Nippon Gases 2719135, Руководство по эксплуатации и технике безопасности, Страница: 12 / 44

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PT
MICROTIG DC 162 / 202 PULSE
Shielding gases: Gases used in TIG welding contribute to:
- To involve the electric arc in an ionisable atmosphere.
- Avoid contamination of the weld by oxygen in the atmosphere.
- To cool the electrode.
Arg o n (Ar)
The most common gas used with a purity grade of 99.9%.
Helium (He)
Pure helium is used for copper welding mixed with argon in percentages varying between 10% and
75%.
Hydrogen (H)
It is an inert gas at room temperature and is used especially in copper soldering. It is not
recommended for soldering in enclosed spaces because it combines with oxygen to create an
unbreathable atmosphere.
4. MMA WELDING (coated electrode)
To establish a welding arc, a potential difference is induced between the electrode and the workpiece.
potential difference between the electrode and the workpiece.
The air between them is ionised and becomes conductive, so that the circuit is closed and creates the
electric arc. The heat of the arc partially melts the base material which is deposited creating a weld
pool. Arc welding is still very common due to the low cost of the equipment and consumables used in
this process.
An electric arc is formed between the electrode and the metal to be welded by means of an electric
current. The temperatures reached cause it to melt and deposit in the welded joint. Metal core
electrodes made of steel or other alloys are coated with a fluxing material which creates a protective
atmosphere that prevents oxidation of the molten metal and facilitates the welding operation.
In DC power sources (rectifiers) the polarity of the electric current affects the mode of metal transfer.
Typically, the electrode is connected to the positive (+) pole, although in welding very thin materials, it
may be connected to the negative (-) pole.
The most favourable welding position is horizontal, while welding can be carried out in any position.
Porta-electrodos
Electrodo revestido
Zona de soldadura
Transferencia
de metal
Atmosfera de
protección de arco
Pieza a soldar
Pinza de masa