SEAM WELDING: -
Seam
welding is type of resistance welding and the process is similar to spot
welding. The important thing in the seam welding is the electrode used in the
process. The electrode are wheel shaped. The wheel will be in contact to the
materials to be joined. Since the wheel will have the rotating nature so the
wheels will rotate on the surfaces and provide continuous welding.
The
principle of the weld joint generation is same as the spot welding, as this
uses the resistance between the mating surfaces of workpiece that will resist
the current flow through the workpieces. The heat generation will takes place
and molten pool is developed in the material to join the specimen. Generally
the lap joint is created by seam welding and butt joint can also be created.
The wheels
would be provided the electrical motor to make it of rotating nature, instead
of being stationary electrodes as in spot welding.
It can be
said that in seam welding, the continuous spot weld is produced. That is why it
is called continuous spot welding.
The copper
electrodes are used in the process because copper dissipates the heat from the
surfaces of the sheets to be joined. The heat generation is dependent on the
rotation of the wheel. The speed of the disc can be manipulated to control the
heat.
PROCESS OF SEAM WELDING: -
- First arrange all the setup of seam welding. Transformer, energy source, wheels with rotating facility.
- Then the specimen is prepared to produce weld. The specimen should be free of dirt, dust or any other foreign particle like oxides, grease etc.
- After this the specimen is placed between the rotating electrodes of copper or copper alloy.
- The wheels will rotate by the motor, both wheels will rotate in opposite direction i.e. one is CW (clock-wise) and another is CCW (counter clock-wise).
- The pressure is applied by the electrodes on the pieces to start the welding.
- The current will flow through the work pieces in controlled intervals to produce the required type of joint.
- When the current flow takes place, the heat is generated at the place where the workpieces is in contact with each other i.e. mating surface. The air gap in between will cause the resistance for the heat generation.
- The heat is then used by the workpieces to melt the material at the required place to generate the appropriate weld joint.
- Then the wheels will continue to rotate till the required series of weld joints is achieved.
- Continuous heat dissipation is needed, it is done by the wheels or water can be used as a coolant.
ADVANTAGES OF SEAM WELDING:-
- The joints with lesser overlap than spot welding can be produced.
- THE heat control is quite nice in the seam welding process.
- It is very energy efficient process, as the process is done with low current usage.
- For mass production the process is very useful in material joining field.
- The process is easy and too much skill is not required for the operator.
- The rate of production is high for continuous joint in the sheets.
- The process is preferred for the production of Air tight and liquid tight containers.
- As there is no use of Flame, so it is environment friendly process and do not produce to much pollution. This also makes it an economical process.
- The gas emission, fumes formation do not takes place.
- Flux is not required in the process.
- Life of electrodes is good.
- Less maintenance is required.
DISADVANTAGES OF SEAM WELDING:-
- Only continuous weld joint can be produced other shapes cannot be welded.
- There is a limit of thickness of sheets to be welded. Very thick specimen cannot be welded.
- A reliable system is needed to produce the continuous and controlled current flow.
- A good controlling system is also needed for the speed control of wheels.
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