A welding technique where the welding torch or gun is directed opposite to the direction of welding.

A material (base metal, weld metal, or granular material) placed at the root of a weld joint for the purpose of supporting molten weld metal.

A shielding gas used on the underside of a weld bead to protect it from atmospheric contamination.

High temperature crystal structure of carbon steel or the room temperature structure of chrome-nickel steel.

Composed mainly of gamma iron with carbon in solution.