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)

Thank you for your attention.

For more information:

k.salonitis@cranfield.ac.uk