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There
within the context of the term welding. One involves the fabrication
of new pieces of equipment and consumer goods; the other is
the maintenance and repair of these goods after they are put
into service. Each area requires the selection of an alloy,
but the selection criteria varies substantially.
Within the OEM category, where welding is used to fabricate
and manufacture all kinds of things, the processes are often
referred to as production type welding. When such an item
is in the planning stage, a decision is made by a welding
engineer or a design committee as to exactly what method of
joining will be used, what specific alloy, the operating temperatures,
the direction of travel and so on, based on their needs to
weld parts together. The finished item is generally designed
so that the combined processes, filler alloys and so on, will
be compatible. One important criteria a manufacturer uses
in the selection of materials and process is one that will
enable him to make a product that will be both profitable
for him and economical to the end user.
AWS specification alloys are available for this purpose. They
are designed to permit a manufacturer to produce goods economically.
The end result: the consumer gets a good product at a reasonable
price and the manufacturer makes a satisfactory profit.
There is, however, another type of welding known primarily
as maintenance welding. Maintenance welding is the upkeep
and on-going repair of existing pieces of equipment and machinery
broadly used by industry all over the world. The machines
that are used to form a shape, cut, scrape, push, load or
move material are subject to wear or breakdown and must be
repaired. Repair work is usually performed by plant and maintenance
people.
Repair welding generally falls into two major categories:
- The
shop environment where a part or
component can be torn down and pulled into a shop where
it can be repaired in a controlled environment or
- The
field repair, which necessitates the piece of equipment
be repaired where it stands. This could be anything from
a large crane or bulldozer in the field operation to rollers,
shafts, wearing surfaces or frames on machines in plants,
where the cost of tearing them down and moving them to a
central operation would be prohibitive or the time required
to do this would not be economically feasible.
There are always a number of considerations to be made when
determining what welding product
and/or procedure will be most efficient in achieving the
desired end result. The burden of this responsibility most
often falls on the maintenance welder. He may or may not
have formal training in maintenance and repair welding.
He may be a well trained journeyman in a specific trade
other than welding and be called upon to do the welding
as part of his normal job description. Sometimes, with a
limited knowledge of metals, processes, and filler alloys,
he is called upon to perform major repairs on equipment
that is vital to the total operation of the company. Before
he can start any repair, he must consider a number of factors:
1. Why did the part break?
2. What is the base metal?
3. What welding processes are available to achieve the repair?
4. Any special considerations, such as the location of the
part, service temperature,
surface preparation, joint preparation,
edge preparation.
5. Type of filler alloy.
The materials shown in this booklet have been designed specifically
with the maintenance person
in mind to help make his job easier and more successful.
If you have a welding problem and need further information,
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