Consumables in GMAW process

The Gas metal arc welding process not only operates in semi automatic modes but also automatic modes. 3 process techniques are: short circuiting metal transfer, globular transfer, and spray arc. The two consumable, but important, elements of the GMAW process are the electrode and the shielding gas.

arc-welding-consumables

CHEMICAL COMPOSITION OF THE ELECTRODE:

  • The chemical composition of the electrode must be selected to achieve the desired properties in the weld metal.
  • The composition is designed with extra deoxidizers or other scavenging agents to compensate for reactions with the atmosphere and the base metal.
  • The deoxidizers most commonly used in steel electrodes are silicon and manganese.
  • Silicon can also be added in all transfer modes to increase weld metal fluidity or it can be added when a 300 series stainless steel electrode is used.

The physical characteristics (finish, straightness, and others) of electrodes used in the GMAW process are important to successful welding.

The material specifications for these electrodes establish manufacturing requirements to ensure that users receive a uniform product that feeds smoothly through the equipment and has these characteristics, as well:

· UNIFORM WINDING ON THE SPOOL OR COIL WITH NO KINKS OR BENDS

· SMOOTH SURFACE FINISH FREE OF SLIVERS, SCRATCHES, OR SCALE

· PRESCRIBED CAST AND HELIX

· UNIFORM DIAMETER

Cast and helix refer to dimensions of a single coil of wire removed from a spool or coil and layed (that is, cast) on a flat surface. If this coil is too small in diameter (cast) or shows an excessive lift from the flat surface (helix) wire, feeding problems during welding can be anticipated.

Shielding Gas

  • The primary function of the shielding gas in most of the welding processes is to protect the surrounding atmosphere from contact with molten metal.
  • In the GMAW process, this gas plays an additional role in that it has a pronounced effect on arc characteristics, mode of metal transfer, and depth of fusion, weld bead profile, welding speed, and cleaning action.
  • Inert gases, such as argon and helium, are commonly used, as is the active gas, CO2.
  • It is also common to use mixtures of these gases and to employ small additions of oxygen.

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