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TRANSCRIPT
LASERS
Efficiency & Strength for Lightweighting
May 11, 2016
Agenda
• Welded Blanks
− Brief history & evolution
− Current & future applications for reducing weight
• Laser Ablation
− Basic principles
− Applications
First Operation Blanking
Laser Welded Blanks (LWB)
Laser welded blanks are manufactured from two or more blanks, of the same or
different steel grades or gauges welded together. A high level of engineering
analysis and laser technology is applied to achieve a reduction in vehicle mass,
number of parts and tooling cost, while improving body strength.
It is important to note, that unlike other welding applications, a welded blank will
be formed after welding. The stresses applied during the forming process
require a very high quality weld placed in the exact location to optimize mass
and material utilization.
Why do we use Welded Blanks?
• Different gauges, materials & coatings can be
incorporated into one blank
− Blank can be engineered to desired properties
• Consolidation of components
− Reduction in number of parts
− Reduced tooling costs
− Reduced assembly operations and equipment
• Material utilization
− Reduction in engineered scrap due to improved blank nesting
• Mass reduction
Shiloh Welded Blank History
• Started welded blank production in 1989
− First welded blank was mash seam welded
− Reclamation of offal from large body blanks
• Moved to laser welding in 1994
− Early systems were 3 kW lamp pumped YAG (4% eff.)
− Current systems are all solid state (45% eff.)
• Current production est. >13,000,000 LWB/yr
• 5 LWB facilities currently
Mash Seam Weld Section & Heat Affected Zones (HAZ)
4.70 mm
0.46
0.9/1.3 mm material welded with Mash Welder, no filler wire
0.31
Laser Weld Section & Heat Affected Zones (HAZ)
0.81 mm
0.2 0.15
0.8/1.6 mm material welded with 4 kW Nd:YAG laser, 600 micron spot, no filler wire
0
20
40
60
80
Thin Base Thin Base
near HAZ
HAZ Thin
Side
Weld Bead HAZ Thick
Side
Thick Base
near HAZ
Thick Base
Har
dnes
s
Advantages of Laser Welding
• Improved speed and flexibility
− Common systems with interchangeable fixtures
• Improved weld quality
− Smaller HAZ
− Reduced work piece distortion
• Improved formability
− Elimination of large step due to overlap welding
− Enhanced capabilities for curvilinear welding
Laser Welding Capabilities
• Linear
• Multi-Linear
• Curvilinear
APPLICATIONS
Current Blank • 15.2 Kg
2 Piece LWB • Total Steel usage = 12.7 Kg
Advantages
• Material savings of
2.5 Kg/part
• Blank A can use
uncoated steel
Applications
Material Optimization – Reduction in engineered scrap
2 Pc. Baseline
Design • Material Usage 5.23 kg
• On Vehicle Mass 2.74 kg
LWB Option • Material Usage 4.38 kg
• On Vehicle Mass 2.38 kg
Reinforcement
1.10 mm
Pillar , 0.90 mm
Blank A, 1.60 mm
Blank B, 0.90 mm
Advantages
• 0.84 kg of Material
savings per side
• 0.36 kg of mass
savings on vehicle per
side (0.72 kg/Veh.)
• Lower stamping die
cost
• No welding or fixture
costs
• Lower press time,
transportation,
inventory
Applications
Part Consolidation
Balance - Formability & Mass Savings B
lan
k
Th
inn
ing
16 % 16 % 33 % 40 %
Vehicle mass optimization example:
For some applications the part geometry requires a high level of material elongation
for forming. Placement of the weld seam is critical. This example shows a solution
to achieve acceptable levels of material thinning by correct placement of the weld
line and mass optimization with curvilinear laser weld.
Applications
Base Design Curvilinear Weld
Option
Blank Gauge in mm
Mass in kg
Thick Blue 1.80 4.75
Thin Green 0.80 4.59
Total 9.34
Blank Gauge in mm
Mass in kg
Thick Pink 1.80 2.75
Thin Brown 0.80 5.48
Total 8.23
-1.11 Kg /Door
Mass Savings
Vehicle Mass Optimization
FUTURE APPLICATIONS
Future Applications
• Advances in laser technology
− Lower cost/kW of laser systems & higher beam quality
− Improved optics and beam delivery
− Short pulse width (laser ablation)
− Removal of coatings prior to welding
− Removal of surface contaminants prior to joining
− Surface structuring
• Laser welding of advanced materials
− AHHS & Gen3 steels
− Thick gauge steels
Future Applications
Thick Gauge Frame Components (3 mm+)
Higher power and lower cost/Kilowatt of the newer solid state
lasers has opened the possibility of bringing welded blank
methodology to thicker gauge truck frame components (3-9 mm
thickness range) to reduce mass and optimize material
utilization.
Initial brainstorming with customers has shown ideas that could
reduce the mass by 25 kg.
Baseline Design Mass = 11.5 Kg
Laser Welded
Option • Mass = 9.6 Kg
Advantage
• 1.9 Kg mass savings
on vehicle
Thick Gauge Laser Welding
Baseline Required blank for stamping
Laser Welding Option
Base blank nesting – not feasible due
to width of the coil (3.0 m or 118”)
Advantages
• Material savings of
25+ kg.
• Several tons of steel
has been taken out of
initial production
which reduces carbon
foot print
• Option to change
material grades and
gages for additional
weight and cost
savings
Thick Gauge Laser Welding
Example – Frame Rail
Rectangular blank
Scrap overlay ~ 25 kg
Blank nesting
PHS & LWB
1. B-Pillar – Hot stamp/AHSS
2. Door Ring – Hot stamp/AHSS
3. A-Pillar – Hot stamp/AHSS
4. Frame rail
5. Side sill
6. Crossmembers
7. Floor pan
8. Cowl side
LASER ABLATION
Pre-Process Surface Preparation
• In many manufacturing applications it is essential to
remove surface contaminants and oxides before further
processing
• Adhesive bonding often requires a “clean” surface so the
adhesive can wet the material creating strong bonds
• Welding components also requires “clean” surfaces to
prevent contaminants from weakening the welds or
causing porosity and leaks
• Some coated PHS must have the coating removed prior to
welding to prevent contaminating the welds
Short Pulse Lasers - Enabling Technology
• Ablation of surface coatings
− Removal of coatings prior to welding
• Ablation of surface contaminants & oxides
− Removal of surface contaminants prior to joining
• Surface structuring
− Texturing to improve or prepare surface for specific
applications
− Creation of super-hydrophobic surfaces
APPLICATION OF SHORT PULSE
LASERS FOR METAL SURFACE
CLEANING
Pulse duration and pulse energy
Two pulses of equal pulse energy but of
different duration
t
Pulse peak power = Pulse energy/time
Oxide Removal
Video courtesy of Trumpf
HOW CLEAN IS CLEAN?
How Clean is Clean?
Everyone will agree that surfaces need to be clean
Not everyone will agree just how clean
the surface needs to be
• Typical cleaning methods include
− Brushing or grinding
− High pressure water blasting
− Attacking with chemicals
• The following developmental work will show:
− A method for estimating Surface energy/cleanliness
using contact angle & Dynes
− Applying a short pulse laser and scanner to clean metals
prior to laser welding or adhesive joining
How Clean is Clean?
• When a drop of liquid is placed on a surface its shape is determined by the
balance of interfacial liquid/solid/vapor forces.
− A high surface tension liquid when placed on a solid of low surface energy will cause
the liquid droplet to form a spherical shape or “bead up”
− Conversely, if the liquid surface tension is lower than the solid surface energy the
droplet has a lower profile and “sheets” or wets the surface.
• By viewing small droplets of liquids the interfacial tension can be observed. The
profile of the droplet can be defined by an angle formed by a line drawn tangent
to the curve of the droplet at the point where the droplet intersects the surface.
The angle formed by this tangent is called the contact angle.
Measuring Material Cleanliness with Dynes
• Contact angle measurement can be used to detect the presence of oxides and contaminants that have a different surface energy than the underlying substrate.
• Fortunate for us, organic contaminants and oxides have much lower surface energies than metals and therefore the contact angle can be taken as a proxy for cleanliness of the surface.
• Surface Tension can be measured in energy units called dynes/cm.
• The most common method of measuring surface energies is by employing ASTM D 7541
Measuring Material Cleanliness with Dynes
EXPERIMENTAL RESULTS
Experimental Procedure
• Empirically determine the laser power density
(fluence) required to achieve the required
cleanliness (dyne) level
• Adjust parameters to optimize cycle times
(Area/sec)
− Avg. laser power
− Spot size/shape
− Pulse repetition rate
− Pulse overlap
− Line overlap
Material Surface Cleaning for Adhesion
Objective
• To provide an efficient surface preparation
process for laminate material joining.
• Material tested:
• Current production coated low carbon steel
• Future non ferrous alloy
Surface Analyst™
Item Name: The Surface Analyst™
Company: Brighton Technologies
Description: Self-contained instrument for
analyzing surface energy
The Surface Analyst™ determines the wetting properties of a surface and
provides a number that correlates to its cleanliness.
Material Surface Analysis Equipment
Approximate Comparisons of
Contact Angle vs Dyne Inks
Surface Condition
Wetting
Tension Range
(dyne/cm)
Contact Angle
Range
(degrees)
Cleanest 72 1-15
50-60 16-32
40-50 33-50
Most
Contaminated 30-40 50-70
Goals & Experimental Set Up
• Goals − Determine if a short pulse laser can obtain required cleanliness
level − Min. 44 dyne
− Determine if cleaning cycle times can meet production requirements − Min. 22.5 cm2/sec
• Experimental set up − Laser
− IPG YLPN-100-25x100-1000-S – max avg. power of 1000 watts − Wavelength 1064 nm − Pulse width 100 ns − Pulse repetition rate 2- 50 kHz
− Scanner − Scanlab intelliSCAN30
− The scanner was mounted on a small gantry system
Surface scanned with an SEM as received.
Contaminants
Surface scanned with an SEM after
20% (200w) ablation power. (Carbon and Oxygen reduced – No Melting)
Surface scanned with an SEM after
30% (300w) ablation power. (Carbon and Oxygen reduced – Melting Begins)
Melting
Galvanized Steel Surface Cleaning
Galvanized Steel Surface Cleaning
Spectrum
Label C O Fe Zn
Cleanliness
(dyne/cm)
As Rec'd 17.85 1.91 0.81 79.43 39
10% 11.81 0.94 0.83 86.42 42
20% 11.05 0.97 0.80 87.18 46
30% 9.55 0.85 0.83 88.76 53
40% 8.52 0.91 0.87 89.69 53
50% 7.56 0.72 0.83 90.90 55
60% 6.30 0.63 0.96 89.25 56
70% 5.98 0.54 0.77 91.70 60
80% 5.70 0.48 1.07 91.75 61
90% 4.85 0.37 0.98 90.69 63
Surface as received 39 Dyne, Target 44 Dyne.
SEM scan - surface cleanliness at different power intervals.
20% (200w) power (Carbon and Oxygen
reduced – No Melting)
30% (300w) power (Carbon and Oxygen
reduced – Melting Begins)
Galvanized Steel Surface Cleaning
Galvanized Low Carbon Steel Summary
• Material received at cleanliness level of 39 dyne/cm − SEM image of the material surface shows visible contaminants
• Surface laser ablation performed; observed that as energy increases,
hydrocarbon contaminations (carbon and oxygen) are reduced − As the fluence increases, the surface becomes cleaner until eventually the surface
begins to melt
• 20% laser power (200 watts) surface cleanliness recorded at 46 dyne/cm − Visual examination of the surface showed a clean surface and no visible
melting points.
• 30% laser power (300 watts) surface cleanliness recorded at 53 dyne/cm − Visual examination of the surface showed again a clean surface but with
some melting points
5182-0 Aluminum Alloy
Surface scanned with an SEM as received.
Contaminants
Aluminum Surface Cleaning
Surface scanned with an SEM after
20% ablation power. (Carbon and Oxygen reduced – No Melting)
Melting
Surface scanned with an SEM after
40% ablation power. (Carbon and Oxygen reduced – Melting Begins)
Surface received 35 Dyne, Target 44 Dyne.
Spectrum
Label C O Mg Al Mn Fe
Cleanliness
(dyne/cm)
As Rec'd 33.86 4.30 3.40 58.04 0.18 0.20 35
10% 16.71 4.01 4.18 74.79 0.19 0.12 41
20% 7.45 3.58 4.48 84.02 0.27 0.19 53
30% 7.59 3.74 4.45 83.82 0.34 0.06 60
40% 8.41 3.59 4.31 85.30 0.24 0.14 63
50% 8.10 3.29 4.15 83.96 0.30 0.21 72
60% 7.57 3.44 4.10 84.34 0.25 0.31 72
70% 8.23 2.93 4.02 84.29 0.28 0.24 72
80% 8.18 2.93 4.00 84.38 0.29 0.23 72
90% 8.04 2.91 3.86 82.15 0.29 0.24 72
Aluminum Surface Cleaning
SEM scan - surface cleanliness at different power intervals.
20% power. (Carbon & Oxygen
reduced – No Melting)
40% power. (Carbon & Oxygen
reduced – Melting Begins)
5182-0 Aluminum Alloy
5182-0 Aluminum Alloy Summary
• Material received at cleanliness level of 35 dyne/cm
— SEM image of the material surface shows visible contaminants
• Surface ablation performed; observed that as energy increases,
hydrocarbon contaminations (carbon and oxygen) were reduced
— As the fluence increases, the surface becomes cleaner until eventually the surface
begins to melt.
• 20% (200 watts) and 30% (300 watts) power surface cleanliness
measured 53 dyne/cm and 60 dyne/cm
— Visual examination of the surface showed a clean surface and no visible melting points.
• 40% (400 watts) power surface cleanliness measured 63 dyne/cm
— Visual examination of the surface showed again a clean surface but with
some melting points.
Aluminum Surface Cleaning
304 Stainless Surface Cleaning
Objective
• To provide an efficient surface preparation process for
stainless steel heat exchanger welding.
• Material tested:
• Current production 304 Stainless steel material.
Goals & Experimental Set Up
Goals • Determine if a short pulse laser can obtain required cleanliness level
− Min. 44 dyne
• Determine if cleaning cycle times can meet production requirements
− Min. 12 cm2/sec
Experimental set up • Laser
− Trumpf TruMicro 7050 disk laser - avg. power of 750 watts, max pulse energy 80 mJ
− Wavelength 1030 nm
− Pulse width 30 ns
− Pulse repetition rate 5-100 kHz
• Scanner
− Scanlab intelliSCAN30
• The scanner was mounted on a small gantry system
Test Material
Target Laser Ablation Results
Clean Rate
(cm2/sec)
Cleanliness
(dyne/cm)
Clean Rate
(cm2/sec)
Cleanliness
(dyne/cm)
Low Carbon Steel 22.5 44
72 46
72 53
5182-0 Aluminum
Alloy 22.5 44
72 53
72 61
304 Stainless
Steel 12 44 30 72
Results Summary
• Data provided supports the proposition that “Short Pulse Laser
Ablation” systems can provide
— Modular and manageable process for many surface cleaning applications
— Desired surface cleanliness
— Expeditious cleaning cycle time
• Future studies to be performed
— Laser ablation cleaning systems with multiple scanner heads sharing energy
form single source laser resonator
— Simultaneous surface cleaning (top & bottom)
— Surface structuring to improve adhesion & lubrication
Conclusions & Future Works
Jim Evangelista [email protected]
Phone: 734-738-1300
Acknowledgments: Short Pulse Laser Development
— Arthur Amidon, IPG
— Bill Shiner, IPG
— Dennis Decker, Trumpf
— Dr. Sascha Weiler, Trumpf
Michael Tymosch [email protected]
Phone: 330-558-2306
Thank You
#GDIS
Presentations will be available May 16
at www.autosteel.org