Transcript Document

University of Miskolc
Department of Mechanical Engineering
Modelling of Laser Surface Treatment
Tutor: Dr. Mária Kocsis Báan
Consultant: Mr. Reza Roshan
By: Mohamad Honeineh
M.Sc. Thesis
Experimental Methodology
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Steel grades C45, C60, S100
(Hungarian standard)
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Workpice dimensions 6056 10
(mm)
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Laser beam diametere 10 (mm)
9 combinations of technological
paramerter:
• Laser power 1,2,3 (kW )
• Sacnning rates 300,500,700
(mm/min)
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Surface coated by graphite
Preparation Stages
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Sectioning was accomplished by
water jet cutting machine
Grinding
Rough and Fine Polishing
The sectioned specimens were
etched in Nital
macro- & microphotos were
placed in synchronization with the
HV microhardness results
Laser Treated C45 Steel
1 mm
1 mm
1 mm
P = 2 kW, v = 300 mm/min
P = 2 kW, v = 500 mm/min
300 mm/min
500 mm/min
700 mm/min
800
600
400
200
0
-6.4 -4.8 -3.2 -1.6
0
1.6
Width(mm)
3.2 4.8
6.4
800
Hardness(HV)
Hardness(HV)
800
Hardness(HV)
P = 2 kW, v = 700 mm/min
600
400
200
0
-6.4 -4.8 -3.2 -1.6
0
1.6
Width(mm)
3.2 4.8
6.4
600
400
200
0
-6.4 -4.8 -3.2 -1.6
0
1.6 3.2
Widht(mm)
4.8 6.4
Experimental Results
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No significant changes were observed for 1 kW laser power
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For 2 and 3 kW laser power, the phase transformation depth
decreased when the scanning speed was the fastest
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Slow scanning speeds caused wider and deeper hardened tracks
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For high laser power with fast scanning rates high hardness was
achieved
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Homogeneous austenite was obtained at slow scanning rate
Three Dimensional Modelling
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The same geometry was built using
SYSWELD SOFTWARE as that in the
original experiments
A Conical heat source was implemented
into the SYSWELD by using simplified
FORTRAN programming
Due to the symmetry of the workpiece,
the fine mesh created resembled only
half the workpiece
3kW Laser Power
v=300 mm/min
v=700 mm/min
v=500 mm/min
Time-Temperature Curves
node 5413
node 5414
node 5415
node 5416
node 5417
node 5418
Temp.(°C)
2000
18 mm
1800
1600
1400
Ac3
1200
1000
Ac3
A3
800
600
400
200
time,s
0
0
1
2
3
4
5
6
7
8
Conical and Gaussian Model
v=500 mm/min
v=500 mm/min
z
qmax
ri
re
y
x
Conical and Gaussian Model
Te m p. (°C )
Time-temp. Cycles for C60 steel, at 2
kW and scanning speed 500 mm/min
for:
1800
Conical heat source model
Gaussian heat source model
1600
1400
1200
1000
800
600
400
200
ti m e , s
0
0
0.5
1
1.5
2
2.5
3
3.5
Simulation Results
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Higher was the laser power, higher the temperature
Spot size was greatly influenced by the laser power and
scanning rate
Time-Temperature Curves indicate that very fast cooling
occurs
Bigger thermal conductivity factor, lower was the
Temperature
Gaussian model obtained steeper and sharper cycles than
that of a conical model
Changing the absorptivity factor by 0.1 step increment
results in 200-300°C difference in maximum temperature