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LEARNING TO WELD
PROCESS SELECTION
By gaining knowledge of the differences between the two processes,
you will be able to select the best process for the job you have at
hand. In selecting a process, you should ask yourself the following
questions:
For GMAW (MIG) Process
1.
Is most of my welding performed on 16 gauge and
lighter materials?
2.
Can I afford the extra expense, space, and lack of
portability required for gas cylinders and gas supply?
3.
Do I require clean, finished-looking welds?
4.
Must the base metal be clean?
If you have answered yes to all the above questions, GMAW may be
the process for you. If you have answered no to any of the above
questions, then you should consider using the FCAW process.
For FCAW (Innershield) Process
1.
Do I want simplicity and portability?
2.
Will welding be performed outdoors or under windy
conditions?
3.
Do I require good all position welding capability?
4.
Will most welding be performed on 16 gauge and
heavier, somewhat rusty or dirty materials?
5.
Must weld be cleaned prior to painting?
6.
Please note that your machine may or may not be set
up to handle both FCAW and GMAW welding
processes. Refer to your "Operators Manual" to
determine which settings are required to adapt your
machine.
COMMON METALS
Most metals found around the farm, small shop or home are low
carbon steel, sometimes referred to as mild steel. Typical items made
with this type of steel include most sheet metal, plate, pipe and rolled
shapes such as channels and angle irons. This type of steel can
usually be easily welded without special precautions. Some steels,
however, contain higher carbon levels or other alloys and are more
difficult to weld. Basically, if a magnet sticks to the metal and you can
easily cut the metal with a file, chances are good that the metal is
mild steel and that you will be able to weld the material. If you plan to
weld on aluminum, special drive rolls or aluminum welding kits may
be required or highly recommended. Consult your machines
Operator's Manual. Pure argon shielding gas and a spool of aluminum
welding wire will also be required. For further information on
identifying various types of steels and other metals, and for proper
procedures for welding them, we again suggest you purchase a copy
of "Metals and How to Weld Them".
Regardless of the type of metal being welded, in order to get a quality
weld, it is important that the metal is free of oil, paint, rust or other
contaminant's.
JOINT TYPES
AND POSITIONS
Five types of welding joints are: Butt joint, Fillet joint, Lap joint, Edge
joint and Corner joint. See Figure 5.
Of these, the Butt Joint and Fillet Joint are the two most common
welds.
Butt joint
Edge joint
FIGURE 5
Butt Joints
Place two plates side by side with a tight fit-up to prevent burn
through when welding.
Securely clamp or tack weld the plates at both ends, otherwise the
heat will cause the plates to move apart. See Figure 6.
Now weld the two plates together. Weld from left to right (if right
handed). Point the wire electrode between the two plates, keeping the
gun slightly tilted in the direction of travel. Watch the molten metal to
be sure it distributes itself evenly on both edges and in between the
plates. This is referred to as the "pull technique." On thin gauge sheet
metal, use the "push technique." See "Welding Techniques for GMAW
(MIG) Process."
FIGURE 6
4
Lap joint
Fillet joint
Corner joint
Capítulos
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