Grind-Hardening Process Modelling 3rd May 2013 Konstantinos Salonitis Lecturer in Manufacturing Systems
What is Grind-Hardening?
Dispatch Raw
Material
Material Removal Processes
Heat Treatment Finishing
Con
vent
iona
l P
rodu
ctio
n C
hain
• Turning • Milling • Drilling
• Tempering • Nitriding • Case hardening
• Grinding • Honing • Super Finishing
• Forming • Gear cutting • …
• …
Dispatch Raw Material
Material Removal Processes
•Grind hardening and •Finishing
Grind- Hardening
Production time and cost saving In
tegr
ated
Pro
duct
ion
chai
n
• Turning • Milling • Drilling
• Forming • Gear cutting • …
What is Grind-Hardening?
Grind hardening is a process that combines material removal and surface hardening of the workpiece at the same time. The heat dissipated in the cutting area is used for the heat treatment of the workpiece.
Process Parameters • Depth of cut: 0.2 – 1.2 mm • Feed speed: 0.3 – 1.2 m/min • Both CBN and Corundum
wheels • MGL or even dry
Grinding machine: • Need for high stiffness • Powerful spindles
required
Workpiece material: • C concentration > 0.3% • 38 MnS 6, 42 CrMo 4, C
42, Cf 53, 100 Cr 6 • Max HRC: ≈ 50 – 60
Research Work Focus
• Use of advanced modelling methods for the prediction of process performance and optimize the process parameters
Modelling simple
geometry Experimental Verification
Process Maps
Programme complex
parts
Process Modelling
Estimation of the HPD
Estimation of the Hardness Distribution
Estimation of the temperature field using FEA
Estimation of the heat entering the workpiece
Estimation of the heat generated
Grinding forces estimation Function of the process parameters, workpiece material and grinding wheel topography
Function of process forces and grinding wheel rotational speed t sP F u= ⋅
Heat partition to the workpiece is a function of process parameters and grinding wheel grits material 40 – 60 % of generated energy is absorbed by the workpiece
FEA of 2-D simple geometries
Using “transformed” CCT diagrams as to account for the rapid heating of the material
• From the Hardness distribution • From the austenitisation temperature depth
Theoretical Analysis – Analytical Modelling
Grinding Forces Heat Generation Heat Partition
lc
us
uw
Wheel
Workpiece
ae
ds/2
FFv
Fh
Fn
Ft
, , ,t t sl t ch t plF F F F= + +
Takes into consideration: • Gr. Wheel topography • Chip formation energy t
c
Pqb l
=⋅
Bonding material Grain
Workpiece
uw
Chip
usΚομμάτι
Λειαντικός τροχός
Απόβλητα
qs
qw
qch
us
uw
e wch ch
c
a uq el⋅
= ⋅
1
1w s sws
w s w w
q uRq q u
ββ
−
= = + ⋅ +
t w s chq q q q= + +( )w ws t chq R q q= ⋅ −
( )t s wP F u u= ⋅ ±
Theoretical Analysis – 2-D FEA Modelling
• Triangular heat source
distribution
• Quasi-stationary problem
• Explicit solution using ANSYS
multiphysics
• Results: Temperature field for
various process parameters
combinations
150 mm
40 m
m
150 mm
40 m
m
D
C
B
A0.25x0.25 mm
0.25x0.5 mm
0.25x1.0 mm
0.25x2.0 mm
30
Theoretical Results – 2-D FEA Results
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5Distance from Surface (mm)
Tem
pera
ture
(o C
)
HF=30.0 HF=25.0
HF=22.5 HF=20.0
HF=17.5 HF=15.0
HF= 5.0 Heat Flux in W/mm2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
15 20 25 30 35 40Heat Flux (W/mm2)
HPD
(mm
)
lc = 9 mm
300 400 6000.27 0.20 0.14
de
ae
0
100
200
300
400
500
600
700
800
900
1000
0.1 1 10 100 1000
M
A+C
Zw
P
Ms
929
Ac
Θερ
μοκρ
ασία
(ο C)
Επιφάνεια: Tpeak = 1165oC
s=0.2 mm: Tpeak = 1006oC
s=0.3 mm: Tpeak = 945oC
Ms για Tpeak = 945oC
Ms για Tpeak = 1006oC
Ms για Tpeak = 1165oC
Χρόνος (sec)
(β)
200
300
400
500
600
700
800
0.0 0.2 0.4 0.6 0.8 1.0
ΘεωρητικόΠειράματα
HPD
1. FEA Estimation of Temperature Distribution 2. Calculation of Metallurgical Transformations 3. Calculation of Micro-Hardness Distribution 4. Process maps – Process knowledge database
1 2
3
4
Distance from Surface (mm)
Mic
ro-H
ardn
ess
(HPD
)
Industrial Application
8
A
A’
• Workpiece material: 100 Cr 6
• Technical Specifications: • Surface hardness: 660 - 750 HV1
• HPD = 0.3 – 0.5 mm
• Maximum allowable depth of cut: 3 mm
• Available grinding wheel: Α 60 L7 V 300
Product requirements
Process parameters from Process maps
Verification
Industrial Application
uw (m/min)
ae (mm)
us (m/s)
Qw (W/mm2) Comment
0.3 0.2 19 16.9 Rejected
0.6 0.2 34 25.5 Approved
0.9 0.2 41 32.0 Approved
1.2 0.2 - - Rejected
0.0
0.2
0.4
0.6
0.8
1.0
1.2
14 18 22 26 30 34 38 42Heat Flux (W/mm2)
HPD
(mm
)
u w=
0.3
m/m
in
u w=
0.6
m/m
inu w
= 0.9
m/m
in
Μέγιστο HPD
Ροή θερμότητας (W/mm2)
Βάθος
διείσδ
υσης
σκλή
ρυνσ
ης–
HPD
(m
m)
300 0.27
400 0.20
600 0.13
de ae
Θεωρητικά
ΔιορθωμέναΘεωρητικά
Heat Flux
Theoretical
Calibrated
Product requirements
Process parameters from Process maps
Verification
Industrial Application
u w =
0.6
m/m
in
Qw =
25.
5 W
/mm
2 u w
= 0
.9 m
/min
Q
w =
32.
0 W
/mm
2
1
25
148.341271.682
395.023518.364
641.705765.045
888.3861012
1153
ANSYS 9.0NODAL SOLUTION
STEP=21SUB =7TIME=2.1TEMP (AVG)RSYS=0SMN =25SMX =1153
1
25
152.233279.466
406.7533.933
661.166788.399
915.6331043
1188
ANSYS 9.0NODAL SOLUTION
STEP=21SUB =7TIME=1.4TEMP (AVG)RSYS=0SMN =25SMX =1188
Product requirements
Process parameters from Process maps
Verification
Industrial Application
Processed guideGrinding wheel
Coolant fluid supply
Grinding machine table
Clamping device
us
uw
500
750
1000
1250
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0250500
7501000
0 1 2 3 4 5 6 7 8 9 10 11 12 13
0
0.2
0.4
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13x (mm)
xy
12
34
56
7
98
1011
12
uw = 0.6 m/min
uw = 0.9 m/min
ae = 0.2 mmA 60 L7 V
Τεχνικέςπροδιαγραφές
25
9201200
N
25
9201200
A
Uw = 0.6 m/min
Uw = 0.9 m/min
0
0.2
0.4
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13x (mm)
HPD
(mm
)
Exp
erim
ents
H
ardn
ess
(HV
) Te
mpe
ratu
re (o
C)
Technical Specifications
HP
D (m
m)