Shielded Metal Arc Welding (SMAW) is also known as Manual Metal Arc Welding (MMAW) or wrapped electrode welding is a process of joining two or more pieces of metal into a fixed connection, using an electric heat source and additional / filler materials in the form of wrapped electrodes. In the wrapped electrode welding process, an electric arc that occurs between the tip of the electrode and the base metal will produce heat. This heat is what locally melts the electrode tip (welding wire) and the workpiece. The electric arc is generated by a welding machine. The electrode used is a wire wrapped in a flux protector. With this melting, the weld seam will be filled with liquid metal from the electrodes and the parent metal, a liquid crater is formed, then freezes, a weldment and slag will occur.
The advantages of SMAW
- Can be used anywhere, outside, in the workshop & in the water.
- Can weld various types of materials.
- Quick set-up and very easy to set up.
- Can be used to weld all positions.
- Electrodes are readily available in many sizes and diameters.
- The equipment used is simple, cheap and easy to carry anywhere.
- Low noise (rectifier).
- Not very sensitive to corrosion, oil & grease.
The disadvantages of SMAW
- Welding is limited to the length of the electrodes and must be made to join.
- Every time you do the next welding, the slag must be cleaned.
- Cannot be used for welding non-ferrous steel materials.
- It is easy to oxidize due to the protective liquid metal, only the welding arc from the flux.
- The electrode diameter depends on the plate thickness and the welding position.
Various types of SMAW Welding Machines
Welding machine is the most important part of welding equipment. This machine must be able to provide the required type of electric power and sufficient voltage to continue a welding arc.
a. Transformer
This machine requires an alternating current source and otherwise provides an alternating current with a lower voltage (voltage) in the welding process. Based on the current control system used, AC electric arc welding machines can be divided into four types, namely: movable core type, moving coil type, saturated reactor type and switch type.
b. Rectifier Welding Machine
This machine converts the incoming alternating current (AC) into direct current (DC). It works quietly and usually has a single control button to adjust the current out. The electric current used to obtain an electric arc flame is direct current. This direct current comes from a welding machine in the form of a direct electric motor dynamo. The dynamo can be driven by an electric motor, gasoline motor, diesel motor, or other driving device that requires equipment that functions as a current rectifier. A rectifier or rectifier functions to convert alternating current (AC) into direct current (DC). This direct current rectifier welding machine has several advantages, including:
a. The resulting arc flame is more stable and quiet;
b. Any type of electrode can be used for welding on a DC machine;
c. Lower noise level;
d. Welding machines are more flexible, because they can be converted to alternating current or direct current.
c. Inverters
In this type the power source uses an inverter. Power comes from the main source which is converted into DC high voltage, high frequency AC between 5 to 30 KHz. The output of the circuit is controlled according to the required welding procedure. High frequency is converted into tension during welding. The advantage of the inverter is that it uses a small transformer, the smaller the transformer the higher the frequency. Can be controlled remotely and someone uses a display.
d. Generator
It consists of a generator of alternating and direct electric currents that run on an engine (gasoline or diesel). Because the energy source is fuel, in use this machine is widely used in the field (away from electricity sources) and emits smoke. Sturdy, the resulting bow is stable, the sound is noisy, heavy, expensive, complicated design and maintenance.
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