TPT May 2008

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Tube & Pipe Welding: Trends & Progress
M ay 2008 98 ›
Often considered the hardest tube to weld,
many producers simply have no option other
than to apply excessive weld power in order
to achieve a weld. One major disadvantage
here is that excess power dissipation within
the weld zone will inevitably turn the tube
blue, significantly reducing its market value
or turning it into scrap.
Applications for small diameter, heavy wall
mechanical tubing continue to increase,
particularly in the automotive, recreational
vehicle, farm and garden machinery market
sectors. Commercial considerations are such
that this type of tube needs to be produced
at economically viable mill speeds.
The advent of a genuinely selectable, solid-
state variable frequency welder has been
a major breakthrough, facilitating higher
mill speeds and a significant increase in
production yields.
To achieve increased productivity the weld
conditions must also be optimised. This will
require the correct selection and positioning
of both work coil and impedor. With the
welding of small diameter, thick wall tube,
sufficient power must be transferred to
the weld vee to obtain a quality weld. Due
to physical size limitations, only a small
diameter impedor can be used.
A weld frequency of 400kHz is generally
accepted to be best suited for the production
of carbon steel tube where the diameter to
thickness ratio is equal to or greater than 4:1.
However, the weld quality can be significantly
improved by varying the weld frequency with
the added benefit of the inside weld bead
becoming less pronounced.
Several producers of small diameter,
thick wall tubing have installed
Thermatool variable frequency welders
to optimise production of this ‘difficult to
weld’ tube.
The welders are extremely beneficial as
they offer the ability to start at a higher weld
frequency and then to reduce it to a point
where the most desirable weld properties
are obtained. Alternatively, the weld
frequency can be reduced to just above the
point where the impedor starts to lose its
magnetic properties.
The Thermatool range of selectable
variable frequency welders greatly assists
the unique characteristics of each tube mill
and/or weld setup.
Thermatool Corporation – USA
Fax: +1 203 468 4281
Email:
Website:
Thermatool IHWT – UK
Fax: +44 1256 467224
Email:
Website:
Flange welding made easy
Bug-O Systems, USA, now offers positioning, turning rolls, manipulators and torch
oscillators for pipe and flange welding automation. The company’s new line of 220lb
(100kg) or 440lb (200kg) capacity
mini-positioners can help improve
weld quality and increase production.
The positioners feature an 8-slot
turntable that tilts from 0-120º and
provides quick mounting for holding
fixtures. The spindle has a 1.38″
through hole for pipe work or gas
purge.
The company’s turning rolls have
a remote foot switch with run/stop
controller, and a forward/stop/reverse
switch with potentiometer for stepless
speed adjustment.
Bug-O Systems’ manipulators are
manual or motor driven and include
pendant control with DC driven drive
and optional arc sensing height
control. The company’s torch oscillators can perform weave welds or straight-line stinger
welds, and feature adjustable independent dwell settings.
Bug-O Systems – USA
Fax: +1 412 331 0383
Email:
Website:
 Thermatool provides advanced variable frequency
welding technology
Breakthrough for welding small diameter, thick wall tube
 Bug-O Systems provides equipment for pipe and
flange welding