OBJECTIVE The objectives of the experiments are 1. To expose students with Metal - Inert Gas (MIG) in practice. 2. To explain the safety during handling MIG welding. 3. To introduce the application of MIG in the industries. INTRODUCTION AND THEORY MIG welding is an abbreviation for Metal Inert Gas Welding. It is a process developed in the 1940’s, and is considered semi-automated. This means that the welder still requires skill, but that the MIG welding machine will continuously keep filling the joint being welded. MIG welders consist of a handle with a trigger controlling a wire feed, feeding the wire from a spool to the weld joint. The wire is similar to an endless bicycle brake cable. The wire runs through the liner, which also has a gas feeding through the same cable to the point of arc, which protects the weld from the air. MIG welding is most commonly used in fabrication shops where production is high, and the possibility of wind blowing away your gas shielding is unlikely. Those seeking a job as a welder would be advised to know all of the names by which this process is known. Employers may use other names in the classifieds or on a written test. When it was first developed it was called (GMA) Gas Metal Arc. It is also known as; GMAW or Gas Metal Arc Welding. Technically the differences in the names are the type of gas used, Inert gas versus non-inert gas. MIG weld welding requires three things, electricity to produce heat, an electrode to fill the joint, and 1
Transcript
OBJECTIVE
The objectives of the experiments are
1. To expose students with Metal - Inert Gas (MIG) in practice.
2. To explain the safety during handling MIG welding.
3. To introduce the application of MIG in the industries.
INTRODUCTION AND THEORY
MIG welding is an abbreviation for Metal Inert Gas Welding. It is a process developed in the 1940’s,
and is considered semi-automated. This means that the welder still requires skill, but that the MIG welding
machine will continuously keep filling the joint being welded. MIG welders consist of a handle with a
trigger controlling a wire feed, feeding the wire from a spool to the weld joint. The wire is similar to an
endless bicycle brake cable. The wire runs through the liner, which also has a gas feeding through the same
cable to the point of arc, which protects the weld from the air. MIG welding is most commonly used in
fabrication shops where production is high, and the possibility of wind blowing away your gas shielding is
unlikely.
Those seeking a job as a welder would be advised to know all of the names by which this process is
known. Employers may use other names in the classifieds or on a written test. When it was first developed it
was called (GMA) Gas Metal Arc. It is also known as; GMAW or Gas Metal Arc Welding. Technically the
differences in the names are the type of gas used, Inert gas versus non-inert gas. MIG weld welding requires
three things, electricity to produce heat, an electrode to fill the joint, and shielding gas to protect the weld
from the air. MIG welding is done using a very small electrode that is fed continuously, while the operator
controls the amount of weld being done. In some cases when a robot takes over this process, it becomes
automatic welding. [1]
The basic technique for GMAW is quite simple, since the electrode is fed automatically through the
torch (head of tip). By contrast, in gas tungsten arc welding, the welder must handle a welding torch in one
hand and a separate filler wire in the other, and in shielded metal arc welding, the operator must frequently
chip off slag and change welding electrodes. GMAW requires only that the operator guide the welding gun
with proper position and orientation along the area being welded. Keeping a consistent contact tip-to-work
distance (the stick out distance) is important, because a long stick out distance can cause the electrode to
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overheat and also wastes shielding gas. Stick out distance varies for different GMAW weld processes and
applications. The orientation of the gun is also important it should be held so as to bisect the angle between
the work pieces that is at 45 degrees for a fillet weld and 90 degrees for welding a flat surface. The travel
angle, or lead angle, is the angle of the torch with respect to the direction of travel, and it should generally
remain approximately vertical. However, the desirable angle changes somewhat depending on the type of
shielding gas used with pure inert gases, the bottom of the torch is often slightly in front of the upper
section, while the opposite is true when the welding atmosphere is carbon dioxide. [2]
Figure 1: MIG welding
TASK
Identify general safety precautions that should be taken when handling MIG welding.
As the precautions steps, first of all, the apron, the gloves wear to protect our body from the welding
process. It prevent the later damage to our body. Next is, wear the safety boots or closed shoes to make sure
our foot fully protected from the molten metal if something happen. During the welding the mask should be
put to prevent the light of the welding to damage the eye. The welding area must occupied with excellent
ventilation to make sure the dust to clear to the air clearly. And lastly, the extinguisher should be put nearby
if something catches fire because welding process produce heat.
EQUIPMENT AND SPECIMENS
1. Wire feeder (mild steel) Ø 0.8, 1.0 and 1.2 mm
2. Mild steel plate bar ¼’’x1 1/2’’x 6’’
3. Gas CO2
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PROCEDURE
1. The work area was cleaned and cleared of grease, oil and any other flammable materials.
2. The welding equipment especially the mild steel cleaned and dried.
3. The current, voltage, wire feed and gas flow is correctly adjusted.
4. There were two pieces of mild steel to make a T-joint.
5. The mild steel was placed as T. the first weld was to join the edge of the joint, where both edge weld
first.
Figure 2: The edge of joint welded
6. When the edge completely sealed, the joint weld properly along the joint.
Figure 3: The welding
7. The metal then brushed with the brush to clean it.3
8. The welding process finished.
RESULT
Figure 4: The result of MIG welding
DISCUSSION
1. Give 5 examples on the use of MIG welding in the industry.
I. Automotive assembly process.
II. Pipework.
III. Fabrication of vessels.
IV. Building of bridges.
V. Brazing.
2. Are there any difficulties that you find during handling TIG welding? Describe.
This welding is the most difficult welding process. First of all, when we wear the mask, we cannot see
where we should start weld. Sometimes I mistook places where I took the different part where I supposed to
weld at the centerline of the work piece.
Secondly, to obtain good result, several factors should be kept. For example the speed and the
distance between the tungsten electrode to the work piece. The speed should be slow to get a better result.
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But to maintain the speed is really difficult. The distance also difficult to kept, where sometimes the distance
is so far from the metal surface caused the welding process is bad.
CONCLUSION
For the conclusion, MIG welding is easier than TIG. MIG process is very versatile in the industries
because relative simple nature of the process and easy to operate. Furthermore, the process is rapid,
economical and welding productivity is doubled compared to Shielded Metal- arc welding SMAW process.
MIG used widely in industry since it is an important process in industry. During the MIG, some precautions
should be take care to avoid any accidents to occur in the welding process. All the precautions should be
followed because welding is dangerous.
REFERENCES
Book
1) Serope Kalpakjian, Steven R. Schimd (2014). Manufacturing Engineering and Technology, 7th
