Welding is a fabrication process that joins materials like metals by melting them together with heat and sometimes pressure. There are different types of welding including arc welding, which uses an electric arc to melt metals, and gas welding (oxyacetylene welding), which uses fuel gases and oxygen applied through a torch. Specific arc welding methods include shielded metal arc welding, gas tungsten arc welding, and others that use consumable or non-consumable electrodes to create the arc and melt the materials. Equipment for gas welding includes oxygen and fuel gas cylinders, regulators, hoses, and a torch.

1. Welding

2. Welding
• Welding is a fabrication process that joins materials,
usually metals or thermoplastics, by causing coalescence. This is often
done by melting the workpieces and adding a filler material to form a
pool of molten material (the weld pool) that cools to become a strong
joint, with pressure sometimes used in conjunction with heat, or by
itself, to produce the weld.

3. Electric Arc welding
• Arc welding is a type of welding that uses a welding power supply to
create an electric arc between an electrode and the base material to
melt the metals at the welding point. They can use either direct (DC)
or alternating (AC) current, and consumable or non-consumable
electrodes.

4. Arc Welding(Consumable electrode)
• One of the most common types of arc welding is shielded metal arc
welding (SMAW), which is also known as manual metal arc welding
(MMAW) or stick welding.
• An electric current is used to strike an arc between the base material
and a consumable electrode rod or stick.
• The electrode rod is made of a material that is compatible with the
base material being welded and is covered with a flux that gives off
vapors that serve as a shielding gas and provide a layer of slag, both
of which protect the weld area from atmospheric contamination.

7. Power supply

8. Non-consumable electrode methods
• Gas tungsten arc welding (GTAW), or tungsten/inert-gas (TIG)
welding, is a manual welding process that uses a non-consumable
electrode made of tungsten, an inert or semi-inert gas mixture, and a
separate filler material.
• Especially useful for welding thin materials, this method is
characterized by a stable arc and high quality welds, but it requires
significant operator skill and can only be accomplished at relatively low
speeds.
• It can be used on nearly all weldable metals, though it is most often
applied to stainless steel and light metals.
• It is often used when quality welds are extremely important, such as
in bicycle, aircraft and naval applications.

10. Gas Welding(Oxyacetylene Welding)
• Oxy-fuel welding (commonly called oxyacetylene welding, oxy
welding, or gas welding in the U.S.) and oxy-fuel cutting are
processes that use fuel gases and oxygen to weld and cut metals,
respectively.
• In oxy-fuel welding, a welding torch is used to weld metals. Welding
metal results when two pieces are heated to a temperature that
produces a shared pool of molten metal.
• The molten pool is generally supplied with additional metal called
filler. Filler material depends upon the metals to be welded.

13. Apparatus
• The apparatus used in gas welding consists basically of an oxygen
source and a fuel gas source (usually cylinders),
two pressure regulators and two flexible hoses (one of each for each
cylinder), and a torch.