Marine FSW Fabrications: FSW Paneling
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In marine applications, friction stir welding is typically used to join multiple extrusions or strips of sheet or plate together to form large panels.
These panels are used for bulkheads, decking, and hull areas.
In the figure, to the right, friction stir welded panels are shown being prepared for assembly into the superstructure. The friction stir welded panels, as delivered, are shown in the low left and lower right portion of the left figure, with a partial assembly of the superstructure with other friction stir welded panels shown in the center of the figure. The final assembly of one module on this ship is shown in the figure to the right. Pictures are courtesy of
Marinette Marine.
Figure 1.
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Figure 2.
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Figure 3.
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A typical or common assembly process of these friction stir welded panels is in the figures to the left. These panels are normally made from a variety of extruded shapes and/or strips of sheet and plate in the figures, the example panel is fabricated from only extrusions. The first extrusion is shown in fig.1 and is referred to as the main extrusion.
The extrusion typically includes an integral stiffener rib, tee, bulb-flat, etc., that performs the function of the welded stiffeners in the traditional assembly
method. The second extrusion shown in fig.2 is referred to as the transition extrusion. This extrusion is used on the ends of the panel to allow the completed FSW
panel to be joined to the next panel in the shipyard. The geometry of the transition area may vary depending on the desired joining method and mating conditions.
The next figure fig.3 then shows the assembly of the main extrusions to the transition extrusions. These extrusions are all friction stir welded together along the
length of the extrusions.
Most of the panels that are in production today range from 8 to 50 feet long to 2 to 40 feet wide, while the individual extrusions vary
from several inches to close to 20 inches wide. These panels consist of anywhere from 2 to 60 individual extrusions.
The panels are made from a variety of
extrusion shapes and can include sheet or plate or strips there of in between the extrusions. For panels with high stiffness requirements, the panels maybe made
of multi-hollow extrusions shown in figure 5. Friction stir welded panels for the marine industry are typically fabricated from 5xxx aluminum or 6xxx aluminum alloy.
Figure 4.
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Figure 5.
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Above is an example of a panel made from solid extrusions and a panel fabricated from multi-hollow extrusions. It can be seen that the friction stir welded panels are very flat, exhibiting little if any distortion. This is critical in allowing shipyards to significantly reduce their assembly costs. These friction stir welded panels generally eliminate the need for costly straightening operations and also greatly simply the setup of the subsequent joining operations, where the panels are welded to form the superstructure. Today, the US Navy uses these panels in
the
Littoral Combat Ship and
Joint High Speed Vessel programs. Friction Stir Link currently fabricates over 200 miles
FSW panels per year for the marine industry.
Another significant application for friction stir welding is over-the-road trailer decking. One such example is shown in the photograph. This example consists of extrusions in both the transverse and longitudinal direction of the deck. All of the extrusions are welded with friction stir welding. The main friction stir welded sub-assemblies are then
arc welded to produce the final assembly. The detail parts also have significant machining content
Additional Machine Information. One production application is for the
Fontaine Revolution trailer. The friction stir welding allows this particular trailed to be the lightest and strongest trailer in the industry, and provide dramatic improvements in fuel economy. This application is believed to be the world’s single largest friction stir welding application with over 300 miles of friction stir weld produced per year at today’s production rates. Eighty percent of this friction stir welding is performed robotically.
In the rail car industry, there are numerous applications for friction stir welding. The largest of the applications include floors, roofs, and sides.
Other applications include ends or bulkheads and other sub-assemblies.
These applications exist both in the passenger car and freight car segments of the industry.
Typically the fabrications consist of joining of multi-hollow or solid extrusions, but can also include joining of plate. One such example is shown in .
Friction Stir Link is the largest provider of rail car fabrications in the North American market. Friction Stir Link is a full service provider in this market, with
the fabrications including significant machining, drilling, arc welding, and various finishing operations. In the application shown, there is in excess of 500 feet
of friction stir welding, hundreds of holes and slots and about 50 feet of arc weld.
There are limits on extrusion size, thickness (thin and thick), weight per foot, etc. that prohibit extrusions from being used in certain applications.
Furthermore, there are also alloy limitations that prevent the fabrication of hollow extrusions (e.g. 2xxx, 5xxx, and 7xxx). With friction stir welding and its
inherent lack of distortion, custom extrusions can be made where these type of extrusions would be desireable. Such examples include large I-beams or angles.
Other examples include fabrication of tubing from smaller c-channel or angles for alloys for which hollow extrusions can not be fabricated. Two examples are
shown here, a rectangular tube fabricated from C-channel and a large I-beam fabricated from tees and plate.
Friction Stir Welding can be used to join standard sized sheet or plate into larger plates.
Larger plate Welding
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While special order wide plate can be procured, it is generally more cost effective to friction stir weld standard sized sheets or plates to create larger plates. The cost of friction stir welding is generally less than the wide sheet or plate surcharges that exist for special orders. The FSW approach also avoids the excessive lead times and the minimum order quantities of special order wide plate. With the low distortion of FSW, the welded plate is nearly as flat as the base material and can typically be produced to within the Aluminum Associates sheet or plate flatness specifications. These wide sheets are used in the marine, rail car, and trucking industries and are applicable to anywhere where over-wide sheet or plate would be of benefit. One large application for wide sheet is for the
US Navy’s LHA program where over one-half million pounds of friction stir welded plate is used per ship.
