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10 Axle Installation & Welding Recommendations
HOW WELDING AFFECTS BEAM MATERIAL
All welds made on the beam create, in effect, an extreme local
heat treatment. The heat generated by the weld causes the
material immediately adjacent to the weld to become hardened,
substituting the undesirable characteristic of brittleness for the
original and desirable quality of ductility. This small hardened area
becomes the weakest part of the tube creating a notch effect.
Since the same characteristics of relative stress apply in both
cases it can be seen that the loss of strength at the weld area can
cause failure. The notch can be at the bottom of the beam as well
as at the top. Either case is at the maximum stress location.
Some welding tips to minimise the notch effect:
1. Make all "tack" welds at least one inch long.
2. Keep the number of tack welds to a minimum – if possible
clamp the bracket tightly to the beam and eliminate tack welds.
3. If more than one bead of weld is required make the second run
(third etc) runs with different start points and BEFORE the first run
cools down (descaling between runs of course).
4. Remove oil, and if possible paint from surfaces to be joined.
RECOMMENDED LOCATION OF WELDS
Fig. 10.3 illustrates the recommended location of the weld fillet for
round beams. All welds should be located in the area of minimum
stress. The direction of welding should be as near the horizontal
as possible.
No Weld
3.75" (95mm)
Fig. 10.3
Max
Weld
o
o
Area
No Weld
Welding around the corners of brackets or spring seats should be
avoided. It is important that all welds should be excluded from an
area of 50º of either side of the bottom vertical centre line of the
beam.
Avoid welds of a circumferential nature on the lower half of the
beam.
Where the brackets fit down the side of the beam they should
have a corner radius of approximately 1" (25mm). The purpose of
this radius is to avoid local concentration of stress.
The illustrations show the recommended weld location for the
various parts to be attached to the axle beam. None of these parts
has been welded to the beam at points of maximum stress.
The welding rod used should meet BS 639 and BS 1719 (British
Standard) specification.
They should not be broken at the end of the fillet, instead the
electrode should be "backed-up" to fill the crater that would
otherwise remain.
Use the voltage and amperage recommended by the electrode
manufacturers. This will provide the best fusion and strongest
weld and will minimise the detrimental side effects such as
localised hardening and residual stress. Deposit the required
amount of metal with the least number of passes practicable –
one pass to be preferred. If a second pass is required first
thoroughly clean the weld.
MOST IMPORTANT
1. Do not test the arc on the axle beam or springs.
2. Fillet welds up to 12mm (1/2") can be used on round axle
beams and the attachment should fit as close as possible to avoid
excessive welding – minimum recommended fitted weld 8mm
(5/16") where practicable. It is important to remove all scale in
fillet welds prior to painting. If this is not adhered to it will
precipitate corrosion in these important weld areas.
Meritor HVS TM Series Axle
46
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