242
D. Sen et al.
7.3.3 Process Parameters
Process parameters play a very important part in obtaining a defect-free FSWed tube.
In FSW of tubular components, the tool does not sit flushed with the tube surface due
to its curvature, thus inadequate heat generation takes place. This short-fall in heat
requirement is compensated suitably by changing the welding process parameters
for a defect-free weld. Parameters such as the rotational speed, transverse speed,
plunge depth and tilt angle are some of the important parameters by which this heat
generation can be controlled.
Researchers studied the contact characteristics and the heat generation between
the tool and the tube by changing the plunge depth during FSW. According to them at
a low plunge depth, adequate heat generation is not produced because of the smaller
interface between the tube surface and the tool shoulder leading to tunnel formation.
By increasing the plunge depth, contact surface between the tube outer surface and the
tool shoulder increases, and as a result more heat generation takes place to soften the
material. Alternatively, excessive increase in plunge depth consequences in thinning
of the tube thickness along the weld line leading to degradation in the mechanical
properties of the welded joint [51].
7.4 Limitations of FSW of Tubes Over Other Welding
Techniques
Even though FSW has got many benefits in manufacturing of tubular components,
still there are some limitations associated with this process. During manufacturing of
tubular structures by FSW process, as the shoulder of the tool comes in contact with
the tube surface for joining, it forms a flat surface in the welded zone. Thus, the tube
formed is not perfectly curved in shape, and hence dimensionally it is not perfect.
Hence, it requires some post weld forming operations to get a perfectly circular tube.
This flatness is more prominent in small diameter tubes, but as the diameter increases
this flatness does not matter much. Another non-avoidable limitation of FSW process
in production of tubular components is keyhole, which gets generated at the end of
the tube resulting from the extraction of the tool pin after welding. This leads to
removal of some portion of the tube material at the end causing material loss.
7.5 Case Study: Longitudinal FSW of Tubes Fabricated
from AA5083
Aluminium alloys are extremely corrosion resistive and have high strength-to-weight
ratio which makes it suitable for application as tubular structures in automotive
D. Sen et al.
7.3.3 Process Parameters
Process parameters play a very important part in obtaining a defect-free FSWed tube.
In FSW of tubular components, the tool does not sit flushed with the tube surface due
to its curvature, thus inadequate heat generation takes place. This short-fall in heat
requirement is compensated suitably by changing the welding process parameters
for a defect-free weld. Parameters such as the rotational speed, transverse speed,
plunge depth and tilt angle are some of the important parameters by which this heat
generation can be controlled.
Researchers studied the contact characteristics and the heat generation between
the tool and the tube by changing the plunge depth during FSW. According to them at
a low plunge depth, adequate heat generation is not produced because of the smaller
interface between the tube surface and the tool shoulder leading to tunnel formation.
By increasing the plunge depth, contact surface between the tube outer surface and the
tool shoulder increases, and as a result more heat generation takes place to soften the
material. Alternatively, excessive increase in plunge depth consequences in thinning
of the tube thickness along the weld line leading to degradation in the mechanical
properties of the welded joint [51].
7.4 Limitations of FSW of Tubes Over Other Welding
Techniques
Even though FSW has got many benefits in manufacturing of tubular components,
still there are some limitations associated with this process. During manufacturing of
tubular structures by FSW process, as the shoulder of the tool comes in contact with
the tube surface for joining, it forms a flat surface in the welded zone. Thus, the tube
formed is not perfectly curved in shape, and hence dimensionally it is not perfect.
Hence, it requires some post weld forming operations to get a perfectly circular tube.
This flatness is more prominent in small diameter tubes, but as the diameter increases
this flatness does not matter much. Another non-avoidable limitation of FSW process
in production of tubular components is keyhole, which gets generated at the end of
the tube resulting from the extraction of the tool pin after welding. This leads to
removal of some portion of the tube material at the end causing material loss.
7.5 Case Study: Longitudinal FSW of Tubes Fabricated
from AA5083
Aluminium alloys are extremely corrosion resistive and have high strength-to-weight
ratio which makes it suitable for application as tubular structures in automotive