Let the Weld Guru guide you through the world of Arc Welding



pipe welding

Arc Welding, SMAW, Stick Welding

A manual process using a flux coated electrode.

Alternating current or direct current forms an arc between the electrode and the base metal.

The flux coating disintegrates and gives off vapors that;

- serve as a shielding gas

- provide a protective layer of slag

both protect the weld area from atmospheric contamination.

SMAW is the world's most popular welding processes.

SMAW is primarily used to weld iron and steels.

SMAW can be used in all positions

- flat

- vertical

- horizontal

- overhead




Arc Welding, SMAW, Stick Welding requires basic equipment and lends itself to field work because it is extremely portable.

Disadvantages

- slag removal

- unused electrode stubs

- spatter

add to the cost and slow relative speed of SMAW.

Spatter and unused electrode stubs account for approx. 44 percent of consumed electrodes.

Entrapment of slag also is an issue in SMAW forming inclusions, which need to be removed.

Process

Arc Welding, SMAW, Stick Welding uses the arc heat melt the base metal and tip of a consumable electrode.

The electrode and base metal are part of an electric circuit or welding circuit.

This circuit includes;

- power source - welding cables - electrode holder - ground clamp - the work or base metal - arc welding electrode.

One cable is attached to the work and the other to the electrode holder.

Welding starts when an arc is struck between the tip of the electrode and base metal.

The heat melts the tip and the surface of the work.

Tiny globules of molten metal form on the electrode tip then transfer through the arc into the molten pool.

Filler is deposited as the electrode is consumed.

The Arc Welding, SMAW, Stick Welding arc is moved; - at an appropriate arc length (approx. equal to the electrode diameter)

- appropriate travel speed

melting and fusing a part of the base metal and adding filler.

The SMAW arc is extremely hot (temperatures in excess of 9000ºF (5000ºC) at its center), melting occurs almost instantly as the arc touches the metal.

For welds made in the flat or the horizontal position, metal transfer is aided by gravity, gas expansion, electric forces, and surface tension.

Welds in other positions, must overcome gravity.

Gravity

In out of position welds, the base metal is unable to retain much molten metal in the crater. Smaller electrodes, lower amperages and lower arc lengths should be used.

Gas expansion

Gases are produced by the melting of the electrode coating and expand due to the heat of the boiling electrode tip.

The coating extends slightly beyond the metal tip of the electrode and controls the direction of gas expansion. This helps direct the molten metal into the weld metal pool.

Electromagnetic forces (arc travel or arc blow)

The tip is a electric conductor and so is the molten globule spray at the tip, so the globule spray is altered by magnetic forces acting at 90 degrees (sideways in most cases) to the direction of the current flow.

This is helpful in the in horizontal, vertical, and overhead position welding.

Higher tensile strength rods have a higher tendency for arc blow.

The placement of the ground cable can have a major effect on these forces

Surface tension The force keeping filler metal and slag in contact with molten base metal in the crater is surface tension.

It helps retain molten metal in horizontal, vertical, and overhead welding, and determines the shape of weld contours