Nelson Nelweld 4000, Operation And Service Manual

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Nelweld Operations and Service Manual
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It is important to keep the ferrules dry. If they
absorb a great deal of moisture, heat from the
weld instantly turns the moisture into steam,
which may cause the ferrule to shatter. If the
ferrule shatters, molten metal will be forcefully
ejected from the weld zone, leading to dangerous
situation for the operator. A very porous and
weak weld would then result.
Ferrule cartons are marked with a warning that
they contain silica, a possible health hazard.
Since the ferrules are made from “green” fireclay
ceramic with binders, and fired at high
temperature, there is no free silica material at
inhalable sizes released during the weld. If
simply broken free of the weld, they are basically
an inert, inorganic material, such as fired
aggregate or rock, and may be disposed of easily
and safely. It would take an extensive amount of
ferrule breakage or grinding to produce sufficient
loose powder to reach any inhalable level
dangerous to the stud welding operator or those
nearby.
Position Welding: Studs of all weld base
configurations and diameters from minimum to
maximum available can be easily welded in the
downhand position. As a general rule, studs up to
and including 3/4” diameter can be welded to the
weld plate vertical position with consistent, full
strength results. Special ceramic ferrules are used
with studs 5/8” and above when welding to the
plate vertical position. There is a special ceramic
ferrule for welding 7/8” diameter studs in the
vertical position, but welding this diameter stud
requires very carefully controlled conditions.
Studs larger than 7/8” cannot be welded in the
vertical position.
Welding overhead can also be done with all stud
diameters. Naturally, the overhead position
causes an increased amount of welding sparks to
fall during welding and suitable operator
protection is needed. There are spark retention
accessories available from Nelson Stud Welding,
Inc.
Ceramic ferrules are also available in a wide
variety of configurations, including but not
limited to, welding studs to round or rectangular
tubing and bars, plate or bar edges, channels, and
struts.
Welding Stainless Steel Studs to Carbon Steel
Base Plates:
Full strength welds are made when
standard carbon steel studs are welded to either
approved stainless steel base or carbon steel plate
materials. Similarly, welds made with stainless
steel studs to stainless steel or carbon steel base
plate materials develop full stud steel capacity in
tension or shear. However, in cases where
stainless steel studs are welded to carbon steel
plates, and are to be subject to repetitive or cyclic
loads, stress corrosion failure in the weld can
occur.
It is good practice to specify that the stainless
studs to be used in such conditions are either
annealed after manufacture or made from
annealed-in-process
stainless steel with a
hardness less than 90 on the Rockwell B scale, in
the finished condition. This minimizes the chance
of weld failures.
Stud Welding In Adverse Weather
Conditions: Studs should not be welded
when the base plate temperature is below
0º F (-18º C), or when the surface of the base
plate is wet, frost covered, or exposed to falling
rain or snow. Additionally, it is not
recommended to use stud welding equipment in
environments where falling rain or snow, or
standing water are present.
A brittle failure by impact testing at low
temperatures in the weld or in the base metal is
quite common. Tension and shear tests done at
temperatures below -40º F (-40º C) on studs
welded at that temperature showed no loss in
strength of the stud weld. It is the impact testing
that causes weld failure. Whenever possible
welding and testing studs at low temperature
welding should be avoided.
2.7.2 Material Selection and Verification
Studs are made from steel supplied to the Nelson
Stud Welding, Inc. by quality, approved steel
suppliers.
Quality assurance procedures
established at the manufacturing facility require
that the steel supplier provide certified mill test