm
16
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ALGORITHM

INPUT DATE



ELECTROMAGNETIC FIELD

μ =μ(B)
B, pv


B = B + ΔB
μ (T)
 (T)
λ (T)
ρc(T)
αc(T) NON-STATIONARY t = t + Δt
αr(T) TEMPERATURE FIELD


HEAT STRESSES FIELD

yes u no


T = T + ΔT



NON-STATIONARY NATURAL
TEMPERATURE FIELD COOLING



NON-STATIONARY
TEMPERATURE FIELD INTENSIVE
COOLING

λ (T) HEAT STRESSES FIELD
ρc(T)
αc (T) u t = t + Δt
yes no
T = T - ΔT


EXPERIMENTAL DATA
METALLURGICAL
FIELD HV = f (vc)


HARDNESS (HV)
MICROSTRUCTURE
I
II
III
T
T

17. WEBINAR
07.05.2015
2:00-3:00 pm
17
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ELECTROMAGNETIC FIELD 
ext
1
curl curl curl 

A + v A J  
extcurl curl j - curl   A + A v A J extcurl curl j A + A J 0A
BASICEQUATIONS
symmetryplanez=0
BOUNDARYCONDITIONS
externalborder0A n

18. WEBINAR
07.05.2015
2:00-3:00 pm
18
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
2D FORMULATION0



A

n
Eddy current density = jJ A , v
p



*
JJ

Volumetric Joule losses

19. WEBINAR
07.05.2015
2:00-3:00 pm
19
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
3D FORMULATIONcurl , div 0, grad   J= T T H T 0
gradHH 0 3
1
d
4π
V
V
r


Jr
H 22
J
curl
w


JT  gradB= T

20. WEBINAR
07.05.2015
2:00-3:00 pm
20
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
TEMPERATURE FIELD  
v
div grad grad -
T
T c v T c p
t
  



- 0
T
n


        
44
c c o r c c r r r
-
T
T T T T T T T T p
n
     

            
     
22
g cr g c o cr cr
-,
T
T T T T T T
n
    

       
   div grad grad 0
T
T c T c
t
  

  

v    
c c r r r s
T
T T T T p p
n
  

        


21. WEBINAR
07.05.2015
2:00-3:00 pm
21
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
STRESS FIELD 
u
1 1 2
E




   
u
21
E



    
2
u u u u u T m
grad div 3 2 grad 0uT          u + f m
f J B

22. WEBINAR
07.05.2015
2:00-3:00 pm
22
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
TEMPERATURE DEPENDENCE ON VELOCITY OF COOLING

23. WEBINAR
07.05.2015
2:00-3:00 pm
23
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
RELATIVE MAGNETIC PERMEABILITY

24. WEBINAR
07.05.2015
2:00-3:00 pm
24
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
OTHER MATERIAL PROPERTIES

25. WEBINAR
07.05.2015
2:00-3:00 pm
25
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INITIAL MICROSTRUCTURE
Initialmicrostructure(beforetheheattreatment)hasadecisive
influenceonthefinalstructureandhardnessdistribution.

26. WEBINAR
07.05.2015
2:00-3:00 pm
26
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
TTA DIAGRAM

27. WEBINAR
07.05.2015
2:00-3:00 pm
27
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
TTC DIAGRAM

28. WEBINAR
07.05.2015
2:00-3:00 pm
28
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
COMPLETE HARDENING
Inparticularthecurvescorrespondingtocoolingrates,higherorequal
tothecriticalone,preventtheintersectionoftheperliteandbainite
transformationregions.cV
Thereforeoccursthecompletetransformationofausteniteinto
martensite,withonlysomepercentageofresidualausteniteifthesteel
ishighlyalloyed,thusrealizingtheso-calledcompletehardening.

29. WEBINAR
07.05.2015
2:00-3:00 pm
29
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INCOMPLETE HARDENING
Themartensiteisahardandbrittleconstituentwhosehardnessis
higher,thehigheristhecontentofcarbon.
However,forlowercoolingrates,oneobtainsvariousmicrostructures
correspondingtothepresenceofthevariousconstituentsdetermined
bythepointsofintersectionbetweenthecoolingcurveandthe
transformationcurve.
Inparticular,forcoolingrateslowerthanthecriticalone,oneobtains
anincompletehardeninginwhichtheaustenitetransformspartially
intobainiteandpartiallyintomartensite;forevenlowerratesone
obtainsthenormalizingofsteelswithmediumalloyingcontent,
whereasthecurve1representsacompleteannealingcycle.

30. WEBINAR
07.05.2015
2:00-3:00 pm
30
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DIFFERENT MICROSTRUCTURES
Inthehardeningofworkpiecesofconsiderabledimensions,itmustbe
takenintoaccountthatthesurfacelayerscooldownwitharatehigher
thanthecriticalone,whereastheinternallayerswithvelocities
progressivelydecreasinginthecross-section,fromthesurfacetowards
thecore.Thisgivesrisetodifferentmicrostructureswithconstant
hardnessintheregionwherethecoolingvelocitiesarehigherthanand
hardnessgraduallydecreasingtowardsthecoretothevalues
characteristicforthethermallyunaffectedmaterial.

31. WEBINAR
07.05.2015
2:00-3:00 pm
31
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ALGORITHM FOR CONTINUAL HARDENING

32. WEBINAR
07.05.2015
2:00-3:00 pm
32
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
BASED ON EXPERIMENT
Inthiscase,theanalyticalcalculationbecomeextremelycomplex,even
undertheconsiderationofconstantmaterialparameters.Therefore,
onemustalwaysrefertoexperimentaldiagrams.
Inthetwocasesofnon-movingworkpieceandscanhardening,the
powerofthehighfrequencygeneratornecessarytohardenagiven
areawillbesubstantiallydifferent.

33. WEBINAR
07.05.2015
2:00-3:00 pm
33
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
QUENCHANTS
Thechoiceofthequenchingfluidhasthesameimportanceasthatoftheheating
regime;thischoicemustbedonetakingintoaccountthemechanicaland
metallurgicalpropertiesrequired,thesteelgrade,andtheshapeaswellasthe
dimensionsoftheworkpiece.
Themostusedquenchingmediaare:
water,
oil,
syntheticpolymersfluids,
otherlikeaqueousemulsionsofoil,solutionsofwaterandsalt,air,bathsofsalt
melts,somemetalmelts.

34. WEBINAR
07.05.2015
2:00-3:00 pm
34
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SPEED OF QUENCHING

35. WEBINAR
07.05.2015
2:00-3:00 pm
35
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INTERNAL STRESSES
1.Asknown,themartensitictransformationcausesavolumeincrease.
2.Toofastorirregulartransformationinducessubstantialinternal
stresseswhichcancausedeformationsandcracks,especiallyinthe
caseofcomplexgeometriesorsurfacedefects.
3.Temperaturedifferencesbetweenthequenchingcurvesofthe
surfacelayersandtheonesofthecore,whichcoolsdownslower,
increasewithhighquenchingrates.
4.Itcausesexpansionoftheinternalmassagainstthehardened
surfacelayerandahigherinternalresidualstresswiththepossibilityof
theworkpiecedistortionandformationofcracks.

36. WEBINAR
07.05.2015
2:00-3:00 pm
36
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SPRAY QUENCHING
Inthecaseofwaterquenching,especiallywithplaincarbonsteels,
optimalresultsareobtainedwithsprayquenching,wherethewater
runsoverthehotsurfaceathighvelocity,preventingtheformationofa
vaporfilmwhichreducestheheattransferbetweentheworkpieceand
thequenchant.
However,itmaysometimescauselocalunhardenedareas.

37. WEBINAR
07.05.2015
2:00-3:00 pm
37
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
LOWER QUENCHING RATES
Withlowerquenchingrates(oilorpolymersolutionquenching),the
differencebetweentheinternalandexternaltemperaturesislower;
therewithderivesthatbeforethesurfacelayerhasreachedthepoint
Mf,causingthebrittlecasingofmartensite,themostinternalpartof
theworkpiecehasbeenalreadytransformedandhasundergonethe
consequentexpansion.
Duetothelowerinternalmasswhichtransformsafterthesurfacelayer
hasfinisheditstransformation,theabovementionedproblemsare
reducedproportionally.

38. WEBINAR
07.05.2015
2:00-3:00 pm
38
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
REDUCTION OF STRESSES
Sometimes, for bodies of complicated shape the quenching in air can
be utile in which, due to the low quenching velocity, the transformation
occurs practically contemporaneous in the whole mass of the piece, so
reducing the internal stress to a minimum and hence the risk of cracks.
Inthecaseofquenchingbyimmersion,theworkpiecesarealwayskept
inrotationandthequenchingbathismaintainedatcontrolled
temperature;duetoitsinflammability,thehardeninginoilisalways
donebyimmersionorinsimilarconditions.

39. WEBINAR
07.05.2015
2:00-3:00 pm
39
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
Steeltubestransportingmixturesofloosematerials(for
examplesands)andwaterhavetobehighlymechanically
resistant,particularlywithrespecttoabrasion.
Thebasicwayhowtomeetthisdemandishardeningof
theirinternalsurfacesthatmayberealizedbymeansof
inductionheating,usingmovableinternalorexternal
inductorandwatersprayer.
INDUCTION HARDENING OF INTERNAL SURFACES
OF STEEL TUBES
Itisnecessarytoharden
theinternalsurfaceofa
longsteeltube.
Thisprocesscanbe
realizedintwobasic
ways:withinternalor
externalinductor.

40. WEBINAR
07.05.2015
2:00-3:00 pm
40
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
Electromagnetic field
depends on
•shapeoftheinductor,
•influenceofthesupplying
conductors(butthese
feedersareusuallyplaced
closetooneanother,so
thattheircontributionto
theresultantmagnetic
fieldislowandmaybe
neglected).
Thearrangementistaken
fullyaxisymmetric.
MATHEMATICAL MODEL

41. WEBINAR
07.05.2015
2:00-3:00 pm
41
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ALGORITHM

42. WEBINAR
07.05.2015
2:00-3:00 pm
42
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland0
1
2
3
4
5
6
0 200 400 600
temperature (deg)
electrical conductivity
(MS/m) 0
500
1000
1500
2000
2500
3000
0 200 400 600 800
temperature (deg)
relative magnetic
permeability (-)
B= 0.5 T0
10
20
30
40
50
60
0 200 400 600
temperature (deg)
specific heat conductivity
(W/mK) 0
200
400
600
800
1000
1 10 100 1000 10000
time (s)
hardness (HV)
MATERIAL PROPERTIES

43. WEBINAR
07.05.2015
2:00-3:00 pm
43
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland0
100
200
300
400
500
600
700
800
900
0 100 200 300 400
time (s)
temperature (deg)
int 0 mm
int 83 mm
ext 0 mm
ext 83 mm
Bottom points
TIME EVOLUTION OF TEMPERATURE

44. WEBINAR
07.05.2015
2:00-3:00 pm
44
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
MAIN WINDOW

45. WEBINAR
07.05.2015
2:00-3:00 pm
45
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INDUCTION HARDENING OF CONICAL MANDRELS
BASIC ARRANGEMENT

46. WEBINAR
07.05.2015
2:00-3:00 pm
46
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland

47. WEBINAR
07.05.2015
2:00-3:00 pm
47
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INPUT DATA
•Mandrel: r
a=0.012 m, r
b=0.020 m, l = 0.4m,
•Coil: r
c= 0.025 m, w = 0.017 m, h= 0.03 m,
•Current density and frequency:
J
ext= 7·10
6
A/m
2
, f= 440 kHz,
•Velocity: v = 0.002 m/s
•Temperatures: T
start= 20 °C, T
0a= 20 °C, T
0w= 10 °C,
•Convective heat transfer coefficients:
heating 
a= 20W/m
2
K, cooling 
w= 500 W/m
2
K.

48. WEBINAR
07.05.2015
2:00-3:00 pm
48
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
Time evolution of the temperature at selected points0
200
400
600
800
1000
1200
0 50 100 150 200
time (s)
temperature (deg)
40 mm
80 mm
120 mm
160 mm
200 mm
240 mm
280 mm
320 mm
360 mm

49. WEBINAR
07.05.2015
2:00-3:00 pm
49
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
HARDNESS DISTRIBUTION650
670
690
710
730
750
770
790
0 100 200 300 400
axial distance (mm)
hardness (HV)

50. 0 0.05-0.05
0.0
5
-0.05
y
artificial boundary inductor
workpiece
hardened surface
A
z
B
C
x STEEL SECTION FOR PLASTIC WORKING

51. r = 1
workpiece
inductor
elsewhere r = r (B)
v 3D ARRANGEMENT
Ac
1=730°C,Ac
3=780°C,M
s=325°C.
Knownaretemperaturedependenciesofitsphysicalproperties(electricalandthermalconductivities,specific
heat).
Axiallengthofthebodyis0.118m.

52. 0
100
200
300
400
500
600
700
800
900
1 10 100 1000 10000
time of cooling (s)
HV HARDNESS DISTRIBUTION
Inductor:massiveconductorofrectangularcross-section3*9mmthatcarriescurrentofdensityJ=10.5A/mm
2
andfrequencyf=20kHz.Itsvelocityis2mm/s.

53. Time evolution of temperature at selected point of the line passing through point A (-0.02, 0.0398),

54. Time evolution of temperature at selected point of the line passing through point B (-0.01, 0.0294),

55. Time evolution of temperature at selected point of the line passing through point C (0, 0.019),

56. Thesawisusedforcuttingironmaterial.Itismadefromsteel40HMproducedinPolanditsdiameterisr=1m,
thicknesst=0.012mandthenumberofteethis315.
CIRCULAR SAW

58. PARAMETERS
Fieldcurrent I= 850 A,
frequency f= 40 kHz.
Convective heat transfer coefficient afor air
was taken 25 W/m
2
K.
Ac
1= 740 °C
Ac
3= 780 °C.

59. TEMPERATURE DISTRIBUTION ON TIME

60. The highest
temperature is
reachedatpointIII(at
thetopoftheleading
edge).
TEMPERATURE DISTRIBUTION

61. WEBINAR
07.05.2015
2:00-3:00 pm
61
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
GEAR WHEELS
One typical example of hardening a geometrically complex workpiece is
the simultaneous hardening of gears, where the purpose of the process
is to obtain a uniform hardened layer along the whole surface, namely
at the tip, along the flanks, and the roots of the teeth.
In this case, the choice of the frequency results to be of fundamental
importance not only from the “electrical” point of view, but also the
thermal one.

62. WEBINAR
07.05.2015
2:00-3:00 pm
62
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INFLUENCE OF FREQUENCY ON TEMPERATURE

63. WEBINAR
07.05.2015
2:00-3:00 pm
63
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SIMULTANEOUS CONTOUR HARDENING
1 –Joule losses
2 –generator power
3-optimal frequency
4 –optimal frequency
5 –heatig time

64. WEBINAR
07.05.2015
2:00-3:00 pm
64
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
INDUCTION HARDENING
OF GEAR WHEELS

65. WEBINAR
07.05.2015
2:00-3:00 pm
65
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
GEAR WHEELS
Thegear-wheelsasthemosttypicalcaseoftheinductionhardeningof
complexgeometries.
Ingearspinhardeningtheentiregearpartisbroughtuptothe
hardeningtemperaturebymeansofaninductorsurroundingitandis
subsequentlycooled.

66. WEBINAR
07.05.2015
2:00-3:00 pm
66
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
VARIOUS PATTERNS
1. The gearsarerotatedduringheating to ensureanevendistribution
of energy.
2. It ispossibleto throughhardenthe gearpart down to the toothroot
(in the same wayas the casehardening) orto hardenthe outersurface
ateithera uniform orirregulardepthfrom the surface.
3. The bestpatternisusuallya uniform thicknessof the hardenedlayer
alongthe contour.
4. Differentpatternsmaybe acceptableorsometimesdesirable
dependingon the application. Breaks in the hardenedlayermaybe
acceptedon the tipsof the teethwheremechanicalloadingisverylow,
whileon the flanksand rootsitmustbe continuousin order to
withstandbig contactpressureand tensilestressesfrom loading.

67. WEBINAR
07.05.2015
2:00-3:00 pm
67
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
MAIN PARAMETERS
The main parameters which play a dominant role in obtaining the
required hardness pattern are:
Field current frequency,
Its power density,
heating time,
quenching conditions and
Geometry of the system.
In particular, contour hardening can be obtained by single-frequency or
dual-frequency processes.

68. WEBINAR
07.05.2015
2:00-3:00 pm
68
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SPIN HARDENING METHODS

69. WEBINAR
07.05.2015
2:00-3:00 pm
69
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SINGLE FREQUENCY TREATMENT
Thesingle-frequencysingle-shothardeningprocessisaspinhardening
inwhichallteetharesimultaneouslycontourhardenedbymeansofa
singlefrequencyinductor.Itrequirestheuseofhighinducedpower
densitiesandveryshortheatingtimesinordertoavoidthediffusionof
heatfromthesurfacelayertothelowermaterialandtheconsequent
throughhardeningoftheteeth.
Theprocessrequiresaconvenientchoiceoftheoperatingfrequencyin
ordertoobtainsuitablevaluesoftheinducedpowerdensitiesatthe
flanks,tipsandrootsoftheteeth.

70. WEBINAR
07.05.2015
2:00-3:00 pm
70
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
JOULE LOSSES
f = 10kHz
f = 500kHz

71. WEBINAR
07.05.2015
2:00-3:00 pm
71
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
OPTIMAL PARAMETERS
As regards frequency, the
following formula has been
proposed for a rough estimate
of the optimal value:
with M–module of the
gear in mm.
1-specificsurfacepower, 2 -heating time,3 -frequency
1 3 25
opt 22
310
, kHz
K
f
MM



72. WEBINAR
07.05.2015
2:00-3:00 pm
72
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
PULSING SINGLE FREQUENCY
Thesinglefrequencycontourhardeningwithpre-heating(thesocalled
also“PulsingSingleFrequency”process)hasbeendevelopedconsisting
ofseveralconsecutivestages
preheatingwithareducedpoweruptoapproximately550-750ºC
(dependentonthematerial),
ashortfinalheatingwithhigherspecificpowertothehardening
temperature,
quenchingandalow-powerheatingstagefortempering.

73. WEBINAR
07.05.2015
2:00-3:00 pm
73
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
PREHEATING
Pre-heating allows to reach a convenient heated depth at the roots of
the gear, enabling to attain an adequately high austenitizing
temperature in the
root circle during the final heating, without overheating the tooth tips;
this process cycle allows in many cases to reach the desired
metallurgical results and to decrease distortion in some materials. The
preheating time, dependent on size and shape of the gear, is followed
by a soak time which allows to achieve a nearly uniform temperature
distribution across the teeth of the gear and a contour-like hardened
profile by using high power density at the final heating stage.

74. WEBINAR
07.05.2015
2:00-3:00 pm
74
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
MICROSTRUCTURE
Itiswellknownthatthemicrostructureconditionsofthe
metalpriortothegearhardeningareoffundamental
importancefortherepeatabilityofthemechanicaland
metallurgicalresultsoftheheattreatment.Inparticular,
initialconditionscharacterisedbyhomogeneousfine-
grainedquenchedandtemperedmartensiticmicrostructure
withhardnessof30-34HRC,areparticularlyfavourablefor
assuringafastandconsistentmetalresponsetotheheat
treatment,reduceddistortionandminimumamountofthe
graingrowth,resultinginhigherhardnessanddeepercase
depthincomparisontotheferritic/perliticinitial
microstructure.

75. WEBINAR
07.05.2015
2:00-3:00 pm
75
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
HARDNESS PROFILES
With pre-heating
With pre-quenching
And tempering

76. WEBINAR
07.05.2015
2:00-3:00 pm
76
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DUAL FREQUENCY HARDENING
Aspreviouslymentioned,theuseoftwodifferentfrequenciesisthe
logicalsolutionforobtainingauniformhardeneddepthalongthe
contourofthegear.However,therangeofthegeardiameterssuitable
forthedualfrequencyprocessislimitedtogearswithdiameterlower
than250mmforeconomicreasons,duetotheveryshortheating
timesandthecorrespondinghighpowerdensities,whichrequirethe
useoffrequencyconvertersatmediumandhighfrequencywithunit
outputpowerrangingfromseveralhundredsofkWtosomeMW.

77. WEBINAR
07.05.2015
2:00-3:00 pm
77
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
SEPARATE FREQUENCY PROCESS
Intheseprocessestwofrequenciesareappliedseparatelyinsequence
tothesameworkpiece:pre-heatingisaccomplishedinthefirststepof
theheatingcyclebyapplyingalowpowerdensityatMF(usuallyinthe
range3-10kHz),whileduringthefinalheatingstageahighpower
densityatHFisusedforcontourhardening.Theselectionofsuitable
valuesofthefrequencyofthefinalpulse,intherange30-450kHz-
dependingonthetypeofgear,itssizeandmaterial–andtheheating
timeallowstoobtainthedesiredhardeneddepth.
InthegreatmajorityofcasestheMFandHFfrequencyconvertersare
connectedtotwodifferentcoils,whicharespatiallyseparated,

78. WEBINAR
07.05.2015
2:00-3:00 pm
78
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DUAL FREQUENCY CYCLE

79. WEBINAR
07.05.2015
2:00-3:00 pm
79
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
PREHEATING
Thegearispreheatedtoatemperaturewhichisusually100-350ºC
belowthecriticaltemperatureAC1,dependingupontypeandsizeof
thegear,toothshape,priormicrostructure,requiredhardnesspattern
anddistortion(whichincreaseswithpreheatingtemperature)and
availablepowersource.
Obviously,thehigheristhepre-heatingtemperature,theloweristhe
powerforthefinalpulse.However,theincreaseofthepre-heating
temperaturecanproduceanincreaseddistortion.

80. WEBINAR
07.05.2015
2:00-3:00 pm
80
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
CONTOUR HARDENING
AfterpreheatingthecontourhardeningwithHFiseffected.Heating
timesareintherangefromtenthsofsecondstoseconds,depending
onthemodule,andthefinalstagerequiresaveryfinecontroloftime
andpower.
Toavoidthroughheatingofthetooth,thefinalaustenitizingoperation
mustbeveryshort(often<1second),whichrequiresveryfasttransfer
oftheworkpiecefromoneinductortotheotherandveryhighpower
switchingspeeds.

81. WEBINAR
07.05.2015
2:00-3:00 pm
81
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ONE INDUCTOR ONLY
A refinement of the dual-frequency method uses one common
inductor, which is first connected to the MF power supply circuit and
then switched into the HF circuit.
A limit of this technique is the time required for power switching,
typically about 0.5 second.

82. WEBINAR
07.05.2015
2:00-3:00 pm
82
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
PRE-HARDENING
Asinthesinglefrequencyprocess,theheatingcyclecancomprisea
pre-quenchingandtemperingstageofthetoothareabeforetheactual
hardeningstep;thisstageisusedforimprovingthefinalmetallurgical
resultsalsowhenthepriormicrostructureofthesteelisnot
particularlysuitableforhardening.

83. WEBINAR
07.05.2015
2:00-3:00 pm
83
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DUAL FREQUENCY CYCLE

84. WEBINAR
07.05.2015
2:00-3:00 pm
84
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
HARDENED PROFILES
MF pre-heating
Thickness 15 mm
Module 2.5 mm
pre-quenching
Thickness 30 mm
Module 3 mm

85. WEBINAR
07.05.2015
2:00-3:00 pm
85
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
DUAL FREQUENCY HARDENING

86. WEBINAR
07.05.2015
2:00-3:00 pm
86
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
CONCLUSIONS
1. Surface induction hardening has provided to distinct improvement of quality of
steel elements.
2. It is characterized by fast heating and immediatequenching
3. Heating depth can be easily changed by:field current frequency, power and heating time.
4. Numerical simulation seems to be a powerful tool supporting effective implementation of
the process to industry
5. Energy efficiency is the important factor deciding about practical implementation of the
surface induction hardening.

87. WEBINAR
07.05.2015
2:00-3:00 pm
87
prof. dr hab. inż. Jerzy Barglik
SilesianUniversityof Technology, Poland
ACKNOWLEDGEMENT
.
Acknowledgement
The presentation was elaborated within the framework of
ongoing Polish grant project PST 21/RM4/2014and Tempus
project