Friction Stir Process Mapping Methodology

25 Pages·2002·3.1 MB·English

by  Kooney, Alex

LOCKHEED M A R T I N_ :;_
Friction Stir Process
Mapping Methodology
Gerry Bjorkman
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Alex Kooney o
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Lockheed Martin Space Systems Company
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Carolyn Russell
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Marshall Space Flight Center 0
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Process Overview ,°,,,,,,
Friction Stir Welding (FSW)
- FSW is a solid-state process using Travel
a rotating tool with a shoulder and
a projecting pin.
Rotation
- The pin tool is rotated and plunged
Heel
into the joint until the shoulder Plunge
contacts the top surface. Penetration
Ligament
- The frictional heating between the
pin tool and the joint plasticizes the
material in the local region near
the pin.
- The material at the weld centerline
is joined through a combination of
forging processes that occurs in
the local region of the pin tool.
- Three significant parameters:
spindle speed, travel speed,
plunge load or plunge position
9/18/2002 Friction Stir Process Mapping Methodology 2
FSW Process
L@©KllEED MARTIN_
A process map summarizes the weld process performance for a given
pin tool geometry and joint configuration.
Targeting a consistent penetration ligament, the process is simplified
into two parameters: travel speed and rotation speed.
Other parameters, such as plunge force, traverse force, weld nugget
geometry, NDE response, and mechanical properties are assumed to
be dependent variables.
YELLOW: Unusual flow
patterns, unstable position and
process loads, excessive flash,
poor mechanical properties
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#. GREEN: Symmetric flow
4,4 ,
patterns, stable position and
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process loads, good strength
RED: NDE rejections,
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volumetric defects, poor
strength, excessive process
wP • IP"
loads
IPM
9/18/2002 Friction Stir Process Mapping Methodology 3
FSW Process
LO¢I(ilEED HARTIN_
A selected rpm/ipm combination (weld schedule) provides a specific
nugget geometry, heat input, and mechanical strength.
The selected nominal weld schedule, or sweet spot, is the best
compromise between process stability, mechanical strength, NDE
response, and machine capability.
Once the nominal schedule is selected, process loads and heel
positions are explored to determine their acceptable operating
windows.
Statistical process control in conjunction with the process map data
provides quality control and grounds for reduced NDE requirements.
Process envelope
(acceptable weld schedules)
Nominal weld schedule
a.
(sweet spot)
Operating Window
(acceptable variation about
nominal weld schedule)
IPM
9/18/2002 Friction Stir Process Mapping Methodology 4
(_ FSW Process
L@¢KHEED MARTIN_
Methodology Overview
Determine joint configuration, pin tool
design, anvil and clamping system
Phase I Quick Look
Phase II Testing
Select weld
schedu
Characterize process with
nominal weld schedule
9/18/2002 Friction Stir Process Mapping Methodology 5
Phase I Quick Look
L@¢KilEED MABTIN_
The "quick look" provides a general overview of the process map
- Three weld schedules are performed on a 24 inch long test panel
- Weld schedules are performed "hot" to "cold" by changing the travel
speed (constant rotation speed)
- Metallographic samples are excised near the end of each weld
schedule
24"
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Schedule #2 : Schedule #3
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4 - 6.0" I II
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Macro 2 : Macro 3
4 - 6.0" Macro 1i,
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Weld Start 4.0" 6.0" 11.0" 14.0" 16.0"
9/18/2002 Friction Stir Process Mapping Methodology 6
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Phase I Quick Look
LOCKllEED MARTIN_
Thin gauge similar alloy configuration
- Low (A), medium (B), and high (C) heat input
C
IPM
9/18/2002 Friction Stir Process Mapping Methodology 8
Phase I Quick Look
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• Thin gauge similar alloy configuration
- Heel plunge vs. travel rate
IPM
9/18/2002 Friction Stir Process Mapping Methodology 9
Phase I Quick Look
L@¢KllEED MARTIN_
Thin gauge similar alloy configuration
- Scaling/Galling
IPM
9/18/2002 Friction Stir Process Mapping Methodology 10